JP2016221912A - Image formation apparatus, image formation method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform discharge of droplets from nozzles arrayed in a row in a main-scanning direction in the discharge state where the occurrence of stripes in a sub-scanning direction is reduced.SOLUTION: An ink jet image formation apparatus 1 moves a conveyance unit 3 fixed with a recording medium P in a conveyance direction along a linear motion stage 2, and drives nozzles of a head unit 5 in which the nozzles are arrayed in a row in a main-scanning direction with a drive signal to discharge ink droplets to the recording medium P. The ink jet image formation apparatus 1 generates a drive signal to each nozzle of the head unit 5 on the basis of image data and adjusts the drive signal to be the drive signal for generating the ink droplet discharge state where the ink droplets discharged from the nozzle driven with the drive signal unite with the ink droplets discharged from another nozzle in the same nozzle array as the nozzle before uniting in the conveyance direction with the ink droplets discharged from the same nozzle on the conveyed recording medium P.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus, an image forming method, and a program, and more particularly, to an image forming apparatus, an image forming method, and a program for forming an image by ejecting droplets onto a recording medium.

  Conventionally, in an image forming apparatus that discharges droplets of a recording agent such as ink onto a recording medium and forms an image on the recording medium, such as an ink jet recording apparatus, the droplets are discharged. An image is formed by reciprocating the recording head on which the nozzles are formed in the main scanning direction. As the recording medium, various recording media such as paper, film and cloth are used.

  Such a droplet discharge type image forming apparatus forms an image by moving the recording head in the main scanning direction, and thus has a limit in improving the recording speed.

  Therefore, conventionally, a recording head in which nozzles are formed over the maximum recording width is arranged in the main scanning direction, and one line (one row) to a plurality of lines (plural rows) are moved without moving the recording head. There is an image forming apparatus of a one-pass droplet discharge method that forms an image in a short time.

  However, since the one-pass droplet discharge type image forming apparatus has a short droplet discharge interval from an adjacent nozzle to a recording medium, the droplets previously discharged onto the recording medium are recorded on the recording medium. Adjacent droplets are ejected onto the recording medium before penetrating the medium. In this case, adjacent droplets ejected on the recording medium are coalesced between the droplets (hereinafter referred to as droplet interference as appropriate), and the image quality deteriorates. In particular, when the recording medium is a non-permeable recording medium such as a film or coated paper, or a slowly permeable recording medium, adjacent droplets are liable to flow and droplet interference easily occurs, resulting in a decrease in image quality. large.

  In particular, in a one-pass image forming apparatus, a dot formation position on a recording medium may be displaced due to a mechanical error such as an assembly accuracy of a recording head for ejecting liquid droplets or an ejection failure. When the dot formation position on the recording medium is displaced, the droplets are not filled and image quality defects such as streaks occur.

  For example, in the conventional image forming apparatus, as illustrated in FIG. 12A, it is assumed that the upstream nozzle rows 101 a to 101 n and the downstream nozzle rows 102 a to 102 n are formed on the recording head 100. Then, according to the conveyance of the recording medium, the conventional image forming apparatus first ejects droplets from the upstream nozzle rows 101a to 101n as shown in FIG. In this case, the dots land continuously in the transport direction of the recording medium (the direction indicated by the arrow Y in FIG. 12, hereinafter referred to as the Y direction as appropriate), and the liquid droplets ejected from the same nozzle immediately As shown in FIG. 12C, a film like a groove extending in the transport direction is formed. Thereafter, the image forming apparatus discharges droplets from the downstream nozzle rows 102a to 102n to fill the unfilled portions. However, for example, when the landing position is shifted as shown in FIG. 12D due to a formation error or ejection failure of the nozzle 102b, the liquid droplets ejected from the nozzle 102b immediately merge into the adjacent liquid pool. However, it becomes difficult to spread in the other adjacent liquid pool, and streaks appear. In this case, if the leveling time is lengthened in order to eliminate streaks, the productivity decreases, and depending on the amount of deviation, even if the leveling time is lengthened to some extent, there is a limit to the spread of wetting. , Streaks appear without being flattened.

  In particular, in recent years, an image forming apparatus using a UV curable droplet discharge method has been developed in which a UV curable droplet is discharged from a nozzle to form an image. In general, resin recording media are easily scratched. For the purpose of protecting the surface of recording media and providing gloss, overcoat with UV curable transparent liquid and hard coat. Form a layer.

  However, in full-surface printing such as overcoat, image quality defects such as streaks appear remarkably. Increasing the amount of droplets as a countermeasure against streaks eliminates the filling, but causes problems such as occurrence of beading and failure to obtain a desired film thickness. In particular, in one-pass printing, it is difficult to deceive the dispersion of the landing position deviation of the droplets, and this problem is particularly noticeable.

  Conventionally, when a liquid droplet is ejected from a recording head having a nozzle row in which a plurality of nozzles for ejecting liquid droplets are arranged to form an image including a dot row composed of continuously arranged dots, A dot of a size and a dot of a smaller size are combined to form a constriction in a dot row in a direction orthogonal to the nozzle row of the recording head, and dots adjacent to each other in the direction along the nozzle row of the recording head There has been proposed an image forming method in which each dot is arranged at a position where a portion of one dot row that is a peak with respect to the constriction corresponds to the constriction of the other dot row (see Patent Document 1).

  In other words, this conventional technique forms a constriction in the dot row in the recording medium conveyance direction (direction orthogonal to the nozzle arrangement) with a combination of large and small dots, and the peaks correspond to the constriction in the nozzle arrangement direction. By arranging it at the position where it will be done, we are trying to eliminate the streaking of streaks.

  However, in the prior art described in the above publication, the dots arranged in the direction perpendicular to the nozzle array are constricted to fill in the streaks, but the dots adjacent in the transport direction of the recording medium are As shown in Fig. 12, unite immediately. Accordingly, the dots are likely to be attracted in the transport direction of the recording medium, and the droplets are likely to spread in the transport direction. As a result, it is difficult for the droplets to spread in the nozzle arrangement direction, and the effect of streaking of the streaks is small.

  Accordingly, an object of the present invention is to discharge droplets from nozzles arranged in a line in the main scanning direction in a discharge state that reduces the occurrence of streaks in the sub-scanning direction.

  In order to achieve the above object, in the image forming apparatus according to claim 1, one or more nozzle rows in which a plurality of nozzles are arranged in the main scanning direction are arranged, and each of the nozzles is driven by a drive signal to generate a droplet. Generating a drive signal to each nozzle of the recording head based on image data, a recording head for discharging the recording medium to the recording medium, a conveying means for conveying the recording medium in a conveying direction orthogonal to the main scanning direction In addition, the liquid droplets ejected from the nozzles driven by the driving signals are transported in the same direction as the liquid droplets ejected from the same nozzles on the recording medium transported by the transport means. Drive signal control means for adjusting to a drive signal for generating a droplet discharge state that combines with droplets discharged from other nozzles in the same nozzle row as the nozzle before This It is characterized in.

  According to the present invention, it is possible to discharge droplets from nozzles arranged in a row in the main scanning direction in a discharge state that reduces the occurrence of streaks in the sub-scanning direction.

1 is a schematic plan view of an inkjet image forming apparatus to which an embodiment of the present invention is applied. 1 is a block diagram of an inkjet image forming apparatus. 1 is a functional block diagram of an inkjet image forming apparatus. Explanatory drawing of the ink droplet coalescence when ejecting ink droplets from every other nozzle. Explanatory drawing of the drive signal production | generation process using a halftone process. Explanatory drawing of the ink droplet coalescence in the case of discharging an ink droplet from a continuous nozzle. Explanatory drawing of the ink droplet coalescence when ejecting ink droplets from nozzles arranged in a staggered pattern. Explanatory drawing of the ink droplet coalescence in the case of coating by ejecting ink droplets from the staggered arrangement of nozzles. The figure which shows the relationship between the magnitude | size of the ink drop of FIG. 8, and the elapsed time after landing. 5 is a flowchart showing image formation control processing. Explanatory drawing of the drive signal production | generation using a mask signal. Explanatory drawing of the ink discharge which causes the conventional image quality fall.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The range of this invention is unduly limited by the following description. However, not all the configurations described in the present embodiment are essential constituent elements of the present invention.

  1 to 11 are diagrams illustrating an embodiment of an image forming apparatus, an image forming method, and a program according to the present invention. FIG. 1 illustrates an embodiment of an image forming apparatus, an image forming method, and a program according to the present invention. It is a schematic plan view of the applied inkjet image forming apparatus.

  In FIG. 1, an inkjet image forming apparatus (image forming apparatus) 1 is provided with a linear motion stage 2 having a predetermined length, and can move linearly on the linear motion stage 2 in the movement direction (Y direction). A transport unit 3 is provided.

  In the inkjet image forming apparatus 1, a surface modification unit 4, a head unit 5, and an irradiation unit 6 are sequentially disposed above the linear motion stage 2 in the movement direction (conveyance direction) of the conveyance unit 3.

  The transport unit 3 has a recording medium P on which an image is formed fixed on the upper surface. As the recording medium P, for example, paper such as normal paper, a film such as ABS resin, or the like is used.

  In the inkjet image forming apparatus 1, the transport unit 3 to which the recording medium P is fixed moves along the linear motion stage 2, and thus passes under the surface modification unit 4, the head unit 5, and the irradiation unit 6. .

  As the surface modification unit 4, a corona treatment machine, a plasma treatment machine, an excimer lamp irradiation machine, or the like is used. The surface modification unit 4 performs corona treatment, plasma treatment, lamp irradiation, and the like when the transport unit 3 on which the recording medium P is fixed passes below the surface modification unit 4, The surface of P is modified so that ink droplets ejected from the head unit 5 to be described later are easily spread.

  The head unit 5 is formed with a plurality of nozzles arranged in the main scanning direction (X direction) orthogonal to the transport direction (Y direction). The head unit 5 includes an energy generation method for ejecting ink droplets (droplets) from nozzles, a piezoelectric conversion element method using a piezoelectric element as an energy generation element, an electromechanical conversion element method using electrostatic attraction between electrodes, and the like. It is used. The head unit 5 drives the nozzles in accordance with a driving signal to the nozzles and a mask signal for masking the driving signals on / off, and drops droplets, for example, ink droplets (hereinafter referred to as ink droplets as appropriate). Droplets) is ejected toward the recording medium P. For example, in the case where the head unit 5 is a piezoelectric transducer using a piezo element, when a drive signal is applied to the piezo element of the nozzle, the piezo element causes a contraction motion, and a pressure change due to the contraction motion occurs. Thus, an ink droplet is ejected from the nozzle.

  The irradiation unit 6 includes a UV (ultraviolet) lamp, and forms a hard coat layer by irradiating the recording medium P fixed to the transport unit 3 passing under the irradiation unit 6 with a predetermined amount of UV. Let

  In other words, when the ink jet image forming apparatus 1 forms an ink layer having a predetermined film thickness on the recording medium P by the head unit 5, the time for smoothing the ink coating film (hereinafter, referred to as leveling time as appropriate). Put. When the leveling time has elapsed, the inkjet image forming apparatus 1 moves the transport unit 3 to the irradiation unit 6 and performs UV irradiation by the irradiation unit 6 to form a hard coat layer on the recording medium P. In this case, in the present invention, the UV curable clear ink is effective as the ink ejected from the head unit 5, but it is limited whether it is UV curable, colored or colorless. Not.

  Although not shown in FIG. 1, the inkjet image forming apparatus 1 linearly moves a maintenance / recovery unit that forcibly discharges ink droplets from the nozzles of the head unit 5 or wipes ink adhering to the head unit 5. It may be provided at one end of the stage 2.

  The inkjet image forming apparatus 1 is configured as a block as shown in FIG. The inkjet image forming apparatus 1 includes a controller unit 11 and a detection group 12, and includes the transport unit 3, the head unit 5, the irradiation unit 6, the surface modification unit 4, and the like.

  The controller unit 11 includes a CPU (Central Processing Unit) 21, a memory 22, an I / F 23, a unit control circuit 24, and the like.

  The detection group 12 is a general term for sensors that detect various states of the inkjet image forming apparatus 1 such as a position detection sensor on the linear motion stage 2 of the transport unit 3 and a recording medium sensor that detects the presence or absence of the recording medium P. It is. The detection group 12 outputs the detection result to the CPU 21.

  The memory 22 includes a ROM (Read Only Memory), a RAM (Random Access Memory), a nonvolatile memory, and the like. The ROM stores a basic program as the inkjet image forming apparatus 1, a program such as a program for executing the image forming method of the present invention, various system data, and the like. The nonvolatile memory uses NVRAM (Nonvolatile Random Access Memory) or the like, and stores data that should be stored even when the power of the inkjet image forming apparatus 1 is off under the control of the CPU 21.

  The CPU 21 executes basic processing as the inkjet image forming apparatus 1 by controlling each part of the inkjet image forming apparatus 1 while using the RAM as a work memory based on a program in the ROM of the memory 22, The image forming method of the invention is executed.

  In particular, the CPU 21 performs a halftone process on the input image data, thereby generating a dot arrangement drive signal that suppresses the occurrence of streaks in the conveyance direction of the recording medium P. For example, the image data input from the information processing device JS is binarized image data in the case of coating, and the CPU 21 has a dot arrangement in which streaks are unlikely to occur with respect to the binarized image data. A halftone process is performed and converted into, for example, 2-bit recording data. In this case, each pixel row corresponds to the position of the nozzle of the head unit 5, and the pixel row corresponding to the nozzle on the upstream side with respect to the conveyance direction of the recording medium P is a combination of large droplets and small droplets. The dot arrangement is such that the dots are easy to coalesce in the nozzle row direction and the dots are difficult to coalesce in the transport direction.

  The inkjet image forming apparatus 1 acquires the relationship between each recording medium P and the dot diameter of the ink and stores it in the memory 22 because the wetting and spreading of dots varies depending on the type of ink and recording medium P. In the image formation, the CPU 21 refers to the relationship between the recording medium P in the memory 22 and the dot diameter of the ink based on conditions such as the ink used for the image formation and the type of the recording medium P, and the contents of the halftone processing To decide.

  The I / F 23 is connected to an information processing device JS such as an external computer via a network or a dedicated line. The I / F 23 communicates with the information processing device JS and transfers data under the control of the CPU 21. In particular, the I / F 23 exchanges data such as print jobs with the information processing apparatus JS.

  The unit control circuit 24 is connected to the CPU 21, and is connected to the transport unit 3, the head unit 5, the irradiation unit 6, and the surface modification unit 4. The unit control circuit 24 controls the operations of the transport unit 3, the head unit 5, the irradiation unit 6, and the surface modification unit 4 under the control of the CPU 21.

  The inkjet image forming apparatus 1 includes a ROM, an EEPROM (Electrically Erasable and Programmable Read Only Memory), an EPROM, a flash memory, a flexible disk, a CD-ROM (Compact Disc Read Only Memory), a CD-RW (Compact Disc Rewritable), The image forming method of the present invention recorded on a computer-readable recording medium such as a DVD (Digital Versatile Disk), USB (Universal Serial Bus) memory, SD (Secure Digital) card, MO (Magneto-Optical Disc), etc. By reading the program to be executed and introducing it into the memory 22, the ejection of ink droplets (droplets) from nozzles arranged in a row in the main scanning direction, which will be described later, is reduced, and the occurrence of streaks in the sub-scanning direction is reduced. As an inkjet image forming apparatus (image forming apparatus) 1 that executes an image forming method performed in a discharge state, It is. This program is a computer-executable program written in a legacy programming language such as assembler, C, C ++, C #, Java (registered trademark), an object-oriented programming language, or the like, and is stored in the recording medium and distributed. be able to.

  In the inkjet image forming apparatus 1, a functional block shown in FIG. 3 is constructed by introducing a program for executing the image forming method. That is, in the inkjet image forming apparatus 1, when the program for executing the image forming method is introduced, the recording head 31, the transport unit 32, and the drive signal control unit 33 are constructed as shown in FIG.

  The recording head 31 is constructed by the head unit 5 and has one or more nozzle rows in which a plurality of nozzles (not shown) are arranged in the main scanning direction shown as the X direction in FIG. To eject ink droplets onto the recording medium P. Therefore, the recording head 31 functions as a recording head. As will be described later, the recording head 31 may have a plurality of nozzle rows in the transport direction. The recording head 31 may have a plurality of rows of nozzles arranged in a staggered pattern.

  The transport unit 32 is constructed by the transport unit 3 and transports the recording medium P in a transport direction (direction indicated as the Y direction in FIG. 3) orthogonal to the main scanning direction (X direction). Therefore, the transport unit 32 functions as a transport unit.

  The drive signal control unit 33 is constructed by the CPU 21 and receives image data from the information processing device JS. The drive signal control unit 33 generates a drive signal for each nozzle of the recording head 31 based on the image data. Further, the drive signal control unit 33 uses the drive signal as the ink ejected from the same nozzle on the recording medium P on which the ink droplets ejected from the nozzle driven by the drive signal are transported by the transport unit 32. Before the droplets are merged in the transport direction, the drive signal is adjusted to generate an ink droplet ejection state that merges with ink droplets ejected from other nozzles in the same nozzle row as the nozzle. Other nozzles in the same nozzle row as this nozzle are usually adjacent nozzles in the same nozzle row. Therefore, the drive signal control unit 33 functions as drive signal control means.

  When the recording head 31 has a plurality of nozzle rows formed in the transport direction, the drive signal control unit 33 detects drive signals before ink droplets ejected from the same nozzle are united on the recording medium P. The drive signal is adjusted to generate an ink droplet ejection state that merges with ink droplets ejected from other nozzles in the same nozzle row as the nozzle.

  Further, when the recording head 31 has nozzles arranged in a plurality of rows arranged in a staggered pattern, the drive signal control unit 33 sends the drive signal to at least the nozzle row upstream in the transport direction. After the ink droplets ejected from the nozzles merge with the ink droplets ejected from the other nozzles in the same nozzle row, the ink droplets from the nozzles arranged in a row on the downstream side in the transport direction The drive signal is adjusted to generate an ink droplet ejection state that lands on the recording medium P.

  In addition, the drive signal control unit 33 performs a halftone process on the input image data so that dots are easily aligned in the nozzle row direction and dots are not easily aligned in the transport direction. May be adjusted to a drive signal for generating the ink droplet ejection state.

  Next, the operation of this embodiment will be described. The inkjet image forming apparatus 1 according to the present exemplary embodiment performs discharge of ink droplets from nozzles arranged in a row in a discharge state that reduces the occurrence of streaks.

  The inkjet image forming apparatus 1 is arranged in a row in the main scanning direction on the recording medium P transported by the transport unit 3 based on the image data sent from the information processing apparatus JS. The nozzle is driven by a drive signal to discharge ink.

  That is, for example, as shown in FIG. 4A, the head unit 5 has a plurality of nozzles N1 to Nn (N1 to N5 are shown in FIG. 4) arranged in a row in the main scanning direction.

  The inkjet image forming apparatus 1 outputs a drive signal based on image data from the controller unit 11 to the head unit 5 while conveying the recording medium P by the conveyance unit 3. The inkjet image forming apparatus 1 drives the nozzles N <b> 1 to Nn of the head unit 5 to eject ink droplets toward the recording medium P being conveyed, and land the dot droplets on the recording medium P.

  At this time, as described above, when the ink droplets are continuously ejected from the same nozzles N1 to Nn in the transport direction (Y direction), the inkjet image forming apparatus 1 causes the ejected ink droplets to be recorded on the recording medium P. There is a risk that streaks occur in the transport direction in the formed image.

  Therefore, in the inkjet image forming apparatus 1 of the present embodiment, the CPU 21 performs streaking on the image data from the information processing apparatus JS based on the arrangement of the nozzles N1 to Nn, the type of ink, and the type of recording medium P. A drive signal is generated by applying a halftone process that results in a dot arrangement that is less likely to occur.

  That is, for example, as illustrated in FIG. 5, when the binary coating image data is input, the CPU 21 determines the image based on the arrangement of the nozzles N1 to Nn, the type of ink, and the type of the recording medium P. A halftone process is performed on the data to generate 2-bit (4-value) image data. The CPU 21 generates a drive signal for driving the nozzles N1 to Nn based on the halftone processed image data. In FIG. 5, “large”, “small”, and “no” indicate the size (large and small) of the ink droplets and no ink droplet (no), respectively.

  For example, as shown in FIG. 4B, the inkjet image forming apparatus 1 uses nozzles N1 and N3 at intervals of nozzles N1 to Nn based on image data obtained by performing halftone processing on input image data. , N5 generates a drive signal for ejecting ink droplets. Now, assuming that the interval at which ink droplets are ejected in the main scanning direction (X direction) is X1, and the dot interval in the transport direction (Y direction) is Y1, X1 <Y1. If the diameter d1 of the ink droplet immediately after landing on the recording medium P is X1 ≦ d1 <Y1, the ink droplet is connected in the X direction and not in the Y direction. Does not occur. Therefore, as shown in FIG. 4C, if the ink droplet that spreads after the landing is D1, let D1 ≧ Y1, and dots in the Y direction are also connected. As a result, ink droplets are spread evenly over the entire recording medium P, and streaks are difficult to see in both the transport direction and the main scanning direction.

  In addition, as shown in FIG. 6, when the ink jet image forming apparatus 1 ejects ink droplets from the adjacent nozzles N <b> 1 to Nn, the ink droplet size is determined based on the ink droplet ejection timing and the adjacent nozzle in the transport direction. The distance is determined in consideration of the distance from N1 to Nn.

  That is, in the case of FIG. 6, the inkjet image forming apparatus 1 ejects ink droplets from the nozzles N1 to Nn adjacent to FIG. In this case, as shown in FIG. 6B, when the nozzle interval is X2 and the dot interval in the Y direction is Y2, the relationship is 2 × X2 = Y2. If the diameter d2 of the ink droplet immediately after landing is X2 ≦ d2 <Y2, the ink droplet with the diameter d2 is connected with dots in the X direction and not connected in the Y direction. Does not occur. Then, as shown in FIG. 6C, if an ink droplet that has spread over time after landing is D2, D2 ≧ Y2, and dots in the Y direction are also connected. Accordingly, ink droplets are spread evenly over the entire recording medium P, and streaks are difficult to see. In the case of FIG. 6, an ink droplet having a dot diameter that is not connected in the Y direction immediately after landing may be arranged between Y2.

  Furthermore, in the inkjet image forming apparatus 1, when the head unit 5 has a plurality of nozzles N11 to N1n and nozzles N21 to N2n arranged in a staggered manner as shown in FIG. The size of the ink (ink droplet size) may be changed. In FIG. 7, two nozzle rows are formed.

  For example, as shown in FIG. 7B, the inkjet image forming apparatus 1 uses the same row of nozzles that simultaneously eject the ink droplets ejected from the nozzles N11 to N1n in the upstream nozzle row of FIG. The ink droplets must have a size that always matches the ink droplets N11 to N1n. Next, the ink jet image forming apparatus 1 places the ink droplets to be ejected into small ink droplets and dot positions that do not coalesce with the previous ink droplets immediately after landing. Further, the inkjet image forming apparatus 1 sets the next ink droplet to the ink droplet size and the dot position that are merged with the simultaneously ejected ink droplets but do not merge with the previous ink droplet. The inkjet image forming apparatus 1 repeats the above discharge pattern until the ink droplets are discharged from the nozzles N21 to N2n in the downstream nozzle row, as shown in FIG. 7C, in the X direction. The ink droplets that merge together merge to form an ink reservoir. In this case, if the ink droplet of a small size is united with this ink reservoir, the filling is further improved. Thereafter, as shown in FIG. 7D, the ink droplets ejected from the nozzles N21 to N2n in the downstream nozzle row land on the ink droplet reservoir, and a film is formed. Thus, since the ink reservoir formed by the ink droplets ejected from the nozzles N11 to N1n of the upstream nozzle row is not a groove, the ink ejected from the nozzles N21 to N2n of the downstream nozzle row Drops are also less likely to form grooves, making streaks difficult to see. The ink size of the nozzles N21 to N2n of the downstream nozzle row ejected at the same Y-direction position as the small ink size ejected from the nozzles N11 to N1n of the upstream nozzle row is more uneven. Since it is suppressed, it is more preferable. Further, even if the landing position deviation occurs in the ink droplets from the nozzles N21 to N2n in the downstream nozzle row, the ink reservoirs ejected from the nozzles N11 to N1n in the upstream nozzle row do not form a groove. , Streaks due to landing position deviation will be difficult to see.

  In the case of FIG. 7, for example, when coating is performed using the head unit 5 as shown in FIG. 8A, the coating becomes as shown in FIGS. Coating could be done. That is, the head unit 5 shown in FIG. 8 has four rows of 150 dpi nozzles N11 to N1n, N21 to N2n, N31 to N3n, and N41 to N4n arranged in a staggered manner, and has a resolution of 600 dpi in one pass. Yes. In FIG. 8, a coating ink is used as the ink, and an ABS film is used as the recording medium P.

  In FIG. 8, in the inkjet image forming apparatus 1, the nozzles N11 to N1n and N21 to N2n in the first row and the second row are large droplets of the first ink droplet, the next droplet is not ejected, and the next droplet is a small droplet. The next is not ejected, and the next droplet is ejected repeatedly as a large droplet. As shown in FIG. 8B, the ink enemies ejected from the nozzles N11 to N1n and N21 to N2n in the first and second rows immediately coalesce with large droplets in the X arrangement direction and move in the Y direction. It becomes difficult to make a groove. Then, before the ink droplets are ejected from the nozzles N31 to N3n and the nozzles N41 to N4n in the third row and the fourth row, the small droplets spread and merge with the large droplets in the Y direction. The ink droplets spread over almost the entire recording medium P by the ink droplets of the eyes. Then, as shown in FIG. 8C, the inkjet image forming apparatus 1 ejects all large droplets from the nozzles N31 to N3n and the nozzles N41 to N4n in the third and fourth rows. As a result, the ink spreads over the entire recording medium P, and a coating film of less than 10 μm can be formed in a short leveling time.

  In addition, the size of the ink droplets in FIG. 8 and the elapsed time after landing are shown in FIG. In FIG. 9, when the droplet is 8 pl, the medium droplet is 15 pl, and the large droplet is 21 pl, after landing on the recording medium P, 0.28 s (seconds), 60 μm, 80 μm, and 92 μm, respectively. They were 80 μm, 100 μm and 110 μm after 60 seconds after landing, respectively.

  Then, in the inkjet image forming apparatus 1, the CPU 21 determines the nozzle order for ejecting the ink droplets and the size of the ink droplets based on the image data and the type of the recording medium P, and performs halftone processing on the image data. To do.

  For example, as shown in FIG. 10, when the CPU 21 receives image data from the information processing apparatus JS via the I / F 23 (step S101), the image data in the memory 22 and the data to be recorded are determined from the type of the image data and the recording medium P. Reference is made to experimental data with the recording medium P. The CPU 21 selects the ink film thickness to be formed from the image data and the type of the recording medium P (step S102).

  When the film thickness is thick (in step S102, when the film is thick), the CPU 21 performs halftone processing C1 previously set for the thick film on the image data (step S103), and print data (Drive signal) is generated (step S104).

  The CPU 21 controls the transport unit 3 and the head unit 5 via the unit control circuit 24 based on the generated drive signal, and ejects ink droplets from the nozzles of the head unit 5 to print an image on the recording medium P. (Step S105). When the nozzles exist over a plurality of nozzle rows, the CPU 21 determines the order of driving the nozzles in each row and the size of the ink droplets to be ejected in the halftone process.

  When printing is completed by ejecting ink droplets, the CPU 21 sends the recording medium P to the irradiation unit 6 by the transport unit 3 and irradiates with UV to form a hard coat layer, and ends the image formation control process. (Step S106).

  In step S102, if the film thickness is a thin film (when the film is a thin film in step S102), the CPU 21 performs halftone processing C2 previously set for the thin film on the image data (step S107). Then, recording data (driving signal) is generated (step S108).

  The CPU 21 controls the transport unit 3 and the head unit 5 via the unit control circuit 24 based on the generated drive signal, and ejects ink droplets from the nozzles of the head unit 5 to print an image on the recording medium P. (Step S105). When the nozzles exist over a plurality of nozzle rows, the CPU 21 determines the order of driving the nozzles in each row and the size of the ink droplets to be ejected in the halftone process, as described above.

  When printing is completed by ejecting ink droplets, the CPU 21 sends the recording medium P to the irradiation unit 6 by the transport unit 3 and irradiates with UV to form a hard coat layer, and ends the image formation control process. (Step S106).

  In FIG. 10, the surface modifying unit 4 is not used, but depending on the type of the recording medium P, when the printing process of step S105 is performed, first, the surface modifying unit 4 uses the recording medium P. The surface may be modified. In this case, the CPU 21 determines the size of the ink droplet and the order of the nozzles that eject the ink droplet in consideration of the modification of the surface of the recording medium P by the surface modification unit 4.

  In the above description, the case where the nozzle is driven by supplying the drive signal generated by the halftone process to the nozzle of the head unit 5 has been described. However, the driving of the nozzle is not limited to the above method.

  For example, as shown in FIG. 11, a method of combining a drive signal and a mask signal having a different ON period and supplying the drive signal to the nozzle only during a period when the mask signal is ON may be used. In FIG. 11, the unit control circuit 24 generates a drive signal having a constant period, and the CPU 21 sends a signal for designating a mask signal corresponding to the dot length determined by the halftone process to the unit control circuit 24. Output. The unit control circuit 24 masks the drive signal with the mask signal designated by the CPU 21 and outputs the drive signal to the nozzle only during the period when the mask signal is ON. Therefore, as shown in FIG. 11, in the case of a mask signal with a short ON period, a small dot, a medium dot in a mask signal with an intermediate ON period, and a large dot ink drop in a mask signal with a long ON period, Will be discharged.

  In the halftone processes C1 and C2, the CPU 21 uses the same drive signal as the droplet ejected from the nozzle driven by the drive signal on the recording medium P transported by the transport unit 3. Before the liquid droplets discharged from the nozzles are merged in the transport direction, the drive signal is adjusted to generate a liquid droplet discharge state that merges with liquid droplets discharged from other nozzles in the same nozzle row as the nozzle.

  Therefore, the occurrence of streaks in the transport direction (Y direction) can be suppressed, and the image quality can be improved.

  In this case, streaks are more likely to occur in the Y direction as the recording medium P is a recording medium P that is less likely to spread ink. In this case, by applying the image forming method of the present invention, it is possible to effectively suppress the occurrence of stripes in the Y direction as the recording medium P is more difficult to spread ink.

  In addition, even when a multilayer film is printed to ensure a thick film thickness, streaking and leveling time can be reduced by applying the image forming method of the present invention to the first layer.

  Furthermore, if a plurality of head units 5 are arranged in the Y direction, the landing time between the nozzle rows can be increased, and the ink droplets ejected first can be spread more uniformly. As a result, the generation of streaks can be further suppressed and the image quality can be improved.

  As described above, in the inkjet image forming apparatus 1 according to the present embodiment, one or more nozzle rows in which a plurality of nozzles are arranged in the main scanning direction are arranged, and each of the nozzles is driven by a drive signal to generate ink droplets (droplets). ) To the recording medium P, a conveyance unit (conveying means) 32 for conveying the recording medium P in a conveyance direction orthogonal to the main scanning direction, and the recording head 31 based on image data. On the recording medium P on which the ink droplets ejected from the nozzles driven by the drive signals are transported by the transport unit 32. Generates an ink droplet ejection state that merges with ink droplets ejected from other nozzles in the same nozzle row as the nozzle before coalescing with ink droplets ejected from the same nozzle in the transport direction That the drive signal controller adjusts the driving signal (drive signal control unit) 33, and a.

  Therefore, the ink droplets can be ejected from the nozzles arranged in a row in the main scanning direction in an ejection state that reduces the occurrence of streaks in the sub-scanning direction (the conveyance direction of the recording medium P). Image quality can be improved.

  In addition, the inkjet image forming apparatus 1 according to the present embodiment is configured so that each nozzle is driven by a drive signal from a recording head 31 in which one or more nozzle rows in which a plurality of nozzles are arranged in the main scanning direction is arranged. A discharge processing step for discharging droplets onto the recording medium P, a transport processing step for transporting the recording medium P in a transport direction orthogonal to the main scanning direction, and the nozzles of the recording head 31 based on image data. A drive signal is generated from the same nozzle on the recording medium P on which the ink droplets ejected from the nozzle driven by the drive signal are transported in the transport processing step. Ink droplet ejection state that coalesces with ink droplets ejected from other nozzles in the same nozzle row as the nozzles before coalescing with ejected ink droplets in the transport direction A drive signal control processing steps for adjusting the drive signal for generating, executing an image forming method of the.

  Therefore, it is possible to discharge ink droplets from nozzles arranged in a row in the main scanning direction in a discharge state that reduces the occurrence of streaks in the sub-scanning direction (the conveyance direction of the recording medium P). Image quality can be improved.

  Further, the inkjet image forming apparatus 1 of the present embodiment is provided for each nozzle from a recording head 31 in which one or more nozzle rows in which a plurality of nozzles are arranged in the main scanning direction are arranged in a computer such as the CPU 21. An ejection process in which ink droplets are ejected onto a recording medium P by being driven by a drive signal having a predetermined driving waveform, a conveyance process in which the recording medium P is conveyed in a conveyance direction orthogonal to the main scanning direction, and image data And generating a drive signal for each nozzle of the recording head 31, and using the drive signal, the ink droplets ejected from the nozzle driven by the drive signal are transported in the transport process. Ink ejected from other nozzles in the same nozzle row as the nozzles before being merged in the transport direction with ink droplets ejected from the same nozzles on the recording medium P It is equipped with a program to be executed and a drive signal control processing for adjusting the drive signal for generating a droplet discharge state coalescence between.

  Therefore, the ink droplets can be ejected from the nozzles arranged in a row in the main scanning direction in an ejection state that reduces the occurrence of streaks in the sub-scanning direction (the conveyance direction of the recording medium P). Image quality can be improved.

  Further, in the inkjet image forming apparatus 1 of the present embodiment, the recording head 31 has a plurality of nozzle rows formed in the transport direction, and the drive signal control unit 33 sends the drive signal from the same nozzle. A drive signal for generating an ink droplet ejection state in which the ejected ink droplets coalesce with ink droplets ejected from other nozzles in the same nozzle row as the nozzles before coalescing on the recording medium P To adjust.

  Therefore, even when a plurality of nozzle rows are formed, ink droplets are ejected from nozzles arranged in a row in the main scanning direction in a discharge state that reduces the occurrence of streaks in the sub-scanning direction. Image quality can be improved.

  Furthermore, in the inkjet image forming apparatus 1 of the present embodiment, the recording head 31 has the nozzles of the plurality of nozzle rows arranged in a staggered manner, and the drive signal control unit 33 outputs at least the drive signal. After the ink droplets ejected from the nozzles in the nozzle row upstream in the transport direction merge with the ink droplets ejected from other nozzles in the same nozzle row, the ink droplets are arranged in a row downstream in the transport direction. The ink droplets from the nozzles provided are adjusted to drive signals that generate an ink droplet ejection state in which the ink droplets land on the recording medium P.

  Accordingly, when the nozzles are arranged in a staggered manner in the main scanning direction, the ink droplets are ejected from the nozzles arranged in a row by effectively using the arrangement of the nozzles. This can be performed in a discharge state in which the generation of streaks is further reduced, and the image quality can be improved.

  Further, in the inkjet image forming apparatus 1 of the present embodiment, the drive signal control unit 33 adjusts the drive signal to a drive signal for generating the ink droplet discharge state by performing halftone processing on the image data. .

  Therefore, by effectively utilizing the image processing function normally installed in the inkjet image forming apparatus 1, ink droplets are ejected from the nozzles arranged in a line in the main scanning direction, and streaks are generated in the sub scanning direction. Can be carried out in a discharge state that reduces the cost at a low cost. As a result, the image quality can be improved at a low cost.

  Further, the ink jet image forming apparatus 1 of the present embodiment further includes a surface modifying portion (modifying means) 4 that modifies the recording medium P so that the ink droplets are easily spread.

  Accordingly, the ink droplets can be more easily spread on the recording medium P, streaks can be further reduced, and the image quality can be improved.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to that described in the above embodiments, and various modifications can be made without departing from the scope of the invention. It goes without saying that it is possible.

DESCRIPTION OF SYMBOLS 1 Inkjet image forming apparatus 2 Linear motion stage 3 Conveyance unit 4 Surface modification part 5 Head unit 6 Irradiation unit N1-Nn, N21-N2n, N31-N3n, N41-N4n Nozzle 11 Controller unit 12 Detection group 21 CPU
22 Memory 23 I / F
24 unit control circuit 31 recording head 32 transport unit 33 drive signal control unit

JP 2008-213427 A

Claims (7)

One or more nozzle rows in which a plurality of nozzles are arranged in the main scanning direction are arranged, each of the nozzles is driven by a drive signal, and a recording head that discharges droplets to a recording medium;
Conveying means for conveying the recording medium in a conveying direction orthogonal to the main scanning direction;
A drive signal for each nozzle of the recording head is generated based on the image data, and droplets ejected from the nozzle driven by the drive signal are transported by the transport means. A droplet discharge state in which droplets discharged from the same nozzle on the recording medium are combined with droplets discharged from other nozzles in the same nozzle row as the nozzle before being combined in the transport direction. Drive signal control means for adjusting the drive signal to generate
An image forming apparatus comprising: The recording head is
A plurality of the nozzle rows are formed in the transport direction,
The drive signal control means includes
A liquid that merges the drive signal with droplets ejected from other nozzles in the same nozzle row as the nozzles before the droplets ejected from the same nozzles coalesce on the recording medium. The image forming apparatus according to claim 1, wherein the adjustment is made to a drive signal for generating a droplet discharge state. The recording head is
The nozzles of the plurality of nozzle rows are arranged in a staggered manner,
The drive signal control means includes
The drive signal is at least downstream in the transport direction after the droplets ejected from the nozzles in the nozzle row upstream in the transport direction are merged with the droplets ejected from other nozzles in the same nozzle row. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus adjusts the driving signal to generate a droplet discharge state in which droplets from the nozzles on the side nozzle row land on the recording medium. The drive signal control means includes
The image forming apparatus according to claim 1, wherein the drive signal is adjusted to a drive signal for generating the droplet discharge state by performing halftone processing on the image data. . The image forming apparatus includes:
Modification means for modifying the recording medium so that the droplets are easily spread,
The image forming apparatus according to claim 1, further comprising: An ejection processing step in which each nozzle is driven by a drive signal to eject droplets onto a recording medium from a recording head in which one or more nozzle rows in which a plurality of nozzles are arranged in the main scanning direction are disposed;
A transport processing step of transporting the recording medium in a transport direction orthogonal to the main scanning direction;
A drive signal for each nozzle of the recording head is generated based on the image data, and droplets ejected from the nozzle driven by the drive signal are transported in the transport processing step. Droplet ejection that merges with droplets ejected from other nozzles in the same nozzle row as the nozzles before coalescing in the transport direction with droplets ejected from the same nozzles on the recording medium A drive signal control processing step for adjusting the drive signal to generate a state;
An image forming method comprising: On the computer,
From a recording head in which one or more nozzle rows in which a plurality of nozzles are arranged in the main scanning direction are arranged, each of the nozzles is driven by a driving signal having a predetermined driving waveform to discharge a droplet onto a recording medium. Discharge processing;
A transport process for transporting the recording medium in a transport direction orthogonal to the main scanning direction;
A drive signal for each nozzle of the recording head is generated based on the image data, and droplets ejected from the nozzle driven by the drive signal are transported by the transport process. A droplet discharge state in which droplets discharged from the same nozzle on the recording medium are combined with droplets discharged from other nozzles in the same nozzle row as the nozzle before being combined in the transport direction. A drive signal control process for adjusting the drive signal to generate
A program characterized by having executed.