Printing apparatus and

Abstract

To provide a printer in which the effect of oscillation is suppressed.SOLUTION: A printing apparatus comprising: an inkjet head including a plurality of nozzles and piezoelectric elements provided for the respective nozzles and configured to operate in accordance with waveforms; and a waveform output unit configured to output a nozzle control waveform to the piezoelectric elements every time a predetermined timing arrives, the nozzle control waveform including a discharge waveform for causing the nozzles to discharge droplets and a swing waveform for swinging ink in pressure chambers provided corresponding to the nozzles.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present disclosure relates to printing devices. [Background technology]

[0002] There is an inkjet printing device used in the coating process of display light-emitting layers for display devices such as organic EL (Electro Luminescence) etc. The inkjet printing device has an ink supply flow channel, multiple pressure chambers connected to the ink supply flow channel and having nozzles, and a piezoelectric element that applies pressure to the ink filled in the pressure chambers.

[0003] In such inkjet printing devices, the ink near the nozzles is constantly exposed to the atmosphere, so evaporation of the ink solvent cannot be ignored. In particular, if ink is not ejected for a long period of time, the ink solvent evaporates, increasing the ink's solids concentration, which in turn increases the ink's viscosity, making it difficult to eject the ink normally.

[0004] For this reason, conventionally, ink in a pressure chamber of a nozzle that does not eject ink is oscillated. FIG. 15 is a diagram showing the oscillation timing in the conventional technology. FIG. 15 shows, as an example, the print patterns of nozzles A to F and the waveforms of each nozzle corresponding to the print pattern. The nozzle waveform indicates the waveform applied to the piezoelectric element, and this waveform includes an ejection waveform, an oscillation waveform, and a flat waveform. The print pattern is shown in black and white, with black indicating a pattern that ejects ink and white indicating a pattern that does not eject ink.

[0005] The ejection waveform is a waveform used when ejecting ink, and as shown in the figure, it oscillates vertically, with a particularly large amplitude in the upward direction. The oscillation waveform is a waveform used when oscillation is performed, and it oscillates downward. The flat waveform is a waveform used when nothing is performed, and is therefore a flat waveform without oscillation.

[0006] As shown in Figure 15, conventionally, when printing starts, non-ejecting nozzles (nozzles corresponding to the white pattern) are controlled to constantly oscillate. This prevents an increase in the solid content concentration of the ink and an increase in the viscosity of the ink. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2019-48452 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-19104 Summary of the Invention [Problem to be solved by the invention]

[0008] Fig. 16 is a diagram showing an example of the configuration of a head of an inkjet printing device. Fig. 16 shows an ink circulation path, multiple heads, and pressure chambers and pressure elements provided for each head. The arrows shown in Fig. 16 indicate the direction of ink flow. In the configuration shown in Fig. 16, ink is supplied to each head from a single ink circulation path.

[0009] Figure 17 is a diagram showing the effects of oscillation. Figure 17 shows the ink flow when oscillation is performed on the second head from the left. As shown in Figure 17, oscillation deforms the piezoelectric element, causing a change in pressure, which in turn sucks ink from the pressure chambers of other heads and causes backflow in the ink circulation path, etc. Furthermore, these adverse effects vary depending on the distance from the head that is oscillated.

[0010] In this way, although the oscillation suppresses the increase in ink viscosity, it has a large effect on other nozzles, so if the nozzle is controlled to always oscillate when no ink is being ejected, as shown in Figure 15, there is a problem in that it has a large effect on other nozzles.

[0011] Non-limiting embodiments of the present disclosure contribute to providing a printing device that suppresses the effects of shaking. [Means for solving the problem]

[0012] A printing device according to one embodiment of the present disclosure includes an inkjet head having a plurality of nozzles, a piezoelectric element provided for each of the nozzles and operating in accordance with a waveform, and a waveform output unit that outputs to the piezoelectric elements each time a predetermined timing arrives a nozzle control waveform including an ejection waveform that causes the nozzles to eject droplets and an oscillation waveform that causes ink in a pressure chamber provided corresponding to the nozzle, and the waveform output unit does not output the oscillation waveform to the piezoelectric elements corresponding to the nozzles that do not eject droplets each time the predetermined timing arrives, but outputs a thinned-out waveform. [Effects of the Invention]

[0013] A non-limiting embodiment of the present disclosure can provide a printing device that suppresses the effects of shaking.

[0014] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features. [Brief explanation of the drawings]

[0015] [Figure 1] A diagram showing a printing device [Figure 2] A diagram showing the cross-sectional structure of an inkjet head [Figure 3] A diagram showing the cross-sectional structure of an inkjet head [Figure 4] FIG. 1 is a diagram showing the electrical configuration of a printing device. [Figure 5] FIG. 1 is a diagram for explaining a control example of the first embodiment. [Figure 6] FIG. 10 is a diagram for explaining a control example of the second embodiment. [Figure 7A]FIG. 10 is a diagram for explaining a control example of the third embodiment. [Figure 7B] A diagram showing an example of code written in a hardware description language [Figure 8] Flowchart showing the flow of swing setting processing [Figure 9] Flowchart showing the process for one nozzle row [Figure 10] Flowchart showing the flow of the farthest ejection position search process [Figure 11] Flowchart showing the flow of the minimum influence position search process [Figure 12] Flowchart showing the flow of the minimum influence position search process [Figure 13] Flowchart showing the flow of impact derivation processing [Figure 14] FIG. 10 is a diagram showing an example of swing setting by swing setting processing; [Figure 15] FIG. 1 is a diagram showing swing timing in the prior art. [Figure 16] FIG. 1 is a diagram showing an example of the configuration of a head of an inkjet printing device. [Figure 17] Diagram showing the effects of oscillation DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functions are designated by the same reference numerals, and redundant description will be omitted.

[0017] 1 is a diagram showing a printing apparatus 10 according to this embodiment. The printing apparatus 10 is used in a coating process for the light-emitting layer of an organic EL panel 31. The printing apparatus 10 is equipped with an X-axis moving stage 32 that moves in an X-axis direction 36 and a Y-axis moving stage 33 that moves in a Y-axis direction 37. The organic EL panel 31, which is subjected to the coating process by the printing apparatus 10, is placed on a suction stage above the Y-axis moving stage 33.

[0018] An inkjet head 34 and a microscope camera 35 that checks the ejection position are mounted on an X-axis moving stage 32 that moves in an X-axis direction 36. The inkjet head 34 and the microscope camera 35 can move in the X-axis direction 36. The inkjet head 34 has a plurality of nozzles that eject ink, which are arranged in the X-axis direction 36.

[0019] 2 and 3 are diagrams showing the cross-sectional structure of the inkjet head 34. The inkjet head 34 has a plurality of nozzles 100 that eject droplets, pressure chambers 110 that communicate with the nozzles, partition walls 111 that separate the pressure chambers 110 that correspond to different nozzles, diaphragms 112 that form part of the pressure chambers 110, piezoelectric elements 130 that vibrate the diaphragms 112, piezoelectric members 140 that support the partition walls 111, and a common electrode (not shown) that applies a voltage to the piezoelectric elements 130.

[0020] The piezoelectric elements 130 and the piezoelectric members 140 supporting the partition walls 111 are separated from one piezoelectric member by dicing. The inkjet head 34 has 100 to 300 nozzles 100 with a diameter of 10 μm to 50 μm, arranged at intervals of 100 μm to 500 μm.

[0021] In the inkjet head 34 configured as described above, when a voltage is applied between the piezoelectric element 130 and a common electrode (not shown) on the back side of the piezoelectric element 130, the piezoelectric element 130 deforms from the state shown in Fig. 2 to the state shown in Fig. 3. When the piezoelectric element 130 on the far right side in Fig. 2 deforms, the volume of the pressure chamber 110 decreases, and pressure can be applied to the liquid. This pressure causes the ink present in the pressure chamber 110 to be ejected to the outside as droplets 150.

[0022] In the inkjet head 34 of the type that circulates ink, the inkjet head 34 has a liquid inlet and outlet (not shown), and ejects ink while circulating the ink.

[0023] 4 is a diagram showing the electrical configuration of the printing device 10. The printing device 10 is made up of a waveform output unit 90, an inkjet head 34, and an encoder 70. The waveform output unit 90 is made up of a head drive circuit 40, a controller 50, and a personal computer 60.

[0024] The personal computer 60 functions as an input device for image data that indicates, in time series, whether or not to cause the nozzles 100 to eject droplets. The personal computer 60 outputs the image data to the controller 50. The personal computer 60 also has an oscillation setting unit 61. The oscillation setting unit 61 is realized by software, and can set data that indicates that the ink in the pressure chambers 110 is to be oscillated in relation to the image data. In this embodiment, there are two types of oscillation: one in which the oscillation is based on data set by the personal computer 60, and one in which the oscillation is caused by hardware in the head drive circuit 40.

[0025] The encoder 70 is configured by, for example, a rotary encoder, and outputs an encoder signal to the controller 50 at a timing corresponding to the printing position of the inkjet head 34.

[0026] The controller 50 includes a calculation device and the like, and controls the entire printing device 10. The controller 50 also includes an image memory 51 and a head data converter 52. The image memory 51 stores image data input from the personal computer 60. The head data converter 52 references the image data stored in the image memory 51, and outputs the image data to the head drive circuit 40 each time an encoder signal input timing arrives.

[0027] The head drive circuit 40 is capable of outputting nozzle control waveforms to each piezoelectric element 130. The nozzle control waveforms include an ejection waveform that causes the nozzle to eject droplets, an oscillation waveform that causes the ink in the pressure chamber 110 provided corresponding to the nozzle 100 to oscillate, and a flat waveform that causes the nozzle 100 to perform neither ejection nor oscillation. These ejection waveforms, oscillation waveforms, and flat waveforms are output each time the above-mentioned input timing arrives.

[0028] Based on the above configuration, four embodiments will be described below. These embodiments have in common that, each time the input timing arrives, an oscillation waveform is not output to the piezoelectric elements 130 corresponding to the nozzles 100 that do not eject droplets, but is output in a thinned manner. That is, in conventional technology, control is performed so that an oscillation waveform is always output to the piezoelectric elements 130 corresponding to the nozzles that do not eject droplets. In contrast, in this embodiment, control is performed so that an oscillation waveform is never output to the piezoelectric elements 130 corresponding to the nozzles that do not eject droplets. As a result, the number of piezoelectric elements 130 that are caused to oscillate is reduced, and the effects of oscillation can be suppressed compared to conventional technology.

[0029] First Embodiment The first embodiment is a form showing control in which the head drive circuit 40 outputs an oscillation waveform to the piezoelectric element 130 corresponding to the nozzle 100 that does not eject droplets once every several times that the input timing arrives.

[0030] First, the above-mentioned "multiple times" will be explained. When this multiple times is α, the condition that α satisfies is determined by the following formula 1. α<Print frequency / Minimum frequency…(Formula 1) Here, the minimum frequency refers to the number of oscillations or ejections per second required to enable normal ink ejection. This value depends on the properties of the ink and is therefore determined for each ink. The printing frequency refers to the number of times per second that a nozzle 100 can eject droplets (the number of times that input timing arrives). Using α that satisfies the above formula, the head drive circuit 40 simply outputs an oscillation waveform to the piezoelectric element 130 corresponding to a nozzle 100 that is not ejecting droplets, once every α times that input timing arrives (or two or more times less than α).

[0031] A specific example where α=4 will be explained using Figure 5. Figure 5 shows, as an example, the print patterns of nozzles A to F and the waveforms of each nozzle corresponding to the print patterns. The nozzle waveform indicates the waveform applied to the piezoelectric element, and includes an ejection waveform, an oscillating waveform, and a flat waveform. The print patterns are shown in black and white, with black indicating a pattern in which ink is ejected and white indicating a pattern in which ink is not ejected. The "movement axis" in the figure indicates the Y axis. In other words, the print pattern indicates an image pattern printed while moving in the Y axis direction in Figure 1. Then, each time the input timing arrives, the image patterns are printed one after another according to the image patterns shown in the print pattern.

[0032] Furthermore, Figure 5 shows the above-mentioned ejection waveform, oscillation waveform, and flat waveform corresponding to the print pattern. The ejection waveform is a waveform that oscillates vertically as shown in the figure, with a particularly large amplitude in the upward direction. The oscillation waveform is a waveform that oscillates when oscillation is performed, and is a waveform that oscillates downward. The flat waveform is a waveform that does not perform any oscillation, so it is a flat waveform without oscillation.

[0033] Based on the above, the control example shown in Fig. 5 will be described. The control example shown in Fig. 5 is a control example in which an oscillation waveform is output to the piezoelectric element 130 corresponding to the nozzle 100 that does not eject droplets once every four times the input timing arrives. This control can be controlled by hardware realized using a hardware description language. In other words, the control shown in the first embodiment is control that does not require software processing on the personal computer 60.

[0034] For example, the head drive circuit 40 is provided with a counter k that is incremented each time an input timing arrives after printing starts. In the case of the control shown in Fig. 5, when k = 3 (mod 4) (the third and seventh times in the figure), an oscillation waveform is output to the piezoelectric element 130 corresponding to the nozzle 100 that does not eject droplets. Note that in Fig. 5, the third and seventh times are patterns in which no nozzle ejects droplets, but if, for example, nozzle A ejects droplets and the other nozzles do not eject droplets on the third time, then nozzle A will eject droplets and the nozzles other than nozzle A will be oscillated.

[0035] By controlling in this way, the number of piezoelectric elements 130 that are oscillated is reduced, so the effects of oscillation can be suppressed compared to conventional technology. In addition, since software processing is not required and implementation can be performed using relatively simple logic, the amount of circuitry required can be reduced.

[0036] Second Embodiment In the second embodiment, the control shown in the first embodiment is performed in principle, but as an exception, if the number of times that a predetermined timing has arrived since droplets were ejected or oscillated in the past is within a predetermined number of times, an oscillation waveform is not output to the piezoelectric element 130 corresponding to the nozzle 100 that is not ejecting droplets. This is because, for example, if oscillation is performed once every β (<α) times, oscillation does not need to be performed if γ (≦α-β) times have not yet passed since droplets were ejected or oscillated.

[0037] A specific explanation will be given using Figure 6. This figure is interpreted in the same way as Figure 5, so its explanation will be omitted. The control example shown in Figure 6 shows an example where α = 7 and β = 5, and is a control example in which, in principle, an oscillation waveform is output to the piezoelectric element 130 corresponding to the nozzle 100 that does not eject droplets once in five input timings arrive. Exceptionally, this is a control example in which an oscillation waveform is not output to the piezoelectric element 130 corresponding to the nozzle 100 that does not eject droplets if two times have not elapsed since the nozzle 100 ejected or oscillated droplets.

[0038] 6, when k=1 (mod 5) (first and sixth times in the figure), an oscillation waveform is output to the piezoelectric elements 130 corresponding to the nozzles 100 that do not eject droplets, in principle. However, nozzles A, C, E, and F ejected droplets on the fifth time, and two times have not yet passed since that ejection, so as an exception, an oscillation waveform is not output to the piezoelectric elements 130 corresponding to nozzles A, C, E, and F.

[0039] The control shown in FIG. 6 requires a determination as to whether the number of times a predetermined timing has arrived since a droplet was ejected or oscillated is within a predetermined number of times. Therefore, the oscillation setting unit 61 of the personal computer 60 sets data indicating that the ink in the pressure chamber 110 is to be oscillated in the image data, and the head drive circuit 40 outputs a waveform in accordance with this image data.

[0040] In addition, in the sixth time in Figure 6, nozzles B and D are not oscillated because they are ejecting, but if they were not ejecting, the number of times the specified timing has arrived since the droplets were ejected or oscillated (second oscillation) would not be within the specified number of times (2 times), so an oscillation waveform would be output to the piezoelectric elements 130 corresponding to nozzles B and D.

[0041] By controlling in this way, the number of piezoelectric elements 130 that are oscillated is reduced, and therefore the influence of the oscillation can be suppressed compared to the conventional technology. Furthermore, although software processing is required, the number of piezoelectric elements 130 that are oscillated can be further reduced compared to the first embodiment, and therefore the influence of the oscillation can be further suppressed.

[0042] <Third embodiment> The third embodiment is a form showing control in which the head drive circuit 40 outputs an oscillation waveform to the piezoelectric elements 130 corresponding to the nozzles 100 that do not eject droplets, so as to suppress the number of nozzles 100 that perform oscillation simultaneously, once every several times when the input timing arrives. This is because the more nozzles 100 that oscillate simultaneously, the greater the effect of the oscillation.

[0043] A specific explanation will be given using FIG. 7A. Since this diagram is interpreted in the same way as FIG. 5, its explanation will be omitted. The control example shown in FIG. 7A shows an example where α=5. When nozzles A and F do not eject droplets at k=1 (mod 5) (first and sixth times in the diagram), an oscillating waveform is output to the piezoelectric element 130 corresponding to nozzles A and F. When nozzle B does not eject droplets at k=2 (mod 5) (second and seventh times in the diagram), an oscillating waveform is output to the piezoelectric element 130 corresponding to nozzle B. When nozzle C does not eject droplets at k=3 (mod 5) (third and eighth times in the diagram), an oscillating waveform is output to the piezoelectric element 130 corresponding to nozzle C. When nozzle D does not eject droplets at k=4 (mod 5) (fourth and ninth times in the diagram), an oscillating waveform is output to the piezoelectric element 130 corresponding to nozzle D. When nozzle E does not eject droplets at k=0 (mod 5) (5th and 10th times in the drawing), an oscillation waveform is output to the piezoelectric element 130 corresponding to nozzle E.

[0044] This control can be performed by hardware. That is, the control shown in the third embodiment does not require software processing on the personal computer 60.

[0045] For example, the head drive circuit 40 is provided with a counter k that is incremented each time an input timing arrives after printing starts. A remainder r is assigned to each nozzle 100, and when the counter value corresponding to a nozzle 100 becomes congruent with the remainder r assigned to the nozzle 100, an oscillation waveform is output to the piezoelectric element 130 corresponding to the nozzle 100.

[0046] An example of code written in a hardware description language will be described below to design hardware that performs control to suppress the number of nozzles 100 that simultaneously perform oscillation as shown in Fig. 7A. Fig. 7B is a diagram showing an example of the code. An overview of the example of the code shown in Fig. 7B will be described below.

[0047] In Figure 7B, "clk" indicates the clock of the synchronization circuit. "n_rst" indicates the reset signal (negative logic) of the synchronization circuit. "ejct" indicates the ejection signal. The frequency of this signal is '1' for only 1 clock. "gazo[n:1]" is image data that instructs nozzles 1 to n to eject at each time, where 1 indicates ejection and 0 indicates no ejection. "i" is the nozzle number (1 to 10). It is assumed that the nozzle oscillates once every 10 ejection timings, with a maximum oscillation interval of 10.

[0048] Next, we will explain the control outline using the code example in Figure 7B. Consider the nozzle whose nozzle number is j. First, let nn = j (mod 10). However, if it is divisible by 10, use 10 instead of 0. cnt[4:0] outputs a counter that increments with each ejection and returns to 1 after 10. The output of the jth nozzle is indicated by out[j]; a value of 2 indicates oscillation, a value of 1 indicates ejection, and a value of 0 indicates no action. When nn[j] is cnt, the output out[j] of the jth nozzle will oscillate, but if gazo[j] was originally ejection, it will remain ejection.

[0049] There are five registers indicating the sample storage elements for the counter and two for the output / nozzle, for a total of 25 registers used for 10 nozzles. Also, because the code in Figure 7B is written in a hardware description language, each begin-end block is executed simultaneously.

[0050] As described above, according to the third embodiment, the piezoelectric elements 130 that are oscillated simultaneously can be suppressed, and therefore the effects of oscillation can be suppressed compared to the prior art. In addition, software processing is not required, and implementation can be performed using relatively simple logic, so the amount of circuitry required can be reduced. Furthermore, since adjacent nozzles 100 do not oscillate simultaneously, the effects of oscillation can be suppressed.

[0051] <Fourth embodiment> The fourth embodiment is a form showing control in which, when oscillation is executed on one nozzle 100, a degree of influence indicating the degree of influence on nozzles 100 nearby the one nozzle 100 is derived, and the oscillation waveform is output based on the derived degree of influence. In the fourth embodiment, the oscillation setting unit 61 of the personal computer 60 sets data indicating that the ink in the pressure chamber 110 is to be oscillated in the image data.

[0052] Before describing the processing of the oscillation setting unit 61, the image data will first be described. The image data used in this embodiment is a two-dimensional array G[i][j]. The subscript i indicates the number of times, and the subscript j indicates the nozzle number. The number of times and the nozzle number are counted from 0. Therefore, for example, the first time shown in FIG. 6 is the 0th time in the array G. To make the explanation easier to understand, the "number of times" of the subscript i may be expressed as "position." Only the expression changes, and the value of the subscript i does not change. For example, if the number of times is 1, the position is also 1.

[0053] For example, in FIG. 6, if the nozzle number of nozzle A is 0, G[i][0] indicates the image data corresponding to nozzle A. Since i is the number of times, in the case of nozzle A in FIG. 6, G[0][0] is set to a value indicating that ejection will occur. In this embodiment, "1" is used as the value indicating that ejection will occur.

[0054] On the other hand, in Figure 6, if the nozzle number of nozzle D is 3, G[i][3] indicates the image data corresponding to nozzle D. In the case of nozzle D in Figure 6, G[2][3] is set to a value indicating no ejection. In this embodiment, "0" is used as the value indicating no ejection.

[0055] Furthermore, in this embodiment, the value "2" is used in array G to indicate oscillation. From the above, if array G is image data showing the waveform pattern shown in Fig. 6, for example, the array corresponding to nozzle D is G[0][3]=2, G[1][3]=1, G[2][3]=0, G[3][3]=0, ...

[0056] Based on the above, the processing according to the fourth embodiment executed by the oscillation setting unit 61 of the personal computer 60 will be described using a flowchart. FIG. 8 is a flowchart showing the flow of the oscillation setting processing. This oscillation setting processing includes various functions, which will be described in order below. Furthermore, before processing by the oscillation setting unit 61 is performed, "1" or "0" is set in array G, and after processing by the oscillation setting unit 61 is performed, "2" is set in array G corresponding to the nozzle number and number of times for which oscillation has been set.

[0057] Furthermore, in the oscillation setting process, i and j in the array G[i][j] are 0≦i≦D-1, 0≦j≦NN-1. Here, D is the maximum number of times, and NN is the total number of nozzles. In the following explanation, the range of array G refers to 0≦i≦D-1, 0≦j≦NN-1.

[0058] In FIG. 8, the oscillation setting unit 61 assigns the maximum allowable number to variable A and the number of nozzles up to the affected nozzles to variable B (step S101). Here, the "maximum allowable number" is a value equal to or less than the above-mentioned α. Furthermore, the "number of nozzles up to the affected nozzles" indicates the number of nozzles up to the affected nozzle when, for example, one nozzle oscillates. For example, if the oscillation of the fifth nozzle affects the eighth nozzle, which is three nozzles away, the "number of nozzles up to the affected nozzles" will be 3.

[0059] The oscillation setting unit 61 assigns 0 to a loop counter n for counting nozzles (step S102). The oscillation setting unit 61 executes a nozzle row process (step S103), which will be described later. This nozzle row process is executed by focusing on one nozzle 100.

[0060] The oscillation setting unit 61 determines whether the loop counter n is equal to NN-1 (step S104). As described above, since the array G is counted from 0, it is determined whether NN-1, which is obtained by subtracting 1 from NN, is equal to the loop counter n. If the loop counter n is equal to NN-1 (step S104: YES), the oscillation setting unit 61 ends the processing. On the other hand, if the loop counter n is different from NN-1 (step S104: NO), the oscillation setting unit 61 increments n (step S105) and returns to step S103.

[0061] Next, the nozzle one-row processing (FIG. 8: step S103) will be described. FIG. 9 is a flowchart showing the flow of the nozzle one-row processing. In FIG. 9, the oscillation setting unit 61 assigns 0 to a variable C (step S201). This C is a variable used to determine the position at which the oscillation is set. The oscillation setting unit 61 assigns C to tc (step S202). This tc is a variable used to determine whether the farthest ejection position has been found in the farthest ejection position search process executed in the next step S203. The oscillation setting unit 61 executes the farthest ejection position search process (step S203), which will be described later. The farthest ejection position refers to the maximum number of ejections from a certain number of times for one nozzle, up to a predetermined number of times from that reference number. For example, if the third ejection for nozzle number 2 is taken as the reference number, and the ejections are the fourth, fifth, and seventh of the eighth ejection times (adding five times from that reference number), then the farthest ejection position is number 7. In this way, the position farthest from the reference position is the farthest ejection position. In this farthest ejection position search process, if the farthest ejection position is found, the farthest ejection position is substituted for C. In other words, tc and C are different.

[0062] The oscillation setting unit 61 determines whether tc and C are different through the farthest discharge position search process (step S204). If tc and C are different (step S204: YES), the oscillation setting unit 61 determines whether C+A (maximum allowable number) is equal to or greater than D (maximum number of times) (step S205). If C+A is equal to or greater than D (step S205: YES), the oscillation setting unit 61 ends the process. If C+A is less than D (step S205: NO), the oscillation setting unit 61 returns to the process of step S202. Note that the existence of the farthest discharge position means that discharge is performed from C a number of times less than α, and therefore oscillation is not required at least from C to the farthest discharge position.

[0063] In step S204, if tc and C are equal (step S204: NO), the oscillation setting unit 61 executes a minimum-influence position search process (step S206), which will be described later. Here, a position where the influence is minimized when oscillation occurs is searched for, and if found, the searched position is set to C. The oscillation setting unit 61 determines whether G[C][n] is 1 (discharge) (step S207). If G[C][n] is 1 (step S207: YES), the oscillation setting unit 61 proceeds to step S205. If G[C][n] is other than 1 (step S207: NO), the oscillation setting unit 61 assigns 2 (oscillation) to G[C][n] (step S208), and proceeds to step S205. In the oscillation setting process, oscillation is set only in step S208.

[0064] Next, the furthest discharge position search process (FIG. 9: step S203) will be described. FIG. 10 is a flowchart showing the flow of the furthest discharge position search process. In FIG. 10, the oscillation setting unit 61 determines whether C+A is equal to or greater than D (step S301). If C+A is equal to or greater than D (step S301: YES), the oscillation setting unit 61 assigns D-1 to variable k (step S302). This k is used as a loop counter. If C+A is less than D (step S301: NO), the oscillation setting unit 61 assigns C+A to k (step S303).

[0065] The oscillation setting unit 61 determines whether G[k][n] is 1 (discharge) (step S304). If G[k][n] is other than 1 (step S304: NO), the oscillation setting unit 61 decrements k (step S305) and determines whether k is equal to C (step S306). If k is different from C (step S306: NO), the oscillation setting unit 61 returns to step S304. If k is equal to C (step S306: YES), the oscillation setting unit 61 ends the process. In this case, the farthest discharge position has not been found.

[0066] In step S304, if G[C][n] is 1 (step S304: YES), the oscillation setting unit 61 assigns k to C (step S307) and ends the process. In this case, k is found as the farthest discharge position.

[0067] As indicated by the decrement in step S305, the farthest ejection position search process is a process of searching for ejection positions in order from a position farthest from C (for example, C+α) to C.

[0068] Next, the minimum influence position search process (FIG. 9: step S206) will be described. FIGS. 11 and 12 are flowcharts showing the flow of the minimum influence position search process. In FIG. 11, the oscillation setting unit 61 determines whether C+A is equal to or greater than D (step S401). If C+A is equal to or greater than D (step S401: YES), the oscillation setting unit 61 assigns D-1 to variable F (step S402). This F is used as a variable indicating the upper limit of the loop counter. If C+A is less than D (step S401: NO), the oscillation setting unit 61 assigns C+A to F (step S403).

[0069] The oscillation setting unit 61 assigns 1000000.0 to the variable J, assigns 0 to the variable h, and assigns C+1 to the variable s (step S404). Here, J is a variable for temporarily storing the influence, and in this process, the smallest influence is stored. h is a variable for temporarily storing the position where the influence is smallest. s is used as a loop counter. Note that 1000000.0 assigned to J is set as an initial value in consideration of the fact that J is updated with a small influence, and for example, the maximum expected influence may be used.

[0070] The fluctuation setting unit 61 executes an influence degree derivation process, which will be described later (step S405). The influence degree derived here is substituted for the variable L. Next, in step S501 of FIG. 12, the fluctuation setting unit 61 determines whether J is equal to or greater than L (step S501). If J is less than L (step S501: NO), the fluctuation setting unit 61 proceeds to step S504. If J is equal to or greater than L (step S501: YES), the fluctuation setting unit 61 substitutes the value of L for J (step S502), substitutes s for h (step S503), and increments s (step S504).

[0071] The oscillation setting unit 61 determines whether s is greater than F (step S505). If s is equal to or less than F (step S505: NO), the oscillation setting unit 61 returns to step S405. If s is greater than F (step S505: YES), the oscillation setting unit 61 assigns h to C (step S506) and ends the process. As a result, the position with the smallest influence is assigned to C. Furthermore, if there are multiple positions with the smallest influence, the position farthest from the position of C used in step S401 is assigned to C.

[0072] Next, the influence derivation process (FIG. 11: step S405) will be described. FIG. 13 is a flowchart showing the flow of the influence derivation process. In this flowchart, an array Q is used. This array Q is an array in which influences are stored. The subscript of array Q is the absolute value of the difference between the reference nozzle number and the affected nozzle number. Therefore, the larger the subscript, the greater the distance between the reference nozzle and the affected nozzle, in which case the influence will be smaller. Therefore, the larger the subscript, the smaller the value of array Q. The value of array Q may be determined based on the measurement results of measuring in advance the volume and ejection speed of droplets ejected from nearby nozzles.

[0073] In FIG. 13, the oscillation setting unit 61 assigns 0.0 to the variable L (step S601). The variable L is a variable to which the influence is assigned, as described above. The oscillation setting unit 61 assigns -B to the variable m (step S602). m is used as a loop counter. The oscillation setting unit 61 assigns n+m to the variable r (step S603). r is used as a variable indicating the nozzle number. In the nozzle row processing and farthest ejection position search processing described above, the nozzle number is fixed and the position (number of times) is changed, but in the influence derivation processing, the position is fixed and the nozzle number is changed. In other words, in the influence derivation processing, the nozzle number is changed to derive the influence on nozzles near one nozzle.

[0074] The oscillation setting unit 61 determines whether r<0, r≧NN, or m=0 (step S604). The conditions r<0, r≧NN are used to determine whether r is within the range of the array G. The condition m=0 is used to exclude the reference n-th nozzle, since when m=0, r=n occurs, which is the n-th nozzle itself.

[0075] When r < 0, r ≥ NN, or m = 0 (step S604: YES), the rocking setting unit 61 proceeds to step S607. When r ≥ 0, r < NN, and m ≠ 0 (step S604: NO), the rocking setting unit 61 determines whether G[s][r] = 1 (discharge) (step S605). If G[s][r] ≠ 1 (step S605: NO), the rocking setting unit 61 proceeds to step S607. If G[s][r] = 1 (step S605: YES), the rocking setting unit 61 substitutes the sum of L and Q[|m|] into L (step S606). Thus, when the discharging nozzle is in the vicinity, L is added using the array Q. Therefore, the greater the number of discharging nozzles in the vicinity, the greater the influence degree.

[0076] The rocking setting unit 61 increments m (step S607) and determines whether m > B (step S608). If m ≤ B (step S608: NO), the rocking setting unit 61 returns to step S604. If m > B (step S608: YES), the rocking setting unit 61 ends the process.

[0077] Thus, in the influence degree derivation process, among the nozzles in the vicinity of the reference nozzle number n (nozzle numbers (n - B to n + B excluding n)), if there is a discharging nozzle, the influence degree is added up to derive the influence degree when rocking at nozzle number n.

[0078] FIG. 14 is a diagram showing an example of rocking setting by the above-described rocking setting process. First, the viewing method of FIG. 14 will be described. "Time" in the upper row indicates the above-described number of times (positions). "PrintData" indicates image data, and "Nozzle_0" to "Nozzle_7" indicate eight nozzles.

[0079] Therefore, in the case of Figure 14, the range of array G[i][j] is 0≦i≦20-1, 0≦j≦8-1. Furthermore, "AddTicle" in the middle row indicates the image data after the oscillation setting process. A white circle indicates ejection, and a black circle indicates that oscillation has been set. Furthermore, the maximum allowable number A is 5, and the number B up to the affected nozzle is 3. "Damage" in the bottom row indicates the degree of impact when oscillation is performed. In the case of Figure 14, array Q is Q[1]=10, Q[2]=5, and Q[3]=2.

[0080] In light of the above, when attention is focused on Nozzle_0 to Nozzle_4, the number of times that Nozzle_0 to Nozzle_4 eject is smaller than the maximum allowable number of 5 in any of the cases, and therefore oscillation is not set.

[0081] On the other hand, Nozzle_5 to Nozzle_7 are set to oscillate because they are discharged a number of times greater than the maximum allowable number of 5. In this case, as explained in the minimum influence position search process, the oscillation is set to the position with the smallest influence. Furthermore, if there are multiple positions with the smallest influence, the oscillation is set to the position farthest from position C used in step S401. For example, in the case of Nozzle_5, 5 is the farthest position, but the oscillation is set to position 2 where the influence is smallest.

[0082] As described above, according to this embodiment, when a predetermined timing arrives, an oscillation waveform is not output to the piezoelectric element 130 corresponding to the nozzle 100 that does not eject droplets, but is output in a thinned manner. As a result, the number of piezoelectric elements 130 that are caused to oscillate is reduced, and the effects of oscillation can be suppressed compared to conventional technology.

[0083] <Summary of the embodiment> A printing device according to one embodiment of the present disclosure includes an inkjet head having a plurality of nozzles, and a piezoelectric element provided for each of the nozzles that operates in accordance with a waveform, and a waveform output unit that outputs to the piezoelectric elements each time a predetermined timing arrives a nozzle control waveform that includes an ejection waveform that causes the nozzles to eject droplets and an oscillation waveform that causes ink in a pressure chamber provided corresponding to the nozzle, and the waveform output unit does not output the oscillation waveform to the piezoelectric elements corresponding to the nozzles that do not eject droplets each time the predetermined timing arrives, but rather outputs a thinned version of the oscillation waveform.

[0084] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the disclosure.

[0085] Although specific examples of the present disclosure have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Industrial Applicability]

[0086] An embodiment of the present disclosure is suitable for a printing device that performs oscillation. [Explanation of symbols]

[0087] 10 Printing device 34 Inkjet head 40 Head drive circuit 50 Controllers 51 Image Memory 52 Head data converter 60 PCs 70 Encoder

Claims

1. an inkjet head including a plurality of nozzles and a piezoelectric element provided for each of the nozzles and operating in response to a waveform; a waveform output unit that outputs, to the piezoelectric element at each predetermined timing, a nozzle control waveform including an ejection waveform that causes the nozzle to eject droplets and an oscillation waveform that causes ink in a pressure chamber provided corresponding to the nozzle, The waveform output unit does not output the oscillation waveform to the piezoelectric element corresponding to the nozzle that does not eject the droplets each time the predetermined timing arrives, but outputs the oscillation waveform in a thinned-out manner.

2. The printing device according to claim 1 , wherein the waveform output unit outputs the oscillation waveform once every multiple times the predetermined timing occurs.

3. 3. The printing device according to claim 2, wherein the waveform output unit does not output the oscillation waveform if the nozzle that is not ejecting the droplet has ejected or oscillated the droplet in the past, and the number of times the specified timing has arrived since the nozzle ejected or oscillated the droplet is within a specified number of times.

4. The printing device according to claim 1 , wherein the waveform output unit outputs the oscillation waveform so as to suppress the number of nozzles that simultaneously perform oscillation once every multiple times that the predetermined timing occurs.

5. The printing device according to claim 1, wherein the waveform output unit derives a degree of influence indicating the degree of influence on the nozzles in the vicinity of a nozzle when oscillation is performed on the nozzle, and determines whether to output the oscillation waveform based on the derived degree of influence.

Images