JP2013132846A - Method of controlling liquid droplet ejecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of controlling a liquid droplet ejecting device adapted to plot an image of which the density variation or the like is suppressed.SOLUTION: The method of controlling a liquid ejecting device which is provided with an ejection head having nozzles and pressure generating means corresponding to the nozzles includes a first heating step in which the pressure generating means are driven until the number of times of driving of the pressure generating means reaches a predetermined number of times of driving, and an image plotting step in which liquid droplets as functional liquids are ejected from the nozzle after the pressure generating means are driven until the number of times of driving of the pressure generating means reaches the predetermined number of times of driving. The image plotting step has a second heating step in which a pressure generating means of which the number of times of driving is smaller than the predetermined number of times of driving is driven at predetermined time intervals until the number of times of driving of the pressure generating means reaches the predetermined number of times of driving.

Description

  The present invention relates to a method for controlling a droplet discharge device.

  Conventionally, as a recording method for making the temperature of the recording head uniform and reducing the variation in the amount of ink discharged from the recording head, for example, for a nozzle that has never been discharged once a predetermined recording is completed A method of increasing the temperature of the nozzle by giving a drive signal that does not eject ink is known (for example, see Patent Document 1).

Japanese Patent Laying-Open No. 2005-41136

  However, in the above recording method, the ink discharge amount changes depending on the temperature of the print head after the discharge at the print head discharge start and after the continuous discharge. There is a problem that density unevenness occurs in the image.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A method for controlling a droplet discharge device according to this application example is a method for controlling a droplet discharge device including a discharge head having a nozzle and a pressure generating unit corresponding to the nozzle, and the pressure generation A first heating step for driving the means until the predetermined number of driving times is reached, and a drawing step for discharging the functional liquid as droplets from the nozzle after driving the pressure generating means until the predetermined number of driving times, The drawing step includes a second heating step of driving the pressure generating unit until the predetermined number of driving times is reached with respect to the pressure generating unit that is less than the predetermined number of driving times at a predetermined time interval.

  According to this configuration, in the stage before drawing, the pressure generating means is driven until the predetermined number of driving times is reached. As a result, the temperature of the ejection head rises and the temperature of the entire ejection head is made uniform. Then, drawing is started. In addition, after the drawing starts, the pressure generating means that is less than the predetermined number of times of driving is driven at a predetermined time interval until the predetermined number of times of driving is reached. As a result, the temperature of the ejection head rises and the temperature of the entire ejection head is made uniform. That is, the temperature is restored to the same temperature as the temperature of the ejection head in the stage before drawing. Therefore, the temperature of the ejection head is controlled to be the same before and after drawing. As a result, the viscosity of the functional liquid in the discharge head is made uniform, and variations in the discharge amount discharged from the nozzles from the start of drawing to the end of drawing are suppressed. Therefore, an image with reduced density unevenness can be formed.

  Application Example 2 In the second heating step of the method for controlling a droplet discharge device according to the above application example, the predetermined time is set as a scanning time unit for scanning by the discharge head.

  According to this configuration, since the temperature of the ejection head is managed in units of scanning time of the ejection head, the temperature of the ejection head can be more easily managed.

  Application Example 3 In the first heating step or the second heating step of the method for controlling a droplet discharge device according to the application example, the pressure is applied in a non-drawing region other than a drawing region in which the functional liquid is discharged and drawn. The generating means is driven.

  According to this configuration, for example, erroneous ejection to a substrate such as a print medium on which an image is formed by drawing can be prevented.

The schematic diagram which shows the structure of a droplet discharge apparatus. Sectional drawing which shows the structure of an ejection head. Explanatory drawing explaining a drive waveform. The flowchart figure which shows the control method of a droplet discharge apparatus. Explanatory drawing explaining the temperature change of an ejection head. FIG. 6 is an operation diagram showing the operation of the droplet discharge device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each configuration is shown different from the actual scale in order to make each configuration recognizable.

(Configuration of droplet discharge device)
First, the configuration of the droplet discharge device will be described. FIG. 1 is a schematic diagram illustrating a configuration of a droplet discharge device. The droplet discharge device is a device that forms (draws) an image by applying a functional liquid onto a substrate. As shown in FIG. 1, the droplet discharge device 1 according to the present embodiment places a head unit 20, an X scanning axis 50 that serves as a guide axis for scanning the head unit 20 in the X axis direction, and a substrate 10. A stage 40 and a Y scanning axis (not shown) serving as a guide axis for scanning the stage 40 in the Y axis direction are provided. The head unit 20 includes a moving unit that moves on the X scanning axis 50, and the stage 40 includes a moving unit that moves on the Y scanning axis. The head unit 20 also includes a carriage 21 connected to the X scanning shaft 50 and an ejection head 22 mounted on the carriage 21. And the control part (not shown) which controls the said member etc. is provided. In addition, the base material 10 of this embodiment is not specifically limited, For example, other than a plastic film, woven fabrics (fabrics), such as cotton cloth, linen, and silk cloth, paper, etc. can be applied. For example, when an ultraviolet curable ink is used as the functional liquid for forming an image, an ultraviolet irradiation unit that irradiates ultraviolet rays can be disposed.

  Next, the configuration of the ejection head will be described. FIG. 2 is a cross-sectional view showing the configuration of the ejection head. As shown in FIG. 2, the ejection head 22 includes a nozzle plate 30, and a nozzle 31 is formed on the nozzle plate 30. A cavity 32 communicating with the nozzle 31 is formed at a position above the nozzle plate 30 and facing the nozzle 31. The functional liquid 33 stored in a storage tank (not shown) is supplied to the cavity 32 of the ejection head 22.

  Above the cavity 32, a vibration plate 34 that vibrates in the vertical direction (Z direction: longitudinal vibration) and expands and contracts the volume in the cavity 32, and a pressure generating means that expands and contracts in the vertical direction to vibrate the vibration plate 34. The piezoelectric element 35 is disposed. The piezoelectric element 35 expands and contracts in the vertical direction to vibrate the diaphragm 34, and the diaphragm 34 pressurizes the cavity 32 by enlarging and reducing the volume in the cavity 32. As a result, the pressure in the cavity 32 varies, and the functional liquid 33 supplied into the cavity 32 is ejected as droplets 36 through the nozzle 31.

  The droplet discharge device 1 scans the head unit 20 in the X-axis direction following the X scanning axis 50 based on a drive signal from the control unit, and drives each piezoelectric element 35 of the discharge head 22 to drop droplets. By discharging 36, an image or the like can be formed (drawn) on the substrate 10. In the present embodiment, an area where the base material 10 is arranged for forming (drawing) an image is defined as a drawing area DA, and an area other than the drawing area DA is defined as a non-drawing area NDA (FIG. 1). reference).

  Next, a driving waveform for controlling the driving of the piezoelectric element 35 of the ejection head 22 will be described. 3A and 3B are explanatory diagrams for explaining the drive waveform. FIG. 3A shows the ejection drive waveform, and FIG. 3B shows the non-ejection drive waveform.

  First, the ejection drive waveform PA will be described. The ejection driving waveform PA is a driving waveform for driving the piezoelectric element 35 in order to eject the functional liquid 33 as the droplet 36 from the nozzle 31 of the ejection head 22. As shown in FIG. 3A, the ejection drive waveform PA has a substantially trapezoidal waveform, and the ejection voltage Vh1, which is the peak value of the drive voltage during ejection, is set to a predetermined voltage for a predetermined time. Applied. By driving the piezoelectric element 35 by applying the ejection drive waveform PA, the wiring board, the circuit board, and the like generate heat in addition to the piezoelectric element 35 itself, and the temperature of the ejection head 22 rises. And it is thought that the temperature of the functional liquid 33 in the ejection head 22 rises due to the heat generation. Here, one of the ejection drive waveforms PA having a substantially trapezoidal waveform shape corresponds to the number of times the piezoelectric element 35 is driven.

  Next, the non-ejection drive waveform PB will be described. The non-ejection drive waveform PB is a drive waveform for driving the piezoelectric element 35 to such an extent that it is not ejected as a droplet 36 from the nozzle 31 of the ejection head 22. As shown in FIG. 3B, the non-ejection voltage Vh2, which is a peak value of the driving voltage at the time of non-ejection, has a substantially trapezoidal waveform, and is within a range in which the liquid droplets 36 are not ejected. It is preferable to set 35 to vibrate greatly. In the present embodiment, for example, the non-ejection voltage Vh2 is a voltage that is about one third of the ejection voltage Vh1. Driving the piezoelectric element 35 by applying the non-ejection drive waveform PB generates heat in the wiring board, circuit board, and the like in addition to the piezoelectric element 35 itself, and the temperature of the ejection head 22 rises. And it is thought that the temperature of the functional liquid 33 in the ejection head 22 rises due to the heat generation.

(Droplet ejection device control method)
Next, a method for controlling the droplet discharge device will be described. In the present embodiment, a control method when the droplet discharge device 1 is used will be described. FIG. 4 is a flowchart showing a method for controlling the droplet discharge device. FIG. 5 is an explanatory diagram for explaining the temperature change of the ejection head, and FIG. 6 is an operation diagram showing the operation of the droplet ejection apparatus. The method for controlling a droplet discharge device according to this embodiment is a method for controlling a droplet discharge device including a discharge head having a nozzle and a pressure generation unit corresponding to the nozzle, and the pressure generation unit reaches a predetermined number of times of driving. And a drawing step for discharging the functional liquid as droplets from the nozzle after driving the pressure generating means up to a predetermined number of times. In the drawing step, the predetermined driving is performed at predetermined time intervals. A second heating step of driving the pressure generating means until the predetermined number of driving times is reached with respect to the pressure generating means less than the number of times. This will be specifically described below.

  As shown in FIG. 4, in step S11 (first heating drive: first heating step), the piezoelectric element 35 as the pressure generating means is driven until a predetermined number of times of driving is reached. In this case, all the piezoelectric elements 35 of the ejection head 22 are driven. In the present embodiment, the number of times of driving the piezoelectric element 35 when the recording duty is 100% is defined as the predetermined number of times of driving. Here, the number of times of driving at a recording duty of 100% is the number of times of driving corresponding to the maximum number of actual recording dots (number of ejections) in the resolution per unit area. In the present embodiment, as shown in FIG. 3B, a non-ejection drive waveform PB is applied to the piezoelectric element 35 serving as a pressure generating unit such that the droplets 36 are not ejected from the nozzle 31. Thereby, the piezoelectric element 35 is driven.

  Further, in the first heating step of the present embodiment, the pressure generating means is driven in the non-drawing area NDA other than the drawing area DA where the functional liquid 33 is discharged to form an image. Specifically, as shown in FIG. 6A, the head unit 20 is moved to the non-image area NDA. Then, the piezoelectric element 35 is driven in the non-image area NDA. Thereby, it is possible to prevent an erroneous discharge or the like to the drawing area DA.

  Next, in step S12, it is determined whether or not a predetermined number of driving times has been reached. If NO (when the predetermined number of driving times has not been reached), the process proceeds to step S11. If YES (when the predetermined number of driving times has been reached), the process proceeds to step S13. Here, the temperature change of the ejection head 22 will be described. In FIG. 5, the horizontal axis indicates the elapsed time (t), and the vertical axis indicates the temperature (T) of the ejection head 22. As shown in FIG. 5, when the piezoelectric element 35 is driven from time t0, the temperature of the ejection head 22 gradually increases. The temperature of the ejection head 22 rises to T1 at time t1 corresponding to the time for reaching the predetermined number of times of driving the piezoelectric element 35.

  Next, in step S13 (drawing drive: drawing step), after the piezoelectric element 35 is driven a predetermined number of times, the functional liquid 33 is ejected as droplets 36 from the nozzle 31 (drawing is started). Specifically, as shown in FIG. 6B, while the head unit 20 is scanned in the X-axis direction, the ejection driving waveform PA shown in FIG. The functional liquid 33 is ejected as droplets 36 in the drawing area DA to be drawn on the substrate 10 placed thereon, and an image is formed (drawn) on the substrate 10.

  Next, in step S14, it is determined whether or not a predetermined time has been reached. If NO (when the predetermined time has not been reached), the process proceeds to step S13. If YES (when the predetermined time has been reached), the process proceeds to step S15. In the present embodiment, the predetermined time is defined as a scanning processing time unit for scanning the ejection head 22. In this case, for example, the first scan (outward path) can be defined as a predetermined time. Further, as shown in FIG. 5, a predetermined time is defined from the time t1 when the drawing is started to the time t2. The discharge head temperature HT during this predetermined time is substantially uniform at the temperature T1. The predetermined time can be set as appropriate. For example, discharge evaluation can be performed in advance based on drawing data drawn on the substrate 10, and a predetermined time can be set according to the obtained change state of the discharge head temperature HT.

  Next, in step S15, it is determined whether drawing has been completed. In the case of NO (when drawing is not completed), the process proceeds to step S16, and in the case of YES (when drawing is completed), the driving of the droplet discharge device 1 is stopped.

  When the process proceeds to step S16 (second heating drive: second heating step), the pressure generating means is driven until the predetermined number of driving times is reached. In the present embodiment, the number of times of driving the piezoelectric element 35 when the recording duty is 100% is defined as the predetermined number of times of driving. Here, the number of times of driving at a recording duty of 100% is the number of times of driving corresponding to the maximum number of actual recording dots (number of ejections) in the resolution per unit area. In the present embodiment, as shown in FIG. 3B, a non-ejection drive waveform PB is applied to the piezoelectric element 35 to such an extent that the droplets 36 are not ejected from the nozzle 31. Thereby, the piezoelectric element 35 is driven.

  Further, in the second heating step S16 of the present embodiment, the pressure generating means is driven in the non-drawing area NDA other than the drawing area DA where the functional liquid 33 is discharged to form an image. In the present embodiment, the number of driving times of the pressure generating means when the recording duty is 100% is defined as the predetermined number of driving times. Then, as shown in FIG. 6A, the head unit 20 is moved to the non-image area NDA. Then, the piezoelectric element 35 is driven in the non-image area NDA. Thereby, it is possible to prevent an erroneous discharge or the like to the drawing area DA.

  Next, in step S17, it is determined whether or not a predetermined number of driving times has been reached. If NO (when the predetermined number of driving times has not been reached), the process proceeds to step S16. If YES (when the predetermined number of driving times has been reached), the process proceeds to step S13. Here, the temperature change of the ejection head 22 will be described. As shown in FIG. 5, when a predetermined time (t1 to t2) in the present embodiment has elapsed, the ejection head temperature HT decreases. This is because, for example, when there is an unused nozzle 31 in the drawing step S13, the piezoelectric element 35 corresponding to the nozzle 31 is not driven, so that the piezoelectric element 35 does not generate heat, and the temperature of the entire ejection head 22 Will go down. Therefore, in the second heating step S <b> 16, the non-ejection drive waveform PB (see FIG. 3B) is applied to the piezoelectric element 35 that has not reached the predetermined number of times to drive the target piezoelectric element 35. As a result, the piezoelectric element 35 generates heat, and the discharge head temperature HT rises. For example, at time t3, the discharge head temperature HT recovers to the temperature T1. Then, drawing is performed again (step S13). Thereafter, the above steps are repeated until drawing is completed.

  As described above, according to the embodiment, the following effects can be obtained.

  (1) In the stage before starting drawing, the piezoelectric element 35 was driven until the predetermined number of times of driving was reached. As a result, the temperature of the ejection head 22 rises and the temperature of the entire ejection head is made uniform. Then, drawing is started. In addition, after the drawing starts, the piezoelectric element 35 that is less than the predetermined number of times of driving is driven at predetermined time intervals until the piezoelectric element 35 reaches the predetermined number of times of driving. As a result, the temperature of the ejection head 22 rises and the temperature of the entire ejection head is made uniform. That is, it is maintained at a temperature equivalent to the temperature of the ejection head 22 in the stage before drawing. Accordingly, the temperature of the ejection head 22 is controlled to be the same before and after drawing. As a result, the viscosity of the functional liquid 33 in the discharge head is also constant, variation in the discharge amount discharged from the nozzle 31 from the start of drawing to the end of drawing is suppressed, and an image with reduced density unevenness can be formed. it can.

  (2) In the first heating step S <b> 11 and the second heating step S <b> 16, a non-ejection drive waveform PB is applied to the piezoelectric element 35 so that the droplets 36 are not ejected from the nozzle 31. Thereby, the temperature of the ejection head 22 can be raised and the waste of the functional liquid 33 can be eliminated. Furthermore, since the functional liquid 33 in the nozzle 31 is agitated, thickening of the functional liquid 33 can be prevented.

  (3) By setting the predetermined number of times of driving to a recording duty of 100%, for example, when one printed matter is formed by repeating drawing driving a plurality of times (long printing), from the nozzle 31 from the drawing start to the drawing end. Since variations in the discharged discharge amount are suppressed, an image with reduced density unevenness can be formed.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment. A modification will be described below.

  (Modification 1) In the above embodiment, the non-ejection drive waveform PB that does not eject the functional liquid 33 as the droplet 36 from the nozzle 31 in the first heating step S11 and the second heating step S16 (see FIG. 3B). ) Is applied to the piezoelectric element 35 and driven, but the present invention is not limited to this. For example, the ejection driving waveform PA (see FIG. 3A) may be applied to the piezoelectric element 35 in the first heating step S11 and the second heating step S16. In this case, a collection unit that collects the droplets 36 discharged from the discharge head 22 may be installed. In this way, the piezoelectric element 35 can be vibrated greatly as compared with the case where the non-ejection drive waveform PB is applied, so that the temperature of the ejection head 22 can be increased more efficiently.

  (Modification 2) In the above-described embodiment, a mode in which the liquid droplets 36 are ejected while the head unit 20 is scanned in the X-axis direction, that is, a serial type apparatus has been described. However, the present invention is not limited to this. For example, it may be a line head type device in which the ejection head 22 is fixed and the drawing is performed only by the movement of the substrate 10. Even if it does in this way, the same effect as the above can be acquired.

  DESCRIPTION OF SYMBOLS 1 ... Droplet discharge apparatus, 10 ... Base material, 20 ... Head unit, 21 ... Carriage, 22 ... Discharge head, 30 ... Nozzle plate, 31 ... Nozzle, 32 ... Cavity, 33 ... Functional liquid, 34 ... Vibrating plate, 35 ... Piezoelectric element, 36 ... Droplet, 40 ... Stage, DA ... Drawing area, NDA ... Non-drawing area, PA ... Discharge drive waveform, PB ... Non-discharge drive waveform.

Claims (3)

A method for controlling a droplet discharge apparatus comprising a discharge head having a nozzle and a pressure generating means corresponding to the nozzle,
A first heating step for driving the pressure generating means until a predetermined number of driving times is reached;
A drawing step of discharging the functional liquid as droplets from the nozzle after driving the pressure generating means up to the predetermined number of driving times, and
In the drawing step,
A liquid droplet ejection apparatus comprising: a second heating step of driving the pressure generating unit until the predetermined number of driving times is reached with respect to the pressure generating unit that is less than the predetermined number of driving times at a predetermined time interval. Control method. In the control method of the droplet discharge device according to claim 1,
In the second heating step,
A method for controlling a droplet discharge apparatus, wherein the predetermined time is set as a scanning time unit for scanning by the discharge head. In the control method of the droplet discharge device according to claim 1 or 2,
In the first heating step or the second heating step,
A control method for a droplet discharge device, wherein the pressure generating means is driven in a non-drawing region other than a drawing region for drawing by drawing the functional liquid.

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