JP2009274063A - Ink jetting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jetting method, by which ink can be applied in a desired pattern using a head having a plurality of nozzles. <P>SOLUTION: A pressure generating element for changing the pressure within a liquid chamber filled with the ink is arranged within a head (1). The liquid chamber is provided with nozzles (13, 14, and 15) for jetting the ink. The jetting quantity and the jetting speed of ink droplets that are jetted from the nozzles (13, 14, and 15) under the same conditions as those for an actual application pattern are obtained by a jetting state monitoring device (2). The thus obtained information is sent to a control device (6). The control device (6) changes a drive waveform of voltage to be applied to the pressure generating element so that at least the ink jetting quantity or the ink jetting speed is uniform at the nozzles (13, 14, and 15). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink discharge method, and more specifically, using a head including a liquid chamber filled with ink, a pressure generating element that changes the pressure in the liquid chamber, and a nozzle provided in the liquid chamber. The present invention relates to an ink ejection method for ejecting ink from nozzles.

  Conventionally, after a metal film is formed on the entire surface of a substrate by vacuum deposition or sputtering, the coating film is processed into a desired pattern by photolithography. However, the photolithography method has problems that the process is complicated and the metal material to be used is wasted.

  On the other hand, a metal ink is also applied on a substrate by an ink jet method (for example, see Patent Document 1). According to this method, a coating film having a desired pattern can be directly formed on the substrate. Therefore, compared to the above-described method, not only can the process be shortened, but also the waste of the metal ink to be used can be reduced.

  2. Description of the Related Art As an ink jet coating apparatus, an apparatus that controls ink ejection by a pressure generating element such as a piezo element (piezoelectric element) is known. In this apparatus, the head often has a plurality of nozzles and pressure generating elements. The pressure generating element causes ink to be ejected using mechanical distortion generated by applying a pulse voltage between the electrodes. Each nozzle is divided into a plurality of sections, and further divided into drive blocks within each section. The pressure generating element is time-division driven for each drive block.

  By the way, the nozzles provided in the head have individual differences due to dimensional variations during manufacturing. For this reason, the amount of ink ejected from each nozzle is not uniform and varies among nozzles. In addition, there is a variation in the ink ejection speed, and a difference occurs in the ink landing position on the substrate depending on the nozzle. If there is a variation in the amount of ink discharged, the dot diameter of the ink that has landed on the substrate varies, resulting in uneven density. In addition, if the ink landing position varies, the pattern accuracy of the coating film is lowered.

  However, manufacturing a nozzle in which the variation among the nozzles is suppressed to a level that does not cause a problem significantly reduces the yield. Even if the variation is small at the beginning of manufacture, the variation may increase for some reason while the operation is repeated.

  Therefore, it is necessary to adjust these so that the discharge amount and discharge speed of ink are uniform among the nozzles. In an inkjet coating apparatus using a pressure generating element, the discharge amount and the discharge speed are made uniform by adjusting the applied voltage. That is, when a voltage is applied to the pressure generating element, its shape changes at a high speed in proportion to the magnitude of the electric field. Therefore, by changing the magnitude and voltage waveform of the voltage applied to the pressure generating element, it is possible to change the ink discharge amount and the discharge speed so that they are uniform (see Patent Document 2).

JP 59-75205 A JP 2005-502447 A

  The above-described head having a plurality of nozzles has an advantage that ink can be applied to an object such as a substrate at high speed. In an ink jet coating apparatus having such a head, the nozzles are divided into a plurality of blocks, and a predetermined number of nozzles are time-division driven for each block. In general, ink is ejected from a plurality of nozzles in order from the end along the direction in which the nozzles are arranged.

  However, as the number of nozzles increases, the distance between adjacent nozzles becomes closer, causing interference (crosstalk) between the nozzles, thereby changing the ink ejection state. Such interference becomes conspicuous in a system in which ink is ejected sequentially along the nozzle arrangement direction in units of a plurality of nozzles. This is because interference between the plurality of nozzles also occurs in addition to the interference within the plurality of nozzles.

  By the way, the degree of interference between the nozzles varies depending on the coating pattern formed on the object. This is because when the application pattern is different, the ejection period of each nozzle and the phase difference between the nozzles of the drive waveform of the voltage applied to the pressure generating element change. However, conventionally, an adjustment application timing has been used when adjusting the voltage applied to the pressure generating element in order to make the discharge amount and discharge speed of ink at each nozzle uniform. For this reason, if it is applied at the actual application timing, there is a problem that a new interference action is added between the nozzles and a desired pattern cannot be formed.

  The present invention has been made in view of these points. That is, an object of the present invention is to provide an ink discharge method that can be applied in a desired pattern using a head having a plurality of nozzles.

  Other objects and advantages of the present invention will become apparent from the following description.

The present invention uses a head including a liquid chamber filled with ink, a pressure generating element that changes the pressure in the liquid chamber, and a nozzle provided in the liquid chamber, to discharge the ink from the nozzle. In the ink ejection method,
The head includes a plurality of the nozzles,
The ink is ejected under the same conditions as for the actual coating pattern, and the drive waveform of the voltage applied to the pressure generating element is set so that at least one of the ink ejection amount and ejection speed from each nozzle is uniform. It is characterized by having a process of changing every time.

  In the present invention, the step is a step of obtaining an average value of ejection amount and ejection speed for a plurality of ink droplets ejected from the same nozzle, and making the average value uniform among the nozzles. Is preferred.

  In the present invention, at least one of the ejection amount and the ejection speed may be achieved by irradiating the ink droplets ejected from the nozzle with illumination light that emits light in synchronization with the ejection timing of the ink droplets. And can be obtained based on the obtained image.

  In the present invention, each of the plurality of nozzles can be discharged with a time difference.

  According to the present invention, the voltage applied to the pressure generating element is such that ink is ejected under the same conditions as for the actual coating pattern and at least one of the ink ejection amount and ejection speed from each nozzle is uniform. Since the driving waveform is changed for each nozzle, even a head having a plurality of nozzles can be applied in a desired pattern.

(A) And (b) is a partial block diagram of the inkjet coating device in this Embodiment. In this Embodiment, it is a schematic diagram which shows the correspondence of a board | substrate and a head. (A)-(c) is an example of the pulse waveform applied to the pressure generating element in the conventional adjustment method. (A)-(c) is an example of the pulse waveform by this Embodiment.

  In the ink jet coating apparatus according to the present embodiment, the head includes a liquid chamber in which ink is filled, a nozzle that is provided in the liquid chamber and ejects ink, and a pressure generating element that changes the pressure in the liquid chamber. . Here, examples of the pressure generating element include a piezoelectric element (piezoelectric element). When a voltage is applied to the pressure generating element, the pressure in the liquid chamber changes and droplets are ejected from the nozzle. The number of heads may be one or two or more.

  In the present embodiment, the nozzles and the pressure generating elements are each provided in the head in a number of 2 or more. The pressure generating element ejects ink using mechanical distortion generated by applying a pulse voltage between electrodes. Each nozzle is divided into a plurality of sections, and further divided into drive blocks within each section. The pressure generating element is time-division driven for each drive block.

  In the present embodiment, it can be driven so that ink is ejected from a plurality of nozzles in order from the end along the direction in which the nozzles are arranged. As a result, the time required for coating can be shortened, and the drive circuit can be simplified.

  The ink jet coating apparatus has a control device that adjusts a driving waveform of a voltage applied to the pressure generating element. This control device can adjust the drive waveform in two directions, the voltage direction and the time direction. The control device may adjust the drive waveform only in one of the voltage direction and the time direction.

  The inkjet coating apparatus has a discharge state observation apparatus. This apparatus is means for observing the ejection state of ink droplets ejected from nozzles. In other words, the same conditions as the actual application, that is, the discharge period of each nozzle and the phase difference between the nozzles of the drive waveform of the voltage applied to the pressure generating element are the same as the conditions for the actual application pattern, It is a means for observing the discharge state.

  In the ejection state observation device, the ink droplets ejected from the nozzles are irradiated with illumination light that emits light in synchronization with the ejection timing of the ink droplets, the ink droplets are imaged with a camera, and the ejection amount is based on the obtained image And a discharge speed can be obtained. Here, a strobe can be used as the illumination light source, and a CCD camera can be used as the camera.

  FIGS. 1A and 1B are examples of a partial configuration diagram of the ink jet coating apparatus according to the present embodiment. FIG. 1A is a diagram viewed from a direction perpendicular to the ink dropping direction, and FIG. 1B is a diagram viewed from the nozzle direction. In FIG. 1B, part of the connection between the control device and each component is omitted. 1A and 1B, reference numeral 1 denotes a head. Although not shown in detail, a liquid chamber filled with ink, a pressure generating element for changing the pressure in the liquid chamber, and a liquid chamber are provided. Nozzle. The number of nozzles is two or more, and ink in the liquid chamber is ejected from these nozzles. (In the example of FIG. 1, three nozzles 13, 14, and 15 are provided.) In addition, reference numeral 2 denotes a discharge state observation device that receives light from the strobe 3 that emits light and light from the strobe 3. A CCD camera 4 that picks up ink droplets, and a discharge speed acquisition unit 5 that acquires the ink discharge speed.

  As described above, if there is a variation in the ejection amount of the ink ejected from the nozzles 13, 14, 15, the dot diameter of the ink that has landed on the object such as the substrate varies, resulting in uneven density. Further, if the ink ejection speed varies, the ink landing position varies. Therefore, before the actual application is performed, it is necessary to adjust the discharge amount and the discharge speed to be uniform.

  In the present embodiment, ink is ejected under the same conditions as for the actual application pattern, that is, under the same conditions as the actual application, and the ejection amount and ejection speed are adjusted. The adjustment is performed by the control device, and specifically by DPN (Drive Per Nozzle) correction. That is, the discharge amount and the discharge speed are obtained for each nozzle, compared with the target values, and the correction coefficient obtained in advance from each relationship between the discharge amount, the discharge speed, and the drive waveform is used so that these become the target values. Then, the drive waveform of each voltage is adjusted for each nozzle.

  The above adjustment is performed by changing the magnitude and time width of the pulse voltage for driving the pressure generating element. Here, when the number of nozzles is small, the discharge rate can be made uniform by making the discharge speed uniform. However, when the number of nozzles increases, it becomes impossible to make the discharge amount uniform even if the discharge speed is made uniform. Therefore, when the number of nozzles is large, first, the discharge amount is adjusted to be uniform, and then the discharge speed is adjusted to be uniform. In this way, by adjusting in two steps, it is possible to control the ink ejection amount and ejection speed with high accuracy.

  Specifically, the adjustment of the ink ejection amount is performed by changing the driving waveform of the voltage applied to the pressure generating element in the voltage direction. For example, it can be performed as follows.

  Ink is ejected under the same conditions as for the actual application pattern, and the ink droplets ejected from the nozzles 13, 14, and 15 are imaged by the ejection state observation device 2. At this time, the strobe 3 is caused to emit light in synchronization with the ejection of the ink droplets, and the flying ink droplets are imaged by the CCD camera 4. The discharge amount is compared based on the obtained image, and the drive waveform is changed for each nozzle 13, 14, and 15 in the control device 6 so that the discharge amount becomes uniform at the nozzles 13, 14, and 15, respectively. If the relationship between the size of the ink droplet and the discharge amount is obtained in advance, the desired discharge amount of ink can be uniformly discharged from the nozzles 13, 14, and 15.

  In addition to the above method using a strobe, the discharge amount can also be known by examining the dot diameter of the ink after the ink droplets discharged from the nozzles have landed on the target substrate or the like. Specifically, ink is ejected onto the substrate under the same conditions as for the actual application pattern. Then, the dot diameters of the ink ejected from the nozzles are compared, and the drive waveform is changed in the voltage direction by the control device so that they have a desired size uniformly. If the relationship between the dot diameter and the discharge amount is determined in advance, a desired discharge amount of ink can be uniformly discharged from each nozzle. However, since the dot diameter of the ink is affected by the surface condition of the substrate, the method obtained from the above-described captured image is preferable.

  Next, the discharge speed is made uniform for the ink droplets having a uniform discharge amount. Specifically, it is performed by changing the drive waveform of the voltage applied to the pressure generating element in the time direction. For example, it can be performed as follows.

  Ink is ejected under the same conditions as for the actual application pattern, and the ink droplets ejected from the nozzles 13, 14, and 15 are imaged twice at different timings by the ejection state observation device 2. Specifically, the strobe 3 synchronized with the driving pulse of the voltage applied to the pressure generating element blinks twice, and the flying ink droplet is imaged by the CCD camera 4. Subsequently, in the ejection speed acquisition unit 5, the position of the ink droplet is obtained from the obtained image, and the ink ejection speed is obtained from the position and the interval of the imaging timing. After this information is sent to the control device 6, the control device 6 compares the ejection speed of the ink ejected from the nozzles 13, 14, and 15. And a drive waveform is changed by the control apparatus 6 for every nozzle 13,14,15 so that these may become uniform.

  In addition to the above method using a strobe, the discharge speed can also be known by examining the position where the ink droplets discharged from the nozzles land on the substrate as the object. This is because if the discharge speed is high, it will land at a position far from the nozzle, while if the discharge speed is low, it will land at a position near the nozzle. In the present embodiment, the discharge speed may be compared by this method. However, since the landing position may be influenced by the surface state of the substrate, the method obtained from the captured image described above is preferable.

  FIG. 2 schematically shows a substrate and a head, where 11 is a head and 12 is a substrate. Moreover, in this figure, the arrow has shown the direction to which the head 11 moves. The substrate and the head may be moved relatively, and the substrate may be moved in the direction opposite to the arrow with the head fixed.

  FIG. 2 shows the positional relationship between the head and the pattern when the actual coating pattern is used. In FIG. 2, reference numeral 101 denotes a position where ink ejected from the nozzle 13 should land. In this example, three drops of ink land to form one pattern 102, and the same pattern is sequentially formed in the direction of the arrow as the head 11 moves. Similarly, reference numeral 103 denotes a position where ink ejected from the nozzle 14 should land, and three drops of ink land to form a pattern 104. Reference numeral 105 denotes a position where the ink ejected from the nozzle 15 should land, and three drops of ink land to form the pattern 106.

  3A and 3B show pulse waveforms applied to the pressure generating element in the conventional adjustment method. FIG. 3A shows the nozzle 13 shown in FIG. 1, FIG. 3B shows the nozzle 14 shown in FIG. Each corresponds to the nozzle 15 in FIG. In these drawings, the horizontal axis represents time and the vertical axis represents voltage.

  In the adjustment method in the conventional ink jet coating apparatus, as shown in FIGS. 3A to 3C, the pulse waveforms are applied to the nozzles 13, 14, and 15 at the same timing (see FIG. 20 and Patent Document 2). (See paragraph 0052.) However, in consideration of the interference between the nozzles, the application unevenness cannot be eliminated if the pulse waveforms are applied to the nozzles 13, 14 and 15 at the same timing.

  FIG. 4 shows pulse waveforms in the present embodiment. (A) shows the nozzle 13 of FIG. 2, (b) shows the nozzle 14 of FIG. 2, and (c) shows the nozzle 15 of FIG. Each corresponds. As shown in this figure, the pulse waveform is out of phase between the nozzles. This is because, in actual application, the head is disposed obliquely in order to match the pattern pitch. The timing at this time is used for adjustment in FIG. As described above, each of the plurality of nozzles is ejected with a time difference, so that the ink ejection amount and the ejection speed can be made uniform while considering the interference between the nozzles corresponding to the actual application pattern. It becomes possible. That is, the discharge amount can be adjusted by individually adjusting the timing of the pulse waveforms in FIGS. 4A to 4C, the adjustment of the voltage direction of the pulse waveform, the voltage application time, and the rise and / or fall of the pulse waveform. Uniformity and uniform discharge speed can be achieved. As described above, these operations are performed by the control device 6. Further, it is not necessary to make both the discharge amount and the discharge speed uniform, and the effect of the present invention can be obtained even when either one is made uniform.

  In this embodiment, when capturing an ink droplet that is flying to obtain the ejection speed, the strobe flashes in consideration of the phase difference of the pulse waveform, and the CCD camera captures the image. . That is, since the pulse waveform between nozzles has a predetermined phase difference, an image of an ink droplet ejected from one nozzle and then an image of an ink droplet ejected from another nozzle are input to the strobe. The trigger signal is shifted by the phase difference calculated from the coating pattern. As a result, the ink droplets ejected from each nozzle can always be imaged by the CCD camera.

  Strictly speaking, even in the same nozzle, there may be a difference in ejection state for each ink droplet. In such a case, within the same nozzle, the trigger signal input to the strobe is shifted by the phase difference corresponding to the coating pattern, and the average value of the discharge amount and discharge speed is calculated for a plurality of ink droplets. It is preferable to make the value uniform among the nozzles. By doing so, it becomes possible to control the ink ejection state with higher accuracy.

  As described above, the ink is ejected under the same conditions as the actual application pattern, that is, under the same conditions as the actual application, and the discharge amount and the discharge speed are adjusted to correspond to the actual application pattern. Adjustment in consideration of interference between nozzles becomes possible. Therefore, even with a head having a large number of nozzles, it is possible to reduce coating unevenness and form a desired pattern.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above embodiment, the ejection speed is adjusted after adjusting the ejection amount of the ink ejected from each nozzle. However, the present invention is not limited to this, and the discharge amount may be adjusted after adjusting the discharge speed. In this case, each adjustment can be performed by the same method as described above.

DESCRIPTION OF SYMBOLS 1 Head 2 Discharge state observation apparatus 3 Strobe 4 CCD camera 5 Discharge speed acquisition part 6 Control apparatus 11 Head 12 Board | substrate 13, 14, 15 Nozzle

Claims (4)

Ink ejection for ejecting the ink from the nozzle using a head including a liquid chamber filled with ink, a pressure generating element for changing the pressure in the liquid chamber, and a nozzle provided in the liquid chamber. In the method
The head includes a plurality of the nozzles,
The ink is ejected under the same conditions as for the actual coating pattern, and the drive waveform of the voltage applied to the pressure generating element is set so that at least one of the ink ejection amount and ejection speed from each nozzle is uniform. An ink discharge method comprising a step of changing each time.   The step is a step of obtaining an average value of discharge amount and discharge speed for a plurality of ink droplets discharged from the same nozzle, and making the average value uniform among the nozzles. The ink ejection method according to claim 1.   At least one of the ejection amount and the ejection speed is such that the ink droplet ejected from the nozzle is irradiated with illumination light that emits light in synchronization with the ejection timing of the ink droplet, and the ink droplet is imaged with a camera, The ink ejection method according to claim 1, wherein the ink ejection method is obtained based on the obtained image. The ink ejection method according to claim 1, wherein each of the plurality of nozzles is ejected with a time difference.

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