JP2006167534A - Measuring method of amount of liquid droplet, method for optimizing driving signal of liquid droplet discharging head, and apparatus for discharging liquid droplet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring method of the amount of a liquid droplet, by which a small amount of the liquid droplet to be discharged can be measured easily and to provide a method for optimizing a driving signal of a liquid droplet discharging head and an apparatus for discharging the liquid droplet, in each of which the measuring method is used. <P>SOLUTION: The apparatus 100 for discharging the liquid droplet is constituted so that the liquid droplet 150 discharged from the liquid droplet discharging head 116 onto the surface 120a of a substrate is irradiated with a pulsed laser beam from a light emitting part 32 as backlight and an image of the irradiated liquid droplet is picked up by a camera 20. The pulsed laser beam is emitted from a laser light source 31, which is used for generating the pulsed laser beam, at the emitting time later than the time to discharge the liquid droplet by a predetermined time. The still image of the liquid droplet just at the emitting time is picked up by the camera 20. A control computer 160 measures numerical data (for example, the contact size and the contact angle) for specifying a shape of the side face of the liquid droplet 150 by using the picked-up image and calculates the volume of the liquid droplet 150 geometrically. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for measuring a droplet amount, a method for optimizing a drive signal for a droplet discharge head using the measurement method, and a droplet discharge apparatus.

  In recent years, droplet discharge devices such as inkjet printers that perform drawing by discharging various liquid materials as droplets onto a substrate have been widely used for paper printing, industrial pattern formation, and the like. A droplet discharge head that discharges droplets has a fine flow path for each nozzle, and the droplets are discharged from the nozzle by pressure generating means (for example, a piezo element) formed in the vicinity of the nozzle. It is the composition to do.

In the droplet discharge head having the above-described configuration, the amount (discharge amount) of droplets discharged from the nozzles depends on manufacturing variations of the droplet discharge head, the type of liquid material to be discharged, and the like. Since the amount of ejected droplets is an important factor that determines the quality of drawing, it is necessary to optimize the drive signal for driving the pressure generating means prior to drawing. As a method for optimizing the drive signal, for example, there is a method in which the discharge amount is measured with a drive signal set to a temporary drive voltage and the appropriate drive voltage is obtained from the difference from the target discharge amount (Patent Document 1).
In the measurement of the ejection amount according to Patent Document 1, the total weight is measured by ejecting a prescribed number of droplets from the droplet ejection head, and the average weight per droplet is obtained by calculation. In addition, the liquid droplets are landed in the dish of the petri dish having a minute depression formed at a predetermined depth, and the surface of the petri dish is covered with a translucent lid to define the height of the liquid droplet. There is also known a method for obtaining the volume of a liquid droplet by obtaining the area of the liquid droplet spread on the image by image processing (Patent Document 2).

JP 2004-90357 A JP 2001-41799 A

  However, in the case of the measurement method according to Patent Document 1, a large number of liquid droplets must be ejected in order to increase the accuracy of weight measurement, and the liquid material is wasted. Further, in the case of the measuring method according to Patent Document 2, a dedicated petri dish must be prepared by fine processing, and the depression formed in the petri dish must be changed according to the amount of droplets to be measured. Preparation was difficult.

  The present invention has been made in order to solve the above-described problems. An appropriate liquid amount measuring method capable of easily measuring the amount of liquid droplets with a small amount of discharge, and optimization of a driving signal for a liquid droplet discharge head using the measurement method. It is an object to provide a method and a droplet discharge device.

The present invention relates to a droplet amount measuring method for discharging a droplet from a droplet discharge head toward one surface of a droplet receiver and measuring the amount of the discharged droplet, A step of observing the droplet landed on the surface from the direction along the one surface and measuring numerical data for specifying a side shape, and an operation for geometrically calculating the amount of the droplet from the numerical data And a step.
In the droplet amount measuring method, the numerical data in the measurement step is measured by an image obtained by imaging the droplet.

Here, the droplet receiver is a target for landing droplets, and is, for example, a plate-like member (substrate) formed of glass, synthetic resin, metal, or the like. At this time, the landing surface of the droplet receiver may be subjected to a surface treatment such as a resin coat or a liquid repellent treatment. In addition, as the liquid material ejected as droplets, materials containing various functional materials and solvents such as colored ink and conductive ink can be used. Further, the numerical data for specifying the side surface shape of the droplet indicates, for example, the contact diameter, contact angle, or height of the droplet with respect to one surface of the droplet receptor.
According to this droplet amount measuring method, numerical data specifying the side surface shape of the droplet is measured by observing the image of the side surface of the droplet on the droplet receiver, and the surface other than the bottom surface of the droplet is a spherical surface. The amount of the droplet can be obtained geometrically by approximating with Thus, the amount of droplets can be easily measured in units of one droplet.
Although the measurer can directly measure the numerical data, it is better in terms of time and accuracy to measure from the captured image.

Further, in the droplet amount measuring method, the measurement of the numerical data in the measuring step is defined such that it is performed at a predetermined timing after the droplet has landed on the droplet receiver. To do.
Preferably, the predetermined timing is defined in a range of 10 μs to 100 μs.

The droplets that have landed on the droplet receptor exhibit dynamic behavior that is governed by surface tension, viscosity, and wetting with the droplet receptor after landing. For example, immediately after landing, the vibration of the liquid droplet is not settled, and the shape of the liquid droplet is not stabilized at such timing. In addition, when the wettability between the droplet and the droplet receiver is high, the droplet spreads wet over time after landing, and the side surface shape of the droplet cannot be captured well. Due to such circumstances, the accuracy of the droplet amount obtained by the calculation varies depending on the timing of measuring the numerical data.
In the droplet amount measuring method of the present invention, the numerical data can be measured with high accuracy by measuring the numerical data at a predetermined timing. In particular, by setting the predetermined timing in the range of 10 μs to 1000 μs, more preferably in the range of 10 μs to 100 μs, even when a low-viscosity liquid is used or when the wettability is good, the shape of the side surface of the droplet Can be accurately measured, and can be effectively applied to various liquid materials and substrates.

The droplet amount measuring method is a method in which, in the measurement step, the droplet is irradiated with a flash, and an image of the droplet at the moment of the irradiation is taken to measure the side surface shape. The flash light is emitted at a timing obtained by adding a predetermined delay time to the droplet ejection timing.
Preferably, the imaging of the droplet by irradiating the flash is performed by a backlighting method.
Preferably, the flash light in the imaging step is a pulsed laser beam.
Preferably, the irradiation with the pulsed laser beam is performed through an optical fiber.

In order to measure the numerical data of the droplet at a predetermined timing as in the droplet amount measuring method described above, for example, a droplet is imaged with a high-speed camera, and the droplet corresponding to the predetermined timing is measured. You may make it measure with respect to this image. However, in such a method, since a high-speed camera is expensive, a large expense is required prior to implementation.
According to the droplet amount measuring method of the present invention, an image at the moment of irradiation is picked up by flash irradiation. Therefore, any timing can be set by flash irradiation control without using a special imaging means such as a high-speed camera. A droplet image (still image) can be obtained.
Further, at this time, by performing imaging using a backlighting method in which the droplet is irradiated with a backlight, the contour of the droplet image can be captured more clearly. At this time, if pulsed laser light is used, it is not affected by chromatic aberration as in white light, and blurring of the image of the droplet is reduced by a sharp change in brightness, and a clearer image can be obtained. . Also, at this time, if the pulse laser beam is irradiated through the optical fiber, the light beam can be focused in a narrow range by the optical fiber, and the phase of the pulse laser beam is dispersed in the process of passing through the optical fiber. As a result, the coherence is reduced, so that the influence of diffraction on the contour (edge) of the droplet can be reduced.

  The present invention relates to a driving signal optimization method for optimizing a driving signal for driving the pressure generating means in a droplet discharge head having pressure generating means provided in the vicinity of a nozzle, and comprising one or more driving signals A discharge step for driving the pressure generating means to discharge the droplet from the nozzle, and a discharge amount for measuring the discharge amount of the droplet discharged in the discharge step using the droplet amount measuring method The method includes a measurement step and an optimization step of optimizing a drive signal based on the one or more drive signals according to the discharge amount measured in the discharge amount measurement step.

Here, the drive signal is a voltage pulse or the like for driving pressure generating means such as a piezo element, and the discharge amount of the liquid droplets discharged from the nozzle changes according to the voltage difference or gradient of the pulse. Has characteristics.
According to this drive signal optimization method, the discharge amount by one or more drive signals (dummy drive signal) is acquired by the above-described droplet amount measurement method, and from the difference between the discharge amount and the ideal discharge amount, Based on the dummy drive signal, it is possible to generate a drive signal for obtaining an ideal discharge amount.

In the drive signal optimization method, the discharge amount is measured corresponding to the plurality of nozzles.
According to this drive signal optimizing method, since the discharge amount is measured corresponding to a plurality of nozzles, it is possible to optimize the drive signal in consideration of variations in the discharge amount among the nozzles.

The present invention has landed on one surface of the droplet receiver, a droplet discharge head that discharges droplets from the nozzle, a mounting portion for mounting a droplet receiver that receives the droplets discharged from the nozzle, and And a measuring means for observing the droplet from a direction along the one surface and measuring numerical data for specifying a side shape of the droplet.
Preferably, the apparatus further comprises a droplet amount calculation unit that geometrically calculates the droplet amount from the side surface shape.

  According to this droplet discharge device, it is possible to measure numerical data for specifying the side surface shape of the droplet by the measuring means. Thus, based on the obtained numerical data, the surface of the droplet other than the bottom surface is approximated by a spherical surface, and the amount of the droplet can be obtained geometrically. The calculation of the amount of droplets is preferably automatically performed by a droplet amount calculation unit provided in the droplet discharge device.

Further, in the droplet discharge device, the measurement unit includes an irradiation unit that irradiates a flash to the droplet landed on one surface of the droplet receptor, and the landed surface of the droplet receptor. Imaging means for imaging a droplet from a direction along the one surface, and the flash irradiation is performed by irradiating the flash at a timing obtained by adding a predetermined delay time to the discharge timing of the droplet. .
According to the droplet discharge device of the present invention, the flashing light is irradiated by the irradiating unit, and the image of the droplet at that moment is captured by the imaging unit. Image (still image) can be obtained. In addition, the flash irradiation timing is accurately measured with the droplet discharge timing as a reference time, so that the side surface shape of the droplet can be measured at an appropriate timing.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.
Note that the embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these forms.

(Overall configuration of droplet discharge device)
First, the overall configuration of the droplet discharge device will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view illustrating a schematic configuration of a droplet discharge device according to the present embodiment. FIG. 2 is a plan view showing the arrangement of the droplet discharge heads in the head unit.
As shown in FIG. 1, a droplet discharge device 100 includes a head mechanism unit 102 having a head unit 110 that discharges droplets on a surface plate 107 supported by support legs 106, and a substrate as a droplet receiver. A substrate mechanism unit 103 for mounting 120 in a movable manner with respect to the head unit 110 and a liquid material supply unit 104 for supplying the liquid material 133 to the head unit 110 are provided. Further, the droplet discharge device 100 includes a control unit 105 that controls the drive control of the head mechanism unit 102 and the substrate mechanism unit 103 and the discharge control of the head unit 110 below the surface plate 107.
Here, as the substrate 120, a glass substrate, a metal substrate, a synthetic resin substrate or the like can be used as long as it is a flat plate. Examples of the liquid material include a filter material for a color filter, a light emitting material for forming an EL light emitting layer in an organic EL device, a fluorescent material for forming a phosphor in a PDP device, and an electrophoretic material in an electrophoretic display device. Electrophoretic material for forming a film, bank material for forming a bank on the surface of the substrate, various coating materials, liquid electrode material for forming an electrode, spacer for forming a minute cell gap between two substrates A solution containing a particle material, a liquid metal material for forming a metal wiring, a lens material for forming a microlens, a resist material, a light diffusing material for forming a light diffuser, etc. It is prepared according to.

  The head mechanism unit 102 includes a head unit 110 that discharges the liquid material 133 as droplets, a carriage 111 on which the head unit 110 is mounted, a Y-axis guide 113 that guides movement of the carriage 111 in the Y-axis direction, and a Y-axis. A Y-axis ball screw 115 installed along the guide 113, a Y-axis motor 114 for rotating the Y-axis ball screw 115 forward and backward, and a lower part of the carriage 111, and screwed with the Y-axis ball screw 115 to form a carriage. And a carriage screwing portion 112 in which a female screw portion for moving 111 is formed.

  The moving mechanism of the substrate mechanism unit 103 is arranged in the X-axis direction with a configuration substantially the same as that of the head mechanism unit 102, and a mounting table 121 as a mounting unit on which the substrate 120 is mounted, and the mounting table 121. An X-axis guide 123 that guides the movement, an X-axis ball screw 125 installed along the X-axis guide 123, an X-axis motor 124 that rotates the X-axis ball screw 125 forward and backward, and a lower part of the mounting table 121. The mounting table screwing portion 122 is configured to screw the X-axis ball screw 125 and move the mounting table 121.

  As shown in FIG. 2, the head part 110 holds a plurality of droplet discharge heads 116 having the same structure. The droplet discharge head 116 for discharging droplets has two nozzle rows extending in the X-axis direction, and one nozzle row has, for example, 180 nozzles 117. The droplet discharge heads 116 are arranged so that the nozzle positions (coordinates) in the X-axis direction are offset at a predetermined interval.

  Returning to FIG. 1 again, the liquid supply unit 104 that supplies the liquid 133 to the head unit 110 includes a tube 131a that forms a flow path that communicates with the head unit 110, a pump 132 that supplies liquid to the tube 131a, a pump The tube 131 b (flow path) that supplies the liquid material 133 to the tube 132 and the tank 130 that communicates with the tube 131 b and stores the liquid material 133 are disposed at one end on the surface plate 107.

  The head mechanism unit 102 and the substrate mechanism unit 103 are respectively provided with position detection means (not shown) for detecting the positions where the head unit 110 and the mounting table 121 have moved. Further, the carriage 111 and the mounting table 121 incorporate a mechanism for adjusting the rotation direction with the Z direction orthogonal to the XY direction as the rotation axis direction, and adjust the rotation direction of the head unit 110 and the rotation direction of the mounting table 121. Adjustment is possible.

  In the above-described configuration, the head unit 110 and the substrate 120 can reciprocate relative to each other in the Y-axis direction and the X-axis direction by driving control of the X-axis motor 124 and the Y-axis motor 114, respectively. Then, in synchronization with this relative movement, the liquid 133 supplied from the liquid supply unit 104 is ejected as droplets from the head unit 110, whereby drawing can be performed on the substrate surface 120a.

  The droplet discharge device 100 includes a camera 20 as an imaging unit, a laser light source 31 as an irradiating unit, an emitting unit 32, an optical fiber 33, and a measurement unit for observing a droplet on the substrate surface 120a. Measuring means moving mechanism portions 91 and 92 and a support bar 90 for moving in the XY-axis direction are provided. The control unit 105, the camera 20, and the laser light source 31 are electrically connected to the control computer 160. The control computer 160 controls the above-described measuring means, the head unit 110, and the like directly or via the control unit 105, and measures the droplet amount and optimizes the drive signal, which will be described later.

  The camera 20 includes an imaging unit 22 having a solid-state imaging device such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) sensor, and a lens barrel 21. The camera 20 is installed so as to be movable in the XY-axis directions by the measuring means moving mechanism units 91 and 92, and can adjust the field of view and focus on an arbitrary place on the substrate surface 120a. The image data acquired by the imaging unit 22 is sent to the control computer 160 and can be subjected to image processing or displayed on the monitor 161.

The laser light source 31 constituting the irradiating means generates pulsed laser light as flash light. It is preferable to select a pulsed laser beam having a wavelength range with high imaging sensitivity in the imaging unit 22. In this embodiment, the laser light source 31 employs Oxford Lasers: HSI1000, and a near-infrared semiconductor pulse laser. Getting light. The optical fiber 33 that guides the pulsed laser light generated by the laser light source 31 is wound along a support bar 90 that can move integrally with the measuring means moving mechanism portions 91 and 92, and from an emitting portion 32 provided at one end thereof. The pulse laser beam is irradiated in the direction facing the camera 20.
Since both the camera 20 and the emitting unit 32 are moved by the measuring means moving mechanism units 91 and 92, the relative positional relationship between them is always kept constant, and the amount of light and the incident angle of light during imaging are also stable. Yes. In the present embodiment, the emission axis of the pulse laser beam is set substantially parallel to the optical axis of the lens barrel 21, and the droplet can be imaged by a so-called backlighting method.

(Droplet discharge head configuration and discharge control)
Next, the configuration of the droplet discharge head and the discharge control will be described with reference to FIGS. FIG. 3 is a schematic perspective view showing the main structure of the droplet discharge head.
As shown in FIG. 3, the droplet discharge head 116 includes a plurality of cavities 140 that are partitioned by partition walls 141, and one nozzle 117 is provided for one cavity 140. The nozzle 117 is formed on a nozzle plate 144 that is bonded and fixed to the lower surface of a member that constitutes the partition wall 141. The liquid material is supplied from the reservoir 145 to the cavity 140 via a supply port 146 located between the pair of partition walls 141. The reservoir 145 serves as a liquid reservoir for storing a fixed amount of liquid material, and the liquid material is supplied to the reservoir 145 through the hole 147.
The upper part of the cavities 140 is a diaphragm 143 as pressure generating means, and the vibrators 142 are located on the diaphragm 143 corresponding to the cavities 140. The vibrator 142 includes a piezoelectric element and a pair of electrodes (not shown) that sandwich the piezoelectric element. By applying a drive signal (see FIG. 4) to the pair of electrodes, the diaphragm 143 at a location corresponding to the vibrator 142 is deformed, the internal pressure of the cavity 140 is changed, and the liquid material is discharged from the nozzle 117. A droplet 150 is discharged.

FIG. 4 is a diagram illustrating an example of the drive signal and the behavior of the liquid material in the nozzle corresponding to the drive signal.
The drive signal 300 shown in FIG. 4 has a configuration in which a series of pulse groups 305 and 305 having a discharge pulse 301, a charge pulse 302, and a discharge pulse 303 are periodically connected at an intermediate potential 304. When the discharge pulse 301 is applied to the vibrator 142 (see FIG. 3), the pressure in the cavity 140 (see FIG. 3) is reduced as the voltage level decreases, and the amount of the liquid 133 in the nozzle 117 decreases (timing Tp). ). Next, when a steep charge pulse 302 is applied to the vibrator 142 (see FIG. 3), the inside of the cavity 140 (see FIG. 3) is pressurized as the voltage level increases, and the liquid 133 protrudes greatly from the nozzle 117. (Timing Te). At this time, pressure vibration called natural vibration is generated in the flow path including the nozzle 117, and the liquid 133 eventually turns into a motion of being drawn into the back of the nozzle 117 according to the natural vibration. For this reason, the liquid 133 is cut at the boundary between the first protruding portion and the nozzle 117 side portion, and the protruding portion flies as a droplet 150 (timing Tb). The discharge pulse 303 plays a role of canceling the residual component of the natural vibration in the cavity 140 (see FIG. 3) and returning the increased potential level to the intermediate potential, and thus the ejection drive for one cycle is completed. Note that the timing at which the droplet 150 is ejected (hereinafter referred to as ejection timing) is not clearly captured as a certain moment, but in the present embodiment, the timing Te that is the end point of the application of the charging pulse 302 is ejected. It shall be treated as timing.

The potential difference components Vc, Vh and time components (pulse slope, connection interval between pulses, etc.) in the drive signal 300, the shape of the pulse group 305, etc. are greatly related to the discharge amount of the droplets, and the intended discharge characteristics. Accordingly, the drive signal 300 is designed in advance. However, due to manufacturing variations of the droplet discharge heads 116, even when the same drive signal 300 is applied, the discharge amount and the like may vary from individual to individual, and a technique for correcting such variations is required.
Therefore, in general, the drive signal is optimized for each droplet discharge device 100 or for each droplet discharge head 116 to cope with the above-described problem. Specifically, for example, it is performed by changing only the voltage component at an equal ratio without changing the basic shape and time component of each pulse, and changing the so-called drive voltage. More specifically, a droplet is ejected at one or two predetermined drive voltages to measure a discharge amount, and an appropriate drive voltage (appropriate voltage) is obtained from a difference between the discharge amount and a target discharge amount. Yes (see Patent Document 1). Such optimization of the drive signal 300 can be applied to a change in the discharge amount accompanying the change of the liquid material, and is effective when a plurality of types of liquid materials are used in one droplet discharge device. The droplet discharge device 100 according to this embodiment is provided with a function for optimizing a drive signal (drive voltage) in advance, and a specific operation procedure will be described in detail later.

FIG. 5 is a circuit diagram showing an example of a drive circuit for the droplet discharge head. FIG. 6 is a diagram illustrating timings of the drive signal and the control signal.
In FIG. 5, a control signal generation circuit 220 and a drive signal generation circuit 230 are provided in the control unit 105 (see FIG. 1). Further, flip-flops 226..., Flip-flops 227..., Transistors 229... Are provided corresponding to the respective piezoelectric vibrators 142. The drive signal generation circuit 230 is connected to each signal line 223, 224, 225, 231.

The control signal generation circuit 220 takes in a data signal (see FIG. 6) sent via the data bus 222, and a print timing signal (see FIG. 6) indicating that the droplet discharge head 116 has reached the print position. At the stage of input to the terminal 221, the fetched data signal is output to the signal line 224 bit by bit. The data signal output to the signal line 224 is input to a data terminal of a flip-flop 226 that is connected in cascade and forms a shift register. Further, a shift clock signal is output to the signal line 225, and the data signal serially transferred by the shift clock signal is transferred to the flip-flops 226. When the data (nozzle ON / OFF information) for all the piezoelectric vibrators 142 is transferred, a latch signal (see FIG. 6) is sent to the signal line 223, and the data is output from the flip-flops 227. Appears on Then, the transistor 229 corresponding to the piezoelectric vibrator 142 that is to perform the printing operation is turned on. On the other hand, when the print timing signal (see FIG. 6) is input via the control signal generation circuit 220 and the signal line 260, the drive signal generation circuit 230 outputs the drive signal (see FIG. 6) from the signal line 231. The piezoelectric vibrator 142 corresponding to the transistor 229 that is turned on is driven.
The shape of the drive signal generated by the drive signal generation circuit 230, the data of the data signal, the application timing of the print timing signal, the frequency, and the like can be freely set by a command from the control computer 160. . Thus, the droplet 150 can be discharged from an arbitrary nozzle of the droplet discharge head 116 at an arbitrary timing by an arbitrary drive signal.

  In FIG. 6, the ejection timing Te is a timing determined depending on the drive signal, and is different from the rising timing of the printing timing signal and the rising timing Tl of the latch signal (hereinafter referred to as latch timing Tl). . However, the discharge timing Te and the latch timing Tl are always in a relationship defined by a constant time interval Ti, and the discharge timing Te can be grasped with the latch timing Tl. The latch signal is sent from the control unit 105 to the control computer 160 (see FIG. 1), and the control computer 160 controls the generation of pulsed laser light in the laser light source 31 and the imaging control of the camera 20 based on the latch timing Tl. It is carried out. That is, the control computer 160 constitutes the irradiation means in the present invention.

(Drop volume measurement operation)
Next, with reference to FIG. 7 to FIG. 10, the operation for measuring the droplet amount (discharge amount) using the droplet discharge device will be described. FIG. 7 is a diagram illustrating a functional configuration of the droplet discharge device according to the droplet amount measurement operation. FIG. 8 is a diagram showing the timing of the drive signal, latch signal, trigger signal, and pulse laser beam output.

As shown in FIG. 7, the nozzle surface 148 of the droplet discharge head 116 and the substrate surface 120a are configured to maintain a constant distance g, and the substrate 120 is moved in the X-axis direction by the substrate mechanism 103. The droplet discharge head 116 can be moved in the Y-axis direction by the head mechanism 102. Further, the camera 20 and the emitting unit 32 can be moved in the X-axis direction and the Y-axis direction by measuring means moving mechanism units 91 and 92. With these configurations, the droplet discharge head 116 can discharge the droplet 150 to an arbitrary position on the substrate 120, and the camera 20 can discharge the droplet 150 discharged from an arbitrary nozzle 117 (see FIG. 2). An image can be taken.
The measurement of the amount of droplets is performed prior to pattern drawing for forming various functional films such as electric wiring. As the substrate 120 as the droplet receiver, a dedicated substrate for measuring the amount of droplets may be prepared, or the drawing substrate may be used as it is. In the latter case, the droplet 150 as a measurement target is ejected to a dummy area that is not drawn. At this time, a resin or inorganic thin film may be formed on the substrate surface 120a, and a lyophilic or liquid repellent treatment may be performed. It is sufficient that a certain level of flatness is ensured, and it is one of the features of the present invention that it is not significantly affected by the state of the substrate surface 120a.

The camera 20 as an imaging unit images the droplet 150 on the substrate surface 120a from a direction along the substrate surface 120a, using a pulse laser beam as flash light emitted from the emitting unit 32 as an irradiation unit as a backlight. The camera 20 can capture an image at the moment when the droplet 150 is irradiated by the emitting unit 32 as a still image. That is, by irradiating the pulse laser beam at an arbitrary timing after the droplet 150 has landed on the substrate surface 120a, an image of the droplet 150 at the timing can be taken.
Since pulsed laser light is used as the light source for irradiation, it is not affected by chromatic aberration like white light, and blurring of the image of the droplet 150 is reduced by a sharp light-dark change, so that a clear still image is obtained. Can be obtained. In addition, since the imaging is performed by the backlighting method in which the droplet 150 is irradiated with the backlight to capture an image, the contour of the droplet image can be captured more clearly. Further, since the pulsed laser light is irradiated through the optical fiber 33, the phase of the pulsed laser light is dispersed, the coherence is lowered, and the influence of diffraction at the edge of the droplet 150 can be reduced. Further, by converging and irradiating the pulse laser beam with the optical fiber 33, the droplet 150 can be effectively irradiated even when the gap g between the nozzle surface 148 and the substrate surface 120a is narrow.

The pulse laser beam irradiation control and imaging control described above are performed by a trigger signal transmitted from the control computer 160. That is, in response to the trigger signal generated by the control computer 160, the laser light source 31 outputs pulse laser light, and the imaging unit 22 images the droplet 150 irradiated with the pulse laser light as a still image. The captured image information is sent to the control computer 160 and subjected to image processing as appropriate.
Here, the trigger signal is generated using the latch signal transmitted from the control signal generation circuit 220 as a synchronization signal. That is, in FIG. 8, a trigger signal is generated at a timing Tf (hereinafter referred to as an imaging timing Tf) obtained by adding a predetermined time = Ti + Td to the latch timing Tl. Here, Ti is a time difference between the latch timing Tl and the ejection timing Te as described above, that is, Td represents a delay time of the imaging timing Tf with respect to the ejection timing Te.
In this manner, by generating a trigger signal with a time difference of Ti + Td using the latch signal as a synchronization signal, irradiation with pulsed laser light and imaging are performed at a timing obtained by adding the delay time Td to the ejection timing Te. Then, by changing the delay time Td, the droplet 150 can be imaged at an arbitrary timing based on the ejection timing Te. The timing Tw shown in the figure represents the timing at which the droplet 150 lands on the substrate surface 120a (hereinafter referred to as the landing timing Tw).

The landing timing Tw is delayed by a certain time with respect to the discharge timing Te, that is, in FIG. 7, a delay corresponding to the time during which the droplet 150 flies through the interval g from the nozzle surface 148 to the substrate surface 120a occurs. For example, if the interval g is 0.7 mm and the average flying speed is 7 m / s, the time from when the droplet 150 is ejected until it reaches the substrate surface 120a corresponds to 100 μs. In this case, if the delay time Td is set to 100 μs or more, the droplet 150 after landing on the substrate surface 120a is imaged.
As described above, since the time difference from the discharge timing Te to the landing timing becomes constant because the interval g is maintained, the delay is based on the discharge timing Te (the latch timing Tl that is directly synchronized with the discharge timing). The elapsed time Tr from the landing timing Tw to imaging can be defined by the time Td.

FIG. 9 shows an example of a droplet image picked up by changing the delay time Td. Here, a dye ink used in a commercially available inkjet printer is used for the droplet 150, and the substrate surface 120a is in a lyophilic state by adsorbing molecules of dodecyl triethoxy silane. It is in.
In the stage immediately after landing shown in FIG. 9A, the droplet 150 does not contain vibrations due to impact at the time of landing, and the side surface shape of the droplet 150 is in an unstable state. When a little time elapses from the landing, such vibrations converge, and the droplet 150 shows a stable spherical shape as shown in FIG. 9B. Then, as time elapses, the droplet 150 spreads wet, and after the state shown in FIG. 9C, becomes steady in a state where the droplet 150 is greatly wet spread as shown in FIG. 9D.
The captured image is subjected to image processing by a control computer 160 that constitutes a measuring unit, and the side shape of the droplet 150 is measured. More specifically, for example, numerical data specifying the side shape such as the contact diameter d, the contact angle θ, the height h, and the image area shown in FIG. 9B is acquired. FIG. 10 shows the relationship between the contact diameter d (FIG. 10 (a)) and the droplet height h (FIG. 10 (b)) thus measured and the elapsed time Tr from landing to imaging. .

As described above, the side surface shape of the droplet 150 varies depending on the elapsed time Tr after landing, and it is difficult to specify the side surface shape due to the effect of residual vibration immediately after landing and due to the effect of wetting and spreading after a long time after landing. become. In the subsequent calculation of the droplet amount, the volume is geometrically determined from the side surface shape of the droplet 150. Therefore, the specification of the side surface shape is a major factor related to the accuracy of volume measurement. That is, the timing (delay time Td, elapsed time Tr) for imaging the droplet 150 is greatly related to the calculation accuracy of the droplet amount.
The timing suitable for imaging is a time range that is not affected by residual vibration or wetting spread immediately after landing, and Tr = 10 μs to 1000 μs, and more preferably 10 μs to 100 μs. The behavior characteristics of the droplet after landing vary depending on the viscosity of the droplet 150 and the wettability with the substrate surface 120a. However, if imaging is performed within this range, a low-viscosity liquid is used. Even in the case where the wettability is good, the shape of the side surface of the droplet 150 can be accurately measured, and it is possible to effectively cope with various liquid materials and substrates. In the droplet discharge device 100 of the present embodiment, the timing for imaging the droplet 150 is defined as a time within the above-described time range (for example, Tr = 15 μs), and the side surface shape of the droplet 150 is accurately measured. Is possible.

  Once the droplet 150 is imaged and the numerical data specifying the side surface shape is measured, the droplet amount is calculated using the acquired numerical data. This calculation is performed by the control computer 160 including a droplet amount calculation unit. In this embodiment, the landing diameter d and the contact angle θ are measured (measurement step), and the droplet is calculated using the calculation formula shown in Equation 1. A volume V of 150 is calculated (calculation step). As described above, since the droplet discharge device 100 according to the present embodiment is configured to obtain the droplet amount geometrically from the side surface shape of the droplet 150, the measurement can be performed in units of one droplet. Further, it is not significantly affected by the state of the substrate surface 120a.

  Equation (1) is a calculation equation that is approximated when the liquid surface of the droplet 150 forms a spherical surface. However, if necessary, a correction coefficient for correcting an error from the actual amount may be multiplied. Further, the calculation of the droplet amount is not limited to the calculation method as described above, and may be a method of calculating from the landing diameter d and the height h, or measuring the area of the side image of the droplet 150. A method of calculating the volume by integration may be used. Further, the mass (weight) may be obtained using the density of the liquid material used instead of the volume of the droplet 150.

(Drive voltage optimization operation)
Next, the operation for optimizing the drive voltage in the drive signal will be described along the flowchart of FIG. 11 with reference to FIGS. FIG. 11 is a flowchart illustrating an example of a droplet amount measurement operation. FIG. 12 is a schematic side view showing the imaging field of view.
Optimization of the drive voltage is performed prior to drawing as necessary. The optimizing operation is necessary when, for example, a part or all of the droplet discharge heads 116 of the head unit 110 (see FIG. 2) is replaced by the maintenance of the droplet discharge device 100, or the liquid 133 This is when the type and composition (see FIG. 1) are changed.

In FIG. 7, when an operation command for optimizing the drive voltage is sent from the control computer 160, first, the first drive voltage is set (step S1 in FIG. 11). The first drive voltage is a provisional drive voltage used in the ejection drive in the optimization operation, and a value is stored in the control unit 105 in advance.
Next, by driving the head mechanism unit 102 and the substrate mechanism unit 103, the droplet discharge head 116 moves to a predetermined relative position with respect to the substrate 120, and the droplet discharge position (landing position) is adjusted (step in FIG. 11). S2). At this time, when the substrate 120 is a drawing substrate, the droplet discharge head 116 moves onto a dummy region in the substrate 120. Prior to this step S2, in order to discard the thickened liquid material in the nozzles of the liquid droplet ejection head 116 (the liquid material whose viscosity has increased due to evaporation of water from the nozzle openings), the liquid droplet ejection device 100 is used. You may make it perform a droplet discharge to the non-illustrated non-illustrated area | region provided.
Next, the camera 20 and the emitting unit 32 are moved by driving the measuring means moving mechanism units 91 and 92, and the imaging positions (field of view and focus) are adjusted (step S3 in FIG. 11). In the present embodiment, as shown in FIG. 12, for one nozzle row (see FIG. 2) of the droplet discharge head 116, three imaging regions f1 to f3 at the center and both ends of the nozzle row are set. 6 nozzles are imaged simultaneously in one area. For example, in the first step S2, the imaging region f1 is an imaging field.

Next, as shown in FIG. 12, droplets 150 are ejected from the droplet ejection head 116 (ejection step S4 in FIG. 11). The discharge conditions at this time are defined in advance, and in this embodiment, droplets are discharged one by one from all the nozzles (180 nozzles) in one row. The reason why the discharge condition is defined is that the discharge amount may vary depending on the number of nozzles that are driven simultaneously due to the structure of the droplet discharge head 116 or the electrical crosstalk of the drive signal. If the design condition permits, one image pickup area: ejection may be performed in units of 6 nozzles.
Next, the droplet 150 on the substrate surface 120a in the imaging region f1 is imaged by irradiating it with a pulsed laser beam (step S5 in FIG. 11), and it is checked whether or not all the designated imaging areas have been completed. (Step S6 in FIG. 11). Note that the imaging conditions in step S5 are the same as those in the measurement of the droplet amount described above.

  In step S6, when the designated imaging area remains, the process returns to step S2, and a series of operations from steps S2 to S6 are performed. Here, step S2 and discharge step S4 for adjusting the discharge position are performed as necessary. For example, only the imaging position may be sequentially moved in the order of f2 and f3 with respect to the previously ejected droplets 150. In this case, the imaging timings at f2 and f3 are delayed from the imaging timing at f1 due to the time required for driving the measuring means moving mechanism units 91 and 92 and the processing speed of the imaging unit 22. However, this is sufficiently effective when the droplet 150 is difficult to get wet with the substrate surface 120a, and the amount of liquid to be consumed and the time required for imaging can be shortened. If it is desired to match the respective image capturing timings, the image capturing position is moved after slightly shifting the ejection position (landing position) in step S2 (step S3), and the liquid droplet ejection (step S4) is performed. S5) is performed in the same procedure as described above.

  In this manner, the same operation is repeated for the other nozzle rows and the other droplet discharge heads 116 (see FIG. 2), and if it is determined in step S6 that all the designated imaging areas have been completed, Numerical data for specifying the side shape is measured for the droplet 150 in the image (measurement step S7 in FIG. 11). Based on the measured numerical data, the volume of the droplet 150, that is, the discharge amount in the discharge step S4 is obtained by calculation (calculation step S8 in FIG. 11). That is, step S5 for imaging the droplet 150, measurement step S7 for measuring numerical data relating to the side surface of the droplet 150, and calculation step S8 for calculating the droplet amount constitute the discharge amount measurement step in the present invention. Yes.

Although the measurement of the discharge amount can be performed from one nozzle unit, in the present embodiment, the measurement for a plurality of nozzles is performed in consideration of the discharge amount variation between the nozzles. By determining the discharge amount as an average value of the nozzle row unit, the droplet discharge head unit 116, or the entire discharge head 110, the influence of such inter-nozzle variation can be reduced and the average characteristics can be known.
In the above-described embodiment, the measurement target is limited to three areas: 18 nozzles for one nozzle array, in order to reduce the time required for measurement. Of course, all nozzles are discharged. The amount may be measured. On the other hand, if the correlation with the average characteristic of the entire droplet discharge head 116 or the entire head unit 110 is already known for one specific nozzle of the droplet discharge head 116, the specific one nozzle is determined. Only the discharge amount may be measured.

When the ejection amount based on the first drive voltage is obtained as described above, it is next determined whether or not the ejection amount based on the second drive voltage has been measured (step S9 in FIG. 11). If the measurement of the discharge amount by the second drive voltage is not yet completed, the second drive voltage is set (step S10 in FIG. 11), and the discharge amount by the second drive voltage is obtained by a series of operations of steps S2 to S9. .
If the discharge amount is measured with the second drive voltage, an appropriate voltage is calculated from the discharge amount with respect to the first drive voltage and the discharge amount with respect to the second drive voltage, and set as the drive voltage (optimization in FIG. 11). Step S11). Specifically, for example, a drive voltage for obtaining a target discharge amount is obtained by linear interpolation from the relationship between the first drive voltage value and the second drive voltage value and the measured discharge amount (see Patent Document 1). In addition, although the accuracy is somewhat inferior, there is also a method of obtaining an appropriate voltage by measuring only the ejection amount by one drive voltage. Thus, by obtaining an appropriate voltage and optimizing the drive signal, accurate drawing based on the designed discharge amount (target discharge amount) can be performed.

  When the droplet discharge device 100 has a print mode using a plurality of types of drive signals, an appropriate voltage is obtained and set for each corresponding drive signal. The appropriate voltage is calculated and set for each drive signal generation circuit 230. For example, if an independent drive signal generation circuit 230 is provided for each nozzle row or each droplet discharge head 116, the average discharge amount is calculated for each nozzle row or droplet discharge head, and the appropriate voltage is set. Calculation and setting are performed to optimize the drive signal.

The present invention is not limited to the above-described embodiment. For example, the drive signals shown in FIG. 4 and the like are merely examples, and the present invention can be applied to drive signals having various shapes (for example, see Patent Document 1). Further, the pressure generating means is not limited to the one using a piezo element, and the present invention can be applied as long as the discharge amount changes depending on the shape of the drive signal.
The drive signal is generally optimized by optimizing the drive voltage as described above, but it does not deny that the drive signal is optimized by changing the time component or the like.
Moreover, the flash light irradiation by the irradiation means is not limited to the pulse laser light, and may be performed by a white strobe.
Further, the timing for imaging the droplet in the measurement of the droplet amount is not limited to being defined at a predetermined timing as in the above-described embodiment. As a requirement for application of the present invention, it is sufficient that numerical data specifying the side shape of the droplet can be measured. For example, when the droplet is difficult to wet with the substrate surface, the droplet is in a steady state. It is sufficient to take an image at an arbitrary timing in the stage. In such a case, since the side surface shape of the droplet does not change at high speed, it is not necessary to capture a still image using flash light.
Moreover, each structure of the above-mentioned embodiment can combine these suitably, can be abbreviate | omitted, or can combine with the other structure which is not shown in figure.

1 is a perspective view illustrating a schematic configuration of a droplet discharge device according to an embodiment. FIG. 3 is a plan view showing the arrangement of droplet discharge heads in the head unit. FIG. 2 is a schematic perspective view showing a main part structure of a droplet discharge head. The figure which shows an example of a drive signal, and the behavior of the liquid body in the nozzle corresponding to the said drive signal. FIG. 3 is a circuit diagram showing an example of a drive circuit for a droplet discharge head. The figure which shows the timing of a drive signal and a control signal. The figure which shows the function structure of the droplet discharge apparatus which concerns on the measurement operation | movement of droplet amount. The figure which shows the timing of a drive signal, a latch signal, a trigger signal, and a pulse laser beam output. The figure which shows an example of a captured image. (A) is a figure which shows the relationship between the elapsed time from landing to imaging, and the contact diameter measured from the captured image. (B) is a figure which shows the relationship between the elapsed time from landing to imaging, and the droplet height measured from the captured image. The flowchart which shows an example of the measurement operation | movement of droplet amount. The schematic side view which shows an imaging visual field.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Camera as an imaging means (measurement means), 21 ... Lens barrel, 22 ... Imaging part, 31 ... Laser light source which comprises irradiation means (measurement means), 32 ... Emitting part which comprises irradiation means (measurement means), 33 ... Optical fiber constituting irradiation means (measurement means), 90 ... Support bar, 91, 92 ... Measurement means moving mechanism section, 100 ... Droplet ejecting device, 102 ... Head mechanism section, 103 ... Substrate mechanism section, 104 ... Liquid body supply unit, 105 ... control unit, 110 ... head unit, 111 ... carriage, 116 ... droplet discharge head, 117 ... nozzle, 120 ... substrate as droplet receiver, 120a ... as one surface of droplet receiver Substrate surface 121. Mounting table as mounting section 133 133 Liquid material 140 Cavity 141 Wall partition 142 Vibrator as pressure generating means 143 Vibration plate 144 Nozzle plate 145 ... Reservoir, 146 ... Supply port, 148 ... Nozzle surface, 150 ... Drop, 160 ... Control computer comprising measuring means and having a droplet amount calculation unit, 161 ... Monitor, 220 ... Control signal generating circuit, 230 ... Drive signal generation circuit, 300 ... drive signal, 301 ... discharge pulse, 302 ... charge pulse, 303 ... discharge pulse, 304 ... intermediate potential, 305 ... pulse group, Te ... discharge timing, Tf ... imaging timing, Td ... delay time, Tr: elapsed time from landing to imaging, d: contact diameter d as numerical data, θ: contact angle as numerical data, h: height of liquid droplet as numerical data.

Claims (13)

A droplet amount measuring method for discharging a droplet from a droplet discharge head toward one surface of a droplet receptor and measuring the amount of the discharged droplet,
A measurement step of observing the droplet landed on one surface of the droplet receptor from a direction along the one surface and measuring numerical data specifying a side shape of the droplet;
And a calculation step of geometrically calculating the droplet amount from the numerical data.   2. The droplet amount measuring method according to claim 1, wherein the numerical data in the measuring step is measured by an image obtained by imaging the droplet.   3. The liquid according to claim 1, wherein the measurement of the numerical data in the measurement step is defined to be performed at a predetermined timing after the droplet has landed on the droplet receiver. Drop volume measurement method.   The droplet amount measuring method according to claim 3, wherein the predetermined timing is defined in a range of 10 μs to 100 μs. 5. The droplet amount measuring method according to claim 3, wherein in the measuring step, the droplet is irradiated with flash light, and an image of the droplet at the moment of the irradiation is taken to measure the side surface shape. Because
The method of measuring a droplet amount, wherein the flash irradiation is performed at a timing obtained by adding a predetermined delay time to the droplet discharge timing.   6. The droplet amount measuring method according to claim 5, wherein the imaging of the droplet by irradiating the flash light is performed by a backlighting method.   The droplet amount measuring method according to claim 5 or 6, wherein the flash light in the imaging step is a pulsed laser beam.   The droplet amount measuring method according to claim 7, wherein the irradiation with the pulsed laser light is performed through an optical fiber. In a droplet discharge head having pressure generation means provided in the vicinity of a nozzle, a drive signal optimization method for optimizing a drive signal for driving the pressure generation means,
A discharge step of driving the pressure generating means by one or more drive signals to discharge the droplets from the nozzle;
A discharge amount measurement step of measuring a discharge amount of the droplets discharged in the discharge step using the droplet amount measurement method according to any one of claims 1 to 8,
A drive signal optimization method, comprising: an optimization step of optimizing a drive signal based on the one or more drive signals according to the discharge amount measured in the discharge amount measurement step.   The drive signal optimization method according to claim 9, wherein the measurement of the ejection amount is performed corresponding to the plurality of nozzles. A droplet discharge head for discharging droplets from a nozzle;
A placement unit for placing a droplet receiver that receives droplets discharged from the nozzle;
A liquid means comprising: a measuring means for observing the liquid droplet that has landed on one surface of the liquid droplet receiver from a direction along the one surface and measuring numerical data for specifying a side surface shape of the liquid droplet; Drop ejection device.   The droplet discharge device according to claim 11, further comprising a droplet amount calculation unit that geometrically calculates the droplet amount from the side surface shape. The measuring means includes an irradiating means for irradiating the droplet landed on one surface of the droplet receiver with flash light, and a direction along the one surface for the droplet landed on one surface of the droplet receiver. Imaging means for imaging from,
13. The droplet discharge device according to claim 11, wherein the flash irradiation is performed by irradiating the flash at a timing obtained by adding a predetermined delay time to the discharge timing of the droplet.

Images