JP2010115866A - Inkjet device and method of controlling delivery liquid amount - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for measuring easily and stably a delivery liquid amount delivered from every nozzle or every set of a plurality of nozzles. <P>SOLUTION: This device provided with an inkjet head includes a container provided in a position opposed to the inkjet head, for sampling a liquid droplet delivered from the inkjet head, and a luminous intensity measuring means for measuring an absorbance or a fluorescent luminous intensity of a liquid in the container, the delivery liquid amount from the inkjet head is determined based on the absorbance or the fluorescent luminous intensity measured by the luminous intensity measuring means, and the delivery liquid amount from the inkjet head is controlled based thereon. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an inkjet apparatus and a discharge liquid amount control method for landing and applying droplets on a substrate.

  The ink jet technology is a simple technology in which energy is given to a discharge liquid and liquid droplets are discharged from a nozzle toward a target substrate, and a micro liquid process can be easily constructed. The most common application is an ink jet recording apparatus that forms dots by ejecting and adhering ink droplets from an ink jet head to a recording medium, and printing an image using the set. On the other hand, in the inkjet technology, various application examples are expected depending on the function of the liquid to be discharged. For example, industrial possibilities such as a film forming process of an organic alignment film and a color filter in a manufacturing process of a flat panel display, and a circuit board wiring technique using a metal fine particle solution are being studied.

  In the inkjet technology, various types of liquid ejection methods have been devised, and a drop-on-demand type is one of them. The drop-on-demand type head is characterized by including a large number of nozzles for discharging droplets and a mechanism for applying energy (pressure) to the droplets for each nozzle. In addition to the drop-on-demand type, there is a continuous type. The continuous type is characterized by having a mechanism for continuously ejecting droplets and selectively collecting the droplets. At the same time as the liquid is pressurized and ejected from the nozzle opening, the liquid column ejected from the nozzle is separated into droplets by applying periodic pressure vibration. The flying droplet is selectively charged by electrostatic induction, and only the charged droplet is deflected in the electrostatic field and collected. Thus, the continuous type requires a mechanism for charging droplets, an electrostatic deflection, a mechanism recovery mechanism, and the like, and the apparatus has a complicated configuration. In contrast, the drop-on-demand type can reduce the size of the entire system.

  Even in the drop-on-demand type, methods such as a piezoelectric method, a thermal method, and an electrostatic method have been devised and put into practical use depending on the method of applying energy (pressure) to the liquid to be discharged. The piezoelectric method includes a piezoelectric element typified by PZT (lead zirconate titanate) in a pressure chamber for applying pressure to a liquid, and the pressure is applied to the liquid by mechanical strain generated by applying a voltage to the piezoelectric element. This is a method characterized by applying (Patent Document 1). On the other hand, in the thermal method, a pressure change caused by providing a heater in a pressure chamber and rapidly heating the heater to bring the liquid into a film boiling is used (Patent Document 2). The electrostatic method is a method in which one surface constituting the pressure chamber is formed by a diaphragm, and droplets are ejected by a pressure change using the bending due to the electrostatic force of the diaphragm (Patent Document 3). Furthermore, the piezoelectric method is classified into a push type (Patent Document 4), a shear type (Patent Document 5), and the like depending on the arrangement of the piezoelectric element with respect to the pressure chamber and the distortion of the used piezoelectric element.

  The drop-on-demand type head is characterized by being provided with a large number of nozzles, but it has been a problem to make the liquid discharge amount constant for each nozzle. For example, in a piezoelectric ink jet head, there are various factors such as the structure, processing and assembly accuracy of members such as flow paths, pressure chambers, and nozzles, as well as variations in the piezoelectric elements themselves to induce pressure changes and assembly uniformity. This is because the liquid discharge is affected. Therefore, conventionally, a means for controlling the mechanism for applying pressure to the pressure chambers communicating with each nozzle for each nozzle and adjusting the amount of liquid droplets discharged from each nozzle is required.

  In such a discharge droplet amount adjusting means, the droplet discharge amount for each nozzle or a plurality of nozzles is measured, and this is fed back to the pressure application mechanism of each nozzle to adjust the appropriate amount of liquid to be discharged. As means for estimating the discharge amount of the above-described droplets, a method of obtaining a droplet mass using a precision balance, a method of photographing a droplet flying with a high-speed camera, and calculating a volume from the two-dimensional image (Patent Document 6) ), A method of calculating the velocity and volume of a droplet from the amount of light or transmittance that is changed by the laser beam being incident on the region where the droplet flies and the laser beam passing through the laser beam (Patent Documents 7 and 8), Has been devised (see Patent Document 9) and the like.

As described above, in the drop-on-demand type head, the means for adjusting the amount of liquid droplets discharged from each nozzle by controlling the pressure fluctuation mechanism for each nozzle is discharged from each nozzle or a plurality of nozzles. A means for measuring the droplet volume is required.
However, the means devised so far require an expensive system such as a laser and a high-speed camera, and furthermore, because it is an optical approach to a micro area, it is affected by vibration and noise of the entire system. Cheap. Furthermore, in the means using a crystal resonator, there is a problem that the frequency is subjected to a very large change just by discharging the liquid directly onto the sensor and the reliability is lacking.

JP 2000-301722 A JP 2002-210975 A JP 2007-89299 A Japanese Patent Laid-Open No. 2003-112422 JP 2002-240304 A JP 2002-347224 A JP 2003-127430 A JP 2007-190865 A JP 2005-262450 A

  Accordingly, an object of the present invention is to provide a means for more simply and stably measuring an appropriate amount of liquid discharged from each nozzle or a plurality of nozzles as described above.

In order to solve the above problems, according to the present invention, as described in claim 1, in an apparatus including an inkjet head, droplets ejected from the inkjet head provided at a position facing the inkjet head are disposed. A container for sampling, and a photometric measuring means for measuring the absorbance or fluorescence of the liquid in the container, and the amount of liquid ejected from the inkjet head is determined from the absorbance or fluorescence measured by the photometric measuring means. It is determined and the amount of liquid discharged from the ink jet head is controlled.
According to a second aspect of the present invention, in the ink jet apparatus according to the first aspect, the measurement light used for the photometric measuring means is ultraviolet light.
In addition, according to a third aspect of the present invention, there is provided a method for controlling the amount of liquid ejected from an ink jet head, wherein the liquid droplet ejected from the ink jet head is disposed at a position facing the ink jet head. A step of sampling with a container for sampling droplets discharged from the head, a step of measuring the absorbance or fluorescence of the liquid in the container, and the ink jet head from the absorbance or fluorescence measured by the photometric means And a step of controlling the amount of liquid discharged from the inkjet head.
According to a fourth aspect of the present invention, in the method for controlling the amount of liquid discharged from the inkjet head according to the third aspect, the measurement light used in the step of measuring the luminous intensity is ultraviolet light. It is characterized by.

  According to the present invention, the amount of liquid droplets discharged from each nozzle in a drop-on-demand type head is stable and less susceptible to disturbance by measuring the liquid droplets discharged from the inkjet head by means of absorbance or fluorescence. Can be made.

Next, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration diagram of an inkjet apparatus according to the present invention.
As the ink jet head 101, a known one can be used. Here, a plurality of channels 102 including nozzles, pressure chambers, and actuators are provided side by side. A head controller 104 is connected to the ink jet head 101, and supplies a voltage to the actuator of each channel 102 and controls the movement of the head 101. The ink 103 is discharged from the head 101 to the measurement mechanism unit 105. The measurement mechanism unit 105 includes a droplet filter 106 having an opening for allowing only droplets from a specific channel 102 to pass through, and only the ink 103 ejected from the specific channel is included in the measurement mechanism unit. The sample is collected in a measurement cell 107 made of a translucent material such as acrylic resin or glass, which is a container for sampling droplets provided in a position facing the head 101 provided in 105. A solvent 108 that does not absorb in the measurement wavelength region such as water, alcohol (methanol, ethanol, isopropyl alcohol), acetone, hexane, or the like, in which the ink 103 is soluble, is injected into the measurement cell 107 in advance. Absorbance or fluorescence is measured with the droplet of ink 103 added to 108. This result is sent to the control unit 112, where the actual discharge amount is calculated, and this discharge amount is fed back to the head controller 104, and when it is necessary to adjust the discharge amount, the head controller The voltage from 104 to the actuator is controlled.

  The measurement cell 107 repeats the following steps from S1 to S5. First, the ink solvent 108 is dispensed into the measurement cell 107 (S1), and then the ink 103 ejected from the single channel 102 is dropped into this cell at a constant frequency for a predetermined time (S2). Thereafter, the solvent 108 and the ink 103 are uniformly stirred by the micro ultrasonic probe 109 (S3). Absorbance is measured with the spectrophotometer 111 as the measurement sample 101 by sufficiently stirring (S4). When the measurement is completed, it is washed and dried (S5), and the measurement of other channels 102 is repeated.

With the above configuration,
(1) The droplet 103 discharged from the inkjet head 101 is
(2) Sampling by the container 107 for sampling the droplet 103 ejected from the inkjet head 101 provided at a position facing the inkjet head 101;
(3) measuring the absorbance or fluorescence of the liquid in the container 107 (mixture of the solvent 108 and the droplet 103);
(4) Absorbance or fluorescence intensity is measured by the photometric measuring means 111, and the amount of discharge liquid actually discharged is determined from the obtained light intensity. In the control unit 112, the actual discharge liquid amount and the control unit 104 Compared with the instructed discharge amount, the control unit 104 controls the discharge liquid amount from the inkjet head 101.

ここで、εは固有の吸光係数、ｌは光路長である。このように、容易に濃度（Ｃ）つまりは液量を算出することが可能である。主に用いる波長領域としては紫外線、可視光線、赤外線が挙げられるが、その中でも、紫外線光を用いることが好ましい。
蛍光光度は、分子乃至イオンがＸ線、紫外線及び可視光線といった固有の波長の電磁波を吸収して電子が励起され、中間励起状態に落ちた後に基底状態に戻る過程で放出されるエネルギーの一部が発光したものを示す。
吸光度、蛍光度共に吐出させる液体材料に依存するため、必ずしも万能ではないが、実際に吐出させる材料が光学的に非吸収で蛍光特性も得られない場合は、当該吐出材料と同等の表面張力や密度、粘度等の特性を有する吸収能を有する計測用試料を用意すれば吸光若しくは蛍光光度によって、吐出される液適量を算出することが可能である。 The absorbance (A) can be measured by the wavelength of an arbitrary electromagnetic wave, is measured from incident light intensity (I ₀ ) and transmitted light intensity (I), and is expressed by the formula (1) from Lambert-Beer law. The

Here, ε is a specific extinction coefficient, and l is an optical path length. Thus, the concentration (C), that is, the liquid amount can be easily calculated. The wavelength region mainly used includes ultraviolet rays, visible rays, and infrared rays, among which ultraviolet rays are preferably used.
Fluorescence intensity is a part of energy released in the process that molecules or ions absorb electromagnetic waves with specific wavelengths such as X-rays, ultraviolet rays, and visible rays, and electrons are excited to return to the ground state after falling into an intermediate excited state. Indicates light emission.
Since it depends on the liquid material to be ejected for both absorbance and fluorescence, it is not necessarily all-purpose.However, if the material to be ejected is optically non-absorbing and fluorescence characteristics cannot be obtained, the surface tension and If a measurement sample having an absorption ability having characteristics such as density and viscosity is prepared, it is possible to calculate an appropriate amount of liquid to be discharged by absorption or fluorescence.

The inkjet head 101 used in the present invention is not limited to the structure described as long as the discharge amount can be controlled.
Further, the control unit 112 has a means for calculating the actual discharge amount from the absorbance or the fluorescence intensity, a means for calculating a difference between the actual discharge amount and the discharge amount instructed from the head controller 104, and A program for functioning means for instructing a specific control amount for the head controller 104 based on the difference and means for referring to a reference table for specifying the control amount of the inkjet head 101 is provided. It can be configured by a computer or the like.
The control unit 112 and the head controller 104 are integrally represented in the illustrated example, but may be separated as long as those having the functions described above are connected so as to function. .

  Further, in the measurement steps S1 to S5 shown by the measurement mechanism unit 105 in FIG. 1, the cleaning step S5 is performed, but the integrated amount of the appropriate amount of liquid from the specific channel 102 is measured except for the cleaning step S5. You may make it do. This is because the measurement accuracy can be improved by using the integrated value when the amount of the droplet 103 is very small.

  In FIG. 1, one channel is used as the specific channel 102, but a plurality of channels may be used.

(Example)
In this example, the apparatus described in the above embodiment is used, N-methylpyrrolidone (NMP) is used as a model of the ink 103, the discharge amount for each nozzle is calculated based on the absorption spectrum in ultraviolet light, and the discharge is performed. The example which adjusted the quantity is shown. As an actuator, a piezoelectric element using PZT (lead zirconate tannate) as a piezoelectric material was used.
The discharge amount calculated from the absorbance in the ultraviolet region when a drive voltage of 80 V was applied to all 64 channels 102 was the result shown in FIG. As a method for measuring absorbance, ethanol was filled in a quartz cell having an optical path length of 1 cm, NMP was discharged into the quartz cell, and absorbance at a wavelength of 200 nm was measured. In FIG. 2, the result plotted with a circle is the result. Also, in the same graph, the graph plotted with ■ is adjusted by the head controller 104 based on the measured discharge amount (◯) so that the discharge amount is 30 pL by the head controller 104. The subsequent discharge amount is shown.

A method for determining the applied voltage in order to control the discharge amount will be described below.
Since the magnitude of the applied voltage of the piezoelectric element and the amount of displacement thereof are approximated by a straight line, the approximate expression is calculated to determine the voltage corresponding to the ejection amount. In this example, the applied voltage was changed to 60, 80, and 100 V, the regression line was obtained from the discharge amount, and the voltage for discharging 30 pL was determined. The relationship between the voltage and the discharge amount in one channel of the channel 102 is shown in Table 1 and FIG.

From FIG. 3, the regression line of the discharge amount with respect to the voltage is
(Discharge rate [pL]) = 0.3383 x (Voltage [V])-0.6672
From this, it can be seen that a voltage of 90.694 V is necessary when discharging 30 pL. When the discharge amount is calculated using this voltage, it is 29.97 pL, and thus it can be seen that there is sufficient accuracy for discharging 30 pL.
By using the above method, it is possible to measure the discharge amount of droplets discharged from a specific channel, compare this with the control unit 112, and adjust the voltage applied to each channel 102.

1 is a schematic configuration diagram of an inkjet apparatus according to an embodiment of the present invention. The graph which shows the discharge amount of each channel of an Example, and the discharge amount after adjustment Graph showing the relationship between applied voltage and discharge rate of piezoelectric element

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Inkjet head 102 Channel 103 Ink 104 Head controller 105 Measurement mechanism part 106 Droplet filter 107 Measurement cell 108 Solvent 112 Control part

Claims (4)

  In an apparatus including an ink jet head, a container for sampling droplets ejected from the ink jet head provided at a position facing the ink jet head, and measuring the absorbance or fluorescence of the liquid in the container And measuring the discharge liquid amount of the inkjet head from the absorbance or fluorescence intensity measured by the light measurement means, and controlling the discharge liquid amount from the inkjet head. Inkjet device.   The inkjet apparatus according to claim 1, wherein the measurement light used for the light intensity measurement unit is ultraviolet light. Droplets ejected from the inkjet head
Sampling with a container for sampling droplets ejected from the inkjet head provided at a position facing the inkjet head;
A step of measuring the absorbance or fluorescence of the liquid in the container; and the amount of liquid ejected from the inkjet head is determined from the absorbance or fluorescence measured by the photometry means, and the amount of liquid ejected from the inkjet head is controlled. And a method for controlling the amount of liquid ejected from the ink jet head.   The method for controlling the discharge liquid amount according to claim 3, wherein the measurement light used in the step of measuring the luminous intensity is ultraviolet light.

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