JP2006297176A - Droplet ejection apparatus and its driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a droplet ejection apparatus capable of accurately forming a function film even if an ink viscosity is varied. <P>SOLUTION: The droplet ejection apparatus is provided with a viscosity measurement means 30 of the ink before ejection; and a control part 70 for determining a drive voltage wave form of an ink jet head 20 based on the viscosity measurement result of the viscosity measurement means 30. The control part 70 determines inclination of a negative slope part of the drive voltage wave form such that a delivery speed of the liquid drop from the ink jet head 20 becomes approximately constant and determines height of the negative slope part of the drive voltage wave form such that a weight after drying of the liquid drop ejected from the ink jet head 20 becomes approximately constant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a droplet discharge device and a driving method thereof.

An ink jet method has been developed as a method for forming functional films such as metal wirings and color filters. The ink jet method is a method of forming a functional film by ejecting ink containing a functional film forming material from an ink jet head. The ink jet head is provided with at least a nozzle for ejecting ink droplets, an ink chamber (pressure chamber) communicating with the nozzle, and a driving element such as a piezo element that causes a pressure change in the pressure chamber. Yes. Then, a driving voltage having a predetermined waveform is applied to the driving element, a pressure change is caused in the ink in the pressure chamber, the ink droplet is ejected from the nozzle, and the droplet is landed on the formation position of the functional film. Furthermore, a plurality of droplets are ejected while moving the inkjet head relative to the substrate on which the functional film is to be formed. Thereafter, if the discharged droplets are dried, a functional film having a predetermined shape is formed. By employing this ink jet method, it becomes possible to accurately apply a predetermined amount of ink to a predetermined position, and a functional film having excellent dimensional accuracy can be formed. In addition, the ink can be used efficiently, and the manufacturing cost can be reduced.
Japanese Patent Laid-Open No. 9-141892 Japanese Patent Laid-Open No. 7-148920

  When the above-described ink jet method is industrially applied to the formation of metal wirings, an ink to be ejected is prepared by dissolving a metal wiring forming material in a solvent. However, when the temperature of the ink changes or the ink is left for a long time, the solvent contained in the ink may evaporate and the ink viscosity may change significantly. Despite such changes in ink viscosity, when an inkjet head is driven with the same drive voltage waveform, the speed of the droplets ejected from the inkjet head changes or the weight of the ejected droplets after drying changes. There is a problem of doing. When the discharge speed of the droplet changes, the landing position of the droplet changes, and the functional film cannot be formed at a predetermined position. If the weight of the droplet after drying changes, the functional film cannot be formed into a predetermined shape.

  For this reason, in Patent Document 1, ink viscosity is measured in an ink supply tank disposed adjacent to the recording head, and the ink temperature always present in the recording head unit is controlled, so that an ink having a constant appropriate viscosity characteristic is always obtained from the recording head. Techniques for discharging are proposed. However, when the ink temperature is controlled, the response speed becomes slow and it is impossible to cope with a sudden change in viscosity.

  Patent Document 2 proposes a technique in which a temperature sensing element for temperature detection is mounted on an ink jet head, the drive waveform of the ink jet head is finely adjusted according to a temperature change, and ink droplet weight is stably ejected. Yes. However, this method cannot cope with the case where the viscosity changes due to factors other than temperature.

  The present invention has been made to solve the above problems, and provides a droplet discharge device and a driving method thereof capable of forming a functional film with high accuracy even when the ink viscosity changes. Objective.

In order to achieve the above object, a liquid droplet ejection apparatus according to the present invention is a liquid droplet ejection apparatus that ejects ink droplets from an inkjet head, the viscosity measuring means for measuring the viscosity of the ink before ejection, And a controller that determines a drive voltage waveform of the inkjet head based on a result of measuring the viscosity of the ink by a viscosity measuring unit.
According to this configuration, even if the ink viscosity changes, the droplet discharge conditions can be adjusted accordingly. Thereby, a functional film can be formed with high accuracy.

The viscosity measuring unit preferably measures the viscosity of the ink inside the ink jet head.
In particular, the viscosity measuring means preferably measures the viscosity of the ink in a pressure chamber that applies pressure to the ink in order to eject the droplets.
According to this configuration, since the viscosity of the ink ejected as a droplet most recently is measured, the droplet ejection conditions can be suitably adjusted. Thereby, a functional film can be formed with high accuracy.

The controller preferably determines the width of the negative gradient portion of the drive voltage waveform so that the ejection speed of the droplets from the inkjet head becomes a predetermined value.
According to this configuration, even when the ink viscosity changes, the droplet ejection speed can be set to a predetermined value. Thereby, it becomes possible to land a droplet on a predetermined position, and a functional film can be accurately formed on a predetermined position.

The controller may determine the height of the negative gradient portion of the drive voltage waveform so that the weight after drying of the droplets ejected from the inkjet head becomes a predetermined value.
According to this configuration, even if the ink viscosity changes, the weight of the discharged droplet after drying can be set to a predetermined value. Thereby, a functional film can be accurately formed in a predetermined shape.

On the other hand, the method for driving a droplet discharge device according to the present invention is a method for driving a droplet discharge device that discharges ink droplets from an inkjet head, the step of measuring the viscosity of the ink before discharge, and the ink And a step of determining a drive voltage waveform of the inkjet head based on the measurement result of the viscosity of the inkjet head.
According to this configuration, even if the ink viscosity changes, the droplet discharge conditions are adjusted accordingly, so that the functional film can be formed with high accuracy.

  Embodiments of the present invention will be described below with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

(Droplet discharge device)
FIG. 1 is a perspective view of a droplet discharge device. In FIG. 1, the X direction is the left-right direction of the base 12, the Y direction is the front-rear direction, and the Z direction is the up-down direction. The droplet discharge device 10 includes a table 46 on which a substrate 31 on which a functional film is to be formed is placed, an inkjet head (hereinafter simply referred to as “head”) 20 that discharges droplets onto the substrate 31, and the head 20. And a control unit 70 for driving the motor.

  The table 46 on which the substrate 31 is placed can be moved and positioned in the Y direction by the first moving means 14, and can be swung and positioned in the θz direction by the motor 44. One head 20 can be moved and positioned in the X direction by the second moving means 16, and can be moved and positioned in the Z direction by the linear motor 62. The head 20 can be swung and positioned in the α, β, and γ directions by motors 64, 66, and 68, respectively. Thereby, the droplet discharge device 10 can accurately control the relative position and posture of the substrate 31 placed on the table 46 and the ink discharge surface 20P of the head 20. .

  The droplet discharge device is provided with a capping unit 22 for capping the ink discharge surface 20P during standby of the droplet discharge device 10 in order to prevent the nozzles in the head 20 from drying. Further, in order to remove clogging of the nozzles in the head 20, a cleaning unit 24 for sucking the inside of the nozzles is provided. The cleaning unit 24 can also wipe the ink discharge surface 20P in order to remove dirt on the ink discharge surface 20P in the head 20.

(Inkjet head)
FIG. 2 is a side sectional view of the inkjet head. The head 20 mainly includes a head main body 90, a nozzle plate 92 mounted on one surface of the head main body 90, and piezo elements 98 mounted on various surfaces of the head main body 90.

  A plurality of nozzles 91 for discharging droplets are arranged in an array on the nozzle plate 92 that forms the ink discharge surface. The head main body 90 is formed with a plurality of pressure chambers 93 communicating with the nozzles 91. Each pressure chamber 93 is connected to a reservoir 95, and the reservoir 95 is connected to an ink inlet 96. The ink 21 is supplied from the ink introduction port 96 through the reservoir 95 to each pressure chamber 93. On the other hand, a flexible diaphragm 94 is attached to the upper end surface of the head main body 90. Piezo elements 98 are provided on opposite sides of the pressure chambers 93 with the diaphragm 94 interposed therebetween. The piezo element 98 is obtained by sandwiching a piezoelectric material such as PZT between electrodes. The electrodes are connected to a control unit 70 described later.

  When a driving voltage is applied from the control unit 70 to the piezo element 98, the piezo element 98 is expanded or contracted. When the piezoelectric element 98 contracts and deforms, the pressure in the pressure chamber 93 decreases, and the ink 21 flows from the reservoir 95 into the pressure chamber 93. Further, when the piezo element 98 is expanded and deformed, the pressure in the pressure chamber 93 is increased, and the droplet of the ink 21 is ejected from the nozzle 91. The droplet discharge conditions can be controlled by controlling the driving voltage applied to the piezo element 98.

  In addition to the above-described piezo method for changing the pressure in the pressure chamber by deformation of the piezo element, a method for changing the pressure in the pressure chamber by heating the ink to generate bubbles (bubbles), etc. Various known techniques can be applied. Of these, the piezo method is superior in that it does not adversely affect the composition of the material because the ink is not heated.

(Viscosity measuring means)
Inside the head 20 described above, viscosity measuring means 30 for measuring the viscosity of the ink before ejection is disposed. A known viscosity sensor can be employed as the viscosity measuring means 30. By arranging the measurement part at the tip of the viscosity sensor in the pressure chamber 93, the viscosity of the ink in the pressure chamber 93 can be measured. The head 20 is provided with a plurality of pressure chambers 93, and the viscosity measuring means 30 may be provided for one of the pressure chambers. In FIG. 2, in addition to the viscosity measuring unit 30 that measures the viscosity of the ink in the pressure chamber 93, a viscosity measuring unit that measures the viscosity of the ink in the reservoir 95 and the ink inlet 96 is provided. The viscosity measuring unit 30 is connected to a control unit 70 described below.

(Control part)
FIG. 3 is a block diagram of the control unit. The control unit 70 determines the drive voltage waveform of the head 20 based on the viscosity measurement result of the viscosity measuring unit 30, and mainly includes an A / D converter 71, a CPU 72, and a drive circuit 76. Yes.
The A / D converter 71 converts the viscosity measurement result of the viscosity measuring means 30 into a digital signal. The CPU 72 includes a viscosity comparison unit 73 and a waveform determination unit 74. The viscosity comparison unit 73 calculates a difference by comparing the viscosity measurement result with the standard viscosity of the ink. The waveform determination unit 74 determines the drive voltage waveform of the head 20 from the calculated difference. The determination method will be described later. The drive circuit 76 includes a D / A converter 77 and an amplifier circuit 78. The D / A converter converts the determined drive voltage waveform of the head 20 into an analog signal. The amplifier circuit 78 amplifies the drive voltage waveform and outputs it to the head.

(Droplet ejection device driving method)
Next, a method for driving the above-described droplet discharge device will be described.
As a premise, the standard viscosity of the ink to be ejected is set in advance. This standard viscosity may be set to the viscosity of the ink at the discharge start time of the droplet discharge device in the standard state.

Further, a standard waveform of the drive voltage applied to the head is determined in advance.
FIG. 4A is an explanatory diagram of the driving voltage waveform of the head. The drive voltage waveform mainly includes a first positive gradient portion w1, a negative gradient portion w2, and a second positive gradient portion w3. In the first positive gradient portion w1 and the second positive gradient portion w3, the piezoelectric element contracts and deforms, the pressure in the pressure chamber decreases, and ink flows into the pressure chamber. In the negative gradient portion w2, the piezoelectric element 98 expands and deforms to increase the pressure in the pressure chamber, and ink is ejected from the nozzle.

  As a standard waveform of such a drive voltage, a waveform is determined so that when a standard viscosity ink is used, a predetermined amount of droplets are applied to a predetermined position. In order to apply a droplet to a predetermined position, it is necessary to set the velocity of the discharged droplet to a predetermined value, and the width T1 of the negative gradient portion w2 that determines the droplet discharge time is determined in advance. Further, in order to apply a predetermined amount of droplets, it is necessary to set the volume of the ejected droplets to a predetermined value, and the height V1 of the negative gradient portion w2 that determines the droplet ejection volume is determined in advance. . The standard waveform determined in this way is applied to the head, and droplet discharge by the droplet discharge device is started.

  In the droplet discharge device, there is a possibility that the solvent contained in the ink evaporates due to a change in the temperature of the ink or the ink is left for a long time, and the ink viscosity changes significantly. Despite such changes in ink viscosity, when the head is driven with the same drive voltage waveform, the speed of the droplets ejected from the head changes, or the weight of the ejected droplets after drying changes. Will do. When the discharge speed of the droplet changes, the landing position of the droplet changes, and the functional film cannot be formed at a predetermined position. If the weight of the droplet after drying changes, the functional film cannot be formed into a predetermined shape.

  Therefore, the drive voltage waveform of the head is adjusted in accordance with the change in ink viscosity. The timing for adjusting the drive voltage waveform is arbitrary, and may be performed for each droplet, for each substrate, or for each lot. Further, the drive voltage waveforms of all the piezo elements formed on the head may be similarly adjusted in accordance with the change in the ink viscosity in one pressure chamber formed on the head.

  First, the viscosity measuring means 30 shown in FIG. 2 measures the viscosity of the ink inside the head 20 and outputs it to the control unit 70. In this embodiment, at least the viscosity of the ink in the pressure chamber 93 is measured. This is because the pressure chamber 93 is closest to the nozzle 91, so that it is possible to measure the viscosity of the ink discharged as a droplet most recently, and the droplet discharge conditions can be suitably adjusted. However, if the viscosity measuring means 30 is disposed in the pressure chamber 93, the flow of ink inside the pressure chamber 93 may be hindered, and a predetermined amount of droplets may not be ejected from the nozzle 91. In this case, it is only necessary to measure the viscosity of the ink in the ink flow path such as the reservoir 95 and the ink inlet 96 on the upstream side of the pressure chamber 93. For example, when the ink viscosity in the reservoir 95 is measured, the relationship between the ink viscosity in the reservoir 95 and the ink viscosity in the pressure chamber 93 is obtained in advance through experiments or the like, and the measurement result of the ink viscosity in the reservoir 95 The ink viscosity may be predicted and output to the control unit 70.

  Next, in the A / D converter 71 of the control unit 70 shown in FIG. 3, the input measurement result of the ink viscosity is converted into a digital signal. Next, the viscosity comparison unit 73 of the CPU 72 compares the measurement result of the ink viscosity with a predetermined standard viscosity, and calculates the difference between the two. When the difference calculated here is sufficiently small, the drive voltage waveform described below need not be adjusted.

  Next, the waveform determination unit 74 of the CPU 72 determines the drive voltage waveform of the head. As the ink viscosity increases, the frictional resistance when passing through the nozzles increases, so the droplet ejection speed decreases. Therefore, the width of the negative gradient portion w2 of the drive voltage waveform is adjusted as shown in FIG. 4B in order to maintain the droplet discharge speed at a substantially constant predetermined value. That is, the slope of the negative slope portion w2 is increased and its width is decreased from T1 to T2. Specifically, the relationship between the difference between the measurement result of the ink viscosity with respect to the standard viscosity and the adjustment amount of the drive voltage waveform is obtained in advance through experiments or the like. Then, an adjustment amount of the drive voltage waveform is obtained from the difference calculated by the viscosity comparison unit, and the drive voltage waveform is determined. Conversely, when the ink viscosity decreases, the droplet ejection speed increases. In this case, the width of the negative gradient portion w2 of the drive voltage waveform is increased in order to maintain the droplet discharge speed at a substantially constant predetermined value.

The increase in the ink viscosity is considered to occur when the ink solvent in the head evaporates from the nozzle or the like. In this case, since the ink density increases, the weight of the discharged droplets after drying increases even if the droplet discharge amount is kept constant. Therefore, as shown in FIG. 4C, the height of the negative gradient portion w2 of the drive voltage waveform is adjusted in order to maintain the dried weight of the discharged droplets at a substantially constant predetermined value. That is, the maximum voltage of the negative gradient portion w2 is decreased or the minimum voltage is increased, and the height is decreased from V1 to V2. Specifically, the relationship between the difference between the measurement result of the ink viscosity with respect to the standard viscosity and the adjustment amount of the drive voltage waveform is obtained in advance through experiments or the like. And the adjustment amount of a drive voltage waveform is calculated | required from the difference calculated in the viscosity comparison part, and a drive voltage waveform is determined. On the other hand, when the ink viscosity decreases, the weight of the discharged droplet after drying decreases. In this case, the height of the negative gradient portion w2 of the drive voltage waveform is increased in order to maintain the dried weight of the discharged droplets at a substantially constant predetermined value.
As described above, the drive voltage waveform is determined.

Next, the determined drive voltage waveform is converted into an analog signal by the D / A converter 77 of the drive circuit shown in FIG. 3, amplified by the amplifier circuit 78, and output to the head 20.
Then, droplets are ejected from the head 20 in the droplet ejection apparatus 10 shown in FIG. A plurality of droplets are ejected while moving the head 20 relative to the substrate 31. Thereafter, the discharged droplets are dried, whereby a functional film having a predetermined shape is formed on the surface of the substrate 31.

  In the present embodiment, the driving voltage waveform of the head 20 is determined so that the ejection speed of the droplets from the head 20 is substantially constant based on the measurement result of the ink viscosity by the viscosity measuring unit. Therefore, even if the ink viscosity changes, it is possible to eject droplets at a substantially constant ejection speed. Thereby, it becomes possible to land a droplet on a predetermined position, and a functional film can be formed on a predetermined position.

  In the present embodiment, the driving voltage waveform of the head 20 is determined based on the measurement result of the ink viscosity by the viscosity measuring unit so that the weight of the discharged droplet after drying is substantially constant. Therefore, even if the ink viscosity changes, the weight of the discharged droplet after drying can be made substantially constant. Thereby, a functional film can be formed in a predetermined shape.

  The droplet discharge device and the driving method thereof according to the present embodiment can be industrially applied to the formation of metal wiring, the formation of color filters, the formation of organic EL elements, the application of liquid crystal materials, etc. Can also be applied. In any case, the functional film can be formed with high accuracy regardless of the change in ink viscosity.

  The technical scope of the present invention is not limited to the above-described embodiments, and includes various modifications made to the above-described embodiments without departing from the spirit of the present invention. That is, the specific materials and configurations described in the embodiments are merely examples, and can be changed as appropriate.

It is a perspective view of a droplet discharge device. It is side surface sectional drawing of an inkjet head. It is a block diagram of a control part. It is explanatory drawing of the drive voltage waveform of a head.

Explanation of symbols

  20. Inkjet head 30 ... Viscosity measuring means 70 ... Control unit

Claims (6)

A droplet discharge device that discharges ink droplets from an inkjet head,
Viscosity measuring means for measuring the viscosity of the ink before ejection;
A control unit for determining a drive voltage waveform of the inkjet head based on a measurement result of the viscosity of the ink by the viscosity measuring unit;
A droplet discharge apparatus comprising:   The liquid droplet ejection apparatus according to claim 1, wherein the viscosity measuring unit measures the viscosity of the ink inside the ink jet head.   3. The droplet discharge device according to claim 1, wherein the viscosity measuring unit measures the viscosity of the ink in a pressure chamber that applies pressure to the ink to discharge the droplet. 4.   4. The control unit according to claim 1, wherein the controller determines a width of a negative gradient portion of the drive voltage waveform so that a discharge speed of the droplets from the inkjet head becomes a predetermined value. 5. The droplet discharge device according to any one of the above.   The control unit determines a height of a negative gradient portion of the drive voltage waveform so that a weight after drying of the droplets discharged from the inkjet head becomes a predetermined value. The droplet discharge device according to claim 4. A method of driving a droplet discharge device that discharges ink droplets from an inkjet head,
Measuring the viscosity of the ink before ejection;
Determining a drive voltage waveform of the inkjet head based on the measurement result of the viscosity of the ink;
A method for driving a droplet discharge device, comprising:

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