KR102601539B1 - Inkjet head, inkjet apparatus using the same, and method for manufacturing device - Google Patents

Abstract

[assignment]
The object is to provide an inkjet head capable of both alleviating discharge abnormalities caused by fluid crosstalk occurring between a plurality of discharge elements and maintaining a desired discharge liquid droplet volume.
[Solution]
A nozzle for discharging droplets, a first pressure chamber connected to the nozzle, a second pressure chamber on the supply side and a second pressure chamber on the discharge side connected to the first pressure chamber, and a third pressure chamber on the supply side connected to the second pressure chamber on the supply side, Article 1: a third pressure chamber on the discharge side connected to the second pressure chamber on the discharge side, an energy generating element that provides discharge force to the liquid in the first pressure chamber, and a supply side between the first pressure chamber and the second pressure chamber on the supply side. a discharge-side first fastener between the first pressure chamber and the discharge-side second pressure chamber, a supply-side second fastener between the supply-side second pressure chamber and the supply-side third pressure chamber, and the discharge-side second pressure chamber. An inkjet head having a plurality of discharge units including a discharge-side second fastener between the chamber and the discharge-side third pressure chamber.

Description

Inkjet head and inkjet apparatus and device manufacturing method using the same {INKJET HEAD, INKJET APPARATUS USING THE SAME, AND METHOD FOR MANUFACTURING DEVICE}

The present invention relates to an inkjet head, an inkjet apparatus using the same, and a method of manufacturing a device.

A drop-on-demand type inkjet head is known as an inkjet head that can apply the required amount of ink when needed according to an input signal. In particular, a piezoelectric (piezoelectric element) type drop-on-demand type inkjet head generally includes an ink supply passage, a plurality of pressure chambers connected to the ink supply passage and having nozzles, and a piezoelectric device that applies pressure to the ink filled in the pressure chamber. It has elements.

Figures 1(a) and 1(b) show the cross-sectional structure of a typical inkjet head.

The inkjet head includes a plurality of nozzles 100 that discharge liquid droplets, a pressure chamber 110 communicating with the nozzles, a partition wall 111 that divides the pressure chambers corresponding to different nozzles, and a diaphragm that forms part of the pressure chamber ( 112), a piezoelectric element 130 that vibrates the diaphragm 112, a piezoelectric member 140 that supports the partition 111, and a common electrode (not shown) that applies a voltage to the piezoelectric element 130. have In addition, although not shown, it has an inlet for liquid.

The piezoelectric element 130 and the piezoelectric member 140 supporting the partition wall 111 are separated from one piezoelectric member by dicing. The nozzles 100 of the inkjet head have a diameter of 10 μm to 50 μm, and 100 to 300 holes are lined up at intervals of 100 μm to 500 μm.

The inkjet head configured in this way operates as follows. When a voltage is applied between the common electrode (not shown) on the back side of the piezoelectric element 130 and the piezoelectric element 130, the piezoelectric element 130 changes from the state of FIG. 1(a) to that of FIG. 1(b). transformed into a state. If the rightmost piezoelectric element 130 in FIG. 1(b) is deformed (the lower part of the piezoelectric element 130 is deformed), the volume of the pressure chamber 110 becomes smaller, allowing pressure to be applied to the liquid. With that pressure, the ink present in the pressure chamber 110 is discharged to the outside as droplets 150.

In addition, in the type of inkjet head that circulates ink, the inkjet head has a liquid inlet and outlet (not shown), and discharges ink while circulating ink. The effect of circulating ink is explained below.

The ink near the nozzle is always in contact with the atmosphere. Since the contact area is very small, evaporation of the ink solvent cannot be ignored. As the solvent of the ink evaporates, the solid content concentration of the ink increases, and as a result, the viscosity of the ink increases, making normal ejection of ink difficult. Here, by circulating the ink near the nozzle, the ink whose viscosity has increased can always be replaced, so the ink discharged near the nozzle is always maintained at a normal ink viscosity. This makes it possible to suppress nozzle clogging and perform normal ejection.

The structure of the inkjet head may be a structure using a thin film piezoelectric element. Figures 2(a) and 2(b) are diagrams showing the structure of a thin film type inkjet head. In Figure 2(a), a nozzle 200 for discharging liquid, a pressure chamber 210 communicating with the nozzle, and a common pressure chamber 230 supplying liquid to the pressure chamber are connected. A thin film piezoelectric element 220 is formed on the top of the diaphragm 212, which forms part of the pressure chamber. The inkjet head configured in this way operates as follows. When voltage is applied to the thin film piezoelectric element 220, the thin film piezoelectric element 220 is transformed from the state of FIG. 2(a) to the state of FIG. 2(b). When the thin film piezoelectric element 220 is deformed, the volume of the pressure chamber 210 becomes smaller, allowing pressure to be transmitted to the liquid. The liquid droplet 150 is discharged by that pressure.

An inkjet head with such a flow path structure drives one piezoelectric element to discharge ink from a nozzle, and the flow of ink at the time of discharge affects other nozzles communicating with the same flow path through a common flow path, causing ejection to occur. A phenomenon such as unstable crosstalk occurs.

Figure 3 shows a cross-sectional view of the inkjet head described in Patent Document 1. Regarding the problem of crosstalk, Patent Document 1 includes a plurality of nozzles 500 that discharge liquid droplets, a plurality of pressure chambers 501 installed corresponding to the plurality of nozzles 500, and a discharge force to the liquid in the pressure chamber. In the inkjet head provided with a plurality of energy generating elements 502 that provide a common flow path 503 for supplying liquid to a plurality of pressure chambers 501, each pressure chamber 501 and a common flow path ( A configuration of installing a fastening part 504 installed in an individual flow path portion connecting 503) is disclosed.

When the pressure wave generated in the pressure chamber 501 passes through the tightening part 504, it is attenuated and becomes difficult to transmit to the pressure chamber 501 of another nozzle, thereby reducing crosstalk.

Japanese Patent Publication No. 2012-11653

However, in the inkjet head shown in Patent Document 1, the flow path resistance in the tightening portion 504 is greater than the flow path resistance of the nozzle 500, and the pressure generated by the vibration of the energy generating element 502 flows to the nozzle 500. It is delivered.

As a result, the droplet volume discharged from the nozzle 500 may become too large, making it impossible to maintain the desired droplet volume.

Additionally, in an inkjet head that can eject very small droplets with a droplet volume of about 1 picoliter, the diameter of the nozzle 500 is about 10 μm, and it is difficult to process holes smaller than this while maintaining processing accuracy.

Therefore, the object of the present application is to provide an inkjet head capable of both alleviating discharge abnormalities due to fluid crosstalk occurring between a plurality of nozzles and maintaining the desired discharge liquid droplet volume, and an inkjet device using the same and a method of manufacturing the device. will be.

In order to solve the above problem, a nozzle for discharging liquid droplets, a first pressure chamber connected to the nozzle, a second pressure chamber on the supply side and a second pressure chamber on the discharge side connected to the first pressure chamber, and a second pressure chamber on the supply side, The third pressure chamber on the supply side is connected to the third pressure chamber on the discharge side, the third pressure chamber on the discharge side is connected to the second pressure chamber on the discharge side, an energy generating element that provides discharge force to the liquid in the first pressure chamber, the first pressure chamber and the A first fastener on the supply side between the second pressure chamber on the supply side, a first fastener on the discharge side between the first pressure chamber and the second pressure chamber on the discharge side, and a second fastener on the supply side between the second pressure chamber on the supply side and the third pressure chamber on the supply side. A plurality of discharge units including a fastener, a discharge-side second fastener between the discharge-side second pressure chamber and the discharge-side third pressure chamber, and each of the supply-side third pressure chambers of the plurality of discharge units. An inkjet head is used having a supply-side common flow path for connecting and a discharge-side common flow path for connecting the discharge-side third pressure chambers of each of the plurality of discharge units.

In addition, a nozzle for discharging liquid droplets, a first pressure chamber connected to the nozzle, a second pressure chamber on the supply side and a second pressure chamber on the discharge side connected to the first pressure chamber, and a third pressure chamber on the supply side connected to the second pressure chamber on the supply side. A pressure chamber, an energy generating element that provides discharge force to the liquid in the first pressure chamber, a first fastener between the first pressure chamber and the second pressure chamber on the supply side, and a second pressure chamber on the discharge side and the first pressure chamber. A plurality of discharge units including a first tightening part between chambers, a second tightening part between the supply-side second pressure chamber and the supply-side third pressure chamber, and between each of the supply-side third pressure chambers of the plurality of discharge units. An inkjet head is used having a supply-side common flow path for connecting and a discharge-side common flow path for connecting the discharge-side second pressure chambers of each of the plurality of discharge units.

In addition, the inkjet head and the drive control means for generating a drive voltage signal to be applied to the energy generating element to control the ejection operation of the inkjet head, and a conveyance means for moving the inkjet head and the drawing medium relative to each other. An inkjet device is used.

According to the inkjet head and inkjet device of the present invention, fluid crosstalk that mutually occurs between a plurality of nozzles can be alleviated. Additionally, it becomes possible to maintain the desired micro-droplet volume, and high-precision droplet discharge can be realized. As a result, the printing quality is improved.

1 is a diagram showing (a) the structure of a conventional bulk inkjet head, and (b) the state of the head in the bulk inkjet head (a) when voltage is applied to the piezoelectric element.
FIG. 2 is a diagram showing (a) the structure of a conventional thin film inkjet head and (b) the state of the head in the thin film inkjet head (a) when voltage is applied to the piezoelectric element.
Figure 3 is a cross-sectional view of the inkjet head of Patent Document 1.
FIG. 4 is (a) a cross-sectional view schematically showing the configuration of the inkjet head according to the embodiment, (b) a cross-sectional view of the
Figure 5 is a diagram showing the speed deviation of the inkjet head in Example 1.
Figure 6 is a cross-sectional view of the inkjet head of Comparative Example 1.
Figure 7 is a diagram showing the speed deviation of the inkjet head of Comparative Example 1.
Figure 8 is a cross-sectional view of the inkjet head of Example 2.
Figure 9 is a diagram showing the speed deviation of the inkjet head in Example 2.
Figure 10 is a cross-sectional view of the inkjet head of Comparative Example 2.
Figure 11 is a diagram showing the speed deviation of the inkjet head of Comparative Example 2.
Figure 12 is a cross-sectional view of the inkjet head of Comparative Example 3.
13 is a diagram showing the speed deviation of the inkjet head of Comparative Example 3.
14 is a cross-sectional view of the inkjet head of Embodiment 2.
Figure 15 is a diagram showing the relationship between particle size and sedimentation speed in Embodiment 2.
16 is a side view of the inkjet device of the embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention will be described with reference to the drawings.

(Embodiment 1)

＜Configuration of the inkjet head＞

FIG. 4(a) is a cross-sectional view schematically showing the configuration of the inkjet head according to Embodiment 1. FIG. 4(b) is a cross-sectional view of the XY cross-section of FIG. 4(a). Figure 4(c) is a top view of the entire inkjet head.

Here, the inkjet head 10 that ejects ink droplets is explained as an example, but in this embodiment, the liquid used for ejection is not limited to ink.

The inkjet head 10 has a nozzle 12 serving as an ink ejection port, and a first pressure chamber 14 communicating with the nozzle 12. The first pressure chamber 14 has an actuator 30, that is, an energy generating element.

As a flow path on the supply side of ink to the first pressure chamber 14, there are the following components. There is a second pressure chamber (15a) on the supply side that communicates with the first pressure chamber (14) through a first fastener (20a) on the supply side that allows liquid to enter and exit the first pressure chamber (14). Additionally, there is a third supply-side pressure chamber 16a communicating with the second supply-side pressure chamber 15a through the second supply-side fastener 22a.

As a flow path on the discharge side of ink from the first pressure chamber 14, there are the following components. There is a second pressure chamber (15b) on the discharge side that communicates with the first pressure chamber (14) through a first fastener (20b) on the discharge side that allows liquid to enter and exit the first pressure chamber (14). Additionally, there is a third discharge-side pressure chamber 16b communicating with the second discharge-side pressure chamber 15b through the second discharge-side fastener 22b.

It is preferable that the supply side flow path and the discharge side flow path are installed to face each other, with the first pressure chamber 14 as the center. In addition, it is preferable that the first pressure chamber 14, the supply side flow path, and the discharge side flow path are arranged in a straight line and arranged parallel to the lower surface of the inkjet head 10.

The first pressure chamber 14 and the ink discharge-side flow path and supply-side flow path are combined to form one discharge unit 11. The inkjet head 10 has a plurality of discharge units 11 arranged in parallel. Additionally, there is a supply-side common passage 51a that communicates the supply-side third pressure chamber 16a of the plurality of discharge units 11. Additionally, there is a discharge-side common passage 51b that communicates the discharge-side third pressure chamber 16b of the plurality of discharge units 11.

The nozzle 12 is a through hole for discharging ink, and its diameter is about 5 to 30 μm. The processing method is a method such as laser processing, etching, or punching.

The first pressure chamber 14 has the function of appropriately collecting the pressure generated by the vibration of the actuator 30. The collected pressure changes depending on the volume of the first pressure chamber 14 or the flow path resistance of the first tightening part 20a on the supply side and the first tightening part 20b on the discharge side. For this reason, it is necessary to optimize the volume of the first pressure chamber 14, etc., depending on the volume and speed of the liquid droplet to be discharged.

Supply side second pressure chamber (15a), discharge side second pressure chamber (15b), supply side third pressure chamber (16a), discharge side third pressure chamber (16b) and supply side common flow path (51a), discharge side supply passage ( 51b) becomes the path through which ink passes.

These pressure chambers and flow paths are produced by thermal diffusion bonding of metal plates processed by etching, etc., or etching of silicon materials, respectively.

＜Supply side damper (25a), discharge side damper (25b)＞

The following substrate may be located in at least one of the supply side flow path and the discharge side flow path. Preferably on both sides.

In addition, at least one of the walls forming the supply-side second tightening part 22a, the discharge-side second tightening part 22b, the supply-side second pressure chamber 15a, and the discharge-side second pressure chamber 15b is elastic. It is formed by this large plate.

They are the supply-side second pressure chamber 15a, the supply-side damper 25a and the discharge-side damper 25b, which absorb vibration waves existing in the discharge-side second pressure chamber 15b.

The supply side damper 25a and the discharge side damper 25b may be a thin metal plate or a resin film, and are not limited to materials. It is installed vertically in the Z direction. The supply side damper 25a and the discharge side damper 25b disposed in the first pressure chamber 14 are maintained by a highly rigid plate 26 (vibration prevention plate). For this reason, there is no dumping effect of the vibration waves, and the vibration waves necessary for ink ejection are not attenuated.

In addition, the supply side damper 25a and the discharge side damper 25b are unnecessary in the first pressure chamber 14, but for the sake of forming the supply side common flow path 51a, the discharge side common flow path 51b, etc. by etching, It is placed.

Meanwhile, the supply side damper 25a disposed in the supply side second pressure chamber 15a, the discharge side second pressure chamber 15b, the supply side third pressure chamber 16a, the discharge side third pressure chamber 16b, and the discharge side third pressure chamber 16b. The damper 25b is not held by the highly rigid plate 26 (vibration damping plate), but its ends are only held in a hollow state. The supply-side damper 25a and the discharge-side damper 25b are in a hollow state, and the supply-side second pressure chamber 15a, the discharge-side second pressure chamber 15b, the supply-side third pressure chamber 16a, and the discharge side. Vibration waves existing in the third pressure chamber 16b are attenuated by the dumping effect, and fluid cross talk occurring in interaction with the adjacent nozzle 12 is alleviated.

<Position of the supply side first tightening part 20a, discharge side first tightening part 20b, supply side second tightening part 22a, and discharge side second tightening part 22b in the Z direction>

As the Z-direction positions of the supply-side first tightening part 20a, the discharge-side first tightening part 20b, the supply-side second tightening part 22a, and the discharge-side second tightening part 22b are different, the actuator 30 The vibration wave generated by the vibration passes through the first tightening part 20a on the supply side and the first tightening part 20b on the discharge side and reaches the second pressure chamber 15a on the supply side and the second pressure chamber 15b on the discharge side, After that, it passes through the supply side second tightening part 22a and the discharge side second tightening part 22b.

As a result, the direction in which the vibration wave travels has many components going directly to the surfaces of the supply side damper 25a and the discharge side damper 25b.

In addition, the different positions in the Z direction mean that the straight line connecting the supply-side first tightening part 20a and the supply-side second tightening part 22a, the discharge-side first tightening part 20b and the discharge-side second tightening part 22b ), each of the straight lines (dotted arrows in FIG. 4(a)) is parallel to the plane perpendicular to the discharge direction of the droplet from the nozzle 12 (the plane of the damper 25 in FIG. 4(a)). It means not. Alternatively, it means that each is not parallel to the flow direction of ink.

Additionally, the discharge direction is parallel to the Z direction. This direction is also perpendicular to the lower surface of the nozzle 12 in FIG. 4(a). In this case, the supply-side first tightening part 20a is farther away from the supply-side damper 25a than the supply-side second tightening part 22a.

The relationship between the direction of vibration wave movement and the direction parallel to the surfaces of the supply side damper 25a and the discharge side damper 25b was analyzed as a fluid. As a result, it was found that the attenuation effect of the vibration wave was large if the direction of movement of the vibration wave was straight to the surfaces of the supply side damper 25a and the discharge side damper 25b.

Therefore, in the structure of the embodiment, the dumping effect increases. The supply side damper 25a and the discharge side damper 25b are arranged to exert the greatest damping effect on the flow of ink in the discharge direction.

<Path resistance of the second tightening part (22a) on the supply side and the first tightening part (20a) on the supply side>

The flow path resistance of the second tightening part 22a on the supply side is greater than the flow resistance of the first tightening part 20a on the supply side. Influence on other discharge units 11 is prevented by the supply-side second tightening portion 22a.

Similarly, the flow path resistance of the second discharge-side throttle 22b is greater than the flow path resistance of the first discharge-side throttle 20b.

＜Overall composition＞

Although FIG. 4(a) shows only one discharge unit 11, that is, only the periphery of one nozzle 12, a plurality of discharge units 11 are installed in the inkjet head 10. For example, in Fig. 4(a), a plurality of discharge units 11 are arranged in the Y direction.

Although not clearly shown in FIG. 4(c), a plurality of discharge units 11 are connected in parallel to the supply-side common flow path 51a and the discharge-side common flow path 51b.

Additionally, the supply-side common flow path 51a and the discharge-side common flow path 51b are connected to an ink resolver (not shown), and the ink resolver is also connected to an ink tank (not shown) serving as an ink supply source. Ink is supplied from the ink resolver to the supply-side common passage 51a through the ink supply port 53, and ink flowing into the plurality of discharge-side common passages 51b arranged in the Y direction is discharged from the ink discharge port 54. do.

The ink resolver is a second ink tank that exists between the supply-side common flow path 51a, the discharge-side common flow path 51b, and the ink tank. By pressurizing or depressurizing the second ink tank, the pressure applied to the nozzle 12 is controlled and ink is ejected in an appropriate state.

The supply-side first tightening part 20a, the discharge-side first tightening part 20b, the supply-side second tightening part 22a, and the discharge-side second tightening part 22b are connected to the first pressure chamber 14 and the supply-side second tightening part 22b. Compared with the pressure chamber 15a, the second pressure chamber 15b on the discharge side, the third pressure chamber 16a on the supply side, and the third pressure chamber 16b on the discharge side, the passage cross-sectional area is sufficiently small and functions as a tightening part.

A pressure difference is set between the ink supply tank connected to the third pressure chamber 16a on the supply side and the ink recovery tank connected to the third pressure chamber 16b on the discharge side, and ink flows. By employing such an ink circulation system, fresh ink can always be supplied to each first pressure chamber 14, and thickening of the ink at a location in contact with the atmosphere near the nozzle 12 can be prevented. This allows stable ejection over a long period of time.

＜Actuator (30)＞

As the actuator 30 in this example, a piezoelectric element is used. The piezoelectric element has a structure in which a piezoelectric material is interposed between a lower electrode and an upper electrode, and multiple layers are stacked. The lower electrode is a common electrode (common electrode) for the plurality of actuators 30, and the upper electrode is a separate electrode for each actuator 30.

When a driving voltage is applied between the electrodes of the actuator 30, the actuator 30 is displaced and the volume of the first pressure chamber 14 changes. Ink is ejected from the nozzle 12 due to this volume change.

In addition, although the d33 mode piezoelectric actuator 30 is illustrated here, the energy generating element is not limited to this and can be used in various forms such as piezoelectric actuators using d31 mode or shear mode, electrostatic actuators, and heat generating elements. is possible. A corresponding energy generating element corresponding to the discharge method employed is used.

In addition, the flow path structure as shown in Figure 4(a) can be manufactured by etching silicon (Si) to form grooves or holes that become flow paths, or by thermal diffusion bonding of each etched metal plate.

<Evaluation of examples and comparative examples>

In the following examples and comparative examples, the influence of fluid crosstalk occurring mutually between a plurality of discharge elements on discharge characteristics was evaluated. The evaluation method is as follows. When all nozzles 12 provided in the inkjet head 10 are discharged, the application timing of the drive waveform applied to the actuator 30 is delayed by 1 microsecond for only one nozzle. The discharge speed of the liquid droplet discharged from the nozzle 12 was evaluated.

Strobe light was emitted in synchronization with the application timing of the drive waveform, the droplets were irradiated, and the droplets were observed by observing them with a camera. Additionally, by delaying the timing of strobe light emission, droplets between two points were observed and the discharge speed of the droplets was evaluated.

The ink used for evaluation was an ink with a viscosity of 8 mPa·s and a surface tension of 33 mN/m. Viscosity was measured using a clay meter AR-G2 (TA Insruments). The surface tension was measured using a surface tensiometer DSA100 (manufactured by KRUSS).

Table 1 shows the conditions and evaluation results of the examples and comparative examples. Additionally, the acceptance criteria for speed fluctuations are 2.5 m/s or less for the inkjet head 10 producing 4pL, and 6.1m/s or less for the inkjet head 10 producing 1pL. This is because it is necessary in the case of application to the display panel described in the discussion below.

The speed fluctuation in Table 1 is the maximum value between the maximum and minimum values.

(Example 1)

The structure of the inkjet head of Example 1 is the same as the head structure shown in Fig. 4(a). Figure 5 shows the results of the above evaluation of the inkjet head of Example 1. In FIG. 5, the horizontal axis represents the delay time (microseconds) of the droplet ejection timing, and the vertical axis represents the droplet ejection speed, and these are evaluation results for three nozzles in one inkjet head 10. The delay time of the discharge timing means the delay time of the application start time of the drive waveform applied to each actuator 30.

CH75, CH150, and CH1 represent the numbers of the nozzle 12. In this example, data was acquired using three representative nozzles (No. 75, No. 150, and No. 1) among the 150 nozzles 12 in one nozzle row. CH150 and CH1 are the nozzles 12 at both ends, and CH75 is the nozzle 12 located in the center.

The point where the delay time is 0 microseconds indicates the discharge speed when all nozzles 12 are discharged simultaneously. Depending on where the nozzle 12 is located (depending on the difference between CH75, CH150, and CH1), the degree of influence of fluid crosstalk is different, and the behavior of speed fluctuations is different. In general, the delay time of the discharge timing is 4 microseconds, It can be seen that at 10 microseconds, the discharge speed of the droplet varies greatly.

It can be considered that the timing at which the vibration wave resonates between the plurality of nozzles 12 corresponds to these times. In the range where the delay time is 15 microseconds or more, the speed fluctuation almost disappears, and it can be considered that the vibration wave is sufficiently attenuated up to this time.

The variation range of the discharge speed with respect to the delay time of the discharge timing is expressed as a value of (maximum value of speed) - (minimum value of speed), No. 75 (CH75) of nozzle 12 is 2.1 m/s, nozzle 12 ) of No. 150 (CH150) is 1.4 m/s, and No. 1 (CH1) of nozzle 12 is 1.2 m/s.

(Comparative Example 1)

Figure 6 shows a cross-sectional view of the inkjet head in Comparative Example 1.

Differences from the structure of the inkjet head 10 in Example 1 will be described below. There is no supply-side second throttle 22a and discharge-side second throttle 22b, and therefore, no supply-side third pressure chamber 16a and discharge-side third pressure chamber 16b exist. Additionally, the supply side damper 25a and the discharge side damper 25b are not disposed. Other structures are the same as the inkjet head in Example 1.

As in Example 1, the results of evaluating the variation in ejection speed when the ejection timing was delayed are shown in FIG. 7.

Since there is no supply-side second fastener 22a and discharge-side second fastener 22b, and no supply-side damper 25a and discharge-side damper 25b, the fluid crosstalk in the inkjet head of Comparative Example 1 It can be seen that the speed variation due to this is large compared to the value in Example 1.

(Example 2)

Figure 8 shows a cross-sectional view of the inkjet head in Example 2. Compared to the structure of Example 1, it can be seen that the volume of the first pressure chamber 14 is small. The volume of the first pressure chamber 14 changes depending on the volume of the liquid droplets to be discharged, but is generally about 0.007 mm ³ when a liquid droplet with a volume of 1 picoliter is discharged. Incidentally, in general, when discharging a liquid droplet with a volume of 4 picoliters, the volume is about 0.025mm ³ .

From Hagenpoisel's equation, assuming that the ink flowing in the microchannel of the inkjet head 10 is a laminar flow, the relationship between the droplet volume and the resonance frequency due to the internal structure of the inkjet head 10 is expressed as Equation 1 can do.

V: Droplet volume, S: Nozzle cross-sectional area, v: Droplet discharge speed, f: Resonant frequency

From this, it can be seen that in order to discharge liquid droplets in a small volume, it is necessary to reduce the volume of the first pressure chamber 14 and increase the resonance frequency of the vibration wave within the first pressure chamber 14.

Since the reciprocal of the resonance frequency is the resonance period, it is necessary to shorten the resonance period. Since the resonance period becomes shorter as the volume of the pressure chamber decreases, reducing the volume of the pressure chamber can be said to be theoretically appropriate as a means of reducing the droplet volume.

That is, the inkjet head 10 of Example 2 shown in FIG. 8 can eject a small volume of liquid droplets.

In addition, the length of the supply-side second tightening part 22a and the discharge-side second tightening part 22b in the It is elongated and the flow path resistance is high. The length in the Y direction is the same.

The supply-side first tightening part 20a and the discharge-side first tightening part 20b are related to the liquid droplet volume to be discharged, and the tightening lengths of the supply-side first tightening part 20a and the discharge-side first tightening part 20b are adjusted. If the resistance is increased by lengthening, the droplet volume coming out of the nozzle 12 increases. Therefore, resistance cannot be raised easily. Therefore, in order to suppress crosstalk, the lengths of the supply-side first tightening part 20a and the discharge-side first tightening part 20b are determined by the droplet volume, and the supply-side second tightening part 22a and the discharge-side second tightening part 20b are determined by the liquid droplet volume. Cross talk is suppressed by the length of the limb 22b. That is, it is preferable that the second tightening part 22a on the supply side and the second tightening part 22b on the discharge side are longer.

As in Example 1, the results of measuring the variation in ejection speed when the ejection timing was delayed are shown in FIG. 9. The variation range of the discharge speed with respect to the delay time of the discharge timing is expressed as the difference between (maximum value of speed) and (minimum value of speed), No. 75 (CH75) of nozzle 12 is 4.6 m/s, nozzle No. 150 (CH150) of (12) is 3.9 m/s, and No. 1 (CH1) of nozzle (12) is 2.6 m/s.

Additionally, the droplet volume is 0.9 picoliter when the discharge speed is 5 m/s.

(Comparative Example 2)

Figure 10 shows a cross-sectional view of the inkjet head in Comparative Example 2. Differences from the structure of the inkjet head in Example 2 will be explained below. There is no supply-side second throttle 22a and discharge-side second throttle 22b, so there is no supply-side third pressure chamber 16a and discharge-side third pressure chamber 16b. Also, the damper is not placed. Other structures are the same as the inkjet head in Example 2.

As in Example 2, the results of evaluating the variation in ejection speed when the ejection timing was delayed are shown in FIG. 11. The variation range of the discharge speed with respect to the delay time of the discharge timing is 7.4 m/s for No. 75 (CH75) of the nozzle 12, 5.0 m/s for No. 150 (CH150) of the nozzle 12, and 5.0 m/s for No. 150 (CH150) of the nozzle 12. Number 1 (CH1) becomes 4.6m/s.

Additionally, the droplet volume is 1.0 picoliter when the discharge speed is 5 m/s.

In the inkjet head of Comparative Example 2, it can be seen that although the droplet volume is small at 1.0 picoliter, the fluid crosstalk between the plurality of discharge elements is large, and the speed fluctuation is large.

(Comparative Example 3)

Figure 12 shows a cross-sectional view of the inkjet head in Comparative Example 3. Differences from the structure of the inkjet head in Example 2 will be explained below. There is no supply-side second throttle 22a and discharge-side second throttle 22b, so there is no supply-side third pressure chamber 16a and discharge-side third pressure chamber 16b. Also, the damper 25 is not disposed. The length of the first tightening part 20a on the supply side and the first tightening part 20b on the discharge side are very long, and the flow resistance is very high. Other structures are the same as the inkjet head in Example 2.

As in Example 2, the results of evaluating the variation in ejection speed when the ejection timing was delayed are shown in FIG. 13. The variation range of the discharge speed with respect to the delay time of the discharge timing is 2.4 m/s for No. 75 (CH75) of the nozzle 12, 1.5 m/s for No. 150 (CH150) of the nozzle 12, and 1.5 m/s for No. 75 (CH75) of the nozzle 12. Number 1 (CH1) becomes 2.0m/s.

Additionally, the droplet volume is 1.6 picoliters when the discharge speed is 5 m/s.

In the inkjet head of Comparative Example 3, it can be seen that the fluid crosstalk between the plurality of discharge elements is reduced, but the droplet volume is increased to 1.6 picoliters. Since the length of the first tightening part 20a on the supply side and the first tightening part 20b on the discharge side are long and the flow path resistance is large, the attenuation of the vibration wave within the individual flow path occurs effectively. However, since the flow path resistance is very large, most of the vibration waves generated by the vibration of the actuator 30 are emitted from the nozzle 12. As a result, the speed change due to crosstalk is small, but the droplet volume is large.

The nozzle diameter of the inkjet head in Comparative Example 3 was 10 μm, and it is difficult to process holes smaller than this while maintaining processing accuracy. The droplet volume is determined by the resolution of the image applied by inkjet, and if the droplet volume is too much larger than the specified value, it becomes difficult to apply ink while maintaining the predetermined landing accuracy.

＜Consideration＞

The object applied with the inkjet head of Example 2 is, for example, ink that forms the red, green, and blue light emitting layers of an organic EL display panel. Data such as the drive waveform for ejection, drive voltage, and image pattern to be applied are sent to the inkjet head from the drive control mechanism.

In response to the signal, the inkjet head discharges ink into the pixels of the organic EL display panel, which is the application target, installed on the movable stage.

When the pixel resolution of an organic EL display is high, the volume of the droplet ejected from the inkjet head is required to be 1 picoliter or less. As the droplet volume increases, the droplet diameter increases, and the margin of the landing position when the ink droplet lands in the pixel becomes small. If the landing position is misaligned, color mixing occurs between red, green, and blue pixels, deteriorating the display quality of the organic EL display panel. In addition, the specific specifications of the speed deviation cannot be determined uniformly, but when applying with high precision, the speed deviation is required to be as small as possible.

Considering the results of Example 2, Comparative Example 2, and Comparative Example 3 from the above point of view, in the inkjet head of Comparative Example 3, the liquid volume is larger than 1.6 picoliter and 1 picoliter, and the organic EL display panel can be produced with the required precision. It is difficult to apply the ink of the light emitting layer to the pixels.

In addition, in the inkjet head of Comparative Example 2, the droplet volume is 1 picoliter, which is within the specification range, but compared to the inkjet head of Example 2, the speed deviation is large, so it can be said that it is not an optimal inkjet head structure.

(Embodiment 2)

Fig. 14 is a cross-sectional view schematically showing the configuration of the inkjet head according to Embodiment 2. The explanation will focus on differences from Embodiment 1. Matters not explained are the same as in Embodiment 1.

(1) The positional relationship in the Z direction between the supply-side first tightening part 20a and the supply-side second tightening part 22a is such that the supply-side first tightening part 20a is away from the nozzle 12.

By taking this positional relationship, in the process of ink flowing, the ink rises in the direction away from the nozzle 12 in the Z direction within the second pressure chamber 15a on the supply side. Accordingly, during the process of ink flowing, coarse particles in the ink settle and remain in the second pressure chamber 15a on the supply side. That is, in order to realize normal discharge, it becomes possible to suppress the entry of coarse particles into the first pressure chamber 14.

(2) In the tightening structure on the ink discharge side, only the first tightening portion 20b on the discharge side is disposed. This is because particles in the ink that have settled in the first pressure chamber 14 are discharged as much as possible.

(3) The discharge-side first fastener 20b on the side through which ink is discharged is disposed at a position close to the Z direction. This can facilitate the discharge of coarse particles that have settled in the first pressure chamber 14.

(4) The supply side damper 27a has higher rigidity than the discharge side damper 27b. Specifically, the width in the X direction is larger in the discharge side damper 27b than in the supply side damper 27a. Here, the width of the damper is the width of the part that is not maintained, and is the width of the part that can vibrate, that is, the width of the part that alleviates vibration. In this case, it is the width of the portion not held by the highly rigid plate 26. The rigidity may be changed by changing the materials of the supply side damper 27a and the discharge side damper 27b.

(5) It is desirable that the supply side damper 27a or the discharge side damper 27b have a higher resonance frequency compared to the diaphragm non-fixed portion 28. The supply side damper 27a or the discharge side damper 27b alleviates the vibration of the ink more than the diaphragm non-fixing portion 28. Details are explained using Table 2.

The diaphragm non-fixed part 28 is a variable part of the diaphragm.

The material of the diaphragm non-fixed part 28 is nickel alloy, the density is 8900 kg/m ³ , and the Young's modulus is 209 GPa. The dimensions within the inkjet head 10 are 4 μm in Z-direction thickness and 50 μm in X-direction width. From these, the secondary moment of inertia of the diaphragm non-fixed portion 28 is determined to be 2.67×10 ^-22 , and the resonance frequency is 2.5×10 ^-4 Hz.

On the other hand, the supply side damper 27a or the discharge side damper 27b is made of stainless steel, has a density of 7930 kg/m ³ , a Young's modulus of 193 GPa, a thickness of 20 μm, and a width of 1000 μm. The secondary moment of inertia of the supply side damper 27a or the discharge side damper 27b is 6.67×10 ^-19 , and the resonance frequency is 3.2×10 ^-4 Hz.

From these, it can be seen that the resonance frequency of the supply side damper 27a or the discharge side damper 27b is greater than that of the diaphragm non-fixed portion 28.

＜If the ink contains particles＞

Here, a case where ink in which particles are dispersed is used as the ink will be described. The physical properties of the ink are adjusted so that the particles can exist stably, such as by adjusting the pH of the dispersant or solution. However, particles in ink may aggregate and produce particles that are coarser than designed. If particles other than the design flow into the nozzle 12, the nozzle becomes clogged, making it impossible to discharge droplets.

However, the particles in the ink settle over time. The sedimentation speed of particles is determined according to the sedimentation speed equation of the stroke expressed in Equation 2 below.

ｖ _s : Sedimentation velocity D _p : Particle diameter ρ _p : Particle density ρ _f : Liquid density

η: Ink viscosity g: Gravity acceleration

Figure 15 shows the sedimentation velocity relative to the particle size of particles dispersed in ink when the ink viscosity is 3 mPa·s, the particle density is 4 g/cm ³ , and the liquid density is 1 g/cm ³ . It can be seen that when particles with a particle size of 1.3 um are dispersed, the particles settle in the liquid at a sedimentation rate of 0.055 mm/min.

Since the height of the second pressure chamber 15a on the supply side in the Z direction is approximately 0.2 mm, it can be seen that the particles settle in approximately 4 minutes. In this way, coarse particles other than the design can be allowed to settle in the second pressure chamber 15a on the supply side, and flow into the nozzle 12 can be suppressed. In the discharge-side second pressure chamber 15b, the discharge-side first fastener 20b is disposed downward in the Z direction to prevent sedimented particles from accumulating.

By using such a head structure, it becomes possible to stably eject even ink with dispersed particles without causing nozzle clogging.

(overall)

Parts of Embodiments 1 and 2 can be combined. In particular, (1) to (5) of Embodiment 2 can each be combined with Embodiment 1. That is, at least one of (1) to (5) can be used in the inkjet head 10 of Embodiment 1.

A side view of the inkjet device 64 using the inkjet head 10 is shown in FIG. 16. An inkjet head 10 that ejects ink, a drive control means 61 that generates a driving voltage signal applied to the actuator 30 and controls the ejection operation of the inkjet head 10, and an inkjet head 10. It includes conveyance means 62 for relatively moving the drawing medium 63.

By applying ink to the drawing medium 63, which is various devices, various devices can be manufactured.

The inkjet head and inkjet device of the present invention can be used to manufacture an organic EL display panel with high-precision pixels. That is, it can be used for application of the light emitting layer of an organic EL display panel, application of decorative ink or resin encapsulation ink using UV curable ink, application of conductive ink, application of water-based ink for cosmetic purposes, etc.

10: inkjet head 11: discharge unit
12: nozzle 14: first pressure chamber
15a: second pressure chamber on the supply side 15b: second pressure chamber on the discharge side
16a: third pressure chamber on the supply side 16b: third pressure chamber on the discharge side
20a: first fastener on the supply side 20b: first fastener on the discharge side
22a: second fastener on the supply side 22b: second fastener on the discharge side
25a: supply side damper 25b: discharge side damper
26: Highly rigid plate (anti-vibration plate)
27a: supply side damper 27b: discharge side damper
28: Diaphragm non-fixing part 30: Actuator
51a: common flow path on the supply side 51b: common flow path on the discharge side
53: ink supply port 54: ink outlet
61: drive control means 62: conveyance means
63: Drawing medium 64: Inkjet device
100: nozzle 110: pressure chamber
111: partition wall 112: diaphragm
130: Piezoelectric element 140: Piezoelectric member
150: droplet 200: nozzle
210: pressure chamber 212: diaphragm
220: thin film piezoelectric element 230: common pressure chamber
500: nozzle 501: pressure chamber
502: Energy generating element 503: Common flow path
504: fastener

Claims (18)

A nozzle that discharges liquid droplets,
A first pressure chamber connected to the nozzle,
a second pressure chamber on the supply side and a second pressure chamber on the discharge side connected to the first pressure chamber;
A third pressure chamber on the supply side connected to the second pressure chamber on the supply side,
a third pressure chamber on the discharge side connected to the second pressure chamber on the discharge side;
an energy generating element that provides discharge force to the liquid in the first pressure chamber;
a supply-side first fastener between the first pressure chamber and the supply-side second pressure chamber;
A first fastener on the discharge side between the first pressure chamber and the second pressure chamber on the discharge side,
a supply-side second fastener between the supply-side second pressure chamber and the supply-side third pressure chamber;
A plurality of discharge units including a second discharge-side fastener between the discharge-side second pressure chamber and the discharge-side third pressure chamber;
a supply-side common passage connecting the supply-side third pressure chambers of each of the plurality of discharge units;
Provided with a discharge-side common passage connecting the discharge-side third pressure chambers of each of the plurality of discharge units,
An inkjet head, wherein the supply-side first tightening part is further away from the nozzle in a height direction than the supply-side second tightening part. In claim 1,
The inkjet head wherein the first pressure chamber, the second pressure chamber on the supply side, the second pressure chamber on the discharge side, the third pressure chamber on the supply side, and the third pressure chamber on the discharge side are arranged in a straight line. In claim 1,
The inkjet head wherein the straight line connecting the first supply-side tightening part and the second supply-side tightening part is not parallel to the flow direction of ink. In claim 1,
An inkjet head wherein a supply-side damper is disposed in the supply-side second pressure chamber. In claim 4,
An inkjet head wherein the supply-side damper is disposed across the supply-side third pressure chamber and the supply-side second pressure chamber. In claim 4,
An inkjet head, wherein a portion of the supply side damper is disposed in a hollow state. In claim 4,
The inkjet head wherein the supply-side first throttle is further away from the supply-side damper than the supply-side second throttle. In claim 1,
The inkjet head wherein the flow path resistance of the supply-side second tightening part is greater than the flow path resistance of the supply-side first tightening part. A nozzle that discharges liquid droplets,
A first pressure chamber connected to the nozzle,
a second pressure chamber on the supply side and a second pressure chamber on the discharge side connected to the first pressure chamber;
A third pressure chamber on the supply side connected to the second pressure chamber on the supply side,
an energy generating element that provides discharge force to the liquid in the first pressure chamber;
a supply-side first fastener between the first pressure chamber and the supply-side second pressure chamber;
A first fastener on the discharge side between the first pressure chamber and the second pressure chamber on the discharge side,
A plurality of discharge units including a supply-side second fastener between the supply-side second pressure chamber and the supply-side third pressure chamber;
a supply-side common passage connecting the supply-side third pressure chambers of each of the plurality of discharge units;
Provided with a discharge-side common passage connecting the discharge-side second pressure chambers of each of the plurality of discharge units,
An inkjet head, wherein the supply-side first tightening part is further away from the nozzle in a height direction than the supply-side second tightening part. In claim 9,
The inkjet head wherein the first pressure chamber, the second pressure chamber on the supply side, the second pressure chamber on the discharge side, and the third pressure chamber on the supply side are arranged in a straight line. In claim 9,
The inkjet head wherein the straight line connecting the first supply-side tightening part and the second supply-side tightening part is not parallel to the flow direction of ink. In claim 9,
Placing a supply side damper in the second pressure chamber on the supply side,
Disposing a discharge-side damper in the second pressure chamber on the discharge side,
The inkjet head wherein the supply side damper has higher rigidity than the discharge side damper. The inkjet head according to any one of claims 1 to 12,
a drive control means for controlling an ejection operation of the inkjet head by generating a drive voltage signal applied to the energy generating element;
An inkjet device comprising conveyance means for moving the inkjet head and the drawing medium relative to each other. A manufacturing method for manufacturing a device by applying ink to the drawing medium using the inkjet device according to claim 13. A nozzle that discharges liquid droplets,
A first pressure chamber connected to the nozzle,
a second pressure chamber on the supply side and a second pressure chamber on the discharge side connected to the first pressure chamber;
A third pressure chamber on the supply side connected to the second pressure chamber on the supply side,
a third pressure chamber on the discharge side connected to the second pressure chamber on the discharge side;
an energy generating element that provides discharge force to the liquid in the first pressure chamber;
a supply-side first fastener between the first pressure chamber and the supply-side second pressure chamber;
A first fastener on the discharge side between the first pressure chamber and the second pressure chamber on the discharge side,
a supply-side second fastener between the supply-side second pressure chamber and the supply-side third pressure chamber;
A plurality of discharge units including a second discharge-side fastener between the discharge-side second pressure chamber and the discharge-side third pressure chamber;
a supply-side common passage connecting the supply-side third pressure chambers of each of the plurality of discharge units;
Provided with a discharge-side common passage connecting the discharge-side third pressure chambers of each of the plurality of discharge units,
The inkjet head, wherein the supply-side second tightening part and the discharge-side second tightening part have lengths longer than the supply-side first tightening part and the discharge-side first tightening part, respectively. A nozzle that discharges liquid droplets,
A first pressure chamber connected to the nozzle,
a second pressure chamber on the supply side and a second pressure chamber on the discharge side connected to the first pressure chamber;
A third pressure chamber on the supply side connected to the second pressure chamber on the supply side,
an energy generating element that provides discharge force to the liquid in the first pressure chamber;
a supply-side first fastener between the first pressure chamber and the supply-side second pressure chamber;
A first fastener on the discharge side between the first pressure chamber and the second pressure chamber on the discharge side,
A plurality of discharge units including a supply-side second fastener between the supply-side second pressure chamber and the supply-side third pressure chamber;
a supply-side common passage connecting the supply-side third pressure chambers of each of the plurality of discharge units;
Provided with a discharge-side common passage connecting the discharge-side second pressure chambers of each of the plurality of discharge units,
The inkjet head wherein the length of the second tightening part on the supply side is longer than the length of the first tightening part on the supply side. delete delete