JP2019048452A - Inkjet head, inkjet device using the same and device manufacturing method - Google Patents

Abstract

To provide an inkjet head that can make both relaxing of a discharge abnormality caused by fluid crosstalk generated between a plurality of discharge elements and maintaining of desired discharge liquid droplet volumes.SOLUTION: An inkjet head comprises a plurality of discharge units which include: a nozzle for discharging liquid droplets; a first pressure chamber joined to the nozzle; a second pressure camber at a supply side and a second pressure chamber at a discharge side, joined to the first pressure chamber; a third pressure chamber at the supply side joined to the second pressure chamber at the supply side; a third pressure chamber at the discharge side joined to the second pressure chamber at the discharge side; an energy generating element for giving discharge force to liquid in the first pressure chamber; a first squeezing part at the supply side between the first pressure chamber and the second pressure chamber at the supply side; a first squeezing part at the discharge side between the first pressure chamber and the second pressure chamber at the discharge side; a second squeezing part at the supply side between the second pressure chamber at the supply side and the third pressure chamber at the supply side; and a second squeezing part at the discharge side between the second pressure chamber at the discharge side and the third pressure chamber at the discharge side.SELECTED DRAWING: Figure 4

Description

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

  Drop-on-demand ink jet heads are known as ink jet heads that can apply the required amount of ink as needed in response to an input signal. In particular, a piezoelectric (piezoelectric element) drop-on-demand type ink jet head generally includes an ink supply flow path, a plurality of pressure chambers connected to the ink supply flow path and having nozzles, and the ink filled in the pressure chamber. Have a piezoelectric element that applies pressure to the

  FIGS. 1A and 1B show the cross-sectional structure of a general inkjet head.

  The ink jet head includes a plurality of nozzles 100 for discharging droplets, a pressure chamber 110 communicating with the nozzles, a partition 111 separating pressure chambers corresponding to different nozzles, a diaphragm 112 forming a part of the pressure chamber, and a diaphragm 112 The piezoelectric element 130 that vibrates, the piezoelectric member 140 that supports the partition 111, and a common electrode (not shown) that applies a voltage to the piezoelectric element 130. Although not shown, it has a liquid inlet.

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

  The ink jet head configured in this way operates as follows. When a voltage is applied between a common electrode (not shown) on the back side of the piezoelectric element 130 and the piezoelectric element 130, the piezoelectric element 130 is deformed from the state of FIG. 1A to the state of FIG. When the rightmost piezoelectric element 130 in FIG. 1B is deformed (the lower part of the piezoelectric element 130 is deformed), the volume of the pressure chamber 110 is reduced, and pressure can be applied to the liquid. At that pressure, the ink present in the pressure chamber 110 is discharged as droplets 150 to the outside.

  Further, in an inkjet head of the type that circulates ink, the inkjet head has a liquid inlet and an outlet (not shown), and the ink is ejected while circulating the ink. The effects of circulating the ink are described below.

  The ink in the vicinity of the nozzles is always in contact with the atmosphere. Since the contact area is very small, the evaporation of the solvent of the ink can not be ignored. By evaporation of the solvent of the ink, the solid concentration of the ink is increased, and as a result, the viscosity of the ink is increased, which may make it difficult to eject the ink normally. Here, by circulating the ink to the vicinity of the nozzle, it is possible to always replace the ink whose viscosity has risen, and therefore the ink ejected in the vicinity of the nozzle is always kept at a normal ink viscosity. As a result, nozzle clogging can be suppressed and normal discharge can be performed regularly.

  The structure of the inkjet head may be a structure using a thin film piezoelectric element. FIG. 2A and FIG. 2B are views showing the structure of a thin film type inkjet head. In FIG. 2A, a nozzle 200 for discharging liquid, a pressure chamber 210 communicating with the nozzle, and a common pressure chamber 230 for supplying liquid to the pressure chamber are connected. A thin film piezoelectric element 220 is formed on the top of a diaphragm 212 forming a part of the pressure chamber. The ink jet head configured in this way operates as follows. When a voltage is applied to the thin film piezoelectric element 220, the thin film piezoelectric element 220 is deformed 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 is reduced and the pressure can be transmitted to the liquid. The pressure causes the droplet 150 to be discharged.

  When an ink jet head having such a flow path structure drives one piezoelectric element to discharge ink from the nozzles, the flow of the ink at the time of discharge is sent to the other nozzles that communicate with the same flow path via the common flow path. There is a phenomenon called crosstalk, which affects the operation and the discharge becomes unstable.

  FIG. 3 shows a cross-sectional view of the ink jet head described in Patent Document 1. As shown in FIG. In order to solve the problem of crosstalk, Patent Document 1 discloses that a plurality of nozzles 500 that discharge droplets, a plurality of pressure chambers 501 provided corresponding to the plurality of nozzles 500, and a discharge force to liquid in the pressure chamber. In an ink jet head including a plurality of energy generating elements 502 to be supplied, a common flow path 503 for supplying liquid to the plurality of pressure chambers 501, an individual flow connecting each pressure chamber 501 and the common flow path 503 A configuration is disclosed that is provided with a throttle portion 504 provided in the road portion.

  When passing through the narrowed portion 504, the pressure wave generated in the pressure chamber 501 is attenuated and hardly transmitted to the pressure chambers 501 of the other nozzles, and crosstalk can be alleviated.

JP 2012-11653 A

  However, in the ink jet head shown in Patent Document 1, the flow path resistance in the narrowed portion 504 is larger than the flow path resistance in the nozzle 500, and a large amount of pressure generated by the vibration of the energy generating element 502 is transmitted to the nozzle 500. .

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

  Particularly in the case of an ink jet head capable of discharging a very small droplet of about 1 picoliter of droplet volume, the diameter of the nozzle 500 becomes about 10 μm, and it is also difficult to process a smaller hole while maintaining processing accuracy. .

  Therefore, the subject of the present application is an inkjet head capable of achieving both the alleviation of discharge abnormality due to fluid crosstalk generated between a plurality of nozzles and the maintenance of a desired discharge droplet volume, and an ink jet apparatus and device using the same. And a method of manufacturing the same.

  In order to solve the above problems, a nozzle for discharging droplets, a first pressure chamber connected to the nozzle, a supply-side second pressure chamber connected to the first pressure chamber, and a discharge-side second pressure chamber, and An energy generating element for applying a discharge force to liquid in the first pressure chamber, the third discharge pressure chamber connected to the second discharge pressure chamber, the third discharge pressure chamber connected to the second discharge pressure chamber, and the third pressure chamber connected to the second discharge pressure chamber A supply-side first throttle portion between the first pressure chamber and the supply-side second pressure chamber, a discharge-side first throttle portion between the first pressure chamber and the discharge-side second pressure chamber, and the supply A supply-side second throttle portion between the side second pressure chamber and the supply-side third pressure chamber; and a discharge-side second throttle portion between the discharge-side second pressure chamber and the discharge-side third pressure chamber A plurality of discharge units, and a supply-side common flow path connecting the supply-side third pressure chambers of the plurality of discharge units Using the inkjet head having respective and discharge-side common flow path connecting between the discharge side third pressure chamber, a plurality of discharge units.

  Further, a nozzle for discharging droplets, a first pressure chamber connected to the nozzle, a supply-side second pressure chamber connected to the first pressure chamber, a discharge-side second pressure chamber, and the supply-side second pressure chamber The supply side third pressure chamber connected, an energy generating element for giving a discharge force to the liquid in the first pressure chamber, a first throttling portion between the first pressure chamber and the supply side second pressure chamber, and A plurality of discharge units including a first expansion portion between the first pressure chamber and the discharge side second pressure chamber, and a second expansion portion between the supply side second pressure chamber and the supply side third pressure chamber; A supply side common flow path connecting the supply side third pressure chambers of the plurality of discharge units, and a discharge side common flow path connecting the discharge side second pressure chambers of the plurality of discharge units; The inkjet head provided with

  Furthermore, the ink jet head, drive control means for generating a drive voltage signal to be applied to the energy generating element, and controlling the discharge operation of the ink jet head, and transport means for relatively moving the ink jet head and the drawing medium And an ink jet apparatus provided with

  According to the ink jet head and the ink jet recording apparatus of the present invention, it is possible to alleviate the fluid crosstalk which is generated mutually between the plurality of nozzles. Furthermore, it is possible to maintain a desired micro droplet volume, and highly accurate droplet discharge can be realized. As a result, printing quality can be improved.

(A) Structure of a conventional bulk-type inkjet head, (b) (a) of the thin-film-type inkjet head showing a state of the head when a voltage is applied to a piezoelectric element (A) Structure of a conventional thin film type inkjet head, (b) A diagram showing the state of the thin film type inkjet head when the voltage is applied to the piezoelectric element in the thin film type inkjet head of (a) Sectional view of the ink jet head of Patent Document 1 (A) A cross-sectional view schematically showing the configuration of the ink jet head according to the embodiment, (b) a cross section of the XY cross section of FIG. 4 (a), (c) a plan view of the entire ink jet head of the first embodiment The figure which shows the speed variation of the ink jet head of Example 1 Cross-sectional view of the inkjet head of Comparative Example 1 The figure which shows the speed variation of the ink jet head of comparative example 1 Sectional view of the ink jet head of Example 2 The figure which shows the speed variation of the inkjet head of Example 2 Cross-sectional view of an inkjet head of Comparative Example 2 The figure which shows the speed variation of the inkjet head of the comparative example 2 Cross-sectional view of the inkjet head of Comparative Example 3 The figure which shows the speed variation of the inkjet head of the comparative example 3 Cross-sectional view of the ink jet head of Embodiment 2 The figure which shows the relationship between the particle size in Embodiment 2, and sedimentation velocity. Side view of the ink jet coating apparatus according to the embodiment

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Embodiment 1
<Configuration of inkjet head>
FIG. 4A is a cross-sectional view schematically showing the configuration of the ink jet head according to the first embodiment. FIG.4 (b) is sectional drawing of XY cross section of Fig.4 (a). FIG. 4C is a plan view of the entire ink jet head.

  Here, although the inkjet head 10 which discharges the droplet of an ink is demonstrated to an example, the liquid used for discharge in this embodiment is not limited to ink.

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

  The following components are provided as a supply side flow path of the ink to the first pressure chamber 14. There is a supply side second pressure chamber 15a that communicates with the first pressure chamber 14 through the supply side first throttle unit 20a. Furthermore, the supply-side second pressure chamber 15a includes a supply-side third pressure chamber 16a that communicates with the supply-side second throttle portion 22a.

  There are the following components as a discharge side flow path from the first pressure chamber 14 to the ink. There is a discharge side second pressure chamber 15b that communicates with the first pressure chamber 14 via the discharge side first throttle unit 20b. Furthermore, the discharge-side second pressure chamber 15b has a discharge-side third pressure chamber 16b in communication with the discharge-side second throttle portion 22b.

  It is preferable that the supply side flow passage and the discharge side flow passage be provided opposite to each other with the first pressure chamber 14 as the center. Further, it is preferable that the first pressure chamber 14, the supply side flow passage, and the discharge side flow passage are linearly arranged and arranged in parallel to the lower surface of the ink jet head 10.

  A combination of the first pressure chamber 14, the ink discharge side flow path, and the supply side flow path is one discharge unit 11. In the inkjet head 10, a plurality of ejection units 11 are arranged in parallel. In addition, there is a supply-side common flow path 51 a that communicates the supply-side third pressure chambers 16 a of the plurality of discharge units 11. Furthermore, there is a discharge side common flow channel 51b that communicates the discharge side third pressure chambers 16b of the plurality of discharge units 11.

  The nozzles 12 are through holes for discharging ink, and the diameter thereof 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 a function to appropriately store the pressure generated by the vibration of the actuator 30. The accumulated pressure changes depending on the volume of the first pressure chamber 14 and the flow path resistance of the supply-side first throttle portion 20 a and the discharge-side first throttle portion 20 b. Therefore, it is necessary to optimize the volume and the like of the first pressure chamber 14 in accordance with the volume and the velocity of the droplet to be ejected.

  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, the supply-side common flow passage 51a, and the discharge side supply passage 52 Become.

  These pressure chambers and flow paths are manufactured by thermal diffusion bonding of a metal plate processed by etching or the like, etching of a silicon material, or the like.

<Supply side damper 25a, Discharge side damper 25b>
The following description should just be in at least one of the supply side flow path and the discharge side flow path. It is preferred to be in both.

  Further, at least one of the walls forming the supply side second throttle portion 22a, the discharge side second throttle portion 22b, or the supply side second pressure chamber 15a, and the discharge side second pressure chamber 15b is a plate having a large elasticity It is formed.

  These are the supply side damper 25a and the discharge side damper 25b which absorb the vibration wave which exists in the supply side second pressure chamber 15a and the discharge side second pressure chamber 15b.

  The supply side damper 25a and the discharge side damper 25b may be a metal plate having a thin plate thickness or may be a resin film, and the material is not limited to the material. It is provided in the direction perpendicular to the Z direction. The supply-side damper 25 a and the discharge-side damper 25 b disposed in the first pressure chamber 14 are held by a high rigidity plate 26 (vibration prevention plate). For this reason, there is no damping effect of the oscillatory wave, and the oscillatory wave necessary for the ejection of the ink is not attenuated.

  Although the supply-side damper 25a and the discharge-side damper 25b are not necessary in the first pressure chamber 14, for convenience of forming the supply-side common flow channel 51a, the discharge-side common flow channel 51b, etc. by etching. Is located in

  On the other hand, the supply-side damper 25a and the discharge-side damper 25b disposed in 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 third pressure chamber 16b are rigid. It is not held by the high plate 26 (vibration preventing plate), but only the end is held in the hollow state. The supply-side damper 25a and the discharge-side damper 25b are in a hollow state, and are supplied to 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 third pressure chamber 16b. The existing vibration wave is damped by the damping effect, and the fluid crosstalk generated by the interaction with the adjacent nozzle 12 is alleviated.

<Position in the Z direction of the supply-side first throttle unit 20a, the discharge-side first throttle unit 20b, the supply-side second throttle unit 22a, and the discharge-side second throttle unit 22b>
The vibration wave generated by the vibration of the actuator 30 because the positions of the supply-side first diaphragm 20a, the discharge-side first diaphragm 20b and the supply-side second diaphragm 22a, and the discharge-side second diaphragm 22b differ from each other in the Z direction. Reaches the supply-side second pressure chamber 15a and the discharge-side second pressure chamber 15b through the supply-side first throttle 20a and the discharge-side first throttle 20b, and then the supply-side second throttle 22a It passes through the side second narrowed portion 22b.

  As a result, in the traveling direction of the vibration wave, the components orthogonal to the surfaces of the supply side damper 25a and the discharge side damper 25b increase.

  Note that the difference in the position in the Z direction means a straight line connecting the supply-side first throttle portion 20a and the supply-side second throttle portion 22a, and connecting the discharge-side first throttle portion 20b and the discharge-side second throttle portion 22b. This means that each of the straight lines (dotted arrows in FIG. 4A) is not parallel to the plane (the plane of the damper 25 in FIG. 4A) perpendicular to the droplet ejection direction from the nozzle 12. Or each means that it is not parallel to the flow direction of the ink.

  The ejection direction is parallel to the Z direction. This direction is also perpendicular to the lower surface on which the nozzle 12 is present in FIG. 4 (a). In this case, the supply-side first throttle unit 20a is farther from the supply-side damper 25a than the supply-side second throttle unit 22a.

  The relationship between the traveling direction of the vibration wave and the direction parallel to the surfaces of the supply side damper 25a and the discharge side damper 25b was subjected to fluid analysis. As a result, it was found that the damping effect of the vibration wave is large if the traveling direction of the vibration wave is orthogonal to the surfaces of the supply side damper 25a and the discharge side damper 25b.

  Therefore, the damping effect is increased in the structure according to the embodiment. The supply-side damper 25a and the discharge-side damper 25b are disposed to exert the damper effect most with respect to the flow of the ink in the discharge direction.

<Flow path resistance of supply side second throttle portion 22a and supply side first throttle portion 20a>
The flow passage resistance of the supply-side second narrowed portion 22a is larger than the flow passage resistance of the supply-side first narrowed portion 20a. The influence on the other discharge units 11 is prevented by the supply-side second narrowed portion 22a.

  Similarly, the flow passage resistance of the discharge-side second narrowed portion 22b is larger than the flow passage resistance of the discharge-side first narrowed portion 20b.

<Overall configuration>
Although FIG. 4A shows only one discharge unit 11, that is, only the periphery of one nozzle 12, the ink jet head 10 is provided with a plurality of discharge units 11. For example, in FIG. 4A, the plurality of discharge units 11 are arranged in the Y direction.

  Although not shown explicitly in FIG. 4C, a plurality of discharge units 11 are connected in parallel to the supply-side common flow channel 51a and the discharge-side common flow channel 51b.

  The supply-side common flow channel 51a and the discharge-side common flow channel 51b are connected to an ink reservoir (not shown), and the ink reservoir is further connected to an ink tank (not shown) serving as an ink supply source. The ink is supplied from the ink reservoir to the supply-side common flow path 51a via the ink supply port 53, and the ink flowing into the plurality of discharge-side common flow paths 51b arranged in the Y direction is discharged from the ink discharge port 54 Be done.

  The ink reservoir is a second ink tank existing between the supply-side common flow channel 51a, the discharge-side common flow channel 51b, and the ink tank. The pressure applied to the nozzle 12 is controlled by pressurizing or depressurizing the second ink tank, and the ink is ejected in an appropriate state.

  The supply-side first throttle 20a, the discharge-side first throttle 20b, the supply-side second throttle 22a, and the discharge-side second throttle 22b include the first pressure chamber 14, the supply-side second pressure chamber 15a, and the discharge-side first Compared with the two pressure chambers 15b, the supply side third pressure chamber 16a, and the discharge side third pressure chamber 16b, the flow passage cross-sectional area is sufficiently small, and functions as a throttling portion.

  A pressure difference is provided between the ink supply tank connected to the supply side third pressure chamber 16a and the ink collection tank connected to the discharge side third pressure chamber 16b, and the ink flows. By adopting such an ink circulation system, it is possible to always supply fresh ink to the respective first pressure chambers 14, and to prevent thickening of the ink in the vicinity of the nozzle 12 in the area in contact with the air. This enables stable discharge for a long time.

<Actuator 30>
A piezoelectric element is used as the actuator 30 in this example. The piezoelectric element has a structure in which a piezoelectric body is interposed between the lower electrode and the upper electrode, and a plurality of layers are stacked. The lower electrode is a common electrode (common electrode) for the plurality of actuators 30, and the upper electrode is an individual separate electrode for each actuator 30.

  By applying a drive voltage 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 by this volume change.

  Although the d33 mode piezoelectric actuator 30 is illustrated here, the energy generating element is not limited to this, and a piezoelectric actuator using a d31 mode or a shear mode, an electrostatic actuator, a heating element, etc. Various aspects are possible. A corresponding energy generating element is used which corresponds to the ejection method employed.

The flow channel structure as shown in FIG. 4A is produced by etching silicon (Si) to form a groove, a hole or the like to be a flow channel portion, or by thermal diffusion bonding of etched metal plates. It is possible.
<Evaluation of Example and Comparative Example>
In the following examples and comparative examples, the influence on the discharge characteristics of the fluid crosstalk which is generated mutually between a plurality of discharge elements was evaluated. The evaluation method is as follows. When all the nozzles 12 included in the inkjet head 10 are discharged, the application timing of the drive waveform applied to the actuator 30 is shifted by 1 microsecond at only one nozzle, and the application timing of the drive waveform is shifted. The discharge speed of droplets discharged from the above was evaluated.

  Strobe light was emitted in synchronization with the application timing of the drive waveform, and the droplet was irradiated and observed with a camera to observe the droplet. In addition, by delaying the timing of strobe light emission, the droplet between two points was observed, and the droplet ejection speed was evaluated.

  The ink used for evaluation is an ink having a viscosity of 8 mPa · s and a surface tension of 33 mN / m. The viscosity was measured using a viscometer AR-G2 (TA Instruments). The surface tension was measured using a surface tension meter DSA100 (manufactured by KRUSS).

  The conditions and evaluation results of Examples and Comparative Examples are shown in Table 1. The acceptance criteria for the speed fluctuation are 2.5 m / s or less for the inkjet head 10 emitting 4 pL and 6.1 m / s or less for the inkjet head 10 emitting 1 pL. This is because it is necessary when applying to a display panel described in the following discussion.

  The velocity fluctuation in Table 1 is the maximum value of the difference between the maximum value and the minimum value.

Example 1
The structure of the ink jet head of Example 1 is the same as the head structure shown in FIG. 4 (a). The result of the said evaluation of the inkjet head of Example 1 is shown in FIG. In FIG. 5, the horizontal axis indicates the delay time (microsecond) of the discharge timing of the droplets, and the vertical axis indicates the discharge speed of the droplets, which 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 indicate the numbers of the nozzles 12. In the present embodiment, of the 150 nozzles 12 in one nozzle array, data is acquired using representative 3 nozzles (No. 75, No. 150, and No. 1). CH 150 and CH 1 are nozzles 12 at both ends, and CH 75 is a centrally located nozzle 12.

  The point at which the delay time is 0 microseconds indicates the discharge speed when all the nozzles 12 are discharging simultaneously. The degree of influence of fluid crosstalk differs depending on where the nozzle 12 is located (due to the difference between CH75, CH150, and CH1), and the behavior of velocity fluctuation differs, but when the delay time of ejection timing is approximately 4 microseconds and 10 microseconds It can be seen that the discharge speed of the droplet fluctuates greatly.

  It is considered that the timing at which the oscillating waves resonate among the plurality of nozzles 12 corresponds to these times. In the region where the delay time is 15 microseconds or more, the velocity fluctuation is almost zero, and it is considered that the vibration wave is sufficiently attenuated by this time.

The fluctuation range of the discharge speed with respect to the delay time of discharge timing can be expressed by the value of (maximum value of speed) − (minimum value of speed), and the 75th (CH75) of the nozzle 12 is 2.1 m / s, The 150th (CH 150) is 1.4 m / s, and the 1st (CH 1) of the nozzle 12 is 1.2 m / s.
(Comparative example 1)
FIG. 6 shows a cross-sectional view of the ink jet head in Comparative Example 1.

  The difference from the structure of the inkjet head 10 in the first embodiment will be described below. There is no supply-side second narrowed portion 22a and the discharge-side second narrowed portion 22b. Therefore, the supply-side third pressure chamber 16a and the discharge-side third pressure chamber 16b do not exist. Moreover, the supply side damper 25a and the discharge side damper 25b are not arrange | positioned, either. The other structure is the same as the ink jet head in the first embodiment.

  As in the first embodiment, FIG. 7 shows the result of evaluating the fluctuation of the discharge speed when the discharge timing is shifted.

Since there is no supply side second throttle part 22a and discharge side second throttle part 22b and there is no supply side damper 25a and discharge side damper 25b, the velocity fluctuation due to fluid crosstalk in the inkjet head of Comparative Example 1 is an example. It can be seen that it is larger than the value at 1.
(Example 2)
FIG. 8 shows a cross-sectional view of the ink jet head in the second embodiment. It can be seen that the volume of the first pressure chamber 14 is smaller than that of the structure of the first embodiment. The volume of the first pressure chamber 14 varies depending on the volume of droplets to be ejected, but is about 0.007 mm ³ when ejecting droplets of a volume of approximately 1 picoliter. Incidentally, the volume in the case of discharging a droplet with a volume of approximately 4 picoliter is about 0.025 mm ³ .

  From the Hagen Poiseuille equation, assuming that the ink flowing in the fine flow path 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 as shown in Equation 1. It can be expressed in

V: droplet volume, S: nozzle cross-sectional area, v: droplet ejection speed, f: resonant frequency From this, in order to eject droplets with a small volume, the volume of the first pressure chamber 14 is reduced, and the first It can be seen that it is necessary to increase the resonant frequency of the oscillating wave in the pressure chamber 14.

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

  That is, the ink jet head 10 of the second embodiment shown in FIG. 8 can discharge droplets of a small volume.

  Further, the lengths in the X direction of the supply-side second narrowed portion 22a and the discharge-side second narrowed portion 22b are respectively longer than the lengths of the supply-side first narrowed portion 20a and the discharge-side first narrowed portion 20b, The flow path resistance is large. The lengths in the Y direction are the same.

  The supply-side first throttle unit 20a and the discharge-side first throttle unit 20b are related to the droplet volume to be discharged, and the resistance of the supply-side first throttle unit 20a and the discharge-side first throttle unit 20b is lengthened to increase the resistance. When raised, the volume of droplets exiting the nozzle 12 increases. Therefore, resistance can not be easily raised. Therefore, in order to suppress the crosstalk, the lengths of the supply-side first narrowed portion 20a and the discharge-side first narrowed portion 20b are determined by the droplet volume, and the supply-side second narrowed portion 22a and the discharge-side second narrowed portion 22b Suppress crosstalk by the length of That is, the length of the supply-side second narrowed portion 22a and the discharge-side second narrowed portion 22b is preferably longer.

  Similar to the first embodiment, FIG. 9 shows the measurement results of the fluctuation of the ejection speed when the ejection timing is shifted. The fluctuation range of the discharge speed with respect to the delay time of the discharge timing can be expressed by the value of the difference between (maximum value of speed) and (minimum value of speed): No. 75 (CH75) of the nozzle 12 is 4.6 m / s, The number 150 (CH150) of the nozzle 12 is 3.9 m / s, and the number 1 (CH1) of the nozzle 12 is 2.6 m / s.

Further, the droplet volume is 0.9 picoliter in size when the ejection speed is 5 m / s.
(Comparative example 2)
FIG. 10 shows a cross-sectional view of the ink jet head in Comparative Example 2. The difference from the structure of the ink jet head in Example 2 will be described below. There is no supply side second throttle portion 22a and discharge side second throttle portion 22b, and therefore there is no supply side third pressure chamber 16a and discharge side third pressure chamber 16b. Also, the damper 25 is not disposed. The other structure is the same as the ink jet head in the second embodiment.

  As in the second embodiment, FIG. 11 shows the result of evaluating the fluctuation of the ejection speed when the ejection timing is shifted. The fluctuation range of the discharge speed with respect to the delay time of the discharge timing is as follows: No. 75 (CH 75) of the nozzle 12: 7.4 m / s, No. 150 (CH 150) of the nozzle 12: 5.0 m / s, No. ) Will be 4.6 m / s.

  In addition, the droplet volume is 1.0 picoliter in size when the ejection speed is 5 m / s.

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

(Comparative example 3)
FIG. 12 shows a cross-sectional view of the ink jet head in Comparative Example 3. The difference from the structure of the ink jet head in Example 2 will be described below. There is no supply side second throttle portion 22a and discharge side second throttle portion 22b, and therefore there is no supply side third pressure chamber 16a and discharge side third pressure chamber 16b. Also, the damper 25 is not disposed. The lengths of the supply side first throttle portion 20a and the discharge side first throttle portion 20b are very long, and the flow path resistance is very large. The other structure is the same as the ink jet head in the second embodiment.

  As in the second embodiment, FIG. 13 shows the result of evaluating the fluctuation of the ejection speed when the ejection timing is shifted. The fluctuation range of the discharge speed with respect to the delay time of discharge timing is 2.4 m / s for No. 75 (CH 75) of nozzle 12, 1.5 m / s for No. 150 of CH 12 (CH 150), No. 1 of CH 12 (CH 1) ) Will be 2.0 m / s.

  In addition, the droplet volume is 1.6 picoliter in size when the ejection speed is 5 m / s.

  In the inkjet head of Comparative Example 3, although the fluid crosstalk between the plurality of ejection elements is reduced, the droplet volume is found to be as large as 1.6 picoliter. Because the length of the supply-side first narrowed portion 20a and the discharge-side first narrowed portion 20b is long and the flow path resistance is large, the damping of the vibration wave in the individual flow path occurs effectively. However, since the flow path resistance is very large, most of the vibration wave generated by the vibration of the actuator 30 is emitted from the nozzle 12. As a result, although the velocity fluctuation due to the crosstalk is small, the droplet volume is large.

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

<Discussion>
An object to be coated by the ink jet head of Example 2 is, for example, an ink for forming a red, green, or blue light emitting layer of an organic EL display panel. Data such as a drive waveform and a drive voltage for ejection and an image pattern to be applied are sent from the drive control mechanism to the inkjet head.

  In response to the signal, the ink jet head ejects the ink into the pixels of the organic EL display panel, which is the application object placed on the operation stage.

  When the pixel resolution of the organic EL display is high, the volume of droplets ejected by 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 decreases. If the landing position shifts, color mixing occurs between the red, green, and blue pixels, and the display quality of the organic EL display panel is degraded. Further, although the specific specification of the speed variation can not be generally determined, it is required that the speed variation be as small as possible when applying with high accuracy.

  Considering the results of Example 2, Comparative Example 2 and Comparative Example 3 from the above viewpoint, in the inkjet head of Comparative Example 3, the liquid volume is 1.6 picoliters and larger than 1 picoliter, and the required accuracy It is difficult to apply the ink of the light emitting layer to the pixels of the organic EL display panel.

  Further, in the inkjet head of Comparative Example 2, the droplet volume is 1 picoliter, which is within the specification range, but the speed variation is large compared to the inkjet head of Example 2, and thus the inkjet head is not the optimum structure. I can say that.

Second Embodiment
FIG. 14 is a cross-sectional view schematically showing the configuration of the ink jet head according to the second embodiment. The differences from Embodiment 1 will be mainly described. Matters not described are the same as in the first embodiment.

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

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

  (2) In the ink discharge side throttle structure, only the discharge side first throttle portion 20b is disposed. This is to discharge the particles in the ink settled in the first pressure chamber 14 as much as possible.

  (3) The discharge side first throttle unit 20b on the side from which the ink is discharged is disposed at a position close to the Z direction. As a result, discharge of coarse particles settled in the first pressure chamber 14 can be facilitated.

  (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 portion that is not held, and the width of the portion that can be vibrated, that is, the width of the portion that reduces the vibration. In this case, it is the width of the portion not supported by the high rigidity plate 26. The rigidity may be changed by changing the material of the supply side damper 27a and the discharge side damper 27b.

  (5) It is preferable that the resonance frequency of the supply side damper 27a or the discharge side damper 27b be higher than that of the diaphragm non-fixed portion 28. The supply-side damper 27 a or the discharge-side damper 27 b reduces the vibration of the ink by the diaphragm non-fixing portion 28. Details will be described using Table 2.

  The diaphragm non-fixing portion 28 is a fluctuating portion of the diaphragm.

The material of the diaphragm non-fixing portion 28 is a nickel alloy, the density is 8900 kg / m ³ , and the Young's modulus is 209 GPa. In the inkjet head 10, the thickness in the Z direction is 4 μm, and the width in the X direction is 50 μm. From these, when the cross-sectional second moment of the diaphragm non-fixed portion 28 is determined, it is 2.67 × 10 ⁻²² , and the resonance frequency is 2.5 × 10 ⁻⁴ Hz.

On the other hand, the material of the supply-side damper 27a or the discharge-side damper 27b is stainless steel, having 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 cross-sectional secondary moment 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 understood from the diaphragm non-fixed portion 28 that the resonance frequency is larger in the supply side damper 27a or the discharge side damper 27b.

<When the ink contains particles>
Here, the case where an ink in which particles are dispersed is used as the ink will be described. The particles adjust the physical properties of the ink so that the particles can be stably present by adjusting the pH of the dispersant or solution. However, in the ink, the particles may agglomerate to form coarse particles for the design. When undesigned particles flow into the nozzle 12, the nozzle is clogged and the droplet can not be discharged.
By the way, particles in the ink settle with time. The settling of particles is determined according to the Stokes settling velocity equation shown by the following equation 2.

v _s : settling velocity D _p : particle size p _p : particle density _{f f} : liquid density
η: Ink viscosity g: Gravity acceleration FIG. 15 shows the sedimentation velocity with respect to the particle size of the particles dispersed in the 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 having 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 supply side second pressure chamber 15a in the Z direction is about 0.2 mm, it can be seen that the particles settle in about 4 minutes. It is possible to prevent the coarse particles outside the design from settling in the supply-side second pressure chamber 15 a by such a method and flowing into the nozzle 12. In the discharge-side second pressure chamber 15b, the discharge-side first throttle portion 20b is disposed downward in the Z direction so that precipitated particles are not deposited.

  With such a head structure, it is possible to stably discharge the ink in which the particles are dispersed without causing the nozzle clogging.

(as a whole)
The first and second embodiments can be partially combined. In particular, (1) to (5) of the second embodiment can be combined with the first embodiment. That is, at least one of (1) to (5) can be used for the inkjet head 10 of the first embodiment.

  A side view of an inkjet device 64 using the inkjet head 10 is shown in FIG. An ink jet head 10 for discharging ink, a drive voltage signal to be applied to the actuator 30 are generated, and a drive control means 61 for controlling the discharge operation of the ink jet head 10, and a transport for relatively moving the ink jet head 10 and the drawing medium 63 And 62.

  Various devices can be manufactured by applying the ink to the medium to be drawn 63 which is various devices.

  The ink jet head and the ink jet recording apparatus of the present invention can be used to manufacture an organic EL display panel having high definition pixels. That is, it can be used for coating a light emitting layer of an organic EL display panel, coating decorative ink or resin sealing ink using a UV curable ink, coating conductive ink, coating aqueous ink for cosmetic use, etc. .

10 inkjet head 11 discharge unit 12 nozzle 14 first pressure chamber 15a supply side second pressure chamber 15b discharge side second pressure chamber 16a supply side third pressure chamber 16b discharge side third pressure chamber 20a supply side first throttle portion 20b discharge Side first throttle portion 22a Supply side second throttle portion 22b Discharge side second throttle portion 25a Supply side damper 25b Discharge side damper 26 High rigidity plate (vibration preventing plate)
27a Supply-side damper 27b Discharge-side damper 28 Diaphragm non-fixing part 30 Actuator 51a Supply-side common flow channel 51b Discharge-side common flow channel 53 Ink supply port 54 Ink discharge port 61 Drive control means 62 Conveying means 63 Target 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 narrowed portion

Claims (14)

A nozzle that discharges droplets;
A first pressure chamber connected to the nozzle;
A supply side second pressure chamber connected to the first pressure chamber and a discharge side second pressure chamber;
A supply side third pressure chamber connected to the supply side second pressure chamber;
A discharge side third pressure chamber connected to the discharge side second pressure chamber;
An energy generating element for applying a discharge force to the liquid in the first pressure chamber;
A supply-side first throttle portion between the first pressure chamber and the supply-side second pressure chamber;
A discharge side first throttle portion between the first pressure chamber and the discharge side second pressure chamber;
A supply-side second throttle portion between the supply-side second pressure chamber and the supply-side third pressure chamber;
A plurality of discharge units including the discharge side second pressure chamber between the discharge side second pressure chamber and the discharge side third pressure chamber;
A supply side common flow path connecting the supply side third pressure chambers of the plurality of discharge units;
A discharge side common flow path connecting between the discharge side third pressure chambers of the plurality of discharge units;
Inkjet head equipped with The first pressure chamber, the supply-side second pressure chamber, the discharge-side second pressure chamber, the supply-side third pressure chamber, and the discharge-side third pressure chamber are linearly arranged. An ink jet head according to claim 1. The ink jet head according to claim 1 or 2, wherein a straight line connecting the supply-side first throttling portion and the supply-side second throttling portion is not parallel to the flow direction of the ink. The ink jet head according to any one of claims 1 to 3, wherein a supply side damper is disposed in the supply side second pressure chamber. The ink jet head according to claim 4, wherein the supply side damper is disposed across the supply side third pressure chamber and the supply side second pressure chamber. The inkjet head according to claim 4, wherein a part of the supply side damper is disposed in a hollow state. The ink jet head according to any one of claims 4 to 6, wherein the first supply-side throttling part is separated from the supply-side second throttling part by a distance from the supply-side damper. The ink jet head according to any one of claims 1 to 7, wherein a flow path resistance of the supply-side second throttle portion is larger than a flow path resistance of the supply-side first throttle portion. A nozzle that discharges droplets;
A first pressure chamber connected to the nozzle;
A supply side second pressure chamber connected to the first pressure chamber and a discharge side second pressure chamber;
The supply side third pressure chamber connected to the supply side second pressure chamber;
An energy generating element for applying a discharge force to the liquid in the first pressure chamber;
A first throttling portion between the first pressure chamber and the supply-side second pressure chamber;
A first throttling portion between the first pressure chamber and the discharge side second pressure chamber;
A plurality of discharge units including a second throttle portion between the supply side second pressure chamber and the supply side third pressure chamber;
A supply side common flow path connecting the supply side third pressure chambers of the plurality of discharge units;
A discharge-side common flow path connecting the discharge-side second pressure chambers of the plurality of discharge units;
Inkjet head equipped with The inkjet head according to claim 9, wherein the first pressure chamber, the supply-side second pressure chamber, the discharge-side second pressure chamber, and the supply-side third pressure chamber are linearly arranged. 11. The ink jet head according to claim 9, wherein a straight line connecting the supply-side first throttling portion and the supply-side second throttling portion is not parallel to the ink flow direction. A supply side damper is disposed in the supply side second pressure chamber,
A discharge side damper is disposed in the discharge side second pressure chamber,
The ink jet head according to any one of claims 9 to 11, wherein the supply side damper is higher in rigidity than the discharge side damper. An ink jet head according to any one of claims 1 to 12,
Drive control means for generating a drive voltage signal to be applied to the energy generating element and controlling the discharge operation of the ink jet head;
Transport means for relatively moving the inkjet head and the drawing medium;
Inkjet device equipped with The manufacturing method which manufactures a device by apply | coating an ink using the inkjet head apparatus of Claim 13.

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