JP5200746B2 - Electrostatic actuator, droplet discharge head, droplet discharge device, and method for manufacturing droplet discharge head - Google Patents

Description

  The present invention relates to an electrostatic actuator, a droplet discharge head, a method for manufacturing a droplet discharge head, and the like used as a drive mechanism for an inkjet head or the like.

  In the actuator-driven droplet discharge head, the diaphragm constituting a part of the discharge chamber is elastically displaced by electrostatic force or the piezoelectric effect of the piezoelectric element, and a droplet is discharged from the nozzle by generating pressure in the pressure chamber. I am doing so. In this type of droplet discharge head, in recent years, the number of nozzles has been increased in order to cope with high-speed printing, and a minute actuator has been demanded from the demand for higher resolution. However, when the actuator is miniaturized and densified, the amount of displacement of the diaphragm becomes insufficient, which causes a problem that sufficient pressure is not generated in the pressure chamber and a necessary droplet discharge amount cannot be obtained. there were.

  Therefore, in a piezoelectric drive type liquid droplet ejection device, a large mechanical driving force is obtained by multilayering an inorganic electret layer on a vibration plate to increase the displacement of the vibration plate (for example, Patent Document 1). ), The diaphragm has a structure in which an inorganic electret layer and a thin film metal heating pattern are laminated, and the electret layer is deformed by applying a voltage, and the electret layer is expanded by the thin film metal heating pattern, so that the diaphragm is greatly displaced. There was something to do (for example, patent document 2).

JP 2004-255605 A JP 2004-255614 A

  In the technique of Patent Document 1, the inorganic electret layer is multilayered on the diaphragm, and in order to support it, it is necessary to increase the thickness of the diaphragm. In the technique of Patent Document 2, since the diaphragm itself is multilayered, the thickness of the diaphragm is similarly increased. In such a configuration, mechanical resistance increases, and it is actually difficult to obtain sufficient diaphragm displacement for stable ejection of droplets. In order to obtain sufficient diaphragm displacement, it is necessary to increase the drive voltage. There was a problem that there was.

  The present invention has been made in view of these points, and an object of the present invention is to provide an electrostatic actuator capable of obtaining a sufficient amount of displacement of a diaphragm by applying a low voltage. It is another object of the present invention to provide a droplet discharge head and a droplet discharge device that include this electrostatic actuator and are capable of high-speed discharge.

According to the electrostatic actuator of the present invention, a flexible and conductive diaphragm is deformed via an insulating film on the electrode layer of the electrode side member in which an electrically polarized electret layer, an insulating layer, and an electrode layer are sequentially laminated. The diaphragms are arranged in close contact with each other, and the diaphragm is deformed by applying a voltage between the diaphragm and the electrode layer.
This electrostatic actuator applies a charge having the same polarity as the charge of the electret layer to the diaphragm, and deforms the diaphragm by the generated repulsive force. In this configuration, since there is no gap between the diaphragm and the electrode layer, by applying a lower voltage, an electric charge is applied to the diaphragm that acts on the electric field of the electret layer to give a repulsive force that deforms the diaphragm. Therefore, the diaphragm can be driven at a low voltage. In addition, since it is not necessary to bring the electrodes that are separated from each other into contact, there is no particular lower limit value of the applied voltage, and an appropriate voltage can be set from a wide range.

  When no voltage is applied between the diaphragm and the electrode layer, it is preferable that the diaphragm, the insulating film, and the electrode layer are in close contact with each other. According to this, since it is sufficient to apply a voltage only when the diaphragm is in operation, energy can be used efficiently.

A droplet discharge head of the present invention includes the electrostatic actuator described above, and the vibration plate forms one of the wall surfaces of a discharge chamber that stores discharge liquid and discharges the liquid from a nozzle. And the electrode layer are applied with a first voltage to deform the diaphragm so that the liquid in the discharge chamber is discharged from the nozzle.
In this electrostatic actuator, a charge having the same polarity as that of the electret layer is applied to the vibration plate, and the vibration plate is deformed by the generated repulsive force, thereby discharging the liquid in the discharge chamber from the nozzle. In this configuration, since there is no gap between the diaphragm and the electrode layer, by applying a lower voltage, an electric charge is applied to the diaphragm that acts on the electric field of the electret layer to give a repulsive force that deforms the diaphragm. Therefore, the diaphragm can be driven at a low voltage. In addition, the effect of the electrostatic actuator can be obtained.

  In the droplet discharge head, it is preferable that a second voltage having a reverse voltage relationship with the first voltage is applied between the diaphragm and the electrode layer after droplet discharge from the nozzle. Thereby, after droplet discharge, a suction force can be generated on the vibration plate to suppress the residual vibration of the vibration plate, thereby enabling high-speed printing.

  The liquid droplet ejection apparatus of the present invention includes the above-described liquid droplet ejection head, and can similarly exhibit the effects exhibited by the liquid droplet ejection head.

The manufacturing method of the droplet discharge head of the present invention includes:
Forming an electrode material on the surface of the glass substrate;
Patterning the deposited electrode material to form an electrode;
Forming an insulating film on the electrode forming side surface of the glass substrate;
Laminating an electrically polarized electret member on the side opposite to the electrode forming side of the glass substrate;
A silicon substrate on which a vibration plate and a discharge chamber are formed is brought into close contact with the electrode through the insulating film of the glass substrate, and a portion other than the region corresponding to the electrode of the glass substrate is used for the glass substrate. An anodic bonding step;
Etching the silicon substrate bonded to the glass substrate to form the diaphragm and the discharge chamber.

A step of forming an electrode material on the surface of the glass substrate;
Patterning the deposited electrode material to form an electrode;
Laminating an electrically polarized electret member on the side opposite to the electrode forming side of the glass substrate;
Forming an insulating film on one surface of the silicon substrate on which the vibration plate and the discharge chamber are formed;
A step of bringing the silicon substrate into close contact with the electrode of the glass substrate through the insulating film, and anodic bonding to the glass substrate using a portion other than a region corresponding to the electrode of the glass substrate;
Etching the silicon substrate bonded to the glass substrate to form the diaphragm and the discharge chamber.

By these methods, a droplet discharge head that can be driven at a low voltage can be obtained. In addition, since there is no gap between the diaphragm and the electrode layer, there is no partition in the glass substrate, and manufacturing defects due to the vibration plate running on the partition are eliminated when the silicon substrate and the glass substrate are joined.
In addition, the accuracy of bonding between the silicon substrate and the glass substrate can be relaxed for the above reason, and the manufacturing process can be simplified.

Embodiment 1 (electrostatic actuator).
FIG. 1 is a schematic diagram showing (a) before voltage application, (b) during voltage application, and (c) after voltage release of the electrostatic actuator according to the first embodiment of the present invention.
The electrostatic actuator according to the first embodiment includes a diaphragm 21 having flexibility and conductivity on the electrode layer 3 of the electrode-side member 10 in which the electret electret layer 1, the insulating layer 2, and the electrode layer 3 are sequentially laminated. Are closely arranged so as to be deformable via the insulating film 25.

The electret layer 1 is made of an electret member, and the electret member is laminated on the surface opposite to the electrode layer 3 forming surface of the glass substrate which is the insulating layer 2. A drive circuit 30 for applying a voltage is connected between the diaphragm 21 and the electrode layer 3.
The electrode layer 3 is also simply referred to as the electrode 3. The insulating film 25 is formed on either one or both of the electrode side member 10 and the diaphragm 21. FIG. 1 shows an example in which the insulating film 25 is formed on the electrode side member 10.

An electret is a member that is semi-permanently electrically polarized, and can have only one electrode charge. Here, an electret having only one electrode charge (for example, -charge) is used. As shown in FIG. 1, by arranging the electret layer 1 that is electrically polarized below the electrode layer 3, the electric field generated by the electret layer 1 acts on the charge stored in the diaphragm 21 to operate the diaphragm 21. It becomes possible to make it. Since the magnitude of the generated electric field is not related to the distance from the electret layer 1, the same force acts on both the electrode layer 3 and the diaphragm 21.
FIG. 7 is an explanatory diagram of an electric field caused by the electret layer. As shown in FIG. 7, when an electret layer having a surface area of S and a charge of Q is formed on one surface of a material having a relative dielectric constant εr, an electric field E generated by the electret layer can be expressed by the following equation (1). .
E = σ / 2 (ε0εrS) (1)
However, the magnitude of the electric field created by the electret layer does not depend on the distance from the electret layer according to the relative dielectric constant (1) where σ = charge density Q / S and ε0 = vacuum.

Next, the operation of the electrostatic actuator will be described.
When no voltage is applied between the electrode layer 3 and the diaphragm 21, no charge is stored in the electrode layer 3 and the diaphragm 21. In this state, the diaphragm 21 is in close contact with the electrode layer 3 via the insulating film 25 (FIG. 1A).
Next, a voltage that generates electric charges having the same polarity as that of the electret layer 1 is applied to the diaphragm 21 between the electrode layer 3 and the diaphragm 21 using the drive circuit 30. As a result, the electric field generated by the electret layer 1 acts on the electric charge stored in the diaphragm 21 to generate a repulsive force on the diaphragm 21 and deform the diaphragm 21 away from the electrode layer 3 (FIG. 1). (B)). In this case, since there is no gap between the diaphragm 21 and the electrode layer 3, it is possible to apply a charge that generates repulsive force to the diaphragm 21 by applying a lower voltage. Can be driven.
When the voltage applied between the electrode layer 3 and the diaphragm 21 is released, the electric charge caused by the voltage disappears, the repulsive force disappears, and the diaphragm 21 returns to the electrode layer 3 side (FIG. 1 (c) )).

  It should be noted that residual vibration may occur before the diaphragm 21 comes into close contact with the electrode layer 3 simply by removing the applied voltage. However, it is necessary to prevent this depending on how the electrostatic actuator is used. In that case, when a voltage opposite to the voltage applied between the electrode layer 3 and the diaphragm 21 is applied between them and the diaphragm 21 is attracted to the electrode layer 3 side, Residual vibration can be eliminated.

Embodiment 2 (Droplet ejection head).
FIG. 2 is a schematic cross-sectional view showing a first example of a droplet discharge head according to Embodiment 2 of the present invention, and FIG. 3 relates to Embodiment 2 of the present invention viewed from a direction orthogonal to FIG. It is a cross-sectional schematic diagram which shows the 2nd example of a droplet discharge head. Although the shapes are different between FIG. 2 and FIG. 3, the substantive configuration is the same. This droplet discharge head uses the operation of the electrostatic actuator shown in the first embodiment, and in FIGS. 2 and 3, the same reference numerals as those in FIG. 1 represent equivalents or equivalents.

The droplet discharge head according to the second embodiment includes an electrode side member 10 in which an electret electret layer 1, an insulating layer 2, and an electrode layer (also referred to as individual electrode) 3 are stacked in order, and a liquid is stored in a nozzle hole. The cavity substrate 20 in which the discharge chamber 21 to be discharged from 41 is formed and the nozzle substrate 40 in which the nozzle holes 41 are formed are laminated.
2 and 3, the drive circuit 30 shown in the first embodiment is not shown, but the following description will be made assuming that it is present.

A plurality of electrode layers 3 are formed on the glass substrate, and each of them functions as an independent electrode, that is, an individual electrode. One end of the electrode layer 3 is drawn out to the edge of the glass substrate to form an electrode terminal 3a. An electret member is laminated on the opposite side of the glass substrate to form an electret layer 1. Therefore, the glass substrate between the electrode layer 3 and the electret layer 1 is the insulating layer 2.
The cavity substrate 20 is made of a silicon substrate, and is formed with a discharge chamber 22 and a reservoir 23 which are flow paths for the discharge liquid by etching. The bottom surface of the discharge chamber, which is one of the wall surfaces of the discharge chamber 22, is formed as the vibration plate 21, and the vibration plate 21 is disposed at a position facing the electrode layer 3.
The nozzle substrate 40 is formed of a silicon substrate or the like, and includes nozzle holes 41 corresponding to the discharge chambers 22 of the cavity substrate 20.

Next, the operation of the droplet discharge head according to the second embodiment will be described.
When no voltage is applied between the electrode layer 3 and the diaphragm 21, no charge is stored in the electrode layer 3 and the diaphragm 21. In this state, the diaphragm 21 is in close contact with the electrode layer 3 through the insulating film 25 (see FIG. 1A).
Next, a voltage having the same polarity as the charge of the electret layer 1 is applied to the diaphragm 21 between the electrode layer 3 and the diaphragm 21 using the drive circuit 30. As a result, the electric field generated by the electret layer 1 acts on the electric charge stored in the diaphragm 21 to generate a repulsive force on the diaphragm 21 and deform the diaphragm 21 away from the electrode layer 3 (FIG. 1). (See (b)). Thereby, the liquid in the discharge chamber 22 is discharged from the nozzle hole 41. In this case, since there is no gap between the diaphragm 21 and the electrode layer 3, it is possible to apply a charge that generates repulsive force to the diaphragm 21 by applying a lower voltage. Can be driven.
Thereafter, when the voltage applied between the electrode layer 3 and the diaphragm 21 is released, the electric charge due to the voltage disappears, the repulsive force disappears, and the diaphragm 21 returns to the electrode layer 3 side (FIG. 1). (See (c)). At this time, since the discharge chamber 22 expands, the discharge liquid is newly supplied from the reservoir 22 to the discharge chamber 22.
Further, when releasing the voltage applied between the electrode layer 3 and the diaphragm 21, when a voltage higher than the applied voltage is applied between them with a voltage opposite to the voltage applied thereto, Since the vibration plate 21 is strongly attracted to the electrode layer 3, residual vibration of the vibration plate 21 is prevented, and high-speed liquid droplet ejection is possible.

2 and 3 show an example in which the electrode layer 3 is formed so as to protrude from the glass substrate. However, as shown in the schematic cross-sectional view of FIG. 4, the electrode layer 3 is embedded in the groove of the glass substrate. Only the surface of the glass substrate may be used.
2 to 4 show the example in which the insulating film 25 is formed on the cavity substrate, the insulating film 25 may be formed on the electrode layer 3 of the glass substrate as shown in FIG. Furthermore, an insulating film 25 having a thickness half that of the thickness provided on one side may be provided on both the glass substrate and the cavity substrate.

Embodiment 3 (Manufacturing method of a droplet discharge head).
In Embodiment 3, an example of a manufacturing method of the droplet discharge head shown in Embodiment 2 will be described with reference to FIG.
(A) First, a glass substrate 2 of borosilicate glass having a thickness of about 1 mm is prepared.
(B) A groove 3 </ b> A for forming an electrode (individual electrode) 3 is formed on one surface of the glass substrate 2.
(C) An electrode member (for example, ITO) 3B is formed on the entire surface of the glass substrate 2 on which the groove 3A is formed.
(D) The electrode member 3B formed on the glass substrate 2 is patterned to form the electrode 3 in the groove 3A.
(E) An insulating film 25 such as silicon oxide is formed on the side surface of the glass substrate 2 where the electrode 3 is formed, and the electrically polarized electret member 1 is laminated on the surface of the glass substrate 2 opposite to the side where the electrode 3 is formed.
(F) On the other hand, a silicon substrate 20 (to be a cavity substrate later) having a thickness of about 500 μm on which a cavity such as the diaphragm 21 is formed is prepared.
(G) Boron is doped on one side of the silicon substrate 20 to form a portion to be the diaphragm 21.
(H) The boron-doped surface of the silicon substrate 20 is brought into close contact with the insulating film 25 of the glass substrate 2, and the silicon substrate 20 and the glass substrate 2 are anodically bonded using the exposed glass portion other than the electrode 3 formation region of the glass substrate. .

Thereafter, the silicon substrate 20 is etched to form the vibration plate 21, the discharge chamber 22, the reservoir 23, and the like, and a liquid protective film is formed on the surfaces of the vibration plate 21, the discharge chamber 22, and the reservoir 23.
Then, the nozzle substrate 40 provided with the nozzle holes 41 is bonded to the openings of the silicon substrate 20 such as the discharge chamber 22 and the reservoir 23 to complete the droplet discharge head.

Here, one example of a droplet discharge head manufactured by the method of Embodiment 3 will be described.
・ Longitudinal dimension of diaphragm 21 2 mm
・ Dimensions of diaphragm 21 in the short direction 100 μm
・ Thickness dimension of diaphragm 21 1μm
・ Insulation film 25 thickness 50 nm
・ Electret charge density 0.0075C / m ²
(Equivalent to the charge density produced by a capacitor with the following applied voltage)
・ Applied voltage 15V

FIG. 5 shows a configuration in which the electrode layer (or electrode) 3 is formed in the groove of the glass substrate 2, but as shown in FIGS. 2 and 3, without forming the groove in the glass substrate 2, The electrode layer (or electrode) 3 may be formed by raising the surface of the glass substrate 2.
In FIG. 5, the insulating film 25 is formed on the glass substrate 2 side, but may be formed on the diaphragm 21 side as shown in FIGS.
Furthermore, in each of the above-described embodiments, the configuration in which the electrically polarized electret member is laminated on the lower portion of the glass substrate 2 on which the electrode layer (or electrode) 3 is formed is shown. It is good also as the electret layer 1 by forming into a film | membrane on the board | substrate 2 and making the formed material into an electret.

Embodiment 4 (Droplet Discharge Device).
FIG. 6 is an external view showing a droplet discharge device according to Embodiment 4 of the present invention. This droplet discharge device is an ink jet printer in which the droplet discharge portion is provided with the droplet discharge head described in the second embodiment. For this reason, ink can be ejected at a low voltage and at a high speed.
Note that the droplet discharge device including the droplet discharge head described in the second embodiment can form a matrix pattern of a color filter, a light emitting portion of an organic EL display device, by changing various liquids to be discharged. The present invention can also be applied to a droplet discharge device that discharges a biological liquid sample.

The schematic diagram which shows (a) before voltage application, (b) during voltage application, and (c) after voltage cancellation of the electrostatic actuator of Embodiment 1 of the present invention. FIG. 6 is a schematic cross-sectional view illustrating a first example of a droplet discharge head according to Embodiment 2. FIG. 4 is a schematic cross-sectional view illustrating a second example of a droplet discharge head according to Embodiment 2 as viewed from a direction orthogonal to FIG. 2. FIG. 9 is a schematic cross-sectional view illustrating a third example of a droplet discharge head according to Embodiment 2 as viewed from a direction orthogonal to FIG. 2. FIG. 6 is a schematic cross-sectional view illustrating a manufacturing process of a droplet discharge head according to Embodiment 3. FIG. 6 is an external view of a droplet discharge device according to a fourth embodiment. Explanatory drawing of the electric field resulting from an electret layer.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Electret layer (electret member), 2 Insulating layer (glass substrate), 3 Electrode layer (electrode or individual electrode), 3a Electrode terminal, 10 Electrode side member, 20 Cavity substrate (silicon substrate), 21 Vibration plate, 22 Discharge chamber , 23 Reservoir, 25 Insulating film, 30 Drive circuit, 40 Nozzle substrate, 41 Nozzle hole.

Claims (7)

A flexible and conductive diaphragm is in close contact with the electrode layer of the electrode-side member in which an electret layer having an electric charge of only one electrode , an insulating layer, and an electrode layer are sequentially laminated via an insulating film. Has been placed,
The diaphragm is deformed by applying a voltage between the diaphragm and the electrode layer to generate a charge having the same polarity as the charge of the electret layer on the diaphragm. Electric actuator.   2. The electrostatic actuator according to claim 1, wherein when no voltage is applied between the diaphragm and the electrode layer, the diaphragm, the insulating film, and the electrode layer are in close contact with each other. Comprising the electrostatic actuator according to claim 1 or 2,
The diaphragm forms one of the wall surfaces of a discharge chamber for storing the discharge liquid and discharging the liquid from the nozzle;
A first voltage, which is a voltage that causes the diaphragm to generate a charge having the same polarity as the charge of the electret layer, is deformed between the diaphragm and the electrode layer, and the diaphragm is deformed. A liquid droplet discharge head, wherein liquid in a chamber is discharged from the nozzle.   4. The liquid according to claim 3, wherein a second voltage having a reverse voltage relationship with the first voltage is applied between the vibration plate and the electrode layer after discharging the droplet from the nozzle. 5. Drop ejection head.   5. A liquid comprising the liquid droplet ejection head according to claim 3 in a liquid droplet ejection unit. Forming an electrode material on the surface of the glass substrate;
Patterning the deposited electrode material to form an electrode;
Forming an insulating film on the electrode forming side surface of the glass substrate;
Laminating an electret member having only the charge of one electrode on the side opposite to the electrode forming side of the glass substrate;
A silicon substrate on which a vibration plate and a discharge chamber are formed is brought into close contact with the electrode through the insulating film of the glass substrate, and a portion other than the region corresponding to the electrode of the glass substrate is used for the glass substrate. An anodic bonding step;
And a step of etching the silicon substrate bonded to the glass substrate to form the diaphragm and the discharge chamber. Forming an electrode material on the surface of the glass substrate;
Patterning the deposited electrode material to form an electrode;
Laminating an electret member having only the charge of one electrode on the side opposite to the electrode forming side of the glass substrate;
Forming an insulating film on one surface of the silicon substrate on which the vibration plate and the discharge chamber are formed;
A step of bringing the silicon substrate into close contact with the electrode of the glass substrate through the insulating film, and anodic bonding to the glass substrate using a portion other than a region corresponding to the electrode of the glass substrate;
And a step of etching the silicon substrate bonded to the glass substrate to form the diaphragm and the discharge chamber.

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