JP2002210953A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet head which is compact and discharges ink with good performance by forming grooves to faces of the side opposite to discrete electrodes of diaphragms and deforming the diaphragms by a low voltage appropriately. SOLUTION: A sealed actuator 14 of the ink jet head has the diaphragm 6 set to a part of each liquid channel to which ink is supplied through a liquid resistance from a common ink channel, and the discrete electrode 4 arranged opposite via a predetermined gap to each diaphragm 6. The groove 15 is formed to the face of the diaphragm 6 at the side of the discrete electrode 4. The volume of the actuator 14 is increased by the groove 15 formed to the diaphragm 6, and therefore a pressure rise generated inside the actuator 14 when the diaphragm is deformed towards the discrete electrode 4 is suppressed. The diaphragm 6 is deformed stably by the low voltage, realizing the performance of discharging ink drops stably. High-speed recording is thus enabled and at the same time, the image quality of recording images can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head, and more particularly, to displacing a diaphragm using electrostatic attraction and compressing a liquid chamber on the diaphragm only when recording is required. The present invention relates to an ink-on-demand type ink-jet head that ejects ink droplets by using an ink jet head.

[0002]

2. Description of the Related Art An ink jet recording apparatus does not require processes such as development and fixing, and can perform recording in a non-contact manner. Therefore, noise during recording is extremely low, and high-speed printing is possible. It has many advantages such as a high degree of freedom of ink and the ability to use inexpensive plain paper.
Among ink jet recording apparatuses, a so-called ink-on-demand type ink jet recording apparatus that discharges ink droplets only when recording is necessary does not require collection of ink droplets unnecessary for recording and maintenance is performed. Because of its simplicity, small size and low cost of the ink jet recording apparatus, it has attracted attention.

As such an ink-on-demand type ink jet head, for example, Japanese Patent Publication No.
As described in Japanese Patent No. 1734, a device using a piezoelectric element as a driving means, and as described in Japanese Patent Publication No. 61-59911, a pressure generated by heating ink to generate bubbles. As described in Japanese Patent Application No. Hei 3-234537, a driving unit includes a driving unit that vibrates a diaphragm using electrostatic force to discharge ink.

[0004] The ink jet head of the system using the electrostatic force has the advantages of small size, high density, high printing quality and long life.

[0005] An ink-jet head using this electrostatic force has a structure in which a nozzle, a discharge chamber, a recording medium cavity and a vibrating plate are provided on a medium substrate made of silicon, as described in, for example, JP-A-5-50601. An upper substrate having a recording material supply port and a lower substrate provided with electrodes facing the diaphragm are integrated with each other by etching. In this inkjet head, an electric field is applied to the vibration plate and the electrodes to vibrate the vibration plate and pressurize the ink in the recording medium cavity to discharge the ink.

In such an ink jet head using electrostatic force, the electrostatic force is proportional to the square of the applied voltage,
Since the distance between the diaphragm and the electrode or the square of the distance between the diaphragm and the insulating film is inversely proportional, when driving at a low voltage, the distance between the diaphragm and the insulator (electrode) needs to be shortened.

However, when the actuator section is sealed, there is a problem that the shorter the distance is, the greater the effect of the increase in the internal pressure of the actuator section due to the displacement of the diaphragm is.

Therefore, conventionally, a nozzle, an ink flow path communicating with the nozzle, a vibration plate formed in a part of the flow path, and an electrode formed facing the vibration plate are provided. In an inkjet recording apparatus having an inkjet head that applies an electric pulse between the vibration plate and the electrode, deforms the vibration plate by electrostatic force, and discharges ink droplets from the nozzles, the vibration plate and the electrode And the actuator including at least the vibration chamber formed by
Wherein the volume V of the actuator is set so that the ratio of the displacement ΔV to the volume ΔV removed by the diaphragm during driving falls within the range of 2 ≦ V / ΔV ≦ 8. (Japanese Patent Laid-Open No. 7-29)
No. 9908). In this ink jet recording apparatus, there is also proposed an ink jet recording apparatus in which the actuator volume V includes the volume of a groove in which a wiring portion connected to the electrode is formed.

Conventionally, a discharge port for discharging a recording medium,
A vibrating plate substrate having a pressurized liquid chamber for applying discharge pressure to the recording body and having a vibrating plate constituting a part of the pressurized liquid chamber is opposed to an electrode plate formed with electrodes. A recording head that disposes the recording medium onto a recording medium by disposing the recording medium at a position, deforming the vibration plate by electrostatic force acting between the electrode and the vibration plate, and discharging the recording medium by pressure generated by deformation of the vibration plate. A recording head has been proposed in which the interval between the formed diaphragm substrate and the electrode is longer at intervals other than immediately below the diaphragm than at the interval immediately below the diaphragm (Japanese Patent Application Laid-Open No. 11-1999). No. 34319).

That is, in this recording head, the volume of the actuator portion is increased in a portion other than immediately below the diaphragm to reduce an increase in internal pressure due to the displacement of the diaphragm.

[0011]

However, in the ink jet recording apparatus described in JP-A-7-299908, the ratio of the volume V of the actuator to the volume ΔV removed by the diaphragm during driving is: 2 ≦ V /
The volume V of the actuator is set so as to fall within the range of ΔV ≦ 8, and the volume of the groove in which the wiring portion connected to the electrode is formed is included in the actuator volume V. The volume of the actuator is increased by using the volume of the formed groove.

However, if the volume of the actuator is increased by using the volume of the groove in which the wiring portion is formed, conversely, even if the wiring is unnecessary, the volume V of the actuator is reduced by the groove of the wiring portion. In order to secure the capacitance within the range of 2 ≦ V / ΔV ≦ 8, there is a problem that the unnecessary wiring portion needs to be created.

In the recording head described in Japanese Patent Application Laid-Open No. 11-34319, the volume of the actuator section is increased in a portion other than immediately below the diaphragm to reduce an increase in internal pressure due to the displacement of the diaphragm. Therefore, in order to sufficiently reduce the increase in the internal pressure of the actuator section, it is necessary to form a space in a portion other than the diaphragm, and there has been a problem that the ink jet head becomes large.

In view of the above, according to the first aspect of the present invention, there is provided a vibration plate provided in a part of each liquid chamber to which ink is supplied from the common liquid chamber through the ink flow path, and faces each vibration plate with a predetermined gap. By forming a groove on the surface of the diaphragm of the actuator section facing the individual electrode, which has the individual electrodes arranged and sealed, the volume inside the actuator section can be increased with a simple configuration. In this way, when the diaphragm is deformed toward the individual electrodes, the pressure rise inside the actuator section is suppressed, and the diaphragm is deformed stably with low power, enabling high-frequency driving and stable ink droplet ejection. High performance (high ink drop ejection characteristics)
It is an object of the present invention to provide a small and inexpensive inkjet head capable of improving the image quality of a recorded image.

According to a second aspect of the present invention, an insulating layer is formed on the surface of the diaphragm facing the individual electrode, and a groove is formed by changing the thickness of the insulating layer, thereby further simplifying the structure. In addition, the volume inside the actuator section is further increased while preventing variations in the thickness of each diaphragm, and the pressure rise that occurs inside the actuator section when the diaphragm is deformed toward the individual electrodes is further suppressed. Deforms the diaphragm stably with low power, enabling high frequency driving,
Provide a small and inexpensive inkjet head that realizes more stable ink droplet ejection performance by preventing ink ejection variation between nozzles, enables high-speed recording, and can further improve the image quality of recorded images. It is intended to be.

According to a third aspect of the present invention, the groove is formed in a portion other than the central portion in the short side direction of the diaphragm, so that the groove is formed in a portion other than a portion where the electrostatic force acts most between the individual electrodes. By suppressing the increase in drive voltage due to the formation of the groove, the pressure rise generated inside the actuator section when the diaphragm is deformed to the individual electrode side is suppressed, and the power is more stably reduced. Deformation of the diaphragm enables high-frequency driving, realizes stable ink droplet ejection performance, enables high-speed recording, and is small and inexpensive that can further improve the image quality of the recorded image. It is intended to provide an ink jet head.

According to a fourth aspect of the present invention, a gas having a pressure propagation speed higher than that of air is sealed in the inside of the actuator section, so that the propagation of a pressure change generated inside the actuator section due to the deformation of the diaphragm is improved. It is an object of the present invention to provide an ink jet head that can realize more stable ink droplet ejection performance even when driven at a high frequency, can perform higher speed recording, and can further improve the image quality of a recorded image. I have.

[0018]

According to a first aspect of the present invention, there is provided an ink jet head comprising: a plurality of liquid chambers filled with ink; and a plurality of ink chambers communicating with the respective liquid chambers for discharging the ink in the liquid chambers. A common liquid chamber that communicates with each of the liquid chambers via an ink flow path and supplies the ink to the liquid chambers;
A diaphragm provided in a part of each of the liquid chambers, and an actuator unit sealed with an individual electrode disposed opposite to each of the diaphragms with a predetermined gap therebetween, In an inkjet head that deforms the vibration plate by electrostatic force generated by a voltage applied between the vibration plate and the individual electrode to generate pressure in the liquid chamber, and ejects the ink in the liquid chamber from the nozzle. The diaphragm achieves the above object by forming a groove on a surface of the diaphragm facing the individual electrode.

According to the above construction, the diaphragm provided in a part of each liquid chamber to which ink is supplied from the common liquid chamber through the ink flow path, and the diaphragms are disposed opposite to each diaphragm with a predetermined gap. A groove is formed on the surface of the vibrating plate of the actuator section facing the individual electrode, which has the sealed individual electrode, so that the volume inside the actuator section can be increased with a simple configuration, The pressure rise inside the actuator when the plate is deformed to the individual electrode side can be suppressed, and the diaphragm can be deformed stably with low power, enabling high frequency driving and stable ink droplet ejection. In addition to realizing the performance (ink droplet ejection characteristics), high-speed recording can be performed, and an ink jet head having good image quality of a recorded image can be made small and inexpensive.

In this case, for example, as described in claim 2, the diaphragm has an insulating layer formed on a surface of the diaphragm facing the individual electrode, and the thickness of the insulating layer is changed to change the thickness of the insulating layer. A groove may be formed.

According to the above configuration, the insulating layer is formed on the surface of the diaphragm facing the individual electrode, and the groove is formed by changing the thickness of the insulating layer. With the configuration, the volume inside the actuator section is further increased while preventing the thickness variation of each diaphragm, and the pressure rise generated inside the actuator section when the diaphragm is deformed toward the individual electrode is further suppressed. High-speed printing by stably deforming the diaphragm with low power, enabling high-frequency driving, and preventing variations in ink ejection between nozzles to achieve more stable ink droplet ejection performance. In addition, it is possible to reduce the size and the cost of the ink jet head, which further improves the image quality of the recorded image.

Further, for example, as described in claim 3, the groove may be formed in a portion other than the center in the short side direction of the diaphragm.

According to the above configuration, since the groove is formed in a portion other than the central portion in the short side direction of the diaphragm, the groove is formed in a portion other than the portion where the electrostatic force acts most on the individual electrodes. By forming the groove, it is possible to suppress an increase in drive voltage due to the formation of the groove, and it is possible to suppress a rise in pressure generated inside the actuator section when the diaphragm is deformed toward the individual electrode, thereby further reducing the pressure. The diaphragm is deformed stably with electric power, enabling high-frequency driving, realizing stable ink droplet ejection performance, enabling high-speed recording, and further improving the image quality of the recorded image. The ink jet head can be small and inexpensive.

Further, for example, as described in claim 4, the actuator portion may be filled with a gas having a pressure propagation speed higher than that of air.

According to the above configuration, since the gas having a pressure propagation speed higher than that of air is sealed in the inside of the actuator section, the propagation of the pressure change generated inside the actuator section due to the deformation of the diaphragm is improved. This makes it possible to achieve more stable ink droplet ejection performance even when driven at a high frequency, perform higher-speed printing, and further improve the image quality of a printed image.

[0026]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. It should be noted that the embodiments described below are preferred embodiments of the present invention, and therefore, various technically preferable limitations are added. However, the scope of the present invention is not limited to the following description. The embodiments are not limited to these embodiments unless otherwise specified.

FIGS. 1 to 4 show a first embodiment of the ink jet head of the present invention. FIG. 1 shows an ink jet head 1 to which the first embodiment of the ink jet head of the present invention is applied. FIG. 3 is a cross-sectional view in the long side direction.

In FIG. 1, the ink jet head 1
The electrode recesses 3 are formed on the upper surface side of the electrode substrate 2, and the individual electrodes 4 are formed in the electrode recesses 3.

On the electrode substrate 2 on which the individual electrodes 4 are formed,
The protective film 5 is formed, and the diaphragm 6 is formed on the protective film 5 at a predetermined interval.

A liquid chamber member 7 is joined on the vibration plate 6,
In the liquid chamber member 7, a liquid chamber 8, a liquid resistor 9, and a common ink flow path (common liquid chamber) 10 are formed. On the liquid chamber member 7,
The lid member 12 on which the nozzle 11 is formed is joined.
The common ink flow path 10 is connected to an ink tank (not shown), and the ink in the common ink flow path 10 is supplied to the liquid chamber 8 through the liquid resistance 9. A nozzle 11 is formed so as to communicate with the liquid chamber 8, and the ink in the liquid chamber 8 is discharged by a pressure increase in the liquid chamber 8 caused by the vibration of the diaphragm 6, as described later. Is discharged from.

The electrode substrate 2 is formed of a material such as single crystal silicon, glass, or ceramics. The electrode recess 3 is formed by forming the upper surface of the electrode substrate 2 such as single crystal silicon on the patterned anisotropic electrode 4. It is formed by performing reactive etching.

The individual electrodes 4 are made of a metal material having a high melting point, such as Al, Cr, or Ni, a semiconductor material doped with impurities, or a conductive ceramic material such as titanium nitride. When silicon is used as the material of the electrode substrate 2, an insulating film such as SiO ₂ is formed between the individual electrode 4 and the electrode substrate 2.

As shown in the sectional view of the short side direction in FIG. 2, the electrode concave portion 3 is formed in a flat bottom substantially square shape.
An individual electrode 4 is formed at the center of the bottom.

The vibrating plate 6 can be made of silicon or the like. When the vibrating plate 6 is formed of silicon, impurities are diffused in the liquid chamber member 7 in advance to stop etching at a desired thickness electrochemically. Method or SOI (silicon-on
-insulator).
The diaphragm 6 has a thickness in the range of 1 to 20 μm, and is bonded to the electrode substrate 2 by a method such as solid-phase bonding with high positional accuracy. When borosilicate glass is used as the electrode substrate 2, the diaphragm 6 can be bonded to the electrode substrate 2 by anodic bonding at a temperature of 300 ° C. by applying an electric field of several hundred volts. When silicon is used as the electrode substrate 2, it can be joined to the electrode substrate 2 by direct joining. By joining the vibration plate 6 to the upper part of the electrode recess 3 of the electrode substrate 2, an air chamber 13 is defined between the individual electrode 4 covered with the protective film 5 and the vibration plate 6.

The liquid chamber member 7 is formed using the same silicon substrate as the vibration plate 6, and the liquid chamber 8, the liquid resistance 9, and the common ink flow path 10 are formed by etching or the like.

The lid member 12 is joined onto the liquid chamber member 7,
The liquid chamber 8, the liquid resistance 9, and the common ink channel 10 are defined between the liquid chamber 8 and the liquid chamber member 7. The liquid chamber member 7 and the lid member 12
May have a laminated structure in which a plurality of substrates are laminated.

After the ink-jet head 1 is assembled and formed, the individual electrodes 4 are connected to the FPC board 20. At this time, the openings are sealed to prevent the vibration plate 6 and the individual electrodes 4 from being contaminated. Then, the actuator section 14 from the electrode substrate 2 to the diaphragm 6 with the air chamber 13 opened is sealed.

As shown in FIG. 2, the diaphragm 6 has a groove 15 having a predetermined depth on a surface facing the individual electrode 4, and the groove 15 is formed, for example, as shown in FIG. As shown in FIG. 4, two large rectangular shapes extending in the long side direction of the diaphragm 6 are formed, but a plurality of small rectangular grooves 16 may be formed as shown in FIG. Also, grooves 15,
16 is not limited to a rectangle.

The grooves 15 and 16 are formed on the surface of the vibration plate 6 on the side facing the individual electrodes 4 by, for example, etching or blasting.

Next, the operation of the present embodiment will be described. In the inkjet head 1 of the present embodiment, even when the actuator section 14 is sealed, the grooves 15 and 16 are formed on the surface of the vibration plate 6 on the side of the individual electrode 4 so that the actuator section 14 is formed.
The feature is that the internal capacity is appropriately increased, the diaphragm 6 is appropriately vibrated without using a large amount of electric power, the size is reduced, and the ink discharge performance is improved.

That is, when a voltage V is applied between the individual electrode 4 and the diaphragm 6 functioning as a common electrode, the inkjet head 1 moves between the individual electrode 4 and the diaphragm 6.
An electrostatic attraction is generated which is inversely proportional to the square of the distance between the electrodes, and the diaphragm 6 is pulled by the electrostatic force, and is displaced until the restoring force and the electrostatic force balance.

When the actuator 14 is sealed, the diaphragm 6 receives a pressure due to a change in volume of the actuator 14 in addition to the electrostatic force and the restoring force of the diaphragm 6 itself. The diaphragm 6 receives the rise of the internal pressure in the actuator section 14 and returns to a position where the sum of the internal pressure and the restoring force of the diaphragm 6 balances the electrostatic force.

In this state, in order to cause the diaphragm 6 to generate a displacement required for ejection, it is necessary to generate an extra electrostatic force that balances the rise in the internal pressure of the actuator section 14. The rise in the internal pressure of the actuator section 14 depends on the volume of the actuator section 14 and the diaphragm 6 in a state where the drive voltage is not applied (the state where the diaphragm 6 is not displaced).
Is determined by the ratio of the volume of the actuator section 14 after the displacement.

In order to reduce the rise in the internal pressure of the actuator section 14 and enable driving at a low voltage, it is necessary to increase the volume of the actuator section 14 in a state where no driving voltage is applied.

Therefore, in the ink jet head 1 of the present embodiment, as described above, the groove 15 or the groove 16 is formed on the surface of the vibration plate 6 on the side facing the individual electrode 4 so that the To increase the volume of the diaphragm 6
This reduces the increase in the pressure inside the actuator section 14 due to the deformation, and enables low voltage driving.

For example, the width (length in the short side direction) of the diaphragm 6
Is 100 μm, the length of the diaphragm 6 (length in the long side direction)
1000 μm, the distance between diaphragm 6 and individual electrode 4
When the groove 15 or the groove 16 is not formed when the thickness is 0.3 μm, the initial volume of the actuator unit 14 is 30 μm.
pl. In this case, the diaphragm 6 has a maximum of 0.5 μm
When displaced, the volume of the actuator unit 14 becomes 14p
and the pressure inside the actuator section 14 becomes
The driving voltage required for raising the pressure by 1 atm and displacing the diaphragm 6 by 0.5 μm, which is the maximum displacement, is 10 V or more compared to the driving voltage required when the actuator section 14 is opened without being sealed. Get higher.

However, when a groove 15 having a width of 56 μm, a depth of 0.3 μm, and a length of 1000 μm is formed on the diaphragm 6 as shown in FIG. 3, the volume in the actuator section 14 increases to 47 pl. Maximum displacement of diaphragm 6 is 0.5μ
The rise in the internal pressure of the actuator section 14 when the pressure becomes m is 0.48 atm, which is half that in the case where the groove 15 is not formed.

Therefore, even when the actuator section 14 is sealed, the volume inside the actuator section 14 can be reduced by a simple structure in which the groove 15 or the groove 16 is formed on the surface of the diaphragm 6 on the side facing the individual electrode 4. By increasing the pressure, it is possible to suppress a rise in pressure generated inside the actuator section 14 when the diaphragm 6 is deformed toward the individual electrode 4, and to stably deform the diaphragm 6 with low power, thereby enabling high-frequency driving. In addition to realizing stable ink droplet ejection performance (ink droplet ejection characteristics), high-speed recording can be performed, and the inkjet head 1 having good image quality of a recorded image can be made small and inexpensive. Can be.

FIGS. 5 and 6 are sectional views in the short side direction of the diaphragm 30 of the ink jet head to which the second embodiment of the ink jet head of the present invention is applied.

This embodiment is applied to an ink jet head similar to the ink jet head 1 of the first embodiment, and in the description of this embodiment, the first embodiment will be described. The same components as those of the inkjet head 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 5, an insulating film 31 is formed on the surface of the diaphragm 30 facing the individual electrode 4, and the surface of the insulating film 31 is selectively etched to form a groove 32.
Are formed.

That is, when a silicon substrate is used as the diaphragm 30 and the two grooves 32 are formed in a large rectangular shape extending in the long side direction of the diaphragm 30, first, as shown in FIG. An insulating film 31 is formed on the surface of the 30 that faces the individual electrode 4. The insulating film 31 is formed, for example, by forming an oxide layer with a predetermined thickness, for example, a thickness of several μm on a surface of the silicon substrate serving as the vibration plate 30 facing the individual electrode 4. Becomes the insulating film 31. Then, on the surface of the insulating film 31, a resist film 33 is formed in a portion other than the portion where the groove 32 is formed, that is, in a portion where the insulating film 31 is left. Thereafter, etching is performed using an etching solution for etching only the insulating film 31 to form the groove 32, so that the groove 32 having the same depth as the insulating film 31 can be formed with high precision. it can.
Thereafter, by removing the resist film 33, the diaphragm 30 having the groove 32 formed in the insulating film 31, as shown in FIG.
Can be formed.

When a silicon substrate is used as the vibration plate 30 and a silicon oxide film is used as the insulating film 31, a hydrofluoric acid-based etching solution (BHF) can be used as the etching solution, and only the insulating film 31 is etched. be able to.

When the grooves 32 are formed in the diaphragm 30 in this manner, the grooves 32 can be formed with high precision between the plurality of diaphragms 30 without variation, and the variation in the thickness of the diaphragm 30 can be reduced. Since the restoring force of the vibration plate 30 is proportional to the cube of the thickness, variations in the ejection of ink from the nozzles 11 can be suppressed. Therefore, the ink droplet ejection performance can be further improved, and the inkjet head 1 having good image quality of a recorded image can be made small and inexpensive.

FIG. 7 is a sectional view in the short side direction of a diaphragm 40 of an ink jet head to which the third embodiment of the ink jet head of the present invention is applied.

Note that this embodiment is applied to an ink jet head similar to the ink jet head 1 of the first embodiment, and in the description of this embodiment, the first embodiment will be described. The same components as those of the inkjet head 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 7, the diaphragm 40 has two large rectangular grooves 41 extending in the long side direction of the diaphragm 40 on the surface facing the individual electrodes 4.
The grooves 41 are formed on both sides of the center of the diaphragm 40 in the width direction (short side direction), and are not formed at the center of the diaphragm 40 in the width direction.

That is, assuming that the width of the diaphragm 40 is a,
The two grooves 41 are respectively formed at positions centered on a / 4, for example, as shown in FIG.

When the groove 41 is formed in a portion other than the widthwise center portion of the vibration plate 40, the electrostatic force applied to the center portion of the vibration plate 40 can be appropriately secured, and the actuator portion 14 Ink droplet ejection performance can be improved by suppressing an increase in internal pressure.

That is, the internal pressure of the actuator section 14 when the diaphragm 40 is displaced is uniformly applied to the diaphragm 40, but the electrostatic force between the individual electrodes 4 and the individual electrodes 4 is applied to the short side direction of the diaphragm 40. Occurs most in the central part.
This is because, when a single force is applied, the central portion of the diaphragm 40 is most displaced, whereby the distance between the diaphragm 40 and the individual electrode 4 is shortened, and the static electricity applied to the diaphragm 40 is reduced. To increase.

However, if a groove is formed at the center of the diaphragm 40 in the width direction, the diaphragm 40 and the individual electrode 4 are formed at the center.
Is increased, the electrostatic force applied to the center of the diaphragm 40 in the width direction is reduced, and the maximum displacement of the diaphragm 40 is reduced.

However, the diaphragm 40 of the present embodiment is
Since the groove 41 is formed in a portion excluding the central portion in the width direction, it is possible to appropriately secure the electrostatic force applied to the central portion of the diaphragm 40 and to suppress an increase in the internal pressure of the actuator portion 14. Thus, the ink droplet ejection performance can be improved.

In each of the above embodiments, a gas having a pressure transmission speed higher than that of air, for example, an inert gas such as nitrogen, helium, or Ar may be sealed in the actuator section 14.

In this way, even when the diaphragm 6 is driven at a high frequency, the pressure inside the actuator section 14 is propagated in a short time, and the local pressure rise in the actuator section 14 is suppressed. Thus, the disturbance of the displacement of the diaphragm 6 can be prevented, and the ink ejection performance can be further improved.

Further, when an inert gas is filled as a gas in the actuator section 14, it is possible to prevent the occurrence of sparks in the protective film 5, thereby improving the reliability of the protective film 5 and the reliability of the ink jet head 1. be able to.

[0066]

Example 1 A diaphragm having grooves shown in FIG. 3 was formed on the ink jet head 1 of the first embodiment under the following conditions, and the diaphragm was driven between the diaphragm and the individual electrodes. The voltage was applied to displace the diaphragm and observed.

That is, in the present embodiment, like the ink jet head 1 of the first embodiment, the electrode substrate 2
The electrode recess 3 is formed on the upper surface of the device, the individual electrode 4 is formed in the electrode recess 3, and the diaphragm 6 facing the individual electrode 4 is formed.
Using silicon, a width of 200 μm and a length of 1000 μm.
m, and a groove 15 having a width of 44 μm centered at a position of 50 μm in the left-right direction from the center in the width direction was formed on the surface of the diaphragm 6 facing the individual electrode 4. The groove 15 was formed to have a depth of 0.25 μm. At this time, the volume of the actuator section 14 was 71 pl.

When this ink jet head was driven, when the driving voltage was 31 V, the maximum displacement of the diaphragm 6 was 0.25 μm.

Comparative Example 1 An ink jet head similar to that of Example 1 was prepared under the following conditions, and the diaphragm was observed while being displaced.

That is, the diaphragm was formed under the same conditions as in Example 1 except that no grooves were formed, and the other conditions were the same as in Example 1. At this time, the volume of the actuator section was 50 pl.

When the driving voltage was applied in this state and the displacement of the diaphragm was observed, the diaphragm was maximally displaced when the driving voltage was 31 V, and the maximum displacement was only 0.095 μm. .

Comparative Example 2 An ink jet head similar to that of Example 1 was prepared under the following conditions, and the diaphragm was displaced to observe the driving voltage.

That is, the diaphragm had a groove formed at the center in the width direction, and the other conditions were the same as those of the first embodiment.

When the driving voltage was applied in this state and the displacement of the diaphragm was observed, the diaphragm was maximally displaced when the driving voltage was 31 V, and the maximum displacement could only be obtained at 0.087 μm. .

Example 2 A diaphragm having grooves similar to that of Example 1 was formed in the same manner as in the second embodiment, and the diaphragm was displaced to observe a drive voltage.

That is, a silicon substrate was used as a diaphragm, and boron was doped at 5 × 10 ²⁰ / cm ³ to a thickness of 0.2
An oxide film having a thickness of μm was formed as an insulating film, and ten actuator portions having the same grooves as those in Example 1 formed in the insulating film were formed on the same chip.

The opening of the actuator was sealed, a driving voltage was applied, and the displacement of the diaphragm was observed.

When a driving voltage of 31 V was applied to each actuator, the vibration plate was 0.25 μm in all chips.
m.

Comparative Example 3 A groove similar to that of Example 1 was formed by sound blast, and a driving voltage was applied to observe the displacement of the diaphragm.

That is, ten actuator portions in which the same grooves as those of the first embodiment were formed by sound blast on the diaphragm were formed on the same chip as in the second embodiment. This groove varied in depth.

The opening of the actuator was sealed, a drive voltage was applied, and the displacement of the diaphragm was observed.

When the displacement at the center of the diaphragm when a drive voltage of 27 V was applied to each actuator was measured, only two diaphragms were displaced by 0.25 μm.

<Embodiment 3> Argon gas was sealed in the actuator section of Embodiment 1 and a driving voltage was applied.
The displacement of the diaphragm was observed.

When the drive frequency is set to 1 KHz and a voltage of 31 V is applied, the maximum displacement of the diaphragm is 0.1.
It was 25 μm.

The driving frequency is 8K.
Hz and 31 V was applied, the maximum displacement of the diaphragm was 0.25 μm.

<Comparative Example 4> The opening of the actuator of Example 1 was sealed with air in, without sealing the argon gas into the actuator, and a driving voltage was applied to observe the displacement of the diaphragm. did.

As the driving voltage, the driving frequency is 20 KHz
When 31 V is applied, the maximum displacement of the diaphragm is
It was 0.105 μm.

Therefore, by enclosing a gas such as argon gas having a pressure transmission speed higher than that of air in the actuator portion, it is possible to prevent the displacement of the diaphragm from being disturbed.
It has been demonstrated that the ink ejection performance is improved.

Although the invention made by the inventor has been specifically described based on the preferred embodiments, the present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the gist of the invention. It goes without saying that it is possible.

[0090]

According to the ink jet head of the first aspect of the present invention, the vibration plate provided in a part of each liquid chamber to which ink is supplied from the common liquid chamber through the ink flow path, and the vibration plate provided with a predetermined Since a groove is formed on the surface of the diaphragm of the actuator portion facing the individual electrode, which has the individual electrodes arranged facing each other with a gap therebetween and is sealed,
Increase the volume inside the actuator with a simple configuration,
The pressure rise that occurs inside the actuator when the diaphragm is deformed toward the individual electrodes can be suppressed, and the diaphragm can be deformed stably with low power, enabling high-frequency driving and stable ink droplets. By realizing the ejection performance (ink droplet ejection characteristics), high-speed recording can be performed, and an ink jet head having good image quality of a recorded image can be made small and inexpensive.

According to the ink jet head of the present invention, an insulating layer is formed on the surface of the diaphragm facing the individual electrode, and a groove is formed by changing the thickness of the insulating layer. Therefore, the volume inside the actuator section is further increased with a simpler structure and the thickness of each diaphragm is prevented, and the pressure generated inside the actuator section when the diaphragm is deformed to the individual electrode side The rise can be further suppressed, and the diaphragm can be deformed stably with low power, enabling high-frequency driving and preventing ink ejection variation between nozzles to achieve more stable ink droplet ejection performance. As a result, high-speed recording can be performed, and an ink jet head having better image quality of a recorded image can be reduced in size and cost.

According to the ink jet head of the third aspect of the invention, since the groove is formed in a portion other than the center in the short side direction of the diaphragm, the largest electrostatic force acts between the diaphragm and the individual electrode. A groove is formed in a portion other than the portion, and an increase in drive voltage due to the formation of the groove can be suppressed, and a rise in pressure generated inside the actuator portion when the diaphragm is deformed toward the individual electrode side can be suppressed. It is possible to stably deform the diaphragm with even lower power, enable high-frequency driving, realize stable ink droplet ejection performance, perform high-speed printing, and Inkjet heads with better image quality can be made smaller and less expensive.

According to the ink jet head of the fourth aspect of the present invention, since a gas having a pressure propagation speed higher than that of air is sealed in the inside of the actuator portion, the pressure change generated in the actuator portion due to the deformation of the diaphragm is reduced. Propagation can be improved, and even when driven at a high frequency, more stable ink droplet ejection performance can be achieved, and higher-speed recording can be performed, and the image quality of the recorded image is further improved. Can be done.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an inkjet head to which an inkjet head according to a first embodiment of the present invention is applied.

FIG. 2 is a cross-sectional view in the short side direction of an individual electrode and a diaphragm portion of the inkjet head of FIG. 1;

FIG. 3 is a plan view of a surface on the individual electrode side of the diaphragm shown in FIG. 2;

FIG. 4 is a plan view of a surface on the individual electrode side of the diaphragm showing another example of a groove formed on the diaphragm of the ink jet head of FIG. 1;

FIG. 5 is a cross-sectional view in the short side direction of a diaphragm of an inkjet head to which an inkjet head according to a second embodiment of the present invention is applied.

FIG. 6 is a cross-sectional view in the short side direction in a state where a resist film is formed to form a groove in the diaphragm of FIG. 5;

FIG. 7 is a plan view of a surface on the individual electrode side of a diaphragm of an inkjet head to which an inkjet head according to a third embodiment of the present invention is applied.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inkjet head 2 electrode substrate 3 electrode recess 4 individual electrode 5 protective film 6 diaphragm 7 liquid chamber member 8 liquid chamber 9 liquid resistance 10 common ink channel 11 nozzle 12 lid member 13 air chamber 14 actuator section 15, 16 groove 20 FPC Substrate 30 Inkjet head 31 Insulating film 32 Groove 33 Resist film 40 Vibration plate 41 Groove

Claims (4)

[Claims] A plurality of liquid chambers filled with ink, a plurality of nozzles communicating with each of the liquid chambers and discharging the ink in the liquid chambers, and communicating with each of the liquid chambers via an ink flow path. A common liquid chamber for supplying the ink to the liquid chamber; a vibration plate provided in a part of each of the liquid chambers; and an individual electrode disposed to face each of the vibration plates with a predetermined gap. Actuator section which is then sealed, comprising: deforming the diaphragm with electrostatic force generated by a voltage applied between the diaphragm and the individual electrodes to generate pressure in the liquid chamber,
In the ink jet head for discharging the ink in the liquid chamber from the nozzle, a groove is formed on a surface of the vibration plate facing the individual electrode. 2. The vibration plate according to claim 1, wherein an insulating layer is formed on a surface facing the individual electrode, and the groove is formed by changing a thickness of the insulating layer. Item 7. The inkjet head according to Item 1. 3. The ink jet head according to claim 1, wherein the groove is formed in a portion other than a center portion of the diaphragm in a short side direction. 4. The ink jet head according to claim 1, wherein the actuator section is filled with a gas having a higher pressure propagation speed than air.