JPH07171960A - Ink jet head and driving method thereof - Google Patents

Abstract

PURPOSE:To provide an ink jet head having a multi-nozzle which can continuously discharge ink droplets excellently. CONSTITUTION:A plurality of partition walls 10a and 10b consisting of piezoelectric devices polarized in the thickness direction are arranged on a base plate 11 so as to form a groove 12. A plurality of pressure chambers 9 are formed by a lid 13 covering the groove 12. An ink discharge opening 16 and an ink supply opening 18 are provided at a part of the pressure chamber 9. By impressing voltage to electrodes 2a and 2b formed on the partition walls 10a and 10b, the shapes of the partition walls 10a, 10b are changed so as to be heightened in the thickness direction, narrowed in the width direction, and shortened in the longitudinal direction, so that the volume of the pressure chamber 9 is increased more than a volume of ink droplets 17 to be discharged. Thereafter, the voltage to be impressed is stopped, the original volume of the pressure chamber 9 is restored, and the ink droplets 17 are discharged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an ink jet head for selectively depositing ink droplets on an image recording medium and a driving method thereof.

[0002]

2. Description of the Related Art Among the non-impact printers whose market is expanding greatly today, an inkjet printer has the simplest principle and is suitable for color printing. Among them, the so-called drop-on-demand (DOD) type in which ink droplets are ejected only during dot formation can be said to be the mainstream.

As the DOD type, for example, Japanese Patent Publication No. 53-
The Kaiser type disclosed in Japanese Patent No. 12138 and the thermal jet type disclosed in Japanese Patent Publication No. 61-59914 are typical methods.

Of these, the former Japanese Patent Publication No. 53-12138
It is difficult to reduce the size of the structure described in Japanese Patent Publication No. 61-59914, and the latter structure described in Japanese Patent Publication No. 61-59914 has a very difficult problem in that the ink is burnt because high heat is applied to the ink. ing.

As a method for simultaneously solving the above-mentioned defects, there has been proposed a stretch mode type structure disclosed in Japanese Patent Publication No. 4-48622, which has a structure using a strip of a piezoelectric material.

The structure of the expansion / contraction mode type ink jet head is shown in the perspective view of FIG. A strip 122 of a piezoelectric material such as PZT (lead zirconate titanate) is fixed in parallel between a conductive support substrate 121 and an insulative lid 123, and a number of elongated strips are provided between the strips 122. Forming a channel.

These channels are alternately provided with an ink channel 125 which is a channel of an ink chamber and an ink flow path for filling ink and a dummy channel 126 of a gap.
And.

The ink channel 125 has one end connected to a common ink reservoir 127, and the ink reservoir 127 is connected to the common ink reservoir 127.
More ink is supplied and a print nozzle in the form of an ink passage is provided at the other end.

The strip 122 of piezoelectric material is polarized in a direction perpendicular to the support substrate 121, as indicated by arrow 7, and the lid 12
Electrodes 124 are provided on the upper surface of the strip 122 on the third side so as to correspond to the ink channels 125.

Here, the electrode 124 has a conductive substrate 121.
If a potential is applied to the strip 122 of piezoelectric material
Causes a deformation of the expansion mode that increases its thickness and decreases its width.

When the voltage application to the two strips is stopped, both strips return to their original shape, which causes the passage volume to decrease sharply. As a result, ink droplets 128 can be ejected from the passage.

[0012]

SUMMARY OF THE INVENTION The present invention is intended to solve the problems described below, which are associated with an ink jet head having a structure using such a conventional strip of piezoelectric material.

The first problem is that since the print nozzle in the form of an ink passage is provided, the length dimension of the ink channel 125 is too long as compared with the cross-sectional area of the channel. Therefore, there is a problem that the conduit resistance is large and the ink supply capacity is limited, and the continuous response of ink droplets is poor.

The ink ejection performance in the expansion / contraction mode type will be described in detail. The above-mentioned Japanese Patent Publication No. 4-4862 shown in FIG.
The size of the typical inkjet head disclosed in Japanese Patent Laid-Open No. 2 is such that the width and height of the strip 122 are 50 μm.
In m, the length dimension of the ink channel 125 is 10 mm.

The thin and long ink channel 125 is thus formed.
In the head formed in (1), there is a problem in continuous ejection of ink droplets, that is, in responsiveness.

In order to continuously eject ink droplets,
The same amount of ink as the ejected ink droplets must be supplied to the ink channel 125 with respect to the ink channel 125 from the common ink reservoir 127 located at the end opposite to the print nozzle.

Therefore, in order to form the ink droplets 128 continuously, it is preferable that the conduit resistance of the ink channel 125 is small and the length of the ink channel 125 is short.

The conduit resistance decreases as the cross-sectional area of the ink channel 125 increases, but in the embodiment disclosed in Japanese Patent Publication No. 4-48622, the ink channel 125 is formed for the purpose of forming a print nozzle in the form of an ink passage. The size of is small, almost square with 50 μm on each side.

Furthermore, since the amount of deformation of the piezoelectric material strip 122 is small, the length of the ink channel 125 must be increased in order to secure the ink amount of the ink droplet 128.

If the length of the ink channel 125 is shortened, the continuous response characteristic of the ink is improved, but the ink droplet 125 becomes small, or the ink droplet 128 is not ejected at all. There is a phenomenon that did not occur when there was a length.

If an electric potential is applied to the electrode 124 with respect to the conductive support substrate 121, the strip 122 of piezoelectric material is
The expansion / contraction mode is deformed such that its thickness is increased and its width is decreased. On the other hand, when the piezoelectric material undergoes the expansion / contraction mode deformation, it actually contracts in the longitudinal direction of the piezoelectric material, that is, in the lengthwise direction of the ink channel 125.

Stretching mode deformations that increase the thickness of strip 122 and reduce its width increase the volume of ink channel 125. However, at this time, the contraction in the longitudinal direction of the ink channel 125 which occurs at the same time is caused by the ink channel 1
Reduce the volume of 25.

The volume change amount of the ink channel 125 becomes the difference between this increase amount and the decrease amount, and this volume change amount becomes a source of generation of the ink droplet 128.

When the voltage application to the electrode 124 is stopped and the ink channel 125 is returned to its original size, the ink corresponding to the volume change amount of the ink channel 125 is pushed out of the ink channel 125.

When observed experimentally, the ink channel 1
It has been confirmed that the ink flow in 25 occurs in the print nozzle direction and the common ink reservoir 128 direction.

If the ink channel 125 has a sufficient length, the rear end of the ink channel 125,
That is, the influence on the ink ejection due to the deformation closer to the ink reservoir 127 can be ignored.

However, as described above, when the length of the ink channel 125 is shortened in order to improve the continuous response of the ink droplets, the volume change amount is reduced due to the contraction of the ink channel 125 in the longitudinal direction. It cannot be ignored.

That is, the component of contraction in the length direction of the ink channel 125 that reduces the volume change amount is the ink droplet 12.
8 is adversely affected.

As a result, there occurs a phenomenon that the ink droplet 128 becomes small or the ink droplet 128 is not ejected at all.

The second problem is that a high voltage must be applied to the piezoelectric material in order to obtain a sufficient volume change of the ink channel.

For this reason, the drive circuit and the electric insulating material must be constructed so as to be compatible with high voltage, resulting in an increase in cost.

An object of the present invention is to solve the problems caused by the individual structures and mechanisms of the ink jet head having the structure using the conventional strip of piezoelectric material as described above, and to improve the continuous ejection property of ink droplets. In addition, the present invention provides a configuration of an inkjet head that can be driven at a lower voltage and a driving method thereof.

[0033]

In order to achieve the above object, the constitution of the ink jet head of the present invention and the driving method thereof adopt the following means.

The first ink jet head according to the present invention is formed by a substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a lid covering the groove. A plurality of pressure chambers, and an ink ejection port and an ink supply port provided in a part of the pressure chamber, and by applying a voltage to the electrodes formed on the partition wall, the partition wall is high in the thickness direction and narrow in the width direction. It is characterized in that the volume of the pressure chamber is increased to be equal to or larger than the volume of the ink droplet to be ejected.

A second ink jet head according to the present invention comprises a substrate and a partition wall composed of a plurality of piezoelectric elements laminated with a plate-shaped piezoelectric material polarized in the thickness direction through a conductive material.
A groove is formed by arranging a plurality of partition walls on the substrate, a plurality of pressure chambers is formed by a lid that covers the grooves, an ink discharge port and an ink supply port provided in a part of the pressure chamber, and a voltage is applied to the conductive material. It is characterized in that the partition wall is deformed to be high in the thickness direction, narrow in the width direction, and short in the length direction by applying the voltage to increase the volume of the pressure chamber to be equal to or more than the volume of the ink droplet to be ejected.

A third ink jet head according to the present invention is formed by a substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a lid covering the groove. A plurality of pressure chambers, and an ink discharge port and an ink supply port provided in a part of the pressure chamber, and by applying a voltage to the electrodes formed on the partition wall, the partition wall is wide in the width direction and low in the thickness direction. It is characterized in that the volume of the pressure chamber is reduced more than the volume of the ink droplet to be ejected.

A fourth ink jet head according to the present invention comprises a substrate and a partition wall composed of a plurality of piezoelectric elements laminated in the thickness direction with a plate-shaped piezoelectric material interposed therebetween with a conductive material interposed therebetween.
A groove is formed by arranging a plurality of partition walls on the substrate, a plurality of pressure chambers is formed by a lid that covers the grooves, an ink discharge port and an ink supply port provided in a part of the pressure chamber, and a voltage is applied to the conductive material. It is characterized in that by applying the voltage, the partition wall is deformed so as to be low in the thickness direction, wide in the width direction and long in the length direction, and the volume of the pressure chamber is reduced to be equal to or more than the volume of ink droplets to be ejected.

A fifth ink jet head according to the present invention is formed by a substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a lid covering the groove. A plurality of pressure chambers, and an ink ejection port and an ink supply port provided in a part of the pressure chamber, and by applying a voltage to the electrodes formed on the partition wall, the partition wall is high in the thickness direction and narrow in the width direction. In a short direction, and then
It is characterized in that the partition wall is deformed to be low in the thickness direction, wide in the width direction and long in the length direction by a voltage in the direction opposite to the applied voltage, and the volume of the pressure chamber is changed to be equal to or larger than the volume of ink droplets to be ejected. .

A sixth ink jet head according to the present invention comprises a substrate, a partition wall composed of a plurality of piezoelectric elements laminated with a plate-shaped piezoelectric material polarized in the thickness direction through a conductive material, and a partition wall.
A groove is formed by arranging a plurality of partition walls on the substrate, a plurality of pressure chambers is formed by a lid that covers the grooves, an ink discharge port and an ink supply port provided in a part of the pressure chamber, and a voltage is applied to the conductive material. By applying the voltage, the partition wall is deformed to be high in the thickness direction, narrow in the width direction, and short in the length direction, and then the voltage in the opposite direction to this applied voltage causes the partition wall to be wide in the width direction and low in the thickness direction. It is characterized in that it is deformed for a long time and the volume of the pressure chamber is changed to be equal to or larger than the volume of ink droplets to be discharged.

The seventh ink jet head according to the present invention is characterized in that the electric field strength in the direction opposite to the applied polarization is not more than the polarization reversal electric field.

In the eighth ink jet head according to the present invention, the electrode exposed in the pressure chamber is coated with a coating film so that the electrode for driving the piezoelectric element exposed in the pressure chamber does not come into contact with the ink filled in the pressure chamber. It is characterized by covering with.

The method of driving an ink jet head according to the present invention comprises a substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a lid covering the groove. In a method of driving an inkjet head including a plurality of pressure chambers to be formed and an ink discharge port and an ink supply port provided in a part of the pressure chamber, a voltage is applied so as to generate an electric field in the same direction as the polarization direction of the piezoelectric element. Then, the application of the voltage is stopped, and the electric charge accumulated in the piezoelectric element is discharged to eject the ink droplet.

The method of driving an ink jet head according to the present invention comprises a substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a lid covering the groove. In a method of driving an inkjet head including a plurality of pressure chambers to be formed and an ink discharge port and an ink supply port provided in a part of the pressure chamber, a voltage is applied so as to generate an electric field in a direction opposite to a polarization direction of a piezoelectric element. And ejects ink droplets.

The method of driving an ink jet head according to the present invention comprises a substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a lid covering the groove. In a method of driving an inkjet head including a plurality of pressure chambers to be formed and an ink discharge port and an ink supply port provided in a part of the pressure chamber, a voltage is applied so as to generate an electric field in the same direction as the polarization direction of the piezoelectric element. Then, after that, a voltage for generating an electric field in a direction opposite to the polarization direction of the piezoelectric element is applied to eject the ink droplets.

[0045]

According to the above-described constitution and driving method of the ink jet head of the present invention, even if the length of the ink pressure chamber is shortened for the purpose of improving the continuous response characteristic of the ink droplet, the deformation of the partition wall composed of the piezoelectric element. The volume change amount of the ink pressure chamber due to is equal to or larger than the volume of the ink droplet.
Therefore, it is possible to form a stable ink droplet having a sufficient size.

Furthermore, since the piezoelectric element is formed by laminating a plurality of plate-shaped piezoelectric materials in which the partition walls are polarized in the thickness direction through a conductive material, it is possible to provide an ink jet head that can be driven even at a low voltage. You can

Furthermore, the electrode for driving the piezoelectric element and the ink filled in the pressure chamber do not come into contact with each other,
The electrode exposed in the pressure chamber is covered with a coating film.
Therefore, the electrodes for driving the piezoelectric element are not corroded or gas is not generated due to the chemical change of the ink, and both the water-based ink and the oil-based ink (non-aqueous) ink can be used.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of an ink jet head and its driving method in an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the ink jet head in a first embodiment of the present invention with a part thereof broken away.

As shown in the perspective view of FIG. 1, a plurality of partition walls 10a, 10 made of a piezoelectric material having polarization 1 in the thickness direction.
Grooves 12 are formed by arranging b and 10c in parallel on a substrate 11 made of an insulating material.

A nozzle plate 15 having a nozzle hole 16 serving as an ink ejection port is adhered to one of the end faces of the groove 12,
An ink supply port 18 connected to a common ink reservoir 19 is arranged on the other side of the groove 12.

Further, a lid 13 is adhered to the upper portion of the groove 12, and the groove 12 and the lid 13 form a pressure chamber 9.

The partitions 10a and 10b function as piezoelectric actuators by applying a voltage to the electrodes 2a and 2b formed on the end faces in the thickness direction.

Then, a voltage is applied to the partition walls 10a and 10b to deform the partition walls 10a and 10b to change the volume of the pressure chamber 9 filled with ink and generate pressure inside the pressure chamber 9 to generate ink. The droplet 17 is ejected.

FIG. 2 is a perspective view showing the structure of the pressure chamber 9 and its driving method. A method of driving the inkjet head shown in FIG. 1 will be described with reference to FIG.

In FIG. 2, the partition wall 1 made of a piezoelectric material is used.
When an electric field in the same direction as the polarization 1 of 0a, 10b is applied, the height H of the partition walls 10a, 10b extends by δH in the direction of arrow 2, the width W contracts by δW in the direction of arrow 3, and the length L further decreases by arrow 4. Contracts by δL in the direction.

When the applied voltage is V, the piezoelectric constant in the thickness direction of the piezoelectric material is d ₃₃ , and the piezoelectric constant in the length direction is d ₃₁ , δH = d ₃₃ × V δW = d ₃₁ × V × W / H δL = d ₃₁ × V × L / H.

Assuming that the width of the pressure chamber 9 is A, the volume A × H × L of the pressure chamber changes to (A + δW) × (H + δH) × (L-δL).

Therefore, the volume change amount of the pressure chamber 9 becomes approximately H × L × δW + A × L × δH−A × H × δL, ignoring the minute term, and ink corresponding to this volume change amount is generated in the pressure chamber 9. Is overfilled inside.

When the application of the voltage is stopped and the pressure chamber 9 is returned to the original size, the ink corresponding to the volume change amount is pushed out of the pressure chamber 9.

When the pressure chamber 9 has a sufficient length, the volume change at the rear end portion of the pressure chamber 9, that is, the ink supply port 18 side, does not affect ink droplet generation. In this case, since the volume change due to the change in the passage cross-sectional area of the pressure chamber is dominant, the amount of decrease in volume by the amount of change in the pressure chamber 9 (−A × H × δL) can be ignored.

In order to improve the continuous ejection property of the ink droplets, that is, the responsiveness, the ink amount of the ejected ink droplets 17 is promptly supplied from the ink supply port 18 to the pressure chamber 9.
Must be supplied to the meniscus of the nozzle hole 16 through.

When the length of the pressure chamber 9 is shortened, the distance from the ink supply port 18 to the nozzle hole 16 is shortened, so that the ink is quickly supplied. Therefore, the continuous response of the ink droplet 17 is improved.

In this way, when the length of the pressure chamber 9 is shortened for the reason of improving the continuous response of the ink droplet 17, the ink flow necessary for generating the ink droplet 17 is reduced to the pressure chamber. It extends to near the rear end of 9. Therefore, the volume is reduced by the volume change amount of the pressure chamber 9 (−A × H × δL).
The effect of cannot be ignored.

Therefore, the partition walls 10a and 10b are shortened to reduce the volume of the pressure chamber 9 (-A × H × δ).
L) should be small.

Further, in consideration of the influence of the escape of the ink flow and the like, in order to form the necessary ink droplet 17, the volume change amount (H
XLxδW + AxLxδH-AxHxδL) is required.

That is, assuming that the radius of the ink droplet 17 is r, H × L × δW + A × L × δH−A × H × δL ≧ 4 / 3τ
If r ³ is satisfied, continuous response is high and stable ink droplet generation is possible.

Therefore, the height, width and length (H,
W, L), groove width dimension (A), piezoelectric constant (d ₃₃ ,
The above-mentioned object can be achieved by setting each constant such as d ₃₁ ) so as to satisfy the above equation.

If this condition is not satisfied, there arises a problem that the ink droplet 17 becomes smaller than a predetermined size or is not ejected at all.

In this way, if the length dimension of the pressure chamber 9 is made sufficiently short so that the volume change amount of the driven pressure chamber 9 is equal to or larger than the volume of the ink droplet 17 to be ejected, the ink droplets are continuously ejected. It is possible to provide an inkjet head having excellent properties and capable of generating stable ink droplets.

FIG. 3 is a perspective view showing a partition and a pressure chamber of an ink jet head in the second embodiment of the present invention. Since the other structure is the same as that of the first embodiment, detailed description will be omitted.

As shown in FIG. 3, the first plate-shaped piezoelectric material 31a polarized in the thickness direction is polarized in the opposite direction to the first plate-shaped piezoelectric material 31a via the first conductive material 32a. The second plate-shaped piezoelectric material 31b is bonded to the second plate-shaped piezoelectric material 31b, and the third plate-shaped piezoelectric material 31c polarized in the opposite direction to the second plate-shaped piezoelectric material 31b is bonded via the second conductive material 32b.

Further, the conductive material and the plate-shaped piezoelectric material are sequentially laminated in the required number by the same means, so that the partition wall 30 is formed.
a and 30b are formed.

Further, the first conductive material 32a, the third conductive material 32c, etc. are made of gold (A) on one end surface of the partition wall 30a.
u) The film is electrically connected to the first collector electrode 33a formed by a thin film forming means such as a vacuum evaporation method.

Further, the second conductive material 32b, the fourth conductive material 32d, etc. are formed in the first end surface region other than the partition wall 30a.
The second collecting electrode 33b formed by the same means as the collecting electrode 33a is electrically connected.

When a voltage is applied between the first collecting electrode 33a and the second collecting electrode 33b with the structure shown in FIG. 3, a voltage is generated between the conductive materials, and an electric field is applied in the thickness direction of the plate-shaped piezoelectric material. Occurs. Therefore, the partition functions as a piezoelectric actuator.

When a voltage V in the same direction as the polarization direction of the second plate-shaped piezoelectric material 31b is applied to the first collecting electrode 33a and the second collecting electrode 33b, the height of the second plate-shaped piezoelectric material 31b is increased. H stretches by δH, width W shrinks by δW, and length L
Contracts by δL.

Here, the piezoelectric constant in the thickness direction of the plate-shaped piezoelectric material is d ₃₃ , the piezoelectric constant in the length direction is d ₃₁ , and the applied voltage is V
Then, δH = d ₃₃ × V δW = d ₃₁ × V × W / H δL = d ₃₁ × V × L / H.

Partition wall 30a and partition wall 30 forming the pressure chamber 9
When the dimension between b and A is A, the volume A × H × L formed by one pair of plate-shaped piezoelectric materials of the partition walls 30a and 30b is (A + δW) × (H + δH) × (L−δL) Change.

Therefore, the amount of change in the volume formed by one pair of plate-shaped piezoelectric materials is approximately H × L × δW + A × L × δH−A × H × δL when the minute term is ignored.

Assuming that the number of stackable plate-shaped piezoelectric materials is n, the volume change amount of the pressure chamber 9 is n times the volume change amount formed by the pair of plate-shaped piezoelectric materials, and n × (H × L × δW + A × L × δH−A × H × δL).

When the voltage application is stopped and the pressure chamber 9 is returned to the original size, the ink corresponding to the volume change amount of the pressure chamber 9 is pushed out of the pressure chamber 9.

In order to form the necessary ink droplets 17, the volume change amount of the pressure chamber 9 (n × (H × L × δW + A × L ×) is obtained for the same reason as described in the first embodiment. δH-
A × H × δL)) requires a volume of the ink droplet 17 or more.

When the partition walls 30a and 30b are formed with a laminated structure of piezoelectric material, compared with the first embodiment,
Even if the applied voltage is reduced by 1 / n of the number of stacked layers,
The equivalent volume change of the pressure chamber 9 can be secured. Therefore, it is possible to provide an inkjet head that can be driven at a low voltage.

In the first and second embodiments, when an electric field opposite to the polarization direction is applied to the partition made of a piezoelectric material, the partition 10a made of the piezoelectric material (see FIGS. 1 and 2) or the partition is formed. The height H of 30a (see FIG. 3) contracts by δH, the width W extends by δW, and the length L extends by δL.

When the applied voltage is V, the piezoelectric constant in the thickness direction is d ₃₃ , and the piezoelectric constant in the length direction is d ₃₁ , δH = d ₃₃ × V δW = d ₃₁ × V × W / H δL = d ₃₁ × V × L / H.

Assuming that the width of the pressure chamber 9 is A, the volume A × H × L of the pressure chamber changes to (A−δW) × (H−δH) × (L + δL).

Therefore, the volume change amount of the pressure chamber 9 becomes approximately −H × L × δW−A × L × δH + A × H × δL when the minute term is ignored. 9 Pushed out.

Next, when the voltage application is stopped and the pressure chamber 9 is returned to the original size, the pressure chamber 9 is filled with the above-mentioned volume change amount of ink.

In order to form the necessary ink droplets 17, the volume change amount of the pressure chamber 9 is the same as that of the ink droplets 17 for the same reason as described in the first and second embodiments. More than the volume is required.

Electric field strength (V /
When H) is set to be equal to or lower than the electric field for reversing the polarization (polarization reversing electric field), the partition wall can be driven without disturbing the polarization direction in the piezoelectric material, so that it has stable characteristics in the long term. An inkjet head can be provided.

In Examples 1 and 2, when an electric field in the same direction as the polarization direction was applied to the partition made of a piezoelectric material, the partition 10a made of a piezoelectric material (see FIGS. 1 and 2),
Alternatively, the height H of the partition wall 30a (see FIG. 3) extends by δH, the width W contracts by δW, and the length L contracts by δL.

When the applied voltage is V, the piezoelectric constant in the thickness direction is d ₃₃ , and the piezoelectric constant in the length direction is d ₃₁ , δH = d ₃₃ × V δW = d ₃₁ × V × W / H δL = d ₃₁ × V × L / H.

Next, the partition walls 10a, 10b or the partition wall 3
When an electric field opposite to the polarization direction is applied to 0a and 30b, the partition wall 10a made of a piezoelectric material or the height H of the partition wall 30a is increased.
Shrinks by δH compared with the original length, the width W extends by δW, and the length L extends by δL.

When such driving is performed, the partition walls 10a, 10
The amount of change in the dimension of b or the partition walls 30a and 30b is doubled, that is, 2δH in the height direction, 2δW in the width direction, and 2δL in the length direction. Therefore, in the fourth embodiment, when the same applied voltage is applied, the amount of dimensional change is doubled as compared with the first, second, and third embodiments.

At this time, the volume change amount of the pressure chamber 9 is H × L × 2δW + A × L × 2δH-A × H × 2δL, where A is the width between the partition walls.

In order to form the necessary ink droplets 17, the volume change amount of the pressure chamber 9 is the same as that of the ink droplets 17 for the same reason as described in the first and second embodiments. More than the volume is required.

When the radius of the ink droplet 17 is r, H × L × 2δW + A × L × 2δH−A × H × 2δL ≧ 4
It becomes / 3τr ³ .

If the electric field strength in the direction opposite to the applied polarization is set to be equal to or less than the polarization reversal electric field, it is possible to provide an ink jet head having stable characteristics for a long time as described above. .

A coating film formed by a chemical vapor deposition method using a polyparaxylene resin is provided on the inner surface of the partition wall forming the pressure chamber 9 shown in the first to fourth embodiments described above. If this coating film is formed, the ink in the pressure chamber 9 does not come into contact with the conductive material that is the electrode.

This coating film has a high electric insulating property and is the first conductive material 32 which is an electrode in contact with the pressure chamber 9.
The second conductive material 32b, the third conductive material 32c, and the like can be electrically insulated from the pressure chamber 9.

When the coating film is provided, the drive electrodes made of a conductive material do not come into contact with ink.

Therefore, the drive electrode is not corroded or gas is not generated due to the chemical change of the ink, and either water-based ink or oil-based ink (non-aqueous) ink can be used.

[0104]

As is clear from the above description, according to the ink jet head of the present invention, since the volume change amount of the pressure chamber can be set to be equal to or larger than the volume of the ink droplet, the ink pressure of a short length can be set. There is an effect that the chamber can be formed and ink droplets can be ejected at a high frequency.

Further, since the plate-shaped piezoelectric materials are laminated, it is possible to provide an ink jet head which can be driven at a low voltage.

Furthermore, the electrodes for driving the piezoelectric elements and the ink filled in the pressure chambers are prevented from coming into contact with each other.
The electrode exposed in the pressure chamber is covered with a coating film.

Therefore, the drive electrode is not corroded or the gas is not generated due to the chemical change of the ink, and both the water-based ink and the oil-based ink (non-aqueous) ink can be used.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a configuration and a driving method of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a pressure chamber of an inkjet head and a driving method according to an embodiment of the present invention.

FIG. 3 is a perspective view showing a structure and a driving method of a pressure chamber of an inkjet head according to another embodiment of the present invention.

FIG. 4 is a perspective view showing a structure of a pressure chamber of an inkjet head in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 polarization 2a electrode 2b electrode 9 pressure chamber 10a partition wall 10b partition wall 10c partition wall 11 substrate 12 groove 13 lid 15 nozzle plate 16 nozzle hole 17 ink droplet 18 ink supply port 19 common ink reservoir

Claims (11)

[Claims] 1. A substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a plurality of pressure chambers formed by a lid covering the groove. An ink discharge port and an ink supply port provided in a part of the pressure chamber are provided, and by applying a voltage to an electrode formed on the partition wall, the partition wall is deformed to be high in the thickness direction, narrow in the width direction, and short in the length direction, thereby An ink jet head, characterized in that the volume of a chamber is increased to a volume of an ejected ink droplet or more. 2. A substrate, a partition wall made of piezoelectric elements in which a plurality of plate-shaped piezoelectric materials polarized in the thickness direction are laminated with a conductive material interposed therebetween, and a groove formed by arranging a plurality of partition walls on the substrate. , A plurality of pressure chambers formed by a lid that covers the groove, and an ink discharge port and an ink supply port provided in a part of the pressure chambers. An ink jet head characterized in that it is deformed to be narrower in the length direction, and the volume of the pressure chamber is increased more than the volume of ink droplets to be ejected. 3. A substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a plurality of pressure chambers formed by a lid covering the groove. An ink discharge port and an ink supply port provided in a part of the pressure chamber are provided, and by applying a voltage to an electrode formed on the partition wall, the partition wall is deformed low in the thickness direction, wide in the width direction, and long in the length direction. An ink jet head, characterized in that the volume of a chamber is reduced to a volume of an ejected ink droplet or more. 4. A substrate, a partition wall composed of piezoelectric elements in which a plurality of plate-shaped piezoelectric materials polarized in the thickness direction are stacked with a conductive material interposed therebetween, and a groove formed by arranging a plurality of partition walls on the substrate. , A plurality of pressure chambers formed by lids that cover the grooves, an ink discharge port and an ink supply port provided in a part of the pressure chambers, and by applying a voltage to the conductive material, the partition wall is made low in the thickness direction and widthwise. An ink jet head characterized by being deformed widely in the longitudinal direction and reducing the volume of the pressure chamber to be equal to or larger than the volume of ink droplets to be ejected. 5. A substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a plurality of pressure chambers formed by a lid covering the groove. An ink discharge port and an ink supply port provided in a part of the pressure chamber are provided, and by applying a voltage to an electrode formed on the partition wall, the partition wall is deformed to be high in the thickness direction, narrow in the width direction, and short in the length direction. The voltage applied in the opposite direction to the applied voltage causes the partition wall to be deformed downward in the thickness direction, wide in the width direction and long in the length direction, and the volume of the pressure chamber is changed to be equal to or larger than the volume of the ink droplet to be ejected. Inkjet head to do. 6. A substrate, a partition wall composed of piezoelectric elements in which a plurality of plate-shaped piezoelectric materials polarized in the thickness direction are laminated with a conductive material interposed therebetween, and a groove formed by arranging a plurality of partition walls on the substrate. , A plurality of pressure chambers formed by a lid that covers the groove, and an ink discharge port and an ink supply port provided in a part of the pressure chambers. Ink that ejects the volume of the pressure chamber by deforming the partition wall low in the thickness direction and wide in the width direction by the voltage in the opposite direction to this applied voltage. An ink jet head characterized by being changed to a volume not less than the volume of a drop. 7. The electric field strength in the opposite direction to the applied polarization is
4. The polarization reversal electric field is equal to or lower than the electric field.
4. The inkjet head according to 4, 5, or 6. 8. The pressure chamber has a coating film covering the electrode exposed in the pressure chamber so that the electrode for driving the piezoelectric element exposed in the pressure chamber and the ink filled in the pressure chamber do not come into contact with each other. Claims 1, 2, 3,
4. The inkjet head according to 4, 5, or 6. 9. A substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a plurality of pressure chambers formed by a lid covering the groove. A method of driving an inkjet head having an ink ejection port and an ink supply port provided in a part of a pressure chamber applies a voltage so as to generate an electric field in the same direction as the polarization direction of a piezoelectric element, and then stops the application of the voltage. A method of driving an ink jet head, characterized in that ink droplets are ejected by discharging electric charges accumulated in the piezoelectric element. 10. A substrate, a partition wall composed of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a plurality of pressure chambers formed by a lid covering the groove.
A method of driving an ink jet head having an ink ejection port and an ink supply port provided in a part of a pressure chamber applies a voltage so as to generate an electric field in a direction opposite to the polarization direction of a piezoelectric element, and ejects ink droplets. A method for driving an inkjet head, comprising: 11. A substrate, a partition wall made of piezoelectric elements polarized in the thickness direction, a groove formed by arranging a plurality of partition walls on the substrate, and a plurality of pressure chambers formed by a lid covering the groove.
A method of driving an inkjet head including an ink discharge port and an ink supply port provided in a part of a pressure chamber is such that a voltage is applied so as to generate an electric field in the same direction as the polarization direction of the piezoelectric element, and then the polarization direction of the piezoelectric element is A method for driving an inkjet head, characterized in that a voltage for generating an electric field in the opposite direction is applied to eject ink droplets.