JP2763724B2 - Inkjet printheads and electronic devices with inkjet printheads - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet print head used for a printer, a facsimile, a plotter, a bar code printer, a digital copy and the like, and an electronic apparatus having the ink jet print head.

[0002]

2. Description of the Related Art Conventional ink jet printers are roughly classified into a continuity type and an on-demand type.
The on-demand type ejects ink only when necessary, and has low head responsiveness, but has the advantage that the apparatus is simple and inexpensive. The on-demand type includes an electrostatic attraction type in which ink is drawn from a nozzle by electrostatic force, and a pressure pulse type in which ink in a pressure chamber is pressurized and ink is pushed out from the nozzle. The pressure pulse type includes a piezoelectric type and a bubble type. The piezoelectric type is a type in which ink is pressurized by a piezoelectric (electrostrictive) element, and a one-chamber type in which ink is supplied through a pressure chamber, and a pressure chamber. There is a two-chamber type having two ink supply chambers. The one-chamber type includes a Kaiser type having a planar pressure chamber and a soltan type having a cylindrical pressure chamber.

FIG. 12 shows a basic principle diagram of a Kaiser-type piezoelectric head unit. An ink supply path 152, a pressure chamber 153, and a nozzle 154 are provided on the surface of a substrate 151.
Are connected. A vibration plate 155 is provided on the surface of the substrate 151, and a piezoelectric element 156 is provided outside the vibration plate 155 so as to face the pressure chamber 153, and a voltage is applied between the front and back surfaces of the piezoelectric element 156. A signal source 157 is connected to apply. The ink supply path 1
An ink container 159 is connected to 52 via a pipe 158.

In the above configuration, when a voltage is applied from the signal generation source 157 to the piezoelectric element 156, the piezoelectric element 156
Causes the diaphragm 155 to deflect, causing the ink 1 in the pressure chamber 153 to deflect.
The ink is ejected from the nozzle 154 to the recording paper 161 as an ink droplet 160a and recorded. And after ink ejection,
When the voltage application to the piezoelectric element 156 is released, the vibration plate 155 returns to the original state, and the ejected ink is supplied to the ink supply path 152 and the pipe 15 by the nozzle capillary force.
8, the ink is supplied from the ink container 159.

A conventional ink jet print head is specifically constructed as shown in FIGS. 10 and 11.
The substrate 1 is made of photosensitive glass and has a number of pressure chambers 2, a common ink path 3 communicating with the pressure chambers 2,
An ink inlet 5 for supplying ink 4 from an ink container (not shown) is formed by etching.
One end of the pressure chamber 2 is tapered, and a nozzle 6 is formed at the tip of the pressure chamber 2 so as to penetrate the substrate 1 at right angles to the pressure chamber 2 so that each nozzle 6 is formed in a straight line. Have been. A vibration plate 7 is attached to the surface of the substrate 1 on which the pressure chamber 2, the common ink path 3, and the ink introduction port 5 are formed. Further, a piezoelectric element 8 made of PZT is provided separately and independently on the outer surface of the diaphragm 7 so as to face each of the pressure chambers 2. The piezoelectric element 8 has a large aspect ratio in order to increase the density of the nozzle, and is connected to a signal source (not shown) via a flexible cable 9a. Here, the flexible cable 9a
Has a base film 92a and a cover film 93a as shown in FIG.
An electrode 92a is provided between the piezoelectric element 8 and the cover film 93a, and the electrode 92a is configured to be slightly in contact with an end of the piezoelectric element 8, so that a driving voltage is applied only from one end of the rectangular piezoelectric element 8. I have.

Here, as described above, the piezoelectric element 8 is attached to the vibration plate 7. At this time, the piezoelectric element 8 is polarized by applying a voltage to the vibration
Generally, a method of adhering it to a substrate is used. An adhesive is used for bonding, and pressure is applied to enhance the bonding effect. Also, as shown in Japanese Patent Application No. 4-151253, there is a method of applying a high voltage and repolarizing after attaching a piezoelectric element.

[0007]

However, when a voltage is applied to the piezoelectric element to eject an ink droplet, the voltage is applied in the same direction as the polarization in order to prevent depolarization. The piezoelectric element is often used so that it expands and contracts in the horizontal direction when a voltage is applied. Then, when bonding after polarization, a tensile stress is applied to the piezoelectric element in the horizontal direction during use, that is, when voltage is applied.
Also, when attaching the piezoelectric element, the diaphragm and the piezoelectric element are deflected to press the piezoelectric element, but when the pressing is completed, the piezoelectric element adheres in a pressurized state, so that tensile stress remains inside the piezoelectric element. Become. In particular, since the pressure chambers and the piezoelectric elements are arranged in a rectangular shape in order to increase the dot density of the printer, the tensile stress in the longitudinal direction increases.

Here, since the piezoelectric element is formed of a ceramic material, and the ceramic is weak in tension, cracks and cracks often occur in the piezoelectric element. In particular, in a rectangular piezoelectric element, cracks and cracks often occur in a direction perpendicular to the longitudinal direction. When a crack or a crack occurs in the piezoelectric element, the voltage cannot be applied to the portion of the piezoelectric element that is not in contact with the electrode due to the crack, because the electrode portion is only in contact with the end of the piezoelectric element, The change in the volume of the pressure chamber has been reduced, and the printing quality has been reduced, and the printing accuracy has been reduced.

Therefore, the present invention provides an ink-jet print head and an ink-jet print that can apply a voltage to the entire length of the piezoelectric element even when the piezoelectric element is cracked or cracked, thereby improving print quality. It is an object of the present invention to provide an electronic device having a head.

[0010]

According to the present invention, first, there is provided a substrate having an ink supply path, a pressure chamber, and a nozzle, a vibrating plate provided on the surface of the substrate, and an outer surface of the vibrating plate. The diaphragm includes a piezoelectric element provided facing the pressure chamber, and a flexible cable having an electrode portion connected to the piezoelectric element, and applying a voltage between both front and back surfaces of the piezoelectric element. Wherein the flexible cable is configured to cover an upper surface of the piezoelectric element, and the electrode portion has a length that extends over substantially the entire length of the piezoelectric element. The second feature is that, in the first configuration, the electrode portion of the flexible cable has a width approximately one third of the width of the piezoelectric element. That.

Thirdly, in the first or second configuration, the electrode portion of the flexible cable is disposed at an end of the piezoelectric element. In the first, second, or third configuration, the flexible cable has an opening above a space between the electrode unit and another electrode unit.

Fifth, an electronic apparatus is provided with the print head according to the first, second, third, or fourth aspect.

[0013]

In the ink jet print head and the electronic apparatus having the ink jet print head according to the present invention, the flexible cable is formed so as to cover the upper surface of the piezoelectric element, and the length of the electrode portion extends over substantially the entire length of the piezoelectric element. Therefore, even if cracks or cracks occur at right angles to the longitudinal direction of the piezoelectric element, a voltage can be applied to the entire longitudinal direction of the piezoelectric element, so that the volume change of the pressure chamber does not decrease. .

In the case where the electrode portion has a length that extends over substantially the entire length of the piezoelectric element as described above, the influence on the vibration of the electrode portion is greater than in the prior art. In a configuration having a width that is approximately one third of the width of the element, the weight of the electrode portion can be reduced due to the increase in the length of the electrode portion, so that the influence on the vibration of the electrode portion is reduced. be able to.

[0015] Even when the electrode portion has a length that is substantially the entire length of the piezoelectric element in the longitudinal direction, if the electrode portion is arranged at the end of the piezoelectric element, the diaphragm is close to the position in contact with the substrate. The effect on the vibration of the part can be reduced.

Furthermore, if the flexible cable has an opening in the upper part of the space between the electrode part and the other electrode part, the vibration of the diaphragm corresponding to a certain piezoelectric element corresponds to another piezoelectric element. The effect on the vibration of the vibrating plate portion can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIGS. 1, 3, and 4 are a plan view and a cross-sectional view of the piezoelectric head unit, respectively. In the piezoelectric head unit according to the present embodiment, the substrate 1 is made of photosensitive glass as in the related art, and has a large number of pressure chambers 2, a common ink path 3 communicating with the pressure chambers 2, and a common ink path 3. An ink inlet 5 for supplying ink 4 from an ink container (not shown) is formed by etching. One end of the pressure chamber 2 is tapered, and a nozzle 6 is formed at the tip of the pressure chamber 2 so as to penetrate the substrate 1 at right angles to the pressure chamber 2 so that each nozzle 6 is linear. Is formed. A vibration plate 7 is attached to the surface of the substrate 1 on which the pressure chamber 2, the common ink path 3, and the ink introduction port 5 are formed.
Further, a piezoelectric element 8 made of PZT is provided separately and independently on the outer surface of the diaphragm 7 so as to face each of the pressure chambers 2.

In the present invention, each piezoelectric element 8 is connected to a signal generation source (not shown) via a flexible cable 9, and the flexible cable 9 has a diaphragm 7 at the bottom as shown in FIG. A cover film 91 in contact with the base film 92 and a base film 92 on the top.
An electrode 93 made of a conductor is provided between the cover film 91 and the cover film 91.
Is provided. Here, as shown in FIG. 2, the base film 92 has a larger area in plan view than the cover film 91, and covers the piezoelectric element 8 as shown in FIGS. 1, 2, and 3. Is formed. The base film 92 of the flexible cable 9 has an elongated opening at the center as shown in FIG. 2, but the supporting portion 12 for supporting the diaphragm 7 is provided on the base 10 as shown in FIG. Because it is provided in. Due to the support portion 12, the deflection of the diaphragm corresponding to a certain piezoelectric element does not cause unnecessary deflection of the portion of the diaphragm corresponding to another piezoelectric element.

The electrode 93 extends to the longitudinal end of the piezoelectric element 8 as shown in FIG.
Is formed to be about one third of the width of the piezoelectric element 8 as shown in FIGS.

In this embodiment, since the electrode 93 is formed to be long in the longitudinal direction of the piezoelectric element 8, even if the piezoelectric element 8 is cracked or cracked in a direction perpendicular to the longitudinal direction, the electrode 93 is kept in the piezoelectric element 8 Therefore, a voltage can be applied to all portions of the piezoelectric element 8 in the longitudinal direction, and a change in the volume of the pressure chamber due to cracking of the piezoelectric element can be prevented. Further, as described above, since the electrode 93 is formed to be about one third of the width of the piezoelectric element 8, the electrode 93 is provided on the entire length of the piezoelectric element in the longitudinal direction. The influence can be reduced.

In the above embodiment, the electrode 93 is arranged at the center of the piezoelectric element 8, but in the embodiment shown in FIG. 6, the electrode 93 is arranged at the end of the piezoelectric element 8 with respect to the direction perpendicular to the longitudinal direction. Have been. In the case of this embodiment, the electrode 9
Since 3 is disposed near the position where the diaphragm contacts the substrate, the influence of the electrodes on the vibration of the diaphragm can be reduced as compared with the case where the diaphragm is disposed at the center of the piezoelectric element 8.
That is, as shown in FIGS. 1 and 3, when the electrode is arranged at the center of the piezoelectric element, the weight of the piezoelectric element exerts an effect such that the diaphragm cannot obtain desired vibration. However, when it is arranged at the end of the piezoelectric element as in the present embodiment, the effect can be reduced.

Next, in the embodiment shown in FIGS. 7 and 8, the base film 92 'of the flexible cable 9'
Have an opening 94, and a cross section 95 between each opening is an electrode 9
3. This is because the vibration of the vibrating plate portion corresponding to a certain piezoelectric element is affected by the vibration of the vibrating plate portion corresponding to another piezoelectric element, because the base film 92 ′ of the flexible cable 9 ′ has a shape covering the piezoelectric element. There is a possibility that the desired vibration may not be obtained due to the influence or the weight of the base film 92 ′ applied to the diaphragm,
By providing the opening in the base film as described above, such a risk can be prevented.

In a printer as an electronic device using the above-mentioned ink jet print head, FIG.
As shown in FIG. 2, an ink jet print head is disposed in a cartridge 100 disposed on a carriage 101. The carriage 101 is slidably provided on two guides 102, and a pulley driven by a motor 103 is provided. The rotation of the wire 104 causes the wire 105 to move left and right, and the carriage 101 moves left and right with the movement of the wire 105. The ink ejection control of the ink jet print head is performed via the flexible cable 106. On the printing surface of the cartridge 100, a platen 1
The paper 110 wound around 07 is opposed, and printing is performed on the paper 110.

[0024]

As described above, according to the ink jet print head and the electronic apparatus having the ink jet print head according to the present invention, even when the piezoelectric element is cracked or cracked, the voltage is applied to the entire length of the piezoelectric element. Can be applied, so that a change in the volume of the pressure chamber can be prevented from decreasing, and the print quality can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a piezoelectric type head unit.

FIG. 2 is a plan view showing a flexible cable.

FIG. 3 is a longitudinal sectional view of the piezoelectric head unit of FIG. 1;

FIG. 4 is a cross-sectional view of the piezoelectric head unit of FIG.

FIG. 5 is a cross-sectional view showing an example in which the piezoelectric head unit of FIG. 1 is assembled on a base.

FIG. 6 is a cross sectional view showing another embodiment of the piezoelectric head unit.

FIG. 7 is a cross-sectional view showing another embodiment of the piezoelectric head unit.

FIG. 8 is a plan view showing another embodiment of the flexible cable.

FIG. 9 is a partial perspective view showing a printer including the piezoelectric head unit according to the embodiment.

FIG. 10 is a plan view showing a conventional piezoelectric head unit.

FIG. 11 is a vertical sectional view of the piezoelectric head unit of FIG. 9;

FIG. 12 is a diagram illustrating the principle of a piezoelectric head unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Pressure chamber 3 Common ink path 4 Ink 5 Ink introduction path 6 Nozzle 7 Vibrating plate 8 Piezoelectric element 9, 9 ', 9a Flexible cable 92, 92', 92a Base film 93, 93a Electrode 94 Opening A Printer

Claims (5)

(57) [Claims] A substrate having an ink supply path, a pressure chamber, and a nozzle; a vibration plate disposed on a surface of the substrate; and a piezoelectric element provided on an outer surface of the vibration plate so as to face the pressure chamber. ,
A flexible cable having an electrode portion connected to the piezoelectric element, wherein an ink jet print head that deflects the diaphragm by applying a voltage between the front and back surfaces of the piezoelectric element and ejects ink from nozzles. An ink jet print head, wherein the flexible cable is configured to cover an upper surface of the piezoelectric element, and the electrode portion has a length extending substantially over the entire length of the piezoelectric element. 2. The ink-jet printhead according to claim 1, wherein the electrode portion of the flexible cable has a width approximately one third of the width of the piezoelectric element. 3. The ink jet print head according to claim 1, wherein the electrode portion of the flexible cable is arranged at an end of the piezoelectric element. 4. The ink-jet printhead according to claim 1, wherein the flexible cable has an opening above a space between the electrode part and another electrode part. 5. An electronic apparatus comprising an ink jet print head, comprising the print head according to claim 1. Description: