JP3432346B2 - Recording head - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head of an ink jet recording apparatus, and more particularly to a driving method for ejecting a recording medium by using electrostatic force.

[0002]

2. Description of the Related Art Conventionally, an ink jet head which ejects ink droplets by utilizing electrostatic force is disclosed in, for example, Japanese Patent Laid-Open No. 7-13.
No. 2598 and Japanese Patent Laid-Open No. 2-289351. According to this, a vibration plate provided in a part of the ink flow path and an electrode facing the vibration plate and provided outside the ink flow path with a gap interposed between the vibration plate and the electrode. A voltage is applied to the vibrating plate to deform the vibrating plate to generate pressure in the flow path and eject ink.

FIG. 13 is a block diagram for explaining an example of the recording head disclosed in Japanese Patent Laid-Open No. 2-289351, and FIG. 14 is a longitudinal sectional view of FIG.
The side wall 21 and the vibrating plate 23 constituting the above are made of silicon by etching, photolithography, or the like.
The top of the channel 27 is closed by the top plate 22. One end of the flow path 27 is an ink ejection port 33, and the other is a common liquid chamber 30 formed of a top plate. Ink is supplied to the common liquid chamber 30 by an ink tank. The individual electrodes 24 are arranged on the back side (the surface not on the flow path side) of the vibrating plate 23 to maintain the insulating properties. In addition, the individual electrode 24
The common electrode 25 is arranged on the substrate 26 and is connected to the power source 32 with a proper gap 34 maintained at a position facing the. The gap 34 sandwiched between the individual electrode 24 and the common electrode 25 is filled with the ferroelectric liquid crystal 28 and is opened to the atmosphere by the atmosphere opening port 29.

In the ink jet recording head having the above-mentioned structure, when a voltage is applied between the individual electrode 24 and the common electrode 25, the diaphragm 23 bends due to electrostatic force,
The volume of the flow path 27 increases and ink is supplied from the common liquid chamber. Here, when the applied voltage is cut off, the deflected diaphragm 23 returns to its original state and pressurizes the ink in the flow path 27. The ink is ejected as ink droplets from the ejection port 33 by the pressurized energy and adheres to the paper 35 to be recorded.

[0005]

In the ink jet recording head as described above, when it is desired to set the driving voltage low, it is necessary to reduce the gap between the diaphragm and the electrode. However, if it is too small, the diaphragm and the electrode may come into contact with each other, causing a failure such as breakage. In addition, if the gap is increased even a little, there is a lack of stability such that a high voltage is required.

In order to realize low voltage driving, it is necessary to make the gap as small as possible. At least 5
It will be made smaller than μm. In this case, the length of the gap fluctuates due to the flatness and strain of the thin film that serves as the vibrating plate, the step difference (or gap spacer) forming the gap, and the like. The force acting on the diaphragm and the electrode is inversely proportional to the square of the length of the gap. Therefore, a slight error causes a large force difference, and the displacement force of the diaphragm changes.

Further, in order to secure the ink ejection volume, a certain amount of vibration plate area is required. At this time, if the lengths of the gaps vary, the smallest gap receives a large electrostatic attractive force and is bent according to the strength of the beam. That is, the location of displacement of the diaphragm corresponding to each nozzle and the amount of displacement differ depending on the variation in the gap. This phenomenon increases the instability of ink ejection and affects the response frequency.

The present invention provides an ink jet head which solves the above problems and is capable of stable ink ejection.

Further, according to the present invention, the vibrating plate and the electrode sandwiching the gap are provided non-parallel to each other to reduce the difference in displacement force caused by the gap error.

Further, in the present invention, in view of the fact that the ink in the flow path or the liquid chamber may be decompressed due to the abrupt displacement of the vibrating plate and bubbles may be generated, in order to prevent this, in the ink flow direction, A non-parallel gap is formed so that the diaphragm is displaced sequentially. By doing so, as another further effect, it is possible to prevent air from being drawn in from the nozzle.

[0011]

According to a first aspect of the present invention, a recording medium channel having a discharge port for discharging a recording medium, a part of the recording medium channel, and acting as a diaphragm. having a first electrode and a second electrode pair toward the first electrode,
A voltage is applied between the first electrode and the second electrode to displace the vibrating member and apply movement energy to the recording medium to eject the recording medium from the ejection port and attach it to the recording medium. In the recording head, the first electrode and the
Part of the second electrode is in contact with an insulating film, characterized in that a gap between the first electrode and the second electrode non-parallel, with in the diaphragm and the insulating coating Of layers
Eliminate shocking collisions and eliminate accidents of destruction
In addition, by making the gap size different, the displacement start point can be set to almost the same position in any nozzle, and the ejection speed of the ink droplet,
This is to suppress the variation in the ink droplet amount.

According to a second aspect of the present invention, in the recording head of the first aspect, the gap between the first electrode and the second electrode is increased along the moving direction of the recording medium. As a characteristic feature, the inflow of ink acts in the direction of the nozzle to prevent the generation of bubbles, the drawing of air from the nozzle, and the like against sudden pressure fluctuations.

[0013]

According to a third aspect of the present invention, in the recording head according to the first or second aspect , a substance having a higher dielectric constant than air is interposed between the first electrode and the second electrode. A characteristic is that a high dielectric constant substance, for example, glycerin is interposed in the gap portions provided non-parallel to each other so that the driving voltage is about several volts and the battery driving is facilitated.

According to a fourth aspect of the present invention, in the recording head according to any one of the first to third aspects, an appropriately oriented ferroelectric liquid crystal is interposed between the first electrode and the second electrode. This is characterized in that the ferroelectric liquid crystal is interposed in the gap portions provided non-parallel to each other so that the driving voltage is about several volts and the battery driving is facilitated.

According to a fifth aspect of the present invention, in the recording head according to any one of the first to fourth aspects, the first or second electrode is divided into a plurality of electrodes, and the plurality of electrodes are individually provided. It is characterized in that the amount or speed of the recording material adhered to the recording medium is varied by applying a voltage and changing the applied electrical energy or timing, and thus, recording with good integration and no fear of heat generation is achieved. It is the one that provides the dead.

[0017]

The invention of claim 6 is any one of claims 1 to 5.
The recording head according to any one of the above is characterized in that a flow path of the recording medium is provided between the first electrode and the second electrode, so that the diaphragm can be attracted with a strong force. , the conventional difficulty off low voltages, and is obtained by allowing injection of stable ink droplet.

[0019]

Figure 1 DETAILED DESCRIPTION OF THE INVENTION, in fragmentary cross-sectional view for explaining an example of a record head, for example, the upper surface of the substrate 1 is composed of glass or silicon electrode 2 is formed . The electrode 2 corresponds to each nozzle or liquid chamber, that is, acts as an individual electrode. An insulating coat layer 3 is applied on the electrode 2. Substrate 4 on which diaphragm 5 is formed corresponding to electrode 2
Are formed in close contact with the substrate 1 via the insulating coat layer 3. The substrate 4 is, for example, a substrate in which the diaphragm 5 is formed by etching silicon. A substrate 8 that forms an ink flow path is provided on the upper surface of the substrate 4. The substrate 8 forms the nozzle 11 in cooperation with the substrate 4 and simultaneously forms the liquid chamber 7, the liquid resistance portion 9 and the ink supply port 12.

[0020] Figure 2 is an enlarged view for explaining the detail of formic cap portion 10, as shown, stepped portions 10 ₁ provided at both ends of the vibration plate 5 formed on the substrate 4, 10 ₂ There are differences in length. For example, a step of 10 ₁ is 0.5 μm, 1
The 0 ₂ step portion is formed with a thickness of 1 μm. Therefore, the diaphragm 5
The gap between the electrode 2 and the electrode 2 is 0.5 μm at the step 10 _1.
± error (manufacturing error, assembly error, etc.). In addition, at the step portion 10 ₂ 1μm ± error (manufacturing error, an assembly error)
Becomes Here, when a voltage is applied between the electrode 2 and the diaphragm 5 from the power source (signal source) 13, the diaphragm 5 is displaced by electrostatic attraction. At this time, the displacement starts from the position where the gap is the smallest. That is, it begins to bend by receiving a large electrostatic absorption force from a flexible portion near the step portion 10 ₁ . Therefore, in FIG. 1, the diaphragm 5 starts to bend from the left side, and the inflow of ink starts.

FIGS. 3 and 4 schematically show how the diaphragm is bent. FIG. 3 shows the beginning of displacement of the diaphragm 5, and FIG. 4 shows the further displaced state. This FIG. 3 and FIG.
Shows that the diaphragm 5 is in contact with the insulating coating layer 3, but the length of the step portions 10 ₁ and 10 ₂ , the magnitude of electrostatic attraction, the thickness, width, and length of the diaphragm 5 are shown. However, the diaphragm 5 may be displaced while maintaining an appropriate gap.

As described above, by providing different gap sizes, the displacement points can be located at substantially the same position in any nozzle. This is a very important point in suppressing the ejection speed of ink drops and the variation in ink. Further, as shown in FIGS. 3 and 4, by providing the nozzle on the right side in the drawing, the inflow of ink acts in the direction of the nozzle, and in response to a sudden pressure fluctuation, bubbles are generated, air is drawn from the nozzle, etc. This is a very effective means.

FIG . 5 shows an embodiment of the recording head according to the present invention .
FIG. 3 is a diagram for explaining an example, which is an example in which the length of the step portion 10 ₁ is set to 0, and the individual electrode 6 is formed on the insulating coat layer 3.
One end of the vibration plate 5 provided with is contacted, and the other end of the vibration plate 5 is kept a slight gap by the step portion 10 ₂ . In this case, as shown in detail in FIG. 6, since an electrostatic attractive force from the portion 10 ₃ having no air gap acts, the vibrating plate 5 is displaced by a very large force, and therefore, the driving voltage is increased. Will be very small. Further, since there is no shocking collision between the diaphragm 5 and the insulating coat layer 3, there is an effect that an accident such as breakage is almost eliminated. The electrode 6 may be eliminated by configuring it as shown in FIG.

FIG. 8 shows the vibrating plate 5 in the direction in which the nozzles 11 are arranged.
And the electrode 2 are provided non-parallel. Although not shown, a combination of both FIG. 7 and FIG. 8, that is, a diaphragm and an electrode that are non-parallel to both the nozzle direction and the nozzle arrangement direction may be used.

[0025] According to the above mentioned such ink jet recording head, changing the properties of the ink, for example, when the ink is a pigment-based, require a strong discharge force viscosity changes. In that case, it is necessary to increase the thickness of the diaphragm 5 to increase the ejection force. The conventional method is insufficient to sufficiently displace the thickened diaphragm 5. That is, according to the recording head described in Japanese Patent Application Laid-Open No. Hei 2-289351 previously proposed by the applicant, the force of bending the diaphragm increases as the dielectric constant of the substance in the space increases, so that, for example, , Glycerin and the like intervene to generate a force 42.5 times that of the dielectric constant.
However, when a large kina force requirements necessary to be et al was slightly insufficient. Therefore, a substance having a high dielectric constant, such as glycerin, or
By interposing a ferroelectric liquid crystal or the like, the driving voltage, which has been about 30 v in the past, becomes about several v, which facilitates battery driving. The same applies to the material of the insulating coat layer 3.

[0026] PZT as actuators or, than those using such heating elements, conventionally, those provided with a plurality of elements with respect to one nozzle, by changing the size of the ink droplets fly to a gradation There is. However,
Providing a plurality of special ones such as PZT and heating elements contradicts increasing the degree of integration and is actually difficult. In addition, a large amount of current flows through these actuators, which may cause heat generation.

FIG . 9 provides a recording head which eliminates the above-mentioned drawbacks and which has good integration and is free from heat generation . In FIG . 9, the individual electrodes 2 corresponding to the diaphragm 5 are provided at 2 ₁ and 2. An example divided into _two is shown. According to the present invention, when only the individual electrode 2 ₁ is driven, when only 2 ₂ is driven, 2 ₁
And 2 ₂ are driven, the size of the ejected ink droplets changes, which makes it possible to provide gradation. Thus, according to the present invention, the actuator is simple in that it has only electrodes other than the diaphragm 5 and the current is considerably smaller than that of the PZT and the heating element, so there is no concern about heat generation even when continuously driven. Few. Since the diaphragm 5 and the electrodes 2 ₁ and 2 ₂ are not parallel to each other,
There is an effect that the driving force of the electrode 2 ₂ acts effectively.

In FIG . 1, a voltage is applied to the diaphragm 5 and the electrode 2 to displace the diaphragm 5. The fluid resistance portion 9 generates pressure in the liquid chamber 7 when the displaced diaphragm 5 returns to its original state,
The pressure serves to increase the ejection efficiency from the nozzle. Considering the supply of ink, it can be said that the fluid resistance portion 9 should not be provided. That is, when the vibrating plate 5 is displaced, the liquid chamber 7 is depressurized and ink is supplied. At this time, the fluid resistance portion 9 functions to prevent the inflow of this ink. The fluid resistance portion 9 is determined by its characteristics such as nozzle diameter and ink viscosity. In addition, when a sudden pressure fluctuation occurs in the liquid chamber, air is drawn in from the nozzle, bubbles are generated in the liquid chamber, and various problems occur depending on the conditions.

FIG. 10 is to solve these problems, there is provided a printhead which performs stable discharge, as shown in FIG shown, constituted by the diaphragm 5 the part of the member constituting the fluid resistance portions 9 As a result, when the diaphragm 5 is displaced in FIG.
The displacement portion starts from the left side of the fluid resistance portion 9 in FIG. Therefore, the ink is smoothly supplied from the ink supply port 12. Further, when the displacement of the vibrating plate 5 becomes large, the ink passes through the fluid resistance portion 9 and flows into the liquid chamber 7. Next, when the applied voltage is turned off, the vibrating plate 5 tries to return to the original state, pressure is generated in the liquid chamber 7, and droplets are ejected from the nozzle. In this way, the vibrating plate 5 can be displaced from the opposite side of the nozzle through the fluid, and the inflow of ink can be made smooth.

FIG. 11 is a diagram showing an example in which the present invention is applied to a side shoot type recording head. In the figure, 14 is a nozzle plate, and the nozzle plate 14 is at a position facing the vibrating plate 5. And is pressurized as described above, and the ink is ejected as an ink droplet from the nozzle 14a of the nozzle plate 14.

[0031] Figure 12 by applying a voltage between the diaphragm 5 and the electrode 2 to form a liquid chamber 7, which also serves as the electrode between the diaphragm 5 and the electrode 2 which also serves as a collector electrode, the liquid The pressure inside the chamber 7 is raised by the vibrating plate 5, and ink droplets are ejected from the nozzle 14a. In this way, it is possible to suck the diaphragm 5 with a strong force from the contact portion ₁₀₃ can be injected prior difficulties low voltage and stable ink droplets off.

[0032]

According to the first aspect of the present invention, there is provided a recording medium channel having a discharge port for discharging a recording medium, and a first electrode which constitutes a part of the recording medium channel and acts as a vibrating plate. And the first
And a second electrode which electrodes to a pair of direction, the first electrode by applying a voltage between the second electrode, said displaces the vibration member, giving movement energy to the recording medium In a recording head for ejecting the recording medium from the ejection port and adhering it to a recording medium, one of the first electrode and the second electrode
The portions are in contact with each other through an insulating film, and the gap between the first electrode and the second electrode is provided in a non-parallel manner. Bump
And the accident of destruction can be eliminated.
In the above, since the displacement start point can be made to be substantially the same position in any nozzle by providing different gap sizes, it is possible to suppress variations in ink droplet ejection speed and ink droplet amount.

According to a second aspect of the present invention, in the recording head of the first aspect, the gap between the first electrode and the second electrode is increased along the moving direction of the recording medium, Since the inflow of ink is made to work toward the nozzle, it is possible to prevent the generation of bubbles, the drawing of air from the nozzle, and the like in response to a sudden pressure change.

[0034]

According to a third aspect of the present invention, in the recording head according to the first or second aspect , a substance having a higher dielectric constant than air is interposed between the first electrode and the second electrode. The driving voltage can be set to about several volts to facilitate battery driving.

According to a fourth aspect of the present invention, in the recording head according to any one of the first to third aspects, an appropriately aligned ferroelectric liquid crystal is interposed between the first electrode and the second electrode. As a result, the driving voltage can be set to about several volts to facilitate battery driving.

According to a fifth aspect of the present invention, in the recording head according to any one of the first to fourth aspects, the first or second electrode is divided into a plurality of electrodes, and the plurality of electrodes are individually provided. Since the amount or speed of the recording material attached to the recording medium is changed by applying a voltage and changing the applied electrical energy or timing, it is possible to provide a recording head having good integration and free from heat generation. You can

[0038]

The invention of claim 6 is any one of claims 1 to 5.
In the recording head according to any Re, since the flow path of the recording material between the first electrode and the second electrode, it is possible to suck the diaphragm with a strong force, the conventional difficulties tinged low voltage In addition, it is possible to stably eject the ink droplets.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part for explaining an embodiment of a recording head according to the present invention.

FIG. 2 is an enlarged view for explaining details of a gap portion which is a feature of the present invention.

FIG. 3 is a diagram schematically showing how the diaphragm is bent, and is a diagram showing the beginning of displacement of the diaphragm.

FIG. 4 is a diagram schematically showing how the diaphragm is bent, and is a diagram showing a state where the diaphragm is further displaced.

FIG. 5 is a cross-sectional view of main parts for explaining another embodiment of the recording head according to the present invention.

FIG. 6 is a diagram showing in detail a main part of the recording head shown in FIG.

FIG. 7 is a cross-sectional view of essential parts for explaining another embodiment of the recording head according to the present invention.

FIG. 8 is a cross-sectional view of essential parts for explaining yet another embodiment of the recording head according to the present invention.

FIG. 9 is a cross-sectional view of main parts for explaining yet another embodiment of the recording head according to the present invention.

FIG. 10 is a cross-sectional view of essential parts for explaining yet another embodiment of the recording head according to the present invention.

FIG. 11 is a cross-sectional view of essential parts for explaining yet another embodiment of the recording head according to the present invention.

FIG. 12 is a cross-sectional view of essential parts for explaining yet another embodiment of the recording head according to the present invention.

FIG. 13 is a main-portion cross-sectional view for explaining an example of a conventional recording head.

14 is another cross-sectional view of the recording head shown in FIG.

[Explanation of symbols]

1 ... Substrate, 2 ... Electrode, 3 ... Insulation coating layer, 4 ... Substrate, 5
... vibrating plate, 6 ... individual electrode, 7 ... liquid chamber, 8 ... substrate, 9 ... fluid resistance part, 10 ₁ , 10 ₂ , 10 ₃ ... step part, 11 ... nozzle, 12 ... ink supply port, 13 ... power supply, 14 ... Nozzle plate.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-39235 (JP, A) JP-A-9-39228 (JP, A) JP-A-9-39229 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/06

Claims (6)

(57) [Claims] 1. A recording medium channel having a discharge port for ejecting a recording medium, a first electrode constituting a part of the recording medium channel and acting as a diaphragm, and the first electrode. and a second electrode that pairs toward the, by applying a voltage between the first electrode and the second electrode, to displace the vibration member, the recording giving moving energy to the recording medium in the recording head to adhere to a recording medium body discharged from the discharge port, before
Note that the first electrode and a part of the second electrode have an insulating film interposed therebetween.
A recording head, wherein the recording head is in contact with and the gap between the first electrode and the second electrode is provided non-parallel. 2. The recording head according to claim 1 , wherein a gap between the first electrode and the second electrode is increased along a moving direction of the recording body. Wherein the between the first electrode and the second electrode, the recording head according to claim 1 or 2, characterized in that by interposing a higher dielectric constant than air substance. 4. A recording head according to any one of claims 1 to 3, characterized in that by interposing a ferroelectric liquid crystal which is oriented appropriately between the first electrode and the second electrode . 5. A recording method in which the first or second electrode is divided into a plurality of electrodes, and a voltage is applied to each of the plurality of electrodes individually to change the electric energy or timing to be applied to the recording medium. The recording head according to any one of claims 1 to 4 , wherein the amount or speed of the body is variable. 6. A recording head according to any one of claims 1 to 5, characterized in that between the first electrode and the second electrode is in the flow path of the recording medium.