JPH10193600A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive ink jet head capable of being subjected to low voltage driving and having high reliability. SOLUTION: In an ink jet head, an electrode 42 is formed to the under surface of a vibration plate 41 and an individual electrode 43 is formed under the electrode 42 through a minute gap 44. In this case, when voltage is applied across the electrode 42 and the individual electrode 43, the vibration plate 41 is attracted by force of static electricity to be bent and the vol. of each ink emitting chamber 45 becomes large to receive the supply of ink from a common liquid chamber 47 through an ink inflow port 48. When applied voltage is cut off, the bent vibration plate 41 is returned to the original state to pressurize the ink in the ink emitting chamber 45. Ink is emitted from an emitting orifice 46 as ink droplets by pressurizing energy and bonded to paper to perform recording. By filling the gap 44 with a substance with a specific dielectric constant ε*, applied voltage for generating the same force of static electricity becomes 1/√ε*.

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 which discharges ink droplets and deposits ink on a recording medium for recording, and more particularly to an ink-jet head which utilizes electrostatic force as a driving method.

[0002]

2. Description of the Related Art When a voltage is applied between two electrodes, a diaphragm bends due to an electrostatic force, and subsequently, when the applied voltage is cut, the vibrating plate returns to its original state. An ink jet head that pressurizes ink by using force and discharges it as ink droplets has the advantages of low noise, small size, high density, high printing quality, and long life.
However, a high applied voltage is required to generate an electrostatic force between the two electrodes to deform the vibration plate and to obtain a force sufficient to eject ink, which increases the cost of the drive circuit. In order to solve the problem, Japanese Patent Application Laid-Open No. 2-289351
Japanese Patent Application Laid-Open Publication No. H11-163873 discloses a structure in which a substance having a relative dielectric constant is filled between two electrodes.

FIG. 5 is a sectional view of an essential part for explaining an example of the above-described ink jet head. FIG. 6 is a sectional view in the longitudinal direction of FIG. 5, where 1 is a side wall, 2 is a top plate, Reference numeral 3 denotes a vibration plate, 4 denotes an individual electrode, 5 denotes a common electrode, 6 denotes a substrate, 7 denotes a channel, 8 denotes a ferroelectric liquid crystal having a relative dielectric constant, 9 denotes an air opening, 10 denotes a common liquid chamber, and 11 denotes a common liquid chamber. An ink tank, 12 is a power supply, 13 is an ink ejection port, 14 is a gap, 15 is paper, and a gap 1 sandwiched between the individual electrode 4 and the common electrode 5 is provided.
4 is filled with a ferroelectric liquid crystal 8 and is opened to the atmosphere through an opening 9 to the atmosphere.

The electrostatic force Pe acting per unit area between the individual electrode 4 and the common electrode 5 is given by the following equation. Pe = ε / 2 · (V / d) ² (1) where V is the applied voltage, d is the distance between the electrodes, ε is the dielectric constant, and the dielectric constant ε is represented by the following equation. ε = ε ₀ ε * (2) Here, ε ₀ is a dielectric constant in a vacuum, and ε * is a relative dielectric constant.

Accordingly, when the electric field strength E (= V / d) is constant, the electrostatic force increases as the material has a higher relative dielectric constant ε *. Also, when a substance having a relative dielectric constant is filled, the applied voltage can be reduced to one-square root of the relative dielectric constant to obtain the same electrostatic force as compared with a case where the substance is not filled.

Further, Japanese Patent Application Laid-Open No. 4-52214 discloses that
Another configuration of an ink jet head is described. FIG. 7 is a diagram showing an example of the configuration. In the case of this example, the electrodes 25 and 27 are arranged so as to face the wall of the pressure chamber 22 containing the ink 32 by using the ink 32 having a high dielectric constant. By applying a voltage between the electrode 25 and the electrode 27, an electrostatic force is generated between the electrodes, the force causes the diaphragm 26 of the pressure chamber 22 to bend, and the ink 32 is pressurized to
No. 3 ejects ink droplets. In this ink jet head, the applied voltage can be reduced by the relative dielectric constant of the ink.

[0007]

However, according to the method described in Japanese Patent Application Laid-Open No. 2-289351, the gap 14 sandwiched between the individual electrode 4 and the common electrode 5 is opened to the atmosphere by the opening 9 to the atmosphere. Therefore, the liquid filled in the gap 14 evaporates and the quality is deteriorated. In addition, dust and the like easily enter through the air release port 9, which leads to a failure.
Since the air opening 9 is preferably as large as possible and preferably open, a large number of the openings 9 are notable in such a case.

In the invention described in JP-A-4-52214, the ink is sandwiched between two electrodes.
Although there is no problem as in Japanese Patent Application No. -289351, the distance between the electrodes is inevitably increased because the ink is interposed between the two electrodes. In order to generate a force enough to eject ink at the large electrode-to-electrode distance at a low applied voltage, a liquid having a relatively large relative dielectric constant is required. It is very difficult to give the liquid safety, reliability, color, viscosity, permeability to paper, water resistance and weather resistance after adhering to paper, etc. Costly.

The present invention has been made in view of the above circumstances, and provides a highly reliable and inexpensive inkjet head which can be driven at a low voltage.

[0010]

According to a first aspect of the present invention, there is provided an ink discharge chamber, a diaphragm provided in a part or all of the ink discharge chamber, and a first electrode provided in the diaphragm. A second electrode provided corresponding to the first electrode outside the ink discharge chamber, and filled with a substance having a relative dielectric constant between the first electrode and the second electrode. Then, a voltage is applied to the first electrode and the second electrode to displace the vibrating plate, and the ink is ejected by a change in the volume of the ink ejection chamber, and the ink is attached to a recording medium to perform recording. Wherein a gap between the first electrode and the second electrode communicates with a pressure absorbing chamber, whereby a substance having a relative dielectric constant between the first electrode and the second electrode is provided. And the gap between the first electrode and the second electrode is compressed. By communicating to the absorption chamber,
The driving voltage can be reduced, and the cost of the driving circuit can be reduced. It also prevents evaporation of liquid in the gap and entry of dust into the gap,
It has improved reliability.

According to a second aspect of the present invention, in the first aspect of the present invention, a diaphragm is provided in a part or the whole of the pressure absorbing chamber. It can be manufactured and cost can be reduced.

According to a third aspect of the present invention, in the second aspect of the present invention, a second electrode is provided corresponding to the diaphragm of the pressure absorbing chamber, thereby restoring the diaphragm of the discharge chamber. The force of the diaphragm of the pressure absorbing chamber is applied to the force, so that the ejection speed of the ink droplets is improved, and good image quality can be obtained.

According to a fourth aspect of the present invention, in the second or third aspect, the diaphragm of the pressure absorbing chamber is more easily displaced than the diaphragm of the discharge chamber. The load on the diaphragm in the discharge chamber of the diaphragm is reduced to enable high efficiency and high frequency response.

[0014]

FIG. 1A is a sectional view of an essential part for explaining an embodiment of an ink jet head according to the present invention. As shown in the drawing, an electrode 42 is formed on the lower surface of a diaphragm 41. An individual electrode 43 is formed below the electrode 42 via a minute gap 44. 45 is an ink discharge chamber, and 46 is an ink discharge port. In the ink jet head having such a configuration, when a voltage is applied between the electrode 42 and the individual electrode 43, the vibration plate 41 is attracted and bent by the electrostatic force, and the volume of the ink discharge chamber 45 increases, and the ink flow is reduced. Common liquid chamber 47 through inlet 48
Supplied by An ink supply pipe 51 supplies ink from an ink tank (not shown). Here, when the applied voltage is turned off, the bent diaphragm 41 returns to its original state, and pressurizes the ink in the ink discharge chamber 45. The ink is ejected as ink droplets from the ejection port 46 by the pressurized energy, and is adhered to paper or the like and recorded.

Here, the electrostatic force acting on the diaphragm 41 is expressed by the above-mentioned equation (1). By filling the gap 44 with a substance having a relative dielectric constant of ε *, the applied voltage for generating the same electrostatic force becomes one-square root of ε *. Gap 4
When the liquid 4 is filled and sealed in the liquid 4, a very large force is required to displace the diaphragm 41 because the contraction rate of the liquid 50 is small.

Therefore, in the present invention, the pressure absorbing chamber 49 is communicated with the gap 44. When a voltage is applied between the electrode 42 and the individual electrode 43 and the diaphragm 41 bends, the liquid 50 filling the gap 44 flows into the pressure absorbing chamber 49. When the applied voltage is turned off, the flexed diaphragm 41 returns to its original state, and the liquid 50 is again discharged from the pressure absorbing chamber 49 into the gap 44.
Is filled in.

In the present invention, the driving voltage can be reduced by filling the gap 44 with liquid. In addition, liquid 5
0 is not in communication with the atmosphere,
It is possible to prevent dust or the like from entering the gap 44 from the atmosphere, and absorb a pressure change in the gap 44 due to the deflection of the diaphragm 41. As the pressure absorbing chamber 49, a bag-shaped one, a cylinder 5 as shown in FIG.
2 and a piston 53, and a gas 54 such as air or nitrogen mixed as shown in FIG. 1C.

The liquid to be filled in the gap 44 preferably has a high insulating property and a large relative dielectric constant. For example, formamide (ε * = 109), glycerin (ε * = 42.5),
Nitrobenzene (ε * = 34.8), polyethylene glycol (ε * = 37.7), pure water (ε * = 80), isoper (ε * = 3), silicone oil (ε * = 2.
2), nitrobenzene mixed with barium titanate to form a jelly (ε * = 200 to 500), ferroelectric liquid crystal (ε * = several hundreds to several thousands), and the like.

FIGS. 2A and 2B are main part structural diagrams for explaining another embodiment of the present invention. FIG. 2A is a front view, and FIG. 2B is a side view. In this embodiment, a vibration plate 61 different from the vibration plate 41 for discharging ink into the pressure absorbing chamber 49 is provided. As shown in FIG. 2C, when an applied voltage is applied between the vibrating plate 41 serving as an electrode and the individual electrode 43, the vibrating plate 41 is attracted by electrostatic force, and the liquid 50 filled in the flexure gap 44 is pressurized. The diaphragm 61 is swept toward the absorption chamber 49 and the diaphragm 61 flexes upward, and the volume of the pressure absorption chamber 49 increases. When the applied voltage is turned off, the warped diaphragm 41 returns to its original state, pressurizes the ink in the ink discharge chamber 45, and discharges the ink from the discharge port 46 as ink droplets.

The ink jet head of this embodiment has a laminated structure in which three substrates 62, 63 and 64 having the structure described below are stacked and joined. The intermediate substrate 62 is a single crystal silicon substrate having a crystal plane orientation of (100), and includes a common liquid chamber 47, an ink inlet 48, an ink discharge chamber 45 having a bottom wall as a diaphragm 41, and a bottom wall as a diaphragm 61. And has a concave portion that forms a space 65 that forms These recesses are formed by anisotropic etching of silicon with an alkaline solution. As the alkaline liquid, an aqueous solution of potassium hydroxide,
Hydrazine, EDP, TMAH and the like can be mentioned.

The lower substrate 6 joined to the lower surface of the substrate 62
3 is made of Pyrex glass (borosilicate glass), and a recess for mounting the individual electrode 43 on the substrate 63 is etched by 1.1 μm. Individual electrode 4 on 63
3 is formed. The individual electrode 43 is manufactured by forming a gold pattern by sputtering 0.1 μm of gold in the concave portion. Further, a Pyrex sputtered film is coated on the entire surface by 0.1 μm to form an insulating layer 67. Besides Pyrex sputter film or the like may be SiO ₂ sputtered film. When the substrate 62 and the substrate 63 are joined, the distance between the individual electrode 43 and the diaphragm 41 becomes 1 μm, and the gap 44 is formed. For the upper substrate 64 bonded to the upper surface of the substrate 62, a SUS plate having a thickness of 100 μm is used, and discharge ports 46 are formed so as to communicate with recesses of the substrate 62 that form the ink discharge chambers 45 on the surface of the substrate 64. And a common liquid chamber 4
An ink supply port 66 is provided so as to communicate with the concave portion of the substrate 62 forming 7.

In this embodiment, the diaphragm 6 of the pressure absorbing chamber 49
1 can be easily manufactured by the same process as the vibration plate 41 of the ink discharge chamber 45. This embodiment is also effective when the liquid is not partially filled in the gap 44 but is partially filled. In addition, even when the liquid is not filled, the present invention is intended to absorb the pressure change in the gap 44 due to the change of the diaphragm 41 and to prevent dust and the like in the air from being mixed in the gap 44. It is valid.

In this embodiment, a silicon substrate having a (100) plane orientation has been described as an example. However, a silicon substrate having a (110) plane orientation may be used. As is well known, a wall structure perpendicular to the substrate surface can be formed on a (110) plane oriented silicon substrate by anisotropic etching using an alkaline solution. By utilizing this fact, the pitch interval when a large number of discharge ports are arranged can be reduced, and the density of nozzles can be increased.

In this embodiment, the space above the space 65 is the substrate 6
Although closed by 4, an opening may be formed at a location corresponding to the space 65 of the substrate 64 to communicate with the atmosphere. By doing so, the pressure change in the space 65 due to the deflection of the diaphragm 61 is eliminated, and the diaphragm 61 can be easily bent.

FIG. 3 is a sectional view of a main part for explaining another embodiment of the present invention. This embodiment corresponds to the vibration plate 61 of the pressure absorbing chamber 49 in the embodiment shown in FIG. The electrode 70 is provided. As in the embodiment shown in FIG. 2, when an applied voltage is applied between the vibrating plate 41 serving as an electrode and the individual electrode 43, the vibrating plate 41 causes the liquid 50 filled in the bending gap 44 attracted by electrostatic force. It is flushed toward the pressure absorbing chamber 49. When the pressure in the pressure absorbing chamber 49 increases, the diaphragm 61 bends. When the applied voltage is turned off, the flexed diaphragm 41 and diaphragm 61 return to the original state.

Here, when a voltage is applied between the vibration plate 61 and the individual electrode 70, the vibration plate 61 bends due to the attraction of the electrostatic force, and the liquid 50 in the pressure absorption chamber 49 is pushed into the gap 44. When the pressure in the gap 44 increases, the diaphragm 41 bends upward and presses the ink in the ejection chamber 45. In the present embodiment, since the force of the vibration plate 61 is also applied to the restoring force of the vibration plate 41 via the liquid in the gap 44, the pressure on the ink in the discharge chamber 45 is large, and the discharge speed of the ink droplets is increased. Can be.

FIG. 4 is a diagram showing the construction of a main part for explaining another embodiment of the present invention. FIG. 4 (A) is an exploded perspective view and FIG. 4 (B).
4A is a cross-sectional view taken along the line AA ′ when the exploded view shown in FIG. 4A is joined and assembled. In this embodiment, the diaphragm 61 of the pressure absorbing chamber 49 has a shape that is more easily displaced than the diaphragm 41. Has become. The ink jet head of this embodiment has five substrates 7
1 to 75. A discharge port 46 is provided in the substrate 71.
And an ink supply port 80 are formed. The substrate 72 has a through hole 77 communicating with the ejection port 46 and a through hole 76 forming a common liquid chamber 81, and the substrate 73 has an ink inlet 82 and a through hole 77 communicating from the common liquid chamber 81 to the ejection chamber 45. A through hole 78 communicating therewith, a discharge chamber 45 having a bottom wall as a vibration plate 41 and a space 55 having a bottom wall as a vibration plate 61 are formed in a substrate 74, and a gap 44 and a pressure absorption chamber 49 are formed in a substrate 75. The electrode 43 is formed at a position corresponding to the diaphragm 41 in the recessed portion. By joining these substrates, an ink jet head is obtained.

In this embodiment, the diaphragm 6 of the pressure absorbing chamber 49
1 has a longer short side than the diaphragm 41. By doing so, the diaphragm 61 is more easily displaced than the diaphragm 41, and when the diaphragm 41 is displaced by the applied voltage,
The load on the diaphragm 41 of the diaphragm 61 is reduced, and high efficiency and high frequency response can be achieved. In order to make the diaphragm 61 easier to displace than the diaphragm 41, besides increasing the short side length, increasing the long side length, increasing the short side length and the long side length,
There is a shape close to a square or a circle. Further, it is also possible to make the thickness of diaphragm 61 thinner than diaphragm 41. In addition, similarly to the embodiment of FIG. 3, a corresponding electrode may be provided on the vibration plate 61 of the pressure absorbing chamber 49 to increase the ink discharge capability.

[0029]

According to the first aspect of the present invention, an ink discharge chamber, a vibration plate provided in a part or all of the ink discharge chamber, a first electrode provided in the vibration plate, and the ink discharge chamber Outside of the first
A second electrode provided corresponding to the first electrode, a material having a relative dielectric constant is filled between the first electrode and the second electrode, and the first electrode and the second electrode are filled. An ink jet head for applying a voltage to the electrodes to displace the vibration plate, ejecting ink from the ink ejection chamber by a change in volume of the ink ejection chamber, and attaching the ink to a recording medium for recording; The gap between the electrode and the second electrode is communicated with the pressure absorbing chamber, whereby the first
A material having a relative dielectric constant is filled between the first electrode and the second electrode, and a gap is formed between the first electrode and the second electrode so as to communicate with the pressure absorbing chamber. The cost of the driving circuit can be reduced. In addition, the evaporation of the liquid in the gap and the entry of dust and the like into the gap can be prevented, and the reliability is improved.

According to the second aspect of the present invention, since the diaphragm is provided in part or all of the pressure absorbing chamber, the pressure absorbing chamber is formed by the same process as the diaphragm of the ink discharge chamber. Fabrication and cost reduction are possible.

According to the third aspect of the present invention, since the second electrode is provided corresponding to the diaphragm of the pressure absorbing chamber, the restoring force of the diaphragm of the ink discharge chamber is reduced. The force of the vibrating plate is also applied, the ejection speed of ink droplets is improved, and good image quality can be obtained.

According to the fourth aspect of the present invention, the diaphragm of the pressure absorbing chamber is more easily displaced than the diaphragm of the discharge chamber. The load on the diaphragm is reduced, and high efficiency and high frequency response can be achieved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part for describing an embodiment of an ink jet head according to the present invention.

FIG. 2 is a main part configuration diagram for explaining another embodiment of the present invention.

FIG. 3 is a sectional view of an essential part for explaining another embodiment of the present invention.

FIG. 4 is a main part configuration diagram (an exploded perspective view and an assembled cross-sectional view) illustrating another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a main part for describing an example of a conventional inkjet head.

6 is a longitudinal sectional view of the ink jet head shown in FIG.

FIG. 7 is a cross-sectional view illustrating a main part of another example of a conventional inkjet head.

[Explanation of symbols]

41: diaphragm, 42: electrode, 43: individual electrode, 44: gap, 45: ink discharge chamber, 46: ink discharge port, 4
7: common liquid chamber, 48: ink inlet, 49: pressure absorption chamber, 50: liquid, 51: ink supply pipe, 52: cylinder, 53: piston, 54: gas, 61: diaphragm,
62, 63, 64: substrate, 65: space, 66: ink supply port, 70: electrode, 71 to 75: substrate, 76, 77, 7
Reference numeral 8: through hole, 80: ink supply port, 81: common liquid chamber, 8
2. Ink inlet.

Claims (4)

[Claims] An ink discharge chamber; a vibration plate provided on a part or all of the ink discharge chamber; a first electrode provided on the vibration plate; and a first electrode provided outside the ink discharge chamber. A second electrode provided corresponding to the first electrode, a material having a relative dielectric constant is filled between the first electrode and the second electrode, and the first electrode and the second electrode are filled. An ink jet head for applying a voltage to the electrodes to displace the vibrating plate, ejecting ink from the ink ejection chamber based on a change in the volume of the ink ejection chamber, and attaching the ink to a recording medium to perform recording. An ink-jet head, wherein a gap between the first electrode and the second electrode communicates with the pressure absorbing chamber. 2. The ink jet head according to claim 1, wherein a diaphragm is provided in a part or all of the pressure absorbing chamber. 3. The ink jet head according to claim 2, further comprising the second electrode corresponding to the vibration plate of the pressure absorbing chamber. 4. The ink jet head according to claim 2, wherein the vibration plate of the pressure absorbing chamber is more easily displaced than the vibration plate of the ink discharge chamber.