JP2003182074A - Liquid drop ejection head and ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an liquid drop ejection head which can deal with a wide range of environmental atmospheric pressure at a low cost by providing a head chip with a small pressure regulating means without requiring any extra component, e.g. a pressure detecting means, and to provide an ink jet recorder comprising it. <P>SOLUTION: The liquid drop ejection head for ejecting a liquid drop by a pressure wave generated from an electrostatic force comprises nozzle holes 31 for ejecting liquid drops, pressure liquid chambers 11 communicating with the nozzle holes and containing a liquid being ejected, a movable plate 13 constituting one wall face of the pressure liquid chamber, an air gap 21 provided oppositely to the pressure liquid chamber in contact with the movable plate, and an electrode 22 disposed oppositely to the movable plate through the air gap wherein a liquid drop is ejected from the ink nozzle hole by flexing the movable plate with an electrostatic force thereby raising the inner pressure of the pressure liquid chamber. A passage 41 interconnecting the air gap and the outer air is provided and partially filled with a nonvolatile or volatilization retardant fluid 43. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a droplet discharge head for discharging droplets of, for example, ink liquid by a pressure wave caused by electrostatic force, and an ink jet recording apparatus using the droplet discharge head.

[0002]

2. Description of the Related Art Among ink jet recording apparatuses that perform recording by ejecting ink droplets directly from a nozzle onto a recording medium, an on-demand method of ejecting ink only when necessary is a mechanism for collecting ink. Since it is not necessary, it is possible to reduce the price and size, and it has the feature of being compatible with colorization. The inkjet recording device
It is used as an image recording apparatus or an image forming apparatus such as a printer, a facsimile, a copying machine, and a plotter.
An inkjet head, which is a droplet discharge head, has a nozzle that discharges ink droplets and a pressurized liquid chamber that communicates with this nozzle (also called a pressure chamber, a discharge chamber, a liquid chamber, an ink flow path, or the like).
And a pressure generating means for pressurizing the ink in the pressurized liquid chamber, and the pressurized ink is ejected as an ink droplet from the nozzle. As an inkjet head, a piezo type and a bubble type are popular, but an electrostatic inkjet head using an electrostatic force as a pressure generating means is also known. The piezo-type inkjet head is an electromechanical conversion system in which a pressure wave is generated in an ink chamber by displacement of a piezo element and ink is ejected from an ink nozzle. The bubble type is an electrothermal conversion method in which bubbles are generated in an ink chamber by a heater that is heated to a high temperature in a short time, and ink is ejected due to volume expansion of the bubbles. In addition, the electrostatic ink jet head applies a voltage between a movable plate that is a wall surface of a part of a pressurized liquid chamber that communicates with an ink nozzle hole, and an electrode that is arranged to face each other through a minute gap. By deforming the movable plate and generating pressure in the pressure chamber,
The ink liquid in the pressurizing chamber is discharged as droplets from the ink nozzle holes. Since this electrostatic ink jet head can be manufactured by a wafer process, it is easy to increase the density, and it is possible to manufacture a large number of specific stable elements. Also, it is based on a planar structure. Therefore, it is easy to downsize (Japanese Patent Laid-Open No. 2-28).
No. 9351, No. 5-050601, No. 6-07188
No. 2). The width of the gap located between the electrode and the movable plate that forms a part of the wall of the pressure chamber of the electrostatic inkjet head is several microns or less, and the gap is left open to the atmospheric environment. Then, dust may enter the voids, and the dust in the voids may hinder the deformation of the movable plate. Further, when water is adsorbed on the surface of the movable plate, the movable plate may be adsorbed on the electrode by the liquid bridge force, which may cause ejection failure. Furthermore, if the movable plate is continuously driven, the gas in the gap will gradually escape to a depressurized state, and the movable plate will bend toward the electrode side and will not recover even when no voltage is applied, and a sufficient ink discharge amount will be obtained. / Pressure may not be obtained. Therefore, the atmosphere opening portion that is normally connected to the void is sealed with a resin or the like so that the void is hermetically sealed.

[0003]

However, if the inside of the space between the movable plate and the electrode is sealed, the space will not be exposed in an environment where the atmospheric pressure is significantly different, such as in a highland where the atmospheric pressure is lower than normal. Due to the pressure difference between the internal pressure and the low external pressure, the movable plate is always bent toward the pressurized liquid chamber side, and defective ejection occurs. When the external pressure is high, the movable plate is bent in the opposite direction. Therefore, JP-A-11-286109 and JP-A-2000-272120
Then, the pressure difference between the inside of the air gap is measured by the atmospheric pressure detection means, the voltage drive waveform is corrected, and a large-area movable plate for separately adjusting the pressure is provided, and the volume of the sealed portion is changed to change the external pressure. The pressure difference between and is being adjusted. However, if atmospheric pressure detection means and large area pressure adjustment means are added,
The head cost becomes high, and it becomes difficult to miniaturize and integrate the chip. The present invention has been made in view of the above, does not require addition of special components such as pressure detection means, and by providing a compact pressure adjusting means on the head chip, a low cost and wide range of environmental pressure It is an object of the present invention to provide a droplet discharge head that can handle the above, and to provide a droplet discharge head using the same and an inkjet recording apparatus.

[0004]

In order to solve the above-mentioned problems, the invention of claim 1 is a droplet discharge head for discharging droplets by a pressure wave due to an electrostatic force, and a nozzle hole for discharging droplets. A pressurized liquid chamber that communicates with the nozzle hole and contains the liquid to be discharged, a movable plate that constitutes a part of the wall surface of the pressurized liquid chamber, and a movable plate that is in contact with the movable plate and is opposite the pressurized liquid chamber. The internal pressure in the pressurized liquid chamber is provided by bending the movable plate by the electrostatic force generated by the voltage applied to the electrode, which is provided with a void provided on the side and an electrode arranged to face the movable plate through this void. In the liquid droplet ejection head for ejecting liquid droplets from the ink nozzle hole, a communication passage that communicates the void with the outside air is provided, and a part of the communication passage is filled with a nonvolatile or non-volatile fluid. It is characterized by being According to this, a non-volatile / non-volatile fluid is filled in a part of the communication passage that connects the void and the outside air interposed between the electrode and the movable plate to keep the void in a sealed state, and Since it is configured to be movable in the communication passage, it is possible to prevent the entry of moisture, dust, etc. into the void, and to provide a droplet discharge head having high durability and reliability, in which displacement failure of the movable plate does not occur. According to a second aspect of the present invention, in the droplet discharge head according to the first aspect, the non-volatile or hardly volatile fluid moves in the communication passage in accordance with the fluctuation of the external pressure to adjust the pressure in the void. It is characterized in that it also serves as a pressure adjusting means. According to this, claim 1
It can bring about the same effect as. According to a third aspect of the present invention, in the droplet discharge head according to the first aspect, the non-volatile or hardly volatile fluid moves in the communication passage in accordance with a change in external pressure and temporarily moves out of the gap. It is characterized in that it is a pressure adjusting means for adjusting the pressure by releasing it to atmospheric pressure. According to this, since the non-volatile / non-volatile fluid moves in the communication passage in accordance with the pressure difference, and temporarily opens the inside of the void to the outside air to adjust the pressure difference. It is possible to provide a droplet discharge head having high durability and reliability, in which the displacement of the movable plate does not occur by preventing the invasion of water and dust into the head.

According to a fourth aspect of the present invention, in the droplet discharge head according to any one of the first to third aspects, the communication passage has a structure in which the flow passage diameter is gradually reduced or gradually increased. Characterize. According to this, even when the pressure in the air gap and the pressure of the outside air are significantly different at high altitudes, the pressure difference can be reduced, so that a head with high environmental reliability can be provided, and pressure detection means and complicated Since no adjusting means is required, it can be manufactured in a small area and at low cost. A droplet discharge head according to a fourth aspect of the present invention is characterized in that the communication passage has a configuration in which the flow passage diameter gradually decreases or gradually increases. According to this, the structure of the pressure correction means can be simplified and the pressure correction means can be manufactured by a simple process, so that the droplet discharge head can be provided at low cost. According to a fifth aspect of the present invention, in the droplet discharge head according to any one of the first to fourth aspects, particles that are sufficiently smaller than the diameter of the communication passage are dispersed in the nonvolatile or hardly volatile fluid. It is characterized by In the droplet discharge head according to the invention of claim 5, particles which are sufficiently smaller than the diameter of the communicating passage are dispersed in the non-volatile / non-volatile fluid to increase the apparent viscosity of the fluid. According to this, by dispersing particles that are sufficiently smaller than the diameter of the communication passage in the non-volatile / hardly volatile fluid, the gradient such as change in atmospheric pressure is small, but the fluidity with respect to force is exerted, while falling or When an impact force such as the reciprocating movement of the carriage is applied, the apparent viscosity of the fluid is increased, so that the droplet discharge head having high durability and high environmental reliability can be provided. Claim 6
According to another aspect of the invention, in an ink cartridge in which a droplet discharge head that discharges an ink droplet and an ink tank that supplies ink to the droplet discharge head are integrated, the droplet discharge head is any one of claims 1 to 5. According to another aspect of the present invention, there is provided an ink cartridge including the droplet discharge head. According to this, by mounting a highly reliable head on the ink tank integrated type head, the reliability of the head integrated type ink cartridge itself can be increased and the capacity of the ink tank can be increased, resulting in a low running cost. A head-integrated ink cartridge can be provided. According to a seventh aspect of the present invention, in an ink jet recording apparatus equipped with a droplet discharge head that discharges ink droplets, the droplet discharge head is the droplet discharge head according to any one of the first to fifth aspects. Is characterized in that. According to this, by using the droplet discharge head according to any one of claims 1 to 5 for an inkjet recording apparatus equipped with an inkjet head that discharges ink droplets, a highly reliable and low-cost inkjet recording apparatus is provided. can do.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An electrostatic type droplet discharge head (inkjet head) according to the present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 is an explanatory top view showing a part of an electrostatic droplet discharge head according to the present invention in a transparent state, and FIG. 2 is a schematic AA ′ cross-sectional explanatory view along the long side direction of the pressurized liquid chamber of the head, FIG. 3 is a schematic BB ′ cross-sectional explanatory view along the short side direction of the pressurized liquid chamber of the same head, and FIG. 4 is a CC ′ cross-sectional explanatory view along the communication passage portion of the same head. This droplet discharge head is, for example, an inkjet head used in an inkjet recording apparatus, and this droplet discharge head is provided with a flow path substrate 1 which is a first substrate and a second flow path substrate 1 which is bonded to a lower side of the flow path substrate 1. The electrode substrate 2 that is a substrate and the nozzle plate 3 that is a third substrate bonded to the upper side of the flow path substrate 1 are stacked and bonded to each other. Further, in this droplet discharge head, a plurality of nozzle holes 31 penetratingly formed at appropriate positions of the nozzle plate 3, a pressurized liquid chamber 11 which is an ink flow path communicating with each nozzle hole 31, and a wall surface of the pressurized liquid chamber 11 are formed. Of the pressurized liquid chamber 11 via a movable plate (vibration plate) 13 that forms a part of the above, and a fluid resistance portion 32 that is a recess formed in the lower surface of the nozzle plate 3.
There is provided a common liquid chamber 12 that communicates with the electrode 22 and an electrode 22 that is arranged to face the lower position via a gap 21 for bending the movable plate 13 by an electrostatic force. Electrode 22
Ink is ejected from the nozzle holes 31 by a pressure wave generated when the movable plate 13 bends toward the gap 21 side by the voltage applied to the movable plate 13 and then returns to the pressurized liquid chamber 11 side. As shown in FIGS. 1 and 3, a plurality of elongated pressurized liquid chambers 11 are arranged in parallel with each other through a partition wall 11 a, and the nozzle plate 3 corresponding to each pressurized liquid chamber 11 has a portion. Each of the nozzle holes 31 is formed so as to penetrate therethrough. When the nozzle plate 3 is bonded onto the flow path substrate 1,
Each pressurizing liquid chamber 11 is defined by a partition wall 11a. The common liquid chamber 12 is arranged so as to extend across the end portions of all the pressurized liquid chambers 11, and has an ink supply port (droplet supply port) 26 that is continuously provided below the common liquid chamber 12. Ink is supplied from an ink tank (not shown) to the common liquid chamber 12, and further, ink is supplied to each pressurized liquid chamber 11 via each fluid resistance portion 32.

FIG. 5 is a top view of the electrode substrate 2 with the nozzle plate 3 and the flow path substrate 1 removed. A partition wall 21a is located between the voids 21 arranged in parallel. Therefore, when the flow path substrate 1 is bonded onto the electrode substrate 2, the gaps 21 are separated from each other by the partition walls 21a. Also,
As shown in FIG. 4, a gap 21 is formed on the upper surface of the electrode substrate 2.
Grooves are formed as two communication passages 41 so as to surround almost the entire outer circumference of the group, and both longitudinal end portions of each void 21 are communicated with each communication passage 41. The diameter and cross-sectional area of the communication passage 41 are set to be narrower than the gap 21. Further, in the communication passage 41, there is provided a pressure adjusting portion 4 which is partially filled with a non-volatile / hardly volatile fluid (pressure adjusting fluid) 43. One or a plurality of outside air ports 14 are arranged, and the communication passage 41 communicates with the outside air via the outside air port 14. As will be described later, in the pressure adjusting unit 4, the void 21 and the communication passage 4 are provided.
The non-volatile / non-volatile fluid 43 moves back and forth in the communication passage 41 in accordance with the pressure difference between the pressure inside 1 and the outside air to adjust the internal pressure. That is, the electrode substrate 2
Electrodes 22 facing the movable plate 13 via a predetermined space 21 are embedded in the interior of the space, and an electrode protection film 23 for preventing a short circuit is formed on the upper surface of the electrode 22. The communication passage 41 is formed to connect to the outside air port 14 and to connect to the outside air port 14. The electrode 22 is extended to the electrode lead-out portion 24 of the electrode substrate 2, and the movable plate 13 is displaced by applying a voltage between the electrode 22 and the movable plate 13 to change the internal volume of the pressurized liquid chamber 11. It constitutes the actuator section. Next, the flow path substrate 1 forming the gap 21 and the communication passage 41 by being bonded to the upper surface of the electrode substrate 2 is connected to the pressurized liquid chamber 11 as a recess located on the nozzle plate 3 (upper surface) side. A movable plate 13 that forms a wall surface that serves as the bottom of the pressurized liquid chamber 11, a through hole 12a that forms the common liquid chamber 12, and a through hole as an outside air port 14 that communicates with the communication passage 41 and the outside air. And an electrode opening 15 that exposes a part of the electrode 22 is formed. On the electrode substrate 2 (lower surface) side, there is a communication passage cavity 42 (a total of four in this example) that constitutes a part of the pressure adjusting unit 4. A recess) is formed.
As a material used for the flow path substrate 1, for example, boron which is a p-type dopant is diffused at a depth position equivalent to the thickness of the movable plate 13 of the silicon substrate having the (110) plane orientation, and this high concentration boron diffusion layer is formed. Anisotropic selective etching can be performed as an etching stop layer to form a concave portion to be the pressurized liquid chamber 11. For example, when a 20 wt% potassium hydroxide aqueous solution containing isopropyl alcohol in a saturated amount or more is used as an etching solution, the etching rate decreases to 1/100 or less at a boron diffusion concentration of about 4 to 5E19 cm ⁻³ , and The movable plate 13 can be formed with a uniform thickness. When the SOI wafer is used as the flow path substrate 1, since the silicon oxide film is provided between the movable plate 13 and the silicon base material that becomes the pressurized liquid chamber 11, the silicon oxide film is used as an etching stop layer for wet etching. Not only I
It is also possible to use dry etching such as CP etching, and it is possible to form an arbitrary liquid chamber / opening shape.

The electrode openings 15 and the outside air openings 14 are formed by forming the movable plate 13 by the method described above and then etching the flow path substrate 1 by dry etching. Further, the recess as the communication passage cavity portion 42 formed on the lower surface of the flow path substrate 1 can be formed by any method of dry etching and wet etching. Communication passage cavity 4
2 is arranged so as to be in a positional relationship capable of communicating with the communication passage 41 located immediately below. A specific manufacturing procedure for forming the voids 21 and the communication passages 41 on the upper surface of the electrode substrate 2 is, for example, polysilicon or nitriding to be the electrodes 22 on the silicon substrate 20 on which the base oxide film 25 is formed by thermal oxidation. Similarly, an electrode material such as titanium is formed into a desired thickness by a thin film forming method such as sputtering, CVD, or vapor deposition, and then an electrode pattern is formed with a photoresist and etched, and then CVD is performed.
A silicon oxide film to be the electrode protective film 23 is laminated by a film forming method such as the above. After planarizing the surface of the oxide film 23 by CMP,
The void 21 and the communication passage 41 are formed in a desired depth and a desired shape by dry etching or wet etching.
In addition, an ink supply path 26 for connecting an external ink tank (not shown) to the common liquid chamber 12 of the liquid chamber substrate also uses the base oxide film 25 as an etching stop layer from the back surface of the electrode substrate 2 (silicon substrate 20). It is formed by wet etching or dry etching. The electrode substrate 2 and the flow channel substrate 1 can be bonded to each other by using low melting point glass and other various adhesive members.
If a high heat-resistant material such as polysilicon or titanium nitride is used as the constituent material of, the direct bonding method can be adopted, and if a Pyrex (registered trademark) glass substrate is used for the electrode substrate 2, the anodic bonding method, A joining process that does not require an adhesive member can be used and productivity can be improved. Normally, the pressurized liquid chamber 11 of the flow channel substrate 1 needs to have a liquid chamber height of about 100 μm. Therefore, due to handling problems, the flow channel substrate 1 having the communication passage cavity portion 42 formed on the lower surface is formed.
And the electrode 22, the void 21, the communication path 41, and the like, are joined together, and then the flow path substrate 1 portion is polished, and then the pressurized liquid chamber 11, the outside air port 14, and the electrode on the flow path substrate side Board 2
The side ink supply paths 26, 12 (12b) are formed. The nozzle plate 3 has a recess serving as the fluid resistance portion 32, a through hole serving as the nozzle hole 31, and a ventilation hole 3 communicating with the outside air port 14.
a is formed by etching or the like.

Next, the structure and operation of the communication passage 41 will be described in more detail. As described above, in order to prevent water and dust from entering the space 21 of the droplet discharge head, it is necessary to keep the space 21 in a sealed state. Normally, the inside of the void 21 is opened to the atmosphere under a constant pressure to equalize the pressure in each head and each void, and then the outside air port 14 and the like are filled with a resin for sealing. However, when the space 21 is completely sealed and used in an environment where the pressure inside the space and the outside air pressure are different, if the outside air pressure is higher, the movable plate 3
Is bent toward the electrode 22 and the width of the gap 21 is narrowed. When the outside air pressure is lower, the movable plate 13 is bent toward the pressurized liquid chamber 11 side and the gap width is expanded. The pressure in the void 21 is P _gap , the pressure of the outside _air is P _air , the short side width of the movable plate is a, the long side width is b, the volume of the sealing portion (void, communication passage) is T, the thickness of the movable plate. Is h, Young's modulus is E, and displacement is δ, ΔP = P _gap −P _air ≈ {(35Eh ³ ) / a ⁴ − (8ab
The relationship of / 15) / T} * δ is established, and the displacement δ of the movable plate 13 also increases in proportion to the pressure difference between the void 21 and the outside air. Movable plate 13 and electrode 2
Assuming that the gap depth is g and the voltage applied between the electrodes is V, the force (electrostatic force) acting between 2 and F is F≈1 / 2ε ₀ {V /
Since there is a relationship of (g−δ)} ² and is inversely proportional to the square of the air gap distance, it becomes difficult to control the displacement of the movable plate when the distance between the movable plate and the electrode changes due to atmospheric pressure fluctuation.

Therefore, in the present invention, as shown in the respective configuration diagrams of FIG. 1 to FIG. 5, a predetermined amount of non-volatile / non-volatile pressure adjusting fluid 43 is injected into the communication passage 41 as a sealant. Then, the fluid 43 is allowed to move in the pressure adjusting portion 4 (communication passage 41, communication passage cavity portion 42) formed in a part of the communication passage 41, and when the pressure difference is large, it is used as a sealant. The pressure adjusting fluid 43 is moved into the communication passage cavity 42 having a large volume to temporarily open the inside of the void 21 to the outside air, thereby reducing the pressure difference between the outside air and the inside void. That is, when the fluid 43 is located in the communication passage 41 having a small diameter, it completely seals the communication passage 41 to prevent the fluid 43 from communicating with the outside air through the outside air port 14, but has a large volume in the hollow portion. When it moves to a position corresponding to 42, the communication passage 41
Is opened to allow the void 21 to communicate with the atmosphere through the outside air port 14. Alternatively, the non-volatile / non-volatile fluid 43 moves back and forth within the range of the communication passage 41 that does not reach the cavity portion 42 in response to fluctuations in the external pressure, and thus finely adjusts the pressure in the void 21. It works effectively. That is, the fluid 43 moves in the communication passage according to the pressure difference and changes the volume of the sealing portion, so that the pressure fluctuation in the void can be reduced, and the droplets can be stably ejected. Is possible.

Next, FIGS. 6A to 6C more specifically describe the configuration and operation of the pressure adjusting unit 4.
The left views of (a), (b), and (c) are vertical cross-sectional views of the main parts of the pressure adjusting unit, and the right views are horizontal cross-sectional views. FIG. 6A shows
This shows a case where the pressure difference between the outside air and the void 21 is small, and the pressure adjusting fluid 43 has a constant flow passage diameter of the communication passage 41 (the diameter gradually increases from the section I toward the left and right sides). The pressure is adjusted by moving in the section I and changing the volume of the sealing portion, and the pressures in the outside air and the void are almost equal (ΔP≈0). On the other hand, when the contact angle formed by the fluid 43 and the inner wall of the communication passage 41 is 90 degrees or less and the concave meniscus portion is formed at the tip of the fluid, the negative pressure lower than the pressure of air is lower in the concave meniscus portion. There is a difference, and the magnitude of the pressure difference is inversely proportional to the magnitude of the radius of curvature of the meniscus portion. At this time, in the steady state (static state), since the meniscus portions formed on both sides of the fluid 43 have a symmetrical shape, the force due to the surface force of the fluid does not work. FIG. 6B shows a case where the pressure of the outside air becomes lower than the pressure in the void 21. In this case, the fluid 43 moves to the outside air side (left side) due to the pressure difference between the inside and the outside, and the communication passage cavity portion 4 in the section II.
When entering the second side, the inside of the void is temporarily opened to the outside air in the cavity portion 42 formed in the communication passage 41. In addition, section II
Then, since the width of the communication passage 41 is gradually increased,
The radius of curvature of the meniscus-shaped portion (arc-shaped portion) is large in the wide portion of the communication passage 41 and small in the narrow portion. Therefore, inside the fluid, the pressure is relatively higher in the wide portion than in the narrow portion, and the force P _meni acts on the fluid to return to the direction in which the communication passage width is narrowed. The pressure obtained by adding the outside air pressure P _air and the meniscus return pressure P _meni balances with the _gap pressure P _gap P _meni + P _air = P
At the time when the _gap is formed, the inside of the gap is sealed with the fluid again. After the pressure is adjusted, the inside of the void becomes higher than the outside air by ΔP = P _meni . If P _meni is designed to be small, for example, the gradient of the change in the width of the communication passage is made small, or the contact angle between the fluid and the surface of the communication passage is made close to 90 degrees, then the pressure difference from the atmospheric pressure can be almost eliminated. FIG. 6C shows the case where the pressure of the outside air becomes larger than the pressure in the void, and conversely, the fluid 43 moves to the void side (right side) and enters the communication passage cavity 42 of the section III. Then, the same operation as in FIG. 6B is performed, and when the difference between the pressure in the void and the outside air pressure becomes only the meniscus pressure, the void is sealed again. In this case, the pressure P _{gap in the gap} is ΔP = − as compared with the outside air pressure P _air.
P _meni lowers.

FIG. 7 is a diagram showing (A) the case where the outside air port 14 is only sealed with resin and (B) the case where a pressure adjusting portion by the meniscus (fluid 43) is provided, and the outside air pressure is shown. Is a comparison of the bending amount δ (vertical axis) of the movable plate 13 when Δ changes by ΔP (horizontal axis). The pressure difference ΔP between the outside air and the space 21 shown on the horizontal axis is the fluid 43 as shown in FIG.
By adjusting the pressure with the meniscus of, even if the pressure of the outside air changes significantly, the pressure difference between the pressure inside the void and the outside air is maintained at | ΔP | = P _meni , so the amount of bending of the movable plate 13 δ can also be made small. Therefore, even if a separate pressure correction means is provided, almost two-valued pressure correction is required as compared with the case where the movable plate bending amount changes continuously as in (A), and therefore the correction mechanism becomes very simple. . Further, the shape of the pressure adjusting portion 4 shown in FIG.
The contact angle is 90 degrees or less. For example, when a fluorine-based silane coupling agent is used to reduce the surface energy of the surface of the communicating passage to retain water and oil repellency,
As shown in FIG. 8A, the width of the flow path 41 is wide at the central portion of the pressure adjusting portion 4 and gradually narrows at the communicating passage hollow portion. When the fluid is positioned in a state of being biased to the left or right as in (b), the pressure of the left convex portion of the fluid 43 having a small radius of curvature becomes higher than that of the right convex portion having a large radius of curvature, When the force for moving the fluid from the narrower side to the wider side acts and the pressure adjustment inside the gap is completed, the fluid automatically returns to the wide neutral portion as shown in (a). Pressure adjusting fluid 4
Also in the case of injecting 3 into the pressure adjusting portion 4, by considering the contact property between the fluid 43 and the communication passage 41 so that the flow passage width gradually changes from the fluid injecting portion to the pressure adjusting portion, It is possible to automatically introduce up to the pressure adjusting unit 4. It should be noted that a plurality of outside air ports are provided in the communication passage 41 in advance, and at the time of injection, another outside air port is opened so that the pressure of the fluid injected from one outside air port does not increase even if the fluid moves in the communication passage. In advance, after the fluid is positioned in the pressure adjusting unit 4, another outside air port that is not injected last is filled with resin to seal the inside of the gap. The non-volatile or hardly volatile fluid 43 to be injected into the communication passage 41 is, for example, a phosphoric acid ester, an adipic acid ester, a trimetic acid ester, a citric acid ester, which is used for an ink backflow prevention fluid such as a ballpoint pen. Any combination of plasticizers such as polyester plasticizers, liquid paraffin, liquid rubbers such as polybutene and polybutadiene, and oils and fats such as mineral oil, vegetable oil and petrolatum can be used. In the case of a droplet discharge head (ink jet head), the width of the communication passage 41 is about several microns to several tens of microns, and the influence of the surface force is larger than the inertial force due to the scale effect. Fluid 4 even if the impact force due to reciprocation is applied
3 is hard to move. However, in order to increase the reliability of preventing the movement of the fluid 43, a spherical shape made of an organic material such as polyethylene or polystyrene having a particle diameter smaller than the diameter of the communication passage 41 or an inorganic material such as glass or quartz is used in the fluid 43. Disperse the particles. Then, the fluid 43 moves as a low-viscosity fluid against a force applied slowly such as a change in atmospheric pressure, while when a shear stress is suddenly applied, the apparent viscosity is increased to prevent fluid leakage or the like. can do. In this embodiment, the outside air port 14 is connected to the flow path substrate 1
Although it is formed on the side, it may be formed on the side of the electrode substrate 2.
Further, the communication passage 41 is formed on the electrode substrate 2 side, and the communication passage cavity portion 42 is formed on the flow passage substrate 1 side, respectively. However, the formed substrate may be reversed, and it may be formed only on one substrate. There is no problem.

Next, an ink cartridge in which the droplet discharge head and the ink tank according to the present invention are integrated is shown in FIG.
Will be described with reference to the external view of FIG. This ink cartridge is one in which the inkjet head (droplet ejection head) 81 of any of the above-described embodiments having a nozzle 80 and the like and an ink tank 82 that supplies ink to the inkjet head 81 are integrated. is there. An inkjet printer using the inkjet head manufactured as described above will be described. FIG. 10 is a perspective explanatory view of a main configuration of an inkjet recording apparatus according to the present invention, and FIG.
1 is a side cross-sectional explanatory view of the same component. This ink jet recording apparatus is a printing mechanism unit including a carriage movable in the main scanning direction inside a recording apparatus main body 81, a recording head including an inkjet head mounted on the carriage, an ink cartridge that supplies ink to the recording head, and the like. A paper feeding cassette (or a paper feeding tray) 84 capable of accommodating a large number of sheets of paper 83 from the front side can be detachably attached to the lower part of the apparatus main body 81. The manual feed tray 85 for manually feeding the paper 83 can be opened, and the paper 8 fed from the paper feed cassette 84 or the manual feed tray 85 can be opened.
3, the desired image is recorded by the printing mechanism unit 82, and then the paper is ejected to the paper ejection tray 86 mounted on the rear surface side.

The printing mechanism section 82 includes a main guide rod 91 and a sub guide rod 92, which are guide members which are laterally mounted on the left and right side plates (not shown), to move the carriage 93 in the main scanning direction (see FIG. 2).
A head composed of an ink jet head for slidably holding the ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk) on the carriage 93. A plurality of ink discharge ports 94 are arranged in a direction intersecting the main scanning direction, and the ink drop discharge direction is downward. Further, each ink cartridge 95 for supplying each color ink to the head 94 is replaceably mounted on the carriage 93.
The ink cartridge 95 has an air port that communicates with the atmosphere above, a supply port that supplies ink to the inkjet head below, and a porous body filled with ink inside, and the capillary force of the porous body is used. The ink supplied to the inkjet head is maintained at a slight negative pressure. Further, although the heads 94 of the respective colors are used as the recording heads here, a single head having nozzle holes for ejecting ink droplets of the respective colors may be used. Further, the inkjet head used as the head 94 is a piezo type in which ink is pressed through a vibration plate forming a wall surface of the liquid chamber by an electromechanical conversion element such as a piezoelectric element, or a heating resistor generates bubbles to apply the ink. A bubble type that presses, or an electrostatic type that presses ink by displacing the diaphragm by the electrostatic force between the diaphragm that forms the wall surface of the ink flow path and the electrode facing the diaphragm can be used. In the embodiment, an electrostatic inkjet head is used.

Here, the carriage 93 is slidably fitted to the main guide rod 91 on the rear side (downstream side in the sheet conveying direction) and the front side (downstream side on the sheet conveying direction) in the sub guide rod 9.
2 is slidably mounted. Then, since the carriage 93 is moved and scanned in the main scanning direction, the main scanning motor 9
A timing belt 100 is stretched between a drive pulley 98 and a driven pulley 99, which are driven to rotate by 7, and the timing belt 100 is fixed to a carriage 93. It is driven back and forth. On the other hand, the paper 8 set in the paper feed cassette 84
3 to the lower side of the head 94, the paper feed roller 101 and the friction pad 102 for separating and feeding the paper 83 from the paper feed cassette 84, the guide member 103 for guiding the paper 83, and the fed paper. A conveyance roller 104 that reverses and conveys 83, and conveyance rollers 105 and conveyance rollers 10 that are pressed against the peripheral surface of the conveyance roller 104.
Tip roller 1 that regulates the feeding angle of the paper 83 from the 4
06 and are provided. The conveyance roller 104 is rotationally driven by the sub-scanning motor 107 via a gear train. Further, there is provided a print receiving member 109 which is a paper guide member for guiding the paper 83 sent out from the carrying roller 104 below the recording head 94 in correspondence with the movement range of the carriage 93 in the main scanning direction. A transport roller 111 and a spur 112 that are driven to rotate in order to send out the paper 83 in the paper discharge direction are provided on the downstream side of the print receiving member 109 in the paper transport direction, and further, the paper 83 is sent to the paper discharge tray 86. A roller 113, a spur 114, and guide members 115 and 116 that form a paper discharge path are provided. At the time of recording, by driving the recording head 94 in accordance with the image signal while moving the carriage 93, ink is ejected onto the stopped paper 83 to record one line, and after the paper 83 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the sheet 83 has reached the recording area, the recording operation is terminated and the sheet 83 is discharged.
A recovery device 117 for recovering the ejection failure of the head 94 is arranged at a position outside the recording area on the right end side of the carriage 93 in the moving direction. The recovery device 117 has a cap means, a suction means, and a cleaning means.
The carriage 93 is moved to the recovery device 117 side while the printing is on standby, the head 94 is capped by the capping means, and the ejection port portion (nozzle hole) is kept wet to prevent ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant, and stable ejection performance is maintained. In case of defective discharge,
The ejection port of the head 94 is sealed by the capping unit, and the bubbles and the like are sucked out from the ejection port by the suction unit through the tube, and the ink and dust adhering to the ejection port surface are removed by the cleaning unit to recover the ejection failure.
Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed in the lower portion of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.

[0016]

As described above, according to the present invention, it is not necessary to add a special component such as a pressure detecting means and a small pressure adjusting means is provided on the head chip, so that the cost is low and the range is wide. It is possible to manufacture a droplet discharge head that can cope with the atmospheric pressure, and provide a droplet discharge head using the same and an inkjet recording apparatus. That is, according to the droplet discharge head of the invention of claim 1, a predetermined amount of the non-volatile / non-volatile fluid (pressure) is provided in a part of the communication passage provided inside the head for connecting the void and the outside air. (Adjusting fluid) to make it movable in the communication passage, while keeping the inside of the gap closed by this fluid, preventing the ingress of moisture, dust, etc. into the gap and preventing the displacement of the movable plate from occurring. A droplet discharge head with high durability and reliability can be provided. According to the droplet discharge head of the second aspect of the invention, the non-volatile / non-volatile fluid moves in the communication passage in accordance with the pressure difference, and the volume of the sealing portion is changed, whereby It is possible to reduce the pressure fluctuation, and it is possible to provide a head capable of stably ejecting droplets. According to the droplet discharge head of the third aspect of the invention, the non-volatile / non-volatile fluid moves in the communication passage according to the pressure difference, and temporarily opens the inside of the void to the outside air, By adjusting the difference, the pressure difference can be reduced even when the pressure in the air gap and the pressure of the outside air are significantly different at high altitudes, etc., so that it is possible to provide a head with high environmental reliability, and to detect the pressure detection means and Since no complicated adjusting means is required, the device can be manufactured in a small area and at low cost. According to the droplet discharge head of the fourth aspect of the present invention, the width of the communication passage is partially narrowed or widened, and the position of the non-volatile / refractory fluid in the communication passage is automatically determined. With such a configuration, the structure of the pressure correction unit can be simplified and can be manufactured by a simple process, and the droplet discharge head can be provided at low cost. According to the droplet discharge head of the fifth aspect of the present invention, by dispersing particles that are sufficiently smaller than the diameter of the communication passage in the non-volatile / non-volatile fluid, the gradient of atmospheric pressure change or the like can be reduced with respect to force. While exhibiting fluidity, the drop ejection head with high durability and environmental reliability can be provided by increasing the apparent viscosity of the fluid when an impact force such as dropping or carriage reciprocation is applied. Can be provided. According to the droplet discharge head of the invention of claim 6, by mounting a highly reliable head on the ink tank integrated type head, the reliability of the head integrated ink cartridge itself is improved, and It is possible to provide a head-integrated ink cartridge that enables a large capacity and as a result has a low running cost. According to the droplet discharge head of the invention of claim 7, the droplet discharge head according to any one of claims 1 to 5 is used in an inkjet recording apparatus equipped with an inkjet head that discharges ink droplets. It is possible to provide a reliable and low-cost inkjet recording device.

[Brief description of drawings]

FIG. 1 is a transparent state plan view of an electrostatic type liquid proper ejection head of the present invention.

FIG. 2 is an explanatory cross-sectional view taken along the long side direction of the pressurized liquid chamber of the electrostatic liquid proper discharge head of the present invention.

FIG. 3 is a cross-sectional explanatory view taken along the short side direction of the pressurized liquid chamber of the electrostatic type appropriate liquid ejection head of the present invention.

FIG. 4 is an explanatory cross-sectional view taken along a passage portion of the electrostatic type liquid proper ejection head of the present invention.

FIG. 5 is an explanatory top view of the electrode substrate of the present invention.

FIG. 6 is an explanatory view showing an operation according to a pressure difference between the outside air and the void according to the present invention.

FIG. 7 is a comparative explanatory diagram of bending of a movable plate due to pressure correction of the present invention.

FIG. 8 is an explanatory view of the shape of the communication passage of the present invention.

FIG. 9 is an explanatory diagram of an ink cartridge of the present invention.

FIG. 10 is a perspective explanatory view of the ink jet recording apparatus of the present invention.

FIG. 11 is a side sectional view of the ink jet recording apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 flow path substrate, 2 electrode substrate, 3 nozzle plate, 4 pressure control part, 11 pressurizing liquid chamber, 12 common liquid chamber, 13 movable plate, 14 outside air port, 15 electrode opening part, 21 void, 2
2 electrodes, 23 electrode protective film, 24 electrode take-out part,
25 base oxide film, 26 ink supply port, 31 nozzle hole, 32 fluid resistance part, 41 communication path, 42 communication path cavity part, 43 pressure adjusting fluid.

Claims (7)

[Claims] 1. A liquid droplet ejection head for ejecting liquid droplets by a pressure wave caused by an electrostatic force, wherein a nozzle hole for ejecting the liquid droplet and a pressurized liquid chamber containing a liquid communicating with and ejecting the nozzle hole. A movable plate forming a part of the wall surface of the pressurized liquid chamber, a gap provided on the side opposite to the pressurized liquid chamber in contact with the movable plate, and arranged to face the movable plate through this gap. A droplet discharge head that discharges droplets from the ink nozzle hole by increasing the internal pressure in the pressurized liquid chamber by bending the movable plate by an electrostatic force generated by a voltage applied to the electrode, A droplet discharge head, comprising: a communication passage that communicates the gap with the outside air, and a part of the communication passage is filled with a non-volatile or hardly volatile fluid. 2. The droplet discharge head according to claim 1, wherein the non-volatile or hardly volatile fluid moves in the communication passage in accordance with a change in external pressure to adjust the pressure in the void. A droplet discharge head which also serves as a means. 3. The droplet discharge head according to claim 1, wherein the non-volatile or hardly volatile fluid moves in the communication passage in response to fluctuations in the external pressure and temporarily changes the pressure in the void to the external pressure. A droplet discharge head, which is a pressure adjusting unit that releases the pressure to adjust the pressure. 4. The droplet discharge head according to claim 1, wherein the communication passage has a configuration in which a passage diameter thereof is gradually reduced or gradually increased. Discharge head. 5. The droplet discharge head according to claim 1, wherein particles that are sufficiently smaller than the diameter of the communication passage are dispersed in the non-volatile or hardly volatile fluid. Characteristic droplet discharge head. 6. A droplet ejection head for ejecting ink droplets,
An ink cartridge in which an ink tank for supplying ink to the droplet discharge head is integrated, wherein the droplet discharge head is the droplet discharge head according to any one of claims 1 to 5. Ink cartridge to do. 7. An ink jet recording apparatus equipped with a droplet discharge head that discharges ink droplets, wherein the droplet discharge head is the droplet discharge head according to any one of claims 1 to 5. An ink jet recording apparatus characterized by the above.