JPH1158739A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an amount of a material for a fluid passage forming substrate forming an actuator unit and to form a reservoir having a sufficient compliance. SOLUTION: This recording head comprises an actuator unit 4 having a pressure generating chamber 7 pressurized by a piezoelectric vibrator 17, a connection plate 2 which hermetically fixates the actuator unit 4 and comprises a connection fluid passage 12 communicated to one end of the pressure generating chamber 7 and a communicating hole 10 that connects the other end of the pressure generating chamber 7 to a nozzle 9 and a head holder 1 which is formed as a frame supporting the connection plate 2 and comprises a passage hole connected thereto via the connection fluid passage 12. A reservoir 11 is so constituted that an opening face of the passage hole is sealed with a thin plate 21 which can be deformed by a pressure of ink which inversely flows from the pressure generating chamber 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head which pressurizes a pressure generating chamber communicating with a nozzle opening by displacement of a piezoelectric vibrator to discharge ink droplets from the nozzle opening.

[0002]

2. Description of the Related Art An ink jet recording head has a reservoir connected to an external ink supply means, a pressure generating chamber pressurized by a piezoelectric vibrator, and a nozzle opening communicating with the pressure generating chamber. The displacement of the piezoelectric generating element causes the pressure generating chamber to expand, causing ink from the reservoir to flow into the pressure generating chamber, and the displacement of the piezoelectric vibrator to the other causes the pressure generating chamber to contract, thereby pressurizing the ink in the pressure generating chamber. The ink droplets are ejected from the nozzle openings.

At the time of pressurizing the pressure generating chamber for discharging ink droplets, a part of the ink in the pressure generating chamber flows back to the reservoir through the ink supply port, and the pressure of the ink in the reservoir increases. As a result, a phenomenon in which the pressure of the pressure generating chamber which does not need to discharge the ink droplets rises and the ink droplets are discharged from the nozzle opening communicating therewith, that is, a so-called crosstalk occurs.

In order to solve such a problem, a part of the partition wall constituting the reservoir is formed so as to be deformable by the pressure of the ink, and the reservoir is compliant so as to absorb the pressure of the ink flowing backward from the pressure generating chamber. Is given.

[0005]

However, in order to satisfy the demand for high-speed printing and high-density printing, it is necessary to increase the arrangement density of the pressure generating chambers by anisotropic etching of the silicon single crystal substrate. Need to be processed,
In particular, if a reservoir formed by a concave portion or opening that is extremely large compared to the pressure generating chamber is formed integrally, an extremely fragile area will be generated in part, and the handling of the flow path forming substrate during assembly will be improved. In addition to the lowering, the assembling work becomes difficult, and there is a problem that the effective use of the expensive silicon single crystal substrate is hindered. The present invention has been made in view of such a problem, and an object of the present invention is to provide a reservoir which does not require a reservoir for a flow path forming substrate and has sufficient compliance to ensure printing quality. It is an object of the present invention to provide an ink jet recording head which can be constituted as follows.

[0006]

According to the present invention, there is provided an actuator unit having a pressure generating chamber which receives pressure fluctuations by a pressure generating means, and the actuator unit is fixed in a liquid-tight manner. A connection passage communicating with one end of the pressure generation chamber, a connection plate provided with a communication hole connecting the other end of the pressure generation chamber to a nozzle opening, and a frame supporting the connection plate, And a holder having a through-hole connected through the connection flow path, and sealing the opening surface of the through-hole with a thin plate elastically deformable by the pressure of the ink flowing backward from the pressure generating chamber to form a reservoir. To be configured.

[0007]

[Function] Since the reservoir is formed in a member separate from the actuator unit which requires precision machining, the material for the reservoir can be saved, and the reservoir is not restricted by the size of the actuator. It can be formed in a size having a sufficient function as a reservoir.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a first embodiment of the present invention. FIGS. 1 and 2 show one embodiment of the present invention. A head holder 1 includes a frame 3 for supporting a peripheral edge of a connection plate 2 described later and a window 5 for accommodating an actuator unit 4. An ink introduction port forming member 6 connected to an external ink tank is provided at one corner of the frame 3.

The connecting plate 2 has a nozzle communication hole 10 connecting one end of the pressure generating chamber 7 to the nozzle opening 9 of the nozzle plate 8, and a reservoir 11 described later on the other end of the pressure generating chamber 7.
The nozzle plate 8 is fixed to the exposed surface side of the head holder 1, and the actuator unit 4 is liquid-tightly fixed to the other surface side.

The connection flow path 12 is formed as a recess having an opening on the nozzle plate 8 side and having a width connecting the connection port 16 of the pressure generating chamber 7 of the actuator unit 4 and a through hole 23 of the head holder 1 described later. Opening grooves 12a and 12b are formed to communicate at both ends.

The actuator unit 4 has, as shown in FIG. 4, a constricted portion serving as an ink supply port 13 near one end in accordance with the arrangement pitch of the nozzle openings 9 by anisotropically etching a silicon single crystal substrate. A flow path forming substrate 14 having a through hole and one surface of the flow path forming substrate 14 are sealed by an elastic plate 15 which can be elastically deformed by a piezoelectric vibrator 17 described later. 2, the pressure generating chamber 7, the ink supply port 13, and the connection port 16 are fixed in a liquid-tight manner.

The connection port 16 communicates with one opening groove 12a of the connection flow path 12 as shown in FIG. 5, and communicates with the reservoir 11 through the other opening groove 12b of the connection flow path 12.

As shown in FIG. 6, at least the surface of the elastic plate 15 constituting the actuator unit 4 is made of a material having conductivity. Element 17 and upper electrode 18
Is built in.

The piezoelectric vibrator 17 has a connection end 18 a extending from the upper electrode 18 and a flexible cable 19.
Connected to an external drive circuit and a drive signal supplied from the transfer gate semiconductor integrated circuit 20.
The elastic plate 15 is configured to be deformed in accordance with the print signal to expand and contract the volume of the pressure generating chamber 7.

On the other hand, the head holder 1 is formed with a step 22 which is one step lower than the connecting channel 12 so that a thin plate 21 which will be described later does not protrude. A through hole 23 that can surround the space 12b and secure a volume as the reservoir 11 is provided.

The through hole 23 is sealed by a thin plate 21 which can be elastically deformed by the pressure of the ink flowing backward from the pressure generating chamber 7 at its opening surface, and communicates with the ink inlet 6a to receive supply of ink from outside. And functions as a reservoir 11.

The thin plate 21 has a larger area and a smaller thickness, that is, the lower the rigidity, the more effective it is in eliminating cross stroke. In particular, since the rigidity is proportional to the cube of the plate thickness, the rigidity can be significantly reduced by reducing the thickness. However, due to the problem of the size of the head, the handleability and the strength of parts, etc., the thin plate 2
The size of 1 is determined to be an optimum thickness with a necessary minimum area according to the pressure generated in the pressure generating chamber 7 and the number of the pressure generating chambers 7.

For example, for a recording head capable of ejecting about 0.01 g of ink droplets per second, a width of 2 mm,
A stainless steel plate of 8 mm in length and 0.01 mm in thickness
1 and is liquid-tightly fixed with an epoxy-based adhesive around the opening surface of the reservoir 11 of the head holder 1.

As a material for forming such a thin plate 21, there is a thin nickel plate having excellent ink resistance, in addition to the above stainless steel.

In this embodiment, when a driving signal is supplied to the piezoelectric vibrator 17 in response to the print signal to charge the piezoelectric vibrator 17, the displacement of the piezoelectric vibrator 17 causes the pressure generating chamber 7 to move.
Expands. Thereby, the ink in the reservoir 11 flows into the connection port 16 of the actuator unit 4 via the connection flow path 12, and further flows into the pressure generating chamber 7 through the ink supply port 13.

When the charge of the piezoelectric vibrator 17 is discharged after a predetermined time has elapsed in this state, the piezoelectric vibrator 17 returns to the original state, and the pressure generating chamber 7 contracts.

As a result, the ink in the pressure generating chamber 7 is pressurized, and a part thereof flows from the communication hole 10 of the connecting plate 2 to the nozzle opening 9.
And ejected as ink droplets from the nozzle opening 9,
Further, a part thereof flows backward to the reservoir 11 via the connection flow path 12. The pressure of the reservoir 11 increases due to the backflow of the ink. However, since the elastic plate 21 constituting the reservoir 11 is elastically deformed to expand the volume, the increase in the pressure is suppressed as much as possible, and other pressure generation occurs. A pressure increase in the chamber 7 is prevented.

Hereinafter, by repeating such a process in accordance with the printing timing, ink droplets are ejected from predetermined nozzle openings 9 without causing crosstalk.

As described above, since the reservoir is formed in a member different from the actuator unit requiring precision machining, for example, when the actuator unit is manufactured from an expensive material such as a silicon single crystal substrate, The material for the reservoir can be saved. At the same time, since there is no fragile portion caused by forming a large through-hole in the flow path forming substrate, handling properties are improved, and mechanization and simplification of assembly work can be achieved. Further, the size of the reservoir can be ensured without being restricted by the size of the actuator or the like, so that a sufficient size of the reservoir can be obtained, and the printing quality can be improved.

Although the thin plate 21 is made of a single material in the above-described embodiment, as shown in FIG. 7A, a polyethylene film 21a and a polyethylene terephthalate film each having a thickness of about 0.02 mm are used. 21b.

According to this embodiment, the reservoir 11 is made of a resin film having a smaller Young's modulus than metal.
Can be made small, and the thin plate 21 can function as the reservoir 11 sufficiently while having a certain thickness.

The thin plate 21 is bonded to the head holder 1 by heat welding while pressing the surface of the polyethylene film 21a against the head holder 1. The polyethylene film 21a not only functions as a bonding layer, but also has a low moisture permeability, so that the ink in the reservoir 11 suppresses evaporation of the solvent as much as possible.
It is possible to prevent the viscosity of the ink from increasing.

Since the polyethylene terephthalate film 21b, which is the second material, is excellent in heat resistance, the thin plate 21 can be prevented from being out of shape at the time of heat welding, and the thin plate 21 can be accurately welded to the reservoir 11. In addition, the low gas permeability prevents the air from entering the reservoir 11 and generating bubbles in the ink flow path.

FIG. 7 (b) shows a polyethylene film 21a having a thickness of about 0.01 mm as a heat welding material, an aluminum foil 21c having a thickness of about 0.005 mm forming an intermediate layer as an air shielding material, and a mold. It is formed by laminating polyethylene phthalate 21b having a thickness of about 0.01 mm as a maintenance material.

The aluminum foil 21c, which is the intermediate layer, has a significantly lower moisture permeability and gas permeability than the polymer material. It is possible to reliably prevent the generation of air bubbles in the inside, and the polyethylene phthalate 21b maintains the entire mold when the polyethylene film 21a is thermally welded to the head holder 1.

In the above-described embodiment, polyethylene is used as the heat-weldable material, but other resin films such as polyamide and polypropylene may be used depending on the material of the head holder 1. Further, as the metal forming the air barrier layer, nickel or the like can be used in addition to aluminum.

Further, in the above-described embodiment, the actuator unit 4 is constituted by the flow path forming substrate 14 and the elastic plate 15 separately, but as shown in FIG. A silicon oxide film 31 is formed on one surface, and the pressure generating chamber 7 is used to function as an elastic plate.
The ink supply port 13 and the connection port 16 are formed by anisotropic etching, and the silicon oxide film 31 is subjected to a conductive treatment to form a lower electrode 32, and a piezoelectric vibrator 33 is formed on the surface by a film forming method. The same operation is exerted even if the configuration is made.

Further, in the above-described embodiment, an example has been described in which the pressure generating chamber is pressurized by the displacement of the piezoelectric vibrator. However, a heating element is built in the pressure generating chamber, and the ink is vaporized. The same effect can be obtained by applying the present invention to a pressurized recording head.

[0034]

As described above, in the present invention,
An actuator unit having a pressure generation chamber that receives pressure fluctuations by the pressure generation means, a connection flow path that fixes the actuator unit in a liquid-tight manner and communicates with one end of the pressure generation chamber, and a nozzle opening at the other end of the pressure generation chamber A connection plate having a communication hole connected to the connection plate, and a holder configured as a frame supporting the connection plate and having a communication hole connected through a connection flow path, and generating pressure on the opening surface of the communication hole. The reservoir is constructed by sealing with a thin plate that can be elastically deformed by the pressure of the ink flowing backward from the chamber, so the material of the actuator unit that requires precision processing can be saved by the amount of the reservoir, and it is fragile from the flow path forming substrate By eliminating unnecessary parts, the handleability can be improved, and the cost of the recording head can be reduced by simplifying the material cost and the assembling work.

Further, the size of the reservoir can be ensured without being restricted by the size of the actuator, etc., so that the size of the reservoir can be ensured, and the printing quality can be improved.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of an ink jet recording head of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure in one pressure generating chamber of the ink jet recording head.

FIG. 3 is an assembled perspective view of the ink jet recording head.

FIG. 4 is a perspective view showing one embodiment of a flow path forming substrate.

FIG. 5 is a diagram showing an embodiment of a flow path substrate of the ink jet recording head in the relation with nozzle openings and flow path communication ports.

FIG. 6 is a view showing one embodiment of a piezoelectric vibrator formed on a surface of an elastic plate.

FIGS. 7A and 7B are cross-sectional views each showing another embodiment of a thin plate for forming a reservoir.

FIG. 8 is a view showing another embodiment of an actuator unit usable in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head holder 2 Connection plate 3 Frame part 4 Actuator unit 5 Window 6 Ink introduction port formation member 7 Pressure generation chamber 8 Nozzle plate 9 Nozzle opening 10 Communication hole 11 Reservoir 12 Connection flow path 13 Ink supply port 14 Flow path formation board 15 Elasticity Plate 16 Connection port 17 Piezoelectric vibrator 19 Flexible cable 21 Thin plate for forming reservoir 23 Through hole for forming reservoir

Claims (14)

[Claims] An actuator unit having a pressure generating chamber which receives pressure fluctuations by a pressure generating means; a connection flow passage which fixes the actuator unit in a liquid-tight manner and communicates with one end of the pressure generating chamber; A connection plate provided with a communication hole connecting the other end of the generation chamber to the nozzle opening; and a holder configured as a frame supporting the connection plate and having a communication hole connected through the connection flow path. An ink jet recording head comprising a reservoir in which an opening surface of the through hole is sealed with a thin plate which can be elastically deformed by a pressure of ink flowing backward from the pressure generating chamber. 2. The ink jet recording head according to claim 1, wherein an ink introduction member is formed in the holder so as to communicate with the reservoir. 3. The ink jet recording head according to claim 1, wherein the connection flow path is formed by sealing a concave portion formed so that a nozzle opening side is opened with an opening surface thereof by a nozzle plate. 4. The ink jet recording head according to claim 3, wherein narrow grooves are formed at both ends of said concave portion, said grooves being open on said actuator side. 5. The ink jet recording head according to claim 1, wherein a step portion is formed on a joining surface of the thin plate. 6. The actuator unit according to claim 1, wherein the flow path forming substrate and the vibration plate are joined, and a piezoelectric vibrator is fixed to a surface of the vibration plate in accordance with an arrangement pitch of the pressure generating chambers. 2. The ink jet recording head according to 1. 7. The ink jet recording head according to claim 6, wherein the flow path forming substrate is formed by anisotropic etching of a silicon single crystal substrate. 8. The ink jet recording head according to claim 1, wherein said actuator unit is formed by anisotropic etching of a silicon single crystal substrate so that a thin film of silicon oxide is used as a vibration member. 9. The ink jet recording head according to claim 1, wherein said pressurizing means comprises a heat generating means for heating ink in the pressure generating chamber. 10. The ink jet recording head according to claim 1, wherein the thin plate is a non-rusting metal plate having a thickness of 0.001 mm to 0.1 mm or less. 11. The ink jet recording head according to claim 1, wherein the thin plate is a laminated film having a thickness of 0.005 mm to 0.5 mm or less, in which resin layers of different materials are laminated. 12. The ink jet recording head according to claim 1, wherein the thin plate is a laminated plate having a thickness of 0.001 mm to 0.5 mm or less in which a metal layer and a resin layer are laminated. 13. The resin layer, wherein a layer facing the holder is made of a heat-sealable resin.
13. The ink jet recording head according to items 1 and 12. 14. The ink jet recording head according to claim 11, wherein one of the resin layers is made of a heat resistant resin.