JP2001030483A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid chamber which meets a small, high-density and multi-bit ink jet head and is richly mass-producible. SOLUTION: A pressure in a pressure chamber 2 communicated with a nozzle 7 is controlled by a pressure generation means (piezoelectric element) 9 set to a part of the pressure chamber 2, whereby ink is jetted from the nozzle 7. A first member 4 has at least two opening parts 13 and 14, and the opening parts 13 and 14 are communicated with each other by a fluid resistance path 12. A second plate member 3 has a groove 12' for forming the fluid resistance path 12 connecting the two opening parts 13 and 14 in cooperation with the first plate member 4. The first and second plate members 4 and 3 are layered and joined, whereby the fluid resistance path 12 for ink to be supplied to the pressure chamber 2 from the ink feed ports 14 is formed.

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, and more particularly, to an actuator which can be used for a recording head such as an ink jet recording apparatus, a copying machine, a facsimile, a printer, a plotter, a micropump, and the like.

[0002]

2. Description of the Related Art In an on-demand type ink jet recording technique, a piezoelectric body is arranged on a part of a wall of a liquid chamber filled with ink, and a pressure in the liquid chamber is changed by applying a voltage to the piezoelectric body. A method of ejecting ink by increasing the pressure and ejecting ink (piezo-on-demand type ink jet) or a method in which a heating element that generates heat by energization is provided in the liquid chamber, and the pressure in the liquid chamber is increased by bubbles generated by the heat generated by the heating element. (Bubble jet type inkjet) is widely known. In addition, even more compact, high density, high speed printing, high quality printing,
As a method for realizing long life and high reliability, a method (electrostatic type ink jet) in which the volume of a liquid chamber is changed by electrostatic force and ink is ejected has been proposed.

The liquid chambers of these ink jet heads are provided with nozzles for discharging ink and ink supply ports for supplying new ink in accordance with ink consumption. In many ink-jet heads, in order to efficiently use the pressure change for ink ejection, the ink supply port is formed as a fine hole or groove to have a function of reducing the backflow of ink. However, in recent years, miniaturization and high density of the head have been advanced, and accordingly, further miniaturization of the ink supply port has been required. Further, in order to achieve high-speed printing by performing ink ejection at a high frequency, it is necessary to increase the rigidity of the liquid chamber member.

[0004]

A known example of a liquid chamber of an ink jet head is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-3 / 1994.
There are JP-A No. 1914 and JP-A-6-23984.
In JP-A-6-31914, a liquid chamber is made of Si or borosilicate glass, and a nozzle,
Although the orifice is formed and is suitable for microfabrication, it is not desirable in terms of reducing the cost of the ink jet head because the material is limited to expensive Si or borosilicate glass. Also, Japanese Patent Laid-Open No. 6-2398
In JP-A No. 4 (1999) -1999, a liquid chamber is formed by using a photosensitive resin, and an uncured portion is left between partition walls so as to reduce mutual interference between bits. Since the chamber is formed, a complicated fine shape can be realized. However, when a resin material such as DFR is used, there is a problem that the liquid chamber spacing wall cannot be made thin because of low rigidity. Further, there is a problem in that the ink ejection energy obtained by the piezoelectric element or the heating element is absorbed by the deformation of the liquid chamber, so that the efficiency is low and the ink cannot be ejected at a high frequency.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described demands, and has as its object to provide a liquid chamber which is compatible with a small, high-density, multi-bit ink jet head and has high mass productivity. It is.

More specifically, the invention of claim 1 is to form a low-cost and highly accurate ink supply port.
The invention is to maintain the height of the ink supply port constant,
The invention according to claim 3 forms a liquid chamber having high planarity,
According to a fourth aspect of the present invention, the flatness of the liquid chamber and good jointability are ensured, and the fifth aspect of the present invention provides a simple processing method of an ink supply port having a shape in which bubble accumulation is unlikely to occur. An object of the invention of claim 6 is to form an ink supply port having less variation in shape by improving workability, and an object of claim 7 is to improve the shape accuracy of the ink supply port.

[0007]

According to the present invention, a pressure generating means provided in a part of a pressurizing chamber communicating with a nozzle is provided.
In an ink jet head that controls the pressure in the pressurizing chamber and ejects ink from the nozzles, a first plate member having at least two openings of an ink pressurizing chamber opening and a common ink flow passage opening, and the two openings are formed by: A second plate member having a groove that communicates and forms a fluid resistance, and these plate members are laminated and joined to form an ink supply port;
The ink is supplied from the common ink passage opening to the pressurizing chamber through the ink supply opening.

Further, in the above invention, the invention according to claim 2 is that the first plate member and the second plate member are high-rigidity members, and the invention according to claim 3 is that the first plate member is The invention according to claim 4, wherein the first plate member and the second plate member are made of the same material and have substantially the same thickness, and the first plate member and the second plate member are made of a metal material. The invention according to claim 5, wherein the surface is oxidized by at least the second
7. The plate member is processed by etching.
The invention according to claim 7, wherein both ends of the groove formed in the second plate member are wide, and the invention according to claim 7, wherein the second plate member is a laminated material sandwiching at least an adhesive layer at the center. That is, it is characterized.

[0009]

FIG. 1 is a diagram showing an example of a basic configuration of a piezo-on-demand type ink jet head.
FIG. 1A is a longitudinal sectional view of a plurality of liquid chambers provided in a row, FIG. 1B is a plan view (a view taken along line BB of FIG. 1A), and 1 in the figure. Vibrating plate, 2 is a pressurized liquid chamber, 3 is a lid member, 4 is a lower plate, 5 is a common ink channel, 6 is a nozzle plate, 7
Is a nozzle, 8 is a common ink channel forming plate, 9 is a piezoelectric element,
Reference numeral 11 denotes a nozzle communication hole, and 14 denotes an ink supply port. As is well known, the pressure inside the pressurized liquid chamber 2 is increased by deforming the vibration plate 1 by the piezoelectric element 9, and ink is ejected from the nozzle 7. is there. The ink passes through a common ink flow path 5 provided over the plurality of liquid chambers,
Are supplied from ink supply ports 14 provided one for each liquid chamber 2. In the case of the ink jet head having the configuration of FIG. 1, the ink supply port 14 is a through hole formed in the plate-shaped lid member 3 provided above the pressurized liquid chamber 2. If the diameter of the through-hole is too small, the liquid resistance increases, so that there is a problem that the ink supply becomes insufficient when the ink is ejected at a high frequency. Conversely, if the size is too large, when the diaphragm 1 is deformed, the amount of ink flowing backward to the common ink flow path 5 increases, and the amount of ink discharged from the nozzles 7 decreases, thereby lowering the discharge efficiency. As described above, the size of the ink supply port (through hole) 14 also has a role as a fluid resistance forming hole that greatly affects ink ejection characteristics.

In the liquid chamber 2 shown in FIG. 1, the lid member 3 is provided with an ink supply port 14 and a nozzle communication hole 11 for sending ink to the nozzle 7, but usually, in order to increase the ink ejection efficiency. Ink supply port 14 from nozzle communication hole 11
Is made quite small. In order to reduce the size of the liquid chamber having such a configuration in accordance with an increase in the density of the ink jet head, further reduction in the diameter of the ink supply port 14 is a major issue.

In order to realize a low-cost ink jet head, an ink supply port 1 provided in each liquid chamber is required.
The method of processing 4 for each hole is not suitable. At present, there is photoetching as a method to realize multi-hole micro-diameter and micro-pitch processing at relatively low cost. However, at present, through-holes with the same diameter as the plate thickness can be processed without variation. is there. As a method capable of machining such a small diameter hole, there is an electric discharge machining, but it is not suitable for mass production because a large number of holes cannot be machined at a time and the time required for machining is extremely long.

FIG. 2 is a view showing the structure of an ink jet head according to the present invention. FIG. 2 (A) is a sectional view, and FIG. 2 (B) is a plan view (as viewed from the direction of the line BB in FIG. 1 (A)). Figure). In FIG. 2 (B), solid lines indicate holes 10 provided in the lid member 3,
11, the shape of the groove 12 'is shown, and the broken line shows the shape of the plate on which the diaphragm is formed. In FIG. 2, the lid member 3 is
It is made of a highly rigid material, and a narrow shallow groove 12 ′ is provided over the openings 13 and 14 of the lower plate 4. This lid member 3
Are stacked on the lower plate 4 to form an ink supply path 12. By making the groove 12 ′ of the lid member 3 shallow, the ink supply channel 12 functions as a fluid resistance. The fluid resistance flow value is mainly determined by the depth, width, and length of the groove 12 '. When the groove cross section is a rectangular cross section with a long side a and a short side b, the flowing flow rate Q is such that the flow rate of the flow in the rectangular cross section pipe is Q∝ab
^Since it is ^3, it is largely controlled by the short side length. Therefore,
By uniformly forming the depth of the groove (corresponding to the short side b), the ink supply channel 12 having stable fluid resistance can be realized. In this configuration, since the processing margin of the groove 12 ′ is shallow, a groove having a stable shape with little variation in depth and width can be realized by a method rich in mass productivity such as etching.

The two plate members 3 and 4 forming the ink supply channel 12 are made of metal, ceramics, S
Highly rigid materials such as i and glass are preferred. When a low-rigidity material is used, when a large pressure is applied at the time of lamination and joining, there arises a problem that the height and width of the gap of the ink supply port portion become narrow, and the fluid resistance becomes non-uniform. In consideration of material cost and workability among the above-described high-rigidity materials, metal plates such as stainless steel, copper, phosphor bronze, and nickel are most suitable. These metal plates are not only inexpensive, but also can be processed with high productivity such as etching. In particular, stainless steel has high marketability, is inexpensive, can be processed by etching, pressing, and the like, and has excellent ink resistance.
Also, a nickel-based material can realize a high-quality fine shape by electroforming. When these metal materials are used, if an oxide layer is formed on the surface by heat treatment or acid treatment, the ink resistance is improved and the wettability is improved, so that the adhesion is also improved. In particular, if the heat treatment is performed not only before bonding but also before drilling, it is possible to avoid warpage at the time of bonding due to a change in shape due to thermal contraction of the metal material, which is effective in realizing a liquid chamber with good dimensional accuracy. .

Although the ink supply port of the present invention has a two-layer structure in which two plate members are laminated and joined, the means for laminating and joining the liquid chamber components often uses heating. Accordingly, if the materials of the laminated members are different, warpage due to a difference in thermal expansion coefficient or the like is likely to occur. Therefore, when joining is performed using plate materials of the same material and the same thickness, joining with less warpage can be realized.

There are several methods for forming grooves in the cover member 3. Etching is excellent in processing method, shape quality, and the like. In this case, if the cross-sectional shape is as shown in FIG. 3A, when the ink flows as shown by the arrow A, the corner (B) becomes a dead space, and bubbles that adversely affect the ink ejection characteristics are formed. Is easily trapped. However, when processing is performed by etching, as shown in FIG. 3B, a smooth ink supply port having no corners can be formed due to the influence of side etching without special measures. In addition, when a groove is formed by such etching, as shown in FIG.
When the shape is such that both end portions are wide, variation in the end shape due to the difficulty of entry of the etchant is reduced, and processing with more stable quality can be realized. However, even in the case where the both ends of the groove are widened in this way, it is preferable to form a pattern without corners as shown in FIG.

FIG. 5 is a view for explaining another means for making the depth more uniform than the depth of the groove 12 'of the ink supply flow path 12. First, as shown in FIG. And a thick plate member 2 in which a common ink flow passage communicating hole 10 is formed.
An adhesive 20 is applied to 1 and a thin plate member 22 having the same thickness as the depth of the groove 12 'of the ink supply port is bonded. Next, as shown in FIG. 5B, the entire surface of the thick plate member 21 and the unprocessed portions of the thin plate member 22 are masked with a resist 23, and etching is performed. When processing is performed in such a process, the groove 1
The etching of the 2 'portion is automatically stopped at the adhesive layer 20, and the shape of the lid member as shown in FIG. 5C can be obtained. According to this method, since the depth of the groove 12 ′ that most affects the fluid resistance value of the ink supply flow path 12 is determined by the thickness of the thin plate member 22, a highly accurate groove shape can be easily obtained. .

(Embodiment 1) FIG. 2 is a view for explaining a first embodiment of the present invention.
Then, a thermal oxide film was formed, the resist was patterned in accordance with the shape of the diaphragm 1, the resist was opened, and the Si was etched using a hydrofluoric acid-based etching solution or a KOH aqueous solution. The thickness of the diaphragm 1 is about 7 μm and the width is 2
The thickness was set to 00 μm. First, zirconia as an intermediate layer for preventing lead in a piezoelectric element from diffusing into Si was formed to a thickness of 1 μm on the back surface of the diaphragm 1 by a sputtering method. A platinum electrode having a thickness of 5 μm was formed on the intermediate layer by a screen printing method. Further, a calcined powder of a piezoelectric material mainly composed of PZT is paste-processed to a thickness of 20 μm.
m, and fired in the air at a temperature of 900 to 1100 ° C. A silver electrode was patterned on the fired piezoelectric body to form a piezoelectric element 9.

A 100 μm thick Kovar plate is used for the cover member 3, and a length of 400 μm and a width of 60 μm for forming the nozzle communication hole 11 and the ink supply channel 12 having a diameter of 200 μm.
A groove 12 ′ having a thickness of 30 μm and a depth of 30 μm was processed by etching. After the cover member 3 was plated with gold, it was positioned and superimposed on the Si on which the vibration plate 1 was formed, and the two were joined by heating at 450 ° C. in a nitrogen atmosphere. On the upper surface of the lid member 3, a common ink flow path forming plate 8 having a nozzle communication hole 11 having a diameter of 200 μm and a common ink flow path 5 is formed by a Kovar plate having a thickness of 100 μm. Using 170, the mixture was cured by heating at 130 ° C.

Finally, a 50 μm-thick nozzle plate 6 having a hole having a diameter of 30 μm formed by electroforming of nickel and having a water-repellent layer of PTFE formed on the surface thereof was joined. When an ink jet head of 100 dpi was formed by such a method and an ejection experiment was performed, good printing characteristics were obtained.

(Embodiment 2) FIG. 6 is a view for explaining a second embodiment of the present invention. In the ink jet head of this embodiment, a vibration plate 1, a pressurized liquid chamber forming plate 16, a fluid resistance It has a five-layer structure of a groove forming plate 17, a common ink flow path forming plate 8, and a nozzle plate 6. The diaphragm 1 and the nozzle plate 6 were formed by nickel electroforming, and the other plates were formed by etching a stainless plate. The width of the pressurized liquid chamber 2 was about 100 μm, and the diameter of the nozzle communication hole 11 was 100 μm. The diaphragm 1 is substantially rectangular and has a length of 2 mm, a width of 4 μm, and a thickness of 30 μm.
The structure is such that the periphery of the pressure part of m is surrounded by a thin part having a thickness of 5 μm. A plate material having a thickness of 100 μm was used for the stainless steel layer.
The ink supply port 14 had a slit shape with a width of 60 μm, a length of 200 μm, and a depth of 20 μm. These members were bonded at a temperature of 210 ° C. and a pressure of 10 kgf / cm ² with a polyimide adhesive having excellent long-term reliability for the ink.
After all of the bondings a to d were performed, the multilayer piezoelectric element 9 as an actuator for driving the vibration plate 1 was joined to assemble an ink jet head, and an ejection test was performed. As a result, it was found that the injection characteristics varied between channels. As a result of the factor analysis, it was found that the processing shapes at both ends of the groove of the ink supply port 14 varied, which affected the ejection characteristics. Therefore, the pattern of the ink supply port 14 was changed so that both ends became wider as shown in FIG. As a result, the groove 12 'of the fluid resistance groove forming plate 17 is formed.
The variation in the processed shape of the portion was improved, and the variation in the injection characteristics was eliminated. Since the liquid chamber parts are all made of metal,
High rigidity, high natural frequency, and stable characteristics were obtained even under the condition of high ink ejection frequency.

(Embodiment 3) As a comparative example of Embodiment 2, as shown in FIG. 7, a lower surface of a connection plate 19 in which a nozzle communication hole 11 and a common ink flow passage communication hole 10 are formed on a stainless steel plate having a thickness of 80 μm. A DFR 18 having a thickness of 22 μm is laminated thereon, and the locations of the nozzle communication hole 11, the common ink flow passage communication hole 10, and the ink supply port 14 are opened through a photolithography process, and the same as the fluid resistance forming plate 17 of FIG. A shaped part was formed. Using these parts, an ink jet head as shown in FIG. 7 was assembled, and the ejection evaluation was performed.
Injection characteristics variation between channels occurred. The cause is
The ink supply port was crushed due to deformation of the DFR. Due to the heating conditions, the bonding of the DFR layer was the final step, so it was necessary to apply a pressure of about 5 kgf / mm ² in order to compensate for the warpage of the liquid chamber components generated up to the previous step. No condition was found in which the DFR was not deformed under such pressurizing conditions.

Example 4 As a comparative example of Example 2, only the thickness of the fluid resistance groove forming plate 17 was set to 50 μm. FIG.
In the ink jet head having the structure described above, the fluid resistance groove forming plate 17 does not need to be thick from a functional point of view. Rather, in order to increase the processing accuracy of etching, a thinner plate thickness is advantageous. As a result, the bonding was performed in the order of c, b, d, and a in FIG. 6, but the board was warped by about 300 μm after bonding at the interface c, which hindered the subsequent bonding process. The cause of the warpage is the pressurized liquid chamber forming plate 1
6 is a difference between the thermal expansion coefficient and the contraction rate due to the difference in the thickness of the fluid resistance groove forming plate 17. Since the curing temperature of the adhesive used in this example was as high as 200 ° C. or higher, the amount of warpage could be reduced by changing to a low-temperature curing type or an adhesive having a high elastic modulus after curing. However, in the present embodiment, the use of plate materials having different thicknesses resulted in a significant reduction in the range of usable adhesives. On the other hand, in Example 2, by laminating and joining materials having the same thickness and material, the selection range of the adhesive was expanded, and an adhesive advantageous in terms of ink resistance and application conditions could be used. As another measure for improving the warpage of the plate and the adhesiveness, the part was heat-treated at 300 ° C. for 1 hour before applying the adhesive, and the surface of the adherend was oxidized, and the adhesive was adhered to the adherend. Was applied more uniformly, and the adhesive strength was improved. Also, it was confirmed that the amount of warpage of the plate after bonding was also reduced. Regarding the adhesive strength, a surface treatment, such as immersing the liquid chamber component in an aqueous ferric chloride solution for several minutes, also had the effect of increasing the adhesive strength.

Example 5 As a comparative example of Example 2, a fluid resistance groove forming plate 17 was formed by laminating and joining two stainless steel plates. First, as shown in FIG.
After forming a nozzle communication hole 11 and a common ink channel communication hole 12 on a 0 μm stainless steel plate by etching, an elastic epoxy adhesive is applied on one side to a thickness of about 5 μm, and a plate thickness of 20 μm.
A μm stainless plate was bonded. Next, as shown in FIG. 5B, a DFR as a resist 21 was laminated on both surfaces of the laminated plate, and a stainless-side DFR having a thickness of 20 μm was exposed and developed in a photolithography process to form a patterning opening. Then, the laminated product was etched to form a fluid resistance groove forming plate as shown in FIG. Using this fluid resistance groove forming plate, an ink jet head as shown in FIG. 6 was assembled and an ink jetting experiment was performed.
Similar good results were obtained.

[0024]

According to the first aspect of the present invention, a first plate member having at least two openings and a groove communicating with the two openings are provided. Since the ink supply port is formed by laminating the second plate member on which is formed, a low-cost and high-precision inkjet head can be realized.

(2) Operation and effect corresponding to the second aspect of the invention According to the ink jet head of the second aspect, since the first plate member and the second plate member are high rigid members, the ink supply port is A high-rigidity ink jet head capable of maintaining a stable shape without crushing at the time of joining and capable of ejecting high-frequency ink can be realized.

(3) Action and effect corresponding to the third aspect of the invention According to the ink jet head according to the third aspect, the first plate member and the second plate member are made of the same material and have substantially the same thickness. Thus, a liquid chamber having high planarity can be formed.

(4) Operation and Effect Corresponding to the Fourth Invention According to the ink jet head according to the fourth invention, the first plate member and the second plate member are made of a metal material, and are subjected to heat treatment or the like before joining. Since the surface is oxidized, the flatness of the liquid chamber and good bonding properties can be ensured.

(5) Action and Effect Corresponding to the Invention of Claim 5 According to the ink-jet head of claim 5, at least the second plate member is processed by etching.
An ink supply port having an excellent bubble discharging property can be realized by a processing method capable of mass-producing.

(6) Action and Effect Corresponding to the Sixth Invention According to the ink jet head according to the sixth invention, since both ends of the groove formed in the second plate member are wide, workability by etching is improved. Improved processing shape quality with less variation can be realized.

(7) Action and Effect Corresponding to the Seventh Invention According to the ink jet head according to the seventh aspect, since the second plate member is a laminated material sandwiching at least the adhesive layer at the center, the adhesive layer Can be used as an etching stop layer, and the shape accuracy of the ink supply port can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a basic configuration of a piezo-on-demand type ink jet head.

FIG. 2 is a diagram illustrating a configuration of an inkjet head according to the present invention.

FIG. 3 is a diagram showing an example of a cross-sectional shape of a groove processing in a fluid resistance portion.

FIG. 4 is a diagram showing an example of a planar shape of a groove processing in a fluid resistance portion.

FIG. 5 is a view for explaining another means for making the depth of the groove 12 'of the ink supply flow path 12 more uniform.

FIG. 6 is a diagram for explaining a second embodiment of the present invention.

FIG. 7 is a diagram for explaining another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... diaphragm, 2 ... pressurized liquid chamber, 3 ... lid member, 4 ... lower plate, 5
... common ink flow path, 6 ... nozzle plate, 7 ... nozzle, 8 ... common ink flow path forming plate, 9 ... pressure generating means (piezoelectric element),
DESCRIPTION OF SYMBOLS 10 ... Common fluid ink flow path connection hole, 11 ... Nozzle communication hole, 12 ... Fluid supply flow path, 12 '... Groove, 13 ... Ink pressure chamber opening, 14 ... Ink supply port, 16 ... Pressure liquid chamber formation Plate, 17: Fluid resistance groove forming plate, 19: Connection plate, 20: Adhesive, 21: Thick plate member, 22: Thin plate member, 23: Resist.

Claims (7)

[Claims] 1. An ink jet head for ejecting ink from said nozzle by controlling the pressure in said pressurizing chamber by a pressure generating means provided in a part of the pressurizing chamber communicating with the nozzle, wherein at least the ink pressurizing chamber A first plate member having two openings, an opening and a common ink passage opening;
A second plate member having a groove that forms a fluid resistance by communicating the two openings, and the plate members are laminated and joined to form an ink supply port, and the ink supply port is formed from the common ink flow path port. An ink jet head, wherein ink is supplied to the pressurized chamber through an opening. 2. The ink jet head according to claim 1, wherein the first plate member and the second plate member are high rigid members. 3. The ink jet head according to claim 1, wherein said first plate member and said second plate member are made of the same material and have substantially the same thickness. 4. The ink jet head according to claim 1, wherein the first plate member and the second plate member are made of a metal material, and their surfaces are oxidized by heat treatment or the like before laminating and joining. 5. The ink jet head according to claim 1, wherein at least the second plate member is processed by etching. 6. The ink jet head according to claim 1, wherein both ends of the groove formed in the second plate member are wide. 7. The ink jet head according to claim 1, wherein the second plate member is a laminated material having at least an adhesive layer sandwiched in the center.