JP2001150676A - Ink-jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of easy generation of clogging by a foreign substance. SOLUTION: A nozzle 5 and a hole 22 of a filter part 21 are formed in the substantially the same round shape.

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.

[0002]

2. Description of the Related Art An ink jet head used in an ink jet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile, a copying machine, and a plotter has a nozzle for discharging ink droplets and a discharge chamber in which the nozzle communicates. (Also referred to as a pressure chamber, a pressurized liquid chamber, a liquid chamber, an ink flow path, etc.) and a pressurizing means for generating energy for pressurizing the ink in the ejection chamber, and driving the pressurizing means. Thus, the ink in the ejection chamber is pressurized to eject ink droplets from the nozzles.

In such an ink-jet head, to meet the demand for higher speed and higher image quality, it is important to improve the ejection frequency of ink droplets and increase the number of nozzles, which greatly contributes to the head performance. In order to achieve image quality, it is necessary to control the shape (circularity) and size of the ink droplets and to make the ejection direction of the droplets uniform.

One of the factors that degrade the image quality by disturbing the direction in which ink droplets are ejected from the head is adhesion of foreign matter such as dust near the nozzles. It is considered that these foreign substances are generated in the manufacturing process, mixed with the ink during the passage of the ink, enter the head, and adhere to the outside by nozzle wiping or the like. In particular, when increasing the total number of nozzles for speeding up,
In order to stably manufacture and maintain good-quality heads, the probability of occurrence of defects due to the adhesion of the above-described foreign matter must be drastically reduced.

Therefore, conventionally, a filter is provided in the flow path, for example, as disclosed in Japanese Patent Laid-Open No. 5-261910.
In Japanese Patent Application Laid-Open No. 8-1952, it is disclosed that a nozzle passage portion and a filter groove portion are formed by anisotropic etching of silicon. No. 2607308 discloses a V-shaped nozzle groove and a V-shaped nozzle groove formed by etching a silicon substrate.
It is described that a letter-shaped ink filter portion is formed.

[0006]

As described above, by making the hole diameter of the filter smaller than the nozzle diameter, foreign matter in the ink that clogs the nozzles can be trapped. The coming foreign matter has various shapes and materials, and there is a large-sized foreign matter that actually passes through the filter. In particular, there is a problem that foreign substances such as organic-based soft foreign substances and gel-like ink insoluble substances cannot be sufficiently removed only by defining the size of the filter.

In the case of forming a nozzle flow path portion and a filter groove portion by etching a silicon substrate, a nozzle forming member is limited to a silicon substrate, and an edge shooter type in which a nozzle is formed at an edge of a head. Limited to those. Further, the nozzle and filter cross-sectional shapes are all polygonal because they are formed by etching. However, organic viscoelastic materials and gel-like foreign materials tend to accumulate in the corners, so that foreign materials cannot be trapped reliably.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an ink jet head capable of reducing ink droplet ejection defects due to foreign matter and stably ensuring high image quality.

[0009]

In order to solve the above problems, an ink jet head according to the present invention is provided with a filter having a hole having substantially the same shape as a nozzle.

Here, it is preferable that the cross-sectional shapes of the nozzle and the hole of the filter portion are substantially circular. Further, it is preferable that the filter section has more holes than the number of nozzles supplied through the filter section. Further, it is preferable that the opening area of the hole of the filter portion is smaller than the opening area of the nozzle.

Further, it is preferable that the hole of the filter portion and the nozzle are formed using the same method. Further, the filter portion and the nozzle can be formed on the same member. This filter part can be formed by an electroforming method.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an exploded perspective view of an electrostatic inkjet head to which the present invention is applied, and FIG.
FIG. 3 is an explanatory top view showing the head in a transmitting state, FIG. 3 is a schematic sectional view taken along the long side of the liquid chamber of the head, and FIG. 4 is a schematic sectional view taken along the short side of the liquid chamber of the head. .

This ink jet head includes a vibration plate / liquid chamber substrate 1, an electrode substrate 3 provided below the vibration plate / liquid chamber substrate 1, and a nozzle plate 4 provided above the vibration plate / liquid chamber substrate 1. A plurality of nozzles 5, a liquid chamber (ejection chamber) 6 as an ink flow path communicating with each nozzle 5, and a common liquid chamber 8 communicating with the liquid chamber 6 via a fluid resistance part (ink supply path) 7. And so on.

The diaphragm / liquid chamber substrate 1 has a liquid chamber 6, a vibration plate 10 serving as a bottom of the liquid chamber 6, a concave portion forming a partition 11 separating the liquid chambers 6, and a concave portion forming a common liquid chamber 8. And so on.

A recess 14 is formed in the electrode substrate 3, and an electrode 15 facing the diaphragm 10 is formed on the bottom surface of the recess 14 with a predetermined gap 16 therebetween. An actuator unit that changes the internal volume of the liquid chamber 6 by displacing the diaphragm 15 is configured. An insulating layer 17 such as SiO ₂ is formed on the electrode 15 of the electrode substrate 3 to prevent the electrode 15 from being damaged by contact with the vibration plate 10. The electrode 15 extends to near the end of the electrode substrate 3 to form an electrode pad portion 15a for connecting to an external drive circuit via a connection means.

The electrode substrate 3 has a concave portion 14 formed on a glass substrate or a Si substrate having a thermal oxide film 3a formed on the surface thereof by etching with an HF aqueous solution or the like.
An electrode material having high heat resistance such as titanium nitride is formed to a desired thickness by a film forming technique such as sputtering, CVD, or vapor deposition, and then a photoresist is formed and etched, so that only the concave portion 14 is formed. The electrode 15 is formed. The electrode substrate 3 and the diaphragm / liquid chamber substrate 1 are joined by processes such as anodic joining and direct joining.

The nozzle plate 4 is composed of a metal plate such as Ni or SUS, a composite base material of glass, Si or resin, and the nozzle 5 is manufactured by a known method such as etching, nickel electroforming, and pressing. can do. A water repellent film is formed on the nozzle surface (surface in the ejection direction) of the nozzle plate 4 by a well-known method such as a plating film or a water repellent coating in order to ensure water repellency with ink.

The nozzle plate 4 also has a groove serving as an ink supply path 7 between the liquid chamber 6 and the common liquid chamber 8, and an ink tank connection port 19 for connecting to an ink tank outside the head (not shown). , This ink tank connection port 19
The ink supply pipe 20 is connected to a filter section 21 according to the present invention.

In this ink-jet head, the diaphragm is charged by applying a drive voltage between the diaphragm 10 and the electrode 15 (one is a common electrode and the other is an individual electrode), and the diaphragm is charged by electrostatic force. The diaphragm 10 is deformed to the electrode 15 side, and subsequently, the electric charge between the diaphragm 10 and the electrode 15 is discharged, whereby the diaphragm 10 is deformed to return to the liquid chamber 6.
When the internal volume (volume) / pressure changes, ink droplets are ejected from the nozzle 5. In this case, it can be driven by either a non-contact driving method in which the diaphragm 10 is not in contact with the electrode 15 or a contact driving method in which the diaphragm 10 is in contact with the electrode 15.

Here, the nozzles 5 of the nozzle plate 4 and the filter section 21 will be described with reference to FIG.
First, as shown in FIGS. 5 (a) and 5 (b) and FIGS. 6 (a) and 6 (b), each of the nozzle 4 and the hole 22 of the filter section 21 has a substantially circular planar shape and a cross-section. The shape is a horn shape, and the nozzle 4 and the hole 22 of the filter part 21 are formed in substantially the same shape.

Therefore, foreign matter that easily passes through the hole 22 of the filter section 21 also easily passes through the nozzle 4 having substantially the same shape, so that clogging of the nozzle 4 can be reduced.
Foreign matter that is difficult to pass through the first hole 22 is also difficult to pass through the nozzle 4 having substantially the same shape, but this is trapped by the filter unit 22, so that clogging at the nozzle 4 can be reduced.

By making the shape of the hole of the nozzle and that of the filter portion substantially the same as described above, it is possible to sort out the foreign matter that is easily clogged in the nozzle and the foreign matter that is easy to pass through in the filter portion. The adverse effect can be reduced, and the durability of the filter section (the period during which the filter function is maintained) can be significantly improved. As a result, ink droplet ejection defects are significantly reduced, and high image quality can be stably ensured for a long period of time.

Further, by making the openings of the nozzle and the filter section substantially circular in shape, foreign substances can be reduced from being trapped in the nozzle section. On the other hand, the opening shape of the hole of the nozzle or the filter portion can be formed into a triangular shape, a trapezoidal shape, or the like by anisotropic etching of a Si substrate or the like. This is not preferable because foreign matter easily adheres to the filter portion, causing clogging of the nozzle and a significant decrease in the performance of the filter portion.

In this case, the inner wall surface of the nozzle 4 and the filter portion 2
By making the surface properties (surface roughness, ink wettability, etc.) with the inner wall surface of the first hole 22 uniform, the above-described sorting function can be further improved.

In order to form the same shape and the same surface property as described above, basically, the same method may be used as the drilling method. Nozzle 4 shown in FIGS. 5 and 6 described above.
And the filter part 21 are manufactured by an electroforming method.
As shown in FIGS. 7 and 8, the nozzle 4 and the filter unit 21 can be manufactured by punching.

Here, a method of forming a nozzle by the electroforming method will be described with reference to FIGS. To manufacture the nozzle plate 4 by the electroforming method, also referring to FIG.
As shown in FIG. 10A, an electroformed support substrate 31 having a metal film formed by sputtering on the surface of a conductive substrate such as SUS or a glass substrate is prepared, and as shown in FIG. Resist 32 on the electroformed support substrate 31
Is applied, and as shown in FIG.
Then, the resist pattern 34 corresponding to the nozzle 5 is formed as shown in FIG.

Thereafter, for example, nickel electroforming is performed so that the nickel electroformed film 35 isotropically protrudes on the resist pattern 34 on the electroformed support substrate 31 as shown in FIG. The electroforming is stopped when a predetermined thickness is obtained. Next, FIG.
As shown in (2), by peeling off the nickel electroformed film 35, the nozzle plate 4 having the nozzle 5 made of the nickel electroformed film 35 is obtained.

Accordingly, a filter member having a hole 22 having substantially the same surface shape as the nozzle 5 is formed by forming a resist pattern corresponding to the hole 22 and performing nickel electroforming on the filter portion 21 in the same manner. can get.

Next, the opening area of the nozzle 5 and the filter section 21 and the number of holes in the filter section 21 will be described with reference to FIGS. First, the opening diameter D1 of the nozzle 5
And the opening diameter D2 of the hole 22 of the filter section 21 is D1> D2
Make a relationship. Accordingly, the size of the foreign matter passing through the hole 22 of the filter unit 21 is surely smaller than the size of the foreign matter passing through the nozzle 5, and it is possible to further reduce the occurrence of defects due to clogging of the foreign matter in the nozzle 5.

The number of holes 22 in the filter section 21 is determined by the number of nozzles to which ink is supplied through the filter section 21. In this embodiment, the filter section 21 is provided in the ink supply pipe 20. The number of filters is set to a number sufficiently larger than the number (the number of channels), preferably 3 to 10 times or more the number of nozzles.

That is, in particular, the hole 22 of the filter section 21
Is smaller than the opening area of the nozzle 5, the amount of ink supplied to the liquid chamber 6 is limited.
Insufficient ink supply may occur. Therefore, by making the number of holes 22 of the filter unit 21 sufficiently larger than the number of nozzles supplied through the filter unit 21,
Insufficient ink supply can be prevented, so that ejection failure does not occur.

Next, another embodiment of the present invention will be described with reference to FIG.
Description will be made with reference also to 1 and later. 11 is an external perspective view showing an example of an ink jet head according to the present invention, FIG. 12 is a cross-sectional view of a main part of the head in a liquid chamber longitudinal direction, and FIG. 13 is a cross-sectional view of a main part of the same head in a nozzle arrangement direction.

This ink jet head includes a drive unit 51, a liquid chamber unit 52, a head case 53, and a nozzle cover 54. The drive unit 51
A plurality of piezoelectric elements 62 are joined and arranged on an insulating substrate 61 made of ceramic, glass epoxy resin, or the like, and the periphery of these piezoelectric elements 62 is surrounded by a liquid chamber unit 52.
The frame 63 which supports the frame 63 is joined.

The liquid chamber unit 52 is formed by laminating and thermally fusing a vibration plate 64, a flow path forming member 65 made of a photosensitive resin member having a two-layer structure, and the like, and a nozzle 67 and a nozzle connection. A passage 68, a pressurized liquid chamber 69 to which the nozzle 67 communicates, a common liquid chamber 71 for supplying ink to each pressurized liquid chamber 69 via a fluid resistance part 70, and the like are formed.

Then, the drive unit 51 and the liquid chamber unit 52 are joined together, and this is held on a head case (spacer member) 53, and a nozzle cover 54 is mounted from above to form an ink jet head.

Here, the substrate 6 is connected via the head case 53.
1 is connected to an ink supply pipe 72 for supplying ink from outside, and is connected to the common liquid chamber 71 through ink supply holes formed in the substrate 61, the frame member 63 and the vibration plate 64 as shown in FIG. The ink is supplied to the supply path 73 provided on the side.

Therefore, a filter section 74 is interposed between the supply path 73 and the common liquid chamber 71. The filter portion 74 is formed on the nozzle plate 66. When the nozzle 66 is formed by an electroforming method or the like, a large number of holes 75 having the same shape as the nozzle 66 are formed on the same plane as the nozzle 66 at the same time. Thereby, the number of steps can be reduced. The shape, the number, and the like of the holes 75 of the filter unit 74 are the same as those in the above-described embodiment.

In this case, since the filter section 74 and the nozzle 66 are formed on the same plane, the liquid chamber forming member 65 is provided in order to three-dimensionally arrange the flow path from the supply path 73 to the common liquid chamber 71. To form a partition wall 78 that separates the supply path 73 from the common liquid chamber 71, and the common liquid chamber 71 is formed in the nozzle plate 66.
Is formed, and members 80 and 81 form a flow path 82 from the filter section 74 to the common liquid chamber 71 through the opening 79.

In the above embodiment, the present invention is applied to an electrostatic ink jet head and a piezo ink jet head using a laminated piezoelectric element. However, other electromechanical transducers such as piezoelectric elements may be used. The present invention can be similarly applied to an inkjet head to be used, an inkjet head that generates bubbles by film boiling using a heating resistor, and the like. In addition to the filter according to the present invention, a metal mesh type filter generally made of SUS or the like, which is conventionally generally used, may be additionally provided.

[0040]

As described above, according to the ink jet head of the present invention, since the filter portion having the hole having substantially the same shape as the nozzle is provided, the foreign matter which causes the nozzle to be clogged can be selected. It is possible to remove ink droplets, thereby reducing ink droplet ejection failure and stably ensuring high image quality.

Here, the cross-sectional shape of the holes of the nozzle and the filter portion is made substantially circular, so that foreign matters are not trapped in the nozzle portion, ink drop ejection failure is greatly reduced, and high image quality is obtained. It can be secured stably.

Further, by providing the filter section with a larger number of holes than the number of nozzles corresponding to the ink flow path supplied through the filter section, it is possible to prevent the ink supply from being insufficient. Further, by making the opening area of the filter section hole smaller than the nozzle opening area, foreign matter that can pass through the filter section can pass through the nozzle, and ink drop ejection failure can be greatly reduced, and high Image quality can be stably secured.

Further, by forming the hole of the filter portion and the nozzle using the same method, not only the shape of the nozzle and the filter portion but also the surface properties (surface roughness, wettability, etc.) of the inner wall are made the same. This makes it possible to more accurately select the type of foreign matter to be trapped in the filter unit, greatly reduce ink droplet ejection failure, and stably ensure high image quality.

Further, by forming the filter portion and the nozzle on the same member, the nozzle and the filter portion can be formed at the same time, the number of parts can be reduced, and the ink droplet ejection failure can be greatly reduced at low cost. Image quality can be stably ensured. Further, by forming the filter portion by the electroforming method, the process time can be made constant regardless of the number of nozzles and the number of holes in the filter portion, and the process time required for producing a multi-nozzle head required for high speed operation can be reduced. Costs can be realized, defective ejection of ink droplets can be significantly reduced, and high image quality can be stably ensured.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an electrostatic inkjet head to which the present invention is applied.

FIG. 2 is an explanatory top view showing the transmission state of the head.

FIG. 3 is a schematic cross-sectional explanatory view along a long side direction of a liquid chamber of the head.

FIG. 4 is a schematic cross-sectional explanatory view of the head along a liquid chamber short side direction.

FIG. 5 is an explanatory top view of a nozzle plate and a filter member.

FIG. 6 is an explanatory sectional view of a nozzle plate and a filter member.

FIG. 7 is an explanatory top view of another example of the nozzle plate and the filter member.

FIG. 8 is an explanatory sectional view of another example of the nozzle plate and the filter member.

FIG. 9 is a flowchart illustrating a procedure for forming a nozzle plate and a filter member by an electroforming method.

FIG. 10 is an explanatory view illustrating a manufacturing process of a nozzle plate by the same method.

FIG. 11 is an external perspective perspective view of a piezo-type inkjet head to which the present invention is applied.

FIG. 12 is an explanatory cross-sectional view of a main part of the head in the liquid chamber longitudinal direction.

FIG. 13 is an explanatory cross-sectional view of a main part of the head in the nozzle arrangement direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... diaphragm / liquid chamber substrate, 2 ... electrode substrate, 4 ... nozzle plate, 5 ... nozzle, 6 ... discharge chamber, 7 ... ink supply path, 8
... common liquid chamber, 10 ... diaphragm, 15 ... electrode, 16 ... gap, 19 ... ink supply port, 20 ... ink supply pipe, 2
DESCRIPTION OF SYMBOLS 1 ... Filter part, 51 ... Drive unit, 52 ... Liquid chamber unit, 64 ... Vibration plate, 65 ... Liquid chamber forming member, 66 ... Slip plate, 67 ... Nozzle, 69 ... Pressurized liquid chamber, 71 ... Common liquid chamber , 74 ... Filter unit.

Claims (7)

[Claims] 1. An ink jet head having a nozzle for discharging ink droplets, an ink flow path communicating with the nozzle, and a pressurizing means for pressurizing ink in the ink flow path, has substantially the same shape as the nozzle. An ink jet head comprising a filter portion having a hole having a shape. 2. An ink jet head according to claim 1, wherein said nozzle and said filter have a substantially circular cross section. 3. The ink-jet head according to claim 1, wherein the filter has a larger number of holes than the number of nozzles supplied through the filter. 4. The ink-jet head according to claim 1, wherein an opening area of a hole of the filter portion is smaller than an opening area of a nozzle. 5. The ink jet head according to claim 1, wherein the holes and the nozzles of the filter unit are formed using the same method. 6. The ink jet head according to claim 1, wherein the filter and the nozzle are formed on the same member. 7. The ink jet head according to claim 1, wherein said filter portion is formed by an electroforming method.