Image forming apparatus, liquid-jet head, and method for manufacturing the liquid-jet head

A liquid-jet head includes a thin film member having a thin part and a thick part, and at least a part of the thin film member is formed of an electroformed film. In the liquid-jet head, the thin film member includes a metallic film forming the thin part, a first electroformed film formed on the metallic film, the first electroformed film forming the thick part, and a second electroformed film covering a connecting part between the metallic film and the first electroformed film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The disclosures herein relate to a liquid-jet head, an image forming apparatus having the liquid-jet head, and a method for manufacturing the liquid-jet head.

2. Description of the Related Art

An inkjet recording apparatus is generally known as an example of a liquid-jet recording type image forming apparatus, such as a printer, a facsimile machine, or a plotter, or a multifunctional peripheral having combination of these functions. The inkjet recording apparatus includes a recording head formed of a liquid-jet head (liquid-drop jet head) that ejects liquid drops.

There is disclosed, as an example of the liquid-jet head, a piezoelectric head including a deformable diaphragm member forming at least one wall surface of a liquid chamber in communication with nozzles ejecting liquid drops, and a multilayered piezoelectric element configured to pressurize a liquid inside the chamber by the deforming diaphragm member.

Japanese Patent No. 3374899 (hereinafter referred to as “Patent Document 1”) discloses an example of such a diaphragm member utilized in the piezoelectric head. In this example, the diaphragm member includes a thick part (i.e., an island-shaped projection part), and a thin part formed in the periphery of the island-shaped projection part. In the diaphragm member, photosensitive resin is formed such that the photosensitive resin covers an outer surface of the island-shaped projection part, and further reaches a part of the thin part, thereby reducing stress concentration applied to a circumference of the island-shaped projection part with concentration due to expansion and contraction of the piezoelectric element.

RELATED ART DOCUMENTS

Patent Document

As described above, when a diaphragm part of the diaphragm member transmits displacement of the piezoelectric element to an individual liquid chamber, the thin part formed in the circumference of the island-shaped projection part (i.e., the thick part) may need to be repeatedly deformed at the same position. In this configuration, a pin angle formed of a resist trace disposed at a boundary between the thick part and the thin part. Hence, the stress is concentrated on the pin angle when the thin part of the diaphragm member is deformably contracted by deforming the piezoelectric element. This eventually cracks the boundary between the thin part and the thick part to result in leakage of the liquid on the piezoelectric element side.

Thus, a step of coating the outer surface of the diaphragm member with the photosensitive resin in order to reduce the stress applied to the thin part as disclosed in Patent Document 1, which may increase manufacturing cost.

Further, when the thick part is formed by electroforming, the boundary between the thick part and thin part may be undercured upon exposure of light due to an overhang part of the thick part blocking off the exposure light reaching the photosensitive resin.

Accordingly, it is a general object of at least one embodiment of the present invention to provide a liquid-jet head and an image forming apparatus having the liquid-jet head, and a method for manufacturing the liquid-jet head capable of reducing stress concentration applied to a boundary part between a thick part and a thin part of a thin film member at low cost, which substantially eliminate one or more problems caused by the limitations and disadvantages of the related art.

SUMMARY OF THE INVENTION

In one embodiment, there is provided a liquid-jet head that includes a thin film member having a thin part and a thick part, and at least a part of the thin film member is formed of an electroformed film. In the liquid-jet head the thin film member includes a metallic film forming the thin part, a first electroformed film formed on the metallic film, the first electroformed film forming the thick part, and a second electroformed film covering a connecting part between the metallic film and the first electroformed film.

Additional objects and advantages of the embodiments will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments are described below, with reference to the accompanying drawings. First, a liquid-jet head according to a first embodiment is described with reference toFIGS. 1 to 3. Note thatFIG. 1is an external perspective diagram illustrating a liquid-jet head according to a first embodiment,FIG. 2is a cross-sectional diagram illustrating the liquid-jet head in a direction orthogonal to a nozzle array direction (a liquid chamber longitudinal direction) taken along an A-A line inFIG. 1, andFIG. 3is a cross-sectional diagram illustrating the liquid-jet head in a direction orthogonal to a nozzle array direction (a liquid chamber short direction) taken along a B-B line inFIG. 1.

The liquid-jet head according to the first embodiment includes a nozzle plate1, a channel plate (a liquid chamber substrate)2, and a diaphragm member3serving as a thin-film member that are bonded in a layered manner. The liquid-jet head according to the first embodiment further includes an actuator11configured to displace the diaphragm member3, and a frame member20serving as a common channel member constituting a frame of the liquid-jet head.

In the liquid-jet head according to the first embodiment, the nozzle plate1, the channel plate2, and the diaphragm member3form, as individual channels, individual liquid chambers (may also be called “pressurizing liquid chambers”, “pressure chambers”, “pressurizing chambers”, and “channels”)6in communication with respective nozzles4configured to eject liquid drops, a liquid supply channel7configured to supply a liquid to each of the individual liquid chambers6and serving as a fluid resistance part, and a liquid introducing part8communicating with the liquid supply channel7.

Accordingly, the liquid-jet head according to the first embodiment supplies a liquid to the plural individual chambers6from a common liquid chamber10serving as a common channel of the frame member20through a filter part9formed in the diaphragm member3, the liquid introducing part8, and the liquid supply channel7.

Note that the nozzle plate1is formed of a metallic plate made of nickel (Ni), which is produced by electroforming. The nozzle plate1is not limited to that formed of the metallic plate made of nickel (Ni), but may be formed of other types of the metallic plate, a resin member, a layered member of a resin layer and a metallic layer, etc. The nozzle plate1may include the nozzles4having a diameter of 10 to 35 μm corresponding to the respective individual liquid chambers6, and may be bonded to the channel plate2with an adhesive. Further, a water repellent layer is formed on a liquid drop ejecting surface (i.e., a surface in an ejecting direction: an ejecting surface, or a surface opposite to the liquid chamber6side) of the nozzle plate1.

The channel plate2includes grooves forming the individual liquid chambers6, the liquid supply channel7, and the liquid introducing part8, which are formed by etching a monocrystalline silicon substrate. Note that the channel plate2may be formed by etching a metallic plate such as a SUS substrate with an acid etching liquid, or may be formed by machining such as press working.

The diaphragm member3includes a deformable oscillating region30corresponding to the individual liquid chamber6. The deformable oscillating region30serves as a wall surface member forming a wall surface of the individual liquid chamber6of the channel plate2.

The piezoelectric actuator11is disposed on a side opposite to the individual liquid chambers6of the diaphragm member3, and includes an electromechanical transducer element serving as a driving part (i.e., an actuator part, and a pressure generating part) configured to deform the oscillating region30of the diaphragm member3.

The piezoelectric actuator11includes plural layered piezoelectric members12bonded on a base members13with an adhesive, and desired numbers of column-shaped piezoelectric devices (i.e., piezoelectric columns)12A and12B, in which grooves are formed by half-cut dicing, are formed in a pectinate configuration at predetermined intervals corresponding to one of the layered piezoelectric members12.

The piezoelectric columns12A and12B of the piezoelectric member12are formed as the same elements. However, the piezoelectric columns12A and12B are differentiated as the piezoelectric column12A serving as a driven pressure column (or a driven column) configured to be driven by being supplied with a driving waveform, and the piezoelectric column12B serving as a non-driven pressure column (or a non-driven column utilized as a supporting column configured not to be supplied with a driving waveform to be driven.

The driven column12A is bonded to an island-shaped projection part3aformed in the oscillating region30of the diaphragm member3. Further, the non-driven column (i.e., the piezoelectric column120) is bonded to a projection part3bof the diaphragm member3.

The piezoelectric member12includes alternate layers of piezoelectric layers and internal electrodes, and external electrodes are formed by drawing the internal electrodes to end faces to which an FPC15for supplying driving signals to the external electrodes of the piezoelectric member12serving as a flexible printed wiring board is connected.

The frame member20may, for example, be made of epoxy resin or thermoplastic resin such as polyphenylene sulfide, which is produced by injection molding. The frame member20includes the common liquid chamber10to which a liquid is supplied from not-illustrated head tanks or liquid cartridges.

In the inkjet head having the above configuration, the potential applied to the driven column12A is lowered from a reference potential to cause the driven column12A to contract, which lowers an oscillating region30of the diaphragm member3and expands the volume of the individual liquid chamber6. As a result, the liquid flows into the individual liquid chamber6to raise the potential applied to the driven column12A, which causes the driven column12A to extend in a stacked direction. This deforms the oscillating region30of the diaphragm member3toward the nozzle4direction to cause the volume of the individual liquid chamber6to contract so that the liquid inside the individual liquid chamber6is pressurized to thereby eject (jet) liquid drops from the nozzles4.

When the voltage applied to the driven column12A returns to the reference potential to restore the oscillating region30of the diaphragm3to an initial position, the individual liquid chamber6expands to generate a negative pressure. As a result, the liquid is supplied into the individual liquid chamber6via the liquid supply channel7from the common liquid chamber10. When the oscillations of meniscus in the nozzles4are damped and stabilized, the liquid-jet head is moved for a next operation.

Note that a method for driving the liquid-jet head is not limited to the above example, but the liquid-jet head may be driven by applying the driving waveform to the piezoelectric column12A in different ways so as to cause the piezoelectric column12A to contract or expand.

Next, details of the diaphragm member3serving as in the ink-jet head is described with reference toFIGS. 4 and 5.FIG. 4is a perspective diagram illustrating a diaphragm member serving as a thin member in the liquid-jet head, andFIG. 5is a cross-sectional diagram of a main part of the diaphragm member in the liquid-jet head according to the first embodiment.

The oscillating region30of the diaphragm member3includes a thin part (i.e., a diaphragm part)31, an island-shaped projection part3aformed by bonding the driven column12A to the thin part31. Thus, the island-shaped projection part3aof the oscillating part30serves as a thick part32. Further, a thick part32including a projection part3bbonded to a driven column12B is formed in the periphery of the oscillating region30of the diaphragm member3.

In this case, a first layer3A forming the thin part31is formed of a metallic film40such as an electroformed film as illustrated inFIG. 5. Note that the metallic film40may be formed of other metallic films other than the electroformed film.

Further, a second layer3B forming the thick part32together with the first layer3A is formed of a first electroformed film41made, for example, of nickel Ni.

A second electroformed film42is formed on surfaces of the metallic film40and the first electroformed film41such that the second electroformed film42is applied to a connecting part between the metallic film40forming the first layer3A and the first electroformed film41forming the second layer3B.

With this configuration, the second electroformed film42may be able to serve a function to disperse the stress applied to the boundary between the metallic film40and the first electroformed film41. That is, the second electroformed film42may be able to serve a function to disperse the stress applied to the boundary between the thin part31and the thick part32, thereby relaxing the concentrated stress applied to the boundary.

Note that this aspect is further described with reference toFIGS. 6 and 7Ato70.FIG. 6is a cross-sectional diagram of a main part of a diaphragm member according to a comparative example, andFIGS. 7A to 7Care diagrams illustrating a deformation operation of a diaphragm member region with driving of a piezoelectric element.

The comparative example illustrated inFIG. 6includes a configuration not having the second electroformed film42of the first embodiment. In the comparative example, a first layer3A is formed of an electroformed film, and a second layer3B formed of the same material of a first electroformed film is layered on the first layer3A. In the configuration of the comparative example, a pin angle (i.e., 90 degrees corner)34is formed at the boundary between the thin part31and the thick part32.

Meanwhile, as described earlier, the driven column12A is contracted and then expanded for driving the liquid-jet head; that is, the driven column12A is deformed from an initial state illustrated inFIG. 7Ato a contracted state illustrated inFIG. 7B, and then expanded in a state illustrated inFIG. 7C. At this moment, the oscillating region30is folded at the boundary between the thin part31and the thick part32(i.e., the projection parts3aand3b).

Accordingly, if the pin angle34is formed at the boundary between the thin part31and the thick part32as illustrated in the configuration of the comparative example, the stress is concentrated on the pin angle34by repeated displacement of the oscillating region30, thereby causing the damage to the diaphragm member region due to cracking35in the boundary as illustrated inFIG. 6.

By contrast, in the liquid-jet head according to the first embodiment, the boundary between the thin part31and the thick part32form an R-shaped angle (an R-shaped corner), thereby preventing the boundary between the thin part31and the thick part32being damaged due to cracking.

In addition, in the liquid-jet head according to the first embodiment, since the second layer3B forming the island-shaped projection part3ais formed of the first electroformed film41, a so-called “overhang shape” (i.e., the overhang part41a) is formed as illustrated inFIG. 5.

Thus, even if the boundary (i.e., the connecting part) between the thin part31and the thick part32is coated with the aforementioned photosensitive resin, the exposure light underreaches the connecting part (the boundary part), thereby allowing the connecting part to remain uncured. However, when the second layer3B forming the island-shaped projection part3ais formed of the first electroformed film41, the connecting part may be securely coated with the photosensitive resin.

Next, a method for manufacturing the liquid-jet head according to the first embodiment is described with reference toFIGS. 8A to 8D.FIGS. 8A to 8Dare cross-sectional diagrams illustrating the method for manufacturing the liquid-jet head according to the first embodiment.

As illustrated inFIG. 8A, an electroformed film40A serving as the metallic film40is formed on a not-illustrated electroformed support substrate by electroforming, a resist pattern501having an opening corresponding to a region in which projection parts3aand3bare formed is formed on the electroformed film40A, and electroforming is then carried out, thereby forming a first electroformed film41.

Subsequently, the resist pattern501is removed as illustrated inFIG. 8G.

Then, a second electroformed film is formed over the first electroformed film41and the electroformed film40A as illustrated inFIG. 8Dby electroforming as illustrated inFIG. 8C.

At this moment, two surfaces (vertical and horizontal surfaces) of a pin angle (i.e., a pin corner) formed at a boundary between the electroformed film40A and the first electroformed film41is encircled by an electroformed material (e.g., Ni). Accordingly, a current is further concentrated to electroform Ni, thereby causing Ni to be concentrated in the pin angle part. As a result, the pin angle is formed in an “R shape”.

As a result, the above-described diaphragm member in the first embodiment may be obtained.

Next, a liquid-jet head according to a second embodiment is described with reference toFIG. 9.FIG. 9is a cross-sectional diagram illustrating a main part of a diaphragm member in a liquid-jet head according to a second embodiment.

In the liquid-jet head according to the second embodiment, a diaphragm member3is formed of a third electroformed film43forming the thick part32(e.g., the projection parts3aand3b), and a fourth electroformed film44forming a thin part31and covering a surface of the third electroformed film43.

In this configuration, the pin angle not formed at the boundary between the thick part32and the thin part31, but an “R shape” is formed at the boundary between the thick part32and the thin part31instead, thereby reducing the stress concentration.

Next, a method for manufacturing the liquid-jet head according to the second embodiment is described with reference toFIGS. 10A to 10D.FIGS. 10A to 10Dare cross-sectional diagrams illustrating a method for manufacturing the liquid-jet head according to the second embodiment.

As illustrated inFIG. 10A, a resist pattern501having an opening corresponding to a region in which projection parts3aand3bare formed is formed on a not-illustrated electroformed support substrate, and electroforming is then carried out, thereby forming a third electroformed film43.

Subsequently, the resist pattern501is removed as illustrated inFIG. 10B.

Then, a fourth electroformed film44serving as a thin part31and covering a surface of the third electroformed film43is formed as illustrated inFIG. 8Dby electroforming as illustrated inFIG. 10C.

As a result, the above-described diaphragm member in the second embodiment may be obtained.

Next, a Liquid-jet head and a method for manufacturing the liquid-jet head according to a third embodiment described with reference toFIGS. 11A to 11D.FIGS. 11A to 11Dare cross-sectional diagrams illustrating the liquid-jet head and the method for manufacturing the liquid-jet head according to the third embodiment.

As illustrated inFIG. 11A, an electroformed film40A is formed on a not-illustrated electroformed support substrate by electroforming, a resist pattern501having an opening corresponding to a region in which projection parts3aand3bare formed is formed on the electroformed film40A, and electroforming is then carried out, thereby forming a first electroformed film41.

Next, the resist pattern501is removed as illustrated inFIG. 11B.

Then, as illustrated inFIG. 11C, a resist pattern503is formed in a region on the electroformed film40A where the second electroformed film42is not formed, the second electroformed film42is formed by electroforming, and the resist pattern503is then removed as illustrated inFIG. 11D.

Thus, in the liquid-jet head according to the second embodiment, the second electroformed film42is not formed in a region of a surface of the electroformed film40A other than a region necessary for applying the photosensitive resin to the connecting part between the thin part31and the thick part32.

Since the thickness of the thin part31of the diaphragm member3largely affects the amount of displacement of the oscillating region30, it is preferable to minimize the thickness of the thin part31and uniformly form the thickness of the thin part31. In the liquid-jet head according to the third embodiment, since the diaphragm member is formed without having the second electroformed film42formed in the unnecessary region, and the thickness of the thin part31is formed with the thickness accuracy of the electroformed film40A, the thickness of the thin part31may be uniformly formed.

Next, a liquid-jet head according to a fourth embodiment is described with reference toFIG. 12.FIG. 12is a cross-sectional diagram illustrating a filter part in the liquid-jet head according to the fourth embodiment.

The liquid-jet head according to the fourth embodiment is provided with a filter member for eliminating extraneous particles. In the liquid-jet head according to the first embodiment, a filter part9having numerous small-sized pores is formed in the diaphragm member3between the common liquid chamber10and the liquid introducing part8as described above.

The filter part9serves as a part of the diaphragm member3. Accordingly, the filter part9includes numerous filter pores61that are formed in the metallic film40serving as the thin part31, a first electroformed film41serving as a projection par connected to a frame member20and forming the thick part32that is layered on the metallic film40, and a second electroformed film42covering the surfaces of the first electroformed film41and the metallic film40, in a manner similar to that of the first embodiment.

Accordingly, a second electroformed film42covers a connecting part between the metallic film40serving as the thin part31forming a filter region62and the first electroformed film41forming the thick part32to obtain the filter part (i.e., the filter member)9having the reduced stress concentration.

Note that in the liquid-jet head according to the fourth embodiment, the filter member is formed of a part of the diaphragm member; however, the filter member may be materials other than the diaphragm member.

Next, a method for the liquid-jet head according to the fourth embodiment is described with reference toFIGS. 13A to 13E.FIGS. 13A to 13Eare cross-sectional diagrams illustrating the method for manufacturing the liquid-jet head according to the fourth embodiment.

As illustrated inFIG. 13A, a resist pattern503is formed on parts of a not-illustrated electroformed film40A corresponding to the filter pores, and then electroforming is carried cut, thereby forming an electroformed film40A having the filter pores61as illustrated inFIG. 13B.

Then, as illustrated inFIG. 10B, a resist pattern501having an opening corresponding to a thick part to be formed on the electroformed film40A is formed, and electroforming is then carried out, thereby forming a first electroformed film41serving as the thick part (i.e., the projection part).

Subsequently, the resist pattern501formed on the electroformed film40A is removed as illustrated inFIG. 13C.

Thereafter, a resist pattern504is formed again in a filter region on the electroformed film40A (i.e., a region where the filter pores61are formed), and then electroforming is carried out as illustrated inFIG. 13D.

As a result, as illustrated inFIG. 13E, a second electroformed film42is formed such that the second electroformed film42covers an entire region including the electroformed film40A and the first electroformed film41, and the resist pattern504is then removed.

The filter member in the liquid-jet head according to the fourth embodiment is thus obtained.

Next, a liquid-jet head according to a fifth embodiment is described with reference toFIG. 14.FIG. 14is a cross-sectional diagram illustrating a filter part in the liquid-jet head according to the fifth embodiment.

Since the filter part9is a part of the diaphragm member3, the filter part9is formed of a third electroformed film43forming the thick part32(e.g., the projection part connected to the frame member20), and a fourth electroformed film44serving as the thin part31that is configured to cover the surface of the third electroformed film43and have numerous filter pores61, similar to the second embodiment.

Thus, a connecting part between the fourth electroformed44serving as the thin part and forming the filter region62and the third electroformed film forming the thick part32forms an R shape, thereby obtaining the filter part (i.e., the filter member)9having the reduced stress concentration.

Note that in the liquid-jet head according to the fifth embodiment, the filter member is formed of a part of the diaphragm member; however, the filter member may be materials other than the diaphragm member.

Next, a method for the liquid-jet head according to the fifth embodiment is described with reference toFIGS. 15A to 15D.FIGS. 15A to 15Dare cross-sectional diagrams illustrating the method for manufacturing the liquid-jet head according to the fifth embodiment.

In this embodiment, as illustrated inFIG. 15A, a resist pattern506having an opening corresponding to a region in which projection parts are formed is formed on a not-illustrated electroformed support substrate, and electroforming is then carried out, thereby forming a third electroformed film43.

Subsequently, the resist pattern506is removed as illustrated inFIG. 15B.

Thereafter, as illustrated inFIG. 15C, a resist pattern507is formed on a not-illustrated electroformed support substrate corresponding to a region in which filter pores61are formed, and electroforming is then carried out as illustrated inFIG. 15C.

As a result, the fourth electroformed film94having the filter pores61is formed, and the resist pattern507is then remove as illustrated inFIG. 15D.

The filter member in the liquid-jet head according to the fifth embodiment is thus obtained.

Next, a liquid-jet head and a method for manufacturing the liquid-jet head according to a sixth embodiment is described with reference toFIGS. 16A to 16D.FIGS. 16A to 16Dare cross-sectional diagrams illustrating the liquid-jet head and the method for manufacturing the liquid-jet head according to the sixth embodiment.

In the liquid-jet head according to the sixth embodiment, a material having a relatively high Young's modulus such as nickel (Ni) is used for the thick part, and a material having a relatively low Young's modulus such as copper (Cu) is used for the thin part in the second embodiment. Note that the above materials may be utilized the embodiments other than the second embodiment.

Thus, utilizing different materials for the thick part and the thin part may provide effects of increasing rigidity of a non-moving part owing to the use of the material having a high Young's modulus, and facilitating displacement of a moving part owing to the use of the material having a low Young's modulus. Accordingly, the thin film member having a higher displacement effect may be obtained.

In the method for manufacturing the liquid-jet head according to the sixth embodiment, a resist pattern501having an opening is formed in a region in which the thick part including the projection parts are formed on a not-illustrated electroformed support substrate, and electroforming is carried out with a first material (e.g., nickel), thereby forming a third electroformed film43A as illustrated inFIG. 16A.

Subsequently, the resist pattern501is removed as illustrated inFIG. 16B.

Then, a fourth electroformed film44A serving as a thin part and covering a surface of the third electroformed film43A is formed as illustrated inFIG. 10Dby electroforming with a second material (e.g., copper Cu) as illustrated inFIG. 16C.

Next, a liquid-jet head according to an eighth embodiment is described with reference toFIG. 17.FIG. 17is a cross-sectional diagram illustrating an oscillating region of a liquid-jet head according to a seventh embodiment.

In the liquid-jet head according to the eighth embodiment, a third electroformed film43A and a fourth electroformed film44B are formed such that the third electroformed film43A has a mean particle size greater than that of the fourth electroformed film44B in the second embodiment. Mote that the configuration in which the third electroformed film has a mean particle size greater than that of the fourth electroformed film may be utilized the embodiments other than the second embodiment.

For example, initially, low electric current density is set to a part of the diaphragm member3allowing to in have a greater mean particle size other than the thin part. Accordingly, a deposition rate atoms may be lower than a crystal growth rate, and as a result, the part having a greater mean particle size (i.e., the third electroformed film43A) is formed.

Subsequently, high electric current density is set to the thin part of the diaphragm member3allowing to have a less mean particle size. Accordingly, a deposition rate atoms may be higher than a crystal growth rate, and as a result, the part having a reduced mean particle size (i.e., the fourth electroformed film44B) is formed.

When the fourth electroformed film44B having a reduced mean particle size is formed, an anchor effect is exhibited on the third electroformed film43A having a greater mean particle size, and the fourth electroformed film44B serving as the thin part includes a reduced number of nests or pinholes, and hence, the fourth electroformed film44B having a plane with a reduced number of projections or recesses may be obtained.

Next, an example of an image forming apparatus having the liquid-jet head according to an embodiment is described with reference toFIGS. 18 and 19. Note thatFIG. 18is a side diagram illustrating an example of a mechanical part of an image forming apparatus having the liquid-jet head according to the embodiments, andFIG. 19is a plan diagram illustrating a main part of the mechanical part.

The image forming apparatus is a serial-type image forming apparatus. The serial-type image forming apparatus includes a carriage233that is slidably supported in main-scanning directions by a driving guide rod231and a driven guide rod232serving as guide members bridging between left-side and right-side plates221A and221B, and that is moved while scanning via a timing belt in arrow directions (carriage main-scanning directions) by a not-illustrated main-scanning motor.

The carriage233includes a recording head234integrally having liquid-jet heads having nozzles respectively ejecting ink drops of yellow (Y), cyan (0), magenta (M), and black (K), and ink tanks containing ink to be supplied to the respective liquid-jet heads. In the recording head234integrally having the liquid-jet heads and the respective ink tanks, a nozzle array formed of the nozzles held by the recording head234is disposed in a sub-scanning directions orthogonal to the main-scanning direction, and ink ejecting directions of the nozzles are downward.

The recording head234includes first and second recording heads234aand234b. Each of the recording heads234aand234bhas two nozzle arrays. One of the nozzle arrays of the first recording head234ais configured to eject black (K) liquid drops, and the other nozzle array of the first recording head234ais configured to eject cyan (C) liquid drops. One of the nozzle arrays of the second recording head234bis configured to eject magenta (M) liquid drops, and the other nozzle array of the second recording head234bis configured to eject yellow (Y) liquid drops. Note that in this example, the recording head234has a two-head configuration for ejecting four color liquid drops; however, the recording head may have a one-head configuration having four nozzle arrays for ejecting four color liquid drops per head.

The ink tank235(i.e., ink tanks235aand235b) of the recording head234is supplied with respective colors of ink from respective colors of ink cartridges210via respective colors of supply tubes236.

The serial-type image forming apparatus further includes a semicircular (sheet-feeding) roll243and a separation pad244made of a material having a high friction coefficient and directed to face the sheet-feeding roller243. The sheet-feeding roll243and the separation pad244are used as a sheet-feeding part for feeding sheets242accumulated on a sheet-accumulating part (platen)241of a sheet-feeding tray202. The sheet-feeding part composed of the sheet-feeding roller243and the separation pad244is configured to feed one sheet242at a time from the sheet-accumulating part241, and the separation pad244is biased toward the sheet-feeding roller243side.

The serial-type image forming apparatus further includes a guide member245for guiding the sheet242, a counter roller246, a transfer guide member247, an edge-pressing roll249, and a presser member248in order to transfer the sheet242fed from the sheet-feeding part to a lower side of the recording head234. The serial-type image forming apparatus also includes a transfer belt251to electrostatically attract the sheet242to transfer the sheet242to a position facing the recording head234.

The transfer belt251is formed of an endless belt that is looped over a transfer roller252and a tension roller253so as to rotationally travel in a belt transferring direction (i.e., a sub-scanning direction). Further, the serial-type image forming apparatus further includes a charging roller256serving as a charging part configured to electrically charge a surface of the transfer belt251. The charging roller256is disposed such that the charging roller256is brought into contact with a surface layer of the transfer belt251to be rotationally driven by the rotation of the transfer belt251. The transfer belt251circumferentially travels in the belt transferring direction driven by the transfer roller252that is rotationally driven by a not-illustrated sub-scanning motor via the timing belt.

The serial-type image forming apparatus further includes a sheet-discharging part. The sheet-discharging part includes a separation claw261for separating the sheet242from the transfer belt251, a sheet-discharge roller262, a sheet-discharge spur263, and a sheet-discharge tray203disposed at a lower side of the sheet-discharge roller262.

The serial-type image forming apparatus further includes a duplex-printing unit271detachably attached at the back of the main body of the serial-type image forming apparatus. The duplex-printing unit271captures the sheet242rotationally transferred in a reverse direction of the transfer belt251, reverses the sheet242, and then feeds the reversed sheet42between the counter roller246and the transfer belt251. The serial-type image forming apparatus further includes a manual bypass tray272on top of the duplex-printing unit271

The serial-type image forming apparatus further includes a maintenance-restoration mechanism281serving as a head maintenance-restoration device including a restoration unit for maintaining and restoring the nozzle states of the recording head234in a non-printing region at one side of the carriage233in the carriage main-scanning direction. The maintenance-restoration mechanism281includes cap members282ato282b(hereinafter called “caps282ato282b” or simply called a “cap282” as a generic name for the cap members282ato282b) for capping the respective nozzle faces of the liquid-jet recording head234, a wiper blade283serving as a wiper blade member for wiping the nozzle faces and a discharged non-printing ink receiver284for receiving non-printing ink discharged from the liquid-jet head284when the thickened recording liquid is discharged as non-printing ink, due to its failure to function as the recording liquid.

The serial-type image forming apparatus further includes a non-printing ink receiver288in a non-printing region at the other side of the carriage233in the carriage main-scanning direction so as to receive the non-printing ink when the recording liquid is thickened and the thickened recording liquid is thus discharged. The non-printing ink receiver288includes an opening289along the nozzle array direction of the recording head234.

In the image forming apparatus having the above configuration, the top sheet242is separated from the others in the sheet-feeding tray202, the sheet242is approximately vertically disposed to be guided by the guide member245, the sheet242is sandwiched between the transfer belt251and the counter roller246to be transferred, the edge of the sheet242is guided by the transfer guide member297, and pressed against the transfer belt251by the edge-pressing roll249, and by then the transfer direction of the sheet242is changed by approximately 90 degrees.

In this state, voltages are alternately applied to the charging roller256to repeatedly output positive and negative charges, such that the transfer belt251is charged with alternate charge voltage patterns corresponding to the charging roller256. That is, the transfer belt251is charged such that the transfer belt251includes alternately disposed positive and negative charged bands having predetermined widths in the sub-scanning direction (i.e., a circumferential traveling direction of the transfer belt251). When the sheet242is fed onto the transfer belt251that is alternately charged with positive and negative charge voltage patterns, the sheet242is electrostatically attracted by the transfer belt251. The sheet292attracted to the transfer belt251is then transferred in the sub-scanning direction by circumferential traveling of the transfer belt251.

The recording head234is driven based on image signals while the carriage233is moved such that the recording head234ejects ink drops onto the stationary sheet242, thereby recording one line with the ejected ink drops. The sheet242is then transferred by a predetermined amount, and a next line is subsequently recorded on the sheet242with next ejected ink drops. The recording operation is terminated when a signal indicates that a rear end of the sheet242has reached a recording region. The sheet242is discharged onto the sheet-discharge tray203.

Since the serial-type image forming apparatus includes the liquid-jet recording head according to the embodiments as the recording head, high-definition images may be stably formed.

Note that in the present application, a material of the “sheet” is not limited to paper, but may be an overhead projector (OHP) film, cloth, glass, and a substrate, to which ink drops or other liquids are attachable. Examples of such materials for the sheet may be called a “recording medium subject to being recorded on”, a “recording medium”, “recording paper”, and a “recording sheet”. Further, the terms “image forming”, “recording”, “printing”, and “copying” may be used as synonyms.

In addition, the term an “image forming apparatus” indicates an apparatus that forms an image onto media such as paper, string, fiber, fabric, leather, metal, plastic, glass, wood, and ceramics by discharging liquid onto such media. Moreover, the term “forming an image” or “image formation” not only indicates providing an image having some kind of mean onto the media such as characters and symbols, but also indicates an image without having any meaning such as patterns (i.e., by simply discharging ink drops onto the media).

Further, the term “k” is not specifically limited to those generally called “ink”, but may include a generically called “liquid” capable of forming an image, such as a recording liquid, a fixing liquid, and a liquid. The term “ink” may further include DNA specimens, resist, a patterning material, resin, and the like.

Moreover, the “image” is not limited to a two-dimensional image, but may include an image applied to a three-dimensionally formed object, or an image applied to a three-dimensional image formed of a molded object.

Further, the term “image forming apparatus” may include both a “serial-type image forming apparatus” and a “line-type image forming apparatus” unless otherwise specified.

According to the disclosed embodiments, the stress concentration applied to the boundary part between the thick part and the thin part of the diaphragm in the liquid-drop head may be reduced at low cost.

This patent application is based on Japanese Priority Patent Application No. 2012-061674 filed on Mar. 19, 2012, the entire contents of which are hereby incorporated herein by reference.