Liquid jet head

A liquid jet head and apparatus prevent an increase in the viscosity of liquid in the liquid path during long term storage. The recording head has a liquid path unit 1 with nozzle openings 8, pressure generation chambers 7, liquid reservoirs 9, and a diaphragm 5, and a head case 2 bonded to the liquid path unit 1. A damper chamber 12 for releasing pressure change inside the liquid reservoir is formed at a part of the head case or seal plate 5 corresponding to the liquid reservoir 9. A release path 14B for releasing pressure in the damper chamber to the air is formed in the head case. A control path 14A communicating with the damper chamber and release path and having a specific flow resistance restricting dispersion of moisture vapor from the liquid is formed in the head case and/or seal plate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid jet head, and a liquid jet apparatus, such as a recording head for an ink jet recording apparatus, an electrode member ejection head for an electrode forming apparatus, an organic substance jet head for a bio chip manufacture apparatus, etc., in which liquid is ejected by deformation of piezoelectric elements formed on a surface of a diaphragm formed as a part of pressure generating chambers communicating with nozzle orifices from which liquid is ejected.

2. Description of Related Art

A typical inkjet recording head (a kind of liquid jet head) using a longitudinally oscillating piezoelectric transducer (referred to below as simply a “recording head”) has, as shown inFIG. 16, an ink path unit1in which a plurality of nozzle openings8and a pressure generation chamber7are formed, and a head case2to which this ink path unit1is bonded and in which piezoelectric transducers6are housed.

The ink path unit1is a laminar construction including a nozzle plate3in which the nozzle openings8are arranged in rows orthogonally to the recording medium surface, a flow channel substrate4in which a pressure generation chamber7is disposed communicating with each of the nozzle openings8, and a diaphragm5covering the bottom opening of each pressure generation chamber7. An ink reservoir9communicating with each pressure generation chamber7by way of ink supply path10and storing the ink supplied to each pressure generation chamber7is formed in the flow channel substrate4. It should be noted that two sets of nozzle openings8and pressure generation chambers7arc shown in the example in FIG.16.

The head case2is made from synthetic resin with the piezoelectric transducers6disposed in through-spaces16, which are vertically oriented as seen in the figure. The spaces16extend in line with the rows of nozzle openings8, and there are two spaces16corresponding to the rows of the nozzle openings8. The back end side of each piezoelectric transducer6is bonded to a fixed plate11affixed to the head case2, and the front end side of each piezoelectric transducer6is bonded to a pad5C on the bottom surface of the diaphragm5.

The piezoelectric transducers6are forced to expand and contract longitudinally by applying a drive signal generated by a drive circuit (not shown in the figure) to the transducers6by way of flexible printed circuit13. Expansion and contraction of the piezoelectric transducers6cause the pad5C of the diaphragm5to vibrate and thereby change the pressure inside the pressure generation chamber7so that ink inside the pressure generation chamber7is discharged from the nozzle opening8as an ink droplet. Also shown inFIG. 16is the ink refilling tube15for refilling the ink reservoir9with ink from an ink cartridge (not shown in the figure).

The diaphragm5in this example is made from a polyphenylene sulfide (PPS) film, and a damper chamber12for absorbing through the diaphragm5pressure change in the ink reservoir9during ink discharge is formed in the head case2at an appropriate position to the ink reservoir9. If this damper chamber12is an independent space that does not communicate with the exterior, air inside the damper chamber12can dissolve into the ink through the diaphragm5made of PPS film, thereby lowering the pressure inside the damper chamber12, increasing the tension of the diaphragm5, and can thus easily make it difficult to achieve the desired damping effect. This pressure drop inside the damper chamber12is therefore prevented by opening an external communication path14passing from the inside surface of the damper chamber12toward and out the back side of the head case2so that the damper chamber12can communicate with the outside.

A problem with the conventional recording head described above is that the damper chamber12is open to the air. When the recording head is left unused or stored for a long time, water in the ink within the ink reservoir9is able to pass as water vapor through the PPS film diaphragm5and the viscosity of ink inside the ink reservoir9gradually increases. The ink can even dry to the point that clogging of the flow path cannot be corrected and ink cannot be normally discharged even after a cleaning operation, for example, that forcibly vacuums ink from within the ink path when the recording head is used the next time. This tendency is particularly pronounced with pigment inks that easily increase in viscosity, and pigment inks are increasingly used in order to achieve a desired print quality.

There is therefore a strong need for an inkjet recording head whereby this increase in ink viscosity can be prevented during extended storage.

It is also desirable in achieving a means for solving this problem to minimize the number of parts and achieve high precision and quality with the simplest possible method.

The present invention is directed to solving these problems and an object of the invention is to provide an inkjet recording head and an inkjet recording apparatus capable of preventing an increase in ink viscosity inside the ink flow paths during long term storage.

SUMMARY OF THE INVENTION

To achieve this object in a liquid jet head having nozzle openings, a pressure generation chamber communicating with each nozzle opening, a liquid reservoir for storing liquid supplied to pressure generation chambers, a liquid path unit including the pressure generation chambers and a seal plate for covering an opening to the liquid reservoir, and a head case to which the liquid path unit is bonded, a liquid jet head in accordance with the invention provides a damper chamber at a part corresponding to the liquid reservoir in the head case or seal plate for releasing pressure change in the liquid reservoir; a release path formed in the head case for releasing pressure in the damper chamber to the air; and a control path imparted with specific flow resistance formed in the head case and/or seal plate for restricting moisture dispersion while communicating the damper chamber with the release path.

In other words, a liquid jet head according to the present invention has a damper chamber for releasing pressure change in the liquid reservoir formed at a part corresponding to the liquid reservoir in the head case or seal plate; a release path formed in the head case for releasing pressure in the damper chamber to the air; and a control path with specific flow resistance formed in the head case and/or seal plate to restrict moisture dispersion while communicating the damper chamber with the release path.

The flow of water vapor from the liquid that passes through the seal plate is therefore restricted by the flow resistance of the control path, and undesirable dispersion of moisture from the liquid is thus suppressed.

Because the outflow of vapor to the air is restricted by the control path, evaporation of moisture from liquid in the liquid reservoir is restricted by the control path and an increase in the viscosity of liquid in the liquid reservoir is prevented even when the recording head is stored unused for a long time. Therefore, when the recording head is used again after being stored for a long time the liquid can be normally discharged after applying a normal cleaning operation, and discharge problems such as those that occur in conventional jet heads can be substantially eliminated.

Preferably, the control path of this liquid jet head is formed in an interfacial surface between the seal plate and head case.

The control path can be easily formed in these opposing surfaces, thus helping to improve the efficiency of recording head production.

Further, preferably the control path is formed in the seal plate.

In this case the depth of the control path is at most the thickness of the seal plate, and a high precision control path can therefore be formed using a press or other simple technique.

In another preferable embodiment the control path is formed in the head case.

In this case the control path can be formed by molding or other process at the same time the head case is manufactured, further contributing to efficient production.

Yet further preferably the seal plate of the liquid jet head has a barrier thin film and an air path formation thin film in which the control path is formed.

Because the control path is formed in a thin film for forming the air path, for example, the control path can be formed easily.

Further preferably in this case the barrier thin film is made from a resin thin film material, and the air path formation thin film is made from a metal thin film material.

Because the control path is formed in a metal thin film in this case the control path can be formed with high precision using a simple method, and the evaporation of liquid vapor can be restricted under optimal conditions.

Yet further preferably the control path is formed in the metal thin film using an etching process.

The etching process can be controlled to achieve a control path with high shape and dimensional precision, and the evaporation of liquid vapor can be restricted under optimal conditions.

Yet further preferably, the flow resistance is set to a permeability characteristic lower than the moisture permeability of the resin thin film.

The flow resistance imparted by this permeability characteristic assures reliable control and restriction of liquid vapor dispersion and evaporation as described above.

The flow resistance of the control path in the present invention is based on the following equations for vapor flow Q per unit time,
Q=(W0−W1)/R
where W0is the vapor density at the path inlet, W1is the vapor density at the path outlet, and R is the flow resistance of the path.
R=L/(D×S)
where L is the length of the path, D is the vapor dispersion coefficient, and S is the section area of the path.

The major factors determining flow resistance are the above L and S.

Further preferably, the resin thin film is a polyphenylene sulfide film.

In this case the moisture permeability of the film itself works ideally in conjunction with the permeability characteristic of the control path, and the dispersion of moisture vapor can be optimally controlled.

Yet further preferably the liquid jet head of this invention also has a connection cavity communicating with the damper chamber formed or connected to the damper chamber, and the connection cavity is disposed to the head case and/or seal plate and communicates with the control path.

In this case alignment error in the relative positions of the control path and damper chamber when the dimensionally precise control path is connected to the damper chamber can be absorbed by the connection cavity. This absorption of alignment error also absorbs misalignment when the seal plate is bonded to the head case, and effectively improves production efficiency.

Further preferably, connection cavities disposed to each of multiple damper chambers communicate with each other.

This configuration enables multiple damper chambers to communicate through the control path with the release path by means of a simple structure. Furthermore, when the damper chambers communicate with the release path through multiple control paths from the connection cavities communicating with the damper chamber, communication between the multiple damper chambers and the air is maintained by the remaining good control paths when flow through part of the control paths becomes obstructed for some reason, and a worst-case increase in the liquid viscosity can also be avoided.

Yet further preferably the seal plate is bonded to the head case using adhesive, and a cavity for holding excess adhesive is formed at least in proximity to the control path.

If excessive adhesive is applied, this configuration captures the excess adhesive in the cavity and prevents the adhesive from flowing into the control path. Furthermore, even if some adhesive gets into the control path the amount will be within the allowable range and normal flow through the control path can be assured.

Further preferably the cavity communicates with the control path.

With this configuration excess adhesive is captured and held in the cavity communicating with the control path. The amount of adhesive penetrating the control path can therefore be minimized and the control path can be kept clear and functional.

Further preferably, the cavity for holding excess adhesive is narrower in width than the control path and communicates with the control path.

By making the cavity for holding excess adhesive narrower than the control path, the likelihood of the control path becoming plugged with adhesive can be reduced.

Further preferably the liquid jet head discharges a pigment ink.

Pigment type inks are particularly susceptible to an increase in viscosity due to evaporation of moisture from the ink. By effectively preventing the evaporation of moisture from ink in the liquid reservoir, the present invention is therefore particularly effective as a means enabling the recording head to be used smoothly again after having been stored for a long time.

The pressure generation element of a liquid jet head according to the present invention is preferably a piezoelectric transducer.

It is therefore possible to prevent evaporation of moisture from liquid in the liquid reservoir of a recording head using a piezoelectric transducer as a pressure generation means, and enable the recording head to be used smoothly again after having been stored for a long time.

Further preferably, the pressure generation element is a longitudinal oscillation mode piezoelectric transducer.

Because resin films such as polyphenylene sulfide films that pass water vapor easily are commonly used as the seal plate in recording heads that use a longitudinal oscillation mode piezoelectric transducer, this configuration of the invention can effectively prevent evaporation of moisture from liquid in the liquid reservoir, and can therefore enable the recording head to be used smoothly again after having been stored for a long time.

Yet further preferably the piezoelectric transducer is contained in the head case and applies a pressure change to the pressure generation chamber.

This configuration helps improve production efficiency because the head case is used both to secure the piezoelectric transducer and to form the control path.

Preferably, the pressure generation element of the recording head is a heating element for heating liquid in the liquid path.

With this configuration the invention can effectively prevent evaporation of moisture from liquid in the liquid reservoir of a recording head using a heating element as the pressure generation means, and can therefore enable the recording head to be used smoothly again after having been stored for a long time.

Alternatively, the control path formed in the air path formation thin film is a straight release path enabling the connection cavity and release path to communicate in a straight line.

Because there are no curves in the control path with this configuration, it is difficult for adhesive to collect inside the control path.

Further preferably, a seal plate cavity is formed in the seal plate at a position appropriate to the liquid reservoir, the seal plate cavity is formed in the air path formation thin film, and a part of the seal plate cavity disposed in proximity to the straight release path formed in the air path formation thin film and opposite the straight release path is substantially parallel to the straight release path.

With this configuration the seal plate cavity and straight release path are formed by removing at least a part of the air path formation thin film. The rigidity of the seal plate cavity and straight release path is therefore weaker than where these parts are not formed and this part is susceptible to wrinkling.

In addition, the part of the seal plate cavity and straight release path disposed in proximity to the easily wrinkled part is even more susceptible to wrinkles.

Therefore, by forming the part of this seal plate cavity that is opposite the straight release path so that it is parallel to the straight release path, external force is applied evenly and not concentrated to one side, thereby reducing susceptibility to wrinkling.

Further preferably a bonding pad is formed in the seal plate cavity.

When the seal plate is bonded to the pressure generation chamber and liquid reservoir opening, this configuration can firmly hold the seal plate at the bonding pad, thereby reducing the likelihood of bonding defects.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention are described below with reference to the accompanying figures. It will be noted that because the embodiment described below are exemplary embodiments of the invention, various technically desirable limitations are also described, but unless otherwise specifically noted the scope of the present invention shall not be limited to the embodiments described below.

FIG. 1toFIG. 7show an inkjet recording head (referred to below simply as a recording head) as a first embodiment of an inkjet recording head disposed to an inkjet recording apparatus according to the present invention. This recording head is basically the same as the recording head shown inFIG. 16, and like parts are therefore identified by like reference numerals below. Furthermore, while there are two rows of nozzle openings8and pressure generation chambers7in the recording head shown inFIG. 16, there are four such rows in the head case2shown in FIG.3. More specifically, the section through either side of the dot-dash line L inFIG. 3corresponds to the views shown inFIG. 1,FIG. 2, and FIG.16.FIG. 3is a top plan view of the head case2.

The ink path unit1is a laminar construction including a nozzle plate3to which nozzle openings8are disposed in rows, a flow channel substrate4in which rows of pressure generation chambers7each communicating with a corresponding nozzle opening8are disposed and in which is formed ink reservoirs9for holding ink for supply to each of the pressure generation chambers7through an ink supply path10, and a diaphragm5(seal plate) for covering the bottom openings of the pressure generation chambers7and ink reservoirs9. InFIG. 3the damper chambers12in the middle are positioned in a mutually compatible shape, and there is a corresponding space16for each damper chamber12.

The head case2is injection molded from a thermosetting resin or thermoplastic resin. The piezoelectric transducers6are housed in the vertically through-passing spaces16at positions corresponding to the pressure generation chambers7. The spaces16extend in line with the rows of nozzle openings8and are disposed corresponding to these rows. The piezoelectric transducers6are longitudinal oscillation mode transducers, the back end side of which is bonded to the fixed plate11affixed to the head case2, and the front end surface is bonded to a pad5C on the bottom surface of the diaphragm5.

The diaphragm5in this embodiment is made of polyphenylene sulfide (PPS) film laminated with a stainless steel pad5C. Damper chambers12for absorbing pressure fluctuations inside the ink reservoirs9through the diaphragm5are formed in the head case2at locations appropriate to the ink reservoirs9.

As shown inFIG. 1toFIG. 3, a seal-side cavity such as diaphragm-side cavity14I is disposed towards the diaphragm5at positions corresponding to the damper chambers12disposed towards the head case2. As shown inFIG. 3, these diaphragm-side cavities14I are substantially identical in shape to the damper chambers12.

The diaphragm (seal)5is a laminate of a thin-film barrier such as resin thin film5A and a thin film such as a metal thin film5B for forming flow channels. The resin thin film5A could be a polyphenylene sulfide (PPS) film. A stainless steel alloy is typically used for the metal thin film5B. The diaphragm-side cavities14I are formed in the metal thin film5B, and are more specifically formed in the diaphragm (seal)5surface facing the head case2.

The diaphragm5(seal) shall not be limited to this configuration and could be electroformed Ni or SUS, for example, or formed from dry film and resin film.

The ink used with an inkjet recording head is generally deaerated in order to prevent bubbles from forming. As a result, if the damper chamber12is an independent space that does not communicate with the exterior, air inside the damper chamber12can dissolve into the ink through the PPS film diaphragm5, thereby lowering the pressure inside the damper chamber12, increasing the tension of the diaphragm5, and thus easily making it difficult to achieve the desired damping effect. This pressure drop inside the damper chamber12is therefore prevented by enabling the damper chamber12to communicate with the outside through an external communication path14disposed to the head case2.

The piezoelectric transducers6are forced to expand and contract longitudinally by applying a drive signal generated by a drive circuit (not shown in the figure) to the piezoelectric transducers6by way of flexible printed circuit13. Expansion and contraction of the transducers6causes the pad5C of the diaphragm5to vibrate and change the pressure inside the pressure generation chamber7so that ink inside the pressure generation chamber7is discharged from the nozzle opening8as an ink droplet. Also shown in the figures are the ink refilling tubes15for refilling the ink reservoir9with ink from an ink cartridge (not shown in the figure), and ink refilling holes20disposed at corresponding positions to the ink refilling tubes15in the diaphragm5.

The external communication path14includes a control path14A to which flow resistance is applied to suppress ink evaporation, and release path14B opening the control path14A to the air. The control path14A is designed so that the path area is small and the path curves in an optimal pattern. The flow resistance of the control path14A itself is determined by appropriately determining the path area and the routing pattern. It should be noted that the exemplary control path14A shown in these figures is shaped like the numeral7.

As shown inFIG. 1toFIG. 3, the control paths14A are formed in the metal thin film5B, and are more specifically formed in the surface of diaphragm5facing the head case2using an etching process.

It should also be noted that the control paths14A could be formed on the head case2side rather than the diaphragm5.

The release path14B is formed in the head case2and is identical to the air hole provided by the external communication path14shown in FIG.16. That is, the release path14B forms a ventilation hole with a large internal diameter and passes through the head case2in the top to bottom direction as seen in FIG.2. The release path14B itself is not used to restrict the flow of ink vapor. Note thatFIG. 4is a plan view showing the layout with the nozzle plate3and flow channel substrate4removed for easier understanding.

As noted above, the diaphragm (seal)5is a laminate of a resin thin film5A and a metal thin film5B. The resin is typically a PPS film and the metal is typically a stainless steel alloy, for example. The control path14A is formed in the metal thin film5B, and more specifically on the surface of the diaphragm (seal)5facing the head case2.

Various methods can be used to form the control path14A, but an etching process as noted above is ideal. The dimensional specifications of the control path14A can be optimally selected according to the specifications of the recording head, and the control path14A in this example is designed to a depth (that is, thickness of the metal thin film5B) of approximately 0.03 mm and a width of approximately 0.3 mm. The control path14A shall also not be limited to the above-described shape of the numeral7, and could be S-shaped, zigzag, or otherwise configured to match the vapor permeability of the diaphragm5. Note that in this case the sectional area of the control path14A is a determining factor of the path resistance.

A connection cavity12A is formed in the damper chamber12to connect and enable communication between the damper chamber12and control path14A. The connection cavity12A is formed as a partial extension of the space in the damper chamber12. More specifically, the connection cavity12A is formed in the head case2by removing a part of the inside wall of the damper chamber12. When seen in plan view as shown inFIG. 4, the area of the damper chamber12is significantly greater than the width of the control path14A.

The release path14B is opened in the head case2. As will also be known fromFIG. 4, the sectional area of the release path14B is significantly greater than the width of the control path14A disposed in the diaphragm5. The one end14C of the control path14A overlaps and communicates with connection cavity12A. The other end14D of the control path14A similarly overlaps and communicates with the release path14B.

It should be noted that the connection cavity12A is disposed to the head case2in this embodiment because it is bonded with an adhesive applied to the head case2, but the connection cavity12A could alternatively be formed in the metal thin film5B of diaphragm5using an etching process.

In this first embodiment of the invention water vapor from ink stored in the damper chamber12gradually flows through connection cavity12A into the control path14A. Because the flow resistance of the control path14A is high, that is, because the vapor permeability characteristic of the control path14A is set lower than the vapor permeability of the thin film5A of the diaphragm5, the flow of water vapor from the ink is restricted by the control path14A.

Because the outflow of water vapor to air is restricted by the control path14A as described above, evaporation of moisture from the ink in the ink reservoir9is restricted by the control path14A even when the recording head is stored for a long time, and an increase in ink viscosity in the ink reservoir9is thereby suppressed. When the recording head is used again after being stored for some time, ink can be discharged normally after applying a normal cleaning operation, and discharge problems such as conventionally occur are substantially eliminated.

The control path14A can be formed to a precise shape and dimensions by etching the control path14A into the metal thin film5B, and this technique is therefore ideal for imparting the appropriate flow resistance to the control path14A. Furthermore, because the connection cavity12A is disposed to the damper chamber12, the size of the connection cavity12A relative to the control path14A enables the connection cavity12A to absorb alignment error when the control path14A and head case2are bonded, thus simplifying process management and precision control during manufacturing.

A second embodiment of the present invention is described with reference to FIG.3and FIG.8. In this embodiment the connection cavities12A of plural damper chambers12communicate with each other. As a result two control paths14A communicate with the mutually communicating connection cavities12A as will be clear from the double-dot dash line in FIG.3. The other ends of the two control paths14A are connected to one release path14B. It is also possible to use only one or to use three or more control paths14A.

Because connection cavities12A communicate with each other in this embodiment, ink vapor from two damper chambers12can be conducted with a simple construction. In addition, when a problem occurs with flow through one control path14A, deficient yet minimal flow control is sustained by the other control path14A. Ink viscosity can therefore be prevented from reaching a worst-case condition, and a pressure drop in the damper chambers can be suppressed.

A third embodiment of the invention is shown in FIG.9and FIG.10. In this embodiment the control paths14A are formed in the head case2.FIG. 9shows the control path14A inset into the surface of the head case2facing the diaphragm (seal)5.FIG. 10shows the control path14A disposed as a narrow ventilation hole in the head case2. Note that a connection cavity12A is not present in the configuration shown in FIG.10.

This embodiment is advantageous in terms of manufacturability because the control path14A can be formed at the same time the head case2is manufactured.

A fourth embodiment of the invention is described with reference to FIG.11. This embodiment has two variations, the first shown in FIG.11(A).

This first variation of the fourth embodiment prevents the adhesive used to bond the ink path unit1and head case2from flowing into the control path14A, and has cavities17for holding any excess adhesive. In this example there are three cavities17, each branching off from and communicating with control path14A. The control path14A also passes completely through and beyond the connection cavity12A to form an extension17A, and likewise passes through and beyond the release path14B to form another extension17B at the opposite end. These extensions17A and17B can also be used as storage cavities for excess adhesive.

These cavities17,17A, and17B can be simultaneously formed when forming the control path14A with an etching process.

Excess adhesive tends to collect easily in the dead-end parts of the cavities17, thus making it more difficult for excess adhesive to collect in the control path14A.

The cavities17can also be made narrower than the control path14A. This further lowers the possibility of the control path14A being clogged with adhesive.

Cavity17shown with a double-dot dash line in FIG.11(A) is independent of the control path14A. It should be noted that the cavities17for holding excess adhesive shall not be limited to a narrow trench shape as described above, and could be a circular, square, or otherwise shaped cavity of a suitable area.

The second variation of this fourth embodiment is shown in FIG.11(B). In this variation the control path14A is a trapezoidally shaped endless path suitable for where mutually communicating connection cavities12A connect with the release path14B. A plurality of cavities17such as described above and shown in FIG.11(A) are formed on the inside of this trapezoidal control path14A.

If too much adhesive is applied when bonding the ink path unit1and head case2together and there is excessive adhesive, the excess collects in the cavities17in this embodiment and adhesive is thereby prevented from flowing into the control path14A. Furthermore, even if some adhesive flows into the control path14A, interference with flow through the control path14A is minimized.

Various configurations can be used to connect the end of the control path14A with the release path14B. One example is a hooked end17C such as shown in FIG.12. This configuration assures dependable communication between the control path14A and release path14B even if the diaphragm5and release path14B are slightly misaligned, and thus simplifies precision control during manufacturing.

The control path14A is designed with a specific fine shape and sectional area determining the flow resistance, but it is alternatively possible to set the flow resistance of the control path14A by inserting an orifice18such as shown in FIG.13. In this case the control path14A is formed to a somewhat large sectional area and a separate orifice element19plate is then inserted from the outside.

FIG. 14is a schematic diagram showing the major parts of a recording head according to a fifth embodiment of the invention.

The configuration of an inkjet recording head according to this embodiment is substantially the same as the inkjet recording head according to the first and second embodiments described above. Like parts are therefore identified by like reference numerals and further description thereof is omitted below where primarily the differences are described.

FIG. 14is a schematic plan view of the head case2. The control path24A formed in the metal thin film5B of diaphragm5is a straight open channel enabling the connection cavity12A and release path14B to communicate in a straight line.

Unlike the control path14A of the first embodiment, this control path24A therefore does not have any curves. It is therefore difficult for excess adhesive to collect in the control path14A when the ink path unit1shown inFIG. 1is bonded to the head case2.

A common connection cavity12A is also formed at the bottom part of the two middle damper chambers12as shown inFIG. 14, and a straight control path24A enabling connection cavity12A and release path14B to communicate in a straight line is also provided.

Because the control path24A is thus straight, a space results in the part enclosed by the connection cavity12A, damper chamber12, and release path14B, unlike the configuration shown in FIG.3. This embodiment uses this space to provide one or more adhesive cavities27for holding excess adhesive. Two cavities27are formed in this embodiment.

When too much adhesive is applied when bonding the ink path unit1to the head case2, the excess adhesive is held in the adhesive cavities27in the present embodiment. This prevents the adhesive from flowing into the control path24A and minimizes any flow interference in case adhesive does enter the control path24A.

A diaphragm-side cavity24I is also disposed near the left-side control path24A, for example, in FIG.14. The part of this diaphragm-side cavity24I opposite the control path24A is substantially parallel to the control path24A.

More specifically, the right side surface24F of the control path24A inFIG. 14is disposed substantially parallel to the left side surface24G at the bottom left end of the diaphragm-side cavity24I. The control path24A and diaphragm-side cavity24I are made from only the resin thin film5A with an etching process removing the metal thin film5B of the diaphragm5as shown in FIG.2.

The parts where the control path24A and diaphragm-side cavity24I are formed are therefore less rigid than the surrounding parts, and are easily wrinkled when external force is applied. Moreover, the part where the easily wrinkled control path24A and diaphragm-side cavity24I are juxtaposed wrinkles even more easily.

However, by arranging the opposing control path24A and right-side surface24F, and the left-side surface24G at the bottom left part of the diaphragm-side cavity24I in this easily wrinkled area so that they are parallel, external force is not concentrated at one part but is applied uniformly. Rigidity is thus improved and wrinkles do not occur easily.

The part where the left-side surface24G of the diaphragm-side cavity24I inFIG. 14is formed is segmented into a substantially triangular shape by the substantially rectangular bonding pad24E.

More specifically, this bonding pad24E remains after etching metal thin film5B of diaphragm5while the ends of the bonding pad24E are etched away, thus forming two channels24H linking the substantially triangular part and the substantially trapezoidal diaphragm-side cavity24I.

When the diaphragm5is bonded to, for example, the flow channel substrate4having openings to the pressure generation chamber and ink reservoir, the diaphragm5is typically held with a tool. Because the bonding pad of the present embodiment contacts the tool or other device at this time, the diaphragm5can be firmly bonded with good precision to the flow channel substrate4.

Variation of Embodiment 5

FIG. 15shows a variation of the fifth embodiment described above. This variation differs from the fifth embodiment shown inFIG. 14in the shape of the bonding pad24E. Like parts are therefore referenced with like reference numerals and further description thereof is therefore omitted below where primarily the differences are described.

As shown inFIG. 15the bonding pads34E adjacent to the left-side surface24G, at the bottom left part of the diaphragm-side cavity34D, in the present embodiment differ from the bonding pad24E in FIG.14. More specifically, a plurality of slender individual bonding pads34E are provided with a channel34H between adjacent bonding pads34E and at the ends. Note that in the example shown inFIG. 15there are four bonding pads34E and five channels34H.

The bonding pads34E are 0.1 mm or less wide. Making the bonding pads34E narrow reduces interference with ink reservoir9after bonding with the flow channel substrate4.

It should be noted that while the present invention has been described with reference to a recording head using longitudinal oscillation mode piezoelectric transducers6, the invention shall not be so limited. For example, the invention can be applied to a recording head using a deflection mode piezoelectric transducer, or to a recording head using a heating element for heating ink inside the ink path as the pressure generation element.

An inkjet recording head and inkjet recording apparatus according to the present invention as described above thus provides a control path through which the damper chamber communicates externally rather than opening the damper chamber directly to the air. Evaporation of moisture from ink held in the ink reservoir is thus restricted by this control path and an increase in the viscosity of ink in the ink reservoir is suppressed even when the recording head is stored without being used for a long time. Therefore, when the recording head is used after being stored for a long time, ink can be discharged normally after performing a normal cleaning operation, and discharge problems such as conventionally occur are substantially eliminated.

Moreover, because formation of the control paths is important, it is not necessary to provide any additional special parts, and the invention thus offers the further advantage of a simple configuration.