1. Field of the Invention
The present invention relates to a liquid jet head for forming an image, a character, or a thin film material on a recording medium by discharging liquid from a nozzle, and relates to a method of manufacturing the liquid jet head and to a liquid jet apparatus using the liquid jet head.
2. Description of the Related Art
In recent years, there has been used an ink jet type liquid jet head for discharging ink droplets on recording paper or the like to render a character or graphics or for discharging a liquid material on a surface of an element substrate to form a pattern of a functional thin film. In such a liquid jet head, ink or a liquid material is supplied from a liquid tank via a supply tube to the liquid jet head, the ink is caused to fill minute space formed in the liquid jet head, and a capacity of the minute space is momentarily changed according to a drive signal to discharge liquid droplets from a nozzle which communicates to a groove.
The actuator substrate 52 and partition walls 54 are made of a piezoelectric material, and the partition walls 54 are subjected to polarization processing in a normal direction of the substrate surface. Electrodes 55 are respectively formed on both side surfaces of each partition wall 54 so as to sandwich the partition wall 54. By giving a drive signal to the electrodes 55, the partition wall 54 slips to be deformed in a thickness direction, to thereby change internal volumes of the grooves 53. Thus, the ink filled in the grooves 53 is caused to jet from the nozzles 58a, and is recorded on the recording medium.
A bending point when the partition wall 54 slips to be deformed in the thickness direction is situated at substantially half a height from a bottom surface of each groove 53 to a top surface of each partition wall 54. With this configuration, it is possible to most efficiently deform and drive the partition wall 54. For that reason, the electrode 55 to be formed on each surface of the partition wall 54 is formed from the bottom surface of the groove 53 to ½ of the height of the partition wall 54, or formed from ½ of the height of the partition wall 54 to the height of the top surface of the partition wall 54. When widths in a depth direction of the electrodes 55 vary in every groove 53, ink discharge performance varies in every nozzle 58a. The recording medium, on which ink droplets are jetted, moves. Accordingly, when flying rate of the ink droplets varies, the jetted positions vary, which leads to degradation in printing quality. Therefore, the electrodes 55 to be formed on the side surfaces of the partition walls 54 need to be formed into the same shape in the respective grooves 53.
In JP 2000-108361 A, metal electrodes are formed on the entire surface including the side surfaces of the partition wall 54 and the bottom surface of the groove 53 by electroless plating processing. Then, a laser beam is irradiated from a direction that is oblique in the direction orthogonal to the grooves 53 with respect to the normal of the surface of the actuator substrate 52, and the upper half of the metal electrode formed on one side surface of the partition wall 54 is removed. Next, the upper half of the metal electrode formed on the other side surface is removed by irradiating the laser beam from the opposite oblique direction. If the metal electrodes are to be removed together by irradiating the laser beam to a large area at the time of removal, an incident angle of the laser beam irradiated to the surface differs in every position, and hence the electrodes vary in width. In order to avoid this, it is necessary to irradiate the laser beam to a small area by limiting the irradiation range.
JP 05-318741 A describes another method of forming the electrodes 55. After a plurality of grooves are formed in an actuator substrate made of a piezoelectric material, a target wire is inserted into each of the grooves, the target wire having a diameter substantially equal to the width of each groove. By irradiating an inert gas ion beam from a direction of upper openings of the plurality of grooves, the target wire embedded in each of the grooves is sputtered. In this way, metal particles sputtered from the target wire adhere to upper portions of side wall surfaces. After that, the target wire is taken out of each of the grooves.
As another electrode forming method, there is known an oblique deposition of depositing a conductive material obliquely.
The electrodes 55 which are formed on the side surfaces of the partition walls 54 need to be formed into the same shape in the respective partition walls 54. In JP 2000-108361 A, in order to form the electrodes 55 into the same shape, the laser beam needs to be irradiated to every side surface of each of the partition walls 54, which requires a greater amount of time for patterning the electrodes 55 as the number of the grooves 53 of the ink jet head increases. Consequently, mass production performance is reduced. Further, a metal material is scattered to the surroundings through irradiation of the laser beam, and the scattered metal material adheres to the grooves 53 again to cause a short circuit and clogging of the nozzles. Further, in the method described in JP 05-318741 A, it is necessary to embed a large number of target wires into a large number of the narrow grooves 53, respectively, the target wires each having a diameter substantially equal to the width of the groove 53. Thus, the mass production performance is low, and the method is not realistic.
As described above, the electrodes 55 formed on the partition walls 54 differ in depth depending on the position of the surface of the actuator substrate 52.
Specific description is made with reference to
As illustrated in
Next, description is made of the case where the electrodes 55 extend across the center portion of the partition wall 54 over the lower side thereof. In
In the case where the electrodes 55 extend over the lower halves of the partition walls 54, as illustrated in
As described above, in the actuator substrate 52 that is uniformly polarized in an upright direction of the partition walls 54, if the areas of the electric field application regions are not constant in the respective partition walls 54, it is impossible to ensure equality of the discharge rate. Further, in order to increase electrostrictive efficiency, and to lower the applied voltage so as to reduce load applied to the drive circuit side, it is necessary that each electrode 55 does not extend over a portion situated below the height h/2 of the partition wall 54 in the depth direction, and that the upper half of the electric field application region Sa is formed as wide as possible. Thus, it has been extremely difficult to form the electrode.
The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is therefore to provide a liquid jet head which is capable of minimizing variations in discharge performance among all the channels, and which is excellent in discharge efficiency.
A liquid jet head according to the present invention includes: an actuator substrate including: a plurality of grooves aligned in parallel to each other in a surface thereof; partition walls separating the plurality of adjacent grooves from each other; and drive electrodes placed on both side surfaces of each of the partition walls; a cover plate bonded onto the surface of the actuator substrate so as to cover the plurality of grooves; and a nozzle plate including nozzles communicating to the plurality of grooves, the nozzle plate being bonded onto an end surface of the actuator substrate, in which the actuator substrate includes a drive region for driving the partition walls so as to deform the partition walls, and for causing liquid filling the plurality of grooves to jet from the nozzles, in which, in the drive region, each of the partition walls is made of a piezoelectric material on a top surface side situated above substantially half a height from a bottom surface of each of the plurality of grooves to a top surface of each of the partition walls, and made of a low-permittivity material, which is lower in permittivity than the piezoelectric material, on a bottom surface side situated below substantially half the height, and in which, in the drive region, each of the drive electrodes is placed so as to extend across each side surface of each of the partition walls made of the piezoelectric material and each side surface of each of the partition walls made of the low-permittivity material.
Further, in the liquid jet head according to the present invention, the drive electrodes are shaped so that ranges, in which the drive electrodes are formed on the plurality of partition walls made of the low-permittivity material, gradually change from one end to another end of the actuator substrate.
Further, in the liquid jet head according to the present invention, the actuator substrate has a double-layer structure made of the low-permittivity material and the piezoelectric material.
Further, in the liquid jet head according to the present invention, the low-permittivity material is higher in thermal conductivity than the piezoelectric material.
Further, in the liquid jet head according to the present invention, the low-permittivity material is lower in mechanical rigidity than the piezoelectric material.
Further, in the liquid jet head according to the present invention, the low-permittivity material is one of a machinable ceramics and a resin material.
A liquid jet apparatus according to the present invention includes: the liquid jet head according to any aspects described above; a moving mechanism for reciprocating the liquid jet head; a liquid supply tube for supplying liquid to the liquid jet head; and a liquid tank for supplying the liquid to the liquid supply tube.
A manufacturing method for a liquid jet head according to the present invention includes: a first bonding step of bonding a piezoelectric substrate onto a surface of a low-permittivity substrate, to thereby form an actuator substrate, the piezoelectric substrate being made of a piezoelectric material, the low-permittivity substrate being made of a low-permittivity material which is lower in permittivity than the piezoelectric material; a groove forming step of forming a plurality of grooves aligned in parallel to each other in a surface of the actuator substrate, and forming partition walls separating the plurality of adjacent grooves from each other, each of the partition walls being made of the piezoelectric material on a top surface side situated above substantially half a height from a bottom surface of each of the plurality of grooves to a top surface of each of the partition walls, and made of the low-permittivity material on a bottom surface side situated below substantially half the height; a conductive film forming step of forming a conductive film on the surface of the actuator substrate and the partition walls in the drive region so that the conductive film extends across each side surface of each of the partition walls made of the piezoelectric material and each side surface of each of the partition walls made of the low-permittivity material, the drive region causing liquid filling the plurality of grooves to jet; an electrode forming step of forming a pattern of the conductive film; and a second bonding step of bonding a cover plate onto the surface of the actuator substrate, and bonding a nozzle plate onto an end surface of the actuator substrate, the nozzle plate including nozzles communicating to the plurality of grooves.
Further, in the manufacturing method for a liquid jet head according to the present invention, the conductive film forming step includes a step of depositing a conductive material by sputtering.
Further, in the manufacturing method for a liquid jet head according to the present invention, the conductive film forming step includes an oblique deposition step of depositing a conductive material obliquely on the surface of the actuator substrate from a direction oblique to a normal of the surface of the actuator substrate.
Further, the manufacturing method for a liquid jet head according the present invention, further includes: a photosensitive resin film forming step of forming a photosensitive resin film on the surface of the actuator substrate after performing the first bonding step; and a pattern forming step of forming a pattern of the photosensitive resin film through exposure and development of the photosensitive resin film before performing the conductive film forming step, in which, in the electrode forming step, the pattern of the conductive film is formed by a lift-off method in which the photosensitive resin film is removed.
A liquid jet head according to the present invention includes: an actuator substrate including: a plurality of grooves aligned in parallel to each other in a surface thereof; partition walls separating the plurality of adjacent grooves from each other; and drive electrodes placed on both side surfaces of each of the partition walls; a cover plate bonded onto the surface of the actuator substrate so as to cover the plurality of grooves; and a nozzle plate including nozzles communicating to the plurality of grooves, the nozzle plate being bonded onto an end surface of the actuator substrate, in which the actuator substrate includes a drive region for driving the partition walls so as to deform the partition walls, and for causing liquid filling the plurality of grooves to jet from the nozzles, in which, in the drive region, each of the partition walls is made of a piezoelectric material on a top surface side situated above substantially half a height from a bottom surface of each of the plurality of grooves to a top surface of each of the partition walls, and made of a low-permittivity material, which is lower in permittivity than the piezoelectric material, on a bottom surface side situated below substantially half the height, and in which, in the drive region, each of the drive electrodes is placed so as to extend across each side surface of each of the partition walls made of the piezoelectric material and each side surface of each of the partition walls made of the low-permittivity material. As described above, a drive section for the partition walls is arranged above substantially half the height of each of the partition walls, and the drive electrodes are formed so as to extend across the piezoelectric material side of the partition walls and the low-permittivity material side. Thus, deformation drive amounts of the respective partition walls are equalized, and it is possible to reduce variations in liquid droplet discharge rate among the nozzles. In addition, the low-permittivity material is interposed between one partition wall and another adjacent partition wall, and hence capacitive coupling is reduced. Thus, a drive signal can be prevented from leaking to the adjacent partition walls and fluctuating liquid droplet discharge characteristics of the adjacent nozzles. In addition, the drive electrodes do not need to be formed with high accuracy so as to align at bending positions of the partition walls, and hence it is extremely easy to form the electrodes.
In the accompanying drawings:
A liquid jet head according to the present invention includes: an actuator substrate including a plurality of grooves separated from each other by partition walls, and including drive electrodes placed on both side surfaces of each of the partition walls; a cover plate bonded onto the actuator substrate so as to cover the respective grooves; and a nozzle plate including nozzles communicating to the respective grooves, the nozzle plate being bonded onto an end surface of the actuator substrate. The actuator substrate includes a drive region for driving the partition walls so as to deform the same, and for causing liquid filling the grooves to jet from the nozzles. Each partition wall in the drive region is made of a piezoelectric material on a top surface side situated above substantially half a height of the partition wall, and made of a low-permittivity material, which is lower in permittivity than the piezoelectric material, on a groove bottom surface side situated below substantially half the height. Further, each drive electrode in the drive region is placed so as to extend across each side surface of the partition wall made of the piezoelectric material and each side surface of the partition wall made of the low-permittivity material.
With this configuration, the partition wall is made of the low-permittivity material on the bottom surface side situated below substantially half the height, and hence the bottom surface side does not exhibit an electrostrictive effect even when the electric field is applied thereto. Thus, deformation drive amounts of the respective partition walls are equalized, and it is possible to reduce variations in liquid droplet discharge rate among the nozzles. In addition, the low-permittivity material is interposed between one partition wall and another adjacent partition wall, and hence capacitive coupling is reduced. Owing to the reduction in capacitive coupling, leakage of a drive signal between the adjacent partition walls is reduced, with the result that liquid discharge characteristics cannot be affected by drive states of the adjacent channels. In addition, each drive electrode in the drive region only needs to be formed to extend across each side surface of the partition wall made of the piezoelectric material and each side surface of the partition wall made of the low-permittivity material situated below the piezoelectric material, and an extending amount does not affect the deformation drive amount of the partition wall. Thus, the electrode forming method is extremely simplified.
Lead zirconate titanate (PZT), barium titanate (BaTiO3), or the like can be used as the piezoelectric material. The piezoelectric material is subjected to polarization processing in advance in a specific direction, for example, a normal direction of the surface of the actuator substrate. A glass material, a metal oxide, a ceramics, a machinable ceramics, a resin material, or the like can be used as the low-permittivity material. In a case of using PZT as the piezoelectric material, a half or less of an amount of PZT can be used when compared to the case of the conventional method, and hence it is possible to remarkably reduce an amount of lead to be used. In a case of using, for example, the machinable ceramics as the low-permittivity material, the machinable ceramics is excellent in processability, and hence the grooves can be formed easily at once in the machinable ceramics and the piezoelectric material bonded onto the surface of the machinable ceramics. By approximating coefficients of thermal expansion of the piezoelectric material and the low-permittivity material to each other, it is possible to improve reliability of bonding. In a case of using, for example, the resin material as the low-permittivity material, the resin material is excellent in processability and die moldability, and hence it is possible to easily form a complex shape. In this case, the resin material can be used also for the cover plate which is bonded onto a top surface of the actuator substrate, and hence it is possible to remarkably reduce manufacturing cost. Further, when using a material higher in thermal conductivity than the piezoelectric material as the low-permittivity material, it is possible to further improve a heat radiation effect of heat generated by deformation drive of the partition walls. Further, mechanical rigidity of the low-permittivity material, for example, Young's modulus thereof can be made smaller than that of the piezoelectric material. Thus, it is possible to deform and drive the partition walls at lower voltage.
A manufacturing method for a liquid jet head according to the present invention includes: a first bonding step of bonding a piezoelectric substrate onto a surface of a low-permittivity substrate, to thereby form an actuator substrate; a groove forming step of forming a plurality of grooves aligned in parallel to each other in a surface of the actuator substrate, and forming partition walls separating the plurality of grooves from each other, each of the partition walls being made of a piezoelectric material on a top surface side situated above substantially half a height from a bottom surface of each of the grooves to the top surface of each of the partition walls, and made of a low-permittivity material on the bottom surface side situated below substantially half the height; a conductive film forming step of forming a conductive film on the surface of the actuator substrate and the partition walls in the drive region so that the conductive film extends across each side surface of each of the partition walls made of the piezoelectric material and each side surface of each of the partition walls made of the low-permittivity material; an electrode forming step of forming a pattern of the conductive film; and a second bonding step of bonding a cover plate onto the surface of the actuator substrate, and bonding a nozzle plate onto an end surface of the actuator substrate.
According to the manufacturing method, each of the partition walls is made of the low-permittivity material on the bottom surface side situated below substantially half the height of the partition wall, and hence the bottom surface side does not exhibit the electrostrictive effect even when the electric field is applied thereto. Accordingly, even when the drive electrode extends over the bottom surface side situated below substantially half the height of the partition wall, the extending drive electrode does not affect the deformation drive of the partition wall, and does not affect the discharge rate of liquid droplets discharged from the nozzles. With this, there is remarkably eased strictness required for pattern formation accuracy of an electrode pattern which is formed on the side surfaces of the partition walls in the conductive film forming step or the electrode forming step. As an electrode forming method, for example, sputtering, deposition, oblique deposition, or plating can be used. In addition, the low-permittivity material is interposed between one partition wall and another adjacent partition wall, and hence it is possible to reduce leakage of the drive signal.
Further, the manufacturing method may further include a photosensitive resin film forming step of forming a photosensitive resin film on the surface of the actuator substrate after performing the bonding step, and include a pattern forming step of forming a pattern through exposure and development of the photosensitive resin film before performing the conductive film forming step. Further, in the electrode forming step, a pattern of the conductive film can be formed by a lift-off method in which the photosensitive resin film is removed to form the above-mentioned pattern. In this way, it is possible to easily form an electrode pattern on the surface of the actuator substrate and the top surface of each partition wall. Hereinafter, specific description of the present invention is made with reference to the drawings.
The liquid jet head 1 includes the actuator substrate 2, a cover plate 3 bonded on the actuator substrate 2, and a nozzle plate 4 bonded to end surfaces of the actuator substrate 2 and the cover plate 3 at front ends FE thereof. The actuator substrate 2 has a configuration in which an upper substrate made of a piezoelectric material 10 is pasted on a lower substrate made of a low-permittivity material 9. A surface of the actuator substrate 2 on the cover plate 3 side includes the plurality of grooves 6 formed in parallel from the front end FE to some midpoint between the front end FE and a rear end RE, and includes a plurality of partition walls 7 separating the respective grooves 6.
As illustrated in
The cover plate 3 includes a liquid supply hole 16 through which liquid is supplied into the respective grooves 6. The nozzle plate 4 includes nozzles 8 which communicate to channels formed by the cover plate 3 and the grooves 6, and is bonded on the end surfaces of the actuator substrate 2 and the cover plate 3 at the front ends FE thereof. A drive signal generated by a drive circuit (not shown) is given to the drive electrodes 11L and 11R formed on both the side surfaces of the partition walls 7 through the wiring electrode (not shown) of the flexible substrate 5. The partition walls 7 are deformed according to the drive signal, to thereby change internal volumes of the grooves 6. In this way, liquid filling the channels is discharged from the nozzles 8 as liquid droplets.
Specifically, the top surfaces 13 of the partition walls 7 are bonded and fixed to the cover plate 3 at a region ranging from the front end FE to the liquid supply hole 16, and hence the partition walls 7 are deformed. The region to be deformed is referred to as a drive region DR. First, deformation of the piezoelectric material 10 as a substantially upper half of the partition wall 7 is described. When a drive voltage is applied to the piezoelectric material 10 of the partition wall 7 through the drive electrodes 11, the cross-section of the piezoelectric material 10 is deformed from a substantially rectangular shape into a substantially parallelogram shape. In this case, because the above-mentioned top surface 13 is fixed to the cover plate 3, under a state in which the top surface 13 remains fixed, the piezoelectric material 10 is deformed into a substantially parallelogram shape in which the top surface 13 serves as an upper side and a portion bonded to the low-permittivity material 9 serves as a lower side. Next, deformation of the low-permittivity material 9 as a substantially lower half of the partition wall 7 is described. Unlike the above-mentioned deformation of the piezoelectric material 10, piezoelectric deformation does not occur in the low-permittivity material 9, and hence the low-permittivity material 9 is deformed following the deformation of the piezoelectric material 10. That is, substantially the center of the partition wall 7 is fixed to the piezoelectric material 10, and hence is deformed following the deformation thereof. However, the lowermost portion of the partition wall 7 is fixed by the low-permittivity material 9, and hence is not deformed. With this, the upper half and the lower half of the partition wall 7 are deformed into a substantially parallelogram shape so as to be vertically symmetric about substantially the center of the partition wall, and hence the partition wall 7 is deformed into a “dogleg shape” in an overall view. The deformation of the partition wall 7 changes the internal volumes of the grooves 6, and as described above, liquid filling the channels is discharged from the nozzles 8 as liquid droplets.
Note that, the drive region DR is normally set to a region in which the depth of each of the grooves 6 is deep and the bottom surface 12 thereof is flat. Therefore, a “height of the partition wall in the drive region from the top surface to the bottom surface of the groove” refers to a height from the flat bottom surface 12 of each of the grooves 6 to the top surface 13, that is, the height h at which the partition wall 7 becomes highest. However, the drive region DR may sometimes extend to a region in which the bottom surface 12 of each of the grooves 6 is inclined, or formed into an arc shape with a trace of a shape of a dicing blade. In this case, the “height of the partition wall in the drive region from the bottom surface of the groove to the top surface” refers to the height excluding the region in which the bottom surface 12 of each of the grooves 6 is inclined and the region in which there is the trace of an arc shape, that is, the height h, at which the partition wall 7 becomes highest, from the flat bottom surface 12 of each of the grooves 6 to the top surface 13.
Next, the shapes of the partition walls 7 and the shapes of the drive electrodes 11 are described. As described in detail below, the drive electrodes 11 are formed by depositing a conductive material by oblique deposition. Thus, depending on the positions of the grooves 6 with respect to an evaporation source for the conductive material, widths in a depth direction of the drive electrodes 11 are unequal. As illustrated in
However, the piezoelectric material 10 exhibits an electrostrictive effect. In the drive region DR, the piezoelectric material 10 of each partition wall 7 is arranged at substantially half the height h above the bottom surface 12 of each groove 6. Thus, the point at substantially half the height h serves as a bending point, and hence can most efficiently develop bending deformation with respect to electric field energy. Further, the low-permittivity material 9 is interposed between one partition wall 7 and another adjacent partition wall 7. Thus, there is reduced a leakage signal which is generated when the drive signal given to the specific partition wall 7 leaks to the adjacent partition walls 7 due to capacitive coupling. As a result, the respective partition walls 7 have substantially the same deformation amount when an electric field is applied on the drive electrodes 11L and 11R of the partition walls 7, and an influence of drive of the adjacent partition walls 7 is reduced.
As described above, it is noted that the drive electrodes 11 of each partition wall 7 gradually change from the shape of the drive electrodes 11L and 11R illustrated in
Similarly, ranges, in which the drive electrodes on the other side of the actuator substrate 2 are formed on the low-permittivity material 9, gradually change from the other end to one end of the actuator substrate 2 (from the right direction to the left direction of the drawing sheet of
In
For example, when driving the discharge channel C1, the drive signal is given to the terminal Ta. Then, both the partition walls 71 and 72 are deformed so as to be symmetric about the discharge channel C1, and liquid filling the discharge channel C1 is discharged from the corresponding nozzle 8 of the nozzle plate 4 (not shown). The other discharge channels are driven similarly. In other words, it is possible to simultaneously discharge liquid droplets from the respective discharge channels C1 to C4 at the same timing.
In
Under any one of the above-mentioned drive conditions, deformation drive amounts of the partition walls 71 to 77 are equalized, and it is possible to reduce variations in liquid droplet discharge rate among the nozzles. In addition, the low-permittivity material 9 is interposed between one partition wall and another adjacent partition wall, and hence capacitive coupling is reduced. Consequently, the drive signal does not leak to the adjacent partition walls, and liquid discharge characteristics do not fluctuate.
In the first embodiment described above, a PZT ceramics is used as the piezoelectric material 10, and a machinable ceramics is used as the low-permittivity material 9. As the machinable ceramics, for example, Macerite, Macor, Photoveel, Shapal (which are all registered trademarks) may be used. The PZT ceramics has a relative permittivity of 2000 or more, a Young's modulus of 70 GPa to 80 GPa, which indicates rigidity, and a thermal conductivity of 1 W/m·K to 1.5 W/m·K. In contrast, the machinable ceramics may have a relative permittivity of 10 or less (for example, a paraelectric material having a relative permittivity of 5 to 6), and have a Young's modulus of from 50 MPa to less than 70 MPa, and a thermal conductivity of 1.5 W/m·K to 90 W/m·K. With this, it is possible to reduce leakage of the drive signal caused by capacitive coupling between the adjacent partition walls 7 to a negligible level. Further, it is possible to improve heat radiation characteristics. Further, substantially lower halves of the partition walls 7 and the bottom surfaces 12 are made of a low-rigidity material, and hence it is possible to improve deformation efficiency with respect to the electric field. Further, the thermal conductivity is increased, and hence it is possible to improve a heat radiation effect. In addition, though the shapes of the electrodes are different in every partition wall 7, the bending point of each partition wall 7 is situated near a boundary between the low-permittivity material 9 and the piezoelectric material 10, in other words, the bending point is situated at the uniform point, i.e., at substantially half the height h above the bottom surface 12 of the groove 6, and the deformation amount of the partition wall 7 with respect to the electric field is uniform. Consequently, it is possible to reduce variations in liquid droplet discharge rate.
Note that, the method of forming the drive electrodes 11 is not limited to the method of depositing the conductive material by oblique deposition, but may be a method of forming a conductive film by deposition, sputtering, plating, or the like and then patterning the conductive film. For the cover plate 3, a material having a coefficient of thermal expansion nearly equal to that of the piezoelectric material 10 can be used, and, for example, the same material as the piezoelectric material 10 can be used. Further, when an aluminum nitride or an aluminum nitride-based machinable ceramics is used as the low-permittivity material 9, the low-permittivity material 9 has the thermal conductivity that is one digit larger than that of the PZT ceramics, and hence it is possible to effectively cool the piezoelectric material 10 and the grooves 6. Further, when a resin material is used for the low-permittivity material 9 and the cover plate 3, the resin material allows a complex shape to be easily formed by a molding method, and hence it is possible to remarkably reduce manufacturing cost.
The liquid jet head 1 includes the actuator substrate 2, the cover plate 3 bonded on the actuator substrate 2, and the nozzle plate 4 bonded to the end surfaces of the actuator substrate 2 and the cover plate 3 at the front ends FE thereof. The actuator substrate 2 has a configuration in which the upper substrate made of the piezoelectric material 10 is pasted on the lower substrate made of the low-permittivity material 9. The surface of the actuator substrate 2 includes the plurality of grooves 6 formed from the front end FE up to the rear end RE, and includes the plurality of partition walls 7 separating the grooves 6. Each of the grooves 6 is made of the piezoelectric material 10 on the top surface 13 side situated above substantially half the height h from the bottom surface 12 of the groove 6 to the top surface 13 of the partition wall 7, and made of the low-permittivity material 9 on the bottom surface 12 side situated below substantially half the height h.
Both of the side surfaces of the partition wall 7 respectively include the drive electrodes 11 for driving the partition wall 7 so as to deform the same. Each of the drive electrodes 11 overlaps at least the entire side surface of the piezoelectric material 10 on the channel side. The drive electrodes 11 of each partition wall 7 are connected to the terminal electrodes 17 formed on the top surface 13 of the partition wall 7 at the vicinity of the rear end RE. That is, the drive electrode 11 formed on one side surface of the partition wall 7 is electrically connected to a terminal electrode 17a formed on the top surface 13 on the one side surface side, and the drive electrode 11 formed on the other side surface is electrically connected to a terminal electrode 17b formed on the top surface 13 on the other side surface side. The terminal electrodes 17a and 17b formed at the vicinity of the rear end RE are electrically connected to the wiring electrode (not shown) of the flexible substrate 5 bonded to the top surface at the rear end RE of the actuator substrate 2.
The cover plate 3 includes the liquid supply hole 16 through which liquid is supplied into the grooves 6, and the cover plate 3 is bonded to the surface of the actuator substrate 2 so as to cover the surface from the front end FE to before the rear end RE. The respective grooves 6 are sealed by a sealing material (not shown) on the rear end RE side with respect to the liquid supply hole 16. With this configuration, the liquid supplied from the liquid supply hole 16 into the grooves 6 does not flow out to the rear end RE side through the grooves 6. The nozzle plate 4 includes the nozzles 8 which communicate to the channels formed by the cover plate 3 and the grooves 6, and is bonded on the end surface at the front end FE of the cover plate 3.
In this way, the grooves 6 are formed straight in parallel with one another from the front end FE to the rear end RE, and hence it is possible to eliminate slanted portions of the bottom surfaces 12 of the grooves 6, and to achieve downsizing of the actuator substrate 2. Here, the drive region DR is situated on the front end FE side with respect to the liquid supply hole 16 of the cover plate 3. Also in this embodiment, the adjacent partition walls 7 are fixed through the low-permittivity material 9, and hence a leakage electric field caused by capacitive coupling is reduced, with the result that the partition walls 7 can be driven without being influenced by the drive signal supplied to the adjacent partition walls. Further, in all of the partition walls 7 in the drive region DR, the drive electrodes 11 overlap at least the entire side surfaces made of the piezoelectric material 10, and hence the respective partition walls 7 have substantially the same deformation amount at the time of driving. As a result, discharge rate of liquid droplets discharged from the nozzles 8 at the time of driving is equalized in the respective channels.
It is noted that there may be adopted such a configuration that the cover plate 3 is bonded so as to cover the plurality of grooves 6 of the actuator substrate 2 without providing the liquid supply hole 16 in the cover plate 3, and a manifold for liquid supply is placed at the rear end RE, to thereby supply liquid into the respective grooves 6 from the rear end RE side. Materials and the like used as the piezoelectric material 10 and the low-permittivity material 9 are similar to those of the first embodiment, and hence description thereof is omitted.
As described above, it is unnecessary to pattern the drive electrodes 11 on the upper half of the partition wall 7 with high accuracy, and hence the conductive film forming step of forming the conductive film 20 by depositing the conductive material, and the electrode forming step of forming the pattern of the conductive film 20 can be performed by an extremely simple method.
A depositing device includes an evaporation source 18 and a holder 22 which are accommodated inside a chamber (not shown). The holder 22 holds the actuator substrate 2 on the evaporation source 18 side. The holder 22 holds the actuator substrate 2 so as to be able to rotate the same about a rotation axis O1, and is configured to be rotatable about a perpendicular direction of the evaporation source 18 as a rotation axis O2.
First, the actuator substrate 2 is set on the holder 22 (at a position on the left side of
Next, the actuator substrate 2 is rotated about the rotation axis O1 by 180°, and the actuator substrate 2 is set on the holder 22 (at a position on the right side of
Here, a general condition of the oblique deposition is as follows, the oblique deposition being performed in such a way that the conductive film 20 is deposited at least on the entire side surfaces of the partition walls 7 made of the piezoelectric material 10 and the conductive material is not deposited on the bottom surfaces 12 of the grooves 6. A condition for performing deposition from the top surface of each partition wall 7 to ½ of the height of the partition wall 7 is expressed by the following equation:
tan(θ1)=2w/h (1),
where the width of the groove 6 is w, the height of the partition wall 7 (depth of the groove 6) is h, the height of the boundary between the piezoelectric material 10 and the low-permittivity material 9 of the partition wall 7 is h/2, and the oblique deposition angle (inclination angle) is θ.
A condition for performing deposition on the entire side surfaces of each partition wall 7 and for not performing deposition on the bottom surface 12 of each groove 6 is expressed by the following equation:
tan(θ2)=w/h (2).
Therefore, the actuator substrate 2 only needs to be placed at a position at which the oblique deposition angle θ satisfies the following expression (3) with respect to the evaporation source 18.
θ2<θ<1=tan−1(w/h)<θ<tan−1(2w/h) (3)
For example, when the width w of the groove 6 is 75 μm and the height h of the partition wall 7 is 360 μm, the oblique deposition angle θ ranges from 12° to 23°. For example, when Zh expressed in
In the liquid jet head 1 manufactured as described above, even if the drive electrodes 11 vary in width in the direction of the bottom surface 12 of the groove 6, the piezoelectric material 10 exhibiting the electrostrictive effect is the same in every partition wall 7. Thus, the respective partition walls 7 have a uniform deformation drive amount, with the result that the variations in liquid droplet discharge rate among the channels are reduced. Further, the low-permittivity material 9 is interposed between one partition wall 7 and another adjacent partition wall 7, and hence capacitive coupling between the partition walls 7 is reduced, with the result that it is possible to prevent such a situation that the drive signal leaks to the adjacent partition wall to fluctuate liquid discharge characteristics of the adjacent nozzle. In addition, it is possible to electrically separate the drive electrodes 11 formed on both the side surfaces of each groove 6 in the oblique deposition step, and hence a step of cutting the electrodes deposited on the bottom surfaces 12 of the grooves 6 is unnecessary, which allows extremely easy formation of the drive electrodes 11. Further, the deposition angle θ at the time of oblique deposition is remarkably moderated so that a depositable range is enlarged, and hence it is possible to improve the productivity.
Next,
As described above, the drive electrodes 11 are patterned by the lift-off method after being deposited by the oblique deposition, and hence it is possible to easily form an electrode pattern on both of the side surfaces of each partition wall 7 and the surface of the actuator substrate 2 by a simple step. In addition, even if the drive electrodes 11 vary in width in the depth direction of the grooves 6, the piezoelectric material 10 exhibiting the electrostrictive effect is the same in every partition wall 7, and hence the partition walls 7 exhibit a uniform deformation drive amount. Further, the low-permittivity material 9 is used, and hence the drive signal does not leak to the adjacent partition wall 7.
It is noted that the pattern forming step for the photosensitive resin film 21 may be performed prior to the groove forming step, and the plurality of grooves 6 may be formed along the pattern of the photosensitive resin film 21. Further, the oblique deposition step for the conductive material is not limited to the methods illustrated in
The liquid jet apparatus 30 includes a moving mechanism 43 for reciprocating liquid jet heads 1 and 1′ according to the present invention described above, liquid supply tubes 33 and 33′ for supplying liquid to the liquid jet heads 1 and 1′, and liquid tanks 31 and 31′ for supplying liquid to the liquid supply tubes 33 and 33′. Each of the liquid jet heads 1 and 1′ is formed of the liquid jet head 1 according to the present invention. That is, each of the liquid j et heads 1 and 1′ includes: an actuator substrate including a plurality of grooves aligned parallelly in a surface thereof, and partition walls separating the adjacent grooves; a cover plate bonded onto the surface of the actuator substrate, for covering the grooves; and a nozzle plate including nozzles communicating to the grooves, the nozzle plate being bonded onto an end surface of the actuator substrate. The actuator substrate includes a drive region for driving the partition walls so as to deform the same, and for causing liquid filling the grooves to jet from the nozzles. Each partition wall in the drive region is made of a piezoelectric material on a top surface side situated above substantially half a height from a bottom surface of the groove to the top surface of the partition wall, and made of a low-permittivity material, which is lower in permittivity than the piezoelectric material, on the bottom surface side situated below substantially half the height.
A specific description is made in the as follows. The liquid jet apparatus 30 includes a pair of conveying means 41 and 42 for conveying a recording medium 34 such as paper in a main scanning direction, the liquid jet heads 1 and 1′ for discharging liquid toward the recording medium 34, pumps 32 and 32′ for pressing liquid stored in the liquid tanks 31 and 31′ into the liquid supply tubes 33 and 33′ for supply, and the moving mechanism 43 for causing the liquid jet head 1 to scan in a sub-scanning direction which is orthogonal to the main scanning direction.
Each of the pair of conveying means 41 and 42 includes a grid roller and a pinch roller which extend in the sub-scanning direction and which rotate with roller surfaces thereof being in contact with each other. A motor (not shown) axially rotates the grid rollers and the pinch rollers to convey, in the main scanning direction, the recording medium 34 sandwiched therebetween. The moving mechanism 43 includes a pair of guide rails 36 and 37 which extend in the sub-scanning direction, a carriage unit 38 which is slidable along the pair of guide rails 36 and 37, an endless belt 39 which is coupled to the carriage unit 38 for moving the carriage unit 38 in the sub-scanning direction, and a motor 40 for rotating the endless belt 39 via a pulley (not shown).
The carriage unit 38 has the plurality of liquid jet heads 1 and 1′ mounted thereon for discharging, for example, four kinds of liquid droplets: yellow; magenta; cyan; and black. The liquid tanks 31 and 31′ store liquid of corresponding colors, and supply the liquid via the pumps 32 and 32′ and the liquid supply tubes 33 and 33′ to the liquid jet heads 1 and 1′. The respective liquid jet heads 1 and 1′ discharge liquid droplets of the respective colors according to a drive signal. By controlling discharge timing of liquid from the liquid jet heads 1 and 1′, rotation of the motor 40 for driving the carriage unit 38, and conveying speed of the recording medium 34, an arbitrary pattern may be recorded on the recording medium 34.
With this configuration, the liquid discharge characteristics of the liquid jet head 1 are equalized in the respective channels. In addition, the drive signal for driving the channels does not leak to the adjacent channels, and hence high-quality recording of liquid can be performed on the recording medium. Further, it is unnecessary to manufacture the liquid jet head 1 through complicated steps, which may simplify the manufacturing steps and may contribute to cost reduction of the apparatus.
Number | Date | Country | Kind |
---|---|---|---|
2010-121965 | May 2010 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
5193256 | Ochiai et al. | Mar 1993 | A |
5311218 | Ochiai et al. | May 1994 | A |
5311219 | Ochiai et al. | May 1994 | A |
5351375 | Ochiai et al. | Oct 1994 | A |
5560090 | Komakine et al. | Oct 1996 | A |
5631680 | Sugahara | May 1997 | A |
6390609 | Shigemura et al. | May 2002 | B1 |
20090109263 | Koseki | Apr 2009 | A1 |
Number | Date | Country |
---|---|---|
0522814 | Jan 1993 | EP |
05318741 | Dec 1993 | JP |
2000108361 | Apr 2000 | JP |
Number | Date | Country | |
---|---|---|---|
20110292135 A1 | Dec 2011 | US |