Piezoelectric ink jet head having electrodes connected by anisotropic adhesive

Abstract

An ink-jet head comprising a plurality of sidewalls each imparting a pressure pulse to an ink pressurizing cell by means of shear mode deformation, and a front wall having a plurality of orifices. The ink in the ink pressurizing cells is ejected from the orifices. Each sidewall comprises a first wall section, a first electrode disposed thereon, an anisotropic adhesive disposed thereon, a second electrode disposed thereon, and a second wall section disposed thereon. Width of the first electrode is narrower than width of the first wall section, and the upper surface of the first wall section has first side areas which are not covered by the first electrode. Width of the second electrode is narrower than width of the second wall section, and the lower surface of the second wall section has second side areas which are not covered by the second electrode. The anisotropic adhesive has conductivity only in a direction perpendicular to the upper surface of the first wall section and the lower surface of the second wall section, and the anisotropic adhesive covers the first and second electrodes so that the first and second electrodes are not exposed to the ink in the ink pressurizing cells.

Description

BACKGROUND OF THE INVENTION

The present invention relates to an ink-jet head for ejecting ink droplets from each ink pressurizing cell and, more particularly, to a sidewall of the ink pressurizing cell for imparting a pressure pulse to the ink pressurizing cell by means of shear mode deformation. The present invention also relates to a manufacturing method of the ink-jet head.

In general, conventional ink-jet heads used in ink-jet recording devices utilized thermal jet systems whereby air bubbles were generated in the ink pressurizing cells by heating elements to thereby pressurize the ink in the ink pressurizing cells (refer to Japanese Patent Kokoku Publication No. 59914/1986). However, in this case, since the ink is heated by the heating elements, the ink is impaired by the heat and printing quality is reduced. Also, since air bubble generation cannot be stabilized, clogging of the orifices occurs, air bubbles enter an ink flow path, and thermal stress produces cracks in the composing parts of the ink-jet head.

An alternative ink-jet head utilizing piezoelectric material is disclosed in, for example, U.S. Pat. Nos. 5,227,813 and 5,235,352. FIG. 1 shows a cross-sectional view of a main part of the ink-jet head disclosed in the above-mentioned publications. As shown in FIG. 1, the ink-jet head comprises a plurality of ink pressurizing cells or channels 14a, 14b, . . . defined by a bottom part 1, sidewalls 2, a top part 3 and a front wall having a plurality of orifices 15a, 15b, . . . .

The bottom part 1 is formed from a lower part of a piezoelectric material base 11 polarized in an array direction P.

Each sidewall 2 comprises a projecting wall section 11a (or 11b, . . . ) which is composed of an upper part of the piezoelectric material base 11, and an intermediate wall section 12a (or 12b, . . . ) made from piezoelectric material polarized in the same direction P as that of the piezoelectric material base 11 and disposed on the projecting wall section 11a (or 11b, . . . ). Electrodes 16a, 16b, . . . are respectively formed at the ends of the projecting wall sections 11a, 11b, . . . . Electrodes 17a, 17b, . . . and electrodes 18a, 18b, . . . are formed at the respective ends of the intermediate wall sections 12a, 12b, . . . . Conductive adhesives 20a, 20b, . . . are disposed between the electrodes 16a, 16b, . . . and the electrodes 17a, 17b, . . . . The intermediate wall sections 12a, 12b, . . . are secured to the projecting wall sections 11a, 11b, . . . of the piezoelectric material base 11 by the conductive adhesive 20a, 20b, . . . .

The top part 3 comprises a top plate 13 and a common electrode 19 formed on a lower surface of the top plate 13. Conductive adhesives 21a, 21b, . . . are disposed between the common electrode 19 and the electrodes 18a, 18b, . . . of the intermediate wall sections 12a, 12b, . . . . The top plate 13 is secured to the intermediate wall sections 12a, 12b, . . . by the conductive adhesive 21a, 21b, . . . .

When the common electrode 19 is grounded, a positive voltage +V is applied to the electrode 16a and a negative voltage -V is applied to the electrode 16b, an electric field is generated through the piezoelectric element base 11 from the projecting wall section 11a to the projecting wall section 11b in the direction shown by a broken line A. Also, an electric field is generated in the intermediate wall section 12a from the electrode 17a toward the common electrode 19 in the direction shown by a broken line B. Also, an electric field is generated in the intermediate wall section 12b from the common electrode 19 toward the electrode 17b in the direction shown by a broken line C. As a result, shear mode deformation (shown by broken lines 60 in FIG. 1) is generated in respectively opposite directions in the projecting wall sections 11a, 11b and the intermediate wall section 12a, 12b. The ink in the ink pressurizing cell 14a is then pressurized, and ink droplets are ejected from the orifice 15a.

In this case, leak current in the direction D flows in the ink pressurizing cell 14a from the electrode 20a to the electrode 20b, the amount of pressurization in the ink pressurizing cell 14a by shear mode deformation is reduced, and an adequate amount of ink droplets cannot be ejected from the orifice 15a. In addition, electrochemical reaction caused by the leak current produces corrosion in the electrodes 16a, 16b and 17a, 17b and the ink quality can be impaired.

As indicated by the double dotted line in the ink pressurizing cell 14b, a method can be considered whereby parts of the piezoelectric material base 11 and the intermediate wall sections 12b, 12c contacting the ink are covered with an insulated coating layer 24, thereby insulating an interior of the ink pressurizing cell 14b from the electrodes 16b, 16c and 17b, 17c.

However, the width of the ink pressurizing cell is set very narrow at 30-100�.mu.m!, making uniform and complete covering by the insulated coating layer 24 difficult. Also, since burrs are easily produced in the end faces of the electrodes 16b, 16c and 17b, 17c when forming the grooves (ink pressurizing cells), pinholes are produced in the insulated coating layer 24, preventing insulation of the ink pressurizing cell 14b from the electrodes 16b, 16c and 17b, 17c.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an ink-jet head and a manufacturing method thereof to enable an adequate amount of ink droplets to be ejected from the orifices.

According to one aspect of the present invention, an ink-jet head comprises: a plurality of ink pressurizing cells (14a), each containing ink; a plurality of sidewalls (2, 4) each forming a longitudinal wall of the ink pressurizing cell (14a) and each imparting a pressure pulse to the ink pressurizing cell (14a) by means of shear mode deformation of the sidewalls (2, 4); a bottom wall (1) forming a lateral wall of the plurality of ink pressurizing cells (14a); a top wall (13, 5) forming a lateral wall of the plurality of ink pressurizing cells (14a); and a front wall (15) forming a longitudinal wall of the ink pressurizing cells (14a) and having a plurality of orifices (15a) each of which passes through the front wall (15), the ink in the ink pressurizing cells (14a) being ejected from the orifices (15a) when the pressure pulse is imparted to the ink pressurizing cell (14a). Each of the sidewalls (2, 4) comprises: a first wall section (11a) made from piezoelectric material; a first electrode (16a) disposed on an upper surface of the first wall section (11a), width (L.sub.1) of the first electrode being narrower than width (L.sub.2) of the first wall section (11a), and the upper surface of the first wall section (11a) having a first side area (E.sub.1) which is not covered by the first electrode (16a); an anisotropic adhesive (31) disposed on the first electrode (16a) and the first side area (E.sub.1) of the first wall section (11a); a second electrode (17a, 52a) disposed on the anisotropic adhesive (31); and a second wall section (12a, 51a) made from piezoelectric material and disposed on the second electrode (17a, 52a), width (L.sub.1) of the second electrode (17a, 52a) being narrower than width (L.sub.2) of the second wall section (12a, 51a), and the lower surface of the second wall section (12a, 51a) having a second side area (E.sub.2) which is not covered by the second electrode (17a, 52a). The anisotropic adhesive (31) has conductivity only in a direction perpendicular to the upper surface of the first wall section (11a) and the lower surface of the second wall section (12a, 52a), and the anisotropic adhesive (31) covers the first and second electrodes (16a, 17a, 52a) so that the first and second electrodes (16a, 17a, 52a) are not exposed to the ink in the ink pressurizing cells (14a).

The second wall section (12a, 52a) is polarized in an array direction (P) in which the plurality of ink pressurizing cells (14a, 14b) are arranged. The first wall section (11a) is polarized in an array direction (P) in which the plurality of ink pressurizing cells (14a, 14b) are arranged.

Each sidewall (1) may comprise a third electrode (18a) disposed on an upper surface of the second wall section (12a); a common electrode (19) disposed on a lower surface of the top wall (13); and a conductive adhesive (21a) for bonding the third electrode (18a) with the common electrode (19).

The bottom wall (1) and the plurality of first wall sections (11a, 11b) forms an one-piece construction (11), and the top wall (51) is made from piezoelectric material, and the top wall (51) and the plurality of second wall sections (51a, 51b) forms an one-piece construction.

According to another aspect of the invention, each of the sidewalls (2) comprises: a first wall section (11a) made from piezoelectric material; a first electrode (16a) disposed on an upper surface of the first wall section (11a), width (L.sub.1) of the first electrode being narrower than width (L.sub.2) of the first wall section (11a), and the upper surface of the first wall section (11a) having a first side area (E.sub.1) which is not covered by the first electrode (16a); an insulating adhesive (55) disposed on the first electrode (16a) and the first side area (E.sub.1) on the upper surface of the first wall section (11a); a second electrode (17a) disposed on the insulating adhesive (55); a second wall section (12a) made from piezoelectric material and disposed on the second electrode (17a), width (L.sub.1) of the second electrode (17a) being narrower than width (L.sub.2) of the second wall section (12a), and the lower surface of the second wall section (12a) having a second side area (E.sub.2) which is not covered by the second electrode (17a). The ink-jet head further comprises conductive members (56) disposed outside of the ink pressurizing cells (14a) and electrically connecting the first electrode (16a) with the second electrode (17a), and the insulating adhesive (55) covers the first and second electrodes (16a, 17a) so that the first and second electrodes (16a, 17a) are not exposed to the ink in the ink pressurizing cells (14a).

Further, a manufacturing method of an ink-jet head according to the present invention comprises the steps of: forming a plurality of stripe patterns of first electrodes (16a, 16b) at predetermined intervals on an upper surface of a first piezoelectric material plate; forming a plurality of stripe-shaped second electrodes (17a, 17b) at predetermined intervals on a lower surface of a second piezoelectric material plate; forming a third electrode (18) on an upper surface of the second piezoelectric material plate; applying an anisotropic adhesive (31) to at least one of the upper surface of the first electrodes (16a, 16b) and the lower surface of the second electrodes (17a, 17b), the anisotropic adhesive (31) having conductivity only in a direction perpendicular to the upper surfaces of the first electrodes (16a, 16b) and the lower surfaces of the second electrodes (17a, 17b); placing the first piezoelectric material plate on the second piezoelectric material plate in such a way that the first electrodes (16a, 16b) and the second electrodes (17a, 17b) face each other across the anisotropic adhesive (31); cutting a plurality of grooves between the first electrodes (16a, 16b) as well as between the second electrodes (17a, 17b) to form a plurality of sidewalls (2) in such a way that the grooves penetrate through the third electrode (18), the second piezoelectric material plate and the anisotropic adhesive (31) and reach a middle of the first piezoelectric material plate and in such a way that width (L.sub.1) of the first electrode (16a, 16a) and the second electrode (17a, 17b) are narrower than width (L.sub.2) of the sidewall (2) and the first and second electrodes (16a, 16b, 17a, 17b) are covered by the anisotropic adhesive (31) not so as to be exposed to the ink in the ink pressurizing cells (14a, 14b); applying a conductive adhesive (21a, 21b) to an upper surface of the third electrode (18a, 18b); and placing a top plate (13) having a common electrode (19) on the conductive adhesive (21a, 21b) in such a way that the common electrode (19) faces the third electrode (18a, 18b) across the conductive adhesive (21a, 21b).

Another manufacturing method of an ink-jet head according to the present invention comprises the steps of: forming a plurality of stripe patterns of first electrodes (16a, 16b) at predetermined intervals on an upper surface of a first piezoelectric material plate; forming a plurality of stripe patterns of second electrodes (17a, 17b) at predetermined intervals on a lower surface of a second piezoelectric material plate; forming a third electrode (18) on an upper surface of the second piezoelectric material plate; applying an insulating adhesive (55) to at least one of the upper surface of the first electrodes (16a, 16b) and the lower surface of the second electrodes (17a, 17b); placing the first piezoelectric material plate on the second piezoelectric material plate in such a way that the first electrodes (16a, 16b) and the second electrodes (17a, 17b) face each other across the insulating adhesive (55); cutting a plurality of grooves between the first electrodes (16a, 16b) as well as between the second electrodes (17a, 17b) to form a plurality of sidewalls (2) in such a way that the grooves penetrate through the third electrode (18), the second piezoelectric material plate and the insulating adhesive (55) and reach a middle of the first piezoelectric material plate and in such a way that width (L.sub.1) of the first electrode (16a, 16a) and the second electrode (17a, 17b) are narrower than width (L.sub.2) of the sidewall (2) and the first and second electrodes (16a, 16b, 17a, 17b) are covered by the insulating adhesive (31) not so as to be exposed to the ink in the ink pressurizing cells (14a, 14b); applying a conductive adhesive (21a, 21b) to an upper surface of the third electrode (18a, 18b); placing a top plate (13) having a common electrode (19) on the conductive adhesive (21a, 21b) in such a way that the common electrode (19) faces the third electrode (18a, 18b) across the conductive adhesive (21a, 21b); and electrically connecting the first electrodes (16a, 16b) and the second electrodes (17a, 17b) in the same sidewall (2) by conductive wires.

BRIEF DESCRIPTION OF THE INVENTION

FIG. 1 is a cross-sectional view showing an essential part of a conventional ink-jet head;

FIG. 2 is a cross-sectional view showing an essential part of an ink-jet head according to a first embodiment of the present invention;

FIG. 3 is a cross-sectional view taken along the line III--III of FIG. 2;

FIGS. 4A-4E are cross-sectional views showing the manufacturing process of the ink-jet head of FIG. 2;

FIGS. 5A and 5B are plan views showing the manufacturing process corresponding to FIGS. 4A and 4B;

FIGS. 6A-6E are cross-sectional views showing another manufacturing process of the ink-jet head of FIG. 2;

FIGS. 7A and 7B are plan views showing the manufacturing process corresponding to FIGS. 6A and 6B;

FIG. 8 is a cross-sectional view showing an essential part of an ink-jet head according to a second embodiment of the present invention; and

FIG. 9 is a cross-sectional view showing an ink-jet head according to a third embodiment of the present invention.

FIG. 10 is a modified view of the embodiment illustrated in FIG. 3.

PREFERRED EMBODIMENTS OF THE INVENTION

Preferred embodiments of the present invention will be described with reference to the attached drawings.

First Embodiment

FIG. 2 shows a cross-sectional view of a main part of an ink-jet head according to a first embodiment of the present invention, and FIG. 3 shows a cross-sectional view taken along the line III--III of FIG. 2.

Referring to FIG. 2 and FIG. 3, the ink-jet head of the first embodiment comprises a plurality of ink pressurizing cells or channels 14a, 14b, . . . defined by a bottom part 1, sidewalls 2, a top part 3 and a front wall 15 having a plurality of orifices 15a, 15b, . . . .

The bottom part 1 is formed from a lower part of a piezoelectric material base 11 polarized in an array direction P (X-axis direction) extending along a row of ink pressurizing cells 14a, 14b, . . . . In FIG. 2, the piezoelectric material base 11 is comb-shaped.

Each sidewall 2 comprises a projecting wall section 11a(or 11b, . . . ) which is composed of an upper part of the piezoelectric material base 11, and an intermediate wall section 12a (or 12b, . . . ) made from piezoelectric material polarized in the same array direction P as that of the piezoelectric material base 11 and disposed on the projecting wall section 11a (or 11b, . . . ).

Electrode 16a, 16b, . . . are respectively disposed on upper surfaces of the projecting wall sections 11a, 11b, . . . . Width L.sub.1 of each electrode 16a, 16b, . . . is narrower than width L.sub.2 of each wall section 11a, 11b, . . . and the upper surfaces of the projecting wall sections 11a, 11b, . . . have first side areas E.sub.1 which are not covered by the electrodes 16a, 16b, . . . .

Electrodes 17a, 17b, . . . are respectively disposed on lower surfaces of the intermediate wall sections 12a, 12b, . . . Width L.sub.1 of each electrode 17a, 17b, . . . is narrower than width L.sub.2 of each intermediate wall section 12a, 12b, . . . , and the lower surfaces of the intermediate wall sections 12a, 12b, . . . have second side areas E.sub.2 which are not covered by the electrodes 17a, 17b, . . . .

Anisotropic adhesives 31 are respectively disposed on the electrodes 16a, 16b, . . . and the first side areas E.sub.1 of the projecting wall sections 11a, 11b, . . . The anisotropic adhesives 31 are conductive only in a direction (Z-axis direction) perpendicular to the upper surfaces of the projecting wall sections 11a, 11b, . . . and the lower surfaces of the second wall sections 12a, 12b, . . . , and not conductive in X-axis and Y-axis directions (horizontal directions). The anisotropic adhesives 31 cover the electrodes 16a, 16b, 17a, 17b so that the electrodes 16a, 16b, 17a, 17b are not exposed to the ink in the ink pressurizing cells 14a, 14b, . . . by closing parts 31a and 31b. The anisotropic adhesive 31 is, for example, an anisotropic epoxy adhesive.

Electrodes 18a, 18b, . . . are disposed on upper surfaces of the intermediate wall sections 12a, 12b, . . . .

The top part 3 comprises a top plate 13 and a common electrode 19 formed on a lower surface of the top plate 13. Conductive adhesives 21a, 21b, . . . are disposed between the common electrode 19 and the electrodes 18a, 18b, . . . of the intermediate wall sections 12a, 12b. . . . The top plate 13 is secured to the intermediate wall sections 12a, 12b, . . . by the conductive adhesive 21a, 21b, . . . .

When the common electrode 19 is grounded, a positive voltage +V is applied to the electrode 16a and a negative voltage -V is applied to the electrode 16b by a driver circuit 57. An electric field is thus generated through the piezoelectric element base 11 from the projecting wall section 11a to the projecting wall section 11b in the direction shown by a broken line A. Also, an electric field is generated in the intermediate wall section 12a from the electrode 17a toward the common electrode 19 in the direction shown by a broken line B. Also, an electric field is generated in the intermediate wall section 12b from the common electrode 19 toward the electrode 17b in the direction shown by a broken line C. As a result, shear mode deformation (shown by broken lines 60 in FIG. 1) is generated in respectively opposite directions in the projecting wall sections 11a, 11b and the intermediate wall section 12a, 12b. The ink in the ink pressurizing cell 14ais then pressurized, and ink droplets are ejected from the orifice 15a. It is also possible to modify this arrangement by coupling the driver circuit to the electrodes 17a and 17b, such as shown in FIG. 10 (but with only the coupling to electrode 17a being shown).

Since the anisotropic adhesive 31 is not conductive in X-axis direction, the ink pressurizing cell 14a is electrically insulated from the electrodes 16a, 16b and 17a, 17b. Consequently, leak current flow in the ink pressurizing cells 14a, 14b, . . . can be decreased.

Also, as indicated by the double dotted chain line in FIG. 2, an insulated coating layer 33 for covering the interior of the ink pressurizing cells 14a, 14b, . . . may be provided. In this case, insulating performance is increased.

A manufacturing process of the ink-jet head of FIG. 2 will be described below. FIGS. 4A-4E are cross-sectional views showing the manufacturing process of the ink-jet head of FIG. 2, and FIGS. 5A and 5B are plan views each corresponding to FIGS. 4A and 4B.

First, as shown in FIG. 4A and FIG. 5A, a piezoelectric material plate 11' is prepared, and a thin metal film is formed on the upper surface of the piezoelectric material plate 11' by a thin film method. The thin metal film is etched so that a plurality of stripe patterns of first electrodes 16a, 16b, . . . are formed on an upper surface of the first piezoelectric material plate 11'. As shown in FIG. 5A, width L.sub.1 of each first electrode 16a, 16b, . . . is in the range of 60 to 75�.mu.m!.

Next, as shown in FIG. 4B and FIG. 5B, another piezoelectric material plate 12 is prepared, and a thin metal films are formed on both surfaces of the piezoelectric material plate 12 by a thin film method. The thin metal film on the lower surface of the piezoelectric material plate 12 is etched so that a plurality of stripe patterns of the second electrodes 17a, 17b, . . . are formed on the lower surface of the piezoelectric material plate 12. As shown in FIG. 5B, width L.sub.1 of each second electrode 17a, 17b, . . . is in the range of 60 to 75 �.mu.m!.

Next, an anisotropic adhesive 31 is applied to at least one of the upper surface of the first electrodes 16a, 16b, . . . and the lower surface of the second electrodes 17a, 17, . . . The anisotropic adhesive 31 has conductivity only in a direction perpendicular to the upper surfaces of the first electrodes 16a, 16b, . . . and the lower surfaces of the second electrodes 17a, 17b, . . . Next, as shown in FIG. 4C, the piezoelectric material plate 12 is placed on the piezoelectric material plate 11' so that the first electrodes 16a, 16b, . . . and the second electrodes 17a, 17b, . . . face each other across the anisotropic adhesive 31. Pressure is applied to the piezoelectric material plate 11'and the second piezoelectric material plate 12, thereby filling the portions between the piezoelectric material plate 11' and the piezoelectric material plate 12 not occupied by the electrodes 16a, 16b and 17a, 17b with the anisotropic adhesive 31.

Next, as shown in FIG. 4D, a plurality of grooves 14' are formed between the second electrodes 17a and 17b as well as between the first electrode 16a and 16b. The grooves 14' penetrate through the third electrode 18, the piezoelectric material plate 12 and the anisotropic adhesive 31, and reach a middle of the piezoelectric material plate 11', thereby forming a comb-shaped piezoelectric material base 11. As a result of forming grooves 14' by cutting, the closing parts 31a and 31b are formed at the respective side edges of the electrodes 16a, 16b and 17a, 17b to separate the electrodes 16a, 16b and 17a, 17b from the ink pressurizing cell 14a, 14b.

Next, as shown in FIG. 4E, conductive adhesives 21a, 21b, . . . are applied to an upper surface of the third electrodes 18a, 18b, . . . , and a top plate 13 having a common electrode 19 is placed on the conductive adhesive 21a, 21b, . . . in such a way that the common electrode 19 faces the third electrode 18a, 18b, . . . across the conductive adhesives 21a, 21b, . . . .

Since the anisotropic adhesive 31 is conductive in the bonding direction (Z-axis direction and reverse direction), the electrodes can be mutually connected electrically. In this case, since the electrode patterns are formed by either a thick film method or a thin film method not based on patterning, cost can be reduced.

Another manufacturing process of the ink-jet head of FIG. 2 will be described below. FIGS. 6A-6E are cross-sectional views showing the manufacturing process of the ink-jet head of FIG. 2, and FIGS. 7A and 7B are plan views each corresponding to FIGS. 6A and 6B.

First, as shown in FIG. 6A and FIG. 7A, a piezoelectric material plate 11' is prepared, and a metal film is formed on the upper surface of the piezoelectric material plate 11' by either a thick film method such as silkscreen method or a thin film method not based on patterning such as plating. The metal film is etched by for example an excimer laser so that a plurality of stripe patterns of electrodes 16a, 16b and 16' are formed on an upper surface of the piezoelectric material plate 11'. In FIG. 7A, width W between the electrode 16a and 16' is in the range of 10 to 20 �.mu.m!.

Next, as shown in FIG. 6B and FIG. 7B, another piezoelectric material plate 12 is prepared, and a metal films are formed on both surfaces of the piezoelectric material plate 12 by either a thick film method such as silkscreen method or a thin film method not based on patterning such as plating. The metal film on the lower surface of the piezoelectric material plate 12 is etched by for example an excimer laser so that a plurality of stripe patterns of the second electrodes 17a, 17b, . . . are formed on the lower surface of the second piezoelectric material plate 12. A shown in FIG. 7B, width W between the electrodes 17a and 17' is in the range of 10 to 20 �.mu.m!.

Next, an anisotropic adhesive 31 is applied to at least one of the upper surface of the first electrodes 16a, 16b, . . . and the lower surface of the second electrodes 17a, 17b, . . . The anisotropic adhesive 31 has conductivity only in a direction perpendicular to the upper surfaces of the first electrodes 16a, 16b, . . . and the lower surfaces of the second electrodes 17a, 17b, . . . Next, as shown in FIG. 6C, the piezoelectric material plate 12 is placed on the piezoelectric material plate 11' so that the first electrodes 16a, 16b, . . . and the second electrodes 17a, 17b, . . . face each other across the anisotropic adhesive 31.

Next, as shown in FIG. 6D, a plurality of grooves 14' are formed in such a way that the grooves 14' penetrate through the third electrode 18, the second piezoelectric material plate 12, the every other second electrodes 17', the anisotropic adhesive 31 and the every other first electrodes 16', and reach a middle of the first piezoelectric material plate 11', thereby forming a comb-shaped piezoelectric material base 11. As a result of forming grooves 14' by cutting, the closing parts 31a and 31b are formed at the respective side edges of the electrodes 16a, 16b and 17a, 17b to separate the electrodes 16a, 16b and 17a, 17b from the ink pressurizing cells 14a, 14b.

Next, as shown in FIG. 6E, a conductive adhesive 21a, 21b, . . . is applied to an upper surface of the third electrodes 18a, 18b, . . . , and a top plate 13 having a common electrode 19 is placed on the conductive adhesives 21a, 21b, . . . in such a way that the common electrode 19 faces the third electrodes 18a, 18b, . . . across the conductive adhesives 21a, 21b, . . . .

In this case, since the electrode patterns are formed by either a thick film method or a thin film method not based on patterning, cost can be reduced.

Second Embodiment

FIG. 8 is a cross-sectional view showing a main part of an ink-jet head according to a second embodiment of the present invention.

Referring to FIG. 8, the ink-jet head of the second embodiment comprises a plurality of ink pressurizing cells 14a, 14b defined by a bottom part 1, sidewalls 4, a top part 5 and a front wall 15 having a plurality of orifices 15a, 15b, . . . .

The bottom part 1 is formed from a lower part of a piezoelectric material base 11 polarized in an array direction P (X-axis direction) extending along a row of ink pressurizing cells 14a, 14b, . . . . In FIG. 8, the piezoelectric material base 11 is comb-shaped.

The top part 5 is formed from an upper part of a piezoelectric material plate 51 polarized in an array direction P (X-axis direction) extending along a row of ink pressurizing cells 14a, 14b. In FIG. 8, the piezoelectric material base 51 is also comb-shaped.

Each sidewall 4 comprises a projecting wall section 11a (or 11b, . . . ) which is composed of an upper part of the piezoelectric material base 11, and a projecting wall sections 51a (or 51b, . . . ) which is composed of a lower part of the piezoelectric material base 51.

Electrode 16a, 16b, . . . are respectively disposed on an upper surfaces of the projecting wall sections 11a, 11b, . . . . Width L.sub.1 of each electrode 16a, 16b, . . . is narrower than width L.sub.2 of each wall section 11a, 11b, . . . , and the upper surfaces of the projecting wall sections 11a, 11b, . . . have first side areas El which are not covered by the electrodes 16a, 16b, . . . .

Electrodes 52a, 52b, . . . are respectively disposed on a lower surface of the projecting wall sections 51a, 51b, . . . . Width L.sub.1 of each electrode 52a, 52b, . . . is narrower than width L.sub.2 of each projecting wall section 51a, 51b, . . . , and the lower surfaces of the projecting wall sections 51a, 51b, . . . have second side areas E.sub.2 which are not covered by the electrodes 52a, 52b, . . . .

Anisotropic adhesives 31 are respectively disposed on the electrodes 16a, 16b, . . . and the first side areas E.sub.1 of the projecting wall sections 11a, 11b, . . . . The anisotropic adhesive 31 is conductive only in a direction (Z-axis direction or reverse direction) perpendicular to the upper surfaces of the projecting wall sections 11a, 11b, . . . and the lower surfaces of the projecting wall sections 51a, 51b, . . . , and not conductive in X-axis and Y-axis directions (horizontal directions). The anisotropic adhesives 31 cover the electrodes 16a, 16b, 17a, 17b so that the electrodes 16a, 16b, 17a, 17b are not exposed to the ink in the ink pressurizing cells 14a, 14b, . . . by the closing parts 31aand 31b.

When a positive voltage +V is applied to the electrode 16a and a negative voltage -V is applied to the neighboring electrode 16b, an electric field is generated through the piezoelectric element base 11 from the projecting wall section 11a to the projecting wall section 11b in the direction shown by a broken line A. Also, an electric field is generated through the piezoelectric element base 51 from the projecting wall section 51a to the projecting wall section 51b in the direction shown by a broken line F. As a result, shear mode deformation (shown by broken lines 60) is generated in respectively opposite directions in the projecting wall sections 11a, 11b and the projecting wall section 51a, 51b. The ink in the ink pressurizing cell 14ais then pressurized, and ink droplets are ejected from the orifice 15a.

Since the anisotropic adhesive 31 is not conductive in X-axis direction, the ink pressurizing cell 14a is electrically insulated from the electrodes 16a, 16b and 52a, 52b. Consequently, leak current flow in the ink pressurizing cell 14a can be decreased.

Also, an insulated coating layer for covering the interior of the ink pressurizing cells may be provided. In this case, insulating performance is increased.

Third Embodiment

FIG. 9 is a cross-sectional view showing the ink-jet head according to a third embodiment of the present invention. The ink-jet head of the third embodiment has the same construction as those of the first embodiment shown in FIG. 2 and FIG. 3, except that the projecting wall sections 11a, 11b, . . . and the intermediate wall sections 12a, 12b, . . . are not bonded by the anisotropic adhesive 55 but an insulating adhesive 55 as well as the first electrodes 16a, 16b, . . . and the second electrodes 17a, 17b, . . . mutually opposing are connected by conductive wires 56 outside the ink pressurizing cells 14a, 14b, . . . .

In the case of the third embodiment, since anisotropic adhesive is not used, the ink-jet head manufacturing cost can be further reduced.

Since the electrodes 16a, 16b, 17a, 17b are insulated from the ink in the ink pressurizing cells 14a, 14b, . . . by the insulating adhesive 55, leak current flow in the ink pressurizing cells 14a, 14b, . . . can be prevented. Consequently, since the ink pressurization amount in the ink pressurizing cells from shear mode deformation is not reduced, an adequate amount of ink droplets can be emitted from the orifices.

A manufacturing method of the ink-jet head of FIG. 9 is the same as that of the first embodiment shown in FIGS. 4A-4E, FIGS. 5A and 5B, or FIGS. 6A-6E, FIGS. 7A and 7B, except that the anisotropic adhesive 31 is replaced by the insulating adhesive 55 and the step for electrically connecting the electrodes 16a, 16b, . . . and the second electrodes 17a, 17b, . . . mutually opposing by conductive wires is added.

The present invention is not limited by the above described embodiments and numerous variations are possible within the scope of the present invention. For example, the anisotropic adhesive 31 of FIG. 8 may be replaced by the insulating adhesive 55 of FIG. 9 by adding the conductive wires 56 of FIG. 9. Moreover, in the above embodiments, a voltage may not be applied to the electrode 16a, 16b, . . . , but the electrode 17a, 17b, . . . by the driver circuit 57.

Claims

1. An ink-jet head having a plurality of ink pressurizing cells, each being for a containment of ink, said ink-jet head comprising:

a plurality of sidewalls, each of said sidewalls forming a respective longitudinal sidewall of a respective one of said plurality of ink pressurizing cells, and each being subjectable to shear deformation to impart a pressure pulse to said ink pressurizing cells;

a bottom wall forming a bottom lateral wall of said plurality of ink pressurizing cells;

a top wall forming a top lateral wall of said plurality of ink pressurizing cells; and

a front wall forming a front longitudinal wall of said plurality of ink pressurizing cells, and having a plurality of orifices, each of said orifices passing through said front wall, the ink in said ink pressurizing cells being ejectable from the ink pressurizing cells and through said orifices when the pressure pulse is imparted to said ink pressurizing cells;

each of said plurality of sidewalls comprising:

a first wall section made from a piezoelectric material, and having a width, and an upper surface,

a first electrode disposed on the upper surface of said first wall section and having a width, with the width of said first electrode being narrower than the width of said first wall section, and said upper surface of said first wall section having a first side area which is not covered by said first electrode,

an anisotropic adhesive disposed on said first electrode and said first side area of said first wall section,

a second electrode disposed on said anisotropic adhesive, and having a width, and

a second wall section made from a piezoelectric material, and having a width and a lower surface, and having said second electrode disposed on the lower surface thereof, with the width of said second electrode being narrower than the width of said second wall section, and with the lower surface of said second wall section having a second side area which is not covered by said second electrode;

wherein said anisotropic adhesive is conductive only in a direction perpendicular to said upper surface of said first wall section and said lower surface of said second wall section, and said anisotropic adhesive covers said first electrode and said second electrode so that said first electrode and said second electrode are not exposed to the ink in said ink pressurizing cells.

2. The ink-jet head of claim 1, wherein said plurality of ink pressurizing cells are arranged in an array direction, and each said second wall section is polarized in the array direction.

3. The ink-jet head of claim 1, wherein said plurality of ink pressurizing cells are arranged in an array direction, and each said first wall section is polarized in the array direction.

4. The ink-jet of claim 1, further comprising a driver circuit coupled to each said first electrode for applying a voltage to each said first electrode.

5. The ink-jet head of claim 1, further comprising a driver circuit coupled to each said second electrode for applying a voltage to each said second electrode.

6. The ink-jet head of claim 1, wherein each of said sidewalls further comprises a third electrode disposed on an upper surface of each said second wall section.

7. The ink-jet head of claim 6, further comprising:

a common electrode disposed on a lower surface of said top wall; and

a conductive adhesive bonding said third electrode with said common electrode.

8. The ink-jet head of claim 1, wherein said bottom wall is made from a piezoelectric material, and said bottom wall and said plurality of first wall sections form a one-piece construction,

said plurality of ink pressurizing cells being arranged in an array direction and said bottom wall and said first wall section being polarized in the array direction.

9. The ink-jet head of claim 8, wherein said top wall is made from a piezoelectric material, and said top wall and said plurality of second wall sections form a one-piece construction,

said plurality of ink pressurizing cells being arranged in an array direction, and said top wall and said second wall section being polarized in the array direction.

10. The ink-jet head of claim 1, further comprising an insulating layer coated on an interior of said respective ink pressurizing cells.