Ink jet head method of production thereof, and jig for producing ink jet head

The present invention relates to an ink jet head for changing the volume in a pressure chamber by deformation of a laminate piezoelectric device and for jetting ink filled in the pressure chamber from the front openings of the pressure chamber through nozzle holes, and particularly to an ink jet head which is characterized by an adhesive layer interposed between the front end surface of the main body forming the pressure chamber and a nozzle plate. The nozzle plate is bonded to the front end surface of the main body via an adhesive layer formed by an adhesive. The adhesive layer is divided into a nozzle seal layer encompassing the nozzle holes and the periphery of the front openings of the pressure chamber, an outer periphery hermetic layer formed annularly around the outer periphery of a region in which the main body and the nozzle plate oppose each other, and a reinforcing layer distributed in an intermediate portion between the nozzle seal layer and the outer periphery hermetic layer.

This application is a PCT/JP96/01588 filed Jun. 12, 1996. 
 TECHNICAL FIELD 
 The present invention relates to an ink jet head for changing the volume in
 a pressure chamber by deformation of a laminate piezoelectric device and 
 for jetting ink filled in the pressure chamber from the front openings of 
 the pressure chamber through nozzle holes, particularly to an ink jet head
 which is characterized by an adhesive layer interposed between the front 
 end surface of the main body forming the pressure chamber and a nozzle 
 plate, a method of manufacturing the same, and a jig for manufacturing the
 ink jet head. 
 BACKGROUND TECHNOLOGY 
 A conventional ink jet head of this type is, for example, disclosed in the 
 laid-open publication of JP-A 3-173651. 
 FIG. 8 shows the entire structure of the ink jet head as disclosed in the 
 same publication, wherein a nozzle forming member 102 is bonded to a 
 piezoelectric converter 101 fixedly secured onto a base member 100 by an 
 adhesive 103. 
 The base member 100, the piezoelectric converter 101 and the nozzle forming
 member 102 are respectively incorporated in a frame 104, wherein an ink 
 chamber 105 is formed in an intermediate portion between the piezoelectric
 converter 101 and the nozzle forming member 102. Ink 106 filled in the ink
 chamber 105 is discharged from nozzle holes 107 by deformation of the 
 piezoelectric converter 101. 
 FIG. 9 is an enlarged sectional view showing in detail a construction of a 
 bonding part between the piezoelectric converter 101 and the nozzle 
 forming member 102 and the periphery thereof shown in FIG. 8. The 
 piezoelectric converter 101 and the nozzle forming member 102 are bonded 
 to each other by the adhesive 103 including space restriction particles 
 110 and conductive particles 111. Each of the space restriction particles 
 110 has a uniform grain size. A given gap, namely, the ink chamber 105, is
 formed between the piezoelectric converter 101 and the nozzle forming 
 member 102 by the space restriction particles 110. 
 Meanwhile, the ink jet head as disclosed in the publication of JP-A 
 3-173651 has a structure that the end part of the nozzle forming member 
 102 is bonded to the piezoelectric converter 101, and the ink chamber 105 
 having a given interval is formed between the piezoelectric converter 101 
 and the nozzle forming member 102 as is evident from FIG. 9. 
 If the bonding spot of the nozzle forming member 102 is limited to the end 
 part alone as set forth above, it is not necessary to consider any harmful
 effect like the nozzle holes 107 being blocked owing to the expansion of 
 the adhesive 103. Accordingly, there is no description in publication JP-A
 3-173651 regarding the amount of coating of the adhesive 103. 
 However, the amount of coating of the adhesive becomes a problem, for 
 example, in the case where an entire back surface of a nozzle plate 201 is
 bonded to an end surface 200a of a piezoelectric module 200 in the ink jet
 head shown in FIG. 10. 
 That is, if the adhesive is coated onto the entire surfaces between the 
 bonding surfaces of the end surface 200a of the piezoelectric module 200 
 and the nozzle plate 201, excess adhesive inevitably expands to the 
 periphery thereof. Particularly, when the adhesive enters gaps 202 forming
 the ink chamber, there is a likelihood that the discharge characteristic 
 of the ink will be deteriorated or nozzle holes 203 will be blocked. 
 The laid-open publication of JP-A 5-220966 discloses a method of preventing
 the ink chamber and the nozzle holes from being blocked by the expansion 
 of the excess adhesive set forth below. 
 That is, a method of manufacturing the ink jet head disclosed in the same 
 publication comprises supplying an adhesive 302 to a recessed plate 300 
 having a recessed part 301 as shown in FIG. 11A, then scraping off the 
 excess adhesive 302 which bulges onto the recessed plate 300 by a blade 
 303 as shown in FIG. 11B, thereby leaving the adhesive 302 in the recessed
 part 301 alone. 
 Successively, the end surface (bonding surface of the nozzle plate) 200a of
 the piezoelectric module 200 is pressed against the recessed part 301, and
 then the piezoelectric module 200 is extracted thereafter so that a small 
 amount of adhesive 302 is uniformly coated onto the end surface 200a of 
 the piezoelectric module 200, as shown in FIG. 11C. 
 In such a manner, the method prevents the expansion of the excess adhesive 
 302 by bonding the nozzle plate 201 to the end surface 200a of the 
 piezoelectric module 200 onto which the adhesive 302 is coated. 
 However, even in the method of manufacturing the ink jet head disclosed in 
 the above-mentioned publication, there is a high possibility that the 
 adhesive 302 filled in the bonding surfaces contains bubbles at random 
 since the adhesive 302 is coated onto the entire bonding surfaces of the 
 piezoelectric module 200 and the nozzle plate 201. 
 If the adhesive 302 hardens while it contains bubbles, hermeticity between 
 the piezoelectric module 200 and the nozzle plate 201 is not maintained 
 depending on the condition or position of the bubbles, thereby leading to 
 a danger that ink leakage will occur and an electrode of the piezoelectric
 module 200 will be short-circuited. 
 The present invention has been made in view of these circumstances, and it 
 is an object of the invention to bond between the front end surface of the
 main body and the nozzle plate strongly with high hermeticity, and to 
 prevent the nozzle holes from being blocked by the expansion of the 
 adhesive. 
 DISCLOSURE OF THE INVENTION 
 To achieve the above object, the ink jet head of the present invention is 
 characterized in being structured as follows. 
 That is, the ink jet head comprises a main body for changing the volume in 
 a pressure chamber by deformation of a laminate piezoelectric device, and 
 feeding ink filled in the pressure chamber toward front openings of the 
 pressure chamber, a nozzle plate having nozzle holes communicating with 
 the front openings of the pressure chamber, and an adhesive layer formed 
 between the front end surface of the main body and the nozzle plate by an 
 adhesive. 
 The adhesive layer formed between the main body of the ink jet head and the
 nozzle plate comprises a nozzle seal layer of an arbitrary width in such a
 manner as to encompass the nozzle holes and the periphery of the front 
 openings of the pressure chamber, an outer periphery hermetic layer of an 
 arbitrary width being formed annularly around the outer periphery of a 
 region in which the main body and the nozzle plate oppose each other, and 
 a reinforcing layer being distributed in an intermediate portion between 
 the nozzle seal layer and the outer periphery hermetic layer. 
 Since the nozzle holes and the front openings of the pressure chamber are 
 sealed by the nozzle seal layer in the present invention having the 
 construction set forth above, it is possible to prevent ink from leaking 
 from the nozzle holes and the front openings. 
 Further, a sealing property can be further enhanced by the outer periphery 
 hermetic layer, and particularly entrance of moisture, dust, etc., from 
 the outside can be prevented. Still further, a large bonding strength can 
 be secured by the reinforcing layer. 
 Further, a plurality of spherical bodies each having an extremely small 
 diameter may be contained in the adhesive layer according to the ink jet 
 head of the present invention. With such a construction, the thickness of 
 the adhesive layer can be maintained constant by the existence of the 
 spherical bodies, and the nozzle seal layer, the outer periphery hermetic 
 layer and the reinforcing layer can be prevented from being collapsed so 
 as to effectively perform their functions. 
 Meanwhile, a method of manufacturing an ink jet head of the present 
 invention, comprising a main body for changing the volume in a pressure 
 chamber by deformation of a laminate piezoelectric device, and feeding ink
 filled in the pressure chamber toward the front openings of the pressure 
 chamber, and a nozzle plate bonded onto the front end surface of the main 
 body in a state where nozzle holes communicate with the front openings of 
 the pressure chamber, is characterized in comprising the following steps. 
 Adhesive coating step 
 In this step, the adhesive is coated onto the nozzle plate in such a manner
 as to encompass the front openings at the front end surface of the main 
 body with an arbitrary width. Further, the adhesive is coated annularly 
 along an outer periphery edge with an arbitrary width in a region where 
 the nozzle plate is bonded to the front end surface of the main body. 
 Still further, the adhesive is coated onto an intermediate region which is
 encompassed by each portion onto which the adhesive is coated in a 
 distributed manner. 
 Since the adhesive is coated in such a manner, the nozzle seal layer, the 
 outer periphery hermetic layer, and the reinforcing layer in the ink jet 
 head of the present invention can be formed as mentioned in the foregoing.
 Overlaying step 
 In this step, the nozzle plate is overlaid on the front end surface of the 
 main body in a state where the nozzle holes conform to the front openings 
 of the pressure chamber. 
 Pressing step 
 In this step, the nozzle plate which is overlaid on the front end surface 
 of the main body in the overlaying step is pressed elastically. Since the 
 nozzle plate is pressed elastically, the pressure applied to the adhesive 
 is appropriately lessened to prevent the adhesive from being collapsed. 
 If a plurality of spherical bodies each having an extremely small diameter 
 are contained in the adhesive used in the adhesive coating step, the 
 thickness of the adhesive layer can be maintained constant by the 
 existence of the spherical bodies so as to prevent the adhesive from being
 collapsed. 
 Each step of the method of manufacturing the ink jet head of the present 
 invention may be carried out in the following method. 
 Adhesive coating step 
 The adhesive is coated onto the nozzle plate in such a manner as to 
 encompass the nozzle holes with an arbitrary width. Further, the adhesive 
 is coated annularly along an outer periphery edge with an arbitrary width 
 in a region where the nozzle plate is bonded to the front end surface of 
 the main body. Still further, the adhesive is coated onto an intermediate 
 region which is encompassed by each portion onto which the adhesive is 
 coated in a distributed manner. 
 Overlaying step 
 The front end surface of the main body is overlaid on the nozzle plate in a
 state where the front openings of the pressure chamber conform to the 
 nozzle holes. 
 Pressing step 
 The nozzle plate overlaid on the front end surface of the main body is 
 elastically pressed. 
 Also in this case, if plural spherical bodies each having an extremely 
 small diameter are contained in the adhesive used in the adhesive coating 
 step, the thickness of the adhesive layer can be maintained constant by 
 the existence of the spherical bodies so as to prevent the adhesive from 
 being collapsed. 
 Still further, the present invention provides a jig adapted for carrying 
 out the method of manufacturing the ink jet head set forth above. 
 That is, the jig for manufacturing an ink jet head of the present invention
 comprises a main body of the jig for supporting the main body of the ink 
 jet head, a pressing plate for supporting the nozzle plate while opposing 
 the main body of the ink jet head supported by the main body of the jig, 
 the pressing plate being freely movable in a direction of the main body of
 the jig, an elastic member provided on the pressing plate for elastically 
 supporting the nozzle plate, and a suction means provided on the pressing 
 plate for suctioning the nozzle plate against the elastic member. 
 Since the nozzle plate is pressed elastically by the elastic member in the 
 jig for manufacturing the ink jet head, the pressing step in the method of
 manufacturing the ink jet head set forth above can be easily performed, 
 and also the pressure applied to the adhesive is appropriately lessened to
 prevent the adhesive from being collapsed.

BEST MODE FOR CARRYING OUT THE INVENTION 
 The best mode for carrying out the present invention will be now described 
 in detail with reference to the attached drawings. 
 The overall construction of an ink jet head will be first described with 
 reference to FIGS. 1 to 4. 
 The ink jet head shown in these figures is provided with a main body 1 and 
 a nozzle plate 2 having a plurality of nozzle holes 2a. The main body 1 
 comprises a pressure chamber 11, a flow path forming member 10 forming an 
 ink flow path to the pressure chamber 11, a laminate piezoelectric device 
 unit 20 which is deformed in the direction of the thickness thereof when a
 voltage is applied, a diaphragm 30 provided between the laminate 
 piezoelectric device unit 20 and the flow path forming member 10, a 
 flexible printed-circuit board 40 for applying a voltage to the laminate 
 piezoelectric device unit 20, and the like. 
 The flow path forming member 10 has a common liquid chamber 12 at the rear 
 end portion thereof. Ink is supplied to the common liquid chamber 12 
 through an ink supply port 13. A plurality of pressure chambers 11 are 
 formed in a line on the bottom surface of the flow path forming member 10 
 extending from the intermediate portion to the front end portion thereof. 
 Each pressure chamber 11 communicates with the common liquid chamber 12 
 through each orifice 14. 
 The laminate piezoelectric device unit 20 is bonded to the bottom surface 
 of the flow path forming member 10 via the diaphragm 30. The laminate 
 piezoelectric device unit 20 includes laminate piezoelectric bodies 21 and
 a base 22. The laminate piezoelectric bodies 21 are structured in such a 
 manner that a plurality of plate-shaped piezoelectric members are 
 laminated while they clamp electrode plates 22a and 22b therebetween as 
 shown in FIG. 2. 
 Exposed ends of the electrode plates 22a and 22b are arranged alternately 
 to the outside. For example, the electrode plates 22a corresponding to odd
 numbers counted from the bottom are exposed from the laminate 
 piezoelectric bodies 21 at the rear end thereof, and the electrode plates 
 22b corresponding to even numbers counted from the bottom are exposed from
 the laminate piezoelectric bodies 21 at the front end portion thereof. 
 The laminate piezoelectric bodies 21 are bonded onto the upper surface of 
 the base 22, and they are divided into a plurality of piezoelectric 
 devices 21a by grooves 23. Each of the piezoelectric devices 21a 
 (excluding piezoelectric devices 21b provided at both ends) is provided so
 as to oppose the pressure chamber 11 via the diaphragm 30. 
 The piezoelectric devices 21b provided on both ends of the laminate 
 piezoelectric bodies 21 serve as a non-driving portion to which no voltage
 is applied, and serve as supporters for supporting the piezoelectric 
 devices 21a provided at the intermediate portion. 
 A driving concentration electrode 24 is formed on the rear end surface of 
 each of the piezoelectric devices 21a opposing the pressure chamber 11, 
 and the electrode plates 22a exposed from the rear end surface of each of 
 the piezoelectric devices 21a is electrically connected to the driving 
 concentration electrode 24. Meanwhile, a common concentration electrode 25
 is formed on the front end surface of each of the piezoelectric devices 
 21a, and the electrode plates 22b exposed from the front end surface of 
 each of the piezoelectric devices 21a are electrically connected to the 
 common concentration electrode 25. 
 A voltage is applied to the driving concentration electrode 24 and the 
 common concentration electrode 25 via the flexible printed-circuit board 
 40 as shown in FIG. 4. A plurality of driving conductive patterns 41 and a
 common conductive pattern 42 are formed on the flexible printed-circuit 
 board 40, and each of the driving conductive patterns 41 is connected to 
 the driving concentration electrode 24 individually. Further, the common 
 conductive pattern 42 extends to the front end surface side of the 
 laminate piezoelectric bodies 21 through one edge of the base 22 on the 
 upper surface thereof, and is connected to the common concentration 
 electrode 25. 
 When the voltage is applied between the driving concentration electrode 24 
 and common concentration electrode 25 via the flexible printed-circuit 
 board 40, each of the piezoelectric devices 21a opposing the pressure 
 chamber 11 is deformed in the direction of the thickness thereof. This 
 deformation is transmitted to the diaphragm 30 to change the volume in the
 pressure chamber 11. As a result, ink filled in the pressure chamber 11 is
 discharged from front openings 11a through the nozzle holes 2a. 
 A frame 50 is provided on the bottom surface of the flow path forming 
 member 10 to cover the periphery of the laminate piezoelectric device unit
 20, and the flow path forming member 10 and the laminate piezoelectric 
 device unit 20 are supported by the frame 50. 
 A front end surface 1a of the main body 1 is formed on the front end 
 surface of the flow path forming member 10, the front end of the diaphragm
 30 and the front end surface of the frame 50 according to the mode for 
 carrying out the invention as shown in FIG. 2. The nozzle plate 2 is 
 joined onto the front end surface 1a of the main body 1. The front 
 openings 11a of the pressure chamber 11 are bored in the front end surface
 1a of the main body 1. 
 The construction of bonding between the front end surface 1a of the main 
 body 1 and the nozzle plate 2 will be now described together with the 
 method of manufacturing the ink jet head (see FIG. 1, FIG. 2 and FIG. 5). 
 The front end surface 1a of the main body 1 and the back surface of the 
 nozzle plate 2 are finished to become a flat surface having a uniform 
 surface roughness by grinding or lapping. 
 Further, a surface to be coated by the adhesive (the front end surface 1a 
 of the main body 1 in this case) is irradiated with UV rays, and an 
 organic substance on the front surface forms molecules having a simple 
 structure due to the high energy of the UV rays, and having a strong 
 oxidation strength due to ozone generated by the UV rays, and is vaporized
 to be removed, so that water repellency is reduced and wettability 
 improves remarkably. As a result, the adhesive can be coated in a desired 
 shape with uniform height. 
 The adhesive to be used is selected arbitrarily considering the material of
 the main body 1 and nozzle plate 2. Single-liquid type epoxy adhesive 
 having 220.+-.20 poids in viscosity is used herein. The adhesive contains 
 a plurality of hard true spherical bodies each having an extremely small 
 diameter. The diameter of each of the hard spherical bodies can be set 
 arbitrarily. It must be considered, however, that the diameter of each 
 hard spherical body determines the thickness of the bonding layer formed 
 between the front end surface 1a of the main body 1 and the nozzle plate 
 2. In this mode for carrying out the invention, hard spherical bodies each
 having a diameter of 0.005 mm are contained in the adhesive. 
 The adhesive containing such hard spherical bodies is printed and coated 
 onto the front end surface 1a of the main body 1 utilizing a screen 
 printing method (adhesive coating step). 
 FIG. 5 shows a printing pattern for the adhesive relative to the front end 
 surface 1a of the main body 1. As shown in the same figure, the adhesive 
 is printed and coated onto the front end surface 1a of the main body 1 
 while being divided into a nozzle seal layer 61, an outer periphery 
 hermetic layer 62 and a reinforcing layer 63. 
 The nozzle seal layer 61 is formed to encompass the periphery of the front 
 openings 1a of each pressure chamber 11. The width of the nozzle seal 
 layer 61 can be set arbitrarily. In this mode for carrying out the 
 invention, the adhesive is printed and coated with a width of 0.06 mm and 
 a height of 0.01 mm, thereby forming the nozzle seal layer 61. 
 The outer periphery hermetic layer 62 is formed annularly with an arbitrary
 width along the outer peripheral edge of the region where the front end 
 surface 1a of the main body 1 and the nozzle plate 2 oppose each other. In
 the mode for carrying out the invention, the adhesive is printed and 
 coated with a width of 0.2 mm and a height of 0.01 mm, thereby forming the
 outer periphery hermetic layer 62. 
 The reinforcing layer 63 is formed in the intermediate portion between the 
 nozzle seal layer 61 and the outer periphery hermetic layer 62 in a 
 distributed manner. In the mode for carrying out the invention, the 
 adhesive is printed and coated in a plurality of circular patterns each 
 having a diameter of 0.2 mm and a height of 0.01 mm, thereby forming the 
 reinforcing layer 63. 
 The back surface of the nozzle plate 2 is overlaid and bonded onto the 
 front end surface 1a of the main body 1 onto which the adhesive is printed
 and coated while it is divided into each layer (overlaying step). At this 
 time, each of the nozzle holes 2a defined in the nozzle plate 2 is 
 permitted to conform to the front openings 11a of the pressure chamber 11,
 thereby positioning the former relative to the latter. 
 Thereafter the nozzle plate 2 is pressed relatively against the main body 1
 so that the adhesive which is printed and coated onto the front end 
 surface 1a of the main body 1 is brought into close contact with the 
 nozzle plate 2 (pressing step). In this pressing step, the nozzle plate 2 
 is pressed elastically, thereby realizing a uniform bonding state. 
 That is, when any foreign matter is stuck to the front end surface 1a of 
 the main body 1 or the back surface of the nozzle plate 2, stress caused 
 by the pressing is concentrated on the portion contacting the foreign 
 matter on the back surface of the nozzle plate 2, whereby there occurs the
 likelihood of the deformation of the nozzle plate 2. 
 Particularly in the mode for carrying out the invention employing the 
 adhesive containing the hard spherical bodies, there occurs distortion in 
 each portion of the nozzle plate 2 causing gaps to be defined when the 
 hard spherical bodies are brought into contact with the nozzle plate 2, 
 whereby there occurs the likelihood of deterioration of the sealing 
 property in the bonding portions. 
 Such drawbacks can be avoided by pressing the nozzle plate 2 elastically as
 set forth below. 
 FIG. 6 is a sectional view showing the jig for manufacturing the ink jet 
 head capable of performing the overlaying step and the pressing step 
 easily and accurately. Further, FIG. 7 is a bottom view of a pressing 
 plate of the jig for manufacturing the ink jet head. 
 The jig for manufacturing the ink jet head is provided with a main body 70 
 of the jig for supporting the main body 1 and a pressing plate 80 for 
 supporting the nozzle plate 2. 
 A positioning fixed portion 71 for positioning the main body 1 is formed in
 the main body 70 of the jig. In the mode for carrying out the invention, 
 the positioning fixed portion 71 for positioning the main body 1 is formed
 by a recessed part having a shape conforming to the shape of the rear end 
 portion of the main body 1, wherein the rear end portion of the main body 
 1 is engaged with the positioning fixed portion 71 while the front end 
 surface 1a of the main body 1 is directed upward so that the main body 1 
 can be automatically positioned and fixed. 
 Positioning pins 72 protrude from both side edge portions of the main body 
 70 of the jig and positioning holes 81 in which the positioning pins 72 
 are engaged are defined in both side edge portions of the pressing plate 
 80. The pressing plate 80 can be slid along the positioning pins 72 in a 
 state where the positioning holes 81 are engaged with the positioning pins
 72 of the main body 70 of the jig. 
 A plate-shaped elastic member 82 is provided on the bottom surface of the 
 pressing plate 80 opposing the positioning fixed portion 71 for 
 positioning the main body as shown in FIG. 7. The elastic member 82 is 
 formed by printing, for example, a liquid silicon rubber having an 
 adhesive property which is excellent in heat resistance onto the bottom 
 surface of the pressing plate 80 by a screen printing process, and 
 thereafter heating and curing it, whereby an elastic member having a 
 Young's modulus of 5 kgf/cm.sup.2 with a height of 0.012 to 0.02 mm is 
 formed. 
 Small grooves 83 each forming a vacuum chuck are defined in the elastic 
 member 82, and vacuum nozzles 84 are bored in the small grooves 83 to form
 a suctioning means for suctioning the nozzle plate 2. The vacuum nozzles 
 84 communicate with a vacuum pump (not shown), and the nozzle plate 2 can 
 be suctioned by and fixed to the elastic member 82 by evacuating the 
 interior of the small grooves 83 by the vacuum pump. 
 Nozzle positioning pins 85 are provided in the pressing plate 80 to 
 protrude to both side edge portions of the elastic member 82. The 
 positioning holes 2b for engaging with the nozzle positioning pins 85 are 
 defined previously in the nozzle plate 2 wherein the nozzle plate 2 can be
 positioned relative to the pressing plate 80 when the positioning holes 2b
 are engaged with the nozzle positioning pins 85. 
 The positioning fixed portion 71 for positioning the main body 1, the 
 positioning pins 72 respectively formed on the main body 70 of the jig, 
 the positioning holes 81, the nozzle positioning pins 85 provided on the 
 pressing plate 80 and the positioning holes 2b defined in the nozzle plate
 2 are respectively adjusted in advance so that the nozzle holes 2a of the 
 nozzle plate 2 which is positioned and fixed to the pressing plate 80 
 oppose the front openings 11a of the pressure chamber 11 in the main body 
 1 which is positioned in the positioning fixed portion 71 of the main body
 70 of the jig. 
 The overlaying step and the pressing step can be easily performed as 
 follows using the jig for manufacturing the ink jet head. 
 First of all, the main body 1 having the front end surface 1a onto which 
 the adhesive is printed and coated is engaged with the positioning fixed 
 portion 71 for positioning the main body 70 of the jig, and the nozzle 
 plate 2 is positioned onto the elastic member 82 of the pressing plate 80 
 to suction the former to the latter. Thereafter, the pressing plate 80 is 
 engaged with the positioning pins 72 to slide the pressing plate 80 toward
 the main body 70 of the jig. 
 After the nozzle plate 2 suctioned by the pressing plate 80 contacts the 
 adhesive which is printed and coated onto the front end surface 1a of the 
 main body 1, a given pressing force is applied so that the nozzle plate 2 
 is bonded to the front end surface 1a of the main body 1. At this time, 
 since the elastic member 82 is interposed between the pressing plate 80 
 and the nozzle plate 2, the nozzle plate 2 is pressed elastically. In this
 state, a heating process is performed for a given time to cure the 
 adhesive. 
 The adhesive layer is formed by the adhesive between the front end surface 
 1a of the main body 1 and the nozzle plate 2 which are bonded to each 
 other as set forth above. The adhesive layer comprises the nozzle seal 
 layer 61, the outer periphery hermetic layer 62 and the reinforcing layer 
 63 as set forth above, and among them, the nozzle seal layer 61 prevents 
 ink discharged from the front openings 11a of the pressure chamber 11 from
 leaking between the bonding surfaces. The outer periphery hermetic layer 
 62 prevents moisture, dust, etc., from entering between the bonding 
 surfaces from the outside. The reinforcing layer 63 sufficiently secures 
 the bonding strength between the main body 1 and the nozzle plate 2. 
 As a result of forming the adhesive layer in the required minimum region, 
 the expansion of adhesive can be restrained, thereby preventing the 
 harmful effect that the nozzle holes 2a are blocked owing to the expansion
 of the adhesive. 
 Further, since the hard spherical bodies are contained in the adhesive in 
 the mode for carrying out the invention, they act as supports when the 
 nozzle plate 2 is pressed and brought into contact with the main body 1, 
 thereby preventing the adhesive layer from being collapsed. As a result, 
 the expansion of the adhesive can be further restrained, thereby forming 
 an adhesive having a uniform thickness, so that the bonding strength is 
 stabilized. 
 Although the adhesive is coated onto the front end surface 1a of the main 
 body 1 in the mode for carrying out the invention set forth above, the 
 adhesive may be coated onto the back surface of the nozzle plate 2 to 
 overlay on the main body 1. 
 Further, as the feature of the present invention resides in the bonding 
 portion between the main body and the nozzle plate, the other components 
 may be appropriately changed in design. 
 INDUSTRIAL APPLICABILITY 
 The present invention has an effect in the improvement of accuracy of the 
 ink jet head employed by an ink jet printer, particularly, in the bonding 
 between the main body and the nozzle plate in appropriate states, thereby 
 lowering the defective fraction of manufactured ink jet heads remarkably.