JP3201004B2 - Inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the construction of a print head of an ink jet printer used for a printer for a computer peripheral terminal or the like.

[0002]

2. Description of the Related Art Many attempts have been made to improve the performance and reduce the cost of a conventional ink-on-demand type ink jet head having a so-called Kaiser type pressure chamber, for example, Japanese Patent Publication No. 53-12138. Was. In particular, Japanese Patent Publication No. Sho 62-33076 and Japanese Patent Application Laid-Open No. 64-6485 disclose using a low elastic modulus material as a substrate material in order to reduce the cost.
No. 6, etc. In these applications, a low-elastic member, a high-elastic member, and a piezoelectric element are stacked, and the piezoelectric element is arranged on a pressurizing chamber. It is discharging. In these configurations, the high elastic member on the low elastic member is provided with a vibration separating portion so that vibration is not transmitted to the adjacent pressurizing chamber, or is caused by joining materials having different thermal expansion coefficients. In order to remove the distortion, the plate has a slit so that it can be expanded and contracted. In the configuration of the diaphragm, the fifth
As shown in the figure, a piezoelectric element 103 and a vibration plate 104 are formed by a pressure chamber 10 formed by a first substrate 101 and a second substrate 102.
It is formed directly above 1C. The piezoelectric element 103, the vibration plate 104, and the first substrate 101 are made of an epoxy adhesive 106.
Are electrically and mechanically coupled. The piezoelectric element 103 and the FPC 105 are electrically and mechanically connected by a conductive adhesive 107. At this time, the conductive adhesive 10
The ends of the piezoelectric element 103 and the vibration plate 104 are widely covered with an insulating agent 108 so that 7 does not protrude to the side surface of the piezoelectric element 103 and short-circuit with the electrode on the vibration plate 104 side. In some cases, the end of the vibration plate 104 does not coincide with the piezoelectric element 103 and extends outside the piezoelectric element attachment portion. In this case, the insulation treatment agent 108 is applied over the entire surface to perform insulation treatment.

[0003]

When the piezoelectric element and the FPC are electrically connected with a conductive adhesive in the above-described configuration of the diaphragm, insulation treatment is performed on the end face of the piezoelectric element and the diaphragm. Must-have. When the piezoelectric element extends outside the piezoelectric element attachment portion, the deformation efficiency of the pressurizing chamber decreases due to the difference in the deformation mode of the diaphragm. Further, the insulation process is difficult to automate and cannot be performed completely, so that the yield is poor and the head cost increases. In this process, an epoxy adhesive is used, and it is difficult to control the amount of the adhesive. Therefore, the thickness may vary depending on the location, and the deformation of the piezoelectric element may be prevented. May be reduced. An object of the present invention is to realize a highly reliable piezoelectric element insulation process that does not affect the deformation of the piezoelectric element by a simple method, and realize a high-yield, low-cost, high-print-quality head with little deformation variation. It is in the thing.

[0004]

In order to achieve the above object, an ink jet head according to the present invention is an ink jet head in which a vibration plate and a piezoelectric element are laminated corresponding to a pressurizing chamber. The vibration plate and the piezoelectric element are joined by a non-conductive adhesive so as to be able to conduct using the roughness of the surface of the piezoelectric element electrode surface so as to form an edge portion having a substantially uniform width over the entire outer periphery thereof, A coating layer made of the non-conductive adhesive is formed on the edge, and the other surface of the piezoelectric element is joined to an FPC by a conductive adhesive. Further, the width of the edge is about the thickness of the piezoelectric element.

By using a piezoelectric element and a vibrating plate having an edge with a substantially uniform width on the outer periphery of the attaching portion of the piezoelectric element, the two are electrically and mechanically joined by using an epoxy adhesive. In this case, since the adhesive itself has no conductivity, in order to electrically connect the two, the surface of the piezoelectric element electrode surface is used to make electrical connection using the convex portion, and the concave portion is formed. Mechanical coupling. The adhesive used has a sufficiently low viscosity and a high fluidity. After this is applied to the vibration plate, the piezoelectric element is pressed while being pressed to perform positioning. In this case, if there is an edge with a substantially uniform width on the outer periphery, the end of the piezoelectric element is effectively wetted with the adhesive by the vibration, and is uniformly held by the surface tension. As a result, the insulating process can be omitted, the yield can be improved, and a cheap and highly reliable head can be realized.

[0005]

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the preferred embodiments shown in the accompanying drawings. FIG. 1 is a plan view of a first embodiment of the present invention, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is a sectional view taken along the line BB of FIG. In the ink jet head of the present invention, a flow path is formed by joining the first substrate 1 and the second substrate 2 with an adhesive, and the flow path is filled with ink. Further, the present invention relates to a so-called Kaiser-type on-demand type head that discharges ink droplets from nozzles 1b by deforming a part of a flow path. The first substrate 1 includes a nozzle 1b for discharging ink droplets, a pressurizing chamber 1c for deforming a flow path for discharging ink, and a front flow path 1 connecting the nozzle 1b and the pressurizing chamber 1c.
a, a restriction 2a having a flow resistance substantially equal to or higher than that of the pressurizing chamber 1c and the nozzle portion, and a rear flow path 1d for guiding ink are formed on the surface thereof. Further, the nozzle surface 1e of the nozzle 1b having the discharge hole is higher than the nozzle-side mounting surface 1f of the pressurizing chamber 1c. The first substrate is made of a plastic having low elasticity.
Made of polysulfone with excellent chemical resistance. The nozzle 1b has a strict hole shape accuracy, and is formed with an excimer laser after forming an extremely thin wall. The second substrate 2 includes the above-described restriction 2a.
Are formed corresponding to the flow paths of the first substrate 1. The second substrate 2 is formed of the same material as the first substrate 1, and the holes of the restriction 2a are formed similarly to the nozzle 1b. The diaphragm 4 is made of a relatively high elastic material such as phosphor bronze or stainless steel, and has a shape slightly larger than that of the piezoelectric element 3 as shown in FIG. On the outer periphery of the bonding portion of the piezoelectric element 3, there are a piezoelectric element bonding portion 4a and a GND electrode portion 4c having edges of substantially uniform width, and these are constituted by a sufficiently deformable connecting portion 4b. Have been. The piezoelectric element 3 is polarized in the thickness direction, and gold or silver electrodes are formed on two surfaces perpendicular to the thickness by sputtering. Although not shown, the FPC 5 is wired with a pattern so as to transmit a print signal from a printer to each piezoelectric element.
The electrodes are exposed at positions corresponding to GND. The first substrate 1 and the second substrate 2 are joined using an adhesive, and a flow path from the nozzle 1b to the restriction 2a is formed. A pressurizing chamber 1c is provided so that a part of this flow path is deformed so that ink droplets can be ejected. The vibration plate 4, the piezoelectric element 3, and the FPC 5 are electrically and mechanically joined to the nozzle-side surface of the pressurizing chamber 1c (see FIG. 3). On the nozzle surface side of the pressurizing chamber 1c of the first substrate 1, the piezoelectric element 3, the vibration plate 4, and the first substrate 1 are electrically and electrically connected by an epoxy adhesive 6.
Mechanically joined. Further, the FPC 5 and the piezoelectric element 3 are electrically and mechanically joined by a conductive adhesive 7. To prevent the conductive adhesive 7 from protruding and short-circuiting to the electrode on the vibration plate 4 side of the piezoelectric element 3, the piezoelectric element 3 is attached to the end of the piezoelectric element 3.
The epoxy-based adhesive used in joining the diaphragm and the diaphragm 4 is adhered and sealed. This sealing is performed when the piezoelectric element 3 and the diaphragm 4 are positioned and joined. In this bonding, the bonding is performed electrically and mechanically using an epoxy adhesive 6. Since the adhesive 6 itself has no conductivity, a rough surface of the electrode surface of the piezoelectric element is used to electrically join the two. The oxide film is removed by pressing the convex portion and vibrating with ultrasonic waves to establish electrical continuity, and the two are joined using the concave portion. In this case, the viscosity of the adhesive used is sufficiently low and the fluidity is high. After this is applied to the vibrating plate 4, the piezoelectric element is pressed and the vibration is applied to position the piezoelectric element. As a result, the end of the piezoelectric element 3 is wetted by the adhesive 6 on the outer periphery with a substantially uniform width, and is held by the surface tension. The thickness of the piezoelectric element 3 is appropriate for the uniform width of the outer periphery of the piezoelectric element sticking portion. In order to hold the adhesive 6, a minimum thickness of the piezoelectric element 3 is necessary. Piezoelectric element 3
From the point of view of the driving efficiency of the pressurizing chamber 1
The deformation mode of c changes, and the driving efficiency of the head decreases.

Next, the operation of the head will be described.

In the initial state, the ink is filled in the flow path (1a to 1d). An ink pool and an ink cartridge (not shown) continue outside the restriction portion 2a of the second substrate 2, and ink is supplied when the head is driven. When a printing signal is applied to the piezoelectric element 3 in a step waveform from a printer (not shown), the piezoelectric element 3 is mechanically joined to the vibration plate 4 to form a unimorph. Deflects in such a direction that becomes smaller. Thus, the ink in the pressurized chamber 1c is pushed out to the front flow path 1a and the rear flow path 1d in the respective directions by the balance of the resistance of the nozzle 1b and the restriction 2a. The ink pushed out to the front flow path side is the nozzle 1
A is printed on recording paper (not shown) as ink droplets ejected from a. The piezoelectric element 3 bends in the opposite direction due to the reaction when the applied voltage of the piezoelectric element 3 becomes 0 V, and increases the volume of the pressurizing chamber 1c. In this case, the pressure in the pressurizing chamber 1c becomes a negative pressure, and ink is mainly supplied from the restriction 2a side. By repeating this, continuous printing can be performed.

Another embodiment will be described with reference to FIG.

FIG. 6 shows a case where the driving plates 4 are all separated. In this case, the GND electrode portion is not provided, but the GND electrode portion is formed on the first substrate 1 by another method such as screen printing using the tongue portion 4a on the diaphragm 4, and the tongue portion 4a is formed.
Is connected to This GND electrode portion is configured to be electrically connected to the FPC 5. In the above description, the diaphragm is provided on the first substrate, but the diaphragm may be provided on the second substrate corresponding to the pressure chamber.

According to the ink jet head of the present invention,
In an ink jet head in which a vibration plate and a piezoelectric element are laminated corresponding to the pressure chamber, one surface of the piezoelectric element is
The diaphragm and the piezoelectric element are joined by a non-conductive adhesive so as to be able to conduct by utilizing the roughness of the surface of the piezoelectric element electrode surface so as to form an edge having a substantially uniform width over the entire outer periphery thereof,
A coating layer made of the non-conductive adhesive is formed on the edge, and the other surface of the piezoelectric element is bonded to the FPC with a conductive adhesive, so that a special insulation to the piezoelectric element and the diaphragm is provided. Without providing a process, it is possible to perform a highly reliable insulation process capable of preventing a failure due to a dripping of a conductive adhesive used when joining the piezoelectric element and the FPC. As a result, it is possible to realize a high-quality print head with good yield, low cost, and little deformation variation.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of an inkjet head according to the present invention.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is an enlarged sectional view taken along line BB in FIG. 1;

FIG. 4 is an assembly plan view of a piezoelectric element and a diaphragm.

FIG. 5 is a partially enlarged sectional view showing a conventional example of an ink jet head.

FIG. 6 is a front view showing another embodiment of the ink jet head according to the present invention.

FIG. 7 is a sectional view taken along line CC in FIG. 6;

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 Piezoelectric element 4 Vibration plate 5 FPC

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/16

Claims (2)

(57) [Claims] 1. An ink jet head in which a vibration plate and a piezoelectric element are laminated corresponding to a pressurizing chamber, wherein one surface of the piezoelectric element forms an edge portion having a substantially uniform width over the entire outer periphery thereof. Along with the vibration plate and the surface of the piezoelectric element electrode surface are joined by a non-conductive adhesive so as to be conductive, and a coating layer of the non-conductive adhesive is formed on the edge portion, The other surface of the piezoelectric element is bonded to an FPC by a conductive adhesive. 2. The ink jet head according to claim 1, wherein the width of the edge is about the thickness of a piezoelectric element.