JP2003211658A - Ink jet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the productivity while reducing the cost of a piezoelectric element and its base member in an ink jet head. <P>SOLUTION: A metallic member is employed in a base member 4 being bonded with a piezoelectric element 5 for driving a diaphragm 3 and an anaerobic adhesive starting polymerization by metal ions is employed for bonding the base member 4 and the piezoelectric element 5. In order to prevent the adhesive from creeping up through the gap between the piezoelectric element arrays, a groove for releasing the adhesive is made in the base member 4 in correspondence with the gap position. In order to prevent the adhesive from creeping up to the outer electrode face of the piezoelectric element, side face of the base member 4 is located on the inside of the outer electrode face of the piezoelectric element and a level difference is provided between both faces. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-demand type ink jet head which ejects ink droplets only when recording is required and adheres to the surface of a recording paper, and in particular, a piezoelectric means as a driving means for ejecting ink droplets. The present invention relates to an inkjet head using an element.

[0002]

2. Description of the Related Art As an inkjet head of this type,
By vibrating a vibrating plate forming a part of the wall of the liquid chamber that communicates with each of the plurality of nozzles with a piezoelectric element bonded to the base member by an adhesive in an arrangement corresponding to the liquid chamber arrangement, the liquid chamber There is an inkjet head for ejecting the ink of No. 1 through a nozzle (for example, Japanese Patent Laid-Open No. 10-9511
No. 0).

Incidentally, as another publicly known document related to the joining between members of an ink jet head, Japanese Patent Laid-Open No. 5-57887 is known.
JP-A-6-155731, JP-A-9-1
796, JP-A-10-67103, JP-A-10-315485 and the like.

[0004]

Conventionally, in such an ink jet head, a ceramic substrate is used as a base member on which the piezoelectric elements are arranged, and heat curing is used as an adhesive for joining the base substrate and the piezoelectric elements. A mold bonding agent or a two-liquid mixed room temperature curing type bonding agent is often used. Therefore, when joining the piezoelectric element and the base member, it was necessary to hold the piezoelectric element and the base member for a long time while being pressurized by the joining device until the joining strength of the adhesive reaches the practical strength. This deteriorates the productivity of the inkjet head and contributes to an increase in the manufacturing cost thereof. Further, since the processing method of the ceramic substrate is limited, it is difficult to reduce the cost, and further, a flat plate is generally used due to the restriction of processing and the degree of freedom of the shape.

The present invention is intended to solve the above problems in the ink jet head. More specifically, one object of the present invention is that the adhesive used for joining the piezoelectric element and the base member can be widely selected, and the time required for curing the adhesive can be shortened, and An object of the present invention is to provide an inkjet head which has a wide degree of freedom in the method of processing the base member and is advantageous in terms of the processing cost and the degree of freedom of the shape. Another object of the present invention is to provide an inkjet head having a structure in which it is difficult for the adhesive to crawl onto the upper surface of the piezoelectric element when the piezoelectric element and the base member are joined. Another object of the present invention is to provide an inkjet head having a structure in which it is difficult for the adhesive to creep up to the external electrode surface of the piezoelectric element when the piezoelectric element and the base member are joined. Another object of the present invention is to provide an inkjet head having a structure that facilitates highly accurate bonding and positioning of a piezoelectric element and a base member. Another object of the present invention is to provide an ink jet head which has a high heat dissipation effect of a base member and can obtain stable ink droplet ejection characteristics.

[0006]

According to a first aspect of the invention, a vibrating plate forming a part of a wall of a liquid chamber communicating with each of a plurality of nozzles is provided corresponding to the arrangement of the liquid chambers. In an inkjet head that ejects ink inside the liquid chamber from the nozzles by vibrating by a piezoelectric element arranged on a base member, the base member is made of a metal, and polymerization is started by metal ions. The base member and the piezoelectric element are bonded by an anaerobic adhesive.

According to a second aspect of the invention, in the ink jet head according to the first aspect, the piezoelectric element is 2
The head member is arranged in rows or more, and the head member has grooves at positions corresponding to the rows of the piezoelectric elements for allowing the adhesive to escape.

According to a third aspect of the present invention, in the ink jet head according to the first or second aspect, the side surface of the base member is located inside the external electrode surface of the piezoelectric element, and there is a step between both surfaces. It is in.

According to a fourth aspect of the invention, in the ink jet head according to the first or second aspect, there is a gap for irradiating ultraviolet rays in a peripheral portion of a joint surface between the base member and the piezoelectric element, and the bonding is performed. The agent is that it is an ultraviolet curable anaerobic adhesive.

The features of the invention described in claim 5 are as follows.
In the inkjet head described in 2, 3, or 4, the base member has a convex portion as a reference for positioning the piezoelectric element.

A sixth aspect of the present invention is the inkjet head according to any one of the first to fifth aspects, in which the base member has a non-planar portion for increasing a heat radiation area.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that the same reference numerals are used for the same portions or corresponding portions in a plurality of drawings in order to reduce duplication of description.

FIG. 1 is a schematic sectional view showing an example of the overall construction of an inkjet head according to the present invention, and FIG. 2 is a schematic exploded perspective view of the inkjet head.

In this ink jet head, as shown in FIG. 1, a plurality of nozzles (ink droplet ejection holes) 11 are formed on the upper surface of a liquid chamber forming member 1 formed of, for example, a silicon substrate by Ni electroforming. The laminated piezoelectric plate, in which the nozzle plate 2 is joined, the diaphragm 3 formed by Ni electroforming or the like is joined to the lower surface of the liquid chamber forming member 1, and the base member 4 is joined to the lower surface of the diaphragm 3. This is the overall configuration in which the element 5 and the frame member 6 are joined together.

Between the nozzle plate 2 and the vibrating plate 3, there is a one-to-one correspondence with the nozzle 11 having a shape according to the internal shape of the liquid chamber forming member 1.
A plurality of liquid chambers 17 corresponding to the above are defined. Each liquid chamber 17
The upper end 12 (FIG. 2) of the corresponding nozzle 11
Communicate with. In addition, the lower end portion of each liquid chamber 17 has a hole 14 (

FIG. 2) communicates with a common flow channel 15 provided in the frame member 6 through 2).

The piezoelectric element 5 has a liquid chamber 17 on the base member 4.
Are arranged (in this example, in two columns). An FPC cable 7 (FIG. 2) is provided on the external electrode surface of each piezoelectric element 5.
Are connected by soldering, and a driving voltage is applied to each piezoelectric element 5 from a driver IC (driving circuit) (not shown) via the FPC cable 7, whereby each piezoelectric element 5 is displaced in the extension direction in the stacking direction (electric field). Displacement in the same direction) occurs.

The operation of this ink jet head is as follows. Ink supply port 16 of frame member 6 from the outside
The ink sent through (FIG. 2) is supplied to the common channel 15
Is supplied to each liquid chamber 17 through. The driving voltage (for example, a pulse voltage of 10V to 50V) corresponding to the recording signal is FP
When applied to the piezoelectric element 5 via the C cable 7, the piezoelectric element 5 is displaced in the stacking direction and the corresponding portion of the vibration plate 3 is deformed and displaced, so that the ink in the corresponding liquid chamber 17 is pressurized. Then, the ink is ejected as a droplet from the corresponding nozzle 11 to the outside. With the completion of ink droplet ejection, the pressure in the liquid chamber is reduced, a negative pressure is generated in the liquid chamber due to the inertia of the ink flow and the discharge process of the driving voltage, and the ink flows into the liquid chamber from the common liquid chamber 15. To do.

Here, the piezoelectric element 5 and its base member 4
A method of joining with and will be described. Generally, as shown in FIG. 3, the adhesive 27 is applied to the base member 4 by a dispenser.
Applied to the upper surface of the base member 4 and the long piezoelectric element material 5
The a and 5b are aligned by a joining device and held in a pressurized state until the adhesive 27 is sufficiently cured. The piezoelectric element materials 5a and 5b adhesively bonded to the base member 4 in this way are cut with a dicing saw, a wire saw, or the like into a groove orthogonal to the channel direction (nozzle arrangement direction) to the upper surface of the base member 4 or its vicinity 2
As can be seen from the above, a method of dividing into a plurality of piezoelectric elements 5 corresponding to the liquid chamber 17 is adopted.

In the present invention, metal is used as the material of the base member 4. Such a metal base member 4
Are formed by, for example, metal injection. The metal injection is advantageous in reducing the cost of the base member 4 and also has a high degree of freedom in shape. In addition,
By using the base member 4 as a metal member, the selection range of the processing method is widened, and in addition to metal injection, processing methods such as press molding and forging can be adopted.

Further, according to the present invention, the piezoelectric element 5 is formed on the base member 4 by using the base member 4 as a metal member.
An anaerobic adhesive that initiates polymerization due to metal ions (mainly Cu ions) can be used as the adhesive 27 for joining to. With such an anaerobic adhesive,
As compared with the case of using a heat-curable adhesive or a two-liquid mixed room-temperature-curable adhesive, the curing time until the bonding strength reaches a necessary and sufficient level is significantly shortened.

According to the first embodiment of the present invention, the base member 4
SUS430 is used as the material of the
An ultraviolet curable anaerobic adhesive is used as 7. SU
S430 has no standard content of Cu, but in the present embodiment, Cu having a composition suitable for curing an ultraviolet curable anaerobic adhesive was prepared by mixing Cu in a metal powder at a rate of 0.09 to 0.1%. The base member 4 is formed by metal injection. In addition, it is also possible to adopt press forming, forging, etc. as a processing method. According to this embodiment, the time required to cure the adhesive 27 is shortened to about 180 seconds. However, in this embodiment, it is also possible to use an anaerobic adhesive that is not an ultraviolet curable type as the adhesive 27.

Now, as shown in FIG. 3B, when the long piezoelectric element materials 5a and 5b are placed on the base member 4 and pressed by the bonding apparatus, the adhesive 27 is applied to the lower surface of the piezoelectric element materials 5a and 5b. spread. At this time, if the amount of the adhesive agent 27 is small, the adhesive agent 27 does not spread over the entire lower surface of the piezoelectric element materials 5a and 5b, so that the bonding force decreases. It is necessary to adjust the application amount in consideration of the application variation of the dispenser so that the shortage of the adhesive 27 does not occur.

However, if the coating amount is adjusted in this way,
Even within the variation range, the amount of the adhesive 27 may be excessive. In this case, a part of the adhesive 27 creeps up the gap 28 (FIG. 3B) between the piezoelectric element materials 5a and 5b,
The adhesive adheres to the upper surfaces of the piezoelectric element materials 5a and 5b and the pressurizing portion (suction hand) of the joining device, and it becomes impossible to maintain the flat surface of the pressurizing portion. As a result, the pressing force becomes nonuniform. Cheap. In addition, a part of the adhesive 27 protrudes outside the piezoelectric element materials 5a and 5b, which is the piezoelectric element material 5
A thin film of an adhesive agent is likely to be formed on the external electrode surface 29 by crawling up between the external electrode surfaces 29 of a and 5b (FIG. 3B) and the holding mechanism of the bonding apparatus. Such a thin film cannot be removed by the flux when the FPC cable 7 is soldered, and causes a connection failure.

In order to prevent the adhesive from creeping up as described above, according to the second embodiment of the present invention, as shown in FIG. 4, at the center of the upper surface (bonding surface) of the base member 4, that is, , Between the piezoelectric element materials 5a and 5b (finally the piezoelectric element 5
A groove 30 for releasing the adhesive is formed at a position corresponding to the gap 28 (between rows). Piezoelectric element material 5a, 5
When b is placed on the base member 4 and pressed as shown in FIG. 5, the adhesive that spreads to the gap 28 side between the piezoelectric element materials 5a and 5b escapes into the groove 30, so that a large amount of adhesive is applied. Even in this case, the creeping up of the adhesive along the gap 28 can be prevented. Further, by adjusting the width and depth of the groove 30, it is possible to easily deal with a change in the adhesive application amount. When the piezoelectric elements 5 are arranged in three or more rows, that is, when three or more long piezoelectric element materials are lined up and bonded to the base member 4, the adhesive is allowed to escape to the positions corresponding to the gaps between the piezoelectric elements. It is sufficient to form the groove (30) for this.

Further, according to the second embodiment, as shown in FIG. 5, when the piezoelectric element materials 5a and 5b are joined to the base member 4, the external electrode surfaces of the piezoelectric element materials 5a and 5b and the base member 4 are formed. The width dimension of the base member 4 is determined so that the step 31 is formed between the side surface and the side surface. For example, the width of the base member 4 is set to a dimension narrower by about 0.1 mm on one side (0.2 mm on both sides) than the dimension obtained by adding the widths of the piezoelectric element materials 5a and 5b and the width of the gap 28. The piezoelectric element materials 5a and 5b are attached to the base member 4
When pressure is applied to the base member 4, the step 31 prevents the adhesive that has spread to the side surface of the base member 4 from creeping up to the external electrode surface of the piezoelectric element materials 5a and 5b.

The material of the base member 4 and the kind of the adhesive in the second embodiment are the same as those in the first embodiment.

An ultraviolet curing anaerobic adhesive is used as the adhesive 27 for joining the piezoelectric element 5 and the base member 4, and the curing time when the ultraviolet irradiation is not performed is 180 as described above.
It is about a second. In other words, the joining device is occupied for the pressure holding of both members for about 180 seconds or more. According to the present invention, in order to further reduce the occupancy time of the bonding apparatus, a gap for irradiating the adhesive with ultraviolet rays is formed in the peripheral portion of the bonding surface between the piezoelectric element materials 5a and 4b and the base member 4. .

In order to make such an ultraviolet irradiation gap,
According to the third embodiment of the present invention, as shown in FIG. 6, the chamfered surface 42 is formed at the upper surface end portion of each long side of the base member 4, and the upper surface end of each short side of the base member 4 is formed. A cutout surface 44 is formed in the portion. The material of the base member 4 is the same as that of the first embodiment.

When the piezoelectric element materials 5a, 5b and the base member 4 are joined, an adhesive 27 (ultraviolet curing anaerobic adhesive) is applied as shown in FIG.
An adhesive reservoir 48 is made in 4. Then, the base member 4 and the piezoelectric element materials 5a and 5b are pressed and held by a bonding device and irradiated with ultraviolet rays from the surroundings, so that FIG.
And, as shown in (c), the adhesive 4 protruding in a bead shape in the gap between the chamfered surface 42 and the piezoelectric element materials 5a and 5b.
7 and the adhesive 48 that fills the gap between the cutout surface 44 and the lower surfaces of the piezoelectric element materials 5a and 5b is hardened in a short time. Since both members are held in the bonded state by the adhesive around the bonding surface that is cured in this way, it is possible to remove the adhesive from the bonding device without waiting until most of the adhesive spread on the bonding surface is cured by the anaerobic reaction. Both members can be taken out. Therefore, since the occupying time of the joining device can be significantly reduced and the operating rate of the joining device can be increased, the number of installed joining devices can be reduced.

The notch surface 44 may be shaped so as not to reach the chamfered surface 42 as shown in FIG. Further, the notch surface 44 may be formed as one surface as shown in FIG. 9 instead of being formed separately on both sides of the adhesive escape groove 30. Further, although not shown, the cutout surface 44
Instead of this, a chamfered surface similar to that on the long side may be formed on the upper surface end portion on the short side of the base member 4. Also, the base member 4
1 in place of the chamfered surface 42 at the upper end of each long side of FIG.
You may form the notch surface 43 as shown in FIG.

Also in the third embodiment, as in the second embodiment, the creeping of the adhesive in the gap between the rows of piezoelectric elements is prevented by the groove 30, and the base member 4 is used.
The step between the side surface of the piezoelectric element material 5a and the external electrode surface of the piezoelectric element material 5a, 5b prevents the adhesive from creeping up to the external electrode surface.

When the base member 4 and the piezoelectric element materials 5a and 5b are bonded, it is necessary to position them relative to each other. When the positioning of the members is performed only on the side of the welding device, it is necessary to equip the holding mechanism of the welding device with a highly accurate position control mechanism, which causes a problem that the welding device becomes complicated and expensive. In order to improve this problem, in the present invention, the base member 4 is provided with a portion serving as a positioning reference with respect to the piezoelectric element 5 (the piezoelectric element materials 5a and 5b during the bonding process).

For example, according to the fourth embodiment of the present invention, FIG.
As shown in FIG. 1, a convex portion 58 as a positioning reference is formed at the center position of the upper surface of the base member 4. The groove 3 in the second or third embodiment is provided on both sides of the convex portion 58.
A groove 50 is formed for the same purpose as zero. The other structure is the same as that of the third embodiment.

When the piezoelectric element materials 5a and 5b are bonded to the base member 4, the bonding device holds the piezoelectric element materials 5a and 5b so as to abut the side surface of the convex portion 58 as shown in FIG. The piezoelectric element material 5
The widthwise positioning of a and 5b can be performed with high accuracy. Therefore, the holding mechanism of the joining device can be simplified and the cost of the joining device can be reduced.

When the ink jet head of the present invention is used, the piezoelectric element 5 has a driver I for driving it.
It is heated by the heat generated by C and the like. When the temperature of the piezoelectric element changes, its capacitance changes, which affects the ejection characteristics of ink droplets. In order to obtain stable ejection characteristics, it is necessary to cool the piezoelectric element 5. The inkjet head of the present invention is advantageous in terms of cooling the piezoelectric element 5 because the base member 4 is made of metal and has a good thermal conductivity, and the base member 4 effectively acts as a heat sink for the piezoelectric element 5. .

In order to further enhance the heat radiation effect of the base member 4, according to the fifth embodiment of the present invention, as shown in FIG.
A comb tooth-shaped portion 59 is formed on the lower surface side of the base member 4.
The other structure is the same as that of the third embodiment. However,
If the heat radiation area is increased, it is possible to form a non-planar shape portion different from the comb tooth-shaped portion 59 on the base member 4. It is also possible to form a similar comb-tooth-shaped portion or non-planar-shaped portion at an appropriate position on the side surface of the base member 4.
In addition, it is a matter of course that the present invention also includes an inkjet head in which the same comb tooth-shaped portion or non-planar shaped portion is provided on the base member 4 in the configuration of the first, second, or fourth embodiment.

[0037]

As is apparent from the above description, (1) According to the invention described in claim 1, the selection range of the method for processing the base member is widened, and the cost of the base member is reduced by adopting, for example, metal injection. By using an anaerobic adhesive that initiates polymerization by metal ions to bond the piezoelectric element and the base member, the time required for curing is shortened, productivity is improved, and bonding is achieved. Since the operating rate of the device is increased and the number of the bonding devices installed can be reduced, the total manufacturing cost of the inkjet head can be reduced. Since the metal base member having good thermal conductivity effectively acts as a heat sink for the piezoelectric element, it is possible to suppress the temperature rise of the piezoelectric element and stabilize the ink droplet ejection performance. (2) According to the invention as set forth in claim 2, the creeping of the adhesive between the upper surface of the piezoelectric element and the bonding apparatus through the gap between the piezoelectric element rows is prevented, and such creeping of the adhesive causes Bonding failure can be prevented. Further, since the creeping up of the adhesive can be prevented, it becomes easy to adjust the amount of the adhesive applied. (3) According to the third aspect of the invention, it is possible to prevent the adhesive from creeping up to the external electrode surface of the piezoelectric element, which causes electrical connection failure. (4) According to the invention described in claim 4, the time required to pressurize and hold the piezoelectric element and the base member by the bonding apparatus can be significantly shortened, so that the productivity of the inkjet head is improved and the bonding is performed. Since the operating rate of the equipment is further increased, it is possible to further reduce the total manufacturing cost. (5) According to the invention described in claim 5, since the piezoelectric element and the base member can be positioned by using the convex portion provided on the base member, the holding mechanism of the bonding apparatus can be simplified. Therefore, since the bonding apparatus can be made inexpensive, the total manufacturing cost of the inkjet head can be reduced accordingly. (6) According to the invention of claim 6, the effect of the heat sink of the base member is further enhanced, and the temperature rise of the piezoelectric element is suppressed more effectively, whereby the ink droplet ejection characteristics can be further stabilized. it can. And so on.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining an example of the overall configuration of an inkjet head according to the present invention.

2 is a schematic exploded perspective view of the inkjet head shown in FIG. 1. FIG.

FIG. 3 is a perspective view for explaining a step of joining the piezoelectric element and the base member.

4A and 4B are a partial plan view and a front view for explaining the shape of a base member according to the second embodiment of the present invention.

FIG. 5 is a front view showing a joined state of the base member and the piezoelectric element material according to the second embodiment of the present invention.

6A and 6B are a partial plan view, a front view, and a partial side view for explaining the shape of a base member in Embodiment 3 of the present invention.

7A and 7B are a partial plan view, a front view, and a partial side view for explaining a joining process between a base member and a piezoelectric element material according to a third embodiment of the present invention.

FIG. 8 is a partial plan view showing a modified example of the base member according to the third embodiment of the present invention.

FIG. 9 is a partial plan view showing a modified example of the base member according to the third embodiment of the present invention.

FIG. 10 is a front view showing a modification of the base member according to the third embodiment of the present invention.

11A and 11B are a partial plan view, a front view, and a partial side view for explaining the shape of a base member according to the fourth embodiment of the present invention.

FIG. 12 is a front view showing a joined state of a base member and a piezoelectric element material in Example 4 of the present invention.

FIG. 13 is a partial side view for explaining the shape of the base member according to the fifth embodiment of the present invention.

[Explanation of symbols]

1 Liquid chamber forming member 2 nozzle plate 3 diaphragm 4 Base member 5 Piezoelectric element 5a, 5b Piezoelectric element material 6 frame members 11 nozzles 16 common channels 17 Liquid chamber 29 External electrode surface 30 Grooves to release adhesive 31 steps 42 Chamfer 44 Notch surface 50 Groove to release adhesive 58 Convex portion as positioning reference 59 Comb-shaped part

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinichi Tsunoda             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Ken Watanabe             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Koji Noma             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F-term (reference) 2C057 AF93 AG48 AP16 AP25 AP75                       AP77 AQ06 BA04 BA14

Claims (6)

[Claims] 1. A vibrating plate constituting a part of a wall of a liquid chamber communicating with each of a plurality of nozzles is vibrated by a piezoelectric element arranged on a base member corresponding to the arrangement of the liquid chambers. In the ink jet head for ejecting the ink inside the liquid chamber from the nozzle, the base member is a member made of metal, and the base member and the piezoelectric element are bonded by an anaerobic adhesive that initiates polymerization by metal ions. Inkjet head characterized by having been made. 2. The ink jet head according to claim 1, wherein the piezoelectric elements are arranged in two or more rows, and the base member has grooves for allowing the adhesive to escape at positions corresponding to the rows of the piezoelectric elements. An inkjet head characterized in that. 3. The inkjet head according to claim 1, wherein the side surface of the base member is located inside the external electrode surface of the piezoelectric element, and has a step between both surfaces. 4. The ink jet head according to claim 1 or 2, wherein a gap for ultraviolet irradiation is provided in a peripheral portion of a joint surface between the base member and the piezoelectric element, and the adhesive is an ultraviolet curable anaerobic adhesive. An inkjet head characterized by being an agent. 5. The inkjet head according to claim 1, 2, 3 or 4, wherein the base member has a convex portion as a positioning reference with respect to the piezoelectric element. 6. The ink jet head according to claim 1, wherein the base member has a non-planar portion for increasing a heat radiation area.