JP2803938B2 - 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 an ink jet head used in an ink jet printer or the like which performs printing by ejecting ink from nozzles onto a recording medium such as paper.

[0002]

2. Description of the Related Art The above-mentioned ink-jet head has a structure in which a piezoelectric element is provided in an ink-jet head having a nozzle-shaped end portion in an ink-jet head unit. By deforming the piezoelectric element to reduce the cross-sectional area of the ink flow path of the ink jet head, the ink in the ink jet head is ejected from the nozzles to land on paper, thereby performing printing.

FIG. 2 is a perspective view showing such a conventional ink jet head.

As shown in FIG. 2, in a conventional ink jet head 1, a plurality of ink flow paths 3, 3... Are formed inside a substrate 2, and one of the ink flow paths 3 is A nozzle 4 for discharging ink is formed on a side surface of the substrate 2 in the longitudinal direction in the figure, and an ink inlet 5 is formed on the other side. A metal layer 6 that is used as an electrode when the surface of the substrate 2 is poor in conductivity is formed on one surface outside the substrate 2, that is, on the upper surface in the figure, and further outside the metal layer 6. Has conductivity so that the substantially disk-shaped piezoelectric element 7 is electrically connected to the lower surface of the piezoelectric element 7 so as to face each of the ink flow paths 3 and correspond to each of the ink flow paths 3. They are joined by an adhesive member (not shown). Further, as shown in FIG. 3, an individual electric circuit portion of a wiring member 8 such as a flexible printed circuit (FPC) is joined (not shown) to the upper surface side of each piezoelectric element 7, and one of the poles (normally Is an anode). Further, a common electric path portion of the wiring member 8 is joined (not shown) to the metal layer 6 as the other pole (usually a cathode). Thus, the piezoelectric element 7 is electrically connected to the wiring member 8 via the metal layer 6. The metal layer 6 disposed on one surface of the substrate 2, the piezoelectric element 7, and the joint of the wiring member 8 are
It is shea Rudo to cover by the sealing member 9,
Insulated from outside.

[0005]

However, in the above-described conventional device, the piezoelectric element 7 and the wiring member 8 are not provided.
By shea Rudo by the sealing member 9 and the like, deformation behavior of the piezoelectric element 7 is suppressed, not able to transmit the desired displacement in each ink channel 3, a desired amount of ink from the nozzles 4 There was a problem that it could not be ejected.

In order to cope with such a problem, conventionally, the bonding strength of the bonding member and the sealing member 9 of the piezoelectric element 7 to the substrate 2 or the metal layer 6 has been appropriately selected.

[0007] However, the adhesive strength of the adhesive member is affected by the surface condition of the surface to be adhered, and there is a problem that the inkjet head 1 of stable quality cannot be obtained.

The present invention has been made in view of these points, and overcomes the above-mentioned problems in the conventional art.
Be sheet <br/> Rudo with a sealing member of the piezoelectric element after bonding an adhesive member to the substrate, without interfering with the displacement operation of the piezoelectric element,
An object is to provide an inkjet head of stable quality.

[0009]

In order to achieve the above-mentioned object, an ink jet head according to the present invention has a piezoelectric element bonded to a conductive base, and is shielded by a sealing member so as to cover the outside of the piezoelectric element. In the ink jet head, the hardness of an adhesive member used for joining the base and the piezoelectric element is A, and the hardness of a sealing member covering the piezoelectric element is B.
A is characterized by being 80 or more in Shore D hardness and B being 85 or less in Shore A hardness.

[0010]

According to the ink jet head of the present invention having the above-described structure, the base and the piezoelectric element are firmly fixed by the hardened adhesive member after curing. The sealing member has low hardness after curing and has flexibility. Therefore,
Variation of piezoelectric element sheet Rudo to cover the outer the sealing member is transmitted accurately to the substrate, the desired displacement is transmitted to the ink flow path, making it possible to reliably inject the desired amount of ink from the nozzle it can.

[0011]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a longitudinal sectional view of a main part in which the present invention is applied to a base having a metal layer.

As shown in FIG. 1, an ink-jet head 10 of this embodiment is provided with a metal layer 6 provided on the surface of an insulating substrate 2 by an appropriate method such as vapor deposition and sputtering. Is formed. On the surface of the metal layer 6 forming the base, the opposing surface 12 (the lower surface in the figure) on which the piezoelectric element 7 faces the substrate 2 via the adhesive member 11
Are joined together. Then, the substrate 2 of the piezoelectric element 7
The conductor 15a formed at one end of the individual electric circuit portion of the wiring member 8 is joined to the opposite facing surface 13 via a joining member 14 such as a conductive paste to constitute an anode.

As the bonding member 11 used for bonding the metal layer 6 and the piezoelectric element 7, an appropriate one such as an epoxy-based two-liquid type having conductivity is used.
The hardness after curing is 80 or more in Shore D hardness.

A conductor 15b formed at one end of the common electric circuit portion of the wiring member 8 is joined to an appropriate position of the metal layer 6 via a joining member 14 such as a conductive paste to form a cathode. I have.

Furthermore, each of the components disposed on the metal layer 6 is shea Rudo so as to cover the outer by the sealing member 16. As the sealing member 16, a material having a hardness after hardening of 85 or less in Shore A hardness is appropriately selected from silicon, butyl rubber, epoxy and the like.

Next, in the ink jet head 10 according to the present embodiment having the above-described structure, the bonding member 11
A performance experiment was performed on the relationship between the hardness after curing of the sealing member 16 and the ink ejection amount. The evaluation method is based on the hardness after curing of the epoxy-based two-liquid mixed type adhesive member 11 having conductivity used for bonding the piezoelectric element 7 and the metal layer 6, and does not use the sealing member 16. Was used as a standard sample, and the ejection amount of ink in this standard sample was taken as a standard ejection amount. A sample having an ejection amount of 85% or more with respect to this standard ejection amount, which had no problem in printing, was accepted.

Table 1 shows the results of the performance experiments.

[0019] As is apparent from the experimental results, the adhesive member 11 having a cured hardness of 80 or more in Shore D hardness and the sealing member 16 having a cured hardness of 85 or less in Shore A hardness are described above. It turned out that it was possible to cross the passing line.

If the hardness of the adhesive member 11 after curing is 70 or less in Shore D hardness, the sealing member 16
It was confirmed that even without using the ink, there was a large variation in the ink discharge amount with respect to the above-mentioned acceptable line of the ink discharge amount, the ink discharge amount became unstable, and the ink could not be used.

When the deformation of the piezoelectric element 7 is transmitted to the substrate, the bonding member 11 has a flexibility such that the hardness after curing is smaller than 80 in Shore D hardness. Because a part of the deformation amount of the element 7 is absorbed, the displacement operation of the piezoelectric element 7 is not accurately transmitted to the base. The sealing member 16 which sheet Rudo piezoelectric element 7 is of course necessary to have a flexibility becomes possible to restrain the deformation behavior of the piezoelectric element 7, the hardness after curing those 85 hard greater than the Shore A hardness In order to secure the desired ink discharge amount, it is not possible to use a piezoelectric element having a larger deformation amount, or to increase the deformation amount of the piezoelectric element 7 by increasing the applied voltage. This is because power consumption must be increased.

For the reasons described above, the hardness of the bonding member 11 between the piezoelectric element 7 and the metal layer 6 formed on the surface of the substrate 2 after hardening is set to 80 or more in Shore D hardness. The joining surface between the element 7 and the metal layer 6 formed on the surface of the substrate 2 is rigidly and integrally joined without being affected by the magnitude of the adhesive strength, and the deformation operation of the piezoelectric element 7 is accurately transmitted. . By setting the hardness after curing of the sealing member 16 to 85 or less in Shore A hardness, it is possible to prevent the displacement operation of the piezoelectric element 7 from being restricted. This makes it possible to always satisfactorily eject ink from the nozzles 4 and to perform extremely high quality printing.

As the substrate to which the piezoelectric element 7 is bonded, the substrate 2 having conductivity at least on the surface can be employed without the metal layer 6 of the above embodiment. In this case, the piezoelectric element 7 is bonded. The member 11 can be directly joined to the substrate 2.

Further, the present invention is not limited to the above-described embodiment, but can be changed as needed.

[0025]

As described above, according to the present invention, the hardness after curing of the adhesive member used for bonding the ink jet head to the base and the piezoelectric element and the hardness after curing of the sealing member are controlled. The simple effect of this is that the displacement operation of the piezoelectric element can be transmitted without disturbing the ink to be always ejected satisfactorily, resulting in an extremely high reliability and an extremely excellent effect of obtaining stable quality. Can be played.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part showing an ink jet head of the present invention.

FIG. 2 is a perspective view of a main part showing a conventional ink jet head.

Similar view to Figure 3 Figure 2 that sheet Rudo a sealing member

[Explanation of symbols]

 2 Substrate 6 Metal layer 7 Piezoelectric element 8 Wiring member 10 Inkjet head 11 Adhesive member 17 Sealing member

Claims (1)

(57) [Claims] 1. A bonding the piezoelectric element to a substrate having conductivity, the ink jet head formed by sheet Lumpur <br/> de so as to cover the outside of the piezoelectric element by the sealing member, and the substrate and the piezoelectric element When the hardness of the adhesive member used for the bonding of A is A and the hardness of the sealing member covering the piezoelectric element is B, A is 80 or more in Shore D hardness, and B is 85 or less in Shore A hardness. Characteristic inkjet head.