JP3306979B2 - 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 a so-called on-demand type ink jet head for printing by discharging ink droplets from nozzles.

[0002]

2. Description of the Related Art Conventionally, an ink jet head presses a pressurizing chamber of an ink flow path provided on a flow path substrate to apply pressure to the ink and discharge ink from a nozzle. A piezoelectric element is adhered to the opposing outer surface. A flexible cable (FPC) is connected to the piezoelectric element in order to supply electric power to the piezoelectric element from an external power supply.

[0003] However, the FPC has a problem in that the conductive pattern is covered with a synthetic resin such as polyimide or polyester, so that it is difficult to attach an adhesive, and thus the adhesive strength is weak. Therefore, besides bonding, using various parts, FPC
Is pressed toward the piezoelectric element to increase the bonding strength. For example, according to JP-A-63-4956, an FPC is superposed on a head substrate via conductive rubber,
A pressing rubber is superimposed on the back of C, and a pressing member is superimposed on the back, and finally fixed by a screw to conduct the FPC and the piezoelectric element.

In addition, when ink discharged from a nozzle goes around the piezoelectric element, there is a danger that a plurality of piezoelectric elements may be short-circuited via the ink. To prevent this, a sealing rubber member is fixed.

[0005]

According to the above-mentioned prior art, a large number of parts are required for conducting the FPC and the piezoelectric element, and the number of assembling steps is increased, thereby increasing the cost. Was invited. Further, another part is required to seal the periphery of the piezoelectric element, and the assembling is complicated and the cost is increased.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet head which can reduce the number of parts, and at the same time, can easily establish conduction between the ink discharging means and the FPC, and can also seal the ink discharging means at the same time. provide. Another object of the present invention is to improve the adhesive strength between the FPC and the flow path substrate or the lid, and to increase the reliability of sealing of the ink discharge means.

[0007]

According to the present invention, there is provided an ink jet head including a flow path substrate having an ink flow path formed therein, a lid plate laminated and joined to the flow path substrate, and one of the flow path substrate and the lid plate. And a flexible cable having a plurality of terminals electrically connected to the ink discharge means, the plurality of ink discharge means formed corresponding to the ink flow paths, and a plurality of ink discharge means around the plurality of ink discharge means. An adhesive layer is arranged so as to surround the plurality of ink discharging means in a common space, and the flexible cable and the adhesive layer are fixed so as to seal the ink discharging means in a liquid-tight manner. And the terminal portion and the ink discharging means are electrically connected. In the ink jet head, the adhesive layer is made of a sheet-like adhesive. Further, in such an ink jet head, the adhesive layer is characterized by being 20 to 50 μm thicker than the thickness of the ink discharging means. Further, in such an ink jet head, a protrusion having a thickness substantially equal to the thickness of the ink discharging means is formed on one of the flow path substrate and the lid plate, and the flexible cable is provided with an adhesive layer interposed therebetween. And is adhered on the protrusion. In such an ink jet head, a metal plating layer is formed on the bonding surface of the flexible cable so as to correspond to the adhesive layer. Further, in such an ink jet head, the flexible cable is a double-sided board, the terminal portion is electrically connected to the conductive pattern provided on the non-adhesive surface through the through hole, and the metal layer provided on the adhesive surface is independent of the conductive pattern. It is characterized by having.

When the adhesive layer is a sheet-like adhesive, the formation of the adhesive layer is facilitated. When the thickness of the adhesive layer is 20 to 50 μm thicker than the thickness of the ink discharging means, the ink discharging means has the best conduction state and the sealed state with the terminal portion of the flexible cable.

A projection having a height substantially equal to the thickness of the ink discharge means is formed on one of the flow path substrate and the cover plate so as to surround the periphery of the ink discharge means.
When the flexible cable is adhered onto the protrusion via the adhesive layer, the degree to which the conductive state and the sealed state depend on the thickness of the adhesive layer is reduced.

On the bonding surface of the flexible cable,
When a metal plating layer is formed to correspond to the adhesive layer,
The reliability of bonding is improved.

Further, the above-mentioned flexible cable is a double-sided board, the terminal portion is electrically connected to the conductive pattern provided on the non-adhesive surface through a through hole, and the metal plating layer provided on the adhesive surface is independent of the conductive pattern. By doing so, the two functions of bonding and conduction can be provided compactly on the flexible cable.

[0012]

The flexible cable and the flow path substrate or the lid plate are adhered by an adhesive layer provided around the ink discharging means,
Since the ink discharging means is located in the space surrounded by the adhesive layer, the joining between them is ensured, and the space where the ink discharging means is located is in a sealed state.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The overall structure of an embodiment of the ink jet head of the present invention will be described with reference to FIGS. The flow path substrate 1 is made of a material such as polysulfone which is strong against ink and suitable for adhesion, and is formed by penetrating a plurality of nozzles 1a... And communication holes 1b in the thickness direction. As shown in FIG. 2, a protrusion 1c is provided on the front surface of the central portion of the flow path substrate 1,
The nozzles 1a are protruded by excimer laser processing.
Drill through c. FIG. 2 shows the nozzle 1a and the ink discharge means 3. On the back of the flow path substrate 1, FIG.
As shown in FIG. 5, a groove-shaped ink flow path is cut out so as to communicate with the communication holes 1b substantially orthogonally. However, a plurality of pressure chambers 1d are provided in a part of the ink flow path. Each pressurizing chamber 1d, each communication hole 1b, and each ink supply hole 2
, 1f,... communicating with a are formed. Therefore, the nozzle 1a communicates with the ink flow path 1e via the communication hole 1b, and the ink supply hole 2a communicates with the ink flow path 1f.

Behind the flow path substrate 1, a first substrate 2, which is a lid plate joined to the ink flow path engraving surface, is laminated.
Are formed through the substrate 2 in the thickness direction. The ink supply holes 2a are formed by excimer laser processing or the like, and the ink flow path 1f is formed as described above. It is open to.

A second substrate 4 is stacked behind the first substrate 2, and an ink supply hole 2 is provided on the front side of the second substrate 4.
A common ink chamber 4a is formed so as to be orthogonal to and communicate with the a. An opening 4b for supplying ink is provided at the center of the common ink chamber 4a.

An ink discharge means 3 is provided on the upper surface of the flow path substrate 1 at a position facing each pressurizing chamber 1d. That is, as shown in FIGS. 2 and 4, the ink discharge means 3 includes a plurality of diaphragms 3a made of metal such as phosphor bronze or brass.
And a plurality of piezoelectric elements 3b are superimposed on each other, and are bonded to the flow path substrate 1 with an adhesive such as epoxy.

Each piezoelectric element 3b has a flexible cable (FPC) 5 on which a pattern electrode electrically connected to an external driver IC (not shown) for driving the piezoelectric element is formed.
Are electrically connected to predetermined electrodes.

As shown in FIG. 5, the bonding surface of the FPC 5 (lower surface in FIG. 1) is formed on a base film 5a by a plurality of terminal portions 5a.
b and a copper foil to be a conductive pattern 5c conducting to the terminal portion are joined by an adhesive, and a portion excluding the terminal portion 5b is
A cover film (not shown) is joined by an adhesive.
The terminal portion 5b is exposed and can contact the piezoelectric element 3b.

As shown in FIG. 1, the FPC 5 is electrically connected to the piezoelectric element 3b at its terminal portion 5b. Between the upper surface of the flow path substrate 1 and the lower surface of the FPC 5, a vibration plate 3a and a piezoelectric element 3b are provided. There is a gap corresponding to a thickness of 0.2 to 0.3 mm with respect to 3b. Therefore, in the present invention, a gap around the ink ejection means 3 in which the vibration plate 3a and the piezoelectric element 3b are laminated is provided.
Adhesive layers 6 and 7 are provided to bond the flow path substrate 1 and the FPC 5, and at the same time, conduct electricity between the piezoelectric element 3b and the FPC 5. A sheet-like adhesive is used for the adhesive layers 6 and 7, and the thickness of the sheet-like adhesive is set to be 20 to 50 μm thicker than the thickness of the gap. Since the vibration plate 3a and the piezoelectric element 3b are located in a ring-shaped space between the two sheet-like adhesives 6 and 7, they are sealed by the adhesion between the flow path substrate 1 and the FPC 5. Are electrically connected to predetermined common electrodes of the FPC 5 by means not shown.

The result of a test on the relationship between the thickness of the vibration plate 3a and the piezoelectric element 3b in the laminated state and the thickness of the adhesive layers 6 and 7 will be described below. Since each of the diaphragm 3a and the piezoelectric element 3b has a thickness of 120 μm, the FPC 5
There is a gap of 240 μm between the substrate and the flow path substrate 1.
When this gap is sealed with a sheet-like adhesive such as epoxy, if the sheet-like adhesive having a thickness of 240 μm or less is used, the flow path substrate 1 and the FPC 5 are not joined, so that the diaphragm 3a and the piezoelectric The element 3b was not sealed. Next, the thickness of the sheet adhesive is 240 to 260 μm.
m, the flow path substrate 1 and the FPC 5 are partially adhered but not adhered to each other.
And the piezoelectric element 3b were not completely sealed, and some of the piezoelectric elements 3b were electrically connected to the terminal portion 5b, but all of them could not be electrically connected. Therefore, the thickness of the sheet adhesive is 260
In the case of about 290 μm, the flow path substrate 1 and the FPC 5 are completely joined, the diaphragm 3 a and the piezoelectric element 3 b are in a sealed state, and all the piezoelectric elements 3 b are completely conducted to the terminal portion 5 b, and the conduction failure occurs Did not occur. Finally, when the thickness of the sheet adhesive is 290 μm or more, the flow path substrate 1 and the FPC 5 are completely joined, so that the sealing state between the vibration plate 3a and the piezoelectric element 3b is perfect, but the piezoelectric element 3b
And the terminal portion 5b could not be conducted. As a result of this test, it was found that an adhesive layer 20 to 50 μm thicker than the thickness of the gap was most desirable.

FIGS. 6 to 8 show another embodiment.
As shown in FIG. 6, the flow path substrate 11 has a plurality of nozzles 11a and communication holes 11b penetrating in the thickness direction in the same manner as described above, a protruding portion 11c on the front surface in the center, and an ink flow path 11e on the back surface. In addition to the chamber 11d and the ink flow path 11f,
Ring-shaped projections 11g and 11h are integrally formed so as to protrude from the upper surface so as to surround a space in which the ink ejection means 13 formed by laminating the vibration plate 13a and the piezoelectric element 13b is located. The heights of the projections 11g and 11h are substantially equal to the thickness of the lamination of the vibration plate 13a and the piezoelectric element 13b.

The FPC 15 is a double-sided board. The upper surface in FIG. 8 is a non-adhesive surface, and the lower surface is an adhesive surface to the flow path substrate 11. FIG. 7 shows an upper surface of the FPC 15, in which a conductive pattern 15i is formed by forming a metal plating layer 15c on a copper foil 15b adhered to an upper surface of a base film 15a with an adhesive (not shown). Then, on the upper surface of the FPC 15, a terminal portion 15 on the bonding surface side described later is provided.
cover coating 15f over the entire area except for the area corresponding to j.
(See FIG. 8) is adhered by an adhesive 15e.

On the other hand, a copper foil 15b and a metal plating layer 15c are also provided on the bonding surface (lower surface) of the base film 15a, and this serves as a terminal portion 15j that can contact the piezoelectric element 13b.

The detailed configuration of the FPC 15 will be further described with reference to FIG. 8 (an enlarged cross-sectional view of a main part of the FPC 15). A hole 15d is provided in the base film 15a. Copper foil 1 on both upper and lower sides)
5b is adhered, and a through-hole 15k is formed by covering the copper foil 15b and providing a metal plating layer 15c on the inner peripheral surface of the hole 15d. The terminal portion 15j on the lower surface of the base film 15a is a through hole 1
The terminal 15j and the conductive pattern 15i are electrically connected because they are continuous with the conductive pattern 15i through the inner peripheral surface of 5k (metal plating layer 15c).

In this way, when an external circuit (not shown) conducts to the conductive pattern 15i on the upper surface of the FPC 15,
The conductive pattern 15i is conducted to the terminal 15j on the lower surface of the FPC 15 through the inner peripheral surface of the through hole 15k, and further contacts the terminal 15j with the piezoelectric element 13b.
To be conducted.

Further, on the bonding surface (lower surface) of the FPC 15,
A copper foil 15g is formed on the lower surface of the base film 15a so as to face the ring-shaped protrusions 11g and 11h (see FIG. 6).
Is adhered by an adhesive (not shown) and a metal plating layer 1
5h are formed. The terminal 15j and the metal plating layer 15h are exposed, and a cover film 15f is adhered to the other portions with an adhesive 15e. The metal plating layer 15h is formed in an independent ring shape on the inside and outside of the terminal portion 15j, respectively.
j and the conductive pattern 15c.

Therefore, as shown in FIG. 6, when the FPC 15 is bonded, first, a thin ring-shaped sheet adhesive 1 is used.
6 and 17 are placed on the protrusions 11g and 11h, and the FPC 1
No. 5 metal plating layer 15h to sheet adhesive (adhesive layer)
16 and 17, and the two piezoelectric elements 13b are opposed to the terminal portions 15j so that the piezoelectric elements 13b face each other. Then, the metal plating layer 15h and the protrusions 11g, 11h are firmly bonded to each other via the sheet adhesives 16, 17 by pressing. Thereby, each terminal 15j and each piezoelectric element 13b come into contact, and each terminal 15j is electrically connected to each conductive pattern 15i. Further, the respective piezoelectric elements 13b and the respective terminal portions 15j may be joined by soldering via the respective through holes 15k.

Therefore, the piezoelectric element 13b is electrically connected to the conductive pattern 15i from the terminal portion 15j, but the metal plating layer 15h does not contribute to the electrical connection.
Conventionally, the base film 15a of the FPC 15 made of polyimide or the like has poor adhesion with an adhesive such as an epoxy resin. However, the provision of the metal plating layer 15h improves the adhesion strength between the flow path substrate 11 and the FPC 15. It will contribute. By this strong bonding, the space where the vibration plate 13a and the piezoelectric element 13b are located can be kept in a sealed state.

In this embodiment, the lid 2 and the second substrate 4, which are the first substrates, are substantially the same as those in the above-described embodiment, and are denoted by the same reference numerals.

When ink is ejected by the ink jet head of the present invention, a driving signal from a driver IC is supplied to the piezoelectric elements 3b, 1 via the flexible cables 5, 15.
3b, the piezoelectric elements 3b, 13b are deformed and the diaphragms 3a, 13a are bent into the pressurizing chambers 1d, 11d,
Thereby, the ink in the pressurizing chamber is pressurized to generate pressure. The ink is ejected from the nozzles 1a, 11a by this pressure through the ink flow paths 1e, 11e and the communication holes 1b, 11b.

When the ink is ejected or when the ink is filled into the ink flow path, the ink may flow out of the nozzle. However, the space in which the ink ejection means 3 and 13 are arranged is as described above. The adhesion between the flow path substrates 1, 11 and the FPCs 5, 15 is strengthened, and the adhesive layers 6, 7, 16, 1
7, the ink does not enter the space, and there is no inconvenience such as a short circuit.

When the FPC is a double-sided substrate, the conductive pattern can be distributed to the non-adhesive surface on one surface of the base film, and the terminal portion and the metal plating layer can be distributed to the adhesive surface on the other surface of the base film. Can be reduced in area.

Incidentally, copper, gold, nickel or the like is appropriately used for the metal plating layer. Further, when the common ink chamber is provided at a different position from the above example, the ink discharge means may be fixed to the outer surface of the lid plate corresponding to the ink flow path.

[0034]

As described above, the ink jet head of the present invention comprises a flow path substrate having an ink flow path formed therein,
A lid plate laminated and joined to the flow path substrate, a plurality of ink discharging means formed on one of the flow path substrate and the lid plate corresponding to the ink flow path, and a plurality of electrical connections with the ink discharging means And a flexible cable having a terminal portion of the above, wherein an adhesive layer is arranged around the plurality of ink ejection means so as to surround the plurality of ink ejection means in a common space, and is bonded to the flexible cable. The terminal layer and the ink discharging means are electrically connected by the liquid layer and the agent layer being fixed so as to seal the ink discharging means in a liquid-tight manner. At the same time as
The plurality of ink ejection units are located in a space sealed by an adhesive layer surrounding the common space. Therefore, it is possible to seal a plurality of ink discharging means simultaneously with conduction with a small number of steps and a small number of parts, and to provide a highly reliable ink jet head at a low cost.

[0035]

[0036]

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a perspective view showing a state before joining the flexible cables of FIG. 1;

FIG. 3 is a rear view of the flow path substrate of FIG. 1;

FIG. 4 is a sectional view taken along line AA of FIG. 2;

FIG. 5 is a bottom view of the flexible cable shown in FIG. 1 in a state where a cover film is removed.

FIG. 6 is a sectional view showing another embodiment of the present invention.

FIG. 7 is a top view of the flexible cable of FIG. 6 in a state where a cover film has been removed;

FIG. 8 is an enlarged sectional view taken along the line 7B-B of FIG.

[Explanation of symbols]

 1,11 flow path substrate 1d, 1e, 1f ink flow path 11d, 11e, 11f ink flow path 11g, 11h protrusion 2 lid 3,13 ink discharge means 5,15 flexible cable 5b, 15j terminal 15i conductive pattern 15k Through hole 15h Metal plating layer 6,7,16,17 Adhesive layer (Sheet adhesive)

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B41J 2/01 B41J 2/045-2/055 B41J 2/16 B41J 29/00

Claims (6)

(57) [Claims] 1. A flow path substrate having an ink flow path formed thereon, a lid plate laminated and joined to the flow path substrate, and one of the flow path substrate and the lid plate corresponding to the ink flow path. And a flexible cable having a plurality of terminals electrically connected to the ink discharging means, the plurality of ink discharging means formed around the plurality of ink discharging means. Ink ejection
The adhesive layer is arranged so as to surround the delivery means in a common space.
And the flexible cable and the adhesive layer are
Is fixed so that the discharge means is liquid-tightly sealed.
As a result, the terminal portion and the ink ejection unit are electrically connected.
Inkjet head characterized by being connected
De. 2. The ink jet head according to claim 1, wherein said adhesive layer is made of a sheet adhesive. 3. The ink jet head according to claim 1, wherein the adhesive layer is thicker by 20 to 50 μm than a thickness of the ink discharge unit. 4. A projection having a thickness substantially equal to a thickness of the ink discharge means is formed on one of the flow path substrate and the lid plate, and the flexible cable is provided with an adhesive. The ink-jet head according to claim 1, wherein the ink-jet head is adhered on the protrusion via a layer. 5. The ink jet head according to claim 1, wherein a metal plating layer is formed on an adhesive surface of the flexible cable so as to correspond to the adhesive layer. 6. The flexible cable is a double-sided board, the terminal portion is electrically connected to a conductive pattern provided on a non-adhesive surface via a through hole, and the metal plating layer provided on the adhesive surface is a conductive material. The ink jet head according to claim 5, wherein the ink jet head is independent of the pattern.