JP3215789B2 - Inkjet recording 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 structure of an ink jet head for selectively depositing ink droplets on an image recording medium.

[0002]

2. Description of the Related Art Nozzles communicating with a pressure chamber by displacing a diaphragm forming one of the walls of a pressure chamber by utilizing the displacement in the thickness direction of a laminated piezoelectric element to pressurize ink filled in the pressure chamber. An ink jet head for ejecting more ink is shown in JP-B-7-57545. Fig. 7 shows the outline of the structure.
As shown in FIG. 5, a plurality of laminated piezoelectric elements 107 that can be independently driven are formed by bonding a laminated piezoelectric material on a rigid member 109 and forming a groove on the laminated piezoelectric material surface, thereby forming one wall of the pressure chamber 102. By displacing the vibration plate 103 to be formed,
Ink is injected from the nozzle 111 communicating with the pressure chamber 102 by pressurizing the ink filled in the ink chamber 02. This configuration is intended to increase the amount of displacement in the thickness direction by laminating the piezoelectric bodies, and as a result, to arrange the pressure chambers with high density. Further, the laminated piezoelectric element 107 is
It is also electrically connected to the electrode pattern 108 formed on the support member 03 and the rigid member 109, and the purpose is to facilitate driving from the outside.

However, in the above structure, the pitch of the laminated piezoelectric element 107 is determined by the processing limit of the groove, and there is a problem in making the nozzle pitch denser. For example, high quality 1
A nozzle arrangement pitch for printing equivalent to 600 dots per inch (600 dpi) cannot be configured because it far exceeds the groove processing limit by a machine. Further, if a multi-nozzle head having more than 60 nozzles is configured, the rigid member 109 cannot sufficiently fix the diaphragm 103 at the central portion.
If it is not made thick and large enough to withstand the reaction force caused by the drive of No. 7, crosstalk will occur.

When a multi-nozzle head having a large number of nozzles is formed, a large number of grooves are formed in the laminated piezoelectric body by machining, so that silver (Ag), which is an electrode component inside the laminated piezoelectric body, is formed of a dielectric. It has been found that the probability of occurrence of a defect in which the insulation resistance is reduced by rubbing against the piezoelectric body wall is increased.
For this reason, there is a problem that the yield is reduced and the productivity is deteriorated. Further, the laminated piezoelectric element 107 is
3 is electrically connected to the electrode pattern 108 formed on the rigid member 109, and the electrode pattern 108 is further connected to an external drive signal line. .

Further, since the supply path of the electric energy is exposed to the external environment, there is a problem that the ink ejected from the nozzle 111 flows onto the laminated piezoelectric element 107 or the electrode pattern 108 to cause an electric short circuit.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such a problem.
A small, high-performance ink jet recording head that arranges a laminated piezoelectric element on a substrate and forms a print head with a vibration plate and a pressure chamber and ejects ink from the end face in the direction in which the laminated piezoelectric element, the substrate and the pressure chamber are arranged. Another object of the present invention is to provide a simple multi-nozzle on-demand ink jet head and to provide a highly productive and reliable ink jet recording head.

[0007]

In order to achieve the above object, an ink jet head according to the present invention employs the following configuration. The first ink jet head according to the present invention comprises:
A laminated piezoelectric element unit in which a plurality of laminated piezoelectric elements are bonded on an insulating substrate, a fixing member for holding the piezoelectric element unit, a vibration plate joined to the free end plane of the laminated piezoelectric element and the fixing member, and A plurality of head units each composed of a pressure chamber adhered to the head and a flow path substrate having an ink supply port are fixed to a frame, and a nozzle plate is bonded to the end surface of the head unit and the surface of the frame.

A second ink jet head according to the present invention is a laminated piezoelectric element unit in which a plurality of laminated piezoelectric elements are bonded on an insulating substrate, a fixing member for holding the piezoelectric element unit, and a free end plane of the laminated piezoelectric element. A diaphragm bonded to a fixed member, a flow path substrate formed with a pressure chamber and an ink supply port bonded to the vibration plate, and a nozzle plate bonded to end faces of the fixed member, the vibration plate, and the flow path substrate Are fixed to the frame so that the intervals between the nozzle rows of the nozzle plate are constant.

A third ink jet head according to the present invention is characterized in that a portion corresponding to an end face of the laminated piezoelectric body on the insulating substrate is chamfered or grooved.

In a fourth ink jet head according to the present invention, the plane formed by the frame and the plane of the nozzle plate are pressed against the flat surface on the jig, and the position of the nozzle row is determined by the positioning mark formed on the nozzle plate. After the determination, the method is characterized in that a plurality of head units are fixed to the frame with an ultraviolet curable adhesive.

A fifth ink jet head according to the present invention is characterized in that a drive signal input line from the outside is directly electrically connected to a collecting electrode portion for applying a voltage to each piezoelectric layer of the laminated piezoelectric element.

In a sixth ink jet head according to the present invention, in the electrical contacts connected to the collecting electrode portion of the laminated piezoelectric element, a drive signal input contact from the outside is a linear electrical contact obtained by stripping the FPC. Features.

[0013]

FIG. 1 is an exploded perspective view showing a schematic structure of an ink jet recording head for explaining a first embodiment of the present invention, and FIG. 2 shows a part of the ink jet recording head. FIG. 3 is an exploded perspective view of the head unit, and FIG. 3 is a sectional view of the head unit. Hereinafter, the schematic configuration of the ink jet recording head will be described with reference to FIG.

As shown in FIG. 3, 20 μm having a piezoelectric effect
A paste-like electrode layer 31 containing silver as a main component is laminated on a paste-like piezoelectric material plate 30 having a thickness of about m, and a plurality of the piezoelectric material plates 30 and the electrode layers 31 are successively laminated, and then fired. 20 is formed. The electrode layers 31 are formed on both surfaces of each piezoelectric material plate, one of which is exposed to the collector 22a on the end face, and the other is exposed to the collector 22b on the opposite end face. The collecting electrodes 22a and 22b are
Chromium, nickel, and gold are sequentially formed by applying thin film forming means such as a vacuum evaporation method. When a voltage is applied between the collecting electrode 22a and the collecting electrode 22b of the laminated piezoelectric body 20, an electric field is generated in each of the piezoelectric material plates 30, and each of the piezoelectric material plates extends by a minute dimension in the thickness direction. As integration, the laminated piezoelectric body 20 is displaced by a required amount in the thickness direction.

As shown in FIG. 2, the laminated piezoelectric body 20 is bonded onto an insulating substrate 21 made of an insulating material such as ceramic. Further, a groove is formed from the upper surface of the laminated piezoelectric body 20 by a mechanical processing means such as a wire saw to divide the laminated piezoelectric body 20 into laminated piezoelectric elements 23 which can be driven independently, thereby forming a piezoelectric element unit 25. External power is FPC
(Flexible, printed, cable) 24 and a contact electrode 22a which are supplied by 24 and become bare near the end.
a, The collector electrode 22b is electrically connected by a method such as soldering. Since the laminated piezoelectric element 23 is displaced in the thickness direction and also in the length direction and the width direction which are the vertical directions at the same time, the electrode pattern is formed on the upper surface or the lower surface of the laminated piezoelectric element 23 or another member, and the collecting electrodes 22a, According to the conventional method of connecting to the surface 22b, disconnection often occurs at the connected portion. When the method of electrically connecting the FPC 24 directly to the collecting electrodes 22a and 22b of the laminated piezoelectric element 23 as in the embodiment of the present invention is adopted, the electrode pattern is changed to the laminated piezoelectric element 23.
Compared to the method of forming on the upper and lower surfaces or other members, since the electrical connection is made only at the collector electrode, the number of electrical contacts is reduced and the reliability is improved. Or even FPC2
Since the front end or the vicinity of the front end is bare and is a linear metal electric contact, the linear metal electric contact extends when the laminated piezoelectric element 23 is deformed in the thickness direction. The deformation of the piezoelectric element 23 is not restricted. Therefore, the electromechanical conversion efficiency is improved.

Further, as shown in FIG. 3, a portion 34a below the collector electrode 22a or the collector electrode 22b located on the end surface of the laminated piezoelectric body 20 and joined to the insulating substrate 21 at the portion below the collector electrode 22a. If the adhesive between the insulating substrate 21 and the laminated piezoelectric body 20 slightly protrudes, the end surface of the insulating substrate 21 and the collecting electrode 22a are flattened by chamfering the groove 34b. The surface between the upper surface of the insulating substrate 21 and the collector electrode 22b can be a perpendicular surface. Therefore, the FPC 24 in that portion is pushed outward by local protrusion of the adhesive, and the collector electrodes 22a, 22b and F
The occurrence of conduction failure in the electrical connection of the PC 24 is eliminated, and the reliability is improved.

As described above, the insulating substrate 21 and the laminated piezoelectric body 2
0 and FPC 24 constituted piezoelectric element unit 2
5 is inserted into a fixing member 26 made of a resin material having a window formed in the center as shown in FIG. Further, as shown in the cross-sectional view of FIG. 2, after the free end face of the laminated piezoelectric element 23 opposite to the bonding face of the insulating substrate 21 and the upper surface of the fixing member 26 are made flat, An adhesive is filled in a gap between the substrate 21 and the fixing member 26 to fix the piezoelectric element unit to the fixing member 26.

The thin vibration plate 27 is laminated on the plane formed by the upper surface of the fixing member 26 and the free end surface of the laminated piezoelectric element 23 in this manner. Further, the vibration plate 27 is bonded to the free end of the laminated piezoelectric element 23 and the upper surface of the fixed member 26. Here, the diaphragm 27 is a nickel plate of about several μm formed by electroforming. Further, a flow path substrate 28 provided with a pressure chamber 32 and an ink supply port 33 corresponding to each of the laminated piezoelectric elements 23 and formed of a resin material is bonded. Such a produced unit is hereinafter referred to as a head unit 10.

As described above, the laminated piezoelectric element 23 is formed by bonding the laminated piezoelectric body 20 on the insulating substrate 21 and forming a groove with a wire saw. Therefore, the silver-palladium powder of the electrode layer 31 cut by the wire is applied to the piezoelectric material plate 3.
0 rubbed against the cut surface. The opposing electrode layers 31 are exposed on the cut surface and the interval between them is 20 μm, which is the thickness of the piezoelectric material plate 30.
m, the insulation resistance easily deteriorates in an external environment such as humidity. Further, although it is not clear, micro-cracks may be generated in the piezoelectric material plate 30 due to mechanical vibration, and moisture may be adsorbed in the micro-cracks to deteriorate the insulation. Here, the insulation failure does not mean an electrical short circuit, but even if it has a resistance of several MΩ, its resistance gradually decreases due to continuous driving, and extra current may flow in addition to driving. This means that a phenomenon is created in which the laminated piezoelectric element 23 is charged or discharged at a timing other than the selected ink droplet ejection to eject extra ink droplets. The occurrence of such insulation failure can be improved to some extent by improving the machining conditions and materials, but if a large number of heads with 64 channels are used, the number of heads that cause insulation failure of about 1 to 2 channels is inevitable. it can. For this reason, the production yield was very poor.

In FIG. 2, for simplicity, four channels are shown by four laminated piezoelectric elements 23 and four pressure chambers 32. However, the head unit 10 is actually composed of 20 to 50 channels. Head unit 1 with this number of channels
When the value is set to 0, the probability of insulation failure of the piezoelectric unit is significantly reduced as compared with the case of 64 channels or more, and the yield of the piezoelectric unit is improved.

The fixing member 26 includes the insulating substrate 21 and the diaphragm 2
7, the deformation of the laminated piezoelectric element 23 can be efficiently linked to the deformation of the vibrating plate 27. Therefore, the conventional U-shaped rigid member 109 shown in FIG. A small and lightweight print head was constructed.
Further, since the vibrating plate 27 at the portion located before and after the laminated piezoelectric element 23 is fixed by the fixing member 26, the occurrence of crosstalk can be suppressed even at the center of the head unit 10.

Still further, the electrodes of the laminated piezoelectric element 23;
The collecting electrodes 22a and 22b of the laminated piezoelectric element 23 and the collecting electrode 2
2a, 22b and FPC are electrically insulated substrate 2
1, the vibration plate 27 and the fixing member 26 eliminate the danger that the ejected ink droplets wrap around and cause a short circuit. Further, when the gap between the insulating substrate 21 and the fixing member 26 is filled with an adhesive or the like, a leak current flowing on the grooved surface of the laminated piezoelectric element 23 can be reduced depending on environmental conditions such as moisture.

FIG. 1 is an exploded perspective view of an ink jet recording head constituted by using a plurality of head units 10 formed as described above. The three head units 10 are inserted into the windows of the frame 11 made of a resin material, and positioned so that the head unit end face 10a and the end face 11a of the frame 11 are flush with each other. The gap between the rib and the head unit 10 is filled with an adhesive and fixed. Thereafter, the nozzle plate 13 on which the three rows of nozzles 12 are formed is attached to the head unit end face 10 a and the frame 11.
To form an ink jet recording head.

The inter-nozzle pitch of each row of the nozzles 12 is the same as that of the head unit 10, except that the pitch between the nozzles is 1/3 of the inter-nozzle pitch from a line based on the scanning direction of the head with respect to the recording paper (perpendicular to the nozzle row). The three head units 10 are arranged by being shifted one by one. Therefore, the printing density can be configured to be three times the pitch of the head unit 10. Actually, the arrangement of the laminated piezoelectric elements 23 or the pressure chambers 32 of the head unit 10 was formed at 120 dpi, and the print density of the ink jet recording head was produced at 360 dpi which is three times as large as this. The arrangement of the laminated piezoelectric elements 23 or the pressure chambers 32 of the head unit 10 is set to 200 dp.
i, and the printing density of the ink jet recording head is 6
00 dpi is also possible.

FIG. 4 is an exploded perspective view showing a schematic structure of an ink jet recording head for explaining a second embodiment of the present invention, and FIG. 5 is a view showing the arrangement of nozzles in this embodiment, and FIG. FIG. 3 is a cross-sectional view illustrating a relationship between a head unit and a frame. As shown in FIG. 4, the second embodiment is formed using the head unit 10 described in the first embodiment. The end surfaces of the fixing member 26, the vibration plate 27, and the flow path substrate 28 of the head unit 10 are flattened by mechanical processing such as lapping, and a nozzle plate 43 having a nozzle 41 formed thereon is bonded to this flat surface. This head unit with nozzle is newly added to head unit 4
Write 0. The difference between the present embodiment and the first embodiment is whether or not ink can be ejected in the state of the head unit 40.

The three head units 40 formed as described above are inserted into the windows of the frame 42 as shown in FIG. As shown in FIG. 5, the positions of the nozzles 41 of the adjacent head units 40 are shifted by ３ of the inter-nozzle pitch. Positioning is performed using a positioning mark 50 provided on the nozzle plate. In this way, an ink jet recording head having a print density three times the pitch between nozzles of the head unit 40 can be formed as in the first embodiment. Next, as shown in FIG. 6, the end surfaces of the nozzle plate 43 and the frame body 42 are pressed against a highly flat surface such as a jig, and the head unit 40 and the frame body 42 are fixed with an ultraviolet curable adhesive 61 from the back side, and ink jet is performed. Form a recording head. A portion of the surface of the frame body 42 that contacts the head unit 40 is chamfered. A resin-based or rubber-based adhesive 63 is poured into this space to seal the ink so that ink does not enter inside.

When a print head is formed as in the second embodiment, a cross-talk does not occur and insulation failure of the laminated piezoelectric element 23 is reduced by using a head unit having a relatively small number of nozzles as in the first embodiment. Although an ink jet recording head having a small print density and a high print density can be formed, the following advantages are also obtained.

The first point is that ink can be ejected from each head unit 40. The ink jet recording head technology has a simple structure, but has many functions required for each component. For example, in the nozzle plate 43, the hole shape, dimensional accuracy, surface roughness of the nozzle 41, hydrophilicity with the ink in the head unit 40 (contact angle between the surface and the ink), water repellency of the surface on the ink ejection side, nozzle 41
Above is complicated, such as a boundary condition between the surface having hydrophilicity and the surface having hydrophobicity, and other components also require a wide variety of functions. Furthermore, when the quantity is produced, the piezoelectric constant of the laminated piezoelectric material varies from 5% to 10% due to the variation in the composition of the material and the production process, so that the performance such as the ink ejection speed and the diameter of the ink droplet varies. Therefore, after the head is completed, it is necessary to check the quality and performance by actually filling the ink or other liquid. If the performance of each unit can be confirmed with a unit configuration having a relatively small number of nozzles, the quality can be improved because an ink jet recording head can be formed by combining head units 40 having the same performance variation without using a defective head. Productivity is improved as much as possible.

As another example, there is a case where three head units 40 are filled with different kinds of inks to constitute a color ink jet recording head. In this case, the physical properties of the ink, such as viscosity and surface tension, are different for each YMC color.
In order to make the ink ejection performance uniform in the ink jet recording head, it is necessary to use head units having different performances. The configuration of the second embodiment is effective for such a requirement, and it is preferable to form an inkjet recording head by combining three head units 40 having different performances confirmed in advance.

As a second advantage, since the nozzle plate 43 is divided by the ink ejection plane, when a color ink jet recording head is formed, the YMC
The point is that color mixing does not occur on one surface. Generally, the ink jet plane is maintained by a wiping mechanism, etc.
In the wiping operation, there is a risk that other inks from the adjacent nozzles are mixed and the colors are mixed on the nozzles 41. Nozzle plate 4 for each color
The color mixing can be prevented by forming the water-repellent surface 45 for holding the ink 3 separately and preventing the ink from flowing between the colors.

[0031]

According to the structure of the ink jet head according to the first and second embodiments of the present invention, a plurality of head units in which an appropriate number of laminated piezoelectric elements are arranged on an insulating substrate are used. A multi-nozzle head having no more than 60 nozzles and no more than 100 nozzles with no crosstalk and no leakage current on the machined surface can be formed.

Further, according to the configuration of the ink jet head in the second embodiment, the ink jet recording head can be configured according to the performance of the head unit, so that a print head optimized for each color of the color ink can be manufactured, and each color of the ink can be formed by a nozzle. No more mixing on the board. In addition, since the quality of the head unit could be controlled, productivity was improved.

Also, a highly reliable ink jet recording head could be formed by directly connecting a linear electric contact having a bare end near the tip of the FPC to the collector electrode of the laminated piezoelectric element.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view illustrating a configuration of an entire inkjet recording head according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a head unit according to the embodiment of the present invention.

FIG. 3 is a sectional view showing a head unit according to the embodiment of the present invention.

FIG. 4 is an exploded perspective view showing the configuration of the entire ink jet recording head according to the embodiment of the present invention.

FIG. 5 is a partial view showing a nozzle arrangement according to the embodiment of the present invention.

FIG. 6 is a partial cross-sectional view showing a relationship between a head unit and a frame according to the embodiment of the present invention.

FIG. 7 is an exploded perspective view showing a conventional technique.

[Explanation of symbols]

 10, 40 head unit 11, 41 frame body 13, 43 nozzle plate 21 insulating substrate 22a, 22b collecting electrode 23, 43 laminated piezoelectric element 24 FPC 25 piezoelectric unit 26 fixing member 27 vibration plate 28 flow path plate

Continued on the front page (72) Inventor Tadashi Mitsashi 840 Takeno, Shimotomi, Tokorozawa-shi, Saitama Examiner, Citizen Watch Co., Ltd. Technical Research Institute Toshihiko Ozaki (56) References JP-A-5-270099 (JP, A JP-A-7-186388 (JP, A) JP-A-6-226971 (JP, A) JP-A-7-108681 (JP, A) JP-A-2-88245 (JP, A) JP-A-7-108 285219 (JP, A) JP-A-7-186386 (JP, A) JP-A-5-238003 (JP, A) JP-A-6-316066 (JP, A) JP-A-4-141432 (JP, A) JP-A-7-9681 (JP, A) JP-A-7-285223 (JP, A) JP-A-5-338154 (JP, A) JP-A-7-195688 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41J 2/045-2/055 B41J 2/16

Claims (3)

(57) [Claims] 1. An ink jet recording head having a nozzle plate, wherein a plurality of head units without the nozzle plate are fixed to a frame, and the nozzle plate is bonded to an end surface of the head unit and the frame surface. Inkjet recording head. 2. The ink jet recording head according to claim 1, wherein said nozzle plate is common to said plurality of head units. 3. An ink jet head using a laminated piezoelectric element, wherein one of the collecting electrodes for applying a voltage to each piezoelectric layer of the laminated piezoelectric element and the other of the collecting electrodes are provided .
On the opposing end faces of the laminated piezoelectric element, respectively.
An ink jet recording head connected to a common FPC and directly electrically connected to the outside using the FPC.