JP2011218640A - Inkjet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform highly accurate joining by preventing bending of a wiring board.SOLUTION: The inkjet head 3 includes nozzles 11 which eject an ink, pressure chambers 41 communicated with the nozzles, ink channels 32, 42, 72, 88 and 92 which supply the ink to the pressure chambers, actuators 60 which give a force for ejecting the ink of pressure chambers from the nozzles, and the wiring board 80 in which wiring lines 87 and 91 connected to the actuators are provided. Insulating layers 70 and 90 of an equal coefficient of thermal expansion are formed on both surfaces of the wiring board.

Description

  The present invention relates to an ink jet head provided in an ink jet recording apparatus.

2. Description of the Related Art Conventionally, an ink jet recording apparatus that records a desired image on a recording medium by ejecting ink droplets from nozzles of an ink jet head is known. This ink jet recording apparatus is used in a wide variety of applications, and types of inks and recording media suitable for each purpose can be used.
An inkjet head includes a piezoelectric head that pressurizes ink in a pressure chamber using displacement of a piezoelectric element and ejects ink droplets from nozzles communicating with the pressure chamber.

In such a piezoelectric head, nozzles are arranged at high density in order to form a high-definition image. For example, a set of nozzles and pressure chambers communicating with the nozzles is arranged two-dimensionally. Is known.
In such a head, the electric wiring for driving each piezoelectric element also becomes high density. In order to solve this, a configuration is known in which a wiring board is provided above a piezoelectric element, and the wiring board is connected to individual piezoelectric elements via bumps (see, for example, Patent Document 1).
It is also known that a common flow path (common ink chamber) for supplying ink to a plurality of pressure chambers is provided in a layer different from the pressure chamber, thereby further reducing the size of the head and arranging the pressure chambers at high density. (For example, refer to Patent Documents 2 and 3).

  As a method for manufacturing such a piezoelectric head, there is known a method of laminating a plurality of base materials on which flow paths and the like are formed and bonding them together. When performing bonding, it is possible to make a head having high-precision ejection characteristics by positioning with high precision.

JP 2003-69103 A JP 2006-264322 A JP 2007-30361 A

  As a method for bonding substrates together, a bonding method involving heating is known. When different types of base materials are joined by heating, there is a risk of misalignment due to the difference in thermal expansion coefficient. Further, for example, a substrate made of a plurality of materials, such as a silicon substrate having a metal wiring or an insulating film formed thereon, may be warped with heating. If joining is performed with warping, the position is likely to be displaced, and there is a high possibility that the communication of the flow path and the connection of the wiring will not be performed reliably, which causes ink leakage and poor conduction. Further, even if the bonding can be performed without being displaced while being warped, the bonded portion is easily peeled off due to the warping stress, and the durability of the head is lowered.

  Therefore, the present invention has been made to solve the above-described problems, and suppresses warpage when the substrates are joined together by heating, improves the positional accuracy and durability of the joining, and improves the ejection accuracy and reliability. An object is to provide an excellent inkjet head.

The invention according to claim 1 is an inkjet head,
A nozzle for ejecting ink;
A pressure chamber in communication with the nozzle;
An ink flow path for supplying ink to the pressure chamber;
An actuator for applying a force for ejecting the ink in the pressure chamber from the nozzle;
A wiring board provided with wiring connected to the actuator,
Insulating layers having the same coefficient of thermal expansion are provided on both sides of the wiring board.

The invention according to claim 2 is the ink jet head according to claim 1,
The insulating layers are formed of the same material.

The invention according to claim 3 is the inkjet head according to claim 1 or 2,
The insulating layer is formed of a resin.

The invention according to claim 4 is the inkjet head according to claim 3,
The resin forming the insulating layer is a photosensitive resin.

According to the first aspect of the present invention, since the insulating layers are provided on both surfaces of the wiring board, not only serves as a protective layer for the wiring provided on the board, but also the thickness of the entire wiring board. And the insulating layers on both sides are formed of a material having the same coefficient of thermal expansion, so that there is an effect of suppressing warpage of the entire wiring board during heating.
Thereby, joining with an adjacent base material can be made highly accurate, and the warpage stress after joining is also reduced.

According to the second aspect of the present invention, since the insulating layers are provided on both surfaces of the wiring board, not only serves as a protective layer for the wiring provided on the board, but also the thickness of the entire wiring board. And the insulating layers on both sides are formed of the same material, so that there is an effect of suppressing warpage of the entire wiring board during heating.
Thereby, joining with an adjacent base material can be made highly accurate, and the warpage stress after joining is also reduced.

  According to invention of Claim 3, the insulating layer is comprised with the resin material. The resin material has a relatively low elastic modulus, and even if warping stress remains after bonding, the stress can be relieved, peeling of the bonded portion can be suppressed, and the durability of the head can be improved.

  According to invention of Claim 4, resin which comprises an insulating layer is photosensitive resin. Since the photosensitive resin is capable of forming a fine pattern by performing exposure and development, a pattern such as a channel hole can be easily formed in the insulating layer.

FIG. 2 is a schematic diagram illustrating a main part of an ink jet recording apparatus. The perspective view of an inkjet head. The bottom view of a nozzle plate. The longitudinal cross-sectional view of an inkjet head. FIG. 5 is an enlarged view of the periphery of the piezoelectric element in FIG. 4. The figure explaining the joining process at the time of assembling an inkjet head. FIG. 7 is an enlarged view of the periphery of the piezoelectric element in FIG. 6.

Hereinafter, an inkjet head will be described with reference to the drawings. The ink jet head according to the present invention is provided in an ink jet recording apparatus.
<Inkjet recording apparatus>
FIG. 1 is a schematic diagram showing a main part of the ink jet recording apparatus 1.
As shown in FIG. 1, the ink jet recording apparatus 1 includes a transport unit 2 that transports the recording medium P in the direction of an arrow Z (hereinafter referred to as a transport direction Z). As the recording medium P, in addition to paper and fabric, it is possible to use a plastic film or metal having no ink absorbability, and is not particularly limited. The paper here includes not only paper for exclusive use of an ink jet printer having ink absorptivity, but also coated paper, art paper, and plain paper having low ink absorptivity.

An inkjet head 3 that ejects ink droplets D onto a recording medium P on the transport unit 2 is disposed above the transport unit 2. In the inkjet head 3, a plurality of nozzles 11 for ejecting ink droplets D are arranged in the X direction and the Y direction in the drawing (see FIG. 2).
The transport unit 2 and the inkjet head 3 are connected to the control unit 5 and controlled by the control unit 5.

FIG. 2 is a perspective view of the inkjet head 3.
As shown in the figure, the inkjet head 3 includes a nozzle plate 20 having a plurality of nozzles 11 for discharging ink droplets D formed at the lower end thereof.
FIG. 3 is a bottom view of the nozzle plate 20.
As shown in FIG. 3, eight nozzles 11 are arranged side by side in the X direction to form a nozzle row 11a, and this nozzle row 11a is arranged in parallel in the Y direction to form a nozzle group 11b. Yes. More specifically, in the nozzle group 11b, the X-direction positions of the nozzles 11 in all the nozzle rows 11a slightly overlap every other row, and the X-direction positions of all the nozzles 11 overlap slightly as a whole. The position of each nozzle 11 in the X direction is shifted. Two sets of the nozzle groups 11b are arranged in the Y direction.

<Configuration of inkjet head>
4 is a longitudinal sectional view of the ink jet head, and FIG. 5 is an enlarged view of the periphery of the piezoelectric element in FIG.
The inkjet head 3 includes a head substrate formed by stacking three substrates, a nozzle plate 20, an intermediate plate 30, and a pressure chamber plate 40, a wiring substrate 80, and a member that connects the head substrate and the wiring substrate 80. And are laminated.

(Nozzle plate)
As shown in FIGS. 4 and 5, the inkjet head 3 includes a nozzle plate 20 as a nozzle substrate on which a plurality of nozzles 11 for ejecting ink are formed. The nozzle plate 20 is positioned in the lowermost layer of the inkjet head 3 when ejected downward from the nozzle 11 with ink. The nozzle plate 20 uses silicon as a base material, and the ink flow path 12 and the nozzle 11 are formed by dry etching.

(Intermediate plate)
The intermediate plate 30 is a substrate made of glass, and an ink flow path connecting an ink flow path 31 leading to the nozzle 11 and a pressure chamber 41 and an ink flow path 42 provided on the pressure chamber plate 40, which will be described later. A path 32 is formed. An example of a method for forming the ink flow paths 31 and 32 is a sand blast method.
The intermediate plate 30 is joined to the nozzle plate 20. An example of the bonding method is anodic bonding. Here, the anodic bonding is a method in which the intermediate plate 30 is heated (300 ° C. to 500 ° C.), a voltage is applied between the nozzle plate 20 and the intermediate plate 30, and both are bonded by electrostatic attraction. By using anodic bonding, an adhesive for bonding the two becomes unnecessary, there is no fear of durability deterioration due to the ink solvent, and reliability can be improved.
The ink flow path 31 is formed at a position communicating with the ink flow path 12 when the intermediate plate 30 is stacked on the nozzle plate 20.

(Pressure chamber plate)
The pressure chamber plate 40 (pressure chamber substrate) is made of a material having the same thermal expansion coefficient as the nozzle plate 20, specifically, a silicon substrate made of the same material as that forming the nozzle plate 20. An inlet (throttle channel) 42 that forms an ink channel to the pressure chamber 41 is formed. An example of a method for forming the pressure chamber 41 and the inlet 42 is dry etching.
The pressure chamber plate 40 is bonded to the intermediate plate 30 that is a glass substrate by anodic bonding. At the time of joining, the pressure chamber 41 is aligned so as to communicate with the ink flow path 31 formed in the intermediate plate 30. The anodic bonding here is also the same method as the bonding of the intermediate plate 30. In the pressure chamber plate 40, a pressure chamber 41 for storing ink ejected from the nozzles 11 is formed so as to penetrate in the thickness direction of the pressure chamber plate 40.

In the pressure chamber plate 40, an inlet (throttle channel) 42 that becomes an ink flow path to the pressure chamber 41 is formed so as to penetrate in the thickness direction of the pressure chamber plate 40. The inlet 42 is formed to be thinner than other ink flow paths by dry etching. As a result, the flow path resistance is defined by the inlet 42, and desired discharge characteristics (droplet diameter, discharge frequency, etc.) can be realized. In addition, parameters such as flow path resistance in the inlet 42 affect the discharge characteristics. However, since the inlet 42 is formed in the pressure chamber plate 40 made of silicon that can be processed with high precision, there is little variation in processing. Also, the discharge characteristics are good.
The pressure chamber 41 and the inlet 42 are formed so as to be independent from each other in the pressure chamber plate 40, but the ink flow path 32 formed in the intermediate plate 30 when the pressure chamber plate 40 is stacked on the intermediate plate 30. It is communicated via. Accordingly, the ink is stored in the pressure chamber 41 through the inlet 42 and the ink flow path 31.

(Diaphragm)
The pressure chamber plate 40 is provided with a diaphragm 50. The diaphragm 50 is provided on the pressure chamber plate 40 so as to cover the opening of the pressure chamber 41 while avoiding the inlet 42. That is, the diaphragm 50 constitutes one wall portion of the pressure chamber 41.
The diaphragm 50 is formed in a thin plate shape, and can change the pressure in the pressure chamber 41 by displacement (elastic deformation) in the thickness direction.

(Piezoelectric element)
The diaphragm 50 is provided with a piezoelectric element 60 at a position facing the pressure chamber 41 across the diaphragm 50.
The piezoelectric element 60 is an actuator made of PZT (lead zirconate titanate), and applies a force for ejecting ink in the pressure chamber 41 from the nozzle 11.
The piezoelectric element 60 is sandwiched between two electrodes 61 and 62 from the upper surface side and the lower surface side, and the electrode 61 on the lower surface side is provided on the diaphragm 5. The piezoelectric element 60 and the electrodes 61 and 62 are provided by patterning the diaphragm 50 by a method such as etching.
When a voltage is applied to the electrodes 61 and 62, the piezoelectric element 60 sandwiched between the electrodes 61 and 62 is displaced, and the diaphragm 50 is also displaced by the displacement of the piezoelectric element 60. By the operation of the vibration plate 50, the ink in the pressure chamber 41 is ejected from the nozzle as an ink droplet D (see FIG. 1).

(Joint part)
The diaphragm 50 is provided with a joint portion 70 as an insulating layer, and the pressure chamber plate 40 is joined to the wiring substrate 80 via the joint portion 70.
The joining part 70 is formed of resin. Here, the resin used has ink resistance (dissolved by the ink, the property does not change, etc.) and is not particularly limited as long as it is an insulating material. For example, an epoxy resin, a polyimide resin, a polyamide resin, a polyurethane resin, a silicone resin, or the like can be used. Of the resins, it is more preferable to use a photosensitive resin. The photosensitive resin can form a fine pattern by performing exposure and development. For example, a photosensitive resin such as PerMX3000 series manufactured by Du Pont can be used.
Moreover, even if it is materials other than resin, you may use various materials which have insulation.

The joint portion 70 is a columnar member in which an ink flow path 72 is formed so as to communicate an inlet 42 formed in the pressure chamber plate 40 and an ink flow path 88 provided in the wiring board 80, which will be described later. It is configured as.
A space 71 that accommodates the piezoelectric element 60 and the electrodes 61 and 62 is formed in the joint portion 70 so as to penetrate in the thickness direction of the joint portion 70 at a position facing the pressure chamber 41 across the diaphragm 50. Yes. A plurality of spaces 71 are formed so as to accommodate each piezoelectric element 60 individually.
In the joining portion 70, an ink flow path 72 is formed so as to penetrate the joining portion 70 in the thickness direction independently of the space 71.
In the region outside the region where the piezoelectric element 60 is provided in the inkjet head 3, the joint portion 70 exists on almost the entire surface, and joins the pressure chamber plate 40 and the wiring substrate 80.

(Wiring board)
A wiring substrate 80 is laminated and bonded to the bonding portion 70. The wiring board 80 is based on a material having the same thermal expansion coefficient as that of the nozzle plate 20 and the pressure chamber plate 40, specifically, silicon that is the same material as the material forming the nozzle plate 20 and the pressure chamber plate 40.
Two layers of insulating layers 82 and 83 of silicon oxide are formed on the lower surface of the wiring board 80, and an insulating layer 84 of silicon oxide is also formed on the upper surface. Of the insulating layers 82 and 83, the insulating layer 83 located below is in contact with and bonded to the upper surface of the bonding portion 70.

In the wiring board 80, an electrode through hole (through hole) 86 through which the through electrode 85 passes in order to apply a driving voltage to the electrodes 61 and 62 to displace the piezoelectric element 60 is formed in the thickness direction of the wiring board 80. ing. One end of an aluminum wiring 87 extending in the horizontal direction is connected to the lower end of the through electrode 85, and a stud bump 63 provided on the electrode 62 on the upper surface of the piezoelectric element 60 is connected to the other end of the aluminum wiring 87. Are connected through the solder 64 exposed in the space 71. The aluminum wiring 87 is protected by being sandwiched between two insulating layers 82 and 83 on the lower surface of the wiring board 80.
The insulating layers 82, 83, 84 provided on the upper and lower surfaces of the wiring board 80 are provided to insulate the aluminum wiring 87 and the copper wiring 91 from the wiring board 80 itself (silicon).
A copper wiring 91 is provided on the upper surface of the wiring board 80 with an insulating layer 84 interposed therebetween, and a protective layer 90 is provided on the copper wiring 91. The protective layer 90 is a photosensitive adhesive for laminating and bonding the upper common ink chamber 100 and is a protective layer for protecting the copper wiring 91. The copper wiring 91 extends in the horizontal direction, and one end is connected to the upper end of the through electrode 85 and the other end is connected to a flexible substrate (not shown). The flexible substrate is connected to a driver, and drives (displaces) the piezoelectric element 60 under the control of the driver.
In the wiring board 80, an ink flow path 88 for guiding ink to the pressure chamber 41 is formed so as to penetrate in the thickness direction of the wiring board 80. The ink flow path 88 is formed so as to communicate with the ink flow path 72 when the wiring substrate 80 is stacked on the joint portion 70.

(Protective layer)
A protective layer 90 as an insulating layer is provided on the upper surface of the wiring substrate 80 (opposite the surface on which the bonding portion 70 is provided) to protect the copper wiring 91 provided on the upper surface of the wiring substrate 80. Yes. As a material constituting the protective layer 90, a material having the same coefficient of thermal expansion as that of the bonding portion 70, and the same material are used.
In the protective layer 90, an ink channel 92 for guiding ink to the pressure chamber 41 is formed so as to penetrate in the thickness direction of the protective layer 90. The ink flow path 92 is formed so as to communicate with the ink flow path 88 formed in the wiring board 80 when the protective layer 90 is laminated on the wiring board 80.

(Common ink chamber)
A common ink chamber 100 is provided on the upper surface of the wiring substrate 80 via a protective layer 90. Members constituting the wall surface of the common ink chamber 100 are joined to the wiring substrate 80 by a fixing means such as an adhesive.
The common ink chamber 100 communicates with the pressure chamber 41 through the ink flow path in each layer. The common ink chamber 100 communicates with all the pressure chambers 41 via the ink flow path, and is formed so that ink can be supplied to all the pressure chambers 41.

<Inkjet head joining method>
FIG. 6 is a diagram for explaining a joining process when assembling the inkjet head, and FIG. 7 is an enlarged view of the periphery of the piezoelectric element in FIG.
As shown in FIGS. 6A and 7, when the inkjet head 3 is assembled, the nozzle plate 20, the intermediate plate 30, the pressure chamber plate 40, the vibration plate 50, and the piezoelectric element 60 are stacked and bonded. The unit 200 and the second unit 300 in which the joining portion 70, the wiring substrate 80, and the protective layer 90 are stacked and joined are manufactured in advance.
Then, as shown in FIG. 6B, the first unit 200 and the second unit 300 are joined. When joining, the stud bump 63 in the first unit 200 and the solder 64 in the second unit 300 are electrically connected, and the inlet 42 and the second unit 300 in the first unit 200 are connected. The alignment is performed with high accuracy so that the ink flow path 72 communicates with each other.
Then, as shown in FIG. 6C, the common ink chamber 100 is joined to the upper surface of the protective layer 90 so as to cover all the ink flow paths 92.
Thus, the first unit 200 and the second unit 300 need to be positioned and joined with high accuracy. If misalignment occurs at the time of joining, not only does the electrical connection become unstable and the piezoelectric element 60 is not driven normally, but also the flow resistance increases and discharge characteristics change. A drop in discharge accuracy occurs. Therefore, in the inkjet head 3, the nozzle plate 20, the pressure chamber plate 40, and the wiring substrate 80 are all formed of a silicon base material. By forming these with the same material, even when heated at the time of joining, occurrence of misalignment due to the difference in thermal expansion coefficient is prevented.

<Action and effect>
As described above, according to the inkjet head 3, the joint portion 70 and the protective layer 90 as insulating layers provided on both surfaces of the wiring substrate 80 are formed of the same photosensitive resin material having the same thermal expansion coefficient. Therefore, it is possible to suppress warpage when the wiring substrate 80 is heat-bonded to another substrate or a base material.
As a result, the wiring board 80 can be bonded to an adjacent substrate or base material with high accuracy, and problems such as ink leakage from the ink flow path due to a shift in the bonding position and poor wiring connection can be prevented. it can.
Further, by preventing the occurrence of such problems, the durability of the inkjet head 3 can be improved, and the inkjet head 3 having excellent ejection accuracy and reliability can be provided to the user.

Moreover, since the joining part 70 and the protective layer 90 are formed with resin, processing becomes easy.
Furthermore, since the resin forming the bonding portion 70 and the protective layer 90 is a photosensitive resin, the work for pattern formation on the bonding portion 70 and the protective layer 90 is facilitated.

Note that the present invention is not limited to the above-described embodiment, and design changes can be freely made without changing the essential part of the invention.
For example, in the above embodiment, the joint portion and the protective layer are formed of the same resin material. However, if each can be configured to have the same thermal expansion coefficient as a whole, it is not always necessary to form the same material. Absent.
Moreover, in the said embodiment, although the pressure chamber plate and the diaphragm were comprised as a separate member, a part of pressure chamber plate may be formed in thin plate shape, and the thin plate part may be used as a diaphragm. In this case, a separate member as a diaphragm is not necessary, and a piezoelectric element is provided on the upper surface of the thin plate portion.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 3 Inkjet head 11 Nozzle 20 Nozzle plate (nozzle substrate)
32 Ink channel 40 Pressure chamber plate (pressure chamber substrate)
41 Pressure chamber 42 Ink flow path 50 Diaphragm 60 Piezoelectric element (actuator)
63 Stud bump 64 Solder 70 Junction (insulating layer)
72 Ink flow path 80 Wiring board 85 Through electrode 87 Aluminum wiring 88 Ink flow path 90 Protective layer (insulating layer)
91 Copper wiring 92 Ink flow path

Claims (4)

A nozzle for ejecting ink;
A pressure chamber in communication with the nozzle;
An ink flow path for supplying ink to the pressure chamber;
An actuator for applying a force for ejecting the ink in the pressure chamber from the nozzle;
A wiring board provided with wiring connected to the actuator,
An ink jet head, wherein insulating layers having the same thermal expansion coefficient are provided on both surfaces of the wiring board.   The inkjet head according to claim 1, wherein the insulating layers are made of the same material.   The inkjet head according to claim 1, wherein the insulating layer is made of a resin.   The inkjet head according to claim 3, wherein the resin forming the insulating layer is a photosensitive resin.

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