JP3173520B2 - Ink jet head and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head of an on-demand type ink jet printer which forms an ink image on a recording medium such as recording paper by discharging ink droplets in response to a print signal, and a method of manufacturing the same.

[0002]

2. Description of the Related Art There are roughly three types of recording heads of so-called on-demand type ink jet printers which fly ink droplets in response to a print signal. The first type is a so-called bubble jet type in which a heater for instantaneously evaporating ink is provided at the tip of a nozzle, and ink droplets are generated and fly by the expansion pressure at the time of ink vaporization. In the second type, a part of a container forming an ink chamber is constituted by a piezoelectric element which is deformed by applying a voltage, and the ink is ejected as droplets by the pressure in the container caused by the deformation of the piezoelectric element. Things. In the third type, a piezoelectric element is provided in an ink chamber provided with a nozzle, and the ink pressure in the ink chamber is changed by expansion and contraction of the piezoelectric element to cause ink to fly from the nozzle as droplets. The on-demand type ink jet head of the third type is disclosed in Japanese Patent Publication No. 2-45885.
As shown in Japanese Patent Application Laid-Open No. HEI 5-52625, the other end of a piezoelectric element having one end fixed to a base is elastically connected to an elastic wall of a container forming an ink chamber via a leg. It is composed. According to the technique of the publication, as shown in FIGS. 3 and 4 of the publications, the elastic wall is bent in advance toward the ink chamber. In this state, the piezoelectric element is contracted to restore the elastic wall, and the piezoelectric element is expanded again, thereby discharging the ink in the ink chamber from the nozzle as droplets. this,
It is disclosed that as a means for bending the elastic wall in advance, a viscoelastic member is pushed between the leg and the elastic wall, and a projection is provided on the leg or the elastic wall.

[0003]

SUMMARY OF THE INVENTION The miniaturization of the recording head,
As the density is increased, the size of the piezoelectric element and the ink chamber becomes smaller.
Therefore, the amount of displacement of the piezoelectric element is reduced, and the displacement of the piezoelectric element must be transmitted to the ink chamber more efficiently. For this reason, it is extremely important to pay attention to the joint between the piezoelectric element and the elastic member, especially the positioning of the piezoelectric element in the displacement direction. However, in the configuration of the above-mentioned publication, the viscoelastic member and the elastic wall around the protruding portion absorb a considerable amount of pressure. Further, with respect to the displacement direction of the piezoelectric element, by providing a structure in which the viscoelastic member or the elastic wall is bent in advance, it is difficult to stabilize the restoring position of the piezoelectric element and the deflection amount is likely to vary. As a result, the speed of the ejected ink droplet, the volume of the ink droplet, and the ejection response frequency are reduced, and the ejection characteristics of the ink droplet may be unstable. Further, since the configuration of the technology employs a structure in which the leg portion is supported in line contact with the bearing portion, loss may occur here.

On the other hand, in the method of manufacturing the head, when a plurality of ink chambers and piezoelectric elements are arranged in parallel, it is important to stabilize the position of the piezoelectric elements in the displacement direction during manufacturing. It is extremely difficult to reduce the variation in the position of the piezoelectric element in the displacement direction at the time of manufacturing.

SUMMARY OF THE INVENTION It is an object of the present invention to realize a head having a small ink pressure loss and capable of stably ejecting ink droplets and a method of manufacturing the same with a simple configuration and a simple method.

[0006]

Means for Solving the Problems To achieve such a problem
The inkjet head of the present invention has a nozzle opening
Forming base provided with a pressure chamber communicating with the reservoir
The body is in contact with the area facing the pressure chamber and
A piezoelectric element for increasing or decreasing the pressure by expansion and contraction in the direction;
Head for fixing the completed piezoelectric substrate and the piezoelectric element
And an ink jet head comprising:
In the contact area of the piezoelectric element of the completed cavity-forming substrate
After forming a curable resin layer, the surface is
A shaped planarization layer is formed.

[0007]

FIG. 1 is a perspective view showing the structure of an embodiment of the present invention, in which parts are disassembled after assembly. 2, 3, and 4 are a partial cross-sectional view illustrating the same embodiment in more detail, a partial perspective view of the same embodiment viewed from below, and a partial plan view of the same embodiment viewed from directly above. . FIG. 4 shows a state in which the components are sequentially peeled from above. 5, 6, 7,
FIG. 8 shows a manufacturing method for forming a flattening layer based on the configuration of the embodiment of the present invention. 9 and 10 are partial cross-sectional views of another embodiment of the present invention, FIG. 11 is a partial cross-sectional view illustrating a problem of the conventional example, and FIG. 12 is a partial cross-sectional view illustrating the effect of the present invention.

In these figures, reference numeral 1 denotes a nozzle substrate. The nozzle substrate 1 is provided with a plurality of nozzles 2.
Reference numeral 3 denotes a cavity forming substrate. Cavity forming substrate 3
Is formed between the nozzle substrate 1 and an elastic member 8 serving as an elastic wall to form a reservoir 4 and an ink chamber 5. Elastic member 8
Has a laminated structure composed of a thin metal plate 6 and a wall member 7.
After the elastic member 8, the cavity forming substrate 3 and the nozzle substrate 1 are sequentially bonded in close contact, a flattening layer 10 described later is formed on the elastic member 8 side, and is closely bonded on the head frame 11.

A piezoelectric element 22 serving as a driving source for ejecting ink droplets
The one half of the surface in the longitudinal direction is fixed to the fixing base 21, and the tip of the non-fixed half is joined to the flattening layer 10. A positive and negative conductive wiring pattern 24 is provided on the fixing base 21, and an electric field controlled by the control board 13 is applied to the piezoelectric element 22 via the lead frame 25. 1
1 is a head frame. 12 is a head frame 11
The fixing table 21 is supported by a mounting hole that penetrates the inside to position the piezoelectric element 22 in the X and Y directions (see XYZ coordinates in FIG. 1). Note that, in the Z direction of the piezoelectric element 22, the joined body in which the flattening layer 10, the elastic member 8, the cavity forming substrate 3, and the nozzle substrate 1 are joined to the head frame 11, and then the tip of the piezoelectric element 22 is flattened. 10 and positioned. Reference numeral 31 denotes an ink 5 from an ink reservoir (not shown).
1 is an ink supply pipe for supplying the ink. Ink supply pipe 31
Are press-fitted to the head frame 11. The ink flow path communicates with the reservoir 4 of the cavity forming substrate 3 and the ink chamber 5 through the ink connection port 32 and the flattening layer 10 in the head frame 11 and the ink communication port 33 in the elastic member 8. The above is the schematic configuration.

Referring to FIG. 2, the structure will be described in more detail. The positive electrode 41 and the negative electrode 42 of the piezoelectric element 22 face each other. The positive electrode 41 is electrically connected to the wiring pattern 24 on the fixed base 21, particularly to the positive electrode conductive pattern at the same time as the bonding. The negative electrode 42 is fixed to the fixed base 21 by the common plate 23.
It is electrically connected to the upper wiring pattern 24, particularly to the negative electrode conductive pattern. The wiring pattern 24 and the control board 13 are connected by a lead frame 25, and the connection portions are fixed by solder. In addition, the fixing plate 21 is such that the piezoelectric element 22 is
In a state of contact with the head frame 11, the head frame 11 is adhered and fixed. That is, the Z direction of the piezoelectric element 22 is
Position at 0. Therefore, the flat surface 60 of the head frame 11 in contact with the flattening layer 10 is finished with high precision by means such as flat polishing. However, in the conventional example in which the flattening layer 10 is not formed, as shown in FIG. 11, if the piezoelectric element 22a and the elastic member 8a are directly adhered after abutting, the production process of the nozzle substrate 1a, the cavity forming substrate 3a, and the elastic member 8a Variations and warpage in the thickness direction cause variations in the gap generated between the elastic member 8a and the tip of the half that is not fixed to the fixed plate of the piezoelectric element 22a. In this gap, an adhesive for fixing the piezoelectric element 22a and the elastic member 8a is interposed. As the method of applying the adhesive, a certain amount of adhesive is generally applied to the piezoelectric element 22a.
Alternatively, the adhesive is applied to the elastic member 8a so that there is no variation between the applied portions, and the two are held in a joined state to cure the adhesive. In addition, for example, after the piezoelectric element 22a and the elastic member 8a are brought into contact with each other, an appropriate amount according to each gap between the piezoelectric element 22a and the elastic member 8a may be filled. The possibility of realizing a large constraint is extremely small. Therefore, a method of applying the adhesive while managing a fixed amount of the adhesive is adopted. Piezoelectric element 22
When the gap between the elastic member 8a and the elastic member 8a varies, as shown in FIG. 11, 9a, 9b, 9c,
As shown by ‥‥, a state with large variations is formed. Here, three representative types are illustrated, but actually more joined states are generated. 9a
Indicates a desirable bonding state, a meniscus is formed in a fluid state before curing, and the bonding is cured in a stable state. This is because the gap between the elastic member 8a and the piezoelectric element 22a is appropriately maintained. On the other hand, 9b shows a state in which the gap between the piezoelectric element 22a and the elastic member 8a is larger than an appropriate gap due to variations or warpage in the thickness direction due to the manufacturing process of the nozzle substrate 1a, the cavity forming substrate 3a, and the elastic member 8a. . In this state, the adhesive provided in the gap between the piezoelectric element 22a and the elastic member 8a is in a state of being pulled in the Z direction, the curing of the adhesive varies, and the Young's modulus of the cured adhesive is generated. Is not stable, and the bonding strength is reduced. 9
c indicates that, for the same reason, variation occurs and the piezoelectric element 2
The state where the gap between the elastic member 2a and the elastic member 8a is smaller than an appropriate gap is shown. In this state, if the gap is too small, the meniscus 9a is broken and flows into the elastic member 8a. When the adhesive flows into the elastic member 8a, it affects the rigidity of the elastic member 8a, and the expansion and contraction of the piezoelectric element 22a cannot be efficiently transmitted to the ink chamber 5.
Further, there is a possibility that the bonding strength between the piezoelectric element 22a and the elastic member 8a is reduced. Therefore, Z of the piezoelectric element 22
It is important to accurately perform the positioning in the direction and to stabilize the gap between the tip of the unfixed half of the piezoelectric element 22 and the contact surface. FIG. 12 is a partial cross-sectional view illustrating an effect obtained by providing the planarization layer 10 according to the present invention. In the same figure, a flattening layer is formed by a method described later,
The state where it was joined to the piezoelectric element 22a is shown. The flattening layer is 10d, 10e, and 10f as shown in FIG. As shown by 9f, it is possible to form a stable meniscus in the adhesive with an appropriate gap. By holding in this state and curing the adhesive, a stable adhesive strength can be obtained, and the adhesive can be prevented from flowing into the elastic member 8a.

On the other hand, an ink chamber 5 filled with ink 51
The reservoir 4 is formed by the cavity forming substrate 3, the nozzle substrate 1, and the elastic member 8. Cavity forming substrate 3
Can be made by etching glass, laminating thin metal plates, exposing a photosensitive resin, forming a resin by injection molding, etc., but in this embodiment, a photosensitive resin which is inexpensive in cost is used. The nozzle substrate 1 that covers the upper surface of the cavity forming substrate 3 is made of a stainless steel plate of about 0.1 mm in which one nozzle 2 is opened in each of the plurality of ink chambers 5 by press working.

The nozzle substrate 1 can also be manufactured by a nickel electroforming method.

The elastic member 8 covering the lower surface of the cavity forming substrate 3 is applied to a thin metal plate 6 formed to a thickness of 5 μm or less by electroforming of nickel by 10 to 10 μm.
It has a structure in which wall members 7 each having a thickness of about 0 μm are laminated. The thin metal plate 6 is preferably as thin as possible in order to efficiently transmit the expansion and contraction of the piezoelectric element 22 to the ink chamber 5, but the ink 51 in the ink chamber 5 must not exude. When the ink 51 exhibits conductivity, the positive electrode 41 of the piezoelectric element 22
This is because the ink 51 adheres to between the negative electrode 42 and the control substrate 13 to cause an electrical short circuit. For the above reasons, the metal sheet 6 cannot be replaced with a resin such as a film. The resin is ink 5 at a thickness of about 5 microns.
1 exudes and the mechanical strength is insufficient. If the piezoelectric element 22 is directly joined to the metal thin plate 6, the configuration becomes simple, but this cannot be done for the following reasons. As one reason, as shown in FIG. 2, when the positive electrode 41 contacts the thin metal plate 6, the adjacent piezoelectric elements are short-circuited. If the positive electrode 41 side is a common electrode, the ink 5
1 will be applied with an electric field. This is because the ink 51
Is ionized with time, leading to deterioration of reliability. That is, by arranging an insulating member, that is, a photosensitive resin on the flattening layer 10, the above problem is solved, and the degree of freedom of wiring for controlling the piezoelectric element 22 is increased. Another reason is that, as shown in FIG.
The cross-sectional shape of the ink chamber 5 differs from the cross-sectional shape of the ink chamber 5 due to cost and manufacturing reasons. This means that when the piezoelectric element 22 pressurizes or depressurizes the ink chamber 5, as shown in FIG. 4, the length (a) of the displaceable elastic member 8 is too short to bend sufficiently, and conversely, The length (b) of the elastic member 8 that can be formed is too long to absorb the generated pressure. Therefore, in order to efficiently transmit the pressure of the displacement of the piezoelectric element 22 to the ink chamber 5, an intermediate member that can appropriately secure the lengths (a) and (b) is required. For the above reason, the wall member 7 is required. The wall member 7 has the shape shown in FIG. 3 by the electroforming method. As shown in the figure, the tip of the piezoelectric element 22 is joined to the island 10a of the flattening layer formed at the tip of the island 7a of the wall member 7. The islands 7a and 10a are designed to be slightly smaller than the projection surface of the ink chamber 5, as shown in FIG.

2, the electric field is applied to the positive electrode 41 and the negative electrode 42 of the piezoelectric element 22 from the control board 13 through the lead frame 25 and the wiring pattern 24 according to the print signal in FIG. The piezoelectric element 22 to which the electric field is applied tends to contract in the longitudinal direction (vertical direction in the figure). At this time, the lower half of the piezoelectric element 22 is fixed to the fixed base 21 held by the head frame 11 and cannot be contracted and displaced. On the other hand, the upper half of the piezoelectric element 22 is contracted and displaced without any other constraint, and the contraction force pulls the elastic member 8 via the flattening layer 10. Flattening layer 1
The thin metal plate 6 of the elastic member 8 that is pulled by the piezoelectric element 22 through the zero flexes downward, and as a result, the volume of the ink chamber 5 expands. When the ink chamber 5 expands, the ink 51 flows from the reservoir 4 through the ink supply port 3a. Then
When the electric field of the piezoelectric element 22 is released, the piezoelectric element 22 expands to its original length and compresses the ink chamber 5. An ink droplet is ejected from the nozzle 2 at this pressure. The island-like portion 10a of the flattening layer for transmitting the displacement of the piezoelectric element 22 to the ink chamber
As described above, since the island-shaped portion 7a is slightly smaller than the projection surface of the ink chamber 5, the pressure in the ink chamber 5 is uniformly increased and reduced while leaving the bent portion of the thin metal plate 6. The above is the ink droplet ejection operation.

On the other hand, in addition to the above embodiment, for example, FIG.
As described above, the flattening layer 14 can be formed on the piezoelectric element 22 side. Also, as shown in FIG. 10, the flattening layer 16 can be formed on the piezoelectric element 22 side, and the flattening layer 15 can be formed on the elastic member 8 side.

Next, a method of manufacturing the planarizing layer 10 will be described with reference to FIGS. FIG. 5 shows a method for manufacturing a joined body 70 of the nozzle substrate side 3a of the cavity forming substrate 3 and the nozzle substrate 1 in the order of steps. First, a photosensitive resin film (hereinafter referred to as a dry film) 61 is laminated on the nozzle substrate 1 processed by the press working or the electroforming as described above. Next, a glass mask 62 on which a pattern to be exposed to ultraviolet light and a pattern to not be exposed are formed is disposed on the dry film 61 side, and exposure is performed by irradiation with ultraviolet light. After the exposure, on the dry film 61,
A portion cured by exposure and an unexposed portion not exposed are formed. Next, the unexposed portion is removed by performing development, and the joined body 70 of the cavity forming substrate 3a and the nozzle substrate 1 is completed.

On the other hand, FIG. 6 shows a method for manufacturing a joined body 80 of the elastic member side 3b of the cavity forming substrate 3 and the elastic member 8 in the order of steps. First, a dry film 71 is laminated on the elastic member 8 processed by the electroforming method as described above. Next, the glass mask 72 is disposed on the dry film 71 side in the same manner as described above, and exposure is performed by irradiating ultraviolet rays.
After the exposure, a portion cured by exposure and an unexposed portion not exposed are formed on the dry film 71. Next, the unexposed portion is removed by performing development, and the joined body 80 of the cavity forming substrate 3b and the elastic member 8 is completed.

FIG. 7 shows a method of manufacturing a bonded body 70 of the cavity-forming substrate 3a and the nozzle substrate 1 and a bonded body 80 of the cavity-forming substrate 3b and the elastic member 8 by fusing both of them. Show. Fusion is 15
Perform at a temperature of 0-170 ° C. At this time, although the surface of the dry film is fused by heat, the amount of crushing of the dry film is determined by the pressing force and time. In addition, it is important that the pressure is equalized in order to reduce the variation in the crush amount of the dry film. However, in practice, an imbalance in the amount of crushing is likely to occur depending on the presence or absence of the fused meat on the dry film, that is, how to arrange the pattern. Moreover, in the process of cooling from the heating at the time of fusion to the room temperature, warpage is likely to occur. For the reasons described above, the thickness h of the completed cavity-formed substrate 90 tends to vary at the time of manufacturing. This causes the gap between the piezoelectric element 22 and the elastic member 8 to vary, as described above.
Does not efficiently transmit the pressure to the ink chamber 5, which results in unstable ink droplet ejection characteristics. Therefore, it is important to provide the planarization layer 10.

FIG. 8 shows a process of forming the flattening layer 10. 90 is a completed cavity-formed substrate. First, on the elastic member 8 side of the completed cavity forming substrate 90,
A fluid material 10b for forming the planarization layer 10 is applied.
If necessary, the elastic member 8 may be subjected to a primer treatment for the purpose of improving the adhesion before application. Examples of the fluid substance 10b include a photosensitive resin, a thermosetting resin, and a room temperature curable resin. In particular, a polyester resin, an acrylic resin, an epoxy resin, an APR resin, and various resists are used. In this embodiment, a polyester resin (photosensitive resin) which is relatively easy to handle and inexpensive is used. Next, a PET film for the purpose of releasability is placed at least in a portion provided with a gap member (not shown) for keeping a predetermined distance from the most convex portion of the elastic member 8 than the fluid material 10b. Place on a wide area. Next, a glass mask 91 (reference plate of claim 4) is placed on the film. The glass mask 91 is provided with a pattern for the purpose of selectively forming an exposed portion and an unexposed portion with respect to the fluid material 10b. Furthermore, at least one side of the glass mask on the film side is flattened to 0.1 to
Finished to about 0.2 microns. After placing the glass mask 91, exposure is performed by irradiating ultraviolet rays having a wavelength of about 300 to 400 nm. Since the fluid substance 10b is hardly exposed to visible light of 400 nm or more, no dark room or special equipment is required. After the exposure,
The fluid substance 10b is divided into two parts, the exposed part undergoes a chemical change and is hardened, and the unexposed part maintains a fluid state.
In this state, a fluid portion is removed from the unexposed portion. Since the fluid substance 10b can be easily removed with a weak alkaline solution or water, the operation is safe and harmless. In addition, post-exposure can be performed as needed for the purpose of more reliably curing the cured portion. By the above method, the planarizing layer 1
0 can be formed, and the flattening layer 10 can be formed with a high level of planar accuracy similar to that of the glass mask 91. It should be noted that, other than the present embodiment, the thermosetting resin and the room temperature curable resin can similarly form the highly accurate flattening layer 10.

The flattening layer 10 formed as described above
Is lighter due to the characteristics of the resin, so that the expansion response of the piezoelectric element 22 is hardly lost and the ejection response frequency can be improved. Further, by providing the flattening layer 10, it is possible to realize a higher accuracy in total than shaving the elastic member 8 for the purpose of improving planar accuracy.

[0021]

As described above , according to the present invention, the key
Special finish processing is required for completed finished body
Without causing the displacement of the piezoelectric element to expand and contract the pressure chamber.
To ensure reliable transmission and to compose a piezoelectric element.
Conduction between the electrode and the conductor of the completed cavity-forming substrate
Can be prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the configuration of one embodiment of the present invention.

FIG. 2 is a partial sectional view of the embodiment.

FIG. 3 is a partial perspective view of the same embodiment as viewed from below.

FIG. 4 is a plan view of the embodiment as viewed from directly above.

FIG. 5 is a view showing one manufacturing method of one embodiment of the present invention.

FIG. 6 is a view showing one manufacturing method of the embodiment.

FIG. 7 is a view showing one manufacturing method of the embodiment.

FIG. 8 is a view showing one manufacturing method of the embodiment.

FIG. 9 is a partial sectional view of another embodiment of the present invention.

FIG. 10 is a partial sectional view of another embodiment of the present invention.

FIG. 11 is a partial cross-sectional view illustrating a problem of a conventional example.

FIG. 12 is a partial cross-sectional view illustrating an effect of the present invention.

[Explanation of symbols]

1, 1a Nozzle substrate 3, 3a Cavity forming substrate 5 Ink chamber 6 Metal thin plate 7 Wall member 8, 8a Elastic member 9a, 9b, 9c, 9d, 9e, 9f Flow hardening state of adhesive 10, 10d, 10e, 10f, 14, 15, 16 Flattening layer 10b Fluid substance 11 Head frame 12 Mounting hole 21 Fixing plate 22, 22a Piezoelectric element 23 Common plate 24 Wiring pattern 25 Lead frame 31 Ink supply pipe 32 Ink connection port 33 Ink connection port 51 Ink 60 Head frame plane 61, 71 Photosensitive resin film (dry film) 62, 72 Glass mask 90 Cavity forming substrate completed body 91 Glass mask (reference plate)

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B41J 2/045 B41J 2/055 B41J 2/16

Claims (4)

(57) [Claims] 1. A pressure chamber communicating with a nozzle opening and a reservoir.
A completed cavity-forming substrate having
And pressurized and decompressed by longitudinal expansion and contraction
A piezoelectric element, the completed cavity-forming base, and the piezoelectric element.
An ink jet head comprising a head frame for fixing the piezoelectric element and the piezoelectric element.
A curable resin layer is formed in the area, and its surface is
An inkjet head on which a molded flattening layer is formed . Wherein said curable resin layer form a photosensitive resin
The inkjet head according to claim 1 which have been made. 3. A pressure chamber communicating with a nozzle opening and a reservoir.
A completed cavity-forming substrate having
And pressurized and decompressed by longitudinal expansion and contraction
A piezoelectric element, the completed cavity-forming base, and the piezoelectric element.
Ink jet consisting of a head frame for fixing the element
In the method for manufacturing a head, a contact area of the piezoelectric element of the completed cavity-formed substrate is provided.
Forming a curable resin layer in the region, and the curable resin layer
Forming the surface of the piezoelectric element flat with a reference flat plate, and placing the tip of the piezoelectric element in the flat molded curable resin bath.
A step of fixing the ends with an adhesive, and a method of manufacturing an ink jet head. 4. The curable resin layer is formed of a photosensitive resin.
The method for manufacturing an ink jet head according to claim 3 , wherein the method is performed.