JP3108775B2 - Ink jet 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 an ink jet recording head in which the density and size of ink discharge nozzles are increased.

[0002]

2. Description of the Related Art As one of the principles of performing recording by causing droplets to fly from fine nozzles, there is a Kaiser system using an electromechanical transducer. Japanese Patent Application Laid-Open No. 3-15555 proposes a method for narrowing the distance between the nozzle 3 and the cavity 4 and reliably transmitting the generated force of the electromechanical transducer to the cavity 4 using this method. A cross-sectional view of this technique is shown in FIG. The piezoelectric element 7 in the figure is of a bimorph type. Nozzle 3 and cavity 4 communicate vertically,
An extremely large number of nozzles 3 are formed on a plane,
In this method, a projection 5 is provided outside the extremely thin (1.4 μm) diaphragm portion, and the end face of the projection 5 is pressed by the piezoelectric element 7. When a voltage is applied to the piezoelectric element 7,
The piezoelectric element 7 is displaced toward the cavity 4 and presses the protrusion. Along with this, the diaphragm portion also deforms and changes the volume of the cavity 4, so that about 1 /
2 (in the case where the ejection efficiency is 50%; usually, about 50% of the change in the volume of the cavity is ejected from the nozzle in the ink jet head).

[0003]

In the prior art, however, the projections are formed on the second substrate 2 by etching or the like.
The center axis of the cavity 4 and the center axis of the protrusion 5 may be deviated when joining the second substrate 2 with the second substrate 2. If the density of the nozzles is increased and the width of the cavity 4 is reduced, even a slight displacement will greatly affect the ink ejection characteristics. If the central axis of the cavity 4 and the central axis of the protrusion 5 are shifted, the deformability of the second substrate 2 is deteriorated.

When the size of the cavity 4 is reduced in accordance with the increase in the density of the nozzles, it is inevitable to obtain a desired amount of ink to be ejected from the nozzle array (in the linear direction connecting the nozzles).
The cavity 4 is extended in a direction orthogonal to the direction of the arrow, and at the same time, the protrusion 5 on the second substrate 2 is extended to increase the area of the second substrate 2 on the cavity 4 and the displacement of the bimorph piezoelectric element or the laminated piezoelectric element is reduced. It must be transmitted to the entire second substrate 2 on the cavity 4.

However, when the projection is extended in a direction orthogonal to the nozzle row and the piezoelectric element 7 is displaced, the projection 5 bends as shown in FIG. Cannot be transmitted efficiently. In the case of a laminated piezoelectric element, the number of layers may be increased so that the entire area in the longitudinal direction of the cavity 4 can be pressed. However, an extreme increase in the cost of the piezoelectric element is caused.

In view of this, the projection 5 caused by the application of a concentrated load
Therefore, there is a need for a method for reducing the deflection. To that end, it is only necessary to increase the dimension a (width) or the dimension b (height) in FIG. 12. However, if the dimension a is too large, the reaction force of the second substrate increases and the deformation occurs. It becomes difficult to do. Therefore, when the dimension b is increased, the height of the protrusion 5 increases, and the center of gravity of the protrusion increases. In this case, the center axis of the piezoelectric element 7 is slightly displaced from the center axis of the projection 5, and the projection 5 is inclined when the piezoelectric element 7 and the projection 5 are joined, and the projection 5 is joined to the piezoelectric element 7 while being inclined. . In this case, the same applies to the case where the center axis of the projection slightly deviates from the center axis of the cavity 4. Further, when the projection is formed by etching, the height of the projection can be formed only about twice as large as the width of the projection. Therefore, the rigidity of the projection is further reduced as the density of the nozzle is increased.

In order to reduce the size of the ink jet recording head and increase the density of the nozzles, a method for efficiently transmitting the displacement of the piezoelectric element to the second substrate is to improve the alignment accuracy of the projections and to assemble the assembly. There is a need for a method for joining the piezoelectric element and the projection within the structure and increasing the rigidity of the projection.

[0008]

Means for Solving the Problems To this end, the present invention provides: A plurality of ink ejection nozzles, a cavity communicating with each of the nozzles, and a pressure generating member for applying a volume change to the cavity to cause droplets to fly from the nozzle, a first projection formed outside the diaphragm of the cavity. In the ink jet type recording head, the second projection is formed on the diaphragm corresponding to the first projection inside the cavity, and the rigidity of the second projection is larger than the rigidity of the first projection. I do. 2. A plurality of ink ejection nozzles, a cavity communicating with each of the nozzles, and a pressure generating member for applying a volume change to the cavity to cause droplets to fly from the nozzle, a first projection formed outside the diaphragm of the cavity. In the ink jet recording head connected to the second projection, the second projection is formed on the diaphragm inside the cavity corresponding to the first projection, and the contact area of the first projection that contacts the diaphragm is the diaphragm of the second projection. Characterized in that the contact area is smaller than the contact area where the contact is made. 3. In such an ink jet recording head, the contact area of the first projection in contact with the diaphragm is smaller than the contact area of the second projection in contact with the diaphragm only in the portion in contact with the pressure generating member. 4. In such an ink jet recording head, a second projection and a wall forming the cavity are formed inside the cavity,
It is characterized by being formed simultaneously.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective sectional view of an embodiment of the present invention. A second substrate 2 which is a thin film of a polymer resin is joined to a first substrate 1 having a nozzle 3 and a cavity 4 formed by injection molding. The second substrate 2 functions as a diaphragm in the cavity 4 portion. A first metal protrusion 5 is formed outside the cavity 4 of the second substrate 2, and a second metal protrusion corresponding to the first protrusion 5 is formed inside the cavity 4. The second substrate 2 is replaced with the first substrate 1
When joining, the second projection 6 always fits in the cavity 4 so that rough positioning can be performed and fine adjustment can be easily performed. At the same time, the rigidity of the projection can be improved. A piezoelectric element 7 that is a member that adds a volume change to the cavity 4 is joined to the first protrusion 5. When a voltage is applied to the piezoelectric element 7, the piezoelectric element 7 is displaced, and the first protrusion 5 and the second The projection 6 is displaced to deform the second substrate 2. As a result, a volume change occurs in the cavity 4, and an ink droplet flies from the nozzle 3. The piezoelectric element 7 is a conventionally known bimorph type,
Any of a stacked type may be used. In this embodiment, a laminated piezoelectric element using a piezoelectric transverse effect that deforms perpendicular to the direction of the electric field is used. The present invention can be applied to a displacement using a piezoelectric longitudinal effect that deforms in parallel to the direction of the electric field.

The flow path of the first substrate 1 (the flow path of the cavity 4 and the liquid communicating therewith) can also be formed by etching glass, metal, polymer resin or the like, or by photosensitive resin. The nozzle 3 may be formed on the first substrate 1 by laser processing, mechanical processing, or the like. In addition, it can be formed by joining the nozzle plate with the nozzle 3 opened to the first substrate 1. The material of the second substrate 2 may be a polymer resin film having ink resistance, being less likely to be plastically deformed, and having a high displacement capability, such as polysulfone, polyimide, polyetherimide, polycarbonate, and polyethersulfone. . The thickness of the second substrate 2 is not only the first protrusion 5 but also
Even if the second protrusion 6 is formed, it is preferable that the second protrusion 6 be as thin as possible so as to minimize the reaction force generated due to the deformation of the second substrate 2 and to make the protrusion difficult to bend. In this example, a 7.5 μm thick polyimide film was used.
Further, the material of the second substrate is within the applicable range of the present invention even if a thin film of nickel, stainless steel, titanium, silicon, glass or the like having ink resistance is used.

The first protrusions 5 and the second protrusions 6 were formed on both surfaces of the resin film by plating the resin film with nickel and performing pattern etching. The material of the projections falls within the applicable range of the present invention as long as they can be plated on a resin film, are easily etched, and have ink resistance.

The width of the first projection 5 (b in FIG. 2) is
2 (a in FIG. 2). The reason for this is that the provision of the projections on both surfaces always causes a slight displacement between the two surfaces, and that when the adhesive is used to join the piezoelectric element 7 and the first projection 5, the adhesive becomes the second adhesive. This is because there is a risk of leaning on the substrate 2. If the positions of the first projection and the second projection are shifted, the actual area of the second substrate 2 acting as a diaphragm is reduced, and the deformability of the second substrate 2 is extremely reduced. Further, as shown in FIG. 9, even when the widths of the first protrusion 5 and the second protrusion 6 exactly match, the piezoelectric element 7 and the first protrusion
When the adhesive drops on the second substrate 2 at the time of bonding (part (a) in FIG. 9), the width of the first protrusion 5 becomes apparently wider, and the second substrate 2
And the deformability of the second substrate 2 is extremely reduced. Since the second substrate 2 is extremely thin in order to enhance the deformability, the slight adhesion of the adhesive inhibits the deformation of the second substrate 2.

In this embodiment, as shown in FIG. 3, the first protrusion comes into contact with the second substrate 2 within a range in which the positional deviation between the protrusions on both surfaces caused by the double-sided etching can be tolerated. The contact area is made smaller than the contact area of the second protrusion contacting the second substrate. This is because when the projections on both sides are displaced in the length direction (a in FIG. 3), the apparent length of the projections becomes longer, the projections are more easily bent, and the width direction of the projections (b in FIG. 3). In addition to the case where the projections on both sides are displaced in (2), when the head is assembled, it appears as a variation in ink discharge characteristics, which causes a poor production yield.

Further, as shown in FIG. 4 (a view of the second substrate 2 in the direction of the cavity 4, the piezoelectric element is shaded in the figure), only the portion of the first projection 5 to which the piezoelectric element 7 is bonded is narrowed. However, the effect of this embodiment can be expected. Since the second protrusions 6 are not constricted, the degree of stress concentration at the constricted portions of the first protrusions 5 is extremely small, and a decrease in the deformability of the second substrate 2 due to the dripping of the adhesive can be prevented.

Further, the rigidity of the first projection 5 is reduced, and
It is also effective to increase the height (c in FIG. 2) of the projection 6 to reinforce it. Even if the rigidity of the projections is increased by increasing the height of the second projections 6, a joining surface between the piezoelectric element 7 and the first projections 5 due to a displacement within the tolerance of the first projections 5, and This is because there is no fear that stress concentration will be applied to the boundary surface between the second substrate 2 and the first protrusion 5.

FIG. 5 is a sectional view showing a second embodiment of the present invention. The present invention is different from the first embodiment in that the second protrusion has a two-step shape. The second protrusion is formed of the second protrusion so as to increase the rigidity of the protrusion and not to hinder the deformation of the second substrate 2.
The portion bonded to the substrate 2 is set to have a width at which the maximum volume changes when a unit pressure is applied, and the second stage has a wider width. According to the present embodiment, if the projection width is such that the maximum change volume of the cavity 4 can be obtained, the rigidity of the projection does not become insufficient. In this example, the shape shown in FIG. 5 was obtained by metal electroforming.

FIG. 6 is a sectional view showing a third embodiment of the present invention. The present embodiment is different from the first embodiment in that the first substrate 5, the diaphragm portion of the second substrate 2, and the second projection 6 are formed by etching the second substrate 2 on both sides.
The material of the second substrate 2 can be etched, and if it has ink resistance, there is no need to ask whether it is metal or nonmetal. Examples include nickel, stainless steel, gold, silver, titanium, silicon, and polyimide, polysulfone, polyetherimide, polycarbonate, polyethersulfone, and the like. In this embodiment, nickel (Ni), which is resistant to corrosion and optimal for etching, is used. According to the method of the present embodiment, one side of Ni is etched,
Compared to the case where only the diaphragm portion of the second substrate 2 and the first protrusion 5 are formed, when the first protrusion 5, the diaphragm portion of the second substrate 2, and the second protrusion 6 are simultaneously formed by double-sided etching, the etching time of the protrusion portion is reduced. There is an advantage that it is possible to greatly reduce the work process time. In addition, the first
Since the projections 5 and the second projections 6 are integrally formed, the second
There is no boundary surface with the substrate 2, and the reliability is dramatically improved as compared with the boundary surface between the projection and the second substrate 2 although they are formed by joining them.

As another effect, when the second substrate 2 is made of metal, it is possible to prevent water vapor from permeating from the cavity 4 to the outside. As a result, the piezoelectric element 7 has a poor reliability against high humidity (a defect such as migration occurs between the electrodes when the humidity is high). It becomes protection.

When Si is used for the second substrate 2, in addition to the above effects, the surface is oxidized to form a SiO2 film, thereby improving the wettability. Here, the wettability is
The degree of the contact area when the droplet adheres to the solid surface,
It is said that the larger the contact area, the better the wetting. The good wettability of SiO2 means that even if air bubbles enter the pressure chamber 4, the air bubbles do not adhere to the pressure chamber 4 and the air bubble discharging property can be improved. In addition, the wetting of the adhesive on the first protrusion 5 is improved, which leads to an improvement in the adhesion between the piezoelectric element 7 and the first protrusion 5.

Since a metal such as Ni has a large elastic coefficient, it must be made extremely thin in order to efficiently convert the displacement of the piezoelectric element 7 into a deformation. There is a danger of failure. If a polymer resin such as Pi (polyimide) is used for the second substrate 2,
Since the elastic modulus is extremely small as compared with Ni or the like, the thickness can be increased, and the thickness of the film can be easily controlled.

Next, a fourth embodiment of the present invention will be described. This embodiment is different from the first embodiment in that the second protrusion 6 is
This is a point that they are integrally molded or are molded at the same time.

As shown in FIG. 7A, the Si (silicon) plate is etched partway along the flow path wall 8, and then the flow path wall 8 and the second protrusion 6 are formed by a second etching (FIG. 7A). 7 (b)). At the time of the second etching, the first protrusion 5 and the second substrate 2 are simultaneously etched. Thus, the flow path wall 8 and the second projection 6 are integrally formed. As the material for forming the second substrate 2, the first protrusion 5, and the second protrusion 6, all of the materials which can be etched described in the second embodiment can be applied.

As another method, as shown in FIG.
The photosensitive resin is used to form the flow path wall 8, and the second protrusion 6 is formed of the photosensitive resin on the second substrate 2 side simultaneously with the flow path wall 8.
The second substrate 2 in which the first protrusion was formed on the nickel thin film by electroforming in advance was used. The second substrate 2 may be a thin film of a polymer resin, a metal, or the like, as long as the first protrusions 5 are formed in advance. The first protrusion 5 is formed by etching or electroforming.

Alternatively, a thin film of polymer resin, metal, etc.
There is also a method of laminating a photosensitive resin on both surfaces of the substrate 2 to form the first protrusion 5, the flow path wall 8, and the second protrusion 6.

According to the embodiment of the present invention, the flow path wall 8 and the second protrusion 6 are formed at the same time, so that the flow path wall 8
The position accuracy of the projections 6 is extremely accurate, and in addition to the effects described in the first embodiment, there is an effect that variations in ink ejection characteristics between individual heads due to head assembly are suppressed, and the yield is improved.

[0027]

The ink jet recording head according to the present invention comprises a plurality of ink discharge nozzles, a cavity communicating with each of the nozzles, and a pressure generating member for applying a volume change to the cavity to cause droplets to fly from the nozzles. In an ink jet recording head connected to a first projection formed outside a diaphragm of a cavity, a second projection is formed on the diaphragm inside the cavity corresponding to the first projection, and the second projection is formed on the diaphragm. Since the rigidity is greater than the rigidity of the first protrusion, the rigidity is lowered by lowering the height in order to lower the center of gravity of the first protrusion, and the displacement between the pressure generating member and the first protrusion within the tolerance is reduced. Even when this occurs, the displacement of the pressure generating member is reduced to the second level without causing stress concentration at the joint surface between the pressure generating member and the first projection and at the interface between the second substrate and the first projection. An effect that can be transmitted to the whole plate.

Further, the ink jet recording head of the present invention comprises a plurality of ink discharge nozzles, a cavity communicating with each of the nozzles, and a pressure generating member for applying a volume change to the cavity to cause droplets to fly from the nozzles. An inkjet recording head connected to a first projection formed outside the diaphragm of the cavity,
A second projection is formed on the diaphragm corresponding to the first projection inside the cavity, and a contact area of the first projection contacting the diaphragm is smaller than a contact area of the second projection contacting the diaphragm. Even when the first projection and the second projection are displaced in the length direction when the double-sided etching is performed, the rigidity of the projection can be maintained within an allowable range. Further, an adhesive is used for joining the pressure generating member and the first protrusion, and when the adhesive is dripped on the second substrate from the first protrusion, the area of the second substrate acting as a diaphragm is not reduced, so that the bonding is performed. This has the effect that deformation inhibition of the second substrate due to the adhesion of the agent can be prevented.

In the ink jet type recording head, the contact area of the first projection in contact with the diaphragm is smaller than the contact area of the second projection in contact with the diaphragm. An adhesive is used for joining the pressure generating member and the first protrusion, and when the adhesive drips from the first protrusion onto the second substrate, the area of the second substrate acting as a diaphragm is not reduced, so that the adhesive is used. This has the effect of preventing deformation inhibition of the second substrate due to adhesion.

In the ink jet recording head, since the second projection and the wall forming the cavity are formed at the same time inside the cavity, the positional accuracy of the flow path wall and the second projection is extremely accurate. Therefore, variations in ink ejection characteristics between individual heads due to head assembly are suppressed, and the yield is improved.

With the above arrangement, the pressure generating member and the projection can be joined within the assembly tolerance and without causing deformation inhibition due to the adhesion of the adhesive to the second substrate, and the rigidity of the projection can be further increased. It is possible to realize high density and downsizing of the inkjet recording head.

[Brief description of the drawings]

FIG. 1 is a perspective sectional view of a first embodiment.

FIG. 2 is a sectional view taken along line AA of the first embodiment.

FIG. 3 is a top view and a side view of the first embodiment.

FIG. 4 is a bird view of the first embodiment.

FIG. 5 is a sectional view of a second embodiment.

FIG. 6 is a sectional view of a third embodiment.

FIG. 7 is a sectional view of each step of the fourth embodiment.

FIG. 8 is a sectional view of a fourth embodiment.

FIG. 9 is a comparative sectional view of the first embodiment.

FIG. 10 is an exploded perspective view of a conventional example.

FIG. 11 is a sectional view of another conventional example.

FIG. 12 is a sectional view of another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 Nozzle 4 Cavity 5 1st protrusion 6 2nd protrusion 7 Piezoelectric element 8 Flow path wall 9 Ink communication flow path 10 Ink supply path 11 Ink supply preparation chamber

Claims (4)

(57) [Claims] 1. A plurality of ink discharge nozzles, a cavity communicating with each of the nozzles, and a pressure generating member for applying a volume change to the cavity for causing droplets to fly from the nozzles, the pressure generating member comprising a diaphragm of the cavity. In the ink jet recording head connected to a first protrusion formed on the outside, a second protrusion is formed on the diaphragm inside the cavity corresponding to the first protrusion, and the rigidity of the second protrusion is formed. Is larger than the rigidity of the first projection. 2. A plurality of ink ejection nozzles, a cavity communicating with each of the nozzles, and a pressure generating member for applying a volume change to the cavity to cause droplets to fly from the nozzles, wherein the pressure generating member is a diaphragm of the cavity. In an ink jet recording head connected to a first protrusion formed on the outside, a second protrusion is formed on the diaphragm inside the cavity corresponding to the first protrusion, and the second protrusion is formed on the diaphragm. 2. An ink jet recording head according to claim 1, wherein the contact area in contact with the diaphragm is smaller than the contact area of the second projection in contact with the diaphragm. 3. An ink jet recording head according to claim 2, wherein the contact area of said first projection in contact with said diaphragm is smaller than the contact area of said second projection in contact with said diaphragm. 4. The ink jet recording head according to claim 1, wherein the second projection and a wall forming the cavity are formed simultaneously inside the cavity.