JPH10202888A - Ink jet printing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the misdirection of ink droplets. SOLUTION: The orifice diameter ϕa on the emitting side of the ink ejecting orifice 15 of a nozzle plate 16 is determined on the basis of the size of an ink droplet to be flown and the orifice diameter ϕb on the side of an ink chamber 11 of the orifice 15 is made larger than the orifice diameter ϕa so as to become a size close to the side wall 5 of the ink chamber 11 to form the tapered ink ejecting orifice 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an on-demand type ink jet printer head using a piezoelectric member.

[0002]

2. Description of the Related Art Conventionally, a nozzle plate having an ink discharge port is fixed to the tip of a large number of ink chambers connected in parallel and connected to an ink supply section. There is an ink-jet printer head which is designed to fly. As a method for increasing the ink pressure in the ink chamber in such an ink jet printer head, there is a technique disclosed in Japanese Patent Application Laid-Open No. 63-247051. That is, at least a part of the side wall arranged on both sides of the ink chamber is formed by a piezoelectric member, an electrode is formed on the side surface of the side wall, and the voltage is applied to the electrode to deform the side wall. By changing the deformation direction of the side wall according to the polarity of the voltage, the volume of the ink chamber is expanded to suck ink from the ink supply unit, or the volume of the ink chamber is reduced to discharge the ink inside from the ink discharge port. It is.

[0003]

In this type of ink jet printer head, the diameter of the discharge side of the ink discharge port is determined by the size of the ink droplet to be ejected. Usually, it is smaller than the width dimension of the communicating ink chamber. On the other hand, it is desirable that the ink ejection port is a tapered hole whose ink chamber side is expanded in order to improve the flying performance of the ink droplet. Therefore, when a high-density ink jet printer head is formed, for example, when the ink discharge ports are arranged at a high density of 150 pieces / inch or more and the ink discharge ports are formed in a tapered shape, the ink discharge ports are formed. May be larger than the width of the ink chamber. Also,
Even if the size does not increase, the end portion of the ink discharge port may cover the side wall of the ink chamber due to a dimensional error between the arrangement pitch of the ink chamber and the arrangement pitch of the ink discharge ports.
In addition, when the end of the ink discharge port protrudes from the side wall of the ink chamber, the adhesive that adheres the nozzle plate protrudes, so that a fluid obstacle exists at the base of the ink discharge port. For this reason, there is a problem that a misdirection in which the ink droplet does not fly straight at the time of ink ejection occurs, thereby deteriorating the print quality.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to prevent the occurrence of misdirection of ink droplets and obtain high print quality.

[0005]

According to the first aspect of the present invention,
A substrate is formed by laminating at least one or more piezoelectric members polarized in the thickness direction, and a plurality of grooves parallel to each other and at least a part of the side walls formed by the piezoelectric members separating these grooves are equally spaced. The electrodes for applying a voltage to the piezoelectric members forming the side walls and the wiring patterns connected to these electrodes are formed on the substrate, and the top plate covering the upper part of the groove and the front part of the groove are formed. In an ink jet printer head having a plurality of ink chambers formed by attaching a covering nozzle plate, a hole diameter φa of an ink discharge port of the nozzle plate is determined based on the size of an ink droplet to be ejected, and the ink chamber is formed. The hole diameter φb on the side
It is characterized in that it is formed as a tapered ink ejection port so as to be larger than a and close to the side wall of the ink chamber. Therefore, the width of the ink chamber is naturally determined based on the pitch of the ink ejection ports determined from the design specifications, and the hole diameter φa of the ink ejection port is determined based on the size of the ink droplet to be ejected. By defining the hole diameter φb of the ink discharge port on the ink chamber side so as to be close to the side wall of the ink chamber, the fluid variation at the base of all the ink discharge ports is eliminated, and all the ink discharge ports are removed. The flying direction of the ink droplet from the ejection port is made constant. In other words, the shape of the ink ejection port is required to be tapered, but the degree of the taper is considered in view of the considerable degree of freedom, and has the greatest influence on the misdirection of the ink droplet. It is intended to improve the point of doing.

According to a second aspect of the present invention, there is provided a substrate on which at least one or more piezoelectric members polarized in the thickness direction are laminated, and a plurality of grooves parallel to each other and at least a portion separating the grooves are formed on the substrate. Forming a side wall made of the piezoelectric member at equal intervals, forming electrodes for applying a voltage to the piezoelectric member forming the side wall and a wiring pattern connected to these electrodes on the substrate, and forming an upper portion of the groove. In the ink jet printer head having a plurality of ink chambers formed by attaching a top plate for covering the nozzle and a nozzle plate for covering the front part of the groove, the ejection of the ink ejection port of the nozzle plate based on the size of the ink droplet to be ejected The side of the ink discharge port on the side of the ink chamber is formed by an arcuate portion curved in an arc shape, and the end position of the arcuate portion is defined by the side of the ink chamber. It is characterized by being substantially coincident with the wall surface. Therefore, the width of the ink chamber is naturally determined based on the pitch of the ink ejection ports determined from the design specifications, and the hole diameter φa of the ink ejection port is determined based on the size of the ink droplet to be ejected. An arc portion is formed on the ink chamber side of the ink ejection port, and the end portion of the arc section substantially matches the surface of the side wall of the ink chamber, so that the fluid variation of the base portion of all the ink ejection ports is reduced. In this case, the flying directions of the ink droplets from all the ink discharge ports are fixed.

[0007]

FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 shows the overall structure of an ink jet printer head, in which a lower substrate 1 and an upper substrate 2 each composed of two piezoelectric members polarized in the thickness direction.
Are bonded so that their polarization directions are opposite to each other.
To form That is, an adhesive such as a heat-curable one-part epoxy adhesive is applied to one surface of the lower substrate 1 by screen printing to a uniform thickness of about 10 to 30 μm, and the upper substrate 2 is bonded.

By forming a groove in the substrate 3 formed as described above, the lower substrate 1
Are formed in parallel with a large number of grooves 4 reaching the inside of the substrate and a plurality of side walls 5 separating the grooves 4. This groove processing is performed using a diamond wheel of a dicing saw used for cutting an IC wafer or the like. These grooves 4 are formed in a shape that opens on the front side of the substrate 3 and closes the back side.
The dimensions of the groove 4 are determined according to the specifications of the ink jet printer head. For example, the depth is 0.2 to 1 mm, the width is 20 to 200 μm, and the length is about 5 to 500 mm.

An electrode 6 is formed on the inner surface of the groove 4 by electroless nickel plating. At this time, the upper substrate 2
The wiring pattern 7 continuous with the electrode 6 is simultaneously formed on the upper surface of the substrate. When the aqueous ink is used, the insulating film 8 is formed on the electrode 6 and the wiring pattern 7 (partly) at least in a portion that comes into contact with the ink. FIG. 2 shows a cross section of the groove 4 after the insulating film 8 is formed. If an electrodeposition paint is used to form the insulating film 8, the insulating film 8 is uniformly formed on the electrode 6 up to the inside of the fine groove 4 by contact with the solution of the electrodeposition paint.

Here, a top plate 9 is formed on the substrate 3 on which the electrodes 6 and the wiring patterns 7 are formed and the insulating film 8 is formed.
Are bonded to each other to form a head body 10, and the top opening 9 of the groove 4 is covered with the bonded top plate 9 to form a large number of ink chambers 11. On the inner surface of the top plate 9, there is formed a common ink chamber 12 intersecting with the ink chamber 11 and communicating with all the ink chambers 11.
An ink supply port 13 communicating with 2 is formed. Thus, the material of the top plate 9, the thermal expansion coefficient of the piezoelectric member is 2~6 × 10 _~ ⁶ / ℃, and has a similar thermal expansion coefficient and the thermal expansion coefficient of the piezoelectric member It is desirable. That, 7 × 10 _~ ⁶ / ℃ must be a material of the following thermal expansion coefficient as the material of the top plate 9 are the same piezoelectric member as the lower substrate 1 and the upper substrate 2 is used.
Then, the substrate 3 in which the lower substrate 1, the upper substrate 2, and the top plate 9 are bonded is put into an autoclave (not shown), and heated under pressure (120 ° C. × 2H, 1 to 5 kgf / cm ² ).
And cure the adhesive. The substrate 3 is mechanically pressed and placed in an oven with the pressurized jig heated and cured (120 ° C x
2H). The head body 10 having the top plate 9 bonded to the substrate 3 as described above has the same top plate 9 made of the same material as the lower substrate 1 and the upper substrate 2 made of a piezoelectric member, and thus has a warp or undulation due to a difference in thermal expansion coefficient. Can be reduced. The curing temperature also varies depending on the adhesive used, but is about 40 to 200 ° C. Note that this temperature is a temperature that does not affect the polarization of the piezoelectric member (attention must be paid because the deterioration of the polarization starts at 200 ° C. or higher).

Next, a nozzle plate 16 having an ink discharge port 15 and having a thickness of about 10 to 100 μm is bonded to the head body 10 so as to cover the opening surface 14 at the tip end of the ink chamber 11. However, this nozzle plate 16
In order to bond the opening, the opening surface 14 must be a flat surface. However, as shown in FIG. 3A, there is a step due to a slight displacement between the substrate 3 and the top plate 9, or as shown in FIG. If either one has an edge or sagging, a dent is formed at the boundary of the opening surface 14, and it is impossible to adhere the nozzle plate 16 with a uniform adhesive layer. That is, if there is such a step or dent, the nozzle plate 16
When bonding is used, it may cause poor bonding. For example,
When an adhesive is used, the ink chamber 11 and the ink ejection port 15
It is necessary to apply the adhesive very thinly in order not to block the adhesive with the adhesive. At this time, if there is a step, a portion that is not adhered is formed. Conversely, if this portion is to be bonded, the thickness of the adhesive becomes large, and the ink chamber 11 and the ink discharge port 15 are blocked. In order to eliminate such steps and dents,
After the substrate 3 and the top plate 9 are bonded, they are cut at the same time, or the opening surface 14 is polished and flattened as shown in FIG.

Next, the shape of the ink discharge port 15 is shown in FIG. In order to improve the ink ejection performance, the adhesive side is expanded and has a tapered cross-sectional shape linearly toward the ink ejection side. Here, the groove 4 formed in the substrate 3 is
When formed at a high density of 0 nozzles / inch or more, the nozzle plate 1
When the hole diameter of the ink discharge port 15 of the ink discharge port 15 on the ink discharge side is φa, the hole diameter of the adhesive side is φb, and the groove width of the groove 4 is d, the dimension satisfying the relational expression of φa <φb ≦ d is satisfied. Then, a nozzle plate 16 is formed. That is, based on the size of the ink droplet to be made to fly, the hole diameter φa of the nozzle plate 16 on the discharge side of the ink discharge port 15 is determined and the ink chamber 11 is formed.
The hole diameter φb on the side is formed to be a tapered ink discharge port 15 so as to be larger than the hole diameter φa and close to the side wall of the ink chamber 11.

In such a configuration, the ink discharging operation is performed as follows. First, in a state where ink is supplied to the ink chamber 11 of the head main body 10, the side walls 5 located on both sides of the ink chamber 11 are curved by shear mode deformation between the lower substrate 1 and the upper substrate 2 whose polarization directions are opposite to each other, and are gradually separated. Then, the ink is rapidly returned to the initial position, and the ink in the ink chamber 11 is pressurized to discharge ink droplets from the ink discharge port 15. At this time, in order to prevent crosstalk, the side wall 5 acting as a pressure generating means is driven so as to press the even-numbered ink chambers 11 and the odd-numbered ink chambers 11 alternately. Further, the side wall 5 is gradually deformed when ink is sucked and filled in the ink chamber 11, and is sharply deformed when the ink filled in the ink chamber 11 is pressurized. In addition, as described above, the ink ejection port 1
5 is formed in a tapered shape so that the inside is expanded and the outside is reduced in diameter, so that the ink pressurized in the ink chamber 11 is efficiently discharged.

However, when the ink is ejected, the force from the ink chamber 11 to the ink is evenly applied when viewed from the center of the ink ejection port 15 of the nozzle plate 16, so that the ink droplets are not mistaken when ejecting the ink. Direction is prevented.
Further, the adhesion of the nozzle plate 16 to the substrate 3 is performed by the above-described substrate 3
Is similar to the case where the top plate 9 is bonded to the
Even if the adhesive slightly protrudes on the bonding surface side of
Since the relational expression a <φb ≦ d is established, the flying direction of the ink droplet does not change.

Next, a second embodiment of the present invention will be described with reference to FIG. The taper of the ink discharge port 15 in the present embodiment has a radius of curvature similar to the thickness of the nozzle plate 16 on the bonding side, the hole diameter of the ink discharge port 15 on the ink discharge side of the nozzle plate 16 is φa, The thickness of the plate 16 is t
The dimensions of the respective parts are set so that φa + 2t ≦ d when the width of the groove 4 is d. That is, based on the size of the ink droplet to be jetted, the nozzle plate 1
6, a hole diameter .phi.a on the discharge side of the ink discharge port 15 is defined, and a side surface of the ink discharge port 15 on the side of the ink chamber 11 is formed by an arcuate portion curved in an arc shape. Is substantially matched with the surface of the side wall 5 of the ink chamber 11. In this case as well, the operation is the same as in the first embodiment described above, so that the occurrence of misdirection of the ink droplet is prevented.

[0016]

According to the first aspect of the present invention, a substrate is formed by laminating at least one or more piezoelectric members polarized in the thickness direction, and at least a plurality of grooves parallel to each other are separated from the substrate. Partially formed side walls made of the piezoelectric member are formed at equal intervals, electrodes for applying voltage to the piezoelectric members forming the side walls, and wiring patterns connected to these electrodes are formed on the substrate, and the groove is formed. An ink jet printer head in which a plurality of ink chambers are formed by attaching a top plate covering the upper part of the groove and a nozzle plate covering the front part of the groove,
Based on the size of the ink droplet to be ejected, the ejection side hole diameter φa of the ink ejection port of the nozzle plate is determined, and the hole diameter φb on the ink chamber side is larger than the hole diameter φa on the side wall of the ink chamber. The width of the ink chamber is naturally determined based on the pitch of the ink ejection ports determined from design specifications because the ink ejection ports are formed to be tapered so that they are close to each other, and the ink ejection ports should be made to fly. The hole diameter φa of the ink discharge port is determined based on the size of the ink droplet, but by defining the hole diameter φb of the ink discharge port on the ink chamber side so as to be close to the side wall of the ink chamber. In addition, there is an effect that the fluid variation at the base of all the ink discharge ports can be eliminated and the flying direction of the ink droplet from all the ink discharge ports can be kept constant.

According to a second aspect of the present invention, a substrate is formed by laminating at least one or more piezoelectric members polarized in the thickness direction, and a plurality of grooves parallel to each other and at least a portion separating the grooves are formed on the substrate. Forming a side wall made of the piezoelectric member at equal intervals, forming electrodes for applying a voltage to the piezoelectric member forming the side wall and a wiring pattern connected to these electrodes on the substrate, and forming an upper portion of the groove. In the ink jet printer head having a plurality of ink chambers formed by attaching a top plate for covering the nozzle and a nozzle plate for covering the front part of the groove, the ejection of the ink ejection port of the nozzle plate based on the size of the ink droplet to be ejected The side of the ink discharge port on the side of the ink chamber is formed by an arcuate portion curved in an arc shape, and the end position of the arcuate portion is defined by the side of the ink chamber. The width of the ink chamber is naturally determined based on the pitch of the ink ejection port determined from the design specifications, and the width of the ink ejection port is determined based on the size of the ink droplet to be ejected. Although the hole diameter φa is determined, a circular arc portion is formed on the ink chamber side of the ink discharge port, and the end portion of the circular arc section substantially matches the surface of the side wall of the ink chamber, so that all the ink discharge ports are formed. There is an effect that the fluid variation of the base can be eliminated and the flying direction of the ink droplet from all the ink discharge ports can be kept constant.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing the entire structure of an ink jet printer head according to a first embodiment of the present invention.

FIG. 2 is a vertical sectional front view showing a state where an electrode and an insulating film are formed in a groove.

FIG. 3 shows a positional relationship between a substrate and a top plate.
(a) shows a state in which both are shifted, (b) shows a state in which a dent is generated between the two, and (c) shows a state in which the opening surface is finished flat.

FIG. 4 is an exploded perspective view of a substrate and a top plate.

FIG. 5 is a perspective view of a head body in which a top plate is bonded to a substrate.

FIG. 6 is a partially enlarged cross-sectional view showing a relationship between an ink ejection port and an ink chamber.

FIG. 7 is a cross-sectional view illustrating a second embodiment of the present invention, in which a part of a relationship between an ink discharge port and an ink chamber is enlarged.

[Explanation of symbols]

 3 Substrate 4 Groove 5 Side wall 7 Wiring pattern 8 Electrode 9 Top plate 11 Ink chamber 15 Ink ejection port 16 Nozzle plate

Claims (2)

[Claims] A substrate is formed by laminating at least one or more piezoelectric members polarized in a plate thickness direction, and a plurality of grooves parallel to each other on the substrate and at least a part separating the grooves is formed of the piezoelectric member. Forming side walls at equal intervals, forming an electrode for applying a voltage to the piezoelectric member forming the side wall and a wiring pattern connected to these electrodes on the substrate;
In an ink jet printer head having a plurality of ink chambers formed by attaching a top plate that covers the upper part of the groove and a nozzle plate that covers the front part of the groove, the ink in the nozzle plate is determined based on the size of the ink droplet to be ejected. The hole diameter φa on the discharge side of the discharge port is determined and the hole diameter φ on the ink chamber side is determined.
An ink jet printer head, wherein b is a tapered ink ejection port so as to be larger than the hole diameter φa and close to the side wall of the ink chamber. 2. A substrate is formed by laminating at least one or more piezoelectric members polarized in a plate thickness direction, and a plurality of grooves parallel to each other and at least a part separating the grooves is formed of the piezoelectric member. Forming side walls at equal intervals, forming an electrode for applying a voltage to the piezoelectric member forming the side wall and a wiring pattern connected to these electrodes on the substrate;
In an ink jet printer head having a plurality of ink chambers formed by attaching a top plate that covers the upper part of the groove and a nozzle plate that covers the front part of the groove, the ink in the nozzle plate is determined based on the size of the ink droplet to be ejected. The diameter of the hole φa on the discharge side of the discharge port is defined, and the side surface of the ink discharge port on the side of the ink chamber is formed by an arcuate portion curved in an arc shape. An ink jet printer head characterized by being substantially coincident with the surface of (1).