JPH04345856A - Ink jet head and fabrication thereof - Google Patents

Abstract

PURPOSE:To improve print image quality by suppressing mutual interference, which causes variation of ink droplet speed between a case where a pie actuator is driven independently and a case where adjacent actuators are driven concurrently, thereby improving frequency characteristics in printing. CONSTITUTION:A piezoelectric element 2 having actuators 9 being sectioned by grooves 2a filled with fillet 6 is jointed to a channel substrate 3 having channels 8 corresponding to the actuators 9 on a substrate 1. Channel board grooves 7 are then made in the barrier wall 3a sectioning the channels 8.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet head and a method of manufacturing the same, and more particularly to an inkjet head with less mutual interference and excellent frequency characteristics and a method of manufacturing the same.

0002

[Prior Art] An on-demand type inkjet head according to the present invention has an electric recording conversion means such as a piezo diaphragm such as a piezoelectric element attached to a part of a partition wall that partitions an ink flow path, and a pressure corresponding to an electric signal. This head is characterized by a simple structure that generates pulses, ejects ink droplets from nozzles connected to the flow path, and records on a recording medium such as paper.

FIG. 5 is an exploded perspective view for explaining a conventional inkjet head, and FIG. 6 is a sectional view taken along the Y-Y arrow in FIG. P
ZT), 12a is a groove, 12b is a convex portion, 13 is a channel substrate,
14 is a nozzle plate, 14a is a nozzle, 15 is a common liquid chamber, 15a is an ink supply pipe, 16 is a filler, 17 is a PCB (printed circuit board), 18 is a flow path (liquid chamber), 1
9 is a lead wire, 20 is a ground line, and 21 is a bonding wire.

In the illustrated inkjet head, the piezoelectric element 12 generates a large displacement even when driven by an actuator at a low voltage, so it is usually a laminated piezoelectric element (PZ).
T) is used. Further, the piezoelectric elements 12 are formed with a plurality of grooves 12a in the longitudinal direction of the stacked piezoelectric elements so that they can be driven individually. A convex portion 12b (hereinafter referred to as an actuator) is formed on the piezoelectric element 12, divided by the groove 12a. Note that the actuator 12b
The width is selected to be slightly smaller than the channel width 18. The flow paths 18 are arranged in the flow path substrate 13 as a large number of parallel flow paths partitioned by partition walls 13a in the longitudinal direction of the flow path substrate 13, and each flow path 18 is provided with a piezoelectric element 12. The piezoelectric elements 12 are arranged to face the actuators 12b provided in the flow path substrate 13 and the piezoelectric elements 12 are bonded to each other.

Furthermore, the grooves 12a between adjacent actuators formed by groove processing of the piezoelectric element 12 are filled with an elastic material 16 having a low Young's modulus, and the stacked piezoelectric elements 12 are filled with an elastic material 16 having a low Young's modulus.
This prevents the insulation between the electrodes from being degraded by the ink, and also maintains the strength of the driven actuator. Further, each channel 18 is provided on one end surface of the channel substrate 13.
A nozzle plate 14 having nozzles 14a corresponding to each other is joined to the nozzle plate 14, and the opening at the other end of each flow path 18 is connected to the common liquid chamber 1.
It communicates within 5. The common liquid chamber 15 is filled with ink supplied from an ink supply pipe 15a.

When a signal based on image information is applied to the above-mentioned inkjet head through the lead wire 19, and the actuator of the selected piezoelectric element 12 is driven based on the signal, the actuator 12b is moved in the thickness direction. The volume of the flow path 18 is reduced. On this occasion,
A pressure wave is generated and an ink droplet is ejected from the nozzle 14a. At this time, due to the displacement of the actuator 12b of the piezoelectric element 12 in the thickness direction, the flow path 1 provided in the flow path substrate 13 is
A force that pushes up the partition wall 13a in the upper direction also acts on the partition wall 13a. This is because the filler 16 filled in the groove 12a of the piezoelectric element 12 is pulled up by the displacement of the actuator 12b of the piezoelectric element 12, and thereby the partition wall where the filler 16 and a part of the bottom are joined. This is because 13a is lifted upward.

FIG. 7 is a cross-sectional view for explaining the displacement of a conventional flow path substrate. In the figure, A, B, and C indicate actuators 12b of the piezoelectric element 12;
, C are all shown filled with filler material 16. Further, parts having the same functions as those in FIG. 6 are given the same reference numerals.

Now, looking at the operation of actuator B, when only actuator B is driven independently, actuator B is displaced by b in the direction of the arrow. At this time, the amount of change in volume of the flow path 18 is determined by the amount b that the actuator B lifts, assuming that the width of the flow path 13a is constant, and the amount b1 that the flow path substrate 13 lifts due to the displacement of the actuator B.
It is expressed as the difference between This lifting amount Δb1 is a relatively small amount. This is the adjacent actuator A,
This is because, since C is not driven, the filler 16 is fixed on the side of the actuators A and C, and the amount by which the partition wall 13a is lifted only by the filler 16 on the actuator B side is small.

On the other hand, actuators A, B, C
When actuators A and C are driven at the same time, actuators A and C are lifted by displacements a and c, respectively, and corresponding flow path substrates 13 are also lifted by displacements Δa and Δc. Therefore, in the actuator B section, actuators A, B, C
The channel substrate 1 is affected by the lifting amount of the filler 16 on the side.
3 is the lifting amount of the displacement Δb2 (>Δb1). As a result, the amount of volume change in the flow path 18 of the actuator B section is
smaller than when driven alone.

For this reason, there is no problem when driving alone, but
When the actuators of a plurality of piezoelectric elements 12 are driven simultaneously, mutual interference occurs between adjacent piezoelectric elements, resulting in variations in the speed of ejected ink droplets and differences in the volume of ink droplets. In addition, there is a phenomenon in which the frequency characteristics are also affected. That is, in the conventional inkjet head having the cross section shown in FIG.
The rate of decrease in the volume of the channel 8 at the center of drive is greater than the rate of decrease in volume of the channels on both sides, which causes a phenomenon in which the velocity of the ink droplet at the center is slower than the velocity of the ink droplets on both sides.

[0011]

[Purpose] The present invention was made in view of the above-mentioned circumstances, and it is possible to change the velocity of ink droplets when a piezoelectric element actuator is driven alone and when actuators on both sides are driven simultaneously. We aim to reduce the mutual interference that occurs, and as a result, improve the frequency characteristics of printing,
This was done for the purpose of improving the quality of printed images, and further for the purpose of providing an inexpensive inkjet head with a high yield in processing the head.

0012

[Structure] In order to achieve the above objects, the present invention provides (1)
A flow path substrate having a number of parallel flow paths spaced apart from each other in the longitudinal direction of the flow path having nozzles for ejecting droplets; It consists of a common liquid chamber that supplies ink, a piezoelectric element that is divided by a groove, has a convex portion corresponding to each of the flow paths, and is bonded to the flow path substrate, and the actuation of a certain flow path is selected. when the selected parallel flow path is displaced perpendicularly to the longitudinal direction of the convex portion of the piezoelectric element,
In the inkjet head that ejects ink droplets from nozzles corresponding to the flow channels, a partition wall between adjacent flow channels of the flow channel plate has a slit formed in a longitudinal direction of the partition wall; (2) a substrate; A first step of bonding the piezoelectric element to the substrate, a second step of forming grooves on the piezoelectric element bonded to the substrate, a third step of filling and hardening the filler into the processed groove, and a third step of bonding the piezoelectric element with the hardened filler. The fourth step is to grind the upper part of the element.
A fifth step of bonding a flow path substrate with a liquid chamber formed on the ground piezoelectric element surface, and a sixth step of machining a flow path plate groove on the upper part of the flow path substrate bonded to the piezoelectric element surface. This was done as a feature. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a perspective view for explaining one embodiment of the ink jet head of the present invention, and FIG. 2 is a sectional view taken along the line Y--Y in FIG. In the figure, 1 is a substrate, 2 is a piezoelectric element, 2a is a groove, 3 is a channel substrate, 3a is a partition, 4 is a nozzle plate, 4a is a nozzle, 5 is a common liquid chamber, 6 is a filler,
7 is a channel plate groove, 8 is a channel (liquid chamber), 9 is an actuator (projection), and 10 is an ink supply pipe.

In the figure, the piezoelectric element 2 is a laminated piezoelectric element that is displaced in the thickness direction by low voltage driving, and is bonded to the substrate 1. A groove 2a is provided in the piezoelectric element 2 in the longitudinal direction to divide the actuator 9 into sections. A filling material 6 is filled in the groove 2a. When the grooves 2a are formed in the piezoelectric element 2, the electrodes of the laminated piezoelectric element are exposed at the end faces of the grooves 2a, so the filler 6 prevents insulation from deteriorating due to ink and improves the strength of the actuator 9. It also serves as a retainer.

A channel substrate 3 made of a glass substrate, a silicon substrate, a metal substrate, or the like is bonded to the piezoelectric element 2. In the flow path substrate 3, a flow path (liquid chamber) 8 corresponding to the actuator 9 and having a groove width slightly wider than the width of the actuator 9 is defined by a partition wall 3a, and is parallel to the longitudinal direction. There are many. Further, a channel plate groove 7 parallel to the channel 8 is provided in the partition wall 3a. The groove processing of these grooves 2a is determined depending on the material, and is processed by machining, etching, resin molding, or the like.

A nozzle plate 4 made of a glass substrate, a silicon substrate, a resin thin film, or a metal substrate is bonded to the end surfaces of the flow path substrate 3 and the piezoelectric element 2. Nozzles 4a are formed in the nozzle plate 4 in correspondence with the flow passages 8. A common liquid chamber 5 communicating with the flow path 8 is joined to the other end surface of the flow path substrate 3 . The common liquid chamber 5 receives ink from the ink supply pipe 10 and stores ink for ejecting ink droplets from the nozzle 4a.

The piezoelectric element 2 selected based on the image information is applied to the inkjet head configured as described above.
When a pulse voltage from a drive circuit (not shown) is applied to the actuator 9, the actuator 9 is displaced in the thickness direction. This displacement causes the volume of the flow path 8 to decrease, and at this time, ink droplets are ejected from the nozzle 4a.

FIG. 3 is a diagram for explaining the displacement of the flow path substrate of the present invention. In the diagram, A, B, and C indicate the actuators 9 of the piezoelectric elements 2 arranged next to each other in sequence. All gaps separating A, B, and C are filled with filler 6.
It is shown in a filled form, and parts having the same functions as those in FIG. 1 are given the same reference numerals.

Now, looking at the displacement of the channel substrate 3 when actuator B is driven independently, it is found that the displacement of actuator B is
When is displaced by b in the thickness direction of the arrow, the portion of the filler 6 in contact with the actuator B is lifted, and as a result, the portion of the corresponding partition wall 3a defined by the channel plate groove 7 is individually microscopic. It is lifted by displacement Δb. Therefore, the amount of change in volume of the flow path 8 is not significantly different from the amount of change in volume of the conventional flow path 18 shown in FIG.

However, by providing the channel plate groove 7,
It is possible to reduce the difference between the amount of change in volume of the flow path 18 of actuator B when actuators A, B, and C are driven simultaneously and the amount of change in volume of the flow path 18 when actuator B is driven alone. . That is, when actuators A, B, and C are driven simultaneously, the actuators A, B, and C are displaced by the same amount a, b, and c in the direction of the arrow. Along with this, the partition walls 3a of the channel plate 3 corresponding to the actuators A, B, and C move in the direction of the arrows △a, △b,
It is lifted by a displacement amount of Δc. However, since the deformation received from actuators A and C deforms the channel plate groove 7 portion, the lifting amount Δb1 of the channel board 3 corresponding to actuator B is small, and the change when actuator B is driven independently The difference with the amount Δb becomes smaller. Therefore,
When actuators A, B, and C are driven simultaneously,
The effect on actuator B is smaller than in the conventional example.

As described above, by providing the flow path plate groove 7 in the flow path substrate 3, the flow path 8 changes between when actuator B is driven alone and when adjacent actuators A and C are driven simultaneously. The difference in volume is smaller, and therefore, fluctuations in ink droplet speed and ink droplet volume during simultaneous driving can be made smaller than in the case of conventional inkjet heads, making it possible to print with excellent image quality. .

However, when attempting to bond to the piezoelectric element 2 after forming the channel plate grooves 7 on the channel substrate 3, the channel substrate 3 is thin and grooved, making it extremely brittle and difficult to bond. It lacks. Therefore, the above-mentioned drawback can be overcome by joining the channel substrate 3 before the groove processing and then processing the channel plate grooves 7. Hereinafter, the steps of the manufacturing method of the present invention will be described with reference to FIGS. 1 and 4.

FIGS. 4(a) to 4(e) are diagrams for explaining the method of manufacturing an inkjet head of the present invention.
Components having the same functions as those in FIG. 2 are given the same reference numerals.

<Manufacturing method> (1) A piezoelectric element is bonded to a substrate (FIG. (a)). The substrate 1 is a flat plate made of stainless steel or aluminum, and the piezoelectric element 2 is a laminated piezoelectric element. Further, as the bonding material, an adhesive such as epoxy can be used. (2) Machining a groove in the piezoelectric element (Figure (b)). Grooves 2a are processed to form individual actuators 9 using a dicing saw. The width of this groove should be as narrow as possible, but currently the only width that can be cut using a narrow blade without breaking the actuator part is 20 to 4.
It is about 0 μm. (3) Fill the groove with a filler and harden it (Figure (c)). The groove 2a cut in the above (2) is filled with a filler 6 for both electrical insulation and reinforcement. As the filler 6, it is necessary to select a resin with a low Young's modulus. This is because when the actuator 9 is driven, if the Young's modulus is high, the movement will be poor, and the neighboring actuators will also be dragged along, resulting in a significant mutual interference effect, which is what the present invention is trying to solve. As the filler, a silicone rubber-based material with a relatively low Young's modulus is selected. (4) Grind the top of the piezoelectric element (Figure (c)). In order to bond the channel substrate 3 to the piezoelectric element 2, grinding is performed to make the upper part flat. (5) Bonding the flow path substrate with a liquid chamber formed therein (
Figure (d)). Epoxy adhesive is suitable as the bonding material. (6) Process the flow path plate groove on the upper part of the flow path board (Figure (e)
)). Channel plate grooves 7 are machined in the upper part of the channel substrate 3 in the same manner as when the piezoelectric element 2 was machined with a dicing saw. (7) Joining the common liquid chamber (not shown). A common liquid chamber 5 for supplying ink to each flow path 8 is connected. (8) Polishing the end face to join the nozzle plate (not shown). After polishing, the common liquid chamber 5 and the ink flow path 8 are cleaned and the dust inside is discharged to the outside. After the cleaning and drying steps are completed, the nozzle plate 4 is joined. (9) A PCB (printed circuit board) for taking out the electrodes is bonded (not shown). (10) Wire bonding is performed between the PCB (printed circuit board) and the piezoelectric element electrode portion (not shown). (11), Attach the connector for external connection (
(not shown). Through the above steps, the channel plate grooves 7 can be processed without damaging the channel substrate 3, so that an inkjet head can be manufactured with a high yield.

[0025]

[Effects] As is clear from the above description, the present invention has the following effects. (1) Since a channel plate groove is machined in the channel partition on the channel substrate, the channel can be used in the case where the piezoelectric element actuator is selected and driven independently, and when it is driven simultaneously with the adjacent actuators. The change in volume change becomes smaller. As a result, changes in ink droplet velocity and ink droplet volume are reduced, high frequency printing becomes possible, and high quality images are obtained. (2) Groove processing of the channel plate grooves is performed in the process where the substrate, piezoelectric element, and channel substrate are bonded together to increase rigidity, so it is possible to manufacture heads with a high yield without damage due to groove processing, and it is possible to manufacture heads at low cost. It is possible to provide a unique inkjet head.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of an inkjet head of the present invention.

FIG. 2 is a sectional view taken along the line Y-Y in FIG. 1.

FIG. 3 is a diagram for explaining the displacement of the channel substrate of the present invention.

FIG. 4 is a cross-sectional view for explaining the method of manufacturing an inkjet head of the present invention.

FIG. 5 is an exploded perspective view for explaining a conventional inkjet head.

6 is a sectional view taken along the YY arrow in FIG. 5. FIG.

FIG. 7 is a diagram for explaining displacement of a conventional flow path substrate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Substrate, 2...Piezoelectric element, 2a...Groove, 3...Flow path board, 3
a... Partition wall, 4... Nozzle plate, 4a... Nozzle, 5... Common liquid chamber, 6... Filler, 7... Channel plate groove, 8... Channel (liquid chamber)
9... Actuator (convex part), 10... Ink supply pipe.

Claims (2)

[Claims] 1. A flow path substrate having a plurality of parallel flow paths spaced apart from each other in the longitudinal direction of the flow path having nozzles for ejecting droplets; It consists of a common liquid chamber that supplies ink to each flow path, and a piezoelectric element that is divided by a groove, has a convex portion corresponding to each flow path, and is bonded to the flow path substrate. When an actuation is selected, at least one surface of the selected parallel flow path causes a displacement perpendicular to the longitudinal direction of the convex portion of the piezoelectric element, and an ink droplet is ejected from a nozzle corresponding to the flow path. An inkjet head characterized in that a partition wall between adjacent channels of the channel substrate has a slit formed in a longitudinal direction of the partition wall. 2. A first step of bonding a piezoelectric element to a substrate; a second step of forming a groove on the piezoelectric element bonded to the substrate;
a third step of filling and hardening a filler in the processed groove;
a fourth step of grinding the upper part of the piezoelectric element with the hardened filler; a fifth step of bonding the channel substrate with a liquid chamber formed on the ground piezoelectric element surface; A method for manufacturing an inkjet head, comprising a sixth step of machining channel plate grooves.