JP2002331671A - Ink jet print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet print head for use in a recorder forming an ink image on a recording medium by discharging ink drops in which variation of the ink discharge characteristics is reduced by making uniform the bonding state of a multilayer piezoelectric element and a diaphragm. SOLUTION: On the side of a diaphragm being bonded with a multilayer piezoelectric element, a plurality of frames for defining spread of adhesive on the diaphragm are arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to office and industrial ink jet printheads.

[0002]

2. Description of the Related Art Conventionally, there have been known various techniques of an ink jet print head which presses ink by a laminated piezoelectric element and discharges ink from a nozzle. For example, Japanese Patent Application Laid-Open No. 1-11563
Japanese Patent Application Laid-Open No. 8 (1996) -1995 is characterized in that the laminated vibrator is formed in a comb shape, and the vibration surface of the laminated vibrator is arranged to face the nozzle. Further, for example, see JP-A-60-907.
As disclosed in Japanese Patent Application Publication No. 70-210, a diaphragm constituting a pressure chamber is configured to abut on the other end of a piezoelectric element having one end fixed to a base, and the diaphragm is deformed by expansion and contraction of the piezoelectric element. There is known a configuration in which the pressure in a pressure chamber is increased to discharge ink in the pressure chamber as droplets from nozzles.

[0003]

In order to perform good printing with an ink jet print head, it is desirable that the ink ejection characteristics such as the ejection speed and the ink weight of ink droplets ejected from a plurality of nozzles be uniform. It is important to manufacture the individual parts with high accuracy in order to make the ink ejection characteristics of each nozzle uniform.In addition, when assembling the individual parts, in particular, the diaphragm and the laminated piezoelectric element are bonded with an adhesive. The step of linking is important. The connecting portion efficiently transmits the displacement of the laminated piezoelectric element to the diaphragm, generates a pressure fluctuation in the pressure chamber, and as a result, has a function of discharging ink from the nozzle. Therefore, a variation in assembling of a portion connecting the vibration plate and the laminated piezoelectric element with an adhesive is immediately reflected in a variation in ink ejection characteristics.
In other words, the adhesive connecting the diaphragm and the laminated piezoelectric element has a uniform amount and hardness of the adhesive at each connection portion.
Necessary for stabilizing ejection characteristics.

Further, if a stress that deforms the diaphragm or the laminated piezoelectric element remains after bonding, the displacement of the laminated piezoelectric element and the diaphragm when a voltage is applied to the laminated piezoelectric element is affected. And, as a result, the variation in the ink ejection characteristics. In particular, in a multi-nozzle long head, when the vibration plate and the supporting substrate have different coefficients of thermal expansion, when the vibration plate and the laminated piezoelectric element are bonded with a thermosetting adhesive, after curing, When the temperature returns to room temperature, distortion remains in the vibration plate or the laminated piezoelectric element due to the difference in thermal expansion coefficient, and the ink ejection characteristics become unstable. This problem occurs especially at the nozzles at both ends, not only deteriorating the print quality, but in the worst case, adversely affecting the life characteristics of the head, such as damage to the laminated piezoelectric element and the diaphragm and peeling off of the adhesive. Exert. However, the above-mentioned prior art does not disclose a method of bonding the diaphragm and the piezoelectric element without variation or a method of alleviating distortion due to a difference in thermal expansion coefficient.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide an ink jet print head which is excellent in reliability and has reduced variations in ink ejection characteristics.

[0006]

According to the present invention, a plurality of pressure chambers for storing ink and a plurality of pressure chambers which correspond to the pressure chambers on a one-to-one basis and generate pressure fluctuations in the pressure chambers by application of an electric signal. A piezoelectric element, a vibration plate that forms at least a part of the wall surface of the pressure chamber and is connected to the laminated piezoelectric element by an adhesive, and a support substrate to which an end of the laminated piezoelectric element is fixed. A restrictor forming a flow path for supplying ink to the plurality of pressure chambers, a housing provided with a common ink supply path for supplying ink to the restrictor, and a plurality of ink jetting ink droplets from the pressure chambers. In an ink jet print head including an orifice plate in which nozzles are formed, the spread of the adhesive on the vibration plate is defined on the surface of the vibration plate on which the laminated piezoelectric element is bonded. A plurality of frames are provided so as not to be connected to the adhesive on the diaphragm.

Further, in the present invention, the adhesive covers the entire inner surface of the frame of the diaphragm.

Further, the present invention is characterized in that a groove is formed between adjacent frames.

Further, in the present invention, a shallow groove lower than the height of the frame is formed in a part of the frame, and the shallow groove communicates with a groove having the same height as the frame. .

Further, according to the present invention, there are provided a plurality of pressure chambers for storing ink, and a plurality of laminated piezoelectric elements which correspond to the pressure chambers on a one-to-one basis and generate pressure fluctuations in the pressure chambers by applying an electric signal. A diaphragm that forms at least a part of a wall surface of the pressure chamber and is connected to the laminated piezoelectric element by an adhesive, a support substrate to which an end of the laminated piezoelectric element is fixed, A restrictor forming a flow path for supplying ink to the pressure chamber, a housing provided with a common ink supply path for supplying ink to the restrictor, and a plurality of nozzles for ejecting ink droplets from the pressure chamber are formed. In the ink jet print head composed of the orifice plate, a plurality of the adhesives are provided on the side of the vibration plate on which the laminated piezoelectric element is bonded, the plurality of adhesives defining the spread of the adhesive on the vibration plate. A frame is provided so as not to be connected to the adhesive on the diaphragm, and the laminated piezoelectric element and the diaphragm are fixed by an adhesive cured at room temperature.

Further, in the present invention, the hardness of the adhesive is not more than 80 degrees (Shore-A).

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view for explaining the structure and parts configuration of the ink jet head according to the first invention, and FIG. 2 is a partial sectional view showing an assembled state of the head of FIG.

Reference numeral 2 denotes an orifice plate on which a plurality of nozzles 1 are formed. The processing accuracy of the opening shape of the nozzle 1 has a great influence on the ink ejection characteristics of the inkjet print head. In order to suppress these variations in nozzle accuracy among the plurality of nozzles 1, high manufacturing accuracy is required for the method of manufacturing the orifice plate 2. For this reason, the orifice plate 2 is formed by electroforming of nickel, precision pressing of a stainless steel plate or the like, or laser processing.

Reference numeral 4 denotes a chamber plate in which the pressure chamber 3 is formed. Reference numeral 6 denotes a restrictor plate which communicates the common ink supply path 12 with the pressure chamber 3 and forms a restrictor 5 for controlling the amount of ink flowing into the pressure chamber 3. The chamber plate 4 and the restrictor plate 6 are made by a stainless steel etching method or a nickel material electroforming method.

Reference numeral 9 denotes a vibration plate 7 for efficiently transmitting the pressure of the laminated piezoelectric element 15 to the pressure chamber, and a common ink passage 12.
This is a diaphragm plate on which a filter section 8 for removing dust and the like in ink flowing into the restrictor 5 from is formed. The diaphragm plate 9 is made of a stainless steel material having a thickness of about 10 μm, and the filter unit 8 forms innumerable fine holes smaller than the hole diameter of the nozzle 1 by laser processing. In addition, the diaphragm plate 9 can be manufactured with the same performance from a nickel electroformed film or a polymer resin film such as a polyimide resin.

Reference numeral 11 denotes a support plate on which a frame 10 is formed to regulate the spread of the adhesive protruding from the bonding portion when the diaphragm 7 and the laminated piezoelectric element 15 are fixed with the adhesive. is there. The support plate 11 is formed by an etching method of a stainless material or an electroforming method of a nickel material.

Reference numeral 13 denotes a housing in which the common ink passage 12 is formed. The housing 13 is made of metal or resin, and is joined to an ink introduction pipe 14 for leading ink from an external ink tank to the common ink passage 12.

In FIG. 1, an orifice plate 2 and
A method of assembling the flow path forming member including the chamber plate 4, the restrictor plate 6, the diaphragm plate 9, the support plate 11, and the housing 13 is performed as follows. Here, each of the plates has one reference hole 22 into which the reference pin 21 fits, and an elongated hole 23.

First, two reference holes 24 of the housing 13 are provided.
Then, two reference pins 21 are press-fitted. Thereafter, the two reference pins 21 are aligned, and the respective plates coated with an appropriate amount of an adhesive such as an epoxy resin are sequentially overlaid and pressed.

Next, a method of assembling the pressure generating means 18 comprising a plurality of laminated piezoelectric elements 15 and a support substrate 16 for fixing the laminated piezoelectric elements will be described.

First, a plurality of rod-shaped laminated piezoelectric elements are aligned and fixed to the support substrate 16. The support substrate 16 includes
In order to efficiently transmit the displacement of the laminated piezoelectric element 15 to the diaphragm 7, a ceramic substrate was used as a material having high rigidity or high Young's modulus. Thereafter, the plurality of rod-shaped laminated piezoelectric elements are divided by cutting using a dicing saw, a wire saw, or the like. At this time, each of the divided laminated piezoelectric elements 15 corresponds to one of the pressure chambers. Further, in order to send an independent electric signal from the external drive circuit to each laminated piezoelectric element 15, a plurality of electrodes 17
Formed. The electrode 17 is a flexible cable 19
Are connected together.

The terminal of the flexible cable 19 is connected to an external drive circuit. When a selective electric signal is applied to the laminated piezoelectric element 15 from an external drive circuit, the laminated piezoelectric element 15 is distorted. Since the laminated piezoelectric element 15 is bonded to the high-rigidity support substrate 16, the diaphragm 7 is preferentially displaced to increase the pressure in the pressure chamber 3.

The ink jet print head described in this embodiment is used in an apparatus that discharges ink from the nozzles 1 and forms an ink image on a recording medium based on such a principle. In this example, the arrangement pitch is 1/100.
Inches and about 254 μm are used, but the number of nozzles, the number of rows, and the unit configuration are not limited to any combination.

The assembling method will be described in more detail with reference to FIG.

The vibrating plate 7 of the flow path forming member and the free end of the laminated piezoelectric element 15 of the pressure generating means 18 are adjusted to an optimum position with an adhesive applied to the free end, and are crimped. Here, the method of applying the adhesive to the free end of the laminated piezoelectric element 15 was performed by a transfer method or a printing method. Assembly is
Usually, it is performed before the adhesive is cured in the state shown in FIG.

FIG. 3 is a partially enlarged view of FIG. 2 showing this state. In FIG. 3, a frame 10 for defining the spread of the adhesive is provided on the diaphragm 7 so as to correspond to each pressure chamber, so that the adhesive 30 is placed in each frame 10 on the diaphragm 7. Settles and hardens. The practical amount of the adhesive can be determined by the width and height of the frame 10 and the distance between the frame 10 and the laminated piezoelectric element 15.

FIG. 4 shows a conventional laminated piezoelectric element 1.
5 shows an example of an adhesion state between the diaphragm 5 and the diaphragm 7.

In FIG. 4, the laminated piezoelectric element 15 of the diaphragm 7 is shown.
The adhesive is connected to the adhesive on the diaphragm because there is no frame 10 on the surface to be joined. In such a case, the adhesive moves before curing due to the surface tension or capillary action of the adhesive, causing a bias. In particular, when the laminated piezoelectric elements 15 are arranged at a high density, the adhesive tends to gather at the center and the adhesive becomes thinner at the outer periphery. As a result, the amount of the adhesive on the vibration plate 7 varies, and as a result, the displacement characteristics of the vibration plate 7 change, and the ink ejection characteristics become non-uniform for each nozzle. Further, in this case, there is a problem that crosstalk occurs between the laminated piezoelectric elements 15 due to the vibration generated when the laminated piezoelectric elements 15 are driven being transmitted through the adhesive, which is an elastic body.

In the present invention, as a result of providing the frame 10 on the diaphragm 7, the above-described vibration using the adhesive as a medium is cut off by the frame 10.
Crosstalk can be prevented.

FIG. 5 shows another example of the state of adhesion between the conventional laminated piezoelectric element 15 and the vibration plate 7.

Even in the case of FIG. 5 in which the amount of the adhesive is reduced, it is practically impossible that the adhesive does not completely protrude from the range of the contact surface between the laminated piezoelectric element and the diaphragm. The adhesive protruded onto the vibrating plate 7, resulting in a difference in the compliance of the vibrating plate, and the ink ejection characteristics were non-uniform in each nozzle.

In the present invention, when the amount of the adhesive is such that it covers the entire inside of the frame 10, the adhesive spreads uniformly throughout the frame, and the thickness of the adhesive on each diaphragm 7 is large. Therefore, the displacement characteristics of the diaphragm 7 with respect to pressure, such as compliance, are uniform with respect to each pressure chamber, and the ink ejection characteristics have less variation.

As described above, the configuration of the present invention makes it possible to improve the discharge characteristics as compared with the conventional configuration having no frame.

FIG. 6 is a partially enlarged view of an ink jet head according to a first modified example of the first invention. FIG. 7 is a view showing a support plate 11 having a frame 10 and a groove 101 formed thereon in a direction in which the laminated piezoelectric elements are bonded. It is the perspective view seen.

As shown in FIG. 6, by arranging the groove 101 between the adjacent frames 10, an amount of adhesive exceeding the upper surface of the frame 10 is applied to the laminated piezoelectric element 15 so that the piezoelectric element 15 can be accommodated in the frame. By flowing the excess surplus adhesive into the groove 101 after passing over the upper surface of the frame 10, not only can it be prevented from directly connecting to the adhesive in another frame on the diaphragm, but also the diaphragm 7 can be prevented. The thickness of the upper adhesive is determined by the height of the frame 10, becomes uniform between the flow paths, and the ink discharge characteristics can be significantly improved. The amount of practical adhesive is
It can be determined by the width and length of the groove 101.

FIGS. 8 and 9 are perspective views showing a second modification and a third modification of the first invention, in which the support plate 11 is viewed from the bonding direction of the laminated piezoelectric element.

FIG. 8 shows a shape in which the common groove 104 surrounds the frame 10, and a similar effect can be obtained with this shape.

FIG. 9 shows that a shallow groove 102 having a height lower than the height of the frame 10 is formed in a part of the frame 10 in a uniform shape in each ink flow path. 7 is another example of the present invention in communication. Even in such a structure, the excess adhesive flows into the communication groove 103 through the shallow groove 102, and as a result, the adhesive in each frame is separated from the adhesive in another frame on the diaphragm by the communication groove 103. Not only can be prevented from being directly connected without passing through the
The thickness of the upper adhesive becomes more uniform, and the ink ejection characteristics are also improved.

Next, the second invention will be described with reference to FIGS.
And Table 1 below. The present invention is particularly intended to improve the ejection characteristics of the nozzles near the ends and reduce variations.

FIG. 10 shows the laminated piezoelectric element 15 and the vibrating plate 7.
Heat-cured at 150 ° C as an adhesive to fix
This is a comparison of ink ejection speed variations of an ink jet print head assembled using a liquid epoxy adhesive or a room temperature curing type two-liquid epoxy adhesive.

In the case of using an adhesive which is cured by heating at 150 ° C., the discharge speed of the nozzles at both ends is reduced. This is because the flow path forming member composed of the diaphragm plate 9 and the like uses a metal material such as stainless steel for reasons such as corrosion resistance with ink and ease of processing. On the other hand, the laminated piezoelectric element 15 and the Since the pressure generating means 18 composed of the fixing substrate 16 and the fixing substrate 16 is made of an inorganic material mainly composed of ceramic, a residual stress and a residual strain are generated after bonding and heat curing due to a difference in thermal expansion coefficient between the two. Is the cause.

For example, in the case of an ink jet print head having a pitch of 0.254 mm and 128 nozzles, the maximum interval between the laminated piezoelectric elements is 32.5 mm, and the thermal expansion coefficients of stainless steel and alumina ceramic are each 17 ×.
10 ^-6 and 8 × 10 ^-6 . Therefore, in the assembly using an adhesive which is cured by heating at 150 ° C., a strain of about 15 μm is generated in the laminated piezoelectric element 15 or the vibration plate 7 at both ends after the assembly.

For this reason, as shown in the partial cross-sectional view of the head end shown in FIG.
Has been deformed in the arrangement direction due to the strain caused by the difference in the thermal expansion coefficient, thereby deteriorating the drive efficiency of the laminated piezoelectric element and the displacement characteristics of the diaphragm, and as a result, the ejection characteristics have been lowered. In order to solve this problem, by using an adhesive cured at room temperature, the problem due to the difference in the coefficient of thermal expansion is eliminated, and good ejection characteristics can be achieved.

Table 1 shows that the mixing ratio of the base resin and the curing agent was varied using EP001 manufactured by Cemedine Co., Ltd., which is a room-temperature curing two-part epoxy adhesive, and as a result, the hardness after curing was varied. 5 is a result of investigating variations in ink ejection speed.

[0046]

[Table 1]

From Table 1, it can be seen that the higher the adhesive hardness, the greater the speed variation. This is the diaphragm 7
This is because even if the adhesive having the same thickness variation is formed thereon, the adhesive having a higher hardness has a greater effect on the compliance of the diaphragm with respect to the thickness variation. By setting the hardness of the adhesive 30 to 80 degrees or less, it becomes almost constant, and the practical speed limit of the ink jet print head, that is, ± 10% or less can be achieved.

[0048]

As described above, according to the present invention, the spread of the adhesive connecting the diaphragm and the laminated piezoelectric element on the diaphragm is defined by the frame installed on the diaphragm. As a result, the displacement characteristics of the diaphragm can be made uniform, the characteristics such as the ink discharge speed and the ink discharge volume are stabilized, the life is improved, and as a result, an ink jet head with improved print quality can be provided.

Further, the laminated piezoelectric element and the diaphragm are bonded with an adhesive cured at room temperature, and have a hardness of 80 degrees (Shore-A).
Due to the following conditions, the speed variation of the end nozzles can be made substantially constant, and as a result, an ink jet head with improved print quality can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating the structure and component configuration of an ink jet print head showing an example of the first invention.

FIG. 2 is a sectional view showing an assembled state of the example of the first invention.

FIG. 3 is an enlarged partial sectional view showing an assembled state of the example of the first invention.

FIG. 4 is an enlarged partial cross-sectional view showing an assembled state of a conventional inkjet print head.

FIG. 5 is an enlarged partial cross-sectional view showing an assembled state of a conventional inkjet print head.

FIG. 6 is an enlarged partial cross-sectional view showing an assembled state in a first modified example of the first invention.

FIG. 7 is a perspective view illustrating a structure of a support plate according to a first modification of the first invention.

FIG. 8 is a perspective view illustrating a structure of a support plate according to a second modification of the first invention.

FIG. 9 is a perspective view illustrating the structure of a support plate according to a third modification of the first invention.

FIG. 10 is a graph comparing the measurement of the variation in the ink ejection speed of the ink jet print head according to the second invention and the conventional ink jet print head.

FIG. 11 is an enlarged partial cross-sectional view showing an assembled state of a conventional inkjet print head.

[Explanation of symbols]

1 is a nozzle, 2 is an orifice plate, 3 is a pressure chamber, 4
Is a chamber plate, 5 is a restrictor, 6 is a restrictor plate, 7 is a diaphragm, 8 is a filter section, 9 is a diaphragm plate, 10 is a frame, 101 is a groove, 102 is a shallow groove, 103 is a communication groove, and 104 is a communication groove. A common groove, 11 a support plate, 12 a common ink supply path, 13 a housing, 14 an ink introduction pipe, 15 a laminated piezoelectric element,
16 is a support substrate, 17 is an electrode, 18 is a pressure generating means, 1
9 is a flexible cable, 21 is a reference pin, 22 is a reference hole, 23 is a long hole, 24 is a reference hole, and 30 is an adhesive.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Nobuhiro Noto 1060 Takeda, Hitachinaka-city, Ibaraki Prefecture Inside Hitachi Koki Co., Ltd. Reference) 2C057 AF23 AF93 AG53 AP02 AP25 BA04 BA14

Claims (6)

[Claims] 1. A plurality of pressure chambers for storing ink, a plurality of laminated piezoelectric elements corresponding to the pressure chambers on a one-to-one basis, and generating pressure fluctuations in the pressure chambers by applying an electric signal; A vibrating plate that forms at least a part of the wall surface of the laminated piezoelectric element and that is connected to the laminated piezoelectric element with an adhesive, a support substrate to which an end of the laminated piezoelectric element is fixed, and ink on the plurality of pressure chambers Restrictor forming a flow path for supplying ink, a housing provided with a common ink flow path for supplying ink to the restrictor, and an orifice plate formed with a plurality of nozzles for discharging ink droplets from the pressure chamber. In the configured ink jet print head, a plurality of frames that regulate the spread of the adhesive on the vibration plate are provided on the surface of the vibration plate on which the laminated piezoelectric element is bonded. Characteristic inkjet print head. 2. The ink jet print head according to claim 1, wherein the adhesive covers the entire surface of the diaphragm in the frame. 3. The ink jet print head according to claim 1, wherein a groove is formed between adjacent frames. 4. The frame according to claim 1, wherein a shallow groove lower than the height of the frame is formed in a part of the frame, and the shallow groove is connected to a communication groove provided near the frame. 3. The inkjet print head according to claim 1. 5. A plurality of pressure chambers for storing ink, a plurality of laminated piezoelectric elements corresponding to the pressure chambers on a one-to-one basis, and generating pressure fluctuations in the pressure chambers by applying an electric signal; A vibrating plate that forms at least a part of the wall surface of the laminated piezoelectric element and that is connected to the laminated piezoelectric element with an adhesive, a support substrate to which an end of the laminated piezoelectric element is fixed, and ink on the plurality of pressure chambers Restrictor forming a flow path for supplying ink, a housing provided with a common ink flow path for supplying ink to the restrictor, and an orifice plate formed with a plurality of nozzles for discharging ink droplets from the pressure chamber. In the configured inkjet print head, a plurality of frames that define the spread of the adhesive on the vibration plate are provided on the surface of the vibration plate on which the laminated piezoelectric element is bonded, and The inkjet print head, wherein the laminated piezoelectric element and the diaphragm are fixed with an adhesive that is cured at room temperature. 6. The adhesive has a hardness of 80 degrees (Shore-hardness).
A) The ink jet print head according to claim 5, wherein: