JP2000238260A - Ink jet recording head and ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording head and an ink jet recorder which can be manufactured inexpensively with high yield. SOLUTION: In an ink jet recording head where ultrasonic wave is radiated into an ink liquid 18 in an ink holding chamber 19 and converged to the vicinity of ink liquid level in order to fly an ink drop toward a recording medium by the pressure of ultrasonic wave, a plurality of flat rod-like individual electrodes 11 are arranged in parallel rows at a constant interval on a planar supporting material 10. Two rectangular piezoelectrics 12, 13 having different resonance frequency are arranged in parallel in the longitudinal direction of the individual electrodes perpendicular to the arranging direction thereof and common electrodes 14, 15 are provided on the other surfaces of the piezoelectrics 12, 13 facing the individual electrodes 11. Furthermore, lenses 16, 17 for converging ultrasonic wave are arranged, respectively, on the other surfaces of the piezoelectrics 12, 13 provided with the common electrodes 14, 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to recording by emitting ultrasonic waves from an ultrasonic vibrator into an ink liquid, focusing the ultrasonic waves near the ink liquid surface, and discharging ink droplets by the ultrasonic pressure. The present invention relates to an ink jet recording head for flying toward a medium, and more particularly to an ink jet recording head for ejecting ink droplets by a pressure of an ultrasonic beam radiated by a piezoelectric element and flying toward a recording medium.

[0002] The present invention also relates to an ink jet recording apparatus for recording an image on a recording medium using the above ink jet recording head.

[0003]

2. Description of the Related Art Conventionally, there has been known an ink jet recording apparatus (printer) that forms recording dots by flying an ink liquid onto a recording medium. This ink jet recording apparatus has the advantages that it has less noise than other recording methods and does not require processing such as development and fixing, and is attracting attention as a plain paper recording technique.

To date, a number of ink jet recording apparatus systems have been devised. In particular, as a method of flying ink droplets by the pressure of steam generated by the heat of a heating element, for example, Japanese Patent Publication No. 56-9429. Gazette and Tokugyo Sho 6
The technique disclosed in Japanese Patent Application Laid-Open No. 1-59911 and the technique disclosed in Japanese Patent Publication No. 53-12138, for example, is a typical method for flying ink droplets by a pressure pulse due to displacement of a piezoelectric body. It is.

However, these methods have a problem that local concentration of ink is apt to occur due to evaporation or volatilization of a solvent, and individual nozzles corresponding to respective resolutions are apt to be finely clogged. In particular, in the method using the pressure of the vapor, adhesion of insoluble matter due to thermal or scientific reaction with the ink liquid, etc., and in the method using the pressure due to the displacement of the piezoelectric material, complicated The structure makes it easier to induce clogging.

In a serial scanning type recording head using several tens to one hundred and several tens of nozzles, the frequency of clogging can be reduced, but a line scanning type recording head requiring thousands of nozzles is used. In the head, clogging occurs at a high probability with a high probability, which is a major problem in terms of reliability. Furthermore, these systems have the disadvantage that they are not suitable for increasing the resolution.

In order to overcome these drawbacks, a method using an ultrasonic wave (I) in which ink droplets fly from an ink liquid surface using the pressure of an ultrasonic beam generated from a thin film piezoelectric material (I
BMTDB, vol. 16, No. 4, pp. 1168
(1973-10), USP-4308547 (198
1), JP-A-63-166548, JP-A-63-166548
JP-A-313157, JP-A-2-184443,
Japanese Patent Application Laid-Open No. 63-162253) has been proposed. Since this method is a nozzleless method that does not require a nozzle for each individual dot or a partition wall for the ink flow path, it is effective for preventing and recovering from clogging, which was a major obstacle in making a line head. Has a structure. Further, since an ink droplet having a very small diameter can be stably ejected, it is suitable for high resolution.

[0008]

However, in the above-described conventional ink jet recording system, when the resolution is increased, the number of piezoelectric bodies that generate ultrasonic waves increases, and the number of driving ICs for driving the piezoelectric bodies also increases. Thus, there is a problem that it becomes expensive.

Further, when the resolution is further improved,
Since the arrangement pitch of the piezoelectric bodies becomes smaller, there is a problem that the yield is deteriorated in the print head manufacturing process.

Accordingly, an object of the present invention is to provide an ink jet recording head and an ink jet recording apparatus which are inexpensive and have a good yield.

[0011]

An ink jet recording head according to the present invention emits ultrasonic waves into an ink liquid, focuses the ultrasonic waves near the ink liquid surface, and discharges ink droplets by the pressure of the ultrasonic waves. An ink jet recording head that flies toward a recording medium, comprising: a plate-shaped support member; a plurality of bar-shaped individual electrodes arranged in parallel in a row at regular intervals on the support material; and the plurality of individual electrodes. Above, at least two rectangular ultrasonic transducers provided in parallel with the longitudinal direction of the individual electrodes perpendicular to the arrangement direction of the individual electrodes, and each of the two ultrasonic transducers facing the individual electrodes. A single common electrode provided on each of the other surfaces, and a common electrode provided on each of the other surfaces provided with the common electrode of the two ultrasonic vibrators, respectively. Super for focusing And it includes a wave focusing member.

Further, the ink jet recording apparatus of the present invention emits an ultrasonic wave into the ink liquid, focuses the ultrasonic wave near the ink liquid surface, discharges the ink droplet by the pressure of the ultrasonic wave, and directs the ink droplet toward the recording medium. An ink jet recording apparatus that records an image by causing the ink droplets to fly on a recording medium, and includes a plurality of rod-like members arranged in parallel at regular intervals in a row on a plate-like support material. Individual electrodes and at least two rectangular ultrasonic transducers provided on the plurality of individual electrodes in parallel to the longitudinal direction of the individual electrodes perpendicular to the arrangement direction of the individual electrodes and having different resonance frequencies. A single common electrode provided on each of the other surfaces of the two ultrasonic transducers facing the individual electrodes, and a respective one of the two ultrasonic transducers provided with the common electrode. Face to face Each of the ultrasonic generators includes an ultrasonic converging member for converging ultrasonic waves generated from the ultrasonic transducer, and an odd number of ultrasonic generators for the plurality of individual electrodes of the ultrasonic generator. Are divided into a plurality of sets of individual electrodes as one set of individual electrodes, and the plurality of sets of individual electrodes are selectively subjected to a first burst wave obtained by combining at least two burst waves according to a recorded image. By applying, the first driving means for driving the one ultrasonic transducer, and a plurality of sets each including an even number of individual electrodes for the plurality of individual electrodes of the ultrasonic generator. The plurality of individual electrode groups are divided into individual electrode groups, and at least two burst waves are combined. A second burst wave having a frequency different from that of the first burst wave is selectively used in accordance with a recorded image. To the other Of which comprises a second drive means for driving the ultrasonic transducer.

According to the present invention, two ultrasonic transducers (for example, piezoelectric bodies) can be driven without increasing the number of driving means such as driving ICs, so that high resolution can be achieved at low cost. .

Further, according to the present invention, since the resolution of an image can be made twice as large as the resolution of individual electrodes, high image quality can be realized without shortening the arrangement pitch of the individual electrodes, and the yield can be improved. Is also good.

[0015]

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

FIG. 1 is a schematic configuration diagram schematically showing the configuration of an ink jet recording apparatus according to the present invention. The inkjet recording apparatus of the present invention is connected to, for example, a personal computer, and transmits information for printing and graphic recording, and starts recording. When a recording start signal is received, a start signal is transmitted from the control unit 1, the paper feed roller 2 is operated, and the paper 3 as a recording medium is transmitted to the transport drum 4. During recording, the transport drum 4 rotates in the direction of the arrow A in the drawing, receives the paper 3 sent by the paper feed roller 2, and transports the paper 3 toward the recording head 5. When the sheet 3 reaches above the recording head 5, the control unit 1 sends a recording start signal to a drive IC of the recording head 5 or the like, and the image recording operation starts.

When the trailing edge of the paper 3 approaches above the recording head 5, a recording end signal is sent from the control unit 1, and the recording operation ends. After the recording is completed, the transport drum 4 rotates in the direction of arrow B in the drawing, and transports the paper 3 to the discharge roller 6. Next, the paper 3 on which the image is recorded is discharged to the paper discharge tray 8 with the aid of the discharge auxiliary member 7. When the sheet 3 is discharged, a series of recording operations is completed, and a standby state for the next recording operation is set.

FIG. 2 schematically shows the structure of the recording head 5. That is, a plurality of flat bar-shaped individual electrodes 11 each having a predetermined width are formed in a row at regular intervals on the plate-shaped support member 10, and on the plurality of individual electrodes 11 Plate-shaped piezoelectric bodies 12 and 13 as ultrasonic vibrators having electrodes (not shown) formed in rows at the same intervals as the individual electrodes 11 are provided on the lower surface side.
It is formed parallel to the longitudinal direction of the individual electrodes 11 perpendicular to the arrangement direction of the individual electrodes 11. In this case, the plurality of individual electrodes 11 are connected to respective corresponding electrodes (not shown) of the piezoelectric bodies 12 and 13 by pressure bonding via an adhesive.

Common electrodes 14 and 15 are formed on the surfaces (upper surfaces) of the piezoelectric bodies 12 and 13 facing the individual electrodes 11, respectively, and an ultrasonic focusing member is provided on the common electrodes 14 and 15. Are formed, respectively. Around the piezoelectric bodies 12 and 13 and the lenses 16 and 17, a pool-shaped ink holding chamber 19 for holding the ink liquid 18 is formed, and the inside thereof is filled with the ink liquid 18. I have.

In the upper part of the ink holding chamber 19, the piezoelectric body 12,
Above the center of the arrangement direction of the lenses 13 and the lenses 16 and 17, slits 20 and 21 which are long in the
Are formed respectively. Here, since the height of the wall surface of the pool-like ink holding chamber 19 is close to the distance at which the sound waves focused by the lenses 16 and 17 are focused, the slits 20 of the slit member 22 formed thereon are formed. The height of 21 is the focus position of the sound wave, and the ink liquid level can be held at the focus position.

The ink liquid 18 is supplied from an ink tank (not shown) to a plurality of supply ports (not shown) provided in the ink holding chamber 19 via a pump and an ink supply tube. Piezoelectric bodies 12 and 13 and electrodes 1 opposed to each other
The piezoelectric elements composed of 1, 14, and 15 are arranged at regular intervals in an array, and by simultaneously driving using a plurality of the piezoelectric elements, an ultrasonic wave is applied to the ink liquid level. The ink droplets are made to fly close to each other so as to fly.

On both sides of the plurality of individual electrodes 11 where the piezoelectric bodies 12 and 13 are not formed, a plurality of extraction electrodes 23 arranged at the same interval as the individual electrodes 11 are formed. 23 is a corresponding individual electrode 1
1 are connected by pressure bonding via an adhesive. The plurality of extraction electrodes 23 are driving ICs for driving the piezoelectric members 12 and 13 disposed on the support member 10 in the vicinity thereof.
(Integrated circuit) It is connected to the terminal of 24 by the bonding wire 25.

In this case, the individual electrodes 11 at the same position on the two piezoelectric bodies 12 and 13 are connected to the driving IC 2 of the same channel.
4 is connected. The upper electrodes 14 and 15 of the piezoelectric bodies 12 and 13 are connected to a common terminal of the driving IC 24 as a common electrode. The driving IC 24 is connected to the control unit 1 that controls driving via a printed wiring board (not shown), a connector, and the like.

The lenses 16 and 17 have irregularities based on the Fresnel zone theory formed parallel to the longitudinal direction of the piezoelectric bodies 12 and 13 (hereinafter, referred to as the main scanning direction). This lens 1
The thicknesses of the concave and convex portions of the lenses 6 and 17 are the lenses 16 and 1 respectively.
(2n + 1) / 4 times the wavelength in 7 (n is an integer of 0 or more)
Is set so as to be close to the piezoelectric material.
By using a material having a value close to the square root of the product of the acoustic impedance of the ink liquid 18 and that of the ink liquid 18, for example, an epoxy resin in which alumina powder is dispersed, the bottom surface on which the lenses 16 and 17 are provided has an acoustic matching layer. It has a structure that also has the function of

A recording operation in the case where the recording head 5 configured as described above is used will be described. In addition, a driving method of the recording head 9 will be described.

FIG. 3 shows the driving IC 24 to the piezoelectric body 12,
13 shows a burst-like signal having a desired width and input to the block 13. The frequency of the burst wave is
The frequency is close to the resonance frequency determined by the thickness and the like. FIG. 4 shows impedance frequency characteristics and phase difference frequency characteristics near the resonance frequency of the piezoelectric body. In general, a piezoelectric body efficiently radiates sound waves near a resonance frequency, and the other parts are capacitive. Therefore, when the frequency of the burst wave is deviated from the resonance frequency, no acoustic wave is emitted from the piezoelectric body, and the device operates electrically as a capacitive load.

In the present embodiment, sound waves are focused by the Fresnel lenses 16 and 17 in the width direction (sub-scanning direction) of the recording head 5, but in the longitudinal direction (main scanning direction) of the recording head 5, 180 degrees of the burst wave
Sound waves are focused by combining the types (hereinafter referred to as 0 phase / π phase).

The piezoelectric bodies 12 and 13 are vibrated by the burst waves, and the sound waves are excited toward the lenses 16 and 17 and the ink liquid 18. Since one cycle of the sound wave is excited in one cycle of the burst wave, the burst width is the wave number of the excited sound wave. In the present embodiment, the wave number of the sound wave is set to “200
0 ".

With one set of several piezoelectric elements formed by the individual electrodes 11, burst waves having different phases are applied to one set of the respective piezoelectric elements to form an image of one dot. In one piezoelectric body (12 or 13) according to the present embodiment, for example, as shown in FIG. 5, a set of eight piezoelectric elements (individual electrodes 11) is used to set a 0-phase and π-phase burst wave to “ 0π
0000π0 ”are applied in this order, and the sound waves in the main scanning direction are focused near the center of the eight piezoelectric elements to form one dot. Further, since the combination pattern of the burst waves is driven by a drive pattern symmetrical from the center of the element to the left and right, the sound waves are focused on the centers of the eight piezoelectric elements.

In order to print one line in the main scanning direction (the width direction of A4 size paper), the drive elements are scanned eight times in the main scanning direction. For this reason, the dots that fly at the same time are dots that are eight dots adjacent in the main scanning direction. The focusing of the sound waves in the sub-scanning direction is focused at the center of the slits 20 and 21 of the slit member 22 using the Fresnel lenses 16 and 17.

FIG. 6 is a sectional view of the vicinity of the slit member 22 in the sub-scanning direction, and is an explanatory diagram for explaining a temporal change of the ink liquid level. In FIG. 6, since both are the same, the slit 2 corresponding to one piezoelectric body 12
Only the portion 0 is shown, and the portion of the slit 21 corresponding to the other piezoelectric body 13 is not shown. Therefore,
Only the description relating to one piezoelectric body 12 will be provided, and the description relating to the other piezoelectric body 13 will be omitted.

In a non-recording state in which no burst wave is applied to the piezoelectric body 12 and no sound wave is excited in the ink liquid 18, the ink liquid 18 is concave on the surface of the slit 20 as shown in FIG. The liquid level.

Next, the burst wave shown in FIG.
2, the sound wave 26 is excited in the ink liquid 18, propagates toward the ink liquid surface, is reflected by the ink liquid surface, and propagates toward the lens 16 and the piezoelectric body 12. As shown in FIG. 3B, when the sound wave 26 is reflected on the ink liquid surface, the ink liquid surface is raised by the pressure of the sound wave 26 (hereinafter, this is referred to as an ink meniscus P1). When the sound wave reflected by the ink surface reaches the piezoelectric body 12, it is reflected by the piezoelectric body 12 and propagates again in the ink surface direction.

As this series of operations is repeated, the ink meniscus P1 continues to grow gradually by the pressure of the sound wave 26 on the ink liquid level, as shown in FIG. As shown in (2), the droplet (ink droplet) P2 is caused to fly. Here, if the next signal is not applied,
The sound waves 26 are attenuated due to the viscosity of the ink liquid 18 and the like, and gradually disappear. Finally, the liquid level returns to a concave shape as shown in FIG.

As described above, the piezoelectric body is driven to be electrically capacitive in a frequency range other than the resonance frequency, and does not emit sound waves. By utilizing this fact and setting the frequency of the burst wave output from one driving IC to two types, the piezoelectric bodies 12 and 13 having different resonance frequencies can be driven by one driving IC. Become. In the recording head 5 of the present embodiment, by utilizing this, one of the piezoelectric
Is a resonance frequency of, for example, 50 MHz, and the other piezoelectric body 13 is a piezoelectric body having a thickness of, for example, a resonance frequency of 60 MHz. By doing so, the two piezoelectric bodies 12 and 13 can be driven without increasing the number of driving ICs, and an inexpensive recording head can be realized.

If the combination pattern of the burst waves is made symmetrical with respect to the center, ink droplets can fly from the center position. As shown in FIG. 7, when the number of burst wave patterns for driving one piezoelectric body 12 is, for example, eight (even number) and the number of burst wave patterns for driving the other piezoelectric body 13 is, for example, nine (odd number), The positions of the ink droplets that fly from the piezoelectric bodies 12 and 13 can be half the arrangement pitch of the individual electrodes 11.

If this is realized by one recording head 5,
The image resolution can be double the resolution of the individual electrodes 11, and high image quality can be achieved without reducing the arrangement pitch of the individual electrodes 11.

The driving method of the recording head 5 according to the present embodiment will be briefly described. FIG. 8 shows the driving IC 24.
1 shows a flow of a signal input to the. That is, a continuous wave having two different frequencies for driving the two piezoelectric bodies 12 and 13 is output from the high-frequency signal generator 27 to the comparator 28. This continuous wave is O /
divided into π. A selection signal also serving as an enabler for selecting one of the two types of burst waves is input from the control unit 1 to the comparator 28 at a predetermined cycle. The continuous wave selected by the selection signal by the comparator 28 becomes a burst wave and is input to the driving IC 24.

Further, drive data corresponding to the combination pattern of the burst waves is sent from the control section 1 to the drive IC 24 together with the clock. Further, a latch signal for latching data and an enable signal for driving the IC are input to the driving IC 24, and the driving IC 24 is driven.

FIG. 9 shows an example of a burst wave output from the driving IC 24. In the present embodiment, as described above, one piezoelectric body 12 is driven by eight elements and the other piezoelectric body 13 is driven by nine elements. Since the two piezoelectric bodies 12 and 13 are driven by using one IC channel, the burst waves must be output at different timings.

For this reason, the burst wave for driving the nine elements is outputted after the burst wave for driving the eight elements is finished, and after that, the burst wave for driving the eight elements is outputted again. It's time. The time during which these two burst waves are output is a recording cycle (main scanning direction) for recording one dot.

As described above, the drive elements must be scanned in the main scanning direction according to the number of drives.
In the case of eight-element drive, eight scans may be performed, but in the case of nine-element drive, nine scans must be performed. Since the number of scans for driving the nine elements is one more than the number of scans for driving the eight elements, the burst wave for driving the eight elements is not output for one recording period (main scanning direction). The two piezoelectric bodies 12 and 13 form one recording cycle (sub-scanning direction) in nine scans.

In FIG. 9, the burst wave for driving the eight elements and the burst wave for driving the nine elements are written separately, but they are originally output from the same IC channel.

By using the control system that operates as described above, the ink jet recording head according to the present embodiment can be driven, and an inexpensive ink jet recording head with good yield and an ink jet recording apparatus using the same can be realized. be able to.

[0045]

As described above, according to the present invention, it is possible to provide an ink jet recording head and an ink jet recording apparatus which are inexpensive and have a good yield.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram schematically showing a configuration of an ink jet recording apparatus according to the present invention.

FIG. 2 is a vertical sectional side view schematically showing a configuration of a recording head.

FIG. 3 is a diagram illustrating a burst wave applied to a piezoelectric element.

FIG. 4 is a diagram showing impedance and phase difference frequency characteristics of a piezoelectric body.

FIG. 5 is a diagram illustrating signals applied to a piezoelectric element.

FIG. 6 is a cross-sectional view in the sub-scanning direction illustrating a temporal change of an ink liquid near a slit member in the recording head.

FIG. 7 is a diagram illustrating a method for driving a recording head.

FIG. 8 illustrates a flow of a signal input to a driving IC.

FIG. 9 is a diagram illustrating an example of a burst wave output from a driving IC.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Control part 2 ... Paper feed roller 3 ... Paper (recording medium) 4 ... Convey drum 5 ... Recording head 6 ... Discharge roller 7 ... Discharge auxiliary member 8 ... Discharge tray 10 ... Support Material 11 individual electrodes 12, 13 piezoelectric body (ultrasonic transducer) 14, 15 common electrode 16, 17 Fresnel lens (ultrasonic focusing member) 18 ink liquid 19 ink chamber 20 , 21... Slit 22... Slit member 23... Leader electrode 24. … High-frequency signal generator 28… Comparator

Claims (6)

[Claims] 1. An ink jet recording head that radiates ultrasonic waves into an ink liquid, focuses the ultrasonic waves near the ink liquid surface, discharges ink droplets by ultrasonic pressure, and flies toward a recording medium. A plate-shaped support member, a plurality of rod-shaped individual electrodes arranged in parallel at regular intervals on the support member, and a plurality of individual electrodes arranged on the plurality of individual electrodes in a direction perpendicular to the arrangement direction of the individual electrodes. At least two rectangular ultrasonic transducers provided in parallel with the longitudinal direction of the individual electrodes, and a single common ultrasonic transducer provided on each of the other surfaces of the two ultrasonic transducers facing the individual electrodes. An electrode, and an ultrasonic focusing member provided on each of the other surfaces of the two ultrasonic transducers on which the common electrode is provided, for focusing ultrasonic waves generated from the ultrasonic transducers. Ink characterized by the following Jet recording head. 2. An ink jet recording head according to claim 1, wherein said at least two rectangular ultrasonic transducers have different resonance frequencies. 3. A drive for driving the at least two rectangular ultrasonic transducers, wherein the individual electrodes corresponding to the same position of the at least two rectangular ultrasonic transducers are connected to the same channel. 3. An ink jet recording head according to claim 2, comprising an integrated circuit. 4. An ultrasonic wave is radiated into the ink liquid, the ultrasonic wave is focused near the ink liquid surface, and the ink droplet is ejected by the pressure of the ultrasonic wave to fly toward a recording medium. An ink jet recording apparatus for recording an image by attaching it on a recording medium, comprising: a plurality of rod-shaped individual electrodes arranged in parallel at regular intervals in a row on a plate-shaped support; At least two rectangular ultrasonic vibrators provided on the electrode in parallel with the longitudinal direction of the individual electrodes perpendicular to the arrangement direction of the individual electrodes and having different resonance frequencies; A single common electrode provided on each of the other surfaces of the transducers facing the individual electrodes, and a single common electrode provided on each of the other surfaces on which the common electrodes of the two ultrasonic transducers are provided; Emitted from the acoustic transducer An ultrasonic generating section comprising an ultrasonic focusing member for converging an ultrasonic wave to be generated; and a plurality of sets of individual sets of an odd number of individual electrodes for the plurality of individual electrodes of the ultrasonic generating section. The plurality of individual electrode groups are selectively applied in accordance with a recorded image by a first burst wave obtained by combining at least two burst waves, whereby the one ultrasonic transducer is divided. A plurality of individual electrode groups each including an even number of individual electrodes as one set for the plurality of individual electrodes of the ultrasonic wave generating unit; An electrode group is formed by combining at least two burst waves, and the other ultrasonic vibration is selectively applied by a second burst wave having a frequency different from that of the first burst wave according to a recorded image. Second driver for driving the child When ink-jet recording apparatus characterized by comprising a. 5. An ink jet recording apparatus according to claim 4, wherein said first and second burst waves are formed by combining at least two types of burst waves having different phases. 6. The first drive so as to drive the at least two rectangular ultrasonic transducers at different timings by applying the first burst wave and the second burst wave at different timings. Means and said second
5. The ink jet recording apparatus according to claim 4, further comprising control means for controlling said driving means.