JP2001171104A - Acoustic ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acoustic ink jet recording head which can be manufactured and mounted easily while exhibiting excellent durability and which can fly an ink drop stably while preventing crosstalk effectively. SOLUTION: The acoustic ink jet recording head comprises a substrate having one side arranged with a plurality of piezoelectric elements 34 at a specified interval and the other side arranged with acoustic lenses 38 corresponding to the piezoelectric elements 34, and an ink holding part 42 formed on the other side of the substrate 30 and provided with ink ejection openings 48 at positions corresponding to the focal position of the acoustic lenses 38. The space between the piezoelectric elements 34 is preferably filled with a substance 102 softer than the piezoelectric elements 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic ink jet recording head, and more particularly, to an acoustic ink jet recording head provided with an integrated acoustic lens array used in an acoustic ink jet recording apparatus.

[0002]

2. Description of the Related Art Ink jet printers which perform printing by adhering fine droplets of ink jetted onto a recording medium such as paper or cloth perform recording with less noise and can be easily miniaturized as compared with other recording systems. Therefore, it is widely used mainly for personal use. Conventionally, various ink jet printers have been proposed. A typical example is a thermal ink jet printer that generates bubbles in ink by thermal energy and ejects ink droplets by the pressure of the generated bubbles (Japanese Patent Publication No. -9492) or a piezo method (JP-B-53-12138) in which a pressure fluctuation is physically generated in an ink chamber using a piezo element to eject ink droplets from the ink chamber. Can be.

However, in a conventional thermal ink jet system or piezo system ink jet printer,
If the diameter of the nozzle is reduced in order to increase the resolution, clogging of the nozzle with ink tends to occur, and there is a problem that reliability is lacking. In addition, the production of such a small-diameter nozzle also requires a high-level production technique, and there is a problem that the production yield is reduced.

Recently, ink droplets are made to fly using ultrasonic waves generated using a vibrator such as a piezo element.
An acoustic ink jet system has also been proposed (KAKrouse
"Inkjet convergence" IBM Technical Disclosu
re Bulletin, Vil. 16, No.4.1973.9, 1168-1170). The principle of ink ejection in the acoustic ink jet system is that ultrasonic waves generated by a vibrator by applying a voltage propagate through an acoustic medium and are converged by an acoustic lens so as to focus on the free surface of the ink. Droplets fly from the surface. Since the recording head of this acoustic ink jet system has a simple structure without a nozzle, the problem of nozzle clogging does not occur. In this regard, the acoustic ink jet method can be said to be a recording method that solves the problems of the thermal ink jet method and the piezo method, which have hitherto been mainstream.

However, when acoustic lenses are integrated in an array, there is a problem that crosstalk occurs due to diffraction of sound waves. That is, in the recording head of the acoustic ink jet system, as shown in FIG.
The piezoelectric element 34 is sandwiched between the second electrode 2 and the counter electrodes 36A, 36B, and 36C. For example, when an RF drive voltage is applied between the drive electrode 32 and the counter electrode 36B, the piezoelectric element 34 vibrates and generates an ultrasonic wave. The generated ultrasonic wave propagates through the substrate 30, and is converted into an acoustic beam by the acoustic lens 38B as a free surface of the ink 44 (gas-liquid interface).
The focus is converged so as to form a focus near 48B, energy is applied to the free surface 48B of the ink 44, and the ink droplet 50B flies. At this time, a part of the ultrasonic waves generated by the piezoelectric element 34 is shared by the piezoelectric element 34 and the
The light diffuses within 0, propagates through the ink, is reflected by the ink holding plate 40, and enters the adjacent acoustic lenses 38A and 38C as reflected waves as indicated by arrows. For this reason, when the acoustic beams are simultaneously converged by the acoustic lenses 38A and 38C, the reflected wave cancels the converged wave to weaken the converged acoustic beam, or changes the focal length.
So-called crosstalk occurs. Crosstalk is a serious problem in acoustic ink jet type recording heads because it lowers the stability of ink flight, such as poor ink drop generation and reduced ink drop speed.

In Japanese Patent Publication No. 6-45233, FIG.
As shown in FIG. 3, a narrow groove is formed in the substrate 30 and separated, and the groove is filled with air or a medium 102 that causes acoustic mismatch with the substrate which is an acoustic medium, and the piezoelectric elements 34A, The formation of the acoustic lenses 38A, 38B, and 3
An acoustic ink jet recording head in which each of 8C is acoustically insulated is disclosed. According to this structure, for example, the ultrasonic waves generated by the piezoelectric element 34B do not diffuse when propagating through the substrate 30, and thus crosstalk can be prevented.

[0007]

However, in the acoustic ink jet recording apparatus, 600 dp is actually used.
Since a recording head having a resolution of i or higher is required and acoustic lenses are arranged at high density, grooves are formed in the substrate to acoustically insulate each acoustic lens by dry etching and wet etching. It is difficult to use techniques such as etching and dicing.

When the acoustic lenses are arranged at a high density, the electrodes of the piezoelectric elements provided corresponding to the acoustic lenses require simplified wiring such as using a common electrode.
As shown in FIG. 14, when a deep groove is formed in a substrate, at least a common drive electrode cannot be used, and it is also difficult to use a common counter electrode because a gap is opened between piezoelectric elements.

Further, when a deep groove is formed in the substrate, the strength of the substrate is significantly reduced, and it is difficult to fill the groove uniformly with another medium.

Therefore, an object of the present invention is to provide an acoustic ink jet recording head which is easy to manufacture and mount, has excellent durability, can effectively prevent crosstalk, and can stably fly ink droplets. To provide.

[0011]

In order to achieve the above object, an acoustic ink jet recording head according to the present invention comprises a plurality of piezoelectric elements arranged on one surface at predetermined intervals, and the other surface comprises a plurality of piezoelectric elements. A substrate provided with an acoustic lens corresponding to each of the piezoelectric elements, and formed between the other surface of the substrate and an ink ejection port provided at a position corresponding to each of the focal positions of the acoustic lens. And an ink holding unit.

In the present invention, since a plurality of piezoelectric elements are arranged at predetermined intervals, vibration is not propagated in the piezoelectric elements, and diffusion of ultrasonic waves can be prevented at an early stage.
Crosstalk can be effectively prevented, and ink droplets can fly stably. In addition, since no groove or the like is provided on the substrate, manufacture and mounting are easy and the durability is excellent.

The gaps between the piezoelectric elements can be filled with a substance softer than the piezoelectric elements, such as a vibration absorbing material. By filling the gap between the piezoelectric elements with a softer substance than the piezoelectric elements, the piezoelectric elements are acoustically insulated from each other.

That is, since no groove is provided in the substrate, the electrode on the substrate side can be used as a common electrode, and when a gap between the piezoelectric elements is filled with a soft substance, a voltage is applied to the piezoelectric elements. At least a portion of at least one of the pair of electrodes can be a common electrode,
Even when acoustic lenses are arranged at high density, simplified wiring is possible.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an acoustic ink jet printer to which an acoustic ink jet recording head of the present embodiment is applied will be described with reference to the drawings.

As shown in FIG. 1, the acoustic inkjet printer 100 is connected to an upper-level host 10 such as a personal computer via a parallel port or a network (not shown), and prints based on recording information from the upper-level host 10. Do. Acoustic inkjet printer 1
A paper feed port 14 is provided at the rear of the upper surface of the sheet 00, and the recording paper 16 is introduced into the acoustic inkjet printer 100 from the paper feed port 14. The introduced recording paper 16 is
Roller 18 driven to rotate by a drive motor (not shown)
The recording paper 22 is conveyed to the downstream side while being pinched by A, and passes immediately below the recording head 22 held by the carriage 20 during the conveyance. The recording head 22 reciprocates in the carriage 20 in a direction perpendicular to the conveying direction in accordance with the paper width, and prints on the recording paper 16 passing immediately below. Recording paper 1 after printing
6 is conveyed to the downstream side while being nipped by a roller 18B rotated by a drive motor (not shown), and is discharged to a paper discharge tray 24 provided at a lower front surface of the acoustic inkjet printer 100.

The recording head 22 includes a substrate 30 made of an acoustic medium and an ink reservoir 42 as an ink holding part, as shown in FIG.

As shown in FIG. 3, on one surface of the substrate 30, n (n ≧ 2) acoustic lenses 38 are arranged in a line at a predetermined resolution, for example, at an interval of 100 dpi. Are arranged in m (m ≧ 2) rows (six rows in this embodiment) so as to be shifted by 1 / n pitch in the arrangement direction of the acoustic lenses 38 in each row, that is, a so-called staggered arrangement. The acoustic lens 38 is formed so as to be integral with the substrate 30, and an ink holding plate 40 is provided at a position separated by the focal length of the acoustic lens 38 so as to face the substrate 30. Between the substrate 30 and the ink holding plate 40,
An ink reservoir 42 as an ink holding unit is formed, and the ink reservoir 42 is filled with ink 44. In addition, in the ink holding plate 40, ink ejection ports 46 are formed in a staggered manner corresponding to the focal positions of the acoustic lenses 38. A free surface (gas-liquid interface) 48 is formed in the ink ejection port 46 by the surface tension of the ink.

On the other hand, on the other surface of the substrate 30, as shown in FIG.
= 1, 2, 3,. . . . . , N) is provided so as to connect the piezoelectric elements corresponding to the lens in series, and serves as a common electrode for the piezoelectric element corresponding to the k-th lens. As shown in FIG. 2, a columnar piezoelectric element 34 is disposed at a position corresponding to each acoustic lens 38 at a predetermined interval on each drive electrode 32, and a piezoelectric element is provided in a gap between the piezoelectric elements. A substance 102 that is softer than the element (hereinafter simply referred to as “soft substance”) 102 is embedded. Each piezoelectric element 3
4, m counter electrodes 36 are provided so as to connect the piezoelectric elements in each column in series, as shown in FIG. The counter electrode 36 serves as a common electrode for the piezoelectric elements in each row.

When an RF driving voltage is applied between the driving electrode 32 and the counter electrode 36 of the recording head 22, the piezoelectric element sandwiched at the intersection of the driving electrode 32 and the counter electrode 36 to which the voltage is applied. 34 vibrates to generate a sound wave. Since each piezoelectric element 34 is arranged separately, the generated sound wave propagates through the substrate 30 without being diffused, and is formed as an acoustic beam by the acoustic lens 38 near the free surface (gas-liquid interface) 48 of the ink 44. Focused and focused, energy is applied to the free surface 48 of the ink 44 and the ink droplet 50 flies.

Next, the manufacturing process of the acoustic ink jet recording head of the present invention will be described.

First, as shown in FIG. 5, an acoustic lens 38 such as a Fresnel lens is formed on one surface of a substrate 30 made of an acoustic medium. The thickness of the substrate can be arbitrarily specified,
It is preferable that the thickness be in the range of 10 mm to 0.1 μm. In addition, a material having a propagation speed much higher than the speed of sound in the ink is used as the substrate material. Specifically, silicon, silicon nitride, fused quartz, glass, or the like can be used.

Next, after a driving electrode material is deposited on the surface of the substrate 30 opposite to the surface on which the acoustic lens 38 is formed, the k-th piezoelectric element in each row is connected in series by a photolithography process. Then, as shown in FIG. 6, n drive electrodes 32 are formed. The drive electrode 32 is preferably as thin as possible so that the vibration of the piezoelectric element can be transmitted to the substrate 30, and the thickness of the drive electrode is 1 μm.
m or more, and particularly preferably about 20 μm. As the electrode material, Al, Ti, Ta or the like is preferable. The electrode may have a single-layer structure or a multi-layer structure. In addition to the Al single-layer electrode, for example, a layer made of Ti-Ta is formed to a thickness of 100 nm, Al is deposited as a lead line to a thickness of 1 μm, and then patterned. An electrode having a layer structure may be used.

Next, as shown in FIG. 7, the piezoelectric element 34 is formed. The thickness of the piezoelectric element is preferably from 0.1 μm to 10 mm, and as the material of the piezoelectric element, PZT,
LiNbNO ₃ , ZnO or the like can be used.

Next, as shown in FIG. 8, a groove 104 is formed by a photolithography step and an etching step, and each of the piezoelectric elements 34 is individually separated into n × m pieces, as shown in FIG. Then, the groove 104 is filled with the soft substance 102 until the height becomes the same as that of the piezoelectric element 34. The soft material is not particularly limited as long as it is softer than the piezoelectric element, but it is preferable to use a vibration absorbing material capable of absorbing the vibration of the piezoelectric element. As the soft substance, rubber, elastomer, thermoplastic plastic, thermoplastic elastomer and the like can be used, but polyamide and polyimide are preferable in terms of excellent heat resistance. For example, when filling with polyimide, after spin-coating the polyimide, heat treatment is performed at 270 ° C. for 1 hour to spread the polyimide inside the groove,
Thereafter, polishing is performed until the height becomes the same as that of the piezoelectric element, and unnecessary polyimide is removed.

Next, after the counter electrode material is deposited, the piezoelectric elements in each row are patterned so as to be connected in series by a photolithography process, and as shown in FIG. m counter electrodes 32 are formed. Al, Ti, Ta, etc. are preferable as the electrode material,
The point that the electrode may have a single-layer structure or a multilayer structure is the same as the drive electrode.

In the acoustic ink jet recording head according to the present embodiment, since a plurality of piezoelectric elements are arranged at predetermined intervals, vibration is not propagated in the piezoelectric elements, and ultrasonic waves are diffused in the initial stage. Therefore, crosstalk can be effectively prevented, and ink droplets can be stably fly.

Also, since no grooves are provided on the substrate,
It is easy to manufacture and mount, and has excellent durability. In particular, in the above embodiment, the gap between the piezoelectric elements is filled with a softer substance than the piezoelectric elements, so that the piezoelectric elements are acoustically more completely insulated from each other. Can be easily provided.

In the above embodiment, the groove 104 is filled with the soft substance 102. However, the groove 104 is filled with a resist material instead of this soft substance, and the counter electrode 32 is formed. The resist material embedded in the groove 104 is removed, and as shown in FIG.
The interior of the groove 104 may be hollow.

In the above embodiment, the counter electrode 32 was formed after the soft substance 102 was embedded in the groove 104. However, as the electrode material, the reinforcing layer 106 of polyimide or the like and the wiring layer 1 were formed.
12, the counter electrode 32 can be formed directly after the formation of the groove 104, as shown in FIG.

[0031]

The acoustic ink jet recording head of the present invention is easy to manufacture and mount, has excellent durability, can effectively prevent crosstalk, and can stably eject ink droplets. To play.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an acoustic ink jet printer to which an acoustic ink jet recording head according to an embodiment is applied.

FIG. 2 is a cross-sectional view illustrating a part of a cut surface of the acoustic inkjet recording head according to the present embodiment in the acoustic lens row direction.

FIG. 3 is a plan view of the substrate of the acoustic ink jet recording head according to the present embodiment as viewed from the acoustic lens side.

FIG. 4 is a plan view of the substrate of the acoustic inkjet recording head according to the present embodiment, as viewed from the piezoelectric element side.

FIG. 5 is a schematic sectional view illustrating a manufacturing process of the acoustic ink jet recording head.

FIG. 6 is a schematic sectional view illustrating a manufacturing process of the acoustic ink jet recording head.

FIG. 7 is a schematic sectional view illustrating a manufacturing process of the acoustic inkjet recording head.

FIG. 8 is a schematic sectional view showing a manufacturing process of the acoustic inkjet recording head.

FIG. 9 is a schematic sectional view illustrating a manufacturing process of the acoustic inkjet recording head.

FIG. 10 is a schematic sectional view showing a manufacturing process of the acoustic ink jet recording head.

FIG. 11 is a schematic sectional view showing a modified example of the acoustic ink jet recording head of the present embodiment.

FIG. 12 is a schematic sectional view showing another modified example of the acoustic ink jet recording head of the present embodiment.

FIG. 13 is a schematic sectional view of a conventional acoustic ink jet recording head.

FIG. 14 is a schematic cross-sectional view of a conventionally proposed cross-talk preventing acoustic ink jet recording head.

DESCRIPTION OF THE SYMBOLS 22 Recording head 30 Substrate 32 Drive electrode 34 Piezoelectric element 36 Counter electrode 38 Acoustic lens 40 Ink holding plate 42 Ink reservoir 44 Ink 46 Ink ejection port 48 Free surface 50 Ink drop 100 Acoustic inkjet printer 102 Vibration absorption Material 104 Groove 106 Reinforcement layer 108 Wiring layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C057 AF40 AF65 AF93 AG15 AG16 AG39 AG40 AG42 AG44 AG62 AG92 AG93 AG94 AP02 AP14 AP22 AP31 AP79 AQ01 AQ02 BF06

Claims (3)

[Claims] 1. A substrate having a plurality of piezoelectric elements arranged on one surface at predetermined intervals and having an acoustic lens corresponding to each of the piezoelectric elements on the other surface, and the other surface of the substrate. And an ink holding part formed between the ink lens and an ink ejection port provided at a position corresponding to each of the focal positions of the acoustic lens. 2. The acoustic ink jet recording head according to claim 1, wherein a material softer than the piezoelectric element is filled between the piezoelectric elements. 3. At least a part of at least one of a pair of electrodes for applying a voltage to the piezoelectric element,
3. The acoustic inkjet recording head according to claim 1, wherein the acoustic inkjet recording head is a common electrode.