JPH08132607A - Ink jet recording apparatus - Google Patents

Abstract

PURPOSE: To provide an ink jet recording apparatus capable of performing recording of required resolving power using a unidimensional piezoelectric element array. CONSTITUTION: An ink jet recording apparatus flying the ink particles formed from the liquid surface of ink by the pressure of ultrasonic beam to record an image on a recording medium consists of a piezoelectric element array 10 constituted by arranging a plurality of piezoelectric elements emitting ultrasonic beams in one row, an ultrasonic interference layer 11 allowing the ultrasonic beams emitted from the respective piezoelectric elements of the piezoelectric element array 10 to interfere each other therein to converge them into the ink in the array direction of the piezoelectric element array 10 and a plurality of the parallel linear strip like partterns extending in the direction same to the array direction of the piezoelectric element array 10 and has a Flesnel diffraction strip plate 17 converging the ultrasonic beams passed through the ultrasonic interference layer 11 into the ink in the direction crossing the array direction at a right angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for recording an image by making liquid ink into particles and flying them on a recording medium, and particularly to the pressure of an ultrasonic beam generated from an ultrasonic wave generating element array. The present invention relates to an inkjet recording device that causes ink particles to fly.

[0002]

2. Description of the Related Art An apparatus for ejecting liquid ink as small droplets called ink particles on a recording medium to form recording dots and recording an image has been put into practical use as an inkjet printer. This ink jet printer has the advantages that it is less noisy than other recording methods and does not require processing such as development and fixing, and is attracting attention as a recording technology for plain paper. Many methods of ejecting ink for inkjet printers have been devised to date. In particular, (a) 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. 56-94).
29, Japanese Patent Publication No. 61-59911, etc.), and (b) a method of ejecting ink droplets by a mechanical pressure pulse generated by a piezoelectric element (for example, Japanese Patent Publication No. 53-12138).
Etc.) is a typical one.

As a recording head used in an ink jet printer, a direction (hereinafter referred to as "main scanning direction") mounted on a carriage and orthogonal to a conveying direction of recording paper (hereinafter referred to as "sub scanning direction"). ), A serial scanning type head that performs recording while moving to is being used. With this serial scanning type head, it is difficult to increase the recording speed because recording is performed while moving mechanically.
Therefore, a so-called line scanning type head, which can increase the recording speed by reducing the mechanically movable part by using a recording head as a long head having the same size as the width of the recording paper, is also considered. Implementing a mold head is not easy for the following reasons.

In the ink jet recording system, the concentration and concentration of the ink are likely to occur locally due to the evaporation and volatilization of the solvent, which causes the clogging of individual thin nozzles corresponding to the resolution. Therefore, in the method of using the pressure of vapor for forming an inkjet, the insoluble matter is attached due to a thermal or chemical reaction with the ink, and in the method of using the pressure of the piezoelectric element, a complicated structure such as an ink flow path is formed. However, it further facilitates inducing clogging. Serial scanning heads that use several tens to hundreds of nozzles can reduce the frequency of clogging, but line scanning heads that require thousands of nozzles. Then, clogging occurs stochastically at a fairly high frequency, which is a big problem in terms of reliability.

Further, the conventional ink jet recording apparatus is
There is also a problem that it is not suitable for improving the resolution. That is, it is difficult to generate ink particles having a diameter of 20 μm or less (which corresponds to a recording dot having a diameter of about 50 and several μm on the recording paper) by the method using the pressure of vapor, and the pressure generated by the piezoelectric element is used. This is because in the method of using, the recording head has a complicated structure, and it is difficult to form a head with high resolution due to processing technology problems.

In order to overcome these drawbacks, a method of ejecting ink from the ink liquid surface by using the pressure of an ultrasonic beam generated by a piezoelectric element array composed of a thin film piezoelectric body is described in IBM TDB, vol. 16, No. 4,
pp. 1168 (1973-10), USP-4308.
547 (1981), USP-469195 (198).
7), USP-4751529 (1988), USP
-4751530 (1988), USP-50418.
49 (1991), JP-A-62-66943, JP-A-63-162253, JP-A-63-166545,
JP-A-63-166546, JP-A-63-16654
8, JP-A-63-312157, JP-A-3-200
199, JP-A-4-296562, JP-A-4-29665.
63, JP-A-4-356328, and JP-A-5-27821.
Proposed by 8 etc. This method is a so-called nozzleless method that does not require a nozzle for each individual dot or a partition of the ink flow path, so it is effective for preventing and recovering from clogging, which was a major obstacle in making a line head. Is. Further, since it is possible to stably generate and fly ink particles having a very small diameter, it is suitable for high resolution.

However, a disadvantage of this method is that the ultrasonic beam is focused in the ink by using an acoustic lens having a diameter larger than the recording image point or the resolution (for example, 30 times the recording image point), and therefore, as a recording head. Is that it is not possible to obtain the required resolution with only one piezoelectric element array, and it is necessary to fill the gap by using a recording head configured by staggering a plurality of piezoelectric element arrays. The recording head having such a staggered array structure has many problems in terms of image quality, such as periodic density unevenness and slight positional deviation from adjacent dots.

In order to focus the ultrasonic beams without arranging the recording heads in a zigzag manner, a one-dimensional piezoelectric element array in which a plurality of piezoelectric elements are arranged in a row is used, and a plurality of adjacent ultrasonic beams are ink-jetted to each other. There is also proposed a method of performing so-called phased array scanning in which light is caused to interfere and focus in a room (JP-A-2-184443). However, such a method has the following disadvantages.
In order to understand this, (1) in the method of ejecting ink into particles using an ultrasonic beam, the particle diameter of the ejected ink particles substantially matches the ultrasonic wavelength in the ink, and ( 2) It is necessary to know the two facts that the interference between parallel ultrasonic beams requires at least the condition that the ultrasonic wavelength is longer than the beam interval.

That is, in order to obtain a certain degree of resolution, it is necessary to use ultrasonic waves having a short wavelength corresponding to it. In this case, in order to cause interference between ultrasonic beams in ink, the wavelength of the ultrasonic waves is larger than the beam interval. Becomes too short, which makes phased array scanning difficult. vice versa,
If an ultrasonic beam with a long wavelength that can perform phased array scanning is used, then the flying ink particles are too large and the required resolution cannot be obtained. Therefore, with this method, it is impossible to satisfy both the ultrasonic wavelength capable of phased array scanning and the ultrasonic wavelength capable of obtaining flying ink particles having a particle size capable of realizing the required resolution at the same time.

When the ultrasonic wave generating elements forming the phased array are separately driven, the following problems are recognized. In a droplet generation mechanism using an acoustic mode that focuses an acoustic beam to generate a droplet, the droplet flies along the focusing direction of the acoustic beam. For example, when an acoustic beam having an angle of several degrees with respect to the vertical direction of the ink liquid surface is focused on the ink liquid surface, it is confirmed by an experiment that ink droplets fly in the direction having the angle. ing. That is, when the acoustic beam is scanned by the phased array method, the flying angle of the ink droplet may change depending on the position where the acoustic beam is focused, and the ink droplet may not fly vertically from the ink surface. This means that image points having different pixel pitches are formed on the recording paper surface. Here, in order to keep the image point pitch on the recording paper surface constant, it is necessary to predict the flying angle of the ink droplet in advance and perform the phase control of the ultrasonic wave generation element. Further, this phase control slightly differs depending on the position of the image point, and it is necessary to control the phase accurately and without interruption. Therefore, the circuit configuration becomes complicated, and a memory capable of accumulating a large amount of correction data is required. There are problems such as costs.

[0011]

As described above, the ultrasonic beam generated from the one-dimensional piezoelectric element array in which a plurality of piezoelectric elements are arranged in a row is caused to interfere in the ink to perform phased array scanning. In the conventional inkjet recording technology that attempts to eject ink droplets, it is necessary to satisfy both the ultrasonic wavelength capable of phased array scanning and the ultrasonic wavelength capable of obtaining flying ink droplets having a particle size corresponding to the required resolution at the same time. However, there is a problem in that it is impossible to perform recording at a required resolution.

In addition, when the ultrasonic wave generating elements forming the phased array are separately driven, there is a problem that the circuit structure becomes complicated and a memory for storing a large amount of correction data is required.

An object of the present invention is to provide an ink jet recording apparatus capable of recording with a required resolution by using a one-dimensional piezoelectric element array. Another object of the present invention is to eliminate periodical density unevenness, slight positional deviation between adjacent dots, etc., and it is possible to eject ink droplets at a uniform interval, and to achieve high-quality image recording. An object of the present invention is to provide an inkjet recording device using a sound wave mode.

[0014]

The present invention has taken the following means in order to solve the above problems. A first aspect of the invention (corresponding to claim 1) is an inkjet recording apparatus for recording an image on a recording medium by ejecting atomized ink from the liquid surface of the ink by the pressure of an ultrasonic beam. And an ultrasonic interference layer for concentrating the ultrasonic beams emitted from the ultrasonic wave generating elements of the ultrasonic wave generating element array, which are arranged in a line, into the ink. To do.

In another invention (corresponding to claim 2) of the first invention, a plurality of ultrasonic wave emitting elements are radiated by simultaneously driving a part of the ultrasonic wave generating element array instead of the ultrasonic wave interference layer. While simultaneously applying the plurality of pulse trains having different phases to the ultrasonic wave generating element, the simultaneous driving elements are sequentially shifted in the main scanning direction so that the ultrasonic waves of FIG. Is characterized by.

According to the first aspect of the invention, when the flying ink particles required for recording are generated by using the ultrasonic beam, the lens effect that requires a large area in the bulk lens is exhibited at a pitch corresponding to the required resolution. In order to realize an ultrasonic wave generation element array in which a plurality of ultrasonic wave generation elements are arranged in a line, interference between a plurality of adjacent ultrasonic beams in the main scanning direction (that is, the ultrasonic wave generation element arrangement direction) is equivalent to a lens. The phased array scanning that works is performed, and it operates as a partially overlapped different lens that was impossible with the bulk lens. In this case, the above-mentioned problem that the ultrasonic wavelength for obtaining flying ink particles corresponding to the required resolution is too short as a wavelength capable of phased array scanning,
The problem is solved by providing an ultrasonic interference layer between the ultrasonic wave generating element array, which is an ultrasonic wave generating element, and the ink chamber for storing ink, and performing a focusing operation inside the ultrasonic interference layer.

That is, before the ultrasonic beam is transmitted to the ink, an ultrasonic wave propagation layer (sonic velocity) having a much higher ultrasonic wave propagation speed (sound velocity) than that of the ink, that is, a medium having a long ultrasonic wave wavelength is used as the ultrasonic interference layer. By concentrating the ultrasonic beams inside the ultrasonic interference layer, it is possible to satisfy both the realization of phased array scanning and the formation of flying ink particles having a particle size corresponding to the required resolution at the same time. You can

Even when the ultrasonic interference layer is not provided, the ultrasonic waves can be focused in the main scanning direction by simultaneously driving some of the ultrasonic wave generating elements, and at the same time, the ultrasonic waves that are simultaneously driven can be focused. By sequentially shifting the sound wave generating elements, it becomes possible to continuously change the focal point of the ultrasonic waves.

Second invention (corresponding to claims 3 and 4)
In an inkjet recording apparatus that records an image on a recording medium by ejecting particle-shaped ink from the liquid surface of the ink by the pressure of an ultrasonic beam, a super-sonic transducer that is configured by arranging a plurality of ultrasonic generating elements in a line. Fresnel diffraction, which consists of a plurality of parallel linear strip patterns extending in the same direction as the ultrasonic wave generating element array direction of the ultrasonic wave generating element array, focuses the ultrasonic beam emitted from each ultrasonic wave generating element into the ink. It is characterized in that a strip plate is provided.

In the second aspect of the invention, in the sub-scanning direction (the direction orthogonal to the ultrasonic wave generating element array direction), an in-plane manufacturing process with high reliability and good uniformity such as photolithography causes structurally large irregularities and curved surfaces. In place of a bulk cylindrical lens, a one-dimensional Fresnel diffraction band plate (also referred to as Fresnel diffraction grating or Fresnel lens) is used as an acoustic lens system with little variation and aberration.

In this Fresnel diffractive band plate, a portion through which a wave passes and a portion where a wave does not pass or a phase shift corresponding to a half wavelength occurs alternately with a width of a ratio based on a certain rule from the center of the cross-sectional pattern. Are arranged side by side, and simply extend as a plurality of linear strip patterns in the ultrasonic wave generating element array direction of the ultrasonic wave generating element array. Therefore, even if the incident angle of the ultrasonic beam with respect to the direction extending in a straight line band changes, the phenomenon that the focal length changes unlike the bulk cylindrical lens does not occur.

Further, such a one-dimensional Fresnel diffraction band plate can be formed in a plane unlike a bulk cylindrical lens in which unevenness including a curved surface is formed in a fine structure. Therefore, it can be formed by a highly reliable and uniform manufacturing process such as optical lithography.
It is possible to focus ultrasonic waves with high accuracy.

The drive circuit (corresponding to claim 5) for driving the ultrasonic wave generating element array in the first invention and the second invention is, for example, a shift register for transferring input image data, and this shift. Depending on the latch that temporarily stores the image data that are output in parallel from the register and the image data that is temporarily stored in this latch, select one of the multiple pulse trains that have different phases and that are input from the multiple common signal lines. , A data selector / driver for driving the ultrasonic wave generating element array according to the pulse train.

In the third invention (corresponding to claim 6), in order to effectively utilize the directivity of the acoustic beam, the ultrasonic wave generating element (vibrator, oscillator, so as to planarly self-focus toward the liquid surface of the ink). Sound wave generating elements) and ink liquid chambers, n ultrasonic wave generating elements (n ≧ 4) are arranged in an array, and m ultrasonic wave generating elements (3 ≦ m <n). )
Grouping the ultrasonic wave generating elements, and controlling the focusing of the ultrasonic beam from the m ultrasonic wave generating elements to one point on the ink liquid surface, and further changing the group of the ultrasonic wave generating elements to generate acoustic waves on the ink liquid surface. The main point is to switch the energy focusing point.

With the above structure, the ink jet recording apparatus according to the third aspect of the present invention uses the standardized control mechanism or signal group to drive the ultrasonic wave generating elements arranged in an array by grouping them. The focusing direction and position of the acoustic beam with respect to the liquid surface are standardized. Therefore, the size and the flight direction of the ink droplets flying from the ink surface are made uniform, and the pixel pitch and the ink droplet diameter are made uniform, so that density unevenness and dot misalignment can be avoided. As a result, high quality images are always recorded.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a diagram schematically showing a part of a recording head portion in an ink jet recording apparatus according to the first embodiment.

In FIG. 1, the ultrasonic interference layer 11 is a support of the recording head, the ultrasonic wave generating element array 10 and the ink 16.
The layer also serves as an acoustic matching layer between the layers, and is made of, for example, glass. The ultrasonic wave generating element array 10 may be composed of a piezoelectric element, a magnetostrictive element, or the like. In the present embodiment, a case where the ultrasonic wave generating element 10 is composed of a piezoelectric element will be described. To do.

A piezoelectric layer 13 is formed on the back surface side of the ultrasonic interference layer 11 via a common electrode 12 made of a metal thin film. The piezoelectric layer 13 is formed of a material such as ZnO or PZT on the entire back surface of the ultrasonic interference layer 11 or in a band shape by a film forming method capable of arbitrarily controlling the film thickness such as sputtering. Ultrasonic interference layer 11
On the surface of, a plurality of individual electrodes 14 are formed at a pitch corresponding to recording dots. The thickness of the piezoelectric layer 13 is determined by the wavelength of the ultrasonic wave used, and is designed so that the total of the equivalent thickness of the metal common electrode 12 and the individual electrode 14 sandwiching the piezoelectric layer 13 is half the ultrasonic wavelength. Has been done.

The common electrode 12, the piezoelectric layer 13 and the individual electrode 14 constitute the piezoelectric element array 10. Although only eight piezoelectric elements are shown in the piezoelectric element array 10 in FIG. 1, an actual inkjet recording apparatus, for example, a line type head having a length corresponding to the longitudinal direction of A4 size with a resolution of 400 dpi is used. In case of about 4
Piezoelectric elements of 800 elements are arranged in a line.

On the surface side of the ultrasonic interference layer 11, the nozzle substrate 15 having a slit-shaped nozzle hole / ink chamber having a trapezoidal cross section is positioned so that the nozzle hole / ink chamber is located directly above the piezoelectric element array 10. Are pasted together. Liquid ink 16 is filled in the nozzle hole / ink chamber.

Further, the piezoelectric element array 10 and the ink 16
A one-dimensional Fresnel diffraction band plate 17 is formed on the boundary between and. This Fresnel diffraction band plate 17 has x = 0 to ¹ K, 3 ^1/2 K to 5 ^{1/2 where} x is the distance from the diffraction center.
^{K, 7 1/2 K~9 1/2 K,} 11 1/2 K~13 1/2 K, ...
The first layer that passes ultrasonic waves at x = 1K to 31 ^/ 2K, 5
^{1/2 K~7 1/2 K, 9 1/2 K~11} 1/2 K, 13 1/2 K
Are arranged by alternately arranging the second layers in which the phase of the ultrasonic wave is shifted by a half wavelength. However, P is the focal length, that is, the thickness of the nozzle substrate 15, λ is the wavelength of the ultrasonic wave used, and K =
(Λp / 2) ^1/2 . Only one of the first layer and the second layer may be formed by photolithography of a metal vapor deposition film, and the thickness thereof is about several μm, which causes a phase shift of half a wavelength due to the difference with the slow sound velocity in the ink. It is selected to be about a dozen or so μm.

Next, the operation of this embodiment will be described with reference to FIG. As a typical method of phased array scanning,
A predetermined number of piezoelectric elements adjacent to each other in the piezoelectric element array are set as one unit, and the piezoelectric element for driving the piezoelectric elements is driven by appropriately shifting the phases so that the ultrasonic beams emitted from each unit interfere with each other. There is a linear scan in which the individual scans are sequentially shifted. Here, the case where linear scanning is performed with four piezoelectric elements as one unit will be described. in this case,
As shown in FIG. 2, an individual electrode 14 of four piezoelectric elements having a burst voltage composed of an alternating current or a pulse train of a predetermined frequency is provided.
It is applied to ₃ , 14 ₄ , 14 ₅ , and 14 ₆ . The frequency of the burst voltage applied at this time needs to be set such that at least the wavelength in the ultrasonic interference layer 11 is longer than the arrangement pitch of the piezoelectric element array 10, and further the ultrasonic interference layer 11 is Is also required to be a certain value or more.

Under these conditions, a burst voltage of a predetermined phase is applied to the individual electrodes 14 ₄ and 14 ₅ of the two inner piezoelectric elements of the four piezoelectric elements, and the two outer piezoelectric elements are applied. When a burst voltage whose phase is ahead of the burst voltage applied to the individual electrodes 14 ₄ and 14 ₅ of the two inner piezoelectric elements is applied to the individual electrodes 14 ₃ and 14 ₆ of the element, the respective piezoelectric elements emit the burst voltage. When the ultrasonic beams are interfered with each other, a lens effect occurs in the piezoelectric element array direction of the piezoelectric element array 10 (hereinafter referred to as “array direction”), that is, in the main scanning direction. However, in the ultrasonic interference layer 11, the ultrasonic beam is not focused in the direction (sub scanning direction) orthogonal to the array direction of the piezoelectric element array 10.

The ultrasonic beam that has reached the boundary surface between the ultrasonic interference layer 11 and the ink chamber is focused by the Fresnel diffraction band plate 17 in a direction orthogonal to the array direction of the piezoelectric element array 10, that is, in the sub-scanning direction. Receive a lens effect that does. That is, the focusing of the ultrasonic beam in the main scanning direction starts from the inside of the ultrasonic interference layer 11 which is also the acoustic matching layer and reaches the ink 16 of the nozzle substrate 15. Focusing of the ultrasonic beam in the sub-scanning direction is performed by the ink 1 on the nozzle substrate 15.
It is done only in 6. In both the main scanning direction and the sub-scanning direction, the ultrasonic beam is focused on the surface of the ink stopped by the surface tension at the slit-shaped opening on the upper surface of the nozzle substrate 15.

In this way, ink particles can be ejected from the ink surface by the pressure of the focused ultrasonic beam, and an image can be recorded on a recording medium such as recording paper (not shown). In this recording method, when the ultrasonic beam is focused into one dot by using four piezoelectric elements as shown in FIG. 3, a division drive for dividing one line into at least 1/4 timing or more is performed. Become. That is, it is necessary to shift in the main scanning direction by linear scanning using four piezoelectric elements as one unit.

Each operation of FIGS. 3A to 3E will be briefly described. FIG. 3A shows grouped individual electrodes 1
Of the 42 to 145, the inner two individual electrodes 143 and 14
Burst voltage is applied to 4 and two outer individual electrodes 14
2 and 14 5 are the inner two individual electrodes 1 as described above.
FIG. 4 is a schematic diagram in the case where a burst voltage having a phase more advanced than 43 and 144 is applied.

FIG. 3B shows the inner two individual electrodes 144 among the individual electrodes 143 to 146 grouped next.
, 145, a burst voltage is applied to the two outer individual electrodes 143, 146, and the inner two individual electrodes 144,
It is a schematic diagram at the time of applying the burst voltage which the phase advanced from 145.

In FIG. 3C, the burst voltage is applied to the two inner electrodes 145 and 146 of the individual electrodes 144 to 147 which have been further grouped, and the outer two individual electrodes 144. , 147 to the inner two individual electrodes 1
It is a schematic diagram at the time of applying the burst voltage which the phase advanced from 45,146.

FIG. 3D shows the individual electrodes 141 to 148.
A group of individual electrodes 141 to 144 and an individual electrode 1
FIG. 14 is a schematic diagram when the ink droplets are divided into groups of 45 to 148, and each group is simultaneously driven to eject two ink droplets at a predetermined pitch.

FIG. 3 (e) shows the same state as FIG. 3 (a). Specifically, it is desirable that the number of the sound wave generating element groups 2 forming a group is 20 or more.

Although the linear scanning using four piezoelectric elements as one unit has been described here, the number of elements in one unit for driving the piezoelectric element array in the linear scanning, that is, the piezoelectric used to record one image point. The number of elements is not limited to this. If more piezoelectric elements are used to record one image point, the wavefront of the ultrasonic beam that is centripetally focused becomes smoother and the energy density becomes higher. The drive voltage of the array 10 can also be lowered.

As described above, the piezoelectric element arrays 10 arranged in an array are grouped, and the grouping is sequentially rearranged, and the burst voltage is switched and applied depending on the position of the piezoelectric element array 10 in the grouping. Since the ink droplets having a constant size are always ejected in a fixed direction by adopting the above-mentioned method, a control mechanism or the like for the flight direction of the ink droplets is not required, which greatly contributes to simplification of the recording apparatus.

On the other hand, the groups of the piezoelectric element array 10 are sequentially rearranged, and a predetermined AC or burst voltage is selectively applied to the piezoelectric element array 10 corresponding to the position within the group. In addition, the energy density of the ultrasonic beam is improved, the variation in the size of the ink droplet is reduced, and high-quality recording can be performed.

The first feature of this embodiment is that the plurality of adjacent ultrasonic beams emitted from the piezoelectric element array 10 interfere with each other inside the ultrasonic interference layer 11 made of a material such as glass which is also an acoustic matching layer. This is a point for focusing in the main scanning direction.

With reference to FIG. 4, description will be given of the effect of the plurality of ultrasonic beams interfering with each other in the ultrasonic interference layer 11 to focus in the main scanning direction. FIG. 4 shows the relationship between the wavelength of the ultrasonic beam emitted from the piezoelectric element array 10 and the recording dot diameter on the recording medium for the wavelengths inside the glass and inside the ink. Further, in FIG. 4, an area showing the relationship between the ultrasonic wave wavelength and the recording dot diameter in which the ultrasonic waves interfere with each other and the phased array scanning is performed is shown as a phased array possible area.

Japanese Unexamined Patent Publication (Kokai) No. 2-184 cited above as the prior art.
In 443, it is proposed that the focusing operation of the ultrasonic beam is performed inside the ink. However, as shown in FIG. 4, the wavelength of ultrasonic waves in the ink is short, and interference between ultrasonic beams does not easily occur. Therefore, in reality, the phased array scanning cannot be performed in the ink, so that the recording image point corresponding to the required resolution cannot be obtained. On the other hand, in a medium having acoustic propagation characteristics (sound velocity) faster than that of ink, for example, in a glass (3.7 times), the wavelength becomes long, so that a plurality of ultrasonic beams interfere with each other. Phased array scanning is possible.

Therefore, as in this embodiment, the ultrasonic interference layer 11 which is also an acoustic matching layer interposed between the ink chamber and the piezoelectric element array 10 is made of, for example, glass to increase its thickness. If the ultrasonic beams are interfered with each other in the acoustic interference layer 11 so that the beams are converged to a certain degree and then guided into the ink 16, the ultrasonic beam is bounded by the boundary between the ultrasonic interference layer 11 and the ink 16. Even after refracting on the surface, focusing continues in the ink 16 as it is,
It is possible to focus within or on the surface of the ink 16.

In the present embodiment, it is desirable that the thickness and sound velocity of the ultrasonic interference layer 11 be set as follows. Thickness d of ultrasonic interference layer 11 and piezoelectric element array 1
Between the pitch of 0 (up to recording resolution = size of recording image point) Ps and the ultrasonic beam transmitted in the ink 16 forms a sharp focus, at least d ≧ 0.5 Ps ... It is required that the relationship of (1) is established. This is based on the following reasoning.

There is the following relationship between the thickness d of the ultrasonic interference layer 11 and the ultrasonic wavelength λ i in the ink 16. .Pitch of the piezoelectric element array Ps = 20.times. (. Lambda.i / 1
0) ^1.5. Pitch of ultrasonic beam at the interface between the ultrasonic interference layer 11 and the ink 16 .pi..lambda.i .. Thickness of the ultrasonic interference layer 11 required under the condition of F = 1. D.gtoreq.Ps-Pi = 0.633.lambda.i. ^1.5 −λi ≧ 0.5 Ps (at 300 dpi to 1250 dpi) Further, the ratio (Rv) of the sound velocity in the ultrasonic interference layer 11 and the sound velocity in the ink 16 is determined by the pitch P of the piezoelectric element array 10.
For s, Rv ≧ A · Ps ^−1/3 (2) However, when Ps is a [dot / inch] expression, A
= 22, when Ps is expressed in [dot / mm], A =
Unless the condition is 7.4, the focusing action of the ultrasonic beam itself does not appear.

The second feature of this embodiment is that the one-dimensional Fresnel diffraction band plate 17 is used as a means for focusing the ultrasonic beam emitted from the piezoelectric element array 10 in the sub-scanning direction. The effect of focusing the ultrasonic beam in the sub-scanning direction using the one-dimensional Fresnel diffraction band plate 17 in this way is as follows.

Conventionally, as the ultrasonic beam focusing means in the sub-scanning direction, a bulk acoustic cylindrical lens having the same shape in any array direction of the piezoelectric element array in the sub-scanning direction has been used. However, among the ultrasonic beams focused with a centripetal wavefront by the phased array scanning, they are incident vertically toward the lens surface or the lens surface near the center of the ultrasonic beam, whereas at both ends of the ultrasonic beam, there is an oblique angle. It will be incident at an angle. In particular, in order to narrow the beam width at the focal point as narrow as possible and increase energy efficiency, the F number (=
If you reduce the focal length / lens aperture to about 1,
The inclination of the incident angle with respect to the vertical axis at both ends is increased to nearly 30 °. When the inclination of the incident angle from the vertical axis becomes large, the curvature of the lens surface in the traveling direction of the incident beam becomes effectively large, so that the focal length for the ultrasonic beam incident on that portion becomes short. As a result, the ultrasonic beam cannot be focused at one point. Therefore, the efficiency is very poor, or the image quality is poor due to the irregular and unstable size of the ink particles, and the operation itself as an inkjet printer is difficult.

On the other hand, when the one-dimensional Fresnel diffraction band plate 17 is used for focusing the ultrasonic beam in the sub-scanning direction as in the present embodiment, the ultrasonic beam is incident in the direction extending in the linear band shape. Since the focal length does not change even if the angle changes, the above-mentioned problems in the case of using the bulk acoustic cylindrical lens are solved.

Further, the Fresnel diffraction band plate 17 having such a linear pattern has an advantage of being advantageous in the manufacturing process. That is, in the present embodiment, as shown in FIG. 5, the Fresnel diffraction band plate 17 having a linear pattern extending in the main scanning direction is formed on the surface of the glass substrate which is the ultrasonic interference layer 11 which also serves as the acoustic matching layer. , The individual electrode 1 having a linear pattern extending in the sub-scanning direction on the back surface of the glass substrate.
4 is formed on the common electrode 12 and the piezoelectric layer 13 which are laminated. Since each pattern is only a straight line without corners, it can be manufactured independently and finely and accurately. The positioning accuracy for combining the patterns on the front and back of the glass substrate may be much less than the accuracy for forming each pattern. Therefore, patterning suitable for high resolution can be produced by using an easy-to-handle manufacturing process.

Another advantage of using the one-dimensional Fresnel diffraction band plate 17 is that, as in the case of a cylindrical lens using a bulk material having a curved structure,
The point is that the focal position does not fluctuate and aberration does not occur depending on the incident angle of the ultrasonic beam.

(Second Embodiment) The basic structure of the second embodiment is the same as that of the first embodiment, but in this embodiment, a magnetostrictive oscillator is used as the ultrasonic wave generating element instead of a piezoelectric element. It is characterized by having been. In the second embodiment, the main structure of the recording head unit is the same as that in FIG.
A detailed description that has been shown and duplicated will be omitted. In the second embodiment, unlike the first embodiment, the magnetostrictive oscillators separated by the electrodes are used as the ultrasonic wave generating elements, and these are arranged in a one-dimensional array.

The magnetostrictive vibrator 13 is Te _0.3 Dy _0.7 Fe.
A material such as ₂ or Te _0.3 Dy _0.7 (Fe _0.9 Mn _0.1 ) ₂ is formed on the entire back surface of the ultrasonic interference layer 11 or in a band shape by a film forming method such as sputtering in which the thickness of the film can be arbitrarily controlled. Magnetic field applying elements (not shown) for applying a bias magnetic field are provided at both ends of the magnetostrictive vibrator 13. As the magnetic field applying element, a permanent magnet that does not have problems such as power consumption and heat generation is preferably used. Magnetostrictive oscillator 13
On the surface of the individual exciting coil 1 paired with the common electrode 12
4 are formed at a pitch corresponding to recording dots. The magnetostrictive vibrator array is formed in the array form.
In the step of forming 3, the step of forming island-shaped magnetostrictive vibrators at a pitch corresponding to the recording bits may be taken, and the thickness of the magnetostrictive vibrators 13 can be matched according to the wavelength of the ultrasonic waves used. Is designed.

The common electrode 12, the magnetostrictive vibrator 13, the magnetic field applying element and the exciting coil 14 constitute a magnetostrictive vibrator array 10 which is an ultrasonic wave generating element array. Also,
Actual inkjet head, eg 600dp resolution
In the case of a line type head having a length corresponding to the size of A4 size in the longitudinal direction of i, magnetostrictive vibrators of about 5000 elements are arranged in a line. In this case, the magnetostrictive oscillator array 10
Are arranged in a line at equal intervals determined by the required recording density. The other configurations are similar to those of the first embodiment, and thus the description thereof will be omitted.

An operation example of the ink jet head according to the second embodiment will be described with reference to FIGS. 6 (a) and 6 (b). FIG. 6A is a sectional view in a direction orthogonal to the magnetostrictive oscillator array, and FIG. 6B is a sectional view in a direction along the magnetostrictive oscillator array. FIG. 6A shows magnetic field applying means 14 a provided at both ends of the magnetostrictive vibrator 13 and applying a bias magnetic field to the magnetostrictive vibrator 13.

A burst voltage composed of an alternating current (or a pulse train) of a predetermined frequency is applied to a part of the arrayed magnetostrictive oscillator array 10, for example, individual exciting coils 141 to 144. Here, the applied AC frequency is at least the glass plate 1 that functions as an ultrasonic interference layer (acoustic matching layer).
The internal wavelength is longer than the pitch of the ultrasonic wave generating element (magnetostrictive vibrator 13) array. Then, of the individual exciting coils 141 to 144, an alternating current is applied to the inner two individual exciting coils 142 and 143, and the inner two individual exciting coils 142 to the outer two individual exciting coils 141 and 144. , 143, the phase is advanced (1/4 in this embodiment) to the burst voltage, mutual ultrasonic beams interfere with each other, and the piezoelectric element array 10 is lined up, as in Embodiment 3-3. A lens effect occurs in the array direction (main scanning direction). In the glass plate 1, there is no focusing in the direction (sub scanning direction) orthogonal to the array direction of the piezoelectric element array 10.

The ultrasonic beam reaching the boundary surface with the ink 16 is orthogonal to the array direction in which the piezoelectric element arrays 10 are arranged (sub-scanning direction) by the Fresnel diffraction band plate 17.
It receives a lens effect that is centripetally focused. That is, focusing in the main scanning direction is performed by the acoustic matching layer (ultrasonic interference layer).
Focusing in the sub-scanning direction is performed only within the ink 16, starting from within the glass plate 1 that functions as. At this time, since the thickness of the nozzle substrate 15 is selected and set in advance so as to be in focus, the nozzle substrate 15 is focused at the slit-shaped opening forming the nozzle hole and at the ink liquid surface stopped by the surface tension. Will be combined. Therefore, due to the ultrasonic beam pressure focused in the main scanning direction and the sub-scanning direction, ink particles easily fly from the surface of the ink liquid, and clear recording without density unevenness on the recording medium surface is performed.

As described above, in the second embodiment, four ultrasonic wave generating elements (magnetostrictive vibrators) are set as one group and
The essence is to shift the line in the main scanning direction at a timing of at least ¼ or to perform division driving to divide the line and perform a linear scanning operation on the plurality of individual exciting coils 14.

FIG. 7 schematically shows a case where four ultrasonic wave generating elements (magnetostrictive vibrators) 2 are grouped and focused into one dot. 7A to 7D
Indicate the following operations, respectively.

FIG. 7A shows that, of the grouped individual exciting coils 142, 143, 144, 145, AC is applied to the inner two individual exciting coils 143, 144 and the outer two individual exciting coils are applied. FIGS. 14A and 14B are schematic diagrams in the case of applying a burst voltage whose phase is advanced to the inner two individual exciting coils 143 and 144.

In FIG. 7B, of the individual exciting coils 143, 144, 145, 146 grouped next, alternating current is applied to the inner two individual exciting coils 144, 145, and the outer two are excited. FIG. 6 is a schematic diagram in the case where a burst voltage having a phase advanced from that of the inner two individual coils 144 and 145 is applied to the individual excitation coils 143 and 146.

In FIG. 7C, of the individual exciting coils 144, 145, 146, 147 which have been further grouped, AC is applied to the inner two individual exciting coils 145, 146, and the outer side 2 Individual excitation coils 144, 147
FIG. 4A is a schematic diagram in the case where a burst voltage whose phase is advanced from the inner two individual exciting coils 145 and 146 is applied.

FIG. 7D shows the individual exciting coils 141, 1
42, 143, 144, 145, 146, 147, 14
8 is the individual exciting coils 141, 142, 143, 144
Group of individual exciting coils 145, 146, 147
, 14 8 groups, and each group is driven at the same time to eject two ink droplets at a predetermined pitch.

In this embodiment, since one image point is recorded,
Four magnetostrictive transducer arrays form one group. However, if the number of magnetostrictive transducer arrays forming one group is increased, side lobes of the ultrasonic beams that are centripetally focused can be prevented and the energy density can be increased. It is possible to reduce the dispersion of ink droplets and the drive current of the magnetostrictive oscillator array.

Further, in the present embodiment, the focus position of the ultrasonic beam is set to the liquid surface with respect to the center of the grouped ultrasonic wave generating element group, and the liquid droplet is caused to fly in the direction perpendicular to the ultrasonic wave generating element group. It is also possible to shift the flight position by changing the timing of applying the burst voltage.

(Third Embodiment) FIG. 8 shows the structure of a recording head portion according to the third embodiment. In the present embodiment, the means for focusing the ultrasonic beam in the main scanning direction uses phased array scanning as in the first embodiment,
As a means for focusing in the sub-scanning direction, a bulk cylindrical lens 19 having the same curved structure as the conventional one is used.

In the case of the present embodiment, as shown in FIG. 9, the central portion (A-A ') which is perpendicularly incident on the lens 19.
Since the focal length (fa) of the beam is different from the focal length (fb) of the beam at the end (BB ′) incident on the lens 19 in an oblique direction, the focal length (fb) of The focusing characteristic is deteriorated, and the beams from both ends are refracted in a complicated three-dimensional surface, so that aberration is also generated.

Therefore, the recording head of this embodiment is more disadvantageous than the first embodiment in terms of energy efficiency for generating flying ink particles and uniformity of ink particles, but on the other hand, the cylindrical lens 19 Since the concave side is the ink chamber as it is, there is an advantage that an ink flow path having a large cross section can be formed. Therefore, only when it is desired to perform a high-speed recording operation, it is possible to supply a sufficient amount of ink to cover the speed, the change in the ink concentration due to the evaporation of the ink solvent from the nozzles is slow, and clogging is less likely to occur. There is an advantage.

(Fourth Embodiment) FIG. 10 shows the structure of a recording head portion according to the present embodiment. In this embodiment, the one-dimensional Fresnel diffraction band plate 17 is used without phased array scanning.
This is an example in which the ultrasonic beam is focused only by using it.

In the present embodiment, the piezoelectric element array 1
The wavelength of the ultrasonic beam emitted from 0 is set to a value sufficiently shorter than the pitch of the piezoelectric element array 10. The ultrasonic beam having such a short wavelength propagates straight in a direction perpendicular to the surface of the piezoelectric layer 13 without spreading, passes through the ink chamber as it is, and strikes the surface of the ink 16 to strike the ink 16 The ink particles 20 having a diameter close to the internal wavelength, that is, a particle diameter sufficiently small (or too small) for the required resolution are ejected.

According to the experiments conducted by the inventors, the ink 1 is ejected with an ultrasonic beam having a relatively longer wavelength than the flying ink particles 20 corresponding to the wavelength size of the ultrasonic beam as in the present embodiment.
Even when the surface of No. 6 is hit, since the ultrasonic beam has an intensity distribution that attenuates outward in the radial direction, the ink particles 20 are accurately and stably ejected from the central portion of the ultrasonic beam.

Regarding the problem that the flying ink droplets 20 are too small compared with the resolution, multiple dots recording, that is, multiple recording in which ink droplets are continuously ejected on the same image point, that is, so-called overwriting, is performed to make the image point It can be solved by gaining weight. The operation of thickening the image points by this overwriting is a high-speed repeating operation that allows the subsequent flying ink to reach before the preceding flying ink is absorbed by the recording paper and fuse the dots in the state of ink drops. It can be put into practical use only by a method capable of generating ink drops in a cycle. Therefore, this can be said to be a peculiar effect unique to the ink jet recording apparatus having the characteristic of high-speed recording.

Further, according to the present embodiment, the burst width of the burst voltage applied to the piezoelectric element is controlled by utilizing the characteristic that it is possible to continuously generate very fine ink particles. It is also possible to realize gradation recording with high image quality, which is practically difficult to realize with the inkjet printer of. In addition, this embodiment is suitable for recording with high resolution because it is a method of using an operation area in which ink particles are fine.

As described in the first embodiment, a high-resolution element array can be realized by combining the linear pattern of the Fresnel diffraction band plate 17 with the linear pattern of the individual electrodes 14 orthogonal to it. Therefore, the Fresnel diffractive band plate 17 has an effect of sufficiently bringing out the capability of this embodiment suitable for high resolution recording.

(Fifth Embodiment) As described in the first embodiment, some restrictions are required to realize phased array scanning such as linear scanning. But,
As the recording resolution (recording density) or the pitch of the piezoelectric element array 10 becomes finer, such a restriction becomes loose. FIG. 11 and FIG. 12 show such a relationship. FIG. 11 shows a phased array possible area when linear scanning recording is performed at a density 1.5 times the pitch of the piezoelectric element array 10, and FIG. 12 shows linear scanning recording when density is twice the pitch of the piezoelectric element array 10. The respective phased array possible areas of are shown.

13 and 14 show the piezoelectric element array 10.
Shows the change in the position of the recording image point on the recording medium when the pitch of the recording medium is changed. Reference numeral 21 is a scale showing the pitch of the piezoelectric element array 10, and reference numeral 22 is a scale showing the resolution of the recording image point. Shows. When the pitch of the piezoelectric element array 10 becomes 330 lines / inch or more,
3, the linear scanning recording with a pitch 1.5 times the piezoelectric element array 10, that is, a resolution of 500 dpi can be performed. Further, when the pitch of the piezoelectric element array 10 becomes 400 lines / inch or more, as shown in FIG.
It is possible to perform a linear scanning recording with a recording density twice as high as the pitch of, that is, 800 dpi.

(Sixth Embodiment) In this embodiment, a method for constructing a drive circuit of a recording head used in the ink jet recording apparatus of the present invention will be described.

In the ink jet recording apparatus of the present invention, the piezoelectric element array 10 generates an ultrasonic beam having a frequency synchronized with the alternating voltage or pulse voltage of a constant frequency applied in a burst manner. In this case, in order to perform the above-mentioned phased array scanning, it is necessary to set the phases of the ultrasonic beams generated from the adjacent piezoelectric elements so that they are focused at predetermined positions.

A drive circuit for performing linear scanning by focusing the ultrasonic beams emitted from a plurality of piezoelectric elements at a fixed depth position has already been put to practical use as an ultrasonic diagnostic apparatus in the field of medical equipment. For example, Japanese Patent Publication No. 62-152
It has been proposed at 15 mag. On the other hand, in a thermal printer head that drives closely arranged heating elements and an inkjet printer head that uses the pressure of steam described above, a configuration in which a drive circuit for linear scanning is integrally mounted on the head substrate is also known. And, for example, JP-A-62-62
-21465 etc. are proposed. However, regarding the configuration in which a drive circuit for performing phased array scanning such as linear scanning is integrally mounted on a head substrate on which a piezoelectric element array that generates an ultrasonic beam is formed, a new and unique effect is obtained. No particular construction method is found.

By the way, in an ink jet recording apparatus using an ultrasonic beam, it has been known that the flying ink particles strongly depend on the frequency of the ultrasonic wave. Is required in the range of several tens of MHz to several hundreds of MHz. In order to drive the piezoelectric element array by applying such a high frequency voltage to each piezoelectric element and to control the drive phase with the accuracy required for performing the phased array scanning, a delay due to a long wiring distance is required. Regarding the size and the delay variation in the scanning circuit, the nanosecond (10
^It is necessary to consider on the order of ^-9 seconds. With respect to this problem, the inventors actually made the following circuits and conducted experiments to compare their performances. That is, as for the oscillator for obtaining the used frequency, (A1) a CR oscillating circuit including a delay circuit including a capacitor and a resistor in each IC chip and a buffer circuit (A2) a ring in which a plurality of buffer circuits are connected in cascade Oscillator (A3) Three configurations of guiding signals from an external crystal oscillator circuit to the IC via the printed wiring on the head substrate, and driving of each piezoelectric element necessary for performing phased array scanning. Regarding the delay control for giving a phase difference, (B1) a delay circuit consisting of capacitors and resistors in each IC chip (B2) a delay circuit in which a plurality of buffer circuits are connected in cascade (B3) delayed by an external circuit The performance of each of the three configurations for leading to the IC via the plurality of printed wirings on the plurality of signal head substrates was compared. As a result of this comparison experiment, the method that can minimize the error in the individual circuit and between the adjacent circuits and obtain the necessary accuracy is (A
3) and (B3).

The results of this experiment suggest that a circuit for driving the individual piezoelectric elements requires a data selector circuit. That is, in reality, a drive circuit which is formed as an IC and arranged on the head substrate is required in accordance with each timing from a plurality of printed wirings that run in parallel with each other and supply pulse trains having different phases. It has been found that an operation of selecting a pulse having a different phase is required and therefore a data selector circuit is required. By providing this data selector circuit, it is possible to realize a compact and simple drive circuit having a function of applying to the piezoelectric element array a burst-like pulse voltage having an accurate predetermined phase difference necessary for performing phased array scanning. be able to.

The most typical example of a compact drive circuit IC mounted on a head substrate is a thermal head drive IC. As shown in FIG. 16, a thermal head driving IC generally has a shift register 41 for image data transfer capable of inputting / outputting to / from another chip and image data sent through the shift register 41 in parallel. And a gate / driver 43 that controls passage of a common pulse that determines the timing and width according to the image data held in the latch circuit 42. The output pulse voltage of the gate / driver 43 causes the thermal The heating dots (heating resistance elements) of the head TPH are configured to be energized and driven.

In order to drive the piezoelectric element array in the ink jet recording apparatus using the ultrasonic beam to perform the phased array scanning, it is necessary to replace the part of the gate / driver 43 in FIG. 16 with another circuit. As described above, in order to realize the phased array scanning, it is preferable to select a necessary pulse train from several types of continuous pulse trains having different phases. That is, it is necessary to make the final stage a data selector instead of a gate.
Therefore, the recording head driving IC of the inkjet recording apparatus using the ultrasonic beam may be composed of the shift register 31, the latch 32, and the data selector / driver 33, as an example is shown in FIG.

That is, in FIG. 15, the shift register 31 sequentially transfers the image data serially input according to the clock pulse. The image data taken in the shift register 31 is transferred to the latch 32 in parallel,
It is temporarily stored. The image data temporarily stored in the latch 32 is the data corresponding to two adjacent piezoelectric elements, and the data selector / driver 33 for driving each piezoelectric element 34 has control signal codes S11, S21, S12, S2.
2, S13, S23, S14, S24, ... (However, S1
4, S24 is given as (not shown). The data selector / driver 33 uses a plurality of pulse trains φ having different phases.
1, φ2, φ3, ... Are given as inputs, and φ1, φ are supplied in accordance with the control signal code supplied from the latch 32.
The piezoelectric element is driven by selecting a pulse train having a phase of 2, φ3, ..., Amplifying the pulse train to an appropriate voltage value and applying it to the individual electrode of the corresponding piezoelectric element. By such operation, phased array scanning becomes possible.

As an example of the operation of this recording head drive circuit, as shown in FIGS. 2 and 3, four adjacent piezoelectric elements are set as one unit and linear scanning is performed by driving them by shifting their phases. This will be specifically described. In this case, the control signal codes supplied from the latch 32 to the data selector / driver 33 are S11 = 0, S12 = 1, S
21 = 1, S22 = 0, S13 = 1, S23 = 0, S1
When 4 = 0 and S24 = 1 are set, for example, the phase φ advanced to φ2 to two outer piezoelectric elements out of the four piezoelectric elements
The burst voltage of 1 is applied, and the burst voltage of phase φ2 is applied to the two inner piezoelectric elements.
Similar to (b), the ultrasonic beam is focused in the main scanning direction and applied to the ink. The image data input to the shift register 31 is the control codes S11, S21, S12, S22, S13, S23, when the recording image points are formed.
Data obtained by converting the original image data by an image data processing circuit (not shown) is input so that S14, S24, ... Have the above values. Original image data is 0,
That is, when the data does not form a recording image point, the image data input to the shift register 31 is S11 and S2.
1, S12, S22, S13, S23, S14, S2
The image data processing circuit performs conversion processing so that all 4, ...

The structure of the drive circuit shown in FIG. 15 is novel in the following points. (1) The final stage is not a simple gate but a data selector (data selector / driver 33).

(2) The plurality of signal wirings for supplying the pulse train selected by the data selector / driver 33 should be wired as a common line for each piezoelectric element in the head substrate.

(3) A multi-bit signal for controlling the data selector / driver 33 is input to the serial input line for inputting image data to the shift register 31.

Regarding (3), parallel input can be used instead of serial input as shown in FIG. The former has the advantage that the number of input / output terminals of the driving IC is small, and the latter has the advantage that the transfer speed does not have to be reduced.

Further, according to such a recording head drive circuit, when it is necessary to control the size of the flying ink particles, the pulse having the required frequency is selected from the continuous pulse trains having different frequencies. The control can be easily realized. The present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made without departing from the scope of the present invention.

[0094]

According to the present invention, the following effects can be obtained. In the ink jet recording apparatus of the first invention, a short ultrasonic wavelength is required to fly small ink particles for high resolution recording, and a long ultrasonic wavelength is required to realize phased array scanning. The conventional conflicting conditions can be eliminated. As a result, in the conventional staggered piezoelectric element array, the image noise caused by the structure of the head was large, whereas in the present invention, the image noise is reduced by using the piezoelectric element array in which the piezoelectric elements are arranged in a line. It is possible to suppress, and at the same time, troubles such as clogging hardly occur, and it is possible to realize a line scanning type nozzleless recording head.

Further, since the ink jet recording apparatus of the first invention can be constructed so as not to use the curved lens, it becomes possible to use the manufacturing process with high accuracy and reliability such as optical lithography in the plane. As a result, it was possible to avoid the peculiar aberration and the like that occurred when performing phased array or linear array scanning with a bulk acoustic lens having a curved surface structure.

Further, according to the present invention, it is possible to obtain a recording head drive circuit having a simple circuit configuration for performing phased array scanning with an ultrasonic beam, and thereby the recording head drive circuit is mounted on the head substrate. It is possible to realize a compact recording head for inkjet recording.

According to the third invention, a linear array head can be easily realized by electronically focusing. This means that it is not necessary to adopt a configuration in which a plurality of arrays are arranged side by side even when the pixel density is increased, and image noise caused by the configuration in which a plurality of arrays are arranged side by side in a staggered manner is also eliminated. Significant reduction and suppression.

Further, since the ink droplets flying from the slit-shaped nozzle holes are always uniform and have a constant direction, a sharp image without density unevenness is recorded. In other words, the clogging of the ink droplets does not occur, and the non-uniformity of the pixel pitch due to the deviation of the flight direction of the ink droplets as in the case of phased array scanning is also eliminated. While it does not require the correction and control mechanism of the above, it functions sufficiently as a nozzleless head for inkjet line production. Therefore, the present invention brings many advantages in practical use in combination with the structure of the recording apparatus, the simplification of the system, the downsizing, and the ease of maintenance. Further, it is possible to realize a high-speed and high-speed line scanning type inkjet recording apparatus.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a recording head unit of an inkjet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the embodiment.

FIG. 3 is an explanatory diagram of phased array scanning in the same embodiment.

FIG. 4 is a diagram showing a relationship between the wavelength of ultrasonic waves and the size of a recording image point.

FIG. 5 is a diagram showing a positional relationship between a Fresnel diffraction band plate and a piezoelectric element array in the same embodiment.

FIG. 6 is a diagram for explaining an operation example of the inkjet head according to the second embodiment.

FIG. 7 is an explanatory diagram of phased array scanning in the same embodiment.

FIG. 8 is a configuration diagram of a recording head unit of an inkjet recording apparatus according to a third embodiment of the invention.

FIG. 9 is a diagram showing a changing focus position in the same embodiment.

FIG. 10 is a configuration diagram of a recording head unit of an inkjet recording apparatus according to a fourth embodiment of the invention.

FIG. 11 is a diagram showing a region where a recording density of 1.5 times the pitch of the piezoelectric element array according to the fifth embodiment is possible.

FIG. 12 is a diagram showing a region where a recording density twice as large as the pitch of the piezoelectric element array according to the same embodiment is possible.

FIG. 13 is a diagram showing recording image point positions during 1.5-fold density recording according to the embodiment.

FIG. 14 is a diagram showing recording image point positions during double-density recording according to the same embodiment.

FIG. 15 is a circuit diagram of an inkjet recording head drive circuit according to a sixth embodiment of the invention.

FIG. 16 is a circuit diagram of a thermal head drive circuit mounted on a conventional head substrate.

[Explanation of symbols]

 10 ... Piezoelectric element array 11 ... Ultrasonic interference layer 12 ... Common electrode 13 ... Piezoelectric layer (magnetostrictive oscillator) 14 ... Individual electrode 15 ... Nozzle substrate 16 ... Ink 17 ... Fresnel diffraction band plate 18 ... Drive circuit 19 ... Cylindrical lens 20 ... Flying ink particles 21 ... Scale showing the pitch of the piezoelectric element array 22 ... Scale showing the resolution of recording image points 31 ... Shift register 32 ... Latch 33 ... Gate / driver 41 ... Shift register 42 ... Latch 43 ... Data selector / driver

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H04N 1/23 101 Z (72) Inventor Hideki Nukata 1 Komukai Toshiba Town, Kawasaki City, Kanagawa Prefecture Incorporated company Toshiba Research and Development Center (72) Inventor Akira Takayama 1 Komukai Toshiba Town, Kouki, Kawasaki City, Kanagawa Prefecture Incorporated Toshiba Research and Development Center (72) Inventor Noriko Kudo Komukai, Kawasaki City, Kanagawa Prefecture Toshiba Town No. 1 Incorporated company Toshiba Research & Development Center (72) Inventor Shiro Saito Komukai, Kouki-ku, Kawasaki City, Kanagawa Prefecture No. 1 Toshiba Town Co. Ltd. Toshiba Research & Development Center (72) Inventor Tsutomu Saito Kawasaki City, Kanagawa Prefecture Komukai-Toshiba-cho, Saiwai-ku 1 Incorporated company Toshiba Research and Development Center (72) Inventor Fumihiko Murakami Komukai-Toshiba-cho, Kawasaki, Kanagawa Stock company Toshiba Research & Development Center (72) Inventor Masami Sugiuchi 70 Yanagimachi, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Yanagimachi Factory, Toshiba Corporation (72) Inventor Chiaki Komukai, Toshiba-cho, Kawasaki City, Kanagawa Prefecture Inside the Toshiba Research and Development Center

Claims (6)

[Claims] 1. In an inkjet recording apparatus for recording an image on a recording medium by ejecting particle-shaped ink from a liquid surface of the ink by the pressure of the ultrasonic beam, a plurality of ultrasonic wave generating elements for emitting the ultrasonic beam are provided. An ultrasonic wave generating element array arranged in a row and ultrasonic wave interference that causes ultrasonic wave beams emitted from each ultrasonic wave generating element of the ultrasonic wave generating element array to interfere with each other inside and to be focused in the ink. An ink jet recording apparatus comprising: a layer. 2. In an ink jet recording apparatus for recording an image on a recording medium by ejecting particulate ink from the liquid surface of the ink by the pressure of the ultrasonic beam, a plurality of ultrasonic wave generating elements for emitting the ultrasonic beam are provided. An ultrasonic wave generating element array arranged in an array, and by simultaneously driving a part of the ultrasonic wave generating element array, a plurality of ultrasonic waves emitted from the ultrasonic wave generating elements interfere with each other in the main scanning direction. A driving unit that applies a plurality of pulse trains having different phases to the ultrasonic wave generating element so that the ultrasonic waves are focused, and sequentially shifts the simultaneous driving elements in the main scanning direction, and a superimposing unit in a direction perpendicular to the main scanning direction. An inkjet recording apparatus comprising: a focusing unit that focuses a sound wave. 3. An ink jet recording apparatus for recording an image on a recording medium by ejecting atomized ink from the liquid surface of the ink by the pressure of the ultrasonic beam, wherein a plurality of ultrasonic wave generating elements for emitting the ultrasonic beam are provided. An ultrasonic wave generating element array arranged in a row and a plurality of ultrasonic waves emitted from the ultrasonic wave generating elements by simultaneously driving a part of the ultrasonic wave generating element array interfere with each other to perform main scanning. So that the ultrasonic waves are focused in a direction, a plurality of pulse trains having different phases are applied to the ultrasonic wave generating element, and the simultaneous drive elements are sequentially displaced in the main scanning direction, and a drive means that is perpendicular to the main scanning direction. Focusing means for focusing the ultrasonic wave on the ultrasonic wave, the focusing means being composed of a plurality of parallel linear band patterns extending in the same direction as the main scanning direction. An ink jet recording apparatus which comprises a Fresnel diffraction zone plate for focusing the ultrasonic beam emitted from the generating element in said ink. 4. In an ink jet recording apparatus for recording an image on a recording medium by ejecting particulate ink from the liquid surface of the ink by the pressure of the ultrasonic beam, a plurality of ultrasonic wave generating elements for emitting the ultrasonic beam are provided. An ultrasonic wave generating element array arranged in a line; and a plurality of parallel linear strip patterns extending in the same direction as the ultrasonic wave generating element array direction of the ultrasonic wave generating element array, An inkjet recording apparatus comprising: a Fresnel diffraction band plate that focuses an ultrasonic beam emitted from each ultrasonic generating element of the generating element array into the ink. 5. A shift register for transferring input image data, a latch for temporarily storing image data output in parallel from the shift register, and a plurality of latches according to the image data temporarily stored in the latch. 7. A drive circuit comprising a data selector / driver that selects one of a plurality of pulse trains having different phases input from a common signal line and drives the piezoelectric element array according to the pulse train. 1 to any one of claim 4
Inkjet recording apparatus according to the item. 6. An ink jet recording apparatus for recording an image on a recording medium by ejecting particle-shaped ink from the liquid surface of the ink by the pressure of an ultrasonic beam, and an ultrasonic wave generating element group arranged in an array, An ink jet nozzle hole in the shape of a slit that receives an ultrasonic beam emitted from the ultrasonic wave generation element group and flies the ink that has been atomized from the ink surface, and one of the ultrasonic wave generation element groups arranged in the array. Ultrasonic beam focusing means for focusing the ultrasonic beam on one point on the ink surface facing the slit-shaped ink jet nozzle hole, and the grouped ultrasonic wave generating element group. Control for sequentially switching the group combination of the above to control the focal point of the ultrasonic beam to the ink surface facing the slit-shaped ink jet nozzle hole. An ink jet recording apparatus characterized by comprising a stage, a.