JPH11235820A - Recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording head capable of recording a high resolution image by ejecting small ink drops without using a nozzle. SOLUTION: When an input signal from a signal generating means 32 is inputted to a vibration generating means 24 in accordance with an image signal, a piezoelectric element 26 is vibrated and a electrode section 28A is excited, then an elastic section 28B of an elastic electrode 28 is subjected to bending vibration. As a result, a capillary wave is generated at a portion in the vicinity of a tip section 34B of the elastic member 34, then small ink drops are continuously ejected one by one. An oil slick material absorption member 40 is provided to a plate 16, then an oil slick 42 is formed by an oil slick material leaking from the oil slick material absorption member 40. By the oil slick 42, the evaporation of water from ink 20 in an ink chamber 18 is prevented so that the ink 20 is not dried. Consequently, the residuary of the ink 20 is not adhered to the elastic member 34, a wall 14 of the ink chamber or the plate 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording head for recording an image by flying ink droplets and landing them at a predetermined position on a recording medium.

[0002]

2. Description of the Related Art A typical example of an ink jet recording system for performing printing by ejecting droplets, particularly ink droplets, onto a surface to be printed is a system using a nozzle. A demand type and a continuous flow type are known.

[0003] The on-demand type is a system in which ink is intermittently ejected from nozzles in accordance with recording information to perform printing, and typical types include a piezo oscillator type and a thermal type. The piezo vibrator type applies a pulse voltage to a piezoelectric element attached to the ink chamber to deform the piezoelectric element, thereby changing the ink liquid pressure in the ink chamber, and ejecting ink droplets from nozzles to form dots on recording paper. It is to be recorded. In the thermal type, ink is heated by a heating element provided in an ink chamber, and ink droplets are ejected from nozzles by bubbles generated thereby to record dots on recording paper.

On the other hand, in the continuous flow type, ink is continuously ejected from a nozzle by applying pressure to ink, and at the same time, vibration is applied by a piezo vibrator or the like to form a protruding ink column into droplets. The recording is carried out by selectively charging and deflecting.

In each of these methods, the diameter of the ink droplet is mainly determined by the diameter of the nozzle. When the nozzle diameter is reduced, nozzle clogging due to dust or dust,
There is a problem that the ink discharge direction changes due to the adhesion of the ink residue to the nozzle circumference.

[0006] On the other hand, there have been proposed some recording systems for performing printing by ejecting ink droplets onto a surface to be printed without using a nozzle. For example, US Pat. No. 4,308,547
As shown in the specification, there is a recording method in which a spherically curved piezoelectric body shell that is concavely curved is disposed in ink, and a voltage is applied to the piezoelectric body shell through an electrode. In this method, longitudinal waves radiated into the ink from the piezoelectric shell are collected at one point on the free ink surface, and ink droplets are ejected from the free ink surface.

Further, as disclosed in Japanese Patent Publication No. 6-45233, a spherical concave portion is provided on a substrate such as glass, which is used as an acoustic lens, and a piezoelectric body and a voltage There is also a recording method in which a vibrator composed of electrodes for applying a voltage is formed and the vibrator is arranged in ink.

Further, Japanese Patent Application Laid-Open No. 3-200199 discloses a recording method in which a thin-film flat plate-shaped phase Fresnel lens is provided on a substrate instead of a concave lens as an inexpensive and sharper focusing lens. It is shown.

In the above-described system in which longitudinal waves are focused on the free ink surface and ink droplets are ejected from the free ink surface, the diameter of the ink drops is substantially equal to the focused diameter of the longitudinal waves, and the focused diameter d is If the drive frequency of f is f and the F value of the lens is F, d to F / f. When the wavelength of the longitudinal wave propagating in the ink is λ and the propagation speed is v, there is a relation v = f · λ between these and the driving frequency f of the vibrator.

Therefore, for example, in a case where a very small ink droplet having a diameter (converging diameter) d of about 15 μm is to be ejected, if the F value of the lens is set to 1, the conventional low-viscosity, aqueous Since the propagation velocity v of the longitudinal wave in the ink is approximately 1500 m / sec, the driving frequency f of the vibrator must be set to a very high frequency such as about 100 MHz. Since it is practically difficult to make the F value of the lens extremely small due to various problems, the diameter d of the ink droplet
If one wishes to reduce, the vibrator must generally be driven at a higher frequency.

As described above, in the method in which longitudinal waves are focused on the free ink surface and ink droplets are ejected from the free ink surface, a plurality of vibrators must be driven at a high frequency of about 100 MHz. Causes the cost problem that the ink becomes expensive, and the heat generated by the absorption changes the ink viscosity, causing the diameter of the ink droplet to fluctuate, or causing the ink itself to dry or solidify in the recording element, making it impossible to discharge the ink. Can cause serious problems.

As a prior art other than the above, Japanese Patent Application Laid-Open No.
Japanese Patent No. 40070 discloses a new on-demand type recording method. This is to resonate a beam of cantilever structure by bending vibration, generate sufficient amplitude at the tip of the beam and fly ink, and it is possible to eject ink at a relatively low excitation frequency and low voltage. This is a recording method that has characteristics. However, this recording method uses a mechanism for forming ink droplets via a nozzle provided at the tip of the beam, and the diameter of the ink droplet is determined by the nozzle diameter, as in the various nozzle-type recording methods described above. Therefore, when the nozzle diameter is reduced, there is a problem that the ink ejection direction changes due to nozzle clogging and adhesion of ink residue to the nozzle circumferential portion. Japanese Unexamined Patent Publication No. 6-3400
The technique disclosed in Japanese Patent No. 70 is one of the technical problems to be solved to reduce the possibility of nozzle clogging as compared with the conventional method, however, the diameter of the ink droplet is determined by the nozzle diameter. It cannot be a fundamental solution.

As yet another prior art, a method of forming fine liquid by applying vibration energy, which is not an ink jet recording method, is disclosed in Japanese Patent Application Laid-Open No. 3-154665.
No., published in Japanese Patent Application Publication No. This method is intended to be applied to an atomizing device, and includes a vibrator including a piezoelectric ceramic,
The vibrating part is fixed to the vibrator and bends and vibrates in the form of a cantilever. A part of the vibrating part is immersed in a liquid, and mist-like liquid droplets are generated by radiation of ultrasonic waves. However, with the technology used in this atomizing device, although it is possible to generate minute diameter ink droplets without using a nozzle,
Since a large number of ink droplets that are not temporally and spatially controlled are generated, the method cannot be applied to an ink jet recording apparatus that needs to accurately land ink droplets at a predetermined position on a recording medium.

As described above, in recent years, high-resolution image recording on a recording medium has been increasingly demanded. However, even if any conventional recording method or a technique in another field such as an atomizing apparatus is used, these demands can be met. Difficult to respond to.

[0015]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a recording head capable of discharging fine ink droplets without using a nozzle and capable of recording a high-resolution image.

[0016]

According to the first aspect of the present invention, a vibration generating means for generating a vibration in response to an image signal, an ink chamber for storing ink, and the vibration chamber disposed in the ink chamber. An elastic member that bends and vibrates in response to the excitation of the generating means; and a recording head that causes ink droplets to fly from a thin ink film formed on the surface of the elastic member that bends and vibrates and adheres the ink droplets to a recording medium. And an oil film material supply means for supplying an oil film material to the surface of the ink stored in the ink chamber.

Therefore, when the vibration generating means generates vibration in response to the image signal, the elastic member bends and vibrates in response to the excitation. The elastic member is disposed in the ink chamber, and ink droplets fly from an ink thin film formed on the surface of the elastic member due to bending vibration, thereby recording dots on a recording medium.

As described above, since fine ink droplets can be ejected without using a nozzle, an ink ejection failure due to nozzle clogging, a change in the ink droplet ejection direction due to adhesion of ink to the periphery of the nozzle, and the like occur. And high-resolution images can always be accurately recorded.

An oil film material is supplied to the ink surface in the ink chamber by oil film material supply means, and an oil film is formed on the ink surface. The oil film prevents the ink from evaporating, so that the ink does not increase in viscosity due to the evaporation, nor does ejection failure due to deposition and adhesion of solid matter occur. Further, wasteful consumption due to evaporation of the ink can be prevented, and the amount of ink consumption can be reduced to the minimum necessary for discharging the ink droplets. The water does not evaporate and the density does not change.

According to a second aspect of the present invention, in the first aspect of the present invention, it is preferable that the oil film material supply means is arranged at a position in contact with the surface of the ink stored in the ink chamber. Features.

That is, since the oil film material supply means is always in contact with the surface of the ink in the ink chamber, the oil film material supplied from the oil film material supply means does not pass through the air or ink. The oil quickly reaches the surface and an oil film is formed. Further, since the oil film material does not adhere to portions other than the surface of the ink (for example, the chamber wall forming the ink chamber), the oil film material supplied from the oil film material supply means is not wasted, An oil film can be formed on the surface of the ink in the ink chamber.

Further, the oil film material supply means can keep the meniscus of the ink by always contacting the surface of the ink in the ink chamber.

According to a third aspect of the present invention, in the second aspect of the present invention, the oil film material supply means comprises an oil film material impregnating member capable of impregnating the oil film material therein. I do.

Therefore, when the film thickness of the oil film formed on the surface of the ink in the ink chamber becomes thin, the oil film material is drawn out from the oil film material impregnated member by the surface tension of the ink, and seeps into the ink surface of the ink chamber. As described above, by using the surface tension of the ink to supply the oil film material, it is possible to always supply an appropriate amount of the oil film material and to keep the film thickness of the oil film constant.

Further, since the surface tension of the ink is used for supplying the oil film material, there is no need to provide a supply device (for example, a pump or the like) for actively supplying the oil film material from the oil film material supply means. It's easy. Further, since the supply device is not required, the thickness of the oil film can be maintained constant regardless of whether the power is on or off.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the oil film material supply means contacts the ink stored in the ink chamber and is separated from the surface of the ink. Characterized by being arranged in

Therefore, the oil film material can be supplied by generating a pressure difference between the oil film material supply means and the ink chamber (particularly, a portion of the ink chamber which communicates with the oil film material supply means). Therefore, the oil film material supply means can be provided at an arbitrary location. The pressure difference can be generated by a pressure difference generating means such as a volume pump or a piezoelectric element.

In consideration of the fact that the oil film material is consumed as the ink flies, the consumption of the oil film material is counted from the ink consumption, and based on the count value, the pressure difference generating means is operated. It can be driven to supply oil film material. This makes it possible to supply an oil film material according to the amount of ink consumed. For example, even when the ink consumption varies depending on the use frequency and use environment, it is possible to supply an appropriate amount of the oil film material correspondingly.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the oil film material supply means is arranged at a position separated from the ink stored in the ink chamber. I do.

Therefore, the oil film material directly reaches the surface of the ink in the ink chamber without moving in the ink, so that the oil film can be formed quickly.

In order to supply the oil film material directly to the surface of the ink in the ink chamber as described above, for example, an oil film material supply means may be disposed directly above the ink chamber, and the oil film material may be dropped by gravity. However, if the oil film material is dropped by using a spray or the like so that the oil film material has a vertically downward velocity component, the oil film material can be supplied more quickly to form an oil film. Further, the oil film material may be supplied in the form of a mist by spraying or the like, and in this case, the oil film material can be quickly supplied to a wide range.

Further, the oil film material supply means does not necessarily need to be arranged directly above the ink chamber. Even if the oil film material supply means is not arranged right above the ink chamber, the dropped oil film material reaches the surface of the ink in the ink chamber,
The oil film material may be dropped with a predetermined horizontal velocity component.

Further, since the oil film material supply means is separated from the ink stored in the ink chamber, the oil film material supply means and the ink chamber can be relatively moved. By performing the relative movement in this manner, even when the area in which the oil film is formed is large, the oil film material can be uniformly supplied to this area by a small number of oil film material supply means. Also, since the number of oil film material supply means is reduced, the degree of freedom in layout such as the mounting position is increased.

Further, in the same manner as in the fourth aspect of the present invention, the consumption of the oil film material can be counted from the ink consumption, and the oil film material can be supplied based on the counted value. This makes it possible to supply an oil film material according to the amount of ink consumed.

[0035]

1 and 2 show a first embodiment of the present invention.
1 shows a schematic configuration of a recording head 10 according to the embodiment.

The recording head 10 has a substrate 12 formed in the shape of a long flat plate, and a width direction of the substrate 12 (the left-right direction in FIG. 1).
It has an ink chamber 18 surrounded by a pair of ink chamber walls 14 erected vertically upward from the vicinity of both ends, and a plate 16 fixed to the upper edge of the ink chamber wall 14. A predetermined amount of ink 20 is stored in the ink chamber 18.
The surface of the ink 20 is in contact with the plate 16, and the plate 16 functions as a meniscus holding unit that holds the meniscus of the ink 20.

An ink supply path 22 is formed at the lower end of one of the ink chamber walls 14 (the left side in FIGS. 1 and 2), and the ink is supplied from an ink tank (not shown) into the ink chamber 18. 20 are supplied.

On the upper surface of the substrate 12, a plurality of vibration generating means 24 are fixed at predetermined intervals along the longitudinal direction of the substrate 12. As shown in detail in FIG. 1, the vibration generating means 24 includes a piezoelectric vibrator 26 formed in a plate shape having a constant thickness,
Electrodes 28 and 30 are attached to the upper and lower surfaces of the piezoelectric vibrator 26 by thermocompression bonding or the like. Signal generating means 32 is connected to the electrodes 28 and 30, and an alternating voltage corresponding to an image signal is input from the signal generating means 32. Thereby, the electrode 2
An alternating electric field is applied between 8 and 30, and the vibration generating means 2
The fourth piezoelectric vibrator 26 vibrates.

As the vibration generating means 24, any means can be used as long as it generates vibration in response to an electric signal input from the signal generating means 32, and a piezoelectric material, a magnetostrictive material, a mechanical actuator, or an electrostatic force is applied. An actuator or the like can be applied. Among them, piezoelectric materials are widely used as functional materials for ink jet printers, and are most suitable because advanced manufacturing techniques have been established.

As the piezoelectric material, quartz, lead zirconate titanate (PZT), barium titanate BaTiO ₃ , lead niobate PbNb ₂ O ₆ , bismuth germanate Bi ₁₂
GeO ₂₀ , lithium niobate LiNbO ₃ , lithium tantalate LiTaO _3, etc., a polycrystalline or single crystal, or a piezoelectric thin film such as ZnO or AlN, or polyurea, P
A piezoelectric polymer such as a copolymer of VDF (polyvinylidene fluoride) and PVDF, or a composite of an inorganic piezoelectric substance such as PZT and a piezoelectric polymer can be used.

The elastic member 3 is provided on the upper surface of the vibration generating means 24.
4 are erected. The elastic member 34 is connected to the recording head 10.
Has a predetermined thickness in the width direction (horizontal direction in FIG. 1), and is formed in a rectangular plate shape in a side view. Also, the base end 34
A is fixed to the vibration generating means 24, and the end portion 34B is a free end, that is, a so-called cantilever shape. The height of the elastic member 34 depends on the ink 20 stored in the ink chamber 18.
The surface of the elastic member 34 has a predetermined height so as to contact the vicinity of the upper end of the elastic member 34 due to surface tension, affinity (wetting) between the ink 20 and the surface of the elastic member 34, gravity acting on the ink 20, and the like.

In order to protect the vibration generating means 24 and the elastic member 34 from deterioration, corrosion, adhesion of foreign matter, etc. due to interference with the ink 20 and the like, the surface of the vibration generating means 24 and the elastic member 34 is formed by a thin film 36 of PTFE or the like. Is effective.

When an alternating electric field is applied between the electrodes 28 and 30 and the piezoelectric vibrator 26 of the vibration generating means 24 vibrates, the vibration excites the elastic member 34 at the resonance frequency.
It bends and vibrates (the direction of arrow A in FIGS. 1 and 3). In particular, since the vicinity of the distal end portion 34B of the elastic member 34 bends and vibrates with a large amplitude, the ink droplet 46 is ejected from the thin film of the ink 20 formed on both sides in the thickness direction of the elastic member 34, and the recording paper as a recording medium is formed. Fly towards.

As the elastic member 34, the vibration generating means 24
The material, shape, and the like are not particularly limited as long as they are members that can convert the vibrations into bending vibrations and can generate a sufficient amplitude for ejecting ink droplets in the vicinity of the distal end portion 34B. From the viewpoint, metal materials such as stainless steel and nickel are preferable. Further, a polymer material such as a polyimide resin, PET, an epoxy resin, and a cyanoacrylate resin can also be used.

A circular hole 38 is formed in the plate 16 at a position corresponding to the elastic member 34. Due to the formation of the hole 38, the vicinity of the upper end of the elastic member 34 protrudes above the plate 16 without hitting the plate 16.

An oil film material impregnating member 40 formed in a ring shape is disposed on the inner edge of the hole 38 as oil film material supply means. The oil film material impregnated member 40 functions as meniscus holding means for holding the meniscus of the ink 20 by contacting the surface of the ink 20 like the plate 16.

The oil film material impregnated member 40 has an oil film material impregnated therein, and the oil film material exuded from the oil film material impregnated member 40 forms an oil film 42 on the surface of the ink 20. As described above, since the oil film 42 is formed on the surface of the ink 20, the evaporation of the water in the ink 20 can be prevented,
The ink 20 is hard to dry, and the density of the ink 20 does not change. Further, the residue of the ink 20 due to the evaporation is generated by the elastic member 3
4. It does not adhere to the ink chamber wall 14, the plate 16, and the like.

As the oil film material impregnating member 40, a material capable of impregnating the oil film material therein or a material having a gap for holding the oil film material therein can be appropriately selected. For example, cloth,
Paper, natural rubber, polymer materials, etc. impregnated with an oil film material may be used, or an inorganic material such as metal or ceramic, or an organic material such as natural rubber or synthetic resin may be provided with a number of gaps capable of holding the oil film material. It may be made of a so-called porous material. Furthermore, it is also effective to subject these porous materials to lipophilic treatment to facilitate penetration and retention of the oil film material.

As the oil film material, any material that can form an oil film on the surface of the ink 20 can be appropriately selected. Conditions that can form an oil film on the surface of the ink 20 include:
Tension at the interface between 0 and air (surface tension of ink 20) γi,
Tension of interface between oil film and air (surface tension of ink 20) γo
, When the interfacial tension between the ink 20 and the oil film is γio, γi
> Γo + γio.
As described above, the oil film material impregnated member 40 is
The oil film material is drawn out of the ink and the oil film 42 is formed, so that means (for example, a pump or the like) for actively supplying the oil film material to the surface of the ink 20 becomes unnecessary.

Further, since the oil film material functions as the oil film 42, it does not dissolve in the ink 20;
It is preferable that the emulsion does not spontaneously emulsify and has a relatively high boiling point and is liquid at room temperature. When the surface of the ink 20 is located above the direction of gravity,
When the specific gravity of the oil film material is smaller, or conversely, when the surface of the ink 20 is located below the direction of gravity, the specific gravity of the oil film material needs to be larger than that of the ink 20. When an aqueous ink is used, examples of the oil film material include hydrocarbons, higher fatty acids, water-insoluble alcohols, vegetable oils, and silicone oils. These may be used alone or as a mixture.

Next, the recording head 10 according to the present embodiment
The operation and operation of the above will be described. First, as shown in FIG.
The case where dots are recorded by flying the ink droplets 46 will be described. That is, when an image signal is input to the signal generation unit 32 pixel by pixel based on the input image information, a drive signal of the vibration generation unit 24 is generated based on the image signal.

The vibration generating means 24 determines the rigidity of the substrate 12,
Thickness of piezoelectric vibrator 26, piezoelectric characteristics, and elastic member 34
Has a unique resonance frequency f ₀ determined by the size, rigidity, etc. Therefore, when the signal generating means 32 drives the vibration generating means 24 by applying a voltage having a frequency f equal to or an integer multiple of f ₀ , the elastic member 34 can be vibrated efficiently. Of course, the drive frequency is not limited to this, and may be any frequency as long as the elastic member 34 can be bent and vibrated at a desired frequency. Further, the waveform of the drive signal has the elastic member 3 as shown in FIG.
4 or a continuous AC voltage equal to the excitation frequency of FIG.
A continuous pulse voltage as shown in (B) can be used. Further, the excitation cycle as shown in FIG.
A burst signal in which at least one or more continuous waveforms are connected for one pixel may be used as a burst wave. However, in this case, each waveform is not limited to a rectangular wave,
A sine wave or triangle wave may be used. In particular, by using a burst wave, the elastic member 34 can be vibrated by applying a burst wave having the resonance frequency f ₀ to the vibration generating means 24 for a short time. In addition, it becomes possible to eject minute ink droplets 46 by the burst wave. On the other hand, when the alternating voltage is continuously applied, relatively large continuous ink droplets are continuously ejected.

The energy for ejecting the ink droplets 46 is determined by the number of waveforms (the number of bursts) having one cycle of the excitation of the vibration generating means 24 and the applied voltage. If the number of bursts is increased, it is possible to eject the ink droplet 46 at a relatively low voltage, while if the number of bursts is reduced,
Although the voltage required for discharging the ink droplet 46 is slightly higher, the ink droplet 46 having a higher flying speed can be discharged.

A drive signal having such a predetermined waveform is applied from the signal generating means 32 to the vibration generating means 24, and the piezoelectric vibrator 26 vibrates, so that the elastic member 34 resonates and the center of the base 34A. To perform bending vibration in the direction of arrow A. As shown in FIG. 3, due to the surface tension of the ink 20, the affinity (wetting) between the ink 20 and the surface of the elastic member 34, the gravity acting on the ink 20, and the like, the vicinity of the tip portion 34B of the elastic member 34 A thin film of the ink 20 having a predetermined liquid thickness (several μm to several hundred μm) in the vibration direction (the direction of arrow A) is formed. Then, the bending vibration of the elastic member 34 generates a capillary wave in the thin film portion.

As shown in FIG. 5, at a certain time t,
On the surface of the ink 20, a capillary wave 44 whose wavelength λ is W = 2λ with respect to the width (width in the direction of arrow B) W of the surface of the elastic member 34 perpendicular to the bending vibration direction (direction of arrow A).
There are two peaks. Time t + Δ after elapse of minute time Δt
At t, as shown in FIG.
One mountain of ink ridges is formed from between the four regions, and these ridges are separated and one ink droplet flies.

By repeatedly applying the driving signal from the signal generating means 32 to the vibration generating means 24, the ink droplets 46 fly from the elastic member 34 one by one in accordance with the driving signal.

As described above, in order to cause the ink droplets 46 to fly stably one by one, the tip portion 34B of the elastic member 34 is required.
, The width of a surface (vibration surface 34C) perpendicular to the bending vibration direction of the elastic member 34 is W, and the value calculated by the following equation is λ. It is desirable that the width W of the portion is approximately 2λ.

Λ = [8πσ / (ρf _e ² )] ^1/3 × 10 ⁴ (μm) (1) where σ is the ink surface tension (mN / m) and ρ is the ink density ( g / cm ³ ) f _e is the excitation frequency (Hz) The above equation (1) is described in a general reference book, for example, Chika Chika, “Ultrasonic Spraying” (Sankaido), Chapter 7, Section 2, the capillary wave It is described as an equation giving the wavelength.

The width W is preferably as close as possible to the value of 2λ, and is preferably in the range of 1.2λ to 2.4λ.
The fine ink droplets thus generated stably fly in a direction perpendicular to the vibration surface 34C of the elastic member 34 by an input signal having an appropriate waveform input from the signal generation means 32 to the vibration generation means 24. .

If the width W is less than 1λ in the vicinity of the distal end portion 34B of the elastic member 34, it becomes difficult to generate a capillary wave, and it is not necessary to increase the excitation voltage of the signal generating means 32 or increase the number of bursts. And ink drops do not fly. Even if the ink droplet flies, it is difficult to fly stably.

On the other hand, even when the width W is 3λ or more in the vicinity of the distal end portion 34B of the elastic member 34, a capillary wave is hardly generated. In this case, similarly to the above, the capillary wave can be generated by increasing the excitation voltage of the signal generating means 32 or increasing the number of bursts. In this case, three or more peaks are generated. A plurality of ink droplets fly at a time, and cannot fly one by one.

On the surface of the ink 20 stored in the ink chamber 18, an oil film 42 is formed by the oil film material that has exuded from the oil film material impregnated member 40. Therefore, the ink droplet 46 generated by the vibration of the elastic member 34 flies to the recording medium while keeping a small amount of the oil film on the surface. The oil film component of the ink droplet 46 penetrates into the recording medium, the water in the ink droplet 46 evaporates, and the color material in the ink droplet 46 is held on the surface of the recording medium to form an image.

The flying of the ink droplet 46 causes the ink chamber 18
Although the ink 20 is consumed, the ink is supplied from an ink tank (not shown) through the ink supply path 22, so that a predetermined amount of the ink 20 is always stored in the ink chamber 18.

Further, with the flight of the ink droplet 46, the oil film 4
The oil film material constituting 2 is also consumed. However, ink 2
0 between the surface tension γi of 0, the surface tension γo of the ink 20, and the interfacial tension γio of the ink 20 and the oil film, γi> γo + γio
The oil film material is selected so as to satisfy the following relationship. Therefore, when the film thickness of the oil film 42 is reduced, the oil film material is impregnated with an appropriate amount (usually a very small amount) from the oil film material impregnated member 40 by utilizing the surface tension. ) Exudation, always constant thickness (several μm to tens of μ)
m) of the oil film 42 is formed. Therefore, the ink chamber 18
The evaporation of water from the ink 20 in the ink is prevented, and the ink 2
0 does not dry, and the ink 20
Of the elastic member 34, the ink chamber wall 14, and the plate 1
6 and so on. Further, means for positively supplying an oil film material to the surface of the ink 20 (for example, a pump or the like)
Becomes unnecessary.

As described above, in the recording head 10 according to the present embodiment, the minute ink droplets 46 are not restricted by the nozzles.
Can be generated, and ink residue and the like do not adhere to the elastic member 34 due to ink drying, so that a high-quality and stable recording apparatus can be realized.

FIG. 7 shows a recording head 50 according to a second embodiment of the present invention. This recording head 50
In this embodiment, the configuration of the oil film material supply means is different from that of the recording head 10 according to the first embodiment. Hereinafter, the same components and members as those of the recording head 10 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the recording head 50, a member corresponding to the plate 16 of the recording head 10 according to the first embodiment is not provided, and the ink chamber 52 is constituted by the substrate 12 and the ink chamber wall 14. (Therefore, the ink chamber 52
Is open upward.)

In the recording head 50, instead of the oil film material impregnated member 40 according to the first embodiment, a tank 54 for storing the oil film material, and the oil film material is supplied from the tank 54 into the ink chamber 18. An oil film material supply device 60 is provided below the substrate 12 and includes a pump 56 for supplying oil film material to the ink chamber 52 from the pump 56. An insertion hole 62 through which the oil film supply passage 58 is inserted is formed in the substrate 12.

When the pump 56 is driven, a pressure difference is generated at the upper end of the oil film supply passage 58 (portion communicating with the ink chamber 52), and the oil film material is supplied into the ink chamber 52 by this pressure difference. Since the oil film material does not mix with the ink 20 and has a lower specific gravity than the ink 20, it rises in the ink 20 to form an oil film 42 having a constant thickness on the surface of the ink 20.

As described above, since the oil film material is supplied by the pressure difference of the portion communicating with the ink chamber 52, the oil film material supply device 60 can be provided at an arbitrary position. In addition, as long as a pressure difference can be generated in a portion communicating with the ink chamber 52, other pressure difference generating means such as a piezoelectric element can be used instead of the pump 56.

The control device 64 is connected to the pump 56. Further, the control device 64 is connected to the signal generating means 32, and
The number of drive signals (the number of printing pulses) applied to 4 is counted and can be stored in an internal memory. Therefore, by controlling the pump 56 by the control device 64, the amount of the oil film material supplied by the pump 56 is controlled (the “print pulse number” used here means that the signal generating means 32 This means the number of signals generated based on the image signal. When the burst wave shown in FIG. 4C is generated, one print pulse is counted for each burst wave generation.) This will be described with reference to the flowchart shown in FIG.

In the control device 64, a predetermined amount of ink used in advance is stored as a count value P ₀ in an internal memory, and the used amount is first read in step 112.

Next, at step 114, the signal generating means 32
Clears the memory (P ₁ = 0) for storing the number of drive signals (the number of print pulses) input to the vibration generating means 24 from ( ₁ ). Then, in step 116, the process enters the standby mode.

In the next step 118, if the input signal is not input from the signal generating means 32 to the vibration generating means 24, the process returns to step 116 to continue the standby mode. When input to the means 24, a printing position driving means (not shown) is driven in step 120. The printing position driving means is means for moving the recording head 50 in the main scanning direction (the direction perpendicular to the plane of FIG. 7).

In the next step 122, it is determined whether or not there is a print pulse. If there is no print pulse, the flow returns to step 120 to drive the print position driving means again. , P ₁ in step 124
Is added to. Further, at step 126, the vibration generating means 24 is driven.

[0076] In the next step 128, when it is determined whether it is greater than a predetermined count value P ₀ where P ₁ is set in advance is larger, the step 130
The pump 56 is driven for a certain period of time to supply a certain amount of oil film material into the ink chamber 52. Step 132
In, to clear the value of _{P 1 (P 1 = 0)} . Then, the process proceeds to step 134. In step 128, if P ₁ is not larger than the predetermined count value P ₀ which is set in advance, control proceeds to step 134.

In step 134, it is determined whether or not printing by the recording head 50 has been completed.
The operation of the pump 56 is terminated. If the printing is not completed, the flow returns to step 120 to drive the printing position driving means, and the same operation is repeated thereafter.

As described above, the number of drive signals (the number of printing pulses) applied from the signal generating means 32 to the vibration generating means 24
Is calculated, the consumption amount of the ink 20 and the usage amount of the oil film material are calculated, the necessary and sufficient oil film material can be supplied into the ink chamber 52, and the film thickness of the oil film 42 can always be maintained at a constant thickness.

Since the value of P ₀ can be set to an arbitrary value, the thickness of the oil film 42 can be set to an arbitrary value according to the use environment and use frequency of the recording head 50. When P ₀ is set small, the supply amount of the oil film material with respect to the consumption amount of the ink 20 can be increased. Conversely, when P ₀ is set large,
The supply amount of the oil film material with respect to the consumption amount of the ink 20 can be reduced.

In addition to counting the number of drive signals applied from the signal generating means 32 to the vibration generating means 24 to calculate the amount of oil film material used, for example,
The use time and non-use time (leaving time) of 0 are counted to calculate the consumption amount of the oil film material, and this count value is compared with a preset value to supply the oil film material. Is also good. For example, when the amount of the oil film material consumed by the flight of the ink droplet 46 (see FIG. 3) is extremely small, the decrease in the film thickness of the oil film 42 is longer than that of the ink droplet 46. It is affected by evaporation and dissolution into the ink 20.
Therefore, even in such a case, the reduced amount of the oil film material can be supplied by driving the pump 56, and the oil film 4 can be always supplied.
2 can be kept constant.

FIG. 9 shows a recording head 70 according to the third embodiment of the present invention. This recording head 70
In this embodiment, the configuration of the oil film material supply means is different from that of the recording head 10 according to the first embodiment. Hereinafter, the same components and members as those of the recording head 10 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In the recording head 70, similarly to the recording head 50 according to the second embodiment, the member corresponding to the plate 16 of the recording head 10 according to the first embodiment is not provided, and the ink chamber is not provided. 52 is composed of the substrate 12 and the ink chamber wall 14.

In the recording head 70, instead of the oil film material impregnated member 40 according to the first embodiment, a tank 74 for storing the oil film material, and the oil film material is supplied from the tank 74 into the ink chamber 52. An oil film material supply device 72 including a pump 76 is provided above the ink chamber 18. The oil film material is taken out of the tank 74 by the drive of the pump 76, dropped from above the ink chamber 52, and supplied to the surface of the ink 20. As described above, the oil film material directly flows without flowing through the ink 20.
Since the oil film material reaches the surface of the ink 20, the oil film material can be supplied quickly.

The oil film material may be dropped only by gravity. For example, a nozzle or a spray may be provided at the outlet of the oil film material (at the lower end of the pump 76) to supply the oil film material in the form of a mist or to supply the velocity component vertically downward. May be dropped in advance. In any case, the oil film material is supplied to the surface of the ink 20 more quickly than when the oil film material is dropped only by gravity.

The oil film material supply device 72 does not need to be disposed directly above the ink chamber 52. In other words, even when the oil film material is not disposed right above the ink chamber 52,
What is necessary is just to add a predetermined velocity component in the horizontal direction in advance so as to reach the surface of zero and drop the droplet.

Further, the oil film material supply device 72 is not required to be provided with one oil film material supply device 72 (dropping port), and a plurality of oil film material supply devices 72 may be provided. For example, a pipe having a tubular shape whose longitudinal direction is
And a plurality of drip ports may be formed on the peripheral surface of the pipe. Accordingly, the oil film material can be supplied from a plurality of dropping ports by simply driving one pump 76, and the oil film material can be supplied to a wide range.

The pump 76 may be connected to a control device 64 similar to that of the second embodiment. This allows
By calculating the consumption of the oil film material, a necessary and sufficient amount of the oil film material can be supplied into the ink chamber 52, and the film thickness of the oil film 42 can always be maintained within a certain range.

In the recording head 70 according to the third embodiment, the oil film material supply device 72 is disposed at the ink 20 in the ink chamber 52 and at a position separated from the surface of the ink 20. It is also possible to supply the oil film material by relatively moving the ink chamber 52 and the oil film material supply device 72. For example, by fixing the oil film material supply device 72 to a housing or the like to which the recording head 70 is attached, the scanning of the recording head 77 (movement in the direction perpendicular to the paper surface of FIG. 9) is used to form the ink chamber 52 and the oil film material. The oil film material can be supplied by relatively moving the supply device 72. In this way, by moving the ink chamber 52 relative to the oil film material supply device 72, even if the number of the oil film material supply devices 72 is reduced, a sufficient amount of the oil film material can be evenly supplied to the surface of the ink 20. Can be. For example, when the print head 70 scans, a sensor detects that a specific position has passed through the print head 70 and the pump 76 is driven to supply the oil film material. For this reason, the number of oil film material supply devices 72 can be reduced, and
As a whole, the number of parts is reduced and the structure is simplified. In addition, the degree of freedom of the shape and layout of the oil film material supply device 72 is increased.

FIG. 10 shows a recording head 80 according to a fourth embodiment of the present invention. This recording head 8
At 0, the configuration of the ink chamber is different from that of the recording head 10 according to the first embodiment. Hereinafter, the same components and components as those of the recording head 10 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The recording head 80 has a hollow portion 8 inside.
4 has a case 82 formed therein. One of the partition walls 86 constituting the hollow portion 84 (the right side in FIG. 10).
Has an opening 88 formed therein. An elastic member 34 is erected from substantially the center of the hollow portion 84 in the width direction (horizontal direction in FIG. 12). 90. A predetermined amount of ink 20 is stored in the ink chamber 90. Therefore, the bottom portion 82A of the case 82 also functions as the substrate 12 according to the first embodiment. The case 82 prevents the disturbance of the meniscus due to the disturbance of the air flow from the outside of the recording head 80 and the dust.

An ink supply passage 92 is formed in the bottom 82A of the case 82. Ink is supplied from an ink tank (not shown) through an ink supply path 92, and is supplied to the ink chamber 9.
A predetermined amount of ink 20 is always stored in zero.

The vibration generating means 24 composed of the electrodes 28 and 30 and the piezoelectric vibrator 26 is attached to the side of the elastic member 34 opposite to the ink chamber 90. Electrodes 28, 3
When an alternating voltage corresponding to the image signal is input from the signal generating means 32 connected to 0, the vibration generating means 24 generates vibration according to the electric signal. When the vibration generating means 24 vibrates, the elastic member 34 is excited at the resonance frequency and vibrates in a bending manner, so that the thin film of the ink 20 formed on one side of the elastic member 34 in the thickness direction (the ink chamber 90 side) is used. The droplet 38 flies, passes through the opening 88, and is ejected toward a recording sheet as a recording medium.

An oil film material impregnating member 40 is fixed to the inner surface of the partition wall 86 as oil film material supply means. The oil film material impregnated member 40 contacts the surface of the ink 20 and holds the meniscus of the ink 20 together with the elastic member 34.

The oil film material impregnated inside the oil film material impregnated member 40 exudes from the oil film material impregnated member 40,
An oil film 42 is formed on the surface of the ink 20. This allows
Evaporation of water in the ink 20 can be prevented, the ink 20 is hard to dry, and the density of the ink 20 does not change. In addition, residues of the ink 20 due to evaporation do not adhere to the elastic member 34, the ink chamber wall 14, and the like.

In the recording head according to each of the above-described embodiments, each of the vibration generating means 24 and the elastic member 34 is used.
Although one ink chamber 18, 52, and 90 is configured as an example in common to the above, the ink chamber 18 may be configured to be divided by a plurality of partition walls. As a result, the vibration of the surface of the ink 20 by the adjacent vibration generating means 24 and the elastic member 34 does not affect each other. For this reason, it is possible to prevent crosstalk caused by vibrations of the surface of the ink 20 that interfere with each other. The partition may be formed for each of the vibration generating units 24, or may be formed for each of the plurality of vibration generating units 24. Further, the partition wall may be erected from the substrate 12, but is not necessarily limited thereto. For example, the partition wall is formed only near the surface of the ink 20, and the ink chambers 18, 52, 9
In the lower part of 0, each of the ink chambers 18, 52, 90 may be in communication.

[0096]

EXAMPLES The present invention will be described in more detail with reference to Examples. However, needless to say, the present invention is not limited to the following embodiments. Example 1 In this example, the recording head 10 according to the first embodiment was used to fly the ink droplets 46 and record dots on the recording material.

As the elastic member 34 of the recording head 10,
Approximately 7μ formed by electroforming
An m-thick nickel was used.

Piezoelectric vibrator 2 constituting vibration generating means 24
Reference numeral 6 denotes a piezoelectric ceramic thin film piezoelectric vibrator 26 made of lead zirconate titanate (PZT). Further, the piezoelectric ceramic thin film piezoelectric vibrator 26 is subjected to a polarization treatment so that the electrode 2
When a voltage was applied between 8, 30 and 30, vibration was made in a direction perpendicular to the electrode surface.

The electrodes 28 and 30 for applying a voltage to the piezoelectric vibrator 26 made of a piezoelectric ceramic thin film have a two-layer structure made of chromium having a thickness of 0.05 μm and gold having a thickness of 1 μm. The frequency for exciting the vibration generating means 24 is 190 k
Hz.

The oil film material impregnated member 40 was made of a porous sintered metal impregnated with low molecular silicon oil.

When the ink droplets 46 were ejected from the recording head 10 having the above configuration, the minute ink droplets 46 could be ejected stably, and a high-resolution image could be obtained. Also, an appropriate amount of oil film material (low molecular silicon oil) exudes from the oil film material impregnating member 40 which is an oil film material supply means, and an oil film 42 having a constant thickness is formed on the surface of the ink 20 in the ink chamber 18. There were no ejection failures due to drying.

[0102]

According to the first aspect of the present invention, vibration generating means for generating vibration in response to an image signal, an ink chamber for storing ink, and excitation of the vibration generating means disposed in the ink chamber. An elastic member that bends and vibrates according to a recording head that causes ink droplets to fly from a thin ink film formed on the surface of the elastic member that bends and vibrates to adhere the ink droplets to a recording medium, Since the oil film material supply means for supplying the oil film material to the surface of the ink stored in the ink chamber is provided, a high-resolution image can always be accurately recorded, and the evaporated ink adheres to the inside of the recording head. Ink drop ejection failure,
The ink is not wasted by evaporation.

According to the second aspect of the present invention, in the first aspect of the present invention, the oil film material supply means is disposed at a position in contact with the surface of the ink stored in the ink chamber. The oil film material supplied from the oil film material supply means quickly reaches the surface of the ink in the ink chamber,
It does not adhere to portions other than the surface of the ink.

According to a third aspect of the present invention, in the second aspect of the present invention, the oil film material supply means is constituted by an oil film material impregnating member capable of impregnating the oil film material therein, so that the surface tension is increased. By using this method, it is possible to always supply an appropriate amount of oil film material and to maintain the film thickness of the oil film constant.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the oil film material supply means contacts the ink stored in the ink chamber and is separated from the surface of the ink. The oil film material supply means can be provided at any location.

According to the fifth aspect of the present invention, in the first aspect of the present invention, the oil film material supply means is disposed at a position separated from the ink stored in the ink chamber. Formation can be performed quickly.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a recording head according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view showing the recording head according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating flying of ink droplets from a recording head according to the present invention.

FIGS. 4A to 4C are diagrams showing voltage waveforms of a drive signal applied from a signal generation unit to a vibration generation unit of the recording head according to the present invention.

FIG. 5 is an explanatory diagram illustrating a state in which a capillary wave is generated from a recording head according to the present invention.

FIG. 6 is an explanatory diagram illustrating a state where a capillary wave is generated from the recording head according to the present invention.

FIG. 7 is a cross-sectional view illustrating a recording head according to a second embodiment of the present invention.

FIG. 8 is a flowchart illustrating an operation of an oil film material supply device in a recording head according to a second embodiment of the present invention.

FIG. 9 is a sectional view showing a recording head according to a third embodiment of the present invention.

FIG. 10 is a sectional view showing a recording head according to a fourth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 recording head 18 ink chamber 20 ink 24 vibration generating means 34 elastic member 40 oil film material impregnated member (oil film material supply means) 42 oil film 46 ink droplet 50 recording head 52 ink chamber 60 oil film material supply device (oil film material supply means) 70 recording Head 72 Oil film material supply device (oil film material supply means) 80 Recording head 90 Ink chamber

Claims (5)

[Claims] A vibration generating means for generating vibration in response to an image signal; an ink chamber in which ink is stored; and an elastic member disposed in the ink chamber and bending and vibrating in response to excitation of the vibration generating means. A recording head for ejecting ink droplets from an ink thin film formed on the surface of the elastic member that bends and vibrates and attaching the ink droplets to a recording medium, wherein a surface of the ink stored in the ink chamber is provided. A recording head for supplying an oil film material to the recording head. 2. The recording head according to claim 1, wherein said oil film material supply means is arranged at a position in contact with a surface of said ink stored in said ink chamber. 3. The recording head according to claim 2, wherein said oil film material supply means comprises an oil film material impregnated member capable of impregnating said oil film material therein. 4. The apparatus according to claim 1, wherein the oil film material supply means is arranged at a position in contact with the ink stored in the ink chamber and at a distance from the surface of the ink. Recording head. 5. The recording head according to claim 1, wherein said oil film material supply means is arranged at a position separated from said ink stored in said ink chamber.