JPH1148471A - Ink jet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording head performing printing by ejecting ink fly droplets to a surface to be printed and capable of stably ejecting ink drops of a small diameter without using a nozzle. SOLUTION: A vibration generating part 200 is formed on one surface of a vibration plate 1 to be bonded to a vibration support plate 201 and an elastic member 5 is arranged to the other surface of the vibration plate 1. An ink chamber 25 constituted of an ink reservoir 103 storing ink 6 and an ink chamber forming member 26 and having ink ejecting apertures 27 is connected thereto. The vibration generating part 200 is vibrated and the elastic member 5 connected thereto is subjected to bending vibration. Ink drops 8 are ejected from the vicinity of the leading end of the elastic member 5. A vapor generating chamber 202 is arranged in the vicinity of the elastic member of the space above the ink surface 7 in the ink chamber 25 and supplies vapor of at least one component of ink components to the space.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink jet recording head for performing printing by ejecting flying ink droplets onto a surface to be printed.

[0002]

2. Description of the Related Art Conventionally, there has been known an ink jet recording system in which ink droplets are ejected from a nozzle to perform printing, and the diameter of a drop of ejected ink is mainly determined by the diameter of the nozzle. Conventionally, in these ink jet technologies, the resolution was about 300 dots / inch, but recently the resolution has been increased to 600 to 720 dots / inch. Accordingly, it is necessary to reduce the diameter of a dot to be printed in accordance with the resolution in order to effectively exhibit the effect of high resolution. Therefore, as a means for reducing the dot diameter in the above conventional method, there is a method of reducing the nozzle diameter to reduce the ejection drop diameter.However, when the nozzle diameter is reduced, nozzle clogging due to dust and drying of the ink surface in the nozzle, Alternatively, a change in the ink discharge direction is likely to occur due to the adhesion of the ink residue to the nozzle circumference, and a defect occurs in the image quality on the recording paper. Therefore, there is a problem that a nozzle diameter required for printing a dot diameter corresponding to the original resolution cannot be adopted.

On the other hand, as a method for solving the problem caused by such a nozzle, a nozzleless ink jet recording method using vibration, acoustic wave, or the like, in which the diameter of a discharge drop is not controlled by the nozzle diameter, has been proposed.

As an example of a first prior art which does not use a nozzle, there is, for example, US Pat. No. 4,308,547, in which a concavely curved spherical piezoelectric shell is arranged in ink, and an electrode is passed through the piezoelectric shell. Some apply a voltage. Longitudinal waves emitted from the piezoelectric shell into the ink are collected at one point on the free surface of the ink, and a drop is ejected from the free surface of the ink. Further, Japanese Patent Publication No. Hei 6-45233 and Japanese Patent Laid-Open Publication No. 3-200199 are known as those capable of improving the productivity and the precision of the structure of this kind of conventional technology. In such prior art,
The vibration generated by the vibrator is focused on a point on the free surface of the ink by an acoustic lens, and a drop is ejected. However, in order to eject a small drop, since driving is performed at a high frequency of about 100 MHz, the driving means is generally expensive, and in addition to the cost problem, the ink viscosity increases due to heat generation and the drop diameter fluctuates. In such a case, a serious problem that the ink itself is dried and solidified and cannot be ejected easily occurs.

[0005] This is because longitudinal waves propagating in the ink are more likely to be attenuated in the ink as driving at a higher frequency, the amount of energy absorbed in the ink increases, and the amount of heat generated also increases. Therefore, in order to solve this problem, there is no other way but to provide a cooling mechanism in the head, and the cost and size of the ink jet recording head increase, which is a problem.

Further, as a second ink jet recording technique without using a nozzle, there is a method in which vibration generated by a vibrator is focused on one point of an ink free surface by an acoustic horn and a drop is ejected. U.S. Pat. No. 4,308,547 discloses that an acoustic horn formed on a vibrator instead of a concave lens focuses vibration, and the vibration acts on an ink thin film conveyed on a belt in contact with the tip of the acoustic horn. This is to discharge ink drops.

Japanese Patent Application Laid-Open No. 4-168050 proposes a configuration in which a sound collector is provided on a piezoelectric body.
The sound collector is formed on a vibrator composed of a piezoelectric body and an electrode for applying a voltage to the piezoelectric body, and is arranged in an ink reservoir holding ink. The sound collector has a tapered shape, and as the distortion incident from the bottom of the sound collector propagates inside the sound collector, its amplitude is amplified, and the large-amplitude waves collected by the sound collector strike ink. The longitudinal wave generated thereby pushes up the free surface of the ink and causes the ink drop to be ejected. In the field of acoustics, generally, when the tip of a sound collector (or an acoustic horn) is vibrated to a large amplitude by resonance to obtain a discharge force, in order for the vibration wave to propagate through the sound collector, It is known that the length (height) of the sound collector in the vertical sectional direction must have a size that is an integral multiple of half the wavelength of the vibration wave. Therefore, in order to reduce the size of the sound collector and manufacture a high-density inkjet head, the wavelength of the vibration wave must be small, that is, the driving frequency for vibrating the vibrator must be increased.

[0008] Therefore, in such prior art,
Attempting to drive the ink at a low frequency so as to suppress the energy attenuation in the ink and to use a relatively inexpensive drive circuit has a problem that the sound collecting body becomes extremely large and a high-density inkjet head cannot be manufactured. Therefore, in order to manufacture an ink jet head having a realistic density, it is necessary to drive the ink jet head at a high frequency of several tens of megahertz to several hundreds of megahertz as in the first prior art. In addition, it is practically difficult to stably transport the ink thin film by the belt in contact with the acoustic horn, and the diameter of the ejection drop tends to vary, which is a problem.

Further, as a third ink jet recording technique without using a nozzle, an electrostatic force is used as an ejection force.
There is a so-called electrostatic suction method, and a method using vibration to form an ink meniscus is also known. For example, in Japanese Patent Application Laid-Open No. 62-222853, a recording needle is made to protrude from the ink surface, and ultrasonic energy that propagates in the axial direction is applied to the recording needle. Ultrasonic flow (acous
Due to the tic streaming phenomenon, the ink in contact with the recording needle moves toward the tip of the recording needle, forming a convex ink bulge (ink meniscus) at the tip of the recording needle.
Therefore, an electrostatic field is applied between the recording needle and the back electrode, the ink is torn off, and ink droplets land on a recording medium disposed between the recording needle and the back electrode. Since an ink meniscus is formed at the tip of the recording needle, a smaller ink drop can be formed as compared with the conventional electrostatic suction method. JP-A-56-28867 also proposes an electrostatic attraction method in which an electrostatic field is applied between a needle electrode and a back electrode, an image signal is applied to the needle electrode, and the needle electrode is vibrated at the same time. Have been. This makes it possible to stabilize the inkjet particles. However, in the electrostatic suction method,
Due to variations in the dielectric thickness of the recording medium due to humidity or variations in the surface roughness of the recording medium, the diameter of the formed drop tends to fluctuate, and such a configuration generates not only an electrostatic field but also an ultrasonic wave. There is a drawback that the device is large and expensive due to the necessity.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet recording head which can discharge a small-diameter ink drop without using a nozzle, is low in cost, and does not generate heat, and is energy efficient with low frequency driving. To provide. In other words, the present invention provides a novel ink jet recording head capable of ejecting a minute drop corresponding to high resolution and performing high-reliability and high-quality printing without instability of ink ejection such as ink clogging and fluctuation of a drop diameter. It is in.

[0011]

The object of the present invention is to provide a vibration generating means which vibrates in response to a pixel signal, an elastic member having a cantilever structure which bends and vibrates in response to excitation of the vibration generating means, and A vapor generating means disposed, wherein the vapor generating means suppresses the evaporation of the ink, and generates a capillary wave on the ink surface by the vibration of the elastic member to cause the ink to fly and adhere to the recording medium. This is achieved by an inkjet recording head that performs The steam generating means generates steam containing at least one component of the ink. Also, if the ink is a water-based ink,
Steam may be generated from the steam generating means.
Further, the steam generating means includes a porous member. Further, the steam generating means may be configured so that at least a part of a surface for generating steam has irregularities.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An ink jet recording head according to one embodiment of the present invention will be described with reference to FIGS. First, a basic configuration and a basic operation principle of the ink jet recording head according to the present embodiment will be described.

The ink jet recording head according to the present embodiment uses a drop discharge phenomenon by a capillary wave. Droplet formation by capillary waves is known as a generating mechanism of ultrasonic spraying as described in, for example, "Ultrasonic Spraying", Sankaido, p.168, 1990. As shown in FIG. 1, a capillary (capillary surface) wave is a phenomenon that is observed in a thin liquid film on a vibrating surface, and is a surface wave of a thin liquid layer on a vibrating body 9 that uses the surface tension of the liquid 6 as a restoring force. is there. If the vibration amplitude of the vibrating body 9 is sufficient, the wave front gradually grows and the liquid droplets are torn off from the wave front.
The interval between the wave fronts is the wavelength λ of the capillary wave and is obtained as follows.

Λ = (8πσ / ρfe ² ) ^1/3

Here, σ and ρ are the surface tension and density of the liquid, and fe is the excitation (drive) frequency. The higher the excitation frequency fe, the smaller the wavelength λ, the smaller the so-called capillary wave, and the smaller the diameter of the droplet splitting from the wave front. The droplet that flies by the action of the capillary wave can be a minute droplet having a wavelength equal to or less than the wavelength. Number k
Since a small drop can be ejected even at a relatively low driving frequency from Hz to several MHz, application to an ink jet recording head has been conventionally studied. However, printing with a single drop has not been realized because multiple drops are likely to occur and the diameter of each drop varies.Therefore, on the assumption that multiple drops are generated, the print dot diameter is set using the nozzle hole arranged at the top. A control method was used. In addition, not only the problem due to the nozzle hole, but also a plurality of droplets were generated, so that the print dot diameter was likely to be widened (increased), and the droplets also scattered around the dots to easily deteriorate the image.

FIGS. 2 and 3 explain the outline of the drop ejection mechanism of the ink jet recording head according to the present embodiment. FIG. 2 is a sectional view of the ejection head.
Is a front view thereof (discharge drops are omitted).

As the vibration generator (vibrator) 9, an electrostrictive element, a magnetostrictive element, a mechanical actuator or the like can be applied. Here, the piezoelectric ceramic thin film 2 on the substrate 1 and the electrodes 3 for driving the piezoelectric ceramic thin film 2, 4 is used as the vibrator 9. On the vibrator 9, an elastic member 5 made of a metal thin film or the like is formed and arranged.

Since the vibrator 9 has a unique resonance frequency f0 determined by the rigidity of the substrate 1, the thickness of the piezoelectric ceramic thin film 2, and the like, the external drive unit 120 applies the same or an integer of the resonance frequency f0 to the vibrator 9. Excitation is performed by applying a voltage at twice the frequency f (the external drive unit is omitted in the following embodiments). At this time, if the size and rigidity of the elastic member and the height and amount of the ink 6 are adjusted so that the resonance frequency f1 of the elastic member connected to the vibrator 9 becomes the same as f0, the vibration of the vibrator 9 , And the elastic member 5 having the cantilever structure can be bent and vibrated. Here, the elastic member 5 was subjected to bending vibration in a direction (bb ′) substantially perpendicular to the main vibration direction (aa ′) of the vibrator 9. In the elastic member having the cantilever structure, the bending stiffness is smaller at the distal end portion than at the base end portion, so that the bending vibration can be more efficiently performed near the distal end of the elastic member and the amplitude can be obtained. The bending stiffness is (second moment of area) x (Young's modulus) of the elastic member.
It is represented by

A sinusoidal AC voltage is applied to the vibrator 9 as a burst wave for a certain period of time, and aa ′ is applied as shown in FIG.
And the elastic member 5 is caused to bend and vibrate. In addition,
The elastic member may be bent and vibrated by vibrating the vibrator in directions other than the aa ′ direction. A burst wave refers to one in which an alternating voltage consisting of one or more waves is applied to the vibrator intermittently while the frequency is kept constant when the vibrator is driven. The vibrator is driven for a certain period of time by burst wave driving to print.

When the driving voltage is appropriately high, a thin liquid layer 6 'of ink is formed near the tip of the elastic member by being lifted from below. Further, a capillary wave is formed in the thin liquid layer 6 'by the subsequent vibration of the elastic member, and finally, a minute ink drop 8 is formed from the wave front of the capillary wave. In order to generate a capillary wave on the surface near the tip of the elastic member, the thickness of the ink should be several μm in consideration of the effects of wetting of ink and the elastic member, the effect of gravity, and the flow action.
m to hundreds of μm. In addition, 1kHz
A drop flight by a capillary wave can be performed at a driving frequency in a range from 10 MHz to 10 MHz.

As the material of the elastic member, various resins such as a cyanoacrylate resin, an epoxy resin, a fluorine resin, and polyimide can be used. In particular, it is important to use a resin whose shape can be precisely processed, such as polyimide. If you want to achieve a large displacement at the tip of the elastic member using resonance, you should select a material and processing method that can precisely form the dimensions of the elastic member. Can be realized. In addition, SiO ₂ , SiO
The elastic member may be formed of N or various inorganic materials such as SiN, AlN, and Al ₂ O ₃ . Al, F
The elastic member may be formed of e, Ti, Cr, Au, Mo, TiW, or the like, or various alloys thereof. However,
These surfaces may be protected with an inorganic film such as SiO ₂ so that they do not corrode while in contact with the ink. Of course, it is needless to say that two or more of the resin, the inorganic material, and the metal may be used. In addition, if the vibration energy can be efficiently transmitted, the distal end and the proximal end of the elastic member may be made of different materials.

When a piezoelectric body is used as the vibrator, it may be constituted by a piezoelectric substrate or a piezoelectric thin film.
As the piezoelectric material, quartz, lead zirconate / titanate (PZT), barium titanate BaTiO ₃ , lead niobate PbNb ₂ O ₆ , bismuth germanate Bi ₁₂ Ge
O 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 may be used.

As is apparent from the above description, the ink jet recording head according to the present embodiment has a relatively low driving frequency, generates little heat, and enables stable printing. It is not necessary to use a so-called nozzle, and a single small ink drop can be ejected, so that high image quality can be stably formed on the image holding member.

However, when a recording head having only the above configuration is used as a printing device, the following points must be noted. Even when the elastic member is stationary, there is a portion near the tip of the elastic member where the thickness of the ink is thin due to surface tension. If the stationary state is kept for a relatively long time, the physical properties of the ink are likely to change due to drying of the ink, especially near the tip of the elastic member. When the ink dries very quickly or when ink that dries easily is used, the ink may solidify and adhere to the vicinity of the tip, the amount of vibration at the tip of the elastic member changes, and the ejection drop diameter and ejection direction change significantly, resulting in poor image quality. Is deteriorated, or the ink cannot be ejected. When printing is completed and the recording head is stopped, the ink surface is placed above the tip of the elastic member, or capping is performed by pressing a cap material against the ejection opening of the device from which the ink drop is ejected and capping the ink component. This problem can be avoided by suppressing evaporation. However, the above problem tends to occur during printing. This is because there is an ejector that does not eject for a relatively long time and enters a standby state depending on the image signal even during printing.

Therefore, in the ink jet recording head, the tip of the elastic member is washed once or plural times before the series of printing operations is completed, or after the series of printing operations is completed, and the vicinity of the tip of the elastic member is cleaned. It is desirable to remove solid matter adhered to the ink or ink matter having increased viscosity. However, in a conventional recording head in which the ink ejection diameter is governed by the nozzle diameter, the ink or the solidified substance adhering around the nozzle hole can be relatively easily removed by wiping or the like, but the recording shown in FIGS. In the head, the bending vibration of the elastic member governs the ink ejection diameter, and it is very difficult to clean the delicate elastic member by wiping it without deforming or damaging it. Therefore, in the recording head having the structure shown in FIGS. 2 and 3, there is a possibility that the image quality may be degraded due to a change in physical properties of the ink generated near the tip of the elastic member.

In the present embodiment, the above-mentioned points to be considered are solved on the basis of the ejection principle that the ink ejection diameter of the ink jet recording head according to the embodiment is not controlled by the nozzle diameter. Specifically, a vapor generation section is provided in each ink chamber of the ejector to suppress evaporation of ink components from ink in the ink chamber. In particular, it is effective that the steam generator supplies steam of at least one component of the ink. The function and basic configuration will be described below.

FIGS. 4 and 5 are main structural views of the ink jet recording head according to the present embodiment. 4 is a sectional view of the apparatus, and FIG. 5 is a front view (discharge drops are not shown). A vibration generating unit 20 is provided on one surface of the diaphragm 1.
Then, the elastic member 5 is disposed on the other surface of the diaphragm 1. The ink reservoir 103 containing the ink 6 and the ink chamber 25 having the ejection opening 27 formed by the ink chamber forming member 26 are connected to the ink reservoir 103. The vibration member 200 vibrates and the elastic member 5 connected thereto
Bend and vibrate. An ink drop 8 is ejected from near the tip of the elastic member 5. Since the discharge drop diameter is determined without using a nozzle, the discharge opening 27 may be larger than the discharge drop diameter.

In the ink jet recording head according to the present embodiment, since the ejection drop diameter is determined without using a nozzle, the ink chamber 25 has a space above the ink surface 7. Therefore, the steam generation section 202 can be arranged near the elastic member by utilizing this space. The steam generation unit 202
Vapors of at least one or more of the ink components can be supplied to this space. Since the saturated vapor pressure in the ink chamber 25 is the sum of the partial pressure P1 from the ink 6 and the partial pressure P2 supplied from the vapor generator, the evaporation of the ink 6 from the ink surface 7 is suppressed, and as a result, the elasticity is reduced. Changes in physical properties of the ink due to drying of the ink near the tip of the member are less likely to occur. Therefore, according to the ink jet recording head of the present embodiment, the ejection drop diameter and the ejection direction are stable, and high-quality printing can be performed. In addition, in order to achieve higher image quality, ink having a component that easily evaporates can be used without any trouble.

First, the configuration of the steam generator 202 will be described with reference to FIG. FIG. 6A shows the case where the steam generating section is made of a porous member, and FIG. 6B shows the case where the hollow object has many holes on the surface. Both cases are rectangular parallelepipeds, and their cross-sectional views are shown. Of course, steam generator 2
The shape of 02 is not limited to this.

The porous member shown in FIG. 6A has a sponge-like structure, and is not limited to a resin, but may be a sintered body obtained by sintering ceramic or a material obtained by solidifying metal powder. The component liquid to be supplied penetrates the inside of the porous member by capillary force,
In each ink chamber, the ink is evaporated and supplied according to the surface area and temperature of the porous member. In the case of the hollow object shown in FIG. 6B, a component liquid (for example, water) to be supplied through the inside of the hollow object is carried to each ink chamber, and through each of the ink chambers through a number of holes. Evaporated and supplied according to the total area and temperature. However, if the holes are too large, they are dropped on the ink surface 7 as droplets, which causes inconvenience. The steam generator is
The present invention is not limited to the configuration in which the vapor component is evaporated from the porous member of the ink chamber or a number of holes in the surface of the hollow object. For example, the ink may be transmitted in a vapor state, and the vapor may be directly supplied to the ink chamber. In any case, the configuration of the steam generating section may be any as long as it can supply a main steam component into the ink chamber, and any configuration can be provided at low cost as long as it does not hinder the ejection of ink drops. Good.

FIG. 7 shows an example of the relationship between the steam generator and each ink chamber. This is the same as the front view of the recording head of FIG. 5 above, but showing a wider portion of the recording head, especially its ends. In this case, the steam generation section 202 is integrated and is arranged so as to penetrate all the ink chambers 25. The vapor generating section 202 is in contact with the component liquid 206 to be supplied at the end of the recording head inside the component liquid reservoir 205. It should be noted that how to supply the evaporation component to the steam generation unit 202 is not limited to such a structure in which the evaporation component is integrated and penetrates each ink chamber. However, in this case, the components can be easily fed at the end of the steam generating section, and the steam generating section and the recording head can be formed at low cost. In the case of the hollow object shown in FIG. 6B, it is necessary to consider the pressure applied to the supplied component liquid on the supply side, but in the case of the porous member shown in FIG. Since the component liquid naturally penetrates, there is no need for this, and a simpler configuration is likely to be obtained.

The extent to which the evaporation of the ink 6 from the ink surface 7 is suppressed is substantially given by the ratio of the partial pressure P1 of the component of interest from the ink 6 to the partial pressure P2 supplied from the steam generator. For example, if P1 = P2, the evaporation from the ink 6 is reduced by half, and if P1 = (1/10) · P2, 1/1
It is reduced to zero. Therefore, the effect is increased as the amount of the partial pressure P2 supplied from the steam generator is increased as much as possible.

Here, the amount of evaporation from the ink surface 7 is determined in part by the concentration of the evaporation suppression component contained in the ink. Therefore, as long as there is no problem in drop ejection,
The ink may contain a humectant such as ethylene glycol. Further, the evaporation amount of the component of interest from the ink surface 7 and the vapor generation unit 202 is determined by the ink chamber 25
It is determined by the existence of convection in the space inside, temperature, or atmospheric pressure. It is also effective to dispose a piezoelectric body in the steam generation section 202 and vibrate it to atomize the component liquid and supply it as steam.

Therefore, in order to increase and increase the partial pressure P2 supplied from the steam generating portion as compared with the partial pressure P1 from the ink surface 7, the steam generating area of the steam generating portion is compared with the area of the ink surface 7. It is effective to make it relatively large. Therefore, the following two methods are effective.

As a first method, the evaporation area of the ink surface 7 can be reduced by arranging the evaporation suppression member 203 on the ink surface 7 as shown in the print head section of FIG. Of course, the shape of the evaporation suppressing member 203 arranged on the ink surface 7 must be set so as not to hinder ink ejection, and there is a limit. Second, the area of the steam generation section 202 itself that generates steam is larger than the area of the ink surface 7. FIG. 9 shows a configuration example for realizing the second method. FIG. 9 is a cross-sectional view of the steam generator.
9 (a) and 9 (b), the surface area of the steam generating section is realized by making the surface uneven. FIG.
FIG. 9A shows a projection formed on the surface of the steam generator, and FIG. 9B shows a depression formed. As described above, a remarkable effect can be expected by increasing the surface area of the vapor generating portion with irregularities as compared with the evaporation area of the ink surface 7.

In the ink jet recording head, a water-based ink is mainly used as an ink in consideration of the environment such as a human body. When printing is performed using the aqueous ink, water may be supplied from the steam generating section to generate water vapor. The end of the steam generating section is connected to a water reservoir containing water. However, since the water to be supplied and the steam generating section itself are inexpensive, the cost of the printing apparatus and its maintenance can be maintained by this embodiment. The costs do not increase significantly.

As described above, from the viewpoint of the driving frequency, in the present embodiment, minute ink droplets are generated at a frequency as low as about several hundred kHz as compared with the conventional technique which requires several hundred MHz using a lens or the like. In addition to eliminating the need for an expensive drive system for high-frequency driving, the amount of heat generated in the ink is reduced, and problems such as fluctuations in the discharge drop diameter and reduced reliability due to solidification of the ink in the head hardly occur. It is possible to provide a small and inexpensive printing device while being able to print stably.

A more detailed and specific example will be described below based on the basic configuration and basic operation principle of the ink jet recording apparatus according to the present embodiment described above.

[Embodiment 1] FIGS. 10 and 11 are main structural views of an ink jet recording head showing Embodiment 1 in the present embodiment. The same members as those in FIGS. 4 and 5 described briefly above are denoted by the same reference numerals. FIG. 10 is a sectional view of the apparatus, and FIG. 11 is a front view (illustration of ink drops is omitted). The recording head mainly includes an ink tank 103 and a print head 33.

A 0.5 μm-thick Ag electrode 3 is deposited and patterned on a 10 μm-thick zirconia diaphragm 1, followed by 30 μm-thick zirconate / lead titanate (PZT). After depositing a piezoelectric ceramic thin film 2 having a thickness of 0.05 μm,
And an electrode 4 consisting of two layers of Au having a thickness of 1 μm was formed by patterning after deposition. The PZT thin film is polarized,
When a voltage is applied between both electrodes, the diaphragm vibrates in the horizontal direction with respect to the diaphragm. However, in relation to the diaphragm, as a result, the vibrator 9 including the piezoelectric ceramic thin film 2 and the electrodes 3 and 4 vibrates. Vibrates perpendicular to the plate. The electrode 3 is a common electrode common to the vibrators, and the electrode 4 is an address electrode for vibrating only a specific vibrator. Although not shown in the figure, these electrode wirings are connected from the ends of the diaphragm to an external drive power supply (not shown) via the connector 104. Further, the vibrator 9
Was covered with a protective film 10 made of SiO ₂ or the like having a thickness of 1 μm. By coating the protective film, moisture that can be brought from the environment does not cause a change in the polarizability of the PZT thin film. If it is possible to prevent the vibrator from being adversely affected by the ink, the vibrator may be formed on the same surface as one surface of the diaphragm on which the elastic member is formed.

Next, one surface of the vibration plate 1 on which the vibrator 9 was formed was bonded via a holding member 20 made of alumina and a support portion 21 thereof. Each vibrator having the elastic member 5 constitutes one ejector for ejection. However, in order to prevent the vibration generated by each ejector at the time of printing from affecting the adjacent ejector, the vibration of each ejector is controlled by the support portion 21. Limit to that part.

Further, the diaphragm 1 on which the vibrators 9 are formed
5 μm thick, 50 μm bottom on the other surface
A sharp elastic member 5 made of a stainless alloy and having a height of 250 μm and a shape as shown in FIG. 5 was formed. The elastic member 5 was sharpened to 70 μm from the tip to 40 μm in the rectangular plate. This manufacturing process is as follows. A rectangular stainless steel alloy is bent at 85 ° and the adhesive layer thickness is 2μm
Then, an epoxy resin is applied to the diaphragm 1 so that one surface of the L-shaped film is adhered to the diaphragm 1. continue,
The other surface standing on the diaphragm 1 was irradiated with a YAG laser from a direction perpendicular to the surface to be processed into the shape described above.

Subsequently, the ink chamber 2 having the ejection opening 27
5 was made of plastic 26. The discharge opening 27 was formed by irradiating the plastic 26 with an excimer laser. In addition, a vapor generation unit 202 was disposed above the ink chamber 25. The steam generating section 202 is made of sponge, and is integrally provided so as to penetrate all the ink chambers 25.
The steam generating section 202 is provided at an end of the recording head.
The component liquid 206 to be supplied is in contact with a component liquid reservoir (not shown). Since the ink used is an aqueous ink, the component liquid 206 is water here. Water vapor is supplied to the upper portion of the ink chamber 25 by the vapor generation section 202, and each ink chamber 25 has a saturated vapor pressure determined by its temperature and pressure. Further, an ink supply port 28 is opened in the plastic 26 and connected to an ink tank 103 filled with the ink 6 via an ink filter 102 for removing foreign substances and stabilizing the supply. The ink pressure was adjusted by an external ink supply pressure adjuster (not shown) so that the tip 50 μm of the elastic member 5 protruded from the ink surface 7. Further, as shown in the figure, an ink surface fixing member 29 is attached to the plastic 26 forming the ink chamber 25 at a position approximately 200 μm from the bottom surface of the ink chamber 25 so as to fix the height of the ink surface 7. This material may be any material that can fix the ink surface without being affected by the ink, but here, the same plastic material as the material constituting the ink chamber is used and integrally formed at low cost.

At the time of printing, an AC power source (not shown) is used to externally apply a vibration to the vibrator 9 at a frequency f which is the same as an inherent resonance frequency f0 determined by the rigidity and shape of the diaphragm 1 or an integral multiple thereof. Excitation was performed by applying a voltage according to the image signal. During printing, a voltage is selectively applied to one or more of the plurality of ejectors. In the present embodiment, in order to form one pixel, 10 Vp-p at 200 kHz is applied to the selected ejector.
A voltage of (maximum amplitude) was applied in bursts for an application time of 50 μsec (the number of bursts was 10). An ink drop having a diameter of 15 μm was ejected almost perpendicularly to the elastic member 5 from only the tip of the elastic member 5 of the ejector selected by the address electrode. The ink drops reach the printing paper 36 arranged at a distance of 1 mm, and a plurality of dots (pixels) are generated according to an image signal to form an image.

FIG. 12 is a structural diagram of a main part of the ink jet recording apparatus of this embodiment. Inkjet recording device 3
Reference numeral 7 denotes a plurality of ink jet recording heads 33 of a number corresponding to each color, which will be described later, are fixed to the carriage 34, and the carriage 34 reciprocates in the paper width direction of the printing paper 36, and the printing paper 36 moves to cover the entire printing paper. Characters and pictures can be printed (the component liquid reservoir is omitted in the figure). In each ink jet recording head 33, a plurality of ejectors each composed of a vibrator and an elastic member are arranged on the diaphragm, but only the ejector selected at each time is driven according to an image signal given from the outside. Discharge ink drop.

Further, the printing paper 36 is moved by a roller 35.
Was rotated. The feed speed of the carriage 34 and the arrangement interval of each vibrator in the inkjet recording head 33 corresponded to 600 dpi (dot per inch). Each ink jet recording head 33 fixed to the carriage 34 is connected to one of black, yellow, magenta, and cyan ink tanks 38. Each ink is supplied to each ink jet recording head 33, and when a voltage is applied to a vibrator corresponding to an image signal, an ink drop is ejected from an ink surface on the selected vibrator to form an image. Although not shown, an electric signal to the inkjet recording head 33 is sent from outside via the carriage 34. The print driving conditions of the ink jet recording head 33 have been described above.

Each dot formed on the printing paper 36 after printing was a uniform small-diameter dot having a diameter of approximately 30 μm for each color ink. By providing the steam generating section, there was no variation in dot diameter or dot landing position accuracy for each color, and small diameter drops could be stably ejected and printed.

Also, since the driving frequency is low, no heat is generated.
There was no problem such as a change in the viscosity of the ink or solidification due to heat generation. In particular, the provision of the steam generating portion enables stable formation of minute dots corresponding to high resolution, and enables high-quality printing. In addition, a small and inexpensive recording device could be realized.

Embodiment 2 FIGS. 13 and 14 are main structural diagrams of an ink jet recording head showing Embodiment 2 of the present embodiment. The same members as those in FIGS. 10 and 11 are denoted by the same reference numerals. 13 is a sectional view of the apparatus, and FIG. 14 is a front view (illustration of ink drops is omitted). The print head portion of the recording head mainly includes an ink tank 103 and a print head 33. Embodiment 2 is different from Embodiment 1 in the configuration of the steam generating section, particularly in the method of connecting to each ink chamber.

An Ag electrode 3 having a thickness of 0.5 μm is deposited and patterned on a diaphragm 1 made of zirconia having a thickness of 10 μm, and subsequently a lead electrode made of zirconate / titanate (PZT) having a thickness of 30 μm. After depositing a piezoelectric ceramic thin film 2 having a thickness of 0.05 μm,
And an electrode 4 consisting of two layers of Au having a thickness of 1 μm was formed by patterning after deposition. The PZT thin film is polarized,
When a voltage is applied between both electrodes, the diaphragm vibrates in the horizontal direction with respect to the diaphragm. However, in relation to the diaphragm, as a result, the vibrator 9 including the piezoelectric ceramic thin film 2 and the electrodes 3 and 4 vibrates. Vibrates perpendicular to the plate. The electrode 3 is a common electrode common to the vibrators, and the electrode 4 is an address electrode for vibrating only a specific vibrator. Although not shown in the figure, these electrode wirings are connected from the ends of the diaphragm to an external drive power supply (not shown) via the connector 104. Further, the vibrator 9
Was covered with a protective film 10 made of SiO ₂ or the like having a thickness of 1 μm. By coating the protective film, moisture brought from the environment did not cause a change in the polarizability of the PZT thin film.

Next, one surface of the vibration plate 1 on which the vibrator 9 was formed was bonded via a holding member 20 made of alumina and a supporting portion 21 thereof. Each vibrator having the elastic member 5 constitutes one ejector for ejection. However, in order to prevent the vibration generated by each ejector at the time of printing from affecting the adjacent ejector, the vibration of each ejector is controlled by the support portion 21. Limit to that part.

Further, the diaphragm 1 on which the respective vibrators 9 are formed
5 μm thick, 50 μm bottom on the other surface
A sharp elastic member 5 made of a stainless alloy and having a height of 250 μm and a shape as shown in FIG. 5 was formed. The elastic member 5 was sharpened to 70 μm from the tip to 40 μm in the rectangular plate. This manufacturing process is as follows. A rectangular stainless steel alloy is bent at 85 ° and the adhesive layer thickness is 2μm
Then, an epoxy resin is applied to the diaphragm 1 so that one surface of the L-shaped film is adhered to the diaphragm 1. continue,
The other surface standing on the diaphragm 1 was irradiated with a YAG laser from a direction perpendicular to the surface to be processed into the shape described above.

Subsequently, the ink chamber 2 having the ejection opening 27
5 was made of plastic 26. The discharge opening 27 was formed by irradiating the plastic 26 with an excimer laser. In addition, a steam generation unit 202 is arranged in an upper part in the ink chamber 25. The steam generating section 202 is made of a sponge, is arranged in each ink chamber 25, and is provided outside the ink chamber 25 and has a supply pipe 2 containing a component liquid 206 to be supplied.
08 and through the opening 207. Supply pipe 2
08 is connected to a component liquid reservoir (not shown) at the end of the recording head. Since the ink used is an aqueous ink, the component liquid 206 is water here. Water vapor is supplied to the upper portion of the ink chamber 25 by the vapor generation section 202, and each ink chamber 25 has a saturated vapor pressure determined by its temperature and pressure. Of course, when a non-aqueous ink is used, a component that easily evaporates in the ink is selected as the component liquid 206. Component liquid 2 to steam generator 202
In this way, if the flow path resistance of the supply pipe 208 is made sufficiently large, for example, by increasing the cross-sectional area, the supply of the component liquid 206 to the steam generation section 202 is performed smoothly, The effect becomes stable. In addition, since the supply of the component liquid 206 is performed smoothly, the amount of the component liquid to be held in advance by the steam generation unit 202 may be small. Therefore, even if the surface area does not change, the volume of the steam generating section 202 can be made smaller than that of the first embodiment, so that the ink chamber can be made smaller and the degree of freedom in designing a printing apparatus increases. In the case of the present embodiment, the vapor generating section may be regarded as being constituted by both the component liquid evaporating section inside the ink chamber and the component liquid supply pipe.

Further, an ink supply port 28 is opened in the plastic 26 and connected to an ink tank 103 filled with the ink 6 via an ink filter 102 for removing foreign substances and stabilizing the supply. The ink pressure was adjusted by an external ink supply pressure adjuster (not shown) so that the tip 50 μm of the elastic member 5 protruded from the ink surface 7. Also, a plastic 26 forming the ink chamber 25 is formed.
As shown in the figure, an ink surface fixing member 29 is attached at a position of about 200 μm from the bottom surface of the ink chamber 25 so as to fix the height of the ink surface 7. This material may be anything that can fix the ink surface without being affected by the ink,
Here, the same plastic material as the material constituting the ink chamber was used, and was integrally formed at low cost.

At the time of printing, an AC power supply (not shown) is used to externally apply a vibration to the vibrator 9 at a frequency f which is the same as an inherent resonance frequency f0 determined by the rigidity and shape of the diaphragm 1 or an integral multiple thereof. Then, a voltage was applied according to the image signal to excite. During printing, a voltage is selectively applied to one or more of the plurality of ejectors. In this embodiment, in order to form one pixel,
10Vp at 200kHz for the selected ejector
A voltage of −p was applied in bursts for an application time of 50 μsec (the number of bursts was 10). The elastic member 5 is provided only from the tip of the elastic member 5 of the ejector selected by the address electrode.
An ink drop having a diameter of 15 μm was ejected almost at right angles. The ink drop reaches the printing paper 36 arranged at a distance of 1 mm and a plurality of dots (pixels) according to the image signal.
Is generated to form an image.

The outline of the entire recording apparatus at this time is described in Embodiment 1.
This is the same as that described with reference to FIG. In the ink jet recording apparatus 37, a plurality of ink jet recording heads 33 of a number corresponding to each color described later are fixed to the carriage 34, and the carriage 34 reciprocates in the paper width direction of the printing paper 36, and prints by moving the printing paper 36. Characters and pictures can be printed on the entire surface of the paper (the component liquid reservoir is not shown in the figure). In each ink jet recording head 33, a plurality of ejectors each composed of a vibrator and an elastic member are arranged on the diaphragm, but only the ejector selected at each time is driven according to an image signal given from the outside. Discharge ink drop.

Further, the printing paper 36 is moved by the roller 35.
Was rotated. The feed speed of the carriage 34 and the arrangement interval of each vibrator in the inkjet recording head 33 corresponded to 600 dpi. Each inkjet recording head 33 fixed to the carriage 34
Means black, yellow, magenta and cyan ink tanks 3
8 is connected. Each ink is supplied to each ink jet recording head 33, and when a voltage is applied to a vibrator corresponding to an image signal, an ink drop is ejected from an ink surface on the selected vibrator to form an image.
Although not shown, the inkjet recording head 33 is not shown.
Is sent from outside via the carriage 34. The print driving conditions of the ink jet recording head 33 have been described above.

Each dot formed on the printing paper 36 after printing was a uniform small-diameter dot having a diameter of approximately 30 μm and uniform for each color ink. By providing the steam generating section, there was no variation in dot diameter or dot landing position accuracy for each color, and small diameter drops could be stably ejected and printed.

Since the driving frequency is low, no heat is generated.
There was no problem such as a change in the viscosity of the ink or solidification due to heat generation. In particular, the provision of the steam generating portion enables stable formation of minute dots corresponding to high resolution, and enables high-quality printing. In addition, a small and inexpensive recording device could be realized.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, the width W of the surface perpendicular to the vibration direction of the bending vibration in the vicinity of the free end of the free end of the cantilever structure of the elastic member 5 may have a region where the length is approximately W = 2λ. . Here, λ is given by the following equation. λ = {8πσ / (ρfe ² )} ^1/3 × 10 ⁴ (μm) where σ is ink surface tension (mN / m) ρ is ink density (g / cm ³ ) fe is excitation frequency ( Hz). By doing so, it is possible to generate two peaks of the capillary wave in the width W, and thereafter, one peak of the ink ridge is formed, and this is separated at the next moment, so that one ink droplet can fly more accurately. .

[0061]

As described above, according to the present invention, unlike the conventional ink-jet technology, it is possible to discharge a minute drop without using a nozzle, and to drive at a lower frequency than the conventional nozzle-less ink-jet technology. By this, it is possible to discharge a small drop corresponding to high resolution,
It is possible to realize an ink jet recording head that eliminates instability of ink ejection such as ink clogging and fluctuation of the ink ejection direction. Further, the provision of the steam generating section makes it possible to realize an ink jet recording head capable of printing with high reliability and high image quality. In addition, a small and inexpensive recording head can be realized. In addition, since the ink can be driven at a low frequency, the energy efficiency is good, the physical properties of usable ink can be widened, and an ink jet recording head applicable to various printing applications can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a discharge mechanism using a capillary wave used in an ink jet recording head according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a basic configuration of an inkjet recording head according to an embodiment of the present invention.

FIG. 3 is a front view illustrating a basic configuration of an inkjet recording head according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a schematic configuration of an inkjet recording head according to an embodiment of the present invention.

FIG. 5 is a front view illustrating a schematic configuration of an inkjet recording head according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view of a vapor generating section of the inkjet recording head according to one embodiment of the present invention.

FIG. 7 is a cross-sectional view of a steam generating section of the inkjet recording head according to one embodiment of the present invention.

FIG. 8 is a diagram showing a modification of the configuration of the inkjet recording head according to the embodiment of the present invention.

FIG. 9 is a diagram showing a modified example of the steam generating section of the inkjet recording head according to one embodiment of the present invention.

FIG. 10 is a cross-sectional view illustrating a schematic configuration of an inkjet recording head of Example 1 according to an embodiment of the present invention.

FIG. 11 is a front view illustrating a schematic configuration of an inkjet recording head of Example 1 according to an embodiment of the present invention.

FIG. 12 is a perspective view illustrating a schematic configuration of an inkjet recording apparatus of Example 1 according to an embodiment of the present invention.

FIG. 13 is a cross-sectional view illustrating a schematic configuration of an inkjet recording head of Example 2 according to an embodiment of the present invention.

FIG. 14 is a front view illustrating a schematic configuration of an inkjet recording head of Example 2 according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vibration plate 2 Piezoelectric ceramic thin film 3, 4 Electrode 5 Elastic member 6 Ink 7 Ink surface 8 Discharge drop 9 Vibrator 10 Protective film 20 Holding member 21 Support part 25 Ink chamber 26 Ink chamber constituent member 27 Discharge opening 28 Ink supply opening Unit 29 Ink surface holding member 33 Recording head 34 Carriage 35 Roller 36 Printing paper 37 Recording device 38 Ink tank 102 Filter 103 Ink tank 104 Signal connector 120 External drive unit 200 Vibration generator 201 Vibration support member 202 Vapor generator 203 Evaporation suppression Member 205 Component liquid reservoir 206 Component liquid 207 Opening 208 Supply pipe

Claims (5)

[Claims] A vibration generating unit that vibrates in response to a pixel signal; an elastic member having a cantilever structure that bends and vibrates in response to excitation of the vibration generating unit; and a steam generating unit disposed near the elastic member. An ink jet method comprising: generating a capillary wave on the surface of the ink by vibrating the elastic member while causing the ink to evaporate by the vapor generating means, causing the ink to fly and adhere to a recording medium. Recording head. 2. An ink jet recording head according to claim 1, wherein said vapor generating means generates vapor containing at least one component of said ink. 3. The ink jet recording head according to claim 1, wherein the ink is a water-based ink, and
An ink jet recording head that generates water vapor. 4. The ink jet recording head according to claim 1, wherein said vapor generating means includes a porous member. 5. The ink jet recording head according to claim 1, wherein said vapor generating means has irregularities formed on at least a part of a surface for generating vapor. head.