JP2001158095A - Ink-jet recording head, and ink-jet recording apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recording head which is free from problem caused by nozzles, can increase resolution of printing dots, has a stable discharge velocity and a stable discharge direction of ink and can print at a high speed, and an ink-jet recording apparatus using the same. SOLUTION: The ink-jet recording head has an ink-holding member 426 for holding the ink 416 with having a part opposite to a recording medium 448 at least partly opened to form an ink discharge port, bubble-generating means 430 and 432 for generating bubbles 410 immediately below a gas-liquid interface 422 correspondingly to image information, and an impulse wave- generating means 434 for making the ink 416 generate impulse waves 418 towards the bubbles 410. The ink-jet recording apparatus uses the ink-jet recording head.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head for ejecting ink to record an image on a recording medium surface, and an ink jet recording apparatus using the ink jet recording head.

[0002]

2. Description of the Related Art Various types of ink jet recording heads have been proposed for printing on the surface of a recording medium by discharging ink droplets in accordance with image information. The main thing is to eject ink droplets according to image information,
There are a so-called drop-on-demand (DOD) type ink jet recording head and a continuous flow type ink jet recording head which continuously discharges ink from nozzles.

A typical drop-on-demand type ink jet recording head uses, for example, a piezoelectric element such as a piezoelectric element (piezo-vibrator type).
And those utilizing the heat generated by a heating element (thermal type). The piezo vibrator type applies a pulse voltage to the piezoelectric element attached to the ink chamber, deforms the piezoelectric element, generates a pressure wave in the ink chamber, discharges ink droplets from the nozzles, and forms dots on the surface of the recording medium Is what you do.

On the other hand, in the thermal type, ink is heated by a heating mechanism provided in an ink chamber, bubbles are generated by instantaneous boiling, and ink is ejected from nozzles by the pressure to form dots on the surface of a recording medium. Form.

[0005] In addition, the thermal type includes a so-called optical addressing type recording head. This is disclosed in
As disclosed in Japanese Patent Application Laid-Open No. 24197 and Japanese Patent Application Laid-Open No. 55-132282, light energy such as a laser beam or a light emitting element is irradiated on ink to give thermal energy to generate bubbles, which are generated at that time. Ink is ejected from the nozzle by the action of the pressure wave. In this method, since the generated pressure does not become sufficiently high, the discharge speed of the ink droplet is at most about 5 to 10 m / s, the discharge direction becomes unstable, and the ink lands on the surface of the recording medium due to air resistance and the like. There are problems such as poor position stability.

On the other hand, a continuous flow type ink jet recording head applies pressure to ink to continuously eject ink from nozzles, and at the same time, applies vibration by a piezo vibrator or the like to form a protruding ink column into droplets. Further, recording is performed by selectively charging and deflecting the droplets.

In an ink jet recording head using these ink ejection principles, in order to increase the recording resolution, the arrangement of nozzles is increased, and the diameter of the nozzles is reduced according to the resolution to discharge minute ink droplets. Although it is necessary, there is a problem that the nozzle cannot easily be clogged by reducing the nozzle diameter, so that the density of the head cannot be increased and the resolution cannot be increased.

Further, when the ink flow path of the nozzle becomes narrower with the increase in density, the flow path resistance received by the ink increases,
There is a problem that sufficient discharge performance cannot be obtained. Further, it is necessary to supply ink from the ink storage device to the nozzles using an ink supply unit. However, in the conventional ink jet recording head, refilling of the nozzles with ink is rate-limiting due to the large flow resistance of the nozzles. As a result, the ink supply speed is limited by the flow path resistance, and as a result, there is a problem in that the printing speed is also reduced.

In addition, when the nozzle diameter is reduced, clogging due to entry of foreign matter into the nozzle or drying of the ink is liable to occur, and the ink ejection direction becomes unstable due to adhesion of residue around the nozzle. As a result, a defect occurs in the image quality of the recording medium surface, or a small bubble of about the nozzle diameter is generated due to the vaporization of oxygen dissolved in the ink or the vibration of the ink, and the bubble blocks the ink flow path, thereby causing a discharge failure. There was a problem.

Therefore, in a conventional ink jet recording head, a vacuum operation for sucking ink from nozzles,
A maintenance operation such as a wiping operation for removing residues and foreign matters on the nozzle surface is indispensable, and the interruption of the printing operation, which also hinders the improvement of the printing speed.

In order to solve such a problem of the ink jet recording head having a nozzle, a nozzleless ink jet recording head has been proposed. As a nozzleless ink jet recording head, there is one using an acoustic wave.

Japanese Patent Application Laid-Open No. Hei.
As disclosed in Japanese Patent Application Laid-Open No. 200199, the radiation pressure of a sound wave is focused on the ink liquid surface, and the energy is used to eject ink droplets from the ink liquid surface. As a problem of the method using sound waves as described above, a vibration source is required to generate sound waves, and it is difficult to increase the density of ink ejection points due to its low degree of freedom in shape. In addition, since a device for concentrating the discharge energy at the ink discharge position is required for each ink discharge position, the device is increased in size and cost, and the number of ink droplets that can be discharged from one recording head cannot be increased. As a result, there is a problem that the address speed and the printing speed are reduced.

[0013]

In consideration of the above facts, the present invention has no problems caused by nozzles, can achieve high resolution of print dots, and has a stable ink discharge speed and discharge direction. It is an object of the present invention to provide an ink jet recording head capable of printing at high speed and an ink jet recording apparatus using the same.

[0014]

The above object is achieved by the present invention described below. That is, a first aspect of the present invention provides an ink holding member that holds ink and at least a part of a portion facing a recording medium is opened to form an ink ejection port, and that the ink holding member has an ink ejection port directly below a gas-liquid interface corresponding to image information. An ink jet recording head, comprising: bubble generating means for generating bubbles; and shock wave generating means for generating a shock wave toward the bubbles in the ink.

According to the first aspect of the present invention, a shock wave is generated by a shock wave generating means toward a bubble (hereinafter, referred to as a "first air bubble") generated immediately below a gas-liquid interface corresponding to image information by a bubble generating means. When the shock wave reaches the bubble interface, the first bubble contracts violently, and then generates a secondary shock wave when re-expanded. At the same time, the deformation of the first bubble toward the gas-liquid interface causes
A strong liquid flow is generated through the first bubble. Ink droplets are ejected from the gas-liquid interface by the action of the secondary shock wave due to the difference in acoustic impedance at the gas-liquid interface and the action of the liquid flow. Then, an image corresponding to the image information is formed on the surface of the recording medium.

As described above, since the first aspect of the present invention has no nozzle, there is no problem caused by the nozzle.
In addition, the resolution of the printing dots can be increased, the ink ejection speed and the ejection direction are stable, and an ink jet recording head capable of printing at high speed can be obtained.

According to a second aspect of the present invention, there is provided the ink jet recording head according to the first aspect of the present invention, which has a bubble control mechanism capable of controlling the diameter of the first bubble generated by the bubble generating means. In the ink jet recording head according to the first aspect of the invention, the first recording head generated by the bubble generating means is used.
There is a correlation between the diameter of the bubble and the diameter of the ejected ink droplet. Therefore, according to the second aspect of the present invention, the diameter of the ink liquid can be modulated by controlling the diameter of the first bubble generated by the bubble generating means. Therefore, it is possible to achieve higher resolution of the obtained image.

A third aspect of the present invention is the ink jet recording head according to the first or second aspect of the present invention, wherein the bubble generating means is configured to generate first bubbles by electrolysis. According to the third aspect of the present invention, the first bubble can be generated accurately at an arbitrary position in the ink corresponding to the image information by the electrolysis of water.

According to a fourth aspect of the present invention, there is provided the ink jet recording head according to the first or second aspect of the present invention, wherein the bubble generating means generates the first bubble using heat. I do. According to the fourth aspect of the present invention, by heating and evaporating the ink, it is possible to accurately generate the first bubble at an arbitrary position in the ink corresponding to the image information.

A fifth aspect of the present invention is the ink jet recording head according to any one of the first to fourth aspects, wherein the shock wave generating means irradiates the ink held by the ink holding member with laser light, It is a laser light generating means for generating a shock wave toward the first bubble in the ink.

According to the fifth aspect of the present invention, by irradiating the ink held by the ink holding member with laser light, high-density energy is given to a minute space in the ink, and the ink is rapidly vaporized. Bubbles (hereinafter, referred to as “second bubbles”) grow. The growth of the second bubble causes a shock wave in the ink. Therefore, it is possible to easily and accurately generate a shock wave in the ink.

A sixth aspect of the present invention is the ink jet recording head according to any one of the first to fourth aspects, wherein the shock wave generating means applies a high voltage inside the ink held by the ink holding member. Discharge means for generating a shock wave in the ink.

According to the sixth aspect of the present invention, a discharge is generated by applying a high voltage inside the ink held by the ink holding member by the discharge generating means comprising at least a pair of electrodes, thereby minimizing the minuteness of the ink. High-density energy is applied to the space, and the ink is rapidly vaporized and the second bubble grows. The growth of the second bubble causes a shock wave in the ink. Therefore, it is possible to easily and accurately generate a shock wave in the ink.

According to a seventh aspect of the present invention, there is provided an ink jet recording apparatus including the ink jet recording head according to any one of the first to sixth aspects of the present invention. According to the seventh aspect of the present invention, since the inkjet recording head according to any one of the first to sixth aspects of the present invention having no nozzle is provided, there is no problem caused by the nozzle and the printing dot of the An ink jet recording apparatus that can achieve high resolution, has a stable ink discharge speed and discharge direction, and can print at high speed.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Principle of the Present Invention) First, the principle of discharging ink by the ink jet recording head of the present invention will be described. 1 to 3 are schematic structural views of an ink jet recording head of the present invention for explaining the principle of the present invention. As shown in FIGS. 1 to 3, the ink jet recording head of the present invention includes an ink holding member 26 and a shock wave generating means 12, and further has a bubble generating means (not shown). The ink holding member 26 holds the ink 16 in a thin layer, and at least a part of a portion facing a recording medium (not shown) is opened to form an ink discharge port.

As shown in FIG. 1, a gas-liquid interface 22 in the ink 16 corresponding to image information
A first bubble 10 is formed immediately below, and then a second bubble 14 grows by the shock wave generating means 12 and the ink 16
Then, a shock wave 18 directed to the first bubble 10 is generated. When the shock wave 18 reaches the interface of the first bubble 10, as shown in FIG. 2, the first bubble 10 contracts violently and then generates a secondary shock wave 20 when re-expanded. At the same time, the first
The first deformation toward the gas-liquid interface 22
An intense liquid flow 50 that penetrates the air bubbles 10 is generated. Secondary shock wave 2 due to difference in acoustic impedance at gas-liquid interface 22
By the action of 0 and the action of the liquid flow 50, a strong discharge force 28 is generated as shown in FIG. 3, and the ink droplet 24 is discharged from the gas-liquid interface 22 while pushing up the liquid surface of the gas-liquid interface 22. Then, the ink droplets 24 land on the surface of the recording medium (not shown), and an image corresponding to the image information is formed.

(Preferred Embodiment) Next, the present invention will be described in detail with reference to preferred embodiments. FIG.
Inkjet recording head 400 according to first embodiment
It is a schematic cross section which shows schematic structure of.

The ink jet recording head 400 has an ink holding member 426, a laser light generator (laser light generating means) 434 as a shock wave generating means, and electrodes 430 and 432 as bubble generating means. The ink holding member 426 holds the ink 416 in a thin layer shape, and at least a part of a portion facing the recording medium 448 is opened to form an ink ejection port. The electrode 430 is an electrode having an exposed surface of a minute metal at the tip, and the electrode 430 is formed according to the area of the exposed surface.
A first bubble is generated at the tip of the.

In the ink jet recording head 400, first, according to the image information, the current generating means (not shown) changes the electrodes 430 and 432 serving as the bubble generating means in accordance with the print signal generated by the printing control device (not shown).
In the meantime, such that the electrode 430 becomes a negative electrode and the electrode 432 becomes a positive electrode,
A voltage is applied. Then, the water in the ink is electrolyzed, and the first bubble 410 of hydrogen is discharged from the electrode 430 which is a negative electrode.
Occurs.

The electrode 430 is located immediately below the gas-liquid interface 422, and the current generating means operates in accordance with the image information.
By applying a voltage between and 432, a first bubble 410 of hydrogen is generated. The tip of the electrode 430 is the gas-liquid interface 4
22, the diameter of the first bubble 410 to be generated is 2 to 10
It is desirable to arrange at a position where it is doubled. As described above, it is desirable that the position of the tip of the electrode 430 be close to the gas-liquid interface 422 because the secondary shock wave 420 generated from the first bubble 410 is a spherical wave, and is diffused until reaching the gas-liquid interface 422. This is because energy loss due to absorption into the ink 416 can be reduced. The electrode 432 is desirably disposed at the end of the inner bottom surface of the ink holding member 426 so as not to hinder the generation of a shock wave 418 described later.

The materials of the electrodes 430 and 432 include
It is preferable to use a corrosion-resistant metal, such as nickel or stainless steel, which hardly deteriorates in the ink. The electrode 430, which is the negative electrode, is covered with an insulating material except for the tip, and can be energized only at the tip, and preferably has a tip curvature radius of 10 μm or less. On the other hand, the positive electrode 432 is
A plate having a larger electrode area and no protrusion structure, or a thin film formed by plating or the like is preferable.

The current generating means has a voltage range of 1 V to 10 V and a pulse width of 1 mS or less.
Preferably, it generates an electric current. In order to make the first bubble 410 of hydrogen a desired size, it is more desirable that the voltage and pulse waveform can be arbitrarily adjusted.

Electrodes 430 and 43 as bubble generating means
The diameter of the first bubble 410 generated in 2 and the diameter of the ejected ink droplet 424 have a substantially correlation. Therefore, the first bubble 4 generated by the bubble generating means
By having a bubble control mechanism capable of controlling the diameter of the ink droplets 10, the ink droplets 424 having an arbitrary diameter can be ejected. As the bubble control mechanism, for example, a voltage,
There is a mechanism for arbitrarily adjusting the pulse waveform. The diameter of the first bubble 410 can be controlled by the amount of current, and the voltage can control the growth rate of the first bubble.

The diameter of the first bubble 410 generated by the bubble generating means is preferably 1 to 50 times the desired diameter of the ink droplet 424 to be ejected, more preferably 1 to 10 times. As large as the desired diameter (1
To about 2 times).

As described above, in the present embodiment, the first bubble 410 of hydrogen is accurately generated at an arbitrary position in the ink 416 corresponding to the image information by utilizing the electrolysis of water. be able to. In FIG. 4, the first bubble 410 is the ink jet recording head 4
00, only one was formed.
It is also possible to form a plurality of 10 at the same time. If two or more first air bubbles 410 are formed in advance, two or more ink droplets 424 can be simultaneously discharged by one shock wave 418. In addition, each first bubble 41 to be formed
The diameter of 0 may be different in size, and ink droplets 424 of different sizes may be ejected simultaneously. Further, by forming one or a plurality of first bubbles 410 at different locations according to the image information, the ink droplets 424 can be ejected from an appropriate location according to the image information.

In order to form two or more first air bubbles 410, a plurality of electrodes 430 in FIG. 4 may be arranged so that their tips are located at predetermined positions. Instead, one or more minute metal exposed surfaces may be provided halfway. When utilizing the electrolysis of water as in this embodiment, the condition is that the ink is conductive and contains water. The electrodes 430 and 432, which are the above-described bubble generating means, allow the ink 416
At the position corresponding to the pixel information just below the gas-liquid interface 422 inside,
A first bubble 410 is generated.

Next, the ink jet recording head 400
In the first embodiment, after the first bubble 410 is generated, a high-density energy is applied to the ink 416 by the laser light generator 434 in response to a print signal controlled so that the shock wave 418 reaches the interface of the first bubble 410. Is done. In the ink 416 to which the high-density energy has been applied, a rapid change in density from a liquid phase to a gas phase occurs, and second bubbles 414 are generated. When the second bubble 414 expands in volume beyond the speed of sound, a shock wave 418 is generated.
6 and reaches the interface of the first bubble 410, the first bubble
Deformation and shrinkage of the air bubble 410 occur, and the secondary shock wave 4
20 and the above-mentioned violent liquid flow (not shown) penetrating the first bubble 410 occurs. By the action of the secondary shock wave 420 and the action of the liquid flow, a strong discharge force is generated, and the gas-liquid interface 4
The ink droplet 424 is ejected from the gas-liquid interface 422 while pushing up the liquid surface of the nozzle 22. Then, the ink droplets 424 land on the surface of the recording medium 448, and an image corresponding to the image information is formed. Note that the second bubble 414 disappears promptly when the shock wave 418 is generated.

In this embodiment, in order to generate the second bubble 414 whose expansion speed exceeds the sound speed, a laser beam 436 having a certain energy or more is generated by a laser beam generator (laser beam generator) 434. The ink 416 is irradiated from the bottom surface of the ink holding member 426.

In this embodiment, the laser light 436
Irradiation may be performed so as to apply energy to the ink 416 in a planar state without condensing the light. The second bubble 414 generated by the planarly irradiated laser light 436 becomes a flat surface and forms a flat shock wave 418. Of course, according to the principle of the present invention described above, it is essential to set the intensity of the laser beam 436 so that the planar shock wave 418 has sufficient energy for the ink droplet 424 to protrude. In order to achieve such an intensity, it is also possible to irradiate the laser light after being focused by the focusing means so as to focus on the vicinity of the boundary between the bottom surface of the ink holding member 426 and the ink 416. The focusing means includes an optical lens and the like.

As described above, two or more first air bubbles 410
Is formed in advance and two or more ink droplets 424 are ejected by one shock wave 418, all the first bubbles 410
It is preferable that the shock wave 418 is generated in a planar manner so that the energy can be applied evenly. At this time, a laser beam having an energy density for generating the second bubble 414 is applied to a region wider than the region where the first bubble 410 is arranged.

Although various types of laser light generators 434 can be used, a pulse laser light generator capable of high output in consideration of the energy required to generate the second bubble 414. It is preferable to use Preferably, the pulse width is 1 to 500 ns, the wavelength is 500 to 1200 nm, and the laser output range is 1 μJ to 1 J. Examples thereof include Cr (ruby), Nd (YAG), glass laser, and semiconductor laser. A continuous oscillation type may be formed into a pulse. Appropriate laser oscillation frequencies are visible light and infrared light that do not significantly change physical properties upon irradiation.

When the laser light generator 434 is used,
The material of the bottom surface of the ink holding member 426 (and the optical lens used as necessary) is 90% laser light transmittance.
The above is desirable. Specifically, those having an intensity to laser light, such as borosilicate glass, fused quartz, and synthetic quartz, are preferable. More preferably, the material has an energy damage threshold of 5 J / cm ² or more. Further, the bottom of the ink holding member 426 (and an optical lens used as needed) is provided with an anti-reflection film (MgF ₂ , Cr, Al + MgF _2, etc.) to prevent reflection of laser light.
It is more desirable that the coating be performed.

According to the ink jet recording head of the first embodiment described above, since it has no nozzle,
Problems caused by nozzles, such as nozzle clogging due to higher resolution, printing speed limit due to high nozzle flow resistance, ejection failure due to nozzle clogging, printing interruption due to maintenance operation, etc. There is no. Therefore, it is possible to increase the resolution of print dots. In the first embodiment, since the ink droplets are ejected by the secondary shock wave generated from the first bubble and the strong liquid flow penetrating the first bubble, the ejection pressure of the ink increases,
The ink ejection speed is high, and stabilization of the printing direction can be easily achieved.

The diameter of the ejected ink droplet depends on the diameter of the first bubble 410 generated by the bubble generating means as described above, and the thickness of the ink 416 stored in a thin layer (the thickness of the ink layer). The thickness of the ink layer can be arbitrarily set regardless of the diameter of the ink droplet 424. Generally, the thickness is preferably in the range of 10 to 1000 μm from the viewpoint of the device design for holding the ink.

However, when the shock wave 418 generated by the shock wave generating means is spherical, not planar, and there are a plurality of first bubbles 410 generated by the bubble generating means, each of the first bubbles 410 Evenly shock wave 4
18 energy does not propagate. Therefore, the second bubble 4
The shock wave 418 becomes closer to a plane wave as the distance between the portion where the 14 is generated (the inner bottom surface of the ink holding member 426) and the first bubble 410 is larger. Therefore, the thickness of the ink layer is desirably thick, specifically, desirably 100 μm or more, and more desirably in the range of 200 to 500 μm.

FIG. 5 is a schematic sectional view showing a schematic configuration of an ink jet recording head 500 according to the second embodiment. The ink jet recording head 500 includes an ink holding member 526, a counter electrode 544 serving as a shock wave generator, and a heater 538 serving as a bubble generator. The ink holding member 526 holds the ink 516 in a thin layer shape, and at least a part of a portion facing the recording medium 548 is opened to form an ink ejection port. In the counter electrode 544, the electrodes 540-1 to 540-3 and the electrodes 542-1 to 542-3 are alternately arranged and form a pair. The heater 538 is provided with a minute heating surface at the tip, and generates air bubbles at the tip of the heater 538 according to the area of the heating surface.

In the ink jet recording head 400, first, in response to the image information, a current is supplied from a current generator (not shown) to the heater 538, which is a bubble generator, in response to a print signal generated by a print controller (not shown). Then, the tip of the heater 538 is heated. Then, the ink 516 generates heat and the first bubble (vapor bubble) 5
10 occurs. The position of the heater 538 is the same as that of the electrode 430 in the first embodiment.

The heater 538 is preferably made by thin film processing, also, the area of the heating surface which is disposed at the distal end portion, is preferably 10000 ² or less, in the range of 1 to 1000 m ² More preferred. The heating surface includes a counter electrode 544 serving as a shock wave generating means.
It is preferable to arrange the shock wave 518 perpendicular to the wavefront of the shock wave 518 so that the shock wave 518 generated from the shock wave 518 can directly act on the first bubble 510. Regarding the diameter of the first bubble 510 generated by the heater 538 serving as the bubble generating means and the control thereof, the electrode 430 in the first embodiment is used.
Is the same as As the bubble control mechanism, for example, a mechanism for arbitrarily adjusting the heating time and the heating temperature of the heater 538 can be mentioned. The heating time is preferably adjusted in the range of 1 μs to 100 μs, and the heating temperature is preferably adjusted in the range of 100 to 300 ° C.

As described above, in the present embodiment, the first bubble 510 of hydrogen can be accurately placed at an arbitrary position in the ink 516 corresponding to image information by evaporating the ink 516 using heat. Can be generated. Although FIG. 5 shows a state in which only one first bubble 510 is formed in the inkjet recording head 500, a plurality of first bubbles 510 may be formed at the same time. If two or more first air bubbles 510 are formed in advance, two or more ink droplets 524 can be simultaneously discharged by one shock wave 518. In addition, the diameter of each first bubble 510 to be formed can be different in size, and ink droplets 524 of different sizes can be ejected simultaneously. Further, by forming one or a plurality of first bubbles 510 at different locations according to the image information, the ink droplets 524 can be ejected from an appropriate location according to the image information.

In order to form two or more first bubbles 510, a plurality of heaters 538 in FIG.
It is sufficient to provide one or more minute heating surfaces not only at the tip of 8, but also halfway. The gas-liquid interface 52 in the ink 516 is generated by the heater 538 as the bubble generating means.
The first bubble 510 is located at a position corresponding to the pixel information immediately below the second bubble 510.
Is generated.

Next, the ink jet recording head 500
In the first embodiment, after the first bubble 510 is generated, a counter electrode, which is a shock wave generating unit, is generated by a current generating unit (not shown) in response to a print signal controlled so that the shock wave 518 reaches the interface of the first bubble 510. A discharge voltage is applied to 544.
This discharge applies high-density energy to the ink 516.

Ink 5 to which high-density energy has been applied
In 16, a sharp density change from the liquid phase to the gas phase occurs,
A second bubble 514 is generated. When the second bubble 514 expands in volume beyond the speed of sound, a shock wave 518 is generated. When the shock wave 518 propagates through the ink 516 and reaches the interface of the first bubble 510, the bubble 510 is deformed and contracted. The next shock wave 520 and the above-described violent liquid flow (not shown) penetrating the first bubble 510 are generated. Secondary shock wave 520
A strong ejection force is generated by the action of the liquid flow and the action of the liquid flow, and the ink droplet 524 is ejected from the gas-liquid interface 522 while pushing up the liquid surface of the gas-liquid interface 522. Then, the ink droplet 524 lands on the surface of the recording medium 548, and an image corresponding to the image information is formed. Note that the second bubble 514
Disappears promptly with the generation of the shock wave 518.

The specific configuration of the counter electrode 544 may be at least a pair of electrodes. In the present embodiment, in order to generate a flat shock wave 518,
It is composed of electrodes 540-1 to 540-3 and electrodes 542-1 to 542-3 in which three pairs of electrodes are arranged. The number of the electrode pairs is not necessarily three as in the present embodiment, and a configuration in which less than three pairs or more than three pairs are formed may be used.

Second bubble 514 generated from a pair of electrodes
Generates a shock wave having a substantially arc shape, which propagates through the ink 516. By forming a plurality of electrode pairs, the shock waves generated between the individual electrode pairs interfere with each other. , And become a substantially planar shock wave 518. Therefore, in order to generate the shock wave 518 in a planar manner, it is desirable that the electrode pairs be arranged as densely as possible. Specifically, the gap between the paired electrodes (for example, the gap between the electrode 540-1 and the electrode 542-1 in FIG. 5) is desirably 1 to 10 μm,
Further, the interval between each pair of electrodes (for example, the interval between the electrode 542-1 and the electrode 540-2 in FIG. 5) is desirably 5 to 10 times the gap between the paired electrodes.

As described above, two or more first bubbles 510
Is formed in advance and two or more ink droplets 524 are ejected by one shock wave 518, all the first bubbles 510 are formed.
It is preferable that the shock wave 518 is generated in a planar manner so that the energy can be applied evenly. Therefore, in this case, it is desirable to arrange the pairs of electrodes with high density in a region wider than the region where the first bubble 510 is arranged.

Since the shock wave generating means in this embodiment can directly apply energy to a predetermined position immediately below the gas-liquid interface 522, high-density energy can be accurately transferred to the ink 516 immediately below the gas-liquid interface 522. Can be granted. The voltage to be applied to the counter electrode 544 is
It is sufficient if the energy is large enough to give sufficient energy to the ink to generate the second bubble 514 capable of generating the shock wave 518 necessary for the ejection of No. 4. Specifically, the gap between the paired electrodes is 1 to 10 μm, and the pulse width is 0.1.
Preferably, the voltage is in the range of 60V to 300V for １００100 μs.

According to the ink jet recording head of the second embodiment, as in the first embodiment, since there is no nozzle, there is no problem caused by the nozzle. Further, it is possible to increase the resolution of print dots. Further, the ink ejection speed is high, the ejection direction is stable, and high-speed printing is possible. The concept regarding the thickness (ink layer thickness) of the ink 516 housed in a thin layer is also described in the first section.
This is the same as the embodiment.

As described above, the ink jet recording head of the present invention has been described in detail with reference to two embodiments. However, the present invention is not limited to these embodiments, and has a configuration to which the above-described principle of the present invention can be applied. If so, any configuration can be adopted. Therefore, it goes without saying that a configuration in which the components described in the first embodiment and the second embodiment are replaced with each other may be used.

The ink-jet recording apparatus of the present invention having the above-mentioned ink-jet recording head having no nozzle has no problems caused by the nozzles, can achieve high resolution of print dots, and has a high ink ejection speed. Fast, the ejection direction is stable, and high-speed printing is possible.

[0060]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. In the embodiment, an ink jet recording head 400 ′ shown in FIG. 6 was used. The ink jet recording head 400 ′ shown in FIG. 6 is a laser beam between the laser light generator (laser light generating means) 434 and the ink holding member 426 in the ink jet recording head 400 of the first embodiment shown in FIG. An optical lens 446 for focusing is provided on the optical path 436. In FIG. 6, members and the like having the same functions as those of the first embodiment are denoted by the same reference numerals.

The electrode 430, which is a negative electrode, is made of stainless steel and has a diameter of 5 μm. The other parts than the end face of the tip are insulated with polyimide resin, and the tip has a radius of curvature of 10 μm. Such an electrode 430 was disposed such that the tip position was at a value of 100 μm from the gas-liquid interface 422. The electrode 432, which is a positive electrode, is made of stainless steel and has a size of 1000
× 1000 × 50 (μm) in thickness, and the shock wave 41 is applied to the end of the inner bottom surface of the ink holding member 426 in the ink 416.
In order not to hinder the generation of 8 ', it was arranged so as to be parallel to the gas-liquid interface 422.

The laser light generator (laser light generating means) 434 is an Nd: YAG pulse laser having a maximum output of 10 mJ and a wavelength of 1064 nm, and the optical lens 446 is a synthetic quartz plano-convex lens (φ10 mm, f = 15).
mm, laser light transmittance 95%, energy damage threshold 6 J / cm ² )

The bottom surface of the ink holding member 426 has a thickness of 1 m.
m of Pyrex glass (laser light transmittance: 95%, energy damage threshold: 8 J / cm ² ), and the optical lens 446 and the bottom surface of the ink holding member 426 are made of Cr
The one coated with an anti-reflection film was used. As the ink 416, a black aqueous ink was used, and the thickness of the ink layer was 450 μm.

A rectangular wave having a voltage of 5 V and 100 μS is applied between the electrodes 430 and 432 by a power supply device (current generating means) (not shown) provided outside the ink jet recording head 400 ′, and the diameter of the electrode 430 is determined by electrolysis. 30
A first bubble of μm hydrogen was produced. Thereafter, a laser beam 436 was oscillated from a laser beam generator 434, and the laser beam 436 was condensed on the bottom surface of the ink holding member 426 by an optical lens 446. Specifically, the laser light 436 transmits through the bottom surface of the ink holding member 426,
The interface between the bottom surface and the ink 416 was focused.

When high-density energy is locally applied to the ink 416 at the irradiation position of the laser beam 436, shock bubbles 414 'are instantaneously generated, and the shock bubbles 414' are generated by volume expansion. Shock wave 418 '
Propagates through the ink 416 at a speed of Mach number 1.1.
The second bubble 414 'generated at this time has a spherical shape unlike the first embodiment, and thus the generated shock wave 418' also has a spherical shape.

When the shock wave 418 ′ reaches the interface of the first bubble 410, the first bubble 410 is deformed and contracted, and the secondary shock wave 420 and the previously described intense liquid flow (not (Shown). Secondary shock wave 420
A strong ejection force is generated by the action of the liquid flow and the action of the liquid flow, and the ink droplet 424 having a diameter of 15 μm in the vertical direction from the gas-liquid interface 422 while pushing up the liquid surface of the gas-liquid interface 422.
Ejected at a speed of about 40 m / s. Then, the ink droplets 424 landed on the surface of the recording medium 448, and an image was formed.

[0067]

According to the present invention, since the ink jet recording head can be made nozzleless, the clogging of the nozzle due to high resolution and the limit of the printing speed due to the high flow resistance of the nozzle, The problems caused by the conventional ink jet recording head having nozzles, such as a discharge failure due to clogging and interruption of printing due to a maintenance operation, can be solved.

In the present invention, since the ink droplet is ejected by the action of the second bubble whose expansion speed exceeds the sound speed,
The ink ejection pressure increases, the ink ejection speed increases,
The printing direction can be easily stabilized.

In the present invention, since there is a correlation between the diameter of the bubble generated by the bubble generating means and the diameter of the ink droplet to be ejected, the diameter of the ink droplet is modulated by controlling the diameter of the bubble. Can be done. Therefore, it is possible to achieve higher resolution of the obtained image.

Further, in the present invention, by arranging a plurality of first bubbles in the ink by the bubble generating means, it is possible to simultaneously eject ink droplets of the same or different diameters by one shock wave generation. In addition, high-speed printing can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an ink jet recording head of the present invention for explaining the principle of the present invention, and shows a state where a first bubble and a shock wave are formed.

FIG. 2 is a schematic configuration diagram of the ink jet recording head of the present invention for explaining the principle of the present invention, and shows a state in which a first bubble is deformed by a shock wave, and a secondary shock wave and a liquid flow are generated. Things.

FIG. 3 is a schematic configuration diagram of the ink jet recording head of the present invention for explaining the principle of the present invention, and shows a state in which a strong discharge resultant force is generated.

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

FIG. 5 is a schematic sectional view illustrating a schematic configuration of an ink jet recording head according to a second embodiment.

FIG. 6 is a schematic sectional view illustrating a schematic configuration of an ink jet recording head used in an example.

[Explanation of symbols]

 10, 410, 510 First bubble 12 Shock wave generating means 14, 414, 414 ', 514 Second bubble 16, 416, 516 Ink 18, 418, 418', 518 Shock wave 20, 420, 520 Secondary shock wave 22, 422, 522 Gas-liquid interface 24, 424, 524 Ink droplet 26, 426, 526 Ink holding member 28 Ejection force 50 Liquid flow 400, 400 ', 500 Ink jet recording head 430 Electrode 432 Electrode 434 Laser light generator 436 Laser light 446 Optical Lens 448, 548 Recording medium 538 Heater 540 Electrode 542 Electrode 544 Counter electrode

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasushi Suwabe 430 Green Tech Nakai, Nakai-cho, Ashigara-kami, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. Inside (72) Inventor Yuji Suemitsu 430 Green Tech Nakai, Nakaicho, Kanagawa Prefecture, Fuji Xerox Co., Ltd. Within Fuji Xerox Co., Ltd. 72) Inventor Yasushi Oki 430 Green Tech Nakai, Nakai-cho, Ashigarakami-gun, Kanagawa Prefecture Fuji Xerox Co., Ltd. F-term (reference) 2C057 AF03 AF43 AF72 AG21 AG37 AG46 BA13

Claims (7)

[Claims] 1. An ink holding member that holds ink and has an ink ejection port formed by opening at least a part of a portion facing a recording medium, and generates air bubbles just below a gas-liquid interface corresponding to image information. An ink jet recording head, comprising: a bubble generating unit that causes a bubble to be generated; and a shock wave generating unit that generates a shock wave toward the bubble in the ink. 2. The ink jet recording head according to claim 1, wherein the bubble generating means has a bubble control mechanism capable of controlling the diameter of the generated bubble. 3. The ink jet recording head according to claim 1, wherein the bubble generating means generates bubbles by electrolysis. 4. The air bubble generating means is configured to generate air bubbles using heat.
3. The ink jet recording head according to item 1. 5. The shock wave generating means according to claim 1, wherein said ink held by said ink holding member is irradiated with laser light to generate a shock wave in said ink. 2. The ink jet recording head according to item 1. 6. The shock wave generating means is a discharge generating means comprising at least one pair of electrodes for generating a discharge by applying a high voltage inside the ink held by the ink holding member and generating a shock wave in the ink. The ink jet recording head according to claim 1, wherein: 7. An ink jet recording apparatus comprising the ink jet recording head according to claim 1.