JPH09136414A - Ink-jet apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase current density and to improve boiling bubble generation efficiency by passing current through conductive ink, boiling the ink between electrodes, generating bubbles, and making the apex angle of the opposite part of a pair of the electrodes which makes a nozzle installed in a part of a pressure chamber discharge ink droplets an isosceles triangle. SOLUTION: The tips of electrodes 13, 14 are suitably in a state which meets an isosceles triangle in which the apex angle of the tip part is 20-160 degree, in gradation printing of different dot diameters, since the alternating current I (t) density passing through conductive ink from the electrodes 13, 14 increases, and the generation efficiency of boiling bubbles 22 and the discharge efficiency of ink droplets increase so that the stable discharge of the ink and the curtailment of powder consumption can be attained. When the apex angle of the tip part exceeds 160 degree, the maximum temperature of the conductive ink between the electrodes 13, 14 is not a part A on the line of the shortest distance between the electrodes 13, 14 but is the end edge parts B of the electrodes 13, 14, when boiling bubbles 22 are generated, stable ink droplets can not obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet device used in a printer, which is an output device such as an office computer or a personal computer, and in particular, an electric current is applied to a conductive ink to cause it to heat and boil to generate bubbles. The present invention relates to an inkjet device that ejects ink droplets from a nozzle by the pressure.

[0002]

2. Description of the Related Art In recent years, printers using ink jet devices have been widely used as output printers for home and office computers because of their quietness during recording, high-speed recording capability, and easy colorization. It's coming. Such inkjet printers make ink droplets and fly them, and then print them by adhering them to the printed material.The ink jet printers are roughly classified into a continuous method and an on-demand method according to the method of generating the droplets and the method of controlling the flight direction. It

The continuous system is a system disclosed in, for example, US Pat. No. 30,60429, in which the ink droplets are electrostatically attracted and the generated droplets are controlled by an electric field according to a recording signal. However, since the droplets are selectively deposited on the printing material to perform recording, a high voltage is required to generate the droplets, and it is difficult to realize multi-nozzle. doing.

[0004] The on-demand system is described in, for example, US Pat.
According to the method disclosed in Japanese Patent No. 4747120, an electric recording signal is added to a piezoelectric vibrating element attached to a recording head having a nozzle hole for ejecting a small droplet, and the electric recording signal is added to a mechanical structure of the piezoelectric vibrating element. Recording is performed by changing to dynamic vibration and ejecting small droplets from the nozzle holes according to mechanical vibration to adhere to the printing material. Since ink is ejected from the nozzle holes on demand, recording is continued. It is not necessary to collect the droplets that were not needed to record the image in the ejected droplets, unlike the ass method.
A simple configuration is possible. However, it is difficult to process the recording head, and it is extremely difficult to miniaturize the piezo-vibration element, making it difficult to make multiple nozzles, and it is difficult to achieve high-speed recording because the droplets are ejected by the mechanical energy of mechanical vibration of the piezo-element. Have the challenges of.

Further, Japanese Patent Publication No. 61-59911, Japanese Patent Publication No. 62-11035, and Japanese Patent Publication No. 61-59914
The publication describes a recording method of a system in which boiling is caused by a heating resistor to cause droplets to fly.

As another example of the on-demand method, the method disclosed in US Pat. No. 3,179,042 describes that heat energy is used instead of mechanical vibration energy by means such as a piezo-vibration element. .
This method is characterized in that the energy conversion efficiency is high and the multi-nozzle is easy compared with the method using mechanical vibration energy.

Next, the ejection principle of a conventional ink jet printer will be described. 7 is a sectional view of the head of the conventional inkjet apparatus, FIG. 8 is a plan view of the head of the conventional inkjet apparatus, FIG. 9 is a control block diagram of the conventional inkjet apparatus, and FIG. 10 is a control timing chart of the conventional inkjet apparatus.

7 to 9, 13 and 14 are a pair of electrodes, 15 is a nozzle corresponding to the electrodes 13 and 14, and 17 is a nozzle.
Is an electrode driving device that drives the electrodes 13 and 14, 4 is a conduction time control device that controls the output voltage from each electrode driving device 17, 11 is conductive ink, and 22 is an alternating current I flowing between the electrodes 13 and 14. A boiling bubble 16 is generated, and 16 is a substrate on which the electrodes 13 and 14 are mounted, and 10 is a CPU that notifies the energization time control device 4 of the start of printing.

In the ink jet device constructed as described above, the ink droplets 21 having the ink ejection amounts Q1 and Q2 (Q1> Q2) that result in the dot diameters D1 and D2 (D1> D2).
The principle of ink ejection for obtaining the above will be described with reference to FIG.

First, the ink ejection operation for obtaining the dot diameter D1 will be described. The CPU 10 outputs a PTM signal notifying the start of printing to the energization time control device 4. As a result, the energization time control device 4 synchronizes with the rising edge of the PTM signal for the application time T1b of the electrodes 13 and 14 corresponding to the nozzles 15 and the timing as shown in FIG. 10 using the electrode driving devices 17a and 17b. Drive with.

Outputs OUT of the electrode driving devices 17a and 17b
1 and OUT2 are 3 MHz with a phase difference of 180 degrees, 25
The voltage waveform is V, and these voltage waveforms are applied to the electrodes 13 and 14, respectively.

The conductive ink 11 is filled between the electrodes 13 and 14 as shown in FIG. 7, and an alternating current I1 flows through the conductive ink 11 by these voltages.

Then, the conductive ink 11 sandwiched between the electrodes 13 and 14 self-heats by the alternating current I1 and the ink resistance value is lowered by the heat, and as shown in FIG. , The value of the alternating current I1 increases.

Therefore, the conductive ink 11 sandwiched between the electrodes 13 and 14 further self-heats, and eventually boiling bubbles 22 as shown in FIG. 7 are generated after the lapse of the period T1a. The pressure of the boiling bubbles 22 causes the PTM to notify the start of printing.
After the lapse of the period T1a from the rise of the signal, the ink droplet 21 of the ink ejection amount Q1 is ejected from the nozzle 15 and adheres to the printing material 9 to form a dot having a diameter D1.

Since the boiling bubbles 22 cover the electrodes 13 and 14, the AC current I1 sharply decreases after the period T1a has elapsed, as shown in FIG.

The same applies to the ejection operation of the conductive ink 11 for obtaining the dot diameter D2, but as shown in FIG. 10, in order to obtain the ink droplet 21 of the ink ejection amount Q2, the applied voltage of 30V is applied. Therefore, the application time T2b is required,
The boiling bubble 22 is generated after the period T2a has elapsed,
The ejection timing of the ink droplet 21 from the nozzle 15 is after the period T2a from the rising of the PTM signal indicating the start of printing.

[0017]

However, when performing gradation printing with different dot diameters by the above-mentioned conventional ink jet device, since the density of the alternating current I1 flowing from the electrodes 13 and 14 to the conductive ink 11 is low, a high voltage is applied. There is a problem that current loss is large, electrolysis bubbles are generated, and ejection failure occurs, which is not suitable for gradation control.

The present invention solves the above-mentioned conventional problems. By increasing the current density, the boiling bubble generation efficiency, and the ink ejection efficiency, stable ink ejection and low power consumption can be achieved. An object is to provide an inkjet device suitable for gradation control.

[0019]

In order to solve the above-mentioned problems, an ink jet device of the present invention applies a voltage to a pair of electrodes provided in a pressure chamber containing a conductive ink to supply a current to the conductive ink. The conductive ink in the space between the electrodes is boiled to generate bubbles, and the ink droplets are ejected from a nozzle provided in a part of the pressure chamber. 1
This is an isosceles triangle of 60 degrees or less, and with this configuration, stable ink ejection and low power consumption can be achieved by increasing current density, boiling bubble generation efficiency, and ink ejection efficiency. It is possible to obtain an inkjet device suitable for adjusting the tone.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is a pressure chamber for accommodating a conductive ink, a nozzle provided in a part of the pressure chamber, and a pair provided in the pressure chamber. And an electrode for discharging ink droplets from the nozzles by applying a voltage to the pair of electrodes to cause a current to flow through the conductive ink to boil the conductive ink between the electrodes to generate bubbles. In addition, the opposing portions of the pair of electrodes are isosceles triangles having an apex angle of 20 degrees or more and 160 degrees or less, and the current density is increased,
It has an effect that current loss at high voltage can be suppressed and boiling bubble generation efficiency and ink ejection efficiency can be improved.

According to a second aspect of the present invention, in the first aspect of the invention, each vertex of the pair of electrodes has an arc shape, and it is possible to avoid a selective current distribution. Has the effect of.

According to a third aspect of the invention, in the invention according to the first or second aspect, the width of the pair of electrodes is 5 μm.
The distance is 200 μm or less, and the shortest distance between the facing portions of the pair of electrodes is 0.5 μm or more and 20 μm or less, which has the effect of suppressing variation in ink droplet volume.

According to a fourth aspect of the present invention, in the first, second or third aspect of the invention, the output voltage from the electrode driving device for energizing the conductive ink is changed so that electric energy is applied to the conductive ink. It is provided with a gradation control means for varying the ink ejection amount, and has an effect that the size of the ink droplet can be controlled.

FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a sectional view of a head of an inkjet device according to an embodiment of the present invention,
FIG. 2 is a plan view of the head of the inkjet device according to the embodiment of the present invention.

In FIGS. 1 and 2, 11 is a conductive ink,
12 is a pressure chamber filled with the conductive ink 11;
4 is a pair of electrodes provided in the pressure chamber 12, 15 is a nozzle for ejecting ink droplets 21, 16 is a substrate on which the electrodes 13 and 14 are arranged, 17 is an electrode drive device, 18 is a nozzle plate, and 20 is The ink flow path 22 is a boiling bubble.

FIG. 3 is a cross-sectional view of a head chip of an ink jet device according to an embodiment of the present invention, in which 24 is a common ink chamber and 25 is a head chip.

FIG. 4 is a block diagram of the connection portion of the ink tank of the ink jet device according to the embodiment of the present invention.
Is an ink cartridge to which the head chip 25 is attached,
Reference numeral 28 is an ink tank provided in the ink cartridge 27, 29 is an ink filter for removing dust and dirt contained in the conductive ink 11 in the ink tank 28, 30
Is an ink introduction path for guiding the conductive ink 11 to the common ink chamber 24.

FIG. 5 is a transparent perspective view of an ink jet device according to an embodiment of the present invention, in which 32 is a carriage for fixing the ink cartridge 27 and the ink tank 28, 33 is a guide shaft for guiding the serially reciprocating carriage 32, and 34. Is a platen roller for feeding the material 9 to be printed.

The operation of the ink jet device constructed as above will be described below.

Here, the conductive ink 11 whose I (t) changes with the lapse of time from the voltage application to the electrodes 13 and 14
It is assumed that the value of the current flowing between them is, R is the resistance of the conductive ink 11, and t is the time from the start of voltage application.

First, the conductive ink 11 in a portion where the alternating current I (t) flows due to Joule loss of the alternating current I (t) represented by integration of I ² × R × Δt from 0 to t self-heats. Then, with the passage of time, boiling starts from the highest temperature portion of the AC current I (t) passing portion of the conductive ink 11 in which the AC current I (t) has flowed, and finally boiling bubbles 22 are generated. With the expansion of the boiling bubbles 22, the conductive ink 1
The alternating current I (t) in 1 is the boiling bubble 22 because the boiling bubble 22 is an insulator and the alternating current I (t) cannot pass through it.
The current density is the highest on the surface of the boiling bubble 22 as it is bent to both sides of. Therefore, the surface of the boiling bubble 22 is heated most and the expansion of the boiling bubble 22 is further accelerated.

At this time, the electrolytic bubbles generated from the surfaces of the electrodes 13 and 14 are taken into the boiling bubbles 22 because the boiling bubbles 22 expand and reach the surfaces of the electrodes 13 and 14. Then, the pressure of the conductive ink 11 in the pressure chamber 12 sharply increases due to the expansion of the boiling bubble 22. The conductive ink 11 having a high pressure tries to move in the direction of the nozzle 15 and the ink flow path 20, but a fluid resistance is applied to the rapid flow of the conductive ink 11 due to a rapid pressure change. Is larger than the nozzle 15, the rapid flow of the conductive ink 11 due to the pressure change is directed to the nozzle 15,
Ink droplets 21 are ejected from 5 and are ejected and adhered to the printing material 9 to form dots.

When the expansion of the boiling bubble 22 reaches the maximum level, the boiling bubble 22 occupies a considerable portion of the passage of the alternating current I (t), so that the alternating current I ( t) is lowered, the heat of the boiling bubble 22 is taken to the conductive ink 11, the electrodes 13 and 14, and the boiling bubble 2
2 contracts rapidly. As the boiling bubble 22 disappears, the conductive ink 11 in the pressure chamber 12 is agitated by the negative pressure at the time of disappearance, so it takes several microseconds to restart boiling from the passage of the alternating current I (t). The above heating time is required. By the time the boiling is started, the electrode driving device 17 stops the application of the voltage between the electrodes 13 and 14 and prevents unnecessary ink droplets 21 from flying due to double boiling of the conductive ink 11. The conductive ink 11 consumed by the flight of the ink droplet 21 is constantly replenished to the pressure chamber 12 from the ink flow path 20 by the surface tension of the conductive ink 11 and returns to the standby state. The temperature distribution of the conductive ink 11 in the pressure chamber 12 returns to the initial state during the standby state due to heat conduction. Residual bubbles (not shown) near the nozzle plate 18 are discharged from the nozzle together with the ink droplets 21 at the next boiling.

An ink jet cartridge 27 is constructed by providing a head chip 25 in which a plurality of nozzles 15 that repeat the above operation are arranged in the ink introducing passage 30. For example, the ink cartridge 27 mounted on the carriage 32 reciprocates along the guide shaft 33 in response to a print signal sent from a computer or the like,
In accordance with the position of the carriage 32, the electrode driving device 17 applies a driving voltage between the arbitrary electrodes 13 and 14, and the ink droplet 2
1 is continuously generated, adheres to the printing material 9 sent by the platen roller 34, and printing with dots on the printing material 9 is performed.

With the printing operation, the conductive ink 11 enters the common ink chamber 24 from the ink tank 28 through the ink filter 29, the ink introduction path 30, and is supplied from the common ink chamber 24 to the pressure chamber 12.

At this time, it is preferable that the tips of the electrodes 13 and 14 have a shape satisfying an isosceles triangle having an apex angle of 20 to 160 degrees. This is because the density of the alternating current I (t) flowing from the electrodes 13 and 14 to the conductive ink 11 is increased when gradation printing with different dot diameters is performed by the inkjet device by using the above-described shape, so that the boiling bubble 2
This is because the generation efficiency of No. 2 and the ejection efficiency of the ink droplet 21 are increased, and stable ejection of the ink droplet 21 and reduction of power consumption are achieved. When the apex angle of the tip exceeds 160 degrees, the maximum temperature of the conductive ink 11 between the electrodes 13 and 14 does not reach the line upper portion A which is the shortest distance between the electrodes 13 and 14, and the tip edge portion of the electrodes 13 and 14 does not exist. When the boiling bubble 22 is generated and the boiling bubble 22 is generated, the stable ink droplet 21 cannot be obtained because the boiling bubble 22 is divided into a plurality or the small boiling bubbles 22 are continuously generated. Conversely, the tip angle of the tip is 2
If the applied voltage during gradation printing is low if it is less than 0 degrees,
A sufficient amount of the boiling bubbles 22 do not occur, and the size of the boiling bubbles 22 becomes small, so that the variable region of the dot diameter becomes narrow.

An arc is suitable for each vertex of the electrodes 13 and 14. This is to prevent the selective current distribution from being provided by rounding the apexes and to extend the stable ejection of the ink droplet 21 and the life of the electrodes 13 and 14.

The shape of the tips of the electrodes 13 and 14 is as follows.
The shape may be a pseudo isosceles triangle, for example, each side may be formed by an arc or a smooth curve.

Further, the volume of the ink droplet 21 is 5 × 1.
In the range of 0 ⁻⁶ mm ³ or more and 2 × 10 ⁻⁴ mm ³ or less, the width a of the electrodes 13 and 14 shown in FIG. 1 is preferably 5 μm or more and 200 μm or less. This is because if the width a of the electrodes 13 and 14 is less than 5 μm, the variation in the volume of the boiling bubble 22 due to the dimensional error will cause the volume variation of the ink droplet 21. On the contrary, when the width a of the electrodes 13 and 14 is larger than 200 μm, the heat storage distribution is easily affected, and the volume of the boiling bubble 22 varies due to the thermal history of the pressure chamber 12 and the heat in the vicinity of the pressure chamber 12. This is because it causes the volume variation of the droplet 21.

Further, when the volume of the ink droplet 21 is within the above range, the shortest distance between the electrodes 13 and 14 is 0.5 μm or more 2
0 μm or less is good. This is because if the distance between the electrodes 13 and 14 is less than 0.5 μm, variation in the volume of the boiling bubble 22 due to an error in the dimensional shape causes a volume variation of the ink droplet 21. On the contrary, when the distance between the electrodes 13 and 14 is larger than 20 μm, the portions of the surfaces of the electrodes 13 and 14 where the temperature of the conductive ink 11 is the highest are separated from each other, and the boiling bubbles 22 are formed from two places, and the ejection force is increased. This is because variations occur and cause a volume change of the ink droplet 21.

Further, the volume resistivity per cm of the conductive ink 11 is preferably 8 Ω · cm or more and 50 Ω · cm or less. When the volume resistivity is less than 8 Ω · cm, the content of the conductivity-imparting agent in the conductive ink 11 increases, so that the dissolution stability of the dye decreases and the clogging property of the nozzle 15 tends to deteriorate. When the volume resistivity exceeds 50 Ω · cm, the content of the conductive compound decreases, so the substrate 1
It becomes impossible to prevent the chemical reaction on 6 and the electrode 1
This is because 3 and 14 are melted and variations in the shapes of the electrodes 13 and 14 cause variations in the boiling bubbles 22, which causes fluctuations in the volume of the ink droplet 21.

Next, a control method for printing in multiple gradations by changing the dot diameter according to the present invention will be described. In FIG. 6A, the horizontal axis represents the heating time, and the vertical axis represents the power applied to the electrodes 13 and 14 and the volume of the boiling bubble 22 that determines the dot diameter. When 0.4 W of electric power is applied to the electrodes 13 and 14,
The heating time until the start of boiling is 7 μs, and E1 = 0.4
Energy of × 7 = 2.8 μJ is applied to the conductive ink 11. The volume of the boiling bubble 22 at that time grows as shown by the curve B1, and the maximum bubble volume becomes 200 pl. Similarly, when 0.23 W of electric power is applied to the electrodes 13 and 14, the heating time until the start of boiling becomes 22 μs, and E2 = 0.23 ×
Energy of 22 = 5.06 μJ is given to the conductive ink 11, and the volume of the boiling bubble 22 at that time grows like B2, and the maximum bubble volume becomes 400 pl. In this way, the time until the start of boiling is determined by the electric power applied to the electrodes 13 and 14, and the heated volume of the conductive ink 11 changes accordingly. The larger the heated volume, the larger the maximum bubble volume. That is, if the heating is performed slowly, larger boiling bubbles 22 can be formed. When boiling starts, the current between the electrodes 13 and 14 is cut off by the boiling bubble 22, so controlling the voltage so that it is cut off immediately after boiling does not affect the maximum bubble volume.

The method of applying electric power may be to change the voltage value as shown in FIG. 6 (b), but FIG. 6 (c) and FIG. 6 (d).
As described above, the volume of the boiling bubble 22 can be controlled even when the pulse value is changed while the voltage value is constant. In this way, the volume of the boiling bubble 22 is changed, and the gradation of the dot diameter can be controlled.

By the way, as the material of the substrate 16, an insulating material such as glass or ceramic, a semiconductor, a metal whose surface is coated with a high resistance material, a metal alloy, an insulator or a semiconductor can be used. As the glass substrate, potash lime glass, soda lime glass, borosilicate glass, crown glass, zinc crown glass, soda potash glass, barium borosilicate glass, 96% silicate glass, 99.5% silicate glass, phosphate glass, low glass Melting point glass, lithium silicate glass, zinc aluminum silicate glass, zirconium silicate glass, etc. can be used. As the ceramic substrate, aluminum oxide (alumina), titanium oxide (titania), MgO / SiO ₂
(Steatite), 2MgO.SiO ₂ (holsterite), BeO (beryllia), MgO.Al ₂ O ₃ (spinel), etc. can be used. As a semiconductor substrate, silicon,
Silicon carbide, diamond, germanium, etc. can be used.

Materials for the electrodes 13 and 14 include Ti group metals (Ti, Zr, Hf) and platinum group metals (Pt, Ru, R).
h, Pd, Os, Ir), refractory metal (W, Ta, M)
o), other V, Cr, Fe, Co, Ni, Nb, A
u, Ag, Al and other single metals or their alloys (Ni-F
e, NiCr, TiCr, etc.) can be used. Further, oxides (titanium oxide, hafnium oxide, tin oxide, indium oxide, etc.), nitrides (titanium nitride, chromium nitride, etc.), carbides (titanium carbide, tungsten carbide, etc.) and borides can also be used.

As a material for forming the ink flow path 20 and a material for the nozzle plate 18, a polymer such as polyimide, acrylic, or polyethylene terephthalate sheet, an insulating material such as glass or ceramic, a semiconductor, or a surface coated with a high resistance material. Metals, metal alloys, insulators and semiconductors can be used.

The conductive ink 1 that can be used in the present invention
1 may be either water-soluble or oil-soluble. Considering odor and safety, water-soluble is preferred. It is bleed to add a dye, a water-soluble organic solvent such as alcohols and glycols as a wetting agent, a surfactant, or a mixture thereof to the conductive ink 11, the drying rate, the boiling state control, the electrode 13 , 14 and the nozzle 15 are prevented from being clogged. In addition, preservatives are used.

In the ink jet device in which the present invention is used, one or a plurality of ink cartridges 27 are mounted on the carriage 32, and ink is ejected from the nozzles 15 of the head chip 25 while reciprocating the front surface of the material 9 to be printed in the main scanning direction. Even in a serial type recording apparatus that ejects droplets 21 and sends a predetermined amount of the printed material 9 in the sub-scanning direction, the nozzles 15 of the head chip 25 are provided over the entire width of the printed material 9 in the main scanning direction. Either of the line type recording devices may be used, in which the printing material 9 is fed by a predetermined amount in the sub-scanning direction for recording.

Further, one or a plurality of ink cartridges 27 are mounted on the carriage 32, and ink droplets 21 are ejected from the recording head to record while moving the front surface of the printing object 9 in the main scanning direction and the sub scanning direction. A so-called plotter type recording device may be used.

[0050]

As described above, according to the present invention, the current density is increased, the current loss at high voltage is suppressed, the boiling bubble generation efficiency and the ink ejection efficiency are improved, the ink ejection is stabilized, and the power consumption is reduced. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a head of an inkjet device according to an embodiment of the present invention.

FIG. 2 is a plan view of a head of an inkjet device according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a head chip of an inkjet device according to an embodiment of the present invention.

FIG. 4 is a configuration diagram of a connection portion of an ink tank of an inkjet device according to an embodiment of the present invention.

FIG. 5 is a transparent perspective view of an inkjet device according to an embodiment of the present invention.

FIG. 6 is a graph showing gradation control of dot diameter of an inkjet device according to an embodiment of the present invention.

FIG. 7 is a sectional view of a head of a conventional inkjet device.

FIG. 8 is a plan view of a head of a conventional inkjet device.

FIG. 9 is a control block diagram of a conventional inkjet device.

FIG. 10 is a control timing chart of a conventional inkjet device.

[Explanation of symbols]

 4 Energization time control device 9 Printed material 10 CPU 11 Conductive ink 12 Pressure chamber 13, 14 Electrode 15 Nozzle 16 Substrate 17 Electrode drive device 18 Nozzle plate 20 Ink flow path 21 Ink drop 22 Boiling bubble 24 Common ink chamber 25 Head chip 27 Ink cartridge 28 Ink tank 29 Ink filter 30 Ink introduction path 32 Carriage 33 Guide shaft 34 Platen roller

Claims (4)

[Claims] 1. A pressure chamber containing a conductive ink, a nozzle provided in a part of the pressure chamber, and a pair of electrodes provided in the pressure chamber, and a voltage is applied to the pair of electrodes. An ink jet device that discharges an ink droplet from the nozzle by causing an electric current to flow through the conductive ink to boil the conductive ink between the electrodes to generate a bubble, and the opposing portions of the pair of electrodes have an apex angle. Is an isosceles triangle of 20 degrees or more and 160 degrees or less. 2. The ink jet apparatus according to claim 1, wherein each vertex of the pair of electrodes has an arc shape. 3. The width of the pair of electrodes is 5 μm or more and 200 μm or more.
3. The inkjet device according to claim 1 or 2, wherein m or less, and the shortest distance between the facing portions of the pair of electrodes is 0.5 μm or more and 20 μm or less. 4. A gradation control means for varying an output voltage from an electrode driving device for energizing a conductive ink to supply electrical energy to the conductive ink and varying an ink ejection amount. The inkjet device according to claim 1, 2, or 3.