JPH1016252A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer allowing the impinging times of ink droplets to a recording material to coincide with each other and capable of increasing the variable width of an ink droplet emitting amt. SOLUTION: In an ink jet printer having a pressure chamber 2 housing conductive ink 1, a nozzle orifice 5 for emitting conductive ink 1, a pair of opposed electrodes corresponding to the nozzle orifice 5 for supplying a current to the conductive ink and an electrode driving part 7 driving the opposed electrodes, the generation position of a boiled air bubble generated in the pressure chamber 2 is made variable as shown by B1, B2 to make it possible to control the emitting time and speed of ink droplets 11. An ink jet apparatus wherein the impinging times of ink droplets 11 to a recording material 9 coincide with each other and the variable width of an ink droplet emitting amt. can be increased is 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 printer which discharges ink as small droplets from a fine opening, and more particularly to an ink jet printer in which the landing timing of ink droplets on a recording material and the variable width of ink droplet discharge amount are improved. Things.

[0002]

2. Description of the Related Art In recent years, ink jet printers have been widely used as output printers for home and office computers because of their quietness at the time of printing, high-speed printing, and easy colorization. It has become. Ink jet printers make ink into small droplets, fly and attach them to a recording material.Inkjet printers are roughly classified into a continuous method and an on-demand method based on the method of generating droplets and the method of controlling the flight direction. The on-demand method is becoming mainstream because of the ease of nozzle formation.

In the on-demand method, an electric recording signal is applied to a piezo element attached to a head chip having a nozzle hole for discharging an ink droplet, and the ink droplet is discharged from the nozzle hole by mechanical vibration to form a recording material. There is a method of attaching. Such a method is described, for example, in US Pat.
No. 20. There is also a method in which a heating resistor is attached to the head chip instead of the piezo element, and the ink droplets are ejected by heating the ink to generate bubbles. For example, US Pat.
No. 42. In these methods, since the ink droplets are ejected from the nozzle holes, the configuration of the head chip is simpler than in the continuous method, and a multi-nozzle method is used, but it is difficult to change the dot diameter in any of the methods. Has the disadvantage that

On the other hand, as another example of the on-demand system,
A method has been proposed in which conductive ink is energized and boiled by using electrodes provided on a head chip, and ink droplets are ejected by the pressure of the boiling bubbles. Such an energizing type ink jet printer has an advantage that the discharge amount of the ink droplet changes according to the current value and that dots having different diameters can be formed on the recording material, but for high quality printing excellent in gradation control. In addition, it is required that the ink droplets land on the recording material at the same time, and the variable width of the ink droplet ejection amount be further increased.

[0005] The configuration of a conventional energized ink jet printer will be described below. FIG. 11 is a sectional view of a main part of a head chip of a conventional energizing type ink jet printer, and FIG. 12 is a plan view of a main part of a head chip of a conventional energizing type ink jet printer.

In FIGS. 11 and 12, 1 is a conductive ink, 2 is a pressure chamber, 5 is a nozzle hole, 6 is a substrate, 7 is an electrode driving device, 8 is a nozzle plate, 9 is a recording material, 10 is an ink flow. The path, 11 is an ink droplet, 12 is a boiling bubble, and 22 and 23 are counter electrodes.

As shown in FIGS. 11 and 12, the substrate 6
The pressure chamber 2 disposed between the nozzle and the nozzle plate 8 is filled with the conductive ink 1, and the pressure chamber 2 has a pair of opposed electrodes 22 and 23 disposed on the substrate 6 and correspondingly. Nozzle plate 8
Has a nozzle hole 5 formed in the hole. In addition, pressure chamber 2
The conductive ink 1 is supplied through an ink supply path 10. The opposing electrodes 22 and 23 are connected to the electrode driving device 7, and by energizing the opposing electrodes 22 and 23,
The conductive ink 1 in the pressure chamber 12 is heated to generate boiling bubbles 1
The ink droplet 11 is ejected from the nozzle hole 5 by the pressure of the boiling bubble 12, and a dot is formed on the recording material 9 by the adhesion of the ink droplet 11.

FIG. 13 is a control block diagram for controlling the voltage applied to the counter electrode of the conventional energizing type ink jet printer, and FIG. 14 is the timing of the voltage and current applied to the counter electrode of the conventional energizing type ink jet printer. FIG.

In FIG. 13, 7a and 7b are drivers,
Reference numeral 24 denotes a CPU, and reference numeral 25 denotes an energization time control device. CPU
When 24 outputs an electric recording signal designating the control format of the power-on time control device 25, an AC voltage is applied to the opposing electrodes 22 and 23 by the drivers 7 a and 7 b disposed in the electrode driving device 7. At this time, the energization time controller 25 controls the time for energizing the counter electrodes 22 and 23 by the drivers 7a and 7b.

Next, a method of driving the counter electrode of the conventional energized ink jet printer having the above configuration will be described with reference to FIGS.

When the CPU 24 outputs a PTM signal notifying the start of driving of the opposing electrodes 22 and 23 to the energization time control device 25, the energization time control device 25 outputs the driver 7a, 7b
14 outputs pulse signals OUT1 and OUT2 whose phases are shifted by 180 degrees as shown in FIG.

As a result, a voltage of 3 MHz and 25 V is applied between the opposing electrodes 22 and 23,
The alternating current I1 flows through the conductive ink in contact with No.3. As the alternating current I1 flows, the temperature of the conductive ink rises, and the resistance value of the conductive ink decreases with the rise of the temperature, so that the value of the conduction current I1 increases as shown in FIG.

[0013] The temperature of the conductive ink further rises due to the increase in the current value, and the conductive ink finally boils.
Boiling bubbles as shown in FIG. 11 are generated. Due to the pressure of the boiling bubbles, after the time T1a has elapsed since the CPU 24 output the PTM signal, the ink amount Q1
Ink droplets are ejected, fly, adhere to the recording material and have a diameter D
One dot is formed. After the elapse of the time T1a, the boiling bubbles cover the opposing electrodes 22 and 23.
As shown in (1), the value of the alternating current I1 sharply decreases.

When forming a dot having a diameter D2 larger than the diameter D1, the CPU 24 outputs a PTM signal notifying the start of driving of the opposing electrodes 22 and 23 to the conduction time control device 25.
During the time T2b (T1b> T2b) after outputting the M signal, the pulse signals OUT3 and OUT4 whose phases are shifted by 180 degrees as shown in FIG. 14 are output to the drivers 7a and 7b.

As a result, a voltage of 3 MHz and 30 V is applied between the opposing electrodes 22 and 23,
An alternating current I2 flows through the conductive ink in contact with 3. Thereafter, by the same operation as that for forming the dot having the diameter D1, a boiling bubble as shown in FIG. 11 is generated. Here, the position where the boiling bubble is generated between the opposed electrodes 22 and 23 and the distance from the position where the boiling bubble is generated to the nozzle hole are the same regardless of whether dots of diameters D1 and D2 are formed.

Due to the pressure of the boiling bubble, the CPU 24
After a lapse of time T2a from the output of the M signal, ink droplets of the ink amount Q2 (Q1> Q2) are ejected from the ejection holes,
It flies and adheres to the recording material to form a dot having a diameter D2. At this time, the maximum bubble volume of the boiling bubble formed during the time T2a is smaller than the boiling bubble formed during the time T1a. Due to such a difference in the maximum bubble volume, it is possible to eject ink droplets having different ink amounts, and it is possible to form dots having different diameters on a recording material.

[0017]

However, in the above-described conventional ink jet printer, even when the maximum bubble volume of the boiling bubble is different, the position where the boiling bubble is generated is fixed, and the position from the position where the boiling bubble is generated to the nozzle hole is fixed. Since the distance was also constant, the ejection timing and ejection speed of the ink droplets differed due to the difference in the maximum bubble volume of the boiling bubbles, causing a shift in the landing timing of the ink droplets on the recording material and causing a shift to the desired position on the recording material. Has a problem that dot formation becomes difficult. Furthermore, since the distance from the boiling bubble generation position to the nozzle hole is constant and the amount of ink retained during the period does not change, the variable width of the ink droplet ejection amount is small and the variable width of the dot diameter is also small. Had.

The present invention has been made to solve the above-mentioned conventional problems. It is possible to control the ejection timing and the ejection speed of ink droplets so that the ink droplets land on the recording material at the same time. It is an object of the present invention to provide an ink jet printer capable of increasing a variable width of the discharge amount of the ink.

[0019]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a pressure chamber containing conductive ink, a nozzle hole for discharging the conductive ink, and a device for supplying electricity to the conductive ink. An ink jet printer having a counter electrode corresponding to a nozzle hole and an electrode driving unit for driving the counter electrode has a configuration in which a position where boiling bubbles generated in a pressure chamber are generated can be changed.

With this configuration, it is possible to change the distance from the position where the boiling bubble is generated to the nozzle hole, and control the ejection timing and the ejection speed of the ink droplet so that the landing timing of the ink droplet on the recording material is matched. In addition, it is possible to provide an ink jet printer capable of increasing the variable width of the ejection amount of ink droplets.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to a first aspect of the present invention is directed to a pressure chamber containing conductive ink, a nozzle hole for discharging the conductive ink, and a nozzle for supplying electricity to the conductive ink. In an ink jet printer having an opposing electrode corresponding to the hole and an electrode driving unit for driving the opposing electrode, the position at which boiling bubbles generated in the pressure chamber are variable can be changed. By changing the distance from the generation position to the nozzle hole, the variable width of the ejection amount of the ink droplet can be increased.

According to a second aspect of the present invention, in the first aspect, the shortest part of the distance between the opposing electrodes is one point, and a straight line connecting the shortest parts is at least one center line of the opposing electrode. Since the positions do not coincide with each other, the generation position of the boiling air bubbles in the pressure chamber can be changed, so that the ink discharge timing and the discharge speed can be controlled.

The invention described in claim 3 is the first or second invention.
In the invention according to any one of the above, the width of the counter electrode is 1 μm to 200 μm, preferably 5 μm to 50 μm,
The distance of the shortest part of the counter electrode is 0.5 μm to 20 μm, preferably 1 μm to 10 μm,
This has the effect of preventing variations in the maximum bubble volume of boiling bubbles generated in the pressure chamber.

[0024] The invention described in claim 4 is the first to third aspects of the present invention.
In the invention according to any one of the above, a voltage of any one of a direct current, an alternating current, and a pulse wave is applied to the opposite electrode, and by changing a voltage waveform applied to the opposite electrode, This has the effect that the maximum bubble volume of boiling bubbles can be controlled.

Hereinafter, a specific example of the embodiment of the present invention will be described. FIG. 1 is a sectional view of a main part of a head chip of an ink jet printer according to an embodiment of the present invention, and FIGS. 2 to 6 are plan views of a main part of a head chip of the ink jet printer according to an embodiment of the present invention. ,
FIG. 7 is a partially cutaway perspective view of the head chip of the ink jet printer according to one embodiment of the present invention.

1 to 7, reference numerals 3 and 4 denote counter electrodes,
Reference numeral 13 denotes a common ink chamber, and 14 denotes a head chip. The conductive ink 1, the pressure chamber 2, the nozzle hole 5, the substrate 6, the electrode driving device 7, the nozzle plate 8, the recording material 9, the ink flow path 10, and the ink droplet 11 are provided. Since the boiling bubbles 12 are the same as those in the conventional example, the same reference numerals are given and the description is omitted. Also, a shown in FIG. 1 is the width of the counter electrodes 3 and 4, B1 and B2 shown in FIGS. 1 and 2 are the positions where the boiling bubbles 12 are generated, and B shown in FIG.
3 is the center point of the boiling bubble 12 having the minimum bubble volume, B4
Is the point at which the straight line connecting the center points of the positions B1 and B2 where the boiling bubbles 12 are generated intersects the nozzle plate 8, and the dashed lines A1 and A2 shown in FIGS. 2 to 6 are the respective center lines of the counter electrodes 3 and 4. It is. Further, as shown in FIG.
Is provided with a plurality of opposing electrodes 3, 4, a pressure chamber 2, and a nozzle hole 5, so that a plurality of ink droplets can be ejected simultaneously. Further, the conductive ink 1 supplied to the pressure chamber 2 is temporarily held in the common ink chamber 13.

Here, the material of the substrate 6 includes (a) an insulating material such as glass and ceramics, (b) a semiconductor,
(C) Metals, metal alloys, insulators, semiconductors, and the like whose surfaces are coated with a high-resistance material can be used.

Examples of the glass substrate include potassium lime glass, soda lime glass, borosilicate glass, crown glass, zinc crown glass, soda potassium glass, barium borosilicate glass, 96% silicate glass, 99.5% silicate glass, phosphate glass, Low melting glass, lithium silicate glass, zinc aluminum silicate glass, zirconium silicate glass, and the like 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) can be used.

As the semiconductor substrate, silicon, silicon carbide, diamond, germanium and the like can be used.

The material of the nozzle plate 8 and the ink flow path 10 may be a polymer such as polyimide, acrylic or polyethylene terephthalate, an insulating material such as glass or ceramics, a semiconductor, a metal whose surface is coated with a high resistance material, or a metal. Alloys, insulators, semiconductors, and the like can be used.

The material of the counter electrodes 3 and 4 is T
i-group metals such as Zr, Hf, Pt, Ru, Rh, P
platinum group metals such as d, Os and Ir; refractory metals such as W, Ta and Mo; V, Cr, Fe, Co, Ni, Nb and Au;
Ag, Al or other single metal or Ni-Fe, NiCr, Ti
Alloys of the above metals such as Cr, titanium oxide, hafnium oxide, tin oxide, oxides such as indium oxide, titanium nitride,
Nitride such as chromium nitride, carbide such as titanium carbide and tungsten carbide, and boride can be used.

The specific resistance of the conductive ink 1 at 25 ° C. is preferably 8 to 50 Ω · cm, particularly preferably 15 to 25 Ω · cm. When the specific resistance is less than 8 Ω · cm, the content of the conductivity-imparting agent in the conductive ink is increased, so that the dissolution stability of the dye is reduced, and the clogging resistance of the nozzle hole tends to be deteriorated. When the AC frequency of the voltage applied to the electrode is low, it is impossible to prevent a chemical reaction on the substrate when the AC frequency of the voltage applied to the electrode is low. Each of them is not preferable because it tends to deteriorate.

The viscosity of the conductive ink is preferably 10 cp or less, particularly preferably 5 cp or less. If the viscosity exceeds 10 cp, it tends to be difficult to discharge ink droplets from the nozzle holes, which is not preferable.

The conductive ink has a surface tension of 28-5.
5 dyne / cm, particularly 30 to 45 dyne / cm, is suitable. When the surface tension is less than 28 dyne / cm,
Fine line bleeding of printing tends to deteriorate and the printing density tends to decrease, and when the surface tension exceeds 55 dyne / cm, the color bleeding of color superimposed printing tends to decrease, which is not preferable.

The pH of the conductive ink is preferably from 6 to 10, particularly preferably from 7 to 9. When the pH is less than 6, the dissolution stability of the dye tends to decrease, and when the pH exceeds 10, the dye tends to fade, which is not preferable.

FIG. 8 is a perspective view of a main part of an ink jet printer according to an embodiment of the present invention. 8, 15 is an ink cartridge, 16 is an ink tank,
Reference numeral 17 denotes an ink filter, and reference numeral 18 denotes an ink introduction path. The head chip 14 is attached to an ink cartridge 15 having an ink tank 16, and
After the conductive ink (not shown) in the filter 6 is cleaned of dust and dirt by the ink filter 17, the conductive ink is guided to the head chip 14 through the ink introduction path 18.

FIG. 9 is a partially cutaway perspective view of an ink jet printer according to an embodiment of the present invention. In FIG. 9, 19 is a carriage, 20 is a guide shaft, 21
Denotes a platen roller, an ink cartridge (not shown) having an ink tank 16 is fixed to a carriage 19, and the carriage 19 continuously reciprocates along a guide shaft 20, and during this reciprocation, the recording material 9 The sheet is sent by the platen roller 21.

The operation of the ink jet printer having the above configuration will be described below. When current is applied between the counter electrodes 3 and 4 having the shape shown in FIG. 2, the conductive ink 1 in the pressure chamber 2 is heated by Joule heat. When the temperature of the conductive ink 1 increases due to the heating, the resistance value of the conductive ink 1 decreases, and the energizing current value increases. For this reason, the temperature of the conductive ink 1 continuously increases, and finally the boiling of the conductive ink 1 starts, and boiling bubbles 12 are generated in the pressure chamber 2. Due to the pressure of the boiling bubbles 12, the conductive ink 1 tends to move in the direction of the nozzle hole 5 and the ink flow path 10. However, since the fluid resistance to the movement of the conductive ink 1 moves to the nozzle hole 5 side, it is smaller. When the boiling bubble 12 reaches the maximum bubble volume, the ink droplet 11 is ejected from the nozzle hole 5, flies, and adheres to the recording material 9 to form a dot.

When the boiling bubble 12 reaches the maximum bubble volume,
Since the ratio of the insulating boiling bubbles 12 occupying between the counter electrodes 3 and 4 increases, the value of the current flowing through the conductive ink 1 gradually decreases, and the heat of the boiling bubbles 12 is reduced by the conductive ink 1 and the counter electrodes 3. 4 and the boiling bubbles 12 contract rapidly. With the disappearance of the boiling bubbles 12, the conductive ink 1 in the pressure chamber 2 is agitated by the negative pressure at the time of disappearance, and requires a heating time of several microseconds or more before starting to boil again. Until the boiling starts, the electrode driving device 7 stops applying the voltage to the counter electrodes 3 and 4, and prevents unnecessary ink droplets 11 from flying due to double boiling of the conductive ink 1. The reduced amount of the conductive ink 1 due to the flying of the ink droplet 11 is constantly replenished into the pressure chamber 2 from the ink flow path 10 due to the surface tension of the conductive ink 1. The temperature distribution of the conductive ink 1 in the pressure chamber 2 returns to the initial state during this standby state due to heat conduction. The residual air bubbles (not shown) in the vicinity of the nozzle plate 8 together with the next ink droplet 11 form the nozzle hole 5.
Is more exhausted.

Head chip 14 having a plurality of nozzle holes 5
Ink cartridge 15 provided in the ink introduction path 18
Is mounted on the carriage 19, and the carriage 19 reciprocates along the guide shaft 20 in response to a print signal sent from a computer or the like. At this time, the carriage 19
The electrode driving device 7 drives an arbitrary pair of opposing electrodes 3 and 4 in accordance with the position of, and ink droplets 11 are continuously generated,
It adheres to the recording material 9 sent by the platen roller 21 and forms dots on the recording material 9. The conductive ink 1 is sent from the ink tank 16 via the ink filter 17 to the common ink chamber 13 through the ink introduction path 18 along with the printing operation, and is supplied from the common ink chamber 13 to the pressure chamber 2.

In the ink jet printer according to this embodiment, one or a plurality of ink cartridges 15 are mounted on a carriage 19, and the nozzle holes 5 of the head chip 14 are moved while reciprocating over the entire surface of the recording material 9 in the main scanning direction. A serial type printer that discharges ink droplets 11 and performs recording by feeding the recording material 9 by a predetermined amount in the sub-scanning direction;
Alternatively, a line type printer in which the nozzle holes 5 of the head chip 14 are provided over the entire width of the recording material 9 in the main scanning direction and the recording material 9 is fed by a predetermined amount in the sub-scanning direction, and
One or a plurality of ink cartridges 15 are
Any of a plotter type printer that discharges ink droplets 11 from the nozzle holes 5 and records while moving the entire surface of the recording material 9 in the main scanning direction and the sub-scanning direction.

Next, a method of driving electrodes when dots having different diameters are formed on a recording material in the ink jet printer according to the present embodiment will be described with reference to FIG.

FIG. 10 shows the relationship between the driving method of the counter electrode of the ink jet printer and the boiling bubble volume in the embodiment of the present invention. FIG. 10 (a) shows the heating time and the power consumed by the counter electrode. 10 (b) to 10 (d) are timing diagrams of the voltage applied to the counter electrode.

In FIG. 10A, the horizontal axis represents the heating time,
The vertical axis indicates the power applied between the opposing electrodes and the volume of boiling bubbles. For example, when a power of 0.4 W is applied between the opposing electrodes, boiling of the conductive ink starts after 7 μs. After the start of boiling, the volume of boiling bubbles changes as shown by curve B1,
At this time, the maximum bubble volume of boiling bubbles is 200 pl. When a power of 0.23 W is applied to the opposing electrode, 22 μs
The boiling of the conductive ink starts later, and the volume of the boiling bubble changes as shown by a curve B2. At this time, the maximum bubble volume of boiling bubbles is 400 pl. That is, the smaller the power applied between the opposed electrodes, the slower the heating of the conductive ink, the longer the time until the start of boiling, but the larger the maximum bubble volume of the generated boiling bubbles.

On the other hand, as shown in FIG.
If the distance between the electrodes is not constant, the current flowing between the opposing electrodes 3 and 4 at the start of energization exhibits a distribution such that the shorter the distance between the opposing electrodes 3 and 4, the greater the current. However, such a current distribution causes boiling bubbles 1 in the pressure chamber 2.
When 2 occurs, the boiling bubbles 12 are bent along the interface between the boiling bubbles 12 and the conductive ink 1 because the boiling bubbles 12 are insulators. Depending on the electric power applied between the counter electrodes 3 and 4, when such a change in the current distribution occurs, the location where the maximum temperature is reached at the interface between the boiling bubble 12 and the conductive ink 1 is as follows.
The change is such that the greater the applied power is, the closer to the portion where the distance between the opposing electrodes 3 and 4 is short, and the smaller the applied power is, the longer the distance between the opposing electrodes 3 and 4 is from the shorter portion. Accordingly, as shown in FIG. 2, the position where the boiling bubble 12 is generated is point B1 when the volume of the boiling bubble is small, and point B2 when the volume of the boiling bubble is large.

Further, at the same time as the position where the boiling bubble 12 is generated changes, the distance from the position where the boiling bubble 12 is generated to the nozzle hole 5 also changes. Thus, boiling bubbles 1
When the distance from the position at which the ink droplets 2 are generated to the nozzle hole 5 changes, the variable amount of the conductive ink 1 held therebetween can be increased. The amount can be increased.

The driving method of the counter electrodes 3 and 4 is shown in FIG.
Although the voltage value may be changed as shown in FIG.
(C) As shown in FIG. 10 (d), a pulse wave having a different duty ratio may be used with a constant voltage value. Thereby, it is possible to change the maximum bubble volume of the boiling bubble 12 to change the ejection amount of the ink droplet.

Next, the shape of the counter electrode in one embodiment of the present invention will be described with reference to FIGS.

The counter electrodes 3 and 4 are desirably rectangular or pseudo-rectangular in which the angle formed by the opposing electrode surfaces of the counter electrodes 3 and 4 is not less than 20 degrees and less than 180 degrees. If the angle of the opposing electrodes 3 and 4 is 180 degrees, current concentrates on a portion connecting the shortest portions of the opposing electrodes 3 and 4, and the temperature of the conductive ink 1 sharply rises only in this portion.
The boiling bubble 12 is divided into a plurality,
This is not preferable because stable ink droplets 11 tend to be unable to be ejected due to continuous occurrence of ink droplets. If the angle of the opposing electrodes is less than 20 degrees, the distribution of the current flowing between the opposing electrodes 3 and 4 is relatively uniform even after the generation of the boiling bubbles 12, so that the current flows between the opposing electrodes 3 and 4. If the total current is small, it is not preferable because the conductive ink 1 does not sufficiently boil and the ejection of the ink droplet 11 tends to be difficult.

The width a of the counter electrodes 3 and 4 shown in FIG. 1 is 1 μm to 200 μm, preferably, when the volume of the ink droplet 11 is 5 × 10 ⁻⁶ mm ³ or more and 2 × 10 ⁻⁴ mm ³ or less. 5 μm ~
50 μm. As the electrode width a becomes smaller than 5 μm, the boiling bubble 12
Of the maximum bubble volume of the ink droplet 11
Is not preferable because the discharge amount tends to vary. Further, as the electrode width a becomes larger than 50 μm, the influence of the heat storage distribution increases, and the maximum bubble volume of the boiling bubble 12 varies due to the heat history of the pressure chamber 2 and the heat near the pressure chamber 2, resulting in an ink droplet. This is not preferable because the ejection amount of No. 11 tends to vary.

The shortest distance between the opposing electrodes 3 and 4 is 0.5 μm to 20 μm, preferably 1 μm when the volume of the ink droplet 11 is 5 × 10 ⁻⁶ mm ³ or more and 2 × 10 ⁻⁴ mm ³ or less. ~ 1
0 μm or less is good. As the distance between the opposing electrodes 3 and 4 becomes smaller than 1 μm, variation in the maximum bubble volume of the boiling bubbles 12 due to an error in the finished electrode size increases, and the ejection amount of the ink droplets 11 tends to vary, which is not preferable. . Further, as the distance between the opposing electrodes 3 and 4 becomes larger than 10 μm,
In this case, the portion where the ink temperature is highest is separated, and boiling bubbles 12 are likely to be generated from two places, and the ink ejection force varies and the ejection amount of the ink droplet 11 tends to vary, which is not preferable.

The straight line connecting the shortest portions of the opposing electrodes 3 and 4 must not coincide with at least one of the center lines A1 and A2 of the opposing electrodes 3 and 4, respectively. If the straight line connecting the shortest portions of the opposed electrodes 3 and 4 has a shape that matches both the center line A1 and the center line A2, the bubbling position of the boiling bubble 12 is always on the line connecting the center line A1 and the center line A2, It becomes impossible to change the foaming position of the boiling bubbles 12.

The center lines A1, A2 of the opposing electrodes 3, 4
It is desirable that at least one of them is disposed closer to the ink flow path 10 than the nozzle hole 5 as shown in FIG. Accordingly, the amount of change in the distance from the position where the boiling bubble 12 is generated to the nozzle hole 5 due to the difference in the maximum bubble volume of the boiling bubble 12 increases, and the variable width of the ejection amount of the ink droplet 11 can be further increased. become.

As another example of the opposing electrodes 3 and 4 having the above-described functions, those having the electrode shapes shown in FIGS. 3, 4, 5 and 6 can be similarly used.

The center position of the nozzle 5 with respect to the opposing electrodes 3 and 4 is desirably disposed above the foaming center B3 shown in FIG. 2 or above a line connecting the foaming centers B3 and B4. As a result, the smaller the maximum bubble volume of the boiling bubble 12 is, the shorter the distance from the nozzle hole 5 to the position where the boiling bubble 12 is generated, and when the conductive ink 1 is ejected, the conductive ink 1 is kept within the pressure chamber 2. The received fluid resistance decreases. Therefore, the ink droplet 1 ejected from the nozzle hole 5
Even when the amount of 1 is small, it is possible to prevent the discharge speed of the ink droplet 11 from being reduced, that is, to prevent the discharge speed of the ink droplet 11 from depending on the discharge amount.

As described above, according to the present embodiment, it is possible to change the position at which the boiling bubble generated in the pressure chamber is generated.
By making it possible to change the distance from the position where the boiling bubble is generated to the nozzle hole, it is possible to control the ejection timing and ejection speed of the ink droplets so that the impact timing of the ink droplets on the recording material can be matched. In addition, it is possible to increase the variable width of the ejection amount of the ink droplet.

[0058]

According to the ink jet printer of the present invention, since the ink ejection timing and the ink ejection speed do not depend on the ink ejection amount, it is possible to perform high-quality gradation printing without deviation in ink droplet landing timing. Excellent effects can be obtained. Further, since the variable width of the ink discharge amount can be increased, an excellent effect that the gradation of the dot diameter can be improved can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a head chip of an ink jet printer according to an embodiment of the present invention.

FIG. 2 is a plan view of a main part of a head chip of the ink jet printer according to the embodiment of the present invention.

FIG. 3 is a plan view of a main part of a head chip of the ink jet printer according to the embodiment of the present invention.

FIG. 4 is a plan view of a main part of a head chip of the ink jet printer according to the embodiment of the present invention.

FIG. 5 is a plan view of a main part of a head chip of the ink jet printer according to the embodiment of the present invention.

FIG. 6 is a plan view of a main part of a head chip of the ink jet printer according to the embodiment of the present invention.

FIG. 7 is a partially cutaway perspective view of a head chip of an ink jet printer according to an embodiment of the present invention.

FIG. 8 is a perspective view of a main part of the inkjet printer according to the embodiment of the present invention.

FIG. 9 is a partially cutaway perspective view of an inkjet printer according to an embodiment of the present invention.

10A is a diagram showing the relationship between the heating time, the power consumed by the counter electrode, and the volume of boiling bubbles. FIG. 10B is a timing chart of the voltage applied to the counter electrode. FIG. 10C is a timing chart of the voltage applied to the counter electrode. (D) Timing diagram of voltage applied to counter electrode

FIG. 11 is a sectional view of a main part of a head chip of a conventional energized ink jet printer.

FIG. 12 is a plan view of a main part of a head chip of a conventional energized ink jet printer.

FIG. 13 is a control block diagram for controlling a voltage applied to a counter electrode of a conventional energization type ink jet printer.

FIG. 14 is a timing chart of voltage and current applied to a counter electrode of a conventional current-carrying type ink jet printer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductive ink 2 Pressure chamber 3,4,22,23 Counter electrode 5 Nozzle hole 6 Substrate 7 Electrode drive device 8 Nozzle plate 9 Recording material 10 Ink flow path 11 Ink droplet 12 Boiling bubble 13 Common ink chamber 14 Head chip 15 Ink Cartridge 16 Ink tank 17 Ink filter 18 Ink introduction path 19 Carriage 20 Guide shaft 21 Platen roller 24 CPU 25 Power-on time control device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koji Matsuo 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] A pressure chamber for accommodating a conductive ink; a nozzle hole for discharging the conductive ink; a counter electrode corresponding to the nozzle hole for supplying a current to the conductive ink; An ink-jet printer having an electrode drive unit for driving the pressure chamber, wherein a position where a boiling bubble generated in the pressure chamber is generated is variable. 2. The apparatus according to claim 1, wherein the shortest part of the distance between the opposed electrodes is one, and a straight line connecting the shortest parts does not coincide with at least one center line of the opposed electrode. Inkjet printer. 3. The method according to claim 1, wherein said counter electrode has a width of 1 μm to 200 μm.
Preferably, the distance between the shortest part of the counter electrode is 0.5 μm to 20 μm, and more preferably 1 μm to 10 μm.
The inkjet printer according to claim 1, wherein the thickness of the inkjet printer is μm. 4. The ink jet printer according to claim 1, wherein a voltage having any one of a direct current, an alternating current, and a pulse wave is applied to the counter electrode.