JPH07156393A - Ink jet recording head and recorder using same - Google Patents

Abstract

PURPOSE:To provide an ink jet recording head and a recorder in which high density and multiplication of discharge ports and liquid passages are facilitated and ink of wide types including non-aqueous ink can be used. CONSTITUTION:An ink jet recording head 1 has a plurality of discharge ports 15 for discharging ink, a plurality of liquid passages 16 for supplying into to the ports 15, and a liquid chamber 17 for storing ink to be suppled to the passages 16, and comprises pressure generating means 40 for pressurizing ink in the plurality of the passages 16, pressure absorbing means provided in one or the plurality of the passages 16, wherein the ink in the passages is pressurized by the means 40, pressure applied to the ink is absorbed by the absorbing means to control an ink discharge amount, thereby discharging ink liquid droplets from the ports 15.

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 and recording device.

[0002]

2. Description of the Related Art An ink jet recording method in which ink is ejected to form flying droplets and the droplets are adhered to a recording medium such as paper to perform recording is known in terms of good print quality, recording speed, and operation time. Since it has advantages such as quietness, it has been increasingly used in recent years.

In recent years, two ink jet recording methods, a BJ method and a piezo method, have become mainstream.

The BJ method is a method in which an electrothermal conversion element provided in the liquid path is heated to generate bubbles in the ink and the pressure generated at that time causes the ink to be ejected.

In the ink jet recording head of the BJ method, since the basic parts of the liquid path such as the electrothermal conversion element and the electrode are manufactured by the thin film process, it is easy to increase the density of the liquid path and the discharge port and to realize the full multi. . However, on the other hand, since the ink is heated at a high temperature to generate bubbles, the ink component is burnt or the burned component is deposited on the surface of the electrothermal conversion element, so that the proper ink ejection state cannot be maintained. , There was a problem. Further, when non-aqueous inks excellent in plain paper recording property and high-speed fixing property are used, there is a problem that the non-aqueous inks cannot be ejected satisfactorily in the BJ method because of a low bubbling pressure. there were.

In order to solve the above problems, methods for removing ink components that cause charring and selecting dyes that do not charcoal have been proposed, but these methods are not limited to the selection of usable ink compositions. Because it narrows the width,
Not preferable. Further, a method of improving the bubbling pressure of the non-aqueous ink by changing the drive waveform has been proposed, but there is a new problem that the ink is easily burnt by changing the drive waveform.

On the other hand, the piezo system is a system in which a piezo oscillator provided in the liquid path is deformed to pressurize the liquid path and eject ink. In this method, problems such as charring of ink and insufficient foaming pressure can be solved. However, in this piezo system, it is difficult to miniaturize the piezo oscillator while maintaining the performance capable of generating the pressure required for ink ejection, or to make a miniaturized piezo oscillator in the recording head. There is a problem that it is difficult to increase the density of the discharge port and the liquid passage and to make the full multi.

A method has been proposed in which a liquid passage or the like is formed in a flat plate-shaped piezo material by etching or the like in order to increase the density and full-multiply the ejection port and the liquid passage of the recording head by the piezo method. When the material is deformed in one liquid passage portion, stress is applied to the piezo material in the adjacent liquid passage portion, the piezoelectric element is deformed even if the driving voltage is not applied, ink overflows from the ejection port, or the driving voltage is applied. However, there is a problem that a predetermined deformation cannot be obtained and the ink ejection amount cannot be controlled.

Further, a method has been proposed in which the side area of the liquid passage is reduced to increase the density of the liquid passage and the discharge port by changing the deformation mode of the piezo material to increase the amount of deformation. Since there is a limit to the amount of deformation of the ink, it is necessary to keep the side area of the liquid passage at a certain level or more in order to maintain a predetermined ink discharge amount, which prevents higher density.

[0010]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, the present invention is capable of high density and full multi,
Moreover, it is an object of the present invention to provide an inkjet recording head and a recording device that can use a wide variety of inks including non-aqueous inks.

[0011]

According to the present invention to achieve the above object, a plurality of ejection ports for ejecting ink, a plurality of liquid paths for supplying ink to the plurality of ejection ports, and a plurality of liquids are provided. In an ink jet recording head including a liquid chamber that stores ink supplied to a passage, pressure generating means capable of pressurizing ink in the plurality of liquid passages, and pressure absorbing means in one or a plurality of liquid passages Is provided, the ink in the plurality of liquid paths is pressurized by the pressure generating means, and the pressure applied to the ink is absorbed by the pressure absorbing means to control the ink ejection amount to control the ink liquid from the ejection port. The inkjet recording head is characterized by discharging droplets.

Further, the ink jet recording head of the present invention includes that the pressure generating means is an electromechanical conversion element.

In the ink jet recording head of the present invention, the pressure generating means includes an electromechanical conversion element and a member having a bottom area larger than the bottom area of the electromechanical conversion element. It is a waste.

Further, the ink jet recording head of the present invention includes that the electromechanical conversion element is an electrokinetic converter.

Further, the ink jet recording head of the present invention includes that the electromechanical conversion element is an electromagnetic converter.

Further, the ink jet recording head of the present invention includes the pressure generating means provided in the middle of the plurality of liquid paths.

Further, the ink jet recording head of the present invention includes the pressure generating means provided in the liquid chamber.

Further, the ink jet recording head of the present invention includes that the pressure generating means changes the generated pressure according to the temperature of the recording head.

Further, the ink jet recording head of the present invention includes that the pressure absorbing means is a bubble generating means.

Further, in the ink jet recording head of the present invention, the bubble generating means includes an electrothermal converting element which generates heat when electric energy is applied to generate bubbles in the ink.

Further, the ink jet recording head of the present invention includes changing the volume of the bubbles to be generated and the ink ejection amount by changing the waveform of the electric power applied to the electrothermal conversion element or the waveform of the applied voltage. It is a waste.

Further, in the ink jet recording head of the present invention, the bubble generating means is composed of an electrode, and an electric current is passed through the electrode to electrolyze the ink component to generate a bubble in the ink. Is included.

Further, the ink jet recording head of the present invention includes changing the volume of bubbles generated by changing the amount of current flowing through the electrodes to change the amount of ejected ink.

Further, the ink jet recording head of the present invention includes changing the ink ejection amount by changing the time from the operation of the bubble generating means to the operation of the pressure generating means.

Further, the ink jet recording head of the present invention includes a full line type in which a plurality of ink ejection ports are provided over the entire width of the recording area of the recording medium.

Further, according to the present invention, there is provided an ink jet recording head according to any one of the above, wherein an ink ejection port is provided facing a recording surface of a recording medium, and a member for mounting the head. An inkjet recording apparatus comprising at least one.

[0027]

When the pressure when the ink in the liquid passage is pressurized is absorbed by the pressure absorbing means provided in the liquid passage, the ink discharge amount changes depending on the magnitude of the absorbed pressure. That is, the ink discharge amount is the maximum when the pressure when the ink in the liquid path is pressurized is not absorbed at all, and as the pressure absorption amount increases, the ink discharge amount decreases and there is a pressure absorption amount. If the level is exceeded, the ink will not break the surface tension and will not be ejected.

As the pressure generating means, it is possible to use an electromechanical conversion element such as a piezoelectric element, an electrodynamic type converter or an electromagnetic type converter.

Further, it is preferable that the pressure generating means changes the generated pressure according to the recording head temperature. If the recording operation time becomes long or the temperature of the recording head changes due to environmental changes, the viscosity of the ink in the liquid path changes, and the ink ejection amount changes even if the pressure generated by the pressure generating means does not change. Therefore, it is possible to maintain a stable ink ejection amount by changing the pressure generated by the pressure generating means in accordance with the recording head temperature.

In the present invention, since it is not necessary to provide the pressure generating means in the liquid passage in a one-to-one correspondence, the liquid passage can be made finer regardless of the size of the pressure generating means. It is suitable for high density and multiple discharge ports.

The pressure generating means may be attached at any position as long as it can press the ink in the plurality of liquid passages and does not hinder the high density of the ink discharge ports and liquid passages. For example, it is preferable to provide a plurality of liquid passages in a common liquid chamber that can be pressurized. Further, a pressure generating unit common to each liquid passage may be attached in the middle of the plurality of liquid passages. In that case, the efficiency of pressure transmission is improved.

As the pressure absorbing means, it is preferable that bubbles absorb the pressure in the ink. As a means for generating bubbles, a method of foaming ink by an electrothermal conversion element that generates heat when electric energy is applied, or a method of energizing an electrode provided in a liquid path to electrolyze the ink to generate ink in the ink A method of generating bubbles is preferred.

In the method of foaming bubbles as the pressure absorbing means by the electrothermal converting element, unlike the BJ method in which the appropriate amount of the discharge liquid directly fluctuates due to the fluctuation of the foaming power.
Even if the size of the generated bubble changes to some extent due to the fluctuation of the foaming power, the pressure absorbing performance is properly maintained as long as the bubble is larger than a predetermined size.

Further, in the BJ method, it is necessary to generate a large amount of power, that is, a high pressure in order to eject the liquid droplets,
For that purpose, it is generally necessary to foam at a high temperature. For example, in the case of a water-based ink, it is desirable to heat it up to about 300 ° C. to foam it, and the pressure becomes about 100 times that when foaming at 100 ° C. Therefore, in the BJ method, the ink was easily burnt.

However, in the present invention, the foaming by the electrothermal conversion element has a sufficient pressure absorbing effect if the volume of the bubbles can be maintained above a certain level, so that it can be foamed at a low temperature at which the ink does not burn. When foaming at a low temperature, the volume of bubbles generated per unit area of the electrothermal conversion element becomes small, but it can be dealt with by increasing the area of the electrothermal conversion element.

When bubbles are used as the pressure absorbing means,
As the bubble volume increases, the amount of pressure absorption increases, so the ink ejection amount decreases and when the bubble volume exceeds a certain size, ink is ejected even when the liquid path is pressurized. Disappear. Therefore, it is possible to control the ink ejection amount by controlling the volume of the generated bubbles.

The volume of the generated bubbles is controlled by changing the waveform of the power or the voltage applied to the electrothermal conversion element, or by changing the amount of current flowing through the electrodes.

Further, the ink ejection amount may be changed by changing the time from the generation of bubbles to the operation of the pressure generating means.

It is also possible to modulate the ink discharge amount by providing a plurality of electrothermal converting elements in one liquid path and controlling the pressure absorption amount according to the number of bubbles to be generated.

[0040]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 An ink jet recording head of the present invention which employs a piezoelectric element as a pressure generating means and a bubble as a pressure absorbing means will be described.

FIG. 6 is a schematic view showing an example of a recording apparatus having an ink jet recording head according to the present invention. In FIG. 6, 1A is a recording head for ejecting yellow color ink, 1B is a recording head for ejecting magenta color ink, 1C is a recording head for ejecting cyan color ink,
1D is a recording head that ejects black color ink, and these recording heads 1A, 1B, 1C and 1D are
It is installed on the carriage 2. Further, these recording heads 1A, 1B, 1C and 1D are of a disposable type in which an ink containing portion which is a supply source of each ink is integrated. The carriage 2 moves left and right along the guide shaft 3, and the moving position is the encoder 4
Detected by. The recording paper (recording medium) 5 is fed while being guided by a plurality of feed rollers 6 installed above and below, and the ink ejection port forming surfaces (hereinafter simply referred to as ejection surfaces) of the recording heads 1A, 1B, 1C and 1D. The discharge surface is kept parallel to the discharge surface.

Next, the recording heads 1A, 1B, 1C and 1
The configuration of D will be described with reference to FIGS. In these figures, one of the recording heads is designated by reference numeral 1.
Is shown as a representative.

The recording head 1 has a structure in which the head chip 11 and the ink containing portion 12 are integrated. The head chip 11 has a bonding structure of a substrate 13 made of Si and a top plate 14 made of glass, and a plurality of ejection nozzles arranged in the up-down direction (the depth direction in FIG. 1) are provided on the ejection surface side at the joints. An outlet 15 is formed. Those outlets 15
Are connected to one common liquid chamber 17 by a plurality of liquid passages 16 that communicate with each other. The wall portion between the plurality of liquid paths 16 is formed of, for example, an ultraviolet curable resin. The common liquid chamber 17 is connected to the inside of the ink containing portion 12 by a tube 18. The top plate 14 is provided with a hole 43 at the position of the common liquid chamber 17, and an elastic body 42 is installed around the hole 43 on the top surface of the top plate. A flat plate diaphragm 41 made of SUS or the like is further provided on the elastic body 42. Diaphragm 4
Reference numeral 1 covers the hole 43 of the top plate 14. Reference numeral 40 denotes a piezoelectric element made of PZT or the like, which expands in the direction of the arrow in the drawing when a voltage is applied by the power supply device 70, and discharges and contracts to its original size when the voltage application is stopped. The supply of voltage to the piezoelectric element 40 of the power supply device 70 is controlled by the controller 72. The lower end of the piezoelectric element 40 is the diaphragm 4
1, and the upper end is fixed to the frame body 44. The frame body 44 is fixed to the entire recording head 1.

On the upper surface of the substrate 13, an electrothermal conversion element 19 for generating bubbles in the ink in each liquid passage 16,
Wiring such as Al for individually supplying electric power is formed by a film forming technique. Electric power is supplied to the electrothermal conversion element 19 by the drive circuit 71. The drive circuit 71 is controlled by the controller 72.

The operation of the recording head will be described below.

First, a liquid passage for ejecting ink and a liquid passage for not ejecting ink are selected according to the image signal. Then, the controller 72 supplies power from the power supply device 70 to the electrothermal conversion element 19 in the liquid path that does not eject ink. When receiving electric power, the electrothermal conversion element 19 generates heat to generate bubbles in the liquid path. The bubbles generated at this time have a foaming power that does not result in ink ejection. Further, the electrothermal conversion element 19 in the liquid path for ejecting ink
There is no power supply to and therefore no bubbles are generated.

After that, electric power is supplied to the piezoelectric element 40 by the power supply device 70, and the piezoelectric element 40 extends in the direction of the arrow in the figure. Then, the common liquid chamber 17 and the liquid passage 16 are rapidly pressurized, and the ink in the liquid passage continues to move toward the ejection port 15 in the liquid passage in which bubbles are not generated until the surface tension is broken and the ejection port 15 is broken. From the discharge.

On the other hand, in the liquid path in which bubbles are generated,
Since the pressure generated by expanding the piezoelectric element 40 is absorbed by the bubbles, the ink is not ejected.

As described above, in the present invention, when a plurality of liquid passages are pressurized by the common pressure generating means, a liquid passage for ejecting ink and a liquid passage for not ejecting are selected and controlled to perform image recording. To do.

In the present embodiment, it is of course possible to change the ink ejection amount by appropriately changing the size of the bubbles to be generated. That is, the piezoelectric element 40 is expanded without generating bubbles, and the common liquid chamber 17 and the liquid passage 16 are
The ink discharge amount when pressurizing is set to the maximum discharge amount, and as the size of the bubble to be generated increases, the absorbed pressure increases, and therefore the ink discharge amount decreases. Therefore, it is possible to directly modulate the ink discharge amount by controlling the size of the bubble to be generated by changing the pattern of the voltage applied to the electrothermal conversion element 19 and to realize high-speed gradation recording. .

Embodiment 2 FIG. 3 is a schematic diagram showing a constitutional example of an ink jet recording head similar to that of Embodiment 1 except that an electrodynamic converter is adopted as the pressure generating means.

Description will be made with reference to FIG. Reference numeral 52 is a magnet, and the symbols N and S in the figure represent the north pole and the south pole, respectively. An outer frame 54 is fixed to the magnet 52, and is also fixed to the recording head 1 by a jig not shown in the drawing.
An end member 55 is fixed to the N pole of the magnet 52. 51
Is loosely coupled to the hole 43 of the top plate 11 with a vibration plate,
It covers the hole 43. The diaphragm 51 is fixed to the outer frame 54 by a coil 53, and a voltage E is applied by the power supply device 70.

When the power supply device 70 applies the voltage E to the coil 53, a current flows through the coil 53. Then, due to the action of the flowing current and magnetic field, the coil 5
3 moves, and the diaphragm 51 moves. Therefore, when an AC voltage is applied to the coil 53, the diaphragm 51 vibrates in the direction of the arrow in the figure. If the ink is ejected from the ejection port 15 by the pressure fluctuation generated at this time, the ink is continuously ejected when the bubble is not generated in the liquid passage 16 and is not ejected only when the bubble is generated in the liquid passage 16.

In Example 1, although the object of the present invention can be achieved, 1) the displacement of the piezoelectric element itself is small, the displacement of the diaphragm cannot be increased so much. The chamber 17 is thermally affected, 3) The expansion process of the piezoelectric element is basically a charging phenomenon, so the degree of freedom of the expansion time constant is small, and the degree of freedom of the generated pressure change with time is small, etc. On the other hand, in the second embodiment, since the displacement amount and displacement speed of the diaphragm can be adjusted by adjusting the magnetic field and the applied voltage, the degree of freedom with respect to the time change of the generated pressure is large. Further, there is an advantage that heat generation is small.

The same effect can be obtained by using an electromagnetic converter as the pressure generating means.

Example 3 FIG. 4 shows an example of the construction of an ink jet recording head similar to that of Example 1 except that an electrode is adopted as a bubble generating means and a bubble is generated by passing an electric current through the ink to cause electrolysis. It is sectional drawing shown.

In FIG. 4, reference numeral 61 denotes an electrode, which is a power generator 73.
When an electric current is applied to this, bubbles are generated in the liquid path 16.

In the first embodiment, since the volume of the bubble to be generated is determined by the thermodynamic state of the heated ink, the modulation width of the volume cannot be wide, whereas in the third embodiment, it is generated. Since the volume of the bubble is determined by the amount of current flowing through the ink, there is an advantage that the modulation width of the volume of the generated bubble can be increased and thus the modulation width of the ink ejection amount can be increased.

Example 4 FIG. 5 is an example except that the time from the generation of bubbles to the start of pressurization by the pressure generating means is changed while the volume of the bubbles generated as the pressure absorbing means is kept constant. 3 is a cross-sectional view showing a configuration example of an inkjet recording head similar to that of FIG.

In FIG. 5, reference numeral 74 denotes a timing generator which determines the time from the supply of electric power to the electrothermal converting element in each liquid path to the operation of the pressure generating means in accordance with the image data. The controller 72 is a timing generator 74
Information is received and the pressure generator is operated, electric power is supplied from the drive circuit 71 to the electrothermal conversion element 19 earlier to generate bubbles, as soon as the time determined in each flow path.

When the pressure generating means is operated during the period from the maximum volume of bubbles to the disappearance of the bubbles, the amount of pressure absorption changes depending on the volume of bubbles when the pressure generating means is operated, and the ink ejection amount is changed. Change. Therefore, the ink ejection amount can be modulated by appropriately controlling the time from the generation of bubbles until the pressurization is started by the pressure generating means.

In the first embodiment, since it is necessary to change the drive waveform in order to change the bubble volume, the modulation width of the bubble volume cannot be increased so much, the load on the circuit becomes large, and the cost becomes high. On the other hand, according to the fourth embodiment, since the pressure generating means can be operated with an arbitrary bubble volume from the maximum volume of the bubble to disappearing, the modulation width can be widened and the timing of operating the pressure generating means in terms of a circuit is also possible. There is an advantage that it can be realized easily and at low cost because it is only changed.

Furthermore, in the present embodiment, since bubbles are generated after the pressure is generated by the pressure generating means, further pressure is applied to the ink moving toward the ejection port, so that bubbles are not generated. The amount of ejected ink becomes larger than that when the ink is simply pressurized and ejected, or when the ink is pressurized and ejected after defoaming. Therefore, the modulation range of the ink ejection amount can be further increased, and the range of gradation expression of the recorded image can be increased.

[0065]

As described above, according to the present invention, it is possible to easily increase the density of discharge ports and liquid paths and increase the number of ink channels, and to use a wide variety of inks including non-aqueous inks. A recording device is provided.

Further, according to the recording head and the recording apparatus of the present invention, the pressure generated by the pressure generating means is absorbed by the pressure absorbing means, so that it is possible to perform gradation recording while keeping the recording speed high. Become.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an aspect of an inkjet recording head of the present invention.

FIG. 2 is a schematic external view of the inkjet recording head shown in FIG.

FIG. 3 is a schematic cross-sectional view showing another aspect of the inkjet recording head of the present invention.

FIG. 4 is a schematic cross-sectional view showing another aspect of the inkjet recording head of the present invention.

FIG. 5 is a schematic cross-sectional view showing another aspect of the inkjet recording head of the present invention.

FIG. 6 is a schematic view showing an example of a recording apparatus including an inkjet recording head according to the present invention.

[Explanation of symbols]

 1 Recording Head 15 Discharge Port 16 Liquid Path 17 Liquid Chamber 19 Electrothermal Conversion Element 40 Piezoelectric Element 41 Diaphragm 51 Vibration Plate 52 Magnet 53 Coil 54 Outer Frame 55 End Member 61 Electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B41J 2/205 B41J 3/04 103 X

Claims (16)

[Claims] 1. A plurality of ejection ports for ejecting ink, and a plurality of liquid paths for supplying ink to the plurality of ejection ports,
In an inkjet recording head including a liquid chamber that stores ink supplied to the plurality of liquid passages, a pressure generating unit capable of pressurizing ink in the plurality of liquid passages, and one or more liquid passages Pressure absorbing means is provided, the ink in the plurality of liquid paths is pressurized by the pressure generating means, and the pressure applied to the ink is absorbed by the pressure absorbing means to control the ink ejection amount and eject the ink. An ink jet recording head, which ejects ink droplets from an outlet. 2. The ink jet recording head according to claim 1, wherein the pressure generating means is an electromechanical conversion element. 3. The ink jet recording head according to claim 1, wherein the pressure generating means comprises an electromechanical conversion element and a member having a bottom area larger than the bottom area of the electromechanical conversion element. 4. The ink jet recording head according to claim 2, wherein the electromechanical conversion element is an electrokinetic converter. 5. The ink jet recording head according to claim 2, wherein the electromechanical conversion element is an electromagnetic converter. 6. The ink jet recording head according to claim 1, wherein the pressure generating means is provided in the middle of the plurality of liquid paths. 7. The ink jet recording head according to claim 1, wherein the pressure generating means is provided in the liquid chamber. 8. The ink jet recording head according to claim 1, wherein the pressure generating means changes the generated pressure according to the temperature of the recording head. 9. The pressure absorbing means is a bubble.
The inkjet recording head according to 1. 10. The ink jet recording head according to claim 9, wherein the bubbles are generated in the ink by an electrothermal conversion element that generates heat when electric energy is applied. 11. The ink jet recording head according to claim 10, wherein the volume of bubbles generated is changed to change the ink ejection amount by changing the waveform of the power applied to the electrothermal conversion element or the voltage applied thereto. 12. The ink jet recording head according to claim 9, wherein the bubbles are generated in the ink by electrolyzing an ink component by passing a current through the electrodes. 13. The ink jet recording head according to claim 12, wherein the volume of bubbles generated by changing the amount of current flowing through the electrode is changed to change the ink ejection amount. 14. The ink jet recording head according to claim 9, wherein the ink ejection amount is changed by changing the time from the generation of the bubbles to the operation of the pressure generating means. 15. The ink jet recording head according to claim 1, wherein the ink jet recording head is a full line type in which a plurality of ink ejection openings are provided over the entire width of the recording area of the recording medium. 16. The ink jet recording head according to claim 1, wherein an ink ejection port is provided facing a recording surface of a recording medium, and a member for mounting the head. An inkjet recording apparatus comprising at least one.