JP2001105590A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an ink jet head by a simple manufacturing method and a simple manufacturing apparatus to dispense with the restriction of the kind of ink to be used and to achieve miniaturization and high integration. SOLUTION: Ink drops are ejected from nozzles 11 by the deformation of the nozzle plate 10 forming a part of an ink pressure chamber 8 caused by the thermal expansion of the nozzle plate and the effect on an adjacent channel is reduced to eliminate a problem of cross talk between channels to stably form an image of good quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head used for an ink jet printer, and more particularly, to miniaturization and high integration.

[0002]

2. Description of the Related Art Ink jet recording systems have attracted attention because they can record without contacting an ink jet head on recording paper, and have a very simple recording process and are suitable for color recording. Various methods have been proposed as the ink jet recording method. At present, a so-called drop-on-demand method in which ink is ejected only when a recording signal is input has become mainstream. The drop-on-demand method includes a bubble jet method and a piezo actuator method.

[0003] The bubble jet method utilizes bubbles generated in ink by thermal energy. For example, as shown in Japanese Patent Publication No. 61-59913, a heater corresponding to an actuator is provided in an ink flow path. In this method, ink is directly and instantaneously heated by the heater to generate bubbles on the surface of the heater, and the pressure in the ink flow path at this time causes ink to be formed into droplets and ejected from nozzles. In this method, the energizing time for heater heating is 5 to 10 μsec, and the heater surface temperature is 40 μs.
Reach 0-450 ° C. The bubble jet method has an advantage that a heater corresponding to an actuator is very small, and high integration and miniaturization of a head are easy.

In the piezo actuator system, a nozzle is formed on a wall of a container forming a liquid chamber, and a piezoelectric element is provided in the liquid chamber in opposition to the nozzle, as shown in Japanese Patent Publication No. 60-8953, for example. And a method in which the piezoelectric element is driven to generate a dynamic pressure in the nozzle area to form ink droplets and eject the ink from the nozzles, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 3-10846. A deformable elastic wall is used as a wall constituting the pressurized liquid chamber, and a piezoelectric element is provided outside the elastic wall, and the inner volume is changed by deforming the wall of the pressurized liquid chamber using the piezoelectric element. Accordingly, there is a method in which pressure is applied to ink in the pressurized liquid chamber to form droplets and the droplets are ejected from nozzles. In this piezo actuator method, a pulse-like pressure increase in the nozzle area or the pressurized liquid chamber on the front surface of the piezoelectric element is required, and the voltage waveform applied to the piezoelectric element is set to a rise time of several μsec to several tens μsec, and the ink has Replenishment is performed by returning the displacement of the piezoelectric element.

In order to increase the number of channels of the ink jet head in this piezo actuator system, a substrate formed by sintering a green sheet made of a piezoelectric material, as shown in, for example, Japanese Patent Application Laid-Open No. 4-16353, is used. A lower conductive layer is provided on the lower conductive element plate, and a piezoelectric element plate serving as a driving piezoelectric element is provided on the lower conductive layer, and an upper conductive layer is formed on the piezoelectric element plate, This laminate is cut at a depth from the upper conductive layer to the lower conductive layer to divide it into two piezoelectric element plates having conductive layers on the upper and lower surfaces, and further cut the two piezoelectric element plates. By cutting in the direction perpendicular to the direction and dividing it into a number of piezoelectric elements, two rows of piezoelectric element rows composed of a plurality of piezoelectric elements arranged in a row are arranged, and on the upper surface of these piezoelectric element rows It is arranged pressurized liquid chamber communicating with the nozzle.

[0006]

The bubble jet method simplifies the manufacturing process and reduces the cost by applying semiconductor technology, but the surface temperature of the heater is set to 400 to 450 ° C. in order to generate bubbles. Need to be higher,
Since the temperature of the substrate is increased by the heater, the driving frequency cannot be increased repetitively. In addition, since the ink is directly heated by the heater, the composition of the ink changes, and further, kogation of the ink occurs at the ink connection portion of the heater. For this reason, the types of inks that can be used are restricted, and pigment ink cannot be used. There is a limit to the improvement in image quality, and the heater deteriorates due to kogation. Disconnection failure of the heater is likely to occur.

In the piezo actuator system, the type of ink that can be used is not limited because the heat generated by the piezoelectric element is negligible. However, mechanical and thermal methods such as dicing and positioning for firing the piezoelectric element and increasing the number of channels are required. Complicated manufacturing steps and manufacturing equipment are required, which increases costs.

[0008] Both the bubble jet method and the piezo actuator method use ink bubble jet or PZT.
In an ink jet head as well, the actuator is generally formed at a lower portion against the nozzle of the head. However, this has a distance to transmit the ink pressure to the nozzle, and there is a problem in crosstalk between the respective channels of the inkjet head.

The present invention has been made to solve the above-mentioned disadvantages, and provides an ink-jet head which can be manufactured by a simple manufacturing process and a manufacturing apparatus, has no restriction on the kind of ink used, and can be reduced in size and highly integrated. It is intended for.

[0010]

According to the present invention, there is provided an ink jet head for ejecting ink in an ink pressure chamber from a nozzle as ink droplets. The nozzle plate is formed by a thermal expansion of a nozzle plate forming a part of the ink pressure chamber. The method is characterized in that an ink droplet is ejected from.

The nozzle plate has a micro heater formed around the nozzle by laminating materials having different coefficients of thermal expansion.

It is desirable that the difference in thermal expansion between the laminated materials of the microheater is at least twice.

It is preferable that the micro heater is provided on the outer surface of the nozzle plate on the side opposite to the ink pressure chamber.

A micro heater provided on the outer surface of the nozzle plate may cover the water repellent film.

A micro heater may be provided on the inner surface of the nozzle plate on the ink liquid chamber side, and the surface of the micro heater may be covered with a protective film.

The micro heater may be formed of a metal or an alloy, or may be formed of conductive new ceramics.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An ink jet head according to the present invention has a liquid chamber unit and an actuator unit joined on the liquid chamber unit. The liquid chamber unit has a frame, a plurality of holes for fluid resistance, a separator attached to the end of the frame, and a common ink liquid chamber formed by the frame and the separator. The actuator unit has an ink pressure chamber partition provided with ink pressure chambers at positions corresponding to the fluid resistance holes of the separator, and a nozzle plate joined to the tip of the ink pressure chamber partition. The nozzle plate has a substrate having a nozzle at a position corresponding to the ink pressure chamber, and a micro heater provided on a peripheral surface of the nozzle of the substrate. The substrate is made of a material having a small coefficient of thermal expansion, for example, ceramics, has a thickness of, for example, 10 μm to 30 μm, and is provided with a plurality of nozzles having a diameter of 30 μm. The microheater is made of a plurality of different materials having a coefficient of thermal expansion larger than that of the substrate, for example, C having a coefficient of thermal expansion of 8 × 10E-6 / ° C.
r and a thermal expansion coefficient of 16 × 10E-6 / ° C. are laminated and formed around the nozzle, and are patterned around the nozzle. One end of the patterned micro heater is connected to a common electrode. On the other end, an individual electrode is provided.

In a state where ink is filled in the ink pressure chamber of the ink jet head, a current having a predetermined current value is supplied from a common electrode and an individual electrode to a micro heater provided around a nozzle having a nozzle plate, thereby forming a micro heater. Is heated to, for example, about 200 ° C., the nozzle portion of the substrate provided with the micro heater has a substrate having a small coefficient of thermal expansion and a Cr layer having a coefficient of thermal expansion of 8 × 10E-6 / ° C. Because the Ni—Cr layer of 16 × 10E-6 / ° C. is laminated, the substrate is positioned outside the ink pressure chamber at the nozzle provided with the microheater that is energized due to the difference in the coefficient of thermal expansion. Expands and deforms. Therefore, the pressure in the ink pressure chamber becomes negative, and the ink flows from the common ink chamber through the fluid resistance hole into the ink pressure chamber. When the current flowing through the micro heater is cut off, the deformed nozzle portion is cooled, contracts, and returns to its original position. The contraction of the nozzle portion pressurizes the ink pressure chamber, and the ink in the ink pressure chamber is ejected as a fixed amount of ink droplet.

In this way, the periphery of the nozzle of the nozzle plate is locally heated and deformed by thermal expansion, and the ink droplet is ejected from the nozzle by this deformation. And the effect on adjacent channels can be reduced.

[0020]

FIG. 1 is a sectional view showing the structure of an embodiment of the present invention. As shown in the figure, the inkjet head 1 has a liquid chamber unit 2 and an actuator unit 3 joined on the liquid chamber unit 2. The liquid chamber unit 2 has a frame 4, a plurality of holes 5 for fluid resistance, and a separator 6 joined to the end of the frame 4, and a common ink liquid chamber is formed by the frame 4 and the separator 6. 7 are formed. The actuator unit 3 includes an ink pressure chamber partition 9 having ink pressure chambers 8 provided at positions corresponding to the fluid resistance holes 5 of the separator 6.
And a nozzle plate 10 joined to the tip of the ink pressure chamber partition 9. The frame 4, the separator 6 and the ink pressure chamber partition 9 are made of an ink-resistant material such as ceramics or stainless steel. The nozzle plate 10 is a substrate 12 having a nozzle 11 at a position corresponding to the ink pressure chamber 8.
And a micro heater 13 provided on a peripheral surface of the nozzle 11 of the substrate 12. The substrate 12 is made of a material having a small coefficient of thermal expansion, for example, ceramics.
A plurality of nozzles 11 having a thickness of 0 μm and having a diameter of 30 μm are provided on the substrate 12. The micro heater 13 is made of a plurality of different materials having a larger coefficient of thermal expansion than the substrate 12, such as Cr having a coefficient of thermal expansion of 8 × 10E-6 / ° C. and Ni—Cr having a coefficient of thermal expansion of 16 × 10 E-6 / ° C. As shown in the perspective view of FIG. 2, one end of the patterned micro-heater 13 is patterned around the nozzle 11, and one end of the patterned micro-heater 13 is connected to the common electrode 14.
And an individual electrode 15 is provided at the other end.

A method of manufacturing the nozzle plate 10 of the ink jet head 1 configured as described above will be described with reference to the process chart of FIG.

As shown in FIG. 3 (a), a hole 17 having a size corresponding to the size of the nozzle 11 is formed in an aluminum (Al) plate 16, and as shown in FIG. Anodized film (β-Al ₂
O ₃ ) 18 is formed to a thickness of 10 μm to 30 μm. Next, the anodic oxide film 18 is sealed in a solution of Mn, Cr, Ba, or the like, and further heated at 300 ° C. to obtain (c)
As shown in (1), a substrate 12 in which β-Al ₂ O ₃ is stabilized to γ-Al ₂ O ₃ to improve chemical resistance is formed. Thereafter, as shown in (d), the heater layer 1 is formed on the surface of the substrate 12.
9 is formed. When the heater layer 19 is formed, the surface of the substrate 12 has a coefficient of thermal expansion of 7.5 × 10E-6 / ° C.
Alternatively, the coefficient of thermal expansion is 8 × 1 to improve adhesion to the substrate 12.
0E-6 / ° C Cr is deposited to a thickness of 0.1 to 0.5 µm by vapor deposition, CVD, electrodeposition, or the like, and a metal material, for example, having a coefficient of thermal expansion of 16 × 10E-6 / ° C is formed on this film. Ni-Cr or Ni having a coefficient of thermal expansion of 15.1 × 10E-6 / ° C. is formed by the same method as described above. After forming the heater layer 19, (e)
As shown in (1), the heater layer 19 is patterned to form the micro-heater 13, the common electrode 14, and the individual electrode 15. Thereafter, as shown in (f), the Al plate 16 holding the substrate 12 is dissolved and removed with an alkali or iron oxide solution to obtain the nozzle plate 10. Thus, the nozzle plate 10 can be manufactured using the semiconductor manufacturing technology. By joining this nozzle plate 10 to the liquid chamber unit 2 via the ink pressure chamber partition 9, the ink jet head 1
Create

When the nozzle plate 10 is formed, the nozzle 11 may be provided on a ceramic substrate 12 having an appropriate thickness, and a pattern may be formed in which a heater layer 19 is formed on the surface of the substrate 12.

Next, the operation of the ink jet head 1 configured as described above will be described. With the ink pressure chamber 8 filled with ink, the nozzle 11 with the nozzle plate 10
The common electrode 14 is attached to the micro heater 13 provided around the
Then, a current having a predetermined current value is supplied from the individual electrode 15 to heat the micro heater 13 to, for example, about 200 ° C. The portion of the nozzle 11 provided with the microheater 13 of the substrate 12 to be heated includes a substrate 12 having a small coefficient of thermal expansion, a Cr layer having a coefficient of thermal expansion of 8 × 10E-6 / ° C., and a coefficient of thermal expansion of, for example, 8 × 10E-6 / ° C. Since the Ni—Cr layer of 16 × 10E-6 / ° C. and a material having a difference in thermal conductivity are laminated, the nozzle 1 provided with the micro heater 13 is provided by the difference in thermal expansion coefficient.
The substrate 12 expands and deforms outward with respect to the ink pressure chamber 8 at the portion 1. As a result, the ink pressure chamber 8 has a negative pressure, and flows from the common ink chamber 7 through the fluid resistance hole 5 to the ink pressure chamber 8.
Flows into the ink. When the current flowing through the micro heater 13 is cut off, the deformed nozzle 11 is cooled, contracts, and returns to its original position. The ink pressure chamber 8 is pressurized by the contraction of the nozzle 11 and the ink in the ink pressure chamber 8 is ejected as a fixed amount of ink droplet.

Thus, the nozzle 11 of the nozzle plate 10
The surroundings are locally heated and deformed due to the difference in thermal expansion coefficient,
Since the ink droplets are ejected from the nozzles 11 by this deformation, the ink droplets can be ejected directly around the nozzles 11 as an actuator, thereby reducing the influence on the adjacent channels and reducing the crosstalk between the channels. The problem can be solved.

Further, since the micro heater 13 has a metal layer such as Ni—Cr bonded to the substrate 12 via a Cr layer or the like, the adhesion between the micro heater 13 and the substrate 12 can be improved, When the portion is expanded and contracted, the micro heater 13 can be prevented from peeling off from the substrate 12.

A portion of the nozzle 11 provided with the microheater 13 has a substrate 12 having a small thermal expansion coefficient, a Cr layer having a thermal expansion coefficient of 8 × 10E-6 / ° C., and a thermal expansion coefficient of, for example, 16 ×. 10E-6 / ℃, twice as much Ni as Cr layer
Since the Cr layer is laminated, the portion of the nozzle 11 provided with the microheater 13 can be largely deformed only by heating the microheater 13 to a temperature of, for example, 200 ° C., so that an ink droplet of an appropriate size can be formed. Can be injected stably. Further, the heating temperature of the micro-heater 13 is controlled to control the nozzle 1 provided with the micro-heater 13.
By varying the degree of deformation of the portion 1, the amount of ejected ink droplets can be controlled, and a multi-valued image can be printed stably.

Furthermore, the nozzle 11 can be locally heated by the micro heater 13 and the heating temperature can be suppressed to a relatively low temperature, so that the composition of the ink used does not change and the ink kogation does not occur. It is possible to print a high-quality color image or the like using a pigment ink or the like without having to consider such factors.

Although the above embodiment has described the case where the surface of the micro heater 13 is exposed, a water repellent film may be formed on the surface of the micro heater 13. In this case, as shown in FIG. 4A, the surface of the substrate 12 made of a material having a low coefficient of thermal expansion such as ceramic
The micro heater 13 is formed by patterning from a conductive material such as Cr, Mo, W, Ni, and Pt having a high coefficient of thermal expansion by vapor deposition or electrodeposition. Next, as shown in (b), a water-repellent film 20 is formed on the surface of the microheater 13 by PTFE eutectoid plating by an electrodeposition method. By forming the water-repellent film 20 on the surface of the micro-heater 13 in this manner, the heating efficiency of the micro-heater 13 can be increased, and the ink droplets can be stably ejected. Further, since the water-repellent film 20 is formed only on the surface of the micro heater 13, the nozzle 1
Even if the portion 1 is deformed, the deformation peeling due to the film shrinkage can be prevented.

In the above embodiment, the case where the micro heater 13 is provided on the outer surface of the substrate 12 has been described. As shown in FIG. 5, the micro heater 13 is provided on the inner surface of the substrate 12 on the ink pressurizing chamber 8 side. The outer surface of the substrate 12 is covered with a water-repellent film 21, and the inner surface of the substrate 12 having the microheater 13 has a heat-resistant temperature of, for example, 3 such as thermo-flexible polyimide.
The Young's modulus is 9.8 × 10 ⁶ to 49 × 10 ⁶ P at about 00 ° C.
The protective film 22 made of a material having electrical insulation may be coated and covered with a.

As described above, when the micro heater 13 is provided around the nozzle 11 on the ink pressurizing chamber 8 side of the substrate 12, the micro heater 13 is energized and heated, so that the nozzle 11 moves to the ink pressurizing chamber 8 side. The ink is ejected from the nozzle 11 by increasing the internal pressure of the ink pressurizing chamber 8. The ejected ink droplets are heated by the micro heater 13 and have a high temperature, so that they can be quickly dried when they adhere to recording paper or the like. When the current flowing through the micro-heater 13 is cut off, the heated micro-heater 13 is rapidly cooled by the ink in the ink pressurizing chamber 8 and deformed.
Part shrinks quickly. Therefore, the driving frequency for ejecting ink droplets can be increased.

The substrate 1 having the micro heater 13
2 is covered with a protective film 22 made of, for example, a heat-flexible polyimide having a bonding temperature of about 250 ° C.
By using this, the nozzle plate 10 can be joined to the ink pressure chamber partition wall 9 and the occurrence of ink kogation can be prevented. Further, by using a heat-flexible polyimide or the like, even if the portion of the nozzle 11 is deformed by heating, it is possible to prevent the protection film 22 from being cracked,
It can be used stably for a long time.

In each of the above embodiments, the micro heater 13 is made of Cr.
Although the case where the micro heater 13 is formed by laminating Ni—Cr or the like has been described, the micro heater 13 may be formed by using a conductive new ceramic such as silicon carbide (SiC) or boron carbide (BC). good. By forming the micro-heater 13 from conductive new ceramics in this way, the durability can be increased and the history due to thermal stress can be reduced. In addition, the adhesion to the water repellent films 20 and 21 and the protective film 22 is improved, and the highly reliable noise plate 10 can be manufactured.

[0034]

According to the present invention, as described above, the ink droplets are ejected from the nozzles by deformation of the nozzle plate forming a part of the ink pressure chamber due to thermal expansion. Can be ejected, the influence on adjacent channels can be reduced, the problem of crosstalk between channels can be solved, and a high-quality image can be stably formed.

Further, by providing a micro heater around the nozzle of the nozzle plate, only the periphery of the nozzle can be locally thermally deformed, and only the periphery of the nozzle can be rapidly heated and cooled. .

Further, the micro heater is formed around the nozzle by laminating materials having different coefficients of thermal expansion.
By thermally deforming only the periphery of the nozzle, ink droplets can be reliably ejected from the nozzle.

Further, by making the difference in thermal expansion of the laminated materials of the microheater at least twice, the periphery of the nozzle can be locally heated at a relatively low temperature and thermally deformed. The composition of the ink does not change due to heat, and various inks can be used stably.

Further, by controlling the heating temperature of the micro heater to vary the degree of deformation around the nozzle,
The amount of ejected ink droplets can be controlled, and a multi-valued image can be printed stably.

By providing the micro heater on the outer surface of the nozzle plate opposite to the ink pressure chamber, it is not necessary to consider the kogation of the ink. Can be printed.

Further, by covering the water repellent film with the micro heater provided on the outer surface of the nozzle plate, the heating efficiency of the micro heater can be increased and the ink droplet can be jetted stably. Further, since the water-repellent film is formed only on the surface of the microheater, even if the periphery of the nozzle is deformed, deformation and peeling due to film shrinkage can be prevented.

Further, by providing a microheater on the inner surface of the nozzle plate on the ink liquid chamber side and covering the surface of the microheater with a protective film, the ink droplets can be heated and ejected and adhere to recording paper or the like. Sometimes can dry quickly. Furthermore, when the current flowing through the micro-heater is cut off, the heated micro-heater is rapidly cooled by the ink in the ink pressure chamber, and the area around the deformed nozzle is quickly contracted and returned to its original state. The driving frequency can be increased.

In addition, since the micro heater is formed of a metal or an alloy, the nozzle plate can be manufactured by utilizing the semiconductor manufacturing technology, and the cost of the jet head can be reduced.

Further, since the micro heater is formed of conductive new ceramics, the durability can be increased and the history due to thermal stress can be reduced. Further, the adhesion to the water-repellent film and the protective film is improved, and a highly reliable noise plate can be manufactured.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an embodiment of the present invention.

FIG. 2 is a perspective view showing the noise plate of the embodiment.

FIG. 3 is a process chart showing a method for manufacturing a noise plate.

FIG. 4 is a process chart showing a method for manufacturing a noise plate according to a second embodiment.

FIG. 5 is a sectional view showing a configuration of a third embodiment.

[Explanation of symbols]

1; inkjet head, 2; liquid chamber unit, 3; actuator unit, 4; frame, 5; fluid resistance hole,
6; separator, 7; common ink liquid chamber, 8; ink pressure chamber,
9; ink pressure chamber partition, 10; nozzle plate, 11; nozzle, 12; substrate, 13; micro heater, 14; common electrode, 15;

Claims (8)

[Claims] An ink jet head for ejecting ink in an ink pressure chamber from a nozzle as an ink droplet, wherein the ink droplet is ejected from a nozzle by deformation of a nozzle plate forming a part of the ink pressure chamber due to thermal expansion. head. 2. The ink jet head according to claim 1, wherein the nozzle plate has a micro heater formed around the nozzle by laminating materials having different coefficients of thermal expansion. 3. The ink jet head according to claim 2, wherein the difference in thermal expansion between the stacked materials of the micro heater is at least twice. 4. The ink jet head according to claim 2, wherein the micro heater is provided on an outer surface of the nozzle plate opposite to the ink pressure chamber. 5. The ink jet head according to claim 4, wherein a micro heater provided on an outer surface of the nozzle plate covers a water repellent film. 6. The ink jet head according to claim 2, wherein the micro heater is provided on the inner surface of the nozzle plate on the ink liquid chamber side, and the surface of the micro heater is covered with a protective film. 7. The ink jet head according to claim 2, wherein the micro heater is made of a metal or an alloy. 8. The ink jet head according to claim 2, wherein said micro heater is made of conductive new ceramics.