JP2002513699A - Ink jet print head with pressure concentrator - Google Patents

Abstract

(57) [Summary] A plurality of ink discharge nozzles (50) formed on the first wafer surface (40), and these ink discharge nozzles (50) collectively form an ink supply group (48). Wherein each ink supply group (48) includes a group ink supply path (45) etched through the wafer (40), an ink discharge nozzle (50), a vibration concentrator (34) and the A vibration concentrating member (34) including a planar element attached to the back surface of the wafer (40) so as to form a cavity including the ink supply path (45) between the vibration concentrating member (34) and the vibration concentrator; A piezoelectric element (31) attached to the member (34) and adapted to impart controlled spatial movement to the vibration concentrating member (34), wherein the concentrating member (34) In order to provide large pressure fluctuations at the nozzle (50), the ink ejection nozzle Adapted to focus the spatial movement to the focus (36) in the vicinity of each of the groups (50), discloses a drop-on-demand ink jet printhead system. Each ink ejection nozzle (50) includes a selection mechanism to enable or disable the ejection of droplets by the nozzle when large pressure fluctuations occur. The selection mechanism heats near the surface layer of ink to be ejected from the ink ejection nozzles, thereby changing its surface tension and spreading around each nozzle to allow ejection. Heater (16) may be included.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of ink jet printers, and more particularly to a novel apparatus for concentrating pressure fluctuations in an ink jet type printer.

[0002] Many context of the present invention of different types of printing was invented, many of these are currently in use.
Known forms of printer have various methods for marking a print medium with a suitable marking medium. Commonly used printing forms include offset printing equipment, laser printing equipment and copying equipment, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and drop-on-demand types And continuous flow type ink jet printers. Each type of printer has its own advantages and disadvantages when considering cost, speed, quality, reliability, simplicity of construction and operation.

In recent years, the field of ink-jet printing, in which individual pixels of ink are obtained from one or more nozzles, has become increasingly popular, mainly because of its inexpensive and flexible nature.

[0004] Many different techniques of ink jet printing have been invented. To explore this area, see a paper by J Moore, "Non-Impact Printing: Introduction and Histo
rical perspective ", Output Hard Copy Devices, Editors R Dubeck and S She
rr, pages 207-220 (1988).

[0005] Inkjet printers themselves fall into many different types. It is believed that the use of continuous flow inks in ink jet printing dates back to at least 1929, when a simple form of continuous flow electrostatic ink jet printing was disclosed in Hansell, U.S. Pat. No. 1,941,001. Sweet US Patent 3,5
No. 96,275 also discloses a method for continuous ink jet printing including a step of modulating an ink jet flow by a high-frequency electrostatic field to cause droplet separation. This technique is still utilized by many manufacturers, including Elmjet and Scitec (see also US Patent No. 3,373,437 to Sweet et al.).

[0006] Piezoelectric inkjet printers are also a form of commonly used inkjet printing apparatus. Piezoelectric systems are described in U.S. Pat.
No., 946,398 (1970) (using diaphragm mode operation), Zo
It is disclosed in U.S. Pat. No. 3,683,212 to Lten (1970), which discloses squeeze mode operation of piezoelectric crystals. Stemme US Patent 3,747
No. 4,120,1972 discloses a bend-type piezoelectric operation, Howkins discloses in U.S. Pat. No. 4,459,601 the operation of a piezoelectric propulsion mode of ink jet flow, and Fischbeck discloses a U.S. Pat. No. 4,584,590 discloses a shear mode piezoelectric conversion element.

[0007] Recently, thermal inkjet printing has become a very popular form of inkjet printing. This ink jet printing technique includes those disclosed in Endo et al., UK Patent 2,007,162 (1979) and Vaught et al., US Pat. No. 4,490,728. Both of the aforementioned references activate an electro-thermal actuator that creates a bubble in a compression space (eg, a nozzle), thereby causing ink to be ejected from the aperture leading to this confined space onto a suitable print medium. Discloses an ink-jet printing technique based on Printing devices that use electrothermal actuators are available from Canon and Hewlett Pack
Manufactured by manufacturers such as ard.

As can be seen from the foregoing, many different types of printing technology are available. Ideally, printing technology should have a number of attributes. These include inexpensive construction and operation, high-speed operation, and safe and long-term operation. Each technology has its advantages and disadvantages in the areas of cost, speed, quality, reliability, power consumption, simplicity of construction and operation, durability and consumables, respectively.

Recently, one of the present inventors has proposed an ink jet printing system that uses a change in the action of surface tension to eject droplets from a chamber. A heater is placed around the outer aperture where the meniscus is formed and a significant portion of the heat is transferred to the area adjacent to the meniscus to reduce surface tension. European Patent Application 96116117.1
Nos. 6,116,1116.3 and 96116118.9 disclose systems that utilize this principle in the construction of printhead devices.

[0010] Unfortunately, many complex interactions occur when forming a printhead array with large nozzles. In addition, the operation of the inkjet printing system is based on many subtle and complex actions.

[0011] SUMMARY An object of the present invention of the present invention is to provide an improved operating configuration of the ink jet printhead.

According to a first feature of the present invention, there are a plurality of ink discharge nozzles formed on the surface of the first wafer, and these ink discharge nozzles are grouped to form an ink supply group. An ink discharge nozzle, including a group ink supply path etched through the wafer, interconnecting the group ink supply path between the pressure vibration concentrator and the backside of the wafer A pressure vibration concentrator mounted on the back side of the wafer to form a cavity containing an ink supply path; and adapted for imparting a controlled spatial motion to the vibration concentrator, mounted on the vibration concentrator. Wherein the vibrating member is located at the ink discharge nozzle at the moment of ink. A drop-on-demand ink jet printhead system adapted to concentrate pressure fluctuations in said group ink supply path near each group of ink discharge nozzles to provide a large pressure fluctuation. You.

[0013] Preferably, each of the ink discharge nozzles includes a selection mechanism for enabling or disabling discharge of droplets by the nozzle when a large instantaneous pressure fluctuation occurs. The selection mechanism may include a heater for heating the vicinity of the surface layer of the ink to be discharged from the ink discharge nozzle.

In one aspect, the vibration concentrator focuses pressure fluctuations to a focus in the ambient atmosphere slightly outside the ink discharge nozzle. In a second aspect, the vibration concentrator focuses pressure fluctuations to a point in the group ink supply path that is slightly above the group of ink discharge nozzles.

[0015] The group ink supply path may be formed by anisotropic etching of the wafer and terminate in a pit at an ink discharge nozzle. The spatial motion may include applying a substantially planar pressure wave to a first surface of the spatial motion member.

[0016] The group ink supply paths are preferably spaced apart from each other across the surface of the wafer, and the wafer is preferably spaced apart from these spaced group inks. It may include a series of elongated wafer pillars between the feed path and the pressure vibration concentrator, the pressure vibration concentrator being adjacent to the wafer concentrator and the adjacent surface of the pressure concentrator on the top surface of the pillar. To concentrate the fluctuation of the ink pressure.

According to a further feature of the present invention, there is provided a method of ejecting droplets on demand from a series of ink ejection nozzles, wherein each of the nozzles, in the vicinity of the nozzle, sequentially receives ink from the nozzle. Inducing a pressure wave fluctuation in an ink supply chamber attached to the ink discharge nozzle, the mechanism including a selection mechanism for causing a physical change causing the discharge, wherein the pressure wave fluctuation is caused near the ink discharge nozzle. Concentrating; selecting a droplet to be ejected from an ink ejection nozzle simultaneously with the pressure wave fluctuation using the selection mechanism.

The step of concentrating the pressure wave fluctuations near the ink ejection nozzle may further include simultaneously dispersing the pressure wave fluctuations spaced apart from the ink ejection nozzle.

[0019] Other forms of any description of the preferred embodiments and other embodiments may but fall within the scope of the present invention, where, as an example, the invention will be described with respect to accompanying drawings.

By studying and simulating various types of printheads, especially those constructed in accordance with the principles of the aforementioned European patent specification, which utilize oscillating pressure to eject ink, the operation of such printheads has been studied. Understanding was improved. In particular, it has been found that when a pulse applied to an actuator mechanism has certain characteristics, a previously unknown certain effect (described below) occurs. The correspondingly obtained pressure experienced at the ink nozzles leads to a very peculiar phenomenon which is believed to be responsible for the ejection of the ink. A preferred embodiment relates to using this phenomenon to enhance the operation of an ink jet printer.

Turning first to FIGS. 1 and 2, the basic operating principles of an ink jet device that is illustrative of the teachings of the preferred embodiment will be described. 1 and 2 are operable according to the principles described in the aforementioned European patent application.

In operation of the preferred embodiment, the fluctuating ink pressure is applied to the ink supply chamber 10.
Apply to The vibration pressure is applied to the piezoelectric vibrating element 1 mounted on the substrate 13.
It may also be through the use of two or other similar mechanisms. Preferably, a series of ink ejection nozzles (eg, 14, 15) are also provided. Each ink discharge nozzle (
For example, 14) has a circular heater (eg, 16) around the outer area of the nozzle in accordance with the teachings of the aforementioned European Patent Application.

Normally, the oscillation of the ink pressure in the nozzle chamber 10 is such that the surface tension effect across each ink ejection nozzle (eg, 14, 15) is sufficient to retain the ink in the nozzle chamber. Has been adjusted. If it is desired to emit droplets from a nozzle (eg, 14), the heater 16 is pulsed to cause a decrease in surface tension due to the temperature rise of the meniscus 14. Therefore, as shown in FIG. 2, during the next high pressure wave, the surface tension around the ink discharge nozzle 14 will be insufficient to retain the ink in the nozzle chamber 10 and the droplet 20 Is released. At the adjacent nozzles 15 where no heat was applied, the surface tension properties were sufficient to retain the ink in the nozzle chamber 15 and
Although the ink protrudes, no ink droplets are emitted.

Studies of systems operable according to the principles of FIGS. 1 and 2 have revealed a myriad of interesting effects.

In order to unambiguously eject a droplet from a nozzle chamber in a controlled manner, events need to occur simultaneously to help eject the droplet. Especially higher than the surroundings,
At a certain pressure, a droplet will be ejected from the chamber. By utilizing the heating of the meniscus, the pressure above this surrounding required for ejection of the droplet is lower, resulting in ejection of the droplet. However, maintaining such a higher than ambient pressure tends to cause the ink to continue to flow out of the nozzles even after the first drop is ejected. Therefore, it was considered that the continuous outflow of the ink from the nozzle was avoided by using the vibration ink pressure.

However, a detailed study of the ink jet device has revealed even more interesting effects. These effects are discussed with respect to FIGS. Turning first to FIG. 3, an example of a pressure oscillation is shown schematically over time. An equilibrium pressure line 22 is provided above which there is insufficient surface tension to retain the ink in the nozzle chamber. If the heater pulse is of insufficient magnitude during period 23, the equilibrium pressure will decrease 24 as a result of the reduction in surface tension. If the pressure pulse 25 is applied simultaneously, no droplets will be ejected from the nozzle.

However, as illustrated in FIG. 4, when a pressure pulse 26 having a magnitude above the above-mentioned equilibrium pressure is applied for a predetermined period of time, the nozzle is forced to drop irrespective of the equilibrium pressure fluctuation 24. Will release.

Surprisingly, as illustrated in FIG. 5, the application of a short high pressure pulse 27 simultaneously with the drop 24 of the equilibrium pressure causes the droplets to be ejected at an irregularly fast rate. Was found. Further, as explained in FIG. 6, if the same high-pressure pulse is applied simultaneously to nozzles that have not undergone any drop in equilibrium pressure, then even if the ink pressure exceeds the equilibrium pressure momentarily, Is not released at all.

Thus, the use of short high pressure pulses is important in ejecting ink from systems such as those described above.

7 to 12 show the results of a detailed fluid flow simulation performed by a computer on the action of the high-pressure pulse (the time axis indicates 10 microseconds). A fluid chamber similar to that shown in FIG. 1 was modeled using the FIDAP simulation system.

In the simulation of the first example, a spike-free pressure pulse or pressure fluctuation was applied around point 11 in FIG. 1 as shown in FIG. The waveform in FIG. 7 shows the pressure fluctuations likely to occur at the meniscus of the simulation system. Simultaneous heating of the meniscus was also performed. FIG. 8 shows the corresponding velocity fluctuations near the back of the meniscus, indicating that no release occurs.

In a second example, as shown in FIG. 9, the same pressure input waveform is
A series of pressure spikes 28, 29 were simulated. In this case, no heating was performed. The fluid velocity fluctuations obtained near the meniscus were found to be similar to those described in FIG. 10, again indicating that no ejection occurred.

In a third example, the pressure waveform of FIG. 9 was re-used with heating, in which case the result is similar to that described in FIG. 11, approximately 2.5 m / s
Droplets were found to be ejected at a terminal velocity of.

The pulse 28 (FIG. 9) represents a short period of high pressure, which is believed to be a major contributor to imparting momentum to the droplet as it is ejected from the nozzle. This leads to a significant improvement of the ink jet device of FIGS. The above simulation concentrates the input pressure wave at or near the surface of the meniscus at the same time that the heater pulse is applied, resulting in an "overpressure pulse" that imparts significant momentum to the ink around the meniscus, resulting in It suggests that it is desirable to fire the ink at a high ink speed.

Thus, it would be desirable to provide a system that enhances the generation of high voltage pulses. Turning to FIG. 12, a cross-sectional view of a first centralized type device 30 is illustrated schematically. Apparatus 30 may include a series of piezoelectric actuators 31 that are controlled to impart a substantially plane wave to the surface of acoustic transmission medium 34, which may include plastic injection molded member 34. The member 34 is bonded 49 to the back surface of the wafer 40. Thus, the plastic injection molded member 34 will be subject to movement according to control signals sent to the piezoelectric actuator member 31. Member 34
The surface profile of will result in a series of plane waves (eg, 35) in each fluid chamber (eg, 45). Unfortunately, these planar pressure waves reflect the anisotropically etched walls 39 of the nozzle chamber in a disorderly manner.
2. This, in turn, causes the membrane (eg, 48) and the ink discharge nozzles (eg, 50) to undergo pressure fluctuations in a random fashion.

In a first refinement described in FIG. 13, the profile of the surface 47 of the member 34 is shaped to focus the emitted waves at a point 36 outside the membrane. This ensures that more uniform pressure reaches membrane 48 and only minimal reflection occurs.

In the second refinement described in FIG. 14, the focal point 36 has been moved in front of the membrane 48. This will result in a better pulse near the membrane.

Turning to FIG. 15, a further improvement is described wherein the position of the surface 47 is adjusted to favorably move the focal point 40 and increase the depth of the path 45.

The use of the preferred and easily formed part 34 allows the printhead to be configured such that upon activation of the piezoelectric transducer, large concentrated pulses are experienced at the nozzle or membrane 48. Therefore, a printhead element containing a large number of anisotropically etched pits 45 (which may have been anisotropically etched from the backside of the wafer utilizing the aforementioned European Patent Application). In the form of 40, it can be formed as shown in FIG. At the bottom of each pit 46, a standard microelectromechanical
cal) (MEMS) processing technology can be used to provide a series of nozzles formed on the surface of the wafer. FIG. 17 illustrates a single pit 45 to more clearly show the ink discharge nozzle 46.

One form of configuration, as illustrated in FIG. 18, is a coupling end (eg, 50) designed to be coupled with adjacent segments to form a composite printhead (FIG. 16). ) Can be formed from a number of smaller segments 40 each having a page width printer.

As shown in FIGS. 19 and 20, the plastic member 34 is secured to the wafer portion 40 and the profiled surface 4 formed in accordance with the foregoing considerations.
7 can be included to provide pressure wave concentration at the bottom of the corresponding pit (eg, 48).

Unfortunately, the use of vibrating plastic member 34 is still available in regions 57 and 58
In FIG. 16 there is a tendency for large reflections that can interfere with the generation of high voltage pulses. This is illustrated in FIG. 21 where the surface 6 of the member 34
The pressure pulse 62 generated at 0 causes significant energy to be reflected 63 to the area of the ink nozzle film. Arrows 64 and 65 illustrate the arrows of the normal of the plane wave in the adjacent nozzle chamber. This problem can be significantly alleviated by further shaping the surface of member 34. Examples of remodeling are shown in FIGS. In FIG. 22, surface 60 has been profiled to focus pulses on surface 57. Similarly, FIG. 23 shows a second example in which the wall of this member is formed to ensure a significant amount of continuous back reflection from surface 57.

Finally, looking at FIG. 24, it is provided to coincide with the end of each pit and to buffer any pressure pulses that are not required according to the principles of FIGS. 22 and 23. A final bottom view of a cross section of a plastic member 34 including a profiled surface 35 for focusing pressure pulses in addition to a cavity 36 that is present is illustrated.

Thus, by utilizing a suitable profiled plastic former member, the planar pressure wave behind the plastic member is concentrated on the bottom of the anisotropically etched bit and the pressure from the ink discharge nozzle is reduced. It is understood that "overpressure pulses" can be provided to aid in the ejection of the ink.

Without departing from the spirit or scope of the invention in its broadest sense, it will be apparent to those skilled in the art that the present invention can be subjected to numerous modifications and / or improvements, as set forth in the above specific embodiments. Will be appreciated. For example, the embodiments disclosed above ignore the effect of the "refractive index" of waves propagating between materials. Furthermore, no impedance mismatch between the material of the member and the fluid or the effects of transient reflections or resonance accumulation in the chamber is taken into account. Furthermore, only a single general piezoelectric element is assumed. Obviously, multiple piezoelectric elements can be used in different diving equipment to provide a predetermined effect. Each of these effects may lead to a slight change in the profile depending on the material utilized. Therefore, the above embodiments are not to be considered in all respects as restrictive, but as illustrative.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of the operating principle of a preferred embodiment.

FIG. 2 is a schematic diagram of the operating principle of a preferred embodiment.

FIG. 3 is a diagram illustrating the use of a differential pressure pulse together with heating.

FIG. 4 is a diagram illustrating the use of a differential pressure pulse together with heating.

FIG. 5 illustrates the use of a differential pressure pulse with heating.

FIG. 6 is a diagram illustrating the use of a differential pressure pulse together with heating.

FIG. 7 illustrates computational hydrodynamic calculations of pressure fluctuations in a modeled inkjet chamber.

FIG. 8 illustrates computational hydrodynamic calculations of pressure fluctuations in a modeled inkjet chamber.

FIG. 9 illustrates computational hydrodynamic calculations of pressure fluctuations in a modeled inkjet chamber.

FIG. 10 illustrates computational hydrodynamic calculations of pressure fluctuations in a modeled inkjet chamber.

FIG. 11 illustrates a computer-induced hydrodynamic calculation of pressure fluctuations in a modeled inkjet chamber.

FIG. 12 is a schematic cross-sectional view of a part of a print head illustrating a concentration mechanism.

FIG. 13 is a schematic cross-sectional view of a part of a print head illustrating a concentration mechanism.

FIG. 14 is a schematic cross-sectional view of a portion of a print head illustrating a concentration mechanism.

FIG. 15 is a schematic cross-sectional view of a portion of a print head illustrating a concentration mechanism.

FIG. 16 is a side perspective view of the elements of a page width printhead.

FIG. 17 is an enlarged view of a part of FIG. 16;

FIG. 18 is a perspective view of the series of elements of FIG.

FIG. 19 is a side perspective view (partial cross section) of a part of the print head.

FIG. 20 is an enlarged view of a part of FIG. 19;

FIG. 21 is a schematic sectional view of an end of an ink discharge pit.

FIG. 22 is a schematic sectional view of an end of an ink discharge pit.

FIG. 23 is a schematic cross-sectional view of an end of an ink discharge pit.

FIG. 24 is a diagram illustrating a surface of a plastic former used for concentration of a pressure pulse according to a preferred embodiment.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Treroll, Peter John Australia, New South Wales 2008, Chippendale, Backland Street 30, Unit 301 F-term (reference) 2C057 AF51 AG44 AG68 AP34 BA10 BA14 [Continued summary] ] It contains a structure. The selection mechanism heats the vicinity of the surface layer of ink to be ejected from the ink ejection nozzle, thereby changing its surface tension around each nozzle to enable ejection. It may include a heater (16) that is widespread.

Claims (10)

[Claims] 1. A plurality of ink discharge nozzles formed on a surface of a first wafer, wherein the ink discharge nozzles collectively form an ink supply group, and each ink supply group passes through the wafer. An etched ink discharge nozzle including a group ink supply path, a cavity including an ink supply path interconnecting the group ink supply path between the vibration concentrating member and the back surface of the wafer; A pressure vibration concentrating member attached to the back surface of the wafer, a spatial motion member attached to the vibration concentrating member and adapted to impart a controlled spatial motion to the vibration concentrating member; The vibrating member provides an instantaneous large pressure fluctuation of the ink at the ink discharge nozzle. It is adapted to concentrate the pressure fluctuations in the ink supply path for the group in the vicinity of each group of click discharge nozzle, drop-on-demand ink jet printhead system. 2. Each of the ink ejection nozzles includes a selection mechanism for enabling or disabling ejection of droplets by the nozzles when the large instantaneous pressure fluctuations occur. 2. The system according to 1. 3. The system according to claim 2, wherein said selection mechanism comprises a heater for heating near a surface layer of ink to be ejected from said ink ejection nozzle. 4. The system of claim 1, wherein the vibration concentrator focuses pressure fluctuations to a focus in the ambient atmosphere slightly outside the ink discharge nozzle. 5. The method according to claim 1, wherein the vibration concentrating member focuses the pressure fluctuation on a point in the group ink supply path slightly above the group of the ink discharge nozzles. System. 6. The method of claim 1, wherein the group ink supply path is formed by anisotropic etching of the wafer and terminates in a pit at the ink discharge nozzle. System. 7. The system of claim 1, wherein the spatial motion imparts a substantially planar pressure wave to a first surface of the spatial motion member. 8. The group ink supply path is spaced apart from each other across the surface of the wafer, and the wafer is separated from the group ink supply path by the group ink supply path. A series of elongated wafer pillars between the pressure-vibration concentrating member, the pressure-vibration concentrating member including ink between the wafer pillar and an adjacent surface of the pressure-concentrating member on a top surface of the pillar; The system according to claim 1, wherein the system focuses pressure fluctuations. 9. A method of ejecting droplets on demand from a series of ink ejection nozzles, wherein each of said nozzles is in the vicinity of said nozzle and in turn causes a physical change to cause ejection of ink from said nozzle. Inducing a pressure wave fluctuation in an ink supply chamber attached to the ink discharge nozzle; concentrating the pressure wave fluctuation in the vicinity of the ink discharge nozzle; Using a mechanism to select droplets to be ejected from said ink ejection nozzles simultaneously with said pressure wave fluctuations. 10. The method of claim 1, wherein the step of focusing pressure wave fluctuations near the ink discharge nozzle further comprises simultaneously dispersing pressure wave fluctuations spaced apart from the ink discharge nozzle. The method described in.