1. Technical Field
The present teachings relate to a printhead maintenance station for a piezoelectric microdeposition (PMD) apparatus.
2. Background
PMD processes are used to deposit droplets of fluid manufacturing materials on substrates without contamination of the substrates or the fluid manufacturing materials. Accordingly, the PMD processes are particularly useful in clean room environments where contamination is to be avoided such as, for example, when manufacturing polymer light-emitting diodes (PLED) display devices, printed circuit boards (PCBs), or liquid crystal displays (LCDs).
PMD methods and systems generally incorporate the use of a PMD tool, which includes a head to deposit fluid manufacturing materials on a substrate and a nozzle assembly including multiple independent nozzles. The PMD head is coupled with computer numerically controlled system for patterning, i.e., precisely depositing droplets of the fluid manufacturing material onto predetermined locations of the substrate and for individually controlling each of the nozzles. In general, the PMD head may contain multiple printhead arrays and is configured to provide a high degree of precision and accuracy when used in combination with the various techniques and methods for forming microstructures on substrates.
Due to extremely high droplet deposition, positional accuracy typically required in PMD applications, and the use of non-traditional ink jet fluids atypical of those used in graphics printers, maintenance methods previously employed in other fields of ink jet printing are often unsatisfactory for avoiding nozzle failure in PMD applications. Accordingly, there is a need for an improved device for maintaining the condition of the PMD heads.
The present teachings include the use of a blotting station with precise dynamic control capability and single printhead interaction capability, a capping and priming station that offers several modes of nozzle maintenance operation and ink mist control, and a drop analysis system that sequentially interact with a printhead array in an automatic fashion.
Another feature is the ability to configure a wiping action of the blotting station for different fluid and printhead types, as well as accommodating variables such as pressure, velocity, and vertical lift off during motion. The inclusion of a single blotting station apparatus within the blotting device to correct the failure of a single printhead is yet another aspect. A drop mist removal system integral to the capping station as part of waste removal to avoid contamination of the substrate being printed is also provided. Active Z movement of the printhead with respect to the maintenance system to optimize each of the functions used with respect to each fluid and printhead type is also considered to be unique.
Still another feature is the dynamic tracking system and the elements thereof used to maintain flatness and integrity of the blotting and wiping station, as well as the dynamic motion capabilities of the various elements of the maintenance station in relation to various elements such as a drop analysis and a drop check assembly of the PMD system.
Yet another feature of the present invention is the ability to fill localized fluid baths under each printhead with a solvent and bring the solvent to a precise distance from the nozzle plate of each printhead to cause a localized vapor-rich atmosphere to stop evaporation of the jetting fluid and density change within the PMD fluid. The use of an appropriate material for the localized fluid bath structure that a contact angle of the fluid to structure is less than 20 degrees is also possible.
To further clarify the above and to demonstrate the advantages and features of the present teachings, a more particular description will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings are not to be considered limiting of the scope of the teachings. The teachings will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
The following description is merely exemplary in nature and is in no way intended to limit the teachings, its application, or uses.
The terms “fluid manufacturing material” and “fluid material” as defined herein, are broadly construed to include any material that can assume a low viscosity form and which is suitable for being deposited, for example, from a PMD head onto a substrate for forming a microstructure. Fluid manufacturing materials may include, but are not limited to, light-emitting polymers (LEPs), which can be used to form polymer light-emitting diode display devices (PLEDs, and PolyLEDs). Fluid manufacturing materials may also include plastics, metals, waxes, solders, solder pastes, biomedical products, acids, photoresists, solvents, adhesives and epoxies. The term “fluid manufacturing material” is interchangeably referred to herein as “fluid material.”
The term “deposition” as defined herein, generally refers to the process of depositing individual droplets of fluid materials on substrates. The terms ‘let,” “discharge,” “pattern,” and “deposit” are used interchangeably herein with specific reference the deposition of the fluid material from a PMD head for example. The terms “droplet” and “drop” are also used interchangeably.
The term “substrate,” as defined herein, is broadly construed to include any material having a surface that is suitable for receiving a fluid material during a manufacturing process such as PMD. Substrates include, but are not limited to, glass plate, pipettes silicon wafers, ceramic tiles, rigid and flexible plastic and metal sheets and rolls. In certain embodiments, a deposited fluid material itself may form a substrate, in as much as the fluid material also includes surfaces suitable for receiving a fluid material during a manufacturing process, such as, for example, when forming three-dimensional microstructures.
The term “microstructures,” as defined herein, generally refers to structures formed with a high degree of precision, and that are sized to fit on a substrate. Inasmuch as the sizes of different substrates may vary, the term “microstructures” should not be construed to be limited to any particular size and can be used interchangeably with the term “structure”. Microstructures may include a single droplet of a fluid material, any combination of droplets, or any structure formed by depositing the droplet(s) on a substrate, such as a two-dimensional layer, a three-dimensional architecture, and any other desired structure.
The PMD systems referenced to herein perform processes by depositing fluid materials onto substrates according to user-defined computer-executable instructions. The term “computer-executable instructions,” which is also referred to herein as “program modules” or “modules,” generally includes routines, programs, objects, components, data structures, or the like that implement particular abstract data types or perform particular tasks such as, but not limited to, executing computer numerical controls for implementing PMD processes. Program modules may be stored on any computer-readable media, including, but not limited to RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium capable of storing instructions or data structures and capable of being accessed by a general purpose or special purpose computer.
Now referring to
PMD apparatus 10 includes a system control/power module 11 which controls operation of the PMD apparatus 10. In this regard, operating parameters such as ink patterns, discharge speed, etc. may be controlled by an operator. Further, module 11 also controls the variable ink jet array 16 and droplet inspection module of the PMD 10. Ink jet array 16 includes various printheads (not shown) that deposit the inks onto the substrates 14.
Inks that are deposited by variable ink jet array 16 are supplied to the array 16 by ink supply modules 17. As a plurality of modules 17 are provided, one skilled in the art will recognize and appreciate that various types of inks suitable for different applications may be stored simultaneously. Also included in PMD apparatus 10 is a solvent cleaning module 17. Solvent cleaning module 17 supplies solvents used to clean the printheads 34 of the variable ink jet array 16 to a maintenance station 20 according to the present invention.
The maintenance system 20 may be positioned relative to the printhead array 16 and the substrate stage 9 such that all maintenance functions can be executed (i.e., purging, soaking, priming, capping, blotting, wiping and drop inspection through the optical system) while the substrate loading, alignment, and unloading are being performed. System throughput may be enhanced as this arrangement allows identification and correction of a jetting problem in parallel with normal operations of the machine without affecting their sequence.
Now referring to
Capping station 40, which provides for capping the printhead nozzle plate 36 (
By movement of the lower maintenance system support stage 32 relative to the printhead array 16, the capping inserts 50 that can be refilled with clean-filtered solvent of the appropriate type can be positioned in a secondary taught position when purging old jetting fluid through the nozzle array so as not to contaminate the capping solvent. Movement of the printhead array 16 with the associated printheads 34 is described in more detail in co-pending U.S. Provisional Application No. 60/674,590 entitled “Printable Substrate Alignment System,” which is hereby incorporated by reference. Each of the three positions ensures that the nozzle plate 36 stays moist when not in use or idle which prevents clogging of the nozzle plate 36 and ensures better performance.
Now referring to
Although the solvent baths 50 of insert 46 may be designed to be movable through various angles, the insert 46 can also be designed such that solvent baths 50 are immovable. It should be understood that with this approach, either the head array can be pitched to the immovable, fixed positions of the solvent baths when the heads require maintenance or, in some PMD applications, a fixed print angle head array may be used. Regardless, referring to
In either design, it should be understood that solvent baths 50 are designed to be a size that allows +/−1.5 mm head clearance to minimize solvent evaporation when the head is capped. Further, the gap 51 enables use of a vacuum mechanism 23, which may evacuate vapors produced by the standing solvent pools to protect clean room integrity. A secondary and equally important function of the vacuum system 23 is to capture floating ink droplets from printheads 34 during halt and fire operations, discussed below. The solvent baths 50 also may include edges 33 which are chamfered (
The capping station 40 is also equipped with a device to adjust the height and level of the module in the PMD apparatus 10. As shown in
By raising and lowering the capping station 40 as necessary, interference with the movement of other modules can be avoided. For example, the height adjustment device 53 enables the capping station 40 to be lowered to a position such that drop analysis system 60 is enabled to be moved along the translation stage 22 to be disposed over capping station 40. That is, the capping station may be raised and lowered by the height adjustment device 53 to provide clearance for the vision system 62 of the drop analysis system. Further, such movement assists in the positioning of the capping station solvent baths 50 accurately in relation to the printheads 34. For example, the capping station 40 can be positioned so that the printheads 34 are in a vapor immersion position, solvent immersion position, or waste removal position as described above.
As stated above, the vapor immersion position of the capping station 40 positions the solvent baths 50 such that the printheads 34 are positioned directly above the solvent located in the baths 50. In such a position, the print heads are suspended over the solvent baths 50 at a distance of 0.5 mm. It should be understood, however, that any distance that satisfactorily immerses the print heads in solvent vapor is acceptable. In this regard, the distance can be determined depending on the type of ink being used. For example, a more viscous ink may require the print head to be suspended more closely to the solvent baths 50 such that the print head is subjected to a higher concentration of solvent vapor. In contrast, a less viscous ink may enable the print head to be suspended further from the solvent bath 50 as a lower concentration of solvent vapor is needed to clean the nozzles in the print head.
Regardless of the distance away from the solvent bath 50, the nozzles of the print head may be spot fired at any frequency from 1 Hz to 1000 Hz by software control that is selected and stored by the user to occur when substrate printing is not active to further eliminate drying of the ink in the printhead 34. At such a frequency, a minimal amount of ink is discharged in a manner that prevents aggolmeration of particles within the printhead 34 for some ink types and deters air bubbles from developing in the nozzle, while still allowing the solvent vapor to inhibit drying of the inks on the face of the nozzle plate 36 to a point where normal blotting and wiping cannot remove the material.
In contrast to the vapor immersion position of the capping station 40, the liquid immersion position of the capping station 40 fully immerses the nozzles of the print head into the solvent located in the solvent baths 50. By immersing the print head into the solvent, the print heads do not need to be spot fired to reduce the risk of air bubbles developing in the nozzles of the print head and deposits that may have built up on the nozzle surface from ink mist can naturally dissolve or soften from extended immersion, followed by a routine wiping action to renew the nozzle plate surface.
In the fluid purging position, the capping station 40 is lowered to using the scissor-lift mechanism 54 to a position that is slightly lower than the vapor immersion position. In combination with movement of the lower maintenance support stage 32, up to a 15 mm horizontal movement of the capping station 40 relative to the head array may be effectuated. In this manner, the nozzles may be positioned over a waste trough 31 that runs substantially parallel to the solvent baths 50 such that waste ink discharged by the nozzles will not be deposited into the solvent baths 50 that is filled with clean solvent. At this position, the nozzles may be spot-fired in the same manner as the vapor immersion position to discharge a minimal amount of ink, while still being cleaned in a vapor-rich atmosphere. In this position, however, the ink is discharged into the waste troughs 31 and insert 46 which includes slots 29. Because the capping station may be connected to a vacuum mechanism 23 that runs continuously, the waste ink may be drawn into tray 42 and through the drain 49 as shown in
Another embodiment of capping station 40 uses a four bar lift mechanism to raise and lower the station 40. This design uses a series of solvent baths 50 which are fixed, for fixed pitch print head arrays.
Now referring to
Base 70 is comprised of a base plate 90 (see
The blotting material 74 may be supplied as a roll that is held by support roller assemblies 76 that include brackets 78 and rollers 81. The blotting material 74 is held at a constant tension force by supply and take-up roller assemblies 94 and 96. Supply roller assembly 94 is attached to supporting plate 72 via bearing assemblies 98. Take-up roller 96 assembly is supported by a support bracket 100 that is attached to bracket 78 of one of the support roller assemblies 76.
The blotting material 74 is preferably held at a constant tension force, even when the material 74 is advancing during a wiping function. The required tension is a function of the particular material and size thereof and can be set and stored through the control/power module 11. The desired tension is achieved by pulling with the take-up roller assembly 96 and holding back with the supply roller assembly 94 until an error of a sufficient magnitude that is equal to the desired tension of the web is sensed by a motion controller system that includes a supply roller motor/encoder 102.
As the diameter of the two rolls changes, the magnitude of the error is adjusted on the supply roller assembly 94 to reflect that a decrease in the applied torque by the servo motor 71 on the supply roller assembly 94 side of the blotting station 30 is needed to sustain the constant tension as the roll size increases on the take-up roller 96 side of the blotting station 40. The roll size is determined by a relationship between an encoder (not shown) that is provided in the servo motor 71 on the supply roller assembly 94 side of the blotting station 30 and the encoder 102 on the fixed diameter linear feed encoder shaft 104 of the supply roller assembly 94.
Shaft 104 is preferably formed of aluminum, sandblasted, and then anodized to provided a sufficiently roughened surface that prohibits slip of the blotting material 74 against its surface, such that linear motion of the blotting material 74 always has a constant relationship to the number of encoder counts that are generated by the rotary optical encoder 102 attached to this shaft 104. If the supply roll is new and at its largest diameter, very few encoder counts will be generated by the encoder in the servo motor 71 on the supply roller assembly 94 side of the blotting station 30 relative to the linear feed encoder roller optical encoder 102. If the supply roll is almost depleted, representing a much smaller diameter, the number of encoder counts on the encoder in the motor 71 will be proportionately larger based on the ratio of diameters. As such, it should be understood that the linear feed encoder roller encoder 102 output is important to the function of the system in maintaining constant web tension leading to the correct compliance of the blotting material 74 cloth relative to the nozzle plate 36 and elimination of wrinkles in the cloth due to extreme tension.
An edge sensor 106, shown in
The design of the blotting station module 30 also allows a vacuum hood (not shown) to be implemented because it may be required to have fume evacuation from near the blotting material rolls and table. Further, the blotting station may be positioned in a secondary containment tray that protects other modules from accidental fluid spills.
As stated above, pop-up section 84 allows for the cleaning of a single print head. The pop-up section 84 may be a through-hole formed in support plate 72 that is in fluid communication with an air cylinder (not shown). Pop-up section 84 is covered by the padding and PTFE sheet that covers plate 72.
As the pop-up section 84 is in fluid communication with an air cylinder, when air is blown through pop-up section 84 the padding and PTFE sheet “pops up” to a height of 0.5 to 1.0 mm above the surrounding surface such that only a single head of interest will contact the blotting material in this area. The printhead array 16 will then move to a second taught Z position that allows precise contact of the target printhead with the popped-up section of blotting material 74. This Z position is set to accommodate the exact pop-up height mentioned above.
The printhead 34 may penetrate against the blotting assembly no more then 0.2 mm+/−0.05 mm to achieve intimate contact without causing undue wear on the nozzle plate surface 36 during wiping. The maintenance translation stage 22 in concert with the printhead array motion controller can locate any printhead 34 from a large array of heads at this singular location. Thus, while only the defective printhead is serviced, thereby reducing use of blotting material 74 and ink, no negative effects are experienced by printheads that are functioning within specified parameters. In this manner, a single print head may be cleaned independently of the other printhead ink jet array 16.
The description is merely exemplary in nature and, thus, variations are not to be regarded as a departure from the spirit and scope of the teachings.
This application claims the benefit of U.S. Provisional Application Nos. 60/674,584, 60/674,585, 60/674,588, 60/674,589, 60/674,590, 60/674,591, and 60/674,592, filed on Apr. 25, 2005. The disclosures of the above applications are incorporated herein by reference.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2006/015650 | 4/25/2006 | WO | 00 | 10/22/2007 |
Number | Date | Country | |
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60674584 | Apr 2005 | US |