# Patent

## Title
Methods and systems for laser processing continuously moving sheet material

## Abstract

Systems and methods for laser processing continuously moving sheet material include one or more laser processing heads configured to illuminate the moving sheet material with one or more laser beams. The sheet material may include, for example, an optical film continuously moving from a first roller to a second roller during a laser process. In one embodiment, a vacuum chuck is configured to removably affix a first portion of the moving sheet material thereto. The vacuum chuck controls a velocity of the moving sheet material as the first portion is processed by the one or more laser beams. In one embodiment, a conveyor includes a plurality of vacuum chucks configured to successively affix to different portions of the sheet material during laser processing.

## Background
RELATED APPLICATION
This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/886,881, filed Jan. 26, 2007.


TECHNICAL FIELD
This disclosure relates generally to laser processing. In particular, this disclosure relates to laser processing systems and method for processing continuously moving or unrolling sheet material.
BACKGROUND INFORMATION
Laser processing may be conducted on numerous different types of workpieces using various lasers to effect a variety of processes. Lasers may be used to form, for example, a hole and/or blind via in a single layer or multilayer workpiece. Semiconductor wafer processing may include various types of laser micromachining including, for example, scribing, dicing, drilling, removal of semiconductor links (fuses), thermal annealing, and/or trimming passive thick or thin film components.
Lasers may be used to process sheets of material, such as plastics or optical films. Large plastic or optical sheets may be cut into smaller pieces for use in flat panel displays, such as those used in, for example, cellular phones, automobile navigation systems, personal digital assistants (PDAs), laptop computers, televisions, and other electronic devices. Typically, a mechanical punching machine is used to cut the sheets of plastic or film material. The punching machines are fast, but many downtimes associated with the frequent replacement and maintenance of molds reduce the effective throughput. Further, the use of lasers to cut large sheets of material has been limited to straight cuts at high velocities.
SUMMARY OF THE DISCLOSURE
The embodiments disclosed herein provide systems and methods for laser processing a moving sheet material. In one embodiment, a system for processing a moving sheet material includes one or more laser processing heads configured to illuminate the moving sheet material with one or more laser beams, and a vacuum chuck configured to removably affix a first portion of the moving sheet material thereto. The vacuum chuck is further configured to control a velocity of the moving sheet material as the first portion is processed by the one or more laser beams.
In another embodiment, a method for processing sheet material with a laser beam includes moving the sheet material from a first roller to a second roller, and removably affixing a chuck to a first portion of the sheet material as it moves from the first roller to the second roller. The method further includes moving the chuck at a predetermined velocity, and illuminating the first portion of the sheet material with the laser beam while it is affixed to the moving chuck.
In another embodiment, a laser processing system includes means for illuminating a sheet material with a laser beam, means for holding portions of the sheet material as the portions are illuminated with the laser beam, means for moving the means for holding at a constant velocity as a first portion of the sheet material and as a second portion of the sheet material are illuminated with the laser beam, and means for feeding the sheet material through a laser processing area without stopping between the illumination of the first portion and the second portion.
Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.



BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A, 1B and 1C illustrate a conventional system for processing films.
FIGS. 2, 3, 4 and 5 are block diagrams of a system for processing sheet material according to certain embodiments.
FIGS. 6A and 6B are block diagrams of a system for processing sheet material according to another embodiment.



DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Lasers may be used to process large sheets of material, such as plastics or optical films. Sheets of plastic or optical film may be used, for example, in flat panel displays for cellular phones, automobile navigation systems, personal digital assistants (PDAs), laptop computers, televisions, and other electronic devices.
Using a laser system to cut a roll of sheet material (e.g., film) into small pieces for a particular monitor size is called conversion. In the conversion process, a roll of sheet material is generally unrolled and placed over another material for processing. The converted pieces of sheet material are then collected. When the roll of sheet material is polarizing film that includes adhesive between multiple film layers, for example, the edges of the converted pieces tend to stick to the material underneath. In such a case, it is generally difficult to pick up the converted pieces without reducing productivity.
Generally, conventional conversion systems are based on a die cutting system in which patterned blades imbedded into a flat plate are used to convert the film. In such systems, a flexible rubber-like material is used in a roll-like conveyor to collect converted pieces.
A. Beam Positioning with Three Stages
Reference is now made to the figures in which like reference numerals refer to like elements. For clarity, the first digit of a reference numeral indicates the figure number in which the corresponding element is first used. In the following description, numerous specific details are provided for a thorough understanding of the embodiments of the invention. However, those skilled in the art will recognize that the invention can be practiced without one or more of the specific details, or with other methods, components, or materials. Further, in some cases, well-known structures, materials, or operations are not shown or described in detail in order to avoid obscuring aspects of the invention. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Some materials, such as rolls of film or discrete film sheets, are generally processed by being positioned and fixed in place under a mechanical punch or conventional laser processing system. For example, FIGS. 1A, 1B and 1C illustrate a conventional system 100 for processing films 110. As shown in FIG. 1A, the film 110 is first moved (as indicated by arrow 112) on a motion stage 113 into a processing area under a conversion system 114 that includes a mechanical punch or conventional laser system with (or without) a galvo on X and Y stages.
As shown in FIG. 1B, after the film 110 is positioned in the processing area, the conversion system 114 performs the processing (as indicated by arrow 116). When the conversion system 114 includes a mechanical punch or a conventional laser system, the motion stage 113 carrying the film 110 must be stopped while the processing (e.g., dicing) takes place. When positioning cutting blades or a laser beam over the film 110 with some accuracy is needed or desired, the conversion system 114 may need to perform an alignment process before the conversion system 114 processes the film 110. As shown in FIG. 1C, after processing, the motion stage 113 moves the converted film 110 out of the processing area (as indicated by arrow 118).
Thus, the overall time used for conversion includes both the time required to move the film 110 into position before processing the film 110 and the time required for processing the film 110. Throughput is reduced drastically by the time required to move and station the film 110 at a certain position before the processing takes place and the time required to align the conversion system 114 (if necessary). Thus, the disclosure herein enables the elimination or reduction of the non-process times to improve the total throughput. Furthermore, the disclosure may reduce the mechanical and optical stress of optical films that could be induced by the ordinary process of step and repeat with dancers (weights located before and after the processing area) to hold the film flat over the process area. Further, in certain embodiments, the continuous flow of the material during laser processing induces optical anisotropy in the material, which may be advantageous. For example, in the case of polarizing film, the induced anisotropy substantially improves image quality.
FIGS. 2, 3, 4 and 5 are block diagrams of a system 200 for processing sheet material 210 according to certain embodiments. The system 200 includes a laser 212, a plurality of vacuum chucks 214 (twelve shown), and a translation stage or conveyor 216 configured to move the vacuum chucks 214 through a processing area of the laser 212. In one embodiment, the system 200 also includes X and Y stages (not shown) to move the laser beam 212 with respect to the sheet material 210. For example, the X and Y stages may include a gantry system. In addition, or in another embodiment, the system 200 may include a galvo (not shown) configured to further align a laser beam from the laser 212 with the sheet material 210.
As discussed above, the sheet material 210 may include, for example, plastic or optical film. In one embodiment, the sheet material 210 has a thickness between approximately 1 mm and approximately 2 mm. However, the embodiments disclosed herein are not limited to this range of thicknesses. Indeed, the system 200 may be configured to process materials having thicknesses substantially less than 1 mm and substantially greater than 2 mm. In certain embodiments, the system 200 processes the sheet material 210 as it is transferred from a first roll to a second roll. In other embodiments, the system 200 processes discrete pieces or sheets of the material 210.
Regardless of whether the sheet material 210 includes discrete sheets or is transferred from a first roll to a second roll, the vacuum chucks 214 are configured to securely hold the sheet material 210 while the conveyor 216 moves the vacuum chucks 214 and the sheet material 210 (as indicated by arrow 218) at a constant velocity. While the conveyor 216 and vacuum chucks 214 move the sheet material 210, the laser 212 delivers a laser beam (as indicated by arrow 220) to the sheet material 210 from the galvo block on the X and Y stages over the conveyor 216.
The laser beam positioning is coordinated through the galvo, the X and Y stages and the conveyor 216. Therefore, the overall processing time includes the beam delivery time without the additional time required for repeated alignment or the time required to repeatedly move material in and out of the processing area under the laser 212.
An artisan will understand from the disclosure herein that the galvo and/or the X and Y stages are not required in every embodiment. For example, in one embodiment, the system 200 includes the conveyor 216 for moving the sheet material 210 to be processed and the gantry of X and Y stages that move the laser beam incident to the work surface. Also, the system disclosed herein can support additional stages, such as one for Z direction to adjust the beam focus or the collimated beam size.
A compound beam positioner, according to one embodiment, provides slow and fast movements in order to process the sheet material 210 without ceasing beam movement. In one embodiment, the entire move may be composed of three or more different moves, namely slow, intermediate, and fast moves. However, the basic algorithm may remain the same as that of a conventional compound beam positioner. The gantry velocity may be maintained constant or may be monitored for adjustment of the beam positioning.
Rough alignment of the material to be processed may be done on a vacuum chuck 214 before the material is moved under the laser 212. For example, FIGS. 3 and 4 illustrate positional sensors 310 (two shown) located near a point along the conveyor 216 where the vacuum chucks 214 are aligned with the sheet material 210. In other embodiments, the sensors 310 may be installed on each vacuum chuck 214 or around the chucks 214. The sensors 310 may be, for example, a charge coupled device (CCD) or any other sensor to sense the position of the sheet material 210 with respect to the vacuum chucks 214. Such sensors 310 may be positioned in parallel in X and/or Y directions.
In some embodiments, small pieces of predetermined size are singulated out of the sheet material 210. In such embodiments, as shown in FIG. 4, singulated pieces 410 may be recovered from a vacuum chuck 214 by turning the vacuum off or by slightly applying a positive air pressure to expel the singulated pieces 410 off the chuck 214 to a nearby receiving tray 412. After expelling the singulated pieces 410, the vacuum chuck 214 may be carried by the conveyor 216 to a position where the vacuum is turned on for alignment with another portion of unprocessed sheet material 210. In another embodiment, if the process does not involve expelling the singulated pieces 410, the vacuum chucks 214 may be moved back and forth (e.g., without circulating around the conveyor 216), or may be moved in a combination of horizontal and vertical moves, to return the vacuum chucks 214 to the original alignment position where the vacuum is turned on.
To improve throughput, a dual head or multiple head system may also be considered. In such embodiments, the move of two heads in the Y direction, which is orthogonal to the flow of the material, may be in mirror image to reduce any vibration that may affect smooth beam movement with respect to the sheet material 210.
One example dual head system 500 is shown in FIG. 5. In this example embodiment, two laser paths each include a continuous wave (CW) laser 510 and an acousto-optic modulator (AOM) 512 configured as a sub-microsecond laser power controller/shutter. The AOM 512 is also configured as a pulser for the CW laser 510. In another embodiment, the AOM 512 may be configured as a pulse picker for a pulsed laser. The AOM 512 may also be configured for adjusting the pulse energy and repetition rate so that the processing can take place not only during the constant velocity periods, but also during the acceleration and deceleration periods.
Each laser path may include optics, such as a first mirror 514 for directing the laser beam from the AOM 512 through a first lens 516, an aperture 518, and a second lens 519 to a second mirror 520 configured to direct the laser beam to a beam splitter 522 or a beam dump 524, depending on a deflection angle selected by the AOM 512. In one embodiment, the beam splitter 522 directs a portion of the laser beam to a power monitor 523 configured to provide laser power control to the AOM 512. Each beam splitter 522 also directs a portion of the laser beam to a respective processing head 526 located on an X, Y stage (gantry) 528. Each processing head 526 directs its respective laser beam to the sheet material 210 aligned on an additional stage work surface 530.
B. Index Free Film Conversion System
FIGS. 6A and 6B are block diagrams of a system 600 for processing sheet material according to another embodiment. This embodiment provides a method for accurately feeding sheet material 210 from a first roll 610 to a second roll 612 as the sheet material 210 is processed by one or more laser processing heads 614 (two shown). An artisan will understand from the disclosure herein that two or more processing heads 614 may be aligned in a direction that is parallel to a flow direction 616 of the sheet material 210 (as shown in FIGS. 6A and 6B) and/or in a direction that is perpendicular to the flow direction 616 of the sheet material 210.
The system 600 provides index free film conversion by coordinating the motion of the sheet material 210 as it travels from the first roll 610 to the second roll 612 with the motions of X and Y linear stages, a vacuum chuck 618, and X and Y galvanometers. In some embodiments, the system 600 also coordinates the motion of the sheet material 210 with a Z stage.
The system 600 also seemlessly provides for recovery of the converted pieces of sheet material 210. The system 600 includes a carrier 620 configured to receive converted pieces of the sheet material 210 and to transport the converted pieces to a location where they can be picked up (e.g., by a user or robotic device) for further processing (as indicated by arrow 622 in FIG. 6A). In one embodiment, the carrier 620 includes a metallic sheet positioned between the sheet material 210 and the vacuum chuck 618. An artisan will recognize from the disclosure herein that in other embodiments the carrier 620 may include non-metallic materials, such as plastic. In one embodiment, the carrier 620 forms a conveyor belt that, when the laser beam is off or blocked (FIG. 6A), travels between the sheet material 210 and the vacuum chuck 618.
In one embodiment, the sheet material 210 continually moves from the first roll 610 to the second roll 612 during the conversion process. To process the sheet material 210, the system 600 positions the processing heads 614 and the vacuum chuck 618 at respective initial positions. As shown in FIG. 6B, the vacuum chuck 628 turns on the vacuum (as shown by arrow 624) to temporarily affix the sheet material 210 and metallic sheet of the carrier 620 in place against the vacuum chuck 618. The metallic sheet is appropriately perforated so as to allow the vacuum chuck 618 to suck the sheet material 210 against the metallic sheet of the carrier 620. The underlying stage then moves the vacuum chuck 618 so as to feed the sheet material 210 at a known velocity and known position so that an accurate motion coordination becomes possible with the X and Y linear stages and the X and Y galvanometers of the processing heads 614.
While the vacuum chuck 618 moves the sheet material 210, the processing heads 614 turn on (or unblock) their respective laser beams to convert pieces of the sheet material 210. After the conversion process is complete for one set of conversion pattern, the laser beam is turned off (or blocked). The vacuum chuck 618 then turns off the vacuum so that the sheet material 210 and metallic sheet of the carrier 620 separate from the vacuum chuck 618. In one embodiment, to achieve a smooth detachment of the sheet material 210, the vacuum chuck 618 may blow air through the holes in metallic sheet of the carrier 620. After separation, the first roller 610 and/or second roller 612 continue to feed the sheet material 210 and the converted pieces remain on the carrier 620. The carrier 620 then transports the converted pieces of the sheet material 210 to a pick up location (see arrow 622 in FIG. 6A).
After the conversion is complete for one portion of the sheet material 210 being fed from the first roller 610 to the second roller 612, the vacuum chuck 618, the X and Y stages, and the X and Y galvanometers move back to their respective initial positions for realignment with an additional portion of the sheet material 210.
When the sheet material 210 is converted, debris or adhesive used between sheet layers may adversely stick to the surface of the metallic sheet of the carrier 620. As the system 600 continues to affix different portions of the sheet material 210 and carrier 620 to the vacuum chuck 618, the debris and adhesive may be transferred between the different portions of the sheet material 210. To avoid such contamination transfer according to one embodiment, the metallic sheet of the carrier 620 is cleaned before being aligned with each portion of the sheet material 210.
In certain embodiments, the first roller 610 and/or the second roller 612 do not provide accurate velocity control of the sheet material 210. Rather, the vacuum chuck 620 with the underlying linear stage provides an accurate reference of the velocity and position during conversion. However, to avoid an adversely large difference in the velocity provided by the rollers 610, 612 and the velocity provided by the vacuum chuck 620, the system 600 may include a velocity controller and feedback sensors to control the relative velocities. Thus, each portion of the sheet material 210 may be quickly aligned with the vacuum chuck 618. The velocity control also allows the sheet material 210 to be fed from the first roller 610 to the second roller 612 at a substantially constant velocity throughout the conversion process of an entire continuous sheet or roll of material.
In some embodiments, the vacuum chuck 618 provides the only movement of the metallic sheet of the carrier 620. In other embodiments, the metallic sheet of the carrier 620 is driven by other rollers 626 (four shown) when not affixed to the vacuum chuck 618. In certain such embodiments, the system 600 includes appropriate velocity control and feedback to reduce the difference between the velocity of the metallic sheet of the carrier 620 and the velocity of the vacuum chuck 618.
It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. The scope of the present invention should, therefore, be determined only by the following claims.

## Claims

1. A system for processing a continuously moving sheet material, the system comprising:
one or more laser processing heads configured to illuminate the moving sheet material with one or more laser beams, the one or more laser processing heads configured to move the one or more laser beams through a laser processing area;
a pair of rollers for feeding the sheet material through the laser processing area at a first velocity;
a moving vacuum chuck on a conveyor configured to removably affix a first portion of the moving sheet material to the moving vacuum chuck, the moving vacuum chuck further configured to move through the laser processing area at a second velocity so as to control movement of the first portion of the moving sheet material at said second velocity as the first portion is processed by the one or more laser beams; and
one or more feedback sensors configured to sense the second velocity relative to the first velocity; and
a controller configured to, based on relative indications between the first and second velocities provided by the one or more feedback sensors, coordinate relative motions between the moving vacuum chuck, the pair of rollers, and the one or more laser processing heads to laser process the moving sheet material, wherein the moving sheet material remains in continuous motion between the pair of rollers at the first velocity; and wherein the moving vacuum chuck transports singulated pieces of the moving sheet material to a receiving tray.

2. The system of claim 1, wherein, once laser processing begins, the sheet material continuously moves from a first roller to a second roller of the pair of rollers.

3. The system of claim 2, wherein at least one of the first roller and the second roller controls the velocity of the moving sheet material when the first portion is not affixed to the vacuum chuck.

4. The system of claim 1, wherein the moving vacuum chuck is further configured to release the first portion of the moving sheet material after the first portion of the sheet material is processed by the one or more laser beams and to removably affix a second portion of the moving sheet material thereto for processing by the one or more laser beams.

5. The system of claim 1, further comprising the conveyor attached to the moving vacuum chuck, the conveyor configured to control the velocity of the moving vacuum chuck.

6. The system of claim 5, wherein the conveyor comprises one or more additional moving vacuum chucks configured to affix to one or more second portions of the moving sheet material during processing of the one or more second portions by the one or more laser beams.

7. The system of claim 5, wherein the one or more laser beams are configured to singulate pieces from the first portion and the one or more second portions, and wherein at least one of the moving vacuum chuck and the additional moving vacuum chucks are further configured to transport the singulated pieces to the receiving tray.

8. The system of claim 1, further comprising a carrier positioned between the moving sheet material and the moving vacuum chuck, the moving vacuum chuck configured to removably affix the carrier thereto with the first portion of the moving sheet material, the carrier configured to receive and transport singulated pieces of the sheet material after being processed by the one or more laser beams.

9. The system of claim 8, wherein the moving vacuum chuck is further configured to apply a positive air pressure to the singulated pieces of the sheet material so as to eject them from the carrier to the receiving tray.

10. The system of claim 8, wherein the carrier comprises a perforated metallic sheet.

11. The system of claim 10, wherein the metallic sheet is configured as a conveyor belt for transporting the singulated pieces.

12. The system of claim 1, further comprising a motion stage configured to move the one or more laser processing heads with respect to the moving sheet material.

13. The system of claim 1, further comprising one or more positional sensors configured to provide data for aligning the moving vacuum chuck with the first portion of the moving sheet material.

14. The system of claim 1, wherein the sheet material comprises optical film.