Patent Publication Number: US-2017361520-A1

Title: Apparatus and method for stretching and taking-away polymer films

Description:
BACKGROUND 
     The present invention relates to systems and methods for stretching polymer films. More particularly, it relates to in-line devices provided with the stretching system for handling or taking-away film following a stretching operation. 
     There are a variety of reasons to stretch polymer films. Stretching can enhance or generate desired mechanical, optical, and other film properties. For example, polymer films can be stretched to provide a desired degree of uniaxial or near uniaxial orientation to provide useful optical properties. In general, perfect uniaxial orientation of a birefringent polymer results in a film (or layers of a film) in which the index of refraction in two of three orthogonal directions is the same (for example, the width and thickness of a film). The index of refraction in the third direction (for example, along the length (L) direction of the film) is different from the indices of refraction in the other two directions. Typically, perfect uniaxial orientation is not required and some degree of deviation from the optimal conditions can be allowed depending on a variety of factors including the end-use application of the polymer film. 
     Regardless of whether uniaxial orientation in the stretched film is achieved or desired, systems for stretching the film in at least one direction typically includes a stretching station or device, and one or more stations or devices downstream of the stretching device that handle and optionally further process the stretched film. The film stretching device can assume various forms. Some conventional film stretching devices are, or are akin to, a tenter, and generally entail gripping opposing edges of the film with tenter clips (or other gripping device). The tenter clips are connected to tenter chains that ride along diverging tracks or rails. This arrangement propels the film forward in a machine direction of film travel and stretches the film in a transverse direction. Conventional tenter-type film stretching devices may not achieve uniaxial stretch. Other film stretching devices have been developed, described for example in U.S. Pat. Nos. 6,916,440; 6,936,209; and 6,939,499 that beneficially achieve uniaxial or substantially uniaxial stretch. 
     While extensive efforts have been made to develop optimized film stretching devices, the film handling stations or devices downstream of the film stretching device have generally remained unchanged. The downstream station is oftentimes referred to as a “take-away” device or station, and transports film received from the stretching device. The take-away device includes a conveyor-type system for transporting the film, conventionally provided as one or more gripping mechanisms carried by a chain or belt. The gripping mechanisms interface with opposing surfaces of the film, normally at or near the film&#39;s edges. The gripping mechanisms can include tenter clips carried by an endless belt and arranged to grip an edge of the film. Other gripping formats include opposing conveyors arranged to interface with (e.g., grip) the opposing major surfaces of the film. The set of opposing conveyors are normally located to contact the film at or near an edge of the film, and can include a series of discrete pads carried by an endless chain (e.g., each pad is attached to an individual link of the chain). The pads each provide a contact face formed of a material selected to minimize damage to the film and enhance gripping of the film. With movement of the chain, then, the pads of the opposing conveyors are sequentially brought into contact with, and thus transport, the film. Due to the viscoelastic property of many films subject to stretching, it is not necessary to have a continuously gripped interface with the film along the take-away device, such that the intermittent interface provided by the discrete pad tracks is highly viable. While the pliant or soft contact face of each pad may not impart overt defects into the film, for many end-use applications, an even minor alteration of the film is unacceptable and oftentimes the region of the film at which interface with the pads occurs must be discarded. In recognition of this process restriction, manufacturers endeavor to minimize the extent to which any defect imparted by the pads propagates across a width of the film by, for example, selecting a soft or pliant material. When handling highly thin films (e.g., on the order of 17 microns or less), however, the likelihood of imparting unacceptably large or problematic imperfections increases substantially regardless of the material utilized for the pad contact face, especially at locations between neighboring pads. 
     In light of the above, a need exists for film stretching apparatuses having a take-away device configured to interface or grip film in a manner that induces minimal defects. 
     SUMMARY 
     Some aspects of the present invention are directed toward an apparatus for processing film. The apparatus includes a stretching device and a take-away device. The stretching device is adapted to stretch a received film. The take-away device receives the film after the stretching device. The take-away device establishes an entrance side, an exit side, and a conveying region interfacing with and transporting the film in a direction of transport from the entrance side to the exit side. The take-away device includes a track comprising opposing, first and second conveyor assemblies arranged to contact opposing surfaces of the film, respectively, along the conveying region. The first conveyor assembly includes a continuous belt driven along a path of travel, and a plurality of discrete pads carried by the belt. Each of the pads forms a contact face opposite the belt for contacting the film along the conveying region. The contact face extends between opposing, leading and trailing edges. The leading edge is arranged downstream of the trailing edge relative to the path of travel. The plurality of pads includes a first pad immediately adjacent a second pad. The first and second pads are configured and arranged such that the trailing edge of the first pad overlaps the leading edge of the second pad as the first and second pads are traversed along the conveying region. In some embodiments, the overlap is characterized by a line perpendicular to the direction of transport passing through the first and second pads. In other embodiments, a shape of the contact face of the first and second pads defines a major central axis that is non-perpendicular and non-parallel with the direction of transport. In other embodiments, the continuous belt is a chain comprising a plurality of interconnected chain links, and respective ones of the pads are attached to individual ones of the chain links. 
     Other aspects of the present invention are directed toward a method of processing film. The method includes conveying and stretching film in a stretching device. The film is transported in a direction of transport downstream of the stretching device with a take-away device. The take-away device includes a track comprising opposing, first and second conveyor assemblies. The first conveyor assembly includes a plurality of discrete pads carried by a continuous belt. The plurality of pads includes first and second pads immediately adjacent one another and each defining a contact face having a leading edge and a trailing edge. In this regard, the step of transporting the film includes the first and second conveyor assemblies engaging opposing surfaces, respectively of the film, with the first and second pads being brought into sequential contact with the film. With this sequential contact, the film is periodically in simultaneous contact with both of the first and second pads along a grip line that is perpendicular to the direction of transport. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a film processing system in accordance with principles of the present invention; 
         FIG. 2  is a schematic illustration of portions of one embodiment of a film processing system in accordance with principles of the present invention; 
         FIG. 3  is a simplified side view of a track useful with a take-away device of the systems of  FIGS. 1 and 2 ; 
         FIG. 4A  is a top plan view of a pad in accordance with principles of the present invention and useful with the track of  FIG. 3 ; 
         FIG. 4B  is the top plan view of  FIG. 4A  with additional element numbers; 
         FIG. 4C  is a side view of the pad of  FIG. 4A ; 
         FIG. 4D  is a rear end view of the pad of  FIG. 4A ; 
         FIG. 4E  is a bottom plan view of the pad of  FIG. 4A ; 
         FIG. 5  is a perspective view of a chain link useful with a continuous belt component of the track of  FIG. 3 , along with mounting components useful for mounting the pad of  FIG. 4A ; 
         FIG. 6  is a top plan view of two of the pads of  FIG. 4A  in a co-planar arrangement and having an overlapping relationship in accordance with principles of the present invention; 
         FIG. 7A  is a simplified side view of a portion of the track of  FIG. 3  and illustrating a relationship between two immediately adjacent pads at a first location along a path of travel; 
         FIG. 7B  is a simplified side view of the portion of  FIG. 7A  and illustrating a relationship between the two adjacent pads at a second location along the path of travel; 
         FIG. 7C  is a simplified top plan view of the arrangement of  FIG. 7B ; 
         FIG. 8  is a simplified top plan view of two immediately adjacent pads of a conventional take-away device and in a co-planar arrangement; 
         FIGS. 9A-9D  illustrate progressive gripped interface with a film with the track of  FIG. 3  employing two of the pads of  FIG. 4A ; and 
         FIG. 10  is a simplified side view of a portion of a continuous belt and the pad of  FIG. 4A . 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     One embodiment of an apparatus or system  20  for processing film in accordance with principles of the present invention is shown in block form in  FIG. 1 . The apparatus  20  includes a stretching device or station  22  and a take-away device or station  24 . In general terms, the stretching device  22  operates to transport and stretch a continuous length of film; the take-away device  24  is located downstream of the stretching device  22  and operates to transport and remove the stretched film from the stretching device  22 . As made clear below, aspects of the present invention relate to handling features provided with the take-away device  24 . Other components of the apparatus  20 , including other components of the take-away device  24  apart from the handling features described below, can assume a wide variety of forms. Further, the apparatus  20  can include one more additional, optional devices or stations, such as a film source device or station  26 , a pre-conditioning device or station  28  and/or a removal device or station  30 . One or more of the film processing attributes embodied by the optional source device  26  and/or the optional pre-conditioning device  28  as described below can be incorporated into the stretching device  22 ; similarly, one or more of the film processing attributes embodied by an optional post-conditioning device  32  as described below can be incorporated into the take-away device  24 . Regardless, aspects of the present invention are applicable generally to a number of different films, materials, and processes. 
     By way of reference,  FIG. 2  illustrates one non-limiting example of the processing apparatus  20  in greater detail, processing a film  50 , and provides context for the handling features of the take-away device  24  of the present invention. The film  50  is initially provided to the apparatus  20  at the optional source device  26  in a manner known in the art (e.g., produced or provided in a roll, a film extruder, etc.). The film  50  may then be processed by the optional pre-conditioning device  28  (that may alternatively be considered part of the stretching device  22 ), such as via an oven  52  or other device. The pre-conditioning device or step  28  may include a preheating zone (see region  54  of the film  50 ) and a heat soak zone (see region  56 ). 
     The film  50  is then stretched at the stretching device  22 . The stretching device  22  includes tracks or other mechanisms for transporting edges of the film  50  along a path  58 . For example, the edges of the film  50  may be grasped by mechanical clips or other gripping means that are moved by rollers  60  in the direction of the arrows. In some embodiments, the path  58  is parabolic or substantially parabolic. Alternatively, the stretching device  22  can assume other forms and/or effectuate other film stretching techniques that may or may not incorporate a parabolic or substantially parabolic path. Regardless, a machine direction MD is established in the film  50 . A transverse direction TD orthogonal to the machine direction MD an in a plane of the film  50  can also be designated, with the film  50  optionally being stretched in the transverse direction TD. 
     The take-away device  24  receives the film  50  downstream of the stretching device  22  as shown. In general terms, the take-away device  24  includes or establishes two or more tracks  70 ,  72 , independent or apart from the transporting mechanisms of the stretching device  22 , that operate to grip and traverse the film  50  in a direction of transport X (represented by arrows in  FIG. 2 ) as described below. The direction of transport X is generally in the downstream direction relative to the stretching device  22  and can be in-line with the machine direction MD. The tracks  70 ,  72  operate to transport the film  50  from an upstream or entrance side  74  of the take-away device  24  to a downstream or exit side  76 . The take-away device  24  can optionally subject the film  50  to further processing, such as by incorporating the post-conditioning device  32 . In other embodiments, the take-away device  24  (and in particular the handling features provided by the tracks  70 ,  72  as described below) can be downstream of the post-conditioning device  32 . Alternatively, the post-conditioning device  32  can be omitted. Where provided, the post-conditioning device  32  can include a first region  80  in which the film  50  may be set, and a second region  82  in which the film  50  may be quenched. A cut or splice may be made at  84 , and flash or unusable portion  86  may be discarded. In some embodiments, quenching is performed outside of the stretching device  22 . Typically, the film  50  is set when at least one component of the film  50  (e.g., one layer type in a multilayer film) reaches a temperature below the glass transition. The film  50  is quenched when all components reach a temperature level below their glass transition. Release of the selvages  86  from a continuous gripping mechanism can be done continuously; however, release from discrete gripping mechanisms, such as tenter clips, should be done so that all the material under any given clip is released at once. 
     The optional removal device  30  receives the film  50  downstream of the take-away device  24 , and generally prepares the film  50  for later use. For example, the film  50  is typically wound on rolls for later use. Alternatively, direct converting may take place after take-away. In some embodiments, features of the removal device  30  can be considered part of the take-away device  24 . Optionally a roller  90  may be used to advance the film  50 , but this may be eliminated. Preferably, the roller  90  is not used as it would contact the stretched film  50  with the attendant potential damage to the stretched film  50 . Another cut  92  may be made and unused portion  94  may be discarded. 
     With the above background in mind, one of the tracks  70  provided with the take-away station  24  is shown in  FIG. 3 , along with the film  50  (a thickness of which is exaggerated in the view for ease of understanding). The track  70  includes opposing, first and second conveyor assemblies  100 ,  102 . In general terms, the first conveyor assembly  100  includes a continuous belt  110  and a plurality of pads  112 . The plurality of pads  112  are carried by the belt  110 , and the belt  110  is driven to traverse the pads  112  along a path of travel T 1  as defined, for example, by opposing guides (e.g., pulleys, sprockets, gears, etc.)  114 ,  116 . The second conveyor assembly  102  also includes a continuous belt  120  and a plurality of pads  122 . The pads  122  are carried by the belt  120 , and the belt  120  is driven to traverse the pads  122  along a path of travel T 2  as defined, for example, by opposing guides (e.g., pulleys, sprockets, gears, etc.)  124 ,  126 . The conveyor assemblies  100 ,  102  may or may not be identical. Regardless, the conveyor assemblies  100 ,  102  are arranged to interface with (e.g., grip) opposing major surfaces  130 ,  132  of the film  50  at a conveying region  140  (referenced generally). In particular, as the belt  110  of the first conveyor assembly  100  is driven along the path of travel T 1 , successive ones of the corresponding pads  112  contact the first major surface  130  along the conveying region  140 ; similarly, as the belt  120  of the second conveyor assembly  102  is driven along the path of travel T 2 , successive ones of the corresponding pads  122  contact the second major surface  132  along the conveying region  150 . When operated in tandem, then, the conveyor assemblies  100 ,  102  transport the film  50  in the direction of transport D from the entrance side  74  to the exit side  76  of the take-away device  24  ( FIG. 2 ). 
     The conveyor assemblies  100 ,  102  may or may not be identical. Further, the pads  112 ,  122  provided with the corresponding conveyor assembly  100 ,  102  may or may not be identical. In some embodiments, however, at least two of the pads  112  of the first conveyor assembly  100  or at least two of the pads  122  of the second conveyor assembly  102  are configured to establish, when arranged immediately adjacent one another, an overlapping relationship along at least a portion of the conveying region  140 . For example, one embodiment of a pad (or “angled pad”)  180  in accordance with principles of the present invention and useful with one or both of the conveyor assemblies  100 ,  102  is shown in  FIGS. 4A-4E . As a point of reference, the illustration of  FIG. 4A  is identical to that of  FIG. 4B  except that various element numbering is omitted from the view of  FIG. 4A  for ease of understanding. The pad  180  includes a base  190  and a contact member  192 . The base  190  is configured to facilitate mounting to the corresponding belt  112 ,  122  ( FIG. 6 ) and to support the contact member  192 . The contact member  192  establishes a contact face  194  configured to interface with, contact, or grip a film. 
     In some embodiments, the base  190  and the contact member  192  are discretely formed of differing materials and subsequently assembled. For example, the base  190  can be a relatively hard material, such as a metal or metal alloy (e.g., aluminum), whereas the contact member  192  is a relatively deformable or resilient material (e.g., silicone rubber) well-suited for non-damaging contact with a thin film. Other materials are also envisioned, and in yet other embodiments, the pad  180  is a homogenous, integral body formed of a single material or composition (e.g., the pad  180  is an integral block of metal, polymer, etc.). Regardless, the pad  180  establishes the contact face  194  to have geometry features conducive to the overlapping relationships mentioned above. 
     For example, the contact face  194  forms or defines a first or leading edge  200  and an opposing second or trailing edge  202 . As a point of reference, the terms “leading” and “trailing” are in reference to a spatial orientation of the contact face  194  as the pad  180  is traversed along the conveying region  140  ( FIG. 3 ) in the direction of transport X (identified in  FIGS. 4B and 4C ) relative to the film  50  ( FIG. 3 ). More particularly, as the contact face  194  enters the conveying region  140 , the contact face  194  initially contacts or grips the film  50  at the leading edge  200  as described in greater detail below. The leading and trailing edges  200 ,  202  each extend between opposing, first and second side edges  204 ,  206 . At least a portion of the leading edge  200  in extension between the first and second side edges  204 ,  206  defines a line or plane that is non-perpendicular to and non-parallel with the direction of transport X. At least a portion of the trailing edge  202  in extension between the first and second side edges  204 ,  206  defines a line or plane that is non-perpendicular to and non-parallel with the direction of transport X. With these optional embodiments, while the shape or arrangement of the leading edge  200  relative to the first and second side edges  204 ,  206  can correlate with that of the trailing edge  202 , the leading and trailing edges  200 ,  202  are reverse mirror images of one another (e.g., a shape of the contact face  194  in the top plan view of  FIGS. 4A and 4B  is non-symmetrical). 
     In some embodiments, extension of the leading edge  200  between the first and second side edges  204 ,  206  includes or defines a first segment  210  and a second segment  212 . The first segment  210  intersects with and extends from the first side edge  204 . The second segment  212  intersects with and extends from the second side edge  206 . In some embodiments, the first and second segments  210 ,  212  are linear in extension (at least in the top plan view of  FIGS. 4A and 4B ), and intersect at a transition point  214 . At least the second segment  212  is arranged to define an angular relationship (e.g., non-perpendicular and non-parallel) with the direction of transport X. For example, a plane or line established by extension of the first segment  210  forms an angle A with a line L 1  parallel to the direction of transport X and passing through the point of intersection of the leading edge  200  and the first side edge  204 . The angle A approximates a right angle in some embodiments (e.g., 89° to 91°). Conversely, a plane or line established by extension of the second segment  212  forms an angle B with a line L 2  parallel to the direction of transport X and passing through the point of intersection of the leading edge  200  and the second side edge  206 . The angle B is acute in some embodiments, for example on the order of 70° to 89°. In some embodiments, majority of a length of the leading edge  200  is defined by the second segment  212  (e.g., a linear length of the second segment  212  (e.g., linear distance between the second side edge  206  and the transition point  214 ) is greater than a linear length of the first segment  210 ). While the leading edge  200  can include or define one or more additional linear segments between the first and second segments  210 ,  212 , with embodiments in which the first and second segments  210 ,  212  intersect at the transition point  214 , an angle C is formed by the first and second segments  210 ,  212 , and can be less than 180° (e.g., on the order of 160°) to 179°. Relative to the direction of transport X, then, the first segment  210  is “ahead” or in front of the second segment  212 . 
     Extension of the trailing edge  202  between the first and second side edges  204 ,  206  can correspond with that of the leading edge  200 , but in a reverse manner. For example, extension of the trailing edge  202  can include first and second segments  220 ,  222 . The first segment  220  intersects and extends from the second side edge  206 . The second segment  222  intersects with and extends from the first side edge  204 . In some embodiments, the first and second segments  220 ,  222  are linear in extension (at least in the top plan view of  FIGS. 4A and 4B ), and intersect at a transition point  224 . At least the second segment  222  is arranged to define an angular relationship with the direction of transport X. For example, the first segment  220  forms an angle D with the line L 2  (that otherwise passes through the point of intersection of the trailing edge  202  and the second side edge  206 ). The angle D can approximate a right angle, and can be identical to the angle A formed by the first segment  210  of the leading edge  200  relative to the first side edge  204 . The second segment  222  forms an angle E with the line L 1  (that otherwise passes through the point of intersection of the trailing edge  202  and the first side edge  204 ). The angle E is acute, and can be identical to the angle B formed by the second segment  212  of the leading edge  200  relative to the second side edge  206 . An angle F can be formed by the first and second segment  220 ,  222  that can be identical to the angle C of the leading edge  200 . Relative to the direction of transport X, then, the first segment  220  is “behind” the second segment  222 . A linear length of the first segments  210 ,  220  can be substantially identical (e.g., within 5% of a truly identical relationship); similarly, a linear length of the second segments  212 ,  222  can be substantially identical (e.g., within 5% of a truly identical relationship). In some embodiments, the second segments  212 ,  222  are substantially parallel (e.g., within 2° of a truly parallel relationship) and combine to define a major axis G of a shape of the contact face  194 . The major axis G is arranged at a non-parallel and non-perpendicular angle relative to the direction of transport X. 
     A shape or geometry of the leading and trailing edges  200 ,  202  can alternatively be described with reference to the first and second side edges  204 ,  206 . For example, in some embodiments, the first and second side edges  204 ,  206  are substantially linear (e.g., within 2° of a truly linear arrangement) in extension between the leading and trailing edges  200 ,  202 , and can be substantially parallel (e.g., within 2° of truly parallel relationship) with the direction of transport X. A first corner  230  defining a first angle H is formed at an intersection of the leading edge  200  and the first side edge  204 , a second corner  232  defining a second angle I is formed at an intersection of the leading edge  200  and the second side edge  206 , a third corner  234  defining a third angle J is formed at an intersection of the trailing edge  202  and the second side edge  206 , and a fourth corner  236  is defining a fourth angle K is formed at an intersection of the trailing edge  202  and the first side edge  204 . With these designations in mind, with embodiments in which the first and second side edges  204 ,  206  are substantially linear and substantially parallel (e.g., within 2° of a truly parallel relationship), the first and third angles H, J can be substantially identical (e.g., within 2° of a truly identical relationship) and can approximate a right angle (e.g., 89° to 91°). Further, the second and fourth angles I, K can be substantially identical (e.g., within 2° of a truly identical relationship) and are obtuse angles, for example on the order of 91° to 110°. 
     While the leading edge  200  has been described as including or defining the discernable first and second segments  210 ,  212  (and the trailing edge  202  as including or defining the discernable first and second segments  220 ,  222 ), in other embodiments, a more singular geometry or angle of extension can be provided (e.g., an entirety of the leading edge  200  and an entirety of the trailing edge  202  forms a non-perpendicular and non-parallel angle relative to the direction of transport X). Alternatively, other angular geometries can be incorporated into the leading and trailing edges  200 ,  202 . In more general terms, geometries of the contact face  194  are such that at least a section or segment of the leading edge  200  is arranged at a non-parallel and non-perpendicular angle relative to the direction of transport X, as is at least a section or segment of the trailing edge  202 . 
     As best reflected by the side view of  FIG. 4C , the pad  180  can form the leading edge  200  along at least the first segment  210  as a curved corner. For example, the contact face  194  can be viewed as defining a major plane P 1 . The leading edge  200  can be defined as an extension between the major plane P 1  and a major plane P 2  established by a leading face  240  of the pad  180 . With these conventions in mind,  FIG. 4C  reflects a curvature along the leading edge  200  (e.g., in a cross-sectional plane parallel to the direction of travel X, the leading edge  200  at the first segment  210  (best seen in  FIGS. 4A and 4B ) is or forms a curved corner). In contrast, a right angle corner can be defined by the trailing edge  202  between the contact face major plane P 1  and a major plane P 3  established by a trailing face  242  of the pad  180 . The optional curved shape or curved corner format of the leading edge  200  minimizes potential damage to a film (not shown) as the leading edge  200  is initially brought into contact with the film. Other constructions of the leading edge  200  that may or may not include a curved format are also acceptable. 
     A perimeter shape of the base  190  mimics a shape or footprint of the contact face  194  as described above in some embodiments. The base  190  forms or defines an engagement face  250  opposite the contact face  194  that is generally configured for abutting interface with a corresponding surface or component of the corresponding belt  112 ,  122  ( FIG. 3 ). The engagement face  250  optionally tapers in extension toward the trailing face  242 , forming an undercut region  252 . As described in greater detail below, the undercut region  252  promotes articulation of the corresponding conveyor assembly  100 ,  102  upon final assembly and during use. Alternatively, the undercut region  252  can be omitted. 
     The base  190  further incorporates features that promote attachment to the corresponding belt  112 ,  122  ( FIG. 3 ). In this regard, in some embodiments the pad  180  is adapted for use with a chain-type belt (e.g., a block chain or a roller chain), with the pad  180  being mounted to, and carried by, a single link of the chain. Mounting of the pad  180  to the chain link can assume a wide variety of forms, with the pad  180  and the chain link incorporating complimentary mounting features. For example, one non-limiting example of a chain link  254  useful with the take-away devices of the present invention and to which the pad  180  ( FIGS. 4A-4E ) can be formatted for mounting is shown in  FIG. 5 , along with various mounting members described below. With cross-reference between  FIGS. 4A-5 , the base  190  can define or contain a central bore  260  corresponding with a central bore  262  in the chain link  254 . As shown, a fastener  264  (e.g., a bolt) attaches the pad  180  to the chain link  254  via the central bores  260 ,  262 . In some embodiments, the central bore  260  can be open to the contact face  194 , and can include a counterbore sized to receive a head  266  of the fastener  264  such that up final assembly, the fastener  264  is flush with, or is below, the contact face  194 . Further, the central bore  260  can be longitudinally off-set between the leading and trailing edges  200 ,  202 . Guide holes  270 ,  272  are also defined in the base  190 , corresponding with guide holes  274 ,  276  in the chain link  254 . The guide hole pairs  270 ,  274  and  272 ,  276  are each sized to receive a corresponding location pin  278 ,  280 ; upon final assembly, the location pins  278 ,  280  serve to limit pivoting movement of the pad  180  relative to the chain link  254 . It will be understood that the mounting constructions reflected by  FIGS. 4A-5  are but one acceptable example, and the chain link  254  can assume a wide variety of other forms (with the pad  180  incorporating alternative mounting features commensurate with a design of the chain link or other continuous belt component). As a point of reference, however, the exemplary chain link  254  further includes or forms complimentary leading and trailing link regions  290 ,  292  each configured for linked connection to a separate, identically formed chain link (e.g., the leading and trailing link regions  290 ,  292  each form a transverse passage sized to receive a linking pin (not shown); the leading link region  290  of a first chain link  254  is pivotally connected to the trailing link region  292  of a second chain link  254  by a linking pin passing through the corresponding transverse passages). Further, a guide assembly  294  (referenced generally) can be connected to the chain link  254  for purposes of effectuating control over a spatial location of the chain link  254  in some embodiments. 
     Returning to  FIG. 3 , the plurality of pads  112  of the first conveyor assembly  100  is identified as having two the above-described angled pads  180   a ,  180   b . It will be recalled that in some embodiments, all the pads  112  can have an identical construction; in other embodiments, only some of the plurality of pads  112  are an angled pad, while others have a more conventional design. Regardless of the how the angled pads  180   a ,  180   b  are mounted to the corresponding individual chain link  254   a ,  254   b  (not specifically shown in the simplified illustration of  FIG. 3 , but referenced generally) or other endless belt component, upon final assembly the first and second angled pads  180   a ,  180   b  are immediately adjacent one another. Relative to the path of travel T 1  (and the direction of transport X), the first pad  180   a  is downstream or “ahead” of the second pad  180   b . As the belt  110  is driven along the path of travel T 1 , an overlap between the first and second pads  180   a ,  180   b  is established along at least a portion of the conveying region  140 . For example,  FIG. 6  represents an arrangement of the first and second pads  180   a ,  180   b  as they are driven in the direction of transport X along the conveying region  140  (referenced generally). As a point of reference, the contact faces  194   a ,  194   b  are substantially co-planar (e.g., within 5° of a truly co-planar relationship) when traversing at least a majority of the conveying region  140 , with the overlapping arrangement of the immediately adjacent pads  180   a ,  180   b  being identifiable in the substantially co-planar state. The trailing edge  202   a  of the first (or “leading”) pad  180   a  is immediately adjacent the leading edge  200   b  of the second (or “trailing”) pad  180   b . In some embodiments, the pads  180   a ,  180   b  are constructed and arranged such that the pads  180   a ,  180   b  do not physically contact one another (e.g., a gap  300  is generated between the first pad trailing edge  202   a  and the second pad leading edge  200   b ). However, a region of overlap  302  is created whereby at least one theoretical line  304  perpendicular to the direction of transport X intersects both of the pads  180   a ,  180   b.    
     The region of overlap  302  can also be established when the contact faces  194   a ,  194   b  are not substantially co-planar. As a point of reference, and as reflected by the partial illustration of the conveyor assembly  100  in  FIG. 7A  (in which only the first and second angled pads  180   a ,  180   b  are shown as being carried by the belt  110 ), the path of travel T 1  includes the conveying region  140  as described above, as well as a wrap region  306  immediately upstream of the conveying region  140  (relative to a direction of the path of travel T 1 ). As described above, when the pads  180   a ,  180   b  simultaneously traverse the conveying region  140 , the corresponding contact faces  194   a ,  194   b  will be substantially co-planar in some embodiments. As the pads  180   a ,  180   b  simultaneously traverse the wrap region  306 , however, the contact faces  194   a ,  194   b  are not substantially co-planar as shown. The gap  300  between the contact faces  194   a ,  194   b  along the wrap region  306  is more pronounced (as compared to a size of the gap  300  along the conveying region  140  in which the contact faces  194   a ,  194   b  are substantially co-planar), and a region of overlap between the pads  180   a ,  180   b  may not exist. As the pads  180   a ,  180   b  are driven along the path of travel T 1  from the wrap region  306  to the conveying region  140 , a relationship between the contact faces  194   a ,  194   b  begins to approach the substantially co-planar spatial arrangement as reflected by  FIG. 7B . The contact faces  194   a ,  194   b  at the stage of  FIG. 7B  are not substantially co-planar, but the region of overlap  302  (referenced generally) exists. More particularly,  FIG. 7C  represents a top view of the arrangement of  FIG. 7B  and the region of overlap  302  is again identified; at least one theoretical line  308  perpendicular to the direction of transport X intersects both of the pads  180   a ,  180   b . Stated otherwise, relative to direction of transport X, at least a portion of the first pad trailing edge  202   a  is “behind” (or upstream of) at least a portion of the second pad leading edge  200   b  as the second pad  180   b  “enters” the conveying region  140 . 
     By way of comparison,  FIG. 8  illustrates a more conventional construction and arrangement of immediately adjacent first and second pads  310   a ,  310   b  of a take-away device of a film stretching apparatus as the pads  310   a ,  310   b  are simultaneously driven through a conveying region. The pads  310   a ,  310   b  both provide a film contact face  312   a ,  312   b  defining a rectangular perimeter shape, with a gap  314  being defined between a trailing edge  316   a  of the first pad  310   a  and a leading edge  318   b  of the second pad  310   b  (e.g., the gap  314  exists when the contact faces  312   a ,  312   b  are substantially co-planar such as when traversing the conveying region of the take-away device). With this conventional construction, no overlap is generated between the first and second pads  310   a ,  310   b  in that no theoretical line perpendicular to the direction of transport X can be drawn that intersects both of the pads  310   a ,  310   b  even when the contact faces  312   a ,  312   b  are substantially co-planar. The absence of overlap (and the complete spacing between the pads  310   a ,  310   b ) is even more pronounced when the contact faces  312   a ,  312   b  are not substantially co-planar, such as a point in time when the second pad  310   b  is transitioning from the wrap region to the conveying region (as described above with respect to  FIGS. 7B and 7C ). 
     The overlapping pad constructions of the present invention promote a more continuous gripped interface with the film being conveyed. For example, the simplified, partial illustration of  FIG. 9A  represents a first point in time of operation of the take-away device  24  in transporting the film  50 , including an operational state of the first conveyor device  100  in which the first pad  180   a  is in partial contact with the film  50  at the conveying region  140  and the second pad  180   b  is “upstream” of the conveying region  140  and not in contact with the film  50 . The first pad  180   a  is spatially arranged such that the leading edge  200   a  bears against the film  50 , with the optionally curved corner of the leading edge  200   a  present a non-damaging or gentle initial gripping interface.  FIG. 9B  is a simplified top view representation of  FIG. 9A , with an area of contact  320  between the film  50  and the conveyor assembly  100  (at the first pad  180   a ) shown by cross-hatching. At the point in time of  FIGS. 9A and 9B , the area of contact  320  includes a portion of the contact face  194   a  of the first pad  180   a  and initiates at a grip line  322  (e.g., the isolating takeaway point of first effective gripper contact). In some embodiments, the grip line  322  is substantially perpendicular (e.g., within 5° of a truly perpendicular relationship) to the direction of transport X. The film  50  is not in contact with the contact face  194   b  of the second pad  180   b.    
       FIG. 9C  is a simplified top view representation of an incrementally-later point in time in which the pads  180   a ,  180   b  have further progressed along the path of travel T 1  ( FIG. 3 ) and in the direction of transport X. While the film  50  is still not yet in contact with the second pad  180   b , the area of contact  320  at the contact face  194   a  of the first pad  180   a  has progressed in a direction of the trailing edge  202   a  (i.e., as compared to the arrangement of  FIG. 9B , the grip line  322  is closer to the trailing edge  202   a ). 
     With further operation of the first conveyor assembly  100  ( FIG. 3 ), contact between the film  50  and the second pad  180   b  is initiated. For example,  FIG. 9D  is a simplified top view representation of an incrementally-later point in time in which the pads  180   a ,  180   b  have further progressed along the path of travel T 1  ( FIG. 3 ) and in the direction of transport X as compared to  FIG. 9C . As shown, the area of contact  320  now includes a portion of the contact face  194   b  of the second pad  180   b . The grip line  322  extends along the contact face  194   a ,  194   b  of both the first and second pads  180   a ,  180   b . That is to say, due to the angled shape of the first and second pads  180   a ,  180   b  relative to the direction of transport X (and thus relative to the grip line  322 ), the grip line  322  will be established along a portion of the second pad contact face  194   b  before “leaving” the first pad contact face  194   a  (i.e., the grip line  322  will not progress entirely upstream of the first pad trailing edge  202   a  before interfacing with or “crossing” the second pad leading edge  200   b ). Thus, a continuous interface with the grip line  322  is established from the first pad  180   a  to the second pad  180   b  as the first conveyor assembly  100  transports the film  50  along the direction of transport X. Alternatively stated, while the grip line  322  may cross over the gap  300 , at least a portion of the grip line  322  is at all times supported by one or both of the contact faces  194   a ,  194   b  as the grip line  322  progresses from the first pad  180   a  to the second pad  180   b . It has surprisingly been found that the overlapping pad constructions of the present invention minimize formation and/or propagation of imperfections in a film progressively gripped by the pads, for example highly thin films having a thickness on the order of 17 microns in some embodiments. 
     Returning to  FIG. 6 , in some embodiments, the pads  180   a ,  180   b  are shaped and arranged such that a width of the gap  300  is non-uniform (including when the corresponding contact faces  194   a ,  194   b  are substantially co-planar as shown). For example, a linear width of the gap  300  is increased along the first segment  220   a  of the first pad trailing edge  202   a , and along the first segment  210   b  of the second pad leading edge  200   b . This optional construction promotes clearance between the pads  180   a ,  180   b  as the pads traverse regions of the path of travel T 1  ( FIG. 3 ) that might otherwise temporarily pivot the pads  180   a ,  180   b  relative to one another. In related embodiments and with additional reference to  FIG. 10 , the optional undercut region  252  facilitates inward articulation or flexing of the belt  110 . For example, with embodiments in which the endless belt  110  is a chain and the pad  180  is mounted to a first chain link  254   a , the chain  110  can be articulated or flexed such that the first chain link  254   a  pivots toward a second, immediately upstream chain link  254   b  (and/or vice-versa). With this motion, the trailing face  242  of the pad  180  is spatially translated toward the second chain link  254   b , including a portion of the second chain link  254   b  now in contact with the engagement face  250  at the undercut region  252 . Where provided, the tapering shape of the engagement face  250  along the undercut region  252  permits a more overt articulation of the two chain links  254   a ,  254   b  relative to one another (as compared to a construction in which the undercut region  252  were omitted). 
     Returning to  FIG. 3 , in some embodiments, all of the plurality of pads  112  provided with the first conveyor assembly  100  can have the construction described above with respect to the angled pad  180  ( FIGS. 4A-4E ). In other embodiments, less than all, but at least some, of the plurality of pads  112  of the first conveyor assembly  100  have the construction described above with respect to the angled pad  180 . For example, some of the plurality of pads  112  can have a differing or more conventional shape and configuration. In related embodiments, some of the plurality of pads  112  can have a contact face that differs from the contact face  194  ( FIGS. 4A-4E ) described above in terms of one or more of size, shape, and material (e.g., not all of the plurality of pads  112  need include a flexible contact member). In some embodiments, for example, the first conveyor assembly  100  is part of an existing take-away device and includes conventional pads; two or more (but not necessarily all) of the conventional pads are replaced or retro-fitted with the angled pads  180  of the present invention. In some embodiments all of the plurality of pads  122  provided with the second conveyor assembly  102  can have the construction described above with respect to the angled pad  180 . In other embodiments, less than all, but at least some of the plurality of pads  122  of the second conveyor assembly  102  have the construction described above with respect to the angled pad  180 . In yet other embodiments, none of the plurality of pads  122  of the second conveyor assembly  102  has the construction described above with respect to the angled pad  180 . For example, the second conveyor assembly  102  can have a conventional format in which no overlapping region is established between any immediately adjacent pair of the pads  122 . Further, some or all of the pads  122  of the second conveyor assembly  102  can be entirely formed of a hard material (e.g., metal) and need not include a flexible contact member. Regardless, as located along the conveying region  140 , individual ones of the pads  122  of the second conveyor assembly  102  need not be aligned with corresponding ones of the pads  112  of the first conveyor assembly  100 . 
     With additional reference to  FIG. 2 , the second track  72  of the take-away device  24  can have any of the constructions described above with respect to the first track  70 . For example, the second track  72  can include opposing conveyor assemblies, at least one of which includes at least two discrete contact pads carried by an endless belt (e.g., a chain) and each have the construction described above with respect to the angled pad  180  ( FIGS. 4A-4E ). While the first and second tracks  70 ,  72  of the take-away device  24  are shown as being parallel and fixed, other formats are also acceptable. For example, any of the take-away device track arrangements described in U.S. Pat. No. 6,936,209 can be incorporated with the take-away device of the present invention (e.g., the tracks  70 ,  72  can be arranged at a non-parallel angle relative to one another (and with respect to a centerline of the film  50 ), a spacing between the tracks  70 ,  72  can be adjustable, etc.). 
     With specific reference to  FIGS. 1 and 2 , the take-away device  24  constructions of the present invention, and in particular the film handling attributes provided with the take-away conveyor assembly film contact pads as described above, can be implemented with a number of different film stretching apparatuses. In some embodiments, aspects of the present invention are believed to be well suited to fabrication of polymeric optical films where the visco-elastic characteristics of materials used in the film are exploited to control the amount, if any, of molecular orientation induced in the materials when the film is drawn during processing. Consideration of the various properties of the materials used to produce optical films may be exploited to produce optical films exhibiting improved characteristics, such as in terms of optical performance, increased resistance to fracture or tear, enhanced dimensional stability, better processability, and the like. With this in mind, the stretching device  22  can be configured to effectuate a uniaxial or substantially uniaxial stretch in the film  50 , as described, for example in U.S. Pat. Nos. 6,916,440; 6,936,209; and 6,939,499. In general terms and in some embodiments, the film  50  is stretched along a first in-plane axis of the film while allowing contraction of the film  50  in a second in-plane axis and in the thickness direction of the film  50 , with the stretching achieved by grasping edge portions of the film  50  and moving the edge portions of the film  50  along predetermined paths which diverge to create substantially the same proportional dimensional changes in the second in-plane axis of the film  50  and in the thickness direction of the film  50 . The predetermined paths can be shaped so as to create substantially the same proportional dimensional changes in the second in-plane axis of the film  50  and in the thickness direction of the film  50 . In some embodiments, at one of the edge portions of the film  50  is moved along a predetermined path that is substantially parabolic. In other embodiments, the speed of the edge of the film  50  is controlled to create substantially the same proportional dimensional changes in the second in-plane axis of the film  50  and in the thickness direction of the film  50 . In yet other embodiments, at least one of the edge portions of the film  50  is moved along a predetermined path at a substantially constant speed. In yet other embodiments, the stretching device  22  can assume other forms known to those of ordinary skill that may or may not be configured to effectuate a uniaxial or substantially uniaxial stretch. 
     Other optional attributes provided with the apparatuses of the present invention and described in one or more of U.S. Pat. Nos. 6,916,440; 6,936,209; and 6,939,499 can also be incorporated, such as devices or techniques for effectuating a slit in the film  50  at the optional removal device  30  and/or the optional post-conditioning device  32 . The slitting can be mobile and re-positionable so that it can vary with the changes in take-away positions needed to accommodate variable final transverse direction draw ratio. A variety of slitting techniques may be used, including a heat razor, a hot wire, a laser, a focused beam of intense IR radiation or a focused jet of heated air. A variety of optical films may be stretched or drawn in accordance with aspects of the present invention. The films may comprise single or multi-layer films. Suitable films are disclosed, for example, in U.S. Pat. Nos. 5,699,188; 5,825,543; 5,882,574; 5,965,247; and 6,096,375; and PCT Publication Nos. WO 95/17303; WO 96/10347; WO 99/36812; and WO 99/36248. 
     Films made in accordance with principles of the present invention may be useful for a wide variety of products including polarizers, reflective polarizers, dichroic polarizers, aligned reflective/dichroic polarizers, absorbing polarizers, retarders (including z-axis retarders). The films may comprise the optical element itself or they can be used as a component in an optical element such as matched z-index polarizers used in beamsplitters for front and rear projection systems, or as a brightness enhancement film used in a display or microdisplay. It should be noted that the apparatuses of the present invention can be used with a length orienter to make a mirror from a multi-layer optical film. 
     The apparatus, systems, devices and methods of the present invention provide a marked improvement over previous designs. The angled and overlapping relationships associated with some or all of the film contact pads provided with a stretching apparatus take-away device approximate a continuous grip from discrete pads or segments. Continuous support of the film in the take-away device can be highly useful with many types of film stretching systems, including those operated to stretch thin films. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present invention. The complete disclosure of all patents, patent documents, and publications cited herein are incorporated by reference.