TWI492835B - Cross-web heat distribution system and method using channel blockers - Google Patents

Description

Horizontal network heat distribution system and method using channel resistance

This invention relates to controlling the thickness variation on extruded, oriented films.

Extruding the film typically causes a thickness variation along the length and width of the film. Prior art methods for controlling thickness variation include adjusting the plug (US 4,409,160, Kogo et al.), adjusting the heating power of the fixed heater during stretching (US 3,347,960, Fenley; JP 52,047,070, Tsutsui), or intentionally on the network. Thick areas and thin areas (GB 1,437,979, Hoechst Aktiengesellschaft; GB 1,437,980, Hoechst Aktiengesellschaft) were created at varying locations to make the finished film roll uniform in appearance.

The present application discloses a system and method for controlling a transverse network thickness profile of a polymeric film by using a lateral network thermal distribution system for providing a selectable heat distribution to a film in an azimuth, the transverse network The heat distribution system includes a heating element and a plurality of channel stops adjacent to a heat distribution zone, wherein each channel blocker is movably positioned such that at least one channel blocker blocks at least a portion of the heat generated by the heating element from reaching the film. The above summary is not intended to describe each disclosed embodiment or every implementation. The drawings and detailed description below more particularly exemplify illustrative embodiments.

This application is directed to controlling the thickness variation in an oriented film. Fabrication of the film typically results in a thickness variation along the length and width of the film. The present application discloses new systems and methods for fine and effective adjustment of the transverse network thickness profile of an oriented film.

The disclosed systems and methods can be used to make films comprising any polymer whose properties can benefit from stretching during film manufacture. The film can comprise one or more polymers. A film having more than one component polymer can have any form or structure, including but not limited to: a miscible blend, wherein one polymer is a continuous phase and one or more polymers are a dispersed phase. Miscible blends, co-continuous blends, interpenetrating polymer networks, and laminate films having any number of layers. The systems and methods disclosed herein are particularly useful for multilayer optical films. These systems and methods are also particularly useful for films comprising polyester.

The multilayer optical film produced by employing the disclosed system or method may include, but is not limited to, a mirror film, a polarizing film such as a reflective polarizer, a display film, an optical filter, a compensation film, an anti-reflection film, or For example, UV or IR screens, tinting, shaded windows (energy control or solar control) membranes are used in construction, automotive, greenhouse or other applications.

The film produced by the present system and method is not necessarily a multilayer optical film. Other high performance films may also benefit from the lateral network thickness control disclosed herein. High performance film applications include, but are not limited to, magnetic media base films for analog or digital recording of audio, video, or data; graphic art films; photocopying films; overhead transparent films; photographic films; x-ray films; Film; photographic printing film; inkjet printing film; plain paper reproduction film; printing plate film; color proofing film; digital printing film; carbon ribbon film; flexible printing film; gravure printing film; drafting and diazo printing film; Holographic film; adhesive tape substrate; abrasive substrate; label film; release liner film; mask film; laminate film; packaging film; heat sealing film; surface decoration film; double heat-resistant film; barrier film; Decorative film; archive and save film; electrical insulation film for wires and cables, motors, transformers and generators; flexible printed circuit film; capacitor film; for cards such as credit cards, prepaid cards, ID cards and "smart cards" Film; window or security film (safety film) for scratch, graffiti or chip protection; diaphragm switch thin ; Touch screen film; medical diagnostic device and a thin film sensor; acoustic insulating film; film acoustic speaker; and the drumhead membrane.

To impart specific optical and/or physical characteristics to the finished film, the polymer can be extruded through a film die, the orifice of which is typically controlled by a series of plugs. The extruded film can then be oriented, for example, by stretching at a ratio determined by the desired characteristics. Longitudinal stretching can be accomplished by a pulling roll in the length director 100 shown in FIG. The length director typically has one or more longitudinal stretch zones. The cross-sectional stretching can be accomplished in a tenter oven 200 as shown in FIG. The tenter oven typically includes at least one preheat zone 210 and a cross section stretch zone 220. Typically, the tenter oven also includes a heat setting zone 230 (shown in Figure 1). The system can be designed to include one or more of any or all of the zones. The film can be biaxially oriented if desired. Biaxial stretching can be accomplished sequentially or simultaneously. It is also possible to form the film only via longitudinal stretching or only by cross-sectional stretching. For uniaxial stretching, the draw ratio is typically close to 3:1 to 10:1. For biaxial stretching, the product of the longitudinal stretch ratio and the cross-sectional stretch ratio is usually in the range of 4:1 to 60:1. Those skilled in the art will appreciate that other draw ratios may be suitable for a given film.

For the purposes of this application, the term "cross-sectional stretch zone" refers to a purely transverse stretch zone or a synchronous biaxial stretch zone in a tenter oven. By "tenter" we mean any device in which the film conveys the edge of the film in the machine direction. Generally, the film is stretched in a tenter. In general, the direction of stretching in the tenter will be perpendicular to the machine direction (transverse or transverse), but will also encompass other directions of stretching, for example, angles at right angles to the direction of travel of the film. Optionally, the tenter can stretch the film in a second direction (machine direction or near machine direction) in addition to stretching the film in a first direction other than the machine direction. The second direction stretching in the tenter can occur synchronously with the first direction, or it can occur separately, or both. Stretching within the tenter can be accomplished in any number of steps, each of which can have a component that is stretched in a first direction, in a second direction, or in both directions. A tenter can also be used to allow a control amount to relax the cross-sectional direction in the contracted film if its edge is not clamped. In this case, relaxation occurs in the relaxation zone.

A conventional industrial useful tenter uses two sets of tenter clips to clamp the two edges of the film. Each set of tenter clips is driven by a chain and the grips ride over the two rails, the positions of which can be adjusted in such a way that when a track passes through the tenter, the two rails are separated from one another. This separation results in stretching in the transverse direction. Variations of this general scheme are well known and are encompassed herein.

Some tenters are capable of stretching the film in the machine direction or in a direction close to the machine while stretching the film in the transverse direction. These generally refer to synchronous biaxial stretching tenters. One type uses a scaler or scissors-like mechanism to drive the fixtures. This allows the clamp on each track to be separated from its nearest fixture on the track as it advances along the track. Of course, as in a known tenter, the clamps on each track are separated from the counterparts on their opposite tracks by the separation of the two tracks from each other. Another type of synchronous biaxial stretching tenter replaces each chain with a screw having a varying pitch. In this arrangement, each set of clamps is driven along its orbit by the motion of the threads, and the distance between the variations provides separation of the clamp along the track. In another type of synchronous biaxial stretching tenter, the clamps are individually electromagnetically driven by a linear motor, thus allowing the clamps to be separated along the tracks. A synchronous biaxial stretching tenter can also be used to stretch only in the machine direction. In this case, the machine direction stretching occurs in a machine direction stretching zone. In the present application, examples of cross-sectional stretching, relaxation, and machine direction tensile deformation, and examples of cross-sectional stretch zone, relaxation zone, or machine direction stretch zone deformation zone. Other methods for providing deformation in both directions within a tenter are also possible and are encompassed by this application.

The film processing method can include extruding a polymeric melt through an extruder die 10. The lip profile can typically be adjusted by a series of plugs. For multilayer films, a plurality of melt streams and a plurality of extruders are employed. The extrudate is cooled on a rotary carousel 12 . This film is now referred to as a "casting network." During orientation, the film or casting network is stretched in the machine direction, cross direction, or both directions depending on the desired characteristics of the finished film. Details of the film treatment are described in, for example, U.S. Patent No. 6,830,713 (Hebrink et al.). For the sake of brevity, the specification will use the term "film" to mean a film at any stage of the process, regardless of the "extrudate", "casting network" or "finished film". However, those skilled in the art will appreciate that films at different points in the process may be represented by the alternative terms listed above as well as other terms known in the art.

Many elements contribute to the change in film thickness uniformity throughout the film manufacturing process. For example, uniformity fluctuations may be due to variations in many lateral network conditions, including lip profile, lateral network mold temperature, lateral network turntable casting machine temperature, updraft in ambient air, non-uniform tenter temperature and/or pressure The above changes, and many other factors that are familiar to those skilled in the art. Film uniformity is important in high quality multilayer films, especially in multilayer optical films. For more and more applications, these films are required to exhibit a high degree of physical and optical uniformity over a large area. The systems and methods disclosed in this application can provide effective lateral network control to achieve uniformity of the film.

A typical method for controlling the thickness of the transverse web in the manufacture of the film involves adjusting the plug in the mold during the formation process of the casting network. These adjustments include changing the physical spacing of the lips by physically adjusting the plug or changing the temperature of the plug. However, the result of the adjustment of the thickness of the film by the plug is rough and slow. Changing the physical spacing of the lips results in a rough adjustment due to the inflexibility of the lips. In most cases, the effect of adjusting a single die plug is to change the film thickness in up to seven die pin landings in the finished film. Therefore, it is difficult to control the fine variations in the thickness of the lateral network by adjusting the die pitch. Changing the plug temperature produces a slow change in thickness adjustment because it takes a considerable amount of time for the plug heater to warm and cool. In addition, since the path from the die to the winder in the film production line is long, the corresponding time for thickness change by the die plug adjustment is usually long, making the thickness profile control difficult and slow.

The disclosed system and method control for controlling the transverse network thickness of the extruded film allows efficient and fine control of the thickness profile during film manufacture. Lateral network thickness control can be achieved by monitoring the lateral network thickness profile and controlling the heat distribution profile delivered to the film during stretching or deformation. Monitoring the lateral network thickness profile can include mapping the measured physical or optical thickness profile and the measured profile to a location to be taken for thermal profile control. Systems and methods for controlling lateral network heat distribution corresponding to the monitored profile will be discussed. The steps of monitoring the thickness and adjusting the heat distribution can form a feedback loop that is used over the reverse until a desired final thickness profile is formed in the film. The disclosed systems and methods can also be used in conjunction with diebolt adjustment to provide fine control of the lateral thickness profile.

In certain disclosed embodiments, a particular technique for controlling the transverse network thickness profile of a dual axially oriented polymeric film is used. For example, in some cases, a channel stop is used to adjust the heat profile, and in some repositionable situations, a pivotable heating element is used to adjust the heat profile. Such techniques can be used in combination, such as during longitudinal stretching, cross-sectional stretching, biaxial deformation, or during controlled relaxation. For example, the channel stop can be employed in a length director for longitudinally stretching a film, or in a tenter for transverse or biaxially stretched film. Similarly, the repositionable, pivotable heating element can be employed in a length director or a tenter. The method of controlling the transverse network thickness profile of a dual axially oriented polymeric film can be used in conjunction with any of the systems disclosed herein and with other methods known in the art.

The disclosed lateral network heat distribution system can transfer heat to the film as it is stretched while providing adjustable position control and adjustable profile control of the transferred heat. If desired, this provides finer control of the lateral network thickness profile than known systems. The disclosed system can also provide a correspondingly faster time than known systems.

A novel method for controlling the transverse network thickness profile of a biaxially oriented film is disclosed. The method is based on controlling the heat distribution in or near the stretch zone of the length director (LO), which in turn deforms the film in the tenter and measures the resulting transverse network after the deformation zone in the tenter The thickness profile, and the heat profile in the LO is adjusted based on the measured thickness profile. In an embodiment, the deformation zone can be located at the end of the production line just before the winder. In another embodiment, the deformation zone can be located between other zones as shown, for example, in FIG. Other embodiments may have additional components, such as a successor second length director.

As will be described in more detail below, these systems and methods can be used alone or in combination with virtually all film production lines to produce films having enhanced lateral direction thickness uniformity. Such systems and methods can also be used (e.g., in multilayer optical film applications where color variations and intentional film thickness variations are desired) to produce films having tailored transverse network thickness profiles.

Two illustrative embodiments are discussed in detail below. The first embodiment employs a channel stop in the length director. The second embodiment employs a repositionable, pivoting heater in a tenter oven.

In certain embodiments, the lateral network heat distribution system includes at least one cross-sectional heating element in combination with a plurality of channel stops. Three examples of such systems are shown in Figures 2a-2c. In these figures, the film is stretched in a length director. In Figures 2a and 2c, the pulling rolls 102, 104 and 106 are arranged in an S-wound configuration. In Figure 2b, the pulling rolls are set in a normal or table configuration. The embodiment depicted in Figures 2a-c, along with a set of channel stop members 170, respectively, employs heating assemblies 150a-c for providing a selective heat distribution to longitudinal stretch zones 140 or 140b of film 20.

In Figure 2a, the heating assembly 150a includes three cross-sectional infrared heating elements 160. The adjustable profile transverse network thermal distribution system also includes a plurality of channel stop members 170 aligned in the machine direction of the film and between the heating assembly 150a and the film 20. Although this particular embodiment employs a set of three heating elements 160 and a plurality of channel stops 170, any number of heating elements and any number of channel stops can be used, depending on the design considerations of the system. For example, a system having a single heating element (heating assembly 150b) is shown in Figure 2b, and a system having five heating elements (heating assembly 150c) is shown in Figure 2c. Another example may include a set of 10 heating elements and a set of 50 channel stops. Each cross-section heating element can be a single heater spanning the entire width of the film area to be controlled, or a plurality of small heaters including a hot spot source configured to provide a desired amount of heat to be controlled Film area. It also covers the combination of hotspot sources and thermal expansion sources.

To allow for fine control of the transverse network thickness profile of the film, the lateral network heat distribution system of Figure 2a transfers heat to the stretch zone of the film via the heating assembly 150a while simultaneously changing the channel stop 170 by The position of each block provides an adjustable profile control of the transferred heat. In each of Figures 2a-c, the channel stops 170 preferentially block a desired portion of heat at a desired lateral network location. When a heating element provides heat to the film, a channel stop or a set of channel stops can be positioned to effectively cast a shadow on the film, thereby reducing the amount of heat transferred to the film at the particular location selected. Each particular channel stop casts a shadow at a location corresponding to the area of the film to be finely controlled. The degree of resolution can be adjusted by the proximity of the channel stop to the film and the size of the channel stop. In Figure 2a, the channel barriers 170 are generally horizontally positioned and parallel to the heating element 160 of the heating assembly 150a. The film of Figure 2a is in an S-wound configuration. Thus, the channel stop members 170 are inclined to the plane of the film of the S-wound configuration. In Figure 2b, the channel barriers 170 are also positioned generally horizontally, but the film is in a table configuration such that the channel stops are parallel to the plane of the film. In Figure 2c, the channel members are angled parallel to the plane of the film and the film is in an S-wound configuration.

The width of each individual channel stop is made to be as narrow as desired and the distance of the resistors to the film can also be tailored. For example, the channel stop can be 10 mm wide and positioned within 50 mm of the film. Thus, the channel stop assembly as a control element can be finely divided, and a tailored lateral network thickness control scale can be tailored to provide perfect thickness control. In addition, since the control position is located at the length of the network acceleration to the line speed orientation station, the lag time from the channel block to the winder is much shorter than the time from the die to the winder. Therefore, the corresponding time for control is shorter, so that the final thickness uniformity is obtained faster. In addition, the length director is typically located in an open space and is easily accessible, making the system easy to install and construct. The channel stop embodiment can also be used in a tenter oven. In such a system, the distance between the winder and the tenter oven can be shorter and the corresponding time can be faster. The heating assembly with the channel stop can be designed to be externally controllable from the tenter oven.

The systems and methods of Figures 2a-c allow for rapid changes in heat transfer to a particular area. As discussed further below, an alternative lateral network heat distribution system can be utilized in which the lateral network heat distribution profile is altered by varying the electrical power supplied to an array of heaters. Alternative systems may have particular benefits, such as no moving parts, but may also have disadvantages depending on the type of heater used, such as lower spatial resolution and slower corresponding time. For example, some industrial grade IR heaters can take up to 5 minutes to cool and 15 minutes to cool. In contrast, systems employing movable channel stops can be designed to have relatively fast corresponding times and high spatial resolution. A channel stop or a set of channel stops cast shadows onto the film, thereby reducing the movement of heat transferred to the film faster than the corresponding time of conventional IR heaters. The corresponding time of the system using the channel stop is limited only by how fast the channel can be moved and the time taken by the network. This will be based on the specific mechanical design of the channel stop assembly and its control mechanism. Those skilled in the art will appreciate a variety of possible designs suitable for mechanically controlled channel block assemblies.

FIG. 3 shows a top view of an exemplary design of a channel stop assembly 300. The channel stop assembly 300 has 34 channel stops positioned adjacent one another that span the entire width of the film to be controlled. The physical dimensions of the film may extend beyond the entire width of the film to be controlled as desired, for example where the outer edge of the film is cut and discarded or recycled, leaving only a portion of the central film available. A transverse network heat distribution system incorporating a channel stop assembly such as one of the channel stop assemblies depicted in FIG. 3 can be used in a length director, tenter, or both.

The feedback mechanism may be used to measure the physical or optical thickness profile, map the measured thickness profile to the stretch zone as appropriate, and adjust the lateral network heat distribution system corresponding to the measured or mapped profile. The feedback mechanism is conventional and will not be described in detail. In short, a feedback mechanism can be in the form of manual control by an operator, which can be computer controlled, or it can be combined with a computer and manual control. For example, the feedback mechanism can be a computer control system with manual override. Preferably, the feedback mechanism employs a computer controlled mapping algorithm that uses any of the mapping methods described herein. A manual mapping algorithm can also be used.

In certain embodiments, the lateral network heat distribution system includes a set of repositionable heating elements disposed in a cross-sectional direction in the tenter. In the exemplary embodiment described below, the transverse network heat distribution system is used in a tenter. The deforming zone of the tenter can be a pure cross-sectional extension, a relaxed zone, a machine direction stretch zone, or a dual axial stretch zone. Such a transverse network heat distribution system comprising a repositionable heating element can also be used in the length director.

Figure 4 illustrates an implementation of this embodiment. In Figure 4, the film is stretched in a cross-sectional direction in a tenter oven 200 (see Figure 1). In this particular implementation, the repositionable heating element can also be pivoted. The transverse network heat distribution system 250 includes five repositionable rod heaters 260a-e mounted on a pair of mounting channels 253. Other implementations are also possible, including (but not limited to): linear configuration or an array of smaller heat sources optimized for the particular shape desired for a particular desired.

Although in the embodiment of Fig. 4, the heater is located in the stretch zone of the abutment, its position is not limited to a stretch zone. The director can have additional zones or other zones of deformation that can be used by the lateral network heat distribution system. Additional zones include, but are not limited to, a preheat zone, an annealing zone, and a heat set zone. When used in a length director, the stretch zone is a longitudinal stretch zone. When used in a tenter, the deformation zone can be a cross-sectional stretch zone, a relaxation zone, a machine direction stretch zone, or a biaxial stretch zone. The lateral network heat distribution system can be located in or adjacent to any of the zones. Although most of the embodiments disclosed herein refer to stretch zones, it is intended that the lateral network heat distribution system may also reside in or near other zones. In the present application, the location in which the lateral network heat distribution system resides in any embodiment is referred to as a heat distribution zone.

In the heat distribution system 250 of Figure 4, the heating element can be repositioned in two ways. First, the heating elements can be moved across the mounting channel to any position on the width of the film. Second, the heating elements can also be pivoted. The benefits of a pivot heater will be discussed below. Other implementations and embodiments are also contemplated. For example, the heating elements can be repositionable such that they can be moved toward or away from the film in a plane perpendicular to the plane of the film.

To map a cross-sectional position to any portion of the film as it moves along the film line, virtual centerlines 22a-e are shown for each landing portion 40a-e, respectively, in FIG. The film landing portions 40a-e are defined by imaginary lines. In Figure 4, each of the centerlines 22a-e also represents the direction of travel of each of the films as the film is stretched. During the cross-sectional stretching, the distance between each pair of imaginary lines increases in proportion to the amount of cross-sectional stretching. In other words, the width of each film landing portion increases as the film cross-sectionally stretches. Ideally, for example, if the film is stretched at a 3:1 ratio, then the width of each film landing will be measured just before the stretch zone 220 and just after the stretch zone 220. Increase by three times. However, in practice, a variety of factors can cause the film landings to be unequal in width. For example, such factors may include: changes in the uniformity of the transverse network prior to stretching; changes in the temperature distribution of the transverse network in the tenter; homogenization changes in the extruded mixture; and edges in a thin film network having a finite width effect.

The rod heaters 260a-e in the lateral network heat distribution system are mounted in such a manner that the heaters can be positioned independently of each other. In addition to the cross-sectional movement, a rod heater can be installed to make it pivotable, as needed. The pivotable heater has two advantages: first, the pivoting rod heater can be aligned with the direction of travel of the particular film landing portion positioned above; second, a pivoting rod heater can be relative to the The direction of travel of the film landing portion is angled to provide a wider heat distribution profile from any single heating rod. This broadening effect on the heat distribution profile will be discussed in detail in the examples below. The pivoting, repositionable heating element provides greater control over the heat transferred to the film, thereby providing a finer profile of the heat distribution profile than known systems.

In Figure 4, each of the heating elements 260a-e is pivotally mounted on two parallel channels 253 across the tenter. In this way, the lateral network position of each heater can be precisely adjusted from outside the tenter oven. The position and orientation of each of the rod heaters 260a-e can be controlled by a variety of methods known in the art. In the embodiment of Figures 5-6, a pair of Acme brand threaded rods 262 are used for each rod heater to control position and orientation. Other methods for position and pivot control (eg, connecting a pair of cables to each rod heater) can also be used.

FIG. 5 shows a close up view of a single repositionable heating element of one of the heat distribution systems 250. The heating element 260 can be positioned in either position along the two mounting channels 253L and 253R. Optionally, the heating element 260 can also be rotated (as indicated by the dashed line) to align with the line 26 so that it forms an angle θ with respect to the machine direction 25. In one embodiment, the rotation system is implemented with a set of bolts 266 and a bolt 268 that allows movement along a taxiway as the heating element 260 rotates. The fixing bolt 266 acts as a pivot point for the heating element and is located in the center of the heating element 260 in this embodiment. When pivoting is not required, the sliding channel 270 can be removed and both bolts can be fixed. Other configurations are also covered.

FIG. 6 shows a partial perspective view of the heat distribution system 250 of FIG. Figure 6 shows two heating elements 260a and 260b mounted on channels 253L and 253R. The position of the heating element 260a is controlled by a pair of threaded rods 262a. Similarly, the position of the heating element 260b is controlled by a pair of threaded rods 262b. The optional rotation of the heating element 260b is achieved by positioning one of the nuts 264b on the fixed (253R) along the threaded rod 262b on the passage 253R in a position while positioning the corresponding nut 264b along the corresponding threaded rod mounted on the passage 253L. Implemented in a different location. This can also be seen in Figure 5. The lateral network position of each heater 260 can be precisely adjusted from the outside of the tenter oven using a pair of screws (not shown) coupled to each pair of threaded rods. Alternatively, the orientation angle of the heater can be precisely adjusted from the outside of the tenter oven by the relative position of the pivot points 266b and 268 controlled by the screw.

A single rod heater that is mounted to be movable in a cross-sectional direction and that can be pivoted relative to the machine direction can provide adjustable thermal profile control of the film as it is stretched and deformed. When used in combination, heater assemblies such as heaters 260a-e can collectively provide an adjustable thermal profile on any selected portion of the film or over the entire width of the film.

As in the channel stop embodiment, this embodiment also has the benefit of fast corresponding time and fine, effective control of heat distribution. When the control position is a length direction station where the network accelerates to the line speed, the lag time from the lateral network heat distribution system to the winder is substantially shorter than the lag time from the mold to the winder. Therefore, the corresponding time of control is short, which results in a short cycle time, so that the desired final thickness uniformity is greatly accelerated. Moreover, the length director is typically located in an open space and is easily accessible, making installation of the lateral network heat distribution system convenient. When the control position is in the tenter, the cycle time and corresponding time can be shorter.

Typically, the thickness profile of the film can be measured at any point downstream of the location of the lateral network heat distribution system. For example, in a system employing any of the disclosed lateral network heat distribution systems of the length director, the lateral network thickness profile can be measured downstream of the length director. In a system employing a transverse network heat distribution system in a tenter oven, the lateral network thickness profile can be measured downstream of the tenter oven. Alternatively, the transverse network thickness profile may also be measured in the tenter oven, just in the deformation zone (where the lateral network heat distribution system is located). In a system employing a transverse network heat distribution system in a length director and also using a tenter for subsequent cross-sectional stretching, downstream of the length director, but upstream of the tenter oven Perform lateral network thickness profile measurements. Applicants have found, however, that controlling the lateral network heat distribution in the length director, then deforming in a tenter, and then measuring the transverse network thickness profile of the film from downstream of the deformation zone provides unexpected results. Example 2 below describes such a system and method.

For optical films, the overall film optical thickness can be detected and monitored via light transmission or reflection spectroscopy using optical thickness gauges. For example, an on-line spectrophotometer can be set to measure the spectral transmittance as it exits the line, thereby providing the necessary information to measure lateral network thickness profile uniformity and provide feedback for process control. An example of such a spectrophotometer is a U-4000 optical spectrometer manufactured by Hitachi Ltd. In some cases, the transmission spectrum can be reduced to a particular level of wavelength as a measure of its optical thickness. In other cases, transmission at a particular wavelength can be used as a measure of its optical thickness. Other methods are possible, including the ability to calibrate the interconnection method using the direct method described above.

As described above, the thickness gauge can measure the physical thickness, optical thickness, or other thickness associated with the properties of the film. In the present application, lateral network thickness refers to optical thickness, physical thickness, a combination of the two, or any other thickness-related characteristic as desired for a particular product design. Those who are familiar with optical or high-energy films will be able to design the right thickness for a particular product. For example, the measurement of the physical thickness of a film can be performed by using online traversing beta gauge scanning devices (eg, a Measurex available from Morristown, New Jersey, Honeywell International, Inc., USA). ^{T M} scanning gauge). Other thickness gauges include, but are not limited to, beta transmission gauges, X-ray transmission gauges, gamma backscatter gauges, contact thickness sensors, and laser thickness sensors. Such gauges are commercially available, for example, from the United States, California, Irwindale, NDC Infrared Engineering.

The measured film thickness profile is mapped as appropriate to the corresponding film location in which the lateral network thermal distribution system is located. For some embodiments, a film thickness profile measured after the cross-sectional stretch zone can be mapped to the film in the longitudinal stretch zone of the length director. For other embodiments, the film thickness profile is measured and mapped to the heat distribution zone downstream of the self-heating distribution system. Mapping can be done in a variety of ways. A simple mapping method involves dividing the width of the film into a set of virtual film landings (e.g., as shown by the phantom lines in Figures 3 and 4). In Fig. 3, the film is divided into 34 film landing portions, and each landing portion corresponds to a channel stopper. In this particular embodiment, the channel stops 301 and 334 are wider than the remaining channel stops 302-333. Therefore, the descending portions 1 and 34 are wider than the descending portion 2-33. In Fig. 4, the five film landing portions 40a-e are indicated by imaginary lines. The centers of each of the five landing portions 40a-e are shown by centerlines 22a-e, respectively.

The transverse network thickness profile is measured downstream of the heat distribution zone in which the lateral network heat distribution system is located. At the measurement position, the film may not have the same width as the width of the film at the location where the control of the heat distribution system occurs. Therefore, a mapping algorithm is used to map a location to another location. A mapping algorithm essentially translates each lateral network location of a film at one location to a corresponding lateral network location on the film at another location. A mapping algorithm may take into account any or all of the factors that may affect how the width between the two locations differs, including but not limited to: stretching, shrinking, bending, whether the film at a location has been removed The change in the edge network, the uniformity of the transverse network before stretching, the change in the temperature distribution of the transverse network in the tenter, or the homogeneity of the extruded mixture.

The additional mapping method can include marking the film entity with an indicator prior to stretching and measuring the position of the indicator after stretching. For example, the first method can include drawing two lines 50 mm from each edge of the film, then measuring the position of the lines after stretching and subdividing the width of the film between the two lines. A descending portion of equal number of widths. This method assumes that each landing is equally stretched or equally deformed. The second method can include drawing 50 indicator lines on the film, then stretching the film and measuring the position of each indicator line after stretching. The third method can include selectively moving one or more of the channel barriers or repositionable heaters and measuring the effect on the stretched film. This method is called active mapping or bump mapping. The fourth method can use the principle of conservation of mass, wherein the transverse network thickness profile of the film is measured before and after stretching. Since the mass is conserved during stretching, the volume of the film remains the same, and the width of a given number of film landings can be calculated from the two measured thickness profiles. Any of these mapping methods can be used to design a suitable mapping algorithm.

For example, in FIG. 4, a film is stretched transversely in a system using a lateral network heat distribution system 250 at a longitudinal location 60. In some embodiments, a transverse network thickness profile is measured at a longitudinal location 70 where the film is wider than the film at location 60. To control the heat distribution at location 60, the measured profile at location 70 is mapped to the location of thermal distribution system 60. The heat distribution system can then be adjusted to smooth any thick or thin spots or irregularities in the film profile. In another example, the system can also be equipped with a second lateral network heat distribution system at location 50. In this case, the transverse network thickness profile measured at location 70 can also be mapped to the location 50 where the second thermal distribution system is located.

Useful lateral network heat distribution systems can be any of the systems disclosed above, for example, systems that use repositionable heating elements, heating elements with channel stops, or a combination of both. It is also possible to use any other known or later developed lateral network thermal distribution system that can transfer heat to a network according to a tailorable lateral network profile. The transverse network heat distribution system can be used in a length director or a tenter. When used in a tenter, an optional heat distribution is provided to the deformation zone of the film. When used in a length director, a thermal profile can be selected to provide a longitudinal stretch zone of the film.

As will be described below in Example 1, if the measured film profile has a thick or high point mapped to the descending portion 08, the corresponding channel stop 308 can be adjusted to transfer more heat to the landing portion 08. . This allows the film to stretch more in the landing, thereby reducing or eliminating thick spots on the finished film. Similarly, if the measured film profile indicates a low point on the film at the location corresponding to the descending portion 22, the channel stop 322 can be moved to block heat from reaching the film at the location (eg, as shown in FIG. 3) Show). In one embodiment, the degree of blocking or non-blocking is adjusted by a passage through a forward of a threaded rod that is pivoted using a mechanical shaft 180. Obviously, this adjustment can be performed infinitely finely, giving perfect control over the heat distribution.

Similarly, as shown in Examples 3 and 4, the thick spots can also be adjusted by using a repositionable heating element in a length director or tenter. If the relocatable elements are also pivotable, the effect can be adjusted more finely. As in the channel stop embodiment, the repositionable heaters can be used to effectively control the transverse network thickness of a film to a desired final profile.

In some embodiments, the length director can then be deformed in a tenter. Under such conditions, it is intuitive to adjust the lateral network heat distribution at the length director rather than the tenter to effectively correct the lateral network thickness distribution in the finished film downstream of the tenter. Example 2 below surprisingly demonstrates that the lateral network thickness can be finely adjusted by selectively blocking a portion of the heat transferred to the heat of the film during longitudinal stretching, thus providing a more uniform biaxially stretched film. Although Example 2 uses a channel stop heat distribution system, this method can also be used in conjunction with any other lateral network heat distribution system (e.g., relocatable heating elements disclosed herein or other lateral network heat distribution systems known in the art). use. The unique manner in which the method controls the heat distribution in the length director during longitudinal stretching to achieve a uniform transverse web thickness of the film that has subsequently been deformed in the tenter provides excellent results.

Instance Example 1.

In the example shown in Figure 7, an IR reflective multilayer optical film is formed by extruding alternating layers of polymethyl methacrylate (PMMA) and polyethylene naphthalate copolymer (co-PEN). The film was first oriented with a draw ratio length of 3.3:1 and then oriented in the tenter at a draw ratio width of 3.3:1. The optical thickness of the film was measured using an optical thickness gauge after the tenter. Curve 7A shows the optical thickness profile of the initial mapping of the film. To control the thickness profile, a heating assembly having three IR rod heaters and a set of 34 channel stops is used in the length director. The IR rod heaters used were Model 5305 Parabolic Strip Heaters manufactured by Minneapolis, Minnesota, Research, Inc., USA. Channel stops 303-331 are shown at the bottom of the chart. The channel width is 12.7 mm. To reduce the peak of one of the curves shown in curve 7A indicating a thick point at a position corresponding to channel 308, channel stop 308 is moved from a starting position of 35.6 mm to a final position of 25.4 mm to 10.2 mm. Moving the lowering of this channel block allows more heat to reach the film at the lateral network location. More heat transferred to this location causes the peak to decrease by allowing the portion of the film to stretch more. The resulting mapped thickness profile is shown in curve 7B at a location corresponding to channel stop 308. Curve 7C shows the percentage change from the initial thickness profile of curve 7A to the final thickness profile of curve 7B. At a position corresponding to the channel stop 308, the curve 7C shows that moving the channel stop 308 by -25.4 mm changes the thickness profile by about -3%. Similarly, the channel blocking effect is shown in curves 7A-C corresponding to the location of channel block 322. The initial thickness profile has a depression indicating a thin point at this location, as shown in curve 7A. By moving the channel stop 322 to a final position of 25.4 mm to 61 mm, more heat is blocked from reaching the film, thereby allowing the film to stretch less than the adjacent portion. This results in an increased thickness profile at the location (as shown in curve 7B). The percentage change at this position (as shown in curve 7C) changes by about 3%.

Example 2.

In the example shown in Figure 8, an IR reflective multilayer optical film was prepared by extruding alternating layers of polymethyl methacrylate (PMMA) and polyethylene naphthalate copolymer (co-PEN). The film was oriented at a draw ratio length of 3.3:1. The film was then stretched in the transverse direction in a tenter at a draw ratio of 3.3:1. The optical thickness of the film was measured after the tenter by using an optical thickness gauge. Curve 8A shows the original transverse network optical thickness profile of the film mapped to the length director station. To control the thickness profile, a heating assembly having three IR rod heaters and a set of 34 channel stops is used in the length director. The IR rod heaters used were Model 5305 Parabolic Strip Heaters manufactured by Minneapolis, Minnesota, Research, Inc., USA. Channel stops 303-331 are shown at the bottom of the chart. The channel width is 12.7 mm.

The profile of the film shown in curve 8A is adjusted by moving a number of stops in the channel stops, as indicated by the final setting of each of the channel stops shown at the bottom of FIG. Table 1 shows the initial and final settings of the channel stop members 303-331. The resulting optical thickness profile is shown in curve 8B. Curve 8C shows the percentage change between the final and initial thickness profiles. Curve 8B demonstrates that the initial film profile shown in curve 8A can be more uniform by using a lateral network heat distribution system with a set of IR heaters and a set of channel stops.

Example 3.

In the example shown in Figure 9, a multilayer optical film is prepared by extruding alternating layers of polyethylene terephthalate and PMMA copolymer. The film was oriented at a draw ratio length of 3.35:1. The film was then oriented in a cross-sectional direction in a tenter at a draw ratio of 3.3:1. The tenter is equipped with a set of repositionable, pivoting heating elements in its cross-sectional stretch zone. Each heating element is 325 mm long and 10 mm wide with a parabolic reflector 80 mm wide. The heating element used was a Raymax 1525 model available from Missouri, St. Louis, Watlow Electric, USA. In this example, the center of the heating element is used as a pivot point and a positioning position. The optical thickness of the film was measured using an optical thickness gauge after the tenter. Curves 9A, 9B, and 9C show optical thickness changes as a function of the lateral network position for different configurations of the lateral network thermal distribution system, demonstrating the effect of the repositionable, pivoting IR heater on the finished film. The heating element power and orientation angle are shown in Tables 2 and 3.

The change in the transverse network optical thickness profile of each of the three curves 9A, 9B, and 9C remains the same when a single heating element is maintained at a constant power and at the same orientation angle. This effect can be observed as a depression on curves 9A, 9B and 9C at a lateral network location of 460 mm corresponding to a first heating element 962. When a single heater is maintained at a constant power and the orientation angle is changed, a widening effect can be observed. The depressions on curves 9A, 9B and 9C at 950 mm demonstrate that this widening effect is attributed to a single rod heater. In this example, the second heater 964 at 950 mm is rotated from 0 degrees in curve 9A to 12.5 degrees in curve B to 25 degrees in curve C.

Example 4.

In the example shown in Figures 10-13, a multilayer optical film is produced by extruding alternating layers of PET and PMMA copolymer. The film was oriented at a draw ratio length of 3.35:1. The film was then oriented in the cross-sectional direction at a draw ratio of 3.3:1. The tenter is equipped with a set of 4 repositionable, pivoting heating elements in the cross-sectional stretch zone. Each heating element is 325 mm long and 10 mm wide with a parabolic reflector 80 mm wide. The heating element used was a Raymax 1525 model available from Missouri, St. Louis, Watlow Electric, USA. The center of each heating element serves as a pivot point. In Tables 4-7, the position of the center of each of the heating elements in this embodiment is shown as "position, right" and the position of the movable bolt for pivoting is shown as "position, left tilt". The optical thickness of the film is measured downstream of the tenter by using an optical thickness gauge. Curve A in each of Figures 10-13 shows an initial optical transverse network thickness profile. Figures 10-13 represent successive iterations that change the heater settings. First, the transverse network thickness profile of the film is measured. The measured data points are plotted as curve A of FIG. Next, the measured transverse network optical thickness profile of the film is mapped onto the cross-sectional stretch zone. The heaters 1-4 are set according to the parameters shown in Table 4 in the first iteration corresponding to the mapped profiles. The resulting transverse network optical thickness profile is measured and shown as curve B of FIG. The resulting optical thickness of the first iteration (curve B of Figure 10) then becomes the initial thickness profile of the second iteration (curve A of Figure 11). Measure the optical thickness profile, map the measured optical thickness profile to the stretch zone, and adjust the lateral network heat distribution system corresponding to the mapped profile to form a feedback loop that repeats until a desired final result is obtained Thickness profile. In the second iteration, the heaters 1-4 are set according to the parameters listed in Table 5. The resulting optical thickness profile is plotted as curve B of FIG. As shown by the heater settings in Tables 6 and 7, this process is repeated through two iterations and the thickness profile is plotted in Figures 12 and 13. The synergistic effect of one of the four repositionable, pivoting IR heaters on the optical transverse network thickness profile of the finished film is illustrated by curve B of FIG. Curve B of Figure 13 in the range of approximately 1300-1850 mm shows that a flat final thickness profile can be obtained by using one of the four repositionable heating elements located in one of the states of interest. Note that the "valley" at a lateral network location beyond 1865 mm can be handled by other means (eg, plug adjustment).

The present invention has been described with respect to the specific embodiments of the present invention, and is not intended to limit the invention. Rather, the invention is to cover modifications, equivalents, and alternatives of the invention and the scope of the invention as defined by the appended claims.

08. . . Lowering

10. . . Extruder die

12. . . Rotary turntable pouring machine

20. . . film

twenty two. . . Lowering

22a-e. . . Center line

25. . . Machine direction

26. . . line

40a-e. . . Film landing

50. . . position

60. . . position

70. . . position

100. . . Length director

102. . . Pulling roller

104. . . Pulling roller

106. . . Pulling roller

140. . . Longitudinal stretching zone

140b. . . Longitudinal stretching zone

150a-c. . . Heating assembly

160. . . Infrared heating element

170. . . Channel stop

180. . . Mechanical shaft

200. . . Tenter oven

210. . . Preheating zone

220. . . Cross-sectional stretch zone

230. . . Heat setting area

250. . . Horizontal network heat distribution system

253. . . Installation channel

253L. . . Installation channel

253R. . . Installation channel

260. . . Heating element

260a-e. . . Rod heater

262. . . Threaded rod

262a. . . Threaded rod

262b. . . Threaded rod

264b. . . Nut

266. . . Fixing bolts

268. . . bolt

270. . . Sliding channel

300. . . Channel resistance assembly

301-334. . . Channel stop

Figure 1 is a schematic illustration of a film production line for a dual axially oriented film.

2a is a schematic illustration of one embodiment of an adjustable profile transverse network heat distribution system in a length director.

2b is a schematic illustration of another embodiment of an adjustable profile lateral network heat distribution system in a length director.

2c is a schematic illustration of another embodiment of an adjustable profile lateral network heat distribution system in a length director.

3 is a schematic top plan view of one embodiment of a channel stop assembly.

4 is a schematic diagram of another embodiment of an adjustable lateral network heat distribution system.

Figure 5 is a schematic illustration of an exemplary repositionable, pivoting heating element of an embodiment.

Figure 6 is a partial perspective view of an assembly of a repositionable, pivoting heating element of an embodiment.

Figure 7 shows the effect of the specific channel stop in Example 1 on the optical thickness.

Figure 8 shows the effect of one of the set of channel stops in Example 2 on optical thickness.

Figure 9 shows the optical thickness profile change and lateral network position in Example 3.

Figure 10 shows the relative optical thickness versus lateral network position comparison for the configuration of the heating element settings in Table 4 of Example 4.

Figure 11 shows the relative optical thickness versus lateral network position comparison for the configuration of the heating element settings in Table 5 of Example 4.

Figure 12 shows a comparison of relative optical thickness versus lateral network position for a configuration corresponding to the heating element settings in Table 6 of Example 4.

Figure 13 shows a comparison of relative optical thickness versus lateral network position for a configuration corresponding to the heating element settings in Table 7 of Example 4.

08. . . Lowering

20. . . film

twenty two. . . Lowering

180. . . Mechanical shaft

300. . . Channel resistance assembly

301-334. . . Channel stop

Claims (23)

A film processing apparatus comprising: an orienter for deforming a polymeric film, the orienter having a heat distribution zone, the orienter being a length director having a stretch zone, wherein the heat distribution zone is disposed at a transverse network heat distribution system of the length director in the stretch zone or adjacent to the stretch zone of the length director; a transverse network heat distribution system for providing an optional heat distribution to the film in the director The transverse network heat distribution system includes a heating element and a plurality of channel blocking members adjacent to the heat distribution region, wherein each channel blocking member is movably positioned such that at least one channel blocking member blocks at least a portion of the heat generated by the heating element Arriving the film; a thickness specification for measuring a transverse network thickness profile of the film, the thickness specification being located downstream of the lateral network heat distribution system; and a thickness profile selection corresponding to the measured transverse network thickness The feedback mechanism of this heat distribution. The film processing apparatus of claim 1, wherein the orienter is a tenter. The film processing apparatus of claim 1, wherein the heat distribution zone is a deformation zone. The film processing apparatus of claim 3, wherein the heat distribution zone is a stretching zone. The film processing apparatus of claim 1, wherein the heat distribution zone is a preheating zone. The film processing apparatus of claim 1, further comprising a tenter. The thin film processing apparatus of claim 1, wherein the feedback mechanism comprises a mapping algorithm. The film processing apparatus of claim 1, wherein the channel blockers are positioned substantially parallel to the film in the longitudinal stretch zone. The film processing apparatus of claim 1, wherein the channel stoppers are positioned within 50 mm of the film. The film processing apparatus of claim 9, wherein the channel stoppers are positioned within 25 mm of the film. The film processing apparatus of claim 1, wherein the longitudinal stretch zone is formed in a table configuration. The film processing apparatus of claim 1, wherein the longitudinal stretch zone is formed in an S-wound configuration. A method of controlling a transverse network thickness profile of a polymeric film, comprising the steps of: deforming the film in an orienter having a transverse network heat distribution system and a stretch zone, wherein the transverse network heat The distribution system includes a heat distribution zone disposed in the stretch zone of the orienter or adjacent to the stretch zone of the director; at a location downstream of the lateral network heat distribution system Measure the transverse network thickness profile of the film; and adjust the lateral network heat distribution system corresponding to the measured lateral network thickness profile by selectively relocating at least one channel stop in the lateral network heat distribution system . The method of claim 13, wherein the adjusting step comprises: The measured lateral network thickness profile is mapped to the location of the lateral network thermal distribution system. The method of claim 13, wherein the director is a length director. The method of claim 13, wherein the director is a tenter. The method of claim 16, further comprising the step of stretching the film in a length director after the step of deforming the film in the tenter. The method of claim 13, further comprising the step of adjusting at least one of the plugs. The method of claim 13 further comprising the step of winding the film. The method of claim 13, wherein the film comprises a multilayer film. The method of claim 13, wherein the transverse network thickness profile in the measuring step comprises a solid thickness profile. The method of claim 13, wherein the transverse network thickness profile in the measuring step comprises an optical thickness profile. The method of claim 14, wherein the adjusting step comprises selectively positioning a channel stop at a lateral network location corresponding to a thick or thin point on the film.