WO2013146397A1 - Method for manufacturing long obliquely stretched film - Google Patents

Abstract

A method for manufacturing a long obliquely stretched film has an obliquely stretching step in which both ends of a supplied long film in the width direction thereof are gripped by grippers arranged at equal intervals, the long film is conveyed while the grippers are moved at a constant speed along opposing rails, and the long film is stretched in the direction oblique to the width direction by changing the conveyance direction of the long film during the conveyance. At the position at which the obliquely stretching step terminates, a line which connects opposing grippers is substantially parallel to the width direction of the long obliquely stretched film.

Description

Manufacturing method of long diagonally stretched film

The present invention relates to a method for producing a long obliquely stretched film in which a long obliquely stretched film is produced by stretching a long film in an oblique direction with respect to the width direction.

A stretched film formed by stretching a resin is used as an optical film that performs various optical functions in various display devices by utilizing its optical anisotropy. For example, in a liquid crystal display device, the stretched film is used as an optical compensation film for optical compensation such as anti-coloring and viewing angle expansion, or by bonding the stretched film and a polarizer, It is known to use as a retardation film that also serves as a polarizing plate protective film.

On the other hand, in recent years, a self-luminous display device such as an organic EL (electroluminescence) display device has attracted attention as a new display device. The self-luminous display device has a room for suppressing power consumption with respect to the liquid crystal display device in which the backlight is always turned on. Furthermore, in a self-luminous display device such as an organic EL display device in which a light source corresponding to each color is turned on, it is not necessary to install a color filter that causes a reduction in contrast, so that the contrast can be further increased. .

However, in an organic EL display device, a reflector such as an aluminum plate is provided on the back side of the display in order to increase the light extraction efficiency. Therefore, external light incident on the display is reflected by the reflector and the image is reflected. There is a problem that the contrast of the image is lowered.

Therefore, in order to improve contrast of light and darkness by preventing external light reflection, it is known that the stretched film and a polarizer are bonded to form a circularly polarizing plate, and this circularly polarizing plate is used on the surface side of the display. At this time, the circularly polarizing plate is obtained by laminating the polarizer and the stretched film so that the in-plane slow axis of the stretched film is inclined at a desired angle with respect to the transmission axis of the polarizer. It is formed.

However, a general polarizer (polarizing film) is obtained by stretching at a high magnification in the transport direction, and its transmission axis coincides with the width direction. On the other hand, a conventional retardation film (stretched film) is produced by longitudinal stretching or lateral stretching, and in principle, the in-plane slow axis is in the direction of 0 ° or 90 ° with respect to the longitudinal direction of the film. For this reason, in order to incline the transmission axis of the polarizer and the slow axis of the stretched film at a desired angle as described above, the long polarizing film and / or the stretched film are cut out at a specific angle and the film pieces are separated from each other. A batch method in which sheets are bonded one by one has to be employed, and problems such as deterioration in productivity and reduction in product yield due to adhesion of chips and the like have been cited as problems.

On the other hand, the film is stretched in a desired angle direction (obliquely) with respect to the long direction, and the direction of the slow axis is not 0 ° or 90 ° with respect to the long direction of the film. Various methods for producing a long retardation film that can be freely controlled have been proposed (see, for example, Patent Documents 1 to 3). In these methods, the resin film is unwound from a direction different from the winding direction of the stretched film, and both ends of the resin film are gripped by a pair of gripping tools and conveyed. And the resin film is extended | stretched in the diagonal direction by changing the conveyance direction of a resin film in the middle. Thereby, the elongate stretched film which has a slow axis in the desired angle of more than 0 degree and less than 90 degrees with respect to the elongate direction is manufactured.

By using a stretched film whose slow axis is inclined with respect to the long direction, a long polarizing film and a stretched film are attached in a roll-to-roll manner instead of conventional batch-type bonding. In addition, a circularly polarizing plate can be manufactured. As a result, the productivity of the circularly polarizing plate can be dramatically improved, and the yield can be greatly improved.

JP 2008-80674 A JP 2009-78474 A JP 2010-173261 A

In general, in a stretching apparatus used when stretching a resin film in the width direction, both ends of the resin film are gripped by gripping tools, and the gripping tools at both ends are moved along a travel path such as a rail. The stretching is performed by changing (expanding) the distance between the gripping tools. In such a stretching apparatus in the width direction, the position of the pair of gripping tools that grip both ends at the start of gripping is a position that is parallel to the width direction. Since the gripping tools at both ends in the stretching process move at the same distance at a constant speed, the positional relationship of the gripping tool that was in a positional relationship parallel to the width direction at the gripping start position will not change until the gripping end (open position). Absent.

However, in the apparatus for stretching the resin film in the oblique direction as described above, the rail to which the gripping tool is attached has a bent portion, and the moving distance of the gripping tool that grips both ends of the bent portion is different. The resin film is stretched obliquely by the gripping tool that becomes shorter. Therefore, even if the left and right gripping tools are aligned in the width direction of the long film at the grip start position and the entrance to the bent portion, that is, the pair of gripping tools that grip both ends are positioned substantially parallel to the width direction of the film. Even if it is in the relationship, the position of the pair of gripping tools that was initially in a positional relationship parallel to the width direction inevitably has an oblique positional relationship with respect to the width direction of the film at the exit of the bent portion.

As such, the principle of the oblique stretching apparatus cannot be avoided, but the movement distance of the right and left gripping tools is different, so the position of the gripping tool that grips both ends of the film after the diagonal stretching process is finished It turned out that it was a problem that it shifted in the direction. In other words, the film that has been subjected to the oblique stretching process at the bent portion is conveyed with both ends held in the same manner as a normal widthwise stretching device, and the film is gradually cooled to fix the orientation direction in the film. In some cases, the orientation direction is adjusted by further stretching in the width direction.

At that time, if the positions of the left and right gripping tools after the oblique stretching process are shifted in the film transport direction, the straight portion after the exit of the bent portion, that is, when fixing the orientation direction or in the width direction In the process of adjusting the orientation direction by stretching, a non-uniform stress is applied in the width direction of the film by the gripping tool shifted in the transport direction, and a long stretched film having uniform retardation characteristics cannot be obtained. It turns out that a problem occurs.

In the present invention, a long diagonally stretched film having a uniform retardation characteristic can be obtained by preventing a non-uniform stress from being applied in the width direction of the film by a gripper after the oblique stretching process is finished. It aims at providing the manufacturing method of an isometrically stretched film.

In order to achieve the above object, the present invention grips both ends in the width direction of a long film to be fed by each gripping tool arranged at equal intervals, and each gripping tool is arranged along a facing rail. While transporting the long film while moving at a high speed, the long film is stretched in an oblique direction with respect to the width direction by changing the transport direction of the long film in the middle, and the long oblique stretched film In the manufacturing method of a long obliquely stretched film having an oblique stretching step, a straight line connecting opposing gripping tools is substantially parallel to the width direction of the long obliquely stretched film at the end position of the oblique stretching step. Features.

In the above method for producing a long obliquely stretched film, it is desirable that a straight line connecting opposing grippers is substantially parallel to the width direction of the long film at the start position of the obliquely stretched process.

Further, in the manufacturing method of the above-mentioned long oblique stretched film, in order to make the straight line connecting the opposing gripping tools substantially parallel to the width direction of the long film at the end position of the oblique stretching step, For this, the difference between the lengths of the opposing rails may be an integral multiple of the pitch of the gripping tool.

Also, in the above-described method for producing a long obliquely stretched film, it is desirable that the length of the opposed rail is variable.

In the above method for producing a long obliquely stretched film, the rail preferably has a curved rail portion that can be arbitrarily bent.

According to the present invention, by aligning the left and right gripping tools at the end position of the oblique stretching process, the gripping tool does not apply uneven stress in the width direction of the long diagonally stretched film after the oblique stretching process, and the uniform A long obliquely stretched film having retardation characteristics can be obtained. Furthermore, wrinkles and the like are less likely to occur by aligning the left and right grippers at the start position of the oblique stretching process.

It is a top view which shows typically the structure of the outline of the manufacturing apparatus of the elongate stretched film which concerns on embodiment of this invention. It is a top view which shows typically the other structure of the said manufacturing apparatus. It is a top view which shows typically the other structure of the said manufacturing apparatus. It is a top view which shows typically an example of the rail pattern of the extending | stretching part of the said manufacturing apparatus. It is sectional drawing which shows the schematic structure of the organic electroluminescent image display apparatus which concerns on the said embodiment. It is a top view which shows typically an example of the rail pattern of the extending | stretching part after the initial installation adjustment which concerns on the said embodiment. It is a top view which shows typically an example of the rail pattern after a feed angle change in FIG. It is a top view which shows typically an example of the rail pattern after rail length change in FIG.

Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not limited to these.

The manufacturing method of the elongate stretched film which concerns on this embodiment is the elongate which has an in-plane slow axis in arbitrary angles with respect to the width direction of the elongate film after extending | stretching the elongate film diagonally. It is a manufacturing method of a stretched film.

Here, the “long” means a film having a length of at least about 5 times the width of the film, preferably a length of 10 times or more, and specifically wound in a roll shape. It is possible to have a length (film roll) that can be stored or transported. In the manufacturing method of a long film, a film can be manufactured to desired arbitrary length by manufacturing a film continuously. In addition, the manufacturing method of a elongate stretched film, after forming a elongate film, this is wound up around a core once, and it is set as a wound body (long film original fabric), and a long film is slanted from this wound body An obliquely stretched film may be produced by supplying it to the stretching process, or by continuously feeding the obliquely stretched film from the film forming process to the obliquely stretched process without winding up the long film after film formation. It may be manufactured. Performing the film forming step and the oblique stretching step continuously can feed back the film thickness and optical value results of the stretched film, change the film forming conditions, and obtain a desired long stretched film. Therefore, it is preferable.

In the method for producing a long stretched film according to the present embodiment, a long stretched film having a slow axis at an angle of more than 0 ° and less than 90 ° with respect to the width direction of the film is produced. Here, the angle with respect to the width direction of the film is an angle in the film plane. Since the slow axis is usually expressed in the stretching direction or a direction perpendicular to the stretching direction, the production method according to this embodiment performs stretching at an angle of more than 0 ° and less than 90 ° with respect to the width direction of the film. Thus, a long stretched film having such a slow axis can be produced. The angle formed by the width direction of the long stretched film and the slow axis, that is, the orientation angle, can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °.

As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by making the positions of the gripping tools at both ends at the end of the oblique stretching process parallel to the width direction of the film. It was. And further examination was advanced and it came to complete this invention based on these knowledge.

That is, according to the embodiment of the present invention, both ends in the width direction of the supplied long film are gripped by each gripping tool arranged at equal intervals, and each gripping tool is fixed at a constant speed along the opposing rail. The long film is transported while being moved at the same time, and the long film is stretched in an oblique direction with respect to the width direction by changing the transport direction of the long film in the middle, In the manufacturing method of a long obliquely stretched film having an oblique stretching step, the straight line connecting the opposing gripping tools is substantially parallel to the width direction of the long obliquely stretched film at the end position of the oblique stretching step. It is a manufacturing method of long slanting stretched film. Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings as appropriate. In the present embodiment, when “long film” is described, it means a long film before oblique stretching.

<About long film>
First, the long film used as the extending | stretching object in this embodiment is demonstrated.

The long film to be stretched in the method for producing a long obliquely stretched film of the present embodiment (details will be described later) is not particularly limited as long as it is a film made of a thermoplastic resin. For example, when the stretched film is used for optical applications, a film made of a resin having a property transparent to a desired wavelength is preferable. Such resins include polycarbonate resins, polyether sulfone resins, polyethylene terephthalate resins, polyimide resins, polymethyl methacrylate resins, polysulfone resins, polyarylate resins, polyethylene resins, polyvinyl chloride resins. Examples thereof include resins, olefin polymer resins having an alicyclic structure (alicyclic olefin polymer resins), and cellulose ester resins.

Among these, polycarbonate resins, alicyclic olefin polymer resins, and cellulose ester resins are preferable from the viewpoints of transparency and mechanical strength. Among these, alicyclic olefin polymer resins and cellulose ester resins, which can easily adjust the phase difference when an optical film is used, are more preferable.

<Long film production method>
The long film of this embodiment made of the above-described resin can be formed by either the solution casting method or the melt casting method described below. Hereinafter, each film forming method will be described. In addition, below, although the case where a cellulose ester-type resin film is formed into a film as a long film is demonstrated, for example, it is applicable also to film forming of another resin film.

[Solution casting method]
From the viewpoints of suppression of film coloring, suppression of foreign matter defects, suppression of optical defects such as die lines, excellent film flatness, and transparency, it is preferable to form a long film by a solution casting method.

(Organic solvent)
An organic solvent useful for forming a dope when the cellulose ester resin film according to this embodiment is produced by a solution casting method is used without limitation as long as it dissolves cellulose acetate and other additives simultaneously. be able to.

For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels and becomes easy to peel off from the metal support. When the proportion of alcohol is small, the role of promoting cellulose acetate dissolution in non-chlorine organic solvent systems There is also.

In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, at least 15 to 45 mass in total of at least three kinds of acrylic resin, cellulose ester resin, and acrylic particles are used. It is preferable that the dope composition is dissolved in%.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Of these, ethanol is preferable because the stability of the dope can be ensured, the boiling point is relatively low, and the drying property is good.

(Solution casting)
The cellulose ester resin film according to this embodiment can be produced by a solution casting method. In the solution casting method, a step of preparing a dope by dissolving a resin and an additive in a solvent, a step of casting the dope on a belt-like or drum-like metal support, and a step of drying the cast dope as a web , A step of peeling from the metal support, a step of stretching or maintaining the width, a step of further drying, and a step of winding up the finished film.

It is preferable that the concentration of cellulose acetate in the dope is high because the drying load after casting on the metal support can be reduced. However, if the concentration is too high, the load during filtration increases and the filtration accuracy deteriorates. The concentration that achieves both of these is preferably 10 to 35% by mass, and more preferably 15 to 25% by mass. The metal support in the casting (casting) step preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support.

The surface temperature of the metal support in the casting process is set to −50 ° C. to a temperature at which the solvent boils and does not foam. A higher support temperature is preferable because the web can be dried at a higher speed, but if it is too high, the web may foam or the flatness may deteriorate.

A preferable support temperature is appropriately determined at 0 to 100 ° C., and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent. The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use hot water because heat is efficiently transmitted and the time until the temperature of the metal support becomes constant is shortened.

When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there is a case where wind at a temperature higher than the target temperature is used while preventing foaming. is there.

Particularly, it is preferable to efficiently dry by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

In order for the cellulose ester resin film to exhibit good planarity, the amount of residual solvent when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or It is 60 to 130% by mass, and particularly preferably 20 to 30% by mass or 70 to 120% by mass. Here, the residual solvent amount is defined by the following equation.
Residual solvent amount (% by mass) = {(MN) / N} × 100
In addition, M is the mass (g) of the sample collected at any time during or after the production of the web or film, and N is the mass (g) after heating M at 115 ° C. for 1 hour.

In the drying step of the cellulose resin film, the web is peeled off from the metal support, and further dried, and the residual solvent amount is preferably 1% by mass or less, more preferably 0.1% by mass or less. Particularly preferably, it is 0 to 0.01% by mass or less.

In the film drying process, generally, a roll drying method (a method in which webs are alternately passed through a plurality of rolls arranged above and below) and a method of drying while transporting the web by a tenter method are employed.

[Melt casting method]
The melt casting method is preferable from the viewpoint that it becomes easy to reduce the retardation Rt in the thickness direction of the film after oblique stretching, which will be described later, and that the amount of residual volatile components is small and the dimensional stability of the film is excellent. Is the law. In the melt casting method, a composition containing an additive such as a resin and a plasticizer is heated and melted to a temperature showing fluidity, and then a melt containing fluid cellulose acetate is cast to form a film. How to do. Methods formed by melt casting can be classified into melt extrusion (molding) methods, press molding methods, inflation methods, injection molding methods, blow molding methods, stretch molding methods, and the like. Among these, the melt extrusion method that can obtain a film having excellent mechanical strength and surface accuracy is preferable. Moreover, it is preferable that the plurality of raw materials used in the melt extrusion method are usually kneaded and pelletized in advance.

The pelletization may be performed by a known method. For example, dry cellulose acetate, plasticizer, and other additives are fed to the extruder with a feeder, kneaded using a single or twin screw extruder, extruded into a strand from a die, water-cooled or air-cooled, and cut. Can be pelletized.

Additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. Moreover, in order to mix a small amount of additives, such as particle | grains and antioxidant, uniformly, it is preferable to mix beforehand.

The extruder is preferably processed at as low a temperature as possible so that it can be pelletized so as to suppress the shearing force and prevent the resin from deteriorating (molecular weight reduction, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

Film formation is performed using the pellets obtained as described above. Of course, the raw material powder can be directly fed to the extruder by a feeder without being pelletized to form a film as it is.

Using a single-screw or twin-screw type extruder, the melting temperature at the time of extrusion is about 200 to 300 ° C, filtered through a leaf disk type filter, etc. to remove foreign matter, and then formed into a film from the T die. Then, the film is nipped between the cooling roll and the elastic touch roll and solidified on the cooling roll.

When the pellets are introduced from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

The extrusion flow rate is preferably carried out stably by introducing a gear pump. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances. The stainless steel fiber sintered filter is a united stainless steel fiber body that is intricately intertwined and compressed, and the contact points are sintered and integrated. The density of the fiber is changed depending on the thickness of the fiber and the amount of compression, and the filtration accuracy is improved. Can be adjusted.

Additives such as plasticizers and particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

The film temperature on the touch roll side when the film is nipped between the cooling roll and the elastic touch roll is preferably Tg (glass transition temperature) or higher and Tg + 110 ° C. or lower. A known roll can be used as the roll having an elastic surface used for such a purpose.

The elastic touch roll is also called a pinching rotator. As the elastic touch roll, a commercially available one can be used.

When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

In addition, the long film formed by each film forming method described above may be a single layer or a laminated film of two or more layers. The laminated film can be obtained by a known method such as a coextrusion molding method, a co-casting molding method, a film lamination method, or a coating method. Of these, the coextrusion molding method and the co-casting molding method are preferable.

<Specifications of long film>
The length of the long film in this embodiment is preferably 30 to 300 μm, more preferably 40 to 150 μm. In this embodiment, the thickness unevenness σm in the flow direction (conveying direction) of the long film supplied to the stretching zone described later maintains the film take-up tension at the oblique stretching tenter inlet described later, and the orientation angle. From the viewpoint of stabilizing optical properties such as retardation and retardation, it is preferably less than 0.30 μm, preferably less than 0.25 μm, more preferably less than 0.20 μm. When the thickness unevenness σm in the flow direction of the long film is 0.30 μm or more, variations in optical properties such as retardation and orientation angle of the long stretched film may be deteriorated.

Further, a film having a thickness gradient in the width direction may be supplied as the long film. The thickness gradient of the long film is empirically determined by stretching a film with various thickness gradients experimentally so that the film thickness at the position where the stretching in the subsequent process is completed can be made the most uniform. Can be sought. The gradient of the thickness of the long film can be adjusted, for example, so that the end portion on the thick side is thicker by about 0.5 to 3% than the end portion on the thin side.

The width of the long film is not particularly limited, but can be 500 to 4000 mm, preferably 1000 to 2000 mm.

The preferable elastic modulus at the stretching temperature at the time of oblique stretching of the long film is 0.01 MPa or more and 5000 MPa or less, more preferably 0.1 MPa or more and 500 MPa or less, expressed as Young's modulus. If the elastic modulus is too low, the shrinkage rate during and after stretching becomes low and wrinkles are difficult to disappear. On the other hand, if the elastic modulus is too high, the tension applied during stretching increases, and it is necessary to increase the strength of the portions that hold the side edges of the film, which increases the load on the tenter in the subsequent step.

As the long film, a non-oriented film may be used, or a film having an orientation in advance may be supplied. Further, if necessary, the distribution in the width direction of the orientation of the long film may be bow-shaped, so-called bowing. In short, the orientation state of the long film can be adjusted so that the orientation of the film at the position where the subsequent stretching has been completed can be made desirable.

<Manufacturing method and manufacturing apparatus for long diagonally stretched film>
Next, the manufacturing method and manufacturing apparatus of a long diagonally stretched film which manufactures a long diagonally stretched film by extending | stretching the long film mentioned above in the diagonal direction with respect to the width direction are demonstrated.

(Outline of the device)
FIG. 1 is a plan view schematically showing a schematic configuration of a manufacturing apparatus 1 for a long obliquely stretched film. FIG. 2 is a plan view schematically showing another configuration of the manufacturing apparatus 1, and FIG. 3 is a plan view schematically showing still another configuration of the manufacturing apparatus 1. As shown in FIG. 1, the manufacturing apparatus 1 according to this embodiment includes, in order from the upstream side in the transport direction of a long film, a film feeding unit 2, a transport direction changing unit 3, a guide roll 4, a stretching unit 5, A guide roll 6, a conveyance direction changing unit 7, and a film winding unit 8 are provided. The details of the extending portion 5 will be described later.

The film feeding unit 2 feeds the above-described long film and supplies it to the stretching unit 5. This film supply part 2 may be comprised separately from the film-forming apparatus of a long film, and may be comprised integrally. In the former case, after the long film is formed, the long film is drawn out from the film paying part 2 by loading the film wound part 2 into the film paying part 2 once wound around the core. On the other hand, in the latter case, the film feeding unit 2 feeds the long film to the stretching unit 5 without winding the long film after the long film is formed.

The conveyance direction changing unit 3 changes the conveyance direction of the long film fed from the film feeding unit 2 to a direction toward the entrance of the stretching unit 5 as an oblique stretching tenter. Such a conveyance direction change part 3 is comprised including the turntable which rotates the turn bar which changes the conveyance direction by, for example, returning while conveying a film, and the turn bar in the surface parallel to a film.

By changing the transport direction of the long film as described above by the transport direction changing unit 3, the width of the entire manufacturing apparatus 1 can be made narrower, and the film feed position and angle are finely controlled. Thus, it becomes possible to obtain a long stretched film with small variations in film thickness and optical value. Further, if the film feeding unit 2 and the conveyance direction changing unit 3 can be moved (slidable and turnable), the left and right clips (gripping tools) sandwiching both ends of the long film in the width direction in the stretching unit 5 can be used. It is possible to effectively prevent the biting into the film.

In addition, the above-described film feeding unit 2 may be slidable and turnable so that a long film can be fed out at a predetermined angle with respect to the entrance of the stretching unit 5. In this case, as shown in FIGS. 2 and 3, it is possible to adopt a configuration in which the installation of the transport direction changing unit 3 is omitted.

At least one guide roll 4 is provided on the upstream side of the stretching portion 5 in order to stabilize the track during running of the long film. In addition, the guide roll 4 may be comprised by a pair of upper and lower rolls which pinch | interpose a film, and may be comprised by several roll pairs. The guide roll 4 closest to the entrance of the extending portion 5 is a driven roll that guides the travel of the film, and is rotatably supported via a bearing portion (not shown). A known material can be used as the material of the guide roll 4. In order to prevent the film from being damaged, it is preferable to reduce the weight of the guide roll 4 by applying a ceramic coat on the surface of the guide roll 4 or applying chrome plating to a light metal such as aluminum.

Further, it is preferable that one of the rolls upstream of the guide roll 4 closest to the entrance of the extending portion 5 is nipped by pressing the rubber roll. By setting it as such a nip roll, it becomes possible to suppress the fluctuation | variation of the drawing tension | tensile_strength in the flow direction of a film.

A pair of bearing portions at both ends (left and right) of the guide roll 4 closest to the entrance of the extending portion 5 includes a first tension detecting device as a film tension detecting device for detecting the tension generated in the film in the roll, A second tension detecting device is provided. For example, a load cell can be used as the film tension detection device. As the load cell, a known tensile or compression type can be used. A load cell is a device that detects a load acting on an applied point by converting it into an electrical signal using a strain gauge attached to the strain generating body.

The load cell is installed in the left and right bearing portions of the guide roll 4 closest to the entrance of the extending portion 5, whereby the force of the running film on the roll, that is, in the film traveling direction generated in the vicinity of both side edges of the film. The tension is detected independently on the left and right. In addition, a strain gauge may be directly attached to a support that constitutes the bearing portion of the roll, and a load, that is, a film tension may be detected based on the strain generated in the support. The relationship between the generated strain and the film tension is measured in advance and is known.

When the position and the transport direction of the film supplied from the film feeding unit 2 or the transport direction changing unit 3 to the stretching unit 5 are shifted from the position toward the entrance of the stretching unit 5 and the transport direction, according to the amount of shift, A difference will arise in the tension | tensile_strength near the both-sides edge of the film in the guide roll 4 nearest to the entrance of the extending | stretching part 5. FIG. Therefore, by providing the above-described film tension detecting device and detecting the above-described tension difference, the degree of the deviation can be determined. That is, if the transport position and transport direction of the film are appropriate (if it is the position and direction toward the entrance of the stretching unit 5), the load acting on the guide roll 4 is roughly uniform at both ends in the axial direction. If not appropriate, there will be a difference in film tension between left and right.

Therefore, the position and the transport direction of the film (angle with respect to the entrance of the stretching unit 5) are changed by, for example, the transport direction changing unit 3 so that the difference in film tension between the left and right sides of the guide roll 4 closest to the entrance of the stretching unit 5 becomes equal. When properly adjusted, the film can be stably held by the gripping tool at the entrance of the stretching portion 5, and the occurrence of obstacles such as detachment of the gripping tool can be reduced. Furthermore, the physical properties in the width direction of the film after oblique stretching by the stretching portion 5 can be stabilized.

At least one guide roll 6 is provided on the downstream side of the stretching portion 5 in order to stabilize the trajectory during travel of the film (long oblique stretching film) that is obliquely stretched in the stretching portion 5.

The transport direction changing unit 7 changes the transport direction of the stretched film transported from the stretching unit 5 to a direction toward the film winding unit 8. The conveyance direction change part 7 can be comprised by the folding | turning mechanism which returns the film after extending | stretching at least 1 time along the direction parallel or perpendicular | vertical to a extending | stretching direction within the surface of a long diagonally stretched film, for example.

Here, in order to cope with fine adjustment of the orientation angle (in-plane slow axis direction of the film) and product variations, the film traveling direction at the entrance of the stretching portion 5 and the film traveling direction at the exit of the stretching portion 5 It is necessary to adjust the angle between the two.

Moreover, it is preferable from the viewpoint of productivity and yield that the film formation and oblique stretching are continuously performed. When the film forming process, the oblique stretching process, and the winding process are continuously performed, the traveling direction of the film is changed by the transport direction changing unit 3 and / or the transport direction changing unit 7, and the film is formed by the film forming process and the winding process. 1, that is, as shown in FIGS. 1 and 3, the traveling direction (feeding direction) of the film fed from the film feeding unit 2 and the film just before being wound by the film winding unit 8 By matching the traveling direction (winding direction), the width of the entire apparatus with respect to the film traveling direction can be reduced.

Note that the film traveling direction and the film winding process do not necessarily coincide with each other in the film forming process and the film winding process, but the transport direction changing unit 3 and the film feeding unit 2 and the film winding unit 8 are arranged so that the film feeding unit 2 and the film winding unit 8 do not interfere with each other. It is preferable that the traveling direction of the film is changed by the transport direction changing unit 7.

The transport direction changing units 3 and 7 as described above can be realized by a known method such as using an air flow roll.

The film take-up unit 8 takes up a film conveyed from the stretching unit 5 via the conveyance direction changing unit 7, and includes, for example, a winder device, an accumulator device, and a drive device. It is preferable that the film winding unit 8 has a structure that can be slid in the horizontal direction in order to adjust the film winding position.

The film take-up unit 8 can finely control the film take-up position and angle so that the film can be taken at a predetermined angle with respect to the outlet of the stretching unit 5. As a result, it is possible to obtain a long stretched film with small variations in film thickness and optical value. In addition, it is possible to effectively prevent wrinkling of the film and to improve the winding property of the film, so that the film can be wound up in a long length. In this embodiment, the take-up tension T (N / m) of the stretched film is preferably adjusted to 100 N / m <T <700 N / m, preferably 150 N / m <T <250 N / m.

When the take-up tension is 100 N / m or less, sagging and wrinkles of the film are likely to occur, and the retardation and orientation angle profile in the film width direction are also deteriorated. On the other hand, when the take-up tension is 700 N / m or more, the variation of the orientation angle in the film width direction may be deteriorated, and the width yield (taken efficiency in the width direction) may be deteriorated.

In the present embodiment, it is preferable to control the fluctuation of the take-up tension T with an accuracy of less than ± 5%, preferably less than ± 3%. When the variation in the take-up tension T is ± 5% or more, the variation in the optical characteristics in the width direction and the flow direction (conveying direction) increases. As a method of controlling the fluctuation of the take-up tension T within the above range, the load applied to the first roll (guide roll 6) on the outlet side of the stretching section 5, that is, the film tension is measured, and the value becomes constant. Thus, the method of controlling the rotational speed of a take-up roll (winding roll of the film winding part 8) by a general PID control system is mentioned. Examples of the method for measuring the load include a method in which a load cell is attached to the bearing portion of the guide roll 6 and a load applied to the guide roll 6, that is, a film tension is measured. As the load cell, a known tensile type or compression type can be used.

The stretched film is released from the outlet of the stretching unit 5 by being held by the gripping tool of the stretching unit 5 and trimmed at both ends (both sides) of the film that has been gripped by the gripping tool. It is wound up by (winding roll) and becomes a wound body of a long stretched film. Note that the above trimming may be performed as necessary.

In addition, before winding the long stretched film, for the purpose of preventing blocking between the films, the masking film may be overlapped with the long stretched film and wound simultaneously, or at least of the long stretched film overlapping by winding. You may wind up, sticking a tape etc. on the edge of one (preferably both). The masking film is not particularly limited as long as it can protect the long stretched film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

(Details of stretched part)
Next, the detail of the extending | stretching part 5 mentioned above is demonstrated. FIG. 4 is a plan view schematically showing an example of the rail pattern of the extending portion 5. However, this is an example, and the present invention is not limited to this.

The apparatus 1 for producing a long stretched film is performed using a tenter (an oblique stretching machine) capable of oblique stretching as the stretching section 5. This tenter is an apparatus that heats a long film to an arbitrary temperature at which it can be stretched and obliquely stretches it. This tenter is composed of a heating zone Z, a pair of rails Ri and Ro on the left and right, and a number of gripping tools Ci and Co that travel along the rails Ri and Ro (in FIG. 4, a set of gripping tools). Only). Details of the heating zone Z will be described later. Each of the rails Ri and Ro is configured by connecting a plurality of rail portions with connecting portions (white circles in FIG. 4 are examples of connecting portions). The gripping tool Ci / Co is composed of a clip that grips both ends of the film in the width direction.

In FIG. 4, the running direction (running direction before stretching) D1 of the long film when fed into the stretching device is the running direction (running direction after stretching) D2 of the long stretched film when fed from the stretching device. The feeding angle θi is different from the running direction D2 after stretching. The feeding angle θi can be arbitrarily set to a desired angle in the range of more than 0 ° and less than 90 °.

Thus, since the traveling direction D1 before stretching and the traveling direction D2 after stretching are different, the rail pattern of the tenter has an asymmetric shape on the left and right. And according to orientation angle (theta) given to the elongate stretched film which should be manufactured, a draw ratio, etc., a rail pattern can be adjusted now manually or automatically. In the oblique stretching machine used in the present embodiment, it is preferable that the positions of the rail portions and the rail connecting portions constituting the rails Ri and Ro can be freely set and the rail pattern can be arbitrarily changed.

In the present embodiment, the tenter gripping tool Ci · Co travels at a constant speed with a constant interval from the front and rear gripping tools Ci · Co. The traveling speed of the gripping tool Ci / Co can be selected as appropriate, but is usually 1 to 150 m / min. The difference in travel speed between the pair of left and right grippers Ci / Co is usually 1% or less, preferably 0.5% or less, more preferably 0.1% or less of the travel speed. This is because if there is a difference in the traveling speed between the left and right sides of the film at the exit of the stretching process, wrinkles and shifts will occur at the exit of the stretching process, so the speed difference between the right and left gripping tools is required to be substantially the same speed. Because. In general tenter devices, etc., there are speed irregularities that occur in the order of seconds or less depending on the period of the sprocket teeth that drive the chain, the frequency of the drive motor, etc. This does not correspond to the speed difference described in the embodiment of the invention.

In the oblique stretching machine used in the manufacturing method according to the embodiment of the present invention, a rail that regulates the trajectory of the gripping tool is often required to have a high bending rate, particularly in a portion where the film is transported obliquely. In order to avoid interference between gripping tools due to sudden bending or local stress concentration, it is desirable that the trajectory of the gripping tool draws a smooth curve at the bent portion (curved portion).

As described above, the obliquely stretched tenter used for imparting the oblique orientation to the long film can freely set the orientation angle of the film by changing the rail pattern in various ways, and further, the orientation axis of the film It is preferred that the tenter be capable of orienting the (slow axis) in the left and right direction with high precision across the film width direction and controlling the film thickness and retardation with high precision.

Next, the stretching operation in the stretching unit 5 will be described. Both ends of the long film are gripped by the left and right grippers Ci · Co, and are conveyed in the heating zone Z as the grippers Ci • Co travel. The left and right gripping tools Ci and Co are opposed to a direction substantially perpendicular to the film traveling direction (traveling direction D1 before stretching) at the entrance of the stretching section 5 (position A in the drawing). The film travels on the asymmetric rails Ri and Ro, and the film held at the exit portion (position B in the drawing) at the end of stretching is released. The film released from the gripping tool Ci · Co is wound around the core by the film winding portion 8 described above. Each of the pair of rails Ri and Ro has an endless continuous track, and the grippers Ci and Co that have released the film at the exit portion of the tenter travel on the outer rail and sequentially return to the entrance portion. It is supposed to be.

At this time, since the rails Ri and Ro are asymmetrical in the left and right directions, in the example of FIG. 4, the left and right gripping tools Ci and Co, which are opposed to each other at the position A in the drawing, move along the rails Ri and Ro. The gripping tool Ci traveling on the Ri side is in a positional relationship that advances relative to the gripping tool Co traveling on the rail Ro side.

That is, among gripping tools Ci and Co that are opposed to a direction substantially perpendicular to the traveling direction D1 before stretching of the film at the position A in the figure, one gripping tool Ci is positioned at the position B at the end of stretching of the film. First, the straight line connecting the grippers Ci and Co is inclined by an angle θL with respect to a direction substantially perpendicular to the running direction D2 after the film is stretched. With the above operation, the long film is obliquely stretched at an angle of θL with respect to the width direction. Here, “substantially vertical” indicates that the angle is in a range of 90 ± 1 °.

Next, the details of the heating zone Z will be described. The heating zone Z of the stretching section 5 is composed of a preheating zone Z1, a stretching zone Z2, and a heat fixing zone Z3. In the stretching unit 5, the film gripped by the gripping tool Ci / Co passes through the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 in this order.

The preheating zone Z1 refers to a section in which the gripping tool Ci / Co that grips both ends of the film travels at the left and right (in the film width direction) at a constant interval at the entrance of the heating zone Z.

The stretching zone Z2 refers to a section from when the gap between the gripping tools Ci and Co that grips both ends of the film opens until a predetermined gap is reached. At this time, the oblique stretching as described above is performed, but the stretching may be performed in the longitudinal direction or the transverse direction before and after the oblique stretching as necessary.

The heat fixing zone Z3 is a section in which the interval between the gripping tools Ci and Co after the stretching zone Z2 becomes constant again, and refers to a section in which the gripping tools Ci and Co at both ends travel while being parallel to each other.

The stretched film passes through the heat setting zone Z3 and then passes through a section (cooling zone) in which the temperature in the zone is set to be equal to or lower than the glass transition temperature Tg (° C.) of the thermoplastic resin constituting the film. May be. At this time, considering the shrinkage of the film due to cooling, a rail pattern that narrows the gap between the gripping tools Ci and Co facing each other in advance may be used.

The temperature of the preheating zone Z1 is set to Tg to Tg + 30 ° C, the temperature of the stretching zone Z2 is set to Tg to Tg + 30 ° C, and the temperature of the heat setting zone Z3 is set to Tg-30 to Tg ° C with respect to the glass transition temperature Tg of the thermoplastic resin. Is preferred.

In addition, in order to control the thickness unevenness of the film in the width direction, a temperature difference may be given in the width direction in the stretching zone Z2. In order to create a temperature difference in the width direction in the stretching zone, a method of adjusting the opening degree of the nozzle for sending warm air into the temperature-controlled room so as to make a difference in the width direction, or controlling the heating by arranging the heaters in the width direction is known. Can be used. The lengths of the preheating zone Z1, the stretching zone Z2, and the heat setting zone Z3 can be appropriately selected. The length of the preheating zone Z1 is usually 100 to 150% with respect to the length of the stretching zone Z2, and the length of the heat setting zone Z3. Is usually 50 to 100%.

When the width of the film before stretching is Wo (mm) and the width of the film after stretching is W (mm), the draw ratio R (W / Wo) in the stretching step is preferably 1.3 to 3. 0, more preferably 1.5 to 2.8. When the draw ratio is in this range, the thickness unevenness in the width direction of the film is preferably reduced. In the stretching zone Z2 of the oblique stretching tenter, if the stretching temperature is differentiated in the width direction, the width direction thickness unevenness can be further improved. In addition, said draw ratio R is equal to a magnification (W2 / W1) when the interval W1 between both ends of the clip held at the tenter inlet portion becomes the interval W2 at the tenter outlet portion.

<Quality of long stretched film>
In the long stretched film obtained by the production method according to the embodiment of the present invention, the orientation angle θ is inclined in the range of, for example, greater than 0 ° and less than 90 ° with respect to the winding direction, and is at least 1300 mm. In the width, it is preferable that the variation in the in-plane retardation Ro in the width direction is 3 nm or less and the variation in the orientation angle θ is less than 0.6 °.

That is, in the long stretched film obtained by the manufacturing method according to the embodiment of the present invention, the variation in the in-plane retardation Ro is 3 nm or less and preferably 1 nm or less at least 1300 mm in the width direction. By making the variation of the in-plane retardation Ro within the above range, a long stretched film is bonded to a polarizer to form a circularly polarizing plate. When this is applied to an organic EL image display device, external light reflection during black display Color unevenness due to light leakage can be suppressed. In addition, when the long stretched film is used as, for example, a retardation film for a liquid crystal display device, the display quality can be improved.

Moreover, in the long stretched film obtained by the manufacturing method according to the embodiment of the present invention, the variation in the orientation angle θ is less than 0.6 ° and less than 0.4 ° in at least 1300 mm in the width direction. It is preferable. A long stretched film with a variation in orientation angle θ of 0.6 ° or more is bonded to a polarizer to form a circularly polarizing plate, and when this is installed on an image display device such as an organic EL display device, light leakage occurs, and light and dark Contrast may be reduced.

For the in-plane retardation Ro of the long stretched film obtained by the manufacturing method according to the embodiment of the present invention, an optimum value is selected depending on the design of the display device used. Note that Ro is a value obtained by multiplying the difference between the refractive index nx in the in-plane slow axis direction and the refractive index ny in the direction perpendicular to the slow axis by the average thickness d of the film (Ro = (nx −ny) × d).

The average thickness of the long stretched film obtained by the production method according to the embodiment of the present invention is preferably 10 to 200 μm, more preferably 10 to 60 μm, and particularly preferably 10 to 35 μm from the viewpoint of mechanical strength and the like. is there. Moreover, since the thickness nonuniformity of the said elongate stretched film affects the propriety of winding, it is preferable that it is 3 micrometers or less, and it is more preferable that it is 2 micrometers or less.

<Circularly polarizing plate>
In the circularly polarizing plate of this embodiment, a polarizing plate protective film, a polarizer, and a λ / 4 retardation film are laminated in this order, and the slow axis of the λ / 4 retardation film and the absorption axis of the polarizer ( Alternatively, the angle formed with the transmission axis is 45 °. The polarizing plate protective film, the polarizer, and the λ / 4 retardation film correspond to the protective film 313, the polarizer 312, and the λ / 4 retardation film 311 in FIG. 5, respectively. In this embodiment, it is preferable that a long polarizing plate protective film, a long polarizer, and a long λ / 4 retardation film (long stretched film) are laminated in this order.

The circularly polarizing plate of this embodiment is manufactured by using a stretched polyvinyl alcohol doped with iodine or a dichroic dye as a polarizer, and laminating with a configuration of λ / 4 retardation film / polarizer. be able to. The thickness of the polarizer is 5 to 40 μm, preferably 5 to 30 μm, particularly preferably 5 to 20 μm.

The polarizing plate can be produced by a general method. The λ / 4 retardation film subjected to the alkali saponification treatment is preferably bonded to one surface of a polarizer produced by immersing and stretching a polyvinyl alcohol film in an iodine solution using a completely saponified polyvinyl alcohol aqueous solution. .

The polarizing plate can be constituted by further bonding a release film on the opposite surface of the polarizing plate protective film of the polarizing plate. The protective film and the release film are used for the purpose of protecting the polarizing plate at the time of shipping the polarizing plate, product inspection, and the like.

<Organic EL image display device>
FIG. 5 is a cross-sectional view showing a schematic configuration of the organic EL image display device 100 of the present embodiment. The configuration of the organic EL image display device 100 is not limited to this.

The organic EL image display device 100 is configured by forming a circularly polarizing plate 301 on an organic EL element 101 via an adhesive layer 201. The organic EL element 101 includes a metal electrode 112, a light emitting layer 113, a transparent electrode (ITO, etc.) 114, and a sealing layer 115 on a substrate 111 made of glass, polyimide, or the like. The metal electrode 112 may be composed of a reflective electrode and a transparent electrode.

The circularly polarizing plate 301 is formed by laminating a λ / 4 retardation film 311, a polarizer 312, and a protective film 313 in order from the organic EL element 101 side. The polarizer 312 is a λ / 4 retardation film 311 and a protective film 313. It is pinched by. The two are bonded so that the angle formed by the transmission axis of the polarizer 312 and the slow axis of the λ / 4 retardation film 311 made of the long stretched film of this embodiment is about 45 ° (or 135 °). Thus, the circularly polarizing plate 301 is configured.

It is preferable that a cured layer is laminated on the protective film 313. The cured layer not only prevents scratches on the surface of the organic EL image display device, but also has an effect of preventing warpage due to the circularly polarizing plate 301. Further, an antireflection layer may be provided on the cured layer. The thickness of the organic EL element 101 itself is about 1 μm.

In the above configuration, when a voltage is applied to the metal electrode 112 and the transparent electrode 114, electrons are injected into the light emitting layer 113 from the electrode serving as the cathode among the metal electrode 112 and the transparent electrode 114, and the electrode serving as the anode. Holes are injected from and recombined in the light emitting layer 113, whereby visible light emission corresponding to the light emission characteristics of the light emitting layer 113 occurs. The light generated in the light emitting layer 113 is directly or after being reflected by the metal electrode 112 and then extracted to the outside through the transparent electrode 114 and the circularly polarizing plate 301.

Generally, in an organic EL image display device, a metal electrode, a light emitting layer, and a transparent electrode are sequentially laminated on a transparent substrate to form a light emitting element (organic EL element). Here, the light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Structures having various combinations such as a laminate of such a light emitting layer and an electron injection layer made of a perylene derivative, a hole injection layer, a light emitting layer, and a laminate of an electron injection layer are known.

In organic EL image display devices, holes and electrons are injected into the light-emitting layer by applying a voltage to the transparent electrode and metal electrode, and the energy generated by the recombination of these holes and electrons excites the fluorescent material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination on the way is the same as that of a general diode, and as can be expected from this, the current and the light emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

In an organic EL image display device, in order to extract light emitted from the light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

In the organic EL image display device having such a configuration, the light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the light emitting layer transmits light almost completely like the transparent electrode. As a result, the light that is incident from the surface of the transparent substrate when not emitting light, passes through the transparent electrode and the light emitting layer, and is reflected by the metal electrode again exits to the surface side of the transparent substrate. The display surface of the EL image display device looks like a mirror surface.

The circularly polarizing plate of this embodiment is suitable for an organic EL image display device in which such external light reflection is particularly problematic.

That is, when the organic EL element 101 is not emitting light, outside light incident from the outside of the organic EL element 101 due to indoor lighting or the like is absorbed by the polarizer 312 of the circularly polarizing plate 301 and the other half is transmitted as linearly polarized light. Then, the light enters the λ / 4 retardation film 311. The light incident on the λ / 4 retardation film 311 is arranged so that the transmission axis of the polarizer 312 and the slow axis of the λ / 4 retardation film 311 intersect at 45 ° (or 135 °). The light is converted into circularly polarized light by passing through the λ / 4 retardation film 311.

When the circularly polarized light emitted from the λ / 4 retardation film 311 is specularly reflected by the metal electrode 112 of the organic EL element 101, the phase is inverted by 180 degrees and reflected as reverse circularly polarized light. The reflected light is incident on the λ / 4 retardation film 311 and converted into linearly polarized light perpendicular to the transmission axis of the polarizer 312 (parallel to the absorption axis). Will not be emitted. That is, external light reflection at the organic EL element 101 can be reduced by the circularly polarizing plate 301.

<Relationship between rail pattern and gripper position>
Next, the change of the rail pattern in the extending part and the details of the positional relationship of the gripping tool will be described. FIG. 6 is a plan view schematically showing an example of the rail pattern of the extended portion after the initial installation adjustment. FIG. 7 is a plan view schematically showing an example of the rail pattern after changing the feeding angle in FIG. 6. FIG. 8 is a plan view schematically showing an example of the rail pattern after the rail length is changed in FIG.

The left and right rails are endless rails. The rail on the right side (the right side in the width direction of the long film) includes a going rail portion 11 that regulates the gripping tool 15 that travels in the traveling direction of the long film, and a gripping tool that travels in the direction opposite to the traveling direction of the long film. And a return rail portion 12 that regulates In this embodiment, the going rail part 11 and the return rail part 12 shall be arrange | positioned substantially parallel. And the going rail part 11 is comprised from the entrance of the extending | stretching part in order from the 1st rail part 11a, the 2nd rail part 11b, the 3rd rail part (curved rail part) 11c, and the 4th rail part 11d.

On the other hand, the rail on the left side (the left side in the width direction of the long film) travels in a direction opposite to the traveling direction of the long film and the going rail portion 13 that regulates the gripping tool 15 that proceeds in the traveling direction of the long film. It is comprised with the return rail part 14 which controls a holding tool. In this embodiment, the going rail part 13 and the return rail part 14 shall be arrange | positioned substantially parallel. The going rail portion 13 is in order from the entrance of the extending portion, and the going rail portion 13 is in order from the entrance of the extending portion, the first rail portion 13a, the second rail portion 13b, the third rail portion (curved rail portion). ) 13c, a fourth rail portion 13d, and a fifth rail portion 13e.

The gripping tool 15 is a member that grips the film with pins or clips, and moves on the rail through a chain (not shown). The gripping tool 15 is provided on the rail at regular intervals. The chain is provided along the rail and meshes with a gear disposed in place. The gear is driven by a motor or the like to drive the chain. In the present embodiment, the left and right grips 15 are assumed to move at a constant speed.

First, the state of FIG. 6 will be described. This is the rail pattern of the extended portion after adjustment in the initial installation, and is a state in which the rail bending rate Ts is small. At this time, when the going rail portions 11 and 13 are viewed, the first rail portions 11a and 13a are parallel and isometric straight lines. The second rail portions 11b and 13b are isometric straight lines that gradually spread in the lateral direction (the width direction of the long film), and correspond to a laterally stretched portion that laterally stretches the long film in the width direction. When the length of the second rail portion 11b is Ld and the length of the second rail portion 13b is La, Ld = La.

The third rail portions 11c and 13c include a curved portion and correspond to an obliquely stretched portion that obliquely stretches a long film. The 3rd rail part 11c consists only of a curved part, and makes the length Le. On the other hand, the third rail portion 13c is composed of a straight portion, a curved portion, and a straight portion in the order of movement of the gripping tool 15, and the lengths thereof are Lb1, Lb2, and Lb3, respectively. Then, Le = Lb1 + Lb2 + Lb3.

The fourth rail part 11d and the fifth rail part 13e are parallel and isometric straight lines. The fourth rail portion 13d on the left side is a straight rail facing the third rail portion 11c, and corresponds to an obliquely extending portion that obliquely extends a long film. That is, the fourth rail portion 13d corresponds to the left and right rail length difference of the obliquely extending portion. When the length is Lc, Lc = nP (n is an integer, P is the pitch of the gripping tool 15). That is, the difference in length between the left and right rails (bound rail portions 11 and 13) facing each other is an integral multiple of the pitch of the gripping tool.

Because of such a rail length, when the left and right gripping tools 15 are aligned at the entrance of the extending portion (the start ends of the first rail portions 11a and 13a), that is, a straight line connecting the left and right gripping tools 15 is a long film. The left and right grips 15 remain aligned even at the start position of the oblique stretching process (starting ends of the third rail portions 11c, 13c), and the end position of the oblique stretching process (third rail). The left and right gripping tools 15 are aligned even at the end of the portion 11c and the fourth rail 13d. Here, the left and right gripping tools 15 are aligned (substantially parallel) at the end position of the oblique stretching step means that the end portions on the downstream side in the transport direction of the pair of gripping tools closest to the position parallel to the width direction of the film The angle Tc formed by the straight line connecting the two and the width direction of the film is 0 ° or more and 0.2 ° or less.

Next, the state of FIG. 7 will be described. This is a rail pattern after changing the feeding angle from the state of FIG. 6, and is a state in which the rail bending rate Ts is large. At this time, when the going rail portions 11 and 13 are viewed, the first rail portions 11a and 13a are parallel and isometric straight lines. The second rail portions 11b and 13b are isometric straight lines that gradually spread in the lateral direction (the width direction of the long film), and correspond to a laterally stretched portion that laterally stretches the long film in the width direction. When the length of the second rail portion 11b is Ld and the length of the second rail portion 13b is La, Ld = La.

The third rail portions 11c and 13c include a curved portion and correspond to an obliquely stretched portion that obliquely stretches a long film. The 3rd rail part 11c consists only of a curved part, and makes the length Le. On the other hand, the third rail portion 13c is composed of a straight portion, a curved portion, and a straight portion in the order of movement of the gripping tool 15, and the lengths thereof are Lb1, Lb2, and Lb3, respectively. Then, Le = Lb1 + Lb2 + Lb3.

The fourth rail portion 11d and the fifth rail portion 13e are parallel straight lines. The fourth rail portion 13d on the left side is a straight rail facing the third rail portion 11c, and corresponds to an obliquely extending portion that obliquely extends a long film. That is, the fourth rail portion 13d corresponds to the left and right rail length difference of the obliquely extending portion. When the length is Lc, mP <Lc <(m + 1) P (m is an integer, P is the pitch of the gripping tool 15). That is, the difference between the lengths of the left and right rails facing each other in the obliquely extending portion is deviated from an integer multiple of the pitch of the gripping tool.

Because of such a rail length, the left and right gripping tools 15 are aligned at the entrance of the extending portion (the start ends of the first rail portions 11a and 13a), that is, the straight line connecting the left and right gripping tools 15 is the length of the long film. When it is substantially parallel to the width direction, the left and right gripping tools 15 remain aligned at the start position of the oblique stretching process (starting ends of the third rail portions 11c and 13c), but the end position of the oblique stretching process (third rail). In the portion 11c and the end of the fourth rail 13d), the left and right grips 15 are displaced and are not substantially parallel. Here, the left and right gripping tools 15 being displaced (not substantially parallel) at the end position of the oblique stretching process means that the angle Tc exceeds 0.2 °.

Therefore, in such a case, the gripping tool 15 is fed either forward or backward while the apparatus is stopped, and the right and left gripping tools at the end position of the oblique stretching process (the end of the third rail portion 11c and the fourth rail 13d). 15 is aligned, that is, adjusted so as to be arranged at a position substantially parallel to the width direction of the film. In this case, the left and right gripping tools 15 are not aligned at the start position of the oblique stretching process (the start ends of the third rail portions 11c and 13c). Even if the positions of the gripping tools 15 are not aligned at the start position of the oblique stretching process, the positions of the gripping tools at both ends of the oblique stretching process proceed while being largely deviated, so that the film characteristics are not affected.

Next, the state of FIG. 8 will be described. This is a rail pattern after the rail length is changed from the state shown in FIG. 7, and is a state in which the right going rail portion 11 is shortened. The shortening of the rail is performed by increasing the overlap at the connecting portion of the rail. Note that the angle Ts is not changed.

At this time, when viewing the going rail portions 11 and 13, the first rail portions 11a and 13a are parallel and isometric straight lines. The second rail portions 11b and 13b are isometric straight lines that gradually spread in the lateral direction (the width direction of the long film), and correspond to a laterally stretched portion that laterally stretches the long film in the width direction. In order to change from the state of FIG. 7 to the state of FIG. 8, the second rail portion 11b is shortened. When the length of the second rail portion 11b is Ld 'and the length of the second rail portion 13b is La', Ld '= La'. The rail part to be shortened may be the first rail part 11a or the third rail part 11c.

The third rail portions 11c and 13c include a curved portion and correspond to an obliquely stretched portion that obliquely stretches a long film. The 3rd rail part 11c is comprised by the bending part and the linear part in order of the movement of the holding | gripping tool 15, and let the length be Le1 and Le2, respectively. On the other hand, the third rail portion 13c is composed of a straight portion, a curved portion, and a straight portion in the order of movement of the gripping tool 15, and the lengths thereof are Lb1, Lb2, and Lb3, respectively. Then, Le1 + Le2 = Lb1 + Lb2 + Lb3.

The fourth rail part 11d and the fifth rail part 13e are parallel and isometric straight lines. The fourth rail portion 13d on the left side is a straight rail facing the third rail portion 11c, and corresponds to an obliquely extending portion that obliquely extends a long film. That is, the fourth rail portion 13d corresponds to the left and right rail length difference of the obliquely extending portion. When the length is Lc, Lc = mP (m is an integer, P is the pitch of the gripping tool 15). That is, the difference in length between the left and right rails (bound rail portions 11 and 13) facing each other is an integral multiple of the pitch of the gripping tool.

Because of such a rail length, when the left and right gripping tools 15 are aligned at the entrance of the extending portion (the start ends of the first rail portions 11a and 13a), that is, a straight line connecting the left and right gripping tools 15 is a long film. The left and right grips 15 remain aligned even at the start position of the oblique stretching process (starting ends of the third rail portions 11c, 13c), and the end position of the oblique stretching process (third rail). The left and right gripping tools 15 are also aligned at the portion 11c and the end of the fourth rail 13d. Here, that the right and left gripping tools 15 are aligned (substantially parallel) at the end position of the oblique stretching step means that the angle is 0 ° or more and 0.2 ° or less. In addition, you may adjust the rail length difference on either side by extending the left going rail part 13. FIG.

As described with reference to FIGS. 6 and 8, if the left and right rail lengths are adjusted so that the difference between the left and right rail lengths is an integral multiple of the pitch of the gripping tool 15, A straight line connecting the left and right grips 15 at the end position of the oblique stretching process can be made substantially parallel to the width direction of the film. On the other hand, as described with reference to FIG. 7, if the left and right rail lengths are not adjusted and the difference between the left and right rail lengths is not an integral multiple of the pitch of the gripping tool 15, the gripping tool 15 is sent to extend diagonally. A straight line connecting the left and right grips 15 at the end position of the process can be substantially parallel to the width direction of the long obliquely stretched film.

In any case, since the left and right grips 15 can be aligned at the end of the oblique stretching step, non-uniform stress is applied by the gripper 15 to the width of the long obliquely stretched film and the transport direction after the end of the oblique stretching step. Thus, a long obliquely stretched film having uniform retardation characteristics can be obtained. Furthermore, if the left and right gripping tools 15 are aligned at the start position of the oblique stretching process, wrinkles and the like are unlikely to occur.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Production of long film>
In the film forming process, long films A1 to C1 were prepared by the following method.

(Long film A1)
The long film A1 is an alicyclic olefin polymer resin film, and was produced by the following production method.

In a nitrogen atmosphere, 500 parts by mass of dehydrated cyclohexane, 1.2 parts by mass of 1-hexene, 0.15 parts by mass of dibutyl ether, and 0.30 parts by mass of triisobutylaluminum were mixed in a reactor at room temperature, and then mixed at 45 ° C. 20 parts by mass of tricyclo [4.3.0.12,5] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as DCP), 1,4-methano-1,4,4a, 140 parts by mass of 9a-tetrahydrofluorene (hereinafter abbreviated as MTF) and 40 parts by mass of 8-methyl-tetracyclo [4.4.0.12, 5.17,10] -dodec-3-ene (hereinafter abbreviated as MTD) A norbornene-based monomer mixture composed of parts and 40 parts by mass of tungsten hexachloride (0.7% toluene solution) were continuously added over 2 hours for polymerization. To the polymerization solution, 1.06 parts by mass of butyl glycidyl ether and 0.52 parts by mass of isopropyl alcohol were added to deactivate the polymerization catalyst and stop the polymerization reaction.

Next, 270 parts by mass of cyclohexane is added to 100 parts by mass of the resulting reaction solution containing the ring-opening polymer, and 5 parts by mass of a nickel-alumina catalyst (manufactured by JGC Catalysts & Chemicals) is added as a hydrogenation catalyst. In addition, the pressure was increased to 5 MPa with hydrogen and the mixture was heated to 200 ° C. with stirring and then reacted for 4 hours to obtain a reaction solution containing 20% of a DCP / MTF / MTD ring-opening polymer hydrogenated polymer.

After removing the hydrogenation catalyst by filtration, a soft polymer (manufactured by Kuraray Co., Ltd .; Septon 2002) and an antioxidant (manufactured by Ciba Specialty Chemicals Co., Ltd .; Irganox 1010) were added to the resulting solutions, respectively. And dissolved (both 0.1 parts by mass per 100 parts by mass of the polymer). Next, cyclohexane and other volatile components, which are solvents, are removed from the solution using a cylindrical concentration dryer (manufactured by Hitachi, Ltd.), and the hydrogenated polymer is extruded in a strand form from an extruder in a molten state. After cooling, it was pelletized and collected. When the copolymerization ratio of each norbornene monomer in the polymer was calculated from the composition of residual norbornenes in the solution after polymerization (by gas chromatography method), it was almost charged at DCP / MTF / MTD = 10/70/20. It was equal to the composition. This hydrogenated ring-opened polymer had a weight average molecular weight (Mw) of 31,000, a molecular weight distribution (Mw / Mn) of 2.5, a hydrogenation rate of 99.9%, and a Tg of 134 ° C.

The obtained ring-opened polymer hydrogenated pellets were dried at 70 ° C. for 2 hours using a hot air dryer in which air was circulated to remove moisture. Next, the pellets were melted by using a short-shaft extruder having a coat hanger type T die (manufactured by Mitsubishi Heavy Industries, Ltd .: screw diameter 90 mm, T die lip member quality is tungsten carbide, peel strength 44N from molten resin). Extrusion molding produced a cycloolefin polymer film having a thickness of 75 μm (the thickness of the long film after drying obtained by the film forming step, not the thickness of the long stretched film produced through the stretching step). In extrusion molding, a long film A1 having a width of 1000 mm was obtained in a clean room of class 10,000 or less under molding conditions of a molten resin temperature of 240 ° C. and a T-die temperature of 240 ° C.

(Long film B1)
The long film B1 is a cellulose ester resin film and was produced by the following production method.

<Fine particle dispersion>
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass Ethanol 89 parts by mass The above was stirred and mixed with a dissolver for 50 minutes, and then dispersed with Manton Gorin.

<Fine particle additive solution>
Based on the following composition, the fine particle dispersion was slowly added to a dissolution tank containing methylene chloride with sufficient stirring. Further, the particles were dispersed by an attritor so that the secondary particles had a predetermined particle size. This was filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle additive solution.
99 parts by mass of methylene chloride 5 parts by mass of fine particle dispersion 1

<Main dope solution>
A main dope solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressure dissolution tank. Cellulose acetate was added to a pressurized dissolution tank containing a solvent while stirring. This is completely dissolved with heating and stirring. This was designated as Azumi Filter Paper No. The main dope solution was prepared by filtration using 244. In addition, the compound synthesize | combined by the following synthesis examples was used for the sugar ester compound and the ester compound. Moreover, the following were used for the compound (B).

<Composition of main dope solution>
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Cellulose acetate propionate (acetyl group substitution degree 1.39, propionyl group substitution degree 0.50, total substitution degree 1.89) 100 parts by mass Compound (B) 5.0 parts by mass Sugar ester compound 5.0 parts by mass Ester compound 2.5 parts by mass Particulate additive solution 1 1 part by mass

(Synthesis of sugar ester compounds)
A sugar ester compound was synthesized by the following steps.

Four-headed Kolben equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen gas inlet tube was charged with 34.2 g (0.1 mol) of sucrose, 180.8 g (0.6 mol) of benzoic anhydride, pyridine 379. 7 g (4.8 mol) was charged, the temperature was raised while bubbling nitrogen gas through a nitrogen gas inlet tube with stirring, and an esterification reaction was carried out at 70 ° C. for 5 hours.

Next, the inside of the Kolben was depressurized to 4 × 10 ² Pa or less, and after excess pyridine was distilled off at 60 ° C., the inside of the Kolben was depressurized to 1.3 × 10 Pa or less and the temperature was raised to 120 ° C. Most of the acid and benzoic acid formed were distilled off.

Finally, 100 g of water is added to the collected toluene layer, and after washing with water at room temperature for 30 minutes, the toluene layer is separated, and toluene is distilled off at 60 ° C. under reduced pressure (4 × 10 ² Pa or less). A mixture (sugar ester compound) of A-1, A-2, A-3, A-4 and A-5 was obtained.

When the obtained mixture was analyzed by HPLC and LC-MASS, A-1 was 1.3% by mass, A-2 was 13.4% by mass, A-3 was 13.1% by mass, and A-4 was 31% by mass. 0.7% by mass and A-5 was 40.5% by mass. The average degree of substitution was 5.5.

<Measurement conditions for HPLC-MS>
1) LC section Equipment: Column oven (JASCO CO-965) manufactured by JASCO Corporation, detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50)
Column: Inertsil ODS-3 Particle size 5 μm 4.6 × 250 mm (manufactured by GL Sciences Inc.)
Column temperature: 40 ° C
Flow rate: 1 ml / min
Mobile phase: THF (1% acetic acid): H ₂ O (50:50)
Injection volume: 3 μl
2) MS unit Device: LCQ DECA (manufactured by Thermo Quest Co., Ltd.)
Ionization method: Electrospray ionization (ESI) method Spray Voltage: 5 kV
Capillary temperature: 180 ° C
Vaporizer temperature: 450 ° C

(Synthesis of ester compounds)
An ester compound was synthesized by the following steps.

251 g of 1,2-propylene glycol, 278 g of phthalic anhydride, 91 g of adipic acid, 610 g of benzoic acid, 0.191 g of tetraisopropyl titanate as an esterification catalyst, 2 L four-neck equipped with a thermometer, stirrer, and slow cooling tube The flask is charged and gradually heated while being stirred until it reaches 230 ° C. in a nitrogen stream. An ester compound was obtained by allowing dehydration condensation reaction for 15 hours, and distilling off unreacted 1,2-propylene glycol under reduced pressure at 200 ° C. after completion of the reaction. The ester compound had an ester of benzoic acid at the end of the polyester chain formed by condensation of 1,2-propylene glycol, phthalic anhydride and adipic acid. The acid value of the ester compound was 0.10, and the number average molecular weight was 450.

Then, using an endless belt casting apparatus, the casting was uniformly performed on a stainless belt support.

In the endless belt casting apparatus, the main dope solution was cast uniformly on a stainless steel belt support. On the stainless steel belt support, the solvent is evaporated until the residual solvent amount in the cast (cast) long film reaches 75%, peeled off from the stainless steel belt support, and transported by many rolls. Drying was terminated, and a long film B1 having a width of 1000 mm was obtained. At this time, the film thickness of the long film B1 was 75 μm (the thickness of the long film after drying obtained by the film forming process, not the thickness of the long stretched film produced through the stretching process).

(Long film C1)
The long film C1 is a polycarbonate resin film, and was produced by the following production method.

<Dope composition>
Polycarbonate resin (viscosity average molecular weight 40,000, bisphenol A type)
100 parts by mass 2- (2′hydroxy-3 ′, 5′-di-t-butylphenyl) -benzotriazole 1.0 part by mass Methylene chloride 430 parts by mass Methanol 90 parts by mass

The above composition was put into a sealed container, kept at 80 ° C. under pressure, and completely dissolved with stirring to obtain a dope composition.

Next, this dope composition was filtered, cooled and kept at 33 ° C., cast uniformly on a stainless steel band, and dried at 33 ° C. for 5 minutes. Thereafter, the drying time was adjusted so that the retardation was 5 nm at 65 ° C., and after peeling from the stainless steel band, drying was completed while being conveyed by a number of rolls, and the film thickness was 75 μm (the length after drying obtained by the film forming process). This is the thickness of the long film, not the thickness of the long stretched film produced through the stretching step), and a long film C1 having a width of 1000 mm was obtained.

[Example 1]
The norbornene-based unstretched film A1 obtained above was stretched under the conditions shown in Table 1 using the oblique stretching apparatus described in FIGS. 6 and 7 to obtain a first long stretched film.

The width of the gripping tool in the transport direction was 40 mm, and the pitch of the gripping tool in the transport direction was 50 mm (that is, the distance between adjacent gripping tools was 10 mm). The stretching part (length from the start of gripping to the grip opening) was 4345 mm for the inner circumference (right side in FIG. 6), 5094 mm for the outer circumference (left side in FIG. 6), and the stretching angle was set to 30 °. Here, the angle formed by the orientation angle (in-plane slow axis) of the obtained film and the film width direction is defined as the stretching angle.

The width of the long film A1 before being put into the oblique stretching apparatus was 1000 mm, and the width after stretching was 1534 mm.

Diagonal stretching was performed under the above stretching conditions, but at that time, the position was adjusted by moving only the inner gripping tool before starting stretching, and the shift in the conveyance direction of the left and right gripping tools at the end of diagonal stretching was performed. It adjusted so that it might become 1 mm. Here, the angle formed by the width direction of the film and the straight line connecting the grips at both ends was 0.037 °.

[Example 2]
A second long stretched film was obtained under the same conditions as in Example 1 except that the long film A1 was used as in Example 1 and the conditions in the oblique stretching step were changed as shown in Table 1.

[Comparative Example 1]
A third long stretched film was obtained under the same conditions as in Example 1 except that the long film A1 was used as in Example 1 and the conditions in the oblique stretching step were changed as shown in Table 1.

[Comparative Example 2]
A fourth long stretched film was obtained under the same conditions as in Example 1 except that the long film A1 was used in the same manner as in Example 1 and the conditions in the oblique stretching step were changed as shown in Table 1.

The results of measuring the width distribution of the orientation angles of the obtained first to fourth long stretched films are shown in Table 1. The width distribution of the orientation angle was measured as follows.

(Width distribution of orientation angle)
The orientation angle θ of the produced first to fourth long stretched films was measured using a phase difference measuring device (manufactured by Oji Scientific Co., Ltd., KOBRA-WXK). As an evaluation method, measurement was performed at an interval of 50 mm in the film width direction of the long stretched film, and the difference between the maximum value and the minimum value of all measured values was regarded as variation. The same measurement was performed at 10 locations in the long direction of the film at intervals of 50 mm, and the average value was defined as the width distribution of the orientation angle of the long stretched film.

The width distribution of the orientation angle obtained by the above measurement is shown in Table 1 as ◎, ○, Δ, × by the following indices.
◎: The width distribution of the orientation angle is 0 ° or more and less than 0.4 ° ○: The width distribution of the orientation angle is 0.4 ° or more and less than 0.6 ° △: The width distribution of the orientation angle is 0.6 ° or more Less than 0.8 ° x: width distribution of orientation angle is 0.8 ° or more

Here, if the width distribution of the orientation angle is less than 0.6 °, there is no practical problem, but it is preferably less than 0.4 °.

As is clear from the results in Table 1, it was revealed that the variation in the orientation angle can be reduced by using an oblique stretching apparatus in which the position of the gripping tool after the oblique stretching is set to be approximately parallel.

The present invention can be used for the production of a long obliquely stretched film applied to a circularly polarizing plate for preventing external light reflection of an organic EL image display device.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus of elongate diagonally stretched film 5 Stretching part 11c, 13c Curved rail part 11b, 12b 1st rail part 15, Ci, Co, Holding tool Ri, Ro rail

Claims (5)

1. Gripping both ends of the supplied long film in the width direction with each holding tool arranged at equal intervals, and transporting the long film while moving each holding tool at a constant speed along the opposing rail In addition, by changing the transport direction of the long film in the middle, the slanting stretching process having a slanting stretching process in which the long film is stretched in a slanting direction with respect to the width direction to form a slanting stretching film. In the film manufacturing method,
   A method for producing a long diagonally stretched film, wherein a straight line connecting opposing gripping tools is substantially parallel to the width direction of the long diagonally stretched film at the end position of the obliquely stretching step.
2. The method for producing a long obliquely stretched film according to claim 1, wherein a straight line connecting opposing gripping tools is substantially parallel to the width direction of the long film at the start position of the obliquely stretching step.
3. The method for producing a long obliquely stretched film according to claim 1 or 2, wherein the difference between the lengths of the opposing rails is an integral multiple of the pitch of the gripping tool.
4. The method for producing a long obliquely stretched film according to any one of claims 1 to 3, wherein the lengths of the opposing rails are variable.
5. The method for producing a long obliquely stretched film according to any one of claims 1 to 4, wherein the rail has a curved rail portion that can be arbitrarily bent.

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