JP6798196B2 - Method for manufacturing diagonally stretched film - Google Patents

Description

The present invention relates to a method for producing a diagonally stretched film.

In a method for producing a diagonally stretched film having a diagonally stretched film in which the film is stretched diagonally with respect to the width direction, after the completion of the diagonally stretched step, each gripping tool that grips the left end and the right end in the width direction of the film is a film. If the film is deviated in the transport direction, non-uniform stress is applied in the width direction of the film due to the left and right grippers deviated in the transport direction, and a long diagonally stretched film having uniform phase difference characteristics can be obtained. become unable. Therefore, for example, in Patent Document 1, the difference between the length of the rail on which the plurality of grippers gripping the left end in the width direction of the film travels and the length of the rail on which the plurality of grippers gripping the right end travels. The positions of the plurality of grippers are adjusted according to the relationship with the pitch of the plurality of grippers in the transport direction. Then, by adjusting the position, the positions of the left and right gripping tools are aligned in the width direction at the end position of the diagonally stretched step, thereby reducing the application of non-uniform stress in the width direction of the diagonally stretched film. An obliquely stretched film having uniform retardation characteristics is obtained.

The obliquely stretched film produced as described above can be applied to a circularly polarizing plate for preventing external light reflection, for example, in an organic EL (electroluminescence) display device. In the above circular polarizing plate, the polarizer and the obliquely stretched film are, for example, a roll-to-roll method so that the in-plane slow-phase axis of the obliquely stretched film is inclined at a desired angle with respect to the transmission axis of the polarizer. It is obtained by pasting together with.

By the way, the portions gripped by the gripping tool at both ends in the width direction of the film are deformed during stretching. If this deformed portion remains at the edge of the film, then when the film comes into contact with the transport roll, the deformed portion of the film is cracked and the production of the film cannot be continued. Therefore, it is necessary to immediately cut off the deformed portion after releasing the grip of the film by the gripper.

At this time, conventionally, in order to suppress the meandering of the film and to apply a uniform force (conveyance tension) in the transport direction at each position in the width direction, both ends of the film in the width direction are held and opened. It was thought that it was necessary to be done at the same time. In fact, for example, in Patent Documents 2 and 3, the gripping and opening of the film is performed substantially simultaneously at both ends in the width direction. Further, also in Patent Document 1, at the outlet of the oblique stretching machine, that is, at the end position of the heat fixing step of fixing the optical axis of the obliquely stretched film after the diagonal stretching step is completed, a pair of both ends in the width direction of the film are gripped. It is gripped by a tool, and it is considered that the grip of the film is released at this position.

However, as in Patent Document 1, when the stretching direction of the film is an oblique direction with respect to the conveying direction, as shown in FIG. 10, the film shrinks in the film plane in the direction perpendicular to the stretching direction. Moreover, since the shrinkage occurs non-uniformly in the film surface, if the gripping and opening by the gripping tool is simultaneously performed at both ends in the width direction of the film, the transport direction of the film is affected by the shrinkage of the film. Therefore, it was found that the film deviates greatly from the original direction (the direction perpendicular to the width direction of the film at the end of diagonal stretching) and fluctuates (oscillates) periodically. The fluctuation range (fluctuation angle range) in the transport direction at this time is indicated by β (°).

When the transport direction of the film fluctuates greatly from the original direction, the angle at which the blade of the cutting member hits the film (for example, perpendicular to the width direction at the end of stretching) when the deformed portion at the end of the film is cut by the cutting member. The angle) fluctuates greatly, which may cause cutting to areas other than the deformed portion, which in turn may lead to breakage of the film. In this way, if the timing of releasing the grip by the grippers at both ends of the film is simultaneously released, the film may be broken as described above. However, in Patent Document 1 described above, no study is made to suppress the breakage of the film. Not done.

It should be noted that, for example, by using a meandering correction device (meandering path control means) as disclosed in Patent Document 4, fluctuations in the film conveying direction (meandering) can be suppressed, thereby suppressing film breakage. Conceivable. Examples of the meandering correction device include an edge position controller (sometimes referred to as EPC) and a center position controller (sometimes referred to as CPC). These devices detect the ear edge of the film with an air servo sensor or an optical sensor, control the film transport direction based on that information, and the film transport position is constant at the center of the film ear edge and width direction. It is intended to be. Specifically, the meandering can be corrected by swinging one or two guide rolls or a driven flat expander roll left and right (or up and down) with respect to the line direction (rotation axis direction), or 2 to the left and right of the film. A set of small pinch rolls (one set on the front side and one on the back side of the film) are installed, and the film is sandwiched between the pinch rolls and pulled to correct the meandering (cross guider method). The principle of meandering correction by these devices is that when the film is running, for example trying to go to the left, the former method tilts the roll so that the film goes to the right, and the latter method is to the right. A set of pinch rolls is nipped and pulls the film to the right.

However, as described above, in the stretched film, the portion gripped by the gripper is deformed at the time of stretching, and if the deformed portion is left and passed through the meandering correction device before cutting, the film is deformed. The meandering worsens due to the catching of the part, or when wrapped on a roll, if the wrapping angle is large, the deformed part will crack and the film will tear as it is. For this reason, it is not appropriate to install the meandering correction device and pass the film through before cutting the deformed portion.

Japanese Patent No. 5825426 (see claim 1, paragraphs [0012] to [0014], [0020], [0187], FIGS. 6 to 8 and the like). Japanese Unexamined Patent Publication No. 2016-108065 (see FIG. 2 etc.) Japanese Unexamined Patent Publication No. 2016-55629 (see FIG. 2 etc.) Japanese Unexamined Patent Publication No. 6-8663 (see paragraph [0012], FIG. 1, etc.)

The present invention has been made to solve the above problems, and an object of the present invention is to appropriately set the timing of releasing the grip by the grippers at both ends in the width direction of the film to correct the meandering. It is an object of the present invention to provide a method for producing a diagonally stretched film, which can appropriately control the transport direction of the film after gripping and opening, and thereby suppresses breakage of the film.

The above object of the present invention is achieved by the following manufacturing method.

1. 1. One end side of the film in the width direction is gripped by a plurality of gripping tools, the other end side is gripped by a plurality of gripping tools, and one gripping tool on the one end side and the other end side is relatively preceded. A diagonal stretching step of stretching the film diagonally with respect to the width direction by transporting the film with the other gripper relatively delayed.
A method for producing a diagonally stretched film, which comprises a heat fixing step of fixing the optical axis of the film after the completion of the diagonally stretched step.
In the heat fixing step, at the end of the diagonal stretching step, both ends of the film in the width direction are gripped by a pair of grippers facing each other in the width direction of the film. Transport,
Of the pair of gripping tools, the gripping tool that travels on the relatively leading side in the diagonal stretching step is used as the first gripping tool, and the gripping tool that travels on the relatively delayed side is used as the second gripping tool. In the heat fixing step, the position where the first gripper releases the grip of the film is defined as the first position, and the position where the second gripper releases the grip of the film is defined as the second position. When you do
In the heat fixing step, the straight line connecting the first position and the second position in the plane of the film is the width direction perpendicular to the transport direction of the film after the completion of the diagonal stretching step. The first gripping tool is used before the second gripping tool so that the first position is obliquely inclined with respect to the second position and the first position is upstream of the second position in the transport direction. A method for producing a diagonally stretched film, which comprises opening the grip of the film.

2. 2. In the plane of the film, the angle formed by the straight line connecting the first position and the second position and the width direction after the completion of the diagonal stretching step is θ (°), and the diagonal stretching is performed. When the angle formed by the width direction after the end of the process and the in-plane slow-phase axis of the film is α (°),
10 ° ≤ α ≤ 50 °
And
When α = 10 °
α-10 ° <θ≤α + 10 °
And
When 10 ° <α ≤ 50 °
α-10 ° ≤ θ ≤ α + 10 °
The method for producing a diagonally stretched film according to 1 above.

3. 3. In the diagonal stretching step, the moving distance of one of the gripping tools on the one end side and the other end side is made shorter than the moving distance of the other gripping tool, so that the one gripping tool is relatively preceded. The method for producing an obliquely stretched film according to 1 or 2, wherein the film is conveyed with the other gripping tool relatively delayed.

4. In the diagonal stretching step, the moving time of one of the gripping tools on the one end side and the other end side is made shorter than the moving time of the other gripping tool, so that the one gripping tool is relatively preceded. The method for producing an obliquely stretched film according to any one of 1 to 3, wherein the film is conveyed with the other gripping tool relatively delayed.

According to the above manufacturing method, in the heat fixing step after the diagonal stretching step, of the pair of gripping tools having a positional relationship facing each other in the film width direction, the second gripping tool (the side delayed in the diagonal stretching step) The film is released from being gripped by the first gripping tool (the gripping tool that travels on the preceding side in the oblique stretching step) before the traveling gripping tool). By doing so, a straight line connecting the positions where the film grip is released (a straight line connecting the first position and the second position) is formed as compared with the case where the grip is released at both ends in the width direction of the film. , The direction perpendicular to the diagonal stretching direction, that is, the direction in which contraction occurs due to the diagonal stretching.

As a result, the influence of shrinkage due to diagonal stretching of the film when the film is gripped and released can be reduced, and the range of fluctuation in the film transport direction is greatly shifted in the width direction by being pulled by the film shrinkage when the film is gripped and released. It can be suppressed. As a result, the maximum value of the amount of fluctuation of the film transport direction from the original direction (the direction perpendicular to the width direction at the end of diagonal stretching) is larger than the case where the grip is simultaneously released at both ends in the width direction of the film. It can be kept small.

Therefore, even when the end portion of the film (the portion gripped by the gripper) is subsequently cut by the cutting member, the angular deviation when the blade of the cutting member hits the film is released at the same time at both ends in the width direction of the film. It can be kept smaller than when it is done. As a result, it is possible to prevent the film from being broken by cutting a portion other than the deformed portion at the time of cutting without correcting the meandering of the film by using a meandering correcting device.

It is a top view which shows typically the schematic structure of the manufacturing apparatus of the diagonally stretched film which concerns on embodiment of this invention. It is a top view which shows typically an example of the rail pattern of the extension part provided in the said manufacturing apparatus. It is a top view which shows the details of the structure of the stretched part. It is explanatory drawing which shows the grip open position of the film in the stretched part. It is explanatory drawing which shows typically the relationship between the straight line connecting the positions which release the grip of the film, and the orientation direction (stretching direction). It is explanatory drawing which shows typically the relationship between the said straight line and an orientation angle. It is explanatory drawing which shows another example of the method of diagonal stretching. It is explanatory drawing which shows still another example of the method of diagonal stretching. It is sectional drawing which disassembled and shows the schematic structure of the organic EL image display apparatus to which the said diagonally stretched film is applied. It is explanatory drawing which shows typically the range which the transport direction of a film fluctuates when the grasping opening by the gripping tool at both ends in the width direction of a film is performed at the same time.

An embodiment of the present invention will be described below with reference to the drawings. In this specification, when the numerical range is expressed as A to B, the numerical range includes the values of the lower limit A and the upper limit B. Moreover, the present invention is not limited to the following contents.

The method for producing a diagonally stretched film according to the present embodiment is a long-shaped film having an in-plane slow-phase axis at an arbitrary angle with respect to the width direction of the stretched film by diagonally stretching the long-shaped film. This is a method for producing a diagonally stretched film.

Here, the long length means a length of at least about 5 times or more with respect to the width of the film, preferably 10 times or more, and specifically, the film is wound in a roll shape. It refers to the length that is stored or transported in the state of a film roll. In the method for producing a long film, the film can be produced to any desired length by continuously producing the film. The method for producing a long diagonally stretched film is to form a long film and then wind it around a winding core to make a winding body (long film original fabric) from this winding body. The elongated film may be supplied to the oblique stretching step to produce the obliquely stretched film, or the elongated film after the film formation may be continuously stretched diagonally from the film forming step without winding up. It may be supplied to the process to produce a diagonally stretched film. By continuously performing the film forming step and the oblique stretching step, the film thickness and the optical value results after stretching are fed back to change the film forming conditions, and a desired long diagonally stretched film is obtained. It is preferable because it can be used.

In the method for producing a diagonally stretched film according to the present embodiment, a long diagonally 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 manufactured. Here, the angle with respect to the width direction of the film is an angle in the film surface. Since the slow-phase axis usually appears in the stretching direction or a direction perpendicular to the stretching direction, in the production method according to the present embodiment, stretching is performed at an angle of more than 0 ° and less than 90 ° with respect to the width direction of the film. By doing so, a long obliquely stretched film having such a slow axis can be produced. The angle formed by the width direction of the elongated obliquely stretched film and the slow axis, that is, the orientation angle can be arbitrarily set to a desired angle within a range of more than 0 ° and less than 90 °. In the present embodiment, when the term "long film" is used, it means a long film before diagonal stretching.

<About long film>
First, a long film to be stretched in the present embodiment will be described.

The long film of the present embodiment is not particularly limited as long as it is a film composed of a thermoplastic resin. For example, when the stretched film is used for optical purposes, it has a desired wavelength. A film made of a resin having a transparent property is preferable. Examples of such resins include polycarbonate-based resins, polyether sulfone-based resins, polyethylene terephthalate-based resins, polyimide-based resins, polymethylmethacrylate-based resins, polysulfone-based resins, polyarylate-based resins, polyethylene-based resins, and polyvinyl chloride-based resins. Examples thereof include resins, olefin polymer-based resins having an alicyclic structure (alicyclic olefin polymer-based resins), and cellulose ester-based resins.

Among these, polycarbonate-based resins, alicyclic olefin polymer-based resins, and cellulose ester-based resins are preferable from the viewpoints of transparency and mechanical strength. Among them, alicyclic olefin polymer resin and cellulose ester resin, which can easily adjust the phase difference in the case of an optical film, are more preferable.

<Long film forming method>
The long film of the present embodiment made of the above-mentioned resin can be formed by either the solution casting method or the melt casting method shown below. Hereinafter, each film forming method will be described. In the following, a case where, for example, a cellulose ester-based resin film is formed as a long film will be described, but of course, it can also be applied to the film formation of other resin films.

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

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

For example, the chlorine-based organic solvent is methylene chloride, and the non-chlorine-based organic solvent is 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 and the like can be mentioned. Therefore, methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

In addition to the above organic solvent, the doping 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 is high, the web gels, facilitating peeling from the metal support, and when the proportion of alcohol is low, the role of promoting the dissolution of cellulose acetate in a non-chlorine organic solvent system. There is also.

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

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 it can ensure the stability of the doping, has a relatively low boiling point, and has good drying properties.

(Solution flow)
The cellulosic ester-based 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-shaped or drum-shaped metal support, and a step of drying the cast dope as a web. , The step of peeling from the metal support, the step of stretching or holding the width, the step of further drying, and the step of winding up the finished film.

A higher concentration of cellulose acetate in the doping is preferable because the drying load after casting on the metal support can be reduced, but if the concentration is too high, the load during filtration increases and the filtration accuracy deteriorates. The concentration at which these are compatible is preferably 10 to 35% by mass, more preferably 15 to 25% by mass. The metal support in the casting process is preferably a mirror-finished surface, and the metal support is preferably a stainless steel belt or a drum whose surface is plated with a casting.

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

The preferred support temperature is appropriately determined from 0 to 100 ° C, and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method to gel the web by cooling and peel it off from the drum in a state containing a large amount of residual solvent. The method of controlling the temperature of the metal support is not particularly limited, but there are a method of blowing hot air or cold air and a method of bringing hot water into contact with the back side of the metal support. It is preferable to use hot water because heat transfer is performed efficiently and the time until the temperature of the metal support becomes constant is shortened.

When using warm air, in consideration of the temperature drop of the web due to the latent heat of vaporization of the solvent, it is possible to use warm air above the boiling point of the solvent while preventing foaming and using air at a temperature higher than the target temperature. is there.

In particular, it is preferable to change the temperature of the support and the temperature of the drying air between casting and peeling to efficiently perform drying.

In order for the cellulose ester-based resin film to exhibit good flatness, the amount of residual solvent when the web is peeled 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 amount of residual solvent is defined by the following formula.
Residual solvent amount (mass%) = {(MN) / N} x 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.

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

In the film drying step, a roll drying method (a method in which the web is alternately passed through a large number of rolls arranged one above the other to dry) or a tenter method in which the web is conveyed and dried is generally adopted.

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

Pelletization may be carried out by a known method. For example, dry cellulose acetate, plasticizer, and other additives are supplied to the extruder with a feeder, kneaded using a single-screw or twin-screw extruder, extruded from a die into strands, water-cooled or air-cooled, and cut. It can be pelletized.

The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders. Further, since a small amount of additives such as particles and antioxidants are mixed uniformly, it is preferable to mix them in advance.

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

Film formation is performed using the pellets obtained as described above. Of course, it is also possible to supply the raw material powder as it is to the extruder with a feeder without pelletizing it and to form a film as it is.

The pellets are extruded using a single-screw or twin-screw type extruder to a melting temperature of about 200 to 300 ° C., and filtered with a leaf disc type filter to remove foreign matter, and then film-like from the T-die. The film is nipped with a cooling roll and an 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 an atmosphere of an inert gas.

It is preferable that the extrusion flow rate is stable by introducing a gear pump or the like. Further, as the filter used for removing foreign substances, a stainless fiber sintered filter is preferably used. The stainless fiber sintered filter is made by creating a complicated entangled state of stainless steel fibers, compressing them, and sintering the contact points to integrate them. The density is changed according to the thickness and compression amount of the fibers to improve the filtration accuracy. 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. It is preferable to use a mixing device such as a static mixer in order to add the mixture uniformly.

The film temperature on the touch roll side when the film is nipated by the cooling roll and the elastic touch roll is preferably Tg (glass transition temperature) or more and Tg + 110 ° C. or less of the film. 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 rotating body. As the elastic touch roll, a commercially available one can also be used.

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

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

<Specifications of long film>
The thickness of the long film in the present embodiment is preferably 30 to 300 μm, more preferably 40 to 150 μm. Further, in the present embodiment, the thickness unevenness σm in the flow direction (conveyance direction) of the long film supplied to the stretching zone described later keeps the take-up tension of the film at the inlet of the oblique stretching tenter described later constant, and the orientation angle. From the viewpoint of stabilizing optical characteristics such as retardation and retardation, it is preferably less than 0.30 μm, preferably less than 0.25 μm, and 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, the variation in optical characteristics such as the retardation and the orientation angle of the long stretched film may be deteriorated.

Further, as a long film, a film having a thickness gradient in the width direction may be supplied. The thickness gradient of the long film is empirically determined by stretching the 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. You can ask. The thickness gradient of the long film can be adjusted so that, for example, the thickness of the end portion on the thick side is about 0.5 to 3% thicker than the thickness of 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 preferred elastic modulus at the stretching temperature during diagonal 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 in terms of 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 becomes large, and it becomes necessary to increase the strength of the portion holding both side edges of the film, which increases the load on the tenter in the subsequent process.

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 of the orientation of the long film in the width direction may be arched, 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 stretching in the subsequent step is completed can be desired.

<Manufacturing method and manufacturing equipment for long diagonally stretched film>
Next, a method and an apparatus for producing a diagonally stretched film, in which the above-mentioned long film is stretched diagonally with respect to the width direction to produce a long diagonally stretched film, will be described.

(Overview of the device)
FIG. 1 is a plan view schematically showing a schematic configuration of a diagonally stretched film manufacturing apparatus 1. In the manufacturing apparatus 1 of the present embodiment, the film feeding portion 2, the transport direction changing portion 3, the guide roll 4, the stretching portion 5, the guide roll 6, and the transport direction are sequentially arranged from the upstream side in the transport direction of the long film. A changing unit 7 and a film winding unit 8 are provided. The details of the stretched portion 5 will be described later.

The film feeding portion 2 feeds out the above-mentioned long film and supplies it to the stretched portion 5. The film feeding portion 2 may be configured separately from the film forming apparatus for a long film, or may be integrally configured. In the former case, the long film is unwound from the film feeding portion 2 by winding the long film around the winding core once after forming the film and loading the wound body into the film feeding portion 2. On the other hand, in the latter case, the film feeding portion 2 is fed to the stretched portion 5 without winding the long film after forming the long film.

The transport direction changing section 3 changes the transport direction of the long film fed from the film feeding section 2 toward the inlet of the stretching section 5 as the diagonal stretching tenter. Such a transport direction changing unit 3 includes, for example, a turn bar that changes the transport direction by folding back while transporting the film, and a rotary table that rotates the turn bar in a plane parallel to the film.

By changing the transport direction of the long film in the transport direction changing unit 3 as described above, the width of the entire manufacturing apparatus 1 can be narrowed, and the film feeding position and angle can be finely controlled. This makes it possible to obtain a long stretched film having a small variation in film thickness and optical value. Further, if the film feeding portion 2 and the transport direction changing portion 3 are movable (sliding and swivelable), the left and right clips (grasping tools) that sandwich both ends of the long film in the width direction in the stretched portion 5 It is possible to effectively prevent poor biting into the film.

The film feeding portion 2 may be slidable and swivelable so that the long film can be fed at a predetermined angle with respect to the inlet of the stretched portion 5. In this case, the configuration may be such that 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 stretched portion 5 in order to stabilize the trajectory of the long film during running. The guide roll 4 may be composed of a pair of upper and lower rolls sandwiching the film, or may be composed of a plurality of roll pairs. The guide roll 4 closest to the inlet of the stretched portion 5 is a driven roll that guides the running of the film, and is rotatably supported by a bearing portion (not shown). As the material of the guide roll 4, a known material can be used. In order to prevent the film from being scratched, it is preferable to reduce the weight of the guide roll 4 by applying a ceramic coat to the surface of the guide roll 4 or chrome plating a light metal such as aluminum.

Further, it is preferable that one of the rolls on the upstream side of the guide roll 4 closest to the inlet of the stretched portion 5 is niped by pressure contacting the rubber roll. By using such a nip roll, it is possible to suppress fluctuations in the feeding tension in the film flow direction.

A pair of bearing portions at both ends (left and right) of the guide roll 4 closest to the inlet of the stretched portion 5 have 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 detection device is provided for each. As the film tension detection device, for example, a load cell can be used. As the load cell, a known tension or compression type load cell can be used. A load cell is a device that converts a load acting on a force point into an electric signal by a strain gauge attached to a strain generating body and detects it.

The load cell is installed in the left and right bearing portions of the guide roll 4 closest to the inlet of the stretched portion 5, so that the force exerted on the roll by the running film, that is, in the film traveling direction generated near both side edges of the film. The tension is detected independently on the left and right. A strain gauge may be directly attached to the support constituting the bearing portion of the roll, and the load, that is, the film tension may be detected based on the strain generated in the support. It is assumed that the relationship between the generated strain and the film tension is measured and known in advance.

If the position and transport direction of the film supplied from the film feeding section 2 or the transport direction changing section 3 to the stretched section 5 deviate from the position toward the inlet of the stretched section 5 and the transport direction, depending on the amount of this misalignment. A difference will occur in the tension near both side edges of the film in the guide roll 4 closest to the inlet of the stretched portion 5. Therefore, the degree of the deviation can be determined by providing the film tension detecting device as described above and detecting the tension difference described above. That is, if the transport position and transport direction of the film are appropriate (if the position and direction are toward the inlet of the stretched portion 5), the load acting on the guide roll 4 is roughly equal at both ends in the axial direction. If it is not appropriate, there will be a difference in film tension between the left and right.

Therefore, for example, the film position and the transport direction (angle with respect to the inlet of the stretched portion 5) are set by the above-mentioned transport direction changing portion 3 so that the difference in film tension between the left and right of the guide roll 4 closest to the inlet of the stretched portion 5 becomes equal. If properly adjusted, the gripping tool at the inlet of the stretched portion 5 can stably grip the film, and the occurrence of obstacles such as the gripping tool coming off can be reduced. Further, the physical properties of the film in the width direction after being obliquely stretched by the stretched portion 5 can be stabilized.

At least one guide roll 6 is provided on the downstream side of the stretched portion 5 in order to stabilize the trajectory of the film (long diagonally stretched film) diagonally stretched by the stretched portion 5 during running.

The transport direction changing section 7 changes the transport direction of the stretched film transported from the stretched section 5 toward the film winding section 8. The transport direction changing portion 7 can be configured by, for example, a folding mechanism that folds back the stretched film at least once along a direction parallel to or perpendicular to the stretching direction in the plane of the long diagonally stretched film.

Here, in order to fine-tune the orientation angle (direction of the in-plane slow-phase axis of the film) and to cope with product variations, the film advancing direction at the inlet of the stretched portion 5 and the film advancing direction at the outlet of the stretched portion 5. It is necessary to adjust the angle of the film.

In addition, continuous film formation and diagonal stretching are preferable in terms of productivity and yield. When the film-forming step, the diagonal stretching step, and the winding step are continuously performed, the traveling direction of the film is changed by the transport direction changing section 3 and / or the transport direction changing section 7, and the film is formed in the film-forming step and the winding step. That is, as shown in FIG. 1, the traveling direction of the film unwound from the film feeding unit 2 (feeding direction) and the traveling direction of the film immediately before being wound by the film winding unit 8 (the traveling direction of the film). By matching the winding direction), the width of the entire device with respect to the film traveling direction can be reduced.

Although it is not always necessary to match the traveling directions of the film between the film forming process and the winding process, the transport direction changing unit 3 and the transport direction changing unit 3 and the film winding unit 8 are arranged so that the film feeding portion 2 and the film winding portion 8 do not interfere with each other. / Or it is preferable to change the traveling direction of the film by the transport direction changing unit 7.

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

The film winding unit 8 winds the film conveyed from the stretching unit 5 via the conveying direction changing unit 7, and is composed of, for example, a winder device, an accumulator device, a drive device, and the like. The film winding unit 8 preferably has a structure that can slide in the lateral direction in order to adjust the film winding position.

The film take-up portion 8 can finely control the take-up position and angle of the film so that the film can be taken up at a predetermined angle with respect to the outlet of the stretched portion 5. This makes it possible to obtain a long stretched film having a small variation in film thickness and optical value. In addition, it is possible to effectively prevent the occurrence of wrinkles in the film and improve the windability of the film, so that the film can be wound in a long length. In the present embodiment, the take-back tension T (N / m) of the stretched film is preferably adjusted between 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, the film is liable to sag or wrinkle, and the retardation and orientation angle profiles in the film width direction are also deteriorated. On the contrary, when the take-up tension is 700 N / m or more, the variation of the orientation angle in the film width direction is deteriorated, and the width yield (take-up efficiency in the width direction) may be deteriorated.

Further, in the present embodiment, it is preferable to control the fluctuation of the take-back tension T with an accuracy of less than ± 5%, preferably less than ± 3%. When the fluctuation of the take-up tension T is ± 5% or more, the variation in the optical characteristics in the width direction and the flow direction (conveyance direction) becomes large. 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 stretched portion 5, that is, the tension of the film is measured, and the value becomes constant. As described above, a method of controlling the rotation speed of the take-up roll (the take-up roll of the film take-up unit 8) by a general PID control method can be 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 the load applied to the guide roll 6, that is, the tension of the film is measured. As the load cell, a known tension type or compression type can be used.

The stretched film is released from the gripping tool of the stretched portion 5, discharged from the outlet of the stretched portion 5, and both ends (both sides) of the film gripped by the gripping tool are trimmed, and then the winding core is sequentially wound. It is wound on a (winding roll) to form a wound body of a long diagonally stretched film. The above trimming may be performed as needed.

Further, before winding the long diagonally stretched film, the masking film may be stacked on the long diagonally stretched film and wound at the same time for the purpose of preventing blocking between the films, or they may be wound by winding. A tape or the like may be attached to at least one (preferably both) ends of the elongated diagonally stretched film and wound up. The masking film is not particularly limited as long as it can protect a long diagonally stretched film, and examples thereof include a polyethylene terephthalate film, a polyethylene film, and a polypropylene film.

Further, the obliquely stretched film manufacturing apparatus 1 of the present embodiment further includes a cutting apparatus 9. The cutting device 9 is a device that cuts (cuts) both ends of the film stretched by the stretched portion 5 in the width direction and held by the gripping tool described later in the stretched portion 5. Is. The cutting device 9 has a cutting member such as a blade and a cutter, and the cutting member cuts a portion held by the film. Since the portion gripped by the gripper is deformed during stretching, by cutting this portion, even when the film comes into contact with various transport rolls thereafter, the grip portion is used as the starting point. As a result, the film does not crack and the production of the film can be continued. In the present embodiment, it is assumed that the cutting member (blade) is installed in a direction substantially parallel to the film width hand direction at the end of the diagonal stretching step described later.

(Details of stretched part)
Next, the details of the stretched portion 5 described above will be described. FIG. 2 is a plan view schematically showing an example of the rail pattern of the stretched portion 5. Further, FIG. 3 is a plan view showing details of the configuration of the stretched portion 5. It should be noted that these are examples, and the present invention is not limited to these configurations.

The manufacturing apparatus 1 is performed by using a tenter (diagonal stretching machine) capable of diagonally stretching as the stretching portion 5. This tenter is a device that heats a long film to an arbitrary temperature at which it can be stretched and stretches it diagonally. This tenter includes a heating zone Z, a pair of rails Ri · Ro on the left and right, and a plurality of gripping tools 15 (in FIG. 2, for convenience, a pair of gripping tools Ci · Co on the left and right of the plurality of gripping tools 15). Only shown) and. The 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, and is an endless track rail (white circles in FIG. 2 are examples of connecting portions). As shown in FIG. 3, the rail Ri on one end side (left side) in the width direction of the film includes the going rail portion 11 for advancing the gripping tool 15 in the transport direction of the long film and the transport direction of the long film. It is configured by connecting the return rail portion 12 for advancing the gripping tool 15 in the opposite direction to the above. The rail Ro on the other end side (right side) in the width direction of the film grips the going rail portion 13 for advancing the gripping tool 15 in the transport direction of the long film and the rail Ro in the direction opposite to the transport direction of the long film. It is configured by connecting the return rail portion 14 for advancing the tool 15.

The gripping tool 15 is composed of clips that grip both ends in the width direction of the film, is provided corresponding to each rail Ri / Ro, and is provided along the film transport direction (each Ri / Ro). Multiple are provided at equal intervals. One end side of the film in the width direction is gripped by a plurality of gripping tools 15 arranged along the transport direction (rail Ri), and the other end side is gripped by a plurality of gripping tools 15 arranged along the transport direction (rail Ro). Then, in this state, the gripping tool 15 travels along the rails Ri and Ro, so that the film is conveyed.

The gripping tool 15 traveling along the left rail Ri travels along the rail portion 11 while gripping one end of the film, releases the grip of the film near the exit of the stretched portion 5, and then returns the rail. The film travels along the portion 12, returns to the vicinity of the entrance of the stretched portion 5, grips one end of the film again, and then repeats the same process as above (circulates along the rail Ri). On the other hand, the gripping tool 15 traveling along the right rail Ro travels along the rail portion 13 while gripping one end of the film, releases the grip of the film near the exit of the stretched portion 5, and then releases the grip. The film travels along the return rail portion 14, returns to the vicinity of the inlet of the stretched portion 5, grips the other end of the film again, and then repeats the same process as above (circulates along the rail Ro).

In FIG. 2, the transport direction D1 before stretching the long film is different from the transport direction D2 after stretching the long film, and a feeding angle θi is formed with the transport 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 °.

As described above, since the transport direction D1 before stretching and the transport direction D2 after stretching are different, the rail pattern of the tenter has an asymmetrical shape on the left and right. The rail pattern can be manually or automatically adjusted according to the orientation angle θ, the draw ratio, and the like given to the long diagonally stretched film to be manufactured. In the diagonal 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 gripping tool 15 travels at a constant speed while maintaining a constant distance from the gripping tools 15 (the gripping tools 15 on the upstream side and the downstream side in the film transport direction) before and after the gripping tool 15. The traveling speed of the gripping tool 15 can be appropriately selected, but is usually 1 to 150 m / min. The difference in running speed between the pair of left and right gripping tools (for example, gripping tools Ci and Co) is usually 1% or less, preferably 0.5% or less, and more preferably 0.1% or less of the running speed. This is because if there is a difference in traveling speed between the left and right sides of the film at the outlet of the stretching process, wrinkles and deviations occur at the exit of the stretching process, so that the speed difference between the left and right grippers is required to be substantially the same. Because. In a general tenter device, there is speed unevenness that occurs on the order of seconds or less depending on the tooth cycle of the sprocket that drives the chain, the frequency of the drive motor, etc., and often causes unevenness of several percent. It does not correspond to the speed difference described in the embodiment of the invention.

In the oblique stretching machine used in the manufacturing method of the present embodiment, a rail that regulates the trajectory of the gripper is often required to have a large refractive index, especially in a place where the film is conveyed at an angle. For the purpose of avoiding interference between grippers 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).

In this way, the diagonally stretched tenter used to impart diagonal orientation to a 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 preferable that the tenter is capable of orienting the (slow-phase axis) evenly on the left and right sides in the film width direction with high accuracy, and can control the film thickness and retardation with high accuracy.

Next, the stretching operation in the stretching portion 5 will be described with reference to FIG. Both ends of the long film are gripped by the left and right gripping tools Ci / Co, and the long film is conveyed in the heating zone Z as the gripping tools Ci / Co travel. The left and right gripping tools Ci and Co face each other in a direction substantially perpendicular to the film traveling direction (transportation direction D1 before stretching) at the inlet portion (position A in the figure) of the stretching portion 5, and are left and right. The films run along the asymmetric rails Ri and Ro, respectively, and the film gripped near the exit portion (position B in the figure) at the end of stretching is released. The details of the grip opening timing will be described later. The film released from the gripping tools Ci and Co is wound around the winding core by the film winding unit 8 described above. As described above, the pair of rails Ri and Ro each have an endless continuous track, and the gripping tools Ci and Co that have released the film grip at the outlet of the stretched portion 5 travel on the outer rail. Then, they are returned to the entrance in sequence.

At this time, since the rails Ri and Ro are asymmetrical, in the example of FIG. 2, the left and right gripping tools Ci and Co, which were opposed to each other at the position A in the figure, move on the rails Ri and Ro as they travel on the rails. The gripping tool Ci running on the Ri side has a positional relationship that precedes the gripping tool Co running on the rail Ro side.

That is, of the gripping tools Ci and Co that were opposed to the transport direction D1 before stretching the film at the position A in the drawing, one gripping tool Ci is the position B at the end of stretching the film. When the film first reaches, the straight line connecting the gripping tools Ci and Co is inclined by an angle θL with respect to the direction substantially perpendicular to the transport direction D2 after stretching the film. With the above actions, the long film is stretched diagonally at an angle of θL with respect to the width direction. Here, substantially vertical means that it is in the range of 90 ± 1 °.

From the above, in the method for producing a diagonally stretched film of the present embodiment, one end side of the film in the width direction is gripped by a plurality of gripping tools 15 (including the gripping tool Ci), and the other end side is gripped by a plurality of gripping tools 15. It is gripped by the tool 15 (including the grip Co), and one grip 15 on one end side and the other end side (for example, a plurality of grip tools 15 traveling along the rail Ri) is relatively preceded and the other grip is held. It is said that a diagonal stretching step of stretching the film diagonally with respect to the width direction is included by transporting the film with a relative delay of the tool 15 (for example, a plurality of gripping tools 15 traveling along the rail Ro). be able to. In the following description, of the one end side and the other end side in the film width direction, the side on which the gripper travels in relative advance is also referred to as "leading side", and the gripper is relatively delayed. The side that travels is also referred to as the "delay side". For example, in FIG. 2, in the film width direction, the side on which the gripping tool Ci travels is the leading side, and the side on which the gripping tool Co travels is the delay side.

Next, the details of the heating zone Z described above will be described. The heating zone Z of the stretched portion 5 is composed of a preheating zone Z1, a stretching zone Z2, and a heat fixing zone Z3. In the stretched portion 5, the film gripped by the gripping tools Ci and 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 at the inlet of the heating zone Z where the gripping tools Ci and Co that grip both ends of the film travel while maintaining a constant interval (in the film width direction) on the left and right sides.

The stretching zone Z2 refers to a section in which the above-mentioned diagonal stretching step is performed. At this time, if necessary, the film may be stretched in the vertical direction or the horizontal direction before and after the diagonal stretching.

The heat fixing zone Z3 is a section in which a heat fixing step of fixing the optical axis (slow phase axis) of the film is performed after the diagonal stretching step is completed.

After passing through the heat-fixing zone Z3, the stretched film 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. You may. At this time, in consideration of the shrinkage of the film due to cooling, the rail pattern may be formed so as to narrow the distance between the gripping tools Ci and Co that face each other in advance.

The temperature of the preheating zone Z1 should be set to Tg to Tg + 30 ° C., the temperature of the stretching zone Z2 should be set to Tg to Tg + 30 ° C., and the temperature of the heat fixing zone Z3 should be set to Tg-30 to Tg ° C. Is preferable.

In addition, in order to control the thickness unevenness of the film in the width direction, a temperature difference may be provided in the width direction in the stretch zone Z2. In order to make a temperature difference in the width direction in the stretching zone, there are known methods such as adjusting the opening degree of the nozzle that sends warm air into the thermostatic chamber so as to make a difference in the width direction, and arranging heaters in the width direction to control heating. Method can be used. The lengths of the preheating zone Z1, the stretching zone Z2, and the heat fixing zone Z3 can be appropriately selected, and 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 fixing zone Z3. Is usually 50-100%.

Further, assuming that the width of the film before stretching is Wo (mm) and the width of the film after stretching is W (mm), the stretching ratio R (W / Wo) in the stretching step is preferably 1.3 to 3. It is 0, more preferably 1.5 to 2.8. When the stretch ratio is in this range, the thickness unevenness in the width direction of the film is reduced, which is preferable. If the stretching temperature is different in the width direction in the stretching zone Z2 of the diagonally stretched tenter, the thickness unevenness in the width direction can be further improved. The stretch ratio R is equal to the magnification (W2 / W1) when the distance W1 between both ends of the clip gripped at the tenter inlet portion becomes the distance W2 at the tenter outlet portion.

<About the position of the gripper after the diagonal stretching process is completed>
As described above, in the diagonal stretching step, the gripping tool 15 (for example, the gripping tool Ci) that grips one end side in the width direction is relatively preceded before the diagonal stretching step, and the gripping tool Co that grips the other end side is relative. Since the film is stretched diagonally by transporting the film with a delay, the positions of the pair of gripping tools Ci and Co that face each other in the width direction before the diagonal stretching are the positions of the gripping tools Ci and Co that are opposed to each other in the width direction. It shifts in the direction. For example, as shown in FIG. 3, a pair of grippers 15a 1 _· 15b ₁ that was in opposing positional relationship in Habate direction before oblique stretching it is at the end of the oblique stretching process, the gripper 15a ₁ '· 15b becomes the position shown by _{1 ',} located displaced relative to the conveying direction (a pair of grippers 15a 1 _· 15b ₁ is not opposed in the width direction). This phenomenon is unavoidable due to the principle of diagonal stretching. Note that the end of the oblique stretching step, when the pair of grippers 15a 1 _· 15b ₁ which was located opposite to the front oblique stretching in Habate direction starts finishing oblique stretching traveling maintaining a predetermined film width refers to the position of the grippers 15a ₁ of the leading side (in FIG. 3, equal to the position of the grippers 15a ₁ ').

At the end of the diagonal stretching step, if each of the gripping tools 15 that grip both ends in the width direction of the film is deviated in the transport direction of the film, the left and right grippers 15 that are deviated in the transport direction move in the width direction of the film. As described above, a non-uniform stress is applied, and a long diagonally stretched film having a uniform phase difference characteristic cannot be obtained. Therefore, in the present embodiment, as in Patent Document 1, at the end of the diagonal stretching step, the pair of gripping tools 15 are positioned so as to face each other in the film plane in the width direction perpendicular to the transport direction (for example). in Figure 3, so that the grippers 15a 1 _'and the gripper 15b ₃ are opposed in the width direction), the relationship between the pitch P of the traveling direction of the difference and the gripper 15 of the length of the rail Ri · Ro It is set and the position of each gripping tool 15 is adjusted.

Specifically, when the difference in length between the opposing rails Ri and Ro is an integral multiple of the pitch P of the gripping tool 15, the gripping tool 15 facing each other in the width direction before entering the oblique stretching step. By locating the gripping tool 15 so that the straight line connecting 15 is substantially parallel to the width direction of the long film, the straight line connecting the opposing gripping tools 15 and 15 is diagonally stretched at the end position of the diagonal stretching step. It is made to be substantially parallel to the width direction of the film. On the other hand, when the difference in length between the opposing rails Ri and Ro deviates from an integral multiple of the pitch P of the gripping tool 15, the straight line connecting the opposing gripping tools 1 and 15 is long at the end position of the diagonal stretching step. The position of the gripping tool 15 is adjusted to either the front or the back in the moving direction with the device for performing the diagonal stretching stopped so as to be substantially parallel to the width direction of the shaku film. The traveling speed of each gripping tool 15 is constant.

By doing so, no matter how the opposing rails Ri and Ro are deformed, the positions of the left and right gripping tools 15 and 15 are aligned in the width direction at the end of the diagonal stretching process, so that the rails are stretched diagonally. It is possible to reduce the application of non-uniform stress in the width direction of the film, and it is possible to obtain a diagonally stretched film having uniform retardation characteristics. That is, it is possible to obtain a diagonally stretched film in which the variation in the orientation angle in the width direction is reduced.

As described above, at the end of the diagonal stretching step, the positions of the left and right gripping tools 15 and 15 are aligned in the width direction. Therefore, in the heat fixing step after the diagonal stretching step, the film is formed at the end of the diagonal stretching step. A pair of gripping tools 15 and 15 facing each other in the width direction grip both ends of the film in the width direction to transport the film in the transport direction.

<Timing of film grip release>
The film obliquely stretched in the stretching zone Z2 is conveyed in the heat fixing zone Z3 to fix the optic axis, and then the gripping tool 15 is released to be gripped and discharged from the stretched portion 5. Hereinafter, details of the timing of gripping and opening the film in the stretched portion 5 will be described.

FIG. 4 is an explanatory view showing a gripping open position in the stretched portion 5 of the present embodiment. Here, in the heat fixing step, of the pair of gripping tools 15 and 15 facing in the width direction of the film, the gripping tool traveling on the preceding side in the diagonal stretching step is gripped by the first gripping tool 15A (for example, in FIG. 3). The gripping tool 15a ₁ ') and the gripping tool running on the delay side (for example, corresponding to the gripping tool 15b ₃ in FIG. 3) are used as the second gripping tool 15B. The position where the first gripping tool 15A releases the grip of the film is set as the first position S1, and the position where the second gripping tool 15B releases the grip of the film is set as the second position S2.

In the present embodiment, in the heat fixing step, the straight line T connecting the first position S1 and the second position S2 in the plane of the film has a width perpendicular to the film transport direction D2 after the completion of the diagonal stretching step. Prior to the second gripper 15B so that the first position S1 is inclined by an angle θ (°) with respect to the hand direction and the first position S1 is on the upstream side of the second position S2 in the transport direction. The grip of the film by the first gripping tool 15A is open.

5 and 6 schematically show the relationship between the straight line T and the oblique stretching direction (orientation direction of the slow axis). In FIG. 6, the angle formed by the width direction and the in-plane slow phase axis of the film after the completion of the diagonal stretching step is defined as the orientation angle α (°). As described above, by releasing the grip of the film by the first grip 15A before the second grip 15B, as compared with the case where the grip is simultaneously released by the pair of grips facing each other in the width direction. , The straight line connecting the positions where the film grip is released, that is, the straight line T connecting the first position S1 and the second position S2 is in the direction perpendicular to the diagonal stretching direction, that is, the film shrinks due to the diagonal stretching. Approaching the direction V (see FIG. 5) where it occurs.

As a result, the influence of shrinkage due to diagonal stretching of the film can be reduced when the film is gripped and released, and the film is pulled by the shrinkage when the film is gripped and released, so that the fluctuation range in the film transport direction is large in the width direction. It is possible to suppress the shift. As a result, when the maximum value of the amount of fluctuation of the film transport direction from the original direction (the direction perpendicular to the film width direction at the end of diagonal stretching) is simultaneously released at both ends in the film width direction. Can be kept smaller than.

That is, in FIG. 5, the range in which the transport direction of the film fluctuates periodically is β (°), which is the same as the conventional one in which the grips at both ends in the width direction are simultaneously released. However, by releasing the grip of the film by the first grip 15A before the second grip 15B, as described above, the film is pulled by the shrinkage of the film when the grip is released, so that the film transport direction is changed. Since it is possible to suppress a large shift in the width direction, the center of the fluctuation range (fluctuation angle) in the film transport direction is closer to the original direction side than in the conventional case. As a result, the maximum value of the fluctuation angle in the transport direction from the original direction can be set to βmax1 (°), which is smaller than βmax2 in the present embodiment, as opposed to the conventional βmax2 (°).

Therefore, even when the end portion of the film (the portion gripped by the gripper) is subsequently cut by the cutting member (cutting device 9), the angle deviation ((the original direction and the blade described above) when the blade of the cutting member hits the film (Angle deviation from the direction in which the film enters) can be suppressed to be smaller than when the grip is released at both ends in the width direction of the film. As a result, the meandering of the film is not corrected by using a meandering correction device. It is possible to prevent the film from being broken by cutting a portion other than the deformed portion at the time of cutting.

Here, if the angle θ is 0 <θ <90 °, the effect of the present embodiment described above can be obtained, but if the angle θ is 75 ° or more, the heat fixing step is performed. The heat fixing zone Z3 must be formed long in the transport direction, which may lead to an increase in the size of the stretched portion 5 and thus the entire manufacturing apparatus 1. Further, when the heat fixing zone Z3 becomes longer in the transport direction, the temperature difference between the upstream side and the downstream side of the heat fixing zone Z3 becomes large (the closer to the stretching zone Z2, the higher the temperature), so that the temperature difference causes diagonal stretching. It is also concerned that unevenness occurs in the contraction in the direction perpendicular to the direction, and this unevenness worsens the fluctuation in the transport direction (increases the amount of fluctuation). Considering the above, it is desirable that the angle θ is 0 <θ <75 °.

In particular, in absolute value, the closer the angle θ is to the orientation angle α, the closer the straight line T connecting the first position S1 and the second position S2 approaches the direction V perpendicular to the oblique stretching direction. Thereby, the influence of shrinkage due to the oblique stretching of the film can be surely reduced. Then, the fluctuation range in the transport direction of the film is suppressed from being greatly shifted in the width direction, and finally, when the film is cut by the cutting member, the portion other than the deformed portion is cut to ensure that the film is broken. Can be suppressed to. In particular, the thinner the diagonally stretched film, the more likely it is that a hole will be formed by the gripper in the deformed portion (the portion gripped by the gripper), and the film will be more likely to break starting from the hole. It is very effective to bring the angle θ close to the orientation angle α in absolute value when obtaining a thin diagonally stretched film. From this point of view, it is desirable that the angle θ satisfies the following conditional expression in relation to the orientation angle α. That is,
α-10 ° ≤ θ ≤ α + 10 ° ・ ・ ・ (1)
10 ° ≤ α ≤ 50 ° ・ ・ ・ (2)
Is. However, when α = 10 °, Eq. (1) falls within the range including θ = 0 °, and “releases the film grip by the first grip 15A before the second grip 15B”. Therefore, the angle θ in (1) shall be considered in the following cases according to the value of α. That is,
When α = 10 °
α-10 ° <θ≤α + 10 °
And
When 10 ° <α ≤ 50 °
α-10 ° ≤ θ ≤ α + 10 °
Is.

<Other methods of diagonal stretching>
In the present embodiment, as shown in FIGS. 1 to 4, in the oblique stretching step, the film transport path is bent in the middle, and the moving distance of the gripping tool Ci on one end side in the film width direction is set to the other end side. By making it shorter than the moving distance of the gripping tool Co, the gripping tool on one end side in the width direction of the film is relatively preceded, and the gripping tool on the other end side is relatively delayed to convey the film. Diagonal stretching is performed. However, the diagonal stretching method is not limited to such a bending type.

7 and 8 show other examples of the diagonal stretching technique. As shown in FIG. 7, the moving time of the gripping tool Ci on one end side in the film width direction is made shorter than the moving time of the gripping tool Co on the other end side (the moving speed of the gripping tool Ci is set to that of the gripping tool Co). Diagonal stretching may be performed by transporting the film with the gripping tool Ci relatively leading and the gripping tool Co relatively delayed (at a speed higher than the moving speed). Further, as shown in FIG. 8, the moving time of the gripping tool Ci on one end side in the film width direction is shorter than the moving time of the gripping tool Co on the other end side, and the moving distance of the gripping tool Co is set to the other end. Diagonal stretching may be performed by shortening the moving distance of the gripping tool Ci on the side so that the gripping tool Ci is relatively preceded and the gripping tool Co is relatively delayed to convey the film. Even in these cases, in the heat fixing step after the diagonal stretching step, the straight line T connecting the first position S1 and the second position S2 is the width perpendicular to the film transport direction at the end of the diagonal stretching step. The first gripping tool 15B is preceded by the first gripping tool 15B so that the first position S1 is inclined by an angle θ with respect to the direction and the first position S1 is on the upstream side in the transport direction from the second position S2. By releasing the grip of the film by the tool 15A, the effect of the present embodiment that suppresses the breakage of the obliquely stretched film can be obtained.

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

That is, in the long diagonally stretched film obtained by the production method according to the embodiment of the present invention, the variation of the in-plane retardation Ro is 3 nm or less and 1 nm or less at least 1300 mm in the width direction. Is preferable. By setting the variation of the in-plane retardation Ro within the above range, a long diagonally stretched film is bonded to a polarizer to form a circular polarizing plate, and when this is applied to an organic EL image display device, black display is performed. Color unevenness due to leakage of reflected external light can be suppressed. Further, 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.

Further, in the elongated diagonally stretched film obtained by the production method according to the embodiment of the present invention, the variation of the orientation angle θ is less than 0.6 ° in at least 1300 mm in the width direction, which is 0.4. It is preferably less than °. When a long diagonally stretched film with an orientation angle θ of 0.6 ° or more is bonded to a polarizing element to form a circular polarizing plate and installed on an image display device such as an organic EL display device, light leakage occurs. , May reduce the contrast between light and dark.

The optimum value of the in-plane retardation Ro of the elongated diagonally stretched film obtained by the production method according to the embodiment of the present invention is selected depending on the design of the display device used. The Ro is a value obtained by multiplying the difference between the refractive index nx in the in-plane slow-phase axis direction and the refractive index ny in the in-plane direction orthogonal to the slow-phase axis by the average thickness d of the film (Ro = (nx). −NY) × d).

The average thickness of the elongated diagonally 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 from the viewpoint of mechanical strength and the like. It is ~ 35 μm. Further, the thickness unevenness in the width direction of the diagonally stretched film affects the possibility of winding, and therefore, it is preferably 3 μm or less, and more preferably 2 μm or less.

<Circular polarizing plate>
In the circular polarizing plate of the present 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 ( Or the angle formed by 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 of FIG. 9, respectively. In the present embodiment, a long polarizing plate protective film, a long polarizer, and a long λ / 4 retardation film (long diagonally stretched film) are laminated in this order. preferable.

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

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

The polarizing plate can be further formed by laminating 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 shipment of the polarizing plate, product inspection, and the like.

<Organic EL image display device>
FIG. 9 is a cross-sectional view showing a schematic configuration of the organic EL image display device 100 of the present embodiment in an exploded manner. 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 circular polarizing plate 301 on the organic EL element 101 via an adhesive layer 201. The organic EL element 101 is configured to have a metal electrode 112, a light emitting layer 113, a transparent electrode (ITO or the like) 114, and a sealing layer 115 in this order 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 circular polarizing plate 301 is formed by laminating a λ / 4 retardation film 311 and a polarizer 312 and a protective film 313 in this order from the organic EL element 101 side, and the polarizer 312 is a λ / 4 retardation film 311 and a protective film 313. It is sandwiched by and. Both 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 elongated diagonally stretched film of the present embodiment is about 45 ° (or 135 °). The circular polarizing plate 301 is formed by laminating the two.

It is preferable that a cured layer is laminated on the protective film 313. The cured layer not only has the effect of preventing scratches on the surface of the organic EL image display device, but also has the effect of preventing warpage due to the circular 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 that becomes the cathode among the metal electrode 112 and the transparent electrode 114, and the electrode becomes the anode. Holes are injected from the light emitting layer 113, and the two are recombined at the light emitting layer 113 to generate visible light emission corresponding to the light emitting characteristics of the light emitting layer 113. The light generated in the light emitting layer 113 is directly reflected by the metal electrode 112 or then taken out to the outside through the transparent electrode 114 and the circularly polarizing plate 301.

Generally, in an organic EL image display device, an element (organic EL element) that is a light emitting body is formed by laminating a metal electrode, a light emitting layer, and a transparent electrode in this order on a transparent substrate. 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 or the like and a light emitting layer made of a fluorescent organic solid such as anthracene, or a laminate thereof. There are known configurations having various combinations such as a laminate of such a light emitting layer and an electron injection layer made of a perylene derivative or the like, a laminate of these hole injection layers, a light emitting layer, an electron injection layer, and the like.

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

In an organic EL image display device, at least one electrode must be transparent in order to extract light emitted from the light emitting layer, 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 substance having a small work function for the cathode, and usually a metal electrode such as Mg-Ag or Al-Li is used.

In the organic EL image display device having such a configuration, the light emitting layer is formed of an extremely thin film having a thickness of about 10 nm. Therefore, the light emitting layer also transmits light almost completely like the transparent electrode. As a result, the light that is incident from the surface of the transparent substrate when it is not emitting light, passes through the transparent electrode and the light emitting layer, and is reflected by the metal electrode is emitted to the surface side of the transparent substrate again. Therefore, when visually recognized from the outside, it is organic. The display surface of the EL image display device looks like a mirror surface.

The circularly polarizing plate of the present 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, half of the external 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 circular polarizing plate 301, and the other half is transmitted as linearly polarized light. Then, it is incident on 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 °). , Λ / 4 It is converted into circularly polarized light by passing through the retardation film 311.

When the circular polarization emitted from the λ / 4 retardation film 311 is mirror-reflected by the metal electrode 112 of the organic EL element 101, the phase is inverted by 180 degrees and the circular polarization is reflected in the reverse direction. When this reflected light is incident on the λ / 4 retardation film 311 it is converted into linearly polarized light perpendicular to the transmission axis of the polarizer 312 (parallel to the absorption axis), so that it is completely absorbed by the polarizer 312 and is externally absorbed. Will not be emitted to. That is, the circularly polarizing plate 301 can reduce the reflection of external light on the organic EL element 101.

<Example>
Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

[Making a long film]

(Preparation of long film A1)
An alicyclic olefin polymer resin film as the long film A1 was produced by the following production method.

In a nitrogen atmosphere, 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 placed in a reactor at room temperature and mixed with 500 parts by mass of dehydrated cyclohexane, and then 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, while maintaining 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] -dodeca-3-ene (hereinafter abbreviated as MTD) A mixture of norbornene-based monomers composed of parts and 40 parts by mass of tungsten hexachloride (0.7% toluene solution) were continuously added and polymerized over 2 hours. 1.06 parts by mass of butyl glycidyl ether and 0.52 parts by mass of isopropyl alcohol were added to the polymerization solution to inactivate the polymerization catalyst and stop the polymerization reaction.

Next, 270 parts by mass of cyclohexane was added to 100 parts by mass of the reaction solution containing the obtained ring-opening polymer, and 5 parts by mass of a nickel-alumina catalyst (manufactured by Nikki Catalyst Kasei Co., Ltd.) was added as a hydrogenation catalyst. In addition, the mixture was pressurized to 5 MPa with hydrogen, heated to a temperature of 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 Chivas Specialty Chemicals Co., Ltd .; Irganox 1010) were added to the obtained solutions, respectively. And dissolved (0.1 parts by mass per 100 parts by mass of the polymer). Next, the solvent cyclohexane and other volatile components were removed from the solution using a cylindrical concentrating dryer (manufactured by Hitachi, Ltd.), and the hydrogenated polymer was extruded in a molten state from an extruder into strands. After cooling, it was pelletized and recovered. When the copolymerization ratio of each norbornene-based monomer in the polymer was calculated from the residual norbornene composition (by gas chromatography) in the solution after polymerization, it was almost charged at DCP / MTF / MTD = 10/70/20. It was equal to the composition. The weight average molecular weight (Mw) of this ring-opening polymer hydrogenated product was 31,000, the molecular weight distribution (Mw / Mn) was 2.5, the hydrogenation rate was 99.9%, and Tg was 134 ° C.

The obtained pellets of the ring-opening polymer hydrogenated product were dried at 70 ° C. for 2 hours using a hot air dryer through which air was passed to remove water. Next, the pellet is melted using a short-screw extruder having a coated hanger type T-die (manufactured by Mitsubishi Heavy Industries, Ltd .: screw diameter 90 mm, T-die lip member is tungsten carbide, peel strength from molten resin is 44 N). A cycloolefin polymer film having a thickness of 75 μm by extrusion molding (the thickness of the long film after drying obtained by the film forming step, not the thickness of the long diagonally stretched film produced through the stretching step). Manufactured. For extrusion molding, a long film A1 having a width of 1500 mm was obtained under molding conditions of a molten resin temperature of 240 ° C. and a T-die temperature of 240 ° C. in a clean room of class 10,000 or less.

(Preparation of long film B1)
A cellulosic ester-based resin film as the long film B1 was produced by the following production method.

<Particle dispersion liquid>
Fine particles (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass Ethanol 89 parts by mass or more was stirred and mixed with a dissolver for 50 minutes, and then dispersed with manton gorin.

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

<Main doping liquid>
A main doping solution having the following composition was prepared. First, methylene chloride and ethanol were added to the pressurized dissolution tank. Cellulose acetate was poured into a pressurized dissolution tank containing a solvent with stirring. It was heated and completely dissolved with stirring. This is Azumi Filter Paper No. made by Azumi Filter Paper Co., Ltd. Filtration was performed using 244 to prepare the main doping solution. As the sugar ester compound and the ester compound, compounds synthesized by the following synthesis examples were used. Moreover, the following was used as compound (B).

<< Composition of main doping 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 Fine particle addition liquid 1 part by mass

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

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

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

Finally, 100 g of water is added to the separated toluene layer, washed 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) to compound the compound. 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. It was 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 unit Equipment: JASCO Corporation column oven (JASCO CO-965), detector (JASCO UV-970-240 nm), pump (JASCO PU-980), degasser (JASCO DG-980-50)
Column: Inertsil ODS-3 Particle diameter 5 μm 4.6 × 250 mm (manufactured by GL Sciences Co., Ltd.)
Column temperature: 40 ° C
Flow velocity: 1 ml / min
Mobile phase: THF (1% acetic acid): H ₂ O (50:50)
Injection volume: 3 μl
2) MS unit Equipment: 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)
The 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, and a 2 L four-neck equipped with a thermometer, a stirrer, and a slow-speed cooling tube. Place in a flask and gradually raise the temperature in a nitrogen stream until the temperature reaches 230 ° C. with stirring. A dehydration condensation reaction was carried out for 15 hours, and after completion of the reaction, unreacted 1,2-propylene glycol was distilled off under reduced pressure at 200 ° C. to obtain an ester compound. The ester compound had an ester of benzoic acid at the end of a polyester chain formed by condensing 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 device, the casting was uniformly spread on the stainless belt support.

In the endless belt casting device, the main doping liquid was uniformly cast on the stainless steel belt support. Evaporate the solvent on the stainless steel belt support until the amount of residual solvent in the cast long film reaches 75%, peel it off from the stainless steel belt support, and transport it with a large number of rolls. Drying was completed to obtain a long film B1 having a width of 1500 mm. At this time, the thickness of the long film B1 is 75 μm (the thickness of the long film after drying obtained by the film forming step, not the thickness of the long diagonally stretched film produced through the stretching step). there were.

(Preparation of long film C1)
A polycarbonate-based resin film as the long film C1 was produced by the following production method.

<Doping 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 part by mass Methanol 90 part by mass

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

The doped composition was then filtered, cooled and kept at 33 ° C., uniformly cast over a stainless band and dried at 33 ° C. for 5 minutes. After that, the drying time was adjusted so that the retardation was 5 nm at 65 ° C., and after peeling from the stainless band, the drying was completed while being conveyed by a large number of rolls, and the film thickness was 75 μm (the length after drying obtained by the film forming step). A long film C1 having a width of 1500 mm was obtained (which is the thickness of the long film, not the thickness of the long diagonally stretched film produced through the stretching step).

[Comparative Example 1]
The rolled body of the unstretched long film A1 of the norbornene-based resin obtained above is set in the film feeding portion 2 of the obliquely stretched film manufacturing apparatus 1 shown in FIG. 1, and is long from the film feeding portion 2. The length film A1 was fed out and supplied to the stretched portion 5, and diagonally stretched at the stretched portion 5 to obtain a long diagonally stretched film 1 having a film thickness of 60 μm. Then, the obliquely stretched film 1 was conveyed to the film winding portion 8 and wound into a roll.

The stretching conditions in the stretched portion 5 are appropriately selected in the range of (Tg-10) ° C. to (Tg + 30) ° C. of the film, and the film width after diagonally stretching is 1.5 with respect to the film width before diagonally stretching. It was stretched diagonally so as to be doubled.

Further, in the stretching portion 5, the lengths of the rails Ri and Ro and the pitch in the conveying direction of the gripping tools 15 are set so that the pair of gripping tools face each other in the film width direction at the end of the diagonal stretching step. Specifically, in the stretched portion 5, the width of the gripping tool 15 in the transport direction is 40 mm, and the pitch in the transport direction is 50 mm (that is, the distance between the grippers adjacent to each other in the transport direction is 10 mm). Further, the length of the rail Ri on the leading side in the stretched portion 5 was set to 4345 mm, and the length of the rail Ro on the delay side was set to 5094 mm. The stretching angle (orientation angle α) of the film in the stretched portion 5 was set to 10 °. The stretching angle refers to the angle formed by the in-plane slow-phase axis of the film and the film width hand direction at the end of the diagonal stretching step. The stretching angle was adjusted by changing the length of the rail, the degree of bending, and the like in the bent portion (stretch zone Z2) of the stretched portion 5.

Further, in Comparative Example 1, in the heat fixing step after the diagonal stretching step is completed, after the film is conveyed, the gripping by the pair of gripping tools 15A and 15B facing each other in the width direction of the film is simultaneously released and the film is stretched diagonally. The film was discharged from the stretched portion 5. The first gripping tool 15A is a gripping tool that travels on the side leading in the diagonal stretching step among a pair of gripping tools facing each other in the film width direction after the completion of the diagonal stretching step, and is a second gripping tool. Reference numeral 15B is a gripping tool that travels on the side of the pair of gripping tools that is delayed in the diagonal stretching step. That is, in FIG. 4, the position where the first gripping tool 15A releases the grip of the film is set as the first position S1, and the position where the second gripping tool 15B releases the grip of the film is set as the second position S2. When the angle formed by the straight line T connecting the first position S1 and the second position S2 and the film width hand direction is θ, θ = 0 ° in Comparative Example 1.

[Examples 1 to 3]
Diagonally stretched films 2 to 4 were obtained in the same manner as in Comparative Example 1 except that the angle θ was changed to the angle shown in Table 1. That is, the film is released from being gripped by the first gripping tool 15A before the second gripping tool 15B so that the angle θ is the angle shown in Table 1, and the elongated diagonally stretched films 2 to 4 are formed. Obtained.

[Comparative Example 2]
A long diagonally stretched film 5 was obtained in the same manner as in Comparative Example 1 except that diagonally stretching was performed so that the orientation angle α was 20 °. Therefore, also in Comparative Example 2, θ = 0 ° as in Comparative Example 1.

[Examples 4 to 6]
Diagonally stretched films 6 to 8 were obtained in the same manner as in Comparative Example 2 except that the angle θ was changed to the angle shown in Table 1. That is, the film is released from being gripped by the first gripping tool 15A before the second gripping tool 15B so that the angle θ is the angle shown in Table 1, and the elongated diagonally stretched films 6 to 8 are formed. Obtained.

[Comparative Example 3]
A long diagonally stretched film 9 was obtained in the same manner as in Comparative Example 1 except that diagonally stretching was performed so that the orientation angle α was 40 °. Therefore, in Comparative Example 3, θ = 0 ° as in Comparative Example 1.

[Examples 7 to 9]
Diagonally stretched films 10 to 12 were obtained in the same manner as in Comparative Example 3 except that the angle θ was changed to the angle shown in Table 1. That is, the film is released from being gripped by the first gripping tool 15A before the second gripping tool 15B so that the angle θ is the angle shown in Table 1, and the elongated diagonally stretched films 10 to 12 are formed. Obtained.

[Comparative Example 4]
A long diagonally stretched film 13 was obtained in the same manner as in Comparative Example 1 except that diagonally stretching was performed so that the orientation angle α was 40 °. Therefore, in Comparative Example 4, θ = 0 ° as in Comparative Example 1.

[Examples 10 to 12]
Diagonally stretched films 14 to 16 were obtained in the same manner as in Comparative Example 4 except that the angle θ was changed to the angle shown in Table 1. That is, the film is released from being gripped by the first gripping tool 15A before the second gripping tool 15B so that the angle θ is the angle shown in Table 1, and the elongated diagonally stretched films 14 to 16 are formed. Obtained.

[Evaluation]
(Film meandering amount)
The meandering amount of the obliquely stretched films 1 to 16 during transportation was evaluated as follows. That is, in the stretched portion 5, while the gripper traveling on the delay side goes around the rail Ro of the stretched portion 5 once, the film end near the exit of the stretched portion 5 is photographed from above with a video camera and photographed. The amount of film meandering was measured from the obtained image. At this time, the position of the film edge when the film is conveyed in the original direction (the direction perpendicular to the film width hand direction at the end of the diagonal stretching step) is used as a reference, and the film edge from the reference position is used as a reference. The maximum value of the amount of fluctuation in the width direction was defined as the amount of film meandering. Then, the amount of film meandering was evaluated based on the following evaluation criteria.
"Evaluation criteria"
◯: The amount of film meandering is 0 mm or more and 5 mm or less.
X ... The amount of film meandering is larger than 5 mm.

(Presence or absence of film breakage)
It was confirmed whether or not there was breakage when the width hand end portion (the portion gripped by the gripper) of the diagonally stretched films 1 to 16 discharged from the outlet of the stretched portion 5 was cut by the cutting device 9. Then, the breakage of the film was evaluated based on the following evaluation criteria.
"Evaluation criteria"
◯ ・ ・ ・ The film did not break.
× ... The film broke.

The evaluation results of the obliquely stretched films 1 to 16 are shown in Table 1. It should be noted that Examples 4, 7 to 12 are merely reference examples of the present invention and do not belong to the present invention.

From Table 1, in Comparative Examples 1 to 4 in which the angle θ was 0 °, the amount of meandering of the film was large, and breakage of the film was also confirmed. In Comparative Examples 1 to 4, since the gripping of both ends of the film in the width direction is simultaneously released after the diagonal stretching is completed, the straight line connecting the gripping and opening positions of both ends of the film in the film surface and the diagonally The direction perpendicular to the stretching direction (the shrinking direction of the film) is significantly deviated. For this reason, the transport direction of the film is greatly affected by the shrinkage of the film and fluctuates greatly so as to be pulled by the shrinkage of the film when the grip is released, and as a result of a large deviation from the original direction, the meandering amount of the film increases. It is thought that it has grown. Further, since the amount of meandering is large, it is considered that the deviation of the angle when the blade of the cutting device 9 hits the film is also large, and as a result, the film is broken.

On the other hand, in Examples 1 to 12, the amount of film meandering was smaller than that of Comparative Examples 1 to 4, and the film was not broken. In Examples 1 to 12, after the oblique stretching, the film is released from being gripped by the first gripping tool 15A running on the preceding side before the second gripping tool 15B running on the delay side. The straight line connecting the gripping and opening positions at both ends of the film approaches the direction perpendicular to the diagonal stretching direction (the film shrinkage direction). As a result, when the film is gripped and opened, the influence of shrinkage due to diagonal stretching of the film is reduced, and it is possible to suppress a large shift in the fluctuation range of the film in the transport direction in the width direction due to the influence of the shrinkage. Therefore, it is considered that the amount of meandering of the film is reduced. Further, it is considered that the reduction in the amount of meandering reduces the deviation of the angle when the blade of the cutting device 9 hits the film, and as a result, the film does not break.

[Comparative Example 5]
A diagonally stretched film 17 was obtained in the same manner as in Comparative Example 1 except that the stretching conditions were changed so that the film thickness was 30 μm and diagonally stretched. In Comparative Example 5, as in Comparative Example 1, θ = 0 °.

[Examples 13 to 31]
Diagonally stretched films 18 to 36 in the same manner as in Example 1 except that the angle θ was changed to the angle shown in Table 2 and the diagonal stretching was performed under the stretching conditions in which the orientation angle α was the angle shown in Table 2. Got

[Evaluation]
With respect to the obtained diagonally stretched films 17 to 36, the amount of film meandering was evaluated in the same manner as described above, and the presence or absence of holes in the portion where the film was gripped by the gripper in the diagonally stretched step was visually observed. Evaluation was made based on the evaluation criteria.
"Evaluation criteria"
◯ ・ ・ ・ There was no hole in the gripped part at the end of the film.
× ... There was a hole in the gripped portion at the end of the film.

The evaluation results of the obliquely stretched films 17 to 36 are shown in Table 2. Examples 15 to 16 and 19 to 31 are merely reference examples of the present invention and do not belong to the present invention.

From Table 2, in Examples 13 to 31, the film is released from being gripped by the first gripping tool 15A running on the preceding side before the second gripping tool 15B running on the delay side after oblique stretching. It is considered that the amount of meandering of the film is smaller than that of Comparative Example 5 because the influence of shrinkage due to the oblique stretching of the film is reduced when the film is gripped and opened.

Further, as in Examples 13 and 14, when α = 10 °, α-10 ° <θ≤α + 10 °, and as in Examples 17, 18, 21, 22, 25, 26, 10 ° < When α ≦ 50 ° and α -10 ° ≦ θ ≦ α + 10 °, there is no hole in the gripped portion. Even if the diagonally stretched film is a thin film having a film thickness of 30 μm, no holes are formed. Therefore, it can be said that the relationship between θ and α is very effective especially when a thin diagonally stretched film is obtained. ..

In the above, an example in which the long film A1 made of norbornene-based resin is diagonally stretched has been described, but even when the long film B1 made of cellulose ester-based resin film is diagonally stretched, the long film made of polycarbonate-based resin film is long. Even when the film C1 is stretched diagonally, the same result as in Examples 1-31 can be obtained by releasing the gripping of the gripping tools at both ends of the width of the film by the same method as in Examples 1-31. confirmed.

The present invention can be used for manufacturing, for example, an optical film (for example, a λ / 4 retardation film) used for a circularly polarizing plate of an organic EL display device.

15 Grip 15A 1st Grip 15B 2nd Grip S1 1st Position S2 2nd Position T Straight Line θ Angle α Angle

Claims (3)

One end side of the film in the width direction is gripped by a plurality of gripping tools, the other end side is gripped by a plurality of gripping tools, and one gripping tool on the one end side and the other end side is relatively preceded. A diagonal stretching step of stretching the film diagonally with respect to the width direction by transporting the film with the other gripper relatively delayed.
A method for producing a diagonally stretched film, which comprises a heat fixing step of fixing the optical axis of the film after the completion of the diagonally stretched step.
In the heat fixing step, at the end of the diagonal stretching step, both ends of the film in the width direction are gripped by a pair of grippers facing each other in the width direction of the film. Transport,
Of the pair of gripping tools, the gripping tool that travels on the relatively leading side in the diagonal stretching step is used as the first gripping tool, and the gripping tool that travels on the relatively delayed side is used as the second gripping tool. In the heat fixing step, the position where the first gripper releases the grip of the film is defined as the first position, and the position where the second gripper releases the grip of the film is defined as the second position. When you do
In the heat fixing step, the straight line connecting the first position and the second position in the plane of the film is the width direction perpendicular to the transport direction of the film after the completion of the diagonal stretching step. The first gripping tool is used before the second gripping tool so that the first position is obliquely inclined with respect to the second position and the first position is upstream of the second position in the transport direction. Release the grip of the film and
In the plane of the film, the angle formed by the straight line connecting the first position and the second position and the width direction after the completion of the diagonal stretching step is θ (°), and the diagonal stretching is performed. When the angle formed by the width direction after the end of the process and the in-plane slow-phase axis of the film is α (°),
10 ° ≤ α ≤ 20 °
And
When α = 10 °
α-10 ° <θ≤α + 10 °
And
When 10 ° <α ≤ 20 °
α-10 ° ≤ θ ≤ α + 10 °
A method for producing a diagonally stretched film. In the diagonal stretching step, the moving distance of one of the gripping tools on the one end side and the other end side is made shorter than the moving distance of the other gripping tool, so that the one gripping tool is relatively preceded. The method for producing an obliquely stretched film according to claim 1, wherein the film is conveyed with the other gripping tool relatively delayed. In the diagonal stretching step, the moving time of one of the gripping tools on the one end side and the other end side is made shorter than the moving time of the other gripping tool, so that the one gripping tool is relatively preceded. The method for producing an obliquely stretched film according to claim 1 or 2, wherein the film is conveyed with the other gripping tool relatively delayed.

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