JP2017185620A - Method for manufacturing stretched film and device for manufacturing stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a stretched film that is hardly broken in a manufacturing step, and to provide a device for manufacturing a stretched film.SOLUTION: The method for manufacturing a stretched film of slitting in a mechanically flowing direction of a raw material stretched film includes a slitting step of splitting the raw material stretched film in a width direction so as to have an interval of 0.5 mm or more.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a stretched film manufacturing method and manufacturing apparatus.

  A polarizing plate is widely used as a polarizing element in an image display device such as a liquid crystal display device. As a polarizing plate, the thing of the structure which bonded the transparent resin film (protective film etc.) on the single side | surface or both surfaces of the polarizing film using the adhesive agent etc. is common.

  The polarizing film is mainly immersed in a dye bath containing a dichroic dye such as iodine, and then immersed in a cross-linking bath containing a cross-linking agent such as boric acid, with respect to the raw film made of polyvinyl alcohol resin. The film is produced by uniaxially stretching the film at any stage. Uniaxial stretching includes dry stretching in which stretching is performed in the air before the immersion treatment and wet stretching in which stretching is performed in a liquid such as the dyeing bath and the crosslinking bath.

  About the polyvinyl alcohol-type resin film extended | stretched as mentioned above, in order to make a film thickness uniform in Unexamined-Japanese-Patent No. 2011-186085 (patent document 1), the slit which removes the width direction both ends is performed, A method for producing a polarizing film is disclosed.

JP 2011-186085 A

  Conventionally, a stretched film sometimes breaks in a stretched film manufacturing process. Such breakage was more likely to occur as the stretched film was thinner.

  An object of the present invention is to provide a stretched film manufacturing method and a stretched film manufacturing apparatus that are less likely to break during the manufacturing process.

  This invention provides the manufacturing method of the stretched film shown below, and the manufacturing apparatus of a stretched film.

  [1] In the method for producing a stretched film that slits the raw material stretched film in the machine flow direction, the stretched film is produced by a slitting process for dividing the raw material stretched film so as to have an interval of 0.5 mm or more in the width direction. Method.

[2] The slit step is performed by a slit member,
The slit member is a slit blade having a cutting edge portion that contacts the raw material stretched film and performs the slit, and a main body portion that performs the cutting by being interposed in the slit portion of the raw material stretched film. The manufacturing method of the stretched film as described in [1] whose maximum thickness of a part is 0.5 mm or more.

[3] The cutting edge portion of the slit blade is linear,
The method for producing a stretched film according to [2], wherein in the slit step, a linear position of the blade edge portion to be brought into contact with the stretched raw material film is changed.

  [4] The method for producing a stretched film according to any one of [1] to [3], wherein in the slit step, the moisture content of the stretched raw material film is 10 to 18% by weight.

  [5] The method for producing a stretched film according to any one of [1] to [4], wherein in the slit step, the stretched raw material film has a thickness of 15 μm or less.

  [6] The method for producing a stretched film according to any one of [1] to [5], wherein the slit step is performed in an environment having a relative humidity of 35% or more.

  [7] The method for producing a stretched film according to any one of [1] to [6], wherein the slit step is performed in an environment having a relative humidity of 65% or less.

  [8] The method for producing a stretched film according to [7], wherein the slit step is performed in an environment where the relative humidity is less than 50%.

  [9] The method for producing a stretched film according to any one of [1] to [8], wherein the stretched raw material film is a polyvinyl alcohol-based resin film.

[10] The method further includes a preparation step of preparing the stretched raw material film to be subjected to the slitting step,
The method for producing a stretched film according to [9], wherein in the preparing step, the polyvinyl alcohol-based resin film is subjected to at least a stretching treatment, a dyeing treatment, and a crosslinking treatment to obtain the stretched raw material film that is a polarizing film.

  [11] In a stretched film manufacturing apparatus that slits a stretched raw material film in the machine flow direction, the stretched film is manufactured having a slit member that divides the stretched raw material so as to have an interval of 0.5 mm or more in the width direction. apparatus.

  [12] The slit member is a slit blade having a cutting edge portion that contacts the raw material stretched film and performs the slit, and a main body portion that performs the cutting by being interposed in the slit portion of the raw material stretched film. The apparatus for producing a stretched film according to [11], wherein the main body has a maximum thickness of 0.5 mm or more.

[13] The slit member has the linear cutting edge part,
The stretched film manufacturing apparatus according to [11] or [12], wherein the linear position of the cutting edge portion that is brought into contact with the raw material stretched film is changed to slit the raw material stretched film.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the stretched film which is hard to produce a fracture | rupture in a manufacturing process, and the manufacturing apparatus of a stretched film can be provided.

It is a flowchart which shows an example of the manufacturing method of the stretched film which concerns on this invention. It is a schematic sectional drawing which shows an example of the longitudinal stretch process using a heat roll. It is a schematic sectional drawing which shows another example of the longitudinal stretch process using a heat roll. It is a schematic sectional drawing which shows an example of the slit process which concerns on this invention. It is the elements on larger scale of a slit blade. It is a schematic sectional drawing which shows an example of the manufacturing method of a polarizing film.

<Method for producing stretched film>
The manufacturing method of the stretched film which concerns on this invention has a slit process which slits a raw material stretched film in a machine flow direction, and divides | segments so that it may have a space | interval of 0.5 mm or more in the width direction. In one form of this invention, as shown in FIG. 1, before slit process S30, process S10 which prepares a polyvinyl alcohol-type resin film, and extending process S20 which extends a polyvinyl alcohol-type resin film and obtains a raw material stretched film Have In the present specification, the stretched film subjected to the slitting step S30 is referred to as “raw material stretched film”. The present inventors have found that when the raw material stretched film is slit and both ends in the width direction are cut off, cracks are likely to occur on the cut surface of the raw material stretched film, which is one of the causes of breakage. did. According to the slitting process S30 according to the present invention, when slitting both ends of the raw material stretched film in the width direction, it is possible to prevent the occurrence of cracks on the cut surface of the raw material stretched film and to suppress breakage. be able to.

  The slitting step S30 is useful for adjusting the length of the stretched film in the width direction, and for cutting off the ends where defects (waving, wrinkles, blue discoloration, etc.) have occurred. Slit process S30 will not be limited if it is after extending process S20. In addition, extending | stretching process S20 can also be implemented in multiple times, and suppose that slit process S30 is performed after the extending | stretching process of at least 1 time is complete | finished. Hereinafter, each step will be described in detail.

  Hereinafter, the polyvinyl alcohol-based resin film is also referred to as “PVA-based resin film”. Further, the machine flow direction of the film is also referred to as “MD”, and the direction orthogonal to the MD, that is, the width direction of the film is also referred to as “TD”.

(1) Step S10 for preparing a PVA-based resin film
The PVA resin film prepared in this step is a film composed of a polyvinyl alcohol resin, and this film is usually long. As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth) acrylamides having an ammonium group. In addition, “(meth) acryl” represents at least one selected from the group consisting of acryl and methacryl. The same applies to other terms with “(meta)”.

  The degree of saponification of the polyvinyl alcohol-based resin can be in the range of 80.0 to 100.0 mol%, preferably in the range of 90.0 to 100.0 mol%, more preferably 94.0. The range is from 10 to 100.0 mol%, and more preferably from 98.0 to 100.0 mol%. When a saponification degree is less than 80.0 mol%, a polarizing film is produced using the obtained stretched film roll, and when a polarizing plate is produced using this, the water resistance and heat-and-moisture resistance of the polarizing plate are reduced. obtain.

The degree of saponification is the unit ratio (mol%) of the proportion of acetate groups (acetoxy groups: —OCOCH ₃ ) contained in polyvinyl acetate resin, which is a raw material for polyvinyl alcohol resins, changed to hydroxyl groups by the saponification step. The following formula:
Degree of saponification (mol%) = 100 × (number of hydroxyl groups) / (number of hydroxyl groups + number of acetate groups)
Defined by The saponification degree can be determined according to JIS K 6726 (1994).

  The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, more preferably 1500 to 8000, and further preferably 2000 to 5000. The average degree of polymerization of the polyvinyl alcohol resin can also be determined according to JIS K 6726 (1994). When the average degree of polymerization is less than 100, when the obtained stretched film roll is used as a raw material for a polarizing film, it is difficult to obtain a polarizing film having a preferable polarizing performance, and when it exceeds 10,000, the solubility in a solvent deteriorates. The formation (film formation) of a PVA-based resin film can be difficult.

In this specification, the “polyvinyl alcohol-based resin” means a resin in which the structural unit of vinyl alcohol (—CH ₂ —CH (OH) —) is 50 mol% or more in all the structural units contained in the resin. .

  The PVA resin film prepared in this step may be a stretched film, but is usually an unstretched film formed by forming the polyvinyl alcohol resin. The film forming method is not particularly limited, and a known method such as a melt extrusion method or a solvent casting method can be employed.

  A PVA-type resin film can contain additives, such as a plasticizer. Preferred examples of the plasticizer are polyhydric alcohols, and specific examples thereof include ethylene glycol, glycerin, propylene glycol, diethylene glycol, diglycerin, triethylene glycol, triglycerin, tetraethylene glycol, trimethylolpropane, polyethylene glycol and the like. . The PVA-based resin film can contain one or more plasticizers. Content of a plasticizer is 5-20 weight part normally with respect to 100 weight part of polyvinyl alcohol-type resin which comprises a PVA-type resin film, Preferably it is 7-15 weight part.

Further, "standard deviation of the film of thickness in the width direction σ 'of the PVA-based resin films, the thickness of each T _1, T ₂ when measuring the thickness for n points of the PVA-based resin film, ..., T _{When n} and the average thickness of the PVA-based resin film is T, the following formula:

  It is represented by The n measurement points are measurement points along the width direction of the film (positioned so as to be parallel to the width direction) and are positioned at intervals of 50 mm over the entire width of the film. Therefore, the specific numerical value of the integer n varies depending on the entire width of the PVA resin film. The “average thickness T” of the PVA-based resin film is an average value of thickness measurement values at n measurement points. For the stretched film and the polarizing film described later, “standard deviation σ of thickness in the film width direction” and “average thickness T” are measured by the same method. A more specific method for measuring “standard deviation σ of thickness in the film width direction” and “average thickness T” follows the description in the section of Examples described later.

  The average thickness T of the PVA-based resin film is usually 65 μm or less, preferably 50 μm or less, more preferably 35 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less. When using a PVA-based resin film as a raw material for a polarizing film, the smaller the average thickness T of the PVA-based resin film, the more advantageous the thinning of the polarizing film. However, generally, when the average thickness T of the PVA-based resin film is reduced, the film breaks easily. According to the present invention, even when the average thickness T of the PVA-based resin film is small, film breakage can be effectively suppressed. The average thickness T of the PVA resin film is usually 5 μm or more, preferably 10 μm or more.

(2) Stretching step S20
This step is a stretching step of stretching the PVA resin film prepared in step S10 to obtain a raw material stretched film. The stretching treatment for the PVA-based resin film may be dry stretching performed in the air or wet stretching performed in a liquid such as water, an aqueous solution, or an organic solvent.

  The stretching treatment for the PVA resin film is usually uniaxial stretching, preferably longitudinal uniaxial stretching. Longitudinal stretching refers to MD of a film, that is, stretching in the longitudinal direction of the film.

  As dry stretching, a film is passed between a heated roll whose surface is heated and a guide roll (or a heated roll) having a different peripheral speed from the heated roll, and heating using a heated roll. Hot roll stretching that performs longitudinal stretching below; Between rolls that perform longitudinal stretching due to the difference in peripheral speed between these two nip rolls while passing heating means (such as an oven) between two nip rolls installed at a distance. Stretching; tenter stretching; compression stretching and the like.

  Among these, dry stretching is preferably hot roll stretching using a hot roll, because a stretched film with good surface properties is relatively easy to obtain. Therefore, this process is a process of continuously producing a stretched film as a long product by introducing it into a hot roll stretching apparatus including a thermal roll while continuously transporting a long PVA resin film, for example. Can be. Hot roll stretching is usually longitudinal uniaxial stretching, more typically free end longitudinal uniaxial stretching.

  The hot roll stretching apparatus includes at least one hot roll, and may include two or more hot rolls. FIG. 2 shows an example of a hot roll stretching process and a hot roll stretching apparatus used therefor. The hot roll stretching apparatus shown in FIG. 2 includes a first nip roll 10, a hot roll 5, and a second nip roll 20 in order from the upstream side of film conveyance. The PVA-based resin film 1 introduced into the hot roll stretching apparatus is transported along a transport path including the first nip roll 10, the hot roll 5, and the second nip roll 20 in this order. That is, the PVA-based resin film 1 first passes between the first nip rolls 10 and 10 and then travels while contacting the surface in a state of being wound around the heat roll 5, and then between the second nip rolls 20 and 20. The raw material stretched film 2 is obtained by passing. The first nip roll 10, the second nip roll 20, and the heat roll 5 are all drive rolls. The drive roll refers to a roll that can give a driving force for film conveyance to a film that contacts the roll, such as a roll directly or indirectly connected to a roll drive source such as a motor. A guide roll may be provided between the first nip roll 10 and the heat roll 5 and / or between the heat roll 5 and the second nip roll 20.

  In the hot roll stretching apparatus shown in FIG. 2, the tension (tensile force) applied to the PVA-based resin film 1 required for longitudinal stretching is between the first nip roll 10 or the second nip roll 20 and the hot roll 5. It is given by the peripheral speed difference. For example, when the peripheral speed of the heat roll 5 is made larger than the peripheral speed of the first nip roll 10, a tension (rear tension) in the direction from the heat roll 5 toward the first nip roll 10 is applied, and PVA is heated under the heat of the heat roll 5. The system resin film 1 is stretched longitudinally. On the other hand, when the peripheral speed of the second nip roll 20 is made larger than the peripheral speed of the heat roll 5, the tension (forward tension) in the direction from the second nip roll 20 to the heat roll 5 is applied, and the heat is applied by the heat roll 5. The PVA resin film 1 is stretched longitudinally.

  Longitudinal stretching occurs when the PVA-based resin film 1 is heated to such an extent that it can be stretched by the hot roll 5 and sufficient tension is applied. When the back tension is applied, the longitudinal stretching can occur at the moment when the PVA-based resin film 1 comes into contact with the surface of the heat roll 5 and / or before and after (for example, before). When forward tension is applied, longitudinal stretching can occur while in contact with the surface of the hot roll 5 and / or immediately thereafter.

  The preferable range of the tension applied to the PVA-based resin film 1 necessary for the longitudinal stretching is 10 to 25 MPa, and more preferably 13 to 22 MPa. When the tension is less than 10 MPa, the transportability of the film is lowered and wrinkles or the like may occur. Further, when the tension exceeds 25 MPa, it becomes difficult to perform uniform longitudinal stretching. The conveyance speed of a film is not specifically limited, For example, it is 2-20 m / min.

  The heat roll 5 is not particularly limited as long as its surface temperature can be increased, and includes a heat source (for example, a heat medium such as hot water, an infrared heater, an induction heating coil, a dielectric heating circuit, etc.), A roll having a surface made of an alloy such as metal or stainless steel can be used.

  As shown in FIG. 3, the hot roll stretching apparatus may include two or more hot rolls. FIG. 3 shows an example including three heat rolls 6, 7 and 8. When two or more hot rolls are included, longitudinal stretching can occur between the two hot rolls and / or while in contact with the surface of the hot roll.

  The draw ratio of the drawing treatment in this step is usually 1.1 to 8 times, preferably 2 to 6 times. From the viewpoint of the optical properties (particularly polarization properties) of the polarizing film when the stretched raw material film 2 is used as a raw material for the polarizing film, the stretching ratio is more preferably 3.5 times or more, and even more preferably 4 times or more. is there.

  The surface temperature of the hot roll during hot roll stretching is, for example, 80 to 150 ° C. If the surface temperature is too high, the strength of the heated PVA-based resin film 1 is lowered, and there is a possibility that it will break during stretching. If the surface temperature is too low, stretching of the PVA-based resin film 1 may be difficult.

  The average thickness T of the stretched raw material film 2 is usually 2 to 40 μm, and preferably 20 μm or less, more preferably 15 μm or less, more preferably from the viewpoint of thinning the polarizing film produced using the same. Is 10 μm or less. Generally, when the average thickness T of the stretched raw material film is reduced, film breakage is likely to occur. According to the present invention, even when the average thickness T of the stretched raw material film 2 is small, film breakage can be effectively suppressed. The raw material stretched film 2 obtained in this way may be wound up once before being subjected to the next process.

(3) Slit process S30
FIG. 4 is a diagram illustrating an example of the slitting process S30 and a slit member used therefor. The slitting process S30 is a process of slitting the raw material stretched film 2 in the machine flow direction (MD) by using the slit members 9 arranged at both ends, and dividing and removing the end 2a. The slit member 9 includes a slit blade 91 and a slit blade holding portion 92. The slit blade holding portion 92 can hold the slit blade 91 in a predetermined position and has a mechanism for adjusting the feeding amount of the slit blade 91. FIG. 5 shows a partially enlarged view of the slit blade 91. The slit blade 91 includes a linear blade edge portion 91a and a main body portion 91b. In the present specification, the blade edge portion 91 a is an end portion in the slit blade 91 that can contact the raw material stretched film 2 and cut the raw material stretched film 2. Therefore, the blade edge portion 91a is also an end portion of the main body portion 91b. The shape of the blade edge portion 91a is preferably a shape that is not limited to one point where the raw material stretched film 2 can be slit by contacting the raw material stretched film 2, even if it is linear as shown in FIG. Or may be curvilinear. As the thickness of the blade edge portion 91a is thinner, a uniform cut surface can be obtained in the stretched raw material film 2 while blade chipping is likely to occur, and the durability of the blade edge portion 91a is inferior, for example, 0.01 mm to 0.1 mm. can do. Even if the main body 91b has a shape having a tapered predetermined region whose thickness gradually decreases toward the cutting edge 91a (see FIG. 5), the main body 91b includes a predetermined cutting edge 91a including a cutting edge 91a thinner than the maximum thickness. Even a shape having a region may be a shape having a substantially uniform thickness as a whole. The slit blade 91 is preferably a leather blade, for example, made of ceramic or stainless steel. Even if the slit blade 91 includes the entire body portion 91b including the blade edge portion 91a as a single member, the predetermined region including the blade edge portion 91a is the remaining region of the body portion 91b. It may be composed of different members.

  As shown in FIG. 4, in the slitting step S30, the edge portion 91a of the slit blade 91 is brought into contact with the raw material stretched film 2 for slitting, and then the end 2a is stretched by the main body 91b interposed in the slit portion. The film 2 is divided and removed. With respect to the divided end portion 2a, the distance A between the stretched film 2 'and the width direction is 0.5 mm or more. In addition, in this specification, let the time when the raw material stretched film 2 passed the slit blade 91 be the time of parting. About the edge part 2a, since the space | interval A with the stretched film 2 'is the narrowest immediately after parting, the part by which the part A was 0.5 mm or more at this time because the space | interval A at this time was set to 0.5 mm or more. The distance A in the width direction between the portion 2a and the stretched film 2 ′ can be set to 0.5 mm or more. In the present invention, by adjusting the distance A in the width direction between the divided end portion 2a and the stretched film 2 ′ in this way, the occurrence of cracks on the end surface of the stretched film 2 ′ is suppressed in the slitting step S30. Can be suppressed.

  The distance A in the width direction between the divided end 2a and the stretched film 2 'can be adjusted by the thickness of the main body 91b of the slit blade 91, the winding direction of the end 2a, and the like. In one example, by setting the maximum thickness B of the main body portion 91b of the slit blade 91 shown in FIG. 5 to 0.5 mm or more, the distance A between the divided end portion 2a and the stretched film 2 ′ is set to 0.5 mm or more. . The interval A between the divided end portions 2a is usually the same as the maximum thickness B of the main body portion 91b of the slit blade 91 immediately after the division, and then increases. The maximum thickness B of the main body portion 91b of the slit blade 91 is preferably 4 mm or less, and more preferably 2 mm or less.

  In the slitting step S30, the slit blade 91 adjusts the feed amount of the slit blade 91 from the slit blade holding portion 92 so that the contact position of the blade edge portion 91a with the raw material stretched film 2 changes continuously / discontinuously. Or the position of the slit blade 91 is preferably changed. When changing discontinuously, the contact position may be changed at every elapse of a predetermined time, at every completion of the slit of the raw material stretched film of a predetermined length, or the raw material stretched film 2 It may be performed as appropriate depending on the degree of wear of the blade edge portion 91a in contact with the blade. For example, every time the raw material stretched film is slit by 100 to 1000 m, the slit blade 91 is fed out by 0.1 to 1 mm more, so that the contact position of the slit blade 91 with the raw material stretched film 2 is the amount that the slit blade 91 is fed out. Can only be changed.

  Thus, by changing the contact position with the raw material stretched film 2 in the blade edge part 91a of the slit blade 91, the blade edge part 91a can be used effectively, and the blade edge part 91a can be used effectively. It is possible to prevent cracks from being generated on the slit end face due to the consumption of.

  The moisture content of the stretched raw material film 2 in the slitting step S30 is preferably 10 to 18% by weight, more preferably 10 to 16% by weight, and further preferably 12 to 13% by weight. If the moisture content is less than 10% by weight, cracks may occur on the slit end face. On the other hand, when the moisture content exceeds 18% by weight, the rigidity of the stretched raw material film is lowered, and it may be difficult to slit uniformly. In addition, the moisture content of a raw material stretched film means the ratio (%) of the moisture weight in the said film with respect to the weight of a raw material stretched film, and is computed by the method as described in the below-mentioned Example.

  Moreover, it is preferable that the atmosphere which performs slit process S30 is temperature 18-30 degreeC, and it is more preferable that it is 20-25 degreeC. The relative humidity is preferably 30% or more, and preferably 65% or less. When the relative humidity is less than 30%, there is a case where the slit becomes non-uniform or unstable due to the presence of moisture at the time of slitting and the occurrence of catching between the film and the slit blade. On the other hand, if the humidity exceeds 65%, the amount of moisture intervening at the time of slitting becomes excessive, and sagging occurs in the film, which may make the slits non-uniform or unstable. If the slit becomes non-uniform or unstable, it may cause cracks on the slit end face. From the viewpoint of performing the slit uniformly and stably, the relative humidity is more preferably 35% or more. Similarly, from the viewpoint of uniformly and stably slitting, the relative humidity is more preferably 60% or less, preferably less than 50%, and more preferably 40% or less.

  In the slitting step S30, the width of each end 2a in the width direction to be cut is, for example, in the range of 50 to 300 mm, preferably in the range of 100 to 200 mm.

<Production method of polarizing film>
In the case of producing a polarizing film as a stretched film, in combination with the stretching step S20 shown in FIG. 1, a treatment step of bringing the polyvinyl alcohol resin film into contact with the treatment liquid and adsorbing and orienting the dichroic dye, and a drying step are performed. Including. The contact with the processing liquid may be a process of immersing in the processing liquid stored in the processing tank, or may be a method of processing the film by adhering the processing liquid to the film surface by spraying, flowing down, dropping, or the like. .

  Examples of the treatment liquid used in the treatment step include a swelling liquid, a dyeing liquid, a crosslinking liquid, and a washing liquid. And as said process process, the swelling process process which makes a swelling liquid contact a raw fabric film, performs the swelling process, the dyeing process process which makes a dyeing liquid contact the film after swelling process, and a dyeing process Examples include a crosslinking treatment step in which a crosslinking solution is brought into contact with the subsequent film and a washing treatment step in which the washing solution is brought into contact with the film after the crosslinking treatment to perform the washing treatment. The treatment process includes at least a dyeing treatment process and a crosslinking treatment process. The stretching step S20 performs a uniaxial stretching process in a wet or dry manner between these series of processing steps (that is, before and after any one or more processing steps and / or during any one or more processing steps). Other processing steps may be added as necessary.

  Slit process S30 will not be limited if it is after extending process S20. The slitting step S30 is useful for adjusting the length of the stretched film in the width direction, and for cutting off the ends where defects (waving, wrinkles, blue discoloration, etc.) have occurred. Since such a defect can occur in the stretching process and the processing process, it is desirable to perform the slit process S30 after the stretching process and the processing process from the viewpoint of efficiently cutting off the end portion where the defect has occurred. FIG. 6 shows an example of a manufacturing method of a polarizing film and a manufacturing apparatus used therefor. Hereinafter, each step will be described in detail.

(1) Swelling treatment step The swelling treatment step is performed for the purpose of removing foreign matter on the surface of the PVA resin film, removing the plasticizer, imparting easy dyeability, and plasticizing the PVA resin film. The treatment conditions are determined within a range in which the object can be achieved and within a range in which problems such as extreme dissolution and devitrification of the PVA resin film do not occur.

  Referring to FIG. 6, in the swelling treatment step, the unstretched or stretched PVA-based resin film 71 is continuously unwound from the film roll 11 while being transported along the film transport path, and the film 71 is placed in the swelling bath 13. It can be carried out by soaking for a predetermined time and then withdrawing. In the example of FIG. 6, the film 71 is transported along the film transport path constructed by the guide rolls 60 and 61 and the nip roll 50 until the film 71 is unwound and immersed in the swelling bath 13. In the swelling process, the film is conveyed along the film conveyance path constructed by the guide rolls 30 to 32.

  As the swelling liquid of the swelling bath 13, in addition to pure water, boric acid (JP-A-10-153709), chloride (JP-A-06-281816), inorganic acid, inorganic salt, water-soluble organic solvent, alcohol It is also possible to use an aqueous solution to which a kind or the like is added in the range of about 0.01 to 10% by weight.

  The temperature of the swelling bath 13 is, for example, about 10 to 50 ° C., preferably about 10 to 40 ° C., and more preferably about 15 to 30 ° C. The immersion time of the raw film 10 is preferably about 10 to 300 seconds, more preferably about 20 to 200 seconds. Moreover, when the raw fabric film 10 is a polyvinyl alcohol-based resin film previously stretched in gas, the temperature of the swelling bath 13 is, for example, about 20 to 70 ° C, preferably about 30 to 60 ° C. The immersion time of the raw film 10 is preferably about 30 to 300 seconds, more preferably about 60 to 240 seconds.

  In the swelling treatment, the problem that the film 71 swells in the width direction and the film is wrinkled easily occurs. As one means for conveying the film while removing the wrinkles, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll is used for the guide rolls 30, 31 and / or 32, a cross guider, a bend bar. Or using other widening devices such as tenter clips. Another means for suppressing the generation of wrinkles is to perform stretching. For example, the uniaxial stretching process can be performed in the swelling bath 13 by utilizing the peripheral speed difference between the nip roll 50 and the nip roll 51.

  In the swelling treatment, the film also swells and expands in the machine flow direction of the film. Therefore, when the film is not actively stretched, for example, before and after the swelling bath 13 in order to eliminate the sag of the film in the machine flow direction. It is preferable to take measures such as controlling the speed of the nip rolls 50 and 51 to be arranged. In addition, for the purpose of stabilizing the film transport in the swelling bath 13, the water flow in the swelling bath 13 is controlled by an underwater shower, or an EPC device (Edge Position Control device: detecting the edge of the film to meander the film. It is also useful to use a device for preventing the above in combination.

  In the example shown in FIG. 6, the film drawn from the swelling bath 13 passes through the guide roll 32 and the nip roll 51 in this order and is introduced into the dyeing bath 15.

(2) Dyeing process The dyeing process is performed for the purpose of adsorbing and orienting the dichroic dye on the polyvinyl alcohol-based resin film after the swelling treatment. The processing conditions are determined within a range in which the object can be achieved and in a range in which defects such as extreme dissolution and devitrification of the film do not occur. With reference to FIG. 6, the dyeing treatment step is carried along the film carrying path constructed by the guide rolls 33 to 35 and the nip roll 51, and the film after the swelling treatment is treated with the dyeing bath 15 (the treatment accommodated in the dyeing tank). (Liquid) for a predetermined time and then withdrawing. In order to enhance the dyeability of the dichroic dye, the film subjected to the dyeing treatment step is preferably a film subjected to at least some uniaxial stretching treatment, or instead of the uniaxial stretching treatment before the dyeing treatment, Alternatively, in addition to the uniaxial stretching process before the dyeing process, it is preferable to perform the uniaxial stretching process during the dyeing process.

  When iodine is used as the dichroic dye, the concentration of the dyeing solution in the dyeing bath 15 is, for example, iodine / potassium iodide / water = about 0.003-0.3 / about 0.1-10 / weight by weight. An aqueous solution of 100 can be used. Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide and other iodides may be used in combination. In addition, compounds other than iodide, for example, boric acid, zinc chloride, cobalt chloride and the like may coexist. When boric acid is added, it is distinguished from the crosslinking treatment described later in terms of containing iodine. If the aqueous solution contains about 0.003 parts by weight or more of iodine with respect to 100 parts by weight of water, the dyeing bath 15 Can be considered. The temperature of the dyeing bath 15 when dipping the film is usually about 10 to 45 ° C., preferably 10 to 40 ° C., more preferably 20 to 35 ° C., and the dipping time of the film is usually 30 to 600 seconds. Degree, preferably 60 to 300 seconds.

  When a water-soluble dichroic dye is used as the dichroic dye, the concentration of the dyeing solution in the dyeing bath 15 is, for example, dichroic dye / water by weight ratio of about 0.001 to 0.1 / 100. An aqueous solution can be used. This dyeing bath 15 may contain a dyeing assistant or the like, and may contain, for example, an inorganic salt such as sodium sulfate or a surfactant. Only one dichroic dye may be used alone, or two or more dichroic dyes may be used in combination. The temperature of the dyeing bath 15 when dipping the film is, for example, about 20 to 80 ° C., preferably 30 to 70 ° C., and the dipping time of the film is usually about 30 to 600 seconds, preferably about 60 to 300 seconds. is there.

  As described above, in the dyeing process, the film can be uniaxially stretched in the dyeing bath 15. Uniaxial stretching of the film can be performed by a method of making a peripheral speed difference between the nip roll 51 and the nip roll 52 arranged before and after the dyeing bath 15.

  Also in the dyeing process, the widening function such as an expander roll, a spiral roll, or a crown roll is provided on the guide rolls 33, 34 and / or 35 in order to convey the polyvinyl alcohol resin film while removing the wrinkles of the film as in the swelling process. Can be used, or other widening devices such as cross guiders, bend bars, tenter clips can be used. Another means for suppressing the generation of wrinkles is to perform a stretching process as in the swelling process.

  In the example shown in FIG. 6, the film drawn from the dyeing bath 15 passes through the guide roll 35 and the nip roll 52 in this order and is introduced into the crosslinking bath 17.

(3) Crosslinking treatment step The crosslinking treatment step is a treatment carried out for the purpose of water resistance and hue adjustment (such as preventing the film from becoming bluish) by crosslinking. With reference to FIG. 6, the crosslinking treatment is carried along the film conveyance path constructed by the guide rolls 36 to 38 and the nip roll 52, and after the dyeing treatment in the crosslinking bath 17 (crosslinking liquid contained in the crosslinking tank). It can be carried out by immersing the film for a predetermined time and then withdrawing it.

  The crosslinking liquid of the crosslinking bath 17 can be an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid with respect to 100 parts by weight of water. When the dichroic dye used in the dyeing treatment is iodine, the crosslinking liquid preferably contains iodide in addition to boric acid. The amount is, for example, 1 to 30 parts by weight with respect to 100 parts by weight of water. It can be. Examples of iodide include potassium iodide and zinc iodide. In addition, compounds other than iodide, for example, zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, sodium sulfate and the like may coexist.

  In the crosslinking treatment, the concentration of boric acid and iodide and the temperature of the crosslinking bath 17 can be appropriately changed depending on the purpose. For example, when the purpose of the crosslinking treatment is water resistance by crosslinking, and the polyvinyl alcohol resin film is subjected to swelling treatment, dyeing treatment and crosslinking treatment in this order, the crosslinking agent-containing liquid in the crosslinking bath has a concentration by weight ratio. It can be an aqueous solution of boric acid / iodide / water = 3 to 10/1 to 20/100. As needed, it may replace with boric acid and may use other crosslinking agents, such as a glyoxal or glutaraldehyde, and may use boric acid and another crosslinking agent together. The temperature of the crosslinking bath when dipping the film is usually about 50 to 70 ° C., preferably 53 to 65 ° C., and the dipping time of the film is usually about 10 to 600 seconds, preferably 20 to 300 seconds, more preferably. Is 20 to 200 seconds. Moreover, when performing the dyeing | staining process and the crosslinking process in this order with respect to the polyvinyl alcohol-type resin film previously extended | stretched before the swelling process, the temperature of the crosslinking bath 17 is about 50-85 degreeC normally, Preferably it is 55-80 degreeC. .

  In the crosslinking treatment for the purpose of adjusting the hue, for example, when iodine is used as the dichroic dye, the concentration of boric acid / iodide / water is 1 to 5/3 to 30/100 in terms of weight ratio. Liquid can be used. The temperature of the crosslinking bath when dipping the film is usually about 10 to 45 ° C., and the dipping time of the film is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

  The crosslinking treatment may be performed a plurality of times, and is usually performed 2 to 5 times. In this case, the composition and temperature of each crosslinking bath used may be the same or different as long as they are within the above range. The cross-linking treatment for water resistance by cross-linking and the cross-linking treatment for hue adjustment may be performed in a plurality of steps, respectively.

  A uniaxial stretching process can also be performed in the crosslinking bath 17 by utilizing the peripheral speed difference between the nip roll 52 and the nip roll 53.

  In the cross-linking treatment, a widening function such as an expander roll, a spiral roll, or a crown roll is provided on the guide rolls 36, 37 and / or 38 in order to convey the polyvinyl alcohol resin film while removing the wrinkles of the film as in the swelling treatment. Can be used, or other widening devices such as cross guiders, bend bars, tenter clips can be used. Another means for suppressing the generation of wrinkles is to perform a stretching process as in the swelling process.

  In the example shown in FIG. 6, the film drawn from the crosslinking bath 17 passes through the guide roll 38 and the nip roll 53 in this order, and is introduced into the cleaning bath 19.

(4) Cleaning treatment step The example shown in FIG. 6 includes a washing treatment step after the crosslinking treatment step. The washing treatment is performed for the purpose of removing excess chemicals such as boric acid and iodine adhering to the polyvinyl alcohol resin film. The cleaning process is performed, for example, by immersing the crosslinked polyvinyl alcohol resin film in the cleaning bath 19. In addition, instead of the step of immersing the film in the cleaning bath 19, the cleaning treatment step is performed by spraying the cleaning liquid on the film as a shower, or by using both immersion in the cleaning bath 19 and spraying of the cleaning liquid. It can also be done.

  FIG. 6 shows an example in which a cleaning process is performed by immersing a polyvinyl alcohol resin film in the cleaning bath 19. The temperature of the washing bath 19 in the washing treatment is usually about 2 to 40 ° C., and the immersion time of the film is usually about 2 to 120 seconds.

  In the cleaning process, a roll having a widening function such as an expander roll, a spiral roll, or a crown roll is used for the guide rolls 39, 40 and / or 41 for the purpose of conveying the polyvinyl alcohol resin film while removing wrinkles. Or other widening devices such as cross guiders, bend bars, tenter clips can be used. In the film cleaning process, a stretching process may be performed in order to suppress generation of wrinkles.

(5) Stretching step S20
As described above, the PVA-based resin film 71 is uniaxially wet or dry during the series of processing steps (that is, before and after any one or more processing steps and / or during any one or more processing steps). Stretched. The stretching process can be performed a plurality of times before the polarizing film 72 is obtained from the PVA-based resin film 71. As described above, the stretching treatment is also advantageous for suppressing the generation of wrinkles on the film. As for the specific method of the uniaxial stretching treatment, the description related to the stretching step S20 described above is applied.

  The final cumulative draw ratio of the polarizing film 72 based on the unstretched PVA-based resin film 71 is usually about 4.5 to 7 times, preferably 5 to 6.5 times. The stretching treatment step may be performed in any processing step, and when the stretching treatment is performed in two or more processing steps, the stretching treatment may be performed in any processing step.

(6) Drying process It is preferable to perform the process which dries a polyvinyl alcohol-type resin film after a washing process. The drying of the film is not particularly limited, but can be performed using the drying furnace 21 as in the example shown in FIG. The drying temperature is, for example, about 30 to 100 ° C., and the drying time is, for example, about 30 to 600 seconds. The average thickness T of the polarizing film 72 obtained as described above is usually 2 to 40 μm, preferably 20 μm or less, more preferably 15 μm or less, and further preferably 10 μm or less. Generally, when the average thickness T of the polarizing film is reduced, film breakage is likely to occur. According to the present invention, even when the average thickness T of the polarizing film is small, film breakage can be effectively suppressed.

(7) Slit process S30
Slit process S30 is given with respect to the polarizing film 72 which is a raw material stretched film obtained as mentioned above. The above description is applied to the specific method of the slitting step S30. The slit process S30 may be before, during or after the drying process. In FIG. 6, the slitting process S <b> 30 can be performed, for example, at a position P <b> 1 that is a front stage of the drying furnace 21 or a position P <b> 2 that is a rear stage of the drying furnace 21. In addition, it is preferable that the moisture content of the polarizing film at the time of performing slit process S30 is 10 to 18 weight%, Therefore, when satisfy | filling this moisture content in the front | former stage of the drying furnace 21, performing a slit process in the position P1. Is preferred. On the other hand, when the moisture content in the front stage of the drying furnace 21 is high, the slit process may be performed at the position P <b> 2 after the drying furnace 21 has been adjusted to achieve the moisture content.

  In addition, the softness | flexibility falls compared with the crosslinked polyvinyl alcohol-type resin film which performed the crosslinking process process to the polyvinyl alcohol-type resin film compared with before bridge | crosslinking. When the slit process is performed on a film having low flexibility, the film breakage tends to occur, and thus the effect of suppressing the film breakage by the present invention becomes more remarkable. Moreover, when performing a slit process to a film with low flexibility, the breakage of the film can be more significantly suppressed by adjusting the moisture content in the film and the moisture content in the atmosphere.

  Specifically, the moisture content of the polarizing film 72 in the slitting step S30 is preferably 10 to 18% by weight, more preferably 10 to 16% by weight, and further 12 to 13% by weight. preferable. Further, the relative humidity of the atmosphere in the slitting step S30 is preferably 30% or more, and preferably 65% or less. When the relative humidity is less than 30%, there is a case where the slit becomes non-uniform or unstable due to the presence of moisture at the time of slitting and the occurrence of catching between the film and the slit blade. On the other hand, if the humidity exceeds 65%, the amount of moisture intervening at the time of slitting becomes excessive, and sagging occurs in the film, which may make the slits non-uniform or unstable. If the slit becomes non-uniform or unstable, it may cause cracks on the slit end face. From the viewpoint of performing the slit uniformly and stably, the relative humidity is more preferably 35% or more. Similarly, from the viewpoint of uniformly and stably performing the slit, the relative humidity is more preferably 60% or less, further preferably less than 50%, and still more preferably 40% or less.

(8) Other processing steps for the PVA-based resin film Processing other than the processing described above can be added. Examples of treatments that can be added include immersion treatment (complementary color treatment) in an aqueous iodide solution that does not contain boric acid, and immersion treatment in an aqueous solution that does not contain boric acid and contains zinc chloride, etc. Zinc treatment).

<Polarizing plate>
A polarizing plate can be obtained by bonding a protective film via an adhesive on at least one surface of the polarizing film produced as described above. As the protective film, for example, a film made of an acetyl cellulose resin such as triacetyl cellulose or diacetyl cellulose; a film made of a polyester resin such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; a polycarbonate resin film, a cyclo Examples include olefin resin films; acrylic resin films; and films made of polypropylene-based chain olefin resins.

  Surfaces such as corona treatment, flame treatment, plasma treatment, ultraviolet irradiation, primer coating treatment, saponification treatment, etc. on the polarizing film and / or protective film bonding surface in order to improve the adhesion between the polarizing film and the protective film Processing may be performed. As an adhesive used for laminating a polarizing film and a protective film, an active energy ray curable adhesive such as an ultraviolet curable adhesive, an aqueous solution of a polyvinyl alcohol resin, or an aqueous solution in which a crosslinking agent is blended. And water-based adhesives such as urethane emulsion adhesives. The ultraviolet curable adhesive may be a mixture of an acrylic compound and a photo radical polymerization initiator, a mixture of an epoxy compound and a photo cationic polymerization initiator, or the like. Alternatively, a cationic polymerizable epoxy compound and a radical polymerizable acrylic compound may be used in combination, and a photo cationic polymerization initiator and a photo radical polymerization initiator may be used in combination as an initiator.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. The measurement of the average thickness T of the PVA-based resin film and the standard deviation σ of the thickness in the film width direction and the measurement of the moisture content of the PVA-based resin film were according to the following methods.

(1) Measurement of average thickness T of PVA-based resin film and standard deviation σ of thickness in width direction A strip-shaped test piece having an MD length of 50 mm × TD length was cut out from the PVA-based resin film. Subsequently, the thickness of the film was measured at intervals of 50 mm in the film width direction using a digital micrometer “MH-15M” manufactured by Nikon Corporation. From the obtained measured values, an average thickness T of the PVA-based resin film was obtained as an average value of these measured values, and a standard deviation σ of the thickness in the width direction of the PVA-based resin film was obtained.

(2) Measurement of moisture content of PVA-based resin film Using a plurality of PVA-based resin film samples with different moisture rates, moisture content by dry weight method and infrared absorption moisture content meter ("Chino Corporation" A calibration curve (conversion formula) showing a correlation with the measured value of “IRMA1100”) was prepared. A measured value was obtained using the moisture meter, and this was substituted into the calibration curve (conversion formula) and converted to a moisture content [wt%] by the dry weight method, which was used as the moisture content of the film. The moisture content by the dry weight method is represented by the following formula when the weight of the PVA resin film sample when heat-treated at 105 ° C. for 120 minutes is W1, and the weight of the PVA resin film sample before heat treatment is W0:
Moisture ratio [wt%] by dry weight method = {(W0−W1) ÷ W0} × 100
Sought according to.

<Example 1>
PVA resin film having an average degree of polymerization of about 2400, a saponification degree of 99.9 mol% or more, and an average film thickness of 20 μm (vinyl alcohol structural unit (—CH ₂ —CH (OH) —) is 90 mol%) The above was uniaxially stretched 4.1 times in a dry manner using a hot roll having a surface temperature of 105 ° C. Subsequently, the sample was immersed in pure water at 30 ° C. with a residence time of 1 minute while maintaining the tension state, and then the residence time in an aqueous solution at 28 ° C. with a weight ratio of iodine / potassium iodide / water of 0.1 / 5/100. Immerse in 45 seconds. Then, it was immersed in a 67 ° C. aqueous solution having a weight ratio of potassium iodide / boric acid / water of 15 / 5.5 / 100 and a residence time of 200 seconds. Subsequently, after washing with pure water at 20 ° C. for 5 seconds, both ends in the width direction of the PVA-based resin film were removed by slitting in the machine flow direction at a position of 95 mm from the end in the width direction, and then at 40 ° C. for 60 seconds. After drying, a polarizing film having a width of 1290 mm in which iodine was adsorbed and oriented was continuously produced. The average thickness T of the obtained polarizing film was 7.8 μm, and the standard deviation σ of the thickness in the width direction was 0.2 μm.

  In the process of slitting both ends in the width direction of the PVA resin film in the machine flow direction, the moisture content of the PVA resin film was 13% by weight, the temperature of the process was 23 ° C., and the relative humidity was 38%. . The slit uses a ceramic leather blade with a maximum body thickness of 0.5 mm, and the leather blade is fed out 0.2 mm every time the PVA resin film is cut by 500 m, so that the PVA resin is used at the blade edge of the leather blade. The position where the film contacts was changed. In addition, the minimum space | interval after the division | segmentation of the cut part after slitting and a PVA-type resin film was the same as the maximum thickness 0.5mm of the main-body part of a leather blade.

  The breaking frequency of the PVA film when slitting both ends in the width direction was 0.0 times / km. The cutting frequency (unit: times / km) indicates the number of film breaks per 1 km length of the slit stretched film. Specifically, the number of breaks is set to 0.0 times / km when a stretched film having a length of 5 km is slit and there is no breakage, and the breakage occurs before the slit of the stretched film having a length of 5 km is completed. In this case, the reciprocal of the length of the film slit until the time when the break occurred was calculated as the number of breaks.

<Examples 2-4, Comparative Examples 1-2>
Table 1 shows the moisture content of the PVA resin film, the relative humidity of the process, and the maximum thickness of the main part of the leather blade used for the slit in the process of slitting both ends in the width direction of the PVA resin film in the machine flow direction. A polarizing film was continuously produced in the same manner as in Example 1 except that the procedure was changed as described above. The cutting frequency of the PVA resin film in the slitting process was as shown in Table 1. In addition, the minimum space | interval after the cutting part and PVA-type resin film after slitting was the same as the maximum thickness of the main-body part of a leather blade.

<Example 5>
In the step of slitting both ends in the width direction of the PVA-based resin film in the machine flow direction, the polarizing film is continuously formed in the same manner as in Example 1 except that the position where the PVA film contacts the blade edge of the leather blade is not changed. Manufactured. Table 1 shows the cutting frequency of the PVA-based resin film when slitting both ends in the width direction.

  1 polyvinyl alcohol-based resin film (PVA-based resin film), 2 raw material stretched film, 2 ′ stretched film, 5, 6, 7, 8 heat roll, 9 slit member, 10 first nip roll, 11 film roll, 13 swelling bath, 15 dyeing bath, 17 crosslinking bath, 19 washing bath, 20 second nip roll, 21 drying furnace, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 60, 61 guide roll , 50, 51, 52, 53, 54, 55 Nip roll, 71 film, 72 polarizing film, 91 slit blade, 91a blade edge portion, 91b main body portion, 92 slit blade holding portion.

Claims (13)

In the method for producing a stretched film that slits the stretched raw material film in the machine flow direction,
The manufacturing method of a stretched film which has a slit process which divides the said raw material stretched film so that it may have a space | interval of 0.5 mm or more in the width direction. The slit process is performed by a slit member,
The slit member is a slit blade having a cutting edge portion that contacts the raw material stretched film and performs the slit, and a main body portion that performs the cutting by being interposed in the slit portion of the raw material stretched film. The manufacturing method of the stretched film of Claim 1 whose maximum thickness of a part is 0.5 mm or more. The cutting edge portion of the slit blade is linear,
The manufacturing method of the stretched film of Claim 2 which changes the linear position of the said blade edge | tip part made to contact the said raw material stretched film in the said slit process.   The manufacturing method of the stretched film of any one of Claims 1-3 whose moisture content of the said raw material stretched film is 10-18 weight% in the said slit process.   The manufacturing method of the stretched film of any one of Claims 1-4 whose thickness of the said raw material stretched film is 15 micrometers or less in the said slit process.   The said slit process is a manufacturing method of the stretched film of any one of Claims 1-5 performed in the environment whose relative humidity is 35% or more.   The said slit process is a manufacturing method of the stretched film of any one of Claims 1-6 performed in an environment whose relative humidity is 65% or less.   The said slit process is a manufacturing method of the stretched film of Claim 7 performed in the environment where relative humidity is less than 50%.   The said raw material stretched film is a manufacturing method of the stretched film of any one of Claims 1-8 which is a polyvinyl alcohol-type resin film. Further comprising a preparation step of preparing the stretched raw material film to be subjected to the slitting step;
The method for producing a stretched film according to claim 9, wherein in the preparation step, the polyvinyl alcohol-based resin film is subjected to at least stretching treatment, dyeing treatment, and crosslinking treatment to obtain the stretched raw material film that is a polarizing film. In a stretched film manufacturing apparatus that slits a stretched raw material film in the machine flow direction,
An apparatus for producing a stretched film, comprising a slit member that divides the stretched raw material so as to have an interval of 0.5 mm or more in the width direction.   The slit member is a slit blade having a cutting edge portion that contacts the raw material stretched film and performs the slit, and a main body portion that performs the cutting by being interposed in the slit portion of the raw material stretched film. The stretched film manufacturing apparatus according to claim 11, wherein the maximum thickness of the part is 0.5 mm or more. The slit member has the linear cutting edge part,
The stretched film manufacturing apparatus according to claim 11 or 12, wherein the raw material stretched film is slit by changing a linear position of the cutting edge portion to be brought into contact with the raw material stretched film.

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