Production method for stretchable film

Abstract

To provide a method that can produce stretchable film with very high productivity as a result of suppressing contamination of the production line and suppressing peeling of the adhesive tape used during production.SOLUTION: The production method for a stretchable film according to an embodiment of the present invention includes: feeding the preceding long raw film to the stretching machine while conveying it in a long direction and stretching it; joining the rear end of the preceding long raw film and the leading edge of the following long raw film with an adhesive tape via an intervening film; stretching the trailing long raw film by feeding it to the stretching machine while conveying it in the longitudinal direction; and the elongation at break of the interlaced film at the stretching temperature is greater than the stretch ratio of the stretching in the stretching machine.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a stretched film.

Background Art

[0002] Stretched films are widely used for various applications. A stretched film can typically be obtained by stretching a master roll film composed of a long resin film according to a stretching method and stretching conditions corresponding to the purpose and desired properties. Examples of the stretching method include free-end uniaxial stretching, fixed-end uniaxial stretching, simultaneous biaxial stretching, and sequential biaxial stretching. Examples of the stretching direction include the longitudinal direction (the conveyance or supply direction of the master roll film), the transverse direction (a direction substantially orthogonal to the conveyance or supply direction of the master roll film), and the diagonal direction (a direction forming a predetermined angle with the conveyance or supply direction of the master roll film).

[0003] By the way, when manufacturing a stretched film, from the viewpoint of improving productivity, the tip portion of a new master roll film is joined to the end portion of a preceding long master roll film (so-called splicing), and the new master roll film is continuously supplied to a processing machine (stretching machine) following the preceding master roll film. Such joining is typically performed using an adhesive tape. However, depending on the stretching method, stretching conditions, etc., the joint between the preceding master roll film and the new master roll film may come apart, the adhesive of the adhesive tape may be exposed, and the production line may be contaminated. Also, depending on the stretching method, stretching conditions, etc., peeling of the adhesive tape may occur.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made to solve the above-described conventional problems, and its main object is to provide a method capable of manufacturing a stretched film with very high productivity by suppressing contamination of the production line and suppressing peeling of the adhesive tape used during production.

Means for Solving the Problems

[0006] [1] The method for manufacturing a stretched film according to an embodiment of the present invention includes supplying a preceding long raw film to a stretching machine and stretching it while conveying it in the longitudinal direction; joining the rear end portion of the preceding long raw film and the front end portion of a subsequent long raw film with an adhesive tape via an intervening film; and supplying the subsequent long raw film to a stretching machine and stretching it while conveying it in the longitudinal direction, wherein the elongation at break of the intervening film at the stretching temperature is greater than the stretching ratio of the stretching in the stretching machine. [2] In the above [1], the elastic modulus of the intervening film is equal to or less than the elastic modulus of the raw film. [3] In the above [1] or [2], the glass transition temperature (Tg) of the intervening film is equal to or less than the glass transition temperature (Tg) of the raw film. [4] In any one of the above [1] to [3], the glass transition temperature of the raw film is 120°C or higher. [5] In any one of the above [1] to [4], the stretching temperature in the stretching machine is Tg (°C) to Tg + 15 (°C) of the raw film. [6] In any one of the above [1] to [5], the stretching in the stretching machine is performed in a direction substantially orthogonal to the conveying direction of the raw film. [7] In any one of the above [1] to [6], the stretching ratio in the stretching machine is 1.5 times or more.

Effects of the Invention

[0007] According to an embodiment of the present invention, it is possible to realize a method capable of manufacturing a stretched film with very high productivity by suppressing contamination of the production line and suppressing peeling of the adhesive tape used during production.

Brief Description of the Drawings

[0008]

Fig. 1A

Fig. 1B

Fig. 2A

Fig. 2B

Fig. 2C

Fig. 3A

Fig. 3B

Fig. 3C

Fig. 4

Embodiments for Carrying Out the Invention

[0009] Hereinafter, representative embodiments of the present invention will be described, but the present invention is not limited to these embodiments. For ease of viewing and understanding, the drawings are depicted schematically or conceptually, and lengths, widths, heights, thicknesses, shapes, sizes, ratios, directions, numbers, etc. may differ from the actual ones. Also, there are parts that do not correspond between the drawings.

[0010] (Meanings of Expressions and Terms) (1) Base Film When simply referred to as "base film" in this specification, it means both the preceding base film and the subsequent base film. When it is necessary to distinguish between the preceding base film and the subsequent base film, "preceding" or "front" or "subsequent" or "rear" shall be specified. (2) Preceding Film or Subsequent Film "Preceding film" means the preceding base film or the stretched film obtained from the preceding base film; "subsequent film" means the subsequent base film or the stretched film obtained from the subsequent base film. (3) Joint "Joint" means the portion where the adhesive tape is bonded at the rear end of the preceding film and the front end of the subsequent film. (4) Length and Width "Length" means the length in the conveyance direction (longitudinal direction) of the base film; "width" means the length in the direction orthogonal to the conveyance direction (longitudinal direction) of the base film.

[0011] A. Outline of the Method for Manufacturing a Stretched Film Referring to FIGS. 1A and 1B, the outline of a method for manufacturing a stretched film according to an embodiment of the present invention will be described. As shown in the illustrated example, the method for manufacturing a stretched film according to an embodiment of the present invention includes supplying a preceding long original film 10a to a stretching machine (not shown) while conveying it in the longitudinal direction and stretching it; joining the rear end portion of the preceding long original film 10a and the front end portion of the succeeding long original film 10b with an adhesive tape 30 via an intervening film 40; and supplying the succeeding long original film 10b to the stretching machine while conveying it in the longitudinal direction and stretching it. In an embodiment of the present invention, the elongation at break of the intervening film at the stretching temperature is greater than the stretching ratio of the stretching in the stretching machine. Hereinafter, the original film, the intervening film, and the adhesive tape used, as well as each manufacturing process, will be specifically described.

[0012] B. Original Film As the base film, any appropriate resin film according to the purpose can be adopted. Examples of the resin constituting the base film include, for example, polycarbonate resins or polyester carbonate resins (which may be collectively referred to simply as polycarbonate resins); polyvinyl acetal resins; polyvinyl alcohol resins; cycloolefin resins such as polynorbornene; acrylic resins such as polymethyl acrylate, polymethyl methacrylate, polyethyl acrylate, and polyethyl methacrylate; cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; olefin resins such as polyethylene and polypropylene; polyurethane resins; vinyl resins such as polyvinyl chloride and polyacrylonitrile; polyamide resins; polyimide resins; polyamideimide resins; fluorine resins such as polytetrafluoroethylene; styrene resins such as polystyrene; polysulfone resins; polyether sulfone resins; polyphenylene sulfide resins; polyether ether ketone resins; polyarylate resins. These resins may be used alone or in combination of two or more (by blending or copolymerization). In one embodiment, as the base film, a cycloolefin resin or a polycarbonate resin having isosorbide monomer units and fluorene monomer units can be used.

[0013] The base film is in a long strip shape as described above. Typically, the base film is roll-fed in the long direction and supplied to the stretching machine.

[0014] The preceding base film and the succeeding base film may be the same or different. Preferably, the preceding base film and the succeeding base film are the same. With such a configuration, the same stretching conditions can be adopted in the stretching machine, so that the same stretched film can be manufactured with extremely excellent productivity.

[0015] The elastic modulus (Young's modulus) of the base film can be appropriately set according to the purpose and the intended use of the resulting stretched film, etc. The elastic modulus of the base film may be, for example, 1800 MPa to 3200 MPa, or may be, for example, 2000 MPa to 3000 MPa, or may be, for example, 2100 MPa to 2800 MPa, or may be, for example, 2200 MPa to 2700 MPa. If the elastic modulus of the base film is within such a range, a stretched film applicable to a wide range of uses can be obtained. If the elastic modulus is too large, shrinkage due to residual stress may occur after stretching and the film may come off the clip of the stretching machine. If the elastic modulus is too small, the film may sag during stretching and poor conveyance may occur in the stretching machine. The elastic modulus can be measured in accordance with JIS K 7127.

[0016] The glass transition temperature (Tg) of the base film can be appropriately set according to the purpose and the intended use of the resulting stretched film, etc. The glass transition temperature (Tg) of the base film may be, for example, 100°C or higher, or may be, for example, 110°C or higher, or may be, for example, 120°C or higher. On the other hand, the glass transition temperature (Tg) of the base film may be, for example, 170°C or lower, or may be, for example, 160°C or lower, or may be, for example, 150°C or lower. If the Tg of the base film is within such a range, a stretched film applicable to a wide range of uses can be obtained. If the Tg is too high, it may not be possible to adapt to the upper limit temperature of the stretching machine and the film may break during stretching. If the Tg is too low, the film may sag during stretching and poor conveyance may occur in the stretching machine.

[0017] The thickness of the base film can be appropriately set according to the purpose and the intended use of the resulting stretched film, etc. The thickness of the base film may be, for example, 40 μm to 300 μm, or may be, for example, 50 μm to 250 μm, or may be, for example, 60 μm to 200 μm.

[0018] C. Intermediate film As described above, the break elongation of the intervening film at the stretching temperature in the stretching machine is greater than the stretching ratio of the stretching in the stretching machine. By using such an intervening film, the exposure of the adhesive layer of the adhesive tape at the joint can be suppressed during stretching and / or conveyance of the raw film, and the contamination of the production line can be suppressed. Further, if the intervening film has such a configuration, the peeling of the adhesive tape at the joint can be suppressed during stretching and / or conveyance of the raw film. As a result, by using the intervening film, a stretched film can be manufactured with very high productivity. The ratio of the break elongation (%) of the intervening film to the stretching ratio (%) (break elongation / stretching ratio) is preferably 1.04 or more, more preferably 1.05 to 1.50, still more preferably 1.06 to 1.45, and particularly preferably 1.15 to 1.40. The specific break elongation of the intervening film can vary depending on the stretching ratio. The break elongation of the intervening film may be, for example, 270% or more, or may be, for example, 300% or more, or may be, for example, 320% or more, or may be, for example, 330% or more. On the other hand, the break elongation of the intervening film may be, for example, 450% or less, or may be, for example, 430% or less, or may be, for example, 400% or less. The break elongation can be measured in accordance with JIS K 7127.

[0019] The elastic modulus of the intervening film is such that the ratio of the elastic modulus of the intervening film to the elastic modulus of the raw film (elastic modulus of the intervening film / elastic modulus of the raw film) is preferably 0.80 to 1.10, more preferably 0.90 to 1.00, still more preferably 0.92 to 1.00, and particularly preferably 0.95 to 1.00. In other words, the elastic modulus of the intervening film is preferably equal to or less than the elastic modulus of the raw film, and the difference from the elastic modulus of the raw film is small. With such a configuration, the shrinkage behavior during and after stretching of the raw film and the intervening film becomes similar, and there is an advantage that the transportability and stretchability can be maintained.

[0020] The Tg of the intervening film is preferably -30°C to +5°C, more preferably -25°C to 0°C, still more preferably -20°C to 0°C, and particularly preferably -10°C to 0°C, relative to the Tg of the base film. In other words, the Tg of the intervening film is preferably equal to or lower than the Tg of the base film, and the difference from the Tg of the base film is small. With such a configuration, the shrinkage behaviors of the base film and the intervening film during and after stretching become similar, and there is an advantage that the transportability and stretchability can be maintained.

[0021] The thickness of the intervening film is preferably 20 μm to 300 μm, more preferably 40 μm to 250 μm, still more preferably 60 μm to 200 μm. If the thickness of the intervening film is too large, the adhesive tape may not follow the step due to the thickness of the intervening film, and the adhesive tape may be easily peeled off. If the thickness of the intervening film is too small, the effect of using the intervening film may not be sufficiently obtained.

[0022] The intervening film can be composed of any suitable resin film as long as it satisfies the elongation at break as described above. Specific examples of the resin include the resins described in Item B above for the base film. In the resin, polymerization conditions (as a result, for example, molecular weight, stereoregularity) etc. are appropriately set, a plurality of resins are blended at an appropriate blend ratio, and / or the types, numbers, combinations, blend ratios etc. of the monomers are appropriately set and copolymerized, whereby an intervening film having a desired elongation at break can be obtained. For example, the intervening film may be composed of the same resin as the base film, or may be composed of a resin different from the base film. In one embodiment, the intervening film can be obtained by cutting out the base film. That is, the intervening film can be composed of the same resin as the base film and can have the same elastic modulus and Tg as the base film.

[0023] D. Adhesive Tape The adhesive tape preferably has an elongation at break of 200% or more, more preferably 300% or more. If the elongation at break of the adhesive tape is within such a range, breakage of the adhesive tape during stretching can be suppressed. Further, due to a synergistic effect with the effect of using the intervening film, peeling of the adhesive tape at the joint can be suppressed. As a result, contamination of the production line by the adhesive layer of the adhesive tape can be suppressed, and a stretched film can be produced with very high productivity. Note that the elongation at break of the adhesive tape can be, for example, 700% or less.

[0024] As long as the adhesive tape satisfies the elongation at break as described above, any suitable configuration can be adopted. The adhesive tape may be, for example, a single-sided adhesive tape including a base material and an adhesive layer formed on one surface of the base material, or a double-sided adhesive tape including a base material and adhesive layers formed on both surfaces of the base material. In one embodiment, the base material includes an olefin-based thermoplastic elastomer, and the adhesive layer includes a polypropylene-based resin and / or an acrylic-based resin.

[0025] The tensile strength of the adhesive tape is preferably 10 MPa to 100 MPa, more preferably 40 MPa to 80 MPa. With such a configuration, it is possible to follow the deformation due to stretching while maintaining the adhesion to the raw film during stretching. Note that the tensile strength can be measured in accordance with JIS K 7127.

[0026] The 10% strain stress relaxation rate of the adhesive tape is preferably 30% or more, more preferably 40% or more. With such a configuration, the adhesive tape can be excellent in adhesion and followability to the raw film. The 10% strain stress relaxation rate is a value obtained by using an adhesive tape having the same shape and dimensions as the tensile test piece described in JIS K 6732 as a test piece, stretching it by 10% at a test speed of 300 mm / min and then holding it, measuring the initial stress F and the residual stress f after 10 minutes, and using the following formula (1). 10% strain stress relaxation rate (%) = (F - f) * 100 / F ··· (1)

[0027] The thickness of the adhesive tape is preferably 20 μm to 300 μm, more preferably 50 to 150 μm. If the thickness of the adhesive tape is within such a range, sufficient adhesion, elongation followability, and strength to the base film can be obtained.

[0028] The specific configuration of the adhesive tape is described, for example, in JP-A-2017-211580. The description of this publication is incorporated herein by reference.

[0029] Commercially available products may be used as the adhesive tape. Specific examples of commercially available products include the product names "No. 33T" and "No. 335PE" manufactured by Nitto Denko Corporation.

[0030] E. Elongation of the base film E-1. Outline of the stretching machine and stretching method As described above, the base film is supplied to a stretching machine (not shown) while being conveyed in the longitudinal direction and is subjected to stretching treatment in the stretching machine. As the stretching method, any appropriate stretching method can be selected according to the purpose and the like. Specific examples of the stretching method include free-end uniaxial stretching, fixed-end uniaxial stretching, simultaneous biaxial stretching, and sequential biaxial stretching. As the stretching direction, the longitudinal direction (the conveying or supplying direction of the base film), the transverse direction (a direction substantially orthogonal to the conveying or supplying direction of the base film), and the diagonal direction (a direction forming a predetermined angle with respect to the conveying or supplying direction of the base film) can be mentioned. Further, the stretching may be performed in one step or in multiple steps. When performed in multiple steps, the stretching ratio described below is the product of the stretching ratios of each step.

[0031] As the stretching machine, any appropriate stretching machine can be used according to the intended stretching method. For example, fixed-end stretching can be performed using a tenter stretching machine. Also, for example, free-end stretching can be performed using a roll stretching machine. Also, for example, simultaneous biaxial stretching can be performed using a simultaneous biaxial stretching machine.

[0032] The draw ratio can be appropriately set according to the purpose, the use of the resulting drawn film, etc. The draw ratio may be, for example, 1.5 times (150%) or more, and may also be, for example, 1.8 times (180%) to 4.0 times (400%), and may also be, for example, 1.9 times (190%) to 3.5 times (350%), and may also be, for example, 2.0 times (200%) to 3.0 times (300%).

[0033] The drawing temperature is preferably the Tg (°C) of the base film to Tg + 15 (°C) of the base film, more preferably Tg + 3 (°C) to Tg + 13 (°C) of the base film, and even more preferably Tg + 5 (°C) to Tg + 10 (°C) of the base film.

[0034] E-2. Bonding of the leading base film and the trailing base film Referring again to FIGS. 1A and 1B, the bonding of the leading base film and the trailing base film will be described. The rear end portion of the leading base film and the front end portion of the trailing base film are bonded in a state where the base film is undrawn. The bonding is performed by arranging the intervening film 40 so as to overlap both the rear end portion of the leading base film and the front end portion of the trailing base film, and pasting the adhesive tape 30 through the intervening film 40. Any appropriate method can be adopted for the arrangement of the intervening film and the pasting of the adhesive tape. Specific examples include manual work and the transfer of a laminate of the intervening film and the adhesive tape. In this way, the joint portion 60 can be formed.

[0035] The width of the intervening film is preferably equal to or less than the width of the base film (FIG. 1B shows the case where the width of the intervening film is the same as the width of the base film). With such a configuration, conveyance failure of the base film due to the extending portion (protruding portion) in the width direction of the joint portion can be suppressed.

[0036] The width of the adhesive tape is preferably equal to or less than the width of the intervening film (FIG. 1B shows the case where the width of the adhesive tape is the same as the width of the intervening film). With such a configuration, the adhesive layer of the adhesive tape is not exposed in the width direction, so that contamination of the production line due to the adhesive layer can be suppressed.

[0037] As shown in FIG. 1A, the adhesive tape 30 extends to both the leading original web film 10a side and the trailing original web film 10b side of the intervening film 40, and is bonded to both the leading original web film 10a and the trailing original web film 10b. As a result, a joint portion 60 is formed. The lengths of the extending portions (the bonded portions of the adhesive tape) on the leading original web film side and the trailing original web film side are each preferably 10 mm to 3000 mm, more preferably 100 mm to 1000 mm. If the lengths of the extending portions are within such a range, the adhesion of the extending portions (the adhesion of the adhesive tape to the original web film) can be ensured. The lengths of the extending portions may be the same or different on the leading original web film side and the trailing original web film side.

[0038] The intervening film 40 and the adhesive tape 30 may be arranged below the original web film as shown in FIG. 1A, or may be arranged above the original web film (not shown). That is, the joint portion 60 may be provided below the original web film or above the original web film. Considering workability, the joint portion can be provided above the original web film.

[0039] The rear end portion of the leading original web film 10a and the front end portion of the trailing original web film 10b may be joined by an adhesive tape via the intervening film in a state where they are butted against each other to form a butted portion 20 as shown in FIGS. 1A and 1B, or may be joined by an adhesive tape via the intervening film with a predetermined interval therebetween.

[0040] The specific procedure for joining the leading raw film and the trailing raw film will be described. The joining can be performed by any suitable method. FIGS. 2A to 2C are schematic diagrams showing an example of the joining method. First, as shown in FIG. 2A, the leading raw film 10a wound in a roll shape is fed out from the feeding section 1 and conveyed in the longitudinal direction in a state L with a length longer than the length to be conveyed during the joining process, and is supplied to and stretched by the stretching machine 3. The stretched film 12a after stretching is wound in a roll shape by, for example, the winding section 4 (in the figure, reference numeral 2 indicates a conveying roller). Next, as shown in FIG. 2B, when all of the leading raw film 10a has been fed out, the trailing raw film 10b is set in the feeding section 1 and feeding is started, and while the leading raw film 10a with the extra length is being conveyed, the rear end portion thereof and the front end portion of the trailing raw film 10b are joined with an adhesive tape 30 via an intervening film 40. Then, as shown in FIG. 2C, the joined leading raw film 10a and trailing raw film 10b are continuously supplied to the stretching machine 3. At this time, the trailing raw film 10b is also conveyed in the longitudinal direction in a state L with a length longer than the length to be conveyed during the joining process, so that joining with a subsequent raw film (not shown) can be performed without stopping the conveyance. According to the embodiment of the present invention, by repeating such joining, three or more (for example, three, four, five, six) raw films can be continuously stretched. Also, for example, the leading raw film can be supplied to the stretching machine while being conveyed in the longitudinal direction, the conveyance can be temporarily stopped before the rear end portion is supplied to the stretching machine, and the front end portion of the trailing raw film can be joined. In such a method, the conveyance of the raw film is restarted after the joining is completed. As shown in the figure, the stretched film can be wound in a roll shape while being joined. In the embodiment of the present invention, by using a combination of an intervening film and an adhesive tape, there is an advantage that the stretched film including the joined portion is difficult to break when wound in a roll shape.

[0041] E-3. Stretching of Raw Film Next, the stretching of the raw film will be specifically described. In one embodiment, the stretching is performed in a direction substantially orthogonal to the conveyance direction of the raw film. That is, the stretching can be transverse stretching. In this case, the stretching machine to which the raw film is supplied is typically a tenter stretching machine. The transverse stretching includes, for example, gripping both side ends of the raw film with a plurality of clips, and uniaxially stretching in the width direction by expanding the clip-to-clip distance in the width direction while conveying the raw film in its longitudinal direction.

[0042] Figs. 3A to 3C are schematic plan views for explaining a series of steps of transverse stretching. First, as shown in Fig. 3A, the preceding raw film 10a is transversely stretched while being conveyed, and a stretched film 12a stretched in the width direction is obtained. Next, as shown in Fig. 3B, the joint portion 60 is transversely stretched. Further, as shown in Fig. 3C, the succeeding raw film 10b is transversely stretched while being conveyed, and a stretched film 12b stretched in the width direction is obtained. In the embodiment of the present invention, even when the joint portion is transversely stretched as shown in Figs. 3A to 3C, it is possible to suppress the exposure of the adhesive layer of the adhesive tape and the peeling of the adhesive tape.

[0043] The effects of the embodiments of the present invention are remarkable in the case of lateral stretching. This will be described with reference to FIG. 4. FIG. 4 is a conceptual plan view for explaining the bowing that may occur at the joint 60. As shown in FIG. 4, in the case of lateral stretching, a bowing 50a convex in the conveyance direction side occurs at the rear end portion of the leading film, and a bowing 50b convex in the opposite side to the conveyance direction occurs at the front end portion of the trailing film. As a result, the rear end portion of the leading film and the front end portion of the trailing film may be separated at the joint 60. In this case, if the joint is constituted only by the adhesive tape, the adhesive layer of the adhesive tape may be exposed and the production line may be contaminated. Further / alternatively, the adhesive tape may be peeled off. On the other hand, according to the embodiment of the present invention, by bonding the adhesive tape through a specific intervening film to constitute the joint, even if bowing occurs, the exposure of the adhesive layer of the adhesive tape and the peeling of the adhesive tape are suppressed. In addition, when stretching in the conveyance direction (that is, longitudinal stretching), neck-in occurs in the width direction in both the leading film and the trailing film, so the separation between the rear end portion of the leading film and the front end portion of the trailing film does not substantially occur. Therefore, the possibility of the exposure of the adhesive layer of the adhesive tape is extremely small. However, it goes without saying that the effects according to the embodiments of the present invention can also be obtained even in the case of longitudinal stretching.

[0044] F. Use of the stretched film The stretched film obtained by the embodiment of the present invention can be widely used in various applications. Specific examples of the applications include food packaging film, food packaging wrap film, base film of adhesive tape, optical film (for example, retardation film, polarizer), surface protection film, window sticker film (ultraviolet cut, heat ray cut, splash prevention, crime prevention, blindfold, decoration), agricultural film, medical film, insulating film, building material film. In one embodiment, the stretched film can be an optical film, and more specifically, it can be a retardation film.

[0045] The thickness of the resulting stretched film can be appropriately set according to the purpose, application, etc. The thickness of the stretched film may be, for example, 15 μm to 200 μm, or may be, for example, 20 μm to 150 μm, or may be, for example, 25 μm to 100 μm.

Example

[0046] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. Unless otherwise specified, "parts" and "%" in the examples are based on weight.

[0047] [Production Example 1: Base Film] 26.2 parts by mass of isosorbide (ISB), 100.5 parts by mass of 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene (BHEPF), 10.7 parts by mass of 1,4-cyclohexanedimethanol (1,4-CHDM), 105.1 parts by mass of diphenyl carbonate (DPC), and 0.591 part by mass of cesium carbonate (0.2 mass% aqueous solution) as a catalyst were respectively charged into a reaction vessel. Under a nitrogen atmosphere, as the first stage of the reaction, the temperature of the heat medium in the reaction vessel was set to 150 °C, and the raw materials were dissolved (about 15 minutes) while stirring as necessary. Next, the pressure in the reaction vessel was changed from normal pressure to 13.3 kPa, and while raising the temperature of the heat medium in the reaction vessel to 190 °C over 1 hour, the generated phenol was extracted out of the reaction vessel. After maintaining the temperature in the reaction vessel at 190 °C for 15 minutes, as the second stage of the reaction, the pressure in the reaction vessel was set to 6.67 kPa, and the temperature of the heat medium in the reaction vessel was raised to 230 °C over 15 minutes, and the generated phenol was extracted out of the reaction vessel. Since the stirring torque of the stirrer increased, the temperature was raised to 250 °C in 8 minutes, and in order to further remove the generated phenol, the pressure in the reaction vessel was reduced to 0.200 kPa or less. After reaching a predetermined stirring torque, the reaction was terminated, the generated reaction product was extruded into water, and then pelletized to obtain a polycarbonate resin of BHEPF / ISB / 1,4-CHDM = 47.4 mol% / 37.1 mol% / 15.5 mol%. The obtained polycarbonate resin was vacuum-dried at 80 °C for 5 hours, and then a film-forming apparatus equipped with a single-screw extruder (manufactured by Isuzu Kako Co., Ltd., screw diameter 25 mm, cylinder set temperature: 220 °C), a T-die (width 200 mm, set temperature: 220 °C), a chill roll (set temperature: 120 - 130 °C), and a winder was used to produce a long polycarbonate resin film (thickness 100 μm). The width-direction ends of this polycarbonate resin film were slit so that the width became 150 mm, and it was used as the raw film 1. The Tg of the raw film 1 was 140 °C, and the elastic modulus was 2650 MPa.

[0048] [Production Example 2: Raw Film] Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux condenser controlled at 100 °C. 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluorene-9-yl]methane, 29.21 parts by mass (0.200 mol) of ISB, 42.28 parts by mass (0.139 mol) of SPG, 63.77 parts by mass (0.298 mol) of DPC, and 1.19×10 -2 parts by mass (6.78×10 -5 mol) of calcium acetate monohydrate as a catalyst were charged. After replacing the inside of the reactor with nitrogen under reduced pressure, it was heated with a heat medium, and stirring was started when the internal temperature reached 100 °C. Forty minutes after the start of temperature increase, the internal temperature reached 220 °C, and while controlling to maintain this temperature, reduced pressure was started and it was made 13.3 kPa in 90 minutes after reaching 220 °C. The phenol vapor by-produced during the polymerization reaction was led to a reflux condenser at 100 °C, the monomer components contained in a small amount in the phenol vapor were returned to the reactor, and the phenol vapor that did not condense was led to a condenser at 45 °C and recovered. Nitrogen was introduced into the first reactor to once return the pressure to atmospheric pressure, and then the oligomerized reaction solution in the first reactor was transferred to the second reactor. Next, heating and reduced pressure in the second reactor were started, and the internal temperature was made 240 °C and the pressure 0.2 kPa in 50 minutes. Thereafter, the polymerization was allowed to proceed until a predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, and the produced polyester carbonate was extruded into water, and the strands were cut to obtain pellets. The obtained polycarbonate resin was vacuum-dried at 80°C for 5 hours, and then a film forming apparatus equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250°C), a T-die (width 300 mm, set temperature: 250°C), a chill roll (set temperature: 120 - 130°C), and a winder was used to produce a long polycarbonate resin film (thickness 90 μm). The width direction ends of this polycarbonate resin film were slit to a width of 150 mm to obtain a raw film 2. The Tg of the raw film 2 was 120°C, and the elastic modulus was 2521 MPa.

[0049] [Production Example 3: Raw Film] A commercially available cycloolefin-based resin film (manufactured by Zeon Corporation, product name "Zeonoa ZF14", thickness 100 μm) was slit at the width direction ends to a width of 150 mm to obtain a raw film 3. The Tg of the raw film 3 was 140°C, and the elastic modulus was 2236 MPa.

[0050] [Production Example 4: Intervening Film] A commercially available acrylic resin film (manufactured by Mitsubishi Chemical Corporation, product name "Acrypren", thickness 100 μm) was cut into a predetermined shape to obtain an intervening film A. The Tg of the intervening film A was 120°C, and the elastic modulus was 2212 MPa.

[0051] [Production Example 5: Intervening Film] A commercially available cycloolefin-based resin film (manufactured by Zeon Corporation, product name "Zeonoa ZF16", thickness 100 μm) was cut into a predetermined shape to obtain an intervening film B. The Tg of the intervening film B was 155°C, and the elastic modulus was 2392 MPa.

[0052] [Example 1] As the leading original film and the trailing original film, the original film 1 of Production Example 1 was used respectively. Each original film was joined by the procedure shown in FIGS. 2A to 2C and stretched by the procedure shown in FIGS. 3A to 3C. Specifically, it was as follows. First, as shown in FIG. 2A, the leading original film wound in a roll shape was fed out from the feeding section, and while leaving more than the length to be conveyed during the time required for the joining process, it was roll-conveyed in the longitudinal direction, supplied to a stretching machine and stretched, and the stretched film after stretching was wound in a roll shape at the winding section. The stretching was performed in the transverse direction using a tenter stretching machine as the stretching machine as shown in FIG. 3A. The stretching temperature was 147°C (Tg of the original film + 7°C), and the stretching ratio was 2.85 times.

[0053] Next, as shown in FIG. 2B, when all of the leading original film was fed out, the trailing original film was set in the feeding section and feeding was started, and while the leading original film with the extra length was being conveyed, the trailing end thereof was butted against the leading end of the trailing original film. An intervening film was placed at the butting portion, and an adhesive tape was extended so as to extend to both the leading original film side and the trailing original film side of the intervening film, and the adhesive tape was bonded to both the leading original film and the trailing original film. The intervening film was cut out from the original film 1 and used. The elongation at break of the intervening film at the stretching temperature (147°C) was 341%. As the adhesive tape, a commercially available product (manufactured by Nitto Denko Corporation, product name "No. 33T") was used. The widths of the intervening film and the adhesive tape were both 150 mm, the same as the width of the original film. The lengths of the extending portions (bonding portions of the adhesive tape) on the leading original film side and the trailing original film side were each 100 mm.

[0054] Next, as shown in FIG. 2C, the joined leading original film and trailing original film were supplied to a stretching machine, and the leading original film and trailing original film were continuously subjected to transverse stretching as shown in FIGS. 3B and 3C. The conditions for transverse stretching were the same as above. In this way, a stretched film was continuously produced from the joined leading original film and trailing original film. The obtained stretched film was a long retardation film having a refractive index characteristic of nx > ny = nz, having a slow axis in the width direction, and having an in-plane retardation Re(550) of 144 nm. In a series of manufacturing processes, the following (1) and (2) were evaluated.

[0055] (1) Adhesive tape peeling In the joining and stretching of the original film, the state of the adhesive tape at the joint was confirmed and evaluated according to the following criteria. The results are shown in Table 1. ◎ (Excellent): No peeling is observed. ○ (Good): Peeling is partially observed, but it has no substantial effect on film conveyance. △ (Unacceptable): Peeling that substantially affects film conveyance is observed. × (Defective): Most of it has peeled off, and it has a significant impact on film conveyance.

[0056] (2) Contamination of the production line In the joining and stretching of the original film, the state of the conveying equipment and stretching machine was confirmed and evaluated according to the following criteria. The results are shown in Table 1. ◎ (Excellent): No contamination is observed. ○ (Good): A part of the clips of the stretching machine is contaminated, but it has no substantial effect. △ (Unacceptable): Contamination that requires cleaning of the conveying equipment and stretching machine is observed. × (Defective): The contamination of the conveying equipment and stretching machine is remarkable.

[0057] [Examples 2 to 5 and Comparative Examples 1 to 2] A continuous stretched film was produced from the joined leading original film and trailing original film in the same manner as in Example 1, except that the original film, the intermediate film, and the adhesive tape were as shown in Table 1. Further, the same evaluations as in Example 1 were performed for the joining and stretching of the original film. The results are shown in Table 1. In Table 1, for example, "Original 1" means the original film 1 of Production Example 1, and "Intermediate A" means the intermediate film A of Production Example 4. Also, "-" in the column for the intermediate film means that no intermediate film was used.

[0058]

Table 1

[0059] [Evaluation] As is clear from Table 1, according to the embodiments of the present invention, in the joining and stretching of the original film, both adhesive tape peeling and contamination of the production line are well suppressed. Therefore, it can be seen that according to the embodiments of the present invention, a stretched film can be obtained with very high productivity.

Industrial Applicability

[0060] The stretched film obtained by the production method according to the embodiment of the present invention can be widely used for various applications.

Explanation of Signs

[0061] 10a Leading original film 10b Trailing original film 12a Leading stretched film 12b Trailing stretched film 20 Butt joint 30 Adhesive tape 40 Intermediate film 50a Bowing of the leading film 50b Bowing of the trailing film 60 Joint

Claims

1. A method for manufacturing a stretched film, comprising: feeding a preceding long original film to a stretching machine while conveying it in the longitudinal direction and stretching the film; joining the rear end portion of the preceding long original film and the front end portion of a succeeding long original film with an adhesive tape via an intervening film; and feeding the succeeding long original film to a stretching machine while conveying it in the longitudinal direction and stretching the film, wherein the elongation at break of the intervening film at the stretching temperature is greater than the stretching ratio of the stretching in the stretching machine. The manufacturing method.

2. The manufacturing method according to claim 1, wherein the elastic modulus of the intervening film is equal to or less than the elastic modulus of the original film.

3. The manufacturing method according to claim 2, wherein the glass transition temperature (Tg) of the intervening film is equal to or less than the glass transition temperature (Tg) of the original film.

4. The manufacturing method according to claim 3, wherein the glass transition temperature of the original film is 120°C or higher.

5. The manufacturing method according to claim 4, wherein the stretching temperature in the stretching machine is Tg (°C) to Tg + 15 (°C) of the original film.

6. The manufacturing method according to any one of claims 1 to 5, wherein the stretching in the stretching machine is performed in a direction substantially orthogonal to the conveying direction of the original film.

7. The manufacturing method according to claim 6, wherein the stretching ratio in the stretching machine is 1.5 times or more.

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