JP2015187629A - Production method of resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method by which a resin film having nearly zero retardation Rth in a thickness direction can be produced by a melt-extrusion process.SOLUTION: The production method of a resin film includes: a step (I) of obtaining a resin film by extruding a resin at temperature equal to or higher than glass transition temperature thereof from a die into a film; and a step (II) of cooling the resin film by receiving the film on a support face of a support body. In the step (II), the resin film includes a first fixed region, a first stretched region, a center region, a second stretched region, and a second fixed region, in this order in a width direction of the resin film. The step (II) includes a step of bringing the first fixed region and the second fixed region of the resin film, into tight contact with the support face; and a stretched amount in the first stretched region and in the second stretched region when the same tension is applied to the film is larger than a stretched amount in the center region.

Description

  The present invention relates to a method for producing a resin film using a melt extrusion method.

  As one method for producing a resin film, there is a melt extrusion method (Patent Documents 1 and 2). In the melt extrusion method, generally, a molten resin is extruded into a film from a die to obtain a film made of the molten resin. Thereafter, the film made of the molten resin is received by a support such as a cast roll and cooled to cure the resin, thereby obtaining a desired resin film.

  In the melt extrusion method, edge pinning is usually performed to prevent neck-in. Here, neck-in refers to a phenomenon in which a film made of molten resin extruded from a die shrinks in the width direction. Moreover, edge pinning means operation which makes the both ends of the width direction of the film received with the support body contact | adhere to a support body. By performing edge pinning, shrinkage of the film can be prevented, so that a resin film having a desired width can be manufactured.

JP-A-2005-99097 JP 2009-166325 A

  For example, since it is used for a protective film for a polarizing plate, a film having optical isotropy may be required. Here, the film having optical isotropy is a film in which the in-plane retardation Re and the thickness direction retardation Rth are close to zero. In general, when the film thickness is reduced, the in-plane retardation Re and the thickness direction retardation Rth of the film tend to be close to zero. For this reason, it has been considered that a film having optical isotropy can be produced by reducing the thickness of a film not subjected to stretching treatment.

  However, it is difficult to obtain a resin film having optical isotropy even if a resin film having a small thickness and not subjected to stretching treatment is produced by a melt extrusion method. Specifically, in the melt extrusion method, the retardation Re in the in-plane direction can be brought close to zero, but it is difficult to bring the retardation Rth in the thickness direction close to zero.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a production method capable of producing a resin film having a retardation Rth in the thickness direction close to zero by a melt extrusion method.

As a result of intensive studies to solve the above-mentioned problems, the present inventor, when cooling and curing a molten resin film on a support in a melt extrusion method, the resin film has a first fixing region, a first stretching region, A central region, a second extension region, and a second fixing region are provided, the first fixing region and the second fixing region are brought into close contact with the support, and the extensibility of the first extension region and the second extension region is extended to the central region. It has been found that a resin film having a retardation Rth in the thickness direction close to zero can be produced by making it higher than the property, and the present invention has been completed.
That is, the present invention is as follows.

[1] Step (I) of extruding a resin having a temperature equal to or higher than the glass transition temperature from a die into a film to obtain a resin film;
Receiving the resin film at the support surface of the support having a support surface and cooling it (II),
In at least the step (II) of the steps (I) and (II), the resin film has a first fixing region, a first extension region, a central region, a second extension region, and a second fixing region, In this order in the width direction of the resin film,
The step (II) includes bringing the first fixing region and the second fixing region of the resin film into close contact with the support surface,
The method for producing a resin film, wherein an extension amount of the first extension region and the second extension region is larger than an extension amount of the central region when the same tension is applied.
[2] The thickness of the first extension region is smaller than the thickness of the central region,
The method for producing a resin film according to [1], wherein the thickness of the second extension region is thinner than the thickness of the central region.
[3] In the resin film immediately after being extruded from the die,
The thickness of the first extension region is not less than 15% and not more than 85% of the thickness of the central region;
[2] The method for producing a resin film according to [2], wherein the thickness of the second extension region is 15% or more and 85% or less of the thickness of the central region.
[4] The resin contained in the central region is different from the resin contained in the first extension region,
The method for producing a resin film according to any one of [1] to [3], wherein the resin contained in the central region is different from the resin contained in the second extension region.
[5] The glass transition temperature of the resin contained in the first extension region is lower than the glass transition temperature of the resin contained in the central region,
The method for producing a resin film according to [4], wherein the glass transition temperature of the resin contained in the second extension region is lower than the glass transition temperature of the resin contained in the central region.
[6] Any one of [1] to [5], wherein a sum of a width of the first extension region and a width of the second extension region is not less than 0.5% and not more than 20% of a width of the central region. The manufacturing method of the resin film of one term.
[7] The method for producing a resin film according to any one of [1] to [6], wherein the central region includes an olefin resin.
[8] Steps (III) including cutting the resin film after the step (II) at a position closer to the central region than the first fixing region and the second fixing region are included. [7] The method for producing a resin film according to any one of [7].

  According to the method for producing a resin film of the present invention, a resin film having a retardation Rth in the thickness direction close to zero can be produced by a melt extrusion method.

FIG. 1 is a schematic view schematically showing a resin film manufacturing apparatus according to the first embodiment of the present invention. FIG. 2 is a perspective view schematically showing the periphery of the cast roll in the manufacturing apparatus according to the first embodiment of the present invention. FIG. 3 is a plan view schematically showing the lip of the die according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view schematically showing a resin film extruded from a die in the manufacturing method according to the first embodiment of the present invention. FIG. 5 is a plan view schematically showing a resin film extruded from a die in the manufacturing method according to the first embodiment of the present invention. FIG. 6 is a schematic view schematically showing a resin film manufacturing apparatus according to the second embodiment of the present invention. FIG. 7 is a perspective view schematically showing the periphery of the cast roll in the manufacturing apparatus according to the second embodiment of the present invention. FIG. 8 is a plan view schematically showing the lip of the die according to the second embodiment of the present invention. FIG. 9 is a cross-sectional view schematically showing a resin film extruded from a die in the manufacturing method according to the second embodiment of the present invention. FIG. 10 is a plan view schematically showing a resin film extruded from a die in the manufacturing method according to the second embodiment of the present invention.

  Hereinafter, the present invention will be described in detail with reference to examples and embodiments. However, the present invention is not limited to the following examples and embodiments, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

  In the following description, the retardation Re in the in-plane direction of the film is a value represented by Re = (nx−ny) × d unless otherwise specified. The retardation Rth in the thickness direction of the film is a value represented by Rth = {(nx + ny) / 2−nz} × d. Here, nx represents a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the film and giving the maximum refractive index. ny represents a refractive index in the in-plane direction of the film and in a direction perpendicular to the nx direction. nz represents the refractive index in the thickness direction of the film. d represents the film thickness of the film. Unless otherwise stated, the retardation measurement wavelength is 590 nm. The retardation can be measured using a commercially available phase difference measuring device (for example, “KOBRA-WPR” manufactured by Oji Scientific Instruments) or the Senarmont method.

[Overview]
The method for producing a resin film of the present invention is a method for producing a resin film using a melt extrusion method, and a step of obtaining a resin film by extruding a resin having a temperature equal to or higher than the glass transition temperature from a die into a film (I And the step (II) of receiving and cooling the resin film on the support surface of the support having the support surface. A resin having a temperature equal to or higher than the glass transition temperature is melted, but the resin is cured when cooled to below the glass transition temperature. Therefore, a desired resin film can be obtained by forming a soft resin having a glass transition temperature or higher into a film and then curing it by cooling.

  Usually, it is difficult to obtain a desired thickness and characteristics of the resin film as described above in the vicinity of both edges in the width direction. Therefore, the resin film is manufactured so as to obtain a desired thickness and characteristics in the central region sandwiched between the regions near the edges as described above.

  In the step (II), the resin film is provided with a first fixing region and a second fixing region for contacting the support surface of the support closer to the edge of the resin film than the central region. The Usually, these 1st fixation area | regions and 2nd fixation area | regions are provided in the vicinity area | region of the edge of the width direction of a resin film. In the method for producing a resin film of the present invention, the step (II) includes bringing the first fixing region and the second fixing region into close contact with the support surface. Thereby, since shrinkage | contraction of the width | variety of the resin film by shrinkage | contraction of the cooled resin can be prevented, neck-in can be prevented or the conveyance stability of a resin film can be improved.

  Furthermore, in at least step (II) of the steps (I) and (II) according to the method for producing a resin film of the present invention, a first extension is performed between the central region and the first fixing region of the resin film. A region is provided, and a second stretched region is provided between the central region of the resin film and the second stretched region. Therefore, in the step (II), the resin film includes a first fixing region, a first extension region, a central region, a second extension region, and a second fixing region in this order in the width direction. In addition, the first extension region and the second extension region are provided so that the extension amount of the first extension region and the second extension region is larger than the extension amount of the central region when the same tension is applied. Yes.

  By having such a configuration, the method for producing a resin film of the present invention can produce a resin film having a thickness direction retardation Rth close to zero in the central region. The reason why the retardation Rth in the thickness direction in the central region of the resin film can be brought close to zero by the method for producing a resin film of the present invention is not necessarily clear, but according to the study of the present inventors, it is assumed as follows. . However, the present invention is not limited by the following inference.

  Consider the state of the resin film when the resin film made of molten resin extruded from a die is received by the support surface of the support and cooled. For example, when the first fixing region and the second fixing region provided at both ends in the width direction of the resin film are brought into close contact with the support surface of the support, the first fixing region and the second fixing region are fixed to the support surface. The Therefore, even if a stress to shrink the resin occurs due to cooling, the first fixing region and the second fixing region do not move in the width direction of the resin film. Not open. Therefore, if there is no first stretching region and second stretching region, the stress generated by cooling causes deformation in the thickness direction in the central region sandwiched between the first fixing region and the second fixing region of the resin film. Acts as if by now. For this reason, since the orientation of the molecules contained in the resin occurs in the thickness direction of the resin film, it is conventionally considered that it has been difficult to bring the retardation Rth in the thickness direction close to zero.

  In contrast, in the method for producing a resin film of the present invention, in the step (II) in which the resin film is cooled, a first extension region is provided between the central region and the first fixing region, and the central region and the first A second extension region is provided between the two fixed regions. Generally, when the first fixing region and the second fixing region of the resin film extruded from the die are brought into close contact with the support surface of the support, the resin film and the support are supported in the region sandwiched between the first fixing region and the second fixing region. An air layer is formed between the body and the support surface. Therefore, the first extension region and the second extension region can be extended without being in close contact with the support surface of the support. Therefore, when stress is generated by cooling the resin in the step (II), these first stretched region and second stretched region have a higher stretchability than the central region. The stretch area stretches. The stress is released by the extension of the first extension region and the second extension region. Therefore, even if stress is generated by cooling the resin in the step (II), the stress does not cause molecular orientation in the central region of the resin film. Therefore, it is presumed that the retardation Rth in the thickness direction can be brought close to zero in the central region of the cured resin film.

[First embodiment]
FIG. 1 is a schematic view schematically showing an apparatus 100 for producing a resin film 10 according to the first embodiment of the present invention. FIG. 2 is a perspective view schematically showing the periphery of the cast roll 120 of the manufacturing apparatus 100 according to the first embodiment of the present invention.
As shown in FIG.1 and FIG.2, the manufacturing apparatus 100 of the resin film 10 which concerns on 1st embodiment of this invention is the die 110, the cast roll 120 as a support body, and the electrostatic pinning apparatus 131 as a contact | adherence apparatus. And 132, a peeling roll 140 as a peeling device, a trimming device 150, and a winding shaft 160 as a winding device.

Die 110, a single resin having a glass transition temperature or higher from the resin supply device, not shown, is provided so as be fed as indicated by arrow A _110. The die 110 is provided so that the resin supplied in this manner is extruded into a film shape through the lip 116 so that the resin film 20 made of a molten resin can be obtained.

FIG. 3 is a plan view schematically showing the lip 116 of the die 110 according to the first embodiment of the present invention.
As shown in FIG. 3, in the die 110 according to the present embodiment, the resin film 20 when cooled by the cast roll 120 has a first fixing region 21, a first extension region 22, and a width direction of the resin film 20. The shape of the lip 116 is set so that the central region 23, the second extension region 24, and the second fixed region 25 are provided in this order.
Specifically, in the lip 116, the resin that forms the first extension region 22 between the portion 111 through which the resin forming the first fixing region 21 passes and the portion 113 through which the resin forming the central region 23 passes. A portion 112 through which is passed is provided. The lip clearance C ₁₁₂ of the portion 112 through which the resin forming the first extension region 22 passes is set smaller than the lip clearance C _{113 of the} portion 113 through which the resin forming the central region 23 passes.
Further, the lip 116 is a portion through which the resin forming the second extension region 24 passes between the portion 115 through which the resin forming the second fixing region 25 passes and the portion 113 through which the resin forming the central region 23 passes. 114 is provided. The lip clearance C ₁₁₄ of the portion 114 through which the resin forming the second extension region 24 passes is set smaller than the lip clearance C _{113 of the} portion 113 through which the resin forming the central region 23 passes.
Here, the lip clearance means the width of the lip 116. By adjusting the lip clearance of the lip 116, the thickness of the resin film 20 formed by the resin extruded through the lip 116 can be controlled. Thus, die 110, the resin film 20 has a configuration capable of reducing the thickness _{T 24} of the thickness _{T 22} and the second stretch region 24 of the first stretch region 22 than the thickness _{T 23} of the central region 23 (see FIG. 4 ).

As shown in FIG. 1, the cast roll 120 is a roll having an outer peripheral surface 121 as a support surface that can receive the resin film 20 extruded from the die 110. The cast roll 120 is provided at a position facing the die 110.
Further, the cast roll 120 is provided so as to be rotated as indicated by an arrow A ₁₂₀ by a driving force applied from a driving device (not shown). Therefore, the cast roll 120 has a configuration capable of transporting the resin film 20 received on the outer peripheral surface 121 by the rotation of the cast roll 120.
Furthermore, the cast roll 120 is provided so that temperature adjustment is possible. Therefore, the cast roll 120 has a configuration capable of cooling the resin film 20 received on the outer peripheral surface 121 to a desired temperature. In this embodiment, the temperature of the cast roll 120 is the glass transition of the resin contained in the resin film 20 during the period from when the resin film 20 is received by the peripheral surface 121 of the cast roll 120 until it is peeled off by the peeling roll 140. It is set so that the resin film 20 can be cooled below the temperature.

  As shown in FIG. 2, the electrostatic pinning device 131 is provided so as to give an electrostatic charge to the first fixed region 21 set in the vicinity of one edge 26 of the resin film 20 received by the cast roll 120. It has been. Further, the electrostatic pinning device 132 is provided so that an electrostatic charge can be given to the second fixed region 25 set in the vicinity of the other edge 27 of the resin film 20 received by the cast roll 120. Usually, the first fixing region 21 and the second fixing region 25 are set apart from the edges 26 and 27 of the resin film 20, respectively. The production apparatus 100 casts the first fixing area 21 and the second fixing area 25 of the resin film 20 by applying electrostatic charges to the first fixing area 21 and the second fixing area 25 from the electrostatic pinning devices 131 and 132, respectively. It has a configuration that can be brought into close contact with the outer peripheral surface 121 of the roll 120.

As shown in FIG. 1, the peeling roll 140 is provided so as to be rotatable in parallel with the cast roll 120 as indicated by an arrow A ₁₄₀ . The peeling roll 140 is provided so that the resin film 20 cooled to below the glass transition temperature of the resin contained in the resin film 20 by the cast roll 120 can be peeled from the outer peripheral surface 121 of the cast roll 120. Further, the peeling roll 140 is provided so that the peeled resin film 20 can be sent to the trimming device 150.

The trimming device 150 is a device for cutting out at least the first fixed region 21 and the second fixed region 25 from the resin film 20 peeled by the peeling roll 140.
The trimming device 150 includes trimming knives 151 and 152 provided in pairs with blades on the outer periphery. These trimming knives 151 and 152 are provided so as to cut the resin film 20 in the vicinity of the boundary between the central region 23 and the first extension region 22 and in the vicinity of the boundary between the central region 23 and the second extension region 24. . Here, the vicinity of the boundary is a position closer to the central area 23 than the fixed areas 21 and 25, may be the boundary itself, may be a position closer to the central area 23 than the boundary, The positions may be on the side of each of the extension regions 22 and 24 from the boundary. Thereby, the trimming apparatus 150 has a configuration in which the end film 28 including the first fixing region 21 and the end film (not shown) including the second fixing region 25 can be cut off from the resin film 20, respectively. Have. Further, the trimming device 150 is provided so that the resin film 10 including the central region 23 remaining after cutting the end film 28 from the resin film 20 can be sent to the winding shaft 160.
Further, the trimming device 150 can convey the end film 28 including the first fixing region 21 and the end film including the second fixing region 25 cut out from the resin film 20 separately from the resin film 10. A transport roll 153 is provided.

The winding shaft 160 is provided such that it can be rotated as indicated by an arrow A ₁₆₀ by a driving device (not shown). Therefore, the winding device 160 has a configuration in which the film roll 30 can be obtained by winding the resin film 10 sent from the trimming device 150.

  The manufacturing apparatus 100 of the resin film 10 which concerns on 1st embodiment of this invention is comprised as mentioned above. When manufacturing the resin film 10 using this manufacturing apparatus 100, the process (I) which obtains the resin film 20 by extruding the resin which has temperature more than a glass transition temperature from the die | dye 110 in a film form, and the resin film 20 The manufacturing method including the step (II) of receiving and cooling at the outer peripheral surface 121 of the cast roll 120 is performed. Hereinafter, this manufacturing method will be described.

  In step (I), as shown in FIG. 1, a resin having a temperature equal to or higher than the glass transition temperature is supplied from a resin supply device (not shown) to the die 110, and this resin is extruded from the die 110 through the lip 116 into a film shape. Since the resin heated to a temperature equal to or higher than the glass transition temperature is in a molten state, the resin film 20 in the molten state can be obtained by extruding the resin from the die 110 as described above.

  Step (II) is performed after the step (I). In step (II), the resin film 20 is received by the outer peripheral surface 121 of the cast roll 120. The resin film 20 received on the outer peripheral surface 121 of the cast roll 120 is conveyed by the rotation of the cast roll 120. And the resin film 20 is cooled and hardened to the temperature below the glass transition temperature of resin contained in the said resin film 20 in the period currently conveyed with the cast roll 120 by process (II).

FIG. 4 is a cross-sectional view schematically showing the resin film 20 extruded from the die 110 in the manufacturing method according to the first embodiment of the present invention. FIG. 5 is a plan view schematically showing the resin film 20 extruded from the die 110 in the manufacturing method according to the first embodiment of the present invention.
In the step (II), the resin film 20 received by the outer peripheral surface 121 of the cast roll 120 is, as shown in FIGS. 4 and 5, in the width direction of the resin film 20, the first fixing region 21, the first An extension region 22, a central region 23, a second extension region 24, and a second fixed region 25 are provided in this order. These first fixing region 21, first extension region 22, central region 23, second extension region 24, and second fixing region 25 are usually band-like regions that continuously extend in the longitudinal direction of the resin film 20. Yes.

  The first fixing region 21 is set in the vicinity of one edge 26 of the resin film 20. The second fixing region 25 is set in the vicinity of the other edge 27 of the resin film 20. As shown in FIG. 2, the step (II) includes bringing the first fixing region 21 and the second fixing region 25 into close contact with the outer peripheral surface 121 of the cast roll 120. Specifically, electrostatic charges are applied to the first fixed region 21 and the second fixed region 25 from the electrostatic pinning devices 131 and 132, respectively, so that the first fixed region 21 and the second fixed region 25 are arranged on the outer periphery of the cast roll 120. It is electrostatically adhered to the surface 121. Thereby, since the 1st fixed area | region 21 and the 2nd fixed area | region 25 are fixed to the outer peripheral surface 121 of the cast roll 120, the width | variety of the resin film 20 can be reduced. Therefore, since the neck-in can be prevented by bringing the first fixing region 21 and the second fixing region 25 of the resin film 20 into close contact with the outer peripheral surface 121 of the cast roll 120 in this way, the width of the resin film 20 is fixed. Is possible. Furthermore, the conveyance stability of the resin film 20 can be improved.

As shown in FIG. 4, the thickness _{T 25} of the thickness _{T 21} and the second fixed region 25 of the first fixed region 21, respectively, the thickness _{T 23} of the central region 23, generally 10% or more, preferably 20% or more, More preferably, it is 30% or more, usually 300% or less, preferably 150% or less, more preferably 100% or less. Here, the thickness represents the thickness of the resin film 20 immediately after being extruded from the die 110. By setting the thickness T ₂₁ and the thickness T ₂₅ of the second fixed region 25 of the first fixed region 21 above the lower limit of the range, to increase the mechanical strength of the first fixed region 21 and the second fixed region 25 Therefore, the prevention of edge pinning and the improvement of the conveyance stability can be performed stably. Moreover, the fall of conveyance stability by only a film edge part becoming thick can be prevented by making it into an upper limit or less. Further, the production cost can be reduced by reducing the amount of resin used for the material. Here, the thickness T ₂₁ of the first fixed region 21 and the thickness T ₂₅ of the second fixed region 25 may be the same or may be different. Moreover, the thickness of each area | region of the resin film 20 can be adjusted with the lip clearance of the lip | rip 116 of the die | dye 110, for example.

Further, as shown in FIG. 5, the width _{W 25} of width _{W 21} and a second fixed region 25 of the first fixed region 21, respectively, typically 5mm or more, preferably 6mm or more, more preferably 7mm or more, usually It is 100 mm or less, preferably 80 mm or less, more preferably 60 mm or less. By setting the width _{W 21} and the width _{W 25} of the second fixing region 25 of the first fixed region 21 above the lower limit of the range, the width _{W 21} and _{W 25} of the first fixed region 21 and the second fixed region 25 Since it can hold | maintain to some extent, the 1st fixing area | region 21 and the 2nd fixing area | region 25 of the resin film 20 can be stuck more stably with respect to the outer peripheral surface 121 of the cast roll 120. FIG. Moreover, since the width | variety of the center area | region 23 can be enlarged by making it into an upper limit or less, productivity of the area | region which made retardation Rth of the thickness direction close | similar to zero can be improved. Here, the width W ₂₁ of the first fixed region 21 and the width W ₂₅ of the second fixed region 25 may be the same or may be different.

Furthermore, as shown in FIG. 5, the first fixed region 21 is usually set away from the edge 26 closer to the first fixed region 21. Further, normally, the second fixed region 25 is set away from the edge 27 closer to the second fixed region 25. In this case, the distance _{D 21} from the first fixed region 21 to the edge 26, and the distance _{D 25} from the second fixed region 25 to the edge 27, respectively, usually 3mm or more, preferably 4mm, more preferably at least 5mm It is usually 100 mm or less, preferably 80 mm or less, more preferably 60 mm or less. Distance D ₂₁ from the first fixed region 21 to the edge _26, and by a distance D ₂₅ from the second fixed region 25 to the edge 27 than the lower limit of the range, the end of the casting roll 120 and the first A certain width dimension can be provided between the fixed region 21 and the second fixed region 25. Thereby, when the resin film 20 meanders, it can prevent that the 1st fixing area | region 21 and the 2nd fixing area | region 25 protrude from the edge part of the cast roll 120, and contact | adherence becomes unstable. In particular, in the case of electrostatic pinning, electric charges are given to the first fixed region 21 and the second fixed region 25 of the resin film 20 by electric discharge, and the first fixed region 21 and the second fixed region 25 are moved to the outer peripheral surface 121 of the cast roll 120. However, it is possible to prevent the cast roll 120 from being damaged due to the discharge being applied to the cast roll 120. Moreover, since the width | variety of the center area | region 23 can be enlarged by making it into an upper limit or less, productivity of the area | region which made retardation Rth of the thickness direction close | similar to zero can be improved. Here, the distance D ₂₁ from the first fixed region 21 to the edge 26 _and, the distance D ₂₅ from the second fixed region 25 to the edge 27 may be the same or may be different.

  As shown in FIGS. 4 and 5, in the width direction of the resin film 20, there are a central region 23, a first extension region 22, and a second extension region 24 between the first fixing region 21 and the second fixing region 25. Is provided. The central region 23 is a region where the retardation Rth in the thickness direction of the cured resin film 20 can approach zero, and is usually set as a region including the center in the width direction of the resin film 20. The first extension region 22 and the second extension region 24 are regions that can be extended with an extension amount larger than the extension amount of the central region 23 when the same tension is applied. As described above, since the resin film 20 includes the first extension region 22 and the second extension region 24 having higher extensibility than the central region 23, the stress generated by the cooling in the step (II) is the first extension region. 22 and the second extension region 24 are opened by deformation. Therefore, the expression of retardation Rth in the thickness direction in the central region 23 due to stress during cooling can be suppressed. Therefore, the film provided with the center area | region 23 which has the retardation Rth of the thickness direction close | similar to zero can be obtained as the resin film 20 after hardening by process (II) which concerns on this embodiment. At this time, the specific elongation difference between the central region 23 and the first stretched region 22 and the second stretched region 24 is such that the retardation Rth in the thickness direction approaches zero in the central region 23 of the cured resin film 20. It can be set appropriately within the range.

In the present embodiment, as shown in FIG. 3, the lip clearance C ₁₁₂ of the portion 112 through which the resin forming the first extension region 22 of the lip 116 of the die 110 passes and the resin forming the second extension region 24 pass. The lip clearance C ₁₁₄ of the portion 114 is smaller than the lip clearance C _{113 of the} portion 113 through which the resin forming the central region 23 passes. Therefore, the resin film 20, as shown in FIG. 4, the thickness _{T 24} of the thickness _{T 22} and the second stretch region 24 of the first stretch region 22 is thinner than the thickness _{T 23} of the central region 23. The first extension region 22 and the second extension region 24 have higher extensibility than the central region 23 due to the difference in thickness.

As shown in FIG. 4, when the first stretch region 22 and the second stretch region 24 exhibit a higher stretchability than the center region 23 due to the difference in thickness, the thickness T ₂₂ of the first stretch region ₂₂ and the second stretch region The thickness T ₂₄ of ₂₄ is usually 15% or more, preferably 25% or more, more preferably 30% or more, and usually 85% or less, preferably 75% or less, of the thickness T ₂₃ of the central region 23. Preferably it is 70% or less. Here, the thickness represents the thickness of the resin film 20 immediately after being extruded from the die 110. By setting the thickness T ₂₂ and the thickness T ₂₄ of the second stretch region 24 of the first stretch region 22 above the lower limit of the range, to increase the mechanical strength of the first stretch region 22 and the second stretch region 24 Therefore, the handling property of the resin film 20 can be improved. Moreover, by setting it to the upper limit value or less, the retardation Rth in the thickness direction can be effectively brought close to zero in the central region 23 of the cured resin film 20. Here, the thickness T ₂₂ of the first stretch region 22 and the thickness T ₂₄ of the second stretch region 24, may be the same or different.

Further, as shown in FIG. 5, at the time immediately after extruded from the die 110, the width _{W 24} of width _{W 22} and the second stretch region 24 of the first stretch region 22, according to the width _{W 23} of the central region 23 Is preferably set. Specifically, at the time immediately after extruded from the die 110, the sum of the width _{W 24} of width _{W 22} and the second stretch region 24 of the first stretch region 22, the width _{W 23} of the central region 23, usually 0 0.5% or more, preferably 1% or more, more preferably 1.5% or more, and usually 20% or less, preferably 15% or less, more preferably 10% or less. First by the sum of the width W ₂₄ of width W ₂₂ and the second stretch region 24 of the stretching region 22 can be at least the lower limit of the above range, the retardation in the thickness direction Rth in the central region 23 of the resin film 20 after curing Can be brought close to zero effectively. Moreover, since the width | variety of the center area | region 23 can be widened by making it into an upper limit or less, productivity of the area | region which made retardation Rth of the thickness direction close | similar to zero can be improved. Here, the width W ₂₂ of the first stretch region 22 and the width W ₂₄ of the second stretch region 24, may be the same or different.

  As shown in FIG. 1, the resin film 20 cooled and cured in the step (II) is then peeled off from the outer peripheral surface 121 of the cast roll 120 by the peeling roll 140 and sent to the trimming device 150.

  In the trimming device 150, the resin film 20 is cut at a position closer to the central region 23 than the first fixed region 21 and the second fixed region 25, and at least the first fixed region 21 and the second fixed region 25 are separated from the resin film 20. Step (III) for removing is performed. Specifically, by the trimming knives 151 and 152, the vicinity of the boundary between the central region 23 and the first extension region 22 and the vicinity of the boundary between the central region 23 and the second extension region 24 of the resin film 20 are cut. The end film 28 including the region 21 and the end film (not shown) including the second fixing region 25 are cut off. These end films 28 are transported and collected separately from the resin film 10 by the transport roll 153.

  The resin film 10 including the central region 23 left by cutting off the end film 28 from the resin film 20 is sent to the winding shaft 160. The take-up shaft 160 winds the sent resin film 10 into a roll shape to obtain a film roll 30.

  As described above, the resin film 10 having optical isotropy is obtained. This resin film 10 has a retardation Rth in the thickness direction close to zero. The value of retardation Rth in the specific thickness direction of the resin film 10 is usually −6 nm or more, preferably −4 nm or more, more preferably −3 nm or more, and usually 4 nm or less, preferably 3 nm or less, more preferably 2 .5 nm or less.

  The retardation Re in the in-plane direction of the resin film 10 is usually a value close to zero. The value of retardation Re in the in-plane direction of the resin film 10 is usually 2 nm or less, preferably 1 nm or less, more preferably 0.5 nm or less, and ideally 0 nm.

  Furthermore, the resin film 10 usually has high transparency from the viewpoint of use as an optical film. Specifically, the total light transmittance in terms of 1 mm thickness of the resin film 10 is preferably 80% or more, and more preferably 90% or more. The haze in terms of 1 mm thickness of the resin film is preferably 0.3% or less, particularly preferably 0.2% or less. Here, the total light transmittance can be measured according to JIS K7361-1997. Moreover, haze can be measured based on JISK7136-1997.

  Furthermore, the thickness of the resin film 10 is usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and usually 150 μm or less, preferably 100 μm or less, more preferably 70 μm or less. The handling property of the resin film 10 can be improved by setting the thickness of the resin film 10 to be equal to or greater than the lower limit of the above range. Moreover, the retardation Re and Rth of the resin film 10 can be brought close to zero effectively by setting it to the upper limit value or less.

  Moreover, the width | variety of the resin film 10 is 400 mm or more normally, Preferably it is 700 mm or more, More preferably, it is 1000 mm or more, and is 3000 mm or less normally, Preferably it is 2500 mm or less, More preferably, it is 2000 mm or less. By making the width of the resin film 10 equal to or greater than the lower limit of the above range, the manufacturing cost of the resin film 10 can be reduced. Moreover, the handleability of the resin film 10 can be improved by making it below an upper limit.

  By the way, the cured resin film 20 usually has the same optical characteristics (Rth, Re, total light transmittance, haze, etc.) and thickness as the resin film 10 in the central region 23. Therefore, since the resin film 20 that has been cooled and cured to below the glass transition temperature of the resin has a retardation Rth in the thickness direction close to zero in at least the central region 23, it is included in the resin film to be manufactured by the manufacturing method of the present invention. Is done.

[Second Embodiment]
In the first embodiment, the first stretched region and the second stretched region of the resin film are formed as regions that are thinner than the central region. However, the configuration of the first extension region and the second extension region is not limited to the region having a smaller thickness than the central region. For example, the first extension region and the second extension region may be formed of a resin different from the resin included in the central region. As a specific example, the first extension region and the second extension region may be formed of a resin having a glass transition temperature lower than the glass transition temperature of the resin included in the central region. Hereinafter, an embodiment will be shown and described.

FIG. 6 is a schematic view schematically showing a production apparatus 200 for the resin film 10 according to the second embodiment of the present invention. FIG. 7 is a perspective view schematically showing the periphery of the cast roll 120 of the manufacturing apparatus 200 according to the second embodiment of the present invention. In the manufacturing apparatus 200 according to the second embodiment, the same parts as those of the manufacturing apparatus 100 according to the first embodiment are denoted by the same reference numerals as those of the manufacturing apparatus 100 according to the first embodiment.
As shown in FIG. 6, the manufacturing apparatus 200 of the resin film 10 which concerns on 2nd embodiment of this invention is 1st embodiment except providing the die | dye 210 provided with the feed block 270 instead of the die | dye 110. FIG. The manufacturing apparatus 100 has the same configuration.

  The feed block 270 is provided so that a plurality of different types of resins can be supplied to the die 210. Specifically, the feed block 270 has a resin (H) in a resin passage (not shown) in the die 210 in a portion through which the resin forming the central region 43 (see FIG. 7) of the resin film 40 passes. ) And the resin (L) can be supplied to the portion through which the resin forming the region other than the central region 43 of the resin film 40 passes. In the present embodiment, an example in which the same resin as that used in the first embodiment is used as the resin (H) and a resin different from the resin (H) is used as the resin (L) will be described.

In addition, as shown in FIG. 6, the die 210 indicates a resin (H) and a resin (L) having a temperature equal to or higher than the glass transition temperature from a resin supply device (not shown) through a feed block 270 by an arrow A ₂₁₀ . It is provided so that it can be supplied. Further, as shown in FIG. 7, the dice 210 is provided so that the supplied resins (H) and (L) are extruded into a film shape through a lip 216 so that a resin film 40 made of a molten resin can be obtained. ing.

FIG. 8 is a plan view schematically showing the lip 216 of the die 210 according to the second embodiment of the present invention.
As shown in FIG. 8, the die 210 has a first fixing region 41, a first extension region 42, a central region 43, a first region in the width direction of the resin film 40 when the resin film 40 is cooled by the cast roll 120. The shape of the lip 216 is set so that the two extension regions 44 and the second fixing region 45 are provided in this order. Therefore, the lip 216 includes a portion 211 through which the resin forming the first fixing region 41 passes, a portion 212 through which the resin forming the first extension region 42 passes, a portion 213 through which the resin forming the central region 43 passes, and a second extension region. And a portion 214 through which resin forming the second fixing region 45 passes. However, the die 210 according to this embodiment is different from the die 110 according to the first embodiment in that the resin forming the lip clearance C _{212 of} the portion 212 through which the resin forming the first extension region 42 passes and the central region 43 are formed. lip clearance _{C 213} of through portions 213 and a lip clearance _{C 214} of the second stretch region 44 parts 214 resin passes to form a is set to be the same. Thus, die 210, the resin film 40 has a configuration capable thickness _{T 43} of the central region 43, the thickness _{T 44} of the thickness _{T 42} and the second stretch region 44 of the first stretching region 42 to the same thickness (Figure 9 reference).

  The manufacturing apparatus 200 of the resin film 10 which concerns on 2nd embodiment of this invention is comprised as mentioned above. When manufacturing the resin film 10 using this manufacturing apparatus 200, the process of obtaining the resin film 40 by extruding resin (H) and resin (L) which have temperature more than a glass transition temperature from the die 210 to a film form ( I) and the process (II) which receives and cools the resin film 40 with the outer peripheral surface 121 of the cast roll 120 are performed. However, in the present embodiment, a resin having a glass transition temperature lower than the glass transition temperature of the resin (H) is used as the resin (L). Hereinafter, this manufacturing method will be described.

  In step (I), as shown in FIG. 6, a resin (H) and a resin (L) having a temperature equal to or higher than the glass transition temperature are supplied to a die 210 from a resin supply device (not shown) through a feed block 270. These resins (H) and resin (L) are extruded from the die 210 through the lip 216 into a film. Since the resin (H) and the resin (L) heated to a temperature equal to or higher than the glass transition temperature are in a molten state, the resin film 40 in a molten state can be obtained by extruding the resin from the die 210 as described above. .

  Step (II) is performed after the step (I). In the step (II), the resin film 40 is received by the outer peripheral surface 121 of the cast roll 120 and cooled while being conveyed by the cast roll 120 as in the manufacturing method according to the first embodiment. Therefore, the resin film 40 is cooled to a temperature lower than the glass transition temperature of the resins (H) and (L) contained in the resin film 40 and cured during the period of being conveyed by the cast roll 120 in the step (II). To do.

FIG. 9 is a cross-sectional view schematically showing the resin film 40 extruded from the die 210 in the manufacturing method according to the second embodiment of the present invention. FIG. 10 is a plan view schematically showing the resin film 40 extruded from the die 210 in the manufacturing method according to the second embodiment of the present invention.
In the step (II), the resin film 40 received by the outer peripheral surface 121 of the cast roll 120 is, as shown in FIGS. 9 and 10, in the width direction of the resin film 40, the first fixing region 41, the first An extension area 42, a center area 43, a second extension area 44, and a second fixing area 45 are provided in this order.

In step (II), the central region 43 of the resin film 40 has the same structure as the central region 23 of the resin film 20 according to the first embodiment.
Moreover, in process (II), the 1st fixing area | region 41 and the 2nd fixing area | region 45 of the resin film 40 are each formed with resin (L) whose glass transition temperature is lower than resin (H), respectively. The first and second fixing regions 21 and 25 of the resin film 20 according to the first embodiment have the same configuration.
Furthermore, in process (II), the 1st extending | stretching area | region 42 and the 2nd extending | stretching area | region 44 of the resin film 40 are each formed with resin (L) whose glass transition temperature is lower than (1) resin (H). And (2) it has the same configuration as the first extension region 22 and the second extension region 24 of the resin film 20 according to the first embodiment except that it has the same thickness as the central region 43.

In general, a resin having a low glass transition temperature has a higher extensibility than a resin having a high glass transition temperature. In the resin film 40, the glass transition temperature Tg _L of the resin (L) included in the first extension region 42 and the second extension region 44 is equal to the glass transition temperature Tg _H of the resin (H) included in the center region 43. Lower than. Therefore, in the resin film 40 according to the second embodiment, the extension amount of the first extension region 42 and the second extension region 44 when the same tension is applied is larger than the extension amount of the central region 43. .

Difference _Tg H -Tg _L between the glass transition temperature Tg _L of the resin glass transition temperature Tg _H and resin (H) (L) is usually 3 ° C. or higher, preferably 5 ° C. or higher, more preferably at 10 ° C. or higher The temperature is usually 50 ° C. or lower, preferably 40 ° C. or lower, more preferably 30 ° C. or lower. By setting the glass transition temperature difference Tg _H -Tg _L to be not less than the lower limit of the above range, the retardation Rth in the thickness direction can be effectively brought close to zero in the central region 43 of the cured resin film 40. Moreover, the extrusion molding using the die | dye 210 can be easily performed by setting it as below an upper limit.

In addition, as shown in FIG. 9, when different stretches are used to cause the first stretch region 42 and the second stretch region 44 to exhibit higher stretchability than the central region 43, the thickness T ₄₂ and the first stretch region 42 of the first stretch region 42 the thickness _{T 44} of the secondary stretching region 44, respectively, can be set arbitrarily. Here, the thickness T ₄₂ of the first stretch region 42 and the thickness T ₄₄ of the second stretch region 44, may be the same or different.

  The process (II) according to the present embodiment for cooling and curing the resin film 40 having such a configuration is similar to the process (II) according to the first embodiment in the first fixing area 41 and the second fixing area. 45 is brought into close contact with the outer peripheral surface 121 of the cast roll 120. Thereby, since the neck-in can be prevented similarly to the first embodiment, the width of the resin film 40 can be fixed. Furthermore, the conveyance stability of the resin film 40 can be improved.

  Further, since the resin film 40 includes the first stretch region 42 and the second stretch region 44 having higher stretchability than the central region 43, the stress generated by the cooling in the step (II) It is released by the deformation of the second extension region 44. Therefore, the expression of retardation Rth in the thickness direction in the central region 43 due to the stress during cooling can be suppressed. Accordingly, in the step (II) according to the present embodiment, as in the step (II) according to the first embodiment, as the cured resin film 40, the central region 43 having a retardation Rth in the thickness direction close to zero. Can be obtained.

  As shown in FIG. 6, the resin film 40 that has been cooled and cured in the step (II) is peeled off from the outer peripheral surface 121 of the cast roll 120 by the peeling roll 140. Thereafter, in the trimming apparatus 150, as in the manufacturing method according to the first embodiment, the end film 48 including at least the first fixing region 41 and the end film including at least the second fixing region 45 (not shown). Is cut off (step (III)). Then, the resin film 10 including the central region 43 remaining by cutting off the end film 48 from the resin film 40 is taken up by the take-up shaft 160, and the film roll 30 is obtained.

  As mentioned above, according to the manufacturing method which concerns on this embodiment, the resin film 10 can be manufactured similarly to the manufacturing method which concerns on 1st embodiment. Therefore, according to the manufacturing method which concerns on this embodiment, the resin film 10 whose retardation Rth of the thickness direction is near zero can be manufactured. Moreover, according to this embodiment, the same advantage as 1st embodiment can be acquired.

[Modification]
The present invention is not limited to the embodiment described above, and may be further modified.
For example, members other than cast rolls may be used as the support. Examples of the support other than the cast roll include a cast drum and an endless belt.

  In addition, for example, as a contact device for bringing the first fixed region and the second fixed region of the resin film into close contact with the support surface of the support, a device other than the electrostatic pinning device may be used. Examples of the contact device other than the electrostatic pinning device include an air nozzle and a touch roll. The air nozzle blows air onto the resin film on the support, and the pressure of the air can bring the first fixed region and the second fixed region of the resin film into close contact with the support surface of the support. Moreover, the touch roll can stick the 1st fixing area | region and 2nd fixing area | region of a resin film to the support surface of a support body by pressing the surface by the side of the support body of a resin film.

  Further, for example, the resin film in the step (II) is between the first fixing region and the first extension region of the resin film, between the first extension region and the center region, and between the center region and the second extension region. In addition, an arbitrary region may be included between the second extension region and the second fixing region.

  For example, you may implement combining 1st embodiment and 2nd embodiment which were mentioned above. Specifically, the thickness of the first stretch region and the second stretch region is made thinner than the thickness of the center region, and the first stretch region and the second stretch region are formed of a resin different from the center region, You may carry out in combination. Further, for example, one of the first extension region and the second extension region may be made thinner than the central region, and the other of the first extension region and the second extension region may be formed of a resin different from the central region.

  Furthermore, in the second embodiment, the first extension region 42 and the second extension region 44 are formed of the same resin (L), but the first extension region and the second extension region may be formed of different resins. .

  Moreover, the manufacturing method of this invention may contain arbitrary processes other than the process demonstrated by embodiment mentioned above. Examples of such a process include a process of bonding an arbitrary film to the resin film, a process of applying a surface treatment to the resin film, and a process of further cooling the cured resin film.

  In addition to the single-layer resin film, the target resin film may be a multilayer film composed of a plurality of layers. As such a multilayer film, for example, an inner layer and an outer layer formed on both sides of the inner layer can be used.

  Also, the lip clearance of the die may vary across the width in a range that satisfies the relationship between the elongation of the central region and the extension region in order to ensure the film thickness uniformity in the central region corresponding to the product part. It can be adjusted as appropriate.

[resin]
A thermoplastic resin can be used as the resin used for producing the resin film. Examples of the thermoplastic resin include polyester resin, polycarbonate resin, cellulose ester resin, olefin resin, and acrylic resin. Among them, an olefin resin is preferable because of excellent mechanical properties, heat resistance, and transparency, and an alicyclic olefin resin is particularly preferable because of excellent low moisture absorption, dimensional stability, and lightness. This alicyclic olefin resin contains an alicyclic olefin polymer and optional components as necessary.

  An alicyclic olefin polymer is a polymer having an alicyclic structure in the structural unit of the polymer, a polymer having an alicyclic structure in the main chain, and a polymer having an alicyclic structure in the side chain. Any combination may be used. Among these, a polymer containing an alicyclic structure in the main chain is preferable from the viewpoint of mechanical strength, heat resistance, and the like.

  Examples of the alicyclic structure include a saturated alicyclic hydrocarbon (cycloalkane) structure and an unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structure. Among these, from the viewpoints of mechanical strength, heat resistance and the like, a cycloalkane structure and a cycloalkene structure are preferable, and a cycloalkane structure is particularly preferable.

  Examples of the alicyclic olefin polymer include a norbornene polymer, a monocyclic olefin polymer, a cyclic conjugated diene polymer, a vinyl alicyclic hydrocarbon polymer, and a hydride thereof. . Among these, the norbornene polymer is particularly preferable because the norbornene resin containing the norbornene polymer has good transparency and moldability.

  Examples of the norbornene polymer include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening copolymer of a monomer having a norbornene structure and an arbitrary monomer, or a hydride thereof; An addition polymer of a monomer having a structure, an addition copolymer of a monomer having a norbornene structure and an arbitrary monomer, or a hydride thereof. Among these, hydrides of ring-opening polymers and ring-opening copolymers of monomers having a norbornene structure are transparent, moldability, heat resistance, low moisture absorption, dimensional stability and light weight. From the standpoints of properties and the like, it can be particularly preferably used.

Examples of the monomer having a norbornene structure include bicyclo [2.2.1] hept-2-ene (common name: norbornene), tricyclo [4.3.0.1 ^2,5 ] deca-3,7. -Diene (common name: dicyclopentadiene), 7,8-benzotricyclo [4.3.0.1 ^2,5 ] dec-3-ene (common name: methanotetrahydrofluorene), tetracyclo [4.4. 0.1 ^2,5 . ^{17, 10} ] dodec-3-ene (common name: tetracyclododecene), and derivatives of these compounds (for example, those having a substituent in the ring). Here, examples of the substituent include an alkyl group, an alkylene group, and a polar group. Moreover, these substituents may be the same or different, and a plurality thereof may be bonded to the ring. Furthermore, the monomer which has a norbornene structure may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Examples of the polar group include a hetero atom or an atomic group having a hetero atom. Examples of the hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, and a halogen atom. Specific examples of the polar group include a carboxyl group, a carbonyloxycarbonyl group, an epoxy group, a hydroxyl group, an oxy group, an ester group, a silanol group, a silyl group, an amino group, a nitrile group, and a sulfone group.

Among the norbornene polymers, those satisfying all the following three requirements are preferable. That is, first, as a structural unit, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane-7 , 9-diyl-ethylene structure. Second, the content of these structural units is 90% by weight or more based on the total structural units of the norbornene polymer. Third, the ratio of the content ratio of X and the content ratio of Y is 100: 0 to 40:60 in terms of a weight ratio of X: Y. By using such a norbornene polymer, it is possible to obtain an optical film having no dimensional change over a long period of time and excellent optical property stability.

  The weight average molecular weight (Mw) of the alicyclic olefin polymer is usually 10,000 or more, preferably 15,000 or more, more preferably 20,000 or more, and usually 100,000 or less, preferably 80,000 or less. More preferably, it is 50,000 or less. Here, the weight average molecular weight (Mw) is a polyisoprene or polystyrene equivalent weight average molecular weight measured by gel permeation chromatography using cyclohexane (toluene when the sample is not dissolved in cyclohexane) as a solvent. It is. When the weight average molecular weight is in such a range, the mechanical strength and the moldability are highly balanced, which is preferable.

  The alicyclic olefin resin may contain other optional components in addition to the alicyclic olefin polymer as long as the effects of the present invention are not significantly impaired. Examples of optional components include colorants such as pigments and dyes; fluorescent brighteners; dispersants; thermal stabilizers; light stabilizers; ultraviolet absorbers; antistatic agents; antioxidants; And other additives such as polymers other than alicyclic olefin polymers. Moreover, an arbitrary component may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The glass transition temperature of the resin is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, particularly preferably 110 ° C. or higher, preferably 350 ° C. or lower, more preferably 250 ° C. or lower, particularly preferably 200 ° C. or lower. . When the glass transition temperature of the resin is equal to or higher than the lower limit of the above range, the heat resistance of the resin film to be manufactured can be increased. Moreover, extrusion molding can be easily performed by being below an upper limit.

  In addition, as in the second embodiment, in the case where the central region of the resin film and the first stretched region and the second stretched region contain different resins, the central region preferably contains the olefin resin described above. Thereby, the resin film which has the outstanding characteristic of an olefin resin, and the retardation Rth of the thickness direction is near zero can be manufactured.

  Furthermore, when each area | region of a resin film is formed with different resin like 2nd embodiment, it is preferable to use combining high affinity resin. For example, you may use combining the resin of the same classification. As a specific example, in the second embodiment described above, an olefin resin may be used as the resin (H), and an olefin resin having a glass transition temperature lower than that of the resin (H) may be used as the resin (L). Thereby, the breakage at the boundary between the regions can be prevented.

  Further, the region other than the central region of the resin film is usually cut off by the step (III). Therefore, in general, the region other than the central region of the resin film is not required to precisely control optical characteristics such as retardation and transparency. Therefore, from the viewpoint of suppressing the manufacturing cost, it is preferable to reuse the resin contained in the end film cut out in the step (III) as the resin for forming the region other than the central region of the resin film. .

[Use of resin film]
The resin film produced by the production method of the present invention is preferably used as an optical film taking advantage of its excellent optical isotropy. More specific applications include a polarizing plate protective film, an optical base film, a base film for laminating an optical functional layer by coating, a touch sensor base film, an optical element cover film, and the like.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.
In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified. Moreover, the following operation was performed in normal temperature normal pressure atmosphere unless otherwise indicated.

[Measurement method of retardation]
The retardation Re in the in-plane direction and the retardation Rth in the thickness direction of the resin film were measured using KOBRA-WPR manufactured by Oji Scientific Instruments. At this time, the measurement wavelength was 590 nm.

[Example 1]
The operations described below were performed while continuously transporting the resin film in the longitudinal direction at a transport speed of 20 m / min.

  As shown in FIG. 1, an alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co., Ltd., glass transition temperature: 136 ° C.) was extruded from a die 110 through a lip 116 to obtain a resin film 20. At this time, the temperature of the die 110 was set to 260 ° C. The length of the lip 116 of the die 110 (the dimension corresponding to the width of the resin film 20) was 1250 mm. Further, as shown in FIG. 3, the lip clearance of the lip 116 of the die 110 was as shown in Table 1.

  The obtained resin film 20 had a first fixing region 21, a first extension region 22, a central region 23, a second extension region 24, and a second fixing region 25, as shown in FIG. The first fixing region 21, the first extension region 22, the central region 23, the second extension region 24, and the second fixing region 25 are band-like regions that are arranged in this order from one side in the width direction of the resin film 20. It was.

The width W ₂₃ of the central region 23 of the resin film 20 was 1050 mm.
Furthermore, the distance from the edge 26 of the resin film 20 to the first extension region 22 and the distance from the edge 27 of the resin film 20 to the second extension region 24 were 40 mm, respectively. The width _{W 24} of width _{W 22} and the second stretch region 24 of the first stretch region 22 was 30mm, respectively.
Furthermore, the width _{W 25} of width _{W 21} and a second fixed region 25 of the first fixed region 21 was approximately 20mm, respectively. The first fixing region 21 is set away from the edge 26 of the resin film 20, and the second fixing region 25 is set from the edge 27 of the resin film 20.

  As shown in FIG. 2, the obtained resin film 20 was received by the outer peripheral surface 121 of the cast roll 120 (diameter 400 mm, temperature 110 ° C.) and conveyed by the rotation of the cast roll 120. An electrostatic charge is applied to the first fixing region 21 and the second fixing region 25 of the resin film 20 immediately after being received by the outer peripheral surface 121 of the cast roll 120 by the electrostatic pinning devices 131 and 132, and the first fixing region 21 and the second fixing region 25. The two fixed regions 25 were brought into close contact with the outer peripheral surface 121 of the cast roll 120.

Thereafter, the resin film 20 was cooled and cured during the period of being conveyed by the cast roll 120. As shown in FIG. 1, the cured resin film 20 is peeled off from the outer peripheral surface 121 of the cast roll 120, and the first fixing region 21, the first extending region 22, the second extending region 24, and the second fixing are performed by the trimming device 150. Region 25 was cut off. Thereafter, the resin film 10 composed of the central region 23 was rolled up and collected. Table 1 shows the width of the recovered resin film 10.
The recovered resin film 10 was measured for in-plane retardation and thickness retardation.

[Example 2]
The clearance of the die lip was changed as shown in Table 1.
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Example 3]
The clearance of the die lip was changed as shown in Table 1.
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Example 4]
The clearance of the die lip was changed as shown in Table 1.
In addition, by supplying different resins to the die using a feed block, the central region of the resin film is formed of an alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co., Ltd., glass transition temperature 136 ° C.), and other than the central region Was formed with an alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co., Ltd., glass transition temperature: 126 ° C.).
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Example 5]
The type of resin was changed to an alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co., Ltd., glass transition temperature: 126 ° C.).
The die temperature was changed to 240 ° C.
Furthermore, the temperature of the cast roll was changed to 100 ° C.
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Example 6]
The clearance of the die lip was changed as shown in Table 1.
In addition, by supplying different resins to the die using a feed block, the central region of the resin film is formed of an alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co., Ltd., glass transition temperature 136 ° C.), and other than the central region The region was formed with an alicyclic olefin resin (“Zeonor” manufactured by Nippon Zeon Co., Ltd., glass transition temperature 100 ° C.).
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Example 7]
The clearance of the die lip was changed as shown in Table 2.
In addition, by supplying different resins to the dice using a feed block, the central region of the resin film is formed of an alicyclic olefin resin (“ZEONOR” manufactured by Nippon Zeon Co., Ltd., glass transition temperature 163 ° C.), and other than the central region Was formed with an alicyclic olefin resin (“Zeonor” manufactured by Nippon Zeon Co., Ltd., glass transition temperature: 136 ° C.).
Further, the die temperature was changed to 280 ° C.
The temperature of the cast roll was changed to 130 ° C.
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Example 8]
By reducing the extrusion amount of the resin, the thickness of the central region of the resin film 20 was set to 30 μm.
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Comparative Example 1]
The clearance of the die lip was changed as shown in Table 2.
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Comparative Example 2]
After the resin film obtained by extruding the resin from the die was received on the outer peripheral surface of the cast roll, the operation for bringing the first fixed region and the second fixed region of the resin film into close contact with the outer peripheral surface of the cast roll was not performed.
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[Comparative Example 3]
The clearance of the die lip was changed as shown in Table 2.
Furthermore, the thickness of the central region of the resin film 20 was set to 30 μm by reducing the amount of resin extrusion.
A resin film was produced and evaluated in the same manner as in Example 1 except for the above items.

[result]
The results of Examples and Comparative Examples are shown in the following table. In the table below, the value of the lip clearance in the column of the central region represents the lip clearance of the portion of the die lip through which the resin forming the central region passes. In the table below, the value of the lip clearance in the column of the first extension region and the second extension region is the lip clearance of the portion of the die lip through which the resin forming the first extension region or the second extension region passes. Represent. Further, in the following table, the value of the lip clearance in the column of the first fixing area and the second fixing area is the lip clearance of the portion of the die lip through which the resin forming the first fixing area or the second fixing area passes. Represent.

In the table below, the meanings of the abbreviations are as follows.
COP: Alicyclic olefin resin Tg: Glass transition temperature Re: Retardation in in-plane direction Rth: Retardation in thickness direction Width: Width of finally obtained resin film. Corresponds to the width of the central region after curing.

[Consideration]
As shown in Comparative Examples 1 and 3, when the resin film cooled by the cast roll does not have the first stretch region and the second stretch region, the thickness direction retardation Rth in the central region is brought close to zero. It is difficult.
In addition, as shown in Comparative Example 2, when cooling with a cast roll, if the first fixing area and the second fixing area of the resin film are not brought into close contact with the outer peripheral surface of the cast roll, neck-in occurs and the resin has a desired width. The film cannot be manufactured. In this case, the in-plane retardation Re is as large as 5 nm.
On the other hand, according to Examples 1-8, both the in-plane retardation Re and the thickness direction retardation Rth are as small as 4 nm or less, and a resin film having a desired width can be obtained.

  In Comparative Example 2, since the resin film is not restrained in the width direction at the time of cooling, the resin film contracts excessively due to stress during cooling. For this reason, the retardation Re in the in-plane direction is increased, and the width of the central region where the desired optical characteristics should be exhibited is reduced. On the other hand, in an Example, a resin film is restrained in the width direction by sticking the 1st fixed field and the 2nd fixed field to the peripheral surface of a cast roll. Moreover, since the resin film of an Example is provided with the 1st extending | stretching area | region and 2nd extending | stretching area | region excellent in the extensibility, the degree of restraint of the center area | region of a resin film becomes loose. In the central region subjected to such gentle restraint, the expression of retardation Re in the in-plane direction and retardation Rth in the thickness direction is suppressed, and shrinkage in the width direction is also suppressed. Therefore, in the Examples, it is considered that the resin film having optical isotropy can be efficiently manufactured as described above.

DESCRIPTION OF SYMBOLS 10 Trimmed resin film 20 and 40 Resin film 21 and 41 First fixed area | region 22 and 42 of resin film First extension area | region 23 and 43 Central area | region 24 and 44 Resin film second extension area | region 25 And 45 Second fixing region of resin film 26 and 27 Edge of resin film 30 Film roll 100 and 200 Manufacturing apparatus 110 and 210 Dies 111 and 211 Part of lip through which resin forming first fixing region of resin film passes 112 and 212 The portion of the lip through which the resin forming the first stretch region of the resin film passes 113 and 213 The portion of the lip through which the resin forming the central region of the resin film passes 114 and 214 The second stretch region of the resin film of the lip Parts 115 and 2 through which the resin to be formed passes 5 Part of lip through which resin forming second fixing region of resin film passes 116 and 216 Lip 120 Cast roll 121 Cast roll outer peripheral surface 131 Electrostatic pinning device 132 Electrostatic pinning device 140 Peeling roll 150 Trimming device 151 Trimming knife 152 Trimming knife 153 Conveying roll 160 Winding shaft 270 Feed block

Claims (8)

A step of obtaining a resin film by extruding a resin having a temperature equal to or higher than the glass transition temperature from a die into a film; and
Receiving the resin film at the support surface of the support having a support surface and cooling it (II),
In at least the step (II) of the steps (I) and (II), the resin film has a first fixing region, a first extension region, a central region, a second extension region, and a second fixing region, In this order in the width direction of the resin film,
The step (II) includes bringing the first fixing region and the second fixing region of the resin film into close contact with the support surface,
The method for producing a resin film, wherein an extension amount of the first extension region and the second extension region is larger than an extension amount of the central region when the same tension is applied. The thickness of the first extension region is smaller than the thickness of the central region,
The method for producing a resin film according to claim 1, wherein the thickness of the second extension region is thinner than the thickness of the central region. In the resin film immediately after being extruded from the die,
The thickness of the first extension region is not less than 15% and not more than 85% of the thickness of the central region;
The method for producing a resin film according to claim 2, wherein the thickness of the second extension region is 15% or more and 85% or less of the thickness of the central region. The resin contained in the central region is different from the resin contained in the first extension region,
The method for producing a resin film according to claim 1, wherein the resin contained in the central region is different from the resin contained in the second extension region. The glass transition temperature of the resin contained in the first extension region is lower than the glass transition temperature of the resin contained in the central region,
The method for producing a resin film according to claim 4, wherein the glass transition temperature of the resin contained in the second extension region is lower than the glass transition temperature of the resin contained in the central region.   The sum of the width of the first extension region and the width of the second extension region is not less than 0.5% and not more than 20% of the width of the central region. A method for producing a resin film.   The manufacturing method of the resin film as described in any one of Claims 1-6 in which the said center area | region contains an olefin resin.   8. The method according to claim 1, comprising a step (III) of cutting the resin film after the step (II) at a position closer to the central region than the first fixing region and the second fixing region. The manufacturing method of the resin film of one term.

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