JP2014126822A - Method for manufacturing taken-up body of optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a taken-up body of an optical film low in generation of a trough.SOLUTION: The method for manufacturing the taken-up body of a long optical film comprises: the step of adding a knurl structure to both ends in a width direction on at least one surface of the optical film; and the take-up step of taking-up the optical film having the added knurl structure in a roll form around a taking-up core. The take-up step adjusts take-up tension in the take-up step and/or height of the knurl structure so as to always satisfy the formula (1) of h/r≤X and the formula (2) of h>0.1 (where, h=r-rand X is a constant) after the outer radius R (mm) of the taking-up core, an outer radius r(mm) of the film center part of the taken-up body in the middle of taking up the film in a width direction and an outer radius r(mm) of an end part of the film of the taken-up body in the middle of taking up the film in the width direction become at least r>1.05R.

Description

  The present invention relates to a method for producing a wound body of an optical film.

  Usually, an industrial optical film is supplied as a roll of a long and wide film. The wound body of the optical film is required to maintain the optical performance of the optical film at the time of winding and during storage and transport after winding.

  As an aspect of deterioration of the optical film in the wound body, deformation due to blocking between overlapping films in the wound body and generation of defects may be mentioned.

  As a technique for preventing blocking without reducing the performance of the film, for example, as described in Patent Document 1, it is proposed to prevent blocking by a knurling process on both ends in the width direction of the film. . That is, it has been proposed to provide a knurled structure or the like at the end of the film, thereby reducing the pressure of contact between the films at locations other than both ends in the width direction of the film, thereby preventing blocking. .

JP-A-8-175708

  However, when a film provided with such a knurl structure is wound, the diameter of the end of the wound body is relatively increased compared to the center, and a trough-like deformation called a trough is generated based on the diameter. In some cases, the film wound around the body is wrinkled, and on the contrary, the optical film is defective.

  Accordingly, an object of the present invention is to provide an optical device in which blocking is effectively reduced and the occurrence of troughs is small. As a result, the optical performance of the optical film is well maintained during winding and storage and transport after winding. It is providing the manufacturing method of the wound body of an optical film which can provide the wound body of a film.

As a result of studies to solve the above-mentioned problems, the present inventor has solved the problems by adjusting the winding tension, the height of the knurl structure, or both in the winding of the optical film according to specific criteria. As a result, the present invention was completed.
That is, the present invention is as follows.

[1] A method for producing a wound body of a long optical film,
Including a step of providing a knurl structure at both ends in the width direction of at least one surface of the optical film, and a winding step of winding the optical film provided with the nar structure in a roll shape around a core.
The winding step
The outer radius R (mm) of the winding core, the outer radius r ₁ (mm) of the central portion of the film of the winding body in the middle of winding, and the width direction of the film of the winding body in the middle of winding After the outer radius r ₂ (mm) of the end portion of at least r ₁ > 1.05R, the following formulas (1) and (2):
Formula (1): h / r ₁ ≦ X
Formula (2): h> 0.1
(Where h = r ₂ −r ₁ and X is a constant determined by the type of optical film)
The winding tension in the winding step, the height of the knurl structure, or both of them are adjusted so as to always satisfy the above.
[2] X is the following formula (3):
Formula (3): X = σmax / E
(Where σmax is the tensile stress (N / m ² ) when the optical film is subjected to a tensile test and trough is generated, and E is the Young's modulus (N / m ² ) of the material constituting the optical film) The production method according to [1].
[3] The production method according to [1] or [2], wherein the optical film has a thickness of 1 to 300 μm.
[4] The manufacturing method according to any one of [1] to [3], wherein the width of the optical film is 500 to 5000 mm.

  According to the present invention, an optical film that effectively reduces blocking and generates less trough, and as a result, the optical performance of the optical film is well maintained during winding and storage and transportation after winding. The manufacturing method of the wound body of an optical film which can provide a wound body can be provided.

FIG. 1 is a side view schematically showing an example of a production line for carrying out the production method of the present invention. FIG. 2 is a rear view schematically showing an example of the shape and positional relationship of the wound body 40 and the diameter measuring device 50 in the production line shown in FIG. FIG. 3 is a perspective view showing in more detail an example of a knurl structure monitor by the knurl structure monitor devices 23 and 24 shown in FIG. FIG. 4 is a cross-sectional view specifically showing the principle of measurement of the height of a knurl structure using a monitor laser beam. FIG. 5 is a schematic diagram schematically showing an example of a state in which a tensile tension is applied to a long film. FIG. 6 is a schematic view schematically showing another example of a state in which a tensile tension is applied to a long film.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and exemplifications, and may be arbitrarily modified and implemented without departing from the scope of the claims of the present invention and its equivalent scope.

  In the following description, “substrate” and “polarizing plate” include not only a rigid member but also a flexible member such as a resin film.

(Outline of manufacturing method)
The production method of the present invention is a method for producing a roll of a long optical film. In the following description, the wound body of the optical film obtained by the production method of the present invention may be simply referred to as “wound body”. Further, in the middle of the process of manufacturing the wound body, a state in which only a part of the optical film of the final wound body is wound is referred to as a “winding body in the middle of winding”, When the context clearly shows, the winding body in the middle of winding may be simply referred to as a winding body.

  The optical film is “long” means that the film has a length of at least about 5 times the width direction of the film, preferably has a length of 10 times or more, Specifically, it refers to a length that is wound in a roll and stored or transported.

  In the production method of the present invention, a process of imparting a knurl structure to both ends in the width direction of at least one surface of the optical film (hereinafter, also simply referred to as “knurl structure imparting process”), and a knurl structure are imparted. And a winding step of winding the optical film into a roll around the core. In the following description, when it is clear from the context, the optical film before imparting the nar structure and the optical film after imparting the nar structure are simply referred to as an optical film without distinction.

  Specific examples of the knurling process and the winding process will be described with reference to the drawings. FIG. 1 is a side view schematically showing an example of a production line for carrying out the production method of the present invention. FIG. 1 shows a state in which such a production line is observed from a side surface of the production line, that is, a direction parallel to the rotation axis of the wound body.

  In FIG. 1, the long optical film 10 is conveyed in the direction indicated by the arrow A <b> 11 and guided between the knurl structure imparting devices 21 and 22. The knurl structure imparting devices 21 and 22 impart a knurl structure to both ends in the width direction of the optical film (nar structure imparting step). The height of the applied knurl structure is measured inline by the knurl structure monitoring devices 23 and 24.

  Subsequently, the optical film 10 to which the knurl structure is imparted is conveyed in the direction indicated by the arrow A <b> 12 and guided to the tension imparting device 30. The tension applying device includes an upstream roll 31, a downstream roll 33, a dancer roll 32 positioned between the upstream roll 31 and the downstream roll 33, and an air cylinder 34. The tip 34T of the air cylinder 34 is connected to the shaft 32S of the dancer roll 32. The air cylinder 34 can urge the tip 34T in the direction of arrow A21 by an appropriate means such as atmospheric pressure, and the magnitude of the urging force can be adjusted. By adjusting the force, the tension applying device 30 can adjust the tension in the longitudinal direction of the optical film 10 in an adjustable manner.

  The optical film 10 carried out from the tension applying device 30 is then conveyed in the direction indicated by the arrow A13 and wound around the core 41 having a cylindrical outer shape (winding step). The winding core 41 is driven to rotate in the direction indicated by the arrow A <b> 22, whereby the optical film 10 is wound up and becomes a wound body 40. For example, a center drive system is preferably used as the winding core drive system. The diameter of the wound body 40 during winding is monitored by the diameter measuring device 50. The diameter measuring device 50 includes a light transmitting part 51 and a light receiving part 52. A part of the light 53 emitted from the light transmitting part 51 is blocked by the wound body 40, and the rest reaches the light receiving part 52. By observing the state of the light 53 by the light receiving unit 52, the diameter of the wound body 40 can be measured in a non-contact manner.

(Adjustment in the winding process)
The winding process in the manufacturing method of the wound body of the present invention includes an outer radius R (mm) of the winding core, an outer radius r ₁ (mm) of the central portion in the width direction of the film of the wound body in the middle of winding, and an outer radius _r 2 of the both end portions in the width direction of the film winding course of the wound body (mm) is, once they become at least _r 1> 1.05R, the following formula (1) and (2):
Formula (1): h / r ₁ ≦ X
Formula (2): h> 0.1
(Where h = r ₂ −r ₁ and X is a constant determined by the type of optical film)
To adjust the winding tension in the winding process, the height of the knurl structure, or both.

  The numerical values defined here will be described with reference to the drawings again. FIG. 2 is a rear view schematically showing an example of the shape and positional relationship of the wound body 40 and the diameter measuring device 50 in the production line shown in FIG. FIG. 2 shows a state observed from the rear surface of the production line, that is, from the side close to the translucent portion 51 in a direction perpendicular to the rotation axis of the wound body and horizontal to the ground.

In FIG. 2, the outer radius R of the winding core 41 of the wound body 40, the outer radius r _{1 at} the center in the width direction, and the outer radius r ₂ at the end in the width direction are the axis 41 </ _b > C of the wound body 40. To the outer surface of the winding core 41, the distance to the outer surface of the winding body at the center in the width direction, and the distance to the outer surface of the winding body at the end in the width direction. The outer radius of the central portion in the width direction is an outer radius at a position corresponding to the midpoint P of the entire length W1 of the wound body 40 in the width direction.

The end portion in the width direction is a portion to which a knurled structure is provided, and is a portion within a range of a predetermined width W2 from the end surface 42 of the wound body 40. In the manufacture of a normal wound body of an optical film, winding is performed uniformly with high accuracy, so that the outer radius r ₂ in the end portion is equal in one end portion and the other end portion (that is, in the present embodiment). There is no error to the extent that it should be taken into account in the implementation of the inventive method), and it is possible to implement the inventive method by measuring r ₂ for only one of the ends. However, in the case where the value of the outer radius r ₂ is greatly different between one end and the other end, it is preferable from the viewpoint of preventing the occurrence of defects to measure r ₂ at the end showing a larger r ₂ .

For example, the outer radius r ₂ can be obtained by installing a diameter measuring device 50 (shown by a broken line in FIG. 2) at the end of the wound body 40 as shown in FIG. 2, and performing measurement here. On the other hand, the outer radius r ₁ can be obtained by installing another diameter measuring device (not shown) at the center in the width direction and performing measurement here.

The constant X in the formula (1) can be obtained empirically for each optical film as a value that enables good winding, but preferably the following formula (3):
Formula (3): X = σmax / E
Can be obtained. Here, σmax is a tensile test (N / m ² ) when a tensile test is performed on the optical film, and E is a Young's modulus (N / m ² ) of the material constituting the optical film.

  In the present invention, the trough is a saddle-like structure generated when a tensile load is applied in a certain direction of the film. The cross section of the film in which the trough has occurred in a plane perpendicular to the direction of the tensile load has a corrugated shape.

  Formula (3) will be specifically described. σmax can be obtained by preparing a sample of an appropriate size for an optical film and conducting a tensile test until a trough is generated. For example, a rectangular film having an appropriate length and width is pulled in the length direction so that the load is evenly applied in the width direction, and the tensile load is gradually increased. The optical film surface is visually observed, and the tensile load at the time when the trough is generated is obtained. By dividing the tensile load by the film cross-sectional area, σmax can be obtained.

  The Young's modulus E is the Young's modulus of the material constituting the optical film. When the optical film is made of a material having anisotropy such as a stretched film, the Young's modulus for the film may be the eigenvalue of the material, but a Young's modulus is separately used by using a sample for Young's modulus measurement. It is preferable to obtain a Young's modulus by performing a tensile test for measurement.

Specifically, the adjustment of the winding tension, the height of the knurl structure, or both of them so as to satisfy the formula (1) is such that h / r ₁ of the winding body during winding approaches the value of X. Once achieved, this can be accomplished by reducing the winding tension, reducing the height of the knurl structure, or both. If formula (1) is transformed, the following (1 ′):
Formula (1 ′): h ≦ r ₁ X
Therefore, the same control may be performed when the height of h approaches the value of r ₁ X. In the following, the value of r ₁ X may be referred to as “allowable end height” in the sense of an upper limit of the allowable height of h.

As for the formula (2), normally, when the height of the knurl structure is set to be higher than a certain level in the start-up of the production of the wound body, the formula (2) is satisfied after r ₁ > 1.05R. Can be maintained. However, if the winding tension, the height of the knurl structure, or both of them are extremely lowered, h may be 0.1 or less. In that case, the winding tension, the height of the knurl structure, or both are increased and adjusted so as to be in the range of 0.1 <h ≦ r ₁ X.
Although there is no restriction | limiting in the outer radius R of a winding core, Usually, it is 30 mm or more, Preferably it is 70 mm or more, Usually, 500 mm or less, Preferably it is 200 mm or less. By setting the outer radius R of the winding core to be equal to or greater than the above lower limit, it is possible to obtain a wound body with a good appearance in which the generation of wrinkles and troughs is suppressed. Moreover, by setting it as the upper limit or less, it can be set as the wound body with a small outer diameter and excellent transport efficiency.

(Tensile tension)
The magnitude of the tensile tension applied to the film in the winding step, that is, the winding tension, is preferably 10 N / m or more, preferably 500 N / m or less, more preferably 300 N / m or less, and particularly preferably 150 N / m or less. is there. By making the winding tension equal to or higher than the lower limit of the above range, winding deviation can be prevented. Moreover, by setting it as the upper limit value or less, blocking of the optical film and deformation of the wound body can be prevented. In the production method of the present invention, the winding tension is preferably adjusted so as to satisfy the expressions (1) and (2) within this range.

  Furthermore, the winding tension may be adjusted so that the tension gradually decreases linearly so that the tension at the winding completion time becomes smaller than the tension at the winding start time. In this way, gradually reducing the winding tension is referred to as providing a tension taper. The ratio of the difference between the tension at the start of winding and the tension at the completion of winding relative to the tension at the start of winding is called the taper ratio of the winding tension. The taper ratio of the winding tension is preferably 3% or more, more preferably 5% or more, particularly preferably 10% or more, preferably 50% or less, more preferably 40% or less, particularly preferably 30% or less. is there. By providing the tension taper in this way, the radial stress in the wound body can be kept low. In the production method of the present invention, the winding tension is preferably adjusted so as to satisfy the expressions (1) and (2) within this range.

  In the winding step, winding may be performed while applying contact pressure to the optical film with a contact pressure roll, if necessary. At this time, the size of the contact pressure is preferably 20 N / m or more, more preferably 30 N / m or more, particularly preferably 40 N / m or more, while preferably 200 N / m or less, more preferably 150 N / m or less. It is. By making the contact pressure equal to or higher than the lower limit of the above range, winding deviation can be prevented. Moreover, by setting it as the upper limit value or less, blocking of the optical film and deformation of the wound body can be prevented.

  The winding speed of the optical film is not limited, but is preferably 5 m / min or more, more preferably 10 m / min or more, while preferably 150 m / min or less, more preferably 100 m / min or less, particularly preferably 80 m / min. Is less than a minute. Manufacturing efficiency can be made favorable by making winding-up speed more than the lower limit of the said range. Moreover, by making it below the upper limit value, it is possible to prevent the entrainment of air and prevent the wound body from being deformed over time.

(Nar structure)
In the present invention, the knurl structure is a convex structure provided on the surface of the optical film. In the optical film used in the present invention, a large number of knurl structures are usually formed in the regions at both ends. Examples of the method for forming a knurl structure include a method of pressing a mold against an optical film and a method of laser light irradiation.

  The method of pressing the mold against the optical film can be performed by, for example, a roll-shaped or ring-shaped mold (for example, knurl) having a concavo-convex pattern corresponding to the shape of the knurled structure on the surface. By pressing the mold against the end of the optical film, the concave / convex pattern can be transferred, and a knurled structure can be imparted to the optical film. Under the present circumstances, the said operation can be performed in the state which heated the optical film and / or the type | mold as needed. In this method of pressing the mold, the degree of freedom in adjusting the height of the knurled structure is low, but the manufacturing method of the present invention can be performed by appropriately adjusting the winding tension.

  The laser beam irradiation method will be described. When the optical film is irradiated with laser light, thermal melting or ablation occurs locally at the location where the laser light is irradiated. For this reason, convex or concave deformation occurs in the optical film at the place irradiated with the laser beam. Such a convex or concave deformation can be used as a knurl structure. In the method using laser light irradiation, the residual stress is less likely to remain than in the method in which a mold is pressed against the optical film, so that even a thin optical film can easily form a knurled structure without causing breakage. The method using laser light irradiation is particularly preferable in the present invention because the height of the knurl structure can be easily adjusted by adjusting the intensity of the laser light.

The laser beam irradiation time is preferably 0.001 ms or more, more preferably 0.005 ms or more, further preferably 0.01 ms or more, preferably 0.5 ms or less, more preferably 0.3 ms or less, and further preferably Is 0.1 ms or less.
Examples of the laser light include ArF excimer laser, KrF excimer laser, XeCl excimer laser, third harmonic or fourth harmonic of YAG laser, third harmonic or fourth harmonic of solid laser of YLF or YVO4, Ti : S laser, semiconductor laser, fiber laser, carbon dioxide laser, etc. may be used. Among these laser beams, a carbon dioxide laser is preferable from the viewpoint of improving productivity due to high output.
The output of the laser beam is preferably 1 W or more, more preferably 5 W or more, further preferably 15 W or more, preferably 30 W or less, more preferably 25 W or less. By making the output of the laser beam equal to or more than the lower limit of the above range, it is possible to prevent the irradiation amount of the laser beam from being insufficient, and to stably form a nal structure on the surface of the optical film. In addition, by making the output of the laser beam below the upper limit of the above range, it is possible to prevent the formation of through holes in the optical film, and to suppress the thermal effect on a wide area around the laser beam irradiation point, It is possible to prevent the desired nar structure from being obtained by unintentionally expanding the nar structure.

  The height of the knurl structure formed by laser light irradiation can be easily monitored by a monitoring device. FIG. 3 is a perspective view showing in more detail an example of a knurl structure monitor by the knurl structure monitor devices 23 and 24 shown in FIG. In the example shown in FIG. 3, the optical film 10 partially illustrated is conveyed in the direction of arrow A31. An end in the width direction is defined within a range of a predetermined width W2 from the edge of the optical film 10. In this example, the lower device 24 is a projector and the upper device 23 is a light receiver. From the projector 24, the monitoring laser light is irradiated in the direction indicated by the arrow A <b> 32, which passes through the optical film 10 and reaches the light receiver 23. By observing the state of the monitoring laser beam with the light receiver 23, the height of the knurl structure can be obtained.

  FIG. 4 is a cross-sectional view specifically showing the principle of measurement of the height of a knurl structure using a monitor laser beam. In FIG. 4, the laser light from the projector proceeds in the direction of the arrow A <b> 32 a and reaches the optical film 10. The laser light that passes through the portion of the optical film 10 where the knurl structure 15 is present is emitted from the optical film 10 as indicated by an arrow A32c with relatively large attenuation. The laser beam that passes through the portion where the knurl structure 15 does not exist is emitted from the optical film 10 as indicated by an arrow A33b with relatively little attenuation. There is a certain correlation between the height of the knurl structure and the degree of attenuation of the monitoring laser beam. Therefore, by using an optical film having a knurled structure formed by laser light irradiation with a known height and measuring the correlation in advance, the height of the knurled structure can be determined based on the attenuation of the monitor laser light Inline and non-contact can be obtained.

  The height of the knurl structure is preferably 1 μm or more, more preferably 3 μm or more, while preferably 30 μm or less, more preferably 20 μm or less. Further, the height of the knurl structure is preferably 1% or more, more preferably 5% or more, preferably 100% or less, more preferably 40% or less, with respect to the thickness of the optical film. In the production method of the present invention, the height of the knurl structure is adjusted so as to satisfy the formulas (1) and (2), preferably within this range.

  Furthermore, the height of the knurled structure may be adjusted so that the height gradually decreases linearly so that the height at the time of winding completion is smaller than the height at the time of winding start. In this way, gradually reducing the height of the knurl structure is referred to as providing a knurl structure height taper. The ratio of the difference between the height at the start of winding and the height at the completion of winding to the height of the knurled structure at the start of winding is referred to as the taper ratio of the height of the knurled structure. The taper ratio of the knurl structure height is preferably 1% or more, more preferably 10% or more, particularly preferably 20% or more, preferably 100% or less, more preferably 80% or less, particularly preferably 50% or less. It is. Thus, by providing the taper with the height of the knurl structure, a wound body wound smoothly can be obtained. In the production method of the present invention, the height of the knurl structure is adjusted so as to satisfy the expressions (1) and (2), preferably within this range.

  The width W2 (width indicated by the arrow W2 in FIGS. 2 and 3) of the end portion of the optical film having a knurl structure is preferably 3 mm or more, more preferably 5 mm or more, preferably 20 mm or less, more preferably It is 15 mm or less, particularly preferably 10 mm or less. The ratio of one width W2 to the entire width of the optical film (corresponding to the width indicated by arrow W1 in FIG. 2) is preferably 0.3% or more, more preferably 0.5% or more, preferably Is 1.0% or less. By setting the width of the end portion to be equal to or greater than the lower limit value of the above range, it is possible to stably prevent the winding deviation of the wound body. Moreover, by setting it as the upper limit value or less, the size of the effective area of the optical film can be secured widely, and the manufacturing cost can be reduced. Here, the effective area | region of an optical film is an area | region where the knurl structure of the optical film is not formed.

  The knurl structure is usually formed over the entire length in the longitudinal direction of the optical film in the region of both ends of the optical film defined by the width W2. Transparency is usually impaired in the end region where the knurl structure is formed. However, since the transparency of the region inside the end portion is not impaired, the inside region can be used as a portion that can effectively exhibit the optical function.

  The shape of each knurl structure is not particularly limited, but examples of the shape when observed from a direction perpendicular to the surface of the optical film include a dot shape and a linear shape. The knurl structure formed by the laser beam irradiation method can usually be a dot shape. By forming a large number of dot-shaped knurl structures at the ends, an effective blocking suppression effect can be obtained without impairing the strength of the film.

The arrangement of the knurl structure in the end region may be random or may be arranged with regularity. The spacing between the knurl structures may be non-uniform or uniform. The density of the knurl structure in the end region is preferably 5 pieces / cm ² or more, more preferably 10 pieces / cm ² or more, particularly preferably 30 pieces / cm ² or more, preferably 100 pieces / cm ² or less. More preferably, it is 80 pieces / cm ² or less, particularly preferably 60 pieces / cm ² or less. By setting the interval of the knurl structure to be equal to or greater than the lower limit of the above range, it becomes easy to create a space between the optical films that overlap each other during winding. Moreover, the crack by the stress concentration to a knurl structure can be suppressed by setting it as an upper limit or less.
The individual nar structure and the arrangement of the nar structure at one end and the other end of the optical film may be the same or different, but by arranging the same nar structure symmetrically. The winding accuracy can be further increased.

(principle)
Although not limited to a specific theory, the following principle can be considered as a principle for obtaining a good wound body by the production method of the present invention.

  Generally, when winding a long film, tensile tension is applied in the longitudinal direction of the film. The tensile tension is uniformly applied in the width direction of the film by an appropriate means such as a dancer roll shown in FIG. FIG. 5 is a schematic diagram schematically showing an example of a state in which a tensile tension is applied to such a long film. In FIG. 5, the optical film 10 a is a winding roll 40 a, but the tensile tension applied at that time is as shown by an arrow A 51 at any position in the width direction of the film. Parallel to the longitudinal direction.

  However, when winding is performed in a state where a knurl structure is imparted to the film, the radius of the end portion in the film width direction of the wound body relatively increases as the winding proceeds. FIG. 6 is a schematic diagram schematically showing an example of such a state. In FIG. 6, the optical film 10b is a take-up wound body 40b. However, the tensile tension applied at that time is in a non-parallel state as indicated by an arrow A52. Wrinkles can be generated on the film wound around the roll.

Such non-uniform tensile tension is non-uniform due to the difference in the length of the film to be wound between the center and the end of the wound body. Specifically, the length L1 of the film wound in one rotation at the center of the wound body is 2r ₁ π, whereas the length L of the film wound in one rotation at the end is 2r ₂ π = 2. (R ₁ + h) π, and the difference ΔL = L−L1 is 2hπ. Therefore, the amount of distortion due to such difference can be estimated as _{ΔL / L1 = h / r 1} . Winding tension so as to keep the amount of strain h / r ₁ below a predetermined value X (that is, to make the end height with respect to the outer radius of the central portion below a predetermined height), the height of the knurl structure By adjusting both or both, good winding can be achieved. The predetermined value X can be a distortion amount that generates troughs. Therefore, a tensile test is performed on a sample of the optical film to obtain a σmax value, and the corresponding strain amount σmax / E is adopted as the value X, so that a good winding process can be achieved.

(Optical film: material)
The optical film used in the method for producing a wound body of the present invention is usually a thermoplastic resin film. A thermoplastic resin film means a film provided with at least one layer formed of a thermoplastic resin. Examples of thermoplastic resins include polyester resins, polyolefin resins, polycarbonate resins, cellulose ester resins, and acrylic resins. Among these, polyolefin resins are more preferable, and alicyclic polyolefin resins are particularly preferable from the viewpoint of satisfying the balance of quality such as mechanical properties, heat resistance, and transparency required for a film for a display device such as a liquid crystal display device.

  The alicyclic polyolefin resin is a resin containing an alicyclic polyolefin polymer having an alicyclic structure in one or both of the main chain and the side chain. Examples of the alicyclic structure include a saturated alicyclic hydrocarbon (cycloalkane) structure and an unsaturated alicyclic hydrocarbon (cycloalkene) structure. Among these, from the viewpoint of mechanical strength and heat resistance, a cycloalkane structure and a cycloalkene structure are preferable, and a cycloalkane structure is particularly preferable.

  The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more per alicyclic structure. The number is preferably 20 or less, particularly preferably 15 or less. When the number of carbon atoms constituting the alicyclic structure falls within the above range, properties such as mechanical strength, heat resistance, and film formability are highly balanced, which is preferable.

  The proportion of the structural unit having an alicyclic structure in the alicyclic polyolefin polymer may be appropriately selected according to the purpose of use, preferably 55% by weight or more, more preferably 70% by weight or more, particularly preferably. 90% by weight or more. By keeping the proportion of the structural unit having an alicyclic structure in the alicyclic polyolefin polymer within the above range, the transparency and heat resistance of the optical film can be improved.

  Examples of alicyclic polyolefin polymers include norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, and hydrides thereof. Can be mentioned. Among these, norbornene-based polymers can be suitably used because of their good transparency and moldability.

  Examples of the norbornene polymer include a ring-opening polymer of a monomer having a norbornene structure, a ring-opening polymer of a monomer having a norbornene structure and another monomer, or a hydride thereof; norbornene An addition polymer of a monomer having a structure, an addition polymer of a monomer having a norbornene structure and another monomer, or a hydride thereof. Among these, a ring-opening (co) polymer hydride of a monomer having a norbornene structure is particularly suitable from the viewpoints of transparency, moldability, heat resistance, low hygroscopicity, dimensional stability, lightness, and the like. Can be used. Here, the (co) polymer means a polymer and a copolymer.

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 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 kind 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.

  Examples of other monomers capable of ring-opening copolymerization with a monomer having a norbornene structure include, for example, monocyclic olefins such as cyclohexene, cycloheptene, and cyclooctene and derivatives thereof; and cyclic conjugates such as cyclohexadiene and cycloheptadiene. Dienes and derivatives thereof; and the like. One of these may be used alone, or two or more of these may be used in combination at any ratio.

  A ring-opening polymer of a monomer having a norbornene structure and a ring-opening copolymer with another monomer copolymerizable with a monomer having a norbornene structure are, for example, known monomers. It can be obtained by polymerization in the presence of a ring polymerization catalyst.

  Examples of other monomers capable of addition copolymerization with a monomer having a norbornene structure include α-olefins having 2 to 20 carbon atoms such as ethylene, propylene, and 1-butene, and derivatives thereof; cyclobutene and cyclopentene. And cycloolefins such as cyclohexene and derivatives thereof; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene; and the like. These monomers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Among these, α-olefin is preferable and ethylene is more preferable.

  Examples of addition polymers of monomers having a norbornene structure and addition copolymers of other monomers copolymerizable with a monomer having a norbornene structure include known monomers for addition polymerization. Can be obtained by polymerization in the presence of.

  A hydrogenated product of a ring-opening polymer of a monomer having a norbornene structure, a hydrogenated product of a ring-opening copolymer of a monomer having a norbornene structure and another monomer capable of ring-opening copolymerization thereof, Hydrogenated products of addition polymers of monomers having a norbornene structure and hydrogenated products of addition polymers of monomers having a norbornene structure and other monomers copolymerizable therewith are not For example, a known hydrogenation catalyst containing a transition metal such as nickel or palladium is mixed into the combined solution, and the carbon-carbon unsaturated bond is preferably hydrogenated by 90% or more.

Among norbornene polymers, as a repeating unit, X: bicyclo [3.3.0] octane-2,4-diyl-ethylene structure and Y: tricyclo [4.3.0.1 ^2,5 ] decane- It has a 7,9-diyl-ethylene structure, and the content of these repeating units is 90% by weight or more with respect to the entire repeating units of the norbornene polymer, and the content ratio of X and the content of Y It is preferable that the ratio to the ratio is 100: 0 to 40:60 in terms of a weight ratio of X: Y. By using such a norbornene-based 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 molecular weight of the alicyclic polyolefin polymer can be appropriately selected according to the purpose of use. The weight average molecular weight (Mw) of the alicyclic polyolefin polymer is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000 or more, preferably 100,000 or less, more preferably 80,000 or less, particularly preferably 50,000 or less. When the weight average molecular weight is in such a range, the mechanical strength and molding processability of the optical film are highly balanced, which is preferable. Here, the weight average molecular weight is a value in terms of polyisoprene or polystyrene measured by gel permeation chromatography using cyclohexane (toluene when the sample polymer is not dissolved) as a solvent.

  The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the alicyclic polyolefin polymer is preferably 1.0 or more, more preferably 1.1 or more, particularly preferably 1.2 or more. Preferably 10.0 or less, more preferably 4.0 or less, and particularly preferably 3.5 or less. By making molecular weight distribution more than the lower limit of the said range, the productivity of a polymer can be improved and cost can be reduced. Further, by making the amount lower than the upper limit value, it is possible to reduce the amount of the low molecular component and reduce the component having a short relaxation time, so that it becomes possible to reduce the alignment relaxation at the time of high temperature exposure.

  The resin constituting the optical film may contain any component other than the above-described polymer as long as the effects of the present invention are not significantly impaired. Examples of optional components include antioxidants, heat stabilizers, light stabilizers, UV absorbers, antistatic agents, dispersants, chlorine scavengers, flame retardants, crystallization nucleating agents, reinforcing agents, and antiblocking agents. , Antifogging agents, mold release agents, pigments, organic or inorganic fillers, neutralizing agents, lubricants, decomposition agents, metal deactivators, antifouling agents, and antibacterial agents. One of these may be used alone, or two or more of these may be used in combination at any ratio. However, the amount of the optional component is within a range not impairing the effects of the present invention, and is usually 50 parts by weight or less, preferably 30 parts by weight or less, more preferably 20 parts by weight or less, particularly 100 parts by weight of the polymer. The amount is preferably 10 parts by weight or less. The lower limit is zero.

  The glass transition temperature of the resin constituting the optical film can be appropriately selected according to the purpose of use, and is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and preferably 250 ° C. or lower. A resin film having a glass transition temperature in such a range is less susceptible to deformation and stress during use at high temperatures, and is excellent in durability.

The absolute value of the photoelastic coefficient C of the resin constituting the optical film is preferably ¹⁰ × 10 -12 ^{Pa -1} or less, more preferably 7 × ¹⁰ -12 ^{Pa -1} or less, 4 × 10 It is particularly preferably ⁻¹² Pa ⁻¹ or less. Here, the photoelastic coefficient C is a value represented by “C = Δn / σ” where birefringence is Δn and stress is σ. By keeping the absolute value of the photoelastic coefficient C of the resin within the above range, variations in in-plane retardation of the optical film can be reduced.

  The optical film may be a single-layer film having only one layer, or may be a multilayer film having two or more layers. For example, the optical film is a film having a multilayer structure provided with a coat layer for the purpose of imparting characteristics such as slipperiness, easy adhesion, and antistatic property to one or both sides of a thermoplastic resin layer as a base material. It is good. In this case, as a material for the coat layer, for example, a thermoplastic resin, a thermosetting resin, a radiation curable resin, a reactive resin, and a mixture thereof can be used. Specific examples of preferred materials include acrylic polymers, urethane polymers, ether polymers, and functional group-modified polymers such as carboxyl groups, amino groups, and methylol groups of these polymers; polyvinyl alcohol systems Polymer or derivatives thereof; ethylene-vinyl alcohol copolymer; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; starches such as oxidized starch, etherified starch and dextrin; containing polar groups such as polyvinylpyrrolidone and sulfoisophthalic acid Examples thereof include copolymerized polyesters; vinyl polymers such as polyhydroxyethyl methacrylate or copolymers thereof; and the like. Moreover, these materials may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. These materials can be produced by, for example, applying the material as a coating liquid dispersed in water or an organic solvent onto the surface of a thermoplastic resin layer serving as a base material and drying it. Further, it is possible to improve the durability of the coating layer by including an optional crosslinking agent in the coating liquid as required.

  Especially, it is preferable that an optical film equips the surface with an easily bonding layer as a coating layer. An optical film provided with an easy-adhesion layer has good adhesiveness when it is attached to another optical film such as a polarizing plate. In addition, when a film provided with such an easy-adhesion layer is wound up to form a wound body, in general, blocking is likely to occur, but in the wound body obtained by the production method of the present invention, blocking is caused by the knurled structure at the end. It can suppress and make it hard to produce a defect at the time of storage. Therefore, it is preferable that the optical film includes an easy-adhesion layer in that the effect of suppressing the occurrence of defects can be effectively utilized.

  The easy-adhesion layer is preferably a layer containing a water-based resin, for example. Examples of the water-based resin include urethane resins, polyester resins, and emulsions of the respective resins, and water-based urethane resins are preferable.

  A water-based urethane resin contains a polyurethane and another component as needed. Examples of the polyurethane contained in the water-based urethane resin include, for example, (i) a polyurethane obtained by reacting a component containing an average of two or more active hydrogens in one molecule and (ii) a polyvalent isocyanate component; The component (i) and the component (ii) are urethanated in an organic solvent that is inert to the reaction and has a high affinity for water under an excess of isocyanate groups to obtain an isocyanate group-containing prepolymer, A polyurethane produced by neutralizing a polymer, chain-extending with a chain extender, and adding water to form a dispersion. These polyurethanes may contain an acid structure (acid residue).

  A known method can be adopted as a method for extending the chain of the isocyanate group-containing prepolymer. For example, water, water-soluble polyamine, glycols or the like may be used as the chain extender, and the isocyanate group-containing prepolymer and the chain extender may be reacted in the presence of a catalyst as necessary.

  The component (i) (that is, a component containing an average of 2 or more active hydrogens in one molecule) is not particularly limited, but preferably has a hydroxylic active hydrogen. Specific examples of such compounds include the following (1) to (5).

(1) Polyol compound:
Examples of the polyol compound include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5- Pentanediol, neopentyl glycol, 1,6-hexane glycol, 2,5-hexanediol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, tricyclodecane dimethanol, 1,4- Examples include cyclohexanedimethanol, 2,2-dimethylpropanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octamethylenediol.

(2) Polyether polyol:
Examples of polyether polyols include alkylene oxide adducts of the aforementioned polyol compounds; ring-opening (co) polymers of alkylene oxides and cyclic ethers (such as tetrahydrofuran); polyethylene glycol, polypropylene glycol, ethylene glycol-propylene glycol copolymer Examples thereof include glycols such as glycol, polytetramethylene glycol, polyhexamethylene glycol, and polyoctamethylene glycol.

(3) Polyester polyol:
Examples of the polyester polyol include dicarboxylic acids such as adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid and phthalic acid or anhydrides thereof, and ethylene glycol and propylene as mentioned in the above (1) Examples thereof include those obtained by polycondensation of polyol compounds such as glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octamethylenediol, neopentyl glycol and the like under hydroxyl-excess conditions. It is done. More specifically, for example, ethylene glycol-adipic acid condensate, butanediol-adipine condensate, hexamethylene glycol-adipic acid condensate, ethylene glycol-propylene glycol-adipic acid condensate, or lactone with glycol as an initiator. And polylactone diol obtained by ring-opening polymerization.

(4) Polyether ester polyol:
As the polyether ester polyol, for example, an ether group-containing polyol (for example, the polyether polyol or diethylene glycol of (2) above) or a mixture of this with another glycol may be a dicarboxylic acid as exemplified in the above (3) or Examples include those obtained by reacting an alkylene oxide in addition to the anhydride. More specifically, examples include polytetramethylene glycol-adipic acid condensate.

(5) Polycarbonate polyol:
Examples of the polycarbonate polyol include a general formula HO-R- (OC (O) -O-R) x-OH (wherein R represents a saturated fatty acid polyol residue having 1 to 12 carbon atoms). And x represents the number of repeating units of the molecule and is usually an integer of 5 to 50). These are a transesterification method in which a saturated aliphatic polyol and a substituted carbonate (for example, diethyl carbonate, diphenyl carbonate, etc.) are reacted under the condition that the hydroxyl group becomes excessive; the saturated aliphatic polyol and phosgene are reacted, or If necessary, it can be obtained by a method of further reacting a saturated aliphatic polyol thereafter.

  The compounds as exemplified in the above (1) to (5) may be used alone or in combination of two or more at any ratio.

  Examples of the component (ii) to be reacted with the component (i) (that is, the polyvalent isocyanate component) include, for example, an aliphatic, alicyclic or aromatic compound containing an average of two or more isocyanate groups in one molecule. Can be used.

  The aliphatic diisocyanate compound is preferably an aliphatic diisocyanate having 1 to 12 carbon atoms, and examples thereof include hexamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, and hexane diisocyanate (HDI). The alicyclic diisocyanate compound is preferably an alicyclic diisocyanate having 4 to 18 carbon atoms, such as 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (HMDI) and the like. Can be mentioned. Examples of the aromatic isocyanate include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and the like.

  Among water-based urethane resins, polyurethane containing an acid structure can be easily dispersed in water without using a surfactant or with a small amount of surfactant. It is expected that the water resistance of the adhesive layer will be improved. This is called a self-emulsifying type, which means that the polyurethane resin can be dispersed and stabilized in water only by molecular ionicity without using a surfactant. Such an easily active layer using a water-based urethane resin does not require a surfactant, and thus has excellent adhesion to, for example, an alicyclic structure-containing polymer resin, a (meth) acrylic resin, and a polyester resin. And high transparency can be maintained.

Examples of the acid structure include acid groups such as a carboxyl group (—COOH) and a sulfonic acid group (—SO ₃ H). In addition, the acid structure may be present in the side chain or at the terminal in the polyurethane. One type of acid structure may be used, or two or more types may be used in combination at any ratio.

  The amount of the acid structure is preferably 20 mgKOH / g or more, more preferably 25 mgKOH / g or more, preferably 250 mgKOH / g or less, more preferably 150 mgKOH / g or less as the acid value in the water-based urethane resin. By making the acid value equal to or higher than the lower limit of the above range, the water dispersibility of the resin can be improved. Moreover, the water resistance of an easily bonding layer can be made favorable by setting it as below an upper limit.

  As a method for introducing an acid structure into polyurethane, for example, by replacing dimethylolalkanoic acid with a part or all of the glycol component described in (2) to (4) above, polyether polyol, polyester polyol, The method of introduce | transducing a carboxyl group into polyetherester polyol etc. is mentioned. Examples of the dimethylol alkanoic acid used here include dimethylol acetic acid, dimethylol propionic acid, and dimethylol butyric acid. Here, dimethylol alkanoic acid may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Moreover, it is preferable to neutralize a part or all of the acid structure contained in the polyurethane. By neutralizing the acid structure, the water dispersibility of the water-based urethane resin can be improved. Examples of neutralizing agents that neutralize the acid structure include organic amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, N-methyldiethanolamine, and triethanolamine; inorganics such as sodium hydroxide, potassium hydroxide, and ammonia Bases; and the like. Here, a neutralizing agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  The number average molecular weight of the polyurethane is preferably 1,000 or more, more preferably 20,000 or more, preferably 1,000,000 or less, more preferably 200,000 or less.

  As the water-based urethane resin, a commercially available water-based urethane resin may be used as it is. Examples of water-based urethane resins include the “Adeka Bon titer” series manufactured by Asahi Denka Kogyo Co., Ltd., the “Olestar” series manufactured by Mitsui Toatsu Chemical Co., Ltd., and the “Bonn” manufactured by Dainippon Ink & Chemicals, Inc. "Dick" series, "Hydran" series, "Imperil" series manufactured by Bayer, "Sofranate" series manufactured by Sofran Japan, "Poise" series manufactured by Kao Corporation, Sanyo Chemical Industries The "Samprene" series, the "Izelux" series made by Hodogaya Chemical Co., Ltd., the "Superflex" series made by Daiichi Kogyo Seiyaku Co., Ltd., the "Neolet's" series made by Zeneca Co., Ltd., etc. it can. One of these water-based urethane resins may be used alone, or two or more thereof may be used in combination at any ratio.

  Moreover, the easily bonding layer may contain particle | grains. Therefore, when the easy-adhesion layer is formed of a water-based resin, the water-based resin may include particles. By including particles in the easy-adhesion layer, irregularities are formed on the surface of the easy-adhesion layer, whereby the surface roughness of the optical film can be set to a desired range.

  For the purpose of improving the mechanical strength of the easy-adhesion layer, the aqueous resin used for the production of the easy-adhesion layer may further contain a crosslinking agent. As a crosslinking agent, the compound which has a functional group which reacts with the reactive group which the polymer contained in aqueous resin has can be used. For example, when a water-based urethane resin is used as the water-based resin, it is possible to use a water-based epoxy compound, a water-based amino compound, a water-based isocyanate compound, a water-based carbodiimide compound, a water-based oxazoline compound, etc. as a crosslinking agent from the viewpoint of versatility of the material. preferable. Among these, it is particularly preferable to use an aqueous epoxy compound, an aqueous amino compound, or an aqueous oxazoline compound from the viewpoint of adhesiveness.

  As the water-based epoxy compound, a compound that is soluble in water or emulsified and has two or more epoxy groups per molecule can be used. Examples of water-based epoxy compounds include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexane glycol, and neopentyl glycol 1 Diepoxy compound obtained by etherification of 1 mol of mol and 2 mol of epichlorohydrin; obtained by etherification of 1 mol of polyhydric alcohols such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol and 2 mol or more of epichlorohydrin Polyepoxy compound: Diepoxy obtained by esterification of 1 mol of dicarboxylic acid such as phthalic acid, terephthalic acid, oxalic acid, adipic acid and 2 mol of epichlorohydrin Epoxy compounds such as shea compounds; and the like.

  As the water-based amino compound, a compound having two or more amino groups per molecule that is soluble in water or emulsified can be used. Examples of water-based amino compounds are carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, glycolic acid Examples thereof include hydrazide compounds such as polyacrylic acid dihydrazide, melamine resins, urea resins, and guanamine resins.

  As the water-based isocyanate compound, a compound having two or more non-blocked isocyanate groups or blocked isocyanate groups per molecule that is soluble in water or emulsified can be used. Examples of the non-blocking isocyanate compound include compounds obtained by reacting a polyfunctional isocyanate compound with a monovalent or polyvalent nonionic polyalkylene ether alcohol. Examples of the block isocyanate compound include 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), 4,4′-diphenylmethane diisocyanate (MDI), Xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), methylcyclohexyl diisocyanate (H6TDI), 4,4'-dicyclohexylmethane diisocyanate (H12MDI), 1,3-bis (isocyanatomethyl) cyclohexane (H6XDI), tetramethylxylylene Range isocyanate (TMXDI), 2,2,4-trimethylhexamethylene diisocyanate (TMHDI), hexamethylene diisocyanate (HDI), norbornene diisocyanate (NBDI) ), 2,4,6-triisopropylphenyl diisocyanate (TIDI), 1,12-diisocyanatododecane (DDI), 2,4, -bis- (8-isocyanatooctyl) -1,3-dioctylcyclobutane (OCDI), n-pentane-1,4-diisocyanate, and isocyanurate-modified products, adduct-modified products, burette-modified products, allophanate-modified products, and polymers having one or more isocyanate groups per molecule. Examples thereof include a compound obtained by modifying with a polyoxyalkylene group, a carboxyl group or the like, making it water-soluble and / or water-dispersible, and masking an isocyanate group with a blocking agent (such as phenol or ε-caprolactam).

  As the water-based carbodiimide compound, a compound having two or more carbodiimide bonds (—N═C═N—) per molecule that is soluble in water or emulsified can be used. A compound having two or more carbodiimide bonds per molecule is obtained, for example, by a method of forming a carbodiimide bond by decarboxylation of two isocyanate groups using two or more polyisocyanate and a carbodiimidization catalyst. be able to. The polyisocyanate and the carbodiimidization catalyst used in preparing a compound having two or more carbodiimide bonds per molecule are not particularly limited, and conventionally known ones can be used.

As the water-based oxazoline compound, a compound having two or more oxazoline groups per molecule that is soluble in water or emulsified can be used.
These crosslinking agents may be used alone or in combination of two or more at any ratio.

  When the easy-adhesion layer is formed of a water-based urethane resin, the amount of the crosslinking agent is preferably 1 part by weight or more, more preferably 5 parts by weight or more, based on 100 parts by weight of polyurethane. Is 70 parts by weight or less, more preferably 65 parts by weight or less. By blending in this way, it becomes possible to achieve both the strength of the easy-adhesion layer and the stability of the aqueous dispersion of the water-based urethane resin.

  Furthermore, for the easy adhesion layer, for example, heat stabilizer, weather stabilizer, leveling agent, antistatic agent, slip agent, antiblocking agent, antifogging agent, lubricant, dye, pigment, natural oil, Synthetic oils, waxes, crosslinking agents and the like may be included. Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

  The thickness of the easy adhesion layer is preferably 0.01 μm or more, more preferably 0.02 μm or more, particularly preferably 0.03 μm or more, more preferably 5 μm or less, more preferably 2 μm or less, and particularly preferably 1 μm or less. Within the above range, sufficient adhesive strength between the other layer of the optical film and the easy-adhesion layer can be obtained, and warping of the optical film can be prevented.

(Optical film: other features)
The optical film used in the present invention may be an unstretched film that has not been subjected to a stretching treatment, or a stretched film that has been subjected to a stretching treatment. Especially, it is preferable that an optical film is a stretched film. According to the wound body obtained by the production method of the present invention, it is usually possible to reduce the molecular orientation relaxation in the film during storage. For this reason, it is possible to suppress a change during storage of the retardation developed in the optical film by stretching, and to prevent defects due to orientation relaxation.

  Examples of uses of the optical film used in the present invention include a retardation plate used in a liquid crystal display device, a viewing angle compensation film, a film before stretching as a raw film of those films, and a polarizing plate protective film. Can be mentioned. From the viewpoint of use in such applications, the optical film (excluding the end portion having a knurl structure) preferably has a total light transmittance in terms of 1 mm thickness of 80% or more, and preferably 90% or more. More preferred. From the same viewpoint, the optical film (excluding the end portion having a knurl structure) preferably has a haze of 1 mm thickness of 0.3% or less, more preferably 0.2% or less. .

  The values of the in-plane retardation Re and the thickness direction retardation Rth of the optical film vary depending on the use of the optical film. Specific values of the retardation of the optical film (excluding the end portion having a Nar structure) are, for example, in the range of 10 nm to 500 nm in the in-plane retardation Re, and −500 nm to 500 nm in the retardation Rth in the thickness direction, It can be selected according to the application.

  The thickness of the optical film is preferably 1 to 300 μm from the viewpoint of increasing mechanical strength and enabling smooth winding. The thickness of the optical film is preferably 1 μm or more, more preferably 5 μm or more, while preferably 300 μm or less, more preferably 200 μm or less.

  The width of the optical film is preferably 500 mm or more, more preferably 1000 mm or more, on the other hand, preferably 5000 mm or less, from the viewpoint of prominently exhibiting the effect that it is difficult to produce defects over time when it is a wound body. More preferably, it is 3000 mm or less.

Although there is no restriction | limiting in the winding frequency of a wound body, Usually, 40 times or more, Preferably it is 60 times or more, Usually, 27000 times or less, Preferably it is 13000 times or less.
Moreover, although there is no restriction | limiting in the outer diameter of a wound body, it is 170 mm or more normally, Preferably it is 200 mm or more, Usually, 2300 mm or less, Preferably it is 1200 mm or less.

(Preparation of optical film)
The optical film before imparting a knurled structure, which is used in the method for producing a wound body of the present invention, is usually prepared by forming a film raw resin into a film. In preparing the optical film, if necessary, for example, an arbitrary step such as a step of forming a coat layer on a resin layer formed into a film or a step of stretching the film can be performed. Furthermore, the process of preparing a film and the process of the manufacturing method of the present invention (a knurl structure imparting process and a winding process) can be continuously performed in-line to achieve efficient production.

Any molding method can be used in the step of molding the resin. For example, an extrusion method and a casting method can be mentioned, and the extrusion method is preferable. The extrusion method is a method in which a molten thermoplastic resin is extruded from a die such as a T die and formed.
When a thermoplastic resin film having a multilayer structure having two or more layers is produced, the film may be formed by, for example, a co-extrusion method or a co-casting method, and the co-extrusion method is particularly preferable. The co-extrusion method is a method of extruding and molding a plurality of thermoplastic resins in a molten state. The coextrusion method is excellent in terms of production efficiency and in that volatile components such as a solvent do not remain in the thermoplastic resin film.

  Examples of the coextrusion method include a coextrusion T-die method, a coextrusion inflation method, and a coextrusion lamination method. Among these, the coextrusion T-die method is preferable. The coextrusion T-die method includes a feed block method and a multi-manifold method. Among them, the multi-manifold method is particularly preferable in that variation in the layer thickness can be reduced.

  The thermoplastic resin layer formed into a film as described above may be used as an optical film as it is. Moreover, when manufacturing an optical film provided with a coat layer in addition to the resin layer, a step of forming a coat layer on the surface of the resin layer obtained by forming the resin can be performed. The step of forming the coat layer can be performed at any time before the film is subjected to the knurled structure providing step.

  When forming the coating layer, for example, a coating solution in which the material of the coating layer is dissolved or dispersed in a solvent is prepared, and this coating solution is applied to the surface of the resin layer and dried. At this time, as the solvent, water or an organic solvent may be used. Moreover, the coating liquid may contain the crosslinking agent as needed. The durability of the coat layer can be improved by the crosslinking agent.

  For example, when forming an easy-adhesion layer with an aqueous resin, an easy-adhesion layer is formed by applying a coating liquid containing an aqueous resin as a coating liquid on the surface of the resin layer and drying the resulting coating liquid film. obtain. For example, when the easy-adhesion layer is formed of a urethane resin, a urethane resin layer as an easy-adhesion layer can be formed by applying an aqueous dispersion of an aqueous urethane resin to the surface of the resin layer and drying it. Good. The aqueous dispersion of the aqueous urethane resin is a liquid composition in which the aqueous urethane resin is dispersed in water, and may be in the form of, for example, an emulsion, a colloidal dispersion, or an aqueous solution.

The coating method of the coating liquid is not particularly limited, and for example, it can be applied using a coater such as a gravure coater, a bar coater, a reverse coater, a kiss coater, or a spray coater.
Also, an oven for drying the coating liquid applied on the resin layer is usually installed on the downstream side of the coater. However, in the manufacturing method using a tenter or float type stretching apparatus, the stretching apparatus can also serve as a drying oven by installing the coater immediately before the stretching apparatus.

  When performing the process of extending | stretching a film, the process of extending | stretching can be performed at the arbitrary time before using a film for a knurl structure provision process. Therefore, the step of stretching the film may be performed before or after the step of forming the coat layer.

  The stretching method is not particularly limited, and for example, either a uniaxial stretching method or a biaxial stretching method may be employed. As an example of the stretching method, an example of the uniaxial stretching method is a method of uniaxial stretching in the longitudinal direction (film longitudinal direction) using a difference in peripheral speed of rolls for film conveyance; A method of uniaxial stretching in the direction (film width direction); and the like. In addition, as an example of the biaxial stretching method, the gap between the clips to be fixed is opened, and the simultaneous biaxial stretching method in which the guide rail extends in the transverse direction at the same time as the longitudinal stretching; between the rolls for film conveyance There are sequential biaxial stretching methods in which the difference between the peripheral speeds is stretched in the longitudinal direction, the both ends thereof are gripped with clips, and stretched in the transverse direction using a tenter stretching machine. Further, for example, by using a tenter stretching machine that can add a feeding force, a pulling force or a pulling force at different speeds in the vertical direction or the horizontal direction, an arbitrary angle θ (0 ° with respect to the width direction of the film). An oblique stretching method in which oblique stretching is continuously performed in a direction satisfying <θ <90 °) may be used.

The stretching temperature is preferably in the range of Tg to Tg + 20 ° C., for example, based on the glass transition temperature Tg of the resin.
There is no restriction | limiting in particular in the heating method of a film, For example, IR heating system between rolls, a float system, etc. are mentioned. Among these, from the viewpoint of obtaining optical uniformity of the optical film, a float heating method is preferable. In particular, it is preferable to employ a float method when stretching in the longitudinal direction.

  The draw ratio can be set to an appropriate range in which desired optical characteristics can be obtained. For example, in the stretching in the longitudinal direction, the stretching ratio can be set in a range of 1.1 to 3.0 times. In the stretching in the transverse direction, the stretching ratio can be set in the range of 1.3 to 3.0 times.

  Moreover, when a film is provided with an easily bonding layer as a coating layer, it is preferable to perform irradiation of the laser beam for forming a knurled structure to the surface of the film on the easily bonding layer side. Thereby, when winding up an optical film in roll shape, adhesion between films can be controlled.

[Usage]
The wound body manufactured by the manufacturing method of the present invention can be used for manufacturing an optical member including an optical film. For example, the optical film can be fed out from the wound body of the present invention and used for manufacturing an optical member in a display device such as a liquid crystal display device or an electroluminescence display device. The optical film fed out from the wound body can be used as a retardation film, a polarizing plate protective film, a polarizing film, a brightness enhancement film, a light diffusing film, a condensing film, a reflecting film and the like in a display device and an optical member.

Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, 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, “%” and “part” representing amounts are based on weight unless otherwise specified. In addition, the operations described below were performed under normal temperature and normal pressure conditions unless otherwise specified.

(Production Example 1: Production of coating liquid A)
In a reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube and a cooling tube, 840 parts of polyester polyol, Maximol FSK-2000 (manufactured by Kawasaki Chemical Industry Co., Ltd .; hydroxyl value 56 mgKOH / g), 119 parts of tolylene diisocyanate, and 200 parts of methyl ethyl ketone was added and reacted at 75 ° C. for 1 hour while introducing nitrogen. After completion of the reaction, the mixture was cooled to 60 ° C., 35.6 parts of dimethylolpropionic acid was added, and reacted at 75 ° C. to obtain a polyurethane solution containing an acid structure. The content of isocyanate groups (—NCO groups) in the polyurethane was 0.5%.

  Next, the polyurethane solution is cooled to 40 ° C., 1,500 parts of water and 120 parts of isophthalic acid dihydrazide (boiling point 224 ° C. or higher) 120 parts (7 parts with respect to 100 parts of polyurethane) are stirred at high speed with a homomixer. Was emulsified. Methyl ethyl ketone was distilled off from the emulsion under heating and reduced pressure to obtain a neutralized polyurethane aqueous dispersion. The solid content concentration of this aqueous dispersion was 40%.

  Further, this aqueous dispersion was separated by an amount such that the contained polyurethane was 100 parts. To the separated aqueous dispersion, 15 parts of glycerol polyglycidyl ether (“Denacol EX-313” manufactured by Nagase ChemteX; epoxy equivalent 141 g / eq) as an epoxy compound and silica fine particles (Nissan Chemical Co., Ltd.) having an average particle diameter of 80 nm 10 parts of “Snowtex ZL” manufactured by Kogyo Co., Ltd. and ethylene oxide adduct of 4,7-dihydroxy-2,4,7,9-tetramethyl-5-decine as a nonionic surfactant (Nisshin Chemical Industry) “Surfinol 465”) and water were blended to obtain a liquid aqueous resin having a solid content concentration of 5% as a coating liquid A as an uncured urethane resin. Here, the addition amount of the nonionic surfactant was set to 100 ppm with respect to the obtained aqueous resin.

Example 1
An alicyclic structure-containing polymer resin is formed into a film shape, stretched in the longitudinal direction, provided with a coat layer, stretched in the lateral direction, imparted with a knurled structure, wound in a roll shape around the core The operation of obtaining a gyrus was continuously performed inline. The specific operation is as follows.

After drying pellets of a thermoplastic resin containing a norbornene-based polymer (trade name “ZEONOR1430”, manufactured by Nippon Zeon Co., Ltd., Young's modulus E = 2.5 N / m ² ) at 100 ° C. for 5 hours, An unstretched film (1) having a thickness of 100 μm was continuously produced using an extruder and a T die.

  The unstretched film (1) is continuously supplied to a longitudinal stretching machine using a float system between adjusting rolls, and stretched 1.2 times in the longitudinal direction at a temperature of 140 ° C. 2) was obtained.

  The longitudinally stretched film (2) was continuously supplied to a two-roll reverse coater. In this reverse coater, the coating liquid A obtained in Production Example 1 was applied to one side of the longitudinally stretched film (2) to obtain a longitudinally stretched film (3) having a layer of the coating liquid A. At this time, the coating amount of the coating liquid A was adjusted so that the thickness of the coating layer obtained after the coating liquid was dried was 90 nm after lateral stretching.

  The longitudinally stretched film (3) having the layer of the coating liquid A was continuously supplied to a transverse stretching machine using a tenter method. When the longitudinally stretched film (3) is heated before stretching is started by the transverse stretching machine, the coating liquid A applied to the longitudinally stretched film is dried, and a coat layer is formed on the surface of the longitudinally stretched film. It was. Thereafter, with the transverse stretching machine, the longitudinally stretched film was stretched 1.4 times in the transverse direction at a temperature of 150 ° C. to obtain a biaxially stretched film (4).

On the other hand, in the production line different from this production line, the same film as the biaxially stretched film (4) was produced in advance, and further cut to obtain a sample having a length of 100 mm and a width of 10 mm. This sample was subjected to a tensile test in which a load was applied in the length direction, and the tensile load at the time when the trough was visually recognized was recorded. Based on this, the tensile stress σmax (N / m ² ) when the trough was generated Asked. The value X was determined from the obtained σmax value and the Young's modulus E of the film, and found to be 0.6%.

  A biaxially stretched film (5) with a knurled structure was obtained by continuously imparting a knurled structure to the biaxially stretched film (4) produced continuously using a laser marker at both ends of the film. The width of each end was 10 mm from the edge of the film. The obtained film (5) had a total width W1 of 1330 mm and a film thickness of 50 μm.

The biaxially stretched film (5) with a knurled structure was continuously wound around a core having an outer radius of 84 mm while applying tension. The line speed during winding was 25 m / min. About the wound body in the middle of winding, the outer radius r _{1 at} the center in the width direction of the film and the outer radius r ₂ at both ends in the width direction of the film are measured using an in-line projection size measuring instrument (trade name, manufactured by Keyence Corporation). TM-065 and TM-3000) were measured, the edge height h value was monitored, the winding tension and the knurl structure height were adjusted based on the measured value, and winding was performed to produce a wound body. .

Specifically, the adjustment of the winding tension and the knurl structure height in this example was as follows.
Winding is started with a winding tension of 140 N / m at the start of winding and a knurl structure height of 5 μm. When the outer radius r ₁ exceeds 115 mm, the end height h is the allowable end height r _1. Since it approached X (= (r ₁ × 0.6) / 100), the winding tension was set to 100 N / m. Outer radius _{r 1} makes a winding until 175mm. As a result, a good wound body was obtained. Winding diameter r ₁ (mm) during winding, allowable end height ((0.6 × r ₁ ) / 100) (mm), tension (N / m), knurl structure height (μm) and end The height h (mm) was as shown in Table 1 below.

(Example 2)
A wound body was manufactured in the same manner as in Example 1 except that the winding tension and the adjustment of the knurl structure height were changed as follows.
In Example 2, winding was started at a winding tension of 140 N / m at the start of winding and the knurl structure height was 5 μm, and when the outer radius r ₁ exceeded 115 mm, the end height h was allowed. Since it approached the end height r ₁ X (= (r ₁ × 0.6) / 100), the knurl structure height was set to 2 μm. Outer radius _{r 1} makes a winding until 175mm. As a result, a good wound body was obtained. Winding diameter r ₁ (mm) during winding, allowable end height ((0.6 × r ₁ ) / 100) (mm), tension (N / m), knurl structure height (μm) and end The part height h (mm) was as shown in Table 2 below.

(Example 3)
A wound body was manufactured in the same manner as in Example 1 except that the winding tension and the adjustment of the knurl structure height were changed as follows.
In Example 3, winding is started with a winding tension at the start of winding of 140 N / m and a knurl structure height of 5 μm, and the end height h is the allowable end height r ₁ X (= (r _A tension taper was provided so as not to approach ₁ × 0.6) / 100). Outer radius _{r 1} makes a winding until 175mm. As a result, a good wound body was obtained. Winding diameter r ₁ (mm) during winding, allowable end height ((0.6 × r ₁ ) / 100) (mm), tension (N / m), knurl structure height (μm) and end The height h (mm) was as shown in Table 3 below.

Example 4
A wound body was manufactured in the same manner as in Example 1 except that the winding tension and the adjustment of the knurl structure height were changed as follows.
In Example 4, winding is started with a winding tension at the start of winding of 140 N / m and a knurl structure height of 5 μm, and the end height h is the allowable end height r ₁ X (= (r _A Knurl structure height taper was provided so as not to approach ₁ × 0.6) / 100). Outer radius _{r 1} makes a winding until 175mm. As a result, a good wound body was obtained. Winding diameter r ₁ (mm) during winding, allowable end height ((0.6 × r ₁ ) / 100) (mm), tension (N / m), knurl structure height (μm) and end The height h (mm) was as shown in Table 4 below.

(Comparative Example 1)
A winding body was manufactured in the same manner as in Example 1 except that the adjustment of the winding tension and the height of the knurl structure was changed as follows.
In Comparative Example 1, winding was started at a winding tension of 140 N / m at the start of winding and a knurl structure height of 5 μm, and the winding tension and knurl structure height were maintained as they were. When the outer radius r ₁ exceeds 115 mm, the end height h exceeds the allowable end height r ₁ X (= (r ₁ × 0.6) / 100), and the film being conveyed is wrinkled at that time. There has occurred. Outer radius _{r 1} has completed the winding when it becomes 130mm. Winding diameter r ₁ (mm) during winding, allowable end height ((0.6 × r ₁ ) / 100) (mm), tension (N / m), knurl structure height (μm) and end The part height h (mm) was as shown in Table 5 below.

(Comparative Example 2)
A winding body was manufactured in the same manner as in Example 1 except that the adjustment of the winding tension and the height of the knurl structure was changed as follows.
In Comparative Example 2, winding was started with a winding tension at the start of winding of 100 N / m and a knurl structure height of 8 μm, and the winding tension and knurl structure height were maintained as they were. When the outer radius r ₁ exceeds 100 mm, the end height h exceeds the allowable end height r ₁ X (= (r ₁ × 0.6) / 100), and the film being conveyed is wrinkled at that time. There has occurred. Outer radius _{r 1} has completed the winding when it becomes 115mm. Winding diameter r ₁ (mm) during winding, allowable end height ((0.6 × r ₁ ) / 100) (mm), tension (N / m), knurl structure height (μm) and end The height h (mm) was as shown in Table 6 below.

  As is clear from the above results, in the examples in which the adjustment satisfying the requirements of the present invention was performed, a favorable wound body could be obtained, but the comparison that did not perform the adjustment satisfying the requirements of the present invention was made. In the example, wrinkles occurred and a good wound body could not be obtained.

10, 10a, 10b: optical film 21: nar structure imparting device 22: nar structure imparting device 23: nar structure monitoring device (light receiver)
24: Knurled structure monitoring device (light projector)
30: tension applying device 31: upstream roll 33: downstream roll 32: dancer roll 34: air cylinder 34T: tip of air cylinder 32S: shaft of dancer roll 41: winding core 40, 40a, 40b: wound body 50: diameter measurement Device 51: Translucent part 52: Light receiving part 53: Light 41C: Axis of wound body 42: End face of wound body 15: Knurled structure

Claims (4)

A method for producing a wound body of a long optical film,
Including a step of providing a knurl structure at both ends in the width direction of at least one surface of the optical film, and a winding step of winding the optical film provided with the nar structure in a roll shape around a core.
The winding step
The outer radius R (mm) of the winding core, the outer radius r ₁ (mm) of the central portion of the film of the winding body in the middle of winding, and the width direction of the film of the winding body in the middle of winding After the outer radius r ₂ (mm) of the end portion of at least r ₁ > 1.05R, the following formulas (1) and (2):
Formula (1): h / r ₁ ≦ X
Formula (2): h> 0.1
(Where h = r ₂ −r ₁ and X is a constant determined by the type of optical film)
The winding tension in the winding step, the height of the knurl structure, or both of them are adjusted so as to always satisfy the above. X is the following formula (3):
Formula (3): X = σmax / E
(Where σmax is the tensile stress (N / m ² ) when the optical film is subjected to a tensile test and trough is generated, and E is the Young's modulus (N / m ² ) of the material constituting the optical film) The manufacturing method according to claim 1, wherein   The manufacturing method of Claim 1 or 2 whose thickness of the said optical film is 1-300 micrometers.   The manufacturing method of any one of Claims 1-3 whose width | variety of the said optical film is 500-5000 mm.

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