A long resin film subjected to knurling

Abstract

To provide a long resin film in which the amount of charge is controlled, and in which the amount of charge until the core portion is suppressed even when the long resin film is wound into a roll shape and stored for a long period of time. This problem can be solved by a long resin film wound into a roll shape, in which the average roll hardness in the width direction (TD direction) of the surface layer of the roll is 300 to 750, and the absolute value of the difference in roll hardness between two points at an interval of 60 mm in the width direction of the surface layer of the roll is 300 or less.

Description

Technical Field

[0001] This invention relates to elongated resin films and laminated films wound into rolls. Additionally, this invention relates to elongated resin films and laminated films subjected to knurling. Background Technology

[0002] Previously, it was known that knurling (thickening) the ends of the film during resin film winding could achieve stable winding and prevent winding deviation and film damage. However, it is known that even when knurling is performed and the film is wound, the knurling near the core of the roll is flattened, failing to fully realize the aforementioned effect. Therefore, various knurling techniques have been proposed, such as methods for controlling the size of the knurling protrusions (e.g., see Patent Documents 1 and 2), methods for providing reinforcements in the concave portions (e.g., see Patent Document 3), methods for setting knurling in a non-contact manner (e.g., see Patent Document 4), and methods for controlling the shape and area of ​​the knurling (e.g., see Patent Document 5), etc.

[0003] On the other hand, resin films are often coated with a layer of material, but when the film has a high charge, problems arise during coating, such as pinholes, increased unevenness in film thickness, and orientation disorder when setting alignment films of liquid crystal compounds. The charge on the film during coating is controlled by removing charge during film winding and unwinding, but this is insufficient for coatings requiring high precision in recent years. To address this problem, a solution has been proposed to perform knurling and suppress relative movement of the wound film to reduce the charge on the wound film (for example, see Patent Document 4), but this is not sufficiently effective. Furthermore, a solution has been proposed to control the shape of the knurling to suppress the charge on the film over time (for example, see Patent Document 5).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: WO11 / 030684

[0007] Patent Document 2: Japanese Patent Application Publication No. 2013-166317

[0008] Patent Document 3: WO10 / 001752

[0009] Patent Document 4: Japanese Patent Application Publication No. 63-74850

[0010] Patent Document 5: WO2021 / 200322 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] As mentioned above, many solutions have been proposed in the past, but they cannot fully control the charge on the film. For example, the charge near the core increases after long-term storage, sometimes making high-precision coating difficult. Furthermore, the extent of the charge increase near the core is unclear unless the film is unwound from the roll, which also leads to problems with coating processes not proceeding as planned.

[0013] The main objective of this invention is to provide a strip-shaped resin film capable of controlling the charge, for example, a strip-shaped resin film in which the charge is suppressed up to the core portion when unwound even after long-term storage in a rolled-up state.

[0014] Solution for solving the problem

[0015] According to the research of the inventors, as a factor contributing to the increase in charge during unwinding of the film after long-term storage, the air entrained in the film is gradually expelled. However, due to the movement of air, a localized thinning of the air layer occurs, resulting in intense friction between the films in this area, leading to a greater charge. Furthermore, the surface hardness of the roll is higher in this area than in other areas. Moreover, it has been found that by reducing drastic changes in the surface hardness of the roll, the charge during unwinding is less likely to increase even after long-term storage.

[0016] Furthermore, according to the research of the inventors, the main reasons for the deterioration of the winding appearance include the reduction in rigidity caused by the thinning of the raw materials and the presence of excessive air layers due to the high knurling. It is believed that, especially in anisotropic films, when the circumferential direction of the roll (also known as the mechanical flow direction, MD direction) is orthogonal to the main orientation direction of the film, it affects the ease with which the film deforms in the MD direction. In particular, the increase in friction at the center caused by the widening of the roll is cited as one of the major reasons. It has been found that, in order to balance charging and winding appearance, it is preferable to keep the raw material thickness, knurling height, and roll width within the optimal range during roll manufacturing.

[0017] Based on the above insights, the inventors conducted further in-depth research and, as a result, completed this invention. That is, this invention includes the methods described in the following items.

[0018] [Item 1]

[0019] A long strip of resin film, which is rolled into a roll.

[0020] The average roll hardness in the width direction (TD direction) of the roll's surface layer is 300~750.

[0021] The absolute value of the hardness difference between two points spaced 60mm apart in the width direction of the roll surface is less than 300.

[0022] [Item 2]

[0023] According to item 1, the elongated resin film has a thickness of 40µm or more.

[0024] Satisfying equations 1 and 2 below,

[0025] 1≤h≤0.1T-1 Equation 1

[0026] W≤40T 2

[0027] Where T: film thickness (µm), W: film width (mm), h: initial knurling height (µm).

[0028] [Item 3]

[0029] According to item 1 or 2, when the elastic modulus in the MD direction of the elongated resin film is set as ME, ME ≤ 4000 MPa is satisfied.

[0030] [Item 4]

[0031] According to any one of items 1 to 3, when the elastic modulus of the elongated resin film in the TD direction is set as TE, TE ≥ 6000 MPa is satisfied.

[0032] [Item 5]

[0033] The elongated resin film according to any one of items 1 to 4 satisfies 2≤TE / ME≤4.

[0034] [Item 6]

[0035] The elongated resin film according to any one of items 1 to 5, wherein the standard deviation of the roll hardness in the width direction of the surface layer of the roll is 80 or less.

[0036] [Item 7]

[0037] The elongated resin film according to any one of items 1 to 6, wherein the thickness in the TD direction is not uniformly less than 2% over the entire length of the roll.

[0038] [Item 8]

[0039] The elongated resin film according to any one of items 1 to 7, wherein the residual amount of knurling in the core of the roll is 1 µm or more.

[0040] [Item 9]

[0041] The elongated resin film according to any one of items 1 to 8 has a retardation amount of 3000 to 30000 nm.

[0042] [Item 10]

[0043] According to any one of items 1 to 9, when the outer surface of the elongated resin film is designated as surface A and the inner surface is designated as surface B, the composition of surface A and surface B are different.

[0044] [Item 11]

[0045] According to any one of claims 1 to 10, when the outer surface of the elongated resin film is designated as surface A and the inner surface is designated as surface B, at least one of surface A or surface B is a coating.

[0046] [Item 12]

[0047] A method for manufacturing a laminated film, comprising:

[0048] The process (A) of rolling out the long strip resin film as described in any one of items 1 to 11; and

[0049] Step (B) involves coating at least one side of the rolled-out elongated resin film with a coating liquid.

[0050] [Item 13]

[0051] According to the manufacturing method described in item 12, the laminated film is a polarizing protective film.

[0052] [Item 14]

[0053] According to the manufacturing method described in item 13, the laminated film is a film for thin film transfer.

[0054] The effects of the invention

[0055] According to one aspect of the present invention, a strip-shaped resin film capable of controlling charge can be provided, for example, a strip-shaped resin film in which the charge is suppressed up to the core portion during unwinding, even after long-term storage in a rolled state. According to another aspect of the present invention, a strip-shaped resin film can be provided that can suppress the generation of winding offset wrinkles and / or deterioration of the winding appearance during storage (especially long-term storage), and can maintain high flatness and / or coating uniformity. Attached Figure Description

[0056] Figure 1 This is a diagram illustrating the location for measuring roll hardness in the elongated resin film roll of the present invention. Detailed Implementation

[0057] As representative methods for manufacturing elongated resin films of the present invention, examples such as (1) to (4) are given below, and their details are described in turn, but the present invention is not limited to these.

[0058] (1) In the membrane process, when the long strip of resin film is wound onto the roller, the thick or thin portion of the film is not continuous for a long distance at 1 in the width direction.

[0059] As specific methods, the following can be cited:

[0060] • Apply sufficient vibration during film formation.

[0061] • Online thickness measurement provides feedback for adjusting the slit width of the die head.

[0062] • To ensure uniform temperature during film formation

[0063] • Manage the temperature of the mold head.

[0064] wait.

[0065] (2) Ensure uniform tension and contact pressure when rolling the long strip of resin film into a roll.

[0066] As specific methods, the following can be cited:

[0067] • Appropriate the position and shape of the contact rollers.

[0068] • Appropriate the material and hardness of the contact roller.

[0069] • To make the diameter of the contact rollers more uniform.

[0070] • To optimize the diameter and hardness of the core,

[0071] • Controls the bending and relaxation of long strip resin films (inhibits saber-shaped deformation), etc.

[0072] (3) Control the amount of air entrained during slitting (SL).

[0073] As a specific method,

[0074] • Control the tension and contact pressure during slitting and winding within a certain range.

[0075] Especially in films with strong anisotropy in elastic modulus, it reduces tension and increases contact pressure compared to isotropic films.

[0076] Especially in knurled rollers, the contact pressure is reduced.

[0077] (4) Control the thickness of raw materials, the width of rollers and the height of knurling.

[0078] Equation 1…1≤h≤0.1T-1

[0079] Equation 2…W≤40T

[0080] Here, T: film thickness (µm), W: film width (mm), h: initial knurling height (µm)

[0081] (Long strip resin film)

[0082] The elongated resin film (hereinafter sometimes simply referred to as "film") is preferably wound into rolls. There are no particular limitations on the resin constituting the film; any resin can be used alone or in combination of two or more. Preferred resins are polyester, polycyclic olefins, triacetyl cellulose, acrylics, polycarbonate, polyamide, polyimide, and polypropylene; more preferably, polyester, polycyclic olefins, and triacetyl cellulose; and even more preferably, polyester. When polyester is used, polyethylene terephthalate and / or polyethylene naphthalate are preferred.

[0083] The elongated resin film can be an unstretched film or a stretched film (uniaxial stretched film or biaxial stretched film). The elongated resin film is preferably a stretched film, and particularly preferably a stretched polyester film.

[0084] The lower limit of the thickness of the elongated resin film is preferably 25µm, more preferably 30µm, further preferably 35µm, and particularly preferably 40µm. Especially in applications such as optical films and release films where high-precision coating processing of the film surface is required, by setting it above this lower limit, a film with sufficient strength can be produced.

[0085] Furthermore, from the perspective of producing a film with a good winding appearance and anisotropic elongated resin film, the lower limit of the film thickness of the elongated resin film is preferably 40µm, more preferably 45µm, further preferably 50µm, and particularly preferably 55µm. The upper limit of the film thickness is preferably 200µm, more preferably 150µm, further preferably 100µm, particularly preferably 90µm, and most preferably 80µm. By setting it below this upper limit, productivity can be improved.

[0086] The lower limit of thickness non-uniformity (TV) in the TD direction (also known as the width direction) over the entire length of the roll is preferably 0%, more preferably 0.1%, and even more preferably 0.2%. The upper limit of TV is preferably 2%, more preferably 1.8%, even more preferably 1.6%, and particularly preferably 1.4%. By setting it below this upper limit, air ingress can be suppressed, reducing wrinkles caused by shrinkage over time and deterioration of the winding appearance. TV can be set within a range by adjusting the slit width of the die head, managing the stretching temperature, managing the heat setting temperature, managing the extrusion temperature, and designing the die head.

[0087] The upper limit of the coefficient of variation of thickness in the TD direction over the entire length of the roll is preferably 18, more preferably 16, further preferably 14, particularly preferably 12, and most preferably 10. By setting it below this upper limit, air ingress can be suppressed, reducing wrinkles caused by shrinkage over time. The lower limit of the coefficient of variation of thickness in the TD direction over the entire length of the roll is preferably 0, more preferably 2, and further preferably 5.

[0088] The thickness non-uniformity and variation coefficient in the TD direction over the entire length of the roll in this specification are values ​​obtained by the methods described in the examples.

[0089] The lower limit of the width of the elongated resin film is preferably 500 mm, more preferably 800 mm, further preferably 1000 mm, and particularly preferably 1200 mm. Films with widths above this lower limit generally improve productivity by increasing the width, but on the other hand, they are prone to increasing charge. However, by applying the present invention, the increase in charge can be suppressed, especially even after long-term storage, the increase in charge up to the core portion can be suppressed. Furthermore, the upper limit of the film width is, for example, 3200 mm, preferably 3000 mm, more preferably 2700 mm, further preferably 2600 mm, and particularly preferably 2500 mm. By setting the upper limit of the film width to 3200 mm or less, the effects of the present invention can be fully utilized; by setting it to 3000 mm or less, the effects of the present invention can be fully realized at the center of the roll width direction.

[0090] The lower limit of the roll length of the elongated resin film is preferably 1000 mm, more preferably 1500 mm, further preferably 2000 mm, and particularly preferably 2600 mm. Films exceeding this lower limit typically tend to experience an increase in charge at the core, but by applying this invention, the increase in charge can be suppressed, particularly even after long-term storage, up to the core, thereby improving productivity. The upper limit of the roll length is preferably 20000 mm, more preferably 15000 mm, further preferably 10000 mm, and particularly preferably 7000 mm. By setting it below these upper limits, post-processing of the film becomes easier, and the effects of this invention can be fully realized.

[0091] In this specification, the outer layer of a roll refers to the area from the end point of the roll to 100m. Conversely, the core of a roll refers to the area from the starting point of the roll to 100m.

[0092] Regarding elongated resin films, when the outer surface of the film winding is designated as surface A and the inner surface as surface B, the compositions of surface A and surface B can be the same or different. When the compositions of surface A and surface B are different, the charge on the film tends to increase when it is unwound. This invention is preferably applied to elongated resin films where the compositions of surface A and surface B are different.

[0093] Examples of situations where the compositions of side A and side B differ include: layering different types of raw material resins through co-extrusion; applying a coating only to one side of side A or side B; and applying coatings with different compositions to both sides A and B. The present invention can be appropriately applied in any of these cases. In particular, the present invention is preferably applied to elongated resin films in which the resin compositions of the coatings constituting side A and side B differ.

[0094] (coating)

[0095] As a coating, preferred examples include easy-adhesive layers, easy-slip layers, smooth layers, hard coatings, and orientation control layers. In particular, the strip-shaped resin film used in this invention is preferably a film with at least one easy-adhesive layer on the surface, and is also preferably a film with easy-adhesive layers on both sides.

[0096] As a coating, it can be applied online during film formation or offline after film formation, preferably applied online on both sides. It should be noted that in this invention, the term "film" sometimes refers to a film including the above-described coating.

[0097] Preferred resins used in coatings include polyesters, acrylics, polyurethanes (polyester polyurethane, polycarbonate polyurethane, polyether polyurethane, etc.), ethylene-vinyl acetate copolymers, polyamides, styrene-acrylic copolymers, and polyvinyl alcohol. Furthermore, when the coating is a hard coating, the resin used in the coating can be a photocurable resin, or a monomer or oligomer containing a double bond.

[0098] The coating is preferably crosslinked. Preferred crosslinking agents include isocyanates, amino resins such as melamine, oxazoline compounds, carbodiimide compounds, and epoxy resins. In the case of photocurable resins, the crosslinking agent can be a compound (monomer or oligomer) containing multiple double bonds, such as trimethylolpropane triacrylate, pentaerythritol tetraacrylate, acrylic-modified polyurethane, or acrylic-modified epoxy resin.

[0099] The coating may contain additives. Examples of additives include particles, surfactants, leveling agents, antistatic agents, catalysts, and combinations thereof.

[0100] The lower limit of the thickness of the coating after drying is preferably 0.001µm, more preferably 0.005µm, further preferably 0.01µm, and particularly preferably 0.02µm. The upper limit of the thickness of the coating after drying is preferably 20µm, more preferably 15µm, further preferably 10µm, particularly preferably 7µm, and most preferably 5µm. When the coating is an easily bondable layer, the upper limit of the thickness of the coating after drying is preferably less than 1µm, more preferably less than 0.5µm, and further preferably less than 0.3µm.

[0101] The lower limit of the arithmetic mean roughness (Sa) of at least one surface of the elongated resin film is preferably 0.2 nm, more preferably 0.4 nm, and even more preferably 0.5 nm. By setting it above this lower limit, even if the knurling is slightly flattened at the core during storage, excessive rise in peel charge can be suppressed, and roll shape abnormalities are reduced by providing uniform sliding properties. In addition, when used as an optical film or release film, high transparency can be ensured, and when coated on a film, defects are less likely to occur in the coating. The upper limit of the arithmetic mean roughness (Sa) of at least one surface of the elongated resin film is preferably 15 nm, more preferably 10 nm, and even more preferably 5 nm. By setting it below this upper limit, even if the knurling is slightly flattened at the core during storage, excessive rise in peel charge can be suppressed, and roll shape abnormalities are reduced by providing uniform sliding properties. In addition, when used as an optical film or release film, high transparency can be ensured, and when coated on a film, defects are less likely to occur in the coating.

[0102] (Knurling)

[0103] The elongated resin film preferably has its two ends in the width direction knurled. The lower limit of the interval between the film end and the knurling position is preferably 0.5 mm, more preferably 1 mm. The upper limit of the interval between each end in the width direction and the knurling position is preferably 20 mm, more preferably 15 mm, and even more preferably 10 mm. By setting these ranges, stable knurling can be performed on both ends in the width direction of the film, and the effective width of the film can be ensured.

[0104] The lower limit of the width of the knurling section is preferably 3 mm, more preferably 5 mm, and even more preferably 7 mm. By setting it above this lower limit, the knurling is less likely to be flattened. The upper limit of the width of the knurling section is preferably 30 mm, more preferably 25 mm, and even more preferably 20 mm. By setting it below this upper limit, the degree of flattening of the knurling can be appropriate, and the effective width of the film can be ensured.

[0105] The lower limit of the spacing between the knurled protrusions is preferably 0.5 mm, more preferably 0.6 mm, and even more preferably 0.7 mm. The upper limit of the spacing between the knurled protrusions is preferably 3 mm, more preferably 2.5 mm, even more preferably 2 mm, and particularly preferably 1.5 mm. It should be noted that the spacing between the protrusions refers to the spacing between the center points of the protrusions.

[0106] The lower limit of the density of the knurled protrusions is preferably 10 per cm³. 2 More preferably 15 per cm 2 Further optimized to 25 per cm 2 The preferred size is 40 pieces / cm. 2 The optimal value is 60 per cm. 2 The upper limit of the density of the knurled protrusions is preferably 400 per cm. 2 More preferably 300 per cm 2 Further optimized to 250 pieces / cm 2 The preferred size is 200 pieces / cm. 2 The optimal value is 160 pieces / cm. 2 The flattening ease of the knurling can be adjusted by controlling the density of the knurling protrusions. By setting it within the aforementioned range, the flattening ease can be adjusted relatively easily with a simple knurling process without placing excessive load on the device. Furthermore, within an appropriate range of the ratio of the height of each knurling protrusion to the area of ​​the protrusion, knurling processes that are difficult to flatten can be easily performed.

[0107] The configuration of the knurled protrusions can be, for example, any of the following: a configuration in which the longitudinal and transverse directions are neatly arranged; an alternating configuration in which adjacent protrusions and concaves are staggered by half a cycle; or an oblique configuration in which adjacent protrusions and concaves are staggered by 1 / 3 or 1 / 4.

[0108] The initial knurling height is as described above. The knurling immediately after processing has portions that are easily flattened when the film is wound into a roll. This is because, in the case of cold knurling, the film is pressed against the opposite side of the knurling blade by the protrusions, thus forming knurling. However, even extruded knurling has portions that are easily dented due to pressure. Similarly, in the case of hot knurling, the protrusions formed on the opposite side of the knurling blade are also flattened, or resin bulges form around the protrusions of the knurling blade. However, these bulges are not uniform in height; rather, they are uneven in height. Therefore, the high-bulging portions are easily flattened even under low pressure. These high-bulging portions are sometimes flattened due to contact with the film's transport rollers and the pressure of the contact rollers during winding. Therefore, the initial knurling height is the height taken from the outermost layer of film immediately after winding into a roll.

[0109] Furthermore, in the film wound into rolls, a phenomenon known as "tightening" occurs during storage, resulting in a reduction in the knurling height. Therefore, it is preferable not only to adjust the initial knurling height but also to adjust the winding conditions, as described later, in a manner that ensures the surface knurling height and / or the core knurling height fall within the range described later.

[0110] In this specification, the surface knurling height and the core knurling height are values ​​measured by the methods described in the embodiments. The lower limit of the surface knurling height is preferably 0.8 µm, more preferably 1 µm, further preferably 1.2 µm, even more preferably 1.3 µm, particularly preferably 1.4 µm, even more preferably 1.5 µm, and most preferably 1.6 µm. By setting it above this lower limit, excessive release of air can be suppressed, which helps to suppress charging. The upper limit of the surface knurling height is preferably 6 µm, more preferably 5 µm, further preferably 4 µm, particularly preferably 3.7 µm, and most preferably 3.5 µm. By setting it below this upper limit, poor appearance caused by excessive air ingress can be suppressed.

[0111] The lower limit of the knurling height (L) of the core is preferably 0.5µm, more preferably 0.7µm, further preferably 0.9µm, particularly preferably 1µm, and most preferably 1.1µm. By setting it above this lower limit, excessive release of the air layer can be suppressed, which helps to suppress charging. The upper limit of the knurling height (L) of the core is preferably 4µm, more preferably 3.5µm, further preferably 3.2µm, and particularly preferably 3µm. By setting it below this upper limit, poor appearance caused by excessive air layer entry can be suppressed.

[0112] The lower limit of the size of the long and short sides of the knurling is preferably 50µm, more preferably 60µm, further preferably 70µm, and particularly preferably 80µm. By setting it above this lower limit, the holding force of the knurling can be ensured. The upper limit of the size of the long and short sides of the knurling is preferably 1000µm, more preferably 900µm, further preferably 800µm, and particularly preferably 700µm. By setting it below this upper limit, excessive entrapment of the air layer can be suppressed.

[0113] (Core roller)

[0114] The elongated resin film is preferably wound onto a cylindrical or cylindrical core. It should be noted that, in this specification, the elongated resin film wound into a roll is sometimes referred to as a film roll or simply a roll.

[0115] The upper limit of the core outer diameter is preferably 350 mm, more preferably 310 mm, further preferably 300 mm, even more preferably 290 mm, and particularly preferably 280 mm. By setting it below this upper limit, it is possible to prevent the winding diameter from becoming too large and improve operability.

[0116] The lower limit of the core outer diameter is preferably 50 mm, more preferably 70 mm, even more preferably 90 mm, and particularly preferably 110 mm. By setting it to this lower limit or above, the deflection caused by its own weight when the film is wound onto the core is reduced, and the formation of wrinkles is easily suppressed. In addition, the winding tension and contact pressure become uniform in the width direction, which makes it easier to make the roll stiffness (sometimes referred to as "stiffness" in this specification) uniform.

[0117] The core width is preferably greater than the film width. The lower limit of the core width-film width ratio is preferably 2 mm, more preferably 4 mm. The upper limit of the core width-film width ratio is preferably 100 mm, more preferably 60 mm, further preferably 40 mm, and particularly preferably 20 mm. By setting it within the above range, the winding operation can be facilitated, and the operability can be improved.

[0118] (film roll stiffness)

[0119] According to the research of the inventors, the charge on the membrane is related to the stiffness of the membrane roll (sometimes referred to in this specification as "the surface stiffness of the membrane roll"). The membrane with higher stiffness exhibits greater charge when the core is unwound. Furthermore, if there are locally high-stiffness areas or areas where the stiffness changes abruptly, the membrane's charge increases. The rationale is that the high-stiffness areas are in strong contact with the membrane, promoting charging. Even when the membrane is wound up, an air layer exists between the membranes. However, it is believed that in areas where the stiffness changes abruptly and becomes higher locally, the air layer moves to the side, locally causing strong contact between the membranes, thus increasing the charge. The present invention is based on the concept of suppressing the increase in charge by reducing such localized air movement between the membranes and suppressing localized strong contact.

[0120] The lower limit of the average roll hardness in the width direction of the surface layer of the membrane roll is preferably 300, more preferably 350, further preferably 400, and particularly preferably 450. By setting it above this lower limit, roll-off of the surface layer caused by air ingress can be suppressed. The upper limit of the average roll hardness in the width direction of the surface layer of the membrane roll is preferably 750, more preferably 730, further preferably 710, particularly preferably 700, and most preferably 690. By setting it below the aforementioned upper limit, the ease of friction of the membrane can be suppressed, thereby suppressing electrostatic charging, and also suppressing roll-off during storage.

[0121] The lower limit of the standard deviation of the surface hardness of the membrane roll is preferably 0, more preferably 5, further preferably 10, and particularly preferably 15. The upper limit of the standard deviation of the surface hardness of the membrane roll is preferably 80, more preferably 75, further preferably 70, and particularly preferably 65. By setting it below this upper limit, the increase in charge caused by friction between the membranes can be reduced.

[0122] The lower limit of the absolute value of the hardness difference between two points spaced 60 mm apart on the surface of the membrane roll is preferably 0, more preferably 10, further preferably 20, particularly preferably 30, and most preferably 40. The upper limit of the absolute value of the hardness difference between two points spaced 60 mm apart on the surface of the membrane roll is preferably 300, more preferably 290, further preferably 280, particularly preferably 270, and most preferably 260. By setting it below this upper limit, the increase in charge caused by local friction between the membranes can be reduced.

[0123] The lower limit of the average roll hardness in the width direction of the membrane roll surface after 2000m of membrane roll unwound is preferably 300, more preferably 350, further preferably 400, and particularly preferably 450. By setting it above this lower limit, winding offset caused by air ingress can be suppressed. The upper limit of the average roll hardness in the width direction at the 2000m position is preferably 750, more preferably 730, further preferably 710, particularly preferably 700, and most preferably 690. By setting it below the aforementioned upper limit, the membrane's abrasiveness can be suppressed, thereby suppressing electrostatic charging. In addition, winding offset during storage can be suppressed. It should be noted that the position where the roll hardness is measured from the membrane roll surface after 2000m of membrane roll unwound is sometimes simply referred to as the 2000m position. This position is not strictly 2000m, as long as it is in the range of 2000~2050m.

[0124] The lower limit of the standard deviation of the roll hardness in the width direction of the membrane roll surface at the 2000m position is preferably 0, more preferably 5, further preferably 10, and particularly preferably 15. The upper limit of the standard deviation of the roll hardness in the width direction at the 2000m position is preferably 80, more preferably 75, further preferably 70, and particularly preferably 65. By setting it below this upper limit, the increase in charge caused by friction between the membranes can be reduced.

[0125] The lower limit of the absolute value of the hardness difference between two points with a 60mm interval at the 2000m position is preferably 0, more preferably 10, further preferably 20, particularly preferably 30, and most preferably 40. It can be set to the above or above. The upper limit of the absolute value of the hardness difference between two points with a 60mm interval at the 2000m position is preferably 300, more preferably 290, further preferably 280, particularly preferably 270, and most preferably 260. By setting it below this upper limit, the increase in charge caused by local friction between the films can be reduced.

[0126] Next, the method for manufacturing the film roll of the present invention will be described.

[0127] The elongated resin film of the present invention is preferably obtained by melting and extruding the resin as a raw material into a sheet, stretching it as needed, and then winding it into a roll. Furthermore, elongated resin films that are cut and wound according to the required width in the case of functional coating are also the subject of the present invention.

[0128] The inventors have studied the main reasons for the increase in charge during the winding of the film, especially after long-term storage, and the following results were obtained.

[0129] • The long strip of resin film wound into a roll has an air layer between the films, which inhibits the charging caused by excessive contact and friction between the films.

[0130] • If the air layer becomes thinner, the membrane is more likely to become charged.

[0131] • The air layer is gradually discharged from the end of the membrane, but due to the movement of air between the membranes, a localized thinning of the air layer occurs. In this part, the membranes rub against each other intensely, and the electric charge increases.

[0132] The movement of air between membranes is not only caused by uneven winding tension and contact pressure, but also by the fact that when thick and thin parts of the membrane are continuous in the same position, it is easy to cause the movement of air between the membranes.

[0133] • The cushioning of the air-expelling section is reduced, and the surface hardness of the roll is increased.

[0134] As a method to suppress the above factors, it has been found that, for example, it is preferable to control and combine the following (1) to (3) to manufacture the film roll.

[0135] (1) In the membrane process, when the long strip of resin film is wound onto the roller, the thick or thin portion of the film is not continuous for a long distance at 1 in the width direction.

[0136] As a specific method,

[0137] • Apply sufficient vibration during film formation.

[0138] • Online thickness measurement provides feedback for adjusting the slit width of the die head.

[0139] • To ensure uniform temperature during film formation

[0140] • Manage the temperature of the mold head.

[0141] wait.

[0142] (2) To ensure uniform tension and contact pressure in the width direction when the long strip of resin film is rolled into a roll.

[0143] As specific methods, the following can be cited:

[0144] • Appropriate positioning and shape of the contact roller

[0145] • Appropriate material and hardness of the contact roller

[0146] • Uniformity of contact roller diameter

[0147] Appropriate core diameter and hardness

[0148] • Control of bending and relaxation of elongated resin films (inhibiting saber-like deformation)

[0149] wait.

[0150] (3) Control the amount of air entrained during slitting (SL).

[0151] As a specific method,

[0152] • Control the tension and contact pressure during slitting and winding within a certain range.

[0153] Especially in films with strong anisotropy in elastic modulus, it reduces tension and increases contact pressure compared to isotropic films.

[0154] Especially in knurled rollers, the contact pressure is reduced.

[0155] wait.

[0156] The manufacturing method of the film roll is described in more detail using a biaxially stretched polyethylene terephthalate (PET) film as an example, but the present invention is not limited thereto.

[0157] PET resin, used as raw material, is fed into an extruder. The molten and mixed resin is extruded from a die with a narrow slit onto a cooling roller to form an unstretched sheet. The temperature of the molten resin is preferably 240~260°C, more preferably 245~255°C. To facilitate uniform thickness of the unstretched sheet, it is preferable to control the resin temperature so that it becomes uniform from the die to the slit. Furthermore, in the die design, it is preferable to design the flow path so that the resin discharge rate is constant in the width direction.

[0158] Preferably, a mechanism for adjusting the slit width is provided in the slit portion of the die head, allowing adjustment of the slit width during film manufacturing. Examples of adjustment methods include motor-driven adjusting bolts, piezoelectric actuators, heating bolts, and hydraulic methods. The slit width adjustment is preferably based on feedback from film thickness data obtained from an online film thickness measuring machine, as described later.

[0159] PET sheets are stretched along the MD (mechanical direction, length direction) direction by rollers with different circumferential speeds. Then, the two ends in the width direction are fixed by clamps and fed into a tenter frame. The MD stretching temperature is preferably 80~120℃, more preferably 85~110℃.

[0160] After the film is preheated to a stretchable temperature in the tenter frame, it is stretched along the TD direction (width direction). The stretching temperature in the width direction is preferably 85~130°C. During the tenter frame stretching process, there are situations where the temperature of the clamping area is difficult to rise, and there are also situations where the temperature is difficult to rise in some areas due to interference from the blown warm air, sometimes resulting in uneven thickness. To suppress uneven thickness, it is preferable to increase the airflow around the clamping area and to use nozzles that blow hot air in a way that ensures a uniform temperature on the film surface. In addition, if the airflow is too low, the film temperature is prone to become uneven; if it is too high, or if it is uneven from top to bottom, the film is prone to bending and slack, and sometimes it is difficult to achieve uniform tension during winding. It should be noted that bending and slack are specified by JISC2151:2019.

[0161] In order to achieve uniform TD stretching, the TD stretching ratio in the tenter frame is preferably 3 times or more, more preferably 3.2 times or more, and even more preferably 3.3 times or more.

[0162] After stretching, the film is heat-fixed. The heat-fixing temperature is preferably 150~250℃, more preferably 170~240℃. During heat-fixing, it is also preferable to form a uniform film temperature in the width direction, similar to the stretching process of the tenter frame. Uniform heat-fixing helps to reduce kinking deformation. After heat-fixing, a relaxation treatment can be performed as needed. The relaxation treatment is preferably 0.5~5%.

[0163] When applying coatings such as an easy-to-adhere layer online, it is preferable to apply the coating just before stretching on the tenter frame. In this case, a separate dryer can be used after coating to dry it, or it can be dried in the preheating to stretching zone of the tenter frame. Furthermore, if the coating is cross-linked, it is preferable to perform cross-linking at the heat-setting temperature; if cross-linking is performed using radiation, it is preferable to perform cross-linking during the period from heat-setting to winding.

[0164] After the portion of the film discharged from the tenter frame that is held by the clamps is cut off, it is wound into a roll.

[0165] Preferably, the film thickness in the width direction is measured during the period up to the time the film is wound up. Methods for measuring film thickness include, for example, methods using ultraviolet light, methods using X-rays, beta rays, or optical interferometry, but are not particularly limited to these. Multiple fixed film thickness gauges can be installed in the TD direction, or one or more film thickness gauges can be used to scan in the TD direction for measurement.

[0166] The obtained film thickness data is preferably used to control the slit width of the die head. That is, it is preferable to control the slit width by narrowing the thicker portions of the film and widening the slit width of the thinner portions, so that the thick and thin portions do not remain continuous for extended periods. Furthermore, as for film quality, even tolerable thickness unevenness can affect film stiffness if there is overlapping during winding; therefore, even when the thick portions are continuous, control can be implemented to make those portions thinner than average. Examples of control methods include P control, PI control, PD control, and PID control.

[0167] The winding device used in the winding process can typically be categorized as either linear winding, in which the film is sequentially wound onto the core with the side edges aligned, or vibratory winding, in which the film is wound onto the core by vibrating the side edges of the film within a certain width direction. Vibratory winding is preferred. By performing vibratory winding, it is possible to prevent thin or thick portions from being continuously wound into the same position.

[0168] The lower limit of the vibration amplitude of the film during vibratory winding is preferably 25 mm, more preferably 35 mm, further preferably 45 mm, and particularly preferably 55 mm. By setting it above this lower limit, the thickness reduction of the product caused by uneven thickness of the raw materials can be suppressed. The upper limit of the vibration amplitude is preferably 500 mm, more preferably 450 mm, further preferably 400 mm, and particularly preferably 350 mm. By setting it below this upper limit, the width of the unproductizable edge portions at both ends of the film width direction can be reduced, thereby improving productivity. It should be noted that the lower limit of the moving speed (winding speed) of the winding machine during vibratory winding is preferably 5 mm / min, more preferably 10 mm / min, further preferably 15 mm / min, and particularly preferably 20 mm / min. By setting it above this lower limit, the deterioration of planarity or charge due to the stacking of fixed uneven thickness portions can be suppressed. The upper limit of the winding speed during vibratory winding is preferably 100 mm / min, more preferably 95 mm / min, further preferably 90 mm / min, and particularly preferably 85 mm / min. If it is below this upper limit, wrinkles can be easily suppressed during membrane transport / winding.

[0169] The manufactured film, wound in this way, can be directly used for the next coating or other processing steps. However, it is preferable to roll out the manufactured film, cut it to the required width and length, and then roll it again. This invention is also applicable to rolls of manufactured film, but is preferably applicable to slit film rolls.

[0170] (Knurling knife)

[0171] Furthermore, as an example of knurling, a method of deforming the film by pressing it against a knurling knife, which is commonly practiced, will be described in detail, but the present invention is not limited thereto.

[0172] The knurling cutter is preferably made of metal. Examples of metals include SUS, stainless steel, aluminum, titanium, and hard chrome. The surface of the knurling cutter can also be plated.

[0173] The lower limit of the diameter of the knurling cutter is preferably 30 mm, more preferably 50 mm. The upper limit of the diameter of the knurling cutter is preferably 300 mm, more preferably 250 mm, and even more preferably 200 mm. By setting it within the above range, a knurling processing device of appropriate size can be obtained.

[0174] The lower limit of the thickness of the knurling cutter is preferably 3 mm, more preferably 5 mm, and even more preferably 7 mm. The upper limit of the thickness of the knurling cutter is preferably 50 mm, more preferably 40 mm, and even more preferably 30 mm.

[0175] On the outer periphery of the knurling cutter, a protrusion is provided to match the configuration of the given protrusion. The lower limit of the height of the protrusion is preferably 0.05 mm, more preferably 0.1 mm, further preferably 0.15 mm, and particularly preferably 0.2 mm. The upper limit of the height of the protrusion is preferably 3 mm, more preferably 2.5 mm, further preferably 2 mm, and particularly preferably 1.5 mm.

[0176] From above, the preferred shapes for the protrusions of the knurling tool are circles, ovals, triangles, squares, rectangles, rhombuses, trapezoids, pentagons, hexagons, and polygons with more than six sides; squares, rectangles, and rhombuses are more preferred. Furthermore, the solid shape can be a cone, a multi-faceted pyramid, or a frustum, but knurling in a frustum shape tends to be more difficult to flatten.

[0177] When the protrusion is frustoconical, the lower limit of the area of ​​the flat portion on the upper side of the protrusion is preferably 40,000 µm². 2 More preferably 50000µm 2 More preferably 60000µm 2 Especially preferred is 80000µm 2 The upper limit of the area of ​​each flat portion on the upper side of the protrusion is preferably 200,000 µm. 2 More preferably 170000µm 2 More preferably 150000µm 2 130000µm is particularly preferred. 2 .

[0178] When the protrusion is frustoconical, the lower limit of the angle of the protrusion's slope is preferably 25°, more preferably 30°, and even more preferably 40°. By setting it above this lower limit, good operability can be achieved. When the protrusion is frustoconical, the upper limit of the angle of the protrusion's slope is preferably 90°, more preferably 80°, and even more preferably 70°.

[0179] When the protrusion is frustoconical, the lower limit of the total area of ​​the flat portion of the upper surface of the protrusion relative to the area of ​​the outer periphery of the knurling cutter with the protrusion is preferably 1%, more preferably 3%, further preferably 5%, particularly preferably 8%, and most preferably 10%. When the protrusion is frustoconical, the upper limit of the total area of ​​the flat portion of the upper surface of the protrusion of the knurling cutter relative to the area of ​​the outer periphery of the knurling cutter with the protrusion is preferably 50%, more preferably 40%, further preferably 30%, and particularly preferably 20%.

[0180] When the protrusion is conical, the lower limit of the angle at the top of the protrusion is preferably 30°, more preferably 60°, further preferably 80°, particularly preferably 90°, and most preferably 100°. The upper limit of the angle at the top of the protrusion is preferably 160°, more preferably 150°, and further preferably 140°.

[0181] The lower limit of the knurling cutter temperature is preferably 10°C, and more preferably 20°C.

[0182] (Roll-up conditions)

[0183] The lower limit of the winding tension is preferably 50 N / m, more preferably 60 N / m, further preferably 70 N / m, particularly preferably 80 N / m, and most preferably 90 N / m. By setting it above this lower limit, air can be appropriately expelled, suppressing wrinkles and winding deviation. The upper limit of the winding tension is preferably 280 N / m, more preferably 270 N / m, further preferably 260 N / m, particularly preferably 250 N / m, and most preferably 240 N / m. By setting it below this upper limit, air can be appropriately introduced, suppressing charging.

[0184] The lower limit of the winding contact pressure of the contact roller is preferably 30 N / m, more preferably 40 N / m, even more preferably 50 N / m, and particularly preferably 60 N / m. By setting it above this lower limit, air can be appropriately expelled, suppressing wrinkles. The upper limit of the winding contact pressure of the contact roller is preferably 600 N / m, more preferably 500 N / m, even more preferably 400 N / m, and particularly preferably 300 N / m. By setting it below this upper limit, air can be appropriately introduced, suppressing charging.

[0185] There are no particular restrictions on the raw materials for the contact roller, such as rubber, resin, metal, ceramics, etc. However, considering the ease of applying uniform pressure to the roller in the width direction, a material with a rubber-based surface is preferred.

[0186] The lower limit of the surface hardness of the contact roller, calculated in Shore A, is preferably 40, more preferably 45, further preferably 50, and particularly preferably 55. The upper limit of the surface hardness of the contact roller, calculated in Shore A, is preferably 100, more preferably 95, further preferably 90, and particularly preferably 85.

[0187] The shape of the contact roller can be any of the following: straight, convex contact roller that follows the deflection of the film roll, tapered convex, or concave. It can be selected based on the positional relationship between the contact roller and the film roll to facilitate uniform contact pressure across the width of the film.

[0188] The lower limit of the contact roller circumference is preferably 100 mm, more preferably 150 mm, further preferably 200 mm, and particularly preferably 250 mm. The upper limit of the contact roller circumference is preferably 800 mm, more preferably 750 mm, further preferably 700 mm, and particularly preferably 650 mm. By setting it within the above range, it is easy to form uniform contact pressure in the film width direction, and the operability is also excellent.

[0189] In this invention, in order to suppress the increase in roll-out charge after long-term storage, such as for more than 3 months, it is preferable that the freshly manufactured film roll has the aforementioned surface roll hardness characteristics, and it is preferable that the surface roll hardness characteristics are maintained even after a long period of time. As for the storage period of the roll, it is preferable that it is more than 3 months (90 days) after manufacturing, and more preferably more than 4 months (120 days). That is, it is preferable that the film roll after 3 months, and more preferably after 4 months, has the roll hardness characteristics of this invention. In addition, the period for maintaining the roll hardness characteristics is preferably longer, and there is no particular upper limit. It is preferable that the roll hardness characteristics of this invention are maintained for 24 months (730 days), more preferably 22 months (670 days), further preferably 20 months (610 days), and particularly preferably 18 months (548 days).

[0190] It should be noted that, according to the research of the inventors, the surface roll hardness stabilizes after 3 months. Afterward, the average roll hardness and roll hardness difference tend to increase slightly, and no decrease is observed. Therefore, it is believed that when measuring the roll hardness characteristics of film rolls manufactured more than 3 months ago, as long as they are within the range of the roll hardness characteristics of the present invention, the roll hardness characteristics will also fall within that range even after 3 months from manufacturing. Preferred storage methods include placing the film rolls and desiccant together in a resin bag such as polyethylene, polypropylene, or nylon and sealing the opening, and storing them at a temperature of 5–30°C and a humidity of 20–80% RH, within the range of seasonal and daily variations.

[0191] (The winding core is electrified)

[0192] Even after long-term storage, the film roll can suppress the charge carried during unwinding, effectively utilizing it in the core portion. The upper limit of the absolute value of the charge carried by the core during unwinding is, for example, 53kV, preferably 45kV, more preferably 40kV, further preferably 35kV, particularly preferably 30kV, and most preferably 25kV. By setting it below this upper limit, unevenness during surface coating can be suppressed.

[0193] In rolls of knurled elongated resin films, winding misalignment and deterioration of the roll's appearance are prone to occur. The inventors have discovered that, in the case of elongated resin films with high anisotropy, especially those with a main orientation axis in the TD direction, it is preferable not only to adjust the initial height of the knurling but also to control the film thickness, roll width, and knurling height. Specifically, (4) it is preferable to adjust the raw material thickness, roll width, and knurling height to the range of Formula 1 and Formula 2.

[0194] Equation 1…1≤h≤0.1T-1

[0195] Equation 2…W≤40T

[0196] Here, T: film thickness (µm), W: film width (mm), h: initial knurling height (µm)

[0197] In the relationship between film width W (mm) and film thickness T (µm), the lower limit of W / T is preferably 20, more preferably 21, further preferably 22, particularly preferably 23, and most preferably 24. By setting it above this lower limit, the width relative to the thickness can be set higher, thus improving productivity. In other words, W ≥ 20T is preferred, W ≥ 21T is more preferred, W ≥ 22T is more preferably preferred, W ≥ 23T is more preferably preferred, and W ≥ 24T is most preferably preferred. Furthermore, the upper limit of W / T is preferably 40, more preferably 38, further preferably 36, particularly preferably 35, and most preferably 34. By setting it below this upper limit, the knurling effect can be fully imparted throughout the roll width direction. In other words, W ≤ 40T is preferred, W ≤ 38T is more preferred, W ≤ 36T is more preferably preferred, W ≤ 35T is more preferably preferred, and W ≤ 35T is most preferably preferred. It should be noted that the film thickness can correspond to the raw material thickness, and the film width can correspond to the roll width.

[0198] Regarding the relationship between film thickness T (µm) and initial knurling height h (µm), the upper limit of the initial knurling height h is preferably 0.1T⁻¹, more preferably 0.1T⁻¹.1, further preferably 0.1T⁻¹.2, and most preferably 0.1T⁻¹.3. By setting it below this upper limit, excessive air entrapment can be prevented, resulting in a good appearance. It should be noted that the thicker the film, the larger h can be. The upper limit of the initial knurling height h (µm) is preferably 15µm or less, more preferably 12µm or less, further preferably 10µm or less, particularly preferably 7µm or less, and most preferably 6µm or less. By setting it below this value, an appropriate knurling speed can be achieved, and the load on the knurling equipment can be reduced, making it less likely to cause breakage or malfunction.

[0199] The lower limit of the initial knurling height h (µm) is preferably (0.1T-5)µm when T≥60, more preferably (0.1T-4.8)µm, further preferably (0.1T-4.6)µm, and most preferably (0.1T-4.4)µm. When T<60µm, the lower limit of the initial knurling height h (µm) is preferably 1µm, more preferably 1.2µm, further preferably 1.4µm, even more preferably 1.5µm, and most preferably 1.6µm, but can also be 2µm or 2.5µm. By setting it above this lower limit, a knurling effect can be imparted to the entire roll width direction. Details regarding knurling are described later. In this specification, the initial knurling height is a value measured by the method described in the examples.

[0200] By controlling equations 1 and 2, a good effect can be achieved in elongated resin films with anisotropic elastic modulus. The lower limit of the elastic modulus ratio TE / ME, calculated by dividing the elastic modulus TE (MPa) in the TD direction by the elastic modulus ME (MPa) in the MD direction, is preferably 2, more preferably 2.1, further preferably 2.2, particularly preferably 2.3, and most preferably 2.4. Setting it above this lower limit can improve productivity. Furthermore, the upper limit of TE / ME is preferably 4.5, more preferably 4.3, further preferably 4.2, particularly preferably 4.1, and most preferably 4. Setting it below this upper limit can reduce the susceptibility to cracking caused by anisotropy.

[0201] The lower limit of the elastic modulus (ME) in the MD direction is preferably 1000 MPa, more preferably 1500 MPa, further preferably 1800 MPa, particularly preferably 2000 MPa, and most preferably 2200 MPa. Setting it above this lower limit increases strength and improves elongation at break. The upper limit of ME is preferably 4000 MPa, more preferably 3800 MPa, further preferably 3600 MPa, particularly preferably 3400 MPa, and most preferably 3200 MPa. Setting it below this upper limit improves anisotropy in the TD direction.

[0202] The upper limit of the elastic modulus (TE) in the TD direction is preferably 20,000 MPa, more preferably 18,000 MPa, further preferably 15,000 MPa, particularly preferably 13,000 MPa, and most preferably 11,000 MPa. By setting it below this upper limit, problems such as increased internal stress and increased thermal shrinkage can be suppressed. The lower limit of TE is preferably 6,000 MPa, more preferably 6,200 MPa, further preferably 6,400 MPa, particularly preferably 6,600 MPa, and most preferably 6,800 MPa. By setting it above this lower limit, the strength increases, and the elongation at break can be improved.

[0203] The lower limit of the average of ME and TE ((ME+TE) / 2: average elastic modulus) is preferably 3000 MPa, more preferably 3500 MPa, and most preferably 4000 MPa. By setting it above this lower limit, the strength increases, and the elongation at break can be improved. The upper limit of the average elastic modulus is preferably 8000 MPa, more preferably 7000 MPa, and most preferably 6000 MPa. By setting it below this upper limit, problems such as high internal stress and high thermal shrinkage can be easily suppressed.

[0204] In addition, in birefringent films such as polyester films, anisotropy can also be expressed using retardation. Retardation is a parameter defined by the product of the anisotropy of the orthogonal biaxial refractive index on the film (ΔNxy = |nx - ny|) and the film thickness d (nm) (ΔNxy × d), and is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) can be determined using the following method: Using a molecular orientation meter (manufactured by Oji Instruments Co., Ltd., MOA-6004 type molecular orientation meter), determine the slow axis direction of the film. Cut a 4cm × 2cm rectangle parallel to the long side of the sample to be measured, and use this rectangle as the sample. For this sample, the orthogonal biaxial refractive indices (refractive index along the slow axis: ny, refractive index along the direction orthogonal to the slow axis: nx) and the refractive index along the thickness direction (nz) were determined using an Abbe refractive index meter (Atago, NAR-4T, measurement wavelength 589 nm). The absolute value of the difference in refractive indices along the biaxial direction (|nx-ny|) was taken as the anisotropy of the refractive index (ΔNxy). The film thickness d (nm) was measured using a Fujiworks Millitron HKT-1202, and the units were converted to nm. The retardation (Re) can be calculated by the product of the anisotropy of the refractive index (ΔNxy) and the film thickness d (nm) (ΔNxy×d).

[0205] The lower limit of the retardation (Re) of the elongated resin film is preferably 3000 nm, more preferably 4000 nm, and most preferably 5000 nm. By setting it above this lower limit, iris spots generated when image display devices are used in polarized environments can be reduced. The upper limit of the retardation is preferably 20000 nm, more preferably 10000 nm, further preferably 9000 nm, and most preferably 8700 nm. By setting it below this upper limit, the situation where high anisotropy makes cracking easy can be suppressed. From the perspective of being able to cope with the thinning of the film in applications such as image display devices, the upper limit of the retardation can be 8500 nm or 8000 nm.

[0206] The lower limit of the ratio Re / Rth, which is the delay amount (Re) to the thickness direction delay amount (Rth), is preferably 0.2, more preferably 0.5, and most preferably 0.6. The upper limit of RE / Rth is preferably 2, and most preferably 1.8.

[0207] The inventors have discovered that, particularly in films with high anisotropy, there is a tendency for the film to become tightly wound, resulting in a poor winding appearance and easy accumulation of charge. These phenomena become more pronounced as the film thickness decreases. Specifically, it has been found that in thin films, increasing the knurling height to control charge tends to worsen the winding appearance after long-term storage, as the cylindrical film roll becomes slightly polygonal, leading to a deterioration in the planarity of the rolled film. In thin films with high anisotropy, by appropriately adjusting the thickness of the strip-shaped resin film, the roll width (width of the strip-shaped resin film), and the knurling height, it is possible to suppress charge accumulation during winding and achieve a good winding appearance and film planarity.

[0208] (Utilization of membrane rolls)

[0209] The film roll can be further processed into laminated films through various post-processing steps. Examples of post-processing steps include coating, vapor deposition, and sputtering, with coating being particularly suitable for use as a laminated film.

[0210] Furthermore, during the film roll-out process in post-processing, static electricity removal can be performed between the roll-out section and the post-processing section, and it is particularly preferable to perform static electricity removal at the roll-out section. Methods for static electricity removal include, for example, contacting a conductive component such as a static eliminator brush, or blowing ions (charged gas).

[0211] In one embodiment, the present invention relates to a method for manufacturing a laminated film, comprising: a step (A) of winding out an elongated resin film, and a step (B) of coating at least one side of the wound elongated resin film with a coating liquid.

[0212] The resin used in the coating liquid is a polyester, acrylic resin, polyurethane (e.g., polyester polyurethane, polycarbonate polyurethane, polyether polyurethane), ethylene vinyl acetate copolymer, polyamide, styrene acrylic copolymer, polyvinyl alcohol, etc. If a radiation-curable coating is desired, acrylic monomers, acrylic oligomers, or polymerizable liquid crystal compounds are preferred. Among these, acrylic monomers, acrylic oligomers, and polymerizable liquid crystal compounds are preferred.

[0213] Toluene, alcohols, ketones, and esters are preferred solvents for coating liquids. If the coating liquid is radiation-curable, solvent-free coating liquids are also acceptable.

[0214] The lower limit of the dried thickness of the coating film obtained by step (B) of applying the coating liquid is preferably 0.001 µm, more preferably 0.005 µm, even more preferably 0.01 µm, and particularly preferably 0.02 µm. The upper limit of the dried thickness of the obtained coating film is preferably 20 µm, more preferably 15 µm, even more preferably 10 µm, particularly preferably 7 µm, and most preferably 5 µm.

[0215] The resulting coating is preferably an optically functional coating such as a hard coating layer, an anti-glare layer, an anti-reflection layer, a low-reflection layer, or a phase difference layer. Alternatively, the resulting coating can be an adhesive or bonding agent.

[0216] For applications involving coatings, anti-glare films, low-reflection films, anti-reflection films, transparent conductive film substrates, polarizer protective films, phase retardation films with phase retardation layers composed of liquid crystal compounds, or thin film transfer films for transferring these functional layers are preferred.

[0217] Example

[0218] The present invention will be described in more detail below through embodiments, but the present invention is not limited to the form of the embodiments described, and appropriate changes can be made without departing from the spirit of the present invention.

[0219] (1) Measurement of the surface hardness of the film roll

[0220] The hardness of the film roll was determined using an Equotip 550 hardness tester manufactured by Proceq GmbH, Switzerland. Specifically, the film roll of the present invention, produced by a slitting machine, was unwound using a film roll unwinding machine, and the hardness was measured. Hardness was measured at 20 mm intervals along the roll width, and the average value of the roll hardness at each location was taken as the average roll hardness. In addition, for each measured value, the difference between it and the measured value at a point 60 mm away was taken, and the maximum absolute value of this difference was taken as the roll hardness difference between the two points at a 60 mm interval.

[0221] The measurement point in the width direction of the membrane roll surface is determined by moving the measurement point 50 mm from the membrane end side (where the winding direction of the membrane roll from the core towards the outermost membrane is clockwise), and then moving 20 mm at a time until the end. If the final position is less than 50 mm from the membrane end, it is excluded from the calculation.

[0222] Further use Figure 1 Please provide a detailed explanation.

[0223] exist Figure 1 In the diagram, the left side is the end of the membrane roll that is wound clockwise from the core towards the outermost membrane. The position 50mm from the left end of the membrane roll is designated as position 1. The position 20mm from the other end (right) is designated as position 2. This 20mm interval is repeated until the distance from the other end is less than 50mm. Positions less than 50mm are not considered for measurement. Therefore, if the position number of the other end is designated as n, then position n is a distance of more than 50mm and less than 70mm from the other end.

[0224] The arithmetic mean of the hardness of the n rolls at positions 1 to n is the average roll hardness.

[0225] Furthermore, the location 60mm away from location 1 is location 4. Calculate the absolute value of the difference between these two points. Repeat this process for locations n-3 and n, calculating the absolute value of the difference between the two points. The maximum absolute value among the n-3 results represents the difference in roll hardness between the two points at a 60mm interval.

[0226] (2) Uneven thickness (TV)

[0227] Using a contact-type continuous thickness gauge from Mikuron Instruments Co., Ltd. (the thickness gauge part is manufactured by Anritsu Electric Co., Ltd.), a rectangular measurement sample of approximately 40 mm in the MD direction was cut from the entire width of the obtained film in the TD direction, excluding the portion 20 mm from the end. That is, the long side of the measurement sample is parallel to the TD direction, the length of the long side is the width of the film roll - 40 mm, and the length of the short side is approximately 40 mm. The thickness of this measurement sample was measured in the TD direction at a speed of 1.5 m / min, and data was continuously imported at 0.1-second intervals. Based on the obtained data, the maximum thickness at each measurement location was set as Tmax, the minimum thickness as Tmin, and the average thickness as Tave. The thickness non-uniformity in the TD direction, TV(%), was calculated as (Tmax - Tmin) / Tave × 100. Furthermore, the standard deviation Stdev and the coefficient of variation (Stdev / Tave × 100) of the thickness measurement values ​​in the TD direction were also calculated from the obtained data.

[0228] Samples were collected from a point 10m from the end of the winding to the beginning of the winding, and then every 400m thereafter. It should be noted that if wrinkles or other irregularities exist at the sampling location, samples should be collected from the unwrinkled sections at the beginning and end.

[0229] The maximum value of TV and coefficient of variation of the samples collected from each position of the roll is used as the value of TV and coefficient of variation over the entire length of each roll.

[0230] (3) Knurling height

[0231] Measurements were performed using a digital micrometer (Sony Manufacturing Systems, Inc. µ-mate M-30).

[0232] Ten points are measured along the MD at approximately 5cm intervals along the central part of the width of the knurled section. The average value of these measurements is taken as the knurled section thickness. Ten points are measured along the MD at approximately 5cm intervals along the inner side approximately 1cm away from the knurling. The average value of these measurements is taken as the film thickness. The difference between the knurled section thickness and the film thickness is taken as the knurling height.

[0233] Immediately after winding, samples were taken from the second layer of film starting from the surface of the roll to measure the knurling height. The average of these measurements from the right and left sides was taken as the initial knurling height. After the film was wound into a roll and stored at room temperature for 4 months, measurements were taken at a total of 4 points on the right and left sides of the film, specifically at the surface and core sections. These measurements were taken as the surface knurling height and the core knurling height, respectively. It should be noted that, in addition to the surface layer, the knurling heights measured at the second and third turns from the outermost layer after storage were also considered as the initial knurling height. This is because it is difficult to apply pressure to the turns starting from the outermost layer, and the knurling height hardly changes even after time, thus it can be considered as the initial knurling height immediately after winding.

[0234] It should be noted that the right side, left side, surface layer, and core layer are described below.

[0235] Right side: The right end of the roll as the observer faces the roll and rolls the membrane out in front of them from the top.

[0236] Left side: The left end of the roll as the observer faces the roll and rolls the membrane out in front of them from the top.

[0237] Surface side: The portion 100m from the end point of the winding of the film into a roll.

[0238] Core section: The portion 100m from the starting point of the film being wound into a roll.

[0239] The abbreviations for the knurling height of each part are as follows.

[0240] Knurling height on the right side of the surface layer: Hner

[0241] Knurling height on the left side of the surface layer: Hnel

[0242] Knurling height on the right side of the core: Hnbr

[0243] Knurling height on the left side of the core: Hnbl

[0244] (4) Knurling Residue Rate

[0245] As described below.

[0246] Knurling residue on the right side: Hnbr / Hner

[0247] Left side knurling residue rate: Hnbl / Hnel

[0248] (5) The charge of the winding

[0249] After being stored indoors at 25±2℃ and 40±20% humidity for 4 months, the rolled film was unwound from the surface at a speed of 100m / min, and the charge on the film in the central part of the core was measured. The measurement was performed using a Kasuga Electric Co., Ltd. KSD-1000, measuring the portion of the film immediately after being unwound from the roll.

[0250] (6) Winding offset

[0251] Observe the end face of the roll film after it has been stored indoors at a temperature of 25±2℃ and a humidity of 40±20% for 4 months.

[0252] ◎: The state is unchanged from when it was first wound up, with no bumps or depressions.

[0253] ○: Confirm that the bumps and depressions have increased slightly or that the shape resembles a bamboo shoot.

[0254] △: Confirmed the increase in bumps and depressions or the bamboo shoot-like deformation, but it is a level that does not pose a problem for actual use.

[0255] ×: Confirmed as an increase in unevenness or bamboo shoot-like deformation at a level that is practically unusable.

[0256] (7) Wrinkles

[0257] After being stored indoors at 25±2℃ and 40±20% humidity for 4 months, the roll-up film was rolled out and the wrinkles along its entire length were observed.

[0258] ◎: Completely wrinkle-free.

[0259] ○: A few wrinkles were confirmed in a portion of the entire length.

[0260] △: A section of the entire length was found to have weak folds, but it was at a level that was not problematic.

[0261] ×: A portion of the total length is identified as a level of fold that is impractical to use.

[0262] (8) Membrane planarity

[0263] After being stored indoors at 25±2℃ and 40±20% humidity for 4 months, the rolled-up membrane was unwound. A section of the membrane 80-90mm from the surface was cut into 3m lengths and placed on a workbench with a flat, matte black ceiling panel. The planarity was evaluated by comparing the shape of the fluorescent lights on the ceiling reflected in the membrane. It should be noted that this was compared to the planarity of the membrane immediately after being rolled up.

[0264] ◎: No change from the sample immediately after being rolled up.

[0265] ○: The flatness deteriorates slightly.

[0266] △: Planarity deteriorates, but is at a level where there are no problems.

[0267] ×: Planarity deterioration, reaching a level that is practically unusable.

[0268] (9)Sa and Sq

[0269] According to ISO 25178, measurements were performed using a non-contact surface shape measurement system (Mitaka Systems, VertScan R550H-M100) under the following conditions. The average value of 5 samples was used.

[0270] (Measurement conditions)

[0271] Measurement mode: WAVE mode

[0272] Objective lens: 10x

[0273] 0.5× lens barrel

[0274] Measurement area: 936µm × 702µm

[0275] (Analysis conditions)

[0276] Surface correction: 4 corrections

[0277] Interpolation processing: Full interpolation

[0278] ISO parameter processing: Specifying a 10µm S-filter

[0279] (10) Delay (Re)

[0280] The retardation is a parameter defined by the product of the orthogonal biaxial refractive index anisotropy (ΔNxy = |nx - ny|) and the film thickness d (nm) (ΔNxy × d), and is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) is determined by the following method: Using a molecular orientation meter (manufactured by Oji Instruments Co., Ltd., MOA-6004 type molecular orientation meter), the slow axis direction of the film is determined, and a 4cm × 2cm rectangle is cut out with the slow axis direction parallel to the long side of the sample to be measured, which serves as the sample for measurement. For this sample, the orthogonal biaxial refractive indices (refractive index along the slow axis: ny, refractive index along the direction orthogonal to the slow axis: nx) and the refractive index along the thickness direction (nz) were determined using an Abbe refractive index meter (Atago, NAR-4T, measurement wavelength 589 nm). The absolute value of the difference in refractive indices along the biaxial axes (|nx-ny|) was taken as the anisotropy of the refractive index (ΔNxy). The film thickness d (nm) was measured using a Fujiworks Millitron HKT-1202, and the units were converted to nm. The retardation (Re) was calculated by the product of the anisotropy of the refractive index (ΔNxy) and the film thickness d (nm) (ΔNxy×d).

[0281] (11) Elastic modulus

[0282] The tear propagation strength of polyethylene terephthalate (PET) resin films was evaluated according to the tensile test procedure in section 7.2 of JIS C2318. The test piece was cut into a rectangle of 180 mm × 10 mm with the direction of elastic modulus measurement as the long side. Lines of 10 mm length parallel to the short sides were drawn 40 mm inside the two short sides of the test piece. The thickness (mm) of the test piece was measured at five points within a 100 mm interval between the lines, and the average value was calculated. The product of this average value and the width (10 mm) of the test piece was taken as the cross-sectional area (mm²) of the test piece. 2 It should be noted that the membrane thickness was measured using a micrometer (Fujiwork, Millitron HKT-1202). Tensile tests were conducted with the long side of the test piece as the tensile direction, holding the area from the marked line to the short side using chucks. The tensile tests were performed using a precision universal testing machine (Shimadzu, Autograph AGX-V), with a chuck spacing of 100 mm and a tensile speed of 100 mm / min. The elastic modulus was calculated from the strain values ​​under a load of 5-10 N.

[0283] Referring to the embodiments in WO2021 / 200322, the resin used to manufacture the coating for the easy-to-adhere layer and the polyester film for the substrate.

[0284] (Preparation of coating solution for easy-to-adhere layer P1)

[0285] The following raw materials are mixed to prepare a coating solution. The coating solution is filtered through a 10µm filter (nominal filtration accuracy: 95% retention of 10µm particles).

[0286] Water 40.61% by mass

[0287] Isopropanol 30.00% by mass

[0288] Polyester aqueous dispersion 11.67% by mass

[0289] Polyvinyl alcohol aqueous solution (solid content concentration 10% by mass): 15.00% by mass

[0290] End-capped isocyanate crosslinking agent (aqueous solution) 0.67% by mass

[0291] Particles (silica sol with an average particle size of 100 nm and a solid content concentration of 40% by mass)

[0292] 1.25% by mass

[0293] Catalyst (organotin compound solid content concentration 14% by mass): 0.3% by mass

[0294] Surfactant (silicone-based, solid content 10% by mass): 0.5% by mass

[0295] • Polyester aqueous dispersion: An aqueous dispersion of a copolyester composed of terephthalic acid, isophthalic acid, and sodium isophthalate-5-sulfonate as acid components, and diethylene glycol and ethylene glycol as glycol components (solid component concentration 30% by mass).

[0296] • End-capped isocyanate crosslinking agent: Methyl ethyl ketone oxime-terminated polyisocyanate (40% by mass solids) is prepared by reacting a polyisocyanate compound with an isocyanurate structure (Asahi Kasei Chemicals, DURANATE TPA) with polyethylene glycol monomethyl ether (average molecular weight 750).

[0297] (Preparation of coating solution for easy-to-adhere layer P2)

[0298] Mix the following ingredients to prepare a coating solution for forming an easy-to-adhere layer with excellent adhesion to the functional layer. Filter the coating solution using a 10µm filter (nominal filtration accuracy: 95% rejection of 10µm particles).

[0299] Water 55.62% by mass

[0300] Isopropanol 30.00% by mass

[0301] Aliphatic polycarbonate-based polyurethane resin aqueous solution (solid content concentration 35% by mass)

[0302] 11.29% of mass

[0303] Aqueous solution of acrylic crosslinking agent containing oxazolinyl group (solid content concentration 40% by mass)

[0304] 2.26% by weight

[0305] Particles (silica sol with an average particle size of 40 nm and a solid content of 40% by mass)

[0306] 0.71% by mass

[0307] Particles (silica sol with an average particle size of 450 nm and a solid content concentration of 40% by mass)

[0308] 0.07% by mass

[0309] Surfactant (silicone-based, solid content concentration 100% by mass): 0.05% by mass

[0310] (Example 1)

[0311] As a membrane raw material, PET granules with an intrinsic viscosity of 0.68 dL / g were dried under reduced pressure (1 Torr) at 135°C for 6 hours and then fed to an extruder to dissolve at 285°C. The molten polymer was filtered through sintered stainless steel filter media (with a nominal filtration accuracy of 95% particle rejection for 5µm particles), extruded into sheets using a T-die, and then wound onto a casting drum at a surface temperature of 30°C using an electrostatic casting method. The film was then cooled and cured to produce an unstretched membrane. The surface roughness Ra of the casting drum was less than 2 nm, and Rz was less than 15 nm. It should be noted that the intrinsic viscosity was measured assuming a Huggins constant of 0.38 in a phenol / tetrachloroethane (60 / 40 mass ratio) solution.

[0312] Next, coating solution P1 was applied to one side of the unstretched PET film, and coating solution P2 was applied to the opposite side, so that the coating weight after drying was 0.12 g / m². 2 Then it is put into a dryer and dried at 80°C for 20 seconds.

[0313] An unstretched film with a coating layer was fed into a tenter frame. While holding the ends of the film with clamps, hot air at 135°C was introduced, stretching it 4.0 times its original width. Then, while maintaining the stretched width, it was treated at 225°C for 30 seconds. Afterward, the cooled film was cut at both ends with a circular cutter and wound up to obtain a uniaxially oriented PET film with a thickness of 60µm. The vibration speed during winding was 20mm / min. It should be noted that the T-die was designed with a flow path tailored to the polyester used, ensuring uniform resin discharge in the width direction. The slit section used a device with heated bolts and adjustable slit spacing. Based on thickness data measured using an online thickness gauge at the tenter frame exit, the die lip gap of the T-die was automatically adjusted by control software to ensure uniform film thickness in the width direction. Furthermore, the airflow in the width direction was fine-tuned within the tenter frame to ensure uniform film temperature in the width direction. The resulting film had an intrinsic viscosity of 0.65 dL / g.

[0314] The film obtained above is rolled out and cut into specified widths. After knurling at both ends, it is wound onto a core with an outer diameter of 7 inches, with the side in contact with the knurling knife as the outer side, to obtain a roll with a length of 3900m. The winding speed is 185m / min.

[0315] Winding tension is the tension when the film is wound onto the core after knurling at both ends. Winding contact pressure is the contact pressure exerted by the contact rollers during winding. The surface of the contact rollers is made of rubber with a hardness of 70. The conditions for knurling are described below.

[0316] The roll is placed in a polyethylene bag and the opening is secured with rubber. Side plates larger than the outer diameter of the roll are embedded at both ends of the core and stored at 25°C. The membrane's Sa is 1.0 nm on the P1 surface and 1.2 nm on the P2 surface, and Sq is 1.3 nm on the P1 surface and 1.5 nm on the P2 surface.

[0317] (Knurling)

[0318] The knurling process involves passing the left and right ends of the slit film between an upper roller that performs the knurling process and a lower roller that performs the mirror finish process. The height of the knurling section is adjusted by changing the pressing pressure of the upper roller. Furthermore, the process is performed at room temperature of 25°C.

[0319] The distance between the knurling section and the end of the film is 3mm.

[0320] (Knurling knife)

[0321] The knurling tool is a disc-shaped material with a thickness of 10 mm and a diameter of 100 mm. Ten protrusions of the following shape are arranged at a 45-degree angle, each 10 mm long (10 x 10 protrusions relative to 10 mm x 10 mm). The protrusions on the knurling tool are in the shape of a four-sided pyramid, with a base length of 1000 µm x 1000 µm and a height of 900 µm.

[0322] (Examples 2-7, Comparative Examples 1-5)

[0323] Except for the conditions described in Table 1, the operation was the same as in Example 1. In Comparative Example 4, a general-purpose T-die head with a heating bolt and adjustable slit spacing was used for the slit section, which is the former for fine-tuning the airflow of the tenter frame.

[0324] (Evaluation of the membrane roll)

[0325] Using the obtained film, set up the coating as described below. It should be noted that, under the same conditions, prepare two rolls of film. One roll will be used for measuring the hardness of the roll, the knurling height, the charge carried on the roll, the roll-up state, and the thickness unevenness. The other roll will be used for coating evaluation.

[0326] The film is rolled out, and the anti-glare coating liquid with the following composition is applied to the easy-to-adhere layer P2 using a gravure coating machine. After drying in an oven at 90°C, the coating is cured by irradiation with ultraviolet light to set the anti-glare layer.

[0327] (Composition of the coating liquid for the anti-glare layer)

[0328] KAYARAD PET-30, manufactured by Nippon Kayaku Co., Ltd., 38.7 parts by weight.

[0329] Viscoat#360, manufactured by Osaka Organic Chemical Industry Co., Ltd., 9.7 parts by weight.

[0330] EPOSTAR MA1006, manufactured by Nippon Shokubai Co., Ltd., 0.1 parts by weight.

[0331] Irgacure 184 1.5 parts by weight

[0332] 30.0 parts by weight of methyl isobutyl ketone

[0333] 20.0 parts by weight of methyl ethyl ketone

[0334] 0.02 parts by weight of fluorinated surfactant

[0335] (Evaluation of film coating uniformity)

[0336] The condition of the anti-glare layer from the starting point of the film roll to 100m~150m is observed as an evaluation of the coating uniformity.

[0337] ◎: There is no unevenness in 50m; it is uniform.

[0338] ○: There are several areas within 50m that are considered to be slightly uneven or have shrinkage cavities.

[0339] △: There are several areas within 50m that are considered to be significantly uneven or have shrinkage cavities.

[0340] ×: Unevenness or shrinkage cavities were frequently observed within 50m.

[0341] The conditions and evaluation results are shown in Table 1.

[0342] [Table 1]

[0343]

[0344] Examples 2-6 are based on online thickness control and vibration during film winding in film formation. Winding is performed under appropriate tension and contact pressure conditions, resulting in an appropriate average hardness, small standard deviation of surface hardness, and small hardness difference between two points spaced 60 mm apart. As a result, roll-off, wrinkles, and flatness are good, and the roll-out charge is low. Uniform and good coatings are obtained when these films are used for coating. Example 1 likely had slight roll-off and wrinkles due to low tension and contact pressure. Consequently, in Comparative Example 2, where tension and contact pressure were reduced, roll-off and wrinkles occurred, resulting in poor flatness.

[0345] Compared to other examples, Example 7 showed a larger standard deviation of surface hardness and a larger hardness difference between two points spaced 60 mm apart, resulting in higher roll-out charge and slightly poorer coating uniformity. This was attributed to the smaller vibration amplitude, leading to increased overlap in the thicker portions of the film. In Comparative Example 3, where no vibration was applied, the standard deviation of surface hardness and the hardness difference between two points spaced 60 mm apart further increased, resulting in higher roll-out charge and poor coating uniformity. In Comparative Example 1, the higher winding tension resulted in higher average hardness, higher roll-out charge, and poor coating uniformity.

[0346] In Comparative Example 4, the thickness unevenness caused by factors such as the T-die and film formation conditions has a significant impact, resulting in a higher standard deviation of surface hardness, a higher hardness difference between two points spaced 60 mm apart, and a higher roll-out charge. This is attributed to continuous thickness unevenness that cannot be eliminated through thickness feedback control and vibration.

[0347] Comparative Example 5 does not perform thickness feedback control. It is assumed that the continuous thickness non-uniformity cannot be completely dispersed by vibration alone.

[0348] (Example 8)

[0349] Except for the conditions shown in Table 2, a uniaxially stretched film was obtained in the same manner as in Example 1.

[0350] (Examples 9-19, Comparative Examples 6-16)

[0351] Except for the conditions shown in Table 2, the film was manufactured in the same manner as in Example 8. The elastic modulus was adjusted by changing the stretch ratio. Specifically, the elastic modulus was increased by increasing the stretch ratio and decreased by decreasing the stretch ratio. In Comparative Examples 8, 11, and 12, the unstretched film was stretched in several MD directions using a roller group with a circumferential speed difference, coated with coating liquids P1 and P2, and stretched using a tenter frame. It should be noted that in Comparative Examples 9 and 10, no vibration was applied during film winding.

[0352] (Evaluation of the membrane roll)

[0353] The obtained membranes were evaluated in the same manner as in Example 1. The evaluation results and membrane properties are shown in Tables 2 and 3.

[0354] [Table 2]

[0355]

[0356] [Table 3]

[0357]

[0358] Comparative Examples 6-8 are examples of high winding tension and contact pressure. Comparative Example 7 is an example of insufficient initial knurling height, resulting in increased average surface hardness of the roll. Comparative Examples 9 and 10 are examples of operation without vibration during winding, resulting in a large hardness difference between two points. Comparative Example 12 is an example of low initial knurling, resulting in increased roll charge. Comparative Examples 13 and 14 are examples of excessive initial knurling, resulting in observed winding misalignment and wrinkles. The surface hardness of the rolls in Comparative Examples 15 and 16 is lower. Furthermore, Comparative Example 15 is an example of a film width that is wider than the film thickness, confirming winding misalignment and wrinkles.

[0359] In Examples 8-19, since the winding was performed under appropriate tension and contact pressure conditions, the average surface hardness was also an appropriate value. Furthermore, the film thickness, film width, and initial knurling height were set to a range that effectively balances charge generation and winding appearance, i.e., satisfying the formula 1 ≤ h ≤ 0.1T⁻¹. As a result, winding offset, wrinkles, and flatness were good, and the roll-out charge was low. When these films were used for coating, a uniform and good coating was obtained even up to the center of the roll width direction. In Examples 8-12, the tension and contact pressure were slightly higher, and the roll-out charge was relatively high, but this was not a problem. Furthermore, even with various changes to the elastic modulus of the film, winding offset, wrinkles, flatness, and coating uniformity were good. Example 19 exhibited good winding offset, wrinkles, and flatness, but minor deviations and pinholes were present within an acceptable range at the center of the film width. It was believed that the film width was slightly wider than in other examples, therefore the knurling effect did not fully reach the center of the roll width.

[0360] Industrial availability

[0361] According to the present invention, a long strip resin film can be provided that suppresses winding deviation and / or wrinkle formation and deterioration of winding appearance during storage (especially long-term storage), without damage to the film surface and with excellent film planarity. Furthermore, according to the present invention, a film can be provided that, even under long-term storage, suppresses the charge during winding to the core portion, thereby reducing the charge during film winding, resulting in fewer pinholes in the coating during coating processing, and enabling the application of a coating with excellent thickness accuracy up to the very end of the film.

Claims

1. A strip-shaped resin film, which is wound into a roll. The average roll hardness in the width direction (TD direction) of the roll's surface layer is 300~750. The absolute value of the hardness difference between two points spaced 60mm apart in the width direction of the roll surface is less than 300.

2. The elongated resin film according to claim 1, wherein, The thickness of the elongated resin film is 40µm or more. The elongated resin film satisfies the following formulas 1 and 2. 1≤h≤0.1T-1 Equation 1 W≤40T 2 Where T: film thickness (µm), W: film width (mm), h: initial knurling height (µm).

3. The elongated resin film according to claim 1, wherein, When the elastic modulus in the MD direction of the elongated resin film is set as ME, it satisfies ME≤4000MPa.

4. The elongated resin film according to claim 1, wherein, When the elastic modulus in the TD direction of the elongated resin film is set as TE, it satisfies TE≥6000MPa.

5. The elongated resin membrane according to claim 1, wherein 2≤TE / ME≤4.

6. The elongated resin film according to claim 1, wherein, The standard deviation of the roll hardness in the width direction of the roll surface layer is below 80.

7. The elongated resin film according to claim 1, wherein, The thickness in the TD direction is not uniformly less than 2% over the entire length of the roll.

8. The elongated resin film according to claim 1, wherein, The residual knurling in the core of the roll is more than 1µm.

9. The elongated resin film according to claim 1, wherein the retardation amount is 3000~30000 nm.

10. The elongated resin film according to claim 1, wherein, When the outer surface of the elongated resin film is designated as surface A and the inner surface is designated as surface B, the composition of surface A and surface B are different.

11. The elongated resin film according to claim 1, wherein, When the outer surface of the elongated resin film is designated as surface A and the inner surface is designated as surface B, at least one of surface A or surface B is a coating.

12. A method for manufacturing a laminated film, comprising: Step (A) of rolling out the elongated resin film according to any one of claims 1 to 11; as well as Step (B) involves applying a coating liquid to at least one side of the rolled-out elongated resin film.

13. The manufacturing method according to claim 12, wherein, The laminated film is a polarizing protective film.

14. The manufacturing method according to claim 13, wherein, The laminated film is a film used for thin film transfer printing.

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