Knurled long resin film

Abstract

A problem to be solved by the present invention is to provide a long resin film in which the amount of electrostatic charge is controlled, for example, a long resin film in which electrostatic charge is suppressed up to a winding core section when unwound even after long-term storage in a state of being wound into a roll shape.　The abovementioned problem is solved by a long resin film wound into a roll shape, wherein the average winding hardness of the surface layer of the roll in the width direction (TD direction) is 300 to 750, and the absolute value of the winding hardness difference between two points that are 60 mm apart in the width direction of the surface layer of the roll is 300 or less.

Description

Long resin film with knurling

[0001] The present invention relates to a long resin film and a laminate film wound into a roll, and also to a long resin film and a laminate film that have been subjected to knurling.

[0002] Conventionally, a technique has been known in which, when winding a resin film, knurling (thickening) both ends of the film enables stable winding and prevents winding misalignment and film damage. However, even when a film is wound after knurling, it is known that the knurls are crushed near the core of the roll, preventing the above-mentioned effect from being fully achieved. To address this issue, various knurling techniques have been proposed, such as a method of controlling the size of the knurl convex portion (see, for example, Patent Documents 1 and 2), a method of providing a reinforcing portion in the concave portion (see, for example, Patent Document 3), a method of providing a knurl using a non-contact method (see, for example, Patent Document 4), and a method of controlling the shape and area of ​​the knurl (see, for example, Patent Document 5).

[0003] On the other hand, resin films are often coated with a coating layer on their surface. However, if the film has a high charge level, problems such as repelling of the coating film during coating, increased unevenness in the coating film thickness, and disruption of the orientation of the liquid crystal compound when an alignment layer is applied are encountered. The charge on the film during coating is controlled by discharging the film when it is wound or unwound, but this is not sufficient for the coating of coatings that require high precision in recent years. To address this problem, there have been proposals to use knurling to suppress the relative movement of the wound film and thereby suppress the charge level of the wound film (see, for example, Patent Document 4), but this does not provide sufficient control. There have also been proposals to control the shape of the knurls to suppress the charge level of the film over time (see, for example, Patent Document 5).

[0004] WO11 / 030684 JP 2013-166317 A WO10 / 001752 JP 63-74850 A WO2021 / 200322

[0005] As mentioned above, many proposals have been made in the past, but none of them can adequately control the amount of electrostatic charge on the film. For example, after long-term storage, the amount of electrostatic charge increases near the core of the film, making high-precision coating difficult. Furthermore, the extent to which the amount of electrostatic charge has increased near the core of the film cannot be determined until the film is unwound from the roll, which creates the problem of coating processes not proceeding as planned.

[0006] The main object of the present invention is to provide a long resin film having a controlled amount of charge, for example, a long resin film that can suppress charge up to the core portion when unwound even after long-term storage in a rolled state.

[0007] According to the inventors' investigations, one factor that causes an increase in electrostatic charge when a film is unwound after long-term storage is that the air entrained in the film gradually escapes, but the movement of the air creates areas where the air layer is thin, causing the films to rub strongly against each other in these areas, increasing the amount of electrostatic charge, and also that the surface hardness of the roll in these areas is higher than in other areas.The inventors have found that by reducing sudden fluctuations in the surface hardness of the roll, the electrostatic charge during unwinding is less likely to increase even after long-term storage.

[0008] Furthermore, according to the inventors' investigations, factors that deteriorate the appearance of the roll include a decrease in rigidity due to the thinning of the raw roll and the inclusion of an excess air layer due to high knurling. In particular, when an anisotropic film is used, and the circumferential direction of the roll (also called the machine direction, or MD) is perpendicular to the main orientation direction of the film, it is thought that this is due to the film's tendency to deform in the MD direction. In particular, an increase in friction at the center due to widening is cited as one of the major factors, and it has been found that in order to achieve both charging and good appearance of the roll, it is preferable to keep the raw roll thickness, knurl height, and roll width within optimal ranges during roll production.

[0009] The present inventors further conducted extensive research based on the above findings, and as a result, they were able to complete the present invention. That is, the present invention encompasses the following aspects. [Item 1] A long resin film wound into a roll, wherein the average winding 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 winding hardness between two points spaced 60 mm apart in the width direction of the surface layer of the roll is 300 or less. [Item 2] The long resin film according to Item 1, wherein the thickness of the long resin film is 40 μm or more and the following formulas 1 and 2 are satisfied: 1≦h≦0.1T-1 (1) W≦40T (2) where T: film thickness (μm), W: film width (mm), and h: initial knurl height (μm). [Item 3] The long resin film according to Item 1 or 2, wherein ME, the modulus of elasticity in the MD direction of the long resin film, satisfies ME≦4000 MPa. [Item 4] The long resin film according to any one of Items 1 to 3, wherein TE is the modulus of elasticity in the TD direction of the long resin film, and TE≧6000 MPa is satisfied. [Item 5] The long resin film according to any one of Items 1 to 4, wherein 2≦TE / ME≦4 is satisfied. [Item 6] The long resin film according to any one of Items 1 to 5, wherein the standard deviation of winding hardness in the width direction of the surface layer of the roll is 80 or less. [Item 7] The long resin film according to any one of Items 1 to 6, wherein the thickness variation in the TD direction over the entire length of the roll is 2% or less. [Item 8] The long resin film according to any one of Items 1 to 7, wherein the amount of remaining knurls in the core portion of the roll is 1 μm or more. [Item 9] The long resin film according to any one of Items 1 to 8, wherein the retardation is 3000 to 30000 nm. [Item 10] The long resin film according to any one of Items 1 to 9, wherein, when the outer surface of the long resin film is side A and the inner surface of the long resin film is side B, the compositions of side A and side B are different. [Item 11] The long resin film according to any one of Items 1 to 10, wherein, when the outer surface of the long resin film is side A and the inner surface of the long resin film is side B, at least one of side A and side B is a coating layer.[Item 12] A method for producing a laminate film, comprising: a step (A) of unwinding the long resin film according to any one of items 1 to 11; and a step (B) of applying a coating liquid to at least one surface of the unwound long resin film. [Item 13] The method for producing a laminate film according to item 12, wherein the laminate film is a polarizer protective film. [Item 14] The method for producing a laminate film according to item 13, wherein the laminate film is a thin film layer transfer film.

[0010] According to one aspect of the present invention, it is possible to provide a long resin film having a controlled amount of charge, for example, a long resin film in which charging at the time of unwinding can be suppressed even to the core portion even after long-term storage in a rolled state. According to another aspect of the present invention, it is possible to provide a long resin film in which the occurrence of wrinkles due to winding misalignment and / or deterioration of the roll appearance during storage (especially long-term storage) is suppressed and high flatness and / or coating uniformity are maintained.

[0011] FIG. 2 is a diagram illustrating the position where winding hardness is measured in the long resin film roll of the present invention.

[0012] Representative methods for producing a long resin film according to the present invention include, for example, (1) to (4) below. Details of these methods will be explained in order, but the present invention is not limited to these. (1) When a long resin film is wound onto a roll during the film production process, thick or thin portions of the film are prevented from continuing over a long distance in one location in the width direction. Specific methods include: - Applying sufficient oscillation during film production; - Measuring the thickness in-line and providing feedback to adjust the die slit width; - Uniforming the temperature during film production; - Controlling the die temperature. (2) Uniforming the tension and contact pressure when winding the long resin film onto a roll. Specific methods include: - Optimizing the position and shape of the contact roll; - Optimizing the material and hardness of the contact roll; - Uniforming the diameter of the contact roll; - Optimizing the diameter and hardness of the core; - Controlling the bending and sagging of the long resin film (suppressing sabre formation). (3) Control the amount of air entrained during slitting (SL). Specific methods include: - Controlling the tension and contact pressure during slitting and winding within a certain range. - Particularly for films with a highly anisotropic elastic modulus, lower the tension and increase the contact pressure compared to isotropic films. - Particularly for rolls with knurls, reduce the contact pressure. (4) Control the thickness of the raw roll, roll width, and knurl height. Formula 1: 1≦h≦0.1T-1 Formula 2: W≦40T Where, T: film thickness (μm), W: film width (mm), h: initial knurl height (μm)

[0013] (Long Resin Film) The long resin film (hereinafter sometimes simply referred to as "film") is preferably wound into a roll. The resin constituting the film is not particularly limited, and any resin can be used alone or in combination of two or more. As the resin, polyester, polycycloolefin, triacetyl cellulose, acrylic, polycarbonate, polyamide, polyimide, and polypropylene are preferred, polyester, polycycloolefin, and triacetyl cellulose are more preferred, and polyester is even more preferred. In the case of polyester, polyethylene terephthalate and / or polyethylene naphthalate are preferred.

[0014] The long resin film may be an unstretched film or a stretched film (uniaxially stretched or biaxially stretched film), and is preferably a stretched film, particularly preferably a stretched polyester film.

[0015] The lower limit of the film thickness of the long resin film is preferably 25 μm, more preferably 30 μm, even more preferably 35 μm, and particularly preferably 40 μm. In particular, in applications such as optical films and release films, which require high-precision coating on the film surface, a film with sufficient strength can be obtained by setting the film thickness at or above this lower limit. Furthermore, in order to obtain a film with good winding appearance in the case of an anisotropic long resin film, the lower limit of the film thickness of the long resin film is preferably 40 μm, more preferably 45 μm, even more preferably 50 μm, and particularly preferably 55 μm. Furthermore, the upper limit of the film thickness is preferably 200 μm, more preferably 150 μm, even more preferably 100 μm, particularly preferably 90 μm, and most preferably 80 μm. Setting the film thickness at or below this upper limit can improve productivity.

[0016] The lower limit of the thickness variation (TV) in the TD direction (also referred to 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 keeping it below this upper limit, air infiltration can be suppressed, and wrinkles caused by shrinkage over time and deterioration of the winding appearance can be reduced. TV can be kept within the range by adjusting the die slit width, stretching temperature control, heat setting temperature control, extrusion temperature control, and die design.

[0017] The upper limit of the coefficient of variation of the thickness in the TD direction over the entire length of the roll is preferably 18, more preferably 16, even more preferably 14, particularly preferably 12, and most preferably 10. By setting it to the upper limit or less, air infiltration can be suppressed and wrinkles caused by shrinkage over time can be reduced. The lower limit of the coefficient of variation of the thickness in the TD direction over the entire length of the roll is preferably 0, more preferably 2, and even more preferably 5.

[0018] In this specification, the thickness unevenness and variation coefficient in the TD direction over the entire length of the roll are values ​​determined by the method described in the Examples.

[0019] The lower limit of the film width of the long resin film is preferably 500 mm, more preferably 800 mm, even more preferably 1000 mm, and particularly preferably 1200 mm. Films with widths above this lower limit can usually be made with an increased width to improve productivity, but this tends to increase the amount of charge. However, by applying the present invention, this increase in the amount of charge can be suppressed, and in particular, the increase in the amount of charge can be suppressed even up to the core portion even after long-term storage. The upper limit of the film width is, for example, 3200 mm, preferably 3000 mm, more preferably 2700 mm, even more 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 exhibited, and by setting it to 3000 mm or less, the effects of the present invention can be fully exhibited up to the center in the roll width direction.

[0020] The lower limit of the winding length of the long resin film is preferably 1000 mm, more preferably 1500 mm, even more preferably 2000 mm, and particularly preferably 2600 mm. Films longer than this lower limit are usually prone to an increase in the amount of charge at the winding core, but by applying the present invention, the amount of charge can be suppressed, and in particular, an increase in the amount of charge can be suppressed even at the winding core even after long-term storage, thereby improving productivity. The upper limit of the winding length is preferably 20,000 mm, more preferably 15,000 mm, even more preferably 10,000 mm, and particularly preferably 7,000 mm. By keeping the length below this upper limit, the film can be easily handled in post-processing and the effects of the present invention can be fully exhibited.

[0021] In this specification, the surface layer of a roll refers to the area from the end of the film wound into a roll to 100 m, and the core of a roll refers to the area from the start of the film wound into a roll to 100 m.

[0022] In a long resin film, when the outer surface of the film is called side A and the inner surface of the film is called side B, the compositions of sides A and B may be the same or different. If the compositions of sides A and B are different, the film is likely to become highly charged when unwound. The present invention is preferably applied to such long resin films in which sides A and B have different compositions.

[0023] Examples of cases where the compositions of the A and B sides are different include cases where different raw resins are laminated by coextrusion, where a coating layer is provided on only one of the A and B sides, and where coating layers with different compositions are provided on both the A and B sides. The present invention is suitably applied in all cases. In particular, the present invention is preferably applied to a long resin film in which the coating layers constituting the A and B sides have different resin compositions.

[0024] (Coating layer) Preferred examples of the coating layer include an easy-adhesion layer, an easy-slip layer, a smoothing layer, a hard coating layer, and an orientation control layer. Among these, the long resin film to which the present invention is preferably applied is a film in which at least one surface layer is an easy-adhesion layer, and it is also preferred that the surface layers on both sides are easy-adhesion layers.

[0025] The coating layer may be provided in-line during film production or off-line after film production, but is preferably provided on both sides in-line. In the present invention, the term "film" may refer to a film including the above-mentioned coating layer.

[0026] Preferred examples of the resin used in the coating layer include polyester, acrylic, polyurethane (such as polyester polyurethane, polycarbonate polyurethane, and polyether polyurethane), ethylene vinyl acetate copolymer, polyamide, styrene acrylic copolymer, polyvinyl alcohol, etc. When the coating layer is a hard coating layer, the resin used in the coating layer may be a photocurable resin, or may be a monomer or oligomer of a double bond-containing compound.

[0027] The coating layer is preferably crosslinked. Preferred examples of the crosslinking agent used include isocyanate, amino resins such as melamine, oxazoline compounds, carbodiimide compounds, and epoxy resins. In the case of a photocurable resin, the crosslinking agent may be a compound (monomer or oligomer) containing multiple double bonds, such as trimethylolpropane triacrylate, pentaerythritol tetraacrylate, acrylic-modified polyurethane, or acrylic-modified epoxy resin.

[0028] The coating layer may contain additives, such as particles, surfactants, leveling agents, antistatic agents, catalysts, and combinations thereof.

[0029] The lower limit of the thickness of the coating layer after drying 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 thickness of the coating layer after drying is preferably 20 μm, more preferably 15 μm, even more preferably 10 μm, particularly preferably 7 μm, and most preferably 5 μm. When the coating layer is an easy-adhesion layer, the upper limit of the thickness of the coating layer after drying is preferably 1 μm or less, more preferably 0.5 μm or less, and even more preferably 0.3 μm or less.

[0030] The lower limit of the arithmetic mean roughness (Sa) of at least one surface of the long resin film is preferably 0.2 nm, more preferably 0.4 nm, and even more preferably 0.5 nm. By setting the arithmetic mean roughness (Sa) at or above this lower limit, even if the knurls are slightly crushed at the winding core during storage, an excessive increase in peel charge can be suppressed, and uniform slippage can be imparted, thereby reducing abnormalities in the roll shape. Furthermore, when used as an optical film or a release film, high transparency can be ensured, and when coated on a film, defects can be reduced in the coating. The upper limit of the arithmetic mean roughness (Sa) of at least one surface of the long resin film is preferably 15 nm, more preferably 10 nm, and even more preferably 5 nm. By setting the arithmetic mean roughness (Sa) at or below this upper limit, even if the knurls are slightly crushed at the winding core during storage, an excessive increase in peel charge can be suppressed, and uniform slippage can be imparted, thereby reducing abnormalities in the roll shape. Furthermore, when used as an optical film or a release film, high transparency can be ensured, and when coated on a film, defects can be reduced in the coating.

[0031] (Knurling) It is preferable that the long resin film is knurled at both ends in the film width direction. The lower limit of the distance between the end of the film and the knurl position is preferably 0.5 mm, more preferably 1 mm. The upper limit of the distance between each end of the film width direction and the knurl position is preferably 20 mm, more preferably 15 mm, and even more preferably 10 mm. By setting the distance within the above range, stable knurling can be performed at both ends in the film width direction, and the effective width of the film can be ensured.

[0032] The lower limit of the width of the knurled portion is preferably 3 mm, more preferably 5 mm, and even more preferably 7 mm. By making it equal to or greater than this lower limit, the knurls can be made less likely to be crushed. The upper limit of the width of the knurled portion is preferably 30 mm, more preferably 25 mm, and even more preferably 20 mm. By making it equal to or less than this upper limit, the degree of knurl crushing can be optimized and the effective width of the film can be ensured.

[0033] The lower limit of the spacing between the protrusions of the knurl 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 protrusions of the knurl is preferably 3 mm, more preferably 2.5 mm, even more preferably 2 mm, and particularly preferably 1.5 mm. The spacing between the protrusions is the spacing between the center points of the protrusions.

[0034] The lower limit of the density of the protrusions of the knurl is preferably 10 pieces / cm ２ and more preferably 15 particles / cm ２ and more preferably 25 particles / cm ２ and particularly preferably 40 particles / cm ２ and most preferably 60 particles / cm ２ The upper limit of the density of the protrusions of the knurls is preferably 400 pieces / cm ２ and more preferably 300 particles / cm ２ and more preferably 250 particles / cm ２ , particularly preferably 200 pieces / cm ２ , most preferably 160 cells / cm ２ The crush resistance of the knurl can be adjusted by the density of the convex portions of the knurl, but by setting it within the above range, it becomes easier to adjust the crush resistance by relatively simple knurl processing without placing excessive load on the equipment. Furthermore, within the appropriate range of the ratio of the height per knurl to the convex portion area, it becomes easier to perform knurl processing that is less likely to be crushed.

[0035] The arrangement of the protrusions of the knurls may be, for example, aligned vertically and horizontally, a staggered arrangement in which adjacent protrusions and recesses are shifted by half a period, or a diagonal arrangement in which adjacent protrusions and recesses are shifted by 1 / 3 or 1 / 4.

[0036] The initial knurl height is as described above. Immediately after knurling, the knurl has a portion that easily collapses when wound into a roll. This may be because, in the cold knurling process, the film is pushed out to the opposite side of the knurl by the knurling projections, forming a knurl. Even the extruded knurl has a portion that easily collapses under pressure. In the hot knurling process, the projections formed on the opposite side of the knurl may collapse in the same way. Furthermore, although the resin bulges around the knurling projections, these bulges are not uniform in height but are of uneven height, meaning that the higher bulges collapse easily even with low pressure. The higher bulges may be crushed by contact with the film transport roll and the pressure of the contact roll during winding. Therefore, the initial knurl height is measured on a sample taken from the outermost film immediately after winding into a roll.

[0037] Furthermore, in a film wound into a roll, a phenomenon called winding tightening occurs during storage, causing the height of the knurls to decrease. Therefore, it is preferable to not only adjust the initial knurl height, but also adjust the winding conditions, etc., as described below, so that the surface knurl height and / or the core knurl height, which will be described later, fall within the ranges described later.

[0038] In this specification, the surface knurl height and the core knurl height are values ​​measured by the method described in the Examples. The lower limit of the surface knurl height is preferably 0.8 μm, more preferably 1 μm, even more preferably 1.2 μm, even more preferably 1.3 μm, particularly preferably 1.4 μm, even more particularly preferably 1.5 μm, and most preferably 1.6 μm. By setting the height at or above the lower limit, excessive release of air layers can be suppressed, contributing to the suppression of charging. The upper limit of the surface knurl height is preferably 6 μm, more preferably 5 μm, even more preferably 4 μm, particularly preferably 3.7 μm, and most preferably 3.5 μm. By setting the height at or below the upper limit, poor appearance due to excessive air layers can be suppressed.

[0039] The lower limit of the core knurl height (L) is preferably 0.5 μm, more preferably 0.7 μm, even more preferably 0.9 μm, particularly preferably 1 μm, and most preferably 1.1 μm. By making it equal to or greater than the lower limit, excessive release of the air layer can be suppressed, which can contribute to suppressing charging. The upper limit of the core knurl height (L) is preferably 4 μm, more preferably 3.5 μm, even more preferably 3.2 μm, and particularly preferably 3 μm. By making it equal to or less than the upper limit, it is possible to suppress poor appearance due to excessive intrusion of the air layer.

[0040] The lower limit of the size of the long side and short side of the knurl is preferably 50 μm, more preferably 60 μm, even more preferably 70 μm, and particularly preferably 80 μm. By making it equal to or greater than the lower limit, the holding power of the knurl can be ensured. The upper limit of the size of the long side and short side of the knurl is preferably 1000 μm, more preferably 900 μm, even more preferably 800 μm, and particularly preferably 700 μm. By making it equal to or less than the upper limit, excessive entrainment of air layers can be suppressed.

[0041] (Core Roll) The long resin film is preferably wound around a cylindrical or columnar core. In this specification, a long resin film wound into a roll may be referred to as a film roll or simply a roll. The upper limit of the core outer diameter is preferably 350 mm, more preferably 310 mm, even more preferably 300 mm, even more preferably 290 mm, and particularly preferably 280 mm. By setting the core outer diameter at or below this upper limit, excessively large winding diameters can be prevented, improving handleability. 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 the core outer diameter at or above this lower limit, deflection due to its own weight when the film is wound around the core is reduced, making it easier to suppress the occurrence of wrinkles. Furthermore, the winding tension and contact pressure become uniform in the width direction, making it easier to uniformize the winding hardness of the roll (sometimes referred to as "hardness" in this specification).

[0042] The core width is preferably larger than the film width. The lower limit of the core width minus the film width is preferably 2 mm, more preferably 4 mm. The upper limit of the core width minus the film width is preferably 100 mm, more preferably 60 mm, even more preferably 40 mm, and particularly preferably 20 mm. By setting the width within the above range, the winding operation can be facilitated and handling can be improved.

[0043] (Film Roll Hardness) According to the inventors' studies, film charging is related to the hardness of the film roll (sometimes referred to herein as "winding hardness of the surface layer of the film roll"). It was found that the higher the hardness of the film roll, the greater the film charging when unwinding the film from the core. Furthermore, it was found that the presence of locally high hardness areas or areas with abrupt changes in hardness increases the film charging. The reason for this is thought to be that the film is in strong contact with the hardness areas, which accelerates charging. Even when a film is wound, air spaces exist between the films. However, in areas where the hardness changes rapidly locally, the air spaces move to neighboring areas, causing localized strong contact between the films, which is thought to increase charging. The present invention is based on the idea of ​​suppressing such localized air movement between films, thereby suppressing localized strong contact and suppressing an increase in the amount of charge.

[0044] The lower limit of the average value of the winding hardness in the width direction of the surface layer of the film roll is preferably 300, more preferably 350, even more preferably 400, and particularly preferably 450. By setting the hardness at or above this lower limit, winding slippage of the surface layer due to air intrusion can be suppressed. The upper limit of the average value of the winding hardness in the width direction of the surface layer of the film roll is preferably 750, more preferably 730, even more preferably 710, particularly preferably 700, and most preferably 690. By setting the hardness at or below this upper limit, the film can be prevented from rubbing easily, static electricity can be suppressed, and winding slippage during storage can be suppressed.

[0045] The lower limit of the standard deviation of the winding hardness of the surface layer of the film roll is preferably 0, more preferably 5, even more preferably 10, and particularly preferably 15. The upper limit of the standard deviation of the winding hardness of the surface layer of the film roll is preferably 80, more preferably 75, even more preferably 70, and particularly preferably 65. By setting the standard deviation at or below the upper limit, it is possible to reduce an increase in charging due to rubbing between films.

[0046] The lower limit of the absolute value of the difference in winding hardness between two points spaced 60 mm apart on the surface layer of the film roll is preferably 0, more preferably 10, even more preferably 20, particularly preferably 30, and most preferably 40. The upper limit of the absolute value of the difference in winding hardness between two points spaced 60 mm apart on the surface layer of the film roll is preferably 300, more preferably 290, even more preferably 280, particularly preferably 270, and most preferably 260. By keeping the value below this upper limit, it is possible to reduce an increase in charging due to local rubbing between films.

[0047] The lower limit of the average winding hardness in the width direction of the surface layer of the film roll after 2000 m of the film has been unwound from the film roll is preferably 300, more preferably 350, even more preferably 400, and particularly preferably 450. By setting the hardness at or above this lower limit, winding slippage due to air intrusion can be suppressed. The upper limit of the average winding hardness in the width direction at the 2000 m position is preferably 750, more preferably 730, even more preferably 710, particularly preferably 700, and most preferably 690. By setting the hardness at or below this upper limit, the film can be prevented from rubbing easily, static electricity can be suppressed, and winding slippage during storage can be suppressed. Note that the position at which the winding hardness is measured on the surface layer of the film roll after 2000 m of the film has been unwound from the roll is sometimes simply referred to as the 2000 m position, and this position does not have to be exactly 2000 m, but may be in the range of 2000 to 2050 m.

[0048] The lower limit of the standard deviation of the winding hardness in the width direction of the surface layer of the film roll at the 2000 m position is preferably 0, more preferably 5, even more preferably 10, and particularly preferably 15. The upper limit of the standard deviation of the winding hardness in the width direction at the 2000 m position is preferably 80, more preferably 75, even more preferably 70, and particularly preferably 65. By setting the value at or below the upper limit, it is possible to reduce an increase in charging due to rubbing between films.

[0049] The lower limit of the absolute value of the difference in winding hardness between two points spaced 60 mm apart at a position 2000 m is preferably 0, more preferably 10, even more preferably 20, particularly preferably 30, and most preferably 40. By making it equal to or greater than the above, it is possible to achieve the above. The upper limit of the absolute value of the difference in winding hardness between two points spaced 60 mm apart at a position 2000 m is preferably 300, more preferably 290, even more preferably 280, particularly preferably 270, and most preferably 260. By making it equal to or less than the upper limit, it is possible to reduce an increase in charging due to local rubbing of films against each other.

[0050] Next, a method for producing a film roll of the present invention will be described. The long resin film of the present invention is preferably one obtained by melting a raw resin, extruding it into a sheet, stretching it if necessary, and then winding it into a roll. Furthermore, the present invention also covers long resin films that are slit to the required width and wound up when functional coating is performed.

[0051] The inventors investigated the factors that cause increased static electricity when a film is unwound, especially after long-term storage, and discovered the following: Long resin films wound into rolls have air layers between the films, which suppress static electricity caused by excessive contact and rubbing between the films. As these air layers become thinner, the film becomes more susceptible to static electricity. The air layers gradually escape from the edges of the film, but the movement of air between the films creates areas where the air layers are thin, causing the films to rub strongly against each other in these areas, increasing the amount of static electricity. Air movement between films is not only caused by uneven winding tension and contact pressure, but also by consecutive thick and thin film sections in the same position. The cushioning properties of the air-loosed areas decrease, increasing the surface hardness of the roll.

[0052] To suppress the above factors, we have found that it is preferable to manufacture a film roll by controlling and combining the following (1) to (3): (1) When winding a long resin film onto a roll in the film production process, prevent a long distance of thick or thin film from forming in one location in the width direction. Specific methods include: ・Applying sufficient oscillation during film production; ・Measuring the thickness in-line and providing feedback to adjust the die slit width; ・Uniformizing the temperature during film production; ・Controlling the die temperature. (2) Uniformizing the tension and contact pressure in the width direction when winding a long resin film onto a roll. Specific methods include: ・Optimizing the position and shape of the contact roll; ・Optimizing the material and hardness of the contact roll; ・Uniformizing the diameter of the contact roll; ・Optimizing the diameter and hardness of the core; ・Controlling the bending and sagging of the long resin film (suppressing sabre formation). (3) Controlling the amount of air entrained during slitting (SL). Specific methods include: - Controlling the tension and contact pressure during slit winding within a certain range; - Lowering the tension and increasing the contact pressure, especially for films with a highly anisotropic elastic modulus, compared to isotropic films; - Reducing the contact pressure, especially for rolls with knurls.

[0053] The method for producing a film roll will be described in more detail using a biaxially stretched polyethylene terephthalate (PET) film as an example, but the present invention is not limited thereto.

[0054] The raw material PET resin is fed into an extruder, and the melt-kneaded resin is extruded through a die with a long, narrow slit onto a cooling roll to form an unstretched sheet. The temperature of the molten resin is preferably 240 to 260°C, more preferably 245 to 255°C. To facilitate uniform thickness of the unstretched sheet, it is preferable to control the temperature of the resin so that it is uniform from the die to the slit. In addition, it is preferable to design the flow path of the die so that the amount of resin extruded is constant in the width direction.

[0055] The slit portion of the die is preferably provided with a mechanism for adjusting the slit width, so that the slit width can be adjusted during film production. Examples of adjustment methods include a motor-driven adjustment bolt, a piezoelectric actuator, a heat bolt, and a hydraulic method. The slit width is preferably adjusted by feeding back film thickness data obtained by an in-line film thickness measuring device, which will be described later.

[0056] The PET sheet is stretched in the MD (machine direction, lengthwise direction) by a group of rolls with different peripheral speeds, and then guided into a tenter with both ends in the width direction fixed with clips. The MD stretching temperature is preferably 80 to 120°C, more preferably 85 to 110°C.

[0057] The film is preheated to a temperature suitable for stretching in a tenter and then stretched in the TD direction (width direction). The width direction stretching temperature is preferably 85 to 130°C. During tenter stretching, the clip section may not heat up easily or there may be areas where the temperature does not rise easily due to mutual interference between hot air blows, resulting in thickness unevenness. To suppress thickness unevenness, it is preferable to adopt methods such as increasing the air volume around the clip or using a nozzle that blows hot air so that the film surface has a uniform temperature. Furthermore, if the air volume is low, the film temperature is likely to be uneven. If the air volume is too high or unevenly distributed between the top and bottom, the film may bend and sag, making it difficult to achieve uniform tension during winding. Note that bending and sag are specified in JIS C2151:2019. To achieve uniform TD stretching, the TD stretch ratio in the tenter is preferably 3x or more, more preferably 3.2x or more, and even more preferably 3.3x or more.

[0058] After stretching, the film is heat-set. The heat-set temperature is preferably 150 to 250°C, more preferably 170 to 240°C. In heat-set, as with tenter stretching, it is preferable to achieve a uniform film temperature in the width direction. Uniform heat-set makes it easier to reduce sabre foam. After heat-set, relaxation treatment may be performed if necessary. The relaxation treatment is preferably 0.5 to 5%.

[0059] When a coating layer such as an easy-adhesion layer is provided in-line, it is preferable to coat it immediately before tenter stretching. In this case, after coating, drying may be performed in a separate dryer, or drying may be performed in the preheating to stretching zone of the tenter. Furthermore, when the coating layer is crosslinked, it is preferable to crosslink it at the heat setting temperature, and when it is crosslinked by radiation, it is preferable to crosslink it after heat setting and before winding.

[0060] The film discharged from the tenter is wound into a roll after the portions held by the clips are cut off. It is preferable to measure the film thickness in the width direction before winding. Examples of film thickness measurement methods include, but are not limited to, ultraviolet light methods, radiation methods such as X-rays and β-rays, and optical interference methods. A plurality of fixed film thickness meters may be installed in the TD direction, or one or several film thickness meters may be scanned in the TD direction to measure.

[0061] The obtained film thickness data is preferably fed back and used to control the die slit width. That is, it is preferable to narrow the slit width in thicker film sections and widen it in thinner film sections to prevent thick or thin sections from continuing for long periods. Furthermore, even if the thickness unevenness is acceptable in terms of film quality, it can affect the hardness of the film when it is wound over, so if there are continuous thick sections, the control may be to make those sections thinner than the average. Control methods include P control, PI control, PD control, and PID control.

[0062] The winding device used in the winding process generally employs straight winding, in which the film is wound around the core in order so that the side edges of the film are aligned, or oscillating winding, in which the film is wound around the core so that the side edges of the film oscillate within a certain range in the width direction, but oscillating winding is preferred. By employing oscillating winding, it is possible to prevent thin or thick portions from being wound continuously in the same position.

[0063] The lower limit of the film amplitude during oscillatory winding is preferably 25 mm, more preferably 35 mm, even more preferably 45 mm, and particularly preferably 55 mm. By setting the amplitude at or above this lower limit, it is possible to suppress a decrease in the thickness of the product due to thickness unevenness caused by the raw roll. The upper limit of the oscillation width is preferably 500 mm, more preferably 450 mm, even more preferably 400 mm, and particularly preferably 350 mm. By setting the amplitude at or below this upper limit, it is possible to reduce the width of the unproductable selvage portions at both ends of the film width direction, thereby improving productivity. The lower limit of the movement speed (winding speed) of the winding machine during oscillatory winding is preferably 5 mm / min, more preferably 10 mm / min, even more preferably 15 mm / min, and particularly preferably 20 mm / min. By setting the amplitude at or above this lower limit, it is possible to suppress deterioration of flatness or charging due to partial accumulation of fixed thickness unevenness. The upper limit of the winding speed in oscillating winding is preferably 100 mm / min, more preferably 95 mm / min, even more preferably 90 mm / min, and particularly preferably 85 mm / min. When the speed is equal to or less than the upper limit, wrinkles can be easily suppressed during transport and winding of the film.

[0064] The film thus wound up after production may be used as is in the next processing step, such as providing a coating layer, but it is preferable to unwind the film after production, slit it to the required width and length, and then wind it up again into a roll. The present invention is applicable to rolls of film after production, but is preferably applied to film rolls after slitting.

[0065] (Knurling) Furthermore, as an example of knurling, a method that is commonly used and in which a film is pressed against knurling to deform the film will be described in detail, but the present invention is not limited to this.

[0066] The knurling material is preferably a metal, such as SUS, stainless steel, aluminum, titanium, hard chrome, etc. The surface of the knurling may be plated.

[0067] The lower limit of the diameter of the knurling is preferably 30 mm, more preferably 50 mm. The upper limit of the diameter of the knurling is preferably 300 mm, more preferably 250 mm, and even more preferably 200 mm. By setting the diameter within the above range, a knurling device of appropriate size can be obtained.

[0068] The lower limit of the knurling thickness is preferably 3 mm, more preferably 5 mm, and even more preferably 7 mm. The upper limit of the knurling thickness is preferably 50 mm, more preferably 40 mm, and even more preferably 30 mm.

[0069] The outer periphery of the knurling has protrusions formed in accordance with the arrangement of the convex portions to be formed. The lower limit of the height of the protrusions is preferably 0.05 mm, more preferably 0.1 mm, even more preferably 0.15 mm, and particularly preferably 0.2 mm. The upper limit of the height of the protrusions is preferably 3 mm, more preferably 2.5 mm, even more preferably 2 mm, and particularly preferably 1.5 mm.

[0070] The shape of the knurling projections, as viewed from above, is preferably a circle, ellipse, triangle, square, rectangle, rhombus, trapezoid, pentagon, hexagon, or polygon of higher order, with square, rectangle, and rhombus being more preferred. Furthermore, the three-dimensional shape may be a pyramid such as a cone or polygonal pyramid, or a truncated pyramid such as a truncated cone or polygonal pyramid, but knurls provided in a truncated pyramid shape tend to be less likely to be crushed.

[0071] When the protrusions are frustum-shaped, the lower limit of the area of ​​each flat portion of the upper side of the protrusion is preferably 40,000 μm ２ and more preferably 50,000 μm ２ and more preferably 60,000 μm ２ and particularly preferably 80,000 μm ２ The upper limit of the area of ​​each flat portion on the upper side of the protrusion is preferably 200,000 μm ２ and more preferably 170,000 μm ２ and more preferably 150,000 μm ２and particularly preferably 130,000 μm ２ is.

[0072] When the protrusions are frustum-shaped, the lower limit of the angle of the inclined surface of the protrusions is preferably 25°, more preferably 30°, and even more preferably 40°. By making the angle equal to or greater than the lower limit, handling properties can be improved. When the protrusions are frustum-shaped, the upper limit of the angle of the inclined surface of the protrusions is preferably 90°, more preferably 80°, and even more preferably 70°.

[0073] When the protrusions are frustum-shaped, the lower limit of the total area of ​​the flat portions on the upper surfaces of the protrusions relative to the area of ​​the outer periphery of the knurling where the protrusions are provided is preferably 1%, more preferably 3%, even more preferably 5%, particularly preferably 8%, and most preferably 10%. When the protrusions are frustum-shaped, the upper limit of the total area of ​​the flat portions on the upper surfaces of the knurling protrusions relative to the area of ​​the outer periphery of the knurling where the protrusions are provided is preferably 50%, more preferably 40%, even more preferably 30%, and particularly preferably 20%.

[0074] When the protrusions are conical, the lower limit of the angle of the apex of the protrusion is preferably 30°, more preferably 60°, even more preferably 80°, particularly preferably 90°, and most preferably 100°. The upper limit of the angle of the apex is preferably 160°, more preferably 150°, and even more preferably 140°.

[0075] The lower limit of the knurling temperature is preferably 10°C, more preferably 20°C.

[0076] (Roll winding conditions) The lower limit of the winding tension is preferably 50 N / m, more preferably 60 N / m, even more preferably 70 N / m, particularly preferably 80 N / m, and most preferably 90 N / m. By setting the tension at or above this lower limit, the air layer can be appropriately removed, and wrinkles and winding misalignment can be suppressed. The upper limit of the winding tension is preferably 280 N / m, more preferably 270 N / m, even more preferably 260 N / m, particularly preferably 250 N / m, and most preferably 240 N / m. By setting the tension at or below this upper limit, the air layer can be appropriately introduced, and charging can be suppressed.

[0077] The lower limit of the winding contact pressure of the contact roll is preferably 30 N / m, more preferably 40 N / m, even more preferably 50 N / m, and particularly preferably 60 N / m. By making it equal to or greater than this lower limit, it is possible to appropriately expel air layers and suppress wrinkles. The upper limit of the winding contact pressure of the contact roll is preferably 600 N / m, more preferably 500 N / m, even more preferably 400 N / m, and particularly preferably 300 N / m. By making it equal to or less than this upper limit, it is possible to appropriately introduce air layers and suppress charging.

[0078] The material of the contact roll is not particularly limited, and examples thereof include rubber, resin, metal, and ceramics. However, it is preferable that the surface of the contact roll is rubber-based, as this makes it easier to apply uniform pressure across the width of the roll.

[0079] The lower limit of the surface hardness of the contact roll is preferably 40, more preferably 45, still more preferably 50, and particularly preferably 55, in Shore A. The upper limit of the surface hardness of the contact roll is preferably 100, more preferably 95, still more preferably 90, and particularly preferably 85, in Shore A.

[0080] The shape of the contact roll may be any of straight, crown contact roll that follows the deflection of the film roll, tapered crown, and inverted crown (concave). The shape can be selected so that the contact pressure is easily uniform in the width direction of the film depending on the positional relationship between the contact roll and the film roll.

[0081] The lower limit of the contact roll circumference is preferably 100 mm, more preferably 150 mm, even more preferably 200 mm, and particularly preferably 250 mm. The upper limit of the contact roll circumference is preferably 800 mm, more preferably 750 mm, even more preferably 700 mm, and particularly preferably 650 mm. By setting the length within the above range, it is easy to apply a uniform contact pressure in the film width direction, and handling is also excellent.

[0082] In the present invention, in order to suppress an increase in unwinding charge after long-term storage, for example, for three months or more, it is preferable that the film roll immediately after production has the above-described surface winding hardness characteristics, and that the surface winding hardness characteristics are maintained even after long-term aging. The aging period of the roll is preferably three months (90 days) or more, and more preferably four months (120 days) or more after production. That is, it is preferable that the film roll has the winding hardness characteristics of the present invention after three months, more preferably four months, have been produced. Furthermore, the longer the period for which the winding hardness characteristics are maintained, the more preferable. Although there is no particular upper limit, it is preferable that the winding hardness characteristics of the present invention be maintained for a period of preferably 24 months (730 days), more preferably 22 months (670 days), even more preferably 20 months (610 days), and particularly preferably 18 months (548 days). According to the inventors' investigations, the state of the surface winding hardness is almost stable after three months, and thereafter, although the average winding hardness and winding hardness difference tend to increase slightly, no decrease is observed. Therefore, if the winding hardness characteristics of a film roll that has been manufactured for more than three months are within the range of the winding hardness characteristics of the present invention when measured, it is considered that the winding hardness characteristics will also be within said range three months after manufacturing. The film roll is preferably stored in a resin bag made of polyethylene, polypropylene, nylon, or the like together with a moisture absorbent, with the opening sealed, at a temperature of 5 to 30°C and a humidity of 20 to 80% RH, within the range of seasonal and daily fluctuations.

[0083] (Core Charging) Even after long-term storage, charging of the film roll when unwound is suppressed, allowing the core portion to be effectively utilized. The upper limit of the absolute value of the core charge when unwound is, for example, 53 kV, preferably 45 kV, more preferably 40 kV, even more preferably 35 kV, particularly preferably 30 kV, and most preferably 25 kV. By keeping the voltage below this upper limit, unevenness during surface coating can be suppressed.

[0084] In a roll of a long resin film provided with knurls, winding slippage and deterioration of the roll appearance are likely to occur. The present inventors have found that in the case of a long resin film with high anisotropy, particularly a film having a main orientation axis in the TD direction, it is preferable to control not only the initial height of the knurls but also the film thickness, roll width, and knurl height. Specifically, (4) it is preferable to adjust the original film thickness, roll width, and knurl height within the ranges of equations 1 and 2. Equation 1: 1≦h≦0.1T-1 Equation 2: W≦40T Where, T: film thickness (μm), W: film width (mm), h: initial knurl height (μm).

[0085] In terms of the relationship between the film width W (mm) and the film thickness T (μm), the lower limit of W / T is preferably 20, more preferably 21, even more preferably 22, particularly preferably 23, and most preferably 24. By setting the value above the lower limit, the cutting width relative to the thickness can be set higher, thereby improving productivity. In other words, W≧20T is preferred, W≧21T is more preferred, W≧22T is even more preferred, W≧23T is particularly preferred, and W≧24T is most preferred. The upper limit of W / T is preferably 40, more preferably 38, even more preferably 36, particularly preferably 35, and most preferably 34. By setting the value below the upper limit, the knurling effect can be fully imparted across the entire roll width direction. In other words, W≦40T is preferred, W≦38T is more preferred, W≦36T is even more preferred, W≦35T is particularly preferred, and W≦35T is most preferred. The film thickness corresponds to the thickness of the raw roll, and the film width corresponds to the roll width.

[0086] In the relationship between the film thickness T (μm) and the initial knurl height h (μm), the upper limit of the initial knurl height h is preferably 0.1T-1, more preferably 0.1T-1.1, even more preferably 0.1T-1.2, and most preferably 0.1T-1.3. By keeping the initial knurl height h below this upper limit, excessive air entrapment can be prevented, resulting in a good appearance. Note that the thicker the film, the larger h can be, but the upper limit of the initial knurl height h (μm) is preferably 15 μm or less, more preferably 12 μm or less, even more preferably 10 μm or less, particularly preferably 7 μm or less, and most preferably 6 μm or less. By keeping it below this value, an appropriate knurl processing speed can be achieved, the load on the knurl processing device is reduced, and breakage and malfunction are less likely to occur. When T≧60, the lower limit of the initial knurl height h (μm) is preferably (0.1T−5) μm, more preferably (0.1T−4.8) μm, even more preferably (0.1T−4.6) μm, and most preferably (0.1T−4.4) μm. When T<60 μm, the lower limit of the initial knurl height h (μm) is preferably 1 μm, more preferably 1.2 μm, even more preferably 1.4 μm, even more preferably 1.5 μm, and most preferably 1.6 μm, and may be 2 μm or 2.5 μm. By making the height equal to or greater than this lower limit, the knurl effect can be imparted to the entire width direction of the roll. Details of the knurls will be described later. In this specification, the initial knurl height is a value measured by the method described in the examples.

[0087] Control using Equations 1 and 2 can exert a good effect on long resin films having 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, even more preferably 2.2, particularly preferably 2.3, and most preferably 2.4. By setting the ratio at or above this lower limit, productivity can be improved. Furthermore, the upper limit of TE / ME is preferably 4.5, more preferably 4.3, even more preferably 4.2, particularly preferably 4.1, and most preferably 4. By setting the ratio at or below this upper limit, it is possible to reduce the tendency to tear due to anisotropy.

[0088] The lower limit of the MD modulus of elasticity (ME) is preferably 1000 MPa, more preferably 1500 MPa, even more preferably 1800 MPa, particularly preferably 2000 MPa, and most preferably 2200 MPa. By setting it to above the lower limit, the strength increases and the breaking elongation can be improved. The upper limit of ME is preferably 4000 MPa, more preferably 3800 MPa, even more preferably 3600 MPa, particularly preferably 3400 MPa, and most preferably 3200 MPa. By setting it to below the upper limit, the anisotropy in the TD direction can be increased.

[0089] The upper limit of the TD modulus of elasticity (TE) is preferably 20,000 MPa, more preferably 18,000 MPa, even more 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 heat shrinkage can be suppressed. The lower limit of TE is preferably 6,000 MPa, more preferably 6,200 MPa, even more preferably 6,400 MPa, particularly preferably 6,600 MPa, and most preferably 6,800 MPa. By setting it above this lower limit, strength can be increased and breaking elongation can be improved.

[0090] The lower limit of the average of ME and TE ((ME + TE) / 2: average modulus) is preferably 3000 MPa, more preferably 3500 MPa, and most preferably 4000 MPa. By setting it at or above this lower limit, strength increases and breaking elongation can be improved. The upper limit of the average modulus is preferably 8000 MPa, more preferably 7000 MPa, and most preferably 6000 MPa. By setting it at or below this upper limit, internal stress increases, making it easier to suppress problems such as an increase in heat shrinkage.

[0091] Furthermore, in birefringent films such as polyester films, anisotropy can also be expressed by retardation. Retardation is a parameter defined by the product (ΔNxy × d) of the anisotropy of the refractive index of two orthogonal axes on the film (ΔNxy = |nx - ny|) and the film thickness d (nm), and is a measure of optical isotropy and anisotropy. The anisotropy of the biaxial refractive index (ΔNxy) can be determined by the following method. Using a molecular orientation meter (MOA-6004 molecular orientation meter manufactured by Oji Measurement Instruments Co., Ltd.), the slow axis direction of the film is determined, and a 4 cm × 2 cm rectangle is cut out so that the slow axis direction is parallel to the long side of the measurement sample, and used as a measurement sample. For this sample, the refractive index of two orthogonal axes (refractive index in the slow axis direction: ny, refractive index in the direction perpendicular to the slow axis direction: nx) and the refractive index in the thickness direction (nz) were measured using an Abbe refractometer (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm), and the absolute value of the difference in refractive index between the two axes (|nx-ny|) was taken as the refractive index anisotropy (ΔNxy). The film thickness d (nm) was measured using a Millitron HKT-1202 manufactured by Fujiwork Co., Ltd., and the unit was converted to nm. The retardation (Re) can be calculated from the product (ΔNxy × d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

[0092] The lower limit of the retardation (Re) of the long resin film is preferably 3000 nm, more preferably 4000 nm, and most preferably 5000 nm. By making it equal to or greater than this lower limit, it is possible to reduce rainbow unevenness that occurs when used in a polarized environment such as an image display device. The upper limit of the retardation is preferably 20000 nm, more preferably 10000 nm, even more preferably 9000 nm, and most preferably 8700 nm. By making it equal to or less than this upper limit, it is possible to suppress high anisotropy and the tendency to tear. The upper limit of the retardation may be 8500 nm or 8000 nm, from the viewpoint of being able to accommodate thinning in applications in which the film is used, such as image display devices.

[0093] The lower limit of the ratio Re / Rth of the retardation (Re) to the thickness retardation (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.

[0094] The present inventors have found that, particularly in highly anisotropic films, tensioning is more likely to occur, the winding appearance is more likely to deteriorate, and static electricity is more likely to occur, and that these phenomena tend to become more pronounced as the film thickness decreases. In particular, they have found that, in thin films, increasing the knurling to control the amount of static electricity can lead to a deterioration in the winding appearance after long-term storage, and the roll of film, which should be cylindrical, can easily become slightly polygonal, resulting in poor flatness of the unwound film. Even in highly anisotropic thin films, optimizing the thickness, roll width (width of the long resin film), and knurling height of the long resin film can suppress unwinding static electricity and improve the winding appearance and flatness of the film.

[0095] (Use of Film Roll) The film roll can be further subjected to various post-processing processes to form a laminated film. Examples of post-processing include coating, vapor deposition, and sputtering, and coating is particularly suitable for use as a laminated film. When unwinding the film in post-processing, the film may be neutralized between the unwinding section and the post-processing section, and neutralization at the unwinding section is particularly preferred. Methods for neutralization include contacting the film with a conductive member such as a neutralization brush, and spraying ions (charged gas).

[0096] In one embodiment, the present invention relates to a method for producing a laminated film, including a step (A) of unwinding a long resin film and a step (B) of applying a coating liquid to at least one surface of the unwound long resin film.

[0097] Resins used in the coating liquid include polyester, acrylic resin, polyurethane (e.g., polyester polyurethane, polycarbonate polyurethane, polyether polyurethane), ethylene vinyl acetate copolymer, polyamide, styrene acrylic copolymer, polyvinyl alcohol, etc., and if a radiation-curable coating film is to be formed, acrylic monomers, acrylic oligomers, and polymerizable liquid crystal compounds are preferably used. Of these, acrylic monomers, acrylic oligomers, and polymerizable liquid crystal compounds are preferably used.

[0098] The solvent for the coating liquid is preferably toluene, alcohol, ketone or ester, but if the coating liquid is radiation-curable, it may be solvent-free.

[0099] The lower limit of the thickness of the coating film obtained by applying the coating liquid in step (B) after drying 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 thickness of the coating film obtained after drying is preferably 20 μm, more preferably 15 μm, even more preferably 10 μm, particularly preferably 7 μm, and most preferably 5 μm.

[0100] The resulting coating film is preferably an optically functional coating film such as a hard coat layer, an antiglare layer, an antireflection layer, a low reflection layer, a retardation layer, etc. The resulting coating film may also be an adhesive or a pressure-sensitive adhesive.

[0101] Preferred uses of the film provided with the coating film include an antiglare film, a low-reflection film, an anti-reflection film, a transparent conductive film substrate, a polarizer protective film, a retardation film whose retardation layer is made of a liquid crystal compound, or a thin film layer transfer film for transferring these functional layers.

[0102] The present invention will be described in more detail below using examples, but the present invention is not limited to the embodiments of these examples and can be modified as appropriate within the scope of the invention.

[0103] (1) Measurement of Winding Hardness of the Surface Layer of the Film Roll The hardness of the film roll was measured using an Equotip 550 hardness tester manufactured by Prosek GmbH, Switzerland. Specifically, the film roll of the present invention, which was wound using a slitter, was unwound using a film unwinder, and the hardness was measured. The hardness was measured at 20 mm intervals across the roll width, and the average winding hardness at each position was taken as the average winding hardness. The difference between each measurement and a measurement taken at a point 60 mm apart was calculated, and the maximum absolute value was taken as the winding hardness difference between two points at 60 mm intervals. The measurement point across the width of the film roll surface was a position 50 mm across from the end of the film where the winding direction of the film from the core toward the outermost surface becomes clockwise, and then a further 20 mm increments were measured to the end. If the final position was less than 50 mm from the end of the film, it was excluded from the calculation.

[0104] This will be explained in more detail with reference to Figure 1. In Figure 1, the film end where the winding direction of the film from the core toward the outermost surface of the film roll is clockwise is the left side, and the position 50 mm from the left end of the film roll is position number 1. The position 20 mm away from the other end (right) is position number 2, and this is repeated at 20 mm intervals until the distance from the other end is less than 50 mm. Positions less than 50 mm are not measured, so if the position number of the other end is n, position number n is 50 mm or more but less than 70 mm from the other end. The arithmetic average of the n winding hardnesses at positions 1 to n is the average winding hardness. Furthermore, the position 60 mm away from position number 1 is position number 4, and the absolute value of the difference between these two points is calculated. This process is repeated up to position numbers n-3 and n to calculate the absolute value of the difference between the two points, and the largest absolute value among the n-3 obtained is the winding hardness difference between two points spaced 60 mm apart.

[0105] (2) Thickness Unevenness (TV) Using a contact-type continuous thickness meter manufactured by Micron Measuring Instruments Co., Ltd. (the thickness meter part was manufactured by Anritsu Electric Co., Ltd.), a rectangular measurement sample was cut out from the obtained film, measuring approximately 40 mm in the MD direction and the entire width in the TD direction excluding a 20 mm portion from the edge. That is, the long side of the measurement sample was parallel to the TD direction, and the length of the long side of the measurement sample was the width of the film roll minus 40 mm, and the length of the short side was 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 acquired at 0.1 second intervals. From the obtained data, the maximum thickness at each measurement position was defined as Tmax, the minimum thickness as Tmin, and the average thickness as Tave, and the thickness unevenness in the TD direction, TV (%), was calculated as (Tmax - Tmin) / Tave x 100. The standard deviation Stdev and coefficient of variation (Stdev / Tave x 100) of the thickness measurements in the TD direction were also calculated from the obtained data. Samples were taken from a position 10 m from the end of the roll toward the beginning of the roll, and then every 400 m thereafter. If wrinkles or the like were found at the sample position, samples were taken from areas without wrinkles before or after. The maximum values ​​of TV and coefficient of variation of the samples taken from each position on the roll were used as the values ​​of TV and coefficient of variation over the entire length of each roll.

[0106] (3) Knurl height Measurements were performed using a digital micrometer (Sony Manufacturing Systems Corporation μ-mate M-30). Ten measurements were taken at approximately 5 cm intervals along the MD at the center of the width of the knurl-processed portion, and the average value was taken as the knurl thickness. Ten measurements were taken at approximately 5 cm intervals along the MD about 1 cm inside from the knurl, and the average value was taken as the film thickness. The knurl thickness minus the film thickness was taken as the knurl height. Immediately after winding, the second layer of film was sampled from the roll surface, and the knurl height was measured. The average of these measurements on the right and left sides was taken as the initial knurl height. After winding, the film was unwound into a roll and stored at room temperature for 4 months. Measurements were performed at a total of four locations on the surface and core of the film on both the right and left sides. These were taken as the surface knurl height and the core knurl height, respectively. For samples after storage, the knurl height measured at the second and third turns from the outermost layer, in addition to the surface layer, can be considered the initial knurl height. This is because pressure is less likely to be applied to the outermost layer and there is almost no change in the knurl height even over time, so it can be considered the initial knurl height immediately after rolling up.

[0107] The terms right side, left side, surface layer, and core are as follows: Right side: The right edge when an observer faces the roll and unwinds the film from the top of the roll towards the observer. Left side: The left edge when an observer faces the roll and unwinds the film from the top of the roll towards the observer. Surface side: 100 m from the end of the film wound into a roll. Core: 100 m from the start of the film wound into a roll.

[0108] The abbreviations for the knurl heights at each location are as follows: Surface right knurl height: Hner Surface left knurl height: Hnel Core right knurl height: Hnbr Core left knurl height: Hnbl

[0109] (4) Nar survival rate The following is the rate of right nar survival: Hnbr / Hner The rate of left nar survival: Hnbl / Hnel

[0110] (5) Unwinding Charge Amount After 4 months of storage in a room at a temperature of 25±2°C and a humidity of 40±20%, the rolled film was unwound from the surface at a speed of 100 m / min, and the film charge amount at the center of the film core was measured. The measurement was carried out using a KSD-1000 manufactured by Kasuga Electric Co., Ltd., and the part of the film immediately after peeling from the roll was measured.

[0111] (6) Winding Misalignment The end surface of the rolled film was observed after 4 months of storage indoors at a temperature of 25±2°C and a humidity of 40±20%. ◎: No change from the state immediately after winding, no irregularities. ○: A slight increase in irregularities or a bamboo-like deformation was observed. △: An increase in irregularities or a bamboo-like deformation was observed, but at a level that did not pose a problem for practical use. ×: An increase in irregularities or a bamboo-like deformation was observed to the extent that it could not be used for practical use.

[0112] (7) Wrinkles After 4 months of storage in a room at a temperature of 25±2°C and a humidity of 40±20%, the roll film was unwound and inspected for wrinkles along its entire length. ◎: No wrinkles at all. ○: Slight wrinkles were observed along a portion of the entire length. △: Weak wrinkles were observed along a portion of the entire length, but to an acceptable level. ×: Wrinkles were observed along a portion of the entire length to the extent that they could not be used in practice.

[0113] (8) Film Flatness After 4 months of storage indoors at a temperature of 25±2°C and a humidity of 40±20%, the rolled film was unwound, and a 3-m length of the film was cut from a position 80 to 90 m from the surface. This was placed on a table with a flat, matte black top, and flatness was evaluated by the shape of the ceiling fluorescent light reflected on the film. The flatness was compared with the flatness of the film immediately after it was wound up. ◎: No change from the sample immediately after it was wound up. ○: Flatness slightly deteriorated. △: Flatness deteriorated, but to an acceptable level. ×: Flatness deteriorated to the point where it could not be used practically.

[0114] (9) Sa and Sq Measurements were made in accordance with ISO 25178 using a non-contact surface shape measurement system (VertScan R550H-M100, manufactured by Ryoka Systems Co., Ltd.) under the following conditions. The average value of five samples was used. (Measurement conditions) Measurement mode: WAVE mode Objective lens: 10x 0.5x Tube lens Measurement area: 936 μm x 702 μm (Analysis conditions) Surface correction: 4th order correction Interpolation processing: Full interpolation ISO parameter processing: S-Filter 10 μm specification

[0115] (10) Retardation (Re) Retardation is a parameter defined by the product (ΔNxy × d) of the anisotropy of the refractive index of two orthogonal axes on a film (ΔNxy = |nx - ny|) and the film thickness d (nm), and is a measure of optical isotropy and anisotropy. The anisotropy of the biaxial refractive index (ΔNxy) was determined by the following method. Using a molecular orientation meter (MOA-6004 molecular orientation meter manufactured by Oji Measurement Instruments Co., Ltd.), the slow axis direction of the film was determined, and a 4 cm × 2 cm rectangle was cut out so that the slow axis direction was parallel to the long side of the measurement sample, and used as a measurement sample. For this sample, the refractive index of two orthogonal axes (refractive index in the slow axis direction: ny, refractive index in the direction perpendicular to the slow axis direction: nx) and the refractive index in the thickness direction (nz) were measured using an Abbe refractometer (manufactured by Atago Co., Ltd., NAR-4T, measurement wavelength 589 nm), and the absolute value of the difference in refractive index between the two axes (|nx-ny|) was taken as the refractive index anisotropy (ΔNxy). The film thickness d (nm) was measured using a Millitron HKT-1202 manufactured by Fujiwork Co., Ltd., and converted to units in nm. The retardation (Re) was calculated from the product (ΔNxy × d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

[0116] (11) Elastic Modulus The tear propagation strength of polyethylene terephthalate resin films was evaluated by a tensile test in accordance with Section 7.2 of JIS C2318. Test specimens were cut into 180 mm x 10 mm rectangles, with the direction of elastic modulus measurement being the long side. 10 mm long marked lines parallel to the short sides were drawn 40 mm inward from both short sides of the test specimen. The thickness (mm) of the test specimen was measured at five points in a 100 mm long section between the marked lines, and the average value was calculated. The product of these values ​​and the width (10 mm) of the test specimen was used as the cross-sectional area (mm2) of the test specimen. The film thickness was measured using an electric micrometer (Millitron HKT-1202, manufactured by Fujiwork Co., Ltd.). The tensile test was performed by gripping the area from the marked lines to the short sides with a chuck so that the long side of the test specimen was the tensile direction. The tensile test was performed using a precision universal testing machine (Shimadzu Corporation, Autograph AGX-V) with a chuck distance of 100 mm and a tensile speed of 100 mm / min. The elastic modulus was calculated from the strain value under a load of 5-10 N.

[0117] With reference to the examples in the specification of WO2021 / 200322, a coating material for an easy-adhesion layer and a resin for a base polyester film were produced.

[0118] (Preparation of Coating Solution for Adhesion Layer P1) The following raw materials were mixed to prepare a coating solution: The coating solution was filtered through a 10 μm filter (nominal filtration accuracy: 95% cutoff of 10 μm particles). Water 40.61% by mass, Isopropanol 30.00% by mass, Polyester aqueous dispersion 11.67% by mass, Polyvinyl alcohol aqueous solution (solid content 10% by mass) 15.00% by mass, Blocked isocyanate crosslinking agent (aqueous solution) 0.67% by mass, Particles (silica sol having an average particle size of 100 nm, solid content 40% by mass) 1.25% by mass, Catalyst (organotin compound, solid content 14% by mass) 0.3% by mass, Surfactant (silicone-based, solid content 10% by mass) 0.5% by mass. Polyester aqueous dispersion: A water dispersion (solid content 30% by mass) of copolymerized polyester whose acid components are terephthalic acid, isophthalic acid, and 5-sodium sulfoisophthalic acid, and whose glycol components are diethylene glycol and ethylene glycol. Blocked isocyanate crosslinking agent: methyl ethyl ketoxime-blocked polyisocyanate (solid content concentration 40% by mass) obtained by reacting a polyisocyanate compound having an isocyanurate structure (Duranate TPA, manufactured by Asahi Kasei Chemicals) with polyethylene glycol monomethyl ether (average molecular weight 750)

[0119] (Preparation of Coating Solution for Adhesion Layer P2) The following raw materials were mixed to prepare a coating solution for forming an adhesion layer with excellent adhesion to the functional layer. The coating solution was filtered through a 10 μm filter (nominal filtration accuracy: 95% cutoff of 10 μm particles). Water: 55.62% by mass, Isopropanol: 30.00% by mass, Aliphatic polycarbonate-based polyurethane resin aqueous solution (solid content: 35% by mass), 11.29% by mass, Oxazoline group-containing acrylic crosslinker aqueous solution (solid content: 40% by mass), 2.26% by mass, Particles (silica sol with an average particle size of 40 nm, solid content: 40% by mass), 0.71% by mass, Particles (silica sol with an average particle size of 450 nm, solid content: 40% by mass), 0.07% by mass, Surfactant (silicone-based, solid content: 100% by mass), 0.05% by mass.

[0120] (Example 1) As a film raw material, PET pellets with an intrinsic viscosity of 0.68 dL / g were dried under reduced pressure (1 Torr) at 135 ° C for 6 hours, then fed into an extruder and melted at 285 ° C. The molten polymer was filtered through a stainless steel sintered filter medium (nominal filtration accuracy 5 μm particle 95% cut), extruded into a sheet form from a T-die, and then wrapped around a casting drum with a surface temperature of 30 ° C. using an electrostatic casting method, cooled and solidified to produce an unstretched film. The surface roughness of the casting drum was Ra 2 nm or less and Rz 15 nm or less. The intrinsic viscosity was measured using a phenol / tetrachloroethane = 60 / 40 (mass ratio) solution, assuming a Huggins constant of 0.38.

[0121] Next, a coating solution for P1 was applied to one side of this unstretched PET film, and a coating solution for P2 was applied to the other side, both in a coating amount of 0.12 g / m after drying. ２ After coating the coating solution so that the coating was uniform, the coating solution was introduced into a dryer and dried at 80° C. for 20 seconds.

[0122] The unstretched film with the coating layer formed was introduced into a tenter stretching machine, and while holding the film's edges with clips, it was introduced into a hot air zone at 135°C and stretched 4.0 times in the width direction. Next, while maintaining the stretched width, the film was treated at 225°C for 30 seconds. The cooled film was then cut at both ends with a round blade and wound up to obtain a uniaxially oriented PET film with a thickness of 60 μm. The oscillation speed during winding was 20 mm / min. The T-die had a flow path designed to match the polyester used to ensure uniform resin discharge in the width direction, and the slit section was equipped with a heat bolt to allow adjustment of the slit spacing. The lip opening of the T-die was automatically adjusted using control software to achieve a uniform film thickness in the width direction based on thickness data measured with an in-line thickness gauge at the tenter outlet. Furthermore, the tenter air volume was finely adjusted in the width direction to ensure a uniform temperature across the film. The intrinsic viscosity of the resulting film was 0.65 dL / g.

[0123] The film obtained as described above was unwound and slit to a predetermined width. Both ends were knurled, and the film was then wound around a core with an outer diameter of 7 inches, with the knurled surface facing outward, to obtain a roll with a length of 3,900 m. The winding speed was 185 m / min. The winding tension was the tension applied when the film was wound around the core after both ends were knurled, and the winding contact pressure was the winding contact pressure of the contact roll pressed against the film during winding. The contact roll had a rubber surface and a hardness of 70. The knurling conditions are as described below. The roll was placed in a polyethylene bag, the opening of which was tied with rubber, and side plates larger than the outer diameter of the roll were fitted to both ends of the core and stored at 25°C. The Sa of the film was 1.0 nm on the P1 surface and 1.2 nm on the P2 surface, and the Sq was 1.3 nm on the P1 surface and 1.5 nm on the P2 surface.

[0124] (Knurling) The knurling was performed by passing both ends of the slit film between a knurled upper roll and a mirror-finished lower roll, and the height of the knurled part was adjusted by adjusting the pressure of the upper roll. The processing was performed at room temperature of 25°C. The distance between the knurled part and the film edge was set to 3 mm.

[0125] (Knurling) The knurling was a disk-shaped piece with a thickness of 10 mm and a diameter of 100 mm, and on the outer peripheral surface, 10 protrusions of the following shape were arranged at a 45-degree angle over a length of 10 mm (10 x 10 protrusions per 10 mm x 10 mm). The shape of the knurling protrusions was a square pyramid, with a base length of 1000 μm x 1000 μm and a height of 900 μm.

[0126] (Examples 2 to 7, Comparative Examples 1 to 5) The conditions were the same as in Example 1 except for those described in Table 1. In Comparative Example 4, a general-purpose T-die equipped with heat bolts to enable adjustment of the slit interval was used for the slit portion, and the tenter air volume was not yet finely adjusted.

[0127] (Evaluation of film roll) Using the obtained film, a coating film was formed as follows: Two rolls of film were prepared under the same conditions, one of which was used to measure the roll hardness, knurl height, unwinding charge amount, roll winding state, and thickness unevenness, and the other was used for coating evaluation.

[0128] The film roll was unwound, and a coating liquid for an antiglare layer having the following composition was applied to the surface of the easy-adhesion layer P2 using a gravure coater, dried in an oven at 90°C, and then irradiated with ultraviolet light to cure the coating film, thereby providing an antiglare layer. (Composition of coating liquid for antiglare layer) KAYARAD PET-30 (manufactured by Nippon Kayaku Co., Ltd.) 38.7 parts by mass Viscoat #360 (manufactured by Osaka Organic Chemical Industry Co., Ltd.) 9.7 parts by mass Eposter MA1006 (manufactured by Nippon Shokubai Co., Ltd.) 0.1 parts by mass Irgacure 184 1.5 parts by mass Methyl isobutyl ketone 30.0 parts by mass Methyl ethyl ketone 20.0 parts by mass Fluorine-based surfactant 0.02 parts by mass

[0129] (Evaluation of Film Coating Uniformity) The state of the antiglare layer in a portion 100m to 150m from the beginning of the film roll was observed and the coating uniformity was evaluated. ◎: No unevenness and uniformity within 50m. ○: There were several locations within 50m where slight unevenness or repelling was observed. △: There were several locations within 50m where unevenness or repelling was clearly observed. ×: Unevenness or repelling was frequently observed within 50m.

[0130] The conditions and evaluation results are shown in Table 1.

[0131] In Examples 2 to 6, in-line thickness control was performed, and the film was oscillated during film formation and wound up under appropriate tension and contact pressure conditions. As a result, the average hardness was appropriate, and the standard deviation of the surface hardness and the difference in hardness between two points spaced 60 mm apart were also small. As a result, winding slippage, wrinkles, and flatness were also good, and the unwinding charge was low, and when these films were used for coating, a uniform and good coating film was obtained. In Example 1, slight winding slippage and wrinkles occurred, possibly due to the low tension and contact pressure. In Comparative Example 2, where the tension and contact pressure were further reduced, winding slippage and wrinkles occurred, resulting in poor flatness.

[0132] In Example 7, the standard deviation of the roll surface hardness and the difference in hardness between two points spaced 60 mm apart were larger than in the other Examples, resulting in a higher unwinding charge and slightly poorer coating uniformity. This is thought to be due to the small oscillation width and the increased overlap of thicker film portions. In Comparative Example 3, in which oscillation was not performed, the standard deviation of the surface hardness and the difference in hardness between two points spaced 60 mm apart were even larger, resulting in a correspondingly higher unwinding charge and poorer coating uniformity. In Comparative Example 1, the high winding tension resulted in a higher average hardness, a higher unwinding charge, and poorer coating uniformity.

[0133] In Comparative Example 4, the influence of thickness unevenness due to the T-die and film-forming conditions, etc., was large, resulting in high standard deviation of surface layer hardness, difference in hardness between two points spaced 60 mm apart, and unwinding charge. This is thought to be due to continuous thickness unevenness that could not be completely resolved even by thickness feedback control and oscillation. In Comparative Example 5, thickness feedback control was not performed. It is thought that the continuous thickness unevenness could not be completely dispersed by oscillation alone.

[0134] Example 8 A uniaxially stretched film was obtained in the same manner as in Example 1, except for the conditions shown in Table 2.

[0135] (Examples 9 to 19, Comparative Examples 6 to 16) Films were produced in the same manner as in Example 8, except for the conditions shown in Table 2. The modulus of elasticity was adjusted by changing the stretching ratio. Specifically, the modulus of elasticity was increased by increasing the stretching ratio, and decreased by decreasing the stretching ratio. In Comparative Example 8, Example 11, and Example 12, the unstretched film was slightly stretched in the MD direction using a group of rolls with different peripheral speeds, and then coated with the P1 coating liquid and the P2 coating liquid, and stretched using a tenter. In Comparative Examples 9 and 10, the film was not oscillated during winding.

[0136] (Evaluation of Film Roll) The obtained film was evaluated in the same manner as in Example 1. The evaluation results and film properties are shown in Tables 2 and 3.

[0137]

[0138]

[0139] Comparative Examples 6 to 8 had high winding tension and contact pressure, and Comparative Example 7 had an insufficient initial knurl height, resulting in a high average hardness of the roll surface. Comparative Examples 9 and 10 were examples in which oscillation was not activated during winding, resulting in a large difference in hardness between two points. Comparative Example 12 was an example in which the initial knurl was low, resulting in a large unwinding charge. Comparative Examples 13 and 14 were examples in which the initial knurl was too high, resulting in winding slippage and wrinkles. Comparative Examples 15 and 16 had low roll surface hardness. Furthermore, Comparative Example 15 was an example in which the film width was wide relative to the film thickness, resulting in winding slippage and wrinkles.

[0140] In Examples 8 to 19, the films were wound under appropriate tension and contact pressure conditions, resulting in appropriate average surface hardness values. Furthermore, the film thickness, film width, and initial knurl height were set within a range that effectively achieved both charge and winding appearance, i.e., satisfying the formula 1≦h≦0.1T-1. As a result, winding slippage, wrinkles, and flatness were good, and the unwinding charge was low. When these films were used for coating, a uniform and good coating film was obtained all the way to the center of the roll width. In Examples 8 to 12, the tension and contact pressure were somewhat high, resulting in a relatively high unwinding charge, but this was not significant enough to be a problem. Furthermore, even when the film's elastic modulus was varied, winding slippage, wrinkles, flatness, and coating uniformity were good. In Example 19, winding slippage, wrinkles, and flatness were good, but slight unevenness and repelling within the acceptable range were observed in the center of the film width. It is believed that the film width was slightly wider than in the other examples, and therefore the effect of the knurling did not reach fully to the center of the roll width.

[0141] According to the present invention, it is possible to provide a long resin film that is free from scratches on the film surface and has excellent film flatness, and that is free from shear and / or wrinkle formation and deterioration of the roll appearance during storage (particularly long-term storage). Furthermore, according to the present invention, even after long-term storage, static electricity buildup at the time of unwinding can be suppressed up to the core portion, so that the amount of static electricity when the film is unwound is small, and when the film is coated, there is little repelling of the coating, and a coating with excellent thickness precision can be formed all the way to the end of the film.

Claims

1. A long resin film wound in a roll shape, wherein the average winding 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 winding hardness between two points at intervals of 60 mm in the width direction of the surface layer of the roll is 300 or less.

2. The long resin film according to claim 1, wherein the thickness of the long resin film is 40 μm or more, and the following Formula 1 and Formula 2 are satisfied. 1 ≤ h ≤ 0.1T - 1 Formula 1 W ≤ 40T Formula 2 Here, T: film thickness (μm), W: film width (mm), h: initial nail height (μm) 3. The long resin film according to claim 1, wherein when the modulus of elasticity in the MD direction of the long resin film is ME, ME ≤ 4000 MPa is satisfied.

4. The long resin film according to claim 1, wherein when the modulus of elasticity in the TD direction of the long resin film is TE, TE ≥ 6000 MPa is satisfied.

5. The long resin film according to claim 1, wherein 2 ≤ TE / ME ≤ 4 is satisfied.

6. The long resin film according to claim 1, wherein the standard deviation value of the winding hardness in the width direction of the surface layer of the roll is 80 or less.

7. The long resin film according to claim 1, wherein the thickness unevenness in the TD direction over the entire length of the roll is 2% or less.

8. The long resin film according to claim 1, wherein the remaining amount of nails in the core part of the roll is 1 μm or more.

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

10. The long resin film according to claim 1, wherein when the outer winding surface of the long resin film is surface A and the inner winding surface is surface B, the compositions of surface A and surface B are different.

11. The long resin film according to claim 1, wherein when the outer winding surface of the long resin film is surface A and the inner winding surface is surface B, at least one of surface A or surface B is a coating layer.

12. A method for manufacturing a laminated film, comprising a step (A) of unwinding the long resin film according to any one of claims 1 to 11, and a step (B) of coating a coating liquid on at least one side of the unwound long resin film.

13. The manufacturing method according to claim 12, wherein the laminated film is a polarizer protection film.

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

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