Film and film roll, method for manufacturing film

Abstract

The film of the present application is a film having a plurality of teardrop-shaped objects at the end portion of the film, and in a case where the maximum width in the long axis direction of the teardrop-shaped objects is set as T2 and the maximum width in the short axis direction is set as T1, the following formula (1) is satisfied. Formula (1): 1.15 ≤ T2 / T1 ≤ 1.90.

Description

Technical Field

[0001] This invention relates to membranes and membrane rolls, and methods for manufacturing membranes. Background Technology

[0002] Resin films primarily composed of cyclic olefin resins and (meth)acrylic resins are used as optical films, for example, as protective films for polarizers, due to their excellent transparency and dimensional stability. From the perspective of operability and manufacturing efficiency, optical films are typically stored or transported in roll form.

[0003] However, when stored or transported in a rolled-up state, significant deformation of the film roll, adhesion between films, or scratches will reduce the quality of the film. Increased waste in the polarizer manufacturing process and increased time for quality inspection will lead to higher product prices.

[0004] To suppress quality degradation caused by film roll deformation, a raised / lowered process called embossing is typically applied to both ends of the film in the width direction (see, for example, Patent Document 1). On the other hand, the embossed portions formed by embossing are easily damaged, making it impossible to adequately suppress adhesion between the films.

[0005] In contrast, methods for forming protrusions at both ends of a film in the width direction are also known (see, for example, Patent Documents 2 and 3). Specifically, methods for forming embossed patterns with raised corners and large convex areas by casting at both ends of a film are known (see Patent Document 2), and methods for forming convex structures at both ends of a film by inkjet printing are known (see Patent Document 3). The protrusions formed by coating have higher strength than the uneven structures formed by embossing and are less prone to crushing, thus effectively suppressing the adhesion of films to each other.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2016-89110

[0009] Patent Document 2: Japanese Patent Application Publication No. 2012-206312

[0010] Patent Document 3: Japanese Patent Application Publication No. 2010-58311 Summary of the Invention

[0011] However, the methods in Patent Documents 1 and 2 cannot sufficiently suppress the deformation of the film roll. Furthermore, the method in Patent Document 3 requires further improvement from the perspective of meeting the high-quality requirements of recent years for 8K televisions and the like.

[0012] In other words, deformation of the film roll and adhesion between films can easily lead to increased deviations in optical properties in polarizing protective films used in display devices, etc.; deviations in optical properties can easily lead to light leakage in black displays of display devices. In particular, optical films used in high-resolution display devices such as 8K require less deviation in optical properties than before, and require more suppression of quality degradation caused by deformation of the film roll and adhesion between films than before.

[0013] The present invention was made in view of the above circumstances, and for example, aims to provide a film and film roll that suppress the deformation of film rolls used for optical films, the adhesion of films to each other, and the reduction of deviations in optical properties, as well as a method for manufacturing the film.

[0014] The above-mentioned problem can be solved according to the following structure.

[0015] The membrane of the present invention is a membrane having a plurality of teardrop-shaped objects at the membrane ends, characterized in that, when the maximum amplitude in the long axis direction of the teardrop-shaped objects is set to T2 and the maximum amplitude in the short axis direction is set to T1, the following formula (1) is satisfied.

[0016] Equation (1): 1.15≤T2 / T1≤1.90

[0017] The membrane roll of the present invention is characterized in that it is formed by winding a membrane having a plurality of teardrop-shaped objects at the membrane end. When the maximum amplitude of the teardrop-shaped objects in the long axis direction is set to T2 and the maximum amplitude in the short axis direction is set to T1, the following formula (1) is satisfied, and the intersection point M of the long axis and the short axis of the teardrop-shaped objects is located on the upstream side of the winding direction relative to the center on the long axis.

[0018] Equation (1): 1.15≤T2 / T1≤1.90

[0019] The method for manufacturing the membrane of the present invention is characterized in that it is a membrane manufacturing method for manufacturing the membrane of the present invention, wherein the teardrop-shaped object is formed by imparting droplets to the resin composition.

[0020] Invention Effects

[0021] According to the present invention, for example, a film and film roll that can suppress adhesion, reduction of winding shape, and reduction of deviation of optical properties during storage of films such as optical films can be provided. Attached Figure Description

[0022] Figure 1A This is a top view of the membrane in this embodiment. Figure 1B yes Figure 1A 1B-1B line cross-section diagram.

[0023] Figure 2A yes Figure 1AA magnified top view of a teardrop-shaped object. Figure 2B yes Figure 1B A magnified cross-sectional view of a teardrop-shaped object.

[0024] Figure 3 yes Figure 1A An enlarged top view of the dashed-lined portion.

[0025] Figure 4 yes Figure 1A A magnified top view of a teardrop-shaped object.

[0026] Figure 5A and Figure 5B This is a top view of a teardrop-shaped object, a variation of the previous one.

[0027] Figure 6A These are top views of the membranes in other variations. Figure 6B yes Figure 6A An enlarged top view of the dashed-lined portion. Detailed Implementation

[0028] A detailed investigation was conducted into why the previous protrusions (coating-type knurling sections) could not adequately suppress the deformation of the film roll. The results were not clear, but it was considered that it might be due to the inability to adequately mitigate the force applied to the protrusions during winding, resulting in unevenly damaged winding.

[0029] Specifically, during winding, the combined force of the "force along the length of the membrane" generated by the membrane transport and the "pressure from above" generated by the membrane being stacked from directly above acts as a "force in the oblique direction" on the protrusion. While the protrusion is subjected to this oblique force from the front of the winding direction (travel direction), the membrane is wound. As a result, the protrusion is unable to adequately mitigate the oblique force and is unevenly crushed, resulting in uneven contact with the membrane during winding, thus causing membrane roll deformation. Such membrane roll deformation is particularly prone to occur in films with low rigidity.

[0030] Based on this hypothesis, in this invention, multiple protrusions are formed in a row, and the top view shape of each of the protrusions is set to a moderately eccentric shape, taking into account the force from the tilting direction during winding; specifically, it becomes a teardrop shape in which the size of the upstream side (front side in the direction of travel) of the winding direction is moderately larger than the size of the downstream side (rear side in the direction of travel) of the winding direction. This reduces poor contact between the membranes caused by uneven crushing of the protrusions and the resulting deformation of the membrane roll. Specifically, it is believed that during membrane winding, by first subjecting the eccentric portion of the teardrop shape to a force in the tilting direction, the force in the tilting direction during winding is sufficiently mitigated, and winding is performed in a state of uniform contact with the membrane (contacting the membrane with an ideal convex shape). Therefore, it is possible to uniformly introduce air while suppressing deformation of the membrane roll.

[0031] Such teardrop-shaped structures are formed by incorporating droplets of the resin composition into the membrane body (membrane base), thus exhibiting high strength and resistance to crushing, unlike conventional embossed sections. Therefore, it is easier to further suppress deformation of the membrane roll and adhesion between membranes. The structure of the present invention will be described below.

[0032] The membrane of the present invention can be a strip membrane or a sheet membrane. Alternatively, the strip membrane can be wound into a roll to form a membrane roll. In the following embodiments, a strip membrane will be used as an example for explanation.

[0033] 1. Membrane

[0034] Figure 1A This is a top view of the strip-shaped membrane in this embodiment. Figure 1B yes Figure 1A 1B-1B line cross-section diagram. Figure 2A yes Figure 1A A magnified top view of the teardrop-shaped object 12. Figure 2B yes Figure 1B A magnified cross-sectional view of the teardrop-shaped object 12. Figure 3 yes Figure 1A An enlarged top view of the dashed line portion. Figure 4 yes Figure 1A An enlarged top view of the teardrop-shaped object 12. It should be noted that... Figure 1B and 2B In the image, the shadow lines of the cross-section are omitted for ease of observation.

[0035] like Figure 1A As shown in Figure B, the strip-shaped membrane 10 of this embodiment includes a membrane base 11 and a plurality of teardrop-shaped objects 12 disposed on its surface at both ends (formed by coating) in the width direction.

[0036] 1-1. Membrane base 11

[0037] The film base 11 may be a resin film, preferably a resin film that can be used as an optical film. The resin film comprises a first resin composition containing a thermoplastic resin.

[0038] (Thermoplastic resin)

[0039] The thermoplastic resin contained in the resin film is not particularly limited as long as it is suitable for optical films. In this example, it includes cyclic olefin resins, (meth)acrylic resins, polyimide, cellulose esters, polyesters, polycarbonates, etc. Among these, from the viewpoint of having good transparency, cyclic olefin resins, (meth)acrylic resins, and cellulose esters are preferred. From the viewpoint of further having low moisture absorption (high dimensional stability), cyclic olefin resins and (meth)acrylic resins are more preferred.

[0040] (Cyclic olefin resins)

[0041] Cycloolefin resins are polymers containing structural units derived from monomers having a norbornene structure (norbornene monomers). Norbornene monomers are represented by the following formula (A).

[0042]

[0043] R in equation (A) 1 ~R 4 These represent hydrogen atoms, halogen atoms, hydrocarbon groups, or polar groups, respectively.

[0044] Examples of halogen atoms include fluorine atoms, chlorine atoms, etc.

[0045] The hydrocarbon group is a hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 4, and more preferably 1 or 2. Examples of hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, and butyl. The hydrocarbon group may further have a divalent linking group containing an oxygen atom, nitrogen atom, sulfur atom, or silicon atom (e.g., carbonyl, imine, ether bond, silane ether bond, thioether bond, etc.).

[0046] Examples of polar groups include linkages such as carboxyl, hydroxyl, alkoxy, alkoxycarbonyl, allyloxycarbonyl, amino, amide, and methylene (-(CH2)). n A group formed by combining these groups (where n is an integer of 1 or more). Preferably, alkoxycarbonyl and aryloxycarbonyl are preferred, and more preferably alkoxycarbonyl is preferred.

[0047] Among them, R 1 ~R 4 At least one of them is preferably a polar group. Cycloolefin resins containing structural units derived from norbornene monomers having polar groups are readily soluble in solvents when film is formed using solution casting, for example, and this readily increases the glass transition temperature of the resulting film. On the other hand, in melt film forming, cycloolefin resins that do not contain structural units derived from norbornene monomers having polar groups may be used.

[0048] Additionally, R 1 ~R 4 In the middle, R 1 and R 2 These two parties (or R) 3 and R 4 Both of these can be hydrogen atoms.

[0049] In formula (A), p represents an integer greater than or equal to 0, preferably 0 or 1. m represents an integer from 0 to 2, and from the viewpoint of improving the heat resistance of the optical film, it is preferably 1 to 2.

[0050] Examples of norbornene monomers with polar groups represented by formula (A) include the following substances.

[0051]

[0052] Examples of norbornene monomers that do not have polar groups include the following substances.

[0053]

[0054] The content of structural units derived from norbornene monomers can be 50 to 100 moles relative to all structural units constituting cyclic olefin resins.

[0055] Cycloolefin resins may further include structural units derived from other monomers that can be copolymerized with structural units derived from norbornene monomers. Examples of other copolymerizable monomers include (in the case where the aforementioned norbornene monomers have polar groups) norbornene monomers without polar groups, cyclobutene, cyclopentene, cycloheptene, dicyclopentadiene, and other cycloolefin monomers that do not have a norbornene skeleton.

[0056] The weight-average molecular weight (Mw) of the cyclic olefin resin is not particularly limited, but is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and even more preferably 40,000 to 200,000. If the Mw of the cyclic olefin resin is within the above range, the molding processability will not be impaired, and the mechanical properties of the film can be improved.

[0057] The molecular weight (Mw) of cyclic olefin resins can be determined using gel permeation chromatography (GPC) based on polystyrene conversion. Specifically, an HLC8220 GPC (Tosoh Corporation) and a column (Tosoh Corporation TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL in series) can be used for determination.

[0058] The glass transition temperature (Tg) of cycloolefin resins is generally preferably above 110°C, more preferably 110–350°C, and even more preferably 120–250°C. If the Tg of the cycloolefin resin is above 110°C, sufficient heat resistance can be easily obtained, and if it is below 350°C, the thermal degradation of the cycloolefin resin during molding and processing can be suppressed.

[0059] Tg can be determined using DSC (Differential Scanning Colorimetry) according to JIS K 7121-2012 or ASTM D 3418-82.

[0060] ((meth)acrylic resin)

[0061] (Meth)acrylic resins are preferably polymers containing structural units derived from methyl methacrylate. The polymer may further contain structural units derived from monomers that can copolymerize with methyl methacrylate.

[0062] Examples of other monomers that can copolymerize with methyl methacrylate include alkyl methacrylates with 1 to 18 carbon atoms other than methyl methacrylate, such as 2-ethylhexyl methacrylate; α,β-unsaturated acids such as (meth)acrylic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; styrene derivatives such as styrene and α-methylstyrene; maleic anhydride; maleimide derivatives such as maleimide and N-phenylmaleimide; and glutaric anhydride.

[0063] The content of structural units derived from methyl methacrylate is preferably 50% by mass or more, more preferably 70% by mass or more, relative to all structural units constituting the polymer.

[0064] The Mw of the (meth)acrylic resin is preferably 400,000 to 3,000,000, more preferably 500,000 to 2,000,000. If the Mw of the (meth)acrylic resin is within the above range, sufficient mechanical strength can be applied to the film. The Mw of the (meth)acrylic resin can be determined using the same method as described above.

[0065] The heat resistance (Tg) of the (meth)acrylic resin is preferably 90°C or higher, more preferably 100–150°C. If the Tg of the (meth)acrylic resin is within the above range, the heat resistance of the optical film is easily improved. The Tg of the (meth)acrylic resin can be determined using the same method as described above.

[0066] The content of cycloolefin resin or (meth)acrylic resin is preferably 50% by mass or more, more preferably 70% by mass or more, relative to the optical film.

[0067] (Other ingredients)

[0068] Optical films can be further incorporating other components as needed. Examples of other components include rubber particles, matting agents, and antioxidants.

[0069] Rubber particles can impart flexibility to the film. The rubber particles are graft copolymers comprising a rubber-like polymer (crosslinked polymer). Examples of rubber-like polymers include butadiene-based crosslinked polymers, (meth)acrylic acid-based crosslinked polymers, and organosiloxane-based crosslinked polymers. From the viewpoint of having a small refractive index difference with methacrylic resins and minimizing damage to the transparency of the optical film, (meth)acrylic acid-based crosslinked polymers are preferred, and acrylic acid-based crosslinked polymers (acrylic rubber-like polymers) are more preferred.

[0070] Matting agents can create unevenness on the surface of optical films, imparting smoothness. Matting agents can be inorganic particles, resin particles, etc. Examples of inorganic particles include microparticles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, and calcium carbonate, with silicon dioxide particles being preferred.

[0071] There are no particular restrictions on antioxidants; for example, hindered phenolic antioxidants can be used.

[0072] [physical properties]

[0073] Since the film base 11 is not subjected to embossing or laser irradiation, it does not have a thin-walled portion formed by heating and pressing with an embossing roller or melting with laser irradiation. That is, the thickness of the film base 11 is constant. The thickness of the film base 11 (the thickness of the film) is not particularly limited, but is preferably 5 to 40 μm, more preferably 10 to 40 μm, and even more preferably 15 to 40 μm.

[0074] The width X (width of the membrane) of the membrane base 11 is preferably 1000 to 3200 mm, more preferably 2400 to 2950 mm.

[0075] The length Y (length of the membrane) of the membrane base 11 is not particularly limited, but is preferably 3000 to 12000 m, and more preferably 6000 to 9000 m.

[0076] (Phase difference Ro and Rt)

[0077] The film substrate 11 may have phase differences Ro and Rt corresponding to its application. For example, the in-plane phase difference Ro of the film substrate 11, measured at a measurement wavelength of 590 nm and an environment of 23°C and 55% RH, preferably satisfies 40 nm ≤ Ro ≤ 60 nm, and the phase difference Rt in the thickness direction preferably satisfies 115 nm ≤ Rt ≤ 145 nm. Such a film substrate 11 is suitable, for example, as a phase retardation film combined with a VA-type liquid crystal cell. Alternatively, if 0 nm ≤ Ro ≤ 10 nm and -20 nm ≤ Rt ≤ 20 nm, it is suitable as a phase retardation film combined with an IPS-type liquid crystal cell.

[0078] Ro and Rt are defined by the following formulas respectively.

[0079] Ro=(nx-ny)×d

[0080] Rt=((nx+ny) / 2-nz)×d(where,

[0081] nx represents the refractive index in the slow axis direction (the direction where the refractive index is maximum) of the film base 11.

[0082] ny represents the refractive index of the film base 11 in the direction orthogonal to the in-plane slow axis.

[0083] nz represents the refractive index in the thickness direction of the film substrate 11.

[0084] d represents the thickness (nm) of the film substrate 11.

[0085] The in-plane slow axis of the film base 11 can be confirmed using an automated birefringence meter phase difference tester (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics).

[0086] Ro and Rt can be determined using the following method.

[0087] 1) The membrane substrate 11 was conditioned at 23°C and 55% RH for 24 hours. The average refractive index of the membrane substrate 11 was measured using an Abbe refractometer, and the thickness d was measured using a commercially available micrometer.

[0088] 2) The phase difference Ro and Rt of the membrane substrate 11 at a measurement wavelength of 550 nm were measured using an automatic birefringence meter phase difference tester (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics). The measurement was conducted at 23°C and 55%RH.

[0089] 1-2. Teardrop-shaped objects 12

[0090] Multiple teardrop-shaped objects 12 are islands of resin composition disposed at both ends of the surface of the membrane base 11 in the width direction. Each teardrop-shaped object 12 has a teardrop shape when viewed from above (see reference). Figure 2A ).

[0091] A teardrop shape refers to a shape having a major axis LA and a minor axis SA, wherein the intersection point M of the major axis LA and the minor axis SA of the teardrop shape 12 is offset from the center of the major axis LA (not coinciding with the center of the major axis LA) (see reference). Figure 2A The major axis LA is preferably along the length direction of the membrane base 11 (the length direction of the membrane, y-direction), and more preferably parallel to the length direction (y-direction) of the membrane base 11. The minor axis SA is preferably along the width direction of the membrane base 11 (the width direction of the membrane, x-direction), and more preferably parallel to the width direction (x-direction) of the membrane base 11. The y-direction can also be the transport direction (travel direction) of the membrane during winding. The major axis LA and the minor axis SA are preferably orthogonal to each other. The teardrop-shaped outline can be a straight line or a curve, or any combination thereof, but a curve is preferred.

[0092] In this embodiment, a plurality of teardrop-shaped objects 12 are arranged at both ends in the width direction of the surface of the membrane base 11 and along the length direction of the membrane base 11 (see reference). Figure 2AIn addition, multiple teardrop-shaped objects 12 are arranged such that their long axis LA direction is along the length direction of the membrane base 11 (see reference). Figure 2A It should be noted that the width direction end of the membrane surface refers to the area within 10%, preferably within 5%, of the width direction of the membrane base 11 from the end side when the width of the membrane base 11 in the width direction is set to 100%. The teardrop-shaped object 12 can be integrated with the membrane base 11 or it can be separate.

[0093] Specifically, when the maximum amplitude in the long axis LA direction is set to T2 and the maximum amplitude in the short axis SA direction is set to T1, the teardrop-shaped object 12 preferably satisfies the following formula (1).

[0094] Equation (1): 1.15 ≤ T2 / T1 ≤ 1.90

[0095] If T2 / T1 is 1.15 or higher, even if a force is applied from the front in an oblique direction during winding, the teardrop-shaped object 12 can still make uniform contact with the membrane after winding, thus suppressing deformation of the membrane roll. If T2 / T1 is 1.9 or lower, it can make uniform contact with the membrane, so the suppression effect of the membrane roll is less likely to be compromised. From the same point of view, T2 / T1 is more preferably 1.3 to 1.6.

[0096] T2 / T1 can be adjusted according to the membrane conveying speed, drying conditions (drying method, drying temperature), resin concentration of the second resin composition (used to form teardrop shapes), drop height, and membrane surface condition. T2 / T1 can be increased by increasing the membrane conveying speed, decreasing the drying temperature, and setting the drying method to hot air drying. Furthermore, T2 / T1 can be increased by appropriately decreasing the resin concentration of the second resin composition and increasing the drop height.

[0097] T1 is not particularly limited, for example it can be 0.9 to 1.5 mm, preferably 1.0 to 1.2 mm.

[0098] When the average distance between the multiple teardrop-shaped objects 12 along the longitudinal direction (y direction) of the membrane base 11 is set as T3, T3 and T2 preferably satisfy the following equation (2) (refer to...). Figure 3 ).

[0099] Equation (2): T3 < T2

[0100] If T3 < T2, then during the winding process while conveying the film, the performance of mitigating the force in the tilting direction can be improved at the front part of the teardrop-shaped object 12 (the region centered on the intersection M of the major axis LA and the minor axis SA), thus further suppressing the uneven damage of the teardrop-shaped object 12 due to the force in the tilting direction. The difference between T2 and T3 (T2 - T3) is not particularly limited, for example, it can be 0.1 mm or more, preferably 0.6 mm or more.

[0101] In addition, when the width of the membrane base 11 is set to X, it is more preferable to satisfy the following equations (3) and (4).

[0102] Equation (3): 0.0003 ≤ T1 / X ≤ 0.0063

[0103] Equation (4): 2400mm≤X≤2950mm

[0104] From the viewpoint of easily suppressing membrane roll deformation, a larger T1 / X is preferred, and when the membrane width is large, unevenness is more likely to occur during membrane transport compared to the past. If T1 / X is within the above range, T1 will not become too large, thus suppressing transport scratches such as wrinkles and roller abrasions caused by excessive restraining force applied to the membrane. From the same viewpoint, T1 / X is more preferably 0.0004 to 0.00051.

[0105] Furthermore, when the average interval between the plurality of teardrop-shaped objects 12 in the length direction (y direction) of the membrane base 11 is set to T3 and the length of the membrane base 11 is set to Y, it is more preferable to satisfy the following equations (5) and (6).

[0106] Equation (5): 1.0 × 10 6 ≤Y / T3≤9.0×10 6

[0107] Equation (6): 6000m≤Y≤9000m

[0108] From the viewpoint of easily suppressing the adhesion between the films, a smaller T3 is preferred (a larger Y / T3 is preferred). On the other hand, if T3 becomes too small, the uniformity of the winding shape is easily compromised. If Y / T3 is within the above-mentioned range, the uniformity of the winding shape can be maintained while highly suppressing the adhesion (contact) between the films. From the same viewpoint, Y / T3 is more preferably 3.0 × 10⁻⁶. 3 ~8.0×10 3 .

[0109] The length X of the membrane in the width direction is preferably 2000-3500 mm, more preferably 2400-2950 mm, as described above. The length Y of the membrane is preferably 500-15000 m, more preferably 6000-9000 m, as described above.

[0110] The average spacing T3 of the plurality of teardrop-shaped elements 12 along the longitudinal direction (y-direction) of the membrane base 11 is not particularly limited as long as it is within the range that satisfies the above ratio. For example, it is preferably 0.5 to 4 mm, and more preferably 1 to 3 mm. If the average spacing T3 of the plurality of teardrop-shaped elements 12 is above the lower limit, it is easy to properly adjust the amount of air contained between the membranes when winding them into a roll. If it is below the upper limit, it is even easier to suppress the adhesion between the membranes caused by the average spacing T3 of the plurality of teardrop-shaped elements 12 being too wide. The average spacing T3 of the plurality of teardrop-shaped elements 12 refers to the minimum distance between the ends of adjacent teardrop-shaped elements 12 along the longitudinal direction (y-direction) of the membrane base 11. The ends of the teardrop-shaped elements 12 refer to the ends of the long axis LA.

[0111] In a cross-section along the width direction (x-direction) of the membrane base 11, passing through the apex (highest point) of the teardrop-shaped object 12, the height t of the teardrop-shaped object 12 is 0.5–3 μm (refer to...). Figure 2B If the height t of the teardrop-shaped object 12 is 0.5 μm or more, the adhesion between the membrane bases 11 can be sufficiently suppressed when the membrane 10 is rolled into a roll. If the height t of the teardrop-shaped object 12 is 3 μm or less, the absolute amount of teardrop-shaped object 12 destroyed when the membrane 10 is rolled into a roll is small, and the membrane roll is less likely to deform. From the same point of view, the height t of the teardrop-shaped object 12 is preferably 1.0 to 2.0 μm. It should be noted that the height t of the teardrop-shaped object 12 is the height from the surface of the membrane base 11 to the apex of the teardrop-shaped object 12.

[0112] The height t of the teardrop-shaped object 12 is preferably 1 to 30% of the thickness of the membrane base 11, more preferably 2 to 10%.

[0113] In the cross-section passing through the apex of the teardrop-shaped object 12 along the width direction (x-direction) of the membrane base 11, the width w of the teardrop-shaped object 12 is not particularly limited, but is preferably 500 to 2000 μm. If the width w of the teardrop-shaped object 12 is 500 μm or more, the supporting area is increased, so the teardrop-shaped object 12 is less likely to be crushed. If it is 2000 μm or less, it is easier to dry when the teardrop-shaped object 12 is formed by solution coating. In addition, it is easier to cool during melt formation, so the membrane of the present invention can be produced efficiently. From the same point of view, the width w of the teardrop-shaped object 12 is more preferably 700 to 1500 μm. The width w of the teardrop-shaped object 12 is the maximum amplitude of the teardrop-shaped object 12 in the above-described cross-section.

[0114] The height t and width w of the teardrop-shaped object 12 can be measured using a laser microscope. For example, a KEYENCE Laser Microscope VK-X1000 can be used. In an area where multiple teardrop-shaped objects 12 are arranged, the height t and width w of the teardrop-shaped object 12 are measured over a length direction (y-direction) of 100 mm from the membrane base 11, and their average value is referred to as "the height t and width w of the teardrop-shaped object 12".

[0115] In a cross-section along the width direction (x direction) of the membrane base 11, passing through the apex of the teardrop-shaped object 12, the shape of the teardrop-shaped object 12 is not particularly limited, and can usually be an arc segment. An arc is a shape formed by connecting the two ends of a circular arc or an elliptical arc with a straight line, including semicircles, semi-ellipses, etc. in this example.

[0116] The intersection point M of the multiple teardrop-shaped objects 12, preferably the major axis LA and the minor axis SA, is configured to be located near the upstream side of the winding direction relative to the center of the major axis LA (see reference). Figure 1A Therefore, even if a force is applied to the teardrop-shaped object 12 in an oblique direction, the uneven destruction of multiple teardrop-shaped objects 12 can be suppressed, thus suppressing the deformation of the membrane roll and the adhesion of the membrane to each other.

[0117] For the teardrop-shaped object 12, the area Su of the region on one end of the long axis LA (the region winding around the upstream side) is different from the area Sd of the region on the other end of the long axis LA (the region winding around the downstream side) across the center line passing through the center C on the long axis LA and orthogonal to the long axis LA. Specifically, Su is preferably larger than Sd (refer to...). Figure 4 Specifically, the Su / Sd ratio is preferably 1.2 to 2.0, more preferably 1.3 to 1.6. If Su / Sd is above the lower limit, the force in the tilting direction can be easily and sufficiently mitigated, thus easily suppressing the deformation of the membrane roll. If it is below the upper limit, the membrane's support is less likely to be damaged, and adhesion between membranes can be easily suppressed. Su can be, for example, 0.5 to 10 mm. 2 Sd can be, for example, 0.4–5.0 mm. 2 .

[0118] The teardrop-shaped object 12 comprises a second resin composition containing a thermoplastic resin.

[0119] The thermoplastic resin contained in the teardrop-shaped object 12 can be the same type as the thermoplastic resin contained in the membrane base 11, or it can be a different type. From the viewpoint of improving the adhesion between the teardrop-shaped object 12 and the membrane base 11, it is preferable to use the same type. For example, if the thermoplastic resin contained in the membrane base 11 is a cycloolefin resin, the resin contained in the teardrop-shaped object 12 is also preferably a cycloolefin resin. If the thermoplastic resin contained in the membrane base 11 and the thermoplastic resin contained in the teardrop-shaped object 12 are the same type, the adhesion between the teardrop-shaped object 12 and the membrane base 11 can be improved.

[0120] The same type of thermoplastic resin refers to thermoplastic resins with the same main component monomer (the most common component), but the type and content of the copolymer monomer, the weight-average molecular weight (Mw) of the resin, the glass transition temperature (Tg) and other physical properties may be different.

[0121] The content of resin is not particularly limited, but it is preferably 60% by mass or more relative to the second resin composition constituting the teardrop shape 12, and more preferably 70 to 100% by mass.

[0122] The teardrop-shaped object 12 may further contain the same components (e.g., microparticles) as the membrane base 11, as needed. In order to prevent slippage between the teardrop-shaped object 12 and the back surface of the membrane base 11 and to facilitate a moderate seal when the membrane 10 is wound, the microparticle content of the teardrop-shaped object 12 is preferably less than that of the microparticles in the membrane base 11, and more preferably, it does not contain microparticles.

[0123] 2. Membrane manufacturing methods

[0124] The membrane of the present invention can be obtained by the following steps: 1) casting a first resin composition on a support to obtain a strip-shaped membrane base 11; 2) applying (dropping) droplets of a second resin composition to both ends of the surface of the strip-shaped membrane base 11 in the width direction to form a plurality of teardrop-shaped objects 12.

[0125] 1) For the process of obtaining membrane base 11

[0126] The first resin composition is cast to obtain a strip-shaped film base 11.

[0127] The casting of the first resin composition can be carried out using either melt casting or solution casting. From the viewpoint of being able to use high molecular weight resins, solution casting is preferred for casting the first resin composition.

[0128] That is, the film base 11 can be obtained by a process of obtaining a coating (first resin composition) (preparation of coating); a process of drying and peeling off the obtained coating on a support to obtain a film (casting); and a process of drying and stretching the obtained film (drying and stretching).

[0129] (Preparation of coatings)

[0130] The first resin composition is prepared by dissolving the resin in a solvent.

[0131] The solvent used must contain at least an organic solvent (good solvent) capable of dissolving the resin. Examples of good solvents may include chlorinated organic solvents such as dichloromethane; and non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran. Dichloromethane is preferred.

[0132] The solvent used may further include undesirable solvents. Examples of undesirable solvents include straight-chain or branched aliphatic alcohols with 1 to 4 carbon atoms. If the proportion of alcohol in the coating increases, the film is more prone to gelation, making it easier to peel off from the metal support. Examples of straight-chain or branched aliphatic alcohols with 1 to 4 carbon atoms include methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, and tert-butanol. Among these, methanol and ethanol are preferred from the viewpoint of stability and drying properties.

[0133] (cast)

[0134] Next, the obtained first resin composition is cast onto a support. The casting of the first resin composition can be carried out by exiting the casting mold. The temperature of the first resin composition during casting is typically 15–30°C, preferably room temperature (23°C).

[0135] Next, after the solvent in the first resin composition cast on the support is moderately evaporated (dried), it is peeled off from the support to obtain a film.

[0136] The residual solvent content of the first resin composition at the time of peeling is preferably 25% by mass or more, more preferably 30 to 37% by mass, and even more preferably 30 to 35% by mass. When the residual solvent content at the time of peeling is 25% by mass or more, the solvent can easily evaporate from the peeled film. In addition, if the residual solvent content at the time of peeling is 37% by mass or less, excessive stretching of the film caused by peeling can be suppressed.

[0137] The amount of residual solvent in the first resin composition during peeling is defined by the following formula. The same applies below.

[0138] Residual solvent content (mass%) = (Mass of the first resin composition before heat treatment - Mass of the first resin composition after heat treatment) / Mass of the first resin composition after heat treatment × 100

[0139] It should be noted that the heat treatment for determining the residual solvent amount refers to a heat treatment at 140℃ for 15 minutes.

[0140] (Drying and stretching)

[0141] The resulting film is then dried. Drying can be carried out in one stage or in multiple stages. Alternatively, drying can be performed while stretching the film as needed.

[0142] Stretching can be performed according to the required optical properties, preferably in at least one direction, but it can also be performed in two mutually orthogonal directions (e.g., biaxial stretching in the width direction (x direction) of the film and the transport direction (y direction) orthogonal to it).

[0143] From the viewpoint of using it as a retardation film, the stretching ratio can be, for example, 1.01 to 2 times. The stretching ratio is defined as (the magnitude of the stretching direction of the film after stretching) / (the magnitude of the stretching direction of the film before stretching). It should be noted that, in the case of biaxial stretching, the above-mentioned stretching ratio is preferably set for each direction in the x and y directions. It should also be noted that the in-plane slow axis direction of the film (the direction with the highest refractive index in the plane) is usually the direction with the highest stretching ratio.

[0144] The drying temperature (stretching temperature) during stretching is preferably (Tg-65)℃~(Tg+60)℃, more preferably (Tg-50)℃~(Tg+50)℃, when the glass transition temperature of the resin is set as Tg. If the stretching temperature is above a certain value, the solvent will easily evaporate moderately, thus making it easy to adjust the stretching tension to an appropriate range. If it is below a certain value, the solvent will not evaporate excessively, thus the stretchability is not easily damaged.

[0145] The amount of residual solvent in the film at the start of stretching is preferably the same as the amount of residual solvent in the film at the time of peeling, for example, preferably 20-30% by mass, more preferably 25-30% by mass.

[0146] Stretching of the film in the x-direction (TD direction) can be achieved, for example, by fixing both ends of the film with clamps and pins and widening the spacing between the clamps and pins in the direction of travel (stretching method). Stretching of the film in the y-direction (MD direction) can be achieved, for example, by applying a peripheral speed difference to multiple rollers and utilizing the roller peripheral speed difference between them (roller method).

[0147] From the viewpoint of further reducing the amount of residual solvent, it is preferable to further dry the film obtained after stretching (post-drying). For example, the film obtained after stretching can be further dried while being conveyed by rollers or the like (under a certain tension).

[0148] When the glass transition temperature of the resin is set to Tg, the drying temperature is preferably (Tg-30)~(Tg+30)℃, more preferably (Tg-20)~Tg℃. If the drying temperature is above a certain value, the evaporation rate of the solvent from the stretched film can be easily increased, thus improving the drying efficiency. If it is below a certain value, deformation caused by the stretching of the film can be easily suppressed.

[0149] 2) The process of forming the teardrop-shaped object 12

[0150] Next, droplets of the second resin composition are applied (dropped) to both ends of the surface of the obtained film base 11 in the width direction to form a plurality of teardrop-shaped objects 12.

[0151] The second resin composition can be a melt or a solution, but a solution is preferred from the viewpoint of easy adjustment of shape and size.

[0152] That is, the teardrop-shaped object 12 can be formed by applying droplets of a second resin composition (knurling solution) containing resin and solvent to both ends of the film base 11 in the width direction and then drying it.

[0153] (Second resin composition)

[0154] The resin contained in the second resin composition is of the same type as the resin contained in the coating.

[0155] The solvent contained in the second resin composition includes at least an organic solvent (good solvent) capable of dissolving the resin. Examples of good solvents include chlorinated organic solvents such as dichloromethane; and non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, tetrahydrofuran, cyclopentanone, and toluene. Among these, dichloromethane, cyclopentanone, and toluene are preferred from the viewpoint of readily dissolving cycloolefin resins.

[0156] The solvent contained in the second resin composition may further include a poor solvent. As a poor solvent, the same solvent as that contained in the coating may be used.

[0157] In solution casting, the resin concentration of the second resin composition is preferably lower than that of the first resin composition, and more preferably 50% by mass or less of the resin concentration of the first resin composition. Specifically, the resin concentration of the second resin composition is preferably more than 2% by mass and less than 10% by mass, more preferably 3% to 7% by mass. By adjusting the resin concentration of the second resin composition, the height of the teardrop-shaped object 12 can be adjusted. For example, by increasing the resin concentration of the second resin composition, the height of the teardrop-shaped object 12 can be increased.

[0158] (Apply)

[0159] The second resin composition can be applied by any method, such as a dispenser or an inkjet printer, but from the viewpoint that it is easier to adjust the teardrop shape, an inkjet printer is more preferred.

[0160] The temperature of the second resin composition during casting is, for example, 10 to 30°C, preferably room temperature (23°C).

[0161] (dry)

[0162] The drying of the second resin composition can be carried out by any method, such as air drying (including warm air drying) or heating drying using electromagnetic waves (e.g., heating drying using an infrared (IR) heater). From the viewpoint of easily adjusting the T2 / T1 ratio of the teardrop-shaped material 12 to the aforementioned range, warm air drying is preferred. Furthermore, in the case of air drying (warm air drying), from the viewpoint of easily adjusting the T2 / T1 ratio of the teardrop-shaped material 12 to the aforementioned range, the airflow direction is preferably parallel to the surface of the membrane, and more preferably opposite to the membrane transport direction.

[0163] The drying temperature is not particularly limited as long as it allows the T2 / T1 ratio of the teardrop-shaped object 12 to be adjusted to the range described above. From the viewpoint of increasing T2 / T1, a higher drying temperature is preferred. Specifically, when the glass transition temperature of the resin contained in the second resin composition is set to Tg, it is preferably carried out at 40 to (Tg-20) °C, more preferably at 80 to (Tg-10) °C. Specifically, it is preferably 40 to 115 °C, more preferably 80 to 100 °C.

[0164] As described above, T2 / T1 can be adjusted by the membrane conveying speed, drying conditions (drying method, drying temperature), resin concentration of the second resin composition (used to form the teardrop shape), drop height, and membrane surface condition. Increasing the membrane conveying speed, decreasing the drying temperature, and using hot air drying can increase T2 / T1. Furthermore, appropriately decreasing the resin concentration of the second resin composition and increasing the drop height can also increase T2 / T1. The teardrop shape area ratio Su / Sd can also be adjusted using the same method.

[0165] The average distance T3 between multiple teardrop-shaped objects can be adjusted by the droplet discharge frequency of the second resin composition, etc. The height of the teardrop-shaped objects can be adjusted, for example, by the droplet volume (discharge rate) of the second resin composition.

[0166] The resulting strip-shaped membrane 10 can be wound into a roll along the length of the membrane.

[0167] 3) Regarding the winding process

[0168] The obtained membrane base 11 is wound along the length of the membrane 10 using a winding machine. Thus, a membrane roll formed by winding the strip-shaped membrane 10 in a roll around the core can be obtained.

[0169] There are no particular restrictions on the winding method; it can be the constant torque method, the constant tension method, the taper tension method, etc.

[0170] There are no particular restrictions on the winding tension of the base 11 of the film during winding, which can be around 50 to 170 N.

[0171] (effect)

[0172] As described above, the membrane of this embodiment has a plurality of teardrop-shaped elements 12 at both ends in the width direction, arranged such that the intersection M of the major axis LA and the minor axis SA is located upstream in the winding direction. Furthermore, the T2 / T1 ratio of each of the plurality of teardrop-shaped elements 12 is adjusted to a predetermined range. Therefore, during winding, even if a force in the oblique direction is applied from the front in the travel direction, the teardrop-shaped elements 12 can mitigate the force in the oblique direction while not easily collapsing unevenly, thus allowing winding to be performed in a state of uniform contact with the membrane (in an ideal convex shape). Therefore, deformation of the membrane roll can be suppressed while uniformly introducing air.

[0173] (use)

[0174] The resulting film 10, after removing the teardrop-shaped portion 12 during use, is used as an optical film for display devices such as liquid crystal displays and organic EL displays. Examples of optical films include polarizer protective films (including retardation films, brightness enhancement films, etc.), transparent substrate films, and light diffusion films. Among these, film 10 is preferably used as a polarizer protective film.

[0175] [Variation Example]

[0176] It should be noted that in the above embodiment, the teardrop-shaped object 12 is shown to have the following characteristics: Figure 2A Examples of the shapes shown are not limited to these.

[0177] Figure 5A Figures B and B are top views of a modified teardrop-shaped object 12. The teardrop-shaped object 12 can have multiple protrusion shapes (see Figure 12). Figure 5A ), or it can have a continuous dotted shape (see Figure 5B ).

[0178] Figure 6A This is a top view of a membrane in another variation. Figure 6B yes Figure 6A An enlarged view of the dotted line portion. (See image below.) Figure 6AAs shown in Figure B, the teardrop-shaped object 12 can have an eccentric, approximately triangular shape. For example, it is possible to make it approximately triangular by blowing warm air perpendicularly from the membrane conveying direction (warm air drying).

[0179] Furthermore, in the above embodiment, an example is shown where the teardrop-shaped object 12 is disposed on only one side of the membrane base 11, but it is not limited to this and may also be disposed on two sides.

[0180] In addition, in the above embodiments, an example is shown where the second resin composition for forming the teardrop shape 12 is a solution containing resin and solvent, but it is not limited to this and may also be a melt.

[0181] That is, in the melt casting method, the roll can also be obtained by 1) casting the molten first resin composition and then cooling and solidifying it to obtain a strip-shaped film base 11, and 2) applying droplets of the molten second resin composition to both ends of the strip-shaped film base 11 in the width direction and then cooling and solidifying it to form a plurality of teardrop-shaped objects 12.

[0182] Example

[0183] The present invention will be specifically described below through embodiments, but the present invention is not limited to these embodiments.

[0184] 1. Membrane roll fabrication

[0185] <Making of Membrane Roll 1>

[0186] (Membrane fabrication)

[0187] Particles of cyclic olefin resin G7810 (manufactured by JSR Corporation) (a cyclic olefin resin (COP) containing structural units derived from norbornene monomers represented by the following formula, Tg: 165°C) are fed into an extruder under a nitrogen atmosphere for melt casting. The melt-cast film is then cooled with cooling rollers and peeled off to obtain a film-like material.

[0188]

[0189] The resulting membrane was stretched twice its original length along its width at 175°C, then heated and conveyed at 100°C until completely dry. The ends were then cut to obtain a membrane with a thickness of 20 μm, a width of 2260 mm, and a length of 10000 m. The membrane was conveyed at a speed of 20 m / min.

[0190] (Preparation of solutions for teardrop-shaped objects)

[0191] A solution for teardrop-shaped materials was prepared by dissolving cycloolefin resin G7810 (manufactured by JSR Corporation) in a solvent at a concentration of 5% by mass. Dichloromethane was used as the solvent.

[0192] (The formation of teardrop-shaped objects)

[0193] After corona treatment and plasma treatment of the membrane surface, a teardrop-shaped solution was applied to both ends of the treated surface in the width direction using a SUPER HI JET (manufactured by Musashi Engineering) as a dispenser. The membrane was then dried using an IR heater at a temperature of 80°C, forming multiple teardrop-shaped structures. The membrane temperature was confirmed using a thermal camera. This resulted in a row of approximately mound-shaped teardrop structures, each 1.2 μm high, forming at both ends of the membrane surface in the width direction.

[0194] Specifically, teardrop-shaped objects such as Figure 2A As shown, in the width direction of the membrane ( Figure 2A It forms 3 mm from the edge of the membrane in the x-direction. The top view of the teardrop-shaped object is as follows: Figure 2A The shape shown has a maximum amplitude T1 of 0.9 mm for the short axis SA, a maximum amplitude T2 of 1.2 mm for the long axis LA, and a T2 / T1 ratio of 1.33. Additionally, the average distance T3 between the multiple teardrop-shaped structures is 1.5 mm. The membrane with the teardrop-shaped structures is then wound onto a core to obtain membrane roll 1.

[0195] <Making of membrane rolls 2, 3, 23 and 24>

[0196] The average distance (T3) between multiple teardrop-shaped objects and T2 / T1 were changed in the manner shown in Table 1. Otherwise, the same operation was performed as with membrane roll 1 to obtain membrane rolls 2, 3, 23 and 24.

[0197] It should be noted that the average distance (T3) and T2 / T1 between the multiple teardrop-shaped objects were adjusted according to the drying conditions (method, temperature). Specifically, in membrane roll 2, the drying temperature was set to 100°C; in membrane roll 3, drying was carried out by blowing warm air at 80°C in the opposite direction (horizontal direction) to the conveying direction of the membrane; for membrane roll 23, drying was carried out by heating at 120°C (Tg-40°C) using an IR heater; and for membrane roll 24, drying was carried out by blowing drying air at room temperature. Otherwise, it was the same as membrane roll 1.

[0198] <Making of Membrane Roll 4>

[0199] (Preparation of coatings)

[0200] First, dichloromethane was added to a pressurized dissolving tank at a flow rate of 400 kg / min, and ethanol at a flow rate of 20 kg / min. Three minutes after the initial solvent addition, cyclic polyolefin resin was added to the pressurized dissolving tank while stirring. Next, five minutes after the initial solvent addition, the particulate additive solution was added, heated to 60°C, and completely dissolved while stirring. The heating temperature was increased from room temperature at 5°C / min, dissolved over 30 minutes, and then cooled at 3°C / min. Anji Filter Paper Co., Ltd.'s No. 244 filter paper (filtration accuracy 0.005 mm) was used at a filtration flow rate of 300 L / m³. 2 •h, filtration pressure 1.0×10 6 The coating with the following composition was prepared by filtration under Pa conditions.

[0201] Cycloolefin resin G7810 (manufactured by JSR Corporation): 100% by mass

[0202] Dichloromethane: 380% by mass

[0203] Ethanol: 20% by mass

[0204] (Membrane fabrication)

[0205] Next, the obtained coating is uniformly cast onto a stainless steel strip support at a temperature of 31°C and a width of 2300 mm using a ring-belt casting device. The temperature of the stainless steel strip is adjusted to 28°C, and the conveying speed of the stainless steel strip is 30 m / min. On the stainless steel strip support, the solvent is allowed to evaporate until the residual solvent content in the cast (cast) coating reaches 30% by mass. Then, it is peeled off from the stainless steel strip support with a peel tension of 110 N / m to obtain a film.

[0206] The obtained film was stretched 1.3 times while being heated to 120°C along the conveying direction (MD direction) using a roller method utilizing the difference in circumferential speed of the conveying rollers. Then, it was stretched 1.65 times while being heated to 130°C along the TD direction using a stretching method. The resulting film was then conveyed at 70°C while being heated until completely dry, and the ends were cut to obtain a membrane with a thickness of 20 μm, a width of 2260 mm, and a length of 10000 m. The membrane conveying speed was set to 20 m / min.

[0207] In addition to using the obtained membrane, the same operation as membrane roll 1 is performed to form multiple teardrop-shaped objects at both ends of the membrane in the width direction to obtain membrane roll 4.

[0208] <Making of Membrane Rolls 5 and 6>

[0209] Except for changes to at least one of the composition of the coating and the composition of the teardrop-shaped solution as shown in Table 1, membrane rolls 5 and 6 were obtained in the same manner as membrane roll 4. It should be noted that TAC is cellulose triacetate and R812 is silica particles.

[0210] <The Making of Membrane Roll 7>

[0211] (Preparation of particulate dispersion)

[0212] The following components were mixed in a dissolver for 50 minutes and then dispersed using a valve homogenizer (Manton-Gaulin). The mixture was then dispersed using a mill to achieve a predetermined secondary particle size, and finally filtered through a FINEMETNF NF filter manufactured by Nippon Seisen Corporation to prepare a particulate dispersion.

[0213] R972V (manufactured by NIPPON AEROSILCO.,LTD.): 4% by mass

[0214] Dichloromethane: 48% by mass

[0215] Ethanol: 48% by mass

[0216] (Coating preparation and film formation)

[0217] The above-mentioned microparticle dispersion was further added at a ratio of 0.2% by mass relative to 100% by mass of cyclic olefin resin G7810 (manufactured by JSR Corporation). Otherwise, the coating was prepared in the same manner as membrane roll 4 to obtain a membrane.

[0218] (Preparation of solutions for teardrop-shaped objects and formation of teardrop-shaped objects)

[0219] The above-mentioned microparticle dispersion was further added in a manner that the amount of microparticles was 0.1% by mass relative to 100% by mass of cyclic olefin resin G7810 (manufactured by JSR Corporation). Otherwise, after preparing a solution for teardrop-shaped material in the same manner as membrane roll 4, a teardrop-shaped material was formed to obtain membrane roll 7.

[0220] <The Making of Membrane Roll 8>

[0221] As shown in Table 1, the height of the teardrop-shaped object is changed, otherwise membrane roll 8 is obtained in the same manner as membrane roll 1. The height of the teardrop-shaped object is adjusted by the discharge rate.

[0222] <Making of Membrane Rolls 9 and 10>

[0223] By changing the thickness of the membrane or the number of teardrop-shaped columns (at each end) as shown in Table 1, and otherwise operating in the same manner as membrane roll 8, membrane rolls 9 and 10 are obtained.

[0224] <Making of Membrane Rolls 11-13>

[0225] As shown in Table 1, the average distance (T3) between the multiple teardrop-shaped objects was changed. Otherwise, membrane rolls 11 to 13 were obtained in the same manner as membrane roll 8. The average distance (T3) between the multiple teardrop-shaped objects was adjusted by the discharge frequency.

[0226] <Making of Membrane Rolls 14-17>

[0227] The membrane width X is changed as shown in Table 1. Otherwise, membrane rolls 14 to 17 are obtained in the same manner as membrane roll 8. It should be noted that for membrane 15, the discharge rate is increased, the drying conditions are adjusted (the temperature of the warm air is reduced, and the angle of the blown warm air is decreased), and the width T1 of the short axis SA of the teardrop shape is further changed as shown in Table 1.

[0228] <Production of membrane rolls 18-21>

[0229] As shown in Table 1, the membrane length Y is changed, otherwise membrane rolls 18 to 21 are obtained in the same manner as membrane roll 8. It should be noted that, for a portion, the discharge frequency is adjusted, and the average interval T3 between the multiple teardrop shapes is further changed as shown in Table 1.

[0230] <The Making of Membrane Roll 22>

[0231] The top view of the teardrop-shaped object was changed as shown in Figure 5. Otherwise, membrane roll 22 was obtained in the same manner as membrane roll 12. The top view of the teardrop-shaped object was adjusted by the drying conditions (temperature of warm air and angle of the blowing warm air).

[0232] <Evaluation>

[0233] In addition, the shape of the teardrop-shaped membrane rolls 1 to 24 and the deformation of the membrane rolls were evaluated by the following methods.

[0234] (1) Size and shape (height, top view, etc.) of teardrop-shaped objects

[0235] The height t (maximum height) of the teardrop-shaped objects, the dimensions of the teardrop-shaped objects when viewed from above (T1, T2), and the average distance between multiple teardrop-shaped objects (T3) in the width-direction section of the membrane were measured using a laser microscope. A KEYENCE Laser Microscope VK-X1000 was used as the laser microscope. Specifically, in the area where the teardrop-shaped objects were arranged, the height t of the teardrop-shaped objects was measured over a 100 mm length direction of the membrane, and their average value was taken as the "height t of the teardrop-shaped object".

[0236] (2) Winding failure (deformation of the membrane roll)

[0237] The wound film roll was wrapped in two layers of polyethylene sheet (with the core axis aligned horizontally), and stored for 5 days at 40°C and 80% humidity with the ends of the core supported by a bracket. Then, the polyethylene sheet was opened, and the surface of the film roll was reflected by a lit fluorescent lamp to observe any deformation or minor irregularities. The film was then evaluated based on the following criteria.

[0238] ◎: Directly visible fluorescent light

[0239] 〇: The fluorescent lamp appears to have only one slightly bent section, but it poses no practical problem.

[0240] ○△: The fluorescent lamp appears to have only two slightly bent areas, but it poses no practical problem.

[0241] △: The fluorescent lamp appears to have only three slightly bent areas, but it has no practical problems.

[0242] ×: There are areas where the fluorescent light is noticeably bent or where the light is dappled; this indicates a problem.

[0243] If it is △ or above, then it is set as the allowable range.

[0244] (3) Display quality of 8K LCD display devices

[0245] (Making of polarizing filters)

[0246] A single side of an amorphous polyester film with a thickness of 100 μm was subjected to corona treatment. An aqueous solution containing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetyl-modified polyvinyl alcohol (Japan Synthetic Chemical Industry "GOHSEFIMER Z200"; degree of polymerization 1200, degree of acetyl-modification 4.6%, degree of saponification 99.0 mol% or more) in a 9:1 mass ratio was coated on the treated surface at 25°C and then dried to obtain a laminate containing an amorphous polyester film substrate and a PVA-based resin layer with a thickness of 11 μm.

[0247] The resulting laminate was uniaxially stretched along its length to 2.0 times its original length by assisted stretching in a gas atmosphere within an oven at 120°C. While being conveyed by rollers, it was sequentially immersed in a 4% boric acid aqueous solution at 30°C for 30 seconds, and then in a dyeing solution (0.2% iodine, 1.0% potassium iodide aqueous solution) at 30°C for 60 seconds. Next, while being conveyed by rollers, the laminate was crosslinked by immersion in a crosslinking solution (3% potassium iodide, 3% boric acid aqueous solution) at 30°C for 30 seconds, and then immersed in a 4% boric acid, 5% potassium iodide aqueous solution at 70°C, while undergoing uniaxial stretching along its length at a total stretch ratio of 5.5 times. Finally, the laminate was immersed in a cleaning solution (4% potassium iodide aqueous solution) at 30°C to obtain a laminate comprising an amorphous polyester film substrate and a 5μm thick PVA-based polarizer.

[0248] (Preparation of active energy line curing adhesive composition)

[0249] The following composition is prepared as an active energy line curing adhesive composition.

[0250] N-hydroxyethylacrylamide: 30 parts by weight

[0251] Acryloylmorpholine: 65 parts by weight

[0252] Tripropylene glycol diacrylate: 5 parts by weight

[0253] 2,4-Diethylthioxanthroline-9-one (initiator): 1.4 parts by weight

[0254] 2-Methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one: 1.4 parts by weight

[0255] The above-mentioned curable adhesive composition is applied to the surface of the polarizer of the above-mentioned laminate with a thickness of about 1 μm, and the film rolled out from the above-mentioned film roll is attached thereon. The cumulative light intensity is 1000 mJ / cm. 2 The ultraviolet light causes the adhesive to cure. The bonding process is performed with the slow axis of the film orthogonal to the absorption axis of the polarizer.

[0256] The amorphous polyester film substrate is peeled off from the laminate, and the above-mentioned active energy line-curing adhesive composition is coated on the surface of the peeled PVA resin layer. After the film is laminated, ultraviolet light is irradiated to cure the adhesive. Thus, a polarizer with a polarizer and a protective film for the polarizer disposed on both sides is obtained.

[0257] The resulting polarizer was then used in an 8K liquid crystal display panel, and the unevenness of light leakage during black display was visually evaluated. Specifically, using a roller laminator, a 20μm thick acrylic adhesive film was bonded to the side of the polarizer in which the slow axis was orthogonally bonded to the absorption axis of the polarizer, to obtain a polarizer with an adhesive layer.

[0258] (Fabrication of a liquid crystal display device)

[0259] The polarizers attached to both sides of the liquid crystal cell of the Sharp-manufactured 60-inch liquid crystal display device 8T-C60BW1 (VA type) are peeled off. The adhesive layer of the polarizer with adhesive sheet prepared above is then attached to both sides of the liquid crystal cell. It should be noted that the direction of the slow axis of the above film and the absorption axis of the polarizer are aligned with the direction of the originally attached polarizer.

[0260] (Light leakage when displaying black)

[0261] The obtained 8K liquid crystal display device was placed in a darkroom, and a full-screen black display was created using external input from a personal computer. Then, the edges were sealed with black tape to ensure that only the black display portion was reliably visible when viewed from the front. In this state, the unevenness of light leakage was observed and evaluated based on the following criteria.

[0262] ◎: Almost no uneven light leakage

[0263] 〇: Minimal light leakage unevenness

[0264] ○△: There is a slight unevenness in light leakage, but it is not a problem in practical use.

[0265] △: There is some uneven light leakage, but it has no practical problems.

[0266] ×: Uneven light leakage, not practical.

[0267] If it is △× or higher, then it is set as the allowable range.

[0268] The fabrication conditions and evaluation results for membrane rolls 1–24 are shown in Table 1. It should be noted that the Su / Sd ratios for membranes 1–3 and 13 are 1.49, 1.28, 1.65, and 1.46, respectively, and the Sd is 0.45 mm. 2 0.49mm 2 0.43mm 2 and 0.46mm 2 .

[0269] [Table 1]

[0270]

[0271] As shown in Table 1, in membrane rolls 1 to 22, it was confirmed that the T2 / T1 ratio of the teardrop-shaped object was within the specified range. Furthermore, it was confirmed that the area Su of the teardrop-shaped object was greater than Sd. Moreover, it was found that membrane rolls 1 to 22 with the T2 / T1 ratio of the teardrop-shaped object within the specified range had fewer winding defects, and the display devices using the obtained membranes also had less light leakage.

[0272] In particular, it can be seen that by satisfying T3 < T2, the deformation of the membrane roll can be further suppressed (comparison of membrane 8 with membranes 10 and 111).

[0273] Furthermore, it can be seen that by satisfying equations (3) and (4), the deformation of the membrane roll can be further suppressed (comparison of membrane 14 or 15 with membrane 16 or 17). Furthermore, it can be seen that by satisfying equations (5) and (6), the deformation of the membrane roll can be further suppressed (e.g., comparison of membrane 19 with 20, etc.).

[0274] In contrast, it can be seen that film rolls 23 and 24, whose T2 / T1 are outside the specified range, both have winding failures, which in turn cause light leakage when manufacturing the display device.

[0275] This application claims priority based on Japanese Patent Application No. 2021-073520, filed on April 23, 2021. All contents described in that application are incorporated herein by reference.

[0276] Industrial availability

[0277] According to the present invention, it is possible to provide films and film rolls that can suppress adhesion, reduction of winding shape, and reduction of deviations in optical properties during storage of films such as optical films.

[0278] Symbol Explanation

[0279] 10: Strip-shaped membrane (membrane roll)

[0280] 11: Membrane base

[0281] 12: Teardrop-shaped objects

Claims

1. A membrane roll, characterized in that, It is a membrane roll formed by winding a membrane with multiple teardrop-shaped features at its ends. The teardrop-shaped object, viewed from above, is indeed teardrop-shaped. The plurality of teardrop-shaped objects are arranged along the length of the membrane. The plurality of teardrop-shaped objects are disposed at both ends of the surface of the membrane in the width direction. When the maximum amplitude along the major axis of the teardrop shape is set to T2 and the maximum amplitude along the minor axis is set to T1, the following equation (1) is satisfied, wherein the major axis is along the length of the membrane. Equation (1): 1.15≤T2 / T1≤1.

90.

2. The membrane roll according to claim 1, characterized in that, When viewed from above, the area of ​​the region on one side of the long axis of the teardrop shape, separated by a centerline passing through the center of the long axis and orthogonal to the long axis, is denoted as Su, and the area of ​​the region on the other side of the long axis is denoted as Sd. Su and Sd are different.

3. The membrane roll according to claim 1, characterized in that, When viewed from above, the area of ​​the region upstream of the long axis of the teardrop-shaped object in the winding direction is defined as Su, and the area of ​​the region downstream of the long axis in the winding direction is defined as Sd, with Su being larger than Sd.

4. The membrane roll according to claim 1, characterized in that, When the average distance between the plurality of teardrop-shaped objects along the length of the membrane is set to T3, T3 and T2 satisfy the following equation (2). Equation (2): T3 < T2.

5. The membrane roll according to claim 1, characterized in that, When the width of the membrane is set to X, the following equations (3) and (4) are satisfied. Equation (3): 0.0003 ≤ T1 / X ≤ 0.0063 Equation (4): 2400mm≤X≤2950mm.

6. The membrane roll according to claim 1, characterized in that, When the average interval between the plurality of teardrop-shaped objects is set to T3 and the length of the membrane is set to Y, the following equations (5) and (6) are satisfied. Equation (5): 1.0 × 10 6 ≤Y / T3≤9.0×10 6 Equation (6): 6000m≤Y≤9000m.

7. The membrane roll according to claim 1, wherein, The thickness of the membrane is 10~40μm.

8. The membrane roll according to claim 1, wherein, The film is an optical film.

9. The membrane roll according to claim 1, characterized in that, The intersection point M of the major and minor axes of the teardrop shape is located on the upstream side of the winding direction relative to the center on the major axis.

10. A method for manufacturing a membrane roll, which is a method for manufacturing a membrane roll according to any one of claims 1 to 9, wherein the teardrop-shaped object is formed by imparting a droplet to a resin composition.

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