WO2022163131A1

WO2022163131A1 - Film, film roll, and method for producing film

Info

Publication number: WO2022163131A1
Application number: PCT/JP2021/044613
Authority: WO
Inventors: 里誌森井; 葉月中江; 崇南條
Original assignee: コニカミノルタ株式会社
Priority date: 2021-01-27
Filing date: 2021-12-06
Publication date: 2022-08-04
Also published as: CN116806234A; JPWO2022163131A1

Abstract

The film of the present invention has a film base and protruding parts disposed on both ends of the surface of the film base. The film base and the protruding parts include the same type of thermoplastic resin, and the height of the protruding parts is 0.5-3 μm. The haze ratio Hz2/Hz1 is 1.1-4.5 when the haze value of the region where the protruding parts are not disposed is defined as Hz1, and the haze value of the regions where the protruding parts are disposed is defined as Hz2.

Description

Film and film roll, method for manufacturing film

The present invention relates to a film, a film roll, and a film manufacturing method.

　Resin films mainly composed of cycloolefin resins and (meth)acrylic resins have good transparency and dimensional stability, so they are used as optical films such as polarizing plate protective films. Optical films are usually stored or transported in a rolled state from the viewpoint of handling and production efficiency.

Knurling (uneven structure) is formed at both ends of the film in the width direction in order to prevent quality failures caused by the film sticking to each other when it is stored or transported in a rolled state. may be As a method for forming the knurled portion, there are a heat pressing method using an emboss roller, a laser irradiation method, and the like.

However, the protrusions formed by these methods are easily crushed or chipped. As a result, not only is it impossible to prevent the films from sticking together, but the chipped portion may become a foreign substance and damage the surface of the film.

On the other hand, there is also known a method of forming knurled portions on both ends of the film in the width direction by a coating method (see Patent Documents 1 to 3, for example). For example, an optical laminate having a substrate film, an optical functional layer such as a hard coat layer, and knurling portions disposed at both ends of the surface in the width direction (for example, Patent Document 2), a substrate, and a hard coat BACKGROUND ART A film material having a coating film such as a layer and thick portions disposed at both ends in the width direction of the surface thereof is known (for example, Patent Document 3). The base film or base (film base) is an acrylic resin film or cellulose triacetate film; It is a cured product of a resin composition containing a curable resin.

JP 2012-206312 A JP 2017-109350 A JP 2014-159137 A

As shown in Patent Documents 2 and 3, the projections made of a cured product of an ultraviolet curable resin composition are not easily crushed when the film is wound into a roll, but the projections are not only too hard, but also , and has residual shrinkage stress at the time of curing, so that the adhesiveness to the film base is low and it is easy to peel off. Therefore, the knurling function is likely to be impaired, and blocking and deterioration of the wound shape of the film roll may occur.

Blocking and deterioration of the wound shape of the film roll tend to cause, for example, an increase in the variation in the optical properties of the optical film; the variation in the optical properties tends to cause light leakage during the black display of the display device. In particular, optical films used in high-resolution display devices such as 8K are required to have less variation in optical properties than ever before. Further suppression is desired.

The present invention has been made in view of the above circumstances, and provides a film and a film roll that can suppress blocking and deterioration of the winding shape during storage of a film such as an optical film, and can reduce variations in optical properties. for the purpose.

The above problems can be solved by the following configuration.

The film of the present invention is a film comprising a film base and protrusions disposed on both ends of the surface of the film base, wherein the film base and the protrusions contain the same type of thermoplastic resin, The height of the projections is 0.5 to 3 μm, and the haze value of the region where the projections are not arranged on the film is Hz1, and the haze value of the region where the projections are arranged is Hz2. At that time, the haze ratio Hz2/Hz1 is 1.1 to 4.5.

The film roll of the present invention includes the film of the present invention.

The method for producing a film of the present invention comprises: 1) a step of casting a first resin composition to obtain a strip-shaped film base; and applying an object to form a convex portion.

According to the present invention, it is possible to provide a film and a film roll that can suppress blocking and deterioration of the winding shape during storage of a film such as an optical film, and can reduce variations in optical properties.

FIG. 1A is a plan view of the film according to this embodiment, and FIG. 1B is a cross-sectional view taken along line 1B-1B of FIG. 1A. 2A is a partially enlarged plan view of the dotted line portion 2A in FIG. 1A, and FIG. 2B is a partially enlarged cross-sectional view of the convex portion in FIG. 1B. 3A is a plan view of a film according to a modification, and FIG. 3B is a cross-sectional view taken along line 3B-3B of FIG. 3A. FIG. 4 is a partially enlarged plan view of a film according to a comparative example.

The present inventors have found that 1) by using the same type of thermoplastic resin contained in the film base and the protrusions, the adhesion of the protrusions (to the film base) is increased, and 2) the height of the protrusions is reduced. In addition, by setting the ratio (Hz2/Hz1) of the haze value Hz1 in the region where the convex portions are not arranged and the haze value Hz2 in the region where the convex portions are arranged in a predetermined range, the convex portions are crushed. The inventors have found that it is possible to reduce deformation when wound into a roll.

The reason for this is not clear, but is presumed as follows.
As in 1) above, if the convex portion containing the thermoplastic resin does not become too hard, and if the thermoplastic resin contained in the film base and the convex portion are of the same type, the affinity between the two is high, resulting in strong adhesion. It's easy to do.
In addition, as in 2) above, by appropriately reducing the height of the protrusions, for example, when a constant radial pressure (force applied in the direction in which the protrusions are crushed) is applied while the film is wound, (If the collapse rate of the convex portion is constant), the lower the height of the convex portion, the smaller the absolute amount of crushing of the convex portion. In addition, variations in the height of the protrusions due to crushing can be reduced. Furthermore, by adjusting the height of the projections, the density of the projections, etc., the haze ratio Hz2/Hz1 is set within a predetermined range, thereby not only reducing the amount of collapse of the projections, but also making it difficult for the projections to collapse. sell. Thereby, it is possible to suppress the roll deformation caused by the crushing of the convex portion.

Furthermore, since the projections are formed by applying a resin composition to the film body (film base), unlike the case where they are formed by conventional embossing or laser irradiation, the obtained film base has a thin portion. It is difficult to form a brittle portion that is degraded by heat. Therefore, even if a winding pressure is applied to the convex portion, the thin portion or the thermally deteriorated fragile portion will not be the starting point for chipping, so that the generation of foreign matter can be suppressed. As a result, the surface of the film can be prevented from being scratched, and the deterioration of the optical properties of the obtained film can be further suppressed.

The film of the present invention may be a strip-shaped film or a sheet-shaped film (a strip-shaped film cut into a predetermined length). Also, the strip-shaped film may be wound into a roll to form a film roll. In the following embodiments, an example of a strip-shaped film will be described.

1. Film FIG. 1A is a plan view of a strip-shaped film according to the present embodiment, and FIG. 1B is a cross-sectional view taken along line 1B-1B of FIG. 1A. 2A is a partially enlarged plan view of the dotted line portion 2A in FIG. 1A, and FIG. 2B is a partially enlarged cross-sectional view of the convex portion in FIG. 1B. In addition, in FIG. 1B, hatching of the cross section is omitted for easy viewing.

As shown in FIGS. 1A and B, the strip-shaped film 10 according to the present embodiment includes a film base 11 and projections 12 arranged (formed by coating) at both ends in the width direction on the surface.

1-1. film base 11
The film base 11 can be a resin film, preferably a resin film that can be used as an optical film. The resin film contains a first resin composition containing a thermoplastic resin.

(Thermoplastic resin)
The thermoplastic resin contained in the resin film is not particularly limited as long as it is suitable for optical films. including polycarbonate. Among them, cycloolefin resins, (meth)acrylic resins, and cellulose esters are preferable from the viewpoint of having good transparency, and from the viewpoint of further having low hygroscopicity (high dimensional stability), cycloolefin resins and (meth) ) Acrylic resin is more preferable.

(Cycloolefin resin)
A cycloolefin-based resin is a polymer containing a structural unit derived from a norbornene-based monomer. A norbornene-based monomer is represented by the following formula (1).

R ¹ to R ⁴ in formula (1) each represent a hydrogen atom, a halogen atom, a hydrocarbon group, or a polar group.

Examples of halogen atoms include fluorine atoms and chlorine atoms.

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

Examples of polar groups include linking groups such as carboxy groups, hydroxy groups, alkoxy groups, alkoxycarbonyl groups, aryloxycarbonyl groups, amino groups, amido groups, and methylene groups (—(CH ₂ ) _n —, where n is 1 Groups in which these groups are bonded via the above integers) are included. Among them, an alkoxycarbonyl group and an aryloxycarbonyl group are preferable, and an alkoxycarbonyl group is more preferable.

Among them, at least one of R ¹ to R ⁴ is preferably a polar group. A cycloolefin resin containing a structural unit derived from a norbornene monomer having a polar group is easily dissolved in a solvent, for example, when forming a film by a solution casting method, and tends to increase the glass transition temperature of the resulting film. . On the other hand, in the melt film-forming method, a cycloolefin-based resin that does not contain a structural unit derived from a norbornene-based monomer having a polar group may be used.

Also, of R ¹ to R ⁴ , both R ¹ and R ² (or both R ³ and R ⁴ ) may be hydrogen atoms.

"p" in formula (1) represents an integer from 0 to 2. From the viewpoint of enhancing the heat resistance of the optical film, p is preferably 1-2.

Among the norbornene-based monomers represented by formula (1), examples of norbornene-based monomers having a polar group include the following.

Examples of norbornene-based monomers without polar groups include:

The content of structural units derived from norbornene-based monomers can be 50 to 100 mol% of the total structural units constituting the cycloolefin-based resin.

The cycloolefin-based resin may further contain a structural unit derived from another monomer copolymerizable with the structural unit derived from the norbornene-based monomer. Examples of other copolymerizable monomers include norbornene-based monomers having no polar group (when the norbornene-based monomer has a polar group), cyclobutene, cyclopentene, cycloheptene, and dicyclopentadiene. Cycloolefinic monomers having no norbornene skeleton such as are included.

The weight average molecular weight Mw of the cycloolefin 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. . When the Mw of the cycloolefin resin is within the above range, the mechanical properties of the film can be enhanced without impairing the moldability.

The Mw of the cycloolefin resin can be measured in terms of polystyrene by gel permeation chromatography (GPC). Specifically, it can be measured using Tosoh Corporation HLC8220GPC) and a column (Tosoh Corporation TSK-GEL G6000HXL-G5000HXL-G5000HXL-G4000HXL-G3000HXL series).

The glass transition temperature Tg of the cycloolefin resin is generally preferably 110°C or higher, more preferably 110 to 350°C, and more preferably 120 to 250°C. When the Tg of the cycloolefin-based resin is 110°C or higher, sufficient heat resistance is likely to be obtained, and when it is 350°C or lower, thermal deterioration of the cycloolefin-based resin during molding can be suppressed.

Tg can be measured by a method based on JIS K 7121-2012 or ASTM D 3418-82 using DSC (Differential Scanning Colorimetry).

((meth)acrylic resin)
The (meth)acrylic resin is preferably a polymer containing structural units derived from methyl methacrylate. The polymer may further comprise structural units derived from monomers copolymerizable with methyl methacrylate.

Examples of other monomers copolymerizable with methyl methacrylate include alkyl (meth)acrylates having 1 to 18 carbon atoms other than methyl methacrylate, such as 2-ethylhexyl methacrylate; saturated acids; unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid; styrenes such as styrene and α-methylstyrene; maleic anhydride; maleimides such as maleimide and N-phenylmaleimide; included.

The content of structural units derived from methyl methacrylate is preferably 50% by mass or more, more preferably 70% by mass or more, based on all structural units constituting the polymer.

The Mw of the (meth)acrylic resin is preferably 400,000 to 3,000,000, more preferably 500,000 to 2,000,000. When the Mw of the (meth)acrylic resin is within the above range, the film can be imparted with sufficient mechanical strength. The Mw of the (meth)acrylic resin can be measured by the same method as described above.

The Tg of the (meth)acrylic resin is preferably 90°C or higher, more preferably 100 to 150°C. When the Tg of the (meth)acrylic resin is within the above range, the heat resistance of the optical film can be easily improved. The Tg of the (meth)acrylic resin can be measured by the same method as described above.

The content of the 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.

(other ingredients)
The optical film may further contain other components as needed. Examples of other ingredients include rubber particles, matting agents, antioxidants, and the like.

The rubber particles can impart flexibility to the film. The rubber particles are graft copolymers containing rubbery polymers (crosslinked polymers). Examples of rubber-like polymers include butadiene crosslinked polymers, (meth)acrylic crosslinked polymers, and organosiloxane crosslinked polymers. Among them, a (meth)acrylic crosslinked polymer is preferable, and an acrylic crosslinked polymer (acrylic rubber-like polymer) is preferable from the viewpoint that the difference in refractive index from that of the methacrylic resin is small and the transparency of the optical film is less likely to be impaired. more preferred.

The matting agent forms unevenness on the surface of the optical film and can impart slipperiness. The matting agent may be inorganic particles, resin particles, or the like. Examples of inorganic particles include fine particles of silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, etc., preferably silicon dioxide particles.

Although the antioxidant is not particularly limited, for example, a hindered phenol-based antioxidant can be used.

[Physical properties]
Since the film base 11 is not embossed or laser-irradiated, it does not have a thin portion formed by being heated and pressed by an embossing roller or melted by laser irradiation. That is, the thickness of the film base 11 is constant. Although the thickness of the film base 11 is not particularly limited, it is preferably 5 to 40 μm, more preferably 10 to 40 μm, even more preferably 15 to 40 μm.

Although the length (winding length) of the film base 11 is not particularly limited, it is preferably 2000 to 15000 m, more preferably 3000 to 12000 m. Although the width of the film base 11 is not particularly limited, it is preferably 950 to 3000 mm.

(Phase difference Ro and Rt)
The film base 11 can have retardation Ro and Rt according to its application. For example, the in-plane retardation Ro measured at a measurement wavelength of 590 nm of the film base 11 at 23° C. and 55% RH preferably satisfies 40 nm≦Ro≦60 nm, and the thickness direction retardation Rt is It is preferable to satisfy 115 nm≦Rt≦145 nm. Such a film base 11 is suitable as a retardation film combined with, for example, a VA liquid crystal cell. Further, when 0 nm≦Ro≦10 nm and −20 nm≦Rt≦20 nm, it is suitable as a retardation film combined with an IPS mode liquid crystal cell.

Ro and Rt are defined by the following formulas, respectively.
Formula (1): Ro = (nx-ny) x d
Formula (2): Rt = ((nx + ny) / 2-nz) x d
(In the formula,
nx represents the refractive index in the in-plane slow axis direction (the direction in which the refractive index is maximized) of the film base 11,
ny represents the refractive index in the direction perpendicular to the in-plane slow axis of the film base 11,
nz represents the refractive index in the thickness direction of the film base 11,
d represents the thickness (nm) of the film base 11 . )

The in-plane slow axis of the film base 11 can be confirmed by an automatic birefringence meter AxoScan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics).

Ro and Rt can be measured by the following methods.
1) The film base 11 is conditioned for 24 hours in an environment of 23° C. and 55% RH. The average refractive index of this film base 11 is measured with an Abbe refractometer, and the thickness d is measured with a commercially available micrometer.
2) The retardation Ro and Rt of the film base 11 after humidity control at a measurement wavelength of 550 nm were measured at 23°C and 55% using an automatic birefringence meter Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by Axometrics). Measured under RH environment.

1-2. Projection 12
The protrusions 12 are a resin composition applied to both ends of the surface of the film base 11 in the width direction. Specifically, the protrusions 12 are arranged discontinuously or continuously along the longitudinal direction of the film base 11 at both ends in the width direction of the surface of the film base 11 . In the present embodiment, the plurality of protrusions 12 are arranged discontinuously (island-like) (see FIG. 2A). The convex portion 12 may be integrated with the film base portion 11 or may be a separate member.

In a cross section along the width direction of the film 10 and passing through the vertex (highest point) of the protrusions 12, the height t of the protrusions 12 is 0.5 to 3 μm (see FIG. 2B). When the height t of the protrusions 12 is 0.5 μm or more, sticking between the film bases 11 can be sufficiently suppressed when the film 10 is wound into a roll. When the height t of the projections 12 is 3 μm or less, when the film 10 is wound into a roll, the absolute amount of crushing of the projections 12 itself is small, making it difficult to deform the film roll. From the same point of view, the height t of the projections 12 is preferably 1.0 to 2.0 μm. The height t of the projections 12 is the height from the surface of the film base 11 to the apex of the projections 12 .

The height t of the projections 12 is preferably 1 to 30%, more preferably 2 to 10%, of the thickness of the film base 11, for example.

In a cross section along the width direction of the film 10 and passing through the vertices of the protrusions 12, the width w of the protrusions 12 is not particularly limited, but is preferably 500 to 2000 μm. When the width w of the protrusions 12 is 500 μm or more, the support area can be increased, so that the protrusions 12 are less likely to be crushed. In addition, the film of the present invention can be efficiently produced because the cooling process proceeds easily during melting and forming. From the same point of view, it is more preferable that the width w of the protrusion 12 is 700 to 1500 μm. The width w of the protrusion 12 is the maximum width of the protrusion 12 in the cross section.

The height t and width w of the convex portion 12 can be measured using a laser microscope. As a laser microscope, for example, a laser Microscope VK-X1000 manufactured by Keyence Corporation can be used. In the area where the convex portion 12 is arranged, the height t of the convex portion is measured for a range of 100 mm in the length direction (Y direction in FIG. 2A) and 15 mm in the width direction (X direction in FIG. 2A). and width w are measured, and their average value is defined as "the height t and the width w of the convex portion".

When the haze value of the region a1 in which the convex portions 12 are not arranged is Hz1 and the haze value of the region a2 in which the convex portions 12 are arranged is Hz2 (see FIG. 1A), the haze ratio Hz2/Hz1 is 1.1 to 4.5. By setting Hz2/Hz1 to 1.1 or more (for example, by setting the height of the projections 12 and the existence density of the projections 12 to a certain level or more), the projections 12 can function as knurling parts, and the projections can be reduced. It can be made difficult to collapse. Further, by setting Hz2/Hz1 to 4.5 or less (for example, by setting the height of the convex portion 12 to a certain value or less), the absolute amount of crushing of the convex portion can be further reduced. From the same point of view, Hz2/Hz1 is preferably 1.5 to 3.0.

The haze ratio Hz2/Hz1 of the film base 11 is the haze ratio of the film base 11 for the area a2 where the projections 12 are arranged and the area a1 where the projections 12 are not arranged (Φ11m of the measurement area, area 95mm2). A haze meter (NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure 10 points at intervals of 10 mm in the longitudinal direction of the optical film under an environment of 23°C and 50% RH. can be calculated from the ratio of

The Hz2/Hz1 of the film base 11 can be adjusted by the height and width of the protrusions 12, the existence density, the composition of the protrusions 12, and the like. For example, the higher the height t of the projections 12, the greater the width of the projections 12, and the higher the density of the projections 12, the higher the Hz2/Hz1 of the film base 11. Further, when the height t of the projections 12 is small and the thermoplastic resin forming the projections 12 and the thermoplastic resin forming the film base 11 are of the same type, Hz2/Hz1 of the film base 11 tends to be small. .

The shape of the protrusions 12 in the cross section along the width direction of the film 10 and passing through the vertices of the protrusions 12 is not particularly limited, and may be quadrangular, triangular, or circular. segment). An arch is a shape obtained by connecting both ends of a circular arc or an elliptical arc with straight lines, and examples thereof include semicircular and semielliptical shapes. In this embodiment, the shape of the protrusion 12 in the cross section is arcuate.

Although the center-to-center distance p of the plurality of projections 12 is not particularly limited, it can be, for example, 0.5 to 10 mm, preferably 1 to 5 mm (see FIG. 2A). When the center-to-center distance p of the plurality of protrusions 12 is 0.5 mm or more, it is easy to appropriately adjust the amount of air contained between the films when the film is wound into a roll. Since the presence density of the portions 12 can be appropriately increased, the protrusions 12 can be made less likely to collapse. Note that the center-to-center distance p is the minimum value among the distances between the centers (centers of gravity) of the plurality of adjacent projections 12 when the film 10 is viewed from above.

The existence density of the protrusions 12 depends on the width of the protrusions 12 and the like, but is preferably, for example, 2 to 160/cm ² , more preferably 10 to 60/cm ² . When the density of the protrusions 12 is within the above range, it is easy to adjust the haze ratio Hz2/Hz1 within the above range.

The convex portion 12 contains a second resin composition containing a thermoplastic resin.

The thermoplastic resin contained in the projections 12 is of the same type as the thermoplastic resin contained in the film base 11 . For example, if the thermoplastic resin contained in the film base 11 is a cycloolefin resin, the resin contained in the projections 12 is also preferably a cycloolefin resin. If the thermoplastic resin contained in the film base 11 and the thermoplastic resin contained in the projections 12 are of the same type, the adhesion between the projections 12 and the film base 11 can be enhanced.

"The same type of thermoplastic resin" refers to thermoplastic resins that have the same main component monomer (the component contained most), the type and content of the copolymer component monomer, the weight average molecular weight (Mw) of the resin, Physical properties such as glass transition temperature (Tg) may differ.

Although the content of the resin is not particularly limited, it is preferably 60% by mass or more, more preferably 70 to 100% by mass, based on the second resin composition that constitutes the projections 12.

The convex portion 12 may further contain the same components as the film base portion 11 (for example, fine particles, etc.) as necessary. However, when the film 10 is wound, the content of fine particles in the convex portion 12 is less than It is preferably less than the content of fine particles, and more preferably contains no fine particles.

2. Method for producing film The film of the present invention comprises: 1) a step of casting a first resin composition on a support to obtain a strip-shaped film base 11; applying the second resin composition to the portion to form the convex portion.

1) About the process of obtaining the film base 11 The strip|belt-shaped film base 11 is obtained by casting a 1st resin composition.

The casting of the first resin composition may be performed by a melt casting method or a solution casting method. Above all, the casting of the first resin composition is preferably carried out by a solution casting method from the standpoint of being able to use a high-molecular-weight resin.

That is, the film base 11 includes a step of obtaining a dope (first resin composition) (preparation of the dope), casting the obtained dope on a support, drying and peeling to obtain a film-like material. It can be obtained through a process (casting) and a process of drying and stretching the resulting film-like material (drying/stretching).

(Preparation of dope)
A resin is dissolved in a solvent to prepare a first resin composition.

The solvent used contains 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. Among them, methylene chloride is preferred.

The solvent used may further contain a poor solvent. Examples of poor solvents include straight or branched chain aliphatic alcohols having 1 to 4 carbon atoms. When the ratio of alcohol in the dope becomes high, the film-like material tends to gel and is easily peeled off from the metal support. Linear or branched aliphatic alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol and tert-butanol. Among them, methanol and ethanol are preferable from the viewpoint of stability and drying property.

(Casting)
The obtained first resin composition is then cast on a support. Casting of the first resin composition can be performed by discharging from a casting die. The temperature of the first resin composition during casting is usually 15 to 30°C, preferably room temperature (23°C).

Next, after the solvent in the first resin composition cast on the support is appropriately evaporated (after drying), it is peeled off from the support to obtain a film-like material.

The amount of residual solvent in the first resin composition after peeling is, for example, preferably 25% by mass or more, more preferably 30 to 37% by mass, and even more preferably 30 to 35% by mass. When the amount of residual solvent at the time of peeling is 25% by mass or more, the solvent is easily volatilized at once from the film after peeling. Further, when the amount of residual solvent at the time of peeling is 37% by mass or less, excessive stretching of the film-like material due to peeling can be suppressed.

The residual solvent amount of the first resin composition at the time of peeling is defined by the following formula. The same applies to the following.
Residual solvent amount (mass%) = (mass of first resin composition before heat treatment - mass of first resin composition after heat treatment)/mass of first resin composition after heat treatment x 100
Note that the heat treatment for measuring the amount of residual solvent means heat treatment at 140° C. for 15 minutes.

(drying/stretching)
Then, the resulting film-like material is dried. Drying may be performed in one step or in multiple steps. Moreover, you may perform drying, extending|stretching as needed.

The stretching may be carried out depending on the desired optical properties, and is preferably stretched in at least one direction. Biaxial stretching in the transport direction (MD direction) may also be performed.

The draw ratio can be, for example, 1.01 to 2 times from the viewpoint of use as a retardation film. The draw ratio is defined as (stretching direction size of the film after stretching)/(stretching direction size of the film before stretching). In addition, when biaxially stretching, it is preferable to set it as the said draw ratio about each of TD direction and MD direction. The in-plane slow axis direction of the film (the direction in which the refractive index is maximized in the plane) is usually the direction in which the draw ratio is maximized.

The drying temperature (stretching temperature) during stretching is preferably (Tg-65)°C to (Tg+60)°C, where Tg is the glass transition temperature of the resin, and (Tg-50)°C to (Tg+50)°C. is more preferable. When the stretching temperature is above a certain level, the solvent tends to volatilize appropriately, so that the stretching tension can be easily adjusted to an appropriate range.

The amount of residual solvent in the filmy material at the start of stretching is preferably about the same as the amount of residual solvent in the filmy material at the time of peeling, for example, preferably 20 to 30% by mass, preferably 25 to 30% by mass. % is more preferred.

Stretching in the TD direction (width direction) of the film can be performed, for example, by fixing both ends of the film with clips or pins and widening the distance between the clips or pins in the direction of travel (tenter method). The film-like material can be stretched in the MD direction, for example, by a method (roll method) in which a plurality of rolls are provided with different peripheral speeds and the difference in peripheral speeds of the rolls is utilized.

From the viewpoint of further reducing the amount of residual solvent, it is preferable to further dry (post-dry) the film-like material obtained after stretching. For example, it is preferable to further dry the film-like material obtained after the stretching while transporting it with rolls (with a certain tension applied).

The drying temperature is preferably (Tg-30) to (Tg+30)°C, more preferably (Tg-20) to Tg°C, where Tg is the glass transition temperature of the resin. When the drying temperature is above a certain level, it is easy to increase the volatilization rate of the solvent from the stretched film, and thus the drying efficiency is likely to be increased. .

2) Step of Forming Protrusions Next, a second resin composition is applied (cast) to both ends of the surface of the obtained film base 11 in the width direction to form protrusions.

The casting of the second resin composition may be a melt casting method or a solution casting method. For example, in the step 1) above, when the first resin composition is cast by a solution casting method, it is preferable to cast the second resin composition by a solution casting method in this step.

That is, the convex portions 12 can be formed by applying a second resin composition (knurling solution) containing a resin and a solvent to both widthwise end portions of the film base portion 11 and then drying it.

(Second resin composition)
The resin contained in the second resin composition is of the same type as the resin contained in the dope.

The solvent contained in the second resin composition contains at least an organic solvent (good solvent) capable of dissolving the resin. Examples of good solvents include chlorinated organic solvents such as methylene chloride; and non-chlorinated organic solvents such as methyl acetate, ethyl acetate, acetone, tetrahydrofuran, cyclopentanone and toluene. Among them, methylene chloride, cyclopentanone, and toluene are preferable from the viewpoint of easily dissolving the cycloolefin resin.

The solvent contained in the second resin composition may further contain a poor solvent. As the poor solvent, the same poor solvent as contained in the dope can be used.

In the solution casting method, the resin concentration of the second resin composition is preferably lower than the resin concentration of the first resin composition, and 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 mass % and 10 mass % or less, more preferably 3 to 7 mass %. By adjusting the resin concentration of the second resin composition, the height of the convex portion can be adjusted. For example, by increasing the resin concentration of the second resin composition, the height of the protrusions can be increased.

(assignment)
Application of the second resin composition can be performed by any method, for example, application by a dispenser or ink jet method, or casting by a die (preferably a reduced pressure die).

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

(dry)
Drying of the second resin composition can be performed by any method, such as hot air drying or heat drying using electromagnetic waves (for example, heat drying using an infrared (IR) heater).

The drying temperature is not particularly limited, but preferably high. Specifically, the drying temperature is preferably 40 to (Tg-20) ° C., and 80 to (Tg-10) ° C., where Tg is the glass transition temperature of the resin contained in the second resin composition. is more preferable. Specifically, it is preferably 40 to 120°C, more preferably 80 to 100°C.

The strip-shaped film 10 thus obtained may be wound into a roll along the longitudinal direction.

3) Winding Step The obtained film base 11 is wound in the longitudinal direction (direction orthogonal to the width direction) of the film 10 using a winder. As a result, a film roll can be obtained by winding the strip-shaped film 10 around the winding core.

The winding method is not particularly limited, and may be a constant torque method, a constant tension method, a taper tension method, or the like.

The winding tension when winding the film base 11 is not particularly limited, but can be about 50 to 170N.

The resulting film 10 is used as an optical film for a display device such as a liquid crystal display device or an organic EL display device after removing the portion where the projections 12 are formed. Examples of optical films include polarizing plate protective films (including retardation films, brightness enhancement films, etc.), transparent substrate films, and light diffusion films. Among them, the film 10 is preferably used as a polarizing plate protective film.

[Modification]
In addition, in the above-described embodiment, an example in which a plurality of island-shaped convex portions 12 are arranged along the longitudinal direction of the film base portion 11 is shown, but the present invention is not limited to this.

3A is a plan view of a film according to a modification, and FIG. 3B is a cross-sectional view taken along line 3B-3B of FIG. 3A. As shown in FIGS. 3A and 3B, the convex portions 12 may be arranged continuously (in a strip shape) along the longitudinal direction of the film base portion 11 .

Further, in the above-described embodiment, an example in which the convex portion 12 is arranged only on one surface of the film base portion 11 is shown, but it is not limited to this, and may be arranged on both surfaces.

Further, in the above-described embodiment, an example (solution casting method) in which the convex portion 12 is formed by applying a knurling solution containing a resin and a solvent and then drying the solution is shown. It may also be formed by a method (melt casting method) in which the resin composition is applied and then solidified by cooling.

That is, in the melt-casting method, the roll body includes: 1) a step of casting a molten first resin composition and then cooling and solidifying to obtain a strip-shaped film base; After applying the molten second resin composition to both ends in the direction, it is cooled and solidified to form convex portions.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these.

1. Production of film roll <Production of film roll 1>
(Preparation of fine particle dispersion)
After stirring and mixing the following components with a dissolver for 50 minutes, they were dispersed with a Manton Gaulin. Further, the secondary particles were dispersed with an attritor so that the particle size of the secondary particles had a predetermined size, and then filtered with Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a fine particle dispersion.
R972V (manufactured by Nippon Aerosil Co., Ltd.): 4% by mass
Dichloromethane: 48% by mass
Ethanol: 48% by mass

(Preparation of dope)
First, dichloromethane was added to a pressurized dissolution tank at a flow rate of 400 kg/min and ethanol at a flow rate of 20 kg/min. Three minutes after starting the addition of the solvent, the cyclic polyolefin resin was charged into the pressurized dissolution tank while stirring. Then, 5 minutes after the start of the addition of the solvent, the fine particle addition liquid was added, heated to 60° C., and completely dissolved with stirring. The heating temperature was raised from room temperature at a rate of 5°C/min, and after dissolution in 30 minutes, the temperature was lowered at a rate of 3°C/min. Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. 244 (filtration accuracy of 0.005 mm) at a filtration flow rate of 300 L/m ² ·h and a filtration pressure of 1.0×10 ⁶ Pa to prepare a dope having the following composition.
Cycloolefin-based resin G7810 (manufactured by JSR Corporation) (cycloolefin-based resin (COP) containing a structural unit derived from a norbornene-based monomer represented by the following formula, Mw: 140,000, Tg: 170°C): 100 mass %
R972V (manufactured by Nippon Aerosil Co., Ltd.): 0.30% by mass
Dichloromethane: 380% by mass
Ethanol: 20% by mass

(film formation)
Then, the obtained dope was uniformly cast on a stainless steel belt support at a temperature of 31° C. and a width of 2300 mm using an endless belt casting apparatus. The temperature of the stainless steel belt was adjusted to 28° C., and the conveying speed of the stainless belt was 30 m/min. After evaporating the solvent on the stainless steel belt support until the residual solvent amount in the cast dope reaches 30% by mass, it is peeled off from the stainless steel belt support with a peel tension of 110 N/m to obtain a film-like material. got
The obtained film-like material was stretched 1.3 times while being heated at 120° C. in the transport direction (MD direction) by a roll method using a peripheral speed difference between transport rolls, and then stretched by a tenter method by 130 in the TD direction. It was stretched 1.65 times while heating to °C. The resulting film-like material was conveyed while being heated at 70° C. until it was completely dried, and the edges were slit to obtain a film having a thickness of 35 μm and a width of 2500 mm (film base, Ro: 50 nm, Rt: 135 nm). Obtained.

(Preparation of solution for forming protrusions)
As the same thermoplastic resin as the film, cycloolefin resin G7810 (manufactured by JSR Corporation) was dissolved in a solvent to a concentration of 4% by mass to obtain a convexity forming solution. A mixed solvent of dichloromethane and cyclopentanone was used as the solvent, and the mixing ratio was set to dichloromethane/cyclopentanone=70/30 (mass ratio).

(Formation of convex portion)
A solution for forming protrusions was applied to both ends in the width direction of the surface of the film, and then dried to form protrusions. The solution for forming protrusions was applied using a SUPER HI JET dispenser manufactured by Musashi Engineering Co., Ltd. to form non-continuous protrusions each having a diameter of 1 mm and a height of 0.5 μm. Specifically, as shown in FIG. 2A, the projections are formed in three rows in the longitudinal direction of the film (the Y direction in FIG. 2A), and in the width direction of the film (the X direction in FIG. 2A), It was formed in a region from a position of 3 mm from the edge of the film to a position of about 5 mm toward the central portion in the width direction. Moreover, the center-to-center distance p between the convex portions was set to 2 mm in both the X direction and the Y direction. Also, the existence density of the protrusions 12 was set to 25/cm ² .

Then, the film on which the projections were formed was wound around a core by a winding length of 4000 m to obtain a film roll 1.

<Production of film rolls 2 to 5>
Film rolls 2 to 5 were obtained in the same manner as film roll 1, except that the height of the protrusions was changed as shown in Table 1 by adjusting the resin concentration of the protrusion-forming solution and the head descending speed of the dispenser. rice field.

<Production of film roll 6>
(Preparation of UV-curable composition)
A UV curable composition containing the following components was prepared.
Dipentaerythritol hexaacrylate (DPHA manufactured by Nippon Kayaku): 100 parts by mass Methyl ethyl ketone: 113 parts by mass Photopolymerization initiator (Irgacure 907, manufactured by Ciba Geiki): 3 parts by mass

(Formation of convex portion)
A film roll 6 was obtained by forming projections in the same manner as in film roll 1, except that the UV-curable composition was applied and then cured by irradiation with ultraviolet rays to form projections.

<Production of film roll 7>
(Preparation of film base)
A film serving as a film base was obtained in the same manner as the film roll 1.

(Knurling (embossing))
A film roll 7 was obtained by knurling (embossing) with a width of 10 mm and a height of 2 μm on both ends of the surface of the film in the width direction (regions 1 to 2 mm from the edge of the film). The knurling process was performed by applying pressure to a heated metal ring having an uneven pattern (a shape in which nine unevennesses were arranged in a row in the width direction). The working pressure of the metal ring was 200 kPa, and the temperature was 230.degree. The resulting film base had a thin portion.

<Production of film roll 8>
(Preparation of film base)
A film serving as a film base was obtained in the same manner as the film roll 1.

(Knurling processing (laser irradiation))
Both ends of the surface of the film in the width direction were irradiated with a laser beam using a laser marker to form an uneven structure, and a film roll 8 was obtained. The concave-convex structure was formed in a region of 1 to 2 mm from the edge of the film with the shape, size and spacing shown in FIG. The resulting film base had a thin portion. As a laser light irradiation device, a CO ₂ laser light irradiation device (LP-430U manufactured by Panasonic Sunkus Co., Ltd., laser wavelength: 10.6 μm) was used. Moreover, the irradiation output of the laser beam was set to 90%.

<Production of film roll 9>
A film roll 9 was obtained in the same manner as the film roll 2 except that the width of the protrusions and the haze ratio were changed as shown in Table 1.

<Production of film roll 11>
Film roll 11 was obtained in the same manner as film roll 2 except that the thickness of the film base was changed as shown in Table 1.

<Production of film rolls 10 and 12>
(Preparation of film base)
Film base (film base, Ro: 5 nm, Rt : −5 nm).

(Preparation of solution for forming protrusions)
Film roll 1 except that the cycloolefin resin G7810 in the convexity forming solution was changed to the above (meth)acrylic resin, and the resin concentration was adjusted so that the height of the convexities was the value shown in Table 1. A convex portion was formed in the same manner as above.

<Evaluation>
In addition, the shape of the projections of the obtained film rolls 1 to 12, the deformation of the film roll, and the like were evaluated by the following methods.

(1) Height of convex portion t, haze ratio Hz2/Hz1
The height t (maximum height) and width w (maximum width) of the protrusions in the cross section of the film in the width direction were measured using a laser microscope. A laser microscope VK-X1000 manufactured by Keyence Corporation was used as a laser microscope. Specifically, in the region where the convex portion is arranged, the height t and the width w of the convex portion are measured for a range of 100 mm in the length direction of the film and 15 mm in the width direction, and the average value of them is the “convex part height t and width w".

The haze value Hz1 of the area a1 where the projections are not arranged and the haze value Hz2 of the area a2 where the projections are arranged (Φ11m of the measurement area, area 95mm ² ) of the film are each measured using NDH2000 manufactured by Nippon Denshoku Industries Co., Ltd. and the ratio between them was calculated as the haze ratio Hz2/Hz1.

(2) Winding Deformation The wound film roll was double-wrapped with a polyethylene sheet, and both ends of the core were supported by a frame (so that the axial direction of the core was horizontal). It was stored for 5 days under conditions of %. After that, the polyethylene sheet was opened, and the tube of the illuminated fluorescent lamp was reflected and projected onto the surface of the film roll, and its distortion or fine disturbance was observed. And it evaluated based on the following references|standards.
◎: The fluorescent lamp looks straight. 〇: There is only one place where the fluorescent lamp looks slightly bent, but there is no practical problem. △: There are only two places where the fluorescent lamp looks very slightly bent. Practically no problem x: Some parts of the fluorescent lamp are clearly bent and spots appear mottled, which is a problem.

(3) Interlayer contact (blocking)
The wound film roll is double-wrapped with a polyethylene sheet, and both ends of the core are supported by a frame (so that the axial direction of the core is horizontal), and the temperature is 40°C and 80%. Stored for 5 days. After that, the film was unwound from the roll, and the state of blocking (sticking) between the overlapping films was visually observed. And it evaluated based on the following references|standards.
◎: No blocking ○: There is blocking, but it is very slight and there is no problem in practical use △: There is a little blocking, but there is no problem in practical use ×: Blocking is clearly present so that it can be seen at a glance △ If so, it was considered acceptable.

(4) Adhesion of Convex Portions In a vibration test, an acceleration of 5.8 m/s ² was applied in the width direction to the wound film roll for 30 minutes. As a vibration tester, TR1000 manufactured by IMV Corporation was used. After that, the film was unwound from the roll, and 100 m of the film between the remaining 300 and 200 m of the winding core was visually checked for the presence or absence of portions where the projections were peeled off from the film base. And it evaluated based on the following references|standards.
◎: No peeling ○: 1 to 2 peeling locations are no problem △: 3 to 4 peeling locations are no problem in practice ×: 5 or more peeling locations are practically problematic level △ If it is more than that, it is considered as the allowable range.

(5) Minute Foreign Matter In a vibration test, an acceleration of 5.8 m/s ² was applied in the width direction to the wound film roll for 30 minutes. As a vibration tester, TR1000 manufactured by IMV Corporation was used. After that, the film was unwound from the roll and sampled, and the vicinity of the knurling was observed with an optical microscope. It was judged as follows.
◎: There are no fine fragments ○: There are very few fine fragments, but there is no practical problem △: There are a few fine fragments, but there is no practical problem ×: There are many fine fragments, which is a problem △ If it is more than that, it is considered as the allowable range.

(6) Display quality of 8K liquid crystal display device (Fabrication of polarizing plate)
One side of an amorphous polyester film with a thickness of 100 μm was subjected to corona treatment, and the treated side was coated with polyvinyl alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and acetoacetyl-modified polyvinyl alcohol (Nippon Synthetic Chemical Industry “Go Sepheimer Z200"; polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more) at a mass ratio of 9:1 was applied and dried at 25 ° C. A laminate containing a crystalline polyester film substrate and a PVA-based resin layer having a thickness of 11 μm was obtained.

The resulting laminate was uniaxially stretched 2.0 times at the free end in the longitudinal direction by in-air auxiliary stretching in an oven at 120°C, and then transported by rolls in a 4% boric acid aqueous solution at 30°C for 30 seconds. It was sequentially immersed in a staining solution (0.2% iodine, 1.0% potassium iodide aqueous solution) at 30° C. for 60 seconds. Next, while conveying the laminate by rolls, it was immersed in a crosslinking solution (aqueous solution containing 3% potassium iodide and 3% boric acid) at 30°C for 30 seconds to carry out a crosslinking treatment. While immersed in a 5% potassium aqueous solution, the free end was uniaxially stretched in the longitudinal direction so that the total draw ratio was 5.5 times. After that, the laminate was immersed in a cleaning solution (4% potassium iodide aqueous solution) at 30° C. to obtain a laminate containing an amorphous polyester film substrate and a PVA-based polarizer with a thickness of 5 μm.

(Preparation of active energy ray-curable adhesive composition)
An active energy ray-curable adhesive composition having the following composition was prepared.
N-hydroxyethyl acrylamide: 30 parts by mass acryloylmorpholine: 65 parts by mass tripropylene glycol diacrylate: 5 parts by mass 2,4-diethylthioxanthen-9-one (initiator): 1.4 parts by mass 2-methyl-1 -(4-Methylthiophenyl)-2-morpholinopropan-1-one: 1.4 parts by mass The curable adhesive composition is applied to the surface of the polarizer of the laminate to a thickness of about 1 μm, and the A film unwound from the film roll was laminated thereon, and the adhesive was cured by irradiating ultraviolet light with an accumulated light quantity of 1000 mJ/cm ² . The lamination was performed so that the slow axis of the film and the absorption axis of the polarizer were orthogonal to each other.

The amorphous polyester film substrate is peeled off from the laminate, the active energy ray-curable adhesive composition is applied to the surface of the peeled PVA resin layer, the film is laminated, and then ultraviolet rays are irradiated. Allow the adhesive to cure. As a result, a polarizing plate having a polarizer and the above films as polarizing plate protective films disposed on both sides of the polarizer was obtained.

Then, the obtained polarizing plate was used in an 8K liquid crystal display panel, and the unevenness of light leakage during black display was visually evaluated. Specifically, an acrylic pressure-sensitive adhesive sheet having a thickness of 20 μm was adhered to the film on the side of the polarizing plate having the slow axis perpendicular to the absorption axis of the polarizer using a roll laminator. Together, a polarizing plate with an adhesive layer was obtained.

(Production of liquid crystal display device)
(A) Using a Polarizing Plate Containing a COP Film The polarizing plates attached to both sides of the liquid crystal cell of a 60-inch liquid crystal display device 8T-C60BW1 (VA system) manufactured by Sharp were peeled off. The pressure-sensitive adhesive layers of the polarizing plate with the pressure-sensitive adhesive sheet prepared above were attached to both sides of the liquid crystal cell. The directions of the slow axis of the film and the absorption axis of the polarizer were made to match the directions of the originally bonded polarizing plate.

(B) When using a polarizing plate containing an Acr film A 60-inch liquid crystal display device 8T-C60BW1 manufactured by Sharp was changed to a 65-inch liquid crystal display device 65NANO99JNA (IPS method) manufactured by LG Electronics, and was produced in the same manner as described above. .

(Light leakage during black display)
The obtained 8K liquid crystal display device was installed in a dark room, and the entire surface was displayed in black by external input from a personal computer. Further, the edges of the four sides were sealed with black tape so that only the black display portion was more reliably exposed when viewed from the front. In this state, the unevenness of light leakage was observed and evaluated based on the following criteria.
◎: Very little unevenness in light leakage 〇: Only slightly unevenness in light leakage △: Some unevenness in light leakage, but no practical problem ×: Much unevenness in light leakage, not suitable for practical use △ If it is more than that, it is considered as the allowable range.

Table 1 shows the production conditions and evaluation results of film rolls 1 to 12.

As shown in Table 1, film rolls 1 to 3 and 9 to 11 (the present invention) did not generate any foreign matter, and there was no winding failure or projection dropout. As a result, it can be seen that light leakage during black display can also be suppressed.

On the other hand, in the film rolls 5 and 12, in which the height of the protrusions is higher than 3 μm, the collapse rate of the protrusions is high, so it can be seen that winding deformation is likely to occur. It can be seen that this causes variations in the optical properties of the film, resulting in light leakage during black display. On the other hand, it can be seen that in the case of the film roll 4 in which the height of the protrusions is less than 0.5 μm, the films tend to stick together (blocking), which causes light leakage during black display. Further, it can be seen that even if the height of the convex portion is lowered, the interlayer adhesion can be suppressed to a high degree by increasing the haze ratio (comparison between film rolls 9 and 2).

In addition, film rolls 7 and 8 have a Hz2/Hz1 higher than 4.5, and foreign matter and winding deformation are likely to occur, so it can be seen that light leakage occurs during black display. This is because the protrusions are formed using plastic deformation at Tg or higher, so fine voids are likely to occur, the voids reduce the strength of the protrusions, and the protrusions are slightly crushed when formed into a roll. According to In addition, when the projections are crushed, minute foreign substances are generated and easily scratched. This is considered to cause light leakage unevenness in the display device.

In addition, it can be seen that in the film roll 6 in which the resin constituting the projections is an ultraviolet curable resin constituting the film base, the projections fall off, impairing the knurling function and causing light leakage during black display.

This application claims priority based on Japanese Patent Application No. 2021-011192 filed on January 27, 2021. All contents described in the specification and drawings are incorporated herein by reference.

10 strip-shaped film (film roll)
11 film base 12 projection

Claims

A film comprising a film base and projections arranged on both ends of the surface of the film base,
The film base and the protrusions contain the same type of thermoplastic resin,
The height of the convex portion is 0.5 to 3 μm,
The haze ratio Hz2/Hz1 is 1.1 to 4.5, where Hz1 is the haze value of the region where the convex portions are not arranged, and Hz2 is the haze value of the region where the convex portions are arranged. be,
the film.
The film base is strip-shaped,
The convex portions are arranged at both ends in the width direction of the surface of the film base,
The film of Claim 1.
The film base does not have a thin portion,
3. The film of claim 1 or 2.
A plurality of the protrusions are arranged in an island shape,
The film according to any one of claims 1-3.
The film base and the convex portion are integral,
The film according to any one of claims 1-4.
The thickness of the film base is 10 to 40 μm,
The film according to any one of claims 1-5.
The thermoplastic resin is a cycloolefin resin or (meth)acrylic resin,
The film according to any one of claims 1-6.
The film base is an optical film,
The film according to any one of claims 1-7.
comprising a film according to any one of claims 1 to 8,
film roll.
A method for producing the film according to any one of claims 1 to 9,
1) a step of casting the first resin composition to obtain a strip-shaped film base;
2) a step of applying a second resin composition to both ends in the width direction of the surface of the strip-shaped film base to form protrusions;
including,
Film production method.