JP7155827B2 - Method for producing long multilayer film and long multilayer film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a long multilayer film manufacturing method and a long multilayer film.

2. Description of the Related Art In manufacturing a multi-layer film, such as an optical film, having two or more layers, a long film is continuously formed. In the production of a long multilayer film, it is common to transport the film continuously in its longitudinal direction. Conventionally, various studies have been made on methods for producing such long multilayer films (see Patent Documents 1 to 6).

WO2016/047465 JP 2015-210459 A Japanese Patent No. 5120379 Japanese Patent No. 5186926 Japanese Patent No. 4565507 Japanese Patent No. 3701022

Various problems may occur when transporting a long film. Therefore, it is required to suppress the occurrence of such problems. For example, during transport of a long film, the film width direction end may curl. Such curling occurs frequently when the long film is a multi-layer film.

Accordingly, an object of the present invention is to provide a method for producing a long multilayer film that suppresses the occurrence of curling during transportation and enables efficient production, and a long multilayer film that causes less curling during transportation. to provide.

The present inventor made studies to solve the above problems. As a result, the present inventors have found that the above problems can be solved by making the ends in the width direction of a specific shape in the production of a long multilayer film, and completed the present invention.
That is, the present invention includes the following.

[1] A method for producing a long multilayer film comprising a substrate film layer (A) and a coating layer (B) provided on the surface thereof, comprising:
Step (1) of preparing a long base film (a);
and a step (2) of applying a coating layer material (b) on the base film (a),
The coating in the step (2) is
The ratio De/ _D10 of the film thickness De at the width direction end of the coating film layer (B) to the film thickness D10 at the position ₁₀ mm from the width direction end of the coating film layer (B) is 85% or less. A method for producing a long multilayer film, wherein
[2] The step (2) is
The widthwise end of the coating layer (B) is located inside the widthwise end of the base film layer (A),
The long film according to [1] is carried out so that the distance We from the widthwise end of the coating layer (B) to the widthwise end of the base film layer (A) is 5 mm or more. A method for producing a multilayer film.
[3] The coating in the step (2) is performed with a die,
In the step (2), the coating layer material (b) from the die is spread outward in the width direction from the width direction end of the opening of the die so that the coating layer material (b) is applied. ), the method for producing a long multilayer film according to [1] or [2], wherein the extrusion pressure is adjusted.
[4] The coating in the step (2) is performed with a die,
In the step (2), a flow rate restricting member is provided inside the die in the vicinity of the widthwise end of the die opening, and the flow rate at the widthwise end of the die opening is adjusted to the widthwise central portion. The method for producing a long multilayer film according to any one of [1] to [3], which is relatively reduced with respect to.
[5] After the step (2), further comprising a step (3) of co-stretching a multilayer material containing a cured product of the substrate film (a) and the coating layer material (b) [1] The method for producing a long multilayer film according to any one of [4].
[6] The method for producing a long multilayer film according to any one of [1] to [5], wherein the coating film layer material (b) has a viscosity of 150 to 1500 cps.
[7] The elongated sheet according to any one of [1] to [6], wherein the coating film layer (B) has an inclined portion whose thickness gradually decreases from the inside to the outside at the widthwise end portion of the coating layer (B). A method for producing a multilayer film.
[8] A long multilayer film comprising a base film layer (A) and a coating layer (B) provided on the surface thereof,
The ratio De/D ₁₀ of the film thickness De at the width direction end of the coating layer (B) with respect to the film thickness D ₁₀ at 10 mm from the width direction end of the coating layer (B) is 85% or less. Long multi-layer film.
[9] the widthwise end of the coating layer (B) is positioned inside the widthwise end of the base film layer (A);
The long multilayer film according to [8], wherein the distance from the widthwise end of the coating layer (B) to the widthwise end of the base film layer (A) is 5 mm or more.
[10] The long multilayer film of [8] or [9], wherein the coating film layer (B) has, at its widthwise end, a sloped portion whose thickness gradually decreases from the inside to the outside.

According to the method for producing a long multilayer film of the present invention, it is possible to suppress the occurrence of curling during transportation and to carry out efficient production. The long multilayer film of the present invention can be less likely to curl during transportation.

FIG. 1 is a cross-sectional view schematically showing the long multilayer film of the present invention obtained by the production method of the present invention. FIG. 2 is an enlarged cross-sectional view showing an enlarged region _R1 in the cross section of the long multilayer film shown in FIG. FIG. 3 is a side view schematically showing application of the coating film layer material (b) to the substrate film (a) by die coating by die coating. 4 is a perspective view schematically showing the vicinity of the opening of the die shown in FIG. 3. FIG. FIG. 5 is a front view schematically showing a specific example of application of the coating film layer material (b) to the substrate film (a) by die coating by die coating. FIG. 6 is a front view schematically showing a die used for another specific example of applying the coating film layer material (b) to the substrate film (a) by die coating by die coating. 7 is a top view of the opening of the die shown in FIG. 6. FIG. FIG. 8 is a front view schematically showing a die used in still another specific example of application of the coating film layer material (b) to the substrate film (a) by die coating by die coating. 9 is a top view of the opening of the die shown in FIG. 8. FIG. FIG. 10 is a front view schematically showing a die used in another specific example of application of the coating film layer material (b) to the substrate film (a) by die coating by die coating. 11 is a top view of the opening of the die shown in FIG. 10. FIG. FIG. 12 is a perspective view schematically showing how curling occurs during general film transport. FIG. 13 is a cross-sectional view schematically showing an example of a cross section of the film 71 along the plane in the rectangular plane region _R2 in FIG. FIG. 14 is a cross-sectional view schematically showing another example of a cross section of the film 71 along the plane in the rectangular plane region _R2 in FIG.

Hereinafter, the present invention will be described in detail by showing embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be arbitrarily modified without departing from the scope of the claims of the present invention and their equivalents.

In the following description, a "long" film refers to a film having a length of 5 times or more, preferably 10 times or more, with respect to the width, specifically a roll A film that is long enough to be rolled up into a shape and stored or transported. The upper limit of the length of the film is not particularly limited, and can be, for example, 100,000 times or less the width.

In the following description, the in-plane retardation Re of a layer is a value represented by Re=(nx−ny)×d unless otherwise specified. Here, nx represents the refractive index in the direction that gives the maximum refractive index among the directions (in-plane directions) perpendicular to the thickness direction of the layer. ny represents the refractive index in the direction orthogonal to the nx direction among the in-plane directions of the layer. nz represents the refractive index in the thickness direction of the layer. d represents the thickness of the layer. The measurement wavelength is 590 nm unless otherwise stated.

In the following description, unless otherwise specified, a material having positive intrinsic birefringence means a material having a higher refractive index in the stretching direction than in the direction perpendicular to it. Further, unless otherwise specified, a material having negative intrinsic birefringence means a material having a lower refractive index in the stretching direction than in the direction perpendicular to it. The intrinsic birefringence value can be calculated from the dielectric constant distribution.

In the following description, unless otherwise specified, an oblique direction of a long film indicates an in-plane direction of the film and a direction neither parallel nor perpendicular to the width direction of the film.

In the following description, unless otherwise specified, the angles formed by the optical axes (absorption axis, slow axis, etc.) of each layer in a member having a plurality of layers represent angles when the layers are viewed from the thickness direction.

In the following description, the slow axis of a film or layer means the slow axis in the plane of the film or layer, unless otherwise specified.

In the following description, the orientation angle of a film or layer represents the angle formed by the slow axis of the film or layer with respect to the width direction of the film or layer, unless otherwise specified.

[1. Overview〕
The long multilayer film of the present invention obtained by the production method of the present invention comprises a substrate film layer (A) and a coating layer (B) provided on the surface thereof. The method for producing a long multilayer film of the present invention comprises a step (1) of preparing a long base film (a), and coating a coating layer material (b) on the base film (a). and step (2).

[2. Step (1)]
In step (1), a long base film (a) is prepared. The base film (a) constitutes the base film layer (A) as it is or after undergoing an arbitrary step such as stretching. As the substrate film (a), a multi-layered film containing two or more layers may be used, but usually a single-layered film containing only one layer may be used.

As a material constituting the base film (a), a thermoplastic resin containing a polymer and, if necessary, an optional component can be used.
In particular, a resin with negative intrinsic birefringence is used as the material of the coating layer (B), and a resin with positive intrinsic birefringence is used from the viewpoint of forming a multilayer film having useful optical performance in combination with it. is preferred.

Resins with positive intrinsic birefringence usually include polymers with positive intrinsic birefringence. Examples of polymers with positive intrinsic birefringence include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyarylene sulfides such as polyphenylene sulfide; polyvinyl alcohol; polyethersulfone; polyallylsulfone; polyvinyl chloride; cyclic olefin polymers such as norbornene polymers; One type of these polymers may be used alone, or two or more types may be used in combination at an arbitrary ratio. Moreover, the polymer may be a homopolymer or a copolymer. Among these, a polycarbonate polymer is preferable because it is excellent in retardation expression and stretchability at low temperatures, and is excellent in mechanical properties, heat resistance, transparency, low moisture absorption, dimensional stability and light weight. Cyclic olefin polymers are preferred.

The proportion of the polymer in the resin contained in the substrate film (a) is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, and particularly preferably 90% to 100% by weight. . By setting the proportion of the polymer within the above range, the obtained long multilayer film can have sufficient heat resistance and transparency.

The resin contained in the base film (a) may contain any component other than the polymer in combination with the polymer. Optional components include, for example, colorants such as pigments and dyes; plasticizers; fluorescent brighteners; dispersants; heat stabilizers; light stabilizers; activators and the like. These components may be used singly or in combination of two or more at any ratio.

The base film (a) may be an optically isotropic film or an optically anisotropic film. When the desired substrate film (a) is an isotropic film, examples of methods for its preparation include melt molding and solution casting. More specific examples of melt molding methods include extrusion molding, press molding, inflation molding, injection molding, blow molding, and stretch molding. In particular, from the viewpoint of mechanical strength and surface precision of the substrate film (a) to be obtained, extrusion molding, inflation molding and press molding are preferable, and among them, extrusion molding is particularly preferable from the viewpoint of production efficiency.

The glass transition temperature TgA of the resin contained in the substrate film (a) is preferably 100°C or higher, more preferably 110°C or higher, particularly preferably 120°C or higher, and preferably 190°C or lower, more preferably 180°C. 170° C. or less is particularly preferable. By setting the glass transition temperature of the resin contained in the base film (a) to be equal to or higher than the lower limit, the durability of the base film layer (A) in a high-temperature environment can be enhanced. Moreover, the drawing process can be easily performed by setting the thickness to the upper limit or less.

When the desired base film (a) is a film having optical anisotropy, the base film (a) can be obtained by further stretching the isotropic film obtained by the method described above. . The specific stretching conditions can be appropriately selected so that the desired optical properties of the multilayer film as the final product can be obtained. The direction of stretching can be, for example, longitudinal stretching (stretching in the longitudinal direction of the film), lateral stretching (stretching in the width direction of the film), diagonal stretching (stretching in the oblique direction of the film), and combinations thereof. In particular, by adopting an obliquely stretched film as the base film (a) and further performing longitudinal stretching in step (3), a long multilayer film having optically useful properties can be easily produced. be able to.

When the base film (a) is an obliquely stretched film, its specific orientation angle is preferably greater than 15°, more preferably greater than 17°, particularly preferably greater than 20°, and preferably 50°. °, more preferably less than 49°, particularly preferably less than 48°. When the orientation angle of the substrate film (a) is within the above range, the long multilayer film obtained by the production method combined with the step (3) can be a broadband wavelength film having preferable optical properties.

The thickness of the base film (a) can be appropriately adjusted so that the resulting long multilayer film can have a desired thickness. The specific thickness of the base film (a) is preferably 20 µm or more, more preferably 25 µm or more, particularly preferably 30 µm or more, and preferably 100 µm or less, more preferably 95 µm or less, and particularly preferably 90 µm or less. .

[3. Any step after step (1) and before step (2)]
The production method of the present invention may include any step after step (1) and before step (2). For example, the step (1(i)) of forming an adhesive layer on the surface of the base film (a) can be included. By performing the step (1(i)), an adhesive layer can be interposed between the substrate film layer (A) and the coating film layer (B) to be obtained, and these can be firmly bonded. Therefore, in the long multilayer film of the present invention produced by the production method of the present invention, the base film layer (A) and the coating film layer (B) may be in direct contact with each other. You may contact through a layer.

Examples of materials for the adhesive layer include acrylic resins, urethane resins, acrylic urethane resins, ester resins, and ethyleneimine resins. Acrylic resins are resins containing acrylic polymers. A urethane resin is a resin containing polyurethane. Polymers such as acrylic polymers and polyurethanes generally have high adhesion to a wide variety of resins and can therefore be preferably used as materials for the adhesive layer. One type of these polymers may be used alone, or two or more types may be used in combination at an arbitrary ratio.

The resin as the material of the adhesive layer is combined with the polymer to form heat stabilizers, weather stabilizers, leveling agents, antistatic agents, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, natural oils, Optional ingredients such as synthetic oils, waxes, and particles may be included. One type of optional component may be used alone, or two or more types may be used in combination at any ratio.

The adhesive layer is formed, for example, by applying an adhesive layer material containing a resin as an adhesive layer material and a solvent onto the substrate film (a), and then subjecting it to curing treatment such as drying and cross-linking, if necessary. can be formed by

Examples of solvents include water, organic solvents and combinations thereof. Examples of the organic solvent include the same examples as the solvent that can be used for forming the layer (B) described later. One type of solvent may be used alone, or two or more types may be used in combination at an arbitrary ratio.

The adhesive layer material can contain any material in addition to the resin and solvent. For example, it may contain a cross-linking agent. By including a cross-linking agent, the mechanical strength and adhesive strength of the adhesive layer can be enhanced. Examples of crosslinkers include epoxy compounds, amino compounds, isocyanate compounds, carbodiimide compounds, and oxazoline compounds. One of these may be used alone, or two or more of them may be used in combination at any ratio. The amount of the cross-linking agent is preferably 1 part by weight or more, more preferably 5 parts by weight or more, preferably 70 parts by weight or less, more preferably 65 parts by weight, with respect to 100 parts by weight of the polymer in the coating liquid. It is below.

Specific examples of the operation of applying the adhesive layer material include the same examples as the operation of applying the coating layer material (b) in step (2).

An example of a method for drying the applied adhesive layer material includes heat drying using an oven. Examples of methods for cross-linking the adhesive layer material include heat treatment and irradiation treatment with active energy rays such as ultraviolet rays.

[4. Step (2)]
In step (2), the coating film layer material (b) is applied onto the substrate film (a). The applied layer of the coating layer material (b) constitutes the coating layer (B) as it is or after undergoing any subsequent steps.

[4.1. Coating layer material (b)]
As the coating film layer material (b), a liquid material containing a resin and, if necessary, an optional component can be used. In particular, from the viewpoint of constructing a multilayer film having useful optical properties, it is preferable to use a liquid material whose intrinsic birefringence becomes negative after curing. As such a liquid material, a material containing a resin having a negative intrinsic birefringence is preferable.

Resins with negative intrinsic birefringence are typically thermoplastic resins and include polymers with negative intrinsic birefringence. Examples of polymers with negative intrinsic birefringence include homopolymers of styrene or styrene derivatives, and polystyrene polymers including copolymers of styrene or styrene derivatives and arbitrary monomers; polyacrylonitrile polymers; Methyl methacrylate polymer; or multiple copolymers thereof; and cellulose compounds such as cellulose esters. Preferred examples of the above optional monomers that can be copolymerized with styrene or styrene derivatives include acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. Among them, polystyrene-based polymers and cellulose compounds are preferred. Moreover, these polymers may be used individually by 1 type, and may be used in combination of 2 or more types by arbitrary ratios.

The proportion of the polymer in the resin having negative intrinsic birefringence is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, and particularly preferably 90% to 100% by weight. By setting the proportion of the polymer within the above range, it becomes easy to impart appropriate optical properties to the coating film layer (B).

The resin contained in the coating film layer material (b) preferably contains a plasticizer. By including a plasticizer, the physical properties of the coating layer (B), such as the glass transition temperature, can be appropriately adjusted, and a long multilayer film having desired optical properties can be obtained. Examples of plasticizers include phthalates, fatty acid esters, phosphate esters, and epoxy derivatives. Specific examples of the plasticizer include those described in JP-A-2007-233114. One type of plasticizer may be used alone, or two or more types may be used in combination at an arbitrary ratio.

Among plasticizers, phosphate esters are preferred because they are readily available and inexpensive. Examples of phosphate esters include trialkyl phosphates, such as triethyl phosphate, tributyl phosphate, trioctyl phosphate; halogen-containing trialkyl phosphates, such as trichloroethyl phosphate; triphenyl phosphate, tricresyl phosphate, triaryl phosphate such as tris(isopropylphenyl) phosphate, cresyl diphenyl phosphate; alkyl-diaryl phosphate such as octyldiphenyl phosphate; tri(alkoxy) such as tri(butoxyethyl) phosphate alkyl) phosphate; and the like.

The amount of the plasticizer is preferably 0.001% by weight or more, more preferably 0.005% by weight or more, particularly preferably 0.005% by weight or more, based on 100% by weight of the resin contained in the coating layer material (b). It is 1% by weight or more, preferably 20% by weight or less, more preferably 18% by weight or less, and particularly preferably 15% by weight or less. By setting the amount of the plasticizer within the above range, the glass transition temperature TgB of the resin contained in the coating layer (B) can be appropriately adjusted, and appropriate optical properties can be imparted to the coating layer (B). easier.

The glass transition temperature TgB of the resin having negative intrinsic birefringence is preferably 80° C. or higher, more preferably 90° C. or higher, still more preferably 100° C. or higher, more preferably 110° C. or higher, particularly preferably 120° C. or higher. Such a high glass transition temperature TgB of the resin with negative intrinsic birefringence can reduce the orientation relaxation of the resin with negative intrinsic birefringence. Although there is no particular upper limit for the glass transition temperature TgB of the resin having negative intrinsic birefringence, it is usually 200° C. or less.

The ratio of the polymer in the coating layer material (b) is preferably expressed as a ratio to the total amount of solids (components remaining in the coating layer (B), usually components other than the solvent in the coating layer material (b)). 50% to 100% by weight, more preferably 70% to 100% by weight, particularly preferably 90% to 100% by weight. By setting the proportion of the polymer within the above range, it becomes easy to impart appropriate optical properties to the coating film layer (B).

The coating layer material (b) may contain a solvent in addition to the resin having a negative intrinsic birefringence. The solvent volatilizes during the steps of the manufacturing method and does not substantially remain in the coating layer (B). Examples of solvents include methyl acetate, ethyl acetate, acetone, methyl ethyl ketone, 3-methyl-2-butanone, methyl isobutyl ketone, tetrahydrofuran, cyclopentyl methyl ether, acetylacetone, cyclohexanone, 2-methylcyclohexanone, 1,3-dioxolane, 1 ,4-dioxane, 2-pentanone, and N,N-dimethylformamide. Moreover, a solvent may be used individually by 1 type, and may be used in combination of 2 or more types by arbitrary ratios.

The coating layer material (b) may contain optional components in combination with the above components such as polymers. Examples of the optional component include the same examples as the optional component of the base film (a). One type of optional component may be used alone, or two or more types may be used in combination at any ratio.

The viscosity of the coating layer material (b) can be adjusted to a desired value by adjusting the solids content. A coating layer (B) having a desired shape can be obtained by adjusting the viscosity to a desired value. The preferred viscosity of the coating layer material (b) may vary depending on the specific coating method in step (2), the desired shape of the coating layer (B), etc., but is preferably 150 cps or more, more preferably 150 cps or more. is greater than or equal to 200 cps, while preferably less than or equal to 1500 cps. By setting the viscosity to a low value equal to or lower than the upper limit, the inclined portion can be easily formed.

[4.2. Application of Coating Layer Material (b): Desired Shape of Coating Layer (B)]
The coating layer material (b) in step (2) is applied so that the coating layer (B) in the long multilayer film obtained by the production method of the present invention has a specific shape.

FIG. 1 is a cross-sectional view schematically showing the long multilayer film of the present invention obtained by the production method of the present invention. This cross-sectional view is taken along a plane perpendicular to the longitudinal direction of the film, and the left and right directions in FIG. 1 correspond to the width direction of the film. In FIG. 1 and other figures, the film is schematically illustrated with its thickness exaggerated for the sake of explanation.

In FIG. 1, the long multilayer film 100 includes a base film layer (A) 110 and a coating layer (B) 120 provided on its upper surface 110U. The coating film layer (B) is provided not on the entire upper surface of the base film layer (A), but only on a portion of the central portion in the width direction thereof. Therefore, the upper surface of the long multilayer film 100 includes a portion 100c covered with the coating layer (B) and portions 100e1 and 100e2 not covered with the coating layer (B). In the following description, such a portion covered with the coating film layer (B) of the long multilayer film may be referred to as a "coated portion". On the other hand, a portion of the long multilayer film on the side provided with the coating layer (B) but not covered with the coating layer (B) may be referred to as a “non-coated portion”. The coated portion 100c is a portion from one widthwise end 120e of the coating film layer (B) to the other widthwise end 120e. ) from the widthwise end 110e to the widthwise end 120e of the inner coating film layer (B) in the widthwise direction.

The coating in step (2) is the ratio De / D ₁₀ of the film thickness De at the width direction end of the coating layer (B) to the film thickness D ₁₀ at the position 10 mm from the width direction end of the coating layer (B). is a ratio within a specific range.

FIG. 2 is an enlarged cross-sectional view showing an enlarged region _R1 in the cross section of the long multilayer film shown in FIG.
_In this example, the distance from the position E1 of the widthwise end 120e of the coating film layer (B) ₁₂₀ to the widthwise inner position E4 (that is, the distance indicated by the arrow _A24 ) is 10 mm. Film thickness D ₁₀ is the thickness of coating layer (B) 120 at location E ₄ (ie, the thickness indicated by arrow A ₂₆ ).

On the other hand, the film thickness De is defined as the film thickness of the coating layer (B) at a position 1 mm apart in the width direction from the position of the end of the coating layer (B) in the width direction. In the example of FIG. ₂ , the distance from the position E1 of the widthwise end portion 120e of the coating layer (B) ₁₂₀ to the widthwise inner position E2 thereof ₍ that is, the distance indicated by the arrow A22) is 1 mm. The film thickness De is the thickness of the coating layer (B) 120 at position E2 ₍ ie, the thickness indicated by arrow _A25 ).

The edge film thickness ratio De/D ₁₀ is a percentage value obtained by the formula (De/D ₁₀ )×100. The coating in step (2) is performed so that the film thickness ratio De/ _D10 at the end portion is 85% or less. The edge thickness ratio De/ _D10 is preferably 70% or less, more preferably 60% or less. According to the findings of the present inventors, the long multilayer film of the present invention obtained by the production method of the present invention can be curled during transportation by setting the edge film thickness ratio De/D ₁₀ within this range. Although it is a multilayer film that tends to cause curling, it can be reduced in curling. Although the lower limit of the edge film thickness ratio De/D ₁₀ is not particularly limited, it can be, for example, 1% or more.

As exemplified in the examples of FIGS. 1 and 2, step (2) is preferably performed such that a non-coated portion is formed. That is, it is preferable that the widthwise end of the coating film layer (B) is located inside the widthwise end of the base film layer (A). In the example of FIG. 2, the position E1 of the width direction end 120e of the coating film layer (B) ₁₂₀ is higher than the position _E0 of the width direction end 110e of the base film layer (A) in the multilayer film width direction. located inside.

The distance We from the width direction end 120e of the coating layer (B) 120 to the width direction end 110e of the base film layer (A) 110 (that is, the distance indicated by arrow A ₂₁ , the width of the uncoated portion) is , a long distance is preferable from the viewpoint of suppressing curling. The distance We is preferably 5 mm or more, more preferably 8 mm or more, still more preferably 10 mm or more. Although the upper limit of the distance We is not particularly limited, the width is preferably narrow to some extent from the viewpoint of yield. For example, We can be 100 mm or less.

An inclined portion is usually formed in the vicinity of the widthwise end of the coating layer (B). The slant portion is a portion where the thickness of the coating film layer (B) is not constant but is slanted. In the example of FIG. ₂ , the thickness of the coating layer ₍ B) increases in the portion from the position E1 to the position E3 of the width direction end 120e of the coating layer (B) 120, and the inclined portion is formed. A flat portion where the thickness of the coating film layer (B) is constant is formed in a region inside the inclined portion.

From the viewpoint of curbing curling, it is preferable that the width of the inclined portion is large. The width of the inclined portion is preferably 5 mm or more, more preferably 10 mm or more. The position _E3 of the inner end of the inclined portion is outside the position _E4 in the _example of _FIG . It can be inside. That is, the width of the inclined portion (the distance from the position E1 to the position E3 in the example of FIG. _{2 ,} the distance indicated by the arrow _A23 ) may be narrower than 10 mm or may be 10 mm or more. Although the upper limit of the width of the inclined portion is not particularly limited, the width is preferably narrow to some extent from the viewpoint of yield. For example, it can be 50 mm or less.

In the example of FIG. 2, the shape of the inclined portion is such that the thickness gradually decreases from the inside to the outside, but the shape of the inclined portion is not limited to this. For example, it may have a shape such that it becomes thicker from the inside to the outside and then becomes thinner. However, from the viewpoint of suppressing curling, it is preferable that the thickness of the inclined portion is thinner than that of the flat portion at any part of the entire shape.

[4.3. Application of Coating Layer Material (b): Specific Operation of Application]
The coating layer (B) having the slope portion of the specific shape described above is obtained by appropriately adjusting the coating conditions in the coating of the coating layer material (b) on the base film (a) in the step (2). You can get it by being able to control it.

Preferably, the application in step (2) is done with a die. That is, application is performed by so-called die coating. By adopting die coating, the desired shape of the coating layer (B) can be obtained efficiently.

FIG. 3 is a side view schematically showing application of the coating film layer material (b) to the substrate film (a) by die coating by die coating. In FIG. 3, the die 320 is shown as a cross-sectional view for convenience of illustration. FIG. 4 is a perspective view schematically showing the vicinity of the opening of the die 320 shown in FIG. In FIG. 3, the base film (a) 11 is transported along the outer peripheral surface of the back roll ₃₁₀ in the direction of arrow A31. The back roll 310 rotates in the direction of arrow A ₃₀ and supports the base film (a) 11 under tension from above, thereby increasing the distance between the base film (a) 11 and the die 320. keep constant. A die 320 is installed at a position below the base film (a) 11 and facing the back roll 310 . By extruding and supplying the coating layer material (b) in the direction of arrow A ₃₂ through the lumen 321 of the die 320, the coating layer material (b) is expelled from the opening 322 to form the substrate film (a ) 11. Thereby, the layer 12 of the coating layer material (b) is continuously formed.

In the die coating, any one or more of the following controls can be performed in order to obtain a coating layer (B) having a slope portion of a specific shape.

Control (1): Adjust the extrusion pressure of the coating layer material (b) from the die so that the coating layer material (b) spreads outward in the width direction from the width direction end of the die opening. .
Control (2): A flow rate limiting member is provided in the vicinity of the width direction end of the die opening inside the die, and the flow rate at the width direction end of the die opening is controlled relative to the flow rate at the width direction center. Decrease.

Control (1) will be described with reference to FIG. FIG. 5 is a front view schematically showing a specific example of application of the coating film layer material (b) to the substrate film (a) by die coating by die coating. In FIG. 5, the shape of lumen 321 of die 320 is a conventional shape. That is, the cross-sectional shape of the lumen 321 (meaning a cross-sectional shape taken along a cross section perpendicular to the extrusion direction A ₃₂ of the coating layer material (b); the same shall apply hereinafter) is the same shape as the opening 322 .

Such a shape is usually adopted as a die shape when performing general coating (coating intended to be flat across the entire width direction without a specific shape of slope; the same applies hereinafter). be. This conventional shape of the lumen near the opening of the die allows the coating layer material (b) to be extruded under pressure to move parallel within the lumen 321, resulting in , the coating film layer material (b) can be stably supplied to the surface of the substrate film (a). In the case of general coating, by adjusting the extrusion pressure of the coating layer material (b) to the die, the coating layer material (b) is expelled from the opening 322 in the shape indicated by the dashed _- dotted line L1. Dispensed. By extruding the coating layer material (b) parallel to the width direction end portions of the die opening in the same manner as in the central portion, a flat coating layer can be formed over the entire width direction.

On the other hand, in coating with control (1), the coating layer material (b) is spread outward in the width direction from the width direction end of the opening of the die, and the coating layer material ( Adjust the extrusion pressure in b). Specifically, the extrusion pressure is adjusted to a pressure higher than that for general coating. By such adjustment, the coating film layer material ( _b ) is discharged from the opening 322 in the shape indicated by the solid line L2. In this way, at the width direction end of the die opening, the coating layer material (b) is spread outward in the width direction from the width direction end of the die opening and applied, so that the area outside the die opening in the width direction The coating film layer material (b) is supplied at , and the amount supplied gradually decreases according to the distance in the width direction from the die opening. As a result, the shape of the layer 12 of the coating layer material (b) is adapted to obtain a coating layer (B) having slopes of a particular shape.

Control (2) will be explained with reference to the drawings. FIG. 6 is a front view schematically showing a die used for another specific example of applying the coating film layer material (b) to the substrate film (a) by die coating by die coating. 7 is a top view of the opening of the die shown in FIG. 6. FIG. 6 and 7, the die 420 differs from the die 320 shown in FIG. 5 in that it has a shim 431 provided within its bore 421, and otherwise has the same shape as the die 320. there is

Each of the pair of shims 431 is provided at the end of the lumen 421 in the width direction so as to cover the entire thickness direction of the lumen 421 (the direction indicated by the arrow A ₄₃ ). Each of the shims 431 is offset from the opening 422 of the die 420 by a distance indicated by arrow A ₄₄ into the die.

In die 420, shim 431 functions as a flow restrictor. That is, since the die 420 has a shim 431, the coating layer material (b) supplied through the bore 421 of the die 420 is extruded generally in the direction of arrow A ₃₂ , while the opening 422 of the die 420 is extruded. Extrusion of the coating layer material (b) is restricted by shims 431 near the ends of . Due to this restriction, the coating film layer material (b) is pushed out from the center to the ends near the ends of the opening ₄₂₂ , as indicated by the arrow A42. As a result, the flow rate at the widthwise ends of the opening 422 of the die 420 decreases relative to the flow rate at the widthwise central portion. As a result, near the end of the opening 422 of the die 420, the supply amount of the coating film layer material (b) gradually decreases according to the distance in the width direction from the die opening. As a result, the shape of the layer of the coating film layer material (b) provided on the substrate film (a) becomes a shape suitable for obtaining the coating film layer (B) having the slope portion of the specific shape.

FIG. 8 is a front view schematically showing a die used in still another specific example of application of the coating film layer material (b) to the substrate film (a) by die coating by die coating. 9 is a top view of the opening of the die shown in FIG. 8. FIG. 8 and 9, the die 520 differs from the die 420 shown in FIGS. 6 and 7 in the position and shape of the shim 531 provided in its lumen 521, and is otherwise the same as the die 420. have a shape.

Each of the pair of shims 531 has a shape that does not block the entirety of the lumen 521 in the thickness direction (the direction indicated by the arrow A ₅₃ ) and has a slit width indicated by the arrow A ₅₄ . It is provided at the direction end. Each of the shims 531 is provided with its top surface level not offset from the opening 522 of the die 520 and aligned with the height of the opening.

In die 520, shim 531 functions as a flow restrictor. That is, since the die 520 has a shim 531, the coating layer material (b) supplied through the bore 521 of the die 520 is extruded generally in the direction of arrow A ₃₂ , while the opening 522 of the die 520 is extruded. Extrusion of the coating layer material (b) is restricted by shims 531 near the ends of . Due to such a restriction, the flow rate at the widthwise ends of the opening 522 of the die 520 is relatively reduced with respect to the flow rate at the widthwise central portion. As a result, near the end of the opening 522 of the die 520, the supply amount of the coating film layer material (b) gradually decreases according to the distance in the width direction from the die opening. As a result, the shape of the layer of the coating film layer material (b) provided on the substrate film (a) becomes a shape suitable for obtaining the coating film layer (B) having the slope portion of the specific shape.

FIG. 10 is a front view schematically showing a die used in another specific example of application of the coating film layer material (b) to the substrate film (a) by die coating by die coating. 11 is a top view of the opening of the die shown in FIG. 10. FIG. 10 and 11, the die 620 is different from the die 420 shown in FIGS. 6 and 7 in the position and shape of the shim 631 provided in its lumen 621, and is otherwise the same as the die 420. have a shape.

Each of the pair of shims 631 is provided at an end portion in the width direction of the lumen 621 in such a shape as to completely close the lumen 621 in the thickness direction (the direction indicated by the arrow A ₆₃ ). Each of the shims 631 is provided with its top surface 632 level not offset from the opening 622 of the die 620 and aligned with the height of the opening. Each of the shims 631 has an inclined surface 633 on the inner side of the upper surface 632 in the width direction.

In die 620, shim 631 functions as a flow restrictor. That is, since the die 620 has a shim 631, the coating layer material (b) fed through the bore 621 of the die 620 is extruded generally in the direction of arrow A ₃₂ , while the opening 622 of the die 620 is extruded. Extrusion of the coating layer material (b) is restricted by shims 631 near the ends of . Due to this limitation, the coating layer material (b) is extruded from the center to the ends along the slope 633 near the ends of the opening 622, as indicated by the arrow _A62 . As a result, the flow rate at the widthwise ends of the opening 622 of the die 620 decreases relative to the flow rate at the widthwise central portion. As a result, near the end of the opening 622 of the die 620, the supply amount of the coating film layer material (b) gradually decreases according to the distance in the width direction from the die opening. As a result, the shape of the layer of the coating film layer material (b) provided on the substrate film (a) becomes a shape suitable for obtaining the coating film layer (B) having the slope portion of the specific shape.

In the specific example of control (2) described above, the flow restricting member was constructed by providing a shim in the bore of a die of ordinary shape, but the flow restricting member is not limited to this. For example, the shape of the bore of the die is such that a part of the flow path of the coating layer material (b) is narrowed, thereby forming a flow path having the same shape as the above-described state in which the shim is provided. good too.

The specific examples of control (2) described above may be implemented by combining them. For example, the shape of the flow restrictor may be offset into the die, as in the example die 420 shown in FIGS. 6 and 7, and constitute a slit, as in the example die 520 shown in FIGS. good too.

Controls (1) and (2) described above may be implemented in combination. For example, the extrusion pressure of the coating layer material (b) from the die may be adjusted to a pressure higher than usual, and a flow restricting member having the characteristics of any one or more of the above-described specific examples may be provided. .

The preferred pressure of the coating layer material (b) inside the die during die coating in step (2) depends on the flow path control method, the shape of the die, the viscosity of the coating layer material (b), and the desired coating layer. For example, when the coating layer material (b) has a viscosity of 500 cps, the preferred pressure for pressing the coating layer material (b) into the die is: It can be preferably 3000 Pa or higher, more preferably 5000 Pa or higher, and even more preferably 7000 Pa or higher. Although the upper limit of the pressure is not particularly limited, it can be, for example, 20000 Pa or less.

Step (2) may include drying the layer of coating layer material (b) after application by an operation such as die coating. Drying removes the solvent and the layer of coating layer material (b) can be cured to form coating layer (B). Drying can be performed by a drying method such as natural drying, heat drying, reduced pressure drying, or reduced pressure heat drying.

[5. Step (3)]
The multilayer product obtained through the step (2), which includes the substrate film (a) and the layer of the cured material of the coating layer material (b) provided on the surface thereof, is used as it is for the production of the present invention. It can be the long multilayer film of the present invention obtained by the method. In this case, the substrate film (a) becomes the substrate film layer (A) in the long multilayer film as it is, and the layer of the cured material of the coating layer material (b) becomes the coating layer (B) as it is. .

Alternatively, the multilayer material obtained through the step (2) can be made into the long multilayer film of the present invention after further undergoing arbitrary steps. As a preferred example, in the method for producing a long multilayer film of the present invention, after the step (2), a multilayer product containing a cured product of the substrate film (a) and the coating layer material (b) is co-stretched. It may further comprise step (3).

That is, the long multilayer film of the present invention includes both those that have not undergone the step (3) and those that have undergone the step (3). Hereinafter, for distinction, the former may be referred to as "multilayer film (I)" and the latter as "multilayer film (II)". Therefore, the step (3) can be a step of stretching the multilayer film (I) to obtain the multilayer film (II).

In the following, for distinction, the base film layer (A) in the multilayer film (I) and the base film layer (A) in the multilayer film (II) are respectively referred to as the base film layer (AI ), and the base film layer (A-II). Furthermore, the coating layer (B) in the multilayer film (I) and the coating layer (B) in the multilayer film (II) are respectively replaced with the coating layer (BI) and the coating layer (B- II).

When it is desired to obtain a multilayer film (I) as the long multilayer film of the present invention, the shape of the coating layer (BI) and other shapes (uncoated portion width We, etc.) are as described above. The coating conditions in step (2) can be adjusted so as to obtain a specific shape. On the other hand, when it is desired to obtain the multilayer film (II) as the long multilayer film of the present invention, the shape of the coating layer (B-II) after the step (3) and other shapes are The coating conditions in step (2) may be adjusted to achieve the specific shapes described above.

The direction of stretching in step (3) is, for example, longitudinal stretching (stretching in the longitudinal direction of the film), lateral stretching (stretching in the width direction of the film), diagonal stretching (stretching in the diagonal direction of the film), and combinations thereof. sell. In particular, by adopting an obliquely stretched film as the base film (a) and further performing longitudinal stretching in step (3), a long multilayer film having optically useful properties can be easily produced. be able to.

The draw ratio in step (3) is preferably 1.3 times or more, more preferably 1.35 times or more, preferably 2.0 times or less, more preferably 1.8 times or less, and particularly preferably 1.8 times or less. 6 times or less. Curling can be suppressed by setting the draw ratio in step (3) to the above upper limit or less. Moreover, desired optical characteristics can be provided by setting the content to be equal to or higher than the lower limit.

The stretching temperature in step (3) is the glass transition temperature TgA of the resin contained in the base film layer (AI) and the glass transition temperature of the resin having negative intrinsic birefringence contained in the coating layer (BI). It is preferable that TgB satisfy both the following conditions (C1) and (C2).
(C1) Stretching temperature is preferably TgA −20° C. or higher, more preferably TgA −10° C. or higher, particularly preferably TgA −5° C. or higher, preferably TgA +30° C. or lower, more preferably TgA +25° C. or lower, particularly preferably is a temperature below TgA + 20°C.
(C2) Stretching temperature is preferably TgB-20°C or higher, more preferably TgB-10°C or higher, particularly preferably TgB-5°C or higher, preferably TgB+30°C or lower, more preferably TgB+25°C or lower, particularly preferably is a temperature below TgB+20°C.
By stretching at such a stretching temperature, the optical properties of the base film layer (A-II) can be adjusted appropriately, and the desired optical properties can be expressed in the coating layer (B-II). can. Therefore, the obtained multilayer film (II) can be a broadband wavelength film having desired optical properties. Further, when free uniaxial stretching in the longitudinal direction is performed at a temperature as low as the above lower limit or lower, the retardation can be efficiently expressed, but curling is likely to occur. In the production method of the present invention, by forming the width direction end portion of the coating layer (B) into a specific shape, curling can be suppressed even when stretching is performed under such conditions.

The stretching in step (3) is preferably carried out by free uniaxial stretching. Here, free uniaxial stretching refers to stretching in a certain direction without applying a restraining force in directions other than the stretching direction. Therefore, for example, free uniaxial stretching in the longitudinal direction of a long multilayer film means stretching in the longitudinal direction without constraining the ends in the width direction of the long multilayer film.

The drawing in step (3) can be performed using any drawing machine, for example, a tenter drawing machine or a roll drawing machine. In particular, when the multilayer film (I) is stretched in its longitudinal direction in step (3), it is preferable to use a roll stretching machine. Free uniaxial stretching can be easily performed by a roll stretching machine. Free uniaxial stretching using a roll stretching machine is usually carried out while continuously conveying the long multilayer film (I) in the longitudinal direction. As the roll stretching machine, for example, the one described in Patent Document 1 can be used.

In general, when a long film is freely uniaxially stretched in the longitudinal direction, many curls occur at the ends of the film. In particular, when the long film is a multi-layer film, such curling occurs frequently. Here, in the production method of the present invention, since the coating layer (B) has a specific shape, curling during free uniaxial stretching in the longitudinal direction as well as during transport of the film is particularly favorable. Suppressed. Therefore, it is possible to satisfactorily suppress the occurrence of curling while enjoying the benefits of roll stretching by a roll stretching machine, such as high efficiency.

[6. Long multilayer film]
The long multilayer film of the present invention is a long multilayer film comprising a substrate film layer (A) and a coating layer (B) provided on the surface thereof, wherein the coating layer (B) The ratio De/ _D10 of the thickness De of the coating film layer (B) widthwise end to the thickness D10 of ₁₀ mm from the widthwise end is 85% or less.

The long multilayer film of the present invention can be produced by the production method described above. The long multilayer film of the present invention may be either multilayer film (I) or (II). In the long multilayer film of the present invention, the preferred value of De/D ₁₀ , the preferred value of We, and other preferred shapes and other preferred shapes of the coating layer (B) are described in the description of step (2). That's right. These preferred shapes are common to both the multilayer film (I) and the multilayer film (II). For example, the preferred range for the distance We from the width direction end of the coating layer (B) to the width direction end of the base film layer (A) is the case of the multilayer film (I) and the multilayer film ( In both cases II), as described in the description for step (2). Since the base film layer (A) is obtained by processing the base film (a) as it is or by processing the base film (a) by an arbitrary process such as stretching, the base film layer (A) is Examples of constituent materials include the same materials as those cited as examples of materials constituting the base film (a). Similarly, examples of materials constituting the coating layer (B) include the same materials as those mentioned as examples of materials constituting the coating layer material (b), except for the solvent.

The long multilayer film of the present invention is preferably the multilayer film (II) obtained through step (3), and the multilayer film (II) preferably has optical properties used as a broadband wavelength film. It is a film with A broadband wavelength film is a film that includes a λ/2 layer and a λ/4 layer in combination, and the combination of these allows the film as a whole to function as a λ/4 wavelength plate, and the broadband wavelength film performs such a function. , over a wide wavelength range. In the multilayer film (II), the layer (A-II) can be a λ/2 layer and the layer (B-II) can be a λ/4 layer.

The λ/2 layer is a layer having an in-plane retardation of usually 240 nm or more and usually 300 nm or less at a measurement wavelength of 590 nm. The λ/4 layer is a layer having an in-plane retardation of usually 110 nm or more and usually 154 nm or less at a measurement wavelength of 590 nm. Since the λ/2 layer and the λ/4 layer have such in-plane retardation, a broadband wavelength film can be realized by combining them.

From the viewpoint of realizing a function as a broadband wavelength film by combining the λ / 2 layer and the λ / 4 layer, the λ / 2 layer has a slow axis in the direction corresponding to the direction of the slow axis of the λ / 4 layer is preferred. In general, a λ/4 layer having a slow axis forming an angle θ (λ/4) with respect to a certain reference direction (for example, the longitudinal direction of the film) and an angle θ (λ/2) with respect to the reference direction If the film combined with the λ / 2 layer having a slow axis of It is a broadband wavelength film that can give in-plane retardation of approximately 1/4 wavelength of the wavelength of light transmitted through the film (see Japanese Patent Application Laid-Open No. 2007-004120). Therefore, in the broadband wavelength film, it is preferable that the slow axis of the λ/2 layer and the slow axis of the λ/4 layer satisfy a relationship close to that represented by the formula X above. Specifically, the angle formed by the slow axis of the λ/2 layer and the slow axis of the λ/4 layer is preferably 67.5°±10°, more preferably 67.5°±5°, particularly It is preferably 67.5°±3°.

A general linearly polarizing film has a transmission axis in its width direction and an absorption axis in its longitudinal direction. From the viewpoint of obtaining a broadband wavelength film that can realize a circularly polarizing film in combination with such a general linearly polarizing film, the slow axis of the λ / 2 layer forms an orientation angle with respect to the width direction of the film, preferably 67.5°±10°, more preferably 67.5°±5°, particularly preferably 67.5°±3°.

The in-plane retardation and the direction of the slow axis of the λ/2 layer and λ/4 layer can be adjusted within the desired ranges described above by appropriately adjusting the conditions in the production method of the present invention. Specifically, the stretching conditions in the production of the base film (a), the stretching conditions in the step (3), and other conditions can be adjusted as appropriate.

The thickness of the base film layer (A) that can function as a λ/2 layer is preferably 20 μm or more, more preferably 25 μm or more, still more preferably 30 μm or more, preferably 80 μm or less, more preferably 70 μm or less, and further It is preferably 60 μm or less. When the thickness is within this range, the mechanical strength of the layer can be enhanced.

The thickness of the coating layer (B) that can function as a λ/4 layer is preferably 3 µm or more, more preferably 4 µm or more, particularly preferably 5 µm or more, preferably 15 µm or less, more preferably 13 µm or less, and particularly preferably is 10 μm or less. When the thickness is at least the lower limit, desired optical properties can be easily obtained, and when it is at most the upper limit, the thickness of the long multilayer film can be reduced.

The total light transmittance of the long multilayer film of the present invention is preferably 80% or higher, more preferably 85% or higher, and particularly preferably 88% or higher. The light transmittance can be measured in a wavelength range of 400 nm to 700 nm using a spectrophotometer according to JIS K0115.

The haze of the long multilayer film of the present invention is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%. Here, haze is measured at 5 points using Nippon Denshoku Industries Co., Ltd.'s "Turbidimeter NDH-300A" in accordance with JIS K7361-1997, and the average value obtained therefrom can be adopted.

The overall thickness of the long multilayer film of the present invention is preferably 30 µm or more, more preferably 35 µm or more, particularly preferably 40 µm or more, and preferably 100 µm or less, more preferably 90 µm or less, and particularly preferably 80 µm or less. . According to the manufacturing method described above, it is possible to easily manufacture such a thin long multilayer film of the present invention.

[7. Suppression of curl]
In the method for producing a long multilayer film of the present invention, the shape of each layer at the end in the width direction is the specific shape described above, so that curling occurs during transportation of the obtained film. can be suppressed, resulting in efficient manufacturing. The long multilayer film of the present invention is a film that can be efficiently produced with less curling during transport because the shape of each layer at the end in the width direction is the specific shape described above. .

Such effects of the present invention will be described with reference to the drawings. FIG. 12 is a perspective view schematically showing how curling occurs during general film transport. FIG. 13 is a cross-sectional view schematically showing an example of a cross section of the film 71 along the plane in the rectangular plane region _R2 in FIG. FIG. 14 is a cross-sectional view schematically showing another example of a cross section of the film 71 along the plane in the rectangular plane region _R2 in FIG.

In FIG. 12, a general long film 71 is sandwiched between two pairs of rolls (a pair of upstream rolls 721 and 722 and a pair of downstream rolls 711 and 712). By driving the two pairs of rolls, the film ₇₁ is conveyed while being biased in the direction of the arrow A70. In order to maintain film tension between the two pairs of rolls, the upstream pair of rolls 721 and 722 are driven slower than the downstream pair of rolls 711 and 712 so that the film 71 therebetween has a tension is applied.

When the film 71 is transported under such tension, the widthwise end portions 71e of the film 71 may curl. Examples of such curls include the C-shaped curl shown in FIG. 13 and the Z-shaped curl shown in FIG.

Such curling occurs frequently when the long film is a multi-layer film. Such curling also often occurs when the tension applied in the longitudinal direction of the film is large, especially when tension is applied in the longitudinal direction to freely uniaxially stretch the film. Here, according to the present inventors, in the long multilayer film of the present invention obtained by the production method of the present invention, the shape of the end portion in the width direction of the film is a specific shape, so that the film Curl generation during transport and during free uniaxial stretching in the longitudinal direction is particularly well suppressed for both the above-described C-shaped curl and Z-shaped curl. As a result, it is possible to efficiently produce a long multilayer film, and particularly in the case of a production method including a step of free uniaxial stretching in the longitudinal direction, it is possible to enjoy the benefit of improved production efficiency.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the examples shown below, and can be arbitrarily modified without departing from the scope of the claims of the present invention and their equivalents.
In the following description, "%" and "parts" representing amounts are by weight unless otherwise specified. In addition, unless otherwise specified, the operations described below were performed under normal temperature and pressure conditions.

[Evaluation method]
[Method for measuring thickness]
Regarding the film before stretching, the base film (a), D ₁₀ and De in the multilayer film (I), D ₁₀ and De in the multilayer film (II), and the thickness in the multilayer film (II), Filmetrics' Measurements were made using F20. For the measurement of D ₁₀ and De, the measurement is performed by focusing on the width direction end of the coating layer (B), and then by moving the focus point by 1 mm toward the width direction center of the film. Site measurements were taken to obtain a thickness profile and the _D10 and De were read from the profile.

[Method for measuring viscosity]
The viscosity of the coating layer material (b) was measured using EMS-1000 manufactured by Kyoto Electronics Co., Ltd. The viscosity was measured at a temperature of 25° C. and a rotation speed of 700 rpm.

[Evaluation method of transport state]
The transport state of the multilayer film (I) is evaluated by visually observing the transported multilayer film (I) at an observation point downstream of the stage where the multilayer film (I) is formed in the production line. gone. The observation points were the same in all the examples and comparative examples. The observation point is a point where the multilayer film (I) is conveyed with tension applied between two pairs of rolls on the upstream and downstream sides, such as a region R2 schematically shown in FIG. , the tension applied in the longitudinal direction of the multilayer film (I) was 250 N, and the distance between the upstream roll and the downstream roll was 1000 mm.
The transport state of the multilayer film (II) is evaluated by visually observing the transported multilayer film (II) at an observation point downstream of the stage where the multilayer film (II) is formed in the production line. gone. The observation points were the same in all the examples and comparative examples. The observation point is a point where the multilayer film (II) is conveyed with tension applied between two pairs of rolls on the upstream and downstream sides, such as a region R2 schematically shown in FIG. , the tension applied in the longitudinal direction of the multilayer film (II) was 250 N, and the distance between the upstream roll and the downstream roll was 1000 mm.

Both the evaluation of the conveying state of the multilayer film (I) and the evaluation of the conveying state of the multilayer film (II) were evaluated based on the following evaluation criteria.

⊚: A state in which the film at the coated edge is flat and can be conveyed.
◯: A state in which the film tends to bend at the coating edge but does not affect transportation.
△: It can be transported somehow, although it can break at any time.
x: Poor transportation. (The edge is curled and the application edge is broken)
In the case of Δ or × (conveyance failure), what kind of phenomenon specifically occurred was noted in the table showing the results.

[Method for measuring optical properties of each layer of multilayer film (II)]
The multilayer film (II) was placed on the stage of a phase difference meter (“AxoScan” manufactured by Axometrics). Then, the change in the polarization state of the polarized light transmitted through the multilayer film (II) before and after transmission was measured as the transmission polarization characteristic of the multilayer film (II). This measurement was performed as a multi-directional measurement at a polar angle of -55° to 55° with respect to the main surface of the multilayer film (II). The above multidirectional measurement was performed at azimuth angles of 45°, 90°, 135° and 180°, with the azimuth direction of the main surface of the multilayer film (II) being 0°. Furthermore, the measurement wavelength for the above measurements was 590 nm.

The in-plane retardation Re and the orientation angle of each layer were obtained by fitting calculation from the transmission polarization characteristics measured as described above. The fitting calculation was performed by setting the three-dimensional refractive index and the orientation angle of each layer included in the multilayer film (II) as fitting parameters. For the fitting calculation, software attached to the phase difference meter (AxoScan) (“Multi-Layer Analysis” manufactured by Axometrics) was used.

[Example 1]
(1-1. Step (1): Base film (a))
A pellet-shaped norbornene-based resin (manufactured by Zeon Corporation; glass transition temperature: 126° C.) was dried at 100° C. for 5 hours. The dried resin was supplied to an extruder, passed through a polymer pipe and a polymer filter, and extruded into a sheet from a T-die onto a casting drum for extrusion molding. The molded resin was cooled to obtain a long unstretched film having a thickness of 70 μm. The obtained unstretched film was wound up on a roll and collected.

The pre-stretched film was pulled off the rolls and fed continuously to the tenter stretching machine. Then, with this tenter stretching machine, the pre-stretched film is stretched in a stretching direction forming an angle of 45° with respect to the width direction of the pre-stretched film at a stretching temperature of 135 ° C. and a stretching ratio of 1.5 times. A long obliquely stretched film was obtained as the material film (a). The obtained obliquely stretched film had an orientation angle of 45° and an in-plane retardation Re of 215 nm. The thickness of the obtained obliquely stretched film was as shown in Table 1. The obtained obliquely stretched film was wound up on a roll and collected.

(1-2. Step (1(i)): Adhesive layer)
A resin containing an acrylic polymer ("DA105" manufactured by Arakawa Chemical) and an isocyanate-based cross-linking agent ("CL series" manufactured by Arakawa Chemical) were mixed at a weight ratio of 10:3 to form a mixture. This mixture was diluted with a mixed solvent of methyl ethyl ketone and isobutyl ketone (1:1 weight ratio) to a solid content of 20% to obtain an adhesive layer material.

The obliquely stretched film obtained in (1-1) was pulled out from the roll and subjected to corona treatment on one side. The corona treatment was performed under the conditions of a line speed of 10 m/min, a nitrogen atmosphere, and an output of 1.5 kW. After that, the adhesive layer material was applied to the corona-treated surface by using a reverse gravure device that rotates in the direction opposite to the transport direction of the film. The applied adhesive layer material was dried at 120°C. Upon drying, cross-linking of the acrylic polymer in the adhesive layer material proceeded to form an adhesive layer containing cross-linked acrylic polymer. As a result, a long multilayer material having a layer structure of (base film (a))/(adhesive layer) was obtained.

(1-3. Step (2): Multilayer film (I))
A styrene-maleic anhydride copolymer resin ("Daylark D332" manufactured by Nova Chemical) was prepared as a resin having a negative intrinsic birefringence. A mixed solvent of methyl ethyl ketone and isobutyl ketone (polymerization ratio 8:2) was also prepared.
100 parts of a styrene-maleic anhydride copolymer resin was dissolved in a mixed solvent, and 5 parts of triphenyl phosphate was added as a plasticizer to obtain a coating layer material (b) having a solid concentration of 12.5% by weight. rice field. The viscosity of the coating layer material (b) was measured. Table 1 shows the results.

The coating layer material (b) was applied to the multilayer material obtained in (1-2) by die coating. Coating was performed on the adhesive layer side of the multilayer material. The extrusion pressure of the coating film layer material (b) from the die was as shown in Table 1. The shape of the die opening was a conventional shape, as in die 320 shown schematically in FIG. The coating film layer material (b) was not applied to the entire surface of the multilayer material, but was applied only to the region inside the widthwise end of the multilayer material.

The applied coating layer material (b) was dried at 120° C. to form coating layer (BI). Thus, a multilayer film (I) was obtained. The multilayer film (I) was a film comprising a base film layer (AI) composed of the base film (a), an adhesive layer, and a coating layer (BI) in this order. The obtained multilayer film (I) was wound up on a roll and collected.

With respect to the obtained multilayer film (I), the film thicknesses _D10 and De of the coating film layer (BI) were measured to obtain the end film thickness ratio De/ _D10 . In addition, the uncoated portion width We of the multilayer film (I) was measured. Furthermore, the conveying state of the multilayer film (I) was evaluated. Table 1 shows the results.

(1-4. Step (3): Multilayer film (II))
The multilayer film (I) obtained in (1-3) was pulled out from the roll and continuously supplied to a longitudinal stretching machine. Then, with this longitudinal stretching machine, the multilayer film (I) was subjected to free uniaxial stretching in the longitudinal direction of the multilayer film at a stretching temperature of 127° C. and a stretching ratio of 1.4 times. Thereby, the multilayer film (I) was stretched to obtain a multilayer film (II). The multilayer film (II) was a film having a base film layer (A-II), a stretched adhesive layer and a coating layer (B-II) in this order. The base film layer (A-II) and the coating layer (B-II) are layers obtained as a result of stretching the base film layer (AI) and the coating layer (BI), respectively. .

With respect to the obtained multilayer film (II), the film thicknesses D10 and De of the coating film layer (B _- II) were measured to obtain the edge film thickness ratio De/ _D10 . Also, the uncoated portion width We of the multilayer film (II) was measured. Furthermore, the conveying state of the multilayer film (II) was evaluated. Table 1 shows the results.

In addition, the thickness of other layers of the multilayer film (II), the thickness of the entire multilayer film (II), and the orientation angle and Re of the base film layer (A-II) and the coating layer (B-II) was measured. Table 1 shows the results.

[Examples 2 to 11 and Comparative Examples 1 to 2]
The thickness of the base film (a), the shape of the opening of the die for extruding the coating layer material (b), the extrusion pressure of the coating layer material (b), the viscosity of the coating layer material (b), the multilayer film ( The uncoated portion width We in I) and the draw ratio in step (3) were changed as shown in Tables 1 and 2. A multilayer film (I) and a multilayer film (II) were produced and evaluated in the same manner as in Example 1 except for these changes. The results are shown in Tables 1 and 2.

The thickness of the base film (a) was changed (Examples 5 and 6) by changing the extrusion conditions in Example 1 (1-1).

The shape of the opening of the die for extruding the coating layer material (b) (Examples 7 and 10) was changed by placing a shim inside the opening of the die in Example 1 (1-3). With such a shim arrangement, the shape of the die opening was such that the shims were provided near the ends in the width direction, as shown schematically in FIGS. As a result, the flow rate at the ends in the width direction of the opening of the die was relatively decreased with respect to the flow rate at the central portion in the width direction.

Changes in the extrusion pressure of the coating layer material (b) (Examples 3, 4, and 7 and Comparative Examples 1 and 2) It was carried out by changing the pressure when supplying to , as shown in Table 1.

The viscosity of the coating layer material (b) was changed by changing the composition of the coating layer material (b). Specifically, in preparing the coating layer material (b) in (1-3) of Example 1, the solid content concentration was changed to 12% by weight (Example 8) or 15% by weight (Examples 9 and 10 ).

The uncoated portion width We of the multilayer film (I) (Examples 2, 4 and 11 and Comparative Example 1) was changed by changing the width of the die opening in step (2).

The change in the draw ratio in step (3) (Examples 5 to 7) was carried out by changing the operating conditions of the longitudinal stretching machine in Example 1 (1-4).

[Comparative Example 3]
A multilayer film (X) and a multilayer film (XX) obtained by subjecting it to the step (3) were produced and evaluated in the same manner as in Example 1 except for the following changes. Table 2 shows the results. For convenience of description, with respect to Comparative Example 3, the results for the multilayer film (X) are described in the column for the multilayer film (I) in the table, and the results for the multilayer film (XX) are Described in the column for the multilayer film (II) in the table.
In (1-3), after obtaining the multilayer film (I), both ends in the width direction of the multilayer film (I) were cut off. As a result, a multilayer film (X) was obtained excluding the non-coated portion and the sloped portion near the coating edge. The multilayer film (X) was wound up on a roll and collected. A roll of the multilayer film (X) was used instead of the roll of the multilayer film (I) in (1-4) and thereafter to obtain a multilayer film (XX).

The meanings of abbreviations in the table are as follows.
(1) Stretch ratio: the stretch ratio for stretching the unstretched film in step (1).
(a) Thickness (μm): Thickness (μm) of the base film obtained in step (1).
(2) Shims: Whether or not shims are used in step (2).
(2) Coating layer material pressure (Pa): Extrusion pressure of coating layer material (b) in step (2).
(2) Viscosity (cps): Viscosity of coating layer material (b) used in step (2).
(BI) D ₁₀ (μm): Film thickness D ₁₀ at a position 10 mm from the end in the width direction of the coating layer (BI) in the multilayer film (I) obtained in step (2).
(BI) De/D ₁₀ (%): Edge thickness ratio De/D ₁₀ of coating layer (BI) in multilayer film (I) obtained in step (2).
(I) We (mm): Width We (mm) of non-coated portion of multilayer film (I) obtained in step (2). By adjusting the application position in the width direction in step (2), We was made to have the same width on the left and right in the width direction of the film in all the examples and comparative examples.
(I) Conveyance state: evaluation result of the conveyance state of the multilayer film (I).
(3) Stretch ratio: the stretch ratio in step (3).
(A-II) Re (nm): in-plane direction retardation (nm) of the substrate film layer (A-II) in the multilayer film (II) obtained in step (3).
(A-II) orientation angle (°): orientation angle (°) of the base film layer (A-II) in the multilayer film (II) obtained in step (3)
(A-II) Thickness (μm): Thickness (μm) of base film layer (A-II) in multilayer film (II) obtained in step (3)
(B-II) Re (nm): In-plane retardation (nm) of coating layer (B-II) in multilayer film (II) obtained in step (3).
(B-II) orientation angle (°): orientation angle (°) of coating layer (B-II) in multilayer film (II) obtained in step (3)
(B-II) D ₁₀ (μm): Film thickness D ₁₀ at a position 10 mm from the end in the width direction of the coating layer (B-II) in the multilayer film (II) obtained in step (3).
(B-II) De/D ₁₀ (%): Edge film thickness ratio De/D ₁₀ of coating layer (B-II) in multilayer film (II) obtained in step (3).
(II) We (mm): width We (mm) of non-coated portion of multilayer film (II) obtained in step (3). By adjusting the application position in the width direction in step (2), We was made to have the same width on the left and right in the width direction of the film in all the examples and comparative examples.
(II) total thickness: total thickness (μm) of multilayer film (II) obtained in step (3)
(II) Conveyance state: evaluation result of the conveyance state of the multilayer film (II).
*1: There was a tendency for the width direction edge part of the film to bend.
*2: The film tended to curl at the edges in the width direction.
*3: A Z-shaped crease occurred at the end of the film in the width direction, resulting in poor transport.
*4: A C-shaped fold occurred at the end of the film in the width direction, resulting in poor transport.
*5: Poor transport due to strong curling.

The base film layer (A-II) and the coating layer (B-II) have optical properties that can function as a λ/2 layer and a λ/4 layer, respectively, and the multilayer film (II) is , could function as a broadband retardation film due to their optical properties.

As is clear from the above results, the long multilayer film of the present invention (multilayer film (I) and multilayer film (II)) produced by the production method of the present invention, in which De/D ₁₀ satisfies the requirements of the present invention. During manufacturing, problems such as curling at the ends in the width direction were suppressed.

11: Base film (a)
12: Layer of coating layer material (b) 71: Film 100: Long multilayer film 100c: Part covered with coating layer (B) (coated part)
100e1: Part not covered with coating layer (B) (non-coated part)
100e2: Part not covered with coating layer (B) (non-coated part)
110: Base film layer (A)
110e: Width direction end of base film layer (A) 110U: Upper surface of base film layer (A) 120: Coating layer (B)
120e: Width direction end of coating layer (B) 320: Die 310: Back roll 321: Die lumen 322: Opening 420: Die 421: Bore 422: Opening 431: Shim 520: Die 521: Bore 522 : opening 531: shim 620: die 621: bore 622: opening 631: shim 632: shim upper surface 633: shim slope R ₂ : rectangular plane area 711: downstream roll 712: downstream roll 71e: width direction end of film Part 721: Upstream roll 722: Upstream roll

Claims (9)

A method for producing a long multilayer film comprising a base film layer (A) and a coating layer (B) provided on the surface thereof,
Step (1) of preparing a long base film (a);
a step (2) of applying a coating film layer material (b) onto the base film (a);
After the step (2), a step (3) of co-stretching a multilayer material containing the cured product of the base film (a) and the coating layer material (b) ,
The coating in the step (2) is
Ratio of the thickness De at a position 1 mm away from the width direction end of the coating layer (B) to the inside in the width direction of the coating layer (B) with respect to the thickness D ₁₀ at the position 10 mm from the width direction end of the coating layer (B) A method for producing a long multilayer film, wherein De/D ₁₀ is 85% or less. The step (2) is
The widthwise end of the coating layer (B) is located inside the widthwise end of the base film layer (A),
The long strip according to claim 1, wherein the distance We from the width direction end of the coating layer (B) to the width direction end of the base film layer (A) is 5 mm or more. A method for producing a multilayer film. The coating in the step (2) is performed with a die,
In the step (2), the coating layer material (b) from the die is spread outward in the width direction from the width direction end of the opening of the die so that the coating layer material (b) is applied. ), the method for producing a long multilayer film according to claim 1 or 2, wherein the extrusion pressure is adjusted. The coating in the step (2) is performed with a die,
In the step (2), a flow rate restricting member is provided inside the die in the vicinity of the widthwise end of the die opening, and the flow rate at the widthwise end of the die opening is adjusted to the widthwise central portion. The method for producing a long multilayer film according to any one of claims 1 to 3, which is relatively reduced with respect to. The method for producing a long multilayer film according to any one of claims 1 to 4 , wherein the coating layer material (b) has a viscosity of 150 to 1500 cps. 6. The production of the long multilayer film according to any one of claims 1 to 5 , wherein a sloping portion whose thickness gradually decreases from the inside to the outside is formed at the end portion in the width direction of the coating layer (B). Method. A long multilayer film comprising a substrate film layer (A) and a coating layer (B) provided on the surface thereof,
The base film layer (A) is a λ/2 layer, the coating layer (B) is a λ/4 layer,
The ratio of the film thickness De at a position 1 mm away from the width direction end of the coating film layer (B) to the inside in the width direction of the coating film layer (B) with respect to the film thickness D ₁₀ at 10 mm from the width direction end of the coating film layer (B) De / A long multilayer film having a _D10 of 85% or less. The width direction end of the coating layer (B) is positioned inside the width direction end of the base film layer (A),
8. The long multilayer film according to claim 7 , wherein the distance from the widthwise end of the coating layer (B) to the widthwise end of the base film layer (A) is 5 mm or more. 9. The long multilayer film according to claim 7 or 8 , wherein the coating film layer (B) has, at its width direction end portions, sloped portions whose thickness gradually decreases from the inside to the outside.

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