WO2019208508A1 - Broadband wavelength film, production method for same, and production method for circularly polarizing film - Google Patents

Abstract

A production method for a broadband wavelength film, the production method including, in order, a first step for preparing a layer (A) that is a resin film that has a slow axis, a second step for obtaining a multilayer film by forming, on layer (A), a layer (B) of a resin that has a positive intrinsic birefringence, and a third step for obtaining a long broadband wavelength film that has a λ/2 layer and a λ/4 layer by stretching the multilayer film in a direction that is neither orthogonal nor parallel to the slow axis of layer (A). The λ/2 layer and the λ/4 layer of the broadband wavelength film satisfy formula (1). (1) θ(λ/4)={45°+2×θ(λ/2)}±5°. (θ(λ/2) is the angle formed by the slow axis of the λ/2 layer relative to the longitudinal direction of the broadband wavelength film, and θ(λ/4) is the angle formed by the slow axis of the λ/4 layer relative to the longitudinal direction of the broadband wavelength film.)

Description

Broadband wavelength film, method for producing the same, and method for producing a circularly polarizing film

The present invention relates to a broadband wavelength film, a method for producing the same, and a method for producing a circularly polarizing film.

Various studies have conventionally been made on methods for producing optical films having two or more layers (see Patent Documents 1 to 3).

International Publication No. 2016/047465 International Publication No. 2009/031433 JP 2009-237534 A

As a broadband wavelength film that can function as a wavelength plate in a wide wavelength band, a film including a combination of a λ / 2 plate and a λ / 4 plate is known. Conventionally, such a broadband wavelength film includes a step of stretching a film to obtain a λ / 2 plate, a step of stretching another film to obtain a λ / 4 plate, and the λ / 2 plate and λ / plate. It is common to manufacture by the manufacturing method including the process of bonding 4 plates and obtaining a broadband wavelength film.

In addition, a technique for obtaining a circularly polarizing film by combining the broadband wavelength film with a linearly polarizing film as a film that can function as a linearly polarizing plate is known. Generally, a long linearly polarizing film has an absorption axis in the longitudinal direction or the width direction. Thus, when a circular polarizing film is obtained by combining a long linear polarizing film with a broadband wavelength film, the slow axis of the λ / 2 plate is required to be in an oblique direction that is neither parallel nor perpendicular to the longitudinal direction. .

As described above, in order to easily produce a desired λ / 2 plate having a slow axis in the oblique direction as described above, the applicant developed a technique of performing stretching twice or more as described in Patent Document 1. did. Then, in the entire method for producing a broadband wavelength film, one or more stretching steps for obtaining a λ / 4 plate and two or more stretching steps for obtaining a λ / 2 plate are performed. The number of stretching is 3 or more. However, when the number of stretching is as large as 3 or more, the operation is complicated.

The present invention was devised in view of the above problems, and a broadband wavelength film that can be efficiently manufactured with a small number of steps and a method for manufacturing the same; and a method for manufacturing a circularly polarizing film including the method for manufacturing the broadband wavelength film The purpose is to provide;

The inventor has intensively studied to solve the above problems. As a result, the inventor prepared a layer (A) as a resin film having a slow axis in the plane; and a layer (B) of a resin having a positive intrinsic birefringence on the layer (A) (B Forming a multilayer film; and stretching the multilayer film in a direction that is neither perpendicular nor parallel to the slow axis of the layer (A) to form a λ / 2 layer and a λ And a third process for obtaining a long broadband wavelength film having a / 4 layer; in this order, it was found that a broadband wavelength film can be efficiently manufactured with a small number of processes, and the present invention was completed.
That is, the present invention includes the following.

[1] a first step of preparing a layer (A) as a resin film having an in-plane slow axis;
A second step of obtaining a multilayer film by forming a layer (B) of a resin having a positive intrinsic birefringence on the layer (A);
The multilayer film is stretched in a direction that is neither perpendicular nor parallel to the slow axis of the layer (A) to obtain a long broadband wavelength film having a λ / 2 layer and a λ / 4 layer. Including three steps in this order,
A method for producing a broadband wavelength film, wherein the λ / 2 layer and the λ / 4 layer of the broadband wavelength film satisfy the following formula (1):
θ (λ / 4) = {45 ° + 2 × θ (λ / 2)} ± 5 ° (1)
(In the above formula (1),
θ (λ / 2) represents the angle formed by the slow axis of the λ / 2 layer with respect to the longitudinal direction of the broadband wavelength film,
θ (λ / 4) represents an angle formed by the slow axis of the λ / 4 layer with respect to the longitudinal direction of the broadband wavelength film. )
[2] The layer (A) prepared in the first step is a long resin film having a slow axis that is not perpendicular to the longitudinal direction of the layer (A). A method for producing a broadband wavelength film.
[3] The method according to [1] or [2], wherein the third step includes stretching the multilayer film in a direction that forms an angle of 45 ° or more with respect to a longitudinal direction of the multilayer film. A method for producing a broadband wavelength film.
[4] The method for producing a broadband wavelength film according to any one of [1] to [3], wherein the angle θ (λ / 2) is in a range of 20 ° ± 10 °.
[5] The method for producing a broadband wavelength film according to any one of [1] to [4], wherein the angle θ (λ / 4) is in a range of 85 ° ± 20 °.
[6] The method for producing a broadband wavelength film according to any one of [1] to [5], wherein the λ / 2 layer is a layer obtained by stretching the layer (A).
[7] The method for producing a broadband wavelength film according to any one of [1] to [6], wherein the λ / 4 layer is a layer obtained by stretching the layer (B).
[8] A step of producing a broadband wavelength film by the production method according to any one of [1] to [7];
A method for producing a circularly polarizing film, comprising: bonding the broadband wavelength film and a long linearly polarizing film.
[9] The method for producing a circularly polarizing film according to [8], wherein the linearly polarizing film has an absorption axis in the longitudinal direction of the linearly polarizing film.
[10] A long broadband wavelength film,
A λ / 2 layer having a slow axis that forms an angle of 20 ° ± 10 ° with the longitudinal direction of the broadband wavelength film;
An elongated broadband wavelength film, which is a co-stretched film comprising a λ / 4 layer having a slow axis that forms an angle of 85 ° ± 20 ° with respect to the longitudinal direction of the broadband wavelength film.

According to the present invention, it is possible to provide a broadband wavelength film that can be efficiently manufactured with a small number of steps and a method for manufacturing the same; and a method for manufacturing a circularly polarizing film including the method for manufacturing the broadband wavelength film.

FIG. 1 is a perspective view schematically showing a layer (A) as a resin film prepared in the first step of the method for producing a broadband wavelength film according to one embodiment of the present invention. FIG. 2 is a perspective view schematically showing a multilayer film obtained in the second step of the method for producing a broadband wavelength film according to one embodiment of the present invention. FIG. 3 is a perspective view schematically showing a broadband wavelength film obtained in the third step of the method for manufacturing a broadband wavelength film according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and exemplifications, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

In the following description, the “long” film means a film having a length of 5 times or more, preferably 10 times or more, and specifically a roll. A film having such a length that it can be wound up and stored or transported. The upper limit of the film length is not particularly limited, and can be, for example, 100,000 times or less with respect to the width.

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

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

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

In the following description, the direction and geometric direction (the longitudinal direction and width of the film) of the optical axis (slow axis, transmission axis, absorption axis, etc.) in the plane of a certain product (broadband wavelength film, circularly polarizing film, etc.) Unless otherwise specified, the angle relationship of the direction is defined as positive in one direction and negative in the other direction, and the positive and negative directions are defined in common in the components in the product. The For example, in a broadband wavelength film, “the angle formed by the slow axis of the λ / 2 layer with respect to the longitudinal direction of the broadband wavelength film is 20 °, and the retardation of the λ / 4 layer with respect to the longitudinal direction of the broadband wavelength film is “An angle formed by the phase axes is 85 °” represents the following two cases:
When the broadband wavelength film is observed from one side thereof, the slow axis of the λ / 2 layer is shifted 20 ° clockwise from the longitudinal direction of the broadband wavelength film, and the slow phase of the λ / 4 layer The axis is shifted by 85 ° clockwise from the longitudinal direction of the broadband wavelength film.
When the broadband wavelength film is observed from one side thereof, the slow axis of the λ / 2 layer is shifted 20 ° counterclockwise from the longitudinal direction of the broadband wavelength film, and the retardation of the λ / 4 layer is The phase axis is shifted by 85 ° counterclockwise from the longitudinal direction of the broadband wavelength film.

In the following description, unless otherwise specified, the oblique direction of a long film refers to the in-plane direction of the film, which is neither parallel nor perpendicular to the longitudinal direction of the film.

In the following description, unless otherwise specified, the front direction of a film means the normal direction of the main surface of the film, specifically, the direction of the polar angle 0 ° and the azimuth angle 0 ° of the main surface. Point to.

In the following description, unless otherwise specified, the inclination direction of a film means a direction that is neither parallel nor perpendicular to the main surface of the film, and specifically, the polar angle of the main surface is larger than 0 ° and 90 °. Point in a direction smaller than °.

In the following description, a material having a positive intrinsic birefringence means a material in which the refractive index in the stretching direction is larger than the refractive index in the direction perpendicular thereto unless otherwise specified. Further, a material having a negative intrinsic birefringence means a material having a refractive index in the stretching direction that is smaller than a refractive index in a direction perpendicular thereto unless otherwise specified. The value of intrinsic birefringence can be calculated from the dielectric constant distribution.

In the following description, “(meth) acryl” includes “acryl”, “methacryl”, and combinations thereof.

In the following description, the in-plane retardation Re of a layer is a value represented by Re = (nx−ny) × d unless otherwise specified. The retardation Rth in the thickness direction of the layer is a value represented by Rth = [{(nx + ny) / 2} −nz] × d unless otherwise specified. Further, the NZ coefficient of the layer is a value represented by (nx−nz) / (nx−ny) unless otherwise specified. Here, nx represents a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the layer and giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the layer and perpendicular to the nx direction. 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 specified.

In the following description, unless the direction of the element is “parallel”, “vertical”, or “orthogonal”, unless otherwise specified, for example, ± 3 °, ± 2 °, or ± 1 °. An error within the range of may be included.

[1. Overview]
FIG. 1 is a perspective view schematically showing a layer (A) 100 as a resin film prepared in the first step of the method for producing a broadband wavelength film according to one embodiment of the present invention. FIG. 2 is a perspective view schematically showing a multilayer film 200 obtained in the second step of the method for producing a broadband wavelength film according to an embodiment of the present invention. FIG. 3 is a perspective view schematically showing a broadband wavelength film 300 obtained in the third step of the method for manufacturing a broadband wavelength film according to an embodiment of the present invention.

The method for manufacturing the broadband wavelength film 300 according to an embodiment of the present invention includes:
(1) As shown in FIG. 1, a first step of preparing a layer (A) 100 as a resin film having a slow axis A _{100 in-} plane;
(2) a second step of forming a resin layer (B) 210 having a positive intrinsic birefringence on the layer (A) 100 to obtain a multilayer film 200 shown in FIG. 2;
(3) a third step of stretching the multilayer film 200 to obtain the long broadband wavelength film 300 shown in FIG. 3;
Are included in this order.

As shown in FIG. 1, the layer (A) 100 prepared in the first step has a slow axis A ₁₀₀ in its plane. After forming the layer (B) 210 on the layer (A) 100 in the second step and obtaining the multilayer film 200 including the layer (A) 100 and the layer (B) 210 as shown in FIG. The multilayer film 200 is stretched in the third step. This stretching is performed in an in-plane that is neither perpendicular nor parallel to the slow axis A ₁₀₀ of the layer (A) so that λ / 2 and λ / 4 layers having a slow axis in the desired direction are obtained. In the direction.

By stretching in the third step, co-stretching for stretching the layer (A) 100 and the layer (B) 210 at the same time is performed. Therefore, as shown in FIG. 3, the layer (A) 100, the direction of adjustment of the slow axis _{A 100,} and the adjustment of the optical properties is performed. On the other hand, the slow axis _{A 210} appears in the layer (B) 210, the optical characteristics are exhibited. The stretched layer (A) 100 functions as one of the λ / 2 layer and the λ / 4 layer, and the stretched layer (B) 210 functions as the other of the λ / 2 layer and the λ / 4 layer. Therefore, the broadband wavelength film 300 having the λ / 2 layer and the λ / 4 layer can be obtained by the above manufacturing method. FIG. 3 shows an example in which the stretched layer (A) 100 functions as a λ / 2 layer and the stretched layer (B) 210 functions as a λ / 4 layer. It is not limited to examples.

The λ / 2 layer and the λ / 4 layer satisfy the following formula (1).
θ (λ / 4) = {45 ° + 2 × θ (λ / 2)} ± 5 ° (1)
Equation (1) shows that θ (λ / 4) is a range where “{45 ° + 2 × θ (λ / 2)} − 5 °” or more and “{45 ° + 2 × θ (λ / 2)} + 5 °” or less. It means that there is. In Equation (1), θ (λ / 2) represents an angle formed by the slow axis A ₁₀₀ of the λ / 2 layer with respect to the longitudinal direction A ₃₀₀ of the broadband wavelength film 300. Θ (λ / 4) represents an angle formed by the slow axis A ₂₁₀ of the λ / 4 layer with respect to the longitudinal direction A ₃₀₀ of the broadband wavelength film 300. By including the combination of the λ / 2 layer and the λ / 4 layer that satisfy this formula (1), the broadband wavelength film 300 can transmit light that passes through the film in a wide wavelength range to approximately ¼ wavelength of the wavelength of the light. It can function as a broadband wavelength film capable of providing in-plane retardation.

The longitudinal _{A 300} of the broadband wave film 300, lambda / 4 layers of longitudinal (not shown), and, lambda / 2 layer in the longitudinal direction (not shown) is consistent. Therefore, the angle θ (λ / 2) represents the orientation angle formed by the slow axis A ₁₀₀ of the λ / 2 layer with respect to the longitudinal direction of the λ / 2 layer. ) ". Further, the angle θ (λ / 4) represents the orientation angle formed by the slow axis A ₂₁₀ of the λ / 4 layer with respect to the longitudinal direction of the λ / 4 layer. ) ".

[2. First step]
In the first step, a layer (A) as a resin film having a slow axis in the plane is prepared. From the viewpoint of obtaining a long broadband wavelength film, a long resin film is usually used as the layer (A). As this layer (A), a resin film having a multilayer structure including two or more layers may be used, but a resin film having a single layer structure including only one layer is usually used.

As the resin for forming the resin film, a thermoplastic resin containing a polymer and further containing optional components as required can be used. In particular, as the resin contained in the layer (A), a resin having a negative intrinsic birefringence may be used. However, a resin having a positive intrinsic birefringence should be used because a broadband wavelength film can be manufactured particularly easily. Is preferred.

The resin having a positive intrinsic birefringence usually contains a polymer having a positive intrinsic birefringence. Examples of polymers having a 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; polycarbonate; polyarylate; Polysulfone; Polysulfone; Polyallyl sulfone; Polyvinyl chloride; Cyclic olefin polymer such as norbornene polymer; Rod-like liquid crystal polymer. These polymers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The polymer may be a homopolymer or a copolymer. Among these, a polycarbonate polymer is preferable because it is excellent in expression of retardation and stretchability at low temperature. In addition, a cyclic olefin polymer is preferable because of excellent mechanical properties, heat resistance, transparency, low moisture absorption, dimensional stability, and light weight.

The proportion of the polymer in the resin contained in the layer (A) is preferably 50% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. When the ratio of the polymer is within the above range, the layer (A) and the broadband wavelength film can obtain sufficient heat resistance and transparency.

The resin contained in the layer (A) may further 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; thermal stabilizers; light stabilizers; ultraviolet absorbers; antistatic agents; Examples include activators. These components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The glass transition temperature TgA of the resin contained in the layer (A) is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, particularly preferably 120 ° C. or higher, preferably 190 ° C. or lower, more preferably 180 ° C. or lower, Especially preferably, it is 170 degrees C or less. When the glass transition temperature of the resin contained in the layer (A) is not less than the lower limit of the above range, the layer (λ / 2 layer or λ / 4 layer) obtained by stretching the layer (A) in a high temperature environment Durability can be increased. Moreover, when the glass transition temperature of the resin contained in the layer (A) is not more than the upper limit of the above range, the stretching treatment can be easily performed.

The direction of the slow axis of the layer (A) prepared in the first step can be arbitrarily set within a range where a desired broadband wavelength film can be obtained. For example, when the intrinsic birefringence of the resin contained in the layer (A) is positive, the slow axis of the layer (A) is usually stretched by stretching the multilayer film in the third step. It changes to approach the direction. Further, for example, when the intrinsic birefringence of the resin contained in the layer (A) is negative, the slow axis of the layer (A) is usually determined by stretching the multilayer film in the third step. It changes so that it may approach the direction perpendicular | vertical to the extending | stretching direction. Therefore, the direction of the slow axis of the layer (A) prepared in the first step can be set according to the stretching direction of the multilayer film in the third step.

The slow axis of the layer (A) prepared in the first step is preferably not perpendicular to the longitudinal direction of the layer (A), and may be parallel to or close to the longitudinal direction of the layer (A). More preferred. Therefore, the orientation angle formed by the slow axis of the layer (A) with respect to the longitudinal direction of the layer (A) is preferably greater than −87 °, more preferably −45 ° or more, and further preferably −30 ° or more. In particular, it is −15 ° or more, preferably less than 87 °, more preferably 45 ° or less, still more preferably 30 ° or less, and particularly preferably 15 ° or less. When the layer (A) having such a slow axis is used, a broadband wavelength film having preferable optical characteristics can be easily obtained.

The optical properties such as retardation and NZ coefficient of the layer (A) prepared in the first step can be set according to the optical properties of the layer obtained by stretching the layer (A).

For example, when the layer (A) is stretched to obtain a λ / 2 layer, the in-plane retardation of the layer (A) is preferably 200 nm or more, more preferably 250 nm or more, and particularly preferably 300 nm or more. The thickness is preferably 500 nm or less, more preferably 450 nm or less, and particularly preferably 400 nm or less. Further, the NZ coefficient of the layer (A) is preferably 1.00 or more, preferably 1.20 or less, more preferably 1.15 or less, and particularly preferably 1.10 or less.

The thickness of the layer (A) prepared in the first step can be arbitrarily set within a range where a desired broadband wavelength film can be obtained. The specific thickness of the layer (A) is preferably 20 μm or more, more preferably 25 μm or more, particularly preferably 30 μm or more, preferably 100 μm or less, more preferably 95 μm or less, and particularly preferably 90 μm or less. When the thickness of the layer (A) is in the above range, a λ / 2 layer or a λ / 4 layer having desired optical properties can be easily obtained by stretching in the third step.

The layer (A) can be obtained by a production method including drawing an appropriate resin film and developing a slow axis in the resin film. In the following description, the resin film before being subjected to the stretching treatment may be referred to as “film before stretching”, and the resin film obtained after stretching may be referred to as “stretched film”.

The film before stretching can be produced by, for example, a melt molding method or a solution casting method. More specific examples of the melt molding method include an extrusion molding method, a press molding method, an inflation molding method, an injection molding method, a blow molding method, and a stretch molding method. Among these methods, in order to obtain a layer (A) excellent in mechanical strength and surface accuracy, an extrusion molding method, an inflation molding method or a press molding method is preferable. Among them, a viewpoint that the layer (A) can be produced efficiently and easily. The extrusion method is particularly preferred. The pre-stretch film is preferably obtained as a long film.

After preparing the pre-stretch film, the pre-stretch film can be stretched to obtain a layer (A) as a stretched film.

The slow axis of the layer (A) is usually expressed by stretching the film before stretching. Therefore, the stretching direction of the film before stretching is preferably set according to the direction of the slow axis of the layer (A). For example, when the pre-stretch film is formed of a resin having a positive intrinsic birefringence, the stretch direction of the pre-stretch film is set in a direction parallel to the slow axis of the layer (A) to be prepared in the first step. It is preferable to do. For example, when the film before stretching is formed of a resin having a negative intrinsic birefringence, the stretching direction of the film before stretching is the direction perpendicular to the slow axis of the layer (A) to be prepared in the first step. It is preferable to set to.

Furthermore, the stretching direction of the film before stretching is preferably not perpendicular to the longitudinal direction of the film before stretching. Therefore, it is preferable that the extending | stretching direction of the film before extending | stretching exists in the longitudinal direction or diagonal direction of the said film before extending | stretching. By using a stretched film obtained by such a production method including stretching in the longitudinal direction or oblique direction as the layer (A), a broadband wavelength film having preferable optical properties can be easily obtained.

The stretch ratio of the pre-stretch film is preferably 1.1 times or more, more preferably 1.2 times or more, preferably 4.0 times or less, more preferably 3.0 times or less. When the draw ratio is not less than the lower limit of the above range, the refractive index in the drawing direction can be increased. Moreover, when a draw ratio is below the upper limit of the said range, the direction of the slow axis of the layer obtained by extending | stretching a layer (A) can be controlled easily.

The stretching temperature of the film before stretching is preferably TgA or higher, more preferably “TgA + 2 ° C.” or higher, particularly preferably “TgA + 5 ° C.” or higher, preferably “TgA + 40 ° C.” or lower, more preferably “TgA + 35 ° C.” or lower, Especially preferably, it is “TgA + 30 ° C.” or less. Here, TgA refers to the glass transition temperature of the resin contained in the layer (A). When the stretching temperature is in the above range, the molecules contained in the pre-stretched film can be reliably oriented, so that the layer (A) having desired optical properties can be easily obtained.

The stretching in the first step may be performed as free uniaxial stretching. Free uniaxial stretching refers to stretching in a certain direction and not applying a restraining force in a direction other than the direction in which the film is stretched. Thus, for example, free uniaxial stretching in the longitudinal direction of the film before stretching refers to stretching in the longitudinal direction performed without restraining the end of the film before stretching in the width direction.

The above-described stretching can usually be performed using an appropriate stretching machine such as a roll stretching machine or a tenter stretching machine while continuously transporting the film before stretching in the longitudinal direction. For example, when a film before stretching is stretched in the longitudinal direction of the film before stretching, it is preferable to use a roll stretching machine. With a roll stretching machine, free uniaxial stretching can be easily performed. As these stretching machines, for example, the one described in Patent Document 1 can be used.

[3. Fourth step]
The method for producing a broadband wavelength film may include a step of forming a thin film layer on the layer (A), if necessary, after preparing the layer (A) in the first step. By forming an appropriate thin film layer, the thin film layer functions as an easy adhesion layer, and the binding force between the layer (A) and the layer (B) can be increased. Moreover, it is preferable that a thin film layer has solvent resistance. Such a thin film layer is usually formed of a resin.

Examples of the material for the thin film layer include acrylic resin, urethane resin, acrylic urethane resin, ester resin, and ethyleneimine resin. The acrylic resin is a resin containing an acrylic polymer. The urethane resin is a resin containing polyurethane. A polymer such as an acrylic polymer and polyurethane usually has a high binding force for a wide variety of resins, so that the binding force between the layer (A) and the layer (B) can be increased. Moreover, these polymers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Resin as a material of the thin film layer is combined with a polymer, heat stabilizer, weather stabilizer, leveling agent, antistatic agent, slip agent, antiblocking agent, antifogging agent, lubricant, dye, pigment, natural oil, Arbitrary components such as synthetic oil, wax, and particles may be included. Arbitrary components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The glass transition temperature of the resin as the material of the thin film layer is higher than the glass transition temperature TgA of the resin contained in the layer (A) and the glass transition temperature TgB of the resin having a positive intrinsic birefringence contained in the layer (B). Preferably it is low. In particular, the difference between the glass transition temperature of the resin as the material of the thin film layer and the lower one of the glass transition temperatures TgA and TgB is preferably 5 ° C. or higher, more preferably 10 ° C. or higher, and particularly preferably 20 ° C. or higher. preferable. Thereby, since it can suppress that a thin film layer expresses retardation by extending | stretching in a 3rd process, the thin film layer in a broadband wavelength film can have optical isotropy. Therefore, it is possible to easily adjust the optical characteristics of the broadband wavelength film.

The thin film layer can be formed, for example, by a method including coating a coating liquid containing a resin as a material for the thin film layer and a solvent on the layer (A). As the solvent, water or an organic solvent may be used. As an organic solvent, the thing similar to the solvent which can be used for formation of the layer (B) mentioned later is mentioned, for example. Moreover, a solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Furthermore, the coating liquid may contain a crosslinking agent. By using a crosslinking agent, the mechanical strength of the thin film layer can be increased, and the binding property of the thin film layer to the layer (A) and the layer (B) can be increased. As a crosslinking agent, an epoxy compound, an amino compound, an isocyanate compound, a carbodiimide compound, an oxazoline compound, etc. can be used, for example. Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. The amount of the crosslinking 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 as follows.

Examples of the coating method of the coating liquid include the same methods as the coating method that can be used for forming the layer (B) described later.

A thin film layer can be formed by applying a coating solution on the layer (A). This thin film layer may be subjected to a curing treatment such as drying and crosslinking as necessary. Examples of the drying method include heat drying using an oven. Moreover, as a crosslinking method, methods, such as heat processing, irradiation processing of active energy rays, such as an ultraviolet-ray, are mentioned, for example.

[4. Second step]
In the first step, a layer (A) is prepared, and after forming a thin film layer as necessary, a second step of obtaining a multilayer film by forming a resin layer (B) having a positive intrinsic birefringence. Do. In the second step, the layer (B) is formed directly on the layer (A) or indirectly via an arbitrary layer such as a thin film layer. Here, “directly” means that there is no arbitrary layer between the layer (A) and the layer (B).

As the resin having a positive intrinsic birefringence for forming the layer (B), any resin can be selected and used from the range of the resins having a positive intrinsic birefringence described as the material for the layer (A) in the first step. . The resin contained in the layer (B) and the resin contained in the layer (A) may be the same or different.

The glass transition temperature TgB of the resin having a positive intrinsic birefringence contained in the layer (B) is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, particularly preferably 120 ° C. or higher, preferably 190 ° C. or lower, more Preferably it is 180 degrees C or less, Most preferably, it is 170 degrees C or less. When the glass transition temperature of the resin contained in the layer (B) is equal to or higher than the lower limit of the above range, the layer (λ / 2 layer or λ / 4 layer) obtained by stretching the layer (B) in a high temperature environment Durability can be increased. Moreover, when the glass transition temperature of the resin contained in the layer (B) is not more than the upper limit of the above range, the stretching treatment can be easily performed.

From the viewpoint of adjusting the optical properties of both the layer (A) and the layer (B) to an appropriate range by stretching in the third step, the glass transition temperature TgA of the resin contained in the layer (A) and the layer (B) The glass transition temperature TgB of the resin to be used is preferably close. Specifically, the absolute value | TgA−TgB | of the difference between the glass transition temperature TgA and the glass transition temperature TgB is preferably 20 ° C. or less, more preferably 15 ° C. or less, and particularly preferably 10 ° C. or less.

The layer (B) may have in-plane retardation and a slow axis. When the layer (B) has an in-plane retardation and a slow axis, the in-plane retardation and the slow axis direction of the layer (B) are adjusted by stretching in the third step. However, the setting of the stretching conditions for performing such adjustment tends to be complicated. Therefore, from the viewpoint of easily obtaining the desired optical characteristics and slow axis direction in the layer (B) after stretching in the third step, the layer (B) formed in the second step has in-plane retardation and slow phase. It is preferable that the in-plane retardation is small even if it does not have an axis. Specifically, the in-plane retardation of the layer (B) is preferably 0 nm to 20 nm, more preferably 0 nm to 15 nm, and particularly preferably 0 nm to 10 nm.

The thickness of the layer (B) formed in the second step can be arbitrarily set within a range where a desired broadband wavelength film can be obtained. The specific thickness of the layer (B) is preferably 3 μm or more, more preferably 4 μm or more, particularly preferably 5 μm or more, preferably 30 μm or less, more preferably 25 μm or less, and particularly preferably 20 μm or less. When the thickness of the layer (B) is in the above range, a λ / 2 layer or λ / 4 layer having desired optical properties can be easily obtained by stretching.

There is no special restriction | limiting in the formation method of a layer (B), For example, formation methods, such as a coating method, an extrusion method, and the bonding method, can be used.

When the layer (B) is formed by the coating method, the second step includes coating a composition containing a resin having a positive intrinsic birefringence on the layer (A). The composition is usually a liquid composition containing a solvent in combination with a resin having a positive intrinsic birefringence. Examples of the solvent 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, N, N-dimethylformamide and the like. Moreover, a solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. The solvent may cause a phenomenon such as dissolution and orientation relaxation in the layer (A). Usually, the coating thickness of the liquid composition is thin, and the coating is dried quickly after coating. The degree of this phenomenon is negligibly small.

Examples of the coating method of the composition include curtain coating method, extrusion coating method, roll coating method, spin coating method, dip coating method, bar coating method, spray coating method, slide coating method, print coating method, and gravure. Examples of the method include a coating method, a die coating method, a gap coating method, and a dipping method.

Also, in the coating method, the second step includes drying the coated composition as necessary after coating the composition on the layer (A). The solvent is removed by drying, and a layer (B) of a resin having a positive intrinsic birefringence can be formed on the layer (A). Drying can be performed by a drying method such as natural drying, heat drying, reduced pressure drying, and reduced pressure heat drying.

When the layer (B) is formed by the extrusion method, the second step includes extruding a resin having a positive intrinsic birefringence on the layer (A). The extrusion of the resin is usually performed in a state where the resin is melted. Moreover, resin is normally extruded to a film form using die | dye. A resin (B) having a positive intrinsic birefringence may be formed on the layer (A) by adhering the extruded resin having a positive intrinsic birefringence to the layer (A) or the thin film layer. it can. When the layer (B) is formed by an extrusion method, the second step usually includes cooling and curing a resin having a positive intrinsic birefringence that has been extruded and adhered to the layer (A).

When the layer (B) is formed by the bonding method, the second step includes bonding a film of a resin having a positive intrinsic birefringence to the layer (A). Examples of a method for producing a resin film having a positive intrinsic birefringence include melt molding methods such as an extrusion molding method, an inflation molding method, and a press molding method; and a solution casting method. Moreover, you may use an adhesive agent or an adhesive as needed for the bonding of the film of resin with a positive intrinsic birefringence, and a layer (A).

Among the methods for forming the layer (B) described above, the coating method is preferable. For example, when the bonding method is used, when the layer (B) is formed on an appropriate support film and this layer (B) is bonded to the layer (A), the layer (A The layer (B) can be formed thereon. However, compared with the laminating method in which many steps of forming the layer (B) on the support film and transferring the layer (B) from the support film to the layer (A) are performed, the coating method is the layer (B). The number of steps required to form the film can be reduced. Furthermore, according to the coating method, an adhesive and a pressure-sensitive adhesive are unnecessary. Further, in the coating method, the thickness of the layer (B) itself can be made thinner than in the extrusion method. Therefore, from the viewpoint of obtaining a thin broadband wavelength film with a small number of steps, it is preferable to form the layer (B) by a coating method.

[5. Third step]
After obtaining the multilayer film provided with the layer (A) and the layer (B) in the second step, the third step of stretching the multilayer film to obtain a long broadband wavelength film is performed. By stretching in the third step, the direction of the slow axis of the layer (A) is adjusted, and the optical characteristics of the layer (A) are adjusted to obtain one of the λ / 2 layer and the λ / 4 layer. . Further, due to the stretching in the third step, the slow axis appears in the layer (B), and the optical characteristics appear in the layer (B), and the other of the λ / 2 layer and the λ / 4 layer is obtained.

The stretching in the third step is performed in a direction that is neither perpendicular nor parallel to the slow axis of the layer (A) contained in the multilayer film. Thereby, usually, retardation can be expressed in the layer (B), and at the same time, the slow axis of the layer (A) can be controlled in an arbitrary direction to obtain the angular relationship of the formula (1). .

The specific stretching direction is set so that a desired broadband wavelength film can be obtained from the in-plane direction of the multilayer film.
For example, when the layer (A) is a resin layer having positive intrinsic birefringence, the direction of the slow axis of the layer (A) changes so as to approach the stretching direction by stretching in the third step. To do. For example, when the layer (A) is a resin layer having a negative intrinsic birefringence, the slow axis direction of the layer (A) is perpendicular to the stretching direction by stretching in the third step. It changes to approach the direction. Thus, normally, the direction of the slow axis of a layer (A) changes with extending | stretching in a 3rd process. Furthermore, in the layer (B), a slow axis usually appears in a direction parallel to the stretching direction due to stretching in the third step. Accordingly, the stretching direction in the third step is delayed in the desired direction by the change in the direction of the slow axis in the layer (A) and the development of the slow axis in the layer (B). It is preferable to set so that λ / 2 layers and λ / 4 layers having axes are obtained.

The specific angle size (absolute value of the angle) formed by the stretching direction of the multilayer film in the third step and the slow axis of the layer (A) is preferably 50 ° or more, more preferably 60 ° or more. The angle is particularly preferably 70 ° or more, preferably 86 ° or less, particularly preferably 85 ° or less. When the multilayer film is stretched in such a stretching direction, it is easy to adjust the slow axes of the λ / 2 layer and the λ / 4 layer so as to satisfy the relationship of the formula (1).

Among these, the third step preferably includes stretching the multilayer film in a stretching direction that forms an angle of 45 ° or more with respect to the longitudinal direction of the multilayer film. More specifically, the angle formed by the stretching direction in the third step with respect to the longitudinal direction of the multilayer film is preferably 45 ° or more, more preferably 60 ° or more, particularly preferably 70 ° or more, preferably It is 135 ° or less, more preferably 110 ° or less, and particularly preferably 100 ° or less. When the multilayer film is stretched in such a stretching direction, the slow axis directions of the λ / 2 layer and the λ / 4 layer can be easily controlled.

The draw ratio in the third step is preferably 1.1 times or more, more preferably 1.15 times or more, particularly preferably 1.2 times or more, preferably 3.0 times or less, more preferably 2.5 times. 2 times or less, particularly preferably 2.2 times or less. When the draw ratio in the third step is not less than the lower limit of the above range, the generation of wrinkles can be suppressed. Moreover, when the draw ratio in the third step is less than or equal to the upper limit of the above range, the direction of the slow axis of the λ / 2 layer and the λ / 4 layer can be easily controlled.

The stretching temperature in the third step is the following condition (C1) with respect to the glass transition temperature TgA of the resin contained in the layer (A) and the glass transition temperature TgB of the resin having a positive intrinsic birefringence contained in the layer (B). ) And (C2) are preferably satisfied.
(C1) The 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 of TgA + 20 ° C. or lower.
(C2) The 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 of TgB + 20 ° C. or lower.
By stretching at such a stretching temperature, the optical properties of the layer (A) can be appropriately adjusted, and desired optical properties can be expressed in the layer (B). Accordingly, a broadband wavelength film having desired optical characteristics can be obtained.

The stretching in the third step described above can be performed using an arbitrary stretching machine, for example, a tenter stretching machine or a roll stretching machine. Stretching using these stretching machines is preferably performed while continuously transporting a long multilayer film in the longitudinal direction.

[6. Any process]
The above-described method for producing a broadband wavelength film may further include an optional step in combination with the above-described steps.
For example, the method for producing a broadband wavelength film may include a step of providing a protective layer on the surface of the broadband wavelength film.

Further, for example, in the method for producing a broadband wavelength film, surface treatment such as corona treatment and plasma treatment is applied to one or more surfaces of the layer (A), the layer (B), and the thin film layer at an arbitrary time. The process to apply may be included. Therefore, for example, after the surface treatment is performed on the surface of the layer (A), the layer (B) or the thin film layer may be formed on the treated surface. Further, for example, after the surface treatment is performed on the surface of the thin film layer, the layer (B) may be formed on the treated surface. By performing the surface treatment, it is possible to enhance the binding property between the layers on the surface-treated surface.

Any of the first to fourth steps and the optional step described above can be performed while continuously transporting films such as the layer (A), the multilayer film, and the broadband wavelength film. The conveyance direction of such a file conveyance is usually the longitudinal direction of the film. Therefore, in the case of the said conveyance, the longitudinal direction and the width direction of a film usually correspond to MD direction (Machine Direction) and TD direction (Transverse Direction) of conveyance.

[7. Broadband wavelength film]
By the manufacturing method described above, a co-stretched film having a λ / 2 layer and a λ / 4 layer can be obtained. The λ / 2 layer and λ / 4 layer of this co-stretched film satisfy the above formula (1). The combination of the λ / 2 layer and the λ / 4 layer satisfying the relationship represented by the formula (1) is such that an in-plane letter having a wavelength that is approximately ¼ wavelength of the light transmitted through the film in a wide wavelength range. It can function as a broadband wavelength film capable of providing a foundation (see JP 2007-004120 A). Therefore, according to the manufacturing method described above, a broadband wavelength film can be obtained as a co-stretched film having a λ / 2 layer and a λ / 4 layer. From the viewpoint of realizing a broadband wavelength film that can function in a wider wavelength range, the λ / 2 layer and the λ / 4 layer preferably satisfy Expression (2), and more preferably satisfy Expression (3). Formula (2) is a range in which θ (λ / 4) is “{+ 45 ° + 2 × θ (λ / 2)} − 4 °” or more and “{+ 45 ° + 2 × θ (λ / 2)} + 4 °” or less. It means that there is. Further, in the formula (3), θ (λ / 4) is “{+ 45 ° + 2 × θ (λ / 2)} − 3 °” or more and “{+ 45 ° + 2 × θ (λ / 2)} + 3 °” or less. It is in the range of.
θ (λ / 4) = {+ 45 ° + 2 × θ (λ / 2)} ± 5 ° (1)
θ (λ / 4) = {+ 45 ° + 2 × θ (λ / 2)} ± 4 ° (2)
θ (λ / 4) = {+ 45 ° + 2 × θ (λ / 2)} ± 3 ° (3)

In the manufacturing method described above, the stretching of the layer (A) and the layer (B) is not performed separately as in the prior art, but is performed together in the third step. Therefore, since the number of stretching processes can be reduced as compared with the prior art, the number of steps required for producing a broadband wavelength film can be reduced, and thus efficient production can be realized. Further, in the above production method for obtaining a broadband wavelength film by co-stretching the layer (A) and the layer (B) by stretching a multilayer film, both the λ / 2 layer and the λ / 4 layer are produced after the production. As in the conventional manufacturing method of bonding, there is no shift in the slow axis direction due to bonding. Therefore, since it is easy to precisely control the direction of the slow axis of each of the λ / 2 layer and the λ / 4 layer, a high-quality broadband wavelength film capable of realizing a circularly polarizing film capable of effectively suppressing coloring. Can be easily obtained.

In the obtained broadband wavelength film, the λ / 2 layer is a layer obtained by stretching one of the layer (A) and the layer (B), and the λ / 4 layer is the layer (A) and the layer (B). The other is a layer obtained by stretching. Among these, since it is particularly easy to produce a broadband wavelength film, the λ / 2 layer is preferably a layer obtained by stretching the layer (A), and the λ / 4 layer is preferably a layer (B ) Is preferably obtained by stretching. Therefore, the λ / 2 layer is preferably a layer made of the same resin as the layer (A), and the λ / 4 layer is preferably a layer made of the same resin as the layer (B).

The λ / 2 layer is a layer having an in-plane retardation of usually 220 nm or more and usually 300 nm or less at a measurement wavelength of 590 nm. When the λ / 2 layer has such in-plane retardation, a broadband wavelength film can be realized by combining the λ / 2 layer and the λ / 4 layer. Among them, from the viewpoint of obtaining a circularly polarizing film excellent in the function of suppressing coloring in the tilt direction, the in-plane retardation of the λ / 2 layer at a measurement wavelength of 590 nm is preferably 230 nm or more, more preferably 240 nm or more, preferably It is 280 nm or less, more preferably 270 nm or less.

The retardation in the thickness direction of the λ / 2 layer at a measurement wavelength of 590 nm is preferably 130 nm or more, more preferably 140 nm or more, particularly preferably 150 nm or more, preferably 300 nm or less, more preferably 280 nm or less, particularly preferably 270 nm. It is as follows. When the retardation in the thickness direction of the λ / 2 layer is in the above range, it is possible to obtain a circularly polarizing film particularly excellent in the function of suppressing coloring in the tilt direction.

The NZ coefficient of the λ / 2 layer is preferably 1.0 or more, more preferably 1.05 or more, particularly preferably 1.10 or more, preferably 1.6 or less, more preferably 1.55 or less, particularly Preferably it is 1.5 or less. When the NZ coefficient of the λ / 2 layer is in the above range, it is possible to obtain a circularly polarizing film particularly excellent in the function of suppressing coloring in the tilt direction. Further, the λ / 2 layer having such an NZ coefficient can be easily manufactured.

The optical properties such as the retardation of the λ / 2 layer and the NZ coefficient include, for example, the retardation and thickness of the layer (A) prepared in the first step; and the stretching temperature, stretching ratio, stretching direction, etc. in the third step. The stretching conditions can be adjusted.

The orientation angle θ (λ / 2) of the λ / 2 layer is preferably in the range of 20 ° ± 10 ° (ie, in the range of 10 ° to 30 °), and in the range of 20 ° ± 8 ° (ie, 12 °). More preferably, it is in the range of 20 ° to 28 °, and particularly preferably in the range of 20 ° ± 5 ° (that is, in the range of 15 ° to 25 °). A general linearly polarizing film has a transmission axis in the width direction and an absorption axis in the longitudinal direction. When the orientation angle θ (λ / 2) of the λ / 2 layer is in the above range, a circularly polarizing film can be easily realized in combination with such a general linearly polarizing film. Moreover, when the orientation angle θ (λ / 2) of the λ / 2 layer is in the above range, the function of suppressing coloring in the front direction of the obtained circularly polarizing film can be improved.

The orientation angle θ (λ / 2) of the λ / 2 layer is, for example, the direction of the slow axis of the layer (A) prepared in the first step; and the stretching conditions such as the stretching direction and the stretching ratio in the third step Can be adjusted.

The thickness of the λ / 2 layer is preferably 20 μm or more, more preferably 25 μm or more, further preferably 30 μm or more, preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less. Thereby, the mechanical strength of the λ / 2 layer can be increased.

The λ / 4 layer is a layer having an in-plane retardation of usually 90 nm or more and usually 154 nm or less at a measurement wavelength of 590 nm. When the λ / 4 layer has such an in-plane retardation, a broadband wavelength film can be realized by combining the λ / 2 layer and the λ / 4 layer. Among them, from the viewpoint of obtaining a circularly polarizing film excellent in the function of suppressing coloring in the tilt direction, the in-plane retardation of the λ / 4 layer at a measurement wavelength of 590 nm is preferably 100 nm or more, more preferably 110 nm or more, preferably 140 nm or less, more preferably 130 nm or less.

The retardation in the thickness direction of the λ / 4 layer at a measurement wavelength of 590 nm is preferably 50 nm or more, more preferably 60 nm or more, particularly preferably 70 nm or more, preferably 135 nm or less, more preferably 125 nm or less, particularly preferably 115 nm. It is as follows. When the retardation in the thickness direction of the λ / 4 layer is in the above range, it is possible to obtain a circularly polarizing film particularly excellent in the function of suppressing coloring in the tilt direction.

The NZ coefficient of the λ / 4 layer is preferably 1.0 or more, more preferably 1.05 or more, particularly preferably 1.10 or more, preferably 1.6 or less, more preferably 1.55 or less, particularly Preferably it is 1.5 or less. When the NZ coefficient of the λ / 4 layer is in the above range, it is possible to obtain a circularly polarizing film particularly excellent in the function of suppressing coloring in the tilt direction. In addition, the λ / 4 layer having such an NZ coefficient can be easily manufactured.

The optical properties such as retardation and NZ coefficient of the λ / 4 layer are, for example, the thickness of the layer (B) formed in the second step; and the stretching conditions such as the stretching temperature, the stretching ratio and the stretching direction in the third step Can be adjusted.

The orientation angle θ (λ / 4) of the λ / 4 layer is preferably in the range of 85 ° ± 20 ° (ie, in the range of 65 ° to 105 °), and in the range of 85 ° ± 15 ° (ie, 70 °). More preferably, it is in the range of 85 ° to 100 °, particularly preferably in the range of 85 ° ± 10 ° (that is, in the range of 75 ° to 95 °). When the orientation angle θ (λ / 4) of the λ / 4 layer is in the above range, it is combined with a general linearly polarizing film having a transmission axis in the width direction and an absorption axis in the longitudinal direction. A polarizing film can be easily realized. Moreover, when the orientation angle θ (λ / 4) of the λ / 4 layer is in the above range, the function of suppressing coloring in the front direction of the obtained circularly polarizing film can be improved.

The direction of the slow axis of the λ / 4 layer can be adjusted by, for example, the stretching direction in the third step.

The thickness of the 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 10 μm or less. When the thickness of the λ / 4 layer is not less than the lower limit of the above range, desired optical characteristics can be easily obtained. Moreover, when the thickness of the λ / 4 layer is not more than the upper limit of the above range, the thickness of the broadband wavelength film can be reduced.

The λ / 2 layer and the λ / 4 layer are preferably in direct contact with each other. Thereby, the thickness of the broadband wavelength film can be reduced.

When the method for producing a broadband wavelength film includes a fourth step of forming a thin film layer, the broadband wavelength film includes a thin film layer between the λ / 2 layer and the λ / 4 layer. The thin film layer of the broadband wavelength film obtained by the manufacturing method described above is thicker than the adhesive layer used in the conventional manufacturing method in which the λ / 2 layer and the λ / 4 layer are bonded together after manufacturing each of the λ / 2 layer and the λ / 4 layer. Can be thinner than that. The specific thickness of the thin film layer is preferably less than 2.0 μm, more preferably less than 1.8 μm, and particularly preferably less than 1.5 μm. Thus, since the thin film layer can be made thin, the thickness of the entire broadband wavelength film can be made thin. The lower limit of the thickness of the thin film layer is preferably as thin as possible, and may be, for example, 0.1 μm.

The broadband wavelength film may include an arbitrary layer in combination with the λ / 2 layer, the λ / 4 layer, and the thin film layer. For example, an adhesive layer or an adhesive layer for adhering the λ / 2 layer and the λ / 4 layer may be provided.

The total light transmittance of the broadband wavelength film is preferably 80% or more, more preferably 85% or more, and particularly preferably 88% or more. 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 broadband wavelength film is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%. Here, the haze can be measured at five locations using “turbidity meter NDH-300A” manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS K7361-1997, and the average value obtained therefrom can be adopted.

The thickness of the broadband wavelength film is preferably 20 μm or more, more preferably 25 μm or more, particularly preferably 30 μm or more, preferably 120 μm or less, more preferably 100 μm or less, and particularly preferably 90 μm or less. According to the manufacturing method described above, it is possible to easily manufacture such a thin broadband wavelength film.

[8. Circularly polarized film]
A long circularly polarizing film can be manufactured using the broadband wavelength film manufactured by the manufacturing method described above. Such a circularly polarizing film can be manufactured by a manufacturing method including a step of manufacturing a broadband wavelength film by the above-described manufacturing method and a step of bonding the broadband wavelength film and a long linear polarizing film. The pasting is usually performed so that the linearly polarizing film, the λ / 2 layer, and the λ / 4 layer are arranged in this order in the thickness direction. Moreover, you may use a contact bonding layer or an adhesion layer for bonding as needed.

The linearly polarizing film is a long film having an absorption axis, and has a function of absorbing linearly polarized light having a vibration direction parallel to the absorption axis and transmitting other polarized light. Here, the vibration direction of linearly polarized light means the vibration direction of the electric field of linearly polarized light.

The linearly polarizing film usually includes a polarizer layer, and a protective film layer for protecting the polarizer layer as necessary.
As the polarizer layer, for example, a film obtained by subjecting a suitable vinyl alcohol polymer film to appropriate treatment in an appropriate order and manner can be used. Examples of such vinyl alcohol polymers include polyvinyl alcohol and partially formalized polyvinyl alcohol. Examples of the film treatment include dyeing treatment with dichroic substances such as iodine and dichroic dyes, stretching treatment, and crosslinking treatment. Usually, in the stretching treatment for producing the polarizer layer, the film before stretching is stretched in the longitudinal direction, and therefore the obtained polarizer layer can exhibit an absorption axis parallel to the longitudinal direction of the polarizer layer. This polarizer layer is capable of absorbing linearly polarized light having a vibration direction parallel to the absorption axis, and is particularly preferably excellent in polarization degree. The thickness of the polarizer layer is generally 5 μm to 80 μm, but is not limited thereto.

As the protective film layer for protecting the polarizer layer, any transparent film can be used. Among these, a resin film excellent in transparency, mechanical strength, thermal stability, moisture shielding properties and the like is preferable. Examples of such resins include acetate resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, cyclic olefin resins, (meth) acrylic resins, and the like. Among them, acetate resin, cyclic olefin resin, and (meth) acrylic resin are preferable in terms of low birefringence, and cyclic olefin resin is particularly preferable from the viewpoint of transparency, low moisture absorption, dimensional stability, lightness, and the like.

The linearly polarizing film can be manufactured, for example, by laminating a long polarizer layer and a long protective film layer. In bonding, an adhesive may be used as necessary.

The linearly polarizing film preferably has an absorption axis in the longitudinal direction of the linearly polarizing film. Such a linearly polarizing film has a λ / 2 layer having an orientation angle θ (λ / 2) of 20 ° ± 10 ° (ie, 10 ° to 30 °) and 85 ° ± 20 ° (ie, 65 °). It is preferable to produce a circularly polarizing film by laminating with a broadband wavelength film including a λ / 4 layer having an orientation angle θ (λ / 4) of ˜105 °. According to the above combination of bonding, it is possible to produce a circularly polarizing film by bonding a long linear polarizing film and a long broadband wavelength film with their longitudinal directions parallel to each other. Therefore, it becomes possible to manufacture a circularly polarizing film by a roll-to-roll method. Therefore, it is possible to increase the manufacturing efficiency of the circularly polarizing film.

In the circularly polarizing film thus obtained, linearly polarized light in a wide wavelength range transmitted through the linearly polarizing film is converted into circularly polarized light by the broadband wavelength film. Therefore, the circularly polarizing film has a function of absorbing one of right circularly polarized light and left circularly polarized light and transmitting the remaining light in a wide wavelength range.

The circularly polarizing film may further include an arbitrary layer in combination with the linearly polarizing film and the broadband wavelength film.
For example, the circularly polarizing film may include a protective film layer for suppressing damage. In addition, for example, the circularly polarizing film may include an adhesive layer or an adhesive layer for adhesion between the linearly polarizing film and the broadband wavelength film.

When the circularly polarizing film is provided on a surface that can reflect light, reflection of external light can be effectively reduced. In particular, the circularly polarizing film is useful in that reflection of external light can be effectively reduced in a wide wavelength range in the visible region. And since reflection of external light can be effectively reduced in such a wide wavelength range, the circularly polarizing film can suppress coloring due to an increase in the reflection intensity of light of some wavelengths. This circularly polarizing film can obtain the above-described effects of reflection suppression and coloration suppression at least in the front direction, and more usually in the tilt direction. In addition, the effects of reflection suppression and coloring suppression in the tilt direction can usually be obtained in all azimuth directions of the film main surface.

[9. Image display device]
By utilizing the function of suppressing reflection of external light as described above, the circularly polarizing film can be used as a reflection suppressing film of an organic electroluminescence display device (hereinafter sometimes referred to as “organic EL display device” as appropriate). .

The organic EL display device includes a circularly polarizing film piece obtained by cutting out from a long circularly polarizing film.
When the organic EL display device includes a circularly polarizing film piece, the organic EL display device usually includes a circularly polarizing film piece on the display surface. By providing the circularly polarizing film piece on the display surface of the organic EL display device so that the surface on the linearly polarizing film side faces the viewing side, the light incident from the outside of the device is reflected inside the device and emitted to the outside of the device. As a result, glare of the display surface of the display device can be suppressed. Specifically, only a part of the linearly polarized light passes through the linearly polarizing film and then passes through the broadband wavelength film, and becomes circularly polarized light. Circularly polarized light is reflected by a component that reflects light in the display device (reflecting electrode, etc.) and passes through the broadband wavelength film again to vibrate in the direction perpendicular to the vibration direction (polarization axis) of the incident linearly polarized light. It becomes linearly polarized light having a direction (polarization axis) and does not pass through the linearly polarizing film. Thereby, a reflection suppression function is achieved. Further, since the reflection suppressing function is obtained in a wide wavelength range, coloring of the display surface can be suppressed.

Further, the circularly polarizing film may be provided in a liquid crystal display device. Such a liquid crystal display device includes a circularly polarizing film piece obtained by cutting out from a long circularly polarizing film.
When the liquid crystal display device includes a circularly polarizing film piece so that the surface on the linearly polarizing film side faces the viewing side, it is possible to prevent light incident from the outside of the device from being reflected inside the device and emitted to the outside of the device. As a result, glare and coloring of the display surface of the display device can be suppressed.
In addition, when the liquid crystal display device includes a circularly polarizing film piece, a broadband wavelength film, a linearly polarizing film, and a liquid crystal cell of the liquid crystal display device arranged in this order from the viewing side, an image can be displayed in a circularly polarized light. . Therefore, it is possible to stably view the light emitted from the display surface with the polarized sunglasses, and the image visibility when wearing the polarized sunglasses can be enhanced.

In particular, when a circularly polarizing film piece is provided in an image display device such as an organic EL display device and a liquid crystal display device so that the surface on the linearly polarizing film side faces the viewing side, warping of the display panel can be suppressed. . Hereinafter, this effect will be described.

Generally, an image display device includes a display panel including a display element such as an organic electroluminescence element and a liquid crystal cell. This display panel includes a base material such as a glass base material in order to increase the mechanical strength of the display panel. And in the display panel in which the circularly-polarizing film piece was provided so that the surface at the side of the linearly polarizing film was directed to the viewing side, the substrate, the broadband wavelength film and the linearly polarizing film were usually provided in this order.

By the way, the polarizer layer of a linearly polarizing film generally tends to shrink in the in-plane direction in a high temperature environment. When the polarizer layer tends to shrink in this way, a stress that tends to warp the display panel is generated in the display panel provided with the linearly polarizing film including the polarizer layer. Since warping of the display panel can cause deterioration in image quality, it is desirable to suppress it. With regard to this warp, it has been found that the warp tends to increase as the distance between the polarizer layer and the substrate of the display panel increases.

The broadband wavelength film manufactured by the conventional manufacturing method in which both the λ / 2 layer and the λ / 4 layer are bonded after manufacturing each of the λ / 2 layer and the λ / 4 layer had a thick adhesive layer, so the entire broadband wavelength film was also thick. Therefore, the conventional broadband wavelength film has a tendency that the warpage of the display panel is increased because the distance between the polarizer layer and the base material of the display panel is increased.
In contrast, a broadband wavelength film manufactured as a co-stretched film as described above has a λ / 2 layer and a λ / 4 layer in direct contact with each other, or is provided between a λ / 2 layer and a λ / 4 layer. The thin film layer can be made thin. Therefore, since the whole broadband wavelength film can be thinned, the distance between the polarizer layer and the substrate of the display panel can be reduced. Therefore, it is possible to suppress warping of the display panel.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

In the following description, “%” and “part” representing the amount are based on weight unless otherwise specified. In addition, the operations described below were performed under normal temperature and normal pressure conditions unless otherwise specified.

[Evaluation methods]
[Measurement method of optical properties of layer (A)]
The in-plane retardation Re, the NZ coefficient, and the orientation angle of the stretched film as the layer (A) obtained in the first step were measured using a phase difference meter (“AxoScan” manufactured by Axometrics). The measurement wavelength was 590 nm.

[Measurement method of optical characteristics of each layer of broadband wavelength film]
The broadband wavelength film to be evaluated was placed on the stage of a phase difference meter (“AxoScan” manufactured by Axometrics). And the change of the polarization state of the polarized light which permeate | transmits a broadband wavelength film before and behind permeate | transmitting the said broadband wavelength film was measured as a transmission polarization characteristic of a broadband wavelength film. This measurement was performed as a multidirectional measurement performed in a polar angle range of −55 ° to + 55 ° with respect to the main surface of the broadband wavelength film. The multidirectional measurement was performed in each azimuth direction of 45 °, 90 °, 135 °, and 180 °, where the azimuth direction with the main surface of the broadband wavelength film was 0 °. The measurement wavelength of the above measurement was 590 nm.

Next, the in-plane retardation Re, the thickness direction retardation Rth, the NZ coefficient and the orientation angle of each layer were determined 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 broadband wavelength film as fitting parameters. For the fitting calculation, the attached software (“Multi-Layer Analysis” manufactured by Axometrics) of the phase difference meter (AxoScan) was used.

[Calculation method of color difference ΔE * ab by simulation]
Using the “LCD Master” manufactured by Shintech Co., Ltd. as a simulation software, the circularly polarizing films manufactured in each of the examples and the comparative examples were modeled, and the color difference ΔE * ab was calculated with the following settings.
In the simulation model, a structure in which a circularly polarizing film was attached to the reflecting surface of the aluminum mirror having a planar reflecting surface so that the λ / 4 layer side of the broadband wavelength film was in contact with the mirror was set. Therefore, in this model, a structure in which a linearly polarizing film, a λ / 2 layer, a λ / 4 layer, and a mirror were provided in this order in the thickness direction was set.
And in the said model, color difference (DELTA) E * ab when light was irradiated to a circularly-polarizing film from D65 light source was calculated in the front direction of the said circularly-polarizing film. In the calculation of the color difference ΔE * ab, the reflected light in the direction of the polar angle 0 ° and the azimuth angle 0 ° of the aluminum mirror not attached with the circularly polarizing film was used as a reference. In the simulation, the surface reflection component actually generated on the surface of the circularly polarizing film is excluded from the calculation of the color difference ΔE * ab. The value of the color difference ΔE * ab means that the smaller the value, the smaller the color change, which is preferable.

[Visual evaluation of circularly polarizing film]
The polarizing plate included in the image display device (Apple “AppleWatch” (registered trademark)) is peeled off, and the display surface of the image display device and the surface of the λ / 4 layer of the circular polarizing film to be evaluated are bonded to the adhesive layer ( The films were bonded together through “CS9621” manufactured by Nitto Denko Corporation. Set the display surface to the black display state (a state where black is displayed on the entire screen), and observe the display surface from all directions of polar angle θ = 0 ° (front direction) and polar angle θ = 60 ° (tilt direction). did. The smaller the luminance and coloring due to reflection of external light, the better the result. The observation results were evaluated according to the following criteria.
“A”: There is no visible level of luminance and coloring.
“B”: Luminance and coloring occur at a visually recognizable level. “C”: Luminance and coloring occur severely.

[Example 1]
(First step: production of layer (A))
A pellet-shaped norbornene resin (manufactured by Nippon Zeon Co., Ltd .; glass transition temperature 126 ° C.) was prepared as a resin having positive intrinsic birefringence and 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 from a T-die onto a casting drum. The extruded resin was cooled to obtain a long unstretched film having a thickness of 110 μm. The obtained film before stretching was wound up on a roll and collected.

The film before stretching was pulled out from the roll and continuously supplied to a roll stretching machine. And by this roll extending machine, the film before extending | stretching was free-uniaxially stretched and the elongate stretched film as a layer (A) was obtained. In this stretching, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the film before stretching was 0 °, the stretching temperature was 132 ° C., and the stretching ratio was 1.9 times. Moreover, the orientation angle of the obtained stretched film was 0 °, the in-plane retardation Re was 350 nm, and the thickness was 80 μm. The obtained stretched film was wound up on a roll and collected.

(Second step: Formation of layer (B))
A liquid composition containing a norbornene resin (manufactured by Nippon Zeon Co., Ltd .; glass transition temperature 135 ° C.) as a resin having positive intrinsic birefringence was prepared. This liquid composition contained cyclohexanone as a solvent, and the concentration of norbornene resin in the liquid composition was 15.0% by weight.

The stretched film was pulled out from the roll, and the liquid composition was applied onto the stretched film. Thereafter, the coated liquid composition was dried to form a norbornene-based resin layer (thickness 10 μm) as a layer (B) on the stretched film. This obtained the multilayer film provided with a layer (A) and a layer (B). The obtained multilayer film was wound up on a roll and collected.

(Third step: stretching a multilayer film)
The multilayer film was pulled out from the roll and continuously supplied to the tenter stretching machine. And it extended | stretched to the multilayer film with this tenter extending | stretching machine. In this stretching, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was 75 °, the stretching temperature was 140 ° C., and the stretching ratio was 2.0 times. Thereby, a broadband wavelength film was obtained as a co-stretched film comprising a λ / 2 layer obtained by stretching the layer (A) and a λ / 4 layer obtained by stretching the layer (B). The obtained broadband wavelength film was evaluated by the method described above.

(Manufacture of circularly polarized films)
A long linear polarizing film having an absorption axis in the longitudinal direction was prepared. The linearly polarizing film and the broadband wavelength film were bonded with their longitudinal directions parallel to each other. This bonding was performed using an adhesive (“CS-9621” manufactured by Nitto Denko Corporation). This obtained the circularly-polarizing film provided with a linearly-polarizing film, (lambda) / 2 layer, and (lambda) / 4 layer in this order. The obtained circularly polarizing film was evaluated by the method described above.

[Example 2]
In the third step, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 80 °.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[Example 3]
In the third step, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 85 °.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[Example 4]
A liquid composition containing a polycarbonate resin (manufactured by Mitsubishi Gas Chemical Company; glass transition temperature of 137 ° C.) as a resin having a positive intrinsic birefringence was prepared. This liquid composition contained cyclopentanone as a solvent, and the concentration of the polycarbonate resin in the liquid composition was 15% by weight. In the second step, the liquid composition containing the polycarbonate resin was used instead of the liquid composition containing the norbornene resin used in Example 1.
In the third step, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 85 °.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[Example 5]
In the first step, a tenter stretching machine was used instead of the roll stretching machine as a stretching apparatus for stretching the film before stretching. Stretching using a tenter stretching machine was not free uniaxial stretching but stretching with a binding force in addition to the stretching direction. Further, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the pre-stretching film was changed to 10 °. Furthermore, the draw ratio of the pre-stretch film was changed to 1.4 times.
In the second step, the liquid composition containing the polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing the norbornene resin used in Example 1.
In the third step, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 90 °.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[Comparative Example 1]
In the second step, the liquid composition containing the polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing the norbornene resin used in Example 1.
In the third step, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 90 °.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[Comparative Example 2]
In the second step, the liquid composition containing the polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing the norbornene resin used in Example 1.
In the third step, a roll stretching machine was used in place of the tenter stretching machine as a stretching apparatus for stretching the multilayer film. Further, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 0 °. Furthermore, the draw ratio of the multilayer film was changed to 1.5 times.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[Comparative Example 3]
In the first step, the stretching temperature of the film before stretching was changed to 138 °.
In the second step, the liquid composition containing the polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing the norbornene resin used in Example 1.
In the third step, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 60 °. Furthermore, the draw ratio of the multilayer film was changed to 1.5 times.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[Comparative Example 4]
In the first step, the stretching temperature of the film before stretching was changed to 138 °.
In the second step, the liquid composition containing the polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing the norbornene resin used in Example 1.
In the third step, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 30 °. Furthermore, the draw ratio of the multilayer film was changed to 1.5 times.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[Comparative Example 5]
In the first step, a tenter stretching machine was used instead of the roll stretching machine as a stretching apparatus for stretching the film before stretching. Further, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the pre-stretching film was changed to 10 °. Furthermore, the draw ratio of the pre-stretch film was changed to 1.4 times.
In the second step, the liquid composition containing the polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing the norbornene resin used in Example 1.
In the third step, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 60 °. Furthermore, the draw ratio of the multilayer film was changed to 1.5 times.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[Comparative Example 6]
In the first step, a tenter stretching machine was used instead of the roll stretching machine as a stretching apparatus for stretching the film before stretching. Further, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the pre-stretching film was changed to 10 °. Furthermore, the draw ratio of the pre-stretch film was changed to 1.4 times.
In the second step, the liquid composition containing the polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing the norbornene resin used in Example 1.
In the third step, a roll stretching machine was used in place of the tenter stretching machine as a stretching apparatus for stretching the multilayer film. Further, the stretching angle formed by the stretching direction with respect to the longitudinal direction of the multilayer film was changed to 0 °. Furthermore, the draw ratio of the multilayer film was changed to 1.5 times.
Except for the above, the same operations as in Example 1 were performed to produce and evaluate a broadband wavelength film and a circularly polarizing film.

[result]
The results of Examples and Comparative Examples are shown in Table 1 and Table 2 below. In the following table, the meanings of the abbreviations are as follows.
COP: Norbornene resin.
PC: Polycarbonate resin.
Re: In-plane retardation.
Rth: retardation in the thickness direction.
Orientation angle: An angle formed by a slow axis with respect to the longitudinal direction.
Total thickness: The total thickness of the λ / 2 layer and the λ / 4 layer.
Oblique: Diagonal direction.
Vertical: Longitudinal direction.

100 layers (A)
200 Multilayer film 210 layers (B)
300 Broadband wavelength film

Claims (10)

1. A first step of preparing a layer (A) as a resin film having a slow axis in the plane;
   A second step of obtaining a multilayer film by forming a layer (B) of a resin having a positive intrinsic birefringence on the layer (A);
   The multilayer film is stretched in a direction that is neither perpendicular nor parallel to the slow axis of the layer (A) to obtain a long broadband wavelength film having a λ / 2 layer and a λ / 4 layer. Including three steps in this order,
   A method for producing a broadband wavelength film, wherein the λ / 2 layer and the λ / 4 layer of the broadband wavelength film satisfy the following formula (1):
   θ (λ / 4) = {45 ° + 2 × θ (λ / 2)} ± 5 ° (1)
   (In the above formula (1),
   θ (λ / 2) represents the angle formed by the slow axis of the λ / 2 layer with respect to the longitudinal direction of the broadband wavelength film,
   θ (λ / 4) represents an angle formed by the slow axis of the λ / 4 layer with respect to the longitudinal direction of the broadband wavelength film. )
2. The broadband wavelength film according to claim 1, wherein the layer (A) prepared in the first step is a long resin film having a slow axis that is not perpendicular to the longitudinal direction of the layer (A). Manufacturing method.
3. The production of a broadband wavelength film according to claim 1 or 2, wherein the third step includes stretching the multilayer film in a direction that forms an angle of 45 ° or more with respect to the longitudinal direction of the multilayer film. Method.
4. The method for producing a broadband wavelength film according to any one of claims 1 to 3, wherein the angle θ (λ / 2) is in a range of 20 ° ± 10 °.
5. The method for producing a broadband wavelength film according to any one of claims 1 to 4, wherein the angle θ (λ / 4) is in a range of 85 ° ± 20 °.
6. 6. The method for producing a broadband wavelength film according to claim 1, wherein the λ / 2 layer is a layer obtained by stretching the layer (A).
7. The method for producing a broadband wavelength film according to any one of claims 1 to 6, wherein the λ / 4 layer is a layer obtained by stretching the layer (B).
8. A step of producing a broadband wavelength film by the production method according to any one of claims 1 to 7;
   A method for producing a circularly polarizing film, comprising: bonding the broadband wavelength film and a long linearly polarizing film.
9. The method for producing a circularly polarizing film according to claim 8, wherein the linearly polarizing film has an absorption axis in the longitudinal direction of the linearly polarizing film.
10. A long broadband wavelength film,
    A λ / 2 layer having a slow axis that forms an angle of 20 ° ± 10 ° with the longitudinal direction of the broadband wavelength film;
    A long broadband wavelength film, which is a co-stretched film comprising a λ / 4 layer having a slow axis that forms an angle of 85 ° ± 20 ° with respect to the longitudinal direction of the broadband wavelength film.

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