TW201945774A - 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 [lambda]/2 layer and a [lambda]/4 layer by stretching the multilayer film in a direction that is neither orthogonal nor parallel to the slow axis of layer (A). The [lambda]/2 layer and the [lambda]/4 layer of the broadband wavelength film satisfy formula (1). (1) [Theta]([lambda]/4)={45 DEG + 2*[Theta]([lambda]/2)} ± 5 DEG. ([Theta]([lambda]/2) is the angle formed by the slow axis of the [lambda]/2 layer relative to the longitudinal direction of the broadband wavelength film, and [Theta]([lambda]/4) is the angle formed by the slow axis of the [lambda]/4 layer relative to the longitudinal direction of the broadband wavelength film.).

Description

Broad-band wavelength film and manufacturing method thereof, and manufacturing method of circularly polarizing film

The present invention relates to a wide-band wavelength film, a method for manufacturing the same, and a method for manufacturing a circularly polarizing film.

Various methods for manufacturing an optical film having two or more layers have been studied in the past (see Patent Documents 1 to 3).

『Patent Literature』
"Patent Document 1": International Patent Publication No. 2016/047465 "Patent Document 2": International Patent Publication No. 2009/031433 "Patent Document 3": Japanese Patent Publication No. 2009-237534

As a wide-band wavelength film capable of functioning as a wavelength plate in a wide wavelength band, a film including a λ / 2 plate and a λ / 4 plate in combination is known. In the past, such a wide-band wavelength film generally includes a process of extending a film to obtain a λ / 2 plate, a process of extending another film to obtain a λ / 2 plate, and the λ / 2 plate and λ / 4. It is manufactured by a manufacturing method of a process of laminating plates to obtain a broadband film.

In addition, a technology of obtaining a circularly polarizing film by combining "the aforementioned wide-band wavelength film" with "a linearly polarizing film serving as a film functioning as a linearly polarizing plate" is known. The long linear polarizing film generally has an absorption axis in the longitudinal direction or width direction. According to this, in the case of obtaining a circularly polarizing film by combining a wide-band wavelength film with a long linear polarizing film, the slow axis of the λ / 2 plate is required to be in an oblique direction that is neither parallel nor perpendicular to its long side direction. .

In order to easily manufacture a desired λ / 2 plate having a slow axis in an oblique direction as described above, the applicant has developed a technique of performing extension twice or more as described in Patent Document 1. If so, in the entire manufacturing method of the broadband wavelength film, it is necessary to perform one or more extensions to obtain a λ / 2 plate and two or more extensions to obtain a λ / 2 plate, so the total number of extensions becomes 3 times or more. However, if the number of extensions is 3 or more, the operation is complicated.

The present invention was created in view of the foregoing problems, and an object thereof is to provide a broadband light-emitting film capable of being efficiently manufactured with a small number of processes, a method for manufacturing the same, and a method for manufacturing a circularly polarizing film including the manufacturing method for the broadband film.

The present inventors have made intensive studies in order to solve the aforementioned problems. As a result, the present inventors found that according to the sequence, a first step is to prepare a layered body (A) as a resin film having a slow axis in the plane; a second step is to form an intrinsic birefringence on the layered body (A) as follows: The positive resin layer (B) obtains a multilayer film; the third step is to extend the multilayer film in a direction that is neither perpendicular nor parallel to the slow axis of the layer (A) to obtain a layer with λ / 2 and λ / 4 layer of strip-shaped wide-band wavelength film; the manufacturing method can efficiently produce a wide-band wavelength film with a small number of steps, and complete the present invention.

That is, the present invention includes the following.

[1] A method for manufacturing a wide-band wavelength thin film, which sequentially includes:
The first step is to prepare a layer (A) as a resin film having a slow axis in the plane;
In the second step, a layer (B) of a resin having a positive birefringence is formed on the aforementioned layer (A) to obtain a multilayer film; and in the third step, the aforementioned multilayer film is slower than the layer (A). The axis is neither perpendicular nor parallel extending, and a long-band wide-band wavelength film having λ / 2 layers and λ / 4 layers is obtained; wherein the aforementioned λ / 2 layer and the aforementioned λ / 4 layer of the aforementioned broadband film The following formula (1) is satisfied. θ (λ / 2) = [45 ° + 2 × θ (λ / 2)] ± 5 ° (1) (In the foregoing formula (1), θ (λ / 2) represents the relative slow axis of the aforementioned λ / 2 layer (Θ (λ / 4) represents the angle between the slow axis of the aforementioned λ / 4 layer and the longitudinal direction of the aforementioned broadband film.)

[2] The method for manufacturing a wide-band wavelength thin film according to [1], wherein the layered body (A) prepared in the first step includes a layer which is not perpendicular to a longitudinal direction of the layered body (A). Slow axis long resin film.

[3] The method for manufacturing a wide-band wavelength film according to [1] or [2], wherein the third step includes: sandwiching the multilayer film by an angle of 45 ° or more with respect to a long side direction of the multilayer film Extending direction.

[4] The method for manufacturing a wide-band 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 manufacturing a wide-band 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 wide-band wavelength thin film according to any one of [1] to [5], wherein the λ / 2 layer is a layer body obtained by extending the layer body (A).

[7] The method for producing a wide-band wavelength film according to any one of [1] to [6], wherein the λ / 4 layer is a layer body obtained by extending the layer body (B).

[8] A method for manufacturing a circularly polarizing film, comprising:
A step of manufacturing a wide-band wavelength film by the manufacturing method described in any one of [1] to [7], and a step of bonding the wide-band wavelength film and a long linear polarizing film.

[9] The method for producing a circularly polarizing film according to [8], wherein the linearly polarizing film has an absorption axis in a longitudinal direction of the linearly polarizing film.

[10] A strip-shaped wide-band wavelength film, which is a co-extended film, the co-extended film having:
The λ / 2 layer has a slow axis with an angle of 20 ° ± 10 ° with respect to the long-side direction of the aforementioned wideband wavelength film, and the λ / 2 layer has a 85 ° with the long-side direction relative to the aforementioned wideband wavelength film Slow axis at an angle of ± 20 °.

According to the present invention, it is possible to provide a wideband wavelength film which can be efficiently manufactured with a small number of processes, a method for manufacturing the same, and a method for manufacturing a circularly polarizing film including the aforementioned method for manufacturing a wideband film.

The embodiments and examples are disclosed below to explain the present invention in detail. However, the present invention is not limited to the implementation modes and examples disclosed below, and can be implemented with arbitrary changes without departing from the scope of the patent application of the present invention and its equivalent scope.

In the following description, the so-called "long strip" film refers to a film having a length of 5 times or more with respect to the width, and preferably a length of 10 times or more. Specifically, it refers to having a rollable film. Films to the extent of roll storage or handling. The upper limit of the length of the film is not particularly limited, and may be determined to be, for example, 100,000 times or less with respect to the width.

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

In the following description, unless otherwise noted, the orientation angle of a film or layer refers to the angle between the slow axis of the film or layer with respect to the long side direction of the film or layer.

In the following description, the angle between the optical axis (slow axis, transmission axis, absorption axis, etc.) of each layer in a component having multiple layers, unless otherwise noted, means that the aforementioned layer is viewed from the thickness direction Body angle.

In the following description, the direction of the optical axis (slow axis, transmission axis, absorption axis, etc.) and the geometric direction (long-side direction of the film) of a product (broadband wavelength film, circularly polarizing film, etc.) And width direction, etc.), unless otherwise noted, the offset in one direction is set to positive, and the offset in other directions is set to negative. The positive and negative directions are in the constituent elements of the product. Developed into the same. For example, in a broadband film, the angle between the slow axis of the λ / 2 layer and the long-side direction of the broadband film is 20 °, and the slow axis of the λ / 2 layer is relative to the wide band. The angle between the long-side direction of the wavelength film is 85 ° ", which indicates the following two cases:
・ If viewed from one side of the wideband wavelength film, the slow axis of the λ / 2 layer is clockwise shifted by 20 ° from the long side direction of the wideband wavelength film, and the slow axis of the λ / 2 layer is from the wide band The wavelength of the wavelength film is shifted clockwise by 85 ° from the long side.
・ If viewed from one side of the wideband wavelength film, the slow axis of the λ / 2 layer is offset by 20 ° along the counterclockwise from the long side direction of the wideband wavelength film, and the slow axis of the λ / 2 layer is from the wide band The long-term direction of the wavelength film is offset from the counterclockwise by 85 °.

In the following description, unless otherwise noted, the oblique direction of a long thin film means the in-plane direction of the film and is neither parallel nor perpendicular to the long-side direction of the film.

In the following description, unless otherwise noted, the frontal direction of a film means the normal direction of the main surface of the film, which specifically refers to the direction of the polar angle of the main surface of 0 ° and the azimuth of 0 °.

In the following description, unless otherwise noted, the oblique direction of a film means a direction that is neither parallel nor perpendicular to the main surface of the film, and specifically means that the polar angle of the aforementioned main surface is greater than 0 ° and less than Direction in the 90 ° range.

In the following description, a material with a positive intrinsic birefringence means a material whose refractive index in the extending direction becomes larger than that in a direction perpendicular to the material unless otherwise noted. In addition, a material having a negative intrinsic birefringence means a material whose refractive index in the direction of extension becomes smaller than that in a direction perpendicular to the material unless otherwise noted. The value of intrinsic birefringence can be calculated from the dielectric constant distribution.

In the following description, "(meth) acrylic acid" includes "acrylic acid", "methacrylic acid", and combinations thereof.

In the following description, the in-plane retardation Re of the layer is a value shown by Re = (nx-ny) × d unless otherwise noted. In addition, the retardation Rth in the thickness direction of the layer is a value shown by Rth = 所示 [(nx + ny) / 2] −nz｝ × d unless otherwise noted. In addition, the NZ coefficient of the layer is a value shown by (nx-nz) / (nx-ny) unless otherwise noted. Here, nx represents a refractive index which is a direction (in-plane direction) perpendicular to the thickness direction of the layer body and which gives the maximum refractive index. ny represents the refractive index of the layer in the aforementioned in-plane direction and a direction orthogonal to the direction of nx. nz indicates the refractive index in the thickness direction of the layer body. d represents the thickness of the layer. Measurement wavelength, unless otherwise noted, is 590 nm.

In the following description, the directions of the components are "parallel", "vertical" and "orthogonal". Unless otherwise noted, within the range not impairing the effect of the present invention, for example, ± 3 °, ± 2 Errors in ° or ± 1 °.

[1. Overview]

FIG. 1 is a schematic perspective view showing a layered body (A) 100 as a resin film prepared in a first step of a method for manufacturing a wideband wavelength film according to an embodiment of the present invention. In addition, FIG. 2 is a schematic perspective view of a multilayer film 200 obtained in a second step of a method for manufacturing a wideband wavelength film according to an embodiment of the present invention. In addition, FIG. 3 is a schematic perspective view of the wideband wavelength film 300 obtained in the third step of the method for manufacturing a wideband wavelength film according to an embodiment of the present invention.

The manufacturing method of the broadband wavelength film 300 related to one embodiment of the present invention includes:
(1) As shown in FIG. 1, a first step of preparing a layered body (A) 100 as a resin film having a slow axis A ₁₀₀ in a plane;
(2) forming a layer (B) 210 of a resin with inherently positive birefringence on the layer (A) 100 to obtain a second step of the multilayer film 200 shown in FIG. 2; and (3) extending the multilayer film 200, The third step of obtaining the strip-shaped wideband wavelength film 300 shown in FIG. 3.

As shown in FIG. 1, the layered body (A) 100 prepared in the first step has a slow axis A _{100 in} its surface. In the second step, a layered body (B) 210 is formed on the layered body (A) 100 to obtain a multilayer film 200 including the layered body (A) 100 and the layered body (B) 210 as shown in FIG. The film 200 is stretched in the third step. This extension is in a plane that is neither perpendicular nor parallel along the slow axis A ₁₀₀ with respect to the layer body (A) in such a way that a λ / 2 layer and a λ / 4 layer with a slow axis in the desired direction can be obtained. Direction.

By the extension in the third step, co-extension can be performed in which the layer body (A) 100 and the layer body (B) 210 are simultaneously extended. Therefore, as shown in FIG. 3, in the layer body (A) 100, adjustment of the direction of the slow axis A ₁₀₀ and adjustment of the optical characteristics can be performed. On the other hand, a slow axis A ₂₁₀ appears in the layer body (B) ₂₁₀ and optical characteristics appear. The extended layer (A) 100 functions as one of the λ / 2 layer and the λ / 4 layer, and the extended layer (B) 210 functions as the other of the λ / 2 layer and the λ / 4 layer. Functions. According to this, by the aforementioned manufacturing method, a wide-band wavelength film 300 having a λ / 2 layer and a λ / 4 layer can be obtained. In FIG. 3, although an example in which the extended layer body (A) 100 functions as a λ / 2 layer and the extended layer body (B) 210 functions as a λ / 2 layer is shown, a wide-band wavelength film The structure of 300 is not limited to this example.

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) indicates that θ (λ / 4) is in a range of "[45 ° + 2 × θ (λ / 2)]-5 °" and "[45 ° + 2 × θ (λ / 2)｝ + 5 °" . In Equation (1), θ (λ / 2) represents the angle between the slow axis A ₁₀₀ of the λ / 2 layer with respect to the long-side direction A _{300 of} the wide-band wavelength film 300. In addition, θ (λ / 4) represents an angle between the slow axis A ₂₁₀ of the λ / 4 layer and the long-side direction A _{300 of} the wide-band wavelength film 300. By including a combination of a λ / 2 layer and a λ / 4 layer satisfying this formula (1), the wideband wavelength film 300 can function as a wideband wavelength film, which can be used in a wide range of wavelengths. The in-plane retardation of approximately 1/4 wavelength of the wavelength of the light given to the light penetrating the film.

Generally, the long-side direction A _{300 of the} broadband wavelength film 300 and the long-side direction (not shown) of the λ / 2 layer and the long-side direction (not shown) of the λ / 2 layer are the same. According to this, the angle θ (λ / 2) represents the orientation angle between the slow axis of the λ / 2 layer and the long side direction A ₁₀₀ of the λ / 2 layer. Therefore, it is sometimes referred to as "orientation angle θ (λ /2)". In addition, the angle θ (λ / 4) represents the orientation angle between the slow axis A ₂₁₀ of the λ / 4 layer and the long side direction of the λ / 4 layer. 4) ".

[2. First step]

In the first step, a layered body (A) is prepared as a resin film having a slow axis in a plane. From the viewpoint of obtaining a long wide-band wavelength film, as the layer body (A), a long resin film is usually used. 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 an arbitrary component may be used as required. In particular, as the resin contained in the layer body (A), a resin having a negative intrinsic birefringence can also be used. However, it is preferable to use a resin having a positive intrinsic birefringence in order to easily manufacture a wide-band wavelength film.

Resins with a positive intrinsic birefringence typically include polymers with a positive intrinsic birefringence. Examples of polymers with positive intrinsic birefringence include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyphenylene sulfide and the like Polyarylene sulfide; Polyvinyl alcohol; Polycarbonate; Polyarylate; Cellulose ester polymer; Polyether fluorene; Polyfluorene; Polyarylene fluorene; Polyvinyl chloride; Cycloolefin polymers such as norbornene polymers; Rods Liquid crystal polymer and so on. 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 in terms of delayed visibility and elongation at low temperature. In addition, a cycloolefin polymer is preferred in terms of excellent mechanical properties, heat resistance, transparency, low hygroscopicity, dimensional stability, and light weight.

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

The resin contained in the layered body (A) may further include any component other than the aforementioned polymer combined with the polymer. Examples of the optional component include colorants such as pigments and dyes; plasticizers; fluorescent whitening agents; dispersants; thermal stabilizers; light stabilizers; ultraviolet absorbers; antistatic agents; antioxidants; fine particles; interfaces Active agent etc. 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 layered body (A) is preferably 100 ° C or higher, more preferably 110 ° C or higher, particularly preferably 120 ° C or higher, and preferably 190 ° C or lower, and 180 ° C or lower. Preferably, 170 ° C or lower is particularly preferred. When the glass transition temperature of the resin contained in the layered body (A) is above the lower limit of the aforementioned range, the layered body (λ / 2 layer or λ / 4 layer) obtained by extending the layered body (A) can be increased. ) Durability in high temperature environments. When the glass transition temperature of the resin contained in the layered body (A) is equal to or lower than the upper limit of the aforementioned range, the stretching treatment can be easily performed.

The direction of the slow axis of the layered body (A) prepared in the first step must be arbitrarily set within a range in which a desired wide-band wavelength film can be obtained. For example, in the case where the intrinsic birefringence of the resin contained in the layer (A) is positive, the slow axis of the layer (A) is usually extended toward this layer due to the extension of the multilayer film in the third step. The manner in which the extension direction of the film approaches is changed. And, for example, when the inherent birefringence of the resin contained in the layer (A) is negative, the slow axis of the layer (A) is usually caused by the extension of the multilayer film in the third step, The approaching direction perpendicular to the extending direction of the multilayer film changes. Accordingly, the direction of the slow axis of the layered body (A) prepared in the first step must be set in accordance with the direction in which the multilayer film is extended in the third step.

It is preferable that the slow axis of the layer body (A) prepared in the first step is not perpendicular to the long side direction of the layer body (A), so as to be parallel to or close to the long side direction of the layer body (A). Is better. According to this, the orientation angle of the slow axis of the layer (A) relative to the long side direction of the layer (A) is preferably greater than -87 °, more preferably -45 ° or more, and more than -30 ° More preferably, it is more preferably -15 ° or more, and preferably less than 87 °, more preferably 45 ° or less, more preferably 30 ° or less, and even more preferably 15 ° or less. When a layered body (A) having such a slow axis is used, a wide-band wavelength film having excellent optical characteristics can be easily obtained.

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

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

The thickness of the layered body (A) prepared in the first step is arbitrarily set within a range in which a desired wide-band wavelength film can be obtained. The specific thickness of the layer body (A) is preferably 20 μm or more, more preferably 25 μm or more, more preferably 30 μm or more, and more preferably 100 μm or less, more preferably 95 μm or less, and 90 It is particularly preferred to be less than μm. In the case where the thickness of the layer body (A) is in the foregoing range, a λ / 2 layer or a λ / 4 layer having desired optical characteristics can be easily obtained by extension in the third step.

The layered body (A) can be obtained by a production method "including the stretching of a suitable resin film so that the resin film exhibits a slow axis." In the following description, the resin film before being stretched may be referred to as a "pre-stretch film", and the resin film obtained after stretching may be referred to as a "stretch film".

The stretched film can be produced by, for example, a melt forming method or a solution casting method. More specific examples of the melt molding method include an extrusion molding method, a pressure molding method, an inflation molding method, an injection molding method, a blow molding method, and an extension molding method. Among these methods, in order to obtain a layered body (A) having excellent mechanical strength and surface accuracy, an extrusion molding method, an inflation molding method, or a press molding method is preferable, among which the layered body (A) can be easily and efficiently manufactured. From the viewpoint of), the extrusion method is particularly preferable. In addition, it is preferable to stretch the pre-film to obtain a strip-shaped film.

After the pre-stretched film is prepared, the pre-stretched film is stretched to obtain a layer body (A) as the stretched film.

The slow axis of the layer (A) is usually revealed by stretching the film before stretching. Accordingly, it is preferable to set the stretching direction of the film before stretching to the direction corresponding to the slow axis of the layer (A). For example, in the case where the thin film before stretching is formed of a resin with inherently birefringence, the stretching direction of the thin film before stretching is set to be parallel to the slow axis of the layer (A) to be prepared in the first step. Direction is better. In addition, for example, when the thin film before stretching is formed of a resin having a negative intrinsic birefringence, the stretching direction of the thin film before stretching is set to be slower than that of the layer (A) to be prepared in the first step. The vertical axis is preferred.

Moreover, it is preferable that the extending direction of the pre-stretched film is not perpendicular to the longitudinal direction of the pre-stretched film. Accordingly, the stretching direction of the pre-stretched film is preferably in the long side direction or oblique direction of the pre-stretched film. By using the stretched film obtained by using such a manufacturing method including extending in a long-side direction or an oblique direction as the layer body (A), a wide-band wavelength film having excellent optical characteristics can be easily obtained.

The stretching ratio of the film before stretching is preferably 1.1 times or more, more preferably 1.2 times or more, more preferably 4.0 times or less, and more preferably 3.0 times or less. When the stretching magnification is at least the lower limit of the aforementioned range, the refractive index in the stretching direction can be increased. In addition, when the stretching magnification is below the upper limit of the aforementioned range, the direction of the slow axis of the layered body obtained by stretching the layered body (A) can be easily controlled.

The stretching temperature of the film before stretching is preferably TgA or higher, more preferably "TgA + 2 ° C" or higher, more preferably "TgA + 5 ° C" or higher, and preferably "TgA + 40 ° C" or lower, and "TgA + 35 ° C" or lower It is particularly preferable that the temperature is "TgA + 30 ° C" or lower. Here, TgA refers to the glass transition temperature of the resin contained in the layered body (A). In the case where the stretching temperature is in the aforementioned range, the molecules contained in the film before stretching can be surely oriented, and thus a layer body (A) having desired optical characteristics can be easily obtained.

The extension in the first step can also be performed as a free uniaxial extension. The so-called free uniaxial extension refers to an extension in a certain direction and an extension that does not impose restraint on a direction other than the extended direction. According to this, for example, the so-called free uniaxial extension in the longitudinal direction of the stretched front film refers to the extension in the longitudinal direction without restricting the end in the width direction of the stretched film.

The stretching described above can usually be carried out using a suitable stretching machine such as a roll stretcher or a tenter stretcher while the film before stretching is continuously conveyed in the longitudinal direction. For example, in the case where the pre-stretched film is stretched in the longitudinal direction of the pre-stretched film, it is preferable to use a roll stretcher. Free uniaxial stretching can be easily performed with a roll stretching machine. As these extension machines, for example, those described in Patent Document 1 may be used.

[3. The fourth step]

The method for manufacturing a wide-band wavelength thin film may further include a step of forming a thin film layer on the layer body (A) after preparing the layer body (A) in the first step. By forming an appropriate thin film layer, the thin film layer can function as an easy-to-bond layer and improve the bonding force between the layer body (A) and the layer body (B). The thin film layer is preferably solvent resistant. Such a thin film layer is usually formed of a resin.

Examples of the material of 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 polyurethane-based resin. Polymers such as acrylic polymers and polyurethanes generally have a high binding force to a wide variety of resins, and therefore can improve the binding force between the layer (A) and the layer (B). Moreover, these polymers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The resin as the material of the film layer may also include a heat stabilizer, a weathering stabilizer, a leveling agent, an antistatic agent, a slip agent, an anti-adhesion agent, an anti-fog agent, a slip agent, a dye, a pigment, a natural oil, and a synthetic oil , Wax, particles, and other components are combined into the polymer. An arbitrary component 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 lower than the glass transition temperature TgA of the resin included in the layer body (A) and the resin having a positive intrinsic birefringence included in the layer body (B). Better. In particular, the difference between the glass transition temperature of the resin which is the material of the film layer and the lower of the glass transition temperatures TgA and TgB is preferably 5 ° C or higher, more preferably 10 ° C or higher, and particularly 20 ° C or higher. good. This can suppress the delay in the development of the thin film layer due to the extension in the third step, so the thin film layer in the broadband film can have optical isotropy. Accordingly, the optical characteristics of the wide-band wavelength film can be easily adjusted.

The thin film layer can be formed by, for example, a method including applying a coating liquid to the layer body (A), the coating liquid including a resin and a solvent as materials of the thin film layer. As the solvent, water or an organic solvent may be used. Examples of the organic solvent include the same solvents as those used in the formation of the layered body (B) described later. The solvents may be used singly or in combination of two or more at any ratio.

The coating solution may contain a crosslinking agent. By using a cross-linking agent, the mechanical strength of the film layer can be improved, and the binding property of the film layer to the layer body (A) and the layer body (B) can be improved. As a crosslinking agent, an epoxy compound, an amine compound, an isocyanate compound, a carbodiimide compound, an oxazoline compound, etc. can be used, for example. In addition, 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, more preferably 70 parts by weight or less, and 65 parts by weight or less with respect to 100 parts by weight of the polymer in the coating solution. good.

As a coating method of a coating liquid, the method similar to the coating method used for formation of the layer body (B) mentioned later is mentioned, for example.

By coating the coating liquid on the layer body (A), a thin film layer can be formed. This film layer can also be subjected to curing treatments such as drying and cross-linking as required. Examples of the drying method include heating and drying using an oven. Examples of the crosslinking method include methods such as heat treatment and irradiation treatment of active energy rays such as ultraviolet rays.

[4. Second process]

In the first step, a layered body (A) is prepared, and a thin-film layer is formed as required, and then a second step of forming a layered body (B) having a resin with a positive intrinsic birefringence is performed to obtain a multilayer film. In this second step, a layered body (B) is directly formed on the layered body (A), or any layered body such as a thin film layer is indirectly formed. Here, the so-called "direct" means that there is no arbitrary layer body between the layer body (A) and the layer body (B).

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

The glass transition temperature TgB of the resin with inherent positive birefringence contained in the layer (B) is preferably 100 ° C or higher, more preferably 110 ° C or higher, particularly preferably 120 ° C or higher, and preferably 190 ° C or lower. It is preferably 180 ° C or lower, and particularly preferably 170 ° C or lower. When the glass transition temperature of the resin contained in the layer body (B) is above the lower limit of the foregoing range, the layer body (λ / 2 layer or λ / 4 layer) obtained by extending the layer body (B) can be increased. ) Durability in high temperature environments. In addition, when the glass transition temperature of the resin contained in the layered body (B) is equal to or lower than the upper limit of the aforementioned range, the stretching treatment can be easily performed.

From the viewpoint of adjusting the optical characteristics of both the layered body (A) and the layered body (B) to an appropriate range by the extension in the third step, the glass transition of the resin contained in the layered body (A) is performed. The temperature TgA is preferably close to the glass transition temperature TgB of the resin contained in the layer (B). Specifically, the absolute value of the difference between the glass transition temperature TgA and the glass transition temperature TgB | TgA-TgB | is preferably 20 ° C or lower, more preferably 15 ° C or lower, and even more preferably 10 ° C or lower.

The layer body (B) may also have an in-plane retardation and a slow axis. When the layer body (B) has in-plane retardation and slow axis, the in-plane delay and slow axis direction of the layer body (B) can be adjusted by extension in the third step. However, the setting of the extension conditions for performing such adjustments tends to be complicated. Therefore, from the viewpoint of easily obtaining the desired optical characteristics and the slow axis direction in the layer body (B) after the extension in the third step, the layer body (B) formed in the second step does not have in-plane The retardation and slow axis, or even if there is, the in-plane retardation is preferably small. Specifically, the in-plane retardation of the layer body (B) is preferably 0 nm to 20 nm, more preferably 0 nm to 15 nm, and even more preferably 0 nm to 10 nm.

The thickness of the layer body (B) formed in the second step is arbitrarily set within a range in which a desired wide-band wavelength film can be obtained. The specific thickness of the layer body (B) is preferably 3 μm or more, more preferably 4 μm or more, particularly preferably 5 μm or more, and more preferably 30 μm or less, more preferably 25 μm or less, and 20 It is particularly preferred to be less than μm. In the case where the thickness of the layer body (B) is in the aforementioned range, a λ / 2 layer or a λ / 4 layer having desired optical characteristics can be easily obtained by extension.

The method for forming the layered body (B) is not particularly limited, and a forming method such as a coating method, an extrusion method, or a pasting method may be used.

When the layer body (B) is formed by a coating method, the second step includes applying a composition including a resin having a positive intrinsic birefringence to the layer body (A). The aforementioned composition is generally a liquid composition which further comprises a solvent combined 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, and acetamidine. Acetone, cyclohexanone, 2-methylcyclohexanone, 1,3-dioxo, 1,4-dioxo, 2-pentanone, N, N-dimethylformamide, and the like. The solvents may be used singly or in combination of two or more at any ratio. The solvent may cause dissolution and directional relaxation of the layer (A), but the thickness of the liquid composition is usually thin and the coating composition dries quickly after coating. Therefore, the degree of the foregoing phenomenon is so small that it can be ignored.

Examples of the coating method of the composition include a curtain coating method, an extrusion coating method, a roll coating method, a spin coating method, a dip coating method, a bar coating method, a spray coating method, a swash plate coating method, a printing coating method, and a concave coating method. Plate coating method, die coating method, gap coating method and dipping method.

Further, in the coating method, the second step includes: after coating the composition on the layer body (A), drying the coated composition as required. By removing the solvent by drying, a layer (B) of a resin having a positive intrinsic birefringence can be formed on the layer (A). The drying can be performed by a drying method such as natural drying, heating drying, drying under reduced pressure, and drying under reduced pressure.

When the layer body (B) is formed by an extrusion method, the second step includes extruding a resin having a positive intrinsic birefringence on the layer body (A). The resin is usually extruded while the resin is molten. In addition, the resin is usually extruded into a film shape using a die. With the extruded resin having a positive intrinsic birefringence attached to the layer body (A) or the film layer, a layer (B) having a resin having a positive intrinsic birefringence can be formed on the layer body (A). In addition, when the layer body (B) is formed by an extrusion method, the second step usually includes cooling and solidifying a resin having positive intrinsic birefringence that is extruded and attached to the layer body (A).

In the case where the layer body (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 body (A). Examples of a method for producing a film having a positive intrinsic birefringence include, for example, an extrusion molding method, an inflation molding method, a compression molding method and other melt molding methods, and a solution casting method. In addition, a bonding agent or an adhesive may be used for bonding the film of the resin having a positive intrinsic birefringence to the layer body (A).

Among the formation methods of the layered body (B) described above, the coating method is preferred. For example, in the case of using a bonding method, if a layer body (B) is formed on a suitable supporting film, and this layer body (B) is bonded to the layer body (A), it can be applied to the layer body (A). The layered body (B) is formed thereon, and the breakage of the layered body (B) is suppressed. However, the coating method can reduce the number of layers compared to the pasting method in which the layer (B) is formed on the support film and the layer (B) is transferred from the support film to the layer (A). (B) The number of steps required to form. Moreover, according to the coating method, a bonding agent and an adhesive are not needed. In addition, in the coating method, it is easier to reduce the thickness of the layer body (B) than in the extrusion method. According to this, it is preferable to form the layer body (B) by a coating method from the viewpoint of obtaining a thin wide-band wavelength film with a small number of steps.

[5. The third process]

After the multilayer film including the layer body (A) and the layer body (B) is obtained in the second step, the third step of extending the multilayer film to obtain a long-band wide-band wavelength film is performed. By extending in the third step, the direction of the slow axis of the layer body (A) can be adjusted and the optical characteristics of the layer body (A) can be adjusted to obtain one of the λ / 2 layer and the λ / 4 layer. In addition, by extending in the third step, a slow axis appears in the layer body (B) and optical characteristics appear in the layer body (B), and the other of the λ / 2 layer and the λ / 4 layer can be obtained.

The extension in the third step is performed along a direction that is neither perpendicular nor parallel to the slow axis of the layer body (A) contained in the multilayer film. With this, the layer body (B) can usually be delayed, and the slow axis of the layer body (A) can be controlled to an arbitrary direction to obtain the angular relationship of the formula (1).

The specific extension direction is set from the in-plane direction of the multilayer film so that a desired wide-band wavelength film can be obtained.

For example, in the case where the layer (A) is a layer of a resin with inherently positive birefringence, the direction of the slow axis of the layer (A) will be extended toward the direction of extension due to the extension in the third step. Way of change. And, for example, in the case where the layer (A) is a layer of a resin having a negative intrinsic birefringence, the direction of the slow axis of the layer (A) will be extended to be vertical due to the extension in the third step. The direction in which the extending direction approaches is changed. As such, the direction of the slow axis of the layer (A) usually changes due to the extension in the third step. In the layer body (B), the slow axis usually appears in a direction parallel to the extending direction due to the extension in the third step. Therefore, the extension direction in the third step is set to be obtained by changing the direction of the slow axis in the layer body (A) and the appearance of the slow axis in the layer body (B), as described above. A λ / 2 layer and a λ / 4 layer having a slow axis in a desired direction are preferable.

In the third step, the specific angle (the absolute value of the angle) between the extending direction of the multilayer film and the slow axis of the layer (A) is preferably 50 ° or more, and more preferably 60 ° or more. Above 70 ° is particularly preferred, below 86 ° is preferred, and below 85 ° is particularly preferred. In the case where a multilayer film is extended in such an extending direction, it becomes easy to adjust the slow axis of the λ / 2 layer and the λ / 4 layer to satisfy the relationship of the formula (1).

The third step preferably includes extending the multilayer film in an extending direction that is at an angle of 45 ° or more with respect to the longitudinal direction of the multilayer film. In more detail, the angle between the extension direction and the long-side direction of the multilayer film in the third step is preferably 45 ° or more, more preferably 60 ° or more, particularly preferably 70 ° or more, and It is preferably below 135 °, more preferably below 110 °, and even more preferably below 100 °. In the case where the multilayer film is extended along such an extension direction, the direction of the slow axis of the λ / 2 layer and the λ / 4 layer can be easily controlled.

The stretching ratio in the third step is preferably 1.1 times or more, more preferably 1.15 times or more, more preferably 1.2 times or more, even more preferably 3.0 times or less, more preferably 2.5 times or less, and 2.2 times The following are particularly preferred. When the stretching ratio in the third step is equal to or more than the lower limit of the aforementioned range, the occurrence of wrinkles can be suppressed. In addition, when the stretching magnification in the third step is equal to or less than the upper limit of the aforementioned range, the direction of the slow axis of the λ / 2 layer and the λ / 4 layer can be easily controlled.

The elongation temperature in the third step is relative to the glass transition temperature TgA of the resin contained in the layer (A) and the glass transition temperature TgB of the resin with positive intrinsic birefringence contained in the layer (B), so as to satisfy the following Conditions (C1) and (C2) are both preferable.
(C1) The elongation temperature is preferably TgA-20 ° C or higher, TgA-10 ° C or higher, TgA-5 ° C or higher, and TgA + 30 ° C or lower, and TgA + 25 ° C or lower. , TgA + 20 ℃ is particularly preferred temperature.
(C2) The elongation temperature is preferably TgB-20 ° C or higher, TgB-10 ° C or higher, TgB-5 ° C or higher, and TgB + 30 ° C or lower, and TgB + 25 ° C or lower. , TgB + 20 ℃ is particularly preferred temperature.

By performing stretching at such an extension temperature, the optical characteristics of the layer body (A) can be appropriately adjusted, and the layer body (B) can exhibit desired optical characteristics. Accordingly, a wide-band wavelength film having desired optical characteristics can be obtained.

The stretching in the third step described above can be performed using any stretching machine, for example, a tenter stretching machine or a roll stretching machine can be used. The stretching using these stretchers is preferably carried out while continuously transporting the long multilayer film in the longitudinal direction.

[6. Arbitrary process]

The method for manufacturing the wide-band wavelength film described above may further include an arbitrary combination of steps to the steps described above.

For example, the method for manufacturing a broadband film may include a step of providing a protective layer on the surface of the broadband film.

Furthermore, for example, a method for manufacturing a wide-band wavelength thin film may include applying corona treatment to one or more surfaces of the layered body (A), the layered body (B), and the film layer at any time point. , Plasma treatment and other surface treatment processes. According to this, for example, after the surface of the layer body (A) is subjected to a surface treatment, a layer body (B) or a thin film layer may be formed on the treated surface. In addition, for example, after the surface of the thin film layer is subjected to a surface treatment, a layer body (B) may be formed on the treated surface. By performing the surface treatment, it is possible to improve the bonding between the layers on the surface to which the surface treatment is applied.

The first to fourth steps and any of the steps described above may be carried out while continuously transporting films such as a layer (A), a multilayer film, and a broadband film. The transport direction of such a transport film is usually the long side direction of the film. Accordingly, during the aforementioned transportation, the longitudinal direction and width direction of the film are generally consistent with the MD direction (Machine Direction) and the TD direction (Transverse Direction) of the film.

[7. Broadband Wavelength Film]

A co-stretched film having a λ / 2 layer and a λ / 4 layer can be obtained by the manufacturing method described above. The λ / 2 layer and λ / 4 layer of this co-stretched film satisfy the aforementioned formula (1). The combination of the λ / 2 layer and the λ / 4 layer that satisfies the relationship shown by the formula (1) can function as a wide-band wavelength film, which can pass through the wide-wavelength range, The light of the film gives an in-plane retardation of approximately 1/4 of the wavelength of the light (refer to Japanese Patent Laid-Open No. 2007-004120). Accordingly, according to the manufacturing method described above, a co-extended film including a λ / 2 layer and a λ / 4 layer can be made, and a wide-band wavelength film can be obtained. From the viewpoint of realizing a wide-band wavelength film capable of functioning in a wider wavelength range, the λ / 2 layer and the λ / 4 layer preferably satisfy the formula (2), and more preferably satisfy the formula (3). Equation (2) indicates that θ (λ / 4) is in a range of "[+ 45 ° + 2 × θ (λ / 2)]-4 °" and "[+ 45 ° + 2 × θ (λ / 2)] + 4 °" . In addition, Equation (3) indicates that θ (λ / 4) is equal to or greater than [[45 ° + 2 × θ (λ / 2)]-3 °] and equal to or less than [+ 45 ° + 2 × θ (λ / 2)] + 3 °. Range.
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 layered body (A) and the layered body (B) are extended together in the third step, rather than separately as in the past. Therefore, the number of stretching processes can be reduced more than in the past, so the number of steps required for manufacturing a wide-band wavelength film can be reduced, and efficient manufacturing can be achieved. In addition, in the aforementioned manufacturing method in which a multilayer film is extended to thereby extend the layer body (A) and the layer body (B) to obtain a wide-band wavelength film, it would not be possible to manufacture a λ / 2 layer and a λ / 4 layer, respectively, as in Conventional manufacturing methods in which the two are bonded later are generally misaligned 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 wide-band wavelength film that can realize a circularly polarizing film that can effectively suppress discoloration can be easily obtained.

Among the obtained broadband films, a layer obtained by extending one of the λ / 2 layered layer (A) and the layer (B), the λ / 2 layered layer (A) and the layer ( B) The layered body obtained by extending the other. Among them, in terms of particularly easily manufacturing a wide-band wavelength film, a layer body obtained by extending the layer body (A) with a λ / 2 layer system is preferable, and a layer body (B) is extended with a λ / 2 layer system. The obtained layer is better. Accordingly, the λ / 2 layer is preferably a layer made of the same resin as the layer (A), and the λ / 2 layer is preferably a layer made of the same resin as the layer (B).

The λ / 2 layer has a layer body with an in-plane retardation at a measurement wavelength of 590 nm, which is usually 220 nm or more and usually 300 nm or less. In the case where the λ / 2 layer has such an in-plane retardation, a λ / 2 layer and a λ / 4 layer can be combined to achieve a wide-band wavelength thin film. Among them, from the viewpoint of obtaining a circularly polarizing film with excellent discoloration suppression function in the oblique direction, the in-plane retardation of the λ / 2 layer with a measurement wavelength of 590 nm is preferably 230 nm or more, and more preferably 240 nm or more. , And preferably below 280 nm, more preferably below 270 nm.

The retardation of the λ / 2 layer in the thickness direction of the measurement wavelength of 590 nm is preferably 130 nm or more, more preferably 140 nm or more, particularly 150 nm or more, more preferably 300 nm or less, and 280 nm or less. For the sake of preference, 270 nm or less is particularly preferred. In the case where the retardation in the thickness direction of the λ / 2 layer is in the aforementioned range, a circularly polarizing film having an excellent discoloration suppression function in the oblique direction can be obtained.

The NZ coefficient of the λ / 2 layer is preferably 1.0 or more, more preferably 1.05 or more, more preferably 1.10 or more, and more preferably 1.6 or less, more preferably 1.55 or less, and even more preferably 1.5 or less. In the case where the NZ coefficient of the λ / 2 layer is in the aforementioned range, a circularly polarizing film having an excellent discoloration suppression function in an oblique direction can be obtained. Moreover, a λ / 2 layer having such an NZ coefficient can be easily manufactured.

The optical characteristics such as the retardation of the λ / 2 layer and the NZ coefficient can be determined by, for example, the retardation and thickness of the layer body (A) prepared in the first step, and the elongation temperature, elongation, and elongation direction in the third step. Extension conditions to adjust.

The orientation angle θ (λ / 2) of the λ / 2 layer is preferably in a range of 20 ° ± 10 ° (that is, a range of 10 ° to 30 °), and preferably in a range of 20 ° ± 8 ° (that is, A range of 12 ° to 28 ° is preferred, and a range of 20 ° ± 5 ° (that is, a range of 15 ° to 25 °) is particularly preferred. Generally, a linear polarizing film has a transmission axis in a width direction and an absorption axis in a long side direction. In the case where the orientation angle θ (λ / 2) of the λ / 2 layer is in the aforementioned range, it can be combined with such a general linear polarizing film to easily realize a circularly polarizing film. In addition, when the orientation angle θ (λ / 2) of the λ / 2 layer is in the foregoing range, the discoloration suppression function of the obtained circularly polarizing film in the front direction can be optimized.

The orientation angle θ (λ / 2) of the λ / 2 layer can be extended by, for example, the direction of the slow axis of the layer body (A) prepared in the first step, and the extension direction and extension magnification in the third step. Conditions to adjust.

The thickness of the λ / 2 layer is preferably 20 μm or more, more preferably 25 μm or more, more preferably 30 μm or more, and more preferably 80 μm or less, more preferably 70 μm or less, and 60 μm or less. Better. This can increase the mechanical strength of the λ / 2 layer.

The λ / 4 layer is a layer body having an in-plane retardation at a measurement wavelength of 590 nm, which is usually 90 nm or more and usually 154 nm or less. In the case where the λ / 4 layer has such an in-plane retardation, a λ / 2 layer and a λ / 4 layer can be combined to realize a wide-band wavelength thin film. Among them, from the viewpoint of obtaining a circularly polarizing film with excellent discoloration suppression function in the oblique direction, the in-plane retardation of the λ / 4 layer with a measurement wavelength of 590 nm is preferably 100 nm or more, and more preferably 110 nm or more. , And preferably below 140 nm, more preferably below 130 nm.

The retardation of the λ / 4 layer in the thickness direction of the measurement wavelength of 590 nm is preferably 50 nm or more, more preferably 60 nm or more, more preferably 70 nm or more, more preferably 135 nm or less, and 125 nm or less. Preferably, 115 nm or less is preferred. In the case where the retardation in the thickness direction of the λ / 4 layer is in the aforementioned range, a circularly polarizing film having an excellent discoloration suppression function in the oblique direction can be obtained.

The NZ coefficient of the λ / 4 layer is preferably 1.0 or more, more preferably 1.05 or more, more preferably 1.10 or more, and more preferably 1.6 or less, more preferably 1.55 or less, and even more preferably 1.5 or less. In the case where the NZ coefficient of the λ / 4 layer is in the foregoing range, a circularly polarizing film having an excellent discoloration suppression function in an oblique direction can be obtained. Moreover, a λ / 4 layer having such an NZ coefficient can be easily manufactured.

Optical characteristics such as retardation of the λ / 4 layer and NZ coefficient can be determined by, for example, the thickness of the layer body (B) formed in the second step, and the elongation conditions such as elongation temperature, elongation, and direction in the third step. To adjust.

The orientation angle θ (λ / 4) of the λ / 4 layer is preferably in a range of 85 ° ± 20 ° (that is, a range of 65 ° to 105 °), and is preferably in a range of 85 ° ± 15 ° (that is, A range of 70 ° to 100 ° is preferred, and a range of 85 ° ± 10 ° (that is, a range of 75 ° to 95 °) is particularly preferred. In the case where the orientation angle θ (λ / 4) of the λ / 4 layer is in the foregoing range, it can be easily combined with a general linear polarizing film having a transmission axis in the width direction and an absorption axis in the long side direction, which can be easily realized. Circular polarizing film. In addition, when the orientation angle θ (λ / 4) of the λ / 4 layer is in the foregoing range, the discoloration suppression function of the obtained circularly polarizing film in the front direction can be optimized.

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

The thickness of the λ / 4 layer is preferably 3 μm or more, more preferably 4 μm or more, even more preferably 5 μm or more, and more preferably 15 μm or less, more preferably 13 μm or less, and 10 μm or less. It's better. In the case where the thickness of the λ / 4 layer is above the lower limit of the foregoing range, desired optical characteristics can be easily obtained. In addition, when the thickness of the λ / 4 layer is below the upper limit of the aforementioned range, the thickness of the wide-band wavelength film can be reduced.

The λ / 2 layer and the λ / 4 layer are preferably directly connected. This makes it possible to reduce the thickness of the wide-band wavelength thin film.

In the case where the method for manufacturing a wideband wavelength film includes a fourth step of forming a thin film layer, the wideband wavelength film includes a thin film layer between the λ / 2 layer and the λ / 4 layer. In general, the bonding layer used in the conventional manufacturing method in which the λ / 2 layer and the λ / 4 layer are manufactured separately and then bonded together is 5 μm or more in thickness. In contrast, it is obtained by the manufacturing method described above. The thin-film layer of the wide-band wavelength thin film can be thinner than it. The thickness of the specific 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. Since the thin film layer can be thinned in this way, the thickness of the entire wide-band wavelength thin film can also be thinned. The thinner the lower limit of the thickness of the thin film layer, the better, and it is, for example, 0.1 μm.

The wide-band wavelength thin film may also have any combination of layers to a λ / 2 layer, a λ / 4 layer, and a thin film layer. For example, a bonding layer or an adhesive layer for bonding the λ / 2 layer and the λ / 4 layer may be provided.

The total light transmittance of the broadband film is preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more. The total light transmittance must be measured in accordance with JIS K0115, using a spectrophotometer in the wavelength range of 400 nm to 700 nm.

The haze of the broadband film is preferably 5% or less, more preferably 3% or less, even more preferably 1% or less, and ideally 0%. Here, the haze can be adopted: in accordance with JIS K7361-1997, the "turbidimeter NDH-300A" manufactured by Nippon Denshoku Industries Co., Ltd. was used to measure 5 points, and the average value was obtained from this.

The thickness of the broadband film is preferably 20 μm or more, more preferably 25 μm or more, more preferably 30 μm or more, and more preferably 120 μm or less, more preferably 100 μm or less, and 90 μm or less. It's better. According to the manufacturing method described above, such a thin wide-band wavelength film can be easily manufactured.

[8. Circular polarizing film]

By using the wide-band wavelength film manufactured by the manufacturing method described above, a long circularly polarizing film can be manufactured. Such a circularly polarizing film can be manufactured by a method including "a step of manufacturing a wide-band wavelength film by the above-mentioned manufacturing method" and a "step of bonding this wide-band wavelength film to a long linear polarizing film" To make. The bonding is usually performed by sequentially arranging a linear polarizing film, a λ / 2 layer, and a λ / 4 layer in the thickness direction. In addition, the bonding may use a bonding layer or an adhesive layer as required.

The linearly polarizing film is a long thin 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 the linearly polarized light means the vibration direction of the electric field of the linearly polarized light.

The linear polarizing film usually includes a polarizer layer, and a protective film layer for protecting the polarizer layer is provided as required.

As the polarizer layer, it is possible to use, for example, a film that has been appropriately treated with a suitable vinyl alcohol-based polymer in an appropriate order and manner. Examples of such a vinyl alcohol polymer include polyvinyl alcohol and partially formalized polyvinyl alcohol. Examples of the treatment of the film include a dyeing treatment, a stretching treatment, and a crosslinking treatment using a dichroic substance such as iodine and a dichroic dye. Generally, in the stretching process for manufacturing a polarizer layer, the pre-stretched film is extended in the longitudinal direction, so that an absorption axis parallel to the longitudinal direction of the polarizer layer in the obtained polarizer layer appears. This polarizer layer is designed to absorb linearly polarized light having a vibration direction parallel to the absorption axis, and particularly preferably one having excellent polarization. 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, an arbitrary transparent film may be used. Among them, a film of a resin excellent in transparency, mechanical strength, thermal stability, moisture shielding property, and the like is preferred. Examples of such resins include acetate resins such as cellulose triacetate, polyester resins, polyether resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and cycloolefin resins. , (Meth) acrylic resin, etc. Among them, in terms of small birefringence, acetate resins, cycloolefin resins, and (meth) acrylic resins are preferred. From the viewpoints of transparency, low hygroscopicity, dimensional stability, and light weight, Cycloolefin resins are particularly preferred.

The linear polarizing film can be manufactured by, for example, bonding a long polarizer layer and a long protective film layer. When bonding, a bonding agent can also be used as required.

The linear polarizing film preferably has an absorption axis in the longitudinal direction of the linear polarizing film. Such a linear polarizing film is preferably manufactured by laminating a wide-band wavelength film including a λ / 2 layer and a λ / 4 layer, and the λ / 2 layer has 20 ° ± 10 ° (that is, 10 ° -30 °), the λ / 4 layer has an orientation angle θ (λ / 4) of 85 ° ± 20 ° (ie, 65 ° to 105 °). According to the combined bonding as described above, a circularly polarizing film can be manufactured by bonding a long linear polarizing film and a long-side wide-band wavelength film in parallel to each other, thereby manufacturing a circularly polarizing film. A circularly polarizing film can be produced by a roll-to-roll method. Therefore, the manufacturing efficiency of a circularly polarizing film can be improved.

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

The aforementioned circularly polarizing film may further include an arbitrary layer combination of a linearly polarizing film and a wide-band wavelength film.

For example, the circularly polarizing film may be provided with a protective film layer for suppressing damage. In addition, for example, the circularly polarizing film may include a bonding layer or an adhesive layer for bonding the linearly polarizing film and the wide-band wavelength film.

The circularly polarizing film can effectively reduce the reflection of external light when the circularly polarizing film is disposed on a surface that reflects light. In particular, the aforementioned circularly polarizing film is useful in that it can effectively reduce the reflection of external light in a wide wavelength range in the visible light region. In addition, since the reflection of external light in a wide wavelength range can be effectively reduced in this way, the aforementioned circularly polarizing film can suppress discoloration caused by the increase in the reflection intensity of a portion of the wavelength light. This circularly polarizing film can obtain the aforementioned effects of suppressing reflection and discoloration at least in the front direction, and usually can also be further obtained in its oblique direction. In addition, the effects of suppressing reflection and discoloration in the oblique direction can usually be obtained in all azimuth directions of the film main surface.

[9. Video display device]

The circularly polarizing film utilizes the function of suppressing reflection of external light as described above, and can be used as an antireflection film of an organic electroluminescence display device (hereinafter referred to as an "organic EL display device" as appropriate).

The organic EL display device includes a circularly polarizing film sheet obtained by cutting out a long circularly polarizing film.

When an organic EL display device includes a circularly polarizing film sheet, the organic EL display device generally includes a circularly polarizing film sheet on a display surface. By providing a circularly polarizing film on the display surface of the organic EL display device such that the surface of the linearly polarizing film side faces the viewing side, it is possible to suppress the light incident from the outside of the device from reflecting inside the device and exiting to the outside of the device. As a result, Suppress glare on the display surface of the display device. Specifically, only a part of the linearly polarized light incident from the outside of the device passes through the linearly polarizing film, and then passes through the wide-band wavelength film, thereby becoming circularly polarized light. The circularly polarized light is reflected by constituent elements (reflective electrodes, etc.) that reflect light in a display device, and passes through a wide-band wavelength film again, thereby having a direction orthogonal to the vibration direction (polarization axis) of the incident linearly polarized light The linearly polarized light in the vibration direction (polarization axis) does not pass through the linearly polarized film. Thereby, a reflection suppression function is achieved. In addition, since the aforementioned reflection suppressing function can be obtained in a wide wavelength range, discoloration of the display surface can be suppressed.

In addition, the circularly polarizing film may be provided in a liquid crystal display device. This liquid crystal display device includes a circularly polarizing film sheet obtained by cutting out a long circularly polarizing film.

When the liquid crystal display device is provided with a circularly polarizing film such that the surface of the linearly polarizing film side faces the viewing side, it is possible to suppress the light incident from the outside of the device from reflecting inside the device and exiting to the outside of the device. As a result, the display device can be suppressed Glare and discoloration of the display surface.

In addition, when the liquid crystal display device includes a circularly polarizing film sheet in which a wide-band wavelength film, a linearly polarizing film, and a liquid crystal cell of the liquid crystal display device are sequentially arranged from the viewing side, an image can be displayed with circularly polarized light. Therefore, it is possible to stably see the light emitted from the display surface by using polarized sunglasses, and to improve the visibility of the image when wearing polarized sunglasses.

In addition, in a case where a circularly polarizing film sheet is provided such that an image display device such as an organic EL display device and a liquid crystal display device has a linearly polarizing film side facing the viewing side, warping of a display panel can be suppressed. This effect is explained below.

The image display device generally includes a display panel including display elements such as an organic electroluminescence element and a liquid crystal cell. This display panel includes a substrate such as a glass substrate in order to improve the mechanical strength of the display panel. Furthermore, in a display panel in which a circularly polarizing film sheet is provided so that the surface of the linearly polarizing film side faces the viewing side, a substrate, a wide-band wavelength film, and a linearly polarizing film are usually provided in this order.

Incidentally, the polarizer layer of the linear polarizing film is generally easy to shrink in an in-plane direction under a high temperature environment. When the polarizer layer is shrunk in this way, a stress is generated on the display panel provided with the linear polarizing film including the polarizer layer, which warps the display panel. The warping of the display panel may cause a reduction in image quality, so it is desirable to suppress it. Regarding this warpage, it has been understood that the larger the distance between the polarizer layer and the substrate of the display panel, the larger the aforementioned warpage tends to become.

The wide-band wavelength film manufactured by the conventional manufacturing method in which the λ / 2 layer and the λ / 4 layer are bonded separately after manufacturing the λ / 2 layer and the λ / 4 layer is thick because the bonding layer is thick. Accordingly, in the conventional wide-band wavelength film, the distance between the polarizer layer and the base material of the display panel is increased, so that the warpage of the display panel tends to be large.

On the other hand, the λ / 2 layer and the λ / 4 layer can be directly connected to the wide-band wavelength film manufactured by making a co-extension film as described above, or the λ / 2 layer and the λ / 4 layer can be provided. Thin film layer in between. Accordingly, since the entire wide-band wavelength film can be thinned, the distance between the polarizer layer and the substrate of the display panel can be reduced. Therefore, warping of the display panel can be suppressed.

『Examples』

The following examples are disclosed to illustrate the present invention in detail. However, the present invention is not limited to the embodiments disclosed below, and can be implemented with arbitrary changes without departing from the scope of the patent application of the present invention and its equivalent range.

In the following description, the "%" and "part" of the amount are based on weight unless otherwise noted. In addition, the operations described below are performed under normal temperature and pressure conditions unless otherwise noted.

[Evaluation method]

[Measurement method of optical characteristics of layer body (A)]

A retardation meter ("AxoScan" manufactured by Axometrics) was used to measure the in-plane retardation Re, NZ coefficient, and orientation angle of the stretched film obtained as the layer (A) in the first step. The measurement wavelength is 590 nm.

[Measurement method of optical characteristics of each layer of a broadband film]

The wide-band wavelength film to be evaluated was set on a stage of a phase difference meter ("AxoScan" manufactured by Axometrics). Then, the change in the polarization state of the polarized light that has passed through the wideband wavelength film before and after the wideband wavelength film is measured is measured. As a wideband wavelength film, the transmission polarization characteristic is obtained. This measurement is performed by a multi-directional measurement in a range from a polar angle of -55 ° to + 55 ° with respect to a main surface of a wide-band wavelength film. In addition, the aforementioned multi-directional measurement is to set a certain azimuth direction of the main surface of the wideband wavelength film to 0 °, and perform the azimuthal directions of 45 °, 90 °, 135 °, and 180 °. The measurement wavelength of the aforementioned measurement is 590 nm.

Secondly, from the measured polarization polarization characteristics as described above, the in-plane retardation Re of each layer, the retardation Rth in the thickness direction, the NZ coefficient, and the orientation angle are obtained by fitting calculation. The aforementioned fitting calculation is performed by setting the three-dimensional refractive index and orientation angle of each layer included in the wide-band wavelength film as fitting parameters. The fitting calculation is performed using software ("Multi-Layer Analysis" manufactured by Axometrics), which is an accessory software of the phase difference meter (AxoScan).

[Calculation method using simulated color difference ΔE * ab]

The "LCD Master" manufactured by Shintech Corporation was used as simulation software to model the circularly polarizing films produced in the examples and comparative examples, and the color difference ΔE * ab was calculated under the following settings.

In the simulation model, a structure was set in which a circularly polarizing film was attached to the reflecting surface of an aluminum mirror having a planar reflecting surface so that the λ / 4 layer side of the broadband film was in contact with the mirror. Therefore, in this model, the following structure is set: a linearly polarizing film, a λ / 2 layer, a λ / 2 layer, and a mirror are sequentially provided in the thickness direction.

Then, in the aforementioned model, the color difference ΔE * ab when the circularly polarizing film is irradiated with light from the D65 light source is calculated in the front direction of the circularly polarizing film. When calculating the chromatic aberration ΔE * ab, the reflected light in the direction of the polar angle 0 ° and the azimuth angle 0 of the aluminum mirror without the circular polarizing film is used as a reference. And, 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, the smaller the value, the better the less color change.

[Visual Evaluation of Circular Polarizing Film]

The polarizing plate included in the image display device ("AppleWatch" (registered trademark) of Apple Inc.) is peeled off, and the display surface of the image display device and the λ / 4 layer of the circular polarizing film of the evaluation target are interposed with an adhesive layer (Nitto Denko "CS-9621"). The display surface is set to a black display state (a state in which the entire screen is displayed in black), and the display surface is viewed from all directions from a polar angle θ = 0 ° (front direction) and a polar angle θ = 60 ° (tilt direction). The smaller the brightness and discoloration caused by the reflection of external light, the better the result. The observation results were evaluated on the following criteria.
"A": No visible brightness and discoloration.
"B": Brightness and discoloration occur to a visible degree.
"C": Brightness and discoloration occur severely.

[Example 1]

(First step: manufacture of layered body (A))

As a resin having a positive intrinsic birefringence, a granular norbornene-based resin (manufactured by Japan's Rui On; glass transition temperature of 126 ° C) was prepared and dried at 100 ° C for 5 hours. The dried resin is supplied to an extruder, extruded into a sheet shape from a T-die on a casting drum through a polymer tube and a polymer filter. The extruded resin was cooled to obtain a strip-shaped stretched front film having a thickness of 110 μm. The obtained pre-stretched film is rolled into a roll and recovered.

The pre-stretched film was pulled out from the roll and continuously fed to a roll stretcher. Then, using this roll stretcher, the film before stretching was freely uniaxially stretched to obtain a long stretched film as a layer (A). In this stretching, the stretching angle between the stretching direction and the longitudinal direction of the film before stretching is 0 °, the stretching temperature is 132 ° C, and the stretching ratio is 1.9 times. 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 is rolled into a roll and recovered.

(Second step: formation of layer (B))

A liquid composition containing a norbornene-based resin (manufactured by Ruon Co., Ltd .; glass transition temperature: 135 ° C) was prepared as a resin having a positive intrinsic birefringence. This liquid composition contains cyclohexanone as a solvent, and the concentration of the norbornene-based resin in the liquid composition is 15.0% by weight.

The stretched film was pulled out from a roll, and the aforementioned liquid composition was coated on the stretched film. After that, the applied liquid composition was dried to form a layered body (10 μm thick) of a norbornene-based resin as a layered body (B) on the stretched film. Thereby, a multilayer film including a layered body (A) and a layered body (B) is obtained. The obtained multilayer film is rolled into a roll and recovered.

(Third step: extension of multilayer film)

The multilayer film was pulled out from the roll and continuously fed to a tenter stretcher. Then, using this tenter stretcher, a multilayer film is stretched. In this stretching, the stretching angle between the stretching direction and the long-side direction of the multilayer film is 75 °, the stretching temperature is 140 ° C, and the stretching ratio is 2.0 times. In this way, a co-extension film having a λ / 2 layer obtained by extending the layer (A) and a λ / 4 layer obtained by extending the layer (B) was prepared, and a broadband film was obtained. The obtained broadband film was evaluated by the method described above.

(Manufacture of circular polarizing film)

A long linear polarizing film having an absorption axis in the longitudinal direction is prepared. The linearly polarizing film and the wide-band wavelength film are parallel to each other in the long-side direction. This bonding is performed using an adhesive ("CS-9621" manufactured by Nitto Denko Corporation). Thereby, a circularly polarizing film having a linearly polarizing film, a λ / 2 layer, and a λ / 4 layer in this order was obtained. The obtained circularly polarizing film was evaluated by the method described above.

[Example 2]

In the third step, the extension angle between the extension direction and the longitudinal direction of the multilayer film is changed to 80 °.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band wavelength film and a circularly polarizing film.

[Example 3]

In the third step, the extension angle between the extension direction and the longitudinal direction of the multilayer film is changed to 85 °.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band wavelength film and a circularly polarizing film.

[Example 4]

A liquid composition containing a polycarbonate resin (manufactured by MITSUBISHI GAS CHEMICAL COMPANY, INC .; glass transition temperature of 137 ° C) was prepared as a resin having a positive intrinsic birefringence. This liquid composition contains cyclopentanone as a solvent, and the concentration of the polycarbonate resin in the liquid composition is 15% by weight. In the second step, this liquid composition containing a polycarbonate resin was used instead of the liquid composition containing a norbornene-based resin used in Example 1.

In the third step, the extension angle between the extension direction and the longitudinal direction of the multilayer film is changed to 85 °.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band wavelength film and a circularly polarizing film.

[Example 5]

In the first step, a tenter stretching machine is used instead of a roll stretching machine as a stretching device for stretching the film before stretching. Tension using a tenter stretcher is not a free uniaxial extension, but an extension that applies a restraining force outside the extension direction. In addition, the stretching angle between the stretching direction and the longitudinal direction of the film before stretching was changed to 10 °. The stretching ratio of the film before stretching was changed to 1.4 times.

In the second step, a liquid composition containing a polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing a norbornene-based resin used in Example 1.

In the third step, the extension angle between the extension direction and the longitudinal direction of the multilayer film is changed to 90 °.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band wavelength film and a circularly polarizing film.

[Comparative Example 1]

In the second step, a liquid composition containing a polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing a norbornene-based resin used in Example 1.

In the third step, the extension angle between the extension direction and the longitudinal direction of the multilayer film is changed to 90 °.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band wavelength film and a circularly polarizing film.

[Comparative Example 2]

In the second step, a liquid composition containing a polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing a norbornene-based resin used in Example 1.

In the third step, a roll stretcher is used instead of the tenter stretcher as the stretcher for stretching the multilayer film. In addition, the extension angle between the extension direction and the longitudinal direction of the multilayer film was changed to 0 °. Furthermore, the stretching ratio of the multilayer film was changed to 1.5 times.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band 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, a liquid composition containing a polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing a norbornene-based resin used in Example 1.

In the third step, the extension angle between the extension direction and the longitudinal direction of the multilayer film is changed to 60 °. Furthermore, the stretching ratio of the multilayer film was changed to 1.5 times.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band 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, a liquid composition containing a polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing a norbornene-based resin used in Example 1.

In the third step, the extension angle between the extension direction and the longitudinal direction of the multilayer film is changed to 30 °. Furthermore, the stretching ratio of the multilayer film was changed to 1.5 times.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band wavelength film and a circularly polarizing film.

[Comparative Example 5]

In the first step, a tenter stretching machine is used instead of a roll stretching machine as a stretching device for stretching the film before stretching. In addition, the stretching angle between the stretching direction and the longitudinal direction of the film before stretching was changed to 10 °. The stretching ratio of the film before stretching was changed to 1.4 times.

In the second step, a liquid composition containing a polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing a norbornene-based resin used in Example 1.

In the third step, the extension angle between the extension direction and the longitudinal direction of the multilayer film is changed to 60 °. Furthermore, the stretching ratio of the multilayer film was changed to 1.5 times.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band wavelength film and a circularly polarizing film.

[Comparative Example 6]

In the first step, a tenter stretching machine is used instead of a roll stretching machine as a stretching device for stretching the film before stretching. In addition, the stretching angle between the stretching direction and the longitudinal direction of the film before stretching was changed to 10 °. The stretching ratio of the film before stretching was changed to 1.4 times.

In the second step, a liquid composition containing a polycarbonate resin prepared in Example 4 was used instead of the liquid composition containing a norbornene-based resin used in Example 1.

In the third step, a roll stretcher is used instead of the tenter stretcher as the stretcher for stretching the multilayer film. In addition, the extension angle between the extension direction and the longitudinal direction of the multilayer film was changed to 0 °. Furthermore, the stretching ratio of the multilayer film was changed to 1.5 times.

Except for the above matters, the same operations as in Example 1 were performed to produce and evaluate a wide-band wavelength film and a circularly polarizing film.

[result]

The results of Examples and Comparative Examples are shown in Tables 1 and 2 below. In the following tables, the meaning of the abbreviations is as follows.
COP: norbornene-based resin.
PC: Polycarbonate resin.
Re: in-plane delay.
Rth: delay in the thickness direction.
Orientation angle: the angle between the slow axis and the long side.
Total thickness: The total thickness of λ / 2 layer and λ / 4 layer.
Oblique: oblique.
Vertical: Long side direction.

[Table 1] [Table 1. Results of Examples]

[Table 2] [Table 2. Results of Comparative Example]

100‧‧‧ layered body (A)

200‧‧‧multi-layer film

210‧‧‧Layer (B)

300‧‧‧ Broadband Wavelength Film

<Fig. 1> Fig. 1 is a schematic perspective view showing a layered body (A) prepared as a resin film in a first step of a method for manufacturing a wide-band wavelength film according to an embodiment of the present invention.

<FIG. 2> FIG. 2 is a schematic perspective view of a multilayer film obtained in a second step of a method for manufacturing a wideband wavelength film according to an embodiment of the present invention.

<FIG. 3> FIG. 3 is a schematic perspective view showing a wideband wavelength film obtained in a third step of a method for manufacturing a wideband wavelength film according to an embodiment of the present invention.

Claims (10)

A method for manufacturing a wide-band wavelength thin film, which includes: a first step of preparing a layered body (A) as a resin film having a slow axis in a plane; and a second step of forming an inherent layer on the aforementioned layered body (A) A layer (B) of a resin having a positive birefringence to obtain a multilayer film; and a third step, extending the foregoing multilayer film in a direction that is neither perpendicular nor parallel to the slow axis of the layer (A) to obtain a film having λ / 2-layer and λ / 4-layer strip-shaped wide-band wavelength films; wherein the λ / 2 layer and the λ / 4 layer of the wide-band wavelength film satisfy the following formula (1): θ (λ / 4) = [45 ° + 2 × θ (λ / 2)] ± 5 ° (1) (In the aforementioned formula (1), θ (λ / 2) indicates that the slow axis of the aforementioned λ / 2 layer is relative to the aforementioned broadband film Θ (λ / 4) represents the angle between the slow axis of the aforementioned λ / 4 layer and the longitudinal direction of the aforementioned broadband film. The method for manufacturing a wide-band wavelength thin film according to claim 1, wherein the layer body (A) prepared in the first step has a slow axis that is not perpendicular to the long side direction of the layer body (A). A long resin film. The method for manufacturing a wide-band wavelength film according to claim 1, wherein the third step includes extending the multilayer film in a direction that is at an angle of 45 ° or more with respect to the long-side direction of the multilayer film. The method for manufacturing a wide-band wavelength thin film according to claim 1, wherein the aforementioned angle θ (λ / 2) is in a range of 20 ° ± 10 °. The method for manufacturing a wide-band wavelength film according to claim 1, wherein the aforementioned angle θ (λ / 4) is in a range of 85 ° ± 20 °. The method for manufacturing a wide-band wavelength thin film according to claim 1, wherein the λ / 2 layer is a layer body obtained by extending the layer body (A). The method for manufacturing a wide-band wavelength thin film according to claim 1, wherein the λ / 4 layer is a layer body obtained by extending the layer body (B). A method for manufacturing a circularly polarizing film, comprising: a step of manufacturing a wide-band wavelength film by the manufacturing method according to any one of claims 1 to 7; Lamination process. The method of manufacturing a circularly polarizing film according to claim 8, wherein the linearly polarizing film has an absorption axis in a longitudinal direction of the linearly polarizing film. A strip-shaped wide-band wavelength film is a co-extended film. The co-extended film includes: λ / 2 layers, and has a slowness of an angle of 20 ° ± 10 ° with respect to the long-side direction of the aforementioned wide-band wavelength film. The axis, and the λ / 4 layer, has a slow axis at an angle of 85 ° ± 20 ° with respect to the long-side direction of the aforementioned broadband film.