TW202214444A - Phase difference film and production method thereof - Google Patents

Abstract

This phase difference film is provided with an A layer which has a slow axis, and a B layer which has a slow axis forming an angle of 85 DEG - 90 DEG to the slow axis of the A layer; the A layer is formed from a resin A having a positive intrinsic birefringence; the B layer is formed from a resin B having a negative intrinsic birefringence; the resin B contains a polyester, a polycarbonate or a polyester carbonate containing a fluorine skeleton; the in-plane retardation of the entire A layer and the in-plane retardation of the entire B layer satisfy a specific relation; the in-plane retardation Re (450) and Re (550) of the phase difference film at wavelengths 450 nm and 550 nm satisfy a specific relation; and the ratio TA/TB of the total thickness TA of the A layer and the total thickness TB of the B layer is 30/70-65/35.

Description

Retardation film and its manufacturing method, polarizing plate and image display device

The present invention relates to a retardation film and a method for producing the same.

A retardation film may be provided in an image display device (Patent Document 1). Such retardation films have a multilayer structure including two or more layers (Patent Documents 2 to 3).

"Patent Documents" "Patent Document 1": Japanese Patent Laid-Open No. 2002-40258 "Patent Document 2": Japanese Patent Laid-Open No. 2017-177342 "Patent Document 3": Japanese Patent Laid-Open No. 2018-128568

In order to reduce the reflection of external light on the display surface, a circular polarizer is sometimes provided in the image display device. As such a circular polarizer, a film obtained by combining a linear polarizer and a retardation film is generally used. However, almost all of the conventional retardation films have forward wavelength dispersion. As a result, most of the conventional circular polarizers can reduce the reflection of external light in a specific narrow wavelength range, but it is difficult to reduce the reflection of external light outside the range, so sometimes a sufficiently high reflection suppression ability cannot be obtained.

In order to improve the reflection suppressing ability, it may be considered to install a retardation film with reverse wavelength dispersion on the circularly polarizing plate. As such a retardation film having reverse wavelength dispersion, there is a combination of a resin having positive intrinsic birefringence and a resin having negative intrinsic birefringence. Generally, this retardation film can exhibit reverse wavelength dispersion by utilizing the difference between the in-plane retardation exhibited by the resin having positive intrinsic birefringence and the in-plane retardation exhibited by the resin having negative intrinsic birefringence. Specifically, the longer the measurement wavelength, the greater the difference in the aforementioned in-plane retardation, thereby achieving reverse wavelength dispersion.

However, a retardation film used in combination with a resin having positive intrinsic birefringence and a resin having negative intrinsic birefringence tends to be inferior in reworkability as described below.

After bonding the retardation film to a member once, it may be required to peel off the retardation film and bond it to the member again. The property that can be easily peeled off and reattached from a part is called "reworkability". For example, in the case where the retardation film is peeled off from the image display device and reattached again after the retardation film is attached to the image display device, it is required to be excellent in such reworkability.

However, the conventional retardation film combining a resin having positive intrinsic birefringence and a resin having negative intrinsic birefringence has poor reworkability. Among them, a retardation film with high reflection suppression capability tends to be significantly inferior in reworkability, and in particular, a thin retardation film is difficult to achieve both the reflection suppression capability and the reworkability.

The present invention is made in view of the aforementioned problems, and aims to provide a retardation film with high reflection suppression capability and excellent reworkability, a method for producing the same, a polarizing plate and an image display device having the retardation film.

The inventors of the present invention have made intensive studies in order to solve the aforementioned problems. As a result, the present inventors discovered that a retardation film provided by combining a layer A formed of a resin A having positive intrinsic birefringence and a layer B formed of a resin B having negative intrinsic birefringence satisfies specific requirements. In this case, the aforementioned problems can be solved, and the present invention can be completed.

That is, the present invention includes the following.

[1] A retardation film comprising one or two or more A layers and one or two or more B layers, wherein the A layer has a slow axis, and the B layer has a phase relative to the above A. The slow axis of the layer sandwiches the slow axis at an angle of 85° to 90°; wherein the aforementioned layer A is formed by resin A with positive inherent birefringence; the aforementioned layer B is formed by resin B with negative inherent birefringence ; The resin B contains at least one polymer selected from the group consisting of polyester, polycarbonate and polyester carbonate; The polymer contains a pyrene skeleton; In the plane of the whole of the layer A with a wavelength of 450 nm Retardation Re (A450), in-plane retardation Re (A550) of the entire A-layer at a wavelength of 550 nm, in-plane retardation Re (B450) of the entire B-layer at a wavelength of 450 nm, and the aforementioned at a wavelength of 550 nm The overall in-plane retardation Re(B550) of the B layer satisfies the following formula (i): |Re(A450)/Re(A550)−Re(B450)/Re(B550)|≧0.10 (i); at a wavelength of 450 The in-plane retardation Re(450) of the retardation film with a wavelength of 550 nm and the in-plane retardation Re(550) of the retardation film with a wavelength of 550 nm satisfy the following formula (ii): 0.60≦Re(450)/Re(550 )≦0.96 (ii); The ratio T _A /TB of the entire thickness T _A of the aforementioned A layer to the aforementioned entire thickness T _B of the _B layer is 30/70 to 65/35.

[2] The retardation film according to [1], wherein the in-plane retardation Re(B450) and Re(B550) of the entire B layer satisfy the following formula (iii). 1.14≦Re(B450)/Re(B550) (iii)

[3] The retardation film according to [1] or [2], wherein the polymer includes a structural unit having a phenyl-9,9-diyl group.

（式中，R ¹表示取代基，k表示0～8的整數，X ^1a及X ^1b分別獨立表示亦可具有取代基的2價之烴基。）所示之茀二羧酸單元及／或由下述式（2）：［化2］

（式中，R ²表示取代基，m表示0～8的整數，X ^2a及X ^2b分別獨立表示亦可具有取代基的2價之烴基，A ^1a及A ^1b分別獨立表示直鏈狀或分枝鏈狀伸烷基，n1及n2表示0以上的整數。）所示之茀二醇單元。 [4] The retardation film according to any one of [1] to [3], wherein the structural unit having a perylene-9,9-diradical includes the following formula (1):

(In the formula, R ¹ represents a substituent, k represents an integer of 0 to 8, and X ^1a and X ^1b each independently represent a divalent hydrocarbon group which may have a substituent.) The perylene dicarboxylic acid unit shown and/or represented by The following formula (2): [Formula 2]

(In the formula, R ² represents a substituent, m represents an integer of 0 to 8, X ^2a and X ^2b each independently represent a divalent hydrocarbon group which may have a substituent, and A ^1a and A ^1b each independently represent a linear or branched Branched alkylene, n1 and n2 represent an integer of 0 or more.) The perylene glycol unit shown.

（式中，Z ^1a及Z ^1b分別獨立表示芳烴環，R ^3a及R ^3b分別獨立表示取代基，p1及p2分別獨立表示0以上的整數，R ²、m、A ^1a及A ^1b、n1及n2分別與前述式（2）相同。）所示之二醇單元。 [5] The retardation film according to [4], wherein the perylene glycol unit contains the following formula (2A):

(In the formula, Z ^1a and Z ^1b each independently represent an aromatic hydrocarbon ring, R ^3a and R ^3b each independently represent a substituent, p1 and p2 each independently represent an integer of 0 or more, R ² , m, A ^1a and A ^1b , n1 and n2 are respectively the same as the diol units represented by the aforementioned formula (2).

[6] The retardation film according to [5], wherein in the diol unit represented by the formula (2A), Z ^1a and Z ^1b are C _{6 -12} aromatic hydrocarbon rings _, and R ^3a and R ^3b are C _{1 -4} alkyl group or C _{6 - 10} aryl group _, p1 and p2 are integers of 0 to 2, A ^1a and A ^1b are straight-chain or branched chain C _{2 - 4} -alkylene groups, n1 and n2 are 0- An integer of 2.

[7] The retardation film according to any one of [4] to [6], wherein in the perylene dicarboxylic acid unit represented by the above formula (1), X ^1a and X ^1b are linear or Branched chain C _{2 - 4} alkylene.

（式中，A ²表示直鏈狀或分枝鏈狀伸烷基，q表示1以上的整數。）所示之烷二醇單元。 [8] The retardation film according to any one of [1] to [7], wherein the resin B further contains the following formula (3):

(In the formula, A ² represents a linear or branched alkylene group, and q represents an integer of 1 or more.) The alkanediol unit shown.

[9] The retardation film according to [8], wherein in the alkanediol unit represented by the formula (3), _A ² is a linear or branched C _{2 -4} alkylene, and q is an integer from 1 to 4.

[10] The retardation film according to any one of [1] to [9], wherein the resin A contains a polymer that does not contain an aromatic ring.

[11] The retardation film according to any one of [1] to [10], wherein the resin A includes a polymer containing an isosorbide skeleton.

[12] The retardation film according to any one of [1] to [11], wherein the in-plane retardation Re(450) and Re(550) of the retardation film satisfy the following formula (iv). Re(450)/Re(550)≦0.91 (iv)

[13] The retardation film according to any one of [1] to [12], wherein the glass transition temperature TgA of the resin A is 100°C or higher and 160°C or lower, The glass transition temperature TgB of the resin B is 100° C. or higher and 160° C. or lower.

[14] The retardation film according to any one of [1] to [13], wherein the difference |TgA-TgB| between the glass transition temperature TgA of the resin A and the glass transition temperature TgB of the resin B is 15° C. the following.

[15] The retardation film according to any one of [1] to [14], wherein the retardation film has a thickness of 90 μm or less.

[16] The retardation film according to any one of [1] to [15], wherein the retardation film has a thickness of 70 μm or less.

[17] A method for producing a retardation film, which is the method for producing a retardation film according to any one of [1] to [16], comprising: A step of preparing a multilayer film including a layer formed of resin A having positive intrinsic birefringence and a layer formed of resin B having negative inherent birefringence; and a step of extending the multilayer film.

[18] The method for producing a retardation film according to [17], wherein the step of preparing the multilayer film includes melt extrusion of the resin A and the resin B.

[19] The method for producing a retardation film according to [17] or [18], wherein the step of stretching the multilayer film includes a temperature of "Tg(h)-10°C" or higher and "Tg(h)+20°C" The stretching is performed at the following stretching temperature (wherein, Tg(h) represents the higher temperature of the glass transition temperature TgA of the resin A and the glass transition temperature TgB of the resin B).

[20] The method for producing a retardation film according to any one of [17] to [19], wherein the step of stretching the multilayer film includes stretching at a stretching ratio of 1.5 times or more and 5.0 times or less.

[21] The method for producing a retardation film according to any one of [17] to [20], wherein the step of stretching the multilayer film includes stretching the multilayer film in an oblique direction.

[22] A polarizing plate comprising the retardation film according to any one of [1] to [16] and a linear polarizer.

[23] An image display device including the retardation film according to any one of [1] to [16].

According to the present invention, it is possible to provide a retardation film having high reflection suppressing ability and excellent reworkability, a method for producing the same, a polarizing plate and an image display device including the retardation film.

Embodiments and examples are disclosed below to describe the present invention in detail. However, the present invention is not limited to the embodiments 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 the scope of its equivalents.

In the following description, the in-plane retardation Re of layers and films having three-dimensional refractive indices nx, ny, and nz represents the value represented by Re=(nx−ny)×d, unless otherwise noted. nx represents the refractive index in the direction perpendicular to the thickness direction (in-plane direction) and in the direction in which the maximum refractive index is given. ny represents the refractive index in the direction orthogonal to the direction of nx, which is the in-plane direction. nz represents the refractive index in the thickness direction. d represents thickness.

The in-plane retardation of a thin film having a plurality of layers having different three-dimensional refractive indices nx, ny, and nz is usually synthesized from the in-plane retardation of each layer. For example, the in-plane retardation of a film formed from a first layer having a slow axis and a second layer having a slow axis perpendicular to the slow axis of the first layer can be expressed as the in-plane retardation of the first layer and the The difference in the in-plane retardation of the second layer. Also, for example, the in-plane retardation of a film formed by a third layer having a slow axis and a fourth layer having a slow axis parallel to the slow axis of the third layer can be expressed as the in-plane retardation of the third layer The sum of the delay and the in-plane delay of the fourth layer.

The specific value of the in-plane retardation was measured using a phase difference meter (“KOBRA-WIST” manufactured by Oji Scientific Instruments Co., Ltd.). Measurement wavelength, unless otherwise noted, is 590 nm.

The so-called slow axis of a layer or film means the slow axis in the in-plane direction of the layer or film unless otherwise noted.

The so-called forward wavelength dispersion property refers to the property that the in-plane retardation Re450 and Re550 satisfies Re450>Re550 at the measurement wavelengths of 450 nm and 550 nm. Generally, the longer the measurement wavelength, the smaller the in-plane retardation of the component with forward wavelength dispersion.

The so-called inverse wavelength dispersion property refers to the property that the in-plane retardation Re450 and Re550 satisfies Re450<Re550 at the measurement wavelengths of 450 nm and 550 nm. Generally, the longer the measurement wavelength, the greater the in-plane retardation of the component with inverse wavelength dispersion.

The angle included by the optical axis (absorption axis, transmission axis, slow axis, etc.) of each layer in a component having a plurality of layers represents the angle when the aforementioned layer is viewed from the thickness direction unless otherwise noted.

The so-called directions of the components are "parallel", "perpendicular" and "orthogonal", unless otherwise noted, they can also be included within the range that does not impair the effect of the present invention (eg ±5°, ±4°, ±3° °, ±2° or ±1°).

"Resin having positive intrinsic birefringence" means a resin whose refractive index in the extending direction becomes higher than the refractive index in the direction orthogonal to the extending direction unless otherwise noted. In addition, the "polymer having positive intrinsic birefringence" means a polymer in which the refractive index in the extending direction becomes higher than the refractive index in the direction orthogonal to the extending direction unless otherwise noted.

"Resin having negative intrinsic birefringence" means a resin whose refractive index in the extending direction becomes smaller than the refractive index in the direction orthogonal to the extending direction unless otherwise noted. The term "polymer having negative intrinsic birefringence" means a polymer whose refractive index in the extending direction becomes smaller than the refractive index in the direction orthogonal to the extending direction unless otherwise noted.

The so-called "strip-shaped" film, unless otherwise noted, refers to a film having a length of 5 times or more relative to the width, preferably 10 times or more in length, and specifically refers to a film with a length that can be recovered. A length of film that is rolled into a roll for storage or handling. The upper limit of the length of the elongated film is not particularly limited, but may be, for example, 100,000 times or less the width.

Unless otherwise noted, "polarizing plate", "circular polarizing plate" and "wavelength plate" include not only rigid members but also flexible members such as resin films.

The so-called cement, unless otherwise noted, includes not only cement in the narrow sense, but also adhesives with a shear storage elastic modulus of less than 1 MPa at 23°C. In addition, the adhesive in a narrow sense refers to an adhesive having a shear storage elastic modulus of 1 MPa to 500 MPa at 23° C. after energy ray irradiation or after heat treatment.

[1. Outline of retardation film]

A retardation film according to an embodiment of the present invention includes one or more A layers formed of resin A having positive intrinsic birefringence, and one or more A layers formed of resin B having negative intrinsic birefringence 2 or more layers of B. The A layer and the B layer are optically anisotropic layers, and accordingly have a slow axis. When the retardation film is viewed from the thickness direction, the slow axis of the A layer is perpendicular to the slow axis of the B layer. Furthermore, resin B contains at least 1 type of polymer chosen from the group which consists of polyester, polycarbonate, and polyester carbonate. This polymer contains a stilbene backbone.

In this embodiment, the difference between the wavelength dispersion properties of the A layer and the wavelength dispersion properties of the B layer is within a specific range. Specifically, the wavelength dispersion of the A layer is represented by Re(A450)/Re(A550). In addition, the wavelength dispersion of the B layer is represented by Re(B450)/Re(B550). In this case, the magnitude of the difference between the wavelength dispersion properties of the A layer and the wavelength dispersion properties of the B layer is represented by |Re(A450)/Re(A550)−Re(B450)/Re(B550)|. In the present embodiment, the magnitude of the difference in wavelength dispersion properties satisfies the following formula (i). ｜Re(A450)/Re(A550)－Re(B450)/Re(B550)｜≧0.10 (i)

Here, Re(A450) represents the in-plane retardation of the entire A-layer at a wavelength of 450 nm. In addition, Re(A550) represents the in-plane retardation of the entire A-layer at a wavelength of 550 nm. When the retardation film is provided with one A layer, the "in-plane retardation of the entire A layer" means the in-plane retardation of the A layer. In addition, when the retardation film includes two or more A layers, the "in-plane retardation of the entire A layer" means the sum of the in-plane retardations of these A layers.

In addition, Re(B450) represents the in-plane retardation of the whole B layer at a wavelength of 450 nm. In addition, Re(B550) represents the in-plane retardation of the entire B layer at a wavelength of 550 nm. When the retardation film includes one B layer, the "in-plane retardation of the entire B layer" refers to the in-plane retardation of the B layer. In addition, when the retardation film includes two or more B layers, the "in-plane retardation of the entire B layer" means the sum of the in-plane retardations of these B layers.

Equation (i) will now be described in further detail. The magnitude of the difference between the wavelength dispersion properties of the A layer and the wavelength dispersion properties of the B layer |Re(A450)/Re(A550)−Re(B450)/Re(B550)| is usually 0.10 or more, preferably 0.12 or more, and 0.14 or more is better. The upper limit is not particularly limited, but is usually 0.8 or less, preferably 0.5 or less, and particularly preferably 0.3 or less. In most cases, the wavelength dispersion property Re(B450)/Re(B550) of the B layer is larger than the wavelength dispersion property Re(A450)/Re(A550) of the A layer, so the wavelength dispersion property of the A layer is larger. The difference "Re(A450)/Re(A550)-Re(B450)/Re(B550)" with the wavelength dispersion property of the B layer may be a negative value.

In this embodiment, the ratio T _A /TB of the overall thickness TA of the _A layer and the overall thickness TB of the _B layer is within _a specific range. Specifically, the thickness ratio _{T A} /TB is usually 30/70 or more, preferably 35/65 or more, more preferably 40/60 or more, and usually 65/35 or less, preferably 60/40 or less good, preferably below 55/45. Here, when the retardation film includes one A layer, the thickness T _A represents the thickness of the A layer. In addition, when the retardation film includes two or more A layers, the thickness T _A represents the sum of the thicknesses of these A layers. In addition, when the retardation film is provided with one B layer, thickness T _B shows the thickness of this B layer. In addition, when the retardation film includes two or more B layers, the thickness T _B represents the sum of the thicknesses of these B layers.

The retardation film of the present embodiment has wavelength dispersion in a specific range. Specifically, the wavelength dispersion of the retardation film is represented by Re(450)/Re(550). Furthermore, the wavelength dispersion Re(450)/Re(550) of the retardation film satisfies the following formula (ii). 0.60≦Re(450)／Re(550)≦0.96 (ii)

Here, Re(450) represents the in-plane retardation of the retardation film at a wavelength of 450 nm. In addition, Re(550) represents the in-plane retardation of the retardation film at a wavelength of 550 nm.

Equation (ii) will now be described in further detail. The wavelength dispersion Re(450)/Re(550) of the retardation film is usually 0.60 or more, preferably 0.70 or more, more preferably 0.80 or more, and usually 0.96 or less, preferably 0.93 or less, preferably 0.92 or less Preferably, it is less than 0.91.

The retardation film of this embodiment, which satisfies the above-mentioned requirements, has high reflection suppressing ability and excellent reworkability. Specifically, when a polarizing plate (usually a circular polarizing plate) is obtained by combining a retardation film with a linear polarizer, the polarizing plate can effectively suppress reflection on the screen of an image display device. In addition, when the retardation film is peeled off after being attached to a member once, the cohesion failure of the retardation film can be effectively suppressed. Thereby, it can suppress that a part of retardation film remains in a member after peeling. Therefore, even when the peeled-off retardation film is bonded to the above-mentioned member again, deterioration in quality can be suppressed.

[2.A floor]

The retardation film includes one or two or more A layers. Layer A has a slow axis. When the retardation film includes two or more A layers, the slow axes of these A layers are usually parallel. Accordingly, when viewed from the thickness direction, the angle between the slow axes of the A layers is usually 0° to 5°, preferably 0° to 4°, preferably 0° to 3° Preferably, it is 0° to 2°, more preferably 0° to 1°, ideally 0°.

Layer A is formed of resin A having positive intrinsic birefringence. Accordingly, the layer A contains the resin A, preferably only the resin A. This resin A is usually a thermoplastic resin. Resin A may contain polymers and optional ingredients as required. Resin A generally has positive intrinsic birefringence by virtue of some or all of the aforementioned polymers having positive intrinsic birefringence.

As a polymer contained in A layer, an alicyclic structure containing polymer is mentioned, for example. The alicyclic structure-containing polymer preferably has positive intrinsic birefringence. The alicyclic structure-containing polymer is a polymer containing an alicyclic structure in the repeating unit, for example, (1) noralkene-based polymer, (2) monocyclic cycloolefin polymer, (3) cyclic copolymer Conjugated diene polymers, (4) ethylene alicyclic hydrocarbon polymers and their hydrogenated products, etc. The aforementioned alicyclic structure-containing polymer can be selected from, for example, polymers disclosed in Japanese Patent Laid-Open No. 2002-321302. Examples of the alicyclic structure-containing polymer include "ZEONOR" manufactured by Zeon Corporation, "ARTON" manufactured by JSR Corporation, and the like. The polymer contained in the A layer preferably contains a hetero atom in the molecule from the viewpoint of reproducibility and adhesion to the B layer.

Moreover, it is preferable that the polymer contained in resin A contains the isosorbide skeleton, and the polycarbonate which contains the isosorbide skeleton is especially preferable. Here, the term "isosorbide skeleton" means a skeleton represented by the following formula (X1). In formula (X1), * represents an atomic bond. The polymer containing an isosorbide skeleton preferably has positive intrinsic birefringence. In the case of using a polymer containing an isosorbide skeleton, especially a polycarbonate containing an isosorbide skeleton, it can effectively improve the adhesion to the layered body of the resin B, the reflection suppression ability of the retardation film, the reproducibility, and the Phase difference change suppression capability when stress is applied.

[Chemical 5]

The polymer contained in the resin A preferably does not contain an aromatic ring. When used in a polymer without an aromatic ring in the molecule, the reflection suppression capability of the retardation film can be effectively improved. In particular, resin A containing a polymer not containing an aromatic ring tends to have a small wavelength dispersive Re(A450)/Re(A550), so it has the same wavelength dispersive Re as containing a ring-containing polyester as described later. (B450)/Re(B550) In the case of the resin B combination of a large polymer, the improvement of the reflection suppression ability is remarkable.

As a polymer which has an isosorbide skeleton, "DURABIO" by Mitsubishi Chemical Corporation is mentioned, for example. In addition, "DURABIO" manufactured by Mitsubishi Chemical Corporation does not contain an aromatic ring in the molecule of the polymer.

A polymer may be used individually by 1 type, and may be used in combination of 2 or more types in arbitrary ratios.

The weight average molecular weight (Mw) of the polymer contained in the resin A is preferably 10,000 or more, preferably 15,000 or more, more preferably 20,000 or more, and preferably 100,000 or less, preferably 80,000 or less, and 50,000 The following are preferred. When the weight average molecular weight is within such a range, the mechanical strength and formability of the A layer can be highly balanced.

The aforementioned weight average molecular weight is the weight average molecular weight in terms of polyisoprene or polystyrene measured by gel permeation chromatography (GPC) using cyclohexane as a solvent. However, toluene can also be used as a solvent when the sample is insoluble in cyclohexane in GPC.

The molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) of the polymer contained in the resin A is preferably 1.2 or more, preferably 1.5 or more, more preferably 1.8 or more, and preferably 3.5 or less. good, preferably below 3.0, particularly preferably below 2.7. When the molecular weight distribution is equal to or more than the lower limit value of the aforementioned range, the productivity of the polymer can be improved, and the production cost can be suppressed. In addition, when the molecular weight distribution is equal to or less than the upper limit value, since the amount of the low molecular weight component becomes small, relaxation during high temperature exposure can be suppressed, and the stability of the A layer can be improved.

The proportion of the polymer in the resin A is preferably 50% by weight to 100% by weight, preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. When the ratio of the polymer is within the aforementioned range, the layer A can obtain sufficient heat resistance and transparency.

Resin A may also further comprise arbitrary components in combination with the polymer. Examples of optional components include stabilizers such as antioxidants, thermal stabilizers, light stabilizers, weather-resistant stabilizers, ultraviolet absorbers, and near-infrared absorbers; plasticizers; and the like. These components may be used alone or in combination of two or more at any ratio.

The glass transition temperature TgA of resin A is preferably 100°C or higher, preferably 110°C or higher, particularly preferably 120°C or higher, and preferably 160°C or lower, preferably 150°C or lower, and 140°C or lower for the best. When the glass transition temperature TgA of the resin A is equal to or more than the lower limit value of the aforementioned range, the heat resistance of the retardation film can be improved. And when the glass transition temperature TgA is below the upper limit of the said range, film formation and drawing in the manufacturing method of a retardation film can be performed smoothly. The glass transition temperature was measured using a differential scanning calorimeter (DSC) with a ramp of 10°C/min. The glass transition temperature of resin A can be adjusted according to the composition of resin A, for example.

The difference between the glass transition temperature TgA of the resin A and the glass transition temperature TgB of the resin B |TgA-TgB| is preferably 15°C or lower, more preferably 10°C or lower, and particularly preferably 8°C or lower. That the glass transition temperature difference |TgA-TgB| is in the aforementioned range means that the glass transition temperature TgA of the resin A and the glass transition temperature TgB of the resin B are close to each other. In this case, when resin A and resin B are co-stretched to manufacture a retardation film, the selection range of the stretching conditions is widened, and it becomes easy to obtain the retardation and thickness of the target retardation film. The glass transition temperature TgA of resin A may be higher or lower than the glass transition temperature TgB of resin B.

The overall in-plane retardation Re (A550) of the A layer with a wavelength of 550 nm is preferably 180 nm or more, preferably 200 nm or more, more preferably 220 nm or more, and preferably 320 nm or less, with 300 nm It is preferably below nm, and particularly preferably below 280 nm. When the overall in-plane retardation Re (A550) of the A layer is within the aforementioned range, both the reflection suppression capability and the reworkability can be particularly optimized.

The difference between the in-plane retardation Re (A550) of the entire A layer at a wavelength of 550 nm and the in-plane retardation Re (B550) of the entire B layer at a wavelength of 550 nm｜Re(A550)−Re(B550)｜ It is better to be in a specific range. The aforementioned specific range is preferably above 90 nm, preferably above 100 nm, particularly preferably above 110 nm, and preferably below 200 nm, preferably below 180 nm, particularly preferably below 160 nm . In the case where the magnitude of the difference in the in-plane retardation |Re(A550)−Re(B550)| is within the aforementioned range, both the reflection suppression capability and the reworkability can be particularly optimized. The overall in-plane retardation Re (A550) of the A layer may be larger or smaller than the overall in-plane retardation Re (B550) of the B layer.

The wavelength dispersion Re(A450)/Re(A550) of the A layer is preferably 0.98 or more, preferably 0.99 or more, more preferably 1.00 or more, more preferably 1.10 or less, preferably 1.06 or less, and 1.04 or less is preferred. In the case where the wavelength dispersion Re(A450)/Re(A550) of the A layer is in the aforementioned range, both the reflection suppressing ability and the reworkability can be particularly optimized. The wavelength dispersion Re(A450)/Re(A550) of the A layer can be adjusted according to the composition of the resin A, for example.

The thickness of one A layer is preferably 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and preferably 100 μm or less, preferably 80 μm or less, and especially 60 μm or less. good. When the thickness of the A layer is equal to or more than the lower limit value of the above-mentioned range, film formation and extension for producing a retardation film having such a thickness of the A layer can be smoothly performed. In addition, when the thickness of the A layer is equal to or less than the upper limit value of the aforementioned range, the thickness of the retardation film can be reduced.

[3.B layer]

The retardation film includes one or two or more B layers. The B layers all have a slow axis. When the retardation film includes two or more B layers, the slow axes of these B layers are usually parallel. Accordingly, when viewed from the thickness direction, the angle between the slow axes of the B layers is usually 0° to 5°, preferably 0° to 4°, preferably 0° to 3° Preferably, it is 0° to 2°, more preferably 0° to 1°, ideally 0°.

When the retardation film is viewed from the thickness direction, the slow axis of the B layer is perpendicular to the slow axis of the A layer. Accordingly, when viewed from the thickness direction, the slow axis of the B layer forms an angle within a specific range with respect to the slow axis of the A layer. Specifically, when viewed from the thickness direction, the angle between the slow axis of the B layer and the slow axis of the A layer is usually 85° to 90°, preferably 86° to 90°, and 87° to 87° to 90°. 90° is preferable, 88° to 90° is more preferable, 89° to 90° is especially preferable, and ideally 90°. When the combination of the slow axis of the A layer and the slow axis of the B layer is two or more sets, the angles between the slow axis of the A layer and the slow axis of the B layer in all combinations are within the aforementioned range. For example, when the retardation film includes two or more A layers and one B layer, since the slow axis of each A layer is combined with the slow axis of the B layer, the slow axis of the A layer and the B layer The combination of slow axes must be two or more. In this case, the angles between the slow axes of the A layers and the slow axes of the B layers in all combinations are within the aforementioned range, and accordingly, the angles between the slow axes of the B layers relative to the slow axes of the A layers are all within the aforementioned range. scope.

Since the slow axis of the A layer is perpendicular to the slow axis of the B layer, the in-plane retardation of the retardation film including the A layer and the B layer usually reflects the difference between the in-plane retardation of the A layer and the in-plane retardation of the B layer. Therefore, in general, the retardation film can have in-plane retardation reflecting the relationship between the wavelength dispersion property of the A layer and the wavelength dispersion property of the B layer represented by the formula (i), so that the retardation film can have the reverse wavelength dispersion property.

The B layer is formed of resin B having negative intrinsic birefringence. Accordingly, the layer B contains the resin B, preferably only the resin B. This resin B is usually a thermoplastic resin. Resin B may contain polymers and optional components as required. Resin B generally has negative intrinsic birefringence by virtue of one of the aforementioned polymers having negative intrinsic birefringence in part or in whole.

The polymer contained in the resin B may be one type or two or more types. Resin B includes at least one polymer selected from the group consisting of polyester, polycarbonate, and polyester carbonate. Such polyesters, polycarbonates and polyestercarbonates preferably have negative intrinsic birefringence. When the resin B contains at least one polymer selected from the group consisting of polyester, polycarbonate and polyester carbonate, the reflection suppression ability and reworkability of the retardation film can be effectively improved.

The aforementioned polymers selected from the group consisting of polyesters, polycarbonates, and polyestercarbonates contain a stilbene skeleton, for example, in a side chain. The aforementioned polymers preferably have negative intrinsic birefringence. In the case where the resin B contains a polymer containing a pyrene skeleton, the reflection suppression ability and reworkability of the retardation film can be effectively improved. Here, the polymer containing a pyrene skeleton in a side chain refers to a polymer containing a structural unit represented by the following (X2).

[Chemical 6]

The polymer contained in the resin B preferably contains a structural unit having a phenyl-9,9-diyl group. In the polymer contained in the resin B, the kind of the structural unit having a phenyl-9,9-diyl group is not limited. For example, the polymer contained in the resin B may also contain a dicarboxylic acid unit (A) having a perylene-9,9-diyl group. The dicarboxylic acid unit (A) represents a structural unit having a structure formed by polymerizing the dicarboxylic acid component (A). In addition, among the dicarboxylic acid units (A), the dicarboxylic acid unit (A) having a perylene-9,9-diyl group may be referred to as "perylenedicarboxylic acid unit (A1)". Furthermore, for example, the polymer contained in the resin B may also contain a diol unit (B) having a perylene-9,9-diyl group. The diol unit (B) represents a structural unit having a structure formed by polymerizing the diol component (B). In addition, among the diol units (B), the diol unit (B) having a perylene-9,9-diyl group may be referred to as "perylene glycol unit (B1)".

As described above, the resin B may contain at least one polyester-based polymer selected from the group consisting of polyester, polycarbonate, and polyestercarbonate. Among these polyester-based polymers, polyester is preferred in terms of moldability and retardation development. Particularly preferred are polyesters containing a pylon skeleton. A polyester containing a perylene skeleton is appropriately called a "perylene ring-containing polyester".

The polyester is usually obtained by polymerizing a polymer component containing a dicarboxylic acid component (A) and a diol component (B). Accordingly, polyesters generally contain dicarboxylic acid units (A) and diol units (B). In the perylene ring-containing polyester, the perylene skeleton may also be contained in a structural unit derived from any of the polymeric components. Accordingly, only the dicarboxylic acid unit (A) may contain a fortium skeleton, only the diol unit (B) may contain a fortium skeleton, or both the dicarboxylic acid unit (A) and the diol unit (B) may contain a fortium skeleton. skeleton. In particular, it is preferable that both the dicarboxylic acid unit (A) and the diol unit (B) contain a perylene skeleton, which can effectively improve the reflection suppression ability and reworkability of the retardation film.

(Dicarboxylic acid unit (A))

The polymer contained in resin B may also contain dicarboxylic acid unit (A). Among them, the polymer contained in the resin B preferably contains a perylene dicarboxylic acid unit (A1). For example, in the case where the resin B contains a polyester, the polyester preferably contains perylene dicarboxylic acid units (A1).

Perylene dicarboxylic acid unit (A1)

As perylene dicarboxylic acid unit (A1), the dicarboxylic acid unit represented by following formula (1) is mentioned, for example.

[Chemical 7]

(In formula (1), R ¹ represents a substituent, k represents an integer of 0 to 8, and X ^1a and X ^1b each independently represent a divalent hydrocarbon group which may have a substituent).

In the aforementioned formula (1), the divalent hydrocarbon group in X ^1a and X ^1b is preferably a divalent alicyclic hydrocarbon group such as a cyclohexylene group or a divalent aliphatic hydrocarbon group, and the divalent aliphatic hydrocarbon group is Excellent. In the case of a divalent alicyclic or aliphatic hydrocarbon group forming X ^1a and X ^1b of the main chain, by combining with the perylene ring structure (perylene-9,9-diyl) of the side chain, the direction of the main chain The refractive index and wavelength dispersion become smaller, and the refractive index and wavelength dispersion in the direction orthogonal to the main chain direction become larger. Therefore, the directional birefringence is negative, and it becomes easy to prepare polymers such as polyesters having cis-wavelength dispersion properties and high wavelength dispersion properties. In particular, when X ^1a and X ^1b are a divalent aliphatic hydrocarbon group, the retardation developability becomes high, and it becomes possible to stretch under more moderate stretching conditions. Furthermore, by improving the toughness (softness) of the polymer, it is possible to form a retardation film that is not easily broken and has excellent formability and handleability. In addition, since thermal shrinkage due to residual stress can be reduced, a thinner retardation film can be formed.

Examples of the divalent aliphatic hydrocarbon group represented by groups X ^1a and X ^1b include straight-chain or branched alkylene, straight or branched alkenylene, straight or branched The branched-chain alkynylene group is preferably a straight-chain or branched-chain alkylene group. Among them, straight _- chain or branched chain C _2-4 alkylene such as ethylidene and _propylidene are preferred, straight _- chain or branched C _2-3 alkylene is preferred _, and Ethylene groups are particularly preferred. Unless otherwise noted, the expression "C _{x - y} " (x and y represent positive integers) before the name of the group indicates that the number of carbon atoms in the group to which the expression is indicated is greater than or equal to x and less than or equal to y. In addition, X ^1a and X ^1b may be different from each other, but are usually the same base.

In the aforementioned formula (1), as the group R ¹ , for example, a non-polymerizable group or a non-reactive substituent which is inert to a polymerization reaction is exemplified. Specific examples of the group R ¹ include a cyano group; a halogen atom such as a fluorine atom, a chlorine atom, and a bromine atom; and a hydrocarbon group such as an alkyl group and an aryl group. As said aryl group _{, C6-10 aryl} groups, such as a phenyl group, etc. are mentioned. Examples of the aforementioned alkyl groups include C _1-12 alkyl groups such as methyl, ethyl, n-propyl, isopropyl, _n -butyl, and tertiary butyl groups, and C _1-8 alkyl groups are preferred, _and C _{1-8 alkyl} groups are preferred. C _1-4 alkyl groups such as _methyl groups are particularly preferred _.

Typical dicarboxylic acid units represented by the aforementioned formula (1) include structural units in which X ^1a and X ^1b are linear or branched C _{2 -6} alkylene _, such as those derived from 9, 9 _- Structural units of 9,9-bis(carboxy C _{2 -6} alkyl) fluoride such as bis(2-carboxyethyl) fluoride, 9,9-bis(2-carboxypropyl) fluoride, etc. These dicarboxylic acid units represented by the aforementioned formula (1) may be used alone, or two or more of them may be used in combination. Among the dicarboxylic acid units represented by the aforementioned formula (1), a structural unit derived from 9,9 _- bis(carboxy C _{2 -6} alkyl) phenylene is preferable, and a structural unit derived from 9,9-bis(carboxy C 2 -6 alkyl) The structural unit of (carboxy C _{2 - 4} alkyl) stilbene is more preferable, to include 9,9-bis(2-carboxyethyl) stilbene, 9,9-bis(2-carboxypropyl) stilbene, etc. 9 , The structural unit of ₉ -bis(carboxy C _{2 -3} alkyl) fluoride is particularly preferred.

2nd dicarboxylic acid unit (A2)

The polymer contained in the resin B may not contain a dicarboxylic acid unit (the second dicarboxylic acid unit (A2)) different from the perylene dicarboxylic acid unit (or the first dicarboxylic acid unit) (A1) as the dicarboxylic acid The unit (A) can be included as required as long as it does not impair the effect of the present invention. For example, when resin B contains polyester, this polyester may also contain 2nd dicarboxylic acid unit (A2).

Examples of the second dicarboxylic acid unit (A2) include those derived from an aromatic dicarboxylic acid component [excluding the perylene dicarboxylic acid component (A1)], an alicyclic dicarboxylic acid component, an aliphatic dicarboxylic acid component, and the like. Structural units.

As the aromatic dicarboxylic acid component, for example, phthalic acid, isophthalic acid, terephthalic acid, 4-methylisophthalic acid, 5-methylisophthalic acid, 1,2-naphthalenedicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, anthracene dicarboxylic acid, phenanthrene dicarboxylic acid Carboxylic acid, 2,2'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, 4,4'-biphenyldicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid, and the like.

Examples of the alicyclic dicarboxylic acid component include 1,4-cyclohexanedicarboxylic acid, decahydronaphthalene dicarboxylic acid, noralkanedicarboxylic acid, adamantane dicarboxylic acid, and tricyclodecane dicarboxylic acid. , cyclohexene dicarboxylic acid, nor alkene dicarboxylic acid and other di- or tricyclic alkene dicarboxylic acids, etc.

As aliphatic dicarboxylic acid components, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, maleic acid, fumaric acid, itonic acid, etc. are mentioned, for example.

These 2nd dicarboxylic acid units (A2) may be independent, or may combine 2 or more types.

The ratio of the perylene dicarboxylic acid unit (A1) can be, for example, 1 mol % or more with respect to the entire dicarboxylic acid unit (A), and specifically can be selected from the range of about 10 mol % to 100 mol %, as A good range, the following stages are 30 mol% or more, 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, 100 mol%—substantially free of the second dicarboxylic acid unit (A2)—is particularly preferred. When the ratio of the perylene dicarboxylic acid unit (A1) is equal to or more than the lower limit value of the aforementioned range, a polymer such as a polyester exhibiting negative directional birefringence and forward wavelength dispersion can be easily obtained.

(diol unit (B))

The polymer contained in the resin B may also contain the diol unit (B). Among them, the polymer contained in the resin B preferably contains a perylene glycol unit (B1). For example, in the case where the resin B comprises a polyester, the polyester preferably comprises perylene glycol units (B1).

Perylene glycol unit (B1)

As the perylene glycol unit (B1), for example, a glycol unit represented by the following formula (2) is mentioned.

[Chemical 8]

(In formula (2), R ² represents a substituent, m represents an integer of 0 to 8, X ^2a and X ^2b each independently represent a divalent hydrocarbon group which may have a substituent, and A ^1a and A ^1b each independently represent a straight chain or branched chain alkylene, n1 and n2 represent an integer of 0 or more).

In the aforementioned formula (2), the substituent represented by R ² and the number of substitution m, including the specific group, the range of the number of substitution, the position of substitution, etc., are the same as those in the aforementioned formula (1), respectively. Among them, the substituent represented by R ¹ and its substitution number k are the same.

In X ^2a and X ^2b , the divalent hydrocarbon group is the same as that of X ^1a and X ^1b in the aforementioned formula (1), for example, divalent lipids such as linear or branched alkylene groups can be exemplified. Divalent alicyclic hydrocarbon group such as cyclohexylene group, divalent aromatic hydrocarbon group such as phenylene group, etc. As a preferable bivalent hydrocarbon group, a bivalent aliphatic hydrocarbon group and a bivalent aromatic hydrocarbon group are mentioned. The types of X ^2a and X ^2b may be different from each other, but are usually the same in many cases.

Examples of the hydrocarbon group represented by R ² include straight-chain or branched chains such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tertiary butyl, and tertiary butyl. Branched C _{1 - 10} alkyl, cyclopentyl, cyclohexyl and other C _{5 - 10} cycloalkyl, phenyl, methylphenyl (or tolyl), dimethylphenyl (or xylyl), etc. C _6-12 aryl groups such as _mono- or tri _- C _1-4 alkyl phenyl, biphenyl, and _naphthyl , _and C _{6-10 aryl} C _1-4 alkyl groups such as benzyl _{and phenethyl .}

Examples of alkylene groups A ^1a and A ^1b include linear chains such as ethylidene, propylidene (1,2-propanediyl), trimethylene, 1,2-butanediyl, and tetramethylene. C _{2 - 6} alkylene in the form of a straight or branched chain, etc., preferably a straight chain or branched C _{2 - 4} alkylene _A C _{2-3 alkylene} group is more preferred, and an ethylidene group is particularly preferred.

The repeating numbers (number of added moles) n1 and n2 of oxyalkylene groups (-OA ^1a -) and (-OA ^1b -) are respectively 0 or more, and can be selected from, for example, an integer range of about 0 to 15, as A good range is 0-10, 0-8, 0-6, 0-4, 0-2, 0-1 in the following steps.

As a representative diol unit represented by the aforementioned formula (2), for example, a diol unit in which X ^2a and X ^2b are linear or branched alkylene groups (hereinafter also simply referred to as dioxane) may be mentioned. perylene glycol unit), the diol unit represented by the formula (2A) described later (hereinafter also simply referred to as a diaryl perylene glycol unit), and the like. These perylene glycol units (B1) may be used alone, or two or more of them may be combined.

Typical examples of dialkyl perylene glycol units include: 9,9-bis(hydroxymethyl) perylene, 9,9-bis(2-hydroxyethyl) perylene, 9,9-bis( Structural units of 9,9-bis(hydroxy straight-chain or branched _- chain C _{1 -6} alkyl) stilbene such as 3-hydroxypropyl) stilbene, 9,9-bis(4-hydroxybutyl) stilbene, etc. These dialkyl perylene glycol units may be used alone, or two or more of them may be combined. Particularly preferred are structural units derived from 9,9-bis(hydroxymethyl) fluoride.

Since the diaryl perylene glycol unit represented by the following formula (2A) is easy to raise the glass transition temperature of the polymer, it can reduce the thermal shrinkage caused by the residual stress and effectively improve the environmental resistance reliability (heat resistance). and water resistance (moisture resistance), dimensional stability to heat or moisture, and retardation stability). That is, the diaryl perylene glycol unit is effective for adjusting the balance between the retardation visibility and wavelength dispersion characteristics, and environmental resistance reliability.

[Chemical 9]

(In formula (2A), Z ^1a and Z ^1b each independently represent an aromatic hydrocarbon ring, R ^3a and R ^3b each independently represent a substituent, p1 and p2 each independently represent an integer of 0 or more, R ² , m, A ^1a and A ^1b , n1 and n2 respectively include good and good aspects, which are the same as those of the aforementioned formula (2).

In the aforementioned formula (2A), examples of the aromatic hydrocarbon rings represented by Z ^1a and Z ^1b include a benzene ring, a naphthalene ring, an indene ring, an anthracene ring, a phenanthrene ring, a biphenyl ring, a phenylnaphthalene ring, and a binaphthyl ring. Base ring and _{bitriphenyl ring, preferably C 6-12 aromatic} hydrocarbon rings such as benzene ring, naphthalene ring, biphenyl ring _, etc. _, preferably C _{6-10 aromatic} hydrocarbon rings such as benzene ring, naphthalene ring, etc., with benzene ring as Excellent.

Examples of the substituents represented by R ^3a and R ^3b include halogen atoms; hydrocarbon groups such as alkyl groups, cycloalkyl groups, aryl groups, and aralkyl groups; alkoxy groups; acyl groups; nitro groups; cyano groups; substituted amines Base et al. Among them, R ^3a and R ^3b are each independently preferably an alkyl group and an aryl group, _and particularly preferably a C _1-4 alkyl group _and a C _{6-10 aryl} group _.

p1 and p2 are each independently preferably 0 or more, more preferably 8 or less, more preferably 4 or less, more preferably 3 or less, and more preferably 2 or less.

As a representative diaryl perylene glycol unit, for example: a diol unit corresponding to 9,9-bis(hydroxyaryl) perylene glycol in which n1 and n2 are 0 in the aforementioned formula (2A); corresponding to n1 and n2 is 1 or more, for example, about 1 to 10 9,9-bis(hydroxy(poly)alkoxyaryl)perylene diol units and the like.

Examples of 9,9-bis(hydroxyaryl)indennes include 9,9-bis(4-hydroxyphenyl)indene, 9,9-bis(4-hydroxy-3-methylphenyl)indene , 9,9-bis(4-hydroxy-3-isopropylphenyl) fluoride, 9,9-bis(4-hydroxy-3,5-dimethylphenyl) fluoride, etc. 9,9-bis[( 9,9-bis(C _{6 - 10} aryl hydroxyphenyl) such as mono- or di) C _{1 - 4} alkylhydroxyphenyl] benzene, 9,9-bis(4-hydroxy-3-phenylphenyl) benzene, etc. ) fluoride, 9,9-bis(6-hydroxy-2-naphthyl) fluoride, 9,9-bis(5-hydroxy-1-naphthyl) fluoride, etc.

Examples of 9,9-bis(hydroxy(poly)alkoxyaryl)perylenes include: 9,9-bis[4-(2-hydroxyethoxy)phenyl]perylenes, 9,9-bis 9,9-bis[ Hydroxy (mono or ten) C _{2 - 4} alkoxyphenyl] fluoride, 9,9-bis[4-(2-hydroxyethoxy)-3-methylphenyl] fluoride, 9,9-bis{ 4-[2-(2-Hydroxyethoxy)ethoxy]-3-methylphenyl}perylene, 9,9-bis[4-(2-hydroxyethoxy)-3,5-dimethyl 9,9-bis[(mono or di)C _{1 - 4} alkylhydroxyl (One or even ten) C _{2 - 4} alkoxy phenyl] pyrene and the like.

Examples of 9,9-bis(arylhydroxy(poly)alkoxyphenyl)perylenes include 9,9-bis[4-(2-hydroxyethoxy)-3-phenylphenyl] Fluorine, 9,9-bis{4-[2-(2-hydroxyethoxy)ethoxy]-3-phenylphenyl}fluorine, 9,9-bis[4-(2-hydroxypropoxy) )-3-phenylphenyl] 9,9-bis[C _{6 - 10} aryl hydroxy (mono or even ten) C _{2 - 4} alkoxyphenyl] benzene, 9,9-bis[6-( 2-Hydroxyethoxy)-2-naphthyl] fluoride, 9,9-bis[5-(2-hydroxyethoxy)-1-naphthyl] fluoride, 9,9-bis{6-[2- 9,9-bis[ Hydroxy (mono or even ten) C _{2 - 4} alkoxy naphthyl] stilbene and the like.

In the perylene glycol unit (B1), the dialkyl perylene glycol unit and the diaryl perylene glycol unit may be used alone, or two or more types may be used in combination.

In addition, the ratio of perylene glycol units (B1) can be selected from the range of, for example, 1 mol% or more, specifically about 10 mol% to 100 mol%, relative to the whole diol unit (B), as a good Range, the following stages are 30 mol% to 100 mol%, 50 mol% to 99 mol%, 60 mol% to 98 mol%, 70 mol% to 97 mol%, 80 mol% ～96 mol%, preferably 85 mol%～95 mol%. When the ratio of the perylene glycol unit (B1) is not less than the lower limit value of the aforementioned range, a polymer such as a polyester exhibiting negative directional birefringence and forward wavelength dispersion can be easily obtained. In addition, when the ratio of the perylene glycol unit (B1) is equal to or less than the upper limit of the aforementioned range, the formability and workability can be optimized.

(poly)alkanediol unit (B2)

The polymer contained in the resin B may also contain the (poly)alkanediol unit (B2) represented by the following formula (3) as the diol unit (B) as required. For example, where resin B comprises a polyester, the polyester may also comprise (poly)alkanediol units (B2). When the (poly)alkanediol unit (B2) is contained, the polymerization reactivity of the polymer can be improved, the molecular weight can be increased, and the toughness can be improved due to the soft chemical structure, so the retardation is excellent in the production of moldability and workability. Thin films are really effective.

[Chemical 10]

(In formula (3), A ² represents a linear or branched alkylene, and q represents an integer of 1 or more).

In the aforementioned formula (3), examples of the alkylene group represented by A ² include ethylidene, propylidene, trimethylene, 1,2-butanediyl, and 1,3-butanediyl. C _{2 - 12} Alkylene etc. Linear or branched C _{2 - 4} alkylene such as ethylidene and propylidene are preferred, straight or branched C _{2 - 3} alkylene is preferred, and ethylidene is preferred. Base is the best.

The repetition number q can be selected from, for example, a range of about 1 to 10, and as a good range, the following steps are 1 to 8, 1 to 6, 1 to 4, 1 to 3, and 1 to 2, with 1 being particularly preferred.

Examples of the diol component corresponding to the (poly)alkanediol unit (B2) include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1,3-butanediol. Diol, butylene glycol (or 1,4-butanediol), 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, 1,10 - Linear or branched C _{2 - 12} alkanes such as decanediol, diethylene glycol, dipropylene glycol, triethylene glycol and other di- or ten straight or branched C _{2 - 12} alkanes Diols etc. These (poly)alkanediol units (B2) may be contained individually, or may be contained in combination of 2 or more types. Particularly preferred are structural units derived from ethylene glycol.

The ratio of the (poly)alkanediol unit (B2) can be selected from the range of about 0 mol % to 100 mol %, for example, 1 mol % to 50 mol % with respect to the whole diol unit (B), as A good range, the following stages are 3 mol% to 30 mol%, 5 mol% to 20 mol%, 7 mol% to 15 mol%, especially 8 mol% to 12 mol% good. When the ratio of the (poly)alkanediol unit (B2) is equal to or less than the upper limit of the aforementioned range, a polymer such as a polyester exhibiting negative directional birefringence and forward wavelength dispersion can be easily obtained. Furthermore, when the ratio of the (poly)alkanediol unit (B2) is equal to or more than the lower limit value of the aforementioned range, the formability and workability can be optimized.

The production method of the polymer is not particularly limited. For example, in the case of producing polyester as a polymer, a conventional method can be used for this production method. For example, the dicarboxylic acid component (A) corresponding to each of the above-mentioned dicarboxylic acid units and the like may be reacted with the diol component (B) corresponding to the above-mentioned diol units, etc., and a transesterification method, a direct polymerization method, etc. may be used. It can be prepared by conventional methods such as melt polymerization, solution polymerization, and interfacial polymerization, but melt polymerization is preferred. In addition, the reaction may be carried out in the presence or absence of a solvent according to the polymerization method. As a specific manufacturing method, for example, the method described in Japanese Patent Laid-Open No. 2017-198956 can be used.

The weight average molecular weight (Mw) of the polymer contained in resin B is preferably 20,000 or more, preferably 25,000 or more, more preferably 30,000 or more, more preferably 35,000 or more, more preferably 40,000 or more, and 50,000 The above is particularly preferable, and 100,000 or less is more preferable, 80,000 or less is more preferable, and 70,000 or less is more preferable. When the weight average molecular weight is in such a range, the production of the B layer by stretching can be smoothly performed.

The proportion of the polymer in the resin B is preferably 50% by weight to 100% by weight, preferably 70% by weight to 100% by weight, and particularly preferably 90% by weight to 100% by weight. When the ratio of the polymer is within the aforementioned range, sufficient heat resistance and transparency can be obtained for the B layer.

Resin B can also further comprise arbitrary components in combination with the polymer. As an arbitrary component, the same example as the arbitrary component which resin A may contain, for example is mentioned. These components may be used alone or in combination of two or more at any ratio.

The glass transition temperature TgB of resin B is preferably 100°C or higher, preferably 110°C or higher, particularly preferably 120°C or higher, and preferably 160°C or lower, preferably 150°C or lower, and 140°C or lower for the best. When the glass transition temperature TgB of the resin B is equal to or more than the lower limit value of the aforementioned range, the heat resistance of the retardation film can be improved. In addition, when the glass transition temperature TgB is below the upper limit of the aforementioned range, film formation and stretching in the method for producing a retardation film can be smoothly performed. The glass transition temperature TgB of the resin B can be adjusted according to the composition of the resin B, for example.

The overall in-plane retardation Re (B550) of the B layer with a wavelength of 550 nm is preferably 60 nm or more, more preferably 80 nm or more, more preferably 100 nm or more, and preferably 180 nm or less, and 160 nm or more. It is preferably below nm, and particularly preferably below 140 nm. When the overall in-plane retardation Re (B550) of the B layer is within the aforementioned range, both the reflection suppression capability and the reworkability can be particularly optimized.

The overall in-plane retardation Re(B450) and Re(B550) of the B layer preferably satisfy the following formula (iii). 1.14≦Re(B450)/Re(B550) (iii)

Specifically, the wavelength dispersion Re(B450)/Re(B550) of the B layer is preferably 1.14 or more, more preferably 1.15 or more, particularly preferably 1.16 or more, more preferably 1.30 or less, and 1.24 or less. Preferably, it is preferably below 1.20. In the case where the wavelength dispersion Re(B450)/Re(B550) of the B layer is in the aforementioned range, both the reflection suppression ability and the reworkability can be optimized in particular. The wavelength dispersion Re(B450)/Re(B550) of the B layer can be adjusted according to the composition of the resin B, for example.

The thickness of one B layer is preferably 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and preferably 100 μm or less, preferably 80 μm or less, and especially 60 μm or less. good. When the thickness of the B layer is equal to or more than the lower limit value of the aforementioned range, film formation and stretching for producing a retardation film having such a thickness of the B layer can be smoothly performed. In addition, when the thickness of the B layer is equal to or less than the upper limit of the aforementioned range, the thickness of the retardation film can be reduced.

[4. Arbitrary layer body]

The retardation film can also have any layer body other than the A layer and the B layer as required. As an example of an arbitrary layer body, the layer body which has optical isotropy is mentioned. A layered body having optical isotropy means a layered body having a small in-plane retardation. The in-plane retardation of the optically isotropic layer body at a wavelength of 550 nm is usually 10 nm or less, preferably 7 nm or less, and more preferably 5 nm or less. As a specific example of an arbitrary layer body, a protective film layer, the adhesive layer which joins each layer body, such as A layer and B layer, etc. are mentioned.

[5. Characteristics of retardation film]

When the above-mentioned retardation film is used in combination with a linear polarizer, a high reflection suppressing ability can be exhibited. The applicant hypothesizes a mechanism by which such a high reflection suppressing ability can be exerted as described below. However, the technical scope of the present invention is not limited to the following mechanisms.

FIG. 1 is a schematic diagram showing an example of the relative relationship between the in-plane retardation ReA of the entire A-layer and the in-plane retardation ReB of the entire B-layer. In FIG. 1 , the horizontal axis represents the wavelength, and the vertical axis represents the magnitude of the in-plane retardation. FIG. 1 illustrates an example in which the in-plane retardation ReA of the entire A layer is larger than the in-plane retardation ReB of the entire B layer.

The in-plane retardation of the combination of the A-layer and the B-layer is represented by the synthesis of the in-plane retardation of the A-layer and the in-plane retardation of the B-layer. When the slow axis of the A layer is perpendicular to the slow axis of the B layer, as shown in FIG. 1 , the in-plane retardation of the combination of the A layer and the B layer is the in-plane retardation of the entire A layer, ReA and the B layer. The difference between ReA and ReB of the in-plane delay ReB. As in the above-mentioned embodiment, when the formula (i) is satisfied by methods such as the selection of the resin A and the selection of the resin B, the slope of the in-plane retardation ReA of the entire A layer and the entire B layer The slopes of the in-plane retardation ReB are different, so the longer the wavelength, the greater the in-plane retardation difference ReA-ReB. Therefore, the combination of the A layer and the B layer exhibits the inverse wavelength dispersion property of "the longer the wavelength, the greater the in-plane retardation". Accordingly, the retardation film including the combination of the A layer and the B layer can have inverse wavelength dispersion properties satisfying the formula (ii). This retardation film with reverse wavelength dispersion can exhibit uniform optical function in a wide range of visible light wavelength region (400 nm to 700 nm), so the polarization state of light passing through the retardation film can be uniformly changed . Therefore, a polarizing plate (usually a circular polarizing plate) provided with the combination of the retardation film and the linear polarizer can effectively suppress the reflection of light in a wide range of the visible light wavelength region. According to this, a high reflection suppression capability can be achieved.

It is excellent in the reworkability of the retardation film described above. The applicant has deduced the mechanism by which such excellent reworkability can be obtained as described below. However, the technical scope of the present invention is not limited to the following mechanisms.

It is assumed that the difference between the inverse wavelength dispersion properties of the resin A and the resin B is small and does not satisfy the formula (i). In this case, the retardation film is required to have a large in-plane retardation of each of the A layer and the B layer in order to express reverse wavelength dispersion. As a method of increasing the in-plane retardation, for example, increasing the degree of orientation of the polymer molecules contained in the resin A and the resin B can be mentioned. The degree of orientation can be increased by stretching at a large stretching ratio or stretching at a low temperature. However, if the degree of orientation of polymer molecules is large, cohesion failure due to delamination becomes easy to occur. If layer A or layer B is delaminated when the retardation film is peeled off after bonding the retardation film to a part once, the damaged part of layer A or layer B may remain on the surface of the part. Accordingly, even if the retardation film is bonded to the member again, desired optical properties cannot be obtained in the portion where a part of the damaged layer A or layer B remains. Accordingly, the reworkability of the thin film that is prone to delamination is poor.

On the other hand, in the retardation film according to the present embodiment, the thickness ratio of the A layer and the B layer falls within a specific value by appropriately combining the resin A having positive intrinsic birefringence and the resin B having negative intrinsic birefringence. The in-plane retardation satisfying the formulas (i) and (ii) can be obtained without excessively increasing the degree of orientation of the polymer molecules. According to this, since delamination accompanying the cohesion failure of the A layer and the B layer is suppressed, excellent reworkability can be obtained.

The retardation film preferably has an in-plane retardation in an appropriate range according to the application. Among them, from the viewpoint of obtaining a polarizing plate with particularly excellent reflection suppression ability in combination with a linear polarizer, the in-plane retardation Re (590) of the retardation film at a measurement wavelength of 590 nm can also be preferably 100 nm or more. More preferably 110 nm or more, more preferably 120 nm or more, and also preferably 180 nm or less, more preferably 170 nm or less, more preferably 160 nm or less. Since the retardation film having the in-plane retardation Re (590) in such a range can function as a quarter-wave plate, it can be combined with a linear polarizer to obtain a circular polarizer.

The total light transmittance of the retardation film is preferably more than 80%, more preferably more than 85%, and more preferably more than 90%. The total light transmittance can be measured in the wavelength range of 400 nm to 700 nm using an ultraviolet/visible light spectrometer.

The haze of the retardation film is preferably 5% or less, preferably 3% or less, particularly preferably 1% or less, and ideally 0%. The haze can be measured using a haze meter in accordance with JIS K7361-1997.

The retardation film preferably has a small photoelastic coefficient from the viewpoint of improving the retardation change suppressing ability when stress is applied. Specifically, the photoelastic coefficient of the retardation film is preferably 30 Brewster or less. The so-called photoelastic coefficient is a value representing the stress dependence of birefringence generated when subjected to stress. Birefringence (difference in refractive index nx-ny) Δn generally has a relationship obtained by the product of stress σ and photoelastic coefficient C (Δn=C·σ). The smaller the absolute value of the photoelastic coefficient is, the better the optical performance can be exhibited even when an impact is given or when it is deformed to fit a display device having a curved display surface.

The measurement of the photoelastic coefficient can be obtained by making a load-Δn curve and its slope. This load-Δn curve can be prepared by performing the following operation to obtain the birefringence value Δn while applying a load to the film in the range of 50 g to 150 g while changing the load. In addition, the measurement of the birefringence value Δn can be obtained by measuring the retardation in the film plane using a retardation measuring device (manufactured by Oji Scientific Instruments Co., Ltd., "KOBRA-21ADH") and dividing it by the thickness of the film.

The retardation film can be a cut film or a long film.

The thickness of the retardation film is preferably 90 μm or less, more preferably 70 μm or less, more preferably 60 μm or less, and particularly preferably 50 μm or less. In the past, it has been particularly difficult to achieve both high reflection suppression capability and excellent reworkability in such a thin retardation film. Accordingly, the retardation film related to the above-mentioned embodiment is useful in that it has high reflection suppressing ability and excellent reworkability and can be thinned. The lower limit of the thickness of the retardation film is not particularly limited, and may be, for example, 10 μm or more, 20 μm or more, 30 μm or more, and the like.

[6. Manufacturing method of retardation film]

The manufacturing method of the retardation film is not limited as long as a desired retardation film can be obtained. For example, the retardation film may also include The first step of preparing a multilayer film having a layer formed by resin A and a layer formed by resin B, and The second step of extending the multilayer film manufacturing method to manufacture. This manufacturing method can easily manufacture the above-mentioned retardation film by controlling the number of steps and simple manufacturing conditions.

[6.1. The first process]

The multilayer film prepared in the first step includes a layer formed of resin A and a layer formed of resin B. In order to distinguish it from the A layer and the B layer included in the retardation film, the "layer body formed of resin A" and the "layer body formed of resin B" before stretching are referred to as "layer (a)" and "Layer (b)".

The layer (a) and the layer (b) included in the multilayer film prepared in the first step must have optical properties different from those of the A layer and the B layer included in the retardation film. Specifically, the layer (a) and layer (b) included in the multilayer film generally do not have large optical anisotropy. Accordingly, the in-plane retardation of the layer (a) and the layer (b) is generally small. In order to give a specific range, the in-plane retardation of the layer (a) and the layer (b) at 550 nm is independently preferably 0 nm to 20 nm, preferably 0 nm to 10 nm, and 0 nm to 0 nm. 5 nm is particularly preferred.

The multi-layer film can also be a film that is cut into sheets, but a long film is preferred. By preparing a multilayer film as a long film, a part or all of each process can be performed on a production line in the case of producing a retardation film, so that it can be produced simply and efficiently.

The manufacturing method of the multilayer film is not limited. Multilayer films can be formed by co-extrusion forming methods such as co-extrusion T-die method, co-extrusion inflation method, co-extrusion lamination method, etc.; co-casting method; coating forming method; dry lamination and other film lamination methods method; and other manufacturing methods to manufacture. Among these, the co-extrusion molding method is preferable from the viewpoint of production efficiency and from the viewpoint of not leaving volatile components such as a solvent in the film. Among the co-extrusion forming methods, the co-extrusion T-die method is preferred. The co-extrusion T-die method includes the feed block method and the multi-manifold method, but the multi-manifold method is particularly preferable in that the variation in thickness of each layer can be reduced.

In the case of producing a multilayer film using a coextrusion method, the first process typically involves melt-extruding resin A and resin B to form layer (a) and layer (b). At this time, the melting temperature of the extruded resin is preferably Tg+80°C or higher, preferably Tg+100°C or higher, and preferably Tg+180°C or lower, preferably Tg+150°C or lower. Here, "Tg" represents the glass transition temperature of resin A and resin B. In addition, the aforementioned melting temperature indicates the melting temperature of the resin in an extruder having a T-die, for example, in the co-extrusion T-die method. When the melting temperature of the extruded resin is equal to or higher than the lower limit value of the aforementioned range, the fluidity of the resin can be sufficiently improved, the moldability can be optimized, and the deterioration of the resin can be suppressed when it is equal to or lower than the upper limit value.

In the co-extrusion molding method, a film-like molten resin extruded from a die gap is usually brought into close contact with a cooling roll, and then cooled and solidified. At this time, as a method of adhering molten resin and a cooling roll, an air knife method, a vacuum box method, an electrostatic adhesion method, etc. are mentioned, for example.

In the case of producing a multilayer film using the coating molding method, the first step usually includes preparing a layer of one of resin A and resin B and applying a layer including the other of resin A and resin B on the prepared layer. coating liquid. The method for preparing the layer of one of the resin A and the resin B is not limited, and for example, it can be prepared using the method described in the bonding method described later.

After the layer body of one of resin A and resin B is prepared, the coating liquid is applied on the layer. The coating liquid usually contains the other of resin A and resin B and a solvent. As the solvent, one that dissolves or disperses the other of resin A and resin B is preferable, and one that dissolves is particularly preferable. The solvent may be used alone or in combination of two or more at any ratio. Examples of the solvent include aromatic solvents such as benzene, toluene, and xylene; ketone solvents such as diacetone alcohol, acetone, cyclopentanone, cyclohexanone, methyl ethyl ketone, and methyl isopropyl ketone; Ester-based solvents such as methyl lactate and ethyl lactate; cycloolefin-based solvents such as cyclohexane, ethylcyclohexane, and 1,2-dimethylcyclohexane; halogen-containing solvents such as dichloromethane and chloroform; tetrahydrofuran, Ether-based solvents such as dioxygen; alcohol-based solvents such as 1-pentanol and 1-butanol. The concentration of the resin in the coating liquid is 1 to 50% by weight from the viewpoint of obtaining a viscosity suitable for coating.

The coating method of the coating liquid is not limited. Examples of the coating method include curtain coating, extrusion coating, roll coating, spin coating, dip coating, bar coating, spray coating, inclined plate coating, printing coating, rotogravure coating, Die coating method, gap coating method and dipping method, etc.

By applying the coating liquid, a film of the coating liquid is formed on the layer of one of the resin A and the resin B. According to this, by drying the coating liquid as needed to remove the solvent, a multilayer film including the layer (a) and the layer (b) can be obtained. The drying method is not limited, and for example, drying methods such as drying by heating and drying under reduced pressure can be used.

Multilayer films can also be fabricated using lamination methods. When a multilayer film is produced using the bonding method, the first step includes a preparation layer (a), a preparation layer (b), and laminating the layer (a) and the layer (b).

The method of preparing layer (a) and layer (b) is not limited. The layer (a) and the layer (b) can be produced by, for example, a melt forming method or a solution casting method, and among them, a melt forming method is preferable. Among the melt forming methods, extrusion forming method, inflation forming method or pressure forming method are preferred, and extrusion forming method is particularly preferred.

The lamination of the layer (a) and the layer (b) may be performed using an adhesive as required. The adhesive is preferably selected according to the types of resin A and resin B. Examples of adhesives include acrylic adhesives, urethane adhesives, polyester adhesives, polyvinyl alcohol adhesives, polyolefin adhesives, modified polyolefin adhesives, polyethylene adhesives Alkyl ether based adhesives, rubber based adhesives, ethylene-vinyl acetate based adhesives, vinyl chloride-vinyl acetate based adhesives, SEBS (styrene-ethylene-butylene-styrene copolymer) based adhesives, SIS (styrene-isoprene-styrene block copolymer) adhesives, vinyl adhesives such as ethylene-styrene copolymers, ethylene-(meth)acrylate copolymers, ethylene-(methyl) ) Acrylic adhesives such as ethyl acrylate copolymer, etc.

In the case of using a bonding agent, a bonding layer is usually formed by the bonding agent between the layer (a) and the layer (b). The average thickness of the bonding layer is preferably 0.1 μm to 10 μm, more preferably 0.5 μm to 5 μm.

[6.2. Second process]

The second process involves extending the multilayer film. By extending in this way, the layer (a) exhibits birefringence and exhibits a slow axis parallel to the extending direction. In addition, the layer (b) exhibits birefringence and exhibits a slow axis perpendicular to the extending direction. Accordingly, according to the aforementioned stretching, a retardation film having an A layer and a B layer having an in-plane retardation and a slow axis satisfying the above-mentioned requirements can be obtained.

The stretching temperature of the multilayer film is preferably "Tg(h)-10°C" or higher, preferably "Tg(h)-5°C" or higher, particularly preferably "Tg(h)°C" or higher, and "Tg(h)°C" or higher. Tg(h)+20°C" or less is preferable, "Tg(h)+15°C" or less is preferable, and "Tg(h)+10°C" or less is more preferable. Here, Tg(h) represents the higher temperature of the glass transition temperature TgA of the resin A and the glass transition temperature TgB of the resin B. When stretching is performed at the stretching temperature in the aforementioned range, a retardation film having particularly excellent reworkability can be obtained.

The stretching ratio of the multilayer film is preferably 1.5 times or more, preferably 1.6 times or more, particularly preferably 1.8 times or more, and preferably 5.0 times or less, preferably 4.0 times or less, and especially 3.0 times or less. good. In the case of stretching at the stretching ratio in the aforementioned range, a retardation film having particularly excellent reworkability can be obtained.

The stretching of the multilayer film can be carried out by a uniaxial stretching method in which stretching is performed in one direction, or by a biaxial stretching method in which extending in two directions.

Examples of the uniaxial stretching method include a method of uniaxially extending in the vertical direction using a difference in peripheral speed between rolls, and a method of uniaxially extending in the transverse direction using a tenter stretching machine.

As the biaxial stretching method, for example, the simultaneous biaxial stretching method, in which the fixed jig is divided into intervals and extended in the longitudinal direction, is extended in the horizontal direction according to the expansion angle of the guide rail; the successive biaxial stretching method is used between the rollers. After the difference of the peripheral speed of 1 is extended in the longitudinal direction, the two edge parts are held by a clamp, and the tenter stretching machine is used to extend in the transverse direction; etc.

In addition, as other stretching methods, there may be mentioned: the diagonal stretching method, which uses a tenter stretching machine that can be operated to apply a feeding force, a stretching force, or a pulling force with different speeds in the horizontal or vertical direction, and the relative stretching machine is used. It extends continuously obliquely at any angle θ in the width direction of the multilayer film. The so-called oblique direction refers to a direction that is neither parallel nor perpendicular to the width direction of the film.

For these stretching methods, for example, a longitudinal uniaxial stretching machine, a tenter stretching machine, a bubble stretching machine, a roll stretching machine, and the like can be used.

Preferably, the second step includes extending the multilayer film in an oblique direction. The retardation film produced through the second process including extending in the oblique direction has a slow axis in the oblique direction. Accordingly, a polarizing plate can be obtained by laminating the retardation film with a general linear polarizer having a transmission axis parallel or perpendicular to the longitudinal direction by a roll-to-roll method. Therefore, a polarizing plate can be efficiently manufactured using the elongated retardation film and the elongated linear polarizer.

[6.3. Arbitrary process]

The manufacturing method of the retardation film may further include any combination of steps to the above-mentioned first step and second step. For example, when an elongated retardation film is obtained using an elongated multilayer film, the manufacturing method of the retardation film may also include a trimming step of cutting the obtained retardation film into a desired shape. According to the trimming step, a cut-out retardation film having a desired shape can be obtained. In addition, the manufacturing method of the retardation film may include, for example, a step of further providing an arbitrary layer body on the retardation film.

[6.4. Other manufacturing methods]

The retardation film can also be produced by a method different from the above-mentioned production method. For example, the phase difference film can be manufactured by a method including the process of preparing the A layer, the process of preparing the B layer, and the process of bonding these A layers and B layers.

The layer A can be produced by a method including, for example, producing the layer (a) by a method such as a melt molding method, a solution casting method, and extending the layer (a). The stretching of the layer (a) is carried out under the same conditions as described in the description of the second step.

The layer B can be produced by, for example, a method including producing the layer (b) by a method such as a melt forming method, a solution casting method, and extending the layer (b). The stretching of the layer (b) is carried out under the same conditions as described in the description of the second step.

The bonding of the A layer and the B layer can also be performed using an adhesive. The type of the adhesive and the thickness of the bonding layer may be the same as the bonding of the layer (a) and the layer (b).

[7. Polarizing plate]

A polarizing plate according to an embodiment of the present invention includes a linear polarizer and a retardation film. The polarizing plate can generally function as a circular polarizing plate, and the reflection of external light can be suppressed by being disposed on the display surface of the image display device.

The polarizing plate may also have a linear polarizer, an A layer and a B layer in sequence. In addition, the polarizing plate may also include a linear polarizer, a B layer, and an A layer in sequence.

In the polarizing plate, it is preferable that the angle between the transmission axis of the linear polarizer and the slow axis of the A layer is in a specific range close to 45°. Specifically, the aforementioned angle is preferably 40° or more, preferably 42° or more, more preferably 43° or more, particularly preferably 44° or more, more preferably 50° or less, preferably 48° or less More preferably, it is 47° or less, more preferably 46° or less.

As the linear polarizer, any linear polarizer must be used. As an example of the linear polarizer, a film obtained by uniaxially extending in a boric acid bath after adsorbing iodine or a dichroic dye on a polyvinyl alcohol film; by adsorbing iodine or a dichroic dye on a The polyvinyl alcohol film is stretched, and a part of the polyvinyl alcohol unit in the molecular chain is further modified into a film obtained by a polyvinyl alcohol unit. Among these, as the linear polarizer, a polarizer containing polyvinyl alcohol is preferable.

If natural light is incident on the linear polarizer, only polarized light in a single direction will penetrate. The degree of polarization of the linear polarizer is not particularly limited, but preferably more than 98%, more preferably more than 99%.

In addition, the thickness of the linear polarizer is preferably 5 μm to 80 μm.

In the above-mentioned polarizing plate, any layer body may be further included. Examples of optional layers include: polarizer protective film layer; bonding layer for bonding linear polarizers and retardation films; hard coat layers such as impact-resistant polymethacrylate resin layers; optimized film smoothness base cushion layer; anti-reflection layer; anti-fouling layer; anti-static layer; etc. Only one layer of these arbitrary layers may be provided, or two or more layers may be provided.

[8. Video display device]

An image display device according to an embodiment of the present invention is provided with the above-mentioned retardation film. Generally, an image display device includes the aforementioned polarizing plate including a retardation film. The polarizing plate is preferably provided in an organic electroluminescence display device (hereinafter sometimes referred to as an "organic EL display device"). This organic EL display device includes a polarizing plate and an organic electroluminescence element (hereinafter sometimes referred to as "organic EL element"). This organic EL display device usually includes a linear polarizer, a retardation film, and an organic EL element in this order.

The organic EL element includes a transparent electrode layer, a light-emitting layer, and an electrode layer in this order, and the light-emitting layer can generate light by applying a voltage from the transparent electrode layer and the electrode layer. As an example of the material which comprises an organic light-emitting layer, the material of a polyparatylene type, a polyphenylene type, and a polyvinyl carbazole type is mentioned. In addition, the light-emitting layer may have a stack of a plurality of layers with different emission colors, or a mixed layer in which a different dye is doped with the layer of a certain dye. Furthermore, the organic EL element may include functional layers such as a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, an equipotential surface forming layer, and a charge generation layer.

The aforementioned image display device can suppress reflection of external light in the display surface. Taking the case where the polarizing plate is a circular polarizing plate as an example, the mechanism of the reflection suppression will be described. The light incident from the outside of the device becomes circularly polarized by only a part of the linearly polarized light passing through the linear polarizer, and then passing through the retardation film. Circularly polarized light is reflected by the constituent elements (such as reflective electrodes in organic EL elements) that reflect light in the image display device, and then passes through the retardation film again, thereby having a vibration orthogonal to the vibration direction of the incident linearly polarized light. direction of the linear polarizer, and becomes not through the linear polarizer. Here, the vibration direction of the linearly polarized light means the vibrational direction of the electric field of the linearly polarized light. Thereby, the function of reflection suppression is achieved.

"Example"

The following examples are disclosed to specifically illustrate the present invention. However, the present invention is not limited to the embodiments disclosed below, and can be arbitrarily modified and implemented without departing from the scope of the patent application of the present invention and its equivalent scope.

In the following description, "%" and "part" indicating the amount are based on weight unless otherwise noted. In addition, unless otherwise noted, the operations described below were performed in the atmosphere at normal temperature and pressure.

[Evaluation method]

(Measurement method of thickness of each layer)

The thickness of each layer was measured using a reflection spectrometer (“FE-3000” manufactured by Otsuka Electronics Co., Ltd.).

(Measurement method for the direction of the slow axis of each layer)

The direction of the slow axis of each layer was measured using a phase difference meter ("KOBRA-WIST" manufactured by Oji Scientific Instruments Co., Ltd.).

(Measurement method of in-plane retardation)

The in-plane retardation was measured using a phase difference meter (“KOBRA-WIST” manufactured by Oji Scientific Instruments Co., Ltd.).

(Measurement method of photoelastic coefficient)

The in-plane retardation of the retardation film was measured while a load was applied to the retardation film in the range of 50 g to 150 g. The measured in-plane retardation was divided by the thickness of the retardation film to obtain the birefringence Δn of the retardation film when the aforementioned load was applied. While changing the load, the operation of obtaining the birefringence value Δn in this manner was performed several times to create a load-Δn curve. The photoelastic coefficient of the retardation film is obtained in the form of the slope of this load-Δn curve.

(Evaluation method of reflection suppression characteristics)

An elongated polarizing plate (“HLC2-5618S” manufactured by SANRITZ, thickness 180 μm) including a protective film, a linear polarizer, and a protective film in this order was prepared. The linear polarizer has a transmission axis in the width direction. The protective film on one side of the polarizing plate was removed, and the retardation film obtained in the example or the comparative example was pasted on this side. The lamination is carried out in such a way that the slow axis of the retardation film and the transmission axis of the linear polarizer sandwich an angle of 45°. In particular, the retardation films of Example 5 and Comparative Example 3 were bonded together by arranging the A layer and the B layer in order from the linear polarizer side. Through the above operations, a polarizing plate sample as a circular polarizing plate, which is sequentially provided with a retardation film, a linear polarizer and a protective film, is obtained.

A commercially available organic EL display device (“OLED55EG9600” manufactured by LG Electronics) provided with an organic EL element and a circular polarizer provided on the viewing side of the organic EL element was prepared. The circular polarizing plate of the organic EL display device was replaced with the above-mentioned polarizing plate sample. When replacing, the polarizing plate samples were arranged in such a manner that the retardation film and the linear polarizer were sequentially arranged from the organic EL element side. In addition, the transmission axis of the linear polarizer included in the polarizer sample of the organic EL display device is located in the same direction as the transmission axis of the linear polarizer of the circular polarizer originally included in the organic EL display device.

While irradiating the display surface of the obtained organic EL display device with a light source, the display surface was observed from the direction (normal line direction) which is the front surface with respect to the display surface. The case where the reflectance of the display surface was significantly suppressed compared to before replacement was judged as "Excellent". The case where the reflectance of the display surface was suppressed compared to that before replacement was determined as "OK". When the reflectance of the display surface was the same or increased as compared with that before replacement, it was evaluated as "defective".

(Evaluation method of adhesion)

An unstretched film (glass transition temperature of 160° C., thickness of 100 μm, manufactured by Zeon Co., Ltd.) was prepared from a resin containing a noralkene-based polymer. Corona treatment was applied to one side of this unstretched film.

Corona treatment was applied to one side of the retardation films obtained in Examples or Comparative Examples. In particular, the retardation films of Example 5 and Comparative Example 3 were subjected to corona treatment on the surface of the A layer side. An adhesive is attached to the corona-treated surface of the retardation film and the corona-treated surface of the unstretched film, and the adhesive-attached surfaces are bonded to each other to cure the adhesive. As the adhesive, an ultraviolet curable adhesive was used. Thereby, the sample film provided with the retardation film and the unstretched film was obtained.

The sample film was cut into a width of 15 mm to obtain a sample sheet. The retardation film side of the sample piece was attached to the surface of the glass slide with an adhesive (double-sided adhesive tape "CS9621" manufactured by Nitto Denko Corporation).

The unstretched film was sandwiched at the front end of the dynamometer and stretched in the normal direction of the surface of the glass slide, thereby implementing a 90-degree peel test. At this time, since the force measured when peeling off the unstretched film is the force required to peel the retardation film and the unstretched film, the magnitude of this force was measured as the peeling strength.

Generally, the larger the peeling strength, the more restrained the damage of the retardation film when the film is reapplied, so the reworkability is excellent. Therefore, in the case where the peel strength was 2.0 N or more, the reworkability was judged to be "excellent". In addition, when the peeling strength was 1.0 N or more and less than 2.0 N, the reworkability was judged to be "ok". In addition, when the peel strength was less than 1.0 N, the reproducibility was judged as "defective".

[Synthesis Example 1]

In FDPM (9,9-bis(2-methoxycarbonylethyl) fluoride) 1.00 mol, BPEF (9,9-bis[4-(2-hydroxyethoxy)phenyl] fluoride, Osaka Gas Chemical (stock) system) 0.90 mol, EG (ethylene glycol) 2.10 mol were added as transesterification catalysts, 2×10 ⁻⁴ mol of manganese acetate tetrahydrate and 8×10 ⁻⁴ mol of calcium acetate monohydrate were added. Heat and melt gradually while stirring. After the temperature was raised to 230°C, 14×10 ⁻⁴ mol of trimethyl phosphate and 20×10 ⁻⁴ mol of germanium oxide were added, and EG was removed while the temperature was gradually increased and the pressure was reduced to 270° C. and 0.13 kPa or less. After reaching the specified stirring torque, the contents were taken out from the reactor to prepare pelylene-containing polyester granules.

The aforementioned FDPM is a dimethyl ester of 9,9-bis(2-carboxyethyl) fluoride (or fluoride-9,9-dipropionic acid). This FDPM was synthesized by comparison, except that tertiary butyl acrylate described in Example 1 of Japanese Patent Laid-Open No. 2005-89422 was changed to methyl acrylate [37.9 g (0.44 mol)].

The obtained particles were analyzed by ¹ H-NMR. As a result, 100 mol % of the dicarboxylic acid units introduced into the perylene ring-containing polyester were derived from FDPM, and 90 mol % of the introduced diol units were derived from BPEF. , 10 mol% is derived from EG.

The glass transition temperature Tg of the obtained perylene ring-containing polyester was 125° C., and the weight average molecular weight Mw was 60,000.

[Example 1]

(1-1. Manufacture of multilayer film)

Prepare a film forming machine including a T-die, a feed module connected to the T-die, an intermediate polymer tube and a polymer filter, and a plurality of uniaxial extruders connected to the feed module.

As resin A, "DURABIO" (a resin containing a polymer containing an isosorbide skeleton and not containing an aromatic ring. Glass transition temperature: 127° C.) manufactured by Mitsubishi Chemical Corporation was prepared. This resin A was supplied to a uniaxial extruder.

As resin B, the perylene ring-containing polyester produced in Synthesis Example 1 was prepared. This resin B was supplied to a uniaxial extruder different from that supplied with resin A.

Using a film forming machine, melt co-extrusion of resin A and resin B was performed. Specifically, resin A and resin B are melted in a uniaxial extruder, respectively, and supplied to a feed module through a polymer tube and a polymer filter. Resin A and Resin B are combined in the feed module, and extruded into a sheet shape on a casting drum through a T-die. The extruded sheet-like resin was cooled on a cooling roller to obtain a long-length multilayer film having a three-layer structure of "layer of resin A/layer of resin B/layer of resin A".

(1-2. Extension of multilayer film)

Using a tensile tester with a constant temperature bath, the multilayer film was uniaxially stretched at the free end along the longitudinal direction under the stretching conditions of a stretching temperature of 135°C and a stretching ratio of 2.0 to obtain a retardation film as a stretched film. The so-called "uniaxial extension of the free end" refers to the extension in a certain direction and does not exert a restraining force in a direction other than the direction in which it is extended. The obtained retardation film has a three-layer structure of "A layer/B layer/A layer", and the ratio of the thickness of these layers is A layer:B layer:A layer=22.5:55:22.5.

The obtained retardation film was evaluated by the method already described above.

(1-3. Measurement of in-plane retardation between A and B layers)

The retardation film was etched from the surface of the retardation film using a dry etching apparatus (“RIE-10NE” manufactured by Samco Inc.). Several samples were taken with the etching time changed every 10 minutes, and the retardation and thickness of the samples were measured respectively. The retardation of each layer was calculated from the amount of change in retardation and thickness.

[Example 2]

By changing the extruded amounts of resin A and resin B, the thickness of the retardation film and the ratio of the thicknesses of the three layers (ie, the A layer and the B layer) included in the retardation film were changed. The thickness ratio is A layer:B layer:A layer=30:40:30. Production and evaluation of the retardation film were performed by the same method as in Example 1 except for the above.

[Example 3]

By changing the extruded amounts of resin A and resin B, the thickness of the retardation film and the ratio of the thicknesses of the three layers (ie, the A layer and the B layer) included in the retardation film were changed. The thickness ratio is A layer:B layer:A layer=17.5:65:17.5. In addition, the stretching method of the multilayer film was changed from free-end uniaxial stretching to diagonal stretching using a tenter stretching machine. In the aforementioned oblique stretching, by adjusting the angle between the traveling direction of the multilayer film supplied to the tenter stretching machine and the traveling direction of the retardation film sent from the tenter stretching machine (slope angle), the multilayer film is stretched along the It extends in the extension direction at an angle of 45° with respect to its width direction. Production and evaluation of the retardation film were performed by the same method as in Example 1 except for the above.

[Example 4]

(4-1. Manufacture of multilayer film)

As resin B, an elongated unstretched film formed of the perylene ring-containing polyester produced in Synthesis Example 1 was prepared.

As the resin A, "ARTON" (a resin containing a polar group-containing alicyclic structure-containing polymer. Glass transition temperature of 130° C.) manufactured by JSR Corporation was prepared. Resin A was dissolved in cyclohexane to obtain a solution having a concentration of 20% by weight. This solution of resin A was applied to one side of the unstretched film formed of resin B using a coating blade and dried to form a layer of resin A. Drying was performed using a drying machine under the conditions of a drying temperature of 120° C. and a drying time of 2 minutes. After that, on the other side of the unstretched film formed of the resin B, the solution of the resin A was applied and dried in the same manner to form a layered body of the resin A. Through the above operation, a long-length multilayer film having a three-layer structure of "layer of resin A/layer of resin B/layer of resin A" was obtained.

(4-2. Extension of multilayer film)

The above-mentioned multilayer film was subjected to uniaxial stretching of the free end along the longitudinal direction using a tensile tester with a constant temperature bath under the conditions of stretching temperature of 135°C and stretching ratio of 2.5 times, to obtain a retardation film as a stretched film. The obtained retardation film has a three-layer structure of "A layer/B layer/A layer", and the ratio of the thickness of these layers is A layer:B layer:A layer=22.5:55:22.5.

The obtained retardation film was evaluated by the method already described above.

(4-3. Measurement of in-plane retardation between A layer and B layer)

The retardation film was etched from the surface of the retardation film using a dry etching apparatus (“RIE-10NE” manufactured by Samco Inc.). Several samples were taken whose etching time was changed every 10 minutes, and the retardation and thickness of the samples were measured respectively. The retardation of each layer was calculated from the amount of change in retardation and thickness.

[Example 5]

(5-1. Fabrication of Layer A)

Prepare a film forming machine with a T-die, a uniaxial extruder connected to the T-die, an intermediate polymer tube, and a polymer filter.

As the resin A, "ZEONOR" (a resin containing a polymer containing an alicyclic structure that does not contain a polar group. Glass transition temperature: 126°C), manufactured by Zeon Corporation, was prepared. This resin A was supplied to a uniaxial extruder and melt-extruded. Specifically, the resin A is melted in a uniaxial extruder, passed through a polymer tube and a polymer filter, supplied to a T-die, and extruded into a sheet shape on a casting drum through the T-die. The extruded sheet-like resin was cooled on a cooling roll to obtain a single-layer pre-stretching film formed of the resin A.

The above-mentioned pre-stretching film was subjected to free-end uniaxial stretching in the longitudinal direction using a tensile tester with a constant temperature bath under the stretching conditions of stretching temperature of 135°C and stretching ratio of 2.5 times, to obtain layer A as a stretched film. The in-plane retardation of the A layer was measured by the above-mentioned measurement method.

(5-2. Fabrication of Layer B)

In place of resin A, the perylene ring-containing polyester produced in Synthesis Example 1 was used as resin B. Furthermore, by changing the rotational speed of the casting drum, the thickness of the film before stretching was changed. Except for the above matters, by the same method as the above-mentioned step (5-1), the B layer, which is a stretched film, is produced. The in-plane retardation of the B layer is measured by the above-mentioned measurement method.

(6-3. Lamination of layer A and layer B)

Prepare the double-sided adhesive tape "CS9621" manufactured by Nitto Denko Co., Ltd. as the adhesive. The adhesive is an optically isotropic adhesive and thus has no in-plane retardation. The A-layer and the B-layer are bonded together through the intermediary of the adhesive to obtain a retardation film. The above-mentioned bonding is performed so that the extending direction of the A layer and the extending direction of the B layer are parallel. The obtained retardation film had a three-layer structure of "layer A/layer of adhesive/layer B", and the thickness ratio of layer A and layer B was layer A:layer B=45:55. Also, the thickness of the adhesive layer was 10 μm.

The obtained retardation film was evaluated by the method already described above.

[Comparative Example 1]

As the resin B, "XIRAN" (polystyrene-containing resin; glass transition temperature: 130° C.) manufactured by POLYSCOPE was prepared in place of the perylene ring-containing polyester prepared in Synthesis Example 1. In addition, by changing the extruded amounts of the resin A and the resin B, the thickness of the retardation film was changed. In addition, the stretching conditions of the multilayer film were changed to a stretching temperature of 130° C. and a stretching ratio of 2.5 times. Production and evaluation of the retardation film were performed by the same method as in Example 1 except for the above.

[Comparative Example 2]

As the resin B, "XIRAN" manufactured by POLYSCOPE was used instead of the perylene ring-containing polyester produced in Synthesis Example 1. Furthermore, by changing the extruded amounts of the resin A and the resin B, the thickness of the retardation film and the ratio of the thicknesses of the three layers (that is, the A layer and the B layer) included in the retardation film were changed. The thickness ratio is A layer:B layer:A layer=20:60:20. In addition, the stretching conditions of the multilayer film were changed to a stretching temperature of 130° C. and a stretching ratio of 3.5 times. Production and evaluation of the retardation film were performed by the same method as in Example 1 except for the above.

[Comparative Example 3]

As resin A, "DURABIO" manufactured by Mitsubishi Chemical Corporation was used instead of "ZEONOR" manufactured by Japan Zeon Corporation. Furthermore, by changing the extruded amounts of the resin A and the resin B, the thicknesses of the A layer and the B layer were changed. In addition, the stretching ratio of the film before stretching was changed to 2.0 times. Moreover, the extending direction of the A layer and the extending direction of the B layer are perpendicular to each other, and the bonding of the A layer and the B layer is performed. Production and evaluation of the retardation film were performed by the same method as in Example 5 except for the above.

[Comparative Example 4]

By changing the extruded amounts of resin A and resin B, the thickness of the retardation film and the ratio of the thicknesses of the three layers (ie, the A layer and the B layer) included in the retardation film were changed. The thickness ratio is A layer:B layer:A layer=10:80:10. Production and evaluation of the retardation film were performed by the same method as in Example 1 except for the above.

[Comparative Example 5]

By changing the extruded amounts of resin A and resin B, the thickness of the retardation film and the ratio of the thicknesses of the three layers (ie, the A layer and the B layer) included in the retardation film were changed. The thickness ratio is A layer:B layer:A layer=35:30:35. Production and evaluation of the retardation film were performed by the same method as in Example 1 except for the above.

[result]

The results in the above-mentioned Examples and Comparative Examples are disclosed in the following table. In the table below, the abbreviations have the following meanings.

The relationship of the slow axis: the relationship between the slow axis of the A layer and the slow axis of the B layer.

Thickness ratio ( _TA /TB ₎ : the ratio of the overall thickness TA of the _A layer to the overall thickness TB of the _B layer, _TA / _TB .

ΔRe450/Re550:｜Re(A450)/Re(A550)－Re(B450)/Re(B550)｜

"Table 1" [Table 1. Results of Examples] Example 1 2 3 4 5 Film manufacturing Resin A DURABIO DURABIO DURABIO ARTON ZEONOR Resin B Synthesis Example 1 Synthesis Example 1 Synthesis Example 1 Synthesis Example 1 Synthesis Example 1 Film production method co-extrusion co-extrusion co-extrusion coating fit extend extension method free uniaxial free uniaxial oblique free uniaxial free uniaxial Elongation ratio [times] 2.0 2.0 2.0 2.5 2.5 Extension temperature [℃] 135 135 135 135 135 The relationship between the A layer and the B layer of the retardation film Layer structure A/B/A A/B/A A/B/A A/B/A A/B slow axis Orthogonal Orthogonal Orthogonal Orthogonal Orthogonal Thickness ratio (T _A /T _B ) 45/55 60/40 35/65 45/55 45/55 Re(A450)/Re(A550) 1.03 1.03 1.03 1.02 1.01 Re(B450)/Re(B550) 1.17 1.17 1.17 1.17 1.17 ΔRe450/Re550 0.14 0.14 0.14 0.15 0.16 Characteristics of retardation films Thickness [μm] 45 35 80 45 40 Re(590)[nm] 140 140 140 140 140 Re(450)/Re(550) 0.88 0.91 0.82 0.91 0.90 Photoelastic coefficient [Brewster] twenty one 18 twenty three 18 18 Reflection suppression characteristics excellent excellent excellent excellent excellent peel strength 2.4 2.3 2.4 1.4 1.3 Heavy-duty excellent excellent excellent Can Can

"Table 2" [Table 2. Results of Comparative Example] Comparative example 1 2 3 4 5 Film manufacturing Resin A DURABIO DURABIO DURABIO DURABIO DURABIO Resin B XIRAN XIRAN Synthesis Example 1 Synthesis Example 1 Synthesis Example 1 Film production method co-extrusion co-extrusion fit co-extrusion co-extrusion extend extension method free uniaxial free uniaxial free uniaxial free uniaxial free uniaxial Elongation ratio [times] 2.5 3.5 2.0 2.0 2.0 Extension temperature [℃] 130 130 135 135 135 The relationship between the A layer and the B layer of the retardation film Layer structure A/B/A A/B/A A/B A/B/A A/B/A slow axis Orthogonal Orthogonal parallel Orthogonal Orthogonal Thickness ratio (T _A /T _B ) 45/55 40/60 45/55 20/80 70/30 Re(A450)/Re(A550) 1.03 1.03 1.03 1.03 1.03 Re(B450)/Re(B550) 1.06 1.06 1.17 1.17 1.17 ΔRe450/Re550 0.03 0.03 0.14 0.14 0.14 Characteristics of retardation films Thickness [μm] 100 100 50 200 30 Re(590)[nm] 140 140 140 140 140 Re(450)/Re(550) 0.99 0.93 1.06 1.60 1.00 Photoelastic coefficient [Brewster] 11 11 twenty one 26 16 Reflection suppression characteristics bad Can bad bad bad peel strength 1.5 0.7 1.7 2.1 1.8 Heavy-duty Can bad Can Can Can

ReA: Overall in-plane retardation of layer A ReB: Overall in-plane retardation of layer B

<FIG. 1> FIG. 1 is a schematic diagram showing an example of the relative relationship between the in-plane retardation ReA of the entire A-layer and the in-plane retardation ReB of the entire B-layer.

none.

Claims (23)

A retardation film comprising one or two or more A layers and one or two or more B layers, wherein the A layer has a slow axis, and the B layer has a slow axis relative to the A layer. The axis clamps the slow axis at an angle of 85° to 90°; wherein the aforementioned layer A is formed of resin A with positive intrinsic birefringence; the aforementioned layer B is formed of resin B with negative intrinsic birefringence; the aforementioned resin B contains at least one polymer selected from the group consisting of polyester, polycarbonate and polyester carbonate; the aforementioned polymer contains a pyrene skeleton; the entire in-plane retardation Re ( A450), the in-plane retardation Re (A550) of the whole of the aforementioned A-layer at a wavelength of 550 nm, the in-plane retardation Re of the whole of the aforementioned B-layer at a wavelength of 450 nm (B450), and the aforementioned B-layer at a wavelength of 550 nm. The overall in-plane retardation Re(B550) satisfies the following formula (i):｜Re(A450)/Re(A550)−Re(B450)/Re(B550)｜≧0.10 (i); The in-plane retardation Re(450) of the retardation film and the in-plane retardation Re(550) of the retardation film at a wavelength of 550 nm satisfy the following formula (ii): 0.60≦Re(450)/Re(550)≦0.96 (ii); _The ratio T _A /TB of the thickness TA of the whole of the aforementioned _A layer to the thickness TB of the whole of the aforementioned _B layer is 30/70 to 65/35. The retardation film according to claim 1, wherein the in-plane retardation Re(B450) and Re(B550) of the entire B layer satisfy the following formula (iii): 1.14≦Re(B450)/Re(B550) ( iii). The retardation film according to claim 1, wherein the polymer comprises a structural unit having a phenyl-9,9-diyl group. The retardation film according to claim 1, wherein the aforementioned structural unit having fluoride-9,9-diradical comprises the following formula (1): [Chemical 1]

(in the formula, R ¹ represents a substituent, k represents an integer of 0 to 8, and X ^1a and X ^1b each independently represent a divalent hydrocarbon group which may have a substituent) The perylene dicarboxylic acid unit represented by the following and/or Formula (2): [Formula 2]

(In the formula, R ² represents a substituent, m represents an integer of 0 to 8, X ^2a and X ^2b each independently represent a divalent hydrocarbon group which may have a substituent, and A ^1a and A ^1b each independently represent a linear or branched branched alkylene, n1 and n2 represent the perylene glycol unit represented by an integer of 0 or more). The retardation film according to claim 4, wherein the perylene glycol unit comprises the following formula (2A): [Chem. 3]

(In the formula, Z ^1a and Z ^1b each independently represent an aromatic hydrocarbon ring, R ^3a and R ^3b each independently represent a substituent, p1 and p2 each independently represent an integer of 0 or more, R ² , m, A ^1a and A ^1b , n1 and n2 is the same as the diol unit represented by the aforementioned formula (2), respectively. The retardation film according to claim ₅ , wherein in the diol unit represented by the formula (2A), Z ^1a and Z ^1b are C _6-12 aromatic hydrocarbon rings _, and R ^3a _and R ^3b are C _{1-4 alkanes} group or C _{6 - 10} aryl group, p1 and p2 are integers of 0 to 2, A ^1a and A ^1b are linear or branched C _{2 - 4} alkylene groups, n1 and n2 are integers of 0 to 2 . The retardation film according to claim 4, wherein in the perylene dicarboxylic acid unit represented by the aforementioned formula (1), X ^1a _and X ^1b are linear or branched C _{2 -4} alkylene groups . The retardation film according to claim 1, wherein the polymer further comprises the following formula (3): [Chemical 4]

(in the formula, A ² represents a linear or branched alkylene group, and q represents an integer of 1 or more) alkanediol unit. The retardation film according to claim 8, wherein in the alkanediol unit represented by the formula (3), A ² is a linear or branched C _{2 -4} alkylene, and q is 1 _to 4 An integer of 4. The retardation film according to claim 1, wherein the aforementioned resin A comprises a polymer that does not contain an aromatic ring. The retardation film according to claim 1, wherein the resin A includes a polymer containing an isosorbide skeleton. The retardation film according to claim 1, wherein the in-plane retardation Re(450) and Re(550) of the retardation film satisfy the following formula (iv): Re(450)/Re(550)≦0.91 (iv ). The retardation film according to claim 1, wherein the glass transition temperature TgA of the resin A is 100°C or higher and 160°C or lower, and the glass transition temperature TgB of the resin B is 100°C or higher and 160°C or lower. The retardation film according to claim 1, wherein the difference |TgA-TgB| between the glass transition temperature TgA of the resin A and the glass transition temperature TgB of the resin B is 15°C or less. The retardation film according to claim 1, wherein the retardation film has a thickness of 90 μm or less. The retardation film according to claim 1, wherein the retardation film has a thickness of 70 μm or less. A method for producing a retardation film, which is the method for producing a retardation film as described in any one of claims 1 to 16, comprising: preparing a layer body formed of a resin A having positive intrinsic birefringence and A step of forming a multilayer film of a layered body from resin B having negative intrinsic birefringence; and a step of extending the aforementioned multilayer film. The method for producing a retardation film according to claim 17, wherein the step of preparing the multilayer film comprises melt-extruding the resin A and the resin B. The method for producing a retardation film according to claim 17, wherein the step of stretching the multilayer film includes stretching at a stretching temperature of "Tg(h)-10°C" or higher and "Tg(h)+20°C" or lower ( Here, Tg(h) represents the higher temperature of the glass transition temperature TgA of the resin A and the glass transition temperature TgB of the resin B). The method for producing a retardation film according to claim 17, wherein the step of stretching the multilayer film includes stretching at a stretching ratio of 1.5 times or more and 5.0 times or less. The manufacturing method of the retardation film according to claim 17, wherein the step of extending the multilayer film comprises extending the multilayer film in an oblique direction. A polarizing plate comprising the retardation film according to any one of claims 1 to 16 and a linear polarizer. An image display device comprising the retardation film according to any one of claims 1 to 16.

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