Phase difference film and method for manufacturing the same

Abstract

This invention relates to a retardation film comprising: an A layer having a slow axis, and a B layer having a slow axis at an angle of 85° to 90° to the slow axis of the A layer; the A layer is formed of a resin A having positive intrinsic birefringence; the B layer is formed of a resin B having negative intrinsic birefringence; the resin B comprises polyester, polycarbonate, or polyester carbonate, wherein the polyester, polycarbonate, or polyester carbonate contains a fluorene framework; the overall in-plane retardation of the A layer and the overall in-plane retardation of the B layer satisfy a specific relationship; the in-plane retardations Re(450) and Re(550) of the retardation film at wavelengths of 450 nm and 550 nm satisfy a specific relationship; the overall thickness T of the A layer... A The overall thickness T of layer B B The ratio of T A / T B It ranges from 30 / 70 to 65 / 35.

Description

Technical Field

[0001] This invention relates to a phase difference film and its manufacturing method. Background Technology

[0002] Phase retardation films are sometimes provided in image display devices (Patent Document 1). Among such phase retardation films, there are multilayer phase retardation films having a structure including two or more layers (Patent Documents 2-3).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2002-40258;

[0006] Patent Document 2: Japanese Patent Application Publication No. 2017-177342;

[0007] Patent document 3: Japanese Patent Application Publication No. 2018-128568. Summary of the Invention

[0008] The problem the invention aims to solve

[0009] In image display devices, circular polarizers are sometimes used to reduce the reflection of ambient light on the display surface. Such circular polarizers typically use a film that combines a linear polarizer and a retardation film. However, almost all existing retardation films exhibit positive wavelength dispersion. Therefore, existing circular polarizers are mostly able to reduce the reflection of ambient light within a specific narrow wavelength range, but struggle to reduce the reflection of ambient light beyond that range, thus sometimes failing to achieve sufficiently high reflection suppression capabilities.

[0010] To improve reflection suppression, a retardation film with anti-wavelength dispersion can be considered for application on a circular polarizer. Such a retardation film can be a combination of a resin with positive intrinsic birefringence and a resin with negative intrinsic birefringence. This retardation film typically exhibits anti-wavelength dispersion by utilizing the difference between the in-plane retardation exhibited by the resin with positive intrinsic birefringence and the in-plane retardation exhibited by the resin with negative intrinsic birefringence. Specifically, the longer the measurement wavelength, the greater the difference in in-plane retardation, thereby achieving anti-wavelength dispersion.

[0011] However, the phase retardation film, which combines a resin with positive intrinsic birefringence and a resin with negative intrinsic birefringence, as shown below, tends to have poor reprocessability.

[0012] Sometimes, it is required that after the retardation film is initially bonded to a component, it be peeled off and re-bonded to the same component. The property of being able to easily peel off and re-bond a component is called "reworkability." For example, excellent reworkability is required when, after bonding a retardation film to an image display device, the film needs to be peeled off and re-bonded.

[0013] However, existing retardation films, which combine resins with positive intrinsic birefringence and resins with negative intrinsic birefringence, have poor reprocessability. In particular, retardation films with high reflection suppression capabilities tend to experience a significant deterioration in reprocessability, and it is especially difficult to achieve both reflection suppression capability and reprocessability in thin retardation films.

[0014] The present invention is made in view of the above-mentioned problems, and its object is to provide: a phase retardation film with high reflection suppression capability and excellent reprocessability, and a method for manufacturing the same; as well as a polarizer and an image display device having the phase retardation film.

[0015] Solution for solving the problem

[0016] In order to solve the above-mentioned problems, the inventors conducted in-depth research. As a result, the inventors discovered that the above-mentioned problems can be solved when a phase retardation film composed of a layer A formed of resin A with positive intrinsic birefringence and a layer B formed of resin B with negative intrinsic birefringence meets specific requirements, thereby completing the present invention.

[0017] That is, the present invention includes the following contents.

[0018] [1] A phase retardation film comprising: one or more A layers having a slow axis, and one or more B layers having a slow axis at an angle of 85° to 90° to the slow axis of the A layers.

[0019] The aforementioned layer A is formed of resin A, which has positive intrinsic birefringence.

[0020] The aforementioned layer B is formed of resin B, which has negative intrinsic birefringence.

[0021] The aforementioned resin B comprises at least one polymer selected from polyester, polycarbonate, and polyester carbonate.

[0022] The above polymer contains a fluorene backbone.

[0023] The in-plane delay Re(A450) of the entire A layer at wavelength 450 nm, the in-plane delay Re(A550) of the entire A layer at wavelength 550 nm, the in-plane delay Re(B450) of the entire B layer at wavelength 450 nm, and the in-plane delay Re(B550) of the entire B layer at wavelength 550 nm satisfy the following equation (i):

[0024] |Re(A450) / Re(A550)-Re(B450) / Re(B550)|≥0.10 (i),

[0025] The in-plane delay Re(450) of the aforementioned retardation film at a wavelength of 450 nm and the in-plane delay Re(550) of the aforementioned retardation film at a wavelength of 550 nm satisfy the following equation (ii):

[0026] 0.60≤Re(450) / Re(550)≤0.96 (ii),

[0027] The overall thickness T of layer A above A The thickness T of layer B as a whole B The ratio of T A / T B It ranges from 30 / 70 to 65 / 35.

[0028] [2] According to the phase retardation film described in [1], wherein the in-plane delay Re(B450) and Re(B550) of the entire B layer satisfy the following equation (iii):

[0029] 1.14≤Re(B450) / Re(B550) (iii).

[0030] [3] The phase difference film according to [1] or [2], wherein the polymer comprises structural units having fluorene-9,9-dimer.

[0031] [4] The phase difference film according to any one of [1] to [3], wherein the above-mentioned structural unit having fluorene-9,9-diyl comprises a fluorene dicarboxylic acid unit represented by the following formula (1) and / or a fluorene diol unit represented by the following formula (2), wherein formula (1) is:

[0032] [Chemical Formula 1]

[0033]

[0034] (where R is in the formula) 1 Indicates a substituent, k represents an integer from 0 to 8, and X... 1a and X 1b (Each can independently represent a divalent hydrocarbon group capable of having substituents)

[0035] Equation (2) is as follows:

[0036] [Chemical Formula 2]

[0037]

[0038] (where R is in the formula) 2 Indicates a substituent, m represents an integer from 0 to 8, X 2a and X 2b Each of these groups independently represents a divalent hydrocarbon group capable of having substituents, A. 1a and A 1b Each of these independently represents a straight-chain or branched alkylene group, with n1 and n2 representing integers greater than or equal to 0.

[0039] [5] According to the phase difference film of [4], wherein the above-mentioned fluorene diol unit comprises a diol unit represented by the following formula (2A), which is:

[0040] [Chemical Formula 3]

[0041]

[0042] (where Z) 1a and Z 1b Each of the aromatic rings is represented independently, R 3a and R 3b Let p1 and p2 represent substituents independently, and let R represent integers greater than or equal to 0 independently. 2 m, A 1a and A 1b n1 and n2 are the same as in equation (2) above.

[0043] [6] According to the phase difference film described in [5], wherein, in the diol unit represented by formula (2A), Z 1a and Z 1b C 6-12 Aromatic ring, R 3a and R 3b C 1-4 Alkyl or C 6-10 aryl, p1 and p2 are integers from 0 to 2, A 1a and A 1b C is either linear or branched. 2-4 Alkylene, n1 and n2 are integers from 0 to 2.

[0044] [7] The phase difference film according to any one of [4] to [6], wherein, in the fluorene dicarboxylic acid unit represented by the above formula (1), X 1a and X 1b C is either linear or branched. 2-4 Alkylene.

[0045] [8] The phase difference film according to any one of [1] to [7], wherein the resin B further comprises an alkylene glycol unit represented by the following formula (3):

[0046] [Chemical Formula 4]

[0047]

[0048] (where A is in the formula) 2 Indicates a straight-chain or branched alkylene group, where q represents an integer greater than or equal to 1.

[0049] [9] According to the phase difference film described in [8], wherein, in the alkylene glycol unit represented by formula (3), A 2 C is either linear or branched. 2-4 Alkylene, where q is an integer from 1 to 4.

[0050]

[10] The phase difference film according to any one of [1] to [9], wherein the resin A comprises a polymer without aromatic rings.

[0051]

[11] The phase difference film according to any one of [1] to

[10] , wherein the resin A comprises a polymer containing an isosorbide backbone.

[0052]

[12] The phase retardation film according to any one of [1] to

[11] , wherein the in-plane delays Re(450) and Re(550) of the phase retardation film satisfy the following equation (iv):

[0053] Re(450) / Re(550)≤0.91 (iv).

[0054]

[13] The phase retardation film according to any one of [1] to

[12] , wherein the glass transition temperature TgA of the above-mentioned resin A is 100°C or higher and 160°C or lower.

[0055] The glass transition temperature (TgB) of the above-mentioned resin B is above 100°C and below 160°C.

[0056]

[14] The phase difference film according to any one of [1] to

[13] , wherein the difference |TgA-TgB| between the glass transition temperature TgA of the above resin A and the glass transition temperature TgB of the above resin B is 15°C or less.

[0057]

[15] The phase retardation film according to any one of [1] to

[14] , wherein the thickness of the phase retardation film is 90 μm or less.

[0058]

[16] The phase retardation film according to any one of [1] to

[15] , wherein the thickness of the phase retardation film is 70 μm or less.

[0059]

[17] A method for manufacturing a phase retardation film, which is the method for manufacturing a phase retardation film as described in any one of [1] to

[16] , the method comprising:

[0060] A process for preparing a multilayer film having a layer formed of resin A and a layer formed of resin B; wherein resin A has positive intrinsic birefringence and resin B has negative intrinsic birefringence; and

[0061] The process of stretching the above-mentioned multilayer film.

[0062]

[18] The method for manufacturing the phase difference film according to

[17] includes the step of melt extruding the resin A and the resin B.

[0063]

[19] The method for manufacturing a phase difference film according to

[17] or

[18] includes a step of stretching the multilayer film at a stretching temperature of "Tg(h)-10°C" or higher and "Tg(h)+20°C" or lower (where Tg(h) represents the higher of the glass transition temperature TgA of the resin A and the glass transition temperature TgB of the resin B).

[0064]

[20] The method for manufacturing a phase difference film according to any one of

[17] to

[19] , wherein the step of stretching the multilayer film includes a step of stretching at a stretching ratio of 1.5 times or more and 5.0 times or less.

[0065]

[21] The method for manufacturing a phase difference film according to any one of

[17] to

[20] , wherein the step of stretching the multilayer film includes the step of stretching the multilayer film in an inclined direction.

[0066]

[22] A polarizer having a phase difference film and a linear polarizer as described in any one of [1] to

[16] .

[0067]

[23] An image display device having a phase difference film as described in any one of [1] to

[16] .

[0068] Invention Effects

[0069] According to the present invention, a phase retardation film with high reflection suppression capability and excellent reprocessability, and a method for manufacturing the same, as well as a polarizer and an image display device having the phase retardation film, can be provided. Attached Figure Description

[0070] Figure 1 This is a graph that schematically illustrates the relative relationship between the overall in-plane delay ReA of layer A and the overall in-plane delay ReB of layer B in an example. Detailed Implementation

[0071] The present invention will be described in detail below with examples and embodiments shown. However, the present invention is not limited to the embodiments and embodiments shown below, and can be arbitrarily modified and implemented without departing from the scope of protection of the present invention and its equivalents.

[0072] In the following description, unless otherwise stated, the in-plane retardation Re of layers and films having three-dimensional refractive indices nx, ny, and nz is represented by Re = (nx - ny) × d. nx represents the refractive index in the direction perpendicular to the thickness direction (in-plane direction) that provides the maximum refractive index. ny represents the refractive index in the direction orthogonal to the direction of nx in the aforementioned in-plane direction. nz represents the refractive index in the thickness direction. d represents the thickness.

[0073] The in-plane retardation of a film with multiple layers having different three-dimensional refractive indices nx, ny, and nz can generally be synthesized from the in-plane retardations of each layer. For example, the in-plane retardation of a film formed by 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 difference between the in-plane retardation of the first layer and the in-plane retardation of the second layer. Furthermore, 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 sum of the in-plane retardation of the third layer and the in-plane retardation of the fourth layer.

[0074] The specific value of the in-plane delay can be measured using a phase difference meter (KOBRA-WIST, manufactured by Oji Measurement & Control Co., Ltd.). Unless otherwise specified, the measurement wavelength is 590 nm.

[0075] Unless otherwise specified, the slow axis of a layer or membrane refers to the slow axis in the in-plane direction of that layer or membrane.

[0076] Positive wavelength dispersion refers to the property that the in-plane retardations Re450 and Re550 at the measurement wavelengths of 450 nm and 550 nm satisfy Re450 > Re550. Generally, the longer the measurement wavelength, the smaller the in-plane retardation of a component with positive wavelength dispersion.

[0077] Inverse wavelength dispersion refers to the property that the in-plane retardations Re450 and Re550 at the measured wavelengths of 450 nm and 550 nm satisfy Re450 < Re550. Generally, the longer the measured wavelength, the greater the in-plane retardation of the component exhibiting inverse wavelength dispersion.

[0078] Unless otherwise specified, the angle formed by the optical axes (absorption axis, transmission axis, slow axis, etc.) of each layer in a multi-layered component represents the angle when the layer is viewed from the thickness direction.

[0079] Unless otherwise stated, the orientation of elements as “parallel,” “perpendicular,” and “orthogonal” may be included within an error range (e.g., ±5°, ±4°, ±3°, ±2°, or ±1°) without impairing the effects of the invention.

[0080] Unless otherwise specified, "resin with positive intrinsic birefringence" means a resin in which the refractive index in the stretching direction is greater than the refractive index in the direction orthogonal to the stretching direction. Furthermore, unless otherwise specified, "polymer with positive intrinsic birefringence" means a polymer in which the refractive index in the stretching direction is greater than the refractive index in the direction orthogonal to the stretching direction.

[0081] Unless otherwise specified, "resin with negative intrinsic birefringence" means a resin in which the refractive index in the stretching direction is less than the refractive index in the direction orthogonal to the stretching direction. Unless otherwise specified, "polymer with negative intrinsic birefringence" means a polymer in which the refractive index in the stretching direction is less than the refractive index in the direction orthogonal to the stretching direction.

[0082] Unless otherwise specified, a "strip" film refers to a film having a length that is five times or more, preferably ten times or more, relative to its width; specifically, it refers to a length sufficient to be rolled up for storage or transport. There is no particular upper limit to the length of a strip film; it can be, for example, less than 100,000 times its width.

[0083] Unless otherwise stated, “polarizer,” “circular polarizer,” and “waveplate” include not only rigid components but also flexible components such as resin films.

[0084] Unless otherwise specified, adhesives include not only adhesives in the narrow sense, but also adhesives with a shear storage modulus of less than 1 MPa at 23°C. Furthermore, adhesives in the narrow sense refer to adhesives with a shear storage modulus of 1 MPa to 500 MPa at 23°C after irradiation with energy rays or heat treatment.

[0085] [1. Overview of Phase Retardation Coatings]

[0086] One embodiment of the retardation film of the present invention comprises: one or more A layers formed of resin A having positive intrinsic birefringence; and one or more B layers formed of resin B having negative intrinsic birefringence. Layers A and B are optically anisotropic layers and therefore have a slow axis. When the retardation film is viewed from the thickness direction, the slow axis of layer A is perpendicular to the slow axis of layer B. Furthermore, resin B comprises at least one polymer selected from polyester, polycarbonate, and polyester-carbonate. This polymer contains a fluorene backbone.

[0087] In this embodiment, the difference between the wavelength dispersion of layer A and layer B is within a specific range. Specifically, the wavelength dispersion of layer A is represented by Re(A450) / Re(A550). Furthermore, the wavelength dispersion of layer B is represented by Re(B450) / Re(B550). In this case, the magnitude of the difference between the wavelength dispersion of layer A and layer B is represented by |Re(A450) / Re(A550)-Re(B450) / Re(B550)|. In this embodiment, the magnitude of this difference in wavelength dispersion satisfies the following equation (i):

[0088] |Re(A450) / Re(A550)-Re(B450) / Re(B550)|≥0.10 (i).

[0089] Here, Re(A450) represents the overall in-plane retardation of layer A at a wavelength of 450 nm. Furthermore, Re(A550) represents the overall in-plane retardation of layer A at a wavelength of 550 nm. When the retardation film has one layer A, "overall in-plane retardation of layer A" means the in-plane retardation of that layer A. Furthermore, when the retardation film has two or more layers A, "overall in-plane retardation of layer A" means the sum of the in-plane retardations of these layers A.

[0090] Furthermore, Re(B450) represents the overall in-plane retardation of the B layer at a wavelength of 450 nm. Additionally, Re(B550) represents the overall in-plane retardation of the B layer at a wavelength of 550 nm. When the retardation film has one B layer, "overall in-plane retardation of the B layer" refers to the in-plane retardation of that B layer. Furthermore, when the retardation film has two or more B layers, "overall in-plane retardation of the B layer" refers to the sum of the in-plane retardations of these B layers.

[0091] Equation (i) will be explained in further detail. The difference between the wavelength dispersion of layer A and layer B, |Re(A450) / Re(A550)-Re(B450) / Re(B550)|, is typically 0.10 or more, preferably 0.12 or more, and more preferably 0.14 or more. There is no particular upper limit, and it can typically be 0.8 or less, preferably 0.5 or less, and particularly preferably 0.3 or less. In most cases, the wavelength dispersion of layer B, Re(B450) / Re(B550), is greater than that of layer A, Re(A450) / Re(A550), therefore the difference between the wavelength dispersion of layer A and layer B, "Re(A450) / Re(A550)-Re(B450) / Re(B550)", can be negative.

[0092] In this embodiment, the overall thickness T of layer A is... A The overall thickness T of layer B B The ratio of TA / T B Within a specific range. Specifically, the thickness ratio T. A / T B Typically, the thickness is 30 / 70 or more, preferably 35 / 65 or more, more preferably 40 / 60 or more, typically 65 / 35 or less, preferably 60 / 40 or less, more preferably 55 / 45 or less. Here, when the retardation film has an A layer, the thickness T... A This indicates the thickness of layer A. Furthermore, in the case where the retardation film has two or more layers A, the thickness T... A This represents the sum of the thicknesses of these A layers. Furthermore, in the case where the retardation film has a B layer, the thickness T... B This indicates the thickness of the B layer. Furthermore, in the case where the retardation film has more than two B layers, the thickness T... B This represents the sum of the thicknesses of these B layers.

[0093] The retardation film of this embodiment has a specific range of wavelength dispersion. Specifically, the wavelength dispersion of the retardation film is represented by Re(450) / Re(550). Moreover, the wavelength dispersion Re(450) / Re(550) of the retardation film satisfies the following equation (ii):

[0094] 0.60≤Re(450) / Re(550)≤0.96 (ii).

[0095] Here, Re(450) represents the in-plane delay of the retardation film at a wavelength of 450 nm. Furthermore, Re(550) represents the in-plane delay of the retardation film at a wavelength of 550 nm.

[0096] Formula (ii) will be explained in further detail. The wavelength dispersivity Re(450) / Re(550) of the phase retardation film is typically 0.60 or more, preferably 0.70 or more, more preferably 0.80 or more, typically 0.96 or less, preferably 0.93 or less, more preferably 0.92 or less, and even more preferably 0.91 or less.

[0097] The retardation film of this embodiment, which meets the above requirements, has high reflection suppression capability and excellent reprocessability. Specifically, when the retardation film is combined with a linear polarizer to obtain a polarizer (typically a circular polarizer), the polarizer can effectively suppress reflections in the image display device's screen. Furthermore, after the retardation film is initially attached to a component, when the retardation film is peeled off, the agglomeration and damage of the retardation film can be effectively suppressed. Thus, after peeling off the retardation film, it is possible to prevent a portion of the retardation film from remaining on the component. Therefore, even when the peeled-off retardation film is reattached to the component, quality degradation can be suppressed.

[0098] [2.A layer]

[0099] The retardation film has one or more A layers. Each A layer has a slow axis. When the retardation film has two or more A layers, the slow axes of these A layers are usually parallel. Therefore, when viewed from the thickness direction, the angle formed between the slow axes of these A layers is usually 0° to 5°, preferably 0° to 4°, more preferably 0° to 3°, further preferably 0° to 2°, particularly preferably 0° to 1°, and ideally 0°.

[0100] Layer A is formed of resin A, which has positive intrinsic birefringence. Therefore, layer A comprises resin A, preferably only resin A. Resin A is typically a thermoplastic resin. Resin A may contain polymers and any other components as needed. Generally, some or all of the aforementioned polymers have positive intrinsic birefringence, thereby allowing resin A to have positive intrinsic birefringence.

[0101] Examples of polymers included in layer A include polymers containing alicyclic structures. Polymers containing alicyclic structures preferably have positive intrinsic birefringence. Polymers containing alicyclic structures are polymers in which alicyclic structures are contained within repeating units, and examples include (1) norbornene polymers, (2) monocyclic cyclic olefin polymers, (3) cyclic conjugated diene polymers, (4) vinyl alicyclic hydrocarbon polymers, and their hydrides. The aforementioned polymers containing alicyclic structures can be selected from polymers disclosed in Japanese Patent Application Publication No. 2002-321302. Examples of polymers containing alicyclic structures include "ZEONOR" manufactured by Zeon Corporation of Japan and "ARTON" manufactured by JSR Corporation of Japan. From the viewpoint of reprocessability and adhesion to layer B, the polymer included in layer A preferably contains heteroatoms within its molecule.

[0102] Furthermore, the polymer contained in resin A preferably contains an isosorbide backbone, and particularly preferably a polycarbonate containing an isosorbide backbone. Here, the isosorbide backbone represents the backbone represented by the following formula (X1). In formula (X1), * indicates a binding site. The polymer containing the isosorbide backbone preferably has positive intrinsic birefringence. When using a polymer containing an isosorbide backbone, especially a polycarbonate containing an isosorbide backbone, it is possible to effectively improve the adhesion of the layer to resin B, the reflection suppression ability of the phase retardation film, the reprocessability, and the ability to suppress phase retardation changes under applied stress.

[0103] [Chemical Formula 5]

[0104]

[0105] The polymer contained in resin A preferably does not contain aromatic rings. When using a polymer that does not contain aromatic rings in its molecules, the reflection suppression capability of the retardation film can be effectively improved. In particular, since resin A, which contains a polymer without aromatic rings, tends to have a small wavelength dispersive Re(A450) / Re(A550), the improvement in reflection suppression capability is significant when it is combined with resin B, which contains a polymer with a large wavelength dispersive Re(B450) / Re(B550), such as a polyester containing fluorene rings, as described later.

[0106] Examples of polymers containing an isosorbide backbone include "DURABIO" manufactured by Mitsubishi Chemical Corporation. Furthermore, "DURABIO" manufactured by Mitsubishi Chemical Corporation does not contain an aromatic ring in its polymer molecule.

[0107] Polymers can be used alone or in combination of two or more in any ratio.

[0108] The weight-average molecular weight (Mw) of the polymer contained in resin A is preferably 10,000 or more, more preferably 15,000 or more, particularly preferably 20,000 or more, preferably 100,000 or less, more preferably 80,000 or less, and particularly preferably 50,000 or less. When the weight-average molecular weight is within such a range, the mechanical strength and molding processability of layer A are highly balanced.

[0109] The weight-average molecular weights mentioned above are converted from the weight-average molecular weights of polyisoprene or polystyrene determined by gel permeation chromatography (GPC) using cyclohexane as a solvent. However, toluene can also be used as a solvent in GPC if the sample is insoluble in cyclohexane.

[0110] The molecular weight distribution (weight-average molecular weight (Mw) / number-average molecular weight (Mn)) of the polymer contained in resin A is preferably 1.2 or more, more preferably 1.5 or more, particularly preferably 1.8 or more, preferably 3.5 or less, more preferably 3.0 or less, and particularly preferably 2.7 or less. When the molecular weight distribution is at or above the lower limit of the above range, the polymer productivity can be improved and manufacturing costs can be reduced. Furthermore, when the molecular weight distribution is below the upper limit, since the amount of low molecular weight components is reduced, relaxation under high temperature exposure can be suppressed, thereby improving the stability of layer A.

[0111] The polymer content in resin A is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, and particularly preferably 90% to 100% by weight. When the polymer content is within the above range, layer A obtains sufficient heat resistance and transparency.

[0112] Resin A may further include any components to combine with the polymer. Examples of such components include: antioxidants, heat stabilizers, light stabilizers, weather stabilizers, UV absorbers, near-infrared absorbers, and other stabilizers; plasticizers, etc. These components may be used alone or in combination of two or more in any ratio.

[0113] The glass transition temperature (TgA) of resin A is preferably 100°C or higher, more preferably 110°C or higher, particularly preferably 120°C or higher, preferably 160°C or lower, more preferably 150°C or lower, and particularly preferably 140°C or lower. When the glass transition temperature (TgA) of resin A is above the lower limit of the above range, the heat resistance of the retardation film can be improved. Furthermore, when the glass transition temperature (TgA) is below the upper limit of the above range, the film forming and stretching processes in the manufacturing method of the retardation film can be performed smoothly. The glass transition temperature can be measured using a differential scanning calorimeter (DSC) with a heating rate of 10°C / min. The glass transition temperature of resin A can be adjusted, for example, according to the composition of resin A.

[0114] The difference between the glass transition temperature TgA of resin A and the glass transition temperature TgB of resin B, |TgA-TgB|, is preferably 15°C or less, more preferably 10°C or less, and particularly preferably 8°C or less. A glass transition temperature difference |TgA-TgB| within this range indicates that the glass transition temperatures TgA of resin A and TgB of resin B are close. In this case, when co-stretching resins A and B to manufacture a retardation film, the range of selection for stretching conditions is widened, making it easier to obtain the desired retardation and thickness of the retardation film. The glass transition temperature TgA of resin A can be higher or lower than the glass transition temperature TgB of resin B.

[0115] The overall in-plane retardation Re(A550) of layer A at a wavelength of 550 nm is preferably 180 nm or more, more preferably 200 nm or more, particularly preferably 220 nm or more, more preferably 320 nm or less, more preferably 300 nm or less, and particularly preferably 280 nm or less. When the overall in-plane retardation Re(A550) of layer A is within the above range, both reflection suppression capability and reprocessability are particularly good.

[0116] The difference between the overall in-plane retardation Re(A550) of layer A at 550 nm and the overall in-plane retardation Re(B550) of layer B at 550 nm, |Re(A550)-Re(B550)|, is preferably within a specific range. This specific range is preferably 90 nm or more, more preferably 100 nm or more, particularly preferably 110 nm or more, more preferably 200 nm or less, more preferably 180 nm or less, and particularly preferably 160 nm or less. When the difference in in-plane retardation |Re(A550)-Re(B550)| is within the above range, both reflection suppression capability and reprocessability are particularly good. The overall in-plane retardation Re(A550) of layer A can be greater than or less than the overall in-plane retardation Re(B550) of layer B.

[0117] The wavelength dispersibility Re(A450) / Re(A550) of layer A is preferably 0.98 or higher, more preferably 0.99 or higher, particularly preferably 1.00 or higher, more preferably 1.10 or lower, more preferably 1.06 or lower, and particularly preferably 1.04 or lower. When the wavelength dispersibility Re(A450) / Re(A550) of layer A is within the above range, both reflection suppression capability and reprocessability are particularly good. The wavelength dispersibility Re(A450) / Re(A550) of layer A can be adjusted, for example, according to the composition of resin A.

[0118] The thickness of the A layer is preferably 5 μm or more, more preferably 10 μm or more, particularly preferably 15 μm or more, more preferably 100 μm or less, more preferably 80 μm or less, and particularly preferably 60 μm or less. When the thickness of the A layer is at or above the lower limit of the above range, the film forming and stretching for manufacturing a retardation film with an A layer of such thickness can be performed smoothly. Furthermore, when the thickness of the A layer is at or below the upper limit of the above range, the thickness of the retardation film can be reduced.

[0119] [3.B Level]

[0120] The retardation film has one or more B layers. Each B layer has a slow axis. When the retardation film has two or more B layers, the slow axes of these B layers are usually parallel. Therefore, when viewed from the thickness direction, the angle formed between the slow axes of these B layers is usually 0° to 5°, preferably 0° to 4°, more preferably 0° to 3°, further preferably 0° to 2°, particularly preferably 0° to 1°, and ideally 0°.

[0121] When the retardation film is viewed from the thickness direction, the slow axis of layer B is perpendicular to the slow axis of layer A. Therefore, when viewed from the thickness direction, the slow axis of layer B forms an angle with the slow axis of layer A within a specific range. Specifically, when viewed from the thickness direction, the angle between the slow axes of layers B and the slow axis of layer A is typically 85° to 90°, preferably 86° to 90°, more preferably 87° to 90°, even more preferably 88° to 90°, particularly preferably 89° to 90°, and ideally 90°. When there are two or more combinations of slow axes of layers A and B, the angle between the slow axes of layers A and B in all combinations is within the aforementioned range. For example, when the retardation film has two or more layers A and one layer B, since the slow axis of each layer A can be combined with the slow axis of layer B, there can be two or more combinations of slow axes of layers A and B. In this case, the angle between the slow axes of layers A and B in all combinations is within the aforementioned range, therefore, the angle between the slow axis of layer B and each slow axis of layer A is within the aforementioned range.

[0122] Since the slow axis of layer A is perpendicular to the slow axis of layer B, the in-plane delay of the retardation film containing layers A and B can usually reflect the difference between the in-plane delay of layer A and the in-plane delay of layer B. Therefore, since the retardation film can typically have in-plane delay that reflects the relationship between the wavelength dispersion of layer A and the wavelength dispersion of layer B as expressed in equation (i), the retardation film can generally have anti-wavelength dispersion.

[0123] Layer B is formed of resin B, which has negative intrinsic birefringence. Therefore, layer B comprises resin B, preferably only resin B. Resin B is typically a thermoplastic resin. Resin B may contain polymers and any other components as needed. Generally, some or all of the aforementioned polymers have negative intrinsic birefringence, thus resin B can also have negative intrinsic birefringence.

[0124] Resin B may contain one or more polymers. Resin B contains at least one polymer selected from polyester, polycarbonate, and polyester carbonate. These polyesters, polycarbonates, and polyester carbonates preferably have negative intrinsic birefringence. When resin B contains at least one polymer selected from polyester, polycarbonate, and polyester carbonate, the reflection suppression capability and reprocessability of the retardation film can be effectively improved.

[0125] The polymers selected from polyesters, polycarbonates, and polyester carbonates contain a fluorene backbone, for example, in the side chains. These polymers preferably have negative intrinsic birefringence. When resin B contains a polymer containing a fluorene backbone, the reflection suppression capability and reprocessability of the retardation film can be effectively improved. Here, a polymer containing a fluorene backbone in the side chains refers to a polymer containing the structural unit represented by the following formula (X2).

[0126] [Chemical Formula 6]

[0127]

[0128] The polymer contained in resin B preferably contains structural units having a fluorene-9,9-diyl group. There is no limitation on the type of structural unit having a fluorene-9,9-diyl group in the polymer contained in resin B. For example, the polymer contained in resin B may contain a dicarboxylic acid unit (A) having a fluorene-9,9-diyl group. The dicarboxylic acid unit (A) represents a structural unit having a structure formed by polymerizing a dicarboxylic acid component (A). Furthermore, in the dicarboxylic acid unit (A), the dicarboxylic acid unit (A) having a fluorene-9,9-diyl group is sometimes referred to as a "fluorene dicarboxylic acid unit (A1)". Furthermore, for example, the polymer contained in resin B may contain a diol unit (B) having a fluorene-9,9-diyl group. The diol unit (B) represents a structural unit having a structure formed by polymerizing a diol component (B). Furthermore, in the diol unit (B), the diol unit (B) having a fluorene-9,9-diyl group is sometimes referred to as a "fluorene diol unit (B1)".

[0129] As described above, resin B may comprise at least one polyester polymer selected from polyester, polycarbonate, and polyester carbonate. Among these polyester polymers, polyester is preferred from the viewpoint of formability and phase difference manifestation. Polyesters containing a fluorene backbone are particularly preferred. Polyesters containing a fluorene backbone are appropriately referred to as "polyesters containing fluorene rings".

[0130] Polyesters are typically obtained by polymerizing a polymeric component comprising a dicarboxylic acid component (A) and a diol component (B). Therefore, polyesters generally contain dicarboxylic acid units (A) and diol units (B). In polyesters containing fluorene rings, the fluorene backbone can be contained in the structural units from any polymeric component. Thus, only the dicarboxylic acid unit (A) may contain the fluorene backbone, only the diol unit (B) may contain the fluorene backbone, or both the dicarboxylic acid unit (A) and the diol unit (B) may contain the fluorene backbone. In particular, it is preferable that both the dicarboxylic acid unit (A) and the diol unit (B) contain the fluorene backbone, as this can particularly effectively improve the reflection suppression capability and reprocessability of the retardation film.

[0131] (Dicarboxylic acid unit (A))

[0132] The polymer contained in resin B may contain dicarboxylic acid units (A). Preferably, the polymer contained in resin B contains fluorene dicarboxylic acid units (A1). For example, if resin B contains a polyester, the polyester preferably contains fluorene dicarboxylic acid units (A1).

[0133] Fluorene dicarboxylic acid unit (A1)

[0134] Examples of dicarboxylic acid units (A1) that are represented by the following formula (1) are examples of dicarboxylic acid units.

[0135] [Chemical Formula 7]

[0136]

[0137] (In equation (1), R) 1 Indicates a substituent, k represents an integer from 0 to 8, and X... 1a and X 1b Each can be represented independently as a divalent hydrocarbon group capable of having substituents.

[0138] In the above equation (1), X is... 1a and X 1b The divalent hydrocarbon group in the X group is preferably a divalent alicyclic hydrocarbon group such as cyclohexyl, or a divalent aliphatic hydrocarbon group, with a particular preference for divalent aliphatic hydrocarbon groups. In the X group forming the main chain... 1a and X 1b When the hydrocarbon group is a divalent alicyclic or aliphatic hydrocarbon, the refractive index and wavelength dispersion along the main chain direction decrease, while the refractive index and wavelength dispersion along the direction orthogonal to the main chain direction increase, due to the combination with the fluorene ring structure (fluorene-9,9-diyl) of the side chain. Therefore, it is easy to prepare polymers such as polyesters that exhibit negative oriented birefringence, positive wavelength dispersion, and large wavelength dispersion. In particular, when X... 1a and X 1b When the group is a divalent aliphatic hydrocarbon, the phase retardation becomes more apparent, allowing for stretching under gentler conditions. This, in turn, improves the polymer's toughness (flexibility), resulting in a phase retardation film that is less prone to breakage and exhibits excellent formability and handling properties. Furthermore, by reducing thermal shrinkage caused by residual stress, a thinner phase retardation film can be formed.

[0139] As group X 1a and X 1b The divalent aliphatic hydrocarbon group represented can be, for example, a straight-chain or branched alkylene group, a straight-chain or branched alkenylene group, or a straight-chain or branched ynylene group, preferably a straight-chain or branched alkylene group. Among these, straight-chain or branched C-groups such as ethylene and propyleneene are preferred. 2-4 Alkylene; more preferably straight-chain or branched C 2-3 Alkylene; particularly preferred is ethylene. Unless otherwise specified, the "C" prefix is ​​added before the name of the group. x-y The notation "(x and y represent positive integers)" indicates that the group with this notation has x or more carbon atoms and y or less. Additionally, X... 1a and X 1b They can be different from each other, but they are usually the same group.

[0140] In the above formula (1), R is the group 1Examples include non-polymerizable groups or non-reactive substituents that are inactive in polymerization reactions. As a group R... 1 Specific examples include: cyano groups; halogen atoms such as fluorine, chlorine, and bromine atoms; and hydrocarbon groups such as alkyl and aryl groups. As examples of the aforementioned aryl groups, phenyl groups, etc., are C... 6-10 Aryl groups, etc. Examples of the aforementioned alkyl groups include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, etc. 1-12 Alkyl, preferably C 1-8 Alkyl groups, particularly preferably methyl groups, etc. 1-4 Alkyl groups, etc.

[0141] As a typical dicarboxylic acid unit represented by the above formula (1), X can be cited as an example. 1a and X 1b C is either linear or branched. 2-6 The alkylene structural units, such as 9,9-bis(2-carboxyethyl)fluorene and 9,9-bis(2-carboxypropyl)fluorene, are derived from 9,9-bis(carboxylated C-hydroxyl) fluorene. 2-6 Alkyl)fluorene structural units, etc. These dicarboxylic acid units represented by formula (1) above can be used alone or in combination of two or more. Among these dicarboxylic acid units represented by formula (1) above, those derived from 9,9-bis(carboxyl) fluorene are preferred. 2-6 The structural unit of alkyl fluorene, more preferably, is derived from 9,9-bis(carboxyl C) fluorene. 2-4 The structural unit of alkyl fluorene is particularly preferred to include 9,9-bis(2-carboxyethyl)fluorene, 9,9-bis(2-carboxypropyl)fluorene, etc., which are 9,9-bis(carboxylated C 2-3 Alkyl)fluorene structural unit.

[0142] Second dicarboxylic acid unit (A2)

[0143] The polymer contained in resin B may not contain a dicarboxylic acid unit (second dicarboxylic acid unit (A2)) that is different from the fluorene dicarboxylic acid unit (or the first dicarboxylic acid unit (A1)) as the dicarboxylic acid unit (A), but may contain it as needed as long as it does not impair the effects of the present invention. For example, if resin B contains a polyester, the polyester may contain the second dicarboxylic acid unit (A2).

[0144] As the second dicarboxylic acid unit (A2), examples of structural units can be derived from aromatic dicarboxylic acid components [of which, except for fluorene dicarboxylic acid components (A1)], alicyclic dicarboxylic acid components, aliphatic dicarboxylic acid components, etc.

[0145] Examples of aromatic dicarboxylic acid components include 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, 2,2'-biphenyl dicarboxylic acid, 3,3'-biphenyl dicarboxylic acid, 4,4'-biphenyl dicarboxylic acid, and 4,4'-diphenylmethane dicarboxylic acid.

[0146] Examples of alicyclic dicarboxylic acid components include 1,4-cyclohexanedicarboxylic acid, naphthanedicarboxylic acid, norbornanedicarboxylic acid, adamantanedicarboxylic acid, tricyclodecanedicarboxylic acid, cyclohexenedicarboxylic acid, norbornenedicarboxylic acid, and other di- or tricyclic olefinic dicarboxylic acids.

[0147] Examples of aliphatic dicarboxylic acid components include succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, and itaconic acid.

[0148] These second dicarboxylic acid units (A2) can be used alone or in combination of two or more.

[0149] The proportion of fluorene dicarboxylic acid units (A1) relative to the overall dicarboxylic acid unit (A1) can be selected from, for example, a range of 1 mol% or more, specifically from about 10 mol% to 100 mol%, with a preferred range being 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, and particularly preferably 100 mol% without substantially containing the second dicarboxylic acid unit (A2). When the proportion of fluorene dicarboxylic acid units (A1) is at or above the lower limit of the above range, polymers such as polyesters exhibiting negative orientation birefringence and positive wavelength dispersion can be readily obtained.

[0150] (Diol unit (B))

[0151] The polymer contained in resin B may contain glycol units (B). Preferably, the polymer contained in resin B contains fluorene glycol units (B1). For example, if resin B contains a polyester, the polyester preferably contains fluorene glycol units (B1).

[0152] Fluorene glycol unit (B1)

[0153] Examples of fluorene diol units (B1) include diol units represented by the following formula (2).

[0154] [Chemical Formula 8]

[0155]

[0156] (In equation (2), R) 2Indicates a substituent, m represents an integer from 0 to 8, X 2a and X 2b Each of these groups independently represents a divalent hydrocarbon group capable of having substituents, A. 1a and A 1b Each of these independently represents a straight-chain or branched alkylene group, with n1 and n2 representing integers greater than or equal to 0.

[0157] In equation (2) above, R 2 The substituents and their substitution number m represent preferred methods, including specific groups, ranges of substitution numbers, and substitution positions, respectively, and are related to R in the above formula (1). 1 The substituents and their substitution numbers k are the same.

[0158] In X 2a and X 2b In this context, as a divalent hydrocarbon group, it interacts with X in the above formula (1). 1a and X 1b Similarly, examples include divalent aliphatic hydrocarbon groups such as straight-chain or branched alkylene groups, divalent alicyclic hydrocarbon groups such as cyclohexene, and divalent aromatic hydrocarbon groups such as phenylene. Preferred divalent hydrocarbon groups are divalent aliphatic hydrocarbon groups and divalent aromatic hydrocarbon groups. X 2a and X 2b The types can be different from each other, but they are usually the same.

[0159] As mentioned above, R 2 Examples of hydrocarbon groups represented include: methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, etc., which are straight-chain or branched C groups. 1-10 Alkyl groups; cyclopentyl, cyclohexyl, etc. (C60) 5-10 Cycloalkyl; phenyl, methylphenyl (or tolyl), dimethylphenyl (or xylyl), etc., one to three C 1-4 Alkyl-phenyl; biphenyl, naphthyl, etc. C 6-12 Aryl; benzyl, phenethyl, etc. C 6-10 Aryl-C 1-4 alkyl.

[0160] As alkylene A 1a and A 1b Examples of linear or branched C-chain compounds include ethylene, propylene (1,2-propanediyl), trimethylene, 1,2-butadiene, and tetramethylene. 2-6 Alkyl groups, preferably linear or branched C4 groups. 2-4 Alkylene, more preferably ethylene, propylene, or other straight-chain or branched C-chain compounds. 2-3 Alkylene, with ethylene being particularly preferred.

[0161] oxyalkylene (-OA) 1a -) and (-OA 1bThe number of repetitions (additional moles) n1 and n2 of -) can be 0 or higher. For example, they can be selected from the range of integers around 0 to 15 as the preferred range. The following stages are 0 to 10, 0 to 8, 0 to 6, 0 to 4, 0 to 2, and 0 to 1.

[0162] As a typical diol unit represented by the above formula (2), examples include X 2a and X 2b These are linear or branched alkylene glycol units (hereinafter also referred to as dialkylfluorene glycol units), glycol units represented by formula (2A) described later (hereinafter also referred to as diarylfluorene glycol units), etc. These fluorene glycol units (B1) can be alone or in combination of two or more.

[0163] Typical dialkylfluorene glycol units include, for example, those derived from 9,9-bis(hydroxymethyl)fluorene, 9,9-bis(2-hydroxyethyl)fluorene, 9,9-bis(3-hydroxypropyl)fluorene, 9,9-bis(4-hydroxybutyl)fluorene, etc., in 9,9-bis(hydroxymethyl)fluorene straight-chain or branched C-chain forms. 1-6 The structural units are alkyl fluorene. These dialkyl fluorene diol units can be used alone or in combination of two or more. Structural units derived from 9,9-bis(hydroxymethyl)fluorene are particularly preferred.

[0164] The bis(aryl)fluorene glycol unit represented by equation (2A) below can reduce thermal shrinkage caused by residual stress by easily increasing the glass transition temperature of the polymer, thus effectively improving environmental reliability (heat resistance and water resistance (moisture resistance), dimensional stability against heat and moisture, and phase difference stability). In other words, the bis(aryl)fluorene glycol unit is effective in balancing phase difference manifestation and wavelength dispersion characteristics with environmental reliability.

[0165] [Chemical Formula 9]

[0166]

[0167] (In equation (2A), Z) 1a and Z 1b Each of the aromatic rings is represented independently, R 3a and R 3b Let p1 and p2 represent substituents independently, and let R represent integers greater than or equal to 0 independently. 2 m, A 1a and A 1b n1 and n2 respectively contain preferred methods, which are the same as those in equation (2) above.

[0168] In the above equation (2A), Z is... 1a and Z 1bThe aromatic rings referred to include, for example, benzene rings, naphthalene rings, indene rings, anthracene rings, phenanthrene rings, biphenyl rings, phenylnaphthalene rings, binaphthalene rings, and terphenyl rings, with benzene rings, naphthalene rings, and biphenyl rings being preferred. 6-12 Aromatic rings, more preferably benzene rings, naphthalene rings, etc. 6-10 Aromatic rings, with benzene rings being particularly preferred.

[0169] As R 3a and R 3b Examples of substituents include: halogen atoms; alkyl, cycloalkyl, aryl, aralkyl, and other hydrocarbon groups; alkoxy groups; acyl groups; nitro groups; cyano groups; and substituted amino groups. Among these, R... 3a and R 3b Alkyl and aryl groups are preferred independently, with C being particularly preferred. 1-4 Alkyl and C 6-10 Aryl.

[0170] p1 and p2 are each preferably 0 or more, preferably 8 or less, more preferably 4 or less, further preferably 3 or less, and even more preferably 2 or less.

[0171] Representative diarylfluorene diol units include, for example, diol units of the 9,9-bis(hydroxyaryl)fluorene class corresponding to n1 and n2 being 0 in the above formula (2A); and diol units of the 9,9-bis[hydroxy(poly)alkoxyaryl]fluorene class corresponding to n1 and n2 being 1 or more, for example, around 1 to 10.

[0172] Examples of 9,9-bis(hydroxyaryl)fluorenes include: 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, 9,9-bis(4-hydroxy-3,5-dimethylphenyl)fluorene, etc. (Note: The last part, "9,9-bis[(one or two)C", appears to be an unrelated fragment and is omitted from the translation.) 1-4 [alkyl-hydroxyphenyl]fluorene; 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, etc. 9,9-bis(C 6-10 Aryl-hydroxyphenyl)fluorene; 9,9-bis(6-hydroxy-2-naphthyl)fluorene, 9,9-bis(5-hydroxy-1-naphthyl)fluorene, etc.

[0173] Examples of 9,9-bis[hydroxy(poly)alkoxyaryl]fluorenes include: 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene, 9,9-bis[4-(2-(2-hydroxyethoxy)ethoxy)phenyl]fluorene, 9,9-bis[4-(2-hydroxyethoxy)ethoxy)phenyl]fluorene, etc. (Note: The last part, "9,9-bis[hydroxy(mono- to deca-hydroxy)C," appears to be a separate, unrelated list of fluorene compounds and is not translated.) 2-4[Alkoxy-phenyl]fluorene; 9,9-bis[4-(2-hydroxyethoxy)-3-methylphenyl]fluorene, 9,9-bis[4-(2-(2-hydroxyethoxy)ethoxy)-3-methylphenyl]fluorene, 9,9-bis[4-(2-hydroxyethoxy)ethoxy)-3-methylphenyl]fluorene, 9,9-bis[4-(2-hydroxypropoxy)-3-methylphenyl]fluorene, 9,9-bis[4-(2-hydroxypropoxy)-3-methylphenyl]fluorene, etc. 9,9-bis[(mono- or di-C] 1-4 alkyl-hydroxy (one to ten)C 2-4 [Alkoxy-phenyl]fluorene, etc.

[0174] Examples of 9,9-bis[aryl-hydroxy(poly)alkoxyphenyl]fluorenes include: 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis[4-(2-(2-hydroxyethoxy)ethoxy)-3-phenylphenyl]fluorene, 9,9-bis(4-(2-hydroxypropoxy)-3-phenylphenyl)fluorene, etc. 6-10 Aryl-hydroxy (one to ten)C 2-4 [Alkoxy-phenyl]fluorene; 9,9-bis[6-(2-hydroxyethoxy)-2-naphthyl]fluorene, 9,9-bis[5-(2-hydroxyethoxy)-1-naphthyl]fluorene, 9,9-bis[6-(2-(2-hydroxyethoxy)ethoxy)-2-naphthyl]fluorene, 9,9-bis[6-(2-hydroxypropoxy)-2-naphthyl]fluorene, etc. 9,9-bis[hydroxy(mono- to deca-)C 2-4 [Alkoxy-naphthyl]fluorene, etc.

[0175] In the fluorene glycol unit (B1), the dialkyl fluorene glycol unit and the diaryl fluorene glycol unit can be used alone or in combination of two or more.

[0176] Furthermore, relative to the total diol unit (B), the proportion of fluorene glycol unit (B1) can be selected from, for example, a range of 1 mol% or more, specifically from about 10 mol% to 100 mol%, with preferred ranges being 30 mol% to 100 mol%, 50 mol% to 99 mol%, 60 mol% to 98 mol%, 70 mol% to 97 mol%, 80 mol% to 96 mol%, and particularly preferably 85 mol% to 95 mol%. When the proportion of fluorene glycol unit (B1) is above the lower limit of the above range, polymers such as polyesters exhibiting negative orientation birefringence and positive wavelength dispersion can be easily obtained. Furthermore, when the proportion of fluorene glycol unit (B1) is below the upper limit of the above range, good moldability and handling properties can be achieved.

[0177] (Poly)alkylene glycol unit (B2)

[0178] The polymer contained in resin B may, as needed, contain a (poly)alkylene glycol unit (B2) as represented by the following formula (3) as a glycol unit (B). For example, if resin B contains a polyester, the polyester may contain a (poly)alkylene glycol unit (B2). When a (poly)alkylene glycol unit (B2) is contained, the molecular weight can be increased by improving the polymerization reactivity of the polymer, or the toughness can be improved by the soft chemical structure, which is effective for preparing phase retardation films with excellent formability and handling.

[0179] [Chemical Formula 10]

[0180]

[0181] (In formula (3), A) 2 Indicates a straight-chain or branched alkylene group, where q represents an integer greater than or equal to 1.

[0182] In the above equation (3), as A 2 Examples of alkylene compounds include, for instance, ethylene, propyleneene, trimethylene, 1,2-butadiene, 1,3-butadiene, tetramethylene, 1,5-pentadiene, 1,6-hexadiene, 1,8-octadiene, and 1,10-decadiene, which are straight-chain or branched C-chain compounds. 2-12 Alkylenes, etc. Preferably, linear or branched C-type compounds such as ethylene and propyleneene. 2-4 Alkylene; more preferably straight-chain or branched C 2-3 Alkylene; particularly preferred is ethylene.

[0183] The number of repetitions q can be selected from a range of about 1 to 10, with the following preferred ranges being 1 to 8, 1 to 6, 1 to 4, 1 to 3, and 1 to 2, with 1 being particularly preferred.

[0184] Examples of diols corresponding to the (poly)alkylene glycol unit (B2) include: ethylene glycol, propylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, tetramethylene glycol (or 1,4-butanediol), 1,5-pentanediol, neopentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, etc., which are straight-chain or branched C-type diols. 2-12 Alkylene glycols; diethylene glycol, dipropylene glycol, triethylene glycol, etc., with two to ten straight-chain or branched C46 ... 2-12 Alkylene glycols, etc. These (poly)alkylene glycol units (B2) may be contained alone or in combination of two or more. Structural units derived from ethylene glycol are particularly preferred.

[0185] The proportion of (poly)alkylene glycol units (B2) relative to the total glycol unit (B) can be selected from a range of 0 mol% to 100 mol%, for example, about 1 mol% to 50 mol%, with preferred ranges being 3 mol% to 30 mol%, 5 mol% to 20 mol%, 7 mol% to 15 mol%, and particularly preferably 8 mol% to 12 mol%. When the proportion of (poly)alkylene glycol units (B2) is below the upper limit of the above range, polymers such as polyesters exhibiting negative orientation birefringence and positive wavelength dispersion can be easily obtained. Furthermore, when the proportion of (poly)alkylene glycol units (B2) is above the lower limit of the above range, good moldability and handling properties can be achieved.

[0186] There are no particular limitations on the manufacturing method of the polymer. For example, when manufacturing polyester as a polymer, conventional methods can be used. For instance, it can be manufactured by reacting the dicarboxylic acid component (A) corresponding to the dicarboxylic acid units, etc., with the diol component (B) corresponding to the diol units, etc., using conventional methods such as transesterification, direct polymerization, melt polymerization, solution polymerization, and interfacial polymerization, with melt polymerization being preferred. Furthermore, the reaction can be carried out with or without a solvent, depending on the polymerization method. Specific manufacturing methods can be, for example, those described in Japanese Patent Application Publication No. 2017-198956.

[0187] The weight-average molecular weight (Mw) of the polymer contained in resin B is preferably 20,000 or more, more preferably 25,000 or more, even more preferably 30,000 or more, even more preferably 35,000 or more, even more preferably 40,000 or more, particularly preferably 50,000 or more, preferably 100,000 or less, more preferably 80,000 or less, and even more preferably 70,000 or less. When the weight-average molecular weight is within this range, the production of the B layer by stretching can be carried out smoothly.

[0188] The proportion of polymer in resin B is preferably 50% to 100% by weight, more preferably 70% to 100% by weight, and particularly preferably 90% to 100% by weight. When the proportion of polymer is within the above range, layer B obtains sufficient heat resistance and transparency.

[0189] Resin B may further include any components to combine with the polymer. Examples of such components include, for instance, any components that may be included in resin A. These components may be used alone or in combination of two or more in any ratio.

[0190] The glass transition temperature (TgB) of resin B is preferably 100°C or higher, more preferably 110°C or higher, particularly preferably 120°C or higher, preferably 160°C or lower, more preferably 150°C or lower, and particularly preferably 140°C or lower. When the glass transition temperature (TgB) of resin B is above the lower limit of the above range, the heat resistance of the retardation film can be improved. Furthermore, when the glass transition temperature (TgB) is below the upper limit of the above range, the film forming and stretching processes in the manufacturing method of the retardation film can be performed smoothly. The glass transition temperature (TgB) of resin B can be adjusted, for example, according to the composition of resin B.

[0191] The overall in-plane retardation Re(B550) of the B layer at a wavelength of 550 nm is preferably 60 nm or more, more preferably 80 nm or more, particularly preferably 100 nm or more, more preferably 180 nm or less, more preferably 160 nm or less, and particularly preferably 140 nm or less. When the overall in-plane retardation Re(B550) of the B layer is within the above range, both reflection suppression capability and reprocessability are particularly good.

[0192] The overall in-plane delays Re(B450) and Re(B550) of layer B preferably satisfy the following equation (iii):

[0193] 1.14≤Re(450) / Re(550) (iii)

[0194] Specifically, the wavelength dispersibility Re(B450) / Re(B550) of layer B is preferably 1.14 or higher, more preferably 1.15 or higher, particularly preferably 1.16 or higher, preferably 1.30 or lower, more preferably 1.24 or lower, and particularly preferably 1.20 or lower. When the wavelength dispersibility Re(B450) / Re(B550) of layer B is within the above range, both reflection suppression capability and reprocessability are particularly good. The wavelength dispersibility Re(B450) / Re(B550) of layer B can be adjusted, for example, according to the composition of resin B.

[0195] The thickness of the B layer is preferably 5 μm or more, more preferably 10 μm or more, particularly preferably 15 μm or more, preferably 100 μm or less, more preferably 80 μm or less, and particularly preferably 60 μm or less. When the thickness of the B layer is at or above the lower limit of the above range, the film forming and stretching for manufacturing a retardation film with a B layer of such thickness can be performed smoothly. Furthermore, when the thickness of the B layer is at or below the upper limit of the above range, the thickness of the retardation film can be reduced.

[0196] [4. Arbitrary layers]

[0197] The retardation film can have any layer other than layer A and layer B, as needed. As an example of an arbitrary layer, an optically isotropic layer can be mentioned. An optically isotropic layer indicates a layer with small in-plane retardation. The in-plane retardation at a wavelength of 550 nm for an optically isotropic layer is typically less than 10 nm, preferably less than 7 nm, and more preferably less than 5 nm. Specific examples of arbitrary layers include: a protective film layer; an adhesive layer that bonds layers A and B, etc.

[0198] [5. Characteristics of retardation films]

[0199] When used in combination with a linear polarizer, the aforementioned retardation film exhibits high reflection suppression capability. The applicant conjectures the following structure that can achieve such high reflection suppression capability. However, the scope of the present invention is not limited to the following structure.

[0200] Figure 1 This is a schematic graph illustrating the relative relationship between the overall in-plane delay ReA of layer A and the overall in-plane delay ReB of layer B in an example. Figure 1 In the diagram, the horizontal axis represents the wavelength, and the vertical axis represents the magnitude of the in-plane delay. Figure 1 The example illustrates how the overall in-plane delay ReA of layer A is greater than the overall in-plane delay ReB of layer B.

[0201] The in-plane retardation of the combination of layers A and B is the resultant of the in-plane retardation of layer A and layer B. When the slow axis of layer A is perpendicular to the slow axis of layer B, such as... Figure 1 As shown, the in-plane retardation of the combination of layer A and layer B is expressed as the difference ReA-ReB between the overall in-plane retardation ReA of layer A and the overall in-plane retardation ReB of layer B. As in the above embodiment, when equation (i) is satisfied by methods such as the selection of resin A and resin B, since the slopes of the overall in-plane retardation ReA of layer A and the overall in-plane retardation ReB of layer B are different, the longer the wavelength, the greater the difference in in-plane retardation ReA-ReB. Therefore, the combination of layer A and layer B exhibits anti-wavelength dispersion, and the longer the wavelength of this anti-wavelength dispersion, the greater the in-plane retardation. Therefore, the retardation film containing this combination of layer A and layer B can have anti-wavelength dispersion satisfying equation (ii). This retardation film with anti-wavelength dispersion can exert uniform optical function over a wide range in the visible wavelength region (400 nm to 700 nm), thus enabling a uniform change in the polarization state of light transmitted through the retardation film. Therefore, a polarizer (typically a circular polarizer) combining this phase difference film with a linear polarizer can effectively suppress light reflection over a wide range of visible wavelengths. This results in high reflection suppression capability.

[0202] The aforementioned retardation film exhibits excellent reprocessability. The applicant conjectures that a structure with such excellent reprocessability can be obtained. However, the scope of the present invention is not limited to the following structure.

[0203] Consider the case where the difference in reverse wavelength dispersion between resin A and resin B is small, and equation (i) is not satisfied. In this case, for the retardation film to exhibit reverse wavelength dispersion, large in-plane retardations are required for both layers A and B. One method to increase the in-plane retardation is, for example, to increase the degree of orientation of the polymer molecules contained in resin A and resin B. This degree of orientation can be increased by stretching at a large stretch ratio or by stretching at a low temperature. However, when the degree of polymer molecule orientation is large, agglomeration damage caused by delamination is likely to occur. After the retardation film is initially bonded to a component, if delamination occurs on layer A or layer B when the film is peeled off, a portion of the damaged layer A or layer B may remain on the surface of the component. Therefore, even if the retardation film is re-bonded to the component, the desired optical properties cannot be obtained at the portion where the damaged layer A or layer B remains. Thus, films prone to delamination have poor reprocessability.

[0204] In contrast, the retardation film of this embodiment achieves the in-plane retardation satisfying formulas (i) and (ii) without excessively increasing the degree of polymer molecule orientation by appropriately combining resin A with resin B having negative intrinsic birefringence and controlling the thickness ratio of layer A to layer B within a specific range. Therefore, since delamination accompanying the aggregation and destruction of layers A and B is suppressed, excellent reprocessability can be obtained.

[0205] The retardation film preferably has an in-plane retardation within a suitable range depending on its application. From the viewpoint of obtaining a polarizer with particularly excellent reflection suppression capability when combined with a linear polarizer, the in-plane retardation Re(590) of the retardation film at a wavelength of 590 nm is preferably 100 nm or more, more preferably 110 nm or more, particularly preferably 120 nm or more, preferably 180 nm or less, more preferably 170 nm or less, and particularly preferably 160 nm or less. A retardation film with such a range of in-plane retardation Re(590) can function as a quarter-wave plate, and therefore can be combined with a linear polarizer to obtain a circular polarizer.

[0206] The total transmittance of the phase retardation film is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. The total transmittance can be measured using an ultraviolet-visible spectrometer in the wavelength range of 400 nm to 700 nm.

[0207] The haze of the phase retardation film is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%. The haze can be measured using a haze meter according to JIS K7361-1997.

[0208] From the viewpoint of improving the ability to suppress phase difference changes under applied stress, the retardation film preferably has a small photoelasticity coefficient. Specifically, the photoelasticity coefficient of the retardation film is preferably 30 Brewster or less. The photoelasticity coefficient is a value that represents the stress dependence of birefringence generated under stress. Generally, birefringence (the difference in refractive index nx-ny)Δn has a relationship obtained by multiplying the stress σ and the photoelasticity coefficient C (Δn=C·σ). The smaller the absolute value of the photoelasticity coefficient, the better the optical performance can be maintained even when subjected to impact or deformed to fit a display device with a curved display surface.

[0209] The photoelasticity coefficient can be determined by creating a load-Δn curve, and its slope can be used as the basis for calculation. This load-Δn curve can be created by applying a load ranging from 50g to 150g to the film while simultaneously changing the load. Furthermore, the birefringence value Δn can be measured using a retardation measurement device (manufactured by Oji Measurement Equipment Co., Ltd., "KOBRA-21ADH"), and the retardation within the film surface can be measured and divided by the film thickness.

[0210] Phase retardation films can be single-sheet films or strip films.

[0211] The thickness of the retardation film is preferably 90 μm or less, more preferably 70 μm or less, even more preferably 60 μm or less, and particularly preferably 50 μm or less. Conventionally, it has been particularly difficult to achieve both high reflection suppression capability and excellent reprocessability in such thin retardation films. Therefore, the retardation film of the above embodiment is useful from the perspective of achieving both high reflection suppression capability and excellent reprocessability while being thinner. There is no particular limitation on the lower limit of the thickness of the retardation film, and it can be, for example, 10 μm or more, 20 μm or more, 30 μm or more, etc.

[0212] [6. Manufacturing method of phase retardation film]

[0213] There are no limitations on the manufacturing method of the retardation film, as long as the desired retardation film can be obtained. For example, the retardation film can be manufactured by a method that includes the following steps:

[0214] The first step of preparing a multilayer film having a layer formed of resin A and a layer formed of resin B; and

[0215] The second step in stretching multilayer films.

[0216] This manufacturing method enables the simple fabrication of the aforementioned phase retardation film with a small number of steps and simple control of manufacturing conditions.

[0217] [6.1. First Process]

[0218] The multilayer film prepared in the first process has a layer formed by resin A and a layer formed by resin B. In order to distinguish the “layer formed by resin A” and “layer formed by resin B” before stretching from the A layer and B layer of the phase retardation film, they are sometimes referred to as “layer (a)” and “layer (b)”.

[0219] The layers (a) and (b) of the multilayer film prepared in the first step may have optical properties different from those of the A and B layers of the retardation film. Specifically, the layers (a) and (b) of the multilayer film typically do not have large optical anisotropy. Therefore, the in-plane retardation of layers (a) and (b) is usually very small. For example, the in-plane retardation of layers (a) and (b) at 550 nm is preferably 0 nm to 20 nm, more preferably 0 nm to 10 nm, and particularly preferably 0 nm to 5 nm.

[0220] Multilayer films can be single-sheet films, but are preferably strip films. By preparing multilayer films in the form of strip films, some or all of the processes can be carried out on the production line when manufacturing phase retardation films, thus enabling simple and efficient manufacturing.

[0221] There are no restrictions on the manufacturing method of multilayer films. Multilayer films can be manufactured by methods such as co-extrusion T-die method, co-extrusion blow molding method, co-extrusion lamination method, etc.; co-casting method; coating method; dry lamination method, etc. Among these, co-extrusion molding method is preferred from the viewpoint of manufacturing efficiency and the absence of residual solvents and other volatile components in the film. Among co-extrusion molding methods, co-extrusion T-die method is preferred. In co-extrusion T-die method, feed block method and manifold method can be cited, and manifold method is particularly preferred from the viewpoint of reducing the variation in thickness of each layer.

[0222] When manufacturing multilayer films using co-extrusion molding, the first step typically includes the step of melt-extruding resin A and resin B to form layers (a) and (b). In this case, the melt temperature of the extruded resin is preferably Tg+80°C or higher, more preferably Tg+100°C or higher, more preferably Tg+180°C or lower, and even more preferably Tg+150°C or lower. Here, "Tg" represents the glass transition temperature of resin A and resin B. Furthermore, the above-mentioned melt temperature, for example, in the co-extrusion T-die method, represents the melt temperature of the resin in an extruder equipped with a T-die. When the melt temperature of the extruded resin is above the lower limit of the above range, the resin's flowability can be sufficiently improved, resulting in good moldability. Furthermore, when the melt temperature of the extruded resin is below the upper limit, resin deterioration can be suppressed.

[0223] In co-extrusion molding, the molten resin film extruded from the die lip is typically cooled and solidified by being brought into close contact with a cooling roller. Methods for bringing the molten resin into contact with the cooling roller include, for example, air knife methods, vacuum box methods, and electrostatic sealing methods.

[0224] When manufacturing multilayer films using a coating molding method, the first step typically includes: preparing a layer of one of resins A and B; and applying a coating liquid containing the other of resins A and B onto the prepared layer. There are no limitations on the method for preparing the layer of one of resins A and B; methods such as those described in the lamination method described later can be used.

[0225] After preparing a layer of one of resins A and B, a coating solution is applied to this layer. The coating solution typically includes the other of resins A and B and a solvent. Preferably, the solvent is capable of dissolving or dispersing the other of resins A and B; particularly preferably, it is capable of dissolving it. A single solvent can be used, or two or more solvents can be used in any ratio. Examples of solvents 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 solvents such as methyl lactate and ethyl lactate; cycloolefin solvents such as cyclohexane, ethylcyclohexane, and 1,2-dimethylcyclohexane; halogen-containing solvents such as dichloromethane and chloroform; ether solvents such as tetrahydrofuran and dioxane; and alcohol solvents such as 1-pentanol and 1-butanol. From the viewpoint of obtaining a suitable viscosity for coating, the concentration of resin in the coating solution can be from 1% to 50% by weight.

[0226] There are no restrictions on the application method of the coating liquid. Examples of application methods include curtain coating, extrusion coating, roller coating, spin coating, dip coating, bar coating, spray coating, sliding coating, printing coating, gravure coating, die coating, gap coating, and impregnation.

[0227] By applying a coating solution, a film of the coating solution is formed on a layer of one of resins A and B. Therefore, if necessary, a multilayer film having layers (a) and (b) can be obtained by drying the coating solution to remove the solvent. There are no restrictions on the drying method; for example, heating drying, vacuum drying, etc., can be used.

[0228] Multilayer films can also be manufactured using the lamination method. When manufacturing multilayer films using the lamination method, the first step includes: preparing layer (a); preparing layer (b); and laminating layer (a) and layer (b).

[0229] There are no restrictions on the methods for preparing layers (a) and (b). Layers (a) and (b) can be manufactured by, for example, melt molding or solution casting, with melt molding being preferred. Among melt molding methods, extrusion molding, blow molding, or compression molding are preferred, with extrusion molding being particularly preferred.

[0230] The bonding of layers (a) and (b) can be performed using an adhesive as needed. The adhesive is preferably selected based on the types of resin A and resin B. Examples of adhesives include acrylic adhesives, polyurethane adhesives, polyester adhesives, polyvinyl alcohol adhesives, polyolefin adhesives, modified polyolefin adhesives, polyvinyl ether adhesives, rubber adhesives, ethylene-vinyl acetate adhesives, vinyl chloride-vinyl acetate adhesives, SEBS (styrene-ethylene-butene-styrene copolymer), SIS (styrene-isoprene-styrene block copolymer), ethylene-styrene copolymers, ethylene-(meth)acrylate copolymers, ethylene-(meth)acrylate copolymers, and ethyl methacrylate copolymers.

[0231] When using an adhesive, an adhesive layer can typically be formed between layers (a) and (b). The average thickness of this adhesive layer is preferably 0.1 μm to 10 μm, more preferably 0.5 μm to 5 μm.

[0232] [6.2. Second Process]

[0233] The second step includes stretching a multilayer film. Through this stretching, birefringence can be manifested in layer (a), resulting in a slow axis parallel to the stretching direction. Furthermore, birefringence can be manifested in layer (b), resulting in a slow axis perpendicular to the stretching direction. Therefore, based on the above stretching, a phase retardation film with in-plane retardation and a slow axis in layers A and B can be obtained, satisfying the aforementioned necessary conditions.

[0234] The stretching temperature of the multilayer film is preferably "Tg(h)-10℃" or higher, more preferably "Tg(h)-5℃" or higher, particularly preferably "Tg(h)℃" or higher, more preferably "Tg(h)+20℃" or lower, more preferably "Tg(h)+15℃" or lower, and particularly preferably "Tg(h)+10℃" or lower. Here, Tg(h) represents the higher of the glass transition temperature TgA of resin A and the glass transition temperature TgB of resin B. When stretching is performed at a stretching temperature within the above range, a phase retardation film with particularly excellent reprocessability can be obtained.

[0235] The stretching ratio of the multilayer film is preferably 1.5 times or more, more preferably 1.6 times or more, particularly preferably 1.8 times or more, preferably 5.0 times or less, more preferably 4.0 times or less, and particularly preferably 3.0 times or less. When stretched at a stretching ratio within the above range, a retardation film with particularly excellent reprocessability can be obtained.

[0236] Multilayer films can be stretched using either uniaxial stretching (stretching in one direction) or biaxial stretching (stretching in two directions).

[0237] Examples of uniaxial stretching methods include: stretching along the longitudinal axis using the difference in circumferential speed between rollers; and stretching along the transverse axis using a stretching machine.

[0238] Examples of biaxial stretching methods include: a biaxial stretching method that stretches longitudinally by opening the gaps between fixed clamps and stretches laterally by extending the guide rail; and a sequential biaxial stretching method that stretches longitudinally by utilizing the difference in circumferential speed between rollers, then clamps both ends with clamps and stretches laterally using a tenter frame.

[0239] In addition, as another stretching method, there is the inclined stretching method, which uses a widening stretching machine capable of applying thrust, tension, or traction at different speeds in the transverse or longitudinal direction to continuously stretch the multilayer film along an inclined direction at an arbitrary angle θ to the width direction of the film. The inclined direction refers to a direction that is neither parallel nor perpendicular to the width direction of the film.

[0240] These stretching methods can be performed using stretching machines such as longitudinal uniaxial stretching machines, expansion stretching machines, bubble stretching machines, and roller stretching machines.

[0241] The second process preferably includes stretching the multilayer film along an inclined direction. The retardation film manufactured through this second process, including stretching along an inclined direction, can have a slow axis in that direction. Therefore, this retardation film can be bonded to a conventional linear polarizer having a transmission axis parallel or perpendicular to its length direction using a roll-to-roll method to obtain a polarizer. Thus, polarizers can be manufactured efficiently using a long strip of retardation film and a long strip of linear polarizer.

[0242] [6.3. Arbitrary Process]

[0243] The method for manufacturing the retardation film may further include any steps that can be combined with the first and second steps described above. For example, when a strip of retardation film is obtained using a strip of multilayer film, the method for manufacturing the retardation film may include a trimming step of cutting the obtained retardation film into a desired shape. According to the trimming step, a monolithic retardation film having the desired shape can be obtained. Furthermore, the method for manufacturing the retardation film may, for example, include a step of further depositing arbitrary layers on the retardation film.

[0244] [6.4. Other manufacturing methods]

[0245] Phase retardation films can be manufactured using methods different from those described above. For example, a phase retardation film can be manufactured by a method including the following steps: preparing layer A, preparing layer B, and bonding layers A and B together.

[0246] Layer A can be manufactured, for example, by a method including the following steps: manufacturing layer (a) by means of melt molding, solution casting, etc.; and stretching layer (a). The stretching of layer (a) can be performed under the same conditions as described in the description of the second step.

[0247] Layer B can be manufactured, for example, by a method including the following steps: manufacturing layer (b) by means of melt molding, solution casting, etc.; and stretching the layer (b). The stretching of layer (b) can be performed under the same conditions as described in the description of the second step.

[0248] The bonding of layers A and B can also be done using adhesive. The type of adhesive and the thickness of the bonding layer can be the same as those used for bonding layers (a) and (b).

[0249] [7. Polarizing filter]

[0250] One embodiment of the polarizer of the present invention has a linear polarizer and a phase difference film. This polarizer typically functions as a circular polarizer, and by being placed on the display surface of an image display device, it can suppress the reflection of external light.

[0251] A polarizer can have a linear polarizer, an A layer, and a B layer in sequence. Alternatively, a polarizer can also have a linear polarizer, a B layer, and an A layer in sequence.

[0252] In the polarizer, the angle between the transmission axis of the linear polarizer and the slow axis of layer A is preferably within a specific range close to 45°. Specifically, the angle is preferably 40° or more, more preferably 42° or more, even more preferably 43° or more, particularly preferably 44° or more, preferably 50° or less, more preferably 48° or less, even more preferably 47° or less, and particularly preferably 46° or less.

[0253] Any linear polarizer can be used. Examples of linear polarizers include: a film obtained by uniaxially stretching a polyvinyl alcohol film after adsorbing iodine or a dichroic dye in a boric acid bath; and a film obtained by adsorbing iodine or a dichroic dye into a polyvinyl alcohol film, stretching it, and then modifying a portion of the polyvinyl alcohol units in the molecular chain into polyvinylene units. Among these, a polarizer containing polyvinyl alcohol is preferred as a linear polarizer.

[0254] When natural light is incident on the linear polarizer, only one type of polarized light is transmitted. The polarization degree of the linear polarizer is not particularly limited, but is preferably 98% or higher, and more preferably 99% or higher.

[0255] Furthermore, the thickness of the linear polarizer is preferably 5μm to 80μm.

[0256] The aforementioned polarizer may also contain any arbitrary layers. Examples of arbitrary layers include: a polarizer protective film layer; an adhesive layer for bonding the linear polarizer and the retardation film; a hard coating such as an impact-resistant polymethyl methacrylate resin layer; a mat layer to improve the smoothness of the film; a reflection suppression layer; an anti-fouling layer; and a charge suppression layer. These arbitrary layers may be provided as a single layer or as two or more layers.

[0257] [8. Image display device]

[0258] An image display device according to one embodiment of the present invention has the aforementioned retardation film. Typically, the image display device has the aforementioned polarizer including the retardation film. The polarizer is preferably disposed in an organic electroluminescent display device (hereinafter sometimes referred to as an "organic EL display device"). This organic EL display device has a polarizer and an organic electroluminescent element (hereinafter sometimes referred to as an "organic EL element"). This organic EL display device typically has a linear polarizer, a retardation film, and an organic EL element in sequence.

[0259] Organic EL devices sequentially comprise a transparent electrode layer, a light-emitting layer, and an electrode layer. By applying a voltage to the transparent electrode layer and the electrode layer, the light-emitting layer can emit light. Examples of materials constituting the organic light-emitting layer include poly(p-phenylene vinylene)-based materials, polyfluorene-based materials, and polyvinylcarbazole-based materials. Furthermore, the light-emitting layer can be a stack of multiple layers emitting different colors, or a mixed layer in which different pigments are doped into a layer containing a single pigment. Moreover, organic EL devices can also have functional layers such as a hole injection layer, a hole transport layer, an electron injection layer, an electron transport layer, an equipotential surface formation layer, and a charge generation layer.

[0260] The aforementioned image display device can suppress the reflection of external light on the display surface. Taking a circular polarizer as an example, the structure for this reflection suppression will be explained. Only a portion of the linearly polarized light incident from outside the device passes through the linear polarizer, then through the retardation film, thus becoming circularly polarized light. This circularly polarized light is reflected by a reflective light structure element within the image display device (such as a reflective electrode in an organic EL element), and passes through the retardation film again, thus becoming linearly polarized light with a vibration direction orthogonal to the vibration direction of the incident linearly polarized light, and thus unable to pass through the linear polarizer. Here, the vibration direction of the linearly polarized light refers to the vibration direction of the electric field of the linearly polarized light. This achieves the function of suppressing reflection.

[0261] Example

[0262] The following embodiments illustrate the present invention in detail. However, the present invention is not limited to the embodiments shown below, and can be implemented in any way without departing from the scope of the claims and their equivalents.

[0263] Unless otherwise stated, in the following instructions, "%" and "parts" refer to quantities based on weight. Furthermore, unless otherwise stated, the operations described below are performed at normal temperature and pressure in an atmospheric environment.

[0264] [Evaluation Method]

[0265] (Methods for measuring the thickness of each layer)

[0266] The thickness of each layer was measured using a reflective spectrophotometer (Otsuka Electronics Co., Ltd. "FE-3000").

[0267] (Methods for determining the direction of the slow axis in each layer)

[0268] The direction of the slow axis of each layer was measured using a phase difference meter (KOBRA-WIST manufactured by Oji Measurement Equipment Co., Ltd.).

[0269] (Methods for measuring in-plane delay)

[0270] In-plane delay was measured using a phase difference meter (KOBRA-WIST manufactured by Oji Measurement Equipment Co., Ltd.).

[0271] (Method for determining the photoelastic coefficient)

[0272] While applying a load of 50g to 150g to the retardation film, the in-plane retardation of the film is measured. The measured in-plane retardation is divided by the thickness of the retardation film to obtain the birefringence Δn of the retardation film under the applied load. This process of obtaining the birefringence value Δn is repeated multiple times while changing the load, and a load-Δn curve is plotted. The photoelastic coefficient of the retardation film is obtained as the slope of the load-Δn curve.

[0273] (Evaluation method for reflection suppression characteristics)

[0274] A strip polarizer (SANRITZ Corporation "HLC2-5618S", 180 μm thick) consisting of a protective film, a linear polarizer, and a protective film in sequence was prepared. The linear polarizer has a transmission axis in the width direction. The protective film on one side of the polarizer was removed, and the retardation film obtained in the examples or comparative examples was bonded to that side. The bonding was performed at a 45° angle between the slow axis of the retardation film and the transmission axis of the linear polarizer. In particular, the retardation films of Example 5 and Comparative Example 3 were bonded with layers A and B arranged sequentially from the linear polarizer side. Through the above operations, a polarizer sample was obtained as a circular polarizer consisting of a retardation film, a linear polarizer, and a protective film in sequence.

[0275] A commercially available organic EL display device (LG Electronics "OLED55EG9600") having an organic EL element and a circular polarizer disposed on the visually confirming side of the organic EL element was prepared. The circular polarizer of the organic EL display device was replaced with the aforementioned polarizer sample. During replacement, the polarizer sample was arranged with the retardation film and the linear polarizer arranged sequentially from the organic EL element side. Furthermore, the transmission axis of the linear polarizer provided in the polarizer sample of the organic EL display device was in the same direction as the transmission axis of the linear polarizer of the original circular polarizer of the organic EL display device.

[0276] While illuminating the display surface of the organic EL display device with a light source, the display surface is observed from the front direction (normal direction) relative to the display surface. If the reflectivity of the display surface is significantly suppressed compared to before replacement, it is judged as "excellent". If the reflectivity of the display surface is suppressed compared to before replacement, it is judged as "acceptable". If the reflectivity of the display surface is equal to or increases compared to before replacement, it is evaluated as "poor".

[0277] (Methods for evaluating fit)

[0278] An unstretched film (glass transition temperature 160°C, thickness 100 μm, manufactured by Zeon Corporation, Japan) was prepared from a resin containing a norbornene polymer. One side of the unstretched film was subjected to corona treatment.

[0279] Corona treatment was performed on one side of the retardation film obtained in the examples or comparative examples. In particular, the retardation films of Example 5 and Comparative Example 3 underwent corona treatment on the surface of layer A. An adhesive was applied to both the corona-treated surface of the retardation film and the corona-treated surface of the unstretched film, and the surfaces with the adhesive were brought into contact with each other, allowing the adhesive to cure. An ultraviolet-curable adhesive was used as the adhesive. Thus, a sample film having a retardation film and an unstretched film was obtained.

[0280] The sample film was cut to a width of 15 mm to obtain a sample sheet. The phase retardation film side of the sample sheet was attached to the surface of the glass slide using an adhesive (double-sided adhesive tape "CS9621" manufactured by Nitto Denko Corporation).

[0281] A 90-degree peel test was performed by clamping the unstretched film at the front end of a force gauge and stretching it along the normal direction of the glass slide surface. The force measured during peeling of the unstretched film is the force required to peel the phase retardation film from the unstretched film; therefore, the magnitude of this force is used as the peel strength.

[0282] Generally, the greater the peel strength, the more the damage to the phase retardation film is suppressed during re-attachment, resulting in superior reprocessability. Therefore, when the peel strength is 2.0 N or higher, the reprocessability is judged as "excellent". Furthermore, when the peel strength is 1.0 N or higher but less than 2.0 N, the reprocessability is judged as "acceptable". Moreover, when the peel strength is less than 1.0 N, the reprocessability is judged as "poor".

[0283] [Synthesis example 1]

[0284] In 1.00 mol of FDPM (9,9-bis(2-methoxycarbonylethyl)fluorene), 0.90 mol of BPEF (9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene, manufactured by Osaka Gas Chemical Co., Ltd.), and 2.10 mol of EG (ethylene glycol), 2 × 10⁻⁶ ppm of fluorene was added as a transesterification catalyst. -4 moles of manganese acetate tetrahydrate and 8 × 10 -4 Calcium acetate monohydrate was melted by slowly heating with stirring. After heating to 230°C, 14 × 10⁻⁶ molten calcium acetate monohydrate was added. -4 molars of trimethyl phosphate, 20 × 10 -4Germanium oxide (EG) was removed by gradually increasing the temperature and reducing the pressure until it reached 270°C and below 0.13 kPa. After reaching the specified stirring torque, the contents were removed from the reactor to prepare granules of polyester containing fluorene rings.

[0285] The aforementioned FDPM is a dimethyl ester of 9,9-bis(2-carboxyethyl)fluorene (or fluorene-9,9-dipropionic acid). This FDPM was synthesized in the same manner, except that the tert-butyl acrylate described in Example 1 of Japanese Patent Application Publication No. 2005-89422 was replaced with methyl acrylate [37.9 g (0.44 mol)].

[0286] pass 1 The results of H-NMR analysis of the obtained pellets showed that 100 mol% of the dicarboxylic acid units introduced into the polyester containing fluorene rings came from FDPM, 90 mol% of the introduced diol units came from BPEF, and 10 mol% came from EG.

[0287] The obtained polyester containing fluorene rings has a glass transition temperature (Tg) of 125℃ and a weight-average molecular weight (Mw) of 60,000.

[0288] [Example 1]

[0289] (1-1. Fabrication of multilayer films)

[0290] Prepare a membrane forming machine having a T-die, a feed block connected to the T-die, and multiple uniaxial extruders connected to the feed block via polymer tubes and polymer filters.

[0291] As resin A, "DURABIO" (a resin containing a polymer with an isosorbide backbone and no aromatic rings, manufactured by Mitsubishi Chemical Corporation; glass transition temperature 127°C) is prepared. Resin A is fed into a uniaxial extruder.

[0292] As resin B, a polyester containing a fluorene ring, prepared in Example 1, is prepared. Resin B is supplied to a uniaxial extruder different from the one supplied with resin A.

[0293] A film forming machine is used for the melt co-extrusion of resin A and resin B. Specifically, resin A and resin B are melted separately in a single-shaft extruder and fed to the feed block via a polymer tube and a polymer filter. Resin A and resin B merge in the feed block and are extruded into sheets through a T-die onto a casting drum. The extruded sheets are cooled on a cooling drum to obtain a long, multilayer film with a three-layer structure of "a layer of resin A / a layer of resin B / a layer of resin A".

[0294] (1-2. Stretching of multilayer films)

[0295] Using a tensile testing machine with a constant temperature bath, the above-mentioned multilayer film was subjected to free-end uniaxial stretching along its length at a stretching temperature of 135℃ and a stretching ratio of 2.0, resulting in a phase retardation film. "Free-end uniaxial stretching" refers to stretching in a specific direction without applying constraint force in directions other than the stretched direction. The resulting phase retardation film has a three-layer structure of "A layer / B layer / A layer," with the thickness ratio of A layer : B layer : A layer = 22.5 : 55 : 22.5.

[0296] The phase difference film obtained was evaluated using the method described above.

[0297] (1-3. Measurement of in-plane retardation of layers A and B)

[0298] The surface of the phase retardation film was etched using a dry etching apparatus (RIE-10NE, manufactured by SAMCO Co., Ltd.). Various samples were collected with etching times varying every 10 minutes, and the delay and thickness of each sample were measured. The delay of each layer was calculated from the changes in delay and thickness.

[0299] [Example 2]

[0300] The thickness of the retardation film and the thickness ratio of the three layers (i.e., layer A and layer B) contained in the retardation film were varied by changing the extrusion amounts of resin A and resin B. The thickness ratio was A layer : B layer : A layer = 30 : 40 : 30. Except for the above, the retardation film was manufactured and evaluated using the same method as in Example 1.

[0301] [Example 3]

[0302] The thickness of the retardation film and the thickness ratio of the three layers (i.e., layer A and layer B) contained in the retardation film are changed by varying the extrusion amounts of resin A and resin B. The thickness ratio is A layer : B layer : A layer = 17.5 : 65 : 17.5. Furthermore, the stretching method of the multilayer film is changed from uniaxial stretching at the free end to inclined stretching using a widening stretching machine. In the inclined stretching described above, the multilayer film is stretched along a stretching direction at a 45° angle to its width direction by adjusting the angle (extraction angle) between the moving direction of the multilayer film supplied to the widening stretching machine and the moving direction of the retardation film discharged from the widening stretching machine. Apart from the above, the retardation film is manufactured and evaluated using the same method as in Example 1.

[0303] [Example 4]

[0304] (4-1. Manufacturing of multilayer films)

[0305] As resin B, a long, unstretched film made of a polyester containing fluorene rings, prepared in Example 1, is to be synthesized.

[0306] As resin A, "ARTON" (a resin containing an alicyclic polymer with polar groups; glass transition temperature 130°C) manufactured by JSR Corporation was prepared. Resin A was dissolved in cyclohexane to obtain a solution with a concentration of 20% by weight. The resin A solution was applied to one side of an unstretched film formed from resin B using a coating blade and dried to form a layer of resin A. Drying was performed using a dryer at a drying temperature of 120°C for 2 minutes. Then, the resin A solution was applied and dried on the other side of the unstretched film formed from resin B using the same method to form a layer of resin A. Through the above operations, a long strip of multilayer film with a three-layer structure of "layer of resin A / layer of resin B / layer of resin A" was obtained.

[0307] (4-2. Stretching of multilayer films)

[0308] Using a tensile testing machine with a constant temperature bath, the above-mentioned multilayer film was subjected to uniaxial stretching at its free end along its length at a stretching temperature of 135℃ and a stretching ratio of 2.5 times, resulting in a phase retardation film. The obtained phase retardation film has a three-layer structure of "A layer / B layer / A layer", with the thickness ratio of these layers being A layer : B layer : A layer = 22.5 : 55 : 22.5.

[0309] The phase difference film obtained was evaluated using the method described above.

[0310] (4-3. Measurement of in-plane retardation of layers A and B)

[0311] The surface of the phase retardation film was etched using a dry etching apparatus (RIE-10NE, manufactured by SAMCO Co., Ltd.). Various samples were collected with etching times varying every 10 minutes, and the delay and thickness of each sample were measured. The delay of each layer was calculated from the changes in delay and thickness.

[0312] [Example 5]

[0313] (5-1. Manufacturing of Layer A)

[0314] Prepare a membrane forming machine, which has: a T-die, and a single-shaft extruder connected to the T-die via a polymer tube and a polymer filter.

[0315] As resin A, "ZEONOR" (a resin containing an alicyclic polymer without polar groups, with a glass transition temperature of 126°C) manufactured by Zeon Corporation of Japan was prepared. Resin A was fed into a uniaxial extruder for melt extrusion. Specifically, resin A was melted in the uniaxial extruder and fed through a polymer tube and a polymer filter to a T-die, where it was extruded into a sheet on a casting drum. The extruded sheet of resin was cooled on a cooling drum to obtain a single-layer pre-stretch film formed from resin A.

[0316] Using a tensile testing machine equipped with a constant temperature bath, the above-mentioned pre-stretch film was subjected to uniaxial stretching along its length at a stretching temperature of 135°C and a stretch ratio of 2.5 times, to obtain layer A as the stretched film. The in-plane retardation of layer A was measured using the above-described method.

[0317] (5-2. Manufacturing of Layer B)

[0318] Instead of resin A, a polyester containing a fluorene ring, prepared in Synthesis Example 1, was used as resin B. Furthermore, the thickness of the pre-stretch film was varied by changing the rotation speed of the casting drum. Except as described above, layer B, as a stretch film, was manufactured using the same method as in step (5-1) described above. The in-plane retardation of layer B was measured using the aforementioned measurement method.

[0319] (5-3. Bonding of layer A and layer B)

[0320] As the adhesive, Nitto Denko Corporation's double-sided adhesive tape "CS9621" was used. This adhesive is optically isotropic and therefore does not have in-plane retardation. Layer A and Layer B were bonded together using this adhesive to obtain a retardation film. The bonding was performed with the stretching direction of Layer A parallel to the stretching direction of Layer B. The resulting retardation film has a three-layer structure of "Layer A / Adhesive Layer / Layer B," with the thickness ratio of Layer A to Layer B being A:B = 45:55. Furthermore, the thickness of the adhesive layer is 10 μm.

[0321] The phase difference film obtained was evaluated using the method described above.

[0322] [Comparative Example 1]

[0323] As resin B, XIRAN (a polystyrene-containing resin with a glass transition temperature of 130°C) manufactured by POLYSCOPE was used instead of the polyester containing fluorene rings prepared in Synthesis Example 1. Furthermore, the thickness of the retardation film was varied by changing the extrusion amounts of resins A and B. Furthermore, the stretching conditions of the multilayer film were changed to a stretching temperature of 130°C and a stretching ratio of 2.5. Apart from the above, the retardation film was manufactured and evaluated using the same method as in Example 1.

[0324] [Comparative Example 2]

[0325] As resin B, XIRAN manufactured by Polyscope was used instead of the polyester containing fluorene rings prepared in Synthesis Example 1. Furthermore, the thickness of the retardation film and the thickness ratio of the three layers (i.e., layer A and layer B) comprising the retardation film were varied by changing the extrusion amounts of resins A and B. The thickness ratio was A layer : B layer : A layer = 20 : 60 : 20. Furthermore, the stretching conditions of the multilayer film were changed to a stretching temperature of 130°C and a stretching ratio of 3.5. Except for the above, the retardation film was manufactured and evaluated using the same method as in Example 1.

[0326] [Comparative Example 3]

[0327] As resin A, "DURABIO" manufactured by Mitsubishi Chemical Corporation was used instead of "ZEONOR" manufactured by Zeon Corporation. Furthermore, the thicknesses of layers A and B were varied by changing the extrusion amounts of resin A and resin B. Furthermore, the stretching ratio of the pre-stretched film was changed to 2.0 times. Additionally, layers A and B were bonded together with the stretching direction of layer A perpendicular to the stretching direction of layer B. Apart from the above, the phase retardation film was manufactured and evaluated using the same method as in Example 5.

[0328] [Comparative Example 4]

[0329] The thickness of the retardation film and the thickness ratio of the three layers (i.e., layer A and layer B) comprising the retardation film were varied by changing the extrusion amounts of resin A and resin B. The thickness ratio was A layer : B layer : A layer = 10 : 80 : 10. Except as described above, the retardation film was manufactured and evaluated using the same method as in Example 1.

[0330] [Comparative Example 5]

[0331] The thickness of the retardation film and the thickness ratio of the three layers (i.e., layer A and layer B) comprising the retardation film were varied by changing the extrusion amounts of resin A and resin B. The thickness ratio was A layer : B layer : A layer = 35 : 30 : 35. Except as described above, the retardation film was manufactured and evaluated using the same method as in Example 1.

[0332] [result]

[0333] The results of the above embodiments and comparative examples are shown in the following table. In the table below, the abbreviations have the following meanings.

[0334] Relationship of slow axes: The relationship between the slow axes of layer A and layer B.

[0335] Thickness ratio (T) A / T B ): The overall thickness T of layer A A The overall thickness T of layer B B The ratio of TA / T B .

[0336] ΔRe450 / Re550: |Re(A450) / Re(A550)-Re(B450) / Re(B550)|

[0337] [Table 1]

[0338] [Table 1. Results of the Examples]

[0339] [Table 2]

[0340] [Table 2. Results of the Comparative Examples]

[0341]

[0342] Explanation of reference numerals in the attached figures

[0343] ReA: Overall In-Plane Delay of Layer A

[0344] The overall in-plane delay of ReB layer B

Claims

1. A phase retardation film comprising: one or more A layers having a slow axis, and one or more B layers having a slow axis at an angle of 85° to 90° to the slow axis of said A layers. Layer A is formed of resin A, which has positive intrinsic birefringence. The B layer is formed of resin B, which has negative intrinsic birefringence. Resin A comprises at least one polymer selected from polymers containing an alicyclic structure and polymers containing an isosorbide backbone but without an aromatic ring. The resin B comprises at least one polymer selected from polyester, polycarbonate, and polyester carbonate. The polymer contained in resin B contains a fluorene backbone. The overall in-plane delay Re(A450) of layer A at wavelength 450 nm, the overall in-plane delay Re(A550) of layer A at wavelength 550 nm, the overall in-plane delay Re(B450) of layer B at wavelength 450 nm, and the overall in-plane delay Re(B550) of layer B at wavelength 550 nm satisfy the following equation (i): ， The in-plane retardation Re(450) of the retardation film at wavelength 450 nm and the in-plane retardation Re(550) of the retardation film at wavelength 550 nm satisfy the following equation (ii): ， The overall thickness T of layer A A The thickness T of the entire B layer B The ratio of T A / T B It ranges from 30 / 70 to 65 / 35.

2. The phase retardation film according to claim 1, wherein, The overall in-plane delays Re(B450) and Re(B550) of layer B satisfy the following equation (iii): 。 3. The phase retardation film according to claim 1 or 2, wherein, The polymer contained in resin B comprises structural units having fluorene-9,9-diyl groups.

4. The phase retardation film according to claim 3, wherein, The structural unit having fluorene-9,9-diyl comprises a fluorene dicarboxylic acid unit represented by formula (1) and / or a fluorene diol unit represented by formula (2), wherein formula (1) is: In the formula, R 1 Indicates a substituent, k represents an integer from 0 to 8, and X... 1a and X 1b Each can be independently represented as a divalent hydrocarbon group capable of having substituents. Equation (2) is as follows: In the formula, R 2 Indicates a substituent, m represents an integer from 0 to 8, X 2a and X 2b Each of these groups independently represents a divalent hydrocarbon group capable of having substituents, A. 1a and A 1b Each of the two groups independently represents a straight-chain or branched alkylene group, with n1 and n2 representing integers greater than or equal to 0.

5. The phase retardation film according to claim 4, wherein, The fluorene diol unit comprises a diol unit represented by the following formula (2A): In the formula, Z 1a and Z 1b Each of the aromatic rings is represented independently, R 3a and R 3b Let p1 and p2 represent substituents independently, and let R represent integers greater than or equal to 0 independently. 2 m, A 1a and A 1b n1 and n2 are the same as those in equation (2) above.

6. The phase retardation film according to claim 5, wherein, In the diol unit represented by equation (2A), Z 1a and Z 1b C 6-12 Aromatic ring, R 3a and R 3b C 1-4 Alkyl or C 6-10 aryl, p1 and p2 are integers from 0 to 2, A 1a and A 1b C is either linear or branched. 2-4 Alkylene, n1 and n2 are integers from 0 to 2.

7. The phase retardation film according to claim 4, wherein, In the fluorene dicarboxylic acid unit represented by formula (1), X 1a and X 1b C is either linear or branched. 2-4 Alkylene.

8. The phase retardation film according to claim 1 or 2, wherein, The polymer contained in resin B further comprises an alkylene glycol unit represented by the following formula (3): In the formula, A 2 It indicates a straight-chain or branched alkylene group, and q represents an integer greater than or equal to 1.

9. The phase retardation film according to claim 8, wherein, In the alkylene glycol unit represented by formula (3), A 2 C is either linear or branched. 2-4 Alkylene, where q is an integer from 1 to 4.

10. The phase retardation film according to claim 1 or 2, wherein, The in-plane delays Re(450) and Re(550) of the phase retardation film satisfy the following equation (iv): 。 11. The phase retardation film according to claim 1 or 2, wherein, The glass transition temperature (TgA) of resin A is above 100°C and below 160°C. The glass transition temperature (TgB) of the resin B is above 100°C and below 160°C.

12. The phase retardation film according to claim 1 or 2, wherein, The difference between the glass transition temperature TgA of resin A and the glass transition temperature TgB of resin B, |TgA-TgB|, is less than 15°C.

13. The phase retardation film according to claim 1 or 2, wherein, The thickness of the phase retardation film is less than 90 μm.

14. The phase retardation film according to claim 1 or 2, wherein, The thickness of the phase retardation film is less than 70 μm.

15. A method for manufacturing a retardation film, as described in any one of claims 1 to 14, the method comprising: A process for preparing a multilayer film having a layer formed of resin A and a layer formed of resin B; Resin A has positive intrinsic birefringence, and resin B has negative intrinsic birefringence; and The process of stretching the multilayer film.

16. The method for manufacturing a retardation film according to claim 15, wherein, The process of preparing the multilayer film includes the step of melt extruding the resin A and the resin B.

17. The method for manufacturing a retardation film according to claim 15 or 16, wherein, The process of stretching the multilayer film includes a stretching step at a stretching temperature above "Tg(h)-10℃" and below "Tg(h)+20℃", where Tg(h) represents the higher of the glass transition temperature TgA of resin A and the glass transition temperature TgB of resin B.

18. The method for manufacturing a retardation film according to claim 15 or 16, wherein, The process of stretching the multilayer film includes a stretching step at a stretching ratio of 1.5 times or more and 5.0 times or less.

19. The method for manufacturing a phase retardation film according to claim 15 or 16, wherein, The process of stretching the multilayer film includes the step of stretching the multilayer film along an inclined direction.

20. A polarizer comprising a phase difference film and a linear polarizer as described in any one of claims 1 to 14.

21. An image display device having a phase difference film according to any one of claims 1 to 14.

Images