Retardation film, elliptically polarizing plate, and organic el display device

Abstract

This retardation film comprises a laminate including a first retardation layer and a second retardation layer overlapping the first retardation layer. Ny1 < Nx1 < Nz1 is established where: Nx1 represents the refractive index of the first retardation layer in a direction in which the in-plane slow axis of the first retardation layer extends; Ny1 represents the refractive index of the first retardation layer in a direction perpendicular to the direction in which the in-plane slow axis of the first retardation layer extends and the thickness direction of the first retardation layer; and Nz1 represents the refractive index of the first retardation layer in the thickness direction thereof. The second retardation layer is a positive A-type retardation layer. The direction in which the in-plane slow axis of the first retardation layer extends and the direction in which the in-plane slow axis of the second retardation layer extends form an angle θ which is 15°-75°. Formulae (i)-(iii) are achieved when: ReAC550 represents the in-plane retardation of the laminate at a wavelength of 550 nm; ReAC450 represents the in-plane retardation of the laminate at a wavelength of 450 nm; and RthAC550 represents the thickness-direction retardation of the laminate at a wavelength of 550 nm.

Description

Retardation film, elliptically polarizing plate and organic EL display device

[0001] The present disclosure relates to a retardation film, an elliptically polarizing plate, and an organic EL display device.

[0002] Conventionally, retardation films that impart a desired phase difference to incident light using a retardation layer have been known, and are applied to display devices that display images, etc. As an example, in an organic electroluminescence (organic EL) display device, a quarter-wave retardation layer is used as a circular polarizer in combination with a linear polarizer. In this example, the circular polarizer functions as an external light antireflection film. Furthermore, conventionally, in display devices, a retardation film that combines a positive A plate having positive A characteristics and a positive C plate having positive C characteristics has been used as a part of a polarizer compensation film in order to increase contrast in an oblique viewing direction (for example, Patent Document 1).

[0003] Patent No. 4592005

[0004] Depending on the manufacturing method, the in-plane refractive index of the retardation layer prepared with the intention of becoming a positive C-type retardation layer may not be constant.In this case, the in-plane refractive index of the retardation layer prepared with the intention of becoming a positive C-type retardation layer may not be constant, which may impair the optical properties of the retardation film.For this reason, there is a demand for a retardation film that can ensure optical properties while using a retardation layer with an inconstant in-plane refractive index as a substitute for a positive C-type retardation layer.

[0005] The present disclosure has been made in consideration of the above points, and aims to provide a retardation film that can ensure optical properties while using a retardation layer having an in-plane refractive index that is not constant as a substitute for a positive C-type retardation layer.

[0006] Embodiments of the present disclosure relate to the following [1] to

[15] .

[0007] [1] A laminate including a first retardation layer and a second retardation layer overlapping the first retardation layer, wherein Nx1 is a refractive index of the first retardation layer in an extension direction of an in-plane slow axis, Ny1 is a refractive index of the first retardation layer in a direction perpendicular to the extension direction of the in-plane slow axis and the thickness direction of the first retardation layer, and Nz1 is a refractive index of the first retardation layer in a thickness direction, where Ny1<Nx1<Nz1; the second retardation layer is a positive A-type retardation layer; the angle θ between the extension direction of the in-plane slow axis of the first retardation layer and the extension direction of the in-plane slow axis of the second retardation layer is 15° or more and 75° or less; and the in-plane retardation of the laminate at a wavelength of 550 nm is Re ＡＣ５５０ The in-plane retardation of the laminate at a wavelength of 450 nm is defined as Re ＡＣ４５０ The thickness direction retardation of the laminate at a wavelength of 550 nm is Rth ＡＣ５５０ When the following formulas (i) to (iii) are satisfied, a retardation film is provided.

[0008] [2] A laminate including a first retardation layer and a second retardation layer overlapping the first retardation layer, wherein Nx1 is a refractive index of the first retardation layer in an extension direction of an in-plane slow axis, Ny1 is a refractive index in a direction perpendicular to the extension direction of the in-plane slow axis and a thickness direction of the first retardation layer, and Nz1 is a refractive index in the thickness direction of the first retardation layer, where Ny1<Nx1<Nz1; the second retardation layer is a positive A-type retardation layer; the angle θ between the extension direction of the in-plane slow axis of the first retardation layer and the extension direction of the in-plane slow axis of the second retardation layer is 0° or more and 45° or less; and the in-plane retardation of the laminate at a wavelength of 550 nm is Re ＡＣ５５０ The in-plane retardation of the laminate at a wavelength of 450 nm is defined as Re ＡＣ４５０ The thickness direction retardation of the laminate at a wavelength of 550 nm is Rth ＡＣ５５０ When the following formulas (iv) to (vi) are satisfied, a retardation film is provided.

[0009] [3] A laminate including a first retardation layer and a second retardation layer overlapping the first retardation layer, wherein Nx1 is a refractive index of the first retardation layer in an extension direction of an in-plane slow axis, Ny1 is a refractive index of the first retardation layer in a direction perpendicular to the extension direction of the in-plane slow axis and the thickness direction of the first retardation layer, and Nz1 is a refractive index of the first retardation layer in the thickness direction, where Ny1<Nx1<Nz1; the second retardation layer is a positive A-type retardation layer; the angle θ between the extension direction of the in-plane slow axis of the first retardation layer and the extension direction of the in-plane slow axis of the second retardation layer is 45° or more and 90° or less; and the in-plane retardation of the laminate at a wavelength of 550 nm is Re ＡＣ５５０ The in-plane retardation of the laminate at a wavelength of 450 nm is defined as Re ＡＣ４５０ The thickness direction retardation of the laminate at a wavelength of 550 nm is Rth ＡＣ５５０ When the following formulas (vii) to (ix) are satisfied, a retardation film is provided.

[0010] [4] The retardation film according to any one of [1] to [3], wherein the second retardation layer is directly adjacent to the first retardation layer.

[0011] [5] The retardation film according to any one of [1] to [4], wherein the second retardation layer contains a polymerizable liquid crystal compound.

[0012] [6] The retardation film according to any one of [1] to [5], wherein the first retardation layer contains a photoalignable component.

[0013] [7] The retardation film according to any one of [1] to [6], wherein the first retardation layer contains an ultraviolet absorber.

[0014] [8] The in-plane retardation of the first retardation layer at a wavelength of 550 nm is Re Ｃ５５０ The thickness direction retardation of the first retardation layer at a wavelength of 550 nm is Rth Ｃ５５０ The retardation film according to any one of [1] to [7], wherein the following formulas (x) to (xi) are satisfied:

[0015] [9] The in-plane retardation of the first retardation layer at a wavelength of 550 nm is Re Ｃ５５０ When this is the case, Re Ｃ５５０ The retardation film according to any one of [1] to [8], wherein the thickness is 0.5 nm or more.

[0016]

[10] The retardation film according to any one of [1] to [9], further comprising a resin substrate directly adjacent to the first retardation layer.

[0017]

[11] The retardation film according to

[10] , wherein the resin substrate is made of any one of polyethylene terephthalate, triacetyl cellulose, an acrylic resin, and a cycloolefin polymer.

[0018]

[12] The retardation film according to

[10] or

[11] , wherein the resin substrate, the first retardation layer, and the second retardation layer are laminated in this order.

[0019]

[13] The resin substrate is a release substrate that can be peeled off from the laminate including the first retardation layer and the second retardation layer.

[10] The retardation film according to any one of

[12] to

[13] .

[0020]

[14] An elliptically polarizing plate comprising: the retardation film according to any one of [1] to

[13] ; and a polarizing plate superimposed on the retardation film.

[0021]

[15] An organic EL display device comprising the elliptically polarizing plate according to

[14] .

[0022] Effect of the Invention According to the embodiments of the present disclosure, a retardation film can be provided that can ensure optical properties while using a retardation layer having an in-plane refractive index that is not constant as an alternative to a positive C plate.

[0023] FIG. 1 is a cross-sectional view showing a retardation film according to an embodiment. FIG. 2 is a cross-sectional view showing a retardation film according to an embodiment. FIG. 3 is a view showing an example of a process for forming a film used as a material for a resin substrate. FIG. 4 is an enlarged view of an area surrounded by a dashed line marked with symbol IV in FIG. 2. FIG. 5 is a view showing an example of an extension direction of an in-plane slow axis of a first retardation layer. FIG. 6 is a cross-sectional view showing an elliptically polarizing plate according to an embodiment. FIG. 7 is a cross-sectional view showing a retardation film according to Modification 1. FIG. 8 is a cross-sectional view showing a retardation film according to Modification 2. FIG. 9 is a cross-sectional view showing a retardation film according to Modification 2. FIG. 10 is a cross-sectional view showing an elliptically polarizing plate according to Modification 2. FIG. 11 is a cross-sectional view showing an elliptically polarizing plate according to Modification 2. FIG. 12 is a cross-sectional view showing a retardation film according to Modification 3.

[0024] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In the drawings accompanying this specification, the scale and aspect ratios of the actual objects have been appropriately changed and exaggerated for the sake of ease of illustration and understanding.

[0025] In this disclosure, the term "alignment force" refers to the action of aligning the liquid crystal compound in the retardation layer in a specific direction. In this disclosure, "horizontal alignment" refers to alignment in a direction perpendicular to the thickness direction of the retardation film 1. In this disclosure, "vertical alignment" refers to alignment in a direction parallel to the thickness direction of the retardation film 1. In this disclosure, "(meth)acrylic" refers to either acrylic or methacrylic. Terms used in this disclosure that specify shape and geometric conditions, as well as their degree, such as "parallel," "vertical," and "same," as well as values ​​of length and angle, are not bound by strict meanings but are interpreted to include a range within which similar functions can be expected. In this specification, terms such as "film" and "plate" are not distinguished from each other solely based on differences in name. In addition, in this disclosure, the term "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the lower and upper limits.

[0026] In the present disclosure, the in-plane retardation (Re) and thickness direction retardation (Rth) can be calculated from Nx, Ny, Nz and the thickness d (nm) of the retardation layer by the following formulas: In-plane retardation (Re) = (Nx - Ny) x d Thickness direction retardation (Rth) = ((Nx + Ny) / 2 - Nz) x d

[0027] In this disclosure, the in-plane retardation (Re) and thickness direction retardation (Rth) of a retarder or retardation layer are values ​​measured using a retardation measurement device (KOBRA-WR, manufactured by Oji Scientific Instruments Co., Ltd.). In this disclosure, the refractive indices Nx, Ny, and Nz are measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.) with a sodium lamp (λ = 589 nm) as a light source. When measuring wavelength dependency, measurements can be made using a multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.) in combination with an interference filter. Values ​​from the Polymer Handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can also be used. Examples of average refractive index values ​​for major optical films are listed below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

[0028] I. Retardation Film In the present disclosure, the refractive index in the direction in which the in-plane slow axis of the retardation layer extends is defined as Nx, the refractive index in the direction perpendicular to the extension direction of the in-plane slow axis of the retardation layer and the thickness direction of the retardation layer is defined as Ny, and the refractive index in the thickness direction of the retardation layer is defined as Nz. The in-plane slow axis is an axis line that faces the axial direction of the highest refractive index along the in-plane of the retardation layer.

[0029] In the present disclosure, a positive A-type retardation layer is a retardation layer that satisfies the relationship Nx>Ny≒Nz. The "≒" in the formula "Nx>Ny≒Nz" encompasses not only the case where both are completely identical, but also the case where both are substantially identical. For example, a case where (Ny-Nz) x d (where d is the thickness of the retardation layer) is -8 to 8 nm is also included in "Ny≒Nz". When "Ny≒Nz", (Ny-Nz) x d may be -5 to 5 nm. In the present disclosure, a positive C-type retardation layer is a retardation layer that satisfies the relationship Nx=Ny<Nz.

[0030] 1 and 2 are cross-sectional views showing a retardation film 1 of this embodiment. As shown in FIGS. 1 and 2, the retardation film 1 includes a laminate 2 including a first retardation layer 10 and a second retardation layer 20 overlapping the first retardation layer 10. The first retardation layer 10 has a first surface 10a facing the surface of the second retardation layer 20 and a second surface 10b located on the opposite side of the first surface 10a. The second retardation layer 20 has a first surface 20a facing the surface of the first retardation layer 10 and a second surface 20b located on the opposite side of the first surface 20a. The laminate 2 is a portion of the retardation film 1 located between the second surface 10b of the first retardation layer 10 and the second surface 20b of the second retardation layer 20. In the example shown in FIGS. 1 and 2, the second retardation layer 20 is directly adjacent to the first retardation layer 10. As shown in FIG. 2, the retardation film 1 may further include a resin substrate 30. In the example shown in FIG. 2, the resin substrate 30, the first retardation layer 10, and the second retardation layer 20 are laminated in this order. The retardation film 1 has a first surface 1a and a second surface 1b located opposite to the first surface 1a. In the retardation film 1 including the resin substrate 30 as shown in FIG. 2, the second surface 1b is the surface formed by the resin substrate 30. The first surface 1a is the surface opposite to the surface formed by the resin substrate 30. In the retardation film 1 not including the resin substrate 30 as shown in FIG. 1, the second surface 1b is the surface formed by peeling the resin substrate 30 from the laminate 2 as described below. The first surface 1a is the surface opposite to the surface formed by peeling the resin substrate 30 from the laminate 2 as described below. In the retardation film 1 of this embodiment, when an optical member such as an elliptically polarizing plate 40 is produced by overlaying a polarizing plate 41 on the retardation film 1 as described later, the first surface 1a faces the polarizing plate 41.

[0031] In this embodiment, the in-plane retardation of the laminate 2 at a wavelength of 550 nm is defined as Re ＡＣ５５０ The in-plane retardation of the laminate 2 at a wavelength of 450 nm is Re ＡＣ４５０ The thickness direction retardation of the laminate 2 at a wavelength of 550 nm is Rth ＡＣ５５０When this is the case, the following formulas (i) to (iii) hold. In this embodiment, as will be described later, the first retardation layer 10 is the first positive C-type corresponding layer 11, and the second retardation layer 20 is the first positive A-type retardation layer 21. In the retardation film 1 including the first retardation layer 10 which is the first positive C-type corresponding layer 11 and the second retardation layer 20 which is the first positive A-type retardation layer 21, the following formulas (i) to (iii) hold. From formula (i), it can be seen that the laminate 2 provides an overall retardation of about λ / 4. From formula (ii), it can be seen that by using the retardation film 1 in a display device or the like described later, the laminate 2 can exhibit the effect of increasing the contrast relative to the field of view from an oblique direction. From formula (ii), it can be seen that by using the retardation film 1 in a display device or the like, the laminate 2 can reduce the effect of the phenomenon (color shift) in which the display color appears different depending on the angle at which the display device is viewed. By virtue of the effect of the above-described formula (ii) being satisfied, when the retardation film 1 is used in a display device or the like, the viewing angle can be increased. ＡＣ５５０ Re ＡＣ４５０ It can be seen that the dispersion is larger, in other words, the laminate 2 exhibits reverse dispersion.

[0032] 1. First Retardation Layer In this embodiment, the first retardation layer 10 has the following characteristics. The refractive index of the first retardation layer 10 in the direction in which the in-plane slow axis extends is defined as Nx1. The refractive index in the direction perpendicular to the extension direction of the in-plane slow axis and the thickness direction of the first retardation layer 10 is defined as Ny1. The refractive index in the thickness direction of the first retardation layer 10 is defined as Nz1. In this case, Ny1<Nx1<Nz1.

[0033] In the first retardation layer 10, Ny1<Nx1. In this respect, the first retardation layer 10 is different from a positive C-type retardation layer in which Nx=Ny. As an example, the in-plane retardation of the first retardation layer 10 at a wavelength of 550 nm is set to Re Ｃ５５０ When this is the case, Re Ｃ５５０is 0.5 nm or more. The in-plane retardation of the first retardation layer 10 is not zero, but is small enough that the first retardation layer 10 exhibits a function corresponding to that of a positive C-type retardation layer in the retardation film 1. As an example, the in-plane retardation of the first retardation layer 10 at a wavelength of 550 nm is defined as Re Ｃ５５０ When this is the case, as shown in the formula (x) described later, Re Ｃ５５０ is smaller than 5 nm. The first retardation layer 10 of this embodiment, which exhibits a function corresponding to that of the positive C-type retardation layer, is particularly referred to as a first positive C-type corresponding layer 11.

[0034] The in-plane retardation and thickness direction retardation of the first retardation layer 10 are determined so that the above-mentioned formulas (i) to (iii) hold for the in-plane retardation and thickness direction retardation of the laminate 2. The in-plane retardation of the first retardation layer 10 at a wavelength of 550 nm is defined as Re Ｃ５５０ The thickness direction retardation of the first retardation layer 10 at a wavelength of 550 nm is defined as Rth Ｃ５５０ In this case, the following formulas (x) to (xi) may be satisfied in the first retardation layer 10. From formula (xi), it can be understood that by using the retardation film 1 in a display device or the like, the first retardation layer 10 can exhibit the effect of increasing the contrast with respect to a field of view from an oblique direction. From formula (xi), it can be understood that by using the retardation film 1 in a display device or the like, the first retardation layer 10 can reduce color shift.

[0035] In this embodiment, the first retardation layer 10 is the first positive C-type corresponding layer 11 and has an alignment regulating force that horizontally aligns the liquid crystalline component of the second retardation layer 20, which is a positive A-type retardation layer described later. This allows the second retardation layer 20 to be formed on the first retardation layer 10 so that the second retardation layer 20 is directly adjacent to the first retardation layer 10. In this embodiment, the first retardation layer 10 contains a photo-alignable component. As an example, the first retardation layer 10 contains a liquid crystalline component that aligns in a direction approximately perpendicular to the surface of the first retardation layer 10 and a photo-alignable component. The first retardation layer 10 of this embodiment may be a cured product of a thermosetting liquid crystal composition that contains a liquid crystalline component, a photo-alignable component, and a thermal crosslinking agent.

[0036] 1-1. Liquid Crystalline Component As the liquid crystal component contained in the first retardation layer 10, it is preferable to use a side-chain liquid crystal polymer having a liquid crystal structural unit containing a liquid crystal moiety in the side chain. By using a side-chain liquid crystal polymer having a liquid crystal structural unit containing a liquid crystal moiety in the side chain as the liquid crystal component contained in the first retardation layer 10, it is possible to easily align the liquid crystal component vertically even when the liquid crystal component is mixed with a photoalignable component. Furthermore, it is easy to impart flexibility to the first retardation layer 10.

[0037] The side-chain liquid crystal polymer (A) used in the present disclosure has a liquid crystalline structural unit containing a liquid crystalline moiety in the side chain, and may further have a non-liquid crystalline structural unit containing an alkylene group in the side chain. The side-chain liquid crystal polymer (A) has a liquid crystalline structural unit containing a liquid crystalline moiety in the side chain, and may further have a non-liquid crystalline structural unit containing an alkylene group in the side chain. Each structural unit in the side-chain liquid crystal polymer (A) will be described below.

[0038] (1) Liquid Crystalline Structural Unit In the present disclosure, the liquid crystal structural unit has a side chain containing a liquid crystalline moiety, i.e., a moiety exhibiting liquid crystallinity. The liquid crystal structural unit is preferably a structural unit containing a mesogen exhibiting liquid crystallinity in the side chain. The liquid crystal structural unit is preferably a structural unit derived from a compound exhibiting liquid crystallinity in which a polymerizable group is bonded to a mesogenic group via a spacer. In the present disclosure, the term "mesogen" refers to a highly rigid moiety exhibiting liquid crystallinity. Examples of mesogens include partial structures having two or more ring structures, preferably three or more ring structures, in which the ring structures are directly bonded to each other or in which the ring structures are connected via one to three atoms. Having such a moiety exhibiting liquid crystallinity in the side chain facilitates vertical alignment of the liquid crystal structural unit. The ring structure may be an aromatic ring such as benzene, naphthalene, or anthracene, or a cyclic aliphatic hydrocarbon such as cyclopentyl or cyclohexyl. Furthermore, when the ring structures are linked via one to three atoms, examples of the structure of the linking portion include -O-, -S-, -O-C(=O)-, -C(=O)-O-, -O-C(=O)-O-, -NR-C(=O)-, -C(=O)-NR-, -O-C(=O)-NR-, -NR-C(=O)-O-, -NR-C(=O)-NR-, -O-NR-, and -NR-O- (R is a hydrogen atom or a hydrocarbon group). Among these, the mesogen is preferably a rod-shaped mesogen in which the ring structures are connected at the para-position in the case of benzene or at the 2- and 6-positions in the case of naphthalene so that they form a rod shape.

[0039] Furthermore, when the liquid crystalline structural unit is a structural unit containing a mesogen exhibiting liquid crystallinity in the side chain, it is preferable that the terminal of the side chain of the structural unit is a polar group or has an alkyl group, from the viewpoint of facilitating vertical alignment of the liquid crystalline structural unit. Specific examples of such polar groups include -F, -Cl, -CN, and -OCF. ３ , -OCF ２ H, -NCO, -NCS, -NO ２ , -NHC(=O)-R', -C(=O)-OR', -OH, -SH, -CHO, -SO ３ H, —NR′ ２, -R", or -OR" (R' is a hydrogen atom or a hydrocarbon group, and R" is an alkyl group).

[0040] The liquid crystal structural unit has a side chain of -R ２ - (L １ -Ar １ ) ａ -R ３ (wherein R ２ is -(CH ２ ) ｍ -, or - (C ２ H ４ O) ｍ’ represents a group represented by -. １ represents a single bond or a linking group represented by -O-, -OCO-, or -COO-, and １ represents an arylene group having 6 to 10 carbon atoms which may have a substituent, and a plurality of L １ and Ar １ may be the same or different. ３ is -F, -Cl, -CN, -OCF ３ , -OCF ２ H, -NCO, -NCS, -NO ２ , -NHCO-R ４ , -CO-OR ４ , -OH, -SH, -CHO, -SO ３ H, -NR ４ ２ , -R ５ , or -OR ５ , R ４ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ５ represents an alkyl group having 1 to 6 carbon atoms; a is an integer of 2 to 4, and m and m' are each independently an integer of 2 to 10.

[0041] R ２ In the formula, m and m' are each independently an integer of 2 to 10. From the viewpoint of facilitating vertical alignment of the liquid crystal structural units, m and m' are preferably 2 to 8, and more preferably 2 to 6.

[0042] Ar １In the formula (I), examples of the arylene group having 6 to 10 carbon atoms which may have a substituent include a phenylene group and a naphthylene group, and among these, a phenylene group is more preferred. ３ Examples of the substituent other than the above include an alkyl group having 1 to 5 carbon atoms, and halogen atoms such as a fluorine atom, a chlorine atom, and a bromine atom.

[0043] R ３ In R ４ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and is preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. ３ In R ５ is an alkyl group having 1 to 6 carbon atoms, and is preferably an alkyl group having 1 to 5 carbon atoms.

[0044] The liquid crystal structural unit is preferably a structural unit derived from a monomer having a polymerizable ethylenic double bond-containing group. Examples of such a monomer having an ethylenic double bond-containing group include derivatives such as (meth)acrylic acid ester, styrene, (meth)acrylamide, maleimide, vinyl ether, or vinyl ester. Among these, the liquid crystal structural unit is preferably a structural unit derived from a (meth)acrylic acid ester derivative, from the viewpoint of facilitating vertical alignment of the liquid crystal structural unit.

[0045] In the present disclosure, the liquid crystalline constitutional unit preferably contains a constitutional unit represented by the following general formula (I), from the viewpoint of facilitating vertical alignment of the liquid crystalline constitutional unit.

[0046] (In general formula (I), R １ represents a hydrogen atom or a methyl group, R ２ is -(CH ２ ) ｍ -, or - (C ２ H ４ O) ｍ’ represents a group represented by -. １ represents a single bond or a linking group represented by -O-, -OCO-, or -COO-, and １ represents an arylene group having 6 to 10 carbon atoms which may have a substituent, and a plurality of L１ and Ar １ may be the same or different. ３ is -F, -Cl, -CN, -OCF ３ , -OCF ２ H, -NCO, -NCS, -NO ２ , -NHCO-R ４ , -CO-OR ４ , -OH, -SH, -CHO, -SO ３ H, -NR ４ ２ , -R ５ , or -OR ５ , R ４ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ５ represents an alkyl group having 1 to 6 carbon atoms; a is an integer of 2 to 4, and m and m' are each independently an integer of 2 to 10.

[0047] In the structural unit represented by general formula (I), -R ２ -(L1-Ar １ ) ａ -R ３ The group represented by may be the same as above.

[0048] Suitable specific examples of the liquid crystalline constitutional unit represented by general formula (I) include, but are not limited to, those represented by the following general formulae (I-1), (I-2) and (I-3).

[0049]

[0050] In the constitutional units represented by the above general formulas (I-1) to (I-3), R ２ , and R ３ are R in general formula (I), ２ , and R ３ is the same as:

[0051] In the present disclosure, the liquid crystal constitutional unit may be used alone or in combination of two or more.

[0052] The copolymer can be synthesized using a monomer such as a (meth)acrylic acid ester derivative that derives a liquid crystalline structural unit. The monomer such as a (meth)acrylic acid ester derivative that derives a liquid crystalline structural unit can be used alone or in combination of two or more.

[0053] The content of the liquid crystalline structural unit in the copolymer may be 100 mol % when the amount of structural units contained in the entire copolymer is taken as 100 mol %. The content of the liquid crystalline structural unit in the copolymer is preferably set within the range of 40 mol % to 90 mol %, more preferably within the range of 40 mol % to 80 mol %, further preferably within the range of 45 mol % to 70 mol %, and particularly preferably within the range of 50 mol % to 65 mol %. By setting the content of the liquid crystalline structural unit in the copolymer within the above range, the liquid crystalline structural unit can be easily aligned vertically. The content of each structural unit in the copolymer is as follows: １ It can be calculated from the integral value obtained by H-NMR measurement.

[0054] (2) Non-liquid crystal structural unit containing an alkylene group in the side chain When the side chain liquid crystal polymer is in a liquid crystal state, the side chain containing the alkylene group has the effect of promoting vertical alignment of the portion (mesogen) exhibiting liquid crystallinity in the side chain of the liquid crystal structural unit. When the non-liquid crystal structural unit containing an alkylene group in the side chain is contained, the side chain liquid crystal polymer (A) is more likely to be vertically aligned and is more likely to dissolve in a solvent. The non-liquid crystal structural unit containing an alkylene group in the side chain has a side chain containing -L ２ -R １３ , or -L ２’ -R １４ (wherein L ２ Ha-(CH ２ ) ｎ represents -, L ２’ Ha-(C ２ H ４ O) ｎ’ represents a linking group represented by -, and R １３ represents a methyl group which may have a substituent, an aryl group which may have an alkyl group, or —OR １５ represents R １４and R １５ each independently represent an alkyl group which may have a substituent or an aryl group which may have a substituent, and n and n′ each independently represent an integer of 1 to 18.

[0055] L ２ Ha-(CH ２ ) ｎ represents -, L ２’ Ha-(C ２ H ４ O) ｎ’ In particular, from the viewpoint of facilitating vertical alignment of the side chain type liquid crystal polymer (A), a linking group represented by -(CH ２ ) ｎ n is an integer of 1 to 18, and preferably an integer of 2 to 18. １３ When n is a methyl group having a substituent or an alkyl group having a substituent, n is preferably an integer of 1. Furthermore, n' is an integer of 1 to 18, preferably an integer of 1 to 8, and more preferably an integer of 2 to 8.

[0056] R １４ and R １５ The alkyl group in R may be linear, branched, or cyclic, but is preferably linear. １４ , and R １５ The alkyl group in is preferably an alkyl group having 1 to 20 carbon atoms, and specific examples thereof include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-octyl, and n-decyl groups, branched alkyl groups such as i-propyl, i-butyl, and t-butyl groups, alkenyl groups such as 1-propenyl and 1-butenyl groups, alkynyl groups such as ethynyl and 2-propynyl groups, cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, norbornyl, and adamantyl groups, and cycloalkenyl groups such as 1-cyclohexenyl groups. In the case of the above cycloalkyl groups, it is preferable that the linear alkyl group is substituted with a cycloalkyl group.

[0057] R １４ and R １５ The alkyl group in is not particularly limited, but is preferably an alkyl group having 1 to 12 carbon atoms in terms of in-plane uniformity of retardation.

[0058] R １３ , R １４ , and R １５ The aryl group in is preferably an aryl group having 6 to 20 carbon atoms, and specific examples thereof include a phenyl group, a naphthyl group, and an anthracenyl group, with a phenyl group or a naphthyl group being preferred, and a phenyl group being more preferred. In the case of the aryl group, it is preferred that the aryl group is substituted with a linear alkyl group.

[0059] The non-liquid crystal structural unit containing an alkylene group in the side chain may have a reactive group as a substituent that reacts with other components, for example, may have a thermally crosslinkable group similar to that of the copolymer (B) described below. Examples of the non-liquid crystal structural unit containing an alkylene group in the side chain include a non-liquid crystal, non-crosslinkable structural unit and a non-liquid crystal, thermally crosslinkable structural unit. The non-liquid crystal structural unit containing an alkylene group in the side chain may contain only a non-liquid crystal, non-crosslinkable structural unit, or may contain only a non-liquid crystal, non-crosslinkable structural unit. From the viewpoint of facilitating vertical alignment of the non-liquid crystal structural unit, the non-liquid crystal structural unit preferably contains at least a non-liquid crystal, non-crosslinkable structural unit. From the viewpoint of further improving durability, it is more preferable that the non-liquid crystal, non-crosslinkable structural unit and the non-liquid crystal, non-crosslinkable structural unit are contained.

[0060] In the non-liquid crystal and non-crosslinkable structural unit containing an alkylene group in the side chain, R １３ The substituents that the methyl group in R １４ and R １５ Examples of the substituent that the alkyl group in the formula (I) may have include non-crosslinkable substituents, such as halogen atoms such as fluorine atom, chlorine atom and bromine atom, alkoxy groups, nitro groups, etc. Among these, halogen atoms such as fluorine atom, chlorine atom and bromine atom are preferred.

[0061] In the non-liquid crystal and non-crosslinkable structural unit containing an alkylene group in the side chain, R１３ , R １４ , and R １５ Examples of the substituent that the aryl group in (I) may have include non-crosslinkable substituents, such as halogen atoms (e.g., fluorine, chlorine, bromine), alkyl groups, alkoxy groups, and nitro groups. Examples of the alkyl group include alkyl groups having 1 to 12 carbon atoms, such as alkyl groups having 1 to 9 carbon atoms. These alkyl groups may be linear alkyl groups or alkyl groups having a branched or cyclic structure. Among these, halogen atoms (e.g., fluorine, chlorine, bromine), and alkyl groups having 1 to 9 carbon atoms are preferred. Specific examples of the alkyl group include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, cyclopentyl, cyclohexyl, cyclohexylmethyl, cyclohexylethyl, and cyclohexylpropyl groups. Hydrogen atoms in the alkyl group may be substituted with halogen atoms.

[0062] In the non-liquid crystalline and thermally crosslinkable structural unit containing an alkylene group in the side chain, a methyl group in R １４ and R １５ The alkyl group in １３ , R １４ , and R １５ The substituent that the aryl group in R may have is preferably a thermally crosslinkable group, and examples thereof include the same thermally crosslinkable groups as those in the copolymer (B) described below, and may be, for example, at least one selected from the group consisting of a hydroxy group, a carboxy group, a mercapto group, a glycidyl group, an amino group, an amide group, a hydroxymethyl group, an alkoxymethyl group, a trialkoxysilyl group, a blocked isocyanate group, and an alkoxy group substituted with a methyl group. The hydroxymethyl group and the alkoxymethyl group, which are self-crosslinking groups, are preferably selected from the group consisting of R １３The methyl group in the formula (I) may be substituted with a hydroxy group or an alkoxy group to form a hydroxymethyl group or an alkoxymethyl group. As the thermally crosslinkable group, a hydroxy group is preferred from the viewpoint of reactivity, and a primary hydroxy group is more preferred. A primary hydroxy group refers to a hydroxy group in which the carbon atom to which the hydroxy group is bonded is a primary carbon atom.

[0063] The non-liquid crystal structural unit is preferably a structural unit derived from a monomer having a polymerizable ethylenic double bond-containing group. Examples of such a monomer having an ethylenic double bond-containing group include derivatives such as (meth)acrylic acid ester, styrene, (meth)acrylamide, maleimide, vinyl ether, or vinyl ester. From the viewpoint of facilitating vertical alignment of the non-liquid crystal structural unit, the non-liquid crystal structural unit is preferably a structural unit derived from a (meth)acrylic acid ester derivative or styrene, and more preferably a structural unit derived from a (meth)acrylic acid ester derivative.

[0064] In the present disclosure, the non-liquid crystal structural unit preferably has a structural unit represented by the following formula (II):

[0065] (In general formula (II), R １１ represents a hydrogen atom or a methyl group, R １２ Is, -L ２ -R １３ , or -L ２’ -R １４ and L represents a group represented by ２ Ha-(CH ２ ) ｎ represents -, L ２’ Ha-(C ２ H ４ O) ｎ’ represents a linking group represented by -, and R １３ represents a methyl group which may have a substituent, an aryl group which may have an alkyl group, or —OR １５ represents R １４ and R １５each independently represents an alkyl group which may have a substituent or an aryl group which may have a substituent, and n and n' each independently represent an integer of 1 to 18.

[0066] In the constitutional unit represented by formula (II), -L ２ -R １３ , or -L ２’ -R １４ The group represented by may be the same as above.

[0067] In the present disclosure, when the non-liquid crystal structural unit is a non-liquid crystal and non-crosslinkable structural unit, examples of the optional substituent contained in the structural unit represented by formula (II) include the above-mentioned non-crosslinkable substituent. In the present disclosure, when the non-liquid crystal structural unit is a non-liquid crystal and thermally crosslinkable structural unit, examples of the optional substituent contained in the structural unit represented by formula (II) include the above-mentioned thermally crosslinkable group. It is preferable that one non-liquid crystal and thermally crosslinkable structural unit has one thermally crosslinkable group, but it may have two or more thermally crosslinkable groups.

[0068] In the present disclosure, when the non-liquid crystalline constituent unit includes a non-liquid crystalline and thermally crosslinkable constituent unit, it is preferable that the non-liquid crystalline constituent unit include a constituent unit represented by the following formula (III) from the viewpoints of improving reactivity and durability.

[0069] (In the above formula (III), Z ａ represents at least one monomer unit selected from the group consisting of the following formulae (a-1) to (a-6), and R １６ is a linear alkylene group having 1 to 11 carbon atoms which may have —O— in the carbon chain, and Y ａ represents a thermally crosslinkable group.)

[0070] (In the above formulas (a-1) to (a-6), R １１ represents a hydrogen atom, a methyl group, a chlorine atom, or a phenyl group; R １７ represents a hydrogen atom or a methyl group, R １８ is a hydrogen atom, a methyl group, a chlorine atom or a phenyl group, R １９ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; L ａrepresents a single bond, —O—, —S—, —COO—, —COS—, —CO—, or —OCO—; L ａ is a single bond, R １６ is directly bonded to the styrene backbone.)

[0071] R １６ is a linear alkylene group having 1 to 11 carbon atoms which may have —O— in the carbon chain, and —(CH ２ ) ｎ” -or- (C ２ H ４ O) ｍ” -C ２ H ４ - (n" is 1 to 11, m" is 1 to 4), preferably n" is 2 to 11, m" is 1 to 4, and preferably n" is 4 to 11, m" is 2 to 4. If n" and m" are too small, the distance between the thermally crosslinkable group and the main skeleton of the copolymer in the thermally crosslinkable constituent unit will be short, making it difficult for the thermal crosslinking agent to bond to the thermally crosslinkable group and potentially reducing the reactivity between the thermally crosslinkable constituent unit and the thermal crosslinking agent. On the other hand, if n" and m" are too large, the chain length of the linking group in the thermally crosslinkable constituent unit will be long, making it difficult for the terminal thermally crosslinkable group to be exposed to the surface and making it difficult for the thermal crosslinking agent to bond to the thermally crosslinkable group, potentially reducing the reactivity between the thermally crosslinkable constituent unit and the thermal crosslinking agent. The thermally crosslinkable group of Ya may be the same as the thermally crosslinkable group described above, and may be, for example, at least one selected from the group consisting of a hydroxy group, a carboxy group, a mercapto group, a glycidyl group, an amino group, an amide group, a hydroxymethyl group, an alkoxymethyl group, a trialkoxysilyl group, a blocked isocyanate group, and an alkoxy group substituted with a methyl group. The hydroxymethyl group and the alkoxymethyl group, which are self-crosslinking groups, may be substituted with a methyl group (R １６ The methylene group in the formula (I) may be substituted with a hydroxy group or an alkoxy group to form a hydroxymethyl group or an alkoxymethyl group.

[0072] Furthermore, in the present disclosure, when the non-liquid crystalline constituent unit includes a non-liquid crystalline and thermally crosslinkable constituent unit, the non-liquid crystalline and thermally crosslinkable constituent unit may be the same as the constituent unit represented by formula (III) described below, which is explained in the side chain liquid crystal polymer (A) of the second present disclosure described below.

[0073] The copolymer may have one type of non-liquid crystal structural unit, or two or more types. Of the structural units represented by general formula (II), examples of non-liquid crystal and non-crosslinkable structural units include the following chemical formulas (II-1) to (II-10). Of the structural units represented by general formula (II), examples of non-liquid crystal and thermally crosslinkable structural units include structures in which one hydrogen atom of the hydrocarbon group of the following chemical formulas (II-1) to (II-10) is substituted with the thermally crosslinkable group. Furthermore, examples of non-liquid crystal and thermally crosslinkable structural units include the following chemical formulas (III-1) to (III-11).

[0074]

[0075]

[0076] In addition, structural units represented by chemical formulas (III-1) to (III-12) described in paragraph 0294 of WO 2022 / 158555 can also be used.

[0077] The copolymer can be synthesized using a monomer such as a (meth)acrylic acid ester derivative that derives the non-liquid crystal structural unit. The monomer such as a (meth)acrylic acid ester derivative that derives the non-liquid crystal structural unit can be used alone or in combination of two or more.

[0078] The content of the non-liquid crystal structural unit in the copolymer is preferably set within the range of 10 mol% to 60 mol%, more preferably within the range of 15 mol% to 50 mol%, even more preferably within the range of 15 mol% to 45 mol%, and particularly preferably within the range of 20 mol% to 40 mol%, when the amount of structural units contained in the entire copolymer is taken as 100 mol%. By setting the content of the non-liquid crystal structural unit in the copolymer within the above range, it is possible to facilitate vertical alignment of the liquid crystal structural unit.

[0079] When the copolymer contains both a non-liquid crystal non-crosslinkable structural unit and a non-liquid crystal thermally crosslinkable structural unit as the non-liquid crystal structural unit, the content of the non-liquid crystal thermally crosslinkable structural unit is preferably set in the range of 10 mol % to 70 mol %, and more preferably set in the range of 30 mol % to 50 mol %, when the total amount of the non-liquid crystal structural units contained in the entire copolymer is taken as 100 mol %. The content of each structural unit in the copolymer is １ It can be calculated from the integral value obtained by H-NMR measurement.

[0080] (3) Other Structural Units The side-chain liquid crystal polymer (A) used in the present disclosure may further contain other structural units. Examples of such structural units include a thermally crosslinkable structural unit that does not contain an alkylene group in its side chain but has the thermally crosslinkable group, and a photoalignable structural unit that contains a photoalignable group in its side chain, which is contained in the copolymer (B) described below. Examples of thermally crosslinkable structural units that do not contain an alkylene group in their side chain but have the thermally crosslinkable group include (meth)acrylic acid, 4-hydroxystyrene, and 4-carboxystyrene. The side-chain liquid crystal polymer (A) used in the present disclosure preferably contains at least one thermally crosslinkable structural unit that contains a thermally crosslinkable group in its side chain, selected from the group consisting of non-liquid crystalline and thermally crosslinkable structural units that contain an alkylene group in their side chain and thermally crosslinkable structural units that do not contain an alkylene group in their side chain but have the thermally crosslinkable group, in order to improve the durability and reliability of the retardation layer. The photoalignable structural unit may be the same as the photoalignable structural unit containing a photoalignable group in the side chain that is contained in the copolymer (B) described below.

[0081] The content of the other structural units in the copolymer is preferably set within a range of 30 mol % or less, and more preferably within a range of 20 mol % or less, when the amount of structural units contained in the entire copolymer is taken as 100 mol %. By setting the content of the other structural units in the copolymer within the above range, it is possible to easily align the liquid crystalline structural units vertically.

[0082] (4) Copolymer of Side Chain Liquid Crystal Polymer (A) In the present disclosure, the side chain liquid crystal polymer (A) may be a block copolymer having a block portion consisting of a liquid crystalline structural unit and a block portion consisting of a non-liquid crystal structural unit containing an alkylene group in the side chain, or may be a random copolymer in which the liquid crystalline structural unit and the non-liquid crystal structural unit containing an alkylene group in the side chain are irregularly arranged.In the present disclosure, from the viewpoint of facilitating vertical alignment of the side chain liquid crystal polymer and making the retardation value more uniform in the plane of the first retardation layer 10, it is preferably a random copolymer.

[0083] The mass average molecular weight Mw of the side chain liquid crystal polymer copolymer is not particularly limited, but is preferably in the range of 10,000 to 100,000, more preferably in the range of 30,000 to 90,000, and even more preferably in the range of 40,000 to 80,000. When the mass average molecular weight Mw is within the above range, the side chain liquid crystal polymer is more likely to be vertically aligned.

[0084] The weight average molecular weight Mw is a value measured by GPC (gel permeation chromatography). Measurements were performed using a Tosoh Corporation HLC-8120GPC, with the elution solvent being N-methylpyrrolidone to which 0.01 mol / liter of lithium bromide had been added, and the polystyrene standards for the calibration curve were Mw 377,400, 210,500, 96,000, 50,400, 206,500, 10,850, 5,460, 2,930, 1,300, and 580 (all manufactured by Polymer Laboratories, Inc. Easi PS-2 series) and Mw 1,090,000 (manufactured by Tosoh Corporation), and the measurement column was a TSK-GEL ALPHA-M × 2 (manufactured by Tosoh Corporation).

[0085] The synthesis method of the copolymer of side chain type liquid crystal polymer (A) can be a method of copolymerizing a monomer that induces a liquid crystal constitutional unit with a monomer that induces a non-liquid crystal constitutional unit that contains an alkylene group in the side chain by a conventionally known production method.The side chain type liquid crystal polymer (A) may be used in the form of a solution when the copolymer is synthesized, or in the form of a powder, or in the form of a solution obtained by redissolving the purified powder in a solvent described below.

[0086] The side-chain liquid crystal polymer (A) may be used alone or in combination of two or more. In the present disclosure, from the viewpoint of facilitating vertical alignment of the side-chain liquid crystal polymer, the content of the side-chain liquid crystal polymer is preferably 20 parts by mass to 80 parts by mass, more preferably 25 parts by mass to 70 parts by mass, and even more preferably 30 parts by mass to 60 parts by mass, per 100 parts by mass of the solid content of the liquid crystal composition. In the present disclosure, the solid content refers to all components excluding the solvent. For example, even if the polymerizable liquid crystal compound described below is in a liquid state, it is included in the solid content.

[0087] 1-2. Photo-alignment component Examples of the photo-alignment component contained in the first retardation layer 10 include a compound containing a photo-alignment group, or a polymer having a photo-alignment structural unit containing a photo-alignment group in a side chain. The photo-alignment component may be a copolymer having a photo-alignment structural unit containing a photo-alignment group in a side chain and a thermally crosslinkable structural unit containing a thermally crosslinkable group in a side chain, or may be a compound having a photo-alignment group and a thermally crosslinkable group different from the copolymer.

[0088] As the photo-alignable component contained in the first retardation layer 10, which is a cured product of a thermosetting liquid crystal composition containing a photo-alignable component and a thermal crosslinking agent, it is preferable to use a copolymer having a photo-alignable structural unit containing a photo-alignable group in a side chain and a thermal crosslinkable structural unit containing a thermal crosslinkable group in a side chain, from the viewpoint of facilitating vertical alignment of the liquid crystal component and sufficiently increasing the alignment control force of the first retardation layer 10. Among these, it is preferable to use a copolymer (B) (photo-alignable copolymer) having a photo-alignable structural unit containing a photo-alignable group in a side chain by a specific structure and a thermal crosslinkable structural unit containing a thermal crosslinkable group in a side chain.

[0089] (1) Photo-alignable structural unit The photo-alignable structural unit of the present disclosure may have a structural unit represented by the following formula (1).

[0090] (In the above formula (1), Z １ represents at least one monomer unit selected from the group consisting of the following formulas (1-1) to (1-6), X represents a photoalignment group, and L １１ represents a single bond, —O—, —S—, —COO—, —COS—, —CO—, —OCO—, or a combination of any of these with an arylene group.

[0091] (In the above formulas (1-1) to (1-6), R ２１ represents a hydrogen atom, a methyl group, a chlorine atom, or a phenyl group; R ２２ represents a hydrogen atom or a methyl group, R ２３ is a hydrogen atom, a methyl group, a chlorine atom or a phenyl group, R ２４ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0092] The monomer unit constituting the photoalignable structural unit may be at least one selected from the group consisting of the above formulas (1-1) to (1-6). １ is at least one selected from the group consisting of formula (1-2), -L １１ -X may be bonded to any of the ortho, meta, and para positions, but -L １１ It is preferable that -X is bonded to the para position, since this tends to reduce the distance between the photo-alignable groups and makes it easier to obtain photo-alignment. As the monomer unit constituting the photo-alignable structural unit, at least one selected from the group consisting of formulas (1-1) and (1-2) is preferred, from the viewpoint of ease of raw material procurement. Furthermore, when at least one selected from the group consisting of formula (1-2) is used, the photo-alignable component such as copolymer (B) tends to become more non-liquid crystal, which makes it easier to phase separate from the liquid crystalline component such as the side-chain liquid crystal polymer (A), making it easier to vertically align the liquid crystalline component such as the side-chain liquid crystal polymer (A), and since the rigidity of the photo-alignable structural unit of the photo-alignable component such as copolymer (B) is increased, the distance between the photo-alignable groups tends to be reduced, making it easier to obtain excellent photo-alignment. This is more preferable.

[0093] When an alignment restraint force is imparted to the first retardation layer 10, the copolymer contains a styrene skeleton and a large amount of π electron systems, which is thought to provide the following effect. As will be described later, the liquid crystalline component of the second retardation layer 20 can be directly laminated on the first retardation layer 10 to which an alignment restraint force is imparted. In this case, the interaction of the π electron systems can increase the adhesion between the first retardation layer 10 formed using the copolymer and the liquid crystalline component of the second retardation layer 20 laminated directly on the first retardation layer 10.

[0094] L １１ represents a single bond, -O-, -S-, -COO-, -COS-, -CO-, -OCO-, or a combination of these with an arylene group, and links the monomer unit with the photo-alignable group X. When the photo-alignable constituent unit such as the copolymer (B) used in the present disclosure does not have a linear alkylene group between the photo-alignable group and the monomer unit, the photo-alignable component is likely to become non-liquid crystal, as described above, and the compatibility with liquid crystalline components such as the side chain liquid crystal polymer (A) decreases, making it more likely to phase separate from the liquid crystalline component such as the side chain liquid crystal polymer (A), and the rigidity increases, making it easier for the distance between the photo-alignable groups to become smaller, and it is presumed that excellent photo-alignment properties can be obtained.

[0095] The above L １１ is a single bond, the photo-alignable group X is a monomer unit Z １ Specific examples of the divalent linking group include -O-, -S-, -COO-, -COS-, -CO-, -OCO-, and -C ６ H ４ -, -C ６ H ４ O-, -OCOC ６ H ４ O-, -COOC ６ H ４ O-, -OC ６ H ４ O-, etc., where -C ６ H ４ - is a phenylene group.

[0096] On the other hand, the photoalignable group is a functional group that undergoes a photoreaction upon irradiation with light to develop anisotropy, and is preferably a functional group that causes a photodimerization reaction or a photoisomerization reaction.

[0097] Examples of photo-alignable groups that cause a photodimerization reaction include cinnamoyl groups, chalcone groups, coumarin groups, anthracene groups, quinoline groups, azobenzene groups, and stilbene groups. The benzene rings in these functional groups may have a substituent. The substituent may be any group that does not interfere with the photodimerization reaction, such as an alkyl group, an aryl group, a cycloalkyl group, an alkoxy group, an aryloxy group, a hydroxy group, a halogen atom, a trifluoromethyl group, and a cyano group.

[0098] The photo-alignable group that undergoes a photoisomerization reaction is preferably one that undergoes a cis-trans isomerization reaction, and examples thereof include a cinnamoyl group, a chalcone group, an azobenzene group, and a stilbene group. The benzene ring in these functional groups may have a substituent. The substituent may be any one that does not interfere with the photoisomerization reaction, and examples thereof include an alkoxy group, an alkyl group, a halogen atom, a trifluoromethyl group, and a cyano group.

[0099] Among these, the photoalignable group is preferably a cinnamoyl group. Specifically, the cinnamoyl group is preferably at least one selected from the group consisting of groups represented by the following formulas (x-1) and (x-2):

[0100]

[0101] In the above formula (x-1), R ３１ represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 1 to 18 carbon atoms, or a cycloalkyl group having 1 to 18 carbon atoms. However, the alkyl group, aryl group, and cycloalkyl group may be bonded via an ether bond, an ester bond, an amide bond, or a urea bond, and may have a substituent. R ３２ ~R ３５R each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 1 to 18 carbon atoms, a cycloalkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, or a cyano group. However, the alkyl group, aryl group, and cycloalkyl group may be bonded via an ether bond, an ester bond, an amide bond, or a urea bond, and may have a substituent. ３６ and R ３７ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 1 to 18 carbon atoms, or an alkoxy group having 1 to 18 carbon atoms. ４１ ~R ４５ R each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 1 to 18 carbon atoms, a cycloalkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, or a cyano group. However, the alkyl group, aryl group, and cycloalkyl group may be bonded via an ether bond, an ester bond, an amide bond, or a urea bond, and may have a substituent. ４６ and R ４７ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 1 to 18 carbon atoms, or an alkoxy group having 1 to 18 carbon atoms.

[0102] In addition, when the photoalignable group is a cinnamoyl group and is a group represented by the above formula (x-1), the benzene ring of the styrene skeleton (formula (1-2)) contained in the monomer unit may be the benzene ring of the cinnamoyl group.

[0103] The cinnamoyl group represented by the above formula (x-1) is more preferably a group represented by the following formula (x-3).

[0104]

[0105] In the above formula (x-3), R ３２ ~R ３７ is the same as in the above formula (x-1). ３８represents a hydrogen atom, an alkoxy group having 1 to 18 carbon atoms, a cyano group, an alkyl group having 1 to 18 carbon atoms, a phenyl group, a biphenyl group, or a cyclohexyl group. However, the alkyl group, phenyl group, biphenyl group, and cyclohexyl group may be bonded via an ether bond, an ester bond, an amide bond, or a urea bond. n represents an integer of 1 to 5, and R ３８ may be bonded at any of the ortho, meta, and para positions. ３８ may be the same or different. Among them, n is 1 and R ３８ is preferably attached at the para position.

[0106] The copolymer may have one or more types of photo-alignable structural units. A monomer having a photo-alignable group that induces the photo-alignable structural unit can be used to synthesize the copolymer. The monomer having a photo-alignable group can be used alone or in combination of two or more types.

[0107] The content ratio of the photo-alignable structural unit in the copolymer can be set within the range of 10 mol% to 90 mol%, preferably within the range of 20 mol% to 80 mol%, when the amount of structural units contained in the entire copolymer is 100 mol%. When the content ratio of the photo-alignable structural unit is equal to or greater than the above-mentioned lower limit, in the manufacturing method of the retardation film 1 described below, in the step of imparting an alignment regulating force to the first retardation layer 10 by irradiating the material of the first retardation layer 10 with polarized ultraviolet light, the sensitivity of the material of the first retardation layer 10 to polarized ultraviolet light can be ensured to be sufficiently high. On the other hand, when the content ratio of the photo-alignable structural unit is equal to or less than the above-mentioned upper limit, the content ratio of the thermally crosslinkable structural unit can be ensured to be high, and sufficient thermosetting properties can be obtained for the material of the first retardation layer 10. From the above, when the content ratio of the photo-alignable structural unit is within the above-mentioned numerical range, the alignment regulating force of the first retardation layer 10 can be sufficiently increased.

[0108] (2) Thermally Crosslinkable Structural Unit The thermally crosslinkable structural unit in the present disclosure is a moiety that bonds with a thermal crosslinking agent upon heating. The thermally crosslinkable structural unit may be a structural unit having a thermally crosslinkable group. The thermally crosslinkable group may be a group that crosslinks upon heating at, for example, 30°C to 250°C, and examples thereof include a hydroxy group, a carboxy group, a phenolic hydroxy group, a mercapto group, a glycidyl group, an amino group, and an amide group. Among these, from the viewpoint of reactivity, an aliphatic hydroxy group is preferred, and a primary hydroxy group is more preferred. Note that a primary hydroxy group refers to a hydroxy group in which the carbon atom to which the hydroxy group is bonded is a primary carbon atom. The thermally crosslinkable group may also be a self-crosslinking group capable of crosslinking with the same crosslinking group. Examples of the self-crosslinking group include a hydroxymethyl group, an alkoxymethyl group, a trialkoxysilyl group, and a blocked isocyanate group. When the thermally crosslinkable structural unit has a self-crosslinking group, the thermally crosslinkable structural unit can also function as a thermal crosslinking agent, which is preferred because it is likely to improve photoalignment performance and solvent resistance. When the thermally crosslinkable structural unit has a self-crosslinking group, it is thought that it is more likely to react with the thermally crosslinkable structural unit in the molecule. Among the thermally crosslinkable structural units, it is preferable to contain at least one selected from the group consisting of a hydroxy group, a carboxy group, and a mercapto group, from the viewpoint of photoalignment performance and solvent resistance. Among the thermally crosslinkable structural units, it is preferable to contain a structural unit having at least one thermally crosslinkable group selected from the group consisting of a hydroxy group, a carboxy group, and a mercapto group, and a structural unit having at least one self-crosslinking group selected from the group consisting of a hydroxymethyl group, an alkoxymethyl group, a trialkoxysilyl group, and a blocked isocyanate group, from the viewpoint of more easily improving photoalignment performance and solvent resistance. The alkoxymethyl group of the self-crosslinking group is preferably one having an alkoxy group with 1 to 6 carbon atoms, and specific examples thereof include a methoxymethyl group, an ethoxymethyl group, various propoxymethyl groups, various butoxymethyl groups, and various pentoxymethyl groups. As the alkoxymethyl group, those having 1 to 4 carbon atoms in the alkoxy group are more preferred, those having 1 to 2 carbon atoms are even more preferred, and methoxymethyl groups and ethoxymethyl groups are preferred in terms of improving crosslinkability.

[0109] Examples of monomer units constituting the thermally crosslinkable constituent unit include acrylic acid esters, methacrylic acid esters, styrene, acrylamide, methacrylamide, maleimide, vinyl ethers, vinyl esters, etc. When the thermally crosslinkable group is a carboxy group, the thermally crosslinkable constituent unit may be a constituent unit derived from acrylic acid or methacrylic acid, and when the thermally crosslinkable group is a hydroxy group, it may be a constituent unit derived from vinyl alcohol.

[0110] An example of the thermally crosslinkable constituent unit is a constituent unit represented by the following formula (2).

[0111] (In the above formula (2), Z ２ represents at least one monomer unit selected from the group consisting of the following formulas (2-1) to (2-6), and R ５０ represents a linear alkylene group having 1 to 11 carbon atoms which may have —O— in the carbon chain, and Y represents a thermally crosslinkable group.

[0112] (In the above formulas (2-1) to (2-6), R ５１ represents a hydrogen atom, a methyl group, a chlorine atom, or a phenyl group; R ５２ represents a hydrogen atom or a methyl group, R ５３ is a hydrogen atom, a methyl group, a chlorine atom or a phenyl group, R ５４ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; L １２ represents a single bond, —O—, —S—, —COO—, —COS—, —CO—, or —OCO—; L １２ is a single bond, R ５０ is directly bonded to the styrene backbone.)

[0113] In addition, Z ２ is at least one selected from the group consisting of formula (2-2), -L １２ -Y may be bonded to any of the ortho, meta, and para positions, but -L １２ It is preferable that —Y is bonded at the para position, since this provides excellent reactivity in thermal crosslinking.

[0114] As the monomer unit constituting the thermally crosslinkable structural unit, from the viewpoint of ease of procurement of raw materials, at least one selected from the group consisting of formulas (2-1) and (2-2) is preferred. Furthermore, at least one selected from the group consisting of formula (2-2) is more preferred because it makes the copolymer (B) more likely to become non-liquid crystal, facilitates phase separation from the side-chain liquid crystal polymer (A), and makes it easier to vertically align the side-chain liquid crystal polymer (A).

[0115] In the above formula (2), the thermally crosslinkable group of Y may be the same as the thermally crosslinkable group described above as the thermally crosslinkable group possessed by the thermally crosslinkable structural unit, or may be a self-crosslinkable group. In the above formula (2), the thermally crosslinkable group of Y may be at least one type of thermally crosslinkable group selected from the group consisting of a hydroxy group, a carboxy group, a mercapto group, a glycidyl group, an amino group, an amide group, a hydroxymethyl group, an alkoxymethyl group, a trialkoxysilyl group, a blocked isocyanate group, and an alkoxy group substituted with a methyl group, or may be at least one type of thermally crosslinkable group selected from the group consisting of a hydroxy group, a carboxy group, a mercapto group, a glycidyl group, an amino group, and an amide group. The hydroxymethyl group and the alkoxymethyl group, which are self-crosslinkable groups, may be substituted with a methyl group (R ５０ The thermally crosslinkable group represented by Y may be a group in which a hydroxy group or an alkoxy group is substituted for the methylene group in the formula (I) to form a hydroxymethyl group or an alkoxymethyl group. From the viewpoint of reactivity, the thermally crosslinkable group represented by Y preferably contains an aliphatic hydroxy group, and more preferably contains a primary hydroxy group.

[0116] In the above formula (2), L １２ represents a single bond, —O—, —S—, —COO—, —COS—, —CO—, or —OCO—. １２ is a single bond, the thermal crosslinkable group Y is a monomer unit Z ２ is directly bonded to R ５０ is a linear alkylene group having 1 to 11 carbon atoms which may have —O— in the carbon chain, and —(CH ２ ) j- or -(C ２ H ４ O) ｋ -C ２ H ４Preferably, j is 1 to 11 and k is 1 to 4, more preferably j is 2 to 11 and k is 1 to 4, and even more preferably j is 4 to 11 and k is 2 to 4. If j and k are too small, the distance between the thermally crosslinkable group and the main skeleton of the copolymer in the thermally crosslinkable constituent unit becomes short, making it difficult for the thermal crosslinking agent to bond to the thermally crosslinkable group, and there is a risk of reducing the reactivity between the thermally crosslinkable constituent unit and the thermal crosslinking agent. On the other hand, if j and k are too large, the chain length of the linking group in the thermally crosslinkable constituent unit becomes long, making it difficult for the terminal thermally crosslinkable group to be exposed to the surface, making it difficult for the thermal crosslinking agent to bond to the thermally crosslinkable group, and there is a risk of reducing the reactivity between the thermally crosslinkable constituent unit and the thermal crosslinking agent.

[0117] The thermally crosslinkable structural unit contained in the copolymer may be one type or two or more types. A monomer having a thermally crosslinkable group that induces the thermally crosslinkable structural unit can be used to synthesize the copolymer. The monomer having a thermally crosslinkable group can be used alone or in combination of two or more types.

[0118] Examples of monomers having a thermally crosslinkable group include, but are not limited to, the following: acrylic acid ester compounds and methacrylic acid ester compounds include, for example, monomers having a hydroxy group and an acrylic group or a methacrylic group, such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 2,3-dihydroxypropyl acrylate, 2,3-dihydroxypropyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, triethylene glycol monoacrylate, tetraethylene glycol monoacrylate, dipropylene glycol monoacrylate, tripropylene glycol monoacrylate, and tetrapropylene glycol monoacrylate. Examples of styrene compounds include monomers having a hydroxy group and a styrene group, such as an ester of 4-vinylbenzoic acid and a diol, an ester of 4-vinylbenzoic acid and diethylene glycol, an ether of hydroxystyrene and a diol, and an ether of hydroxystyrene and diethylene glycol. Specific examples of other monomers that form thermally crosslinkable structural units include the monomers described in paragraphs 0075 to 0079 of Japanese Patent No. 5,626,493. Furthermore, the hydroxy group in the examples may be substituted with a carboxy group or a glycidyl group.

[0119] Among the monomers having a thermal crosslinkable group, examples of the monomer having a self-crosslinking group include acrylamide compounds or methacrylamide compounds substituted with a hydroxymethyl group or an alkoxymethyl group, such as N-hydroxymethylacrylamide, N-hydroxymethylmethacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-ethoxymethylacrylamide, N-ethoxymethylmethacrylamide, N-butoxymethylacrylamide, and N-butoxymethylmethacrylamide; monomers having a trialkoxysilyl group, such as 3-trimethoxysilylpropyl acrylate, 3-triethoxysilylpropyl acrylate, 3-trimethoxysilylpropyl methacrylate, and 3-triethoxysilylpropyl methacrylate; and monomers having a blocked isocyanate group, such as 2-(0-(1'-methylpropylideneamino)carboxyamino)ethyl methacrylate and 2-(3,5-dimethylpyrazolyl)carbonylaminoethyl methacrylate.

[0120] The content ratio of the thermally crosslinkable structural unit in the copolymer can be set within the range of 5 mol% to 90 mol%, preferably within the range of 20 mol% to 80 mol%, when the amount of structural units contained in the entire copolymer is 100 mol%. When the content ratio of the thermally crosslinkable structural unit is equal to or greater than the above-mentioned lower limit, sufficient thermosetting properties can be obtained for the material of the first retardation layer 10. When the content ratio of the thermally crosslinkable structural unit is equal to or less than the above-mentioned upper limit, a large content ratio of the photo-alignable structural unit is ensured, and in the process of imparting an alignment regulating force to the first retardation layer 10 by irradiating the material of the first retardation layer 10 with polarized ultraviolet light in the manufacturing method of the retardation film 1 described below, the sensitivity of the material of the first retardation layer 10 to polarized ultraviolet light can be sufficiently ensured. From the above, when the content ratio of the photo-alignable structural unit is within the above-mentioned numerical range, the alignment regulating force of the first retardation layer 10 can be sufficiently increased.

[0121] (3) Other Structural Units In the present disclosure, the copolymer may have, in addition to the photo-alignable structural unit and the thermally crosslinkable structural unit, a structural unit that does not have either a photo-alignable group or a thermally crosslinkable group. By including other structural units in the copolymer, for example, solvent solubility, heat resistance, reactivity, etc. can be improved.

[0122] Examples of monomer units constituting a structural unit having neither a photoalignable group nor a thermally crosslinkable group include acrylic acid esters, methacrylic acid esters, maleimides, acrylamides, acrylonitrile, maleic anhydride, styrene, vinyl, etc. Among these, acrylic acid esters, methacrylic acid esters, and styrene are preferred, as with the thermally crosslinkable structural unit.

[0123] Examples of monomers that form a structural unit that does not have such a photoalignment group or a thermal crosslinking group include acrylic acid ester compounds, methacrylic acid ester compounds, maleimide compounds, acrylamide compounds, acrylonitrile, maleic anhydride, styrene compounds, vinyl compounds, etc. Specifically, for example, among the monomers described in paragraphs 0036 to 0040 of WO 2010 / 150748, monomers that do not have either the photoalignment group or the thermal crosslinking group can be used.

[0124] As other structural units, for example, a structural unit derived from a monomer having a fluorinated alkyl group may be included. In this case, the copolymer (B) is more likely to be localized on the coating film surface, and the photoalignable groups are more likely to be oriented on the coating film surface. In order to make the copolymer (B) more likely to be localized on the coating film surface, the fluorinated alkyl group of the monomer having a fluorinated alkyl group may be a fluorinated alkyl group having 2 to 8 carbon atoms to which fluorine atoms are directly bonded.

[0125] The copolymer may contain one or more types of structural units that do not have a photoalignable group or a thermally crosslinkable group.

[0126] The content ratio of the structural unit not having the photo-alignable group or the thermally crosslinkable group in the copolymer is preferably in the range of 0 mol% to 50 mol%, and more preferably in the range of 0 mol% to 30 mol%, when the amount of structural units contained in the entire copolymer is taken as 100 mol%. By ensuring that the content ratio of the structural unit is equal to or less than the above-mentioned upper limit, the content ratio of the photo-alignable structural unit and the thermally crosslinkable structural unit can be ensured. This ensures that the sensitivity of the material of the first retardation layer 10 to polarized ultraviolet light is sufficiently high. Furthermore, sufficient thermosetting properties can be obtained for the material of the first retardation layer 10. This ensures that the alignment control force of the first retardation layer 10 is sufficiently high.

[0127] (4) Copolymer (B) The weight average molecular weight of copolymer (B) is not particularly limited and can be, for example, about 3,000 to 200,000, preferably in the range of 4,000 to 100,000. By having the weight average molecular weight equal to or less than the upper limit described above, the solubility in solvents is increased, the viscosity is reduced, making the material easier to handle, and it is easier to form a uniform film. By having the weight average molecular weight equal to or greater than the lower limit described above, the material can be sufficiently cured during thermal curing, and solvent resistance and heat resistance can be sufficiently increased. The weight average molecular weight can be measured by gel permeation chromatography (GPC).

[0128] The copolymer (B) may be synthesized by copolymerizing a monomer having a photoalignable group with a monomer having a thermal crosslinkable group by a conventionally known method. The copolymer (B) may be used in the form of a solution obtained when the copolymer is synthesized, in the form of a powder, or in the form of a solution obtained by redissolving a purified powder in a solvent described below.

[0129] The copolymer (B) may be used singly or in combination of two or more. In the present embodiment, from the viewpoint of exerting an alignment control force on the liquid crystal component to be directly laminated, the content ratio of the copolymer (B) is preferably 1 part by mass to 50 parts by mass, more preferably 5 parts by mass to 40 parts by mass, and even more preferably 10 parts by mass to 30 parts by mass, relative to 100 parts by mass of the solid content of the positive C-type retardation composition.

[0130] 1-3. Thermal Crosslinking Agent When the first retardation layer 10 is a cured product of a thermosetting liquid crystal composition containing a vertically aligning liquid crystal component, a photoalignable component, and a thermal crosslinking agent, a thermal crosslinking agent is used to form the first retardation layer 10. The thermal crosslinking agent may be a thermal crosslinking agent that bonds with the thermal crosslinking group of the thermal crosslinking structural unit. The thermal crosslinking agent can improve heat resistance and solvent resistance by bonding with at least the thermal crosslinking group of the copolymer. In addition, the thermal crosslinking agent can also bond with the side-chain liquid crystal polymer (A) containing a thermal crosslinking group in its side chain, which may be optionally contained, or a compound having a thermal crosslinking group, thereby improving the durability of the cured film and contributing to the improvement of each function.

[0131] The thermal crosslinking agent is selected from compounds that bond with the thermal crosslinkable group of the thermal crosslinkable structural unit. Examples of such thermal crosslinking agents include compounds having a crosslinkable group that can react with the thermal crosslinkable group. Examples of crosslinkable groups possessed by the thermal crosslinking agent include epoxy groups, methylol groups, isocyanate groups, blocked isocyanate groups, carboxyl groups, protected carboxyl groups, and maleimide groups. The number of crosslinkable groups possessed by the thermal crosslinking agent is preferably two or more, and more preferably two to six. Examples of thermal crosslinking agents include epoxy compounds, methylol compounds, and isocyanate compounds. Among these, methylol compounds are preferred due to the stability of the thermosetting liquid crystal composition (coating liquid) and the ability to use mild curing conditions. Specific examples of methylol compounds include compounds such as alkoxymethylated glycoluril, alkoxymethylated benzoguanamine, and alkoxymethylated melamine. Other specific examples of the thermal crosslinking agent include the thermal crosslinking agents described in paragraphs 0144 to 0148 of WO 2022 / 158555.

[0132] These thermal crosslinking agents may be used alone or in combination of two or more. In the present disclosure, in order to improve the durability of the cured film, the content of the thermal crosslinking agent may be 0.1 parts by mass to 30 parts by mass relative to 100 parts by mass of the solid content of the photoalignable thermosetting liquid crystal composition. The content of the thermal crosslinking agent may be 0.5 parts by mass to 25 parts by mass, or may be 1 part by mass to 20 parts by mass, relative to 100 parts by mass of the solid content of the photoalignable thermosetting liquid crystal composition. The content of the thermal crosslinking agent in the photoalignable thermosetting liquid crystal composition of the present disclosure may be 1 part by mass to 30 parts by mass relative to 100 parts by mass of the side-chain liquid crystal polymer (A) and the copolymer (B) combined. The content of the thermal crosslinking agent in the photoalignable thermosetting liquid crystal composition may be 2 parts by mass to 25 parts by mass, or may be 3 parts by mass to 25 parts by mass, relative to 100 parts by mass of the side-chain liquid crystal polymer (A) and the copolymer (B), with the upper limit being less than 10 parts by mass. When the content of the thermal crosslinking agent is equal to or greater than the above-mentioned lower limit, the heat resistance and solvent resistance of the cured film formed from the photo-alignable thermosetting liquid crystal composition can be increased. When the content of the thermal crosslinking agent is equal to or less than the above-mentioned upper limit, the first retardation layer 10 can be stored more stably. Furthermore, when the content of the thermal crosslinking agent is within the above-mentioned numerical range, the liquid crystal component can be easily aligned vertically, and the alignment control force of the first retardation layer 10 can be increased.

[0133] The structures derived from the liquid crystal component, photo-alignment component, and thermal crosslinker contained in the first retardation layer 10 can be analyzed using NMR, IR, GC-MS, XPS, TOF-SIMS, or a combination of these methods. For example, material can be collected from the first retardation layer 10, and the chemical structures of the liquid crystal component, photo-alignment component, and thermal crosslinker component can be analyzed using nuclear magnetic resonance spectroscopy (NMR). Fragments derived from, for example, photo-alignment groups can be detected using time-of-flight secondary ion mass spectroscopy (TOF-SIMS). Furthermore, peaks of bonds and functional groups derived from the thermal crosslinker and photo-alignment component can be confirmed using X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), and Raman spectroscopy. The structure of the components contained in the first retardation layer 10 can be analyzed by combining the results of these analyses.

[0134] 1-4. Acid or Acid Generator When the first retardation layer 10 is a cured product of the thermosetting liquid crystal composition, the thermosetting liquid crystal composition may contain an acid or an acid generator. The acid or the acid generator can promote the thermal curing reaction of the thermosetting liquid crystal composition.

[0135] The acid or acid generator is not particularly limited as long as it is a sulfonic acid group-containing compound, hydrochloric acid or its salt, or a compound that generates an acid by thermal decomposition during drying and heat curing of the coating film, i.e., a compound that generates an acid by thermal decomposition at a temperature of 50° C. to 250° C. Specifically, those described in paragraph 0054 of WO 2010 / 150748 can be used.

[0136] The content of the acid or acid generator in the photoalignable thermosetting liquid crystal composition of the present disclosure may be 0.01 parts by mass to 20 parts by mass relative to 100 parts by mass of the solid content of the photoalignable thermosetting liquid crystal composition. The content of the acid or acid generator in the photoalignable thermosetting liquid crystal composition may be 0.05 parts by mass to 10 parts by mass, or 0.05 parts by mass to 5 parts by mass. The content of the acid or acid generator in the photoalignable thermosetting liquid crystal composition of the present disclosure may be 0.05 parts by mass to 20 parts by mass relative to 100 parts by mass of the side-chain liquid crystal polymer (A) and the copolymer (B) combined. The content of the acid or acid generator in the photoalignable thermosetting liquid crystal composition may be 0.1 parts by mass to 15 parts by mass, or 0.1 parts by mass to 10 parts by mass, with the upper limit being less than 1 part by mass.

[0137] 1-5. Other Components The composition used in the first retardation layer 10 may contain other components. The other components can be appropriately selected and used as long as they do not impair the effects of the present disclosure. Specific examples of other components include other polymerizable liquid crystal compounds, polymerizable compounds having two or more polymerizable groups in one molecule to improve the hardness and durability of the coating film, photopolymerization initiators, compounds having a polymerizable group and a thermally crosslinkable group, other compounds having a photoalignment group and a thermally crosslinkable group, sensitizers, leveling agents, polymerization inhibitors, antioxidants, light stabilizers, etc. The other components may be similar to the other components described in paragraphs 0155 to 0173 of WO 2022 / 158555, for example.

[0138] The first retardation layer 10 may contain an ultraviolet absorber. The ultraviolet absorber that can be contained in the first retardation layer 10 will be described. The ultraviolet absorber preferably has a lower limit of the maximum absorption wavelength of 350 nm or more, more preferably 365 nm or more, and preferably has an upper limit of the maximum absorption wavelength of 405 nm or less, more preferably 403 nm or less. The ultraviolet absorber preferably includes one having a maximum absorption wavelength in the short wavelength region of visible light.

[0139] The ultraviolet absorber preferably has a narrow absorption wavelength range. Specifically, when the absorbance at the maximum absorption wavelength is defined as X, the wavelength range (so-called full width at half maximum) at which the absorbance shows X / 2 is preferably 70 nm or less, more preferably 65 nm or less. The lower limit of the wavelength range at which the absorbance shows X / 2 is not particularly limited, but is usually about 20 nm, preferably 30 nm or more. The absorbance can be measured, for example, using a solution prepared by dissolving 10 mg of the ultraviolet absorber in 1000 ml of a solvent such as chloroform.

[0140] Examples of ultraviolet absorbers include benzophenone compounds, benzoxazinone compounds, benzophenone compounds, anthracene compounds, benzotriazole compounds, indole compounds, and methine compounds. Among these, benzotriazole compounds, indole compounds, and methine compounds are preferred. As benzotriazole compounds, sesamol-type benzotriazole compounds and resorcinol-type benzotriazoles are preferred, and sesamol-type benzotriazole compounds are more preferred. As ultraviolet absorbers, those having a polymerizable functional group capable of reacting with the binder component are also preferred.

[0141] Examples of the sesamol-type benzotriazole compound include a compound in which sesamol is bonded to the nitrogen atom at the 2-position of the benzotriazole ring (sesamol-type benzotriazole monomer), and a polymer of a composition containing the compound. The ultraviolet absorber is, for example, the ultraviolet absorber described in paragraphs 0045 to 0056 of JP 2021-189224 A.

[0142] By including an ultraviolet absorber in the first retardation layer 10, the first retardation layer 10 can be endowed with the function of absorbing ultraviolet rays. By having the first retardation layer 10 have the function of absorbing ultraviolet rays, the following effects can be obtained. The retardation layer included in the retardation film 1, such as the first retardation layer 10, can be protected from ultraviolet rays. This makes it less likely that the retardation layer included in the retardation film 1 will deteriorate due to ultraviolet rays. Furthermore, when the retardation film 1 is used in a display device or the like, the color caused by reflection of external light on the surface of the display device or the like can be adjusted by the ultraviolet absorber. In particular, reflected light that has been tinted, such as blue, becomes less likely to be visible to the user of the display device or the like. Furthermore, as will be described later, when the retardation film 1 is used in a display device 100, particularly an organic EL display device 101, the display device main body 102 can be protected from ultraviolet rays.

[0143] The liquid crystal component and photo-alignable component used in forming the first retardation layer 10 are not limited to the above specific examples and can be appropriately selected from conventionally known components. For example, a thermosetting liquid crystal composition having the second photo-alignment property described in paragraphs 0244 to 0350 of WO 2022 / 158555 may be appropriately selected and used. In order to promote vertical alignment of the liquid crystal component of the first retardation layer 10, a vertical alignment promoter described in paragraphs 0100 to 0185 of WO 2013 / 100115 or a liquid crystal dendrimer described in Japanese Patent No. 5717086 may be used.

[0144] 1-6. Structure of the first retardation layer The first retardation layer 10 may be a film that is cured in a state in which the liquid crystalline portion of the liquid crystalline component is aligned in a direction approximately perpendicular to the surface of the first retardation layer 10, and the photo-alignable group of the photo-alignable component present on the surface is in a photodimerization structure or a photoisomerization structure. When the first retardation layer 10 contains a thermal crosslinking agent, it may be a structure that contains, in one layer, a liquid crystalline component such as the side chain liquid crystal polymer aligned in a direction approximately perpendicular to the surface of the first retardation layer 10, a photodimerization structure or a photoisomerization structure of the photo-alignable group, and a crosslinked structure formed by bonding a thermal crosslinkable group and a thermal crosslinking agent. The first retardation layer 10 may have a structure containing, in one layer, the side chain type liquid crystal polymer oriented in a direction approximately perpendicular to the surface of the first retardation layer 10, and a copolymer having a crosslinked structure formed by bonding a photodimerization structure or a photoisomerization structure of a photoalignment group possessed by a photoalignment constituent unit and a thermal crosslinking group possessed by a thermal crosslinking constituent unit and a thermal crosslinking agent.

[0145] The photodimerization structure of the photoalignment group contained in the first retardation layer 10 is, for example, a structure in which photoalignment groups of the photoalignment structural unit represented by the above formula (1) are crosslinked by a photodimerization reaction, and has a cyclobutane skeleton. The photodimerization reaction is a reaction as shown below, in which an olefin structure contained in the photoalignment group forms a cyclobutane skeleton by photoreaction. Xa to Xd and Xa' to Xd' vary depending on the type of photoalignment group.

[0146]

[0147] The photodimerization structure is preferably a photodimerization structure of a cinnamoyl group. Specifically, a structure in which the cinnamoyl groups are crosslinked by a photodimerization reaction is preferred. In particular, it is preferred to include a photodimerization structure represented by the following formulas (x-4) and (x-5). In the following formulas, the symbols are the same as those in the above formulas (x-1), (x-2), and (x-3).

[0148]

[0149] When the first retardation layer 10 has a photodimerization structure represented by the above formulas (x-4) and (x-5), many aromatic rings are arranged and many π electrons are included. Therefore, it is considered that the affinity with the second retardation layer 20 formed on the first retardation layer 10 is increased, the alignment control force of the first retardation layer 10 is increased, and the adhesion with the second retardation layer 20 is further increased.

[0150] The photoisomerizable structure is a structure in which the photo-aligning group of the photo-alignable structural unit is isomerized by a photoisomerization reaction. For example, in the case of a cis-trans isomerization reaction, the photoisomerizable structure may be either a structure in which a cis isomer is changed to a trans isomer, or a structure in which a trans isomer is changed to a cis isomer. For example, when the photo-aligning group is a cinnamoyl group, the photoisomerization reaction is as shown below, in which an olefin structure contained in the photo-aligning group forms a cis isomer or a trans isomer by photoreaction. Xa to Xd vary depending on the type of photo-aligning group.

[0151]

[0152] The photoisomerizable structure is preferably a photoisomerizable structure of a cinnamoyl group. Specifically, a structure in which the cinnamoyl group is isomerized by a photoisomerization reaction is preferred. In this case, the photoisomerizable structure may be either a structure in which a cis isomer is converted to a trans isomer, or a structure in which a trans isomer is converted to a cis isomer. In particular, the alignment layer preferably has a photoisomerizable structure of a cinnamoyl group represented by the above formulas (x-1) and (x-2), as shown in the following formulas (x-6) and (x-7).

[0153]

[0154] When a thermal crosslinking agent is used in forming the first retardation layer 10, the thermal crosslinking group bonds with the thermal crosslinking agent. Therefore, the crosslinked structure is a structure in which the thermal crosslinking group and the thermal crosslinking agent are crosslinked by heating, forming a three-dimensional network structure. Examples of the crosslinked structure include a crosslinked structure in which a thermal crosslinking group in a thermal crosslinking structural unit of the copolymer is bonded to a thermal crosslinking agent, and a crosslinked structure in which a thermal crosslinking group in another component is bonded to a thermal crosslinking agent. For example, when the non-liquid crystalline and thermally crosslinkable structural unit of the side-chain liquid crystal polymer has a thermal crosslinking group, the crosslinked structure may include a crosslinked structure in which a thermal crosslinking group in the side-chain liquid crystal polymer is bonded to a thermal crosslinking agent. The crosslinked structure does not include a structure in which photo-alignable groups are crosslinked by a photodimerization reaction, or a structure in which ethylenically unsaturated double bond groups are polymerized together. However, as long as the effect of the present invention is not impaired, the first retardation layer 10 of the present disclosure may further contain a structure in which ethylenically unsaturated double bond groups are polymerized together. The crosslinked structure contains residues of the thermal crosslinking agent after the reaction of the thermal crosslinking agent.

[0155] The first retardation layer 10 may further contain an acid or an acid generator, the other components described above, and decomposition products thereof.

[0156] It can be confirmed that the first retardation layer 10 contains the photodimerization structure or the photoisomerization structure, the crosslinked structure, and the contained components by collecting and analyzing a material from the first retardation layer 10. As the analysis method, NMR, IR, GC-MS, XPS, TOF-SIMS, and a combination of these methods can be applied.

[0157] In the retardation film 1 of the present disclosure, it is preferable to adjust the composite elastic modulus of the first retardation layer 10 in order to obtain a retardation plate with high resistance to bending. The composite elastic modulus of the first retardation layer 10 may be 4.5 GPa or more and 9.0 GPa or less, 5.0 GPa or more and 8.5 GPa or less, or 5.0 GPa or more and 8.0 GPa or less. When the first retardation layer 10 is a cured product of a thermosetting liquid crystal composition, the composite elastic modulus can be easily adjusted. The composite elastic modulus of the first retardation layer 10 is determined by the indentation hardness (H ＩＴ ) The contact projection area A obtained when measuring ｐ E calculated from the following formula (xii) using ｒ The "indentation hardness" is a value determined from a load-displacement curve from loading to unloading of an indenter obtained by hardness measurement using a nanoindentation method. The composite elastic modulus of the first retardation layer 10 is an elastic modulus that includes the elastic deformation of the first retardation layer 10 and the elastic deformation of the indenter.

[0158] (In the above formula (xii), A ｐ is the contact projection area, and E ｒ is the composite elastic modulus of the retardation layer, and S is the contact stiffness.

[0159] Specifically, the composite elastic modulus of the first retardation layer 10 included in the retardation film 1 can be determined by the following method. First, the surface of the retardation film 1 comprising the second retardation layer 20 as shown in FIG. 2 is attached to glass coated with a cyanoacrylate-based instant adhesive (Aron Alpha (registered trademark) EXTRA Quick-Acting Multipurpose, manufactured by Toagosei Co., Ltd.). Next, glass is applied to the surface of the retardation film 1 comprising the resin substrate 30, and the retardation film 1 is sandwiched between the glass and the glass coated with the cyanoacrylate-based instant adhesive. Next, the pair of glasses sandwiching the retardation film 1 are pressed for 1 minute to apply pressure to the adhesive layer formed by the cyanoacrylate-based instant adhesive so that the thickness of the adhesive layer formed by the cyanoacrylate-based instant adhesive is 45 μm. Thereafter, the retardation film 1 and the adhesive layer are left to stand for 10 minutes. Thereafter, the glass applied to the surface of the retardation film 1 comprising the resin substrate 30 is removed, and the resin substrate 30 is peeled off from the first retardation layer 10. As a result, the first retardation layer 10 and the second retardation layer 20 are transferred to the glass. As a result, a measurement sample can be produced in which the first retardation layer 10 / the second retardation layer 20 / the adhesive layer / the glass are laminated in this order. Using this measurement sample, the resin substrate 30 of the first retardation layer 10 is peeled off to measure the indentation hardness of the exposed surface. Indentation hardness (H ＩＴ The measurement of the maximum load Pmax (μN) and the maximum contact area A are measured using a nanoindenter (TI950 TriboIndenter manufactured by BRUKER). In this measurement, a Berkovich indenter (triangular pyramid, TI-0039 manufactured by BRUKER) is pressed vertically into the surface of the first retardation layer 10 for 10 seconds until the maximum indentation load reaches 3 μN under the following measurement conditions. After that, the sample is held for a certain time to relax the residual stress, and then the sample is unloaded for 10 seconds to measure the maximum load after relaxation. The maximum load Pmax (μN) and the contact projected area A are then calculated. ｐ (nm ２ ) and Pmax / A ｐ The indentation hardness (H ＩＴ) is calculated. The above contact projected area is the contact projected area corrected for the indenter tip curvature by the Oliver-Pharr method using a standard sample of fused quartz (5-0098 manufactured by BRUKER). If any of the measured values ​​deviate from the arithmetic mean value by ±20% or more, that measured value is excluded and remeasured. (Measurement conditions) Loading rate: 0.3 μN / sec Holding time: 5 seconds Loading and unloading rate: 0.3 μN / sec Measurement temperature: 25°C

[0160] Next, the indentation hardness (H ＩＴ ) the contact projected area A ｐ Using the formula (xii), the composite elastic modulus E ｒ Ask for.

[0161] The thickness of the first retardation layer 10 can be set appropriately, for example, to 0.1 μm to 4 μm, or may be 0.3 μm to 2 μm.

[0162] 2. Second Retardation Layer In this embodiment, the second retardation layer 20 is a positive A-type retardation layer. In this embodiment, the second retardation layer 20, which is a positive A-type retardation layer, exhibits horizontal alignment (homogeneous alignment). In this embodiment, the second retardation layer 20, which is a positive A-type retardation layer, is particularly referred to as a first positive A-type retardation layer 21.

[0163] The in-plane retardation and thickness direction retardation of the second retardation layer 20 are determined so that the above-mentioned formulas (i) to (iii) are satisfied for the in-plane retardation and thickness direction retardation of the laminate 2. The in-plane retardation of the second retardation layer 20 at a wavelength of 550 nm is defined as Re Ａ５５０ The in-plane retardation of the second retardation layer 20 at a wavelength of 450 nm is defined as Re Ａ４５０ In this case, the following formulas (xiii) to (xiv) may be satisfied in the second retardation layer 20, which is the first positive A-type retardation layer 21. In this case, it can be understood from formula (xiii) that the second retardation layer 20, which is the first positive A-type retardation layer 21, functions as a λ / 4 retardation plate. From formula (xiv), Re Ａ５５０ Re Ａ４５０It can be seen that the second retardation layer 20, which is the first positive A-type retardation layer 21, exhibits reverse dispersion.

[0164] In the present disclosure, the second retardation layer 20 contains a liquid crystalline component. The liquid crystalline component contained in the second retardation layer 20 can be horizontally aligned. The molecular weight of the liquid crystalline component contained in the second retardation layer 20 is, for example, 250 to 2000.

[0165] The liquid crystalline component contained in the second retardation layer 20 may be a polymerizable liquid crystal compound having a polymerizable group. That is, the second retardation layer 20 may contain a polymerizable liquid crystal compound. As the liquid crystalline component, a component containing a polymerizable liquid crystal compound having a polymerizable group can be used. As the liquid crystalline component, a component used as a liquid crystalline component of a general positive A-type retardation layer can be used. Examples of the polymerizable group contained in the polymerizable liquid crystal compound include cyclic ether-containing groups such as oxirane rings and oxetane rings, and ethylenic double bond-containing groups. Among these, ethylenic double bond-containing groups are preferred because they exhibit photocurability and are easy to handle. Examples of the ethylenic double bond-containing group include vinyl groups, allyl groups, and (meth)acryloyl groups, and among these, (meth)acryloyl groups are preferred.

[0166] The second retardation layer 20 may contain a polymerizable liquid crystal composition. In this case, the polymerizable liquid crystal composition contained in the second retardation layer 20 preferably contains a polymerizable liquid crystal compound that exhibits liquid crystallinity and has a polymerizable group in the molecule. As the polymerizable liquid crystal compound, any of conventionally known polymerizable liquid crystal compounds that can be horizontally aligned can be appropriately selected and used. The polymerizable liquid crystal composition may be composed of one liquid crystal compound or a mixture of two or more liquid crystal compounds.

[0167] The polymerizable liquid crystal composition in the second retardation layer 20 is preferably, for example, a polymerizable liquid crystal compound having a polymerizable group at at least one end of a rod-shaped mesogen, and may be a polymerizable liquid crystal compound having polymerizable groups at both ends of a rod-shaped mesogen. The mesogen or rod-shaped mesogen contained in the polymerizable liquid crystal compound may be the same as the mesogen or rod-shaped mesogen contained in the liquid crystalline constituent unit in the side chain liquid crystal polymer.

[0168] In the present embodiment, the polymerizable liquid crystal compound may be one or more compounds selected from the group consisting of a compound represented by the following general formula (IV) and a compound represented by the following general formula (V), in that they are easily oriented and have excellent heat resistance:

[0169] (In general formula (IV), R ６１ represents a hydrogen atom or a methyl group, R ６２ is -(CH ２ ) ｐ -, or - (C ２ H ４ O) ｐ’ represents a group represented by -. ３ represents a direct bond or a linking group represented by -O-, -O-C(=O)-, or -C(=O)-O-, and ３ represents an arylene group having 6 to 10 carbon atoms which may have a substituent, and a plurality of L ３ and Ar ３ may be the same or different. ６３ is -F, -Cl, -CN, -OCF ３ , -OCF ２ H, -NCO, -NCS, -NO ２ , -NHC(=O)-R ６４ , -C(=O)-OR ６４ , -OH, -SH, -CHO, -SO ３ H, -NR ６４ ２ , -R ６５ , or -OR ６５ , R ６４ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R ６５represents an alkyl group having 1 to 6 carbon atoms; b is an integer of 2 to 4; and p and p' are each independently an integer of 2 to 10.

[0170] (In general formula (V), R ７１ and R ７２ each independently represents a hydrogen atom or a methyl group, R ７３ is -(CH ２ ) ｑ -, or - (C ２ H ４ O) ｑ’ - is represented by R ７４ is -(CH ２ ) ｒ - or - (OC ２ H ４ ) ｒ’ represents a group represented by -. ４ represents a direct bond or a linking group represented by -O-, -O-C(=O)-, or -C(=O)-O-, and ４ represents an arylene group having 6 to 10 carbon atoms which may have a substituent, and a plurality of L ４ and Ar ４ may be the same or different, c is an integer of 2 to 4, and q, q', r, and r' are each independently an integer of 2 to 10.

[0171] L ３ and L ４ represents L in the general formula (I). ２ Ar can be the same as ３ and Ar ４ represents Ar in the general formula (I). １ The compound represented by general formula (IV) and the compound represented by the following general formula (V) can be specifically the polymerizable liquid crystal compounds described in paragraphs 0057 to 0064 of WO 2018 / 003498.

[0172] As described above, the second retardation layer 20, which is the first positive A-type retardation layer 21 of this embodiment, exhibits reverse dispersion. The in-plane retardation of the second retardation layer 20 at a wavelength of 650 nm is defined as Re Ａ６５０ In this case, Re Ａ４５０ , ReＡ５５０ and Re Ａ６５０ may satisfy the following formula (xv). By using a reverse dispersion layer satisfying formula (xv) as the second retardation layer 20, reverse dispersion can be imparted to the entire laminate 2 including the first retardation layer 10 and the second retardation layer 20. As a result, by using the retardation film 1 including the laminate 2 in a display device or the like, reflection of external light in a wavelength range outside 550 nm can be more effectively prevented, and the display device or the like can be more easily viewed.

[0173] In order to form the second retardation layer 20 exhibiting reverse dispersion, a polymerizable liquid crystal compound exhibiting reverse dispersion may be used. Specific examples of the polymerizable liquid crystal compound in the second retardation layer 20 include the polymerizable liquid crystal compound represented by the following general formula (1) described in Japanese Patent No. 6473537, as well as the polymerizable liquid crystal compounds described in Japanese Patent Nos. 5463666, 4186981, 5962760, 5826759, 6568103, 6427340, JP-A-2016-166344, and Recueil des Travaux Chimiques des Pays-Bas (1996), 115 (6), 321-328. As the polymerizable liquid crystal composition in the second retardation layer 20, the compositions described in paragraphs 0133 to 0143 of JP-A-2014-174468 and the compositions described in paragraphs 0083 to 0092 of Japanese Patent No. 6739621 can be used.

[0174] (The symbols in the general formula (1) are as described in Japanese Patent No. 6473537.)

[0175] The polymerizable liquid crystal composition in the second retardation layer 20 may further contain a photopolymerization initiator and a solvent in addition to the liquid crystal compound, and may further contain other components as described with respect to the first retardation layer 10.

[0176] As an example, the first retardation layer 10 is located closer to the second surface 1b in the thickness direction of the retardation film 1 than the second retardation layer 20. In the example shown in Figures 1 and 2, the first retardation layer 10, which is the first positive C-type corresponding layer 11, is located closer to the second surface 1b in the thickness direction of the retardation film 1 than the second retardation layer 20, which is the first positive A-type retardation layer 21.

[0177] 3. Resin Substrate The retardation film 1 may further include a resin substrate 30, as shown in FIG. 2, for example. The resin substrate 30 of the present embodiment is directly adjacent to the first retardation layer 10 as shown in FIG. 2. The resin substrate 30 is preferably transparent. As an example, the resin substrate 30 is a transparent polymer substrate, i.e., a transparent substrate made of a polymer. The resin substrate 30 is preferably made of any one of a polyester-based resin, a cellulose-based resin, an acrylic-based resin, and an olefin-based resin. As the polyester-based resin, polyethylene terephthalate (PET) or polyethylene naphthalate (PEN) can be used. As the polyester-based resin, polyethylene terephthalate is particularly preferably used. As the cellulose-based resin, triacetyl cellulose (TAC) is particularly preferably used. As the olefin-based resin, cycloolefin polymer (COP) is particularly preferably used. That is, the resin substrate 30 is preferably made of any one of polyethylene terephthalate, triacetyl cellulose, an acrylic-based resin, and a cycloolefin polymer.

[0178] The resin substrate 30 preferably has a transmittance of 80% or more, and more preferably 90% or more, in the visible light region. The transmittance of the resin substrate 30 can be measured according to JIS K7361-1 (Test method for total light transmittance of plastic transparent materials).

[0179] When the retardation layer is formed by a roll-to-roll method, the resin substrate 30 is preferably a flexible material having flexibility that allows it to be wound into a roll. From the viewpoint of making the resin substrate 30 a flexible material, it is preferable that the resin substrate 30 be made of polyethylene terephthalate or triacetyl cellulose. Since triacetyl cellulose has particularly excellent optical isotropy, by using triacetyl cellulose as the material for the resin substrate 30, it is possible to make the resin substrate 30 have excellent optical properties. From the viewpoint of increasing the transparency of the resin substrate 30 and making the mechanical properties of the resin substrate 30 favorable, it is preferable that the resin substrate 30 be made of polyethylene terephthalate.

[0180] As will be described later, a composition formed by dissolving the components constituting the first retardation layer 10 in a solvent is applied to the resin substrate 30, and the composition is then dried, thereby forming the first retardation layer 10 on the resin substrate 30. At this time, it may be necessary to use a strong solvent that has a particularly strong ability to dissolve the components as the solvent for dissolving the components constituting the first retardation layer 10. In this case, from the viewpoint of making the resin substrate 30 less soluble in solvents, it is preferable that the resin substrate 30 be made of any of polyethylene terephthalate, triacetyl cellulose, acrylic resin, and cycloolefin polymer. From the viewpoint of making the resin substrate 30 less soluble in solvents, it is more preferable that the resin substrate 30 be made of polyethylene terephthalate or triacetyl cellulose, and even more preferable that the resin substrate 30 be made of polyethylene terephthalate. From the viewpoint of making the resin substrate 30 less soluble in solvents, it is preferable that the resin substrate 30 does not include a primer layer or a hard coat layer that covers the main body portion of the resin substrate 30. In particular, the resin substrate 30 is preferably a polyethylene terephthalate film that does not include a primer layer or a hard coat layer that covers the main body of the resin substrate 30 .

[0181] The resin substrate 30 can be a film formed by stretching, particularly biaxial stretching (biaxially stretched film). In particular, a film formed by sequential biaxial stretching can be used. By using a biaxially stretched film as the resin substrate 30, the strength of the resin substrate 30 can be sufficiently increased while keeping the cost required for the material of the resin substrate 30 low. It is preferable to use a biaxially stretched PET film, particularly a sequentially biaxially stretched PET film, as the resin substrate 30.

[0182] The thickness of the resin substrate 30 is not particularly limited as long as it can support the retardation film 1 depending on the application of the retardation film 1, but is usually about 10 μm to 200 μm. The thickness of the resin substrate 30 is preferably 25 μm to 125 μm, and more preferably 30 μm to 100 μm. When the thickness is equal to or less than the above-mentioned upper limit, the amount of processing waste generated can be reduced, and the rate at which the cutting blade wears can be slowed, particularly when a long retardation film 1 is formed and the formed retardation film 1 is cut into sheets of alignment film and retardation film.

[0183] The resin substrate 30 may be a release substrate that can be peeled from the laminate 2 including the first retardation layer 10 and the second retardation layer 20. Thereby, when attaching the retardation film 1 to another member, the surface of the retardation film 1 that is not formed by the resin substrate 30 can be attached to the other member, and then the resin substrate 30 can be peeled from the laminate 2. For example, when producing an elliptical polarizing plate 40 using the retardation film 1 as described later, the retardation film 1 and a polarizing plate 41 described later are bonded together, and then the resin substrate 30 can be peeled from the laminate 2.

[0184] 4. Retardation Film In the retardation film 1 of the embodiment, the total thickness of the first retardation layer 10 and the second retardation layer 20 may be 0.2 μm to 6 μm. The total thickness of the first retardation layer 10 and the second retardation layer 20 may be 0.8 μm to 5 μm, or 1 μm to 4 μm. The total thickness of the first retardation layer 10 and the second retardation layer 20 can be determined using a scanning transmission electron microscope (STEM). More specifically, the total thickness of the first retardation layer 10 and the second retardation layer 20 can be determined by the following method. Using a scanning transmission electron microscope (STEM) (product name "S-4800", manufactured by Hitachi High-Technologies Corporation), cross sections of the first retardation layer 10 and the second retardation layer 20 are photographed. The thicknesses of the first retardation layer 10 and the second retardation layer 20 are measured at 10 points in the image of the cross section. The arithmetic mean value of the film thicknesses at the 10 locations is set as the measured value of the thickness of the first retardation layer 10 and the second retardation layer 20. The total thickness of the first retardation layer 10 and the second retardation layer 20 can be calculated by adding the measured value of the thickness of the first retardation layer 10 and the measured value of the thickness of the second retardation layer 20.

[0185] In the retardation film 1 of the present embodiment, the second retardation layer 20 is laminated so as to be directly adjacent to the first retardation layer 10. Therefore, the retardation film 1 does not include a substrate, an alignment film, an adhesive layer, or the like for the second retardation layer 20. This allows the retardation film 1 to be made thinner. The retardation film 1 of the present embodiment can be suitably used as an optical member for various display devices that are intended to be made thinner.

[0186] By using the retardation film 1 in a display device or the like, the first retardation layer 10, which is the first positive C-type corresponding layer 11, can enhance contrast when viewed from an oblique direction and reduce color shift. The second retardation layer 20, which is the first positive A-type retardation layer 21, functions as a λ / 4 retardation plate. As a result, the laminate 2 of this embodiment provides an overall retardation of approximately λ / 4. Furthermore, by using the retardation film 1 in a display device or the like, the laminate 2 can enhance contrast when viewed from an oblique direction and reduce color shift. The retardation film 1 of this embodiment, which includes the first retardation layer 10 and the second retardation layer 20, is combined with a polarizing plate, particularly a linear polarizing plate, as described below. This allows the production of an elliptical polarizing plate comprising the retardation film 1 and a linear polarizing plate. By using the elliptical polarizing plate in a display device, particularly an organic EL display device (organic electroluminescence display device), reflection of external light on the display surface of the display device can be reduced. That is, the elliptically polarizing plate can be used as an external light antireflection film. Furthermore, by using the elliptically polarizing plate in a display device, the contrast when viewed from an oblique direction can be enhanced and color shift can be reduced. Thus, the elliptically polarizing plate can be suitably used as a polarizing compensation film in a display device.

[0187] In the retardation film 1 of the present embodiment, the second retardation layer 20, which is the first positive A-type retardation layer 21, exhibits reverse dispersion. This feature makes it possible to manufacture the retardation film 1 used for manufacturing an elliptically polarizing plate, etc., without stacking a plurality of positive A-type retardation layers. This allows the retardation film 1 to be made thinner.

[0188] 5. Method for Producing Retardation Film A method for producing the retardation film 1 of this embodiment will be described. First, a method for forming the first retardation layer 10 will be described. As an example, the first retardation layer 10 of this embodiment is prepared by dissolving or diluting the components constituting the first retardation layer 10 as described above in a solvent to prepare a composition (coating liquid) for the first retardation layer 10. Subsequently, the composition is applied onto a support and dried. The support is the resin substrate 30 described above.

[0189] As the solvent, for example, a solvent similar to the solvents described in paragraphs 0153 to 0154 of WO 2022 / 158555 can be used. The components constituting the first retardation layer 10 of the present embodiment may contain a component that is difficult to dissolve in a solvent. In particular, as described below, when the first retardation layer 10 is formed by aligning a liquid crystalline component by heating, the components constituting the first retardation layer 10 contain a component that is difficult to dissolve in a solvent. In this case, in order to dissolve the component, a strong solvent that has a particularly strong effect of dissolving the component may be used. The strong solvent is, for example, a ketone-based solvent. As a coating method for applying the composition to the support, a method that can accurately form the first retardation layer 10 to the desired thickness can be appropriately selected.

[0190] The composition for the first retardation layer 10 is applied to a support, and the liquid crystalline component is heated during the process of removing the solvent. The temperature at which the liquid crystalline component is heated is adjusted to a temperature at which the liquid crystalline component can be aligned in a direction substantially perpendicular to the surface of the first retardation layer 10. Specifically, the liquid crystalline component is heated to a temperature equal to or higher than the liquid crystal phase transition temperature and equal to or lower than the isotropic transition temperature (preferably lower than the isotropic transition temperature). This allows the liquid crystalline component to be aligned in a direction substantially perpendicular to the surface of the first retardation layer 10. The heat treatment allows at least the liquid crystalline portion of the liquid crystalline component to be aligned and dried, and the alignment state can be maintained and fixed. The temperature at which the liquid crystalline component can be aligned in a direction substantially perpendicular to the surface of the first retardation layer 10 varies depending on the substance in the liquid crystal composition, and therefore needs to be adjusted appropriately. For example, the heating may be performed within a range of 40°C to 200°C, or even within a range of 40°C to 150°C.

[0191] When the composition for the first retardation layer 10 is thermosetting, the heat treatment also progresses the thermal curing of the composition. At this time, the more the thermal curing progresses, the more difficult it becomes to align the liquid crystalline component. For this reason, the amount of the thermal crosslinker and the amount of the acid catalyst in the composition are adjusted to a small amount that can sufficiently align the liquid crystalline component regardless of the thermal curing of the composition. The degree of curing is adjusted, for example, to a level that can sufficiently increase the alignment control force of the first retardation layer 10.

[0192] The heating time of the liquid crystalline component may be appropriately selected, for example, within a range of 10 seconds to 60 minutes, preferably 20 seconds to 30 minutes. Heating means may be appropriately selected from known heating and drying means, such as a hot plate or an oven. The heat treatment aligns the liquid crystalline component contained in the composition and thermally cures the composition. As a result, a cured film having a retardation is formed from the composition.

[0193] The method for forming the first retardation layer 10 of this embodiment further includes a step of irradiating the cured film having retardation obtained by the above-described method with polarized UV light to impart an alignment restraining force to the cured film. This step is performed so that the cured film is imparted with an alignment restraining force that horizontally aligns the liquid crystalline component on the surface of the cured film. As an example, the cured film is irradiated with polarized UV light. This causes the photo-alignable groups of the photo-alignment component, such as copolymer (B), contained in the cured film to undergo a photoreaction and exhibit anisotropy. In this case, the wavelength of the irradiated polarized UV light is typically within the range of 150 nm to 450 nm. The irradiation direction of the polarized UV light can be perpendicular or oblique to the surface of the support (resin substrate 30). In this way, an alignment restraining force can be imparted to the cured film. As a result, a first retardation layer 10 having an alignment restraining force that horizontally aligns the liquid crystalline component of the second retardation layer 20 can be formed on the resin substrate 30.

[0194] Next, a method for forming the second retardation layer 20 of this embodiment will be described. First, a polymerizable liquid crystal composition is applied to the first retardation layer 10, which is provided with an alignment restraining force as described above and also functions as an alignment layer. Next, the applied polymerizable liquid crystal composition is heated to the phase transition temperature of the polymerizable liquid crystal composition to align the liquid crystalline component contained in the polymerizable liquid crystal composition. Thereafter, the coating film of the polymerizable liquid crystal composition in which the liquid crystalline component has been aligned is irradiated with light. In this way, the second retardation layer 20 can be formed.

[0195] When forming the second retardation layer 20, a conventionally known method may be used for the method of forming a coating film of the polymerizable liquid crystal composition and the method of heating the coated polymerizable liquid crystal composition to a phase transition temperature in the step of aligning the liquid crystalline component, and there are no particular limitations thereon. As the coating method and heating method of the polymerizable liquid crystal composition, the same methods as the coating method and heating method in the manufacturing method of the first retardation layer 10 may be used.

[0196] In the step of irradiating the coating film with light when forming the second retardation layer 20, a polymerization reaction is caused by irradiating the coating film of the polymerizable liquid crystal composition in which the liquid crystalline component is aligned with light, thereby polymerizing the polymerizable groups of the polymerizable liquid crystal compound contained in the first retardation layer 10. Furthermore, when the second retardation layer 20 contains a compound containing a polymerizable group, the polymerizable group of the compound containing a polymerizable group in the first retardation layer 10 may be polymerized with the polymerizable group of the polymerizable liquid crystal compound contained in the second retardation layer 20 at the interface with the second retardation layer 20. As the light irradiation method in the step of irradiating the coating film with light, a conventionally known method can be used.

[0197] By the above-described manufacturing method, it is possible to manufacture the retardation film 1 in which the resin substrate 30, the first retardation layer 10, and the second retardation layer 20 are laminated in this order as shown in FIG.

[0198] 6. Effects of Retardation Film In the retardation film 1 described above, the in-plane refractive index of the first retardation layer 10 is not constant. In the first retardation layer 10, Ny1<Nx1. Such variation in the in-plane refractive index of the first retardation layer 10 occurs, for example, for the following reasons. As described above, the first retardation layer 10 can be formed by a formation method including the steps of applying a composition for the first retardation layer 10 onto a resin substrate 30 and aligning a liquid crystalline component in the composition by heating. At this time, the temperature to which the liquid crystalline component is heated is adjusted to a temperature at which the liquid crystalline component can be oriented in a direction approximately perpendicular to the plane of the first retardation layer 10.

[0199] On the other hand, as described above, the material of the resin substrate 30 is selected taking into consideration the strength required for the resin substrate 30, the cost required for the material of the resin substrate 30, etc. When a forming method including a step of applying a composition for the first retardation layer 10 onto the resin substrate 30 is adopted as the method for forming the first retardation layer 10, the material of the resin substrate 30 can be selected so that the resin substrate 30 is not dissolved in the solvent contained in the composition. In consideration of such circumstances, when forming the first retardation layer 10 on the resin substrate 30, it may be necessary to select a material that can affect the alignment direction of the liquid crystalline component of the first retardation layer 10 as the material of the resin substrate 30.

[0200] As an example of such a case, consider the case where a film formed by biaxial stretching, particularly sequential biaxial stretching, is used as the material for the resin substrate 30. FIG. 3 is a diagram showing an example of a process for forming a film by sequential biaxial stretching. In the example shown in FIG. 3, the film material M is stretched while being conveyed in the conveying direction d1. In the example shown in FIG. 3, the material M is first stretched in a direction d2 parallel to the conveying direction d1. Then, the material M is stretched in a direction d3 perpendicular to the conveying direction d1 and the direction d2. At this time, an alignment restraining force that aligns the liquid crystalline component on the film is applied to the formed biaxially stretched film. The line marked L1 in FIG. 3 indicates the direction in which the formed biaxially stretched film aligns the liquid crystalline component. When a film is formed by biaxial stretching, particularly sequential biaxial stretching, the formed biaxially stretched film may have regions with different orientation angles that align the liquid crystalline component (regions with different directions in which the liquid crystalline component is aligned) due to the bowing phenomenon, as shown in FIG. 3. As described above, depending on the method for forming the resin substrate 30, an orientation restricting force may be generated in the resin substrate 30, and in particular, regions with different orientation angles may be generated in the resin substrate 30.

[0201] 4 is an enlarged view of the area surrounded by the dashed line marked with the symbol IV in FIG. 2. Consider the case where a film to which an alignment regulating force is imparted as shown in FIG. 3 is used as the material of the resin substrate 30, and the first retardation layer 10 is formed on the resin substrate 30 by the above-mentioned method. In this case, near the boundary between the first retardation layer 10 and the resin substrate 30, the liquid crystalline component of the first retardation layer 10 is affected by the alignment regulating force of the resin substrate 30. The liquid crystalline component of the first retardation layer 10 tilts from the direction perpendicular to the surface of the first retardation layer 10 so as to rotate around an axis perpendicular to the direction in which the liquid crystalline component of the resin substrate 30 is aligned and parallel to the surface of the first retardation layer 10. As a result, the liquid crystalline component 14 of the first retardation layer 10 near the boundary with the resin substrate 30 is tilted with respect to the direction perpendicular to the surface of the first retardation layer 10, as shown in FIG. 4. For this reason, the in-plane refractive index of the first retardation layer 10 shown in FIG. 4 is not constant.

[0202] Furthermore, since the film used as the resin substrate 30 has regions with different orientation angles as shown in FIG. 3, regions in which the liquid crystalline component tilts in different directions are generated in the first retardation layer 10. As a result, regions in which the in-plane slow axis extends in different directions are generated in the first retardation layer 10. FIG. 5 is a diagram showing an example of the extension direction of the in-plane slow axis of the first retardation layer 10 when the first retardation layer 10 is formed using the film shown in FIG. 3 as the resin substrate 30. FIG. 5 shows the first retardation layer 10 observed from the thickness direction of the first retardation layer 10. The solid line marked with symbol L2 in FIG. 5 indicates the extension direction of the in-plane slow axis of the first retardation layer 10. As such, depending on the method of forming the first retardation layer 10, the in-plane refractive index of the first retardation layer 10 may not be constant, and in particular, regions in which the in-plane slow axis extends in different directions may be generated in the first retardation layer 10.

[0203] Consider a retardation film 1 manufactured by superposing a second retardation layer 20, which is a positive A-type retardation layer, on a first retardation layer 10 having regions with different in-plane slow axis extension directions, as shown in FIG. 5. The dashed line marked with symbol L3 in FIG. 5 indicates the extension direction of the in-plane slow axis of the second retardation layer 20 when the second retardation layer 20 is superposed on the first retardation layer 10. In the example shown in FIG. 5, the extension direction of the in-plane slow axis of the second retardation layer 20 is the same throughout the second retardation layer 20. The direction d4 shown in FIG. 5 indicates the extension direction of the absorption axis of the polarizing plate 41 superposed on the retardation film 1 when an elliptical polarizing plate 40 is manufactured by superposing a polarizing plate 41 on the retardation film 1, as described below. FIG. 5 is drawn so that the extension direction d4 of the absorption axis of the polarizing plate 41 faces the left-right direction of the paper. In the example shown in FIG. 5, the direction in which the in-plane slow axis of the second retardation layer 20 extends and the direction d4 in which the absorption axis of the polarizing plate 41 superposed on the retardation film 1 extends form an angle of 45°.

[0204] In the retardation film 1 manufactured as described above, there are regions in which the angle θ formed between the extension direction of the in-plane slow axis of the first retardation layer 10 and the extension direction of the in-plane slow axis of the second retardation layer 20 is different. The angle θ is an angle of 90° or less formed between the extension direction of the in-plane slow axis of the first retardation layer 10 and the extension direction of the in-plane slow axis of the second retardation layer 20. For example, in FIG. 5, the angle θ formed between the extension direction of the in-plane slow axis of the first retardation layer 10 indicated by the solid line marked with symbol L21 and the extension direction of the in-plane slow axis of the second retardation layer 20 indicated by the solid line marked with symbol L31 is the angle marked with symbol θ1. The angle θ between the extension direction of the in-plane slow axis of the first retardation layer 10 indicated by the solid line marked with symbol L22 and the extension direction of the in-plane slow axis of the second retardation layer 20 indicated by the solid line marked with symbol L32 is the angle marked with symbol θ2. When the extension direction of the in-plane slow axis of the first retardation layer 10 and the extension direction of the in-plane slow axis of the second retardation layer 20 coincide with each other, the angle θ is considered to be 0°. In this way, by using the first retardation layer 10 having regions in which the in-plane refractive index is not constant and the in-plane slow axis extends in different directions in the retardation film 1, regions with different angles θ are generated in the retardation film 1.

[0205] The present inventors have conducted extensive research and found that the optical properties of the retardation film 1 may be deteriorated when a first retardation layer 10 having an in-plane refractive index that is not constant is used in place of a positive C-type retardation layer that is overlaid on a positive A-type retardation layer in the retardation film 1. In particular, they found that when the retardation film 1 is observed from the thickness direction of the retardation film 1 and from the side that is viewed when the retardation film 1 is used in a display device or the like, regions of different colors may be observed. In particular, they found that when the retardation film 1 is used in a display device, even when the display device is not displaying an image on the display surface and the display surface is black, regions of different colors may be observed when the display surface is observed through the retardation film 1. The following reasons are thought to be the reason why such regions of different colors may be observed. Consider a case where a positive C-type retardation layer having a constant in-plane refractive index is used, and external light traveling in a direction parallel to the thickness direction of the retardation film 1 is converted into linearly polarized light and then passes through the positive A-type retardation layer and the positive C-type retardation layer in this order. In this case, the linearly polarized light is converted into circularly polarized light by passing through the positive A-type retardation layer, and passes through the positive C-type retardation layer without its polarization state being converted. On the other hand, when a first retardation layer 10 having an in-plane refractive index that is not constant is used, the light converted into circularly polarized light by passing through the positive A-type retardation layer has its polarization state further converted when passing through the first retardation layer 10. In particular, it is considered that the light is converted into elliptically polarized light that is slightly different from circularly polarized light when passing through the first retardation layer 10. It is considered that the polarization state of the light is disturbed by this conversion by the first retardation layer 10, and therefore regions with different colors are observed.

[0206] Furthermore, the present inventors have found that the optical properties of the retardation film 1 can be ensured by minimizing the variation in the angle θ in the retardation film 1. In particular, they have found that when the retardation film 1 is observed from the thickness direction of the retardation film 1 and from the side from which the retardation film 1 is viewed when used in a display device or the like, regions with different colors are less likely to be observed. Based on this, the present inventors have found a numerical range of the angle θ that can ensure the optical properties of the retardation film 1, and have completed the present invention.

[0207] The numerical range of the angle θ in the retardation film 1 of this embodiment, which includes the first retardation layer 10 that is the first positive C-type corresponding layer 11 and the second retardation layer 20 that is the first positive A-type retardation layer 21, will be described. In this embodiment, the angle θ between the extension direction of the in-plane slow axis of the first retardation layer 10 and the extension direction of the in-plane slow axis of the second retardation layer 20 is 15° or more and 75° or less. This makes it possible to ensure the optical characteristics of the retardation film 1 while using the first retardation layer 10, which has an in-plane refractive index that is not constant, as a substitute for the positive C-type retardation layer that is overlapped with the positive A-type retardation layer (second retardation layer 20). In particular, when the retardation film 1 is observed from the thickness direction of the retardation film 1 and from the side that is visible when the retardation film 1 is used in a display device or the like, regions with different colors are difficult to observe. In particular, when the display surface of a display device in which no image is displayed on the display surface and the display surface is black is observed through the retardation film 1, regions with different colors are less likely to be observed. The reason why the above-mentioned effect can be obtained by limiting the numerical range of the angle θ is thought to be as follows. As described above, it is thought that light converted into circularly polarized light by passing through the second retardation layer 20, which is a positive A-type retardation layer, is converted into elliptically polarized light that is slightly different from circularly polarized light when passing through the first retardation layer 10. In this case, by limiting the numerical range of the angle θ, it is possible to control the degree to which circularly polarized light is converted into elliptically polarized light by passing through the first retardation layer 10. In particular, by limiting the numerical range of the angle θ, it is possible to maintain a polarization state close to circularly polarized light even after passing through the first retardation layer 10. For this reason, it is thought that by limiting the numerical range of the angle θ, regions with different colors are less likely to be observed.

[0208] The direction in which the first retardation layer 10 having an alignment regulating force aligns the liquid crystalline component of the second retardation layer 20 is adjusted from the viewpoint of setting the angle θ in the above-mentioned numerical range. From the viewpoint of setting the angle θ in the above-mentioned numerical range, the angle formed by the in-plane slow axes of the first retardation layer 10 is preferably 0° or more and 60° or less. Furthermore, from the viewpoint of setting the angle θ in the above-mentioned numerical range, the angle formed by the directions in which the liquid crystalline component of the material of the resin substrate 30 is aligned (angle α shown in FIG. 3) is preferably 0° or more and 60° or less. The angle α formed by the directions in which the liquid crystalline component of the material of the resin substrate 30 is aligned is more preferably 0° or more and 6° or less. An example of a material for the resin substrate 30 that can set the angle α in the range of 0° to 6° is "Cosmoshine SRF (registered trademark)" manufactured by Toyobo Co., Ltd.

[0209] II. Elliptical Polarizing Plate The present disclosure provides an elliptical polarizing plate 40 including the retardation film 1 of the present embodiment and a polarizing plate 41 superimposed on the retardation film 1. The concept of an elliptical polarizing plate includes a circular polarizing plate. Figure 6 is a cross-sectional view showing a display device 100 of the present embodiment including the elliptical polarizing plate 40 of the present embodiment.

[0210] The elliptical polarizing plate 40 in Fig. 6 includes the retardation film 1 of the present embodiment and a polarizing plate 41 positioned adjacent to the retardation film 1. The elliptical polarizing plate 40 may include an adhesive layer (not shown) positioned between the retardation film 1 and the polarizing plate 41, if necessary. In the example of the elliptical polarizing plate 40 in Fig. 6, the polarizing plate 41 is disposed on the retardation film 1 in which the second retardation layer 20 is directly adjacent to the first retardation layer 10.

[0211] In the present embodiment, the polarizing plate 41 is a plate-like plate that transmits only light vibrating in a specific direction. The polarizing plate 41 may be any polarizing plate appropriately selected from conventionally known polarizing plates. In the present embodiment, the polarizing plate 41 is a linear polarizing plate. As an example, the linear polarizing plate that is the polarizing plate 41 includes a polarizer and a polarizer protective layer provided on at least one side of the polarizer. The polarizer is, for example, a stretched film or stretched layer to which a dye having absorption anisotropy is adsorbed. The polarizer may also be a film formed by applying and curing a dye having absorption anisotropy. The dye having absorption anisotropy is, for example, a dichroic dye. Specific examples of the dichroic dye include iodine and dichroic organic dyes. Examples of stretched films to which a dye having absorption anisotropy is adsorbed include polyvinyl alcohol films, polyvinyl formal films, polyvinyl acetal films, and saponified ethylene-vinyl acetate copolymer films that are dyed with iodine or a dye and stretched. For details of the linear polarizer used, see, for example, paragraphs 0025 to 0059 of JP 2021-51287 A. The thickness of the polarizer is, for example, 2 μm to 100 μm, and preferably 10 μm to 60 μm.

[0212] In this embodiment, the adhesive or pressure-sensitive adhesive for the adhesive layer (adhesive layer) can be appropriately selected from conventionally known adhesives. Any adhesive form, such as a pressure-sensitive adhesive, a two-component curing adhesive, an ultraviolet-curing adhesive, a heat-curing adhesive, or a hot-melt adhesive, can be suitably used as the adhesive or pressure-sensitive adhesive for the adhesive layer (adhesive layer). From the viewpoints of transparency, weather resistance, heat resistance, and the like, the adhesive for the adhesive layer may preferably be an adhesive composition having a (meth)acrylic resin as the base polymer. The thickness of the adhesive layer (adhesive layer) is determined depending on its adhesive strength, etc., and may be, for example, 1 μm to 50 μm, preferably 2 μm to 45 μm, more preferably 3 μm to 40 μm, and even more preferably 5 μm to 35 μm.

[0213] The elliptical polarizing plate 40 of the present embodiment may further include other layers included in known optical members, such as known circular polarizing plates and known elliptical polarizing plates, in addition to the retardation film 1, the polarizing plate, and the adhesive layer (adhesive layer). The other layers are not particularly limited as long as they are layers included in known optical members. Examples of the other layers include retardation layers different from the first retardation layer 10 and the second retardation layer 20 of the present embodiment, as well as antireflection layers, diffusion layers, antiglare layers, antistatic layers, protective films, and the like.

[0214] The elliptically polarizing plate 40 of this embodiment can be suitably used as an optical member for suppressing reflection of external light in a display device.

[0215] III. Manufacturing Method of Elliptical Polarizing Plate A method for manufacturing the elliptical polarizing plate 40 of the present embodiment will be described. The manufacturing method of the elliptical polarizing plate 40 includes a step of preparing a polarizing plate 41, a step of preparing a retardation film 1, and a step of laminating the retardation film 1 and the polarizing plate 41 together.

[0216] 1. Process for Preparing a Polarizing Plate As an example of the process for preparing a polarizing plate 41, the preparation of a polarizing plate 41 using a stretched film adsorbed with a dye having absorption anisotropy as a polarizer will be described. A stretched film adsorbed with a dye having absorption anisotropy can typically be produced through the following steps: uniaxially stretching a polyvinyl alcohol-based resin film; dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye; treating the polyvinyl alcohol-based resin film with the adsorbed dichroic dye with a boric acid aqueous solution; and washing the film with water after the boric acid aqueous solution treatment. The polarizing plate 41 can be produced by laminating a polarizer protective layer to one or both sides of the obtained polarizer. The polarizing plate 41 can be prepared, for example, by referring to paragraphs 0025 to 0059 of JP 2021-51287 A.

[0217] 2. Step of Preparing Retardation Film 1 The step of preparing the retardation film 1 of the present embodiment is not particularly limited as long as it can prepare the retardation film 1 of the present embodiment. The step of preparing the retardation film 1 of the present embodiment can be performed by the same method as the above-mentioned method for producing the retardation film 1. For example, the step of preparing the retardation film 1 may include the steps of: forming a film of a composition for the first retardation layer 10, the composition containing: a side-chain liquid crystal polymer having a liquid crystalline constituent unit containing a liquid crystalline moiety in a side chain; a copolymer having a photo-alignable constituent unit and a thermally crosslinkable constituent unit containing a thermally crosslinkable group in a side chain; and a thermal crosslinking agent that bonds to the thermally crosslinkable group of the thermally crosslinkable constituent unit; heating the formed film of the composition to form a cured film having a retardation; irradiating the cured film having a retardation with polarized ultraviolet light to form the first retardation layer 10 to which an alignment restraining force has been imparted; applying a polymerizable liquid crystal composition on the first retardation layer 10 to form a coating film of the polymerizable liquid crystal composition, and heating the coating film to a phase transition temperature of the polymerizable liquid crystal composition to align the liquid crystal molecules by the first retardation layer 10; and forming a second retardation layer 20 by irradiating the coating film of the polymerizable liquid crystal composition in which the liquid crystal molecules have been aligned with light to cure it. In this way, a retardation film 1 including a laminate 2 including the first retardation layer 10 and the second retardation layer 20 and a resin substrate 30 as shown in FIG. 2 can be prepared.

[0218] When preparing the retardation film 1, when forming a laminate 2 including the first retardation layer 10 and the second retardation layer 20 on the resin substrate 30, it is preferable to prepare the retardation film 1 so that the resin substrate 30 can be peeled from the laminate 2. The means for making the resin substrate 30 peelable from the laminate 2 is not particularly limited. For example, the resin substrate 30 can be surface-treated so that the resin substrate 30 can be peeled from the laminate 2. The resin substrate 30 may be subjected to a release treatment so that the resin substrate 30 can be peeled from the laminate 2. A release layer may be formed on the surface of the resin substrate 30 so that the resin substrate 30 can be peeled from the laminate 2. Even when the resin substrate 30 is surface-treated in this way, the liquid crystalline component of the first retardation layer 10 may be affected by the alignment regulating force of the resin substrate 30.

[0219] 3. Step of Laminating Retardation Film and Polarizing Plate In the step of laminating the retardation film 1 and the polarizing plate 41, the retardation film 1 and the polarizing plate 41 may be bonded to each other via an adhesive layer (adhesive layer). As the adhesive layer (adhesive layer), the same adhesive layer (adhesive layer) as the above-mentioned adhesive layer (adhesive layer) can be used.

[0220] When an elliptical polarizer 40 is produced using a retardation film 1 including a first retardation layer 10 that is a first positive C-type corresponding layer 11 and a second retardation layer 20 that is a first positive A-type retardation layer 21, the angle between the extension direction of the in-plane slow axis of the second retardation layer 20 and the extension direction of the absorption axis of the polarizer 41 will be described. When the retardation film 1 and the polarizer 41 are laminated, the angle between the extension direction of the in-plane slow axis of the second retardation layer 20 and the extension direction of the absorption axis of the polarizer 41 is preferably 45°±5°. As shown in the example of FIG. 5, the angle between the extension direction of the in-plane slow axis of the second retardation layer 20 and the extension direction of the absorption axis of the polarizer 41 may be 45°. When the first retardation layer 10 is formed, the direction in which the first retardation layer 10 having an alignment control force aligns the liquid crystalline component of the second retardation layer 20 is adjusted, whereby the angle formed by the extension direction of the in-plane slow axis of the second retardation layer 20 and the extension direction of the absorption axis of the polarizing plate 41 can be set to the above-mentioned numerical range.

[0221] In the step of laminating the retardation film 1 and the polarizing plate 41, when the retardation film 1 and the polarizing plate 41 are bonded to each other via an adhesive layer (adhesive layer), it is preferable to peel the resin substrate 30 from the laminate 2 after bonding. By peeling the resin substrate 30 later, an optical member such as an elliptically polarizing plate 40 can be obtained, which includes the polarizing plate 41 and the retardation film 1 that includes the first retardation layer 10 and the second retardation layer 20 but does not include the resin substrate 30. As described above, by preparing the retardation film 1 so that the resin substrate 30 can be peeled from the laminate 2, the resin substrate 30 can be peeled from the laminate 2 after the retardation film 1 and the polarizing plate 41 are bonded to each other.

[0222] IV. Display Device The display device 100 of the present embodiment includes the retardation film 1 of the present embodiment or an optical member including the retardation film 1. The display device 100 shown in FIG. 6 includes the retardation film 1 and a display device main body 102 that displays images, etc. The second surface 1b of the retardation film 1 faces the display device main body 102. The optical member included in the display device 100 of the present embodiment is, for example, an elliptical polarizing plate 40 that includes the retardation film 1 of the present embodiment and a polarizing plate 41. Examples of the display device 100 include, but are not limited to, a light-emitting display device and a liquid crystal display device. The display device 100 may be a touch panel including a touch sensor. The display device 100 may also be a flexible display device.

[0223] Like the retardation film and retardation layer incorporated in the display device 100 described above, the retardation film and retardation layer of the present embodiment may be incorporated into a laminate such as a panel. In such cases, when evaluating the optical properties of the retardation film or retardation layer, the optical properties can be evaluated by removing the retardation film or retardation layer from the laminate. At this time, the retardation film or retardation layer can be removed by peeling off other layers constituting the laminate from the retardation film or retardation layer using a known solvent. The operation of peeling off other layers constituting the laminate from the retardation film or retardation layer, and the selection of the solvent used for this operation, are performed so as not to dissolve the retardation film or retardation layer to be removed from the laminate. A laminate incorporating a retardation film or retardation layer may include a substrate film such as the resin substrate 30 described above. When evaluating the optical properties of a retardation film or retardation layer incorporated in a laminate including a substrate film, it may be considered that the substrate film does not optically affect the optical properties being evaluated. In this case, the optical properties of the retardation film or the retardation layer can be evaluated without peeling the substrate film from the retardation film or the retardation layer.

[0224] The display device 100 of the present embodiment is preferably a light-emitting display device. When the display device is a light-emitting display device and includes the retardation film 1 of the present embodiment or the optical member of the present embodiment, the viewing angle can be increased while reducing reflection of external light on the display surface of the display device 100. In particular, in a light-emitting display device having a transparent electrode layer, a light-emitting layer, and an electrode layer in this order, the viewing angle can be increased while reducing reflection of external light on the display surface. In the example shown in FIG. 6 , the display device 100 is an organic EL display device 101. The organic EL display device 101 shown in FIG. 6 includes the elliptically polarizing plate 40 of the present embodiment. The organic EL display device 101 including the elliptically polarizing plate 40 of the present embodiment can increase the viewing angle while reducing reflection of external light on the display surface.

[0225] The display device 100 of the present embodiment is preferably a flexible display device. When the display device 100 is a flexible display device, the thickness of the display device 100 can be reduced. Furthermore, the retardation film 1 included in the display device 100 of the present embodiment has high adhesion between the layers constituting the retardation film 1. In addition, the retardation film 1 and the optical member included in the display device 100 of the present embodiment have high resistance to bending. Therefore, when the display device 100 is a flexible display device, it has high resistance to bending. The flexible display device may be a foldable display device. In the display device 100 of the present embodiment, components other than the retardation film 1 or the optical member can be appropriately selected from known components of general display devices.

[0226] The display device 100 of the present embodiment may be one that is expected to be rotated by a user. For example, the display device 100 may be one that can be rotated around an axis perpendicular to the display surface. Examples of display devices that are expected to be rotated by a user include smartphones and tablet terminals.

[0227] <Modifications> Next, various modifications of the present embodiment will be described with reference to Figures 7 to 12. In Figures 7 to 12, the same parts as those in the embodiment shown in Figures 1 to 6 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0228] <Modification 1> In the above-described embodiment, the retardation film 1 has been described in which the first retardation layer 10 has an alignment regulating force and the second retardation layer 20 is directly adjacent to the first retardation layer 10. However, the first retardation layer 10 does not have to have an alignment regulating force. Furthermore, the second retardation layer 20 does not have to be directly adjacent to the first retardation layer 10. FIG. 7 is a cross-sectional view showing a retardation film 1 of Modification 1. In the example shown in FIG. 7, the retardation film 1 further includes a bonding layer 51, a substrate 52, and an alignment film 53. In the retardation film 1 shown in FIG. 7, the resin substrate 30, the first retardation layer 10, the bonding layer 51, the substrate 52, the alignment film 53, and the second retardation layer 20 are laminated in this order. Therefore, in the retardation film 1 shown in FIG. 7, the second retardation layer 20 is not directly adjacent to the first retardation layer 10.

[0229] The retardation film 1 of Modification 1 is manufactured by, for example, the following method. A composition is prepared that is the same as the composition for the first retardation layer 10 of the above-described embodiment, except that it does not contain a photoalignment component. Subsequently, the first retardation layer 10 is formed on the resin substrate 30 using the prepared composition by a method similar to the method for forming the first retardation layer 10 on the resin substrate 30 using the composition for the first retardation layer 10 in the above-described embodiment, except that it does not include a step of imparting an alignment restraining force.

[0230] Furthermore, a laminate of a substrate 52 and an alignment film 53 is prepared. In preparing the laminate, for example, the substrate 52 is first prepared. The material of the substrate 52 can be appropriately selected from conventionally known transparent substrate materials. The material of the substrate 52 may be the same as the material of the resin substrate 30. Next, an alignment film 53 is formed on the substrate 52. As the alignment film 53, an alignment film having an alignment regulating force that horizontally aligns the liquid crystal component of the second retardation layer 20, which is a positive A-type retardation layer, is formed. The method for forming the alignment film 53 is not particularly limited as long as the alignment film 53 having the above-mentioned alignment regulating force can be formed. As a method for forming the alignment film 53, a conventionally known alignment film formation method can be adopted. The alignment film 53 may be formed by rubbing a polyimide resin layer. The alignment film 53 may also be formed by photo-aligning a so-called photo-alignment film material layer. Subsequently, the second retardation layer 20 is formed on the alignment film 53 by the same method as the method of forming the second retardation layer 20 on the first retardation layer 10 that also functions as an alignment layer in the above-described embodiment.

[0231] Next, the first retardation layer 10 and the substrate 52 are bonded via a bonding layer 51. The bonding layer 51 is, for example, a layer similar to the above-mentioned pressure-sensitive adhesive layer (adhesive layer). That is, the first retardation layer 10 and the substrate 52 may be bonded by being stuck together using the above-mentioned pressure-sensitive adhesive or adhesive. By the above-mentioned method, the retardation film 1 shown in FIG. 7 can be produced.

[0232] 7 , by setting the angle θ to be 15° or more and 75° or less, it is possible to ensure the optical characteristics of the retardation film 1 while using the first retardation layer 10 whose in-plane refractive index is not constant. When the first retardation layer 10 and the base material 52 are bonded via the bonding layer 51, the orientation of the second retardation layer 20 with respect to the first retardation layer 10 is adjusted from the viewpoint of setting the angle θ to be in the above-mentioned numerical range.

[0233] From the viewpoint of reducing the thickness of the retardation film 1 and improving productivity, it is preferable that the second retardation layer 20 is directly adjacent to the first retardation layer 10. Furthermore, according to the retardation film 1 in which the second retardation layer 20 is directly adjacent to the first retardation layer 10, the distance between the first retardation layer 10 and the second retardation layer 20 is zero. Therefore, deterioration of optical properties caused by the positional relationship between the first retardation layer 10 and the second retardation layer 20 can be effectively suppressed. In addition, due to the synergistic effect of setting the numerical range of the angle θ and the distance between the first retardation layer 10 and the second retardation layer 20 being zero, deterioration of optical properties caused by the positional relationship between the first retardation layer 10 and the second retardation layer 20 can be particularly effectively suppressed. For this reason, it is preferable that the second retardation layer 20 is directly adjacent to the first retardation layer 10, also from the viewpoint of suppressing deterioration of optical characteristics due to the positional relationship between the first retardation layer 10 and the second retardation layer 20.

[0234] <Modification 2> The numerical ranges of the phase difference and angle θ of the retardation film 1 are not limited to the examples described above in the above-described embodiment and modification. An example of a retardation film 1 of modification 2 will be described. Like the retardation film 1 of the above-described embodiment, the retardation film 1 of modification 2 also includes a laminate 2 including a first retardation layer 10 and a second retardation layer 20. The in-plane retardation of the first retardation layer 10 is not zero, but is small enough to allow the first retardation layer 10 to exhibit a function corresponding to that of a positive C-type retardation layer in the retardation film 1. The second retardation layer 20 is a positive A-type retardation layer. In an example of the retardation film 1 of modification 2, the in-plane retardation of the laminate 2 at a wavelength of 550 nm is set to Re ＡＣ５５０ The in-plane retardation of the laminate 2 at a wavelength of 450 nm is Re ＡＣ４５０ The thickness direction retardation of the laminate 2 at a wavelength of 550 nm is Rth ＡＣ５５０When the above formulas (iv) to (vi) are satisfied, the first retardation layer 10 is referred to as a second positive C-type layer 12. When the following formulas (iv) to (vi) are satisfied, the second retardation layer 20 is referred to as a second positive A-type retardation layer 22. From formula (iv), it can be seen that the laminate 2 provides an overall retardation of about λ / 4. From formula (v), it can be seen that by using the retardation film 1 in a display device or the like described below, the laminate 2 can enhance the contrast relative to the field of view from an oblique direction. From formula (v), it can be seen that by using the retardation film 1 in a display device or the like, the laminate 2 can reduce the effect of the phenomenon (color shift) in which the display color appears different depending on the angle at which the display device is viewed. Due to the effect of formula (v) being satisfied, the viewing angle can be increased when the retardation film 1 is used in a display device or the like. From formula (vi), in this embodiment, Re ＡＣ５５０ Re ＡＣ４５０ It can be seen that the dispersion is smaller, in other words, the laminate 2 exhibits normal dispersion.

[0235] FIG. 8 is a cross-sectional view showing an example of a retardation film 1 of Modification 2. The retardation film 1 shown in FIG. 8 includes a laminate 2 including a first retardation layer 10 that is the second positive C-type corresponding layer 12 and a second retardation layer 20 that is the second positive A-type retardation layer 22. The retardation film 1 shown in FIG. 8 further includes a resin substrate 30. Although not shown, the retardation film 1 including the laminate 2 including the first retardation layer 10 that is the second positive C-type corresponding layer 12 and the second retardation layer 20 that is the second positive A-type retardation layer 22 may not include the resin substrate 30. The retardation film 1 including the second positive C-type corresponding layer 12 and the second positive A-type retardation layer 22 as shown in FIG. 8 is also referred to as a first retardation film 1c.

[0236] The first retardation layer 10, which is the second positive C-type corresponding layer 12, and the method for forming the first retardation layer 10 on the resin substrate 30 are the same as the first retardation layer 10, which is the first positive C-type corresponding layer 11 described above, and the method for forming the first retardation layer 10 on the resin substrate 30, except for the points described below.

[0237] The in-plane retardation and thickness direction retardation of the first retardation layer 10, which is the second positive C-type corresponding layer 12, are determined so that the above-mentioned formulas (iv) to (vi) hold for the in-plane retardation and thickness direction retardation of the laminate 2. The direction in which the first retardation layer 10 aligns the liquid crystalline component of the second retardation layer 20 is adjusted so that, when an elliptically polarizing plate 40 is produced using the retardation film 1, the angle formed between the extension direction of the in-plane slow axis of the second retardation layer 20, which is the second positive A-type retardation layer 22, and the extension direction of the absorption axis of the polarizing plate 41 falls within the numerical range described below. The direction in which the first retardation layer 10 aligns the liquid crystal component of the second retardation layer 20 is adjusted so that the angle θ formed by the extension direction of the in-plane slow axis of the first retardation layer 10, which is the second positive C-type corresponding layer 12, and the extension direction of the in-plane slow axis of the second retardation layer 20, which is the second positive A-type retardation layer 22, falls within a numerical range described later.

[0238] The second retardation layer 20, which is the second positive A-type retardation layer 22, and the method for forming it on the first retardation layer 10 are the same as the second retardation layer 20, which is the first positive A-type retardation layer 21, and the method for forming it on the first retardation layer 10, except for the points described below.

[0239] The in-plane retardation and thickness direction retardation of the second retardation layer 20, which is the second positive A-type retardation layer 22, are determined so that the above-mentioned formulas (iv) to (vi) hold for the in-plane retardation and thickness direction retardation of the laminate 2. In the second retardation layer 20, which is the second positive A-type retardation layer 22, the following formulas (xvi) to (xvii) may hold. In this case, it can be understood from formula (xvi) that the second retardation layer 20, which is the second positive A-type retardation layer 22, functions as a λ / 4 retardation plate. From formula (xvii), Re Ａ５５０ Re Ａ４５０ In other words, it can be seen that the second retardation layer 20, which is the second positive A-type retardation layer 22, exhibits positive dispersion.

[0240] When the elliptically polarizing plate 40 is produced using the retardation film 1, the angle formed by the extension direction of the in-plane slow axis of the second retardation layer 20, which is the second positive A-type retardation layer 22, and the extension direction of the absorption axis of the polarizing plate 41 is preferably 73°±5°. The angle formed by the extension direction of the in-plane slow axis of the second retardation layer 20, which is the second positive A-type retardation layer 22, and the extension direction of the absorption axis of the polarizing plate 41 may also be 73°.

[0241] The material and forming method of the second retardation layer 20, which is the second positive A-type retardation layer 22, are not particularly limited as long as they are materials and forming methods that can form a positive A-type retardation layer exhibiting positive dispersion on a layer that functions as an alignment layer such as the first retardation layer 10 having an alignment regulating force. As the material and forming method of the second retardation layer 20, which is the second positive A-type retardation layer 22, a conventionally known material and forming method of a positive A-type retardation layer exhibiting positive dispersion can be adopted. As long as a positive A-type retardation layer exhibiting positive dispersion can be formed as the second retardation layer 20, which is the second positive A-type retardation layer 22, some of the material and forming method of the second retardation layer 20, which is the second positive A-type retardation layer 22, may be the same as the material and forming method of the second retardation layer 20, which is the first positive A-type retardation layer 21 described above.

[0242] The angle θ formed by the extension direction of the in-plane slow axis of the first retardation layer 10, which is the second positive C-type corresponding layer 12, and the extension direction of the in-plane slow axis of the second retardation layer 20, which is the second positive A-type retardation layer 22, is 0° or more and 45° or less.

[0243] Even in the retardation film 1 including the first retardation layer 10 that is the second positive C-type corresponding layer 12 and the second retardation layer 20 that is the second positive A-type retardation layer 22, by setting the angle θ to be 0° or more and 45° or less, it is possible to ensure the optical characteristics of the retardation film 1 while using the first retardation layer 10 whose in-plane refractive index is not constant. In particular, when the retardation film 1 is observed from the thickness direction of the retardation film 1 and from the side that is viewed when the retardation film 1 is used in a display device or the like, regions with different colors are difficult to observe.

[0244] Another example of the retardation film 1 of Modification 2, which is different from the example shown in FIG. 8, will be further described. In another example of the retardation film 1 of Modification 2, the in-plane retardation of the laminate 2 at a wavelength of 550 nm is set to Re ＡＣ５５０ The in-plane retardation of the laminate 2 at a wavelength of 450 nm is Re ＡＣ４５０ The thickness direction retardation of the laminate 2 at a wavelength of 550 nm is Rth ＡＣ５５０ When the above formulas (vii) to (ix) are satisfied, the first retardation layer 10 is referred to as a third positive C-type layer 13. When the following formulas (vii) to (ix) are satisfied, the second retardation layer 20 is referred to as a third positive A-type retardation layer 23. From formula (vii), it can be seen that the laminate 2 provides an overall retardation of about λ / 2. From formula (viii), it can be seen that by using the retardation film 1 in a display device or the like described below, the laminate 2 can exhibit the effect of enhancing the contrast relative to the field of view from an oblique direction. From formula (viii), it can be seen that by using the retardation film 1 in a display device or the like, the laminate 2 can reduce the effect of the phenomenon (color shift) in which the display color appears different depending on the angle at which the display device is viewed. By virtue of the effect of the above-described formula (viii) being satisfied, when the retardation film 1 is used in a display device or the like, the viewing angle can be increased. ＡＣ５５０ Re ＡＣ４５０ It can be seen that the dispersion is smaller, in other words, the laminate 2 exhibits normal dispersion.

[0245] 9 is a cross-sectional view showing another example of the retardation film 1 of Modification 2, different from the example shown in FIG. 8. The retardation film 1 shown in FIG. 9 includes a laminate 2 including a first retardation layer 10 that is the third positive C-type corresponding layer 13 and a second retardation layer 20 that is the third positive A-type retardation layer 23. The retardation film 1 shown in FIG. 9 further includes a resin substrate 30. Although not shown, the retardation film 1 including the laminate 2 including the first retardation layer 10 that is the third positive C-type corresponding layer 13 and the second retardation layer 20 that is the third positive A-type retardation layer 23 may not include the resin substrate 30. The retardation film 1 including the third positive C-type corresponding layer 13 and the third positive A-type retardation layer 23 as shown in FIG. 9 is also referred to as a second retardation film 1d.

[0246] The first retardation layer 10, which is the third positive C-type corresponding layer 13, and the method for forming the first retardation layer 10 on the resin substrate 30 are the same as the first retardation layer 10, which is the second positive C-type corresponding layer 12 described above, and the method for forming the first retardation layer 10 on the resin substrate 30, except for the points described below.

[0247] The in-plane retardation and thickness direction retardation of the first retardation layer 10, which is the third positive C-type corresponding layer 13, are determined so that the above-mentioned formulas (vii) to (ix) hold for the in-plane retardation and thickness direction retardation of the laminate 2. The direction in which the first retardation layer 10 aligns the liquid crystalline component of the second retardation layer 20 is adjusted so that, when an elliptically polarizing plate 40 is produced using the retardation film 1, the angle formed between the extension direction of the in-plane slow axis of the second retardation layer 20, which is the third positive A-type retardation layer 23, and the extension direction of the absorption axis of the polarizing plate 41 falls within the numerical range described below. The direction in which the first retardation layer 10 aligns the liquid crystal component of the second retardation layer 20 is adjusted so that the angle θ formed by the extension direction of the in-plane slow axis of the first retardation layer 10, which is the third positive C-type corresponding layer 13, and the extension direction of the in-plane slow axis of the second retardation layer 20, which is the third positive A-type retardation layer 23, falls within a numerical range described later.

[0248] The method for forming the second retardation layer 20, which is the third positive A-type retardation layer 23, on the first retardation layer 10, which is the third positive C-type corresponding layer 13, is the same as the method for forming the second retardation layer 20, which is the second positive A-type retardation layer 22, on the first retardation layer 10, except for the points described below.

[0249] The in-plane retardation and thickness direction retardation of the second retardation layer 20, which is the third positive A-type retardation layer 23, are determined so that the above-mentioned formulas (vii) to (ix) hold for the in-plane retardation and thickness direction retardation of the laminate 2. In the second retardation layer 20, which is the third positive A-type retardation layer 23, the following formulas (xviii) to (xix) may hold. In this case, it can be understood from formula (xviii) that the second retardation layer 20, which is the third positive A-type retardation layer 23, functions as a λ / 2 retardation plate. From formula (xix), Re Ａ５５０ Re Ａ４５０ In other words, it can be seen that the second retardation layer 20, which is the third positive A-type retardation layer 23, exhibits positive dispersion.

[0250] When the elliptically polarizing plate 40 is produced using the retardation film 1, the angle formed between the extension direction of the in-plane slow axis of the second retardation layer 20, which is the third positive A-type retardation layer 23, and the extension direction of the absorption axis of the polarizing plate 41 is preferably 15°±5°. The angle formed between the extension direction of the in-plane slow axis of the second retardation layer 20, which is the third positive A-type retardation layer 23, and the extension direction of the absorption axis of the polarizing plate 41 may also be 15°.

[0251] The angle θ between the extension direction of the in-plane slow axis of the first retardation layer 10, which is the third positive C-type corresponding layer 13, and the extension direction of the in-plane slow axis of the second retardation layer 20, which is the third positive A-type retardation layer 23, is 45° or more and 90° or less.

[0252] Even in the retardation film 1 including the first retardation layer 10 that is the third positive C-type corresponding layer 13 and the second retardation layer 20 that is the third positive A-type retardation layer 23, by setting the angle θ to 45° or more and 90° or less, it is possible to ensure the optical characteristics of the retardation film 1 while using the first retardation layer 10 whose in-plane refractive index is not constant. In particular, when the retardation film 1 is observed from the thickness direction of the retardation film 1 and from the side that is viewed when the retardation film 1 is used in a display device or the like, regions with different colors are difficult to observe.

[0253] An elliptical polarizer 40 using the retardation film 1 of Modification 2 will be described. FIG. 10 is a diagram showing an example of the elliptical polarizer 40 using the retardation film 1 of Modification 2. FIG. 11 is a diagram showing another example of the elliptical polarizer 40 using the retardation film 1 of Modification 2, different from that shown in FIG. 10 . In the example shown in FIGS. 10 and 11 , the elliptical polarizer 40 includes two retardation films 1: a retardation film 1 including a second positive C-type corresponding layer 12 and a second positive A-type retardation layer 22, and a retardation film 1 including a third positive C-type corresponding layer 13 and a third positive A-type retardation layer 23. The elliptical polarizer 40 further includes a bonding layer 55 that bonds the two retardation films 1 together.

[0254] In the elliptical polarizer 40, the third positive A-type retardation layer 23 is disposed closer to the polarizer 41 than the second positive A-type retardation layer 22. In FIGS. 10 and 11 , the retardation film 1 including the third positive A-type retardation layer 23 is disposed closer to the polarizer 41 than the retardation film 1 including the second positive A-type retardation layer 22. In the elliptical polarizer 40 shown in FIG. 10 , the second positive C-type corresponding layer 12, the second positive A-type retardation layer 22, the bonding layer 55, the third positive C-type corresponding layer 13, the third positive A-type retardation layer 23, and the polarizer 41 are laminated in this order. In the elliptical polarizer 40 shown in FIG. 11 , the second positive C-type corresponding layer 12, the second positive A-type retardation layer 22, the bonding layer 55, the third positive A-type retardation layer 23, the third positive C-type corresponding layer 13, and the polarizer 41 are laminated in this order.

[0255] As shown in FIGS. 10 and 11 , the elliptical polarizing plate 40 may further include a λ / 4 retardation plate 42. In the examples shown in FIGS. 10 and 11 , the λ / 4 retardation plate 42 forms the surface of the elliptical polarizing plate 40. The λ / 4 retardation plate 42 and the retardation film 1 sandwich the polarizing plate 41. The λ / 4 retardation plate 42 provides the following effects. When the elliptical polarizing plate 40 is used in a display device, light emitted from the display device is converted into linearly polarized light by the polarizing plate 41, which is a linear polarizing plate. By further including the λ / 4 retardation plate 42 in the elliptical polarizing plate 40, the light converted into linearly polarized light by the polarizing plate 41 can be further converted into circularly polarized light. This prevents the user from being unable to see the light from the display device depending on the angle of rotation, even when the user of the display device using the elliptical polarizing plate 40 wears polarized sunglasses and rotates the display device.

[0256] 6 , an elliptical polarizer 40 including a first retardation layer 10 that is a first positive C-type corresponding layer 11 and a second retardation layer 20 that is a first positive A-type retardation layer 21 may further include a λ / 4 retardation plate 42. In this case, the first positive C-type corresponding layer 11, the first positive A-type retardation layer 21, the polarizer 41, and the λ / 4 retardation plate 42 are laminated in this order in the elliptical polarizer 40. Even with such an elliptical polarizer 40, when a user of a display device using the elliptical polarizer 40 wears polarized sunglasses and rotates the display device by the user, it is possible to prevent the user from being unable to see light from the display device depending on the angle of rotation.

[0257] As a manufacturing method of the elliptical polarizer 40 of the second modification, first, a manufacturing method of the elliptical polarizer 40 shown in FIG. 10 will be described. First, a first retardation film 1c shown in FIG. 8, a second retardation film 1d shown in FIG. 9, and a polarizing plate 41 are prepared. Next, the second retardation film 1d and the polarizing plate 41 are laminated. At this time, the second retardation film 1d and the polarizing plate 41 are laminated so that the first surface 1a of the second retardation film 1d faces the polarizing plate 41. As an example, the second retardation film 1d and the polarizing plate 41 can be laminated by bonding the first surface 1a of the second retardation film 1d to the surface of the polarizing plate 41 with an adhesive layer (bonding layer). In this case, the adhesive layer (bonding layer) can be the same as the adhesive layer (bonding layer) described above. Next, the resin substrate 30 is peeled off from the laminate 2 of the second retardation film 1d. Next, the second retardation film 1d and the first retardation film 1c are bonded together via a bonding layer 55. At this time, the second retardation film 1d and the first retardation film 1c are bonded together so that the first surface 1a of the first retardation film 1c faces the second retardation film 1d. The bonding layer 55 is, for example, the same layer as the bonding layer 51 described above. Next, the resin substrate 30 is peeled off from the laminate 2 of the first retardation film 1c. When manufacturing an elliptical polarizing plate 40 including a λ / 4 retardation plate 42, the surface of the polarizing plate 41 and the surface of the λ / 4 retardation plate 42 are further bonded together. The surface of the polarizing plate 41 and the surface of the λ / 4 retardation plate 42 can be bonded together by laminating them with an adhesive layer (adhesive layer). In this case, the adhesive layer (adhesive layer) can be the same as the adhesive layer (adhesive layer) described above. Through the above steps, the elliptical polarizing plate 40 shown in FIG. 10 can be manufactured.

[0258] Next, a method for manufacturing the elliptical polarizing plate 40 shown in FIG. 11 will be described. First, a first retardation film 1c shown in FIG. 8, a second retardation film 1d shown in FIG. 9, and a polarizing plate 41 are prepared. Next, the first retardation film 1c and the second retardation film 1d are bonded together via a bonding layer 55. At this time, the first retardation film 1c and the second retardation film 1d are bonded together so that the first surface 1a of the first retardation film 1c and the first surface 1a of the second retardation film 1d face each other. Next, the resin substrate 30 is peeled off from the laminate 2 of the second retardation film 1d. Next, the second retardation film 1d and the polarizing plate 41 are laminated together. At this time, the second retardation film 1d and the polarizing plate 41 are laminated together so that the second surface 1b of the second retardation film 1d faces the polarizing plate 41. As an example, the second retardation film 1d and the polarizing plate 41 can be laminated by bonding the second surface 1b of the second retardation film 1d to the surface of the polarizing plate 41 with an adhesive layer (adhesive layer). In this case, the adhesive layer (adhesive layer) can be the same as the adhesive layer (adhesive layer) described above. Next, the resin substrate 30 is peeled off from the laminate 2 of the first retardation film 1c. When manufacturing an elliptical polarizing plate 40 including a λ / 4 retardation plate 42, the surface of the polarizing plate 41 and the surface of the λ / 4 retardation plate 42 are further bonded. The surface of the polarizing plate 41 and the surface of the λ / 4 retardation plate 42 can be bonded by bonding them with an adhesive layer (adhesive layer). In this case, the adhesive layer (adhesive layer) can be the same as the adhesive layer (adhesive layer) described above. In this manner, the elliptical polarizing plate 40 shown in FIG. 11 can be manufactured.

[0259] The function of the elliptical polarizer 40 of Modification 2 will be described. The elliptical polarizer 40 of Modification 2 includes a second positive A-type retardation layer 22 that functions as a λ / 4 retardation plate and exhibits positive dispersion, and a third positive A-type retardation layer 23 that functions as a λ / 2 retardation plate and exhibits positive dispersion. The angle between the extension direction of the in-plane slow axis of the second positive A-type retardation layer 22 and the extension direction of the absorption axis of the polarizer 41 is 73°±5°. The angle between the extension direction of the in-plane slow axis of the third positive A-type retardation layer 23 and the extension direction of the absorption axis of the polarizer 41 is 15°±5°. Such an elliptical polarizer 40 provides functions corresponding to those described in paragraphs 0018 to 0020 of JP-A-10-68816. As shown in FIG. 6 , when the elliptically polarizing plate 40 is used in a display device or the like, external light is converted into linearly polarized light by passing through the polarizing plate 41 and then enters the third positive A-type retardation layer 23. That is, the following effect is obtained. The wavelength of light at which the second positive A-type retardation layer 22 functions as a λ / 4 retardation plate and the third positive A-type retardation layer 23 functions as a λ / 2 retardation plate is referred to as the reference wavelength. The reference wavelength is, for example, 550 nm. Consider a case where linearly polarized light passes through the third positive A-type retardation layer 23 and the second positive A-type retardation layer 22 in this order. When linearly polarized light having the reference wavelength passes through, the polarization direction of the light is rotated when the light passes through the third positive A-type retardation layer 23, and becomes circularly polarized when the light passes through the second positive A-type retardation layer 22. As a result, linearly polarized light having a reference wavelength is converted into circularly polarized light by passing through the third positive A-type retardation layer 23 and the second positive A-type retardation layer 22. Next, consider the case where linearly polarized light having a wavelength shorter than the reference wavelength passes through. In this case, when light passes through the third positive A-type retardation layer 23, the retardation of the third positive A-type retardation layer 23 is excessive to convert the linearly polarized light into linearly polarized light with a rotated polarization direction. Next, when light having a short wavelength further passes through the second positive A-type retardation layer 22, the retardation of the second positive A-type retardation layer 22 is excessive to convert the linearly polarized light into circularly polarized light.The excess retardation of the third positive A-type retardation layer 23 and the excess retardation of the second positive A-type retardation layer 22 cancel each other out, resulting in light with a short wavelength being converted into circularly polarized light or elliptically polarized light that is relatively close to circularly polarized light. Next, consider the case where linearly polarized light with a wavelength longer than the reference wavelength passes through. In this case, when light passes through the third positive A-type retardation layer 23, the retardation of the third positive A-type retardation layer 23 is insufficient to convert linearly polarized light into linearly polarized light with a rotated polarization direction. Next, when light with a long wavelength further passes through the second positive A-type retardation layer 22, the retardation of the second positive A-type retardation layer 22 is insufficient to convert linearly polarized light into circularly polarized light. The retardation deficiency of the third positive A-type retardation layer 23 and the retardation deficiency of the second positive A-type retardation layer 22 cancel each other out, resulting in light having a long wavelength being converted into circularly polarized light or elliptically polarized light that is relatively close to circularly polarized light. In this way, in the elliptical polarizer 40 including the second positive A-type retardation layer 22 and the third positive A-type retardation layer 23, light having a wide wavelength centered on the reference wavelength can be converted into circularly polarized light or elliptically polarized light that is relatively close to circularly polarized light by passing light through the third positive A-type retardation layer 23 and the second positive A-type retardation layer 22. By using such an elliptical polarizer 40 in a display device or the like, reflection of external light having a wide wavelength centered on the reference wavelength can be more effectively prevented, making the display device or the like more visible.

[0260] The retardation film 1 of the second modification includes two positive A-type retardation layers: a second positive A-type retardation layer 22 and a third positive A-type retardation layer 23. The second positive A-type retardation layer 22 exhibits normal dispersion. The third positive A-type retardation layer 23 exhibits normal dispersion. This feature provides the following effects. In general, liquid crystal compounds used to form retardation layers exhibiting normal dispersion have relatively good weather resistance. Therefore, when the positive A-type retardation layer included in the retardation film 1 exhibits normal dispersion, the weather resistance of the retardation film 1 can be improved. In particular, liquid crystal compounds used to form retardation layers exhibiting normal dispersion have relatively high resistance to ultraviolet light. Therefore, when the positive A-type retardation layer included in the retardation film 1 exhibits normal dispersion, the resistance of the retardation film 1 to ultraviolet light can be improved.

[0261] Furthermore, the elliptical polarizer 40 of Modification 2 includes a second positive C-type corresponding layer 12 and a third positive C-type corresponding layer 13. When the elliptical polarizer 40 is used in a display device or the like, the second positive C-type corresponding layer 12 and the third positive C-type corresponding layer 13 act to enhance contrast relative to an oblique viewing direction and reduce color shift. Although not shown, the elliptical polarizer 40 does not necessarily include either the second positive C-type corresponding layer 12 or the third positive C-type corresponding layer 13. In the elliptical polarizer 40, the second positive A-type retardation layer 22, the third positive A-type retardation layer 23, the third positive C-type corresponding layer 13, and the polarizer 41 may be stacked in this order. In the elliptical polarizer 40, the second positive C-type corresponding layer 12, the second positive A-type retardation layer 22, the third positive A-type retardation layer 23, and the polarizer 41 may be stacked in this order. Even in this case, the contrast when viewed from an oblique direction can be increased and color shift can be reduced by providing the elliptically polarizing plate 40 with either the second positive C-type corresponding layer 12 or the third positive C-type corresponding layer 13. From the viewpoint of further enhancing the effect of increasing the contrast when viewed from an oblique direction and the effect of reducing color shift, it is preferable that the elliptically polarizing plate 40 include both the second positive C-type corresponding layer 12 and the third positive C-type corresponding layer 13.

[0262] From the viewpoint of improving the durability of the elliptical polarizer 40, the elliptical polarizer 40 including the second positive C-type corresponding layer 12 and the third positive C-type corresponding layer 13 shown in Figures 10 and 11 is more preferable than the elliptical polarizer 40 including the first positive A-type corresponding layer 21 shown in Figure 6. From the viewpoint of reducing the thickness of the elliptical polarizer 40, the elliptical polarizer 40 including the first positive A-type corresponding layer 21 shown in Figure 6 is more preferable than the elliptical polarizer 40 including the second positive C-type corresponding layer 12 and the third positive C-type corresponding layer 13 shown in Figures 10 and 11.

[0263] <Modification 3> The retardation film 1 may include both the second positive A-type retardation layer 22 and the third positive A-type retardation layer 23 described in Modification 2. FIG. 12 is a cross-sectional view showing a retardation film 1 of Modification 3. In the retardation film 1 shown in FIG. 12, a resin substrate 30, a second positive C-type corresponding layer 12, a second positive A-type retardation layer 22, a third positive C-type corresponding layer 13, and a third positive A-type retardation layer 23 are laminated in this order. In the retardation film 1 shown in FIG. 12, the second positive A-type retardation layer 22 is directly adjacent to the third positive C-type corresponding layer 13. Although not shown, the retardation film 1 including both the second positive A-type retardation layer 22 and the third positive A-type retardation layer 23 may not include the resin substrate 30. 12 includes a second positive C-type corresponding layer 12 and a second positive A-type retardation layer 22, and therefore it can be said that the retardation film 1 includes a laminate 2 including a first retardation layer 10 and a second retardation layer 20. Furthermore, the retardation film 1 shown in FIG. 12 includes a third positive C-type corresponding layer 13 and a third positive A-type retardation layer 23, and therefore it can be said that the retardation film 1 includes a laminate 2 including a first retardation layer 10 and a second retardation layer 20. That is, it can be said that the retardation film 1 shown in FIG. 12 includes two laminates 2.

[0264] A manufacturing method of the retardation film 1 shown in Fig. 12 will be described. First, a first retardation film 1c shown in Fig. 8 is prepared. Next, a third positive C-type corresponding layer 13 is formed on the second positive A-type retardation layer 22 of the first retardation film 1c by a method similar to the method for forming the third positive C-type corresponding layer 13 on the resin substrate 30. Next, a third positive A-type retardation layer 23 is formed on the third positive C-type corresponding layer 13 by a method similar to the method for forming the third positive A-type retardation layer 23 on the first retardation layer 10, which is the third positive C-type corresponding layer 13.

[0265] An elliptically polarizing plate 40 can be produced by overlaying a polarizing plate 41 on the retardation film 1 of Modification 3 so that the polarizing plate 41 faces the first surface 1 a. The elliptically polarizing plate 40 produced in this manner also has the same effect as the elliptically polarizing plate 40 of Modification 2.

[0266] The retardation film 1 of Modification 3 also uses the first retardation layer 10 whose in-plane refractive index is not constant, while ensuring the optical properties of the retardation film 1. In particular, when the retardation film 1 is observed from the thickness direction of the retardation film 1 and from the side from which the retardation film 1 is viewed when used in a display device or the like, regions with different colors are difficult to observe. In the retardation film 1 of Modification 3, the first retardation layer 10 also increases the contrast relative to the field of view from an oblique direction and reduces color shift. Furthermore, when the retardation film 1 of Modification 3 is used in a display device or the like, reflection of external light of a wide wavelength can be more effectively prevented, making the display device or the like easier to view.

[0267] From the viewpoint of improving the durability of the retardation film 1, the retardation film 1 including the second positive C-type corresponding layer 12 and the third positive C-type corresponding layer 13 shown in Fig. 12 is more preferable than the retardation film 1 including the first positive A-type corresponding layer 21 shown in Fig. 6. From the viewpoint of reducing the thickness of the elliptically polarizing plate 40, the retardation film 1 including the first positive A-type corresponding layer 21 shown in Fig. 6 is more preferable than the retardation film 1 including the second positive C-type corresponding layer 12 and the third positive C-type corresponding layer 13 shown in Fig. 12.

[0268] <Experimental Example> The present inventors conducted an experiment to confirm the effects of the retardation film 1 of the present disclosure. The experiment will be described below.

[0269] (Experimental Example 1) The retardation film 1 shown in FIG. 2 was produced by the following method. First, a liquid crystal composition formulated with reference to International Publication No. WO 2022 / 158555 was applied to a resin substrate 30 made of polyethylene terephthalate. The formulation of the liquid crystal composition was adjusted so that the liquid crystal composition could form a first retardation layer 10 that has an alignment regulating force for horizontally aligning the liquid crystal component of the second retardation layer 20 and exhibits a function corresponding to the function of a positive C-type retardation layer. Furthermore, the formulation of the liquid crystal composition was adjusted so that an evaluation region could be formed in which the angle θ between the extension direction of the in-plane slow axis of the first retardation layer 10 and the extension direction of the in-plane slow axis of the second retardation layer 20 was 15°. Furthermore, the formulation of the liquid crystal composition was adjusted so that the Re in the evaluation region Ｃ５５０ , Rth Ｃ５５０ , Re ＡＣ５５０ , Rth ＡＣ５５０ The liquid crystal composition was then dried. Then, the coating film of the liquid crystal composition was irradiated with an integrated light amount of 20 mJ / cm. ２ The film was irradiated with polarized ultraviolet light (wavelength 310 nm). At this time, the method of irradiating the polarized ultraviolet light was adjusted so that an evaluation region with an angle θ of 15° could be formed on the retardation film 1. As a result, a first retardation layer 10 was formed on the resin substrate 30, which had an alignment regulating force for horizontally aligning the liquid crystalline component of the second retardation layer 20 and exhibited a function corresponding to the function of a positive C-type retardation layer.

[0270] The in-plane retardation of the formed first retardation layer 10 at a wavelength of 550 nm is defined as Re Ｃ５５０ , the thickness direction retardation at a wavelength of 550 nm is Rth Ｃ５５０ Then, Re in the evaluation area Ｃ５５０ is 3.0 nm, Rth Ｃ５５０ was −71.0 nm.

[0271] Next, a coating liquid for forming a second retardation layer 20 was applied onto the first retardation layer 10. The coating liquid used was the same as "Positive A Layer Coating Liquid 1" described in paragraph 0112 of JP-A No. 2021-189224. The coating liquid was applied using a bar coater so that the film thickness after drying would be 2.5 μm. Thereafter, the coating liquid was dried and irradiated with ultraviolet light. At this time, the Re in the evaluation area ＡＣ５５０ and Rth ＡＣ５５０ The amount of the coating solution was adjusted so that the value described below was obtained. As a result, a second retardation layer 20, which was a positive A-type retardation layer, was formed on the first retardation layer 10. As a result, a retardation film 1 including a laminate 2 including the first retardation layer 10 and the second retardation layer 20, as shown in FIG. 2, was produced.

[0272] The retardation film 1 of Experimental Example 1 was manufactured so as to form an evaluation region in which the angle θ between the extension direction of the in-plane slow axis of the first retardation layer 10 and the extension direction of the in-plane slow axis of the second retardation layer 20 was 15°. ＡＣ５５０ The thickness direction retardation of the laminate at a wavelength of 550 nm is Rth ＡＣ５５０ Then, Re in the evaluation area ＡＣ５５０ is 141.0 nm, Rth ＡＣ５５０ Furthermore, the in-plane retardation of the laminate 2 at a wavelength of 450 nm was Re ＡＣ４５０ Then, Re ＡＣ５５０ Re ＡＣ４５０ That is, the second retardation layer 20 exhibited reverse dispersion.

[0273] Subsequently, the laminate 2 of the produced retardation film 1 was transferred to a polarizing plate 41. In the transfer, the second retardation layer 20 of the laminate 2 was bonded to the polarizing plate 41, and then the resin substrate 30 was peeled off from the laminate 2. A linear polarizing plate containing iodine-doped stretched PVA as a polarizer was used as the polarizing plate 41. The transfer was performed so that the angle between the extension direction of the in-plane slow axis of the second retardation layer 20 and the extension direction of the absorption axis of the polarizing plate 41 was 45° in the evaluation region.

[0274] Next, a laminate of a glass substrate and aluminum foil was prepared. The aluminum foil had a glossy surface and a matte surface. In preparing the laminate, the glossy surface of the aluminum foil was bonded to the glass substrate. Then, the matte surface of the aluminum foil was bonded to the first retardation layer 10 of the laminate 2.

[0275] As described above, a sample was prepared in which the glass substrate, aluminum foil, first retardation layer 10, second retardation layer 20, and polarizing plate 41 were laminated in this order. The bonding between the glass substrate and the aluminum foil, the bonding between the aluminum foil and the first retardation layer 10, and the bonding between the second retardation layer 20 and the polarizing plate were performed by providing an adhesive layer between the two layers to be bonded. As the adhesive layer, a 10 μm thick optical adhesive manufactured by Lintec Corporation was used.

[0276] In the evaluation region, the angle θ between the direction in which the in-plane slow axis of the first retardation layer 10 extends and the direction in which the in-plane slow axis of the second retardation layer 20 extends was set to 45°. Other than this, the same conditions as in Experimental Example 1 were used.

[0277] In the evaluation region, the angle θ between the direction in which the in-plane slow axis of the first retardation layer 10 extends and the direction in which the in-plane slow axis of the second retardation layer 20 extends was set to 75°. Other than this, the same conditions as in Experimental Example 1 were used.

[0278] (Experimental Example 4) In the evaluation region, the angle θ formed between the extension direction of the in-plane slow axis of the first retardation layer 10 and the extension direction of the in-plane slow axis of the second retardation layer 20 was set to 0°. That is, the retardation film 1 was produced so that the extension direction of the in-plane slow axis of the first retardation layer 10 and the extension direction of the in-plane slow axis of the second retardation layer 20 were parallel to each other in the evaluation region. Except for this, the same conditions as in Experimental Example 1 were used.

[0279] In the evaluation region, the angle θ between the direction in which the in-plane slow axis of the first retardation layer 10 extends and the direction in which the in-plane slow axis of the second retardation layer 20 extends was set to 90°. Other than this, the same conditions as in Experimental Example 1 were used.

[0280] In Experimental Examples 1 to 5, it is considered that the colors observed when the display surface of the display device is viewed through a retardation film 1 including a first retardation layer 10 that is a first positive C-type corresponding layer 11 and a second retardation layer 20 that is a first positive A-type retardation layer 21 are expressed. In particular, it is considered that the evaluation area of ​​Experimental Example 1 expresses the colors observed when the display surface of the display device is viewed through a region of the retardation film 1 where the angle θ is 15°. Similarly, it is considered that the evaluation areas of Experimental Examples 2 to 5 express the colors observed when the display surface of the display device is viewed through regions of the retardation film 1 where the angle θ is 45°, 75°, 0°, and 90°.

[0281] (1) L ＊ a ＊ b ＊ Testing by color system For the evaluation area of ​​the samples in Experimental Examples 1 to 5, L ＊ a ＊ b ＊ Tests were conducted using a color system. ＊ a ＊ b ＊ In the test using the color system, the evaluation area is observed from the polarizing plate 41 side and in the thickness direction of the sample, and the L ＊ a ＊ b ＊ The color was measured in the color system. ＊ a ＊ b ＊ When measuring the colors in the color system, a spectrophotometer (manufactured by Konica Minolta, Inc., product name "CM-2600d") was used as the measuring device.

[0282] (2) Sensory Evaluation Test for Color Tone A sensory evaluation test for color tone was conducted on the evaluation areas of the samples in Experimental Examples 1 to 5. In the sensory evaluation test for color tone, subjects were asked to observe the evaluation areas from the polarizing plate 41 side and from the thickness direction of the sample. Then, the subjects were asked to evaluate the observed color tone.

[0283] When the subject was asked to observe the evaluation area, the sample was placed on a flat table illuminated with white light in a bright room. The illuminance of the evaluation area of ​​the sample was 1000 lux. The distance between the subject's eyes and the evaluation area of ​​the sample was 30 cm.

[0284] L ＊ a ＊ b ＊ The results of the color system test and the sensory evaluation test of color are shown in Table 1. The "Angle" column in Table 1 indicates the angle θ between the extension direction of the in-plane slow axis of the first experimental retardation layer and the extension direction of the in-plane slow axis of the second experimental retardation layer in each experimental example. The "Sensory Evaluation Test of Color" column in Table 1 indicates what kind of color the subjects evaluated as being observed.

[0285]

[0286] In Experimental Examples 1 to 3, L ＊ In Experimental Examples 1 to 3, the value of a ＊ In Experimental Examples 1 to 3, the value of b ＊ The value of was -2.38 or more. Furthermore, in all of Experimental Examples 1 to 3, in the sensory evaluation test of color, the subjects evaluated that a pure black color was observed. From this, it was found that in the retardation film 1 including the first retardation layer 10 which is the first positive C-type corresponding layer 11 and the second retardation layer 20 which is the first positive A-type retardation layer 21, when the angle θ is 15° or more and 75° or less, regions with different colors are difficult to observe.

[0287] The components disclosed in the above-described embodiment and each modification may be combined as needed, or some components may be omitted from all the components shown in the above-described embodiment and each modification.

[0288] REFERENCE SIGNS LIST 1 Retardation film 2 Laminate 10 First retardation layer 11 First positive C-type corresponding layer 12 Second positive C-type corresponding layer 13 Third positive C-type corresponding layer 20 Second retardation layer 21 First positive A-type retardation layer 22 Second positive A-type retardation layer 23 Third positive A-type retardation layer 30 Resin substrate 40 Elliptical polarizing plate 41 Polarizing plate 100 Display device 101 Organic EL display device

Claims

1. A laminate including a first retardation layer and a second retardation layer overlapping the first retardation layer, wherein when the refractive index in the direction in which the in-plane slow axis of the first retardation layer extends is Nx1, the refractive index in the direction in which the in-plane slow axis of the first retardation layer extends and in the direction perpendicular to the thickness direction of the first retardation layer is Ny1, and the refractive index in the thickness direction of the first retardation layer is Nz1, Ny1 < Nx1 < Nz1; the second retardation layer is a positive A-type retardation layer; the angle θ formed by the direction in which the in-plane slow axis of the first retardation layer extends and the direction in which the in-plane slow axis of the second retardation layer extends is 15° or more and 75° or less; and the in-plane retardation at a wavelength of 550 nm of the laminate is Re ＡＣ５５０ and the in-plane retardation at a wavelength of 450 nm of the laminate is Re ＡＣ４５０ and the thickness-direction retardation at a wavelength of 550 nm of the laminate is Rth ＡＣ５５０ A retardation film in which the following formulas (i) to (iii) are satisfied.

2. A laminate including a first retardation layer and a second retardation layer overlapping the first retardation layer, wherein when the refractive index in the direction in which the in-plane slow axis of the first retardation layer extends is Nx1, the refractive index in the direction in which the in-plane slow axis of the first retardation layer extends and in the direction perpendicular to the thickness direction of the first retardation layer is Ny1, and the refractive index in the thickness direction of the first retardation layer is Nz1, Ny1 < Nx1 < Nz1; the second retardation layer is a positive A-type retardation layer; the angle θ formed by the direction in which the in-plane slow axis of the first retardation layer extends and the direction in which the in-plane slow axis of the second retardation layer extends is 0° or more and 45° or less; and the in-plane retardation at a wavelength of 550 nm of the laminate is Re ＡＣ５５０ and the in-plane retardation at a wavelength of 450 nm of the laminate is Re ＡＣ４５０ and the thickness-direction retardation at a wavelength of 550 nm of the laminate is Rth ＡＣ５５０ A retardation film in which the following formulas (iv) to (vi) are satisfied.

3. A laminate including a first retardation layer and a second retardation layer overlapping the first retardation layer, wherein when the refractive index in the direction in which the in-plane slow axis of the first retardation layer extends is Nx1, the refractive index in the direction in which the in-plane slow axis of the first retardation layer extends and in the direction perpendicular to the thickness direction of the first retardation layer is Ny1, and the refractive index in the thickness direction of the first retardation layer is Nz1, Ny1 < Nx1 < Nz1; the second retardation layer is a positive A-type retardation layer; the angle θ formed by the direction in which the in-plane slow axis of the first retardation layer extends and the direction in which the in-plane slow axis of the second retardation layer extends is 45° or more and 90° or less; when the in-plane retardation at a wavelength of 550 nm of the laminate is Re ＡＣ５５０ and the in-plane retardation at a wavelength of 450 nm of the laminate is Re ＡＣ４５０ and the thickness-direction retardation at a wavelength of 550 nm of the laminate is Rth ＡＣ５５０ , a retardation film in which the following formulas (vii) to (ix) are satisfied.

4. The retardation film according to any one of claims 1 to 3, wherein the second retardation layer is directly adjacent to the first retardation layer.

5. The retardation film according to any one of claims 1 to 3, wherein the second retardation layer contains a polymerizable liquid crystal compound.

6. The retardation film according to any one of claims 1 to 3, wherein the first retardation layer contains a photo-aligning component.

7. The retardation film according to any one of claims 1 to 3, wherein the first retardation layer contains an ultraviolet absorber.

8. Let the in-plane retardation at a wavelength of 550 nm of the first retardation layer be Re Ｃ５５０ and the thickness-direction retardation at a wavelength of 550 nm of the first retardation layer be Rth Ｃ５５０ The retardation film according to any one of claims 1 to 3, wherein the following formulas (x) to (xi) are satisfied.

9. When the in-plane retardation at a wavelength of 550 nm of the first retardation layer is Re Ｃ５５０ , Re Ｃ５５０ is 0.5 nm or more, and the retardation film according to any one of claims 1 to 3.

10. The retardation film according to any one of claims 1 to 3, further comprising a resin substrate directly adjacent to the first retardation layer.

11. The retardation film according to claim 10, wherein the resin substrate is made of any one of polyethylene terephthalate, triacetyl cellulose, an acrylic resin, and a cycloolefin polymer.

12. The retardation film according to claim 10, wherein the resin substrate, the first retardation layer, and the second retardation layer are laminated in this order.

13. The retardation film according to claim 10, wherein the resin substrate is a release substrate that can be peeled off from the laminate including the first retardation layer and the second retardation layer.

14. An elliptical polarizing plate comprising the retardation film according to any one of claims 1 to 3 and a polarizing plate laminated on the retardation film.

15. An organic EL display device comprising the elliptical polarizing plate according to claim 14.

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