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

Abstract

This retardation film comprises: a first positive C-type retardation layer; a first positive A-type retardation layer; and a laminate including a second positive C-type retardation layer and a second positive A-type retardation layer, said retardation layers being laminated in this order. The first positive C-type retardation layer is directly contiguous to the first positive A-type retardation layer. The second positive C-type retardation layer is directly contiguous to the second positive A-type retardation layer. When the thickness direction retardation at a wavelength of 550 nm of the first positive C-type retardation layer is denoted by RthC1(550), the thickness direction retardation at a wavelength of 550 nm of the second positive C-type retardation layer is denoted by RthC2(550), the in-plane retardation at a wavelength of 550 nm of the first positive A-type retardation layer is denoted by ReA1(550), and the in-plane retardation at a wavelength of 550 nm of the second positive A-type retardation layer is denoted by ReA2(550), expressions (i)-(iv) hold.

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. In particular, retardation films including multiple retardation layers are known. As an example, in a display device, a quarter-wave plate (a retardation layer in which the phase difference of birefringent light is a quarter wavelength) and a half-wave plate (a retardation layer in which the phase difference of birefringent light is a half wavelength) are used as a circular polarizer in combination with a linear polarizer (e.g., Patent Document 1). In this example, when applied to a display device, the circular polarizer has the effect of preventing reflection of external light.

[0003] Japanese Patent Application Publication No. 10-68816

[0004] In a retardation film in which a plurality of retardation layers are superposed, the appearance of the retardation film may differ depending on the direction from which the retardation film is viewed. Therefore, in a retardation film in which a plurality of retardation layers are superposed, it is required to minimize the difference in the appearance of the retardation film depending on the direction from which the retardation film is viewed.

[0005] The present disclosure has been made in consideration of the above points, and has an object to provide a retardation film in which the difference in appearance depending on the direction from which the retardation film is viewed is kept small.

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

[15] .

[0007] [1] A laminate including a first positive C-type retardation layer, a first positive A-type retardation layer, a second positive C-type retardation layer, and a second positive A-type retardation layer, which are laminated in this order, wherein the first positive C-type retardation layer is directly adjacent to the first positive A-type retardation layer, and the second positive C-type retardation layer is directly adjacent to the second positive A-type retardation layer, and a thickness direction retardation at a wavelength of 550 nm of the first positive C-type retardation layer is Rth Ｃ１（５５０）The thickness direction retardation of the second positive C-type retardation layer at a wavelength of 550 nm is Rth Ｃ２（５５０） The in-plane retardation of the first positive A-type retardation layer at a wavelength of 550 nm is defined as Re Ａ１（５５０） The in-plane retardation of the second positive A-type retardation layer at a wavelength of 550 nm is defined as Re Ａ２（５５０） When the following formulas (i) to (iv) are satisfied, a retardation film is provided.

[0008] [2] The first positive C-type retardation layer, the first positive A-type retardation layer, the second positive C-type retardation layer, and the second positive A-type retardation layer are laminated in this order. The retardation film according to [1].

[0009] [3] The first positive C-type retardation layer, the first positive A-type retardation layer, the second positive A-type retardation layer, and the second positive C-type retardation layer are laminated in this order. The retardation film according to [1].

[0010] [4] The retardation film according to any one of [1] to [3], further comprising an adhesive layer that bonds the first positive A-type retardation layer and the laminate.

[0011] [5] The retardation film according to any one of [1] to [3], wherein the first positive A-type retardation layer is directly adjacent to the laminate.

[0012] [6] The retardation film according to any one of [1] to [5], wherein the first positive A-type retardation layer and the second positive A-type retardation layer contain a polymerizable liquid crystal compound.

[0013] [7] The retardation film according to any one of [1] to [6], wherein the distance between the first positive C-type retardation layer and the second positive C-type retardation layer is 1 μm or more.

[0014] [8] The retardation film according to any one of [1] to [7], wherein the first positive C-type retardation layer and the second positive C-type retardation layer contain a photoalignable component.

[0015] [9] The in-plane retardation of the first positive A-type retardation layer at a wavelength of 550 nm is Re Ａ１（５５０） The in-plane retardation of the first positive A-type retardation layer at a wavelength of 450 nm is defined as Re Ａ１（４５０） The in-plane retardation of the second positive A-type retardation layer at a wavelength of 550 nm is defined as Re Ａ２（５５０） The in-plane retardation of the second positive A-type retardation layer at a wavelength of 450 nm is defined as Re Ａ２（４５０） The retardation film according to any one of [1] to [8], wherein the following formulas (v) to (vi) are satisfied:

[0016]

[10] The retardation film according to any one of [1] to [9], wherein the first positive C-type retardation layer and the second positive C-type retardation layer contain a silicone-based leveling agent.

[0017]

[11] The retardation film according to any one of [1] to

[10] , further comprising a resin substrate directly adjacent to the first positive C-type retardation layer.

[0018]

[12] The retardation film according to

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

[0019]

[13] The retardation film according to

[11] or

[12] , wherein the resin substrate is a release substrate that can be peeled off from the first positive C-type retardation layer.

[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 in which the difference in appearance depending on the direction from which the retardation film is viewed is minimized.

[0023] FIG. 1 is a cross-sectional view of an elliptical polarizing plate according to an embodiment. FIG. 2 is a cross-sectional view of an elliptical polarizing plate according to an embodiment. FIG. 3 is a cross-sectional view of an elliptical polarizing plate according to an embodiment. FIG. 4 is a cross-sectional view of a display device according to an embodiment. FIG. 5 is a diagram illustrating a method for manufacturing a retardation film according to an embodiment. FIG. 6 is a diagram illustrating a method for manufacturing a retardation film according to an embodiment. FIG. 7 is a cross-sectional view of an elliptical polarizing plate according to Modification 1. FIG. 8 is a cross-sectional view of a retardation film according to Modification 2. FIG. 9 is a cross-sectional view of an elliptical polarizing plate according to Modification 2. FIG. 10 is a diagram illustrating an experimental method in an experimental example. FIG. 11A is a diagram illustrating an experimental method in an experimental example. FIG. 11B is a diagram illustrating an experimental method in an experimental example. FIG. 12A is a graph showing a change in color in Experimental Example 1. FIG. 12B is a graph showing a change in color in Experimental Example 2. FIG. 12C is a graph showing a change in color in Experimental Example 3. FIG. 12D is a graph showing a change in color in Experimental Example 4. FIG. 12E is a graph showing a change in color in Experimental Example 5. Fig. 12F is a graph showing the change in color in Experimental Example 6. Fig. 12G is a graph showing the change in color in Experimental Example 7. Fig. 12H is a graph showing the change in color in Experimental Example 8. Fig. 12I is a graph showing the change in color in Experimental Example 9. Fig. 12J is a graph showing the change in color in Experimental Example 10.

[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] In the present disclosure, the refractive index of the retardation layer in the direction in which the in-plane slow axis extends is defined as Nx, the refractive index of the retardation layer in the direction perpendicular to the extension direction of the in-plane slow axis and the thickness direction of the retardation layer is defined as Ny, and the refractive index of the retardation layer in the thickness direction is defined as Nz. The in-plane slow axis is an axis line that faces the axial direction with the highest refractive index along the 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, "Ny≒Nz" also includes the case where (Ny-Nz)×d (where d is the thickness of the retardation layer) is -8 to 8 nm. When "Ny≒Nz", (Ny-Nz)×d may be -5 to 5 nm.

[0030] A retardation layer containing a horizontally aligned liquid crystalline component may correspond to the positive A-type retardation layer in the present disclosure. The positive A-type retardation layer in the present disclosure may be a retardation layer containing a liquid crystalline component that is horizontally aligned and not twisted. The positive A-type retardation layer in the present disclosure may be a retardation layer containing a liquid crystalline component that is horizontally aligned and twisted with the thickness direction of the retardation film 1 as the helical axis.

[0031] In the present disclosure, a positive C-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 (Nx-Ny) x d (where d is the thickness of the retardation layer) is 0 to 3 nm is also included in "Nx≒Ny". When "Nx≒Ny", (Nx-Ny) x d may be 0 to 2 nm.

[0032] I. Retardation Film FIGS. 1 and 2 are cross-sectional views showing an elliptical polarizer 70 including a retardation film 1 according to the present embodiment. As shown in FIGS. 1 and 2, the retardation film 1 includes a first positive C-type retardation layer 10, a first positive A-type retardation layer 20, and a laminate 2. The first positive C-type retardation layer 10, the first positive A-type retardation layer 20, and the laminate 2 are laminated in this order. The laminate 2 includes a second positive C-type retardation layer 30 and a second positive A-type retardation layer 40. In the example shown in FIGS. 1 and 2, the laminate 2 is composed only of the second positive C-type retardation layer 30 and the second positive A-type retardation layer 40. In the example shown in FIGS. 1 and 2, the surface of the laminate 2 facing the first positive A-type retardation layer 20 is composed of the second positive C-type retardation layer 30. As a result, in the example shown in FIGS. 1 and 2, the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, the second positive C-type retardation layer 30, and the second positive A-type retardation layer 40 are laminated in this order.

[0033] The first positive C-type retardation layer 10 is directly adjacent to the first positive A-type retardation layer 20. The second positive C-type retardation layer 30 is directly adjacent to the second positive A-type retardation layer 40.

[0034] In the examples shown in FIGS. 1 and 2, the retardation film 1 further includes a bonding layer 51 that bonds the first positive A-type retardation layer 20 and the laminate 2. The retardation film 1 may further include a resin substrate 60 as shown in FIG. 2. In the example shown in FIG. 1, the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, the bonding layer 51, the second positive C-type retardation layer 30, and the second positive A-type retardation layer 40 are laminated in this order. In the example shown in FIG. 2, the resin substrate 60, the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, the bonding layer 51, the second positive C-type retardation layer 30, and the second positive A-type retardation layer 40 are laminated in this order. The retardation film 1 has a first surface 1a and a second surface 1b located on the opposite side to the first surface 1a. In a retardation film 1 including a resin substrate 60 as shown in FIG. 2 , the second surface 1b is a surface formed by the resin substrate 60. The first surface 1a is a surface opposite to the surface formed by the resin substrate 60. In a retardation film 1 including no resin substrate 60 as shown in FIG. 1 , the second surface 1b is a surface formed by peeling the resin substrate 60 from other portions of the retardation film 1 as described later. The first surface 1a is a surface opposite to the surface formed by peeling the resin substrate 60 from other portions of the retardation film 1. In the retardation film 1 of the present embodiment, when an optical member such as an elliptical polarizing plate 70 is produced by overlaying a polarizing plate 71 on the retardation film 1 as described later, the first surface 1a faces the polarizing plate 71.

[0035] The thickness direction retardation of the first positive C-type retardation layer 10 at a wavelength of 550 nm is defined as Rth Ｃ１（５５０） The thickness direction retardation of the second positive C-type retardation layer 30 at a wavelength of 550 nm is defined as Rth Ｃ２（５５０） The in-plane retardation of the first positive A-type retardation layer 20 at a wavelength of 550 nm is defined as Re Ａ１（５５０） The in-plane retardation of the second positive A-type retardation layer 40 at a wavelength of 550 nm is defined as Re Ａ２（５５０） In this case, the following formulas (i) to (iv) are established. Formula (ii) is defined as "Rth Ｃ１（５５０） -Rth Ｃ２（５５０）" means that the absolute value of " is 0 nm or more and 40 nm or less.

[0036] The in-plane retardation of the first positive A-type retardation layer 20 at a wavelength of 550 nm is defined as Re Ａ１（５５０） The in-plane retardation of the first positive A-type retardation layer 20 at a wavelength of 450 nm is defined as Re Ａ１（４５０） The in-plane retardation of the second positive A-type retardation layer 40 at a wavelength of 550 nm is defined as Re Ａ２（５５０） The in-plane retardation of the second positive A-type retardation layer 40 at a wavelength of 450 nm is defined as Re Ａ２（４５０） In this case, the following equations (v) to (vi) are established. From equation (v), Re in this embodiment Ａ１（５５０） Re Ａ１（４５０） It can be seen from the formula (vi) that Re is smaller than 1 / 2, in other words, the first positive A-type retardation layer 20 exhibits positive dispersion. Ａ２（５５０） Re Ａ２（４５０） It can be seen that the in-plane retardation of the first positive A-type retardation layer 20 at a wavelength of 650 nm is smaller than Re Ａ１（６５０） In this embodiment, Re Ａ１（６５０） Re Ａ１（５５０） The in-plane retardation of the second positive A-type retardation layer 40 at a wavelength of 650 nm is defined as Re Ａ２（６５０） In this embodiment, Re Ａ２（６５０） Re Ａ２（５５０） Smaller than.

[0037] 1. First Positive C-Type Retardation Layer The first positive C-type retardation layer 10 is a retardation layer corresponding to the above-mentioned positive C-type retardation layer. By using the retardation film 1 in a display device or the like, the first positive C-type retardation layer 10 can enhance the contrast with respect to a view from an oblique direction. Furthermore, by using the retardation film 1 in a display device or the like, the first positive C-type retardation layer 10 can reduce color shift.

[0038] The thickness direction retardation of the first positive C-type retardation layer 10 is determined so that the above-mentioned formulas (i) to (ii) hold in the retardation film 1. As an example, the thickness direction retardation Rth of the first positive C-type retardation layer 10 at a wavelength of 550 nm is Ｃ１（５５０） is greater than -60 nm and smaller than -40 nm. Ｃ１（５５０） is in the above-mentioned range, the thickness direction retardation Rth of the second positive C-type retardation layer 30 at a wavelength of 550 nm Ｃ２（５５０） It becomes easy to adjust the above so that the above formulas (i) to (ii) are satisfied.

[0039] In this embodiment, the first positive C-type retardation layer 10 is a positive C-type retardation layer and has an alignment regulating force that horizontally aligns the liquid crystalline component of the first positive A-type retardation layer 20 described later. This allows the first positive A-type retardation layer 20 to be formed on the first positive C-type retardation layer 10 so that the first positive C-type retardation layer 10 is directly adjacent to the first positive A-type retardation layer 20. In this embodiment, the first positive C-type retardation layer 10 contains a photo-alignable component. As an example, the first positive C-type retardation layer 10 contains a vertically alignable liquid crystalline component and a photo-alignable component. The first positive C-type retardation layer 10 of this embodiment may be a cured product of a thermosetting liquid crystal composition containing a liquid crystalline component, a photo-alignable component, and a thermal crosslinking agent.

[0040] 1-1. Liquid Crystalline Component As the liquid crystal component contained in the first positive C-type 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 positive C-type 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 positive C-type retardation layer 10.

[0041] 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.

[0042] (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.

[0043] 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).

[0044] 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 ５represents 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.

[0045] 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.

[0046] Ar １ In 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] (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 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.

[0051] 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.

[0052] 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).

[0053]

[0054] 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:

[0055] In the present disclosure, the liquid crystal constitutional unit may be used alone or in combination of two or more.

[0056] 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.

[0057] 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.

[0058] (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 １４ and 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.

[0059] 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.

[0060] R １４ and R １５ The alkyl group in R may be linear, branched, or cyclic, but is preferably linear. １４ , and R １５The 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] In the non-liquid crystal and non-crosslinkable structural unit containing an alkylene group in the side chain, R １３ , R １４ , and R １５Examples 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.

[0066] 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 １３ The 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.

[0067] 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.

[0068] In the present disclosure, the non-liquid crystal structural unit preferably has a structural unit represented by the following formula (II):

[0069] (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 １５ each 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] (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.)

[0074] (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 ａ represents 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.)

[0075] 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 H４ 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.

[0076] 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.

[0077] 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).

[0078]

[0079]

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] (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.

[0085] 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.

[0086] (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 a 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 a 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 positive C-type retardation layer 10, it is preferable to be a random copolymer.

[0087] 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.

[0088] 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).

[0089] 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.

[0090] 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.

[0091] 1-2. Photo-alignment component The photo-alignment component contained in the first positive C-type retardation layer 10 may be 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 thermal crosslinking structural unit containing a thermal crosslinking group in a side chain, or may be a compound having a photo-alignment group and a thermal crosslinking group different from the copolymer.

[0092] As the photo-alignable component contained in the first positive C-type 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 positive C-type retardation layer 10. Among them, 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.

[0093] (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).

[0094] (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 １１represents a single bond, —O—, —S—, —COO—, —COS—, —CO—, —OCO—, or a combination of any of these with an arylene group.

[0095] (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.

[0096] 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.

[0097] When an alignment restraint force is imparted to the first positive C-type retardation layer 10, the copolymer contains a styrene skeleton and a large amount of π-electron systems, which is thought to provide the following effects. As will be described later, the liquid crystal component of the first positive A-type retardation layer 20 is directly laminated on the first positive C-type 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 positive C-type retardation layer 10 formed using the copolymer and the liquid crystal component of the first positive A-type retardation layer 20 laminated directly on the first positive C-type retardation layer 10.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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):

[0104]

[0105] 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.

[0106] 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.

[0107] The cinnamoyl group represented by the above formula (x-1) is more preferably a group represented by the following formula (x-3).

[0108]

[0109] 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.

[0110] 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.

[0111] 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 later, in the step of imparting an alignment regulating force to the first positive C-type retardation layer 10 by irradiating the material of the first positive C-type retardation layer 10 with polarized ultraviolet light, the sensitivity of the material of the first positive C-type 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 positive C-type 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 positive C-type retardation layer 10 can be sufficiently increased.

[0112] (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.

[0113] 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.

[0114] An example of the thermally crosslinkable constituent unit is a constituent unit represented by the following formula (2).

[0115] (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.

[0116] (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.)

[0117] 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.

[0118] 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).

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] The content ratio of the thermally crosslinkable structural unit in the copolymer can be set within a range of 5 mol% to 90 mol%, preferably within a range of 20 mol% to 80 mol%, when the amount of structural units contained in the entire copolymer is taken as 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 positive C-type 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. In the manufacturing method of the retardation film 1 described below, in the step of imparting an alignment regulating force to the first positive C-type retardation layer 10 by irradiating the material of the first positive C-type retardation layer 10 with polarized ultraviolet light, the sensitivity of the material of the first positive C-type 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 positive C-type retardation layer 10 can be sufficiently increased.

[0125] (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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] The copolymer may contain one or more types of structural units that do not have a photoalignable group or a thermally crosslinkable group.

[0130] 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 material of the first positive C-type retardation layer 10 has sufficiently high sensitivity to polarized ultraviolet light. Furthermore, the material of the first positive C-type retardation layer 10 has sufficient thermosetting properties. This ensures that the alignment control force of the first positive C-type retardation layer 10 is sufficiently high.

[0131] (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).

[0132] 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.

[0133] 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.

[0134] 1-3. Thermal Crosslinking Agent When the first positive C-type 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 positive C-type 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 may also bond with the optionally contained side-chain liquid crystal polymer (A) containing a thermal crosslinking group in its side chain or a compound having a thermal crosslinking group, thereby improving the durability of the cured film and contributing to the improvement of each function.

[0135] 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.

[0136] 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 improved. When the content of the thermal crosslinking agent is equal to or less than the above-mentioned upper limit, the first positive C-type 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 positive C-type retardation layer 10 can be increased.

[0137] The structures derived from the liquid crystal component, photo-alignment component, and thermal crosslinker contained in the first positive C-type 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 positive C-type 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 positive C-type retardation layer 10 can be analyzed by combining the results of these analyses.

[0138] 1-4. Acid or Acid Generator When the first positive C-type 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 accelerate the thermal curing reaction of the thermosetting liquid crystal composition.

[0139] 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.

[0140] 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.

[0141] 1-5. Other Components The composition used in the first positive C-type 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.

[0142] In particular, the composition used for the first positive C-type retardation layer 10 may contain a leveling agent. By including a leveling agent in the composition, a more uniform first positive C-type retardation layer 10 can be formed. When the composition includes a leveling agent, the formed first positive C-type retardation layer 10 also includes a leveling agent. As an example, the first positive C-type retardation layer 10 includes a silicone-based leveling agent. When the first positive C-type retardation layer 10 includes a silicone-based leveling agent, the following effects can be obtained compared to when the first positive C-type retardation layer 10 includes a fluorine-based leveling agent. During the production and disposal of the retardation film 1, the emission of organic fluorine compounds (PFAS) due to the leveling agent can be suppressed. This reduces the environmental impact during the production and disposal of the retardation film 1. Furthermore, when the first positive C-type retardation layer 10 contains a silicone-based leveling agent, the surface tension of the composition used for the first positive C-type retardation layer 10 can be reduced compared to when the first positive C-type retardation layer 10 contains a fluorine-based leveling agent, etc. This allows the coating film to be the first positive A-type retardation layer 20 to be further formed on the formed first positive C-type retardation layer 10, and the coating film and the first positive C-type retardation layer 10 to be more firmly adhered to each other.

[0143] The liquid crystal component and photo-alignable component used in forming the first positive C-type retardation layer 10 are not limited to the 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 positive C-type 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 Positive C-Type Retardation Layer The first positive C-type retardation layer 10 may be a film in which the liquid crystalline portion of the liquid crystalline component is vertically aligned, and the photo-alignable group of the photo-alignable component present on the surface is in a photodimerized structure or a photoisomerized structure, and is cured. When the first positive C-type retardation layer 10 contains a thermal crosslinking agent, it may have a structure containing a liquid crystalline component such as the vertically aligned side-chain liquid crystal polymer, a photodimerized structure or a photoisomerized structure of the photo-alignable group, and a crosslinked structure formed by bonding a thermal crosslinkable group and a thermal crosslinking agent in one layer. The first positive C-type retardation layer 10 may have a structure containing a vertically aligned side-chain liquid crystal polymer, and a copolymer having a photodimerized structure or a photoisomerized structure of the photo-alignable group of the photo-alignable structural unit, and a crosslinked structure formed by bonding a thermal crosslinkable group of the thermal crosslinkable structural unit and a thermal crosslinking agent in one layer.

[0145] The photodimerization structure of the photoalignment group contained in the first positive C-type 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 positive C-type 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 first positive A-type retardation layer 20 formed on the first positive C-type retardation layer 10 is increased, the alignment control force of the first positive C-type retardation layer 10 is increased, and the adhesion with the first positive A-type 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 positive C-type 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 the thermal crosslinking group of the thermal crosslinking structural unit of the copolymer is bonded to the thermal crosslinking agent, and a crosslinked structure in which the thermal crosslinking group of another component is bonded to the 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 the thermal crosslinking group of the side-chain liquid crystal polymer is bonded to the 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 positive C-type 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 positive C-type retardation layer 10 may further contain an acid or an acid generator, the above-mentioned other components, and decomposition products thereof.

[0156] It can be confirmed that the first positive C-type 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 positive C-type retardation layer 10. As the analysis method, NMR, IR, GC-MS, XPS, TOF-SIMS, and a combination thereof 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 positive C-type retardation layer 10 in order to obtain a retardation plate with high resistance to bending. The composite elastic modulus of the first positive C-type 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 positive C-type 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 positive C-type retardation layer 10 is determined by measuring the indentation hardness (H ＩＴ ) The contact projection area A obtained when measuring ｐ E calculated from the following formula (vii) using ｒ The "indentation hardness" is a value determined from a load-displacement curve from loading to unloading of an indenter, which is obtained by hardness measurement using a nanoindentation method. The composite elastic modulus of the first positive C-type retardation layer 10 is an elastic modulus that includes the elastic deformation of the first positive C-type retardation layer 10 and the elastic deformation of the indenter.

[0158] (In the above formula (vii), 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 positive C-type retardation layer 10 included in the retardation film 1 can be determined by the following method. To measure the composite elastic modulus of the first positive C-type retardation layer 10, a film 3 in which a resin substrate 60, a first positive C-type retardation layer 10, and a first positive A-type retardation layer 20 are laminated in this order, as shown in FIG. 5, which will be described later, is used. In the measurement, first, the surface of the film 3 as shown in FIG. 5, which is composed of the first positive A-type retardation layer 20, 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 placed on the surface of the film 3 composed of the resin substrate 60, and the film 3 is sandwiched between the glass and the glass coated with the cyanoacrylate-based instant adhesive. Next, a pair of glasses sandwiching the film 3 is pressed for 1 minute to apply pressure to the adhesive layer so that the thickness of the adhesive layer formed by the cyanoacrylate instant adhesive becomes 45 μm. Then, the film 3 and adhesive layer are left to stand for 10 minutes. After that, the glass applied to the surface of the film 3 constituted by the resin substrate 60 is removed, and the resin substrate 60 is peeled off from the first positive C-type retardation layer 10. As a result, the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20 are transferred to the glass. In this way, a measurement sample can be prepared in which the first positive C-type retardation layer 10 / first positive A-type retardation layer 20 / adhesive layer / glass are laminated in this order. Using this measurement sample, the indentation hardness of the surface exposed by peeling off the resin substrate 60 of the first positive C-type retardation layer 10 is measured. Indentation hardness (H ＩＴThe measurement of the maximum load Pmax (μN) and the maximum load Amax (μN) are calculated by dividing the maximum load Pmax (μN) and the projected contact area Amax (μN) by the maximum load Amax (μN). 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 by more than ±20% from the arithmetic mean value, 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 positive C-type retardation layer 10 can be appropriately set, for example, to 0.1 μm to 4 μm, or may be 0.3 μm to 2 μm.

[0162] 2. First Positive A-Type Retardation Layer The first positive A-type retardation layer 20 is a retardation layer corresponding to the above-mentioned positive A-type retardation layer. In the present embodiment, the first positive A-type retardation layer 20, which is a positive A-type retardation layer, exhibits horizontal alignment (homogeneous alignment).

[0163] In-plane retardation Re of the first positive A-type retardation layer 20 at a wavelength of 550 nm Ａ１（５５０） The above-mentioned formula (iii) holds. From the formula (iii), it can be understood that the first positive A-type retardation layer 20 functions as a λ / 4 retardation plate.

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

[0165] The liquid crystalline component contained in the first positive A-type retardation layer 20 may be a polymerizable liquid crystal compound having a polymerizable group. That is, the first positive A-type retardation layer 20 may contain a polymerizable liquid crystal compound. A liquid crystalline component containing a polymerizable liquid crystal compound having a polymerizable group can be used as the liquid crystalline component. A liquid crystalline component commonly used in positive A-type retardation layers can be used as the liquid crystalline component. The first positive A-type retardation layer 20 may contain a polymerizable liquid crystal composition as the liquid crystalline component. In this case, the polymerizable liquid crystal composition contained in the first positive A-type retardation layer 20 preferably exhibits liquid crystallinity and contains a polymerizable liquid crystal compound having a polymerizable group in the molecule. The polymerizable liquid crystal compound can be appropriately selected from conventionally known polymerizable liquid crystal compounds capable of horizontal alignment. The polymerizable liquid crystal composition may consist of a single liquid crystal compound or a mixture of two or more liquid crystal compounds.

[0166] As described above, the first positive A-type retardation layer 20 of the present embodiment exhibits normal dispersion. The material and forming method of the first positive A-type retardation layer 20 are not particularly limited as long as they are a material and forming method that can form a positive A-type retardation layer exhibiting normal dispersion on a layer that functions as an alignment layer such as the first positive C-type retardation layer 10 having an alignment regulating force. As the material and forming method of the first positive A-type retardation layer 20, a material and forming method of a positive A-type retardation layer exhibiting normal dispersion that are conventionally known can be adopted. In order to form the first positive A-type retardation layer 20 exhibiting normal dispersion, a polymerizable liquid crystal compound exhibiting normal dispersion may be used.

[0167] The polymerizable liquid crystal composition in the first positive A-type 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 regarding the first positive C-type retardation layer 10.

[0168] The liquid crystal component contained in the first positive A-type retardation layer 20 may be horizontally aligned and not twisted. The liquid crystal component contained in the first positive A-type retardation layer 20 may be horizontally aligned and twisted with the thickness direction of the retardation film 1 as the helical axis. When the liquid crystal component contained in the first positive A-type retardation layer 20 is twisted, the first positive A-type retardation layer 20 may exhibit a chiral nematic liquid crystal phase or a cholesteric liquid crystal phase having a so-called helical structure. As an example, the liquid crystal composition used for the liquid crystal component of the first positive A-type retardation layer 20 is a liquid crystal composition exhibiting a nematic liquid crystal phase. When forming the above phase, a mixture of a liquid crystal composition exhibiting a nematic liquid crystal phase and a chiral agent described later may be used as the composition used for the liquid crystal component of the first positive A-type retardation layer 20. The liquid crystal composition used for the liquid crystal component of the first positive A-type retardation layer 20 may contain a liquid crystal compound exhibiting a cholesteric liquid crystal phase. In this case, the first positive A-type retardation layer 20 may be a cholesteric liquid crystal layer. The cholesteric liquid crystal layer is a layer made of liquid crystal molecules exhibiting cholesteric regularity. The first positive A-type retardation layer 20 exhibiting normal dispersion may contain a liquid crystal component twist-oriented with the thickness direction of the retardation film 1 as the helical axis.

[0169] In this embodiment, the first positive C-type retardation layer 10 is located closer to the second surface 1 b side than the first positive A-type retardation layer 20 in the thickness direction of the retardation film 1 .

[0170] 3. Second Positive C-Type Retardation Layer The second positive C-type retardation layer 30 is a retardation layer corresponding to the above-mentioned positive C-type retardation layer. By using the retardation film 1 in a display device or the like, the second positive C-type retardation layer 30 can enhance the contrast relative to a view from an oblique direction. Furthermore, by using the retardation film 1 in a display device or the like, the second positive C-type retardation layer 30 can reduce color shift.

[0171] The thickness direction retardation of the second positive C-type retardation layer 30 is determined so that the above-mentioned formulas (i) to (ii) hold in the retardation film 1. As an example, the thickness direction retardation Rth of the second positive C-type retardation layer 30 at a wavelength of 550 nm is Ｃ１（５５０） is greater than -60 nm and smaller than -40 nm. Ｃ１（５５０） is in the above-mentioned range, the thickness direction retardation Rth of the first positive C-type retardation layer 10 at a wavelength of 550 nm Ｃ２（５５０） It becomes easy to adjust the above so that the above formulas (i) to (ii) are satisfied.

[0172] In the present embodiment, the second positive C-type retardation layer 30 is a positive C-type retardation layer and has an alignment regulating force that horizontally aligns the liquid crystalline component of the second positive A-type retardation layer 40 described later. This allows the second positive A-type retardation layer 40 to be formed on the second positive C-type retardation layer 30 so that the second positive C-type retardation layer 30 is directly adjacent to the second positive A-type retardation layer 40. As an example, the components contained in the second positive C-type retardation layer 30 are the same as the components contained in the first positive C-type retardation layer 10. In the present embodiment, the second positive C-type retardation layer 30 contains a photo-alignable component. As an example, the second positive C-type retardation layer 30 contains a vertically alignable liquid crystalline component and a photo-alignable component. The second positive C-type retardation layer 30 of the present embodiment may be a cured product of a thermosetting liquid crystal composition containing a liquid crystalline component, a photo-alignable component, and a thermal crosslinking agent. When the second positive C-type retardation layer 30 is a cured product of a thermosetting liquid crystal composition, the thermosetting liquid crystal composition may contain an acid or an acid generator.

[0173] As the liquid crystalline component contained in the second positive C-type retardation layer 30, those exemplified as the liquid crystalline component contained in the first positive C-type retardation layer 10 can be used. As the photo-alignable component contained in the second positive C-type retardation layer 30, those exemplified as the photo-alignable component contained in the first positive C-type retardation layer 10 can be used. As the thermal crosslinking agent contained in the composition used in the second positive C-type retardation layer 30, those exemplified as the thermal crosslinking agent contained in the first positive C-type retardation layer 10 can be used. As the acid or acid generator contained in the composition used in the second positive C-type retardation layer 30, those exemplified as the acid or acid generator contained in the first positive C-type retardation layer 10 can be used. As other components contained in the composition used in the second positive C-type retardation layer 30, those exemplified as other components contained in the first positive C-type retardation layer 10 can be used.

[0174] In particular, the composition used for the second positive C-type retardation layer 30 may contain a leveling agent. When the composition contains a leveling agent, the formed second positive C-type retardation layer 30 also contains a leveling agent. As an example, the second positive C-type retardation layer 30 contains a silicone-based leveling agent. When the second positive C-type retardation layer 30 contains a silicone-based leveling agent, the environmental impact during the production and disposal of the retardation film 1 can be reduced, as in the case where the first positive C-type retardation layer 10 contains a silicone-based leveling agent. The first positive C-type retardation layer 10 and the second positive C-type retardation layer 30 may contain a silicone-based leveling agent. When both the first positive C-type retardation layer 10 and the second positive C-type retardation layer 30 contain a silicone-based leveling agent, the environmental impact during the production and disposal of the retardation film 1 can be further reduced. Furthermore, when the first positive C-type retardation layer 10 contains a silicone-based leveling agent, it is possible to reduce the surface tension of the composition used for the first positive C-type retardation layer 10. This allows the first positive C-type retardation layer 10 to be more firmly adhered to a coating film that will become the first positive A-type retardation layer 20 when the coating film is further formed on the formed first positive C-type retardation layer 10.

[0175] As an example, the configuration of the second positive C-type retardation layer 30 is the same as the configuration of the above-mentioned first positive C-type retardation layer 10. For example, like the first positive C-type retardation layer 10, the second positive C-type retardation layer 30 may be a film that is cured in a state in which the liquid crystalline portion of the liquid crystalline component is vertically aligned and the photo-alignable group of the photo-alignable component present on the surface has a photo-dimerized structure or a photo-isomerized structure.

[0176] As an example, the first positive C-type retardation layer 10 and the second positive C-type retardation layer 30 contain a photo-alignable component. Since both the first positive C-type retardation layer 10 and the second positive C-type retardation layer 30 contain a photo-alignable component, an alignment control force can be imparted to both the first positive C-type retardation layer 10 and the second positive C-type retardation layer 30. This allows the liquid crystal component of the first positive A-type retardation layer 20 to be aligned while the first positive C-type retardation layer 10 is directly adjacent to the first positive A-type retardation layer 20. Furthermore, the liquid crystal component of the second positive A-type retardation layer 40 can be aligned while the second positive C-type retardation layer 30 is directly adjacent to the second positive A-type retardation layer 40.

[0177] The physical properties of the second positive C-type retardation layer 30, such as the composite elastic modulus, may be the same as those of the first positive C-type retardation layer 10. The method for measuring the composite elastic modulus of the second positive C-type retardation layer 30 is the same as the method for measuring the composite elastic modulus of the first positive C-type retardation layer 10, except for the points described below. For measuring the composite elastic modulus of the second positive C-type retardation layer 30, a film 4 in which a substrate 52, a second positive C-type retardation layer 30, and a second positive A-type retardation layer 40 are laminated in this order, as shown in FIG. 6 described later, is used. In the measurement, the second positive C-type retardation layer 30 and the second positive A-type retardation layer 40 are transferred to glass by the same method as the method for transferring the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20 to glass in measuring the composite elastic modulus of the first positive C-type retardation layer 10. At this time, the substrate 52 of the film 4 is peeled off from the second positive C-type retardation layer 30 by the same method as that used to peel off the resin substrate 60 from the first positive C-type retardation layer 10 in measuring the composite elastic modulus of the first positive C-type retardation layer 10. In this manner, a measurement sample is prepared in which the second positive C-type retardation layer 30 / second positive A-type retardation layer 40 / adhesive layer / glass are laminated in this order. Using this measurement sample, the indentation hardness of the surface of the second positive C-type retardation layer 30 exposed by peeling off the substrate 52 is measured.

[0178] The distance w1 between the first positive C-type retardation layer 10 and the second positive C-type retardation layer 30 shown in Fig. 1 is 1 µm or more. As a result, when the retardation film 1 is used in a display device, particularly when the display device is a foldable device, color unevenness is less likely to be visible even when the foldable device is viewed in a folded state. The distance w1 is, for example, 40 µm or less.

[0179] 4. Second Positive A-Type Retardation Layer The second positive A-type retardation layer 40 is a retardation layer corresponding to the above-mentioned positive A-type retardation layer. In the present embodiment, the second positive A-type retardation layer 40, which is a positive A-type retardation layer, exhibits horizontal alignment (homogeneous alignment).

[0180] In-plane retardation Re of the second positive A-type retardation layer 40 at a wavelength of 550 nm Ａ２（５５０） The above-mentioned formula (iv) holds. From formula (iv), it can be understood that the second positive A-type retardation layer 40 functions as a λ / 2 retardation plate.

[0181] As described above, the second positive A-type retardation layer 40 of the present embodiment exhibits normal dispersion. The material and forming method of the second positive A-type retardation layer 40 are not particularly limited as long as they are a material and forming method that can form a positive A-type retardation layer exhibiting normal dispersion on a layer that functions as an alignment layer such as the second positive C-type retardation layer 30 having an alignment regulating force. As the material and forming method of the second positive A-type retardation layer 40, a material and forming method of a positive A-type retardation layer exhibiting normal dispersion that are conventionally known can be used. A polymerizable liquid crystal compound exhibiting normal dispersion may be used to form the second positive A-type retardation layer 40 exhibiting normal dispersion.

[0182] As an example, the component contained in the second positive A-type retardation layer 40 is the same as the component contained in the first positive A-type retardation layer 20. In the present embodiment, the second positive A-type retardation layer 40 contains a liquid crystalline component. As the liquid crystalline component contained in the second positive A-type retardation layer 40, the same liquid crystalline component as the liquid crystalline component contained in the first positive A-type retardation layer 20 can be used.

[0183] As an example, the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40 contain a polymerizable liquid crystal compound. By containing the polymerizable liquid crystal compound in both the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40, the polymerizable liquid crystal compound can be horizontally aligned, thereby making the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40 function as positive A-type retardation layers.

[0184] The liquid crystal component contained in the second positive A-type retardation layer 40 may be horizontally aligned and not twisted. The liquid crystal component contained in the second positive A-type retardation layer 40 may be horizontally aligned and twisted with the thickness direction of the retardation film 1 as the helical axis. When the liquid crystal component contained in the second positive A-type retardation layer 40 is twisted, the second positive A-type retardation layer 40 may exhibit a chiral nematic liquid crystal phase or a cholesteric liquid crystal phase having a so-called helical structure. As an example, the liquid crystal composition used for the liquid crystal component of the second positive A-type retardation layer 40 is a liquid crystal composition exhibiting a nematic liquid crystal phase. When forming the above phase, a mixture of a liquid crystal composition exhibiting a nematic liquid crystal phase and a chiral agent described later may be used as the composition used for the liquid crystal component of the second positive A-type retardation layer 40. The liquid crystal composition used for the liquid crystal component of the second positive A-type retardation layer 40 may contain a liquid crystal compound exhibiting a cholesteric liquid crystal phase. In this case, the second positive A-type retardation layer 40 may be a cholesteric liquid crystal layer. The cholesteric liquid crystal layer is a layer made of liquid crystal molecules exhibiting cholesteric regularity. The second positive A-type retardation layer 40 exhibiting normal dispersion may contain a liquid crystal component that is twist-oriented with the thickness direction of the retardation film 1 as the helical axis.

[0185] In this embodiment, the second positive C-type retardation layer 30 is located closer to the second surface 1 b side than the second positive A-type retardation layer 40 in the thickness direction of the retardation film 1 .

[0186] 5. Resin Substrate The retardation film 1 may further include a resin substrate 60, as shown in FIG. 2, for example. The resin substrate 60 of this embodiment is directly adjacent to the first positive C-type retardation layer 10 as shown in FIG. 2. The resin substrate 60 is preferably transparent. As an example, the resin substrate 60 is a transparent polymer substrate, i.e., a transparent substrate made of a polymer. The resin substrate 60 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 60 is preferably made of any one of polyethylene terephthalate, triacetyl cellulose, an acrylic-based resin, and a cycloolefin polymer.

[0187] The resin substrate 60 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 60 can be measured according to JIS K7361-1 (Test method for total light transmittance of plastic transparent materials).

[0188] When the retardation layer is formed by a roll-to-roll method, the resin substrate 60 is preferably a flexible material having flexibility that allows it to be wound into a roll. From the viewpoint of making the resin substrate 60 a flexible material, it is preferable that the resin substrate 60 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 60, it is possible to make the resin substrate 60 have excellent optical properties. From the viewpoint of increasing the transparency of the resin substrate 60 and making the mechanical properties of the resin substrate 60 favorable, it is preferable that the resin substrate 60 be made of polyethylene terephthalate.

[0189] As will be described later, a composition formed by dissolving the components of the first positive C-type retardation layer 10 in a solvent is applied to the resin substrate 60, and the composition is then dried, thereby forming the first positive C-type retardation layer 10 on the resin substrate 60. 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 of the first positive C-type retardation layer 10. In this case, from the viewpoint of making the resin substrate 60 less soluble in solvents, it is preferable that the resin substrate 60 be made of any one of polyethylene terephthalate, triacetyl cellulose, an acrylic resin, and a cycloolefin polymer. From the viewpoint of making the resin substrate 60 less soluble in solvents, it is more preferable that the resin substrate 60 be made of polyethylene terephthalate or triacetyl cellulose, and even more preferable that the resin substrate 60 be made of polyethylene terephthalate. From the viewpoint of making the resin substrate 60 less soluble in solvents, it is preferable that the resin substrate 60 not include a primer layer or a hard coat layer that covers the main body of the resin substrate 60. In particular, the resin substrate 60 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 60 .

[0190] As the resin substrate 60, a film formed by stretching, particularly biaxial stretching (biaxially stretched film) can be used. In particular, a film formed by sequential biaxial stretching can be used. By using a biaxially stretched film as the resin substrate 60, the strength of the resin substrate 60 can be sufficiently increased while keeping the cost required for the material of the resin substrate 60 low. It is preferable to use a biaxially stretched PET film, particularly a sequentially biaxially stretched PET film, as the resin substrate 60.

[0191] The thickness of the resin substrate 60 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 typically about 10 μm to 200 μm. The thickness of the resin substrate 60 is preferably 25 μm to 125 μm, more preferably 30 μm to 110 μm, more preferably 30 μm to 100 μm, and even more preferably 40 μm to 100 μm. By having the thickness be equal to or less than the above-mentioned upper limit, the amount of processing waste generated can be reduced, and the rate of wear of the cutting blade can be reduced, particularly when forming a long retardation film 1 and cutting the formed retardation film 1 into sheets of alignment film and retardation film. The thickness of the resin substrate 60 is, for example, 100 μm.

[0192] The resin substrate 60 may be a release substrate that can be peeled off from the first positive C-type retardation layer 10. Thereby, when attaching the retardation film 1 to another member, after attaching the surface of the retardation film 1 that is not constituted by the resin substrate 60 to the other member, peeling can be caused at the interface between the resin substrate 60 and the first positive C-type retardation layer 10, and the resin substrate 60 can be removed from the portion of the retardation film 1 other than the resin substrate 60. For example, when an elliptical polarizing plate 70 is produced using the retardation film 1 as described later, the retardation film 1 and a polarizing plate 71 described later are bonded together, and then the resin substrate 60 can be removed from the portion of the retardation film 1 other than the resin substrate 60.

[0193] 6. Bonding Layer The retardation film 1 of the present embodiment further includes a bonding layer 51 that bonds the first positive A-type retardation layer 20 and the laminate 2. In the example shown in FIGS. 1 and 2, the bonding layer 51 bonds the first positive A-type retardation layer 20 and the second positive C-type retardation layer 30 together, thereby bonding the first positive A-type retardation layer 20 and the laminate 2. As an example, the bonding layer 51 is an adhesive layer (adhesive layer) located between the first positive A-type retardation layer 20 and the laminate 2. In this case, the adhesive or adhesive for the adhesive layer (adhesive layer) can be appropriately selected from conventionally known adhesives. As the adhesive or adhesive for the adhesive layer (adhesive layer), any adhesive type such as a pressure-sensitive adhesive (adhesive), a two-component curing adhesive, an ultraviolet curing adhesive, a heat-curing adhesive, or a hot-melt adhesive can be suitably used. The adhesive of the adhesive layer may be a pressure-sensitive adhesive composition that preferably uses a (meth)acrylic resin as a base polymer in terms of transparency, weather resistance, heat resistance, etc. The thickness of the pressure-sensitive 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, more preferably 4 μm to 35 μm, more preferably 5 μm to 35 μm, and even more preferably 5 μm to 25 μm. The thickness of the pressure-sensitive adhesive layer (adhesive layer) is, for example, 5 μm.

[0194] 7. Retardation Film In the retardation film 1 of the present embodiment, the total thickness of the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20 may be 0.2 μm to 6 μm. The total thickness of the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20 may be 0.8 μm to 5 μm, or 1 μm to 4 μm. The total thickness of the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20 can be determined using a scanning transmission electron microscope (STEM). More specifically, the total thickness of the first positive C-type retardation layer 10 and the first positive A-type 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 positive C-type retardation layer 10 and the first positive A-type retardation layer 20 are photographed. The thicknesses of the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20 are measured at 10 points in the captured cross-sectional image. The arithmetic average of the film thicknesses at the 10 points is taken as the measured thickness of the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20. The total thickness of the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20 can be calculated by adding the measured thickness of the first positive C-type retardation layer 10 and the measured thickness of the first positive A-type retardation layer 20. The numerical range of the total thickness of the second positive C-type retardation layer 30 and the second positive A-type retardation layer 40 may be the same as the numerical range of the total thickness of the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20. The total thickness of the second positive C-type retardation layer 30 and the second positive A-type retardation layer 40 can be measured by the same method as the method for measuring the total thickness of the first positive C-type retardation layer 10 and the first positive A-type retardation layer 20.

[0195] In the retardation film 1 of this embodiment, the first positive C-type retardation layer 10 is directly adjacent to the first positive A-type retardation layer 20. Therefore, the retardation film 1 does not include a substrate and an alignment film for forming the first positive A-type retardation layer 20, nor an adhesive layer for bonding the first positive A-type retardation layer 20 to the first positive C-type retardation layer 10. Furthermore, in the retardation film 1 of this embodiment, the second positive C-type retardation layer 30 is directly adjacent to the second positive A-type retardation layer 40. Therefore, the retardation film 1 does not include a substrate and an alignment film for forming the second positive A-type retardation layer 40, nor an adhesive layer for bonding the second positive A-type retardation layer 40 to the second positive C-type retardation layer 30. This allows the retardation film 1 to be made thinner. The retardation film 1 of this embodiment can be suitably used as an optical member for various display devices that are intended to be made thinner. Furthermore, the retardation film 1 of the present embodiment does not require the above-described substrate, alignment film, adhesive layer, etc., and therefore can improve the productivity of the retardation film 1. Furthermore, it is possible to suppress deterioration of optical properties caused by the above-described substrate, alignment film, adhesive layer, etc.

[0196] II. Elliptical Polarizing Plate The present disclosure provides an elliptical polarizing plate 70 including the retardation film 1 of the present embodiment and a polarizing plate 71 superimposed on the retardation film 1. The concept of an elliptical polarizing plate includes a circular polarizing plate.

[0197] 1 and 2 includes the retardation film 1 of the present embodiment and a polarizing plate 71 positioned adjacent to the retardation film 1. The elliptical polarizing plate 70 may include an adhesive layer (not shown) positioned between the retardation film 1 and the polarizing plate 71, if necessary.

[0198] In the elliptical polarizing plate 70, the second positive A-type retardation layer 40 is disposed closer to the polarizing plate 71 than the first positive A-type retardation layer 20. In the elliptical polarizing plate 70 shown in Figures 1 and 2, the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, the bonding layer 51, the second positive C-type retardation layer 30, the second positive A-type retardation layer 40, and the polarizing plate 71 are laminated in this order.

[0199] In the present embodiment, the polarizing plate 71 is a plate-like plate that transmits only light vibrating in a specific direction. The polarizing plate 71 may be any polarizing plate appropriately selected from conventionally known polarizing plates. In the present embodiment, the polarizing plate 71 is a linear polarizing plate. As an example, the linear polarizing plate that is the polarizing plate 71 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.

[0200] In the present embodiment, the adhesive layer (bonding layer) located between the retardation film 1 and the polarizing plate 71 can be the adhesive layer (bonding layer) described above as the adhesive layer (bonding layer) used as the joining layer 51.

[0201] The elliptical polarizing plate 70 of the present embodiment may further include other layers included in known optical members, such as known circular polarizing plates and known elliptically 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 positive C-type retardation layer 10 and the first positive A-type retardation layer 20 of the present embodiment, as well as antireflection layers, diffusion layers, antiglare layers, antistatic layers, protective films, and the like.

[0202] As an example, the elliptical polarizing plate 70 may further include a λ / 4 retardation plate 72, as shown in FIG. 3 . In the example shown in FIG. 3 , the λ / 4 retardation plate 72 forms the surface of the elliptical polarizing plate 70. The λ / 4 retardation plate 72 and the retardation film 1 sandwich a polarizing plate 71 between them. The λ / 4 retardation plate 72 provides the following effects. When the elliptical polarizing plate 70 is used in a display device, light emitted from the display device is converted into linearly polarized light by the polarizing plate 71, which is a linear polarizing plate. By further including the λ / 4 retardation plate 72 in the elliptical polarizing plate 70, the light converted into linearly polarized light by the polarizing plate 71 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 70 wears polarized sunglasses and rotates the display device.

[0203] In the elliptical polarizing plate 70, the angle formed between the extension direction of the in-plane slow axis of the first positive A-type retardation layer 20 and the extension direction of the absorption axis of the polarizing plate 71 is preferably 73°±5°. The angle formed between the extension direction of the in-plane slow axis of the first positive A-type retardation layer 20 and the extension direction of the absorption axis of the polarizing plate 71 may be 73°. When forming the first positive C-type retardation layer 10, the angle formed between the extension direction of the in-plane slow axis of the first positive A-type retardation layer 20 and the extension direction of the absorption axis of the polarizing plate 71 can be set to the above-mentioned numerical range by adjusting the direction in which the first positive C-type retardation layer 10 having an alignment regulating force aligns the liquid crystalline component of the first positive A-type retardation layer 20. In the elliptical polarizing plate 70, the angle formed between the extension direction of the in-plane slow axis of the second positive A-type retardation layer 40 and the extension direction of the absorption axis of the polarizing plate 71 is preferably 15°±5°. The angle formed between the extension direction of the in-plane slow axis of the second positive A-type retardation layer 40 and the extension direction of the absorption axis of the polarizing plate 71 may be 15°. When the second positive C-type retardation layer 30 is formed, the angle formed between the extension direction of the in-plane slow axis of the second positive A-type retardation layer 40 and the extension direction of the absorption axis of the polarizing plate 71 can be set to the above-mentioned numerical range by adjusting the direction in which the second positive C-type retardation layer 30 having an alignment regulating force aligns the liquid crystalline component of the second positive A-type retardation layer 40.

[0204] The elliptically polarizing plate 70 of this embodiment can be suitably used as an optical member for suppressing reflection of external light in a display device.

[0205] III. 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. FIG. 4 is a cross-sectional view showing the display device 100 of the present embodiment including the elliptically polarizing plate 70 of the present embodiment. The display device 100 shown in FIG. 4 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 elliptically polarizing plate 70 including the retardation film 1 of the present embodiment and a polarizing plate 71. 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.

[0206] 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 60 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.

[0207] 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 function of the retardation film 1 described below can increase the viewing angle 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. 4 , the display device 100 is an organic EL display device (organic electroluminescence display device) 101. The organic EL display device 101 shown in FIG. 4 includes the elliptical polarizer 70 of the present embodiment. The organic EL display device 101 including the elliptical polarizer 70 of the present embodiment can increase the viewing angle while reducing reflection of external light on the display surface.

[0208] 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.

[0209] 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.

[0210] IV. Manufacturing Method of Retardation Film and Elliptical Polarizer A manufacturing method of the retardation film 1 of the present embodiment will be described. As an example, a manufacturing method of the retardation film 1 in which the retardation film 1 is superimposed on a polarizing plate 71 to form an elliptical polarizer 70 as shown in FIGS. 1 and 2 will be described. In addition, a manufacturing method of the elliptical polarizer 70 will be described. First, a first positive C-type retardation layer 10 is formed. As an example, the first positive C-type retardation layer 10 of the present embodiment is prepared by dissolving or diluting the components constituting the first positive C-type retardation layer 10 in a solvent to prepare a composition (coating liquid) for the first positive C-type retardation layer 10. Subsequently, the composition is applied to a support and dried. The support is the resin substrate 60 described above. As an example, the resin substrate 60 is a release substrate that can be peeled from the first positive C-type retardation layer 10. The means for making the resin substrate 60 peelable from the first positive C-type retardation layer 10 is not particularly limited. For example, the resin substrate 60 may be subjected to a surface treatment so that the resin substrate 60 can be peeled off from the first positive C-type retardation layer 10. The resin substrate 60 may be subjected to a release treatment so that the resin substrate 60 can be peeled off from the first positive C-type retardation layer 10. A release layer may be formed on the surface of the resin substrate 60 so that the resin substrate 60 can be peeled off from the first positive C-type retardation layer 10.

[0211] As the solvent, for example, the same solvent as that described in paragraphs 0153 to 0154 of WO 2022 / 158555 can be used. The components constituting the first positive C-type 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 positive C-type retardation layer 10 is formed by aligning a liquid crystalline component by heating, the components constituting the first positive C-type 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 coating the composition on the support, a method that can accurately form the first positive C-type retardation layer 10 to the desired thickness can be appropriately selected.

[0212] The composition for the first positive C-type retardation layer 10 is applied to a support, and the liquid crystal component is heated during the process of removing the solvent. The temperature to which the liquid crystal component is heated is adjusted to a temperature at which the liquid crystal component can be vertically aligned. Specifically, the liquid crystal component is heated to a temperature above the liquid crystal phase transition temperature and below the isotropic transition temperature (preferably below the isotropic transition temperature). This allows the liquid crystal component to be vertically aligned. By the heat treatment, at least the liquid crystal portion of the liquid crystal component can be aligned and dried, and the liquid crystal component can be fixed while maintaining this alignment state. The temperature at which the liquid crystal component can be vertically aligned varies depending on the substances in the liquid crystal composition and must 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.

[0213] When the composition for the first positive C-type retardation layer 10 is thermosetting, the heat treatment also progresses the thermosetting of the composition. At this time, the more the thermosetting 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 thermosetting 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 positive C-type retardation layer 10.

[0214] 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.

[0215] The method for forming the first positive C-type 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 restraint force to the cured film. This step is performed so that the cured film is imparted with an alignment restraint 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 a photoreaction of the photoalignment group of the photoalignment component, such as copolymer (B), contained in the cured film to 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 60). In this way, an alignment restraint force can be imparted to the cured film. As described above, a first positive C-type retardation layer 10 having an alignment restraint force that horizontally aligns the liquid crystalline component of the first positive A-type retardation layer 20 can be formed on the resin substrate 60.

[0216] Next, the first positive A-type retardation layer 20 of this embodiment is formed. First, a polymerizable liquid crystal composition is applied onto the first positive C-type 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 crystal component contained in the polymerizable liquid crystal composition. Thereafter, the coating film of the polymerizable liquid crystal composition in which the liquid crystal component has been aligned is irradiated with light. In this way, the first positive A-type retardation layer 20 can be formed.

[0217] A method for forming a coating film of a polymerizable liquid crystal composition and a method for heating the coated polymerizable liquid crystal composition to a phase transition temperature in the step of aligning a liquid crystalline component when forming the first positive A-type retardation layer 20 may be a conventionally known method and are not particularly limited. As the coating method and heating method for the polymerizable liquid crystal composition, the same methods as the coating method and heating method in the manufacturing method of the first positive A-type retardation layer 20 may be used.

[0218] In the step of irradiating the coating film with light when forming the first positive A-type 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 oriented with light, thereby polymerizing the polymerizable groups of the polymerizable liquid crystal compound contained in the first positive A-type retardation layer 20. Furthermore, when the first positive A-type retardation layer 20 contains a compound containing a polymerizable group, the polymerizable group of the compound containing a polymerizable group in the first positive A-type retardation layer 20 may be polymerized with the polymerizable group of the polymerizable liquid crystal compound contained in the first positive A-type retardation layer 20 at the interface with the first positive A-type 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.

[0219] By the above-described manufacturing method, the film 3 in which the resin substrate 60, the first positive C-type retardation layer 10, and the first positive A-type retardation layer 20 are laminated in this order as shown in FIG. 5 is manufactured.

[0220] Furthermore, the second positive C-type retardation layer 30 is formed on the substrate 52. 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 60. In the present embodiment, the substrate 52 is a release substrate that can be peeled off from the second positive C-type retardation layer 30. The means for making the substrate 52 peelable from the second positive C-type retardation layer 30 is not particularly limited. As the means for making the substrate 52 peelable from the second positive C-type retardation layer 30, the means described above as the means for making the resin substrate 60 peelable from the first positive C-type retardation layer 10 can be adopted. The method for forming the second positive C-type retardation layer 30 on the substrate 52 is the same as the method for forming the first positive C-type retardation layer 10 on the resin substrate 60, except for the points described below.

[0221] The thickness direction retardation of the second positive C-type retardation layer 30 is adjusted so as to satisfy the above-mentioned formulas (iii) to (iv). The direction in which the second positive C-type retardation layer 30 aligns the liquid crystalline component of the second positive A-type retardation layer 40 is adjusted so that, when an elliptically polarizing plate 70 is produced using the retardation film 1, the angle formed between the extension direction of the in-plane slow axis of the second positive A-type retardation layer 40 and the extension direction of the absorption axis of the polarizing plate 71 falls within the above-mentioned numerical range.

[0222] Subsequently, the second positive A-type retardation layer 40 is formed on the second positive C-type retardation layer 30. The method for forming the second positive A-type retardation layer 40 on the second positive C-type retardation layer 30 is the same as the method for forming the first positive A-type retardation layer 20 on the first positive C-type retardation layer 10, except for the following points.

[0223] The in-plane retardation of the second positive A-type retardation layer 40 is adjusted so that the above-mentioned formula (iv) is satisfied. The in-plane retardation of the second positive A-type retardation layer 40 is adjusted so that the above-mentioned formula (vi) is satisfied. The extension direction of the in-plane slow axis of the second positive A-type retardation layer 40 is adjusted so that, when an elliptically polarizing plate 70 is produced using the retardation film 1, the angle formed between the extension direction of the in-plane slow axis of the second positive A-type retardation layer 40 and the extension direction of the absorption axis of the polarizing plate 71 falls within the above-mentioned numerical range.

[0224] By the above-described manufacturing method, the film 4 is manufactured, in which the substrate 52, the second positive C-type retardation layer 30, and the second positive A-type retardation layer 40 are laminated in this order, as shown in FIG.

[0225] Next, a step of preparing a polarizing plate 71 is performed. As an example of the step of preparing a polarizing plate 71, a case where a stretched film having an absorption anisotropy dye adsorbed thereon is used as a polarizer will be described. A stretched film having an absorption anisotropy dye adsorbed thereon can typically be manufactured through the steps of 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 having 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 71 can be manufactured by laminating a polarizer protective layer to one or both sides of the obtained polarizer. The polarizing plate 71 can be prepared, for example, by referring to paragraphs 0025 to 0059 of JP 2021-51287 A.

[0226] Next, the film 4 and the polarizing plate 71 shown in FIG. 6 are laminated. When laminating the film 4 and the polarizing plate 71, the film 4 and the polarizing plate 71 are laminated so that the surface of the film 4 opposite to the surface formed by the substrate 52 faces the polarizing plate 71. As an example, the film 4 and the polarizing plate 71 can be laminated by bonding the surface of the film 4 and the surface of the polarizing plate 71 with an adhesive layer (adhesive layer). Next, the substrate 52 is peeled off from the second positive C-type retardation layer 30 of the film 4. Next, the second positive C-type retardation layer 30 and the film 3 shown in FIG. 5 are bonded via the bonding layer 51. At this time, the second positive C-type retardation layer 30 and the film 3 are bonded so that the surface of the film 3 opposite to the surface formed by the resin substrate 60 faces the second positive C-type retardation layer 30. In this way, the retardation film 1 in a state where it is superimposed on the polarizing plate 71 as shown in FIG. 2 can be manufactured. In other words, the elliptically polarizing plate 70 shown in Fig. 2 can be manufactured. Subsequently, the resin substrate 60 is peeled off from the first positive C-type retardation layer 10. In this manner, the retardation film 1 in a state where it is superimposed on the polarizing plate 71 as shown in Fig. 1 can be manufactured. In other words, the elliptically polarizing plate 70 shown in Fig. 1 can be manufactured.

[0227] In the retardation film 1 of the present embodiment, a first positive C-type retardation layer 10, a first positive A-type retardation layer 20, a bonding layer 51, a second positive C-type retardation layer 30, and a second positive A-type retardation layer 40 are laminated in this order. The above-described retardation film 1 can be easily manufactured by the above-described method. Furthermore, using the above-described retardation film 1, an optical member such as an elliptical polarizing plate 70 can be easily manufactured by the above-described method. In particular, by controlling the bonding strength between each layer as follows, the elliptical polarizing plate 70 including the retardation film 1 shown in FIGS. 1 and 2 can be manufactured by the above-described method. The bonding strength between the second positive C-type retardation layer 30 and the substrate 52 is set to be smaller than the bonding strength between the polarizing plate 71 and the second positive A-type retardation layer 40. The bonding strength between the first positive C-type retardation layer 10 and the resin substrate 60 is set to be smaller than the bonding strength between the polarizing plate 71 and the second positive A-type retardation layer 40 and the bonding strength between the second positive C-type retardation layer 30 and the first positive A-type retardation layer 20 via the bonding layer 51. This makes it easy to control the bonding strength between each layer to a strength suitable for producing optical members such as the retardation film 1 and the elliptically polarizing plate 70.

[0228] V. Effects of Retardation Film and Elliptical Polarizer The effects of the retardation film 1 of this embodiment will be described. In particular, the effects of the retardation film 1 when it is stacked with a polarizer 71 (described later) to form an elliptical polarizer 70 as shown in FIGS. 1 and 2 will be described. The effects of the elliptical polarizer 70 of this embodiment will also be described. The retardation film 1 of this embodiment includes a first positive A-type retardation layer 20 that functions as a λ / 4 retardation plate and exhibits positive dispersion, and a second positive A-type retardation layer 40 that functions as a λ / 2 retardation plate and exhibits positive dispersion. In the elliptical polarizer 70 including such a retardation film 1, the angle formed between the extension direction of the in-plane slow axis of the first positive A-type retardation layer 20 and the extension direction of the absorption axis of the polarizer 71 is 73°±5°. The angle between the direction in which the in-plane slow axis of the second positive A-type retardation layer 40 extends and the direction in which the absorption axis of the polarizing plate 71 extends is 15°±5°. Such an elliptical polarizing plate 70 provides the effects described in paragraphs 0018 to 0020 of JP-A-10-68816. That is, the following effects are obtained. As shown in FIG. 4 , when the elliptical polarizing plate 70 is used in a display device or the like, external light passes through the polarizing plate 71 and is converted into linearly polarized light before entering the second positive A-type retardation layer 40. The wavelength of light at which the first positive A-type retardation layer 20 functions as a λ / 4 retardation plate and the second positive A-type retardation layer 40 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 in which linearly polarized light passes through the second positive A-type retardation layer 40 and the first positive A-type retardation layer 20 in this order. When linearly polarized light having a reference wavelength passes through, the polarization direction of the light is rotated when the light passes through the second positive A-type retardation layer 40, and is converted into circularly polarized light when the light passes through the first positive A-type retardation layer 20. As a result, the linearly polarized light having the reference wavelength is converted into circularly polarized light by passing through the second positive A-type retardation layer 40 and the first positive A-type retardation layer 20. 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 second positive A-type retardation layer 40, the retardation of the second positive A-type retardation layer 40 is excessive to convert linearly polarized light into linearly polarized light with a rotated polarization direction. Subsequently, when light having a short wavelength further passes through the first positive A-type retardation layer 20, the retardation of the first positive A-type retardation layer 20 is excessive to convert linearly polarized light into circularly polarized light. Since the excess retardation of the second positive A-type retardation layer 40 and the excess retardation of the first positive A-type retardation layer 20 cancel each other out, as a result, light having a short wavelength is 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 having a wavelength longer than the reference wavelength passes through. In this case, when light passes through the second positive A-type retardation layer 40, the retardation of the second positive A-type retardation layer 40 is insufficient to convert linearly polarized light into linearly polarized light with a rotated polarization direction. Subsequently, when light having a long wavelength further passes through the first positive A-type retardation layer 20, the retardation of the first positive A-type retardation layer 20 is insufficient to convert linearly polarized light into circularly polarized light. The insufficient retardation of the second positive A-type retardation layer 40 and the insufficient retardation of the first positive A-type retardation layer 20 cancel each other out, resulting in the 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 70 including the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40, 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 second positive A-type retardation layer 40 and the first positive A-type retardation layer 20. By using such an elliptical polarizer 70 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 easier to view.

[0229] Furthermore, by using the retardation film 1 in a display device or the like, the contrast with respect to a view from an oblique direction can be increased and color shift can be reduced due to the actions of the first positive C-type retardation layer 10 and the second positive C-type retardation layer 30. This allows the viewing angle of the display device or the like to be widened. The retardation film 1 of the present embodiment includes both the first positive C-type retardation layer 10 directly adjacent to the first positive A-type retardation layer 20 and the second positive C-type retardation layer 30 directly adjacent to the second positive A-type retardation layer 40, and therefore can particularly effectively increase the contrast with respect to a view from an oblique direction and reduce color shift.

[0230] By using the elliptical polarizer 70 of this embodiment, which includes the retardation film 1 and the polarizer 71, in a display device, particularly an organic EL display device, it is possible to reduce reflection of external light on the display surface of the display device, as described above. That is, the elliptical polarizer can be used as an external light anti-reflection film. Furthermore, by using the elliptical polarizer 70 in a display device, it is possible to increase contrast when viewed from an oblique direction and reduce color shift. This allows the viewing angle of the display device to be increased. In this way, the elliptical polarizer can be suitably used as a polarizer compensation film in a display device.

[0231] The retardation film 1 described above includes a plurality of stacked retardation layers. In particular, the retardation film 1 includes two positive C-type retardation layers, i.e., a first positive C-type retardation layer 10 and a second positive C-type retardation layer 30. Through extensive research, the present inventors have found that, with respect to a retardation film 1 including two positive C-type retardation layers, the appearance of the retardation film 1 may differ depending on the viewing direction of the retardation film 1. In particular, they have found that, when the retardation film 1 is used in a display device or the like, reflected light reflected on the surface of the display device or the like may be noticeable depending on the viewing direction of the retardation film 1. Furthermore, they have found that, depending on the viewing direction of the retardation film 1, regions of different colors may appear in the retardation film 1. In particular, they have found that, when the retardation film 1 is used in a display device, even when the display surface of the display device is not displaying an image and the display surface is black, regions of different colors may be observed when the display surface is viewed through the retardation film 1.

[0232] Furthermore, the inventors of the present invention have found that the thickness direction retardation Rth of the first positive C-type retardation layer 10 at a wavelength of 550 nm is Ｃ１（５５０） and the thickness direction retardation Rth of the second positive C-type retardation layer 30 at a wavelength of 550 nm. Ｃ２（５５０） However, it has been found that by satisfying the above formulas (i) to (ii), differences in appearance depending on the viewing direction of the retardation film 1 can be minimized. In particular, it has been found that by satisfying the above formulas (i) to (ii), differences in appearance depending on the viewing direction of the retardation film 1 can be minimized when the viewing angle at which a display device or the like is viewed is 60° or less. Furthermore, it has been found that by satisfying the above formulas (i) to (ii), reflected light reflected on the surface of a display device or the like can be made less noticeable. Furthermore, it has been found that by satisfying the above formulas (i) to (ii), regions of different colors are less likely to be observed. Based on the above, the present inventors have completed the present invention. The present inventors discovered the problem of differences in appearance of the retardation film 1 depending on the viewing direction, and an example of an experiment conducted to find the above formulas (i) to (ii) will be described later.

[0233] In this way, the retardation film 1 in which the difference in appearance depending on the viewing direction is kept small is considered to have small difference in appearance caused by rotation even when a user views the retardation film 1 while rotating it around an axis perpendicular to the surfaces 1 a and 1 b of the retardation film 1. Such a retardation film 1 is particularly suitable for use in a display device that is expected to be rotated by a user, as will be described later.

[0234] As a retardation film having a function of preventing reflection of external light, a retardation film having one positive A-type retardation layer and one positive C-type retardation layer exhibiting reverse dispersion has also been known (for example, Japanese Patent No. 4592005). However, from the viewpoint of improving the durability of optical components such as a retardation film and an elliptically polarizing plate, the retardation film 1 having the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, the second positive C-type retardation layer 30, and the second positive A-type retardation layer 40 of the present embodiment is preferable to a retardation film having one positive A-type retardation layer and one positive C-type retardation layer.

[0235] <Modifications> Next, various modifications of the present embodiment will be described with reference to Figures 7 to 9. In Figures 7 to 9, 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.

[0236] <Modification 1> In the above-described embodiment, the retardation film 1 in which the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, the second positive C-type retardation layer 30, and the second positive A-type retardation layer 40 are laminated in this order has been described. However, the lamination order of the retardation layers is not limited thereto. FIG. 7 is a cross-sectional view showing an elliptically polarizing plate 70 including the retardation film 1 of Modification 1. The retardation film 1 of Modification 1 also includes a laminate 2 including the second positive C-type retardation layer 30 and the second positive A-type retardation layer 40, similar to the retardation film 1 of the above-described embodiment. In the retardation film 1 of Modification 1, the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, and the laminate 2 are also laminated in this order. However, in the retardation film 1 of the modified example 1, as shown in FIG. 7, the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, the second positive A-type retardation layer 40, and the second positive C-type retardation layer 30 are laminated in this order.

[0237] In the retardation film 1 of the first modification, the above-mentioned formulas (i) to (ii) are also satisfied, and thus, the difference in appearance depending on the direction from which the retardation film 1 is viewed can be suppressed to be small while using two positive C-type retardation layers.

[0238] Next, a manufacturing method of the retardation film 1 shown in FIG. 7 will be described. Additionally, a manufacturing method of the elliptical polarizing plate 70 shown in FIG. 7 will be described. First, the film 3 shown in FIG. 5, the film 4 shown in FIG. 6, and the polarizing plate 71 are prepared. Next, the film 3 and the film 4 are bonded via a bonding layer 51. At this time, the film 3 and the film 4 are bonded so that the surface of the film 3 opposite the surface formed by the resin substrate 60 faces the surface of the film 4 opposite the surface formed by the substrate 52. Next, the substrate 52 is peeled from the second positive C-type retardation layer 30. Next, the second positive C-type retardation layer 30 and the polarizing plate 71 are laminated. As an example, the second positive C-type retardation layer 30 and the polarizing plate 71 can be laminated by bonding the surfaces of the second positive C-type retardation layer 30 and the polarizing plate 71 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. Subsequently, the resin substrate 60 is peeled off from the first positive C-type retardation layer 10. In this manner, the elliptically polarizing plate 70 shown in FIG.

[0239] In the retardation film 1 of the first modification, the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, the bonding layer 51, the second positive A-type retardation layer 40, and the second positive C-type retardation layer 30 are laminated in this order. According to the retardation film 1 as described above, the distance w1 between the first positive C-type retardation layer 10 and the second positive C-type retardation layer 30 can be increased. In particular, as described above, the distance w1 is preferably 1 μm or more, and according to the retardation film 1 as described above, the distance w1 can be easily set to 1 μm or more.

[0240] <Modification 2> In the above-described embodiment, the retardation film 1 including the bonding layer 51 bonding the first positive A-type retardation layer 20 and the laminate 2 has been described. However, the layer configuration of the retardation film 1 is not limited to this. FIG. 8 is a cross-sectional view showing the retardation film 1 of Modification 2. As shown in FIG. 8, the retardation film 1 of Modification 2 does not include the bonding layer 51 bonding the first positive A-type retardation layer 20 and the laminate 2. In the retardation film 1 of Modification 2, the first positive A-type retardation layer 20 is directly adjacent to the laminate 2. In the example shown in FIG. 8, the first positive A-type retardation layer 20 is directly adjacent to the second positive C-type retardation layer 30. As a result, the first positive A-type retardation layer 20 is directly adjacent to the laminate 2.

[0241] A manufacturing method of the retardation film 1 shown in Fig. 8 will be described. First, the film 3 shown in Fig. 5 is prepared. Subsequently, the second positive C-type retardation layer 30 is formed on the first positive A-type retardation layer 20 of the film 3 shown in Fig. 5 by the same method as the method for forming the second positive C-type retardation layer 30 on the substrate 52 described above. Subsequently, the second positive A-type retardation layer 40 is formed on the second positive C-type retardation layer 30 by the same method as the method for forming the second positive A-type retardation layer 40 on the second positive C-type retardation layer 30 described above.

[0242] An elliptical polarizer 70 as shown in FIG. 9 can be produced by overlaying a polarizer 71 on the retardation film 1 of Modification 2 so that the polarizer 71 faces the first surface 1a, and peeling off the resin substrate 60 from the first positive C-type retardation layer 10. The elliptical polarizer 70 produced in this manner also has the same effect as the elliptical polarizer 70 of the above-described embodiment. Furthermore, a display device 100 as shown in FIG. 9 can be produced by using the elliptical polarizer 70 of Modification 2.

[0243] In the retardation film 1 of the modified example 2, the above-mentioned formulas (i) to (ii) are also satisfied, and thus, the difference in appearance depending on the direction from which the retardation film 1 is viewed can be suppressed to be small while using two positive C-type retardation layers.

[0244] In the retardation film 1 of Modification 2, the first positive C-type retardation layer 10, the first positive A-type retardation layer 20, the second positive C-type retardation layer 30, and the second positive A-type retardation layer 40 are laminated in this order. The retardation film 1 of Modification 2 does not include the bonding layer 51 that bonds the first positive A-type retardation layer 20 to the laminate 2. In the retardation film 1 of Modification 2, the first positive A-type retardation layer 20 is directly adjacent to the laminate 2. According to the retardation film 1 as described above, since the bonding layer 51 is not provided, the retardation film 1 can be made thinner.

[0245] <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.

[0246] The display device 100 shown in FIG. 9 was modeled by simulation. Next, when natural light was irradiated onto the display surface of the modeled display device 100 as external light, the luminance distribution was calculated when the luminance on the display surface was measured from different directions. Furthermore, when natural light was irradiated onto the display surface of the modeled display device 100, the color distribution observed when the color on the display surface was observed from different directions was calculated. The simulation was performed using LCD-MASTER (Shintech Co., Ltd.). In the simulation, the angle between the extension direction of the in-plane slow axis of the first positive A-type retardation layer 20 and the extension direction of the absorption axis of the polarizing plate 71 was set to 73°. In the simulation, the angle between the extension direction of the in-plane slow axis of the second positive A-type retardation layer 40 and the extension direction of the absorption axis of the polarizing plate 71 was set to 15°.

[0247] Specifically, the luminance distribution and color distribution were calculated as follows. When natural light is irradiated onto the display device 100 shown in FIG. 9 as external light, the irradiated external light is considered to travel, for example, along the optical path indicated by the dashed line L1 in FIG. 9 . That is, the external light passes through the retardation film 1 from the first surface 1a to the second surface 1b, reaches the surface 102a of the display device main body 102, and is reflected by the surface 102a. The external light reflected by the surface 102a passes through the retardation film 1 from the second surface 1b to the first surface 1a, exits the display device 100, and reaches the viewer's eye. In this way, the external light first passes through the retardation film 1 from the first surface 1a to the second surface 1b, and then passes through the retardation film 1 from the second surface 1b to the first surface 1a. For this reason, when natural light is irradiated onto the first surface 5a of the laminate 5 having a first surface 5a and a second surface 5b shown in Fig. 10, the luminance distribution on the second surface 5b was calculated by simulation, and this was regarded as the luminance distribution on the display surface of the display device 100 shown in Fig. 9. Furthermore, when natural light is irradiated onto the first surface 5a of the laminate 5 shown in Fig. 10, the color distribution on the second surface 5b was calculated by simulation, and this was regarded as the color distribution on the display surface of the display device 100 shown in Fig. 9. 10, from the first surface 1a to the second surface 1b, a polarizing plate 71, a first positive C-type retardation layer 10, a first positive A-type retardation layer 20, a second positive C-type retardation layer 30, a second positive A-type retardation layer 40, a second positive A-type retardation layer 40, a second positive C-type retardation layer 30, a first positive A-type retardation layer 20, a first positive C-type retardation layer 10, and a polarizing plate 71 are laminated in this order. In the laminate 5 used in the simulation, the extension directions of the absorption axes of the two polarizing plates 71 and the extension directions of the in-plane slow axes of the two first positive A-type retardation layers 20 were adjusted so that the state of external light passing through the optical path indicated by the dashed line L2 in FIG. 10 coincides with the state of external light passing through the optical path indicated by the dashed line L1 in FIG.

[0248] 11A and 11B are schematic diagrams showing a method for calculating the luminance distribution and color distribution of the laminate 5. In the example shown in FIGS. 11A and 11B, the luminance and color of point P located on the second surface 5b of the laminate 5 are measured from direction d1. FIG. 11A shows the laminate 5 observed from a direction parallel to the second surface 5b. FIG. 11B shows the second surface 5b of the laminate 5 observed from a direction perpendicular to the second surface 5b. As shown in FIG. 11A, the angle θ is the angle between the direction d1 in which the luminance and color are measured and an imaginary line n1 extending from point P and perpendicular to the second surface 5b. As shown in FIG. 11B, when observing the laminate 5 from a direction perpendicular to the second surface 5b, the angle ψ is the angle between the direction d1 in which the luminance and color are measured and an imaginary reference line n2 extending from point P and parallel to the second surface 5b. In calculating the luminance distribution and color distribution of the laminate 5, the angle θ was fixed at 60° and the angle ψ was changed by 5° in 72 directions, and the luminance and color were measured from a direction perpendicular to the second surface 5b.

[0249] In measuring the color, more specifically, the L defined in JIS Z8781:2013 ＊ a ＊ b ＊ Chromaticity a in the color system ＊ and chromaticity b ＊ The values ​​of and were measured.

[0250] The luminance distribution was calculated from the measured luminance. Specifically, as an index representing the luminance distribution, the luminance measured from each of 72 directions with the angle θ fixed at 60° was divided by the luminance measured from a direction perpendicular to the second surface 5b to calculate the luminance ratio. The average and maximum values ​​of these luminance ratios were calculated to be used as an index representing the luminance distribution.

[0251] The color distribution was calculated from the measured colors. Specifically, as an index representing the color distribution, the color difference ΔE that occurred when the angle ψ was changed 72 times by 5° while the angle θ was fixed at 60° was calculated. The color difference ΔE was calculated by dividing the chromaticity a ＊ , chromaticity b ＊ a ＊ １ , b＊ １ After changing the angle ψ by 5°, the chromaticity a ＊ , chromaticity b ＊ a ＊ ２ , b ＊ ２ The average and maximum values ​​of the calculated 72 color differences ΔE were calculated and used as indices representing the color distribution.

[0252] Furthermore, the chromaticity a when the angle θ is fixed at 60° and the angle ψ is changed 72 times by 5° is measured. ＊ , chromaticity b ＊ As shown in FIGS. 12A to 12J, the horizontal axis represents the chromaticity a ＊ The vertical axis is the chromaticity b ＊ Furthermore, the chromaticity a measured from a direction where the angle ψ differs by 5° is shown in the graph. ＊ , chromaticity b ＊ The points representing the sets of θ and ψ are connected by straight lines. The succession of these straight lines is considered to indicate the change in color when the angle ψ is changed while the angle θ is fixed at 60°. The graphs shown in Figures 12A to 12J were used as indices representing the color distribution.

[0253] The luminance distribution and the color distribution were calculated based on the thickness direction retardation Rth of the first positive C-type retardation layer 10 of the retardation film 1 at a wavelength of 550 nm. Ｃ１（５５０） and the thickness direction retardation Rth of the second positive C-type retardation layer 30 at a wavelength of 550 nm Ｃ２（５５０） The experiment was carried out on the display devices 100 of Experimental Examples 1 to 10 in which the above parameters were changed.

[0254] Rth set in each of Experimental Examples 1 to 10 Ｃ１（５５０） and Rth Ｃ２（５５０） The values ​​of Rth are shown in Table 1. Ｃ１（５５０） and Rth Ｃ２（５５０） and Rth Ｃ１（５５０） and Rth Ｃ２（５５０）The absolute value of the difference between the Rth and the average value of the color difference ΔE calculated in each of Experimental Examples 1 to 10 is shown in Table 1. Furthermore, the average value and maximum value of the luminance ratio and the average value and maximum value of the color difference ΔE calculated in each of Experimental Examples 1 to 10 are shown in Table 1. Furthermore, the difference obtained by subtracting the average value of the luminance ratio from the maximum value of the luminance ratio is shown in Table 1. Ｃ１（５５０） is 0 means that the laminate 5 for which the luminance distribution and the color distribution are to be calculated includes, instead of the first positive C-type retardation layer 10, a layer 11 that is the same as the first positive C-type retardation layer 10 except that it does not have a thickness direction retardation. Ｃ２（５５０） is 0 means that the laminate 5 for which the luminance distribution and the color distribution are to be calculated includes, instead of the second positive C-type retardation layer 30, a layer 31 similar to the second positive C-type retardation layer 30 except that it does not have a thickness direction retardation. FIG. 12A is a graph showing a change in color when the angle ψ is changed in Experimental Example 1. FIG. 12B is a graph showing a change in color when the angle ψ is changed in Experimental Example 2. FIG. 12C is a graph showing a change in color when the angle ψ is changed in Experimental Example 3. FIG. 12D is a graph showing a change in color when the angle ψ is changed in Experimental Example 4. FIG. 12E is a graph showing a change in color when the angle ψ is changed in Experimental Example 5. FIG. 12F is a graph showing a change in color when the angle ψ is changed in Experimental Example 6. FIG. 12G is a graph showing a change in color when the angle ψ is changed in Experimental Example 7. FIG. 12H is a graph showing a change in color when the angle ψ is changed in Experimental Example 8. Fig. 12I is a graph showing the change in color tone when the angle ψ is changed in Experimental Example 9. Fig. 12J is a graph showing the change in color tone when the angle ψ is changed in Experimental Example 10.

[0255]

[0256] In each of Experimental Examples 1 to 10, the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40 exhibited positive dispersion. Specifically, in each of Experimental Examples 1 to 10, the in-plane retardation of the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40 was set to Re Ａ１（５５０）= 120 nm, Re Ａ２（５５０） = 240 nm, Re Ａ１（４５０） / Re Ａ１（５５０） = 1.10, Re Ａ２（４５０） / Re Ａ２（５５０） Furthermore, the wavelength dispersion characteristics of the first positive C-type retardation layer 10 and the second positive C-type retardation layer 30 were set as follows. The thickness direction retardation of the first positive C-type retardation layer 10 at a wavelength of 450 nm was set as Rth ｃ１（４５０） The thickness direction retardation of the first positive C-type retardation layer 10 at a wavelength of 550 nm is defined as Rth ｃ１（５５０） The thickness direction retardation of the second positive C-type retardation layer 30 at a wavelength of 450 nm is defined as Rth ｃ２（４５０） The thickness direction retardation of the second positive C-type retardation layer 30 at a wavelength of 550 nm is defined as Rth ｃ２（５５０） Then, Rth Ｃ１（４５０） / Rth Ｃ１（５５０） = 1.10, Rth Ｃ２（４５０） / Rth Ｃ２（５５０） = 1.10.

[0257] The calculation results of the luminance distribution and the color distribution in each of Experimental Examples 1 to 10 were obtained by plotting the thickness direction retardation Rth of the first positive C-type retardation layer 10 at a wavelength of 550 nm. Ｃ１（５５０） and the thickness direction retardation Rth of the second positive C-type retardation layer 30 at a wavelength of 550 nm Ｃ２（５５０） are set as shown in Table 1, and are regarded as the calculation results of the luminance distribution and color distribution in the display device 100 shown in FIG.

[0258] Rth in each of Experimental Examples 1 to 4 Ｃ１（５５０） and Rth Ｃ２（５５０） Therefore, the calculation results of the luminance distribution and the color distribution in each of Experimental Examples 1 to 4 are Ｃ１（５５０） and Rth Ｃ２（５５０） can be regarded as the calculation results of the luminance distribution and the color distribution in the display device 100 including the retardation film 1 that satisfies the above-mentioned formulas (i) to (ii). Ｃ１（５５０） and RthＣ２（５５０） does not satisfy at least one of the above-mentioned formulas (i) to (ii). Therefore, the calculation results of the luminance distribution and the color distribution in each of Experimental Examples 5 to 10 are Ｃ１（５５０） and Rth Ｃ２（５５０） can be regarded as the calculation results of the luminance distribution and color distribution in a display device including a retardation film that does not satisfy at least one of the above-mentioned formulas (i) to (ii).

[0259] The calculation results of the luminance distribution in each of Experimental Examples 1 to 10 revealed the following. It was found that the maximum value of the luminance ratio in Experimental Examples 1 to 4 was smaller than the maximum value of the luminance ratio in Experimental Examples 5 to 10. From this, it was found that in Experimental Examples 1 to 4, the ratio of the luminance measured from the direction at an angle θ of 60° to the luminance measured from the direction perpendicular to the second surface 5b was generally kept small regardless of the angle ψ. On the other hand, it was found that in Experimental Examples 5 to 10, the luminance measured from the direction at an angle θ of 60° was particularly large compared to the luminance measured from the direction perpendicular to the second surface 5b, depending on the angle ψ. From this, it was found that when the above-mentioned formulas (i) to (ii) are established in the retardation film 1, the ratio of the luminance measured from the direction at an angle of 60° with respect to a virtual line perpendicular to the surfaces 1a and 1b of the retardation film 1 to the luminance measured from the direction perpendicular to the surfaces 1a and 1b of the retardation film 1 can be reduced. From the above, it has been found that when the formulas (i) to (ii) are established, when the viewing angle at which the display device 100 using the retardation film 1 is viewed is 60° or less, a viewing direction in which reflected light reflected on the surface of the display device or the like is particularly noticeable is unlikely to occur.

[0260] Furthermore, it was found that the difference obtained by subtracting the average value of the luminance ratio from the maximum value of the luminance ratio in Experimental Examples 1 to 4 was smaller than the difference obtained by subtracting the average value of the luminance ratio from the maximum value of the luminance ratio in Experimental Examples 5 to 10. From this, it was found that in Experimental Examples 1 to 4, when the angle ψ was changed while the angle θ was fixed at 60°, the amount of change in luminance corresponding to the change in the angle ψ could be kept small. On the other hand, it was found that in Experimental Examples 5 to 10, when the angle ψ was changed while the angle θ was fixed at 60°, the amount of change in luminance corresponding to the change in the angle ψ was particularly large. From this, it was found that when the above-mentioned formulas (i) to (ii) are satisfied in the retardation film 1, the amount of change in luminance measured from a direction that forms an angle of 60° with respect to a virtual line perpendicular to the surfaces 1a and 1b of the retardation film 1 can be reduced. From the above, it has been found that, when the formulas (i) to (ii) are satisfied, even if a user views the retardation film 1 while rotating it around an axis perpendicular to the surfaces 1a and 1b, reflected light can be prevented from being particularly noticeable when the retardation film 1 is directed in a specific direction.

[0261] Furthermore, it was found that the average value of the luminance ratio in Experimental Examples 1 to 4 was smaller than the average value of the luminance ratio in Experimental Examples 5, 7, 8, 9, and 10. From this, it was found that in Experimental Examples 1 to 4, the ratio of the luminance measured from the direction at an angle θ of 60° to the luminance measured from the direction perpendicular to the second surface 5b can be made smaller overall. From the above, it was found that when the formulas (i) to (ii) are established, when the viewing angle at which the display device 100 using the retardation film 1 is visible is 60° or less, reflected light reflected on the surface of the display device or the like becomes less noticeable.

[0262] The calculation results of the color distribution in each of Experimental Examples 1 to 10 revealed the following. It was found that the maximum value of the color difference ΔE in Experimental Examples 1 to 4 was smaller than the maximum value of the color difference ΔE in Experimental Examples 5, 6, 8, and 10. From this, it was found that in Experimental Examples 1 to 4, the color difference ΔE when the angle ψ was changed for the color measured from a direction where the angle θ was 60° was generally kept small regardless of the angle ψ. On the other hand, it was found that in Experimental Examples 5, 6, 8, and 10, the above-mentioned color difference ΔE became particularly large depending on the angle ψ. From this, it was found that when the above-mentioned formulas (i) to (ii) are established in the retardation film 1, the color difference of the color observed from a direction where the angle with respect to a virtual line perpendicular to the surfaces 1a and 1b of the retardation film 1 is 60° can be reduced. From the above, it has been found that, when the formulas (i) to (ii) are established, even if a user views the retardation film 1 while rotating it around an axis perpendicular to the surfaces 1a and 1b, it is possible to suppress a change in color from being particularly noticeable when the retardation film 1 is oriented in a specific direction.

[0263] Furthermore, it was found that the average value of the color difference ΔE in Experimental Examples 1 to 4 was smaller than the average value of the color difference ΔE in Experimental Examples 5, 6, 7, and 9. From this, it was found that the color difference ΔE measured from the direction where the angle θ was 60° could be reduced overall in Experimental Examples 1 to 4. From the above, it was found that when the formulas (i) to (ii) are established, when a user visually observes the retardation film 1 while rotating it around an axis perpendicular to the surfaces 1a and 1b, a change in color due to rotation becomes less noticeable.

[0264] 12A to 12J , which show the change in color when the angle ψ is changed, the following was found: The change in color in Experimental Examples 1 to 4 shown in Fig. 12A to 12D occurred in a narrower range than the change in color in Experimental Example 6 shown in Fig. 12F , for example. This shows that when the above-mentioned formulas (i) to (ii) are satisfied in the retardation film 1, the change in color observed from a direction at an angle of 60° with respect to a virtual line perpendicular to the surfaces 1a and 1b of the retardation film 1 can be reduced.

[0265] 12F, for example, compared to the graph of Experimental Example 6 shown in Figure 12F, the graphs of Experimental Examples 1 to 4 shown in Figures 12A to 12D do not include particularly long lines connecting points, and all of the lines included in the graphs are relatively short. From this, it was found that by satisfying formulas (i) to (ii), it is possible to suppress noticeable changes in color, especially when the retardation film 1 is oriented in a specific direction, even when a user views the retardation film 1 while rotating it around an axis perpendicular to the surfaces 1a and 1b. From the above, it was found that by satisfying formulas (i) to (ii), it is difficult to observe regions with different colors when the viewing angle at which the display device 100 using the retardation film 1 is viewed is 60° or less.

[0266] From the above, it was found from the experimental examples that when the above-mentioned formulas (i) and (ii) are established, the difference in appearance depending on the direction from which the retardation film 1 is viewed can be kept small.

[0267] The above-described experimental example was performed on a display device 100 modeled by simulation. In the above-described experimental example, it was assumed that the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40 were retardation layers containing liquid crystal components that were not twist-oriented. However, the present inventors also conducted an experiment in which a retardation film 1 was actually manufactured. In this experiment, a retardation film 1 in which at least one of the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40 contained a twist-oriented liquid crystal component was actually manufactured. In this experiment, the performance of the actually manufactured retardation film 1 was evaluated. As a result of this evaluation, the above-described formulas (i) to (ii) were established even in a retardation film 1 in which at least one of the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40 contained a twist-oriented liquid crystal component, and thus the difference in appearance depending on the direction from which the retardation film 1 was viewed was minimized. In particular, even in the retardation film 1 in which at least one of the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40 contains a twist-oriented liquid crystal component, the difference in appearance depending on the direction from which the retardation film 1 is viewed was kept small to at least the same extent as in the retardation film 1 in which the first positive A-type retardation layer 20 and the second positive A-type retardation layer 40 contain a non-twist-oriented liquid crystal component.

[0268] 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.

[0269] REFERENCE SIGNS LIST 1 Retardation film 2 Laminate 10 First positive C-type retardation layer 20 First positive A-type retardation layer 30 Second positive C-type retardation layer 40 Second positive A-type retardation layer 51 Bonding layer 60 Resin substrate 70 Elliptical polarizing plate 71 Polarizing plate 100 Display device 101 Organic EL display device

Claims

1. A laminate including a first positive C-type retardation layer, a first positive A-type retardation layer, a second positive C-type retardation layer, and a second positive A-type retardation layer laminated in this order, wherein the first positive C-type retardation layer is directly adjacent to the first positive A-type retardation layer, the second positive C-type retardation layer is directly adjacent to the second positive A-type retardation layer, and the thickness-direction retardation of the first positive C-type retardation layer at a wavelength of 550 nm is Rth Ｃ１（５５０） and the thickness-direction retardation of the second positive C-type retardation layer at a wavelength of 550 nm is Rth Ｃ２（５５０） and the in-plane retardation of the first positive A-type retardation layer at a wavelength of 550 nm is Re Ａ１（５５０） and the in-plane retardation of the second positive A-type retardation layer at a wavelength of 550 nm is Re Ａ２（５５０） A retardation film in which the following formulas (i) to (iv) are satisfied.

2. The retardation film according to claim 1, wherein the first positive C-type retardation layer, the first positive A-type retardation layer, the second positive C-type retardation layer, and the second positive A-type retardation layer are laminated in this order.

3. The retardation film according to claim 1, wherein the first positive C-type retardation layer, the first positive A-type retardation layer, the second positive A-type retardation layer, and the second positive C-type retardation layer are laminated in this order.

4. The retardation film according to claim 1, further comprising a bonding layer that bonds the first positive A-type retardation layer and the laminate.

5. The retardation film according to claim 1, wherein the first positive A-type retardation layer is directly adjacent to the laminate.

6. The retardation film according to claim 1, wherein the first positive A-type retardation layer and the second positive A-type retardation layer contain a polymerizable liquid crystal compound.

7. The retardation film according to claim 1, wherein the distance between the first positive C-type retardation layer and the second positive C-type retardation layer is 1 μm or more.

8. The retardation film according to claim 1, wherein the first positive C-type retardation layer and the second positive C-type retardation layer contain a photo-alignment component.

9. Let the in-plane retardation at a wavelength of 550 nm of the first positive A-type retardation layer be Re Ａ１（５５０） and the in-plane retardation at a wavelength of 450 nm of the first positive A-type retardation layer be Re Ａ１（４５０） and the in-plane retardation at a wavelength of 550 nm of the second positive A-type retardation layer be Re Ａ２（５５０） and the in-plane retardation at a wavelength of 450 nm of the second positive A-type retardation layer be Re Ａ２（４５０） The retardation film according to claim 1, wherein the following formulas (v) to (vi) are satisfied.

10. The retardation film according to claim 1, wherein the first positive C-type retardation layer and the second positive C-type retardation layer contain a silicone-based leveling agent.

11. The retardation film according to claim 1, further comprising a resin substrate directly adjacent to the first positive C-type retardation layer.

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

13. The retardation film according to claim 11, wherein the resin substrate is a peelable substrate that can be peeled from the first positive C-type retardation layer.

14. An elliptical polarizing plate comprising the retardation film according to any one of claims 1 to 13 and a polarizing plate laminated on the retardation film.

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

Images