Retardation film, image display device, lens, and virtual reality display device

Abstract

The present invention is related to this retardation film having high ellipticity over a wide wavelength range and being capable of achieving high ellipticity even with respect to oblique incidence. The present invention is also related to an image display device and a lens which, when being applied to a virtual reality display device using a pancake lens, inhibit occurrence of a ghost image. The retardation film includes at least a first optical anisotropic layer, a second optical anisotropic layer, and a first positive C plate. The first optical anisotropic layer is a positive A plate having reverse wavelength dispersibility. The second optical anisotropic layer has reverse wavelength dispersibility, and is formed by fixing a liquid crystalline compound in a twisted alignment using the thickness direction as a spiral axis.

Description

Phase difference film, image display device, lens, and virtual reality display device

[0001] The present invention relates to a phase difference film, an image display device, a lens, and a virtual reality display device.

[0002] Phase difference films are sometimes used to convert the polarization state of light emitted from a display device to a different polarization state. For example, they are used in optical compensation films for liquid crystal displays and anti-reflective films for organic EL displays. They are also sometimes used in image display devices or lenses that constitute virtual reality displays and augmented reality displays. In particular, in virtual reality displays that employ a folded optical system called a pancake lens, phase difference films are essential components for displaying virtual images and reducing ghost images. Image display devices using phase difference films and virtual reality displays including pancake lenses are described in Patent Documents 1 and 2.

[0003] In the applications described above, phase difference films are often used as λ / 4 phase difference plates. λ / 4 phase difference plates are useful for polarization conversion because they can convert linearly polarized light to circularly polarized light and circularly polarized light to linearly polarized light.

[0004] Ellipticity is often used as an indicator of the performance of a λ / 4 phase difference plate. Specifically, the ellipticity of the circularly polarized light emitted when linearly polarized light with an appropriate polarization axis angle is incident on a λ / 4 phase difference plate is used as the evaluation index. The maximum value of ellipticity is 1, and the closer the ellipticity is to 1, the closer the emitted light is to perfectly circularly polarized light, which is a desirable characteristic.

[0005] Positive A plates or negative A plates using polymers or liquid crystal compounds having inverse wavelength dispersion are known as λ / 4 phase difference plates that achieve high ellipticity. Such phase difference films are described in Patent Documents 3 and 4. Furthermore, it is known that laminates using multiple positive A plates or negative A plates using polymers or liquid crystal compounds having forward wavelength dispersion, bonded together at different angles, also function as λ / 4 phase difference plates and achieve high ellipticity. Such a phase difference film is described in Patent Document 5.

[0006] Japanese Patent Publication No. 2020-519964, U.S. Patent No. 10394040, Japanese Unexamined Patent Publication No. 2017-049574, Japanese Unexamined Patent Publication No. 2020-084070, Japanese Patent No. 05745686

[0007] The phase difference films described in Patent Documents 3 and 4 can convert linearly polarized light incident perpendicularly into circularly polarized light with high ellipticity in a specific wavelength range of visible light. However, obtaining sufficiently high ellipticity over a wide wavelength range of visible light has been difficult due to the less-than-ideal wavelength dispersion characteristics of the polymer and liquid crystal compound. Furthermore, the ellipticity of the output light obtained for linearly polarized light incident obliquely was also insufficient.

[0008] The phase difference film described in Patent Document 5 achieves high ellipticity over a relatively wide wavelength range by laminating a positive A plate and a negative A plate at a specific angle, thereby compensating for the shortcomings of their respective wavelength dispersion characteristics. Furthermore, the combination of the positive A plate and the negative A plate compensates for the phase difference (Rth) in the thickness direction between them, allowing high ellipticity to be obtained even for linearly polarized light incident at an oblique angle. However, the ellipticity obtained is still insufficient in both the case of perpendicular and oblique incidence, and further improvement was needed for a phase difference film suitable for pancake lenses used in virtual reality display devices.

[0009] Furthermore, the phase difference film described in Patent Document 5 is a laminate of two different types of films, and therefore undesirable interfacial reflection occurs at the interface of the laminate or at the interface with the adhesive layer used for lamination. This causes a change in the rotation direction of circularly polarized light (for example, right-circularly polarized light changes to left-circularly polarized light due to interfacial reflection), resulting in a problem of reduced ellipticity of the resulting emitted light.

[0010] The present invention has been made in view of the above problems, and the problem that the present invention aims to solve is to provide a phase difference film that has high ellipticity over a wide wavelength range and can obtain high ellipticity even for oblique incidence. Furthermore, the present invention aims to provide an image display device and lens that suppress the occurrence of ghosting when applied to a virtual reality display device using a pancake lens.

[0011] The inventors of the present invention have conducted extensive research on the above-mentioned problems and have found that the above problems can be solved by the following configuration.

[0012] [1] A phase difference film comprising at least a first optical anisotropy layer, a second optical anisotropy layer, and a first positive C plate, wherein the first optical anisotropy layer is a positive A plate having reverse wavelength dispersion, and the second optical anisotropy layer is a layer on which a liquid crystalline compound having reverse wavelength dispersion and being twisted oriented with the thickness direction as the helical axis is fixed. [2] The phase difference film according to [1], comprising the first optical anisotropy layer, the second optical anisotropy layer, and the first positive C plate in this order. [3] The phase difference film according to [1], comprising the first optical anisotropy layer, the first positive C plate, and the second optical anisotropy layer in this order. [4] The phase difference film according to [1], comprising the first positive C plate, the first optical anisotropy layer, and the second optical anisotropy layer in this order. [5] The phase difference film according to [1], wherein the first positive C plate has reverse wavelength dispersion. [6] A phase difference film according to any one of [1] to [5], wherein a first optical anisotropy layer, a second optical anisotropy layer, and a first positive C plate are directly laminated together. [7] A phase difference film according to any one of [1] to [5], wherein at least two of the first optical anisotropy layer, the second optical anisotropy layer, and the first positive C plate are laminated together via an adhesive layer, and the refractive index of the adhesive layer is the value between the average refractive indices in each plane of two layers adjacent to the adhesive layer. [8] A phase difference film according to [1], further comprising at least a second positive C plate. [9] A phase difference film according to [8], comprising a first optical anisotropy layer, a first positive C plate, a second optical anisotropy layer, and a second positive C plate in this order.

[10] A phase difference film according to [8], comprising a first positive C plate, a first optical anisotropy layer, a second positive C plate, and a second optical anisotropy layer in this order.

[11] The phase difference film according to [8], comprising a first positive C plate, a first optical anisotropy layer, a second optical anisotropy layer, and a second positive C plate in this order.

[12] The phase difference film according to [8], wherein at least one of the first positive C plate and the second positive C plate is inverse wavelength dispersive.

[13] A phase difference film according to any one of [8] to

[12] , wherein a first optical anisotropy layer, a second optical anisotropy layer, a first positive C plate, and a second positive C plate are directly laminated together.

[14] A phase difference film according to any one of [8] to

[12] , wherein at least two of the first optical anisotropy layer, the second optical anisotropy layer, the first positive C plate, and the second positive C plate are laminated together via an adhesive layer, the refractive index of the adhesive layer being the value between the average in-plane refractive indices of two layers adjacent to the adhesive layer.

[15] A phase difference film according to [1], further comprising at least a second positive C plate and a third positive C plate, wherein the first positive C plate, the first optical anisotropy layer, the second positive C plate, the second optical anisotropy layer, and the third positive C plate are at least included in this order.

[16] The phase difference film according to

[15] , wherein at least one of the first positive C plate, the second positive C plate, and the third positive C plate is inverse wavelength dispersive.

[17] The phase difference film according to

[15] or

[16] , wherein a first optical anisotropy layer, a second optical anisotropy layer, a first positive C plate, a second positive C plate, and a third positive C plate are directly laminated together.

[18] The phase difference film according to

[15] or

[16] , wherein at least two of the first optical anisotropy layer, the second optical anisotropy layer, the first positive C plate, the second positive C plate, and the third positive C plate are laminated together via an adhesive layer, the refractive index of the adhesive layer being the value between the average in-plane refractive indices of two layers adjacent to the adhesive layer.

[19] An image display device comprising at least the phase difference film according to any one of [1] to [5], [8] to

[12] ,

[15] and

[16] , and an absorbing linear polarizer.

[20] A lens having at least a phase difference film according to any of [1] to [5], [8] to

[12] ,

[15] and

[16] , and a reflective linear polarizer.

[21] A virtual reality display device having the image display device according to

[19] .

[22] A virtual reality display device having the lens according to

[20] .

[0013] According to the present invention, it is possible to provide a phase difference film that has high ellipticity over a wide wavelength range and can obtain high ellipticity even for oblique incidence. Furthermore, according to the present invention, it is possible to provide an image display device and lens that suppress the occurrence of ghosting when applied to a virtual reality display device using a pancake lens.

[0014] This is a schematic diagram showing an example of the configuration of a virtual reality display device using the phase difference film of the present invention. This is a schematic diagram showing an example of the configuration of a conventional virtual reality display device. This is a schematic diagram illustrating the occurrence of ghosting in a virtual reality display device. This is a schematic diagram illustrating the occurrence of ghosting in a virtual reality display device. This is a schematic diagram showing an example of the phase difference film of the present invention. This is a schematic diagram showing another example of the phase difference film of the present invention. This is a schematic diagram showing another example of the phase difference film of the present invention. This is a schematic diagram showing another example of the phase difference film of the present invention. This is a schematic diagram showing another example of the phase difference film of the present invention.

[0015] The present invention will now be described in detail. The following descriptions of constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits.

[0016] Furthermore, the terms "liquid crystal composition," "liquid crystal compound," and "liquid crystal compound" in this specification also conceptually include materials that no longer exhibit liquid crystal properties due to curing or other reasons.

[0017] In this specification, "orthogonal" does not mean exactly 90°, but rather 90°±10°, preferably 90°±5°. Similarly, "parallel" does not mean exactly 0°, but rather 0°±10°, preferably 0°±5°. Furthermore, "45°" does not mean exactly 45°, but rather 45°±10°, preferably 45°±5°.

[0018] In this specification, unless otherwise specified, "phase difference" means "in-plane phase difference," or "in-plane retardation," and is denoted as Re(λ). Here, Re(λ) represents the in-plane retardation at wavelength λ, and unless otherwise specified, wavelength λ is 550 nm. Furthermore, retardation in the thickness direction at wavelength λ is denoted as Rth(λ) in this specification. Unless otherwise specified, wavelength λ is 550 nm. In addition, "lagging axis" means the direction in which the refractive index is maximum within the plane.

[0019] The Re(λ), Rth(λ), and orientation of the slow axis of the phase difference film can be obtained using values ​​measured at wavelength λ, for example, with an AxoScan OPMF-1 (manufactured by OptoScience). By inputting the average refractive index ((nx + ny + nz) / 3) and film thickness (d (μm)) into AxoScan, the following can be calculated: • Slow axis orientation (°) • Re(λ) = R0(λ) • Rth(λ) = ((nx + ny) / 2 - nz) × d Note that R0(λ) is displayed as a value calculated by AxoScan, but it means Re(λ).

[0020] In this specification, inverse wavelength dispersion refers to the characteristic that, when the in-plane retardation (Re) value at a specific wavelength (visible light range) is measured, the Re value increases as the measured wavelength increases. It is preferable that the optical anisotropic layer or phase difference film having inverse wavelength dispersion satisfies Re(450) / Re(550) < 1.00 and Re(650) / Re(550) > 1.00. On the other hand, forward wavelength dispersion refers to the characteristic that, when the in-plane retardation (Re) value at a specific wavelength (visible light range) is measured, the Re value decreases as the measured wavelength increases. It is preferable that the optical anisotropic layer or phase difference film having forward wavelength dispersion satisfies Re(450) / Re(550) > 1.00 and Re(650) / Re(550) < 1.00. In this specification, visible light refers to electromagnetic waves with wavelengths visible to the human eye, specifically light in the wavelength range of 380 to 780 nm.

[0021] In this specification, unless otherwise specified, ellipticity refers to the ellipticity of the emitted light when linearly polarized light with an appropriate polarization axis angle is incident on one face of a phase difference film. The appropriate polarization axis angle is 45° with respect to the lagging axis orientation when the phase difference film is substantially a λ / 4 wave plate. Alternatively, in the usage configuration of the phase difference film, the polarization axis orientation of the emitted light can be measured when right-circularly polarized or left-circularly polarized light is incident perpendicularly from the face opposite to the face on which the linearly polarized light is incident, and this can be set to an appropriate angle. The ellipticity of a phase difference film can be obtained, for example, by arranging the phase difference film and a linear polarizer at an angle adjusted so that the incident polarization has the appropriate polarization axis angle described above, and using an AxoScan OPMF-1, incident light of wavelength λ from the side of the linear polarizer and measuring the ellipticity of the emitted light. Alternatively, for a phase difference film that is not laminated with a linear polarizer, the Müller matrix at wavelength λ can be measured using AxoScan OPMF-1, and the Stokes parameter representing linear polarization with the appropriate polarization axis angle mentioned above can be multiplied by this Müller matrix to calculate the value based on the resulting Stokes parameter.

[0022] In this specification, "absorption axis" refers to the polarization direction in which the absorbance is maximized in the plane when linearly polarized light is incident on an absorbing linear polarizer. "Reflection axis" refers to the polarization direction in which the reflectance is maximized in the plane when linearly polarized light is incident on a reflective linear polarizer. "Transmission axis" refers to the direction in the plane that is perpendicular to the absorption axis or reflection axis.

[0023] The present invention will now be described in detail with reference to the drawings. The following descriptions of the constituent elements may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments.

[0024] <Phase Difference Film> The phase difference film of the present invention preferably has the function of converting the emitted light into linearly polarized light when circularly polarized light is incident on it from at least one surface, and converting the emitted light into circularly polarized light when linearly polarized light is incident on it from the other surface. In order to realize these functions, the phase difference film preferably has an in-plane phase difference that is substantially λ / 4 with respect to the wavelength λ of the incident light.

[0025] The phase difference film of the present invention comprises at least a first optical anisotropic layer, a second optical anisotropic layer, and a first positive C plate, wherein the first optical anisotropic layer is a positive A plate having inverse wavelength dispersion, and the second optical anisotropic layer is a layer on which a liquid crystalline compound having inverse wavelength dispersion and torsion orientation with the thickness direction as the helical axis is fixed. With this configuration, the phase difference film can achieve a substantial in-plane phase difference of λ / 4 over a wide wavelength range of visible light. That is, the phase difference film can convert linearly polarized light to ideal circularly polarized light and convert circularly polarized light to ideal linearly polarized light over a wide wavelength range of visible light.

[0026] Hereafter, when referring to features common to both the first and second optical anisotropic layers of the above-mentioned phase difference film, the first and second optical anisotropic layers will not be distinguished, and will simply be referred to as "optical anisotropic layer." Furthermore, an optical anisotropic layer comprising a liquid crystalline compound having inverse wavelength dispersion and a torsion orientation with the thickness direction as the helical axis will also be referred to as "optical anisotropic layer RT."

[0027] The first optically anisotropic layer, a positive A plate having inverse wavelength dispersion, is a positive A plate that satisfies Re(450) / Re(550) < 1.00 and Re(650) / Re(550) > 1.00. The optically anisotropic layer having inverse wavelength dispersion can be produced, for example, by uniaxially stretching a polymer film such as a modified polycarbonate resin film having inverse wavelength dispersion, referring to Japanese Patent Application Publication No. 2017-049574. Alternatively, the optically anisotropic layer having inverse wavelength dispersion can also be produced, for example, by oriented and immobilizing a rod-shaped liquid crystalline compound having inverse wavelength dispersion, referring to Japanese Patent Application Publication No. 2020-084070.

[0028] The optically anisotropic layer RT, which is formed by fixing a torsionally oriented liquid crystalline compound with the thickness direction as the helical axis, is preferably a layer in which a rod-shaped liquid crystalline compound with inverse wavelength dispersion and torsionally oriented with the thickness direction as the helical axis is fixed, and the molecular axis of the rod-shaped liquid crystalline compound is horizontal to the surface of the optically anisotropic layer, thus forming a chiral nematic phase with a so-called helical structure. When forming the above layer, it is preferable to use a mixture of a liquid crystalline compound exhibiting a nematic liquid crystal phase and a chiral agent. In this specification, the molecular axis means the long axis (molecular long axis) when the liquid crystalline compound is a rod-shaped liquid crystalline compound, and the axis parallel to the direction normal to the disk surface of the disk-shaped liquid crystalline compound when the liquid crystalline compound is a disk-shaped liquid crystalline compound. In this specification, the "fixed" state means a state in which the orientation of the liquid crystalline compound is maintained. Specifically, it is preferable that the layer is non-fluid and can maintain a stable, fixed orientation without being altered by external fields or forces, typically in a temperature range of 0 to 50°C, or -30 to 70°C under more severe conditions.

[0029] In this specification, "liquid crystal compound having inverse wavelength dispersion" means a compound that, when the in-plane retardation (Re) value of a positive A plate made using the same is measured at a specific wavelength (visible light range), exhibits that the Re value becomes equivalent or higher as the measured wavelength increases, that is, a compound that satisfies Re(450) / Re(550) < 1.00 and Re(650) / Re(550) > 1.00.

[0030] The inverse wavelength-dispersive liquid crystalline compounds are not particularly limited as long as they can form an inverse wavelength-dispersive film. Examples include compounds represented by general formula (I) described in Japanese Patent Application Publication No. 2008-297210 (particularly the compounds described in paragraphs

[0034] to

[0039] ), compounds represented by general formula (1) described in Japanese Patent Application Publication No. 2010-084032 (particularly the compounds described in paragraphs

[0067] to

[0073] ), and compounds represented by general formula (1) described in Japanese Patent Application Publication No. 2016-081035 (particularly the compounds described in paragraphs

[0043] to

[0055] ). Furthermore, examples include the compounds described in paragraphs

[0027] to

[0100] of Japanese Patent Publication No. 2011-006360, paragraphs

[0028] to

[0125] of Japanese Patent Publication No. 2011-006361, paragraphs

[0034] to

[0298] of Japanese Patent Publication No. 2012-207765, paragraphs

[0016] to

[0345] of Japanese Patent Publication No. 2012-077055, paragraphs

[0017] to

[0072] of WO12 / 141245, paragraphs

[0021] to

[0088] of WO12 / 147904, and paragraphs

[0028] to

[0115] of WO14 / 147904.

[0031] In the phase difference film of the present invention, it is preferable that both the first optical anisotropy layer and the second optical anisotropy layer are layers in which liquid crystalline compounds are fixed. Since the liquid crystalline compounds can be oriented to any direction using an alignment film or the like, the manufacturing process of the phase difference film can be simplified.

[0032] The first optically anisotropic layer is a positive A plate having inverse wavelength dispersion. Here, the positive A plate is defined as follows: The positive A plate satisfies the relationship in equation (A1) when the refractive index in the slow axis direction in the film plane (the direction in which the refractive index in the plane is maximum) is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, and the refractive index in the thickness direction is nz. Note that the positive A plate exhibits a positive value for Rth. Equation (A1) nx > ny ≈ nz Note that the above "≈" includes not only the case where the two are completely identical, but also the case where the two are substantially identical. "Substantially identical" means, for example, that (ny - nz) × d (where d is the thickness of the film) is -10 to 10 nm, preferably -5 to 5 nm, which is included in "ny ≈ nz". Furthermore, the product of the refractive index anisotropy Δn1 and the thickness d1 at a wavelength of 550 nm is preferably 140 nm or more at the lower limit, more preferably 180 nm or more, and even more preferably 190 nm or more, and the upper limit is preferably 240 nm or less, more preferably 220 nm or less, and even more preferably 210 nm or less. In particular, it is preferable that the product of the refractive index anisotropy Δn1 and the thickness d1 at a wavelength of 550 nm satisfies the following equation (1): Equation (1) 140 nm ≤ Δn1 × d1 ≤ 240 nm It is also more preferable that it satisfies the following equation (2): Equation (2) 180 nm ≤ Δn1 × d1 ≤ 220 nm It is also even more preferable that it satisfies the following equation (3). Equation (3) 190 nm ≤ Δn1 × d1 ≤ 210 nm Furthermore, the thickness d1 of the first optical anisotropy layer is preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. Note that the above Δn1 × d1 in the first optical anisotropy layer is the same value as the in-plane phase difference Re. Δn1 × d1 can be measured using an AxoScan OPMF-1 and the analysis software attached to the device.

[0033] The second optically anisotropic layer is a layer formed by fixing a liquid crystalline compound that has inverse wavelength dispersion and is twist-oriented with the thickness direction as the helical axis. Furthermore, the product of the refractive index anisotropy Δn2 and the thickness d2 at a wavelength of 550 nm is preferably 150 nm or more at the lower limit, more preferably 180 nm or more, even more preferably 190 nm or more, and preferably 230 nm or less at the upper limit, more preferably 220 nm or less, and even more preferably 210 nm or less. In particular, it is preferable that the product of the refractive index anisotropy Δn2 and the thickness d2 at a wavelength of 550 nm satisfies the following equation (4): Equation (4) 150 nm ≤ Δn2 × d2 ≤ 230 nm It is also more preferable that it satisfies the following equation (5): Equation (5) 180 nm ≤ Δn2 × d2 ≤ 220 nm It is also even more preferable that it satisfies the following equation (6). Equation (6) 190 nm ≤ Δn² × d² ≤ 210 nm Furthermore, the thickness d² of the second optical anisotropy layer is preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. Note that the above Δn² × d² in the second optical anisotropy layer can be measured using AxoScan OPMF-1 and the analysis software attached to the device.

[0034] Furthermore, the torsion angle of the second optical anisotropy layer (the torsion angle of the orientation direction of the liquid crystalline compound) is preferably within the range of 85 ± 20°. The torsion angle is more preferably within the range of 75 to 95°, and most preferably within the range of 80 to 90°. The torsion angle of the second optical anisotropy layer is the sum of the rotation angles of the liquid crystalline compound that is spirally torsion oriented from one main surface of the second optical anisotropy layer toward the other main surface. The torsion can be right-handed or left-handed, and either is acceptable. Right-handed torsion means that when observing from one main surface of the optical anisotropy layer toward the other main surface, the in-plane slow axis shifts clockwise relative to the in-plane slow axis at the main surface on the observer's side, which serves as the reference axis, as one moves toward the opposite main surface. Left-hand twist refers to the phenomenon where, when observing an optically anisotropic layer from one main surface to the other, the in-plane slow axis shifts counterclockwise relative to the reference axis at the observer's side of the layer as one moves towards the opposite main surface.

[0035] The above-mentioned twist angle measurement method can be measured using AxoScan OPMF-1 and the analysis software attached to the apparatus. The twist angle of the liquid crystalline compound can be appropriately adjusted depending on the type of the liquid crystalline compound, the temperature at the time of alignment fixation, and the type and amount of the chiral agent, etc.

[0036] Furthermore, in the retardation film of the present invention, there is no particular limitation on the angle formed between the azimuth of the in-plane slow axis of the first optically anisotropic layer and the azimuth of the in-plane slow axis on the first optically anisotropic layer side of the second optically anisotropic layer, but the angle is preferably in the range of 0±10°, and more preferably 0°. Here, as will be described later, the retardation film of the present invention can be used in combination with an absorptive linear polarizer or a reflective linear polarizer (hereinafter collectively referred to as a linear polarizer). When the retardation film is used in combination with a linear polarizer, the first optically anisotropic layer and the second optically anisotropic layer are arranged in this order from the linear polarizer side. Hereinafter, examples of suitable combinations of the angle formed between the transmission axis of the linear polarizer and the azimuth of the in-plane slow axis of the first optically anisotropic layer, and the twisting direction of the second optically anisotropic layer when the retardation film and the linear polarizer are combined will be described.

[0037] When observed from the linear polarizer side, the angle formed between the transmission axis of the linear polarizer and the azimuth of the in-plane slow axis of the first optically anisotropic layer is preferably in the range of 60° to 90° counterclockwise from the transmission axis of the linear polarizer, and more preferably in the range of 70° to 80°. Further, as described above, the angle formed between the azimuth of the in-plane slow axis of the first optically anisotropic layer and the azimuth of the in-plane slow axis on the first optically anisotropic layer side of the second optically anisotropic layer is preferably in the range of 0±10°, and more preferably 0°. Furthermore, the twist angle of the second optically anisotropic layer is preferably right-handed twist when observed from the linear polarizer side.

[0038] When observed from the linear polarizer side, the angle formed between the transmission axis of the linear polarizer and the azimuth of the in-plane slow axis of the first optically anisotropic layer is preferably in the range of 0 to 30° counterclockwise, and more preferably in the range of 10 to 20°. In this case, the angle formed between the in-plane slow axis of the first optically anisotropic layer and the azimuth of the in-plane slow axis of the second optically anisotropic layer on the first optically anisotropic layer side is preferably in the range of 0±10°, and more preferably 0°. Further, in this case, the twist angle of the second optically anisotropic layer is preferably left-handed twist when observed from the linear polarizer side.

[0039] When observed from the linear polarizer side, the angle formed between the transmission axis of the linear polarizer and the azimuth of the in-plane slow axis of the first optically anisotropic layer is preferably in the range of 60 to 90° clockwise, and more preferably in the range of 70 to 80°. In this case, the angle formed between the in-plane slow axis of the first optically anisotropic layer and the azimuth of the in-plane slow axis of the second optically anisotropic layer on the first optically anisotropic layer side is preferably in the range of 0±10°, and more preferably 0°. Further, in this case, the twist angle of the second optically anisotropic layer is preferably left-handed twist when observed from the linear polarizer side.

[0040] When observed from the linear polarizer side, the angle formed between the transmission axis of the linear polarizer and the azimuth of the in-plane slow axis of the first optically anisotropic layer is preferably in the range of 0 to 30° clockwise, and more preferably in the range of 10 to 20°. In this case, the angle formed between the in-plane slow axis of the first optically anisotropic layer and the azimuth of the in-plane slow axis of the second optically anisotropic layer on the first optically anisotropic layer side is preferably in the range of 0±10°, and more preferably 0°. Further, in this case, the twist angle of the second optically anisotropic layer is preferably right-handed twist when observed from the linear polarizer side.

[0041] When the first optically anisotropic layer and the second optically anisotropic layer have the above configuration, the retardation film can function as a λ / 4 retardation layer in a wider wavelength range.

[0042] The phase difference film of the present invention includes a positive C plate. In particular, configurations including a first positive C plate, a configuration including a first positive C plate and a second positive C plate, and a configuration including a first positive C plate, a second positive C plate, and a third positive C plate are possible. When it is not necessary to distinguish between the first to third positive C plates, they are collectively referred to as a positive C plate. Here, a positive C plate is defined as follows: That is, a positive C plate satisfies the relationship in equation (C1) when the refractive index in the slow axis direction in the film plane (the direction in which the refractive index in the plane is maximum) is nx, the refractive index in the direction perpendicular to the slow axis in the plane is ny, and the refractive index in the thickness direction is nz. Note that for a positive C plate, Rth is a negative value. nz > nx ≈ ny Equation (C1) Note that "≈" includes not only the case where the two are completely identical, but also the case where the two are substantially identical. "Substantially identical" means, for example, that (nx - ny) × d (where d is the thickness of the film) is 0 to 10 nm (preferably 0 to 5 nm), which is included in "nx ≈ ny". A positive C plate can be obtained, for example, by vertically oriented a rod-shaped liquid crystalline compound. Details of the manufacturing method of the positive C plate can be found in, for example, Japanese Patent Publication No. 2017-187732, Japanese Patent Publication No. 2016-053709, and Japanese Patent Publication No. 2015-200861. The positive C plate functions as an optical compensation layer to increase the polarization degree of transmitted light for light incident at an oblique angle. When light is incident on a phase difference film at an oblique angle, the polarization state of the transmitted light may change due to the action of Rth of the phase difference film, and the polarization degree of the transmitted light may decrease. If the phase difference film has a positive C plate, the change in the polarization state of obliquely incident light can be suppressed, and the decrease in the polarization degree of transmitted light can be suppressed.

[0043] The positive C plate used in the phase difference film of the present invention can be placed at any location within the phase difference film. When the phase difference film includes only the first positive C plate as the positive C plate, it is preferable to include the first optical anisotropy layer, the second optical anisotropy layer, and the first positive C plate in this order, but the position of the positive C plate is not limited to this. For example, it may include the first optical anisotropy layer, the first positive C plate, and the second optical anisotropy layer in this order, or it may include the first positive C plate, the first optical anisotropy layer, and the second optical anisotropy layer in this order.

[0044] Furthermore, if the phase difference film includes a first positive C plate and a second positive C plate, it is preferable to include the first optical anisotropy layer, the first positive C plate, the second optical anisotropy layer, and the second positive C plate in this order, but the position of the positive C plate is not limited to this. For example, the first positive C plate, the first optical anisotropy layer, the second positive C plate, and the second optical anisotropy layer may be included in this order, or the first positive C plate, the first optical anisotropy layer, the second optical anisotropy layer, and the second positive C plate may be included in this order.

[0045] Furthermore, if the phase difference film includes a first positive C plate, a second positive C plate, and a third positive C plate, it is preferable that the first positive C plate, the first optical anisotropy layer, the second positive C plate, the second optical anisotropy layer, and the third positive C plate are included in this order.

[0046] The positive C plate used in the phase difference film of the present invention preferably has a Re(550) of 10 nm or less, more preferably 5 nm or less, and even more preferably 1 nm or less. Furthermore, the Rth(550) is preferably -120 nm to -20 nm, more preferably -100 nm to -25 nm, and even more preferably -90 nm to -30 nm. The positive C plate is also preferably inversely dispersive. An inversely dispersive positive C plate can be obtained, for example, by vertically oriented an inversely dispersive rod-shaped liquid crystalline compound. Inversely dispersive positive C plates are preferable because they allow for higher ellipticity over a wider wavelength range, even for oblique incidence. When multiple positive C plates are used, it is preferable that at least one has inversely dispersive properties, and more preferably all have inversely dispersive properties. For example, when using a first positive C plate and a second positive C plate, it is preferable that at least one of them has inversely dispersive properties, and more preferably all have inversely dispersive properties. Furthermore, when using the first positive C plate, the second positive C plate, and the third positive C plate, it is preferable that at least one of them has inverse wavelength dispersion, and it is more preferable that all three have inverse wavelength dispersion. Inverse wavelength dispersion in a positive C plate refers to the characteristic that when the retardation (Rth) value in the thickness direction at a specific wavelength (visible light range) is measured, the absolute value of the Rth value increases as the measured wavelength increases. A positive C plate having inverse wavelength dispersion preferably satisfies Rth(450) / Rth(550) > 1.00 and Rth(650) / Rth(550) < 1.00. Forward wavelength dispersion in a positive C plate refers to the characteristic that when the retardation (Rth) value in the thickness direction at a specific wavelength (visible light range) is measured, the absolute value of the Rth value decreases as the measured wavelength increases. The optically anisotropic layer or phase difference film having forward wavelength dispersion preferably satisfies Rth(450) / Rth(550) < 1.00 and Rth(650) / Rth(550) > 1.00.

[0047] Thus, the phase difference film of the present invention can achieve high ellipticity even for oblique incidence over a wide wavelength range by appropriately arranging each positive C plate in the cases where a first positive C plate is used, where a first positive C plate and a second positive C plate are used, and where a first positive C plate, a second positive C plate, and a third positive C plate are used. Therefore, the phase difference film of the present invention can exhibit excellent performance in virtual reality display devices and other optical devices.

[0048] An example of an embodiment of the phase difference film of the present invention is shown in Figures 5 to 9. Figures 5, 6, and 8 show an embodiment in which the phase difference film has a first positive C plate and a second positive C plate, Figure 7 shows an embodiment in which the phase difference film has a first positive C plate, a second positive C plate and a third positive C plate, and Figure 9 shows an embodiment in which the phase difference film has a first positive C plate. In Figure 5, a first optical anisotropy layer 51, a first positive C plate 52, a high refractive index adhesive 53, a second optical anisotropy layer 54, a second positive C plate 55, an adhesive 56, and a PMMA (polymethyl methacrylate) substrate 57 are laminated in this order. Figure 6 is the same as Figure 5 except that adhesive 56 is used instead of high refractive index adhesive 53. Figure 7 shows the first positive C plate 52, high refractive index adhesive 53, first optical anisotropy layer 51, second positive C plate 55, high refractive index adhesive 53, second optical anisotropy layer 54, third positive C plate 58, adhesive 56, and PMMA substrate 57 stacked in this order. Figure 8 shows the first optical anisotropy layer 51, first positive C plate 52, second optical anisotropy layer 54, second positive C plate 55, adhesive 56, and PMMA substrate 57 stacked in this order. Figure 8 shows an embodiment in which each optical anisotropy layer and each positive C plate are directly stacked. Figure 9 shows the first optical anisotropy layer 51, high refractive index adhesive 53, second optical anisotropy layer 54, first positive C plate 52, adhesive 56, and PMMA substrate 57 stacked in this order. Figure 9 shows an embodiment in which only one positive C plate is included. Adhesive layers, such as adhesives and high refractive index adhesives, as described later, may be appropriately provided between each optical anisotropic layer and each positive C plate. In embodiments including a first optical anisotropic layer, a second optical anisotropic layer, and a first positive C plate, the embodiment is not limited to the embodiment shown in Figure 9, and the adhesive layer only needs to be provided between at least two of the first optical anisotropic layer, the second optical anisotropic layer, and the first positive C plate, and the stacking order can also be appropriately designed.In embodiments including a first optical anisotropy layer, a second optical anisotropy layer, a first positive C plate, and a second positive C plate, the configuration is not limited to the configurations shown in Figures 5-6. The adhesive layer only needs to be present between at least two of the first optical anisotropy layer, the second optical anisotropy layer, the first positive C plate, and the second positive C plate, and the lamination order can be designed as appropriate. In embodiments including a first positive C plate, a first optical anisotropy layer, a second positive C plate, a second optical anisotropy layer, and a third positive C plate, the configuration is not limited to the configuration shown in Figure 7. The adhesive layer only needs to be present between at least two of the first positive C plate, the first optical anisotropy layer, the second positive C plate, the second optical anisotropy layer, and the third positive C plate. As will be described later, it is preferable that the refractive indices of two layers adjacent to the adhesive layer (each optical anisotropy layer, each positive C plate, etc.) and the refractive index of the adhesive layer (high refractive index adhesive, adhesive) satisfy a specific relationship.

[0049] The embodiments of the phase difference film of the present invention are not limited to the above examples. For example, in an embodiment in which the phase difference film has a first positive C plate, the arrangement order of the first optical anisotropy layer 51, the second optical anisotropy layer 54, and the first positive C plate 52 can be appropriately selected as described above, and the first optical anisotropy layer 51, the second optical anisotropy layer 54, and the first positive C plate 52 may all be directly laminated. Furthermore, any of the layers of the first optical anisotropy layer 51, the second optical anisotropy layer 54, and the first positive C plate 52 may be laminated with an adhesive layer in between.

[0050] Furthermore, in an embodiment in which the phase difference film has a first positive C plate and a second positive C plate, the arrangement order of the first optical anisotropy layer 51, the second optical anisotropy layer 54, the first positive C plate 52, and the second positive C plate 55 can be appropriately selected as described above, and the first optical anisotropy layer 51, the second optical anisotropy layer 54, the first positive C plate 52, and the second positive C plate 55 may all be directly laminated. Also, any of the layers of the first optical anisotropy layer 51, the second optical anisotropy layer 54, the first positive C plate 52, and the second positive C plate 55 may be laminated with an adhesive layer in between.

[0051] Furthermore, in an embodiment in which the phase difference film has a first positive C plate, a second positive C plate, and a third positive C plate, the arrangement order of the first optical anisotropy layer 51, the second optical anisotropy layer 54, the first positive C plate 52, the second positive C plate 55, and the third positive C plate 58 can be appropriately selected as described above, and the first optical anisotropy layer 51, the second optical anisotropy layer 54, the first positive C plate 52, the second positive C plate 55, and the third positive C plate 58 may all be directly laminated. Also, any of the layers of the first optical anisotropy layer 51, the second optical anisotropy layer 54, the first positive C plate 52, the second positive C plate 55, and the third positive C plate 58 may be laminated with an adhesive layer in between.

[0052] [Method for Manufacturing Phase Difference Film] (Manufacturing of Phase Difference Film by Bonding Each Layer) The method for manufacturing the phase difference film of the present invention is not particularly limited and can be manufactured based on known methods. A phase difference film may be manufactured by manufacturing the first optical anisotropy layer, the second optical anisotropy layer, and the positive C plate in separate processes, and then bonding them together to form a laminate. Bonding can be performed using an adhesive layer such as an adhesive or tack.

[0053] From the viewpoint of suppressing interfacial reflection, it is preferable that the refractive index of the adhesive layer between each layer be adjusted (refractive index matching) to match the refractive index of the two layers adjacent to the adhesive layer. It is preferable that the refractive index of the adhesive layer is a value between the average in-plane refractive indices of the two layers adjacent to the adhesive layer. Here, for the first optical anisotropy layer and the second optical anisotropy layer, the average in-plane refractive index can be defined as the average value of the anomalous principal refractive index (ne) and the normal principal refractive index (no) of the liquid crystalline compound constituting the optical anisotropy layer. Furthermore, it can be assumed that the average in-plane refractive index of the positive C plate coincides with the normal principal refractive index (no) of the liquid crystalline compound constituting the positive C plate. In addition, the above refractive index relationship only needs to hold at any wavelength in the visible range, but the wavelength may be set according to the wavelength to be used. For example, it is preferable that the above relationship holds at a wavelength of 550 nm. It is preferable that the above refractive index relationship holds because it can suppress interfacial reflection between each layer and improve the ellipticity of the light obtained using the phase difference film. The refractive index of the adhesive layer is not particularly restricted as long as the above-mentioned refractive index relationship is satisfied. However, if the adjacent optical anisotropy layer or positive C plate is a liquid crystalline compound, the refractive index range of the liquid crystalline compound is generally around 1.51 to 1.60, so it is preferable that the refractive index of the adhesive layer be 1.51 to 1.60.

[0054] The refractive indices of the optically anisotropic layer, positive C plate, and adhesive layer can be measured using an Abbe refractive system, spectroscopic ellipsometer, etc. Alternatively, the reflectance of p-waves and s-waves on the surface can be measured using a specular reflectance meter, and the in-plane refractive index can be calculated based on the measured reflectances.

[0055] There are no particular restrictions on the type of adhesive layer, but adhesives or tacks can be used. Examples of high refractive index adhesives include acrylic adhesives and epoxy adhesives. Examples of high refractive index tacks include acrylic adhesives, silicone adhesives, urethane adhesives, epoxy adhesives, and polyimide adhesives. For example, Japanese Patent Application Publication No. 2010-196064 discloses an acrylic adhesive with a refractive index of 1.49 to 1.60.

[0056] The thickness of the adhesive layer can be set arbitrarily, but from the viewpoint of reducing the thickness of the phase difference film and improving the smoothness of the phase difference film, it is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 5 μm or less. Furthermore, if the adhesive layer is an adhesive, a thickness of 3 μm or more is preferable from the viewpoint of obtaining sufficient adhesive strength. If the adhesive layer is an adhesive, sufficient adhesive strength can be obtained even if the adhesive layer is 3 μm or less. In addition, if the thickness of the adhesive layer is 100 nm or less, visible light does not perceive the refractive index difference, and interfacial reflection can be suppressed more effectively, so a thickness of 100 nm or less is preferable.

[0057] One method for forming an adhesive layer with a thickness of 100 nm or less is to deposit a ceramic adhesive, such as a silicon dioxide (SiOx) layer, onto the adhesive surface of an optically anisotropic layer or a positive C plate. The adhesive surface can be subjected to surface modification treatments such as plasma treatment, corona treatment, and saponification treatment before bonding, and a primer layer can also be applied. Furthermore, if there are multiple adhesive surfaces, the type and thickness of the adhesive layer can be adjusted for each surface.

[0058] Specifically, an adhesive layer with a thickness of 100 nm or less can be provided by, for example, the following procedure: (1) The layers to be laminated are bonded to a temporary support made of a glass substrate. (2) A SiOx layer with a thickness of 100 nm or less is formed on both the surface of the layer to be laminated and the surface of the layer to be laminated by vapor deposition or the like. Vapor deposition can be carried out using SiOx powder as the deposition source, for example, using a vapor deposition apparatus (model number ULEYES) manufactured by ULVAC, Inc. It is also preferable to apply plasma treatment to the surface of the formed SiOx layer. (3) After bonding the formed SiOx layers together, the temporary support is peeled off. Adhesion is preferably carried out at a temperature of, for example, 120°C.

[0059] The application of adhesives and tacks to each layer, the formation of adhesive layers such as the SiOx layer, and bonding may be carried out by roll-to-roll or sheet-fed methods. The roll-to-roll method is preferred from the viewpoint of improving productivity and reducing misalignment of each layer. On the other hand, the sheet-fed method is preferred because it is suitable for small-volume, high-mix production and because it allows for the selection of special bonding methods, such as those described above, where the thickness of the adhesive layer is 100 nm or less. Examples of known methods for applying adhesives and tacks to the substrate include roll coating, gravure printing, spin coating, wire bar coating, extrusion coating, direct gravure coating, reverse gravure coating, die coating, spraying, and inkjet.

[0060] (Manufacturing of phase difference film by direct lamination of each layer) In the phase difference film of the present invention, it is also preferable that there are no adhesive layers between each layer. A phase difference film without adhesive layers between each layer can be manufactured by directly applying the composition for forming the other optical anisotropic layer or positive C plate onto an already formed optical anisotropic layer or positive C plate. It is preferable that there are no adhesive layers because it is possible to suppress interfacial reflection between each layer and improve the ellipticity of the light rays transmitted through the phase difference film. In an embodiment including a first optical anisotropic layer, a second optical anisotropic layer and a first positive C plate, it is preferable that each optical anisotropic layer and the first positive C plate are directly laminated, and the lamination order can be designed as appropriate. In an embodiment including a first optical anisotropic layer, a second optical anisotropic layer, a first positive C plate and a second positive C plate, it is preferable that each optical anisotropic layer and each positive C plate are directly laminated, and the lamination order can be designed as appropriate. In an embodiment including a first positive C plate, a first optically anisotropic layer, a second positive C plate, a second optically anisotropic layer, and a third positive C plate, it is preferable to directly laminate them in this order.

[0061] Furthermore, when the first optical anisotropic layer and the second optical anisotropic layer are directly laminated, it is preferable that both layers contain a liquid crystalline compound. In this case, it is preferable to form the layers so that the orientation direction of the liquid crystalline compound changes continuously at the interface between the first optical anisotropic layer and the second optical anisotropic layer, thereby reducing the refractive index difference in all directions within the plane and suppressing interfacial reflection. For example, by directly applying a composition for forming a second optical anisotropic layer containing a liquid crystalline compound to a first optical anisotropic layer containing a liquid crystalline compound, the orientation-regulating force of the liquid crystalline compound in the first optical anisotropic layer can cause the liquid crystalline compound on the surface of the second optical anisotropic layer facing the first optical anisotropic layer to be oriented in a direction substantially parallel to the orientation direction of the liquid crystalline compound in the first optical anisotropic layer, so that the orientation directions of the liquid crystalline compounds in both layers are continuous at the interface.

[0062] (Manufacturing of phase difference film by one-component two-layer coating) Alternatively, the first optical anisotropy layer and the second optical anisotropy layer can be formed by coating the same forming composition and then separating it into two layers by various methods, with each becoming the first optical anisotropy layer and the second optical anisotropy layer. For example, they can be produced by the following steps 1 to 5. Step 1: A step of coating a polymerizable liquid crystal composition containing a chiral agent that contains a photosensitive chiral agent whose helical induced force changes upon light irradiation, and a reverse wavelength dispersive liquid crystal compound having polymerizable groups (hereinafter, in the description of steps 1 to 5, it will also simply be referred to as "liquid crystal compound") onto a support to form a composition layer. Step 2: A step of heating the composition layer to orient the liquid crystal compound in the composition layer. Step 3: After step 2, a step of irradiating the composition layer with light under conditions of an oxygen concentration of 1 volume% or more. Step 4: After step 3, a step of heating the composition layer. Step 5: After step 4, the composition layer is subjected to a curing treatment to fix the orientation of the liquid crystalline compound and form a first optical anisotropy layer and a second optical anisotropy layer. The above-described process for manufacturing a phase difference film can refer to, for example, the process disclosed in International Publication No. 2021 / 261435.

[0063] The shape of the phase difference film may be flat or curved. In a virtual reality display device, in order to correct aberrations in the displayed image and achieve higher quality display, it is preferable to make the surface shape of the lens substrate curved, and in this case, it is also preferable to make the phase difference film curved to match the surface shape of the lens substrate.

[0064] [Optical Interference Layer] The phase difference film of the present invention may include other functional layers internally (between each layer) or on the surface, as long as they do not impair the optical properties. For example, it is preferable to have an optical interference layer to suppress interfacial reflection.

[0065] The optical interference layer may consist of a single layer, or it may be constructed by laminating two or more optical interference layers using methods such as bonding or sequential formation. The thickness of the single layer of optical interference is preferably in the range of 60 nm to 110 nm or 230 nm to 330 nm, more preferably in the range of 75 nm to 100 nm or 245 nm to 300 nm, and most preferably in the range of 80 nm to 95 nm or 260 nm to 285 nm.

[0066] For optically anisotropic layers, positive C plates, and adhesive layers having arbitrary refractive indices, the preferred range of the optical interference layer can be generalized using the average refractive index of adjacent layers under the following conditions: That is, if the refractive index of one layer adjacent to the optical interference layer is nA and the average refractive index of the other layer is nL, then the refractive index nI of the optical interference layer is (nA × nL). １／２ -0.03 ≤ nI ≤ (nA × nL) １／２ It is preferable that it be +0.03, (nA × nL) １／２ -0.02 ≤ nI ≤ (nA × nL) １／２ It is more preferable that it be +0.02, (nA × nL) １／２ -0.01 ≤ nI ≤ (nA × nL) １／２ A refractive index of +0.01 is most preferable. By setting the refractive index of the optical interference layer within this range, the amplitude reflectance on both sides of the optical interference layer can be made to be of roughly the same magnitude, thereby effectively suppressing interfacial reflection. When using general liquid crystal materials and adhesive layers, the refractive index of the optical interference layer is preferably 1.50 to 1.70, and more preferably 1.53 to 1.59.

[0067] Materials that form the optical interference layer can include hard coat materials with crosslinked monomers and photoalignment films. Of these, photoalignment films are preferred because they also play a role in aligning liquid crystals when forming an optical anisotropy layer on top of them using liquid crystal materials.

[0068] [Other Functional Layers] The phase difference film of the present invention may be laminated with other functional layers and provided as a laminated optical body. Examples of other functional layers include polarizers such as reflective linear polarizers, reflective circular polarizers, and absorptive linear polarizers. By laminating polarizers, various optical functions of the virtual reality display device can be integrated. This reduces manufacturing costs by requiring only one step in attaching the laminated optical body to the image display device or lens substrate.

[0069] As reflective linear polarizers, for example, films made by stretching a dielectric multilayer film and wire grid polarizers can be used. As reflective circular polarizers, for example, reflective circular polarizers containing a cholesteric liquid crystal layer can be used. The cholesteric liquid crystal layer is a layer having a liquid crystal phase (cholesteric liquid crystal phase) in which the liquid crystal compound is in a cholesteric orientation state. As reflective circular polarizers having a cholesteric liquid crystal layer, films obtained by curing a liquid crystalline compound while exhibiting a cholesteric liquid crystal phase can be suitably used. As absorbing polarizers, polarizers made by stretching a polyvinyl alcohol film and impregnating it with an iodine complex, and polarizers containing a dichroic dye in a stretched polymer or a uniformly oriented liquid crystalline compound can be used.

[0070] Furthermore, the laminated optical body may have functional layers different from those of the polarizer described above, for the purpose of further improving its optical properties. Examples of functional layers include anti-reflective layers, ultraviolet absorbing layers, shock absorbing layers, and hard coat layers. It is also preferable for the laminated optical body to have these functional layers.

[0071] [Support] The phase difference film of the present invention may further have a support. The support can be installed at any location, for example, if the phase difference film is a film that is transferred from a temporary support, the support can be used as the transfer destination.

[0072] The type of support is not particularly limited, but it is preferably transparent. Specifically, films such as cellulose acetate, polycarbonate, polysulfone, polyethersulfone, polyacrylate and polymethacrylate, cyclic polyolefin, polyolefin, polyamide, polystyrene, and polyester can be used. Among these, cellulose acetate film, cyclic polyolefin film, polyacrylate film, and polymethacrylate film are preferred. Commercially available cellulose acetate films (for example, "TD80U" and "Z-TAC" manufactured by Fujifilm Corporation) can also be used.

[0073] From the viewpoint of suppressing the influence on the polarization degree of transmitted light and facilitating optical inspection of the multilayer optical body, it is preferable that the support has a small phase difference. Specifically, it is preferable that the size of Re is 10 nm or less, and the absolute value of the size of Rth is 50 nm or less.

[0074] When a laminated optical body is stretched or molded, the support preferably has a tanδ peak temperature of 170°C or lower. From the viewpoint of enabling molding at low temperatures, the tanδ peak temperature is preferably 150°C or lower, and more preferably 130°C or lower.

[0075] Here, we describe the method for measuring tanδ. Using a dynamic viscoelasticity measuring device (DVA-200 manufactured by IT Measurement Control Co., Ltd.), a film sample that has been pre-conditioned for more than 2 hours at a temperature of 25°C and a humidity of 60% Rh is used to measure E'' (loss modulus) and E' (storage modulus) under the following conditions, and use these values ​​to determine tanδ (= E'' / E'). Device: DVA-200 manufactured by IT Measurement Control Co., Ltd. Sample: 5 mm, length 50 mm (gap 20 mm) Measurement conditions: Tensile mode Measurement temperature: -150°C to 220°C Heating rate: 5°C / min Frequency: 1 Hz In general, in optical applications, stretched resin substrates are often used, and the stretching treatment often results in a high peak temperature for tanδ. For example, the peak temperature of tanδ for TAC (triacetylcellulose) substrate (TG40, manufactured by Fujifilm Corporation) is 180°C or higher.

[0076] Supports with a tanδ peak temperature of 170°C or lower can use a variety of resin substrates without particular limitations. Examples include polyolefins such as polyethylene, polypropylene, and norbornene polymers; cyclic olefin resins; polyvinyl alcohol; polyethylene terephthalate; acrylic resins such as polymethacrylate and polyacrylic acid esters; polyethylene naphthalate; polycarbonate; polysulfone; polyethersulfone; polyetherketone; and polyphenylene sulfide and polyphenylene oxide. Among these, cyclic olefin resins, polyethylene terephthalate, or acrylic resins are preferred due to their readily available market availability and excellent transparency, and cyclic olefin resins or polymethacrylate esters are more preferred.

[0077] Examples of commercially available resin substrates include Technoloy S001G, Technoloy S014G, Technoloy S000, Technoloy C001, Technoloy C000 (Sumika Acrylic Sales Co., Ltd.), Lumirror U-type, Lumirror FX10, Lumirror SF20 (Toray Industries, Inc.), HK-53A (Higashiyama Film Co., Ltd.), Teflex FT3 (Teijin DuPont Films Ltd.), SCSina and SCA40 (Sekisui Chemical Co., Ltd.), Zeonor Film (Optes Co., Ltd.), and Arton Film (JSR Corporation).

[0078] The thickness of the support is not particularly limited, but is preferably 5 to 300 μm, more preferably 5 to 100 μm, and even more preferably 5 to 30 μm.

[0079] <Image Display Device> The image display device of the present invention comprises an absorptive linear polarizer and a phase difference film of the present invention. The image display device may have an image display panel, and examples of image display panels include liquid crystal display panels, organic EL display panels, and micro-LED display panels.

[0080] The image display device of the present invention may have an image display panel, a phase difference film of the present invention, and an absorbing linear polarizer in this order. That is, the phase difference film and the absorbing linear polarizer may be located on the display surface side of the image display panel. In this case, the phase difference film of the present invention can provide excellent anti-reflective properties for external light incident from the front and obliquely. In this case, the phase difference film is arranged in such a way that the first optical anisotropy layer and the second optical anisotropy layer are arranged from the side of the absorbing linear polarizer (opposite the image display panel).

[0081] Furthermore, the image display device of the present invention may have the phase difference film of the present invention on the side opposite to the image display panel relative to the absorbing linear polarizer. In this case, the phase difference film of the present invention can convert the light emitted from the image display device into circularly polarized light with high ellipticity. Such an image display device can be suitably used as an image display device for virtual reality display devices and augmented reality display devices employing pancake lenses. In this case, the phase difference film is arranged in a direction such that the first optical anisotropy layer and the second optical anisotropy layer are in that order from the absorbing linear polarizer side (image display panel side).

[0082] Furthermore, the image display device of the present invention may include, in addition to the phase difference film of the present invention, known components for image display devices such as an anti-reflective layer, an ultraviolet absorbing layer, an impact absorbing layer, an anti-fingerprint layer, and a hard coat layer.

[0083] <Lens> The lens of the present invention comprises the phase difference film of the present invention and a reflective linear polarizer.

[0084] The lens of the present invention may have a lens substrate, and it is preferable that it has a lens substrate. Glass or transparent resin is preferred as the material of the lens substrate. It is preferable that the lens substrate does not change the polarization state of the light rays, and it is desirable that the phase difference (Re and Rth) is zero. Furthermore, the lens of the present invention may be a combination of multiple lens substrates.

[0085] The lens may have layers other than the phase difference film, reflective linear polarizer, and lens substrate of the present invention. Examples of other layers include a half mirror, an anti-reflective layer, an ultraviolet absorbing layer, and a hard coat layer. Examples of half mirrors include a vapor-deposited film of a metal such as aluminum.

[0086] The lens may also further include an absorptive linear polarizer. The reflective linear polarizer and the absorptive linear polarizer may be included in the laminated optical system provided together with the phase difference film. Furthermore, if the lens consists of a combination of multiple lens substrates, the phase difference film, the reflective linear polarizer, and the absorptive linear polarizer of the present invention may each be bonded to a separate lens substrate.

[0087] Specific examples of the lens configuration of the present invention are as follows: • A lens having a reflective linear polarizer, the phase difference film of the present invention, a lens substrate, and a half mirror in that order. • A lens having an absorptive linear polarizer, a reflective linear polarizer, the phase difference film of the present invention, a lens substrate, and a half mirror in that order. • A lens having the phase difference film of the present invention, a reflective linear polarizer, an absorptive linear polarizer, and a lens substrate in that order. Preferred embodiments of each component included in the above configuration examples are as described above.

[0088] In the lens of the present invention, the phase difference film is arranged in such a way that the first optical anisotropy layer and the second optical anisotropy layer are in that order from the reflective linear polarizer side.

[0089] The shape of the lens substrate is not particularly limited, but it is preferable that at least one surface is curved. When the lens substrate has a curved surface, aberrations in the displayed image can be corrected in a virtual reality display device, resulting in a higher quality display. The curved surface may be part of a sphere or an aspherical surface.

[0090] As lens substrates, convex lenses, concave lenses, and meniscus lenses can be used. As convex lenses, biconvex lenses, plano-convex lenses, and convex meniscus lenses can be used. As concave lenses, biconcave lenses, plano-concave lenses, and concave meniscus lenses can be used.

[0091] The lens of the present invention can be suitably used as a pancake lens in a virtual reality display device.

[0092] Figure 1 schematically shows an example of the configuration of the image display device and the virtual reality display device using the lens of the present invention. The virtual reality display device 1 shown in Figure 1 has a lens 2 and an image display device 3. The lens 2 has a reflective linear polarizer 21, a first phase difference film 22, a lens substrate 23, and a half mirror 24 in that order. The image display device 3 has a second phase difference film 31, an absorptive linear polarizer 32, and an image display panel 33. In the example shown in Figure 1, the lens 2 is positioned so that the half mirror 24 side faces the second phase difference film 31 side of the image display device 3.

[0093] In the virtual reality display device 1 shown in Figure 1, both the first phase difference film 22 and the second phase difference film 31 are phase difference films of the present invention. That is, the lens 2 shown in Figure 1 is an example of the lens configuration of the present invention, and the image display device 3 is an example of the image display device configuration of the present invention.

[0094] To explain the operation of the image display device and the virtual reality display device using the lens of the present invention, Figure 2 schematically shows an example of the configuration of a conventional virtual reality display device. The virtual reality display device 1000 shown in Figure 2 has, from left to right in the figure, a reflective linear polarizer 100, a first phase difference layer 200, a lens substrate 600, a half mirror 300, a second phase difference layer 400, and an image display device 500.

[0095] The virtual reality display device 1000 can reduce the overall thickness of the headset by folding light rays using the following mechanism. Specifically, a light ray 10, which is part of the light rays emitted from the image display device 500, is converted to circular polarization by the second phase difference layer 400, then passes through the half mirror 300, is converted to linear polarization by the first phase difference layer 200, and then incident on the reflective linear polarizer 100 and reflected. After that, the light ray 10 passes through the first phase difference layer 200 again, is converted to circular polarization, and is reflected by the half mirror 300. At this time, the polarization state of the light ray 10 is converted to an orthogonal polarization state. The light ray 10 reflected by the half mirror 300 then passes through the first phase difference layer 200 again, is converted to linear polarization, and is incident on the reflective linear polarizer 100. At this time, the light rays incident on the reflective linear polarizer 100 are in a polarization state perpendicular to the polarization state when they first entered the reflective linear polarizer 100, so they pass through the reflective linear polarizer 100 and the light rays 10 are delivered to the user's eyes. In this way, the virtual reality display device 1000 can reduce the overall thickness of the headset by folding the light rays 10 between the half mirror 300 and the reflective linear polarizer 100.

[0096] First, the operation of the image display device of the present invention will be explained.

[0097] According to the inventors' studies, as shown in Figure 3, in the conventional virtual reality display device 1000, a portion of the light rays (light rays 11) emitted from the image display device 500 are emitted without being refolded between the half mirror 300 and the reflective linear polarizer 100, and may be perceived as a ghost image. The inventors believe that the cause of this is that some of the light rays emitted from the image display device 500, within a certain wavelength range, are not converted into perfectly linearly polarized light when they pass through the second phase difference layer 400, then the half mirror 300, and then the first phase difference layer 200, but become elliptically polarized light. The reason why the light rays become elliptically polarized is thought to be that the in-plane phase difference (Re) of the first phase difference layer 200 and the second phase difference layer 400 are different, or that the slow axis orientations of the first phase difference layer 200 and the second phase difference layer 400 are not orthogonal to each other. In other words, because the wavelength dispersion characteristics of the second phase difference layer 400 are not ideal, the ellipticity of some of the light rays transmitted through the second phase difference layer 400 becomes low, and the ellipticity of the light obtained for linearly polarized light incident at an oblique angle also becomes low. Even in this case, if the in-plane phase difference (Re) of the first phase difference layer 200 and the second phase difference layer 400 are exactly the same, and the lagging axis orientations of the first phase difference layer 200 and the second phase difference layer 400 are exactly orthogonal to each other, the light will be converted to perfectly linearly polarized light when transmitted through the first phase difference layer 200. However, since precise angle adjustment is difficult, it is thought that the light becomes elliptically polarized when transmitted through the first phase difference layer 200. As a result, some of the light rays are visible as ghost images.

[0098] In contrast, the image display device 3 of the present invention includes an absorbing linear polarizer 32, an image display panel 33, and a second phase difference film 31, which is the phase difference film of the present invention. Since the phase difference film of the present invention can make the in-plane phase difference λ / 4 phase difference over a wide wavelength range of visible light, the second phase difference film 31 can convert linearly polarized light to circularly polarized light with high ellipticity, and can also convert circularly polarized light to linearly polarized light over a wide wavelength range of visible light.

[0099] In an image display device 3 having such a second phase difference film 31, the light ray 10 emitted from the image display panel 33 and transmitted through the absorbing linear polarizer 32, the second phase difference film 31, and the half mirror 24 becomes ideally circularly polarized over a wide wavelength range in the visible region. Therefore, the light ray 10 is converted to ideally linearly polarized light by the first phase difference film 22, incident on the reflective linear polarizer 21, reflected, and folded back between the half mirror 24 and the reflective linear polarizer 21. As a result, in the virtual image display device 1 of the present invention, it is possible to reduce the amount of light rays (light rays 11 shown in Figure 3) that are emitted without traveling back and forth between the reflective linear polarizer 21 and the half mirror 24 and become ghost images.

[0100] Furthermore, the light rays that pass through the half-mirror 24 on the first pass and reach the first phase difference film 22 are ideally circularly polarized over a wide wavelength range of visible light and have no polarization axis. Therefore, when assembling the lens 2 having the reflective linear polarizer 21 and the first phase difference film 22, the ghost image does not increase even if the lagging axis orientation of the first phase difference film 22 is not perpendicular to the lagging axis orientation of the second phase difference film 31. In other words, when manufacturing the virtual reality display device 1 to which the image display device 3 is applied, precise angle adjustment when assembling the lens 2 becomes unnecessary, thus greatly simplifying the lens assembly process. Furthermore, this can contribute to reducing the manufacturing cost of the virtual reality display device. Moreover, the phase difference film of the present invention can convert linearly polarized light incident at an oblique angle into circularly polarized light with high ellipticity. In virtual reality display devices using pancake lenses, there are also light rays that are emitted from the image display device at a large angle, and these can produce ghost images, but the image display device using the phase difference film of the present invention can effectively suppress ghost images caused by such light rays.

[0101] Next, the operation of the lens of the present invention will be described.

[0102] According to the inventors' investigation, as shown in Figure 4, in the conventional virtual reality display device 1000, a portion of the light rays (light rays 12) emitted from the image display device 500 sometimes travel back and forth between the half mirror 300 and the reflective linear polarizer 100 two or more times, resulting in the appearance of a ghost image. The inventors believe that the cause of this is that some of the light rays (linearly polarized) reflected by the reflective linear polarizer 100, within a certain wavelength range, are not converted to perfectly circular polarization when transmitted through the first phase difference layer 200, but instead become elliptically polarized. When the light rays emitted from the first phase difference layer 200 are elliptically polarized, they are reflected by the half mirror 300 and, upon re-transmission through the first phase difference layer 200, contain a component parallel to the reflection axis of the reflective linear polarizer 100. This component is then reflected again by the reflective linear polarizer 100, resulting in the generation of light rays 12 that travel back and forth repeatedly.

[0103] In contrast, the lens 2 of the present invention has a first phase difference film 22, which is the phase difference film of the present invention. Since the phase difference film of the present invention can make the in-plane phase difference λ / 4 phase difference over a wide wavelength range of visible light, the first phase difference film 22 can convert linearly polarized light to ideal circularly polarized light and also convert circularly polarized light to ideal linearly polarized light over a wide wavelength range of visible light.

[0104] In a lens 2 having such a first phase difference film 22, linearly polarized light reflected from the reflective linear polarizer 21 is converted into ideal circularly polarized light over a wide wavelength range in the visible region when it passes through the first phase difference film 22. Next, when reflected by the half mirror 24, the light ray is converted into orthogonal circularly polarized light, which is also ideally circularly polarized. Furthermore, the light ray that has passed through the first phase difference film 22 again is converted into ideal linearly polarized light and passes through the reflective linear polarizer 21 with high efficiency. That is, it is possible to reduce the number of light rays that travel back and forth between the reflective linear polarizer 21 and the half mirror 24 two or more times (light rays 12 shown in Figure 4), and the generation of ghost images can be suppressed. Furthermore, the phase difference film of the present invention can also convert linearly polarized light that is incident at an oblique angle into circularly polarized light with high ellipticity. In virtual reality display devices using pancake lenses, light rays may be incident at a very large angle to the lens surface, which can cause ghost images, but the lens using the phase difference film of the present invention can effectively suppress ghost images caused by such light rays.

[0105] Furthermore, when forming a phase difference film to bond it to a curved surface of a lens substrate, the phase difference may change or the axis may shift due to the stretching of the phase difference film during forming, which can reduce the ellipticity of the resulting circularly polarized light. In contrast, the phase difference film of the present invention suppresses the reduction in ellipticity because, even when changes in film thickness occur due to forming and stretching, the orbital changes between the first optical anisotropy layer and the second optical anisotropy layer on the Poincaré sphere cancel each other out.

[0106] As described above, the phase difference film of the present invention is particularly useful in various optical devices, such as virtual reality display devices and augmented reality display devices, due to its configuration and characteristics. By devising the combination and arrangement of each layer, it is possible to achieve excellent optical properties over a wide wavelength range and realize high-quality display performance.

[0107] The features of the present invention will be further described in detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown below can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Furthermore, configurations other than those shown below are also possible, as long as they do not depart from the spirit of the present invention.

[0108] [Preparation of Cellulose Acylate Film] (Preparation of Core Layer Cellulose Acylate Dope) The following composition was placed in a mixing tank and stirred to dissolve each component, and a cellulose acetate solution to be used as the core layer cellulose acylate dope was prepared. --------------------------------------------------- Core Layer Cellulose Acylate Dope --------------------------------------------------- ・Cellulose acetate with acetyl substitution degree of 2.88 100 parts by mass ・Polyester compound B described in the examples of Japanese Patent Application Publication No. 2015-227955 12 parts by mass ・Compound F below 2 parts by mass ・Methylene chloride (first solvent) 430 parts by mass ・Methanol (second solvent) 64 parts by mass ---------------------------------------------------

[0109] Compound F

[0110]

[0111] (Preparation of outer layer cellulose acylate dope) 10 parts by mass of the following mat agent solution were added to 90 parts by mass of the above core layer cellulose acylate dope to prepare a cellulose acetate solution to be used as the outer layer cellulose acylate dope.

[0112] --------------------------------------------------------------------------- Mat Solution --------------------------------------------------------------------------- Silica particles with an average particle size of 20 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass Methylene chloride (first solvent) 76 parts by mass Methanol (second solvent) 11 parts by mass Cellulose acylate dope for the above core layer 1 part by mass --------------------------------------------------------------------------- Mat Solution --------------------------------------------------------------------------- Silica particles with an average particle size of 20 nm (AEROSIL R972, manufactured by Nippon Aerosil Co., Ltd.) 2 parts by mass Methylene chloride (first solvent) 76 parts by mass Methanol (second solvent) 11 parts by mass Cellulose acylate dope for the above core layer 1 part by mass

[0113] (Preparation of Cellulose Acrylate Film 1) The core layer cellulose acylate dope and the outer layer cellulose acylate dope were filtered using filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm. Then, the core layer cellulose acylate dope and the outer layer cellulose acylate dope on both sides were simultaneously cast from the casting port onto a drum at 20°C (band casting machine). Next, the film was peeled off when the solvent content was approximately 20% by mass, and both ends in the width direction of the film were fixed with tenter clips. The film was then dried while being stretched transversely at a stretching ratio of 1.1 times. After that, it was further dried by being transported between the rolls of a heat treatment device to produce an optical film with a thickness of 40 μm, which was used as Cellulose Acrylate Film 1 to be used as a temporary support for a specific phase difference layer. The in-plane phase difference of the obtained Cellulose Acrylate Film 1 was 0 nm.

[0114] [Formation of Phase Difference Film] (Formation of the Second Optical Anisotropic Layer) The cellulose acylate film 1 prepared above was used as a temporary support. The photo-alignment film forming coating solution E1 with the following composition was continuously applied to the cellulose acylate film 1 using a wire bar. The support with the coated film was dried with 140°C hot air for 120 seconds, and then polarized ultraviolet light was irradiated onto the coating film (10 mJ / cm²). ２ By using an ultra-high pressure mercury lamp, a photo-alignment film E1 with a thickness of 0.2 μm was formed, and a film with a photo-alignment film was obtained.

[0115] ------------------------------------------------------------------- Photo-alignment film forming coating solution E1 ------------------------------------------------------------------- ・100.00 parts by mass of the polymer PA-2 below ・5.00 parts by mass of the acid generator PAG-1 below ・0.005 parts by mass of the acid generator CPI-110TF below ・16.50 parts by mass of isopropyl alcohol ・1072.00 parts by mass of butyl acetate ・268.00 parts by mass of methyl ethyl ketone -------------------------------------------------------------------

[0116] Acid Generator CPI-110TF

[0117] Spray PA-2

[0118] Acid Generator PAG-1

[0119]

[0120] An optically anisotropic layer coating solution (A) with the following composition was applied onto the photo-alignment film E1 using a bar coater and heated at 80°C for 60 seconds. Afterward, the film with the coating was subjected to an irradiation dose of 500 mJ / cm² at 80°C under a nitrogen atmosphere. ２ By irradiating the material with light from a metal halide lamp (manufactured by iGraphics Co., Ltd.), the orientation of the liquid crystalline compound was fixed, and a second optically anisotropic layer A2 was fabricated. The product of Δn and d at a wavelength of 550 nm, Δnd, of the second optically anisotropic layer A2 was 194 nm, indicating inverse wavelength dispersion. The twist angle of the second optically anisotropic layer A2 was 85°, indicating a right-hand twist. The thickness of the second optically anisotropic layer A2 was 4.1 μm. Furthermore, the molecular axis of the liquid crystalline compound was horizontal to the surface of the cellulose acylate film (or the surface of the optically anisotropic layer).

[0121] Composition of the optically anisotropic layer coating solution (A) -------------------------------------------------- 40 parts by mass of the following rod-shaped liquid crystalline compound (A) 40 parts by mass of the following rod-shaped liquid crystalline compound (B) 20 parts by mass of the following rod-shaped liquid crystalline compound (C) 4 parts by mass of ethylene oxide-modified trimethylolpropane triacrylate (V#360, manufactured by Osaka Organic Chemical Co., Ltd.) 3 parts by mass of photopolymerization initiator (Irgacure 819, manufactured by Ciba Japan) 0.46 parts by mass of the following chiral agent (A) 0.5 parts by mass of the following polymerizable polymer (X) 0.1 parts by mass of the following polymer (A) 325 parts by mass of methyl isobutyl ketone --------------------------------------------------

[0122] Rod-shaped liquid crystalline compound (A) (In the formula below, t-Bu represents a tert-butyl group.)

[0123]

[0124] Rod-shaped liquid crystal compound (B)

[0125]

[0126] Rod-shaped liquid crystalline compound (C) (hereinafter referred to as a mixture of liquid crystalline compounds. A mixture of the following liquid crystalline compounds (RA), (RB), and (RC) in a mass ratio of 83:15:2, where Me represents a methyl group.)

[0127]

[0128] Chiral agent (A)

[0129]

[0130] Polymerizable polymer (X)

[0131]

[0132] Polymer (A)

[0133]

[0134] (Formation of first optically anisotropic layer) A film with a photo-alignment layer, in which a photo-alignment layer E1 with a thickness of 0.2 µm was formed on a cellulose acylate film 1 in the same manner as described above, was prepared. Next, a coating liquid obtained by removing the chiral agent (A) from the above optically anisotropic layer coating liquid (A) was applied onto the photo-alignment layer E1 using a bar coater, and heated at 80° C. for 60 seconds. Thereafter, under a nitrogen atmosphere, the film on which the coating film was formed was irradiated at 80° C. with an irradiation dose of 500 mJ / cm ２ of light from a metal halide lamp (manufactured by Eyegraphics Co., Ltd.) to fix the alignment state of the liquid crystal compound, thereby producing the first optically anisotropic layer A1. The first optically anisotropic layer A1 was a positive A plate having a product Δnd of Δn and d of 205 nm at a wavelength of 550 nm, and had reverse wavelength dispersion. Further, the thickness of the first optically anisotropic layer A1 was 4.4 µm.

[0135] (Formation of positive C plate) Next, the first optically anisotropic layer A1 was subjected to a discharge amount of 150 W·min / m ２ After performing corona treatment with , a positive C plate coating liquid (C) having the following composition was applied onto the corona-treated surface using a bar coater, and heated at 80° C. for 60 seconds. Thereafter, under a nitrogen atmosphere, the film on which the coating film was formed was irradiated at 80° C. with an irradiation dose of 500 mJ / cm ２ of light from a metal halide lamp (manufactured by Eyegraphics Co., Ltd.) to fix the alignment state of the liquid crystal compound, thereby producing a first positive C plate C1. The Rth of the first positive C plate C1 at a wavelength of 550 nm was -55 nm, and the first positive C plate C1 had reverse wavelength dispersion. Further, the thickness of the first positive C plate C1 was 1.1 µm.

[0136] Composition of coating solution (C) for positive C plate ---------------------------------------------------------------- ・The above rod-shaped liquid crystalline compound (A) 19.2 parts by mass ・The above rod-shaped liquid crystalline compound (B) 19.2 parts by mass ・The above rod-shaped liquid crystalline compound (C) 50.5 parts by mass ・Ethylene oxide modified trimethylolpropane triacrylate (V#360, manufactured by Osaka Organic Chemical Co., Ltd.) 6.2 parts by mass ・Photopolymerization initiator (Irgacure 819, manufactured by Ciba Japan Co., Ltd.) 2.3 parts by mass ・The following additive (L) 2.3 parts by mass ・The above polymer (A) 0.3 parts by mass ・Methyl ethyl ketone 90 parts by mass ・Cyclopentanone 210 parts by mass ----------------------------------------------------------------

[0137] Additives (L)

[0138]

[0139] Similarly, the second optically anisotropic layer A2 has a discharge rate of 150 W·min / m ２ After corona treatment, the above-mentioned coating solution (C) for positive C plates was applied to the corona-treated surface using a bar coater and heated at 80°C for 60 seconds. Subsequently, the film with the formed coating was irradiated at 80°C with an irradiation dose of 500 mJ / cm² under a nitrogen atmosphere. ２ By irradiating the crystalline compound with light from a metal halide lamp (manufactured by I-Graphics Co., Ltd.), the orientation state was fixed, and a second positive C plate C2 was fabricated. The Rth of the second positive C plate C2 at a wavelength of 550 nm was -35 nm, indicating inverse wavelength dispersion. The thickness of the second positive C plate C2 was 0.7 μm.

[0140] (Preparation of Phase Difference Film 1) A laminate of the second optical anisotropy layer A2 and the second positive C plate C2 was bonded to a PMMA film "Technoloy S001G" manufactured by Sumika Acrylic Sales Co., Ltd. using an adhesive sheet "NCF-D692(5)" manufactured by Lintec Corporation, with the second positive C plate C2 side adjacent to Technoloy S001G, and the temporary support was peeled off. Next, a laminate of the first optical anisotropy layer A1 and the first positive C plate C1 was bonded to the surface of the second optical anisotropy layer A2 using a high refractive index adhesive, with the first positive C plate C1 side adjacent to the second optical anisotropy layer A2, and the temporary support was peeled off. In this way, a phase difference film 1 to be used as Example 1 was obtained. The phase difference film 1 was laminated in the following order: Technoloy S001G (PMMA substrate), NCF-D692(5) (adhesive), second positive C plate C2, second optical anisotropy layer A2, high refractive index adhesive, first positive C plate C1, and first optical anisotropy layer A1. The configuration of the phase difference film 1 is shown in Figure 5. The angles were adjusted and the layers were bonded together so that the orientation of the liquid crystalline compound molecules on the surface adjacent to the high refractive index adhesive of the second optical anisotropy layer A2 matched the orientation of the liquid crystalline compound molecules in the first optical anisotropy layer A1. The average in-plane refractive index at a wavelength of 550 nm was 1.58 on both surfaces of the first optical anisotropy layer A1 and the second optical anisotropy layer A2. The average in-plane refractive index at a wavelength of 550 nm was 1.54 on both surfaces of the first positive C plate C1 and the second positive C plate C2. The adhesive sheet NCF-D692(5) had a refractive index of 1.47 at a wavelength of 550 nm. The high refractive index adhesive had a refractive index of 1.55 at a wavelength of 550 nm.

[0141] (Preparation of Phase Difference Film 2) Except for changing the high refractive index adhesive to NCF-D692(5) (adhesive), phase difference film 2 to be used as Example 2 was obtained in the same manner as phase difference film 1. The configuration of phase difference film 2 is shown in Figure 6.

[0142] (Preparation of phase difference film in Example 9) A polyvinyl alcohol aqueous solution was applied to a cellulose acylate film 1 and dried to form a polyvinyl alcohol film 1 with a thickness of 0.2 μm. Using the polyvinyl alcohol film 1 with the cellulose acylate film attached as a temporary support, the above-mentioned coating solution (C) for positive C plates was applied on it using a bar coater and heated at 80°C for 60 seconds. After that, the film with the coating film formed was irradiated at 80°C with an irradiation dose of 500 mJ / cm² under a nitrogen atmosphere. ２ The orientation state of the liquid crystalline compound was fixed by irradiating it with light from a metal halide lamp (manufactured by iGraphics Co., Ltd.), thereby fabricating the first positive C plate C19. Next, a laminate of the first optical anisotropy layer and the second positive C plate was fabricated in the same manner as the laminate of the first optical anisotropy layer and the first positive C plate in phase difference film 1, except that the film thickness of each layer was adjusted. Similarly, a laminate of the second optical anisotropy layer and the third positive C plate was fabricated in the same manner as the laminate of the second optical anisotropy layer and the second positive C plate in phase difference film 1, except that the film thickness of each layer was adjusted. The Δnd, torsion angle, and in-plane average refractive index of each layer are shown in Table 2. Next, the laminate of the second optical anisotropy layer and the third positive C plate was bonded to the PMMA film "Technoloy S001G" using Lintec adhesive sheet "NCF-D692 (5)" so that the third positive C plate side was adjacent to Technoloy S001G, and the temporary support was peeled off. Then, the laminate of the first optical anisotropy layer and the second positive C plate was bonded onto the second optical anisotropy layer using a high refractive index adhesive so that the second positive C plate side was adjacent to the second optical anisotropy layer, and the temporary support was peeled off. Furthermore, the first positive C plate C19 was bonded on top of that using a high refractive index adhesive, and the temporary support was peeled off. In this way, the phase difference film of Example 9 described in Table 2 was obtained. The structure of the phase difference film of Example 9 is shown in Figure 7.

[0143] (Preparation of other phase difference films) In preparing the first optical anisotropy layer, the second optical anisotropy layer, the first positive C plate, and the second positive C plate, the film thickness was adjusted to adjust Δnd for each, and the phase difference films of the examples and comparative examples listed in Table 1 were prepared. The phase difference film of Example 3 was prepared by discharging 150 W・min / m onto the first positive C plate. ２ After corona treatment, a second optical anisotropy layer is applied, and then a discharge of 150 W・min / m is applied on top of that. ２ After corona treatment, a second positive C plate was applied to obtain a phase difference film without an adhesive layer. The structure of the phase difference film of Example 3 is shown in Figure 8. The phase difference film of Example 8 was manufactured in the same manner as the phase difference film of Example 1, except that a positive C plate was not applied on the first optical anisotropy layer, and a positive C plate with adjusted film thickness was applied on the second optical anisotropy layer. In the phase difference film of Example 8, the positive C plate applied on the second optical anisotropy layer is considered to be the first positive C plate. The structure of the phase difference film of Example 8 is shown in Figure 9. The phase difference film of Comparative Example 1 was manufactured in the same manner as the phase difference film of Example 1, except that the first and second positive C plates were not provided.

[0144] (Fabrication of image display devices, lenses, and virtual reality display devices)

[0145] The Meta Quest3 virtual reality display device, manufactured by Meta Corporation and employing a pancake lens, was disassembled, and the image display device and lens were removed. The Meta Quest3's image display device was a liquid crystal display device, and a phase difference film, which is an absorbing linear polarizer and a λ / 4 wave plate, was bonded to its surface. The phase difference film was peeled off, and the respective phase difference films of the example and comparative example were bonded in its place. Furthermore, an anti-reflective film "DSG-17" manufactured by Dai Nippon Printing Co., Ltd. was bonded to create an image display device. However, at this time, when observed from the side of the absorbing linear polarizer, the orientation of the in-plane slow phase axis of the first optical anisotropy layer in each example and comparative example was adjusted so that it was 14° clockwise from the transmission axis of the absorbing linear polarizer. The Meta Quest3's lens is a pancake lens combining two plano-convex lenses, and a phase difference film, which is a λ / 4 wave plate, was bonded to the plano-convex lens closer to the image display device. The phase difference film was peeled off, and the respective phase difference films of the example and comparative example were laminated in its place. Furthermore, the anti-reflective film "DSG-17" was laminated to create the lens. Note that a reflective linear polarizer was used for the plano-convex lens on the side farther from the Meta Quest 3 image display device. At this time, when observed from the side of the reflective linear polarizer, the orientation of the in-plane slow phase axis of the first optical anisotropy layer in each example and comparative example was adjusted to 76° counterclockwise from the transmission axis of the reflective linear polarizer. The fabricated image display device and lens were assembled back to create a virtual reality display device.

[0146] <Evaluation of Ellipticity> For each fabricated phase difference film, light of each wavelength was incident perpendicularly from the side of the first optical anisotropy layer using AxoScan OPMF-1, and the Müller matrix in the wavelength range of 450 nm to 650 nm was measured. The ellipticity for each wavelength was calculated from the obtained Stokes parameter by multiplying the Müller matrix by a Stokes parameter representing linear polarization with an appropriate polarization axis angle. The results are shown in Tables 1 and 2. For ellipticity under perpendicular incidence, the minimum value of the ellipticity in the wavelength range of 450 nm to 650 nm was used as the evaluation index. The minimum ellipticity under perpendicular incidence is preferably 0.80 or higher, more preferably 0.90 or higher, and even more preferably 0.95 or higher. Furthermore, light of each wavelength was incident on each fabricated phase difference film at an extreme angle of 60°, and the Müller matrix in the wavelength range of 450 nm to 650 nm was measured. The ellipticity for each wavelength was calculated from the obtained Stokes parameters by multiplying the Müller matrix by Stokes parameters representing linear polarization with an appropriate polarization axis angle. The results are shown in Tables 1 and 2. For ellipticity at an extreme angle of 60° incidence, the minimum value of the ellipticity in the wavelength range of 450 nm to 650 nm was used as the evaluation index. The minimum ellipticity at an extreme angle of 60° incidence is preferably 0.60 or higher, and more preferably 0.70 or higher.

[0147] <Evaluation of Ghost Visibility> A black and white checkerboard pattern was displayed on the image display device of each virtual reality display device that was fabricated. The virtual reality display device was worn, and the displayed black and white checkerboard pattern was observed visually, and the ghost visibility was evaluated based on the following four evaluation criteria: A: No ghost is visible, or only a slight ghost is visible and not bothersome. B: A weak ghost is visible. C: A moderately strong ghost is visible. D: A strong ghost is visible. The results are shown in Tables 1 and 2.

[0148]

[0149]

[0150] As shown in Tables 1 and 2 above, it was confirmed that the phase difference film of the present invention can obtain high ellipticity over a wide wavelength range in both perpendicular and oblique incidence conditions. Furthermore, the image display device and virtual reality display device using the phase difference film and lens of the present invention suppressed ghost images across the entire field of view, resulting in good visibility.

[0151] 1,1000 Virtual reality display device 2 Lens 3,500 Image display device 10 Light rays that form the main image 11,12 Light rays that form the ghost image 21,100 Reflective linear polarizer 22 First phase difference film 23,600 Lens substrate 24,300 Half mirror 31 Second phase difference film 32 Absorbing linear polarizer 33 Image display panel 50,60,70,80,90 Phase difference film 51 First optical anisotropy layer 52 First positive C plate 53 High refractive index adhesive 54 Second optical anisotropy layer 55 Second positive C plate 56 Adhesive 57 PMMA substrate 58 Third positive C plate 200 First phase difference layer 400 Second phase difference layer

Claims

1. A phase difference film comprising at least a first optically anisotropic layer, a second optically anisotropic layer, and a first positive C plate, wherein the first optically anisotropic layer is a positive A plate having reverse wavelength dispersion, and the second optically anisotropic layer is a layer on which a liquid crystalline compound having reverse wavelength dispersion and torsion orientation with the thickness direction as the helical axis is fixed.

2. The phase difference film according to claim 1, comprising the first optical anisotropy layer, the second optical anisotropy layer, and the first positive C plate in this order.

3. The phase difference film according to claim 1, comprising the first optical anisotropy layer, the first positive C plate, and the second optical anisotropy layer in this order.

4. The phase difference film according to claim 1, comprising the first positive C plate, the first optical anisotropy layer, and the second optical anisotropy layer in this order.

5. The phase difference film according to claim 1, wherein the first positive C plate is inverse wavelength dispersive.

6. The phase difference film according to any one of claims 1 to 5, wherein the first optical anisotropy layer, the second optical anisotropy layer, and the first positive C plate are directly laminated together.

7. The phase difference film according to any one of claims 1 to 5, wherein at least two of the first optical anisotropy layer, the second optical anisotropy layer, and the first positive C plate are laminated with an adhesive layer, and the refractive index of the adhesive layer is the value between the average in-plane refractive indices of two layers adjacent to the adhesive layer.

8. The phase difference film according to claim 1, further comprising at least a second positive C plate.

9. The phase difference film according to claim 8, comprising the first optical anisotropy layer, the first positive C plate, the second optical anisotropy layer, and the second positive C plate in this order.

10. The phase difference film according to claim 8, comprising the first positive C plate, the first optical anisotropy layer, the second positive C plate, and the second optical anisotropy layer in this order.

11. The phase difference film according to claim 8, comprising the first positive C plate, the first optical anisotropy layer, the second optical anisotropy layer, and the second positive C plate in this order.

12. The phase difference film according to claim 8, wherein at least one of the first positive C plate and the second positive C plate is inverse wavelength dispersive.

13. A phase difference film according to any one of claims 8 to 12, wherein the first optical anisotropy layer, the second optical anisotropy layer, the first positive C plate, and the second positive C plate are directly laminated together.

14. The phase difference film according to any one of claims 8 to 12, wherein the first optical anisotropy layer, the second optical anisotropy layer, the first positive C plate, and at least two of the second positive C plates are laminated with an adhesive layer, and the refractive index of the adhesive layer is the value between the average in-plane refractive indices of two layers adjacent to the adhesive layer.

15. The phase difference film according to claim 1, further comprising a second positive C plate and a third positive C plate, and comprising, in this order, a first positive C plate, a first optical anisotropy layer, a second positive C plate, a second optical anisotropy layer, and a third positive C plate.

16. The phase difference film according to claim 15, wherein at least one of the first positive C plate, the second positive C plate, and the third positive C plate is inverse wavelength dispersive.

17. The phase difference film according to claim 15 or 16, wherein the first optical anisotropy layer, the second optical anisotropy layer, the first positive C plate, the second positive C plate, and the third positive C plate are directly laminated together.

18. The phase difference film according to claim 15 or 16, wherein at least two of the first optical anisotropy layer, the second optical anisotropy layer, the first positive C plate, the second positive C plate, and the third positive C plate are laminated with an adhesive layer, and the refractive index of the adhesive layer is the value between the average in-plane refractive indices of two layers adjacent to the adhesive layer.

19. An image display device comprising at least a phase difference film according to any one of claims 1 to 5, 8 to 12, 15 and 16, and an absorbing linear polarizer.

20. A lens comprising at least a phase difference film according to any one of claims 1 to 5, 8 to 12, 15 and 16, and a reflective linear polarizer.

21. A virtual reality display device having the image display device described in claim 19.

22. A virtual reality display device having the lens described in claim 20.

Images