WO2025063012A1 - Retardation film, retardation film set, or method for manufacturing lens part or display system - Google Patents

Abstract

Provided is a method for manufacturing a display system 10 for displaying an image to a user, the display system 10 comprising: a display element 12 having a display surface for emitting light representing an image forward through a polarization member; a reflective polarization member 14 disposed in front of the display element 12 and reflecting the light emitted from the display element 12; a first lens part 16 disposed on an optical path between the display element 12 and the reflective polarization member 14 and having a curved main surface; a half mirror 18 disposed between the display element 12 and the first lens part 16, transmitting light output from the display element 12, and reflecting light reflected by the reflective polarization member 14 toward the reflective polarization member 14; a first λ/4 member 20 disposed on an optical path between the display element 12 and the half mirror 18; and a second λ/4 member 22 disposed on an optical path between the half mirror 18 and the reflective polarizing member 14. The method includes integrating a retardation film with the first lens part 16 as the second λ/4 member 22, the retardation film having an in-plane retardation Re (550) of 100 nm to 190 nm and in which the absolute value of a phase difference change value RS per unit thickness is 0.07 or less (where the phase difference change value RS is the slope of an approximate straight line of the in-plane retardation Re (550) of the retardation film as measured in a state of being given the tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg).

Description

Method for manufacturing retardation film, retardation film set, lens unit, or display system

The present invention relates to a method for manufacturing a retardation film, a retardation film set, or a lens section or display system.

Image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices), are rapidly becoming popular. In image display devices, optical components such as polarizing components and phase difference components are generally used to realize image display and improve image display performance (see, for example, Patent Document 1).

In recent years, new applications for image display devices have been developed. For example, goggles with displays (VR goggles) that realize Virtual Reality (VR) have begun to be commercialized. As VR goggles are being considered for use in a variety of situations, there is a demand for them to be lightweight and have improved visibility.

JP 2021-103286 A

The weight of the VR goggles can be reduced, for example, by making the lenses used in the VR goggles thinner. At the same time, there is also a demand for the development of optical components suitable for display systems that use thin lenses.

In view of the above, the main object of the present invention is to provide a retardation film, a retardation film set, or a method for manufacturing a lens portion or a display system that can effectively reduce the weight of VR goggles while improving visibility.

[1] According to one aspect of the present invention, there is provided a manufacturing method for a display system that displays an image to a user, the display system including: a display element having a display surface that emits light representing an image forward via a polarizing member; a reflective polarizing member that is arranged in front of the display element and reflects the light emitted from the display element; a first lens unit that is arranged on an optical path between the display element and the reflective polarizing member and has a curved main surface; a half mirror that is arranged between the display element and the first lens unit, transmits the light emitted from the display element and reflects the light reflected by the reflective polarizing member toward the reflective polarizing member; the retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS per unit thickness of 0.07 or less (wherein the retardation change value RS is the slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured under conditions of applying tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg) is integrated with the first lens section as the second λ/4 member.
[2] The manufacturing method described in [1] above may include preparing two of the retardation films, integrating one of the retardation films with the display element as the first λ/4 member, and integrating the other of the retardation films with the first lens portion as the second λ/4 member.
[3] According to another aspect of the present invention, there is provided a method for manufacturing a lens unit used in a display system for displaying an image to a user, the lens unit including: a reflective polarizing member that reflects light that is emitted forward from a display surface of a display element that displays an image and that has passed through a polarizing member and a first λ/4 member; a first lens unit that is disposed on an optical path between the display element and the reflective polarizing member and has a curved main surface; and a half-mirror that is disposed between the display element and the first lens unit, transmits light emitted from the display element, and reflects light reflected by the reflective polarizing member toward the reflective polarizing member. and a second λ/4 member disposed on an optical path between the half mirror and the reflective polarizing member, the second λ/4 member being integrated with the first lens section as the second λ/4 member. The second λ/4 member is a retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS per unit thickness of 0.07 or less (wherein the retardation change value RS is the slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured under conditions of applying tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg).
[4] According to yet another aspect of the present invention, there is provided a retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm, an absolute value of a retardation change value RS per unit thickness of 0.07 or less, and the retardation change value RS being a slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg.
[5] The retardation film according to the above [4] may have in-plane retardations Re(450), Re(550), and Re(650) satisfying the following relationships (i) to (iii):
(i) 100nm<Re(550)<160nm,
(ii) Re(450)/Re(550)<1,
(iii) Re(650)/Re(550)>1.
[6] The retardation film according to the above [4] or [5] may have a dimensional change rate of 0.02% or less before and after a heat treatment at 85° C. for 500 hours.
[7] In the retardation film according to any one of the above [4] to [6], the absolute value of the difference in in-plane retardation Re(550) before and after heat treatment at 85° C. for 500 hours may be 3.5 nm or less.
[8] The retardation film according to any one of the above [4] to [7] may be a stretched resin film.
[9] In the retardation film according to the above [8], the resin film may contain a polycarbonate-based resin.
[10] The retardation film according to any one of the above [4] to [9] may be integrated with a member having a curved surface.
[11] The radius of curvature of the curved surface of the member having the curved surface to which the retardation film according to the above [10] is integrated may be 20 mm or more.
[12] In the retardation film according to any one of [4] to [11] above, when the retardation film is integrated with a member having a curved surface with a radius of curvature of 75 mm, a difference between the ellipticity of transmitted light having a wavelength of 550 nm when linearly polarized light whose polarization direction forms an angle of 45° with respect to the slow axis is incident on the center portion and the ellipticity before integration may be 0.06 or less.
[13] The retardation film according to any one of [4] to [12] above may be used as the second λ/4 member in a display system including: a display element having a display surface that emits light representing an image forward through a polarizing member; a reflective polarizing member arranged in front of the display element and reflecting the light emitted from the display element; a first lens unit arranged on an optical path between the display element and the reflective polarizing member and having a curved main surface; a half mirror arranged between the display element and the first lens unit, transmitting the light emitted from the display element and reflecting the light reflected by the reflective polarizing member toward the reflective polarizing member; a first λ/4 member arranged on the optical path between the display element and the half mirror; and a second λ/4 member arranged on the optical path between the half mirror and the reflective polarizing member.
[14] According to another aspect of the present invention, there is provided a display system comprising: a display element having a display surface that emits light representing an image forward via a polarizing member; a reflective polarizing member that is arranged in front of the display element and reflects the light emitted from the display element; a first lens section that is arranged on an optical path between the display element and the reflective polarizing member and has a curved main surface; a half mirror that is arranged between the display element and the first lens section and transmits the light emitted from the display element and reflects the light reflected by the reflective polarizing member toward the reflective polarizing member; a first λ/4 member that is arranged on the optical path between the display element and the half mirror; and a second λ/4 member that is arranged on the optical path between the half mirror and the reflective polarizing member, wherein the second λ/4 member and the first lens section are integrated. and a set of a first retardation film for constituting the first λ/4 member and a second retardation film for constituting the second λ/4 member, wherein the first retardation film and the second retardation film each have an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS per unit thickness of 0.07 or less (wherein the retardation change value RS is the slope of an approximate straight line of the in-plane retardation Re(550) of the retardation film measured in a state in which tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg are applied), and the absolute value of the difference between the in-plane retardation Re(550) of the first retardation film and the in-plane retardation Re(550) of the second retardation film is 5 nm or less.

The retardation film, retardation film set, or lens section or display system manufacturing method according to the embodiment of the present invention can effectively reduce the weight of VR goggles while improving visibility.

FIG. 1 is a schematic cross-sectional view illustrating an example of a method for integrating a retardation film with a member having a curved surface. FIG. 1A is a schematic cross-sectional view illustrating a method for measuring ellipticity in a state in which a retardation film and a member having a curved surface are integrated, and FIG. 1B is a schematic view of the state of FIG. 1A when viewed from the retardation film side. 1 is a schematic diagram showing a general configuration of an example of a display system for VR goggles. FIG. 2 is a schematic cross-sectional view illustrating a configuration of an example of an integrated product of a retardation film and a member having a curved surface, and a partially enlarged cross-sectional view thereof. FIG. 2 is a schematic cross-sectional view illustrating a configuration of an example of an optical laminate including a retardation film. FIG. 13 is a diagram for explaining a method for measuring the thickness variation. FIG. 2 is a diagram for explaining a method for measuring an ISC value.

Below, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. In order to make the description clearer, the drawings may show the width, thickness, shape, etc. of each part diagrammatically compared to the embodiments, but these are merely examples and do not limit the interpretation of the present invention. In addition, in the drawings, the same or equivalent elements are given the same reference numerals, and duplicate descriptions may be omitted.

(Definition of terms and symbols)
The definitions of terms and symbols used in this specification are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Retardation in the thickness direction (Rth)
"Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23° C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23° C. Rth(λ) is calculated by the formula: Rth(λ)=(nx-nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz Coefficient The Nz coefficient is calculated by Nz=Rth/Re.
(5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise angles with respect to a reference direction. Thus, for example, "45°" means ±45°.

A. Retardation film According to one aspect of the present invention, a retardation film is provided in which the absolute value of the retardation change value RS per unit thickness (unit: μm) is 0.07 or less. The retardation film can be suitably used in a state where it is integrated with a member having a curved surface. The retardation change value "RS" is the slope of the approximate straight line of the in-plane retardation Re (550) of the retardation film measured in a state where tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg are applied, and can be an index of the degree of change in the in-plane retardation when tension is applied to the retardation film. Specifically, a small absolute value of RS means that the in-plane retardation is unlikely to change when tension is applied to the retardation film. When integrated with a member having a curved surface, tension is applied to the retardation film, and as a result, the retardation may change, but when the absolute value of RS per unit thickness is within the above range, the retardation change can be suppressed. In addition, dimensional changes and retardation changes caused by heating can also be suppressed. The absolute value of RS per unit thickness may be, for example, 0.06 or less or 0.05 or less, or may be, for example, 0.005 or more. The absolute value of RS of the retardation film may be, for example, 0.005 to 5.00, or, for example, 0.10 to 4.00.

The retardation film preferably has a refractive index characteristic that satisfies the relationship nx>ny≧nz. Here, "ny=nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny<nz, as long as the effect of the present invention is not impaired. The Nz coefficient of the retardation film is preferably 0.9 to 3, more preferably 0.9 to 2.5, even more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3.

The in-plane retardation Re(550) of the retardation film is, for example, 100 nm to 190 nm, may be 110 nm to 180 nm, may be 130 nm to 160 nm, or may be 135 nm to 155 nm. In one embodiment, the retardation film satisfies the relationship 100 nm < Re(550) < 160 nm.

The retardation film preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. The Re(450)/Re(550) of the retardation film is, for example, less than 1 and may be 0.95 or less, or may be less than 0.90 or even 0.85 or less. The Re(450)/Re(550) of the retardation film is, for example, 0.75 or more. The Re(650)/Re(550) of the retardation film may be, for example, greater than 1, greater than 1 and 1.2 or less, or may be 1.01 to 1.15. A retardation film exhibiting an inverse dispersion wavelength characteristic can contribute to improved visibility when applied to a display system such as VR goggles.

When linearly polarized light whose polarization direction forms an angle of 45° with respect to the slow axis is incident on the retardation film from the normal direction, the ellipticity of the transmitted light with a wavelength of 550 nm measured at a polar angle of 0° (normal direction) is, for example, 0.80 or more, preferably 0.85 or more, and more preferably 0.90 to 1. Ellipticity is the ratio of the minor axis/major axis of circularly polarized light; for example, the ellipticity of completely circularly polarized light is 1, and the ellipticity of completely linearly polarized light is 0. A retardation film exhibiting the above ellipticity can contribute to improved visibility when applied to a display system such as VR goggles.

When the retardation film is subjected to heat treatment at 85°C for 500 hours, the dimensional change rate before and after the heat treatment ((dimension before heat treatment - dimension after heat treatment) / dimension before heat treatment x 100) is, for example, 0.02% or less, and may be 0.015% or less, or 0.01% or less. A retardation film that exhibits the above dimensional change rate has the advantage that peeling due to heating is unlikely to occur when used as a laminate with other members.

When the retardation film is subjected to heat treatment at 85°C for 500 hours, the difference in in-plane retardation Re(550) before and after the heat treatment (|Re(550) before heat treatment - Re(550) after heat treatment|) is, for example, 3.5 nm or less, and may be 3.3 nm or less, or 3 nm or less. A retardation film that exhibits the above-mentioned in-plane retardation difference can suppress a decrease in visibility due to heating when applied to a display system such as VR goggles.

The ISC value of the retardation film is, for example, 50 or less, preferably 40 or less, more preferably 30 or less, and even more preferably 20 or less. The ISC value can be an index of smoothness or unevenness. A retardation film that satisfies such an ISC value and also satisfies the absolute value of RS per unit thickness can suppress the occurrence of retardation unevenness when integrated with a member having a curved surface.

The thickness variation of the retardation film is preferably 1 μm or less, more preferably 0.8 μm or less, even more preferably 0.6 μm or less, and even more preferably 0.4 μm or less. Such thickness variation can, for example, satisfactorily achieve the above ISC value. Here, the thickness variation can be determined by measuring the thickness of a first portion located within the plane of the retardation film and the thickness of a position spaced a predetermined distance (e.g., 5 mm to 15 mm) from the first portion in any direction (e.g., upward, downward, leftward, and rightward).

The ISC value per unit thickness of the retardation film is preferably 1 or less, more preferably 0.7 or less, and even more preferably 0.5 or less. The ISC value per unit thickness can be calculated, for example, by dividing the ISC value by the thickness (unit: μm).

As described above, the retardation film may be used in a state where it is integrated with a member having a curved surface. More specifically, the retardation film may be used in a state where it is integrated with the curved surface of a member having a curved surface. The curved surface may be a concave surface or a convex surface. The radius of curvature of the curved surface is, for example, 20 mm or more, for example, 25 mm or more, or for example, 30 mm or more, and is, for example, 150 mm or less, preferably 125 mm or less, more preferably 110 mm or less, and may be 90 mm or less. The diameter (major axis) of the member having a curved surface may be, for example, 20 mm to 80 mm, or for example, 30 mm to 70 mm. A preferred example of a member having a curved surface is a lens having a concave surface.

The retardation film and the member having a curved surface can be integrated by any suitable method. FIG. 1 is a schematic diagram for explaining an example of a method for integrating a retardation film and a member having a curved surface. In FIG. 1(a), the retardation film 1 is arranged on the member L, which is an adherend, in the state of the retardation film 3 with the adhesive layer 2 provided on one side. The member L is circular in plan view and has a concave shape on the top in cross-sectional view. The retardation film 3 with the adhesive layer can be arranged in a predetermined position by chucking its end to a fixing jig (not shown). The retardation film 3 with the adhesive layer is arranged in a position where the adhesive layer 2 contacts the edge of the concave surface of the member L, and is pressed into the concave surface side using a jig or the like in a heated and softened state, so that it is bonded over the entire concave surface of the member L as shown in FIG. 1(b). Thereafter, as shown in FIG. 1(c), unnecessary parts of the retardation film 3 with the adhesive layer (for example, parts protruding from the member L in plan view) can be removed to obtain an integrated product.

When integrating with the curved surface, typically the retardation film can be stretched. For example, the retardation film can be stretched from a planar shape (circular shape) that corresponds to the planar shape of the member L to a curved shape that follows the curved shape of the member L. In this way, tension can be applied to the retardation film when integrating with the curved surface, and since the absolute value of RS per unit thickness of the retardation film is small, the change in phase difference associated with the application of tension can be suppressed.

As shown in FIG. 2, when the retardation film 1 is integrated with a member L having a circular shape with a radius of 32.5 mm when viewed from the concave side and a concave curvature radius of 75 mm, and linearly polarized light whose polarization direction forms an angle of 45° with respect to the slow axis is incident from the convex side in the normal direction to the center C of the member L (in other words, the center 1c of the retardation film 1), the difference between the ellipticity of transmitted light with a wavelength of 550 nm measured on the concave side in the normal direction and the above ellipticity in the part corresponding to the center 1c of the retardation film 1 before integration (ellipticity before integration - ellipticity after integration) is, for example, 0.06 or less, preferably 0.05 or less, and more preferably 0 to 0.04. Such a retardation film can contribute to improving display characteristics when used in a display system in a state where it is integrated with a member having a curved surface.

As shown in FIG. 2, when the retardation film 1 is integrated with the member L, the difference between the Re(550) at the center 1c of the curved retardation film 1 after integration and the Re(550) at the portion of the retardation film corresponding to the center 1c before integration (|Re(550) before integration - Re(550) after integration|) is, for example, 6 nm or less, preferably 5 nm or less, and more preferably 4 nm or less. Such a retardation film can contribute to improving display characteristics when used in a display system in a state where it is integrated with a member having a curved surface.

As shown in FIG. 2, when the retardation film 1 is integrated with the member L, the maximum absolute value of the difference between Re(550) at the center 1c of the retardation film 1 and Re(550) at the other portion (outer portion) may be, for example, 30 nm or less, 25 nm or less, or 20 nm or less, or may be, for example, 1 nm or more. When stretched during integration with the member L, variation in in-plane retardation may occur within the plane (curved surface) of the retardation film. For example, in a curved retardation film after integration, the Re(550) of a portion far from the center may be significantly different from the Re(550) of the center. With a retardation film having the above absolute value of RS per unit thickness, variation in in-plane retardation within the plane can be reduced even when stretched during integration with the member L.

The retardation film is formed of any suitable material that can satisfy the above characteristics. The retardation film can be, for example, a stretched resin film or an oriented and solidified layer of a liquid crystal compound.

The resin contained in the resin film may be a polycarbonate-based resin, a polyester carbonate-based resin, a polyester-based resin, a polyvinyl acetal-based resin, a polyarylate-based resin, a cycloolefin-based resin, a cellulose-based resin, a polyvinyl alcohol-based resin, a polyamide-based resin, a polyimide-based resin, a polyether-based resin, a polystyrene-based resin, an acrylic-based resin, or the like. These resins may be used alone or in combination (e.g., blended or copolymerized). When the retardation film exhibits reverse dispersion wavelength characteristics, a resin film containing a polycarbonate-based resin or a polyester carbonate-based resin (hereinafter sometimes simply referred to as a polycarbonate-based resin) may be preferably used.

As the polycarbonate-based resin, any suitable polycarbonate-based resin can be used as long as the effects of the present invention can be obtained. For example, the polycarbonate-based resin contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from at least one dihydroxy compound selected from the group consisting of alicyclic diol, alicyclic dimethanol, di-, tri- or polyethylene glycol, and alkylene glycol or spiro glycol. Preferably, the polycarbonate-based resin contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, a structural unit derived from an alicyclic dimethanol and/or a structural unit derived from a di-, tri- or polyethylene glycol; more preferably, it contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from a di-, tri- or polyethylene glycol. The polycarbonate-based resin may contain a structural unit derived from another dihydroxy compound as necessary. Details of polycarbonate-based resins that can be suitably used in retardation films and methods for forming retardation films are described, for example, in JP-A-2014-10291, JP-A-2014-26266, JP-A-2015-212816, JP-A-2015-212817, and JP-A-2015-212818, and the descriptions in these publications are incorporated herein by reference.

When the retardation film is a stretched resin film, its thickness is, for example, 20 μm to 150 μm, preferably 30 μm to 100 μm, more preferably 35 μm to 80 μm, and even more preferably 40 μm to 70 μm.

The above-mentioned liquid crystal compound oriented solidified layer is a layer in which the liquid crystal compound is oriented in a predetermined direction within the layer, and the oriented state is fixed. The "oriented solidified layer" is a concept that includes an oriented solidified layer obtained by solidifying a liquid crystal monomer as described below. Typically, rod-shaped liquid crystal compounds are oriented in the slow axis direction of the retardation film (homogeneous orientation). Examples of rod-shaped liquid crystal compounds include liquid crystal polymers and liquid crystal monomers. The liquid crystal compound is preferably polymerizable. If the liquid crystal compound is polymerizable, the orientation state of the liquid crystal compound can be fixed by aligning the liquid crystal compound and then polymerizing it.

The alignment solidified layer of the liquid crystal compound (liquid crystal alignment solidified layer) can be formed by performing an alignment treatment on the surface of a specified substrate, applying a coating liquid containing a liquid crystal compound to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, and fixing the alignment state. Any appropriate alignment treatment can be adopted as the alignment treatment. Specific examples include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique deposition and photoalignment treatment. Any appropriate treatment conditions can be adopted for the various alignment treatments depending on the purpose.

The alignment of liquid crystal compounds is achieved by treating them at a temperature that exhibits a liquid crystal phase according to the type of liquid crystal compound. By carrying out such temperature treatment, the liquid crystal compounds take on a liquid crystal state, and the liquid crystal compounds are aligned according to the alignment treatment direction of the substrate surface.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. If the liquid crystal compound is polymerizable or crosslinkable, the alignment state is fixed by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or crosslinking treatment.

Any suitable liquid crystal polymer and/or liquid crystal monomer can be used as the liquid crystal compound. The liquid crystal polymer and the liquid crystal monomer can be used alone or in combination. Specific examples of liquid crystal compounds and methods for producing a liquid crystal alignment solidified layer are described in, for example, JP 2006-163343 A, JP 2006-178389 A, and WO 2018/123551 A. The descriptions in these publications are incorporated herein by reference.

When the retardation film is an oriented solidified layer of a liquid crystal compound, its thickness is, for example, 1 μm to 10 μm, preferably 1 μm to 8 μm, more preferably 1 μm to 6 μm, and even more preferably 1 μm to 4 μm.

In the manufacture of the above retardation film, the RS per unit thickness of the obtained retardation film can be changed by changing the forming materials, manufacturing conditions, etc. For example, in a retardation film which is a stretched resin film, the absolute value of RS per unit thickness tends to become smaller by decreasing the stretching ratio, etc. In addition, in the case of a resin film containing a polycarbonate-based resin, the absolute value of RS per unit thickness tends to become smaller by increasing the content ratio of structural units derived from a fluorene-based dihydroxy compound. On the other hand, a retardation film which is a liquid crystal alignment solidified layer can have a very small absolute value of RS per unit thickness.

B. Display system FIG. 3 is a schematic diagram showing the general configuration of a display system according to one embodiment of the present invention, and shows the arrangement and shape of each component of the display system. The display system 10 includes a display element 12, a reflective polarizing member 14, a first lens unit 16 having a curved main surface, a half mirror 18, a first λ/4 member 20, a second λ/4 member 22, and a second lens unit 24. The reflective polarizing member 14 is disposed in front of the display surface 12a of the display element 12, and can reflect light emitted from the display element 12. The first lens unit 16 is disposed on the optical path between the display element 12 and the reflective polarizing member 14, and the half mirror 18 is disposed between the display element 12 and the first lens unit 16. The first λ/4 member 20 is disposed on the optical path between the display element 12 and the half mirror 18, and the second λ/4 member 22 is disposed on the optical path between the half mirror 18 and the reflective polarizing member 14. Although not shown, from the viewpoint of improving visibility, the display system 10 may further include an absorptive polarizing member. The absorptive polarizing member may be disposed in front of the reflective polarizing member 14 such that the reflection axis of the reflective polarizing member 14 and the absorption axis of the absorptive polarizing member are approximately parallel to each other.

The half mirror, or the components arranged in front of the first lens section (in the illustrated example, the half mirror 18, the first lens section 16, the second λ/4 member 22, the reflective polarizing member 14, and the second lens section 24) may be collectively referred to as the lens section (lens section 4).

The display element 12 is, for example, a liquid crystal display or an organic EL display, and has a display surface 12a for displaying an image. The light emitted from the display surface 12a passes through, for example, a polarizing member that may be included in the display element 12, and is converted into a first linearly polarized light.

The first λ/4 member 20 can convert the first linearly polarized light incident on the first λ/4 member 20 into the first circularly polarized light. The first λ/4 member 20 may be integrally provided with the display element 12.

The half mirror 18 transmits the light emitted from the display element 12 and reflects the light reflected by the reflective polarizing element 14 toward the reflective polarizing element 14. The half mirror 18 is integrally provided with the first lens portion 16.

The second λ/4 member 22 can transmit the light reflected by the reflective polarizing member 14 and the half mirror 18 through the reflective polarizing member 14. The second λ/4 member 22 is integrally formed with the first lens portion 16.

The first circularly polarized light emitted from the first λ/4 member 20 passes through the half mirror 18 and the first lens portion 16, and is converted into the second linearly polarized light by the second λ/4 member 22. The second linearly polarized light emitted from the second λ/4 member 22 is reflected toward the half mirror 18 without passing through the reflective polarizing member 14. At this time, the polarization direction of the second linearly polarized light incident on the reflective polarizing member 14 is the same as the reflection axis of the reflective polarizing member 14. Therefore, the second linearly polarized light incident on the reflective polarizing member 14 is reflected by the reflective polarizing member 14.

The second linearly polarized light reflected by the reflective polarizing element 14 is converted into a second circularly polarized light by the second λ/4 element 22, and the second circularly polarized light emitted from the second λ/4 element 22 passes through the first lens unit 16 and is reflected by the half mirror 18. The second circularly polarized light reflected by the half mirror 18 passes through the first lens unit 16 and is converted into a third linearly polarized light by the second λ/4 element 22. The third linearly polarized light passes through the reflective polarizing element 14. At this time, the polarization direction of the third linearly polarized light incident on the reflective polarizing element 14 is the same as the transmission axis of the reflective polarizing element 14. Therefore, the third linearly polarized light incident on the reflective polarizing element 14 passes through the reflective polarizing element 14.

The light that passes through the reflective polarizing element 14 passes through the second lens portion 24 (the absorptive polarizing element 28 and the second lens portion 24) and enters the user's eye 26.

The absorption axis of the polarizing member included in the display element 12 and the reflection axis of the reflective polarizing member 14 may be arranged approximately parallel to each other or approximately perpendicular to each other. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the first λ/4 member 20 is, for example, 40° to 50°, may be 42° to 48°, or may be about 45°. The angle between the absorption axis of the polarizing member included in the display element 12 and the slow axis of the second λ/4 member 22 is, for example, 40° to 50°, may be 42° to 48°, or may be about 45°.

The in-plane phase difference Re(550) of the first λ/4 member 20 is, for example, 100 nm to 190 nm, and may be 110 nm to 180 nm, 130 nm to 160 nm, or 135 nm to 155 nm. The first λ/4 member 20 preferably exhibits an inverse dispersion wavelength characteristic in which the phase difference value increases according to the wavelength of the measurement light. The Re(450)/Re(550) of the first λ/4 member 20 may be, for example, 0.75 or more and less than 1, or 0.8 or more and 0.95 or less.

The in-plane phase difference Re(550) of the second λ/4 member 22 is, for example, 100 nm to 190 nm, may be 110 nm to 180 nm, may be 130 nm to 160 nm, or may be 135 nm to 155 nm. The second λ/4 member 22 preferably exhibits an inverse dispersion wavelength characteristic in which the phase difference value increases according to the wavelength of the measurement light. The Re(450)/Re(550) of the second λ/4 member 22 may be, for example, 0.75 or more and less than 1, or 0.8 or more and 0.95 or less. Unless otherwise specified, the in-plane phase difference of the second λ/4 member is the in-plane phase difference measured at a portion corresponding to the center of the first lens portion. The center of the first lens portion may be a portion that is generally recognized as the center. For example, the center of the first lens portion may be the center of a circumscribing circle of its planar shape.

In the display system 10, the second λ/4 member 22 is composed of the retardation film described in Section A, and is integrated with the first lens section 16 having a curved surface. The integration of the second λ/4 member 22 and the first lens section 16 can be performed by integrating the above-mentioned retardation film as the second λ/4 member 22 with the first lens section. The second λ/4 member (the retardation film described in Section A) 22 can be integrated with the first lens section 16, for example, as an optical laminate that optionally further includes other optical members and has an adhesive layer (e.g., a pressure-sensitive adhesive layer) on the outermost layer.

The radius of curvature of the curved surface of the first lens portion 16 is, for example, 20 mm or more, for example, 25 mm or more, or for example, 30 mm or more, and may be, for example, 150 mm or less, preferably 125 mm or less, more preferably 110 mm or less, or may be 90 mm or less. The diameter (major axis) of the first lens portion 16 may be, for example, 20 mm to 80 mm, or for example, 30 mm to 70 mm. In the illustrated example, the second λ/4 member 22 is integrated with the concave surface of the first lens portion 16, but it may be integrated with the convex surface. The method of integrating the second λ/4 member or the optical laminate with the first lens portion is not particularly limited, and for example, the same method as the method of integrating the retardation film with a member having a curved surface described in Section A can be used.

FIG. 4 is a schematic cross-sectional view and an enlarged view of a main part of an integrated product 100 in which an optical laminate 70 including a second λ/4 member (a retardation film described in Section A) 22 and a first lens portion 16 are integrated. The optical laminate 70 includes a member (a so-called second positive C plate) 72 whose refractive index characteristics can show the relationship nz>nx=ny, which is arranged on one side of the second λ/4 member 22, and a second protective member 74 arranged on the other side. The second λ/4 member 22, the second positive C plate 72, and the second protective member 74 are typically laminated via an adhesive layer (adhesive layer, pressure-sensitive adhesive layer, etc.). The optical laminate 70 further includes a second pressure-sensitive adhesive layer 76 on the side of the second positive C plate 72 opposite to the side on which the second λ/4 member 22 is arranged. The optical laminate 70 is bonded to the first lens portion 16 by the second adhesive layer 76 so as to conform to the concave surface 16a of the first lens portion 16.

The thickness direction retardation Rth(550) of the second positive C plate is preferably -20 nm to -200 nm, more preferably -30 nm to -180 nm, even more preferably -40 nm to -160 nm, and particularly preferably -50 nm to -140 nm. Here, "nx = ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. The in-plane retardation Re(550) of the second positive C plate is, for example, less than 10 nm.

The second positive C plate may be formed of any suitable material, but is preferably composed of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of such liquid crystal compounds and methods for forming the second positive C plate include the liquid crystal compounds and methods for forming the retardation layer described in [0020] to [0028] of JP 2002-333642 A. In this case, the thickness of the second positive C plate is preferably 0.5 μm to 5 μm.

The second protective member typically includes a substrate. The substrate may be made of any suitable film. Materials that are the main components of the film that constitutes the substrate include, for example, cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, cycloolefin-based resins such as polynorbornene, polyolefin-based, (meth)acrylic-based, acetate-based, and other resins. The thickness of the substrate is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 15 μm to 35 μm.

The second protective member preferably has a substrate and a surface treatment layer formed on the substrate. The second protective member having the surface treatment layer may be arranged so that the surface treatment layer is located on the front side. The surface treatment layer may have any appropriate function. For example, from the viewpoint of improving visibility, the surface treatment layer preferably has an anti-reflection function. The surface treatment layer may also include a hard coat layer. The thickness of the surface treatment layer is preferably 1 μm to 20 μm, more preferably 2 μm to 15 μm, and even more preferably 3 μm to 10 μm.

The adhesive constituting the second adhesive layer typically contains a (meth)acrylic polymer, a urethane polymer, a silicone polymer, or a rubber polymer as a base polymer. Preferably, the adhesive is a (meth)acrylic adhesive containing a (meth)acrylic polymer as a main component. The thickness of the second adhesive layer is, for example, 12 μm or more, preferably 15 μm or more, and, for example, 100 μm or less, preferably 80 μm or less.

In the display system 10, the first λ/4 member 20 may also be composed of the retardation film described in Section A. In this case, the first λ/4 member (the retardation film described in Section A) 20 may be integrated with the display surface 12a of the display element 12. The display surface of the display element may be flat. As described above, the retardation film described in Section A has a small absolute value of RS per unit thickness, and the change in optical properties due to integration with a curved member is small. Therefore, when the retardation film described in Section A is integrated as the first λ/4 member and the second λ/4 member along the display surface of the display element, which is flat, and the curved surface of the first lens part, which has a curved surface, respectively, a display system in which the difference in in-plane retardation between the two is small can be preferably obtained. In such a display system, the absolute value of the difference between the in-plane retardation Re(550) of the retardation film (first λ/4 member) integrated with the display element and the in-plane retardation Re(550) of the retardation film (second λ/4 member) integrated with the first lens portion is, for example, 6 nm or less, preferably 5 nm or less, more preferably 4 nm or less, and even more preferably 3.5 nm or less, and may be, for example, 3.0 nm or less, 2.5 nm or less, 2.0 nm or less, 1.5 nm or less, or 1.0 nm or less.

The first λ/4 member (the retardation film described in Section A) 20 may, for example, further include any other suitable optical member and may be integrated with the display element 12 as an optical laminate having an adhesive layer (e.g., a pressure-sensitive adhesive layer) on the outermost layer.

FIG. 5 is a schematic cross-sectional view illustrating an example of the configuration of an optical laminate 80 including a first λ/4 member (a retardation film described in Section A) 20. The optical laminate 80 includes a polarizing member 82 arranged on one side of the first λ/4 member 20, and a first positive C plate 84 and a first protective member 86 arranged in this order on the other side. The polarizing member 82 is a polarizing member that can be included in the display element 12. The optical laminate 80 further includes a first adhesive layer 88 on the side of the polarizing member 82 opposite to the side on which the first λ/4 member 20 is arranged. The optical laminate 80 can be attached to the front side of the display element by the first adhesive layer 88.

The polarizing member is typically an absorptive polarizing member, and may include a resin film containing a dichroic material (sometimes referred to as an absorptive polarizing film). The thickness of the absorptive polarizing film is, for example, 1 μm or more and 20 μm or less, and may be 2 μm or more and 15 μm or less, 12 μm or less, 10 μm or less, 8 μm or less, or 5 μm or less.

The absorptive polarizing film may be made from a single layer of resin film, or may be made using a laminate of two or more layers.

When made from a single-layer resin film, for example, an absorptive polarizing film can be obtained by subjecting a hydrophilic polymer film such as a polyvinyl alcohol (PVA)-based film, a partially formalized PVA-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film to a dyeing process using a dichroic substance such as iodine or a dichroic dye, a stretching process, etc. Among these, an absorptive polarizing film obtained by dyeing a PVA-based film with iodine and stretching it uniaxially is preferred.

The dyeing with iodine is carried out, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing process, or may be carried out while dyeing. Alternatively, the film may be stretched and then dyed. If necessary, the PVA-based film may be subjected to a swelling process, a crosslinking process, a washing process, a drying process, etc.

When the laminate is produced using the above-mentioned laminate of two or more layers, examples of the laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. The absorptive polarizing film obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; and stretching and dyeing the laminate to make the PVA-based resin layer into an absorptive polarizing film. In this embodiment, preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. The stretching typically includes immersing the laminate in an aqueous boric acid solution to stretch it. Furthermore, the stretching may further include air-stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the boric acid aqueous solution, as necessary. In addition, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being conveyed in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, it is possible to increase the crystallinity of PVA even when PVA is applied onto a thermoplastic resin, and it is possible to achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution can be prevented when the PVA is immersed in water in the subsequent dyeing step or stretching step, and it is possible to achieve high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of the absorptive polarizing film obtained by immersing the laminate in a liquid in a treatment process such as a dyeing process and an underwater stretching process. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction by a drying shrinkage process. The obtained resin substrate/absorptive polarizing film laminate may be used as it is (i.e., the resin substrate may be used as a protective layer for the absorptive polarizing film), or any suitable protective layer may be laminated on the peeled surface obtained by peeling the resin substrate from the resin substrate/absorptive polarizing film laminate, or on the surface opposite to the peeled surface. Details of the manufacturing method of such an absorptive polarizing film are described in, for example, JP 2012-73580 A and JP 6470455 A. The entire disclosures of these publications are incorporated herein by reference.

The crossed transmittance (Tc) of the absorptive polarizing member (absorptive polarizing film) is preferably 0.5% or less, more preferably 0.1% or less, and even more preferably 0.05% or less. The single transmittance (Ts) of the absorptive polarizing member (absorptive polarizing film) is, for example, 41.0% to 45.0%, and preferably 42.0% or more. The degree of polarization (P) of the absorptive polarizing member (absorptive polarizing film) is, for example, 99.0% to 99.997%, and preferably 99.9% or more.

The crossed transmittance, single transmittance and degree of polarization can be measured, for example, using an ultraviolet-visible spectrophotometer. The degree of polarization P can be calculated by measuring the single transmittance Ts, parallel transmittance Tp and crossed transmittance Tc using an ultraviolet-visible spectrophotometer, and using the obtained Tp and Tc, according to the following formula. Note that Ts, Tp and Tc are Y values measured using a 2-degree visual field (C light source) according to JIS Z 8701 and corrected for visibility.
Polarization degree P (%) = {(Tp-Tc)/(Tp+Tc)} ^1/2 ×100

The same explanations as for the second positive C plate, second protective member, and second adhesive layer can be applied to the first positive C plate, first protective member, and first adhesive layer, respectively.

C. Set of Retardation Films According to another aspect of the present invention, a set of two retardation films is provided, each of which independently has an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of the retardation change value RS per unit thickness of 0.07 or less. The absolute value of the difference between the in-plane retardation Re(550) of the two retardation films included in the set is, for example, 10 nm or less, preferably 7 nm or less, more preferably 0 nm to 5 nm. Each of the two retardation films included in the set is preferably the retardation film described in section A.

As shown in FIG. 3, the display system may include a planar first λ/4 member and a curved second λ/4 member. In such a display system, by using one of the retardation films to form the first λ/4 member and the other to form the second λ/4 member, even when the other retardation film is deformed to follow the curved surface of the first lens portion, the difference in in-plane retardation between the first λ/4 member and the second λ/4 member can be made small (for example, the absolute value of the difference in in-plane retardation Re(550) is 10 nm or less, preferably 7 nm or less, more preferably 5 nm or less, and even more preferably 0 nm to 3.5 nm), and as a result, a display system with excellent visibility can be preferably obtained.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The thickness and retardation were measured by the following measuring methods.
<Thickness>
The thickness of 10 μm or less was measured using a scanning electron microscope (manufactured by JEOL Ltd., product name "JSM-7100F"), and the thickness of more than 10 μm was measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C").
<Phase difference>
The in-plane retardation at 23° C. was measured using a birefringence mapping measurement device (manufactured by Photoron, product name “KAMAKIRI X stage”).

[Example 1]
Into a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and reflux condensers controlled at 100°C, 42.47 parts by weight (0.066 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by weight (0.200 mol) of isosorbide (ISB), 42.28 parts by weight (0.139 mol) of spiroglycol (SPG), 63.77 parts by weight (0.298 mol) of diphenyl carbonate (DPC), and 1.19×10 ⁻² parts by weight (6.78×10 ⁻⁵ mol) of calcium acetate monohydrate as a catalyst were charged.
After the inside of the reactor was purged with nitrogen under reduced pressure, the reactor was heated with a heat medium, and stirring was started when the inside temperature reached 100°C. 40 minutes after the start of the temperature rise, the inside temperature reached 220°C, and the pressure was controlled to maintain this temperature while simultaneously starting the pressure reduction, and the pressure was reduced to 13.3 kPa in 90 minutes after the temperature reached 220°C. Phenol vapor by-produced with the polymerization reaction was led to a reflux condenser at 100°C, a small amount of monomer components contained in the phenol vapor were returned to the reactor, and uncondensed phenol vapor was led to a condenser at 45°C and recovered. Nitrogen was introduced into the first reactor to restore the pressure to atmospheric pressure once, and the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature rise and pressure reduction in the second reactor were started, and the inside temperature was 240°C and the pressure was 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore pressure, and the produced polyester carbonate resin was extruded into water and the strands were cut to obtain pellets.
The obtained polyester carbonate-based resin (pellets) was vacuum-dried at 80°C for 5 hours, and then a long resin film having a thickness of 118 μm was produced using a film-forming device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250°C), a T-die (width 200 mm, setting temperature: 250°C), a chill roll (setting temperature: 120 to 130°C) and a winder.
The obtained long resin film was stretched in the width direction at a stretching temperature of 139° C. and a stretching ratio of 2.5 times, and then wound into a roll to obtain a retardation film 1 having a thickness of 47 μm, an Re(590) of 140 nm, and an Nz coefficient of 1.2.
The Re(450)/Re(550) of the retardation film 1 was 0.859, and the retardation film 1 exhibited reverse dispersion wavelength characteristics.

[Example 2]
The amount of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane was 29.60 parts by weight (0.046 mol), a long resin film having a thickness of 120 μm was produced, and the resin film was stretched in the width direction at a stretching temperature of 137° C. and a stretching ratio of 2.1 times. The same procedures as in Example 1 were carried out to obtain a retardation film 2 having a thickness of 57 μm, an Re(590) of 140 nm, and an Nz coefficient of 1.2.
The Re(450)/Re(550) of the retardation film 2 was 0.859, and the retardation film 2 exhibited reverse dispersion wavelength characteristics.

[Example 3]
A long resin film having a thickness of 114 μm was prepared, and the resin film was stretched in the width direction at a stretching temperature of 136° C. and a stretching ratio of 2.0 times. The same procedure as in Example 1 was performed to obtain a retardation film 3 having a thickness of 57 μm, an Re(590) of 140 nm, and an Nz coefficient of 1.2.
The retardation film 3 had an Re(450)/Re(550) of 0.859, and exhibited inverse dispersion wavelength characteristics.

[Comparative Example 1]
The amount of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane was 29.60 parts by weight (0.046 mol), a long resin film having a thickness of 122 μm was produced, and the resin film was stretched in the width direction at a stretching temperature of 143° C. and a stretching ratio of 3.3 times. The same procedure as in Example 1 was used to obtain a retardation film C1 having a thickness of 37 μm, an Re(590) of 140 nm, and an Nz coefficient of 1.2.
The retardation film C1 had an Re(450)/Re(550) of 0.859 and exhibited reverse dispersion wavelength characteristics.

[Comparative Example 2]
A long resin film having a thickness of 115 μm was prepared, and the resin film was stretched in the width direction at a stretching temperature of 142 ° C. and a stretching ratio of 3.1 times. The same procedure as in Example 1 was performed to obtain a retardation film C2 having a thickness of 37 μm, an Re (590) of 140 nm, and an Nz coefficient of 1.2.
The retardation film C2 had an Re(450)/Re(550) of 0.859 and exhibited reverse dispersion wavelength characteristics.

[Comparative Example 3]
The amount of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane was 29.60 parts by weight (0.046 mol), a long resin film having a thickness of 130 μm was produced, and the resin film was stretched in the width direction at a stretching temperature of 140° C. and a stretching ratio of 2.7 times. The same procedure as in Example 1 was used to obtain a retardation film C3 having a thickness of 47 μm, an Re(590) of 140 nm, and an Nz coefficient of 1.2.
The retardation film C3 had an Re(450)/Re(550) of 0.859 and exhibited inverse dispersion wavelength characteristics.

<Phase difference change value RS>
The retardation films obtained in the Examples and Comparative Examples were attached to an acrylic film (Re(550)≈0 nm) via an acrylic pressure-sensitive adhesive layer (thickness 5 μm) to obtain a laminate. The obtained laminate was cut into a length of 150 mm and a width of 15 mm so that the slow axis direction of the retardation film was the longitudinal direction, to obtain a sample. The acrylic film is a film that hardly changes the retardation when the following tension is applied.
A tension meter (MYCARBON, product name "Digital Luggage Scale") was used to apply tension in the length direction of the obtained sample. At tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg, the in-plane retardation (Re (550)) was measured using a retardation measuring device (Axometrics, product name: Axo Scan). Using an Excel function, the tension was plotted on the x-axis and Re (550) on the y-axis, and the Re (550) values measured at each tension were plotted to create an approximate straight line, and the slope of the approximate straight line was taken as the retardation change value RS. The obtained RS was divided by the film thickness (μm) of each retardation film to calculate the absolute value of RS per unit thickness.

<Thickness variation>
The retardation films obtained in the examples and comparative examples were cut into a size of 100 mm x 100 mm to prepare measurement samples. As shown in Fig. 6, the thickness was measured at five points in total, including the center of the measurement sample and four points 10 mm apart from the center on each of the top, bottom, left and right sides, and the difference between the maximum and minimum values was taken as the thickness variation.

<ISC value>
The ISC value of the retardation films obtained in the examples and comparative examples was measured using EyeScale-4W manufactured by I-System Co., Ltd. Specifically, based on the specifications of the measuring device, the in-plane unevenness was calculated as the ISC value in the ISC measurement mode of the 3CCD image sensor.
7 is a diagram for explaining a method for measuring the ISC value, and is a schematic diagram of the arrangement of a light source, a retardation film, a screen, and a CCD camera viewed from above. As shown in FIG. 7, the light source Ls, the retardation film M, and the screen S were arranged in this order, and the transmitted image projected onto the screen S was measured by the CCD camera C. The retardation film M was attached to an alkali-free glass plate (manufactured by Corning, 1737) and was used for measurement in a state in which the glass plate was arranged on the light source Ls side.
The light source Ls was arranged so that the distance in the X-axis direction from the light source Ls to the retardation film M was 10 to 60 cm. The light source Ls was arranged so that the distance in the X-axis direction from the screen S was 70 to 130 cm. The CCD camera C was arranged so that the distance in the Y-axis direction from the retardation film M was 3 to 30 cm. The CCD camera C was arranged so that the distance in the X-axis direction from the screen S was 70 to 130 cm.

<Production and evaluation of curved surface integrated products>
1. Preparation of Lens with Retardation Film An acrylic adhesive layer (thickness 15 μm) was provided on one side of the retardation film obtained in the examples and comparative examples, and the planar shape was a circle with a diameter of 65 mm, and the concave surface of a lens with a curvature radius of 75 mm was attached to the concave surface of the lens through the adhesive layer. Specifically, as shown in FIG. 1, the retardation film with adhesive layer was set so that the surface of the adhesive layer was in contact with the edge of the concave side of the lens, and the film was heated to 120° C. to soften it, and pressed into the concave side to be attached to the concave surface of the lens. This resulted in a lens with retardation film, which is an integrated product of the retardation film and the lens.

2. Retardation change For the lens with retardation film obtained in 1, the in-plane retardation Re(543) _a of the retardation film at the center was measured. The absolute value of the difference (Re(543) b - Re(543) _a) between Re(543) _b and Re(543) _a of the portion corresponding to the center of the retardation film before _lamination was calculated as the retardation change at the center due to lamination to a curved surface. Note that the retardation change due to lamination to a curved surface can be evaluated as "poor (x)" when the difference is 6.0 nm or more, and "good (o)" when it is less than 6.0 nm.

3. Change in ellipticity Using a Mueller matrix polarimeter (manufactured by Axometrics, product name "Axoscan"), linearly polarized light was made incident from the normal convex side so as to pass through the central part of the concave surface of the lens with retardation film at 23°C, and the ellipticity _a of transmitted light with a wavelength of 550 nm in the normal direction was measured. The angle between the polarization direction of the linearly polarized light and the slow axis of the retardation film was 45°. The difference between this and the ellipticity _b measured in the same manner for the retardation film before lamination (ellipticity _b - ellipticity _a ) was calculated as the change in ellipticity at the center due to lamination of the curved surface.

4. Peeling test The lens with the retardation film was placed in an oven at 80° C. and 0% RH, and taken out after 120 hours. The appearance was visually inspected to evaluate whether or not the retardation film had peeled off.

<Production and evaluation of planar integrated products>
1. Preparation of glass plate with retardation film The retardation films obtained in the examples and comparative examples were cut into squares of 100 mm x 100 mm size with the slow axis direction and width direction as side directions, and an acrylic adhesive layer (thickness 5 μm) was provided on one side of the square, and the square was attached to a flat glass plate (thickness 1.1 mm) via the adhesive layer. In this way, a glass plate with a retardation film, which is an integrated product of the retardation film and the glass plate, was obtained.

The glass plate with the retardation film obtained in 1 was placed in an oven at 85° C. and 0% RH, and taken out after 500 hours. The dimensions of the retardation film on the glass plate were then measured, and the dimensional change rate before and after heating in the slow axis direction [(dimension before heating−dimension after heating)/dimension before heating×100] was calculated as the dimensional change rate.

3. Retardation change 1. The in-plane retardation Re (543) of the retardation film was measured for the glass plate with retardation film obtained in. Thereafter, the glass plate with retardation film was placed in an oven at 85 ° C. and 0% RH, and after 500 hours, it was taken out and the in-plane retardation Re (543) of the retardation film was measured. The absolute value of the difference between Re (543) _b of the retardation film before heat treatment and Re (543) _a after heat treatment (Re (543) _b - Re (543) _a ) was calculated as the retardation change due to heating. In addition, the retardation change due to heating can be evaluated as "poor (x)" when the difference is 4.0 nm or more, "good (◯)" when it is 3.5 nm or less, and "pass (△)" when it is more than 3.5 nm and less than 4.0 nm.

The results are shown in Table 1.

The retardation film of the embodiment, which has a small absolute value of RS per unit thickness, exhibits small changes in phase difference and ellipticity of transmitted light when attached to a lens having a curved surface, and is also less susceptible to peeling due to heating. When such a retardation film is applied to a display system as an integrated product with a lens having a curved surface, it can exhibit the desired optical properties and contribute to improved visibility.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configurations shown in the above-described embodiments can be replaced with configurations that are substantially the same as those shown in the above-described embodiments, that have the same effects, or that can achieve the same purpose.

The manufacturing method of a display system according to an embodiment of the present invention can be suitably used for manufacturing display systems such as VR goggles, for example.

REFERENCE SIGNS LIST 1 Retardation film 10 Display system 12 Display element 14 Reflective polarizing member 16 First lens section 18 Half mirror 20 First λ/4 member 22 Second λ/4 member 24 Second lens section

Claims (14)

1. A method for manufacturing a display system for displaying an image to a user, comprising the steps of:
The display system comprises:
a display element having a display surface that emits light representing an image forward via a polarizing member;
a reflective polarizing member disposed in front of the display element and reflecting light emitted from the display element;
a first lens portion disposed on an optical path between the display element and the reflective polarizing member, the first lens portion having a curved main surface;
a half mirror disposed between the display element and the first lens portion, the half mirror transmitting light emitted from the display element and reflecting light reflected by the reflective polarizing member toward the reflective polarizing member;
a first λ/4 member disposed on an optical path between the display element and the half mirror;
a second λ/4 member disposed on an optical path between the half mirror and the reflective polarizing member;
Equipped with
a retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS per unit thickness of 0.07 or less (wherein the retardation change value RS is a gradient of an approximation line of the in-plane retardation Re(550) of the retardation film measured under conditions of applying tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg) to the first lens portion as the second λ/4 member. Preparing two of the retardation films;
One of the retardation films is integrated with the display element as the first λ/4 member, and the other of the retardation films is integrated with the first lens portion as the second λ/4 member;
The method of claim 1 , comprising: A method for manufacturing a lens portion used in a display system that displays an image to a user, comprising the steps of:
The lens portion is
a reflective polarizing member that reflects light that is emitted forward from a display surface of a display element that displays an image and that has passed through the polarizing member and the first λ/4 member;
a first lens portion disposed on an optical path between the display element and the reflective polarizing member, the first lens portion having a curved main surface;
a half mirror disposed between the display element and the first lens portion, the half mirror transmitting light emitted from the display element and reflecting light reflected by the reflective polarizing member toward the reflective polarizing member;
a second λ/4 member disposed on an optical path between the half mirror and the reflective polarizing member;
a retardation film having an in-plane retardation Re(550) of 100 nm to 190 nm and an absolute value of a retardation change value RS per unit thickness of 0.07 or less (wherein the retardation change value RS is a gradient of an approximation line of the in-plane retardation Re(550) of the retardation film measured under conditions of applying tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg) to the first lens portion as the second λ/4 member. The in-plane retardation Re(550) is 100 nm to 190 nm,
The absolute value of the phase difference change value RS per unit thickness is 0.07 or less,
The retardation change value RS is the slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg.
Phase contrast film. 5. The retardation film according to claim 4, wherein in-plane retardations Re(450), Re(550), and Re(650) satisfy the following relationships (i) to (iii):
(i) 100nm<Re(550)<160nm,
(ii) Re(450)/Re(550)<1,
(iii) Re(650)/Re(550)>1. The retardation film according to claim 4, in which the dimensional change rate before and after heat treatment at 85°C for 500 hours is 0.02% or less. The retardation film according to claim 4, in which the absolute value of the difference in in-plane retardation Re(550) before and after heat treatment at 85°C for 500 hours is 3.5 nm or less. The retardation film according to claim 4, which is a stretched resin film. The retardation film according to claim 8, wherein the resin film contains a polycarbonate resin. The retardation film according to claim 4, which is integrated with a member having a curved surface. The retardation film according to claim 10, wherein the radius of curvature of the curved surface is 20 mm or more. The retardation film according to claim 4, in which, when integrated with a member having a curved surface with a radius of curvature of 75 mm, the difference between the ellipticity of transmitted light with a wavelength of 550 nm when linearly polarized light whose polarization direction forms an angle of 45° with respect to the slow axis is incident on the center portion and the ellipticity before integration is 0.06 or less. a display element having a display surface that emits light representing an image forward via a polarizing member;
a reflective polarizing member disposed in front of the display element and reflecting light emitted from the display element;
a first lens portion disposed on an optical path between the display element and the reflective polarizing member, the first lens portion having a curved main surface;
a half mirror disposed between the display element and the first lens portion, the half mirror transmitting light emitted from the display element and reflecting light reflected by the reflective polarizing member toward the reflective polarizing member;
a first λ/4 member disposed on an optical path between the display element and the half mirror;
a second λ/4 member disposed on an optical path between the half mirror and the reflective polarizing member;
A display system comprising:
The retardation film according to claim 4 , wherein the second λ/4 member is integrated with the first lens portion. a display element having a display surface that emits light representing an image forward via a polarizing member;
a reflective polarizing member disposed in front of the display element and reflecting light emitted from the display element;
a first lens portion disposed on an optical path between the display element and the reflective polarizing member, the first lens portion having a curved main surface;
a half mirror disposed between the display element and the first lens portion, the half mirror transmitting light emitted from the display element and reflecting light reflected by the reflective polarizing member toward the reflective polarizing member;
a first λ/4 member disposed on an optical path between the display element and the half mirror;
a second λ/4 member disposed on an optical path between the half mirror and the reflective polarizing member;
Equipped with
In a display system in which the second λ/4 member and the first lens unit are integrated, a set of a first retardation film for constituting the first λ/4 member and a second retardation film for constituting the second λ/4 member,
The first retardation film and the second retardation film each have an in-plane retardation Re(550) of 100 nm to 190 nm, and an absolute value of a retardation change value RS per unit thickness of 0.07 or less (wherein the retardation change value RS is the slope of an approximation line of the in-plane retardation Re(550) of the retardation film measured under tensions of 0 kg, 0.5 kg, 1 kg, 1.5 kg, and 2 kg);
The absolute value of the difference between the in-plane retardation Re(550) of the first retardation film and the in-plane retardation Re(550) of the second retardation film is 5 nm or less;
A set of phase contrast films.

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