Optical film and display device

Abstract

To provide an optical film with which it is possible to improve the view angle characteristics of an image displayed by a light deflection layer and suppress an external light reflection suppression function by a circular light polarizing plate from being impaired by the light deflection layer.SOLUTION: In one embodiment, an optical film 100 comprises: a first retardation layer 101; a second retardation layer 102; and a light deflection layer 110 for causing light to be deflected in an interface where a diffractive index changes over and located between the first retardation layer 101 and the second retardation layer 102. The first retardation layer 101 is a positive C plate or a negative C plate, and the second retardation layer 102 is a negative C plate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an optical film and a display device that improves the display quality of an image. [Background technology]

[0002] Optical films are known that are incorporated into display devices to improve the display quality of images displayed on the display devices. Objectives of optical films include widening the viewing angle, improving viewing angle characteristics, and suppressing external light reflection. For example, Patent Document 1 filed by the present applicant discloses an optical film that suppresses external light reflection using a circular polarizing plate.

[0003] In liquid crystal display devices and organic EL display devices, the color of an image when viewed obliquely can differ significantly from that when viewed from the front. Optical films for suppressing such color changes have been known.

[0004] An example of an optical film for suppressing color change is one in which the interface between two layers with different refractive indices is formed into an uneven shape, and the uneven interface deflects light for forming a display image over a wide range of angles.

[0005] The optical film having the light deflection function deflects light traveling toward the front viewing side toward a higher angle, and deflects light traveling toward a higher angle toward the front viewing side. By mixing the light within the viewing angle in this way, color change within the viewing angle can be suppressed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-69156 Summary of the Invention [Problem to be solved by the invention]

[0007] The circular polarizer includes a linear polarizer and a λ / 4 wavelength plate. The circular polarizer converts incident isotropic external light into linearly polarized light, which is then converted into circularly polarized light in a specific direction by the λ / 4 wavelength plate and transmitted. The transmitted light is reflected by, for example, a metal electrode of the display panel and becomes returned light. The returned light is reflected and becomes circularly polarized light in the opposite direction to the specific direction. The returned light then enters the circular polarizer and is converted into linearly polarized light by the λ / 4 wavelength plate. The linearly polarized light is then absorbed by the linear polarizer. This prevents the returned light from leaking to the outside, thereby suppressing external light reflection.

[0008] In a circular polarizer, the circular polarization of the returning light may be disturbed, resulting in a failure to achieve perfect circular polarization. In this case, the light component not absorbed by the linear polarizer may increase. As a result, the amount of reflected external light may increase. In circularly polarized light, the phase difference between the S wave and the P wave is ideally 90 degrees. However, for example, if the propagation direction of a light ray incident on a circular polarizer is tilted from the vertical, the phase difference between the P wave and the S wave of the transmitted light may deviate from 90 degrees, resulting in a phase shift from the ideal phase difference between the P wave and the S wave of circularly polarized light. When such a phase shift occurs, the circular polarization state of the light transmitted through the circular polarizer is disturbed, and the circular polarization state of the returning light may remain disturbed or may become even more disturbed. Note that the "phase shift" referred to here and in the following embodiments refers to a state in which the wavefront of the P wave is shifted relative to the S wave, resulting in a deviation from the ideal 90-degree phase difference between the P wave and the S wave of circularly polarized light. The terms S-waves and P-waves are used assuming that light rays pass through various interfaces of the optical film obliquely, but for convenience they are also used when light rays pass through perpendicularly.

[0009] There are two factors that cause the phase shift described above, which disrupts the circular polarization of the returning light. The first factor, which overlaps with the above, is a phase shift from the ideal phase difference of circularly polarized light that can occur when obliquely traveling external light (light beam) first passes through a λ / 4 wave plate. The second factor is a phase shift from the ideal phase difference of circularly polarized light that occurs when obliquely traveling circularly polarized external light that has passed through a λ / 4 wave plate is reflected by a metal electrode or the like, causing the wavefront of the P wave to shift relative to the S wave.

[0010] To suppress the phase shift described above, a retardation plate may be provided between the circular polarizer and the position where external light is reflected. If there is no component between the circular polarizer and the display panel, the angle of incidence of external light when it passes obliquely through the λ / 4 wavelength plate will be the same as the angle of emergence when the external light is reflected by a metal electrode or the like. Therefore, the phase shift from the ideal phase difference of circularly polarized light that may occur when light passes obliquely through the λ / 4 wavelength plate and the phase shift from the ideal phase difference of circularly polarized light that occurs when the wavefront of the P wave shifts relative to the S wave when light traveling obliquely through the λ / 4 wavelength plate is reflected can be relatively easily compensated for by setting the phase difference in a single retardation plate without excessively complicated considerations.

[0011] On the other hand, the optical film may have a light deflection layer for deflecting light in addition to the circular polarizer. The light deflection layer may be disposed between the circular polarizer and the display panel. However, in this configuration, for example, there may be a large amount of external light components whose incident angle when passing obliquely through a λ / 4 wavelength plate does not match the exit angle when the external light is reflected. This makes it difficult to adequately compensate for the phase shift from the ideal phase difference of circularly polarized light using a single retardation plate. As a result, it may be difficult to sufficiently suppress external light reflection.

[0012] The object of the present disclosure is to provide an optical film and a display device that can improve the viewing angle characteristics of a displayed image by using a light deflection layer while preventing the external light reflection suppression function of a circular polarizer from being impaired by the light deflection layer. [Means for solving the problem]

[0013] An optical film according to one embodiment includes a first retardation layer, a second retardation layer, and a light deflection layer disposed between the first retardation layer and the second retardation layer, the light deflection layer deflecting light at an interface where the refractive index changes, the first retardation layer being a positive C plate or a negative C plate, and the second retardation layer being a negative C plate.

[0014] the first retardation layer is a positive C plate, The following formula (1) may be established between the thickness direction retardation Rth1 (nm) of the first retardation layer and the thickness direction retardation Rth2 (nm) of the second retardation layer. -1.25×Rth2-75 <Rth1<-Rth2+50…(1)

[0015] Furthermore, the following formula (2) may also be true: -1.25×Rth2-37.5 <Rth1<-Rth2+25…(2)

[0016] Furthermore, the following formula (3) may also hold. -50 <Rth1+Rth2<0…(3)

[0017] The light deflection layer may have a first layer and a second layer having different refractive indices, and the interface may be an uneven interface between the first layer and the second layer.

[0018] The first layer may have a plurality of pillar portions embedded in the second layer, the plurality of pillar portions being arranged at intervals, and the contact surface between the pillar portions and the second layer may form part of the interface having an uneven shape.

[0019] The pillar portion may have a tapered shape in the direction in which it is embedded in the second layer, and the inclination angle defined by the acute angle that the side surface of the pillar portion makes with respect to the normal to the optical film may be between 0 degrees and 20 degrees.

[0020] The tilt angle may be 12 degrees or more and 15 degrees or less, the first retardation layer may be a positive C plate, and the thickness direction retardation Rth1 (nm) of the first retardation layer and the thickness direction retardation Rth2 (nm) of the second retardation layer may satisfy the following formulas (4) and (5): -125≦Rth1≦-50…(4) 25≦Rth2≦100…(5)

[0021] The light deflection layer may include a diffraction grating, and the interface may be formed in the uneven shape of the diffraction grating.

[0022] The light deflection layer may have light-transmitting particles and a holding layer that holds the particles, and the interface may be an interface between the particles and the holding layer.

[0023] The first retardation layer may be disposed so as to face the circular polarizer.

[0024] The liquid crystal display device may further include a circular polarizer provided on the side of the first retardation layer opposite to the light deflection layer.

[0025] The circular polarizer may include a linear polarizer and a λ / 4 wavelength plate, the thickness direction retardation of the λ / 4 wavelength plate being greater than 0, and the first retardation layer may be a positive C plate.

[0026] The circular polarizer may include a linear polarizer and a λ / 4 wavelength plate, the thickness direction retardation of the λ / 4 wavelength plate may be smaller than 0, and the first retardation layer may be a negative C plate.

[0027] The second retardation layer may be disposed so as to face the display panel.

[0028] It is assumed that light passing through the second retardation layer from the light deflection layer side is reflected by a metal member of the display panel, The in-plane refractive indexes Nx and Ny and the thickness direction refractive index Nz of the second retardation layer may be determined so as to satisfy the following formula (6).

number

[0029] The second retardation layer may be a TAC film.

[0030] Moreover, a display device according to one embodiment includes an organic EL panel and an optical film, the optical film including a first retardation layer, a second retardation layer, and a light deflection layer disposed between the first retardation layer and the second retardation layer, the light deflection layer deflecting light at an interface where a refractive index changes, the first retardation layer being a positive C plate or a negative C plate, the second retardation layer being a negative C plate, and the optical film being disposed so that the second retardation layer faces a light output surface of the organic EL panel.

[0031] Moreover, a display device according to one embodiment includes a liquid crystal panel and an optical film, the optical film including a first retardation layer, a second retardation layer, and a light deflection layer disposed between the first retardation layer and the second retardation layer, the light deflection layer deflecting light at an interface where a refractive index changes, the first retardation layer being a positive C plate or a negative C plate, the second retardation layer being a negative C plate, and the optical film being disposed so that the second retardation layer faces a light output surface of the liquid crystal panel. [Effects of the Invention]

[0032] According to the present disclosure, the viewing angle characteristics of a displayed image can be improved by the light deflection layer, while the external light reflection suppression function of the circular polarizer can be prevented from being impaired by the light deflection layer. [Brief explanation of the drawings]

[0033] [Figure 1] 1 is a schematic diagram of a display device including an optical film according to an embodiment. [Figure 2A] 1 is a cross-sectional view in the thickness direction of a light deflection layer of an optical film according to an embodiment. [Figure 2B] 2B is a diagram of a low refractive index layer in the light deflection layer shown in FIG. 2A viewed in the thickness direction. [Figure 3] 2 is a diagram illustrating the optical effect of external light incident on the display device shown in FIG. 1. FIG. [Figure 4] FIG. 10 is a diagram showing an optical film according to a modified example. [Figure 5] FIG. 10 is a diagram showing an optical film according to another modified example. [Figure 6] 2 is a diagram showing the results of a simulation of the reflectance of external light when the external light is incident on the display device shown in FIG. 1. FIG. [Figure 7] FIG. 10 is a diagram showing a simulation result of the reflectance of external light when the external light is incident on a display device including an optical film according to another embodiment. [Figure 8] 8 is a diagram showing the results of comparing the results of FIG. 6 and FIG. 7 under the same conditions of thickness direction retardation. [Figure 9] 2 is a diagram showing the results of a simulation of the reflectance of external light when the external light is incident on the display device shown in FIG. 1. FIG. [Figure 10] 10 is a diagram showing the results of a simulation of the reflectance of external light when the external light is incident on the display device shown in FIG. 1, and is a diagram showing the results of a simulation in which the conditions of the light deflection layer are different from those in FIG. 9. [Figure 11] 11 is a diagram showing the results of a simulation of the reflectance of external light when the external light is incident on the display device shown in FIG. 1, and is a diagram showing the results of a simulation in which the conditions of the light deflection layer are different from those in FIGS. 9 and 10. FIG. [Figure 12] 12 is a diagram showing the results of a simulation of the reflectance of external light when the external light is incident on the display device shown in FIG. 1, and is a diagram showing the results of a simulation in which the conditions of the light deflection layer are different from those in FIGS. 9 to 11. FIG. [Figure 13] 13 is a diagram showing the results of a simulation of the reflectance of external light when the external light is incident on the display device shown in FIG. 1, and showing the results of a simulation in which the conditions of the light deflection layer are different from those in FIGS. 9 to 12. FIG. [Figure 14] FIG. 14 is a table showing the reflectance (SCE relative value) that was the smallest value in the simulation results of FIGS. 9 to 13, corresponding to the simulation conditions. [Figure 15]FIG. 14 is a graph showing the simulation results of color change under the simulation conditions in which the reflectance (SCE relative value) was the smallest in the simulation results of FIGS. [Figure 16] FIG. 14 is a graph showing the simulation conditions under which the reflectance (SCE relative value) was smallest in the simulation results of FIGS. 9 to 13, and the corresponding SCE relative value. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, an optical film and a display device according to an embodiment will be described.

[0035] <Display device> FIG. 1 is a schematic diagram of an optical film-equipped display device 10 (hereinafter simply referred to as display device 10) that includes an optical film 100.

[0036] 1 includes a display panel 20 and an optical film 100. The display panel 20 has a display surface 20A, and the optical film 100 is provided so as to overlap the display surface 20A of the display panel 20. The display panel 20 displays an image on the display surface 20A, and the image displayed on the display surface 20A is projected onto the viewer's side through the optical film 100.

[0037] In the figures used in the following description, including FIG. 1, the symbol Z indicates the direction in which the display panel 20 and the optical film 100 overlap. Hereinafter, the direction indicated by Z is defined as the thickness direction Z. Furthermore, the plane perpendicular to the thickness direction Z may be referred to as the film plane.

[0038] The display device 10 may be a smartphone, a tablet terminal, a television, a computer display, a car navigation system, etc. The display device 10 may further include a touch panel and a cover glass that are overlaid on the optical film 100. In this case, the image displayed on the display surface 20A is projected to the viewer's side through the optical film 100, the touch panel, and the cover glass.

[0039] The display panel 20 shown in the figure is an organic LED (organic light emitting diode) panel. The type of organic LED panel display panel 20 is not particularly limited, and may have a microcavity structure or a color filter system. In general, organic LED panels are prone to blue shift in images viewed from an oblique angle, which can result in significant color change within the viewing angle. Blue shift is a phenomenon in which, when white is displayed on an organic LED panel, the image appears more blue when viewed from an oblique angle than when viewed from the front. Therefore, the display device 10 uses the optical film 100 to suppress color change within the viewing angle.

[0040] 1 denotes a metal electrode 21 as an example of a metal member provided on the display panel 20. In the display device 10, external light may enter the interior and be reflected by the metal electrode 21. This reflected light may be visible to a viewer, impairing the visibility of the image. Therefore, in the display device 10, the optical film 100 is used to suppress external light reflection.

[0041] The display panel 20 generates light for forming an image by supplying current to the organic light-emitting elements and controlling the amount of current via a drive circuit. The metal electrode 21 may be part of such a drive circuit. Generally, organic LED panels control organic light-emitting elements using TFTs (Thin Film Transistors) as drive circuits. The metal electrode 21 may be part of the TFT. That is, the metal member referred to in this disclosure is a metal member that causes an increase in external light reflection, and the metal electrode 21 is an example of a metal member. The display panel 20 may also be a liquid crystal panel. The material of the metal electrode 21 is not particularly limited, and may be silver, an MgAg alloy, copper, a copper alloy, gold, aluminum, an aluminum alloy, or the like. The formation of the metal electrode 21 is also not particularly limited, and may be formed, for example, from a foil, by sputtering, or by vapor deposition.

[0042] <Optical film> The optical film 100 includes a first retardation layer 101, a second retardation layer 102, a light deflection layer 110, and a circular polarizer 120. Of these, the light deflection layer 110 exhibits a function of suppressing color change by deflecting light for image formation from the display panel 20. The circular polarizer 120 exhibits a function of suppressing external light reflection.

[0043] The light deflection layer 110 is disposed between the first retardation layer 101 and the second retardation layer 102. The circular polarizer 120 is provided on the side of the first retardation layer 101 opposite to the light deflection layer 110 side. The optical film 100 is used by being disposed so that the second retardation layer 102 faces the display panel 20. Therefore, in the illustrated example, the circular polarizer 120 is located on the side of the optical film 100 closest to the viewer. The circular polarizer 120 has a linear polarizer 121 and a λ / 4 wavelength plate 122, and the linear polarizer 121 faces the viewer.

[0044] In FIG. 1 , gaps are shown between the first retardation layer 101 and the light deflection layer 110, between the second retardation layer 102 and the light deflection layer 110, and between the first retardation layer 101 and the circular polarizer 120. However, in practice, adjacent layers are directly or indirectly bonded to each other. When the layers are indirectly bonded to each other, the adjacent layers may be bonded via an OCA (Optical Clear Adhesive). For example, the optical film 100 may be composed of the first retardation layer 101, the second retardation layer 102, and the light deflection layer 110, and may be disposed adjacent to a separate circular polarizer 120 when assembled into the display panel 20. The light deflection layer 110 may be provided with a light-transmitting substrate. This substrate may be, for example, a TAC film or a film mainly composed of polyethylene terephthalate, polyolefin, polycarbonate, polyacrylate, or polyamide.

[0045] 1 also shows a gap between the display panel 20 and the optical film 100. The display panel 20 and the optical film 100 may be separated from each other or may be bonded to each other in direct or indirect contact. When the display panel 20 and the optical film 100 are bonded to each other in indirect contact, the display panel 20 and the optical film 100 may be bonded via an OCA.

[0046] (1st retardation layer) In this embodiment, the first retardation layer 101 is a positive C plate. The relationship between the in-plane refractive indexes Nx and Ny and the thickness direction refractive index Nz of the first retardation layer 101 is Nz>Nx, Nz>Ny, and Nx=Ny. Note that Nx=Ny is a concept that also includes the fact that these are approximately equal (Nx≒Ny).

[0047] The first retardation layer 101 may be a film in which a liquid crystal compound is aligned. In this case, the liquid crystal compound is homeotropically aligned, that is, the longitudinal direction of the liquid crystal compound is aligned along the thickness direction of the film.

[0048] Although the details will be described later, the λ / 4 wavelength plate 122 in the circular polarizer 120 has a characteristic of having a so-called rugby ball-shaped refractive index ellipsoid, and the rugby ball shape has the longitudinal direction along the plate surface. In this embodiment, the first retardation layer 101 is a positive C plate so as to cancel out such a characteristic of the circular polarizer 120.

[0049] The thickness of the first retardation layer 101 is not particularly limited, but may be, for example, 0.5 μm or more and 10 μm or less. The thickness direction retardation Rth1 of the first retardation layer 101 is not particularly limited, but may be determined in consideration of the refractive index characteristics of the circular polarizer 120. The thickness direction retardation Rth1 may be, for example, less than 0 and -200 nm or more. The thickness direction retardation Rth1 may be -175 nm or more and -25 nm or less, -150 nm or more and -25 nm or less, or -125 nm or more and -50 nm or less.

[0050] Incidentally, the thickness-direction retardation Rth (such as the above Rth1 or the following Rth1) can be calculated from the following formula (0). Rth = ((Nx + Ny) / 2 - Nz) × d…(0) Here, Nx and Ny are in-plane refractive indices, Nz is the thickness-direction refractive index, and d is the thickness of the plate or film to be calculated. Rth can be measured, for example, using the product “AxoScan” of the polarimeter manufactured by Axsometrics.

[0051] (Second retardation layer) The second retardation layer 102 is a negative C-plate, and the relationship between the in-plane refractive indices Nx, Ny and the thickness-direction refractive index Nz in the second retardation layer 102 is Nz < Nx, Nz < Ny, and Nx = Ny. Similar to the above, Nx = Ny is a concept including the case where they are substantially equal (Nx ≒ Ny).

[0052] The second retardation layer 102 may be a film in which a liquid crystal compound is oriented, or a biaxially stretched resin film. When the second retardation layer 102 is a film in which a liquid crystal compound is oriented, the liquid crystal compound may have a random homogeneous orientation. When the second retardation layer 102 is a biaxially stretched resin film, the second retardation layer 102 may be a TAC film. That is, the second retardation layer 102 may be a film mainly composed of triacetyl cellulose.

[0053] Also, if the second retardation layer 102 can function as a negative C-plate, the second retardation layer 102 may be a film mainly composed of, for example, polyethylene terephthalate, polyolefin, polycarbonate, polyacrylate, or polyamide. Here, the main component means a component contained at a ratio of 50% or more or the most contained component with respect to the whole substance composed of a plurality of components of a certain substance.

[0054] The thickness of the second retardation layer 102 is not particularly limited, but may be, for example, 0.5 μm to 10 μm. External light incident on the display device 10 may reach and be reflected by the metal electrode 21 of the display panel 20. When the external light is reflected by the metal electrode 21, the phases of the P and S waves of the reflected light shift depending on the angle of travel of the light. Specifically, for light that is obliquely incident on the metal electrode 21 and reflected, the P wave is delayed relative to the S wave compared to light that is perpendicularly incident and reflected. This means that the wavefront of the P wave shifts toward the light source relative to the S wave. As a result, external light that passes through the circular polarizer 120 and is reflected by the metal electrode 21 may exhibit a phase shift from the ideal phase difference of circularly polarized light. The second retardation layer 102 has a function of compensating for this phase shift of the reflected light caused by reflection at the metal electrode 21 of the display panel 20. The thickness direction retardation Rth2 of the second retardation layer 102 is not particularly limited, and may be determined in consideration of the reflection characteristics of the metal electrode 21. The thickness direction retardation Rth2 may be, for example, greater than 0 and less than or equal to 150 nm. The thickness direction retardation Rth2 may be 25 nm or more and 150 nm or less, 50 nm or more and 150 nm or less, or 75 nm or more and 125 nm or less.

[0055] (light deflection layer) 2A is a cross-sectional view of the light deflection layer 110 in the thickness direction Z. As shown in FIGS. 1 and 2A, the light deflection layer 110 has a low refractive index layer 111 and a high refractive index layer 112. The low refractive index layer 111 and the high refractive index layer 112 are stacked in this order from the side of the display device 10 where a viewer is located toward the organic LED panel 15. The refractive index of the low refractive index layer 111 is different from and smaller than the refractive index of the high refractive index layer 112. The low refractive index layer 111 corresponds to a first layer, and the high refractive index layer 112 corresponds to a second layer.

[0056] 2B is a diagram of the low refractive index layer 111 in the light deflection layer 110 shown in Fig. 2A when viewed in the thickness direction Z. The low refractive index layer 111 integrally includes a film-like land portion 111A having a front surface and a back surface, and a plurality of pillar portions 111B which are optical elements arranged two-dimensionally at intervals along a first arrangement direction D1 and a second arrangement direction D2 on the back surface of the land portion 111A.

[0057] The high-refractive-index layer 112 is bonded to the low-refractive-index layer 111 so as to cover the pillar portions 111B and fill the spaces between the pillar portions 111B. As a result, in this embodiment, the interface between the low-refractive-index layer 111 and the high-refractive-index layer 112 has an uneven shape. Here, the contact surface between the pillar portions 111B and the high-refractive-index layer 112 forms part of the uneven interface. When the low-refractive-index layer 111 has multiple pillar portions 111B, the high-refractive-index layer 112 has a film shape with multiple holes that accommodate the multiple pillar portions 111B, and is at least partially lattice-shaped. The light deflection layer 110 refracts or reflects incident light at the uneven interface between the low-refractive-index layer 111 and the high-refractive-index layer 112, where the refractive index changes. This deflects the light, i.e., changes the direction of travel of the light.

[0058] The pillar portion 111B in this embodiment has a tapered shape toward the direction where it is embedded in the high refractive index layer 112. As an example, the pillar portion 111B has a truncated quadrangular pyramid shape, and the pillar portion 111B has a tip 111T and a side surface 111S connecting the tip 111T and the base end. The tip 111T shown in the figure is a flat surface parallel to the film surface. The side surface 111S is also a flat surface. However, the side surface 111S may be curved or stepped.

[0059] The symbol θ in FIG. 2A indicates the inclination angle, which is defined as an acute angle between the side surface 111S and the normal line N of the optical film 100. The inclination angle θ may be 0 degrees or more and 30 degrees or less. The inclination angle θ may be 0 degrees or more and 26 degrees or less, 0 degrees or more and 20 degrees or less, 6 degrees or more and 26 degrees or less, 6 degrees or more and 20 degrees or less, 8 degrees or more and 18 degrees or less, 10 degrees or more and 16 degrees or less, or 12 degrees or more and 15 degrees or less. The inclination angle θ may be 13.5 degrees or more and 14.5 degrees or less, or may be 14 degrees. The inclination angle θ is defined as the angle between the normal line N and a tangent line at the midpoint of the side surface 111S in the thickness direction Z in the thickness direction cross section.

[0060] As described above, the pillar portions 111B are arranged two-dimensionally at intervals. Specifically, the pillar portions 111B are arranged at intervals in each of the first arrangement direction D and the second arrangement direction D2 intersecting the first arrangement direction D1 shown in FIGS. 2A and 2B.

[0061] 2A and 2B, the reference symbol P1 indicates the first direction pitch of the pillar portions 111B spaced apart in the first array D1. The reference symbol P2 in Fig. 2B indicates the second direction pitch of the pillar portions 111B spaced apart in the second array direction D2.

[0062] The first direction pitch P1 may be 1 μm or more, 2 μm or more, or 4 μm or more. The first direction pitch P1 may be 200 μm or less, 100 μm or less, 50 μm or less, 20 μm or less, or 10 μm or less. The second direction pitch P2 may be 1 μm or more, 2 μm or more, or 4 μm or more. The second direction pitch P2 may be 200 μm or less, 100 μm or less, 50 μm or less, 20 μm or less, or 10 μm or less.

[0063] In this embodiment, the first direction pitch P1 and the second direction pitch P2 are the same value, but they may be different values. Also, the first arrangement D1 and the second arrangement direction D2 are orthogonal to each other, but they may also intersect obliquely.

[0064] Furthermore, the side surface 111S of the pillar portion 111B, which is shaped like a truncated square pyramid, has a pair of first element surfaces 111S1 facing each other and a pair of second element surfaces 111S2 facing each other in a direction perpendicular to the direction in which the first element surfaces 111S1 face each other. The symbol W1 in FIG. 2B indicates the width of the first element surface 111S1 on the side surface 111S, and the symbol W2 in FIGS. 2A and 2B indicates the width of the second element surface 111S2 on the side surface 111S. Because the pillar portion 111B shown in the figure has a truncated square pyramid shape, the width W1 of the first element surface 111S1 and the width W2 of the second element surface 111S2 have the same value. However, the pillar portion 111B does not have to have a truncated square pyramid shape, and the width W1 and the width W2 may have different values.

[0065] The width W1 of the first element surface 111S1 and the width W2 of the second element surface 111S2 may be, for example, 0.5 μm or more, 1 μm or more, 2 μm or more, or 4 μm or more. The width W1 of the first element surface 111S1 and the width W2 of the second element surface 111S2 may be 200 μm or less, 100 μm or less, 50 μm or less, 20 μm or less, 10 μm or less, or 5 μm or less.

[0066] In the illustrated example, the direction in which the first element surfaces 111S1 extend along the film surface is parallel to the second array D2, and the direction in which the second element surfaces 111S2 extend along the film surface is the first array direction D1. The first duty is determined by dividing the dimension in the first array D1 between the midpoints of the pair of first element surfaces 111S1 in the normal direction to the film surface by the first-direction pitch P1. The second duty is determined by dividing the dimension in the second array D2 between the midpoints of the pair of second element surfaces 111S2 in the normal direction to the film surface by the second-direction pitch P2. The first duty and the second duty may be, for example, 0.5 or more and 0.8 or less. In this case, the optical effect of the side surface 111S of the pillar portion 111B can function effectively.

[0067] As described above, the circular polarizer 120 has the linear polarizer 121. Here, it is preferable that either the direction in which the first element surface 111S1 extends along the film surface or the direction in which the second element surface 111S2 extends along the film surface is parallel to the transmission axis of the linear polarizer 121, and it is preferable that the other of the direction in which the first element surface 111S1 extends along the film surface or the direction in which the second element surface 111S2 extends along the film surface is parallel to the absorption axis of the linear polarizer 121.

[0068] In the illustrated example, the direction in which the first element surfaces 111S1 extend along the film surface is parallel to the second array D2, and the direction in which the second element surfaces 111S2 extend along the film surface is parallel to the first array direction D1. However, instead of this, the direction in which the first element surfaces 111S1 extend along the film surface may be non-parallel to the second array D2 and the first array direction D1, and the direction in which the second element surfaces 111S2 extend along the film surface may be non-parallel to the first array direction D1 and the second array direction D2. However, even in this case, it is preferable that either the direction in which the first element surface 111S1 extends along the film surface or the direction in which the second element surface 111S2 extends along the film surface is parallel to the transmission axis of the linear polarizer 121, and it is preferable that the other of the direction in which the first element surface 111S1 extends along the film surface or the direction in which the second element surface 111S2 extends along the film surface is parallel to the absorption axis of the linear polarizer 121.

[0069] Furthermore, it is preferable that the first slope ratio, which is the ratio of the dimension of the tip 111T in the second arrangement D2 to the width W1 of the first element face 111S1, and the second slope ratio, which is the ratio of the dimension of the tip 111T in the first arrangement D1 to the width W2 of the second element face 111S2, are 0.3 to 0.95, inclusive. In this case, a good balance is achieved between suppressing color shift and ensuring front brightness.

[0070] 2A indicates the height, which is the dimension in the thickness direction Z, of the pillar portion 111B. The height of the pillar portion 111B is, for example, 1.0 μm or more and 30 μm or less. The dimension (thickness) in the thickness direction Z of the land portion 111A in the low refractive index layer 111 is, for example, 0.5 μm or more and 30 μm or less. The thickness of the high refractive index layer 112 is, for example, 5 μm or more and 100 μm or less.

[0071] Although the pillar portion 111B shown in the figure has a quadrangular pyramid shape, the pillar portion 111B may also have a quadrangular pyramid shape, a cone shape, a truncated cone shape, an octagonal pyramid shape, or the like. The low-refractive index layer 111 may not have the land portion 111A and may be configured by a collection of multiple pillar portions 111B. The optical film 100 may not include the high-refractive index layer 112. The low-refractive index layer 111 may be omitted. That is, the low-refractive index layer 111 may be formed of an air layer. In the present embodiment, the high-refractive index layer 112 of the low-refractive index layer 111 and the high-refractive index layer 112 is disposed closer to the display panel 20 than the low-refractive index layer 111, but this arrangement order may be reversed. The pillar portion 111B may also extend linearly along the film surface. To combat moire, the pillar portions 111B may be arranged randomly, for example, in a precise grid arrangement.

[0072] The refractive index of the low-refractive-index layer 111 (land portion 111A and pillar portion 111B) is, for example, 1.40 or more and 1.55 or less. The refractive index of the high-refractive-index layer 112 is, for example, 1.55 or more and 1.90 or less, which is higher than the refractive index of the low-refractive-index layer 111. In the present embodiment, as an example, the low-refractive-index layer 111 and the high-refractive-index layer 112 are selected so that the difference in refractive index between the low-refractive-index layer 111 and the high-refractive-index layer 112 is in the range of 0.05 or more and 0.50 or less.

[0073] The low refractive index layer 111 and the high refractive index layer 112 may be formed by curing, for example, an ultraviolet curable resin, an electron beam curable resin, or a thermosetting resin. When the low refractive index layer 111 and the high refractive index layer 112 are formed by curing an ultraviolet curable resin, the ultraviolet curable resin may contain an acrylic resin or an epoxy resin.

[0074] (Circular polarizer) Returning to FIG. 1 , as described above, the circular polarizer 120 includes a linear polarizer 121 and a λ / 4 wavelength plate 122. The linear polarizer 121 has an absorption axis and a transmission axis perpendicular to the absorption axis, and transmits a linearly polarized component of isotropic light in one direction. The linear polarizer 121 also absorbs a linearly polarized component perpendicular to the one direction at the absorption axis. The linear polarizer 121 may be a stretched film having a dichroic dye adsorbed thereon, or a film in which a liquid crystal compound is oriented.

[0075] The λ / 4 wave plate 122 converts the linearly polarized light component in one direction that has passed through the linear polarizer 121 into circularly polarized light and transmits it. The λ / 4 wave plate 122 has a thickness direction retardation Rthq that is greater than 0, and in this example, has the relationship Nx>Ny≧Nz. Due to these characteristics, the λ / 4 wave plate 122 has a so-called rugby ball-shaped index ellipsoid, and the rugby ball shape has its longitudinal direction aligned with the plate surface.

[0076] As a modified example, the thickness direction retardation of the λ / 4 wave plate 122 may be smaller than 0 and may further satisfy the relationship Nz≧Nx>Ny. In this case, a negative C plate is used as the first retardation layer 101. That is, the optical film according to this modified example includes the first retardation layer 101, the second retardation layer 102, the light deflection layer 110, and the circular polarizer 120, and the circular polarizer 120 has a linear polarizer 121 and a λ / 4 wave plate 122 whose thickness direction retardation is smaller than 0 and optionally satisfies Nz≧Nx>Ny. The first retardation layer 101 serves as a negative C plate, and the second retardation layer 102 serves as a negative C plate.

[0077] The λ / 4 wave plate 122 may be configured by laminating a λ / 4 retardation layer and a λ / 2 retardation layer. In this case, if the sum of the thickness direction retardations of the λ / 4 retardation layer and the λ / 2 retardation layer is greater than 0, the λ / 4 wave plate 122 is evaluated as having the relationship Nx>Ny≧Nz. On the other hand, if the sum of the thickness direction retardations of the λ / 4 retardation layer and the λ / 2 retardation layer is greater than 0, the λ / 4 wave plate 122 is evaluated as having the relationship Nz≧Nx>Ny.

[0078] <Setting the thickness direction retardation> The following describes how to set the thickness direction retardation of a plurality of layers in this embodiment.

[0079] As described above, in the present embodiment, the thickness direction retardation Rthq of the λ / 4 wave plate 122 is greater than 0, and the λ / 4 wave plate 122 has the relationship Nx>Ny≧Nz. Correspondingly, the first retardation layer 101 is a positive C plate. According to this relationship between the λ / 4 wave plate 122 and the first retardation layer 101, a phase shift from an ideal circularly polarized light retardation that may occur in light that passes obliquely through the λ / 4 wave plate 122 toward the first retardation layer 101 can be compensated for by the first retardation layer 101.

[0080] In addition, the second retardation layer 102 is a negative C plate. This allows the second retardation layer 102 to compensate for a phase shift that may occur when P waves lag behind S waves in light that is obliquely incident on and reflected from the metal electrode 21 of the display panel 20. Due to the relationship between the plate members as described above, external light that is incident on the display device 10 and reflected by the metal electrode 21 is polarized in a state that makes it easy for the external light to be absorbed by the linear polarizer 121 of the circular polarizer 120, and the circular polarizer 120 can effectively suppress external light reflection.

[0081] The above-described effective suppression of external light reflection according to the present disclosure is achieved by the relationship between the above-described plate members constituting the optical film 100. More specifically, the first retardation layer 101 is a positive C plate whose thickness direction retardation Rth1 is smaller than 0 corresponding to the λ / 4 wave plate 122 whose thickness direction retardation Rthq is larger than 0, and the second retardation layer 102 is a negative C plate to compensate for the phase shift caused by the delay of the P wave relative to the S wave of light obliquely reflected by the metal electrode 21, thereby achieving effective suppression of external light reflection.

[0082] On the other hand, the present inventors have found that, in the relationship between the above-mentioned components constituting the optical film 100, it is preferable that the following formula (1) holds between the thickness direction retardation Rth1 (nm) of the first retardation layer 101 and the thickness direction retardation Rth2 (nm) of the second retardation layer 102, it is more preferable that formula (2) holds, and it is also more preferable that formula (3) holds.

[0083] -1.25×Rth2-75 <Rth1<-Rth2+50…(1)

[0084] -1.25×Rth2-37.5 <Rth1<-Rth2+25…(2)

[0085] -50 <Rth1+Rth2<0…(3)

[0086] The present inventors have confirmed that when formula (1) is satisfied, the reflectance of external light incident on the display device 10 can be suppressed, and when formula (2) is satisfied, the reflectance of external light incident on the display device 10 can be more effectively suppressed. Furthermore, the present inventors have confirmed that when formula (3) is satisfied, the reflectance of external light incident on the display device 10 can also be more effectively suppressed.

[0087] Furthermore, the present inventors have discovered that, as a shape condition of the light deflection layer 110, when the inclination angle θ that the side surface 111S of the pillar portion 111B makes with respect to the normal line N of the optical film 100 is 6 degrees or more and 15 degrees or less, preferably 10 degrees or more and 15 degrees or less, more preferably 12 degrees or more and 15 degrees or less, even more preferably 13 degrees or more and 14.5 degrees or less, and even more preferably 14 degrees, the following formulas (4) and (5) are satisfied, and a specific effect can be obtained.

[0088] -125≦Rth1≦-50…(4) 25≦Rth2≦100…(5)

[0089] The unique effect obtained when the above formulas (4) and (5) are satisfied is an effect of sharply improving the effect of suppressing the reflectance of external light incident on the display device 10 and sharply improving the effect of suppressing color change displayed on the display device 10. Specifically, when the tilt angle θ is 10 degrees or more and 15 degrees or less, the effect of suppressing the reflectance of external light increases particularly sharply, and it has been confirmed that, for example, the reflectance can be reduced by approximately 20% or more compared to when the tilt angle θ is less than 6 degrees and greater than 20 degrees.

[0090] The above formulas (1) to (5) hold regardless of the specific values ​​of the thickness direction retardations Rth1 and Rth2. On the other hand, as described above, the thickness direction retardation Rth1 may be, for example, less than 0 and not less than −200 nm. The thickness direction retardation Rth1 may be, for example, not less than −175 nm and not more than −25 nm, not more than −150 nm and not more than −25 nm, or not more than −125 nm and not more than −50 nm. The thickness direction retardation Rth2 may be, for example, not more than 0 and not more than 150 nm. The thickness direction retardation Rth2 may be, for example, not less than 25 nm and not more than 150 nm, not more than 50 nm and not more than 150 nm, or not more than 75 nm and not more than 125 nm. The above-listed numerical examples are relatively small. From the viewpoint of reducing the thickness of the optical film 100, the above-listed numerical example is preferable, and it is preferable that formulas (1) to (5) hold within the above-listed numerical example range.

[0091] Further, the second retardation layer 102 is a negative C-plate and has the characteristics of Nz < Nx, Nz < Ny, and Nx = Ny. Thereby, the second retardation layer 102 compensates for the phase shift caused by the delay of the P wave with respect to the S wave, which may occur in the external light that obliquely enters the metal electrode 21 of the display panel 20 and is reflected by the metal electrode 21. Specifically, the light that obliquely enters and is reflected by the metal electrode 21 has a delay of the P wave with respect to the S wave compared to the light that vertically enters and is reflected, which may cause a phase shift. In contrast, the negative C-plate can advance the phase of the P wave of the incident light. Therefore, the second retardation layer 102, which is a negative C-plate, can compensate for the phase shift of the external light reflected by the metal electrode 21.

[0092] The in-plane refractive indices Nx, Ny and the thickness-direction refractive index Nz of the second retardation layer 102 as such a negative C-plate may be determined so as to satisfy the following formula (6) in consideration of the fact that the external light before reflection and the external light after reflection pass obliquely through the second retardation layer 102, and the phase shift in which the P wave at the metal electrode 21 as an example of the metal member is delayed with respect to the S wave varies depending on the material and properties (foil formation, sputter formation, etc.).

Equation

[0093] Here, θ related to formula (6) is the critical angle of the second retardation layer 102 obtained by the following formula and is the angle of the most inclined ray among the external lights incident on and reflected by the metal electrode 21. n = 1 / sinθ "(1 + cosδ , , , Total , , ) / 2" in formula (6) is the reflectance defined by the ratio of the light that is incident from the outside, passes through the first retardation layer and the second retardation layer at an angle θ, is reflected by the metal electrode 21, and finally passes through circularly polarized light and exits to the outside, with respect to the incident light from the outside, when the influence of Fresnel loss and deflection in the light deflection layer is ignored. That is, formula (6) is a condition for making the reflectance of the ray with the largest reflectance among the ray group of the external light 4% or less, which is the surface reflectance of general glass or film. When the above conditions are satisfied, only 4% or less of the light reflected by the metal electrode 21 passes through the circular polarizer 120, and therefore almost no light escapes to the outside. Furthermore, the light that passes through the second retardation layer 102 and proceeds toward the circular polarizer 120 is easily absorbed by the linear polarizer 121 and is less likely to escape to the outside because the phase shift from the phase difference of ideal circularly polarized light has been compensated for.

[0094] <Optical effect on external light passing through optical film> Fig. 3 is a diagram illustrating the optical effect of external light incident on the display device 10. Fig. 3 shows, from above, the λ / 4 wave plate 122, first retardation layer 101, light deflection layer 110, and second retardation layer 102 of the circular polarizer 120 constituting the optical film 100. For ease of explanation, an index ellipsoid corresponding to each layer is virtually shown within each of the λ / 4 wave plate 122, first retardation layer 101, and second retardation layer 102. Also shown below the second retardation layer 102 are the display panel 20 and the metal electrode 21.

[0095] In the display device 10, when obliquely traveling external light first passes through the λ / 4 wavelength plate 122, the external light may experience a phase shift from the ideal phase difference of circularly polarized light. Furthermore, when external light that is obliquely incident on the metal electrode 21 is reflected by the metal electrode 21, the phase may also shift from the ideal phase difference of circularly polarized light. The light deflection layer 110 is disposed between the λ / 4 wavelength plate 122 and the metal electrode 21. The provision of the light deflection layer 110 complicates the traveling direction and polarization state of the external light. If the phases of the P and S waves of the external light that are reflected by the metal electrode 21 and return to the circular polarizer 120 deviate significantly from the ideal phase difference of circularly polarized light, the circularly polarized light is not properly maintained, and many components are not absorbed by the linear polarizer 121.

[0096] In contrast, the optical film 100 according to the present embodiment uses the first retardation layer 101 to compensate for phase shifts from the ideal phase difference of circularly polarized light that may occur when external light obliquely passes through the λ / 4 wavelength plate 122. Furthermore, the second retardation layer 102 compensates for phase shifts from the ideal phase difference of circularly polarized light that may occur when external light obliquely enters the metal electrode 21 and is reflected by the metal electrode 21. In this way, the optical film 100 according to the present embodiment has two separate positions where the compensation function is exerted. The optical properties of the first retardation layer 101 are set to suitably suppress phase shifts from the ideal phase difference of circularly polarized light that may occur when external light obliquely enters the λ / 4 wavelength plate 122, and the optical properties of the second retardation layer 102 are set to suitably suppress phase shifts from the ideal phase difference of circularly polarized light that may occur when external light obliquely enters the metal electrode 21 and is reflected by the metal electrode 21. This achieves effective suppression of external light reflection. The phase compensation will be specifically described below.

[0097] The symbol L1 in FIG. 3 indicates an external light component that passes obliquely through the λ / 4 waveplate 122. The λ / 4 waveplate 122 has a thickness direction retardation Rthq greater than 0, and in this example, the relationship Nx>Ny≧Nz holds. Therefore, the refractive index ellipsoid of the λ / 4 waveplate 122 is rugby ball-shaped and lies flat along the film surface. The external light component L1 that passes obliquely through the λ / 4 waveplate 122 with such refractive index characteristics experiences a phase shift from the ideal circularly polarized light phase difference due to the P wave traveling faster than the S wave. The phase shift caused by the P wave traveling relative to the S wave increases as the angle of incidence of the external light component L1 on the λ / 4 waveplate 122 becomes more inclined with respect to the direction perpendicular to the film surface.

[0098] The external light component L1 with a phase difference is then incident obliquely on the first retardation layer 101, which is a positive C plate. Therefore, the refractive index ellipsoid of the first retardation layer 101 is rugby-ball shaped and stands upright in the thickness direction. In the external light component L1 that passes obliquely through the first retardation layer 101 with such refractive index characteristics, the P wave is delayed relative to the S wave. Therefore, the first retardation layer 101 compensates for the phase shift of the external light component L1, which occurs when the P wave advances more than the S wave in the λ / 4 wavelength plate 122, by offsetting it toward the ideal phase difference of circularly polarized light. The delay of the P wave relative to the S wave in the first retardation layer 101 increases as the angle of incidence of the external light component L1 on the first retardation layer 101 increases with respect to the direction perpendicular to the film surface.

[0099] Thereafter, the external light component L1 enters the light deflection layer 110. The travel angle of the external light component L1 is changed by reflection or refraction at the interface between the low refractive index layer 111 and the high refractive index layer 112. At this time, the travel angle of the external light component L1 that has passed through the light deflection layer 110 may be changed, but the phase shift from the phase difference of ideal circularly polarized light is suppressed.

[0100] Thereafter, the external light component L1 that has passed through the light deflection layer 110 is incident on the second retardation layer 102. In the example shown in the figure, the external light component L1 that has passed through the light deflection layer 110 passes obliquely at a relatively large inclination angle. However, there are also cases where the external light component L1 that has passed through the light deflection layer 110 passes at an angle close to perpendicular to the film surface.

[0101] The second retardation layer 102 is a negative C plate, and its refractive index ellipsoid is an anpan type lying along the film surface. With such refractive index characteristics, the P wave propagates faster than the S wave in the external light component L1 that passes obliquely through the second retardation layer 102. The phase shift caused by the P wave propagating faster than the S wave increases as the angle of incidence of the external light component L1 on the second retardation layer 102 becomes more inclined with respect to the direction perpendicular to the film surface.

[0102] Thereafter, in the external light component L1 that passes through the second retardation layer 102, the P wave advances more than the S wave, but when the external light component L1 is reflected by the metal electrode 21, the P wave lags behind the S wave (in the case of vertical propagation, the front and rear of the P wave and the S wave are symmetrically reversed, but compared to this ideal state). Then, when the external light component L1 reflected by the metal electrode 21 passes through the second retardation layer 102 again at an angle, the P wave advances more than the S wave. That is, assuming that the P wave lags more than the S wave when the external light component L1 is reflected by the metal electrode 21, the second retardation layer 102 advances the P wave when the external light component L1 first passes through, and also advances the P wave after reflection, thereby making it possible to compensate for and reduce the phase shift caused by reflection.

[0103] Then, the external light component L1 that is reflected by the metal electrode 21 and passes through the second retardation layer 102 is incident on the light deflection layer 110. The travel angle of the external light component L1 is changed by reflection or refraction at the interface between the low refractive index layer 111 and the high refractive index layer 112. However, although the angle at which the external light component L1 that has passed through the light deflection layer 110 is changed relative to the angle at which it is incident, the phase deviation from the phase difference of ideal circularly polarized light is suppressed.

[0104] The external light component L1 returning from the light deflection layer 110 to the linear polarizer 121 via the first retardation layer 101 and the λ / 4 wavelength plate 122 passes through the λ / 4 wavelength plate 122 with the phase shift having been cancelled out in advance by the first retardation layer 101. Therefore, the external light component L1 that has been converted into linearly polarized light by the λ / 4 wavelength plate 122 and returned is in a state that is easily absorbed by the linear polarizer 121. Therefore, reflection of external light is suppressed.

[0105] As described above, the optical film 100 according to the present embodiment includes the first retardation layer 101, the second retardation layer 102, and the light deflection layer 110 disposed between the first retardation layer 101 and the second retardation layer 102. The first retardation layer 101 is disposed so as to face the circular polarizer 120.

[0106] In this optical film 100, the thickness direction retardation Rthq of the λ / 4 wave plate 122 is greater than 0, and the relationship Nx>Ny≧Nz is satisfied. Correspondingly, the first retardation layer 101 is a positive C plate. This relationship between the λ / 4 wave plate 122 and the first retardation layer 101 allows the first retardation layer 101 to compensate for a phase shift from the ideal phase shift of circularly polarized light that may occur in light that passes obliquely through the λ / 4 wave plate 122 toward the first retardation layer 101. Furthermore, the second retardation layer 102 is a negative C plate. This allows for compensation for a phase shift from the ideal phase shift of circularly polarized light that may occur when P waves are delayed relative to S waves due to reflection at the metal electrode 21 of the display panel 20. Due to the relationship between the components described above, external light that enters the display device 10 and is reflected by the metal electrode 21 is polarized in a state that is easily absorbed by the linear polarizer 121 of the circular polarizer 120, allowing the circular polarizer 120 to effectively suppress external light reflection.

[0107] Therefore, the viewing angle characteristics of the image to be displayed can be improved by the light deflection layer 110, while the function of the circular polarizer 120 to suppress reflection of external light can be prevented from being impaired by the light deflection layer 110.

[0108] <Modification> In the embodiment described above, the low refractive index layer 111 of the light deflection layer 110 has a plurality of pillar portions 111B embedded in the high refractive index layer 112, and the plurality of pillar portions 111B are arranged at intervals. However, the light deflection layer 110 is not limited to a structure having pillar portions 111B.

[0109] FIG. 4 shows a light deflection layer 210 according to a modified example. The light deflection layer 210 has light-transmitting particles 212 and a retaining layer 211 that holds the particles 212. The refractive index of the particles 212 is higher than that of the retaining layer 211. The refractive indexes that can be set for the particles 212 and the retaining layer 211 are the same as those of the low-refractive-index layer 111 and the high-refractive-index layer 112. The retaining layer 211 is formed by curing a resin, and holds the particles 212 dispersed therein. The light deflection layer 210 can deflect light at the interface between the particles 212 and the retaining layer 211.

[0110] 5 shows a light deflection layer 310 according to yet another modification. The light deflection layer 310 includes a diffraction grating 312. The diffraction grating 312 can deflect light by using the structure of an interface with an air layer or an interface between materials with different refractive indexes. The interface is formed by a concave-convex shape on the diffraction grating 312.

[0111] 4 and 5 are combined with the first retardation layer 101, the second retardation layer 102, and the circular polarizer 120 described in the embodiment, the viewing angle characteristics of the displayed image can be improved by the light deflection layers 210 and 310, while the external light reflection suppression function of the circular polarizer 120 can be prevented from being impaired by the light deflection layers 210 and 310. On the other hand, the present inventors have found that when the light deflection layer 110 has a structure including pillar portions 111B, it can suppress external light reflection more effectively than the light deflection layer 210 having particles 212. This is because, in the structure including the pillar portions 111B, light rays pass through interfaces only one to three times, whereas in the structure including the particles 212, the frequency of passing through interfaces three or more times increases. Another reason is that the structure having the pillar portions 111B is composed only of surfaces with inclination angles that are effective for reducing blue shift, whereas the structure having the particles 212 also includes surfaces with inclination angles that are unsuitable for reducing blue shift. As a result, the direction of light propagation becomes complicated, and retardation compensation may not be effectively achieved. Therefore, in order to satisfactorily suppress both external light reflection and color shift, a combination of the light deflection layer 110 having the pillar portions 111B and the first and second retardation layers 101 and 102 is particularly effective.

[0112] <Simulation example> Next, a simulation example according to the above embodiment will be described.

[0113] (Simulation example 1) In Simulation Example 1, the reflectance of external light was simulated when the external light was incident on a display device 10 including the optical film 100 according to the embodiment described with reference to Figures 1 to 3. Figure 6 shows a table illustrating the simulation results of Simulation Example 1.

[0114] In Simulation Example 1, Nx, Ny, and Nz of the λ / 4 wave plate 122 of the circular polarizer 120 are 1.5412, 1.5167, and 1.5412, respectively. The thickness of the λ / 4 wave plate 122 is 56 μm. The metal electrode 21 is assumed to be made of silver, and its complex refractive index (n, k) is set to (0.055, 3.32).

[0115] In Simulation Example 1, the refractive index of the low-refractive-index layer 111 in the light deflection layer 110 of the optical film 100 is 1.48, and the refractive index of the high-refractive-index layer 112 is 1.65. The inclination angle θ of the side surface 111S of the pillar portion 111B with respect to the normal N of the optical film 100 is 6.7 degrees. The first-direction pitch P1 of the pillar portions 111B arranged at intervals in the first arrangement D1 and the second-direction pitch P2 of the pillar portions 111B arranged at intervals in the second arrangement direction D2 are 8.5 μm. The width W1 of the first element surface 111S1 and the width W2 of the second element surface 111S2 on the side surface 111S of the pillar portion 111B are 5.2 μm. The height H, which is the dimension in the thickness direction Z of the pillar portion 111B, is 4.2 μm. The first duty, which is determined by dividing the dimension in the first arrangement D1 between the midpoints of the pair of first element surfaces 111S1 in the normal direction to the film surface by the first direction pitch P1, is 0.55. The second duty, which is determined by dividing the dimension in the second arrangement D2 between the midpoints of the pair of second element surfaces 111S2 in the normal direction to the film surface by the second direction pitch P2, is 0.55.

[0116] The color shift suppression performance obtained by the light deflection layer 110 was evaluated by calculating the color shift Δu'v' (0-45deg). The color shift Δu'v' (0-45deg) is a distance on the u'v' chromaticity diagram, and indicates the degree of change in the color of an image when viewed obliquely at 45 degrees compared to the color of the image when viewed from the front (0deg). The lower the color shift Δu'v' (0-45deg), the smaller the degree of color shift. The specific value of the color shift Δu'v' (0-45deg) was 0.0115.

[0117] In FIG. 6, the vertical columns at the left end of the table show thickness direction retardation Rth1 set in the first retardation layer 101 in increments of 25. The horizontal columns at the top of the table show thickness direction retardation Rth2 set in the second retardation layer 102 in increments of 25. The table also shows the diffuse reflectance SCE (Specular Component Exclude) in % for each combination of Rth1 and Rth2. The diffuse reflectance SCE was calculated by simulation under conditions conforming to JIS Z 8722 Condition C. A lower diffuse reflectance SCE indicates greater suppression of reflection.

[0118] The diffuse reflectance SCE of "0.208" enclosed by a bold frame in Figure 6 is the result when Rth1 = 0 and Rth2 = 0, and is an index of the degree of reflectance suppression of only the circular polarizer 120, when the first retardation layer 101 and the second retardation layer 102 are not present. In contrast, among the numerical values ​​below the bold frame, which assume the presence of only the first retardation layer 101, even the lowest diffuse reflectance SCE is 0.195, which is only slightly different from the case where the first retardation layer 101 and the second retardation layer 102 are not present. This means that the presence of the light deflection layer 110 prevents the first retardation layer 101 alone from properly compensating for the phase difference.

[0119] When Rth1 becomes negative (positive C plate) and Rth2 becomes positive (negative C plate), as shown in the dotted area, it can be seen that the diffuse reflectance SCE can be significantly reduced compared to the case where there are no first retardation layer 101 or second retardation layer 102. In the table, when Rth1=-75 and Rth2=50, as surrounded by the dashed line, the diffuse reflectance SCE is the lowest, at 0.145.

[0120] The simulation results shown in FIG. 6 confirm that the combination of the first retardation layer 101, which is a positive C plate, and the second retardation layer 102, which is a negative C plate, can suitably suppress external light reflection.

[0121] (Simulation example 2) Fig. 7 shows a table illustrating the results of a simulation of the reflectance of external light when the external light is incident on a display device including an optical film according to another embodiment. Specifically, Fig. 7 shows the results of a simulation of a display device including an optical film in which the light deflection layer 210 having the particles 212 shown in Fig. 4 is combined with the first retardation layer 101, the second retardation layer 102, and the circular polarizer 120. The simulation was performed under the same conditions as in Simulation Example 1, except that the light deflection layer 210 was used.

[0122] The conditions for the light deflection layer 210 are that the refractive index of the retention layer 211 is 1.48 and that of the particles 212 is 1.65. The radius of the particles 212 is 0.51 μm, and the distance between adjacent particles 212 is 4 μm. The number of particles 212 is set so that the value of the color change Δu'v' (0-45 deg) is 0.0113, which is equivalent to 0.0115.

[0123] 7, the diffuse reflectance SCE of "0.512" surrounded by a bold frame is the result when Rth1 = 0 and Rth2 = 0, and corresponds to the degree of reflectance suppression of only the circular polarizer 120, without the first retardation layer 101 and the second retardation layer 102. In contrast, among the numerical values ​​below the bold frame, which assume the presence of only the first retardation layer 101, the lowest diffuse reflectance SCE is 0.467, which is only slightly different from the case where the first retardation layer 101 and the second retardation layer 102 are not present.

[0124] When Rth1 becomes negative (positive C plate) and Rth2 becomes positive (negative C plate), as shown in the dotted area, the diffuse reflectance SCE can be reduced more than when there are no first retardation layer 101 or second retardation layer 102. In the table, when Rth1=-75 and Rth2=25, as surrounded by the dashed line, the diffuse reflectance SCE is the lowest, at 0.456.

[0125] The simulation results shown in FIG. 7 confirm that the combination of the first retardation layer 101, which is a positive C plate, and the second retardation layer 102, which is a negative C plate, can suitably suppress external light reflection.

[0126] (Comparative evaluation of simulation examples 1 and 2) 6 and 7, the value of the diffuse reflectance SCE shown in Fig. 6 is generally lower than the diffuse reflectance SCE shown in Fig. 7. That is, the structure in which the light deflection layer 110 has the pillar portions 111B can more effectively suppress external light reflection than the light deflection layer 210 having the particles 212.

[0127] On the other hand, the lower the value of the diffuse reflectance SCE, the more difficult it generally is to further reduce it. However, in an optical film 100 using a structure in which the light deflection layer 110 has pillar portions 111B, there exist conditions of Rth1 and Rth2 (hereinafter referred to as the maximum effect Rth condition) that can significantly reduce the diffuse reflectance SCE. Here, even if this maximum effect Rth condition is applied to a case in which the light deflection layer 210 has particles 212, the diffuse reflectance SCE is not significantly reduced. Therefore, it can be evaluated that the effect of reducing the diffuse reflectance SCE under this maximum effect Rht condition can be uniquely achieved by the combination of the first retardation layer 101 which is a positive C plate, the second retardation layer 102 which is a negative C plate, the structure in which the light deflection layer 110 has pillar portions 111B, and the maximum effect Rth condition.

[0128] Specifically, in FIG. 6, when Rth1 = -75 and Rth2 = 50, the diffuse reflectance SCE is lowest at 0.145. This value is approximately 30% lower than the diffuse reflectance SCE of 0.208 when the first retardation layer 101 and the second retardation layer 102 are not present. On the other hand, in FIG. 7, when Rth1 = -75 and Rth2 = 25, the diffuse reflectance SCE is lowest at 0.456. This value is approximately 11% lower than the diffuse reflectance SCE of 0.512 when the first retardation layer 101 and the second retardation layer 102 are not present. If the trends in FIGS. 6 and 7 were the same, in which the first retardation layer 101 and the second retardation layer 102 suppress external light reflection, the result in FIG. 6 would be approximately 0.185, an 11% decrease from 0.208. However, the actual simulation results differ significantly. Contrary to the expectation of this tendency, the conditions under which the diffuse reflectance SCE can be reduced significantly more than in the case of the particles 212 correspond to the maximum effect Rth conditions, for example, Rth1=-75 and Rth2=50 in FIG.

[0129] Fig. 8 is a diagram showing the results of comparing the results of Fig. 6 and Fig. 7 under the same conditions of thickness direction retardation. Fig. 8 shows a table for evaluating the conditions when the pillar portion 111B is used, which can reduce the diffuse reflectance SCE more significantly than the case of the particles 212.

[0130] The figures shown in FIG. 8 are calculated using the following procedure. A value X is calculated by dividing the diffuse reflectance SCE in FIG. 6 under certain conditions where Rth1 and Rth2 are not 0 by the diffuse reflectance SCE under the same conditions in FIG. A value Y is calculated by dividing the diffuse reflectance SCE (0.208) in FIG. 6 where Rth1 and Rth2 are 0 by the diffuse reflectance SCE (0.512) in FIG. 7 where Rth1 and Rth2 are 0. Then, X is divided by Y to express the result as a percentage, and the value obtained is entered in the table under the conditions where Rth1 and Rth2 are not 0.

[0131] For example, dividing the diffuse reflectance SCE of 0.145 when Rth1=-75 and Rth2=50 by the diffuse reflectance SCE of 0.46 under the same conditions in Figure 7 gives X=0.315. Dividing this X by (0.208 / 0.512) gives the figure 78%, which corresponds to Rth1=-75 and Rth2=50 in Figure 8.

[0132] 8, the condition where the Rth is 85% or less can be evaluated as the condition when the pillar portion 111B is used, where the diffuse reflectance SCE can be reduced significantly more than in the case of the particles 212, that is, the condition where the Rth is most effective. Specifically, when "-100≦Rth1≦-50 and Rth2 is 50" or "-125≦Rth1≦-75 and Rth2 is 75", the diffuse reflectance SCE can be reduced significantly.

[0133] As described above, between the thickness direction retardation Rth1 (nm) of the first retardation layer 101 and the thickness direction retardation Rth2 (nm) of the second retardation layer 102, it is preferable that the following formula (1) holds, it is more preferable that formula (2) holds, and it is also more preferable that formula (3) holds.

[0134] -1.25×Rth2-75 <Rth1<-Rth2+50…(1) -1.25×Rth2-37.5 <Rth1<-Rth2+25…(2) -50 <Rth1+Rth2<0…(3)

[0135] By comparing the simulation results of FIGS. 6 to 8 with the above formulas (1) to (3), the effectiveness and validity of the formulas (1) to (3) can be evaluated.

[0136] (Simulation example 3) In Simulation Example 3, the diffuse reflectance SCE was simulated for each of the cases where the inclination angle θ of the side surface 111S of the light deflection layer 110 was set to 0 degrees, 6.7 degrees, 14 degrees, 20 degrees, and 26 degrees.

[0137] Simulation results for tilt angles θ of 0 degrees, 6.7 degrees, 14 degrees, 20 degrees, and 26 degrees are shown in FIGS. 9 to 13, respectively. The values ​​shown in FIGS. 9 to 13 were calculated using the same procedure as for the values ​​shown in FIG. 8. That is, similar to the calculation of FIG. 8, at each tilt angle θ, the diffuse reflectance SCE for each Rth1 and Rth2 pair was divided by the diffuse reflectance SCE under the same conditions in FIG. 7 to obtain value X. The diffuse reflectance SCE for each figure where Rth1 and Rth2 are 0 was then divided by the diffuse reflectance SCE (0.512) for Rth1 and Rth2 in FIG. 7 where Rth1 and Rth2 are 0 to obtain value Y. X was then divided by Y, expressed as a percentage, and the resulting value is listed in the tables for conditions where Rth1 and Rth2 are not 0. Hereinafter, values ​​corresponding to conditions other than Rth1=0 and Rth2=0 shown in FIGS. 9 to 13 are referred to as SCE relative values.

[0138] In the simulation results at 0° shown in FIG. 9, when Rth1 is −50 and Rth2 is 50, the SCE relative value is the lowest, at 94.4%.

[0139] The simulation results at 6.7 degrees shown in FIG. 10 are the same as those in Simulation Example 1. Therefore, the SCE relative value is lowest when Rth1=-100 and Rth2=75. The SCE relative value is 75.5%. In the simulation results at 6.7 degrees shown in FIG. 10, the SCE relative value is low in the relatively wide condition range 10-1. In the further narrowed condition range 10-2, the SCE relative value is significantly lower.

[0140] In the simulation results for 14 degrees shown in Figure 11, the relative SCE value was lowest at 57.9% when Rth1 was -75 and Rth2 was 75. In the simulation results for 14 degrees shown in Figure 11, the relative SCE value was significantly low in the relatively wide condition range 11-1. In the further narrowed condition range 11-2, the relative SCE value was extremely low.

[0141] In the simulation results at 20 degrees shown in Fig. 12, the SCE relative value is lowest at 81.1% when Rth1 is -75 and Rth2 is 75. In the simulation results at 20 degrees shown in Fig. 12, the SCE relative value is significantly low in the relatively wide condition range 12-1.

[0142] In the simulation results for 26 degrees shown in FIG. 13, when Rth1 is −50 and Rth2 is 50, the SCE relative value is the lowest, at 90.0%.

[0143] Fig. 14 is a table showing the reflectance (SCE relative value) that was smallest in the simulation results of Fig. 9 to Fig. 13, corresponding to the simulation conditions. Fig. 14 also shows the value of color change Δu'v' (0-45 deg) under the simulation condition that calculated the smallest SCE relative value.

[0144] Fig. 15 is a graph showing the value of color change Δu'v' (0-45°) under the simulation conditions that resulted in the smallest reflectance (SCE relative value) in the simulation results of Fig. 9 to Fig. 13. Note that Fig. 15 also shows a line of 0.159, which is the value of color change Δu'v' (0-45°) when optical film 100 is not provided.

[0145] FIG. 16 is a graph showing the simulation conditions under which the reflectance (SCE relative value) was smallest in the simulation results of FIGS. 9 to 13, and the corresponding SCE relative value.

[0146] 14 to 16, when the tilt angle θ is between 6.7 degrees and 20 degrees, both the diffuse reflectance SCE and color change are effectively suppressed. In particular, when the tilt angle is 14 degrees, the diffuse reflectance SCE is significantly reduced.

[0147] In the above-described embodiment, it has been explained that when the shape condition of the light deflection layer 110 is such that the inclination angle θ of the side surface 111S of the pillar portion 111B relative to the normal line N of the optical film 100 is 6 degrees or more and 15 degrees or less, preferably 10 degrees or more and 15 degrees or less, more preferably 12 degrees or more and 15 degrees or less, even more preferably 13 degrees or more and 14.5 degrees or less, and even more preferably 14 degrees, the following formulas (4) and (5) are satisfied, thereby obtaining a unique effect.

[0148] -125≦Rth1≦-50…(4) 25≦Rth2≦100…(5)

[0149] The results of Simulation Example 3 also enable us to evaluate the effectiveness and validity of Equations (4) and (5).

[0150] Although the embodiments and modifications of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and modifications, and various modifications can be made. The above-described simulation examples are examples that support the effects of the present disclosure, but should not be construed as limiting the scope of the present disclosure. [Explanation of symbols]

[0151] 10…Display device 20...Display panel 20A…Display surface 21...Metal electrode 100...Optical film 101...First retardation layer 102...Second retardation layer 110, 210, 310...light deflection layer 111...Low refractive index layer 111A...Land section 111B...Pillar section 111T...tip 111S…Side 111S1...1st element surface 111S2…Second element surface 112...High refractive index layer 120...Circular polarizer 121...Linear polarizer 122...λ / 4 wavelength plate 211...Retention layer 212…Particle 312...Diffraction grating Z: thickness direction D1: First array direction D2: Second arrangement direction

Claims

1. A first retardation layer; A second retardation layer; a light deflection layer that deflects light at an interface where the refractive index is switched and is disposed between the first retardation layer and the second retardation layer; the first retardation layer is a positive C plate, The second retardation layer is a negative C plate, At least one of the following formula (2) and the following formula (3) is satisfied between the thickness direction retardation Rth1 (nm) of the first retardation layer and the thickness direction retardation Rth2 (nm) of the second retardation layer, the light deflection layer has a first layer and a second layer having different refractive indices; the interface is an uneven interface between the first layer and the second layer, the first layer has a plurality of pillar portions embedded in the second layer; The plurality of pillar portions are arranged at intervals, a contact surface between the pillar portion and the second layer forms a part of the interface having an uneven shape; the pillar portion has a shape tapered toward a direction in which it is embedded in the second layer, and an inclination angle, which is an acute angle formed by a side surface of the pillar portion with respect to a normal line of the optical film, is equal to or greater than 6 degrees and equal to or less than 20 degrees; The optical film, wherein the first retardation layer has a thickness direction retardation Rth1 (nm) of −125 or more, and the second retardation layer has a thickness direction retardation Rth2 (nm) of 25 or more. -1.25×Rth2-37.5<Rth1<-Rth2+25...(2) -50<Rth1+Rth2<0...(3)

2. An optical film as described in claim 1, in which the formula (2) holds.

3. An optical film described in claim 1 or 2, wherein the formula (3) holds.

4. The inclination angle is 12 degrees or more and 15 degrees or less, 4. The optical film according to claim 1, wherein the thickness direction retardation Rth1 (nm) of the first retardation layer and the thickness direction retardation Rth2 (nm) of the second retardation layer satisfy the following formulas (4) and (5): −125≦Rth1≦−50 (4) 25≦Rth2≦100 (5)

5. The optical film according to claim 1 , wherein the first retardation layer is disposed so as to face a circular polarizing plate.

6. The optical film according to claim 1 , further comprising a circular polarizer provided on the side of the first retardation layer opposite to the light deflection layer side.

7. the circular polarizer includes a linear polarizer and a λ / 4 wavelength plate, The optical film according to claim 5 or 6, wherein the thickness direction retardation of the λ / 4 wave plate is greater than 0.

8. The optical film according to claim 1 , wherein the second retardation layer is disposed so as to face a display panel.

9. It is assumed that light passing through the second retardation layer from the light deflection layer side is reflected by a metal member of the display panel, The optical film according to claim 8 , wherein the in-plane refractive indexes Nx and Ny and the thickness direction refractive index Nz of the second retardation layer are determined so as to satisfy the following formula (6): [Equation 1]

10. The optical film according to claim 1 , wherein the second retardation layer is a TAC film.

11. an organic EL panel; an optical film; the optical film includes a first retardation layer, a second retardation layer, and a light deflection layer that deflects light at an interface where a refractive index is switched and is disposed between the first retardation layer and the second retardation layer, the first retardation layer being a positive C plate, and the second retardation layer being a negative C plate; the optical film is disposed so that the second retardation layer faces a light output surface of the organic EL panel, At least one of the following formula (2) and the following formula (3) is satisfied between the thickness direction retardation Rth1 (nm) of the first retardation layer and the thickness direction retardation Rth2 (nm) of the second retardation layer, the light deflection layer has a first layer and a second layer having different refractive indices; the interface is an uneven interface between the first layer and the second layer, the first layer has a plurality of pillar portions embedded in the second layer; The plurality of pillar portions are arranged at intervals, a contact surface between the pillar portion and the second layer forms a part of the interface having an uneven shape; the pillar portion has a shape tapered toward a direction in which it is embedded in the second layer, and an inclination angle, which is an acute angle formed by a side surface of the pillar portion with respect to a normal line of the optical film, is equal to or greater than 6 degrees and equal to or less than 20 degrees; a thickness direction retardation Rth1 (nm) of the first retardation layer is −125 or more, and a thickness direction retardation Rth2 (nm) of the second retardation layer is 25 or more. -1.25×Rth2-37.5<Rth1<-Rth2+25...(2) -50<Rth1+Rth2<0...(3)

12. An LCD panel, an optical film; the optical film includes a first retardation layer, a second retardation layer, and a light deflection layer that deflects light at an interface where a refractive index is switched and is disposed between the first retardation layer and the second retardation layer, the first retardation layer being a positive C plate, and the second retardation layer being a negative C plate; the optical film is disposed so that the second retardation layer faces the light output surface of the liquid crystal panel, At least one of the following formula (2) and the following formula (3) is satisfied between the thickness direction retardation Rth1 (nm) of the first retardation layer and the thickness direction retardation Rth2 (nm) of the second retardation layer, the light deflection layer has a first layer and a second layer having different refractive indices; the interface is an uneven interface between the first layer and the second layer, the first layer has a plurality of pillar portions embedded in the second layer; The plurality of pillar portions are arranged at intervals, a contact surface between the pillar portion and the second layer forms a part of the interface having an uneven shape; the pillar portion has a shape tapered toward a direction in which it is embedded in the second layer, and an inclination angle, which is an acute angle formed by a side surface of the pillar portion with respect to a normal line of the optical film, is equal to or greater than 6 degrees and equal to or less than 20 degrees; a thickness direction retardation Rth1 (nm) of the first retardation layer is −125 or more, and a thickness direction retardation Rth2 (nm) of the second retardation layer is 25 or more. -1.25×Rth2-37.5<Rth1<-Rth2+25...(2) -50<Rth1+Rth2<0...(3)

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