Under-display camera type display device

Abstract

To provide a display device with an under-display camera, which can suppress appearance of in-plane color unevenness of an image captured by a front camera.SOLUTION: A display device with an under-display camera is provided, comprising a display element and a front camera arranged in the described order, where the display element has at least a birefringent base material, and a depolarizing member is provided between the display element and the front camera.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an under-display camera type display device. [Background technology]

[0002] Many models of portable information terminals such as smartphones and display devices such as notebook PCs have a front camera and a rear camera. In many display devices, the front camera and the display element are arranged in parallel at the same position in the thickness direction of the display device. In addition, in many display devices, the front camera is arranged at the top, bottom, or corner of the display device so that the front camera is not noticeable. For this reason, a display device having a front camera needs a hole or the like due to the front camera in the front part, and it is not possible to display an image on the entire front part.

[0003] In 2020, an under-display camera type display device was announced in which a front camera is arranged on the rear side of a display element (see Non-Patent Document 1, etc.). "The rear side of the display element" means the opposite side to the light output surface of the display element. Under-display camera type display devices are sometimes abbreviated as "UDC" or called "display with built-in camera type display device."

[0004] Under-display camera type display devices have no holes in the front part due to the front camera, and can display images over the entire front part, making them excellent in design and functionality. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Yukiko Sato, "ZTE releases "Axon 20 5G" with "under-display" in-camera for $449", ITmedia, December 22, 2020, [Retrieved February 1, 2021], Internet <URL: https: / / www.itmedia.co.jp / mobile / articles / 2012 / 22 / news093.html> Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a picture is taken with the front camera of an under-display camera type display device, color unevenness may occur within the plane of the picture.

[0007] The present invention aims to provide an under-display camera type display device that can suppress the occurrence of color unevenness within the surface of a photograph taken with a front camera. [Means for solving the problem]

[0008] The present invention provides the following [1] to [4]. [1] An under-display camera type display device having a display element and a front camera in this order, An under-display camera type display device, wherein the display element has at least a birefringent substrate, and a depolarizing member is provided between the display element and the front camera. [2] The under-display camera type display device described in [1], wherein the display element is an organic EL display element having at least the birefringent substrate, a first electrode, a second electrode, and an emitting layer sandwiched between the first electrode and the second electrode. [3] The under-display camera type display device according to [1] or [2], further comprising a circular polarizing plate on a light exit surface of the display element. [4] The under-display camera type display device according to any one of [1] to [3], wherein the depolarizing member has a liquid crystal layer in which a plurality of regions having different thicknesses are arranged. Effect of the Invention

[0009] The under-display camera type display device of the present invention can suppress the occurrence of color unevenness within the plane of a photograph taken by the front camera. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view illustrating an embodiment of an under-display camera type display device according to the present disclosure. [Diagram 2] 1 is a plan view showing an embodiment of a display element constituting an under-display camera type display device according to the present disclosure. [Diagram 3] FIG. 2 is a partially enlarged view showing an embodiment of an array of pixels of a display element constituting an under-display camera type display device of the present disclosure. [Figure 4] FIG. 4(a) is a perspective view of the depolarizing member 10, and FIG. 4(b) is an exploded perspective view of the depolarizing member 10. As shown in FIG. [Diagram 5] 2 is a cross-sectional view of a depolarizing member 10. FIG. [Figure 6] 2 is a cross-sectional view of a depolarizing member 20. FIG. [Figure 7] 4 is a graph illustrating the function of the depolarizing member 20. [Figure 8] 4 is a graph illustrating the function of the depolarizing member 20. [Figure 9] 3 is a cross-sectional view of a depolarizing member 30. FIG. [Figure 10] 3 is a cross-sectional view of a depolarizing member 40. FIG. [Figure 11] FIG. 11( a ) is a cross-sectional view of the depolarizing member 50 , and FIG. 11( b ) is a cross-sectional view of the depolarizing member 60 . [Figure 12] 4 is a cross-sectional view of a depolarizing member 70. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described. [Display device] The under-display camera type display device of the present disclosure is an under-display camera type display device having a display element and a front camera in this order, The display element has at least a birefringent substrate, and a depolarizing member is provided between the display element and the front camera.

[0012] FIG. 1 is a cross-sectional view of an embodiment of an under-display camera type display device 800 of the present disclosure. The display device 800 of FIG. 1 has a display element 200 and a front camera 100 in this order. In FIG. 1, the light exit surface of the display element 200 is the upper surface of FIG. 1. That is, in FIG. 1, the front camera 100 is located on the opposite side to the light exit surface of the display element 200. In the under-display camera type display device of FIG. 1, the viewer views an image from the upper side of FIG. 1. Therefore, the under-display camera type display device of FIG. 1 has the display element 200 and the front camera 100 in this order from the viewer side. The display device 800 in FIG. 1 also has a depolarizing member 10 between the display element 200 and the front camera 100. Moreover, the display device 800 in FIG. 1 has a circular polarizer 300 on the light exit surface of the display element 200. In this specification, "the under-display camera type display device of the present disclosure" may be abbreviated as "the display device of the present disclosure."

[0013] <Display element> In the display device of the present disclosure, the front camera takes a picture through the display element, which therefore needs to transmit visible light in an area of ​​the display element that overlaps with the front camera. In this specification, the area of ​​the display element that overlaps with the front camera may be referred to as the "overlap area." Reference numeral 260 in Figures 1 and 2 indicates the overlap area. In addition, in this specification, the area of ​​the display element that does not overlap with the front camera may be referred to as the "non-overlap area."

[0014] As described above, the display element must transmit visible light at least in the overlapping region. The display element is not particularly limited as long as at least the overlapping region has visible light transmittance, and a general-purpose display element can be used.

[0015] The overlapping area of ​​the display elements preferably has a total light transmittance of 10% or more, more preferably 20% or more, and even more preferably 30% or more, so as to transmit visible light and facilitate good imaging performance of the front camera. The total light transmittance of the non-overlapping region of the display element is not particularly limited as long as it is within a range that does not impair the effects of the present invention. In this specification, the total light transmittance means the total light transmittance defined in JIS K7361-1: 1997. In addition, in this specification, the haze means the haze defined in JIS K7136: 2000.

[0016] Among display elements, organic EL display elements have excellent visible light transmittance, and organic EL display elements with a see-through back surface have already been announced as of 2020. For this reason, the display element of the display device of the present disclosure is preferably an organic EL display element.

[0017] An example of an organic EL display element has a configuration including a birefringent substrate, a first electrode, a second electrode, and a light-emitting layer sandwiched between the first electrode and the second electrode (Configuration 1). In Configuration 1, the birefringent substrate can be used, for example, as a substrate for the first electrode or the second electrode. Further, the organic EL display element may have a configuration having a first electrode, a hole transport layer, a light emitting layer, an electron transport layer and a second electrode on a first substrate (Configuration 2). The configuration 2 preferably has a second substrate on the opposite side to the second electrode. In the configuration 2, a birefringent substrate can be used as the first substrate. In the configuration 2, when the device has a first substrate and a second substrate, a birefringent substrate can be used for at least one of the first substrate and the second substrate. In the configuration 1 and the configuration 2, one of the first electrode and the second electrode is an anode, and the other is a cathode. The above-mentioned configurations 1 and 2 are basic configurations of an organic EL display element. For example, as a display element of the display device of the present disclosure, an organic EL display element having another configuration added thereto in addition to the above-mentioned configurations 1 and 2 may be used. By using materials with good visible light transmittance as the organic materials contained in the hole transport layer, the light emitting layer, and the electron transport layer, and the conductive materials contained in the anode and the cathode, the visible light transmittance of the organic EL display element can be improved. Note that, while it is preferable to use a material with good visible light transmittance in the overlapping region, a material with good visible light transmittance or a material with poor visible light transmittance may be used in the non-overlapping region. As the organic materials contained in the hole transport layer, the light emitting layer and the electron transport layer, and the conductive materials contained in the anode and the cathode, general-purpose materials can be used.

[0018] A first method for improving the visible light transmittance of the overlapping region of an organic EL display element is to increase the transparency of the anode and cathode. In conventional organic EL display elements, metal electrodes such as aluminum are used as the anode or cathode. In the display device of the present disclosure, it is preferable to use metal oxide electrodes having excellent transparency as the anode and cathode. In addition, in the display device of the present disclosure, when a metal electrode is used as the anode or cathode, it is preferable to reduce the thickness of the metal electrode. A second means for improving the visible light transmittance of the overlapping region of the organic EL display element is to reduce the size of the pixels in the overlapping region. The organic EL display element has a light-emitting element for each pixel. In addition, since the anode and cathode are substantially not present in the portion where the pixel of the organic EL display element does not exist, the transmittance of visible light is high. For this reason, the visible light transmittance of the overlapping region can be improved by reducing the size of the pixels in the overlapping region. In the case of the second means, it is preferable that the size of the pixels in the non-overlapping region is larger than the size of the pixels in the overlapping region. With such a configuration, it is possible to improve the imaging performance of the front camera while maintaining the display performance of the non-overlapping region. In addition, in order to make it difficult to recognize the difference between the images of the non-overlapping region and the overlapping region, it is preferable that the size of the pixels in the overlapping region is not made too small relative to the size of the pixels in the non-overlapping region. A third means for improving the visible light transmittance of the overlapping region of the organic EL display element is to reduce the pixel density of the overlapping region. The organic EL display element has a light-emitting element for each pixel. In addition, since the anode and cathode are substantially not present in the portion where the pixel of the organic EL display element does not exist, the transmittance of visible light is high. Therefore, by reducing the pixel density of the overlapping region, the visible light transmittance of the overlapping region can be improved. In the case of the third means, it is preferable that the pixel density of the non-overlapping region is higher than the pixel density of the overlapping region. With such a configuration, it is possible to improve the imaging performance of the front camera while maintaining the display performance of the non-overlapping region. In addition, in order to make it difficult to recognize the difference between the images of the non-overlapping region and the overlapping region, it is preferable that the pixel density of the overlapping region is not too low relative to the pixel density of the non-overlapping region. In order to improve the visible light transmittance of the overlapping region of the organic EL display element, it is preferable to appropriately combine the above-mentioned first, second, and third measures. In the partially enlarged view of the display element 200 in Fig. 3, when the pixels 220 in the non-overlapping region 270 are compared with the pixels 210 in the overlapping region 270, the pixels 210 in the overlapping region 270 are larger in size and have a lower density. In addition, the display device of the present disclosure preferably appropriately combines the above-mentioned first means, second means, and third means, and does not display pixels in the overlapping area when shooting with the front camera. Also, if only the pixels in the overlapping area are not displayed, an awkward feeling will occur on the screen. For this reason, when shooting with the front camera, it is acceptable to not display pixels in the overlapping area, and not display pixels in the non-overlapping area adjacent to the overlapping area. For example, in the area of ​​the dot with the symbol m in FIG. 2, it is acceptable to not display pixels in the non-overlapping area.

[0019] In the display device of the present disclosure, the display element has at least a birefringent substrate. When the display element has a birefringent substrate, light interfered by the birefringent substrate enters the front camera, and color unevenness may occur in the plane of the photograph. However, since the display device of the present disclosure has a depolarizing member between the display element having the birefringent substrate and the front camera, even if the display element has a birefringent substrate, color unevenness in the plane of the photograph can be suppressed.

[0020] The birefringent substrate may be a plastic film. Examples of the plastic film as the birefringent substrate include plastic films such as polyester, triacetyl cellulose (TAC), cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, polypropylene, polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, polyurethane, and amorphous olefin (Cyclo-Olefin-Polymer: COP). The plastic film as the birefringent substrate preferably has a thickness of 1 μm or more, more preferably 5 μm or more, and preferably has a thickness of 50 μm or less, more preferably 30 μm or less.

[0021] In this specification, the birefringent substrate means a substrate having a thickness direction retardation of 50 nm or more.The thickness direction retardation of the birefringent substrate is preferably 100 nm or more, more preferably 200 nm or more, and even more preferably 300 nm or more.In addition, the thickness direction retardation of the birefringent substrate is preferably 10000 nm or less, more preferably 5000 nm or less, and even more preferably 2000 nm or less.

[0022] As described above, the organic EL display element may have a birefringent substrate, a first electrode, a second electrode, and a light-emitting layer sandwiched between the first electrode and the second electrode (structure 1). In structure 1, the birefringent substrate can be used as, for example, a substrate for the first electrode or the second electrode. As described above, an example of the configuration of an organic EL display element is a configuration having a first electrode, a hole transport layer, a light-emitting layer, an electron transport layer, and a second electrode on a first substrate (Configuration 2). The configuration 2 preferably has a second substrate on the opposite side to the second electrode. In the configuration 2, a birefringent substrate can be used as the first substrate. In the configuration 2, when the first substrate and the second substrate are provided, both the first substrate and the second substrate may be birefringent substrates, or only one of the first substrate and the second substrate may be a birefringent substrate. The first substrate and the second substrate may be made of the above-mentioned plastic film, glass, or the like.

[0023] In this specification, the in-plane retardation (Re) and the thickness retardation (Rth) are expressed by the following formulas (1) and (2) using the refractive index nx in the slow axis direction, which is the direction in which the refractive index at each measurement point is the largest, the refractive index ny in the fast axis direction, which is the direction perpendicular to the slow axis direction at each measurement point, the refractive index nz in the thickness direction of the polyester film, and the thickness T [nm] of the polyester film. In this specification, the in-plane retardation and the thickness retardation mean values ​​at a wavelength of 550 nm. In addition, in this specification, the in-plane retardation may be referred to as Re, and the thickness retardation may be referred to as Rth. Re = (nx-ny) × T [nm] (1) Rth = ((nx + ny) / 2 - nz) × T [nm] (2)

[0024] The direction of the slow axis, Re and Rth can be measured, for example, by using a product called "RETS-100" manufactured by Otsuka Electronics Co., Ltd. When measuring Re and the like using the product name "RETS-100" manufactured by Otsuka Electronics Co., Ltd., it is preferable to prepare for the measurement according to the following procedures (A1) to (A4).

[0025] (A1) First, turn on the RETS-100 light source and leave it for 60 minutes or more to stabilize it. After that, select the rotating analyzer method and select θ mode (angle direction phase difference measurement and Rth calculation mode). By selecting this θ mode, the stage becomes a tilt rotation stage. (A2) Next, enter the following measurement conditions into the RETS-100. (Measurement conditions) In-plane phase difference measurement range: Rotating analyzer method Measurement spot diameter: φ5mm Tilt angle range: 0° Measurement wavelength range: 400nm to 800nm The average refractive index of the substrate to be measured. For example, in the case of a polyethylene terephthalate substrate, N=1.617. The average refractive index N of the substrate can be calculated from nx, ny, and nz using the formula (N=(nx+ny+nz) / 3). Thickness: Thickness measured separately using SEM or optical microscope (A3) Next, background data is obtained without placing a sample in the instrument, in a closed system, and every time the light source is turned on. (A4) After that, the sample is placed on the stage inside the device and measured.

[0026] <Front camera> The front camera is located on the rear side of the display element, in other words, on the opposite side to the light exit surface of the display element. The front camera 100 shown in FIG.

[0027] <Circular polarizing plate> The display device of the present disclosure may have a circular polarizer on the light exit surface of the display element. By having a circular polarizer on the light exit surface of the display element, reflection of external light can be suppressed.

[0028] When a member that aligns the phase state of light, such as a circular polarizer, is present on the light exit surface of the display element, color unevenness is likely to occur within the plane of the photograph taken by the front camera. The reason for this is that light with aligned phases (=light with a high degree of polarization) is more likely to interfere when passing through a birefringent substrate. However, since the display device of the present disclosure has a depolarizing member between the display element having a birefringent substrate and the front camera, color unevenness within the plane of the photograph can be suppressed even if a circular polarizer is present on the light exit surface of the display element.

[0029] The circular polarizing plate 300 may have a laminated structure of a polarizer 310 and a retardation layer 320, for example, as shown in FIG.

[0030] Examples of polarizers include sheet-type polarizers (polyvinyl alcohol film, polyvinyl formal film, polyvinyl acetal film, ethylene-vinyl acetate copolymer saponified film, etc.) made by stretching a film dyed with iodine or the like, wire grid-type polarizers made of a large number of metal wires arranged in parallel, coating-type polarizers coated with lyotropic liquid crystal and a dichroic guest-host material, multilayer thin film-type polarizers, etc. These polarizers may be reflective polarizers that have the function of reflecting polarized components that are not transmitted. Both sides of the polarizer are preferably protected by a transparent protective member. As one of the transparent protective members, a retardation layer constituting a circular polarizing plate, a transparent plastic film, transparent glass, etc. can be used. As the other transparent protective member, a transparent plastic film, transparent glass, etc. can be used.

[0031] The retardation layer preferably has at least a λ / 4 retardation layer. In addition, the retardation layer more preferably has a λ / 4 retardation layer and a λ / 2 retardation layer in order to suppress external light reflection in a wide range of wavelengths. The retardation layers such as the λ / 4 retardation layer and the λ / 2 retardation layer can be made of general-purpose materials.

[0032] When only a λ / 4 retardation layer is used as the retardation layer, the angle between the alignment axis of the λ / 4 retardation layer and the absorption axis of the polarizer is preferably 45±5°, more preferably 45±2°.

[0033] When a λ / 4 retardation layer and a λ / 2 retardation layer are used as the retardation layers, the angle between the alignment axis of each retardation layer and the absorption axis of the polarizer is preferably within the range of (i) or (ii) below. (i) As a first example, the angle between the slow axis of the λ / 2 retardation layer and the absorption axis of the polarizer layer is preferably 15±8°, more preferably 15±6°, and in this case, the angle between the slow axis of the λ / 4 retardation layer and the absorption axis of the polarizer layer is preferably 75±15°, more preferably 75±13°. (ii) As a second example, the angle between the slow axis of the λ / 2 retardation layer and the absorption axis of the polarizer layer is preferably 75±15°, more preferably 75±13°, and in this case, the angle between the slow axis of the λ / 4 retardation layer and the absorption axis of the polarizer layer is preferably 15±8°, more preferably 15±6°.

[0034] <Depolarizing material> The display device of the present disclosure is required to have a depolarizing member between the display element and the front camera. By having a depolarizing member between the display element and the front camera, the display device of the present disclosure can suppress the occurrence of color unevenness within the plane of a photograph even if the display element has a birefringent substrate.

[0035] If the outer shape of the depolarizing member when the display device of the present disclosure is viewed from the planar direction is defined as outer shape 1, and the outer shape of the front camera when the display device of the present disclosure is viewed from the surface direction is defined as outer shape 2, then outer shape 1 is preferably large enough to cover outer shape 2. In other words, the size of outer shape 1 is preferably equal to or larger than the size of outer shape 2. By satisfying the above-mentioned conditions, the light incident on the front camera can be made to pass through the depolarizing member.

[0036] The depolarizing member may be any of the following members (1) to (3). (1) A component with an in-plane retardation of 4000 nm or more. (2) A component in which inorganic particles having birefringence are dispersed in a transparent medium. (3) A member having a plurality of regions with different in-plane retardation within the plane.

[0037] Among the above (1) to (3), the member (3) is preferred. The member (1) is prone to becoming thick, and since the transmittance varies greatly depending on the wavelength, even if no color unevenness occurs within the plane of the photograph, the actual color may differ from the color in the photograph. The member (2) can eliminate the polarization state by randomly refracting light. However, the member (2) has inorganic particles with a refractive index different from that of the transparent medium dispersed in a transparent medium such as a transparent resin, so that the haze of the light transmitted through the depolarizing member increases, and the clarity of the photograph is likely to decrease. The member (3) is preferred in that it is less likely to cause problems with color and haze.

[0038] The depolarizing member preferably has a total light transmittance of 60% or more, more preferably 70% or more, and even more preferably 85% or more. The depolarizing member preferably has a haze of 5% or less, more preferably 4% or less, and even more preferably 3% or less.

[0039] It is preferable that the depolarizing member satisfies the following (A) and (B). A depolarizing member that satisfies the following (A) and (B) has excellent performance in eliminating polarization, and can therefore further suppress color unevenness in photographs.

[0040] (A) A laminate in which polarizer 1, depolarizing member, and polarizer 2 are laminated in this order is designated as laminate A. In laminate A, the absorption axis of polarizer 1 and the absorption axis of polarizer 2 are perpendicular to each other. When the depolarizing member has an optical axis in the plane, in laminate A, the angle between the absorption axis of polarizer 1 and the optical axis of the depolarizing member is set to 45 degrees. Under the above prerequisites, laminate A preferably has a transmittance of 20% or more and 80% or less at any wavelength in the wavelength range of 380 nm or more and 780 nm or less, more preferably has a transmittance of 30% or more and 70% or less at any wavelength, and even more preferably has a transmittance of 40% or more and 60% or less at any wavelength. (B) A laminate in which polarizer 1, depolarizing member, and polarizer 2 are laminated in this order is designated laminate B. In laminate B, the absorption axis of polarizer 1 is parallel to the absorption axis of polarizer 2. When the depolarizing member has an optical axis in the plane, the angle between the absorption axis of polarizer 1 and the optical axis of the depolarizing member in laminate B is set to 45 degrees. Under the above prerequisites, it is preferable that Laminate A and Laminate B have a transmittance of 20% or more and 80% or less at any wavelength in the wavelength range of 380 nm or more and 780 nm or less, it is more preferable that the transmittance is 30% or more and 70% or less at any wavelength, and it is even more preferable that the transmittance is 40% or more and 60% or less at any wavelength.

[0041] When an alignment film is not used in the "member having a liquid crystal layer in which a plurality of regions with different thicknesses are arranged" described below, the direction of the unevenness is the direction of the optical axis in the above (A) and (B). When an alignment film is used in the "member having a liquid crystal layer in which a plurality of regions with different thicknesses are arranged" described below, the direction of the optical axis in the above (A) and (B) is the predetermined direction determined by polarized light exposure or the direction perpendicular to the predetermined direction determined by polarized light exposure.

[0042] The above (3) "member having a plurality of regions with different in-plane retardation in the plane" includes a member having a liquid crystal layer in which a plurality of regions with different thicknesses are arranged. The "member having a liquid crystal layer in which a plurality of regions with different thicknesses are arranged" is described in, for example, International Publication No. WO2018 / 043618.

[0043] <<Depolarizing member having a liquid crystal layer>> Hereinafter, a preferred embodiment of the depolarizing member, "a member having a liquid crystal layer in which a plurality of regions with different thicknesses are arranged" will be described. In this specification, "a member having a liquid crystal layer in which a plurality of regions with different thicknesses are arranged" may be referred to as "a depolarizing member having a liquid crystal layer".

[0044] The liquid crystal layer may have an arrangement in which a plurality of convex portions and concave portions formed between adjacent convex portions are arranged on at least one surface. The liquid crystal layer may have a plurality of irregularly arranged convex portions and concave portions formed between adjacent convex portions on at least one surface of the liquid crystal layer. The concave portions may be provided with an irregularity-forming layer made of a transparent resin. The depolarizing member having a liquid crystal layer may have a configuration in which the liquid crystal layer and the unevenness-forming layer are laminated on one surface of a transparent substrate.

[0045] Fig. 4 is a diagram illustrating a first embodiment of a depolarizing member having a liquid crystal layer. Fig. 4(a) is a perspective view of the first embodiment, and Fig. 4(b) is an exploded perspective view of the second embodiment. As can be seen from Figs. 4(a) and 4(b), the depolarizing member 10 of this embodiment is composed of a substrate 11, an unevenness-forming layer 12, and a liquid crystal layer 15.

[0046] The substrate 11 is a transparent layer that serves as a substrate for laminating the unevenness-forming layer 12 and the liquid crystal layer 15 on one surface thereof. Various materials can be used as the material for the substrate 11, but a material having good mechanical properties, optical properties, stability, and processability is preferable. Examples of such materials include polymer resins having an alicyclic structure, methacrylic resins, polycarbonate resins, polystyrene resins, acrylonitrile-styrene copolymers, methyl methacrylate-styrene copolymers, ABS resins, polyethersulfone, triacetyl cellulose, polyethylene terephthalate, epoxy acrylate, urethane acrylate, and other resins, and glass, and resins are preferable. The thickness of the substrate can be in the range of 10 μm to 1000 μm.

[0047] The unevenness-forming layer 12 is a layer that provides a plurality of regions of different thickness to the liquid crystal layer 15, and in this embodiment, a plurality of protrusions 13 are arranged at intervals. Therefore, protrusions 12a are formed at the locations where the protrusions 13 are arranged, and recesses 12b are formed between the protrusions 13, and these protrusions 12a and recesses 12b are arranged repeatedly. In this embodiment, the ridges 13 are in the form of a quadrangular column having a quadrangular cross section, and a plurality of the ridges 13 are arranged along one surface of the base material 11 such that the axes of the columns are parallel to each other.

[0048] Various materials can be used as the material for forming the ridges 13 of the unevenness-forming layer 12, but materials with good mechanical properties, optical properties, stability, and processability are preferred. Examples of such materials include polymer resins having an alicyclic structure, methacrylic resins, polycarbonate resins, polystyrene resins, acrylonitrile-styrene copolymers, methyl methacrylate-styrene copolymers, ABS resins, polyethersulfone, triacetyl cellulose, polyethylene terephthalate, epoxy acrylate, and urethane acrylate.

[0049] The substrate 11 and the irregularity-forming layer 12 may be in an integrated form with no boundary therebetween, or the irregularity-forming layer 12 may be laminated on the surface of the substrate 11 . Examples of the manufacturing process include extrusion molding, molding, and photolithography. When manufactured by extrusion molding, the base material 11 and the unevenness-forming layer 12 can be integrally formed. When manufactured by molding, the unevenness-forming layer 12 can be formed by molding on the base material 11. In the case of molding, the base material layer 11 and the unevenness-forming layer 12 may be made of the same resin material or different materials.

[0050] The liquid crystal layer 15 is a layer made of a liquid crystal material laminated on the irregularity-forming layer 12. Therefore, the surface of the liquid crystal layer 15 that contacts the irregularity-forming layer 12 has irregularities opposite to those of the irregularity of the irregularity-forming layer 12. That is, the liquid crystal layer 15 has protrusions 15a that fill the recesses 12b of the irregularity-forming layer 12, and has recesses 15b that are filled by the protrusions 12a of the irregularity-forming layer 12. Therefore, in this embodiment, the irregularity-forming layer 12 and the liquid crystal layer 15 are in contact with each other with an irregular interface therebetween. On the other hand, in the liquid crystal layer 15, the surface opposite to the uneven surface side is a smooth surface in this embodiment, but is not limited to this and other uneven surfaces may be formed.

[0051] Regarding the liquid crystal constituting the liquid crystal layer 15, when the birefringence at a wavelength of 450 nm is Δn450, the birefringence at a wavelength of 550 nm is Δn550, and the birefringence at a wavelength of 650 nm is Δn650, Δn450>Δn550>Δn650 In other words, a liquid crystal layer having wavelength dispersion (positive dispersion) in which the phase difference decreases from the short wavelength side to the long wavelength side in the visible light region can be used. Here, the "birefringence" for each wavelength was calculated by aligning the liquid crystal on a glass substrate, measuring the phase difference, and then dividing by the liquid crystal film thickness. Conventionally, a polycarbonate copolymer resin using fluorene has been known as a material with reverse dispersion, which has characteristics opposite to those of normal dispersion, but the use of this material results in a thick member. (Reverse dispersion is a wavelength dispersion in which the phase difference increases from the short wavelength side to the long wavelength side in the visible light region.) Among liquid crystal materials, there are polymerizable liquid crystal compounds having reverse dispersion. However, although such polymerizable liquid crystal compounds can be used to form thin films, they are more expensive than normal dispersion materials, which is problematic from the viewpoint of widespread product supply. The display device of the present disclosure can suppress the occurrence of color unevenness in the plane of a photograph taken with a front camera even if a normal dispersion liquid crystal material is used as the liquid crystal material of a depolarizing member having a liquid crystal layer. In addition, when a normal dispersion liquid crystal material is used, the thickness of the depolarizing member can be made thin.

[0052] The liquid crystal material constituting the liquid crystal layer 15 is not particularly limited, but examples thereof include rod-shaped liquid crystal materials such as those represented by the following chemical formulas (1) to (17).

[0053] [ka]

[0054] [ka]

[0055] Among the liquid crystal materials, polymerizable rod-shaped liquid crystal materials are preferred. Examples of the polymerizable functional group of the polymerizable rod-shaped liquid crystal material include those that are polymerized by the action of ionizing radiation such as ultraviolet light or electron beams, or heat. Specific examples include radically polymerizable functional groups. Examples of the radically polymerizable functional group include functional groups having at least one ethylenically unsaturated double bond capable of addition polymerization, and more specifically, examples of the radically polymerizable functional group include vinyl groups and acrylate groups (a general term including acryloyl groups, methacryloyl groups, acryloyloxy groups, and methacryloyloxy groups) with or without substituents.

[0056] In addition to the rod-shaped liquid crystal materials, discotic liquid crystals, which are disc-shaped liquid crystal materials, can also be used as liquid crystal materials. Discotic liquid crystals have a disc-shaped core and side chains extending radially from the core.

[0057] The liquid crystal layer 15 as described above can be formed, for example, by applying a liquid crystal material onto the concave-convex forming layer 12 .

[0058] The depolarizing member 10 having the above-mentioned structure may have, for example, the following form: Fig. 5 shows a cross-sectional view for explanation. In this embodiment, the unevenness-forming layer 12 causes the liquid crystal layer 15 to have two different thickness regions arranged alternately. That is, a region having a liquid crystal thickness indicated by d1 in FIG. 5 and a region having a liquid crystal thickness indicated by d2. The liquid crystal thickness indicated by d1 is the thickness of the region due to the convex portion 15a of the liquid crystal layer 15, and the liquid crystal thickness indicated by d2 is the thickness of the region due to the concave portion 15b of the liquid crystal layer 15. The thickness (d1) of the liquid crystal layer 15 for acting as described later can be in the range of 1 μm to 10 μm. It is also possible to obtain the effect even if the thickness is in the range of 1 μm to 5 μm. In the liquid crystal layer 15, the difference in thickness between the thickest portion (the portion d1 in this embodiment) and the thinnest portion (the portion d2 in this embodiment) is preferably 5 μm or less.

[0059] The pitch p between adjacent convex portions 15a shown in Fig. 5 is preferably 50 nm or more and 100 µm or less. If the pitch is smaller than 50 nm, the alignment of the liquid crystal deteriorates. If the pitch is larger than 100 µm, the unevenness may become visible. A more preferable pitch is 20 µm or less. Furthermore, the ratio of the convex portions 15a to the concave portions 15b within one pitch is not particularly limited, and can be set appropriately based on the required depolarization and transmittance characteristics for each wavelength.

[0060] Since a depolarizing member having a liquid crystal layer uses a liquid crystal layer, it can eliminate the polarization state even if it is a thin film. For example, the thickness of the depolarizing member 10 shown as d0 in FIG. 5 can be made 20 μm or less. Furthermore, since the liquid crystal layer can be made of a flexible material, the depolarizing member can be made flexible, allowing it to flexibly accommodate the shape of the object to which the depolarizing member 10 is applied.

[0061] A depolarizing member having a liquid crystal layer converts light into a plurality of lights with different phase differences using liquid crystal, and therefore does not increase the haze that occurs when inorganic particles are dispersed, and can transmit light without increasing the haze. Specifically, it is possible to form a depolarizing member with a haze value of 5% or less.

[0062] The depolarizing member 10 having the above-mentioned configuration operates, for example, as follows. Light that is in phase with the light (in a predetermined polarization state) is incident on the depolarizing member 10. This light then passes through the liquid crystal layer 15. In the depolarizing member 10 of this embodiment, the liquid crystal layer 15 has two types of regions with different thicknesses: a region having a thickness d1 formed by the convex portions 15a, and a region having a thickness d2 formed by the concave portions 15b. The phase difference (Re: retardation) that occurs in the light passing through the liquid crystal layer is determined by the product of the refractive index difference Δn of the birefringent light that depends on the liquid crystal material and the thickness d of the liquid crystal layer. That is, Re = Δn × d It is.

[0063] Therefore, in the depolarizing member 10 of this embodiment, when light with the same phase (in a predetermined polarization state) passes through the depolarizing member 10, Re1 = Δn × d1 Re2 = Δn × d2 This results in light having two types of phase difference, and the single phase difference (polarization) state can be eliminated. In this way, the depolarizing member 10 of this embodiment can eliminate the polarization state, thereby suppressing unevenness in the photograph.

[0064] In the case of a depolarizing member having a liquid crystal layer, when the above-mentioned alignment film is not used, the direction of the unevenness is the direction of the optical axis. In addition, the direction of the unevenness can be easily controlled with high precision. Therefore, the depolarizing member having a liquid crystal layer can control the optical axis with high precision. Furthermore, in the case where an alignment film is used as in the embodiment described later, any direction determined by the polarized light exposure can be set as the optical axis. It is preferable that the optical axes are aligned in the regions of different thicknesses in the liquid crystal layer 15 of the depolarizing member 10. Specifically, it is preferable that the directions of the slow axes are aligned within a range of ±1° between the regions.

[0065] Figure 6 is a diagram for explaining a depolarizing member 20 which is a second embodiment of a modified example of the depolarizing member, and corresponds to Figure 5 of the first embodiment. In the above-described depolarizing member 10, the liquid crystal layer 15 is formed to have two different thicknesses (d1, d2), but in the depolarizing member 20, the liquid crystal layer 25 is formed to have three different thicknesses, d21, d22, and d23. That is, the unevenness-forming layer 22 has a first convex portion 22a, a second convex portion 22b having a different height (thickness) from the first convex portion 22a, and a concave portion 22c. Therefore, a concave portion 22c is formed between the first convex portion 22a and the second convex portion 22b. Correspondingly, the liquid crystal layer 25 has a convex portion 25a, a first concave portion 25b, and a second concave portion 25c. The basic configuration is the same as that of the depolarization member 10. According to this, as also shown in FIG. 6, the liquid crystal layer 25 is thickest in the region of the convex portion 25a (thickness d21), next thickest in the region of the first concave portion 25b (thickness d22), and thinnest in the region of the second concave portion 25c (thickness d23).

[0066] According to such a depolarization member 20, the transmitted light has three different phase differences (unpolarized states), so that depolarization is further ensured. Fig. 7 and Fig. 8 are diagrams showing the transmittance of the depolarization member 20 of the second embodiment at wavelengths of 380 nm or more and 780 nm or less. Fig. 7 shows the transmittance in the state of the above-mentioned laminate A, and Fig. 8 shows the transmittance in the state of the above-mentioned laminate B. In Fig. 7 and Fig. 8, the solid line shows the transmittance of the region of convex portion 25a, the dashed line shows the transmittance of the region of convex portion 25b, the dashed line shows the transmittance of the region of convex portion 25c, and the dotted line shows the combined transmittance of the three regions. As shown in the combined transmittance in Figures 7 and 8, when viewed as a whole, the depolarizing member 20 can obtain approximately the same transmittance (50%) for all wavelengths of visible light, confirming that polarization is eliminated. 7 and 8 show values ​​calculated using a general-purpose formula assuming that the phase difference in the region of convex portion 25a is 510 nm, the phase difference in the region of convex portion 25b is 300 nm, the phase difference in the region of convex portion 25c is 100 nm, and the area ratio between convex portion 25a, convex portion 25b, and convex portion 25c is 0.4:1.0:1.4.

[0067] In the crossed Nicols configuration, the light intensity I that transmits through a uniformly aligned liquid crystal layer can be expressed by the following formula (A): In the parallel Nicols configuration, the light intensity I' that transmits through a uniformly aligned liquid crystal layer can be expressed by the following formula (B): In the following formulas (1) and (2), "Re 550 " indicates the retardation value of the liquid crystal layer at a wavelength of 550 nm, "N(λ)" indicates the birefringence of the liquid crystal layer at each wavelength from 380 nm to 780 nm / birefringence of the liquid crystal layer at a wavelength of 550 nm, and "θ" indicates the angle between the absorption axis of the polarizer and the optical axis of the liquid crystal layer. I = I0 sin 2 (2θ) sin 2 (π N(λ) Re 550 / λ) (A) I'=I0-I0·sin 2 (2θ) sin 2 (π N(λ) Re 550 / λ) (B)

[0068] In this modification, the liquid crystal layer 25 is configured to have three different thicknesses, but the liquid crystal layer may have convex and concave portions so as to have even more thicknesses. In this case, the arrangement of the concaves and convexes may be regular or irregular. Here, "irregular" means that, when ten convex portions are taken as one unit, there is no regularity between the shape of the convex portions of one unit and the shape of the convex portions of another unit adjacent thereto.

[0069] A pseudo evaluation device including the second embodiment of the depolarizing member 20 was fabricated to evaluate the suppression of color unevenness. The depolarizing member 20 used in the evaluation had the transmittance shown in Figs. Specifically, a commercially available smartphone (Apple's iPhone (registered trademark) 8. A display device in which a front camera and a display element are arranged in parallel at the same position in the thickness direction of the display device) was prepared. A depolarizing member, a birefringent member (a PET film with a thickness direction retardation of 7500 nm), and a polarizer were laminated in this order on the front camera of the smartphone, and a photograph was taken with the front camera. This case is referred to as Reference Example 1. On the other hand, the birefringent member and the polarizer were laminated in this order on the front camera of the smartphone, and a photograph was taken with the front camera. This case is referred to as Reference Example 2. In the above evaluation, in Reference Example 1, no color unevenness was observed within the plane of the photograph, whereas in Reference Example 2, streaky color unevenness was observed within the plane of the photograph.

[0070] Fig. 9 is a diagram for explaining a depolarizing member 30 of the third embodiment, and corresponds to Fig. 5 of the first embodiment. This embodiment differs from the depolarizing member 10 in that it does not have the base material 11. Other parts are similar to the depolarizing member 10. Fig. 10 is a diagram for explaining a depolarizing member 40 of the fourth embodiment, and corresponds to Fig. 5 of the first embodiment. The fourth embodiment differs from the depolarizing member 10 in that it does not have the base material 11 and the unevenness-forming layer 12. The depolarizing members of the third and fourth types can be made even thinner. The depolarizing members of the third and fourth embodiments can be produced, for example, by producing the depolarizing member of the first embodiment and then peeling off only the substrate, or peeling off the substrate and the unevenness-forming layer.

[0071] Fig. 11(a) is a diagram for explaining a depolarizing member 50 of the fifth embodiment, and Fig. 11(b) is a diagram for explaining a depolarizing member 60 of the sixth embodiment. These depolarizing members 50 and 60 are examples in which an alignment film 51 is provided on the surface of the liquid crystal layer 15 on which the unevenness is formed. That is, the depolarizing member 50 shown in Fig. 11(a) is an example in which the alignment film 51 is provided on the surface of the liquid crystal layer 15 of the above-mentioned depolarizing member 10 on which the unevenness is formed, and the depolarizing member 60 shown in Fig. 11(b) is an example in which the alignment film 51 is provided on the surface of the liquid crystal layer 15 of the above-mentioned depolarizing member 40 on which the unevenness is formed. The alignment film 51 can easily align the alignment state of the liquid crystal molecules in the liquid crystal layer 15 in a desired direction. In addition, since the alignment film can set the optical axis in a desired direction, the optical axis can be controlled with high precision. For example, when a polymerizable rod-like liquid crystal is used as the liquid crystal layer, the alignment film can be used to set the direction of the slow axis of the polymerizable rod-like liquid crystal to be different from the direction in which the convex portions of the liquid crystal layer extend. A known form may be applied as necessary as a specific embodiment of the alignment film 51. Also, depending on the type of the alignment film, it is not necessary for the alignment film to remain laminated on the liquid crystal layer, and even if an alignment film is used in the manufacturing stage, it is possible to make the alignment film not remain in the final product.

[0072] The depolarizing member 60 can be produced, for example, by subjecting the surfaces of the substrate 11 and the unevenness-forming layer 12 on which the alignment film 51 is laminated to a treatment for making them easier to peel off, forming the unevenness-forming layer 12 on the substrate 11, forming the alignment film 51 and the liquid crystal layer 15, and then peeling off the substrate 11 and the unevenness-forming layer 12.

[0073] Fig. 12 is a diagram illustrating a seventh embodiment of a depolarizing member 70. The depolarizing member 70 is an example in which a single unit of unevenness indicated by p in Fig. 12 is provided with a plurality of stepped convex parts 15a with different heights (thicknesses).

[0074] A display element has pixels that form a regular lattice pattern, and therefore moire may occur due to the regular pattern of the pixels and the regular configuration of the depolarizing member. The above-mentioned depolarizing member having a liquid crystal layer can reduce the occurrence of moire because there are many elements that can be changed, such as the pitch of the unevenness, the direction in which the unevenness extends, the shape in the extending direction (straight line, wavy, etc.), the size of the unevenness, etc. For example, in a depolarizing member having a rectangular outer shape (edge ​​shape), if the unevenness is formed to extend at an angle (greater than 0 degrees and less than 90 degrees) other than the angle parallel to or perpendicular to the edge of the edge, it can be tilted at an angle greater than 0 degrees and less than 90 degrees with respect to the regular arrangement direction of the pixels, making it easier to suppress the occurrence of moire.

[0075] In addition, the depolarizing member having the liquid crystal layer of each of the above-mentioned forms has a form in which the convex and concave portions in the concave-convex layer have a predetermined cross section and extend in one direction, and the concaves and convexities are repeated in the other direction. However, the concave-convex layer is not limited to this, and it is sufficient that a liquid crystal layer made of liquid crystal in which multiple regions of different thicknesses are arranged is formed. Therefore, the form may be such that multiple convex portions are scattered in a plane, whether regularly or irregularly, and the spaces between them are concave portions. Specifically, dot shapes, island shapes, staggered arrangement shapes, etc. can be mentioned. In addition, the above-described example has been described in which the cross-sectional shape of the convex portion and the concave portion of the liquid crystal layer is a rectangle. However, the present invention is not limited to this, and the cross-sectional shape may be, for example, a triangle, a trapezoid, a semicircle, a semi-ellipse, or the like.

[0076] <Other materials> The display device of the present disclosure may further include other members. 1, the display element 200 and the circularly polarizing plate 300 may be attached to each other via an adhesive layer. The display device may also include a functional film such as a hard coat film or an antistatic film, a touch panel, a surface protection plate, or the like. [Explanation of symbols]

[0077] 10, 20, 30, 40, 50, 60, 70: Depolarizing material 11: Base material 12: Irregularity forming layer 13: Convex stripe 15: Liquid crystal layer 15a: Convex part 15b: Recess 100: Front camera 110: Lens 120: Light receiving part 200: Display element 210,220:pixels 260: Overlapping area 270: Non-overlapping area 300: Circular polarizing plate 310: Polarizer 320: Retardation layer 800: Under-display camera type display device

Claims

1. An under-display camera type display device having a display element and a front camera in this order, An under-display camera type display device, wherein the display element has at least a birefringent substrate, and a depolarizing member is provided between the display element and the front camera.

2. 2. The under-display camera type display device according to claim 1, wherein the display element is an organic EL display element having at least the birefringent substrate, a first electrode, a second electrode, and a light-emitting layer sandwiched between the first electrode and the second electrode.

3. The under-display camera type display device according to claim 1 , further comprising a circular polarizing plate on a light exit surface of the display element.

4. 4. The under-display camera type display device according to claim 1, wherein the depolarizing member has a liquid crystal layer in which a plurality of regions having different thicknesses are arranged.

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