Patent Description:
A display device such as liquid crystal display ("LCD"), an organic light emitting device (organic light emitting diode display, "OLED" display), an electrophoretic display, and the like includes a field generating electrode and an electro-optical active layer. For example, the OLED display contains an organic emission layer as an electro-optical active layer. The field generating electrode may be connected to a switching element such as a thin film transistor to receive a data signal, and the electro-optical active layer converts the data signal into an optical signal to display an image.

The display device may include a display portion having a function of displaying an image and an optical unit having an optical function. The optical portion may include, for example, a polarization portion may change a polarization state of light.

Polarization characteristics may be different when viewing such a display device from the front and from the side. For example, light leakage may not occur from the front due to the polarization portion, and light leakage may occur from the side. For example, <CIT> discloses a liquid crystal display device that comprises a first polarizer, a first optical compensation layer, a second optical compensation layer, a third optical compensation layer functioning as a λ/<NUM> phase-difference plate, a liquid crystal cell, a fourth optical compensation layer functioning as a λ/<NUM> phase-difference plate, and a second polarizer in this order. The first optical compensation layer is configured such that the in-plane phase difference Re is <NUM> or less and the phase difference Rth in a thickness direction is -<NUM> or less. The second optical compensation layer is configured such that the in-plane phase difference Re is <NUM> to <NUM>, <NUM> ≤ Nz ≤ <NUM> is satisfied, and the in-plane slow axis is substantially parallel to the absorption axis of the first polarizer.

Embodiments are to provide a display device that can prevent light leakage from occurring on front and side surfaces.

A display device according to an embodiment includes: a display panel and an optical member positioned on the display panel, where the optical member includes: a polarization layer positioned on the display panel; a first compensation layer positioned between the display panel and the polarization layer; a second compensation layer positioned between the display panel and the first compensation layer; a third compensation layer positioned between the display panel and the second compensation layer; and a fourth compensation layer positioned between the display panel and the third compensation layer. The first compensation layer is a positive C plate and a thickness direction phase delay value (Rth) of the first compensation layer is -<NUM> nanometers (nm) to -<NUM>, and the second compensation layer is a positive A plate and an in-plane phase delay value (Ro) of the second compensation layer is <NUM> to <NUM>. The third compensation layer is a positive A plate, the fourth compensation layer is a positive C plate. A thickness direction phase delay value of the fourth compensation layer is -<NUM> to -<NUM>.

The display panel may include: a substrate; a transistor positioned in the substrate; a pixel electrode connected to the transistor; an emission layer positioned on the pixel electrode; a common electrode positioned on the emission layer; a buffer electrode positioned between the emission layer and the common electrode; a capping layer positioned on the common electrode; and an encapsulation layer positioned on the capping layer, and a thickness direction phase delay value (Rth) of the display panel may be -<NUM> to <NUM>.

The buffer electrode may contain ytterbium.

The encapsulation layer may include: a first inorganic encapsulation layer; an organic encapsulation layer positioned on the first inorganic encapsulation layer; and a second inorganic encapsulation layer positioned on the organic encapsulation layer, and the first inorganic encapsulation layer may include a plurality of layers having different refractive indices.

The first inorganic encapsulation layer may contain at least one of lithium fluoride (LiF), a silicon nitride (SiNx), a silicon oxide (SiOx), and a silicon oxynitride (SiOxNy).

The third compensation layer may be a quarter wave plate.

An angle between a slow axis of the third compensation layer and a transmissive axis of the polarization layer may be <NUM> degrees.

An in-plane phase delay value of the third compensation layer may be <NUM> to <NUM>.

The thickness direction phase delay value (Rth) of the fourth compensation layer may be -<NUM>.

Aa slow axis of the second compensation layer and a transmissive axis of the polarization layer may be orthogonal.

The in-plane phase delay value (Ro) of the second compensation layer may be <NUM>.

The thickness direction phase delay value (Rth) of the first compensation layer may be -<NUM>.

The first compensation layer, the second compensation layer, the third compensation layer, and the fourth compensation layer may each be formed of a film type or liquid crystal coating layer.

The display device according to the embodiment may further include: a first adhesive member positioned between the second compensation layer and the third compensation layer; and a second adhesive member positioned between the third compensation layer and the fourth compensation layer.

The display device according to the embodiment may further include a window positioned on the optical member, wherein the optical member may be positioned between the display panel and the window.

The display device according to the embodiment may further include: a third adhesive member positioned between the optical member and the window; and a fourth adhesive member positioned between the optical member and the display panel.

The display device according to the embodiment may further include: a rear film positioned under the display panel; and a cushion film positioned under the rear film.

The display device according to the embodiment may further include: a fifth adhesive member positioned between the display panel and the rear film; and a sixth adhesive member positioned between the rear film and the cushion film.

According to the embodiment, it is possible to prevent light leakage from occurring on the front and side surfaces of the display device.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawing, and thus a person of an ordinary skill can easily perform it in the technical field to which the present invention belongs. The present invention may be implemented in several different forms and is not limited to the embodiments described herein.

In order to clearly explain the present invention, parts irrelevant to the description are omitted, and the same reference sign is designated to the same or similar constituent elements throughout the specification.

In addition, since the size and thickness of each component shown in the drawing are arbitrarily indicated for better understanding and ease of description, the present invention is not necessarily limited to the drawings. In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. In addition, in the drawings, the thicknesses of some layers and regions are exaggerated for better understanding and ease of description.

In addition, unless explicitly described to the contrary, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of stated elements but not the exclusion of any other elements.

In addition, throughout the specification, "on a plane" or "in a plan view" means when the target part is viewed from z-axis direction, and "on a cross-section" means when the target part is vertically cut cross-section when viewed from the side.

Hereinafter, referring to <FIG>, a display device according to an embodiment will be described.

<FIG> is a schematic cross-sectional view of a display device according to an embodiment.

As shown in <FIG>, a display device according to an embodiment includes a display panel that can display an image, a window <NUM> positioned on the display panel <NUM>, and an optical member <NUM> positioned between the display panel <NUM> and the window <NUM>.

The display panel <NUM> may include a plurality of pixels and a plurality of signal lines connected thereto. Each of the plurality of pixels may include a plurality of transistors and a light emitting element connected thereto. In this case, the light emitting element may be an organic light emitting element, and the display panel <NUM> may be formed as an organic light emitting panel. However, the type of display panel <NUM> is not limited thereto, and may be formed of or include various types of panels. For example, the display panel <NUM> may be formed of or include a liquid crystal panel, an electrophoretic display panel, an electrowetting display panel, or the like. In addition, the display panel <NUM> may be formed of or include a next-generation display panel such as a micro light emitting diode ("LED") (Micro LED) display panel, a quantum dot light emitting diode ("QLED") display panel, and a quantum dot organic light emitting diode ("QD-OLED") display panel.

The display device according to an embodiment may further include a touch sensor <NUM> positioned on the display panel <NUM>. The touch sensor <NUM> may detect a touch or hovering of an external object. The touch sensor <NUM> may be provided as a separate panel or film and attached to the display panel <NUM>, or may be provided in the form of a touch layer positioned on the display panel <NUM>.

The window <NUM> is a member that protects the display panel <NUM>, may be positioned on the light emission surface of the display panel <NUM>, and may be formed of or include a transparent material. The window <NUM> may include at least one window layer, and each window layer may include a polymer such as plastic or an insulating material such as glass. An adhesive member may be positioned between the stacked plurality of window layers. Although not shown, a window protective layer may be further positioned on the window <NUM>.

The optical member <NUM> may prevent reflected light from being recognized from the outside by reducing light reflectance of external light incident from the outside. For example, external light is converted to right-circularly polarized light while passing through the optical member <NUM> and reflected from an electrode or wiring of the display panel <NUM> to become left-circularly polarized light, and then the reflected light may not be visible from the outside. Accordingly, in the display panel <NUM>, only light according to an image signal is transmitted through the optical member <NUM> such that the quality of an image to be displayed can be improved.

The display device according to an embodiment may further include an adhesive member <NUM> positioned between the window <NUM> and the optical member <NUM>, and an adhesive member <NUM> positioned between the optical member <NUM> and the touch sensor <NUM>. The adhesive members <NUM> and <NUM> may be formed of or include an optically transparent adhesive ("OCA"), an optically transparent adhesive resin ("OCR"), a pressure sensitive adhesive ("PSA"), an ultraviolet rays curing adhesive, or the like. The adhesive members <NUM> and <NUM> may be formed of or include a transparent material. The display device according to an embodiment may further include a rear film <NUM> and a cushion film <NUM> positioned under the display panel <NUM>.

The rear film <NUM> may include polyimide ("PI"), polyethylene terephthalate ("PET"), polycarbonate ("PC"), polyethylene ("PE"), polypropylene ("PP"), polysulfone ("PSF"), polymethyl methacrylate ("PMMA"), triacetyl cellulose ("TAC"), cycloolefin polymer ("COP"), or the like. The rear film <NUM> may include a functional layer on at least one side. The functional layer may include, for example, a light absorbing layer. The light absorbing layer may include a light absorbing material such as black pigment or dye. The light absorbing layer is black ink and may be formed on the rear film <NUM> by coating or printing.

The cushion film <NUM> may absorb external impact and serve to prevent the display panel <NUM> from being damaged. The cushion film <NUM> may be formed of a single layer or a plurality of multilayer. The cushion film <NUM> may include, for example, a material having elasticity such as polyurethane or polyethylene resin. The cushion film <NUM> may be made of a foam material similar to a sponge.

The display device according to an embodiment may further include an adhesive member <NUM> positioned between the display panel <NUM> and the rear film <NUM>, and an adhesive member <NUM> positioned between the rear film <NUM> and the cushion film <NUM>. The adhesive members <NUM> and <NUM> may be formed of or include an optically transparent adhesive (OCA), an optically transparent adhesive resin (OCR), a pressure sensitive adhesive (PSA), ultraviolet rays curing adhesive, or the like. The adhesive members <NUM> and <NUM> may be made of a transparent material.

Although not shown, a support member, a heat dissipation member, or the like may be further positioned under the cushion film <NUM>. The support member may be made of a metal material or a non-metal material. The support member may be formed of or include a non-metal material, for example, carbon fiber reinforced plastic ("CFRP"), glass fiber reinforced plastic ("GFRP"), aramid fiber reinforced plastic ("AFRP") and the like. The heat dissipation member may serve to diffuse heat generated from the display panel <NUM> or the like. The heat dissipation member may include a metal having excellent thermal conductivity such as copper or silver, graphite, or carbon nanotube.

Hereinafter, referring to <FIG>, the display panel <NUM> of the display device according to an embodiment will be described.

<FIG> is a cross-sectional view of the display panel of the display device according to an embodiment.

As shown in <FIG>, the display panel <NUM> of the display device according to an embodiment may include a substrate <NUM>, a transistor TFT positioned on the substrate <NUM> and including a semiconductor <NUM>, a gate electrode <NUM>, a source electrode <NUM>, and a drain electrode <NUM>, a gate insulating layer <NUM>, a first interlayer-insulating layer <NUM>, a second interlayer-insulating layer <NUM>, a pixel electrode <NUM>, an emission layer <NUM>, a partitioning wall <NUM>, and a common electrode <NUM>. Here, the pixel electrode <NUM>, the emission layer <NUM>, and the common electrode <NUM> may form a light emitting diode LED.

The substrate <NUM> may include a material having rigid characteristics such as glass or a flexible material such as plastic or polyimide. A buffer layer <NUM> for flattening the surface of the substrate <NUM> and blocking penetration of impurity elements may be further positioned on the substrate <NUM>. The buffer layer <NUM> may include an inorganic material, and may include an inorganic insulating material such as, for example, a silicon nitride (SiNx), a silicon oxide (SiOx), and a silicon oxynitride (SiOxNy). The buffer layer <NUM> may have a single-layer or multi-layered structure of the material. A barrier layer (not shown) may be further positioned on top of the substrate <NUM>. In this case, the barrier layer may be positioned between the substrate <NUM> and the buffer layer <NUM>. The barrier layer may include an inorganic insulating material such as a silicon nitride (SiNx), a silicon oxide (SiOx), and a silicon oxynitride (SiOxNy). The barrier layer may be a single layer or multi-layered structure of the material.

The semiconductor <NUM> may be positioned on the substrate <NUM>. The semiconductor <NUM> may include any one of amorphous silicon, polycrystalline silicon, and an oxide semiconductor. For example, the semiconductor <NUM> includes an oxide semiconductor containing low temperature polysilicon ("LTPS") or containing at least one of zinc (Zn), indium (In), gallium (Ga), tin (Sn), and a mixture thereof. For example, the semiconductor <NUM> may include an indium-gallium-zinc oxide ("IGZO"). The semiconductor <NUM> may include a channel region, a source region, and a drain region classified according to impurity doping. The source region and drain region may be positioned on either side of the channel region. The source region and drain region may have conductivity characteristics corresponding to conductors.

The gate insulating layer <NUM> may cover the semiconductor <NUM> and the substrate <NUM>. The gate insulating layer <NUM> may include an inorganic insulating material such as a silicon nitride (SiNx), a silicon oxide (SiOx), and a silicon oxynitride (SiOxNy). The gate insulating layer <NUM> may have a single-layer or multi-layered structure of the material.

The gate electrode <NUM> may be positioned on the gate insulating layer <NUM>. The gate electrode <NUM> may include a metal such as copper (Cu), molybdenum (Mo), aluminum (Al), silver (Ag), chromium (Cr), tantalum (Ta), or titanium (Ti), or a or metal alloy thereof. The gate electrode <NUM> may be formed of a single layer or multiple layers. A region overlapping the gate electrode <NUM> on a plane of the semiconductor <NUM> may be a channel region.

The first interlayer-insulating layer <NUM> may cover the gate electrode <NUM> and the gate insulating layer <NUM>. The first interlayer-insulating layer <NUM> may include an inorganic insulating material such as a silicon nitride (SiNx), a silicon oxide (SiOx), and a silicon oxynitride (SiOxNy). The first interlayer-insulating layer <NUM> may have a single-layer or multi-layered structure of the material.

The source electrode <NUM> and drain electrode <NUM> may be positioned on the first interlayer-insulating layer <NUM>. The source electrode <NUM> and the drain electrode <NUM> are connected to the source region and drain region of the semiconductor <NUM>, respectively, through openings formed in the first interlayer-insulating layer <NUM> and gate insulating layer <NUM>. Accordingly, the aforementioned semiconductor <NUM>, the gate electrode <NUM>, the source electrode <NUM>, and the drain electrode <NUM> form one transistor TFT. Depending on embodiments, the transistor TFT may include only the source region and the drain region of the semiconductor <NUM> instead of the source electrode <NUM> and the drain electrode <NUM>.

The source electrode <NUM> and the drain electrode <NUM> may include a metal such as aluminum (Al), copper (Cu), silver (Ag), gold (Au), platinum (Pt), palladium (Pd), nickel (Ni), molybdenum (Mo), tungsten (W), titanium (Ti), chromium (Cr), tantalum (Ta), or a metal alloy thereof. The source electrode <NUM> and the drain electrode <NUM> may be formed of a single layer or multiple layers. For example, the source electrode <NUM> and the drain electrode <NUM> may be formed of a triple layer including an upper layer, a middle layer, and a lower layer, and the upper layer and the lower layer may include titanium (Ti) and the middle layer may include aluminum (Al).

The second interlayer-insulating layer <NUM> may be positioned on the source electrode <NUM> and the drain electrode <NUM>. The second interlayer-insulating layer <NUM> may cover the source electrode <NUM>, the drain electrode <NUM>, and the first interlayer-insulating layer <NUM>. The second interlayer-insulating layer <NUM> may be provided for planarizing the surface of the substrate <NUM> equipped with the transistor TFT, may be an organic insulator, and may include a at least one metal selected from a group consisting of polyimide, polyamide, acryl resin, benzocyclobutene, and phenol resin.

The pixel electrode <NUM> may be positioned on the second interlayer-insulating layer <NUM>. The pixel electrode <NUM> is also called an anode, and may be formed of a single layer including a transparent conductive oxide film or a metal material or a multi-layer including these. The transparent conductive oxide layer may include an indium tin oxide ("ITO"), a poly-ITO, indium zinc oxide ("IZO"), an indium gallium zinc oxide (IGZO), and an indium tin zinc oxide ("ITZO"). The metal material may include silver (Ag), molybdenum (Mo), copper (Cu), gold (Au), and aluminum (Al). For example, the pixel electrode <NUM> may be formed of a triple layer including an upper layer, an intermediate layer, and a lower layer, the upper and lower layers may include ITO, and the middle layer may include silver (Ag).

The second interlayer-insulating layer <NUM> may include a via-hole <NUM> exposing the drain electrode <NUM>. The pixel electrode <NUM> may be physically and electrically connected to the drain electrode <NUM> through the via-hole <NUM> of the second interlayer-insulating layer <NUM>. Accordingly, the pixel electrode <NUM> may be connected to a transistor TFT, and the pixel electrode <NUM> may receive an output current to be transmitted from the drain electrode <NUM> to the emission layer <NUM>.

A partitioning wall <NUM> may be positioned on the pixel electrode <NUM> and the second interlayer-insulating layer <NUM>. The partitioning wall <NUM> is also referred to as a pixel defining layer PDL, and includes a pixel opening <NUM> overlapping at least a part of the pixel electrode <NUM>. In this case, the pixel opening <NUM> may overlap a center of the pixel electrode <NUM> and may not overlap an edge of the pixel electrode <NUM>. Therefore, the size of the pixel opening <NUM> may be smaller than the size of the pixel electrode <NUM>. The partitioning wall <NUM> may partition a formation position of the emission layer <NUM> such that the emission layer <NUM> may be positioned on a portion where an upper surface of the pixel electrode <NUM> is exposed. The partitioning wall <NUM> may be an organic insulator containing at least one material selected from a group consisting of polyimide, polyamide, acryl resin, benzocyclobutene, and phenol resin. Alternatively, the partitioning wall <NUM> may include an inorganic insulating material such as a silicon nitride (SiNx), a silicon oxide (SiOx), and a silicon oxynitride (SiOxNy). Alternatively, the partitioning wall <NUM> may include a light blocking material. In this case, the light blocking material may include carbon black, carbon nanotube, resin containing black dye or paste, a metal particle, for example, nickel, aluminum, molybdenum, and its alloy, a metal oxide particle (e.g., chromium oxide) or a metal nitride particle (e.g., chromium nitride) and the like. When the partitioning wall <NUM> includes a light blocking material, reflection of external light by metal structures disposed under the partitioning wall <NUM> may be reduced. However, it is not limited thereto, and the partitioning wall <NUM> may include a light-transmitting organic insulating material instead of a light-blocking material.

The emission layer <NUM> may be positioned within the pixel opening <NUM> partitioned by the partitioning wall <NUM>. The emission layer <NUM> may overlap the pixel electrode <NUM>. Within the pixel opening <NUM>, the emission layer <NUM> may be positioned directly above the pixel electrode <NUM>. The emission layer <NUM> may include an organic material emitting red, green, and blue light. The emission layer <NUM> may include a low-molecular or high-molecular organic material. In <FIG>, although the emission layer <NUM> is shown as a single layer, an auxiliary layer such as a hole injection layer ("HIL"), a hole transporting layer ("HTL"), and an electron transporting layer ("ETL"), and an electron injection layer ("EIL") may be further positioned above and below the emission layer <NUM>. In this case, the hole injection layer and hole transport layer may be positioned below the emission layer <NUM>, and the electron transport layer and electron injection layer may be positioned above the emission layer <NUM>.

The common electrode <NUM> may be positioned on the partitioning wall <NUM> and the emission layer <NUM>. The common electrode <NUM> is also called a cathode, and may include a reflective metal including calcium (Ca), barium (Ba), magnesium (Mg), aluminum (Al), silver (Ag), platinum (Pt), palladium (Pd), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), or transparent conductive oxide such as an indium tin oxide (ITO), an indium zinc oxide (IZO), and the like.

The pixel electrode <NUM>, the emission layer <NUM>, and the common electrode <NUM> may together form a light emitting diode LED. The light emitting diode LED may be connected to the transistor TFT. In this case, the pixel electrode <NUM> may be an anode that is a hole injection electrode, and the common electrode <NUM> may be a cathode that is an electron injection electrode. However, it is not limited to this, and the anode and cathode may be formed in the opposite way according to a driving method of the display device.

Holes and electrons are injected into the emission layer <NUM> from the pixel electrode <NUM> and the common electrode <NUM>, respectively, and light emission occurs when the exciton combined with the injected holes and electrons falls from the excited state to the ground state.

The display device according to an embodiment may further include a buffer electrode <NUM> positioned between the emission layer <NUM> and the common electrode <NUM>. The buffer electrode <NUM> may be positioned over the emission layer <NUM> and the partitioning wall <NUM>. The buffer electrode <NUM> may be positioned in most regions on the substrate <NUM>. The buffer electrode <NUM> may include a metal material, for example, ytterbium (Yb).

The display device according to an embodiment may further include a capping layer <NUM> positioned on the common electrode <NUM>. The capping layer <NUM> may be formed to cover the entire common electrode <NUM>. The capping layer <NUM> may be positioned over most regions on the substrate <NUM>. The capping layer <NUM> may increase optical efficiency by adjusting the refractive index. The capping layer <NUM> may include an organic insulating material or an inorganic insulating material.

The display device according to an embodiment may further include an encapsulation layer <NUM> positioned on the capping layer <NUM>. The encapsulation layer <NUM> may include at least one inorganic layer and at least one organic layer. In the present embodiment, the encapsulation layer <NUM> may include a first inorganic encapsulation layer <NUM>, an organic encapsulation layer <NUM>, and a second inorganic encapsulation layer <NUM>. A first inorganic encapsulation layer <NUM> may be positioned on the capping layer <NUM>, an organic encapsulation layer <NUM> may be positioned on the first inorganic encapsulation layer <NUM>, and a second inorganic encapsulation layer <NUM> may be positioned on the organic encapsulation layer <NUM>. However, this is only one example, and the number and stacking order of the inorganic and organic layers forming the encapsulation layer <NUM> may be variously changed. The first inorganic encapsulation layer <NUM>, the organic encapsulation layer <NUM>, and the second inorganic encapsulation layer <NUM> may be positioned in most regions above the substrate <NUM>. The encapsulation layer <NUM> is to protect the light emitting diode LED from moisture or oxygen that may inflow from the outside, and the ends of the first inorganic encapsulation layer <NUM> and the second inorganic encapsulation layer <NUM> may directly contact.

The first inorganic encapsulation layer <NUM> may include a plurality of layers having different refractive indices. For example, the first inorganic encapsulation layer <NUM> may include three material layers or four material layers having different refractive indices. The first inorganic encapsulation layer <NUM> may include an inorganic insulating material such as lithium fluoride (LiF), silicon nitride (SiNx), silicon oxide (SiOx), and silicon oxynitride (SiOxNy).

The characteristics of the display panel <NUM> may vary according to the refractive index, thickness, or the like of various material layers that form the display panel <NUM> of the display device according to an embodiment.

For example, a display panel <NUM> of a display device according to Embodiment <NUM> may include a buffer electrode <NUM>, a common electrode <NUM>, a capping layer <NUM>, and a first inorganic encapsulation layer <NUM>. In this case, the buffer electrode <NUM> may include ytterbium (Yb), and a thickness of the buffer electrode <NUM> may be about <NUM> nanometers (nm). The common electrode <NUM> may include AgMg, and the common electrode <NUM> may have a thickness of about <NUM>. A refractive index of the capping layer <NUM> may be about <NUM>, and a thickness of the capping layer <NUM> may be about <NUM>. The first inorganic encapsulation layer <NUM> may formed in a form in which lithium fluoride (LiF) with a refractive index of about <NUM> and a thickness of about <NUM>, silicon oxynitride (SiOxNy) with a refractive index of about <NUM> and a thickness of about <NUM>, silicon oxynitride (SiOxNy) with a refractive index of about <NUM> and a thickness of about <NUM>, and silicon oxide (SiOx) having a refractive index of about <NUM> and a thickness of about <NUM> are sequentially stacked. A thickness direction phase delay value Rth of the display panel <NUM> may be about <NUM>. (Based on when the incident light wavelength is <NUM>) As used herein, the "thickness" is measured in a thickness direction (i.e., z-axis direction).

As another example, a display panel <NUM> of a display device according to Embodiment <NUM> may include a buffer electrode <NUM>, a common electrode <NUM>, a capping layer <NUM>, and a first inorganic encapsulation layer <NUM>. In this case, the buffer electrode <NUM> may include ytterbium (Yb), and a thickness of the buffer electrode <NUM> may be about <NUM>. The common electrode <NUM> may include AgMg, and the common electrode <NUM> may have a thickness of about <NUM>. A refractive index of the capping layer <NUM> may be about <NUM>, and a thickness of the capping layer <NUM> may be about <NUM>. The first inorganic encapsulation layer <NUM> may be formed in a format in which about <NUM> of silicon oxide (SiOx) with a refractive index of about <NUM>, about <NUM> of silicon oxynitride (SiOxNy) with a refractive index of about <NUM>, and about <NUM> of silicon oxynitride (SiOxNy) with a refractive index of about <NUM> are sequentially stacked. A thickness direction phase delay value Rth of the display panel <NUM> may be about -<NUM>.

In addition to the two examples, the refractive index and thickness of various material layers that form the display panel <NUM> of the display device according to an embodiment may be variously changed. Accordingly, the thickness direction phase delay value Rth of the display panel <NUM> of the display device according to an embodiment may be variously changed in a range of about -<NUM> to about <NUM>.

Hereinafter, an optical member <NUM> of a display device according to an embodiment will be described with reference to <FIG>.

<FIG> is a cross-sectional view of an optical member according to display device according to an embodiment, <FIG> and <FIG> show a structure of some layers of the optical member of the display device according to an embodiment, and <FIG> shows a transmissive axis and a slow axis of some layers of the optical member of the display device according to an embodiment. <FIG> shows a structure of a first compensation layer of the optical member, and <FIG> shows a structure of a second compensation layer of the optical member.

As shown in <FIG>, an optical member <NUM> of a display device according to an embodiment includes a polarization layer <NUM>, a first compensation layer <NUM>, a second compensation layer <NUM>, a third compensation layer <NUM>, and a fourth compensation layer <NUM> that are positioned below the polarization layer <NUM>.

The polarization layer <NUM> may be positioned between the display panel <NUM> and the window <NUM>. The polarization layer <NUM> may be a straight line polarizer that converts incident light incident from the outside into the optical member <NUM> into linear polarization. The polarization layer <NUM> may include a transmissive axis and an absorption axis. The polarization layer <NUM> may pass light vibrating in a transmissive axis direction and block light vibrating in an absorption axis direction that is perpendicular to the transmissive axis.

The polarization layer <NUM> may include polyvinyl alcohol ("PVA") as a polarization material. Specifically, in the polarization layer <NUM>, a dichroism dye such as iodine is oriented and adsorbed to a layer containing stretched polyvinyl alcohol, and may have a polarization function. The polarization layer <NUM> may be in the form of a film, or may be a liquid crystal coating type polarizer including aligned liquid crystals.

The optical member <NUM> of the display device according to an embodiment may further include a first protective layer <NUM> and a second protective layer <NUM> positioned on different surfaces of the polarization layer <NUM>, respectively. The first protective layer <NUM> may be positioned on the polarization layer <NUM>. Accordingly, the first protective layer <NUM> may be positioned between the polarization layer <NUM> and the window <NUM>. The second protective layer <NUM> may be positioned under the polarization layer <NUM>. Therefore, the second protective layer <NUM> may be positioned between the polarization layer <NUM> and the first compensation layer <NUM>.

The first protective layer <NUM> and the second protective layer <NUM> may serve to protect the polarization layer <NUM> and may be formed of or include a general protective film without phase retardation. For example, the first protective layer <NUM> and the second protective layer <NUM> may include materials such as triacetyl cellulose (TAC), cycloolefin polymer (COP), polymethyl methacrylate ("PMMA"), and polyethylene terephthalate (PET).

The first compensation layer <NUM>, second compensation layer <NUM>, third compensation layer <NUM>, and fourth compensation layer <NUM> may each be formed in the form of a film. For example, the first compensation layer <NUM>, the second compensation layer <NUM>, the third compensation layer <NUM>, and the fourth compensation layer <NUM> use materials such as polycarbonate (PC), triacetyl cellulose (TAC), and cycloolefin polymer (COP). In the case of film, the desired phase difference can be obtained by adjusting a stretching ratio of the materials. However, it is not limited thereto, and the first compensation layer <NUM>, the second compensation layer <NUM>, the third compensation layer <NUM>, and the fourth compensation layer <NUM> may each be formed of or include a liquid crystal coating layer in another embodiment. The first compensation layer <NUM>, the second compensation layer <NUM>, the third compensation layer <NUM>, and the fourth compensation layer <NUM> may each include one or more monomeric liquid crystals. For example, the liquid crystal monomer may include a compound represented by Chemical Formula <NUM>.

The first compensation layer <NUM>, the second compensation layer <NUM>, the third compensation layer <NUM>, and the fourth compensation layer <NUM> may each include a positive C plate or a positive A plate. As shown in <FIG>, in the case of positive C plate, the liquid crystal monomers may be arranged vertically with respect to the plane direction, that is, in parallel with the thickness direction (i.e., z-axis direction). In this case, the slow axis of the positive C plate may be parallel to the thickness direction. As shown in <FIG>, in the case of positive A plate, the liquid crystal monomers can be aligned in the plane direction. In this case, the slow axes of the positive A plate may be parallel to the plane direction. Here, the plane direction is a direction on a plane defined by x-axis direction and y-axis direction and perpendicular to the thickness direction.

The first compensation layer <NUM>, the second compensation layer <NUM>, the third compensation layer <NUM>, and the fourth compensation layer <NUM> may each have refractive index values nx, ny, and nz in x, y, and z-axis directions, respectively. The first compensation layer <NUM>, the second compensation layer <NUM>, the third compensation layer <NUM>, and the fourth compensation layer <NUM> may each have a predetermined in-plane phase delay value Ro and a thickness direction phase delay value Rth. The in-plane phase delay value Ro and the thickness direction phase delay value Rth are values defined by Equation <NUM> and Equation <NUM> below, respectively, and d means a thickness of the compensation layer. These optical characteristics can be expressed based on the case where the wavelength of the light source is <NUM>. <MAT> <MAT>.

The first compensation layer <NUM> may be positioned under the polarization layer <NUM>. The first compensation layer <NUM> may be positioned between the display panel <NUM> and the polarization layer <NUM>. The second protective layer <NUM> may further be positioned between the polarization layer <NUM> and the first compensation layer <NUM>. The first compensation layer <NUM> may be made of a positive C plate. A thickness direction phase delay value Rth of the first compensation layer <NUM> may be about -<NUM> to about -<NUM>. More preferably, the thickness direction phase delay value Rth of the first compensation layer <NUM> may be about -<NUM>.

The second compensation layer <NUM> may be positioned below the first compensation layer <NUM>. The second compensation layer <NUM> may be positioned between the display panel <NUM> and the first compensation layer <NUM>. The second compensation layer <NUM> may be formed of or include a positive A plate. An in-plane phase delay value Ro of the second compensation layer <NUM> may be about <NUM> to about <NUM>. More preferably, the in-plane phase delay value Ro of the second compensation layer <NUM> may be about <NUM>. As shown in <FIG>, the slow axis (Posi A #<NUM> Slow Axis) of the second compensation layer <NUM> may be orthogonal to the transmissive axis (PVA transmittance axis) of the polarization layer <NUM>.

The third compensation layer <NUM> may be positioned below the second compensation layer <NUM>. The third compensation layer <NUM> may be positioned between the display panel <NUM> and the second compensation layer <NUM>. According to the present invention, the third compensation layer <NUM> is formed of or includes a positive A plate. The third compensation layer <NUM> may include a λ/<NUM> phase retarder (i.e., quarter wave plate, "QWP"). The λ/<NUM> phase retarder (QWP) may convert linear polarization into circular polarization by assigning a phase difference of λ/<NUM>. An in-plane phase delay value Ro of the third compensation layer <NUM> may be about <NUM> to about <NUM>. More preferably, the in-plane phase delay value Ro of the third compensation layer <NUM> may be about <NUM>. As shown in <FIG>, an angle between the slow axis (Posi A #<NUM> Slow Axis) of the third compensation layer <NUM> and the transmissive axis (PVA Transmittance Axis) of the polarization layer <NUM> may be about <NUM> degrees.

The fourth compensation layer <NUM> may be positioned under the third compensation layer <NUM>. The fourth compensation layer <NUM> may be positioned between the display panel <NUM> and the third compensation layer <NUM>. According to the present invention, the fourth compensation layer <NUM> is formed of or include a positive C plate. A thickness direction phase delay value Rth of the fourth compensation layer <NUM> is about -<NUM> to about -<NUM>. More preferably, the thickness direction phase delay value Rth of the fourth compensation layer <NUM> may be about -<NUM>.

The optical member <NUM> of the display device according to an embodiment may further include an adhesive member <NUM> positioned between the second compensation layer <NUM> and the third compensation layer <NUM>, and an adhesive member <NUM> positioned between the third compensation layer <NUM> and the fourth compensation layer <NUM>. The adhesive members <NUM> and <NUM> may contain an acryl-based copolymer that has excellent elasticity and adhesion characteristics and can prevent peeling by reducing the generation of fine vapor. For example, the adhesive members <NUM> and <NUM> may be made of pressure sensitive adhesive (PSA) or the like. The adhesive members <NUM> and <NUM> may serve protect the compensation layers or the display panel <NUM> from external impact by having a certain elasticity as well as an adhesive role.

As described above, the first compensation layer <NUM> of the optical member <NUM> of the display device according to an embodiment may be positioned under the polarization layer <NUM>, and the second compensation layer <NUM> may be positioned under the first compensation layer <NUM>. However, it is not limited thereto, and positions of the first compensation layer <NUM> and the second compensation layer <NUM> may be interchanged. For example, the second compensation layer <NUM> may be positioned under the polarization layer <NUM>, and the first compensation layer <NUM> may be positioned under the second compensation layer <NUM>. That is, the second compensation layer <NUM> may be positioned between the polarization layer <NUM> and the first compensation layer <NUM>.

As described above, the third compensation layer <NUM> of the optical member <NUM> of the display device according to an embodiment may be formed of or include a positive A plate made of a λ/<NUM> phase retarder (QWP) single layer. In this case, the in-plane phase delay value Ro of the third compensation layer <NUM> may be about <NUM> to about <NUM>, and an angle between the slow axis (Posi A #<NUM> Slow Axis) of the third compensation layer <NUM> and the transmissive axis (PVA Transmittance Axis) of the polarization layer <NUM> may be about <NUM> degrees. However, it is not limited thereto, and the third compensation layer <NUM> may be formed of or include a positive A plate including two layers. Two layers forming the third compensation layer <NUM> may include a λ/<NUM> phase retarder ("HWP") and a λ/<NUM> phase retarder (QWP). In this case, an in-plane phase delay value Ro of the λ/<NUM> phase retarder HWP may be about <NUM> to about <NUM>, and an in-plane phase delay value Ro of the λ/<NUM> phase retarder QWP may be about <NUM> to about <NUM>. An angle between the slow axis of the λ/<NUM> phase retarder (HWP) and the transmissive axis of the polarization layer <NUM> may be about <NUM> degrees, and an angle between the slow axis of the λ/<NUM> phase retarder (QWP) and the λ/<NUM> phase retarder (HWP) may be about <NUM> degrees. When the third compensation layer <NUM> includes a λ/<NUM> phase delay (HWP) and a λ/<NUM> phase delay (QWP), the fourth compensation layer <NUM> can be omitted, and the thickness direction phase delay value Rth of the first compensation layer <NUM> may be about -<NUM> to about -<NUM>. More preferably, the thickness direction phase delay value Rth of the first compensation layer <NUM> may be about -<NUM> to about -<NUM>.

Hereinafter, a display device according to an embodiment and a display device according to a referential example will be compared with reference to <FIG>.

<FIG> is a cross-sectional view of an optical member of a display device according to a referential example. <FIG> shows an absorption axis and a slow axis of some layers of the optical member of the display device according to the reference example, <FIG> shows a light path within the optical member of the display device according to the reference example, and <FIG> shows a polarization state according to the light path on the Poincaré sphere in the optical member of the display device according to the reference example. <FIG> shows an absorption axis and a slow axis of some layers of an optical member of a display device according to a reference example, <FIG> shows a light path within the optical member of the display device according to the reference example, and <FIG> shows a polarization state according to the light path on the Poincaré sphere in the optical member of the display device according to the reference example. <FIG> shows a light path in an optical member of a display device according to an embodiment, and <FIG> shows a polarization state according to the light path on the Poincaré sphere in the optical member of the display device according to the embodiment. <FIG> are drawings based on a view from the front, <FIG> are drawings based on a side view.

As shown in <FIG>, an optical member of a display device according to the reference example includes a polarization layer <NUM>, a third compensation layer <NUM>, and a fourth compensation layer <NUM> positioned under the polarization layer <NUM>. The optical member of the display device according to the reference example differs from the optical member of the display device according to an embodiment in that the first and second compensation layers are not positioned between the polarization layer <NUM> and the third compensation layer <NUM>.

The third compensation layer <NUM> may be positioned between the polarization layer <NUM> and the fourth compensation layer <NUM>. The third compensation layer <NUM> may be formed of or include a positive A plate. The third compensation layer <NUM> may include a quarter wave plate QWP. An in-plane phase delay value Ro of the third compensation layer <NUM> may be about <NUM>.

The fourth compensation layer <NUM> may be formed of or include a positive C plate. A thickness direction phase delay value Rth of the fourth compensation layer <NUM> may be about -<NUM>.

As shown in <FIG>, when viewed from the front (i.e., view in z-axis direction), an angle between the slow axis of the third compensation layer <NUM> and the absorption axis of the polarization layer <NUM> of the optical member of the display device according to the reference example may be about <NUM> degrees.

As shown in <FIG> and <FIG>, when viewed from the front (On_Axis), light incident from the outside to the optical member of the display device according to the reference example may be changed to linearly polarized light while passing through the polarization layer <NUM>, and is positioned at ① on the Poincaré sphere. The light passing through the polarization layer <NUM> may be changed from the linearly polarized light to right-circularly polarized light while passing through the third compensation layer <NUM>, and is positioned at ②, which is S3 (target point), on the Poincaré sphere. The light passing through the third compensation layer <NUM> is not phase delayed while passing through the fourth compensation layer <NUM>, and is positioned at the same position as ② and ③. Light passing through the fourth compensation layer <NUM> may change from right-circularly polarized light to left-circularly polarized light while being reflected on the display panel <NUM>. Light reflected from the display panel <NUM> may be changed to linearly polarized light while passing through the third compensation layer <NUM> without being phase delayed while passing through the fourth compensation layer <NUM>. A vibration direction of the linearly polarized light incident from the outside and passing through the polarization layer <NUM> is parallel to the transmissive axis of the polarization layer <NUM>, and a vibration direction of linearly polarized light reflected from the display panel <NUM> and passing through the third compensation layer <NUM> may be perpendicular to the transmissive axis of polarization layer <NUM>. That is, the vibration direction of the linearly polarized light that is reflected on the display panel <NUM> and passes through the third compensation layer <NUM> may be parallel to the absorption axis of the polarization layer <NUM>. Accordingly, light reflected by the display panel <NUM> and passing through the third compensation layer <NUM> may be absorbed by the polarization layer <NUM>, and external light may be prevented from being reflected and viewed when viewed from the front.

As shown in <FIG>, when viewed from the side, an angle between the slow axis of the third compensation layer <NUM> and the absorption axis of the polarization layer <NUM> of the optical member of the display device according to the reference example is less than <NUM> degrees.

As shown in <FIG> and <FIG>, when viewed from the side (Off_Axis) (for example, when viewed at a viewing angle of <NUM> degrees), light incident from the outside to the optical member of the display device according to the reference example may be changed to oblique-linearly polarized light due to distortion of the absorption axis of the polarization layer <NUM> while passing through the polarization layer <NUM> and may be positioned at ① on the Poincaré sphere. Light passing through the polarization layer <NUM> may be changed to incomplete right-circularly polarized light (for example, it may be elliptical polarized light) due to distortion of the slow axis of the third compensation layer <NUM> while passing through the third compensation layer <NUM>, and may be positioned at ② on the Poincaré sphere, which falls short of S3 (target point). Light passing through the third compensation layer <NUM> may be corrected for its movement amount by a thickness direction phase delay value Rth while passing through the fourth compensation layer <NUM>, and is positioned at ③ on the Poincaré sphere. Light passing through the fourth compensation layer <NUM> may change from incomplete right-circularly polarized light to incomplete left-circularly polarized light while being reflected on the display panel <NUM>. Light reflected from the display panel <NUM> may be changed to imperfect linearly polarized light while passing through the fourth compensation layer <NUM> and then the third compensation layer <NUM>. A vibration direction of the linearly polarized light that is reflected on the display panel <NUM> and passes through the third compensation layer <NUM> may not be parallel to the absorption axis of the polarization layer <NUM>. Accordingly, a part of the light reflected by the display panel <NUM> and passing through the third compensation layer <NUM> may be absorbed by the polarization layer <NUM>, and the other part may be transmitted and recognized as light leakage.

As shown in <FIG> and <FIG>, when viewed from the side (Off_Axis) (for example, when viewed from a viewing angle of <NUM> degrees), light incident from the outside into the optical member of the display device according to an embodiment may be changed to oblique-linearly polarized light due to distortion of the absorption axis (Absorption Axis) of the polarization layer <NUM> while passing through the polarization layer <NUM>. The light passing through the polarization layer <NUM> may move as much as ① and ② on the Poincaré sphere while passing through the first compensation layer <NUM> and the second compensation layer <NUM>, respectively, to compensate for the position of the distortion of the absorption axis of the polarization layer <NUM>. Accordingly, a vibration direction of the compensated linearly polarized light may be parallel to the transmissive axis of the polarization layer <NUM>. Light passed through the first compensation layer <NUM> and the second compensation layer <NUM> may change from linear polarization to right circle polarization while passing through the third compensation layer <NUM>. In this case, the light passing through the third compensation layer <NUM> is positioned at ③ on the Poincaré sphere that is short of (close to) S3 (target point) due to the distortion of the slow axis of the third compensation layer <NUM>. The light passing through the third compensation layer <NUM> may correct a movement amount by a thickness direction phase delay value Rth while passing through the fourth compensation layer <NUM>, and is positioned at ④, which is S3 (target point), on the Poincaré sphere. While passing through the fourth compensation layer <NUM>, the light completely right-circularly polarized light at S3 (target point) may be reflected on the display panel <NUM> and changed to left circularly polarized light. Light reflected from the display panel <NUM> may passes through the fourth compensation layer <NUM> and then may be change to linearly-polarized light while passing through the third compensation layer <NUM>. A vibration direction of the linearly polarized light that is reflected on the display panel <NUM> and passed through the third compensation layer <NUM> may be parallel to the absorption axis of the polarization layer <NUM>. Accordingly, light reflected by the display panel <NUM> and passed through the third compensation layer <NUM> may be absorbed by the polarization layer <NUM>, and external light may be prevented from being reflected and recognized when viewed from the side of the display device according to an embodiment.

In summary, when viewing the display device according to the reference example from the front, the reflection of external light may be reduced by the optical member, but when viewing from the side, light leakage occurs due to the distortion of the absorption axis of the polarization layer and the slow axis of the compensation layer. However, in the display device according to an embodiment, distortion of the absorption axis of the polarization layer and the slow axis of the compensation layer may be compensated for by the first and second compensation layers <NUM> and <NUM> of the optical member, and reflection of external light may be effectively reduced not only when viewed from the front but also from the side.

Next, referring to <FIG>, the amount of light leakage of the display device according to an embodiment and the display device according to the reference example are compared.

<FIG> shows light reflectance according to a viewing angle of the display device according to the reference example, and <FIG> shows color coordinates (azimuthal reflect color) of azimuthal reflected light of the display device according to the reference example. <FIG> shows the light reflectance according to a viewing angle of the display device according to an embodiment, <FIG> shows color coordinates of the azimuthal reflected light of the display device according to an embodiment. <FIG> shows light reflectance and color coordinates of azimuthal reflected light according to viewing angles of a display device according to a display device and an embodiment according to a reference example. <FIG> shows the light reflectance according to a viewing angle of the display device according to an embodiment, <FIG> shows color coordinates of the azimuthal reflected light of the display device according to an embodiment.

Color coordinates in <FIG>, <FIG>, <FIG>, and <FIG> indicate coordinates in the CIE L*a*b* color space, and indicate colors as coordinates on a uniform color space composed of lightness L* and chromanetics indices a* and b*. In a*, a positive direction represents red and a negative direction represents green. In b*, a positive direction represents yellow and a negative direction represents blue.

As described above, the characteristics of the display panel may vary depending on the refractive index, thickness, or the like of various material layers that form the display panel of the display device according to an embodiment. The display panel of the display device according to Embodiment <NUM> may have a thickness direction phase delay value Rth of about <NUM>, and the display panel of the display device according to Embodiment <NUM> may have a thickness direction phase delay value Rth of about -<NUM>. Depending on a difference in characteristics of the display panel, the light reflectance of the display device and the color coordinate of the reflected light may vary. <FIG> shows the case where the display panel of the display device according to Embodiment <NUM> is applied, and <FIG> and <FIG> shows the case where the display panel of the display device according to Embodiment <NUM> is applied.

For the light reflectance of the display device according to the reference example (Ref.) with reference to <FIG>, it may be determined that the light reflectance is high in the <NUM> degree direction, <NUM> degree direction, <NUM> degree direction, <NUM> degree direction and their surroundings with respect to the front (i.e., z-axis direction). The coordinate of viewing angles used for <FIG>, <FIG>, and <FIG> is the same as the coordinate of viewing angles used for <FIG>.

For color coordinates of the reflected light of the display device according to the reference example (Ref.) with reference to <FIG>, the value of a* has a range of about - <NUM> to about <NUM>, and the value of b* has a range of about -<NUM> to about <NUM>.

For the light reflectance of the display device according to an embodiment (when the display panel of the display device according to Embodiment <NUM> is applied) with reference to <FIG>, it may be determined that there is some difference according to a thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer, an in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer, and a thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer.

In each case, the in-plane phase delay value of the third compensation layer is <NUM>. Overall, it can be determined that the light reflectance of the display device according to the embodiment is lower than the light reflectance of the display device according to the reference example.

When a thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer is -<NUM>, an in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer is <NUM>, and a thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer is -<NUM>, it can be determined that the light reflectance of the display device according to an embodiment is relatively high in the <NUM>-degree direction and <NUM>-degree direction and its surroundings based on the front.

When a thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer is -<NUM>, an in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer is <NUM>, and a thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer is -<NUM>, it can be determined that the light reflectance of the display device according to an embodiment is relatively high in the <NUM>-degree direction, the <NUM>-degree direction, and its surroundings based on the front.

When a thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer is -<NUM>, an in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer is <NUM>, and a thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer is -<NUM> or -<NUM>, it can be determined that the overall light reflectance of the display device according to an embodiment is low.

When a thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer is -<NUM>, -<NUM>, or -<NUM>, an in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer in is <NUM>, and a thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer is -<NUM> or -<NUM>, it can be determined that the overall light reflectance of the display device according to an embodiment is low.

The thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer is -<NUM>, the in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer is <NUM>, and the thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer is -<NUM> or -<NUM>, it can be seen that the overall light reflectance of the display device according to an embodiment is low.

Regarding the color coordinates of the reflected light of the display device according to an embodiment (in the case that the display panel of the display device according to Embodiment <NUM> is applied) with reference to <FIG>, it can be determined that there is some difference according to the thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer, the in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer, and the thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer. In each case, the in-plane phase delay value of the third compensation layer is <NUM>. Overall, compared to the display device according to the reference example, it can be determined that the color coordinate of the reflected light of the display device according to an embodiment has a relatively reduced scattering range and is closer to the center representing black.

In the following, referring to <FIG>, an example that is relatively superior in terms of light reflectance and color coordinate characteristic of reflected light and the most ideal example derived from it among the various examples shown in <FIG> and <FIG> will be compared with the reference example.

As shown in <FIG>, when the thickness direction phase delay value of the first compensation layer (Posi C #<NUM> Rth), the in-plane phase delay value of the second compensation layer (Posi A #<NUM> Ro), the in-plane phase delay value of the third compensation layer (Posi A #<NUM> Ro), and the thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer are -<NUM>/<NUM>/<NUM>/-<NUM> (Example <NUM>), respectively, -<NUM>/<NUM>/<NUM>/-<NUM> (Example <NUM>), respectively, and -<NUM>/<NUM>/<NUM>/-<NUM> (Example <NUM>), respectively, it can be determined that the light reflectance of Example <NUM> is low overall, the dispersion of the color coordinate of the reflected light is small, and it is close to black.

In the case of the reference example, the first and second compensation layers are not included, the in-plane phase delay value (Posi A #<NUM> Ro) of the third compensation layer is <NUM>, and the thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer is - <NUM>, the light reflectance appears high at some viewing angles, the scattering range of the color coordinate of the reflected light is wide and far from black.

From this, an ideal case (Idle) of the light reflectance and the color coordinate characteristic of the reflected light can be derived, which is a case that a thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer, an in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer, an in-plane phase delay value (Posi A #<NUM> Ro) of the third compensation layer, and a thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer are -<NUM>/<NUM>/<NUM>/-<NUM>, respectively ,and it can be determined that the light reflectance is the lowest overall, the dispersion of the color coordinates of the reflected light is the smallest, and the closest to black.

In the light reflectance of the display device according to an embodiment (when the display panel of the display device according to Embodiment <NUM> is applied) with reference to <FIG>, it can be determined that there are some differences according to the thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer, the in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer, and the thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer. In each case, the in-plane phase delay value of the third compensation layer is <NUM>. Overall, it can be determined that the light reflectance of the display device according to an embodiment is lower than the light reflectance of the display device according to the reference example.

In particular, when the thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer, the in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer, the in-plane phase delay value (Posi A #<NUM> Ro) of the third compensation layer, and the thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer are -<NUM>/<NUM>/<NUM>/-<NUM>, respectively, it can be determined that the light reflectance of the display device according to an embodiment is generally low.

In the color coordinates of the reflected light of the display device according to an embodiment (when the display panel of the display device according to Embodiment e is applied) with reference to <FIG>, it can be determined that there are some difference according to the thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer, the second compensation the in-plane phase delay value (Posi A #<NUM> Ro) of the layer and the thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer. In each case, the in-plane phase delay value of the third compensation layer is <NUM>.

In particular, when the thickness direction phase delay value (Posi C #<NUM> Rth) of the first compensation layer, the in-plane phase delay value (Posi A #<NUM> Ro) of the second compensation layer, the in-plane phase delay value (Posi A #<NUM> Ro) of the third compensation layer, and the thickness direction phase delay value (Posi C #<NUM> Rth) of the fourth compensation layer are -<NUM>/<NUM>/<NUM>/-<NUM>, respectively, it can be determined that the color coordinate of the reflected light of the display device according to an embodiment has a relatively reduced scattering range and is closer to the center representing black.

Next, various exemplary variations of the optical member of the display device according to an embodiment will be described with reference to <FIG>.

An optical member of a display device according to an embodiment shown in <FIG> is almost the same as the optical member of the display device according to the embodiment shown in <FIG>, the description of the same part is omitted. The present embodiment is partially different from the previous embodiment in that some layers constituting optical members are omitted, which will be further described below.

<FIG> are cross-sectional views of various embodiments of an optical member of a display device according to an embodiment.

As shown in <FIG>, am optical member <NUM> of a display device according to an embodiment includes a polarization layer <NUM>, and a first compensation layer <NUM>, a second compensation layer <NUM>, a third compensation layer <NUM>, and a fourth compensation layer <NUM> positioned below the polarization layer <NUM>. In the embodiment of <FIG>, the second protective layer may be positioned between the polarization layer <NUM> and the first compensation layer <NUM>, but in the present embodiment, a separate protective layer may not be positioned between the polarization layer <NUM> and the first compensation layer <NUM>. Therefore, the polarization layer <NUM> may be positioned directly above the first compensation layer <NUM>. That is, the polarization layer <NUM> may directly contact the first compensation layer <NUM>.

As shown in <FIG>, an optical member of a display device according to an embodiment includes a polarization layer <NUM>, and a first compensation layer <NUM>, a second compensation layer <NUM>, a third compensation layer <NUM>, and a fourth compensation layer <NUM> positioned below the polarization layer <NUM>. In the embodiment of <FIG>, the first protective layer may be positioned on the polarization layer <NUM>, but in the present embodiment, a separate protective layer may not be positioned on the polarization layer <NUM>. Therefore, a separate protective layer may not be positioned between the polarization layer <NUM> and the window.

As shown in <FIG>, an optical member <NUM> of a display device according to an embodiment includes a polarization layer <NUM>, and a first compensation layer <NUM>, a second compensation layer <NUM>, a third compensation layer <NUM>, and a fourth compensation layer <NUM> positioned below the polarization layer <NUM>. In the embodiment of <FIG>, the first protective layer and the second protective layer are positioned above and below the polarization layer <NUM>, but in the present embodiment, a separate protective layer may not be positioned above and below the polarization layer <NUM>. Therefore, the polarization layer <NUM> may directly contact the first compensation layer <NUM>, and a separate protective layer may not be positioned between the polarization layer <NUM> and a window.

As shown in <FIG>, an optical member <NUM> of a display device according to an embodiment includes a polarization layer <NUM>, and a first compensation layer <NUM>, a second compensation layer <NUM>, a third compensation layer <NUM>, and a fourth compensation layer <NUM> positioned below the polarization layer <NUM>. In the embodiment of <FIG>, the adhesive member may be positioned between the second compensation layer <NUM> and the third compensation layer <NUM>, but in the present embodiment, a separate adhesive member may not be positioned between the second compensation layer <NUM> and the third compensation layer <NUM>. For example, the third compensation layer <NUM> may be directly coated on one side of the second compensation layer <NUM>.

In the above, numerous variations embodiment of the optical member of the display device according to the embodiment have been described, but is not limited thereto. In addition, the structure of the optical member of the display device according to the embodiment may be variously changed.

Claim 1:
A display device comprising
a display panel (<NUM>), and
an optical member (<NUM>) positioned on the display panel (<NUM>),
wherein the optical member (<NUM>) comprises:
a polarization layer (<NUM>) positioned on the display panel (<NUM>);
a first compensation layer (<NUM>) positioned between the display panel (<NUM>) and the polarization layer (<NUM>);
a second compensation layer (<NUM>) positioned between the display panel (<NUM>) and the first compensation layer (<NUM>);
a third compensation layer (<NUM>) positioned between the display panel (<NUM>) and the second compensation layer (<NUM>); and
a fourth compensation layer (<NUM>) positioned between the display panel (<NUM>) and the third compensation layer (<NUM>),
wherein the first compensation layer (<NUM>) is a positive C plate, and a thickness direction phase delay value of the first compensation layer is -<NUM> to -<NUM>, and
the second compensation layer (<NUM>) is a positive A plate, and an in-plane phase delay value of the second compensation layer is <NUM> to <NUM>, characterized in that
the third compensation layer (<NUM>) is a positive A plate,
the fourth compensation layer (<NUM>) is a positive C plate; and
a thickness direction phase delay value of the fourth compensation layer (<NUM>) is -<NUM> to -<NUM>.