Polarizing plate and optical display apparatus comprising the same

Abstract

A polarizer and an optical display device comprising the same are provided, the polarizer; and an optical functional layer laminated on at least one surface of the polarizer, wherein the optical functional layer comprises core-shell particles composed of a magnetic core and a shell surrounding the magnetic core, and wherein the plurality of core-shell particles are aligned in one direction of the optical functional layer.

Description

Technology Field

[0001] The present invention relates to a polarizing plate and an optical display device including the same. Background Technology

[0003] A liquid crystal display is driven by light emitted from a backlight unit passing through a light source-side polarizer, a liquid crystal panel, and a viewing-side polarizer in that order. Light emitted from the light source diffuses as it passes through the backlight unit before being incident on the light source-side polarizer. Therefore, since the light passes through the light source-side polarizer, the liquid crystal panel, and the viewing-side polarizer, there is a problem in that the contrast ratio decreases from the front to the side.

[0004] A method for improving contrast ratio or visibility from the front and side by including a contrast ratio or visibility improvement layer in a polarizing plate on the viewing side has been developed. The contrast ratio or visibility improvement layer improves contrast ratio and visibility by providing a predetermined embossed or intaglio optical pattern at the interface between a low-refractive-index layer and a high-refractive-index layer, thereby causing light to be refracted at the pattern and emitted when transmitted.

[0005] However, the contrast ratio or visibility improvement layer having the above pattern is manufactured by a method that essentially includes a pattern manufacturing process. The pattern manufacturing process utilizes hard molding and soft molding methods, in which a pattern with a specific pitch is cut onto a pattern roll and then transferred onto a film. If a minute defect occurs on the pattern roll during the pattern manufacturing process, the defect is immediately reflected in the transferred film, which may make commercialization difficult. This can complicate the manufacturing of the polarizer, incur additional costs, and increase the thickness of the polarizer.

[0006] The background technology of the present invention is disclosed in Korean Published Patent No. 2018-0047569, etc. The problem to be solved

[0008] The objective of the present invention is to provide a polarizer that improves lateral contrast ratio and viewing angle without including an optical pattern, a pattern layer including an optical pattern, or a laminate of two or more layers with different refractive indices.

[0009] Another objective of the present invention is to provide a polarizer that increases the relative contrast ratio from the side to the front without including an optical pattern, a pattern layer including an optical pattern, or a contrast ratio or visibility improvement layer having two or more layers with different refractive indices.

[0010] Another objective of the present invention is to provide a polarizing plate that can achieve an effect of improving lateral contrast ratio even when the particles for improving contrast ratio or visibility are included in a small amount due to their high degree of orientation. means of solving the problem

[0012] One aspect of the present invention is a polarizing plate.

[0013] 1. A polarizing plate comprises a polarizer; and an optical functional layer laminated on one side of the polarizer, wherein the optical functional layer comprises a plurality of core-shell particles, each consisting of a magnetic core and a shell surrounding the magnetic core, and wherein the core-shell particles are aligned in one direction within the optical functional layer.

[0014] In 2.1, the core-shell particle may have a ratio of the major axis length to the minor axis length (aspect ratio) of 2 or more.

[0015] In 3.1-2, the major axis length may be 5㎛ or more, and the minor axis length may be 10㎛ or less.

[0016] In 4.1-3, in the optical functional layer, the short axis of the core shell particle may be parallel or perpendicular to the direction of the light absorption axis of the polarizer.

[0017] In 5.1-4, the degree of orientation of the core-shell particles of Formula 1 below in the optical functional layer may be 95% or more:

[0018] [Equation 1]

[0019] Orientation = A / B x 100

[0020] (In the above Equation 1,

[0021] A is the total number of core-shell particles in the optical functional layer whose short axis is parallel to the light absorption axis of the polarizer.

[0022] B is the total number of core-shell particles contained in the optical functional layer).

[0023] In 6.1-5, the entire core-shell particle may be aligned as a single layer parallel to the in-plane direction of the optical functional layer.

[0024] In 7.1-6, the core-shell particles may be included in the optical functional layer in an amount of 1% to 30% by weight.

[0025] In 8.1-7, the optical functional layer may have a haze of 30% or less.

[0026] In 9.1-8, the orientation of the core-shell particles in the optical functional layer may not change when a magnetic field is applied.

[0027] In 10.1-8, the magnetic core may have a major axis and a minor axis.

[0028] In 11.1-10, the magnetic core may be formed of a metal oxide.

[0029] In 12.1-11, the shell is non-magnetic and can be formed from one or more of organic and inorganic materials.

[0030] In 13.1-12, the optical functional layer may further include a matrix in which the core-shell particles are impregnated.

[0031] In 14.13, the difference between the refractive index of the shell and the refractive index of the matrix may be 0.01 or greater.

[0032] In 15.13-14, the matrix may be a non-adhesive layer or an adhesive layer.

[0033] In 16.1-15, the polarizer may further include one or more of a first protective layer laminated on the upper surface of the optical functional layer, a second protective layer laminated between the polarizer and the optical functional layer, and a third protective layer laminated on the lower surface of the polarizer.

[0034] In 17.16, at least one of the first protective layer and the second protective layer may have an in-plane phase difference of 4000 nm or more at a wavelength of 550 nm.

[0035] In 18.1-17, the polarizer is a light-absorbing polarizer, and the optical functional layer may be laminated on the light-emitting surface of the polarizer.

[0036] In 19.1-18, the optical functional layer may be a contrast ratio improvement layer.

[0037] In 20.1-19, the optical functional layer may have a lower surface and an upper surface that are each entirely flat.

[0038] Another aspect of the present invention is an optical display device.

[0039] The optical display device includes the polarizing plate of the present invention. Effects of the invention

[0041] The present invention provides a polarizer that improves side contrast ratio and viewing angle without including an optical pattern, a pattern layer including an optical pattern, or a laminate of two or more layers with different refractive indices, or a contrast ratio or visibility improvement layer.

[0042] The present invention provides a polarizer that increases the relative contrast ratio from the side to the front without including an optical pattern, a pattern layer including an optical pattern, or a contrast ratio or visibility improvement layer having two or more layers with different refractive indices.

[0043] The present invention provides a polarizing plate that can obtain an effect of improving side contrast ratio even when the amount of particles for improving contrast ratio or visibility is low, due to the high degree of orientation of the particles. Brief explanation of the drawing

[0045] FIG. 1 is a conceptual diagram of a polarizing plate according to one embodiment of the present invention. Figure 2 is a diagram illustrating a core-shell particle. Figure 3 is a cross-sectional view showing another embodiment of a core-shell particle. Specific details for implementing the invention

[0046] With reference to the attached drawings, embodiments are described in detail so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0047] In order to clearly explain the invention in the drawings, parts unrelated to the explanation have been omitted, and identical or similar components throughout the specification are denoted by the same reference numerals.

[0048] In this specification, "upper" and "lower" are defined based on the drawings, and depending on the viewing perspective, "upper" may be changed to "lower" and "lower" to "upper." Additionally, terms referred to as "on" or "on" may include not only the direct upper portion but also cases where other structures are interposed in between. Conversely, terms referred to as "directly on," "immediately above," "directly formed," or "formed in direct contact" mean that no other structures are interposed in between.

[0049] In this specification, "in-plane phase difference (Re)" is a value at a wavelength of 550 nm and is represented by the following formula A:

[0050] [Essence A]

[0051] Re = (nx - ny) xd

[0052] (In the above Equation A, nx and ny are the refractive indices of the protective layer in the slow axis and fast axis directions, respectively, at a wavelength of 550 nm, and d is the thickness of the protective layer (unit: nm).

[0053] In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0054] In this specification, "refractive index" is a value at a wavelength of 380 nm to 780 nm, specifically 550 nm, and can be measured using a conventional refractive index meter known to those skilled in the art.

[0055] All lengths mentioned for core-shell particles in this specification may be measured via SEM and mean average values ​​unless specifically stated otherwise. Here, 'average value' means the sum of the total lengths measured for N core-shell particles (N is 1 to 20) contained within a predetermined cross-sectional area of ​​the optical functional layer divided by N.

[0056] In this specification, when describing numerical ranges, "X to Y" means "X ≤ and ≤Y".

[0057] The polarizing plate of the present invention has an optical functional layer as described below, and even without having a conventional contrast ratio or visibility improvement layer having an optical pattern, a pattern layer including an optical pattern, or a laminate of two or more layers with different refractive indices formed on an interface, the contrast ratio and / or brightness is improved in the front and side compared to a polarizing plate that does not have the optical functional layer.

[0058] The polarizing plate of the present invention does not need to have the optical pattern, pattern layer, or laminate, thereby improving the manufacturing processability of the polarizing plate and providing a thinning effect.

[0059] The polarizing plate of the present invention includes particles for improving side contrast ratio or visibility (hereinafter referred to as core-shell particles), wherein the orientation degree of the particles for improving side contrast ratio or visibility is significantly high, so that even if said particles are included in a relatively small amount, it provides an effect of improving front and / or side contrast ratio and an effect of improving the relative contrast ratio from the side to the front. If the relative contrast ratio from the side to the front is high, the contrast ratio between the front and the side becomes more uniform, thereby enabling excellent screen quality.

[0060] The polarizing plate of the present invention comprises a polarizer; and an optical functional layer laminated on one side of the polarizer, wherein the optical functional layer comprises a plurality of core-shell particles, each comprising a core having magnetism and a shell surrounding the core having magnetism, and wherein the core-shell particles are aligned in one direction of the optical functional layer.

[0061] Hereinafter, a polarizing plate according to one embodiment of the present invention will be described with reference to the drawings.

[0062] Referring to FIG. 1, the polarizing plate includes a polarizer (100) and an optical functional layer (200) laminated on one side of the polarizer (100).

[0063] In one embodiment, one surface of the polarizer (100), particularly the upper surface of the polarizer (100), may become the light emission surface of the polarizer's internal light when the polarizer is applied to an optical display device. Accordingly, the optical functional layer (200) may be laminated on the light emission surface of the polarizer's internal light. However, the present invention is not limited thereto, and the optical functional layer (200) may be laminated on the light incident surface of the polarizer's internal light.

[0064] Preferably, the optical functional layer (200) may be laminated on the light emission surface of the internal light of the polarizer (100), in which case the effects of the present invention may be better realized. The "internal light" refers to light emitted from a light source such as a backlight unit and emitted through the polarizer.

[0065] Optical functional layer (200)

[0066] The optical functional layer (200) is included in the polarizer and can function as a contrast ratio and / or brightness improvement layer in the front and side.

[0067] In one embodiment, the polarizer may not have a conventional contrast ratio and / or visibility improvement layer, that is, a pattern layer composed of two or more layers including an optical pattern at the interface, or a pattern layer composed of two or more layers including an optical pattern at the interface and having different refractive indices for each layer.

[0068] In one embodiment, the polarizing plate may consist only of a polarizer; an optical functional layer; and one or more protective layers that do not have an optical pattern on at least one surface. Of course, the polarizing plate may additionally have an adhesive layer or adhesive layer for laminating the polarizer, the optical functional layer, and one or more protective layers together.

[0069] The optical functional layer (200) includes core-shell particles (220). The optical functional layer (200) includes a plurality of core-shell particles (220). The core-shell particles are described with reference to FIG. 2.

[0070] Referring to FIG. 2, (A) shows a cross-sectional view in the thickness direction of a core-shell particle, and (B) is a side view when the core-shell particle is cut in-plane at half the thickness direction of the core-shell particle. Here, the 'thickness direction' refers to the normal direction to a plane when the core-shell particle is placed on a plane such that the major axis of the core-shell particle (the major axis is described below) is parallel to the plane.

[0071] The core shell particle (220) has a core (221) and a shell (222) surrounding the core (221).

[0072] The core shell particle (220) may have a long axis (LA) and a short axis (SA) to improve lateral contrast and / or brightness by dispersing light incident perpendicularly from the polarizer in the left and right directions. Since the long axis (LA) and the short axis (SA) have different lengths, it may be easier to disperse light incident perpendicularly from the polarizer in the left and right directions.

[0073] Here, the major axis (LA) and minor axis (SA) are defined such that when a core-shell particle (220) is placed on the aforementioned plane and a cross section parallel to the aforementioned plane and having the maximum width is obtained among several cross sections that can be obtained from the core-shell particle (220), the axis corresponding to the maximum width among the cross sections is defined as the major axis (LA), and the axis corresponding to the minimum width among the cross sections is defined as the minor axis (SA). In one embodiment, the major axis and the minor axis may be substantially orthogonal.

[0074] The ratio between the major axis (LA) and the minor axis (SA), i.e., the aspect ratio (length of the major axis / length of the minor axis), can be 2 or greater. Within the above range, it may be easy to improve the side contrast ratio and / or brightness, and it may be easy to incorporate core-shell particles into the optical functional layer. Specifically, the aspect ratio can be 2 to 30, more specifically 5 to 10.

[0075] The length of the major axis (LA) of the core-shell particles can be 5 μm or more, specifically 5 μm to 50 μm, and more specifically 10 μm to 30 μm. Within the above range, the aspect ratio can be easily reached, and the manufacturing of the core-shell particles can be easy.

[0076] The length of the short axis (SA) of the core-shell particle can be 10 μm or less, specifically 1 μm to 10 μm, 1 μm to 5 μm, and more specifically 1 μm to 3 μm. Within the above range, the aspect ratio can be easily reached, and the manufacturing of the core-shell particle can be easy.

[0077] The maximum diameter of the core-shell particles is substantially equal to the length of the major axis (LA) and can be 5 µm or more, specifically 5 µm to 50 µm, more specifically 10 µm to 30 µm. Within the above range, the aspect ratio can be easily reached, and the manufacturing of the core-shell particles can be easy.

[0078] Among the core-shell particles, the core may also have a major axis and a minor axis. Here, the major axis and minor axis are defined as the axis corresponding to the maximum width of the core among the cross-sections obtained when a cross-section having the maximum width is obtained among several cross-sections that can be obtained from the core-shell particle, and the axis corresponding to the minimum width of the core among the cross-sections is defined as the minor axis. In one embodiment, the major axis of the core and the minor axis of the core may be substantially orthogonal.

[0079] The length of the major axis of the core can be 1 μm or more, specifically 5 μm to 30 μm, and more specifically 5 μm to 20 μm. Within this range, the aspect ratio can be easily reached, and the manufacture of core-shell particles can be easy. The length of the minor axis of the core is smaller than the length of the major axis of the core and can be 0.1 μm or more, specifically 0.5 μm to 3 μm, and more specifically 0.5 μm to 2 μm. Within this range, the aspect ratio can be easily reached, and the manufacture of core-shell particles can be easy.

[0080] The aspect ratio of the core (the ratio of the major axis length of the core to the minor axis length of the core) may be the same as or different from the aspect ratio of the core shell particles. In one embodiment, the aspect ratio of the core may be 2 or more, specifically 2 to 20, and more specifically 5 to 10. Within the above range, the effects of the present invention may be easily realized.

[0081] Referring to FIG. 2, the outermost surface of the core is completely curved, and the cross-section of the core can be elliptical. However, the present invention is not limited thereto.

[0082] FIG. 3 is a cross-sectional view of core-shell particles (220a), (220b), and (220c) of another embodiment of the present invention. The core-shell particle (220a) comprises a core (221a) and a shell (222a). The core-shell particle (220b) comprises a core (221b) and a shell (222b). The core-shell particle (220c) comprises a core (221c), an intermediate layer (223c), and a shell (222c).

[0083] Referring to FIG. 3(a), the core (221a) may have a major axis and a minor axis, and may be in a form that is a mixture of a flat surface and a curved surface. For example, the cross-section of the core may consist of a first surface and a second surface facing each other in the direction of the major axis, a third surface and a fourth surface facing each other in the direction of the minor axis, and a curved surface connecting these planes. In this case, the first surface, the second surface, the third surface, and the fourth surface may each consist of one or more flat surfaces or one or more curved surfaces.

[0084] Although not illustrated in this specification, the core has a major axis and a minor axis, and the cross-section of the core may be rectangular, consisting of a first surface and a second surface facing each other in the direction of the major axis, and a third surface and a fourth surface facing each other in the direction of the minor axis.

[0085] The core (221) is a magnetic material and may have magnetism. As will be explained below, the core-shell particles must not only have the above-mentioned major and minor axes, but also be aligned in one direction within the optical functional layer to facilitate the improvement of the side contrast ratio and / or brightness of the present invention. By including core-shell particles having a magnetic core in the optical functional layer, the present invention facilitates the alignment of the core-shell particles in one direction by applying a magnetic field of a predetermined range when manufacturing the optical functional layer, and by increasing the degree of alignment, the degree of orientation of the core-shell particles is high, so that even if they are included in a relatively small amount, the effect of improving the side contrast ratio and / or visibility can be obtained.

[0086] In one embodiment, the degree of orientation of the core-shell particles in the polarizer or optical functional layer may be 95% or more, specifically 99% to 100%. Within the above range, the side contrast ratio and / or visibility improvement effect of the present invention may be significant.

[0087] The above "orientation degree" can be calculated using the following Equation 1 or Equation 2:

[0088] [Equation 1]

[0089] Orientation = A / B x 100

[0090] (In the above Equation 1,

[0091] A is the total number of core-shell particles in the optical functional layer whose short axis is substantially parallel to the direction of the polarizer's light absorption axis.

[0092] B is the total number of core-shell particles contained in the optical functional layer)

[0093] [Equation 2]

[0094] Orientation = C / B x 100

[0095] (In the above Equation 1,

[0096] C is the total number of core-shell particles in the optical functional layer whose short axis is substantially orthogonal to the direction of the polarizer's light absorption axis.

[0097] B is the total number of core-shell particles contained in the optical functional layer)

[0098] When measuring the degree of orientation mentioned above, B among the number of core-shell particles can be obtained by preparing a specimen by cutting a polarizer to a predetermined size and counting the number of core-shell particles included in the specimen using a microscope transmission mode. A and C can be measured by counting the number of core-shell particles included in the specimen in which the short axis of the core-shell particle is substantially parallel or substantially orthogonal to the direction of the light absorption axis of the polarizer using a microscope transmission mode.

[0099] However, since the core-shell particles are applied to an optical display device, their orientation does not change even when a magnetic field within a predetermined range is applied. Only by doing so can the effect of improving side contrast ratio due to orientation change be avoided when the polarizer is applied to an optical display device. The magnetic field can be 1,000 Gauss (G) or less. That is, a unit area of ​​1 cm² on the polarizer 2 When a magnetic field of 1000 Gauss (G) or less is applied, the change in orientation measured by Equation 1 or Equation 2 of the polarizer or optical functional layer may be 5% or less, for example, 0% to 5%.

[0100] The core shell particles (220) are aligned in one direction within the optical functional layer (200), making it easier to provide a side contrast ratio and / or brightness improvement effect. This allows for providing a side contrast ratio and / or brightness improvement effect even though the upper surface of the optical functional layer (200), i.e., the light emission surface, and the lower surface, i.e., the light incident surface, of the optical functional layer (200) are each entirely flat and not patterned, as shown in FIG. 1.

[0101] The core-shell particles are aligned such that the direction of the polarizer's light absorption axis and the direction of the core-shell particles are substantially parallel or substantially orthogonal. This facilitates the diffusion of perpendicular light incident from the polarizer. The polarizer's light absorption axis can be the polarizer's MD.

[0102] In this specification, 'substantially parallel' means -5° to 5°, preferably 0°, and 'substantially orthogonal' means 85° to 95°, preferably 90°.

[0103] The core shell particles of the present invention can provide sufficient front and / or side contrast ratio and relative contrast ratio improvement effects even if they are aligned as a single layer parallel to the in-plane direction of the optical functional layer due to a high degree of orientation of Formula 1 or Formula 2.

[0104] Referring to FIG. 1, X represents the light absorption axis of the polarizer, Y represents the light transmission axis of the polarizer, and Z represents the thickness direction of the polarizer, and X, Y, and Z are orthogonal to each other. FIG. 1 shows that the light absorption axis of the polarizer and the short axis of the core-shell particle are aligned orthogonally, where (A) shows the cross-section when the core-shell particle is cut in the Y direction, and (B) shows the cross-section when the core-shell particle is cut in the X direction. Referring to FIG. 1, the core-shell particles are independently dispersed without clumping within the optical functional layer and are aligned in one direction.

[0105] Referring to FIG. 2, the outermost surface of the shell (222) is completely curved, and the cross-section of the shell may be elliptical. However, the present invention is not limited thereto.

[0106] Referring to FIG. 3(a), the shell (222a) may have a major axis and a minor axis, and may be in a form that is a mixture of a flat surface and a curved surface. For example, the cross-section of the shell may consist of a first surface and a second surface facing each other in the direction of the major axis, a third surface and a fourth surface facing each other in the direction of the minor axis, and a curved surface connecting these planes. In this case, the first surface, the second surface, the third surface, and the fourth surface may each consist of one or more flat surfaces or one or more curved surfaces.

[0107] Although not shown in the specification, the shell (222a) has a major axis and a minor axis, and the cross-section of the core may be rectangular, consisting of a first plane and a second plane facing each other in the direction of the major axis, and a third plane and a fourth plane facing each other in the direction of the minor axis.

[0108] Referring to FIG. 3(b), the shell (222b) may have fine irregularities formed on its outermost surface. Fine irregularities can further enhance the light diffusion effect.

[0109] In one embodiment, the core-shell particle may consist of a core and a shell surrounding the core. In this case, the core and the shell may be in direct contact.

[0110] In another embodiment, the core-shell particle comprises a core and a shell surrounding the core, and an intermediate layer may be further formed between the core and the shell.

[0111] Referring to FIG. 3(c), the intermediate layer (223c) may facilitate adhesion between the core and the shell or provide additional functions to the core-shell particles. The intermediate layer (223c) may contain a material different from the core and the shell.

[0112] The optical functional layer (200) may have a haze of 30% or less, preferably 0% to 30%, more preferably 10% to 30%, and most preferably 20% to 30%. Within the above range, it may help provide an effect of improving contrast ratio and / or visibility in the optical functional layer comprising magnetic core-shell particles. The haze of the optical functional layer can be achieved by controlling the refractive index and the difference in refractive index between the matrix and the shell in the optical functional layer, the content of core-shell particles in the optical functional layer, and / or the alignment state of the core-shell particles.

[0113] The core, shell, and intermediate layer among the core-shell particles are described in detail.

[0114] The core-shell particle consists of a core and a shell. In one embodiment, the core may be an inorganic-organic hybrid particle formed from an inorganic material and the shell from an organic material.

[0115] The core includes a magnetic material. The magnetic material may be selected and included from a material such that, as described below, when a magnetic field of a predetermined range is applied during the manufacture of the optical functional layer, the core-shell particles are aligned in one direction, and even when a magnetic field of a predetermined range is applied after the manufacture of the optical functional layer, the orientation of the core-shell particles is not easily changed.

[0116] In one embodiment, the magnetic material may be one or more of a ferromagnet, a superparamagnet, a paramagnet, a diamagnet, or a ferrimagnet. For example, the magnetic material may be a metal such as titanium, cobalt, iron, nickel, aluminum, barium, platinum, sodium, strontium, magnesium, dysprosium, manganese, gadolinium, silver, copper, chromium, etc.; a metal oxide, etc. Preferably, the magnetic material may be a metal oxide, and may be one or more of the metal oxides of iron, zinc, cobalt, nickel, copper, and manganese.

[0117] The magnetic material may be contained in the core in an amount of 95% by weight or more, preferably 99% to 100% by weight.

[0118] The shell surrounds the core and may be one or more coating layers. The shell may consist of two or more layers with different refractive indices, but may also consist of a single layer to facilitate haze control of the optical functional layer.

[0119] Since the shell does not contain magnetic material, it does not exhibit magnetism (non-magnetic), but it provides a difference in refractive index with the matrix, improves compatibility with the matrix, and prevents core-shell particles from clumping together, thereby providing lateral contrast ratio and suppressing haze rise.

[0120] The shell is a surface in the optical functional layer that comes into direct contact with the matrix and must have a refractive index difference within an appropriate range relative to the matrix. Through this, an effect of improving lateral contrast ratio and / or brightness can be obtained from the core-shell particles. The difference in refractive index between the shell and the matrix can be 0.01 or more, specifically 0.01 to 1, and more specifically 0.05 to 0.2. Within the above range, the effect of the present invention can be easily implemented.

[0121] In one embodiment, the shell may have a lower or higher refractive index relative to the matrix, but preferably, the shell may have a higher refractive index relative to the matrix.

[0122] The shell may have a refractive index of 1 or more, specifically 1 to 5, more specifically 1 to 2. Within the above range, it may be easy to provide a difference in refractive index.

[0123] The shell may be formed from one or more of organic and inorganic materials, provided that it can provide the aforementioned refractive index. Preferably, it may be formed from an organic material to improve compatibility with the matrix.

[0124] In one embodiment, the shell is formed from a composition comprising one or more radical polymerizable monomers, wherein the radical polymerizable monomers include aromatic radical polymerizable monomers including styrene, p-methylstyrene, m-methylstyrene, p-ethylstyrene, m-ethylstyrene, p-chlorostyrene, m-chlorostyrene, p-chloromethylstyrene, m-chloromethylstyrene, styrenesulfonic acid, pt-butoxystyrene, mt-butoxystyrene, fluorostyrene, alpha-methylstyrene, vinyltoluene, chlorostyrene, etc., alkyl (meth)acrylates including methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, octyl (meth)acrylate, etc., stearyl (meth)acrylate, benzyl (meth)acrylate, It may be one or more compounds selected from the group consisting of perfluoroalkyl (meth)acrylates including glycidyl (meth)acrylate, fluoroethyl (meth)acrylate, trifluoroethyl (meth)acrylate, pentafluoropropyl (meth)acrylate, hexafluorobutyl (meth)acrylate, hexafluoroisopropyl (meth)acrylate, etc., octafluorophenyl (meth)acrylate, vinyl acetate, vinyl propionate, vinyl butylate, vinyl ether, allyl butyl ether, allyl glycidyl ether, (meth)acrylic acid, maleic acid, alkyl (meth)acrylamide, and (meth)acrylonitrile. Preferably, the shell may be formed from a composition comprising an aromatic radical polymerizable monomer.

[0125] The intermediate layer can facilitate adhesion between the core and the shell or provide additional functions to the core-shell particles. However, if the functions of the core-shell particles can be realized without the intermediate layer, it may be omitted. The intermediate layer can be formed from one or more types of organic and inorganic materials.

[0126] Core-shell particles may be included in the optical functional layer in an amount of 1% to 30% by weight, specifically 5% to 20% by weight. Within the above range, the effect of improving the side contrast ratio is sufficient, and there may be no increase in haze due to the excessive inclusion of particles.

[0127] In one embodiment, the optical functional layer (200) may have a light transmittance of 90% or more, specifically 90% to 100%. Within this range, it can be applied to a polarizer and may help provide an effect of improving contrast ratio and brightness by having low cloudiness.

[0128] The core shell particles (220) may be included in the optical functional layer (200) in an amount of 95% or more by weight, specifically 99% to 100% by weight, of the total number of particles (total of organic and inorganic particles). Within this range, the effects of the present invention may be easily realized.

[0129] Core-shell particles can be manufactured by conventional methods known to those skilled in the art. For example, core-shell particles can be manufactured by seed polymerization. For example, they can be formed by polymerizing the shell portion by using a particle to be the core portion as a seed particle and introducing it into a shell-forming composition, and then polymerizing to coat the seed particle.

[0130] A method for aligning core-shell particles (220) in one direction within an optical functional layer (200) is described. By coating a composition for an optical functional layer to a predetermined thickness on a substrate film or a first protective layer, applying a magnetic field, and then curing it, the core-shell particles can be aligned in one direction within the optical functional layer. For example, the magnetic field may be applied at 1000G to 5000G, and it may be easy to manufacture an optical functional layer in which the effects of the present invention are produced within the above range.

[0131] The optical functional layer (200) may further include a matrix (210) impregnated with core-shell particles (220). The optical functional layer (200) may be an adhesive and / or non-adhesive non-adhesive layer or non-adhesive layer, or an adhesive layer or adhesive layer.

[0132] The matrix (210) can help stabilize the core-shell particles (220) and inhibit clumping or aggregation of the core-shell particles (220). The matrix (210) refers to the remaining components of the optical functional layer (200), excluding the entire particle including the core-shell particles (220).

[0133] The matrix (210) may have a refractive index of 1.0 to 2.0, specifically 1.2 to 1.5. Within this range, the effects of the present invention may be easily implemented.

[0134] The matrix (210) can be formed from a thermal curing composition or an active energy beam curing composition.

[0135] The thermosetting composition may include a thermosetting resin. The thermosetting resin is a resin that is cured by heat or aging, and may include, for example, a resin having a thermosetting reactive group. For example, the thermosetting reactive group may be a vinyl group, an acrylate group, or a methacrylate group. For example, the thermosetting composition may be a pressure-sensitive adhesive (PSA).

[0136] The thermosetting composition may further include a curing agent for curing the thermosetting resin, for example, a thermosetting curing agent.

[0137] The active energy beam curable composition may include an active energy beam curable resin. The active energy beam curable resin is a resin that is cured by ultraviolet rays including UV, and may include, for example, a resin having a photocurable reactive group. For example, the photocurable reactive group may be a vinyl group, an acrylate group, or a methacrylate group, and the active energy beam curable resin may have one or more of the above photocurable reactive groups.

[0138] For example, the active energy beam curable resin may be selected and used from among resins such as (meth)acrylate-based, urethane (meth)acrylate-based, epoxy (meth)acrylate-based, and silicone (meth)acrylate that can realize the effects of the present invention.

[0139] The above composition may further include one or more of the following: an initiator comprising a photoinitiator capable of curing an active energy beam curable resin, a crosslinking agent comprising a multifunctional photocurable monomer, etc., and various additives. The initiator may be selected from photoinitiators commonly known to those skilled in the art, and may include, for example, photoradical initiators such as phosphorus-based, phosphine oxide-based, ketone-based, or cyclohexyl ketone-based initiators. The multifunctional photocurable monomer may be selected from conventional types known to those skilled in the art as monomers having two or more photocurable reactive groups, for example, two to six. A dispersant may be included as an additive.

[0140] The above composition may further include various additives, etc., to provide additional functions to the optical functional layer.

[0141] The viscosity of the above composition may be adjusted to facilitate the alignment of core-shell particles in the optical functional layer.

[0142] The optical functional layer (200) may have a thickness of 100 μm or less, specifically greater than 0 μm and less than 50 μm, more specifically between 5 μm and 30 μm. Within the above range, it may be easy to ensure the hardness of the polarizer.

[0143] Polarizer (100)

[0144] The polarizer (100) can polarize light incident from the liquid crystal panel and transmit it to the optical functional layer (200). The polarizer (100) can be laminated to the light incident surface of the internal light of the optical functional layer (200).

[0145] The polarizer (100) is a light-absorbing polarizer and may include a polyvinyl alcohol-based polarizer manufactured by uniaxially stretching a polyvinyl alcohol-based film.

[0146] The polarizer (100) may have a thickness of 5 μm to 40 μm. Within this range, it may be used in an optical display device.

[0147] A protective layer may be further laminated on one or more of the following: the lower surface of the polarizer, the space between the polarizer and the optical functional layer, and the upper surface of the optical functional layer. This will be explained in detail.

[0148] A first protective layer may be further laminated on the upper surface of the optical functional layer.

[0149] The first protective layer serves as a support for forming an optical functional layer, and the first protective layer can be a conventional optically transparent protective film known to those skilled in the art.

[0150] In one embodiment, the first protective layer may have an in-plane phase difference of 4,000 nm or more at a wavelength of 550 nm. Within this range, when combined with an optical functional layer, it may help improve contrast ratio and / or brightness. Preferably, the in-plane phase difference may be 6,000 nm or more, 8,000 nm or more, specifically 10,000 nm or more, more specifically exceeding 10,000 nm, more specifically 10,100 nm to 30,000 nm, or 10,100 nm to 15,000 nm.

[0151] In another embodiment, the first protective layer may have an in-plane phase difference of less than 4000 nm at a wavelength of 550 nm. For example, the first protective layer may have an in-plane phase difference of 0 nm to 1000 nm or 10 nm to 500 nm at a wavelength of 550 nm.

[0152] The first protective layer may include a transparent substrate. The transparent substrate may have a different refractive index compared to the optical functional layer. The transparent substrate may have a higher or lower refractive index compared to the optical functional layer. Preferably, the transparent substrate may have a higher refractive index compared to the optical functional layer. This can help improve contrast ratio and brightness.

[0153] The transparent substrate may include an optically transparent resin film having a light incident surface; and a light exit surface facing the light incident surface. The transparent substrate may be composed of a single layer of resin film, but multiple resin films may be laminated. The resin may include one or more of the following: a cellulose ester resin including triacetylcellulose (TAC), etc.; a cyclic polyolefin resin including amorphous cyclic polyolefin (COP), etc.; a polycarbonate resin; a polyester resin including polyethylene terephthalate (PET), etc.; a polyethersulfone resin; a polysulfone resin; a polyamide resin; a polyimide resin; acyclic-polyolefin resin; a polyacrylate resin including polymethyl methacrylate resin, etc.; a polyvinyl alcohol resin; a polyvinyl chloride resin; and a polyvinylidene chloride resin, but is not limited thereto. Preferably, the transparent substrate may include a polyester-based resin containing polyethylene terephthalate (PET), etc., thereby further enhancing the contrast ratio and brightness improvement effects.

[0154] The transparent substrate may have a haze of 30% or less, specifically 2% to 30%. Within the above range, it may be applied to a polarizer.

[0155] The thickness of the transparent substrate can be 5㎛ to 200㎛, for example, 30㎛ to 120㎛. Within the above range, it can be used in a polarizer.

[0156] The first protective layer may have a light transmittance of 90% or more, for example, 90% to 100%. Within this range, it can transmit light without affecting incident light. The first protective layer may have a haze of 30% or less, specifically 1% to 30% or 2% to 20%. Within this range, it can be applied to a polarizer and, having low cloudiness, can help provide an effect of improving contrast ratio and brightness.

[0157] A functional coating layer may be further laminated on the upper or lower surface of the first protective layer.

[0158] The functional coating layer may include one or more of a hard coating layer, a scattering layer, a low-reflection layer, an ultra-low-reflection layer, a primer layer, an anti-fingerprint layer, an anti-reflection layer, and an anti-glare layer.

[0159] One or more second protective layers may be laminated between the optical functional layer and the polarizer.

[0160] The second protective layer serves to protect the optical functional layer and the polarizer, and the second protective layer may be a conventional optically transparent protective film known to those skilled in the art.

[0161] In one embodiment, the second protective layer may have an in-plane phase difference of 4,000 nm or more at a wavelength of 550 nm. Within this range, when combined with an optical functional layer, it may help improve contrast ratio and / or brightness. Preferably, the in-plane phase difference may be 6,000 nm or more, 8,000 nm or more, specifically 10,000 nm or more, more specifically exceeding 10,000 nm, more specifically 10,100 nm to 30,000 nm, or 10,100 nm to 15,000 nm.

[0162] In another embodiment, the second protective layer may have an in-plane phase difference of less than 4000 nm at a wavelength of 550 nm. For example, the second protective layer may have an in-plane phase difference of 0 nm to 1000 nm or 10 nm to 500 nm at a wavelength of 550 nm.

[0163] In one embodiment, at least one of the first protective layer and the second protective layer may have an in-plane phase difference of 4000 nm or more at a wavelength of 550 nm. Within this range, when combined with an optical functional layer, it may help improve contrast ratio and / or brightness.

[0164] The second protective layer may also include a transparent substrate substantially identical to the transparent substrate described in the first protective layer.

[0165] One or more third protective layers may be laminated on the lower surface of the polarizer.

[0166] The third protective layer supports the polarizer and can be a conventional optically transparent protective film known to those skilled in the art.

[0167] The third protective layer may also include a transparent substrate substantially identical to the transparent substrate described in the first protective layer.

[0168] In one embodiment, the third protective layer may have an in-plane phase difference of 4,000 nm or more at a wavelength of 550 nm. Within this range, when combined with an optical functional layer, it may help improve contrast ratio and / or brightness. Preferably, the in-plane phase difference may be 6,000 nm or more, 8,000 nm or more, specifically 10,000 nm or more, more specifically exceeding 10,000 nm, more specifically 10,100 nm to 30,000 nm, or 10,100 nm to 15,000 nm.

[0169] In another embodiment, the third protective layer may have an in-plane phase difference of less than 4000 nm at a wavelength of 550 nm. For example, the third protective layer may have an in-plane phase difference of 0 nm to 1000 nm or 10 nm to 500 nm at a wavelength of 550 nm.

[0170] An adhesive layer or an adhesive layer may be further laminated on one or more of the following: the lower surface of the polarizer, the space between the polarizer and the optical functional layer, and the upper surface of the optical functional layer.

[0171] The optical display device of the present invention includes the polarizing plate of the present invention.

[0172] The optical display device may be a light-emitting element display device including a liquid crystal display device, an organic light-emitting display device, etc.

[0173] In one embodiment, the optical display device of the present invention may include the polarizing plate of the present invention as a viewing-side polarizing plate with respect to a liquid crystal panel. The "viewing-side polarizing plate" is a polarizing plate positioned opposite to the screen side, i.e., the light source side, with respect to the liquid crystal panel.

[0174] In one embodiment, the liquid crystal display device comprises a light-concentrating backlight unit, a light source-side polarizer, a liquid crystal panel, and a viewing-side polarizer stacked sequentially, and the viewing-side polarizer may include the polarizer of the present invention. The "light source-side polarizer" is a polarizer disposed on the light source side. The liquid crystal panel may adopt a VA (vertical alignment) mode, an IPS mode, a PVA (patterned vertical alignment) mode, or an S-PVA (super-patterned vertical alignment) mode, but is not limited thereto.

[0175] The optical display device can be a foldable or flexible optical display device or a non-foldable or non-flexible optical display device.

[0177] Hereinafter, the structure and operation of the present invention will be explained in more detail through preferred embodiments of the present invention. However, the following embodiments are intended to aid in understanding the present invention, and the scope of the present invention is not limited to the following embodiments.

[0179] Example 1

[0180] (1) A core-shell particle was prepared comprising a core containing magnetic nickel oxide and a shell formed of an organic material, a styrene polymer, surrounding the core. The specific composition of the core-shell particle is shown in Table 1 below. The core-shell particle has the shape shown in Fig. 2.

[0181] A composition for an optical functional layer was prepared by mixing 10 parts by weight of core-shell particles and 90 parts by weight of a (meth)acrylic adhesive (including a (meth)acrylic adhesive resin and a curing agent) based on solid content.

[0182] A polyethylene terephthalate (PET) film (in-plane phase difference at wavelength 550 nm: 400 nm) was used as the first protective layer.

[0183] The composition for the optical functional layer was coated to a thickness of 20 μm on the lower surface of the PET film using a coating bar, and then a magnetic field of 5000 G was applied in a certain direction and heat-cured to form an optical functional layer (refractive index of the matrix for the optical functional layer: 1.38, refractive index of the shell among the core-shell particles: 1.54, thickness: 20 μm) on the lower surface of the first protective layer.

[0185] (2) A polyvinyl alcohol-based film was stretched 3 times at 60°C and iodine was adsorbed, and then stretched 2.5 times in an aqueous boric acid solution at 40°C to produce a polarizer (thickness: 13 μm, light transmittance: 44%).

[0187] (3) A polyethylene terephthalate (PET) film, which is a second protective layer (in-plane phase difference at wavelength 550 nm: 400 nm), was adhered to the upper surface of the polarizer manufactured above, and a cyclic olefin polymer (COP) film, which is a third protective layer (in-plane phase difference at wavelength 550 nm: 400 nm), was adhered to the lower surface of the polarizer manufactured above. Then, the upper surface of the second protective layer and the optical functional layer were laminated to manufacture a polarizing plate laminated in the order of the first protective layer - optical functional layer (where the short axis of the core-shell particles is aligned in one direction parallel to the light absorption axis of the polarizer) - second protective layer - polarizer - third protective layer.

[0189] Examples 2 to 4

[0190] A polarizer was manufactured in the same manner as in Example 1, except that the core-shell particles in Example 1 were changed to the core-shell particles of Table 1 below.

[0192] Comparative Example 1

[0193] Referring to Example 1, a polarizing plate was manufactured by stacking in the order of a second protective layer - a polarizer - a third protective layer.

[0195] Comparative Example 2

[0196] In Example 1, particles were prepared that were formed from an organic material, a styrene polymer, without a core made of a magnetic material, had an outer surface as shown in FIG. 2, and had the specifications of Table 1 below. Then, a polarizer was prepared in the same manner as in Example 1, except that no magnetic field was applied, with the layers stacked in the order of a first protective layer - an optical functional layer - a second protective layer - a polarizer - a third protective layer.

[0198] For the polarizers manufactured in the examples and comparative examples, a model for measuring the viewing angle below was manufactured, and the physical properties of Table 1 below were evaluated.

[0199] A model for measuring a viewing angle was manufactured by removing the viewing-side polarizer from the liquid crystal panel model UN55KS8000F (55-inch, Samsung Electronics 4K TV) and laminating the polarizer manufactured in the example and comparison as the viewing-side polarizer. Among the models for measuring a viewing angle, the light source-side polarizer is laminated from the liquid crystal panel in the order of COP film - polarizer - PET film.

[0201] The following physical properties were evaluated, and the results are shown in Table 1 below.

[0202] (1) Contrast ratio (unit: %): An LED light source, a light guide plate, and the above-mentioned model for measuring viewing angles were assembled to manufacture a liquid crystal display device including a single-edge LED light source (with the same configuration as a Samsung TV (55-inch, model name: UN55KS8000F), excluding the configuration of the module for the liquid crystal display device of the example and comparative example). Using an EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM), the luminance in white mode and black mode was measured at the front (0°, 0°), side (30°, 0°), and side (60°, 0°), respectively. The contrast ratio was calculated as (luminance in white mode) / (luminance in black mode).

[0203] (2) Relative contrast ratio from the side to the front (unit: %): Calculated using the result from (1). The relative contrast ratio from the side to the front was calculated as (contrast ratio from the side (60°, 0°)) / (contrast ratio from the front (0°, 0°)) x 100. The relative contrast ratio must be 8% or higher for the screen quality between the front and the side to be uniform.

[0204] Examples Comparative example 1 2 3 4 1 2 Core shell particles form Core shell (Fig. 2) Core shell (Fig. 2) Core shell (Fig. 2) Core shell (Fig. 2) bare non-core shell Major axis length (㎛) 50 35 25 15 - 15 Shortened length (㎛) 5 3.5 2.5 1.5 - 1.5 Aspect ratio 10 10 10 10 - 10 Optical functional layer Particle content (weight%) 10 10 10 10 - 10 Particle orientation (%) 99% 99% 99% 99% - 50% refractive index difference 0.16 0.16 0.16 0.16 - 0.16 Hayes 28 27 27 26 - 27 Contrast ratio (0°, 0°) 4561 4226 4193 4106 7325 3986 (30°, 0°) 1598 1701 1785 1831 1416 1512 (60°, 0°) 397 411 512 517 289 312 Relative contrast ratio 8.7 9.7 12.2 12.6 3.9 7.8

[0206] In Table 1 above,

[0207] Particle orientation: Value calculated according to Equation 1 above.

[0208] Refractive index difference: In an optical functional layer, the refractive index of the shell among the core-shell particles minus the refractive index of the matrix.

[0210] As shown in Table 1 above, the polarizing plate of the present invention had high front contrast ratio and side contrast ratio, and increased the relative contrast ratio from the side to the front, even without including an optical pattern, a pattern layer including an optical pattern, or a contrast ratio or visibility improvement layer having two or more layers with different refractive indices. In addition, the polarizing plate of the present invention provided an effect of improving the side contrast ratio and relative contrast ratio even when included in a small amount, as the degree of orientation of the particles for improving contrast ratio or visibility was high.

[0211] On the other hand, the polarizing plate of Comparative Example 1, which does not have the core-shell particles of the present invention, had a low side contrast ratio and a significantly low relative contrast ratio. The polarizing plate of Comparative Example 2, which has core-shell particles without a magnetic core, had a significantly lower contrast ratio in the front and side views and a significantly lower relative contrast ratio compared to the example.

[0213] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations or modifications are considered to be included within the scope of the present invention.

Claims

Claim 1 A polarizer comprising: a polarizer; and an optical functional layer laminated on one surface of the polarizer, wherein the optical functional layer comprises a plurality of core-shell particles each composed of a magnetic core and a shell surrounding the magnetic core, wherein the core-shell particles are aligned in one direction of the optical functional layer, wherein the ratio of the major axis length to the minor axis length (aspect ratio) of the core-shell particles is 2 or more, wherein the major axis length is 5 μm or more and the minor axis length is 10 μm or less, wherein the orientation of the core-shell particles does not change when a magnetic field is applied to the optical functional layer, and wherein the magnetic core has a major axis and a minor axis. Claim 2 delete Claim 3 delete Claim 4 A polarizer according to claim 1, wherein in the optical functional layer, the short axis of the core-shell particle is parallel or perpendicular to the direction of the light absorption axis of the polarizer. Claim 5 In claim 1, a polarizer wherein the degree of orientation of the core-shell particles in the optical functional layer according to the following Equation 1 is 95% or more: [Equation 1] Degree of orientation = A / B x 100 (wherein A is the total number of core-shell particles in the optical functional layer whose short axis is parallel to the direction of the light absorption axis of the polarizer, and B is the total number of core-shell particles contained in the optical functional layer). Claim 6 A polarizing plate according to claim 1, wherein the entire core-shell particle is aligned as a single layer parallel to the in-plane direction of the optical functional layer. Claim 7 A polarizing plate according to claim 1, wherein the core-shell particles are included in the optical functional layer in an amount of 1% to 30% by weight. Claim 8 A polarizing plate according to claim 1, wherein the optical functional layer has a haze of 30% or less. Claim 9 delete Claim 10 delete Claim 11 A polarizing plate according to claim 1, wherein the magnetic core is formed of a metal oxide. Claim 12 A polarizing plate according to claim 1, wherein the shell is non-magnetic and is formed of one or more of organic and inorganic materials. Claim 13 A polarizing plate according to claim 1, wherein the optical functional layer further comprises a matrix in which the core-shell particles are impregnated. Claim 14 A polarizing plate according to claim 13, wherein the difference between the refractive index of the shell and the refractive index of the matrix is ​​0.01 or greater. Claim 15 In paragraph 13, the above matrix is ​​a non-adhesive layer or an adhesive layer, a polarizing plate. Claim 16 The polarizing plate according to claim 1, wherein the polarizing plate further comprises one or more of a first protective layer laminated on the upper surface of the optical functional layer, a second protective layer laminated between the polarizer and the optical functional layer, and a third protective layer laminated on the lower surface of the polarizer. Claim 17 A polarizing plate according to claim 16, wherein at least one of the first protective layer and the second protective layer has an in-plane phase difference of 4000 nm or more at a wavelength of 550 nm. Claim 18 A polarizing plate according to claim 1, wherein the polarizer is a light-absorbing polarizer and the optical functional layer is laminated on the light-emitting surface of the polarizer. Claim 19 A polarizing plate according to claim 1, wherein the optical functional layer is a contrast ratio improvement layer. Claim 20 A polarizing plate according to claim 1, wherein the optical functional layer has a lower surface and an upper surface that are each entirely flat. Claim 21 An optical display device comprising a polarizing plate according to any one of claims 1 to 20.

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