Patent Publication Number: US-9411164-B2

Title: Optical filter

Description:
This application is a Utility Application which claims priority to and the benefit of Korean Patent Application Nos. 10-2011-0078995, filed on Aug. 9, 2011 and 10-2012-0085809, filed on Aug. 6, 2012, which are hereby incorporated by reference in their entirety herein. 
     BACKGROUND 
     1. Field 
     The present application relates to an optical filter and a display device. 
     2. Related Art 
     A technique of dividing light into at least two kinds of light having different polarized states may be available in various fields. 
     The light division technique may be applied in manufacturing a three-dimensional (3D) image. A 3D image may be realized using binocular disparity. For example, when two of two-dimensional images are respectively input to the left eye and the right eye of a human, input data is delivered to the brain and fused, and thus he/she experiences 3D perspective and reality. In such a process, the light division technique may be used. 
     A technique of generating a 3D image may be available in 3D measurement, a 3D TV, a camera or computer graphics. 
     Examples relating to stereoscopic image display devices to which the light division technique is applied are disclosed in Korean Patent No. 0967899 and Korean Patent Publication No. 2010-0089782. 
     Crosstalk phenomenon may become a problem in stereoscopic image display devices. The crosstalk phenomenon may occur when a signal to be incident to the left eye of an observer is incident to the right eye, or a signal to be incident to the right eye thereof is incident to the left eye. Due to the crosstalk phenomenon, a viewing angle may be reduced in observation of a 3D image. While various methods may be considered to prevent the crosstalk phenomenon, it is difficult to ensure a wide viewing angle by preventing the crosstalk phenomenon without loss of brightness of a 3D image. 
     SUMMARY 
     The present application is directed to providing an optical filter and a display device. 
     In one embodiment, an optical filter may include a liquid crystal layer. The liquid crystal layer may include first and second regions such that light incident to the optical filter may be divided into at least two kinds of light having different polarized states, and emitted. The first and second regions may be disposed adjacent to each other. 
     The liquid crystal layer may include a polymerizable liquid crystal compound. In one embodiment, the liquid crystal layer may include a polymerizable liquid crystal compound in a polymerized form. The term “polymerizable liquid crystal compound” may be a compound including a part exhibiting liquid crystallinity, for example, a mesogen backbone, and also including at least one polymerizable functional group. In addition, the phrase “including a polymerizable liquid crystal compound in a polymerized form” may refer to a state in which the liquid crystal compound is polymerized and thus a liquid crystal polymer is formed in the liquid crystal layer. 
     The liquid crystal layer may include a polymerizable liquid crystal compound in an un-polymerized state, or may further include a known additive such as a polymerizable non-liquid crystal compound, a stabilizer, an un-polymerizable non-liquid crystal compound or an initiator. 
     In one embodiment, the polymerizable liquid crystal compound included in the liquid crystal layer may include a multifunctional polymerizable liquid crystal compound and a monofunctional polymerizable liquid crystal compound. 
     The term “multifunctional polymerizable liquid crystal compound” may refer to a compound including at least two polymerizable functional groups in the liquid crystal compound. In one embodiment, the multifunctional polymerizable liquid crystal compound may include 2 to 10, 2 to 8, 2 to 6, 2 to 5, 2 to 4, 2 to 3, or 2 polymerizable functional groups. In addition, the term “monofunctional polymerizable liquid crystal compound” may refer to a compound including one polymerizable functional group in the liquid crystal compound. 
     When the multifunctional and monofunctional polymerizable compounds are used together, phase retardation characteristics of the liquid crystal layer may be effectively controlled, and realized phase retardation characteristics, for example, an optical axis of a phase retardation layer, or a phase retardation value may be stably maintained. The term “optical axis” used herein may refer to a slow axis or a fast axis when light is transmitted through a corresponding region. 
     The liquid crystal layer may include the monofunctional polymerizable liquid crystal compound at more than 0 to less than 100 parts by weight, 1 to 90 parts by weight, 1 to 80 parts by weight, 1 to 70 parts by weight, 1 to 60 parts by weight, 1 to 50 parts by weight, 1 to 30 parts by weight or 1 to 20 parts by weight, based on 100 parts by weight of the multifunctional polymerizable liquid crystal compound. 
     In the above-mentioned range, a mixing effect of the multifunctional and monofunctional polymerizable liquid crystal compounds may be maximized, and the liquid crystal layer may have excellent adhesive properties to an adhesive layer. Unless particularly defined otherwise, the unit “parts by weight” used herein may refer to a weight ratio. 
     The liquid crystal layer may satisfy the condition of General Expression 1.
 
 X&lt; 8%  [General Expression 1]
 
     In Expression 1, X is a percentage of the absolute value of a change in value of phase difference after the liquid crystal layer is left at 80° C. for 100 or 250 hours, based on initial phase difference of the liquid crystal layer. 
     X may be calculated by “100×(|R 0 −R 1 |)/R 0 .” Here, R 0  is a value of the initial phase difference of the liquid crystal layer, and R 1  is phase difference after the liquid crystal layer is left at 80° C. for 100 or 250 hours. X may be 7%, 6%, or 5% or less. 
     In one embodiment, the multifunctional or monofunctional polymerizable liquid crystal compound may be a compound represented by Formula 1. 
     
       
         
         
             
             
         
       
     
     In Formula 1, A is a single bond, —COO— or —OCO—, R 1  to R 10  are each independently hydrogen, halogen, an alkyl group, an alkoxy group, an alkoxycarbonyl group, a cyano group, a nitro group, —O-Q-P or a substituent of Formula 2, or a pair of adjacent substituents among R 1  to R 5  or a pair of adjacent substituents among R 6  to R 10  form a benzene ring substituted with —O-Q-P by being connected to each other, with the proviso that at least one of R 1  to R 10  is —O-Q-P or a substituent of Formula 2, or a pair of adjacent substituents among R 1  to R 5  or a pair of adjacent substituents among R 6  to R 10  form the benzene ring substituted with —O-Q-P, where Q is an alkylene group or an alkylidene group, and P is a polymerizable functional group such as an alkenyl group, an epoxy group, a cyano group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group. 
     
       
         
         
             
             
         
       
     
     In Formula 2, B is a single bond, —COO— or —OCO—, R 11  to R 15  are each independently hydrogen, halogen, an alkyl group, an alkoxy group, an alkoxycarbonyl group, a cyano group, a nitro group, or —O-Q-P, or a pair of adjacent substituents among R 11  to R 15  may form a benzene ring substituted with —O-Q-P by being connected, with the proviso that at least one of R 11  to R 15  is —O-Q-P, or a pair of adjacent substituents among R 11  to R 15  form the benzene ring substituted with —O-Q-P by being connected, where Q is an alkylene group or an alkylidene group, and P is a polymerizable functional group such as an alkenyl group, an epoxy group, a cyano group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group. 
     In Formulas 1 and 2, the forming of the benzene ring substituted with —O-Q-P by being connected to each other may mean that the two adjacent substituents are connected to each other, and thereby a naphthalene backbone substituted with —O-Q-P is formed. 
     In Formula 2, the mark “—” on the left of B may indicate that B is directly connected to the benzene of Formula 1. 
     In Formulas 1 and 2, the term “single bond” refers that there is no atom at the part represented as A or B. For example, in Formula 1, when A is a single bond, the benzenes at both sides of A may be directly connected to each other, thereby forming a biphenyl structure. 
     In Formulas 1 and 2, the halogen may be chlorine, bromine or iodine. 
     The term “alkyl group” may be, unless particularly defined otherwise, a linear or branched alkyl group having 1 to 20, 1 to 16, 1 to 12, 1 to 8 or 1 to 4 carbon atoms, or a cycloalkyl group having 3 to 20, 3 to 16 or 4 to 12 carbon atoms. The alkyl group may be optionally substituted with at least one substituent. 
     The term “alkoxy group” may be, unless particularly defined otherwise, an alkoxy group having 1 to 20, 1 to 16, 1 to 12, 1 to 8 or 1 to 4 carbon atoms. The alkoxy group may be a linear, branched or cyclic type. In addition, the alkoxy group may be optionally substituted with at least one substituent. 
     The term “alkylene group” or “alkylidene group” may be, unless particularly defined otherwise, an alkylene or alkylidene group having 1 to 12, 4 to 10 or 6 to 9 carbon atoms. The alkylene or alkylidene group may be a linear, branched or cyclic type. In addition, the alkylene or alkylidene group may be optionally substituted with at least one substituent. 
     In addition, the term “alkenyl group” may be, unless particularly defined otherwise, an alkenyl group having 2 to 20, 2 to 16, 2 to 12, 2 to 8, or 2 to 4 carbon atoms. The alkenyl group may be a linear, branched or cyclic type. In addition, the alkenyl group may be optionally substituted with at least one substituent. 
     In addition, in Formulas 1 and 2, P may be an acryloyl group, a methacryloyl group, an acryloyloxy group or a methacryloyloxy group, preferably, an acryloyloxy group or a methacryloyloxy group, and in another embodiment, an acryloyloxy group. 
     In the specification, as a substituent capable of being substituted with a specific functional group, an alkyl group, an alkoxy group, an alkenyl group, an epoxy group, an oxo group, an ocetanyl group, a thiol group, a cyano group, a carboxyl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group or an aryl group may be used, but the present application is not limited thereto. 
     The —O-Q-P which may be at least one in Formulas 1 and 2, or the residue of Formula 2 may be present at R 3 , R 8  or R 13  position. In addition, the substituents which are connected to each other and thus constitute the benzene substituted with —O-Q-P may be R 3  and R 4  or R 12  and R 13 . Moreover, in the compound of Formula 1 or the residue of Formula 2, a substituent, other than —O-Q-P or the residue of Formula 2, or a substituent, other than the substituents connected to form benzene, may be hydrogen, halogen, a linear or branched alkyl group having 1 to 4 carbon atoms, an alkoxycarbonyl group including a linear or branched alkoxy group having 1 to 4 carbon atoms, a cycloalkyl group having 4 to 12 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group or a nitro group, and in another embodiment, chlorine, a linear or branched alkyl group having 1 to 4 carbon atoms, a cycloalkyl group having 4 to 12 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkoxycarbonyl group including a linear or branched alkoxy group having 1 to 4 carbon atoms or a cyano group. 
     The polymerizable liquid crystal compound may be included in the liquid crystal layer in a parallel-aligned state. In one embodiment, the compound may be included in the liquid crystal layer in a parallel-aligned polymerized state. The term “parallel-alignment” used herein may mean that an optical axis of the liquid crystal layer including the liquid crystal compound has a tilt angle of approximately 0 to 25, 0 to 15, 0 to 10, 0 to 5 or 0 degrees based on the plane of the liquid crystal layer. 
     In one embodiment, the liquid crystal layer may have a difference between an in-plane refractive index of a slow axis direction of the liquid crystal layer and an in-plane refractive index of a fast axis direction of the liquid crystal layer to be within a range of 0.05 to 0.2, 0.07 to 0.2, 0.09 to 0.2, or 0.1 to 0.2. The in-plane refractive index of the slow axis direction may refer to a refractive index in a direction exhibiting the highest refractive index on a plane of the liquid crystal layer, and the in-plane refractive index of the fast axis direction may refer to a refractive index in a direction exhibiting the lowest refractive index on a plane of the liquid crystal layer. Usually, the fast axis is perpendicular to the slow axis in the optically-anisotropic liquid crystal layer. The refractive indexes may be measured with respect to light with wavelengths of 550 and 589 nm, respectively. The difference in refractive index may be measured using Axoscan produced by Axomatrix. In addition, the liquid crystal layer may have a thickness of approximately 0.5 to 2.0 μm or 0.5 to 1.5 μm. 
     The liquid crystal layer having the relationship of the refractive indexes and the thickness may realize a phase retardation characteristic suitable for a purpose to be applied. 
     The liquid crystal layer may be formed to divide incident light, for example, light incident from one side of the optical filter into two kinds of light having different polarized states, and to emit the light to the other side of the optical filter. To this end, the liquid crystal layer may include the first and second regions having different phase retardation characteristics. In the specification, “the first and second regions having different phase retardation characteristics” may refer to the first and second regions having optical axes formed in the same or different directions and different phase retardation values, or the first and second regions having the same phase retardation values and optical axes formed in different directions when both of the first and second regions have phase retardation characteristics. In another embodiment, “the first and second regions having different phase retardation characteristics” may mean that one of the first and second regions has phase retardation characteristics, and the other region is an optically isotropic region that does not have phase retardation characteristics. In this case, the liquid crystal layer may have all of a region having a liquid crystal compound, and a region not having a liquid crystal compound. Phase retardation characteristics in the first or second region may be controlled by controlling the alignment state of the liquid crystal compound, the relationship of a refractive index of the liquid crystal layer, or the thickness of the liquid crystal layer. 
     The first and second regions A and B, as shown in  FIG. 1 , may be closely and alternately disposed in a stripe shape extending in the same direction, or as shown in  FIG. 2 , may be closely and alternately disposed in a lattice pattern. 
     For example, when the optical filter is used in a display device displaying a 3D image, one of the first and second regions may be a region for controlling polarization of an image signal for the left eye (hereinafter referred to as an “LC region”), and the other may be a region for controlling polarization of an image signal for the right eye (hereinafter referred to as an “RC region”). 
     At least two kinds of light having different polarized states, which are divided by the liquid crystal layer including the first and second regions, may include two kinds of linearly polarized light having substantially different polarized states, or left-circular polarized light and right-circular polarized light. 
     In the specification, the terms “vertical,” “horizontal,” “perpendicular” and “parallel” used to define angles refer to, unless particularly defined otherwise, substantially vertical, horizontal, perpendicular and parallel. The terms include an error or a variation, which may include an error within approximately ±15, 10 or 5, which may be considered for each term. 
     In one embodiment, one of the first and second regions may be a region capable of transmitting incident light without revolving a polarizing plate, and the other may be a region capable of transmitting incident light after a polarizing axis of the incident light is revolved in a perpendicular direction with respect to a polarizing axis of light transmitted through a different region. In this case, in the liquid crystal layer, the region including a polymerizable liquid crystal compound may be formed in only one of the first and second regions. A region in which the liquid crystal layer is not formed may be an empty space, or have glass or an optically isotropic resin layer or a resin film or sheet. 
     In another embodiment, one of the first and second regions may be a region capable of converting incident light into left-circular polarized light to transmit, and the other may be a region capable of converting incident light into right-circular polarized light to transmit. In this case, the first and second regions have the same phase retardation values and optical axes formed in different directions, one region may retard a wavelength of incident light by ¼ of the wavelength thereof, and the other may phase-retard a wavelength of incident light by ¾ of the wavelength thereof. 
     In one embodiment, the first and second regions may have the same phase-retardation value, for example, values capable of phase-retarding a wavelength of incident light by ¼ of the wavelength thereof. In addition, the first and second regions may have optical axes formed in different directions. 
     The optical filter may include a light transmission control region (hereinafter referred to as a “TC region”) present on the boundary between the first and second regions.  FIG. 3  is a schematic diagram of the optical filter, in which the TC region is present on the boundary between the first and second regions A and B. 
     The term “TC region” may refer to a region formed to block light incident to the region, or to transmit only some of light incident to the region when the light is incident to the region. In one embodiment, the TC region may refer to a region having a transmission rate of incident light, that is, light transmission rate, of 0 to 20%, 0 to 15%, 0 to 10%, or 0 to 5%. 
     In addition, the presence of the TC region on the boundary between the first and second regions may refer to the presence of the TC region at a position to block light incident to the TC region by the TC region, or transmit some of the light incident to the TC region through the TC region, by entering at least some of the incident light to the TC region at one time during emitting light incident to the optical filter through the optical filter. 
       FIG. 4  shows arrangement of the first and second regions A and B of  FIG. 1  in consideration of the presence of the TC region, and  FIG. 5  shows arrangement of the LC and RC regions of  FIG. 2  in consideration of the presence of the TC region. In  FIGS. 4 and 5 , the TC region is drawn with a diagonal line. In the optical filter, the TC region may be formed in suitable numbers and places when necessary. 
     On the boundary between the first and second regions, the first region, the TC region and the second region may be sequentially disposed on the same plane, or the TC region may be disposed on a top or bottom surface of the plane having the first and second regions. When the TC region is disposed on a top or bottom surface of the plane having the first and second regions, the TC region may be overlapped with at least a part of the first and/or second region(s) when the optical filter is observed from front. 
     In one embodiment, when the first and second regions of the liquid crystal layer include axes formed in different directions, the TC region may be formed parallel to a line bisecting an angle between having the optical axes in the first and second regions, or formed on the bisector. The TC region formed as described above may ensure a wide viewing angle without loss of brightness when being applied to a display device to be described below. 
       FIG. 4  shows arrangement of axes when the first and second regions A and B of  FIG. 1 or 2  have the optical axes formed in different directions. A line of bisecting an angle between the optical axes of the first and second regions A and B may refer to a line bisecting an angle of (Θ1+Θ2). For example, when Θ1 and Θ2 are the same angle, the bisector may be formed in a direction formed parallel to a boundary L between the first and second regions A and B. In addition, the angle between the optical axes in the first and second regions may be (Θ1+Θ2), that is, 90 degrees. 
     The TC region may be formed using light blocking or absorbing ink. In this case, the TC region may include the ink. For example, in consideration of desired shape, pattern and location of the TC region, the TC region may be formed by a method of printing light blocking or absorbing ink. 
     A width of the TC region (for example, H 2  of  FIG. 3 ) may be defined in the relationship with a first light transmission control region of the display device to be described below. In one embodiment, the width of the TC region may be determined in the range of more than 0 to 1000 μm. The lower limit of the width may be 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 or 80 μm. In addition, the upper limit of the width may be 900, 800, 700, 600, 500, 400, 300, 290, 280, 270, 260, 250, 240, 230, 220, 210 or 200 μm. In the above-mentioned ranges of the upper and lower limits, the width of the TC region may be defined by selecting and combining various values. 
     The optical filter may further include a base layer. In this case, the liquid crystal layer may be formed on one surface of the base layer. In addition, the TC region may be present between the base layer and the liquid crystal layer, or on a surface of the liquid crystal layer that does not come in contact with the base layer. 
     The optical filter may further include an alignment layer present between the base layer and the liquid crystal layer. In this case, the TC region may be present between the alignment layer and the liquid crystal layer, or between the alignment layer and the base layer. 
       FIG. 7  shows an illustrative optical filter  50 . The optical filter  50  includes a liquid crystal layer  51 , an alignment layer  52  and a base layer  53 , which are sequentially formed thereon. Here, a TC region (TC) is present between the liquid crystal layer and the alignment layer. In addition,  FIGS. 8 and 9  also show illustrative optical filters  60  and  70 , in which a TC region TC is present between the base layer  53  and the alignment layer  52 , or on a surface of the liquid crystal layer  51  that does not come in contact with the base layer  53 . In  FIG. 9 , the TC region is present above the liquid crystal layer  51 . 
     The base layer may be glass or a plastic base layer. As a plastic base layer, a sheet or film including a cellulose resin such as triacetyl cellulose (TAC) or diacetyl cellulose (DAC); a cyclo olefin polymer (COP) such as a norbornene derivative; an acryl resin such as poly(methyl methacrylate) (PMMA); polycarbonate (PC); polyolefin such as polyethylene (PE) or polypropylene (PP); polyvinyl alcohol (PVA); poly ether sulfone (PES); polyetheretherketon (PEEK); polyetherimide (PEI); polyethylenenaphthalate (PEN); polyester such as polyethyleneterephthalate (PET); polyimide (PI); polysulfone (PSF) or a fluorine resin, may be illustrated. 
     The base layer, for example, a plastic base layer, may have a lower refractive index than the liquid crystal layer. An illustrative refractive index of the base layer may be approximately 1.33 to 1.53. When the base layer has a lower refractive index than the liquid crystal layer, brightness is improved, reflection is prevented, and contrast characteristics are improved. 
     The plastic base layer may be optically isotropic or anisotropic. When the base layer is optically anisotropic, an optical axis of the base layer may be disposed to be vertical or horizontal to the line bisecting the angle between the optical axes of the first and second regions. 
     In one embodiment, the base layer may include a UV blocking agent or a UV absorbing agent. When the UV blocking agent or the UV absorbing agent is included in the base layer, deterioration of the liquid crystal layer due to UV rays may be prevented. The UV blocking or absorbing agent may be an organic material such as a salicylic acid ester compound, a benzophenone compound, an oxybenzophenone compound, a benzotriazol compound, a cyanoacrylate compound or a benzoate compound, or an inorganic material such as zinc oxide or nickel complex salt. The content of the UV blocking or absorbing agent in the base layer is not particularly limited, and may be suitably selected in consideration of a desired effect. For example, in a process of manufacturing a plastic base layer, the UV blocking or absorbing agent may be included in a weight ratio of approximately 0.1 to 25 wt % based on a main material of the base layer. 
     The thickness of the base layer is not particularly limited, and may be suitably selected according to a desired use. 
     The alignment layer, which may be present between the base layer and the liquid crystal layer, may be a layer serving to form the first and second regions by aligning a liquid crystal compound of the liquid crystal layer. As the alignment layer, a conventional alignment layer, which is known in the art, for example, an alignment layer formed by an imprinting method, an optical alignment layer or a rubbing alignment layer may be used. The alignment layer is an optional component, and in some cases, alignment capability may be provided without an alignment layer by directly rubbing or extending the base layer. 
     In one embodiment, the optical filter may be a filter applied to a stereoscopic image display device (hereinafter, referred to as a “3D device”). In one embodiment, the 3D device may be a device including a display part. When the optical filter is applied to the display device, the optical filter may be disposed to deliver a signal emitted from the display device to an observer after the signal is transmitted through the filter. The 3D device may be a device for observing a 3D image when an observer wears glasses for observing a 3D image (hereinafter referred to as “3D glasses”). 
     The display part may include a signal generating region for the right eye (hereinafter referred to as an “RS region”) for generating a signal for the right eye (hereinafter referred to as an “R signal), and a signal generating region for the left eye (hereinafter referred to as an “LS region”) for generating a signal for the left eye (hereinafter referred to as an “L signal”) in a driving state. The term “driving state” may refer to a state in which a 3D device displays an image, for example, a 3D image. 
     The optical filter may be applied to the 3D device and serve to control polarized states of the R and L signals, for example, to control the R and L signals to have different polarized states. 
     The display part may also include a light transmission control region (TC region) adjacent to the RS and LS regions. Hereinafter, in the specification, for distinction between the TC regions, a TC region included in the display part may be referred to as a TC 1  region, and a TC region included in the optical filter may be referred to as a TC 2  region. 
     The TC 1  region may also mean a region having a light transmission rate of 0 to 20%, 0 to 15%, 0 to 10%, or 0 to 5%. 
     In addition, the TC region adjacent to the RS and LS regions may mean that the TC region is present at such a location that a signal incident to the TC region may be blocked by the TC region or some of the signal incident to the TC region is transmitted through the TC region, and then delivered to the optical filter by entering at least a part of the R and/or L signal to the TC region during the delivery of the R and/or L signal generated in the RS and/or LS region(s) to the optical filter when an image is observed at at least one angle included in a range of the viewing angle. 
     The term “viewing angle” may refer to a range of an angle in which the L signal generated in the LS region may be transmitted through a signal polarization control region for a left eye (hereinafter, referred to as a “LG region”), which is one of the first and second regions of the optical filter, but not transmitted through a signal polarization control region for a right eye (hereinafter, referred to as a “RG region”), which is the other of the first and second regions, and then may be delivered to an observer, or a range of an angle in which the R signal generated in the RS signal may be transmitted through the RG region of the optical filter but not transmitted through the LG region, and then delivered to the observer. At an angle exceeding the viewing angle, the L signal may be transmitted through the RG region, or the R signal may be transmitted through the LG region, and then delivered to the observer. 
     The TC 1  region adjacent to the RS and LS regions may be disposed between the RS and LS regions. In an aspect in which the TC 1  region is present between the RS and LS regions, the RS, TC 1  and LS regions may be sequentially disposed on the same plane, or the TC 1  region may be disposed on a top or bottom surface of a plane having the RS and LS regions. When the TC 1  region is disposed on a top or bottom surface of a plane having the RS and LS regions, the TC 1  region may be overlapped with at least a part of the RS and/or LS region(s) when observed from front. 
       FIG. 10  is a schematic diagram of an illustrative 3D device  80  to which the optical filter  801  is applied. The illustrative 3D device  80  to which the optical filter  801  is applied as shown in  FIG. 10 , may include a display part  81  and the optical filter  801 . The display part  81  may include a light source  821 , a first polarizing plate  822 , an image generating region  823  and a second polarizing plate  824 . RS and LS regions may be included in the image generating region  823 , and the first polarizing plate  822  and the light source  821  may be sequentially included at one side of the image generating region  83 . 
     As the light source  821 , a direct-type or edge-type back light unit (BLU), which is conventionally used as the light source in a display device such as a liquid crystal display (LCD), may be used. As the light source  821 , other than that, various kinds of light sources may be used. 
     In the display part  81 , the first polarizing plate  822  may be disposed between the light source  821  and the image generating region  823 . Due to such arrangement, light emitted from the light source  821  may be incident to the image generating region  823  through the first polarizing plate  822 . The first polarizing plate may be an optical element having a transmission axis and an absorption axis perpendicular to the transmission axis. When light is incident to the first polarizing plate, among incident light, only light having a polarizing axis parallel to a direction of the transmission axis of the polarizing plate may be transmitted. 
     The image generating region  823  may include the LS region capable of generating an L signal, and an RS region capable of generating an R signal in a driving state. 
     In one embodiment, the image generating region  83  may be a region formed by a transparent liquid crystal panel having a liquid crystal layer interposed between two sheets of substrates, or a region formed in the liquid crystal panel. The liquid crystal panel may include a first substrate, a pixel electrode, a first alignment layer, a liquid crystal layer, a second alignment layer, a common electrode and a second substrate, which are sequentially disposed from the light source  821 . The first substrate may have an active driving circuit including a thin film transistor (TFT) as a driving element electrically connected to a transparent pixel electrode and an interconnection. The pixel electrode may include a metal oxide such as indium tin oxide (ITO) and serve as an electrode per pixel. In addition, the first or second alignment layer may serve to orient a liquid crystal of the liquid crystal layer. The liquid crystal layer may include a vertical alignment (VA)-, twisted nematic (TN)-, super twisted nematic (STN)- or in plane switching (IPS)-mode liquid crystal. The liquid crystal layer may function to transmit or block light emitted from the light source  821  by pixel by a voltage applied from the driving circuit. The common electrode may serve as a counter electrode. 
     The image generating region  823  may include LS and RS regions including at least one pixel as regions capable of generating L and R signals in a driving state. For example, the LS or RS region may be formed of a unit pixel including liquid crystals, which is sealed between the first and second alignment layers of the liquid crystal panel. The LS and RS regions may be disposed in column and/or row direction(s). 
       FIGS. 11 and 12  show illustrative arrangements of RS and LS regions.  FIGS. 11 and 12  may show arrangements of the RS and LS regions when the 3D device is observed from front. In one embodiment, as shown in  FIG. 11 , the RS and LS regions may have stripe shapes extending in the same direction, for example, a length direction, and may be closely and alternately disposed. In another embodiment, as shown in  FIG. 12 , the RS and LS regions are closely and alternately disposed in a lattice pattern. However, the arrangement of the RS and LS regions are not limited to those of  FIGS. 11 and 12 , and thus various designs known in the art may be applied. 
     The display part  81  may generate image signals including R and L signals by driving a pixel in each region in response to a signal in a driving state. 
     For example, referring to  FIG. 10 , when light emitted from the light source  821  is incident to the first polarizing plate  822 , only light polarized parallel to the transmission axis of the polarizing plate  822  may be transmitted through the polarizing plate  822 . Such transmitted light is incident to the image generating region  823 . When the light is incident to the image generating region  823 , light transmitted through the RS region may be converted into an R signal, and light transmitted through the LS region may be converted into an L signal. 
     The display part  81  may include the TC 1  region. The TC 1  region may be adjacent to the RS and LS regions. In  FIG. 10  schematically showing the illustrative device  80 , the TC 1  region is disposed on a top surface of the plane of the image generating region  823  having the RS and LS regions, and overlapped with a part of the RS and LS regions between the RS and LS regions when viewed form front. However, the location of the TC 1  region is not limited to the arrangement shown in  FIG. 10 . For example, the TC 1  region may be disposed on a bottom surface of the plane having the RS and LS regions, or on the same plane as the plane having the RS and LS regions.  FIG. 13  shows the arrangement of the LS and RS regions shown in  FIG. 11  again in consideration of the presence of the TC 1  region, and  FIG. 14  shows the arrangement of the LS and RS regions show in  FIG. 12  again in consideration of the presence of the TC 1  region. In  FIGS. 13 and 14 , the TC 1  regions are drawn with a diagonal line. 
     The TC 1  region may be combined with a TC 2  region for the 3D device to display an image at a wide viewing angle without loss of brightness. 
     In one embodiment, the TC 1  region may be a black matrix. For example, when the image generating region  823  is a region formed by a transparent liquid crystal panel or a region formed therein, the TC 1  region may be a black matrix included in a color filter conventionally present in the second substrate capable of being included in the liquid crystal panel as described above. In one embodiment, the TC 1  region may be a region formed to include a resin layer including a pigment such as chromium (Cr), a double film of chromium and chromium oxide (double film of Cr/CrOx), carbon black, or a carbon pigment or graphite. A method of forming the TC 1  region using the above-described material is not particularly limited. For example, the TC 1  region may be formed by photolithography or a lift-off method, which is a conventional method of forming the black matrix. 
     In the 3D device, the second polarizing plate  824  may be included between the image generating region  823  and the optical filter  801 . The optical filter  801  includes the LG region, which is one of the first and second regions, and the RG region, which is the other thereof. In addition, the TC 2  region may be adjacent to the LG and RG regions. 
     A signal output from the image generating region  823  may be delivered to an observer sequentially through the second polarizing plate  824  and the optical filter  801 . In addition, at least a part of the R and/or L signal(s) may be incident to the TC 2  region at one time during the transmission of the signals through the optical filter  801  when observed at one angle in the range of the viewing angle. 
     Like the first polarizing plate  822 , the second polarizing plate  824  may be an optical element having a transmission axis and an absorption axis perpendicular to the transmission axis, and may transmit only a signal having a polarizing axis parallel to a direction of the transmission axis when light is incident. The first and second polarizing plates  822  and  824  included in the 3D device  80  may be disposed such that the absorption axes are vertical to each other. The transmission axes of the first and second polarizing plates  822  and  824  may also be vertical to each other. Here, “vertical” means substantially vertical, and may include an error within ±15, 10, or 5. 
     The RG and LG regions included in the optical filter  801  may control polarized states of the R and L signals, respectively. According to the above descriptions, the RG and LG regions may be regions serving to output the R and L signals with different polarized states from the 3D device. 
     The RG region may be disposed at a location approximately corresponding to the RS region to have a size approximately corresponding to the RS region such that the R signal generated and delivered from the RS region is incident thereto in a driving state, and the LG region may be disposed at a location approximately corresponding to the LS region to have a size approximately corresponding to the LS region such that the L signal generated and delivered from the RS region is incident thereto in a driving state. The forming of the RG or LG regions at a location corresponding to the RS or LS region to have a size corresponding to the RS or LS region may mean that the RG or LG region has the location and size in which the R signal generated in the RS region is capable of being incident to the RG region, or the L signal generated in the LS region is capable of being incident to the LG region. However, it does not mean that the RG and LG regions are necessarily formed at the same location to have the same size. 
     The RG and LG regions may be formed in a stripe shape extending in the same direction corresponding to the arrangement of the RS and LS regions, for example, a length direction, and closely and alternately disposed, or may be closely and alternately disposed in a lattice pattern. 
     The 3D device including the optical filter includes the TC 1  and TC 2  regions. Such a device may display a 3D image at a wide viewing angle without the loss of brightness. 
     In one embodiment, when the optical filter is a filter applied to the 3D device, the TC 1  and TC 2  regions may satisfy Expression 1. Accordingly, the wide viewing angle may be exhibited while suitably ensuring brightness characteristics of the 3D device within a range satisfying Expression 1.
 
 H   1   +H   2 ≦( P   L   +P   R )/2  [Expression 1]
 
     In Expression 1, H 1  is the width of the TC 1  region, H 2  is the width of the TC 2  region, P L  is the width of the LG region, that is, the width of the first or second region, and P R  is the width of the RG region, that is, the width of the second or first region. 
       FIG. 15  schematically shows only the image generating region  823  including the TC 1  region, the second polarizing plate  824  and the optical filter  801  in the 3D device including the optical filter when viewed from the side, and here, “H 1 ”, “H 2 ”, “P L ”, and “P R ” each are shown. 
     In the 3D device, a specific range of “H 1 ” and “H 2 ” may be suitably selected in consideration of the range satisfying Expression 1 according to the specifications of the 3D device, and specific values are not particularly limited. For example, H 2 , that is, the width of the TC 2  region, may be selected within the above-described range. 
     In addition, “H 1 ” may be selected to be a sum of H 1  and H 2  within a range of approximately more than 0 to 2,000 μm. The lower limit of the sum of H 1  and H 2  may be 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 or 160 μm. In addition, the upper limit of the sum of H 1  and H 2  may be 1900, 1800, 1700, 1600, 1500, 1400, 1300, 1200, 1100, 1000, 900, 800, 700, 600, 500, 400, or 300 μm. In the ranges of the upper and lower limits, various values may be selected and combined to define the range of the sum of H 1  and H 2 . 
     In the 3D device, a specific range of “P R ” or “P L ,” that is, the width of the first or second region of the optical filter, may be also selected according to the specification of the 3D device, and a specific value is not particularly limited. In one embodiment, when the 3D device is a 47-inch device, the specific ranges of “P R  and “P L ” may be selected within the range of 150 to 350 μm, respectively. In consideration of the specification of a conventional device, the specific ranges of “P R  and “P L ” may be within the range of 150 to 1,000 μm. 
     The width H 2  of the TC 2  region of the optical filter may be the same as or smaller than the width H 1  of the TC 1  region of the 3D device to which the filter is applied. In one embodiment, the difference (H 1 −H 2 ) between the width H 1  of the TC 1  region and the width H 2  of the TC 2  region may be approximately 1,000, 900, 800, 700, 600, 500, 400, 300, 175, 150, 125, 100, 75, 50, or 25 μm, or substantially 0 μm. In such a state, the 3D device may ensure a wide viewing angle without loss of brightness. 
     The 3D device to which the optical filter is applied may have relative brightness of 60%, 65% or 70% or more when viewed from the front. The term “relative brightness” may refer to a ratio (I T /I O ) of brightness I T  of a 3D device having TC 1  and TC 2  regions formed with respect to brightness I O  of a 3D device having neither TC 1  nor TC 2  regions. 
     The TC 2  region of the optical filter applied to the 3D device may have the maximum values of an angle (θ U ) satisfying Expression 2 and an angle (θ L ) satisfying Expression 3 of 3, 5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5 or 15 or more, respectively.
 
tan θ U =( H   1 +2 y )/2 T   [Expression 2]
 
tan θ L =( H   1 +2 H   2 −2 y )/2 T   [Expression 3]
 
     In Expressions 2 and 3, H 1  is the width of the TC 1  region, H 2  is the width of the TC 2  region, T is the distance from the display part of the 3D device to which the optical filter is applied to the optical filter, and y is the distance from a spot at which an imaginary normal line of a line bisecting the width of the TC 1  region of the 3D device to which the optical filter is applied with respect to a surface of the TC 1  region is in contact with the TC 2  region to a part of the TC 2  region. 
     “θ U ” and “θ L ” may refer to viewing angles of the 3D device, respectively. Expressions 2 and 3 will be described in detail with reference to  FIG. 16 . 
     Considering that the term “viewing angle” refers to a range of an angle in which the L signal generated from the image generating region is transmitted through the LG region, but not through the RG region, to be delivered to an observer, or a range of an angle in which the L signal generated from the image generating region is transmitted through the RG region, but not through the LG region, to be delivered to an observer, the viewing angle is represented as “θ U ” or “θ L ” in  FIG. 16 . 
     As shown in  FIG. 16 , the viewing angle may be determined according to the distance T from the image generating region to the optical filter and the widths of the TC 1  and TC 2  regions. The distance T from the image generating region to the optical filter may be a distance from a surface of the image generating region facing the optical filter to the position at which the TC 2  region of the optical filter ends. For example, when the image generating region is a region formed by a liquid crystal panel, the surface of the image generating region facing the optical filter may refer to a surface of the liquid crystal layer of the liquid crystal panel facing the optical filter. 
     The distance T is determined according to the specification of the 3D device, and is not particularly limited. For example, the distance T may be 5 nm or less, or approximately 0.5 to 5 mm. 
     Referring to  FIG. 16 , it is seen that the viewing angles “θ U ” and “θ L ” are determined according to the widths (H 1  and H 2 ) of the TC 1  and TC 2  regions and relative locations of the TC 1  and TC 2  regions when the distances T are the same as each other. 
     That is, it is seen that the viewing angle “θ U ” is determined for tan θ U  to be the same as a value obtained by dividing the sum (H 1 /2+y) of a value of half of the width H 1  of the TC 1  region and the distance y from a point at which an imaginary normal line C of a line bisecting the width of the TC 1  region with respect to a surface of the TC 1  region or image generating region is in contact with the TC 2  region to a part in which the TC 2  region is present by the distance T. In addition, it is seen that the viewing angle “θ L ” is determined for tan θ L  to be the same as a value obtained by dividing the sum (H 1 /2+y) of a value of half of the width H 1  of the TC 1  region and the distance y from a point at which an imaginary normal line C of a line bisecting the width H 1  of the TC 1  region with respect to a surface of the TC 1  region or image generating region is in contact with the TC 2  region in the width H 2  of the TC 2  region to a part in which the TC 2  region is present by the distance T. 
     In the 3D device including the TC 1  and TC 2  regions, sizes, for example, widths, and relative positions of the TC 1  and TC 2  regions may be suitably controlled to ensure a wide viewing angle and excellent brightness characteristics when a 3D image is observed. 
     In the 3D device, relative brightness, when observed from front, may be 60, 65, or 70% or more, and at the same time, the maximum value of the angle “θ U ” satisfying Expression 2 and the maximum value of the angle “θ L ” satisfying Expression 3 are 3, 5, 8, 8.5, 9, 0.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5 or 15 degrees or more. 
     In another aspect, a display device, and specifically, a 3D device including the above-described optical filter is provided. Detailed descriptions of the 3D device have been described above. 
     In still another aspect, a method of manufacturing the optical filter is provided. The illustrative manufacturing method may include forming a TC 2  region on the boundary of a liquid crystal layer including first and second regions, which have different phase retardation characteristics and are adjacent to each other. Here, the TC 2  region may be formed before or after the liquid crystal layer is formed, or together with the liquid crystal layer. 
     The liquid crystal layer may be manufactured by forming an alignment layer on a base layer, forming a coating layer of a liquid crystal composition including the polymerizable liquid crystal compound on the alignment layer, and polymerizing the aligned liquid crystal composition. 
     The alignment layer may be formed by forming a polymer film such as a polyimide film on the base layer and rubbing the polymer film, or coating a photo-alignment compound and aligning the photo-alignment compound through irradiation of linearly polarized light or nano-imprinting the photo-alignment compound. Depending on a desired alignment pattern, for example, the patterns of the first and second regions, various methods of forming an alignment layer are known in related art. 
     The coating layer of the liquid crystal composition may be formed by coating the composition on the alignment layer of the base layer by a known method. The composition may be aligned according to an alignment pattern of the alignment layer present under the coating layer and then polymerized, thereby forming the liquid crystal layer. 
     The TC 2  region may be formed by a printing method using the above-described light blocking or absorbing ink in consideration of the positions of the first and second regions to be formed before and after the liquid crystal layer is formed. In this case, the printing may be executed on a surface of the base layer on which the alignment layer will be formed, the alignment layer on which the liquid crystal layer will be formed or the liquid crystal layer, and, for example, in consideration of the accuracy of a position of the TC 2  region to be formed, the printing may be executed on a surface of the alignment layer. 
     For example, the printing process may be performed using a printing ink prepared by blending light blocking or absorbing ink including an inorganic pigment such as carbon black, graphite or iron oxide, or an organic pigment such as an azo-based pigment or phthalocyanine-based pigment with a suitable binder and/or solvent. For example, light transmission rate of the TC region may be controlled by controlling the blending amount or kind of pigment. The printing method may be, but is not particularly limited to, a printing type method such as screen printing or gravure printing, or a selective jetting type method such as inkjet printing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 2  show arrangements of first and second regions of an illustrative optical filter; 
         FIG. 3  shows formation of optical axes of first and second regions; 
         FIG. 4  shows an illustrative optical filter; 
         FIGS. 5 and 6  show arrangements of first and second regions, and a TC region of an illustrative optical filter; 
         FIGS. 7 to 9  show shapes of the illustrative optical filter; 
         FIG. 10  shows an illustrative 3D device; 
         FIGS. 11 and 12  are schematic diagrams showing illustrative arrangement of LS and RS regions; 
         FIGS. 13 and 14  are schematic diagrams showing illustrative arrangement of LS and RS regions and a TC 1  region; 
         FIG. 15  shows an illustrative 3D device; and 
         FIG. 16  is a schematic diagram for explaining formation of a viewing angle in a 3D device. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, an optical filter and a 3D device will be described in detail with reference to Examples according to the present application and a Comparative Example not according to the present application, but the optical filter and 3D device are not limited to the following Examples. 
     Example 1 
     A composition for forming a photo-alignment layer was coated on one surface of a TAC base (refractive index: 1.49, thickness: 80,000 nm) to have a dry thickness of approximately 1,000 Å, and then dried in an 80° C. oven for 2 minutes. As the composition for forming a photo-alignment layer, a composition prepared by mixing a mixture of polynorbornene (molecular weight (M w )=150,000) having a cinnamate group of Formula 3 and an acryl monomer with a photoinitiator (Irgacure 907), and dissolving the resulting mixture in a toluene solvent to have a solid content of polynorbornene of 2 wt % was used (polynorbornene:acryl monomer:photoinitiator=2:1:0.25 (weight ratio)). 
     
       
         
         
             
             
         
       
     
     Subsequently, the dried composition for forming a photo-alignment layer was aligned according to the method disclosed in Korean Patent Application No. 2010-0009723 to form a photo-alignment layer including first and second alignment regions, which were aligned in different directions. In detail, a pattern mask having stripe-shaped light transmission and light blocking parts each having a width of approximately 450 μm and alternately formed in vertical and lateral directions was disposed on the dried composition for a photo-alignment layer, and a polarizing plate having two regions transmitting different polarized light, respectively, was disposed on the pattern mask. Afterward, with transferring the TAC base 30 having the photo-alignment layer at a rate of approximately 3 m/min, alignment was executed by irradiating a UV ray (300 mW/cm 2 ) to the composition for forming a photo-alignment layer for approximately 30 seconds by means of the polarizing plate and the pattern mask. By such alignment, a first alignment region A and a second alignment region B were formed in the shape shown in  FIG. 1 . The angle between alignment directions of the respective alignment regions was 90 degrees, and the angle between the alignment direction of each alignment region and the boundary between the first and second regions A and B was 45 degrees in a clockwise or counter-clockwise direction. Subsequently, as light absorbing ink, ink prepared by mixing a carbon black dispersion to a mixture of an acrylate-based binder (dipentaerythritol hexaacrylate) and a carbonyl-based solvent in a concentration of approximately 70 wt % and further blending approximately 2 wt % of a photoinitiator (Irgacure 907), was printed to a thickness of approximately 3 μm using inkjet equipment (Dymatrix DMP2800, Fuji film) to be parallel to a bisector of an angle between alignment directions of the first and second regions on the boundary of the first and second regions A and B and cured, thereby forming a TC region. The printing was executed by an inkjet-type method. A liquid crystal layer was then formed in the aligned alignment layer and the TC region. In detail, as a liquid crystal composition, a liquid crystal composition including 70 parts by weight of a multifunctional polymerizable liquid crystal compound represented by Formula A, 30 parts by weight of a monofunctional polymerizable liquid crystal compound represented by Formula B, and a suitable amount of a photoinitiator was coated to have a dry thickness of approximately 1 μm and then aligned according to alignment of the underlying alignment layer. Liquid crystals were crosslinked and polymerized by irradiating a UV ray (300 mW/cm 2 ) for approximately 10 seconds, and thus a liquid crystal layer having first and second regions having optical axes perpendicular to each other according to the alignment of the underlying photo-alignment layer. As measurement results using Axoscan produced by Axomatrix, the difference in refractive index between the slow axis direction and the fast axis direction was approximately 0.125. In addition, the liquid crystal layer was formed to a thickness of approximately 1 μm. 
     
       
         
         
             
             
         
       
     
     Example 2 
     An optical filter was manufactured by the same method as described in Example 1, except that printing for forming a TC region was executed on a liquid crystal layer after the liquid crystal layer was formed. 
     Example 3 
     An optical filter was manufactured by the same method as described in Example 1, except that printing for forming a TC region was executed on a surface of the base layer (TAC base). 
     Examples 4 to 7 
     A system was configured to include an optical filter  801  manufactured by the same method as described in Example 1 and having the structure shown in  FIG. 10 . In the system, an image generating region  823  was a transparent liquid crystal panel, RS and LS regions were disposed as shown in  FIG. 11 , and a TC 1  region was formed by a black matrix of a color filter of the liquid crystal panel, and disposed between the RS and LS regions to be partially overlapped with the RS and LS regions as shown in  FIG. 13 . The TC 1  region was formed such that a range overlapped with the RS region was the same as a range overlapped with the LS region. In addition, first and second regions of the optical filter  801  were disposed in a shape as shown in  FIG. 1 . A TC 2  region was formed to be overlapped with a part of the first and second regions A and B and disposed as shown in  FIG. 5  between the regions A and B. The TC 2  region was formed such that a range overlapped with the RG region (one of the first and second regions) was the same as a range overlapped with the LG region (the other of the first and second regions) (that is, referring to  FIG. 16 , the TC 2  region was formed such that y was H 2 /2). A region of the liquid crystal layer, the RG region, was a phase retardation layer (¼ wavelength layer) in which a slow axis was formed in a counter-clockwise direction to have an angle of 45 degrees with an absorption axis of a second polarizing plate  824 , and a region of the liquid crystal layer, the LG region, was a phase retardation layer (¼ wavelength layer) in which a fast axis was formed in a clockwise direction to have an angle of 45 degrees with the absorption axis of the second polarizing plate  824 . The optical axis of the second polarizing plate  824  was arranged in a vertical direction with respect to an optical axis of the first polarizing plate. The distance from a display part to the optical filter (T in Expressions 2 and 3) was approximately 1 mm, the sum of widths of the LG and RG regions (“P L +P R ” in Expression 1) was approximately 545 μm, and the widths of the LG and RG regions were almost the same as each other. In the system, while widths (H 1  and H 2 ) of the TC 1  and TC 2  regions were controlled to ensure the maximum viewing angle (“θ U ” or “θ L ”) of approximately 13.5 degrees in every embodiment. In each embodiment, the system was driven with changing the widths (H 1  and H 2 ) of the TC 1  and TC 2  regions as shown in Table 1. Relative brightness according to each viewing angle (“θ U ” or “θ L ”) was measured using a brightness meter (SR-UL2 spectrometer), and the results are shown in Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
            
               
                   
                 Example 
                   
               
            
           
           
               
               
               
               
               
            
               
                   
                 4 
                 5 
                 6 
                 7 
               
               
                   
               
               
                 H 1 (unit: μm) 
                 210 
                 180 
                 150 
                 120 
               
               
                 H 2 (unit: μm) 
                 30 
                 60 
                 90 
                 120 
               
               
                 H 1  + H 2 (unit: μm) 
                 240 
                 240 
                 240 
                 240 
               
               
                   
               
            
           
           
               
               
            
               
                 Viewing Angle 
                   
               
               
                 (unit: degree) 
                 Relative Brightness (unit: %) 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 0 
                 61.1 
                 66.7 
                 72.5 
                 78 
               
               
                 2 
                 61.1 
                 66.7 
                 72.5 
                 74.8 
               
               
                 4 
                 61.1 
                 66.7 
                 69.3 
                 71.6 
               
               
                 6 
                 61.1 
                 66.7 
                 66.1 
                 68.4 
               
               
                 8 
                 61.1 
                 65 
                 62.9 
                 65.2 
               
               
                 10 
                 61.1 
                 62.2 
                 62 
                 61.9 
               
               
                 12 
                 58.3 
                 59 
                 58.8 
                 58.7 
               
               
                 13 
                 56 
                 56 
                 56 
                 56 
               
               
                   
               
            
           
         
       
     
     Comparative Example 1 
     Systems were designed as described in Examples 4 to 7. An optical filter was manufactured by the method described in Example 1, but did not go through a printing process for forming a TC region. That is, an optical filter not including a TC 2  region was used. Like in the Examples, the system was configured by controlling the width (H 1 ) of a TC 1  region to ensure the maximum viewing angle (“θ U ” or “θ L ”) of approximately 13.5. With driving the system, relative brightness according to each viewing angle (“θ U ” or “θ L ”) was measured using a brightness meter (SR-UL2 spectrometer), and the results are shown in Table 2. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
             
            
               
                   
                   
                 Comparative Example 1 
               
               
                   
                   
               
               
                   
                 H 1  (unit: μm) 
                 240 
               
               
                   
                 H 2  (unit: μm) 
                 0 
               
               
                   
                 H 1  + H 2  (unit: μm) 
                 240 
               
               
                   
                   
               
               
                   
                 Viewing Angle (unit: degree) 
                 Relative Brightness (unit: %) 
               
               
                   
                   
               
               
                   
                 0 
                 56 
               
               
                   
                 2 
                 56 
               
               
                   
                 4 
                 56 
               
               
                   
                 6 
                 56 
               
               
                   
                 8 
                 56 
               
               
                   
                 10 
                 56 
               
               
                   
                 12 
                 56 
               
               
                   
                 13 
                 56 
               
               
                   
                   
               
            
           
         
       
     
     An illustrative optical filter may be applied to a 3D device so that the 3D device can display a 3D image at a wide viewing angle without loss of brightness.