Abstract:
An organic light emitting display apparatus includes a first substrate, a plurality of organic light emitting pixels formed on the substrate, a second substrate bonded to the substrate to seal the organic light emitting pixels. A black matrix layer is formed on a surface of the second substrate facing the first substrate and provides a plurality of openings. One of the openings and one of the pixels are aligned. The pixel has a first edge and a second edge and the opening has a first edge and a second edge. The first edge of the pixel is closer to the first edge of the opening than the second edge of the opening. The two edges of the opening are interposed between the two edges of the pixels when viewed from a direction perpendicular to the surface. Where L is an imaginary straight line passing the first edge of the pixel and the second edge of the opening in an imaginary plane perpendicular to a direction in which the edges extend, the imaginary line L and the first surface form an acute angle which is greater than about 30° and smaller than about 45°.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2007-0012366, filed on Feb. 6, 2007, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present disclosure relates to an organic light emitting display apparatus, and more particularly, to an organic light emitting display apparatus with a limited viewing angle. 
         [0004]    2. Discussion of the Related Technology 
         [0005]    Recently, thin, flat, and portable display apparatuses such as field emission display apparatuses have been introduced. Due to their wide viewing angle, high contrast, and short response time, the field emission display apparatuses (emissive display apparatuses) have been considered to be the next generation of display apparatuses. Among the field emission display apparatuses, an organic light emitting display apparatus including a light emitting layer formed of an organic material has the advantages of high brightness, low driving voltage, short response time, and multi-color display over an inorganic light emitting display apparatus. 
         [0006]    Also, the organic light emitting display apparatus is thin and lightweight, and thus, can obtain information anyplace or any time. However, when it is used in a public place, an image displayed on the organic light emitting display apparatus can be viewed not only by the user of the organic light emitting display apparatus but also by other people. Accordingly, there is a need for a portable display apparatus that can be used safely in a public place. 
         [0007]    The discussion in this section is to provide general background information, and does not constitute an admission of prior art. 
       SUMMARY 
       [0008]    An aspect of the invention provides an organic light emitting display apparatus comprising: a substrate; a display device formed on the substrate, the display device comprising a plurality of organic light emitting pixels, each pixel is spaced from an immediately neighboring pixel by a non-light emitting area; a sealing member bonded to the substrate such that the organic light emitting pixels are interposed between the substrate and the sealing member; and a black matrix formed on a surface of the sealing member facing the substrate and overlapping with the non-light emitting area when viewed in a first direction perpendicular to the surface, wherein a first one of the organic light emitting pixels overlaps with the black matrix when viewed in the first direction, wherein a is a width of the first pixel, wherein b is a width of a first area of the first pixel overlapping with the black matrix, wherein the width a and the width b are measured in a second direction parallel to the surface, wherein t 2  is a distance between the sealing member and the first pixel, wherein the black matrix and the first pixel are arranged so as to satisfy the following relationship: a−√{square root over (3)}×t 2 ≦b≦a−t 2 . 
         [0009]    In the foregoing apparatus, the first pixel may comprise a second area overlapping with the black matrix, wherein the second area may have a width which is measured in the second direction and substantially equal to the width b. The distance between the substrate and the sealing member may be about 5 to about 20 μm. The black matrix may have a thickness of about 0.05 to about 5 μm. The display device may have a thickness of about 0.05 to about 0.5 μm. 
         [0010]    Another aspect of the invention provides an organic light emitting display device comprising: a first substrate; a second substrate opposing the first substrate and comprising a first surface facing the first substrate; an array of organic light emitting pixels interposed between the first substrate and the second substrate, wherein the array comprises a first pixel configured to emit visible light; a black matrix layer formed on the first surface, wherein the black matrix provides a plurality of openings comprising a first opening configured to pass visible light therethrough, wherein the first opening is aligned with the first pixel such that visible light from the first pixel can pass through the first opening; wherein the first opening comprises a first edge and a second edge, both of which extend generally in a first direction parallel to the first surface; wherein the first pixel comprises a first edge and a second edge, both of which extend generally in the first direction, wherein the first edge of the first pixel is closer to the first edge of the first opening than the second edge of the first opening; wherein the first edge of the first opening is located between the first and second edges of the first pixel when viewed from a direction perpendicular to the first surface; wherein L is an imaginary straight line passing the first edge of the first pixel and the second edge of the first opening in an imaginary plane perpendicular to the first direction; and wherein the imaginary line L and the first surface form an acute angle which is greater than about 30°. 
         [0011]    In the foregoing device, the acute angle may be smaller than about 45°. The first pixel and the first opening may be arranged so as to satisfy the following relationship: t 2 ≦c≦√{square root over (3)}×t 2 , wherein c is the distance between the first edge of the first opening and the second edge of the first pixel measured in a second direction perpendicular to the first direction and parallel to the first surface, and wherein t 2  is the distance between the first surface and a top surface of the pixel in a third direction perpendicular to the first and second directions, wherein the top surface faces the first surface. The first pixel and the first opening may be arranged so as to satisfy the following relationship: c=a−b, wherein a is the distance between the first edge of the first pixel and the second edge of the first pixel measured in a second direction perpendicular to the first direction and parallel to the first surface, and wherein b is the distance between the first edge of the first opening and the first edge of the first pixel measured in a second direction perpendicular to the first direction and parallel to the first surface. The distance a may be from about 10 μm to about 100 μm. The distance b may be from about 0.5 μm to about 10 μm. The distance t 2  may be from about 1 μm to about 50 μm. The first edge of the pixel may be on a top surface thereof, which faces the first surface. The first pixel may be configured to emit visible light between the first edge and the second edge. The first and second edges of the first opening may contact the first surface. The second edge of the first opening may be located between the first and second edges of the first pixel when viewed from the second substrate in the direction perpendicular to the first surface. The first pixel may overlap with the black matrix when viewed from the second substrate in the direction perpendicular to the first surface. 
         [0012]    Yet another aspect of the invention provides an organic light emitting display device comprising: a first substrate; a second substrate opposing the first substrate and comprising a first surface facing the first substrate; an array of organic light emitting pixels interposed between the first substrate and the second substrate, wherein the array comprises a first pixel configured to emit visible light; a black matrix layer formed on the first surface, wherein the black matrix provides a plurality of openings comprising a first opening configured to pass visible light therethrough, wherein the first opening is aligned with the first pixel such that visible light from the first pixel can pass through the first opening; wherein the first opening comprises a first edge and a second edge, both of which extend generally in a first direction parallel to the first surface; wherein the first pixel comprises a first edge and a second edge, both of which extend generally in the first direction, wherein the first edge of the first pixel is closer to the first edge of the first opening than the second edge of the first opening; wherein the first edge of the first opening is located between the first and second edges of the first pixel when viewed from a direction perpendicular to the first surface wherein the first pixel and the first opening are arranged so as to satisfy the following relationship: t 2 ≦a−b≦√{square root over (3)}×t 2 ; wherein a−b is the distance between the first edge of the first opening and the second edge of the first pixel measured in a second direction perpendicular to the first direction and parallel to the first surface; and wherein t 2  is the distance between the first surface and a top surface of the pixel in a third direction perpendicular to the first and second directions, wherein the top surface faces the first surface. 
         [0013]    A further aspect of the present invention provides an organic light emitting display apparatus that has a limited viewing angle so that an image displayed thereon can be viewed only by a user of the organic light emitting display apparatus. 
         [0014]    An aspect of the present invention provides an organic light emitting display apparatus comprising: a substrate; a plurality of display units formed on the substrate, each of the display units having an organic light emitting pixel; a sealing member bonded against a surface of the substrate to seal the organic light emitting pixel; and a black matrix unit formed on a surface of the sealing member facing the substrate and corresponding to spaces between the display units separated from each other, wherein, when a is a width of the display unit, b is a width formed by overlapping the black matrix unit with the display unit, t 1  is a thickness of the display unit, and t 2  is a gap between the sealing member and the display unit, the inequality a−√{square root over (3)}×t 2 ≦b≦a−t 2  is satisfied. 
         [0015]    The width of an edge of the display unit that overlaps with the black matrix unit and the width of another edge of the display unit that overlaps with the black matrix unit may be equal to each other. The gap between the substrate and the sealing member may be about 5 to about 20 μm. The black matrix unit may have a thickness of about 0.05 to about 5 μm. The display unit may have a thickness of about 0.05 to about 0.5 μm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
           [0017]      FIG. 1  is a schematic cross-sectional view illustrating an organic light emitting display apparatus according to an embodiment of the present invention; 
           [0018]      FIG. 2  shows a right-angled triangle for explaining a relationship between a display unit and the configuration of a black matrix in the organic light emitting display apparatus of  FIG. 1 ; 
           [0019]      FIG. 3  is schematic cross-sectional view illustrating an organic light emitting display apparatus having a limited viewing angle of 90° from left to right, according to an embodiment of the present invention; 
           [0020]      FIG. 4  is schematic cross-sectional view illustrating an organic light emitting display apparatus having a limited viewing angle of 120° from left to right, according to an embodiment of the present invention; 
           [0021]      FIG. 5  is a plan view of the organic light emitting display apparatus of  FIG. 1  seen from a direction indicated by the arrow, according to an embodiment of the present invention; 
           [0022]      FIG. 6  is a plan view of a modified organic light emitting display apparatus according to an embodiment of the present invention; and 
           [0023]      FIG. 7  is a cross-sectional view of a display unit of the organic light emitting display apparatus of  FIG. 1 , in which the display unit is an active matrix type organic light emitting pixel. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0024]    Embodiments of the present invention will now be described more fully with reference to the accompanying drawings in which exemplary embodiments of the invention are shown. 
         [0025]      FIG. 1  is a schematic cross-sectional view illustrating an organic light emitting display apparatus according to an embodiment of the present invention, and  FIG. 2  shows a right-angled triangle for explaining a relationship between a display unit and the configuration of a black matrix in the organic light emitting display apparatus of  FIG. 1 . The organic light emitting display apparatus of  FIG. 1  includes a substrate  10 , a plurality of display units  11 , a sealing member or second substrate  20 , and a black matrix unit or layer  22 . 
         [0026]    The substrate  10  can be formed of a transparent glass material having SiO 2  as a main component. However, the substrate  10  can also be formed of a transparent plastic material. The plastic substrate can be formed of an insulating organic material selected from the group consisting of polyethersulphone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethyelenen napthalate (PEN), polyethyeleneterepthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate (PC), cellulose tiracetate (TAC), and cellulose acetate propinonate (CAP). If the organic light emitting display apparatus is a bottom emission type, that is, an image is displayed through the substrate  10 , the substrate must be formed of a transparent material. However, as depicted in  FIG. 1 , if the organic light emitting display apparatus is a top emission type, that is, an image is displayed in a direction opposite to the substrate  10 , the substrate  10  is not necessarily formed of a transparent material. In this case, the substrate  10  can be a metal substrate formed of a material selected from the group consisting of carbon, iron, chrome, nickel, titanium, molybdenum, stainless steel (SUS), invar alloy, zinconel alloy, and kovar alloy, but the present invention is not limited thereto. The metal substrate  10  can also be a metal foil. 
         [0027]    The display units  11  are formed on a surface of the substrate  10 . Each of the display units  11  includes an organic light emitting pixel that displays an image. The display units  11  can have a thickness of about 0.05 to about 0.5 μm. The organic light emitting device can be either an active matrix (AM) type device or a passive matrix (PM) type device. 
         [0028]    The sealing member  20  is disposed to face a surface of the substrate  10 . The black matrix unit  22  is formed on the sealing member  20  to correspond to spaces between the display units  11  on the substrate  10 . The black matrix unit  22  can have a thickness of about 0.05 to about 5 μm. The sealing member  20  protects the organic light emitting pixels from external moisture or oxygen, and is formed of a transparent material. For this purpose, the sealing member  20  can be formed of glass or plastic, or a stacked structure of organic materials and inorganic materials. 
         [0029]    The black matrix unit  22  is formed on one of surfaces of the sealing member  20  facing the substrate  10 . The black matrix unit  22  can be formed of various dark black materials that can absorb external light, such as graphite or chrome. The black matrix unit  22  is disposed to overlap at least an outer edge of a display unit  11  and another outer edge of a display unit  11  opposing and parallel to the outer edge of the display unit  11 . Referring to  FIG. 1 , a is the width of the display unit  11 , t 1  is the height of the display unit  11 , b is the width formed by overlapping the black matrix unit  22  and the display unit  11 , and t 2  is the gap distance between the display unit  11  and the sealing member  20 . In order to maintain the gap between the display unit  11  and the sealing member  20 , the thickness of a seal (not shown) that seals a space between the substrate  10  and the sealing member  20  can be controlled or spacers can be used. 
         [0030]    The organic light emitting display apparatus according to an embodiment of the present invention can limit a viewing angle. A viewing angle is a range of angle in which the user can see an image. In an embodiment of the present invention, the viewing angle is measured using a triangle formed between the substrate  10  and the sealing member  20 . That is, referring to  FIG. 1 , an isosceles triangle is formed by respectively connecting ends of the display unit  11  to ends of two neighboring portions of the black matrix unit  22 , and, at this point, the angle at the apex of the isosceles triangle is the viewing angle. 
         [0031]    In the organic light emitting display apparatus according to an embodiment of the present invention, since the black matrix unit  22  is disposed to overlap outer edges of the display unit  11 , the viewing angle in the left and right directions can be limited. That is, since the viewing angle is limited to as much as 90−θ in each of the left and right directions, the viewing angle in the right and left sides is limited to as much as 180−2×θ. 
         [0032]    Referring to  FIG. 2 , the viewing angle can be controlled according to the mutual relationship between the width b of an area of the pixel  11  overlapping with the black matrix unit  22 , the width a of the display unit  11 , and the gap distance t 2  between the display unit  11  and the sealing member  20 . That is, in the triangle of  FIG. 2 , the equation tan θ=t 2 /(a−b) holds, and this equation can be rearranged as b=a−t 2 /tan θ. The width of the black matrix units  22  required for limiting a desired viewing angle can be determined using the above equation. In order to prevent an image from being viewed by people in the left and right sides, the limited viewing angle may be about 90° to about 120°. 
         [0033]      FIG. 3  is schematic cross-sectional view illustrating an organic light emitting display apparatus having a limited viewing angle of 90° from left to right, according to an embodiment of the present invention, and  FIG. 4  is schematic cross-sectional view illustrating an organic light emitting display apparatus having a limited viewing angle of 120° from left to right, according to an embodiment of the present invention. 
         [0034]    Referring to  FIG. 3 , in order to limit the viewing angle to 90°, since θ is 45°, the width b formed by overlapping the black matrix unit  22  with the display unit  11  is a−t 2 /tan 45°=a−t 2 . Referring to  FIG. 4 , in order to limit the viewing angle to 120°, since θ is 60°, the width b formed by overlapping the black matrix unit  22  with the display unit  11  is a−t 2 /tan 30°=a−t 2 ×√{square root over (3)}. In order to identically limit the left and right viewing angles, the black matrix unit  22  may overlap with the display unit  11  with the same width at the both edges of the display unit  11 . If the width b formed by overlapping the black matrix unit  22  with the display unit  11  satisfies the inequality a−√{square root over (3)}×t 2 ≦b≦a−t 2 , the viewing angle can be limited from 90° to 120°. Therefore, the image cannot be seen by others. 
         [0035]      FIG. 5  is a schematic plan view of the organic light emitting display apparatus of  FIG. 1  seen from a direction indicated by the arrow. Viewing angles in left and right sides can be limited since the black matrix unit  22  overlaps with both edges of the display unit  11 . 
         [0036]      FIG. 6  is a schematic plan view illustrating a modified organic light emitting display apparatus according to an embodiment of the present invention. Referring to  FIG. 6 , the black matrix unit  22  overlaps not only with the both left and right edges of the display unit  11 , but also with both upper and lower edges of the display unit  11 . In this case, the viewing angles in left and right sides and upper and lower sides are limited. When the viewing angles in left and right sides are limited, an image cannot be usually viewed by other people than the user of the organic light emitting display apparatus. However, when it is necessary, the viewing angles of upper and lower sides can also be limited. 
         [0037]    A method of manufacturing the organic light emitting display apparatus according to an embodiment of the present invention can be applied to various types of organic light emitting display apparatuses.  FIG. 7  is a cross-sectional view of the display unit  11  of the organic light emitting display apparatus of  FIG. 1 . The organic light emitting display apparatus includes an AM type organic light emitting device. A buffer layer  41  can be formed on the upper surface of the substrate  10  using SiO 2  and/or SiNx to have the same planarity as the substrate  10  and to prevent the penetration of impure elements. A thin film transistor (TFT) is formed on the upper surface of the substrate  10 . At least one TFT electrically connected to an organic light emitting pixels  50  is formed in each pixel. More specifically, a semiconductor layer  42  having a predetermined pattern is formed on the buffer layer  41 . The semiconductor layer  42  can be formed of an inorganic semiconductor such as amorphous silicon or poly silicon or an organic semiconductor, and includes a source region, a drain region, and a channel region. 
         [0038]    A gate insulating film  43  is formed on the semiconductor layer  42  using SiO 2  or SiNx, and a gate electrode  44  is formed in a predetermined region on the gate insulating film  43 . The gate electrode  44  can be formed of MoW or Al/Cu, but is not limited thereto. That is, the gate electrode  44  can be formed of various materials in consideration of tightness with adjacent layers, planarity of stacked layers, electrical resistance, processability, etc. The gate electrode  44  is connected to a gate line (not shown) that applies on/off signals for the TFT. An interlayer insulating film  45  is formed on the gate electrode  44 . A source electrode  46  and a drain electrode  47  are respectively connected to the source region and the drain region of the semiconductor layer  42  through contact holes. The TFT is protected by a passivation film  48 . 
         [0039]    The passivation film  48  can be an inorganic insulating film and/or an organic insulating film. The inorganic insulating film can be formed of SiO 2 , SiNx, SiON, Al 2 O 3 , TiO 2 , Ta 2 O 5 , HfO 2 , ZrO 2 , BST, or PZT. The organic insulating film can be formed of an ordinary polymer such as poly methylmethacrylate (PMMA) and polystyrene (PS), polymer derivatives having a phenol group, an acryl polymer, an imide polymer, an arylester polymer, an amide polymer, a fluoride polymer, a p-gilyrene polymer, a vinyl alcohol polymer, or a blended polymer of these materials. The passivation film  48  can be formed in a composite stack of inorganic insulating layers and organic insulating layers. 
         [0040]    A first electrode  51  that acts as an anode electrode of the organic light emitting device  50  is formed on the passivation film  48 , and a pixel define layer  49  covering the first electrode  51  is formed of an insulating material. After a predetermined opening is formed in the pixel define layer  49 , an organic light emitting layer  52  of the organic light emitting device  50  is formed in a region defined by the opening. A second electrode  53  that acts as a cathode electrode of the organic light emitting device  50  is formed to cover all pixels. The polarity of the first electrode  51  and the second electrode  53  may be reversed. 
         [0041]    The organic light emitting device  50  displays an image by emitting light according to a current flow, and includes the first electrode  51  electrically connected to the drain electrode  47  of the TFT through a contract hole, the organic light emitting layer  52 , and the second electrode  53 . The first electrode  51  can be patterned to a predetermined pattern using a photolithography method. The pattern of the first electrode  51  can be formed in stripe shaped lines separated a predetermined distance from each other if the organic light emitting display apparatus is a passive matrix (PM) type, and can be formed in a shape corresponding to the pixel if the organic light emitting display apparatus is an AM type. The second electrode  53  is disposed above the first electrode  51 , and can be used as a cathode electrode by connecting to an external terminal (not shown). The second electrode  53  can be formed in a stripe shape perpendicularly crossing the pattern of the first electrode  51  if the organic light emitting display apparatus is a PM type, and can be formed on the entire active region where an image is displayed if the organic light emitting display apparatus is an AM type. The polarity of the first electrode  51  and the second electrode  53  may be reversed. 
         [0042]    As depicted in  FIG. 1 , if the organic light emitting display apparatus is a top emission type, that is, an image is displayed in a direction of the second electrode  53 , the first electrode  51  can be a reflective electrode and the second electrode  53  can be a transparent electrode. The reflective electrode that acts as the first electrode  51  can be formed such that, after a reflective film is formed using Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, or a compound of these materials, a material having a high work function such as ITO, IZO, In2O3, or ZnO is deposited on the reflective film. The transparent electrode that acts as the second electrode  53  can be formed such that, after depositing a material film using a metal having a low work function, such as Li, Ca, LiF/Ca, LiF/Al, Al, Ag, Mg, or a compound of these metals, and an auxiliary electrode layer or a bus electrode line formed of a transparent conductive material such as ITO, IZO, ZnO or In2O3 can be formed on the material film. 
         [0043]    The organic light emitting layer  52  interposed between the first electrode  51  and the second electrode  53  emits light in response to electrical driving of the first electrode  51  and the second electrode  53 . The organic light emitting layer  52  can be formed of a low molecular weight organic material or a polymer organic material. If the organic light emitting layer  52  is formed of a low molecular weight organic material, a hole transport layer (HTL) and a hole injection layer (HIL) are stacked in a direction towards the first electrode  51  from the organic light emitting layer  52 , and an electron transport layer (ETL) and an electron injection layer (EIL) can be stacked in a direction towards the second electrode  53  from the organic light emitting layer  52 . Besides the above layers, various layers can be stacked as necessary. The low molecular weight organic material can include copper phthalocyanine (CuPc), N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), or tris-8-hydroxyquinoline aluminum (Alq3). 
         [0044]    If the organic light emitting layer  52  is formed of a polymer organic material, only an HTL can be included in a direction towards the first electrode  51  from the organic light emitting layer  52 . The polymer HTL is formed of poly-(2,4)-ethylene-dihydroxy thiophene (PEDOT) or polyaniline (PANI) on the first electrode  51  using an inkjet printing method or a spin coating method, and the organic light emitting layer  52  is formed of poly-phenylenevinylene (PPV), soluble PPV&#39;s, cyano-PPV, or polyfluorene and can be formed to a color pattern using a method such as a screen printing method, an inkjet printing method, or a thermal transfer method using a laser. 
         [0045]    Up to now, the AM type organic light emitting display apparatus having a top gate structure of  FIG. 7  has been described. However, the present invention is not limited thereto, and can be applied to various types of organic light emitting display apparatuses. 
         [0046]    The organic light emitting display apparatus according to an embodiment of the present invention can protect an image from being viewed by other people than the user of organic light emitting display apparatus by limiting viewing angles. 
         [0047]    While embodiments of the present invention has been particularly shown and described, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.