Abstract:
An organic light emitting display device has improved strength. The organic light emitting display device includes a first substrate and a second substrate sealing the first substrate, wherein the thickness of the first substrate is different from the thickness of the second substrate. A method of making an organic light emitting display device comprises forming elements in a first substrate and sealing the first substrate with a second substrate having a thickness different from a thickness of the first substrate. Finally, an organic light emitting display device comprises a panel and a frame, wherein the panel comprises a first substrate and a second substrate for sealing the first substrate, wherein the thickness of the first substrate is different from the thickness of the second substrate.

Description:
CLAIM OF PRIORITY 
       [0001]    This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on 7 Jan. 2010 and there duly assigned Serial No. 10-2010-0001200. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an organic light emitting display device and a method of making the same and, more particularly, to an organic light emitting display device having improved strength and a method of making the same. 
         [0004]    2. Description of the Related Art 
         [0005]    In recent years, various flat panel displays capable of reducing weight and volume, which are deficiencies of a cathode ray tube, have been developed. Examples of the flat panel displays include a liquid crystal display, a field emission display, a plasma display panel, and an organic light emitting display. 
         [0006]    Among the flat panel displays, the organic light emitting display displays an image by using an organic light emitting diode (OLED) which generates light by recombination of electrons and holes which are generated in response to the flow of current. 
         [0007]    In application fields of the organic light emitting display, the organic light emitting display is used for a personal data assistant (PDA), an MP3 player, etc., in addition to a cellular phone, such that the market for the organic light emitting display is being substantially extended due to its various advantages, such as excellent color reproducibility and thinness. 
         [0008]    In the organic light emitting display, a transistor, an organic light emitting diode, a capacitor, etc. and, in addition, wires are formed on a first substrate, and the first substrate is sealed with a second substrate. 
         [0009]    At this point, the organic light emitting display can improve its strength by attaching a frame, etc. to the first substrate and the second substrate. However, the improvement in strength is limited. 
         [0010]    Furthermore, heat treatment of the first substrate is performed at the time of forming the transistor, the organic light emitting diode, the capacitor and the wires, and as a result, the mechanical strength of the first substrate is deteriorated in comparison to the second substrate. 
       SUMMARY OF THE INVENTION 
       [0011]    Accordingly, the present invention provides an organic light emitting display having improved strength, and a method of making the same. 
         [0012]    According to an aspect of the present invention, an organic light emitting display device includes a first substrate and a second substrate for sealing the first substrate, wherein the thickness of the first substrate is different from the thickness of the second substrate. 
         [0013]    Additionally, a resonance frequency of the first substrate and a resonance frequency of the second substrate are set to be different from each other by the difference in thickness between the first substrate and the second substrate. 
         [0014]    Furthermore, the thickness of the first substrate is larger than the thickness of the second substrate. 
         [0015]    According to another aspect of the present invention, a method of making an organic light emitting display device includes forming elements on a first substrate, and sealing the first substrate with a second substrate having a thickness different from the first substrate. 
         [0016]    Additionally, a resonance frequency of the first substrate and a resonance frequency of the second substrate are set to be different from each other by the difference in thickness between the first substrate and the second substrate. 
         [0017]    Furthermore, the thickness of the first substrate is larger than the thickness of the second substrate. 
         [0018]    In accordance with the present invention, an organic light emitting display device and a method of making the same can improve its strength because thicknesses of a first substrate and a second substrate are set to be different. In particular, it is possible to further reinforce the first substrate, which would otherwise have its strength deteriorated through the heat treatment, etc., by making the thickness of the first substrate larger than the thickness of the second substrate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein: 
           [0020]      FIG. 1  is an exploded perspective view showing the structure of an organic light emitting display device according to a first embodiment of the present invention. 
           [0021]      FIG. 2  is a cross-sectional view showing a first substrate of the organic light emitting display device shown in  FIG. 1 . 
           [0022]      FIG. 3  is a cross-sectional view showing a first embodiment of a panel of the organic light emitting display device shown in  FIG. 1 . 
           [0023]      FIG. 4  is a cross-sectional view showing an organic light emitting display device according to a second embodiment of the present invention. 
           [0024]      FIG. 5  is a diagram showing an impact test result depending on the thickness of a first substrate and the thickness of a second substrate in an organic light emitting display device according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art will realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. In addition, when an element is referred to as being “on” another element, it can be directly on the another element or be indirectly on the another element with one or more intervening elements interposed therebetween. Also, when an element is referred to as being “connected to” another element, it can be directly connected to the another element or be indirectly connected to the another element with one or more intervening elements interposed therebetween. Hereinafter, like reference numerals refer to like elements. 
         [0026]    Embodiments of the present invention will now be described with reference to the accompanying drawings. 
         [0027]      FIG. 1  is an exploded perspective view showing the structure of an organic light emitting display device according to a first embodiment of the present invention. Referring to  FIG. 1 , the organic light emitting display device includes a panel  100  (constituting a screen), a frame  110 , a tape  120 , a printed circuit board (PCB)  130 , and a PCB tape  140 . 
         [0028]    The panel  100  includes a first substrate (not shown) and a second substrate (not shown). The first substrate is sealed with the second substrate by a sealant (not shown). In addition, a pixel (not shown) constituted by a transistor, a capacitor, an organic light emitting diode, etc. is formed on the first substrate. The thicknesses of the first substrate and the second substrate are set to be different from each other in order to reinforce the strength of the panel  100 . 
         [0029]    The frame  110  protects the sides and the rear surface of the panel  100 . The strength of the organic light emitting display device is reinforced by the material, the structure, etc. of the frame  110 . 
         [0030]    The tape  120  is attached to a rear surface of the panel  100  relative to the direction in which light of the panel  100  is radiated. The tape  120  allows the panel  100  to be attached and fixed to the frame  110 . Furthermore, damage to the organic light emitting display device by an impact can be reduced by using the tape  120 . 
         [0031]    The PCB  130  supplies signals and power to the panel  100 . A flexible printed circuit board (FPCB) having flexibility may be used for the PCB  130 . 
         [0032]    The PCB tape  140  connects the PCB  130  to the panel  100 , and prevents easy disconnection because the panel  100  and the PCB  130  adhere to each other. Furthermore, the PCB tape  140  can absorb impact, and thus the strength of the organic light emitting display device is reinforced by the PCB tape  140 . 
         [0033]      FIG. 2  is a cross-sectional view showing a first substrate of the organic light emitting display device shown in  FIG. 1 . Referring to  FIG. 2 , on the substrate  200 , an active layer  210  is formed and, thereafter, a first insulating layer  220  is formed. In addition, a first conductive layer is formed and patterned on top of the first insulating layer  220  to form a gate electrode  230   a  on top of the first insulating layer  220  and above the active layer, and a first electrode  230   b  of a storage capacitor is formed on the first insulating layer  220  above the substrate  200 . At this point, scan lines are formed by the first conductive layer and are connected to the gate electrode  230   a . A first electrode  230   b  of a storage capacitor having a blue pixel among the first electrodes  230   b  of the storage capacitor is formed at an opening of a white pixel. That is, the gate electrode  230   a  and the wires are formed on the first conductive layer where the blue pixel is formed and the gate electrode  230   a , a first electrode  230   b  of the storage capacitor of the blue pixel, and a second electrode of a storage capacitor of the white pixel are formed on the first conductive layer where the white pixel is formed. The wires formed in the blue pixel are connected with the storage capacitor of the blue pixel formed in the white pixel. 
         [0034]    In addition, after a second insulating layer  240  is formed on top thereof, a second electrode  250  of the storage capacitor is formed at a location opposite to the first electrode  230   b  of the storage capacitor. Therefore, the second electrode  250  of the storage capacitor of the blue pixel is formed in a white pixel area. In addition, a third insulating layer  260  is formed on top thereof. 
         [0035]    In addition, first to third contact holes  300   a  to  300   c  are formed, and source-drain metal  270   a ,  270   b  is formed. Thus, the source-drain metal  270   a ,  270   b  is in electrical contact with the active layer  210  and a second electrode  250  of the storage capacitor through the first to third contact holes  300   a  to  300   c . In addition, a fourth insulating layer  280  is formed on top thereof. At this point, source-drain metal  270   a  connected to the active layer  210  through the contact hole  300   a  is formed as a source electrode of a thin-film transistor, and source-drain metal  270   b  connected to the active layer  210  through the second contact hole  300   b  is formed as a drain electrode of the thin-film transistor. Furthermore, source-drain metal  270   b  connected with the second electrode of the storage capacitor through the third contact hole  300   c  is connected to a drain electrode of the thin-film transistor. As a result, signals transmitted through the transistor are transmitted to the storage capacitor. 
         [0036]    In addition, a planarization layer  290  is formed, a fourth contact hole  300   d  which contacts the source-drain metal  270   b  is formed, and a pixel electrode  300  is formed. Accordingly, the pixel electrode  300  contacts the source-drain metal  270   b  through the fourth contact hole  300   d  so as to receive a signal transmitted through the thin-film transistor. 
         [0037]      FIG. 3  is a cross-sectional view showing a first embodiment of a panel of the organic light emitting display device shown in  FIG. 1 . Referring to  FIG. 3 , the panel of the organic light emitting display device includes a first substrate  200   a  and a second substrate  400   a.    
         [0038]    An organic light emitting diode, a pixel circuit, scan lines, data lines, and power lines are formed on the first substrate  200   a . When the organic light emitting diode, pixel circuit, scan lines, data lines, and power lines are formed on the first substrate  200   a , an etching process for crystallizing and patterning a silicon layer and a heat treatment process are performed. 
         [0039]    The second substrate  400   a  is positioned so as to face the first substrate  200   a . The second substrate  400   a  seals the first substrate  200   a  so as to prevent moisture, air, etc. from permeating from the outside. For this purpose, the second substrate  400   a  is adhered to the first substrate  200   a  by using a sealant  500   a.    
         [0040]    At this point, the thickness W 1   a  of the first substrate  200   a  is larger than the thickness W 2   a  of the second substrate  400   a . In addition, the first substrate  200   a  and the second substrate  400   a  have a thickness difference so as to set resonance frequencies of the first substrate  200   a  and the second substrate  400   a  to be different from each other. Therefore, the first substrate  200   a  and the second substrate  400   a  are prevented from being damaged due to a small impact by a resonance. 
         [0041]      FIG. 4  is a cross-sectional view showing an organic light emitting display device according to a second embodiment of the present invention. 
         [0042]    Referring to  FIG. 4 , an organic light emitting diode, a pixel circuit, scan lines, data lines, and power lines are formed on a first substrate  200   b . When the organic light emitting diode, pixel circuit, scan lines, data lines, and power lines are formed on the first substrate  200   b , a silicon layer, an insulating layer, a metallic layer, etc. are vapor-deposited and etched. 
         [0043]    A second substrate  400   b  is positioned so as to face the first substrate  200   b . The second substrate  400   b  seals the first substrate  200   b  so as to prevent moisture, air, etc. from permeating from the outside. For this purpose, the second substrate  400   b  is adhered to the first substrate  200   b  by using a sealant  500   b.    
         [0044]    At this point, the thickness W 2   b  of the second substrate  400   b  is larger than the thickness W 1   b  of the first substrate  200   b . In addition, the first substrate  200   b  and the second substrate  400   b  have a thickness difference so as to set resonance frequencies of the first substrate  200   b  and the second substrate  400   b  to be different from each other. Therefore, the first substrate  200   b  and the second substrate  400   b  are prevented from being damaged due to a small impact by a resonance. 
         [0045]      FIG. 5  is a diagram showing an impact test result depending on the thickness of a first substrate and the thickness of a second substrate in an organic light emitting display device according to an embodiment of the present invention. 
         [0046]    Referring to  FIG. 5 , type 1 represents a case in which the thicknesses of the first substrate and the second substrate are the same as each other, and type 2 represents a case in which the thickness of the first substrate is 0.5 t and the thickness of the second substrate is 0.4 t. Type 3 represents a case in which the thicknesses of the first substrate and the second substrate are 0.4 t, and Type 4 represents a case in which the thicknesses of the first substrate and the second substrate are 0.3 t. 
         [0047]    At this point, the impact test is performed with respect to 10 organic light emitting display devices for each of type 1 to type 4. 
         [0048]    Type 1 acquired a point of 5.2, type 2 acquired a point of 11, type 3 acquired a point of 8, and type 4 acquired a point of 8.3 from the impact test result. That is, according to the impact test result of type 1, type 3, and type 4, as the thicknesses of the first substrate and the second substrate are smaller, a higher point in the impact test is acquired. However, although the thickness of the first substrate of type 2 is 0.5 t and the thickness of the second substrate of type 2 is 0.4 t, type 2 acquired a higher point than the type 1, type 3 and type 4. 
         [0049]    From the test results, when the thicknesses of the first substrate and the second substrate are different from each other, particularly, the thickness of the first substrate is the larger, a higher point is acquired. When the transistor, organic light emitting diode, capacitor, etc. are formed on the first substrate, a crystallization process and an etching process are performed. At this point, an additional heat treatment process is performed on the first substrate and, as a result, the first substrate may be lower than the second substrate in strength. 
         [0050]    Accordingly, it is possible to improve the strength of the organic light emitting display device by making the thicknesses of the first substrate and the second substrate different from each other, in particular, by making the thickness of the first substrate larger than the thickness of the second substrate. 
         [0051]    While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.