Abstract:
A flat panel display device and a method of manufacturing the same, the flat panel display device including: a glass substrate; a metal encapsulation substrate facing the glass substrate; a light-emitting unit interposed between the glass substrate and the metal encapsulation substrate; a first sealing unit interposed between the glass substrate and the metal encapsulation substrate, arranged around the light-emitting unit, and comprising a first sealant and a second sealant. The first sealant is disposed around the light-emitting unit and may include a UV-curable material. The second sealant is coated on the first sealant and may include a thermally-curable material.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2010-0029999, filed on Apr. 1, 2010, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein, by reference. 
     BACKGROUND 
     1. Field 
     One or more embodiments of the present invention relate to a flat panel display device and a method of manufacturing the flat panel display device 
     2. Description of the Related Art 
     Recently, flat panel display devices have increased in popularity. Among flat panel display devices, electroluminescent display devices, which are self-emitting display devices, have attracted attention as the next generation of display devices, because of their wide viewing angle, excellent contrast ratio, and short response time. Organic light-emitting display devices include a light-emitting layer formed of an organic material, and form brighter images, have a lower driving voltage, and a shorter response time, as compared to inorganic light-emitting display devices. 
     However, a light-emitting unit of the organic light-emitting display device may deteriorate, due to the penetration of moisture. Thus, in order to prevent the penetration of external moisture, an organic light-emitting display device should include an encapsulation structure, so as to seal and protect the light-emitting unit. 
     According to the related art, an encapsulation structure includes a glass encapsulation substrate formed over a light-emitting unit disposed on a glass substrate. A sealant is used to seal a gap between the glass substrate and the encapsulation substrate. The sealant, may comprise an ultraviolet (UV)-curable material. The sealant is coated around the light-emitting unit, on the glass substrate, to attach the encapsulation substrate to the glass substrate. Then UV rays are radiated to cure the sealant, so that the glass substrate and the encapsulation substrate are tightly adhered to each other. 
     However, this encapsulation structure uses an expensive glass material as the encapsulation substrate. In order to solve this problem, a solution has been proposed where the encapsulation substrate is formed of a metal, such as stainless steel or aluminum. However, such a metal encapsulation substrate reflects UV rays, making it difficult to use a UV-curable material sealant. In addition, even if a different type of sealant is used, sealants capable of adhering different materials often suffer from degradation over time and/or weak bonding strength. 
     Thus, there is a demand for a sealing unit that insures a strong adhesion between a low cost metal encapsulation substrate and a glass substrate. 
     SUMMARY 
     One or more embodiments of the present invention include a flat panel displace device having a strong adhesion between a metal encapsulation substrate and a glass substrate, and a method of manufacturing the flat panel displace device. 
     According to one or more embodiments of the present invention, a flat panel display device includes a glass substrate; a metal encapsulation substrate facing the glass substrate; a light-emitting unit interposed between the glass substrate and the metal encapsulation substrate; and a sealing unit disposed around the light-emitting unit, comprising a first sealant disposed around the light-emitting unit, and a second sealant coated on the first sealant. 
     According to various embodiments, the first sealant may be coated so as form a structure that projects from the surface of the metal encapsulation substrate, toward the glass substrate. 
     According to various embodiments, the first sealant may include a UV-curable material coated on a desiccant. 
     According to various embodiments, the second sealant may include an epoxy-based adhesive, a silicon adhesive, or an acryl adhesive. 
     According to various embodiments, the viscosity of the second sealant may be less than the viscosity of the first sealant, during the coating of the second sealant. 
     According to various embodiments, a desiccant may be filled in an internal space between the glass substrate and the metal encapsulation substrate. The desiccant may include calcium oxide (CaO), barium oxide (BaO), Zeolite, an Aluminum (Al)-based organic metal complex, or a polyacrylic acid. 
     According to one or more embodiments of the present invention, a method of manufacturing a flat panel display device includes: forming a light-emitting unit on a glass substrate; coating a first sealant on a surface of a metal encapsulation substrate; partially curing the first sealant; coating a second sealant on the first sealant; adhering the metal encapsulation substrate and the glass substrate; and curing the second sealant and the first sealant. 
     According to various embodiments, the first sealant may be coated so as to form a structure that projects away from the surface of the metal encapsulation substrate, toward the glass substrate. 
     According to various embodiments, the first sealant may include a UV-curable material coated on a desiccant. 
     According to various embodiments, the second sealant may include an epoxy-based adhesive, a silicon adhesive, or an acryl adhesive. 
     According to various embodiments, the viscosity of the second sealant may be less than the viscosity of the first sealant, during the coating of the second sealant. 
     According to various embodiments, the method may further include disposed a desiccant in an internal space formed between the glass substrate and the metal encapsulation substrate. The desiccant may include calcium oxide (CaO), barium oxide (BaO), Zeolite, an Aluminum (Al)-based organic metal complex, or a polyacrylic acid. 
     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings, of which: 
         FIG. 1  is a diagram of a flat panel display device, according to an exemplary embodiment of the present invention; 
         FIG. 2  is a magnified partial view of a portion of the flat panel display device of  FIG. 1 ; 
         FIGS. 3A through 3C  are cross-sectional views describing a method of manufacturing the flat panel display device of  FIG. 1 ; and 
         FIG. 4  is a diagram of a flat panel display device, according to another exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The exemplary embodiments are described below, in order to explain the aspects of the present invention, by referring to the figures. 
       FIG. 1  is a diagram of a flat panel display device  100 , according to an exemplary embodiment of the present invention. As illustrated in  FIG. 1 , the flat panel display device  100  includes a glass substrate  110 , a light-emitting unit  120  formed on the glass substrate  110 , and a metal encapsulation substrate  130  covering the light-emitting unit  120 . 
     The light-emitting unit  120  may be an organic light-emitting unit, in which an organic layer is formed between a pair of opposing electrodes. Although not illustrated in  FIG. 1 , a passivation layer may be formed on the light-emitting unit  120  to protect the same. 
     The metal encapsulation substrate  130  prevents the penetration of external moisture into the light-emitting unit, by covering the light-emitting unit  120 . The metal encapsulation substrate  130  may be formed of, for example, stainless steel or aluminum. The metal encapsulation substrate  130  material is substituted for an expensive glass encapsulation substrate used in the related art and thus, reduces costs. A sealing unit  140  is provided between the encapsulation substrate  130  and the substrate  110 . That is, the metal encapsulation substrate  130  and the glass substrate  110  are adhered to each other using the sealing unit  140 , so as to seal an internal space in which the light-emitting unit  120  is arranged. 
     The sealing unit  140  includes a first sealant  141  and a second sealant  142 . The first sealant  141  includes a UV-curable material. The second sealant  142  includes a thermally-curable material. The second sealant  142  is coated on the first sealant  141 , such that the first sealant  141  is disposed within the second sealant  142 . The second sealant  142  operates to adhere and seal the glass substrate  110  and the metal encapsulation substrate  130 . The first sealant  141  enlarges the surface area of the sealing unit  140 , thereby increasing the adhesiveness thereof. 
     The first sealant  141  is applied to the metal encapsulation substrate  130 , so as to have an embossment shape. In other words, the first sealant  141  is coated so as to form a structure that projects away from the encapsulation substrate  130 . More specifically, the first sealant  141  may be coated so as to contact a greater surface area of the encapsulation substrate  130  than the glass substrate  100 , when the same are attached. 
     The second sealant  142  is coated on the first sealant  141 . A contact area of the glass substrate  110  and the sealing unit  140  is thereby increased, so that the adhesion of the sealing unit  140  is also increased. In particular, the second sealant  142  may be coated so as to contact a larger surface area of the glass substrate  110  than the first sealant  141 , and may contact a smaller surface area of the encapsulation substrate  130  than the first sealant  141 . Also, since the second sealant  142  is heat cured, performs the adhering and sealing operations, it is possible to prevent a problem in which ultraviolet rays are reflected on the metal encapsulation substrate  130 , such that a curing operation is not appropriately performed, as when only a UV-curable material is used. 
     The flat panel display device  100  may be manufactured via processes shown in  FIGS. 3A through 3C . As illustrated in  FIG. 3A , the first sealant  141  is coated on edge portions of the metal encapsulation substrate  130 , so as to form a raised structure on the substrate  130 . The first sealant  141  may include only the UV-curable material, or as illustrated in  FIG. 2 , the first sealant  141  may include a desiccant  141   a  that is coated with a UV-curable material  141   b . The desiccant  141   a  may operate as a barrier to the penetration of external moisture. After applying the first sealant  141 , ultraviolet rays are radiated to cure the first sealant  141 . 
     However, the first sealant  141  is generally not completely cured. Instead, the first sealant  141  is approximately 70-80% cured. The second sealant  142  is heated, during the subsequent thermal curing of the second sealant  142 , such that the remaining 20-30% of the curing process of the first sealant  141  occurs. The first sealant  141  is partially cured to the extent that the shape of the first sealant  141  may be maintained. If the first sealant  141  is completely cured by the UV light, when the metal encapsulation substrate  130  and the glass substrate  110  are adhered, the adhesion between the first sealant  141  the glass substrate  110  may be reduced. 
     After the first sealant  141  is coated and partially cured, as illustrated in  FIG. 3B , the second sealant  142  coated on the first sealant  141 . The second sealant comprises a thermally-curable material, such as an epoxy-based adhesive, a silicon adhesive, an acryl adhesive, or the like, or a combination thereof. The second sealant  142  is coated around and between the shaped first sealant  142 . The second sealant  142  may have a viscosity that is less than that of the first sealant  141 , during the coating, so as to facilitate the coating. 
     Afterward, as illustrated in  FIG. 3C , the metal encapsulation substrate  130  is adhered to the glass substrate  110 , such that the light-emitting unit  120  is sealed in a space formed between the substrate  110 , the encapsulation substrate  130 , and the sealing unit  140 . Heat is then applied to the sealing unit  140  to cure the first sealant  141  and the second sealant  142 , so that a firmly adhered and sealed state is achieved. Since the second sealant  142  directly contacts the glass substrate  110  and is coated on the first sealant  141 , the adhesive surface area of the second sealant  142  is increased, as compared to a case in which the second sealant  142  is directly coated on the flat surface of the metal encapsulation substrate  130 . Accordingly, the overall adhesion of the sealing unit  140  may be increased accordingly. 
     Therefore, the flat panel display device  100  has a sealing structure, in which the deterioration of adhesion may be prevented. In other words, excellent adhesion can be obtained, even though the low-priced metal encapsulation substrate  130  is used. 
     As illustrated in  FIG. 4 , a desiccant  150  may be formed on the light-emitting unit, so as to fill an internal space formed between the glass substrate  110 , the metal encapsulation substrate  130 , and the sealing unit  140 . The desiccant  150  may include calcium oxide (CaO), barium oxide (BaO), Zeolite, an Aluminum (Al)-based organic metal complex, a polyacrylic acid, or the like, or a combination thereof. By filling the internal space with the desiccant  150 , it is possible to prevent moisture that penetrates the device  100  from degrading the light-emitting unit  120 . 
     According to various embodiments of the present invention, provided is a flat panel display device having excellent adhesion between a glass substrate and a metal encapsulation substrate, due to having a multi-sealant structure. Accordingly, a low-priced metal encapsulation substrate may be utilized in place of an expensive glass encapsulation substrate. The improved adhesion also increases the reliability of the display device. 
     Although a few exemplary embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these exemplary embodiments, without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.