Abstract:
In a flexible organic light-emitting display device and a method of manufacturing the same, a photolysis layer and an electrostaticity prevention layer are sequentially formed on a carrier substrate, a first flexible substrate is formed on the electrostaticity prevention layer, a display unit is formed on the first flexible substrate, the display unit is covered with the second flexible substrate, and light is irradiated so as to decompose the photolysis layer and to remove the carrier substrate. The formed flexible organic light-emitting display device may have improved flexibility because a flexible substrate is used instead of a typical strong and thick glass substrate. In addition, occurrence of electrostaticity during the separation of the carrier substrate is suppressed by the electrostaticity prevention layer, and thus, damage of the display unit due to electrical impacts is also reduced.

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 the 7 Aug. 2012 and there duly assigned Serial No. 10-2012-0086397. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a flexible organic light-emitting display device and a method of manufacturing the same, and in particular, to a flexible organic light-emitting display device that is improved so that, when a carrier substrate is separated from a thin film layer, the display unit is not damaged in the manufacturing procedure, and a method of manufacturing the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Organic light-emitting display devices can be manufactured as thin and flexible devices due to their driving characteristics, and much research into organic light-emitting display devices is being performed. 
         [0006]    However, a display unit of an organic light-emitting display device may deteriorate due to permeation of water molecules. Accordingly, to prevent the permeation of external water molecules, a sealing structure for sealing the display unit is required. 
         [0007]    Typically, as the sealing structure, a glass substrate with a display unit thereon is covered by a sealing substrate formed of the same glass material as in the glass substrate, and a space formed between the glass substrate and the sealing substrate is sealed by a sealant. That is, a sealant, such as an ultraviolet hardener, is coated on a peripheral region of a display unit of a thick and strong glass substrate, and then, the resultant structure is covered by a thick and strong sealing substrate, followed by irradiation of ultraviolet light to harden the sealant, thereby sealing. 
         [0008]    However, such a typical sealing structure may not satisfy flexible bending characteristics which are recently required for organic light-emitting display devices. That is, recently, there is a demand for a flexible organic light-emitting display device with flexibility that is installed, even in a bending state. However, when the thick and strong glass substrate and the sealing substrate are used, such a demand may not be satisfied. 
         [0009]    Accordingly, to solve the problem, a thin film sealing structure using, instead of a glass substrate, a thin film layer formed of, for example, a polymer, has been disclosed. In detail, forming a display unit on a glass substrate and forming a thin film layer covering upper and lower portions of the display unit are respectively performed, and then, the glass substrate is separated from the resultant structure, thereby enabling sealing of the thin film layer with respect to the display unit. That is, the glass substrate functions as only a carrier substrate in the manufacturing procedure. 
         [0010]    However, the problem in this regard is that, when the glass substrate is separated from the thin film layer to manufacture such a thin film sealing structure, several kV or more of electrostaticity frequently occurs on the separation surface. In this case, the display unit may be highly likely to be damaged due to electrostaticity. Accordingly, there is a need to prevent this problem. 
       SUMMARY OF THE INVENTION 
       [0011]    Embodiments of the present invention provide a flexible organic light-emitting display device that has a flexible thin film sealing structure and is improved so that damage of a display unit due to electrostaticity is reduced, and a method of manufacturing the flexible organic light-emitting display device. 
         [0012]    According to an aspect of the present invention, there is provided a flexible organic light-emitting display device including: a first flexible substrate; a display unit formed on a surface of the first flexible substrate; an electrostaticity prevention layer formed on another surface of the first flexible substrate; and a second flexible substrate covering the display unit. 
         [0013]    The electrostaticity prevention layer may include a crystalline ITO layer, and the crystalline ITO layer may have a thickness of 200 nm or less. 
         [0014]    The first flexible substrate may include a first polymer layer and a first barrier layer which are sequentially stacked, and the second flexible substrate may include a second barrier layer and a second polymer layer which are sequentially stacked. 
         [0015]    The first flexible substrate may include a glass substrate having a thickness of 0.1 mm or less, and the second flexible substrate may include a barrier layer and a polymer layer sequentially stacked. 
         [0016]    According to another aspect of the present invention, there is provided a method of manufacturing a flexible organic light-emitting display device, the method including: sequentially forming a photolysis layer and an electrostaticity prevention layer on a carrier substrate; forming a first flexible substrate on the electrostaticity prevention layer; forming a display unit on the first flexible substrate; covering the display unit with the second flexible substrate; and, irradiating light to decompose the photolysis layer and to remove the carrier substrate. 
         [0017]    The photolysis layer may include a polyimide layer, and the polyimide layer may have a thickness of 100 nm or less. 
         [0018]    The electrostaticity prevention layer may include an ITO layer, and the ITO layer may have a thickness of 200 nm or less. 
         [0019]    Before the irradiating of light, the ITO layer may be an amorphous ITO layer, and after the irradiating of light, the ITO layer may turn into a crystalline ITO layer. 
         [0020]    The first flexible substrate may include a first polymer layer and a first barrier layer which are sequentially stacked, and the second flexible substrate may include a second barrier layer and a second polymer layer which are sequentially stacked. 
         [0021]    The first flexible substrate may include a glass substrate having a thickness of 0.1 mm or less, and the second flexible substrate may include a barrier layer and a polymer layer which are sequentially stacked. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    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: 
           [0023]      FIG. 1  is a cross-sectional view of a flexible organic light-emitting display device according to an embodiment of the present invention; 
           [0024]      FIGS. 2A to 2C  are views illustrating a method of manufacturing the flexible organic light-emitting display device of  FIG. 1 ; 
           [0025]      FIG. 3  is a flowchart of the method of manufacturing the flexible organic light-emitting display device of  FIG. 1 ; 
           [0026]      FIG. 4  is a cross-sectional view of a flexible organic light-emitting display device according to another embodiment of the present invention; 
           [0027]      FIGS. 5A to 5C  are views illustrating a method of manufacturing the flexible organic light-emitting display device of  FIG. 4 ; and 
           [0028]      FIG. 6  is a flowchart of the method of manufacturing the flexible organic light-emitting display device of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
         [0030]    Hereinafter, embodiments of the present invention are described in detail with reference to the attached drawings. 
         [0031]      FIG. 1  is a cross-sectional view of a flexible organic light-emitting display device according to an embodiment of the present invention. In the present embodiment, the flexible organic light-emitting display device is a top emission type display device. 
         [0032]    As illustrated in  FIG. 1 , the flexible organic light-emitting display device  100  according to the present embodiment includes a first flexible substrate  110  including a first polymer layer  111  and a first barrier layer  112 , a display unit  130  including, for example, a thin film transistor (not shown) and an emission layer (not shown), a second flexible substrate  120  including a second barrier layer  122  and a second polymer layer  121 , which are sequentially stacked in this order. That is, instead of a thick and strong glass substrate, the first and second flexible substrates  110  and  120 , respectively, including the polymer layers  111  and  121 , respectively, and the barrier layers  112  and  122 , respectively, are used to seal the display unit  130 , thereby embodying a sealing structure. 
         [0033]    An electrostaticity prevention layer  140  is formed on an outer surface of the first flexible substrate  110 . The electrostaticity prevention layer  140  is a crystalline ITO layer having low resistance, and the electrostaticity prevention layer  140  prevents the display unit  130  from being exposed to electrostaticity impacts. Originally, the electrostaticity prevention layer  140  is an amorphous ITO layer. However, when the electrostaticity prevention layer  140  absorbs light irradiated in the manufacturing procedure, the electrostaticity prevention layer  140  turned into crystalline with low resistance. This process will be described in detail later. 
         [0034]    In addition, the first polymer layer  111  of the first flexible substrate  110  may be formed of heat-resistant polyimide having a glass transition temperature of 500° C. or more, and the heat-resistant polyimide may be formed by polymerizing BPDA-biphenyl-tetracarboxylic acid dianhydride (3,3′,4,4′-biphenyl tetracarboxylic dianhydride) and p-phenylenediamine (PDA). A thickness of the first polymer layer  111  may be in a range of about 1 to 10 μm, and since the display unit  130  is stacked thereon, followed by a few exposing processes for patterning to prevent deterioration, the first polymer layer  111  may also have high heat resistance. Instead of a glass substrate, the first polymer layer  111  functions as a lower substrate, and is a very flexible thin film substrate having a thickness of about 1 to 10 μm. 
         [0035]    The first barrier layer  112  stacked on the first polymer layer  111  is a layer having a water repellent property for the prevention of permeation of external water molecules, and may be, for example, a multi-layered film formed of SiO/SiN. That is, SiO and SiN are deposited to form a multi-layered structure, and the first barrier layer  112  having such a multi-layered structure has a water vapor transmission rate of 10 −5  g/m 2 ·day or less. That is, the first barrier layer  112  has an excellent water repellent property. The first barrier layer  112  may be formed on the first polymer layer  111  by deposition. 
         [0036]    The second barrier layer  122  of the second flexible substrate  120  stacked on the display unit  130  is a layer having a water repellent property for the prevention of permeation of external water molecules, and may be, for example, a multi-layered film formed of SiO/SiN. That is, SiO and SiN are deposited to form a multi-layered structure, and the first barrier layer  112  having such a multi-layered structure has a water vapor transmission rate of 10 −5  g/m 2 ·day or less. That is, the first barrier layer  112  has an excellent water repellent property. 
         [0037]    The second polymer layer  121  formed on the second barrier layer  122  may be formed of a transparent polyimide having a glass transition temperature of 350° C. or more. The transparent polyimide may be a polymer of one or more selected from a dianhydride monomer, a diamine monomer, and an amide monomer. For example, the transparent polyimide may be a polymer of a dianhydride monomer and a diamine monomer, or a polymer of a dianhydride monomer and an amide monomer. Unlimiting examples of the dianhydride monomer are pyromellitic dianhydride (PMDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), and the like. An unlimiting example of the diamine monomer is trans-1,4-cyclohexanediamine (CHDA). An unlimiting example of the amide monomer is hexamethylphosphoramide (HMPA). Since the flexible organic light-emitting display device  100  is a top emission type display device, an image embodied by the display unit  130  may be viewed on the side of the second polymer layer  121 . Accordingly, the second polymer layer  121  needs to be a transparent layer that allows the image embodied by the display unit  130  to pass therethrough. Although a transparent polymer has a lower heat resistance than that of the first polymer layer  111  which is not transparent, the lower heat resistance is tolerable because, unlike the first polymer layer  111 , the second polymer layer  121  does not undergo a pattering process of the display unit  130 . In this regard, however, when the carrier substrate  160  is separated, the second polymer layer  121  may be exposed to ultraviolet light. Accordingly, the second polymer layer  121  needs to have a glass transition temperature of 350° C. or more to prevent damage thereof. Herein, although the heat resistance of the second polymer layer  121  is relatively lower than that of the first polymer layer  111 , the second polymer layer  121  is itself a heat resistance layer that endures a temperature of 350° C. 
         [0038]    A thickness of the second polymer layer  121  may be in a range of about 1 to 10 μm. Instead of a typical glass substrate, the second polymer layer  121  functions as an upper substrate, and may be a very flexible thin film substrate having a thickness of about 1 to 10 μm. 
         [0039]    The flexible organic light-emitting display device  100  having such a structure may be manufactured in the following processes. 
         [0040]      FIGS. 2A to 2C  are views illustrating a method of manufacturing the flexible organic light-emitting display device of  FIG. 1 , and  FIG. 3  is a flowchart of the method of manufacturing the flexible organic light-emitting display device of  FIG. 1 . 
         [0041]    First, as illustrated in  FIG. 2A , the carrier substrate  160  formed of a glass material is prepared ( FIG. 3 , block  300 ), and then, thin film layers are formed thereon. 
         [0042]    That is, first, a photolysis layer  150  formed of polyimide having a thickness of 100 nm or less is formed on the carrier substrate  160  ( FIG. 3 , block  301 ). The photolysis layer  150  is to be decomposed due to irradiation of laser light, and may function as a sacrificial layer for removing the carrier substrate  160 . 
         [0043]    Second as the electrostaticity prevention layer  140 , an amorphous ITO layer having a thickness of 200 nm or less is formed on the photolysis layer  150  ( FIG. 3 , block  302 ). That is, originally, ITO of the electrostaticity prevention layer  140  may be in an amorphous state. 
         [0044]    Subsequently, the first polymer layer  111  and the first barrier layer  112  of the first flexible substrate  110  are sequentially formed on the electrostaticity prevention layer  140  ( FIG. 3 , block  303 ), and then, the display unit  130  is patterned ( FIG. 3 , block  304 ). 
         [0045]    In addition, the second barrier layer  122  and the second polymer layer  121  of the second flexible substrate  120  are sequentially formed on the display unit  130  ( FIG. 3 , block  305 ). 
         [0046]    Once such a stack structure is manufactured, laser light is irradiated onto the entire surface of the carrier substrate  160 , as illustrated in  FIG. 2B  ( FIG. 3 , block  306 ). When irradiated, the photolysis layer  150  begins to be decomposed due to the laser light, and the amorphous ITO of the electrostaticity prevention layer  140  absorbs laser light so as to turn into crystalline ITO having low resistant characteristics. If the electrostaticity prevention layer  140  is not formed, laser light may reach up to the display unit  130 , thereby damaging the thin film transistor or the emission layer. However, since the electrostaticity prevention layer  140  absorbs energy of laser light, the damage due to the laser light may be prevented. 
         [0047]    Thereafter, as illustrated in  FIG. 2C , the carrier substrate  160  is separated from a main body ( FIG. 3 , block  307 ). In this regard, when the deposition of the photolysis layer  150  is completed, the carrier substrate  160  is naturally separated from the main body. Furthermore, when the electrostaticity prevention layer  140  is not formed, electrostaticity accumulated between the carrier substrate  160  and the first polymer layer  111  may be discharged during the separation process of the carrier substrate  160 , thereby damaging the display unit  130 . In the present embodiment, however, this problem can be solved because the electrostaticity prevention layer  140 , which has turned into a crystalline ITO layer having low resistance characteristics, prevents the accumulation of electrostaticity. That is, due to the electrostaticity prevention layer  140  having low resistance characteristics, electrostaticity disperses, instead of being accumulated between the carrier substrate  160  and the first polymer layer  111 , and accordingly, when the carrier substrate  160  is separated, an electrical impact of several kV or more on the display unit  130  occurring due to the all-at-once discharging of electrostaticity accumulated on the separation surface during the separation may be prevented. 
         [0048]    Regarding the organic light-emitting display devices  100  embodied as described above, a typical strong and thick glass substrate is replaced with the first and second flexible substrates  110  and  120  as a thin film layer. Accordingly, a flexible device may be obtained. In addition, since the first and second barrier layers  112  and  122  have a multi-layered film structure of SiO/SiN having a water vapor transmission rate of 10 −5  g/m 2 ·day or less, excellent water repellent properties may be obtained. 
         [0049]    Also, damage of the display unit  130  due to heat or electrostaticity impacts during the irradiation of laser light or the separation of the carrier substrate  160  may be prevented by the electrostaticity prevention layer  140 . In addition, since the electrostaticity prevention layer  140  prevents the accumulation of electrostaticity even during use of a final product, damages due to electrostaticity during use may be prevented. 
         [0050]    Also, in the present embodiment, materials for forming the first and second flexible substrates  110  and  120 , respectively, are not glass. However, as in an flexible organic light-emitting display device according to another embodiment of the present invention, a thin glass substrate having a thickness of 0.1 mm or less may be used as a first flexible substrate. That is, a glass substrate having a thickness of 0.1 mm or less is so thin that the glass substrate has flexible bending characteristics, although the glass substrate is formed of glass. Accordingly, a flexible organic light-emitting display device, including a first flexible substrate that is a thin glass substrate, may be embodied. 
         [0051]      FIG. 4  is a cross-sectional view of a flexible organic light-emitting display device according to another embodiment of the present invention,  FIGS. 5A to 5C  are views illustrating a method of manufacturing the flexible organic light-emitting display device of  FIG. 4 , and  FIG. 6  is a flowchart of the method of manufacturing the flexible organic light-emitting display device of  FIG. 4 . 
         [0052]    The flexible organic light-emitting display device  100 ′ of  FIG. 4  according to the present embodiment may be manufactured in the following processes. 
         [0053]    First, as illustrated in  FIG. 5A , the carrier substrate  160  formed of a glass material is prepared ( FIG. 6 , block  600 ), and then thin film layers are formed thereon. 
         [0054]    That is, first, the photolysis layer  150  formed of polyimide having a thickness of 100 nm or less is formed on the carrier substrate  160  ( FIG. 6 , block  601 ). The photolysis layer  150  is to be decomposed due to irradiation of laser light, and may function as a sacrificial layer for removing the carrier substrate  160 . 
         [0055]    Second, as the electrostaticity prevention layer  140 , an amorphous ITO layer having a thickness of 200 nm or less is formed on the photolysis layer  150  ( FIG. 6 , block  602 ). That is, originally, ITO of the electrostaticity prevention layer  140  may be in an amorphous state. 
         [0056]    Subsequently, a glass substrate having a thickness of 0.1 mm or less, which is the first flexible substrate  110 ′, is formed on the electrostaticity prevention layer  140  ( FIG. 6 , block  603 ), and then the display unit  130  is patterned ( FIG. 6 , block  604 ). 
         [0057]    In addition, the barrier layer  122  and the polymer layer  121  of the second flexible substrate  120  are sequentially formed on the display unit  130  ( FIG. 6 , block  605 ). 
         [0058]    Once such a stack structure is manufactured, as illustrated in  FIG. 4B , laser light is irradiated onto the entire surface of the carrier substrate  160  ( FIG. 6 , block  606 ). When irradiated, the photolysis layer  150  begins to be decomposed due to the laser light, and the amorphous ITO of the electrostaticity prevention layer  140  absorbs laser light so as to turn into crystalline ITO having low resistant characteristics. If the electrostaticity prevention layer  140  is not formed, laser light may reach up to the display unit  130 , thereby damaging the thin film transistor or the emission layer. However, since the electrostaticity prevention layer  140  absorbs energy of laser light, damage due to the laser light may be prevented. 
         [0059]    Thereafter, as illustrated in  FIG. 4C , the carrier substrate  160  is separated from a main body ( FIG. 6 , block  607 ). In this regard, when the deposition of the photolysis layer  150  is completed, the carrier substrate  160  is naturally separated from the main body. In this regard, when the electrostaticity prevention layer  140  is not formed, electrostaticity accumulated between the carrier substrate  160  and the first polymer layer  110  may be discharged during the separation process of the carrier substrate  160 , thereby damaging the display unit  130 . In the present embodiment, however, this problem can be solved because the electrostaticity prevention layer  140 , which has turned into a crystalline ITO layer having low resistance characteristics, prevents the accumulation of electrostaticity. That is, due to the electrostaticity prevention layer  140  having low resistance characteristics, electrostaticity disperses, instead of being accumulated between the carrier substrate  160  and the first polymer layer  110 , and accordingly, when the carrier substrate  160  is separated, an electrical impact of several kV or more on the display unit  130  occurring due to the all-at-once discharging of electrostaticity accumulated on the separation surface during the separation may be prevented. 
         [0060]    Regarding the organic light-emitting display devices  100 ′ according to the present embodiment, a typical strong and thick glass substrate is replaced with the very thin first flexible substrates  110 ′ and the second flexible substrate  120 . Accordingly, a flexible device may be obtained. In addition, since the second barrier layer  122  has a multi-layered film structure of SiO/SiN having a water vapor transmission rate of 10 −5  g/m 2 ·day or less, excellent water repellent properties may be obtained. 
         [0061]    Also, damage of the display unit  130  due to heat or electrostaticity impacts during the irradiation of laser light or the separation of the carrier substrate  160  may be prevented by the electrostaticity prevention layer  140 . In addition, since the electrostaticity prevention layer  140  prevents the accumulation of electrostaticity even during use of a final product, damage due to electrostaticity during use may be prevented. 
         [0062]    While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.