Patent Publication Number: US-2015069346-A1

Title: Organic light emitting diode display and manufacturing method thereof

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of Korean Patent Application No. 10-2013-0107983, filed on Sep. 9, 2013, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     1. Field 
     Exemplary embodiments of the present invention relate to an organic light emitting diode (OLED) display and a manufacturing method thereof. 
     2. Discussion of the Background 
     In general, a touch panel is a device for an image display device, e.g., an organic light emitting diode (OLED) display that recognizes a contact location corresponding to a character or an image displayed on a screen thereof, touched by a user hand or an object. 
     Particularly, an electrostatic capacity touch panel display device is manufactured by forming a capacitive pattern at an upper portion of a display panel thereof, and attaching a retardation film and a polarizing plate thereon, or by attaching the retardation film and the polarizing plate on an upper portion of the display panel, and attaching the capacitive pattern layer thereon. For the retardation film, a λ/4 retardation film is used to change linear polarization into circular polarization or change circular polarization into linear polarization. 
     However, the conventional methods have a problem of increasing an entire thickness of the display panel by forming an additional layer of the capacitive pattern at the upper portion. Further, the light emitted from an organic light emitting element may be absorbed by an electrode such as indium tin oxide (ITO) or the like which is additionally disposed at a front surface of an encapsulation film, thereby reducing the luminance of emitted light. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     Exemplary embodiments of the present invention provide an organic light emitting diode (OLED) display having a touch function and a manufacturing method thereof, having advantages of reducing thickness and weight of the OLED display and improving screen visibility. 
     Additional features of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. 
     An exemplary embodiment provides an OLED display including a display substrate, a display element layer disposed on the display substrate and comprising a plurality of pixels, a thin film encapsulation layer disposed on the display substrate and the display element layer, a retardation film disposed on the thin film encapsulation layer, a capacitive pattern disposed on the retardation film; a polarizing plate disposed on the capacitive pattern, and a window disposed on the polarizing plate. 
     An exemplary embodiment also provides a manufacturing method of an OLED display, including attaching a retardation film on a base substrate, forming a capacitive pattern on the retardation film, detaching the substrate and the retardation film from each other, and attaching a polarizing plate on the capacitive pattern. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention. 
         FIG. 1  is a cross-sectional view showing an organic light emitting diode (OLED) display in accordance with an exemplary embodiment. 
         FIG. 2  is a cross-sectional view schematically showing a structure of the OLED display in which a retardation film, a capacitive pattern, and a polarizing plate are stacked in accordance with the present exemplary embodiment. 
         FIG. 3  shows an equivalent circuit of the OLED display in accordance with the present exemplary embodiment. 
         FIG. 4  is a flowchart showing a manufacturing method of the OLED display in accordance with the present exemplary embodiment. 
         FIGS. 5A ,  5 B,  5 C, and  5 D are stepwise cross-sectional views showing the manufacturing method of the OLED display in accordance with the present exemplary embodiment. 
         FIG. 6  is a cross-sectional view schematically showing a structure of the OLED display in which a retardation film, a capacitive pattern, and a polarizing plate are stacked in accordance with another exemplary embodiment. 
         FIG. 7  is a cross-sectional view schematically showing a structure of the OLED display in which a retardation film, a capacitive pattern, and a polarizing plate are stacked in accordance with yet another exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, an exemplary embodiment will be described in detail with reference to the attached drawings such that the present invention can be easily put into practice by those skilled in the art. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
     In addition, in various exemplary embodiments, the same constituent elements are denoted by the same reference numerals and are representatively described in an exemplary embodiment, and different elements from the elements of the exemplary embodiment are described in other exemplary embodiments. 
     The drawings are schematic and are not illustrated in accordance with a scale. The relative sizes and ratios of the parts in the drawings are exaggerated or reduced for clarity and convenience in the drawings, and the arbitrary sizes are only exemplary and are not limiting. The same structures, elements, or parts illustrated in no less than two drawings are denoted by the same reference numerals in order to represent similar characteristics. When a part is referred to as being “on” another part, it can be directly on the other part or intervening parts may also be present. In contrast, when an element or layer is referred to as being “directly on” or “directly connected to” another element or layer, there are no intervening elements or layers present. It will be understood that for the purposes of this disclosure, “at least one of X, Y, and Z” can be construed as X only, Y only, Z only, or any combination of two or more items X, Y, and Z (e.g., XYZ, XYY, YZ, ZZ). 
     Exemplary embodiments are illustrated in detail. As a result, various modifications are expected to be made. Therefore, the exemplary embodiments are not limited to a specific shape of an illustrated region, but, for example, include changes in shape in accordance with manufacturing. 
     An organic light emitting diode (OLED) display in accordance with an exemplary embodiment will now be described with reference to  FIG. 1  and  FIG. 2 . 
       FIG. 1  is a cross-sectional view showing an organic light emitting diode (OLED) display in accordance with an exemplary embodiment, and  FIG. 2  is a cross-sectional view schematically showing a structure of the OLED display in which a retardation film, a capacitive pattern, and a polarizing plate are stacked in accordance with the present exemplary embodiment. 
     Referring to  FIG. 1  and  FIG. 2 , the OLED display  100  in accordance with the present exemplary embodiment includes a display substrate  10 , a display element layer  20 , a thin film encapsulation layer  30 , a retardation film  40 , a capacitive pattern  50 , a polarizing plate  60 , and a window  70 . 
     The display substrate  10  may be a liquid crystal display panel including a liquid crystal, or an organic light emitting panel including an organic light emitting unit. Alternatively, the display substrate  10  may be a transparent flexible substrate such as a polymer film. 
     The display element layer  20  is formed on the display substrate  10  and includes an element region in which an active element such as a thin film transistor (TFT) is formed and a light emitting region in which an emission layer is formed. The element region and the light emitting region may be located separately from each other or overlapping each other. 
     The thin film encapsulation layer  30  is formed on the display element layer  20  facing the display substrate  10 . The thin film encapsulation layer  30  can protect the display element layer  20  against oxygen and moisture from the outside. 
     The retardation film  40  is provided on the thin film encapsulation layer  30 . The retardation film  320  may be a λ/4 retardation film to change linear polarization into circular polarization or change circular polarization into linear polarization. The retardation film  40  may be a birefringence film, an alignment film of a liquid crystal polymer, or a film supported with the alignment layer of the liquid crystal polymer, formed by stretching the film made of at least one polymer of a polycarbonate, a polyvinyl alcohol, a polystyrene, a polymethylmethacrylate, a polypropylene, a polyolefin, a polyarylate, and a polyamide. Alternatively, the retardation film  40  may be formed of cyclic olefin polymer (COP), such as a Zeonor resin or an Arton resin. 
     The capacitive pattern  50  may be formed on the retardation film  40 . The capacitive pattern  50  may include a plurality of pattern units disposed in a matrix pattern, but is not limited thereto. 
     The polarizing plate  60  is provided on the retardation film  40  on which the capacitive pattern  50  is formed. The polarizing plate  60  may include a polarizer layer  62  and an upper support  64  formed on the polarizer layer  62 . The polarizing plate  60  may further include a lower support  66  formed below the polarizer layer  62 . The polarizer layer  62  may be formed of polyvinyl alcohol (PVA), and the lower support  66  and the upper support  64  may be formed of triacetyl cellulose (TAC). 
     The window  70  is attached on the polarizing plate  60 . The window  70  may be made of a transparent material to cover and protect the display element layer  20 . 
     The OLED display  100  may further include an adhesion layer  68  between the polarizing plate  60  and the capacitive pattern  50 . The adhesion layer  68  may be a pressure sensitivity adhesive layer (PSA) and be formed of a film including an adhesive agent to perform an adhering operation in response to a pressure transferred from the outside. The adhesive agent may include an acryl-based or rubber-based adhesive agent that has a refractive index in the range of 1.46 to 1.52, or an adhesive agent that includes particulates such as zirconia and the like in order to adjust the refractive index of the adhesive agent. 
       FIG. 3  shows an equivalent circuit of the OLED display in accordance with the present exemplary embodiment. 
     Referring to  FIG. 3 , the display element layer  20  includes a plurality of signal lines  121 ,  171 , and  172 , and a plurality of pixels PX connected to the signal lines  121 ,  171 , and  172  and arranged substantially in a matrix shape. 
     The signal lines  121 ,  171 , and  172  include a plurality of gate lines  121  transmitting a gate signal (or, scan signal), a plurality of data lines  171  transmitting a data signal, and a plurality of driving voltage lines  172  transmitting a driving voltage. The gate lines  121  are extended in a row direction and almost parallel with each other, and the data lines  171  and the driving voltage lines  172  are approximately arranged in a column direction and almost parallel with each other. 
     Each pixel PX includes a switching thin film transistor Qs, a driving thin film transistor Qd, a storage capacitor Cst, and an organic light emitting diode (OLED) LD. 
     The switching thin film transistor Qs includes a control terminal, an input terminal, and an output terminal. The control terminal is connected to the gate line  121 , the input terminal is connected to the data line  171 , and the output terminal is connected to the control terminal of the driving thin film transistor Qd. The switching thin film transistor Qs transmits a data signal applied to the data line  171  to the driving thin film transistor Qd in response to a scan signal applied to the gate line  121 . 
     The driving thin film transistor Qd includes a control terminal, an input terminal, and an output terminal. The control terminal is connected to the output terminal of the switching thin film transistor Qs, the input terminal is connected to the driving voltage line  172 , and the output terminal is connected to the anode of the OLED LD. The driving thin film transistor Qd transfers an output current I LD  of which magnitude varies depending on a voltage between the control terminal and the output terminal thereof. 
     The capacitor Cst is connected between the control terminal and the input terminal of the driving thin film transistor Qd. The capacitor Cst charges the data signal applied to the control terminal of the driving thin film transistor Qd and maintains the charge of the data signal after the switching thin film transistor Qs is turned off. 
     The OLED LD includes an anode connected to the output terminal of the driving thin film transistor Qd and a cathode connected to a common voltage Vss. The OLED LD emits light with intensity corresponding to the output current I LD  of the thin film transistor Qd to display an image. 
     The switching thin film transistor Qs and the driving thin film transistor Qd are n-channel field effect transistors (FETs). However, at least one of the switching thin film transistor Qs and the driving thin film transistor Qd may be a p-channel field effect transistor. Further, the thin film transistors Qs and Qd, the capacitor Cst, and the OLED LD may have different interconnection. 
       FIG. 4  is a flowchart showing a manufacturing method of the OLED display in accordance with the present exemplary embodiment, and  FIG. 5A  to  FIG. 5D  are stepwise cross-sectional views showing the manufacturing method of the OLED display in accordance with the present exemplary embodiment. 
     Referring to  FIG. 4  to  FIG. 5D , a retardation film  40  is first attached on a base substrate  80  (S 401 , see  FIG. 5A ). The base substrate  80  may be made of a bare glass material, and the retardation film  40  is attached on the base substrate  80  by using an adhesive  82 . 
     Thereafter, a capacitive pattern  50  is formed on the retardation film  40  (S 402 , see  FIG. 5B ). The capacitive pattern  50  may be obtained by forming an indium tin oxide (ITO) pattern and a plurality of openings at locations corresponding to the pixels of the organic light emitting element. The capacitive pattern  50  may include a plurality of pattern units disposed in a matrix pattern, but is not limited thereto. 
     Next, the base substrate  80  is detached from the retardation film  40  (S 403 , see  FIG. 5C ). Then, a polarizing plate  60  is attached on the capacitive pattern  50  by using an adhesion layer  68  (S 404 , see  FIG. 5D ). A protection film (not shown) may be attached beneath the retardation film  40  to prevent damage to the retardation film  40  caused by scratches and the like. The protective film may be an acetate-based resin such as triacetyl cellulose or a triacetyl cellulose film with surface saponified with an alkali and the like. The adhesion layer  68  may include an acryl-based or rubber-based adhesive agent that has a refractive index ranging from 1.46 to 1.52, or an adhesive agent that includes particulates such as zirconia and the like in order to adjust the refractive index of the adhesive agent. 
       FIG. 6  is a cross-sectional view schematically showing a structure of the OLED display in which a retardation film, a capacitive pattern, and a polarizing plate are stacked in accordance with another exemplary embodiment, and  FIG. 7  is a cross-sectional view schematically showing a structure of the OLED display in which a retardation film, a capacitive pattern, and a polarizing plate are stacked in accordance with yet another exemplary embodiment. 
     Referring to  FIG. 6  and  FIG. 7 , the polarizing plate  60  may include a polarizer layer  62  and an upper support  64  formed on the polarizer layer  62 , or may include the polarizer layer  62 , the upper support  64  formed on the polarizer layer  62 , and a lower support  66  formed below the polarizer layer  62 . The polarizer layer  62  may be formed of polyvinyl alcohol (PVA), and the lower support  66  and the upper support  64  may be formed of triacetyl cellulose (TAC). 
     According to the OLED display and the manufacturing method thereof in accordance with the exemplary embodiments, the capacitive pattern can be directly formed on the retardation film to thereby reduce thickness and weight of the OLED display and omit a capacitive pattern layer. Thus, light transmittance and screen visibility can be increased, and manufacturing cost can be reduced. 
     While this disclosure has been described in connection with what is presently considered to be practical 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.