Abstract:
A method of manufacturing a display device comprises the steps of: forming a protective film on a first surface of a first base substrate; forming a polarizer including a plurality of wire grid patterns provided on a second surface of the first base substrate facing the first surface; removing the protective film from the first surface; and forming a pixel array layer on the first surface.

Description:
CLAIM OF PRIORITY 
       [0001]    This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2015-0007291 filed on Jan. 15, 2015, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a method of manufacturing a display device, and more particularly, to a method of manufacturing a display device employing a wire grid polarizer. 
         [0003]    In general, metal wires arrayed spaced apart from each other selectively transmit or reflect polarized light of an electromagnetic wave. That is, when an arranging period of the metal wires is shorter than a period of a wavelength of an incident electromagnetic wave, a polarized light component parallel to the metal wires is reflected and a polarized light component vertical to the metal wires is transmitted. 
         [0004]    A polarizer having excellent polarized light efficiency, high transmittance, and a wide viewing angle may be manufactured by using this phenomenon, and this polarizer is called a wire grid polarizer. 
         [0005]    The wire grid polarizer is recently employed in display devices. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a method of manufacturing a device which may prevent a failure in a manufacturing process of a display device employing a wire grid polarizer. 
         [0007]    Embodiments of the invention provide methods of manufacturing a display device including: forming a protective film on a first surface of a first base substrate; forming a polarizer including a plurality of wire grid patterns provided on a second surface of the first base substrate facing the first surface; removing the protective film from the first surface; and forming a pixel array layer on the first surface. 
         [0008]    In other embodiments of the invention, methods of manufacturing a display device include: forming a protective film on a first surface of a first base substrate; forming a polarizer including a plurality of wire grid patterns provided on a second surface of the first base substrate facing the first surface; patterning the protective pattern to form a metal wire; and forming a pixel array layer on the metal wire. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the invention and, together with the description, serve to explain principles of the invention. In the drawings: 
           [0010]      FIG. 1  is a cross-sectional view illustrating a display device according to an embodiment of the invention; 
           [0011]      FIG. 2  is an equivalent circuit diagram of the pixel illustrated in  FIG. 1 ; 
           [0012]      FIG. 3  is a perspective view illustrating a polarizer illustrated in  FIG. 1 ; 
           [0013]      FIG. 4  is an enlarged view of portion “I” illustrated in  FIG. 3 ; 
           [0014]      FIGS. 5A to 5K  are process flow diagrams illustrating a manufacturing process of the first substrate illustrated in  FIG. 1 ; and 
           [0015]      FIGS. 6A to 6B  are process flow diagrams illustrating a manufacturing process of a display device according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Various modifications and variations can be made in the invention without departing from the spirit or scope of the invention. Exemplary embodiments of the invention will be described below in more detail with reference to the accompanying drawings. It should be understood, however, that it is not intended to limit the invention to the particular form disclosed, but rather it is intended that the invention cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims. 
         [0017]    In the drawings, like reference numerals refer to like elements throughout. In the drawings, the dimensions of layers and regions are exaggerated for clarity of illustration. Although terms like “first” and “second” are used to describe various components, the components are not limited to these terms. These terms are used only to differentiate one component from another one. For example, without departing from the scope of the invention, a first element could be termed a second element, and similarly a second element could be termed a first element. The terms of a singular form may include plural forms unless referred to in the contrary. 
         [0018]    Throughout the specification, when it is said that a part “includes” or “has”, it means that the part may be further intended to designate features, integers, steps, operations, elements, components, or the combination thereof. Furthermore, it means that one or more other features, integers, steps, operations, elements, parts or combinations thereof, or the additional possibility, are not precluded. It will also be understood that, when a layer, a film, a region, or a plate is referred to as being ‘on’ another layer, film, region, or plate, it can be directly on the other layer, film, region, or plate, or intervening layers, films, regions, or plates may also be present. Furthermore, it will be understood that, when a layer, a film, a region, or a plate is referred to as being ‘under’ another layer, film, region, or plate, it can be directly under the other layer, film, region, or plate, and one or more intervening layers, films, regions, or plates may also be present. 
         [0019]      FIG. 1  is a cross-sectional view illustrating a display device according to an embodiment of the invention and  FIG. 2  is an equivalent circuit diagram of the pixel illustrated in  FIG. 1 . 
         [0020]    Referring to  FIG. 1 , a display device  600  according to an embodiment of the invention includes a backlight unit  500  emitting light and a display panel  300  displaying an image by using the light. 
         [0021]    The backlight unit  500  includes a light source (not shown) emitting light, a light guide plate  510  receiving the light from the light source so as to guide the light toward the display panel  300 , and a reflector  520  reflecting leaked light from the light guide plate  510  so that the leaked light is re-incident toward the light guide plate  510 . 
         [0022]    The backlight unit  500  is provided adjacent to a rear surface of the display panel  300 , and the light guide plate  510  is formed in a size corresponding to the display panel  300  so as to emit the light toward a front surface. The reflector  520  is provided in a size corresponding to a bottom surface of the light guide plate  510 , and is formed of a material having high reflectivity so as to reflect the light leaked through the bottom surface. 
         [0023]    The display panel  300  includes a first substrate  350 , a second substrate  380  facing the first substrate  350 , and a liquid crystal layer  390  interposed between the first substrate  350  and the second substrate  380 . 
         [0024]    The first substrate  350  includes a first base substrate  310 , a pixel array layer  340  provided on a first surface  311  of the first base substrate  310 , and a polarizer  320  provided on a second surface  312  of the first base substrate  310  facing the first surface  311 . 
         [0025]    The display panel  300  is divided into a display area DA and a non-display area NDA. The polarizer  320  includes a plurality of wire grid patterns provided on the second surface  312  corresponding to the display area DA. The polarizer  320  may further include a reflective pattern  324  provided on the second surface  312  corresponding to the non-display area NDA. 
         [0026]    As for the wire grid patterns  323 , among the light provided from the backlight unit  500 , an S wave that is a polarized light component parallel to an extension direction of the wire grid patterns  323  is reflected by a metal property (e.g., aluminum) of the wire grid patterns  323 , and a P wave that is a polarized light component parallel to a direction perpendicular to the extension direction of the wire grid patterns  323  is recognized as an effective refractive medium to be transmitted. 
         [0027]    The reflective pattern  324  is formed of a material having high reflectivity such as aluminum, thus being able to reflect the light provided from the backlight unit  500 . Light reflected through the reflective pattern  324  is reflected by the reflector  520  of the backlight unit  500  so as to be re-incident toward the display panel  300 . Accordingly, light use efficiency may be improved by the reflective pattern  324  of the polarizer  320 . 
         [0028]    The reflective pattern  324  is formed in a size corresponding to the non-display area NDA, thus reflecting incident light toward the non-display area NDA so as to be reused. Accordingly, an amount of light that is re-incident toward the display area DA is increased by the reflective pattern  324 , and therefore, light use efficiency of the display device  600  may be improved by the reflective pattern  324 . 
         [0029]    The display device  600  may further include a transparent protective film  335  formed on the polarizer  320 . The transparent protective film  335  may be formed of any one of TiOx and AlOx. 
         [0030]    The display panel  300  may include a plurality of pixels, a plurality of gate lines, and a plurality of data lines. Each of the plurality of pixels includes a thin film transistor TR, a liquid crystal capacitor Clc, and a storage capacitor Cst. The storage capacitor Cst may be omitted. 
         [0031]      FIG. 2  illustrates an equivalent circuit diagram of a (i×j)-th pixel of the plurality of pixels. In the (i×j)-th pixel, the thin film transistor TR is connected to the i-th gate line GLi of the plurality of gate lines and the j-th data line of the plurality of data line DLj. Thus, the thin film transistor TR responds to a gate signal received from the i-th gate line GLi so as to output a pixel voltage corresponding to a data signal received from the j-th data line DLj. 
         [0032]    The liquid crystal capacitor Clc is charged with a pixel voltage output from the pixel transistor TR. An arrangement of liquid crystal molecules included in the liquid crystal layer  390  is changed according to the charge amount charged in the liquid crystal capacitor Clc. Transmittance of incident light into the liquid crystal layer  390  is adjusted according to the arrangement of liquid crystal molecules. 
         [0033]    The storage capacitor Cst is connected in parallel with the liquid crystal capacitor Clc. The storage capacitor Cst allows the arrangement of the liquid crystal molecules to be maintained for a certain period. 
         [0034]    The pixel array layer  340  may include a thin film transistor TR, an interlayer insulating layer  346 , and a pixel electrode  347  which constitute each pixel. Furthermore, the pixel array layer  340  may include a plurality of gate lines and a plurality of data lines. The thin-film transistor TR may include a gate electrode  341 , a source electrode  344 , and a drain electrode  345 . Specifically, the gate electrode  341  is formed on the first surface  311  of the first base substrate  310 , and the gate electrode  341  is branched off from a corresponding gate line. The plurality of gate lines and the gate electrode  341  are covered by the gate insulating layer  342 . A semiconductor layer  343  is formed on the gate insulating layer  342  corresponding to the gate electrode  341 , and the source electrode  344  and the drain electrode  345  are disposed on the semiconductor layer  343  spaced apart at a predetermined distance from each other. 
         [0035]    The interlayer insulating film  346  is formed on the gate insulating film  342  for covering the thin film transistor TR, and the pixel electrode  347  is formed on the interlayer insulating film  346 . A contact hole  346   a  exposing the drain electrode  345  of the thin film transistor TR is formed on the interlayer insulating film  346 , and the pixel electrode  247  may be electrically connected to the drain electrode  345  through the contact hole  346   a.    
         [0036]    The structure of the pixel array layer  340  illustrated in  FIG. 1  is presented as an embodiment of the invention, and the invention is not limited thereto. 
         [0037]    The second substrate  380  includes a second base substrate  360 , a color filter layer  371 , and a black matrix  372 . The second base substrate  360  is disposed so as to face the first base substrate  310 , and the black matrix  372  is provided on the second base substrate  360  corresponding to the non-display area NDA. The color filter layer  371  includes red, green and blue color pixels, and each of the color pixels at least corresponds to the display area DA. However, each of the color pixels may overlap the black matrix  372 . 
         [0038]    The second substrate  380  further includes an overcoat layer  373  and a common electrode  374 . The overcoat layer  373  is an insulating layer formed so as to reduce a step difference between the black matrix  372  and the color filter layer  371 , and the common electrode  374  is formed on the overcoat layer  373  and faces the pixel electrode  347  so as to form the liquid crystal capacitor Clc. 
         [0039]    The liquid crystal layer  390  is provided between the first substrate  350  and the second substrate  380 . Liquid crystal molecules in the liquid crystal layer  390  may be arranged according to magnitude of an electric field formed between the pixel electrode  347  and the common electrode  374 . 
         [0040]    Furthermore, a dichroic polarizer  400  is provided on the display panel  300 . The dichroic polarizer  400  is made in the form of a sheet so as to be able to be attached on the display panel  300 . A polarization axis of the dichroic polarizer  400  may be parallel or perpendicular to the extending direction of the wire grid patterns  323  of the polarizer  320 . 
         [0041]      FIG. 3  is a perspective view illustrating the polarizer illustrated in  FIG. 1  and  FIG. 4  is an enlarged view of portion “I” illustrated in  FIG. 3 . 
         [0042]    Referring to  FIGS. 3 and 4 , according to one embodiment of the invention, the polarizer  320  includes the plurality of wire grid patterns  323  provided on the second surface  312  of the first base substrate  310 . 
         [0043]    The first base substrate  310  may be a substrate of a material through which light is transmittable, for example, silicon. In addition, the first base substrate  310  may be a substrate having a rectangular shape. 
         [0044]    Each of the wire grid patterns  323  is extended long in a first direction D 1 . The first direction D 1  may be a direction parallel to two sides parallel to each other of the four sides of the first base substrate  310 . In addition, the wire grid patterns  323  are arranged in parallel with each other, and spaced apart at a predetermined interval from each other in the second direction D 2  perpendicular to the first direction D 1 . 
         [0045]    The polarizer  320  polarizes incident light Li through the wire grid patterns  323 . An S wave among the incident light Li is a polarized light component parallel to an extension direction (that is, the first direction D 1 ) of the wire grid patterns  323 , and is reflected by a metal property of the wire grid patterns  323 . A P wave among the incident light Li is a polarized light component parallel to a direction (that is, the second direction D 2 ) perpendicular to the extension direction of the wire grid patterns  323 , and is recognized as an effective refractive medium to be transmitted. 
         [0046]    When “T” is an arrangement period of the wire grid patterns  323  and a wavelength of the incident light Li is shorter than an arrangement period T, reflection and transmission occurring according to a polarized light component. 
         [0047]      FIGS. 5A to 5K  are process flow diagrams illustrating a manufacturing process of the first substrate illustrated in  FIG. 1 . 
         [0048]    Referring to  FIG. 5A , a protective layer  330  is formed on the first surface  311  of the first base substrate  310 . The protective layer  330  may be formed of a metal material. In one embodiment of the invention, the protective layer  330  may be formed of molybdenum, aluminum (Al) or an alloy thereof. 
         [0049]    As illustrated in  FIG. 5B , a metal layer  313  is formed on the second surface  312  of the first base substrate  310 . The metal layer  313  may be formed of aluminum (Al). As illustrated in  FIG. 5C , photoresist patterns  314  are formed on the metal layer  313 . In one embodiment of the invention, the photoresist patterns  314  are provided in correspondence with the non-display area NDA, and the photoresist patterns  314  are not provided in the display area DA. 
         [0050]    Referring to  FIG. 5D , a space between the photoresist patterns  314  is filled with a copolymer layer  315 . Herein, the copolymer layer  315  may be formed at a smaller height than the height of each of the photoresist patterns  314 . In one embodiment of the invention, the copolymer layer  315  includes a first polymer and a second polymer which are distributed in unspecified directions. The first and second polymers may be poly methylmethacrylate (PMMA) and poly styrene (PS), respectively. 
         [0051]    When heat-treated, the copolymer layer  315  is phase separated into the first and second polymers  316  and  317 , respectively, as illustrated in  FIG. 5E . In particular, the first and second polymers  316  and  317 , respectively, may be alternately arranged between two photoresist patterns  314 . 
         [0052]    Then, when any one of the first and second polymers  316  and  317  is removed, the remaining one type polymers are spaced apart from each other between the two photoresist patterns  314  to form a nano-grid pattern  318  as illustrated in  FIG. 5F . In one embodiment of the invention, the first polymer  316  formed of PMMA is removed and the second polymer  317  may be left to form the nano-grid pattern  318 . 
         [0053]    Thereafter, the metal layer  313  is etched by using the nano-grid pattern  318  and the photoresist patterns  314  as masks. Then, the wire grid patterns  323  and the reflective pattern  324  are formed on the second surface  312  as illustrated on  FIG. 5G . 
         [0054]    Referring to  FIG. 5H , the photoresist pattern  314  and the nano-grid pattern  318  which remain on upper surfaces of the wire grid patterns  323  and the reflective pattern  324  may be removed through a strip process. Thus, the polarizer  320  is formed on the second surface  312  of the first base substrate  310 . 
         [0055]    Referring to  FIG. 5I , a transparent protective film  335  may be further formed on the polarizer  320 . The transparent protective film  335  may be formed of any one of TiOx and AlOx. The transparent protective film  335  may protect the polarizer  320  from a subsequent process. 
         [0056]    As illustrated on  FIG. 5J , the protective film  330  on the first surface  311  of the first base substrate  310  is removed through an etching process. The protective film  330  is formed to prevent a failure in which a foreign substance is adsorbed on the first surface  311  or a scratch occurs on the first surface  311  in a process of forming the polarizer  320  on the second surface  312  of the first base substrate  310 . The protective film  330  may be formed on the first surface  311  in advance before a process of forming the polarizer  320  on the second surface  312  starts, and the protective film  330  may be removed from the first surface  311  through the etching process after the process of forming the polarizer  320  is completed. 
         [0057]    Thereafter, when the protective film  330  is removed, a process for forming a pixel array layer  340  on the first surface  311  of the first base substrate  310  is performed as illustrated  FIG. 5K . Detailed description of the specific process steps of the pixel array layer  340  will be omitted. 
         [0058]      FIGS. 6A to 6B  are process flow diagrams illustrating a manufacturing process of a display device according to another embodiment of the invention. However, since a process of forming the polarizer  320  on the second surface  312  of the first base substrate  310  is the same as illustrated in  FIGS. 5A to 5I , a description of the process of forming the polarizer  320  will be omitted to avoid repetition. 
         [0059]    Referring to  FIG. 6A , when the step of forming the polarizer  320  on the second surface  312  of the first base substrate  310  is completed, the protective film  330  (see  FIG. 5I ) formed on the first surface  311  of the first base substrate  310  is patterned. The protective film  330  may be formed of a metal material such as aluminum, molybdenum, or an alloy thereof. Gate lines GLi and GLi+1 and gate electrodes  341  may be formed on the first surface  311  by patterning the protective film  330 . 
         [0060]    In consideration of a wire resistance, when it is intended to form the gate lines GLi and GLi+1 and the gate electrode  341  in a double layer or triple layer, the protective film  330  may be formed in a double layer or triple layer in the step of forming the protective layer  330 . 
         [0061]    When the gate lines GLi and GLi+1 and the gate electrodes  341  are formed by patterning the protective film  330 , the step (that is, illustrated in the  FIG. 5J ) of completely etching the protective layer  330  may be omitted. Furthermore, a step of depositing a metal layer for forming the gate lines GLi and GLi+1 and gate electrodes  341  may be omitted in the process of forming the pixel array layer  340 . 
         [0062]    Even when a scratch or foreign substance absorption on the protective film  330  occurs in the process of forming the polarizer  320 , most of the scratch or foreign absorption substances are removed through the patterning process, and also when the protective film  330  is formed in a double layer or a triple layer, the scratch or the like occurring on the gate lined GLi and GLi+1 does not result in a failure. 
         [0063]    According to embodiments of the invention, a protective film is formed on the first surface before a process of forming a polarizer on the second surface of the first base substrate starts, thus preventing a failure in which a foreign substance is absorbed on the first surface or a scratch occurs on the first surface in a process of manufacturing the polarizer. 
         [0064]    Therefore, failure occurrence in a process of forming a pixel array layer on the first surface may be prevented. 
         [0065]    The above-disclosed subject matter is to be considered illustrative and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments which fall within the true spirit and scope of the invention. Thus, to the maximum extent allowed by law, the scope of the invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.