Abstract:
A flat panel display includes a first substrate, a thin film transistor formed on the first substrate, a second substrate facing the first substrate, and a light controller formed on the second substrate, wherein the light controller is electrically connected to the thin film transistor, wherein the light controller includes an opening plate having a plurality of first openings and a light blocker moving horizontally with respect to the opening plate to selectively pass light through the first openings.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to Korean Patent Application No. 10-2008-0115690 filed on Nov. 20, 2008, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    (a) Technical Field 
         [0003]    The present disclosure relates to a flat panel display and a manufacturing method thereof, and more particularly to a flat panel display having an electro mechanical light controller and a manufacturing method thereof. 
         [0004]    (b) Discussion of the Related Art 
         [0005]    As currently popular flat panel displays, there are a liquid crystal display (LCD), a plasma display device (PDP), an organic light emitting device (OLED), a field effect display (FED), and an electrophoretic display device. 
         [0006]    Among them, the liquid crystal display is widely used as a monitor and a television, the plasma display device is used as a television of a large size, and the organic electric field emissive display device is used for a window of a mobile phone, but research on applying it to a display device of a medium size and a large size has been actively undertaken. Research on applying the electric field effect display device or the electrophoretic display to a monitor, a television, or electric paper has been undertaken. However, the display devices that are currently known each have their drawbacks. Particularly, the liquid crystal display has drawbacks such as a narrow viewing angle, a slow response speed, and low efficiency. As a flat panel display without these drawbacks, a flat panel display having merits such as high photo-efficiency and a high speed switching characteristic, and based on a micro electromechanical system (MEMS) has been researched. 
         [0007]    The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention 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 OF THE INVENTION 
       [0008]    According to an exemplary embodiment of the present invention, a flat panel display includes a first substrate, a thin film transistor formed on the first substrate, a second substrate facing the first substrate, and a light controller formed on the second substrate, wherein the light controller is electrically connected to the thin film transistor, wherein the light controller includes an opening plate having a plurality of first openings and a light blocker moving horizontally with respect to the opening plate to selectively pass light through the first openings. 
         [0009]    The thin film transistor may include a gate electrode, a source electrode, and a drain electrode, and a protrusion electrode connected to the drain electrode. 
         [0010]    The first substrate may further include a protrusion, and the protrusion electrode is formed on the protrusion. 
         [0011]    The light blocker can be formed on an inner surface of the second substrate and between the first substrate and the second substrate. 
         [0012]    The light blocker may include a light blocking portion having a plurality of second openings and a blocking portion, an electrode providing an electric force to horizontally move the light blocking portion, and a restoring portion providing a restoring force to move the light blocking portion to an original position. 
         [0013]    The light blocking portion can be separated from the second substrate by a predetermined interval. 
         [0014]    The electrode may include a first supporter formed on the second substrate, a flexible beam connected to the first supporter and curved with a bow shape, and a connection beam separated from the flexible beam by a predetermined interval and connected to the light blocking portion. 
         [0015]    The first supporter may contact the protrusion electrode. 
         [0016]    An electric signal of the protrusion electrode can be transmitted to the electrode through the first supporter. 
         [0017]    The flat panel display may further comprise a second supporter supporting the second connection beam. 
         [0018]    The opening plate can be formed on an outer surface of the second substrate. 
         [0019]    The first substrate and the light blocking portion can maintain an interval by the height of the protrusion. 
         [0020]    A transmittance of light passing through the first openings can be controlled by controlling respective positions of the second openings by the movement of the light blocker. 
         [0021]    According to an exemplary embodiment of the present invention, a method for manufacturing a flat panel display comprises forming a thin film transistor on a first substrate, forming a protrusion electrode connected to the thin film transistor, forming an opening plate having a plurality of first openings on a first surface of a second substrate, and forming a light blocker having a first supporter on a second surface of the second substrate. 
         [0022]    The method may further comprise combining the first substrate and the second substrate by contacting the protrusion electrode with the first supporter of the light blocker. 
         [0023]    The method may further comprise forming the light blocker comprises turning over the second substrate and mounting the second substrate on a stage. 
         [0024]    The first surface can be separated from a bottom surface of the stage by a predetermined interval. 
         [0025]    The opening plate can be formed by using a printing roller. 
         [0026]    The opening plate can be formed by a selection printing through a surface treatment. 
         [0027]    Forming the light blocker may include forming a buffer layer having a plurality of holes, forming the light blocker inside the plurality of holes, and removing the buffer layer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    Exemplary embodiments of the present invention can be understood in more detail from the following descriptions taken in conjunction with the accompanying drawings, in which: 
           [0029]      FIG. 1  is a layout view of a first substrate of a flat panel display according to an exemplary embodiment of the present invention; 
           [0030]      FIG. 2  is a cross-sectional view of the first substrate taken along the line II-II′ of  FIG. 1  according to an exemplary embodiment of the present invention; 
           [0031]      FIG. 3  is a perspective view of a second substrate of a flat panel display according to an exemplary embodiment of the present invention; 
           [0032]      FIG. 4  is a cross-sectional view of the second substrate taken along the line IV-IV′ of  FIG. 3  and a first substrate disposed thereon according to an exemplary embodiment of the present invention; 
           [0033]      FIG. 5  to  FIG. 8  show a method of forming a second substrate in a flat panel display according to an exemplary embodiment of the present invention; and 
           [0034]      FIG. 9  shows a method of combining a first substrate and a second substrate of a flat panel display according to an exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0035]    The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. 
         [0036]    It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. 
         [0037]      FIG. 1  is a layout view of a first substrate of a flat panel display according to an exemplary embodiment of the present invention.  FIG. 2  is a cross-sectional view of the first substrate taken along the line II-II′ of  FIG. 1  according to an exemplary embodiment of the present invention. 
         [0038]    Referring to  FIG. 1  and  FIG. 2 , a blocking layer  111  comprising silicon oxide (SiOx) or silicon nitride (SiNx) is formed on a first transparent insulation substrate  110 . The blocking layer  111  improves cohesion between the insulation substrate  110  and a polysilicon layer  150 , and can prevent a conductive impurity existing in the first transparent insulation substrate  110  from being diffused into the polysilicon layer  150 . 
         [0039]    The polysilicon layer  150  including a source region  153 , a drain region  155 , a channel region  154 , and a lightly doped extrinsic region  152  is formed on the blocking layer  111 . 
         [0040]    The lightly doped extrinsic region  152  prevents leakage current or punch-through. The source region  153  and the drain region  155  are doped with N-type or P-type conductive impurities with a high concentration, and the channel region  154  is not doped with impurities. 
         [0041]    A gate insulating layer  140  is formed on the polysilicon layer  150 . 
         [0042]    A gate line  121  extending in one direction is formed on the gate insulating layer  140 . A portion of the gate line  121  is extended thereby overlapping the channel region  154  of the second polysilicon layer  150 . The extended portion of the gate line  121  is used as a gate electrode  124  of a thin film transistor. One end of the gate line  121  may have a wider area than the width of the gate line  121  for a connection with an external circuit. 
         [0043]    A storage electrode line  131  for increasing storage capacitance of a pixel is formed parallel to the gate line  121 . In an exemplary embodiment, the storage electrode line  131  can comprise a same material as the gate line  121 . A portion of the storage electrode line  131  overlapping the polysilicon layer  150  is a storage electrode  133 . The polysilicon layer  150  overlapping the storage electrode  133  is a storage electrode region  157 . 
         [0044]    The gate line  121  and the storage electrode line  131  may include a conductive layer having low resistance such as, for example, aluminum (Al), an aluminum-based metal, aluminum alloys, silver (Ag), a silver-based metal, or silver alloys. The gate line  121  and the storage electrode line  131  may have a multilayered structure including a conductive layer having good electrical and physical contact characteristics with a different material such as, for example, ITO or IZO. The conductive layer of the multilayered structure can be such as, for example, chromium (Cr), titanium (Ti), tantalum (Ta), molybdenum (Mo), or alloys thereof. In an exemplary embodiment, a molybdenum-tungsten (MoW) alloy can be used as the conductive layer of the multilayered structure. An example of a combination of the lower layer and the upper layer in the multilayered structure may be chromium/aluminum-neodymium (Nd) alloy. 
         [0045]    An interlayer insulating layer  601  is formed on the gate insulating layer  140  where the gate line  121  and the storage electrode line  131  are formed. The interlayer insulating layer  601  may comprise double layers of SiO 2 /SiN. When the interlayer insulating layer  601  comprises SiO 2 /SiN, the reliability of the thin film transistor is improved as compared to when the interlayer insulating layer  601  comprises a single layer of SiO 2 . 
         [0046]    The interlayer insulating layer  601  includes first and second contact holes  141  and  142  respectively exposing the source region  153  and the drain region  155 . 
         [0047]    A protrusion  161  having a height d 1  is formed on the interlayer insulating layer  601 . A data line  171  intersecting the gate line  121  is formed on the interlayer insulating layer  601 . A portion or a branch of the data line  171  is connected to the source region  153  through the first contact hole  141 . The portion connected to the source region  153  is used as a source electrode  173  of the thin film transistor. One end of the data line  171  may be wider than the width of the data line  171  for a connection with an external circuit. 
         [0048]    A drain electrode  175  connected to the drain region  155  through the second contact hole  142  is formed with the same layer as the data line  171 , and is separated from the source electrode  173  by a predetermined distance. The drain electrode  175  is extended on the protrusion  161 , thereby forming a protrusion electrode  175   a.  The protrusion electrode  175   a  may be formed through photolithography according to an exemplary embodiment of the present invention. 
         [0049]    The data line  171  and the drain electrode  175  may comprise a conductive layer having good electrical and physical contact characteristics with ITO or IZO. The data line  171  and the drain electrode  175  may comprise such as, for example, a molybdenum-based metal or a molybdenum alloy. In an exemplary embodiment, the conductive layer may comprise a molybdenum-tungsten (MoW) alloy. The data line  171  and the drain electrode  175  may include a conductive layer having low resistance such as an aluminum-based metal aluminum alloys, a silver-based metal or silver alloys. The data line  171  and the drain electrode  175  may have a multilayered structure including the conductive layer having low resistance and a different conductive layer comprising chromium (Cr), titanium (Ti), tantalum (Ta), molybdenum (Mo), and alloys thereof. In an exemplary embodiment, the different conductive layer can be a molybdenum-tungsten (MoW) alloy. 
         [0050]    In an exemplary embodiment of the present invention, the thin film transistor comprises the polysilicon layer  150 . In an exemplary embodiment, the thin film transistor comprises an amorphous silicon layer. 
         [0051]      FIG. 3  is a perspective view of a second substrate of a flat panel display according to an exemplary embodiment of the present invention.  FIG. 4  is a cross-sectional view of the second substrate shown in  FIG. 3  taken along the line IV-IV and a first substrate disposed thereon according to an exemplary embodiment of the present invention. 
         [0052]    Referring to  FIG. 3  and  FIG. 4 , light controllers controlling the transmittance of light through a mechanical operation are formed on a second transparent insulation substrate  210 . The light controllers include an opening plate  220  formed on one surface of the second transparent insulation substrate  210 , and a light blocker  300  formed on the other surface of the second transparent insulation substrate  210 . The opening plate  220  is formed on the outside surface of the second transparent insulation substrate  210 , and the light blocker  300  is formed on the surface facing the first transparent insulation substrate  110 . 
         [0053]    A plurality of first openings  221  are formed in the opening plate  220 , and light generated from a light source is transmitted through the first openings  221 . An absorption layer for suppressing reflection of external light may be coated on the outside surface of the opening plate  220 , and a reflection layer for reflecting the light may be coated on the surface contacting the second transparent insulation substrate  210 . 
         [0054]    The light blocker  300  includes a light blocking portion  334 , electrodes  348 ,  346 , and  336 , and a restoring portion  337 . The electrodes  348 ,  346  and  336  move the light blocking portion  334  using an electrical attraction or repulsive force. The restoring portion  337  move the light blocking portion  334  into the original position through an elastic force. The light blocking portion  334  is disposed in the pixel area for displaying the images, and the electrodes  348 ,  346 , and  336  and the restoring portion  337  are disposed corresponding to the region where the gate line  121  and the data line  171  of the first substrate are disposed. 
         [0055]    In an exemplary embodiment, the light blocking portion  334  has a plate shape, and includes a plurality of second openings  333  and a blocking portion  332 . The second openings  333  may comprise the same shape and size as the first openings  221 . The light blocking portion  334  is separated from the second insulation substrate  210  by the distance d 2  to move horizontally. 
         [0056]    The electrodes  348 ,  346 , and  336  include a first supporter  348  formed on the second insulation substrate  210 , a flexible beam  346  connected to the first supporter  348 , and a connection beam  336  disposed apart from the flexible beam  346  by a predetermined interval. The first supporter  348  contacts the protrusion electrode  175   a.  Accordingly, the data voltage signal applied to the protrusion electrode  175   a  is transmitted to the flexible beam  346  through the first supporter  348 . The light blocking portion  334  is separated from the interlayer insulating layer  601  of the first substrate by the distance d 1  through the protrusion electrode  175   a  to move horizontally. 
         [0057]    One end of the flexible beam  346  is fixed to the first supporter  348 , and the other end of the flexible beam  346  is extended with, for example, a bow shape from the first supporter  348  such that the other end may be freely moved. 
         [0058]    One end of the connection beam  336  is connected to the light blocking portion  334 , and the other end of the connection beam  336  is fixed to a second supporter  358  disposed on the second insulation substrate  210  such that the light blocking portion  334  is separated from the second insulation substrate  210  by the predetermined interval, thereby being floated. The second supporter  358  is applied with a predetermined voltage. 
         [0059]    In an exemplary embodiment, the restoring portion  337  having a spring function has, for example, a cross shape to have elasticity. One end of the restoring portion  337  is connected to the light blocking portion  334 . The other end of the restoring portion  337  contacts a third supporter  338 . The restoring portion  337  having a function of a spring is manufactured with the cross shape in the present exemplary embodiment, but may be manufactured with shapes of various springs. 
         [0060]    The other end of the flexible beam  346  pushes the connection beam  336  by the electrical force of the data voltage transmitted to the flexible beam  346  through the first supporter  348  and the predetermined voltage transmitted to the connection beam  336  through the second supporter  358 , such that the light blocking portion  334  connected to the connection beam  336  is horizontally moved. Then, the restoring portion  337  is contracted, thereby having the restoring force. When a voltage difference exists between the flexible beam  346  and the connection beam  336 , the light blocking portion  334  returns to its original position by the restoring force of the restoring portion  337 . 
         [0061]    Accordingly, the light blocking portion  334  is horizontally moved such that the portion of the second opening  333  may be controlled. The position of the second opening  333  of the light blocking portion  334  is aligned to be accorded with the position of the first opening  221  of the opening plate  220  such that the transmittance of light passing through the first opening  221  may be controlled. In the flat panel display according to an exemplary embodiment of the present invention, the light controllers controlling the transmittance of the light by the mechanical operation are manufactured through a micro electro-mechanical system (MEMS) such that the light usage efficiency is higher than in the liquid crystal display that controls the arrangement of liquid crystal. That is, the light incident to the first opening  221  from the light source is not influenced by the light path unlike the liquid crystal display. The light loss by the first insulation substrate  110  and the second insulation substrate  210  comprising a transparent glass, and the influence of interference and diffraction between neighboring pixels may be ignored such that most of the light is vertically incident Accordingly, in exemplary embodiments of the present invention, the light usage efficiency is increased, and thereby the power consumption is reduced. 
         [0062]    In a conventional art, a spacer having a thickness of 10 μm must be formed between the substrate including the light blocker  300  and the substrate including the opening plate  220  for preventing an obstacle to the horizontal operation of the light blocker  300 , however the thickness of the spacer is thick compared with the fact that it is possible for the column spacer to be formed to a maximum of 5 μm in a manufacturing process of the liquid crystal display in this case, and a large quantity of spacers must be formed to maintain a uniform interval between the substrate formed with the light blocker  300  and the substrate formed with the opening plate  220  such that there is a difficulty in terms of manufacturing process. In an exemplary embodiment, the light blocker  300  and the opening plate  220  are respectively formed on both surfaces of the second transparent insulation substrate  210 , and the protrusion electrode  175   a  is formed on the substrate formed with the thin film transistor such that the space for the horizontal operation of the light blocker  300  by the protrusion electrode  175   a  is provided. Accordingly, the process for forming the spacer to maintain the interval between the light blocker  300  and the opening plate  220  is omitted, thereby simplifying the manufacturing process. 
         [0063]    The light blocker  300  and the opening plate  220  are respectively formed on both surfaces of one second transparent insulation substrate  210  such that the light passing through the light blocker  300  and the light incident to the opening plate  220  progress through the second insulation substrate  210  as the same medium. Accordingly, the progressing path between the light passing through the light blocker  300  and the light incident to the opening plate  220  is not changed, such that an oil injection process to accord the refractive index between different mediums may be omitted, thereby simplifying the manufacturing process. 
         [0064]      FIG. 5  to  FIG. 8  show a method of forming a second substrate in a flat panel display according to an exemplary embodiment of the present invention.  FIG. 9  shows a method of combining a first substrate and a second substrate of a flat panel display according to an exemplary embodiment of the present invention. 
         [0065]    Referring to  FIG. 1  and  FIG. 2 , a thin film transistor including the gate electrode  124 , the source electrode  173 , the drain electrode  175 , and the protrusion electrode  175   a  are formed on a first insulation substrate  110  to form a first substrate. 
         [0066]    Referring to  FIG. 5 , an opening plate  220  including a plurality of first openings  221  is formed on one surface of the second transparent insulation substrate  210 . The opening plate  220  may be formed by printing the first opening  221  on one surface of the transparent second insulation substrate  210  by using, for example, a printing roller that can be transcribed. A micro-contact printing device including protrusions and depressions with a hydrophilic material formed on the surface thereof contacts one surface of the second transparent insulation substrate  210  to attach the hydrophilic material to the one surface of the second transparent insulation substrate  210 . The hydrophilic material is adhered to one surface of the second insulation substrate  210  through a surface treatment such that the opening plate  220  having the first openings  221  may be formed In an exemplary embodiment, a method for forming the opening plate  220  can include disposing a film including the first opening on the second transparent insulation substrate  210 . 
         [0067]    Referring to  FIG. 6 , the second insulation substrate  210  formed with the opening plate  220  is turned over and is loaded on a stage  500 . An edge of the second insulation substrate  210  contacts a supporter  510  that is formed with, for example, a step shape inside the stage  500 . Accordingly, the surface of the opening plate  220  is separated from the surface  520  of the stage  500  by the interval d 3  such that damage to the opening plate  220  may be prevented when the light blocker  300  is formed on the second transparent insulation substrate  210 . 
         [0068]    Referring to  FIG. 7 , a buffer layer  10  is formed on the other surface of the second insulation substrate  210 . Supporting holes  11  and  12  to form the first supporter  348  and the third supporter  338  are respectively formed on the buffer layer  10 . A supporting hole to form the second supporter  358  is formed. The light blocker  300  comprising metal is formed on the buffer layer  10  and inside the supporting holes  11  and  12 . The light blocker  300  includes the light blocking portion  334 , electrodes  348 ,  346 , and  336  for providing an elastic force to horizontally move the light blocking portion  334 , and the restoring portion  337  for providing a restoring force to restore the light blocking portion  334  to the original position of the light blocking portion  334 . The light blocker  300  may be formed, for example, through electrolysis or electroless plating, or through deposition and photolithography of a thin film. 
         [0069]    Referring to  FIG. 8 , the buffer  10  is removed through an etching process to form a second substrate in which the light blocking portion  334  is separated from the second transparent insulation substrate  210 . Conventionally, the thin film transistor and the light blocker  300  are formed together on one substrate such that the process for forming a thick polymer layer on the thin film transistor is added to separate the thin film transistor and the light blocker  300  from each other and to planarize the surface of the thin film transistor Accordingly, the flat panel display becomes thick, the process is complicated, and the light blocker  300  is poorly manufactured when the planarization is deteriorated. 
         [0070]    In an exemplary embodiment, the thin film transistor  124 ,  171 , and  175  and the light blocker  300  are respectively formed on separate substrates such that the planarization process of the substrate formed with the thin film transistor is eliminated to thereby simplify the manufacture process, and a thick polymer layer separating the thin film transistor and the light blocker  300  can be omitted. 
         [0071]    Referring to  FIG. 9 , the first substrate formed with the thin film transistor  124 ,  171 , and  175  and the protrusion electrode  175   a,  and the second substrate formed with the light blocker  300  and the opening plate  220 , are combined. The protrusion electrode  175   a  contacts the first supporter  348  of the light blocker  300 . 
         [0072]    Conventionally, there is an overlapping region where the first opening  221  of the opening plate  220  and the second opening  333  of the light blocker  300  are overlapped with each other to smooth an alignment error in the process of attaching the substrate formed with the light blocker  300  and the substrate formed with the opening plate  220 . When the overlapping region is increased, the opening region through which the light passes is decreased to thereby deteriorate the light usage efficiency. In an exemplary embodiment, the light blocker  300  and the opening plate  220  are respectively formed on both surfaces of the second transparent insulation substrate  210  such that the alignment between the light blocker  300  and the opening plate  220  is simple, thereby reducing the overlapping region and maximizing the light usage efficiency. 
         [0073]    Although the exemplary embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the present invention should not be limited to those precise embodiments and that various other changes and modifications may be affected therein by one of ordinary skill in the related art without departing from the scope or spirit of the invention. All such changes and modifications are intended to be included with the scope of the invention as defined by the appended claims.