Patent Publication Number: US-2007099318-A1

Title: Mold for display device and method for manufacturing display device using the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority from Korean Patent Application No. 2005-0104510, filed on Nov. 2, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
     FIELD OF INVENTION  
      The present invention relates to a method for manufacturing display devices and, more particularly, to the manufacture of reflective and transreflective display devices.  
     DESCRIPTION OF THE RELATED ART  
      In general, a display device can be classified as a light-transmitting type, a transflective type or a reflection type. In the light-transmitting type of display, a backlight unit is disposed behind a display panel and light emitted from the backlight unit is transmitted through the panel. The reflection type display device uses outside light and eliminates the backlight unit which consumes 70% of the entire electric power of the device. The transflective type display device combines the advantages of both types of display, utilizing both outside light and the backlight unit to provide good brightness regardless of a variation of the ambient luminous intensity.  
      In the manufacture of the transflective type and the reflection type of display devices, a passivation layer is formed on a substrate on which a thin film transistor is formed and a concave-convex pattern is formed on the passivation layer. If the reflective layer is formed on the entire surface of the concave-convex pattern, the reflection type display device is obtained and, if the reflective layer is formed partially on the concave-convex pattern, the transflective type of device is obtained.  
      To make the concave-convex pattern, a mold on which concaves-convexes are formed is arranged on the passivation layer and pressurized to form the concave-convex pattern.  
      However, there are problems that it is sometimes difficult to separate the mold from the passivation layer causing the shape of the mold to become deformed, making for poor reproducibility of the concave-convex pattern. To reduce the deforming of the mold, a supporting layer may be formed on the other surface of the mold. However, the difference between the coefficients of thermal expansion of the supporting layer and other part of the mold tend to deform the mold into a dish shape which also makes for poor reproducibility. Further, the dish shape may prevent a portion of the passivation layer from being removed from the mold.  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an aspect of the present invention to provide a better method for molding the concave-convex pattern used in a reflective or transreflective display device. The method for manufacturing a display device, comprises; providing an insulating substrate; forming a passivation layer on the insulating substrate; arranging a mold including a supporting layer, a pattern forming layer provided on a first surface of the supporting layer and having concaves-convexes formed thereon and a buffer layer formed on the other surface of the supporting layer so that the pattern forming layer faces the passivation layer; and pressurizing the mold to form a concave-convex pattern corresponding to the concaves-convexes on the passivation layer.  
      According to an aspect of the present invention, the method for manufacturing the display device further comprises forming gate wires extended in a first direction on the insulating substrate and data wires intersecting insulatively gate wires to define a pixel area before forming the passivation layer; and forming a thin film transistor at an intersection area of gate wires and data wires, wherein the concaves-convexes are provided to correspond to at least a portion of the pixel area.  
      According to an aspect of the present invention, the thin film transistor comprises a source electrode and a drain electrode spaced apart from the source electrode to define a channel region, the pattern forming layer comprises a protrusion part protruded from a first surface of the pattern forming layer, and an end portion of the protrusion part is contacted with the drain electrode when the mold is pressurized.  
      According to an aspect of the present invention, the method for manufacturing the display device further comprises forming a pixel electrode on the passivation layer after removing the mold; and forming a reflective layer on at least some portion of the pixel electrode.  
      According to an aspect of the present invention, the passivation layer contains polymer and is cured by at least one of heat and light.  
      According to an aspect of the present invention, the passivation layer is cured when the mold is pressurized.  
      According to an aspect of the present invention, the pattern forming layer and the buffer layer comprise the same material.  
      According to an aspect of the present invention, a coefficient of thermal expansion of the buffer layer is substantially the same as that of the pattern forming layer.  
      According to an aspect of the present invention, a modulus of elasticity of the buffer layer is substantially the same as that of the pattern forming layer.  
      According to an aspect of the present invention, a value obtained from multiplying the thickness of the buffer layer by a coefficient of thermal expansion of the buffer layer is 80% to 120% of a value obtained from multiplying the thickness of the pattern forming layer by a coefficient of thermal expansion of the pattern forming layer.  
      According to an aspect of the present invention, the supporting layer comprises a film comprising at least one of polyethylene terephthalate (PET) and polycarbonate (PC)  
      According to an aspect of the present invention, the mold a transparent material through which light is transmitted.  
      The foregoing and/or other aspects of the present invention can be achieved by providing a mold for a display device, comprising: a supporting layer; a pattern forming layer provided on a first surface of the supporting layer and having concaves-convexes formed thereon; and a buffer layer formed on a second surface of the supporting layer.  
      According to an aspect of the present invention, the pattern forming layer and the buffer layer comprise the same material.  
      According to an aspect of the present invention, a coefficient of thermal expansion of the buffer layer is substantially the same as that of the pattern forming layer.  
      According to an aspect of the present invention, a modulus of elasticity of the buffer layer is substantially the same as that of the pattern forming layer.  
      According to an aspect of the present invention, a value obtained from multiplying the thickness of the buffer layer by a coefficient of thermal expansion of the buffer layer is 80% to 120% of a value obtained from multiplying the thickness of the pattern forming layer by a coefficient of thermal expansion of the pattern forming layer.  
      According to an aspect of the present invention, the concaves-convexes comprise a concave lens shape.  
      According to an aspect of the present invention, the concaves-convexes comprise an embossing shape.  
      According to an aspect of the present invention, the pattern forming layer further comprises a protrusion part protruded from the surface of the pattern forming layer.  
      According to an aspect of the present invention, the supporting layer is a film comprising at least one of polyethylene terephthalate (PET) and polycarbonate (PC)  
      According to an aspect of the present invention, the pattern forming layer, the supporting layer and the buffer layer comprise transparent material through which light is transmitted.  
      According to an aspect of the present invention, at least one of the pattern forming layer and the buffer layer comprise polydimethylsiloxane (PDMS). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The foregoing and other aspects and advantages of the prevent invention will become apparent from a reading of the ensuing description, together with the drawing, in which:  
       FIG. 1  is a view showing an arrangement of a thin film transistor substrate according to an embodiment of the present invention;  
       FIG. 2  is a sectional view, taken along line II-II in  FIG. 1 ;  
       FIGS. 3A  through  FIG. 3C  are sectional views sequentially illustrating a method for manufacturing the liquid crystal display device according to the embodiment of the present invention;  
       FIGS. 4   a  and  FIG. 4   b  are sectional views of a conventional mold used for manufacturing a liquid crystal display device; and  
       FIG. 5   a  and  FIG. 5   b  are sectional views of a mold used for manufacturing the liquid crystal display device according to the embodiment of the present invention. 
    
    
     DESCRIPTION OF THE EMBODIMENTS  
      In the following description, if a layer is said to be formed ‘on’ another layer, then a third layer may be disposed between the two layers or the two layers may be contacted with each other. In other words, 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. Further, if a layer is said to be formed ‘directly on’ another layer, then the two layers are contacted with each other.  FIG. 1  is a view showing an arrangement of a thin film transistor substrate according to an embodiment of the present invention, and  FIG. 2  is a sectional view taken along line II-II in  FIG. 1 .  
      In the ensuing description, a liquid crystal display device is illustrated as one example among the various flat display devices. However, the present invention is not limited thereto and is applicable to other flat display device such as an organic light emitting diode device (OLED), a plasma display panel (PDP) and the like. In addition, in the embodiment of the present invention, although the transflective type liquid crystal display device is described as one example, the present invention is applicable to the reflection type liquid crystal display device.  
      A liquid crystal display device  1  according to the present invention comprises a liquid crystal panel. The liquid crystal panel comprises a thin film transistor substrate  100  (hereinafter, referred to as “first substrate) provided with a thin film transistor (TFT) for controlling and driving each pixel, a color filter substrate  200  (hereinafter, referred to as “second substrate”) facing and attached to the first substrate  100 , and a liquid crystal layer  300  located between the substrates  100  and  200 .  
      The first substrate  100  comprises a first insulating substrate  110 ; a plurality of gate wires  121 ,  122  and  123  and a plurality of data wires  161 ,  162 ,  163  and  164  formed on the first insulating substrate  110  in the form of a matrix; a thin film transistor (TFT) T which is a switching element formed at an intersection portion of gate wires  121 ,  122 ,  123  and data wires  161 ,  162 ,  163 ,  164 ; and a pixel electrode  180  connected to the thin film transistor T. A signal voltage is applied to the liquid crystal layer  300  formed between pixel electrode  180  and a common electrode  250  of the color filter substrate  200  (to be described below) through the thin film transistor T. The molecules of the liquid crystal layer  300  are arranged according to the applied signal voltage, varying the light transmissivity of the liquid crystal layer.  
      A substrate made of insulating material such as glass, quartz, ceramic or plastics or the like can be used as the first insulating substrate  110 . The first insulating substrate  110  may be made of a plastic material to make the liquid crystal display device  1  flexible. Suitable plastic material may include polycarbonate, polyimide, polynorborene (PNB), polyether sulfone (PES), polyarylate (PAR), polyethylenaphthalate (PEN) or polyethylene terephthalate (PET). The first insulating substrate  110  is divided into a display region on which an image is formed and a peripheral region disposed around the display region. Various lines and the thin film transistor described below are provided on the display region.  
      Gate wires  121 ,  122  and  123  are formed on the first insulating substrate  110 . Gate wires  121 ,  122  and  123  may be one-layered or multiple-layered. Gate wires  121 ,  122  and  123  comprises the gate line  121  extended in a transverse direction, a gate electrode  122  connected to the gate line  121  and a gate pad  123  provided at an end portion of the gate line  121  and connected to a gate driving circuit (not shown) for receiving a driving signal.  
      A gate insulating layer  130  made of silicon nitride (SiN x ) and the like covers gate wires  121 , 122  and  123 .  
      A semiconductor layer  140  made of a semiconductor such as amorphous silicon and the like is formed on the gate insulating layer  130 , and an ohmic contact layer  150  made of n+ hydrogenated amorphous silicon doped with n type impurity with high concentration are formed on the semiconductor layer  140 . A portion of the ohmic contact layer  150  corresponding to a channel section formed between the source electrode  162  and the drain electrode  163  is removed.  
      Data wires  161 ,  162 ,  163  and  164  are formed on the ohmic contact layer  150  and the gate insulating layer  130 . Data wires  161 ,  162 ,  163  and  164  may also be one-layered or multi-layered and comprise metal. Data wires  161 ,  162 ,  163  and  164  comprises a data line  161  formed in the lengthwise direction and intersecting the gate line  121  to form the pixel, a source electrode  162  which is a branch of the data line  161  and extended to an upper side of the ohmic contact layer  150 , the drain electrode  163  separated from the source electrode  162  and contacted with an upper portion of the ohmic contact layer  150  formed at an opposite side of the source electrode  162 , and the data pad  164  provided at an end portion of the data line  161  and connected to the data driving circuit (not shown) for receiving an image signal.  
      A passivation layer  170  is formed on data wires  161 ,  162 ,  163  and  164  and a portion of the semiconductor layer  140  which is not covered with data wires  161 ,  162 ,  163  and  164 .  
      A concave-convex pattern  175 , a drain contact hole  171  through which the drain electrode  163  is exposed, a gate pad contact hole  172  connecting the gate line  121  to the gate driving circuit (not shown) for applying a driving signal to the gate line  121 , and a data pad contact hole  173  connecting the data line  161  to the data driving circuit (not shown) for applying a driving signal to the data line  161  are formed in passivation layer  170 . The concave-convex pattern  175  formed on a surface of passivation layer  170  is provided such that the concave-convex pattern  175  corresponds to the display area of the first insulating substrate  110  and formed for causing light scattering to increase a reflecting efficiency and enhance a reflectance of the light toward the front. Here, to secure a reliability of the thin film transistor T, an inorganic insulating layer such as a silicon nitride layer can be formed between passivation layer  170  and the thin film transistor T.  
      Pixel electrode  180  is formed on passivation layer  170  on which the concave-convex pattern  175  is formed. Typically, pixel electrode  180  is formed from transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). Pixel electrode  180  is connected electrically to the drain electrode  163  through the drain contact hole  171 . Contact subsidiary layers  181  and  182  are formed on the gate pad contact hole  172  and the data pad contact hole  173 , respectively. In general, the contact subsidiary layers  181  and  182  are also formed from transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). A concave-convex pattern is formed on pixel electrode  180  by the underlying concave-convex pattern  175 .  
      A reflective layer  190  is formed on an upper surface of pixel electrode  180 . Here, the pixel area formed by the gate line  121  and the data line  161  is divided into a light-transmitting area on which the reflective layer  190  is not formed and a reflective area on which the reflective layer  190  is formed. The light emitted from a backlight unit (not shown) is penetrated through the light-transmitting area on which the reflective layer  190  is not formed and then radiated to an outside of the liquid crystal panel  10 , the light radiated from an outside is reflected on the reflective area on which the reflective layer  190  is formed and then radiated again to an outside of the liquid crystal panel  10 . The reflective layer  190  may be formed of aluminum or silver, and may be formed of a double-layered structure of aluminum layer/molybdenum layer. The reflective layer  190  is formed on pixel electrode  180 . In another embodiment, the reflective layer  190  may not formed in the drain contact hole  171 . A concave-convex pattern is formed on the reflective layer  190  by the underlying concave-convex pattern formed on a surface of pixel electrode  180 .  
      Below, the second substrate  200  is described. Black matrixes  220  are formed on the second insulating substrate  210 . The second insulating substrate  210  is divided into a display region on which an image is formed and a peripheral region provided around the display region. The black matrix  220  and a color filter  230  described below are provided on the display region. The black matrix  220  generally divides the red-colored filter, the green-colored filter and the blue-colored filter and blocks the light radiated directly to the thin film transistor T formed on the first substrate  100 . In general, the black matrix  220  is made from a photosensitive organic material containing black pigment. Carbon black or titanium oxide is used as the black pigment  
      Color filter  230  comprises repeatedly arranged red-colored filters, green-colored filters and blue-colored filters. The color filter  230  converts the light radiated from the backlight unit (not shown) and penetrated through the liquid crystal layer  300  to a colored light. In general, the color filter  230  is made from a photosensitive organic material.  
      An overcoating layer  240  is formed on the color filter  230  and a portion of the black matrix  220  which is not covered with the color filter  230 . The overcoating layer  240  is formed for planarizing the color filter  230  and protecting the color filter  230 . The overcoating layer  240  generally comprises an acrylic epoxy material.  
      Common electrode  250  is formed on the over coating layer  240 . The common electrode  250  is formed from transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The common electrode  250  and pixel electrode  180  apply the voltage to the liquid crystal layer  300 .  
      A liquid crystal is disposed between the first substrate  100  and the second substrate  200  to form the liquid crystal layer  300 . The substrates  100  and  200  are bonded to each other by sealant (not shown).  
      Below, the method for manufacturing the liquid crystal display device according to one embodiment of the present invention is described mainly explaining the method for manufacturing a thin film transistor substrate.  
      First, as shown in  FIG. 1  and  FIG. 2 , a gate wires forming layer is deposited on the first insulating substrate  110  and patterned through a photolithography process using a mask to form gate wires  121 ,  122 ,  123  including the gate line  121 , the gate electrode  122  and the gate pad  123 . Then, the gate insulating layer  130 , the semiconductor layer  140  and the ohmic contact layer  150  are formed sequentially.  
      Then, the semiconductor layer  140  and the ohmic contact layer  150  are photolithographed to form the semiconductor layer  140  on the gate insulating layer  130  formed on the gate electrode  122 . Here, the ohmic contact layer  150  is formed on the semiconductor layer  140 .  
      Then, data wires forming layer is deposited and patterned through a photolithography process using a mask to form the date wires  161 ,  162 ,  163  and  164  including the data conductor  161  intersecting the gate line  121 , the source electrode  162  connected to the data line  161  and extended to an upper side of the gate electrode  122 , the drain electrode  163  faced to the source electrode and the data pad  164  provided at an end portion of the data line  161 . Next, a portion of the ohmic contact layer  150  which is not covered with the date wires  161 ,  162 , 163  and  164  is etched, and so the ohmic layer  150  is divided into two parts with the gate electrode  122  as a center and a portion of the semiconductor layer  140  is exposed therebetween. In this process, almost all of the ohmic layer  150  is removed and some of the semiconductor layer  140  is etched. It is preferable to carry out an oxygen plasma treatment process to stabilize an exposed surface of the semiconductor layer  140 .  
      Next, passivation layer  170  is formed through a spin coating or a slit coating. At this time, in order to secure the reliability of the thin film transistor T, an inorganic insulating layer such as a silicon nitride layer can be further formed between the passivation  170  and the thin film transistor T.  
      Here, passivation layer  170  may comprise polymer and can be cured by heat and/or ultraviolet rays.  
      Subsequently, as shown in  FIG. 3   a , a mold  400  is arranged and disposed on passivation layer  170 . The mold  400  is provided with concaves-convexes  415  corresponding to the display region. The concaves-convexes  415  of the mold  400  may be provided to correspond to each pixel area or may be provided to correspond to the entire surface of the display region regardless of the pixel area. The mold  400  is arranged and disposed such that the concaves-convexes  415  face passivation layer  170 .  
      The mold  400  used in the method for manufacturing the liquid crystal display device according to the present invention comprises a supporting layer  420 , a pattern forming layer  410  provided on one surface of the supporting layer  420  and having the concaves-convexes  415  formed thereon and a buffer layer  430  formed on the other surface of the supporting layer  420 . The pattern forming layer  410  further comprises a protrusion part  417  formed on and protruded from the surface on which the concaves-convexes  415  are formed.  
      The concaves-convexes  415  are formed on surface of the pattern forming layer  410 . A concave-convex pattern  175  corresponding to the concaves-convexes  415  is formed on passivation layer  170  by the concaves-convexes  415 . The protrusion part  417  of the pattern forming layer  410  forms the drain contact hole  171  through which at least portion of the drain electrode  163  is exposed. It is desirable that the protrusion part  417  has a height such that the end of the protrusion part  417  and the drain electrode  163  come in contact with each other when the mold  400  is pressurized. The pattern forming layer  410  is made from soft material so as to make the mold  400  contact uniformly with passivation layer  170  and so that mold  400  can be used repeatedly. In addition, the pattern forming layer  410  may be made from material through which ultraviolet rays can penetrates and may be made of PDMS (polydimethylsiloxane).  
      The supporting layer  420  reduces the difficulty of releasing the mold  400  from passivation layer  170  caused by the characteristics of the material of the pattern forming layer  410  and the deformation of the shape of the pattern forming layer  410  when the mold  400  is released. Since the deformation of the mold  400  is minimized by the supporting layer  420 , the misalignment of the mold  400  and damage to the shape of the concave-convex pattern  175  are reduced. The supporting layer  420  may be a film comprising at least one of polyethylene terephthalate (PET) and polycarbonate (PC).  
      Since the material used for forming the pattern forming layer  410  has the coefficient of thermal expansion which differs from that of material used for forming the supporting layer  420 , the shape of the mold  400  may be deformed into a dish shape or an overturned dish shape. The buffer layer  430  prevents the shape of the mold  400  from being deformed. When different materials are in a surface contact in the mold  400  and heat is applied to the mold  400 , the shape of the mold  400  is deformed since the materials have different coefficients of thermal expansion. If the coefficient of thermal expansion of the lower layer is larger than that of the upper layer, the shape of the mold  400  is deformed into a dish shape. If the coefficient of thermal expansion of the lower layer is smaller than that of the upper layer, a shape of the mold is deformed into an overturned dish shape. Due to such deformation, the reproducibility and yield of the concave-convex pattern  175  becomes poor. Further, the end portion of the protrusion part  417  may not make contact with the drain electrode  163  so that a contact failure occurs or an additional subsequent process for removing the remained layer is required to be performed. The buffer layer  430  reduces the deforming force, which is caused by the difference between the coefficients of thermal expansion of the pattern forming layer  410  and the supporting layer  420  and makes the degree of lateral expansion of the layers  410  and  420  different, so that the shape deformation of mold  400  is reduced.  
      It is desirable that the pattern forming layer  410  and the buffer layer  430  are formed from materials which have substantially the same coefficient of thermal expansion and modulus of elasticity so as to minimize deformation of the shape of mold  400 . The thickness of the buffer layer  430  can be determined in inverse proportion to the coefficient of thermal expansion of the pattern forming layer  410 . That is, if a coefficient of thermal expansion of the pattern forming layer  410  is smaller than that of the buffer layer  430 , it is possible to minimize shape deformation of the mold  400  by increasing the thickness of the buffer layer  430 . Here, in order to minimize shape deformation of the mold  400 , a value obtained from multiplying the thickness by the coefficient of thermal expansion of the buffer layer  430  can be 80% to 120% of the value obtained from multiplying the thickness by the coefficient of thermal expansion of the pattern forming layer  410 . The buffer layer  430  can be formed of transparent material through which ultraviolet rays can penetrate. For one example, polydimethylsiloxane (PDMS) may be used for forming the buffer layer  430 .  
      As shown in  FIG. 3B , the mold  400  is pressurized toward passivation layer  170  to form the concave-convex pattern  175  on the surface of passivation layer  170 . The mold  400  and the first insulating substrate  110  may be pressurized against each other. When the mold is pressurized, light and heat is applied to cure passivation layer  170  during pressurizing. The passivation layer  170  may contain a thermo-initiator or a photo-initiator.  
      Then, as shown in  FIG. 3C , the mold  400  is removed. Since the mold  400  comprises the supporting layer  420 , it is easy to release the mold  400  from passivation layer  170 . Since the mold comprises the buffer layer  430 , the deformation of the mold  400  shape is minimized. Accordingly, the reproducibility and yield of the concave-convex pattern  175  are improved. Since the shape deformation of the mold  400  is minimized, the end portion of the protrusion part  417  make contact with the drain electrode  163  to accurately and reliably form drain contact hole  171  through which the drain electrode  163  is exposed. Passivation layer  170  does not remain on the drain electrode  163  so that contact failure does not occur thereby eliminating the need for a subsequent process to remove a portion of the passivation layer. Here, a mold release agent may be applied on a surface of the mold  400 .  
      After providing passivation layer  170  on which the concave-convex pattern  175  is formed, ITO or IZO is deposited on passivation layer  170  and photolithographed to form pixel electrode  180  which is connected to the drain electrode  163  through the drain contact hole  171 . Pixel electrode  180  has a concave-convex pattern formed by the underlying concave-convex pattern  175  of passivation layer  170 . At the same time, the contact subsidiary layers  181  and  182 , which are connected to the gate pad  123  and the data pad  164  through the gate pad contact hole  172  and the data pad contact hole  173 , respectively, are formed.  
      After pixel electrode  180  is formed, a reflective layer forming layer is deposited on pixel electrode  180  and patterned to form the reflective layer  190 . Silver, chrome or alloy thereof can be used for the reflective layer  190 . However, an aluminum layer or a double layered structure comprising an aluminum/molybdenum layer can be used as the reflective layer  190 . The reflective layer  190  is formed on the reflective area and is not formed on the light-transmitting area. The reflective layer  190  also has a concave-convex pattern formed by the concave-convex pattern  175  as described above. The reflective layer  190  receives the electrical signal through pixel electrode  180  and this signal is transmitted to the liquid crystal layer  300  disposed on the reflective layer  190 .  
      Then, an alignment film (not shown) is formed to provide the thin film transistor substrate  100  according to the embodiment of the present invention.  
      The black matrix  220 , the color filter  230 , the overcoating layer  240 , the common electrode  250  and the alignment film (not shown) are formed on the second insulating substrate  210  by the known method to complete the second substrate  200 . The first and second substrates  100  and  200  provided as described above are bonded to each other and the liquid crystal is injected into a gap between two substrates  100  and  200  to complete the liquid crystal panel  1 .  
      Hereinafter, the mold for manufacturing the liquid crystal display device according to another purpose of the present invention is described.  FIG. 4   a  and  FIG. 4   b  are sectional views of the conventional mold used for manufacturing the liquid crystal display device, and  FIG. 5   a  and  FIG. 5   b  are sectional views of a mold used for manufacturing the liquid crystal display device according to the embodiment of the present invention.  
      As shown in  FIG. 4A , the conventional mold  400  comprises the pattern forming layer  410  on which the concaves-convexes  415  are formed and the supporting layer  410  formed on the pattern forming layer  410 . The pattern forming layer  410  further comprises the protrusion part  417  formed on and protruded from one surface on which the concaves-convexes  415  are formed.  
      The mold  400  as described above is arranged and disposed on passivation layer  170  and then pressurized to form the concave-convex pattern  175  on passivation layer  170 . As shown in  FIG. 4B , however, in the conventional mold  400 , since the pattern forming layer  410  is face-to-face contacted with the supporting layer  420  and the materials used for forming both layers  410  and  420  have coefficients of thermal expansion which differ from each other, a shape of the mold  400  is deformed when heat is applied. If the coefficient of thermal expansion of the pattern forming layer  410  which is a lower layer is lager than that of the supporting layer  420 , a shape of the mold  400  is deformed into a dish shape, and if the coefficient of thermal expansion of the pattern forming layer  410  is smaller than that of the supporting layer  420 , the shape of the mold  400  is deformed into an overturned dish shape. The above phenomenon is called as the OPD (out of distortion). Due to the OPD, passivation layer  170  corresponding to a central portion of the mold  400  differs from other portion thereof corresponding to an edge portion of the mold  400  in the thickness. Due to such shape deformation of the mold  400 , the reproducibility and yield of the concave-convex pattern  175  becomes poor. Also, as indicated the section “A” in  FIG. 4   b , an end portion of the protrusion part  417  is not contacted with the drain electrode  163  so that a contact failure is generated or an additional subsequent process for removing the remained layer should be performed.  
      Accordingly, in order to solve above mentioned problems, the present invention provides an improved structure of the mold  400  which can minimize a shape deformation. As shown in  FIG. 5 , the mold  400  according to the present invention comprises the supporting layer  420 , the pattern forming layer  410  provided on one surface of the supporting layer  420  and having the concaves-convexes  415  formed thereon and the buffer layer  430  formed on the other surface of the supporting layer  420 . The pattern forming layer  410  further comprises the protrusion part  417  formed on and protruded from one surface on which the concaves-convexes  415  are formed.  
      The concaves-convexes  415  are formed on one surface of the pattern forming layer  410  and the concave-convex pattern  175  corresponding to the concaves-convexes  415  is formed on passivation layer  170  by the concaves-convexes  415 . Here, concaves-convexes  415  can be formed into a concave lens shape, a convex lens shape, or an embossing shape. The protrusion part  417  of the pattern forming layer  410  is formed for forming the drain contact hole  171  through which at least portion of the drain electrode  163  is exposed. It is desirable that the protrusion part  417  is provided such that an end of the protrusion part  417  and the drain electrode  163  come in contact with each other when the mold  400  is pressurized. The pattern forming layer  410  is made from soft material so as to make the mold  400  contact uniformly with passivation layer  170  and to use the mold  400  repeatedly. In addition, the pattern forming layer  410  can be made from material through which ultraviolet rays can be penetrated and may be made of PDMS (polydimethylsiloxane).  
      The supporting layer  420  solves the problems that it is difficult to release the mold  400  from passivation layer  170  due to a characteristic of material of the pattern forming layer  410  and a shape of the pattern forming layer  410  is deformed when the mold  400  is released, and so the eproducibility and yield of the concave-convex pattern  175  becomes poor Since a shape deformation of the mold  400  is minimized by the supporting layer  420 , a misalignment of the mold  400  and a damage to the shape of the concave-convex pattern  175  are minimized. The supporting layer  420  may be a film comprising at least one of polyethylene terephthalate (PET) and polycarbonate (PC). The supporting layer  420  can be formed from material through which light can be transmitted.  
      Since material used for forming the pattern forming layer  410  has the coefficient of thermal expansion which differs from that of material used for forming the supporting layer  420 , a shape of the mold  400  may be deformed into a dish shape or an overturned dish shape. The buffer layer  430  prevents the shape of the mold  400  from being deformed. According to the present invention, by providing the buffer layer  430  on the supporting layer  420 , the buffer layer  430  reduces a deforming force caused by a difference between the coefficients of thermal expansion of the pattern forming layer  410  and the supporting layer  420  and makes the degree of lateral expansion of the layers  410  and  420  different, thus the shape deformation of the mold  400  is minimized. Here, it is desirable that the pattern forming layer  410  and the buffer layer  430  are formed from the materials which have substantially the same coefficient of thermal expansion and modulus of elasticity to minimize a shape deformation of the mold  400 . The thickness of the buffer layer  430  can be determined in inverse proportion to the coefficient of thermal expansion of the pattern forming layer  410 . That is, if a coefficient of thermal expansion of the pattern forming layer  410  is smaller than that of the buffer layer  430 , it is possible to minimize a shape deformation of the mold  400  by increasing a thickness of the buffer layer  430 . Here, in order to minimize a shape deformation of the mold  400 , a value obtained from multiplying a thickness by a coefficient of thermal expansion of the buffer layer  430  may be 80% to 120% of a value obtained from multiplying a thickness by a coefficient of thermal expansion of the pattern forming layer. The buffer layer  430  can be formed of transparent material through which ultraviolet rays can be penetrated. For one example, polydimethylsiloxane (PDMS) can be used for forming the buffer layer.  
      Due to the above structure, as shown in  FIG. 5   b , although the concave-convex pattern  175  is formed on passivation layer  170  by using the mold  400 , it is easy to release the mold  400  due to the supporting layer  420  and, a shape deformation of the mold  400  is minimized due to the buffer layer  430 . Accordingly, the reproducibility and yield of the concave-convex pattern  175  are enhanced. Further, since a shape deformation of the mold  400  is minimized, an end portion of the protrusion part  417  can be contacted with the drain electrode  163 , and so the drain contact hole  171  through which the drain electrode  163  is exposed is formed without remaining layer. Because there is no remaining layer on the drain electrode  163 , the contact failure is not generated and a subsequent process for removing a remained layer is not required.  
      As described above, according to the present invention, a method for manufacturing the liquid crystal display device which can enhance the reproducibility and yield of the concave-convex pattern is provided. Also, the mold for the display device in which a shape deformation is minimized is provided.  
      Although a few exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention.