Abstract:
A photo-mask is capable of preventing stain defects and a method for fabricating a liquid crystal display device using the photo-mask which achieves the same capability. The photo-mask includes a transparent substrate configured to transmit ultraviolet light and a light shielding layer configured to block ultraviolet light on a surface of the transparent substrate. The light shielding layer includes an absorption layer configured to absorb ultraviolet light.

Description:
CLAIM OF PRIORITY 
       [0001]    This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application earlier filed in the Korean Intellectual Property Office on the Dec. 6, 2010 and there duly assigned Serial No. 10-2010-0123795. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method for manufacturing a display device, and more particularly, to a photo-mask which selectively blocks ultraviolet light and a display device adopting the same. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a display device may include a liquid crystal between a plurality of substrates which face each other. The liquid crystal may be sealed between the substrates by a sealant. The sealant may be hardened by ultraviolet light after the substrates are bonded to each other. However, ultraviolet light may also radiate to the liquid crystal, causing stain defects. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a photo-mask capable of controlling ultraviolet light and a method for fabricating a display device using the same. 
         [0007]    The present invention also provides a photo-mask capable of preventing stain defects and a method for fabricating a display device using the same. 
         [0008]    Embodiments of the present invention provide photo-masks which include a transparent substrate configured to transmit ultraviolet light and a light shielding layer configured to block ultraviolet light on a surface of the transparent substrate, wherein the light shielding layer includes an absorption layer configured to absorb ultraviolet light. 
         [0009]    In some embodiments, the absorption layer may include polycrystal silicon or amorphous silicon. The polycrystal silicon may absorb ultraviolet light having a wavelength smaller than about 380 nm. 
         [0010]    In other embodiments, the transparent substrate may include a transmissive region and a shelter region, wherein the polycrystal silicon or the amorphous silicon may be formed at the shelter region. 
         [0011]    In still other embodiments, the light shielding layer may further include a reflection layer on the absorption layer of the shelter region. The reflection layer may include chrome. 
         [0012]    In even other embodiments, the polycrystal silicon may be formed over the transparent substrate, including the transmissive region and the shelter region. 
         [0013]    In other embodiments of the present invention, methods for fabricating a liquid crystal display device comprise preparing a first substrate and a second substrate including cell regions, forming a sealant at a peripheral region of the cell regions of at least one of the first and second substrates, dispensing a liquid crystal within the cell regions, joining the first and second substrates, and selectively hardening the sealant by ultraviolet light using a photo-mask, wherein the photo-mask includes a transparent substrate configured to transmit ultraviolet light and a light shielding layer configured to block ultraviolet light on a surface of the transparent substrate, and wherein the light shielding layer includes an absorption layer configured to absorb ultraviolet light. 
         [0014]    In some embodiments, the sealant may include a first reactive resin and a first photoinitiator. The first photoinitiator may be reactive to ultraviolet light having a wavelength range of from about 380 nm to about 400 nm. The first photoinitiator may include benzoin ether or benzophenone/amine. 
         [0015]    In other embodiments, a layer of the liquid crystal may include a second reactive resin and a second photoinitiator. The second photoinitiator may be reactive to ultraviolet light having a wavelength smaller than about 380 nm. The photoinitiator may include thioxanthone. 
         [0016]    In still other embodiments, the absorption layer may include polycrystal silicon or amorphous silicon. The polycrystal silicon may absorb ultraviolet light having a wavelength smaller than about 380 nm. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain principles of the present invention. In the drawings: 
           [0018]      FIGS. 1  thru  7  are planar diagrams illustrating a method for fabricating a display device according to an embodiment of the present invention; 
           [0019]      FIG. 8  is a graph illustrating transmittances of polycrystal silicon and amorphous silicon according to a wavelength change of light; 
           [0020]      FIGS. 9  thru  12  are cross-sectional views illustrating photo-masks sectioned along a line IX-IX of  FIG. 5  according to first thru fourth embodiments of the present invention; 
           [0021]      FIG. 13  is a graph illustrating a hardening rate of a sealant according to a wavelength change of light; and 
           [0022]      FIGS. 14  thru  17  are cross-sectional views along a line XIV-XIV of  FIG. 7  illustrating a method for aligning a liquid crystal. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Preferred embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be constructed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Like reference numerals refer to like elements throughout. 
         [0024]    The terms used in the specification are not for limiting the present invention but are for describing the embodiments. The terms of a singular form may include plural forms unless otherwise specified. The meaning of the terms “include,” “comprise,” “including,” or “comprising,” specifies a property, a region, a fixed number, a step, a process, an element and/or a component but does not exclude other properties, regions, fixed numbers, steps, processes, elements and/or components. Also, the reference numerals given according to the sequence of description are not limited to the sequence. 
         [0025]      FIGS. 1  thru  7  are planar diagrams illustrating a method for fabricating a display device according to an embodiment of the present invention,  FIG. 8  is a graph illustrating transmittances of polycrystal silicon and amorphous silicon according to a wavelength change of light,  FIGS. 9  thru  12  are cross-sectional views illustrating photo-masks sectioned along a line IX-IX of  FIG. 5  according to the first to fourth embodiments of the present invention, and  FIG. 13  is a graph illustrating a hardening rate of a sealant according to a wavelength change of light. 
         [0026]    Referring to  FIG. 1 , a thin film transistor substrate (not illustrated) and a color filter substrate  20  may be provided. The thin film transistor substrate and the color filter substrate  20  may respectively include cell regions  32  and peripheral regions  34  outside the cell regions  32 . The cell regions  32  may include a plurality of pixels (not illustrated) defined by a data line (not illustrated) and a gate line (not illustrated) of the thin film transistor substrate. The peripheral regions  34  may include an encapsulation region (not illustrated) and a cutting region (not illustrated). 
         [0027]    Although not illustrated, the thin film transistor substrate may be a first substrate including a thin film transistor (not illustrated). The thin film transistor substrate may include a storage electrode, a gate insulation layer, a passivation layer, a pixel electrode, and a first alignment layer. Also, the color filter substrate  20  may be a second substrate including a color filter. The color filter substrate  20  may include a black matrix layer, a common electrode, and a second alignment layer. 
         [0028]    Referring to  FIG. 2 , a sealant  36  may be formed on the color filter substrate  20 . The sealant  36  may surround the cell regions  32  at the peripheral regions  34 . The sealant  36  may be printed on the color filter substrate  20  in a liquid state. For instance, the sealant  36  may include an acrylate-based first reactive resin, such as epoxy acrylate and urethane acrylate. Also, the sealant  36  may include a first photoinitiator which raises a hardening reaction of reactive resin. The first photoinitiator generates a radical by ultraviolet light, and may induce a hardening reaction of the first reactive resin. The first photoinitiator may include benzoin ether or benzophenone/amine having an excellent chemical resistance. For instance, the benzoin ether or benzophenone/amine may generate the radical by ultraviolet light having a wavelength range of from about 380 nm to about 400 nm. 
         [0029]    Referring to  FIG. 3 , a liquid crystal  38  may be disposed on each of the cell regions  32  of the color filter substrate  20 . The liquid crystal  38  may be disposed on the center of each cell region  32 . The liquid crystal  38  may be disposed before formation of the sealant  36 , and may be disposed simultaneously with formation of the sealant  36 . The liquid crystal  38  may be disposed on the thin film transistor substrate  10  or the color filter substrate  20  where the sealant  36  is formed. 
         [0030]    The liquid crystal  38  may include a VA mode, an IPS mode, and a TN mode. The liquid crystal  38  may also include Reactive Mesogens (RM) for compensating a viewing angle. The RM may include an acrylate-based second reactive resin, such as polyester acrylate or silicon acrylate. Also, the liquid crystal  38  may include a second photoinitiator. The second photoinitiator may include thioxanthone. For instance, the thioxanthone may generate a radical by ultraviolet light having a weak wavelength. The second photoinitiator may induce a reaction for connecting the RM to the first and second alignment layers by ultraviolet light having a wavelength smaller than about 360 nm. 
         [0031]    Referring to  FIG. 4 , the thin film transistor substrate  10  may be joined to the color filter substrate  20 . The thin film transistor substrate  10  and the color filter substrate  20  may be joined together in a low vacuum state. The thin film transistor substrate  10  and the color filter substrate  20  may also be joined together in a chamber (not illustrated). The liquid crystal  38  may have lower viscosity than that of the sealant  36 . The liquid crystal  38  may gradually float from the centers of the cell regions  32  to edges between the thin film transistor substrate  10  and the color filter substrate  20 . Even though the thin film transistor substrate  10  and the color filter substrate  20  are exposed to atmospheric pressure from low vacuum, the liquid crystal  38  may be filled within the cell regions  32  in a certain time. For instance, the liquid crystal  38  may be completely filled within the cell regions  32  after about 1 hour has passed under atmospheric pressure outside the chamber. The sealant  36  may join the thin film transistor substrate  10  and the color filter substrate  20  at the peripheral region  34 . 
         [0032]    Referring to  FIGS. 5 and 8  thru  12 , a photo-mask  40  for sheltering the cell regions  32  may be aligned on the thin film transistor substrate  10  and the color filter substrate  20 . Ultraviolet light  56  ( FIGS. 9  thru  12 ) may be made selectively incident on the sealant  36  using the photo-mask  40 . For instance, ultraviolet light  56  may be incident within from about 1 minute to about 2 minutes from the outside of the chamber after joining the thin film transistor substrate  10  and the color filter substrate  20 . This is because mismatching of the thin film transistor substrate  10  and the color filter substrate  20  may be minimized at a following process. Ultraviolet light  56  may be generated from a light source, such as a mercury discharge tube and a deuterium lamp. The light source may generate ultraviolet light having a wavelength range of from about 200 nm to about 400 nm. The liquid crystal  38  may be partially filled within the cell regions  32 . As described above, this is because the liquid crystal  38  is gradually filled within the cell regions  32 . For instance, the liquid crystal  38  may not be filled to edges of the cell regions  32  having square shapes. 
         [0033]    The photo-mask  40  may include a transmissive region  42  ( FIG. 5 ) and a shelter region  44 . The transmissive region  42  may expose the sealant  36 , and the shelter region  44  may shelter the cell regions  32 . The shelter region  44  may shelter the peripheral region  34 , except for the sealant  36 . The photo-mask  40  may include a transparent substrate  46  ( FIGS. 9  thru  12 ) and a light shielding layer  50 . The light shielding layer  50  may include an absorption layer  52 . The absorption layer  52  may include polycrystal silicon (Si) ‘a’ or amorphous silicon (Si) ‘b’. 
         [0034]    Referring to  FIG. 8 , the polycrystal silicon ‘a’ may be passed through by ultraviolet light  56  having a wavelength larger than about 380 nm. The photo-mask  40 , including the absorption layer  52  of the polycrystal silicon ‘a’, may be passed through by ultraviolet light  56  having a wavelength range of from about 380 nm to about 400 nm. Also, the absorption layer  52  of the polycrystal silicon ‘a’ may absorb ultraviolet light having a wavelength smaller than about 380 nm. The amorphous silicon ‘b’ may be passed through by visible light and infrared light having a wavelength larger than about 500 nm. The absorption layer  52  of the amorphous silicon ‘b’ may absorb light of all ultraviolet regions. Embodiments of the photo-mask  40 , including the absorption layer  52  composed of the polycrystal silicon ‘a’ or the amorphous silicon ‘b’, will be described. 
         [0035]    Referring to  FIGS. 8 and 9 , the photo-mask  40  according to the first embodiment of the present invention may include the absorption layer  52  and a reflection layer  54  on the shelter region  44  of the transparent substrate  46 . The absorption layer  52  and the reflection layer  54  may be the light shielding layer  50 . The reflection layer  54  may include a chrome (Cr) layer. The absorption layer  52  may include the polycrystal silicon ‘a’ or the amorphous silicon ‘b’. Ultraviolet light  56  incident on the shelter region  44  may be reflected by the reflection layer  54  upward from the photo-mask  40 . The light  56  incident on the transmissive region  42  may be absorbed by the sealant  36 . The light  56  passing through the transmissive region  42  may include all ultraviolet regions of wavelength smaller than about 400 nm. The light  56  may be reflected toward the photo-mask  40  by an upper surface of the thin film transistor substrate  10  corresponding to the transmissive region  42 . 
         [0036]    Ultraviolet light  56 , reflected by the upper surface of the thin film transistor substrate  10 , may be absorbed by the absorption layer  52 . For instance, the absorption layer  52  of the amorphous silicon ‘b’ may absorb light of all ultraviolet regions having a wavelength smaller than about 400 nm. 
         [0037]    The absorption layer  52  of the polycrystal silicon ‘a’ may absorb ultraviolet light  56  having a wavelength smaller than about 380 nm, and may be passed through by ultraviolet light  56  having a wavelength range of from about 380 nm to about 400 nm. Ultraviolet light  56  having a wavelength range of from about 380 nm to about 400 nm may be re-reflected by the reflection layer  54  toward the liquid crystal  38  of the cell regions  32 . The liquid crystal  38  may not be polymerized by ultraviolet light  56  having a wavelength range of from about 380 nm to about 400 nm. This is because the second photoinitiator of the liquid crystal  38  is polymerized by ultraviolet light  56  having a wavelength smaller than about 380 nm. Therefore, the photo-mask  40  according to the first embodiment of the present invention may prevent stain defects due to the polymerization of the liquid crystal  38 . 
         [0038]    Referring to  FIGS. 8 and 10 , the photo-mask  40  according to the second embodiment of the present invention may include the absorption layer  52  on the shelter region  44  of the transparent substrate  46 . The absorption layer  52  may absorb ultraviolet light  56  having a wavelength smaller than about 380 nm which polymerizes the liquid crystal  38  at the shelter region  44 . The absorption layer  52  may include the polycrystal silicon ‘a’ or the amorphous silicon ‘b’. 
         [0039]    The absorption layer  52  of the polycrystal silicon ‘a’ may absorb ultraviolet light  56  having a wavelength smaller than about 380 nm. The absorption layer  52  of the polycrystal silicon ‘a’ may transmit ultraviolet light  56  having a wavelength range of from about 380 nm to about 400 nm to the liquid crystal  38 . The liquid crystal  38  may not be polymerized by ultraviolet light  56  having a wavelength range of from about 380 nm to about 400 nm. The absorption layer  52  of the amorphous silicon ‘b’ may absorb light of all ultraviolet regions having a wavelength smaller than about 400 nm. Therefore, the absorption layer  52  of the polycrystal silicon ‘a’ or the amorphous silicon ‘b’ may absorb ultraviolet light  56  having a wavelength smaller than about 380 nm, which polymerizes the liquid crystal  38  at the shelter region  44 . 
         [0040]    The light  56  transmitted to the transmissive region  42  of the transparent substrate  46  may include an ultraviolet region having a wavelength smaller than about 400 nm. The light  56  transmitted to the transmissive region  42  may be reflected toward the photo-mask  40  by an upper surface of the thin film transistor substrate  10 . The absorption layer  52  of the photo-mask  40  may absorb and transmit ultraviolet light  56  reflected by the upper surface of the thin film transistor substrate  10 . The absorption layer  52  of the polycrystal silicon ‘a’ may absorb ultraviolet light having a wavelength smaller than about 380 nm. The absorption layer  52  of the polycrystal silicon ‘a’ may transmit ultraviolet light  56  having a wavelength range of from about 380 nm to about 400 nm to an upper part of the photo-mask  40 . The absorption layer  52  of the amorphous silicon ‘b’ may absorb light of all ultraviolet regions having a wavelength smaller than about 400 nm. Therefore, the photo-mask  40  according to the second embodiment of the present invention may prevent stain defects due to the polymerization of the liquid crystal  38 . 
         [0041]    Referring to  FIGS. 8 and 11 , the photo-mask  40  according to the third embodiment of the present invention may include the absorption layer  52  over the transparent substrate  46  and the reflection layer  54  on the transparent substrate  46  of the shelter region  44 . The reflection layer  54  may reflect light  56  of all ultraviolet regions having a wavelength smaller than about 400 nm upward from the photo-mask  40  toward the shelter region  44 . The absorption layer  52  may be exposed at the transmissive region  42 . The absorption layer  52  may include the polycrystal silicon ‘a’ which absorbs ultraviolet light  56  having a wavelength smaller than about 380 nm. The absorption layer  52  exposed at the transmissive region  42  may absorb ultraviolet light  56  having a wavelength smaller than about 380 nm, and may transmit ultraviolet light  56  having a wavelength range of from about 380 nm to 400 nm. Ultraviolet light  56  having a wavelength range of from about 380 nm to 400 nm may not induce the polymerization of the liquid crystal. Ultraviolet light  56  having a wavelength range of from about 380 nm to 400 nm may selectively harden the sealant  36 . Therefore, the photo-mask  40  according to the third embodiment of the present invention may prevent stain defects due to the polymerization of the liquid crystal  38 . 
         [0042]    Referring to  FIGS. 8 and 12 , the photo-mask  40  according to the fourth embodiment of the present invention may include the absorption layer  52  over the transparent substrate  46 . The absorption layer  52  may include the polycrystal silicon ‘a’. The absorption layer  52  may absorb ultraviolet light  56  having a wavelength smaller than about 380 nm, and may transmit ultraviolet light  56  having a wavelength range of from about 380 nm to 400 nm. Ultraviolet light  56  having a wavelength range of from about 380 nm to 400 nm may selectively harden the sealant  36 . Therefore, the photo-mask  40  according to the fourth embodiment of the present invention may prevent stain defects due to the polymerization of the liquid crystal  38 . 
         [0043]    Referring to  FIGS. 6  thru  13 , the sealant  36  may be reactive to ultraviolet light  56  having a wavelength range of from about 380 nm to 400 nm so as to be hardened. As described above, the sealant  36  may include the first photoinitiator and the first reactive resin. The first photoinitiator may generate the radical by ultraviolet light  56  having a wavelength range of from about 380 nm to 400 nm. Also, the radical may induce a hardening reaction of the first reactive resin. Accordingly, the sealant  36  may be hardened by ultraviolet light  56  having a wavelength range of from about 380 nm to 400 nm transmitted from the photo-mask  40  according to the first thru fourth embodiments of the present invention. The horizontal axis of  FIG. 13  denotes a wavelength of light, and the vertical axis thereof denotes a hardening rate. The hardening rate may be measured by a Fourier Transform Spectroscopy (FT-IR) device. 
         [0044]    Referring to  FIG. 7 , if a certain time has passed after the sealant  36  is hardened, the liquid crystal  38  may be completely filled within the cell regions  32 . As described above, if about one hour under the atmospheric pressure has passed, the liquid crystal  38  may be completely filled within the cell regions  32 . The liquid crystal may be aligned between the thin transistor film substrate  10  and the color filter substrate  20  by ultraviolet light having a wavelength smaller than about 380 nm as described below. 
         [0045]      FIGS. 14  thru  17  are cross-sectional views along a line XIV-XIV of  FIG. 7  illustrating a method for aligning the liquid crystal. 
         [0046]    Referring to  FIG. 14 , the liquid crystal  38  may include directors  37 , reactive mesogens  39 , and the second photoinitiator between the thin film transistor substrate  10  and the color filter substrate  20 . The directors  37  may include monomers having polarizations. The directors  37  may be arranged in a certain direction between a first alignment layer  12  of the thin film transistor substrate  10  and a second alignment layer  22  of the color filter substrate  20 . For instance, the directors  37  may be arranged vertically relative to the thin film transistor substrate  10  and the color filter substrate  20  by the polarizations. 
         [0047]    Referring to  FIG. 15 , by applying a voltage provided by a power source  60  to a pixel electrode  14  of the thin film transistor substrate  10  and a common electrode  24  of the color filter substrate  20 , the directors  37  of the liquid crystal  38  may be rotated. The directors  37  of the liquid crystal  38  may be rotated along an electric field induced between the pixel electrode  14  and the common electrode  24 . 
         [0048]    Referring to  FIG. 16 , by irradiating ultraviolet light  56  onto the liquid crystal  38 , the reactive mesogens  39  may be networked to surfaces of the first and second alignment layers  12  and  22 , respectively. The reactive mesogens  39  may be networked to the surfaces of the first and second alignment layers  12  and  22 , respectively, by the second photoinitiator which is polymerized by ultraviolet light  56 . The second photoinitiator may be polymerized by ultraviolet light  56  having a wavelength smaller than about 380 nm. The reactive mesogens  39  may be most stabilized on the surfaces of the first and second alignment layers  12  and  22 , respectively. The reactive mesogens  39  may be networked along the directors  37  on the surfaces of the first and second alignment layers  12  and  22 , respectively. The director  37  may be rotated or inclined by the electric field (not illustrated) induced between the pixel electrode  14  and the common electrode  24 . Accordingly, the reactive mesogens  39  may be networked at a certain pretilt angle on the surfaces of the first and second alignments layers  12  and  14 , respectively. 
         [0049]    Referring to  FIG. 17 , the power source  60  applying a voltage to the pixel electrode and the common electrode may be removed. The directors  37  adjacent to the surfaces of the first and second alignment layers  12  and  22 , respectively, may be aligned at a pretilt angle by the reactive mesogens  39 . The reactive mesogens  39  may restrain the directors  37  on the surfaces of the first and second alignment layers  12  and  22 , respectively. That is, the reactive mesogens  39  may fix the pretilt angle of the directors  37  adjacent to the first and second alignment layers  12  and  22 , respectively. The directors  39  located at a center between the thin film transistor substrate  10  and the color filter substrate  20  may be vertically arranged by polarizations. 
         [0050]    As described above, the photo-mask according to the embodiments of the present invention may include an absorption layer of the polycrystal silicon which transmits ultraviolet light having a wavelength range of from about 380 nm to about 400 nm and absorbs ultraviolet light having a wavelength smaller than about 380 nm. The sealant may include the first photoinitiator which is polymerized by ultraviolet light having a wavelength range of from about 380 nm to about 400 nm. The liquid crystal may include the second photoinitiator which is polymerized by ultraviolet light having a wavelength smaller than 380 nm. Therefore, the sealant can be selectively hardened by ultraviolet light having a wavelength range of from about 380 nm to about 400 nm transmitted from the photo-mask. 
         [0051]    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 present invention. Thus, to the maximum extent allowed by law, the scope of the present 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.