Patent Publication Number: US-2009224246-A1

Title: Thin film transistor, display device using the same, and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2008-0020392 filed in the Korean Intellectual Property Office on Mar. 5, 2008, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates to a display device and a method of manufacturing the display device. 
     (b) Description of the Related Art 
     There are various types of display devices. Recently, a display device that can display images with relatively small driving power by using electrophoresis has been developed. 
     A display device using electrophoresis includes a pair of electrodes that generate electric fields and electrophoretic particles disposed between the pair of electrodes. In the display device, a potential difference of voltages applied to the pair of electrodes is controlled to operate the electrophoretic particles. Namely, the display device displays an image according to the electrostatic movement of particles floating in space. 
     A display device using electrophoresis is basically a reflective display device that displays images by allowing ambient light to be reflected by the electrophoretic particles. Ambient light is mostly reflected by the electrophoretic particles, and in this case, a portion of the light is substantially transmitted through the electrophoretic particles. 
     The transmitted light causes degradation of the characteristics of the thin film transistors (TFTs) used as switching elements. This is because external light is introduced into a semiconductor layer of the TFT which in turn degrades the semiconductor layer. 
     The above information disclosed in this Background section is only for enhancing the understanding of the background of the invention and therefore it may contain information that does not constitute the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     [Narrative version of the claim language: go back and edit once the claims have been edited] An exemplary embodiment of the present invention provides a thin film transistor (TFT) substrate including: a substrate; a thin film transistor (TFT) formed on the substrate, the TFT having a gate electrode, a semiconductor layer, a source electrode, and a drain electrode; a pixel electrode formed on the TFT and electrically connected with the drain electrode; and a light blocking film formed on the pixel electrode and overlapping with the semiconductor layer. 
     The light blocking film may include a material that blocks light of a wavelength range that degrades the semiconductor layer of the TFT. 
     The light blocking film may block light of a wavelength within the range of about 100 nm to 600 nm. 
     The light blocking film may include amorphous silicon. 
     The light blocking film may include a photosensitive polymer material (photoresist). 
     The light blocking film and the pixel electrode may have substantially the same shape, in plan view. 
     Another embodiment of the present invention provides a method for fabricating a thin film transistor substrate, including: forming a thin film transistor (TFT) including a gate electrode, a semiconductor layer, a source electrode, and a gate electrode on a substrate; forming a pixel electrode electrically connected with the drain electrode of the TFT; and forming a light blocking film on the pixel electrode such that the light blocking film overlaps with the semiconductor layer. 
     The light blocking film may include a material that blocks light of a wavelength range that degrades the semiconductor layer of the TFT. 
     The light blocking film may include amorphous silicon. 
     The light blocking film may include a photosensitive polymer material. 
     Yet another embodiment of the present invention provides a method for fabricating a thin film transistor, including: forming a thin film transistor (TFT) including a semiconductor layer on a substrate; forming a passivation layer on the TFT; forming a conductive layer on the passivation layer; depositing a photosensitive polymer material on the conductive layer; etching the photosensitive polymer material such that it overlaps with the semiconductor layer to form a photosensitive polymer pattern; and etching the conductive layer by using the photosensitive polymer pattern to form a pixel electrode. 
     Still another embodiment of the present invention provides a display device including a thin film transistor substrate and an electrophoretic display unit. The thin film transistor (TFT) substrate may include: a substrate; a TFT including a gate electrode, a semiconductor layer, a source electrode, and a drain electrode, and that is formed on the substrate; a pixel electrode formed on the TFT and electrically connected with the drain electrode; and a light blocking film formed on the pixel electrode and overlapping with the semiconductor layer. 
     The light blocking film may include a material that blocks light of a wavelength range that degrades the semiconductor layer of the TFT. 
     The light blocking film may block light of a wavelength within the range of about 100 nm to 600 nm. 
     The light blocking film may include amorphous silicon. 
     The light blocking film may include a photosensitive polymer material. 
     The light blocking film and the pixel electrode may have substantially the same shape, in plan view. 
     The electrophoretic display unit may include: an electrophoretic display layer formed on the light blocking film; a transparent electrode formed on the electrophoretic display layer; and a transparent base film disposed on the transparent electrode, wherein the electrophoretic display layer includes electrophoretic particles with charges. 
     The display device may further include an adhesive layer disposed between the light blocking film and the electrophoretic display unit. 
     Another embodiment of the present invention provides a method for fabricating a display device, including: forming a thin film transistor (TFT) on a substrate, the TFT including a gate electrode, a semiconductor layer, a source electrode, and a drain electrode; forming a pixel electrode electrically connected with the drain electrode of the TFT; forming a light blocking film on the pixel electrode such that the light blocking film overlaps with the semiconductor layer; preparing an electrophoretic display unit; and disposing the electrophoretic display unit on the light blocking film. 
     The light blocking film may include a material that blocks light of a wavelength range that degrades the semiconductor layer of the TFT. 
     The light blocking film may be made to include amorphous silicon. 
     The light blocking film may include a photosensitive polymer material. 
     The electrophoretic display unit may include: an electrophoretic display layer formed on the light blocking film; a transparent electrode formed on the electrophoretic display layer; and a transparent base film disposed on the transparent electrode, wherein the electrophoretic display layer may include electrophoretic particles with electric charges. 
     The fabricating method may further include disposing an adhesive layer between the light blocking film and the electrophoretic display unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a layout view of a thin film transistor (TFT) substrate according to a first exemplary embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of a display device having the TFT substrate in  FIG. 1 . 
         FIG. 3  is a graph showing transmittance of amorphous silicon and a photosensitive polymer material. 
         FIG. 4  is a schematic view showing a driving principle of the display device in  FIG. 1 . 
         FIGS. 5 to 7  are cross-sectional views sequentially showing a method for fabricating the display device in  FIG. 1 . 
         FIG. 8  is a cross-sectional view of a display device according to a second exemplary embodiment of the present invention. 
         FIG. 9  is a cross-sectional view showing a method for fabricating the display device in  FIG. 8 . 
         FIG. 10  is a cross-sectional view of a display device according to a third exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS INDICATING PRIMARY ELEMENTS IN THE  DRAWINGS  
       110 : substrate member 
       124 : gate electrode 
       130 : gate insulating layer 
       140 : semiconductor layer 
       165 : source electrode 
       166 : drain electrode 
       170 : passivation layer 
       180 : pixel electrode 
       191 : light blocking film 
       200 : electrophoretic display unit 
       210 : base film 
       220 : transparent electrode 
       250 : electrophoretic display layer 
       270 : electrophoretic passivation layer 
       290 : adhesive layer 
       2511 : microcapsule 
       2512 : binder 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
     In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like reference numerals designate like elements throughout the specification. 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. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     In the accompanying drawings, a display using an amorphous silicon (a-Si) thin film transistor (TFT) formed through a masking process that uses five sheets of masks is illustrated. 
     In order to clarify the present invention, parts that are not connected with the description will be omitted, and the same elements or equivalents are referred to by the same reference numerals throughout the specification. 
     In describing the exemplary embodiments of the present invention, the same reference numerals are used for elements having the same constructions and representatively described in a first exemplary embodiment of the present invention, and in other remaining exemplary embodiments of the present invention, only different constructions from those of the first exemplary embodiment will be described. 
     A TFT substrate  100  and a display device  901  having the same according to a first exemplary embodiment of the present invention will now be described with reference to  FIGS. 1 and 2 . 
     With reference to  FIG. 2 , the display device  901  includes the TFT substrate  100  and an electrophoretic display unit  200 . The display device  901  further includes an adhesive layer  290  disposed between the TFT substrate  100  and the electrophoretic display unit  200 . 
     The TFT substrate  100  includes a substrate  110 , a TFT  101  formed on the substrate  110 , a pixel electrode  180  formed on the TFT  101 , and a light blocking film  191  formed on the pixel electrode  180  and covering the TFT  101 . 
     The TFT  101  includes a gate electrode  124 , a semiconductor layer  140 , a source electrode  165 , ohmic contact layers  155  and  156 , and a drain electrode  166 , wherein the drain electrode  166  is electrically connected with the pixel electrode  180 . The TFT  101 , which is a switching element, forms an electric field between the pixel electrode  180  and a transparent electrode  220  of the electrophoretic display unit  200  (described later). 
     The light blocking film  191  is formed to substantially overlap with the semiconductor layer  140  of the TFT  101 . Thus, the light blocking film  191  suppresses introduction of light to the semiconductor layer  140  of the TFT  101 . The light blocking film  191  is made of a material that blocks light of a wavelength band that degrades the semiconductor layer  140  of the TFT  101 . In particular, the light blocking film  191  may have an effect of blocking light of a wavelength ranging from about 100 nm to 600 nm. 
       FIG. 3  is a graph showing transmittance as a function of wavelength. The transmittance is of light passing through amorphous silicon commonly used as a material of the semiconductor layer  140  (solid line) and a photosensitive polymer material (photoresist: PR) (broken line). Namely,  FIG. 3  shows the transmittance of different wavelengths of bands of light that pass through the amorphous silicon and the photosensitive polymer material. As shown in  FIG. 3 , it is noted that amorphous silicon does not allow light of wavelength bands close to ultraviolet rays to be easily transmitted. The photosensitive polymer material is similar to the amorphous silicon in that both materials allow little light to be transmitted in the lower-wavelength region. 
     The light of the wavelength bands that fail to be transmitted through amorphous silicon is absorbed by amorphous silicon and changed into heat energy. This means that the light of the wavelength bands that fail to be transmitted through amorphous silicon may react on the semiconductor layer  140  to degrade the semiconductor layer  140 . Thus, the light blocking film  191  should block the light of the wavelength bands that cannot transmit through the amorphous silicon. 
     However, the present invention is not limited thereto. Thus, if the semiconductor layer  140  is made of a different material that is not amorphous silicon, the light blocking film  191  must also block light of the wavelength bands that react on the substance used as the material of the semiconductor layer  140 . 
     In the first exemplary embodiment of the present invention, the light blocking film  191  is made of a photosensitive polymer material (photoresist). As mentioned above with reference to  FIG. 3 , the photosensitive polymer material does not transmit light of the wavelength bands that do not transmit through amorphous silicon. Namely, the light blocking film  191  made of photosensitive polymer material can block light that fails to transmit through the semiconductor layer  140  made of amorphous silicon and that thus degrades the semiconductor layer  140 , to a degree. Accordingly, the light blocking film  191  made of photosensitive polymer material can block light of the wavelength bands that would react on the semiconductor layer  140  to degrade the semiconductor layer  140 . 
     In addition, the light blocking film  191  made of photosensitive polymer material may have the same shape, in plan view, as that of the pixel electrode  180 . In this case, the pixel electrode  180  is formed to cover the semiconductor layer  140  of the TFT  101  together with the light blocking film  191  made of photosensitive polymer material. 
     With reference to  FIG. 2 , the electrophoretic display unit  200  includes a base film  210 , a transparent electrode  220 , the electrophoretic display layer  250 , and an electrophoretic passivation layer  270 . The electrophoretic display layer  250  includes electrophoretic particles having electrical charges. 
     The structure of the display device  901  will now be described based on the stacking order. 
     Gate wiring including a plurality of gate lines  121  and gate electrodes  124 , as shown in  FIG. 1 , is formed on the substrate  110 , as shown in  FIG. 2 . Although not shown, the gate wiring may further include a plurality of first storage electrodes. Here, the substrate  110  may be formed as an insulation substrate made of glass, quartz, ceramic, plastic, or the like. If the substrate  110  is made of a material with flexibility like plastic, the usability of the display device  901  can be enhanced because the utilization range of the display device  901  can be extended. In particular, because the electrophoretic display unit  200  has flexibility, if the substrate  110  is also made of a flexible material, the display device  901  would be formed to be flexible overall, so its usability would be increased. 
     In addition, the substrate  110  may not necessarily need to be made of a transparent material. For instance, an insulation-processed metal plate may be used as the substrate  110 . 
     The gate wiring including the gate electrodes  124  is made of metals such as Al, Ag, Cr, Ti, Ta, Mo, etc., or their alloys. In  FIG. 1 , the gate wiring is illustrated as a single layer, but the gate wiring may be formed as a multi-layer including a metal layer of Cr, Mo, Ti, Ta, or their alloys having good physical and chemical characteristics, and an Al-based or Ag-based metal layer having low resistivity. 
     A gate insulating layer  130  made of silicon nitride (SiNx), etc., is formed on the gate wiring. 
     On the gate insulating layer  130 , there are data wiring formed, the data wiring including a plurality of source electrodes  165  each having at least one region overlapping with the gate electrodes  124 , a plurality of drain electrodes  166  disposed to be separated from the source electrodes  165  and each having at least one region overlapping with the gate electrodes  124 , and a plurality of data lines  161  crossing the gate lines  121  and connected with the source electrodes  165 . Although not shown, the data wiring may further include a plurality of second storage electrode lines overlapping with the first storage electrodes. 
     Like the gate wiring, the data wiring may also be made of a conductive material such as chromium (Cr), molybdenum (Mo), aluminum (Al), or their alloys, and may be formed as a single layer or a multi-layer. 
     The semiconductor layer  140  is formed on the gate electrode  124 , contacting the source electrode  165  and the drain electrode  166 . Here, the gate electrode  124 , the source electrode  165 , and the drain electrode  166  are three electrodes of the TFT  101 . If light is introduced into the semiconductor layer  140 , the characteristics of the TFT  101  deteriorate. Here, the TFT  101  is not limited to having the structure as shown in the accompanying drawings, and may have various other known structures within the scope in which a person skilled in the art may easily change. 
     Ohmic contact layers  155  and  156  are formed between the semiconductor layer  140  and the source and drain electrodes  165  and  166  in order to reduce contact resistance therebetween. The ohmic contact layers  155  and  156  are made of silicide, amorphous silicon, or the like, in which n-type impurities are doped in a high density. 
     The passivation layer  170 , which is made of an inorganic insulating material such as silicon nitride, silicon oxide, etc., or an insulating material with a low dielectric constant (k) such as a-Si:C:O, a-Si:O:F, etc., formed through plasma enhanced chemical vapor deposition (PECVD), is formed on the data wiring. 
     The plurality of pixel electrodes  180  are formed on the passivation layer  170 . The pixel electrodes  180  may be made by using a transparent conductor such as indium tin oxide (ITO) or indium zinc oxide (IZO), etc., or an opaque conductor such as aluminum (Al). 
     The passivation layer  170  includes a plurality of contact holes  171  exposing portions of the drain electrode  166 . The pixel electrodes  180  and the drain electrodes  166  are electrically connected via the contact holes  171 . 
     The light blocking films  191  are formed on the pixel electrodes  180 . Here, the light blocking films  191  are made of a photosensitive polymer material (photoresist) including a component that can block light of wavelength bands that react with the semiconductor layer  140  of the TFTs  101 . 
     The light blocking film  191  made of photosensitive polymer material has the same shape, in plan view, as that of the pixel electrode  180 , and is positioned on the semiconductor layer  140  of the TFT  101  to block light of wavelength bands reacting with the semiconductor layer  140 . 
     The adhesive layer  290  is formed on the light blocking films  191 . The electrophoretic passivation layer  270 , the electrophoretic display layer  250 , the transparent electrode  220 , and the base film  210  are sequentially formed on the adhesive layer  290 . That is, the adhesive layer  290  bonds the electrophoretic display unit  200  on the light blocking films  191 . In general, the electrophoretic display unit  200  is separately formed and then disposed to be bonded on the light blocking films  191 . At this time, the electrophoretic display layer  250  is disposed to be positioned between the pixel electrodes  180  and the transparent electrode  220 . With such a structure, the electrophoretic display layer  250  displays an image according to an electric field formed between the pixel electrodes  180  and the transparent electrode  220 . 
     The adhesive layer  290  may be made of a water soluble resin such as a polyester-based resin, an acryl-based resin, an epoxy-based resin, a urethane-based resin, an oxazoline-based resin, a PVP(polyvinylpyrrolidone)-based resin, a polyoxyalkylene-based resin, or a cellulose-based resin, or an emulsion-based resin. The adhesive layer  290  may be coated on the light blocking films  191  according to various known methods. 
     The electrophoretic passivation layer  270  may be disposed on the adhesive layer  290 . The electrophoretic passivation layer  270  protects the electrophoretic display layer  250  such that the electrophoretic display layer  250  cannot be separated from the base film  210 , or damaged. The electrophoretic passivation layer  270  may be variably made of an organic material or an inorganic material. Also, the electrophoretic passivation layer  270  may be made of a polymer material. Then, because the electrophoretic passivation layer  270  has viscoelasticity, it can be advantageous to flexibly form the electrophoretic display unit  200 . 
     However, the adhesive layer  290  and the electrophoretic passivation layer  270  are not essential elements and may be omitted. Namely, the electrophoretic display layer  250  may be directly formed on the light blocking films  191 , on which the transparent electrode  220  and the base film  200  may be then sequentially disposed. 
     The electrophoretic display layer  250  may be formed on the electrophoretic passivation layer  270 . The electrophoretic display layer  250  includes a binder  252  and electrophoretic microcapsules  251  mixed in the binder  252 . The electrophoretic display layer  250  substantially displays an image by electrophoresis generated by the microcapsules  251 . 
     The binder  252  serves to adhere the microcapsules  251  onto the transparent electrode  220 . Further, the binder  252  may serve to protect the microcapsules  251  according to the circumstances. Various organic binders may be used as the binder  252 . The binder  252  may also have sufficient adhesive power to allow the electrophoretic passivation layer  270  to be bonded to the electrophoretic display layer  250 . 
     The microcapsules  251  each includes a capsule shell, electrophoretic particles and a dispersion medium included in the capsule shell. As the electrophoretic particles of the microcapsules  251  operate in the dispersion medium according to an electric field, the electrophoretic display unit  200  displays an image. 
     In the first exemplary embodiment of the present invention, the microcapsules  251  have a spherical shape. However, the present invention is not limited thereto, and the microcapsules  251  may have various other shapes such as a cylindrical shape, a hexahedral shape, etc. 
     The microcapsules  251  have an average diameter within the range of about 10 μm to 150 μm. If the average diameter of the microcapsules  251  is smaller than 101 μm, the electrophoretic display unit  200  cannot obtain the sufficient density required to display an image. If the average diameter of the microcapsules  251  is greater than 150 μm, the microcapsules  251  cannot have sufficient mechanical strength, possibly causing a problem in which the microcapsules  251  are broken. 
     The electrophoretic particles refer to solid particles that have positive or negative charges to substantially operate in the dispersion medium in response to an electric field. The electrophoretic particles may have an average diameter within the range of 0.1 μm to 5 μm. If the size of the electrophoretic particles is smaller than 0.1 μm, sufficient chromaticity cannot be obtained and the contrast would be degraded to result in the display of an indistinct and dim image. If the size of the electrophoretic particles is greater than 5 μm, the electrophoretic particles cannot move sufficiently fast which in turn degrades the response speed. 
     A known dispersion medium may be used as the dispersion medium without being limited, and an organic solvent is preferably used. 
     The transparent electrode  220  may be formed on the electrophoretic display layer  250 . The transparent electrode  220  may be made of indium tin oxide (ITO), indium zinc oxide (IZO), an inorganic conductive material such as metal particles, a metal ultra-thin film, etc., or an organic conductive material such as polyacetylene, polyaniline, polypyrole, polyethylenedioxythiophene, polythiophene, etc. 
     The base film  210  is disposed on the transparent electrode  220 . The base film  210  is made of a transparent plastic with good light transmittance. Specifically, the plastic used as the material of the base film  210  may include an acrylic resin, a polyester-based resin, a polyolefin-based resin, a polycarbonate-based resin, a polyimide-based resin, or the like. Among them, the polyester-based resin is preferably used, and polyethyleneterephthalate (PET) with good transmittance, heat resistance, rigidity, and electrical properties is more preferably used. 
     The electrophoretic display unit  200  may have a thickness within the range of about 20 μm to about 200 μm. If the thickness of the electrophoretic display unit  200  is smaller than 20 μm, the electrophoretic display unit  200  would be easily rumpled when attached on the light blocking films  191 . If the thickness of the electrophoretic display unit  200  is greater than 200 μm, it would be difficult to roll the electrophoretic display unit  200  so as to be carried or attach the electrophoretic display unit  200  onto the light blocking films  191 . 
     Generally, the light blocking films  191  made of photosensitive polymer material have a thickness of substantially 1 μm. Because the electrophoretic display unit  200  has a thickness within the range of about 20 μm to about 200 μm, there is no substantial influence of the light blocking films  191  employed for the display device  901  on the behavior of the electrophoretic particles. 
     With such a configuration, the degradation of the semiconductor layer  140  of the TFTs  101  by external light can be effectively suppressed. Accordingly, the overall durability of the display device  901  can be improved. 
     A driving principle of the display device  901  using electrophoresis will now be described in detail with reference to  FIG. 4 . 
     As shown in  FIG. 4 , the display device  901  includes a pair of electrodes  180  and  220  to form an electric field. One of the pair of electrodes is the pixel electrode  180 , and the other is the transparent electrode (common electrode)  220  to which a common voltage is applied. A potential difference between the pixel electrode  180  and the transparent electrode  220  is formed according to a voltage applied to the pixel electrode  180  through the TFTs  101  (in  FIG. 2 ), which are switching elements. 
     The electrophoretic microcapsules  251  are disposed between the pixel electrode  180  and the common electrode  220 . Each microcapsule  251  includes a capsule shell  2515 , and electrophoretic particles  2511  and a dispersion medium  2512  included in the capsule shell  2515 . The electrophoretic particles  2511  are positive or negative polarity. 
     When a voltage is applied to the facing pixel electrode  180  and transparent electrode  220  to form a potential difference (+, −) between the electrodes  180  and  220 , the electrophoretic particles  2511  move toward one of the electrodes  180  and  220  of the opposite polarity. 
     Then, a user perceives light that is reflected from the electrophoretic particles  2511  after the light is made incident from the exterior. If the electrophoretic particles  2511  move upward, toward the user, the user can recognize the intense color of the electrophoretic particles  2511 . If the electrophoretic particles  2511  move downward a weak color will be viewed by the user. 
     The movement of the electrophoretic particles  2511  is caused by electrophoresis which refers to a phenomenon in which particles assuming a surface charge move toward electrodes assuming the opposite charge in the electric field. 
     Based on such a principle, the display device  901  using electrophoresis displays images. 
     The fabrication process of the display device  901  according to the first exemplary embodiment of the present invention will now be described with reference to  FIGS. 5 to 7 . 
     First, as shown in  FIG. 5 , the TFTs  101  each including the gate electrode  124 , the semiconductor layer  140 , the source electrode  165 , the ohmic contact layers  155  and  156 , and the drain electrode  166  are formed on the substrate  110 . Here, the TFT  101  is not limited to having the structure shown in the accompanying drawings, and may have various other known structures within the scope in which a person skilled in the art may easily change. 
     The passivation layer  170  covering the TFTs  101  is then formed. The passivation layer  170  includes contact holes  171  exposing portions of the drain electrode  165  of the TFTs  101 . 
     Next, a conductive layer  185  is formed on the passivation layer  170 . The conductive layer  185  may be made of a transparent conductive material such as ITO or IZO, or an opaque reflective material such as a metal film. 
     Thereafter, as shown in  FIG. 6 , photosensitive polymer patterns covering the TFTs  101  is formed on the conductive layer  185 . A photosensitive polymer pattern (photoresist pattern) may be formed by coating a photosensitive polymer material and then performing photolithography using a mask thereon. The photosensitive polymer material used as the material of the photosensitive polymer pattern includes a component that can block light of a wavelength band reacting with the semiconductor layer  140  of the TFT  101 . The photosensitive polymer pattern becomes the light blocking film  191 . 
     Then, as shown in  FIG. 7 , the conductive layer  185  is etched by using the photosensitive polymer pattern to form the pixel electrode  180 , and in this case, the light blocking film  191  and the pixel electrode  190  may have substantially the same shape, in plan view. The pixel electrode  180  covers the semiconductor layer  140  of the TFT  101  together with the photosensitive polymer pattern, namely, the light blocking film  191 . 
     As shown in  FIG. 2 , the adhesive layer  290  is subsequently coated on the photosensitive polymer pattern, which is the light blocking film  191 , on which the electrophoretic display unit  200  is attached, to form the display device  901  as shown in  FIG. 1 . 
     According to such method for manufacturing the display device  901 , the display device  901  in which the degradation of the semiconductor layer  140  of the TFT  101  by external light can be effectively suppressed can be manufactured. Thus, the display device  901  can have improved durability. 
     The TFT substrate  100  and a display device  902  having the same according to a second exemplary embodiment of the present invention will now be described with reference to  FIG. 8 . 
     As shown in  FIG. 8 , the display device  902  includes the TFT substrate  100  and the electrophoretic display unit  200 . The display device  902  further includes an adhesive layer  290  disposed between a light blocking film  192  and the electrophoretic display unit  200 . 
     The TFT substrate  100  includes the substrate  110 , the TFT  101  formed on the substrate  110 , and the light blocking film  192  covering the semiconductor layer  140 . The TFT substrate  100  further includes the pixel electrode disposed between the light blocking film  192  and the TFT  101 . Namely, the light blocking film  192  is formed on the pixel electrode  180  to cover the semiconductor layer  140  of the TFT  101 . Here, the light blocking film  192  may not be formed only at positions corresponding to the pixel electrode, but may cover the TFT  101  regardless of the disposition of the pixel electrode  180 . 
       FIG. 8  shows the case where the pixel electrode  180  covers the TFT  101  and the light blocking film  192  covers the entire surface including the upper portion of the TFT  101 , but the second exemplary embodiment of the present invention is not limited thereto. Namely, the pixel electrode  180  may be designed differently, and the light blocking film  192  may only be formed on the portion that covers the semiconductor layer  140  of the TFT  101  regardless of the pixel electrode  180 . 
     The light blocking film  192  is made of a material including amorphous silicon that is mainly used as a material for the semiconductor layer  140 . Thus, the light blocking film  192  may more effectively suppress the introduction of light onto the  25  semiconductor layer  140  of the TFT  101 . That is, because the light blocking film  192  is made of a component that is substantially similar to that of the semiconductor layer  140 , light that may affect the semiconductor layer  140  can be effectively blocked. 
     Generally, the light blocking film  192  made of amorphous silicon may have a thickness even smaller than 1 μm. In comparison, the electrophoretic display unit  200  has a thickness within the range of 20 μm to 200 μm, so the light blocking film  192  added to the display device  902  cannot substantially affect the operation of the electrophoretic particles. 
     With such a configuration, the degradation of the semiconductor layer  140  of the TFT  101  by external light can be effectively suppressed. Thus, the overall durability of the display device can be improved. 
     The manufacturing process of the display device  902  according to the second exemplary embodiment of the present invention will now be described with reference to  FIG. 9 . 
     The TFT  101  including the gate electrode  124 , the semiconductor layer  140 , the source electrode  165 , the drain electrode  166 , the ohmic contact layers  155  and  156 , and the pixel electrode  180  electrically connected with the drain electrode  166  are formed on the substrate  110 . That is, the steps of the manufacturing method leading up to the process of forming the pixel electrode  180  by using the photosensitive polymer pattern in the second exemplary embodiment of the present invention are the same as that in the method for manufacturing the display device  901  according to the first exemplary embodiment of the present invention. However, in the method for manufacturing the display device  902  according to the second exemplary embodiment of the present invention, after the pixel electrode  180  is formed, the photosensitive polymer pattern is removed. 
     Next, as shown in  FIG. 9 , the light blocking film  192  is formed with a material of amorphous silicon. The light blocking film  192  covers the semiconductor layer  140  of the TFT  101 , and the amorphous silicon is commonly used as a material of the semiconductor layer  140 . 
     As shown in  FIG. 8 , the adhesive layer  290  is then coated on the light blocking film  192 , on which the electrophoretic display unit  200  is then attached to form the display device  902 . 
     According to such method for manufacturing the display device  902 , the display device  902  in which the degradation of the semiconductor layer  140  of the TFT  101  by external light can be effectively suppressed can be manufactured. Thus, the display device  902  can have improved durability. 
     A display device  903  according to a third exemplary embodiment of the present invention will now be described with reference to  FIG. 10 . 
     As shown in  FIG. 10 , the display device  903  includes the TFT  100  and the electrophoretic display unit  200 . In addition, the display device  903  may further include an adhesive layer (not shown in  FIG. 10  but shown as adhesive layer  290  in  FIG. 8 ) disposed between the light blocking film  192  and the electrophoretic display unit  200 . 
     The TFT substrate  100  includes the substrate  110 , the TFT  101  formed on the substrate  110 , and the light blocking film  192  covering the TFT  101 . Further, the TFT substrate  100  includes the pixel electrode  180  disposed between the light blocking film  192  and the TFT  101 . That is, the light blocking film  192  is formed on the pixel electrode  180  and covers the semiconductor layer  140  of the TFT  101 . 
     The electrophoretic display unit  200  of the display device  903  according to the third exemplary embodiment of the present invention is not separately formed and attached but is directly formed on the light blocking film  192 . 
     The electrophoretic display unit  200  includes barrier rib members  280 , the electrophoretic particles  2511 , the dispersion medium  2512 , a sealing adhesive layer  225 , the transparent electrode  220 , and a transparent base substrate  211 . The transparent base substrate  211  may be an insulation substrate made of a material such as glass, plastic, etc., or a transparent base film. 
     The barrier rib members  280  are formed on the light blocking film  192  and distinguish a space above one pixel electrode  180  from that of another pixel electrode  180 . Namely, the barrier rib members  280  have a receiving portion formed to receive the electrophoretic particles  2511  and the dispersion medium  2512  at every upper portion of each pixel electrode  180 . 
     The electrophoretic particles  2511  and the dispersion medium  2512  are disposed in the receiving portion formed by the barrier rib members  280 . 
     The sealing adhesive layer  225  is attached to the barrier rib members  280  to prevent the electrophoretic particles  236  on one pixel electrode  180  from moving onto another pixel electrode  180 . The sealing adhesive layer  225  may be made of a polymer-based material. 
     The transparent electrode  220  (also known as the common electrode) forms an electric field together with the pixel electrode  180  to operate the electrophoretic particles  2511  disposed in the receiving portions of the barrier rib members  280 . 
     With such a configuration, the degradation of the semiconductor layer  140  of the TFTs  101  by external light can be effectively suppressed. Thus, the overall durability of the display device  903  can be improved. 
     According to the present invention, the degradation of the semiconductor layers of the TFTs by external light can be effectively suppressed. Thus, the overall durability of the display device  903  can be improved. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.