Patent Publication Number: US-2011058135-A1

Title: Display device

Description:
TECHNICAL FIELD 
     The present invention relates to display devices, and more particularly, relates to a display device in which a pair of substrates are bonded together at an outer circumference portion with a sealant. 
     BACKGROUND ART 
     Liquid crystal display devices, which are a type of display device, are thin and light weight, and have been widely used for mobile devices such cellular phones, AV devices such as liquid crystal TV sets, and the like. Liquid crystal display panels used as a component of such liquid crystal display devices include a first substrate and a second substrate arranged to face each other and a liquid crystal layer provided between the substrates. 
     In such a liquid crystal display panel, the first substrate and the second substrate are bonded together with seal portions each being formed in a non-display region provided at an outer circumference portion of each of the substrates. 
     In general, the seal portions are made of a sealing material such as epoxy resin, and therefore, tend to have low adhesion strength, for example, with an organic insulating film formed on a surface of each substrate. 
     Recently, as the thickness of liquid crystal display panels has become smaller and smaller, the thickness of each substrate as a component of such a liquid crystal display panel is reduced accordingly, and thus, the substrate is easily deformed. In particular, when a liquid crystal display panel is produced and mounted components such as external connection terminals are mounted on the liquid crystal display panel, the substrates are deformed under load, and thus, the pair of substrates bonded together with seal portions might be separated from each other. 
     Also, in recent years, there are an increasing number of cases where, in a liquid crystal display panel fabrication process, the liquid crystal dropping/bonding method having a higher productivity than that of the known dip injection method is used as a method for supplying a liquid crystal material between a pair of substrates to form a liquid crystal layer. In the liquid crystal dropping/bonding method, for example, a seal portion having a rectangular frame shape is formed in one of a pair of substrates, and then, a liquid crystal material is dropped into the inside of the seal portion of the substrate, thereby bonding the one of the substrates to the other one of the substrate. It is likely that the adhesion strength of a liquid crystal display panel formed using the liquid crystal dropping/bonding method is lower than that of a liquid crystal display panel formed using the dip injection method because of differences in material used for the seal portion. Therefore, there are still cases where the substrates are separated from each other. 
     Furthermore, specifically, in a mobile device such as a cellular phone, the frame narrowing technique in which a non-display region in an outer circumference portion which does not contribute to display of a liquid crystal display panel is narrowed is developed, and therefore, the width of the seal portion provided in the non-display region is expected to be reduced. To reduce the width of the seal portion, a pair of substrates have to be bonded to together in a limited area, and thus, it is highly possible that the substrates are separated from one another. 
     As described above, in such a liquid crystal display panel, it is likely that substrates are easily separated from each other due to reduction in thickness of the liquid crystal display panel, a fabrication process, frame narrowing, and the like. Therefore, improvement of the adhesive strength of the seal portion between a pair of substrates is required. 
     To solve the above-described problems, for example, PATENT DOCUMENT 1 discloses a liquid crystal display device  100  having a configuration shown in  FIGS. 11 and 12 .  FIG. 11  is a plan view of the known liquid crystal display device  100  of PATENT DOCUMENT 1, and the like.  FIG. 12  is an enlarged plan view of a seal region  117 ′ within a dotted frame S of  FIG. 11 . 
     As shown in  FIG. 11 , the liquid crystal display device  100  includes a thin film transistor substrate  112  having terminal portions  115 , and a liquid crystal display panel  111  comprised of a color filter substrate  113 . The thin film transistor substrate  112  and the color filter substrate  113  are bonded to together with a sealant  117  so that a liquid crystal layer is interposed between the thin film transistor substrate  112  and the color filter substrate  113 . The sealant  117  is provided in the seal region  117 ′ located around a display region  116 . 
     As shown in  FIG. 12 , in the seal region  117 ′, a gate layers  120  is formed into strips and the plurality of strips of the gate layers  120  are arranged with a predetermined space between one another so that each of the strips of the gate layer  120  extends along the width direction of the seal region  117 ′. Step portions are formed by the strips of the gate layer  120  to increase an adhesion area with the sealant  117 , thereby improving the adhesion strength. 
     CITATION LIST 
     Patent Document 
     PATENT DOCUMENT 1: Japanese Patent Publication No. 09-33933 
     SUMMARY OF THE INVENTION 
     Technical Problem 
     In the liquid crystal display device  100 , when the thin film transistor substrate  112  and the color filter substrate  113  are bonded at a predetermined position, desired adhesion strength can be achieved between the two substrates. However, if the substrates are misaligned to be shifted from each other when being bonded, the sealant  117  is not arranged at a predetermined position, and a problem in which a space between the thin film transistor substrate  112  and the color filter substrate  113 , i.e., a cell thickness varies arises. 
     Also, since the strips of the gate layer  120  are arranged with a predetermined space between one another so that each of the strips of the gate layer  120  extends along the width direction of the seal region  117 ′, moisture and a foreign matter might externally enter between the strips of the gate layer  120  to be mixed in the display region  116 , thereby causing a display defect. 
     In view of the above-described points, the present invention has been devised and it is therefore an object of the present invention to provide a display device having good adhesive strength between bonded substrates, a reliably controlled cell thickness, and good display quality. 
     Solution to the Problem 
     A display device according to the present invention includes: first and second substrates arranged to face each other, each including an insulating base material; a display medium layer provided between the first and second substrates; and a sealant provided in a seal region surrounding the display medium layer for bonding the first and second substrates, in a part of the first substrate located in the seal region, a plurality of structures are formed on the insulating base material to be arranged in a direction in which the seal region extends, at least one eave portion is formed on the plurality of structures to protrude in a direction along a surface of the insulating base material and provide voids under the at least one eave portion, and the sealant is provided over the at least one eave portion to adhere to the at least one eave portion and is filled in the voids to adhere to the structures. 
     The display device of the present invention may be configured so that each of the structures is formed into a raised shape. 
     The display device of the present invention may be configured so that the structures are formed on the insulating base material and are made of the same insulating layer as an insulating layer provided in a display region. 
     The display device of the present invention may be configured so that each of the voids is a side portion of an associated one of notches formed in the insulating layer. 
     The display device of the present invention may be configured so that the at least one eave portion is made of the same semiconductor film as a semiconductor film provided on a part of the insulating layer located in a display region. 
     The display device of the present invention may be configured so that upper structures each having a raised shape are formed on the at least one eave portion, and upper eave portions are formed on the upper structures to protrude in a direction along the surface of the insulating base material and provide voids under the upper eave portions. 
     The display device of the present invention may be configured so that the upper structures are made of the same semiconductor film as a semiconductor film provided in a display region. 
     The display device of the present invention may be configured so that the upper eave portions are made of the same metal thin film as a metal thin film provided in a display region. 
     The display device of the present invention may be configured so that the structures are formed to be arranged along an entire circumference of the seal region surrounding the display medium layer. 
     ADVANTAGES OF THE INVENTION 
     According to the present invention, a display device having good adhesive strength between bonded substrates, a reliably controlled cell thickness, and good display quality can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a liquid crystal display device according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the liquid crystal display device of the first embodiment of the present invention. 
         FIG. 3  is a cross-sectional view of a thin film transistor substrate. 
         FIG. 4  is a cross-sectional view of a color filter substrate. 
         FIG. 5  is an enlarged plan view of a seal region and its periphery within a doted frame S of  FIG. 1 . 
         FIG. 6  is a cross-sectional view of the thin film transistor substrate taken along the line A-A′ of  FIG. 5 . 
         FIG. 7  is an enlarged plan view of a seal region and its periphery in a liquid crystal display device according to a second embodiment of the present invention. 
         FIG. 8  is a cross-sectional view of a thin film transistor substrate taken along the line A-A′ of  FIG. 7 . 
         FIG. 9  is an enlarged plan view of a seal region and its periphery in a liquid crystal display device according to a third embodiment of the present invention. 
         FIG. 10  is a cross-sectional view of a thin film transistor substrate taken along the line A-A′ of  FIG. 9 . 
         FIG. 11  is a plan view of a known liquid crystal display device. 
         FIG. 12  is an enlarged plan view of a seal region within a dotted frame S of  FIG. 11 . 
     
    
    
     DESCRIPTION OF REFERENCE CHARACTERS 
     
         
           10 ,  30 ,  50  Liquid Crystal Display Device 
           11  Liquid Crystal Display Panel 
           12 ,  32 ,  52  Thin Film Transistor Substrate 
           13  Color Filter Substrate 
           16 ,  36 ,  56  Display Region 
           20 ,  40 ,  60  Glass Substrate 
           21 ,  41 ,  61  Liquid Crystal Layer 
           22 ,  42 ,  62  Gate Insulating Film 
           23 ,  43 ,  63  Interlevel Insulating Film 
           24 ,  44 ,  64  Protective Film 
           25 ,  45 ,  65  Structure 
           29 ,  48 ,  68  Semiconductor Film 
           26 ,  46 ,  66  Eave Portion 
           27 ,  47 ,  67 ,  92  Void 
           17 ,  37 ,  57  Sealant 
           17 ′,  37 ′,  57 ′ Seal Region 
           49 ,  69 ,  73  n +  semiconductor film 
           72  Gate Electrode 
           75  Source Electrode 
           76  Drain Electrode 
           77  Thin Film Transistor 
           90  Upper Structure 
           91  Upper Eave Portion 
       
    
     DESCRIPTION OF EMBODIMENTS 
     According to embodiments of the present invention, structures of a display device, and methods for fabricating a display device will be described in detail hereinafter with reference to the accompanying drawings. A liquid crystal display device will be described as an example of a display device according to the present invention. Note that the present invention is not limited to the following embodiments. 
     First Embodiment 
     Structure of Liquid Crystal Display Device  10   
       FIG. 1  is a plan view of a liquid crystal display device  10  according to a first embodiment of the present invention.  FIG. 2  is a cross-sectional view of the liquid crystal display device  10 .  FIG. 3  is a cross-sectional view of a thin film transistor substrate  12 .  FIG. 4  is a cross-sectional view of a color filter substrate  13 . The liquid crystal display device  10  is comprised of a liquid crystal display panel  11  and a back light  19 . 
     The liquid crystal display panel  11  is comprised of the thin film transistor substrate  12  (first substrate) and the color filter substrate  13  (second substrate) each of which is a thin film layered device in which a plurality of thin films are stacked on an insulating base material such as a glass substrate and the like. The liquid crystal display panel  11  includes a liquid crystal layer  21  formed between the thin film transistor substrate  12  and the color filter substrate  13 . 
       FIG. 3  is a cross-sectional view of the thin film transistor substrate  12 . In the thin film transistor substrate  12 , a plurality of pixels (not shown) are provided, and a thin film transistor  77  is formed in each pixel. An orientation film  18  is provided on a surface of the thin film transistor substrate  12  located closer to the liquid crystal layer  21 , and a polarizing plane  28  is provided on a surface of the thin film transistor substrate  12  located at the opposite side. 
     The thin film transistor substrate  12  is comprised of, for example, a glass substrate  20  having a thickness of 0.7 mm On one of surfaces of the glass substrate  20 , a SiNx film (not shown) is formed as a base coating layer to have a thickness of, for example, 150 nm In a part of the SiNx film corresponding each pixel, a gate electrode  72  made of, for example, Ti, is formed to have a thickness of about 200 nm, and a gate insulating film  22 , for example, comprised of a SiNx layer is formed to cover the SiNx film and the gate electrode  72  and to have a thickness of about 400 nm. 
     A semiconductor film  29  is formed on the gate insulating film  22  to entirely cover the gate electrode  72  with the gate insulating film  22  interposed between the gate electrode  72  and the semiconductor film  29  and to have a thickness of, for example, about 150 nm. For example, the semiconductor film  29  is made of at least one of amorphous Si (a-Si), polycrystalline Si, microcrystalline Si, oxide semiconductor, and the like. 
     On the semiconductor film  29 , an n +  semiconductor film  73 , which is doped with a high concentration of an n-type impurity, is formed to have a thickness of, for example, about 50 nm. A source electrode  75  and a drain electrode  76  each being made of, for example, Ti, are formed above the n +  semiconductor film  73  and the gate insulating film  22  so that each of the source electrode  75  and the drain electrode  76  has a thickness of about 200 nm. As described above, the thin film transistor  77  having the gate electrode  72 , the n +  semiconductor film  75 , and the drain electrode  76  is formed in the thin film transistor substrate  12 . The thin film transistor  77  is covered by an interlevel insulating film  23  and a protective film  24  each of which is comprised of, for example, a SiNx layer. Although not shown in  FIG. 3 , a pixel electrode which is a component of each pixel is formed on the drain electrode  76  with the interlevel insulating film  23  and the protective film  24  interposed between the drain electrode  76  and the pixel electrode, and the drain electrode  76  is electrically coupled to the pixel electrode through a contact hole formed in the interlevel insulating film  23  and the protective film  24 . 
     The thin film transistor substrate  12  is formed to have a larger area than that of the color filter substrate  13 , and thus, as shown in  FIG. 1 , a region (margin region  14 ) in which a part of the thin film transistor substrate  12  is left as a margin is created when the thin film transistor substrate  12  and the color filter substrate  13  are bonded together. Terminal portions  15  for transmitting an external signal and the like are formed in the margin region  14 . 
     The color filter substrate  13  is comprised of a glass substrate  80  (insulating base material) and, for example, a SiNx film (not shown) is formed as a base coating layer on the glass substrate  80  to have a thickness of 150 nm. A plurality of color filter layers  82 , each of which is a component of each pixel, are formed on the SiNx film with a predetermined space therebetween. A black matrix layer  83  is formed between adjacent ones of the color filter layers  82  to define a boundary between the adjacent ones of the color filter layers  82 , and a counter electrode  84  is formed to cover the color filter layers  82  and the black matrix layers  83 . An orientation film  18 ′ is provided on a surface of the color filter substrate  13  located closer to the liquid crystal layer  21 , and a polarizing plane  28 ′ is provided on a surface of the color filter substrate  13  located at the opposite side to the liquid crystal layer  21 . 
     The liquid crystal layer  21  is surrounded by a sealant  17  provided between the thin film transistor substrate  12  and the color filter substrate  13 , and is sealed by the sealant  17 . To provide a uniform space between the thin film transistor substrate  12  and the color filter substrate  13 , a column-shaped spacer (not shown) made of, for example, plastic, glass, and the like is provided between the thin film transistor substrate  12  and the color filter substrate  13 . 
     Next, a seal region  17 ′ and its periphery in the liquid crystal display device  10  will be described.  FIG. 5  is an enlarged plan view of the seal region  17 ′ and its periphery within a dotted frame S of  FIG. 1 .  FIG. 6  is a cross-sectional view of the thin film transistor substrate  12  taken along the line A-A′ of  FIG. 5 . 
     The gate insulating film  22 , the interlevel insulating film  23 , and the protective film  24  which are stacked in a display region  16  are located also in a part of the thin film transistor substrate  12  located in the seal region  17 ′. The stacked films are notched in the seal region  17 ′, and the glass substrate  20  is exposed in the seal region  17 ′. Structures  25  made of the same material as that of the gate insulating film  22  are provided on the glass substrate  20 . 
     The plurality of the structures  25  are formed on the part of the glass substrate  20  located in the seal region  17 ′ to be arranged in the direction in which the seal region  17 ′ extends along the entire circumference of the seal region  17 ′. Each of the structures  25  is formed into a raised shape. More specifically, each of the structures  25  is formed to have a circular column shape, for example, having a height of about 400 nm and a diameter of about 400 nm. However, the shape of each of the structures  25  is not particularly limited and, as long as the structure  25  is formed into a raised shape, each of the structures  25  may be formed to have a rectangular column shape, a tapered shape, an inverse tapered shape, and the like. 
     Eave portions  26  are provided on the plurality of structures  25 . Each of the eave portions  26  is formed to have a circular column shape having, for example, a height of about 100 nm and a diameter of about 500 nm. Each of the eave portions  26  protrudes in a direction along a surface of the glass substrate  20  to provide a void  27  under the eave portion  26 . Each of the voids  27  is a side portion of an associated one of notches  27 ′ formed in the gate insulating film  22 . The shape of the eave portions  26  is not particularly limited and, as long as the voids  27  can be provided by the eave portions  26 , each of the eave portions  26  may be formed to have a rectangular column shape, a tapered shape, and the like. The eave portions  26  are made of the same material as that of the semiconductor film  29  provided in the display region  16 . 
     The sealant  17 , which is provided between the thin film transistor substrate  12  and the color filter substrate  13  and in the seal region  17 ′ to surround the liquid crystal layer  21 , is located over the eave portions  26  to adhere to the eave portions  26 , and also is filled in the voids  27  formed in the gate insulating film  22  to adhere to the structures  25 . 
     (Method for Fabricating Liquid Crystal Display Device  10 ) 
     Next, a method for fabricating the liquid crystal display device  10  according to an embodiment of the present invention will be described. Note that the following fabrication method is merely an example, and the liquid crystal display device  10  according to the present invention is not limited to a liquid crystal display device fabricated by the following method. 
     First, a glass substrate  20  to serve as a base of the thin film transistor substrate  12  is prepared. Then, a base coating layer is formed on the glass substrate  20 . Subsequently, a Ti film is formed on the base coating layer by sputtering to have a thickness of about 200 nm, and then, patterning is performed using photolithography to form gate electrodes  72 . Next, a SiN film (400 nm), an a-Si (150 nm), and n + Si (50 nm) are continuously formed as a gate insulating film  22 , a semiconductor film  29 , and an n +  semiconductor film  73  at high temperature of 250° C. by CVD. Subsequently, a-Si and n + Si are patterned into islands using photolithography. At the same time, the semiconductor film  29  in the seal region  17 ′ is patterned using the same patterning mask so that a plurality of circular regions are formed to be arranged in the direction in which the seal region  17 ′ extends along the entire circumference of the seal region  17 ′. 
     Next, a Ti film is formed by sputtering over parts of the gate insulating film  22 , the semiconductor film  29 , and the n +  semiconductor film  73  located in a display region  16  to have a thickness of about 200 nm, and then, patterning is performed using photolithography to form source electrodes  75  and drain electrodes  76 . 
     Subsequently, an interlevel insulating film  23  and a protective film  24  are formed using the SiNx layer and the like, and etching is performed to form contact holes in the interlevel insulating film  23  and the protective film  24  so that each of the contact holes extends from a surface of the protective film  24  to the drain electrode  76 . At the same time, etching is performed to remaining parts of the semiconductor film  29  and the gate insulating film  22  in the seal region  17 ′ using the same mask. In this case, an etching speed of etching of the gate insulating film  22  (SiN) is higher than an etching speed of etching of the semiconductor film  29  (a-Si), and thus, other (exposed) parts of the gate insulating film  22  than parts thereof located under the plurality of circular regions made of the semiconductor film  29  are etched faster than the semiconductor film  29 . By further performing etching, a large part of the gate insulating film  22  is etched, and the gate insulating film  22  becomes narrow. Thus, structures  25  are formed, and eave portions  26  are made of the semiconductor film  29  on the structures  25  so that each of the eave portions  26  protrudes in a direction along a surface of the glass substrate  20  to provide a void  27  under the eave portion  26 . 
     Next, pixel electrodes are formed on the protective film  24  so that each of the pixel electrodes is electrically coupled to an associated one of the drain electrodes  76  through an associated one of the contact holes, and subsequently, an orientation film  18  is formed, thus forming a thin film transistor substrate  12 . 
     Next, a glass substrate  80  to serve as a base of the color filter substrate  13  is prepared. Then, thin films, i.e., a color filter layer  82 , a counter electrode  84 , and the like, and an orientation film  18 ′ are formed, thus forming a color filter substrate  13 . 
     Subsequently, a sealant  17  is applied to one of the thin film transistor substrate  12  and the color filter substrate  13  at a part thereof located closer to the orientation film  18  or  18 ′ and in a seal region  17 ′ so as to have a substantially frame shape. Thus, the sealant  17  is provided on the eave portions  26  to adhere to the eave portions  26 , and is filled in the voids  27  formed in the gate insulating film  22  to adhere to the structures  25 . Note that the sealant  17  is formed so that an inlet for injecting a liquid crystal material is formed when the thin film transistor substrate  12  and the color filter substrate  13  are bonded together. 
     Next, the thin film transistor substrate  12  and the color filter substrate  13  are bonded together with the sealant  17  interposed therebetween so that a surface of the thin film transistor substrate  12  on which the orientation film  18  is provided faces a surface of the color filter substrate  13  on which the orientation film  18 ′ is provided. Then, after the liquid crystal material is injected through the inlet, the inlet is sealed, thus forming a liquid crystal layer  21 . 
     Next, polarizing planes  28  and  28 ′ are respectively bonded to surfaces of the thin film transistor substrate  12  and the color filter substrate  13  each of which is located at an opposite side to the liquid crystal layer  21  to form a liquid crystal display panel  11 . Then, a back light  19  is provided to the liquid crystal display panel  11  to complete a liquid crystal display device  10 . 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described.  FIG. 7  is an enlarged plan view of a seal region  37 ′ and its periphery in a liquid crystal display device  30  according to the second embodiment of the present invention.  FIG. 8  is a cross-sectional view of a thin film transistor substrate  32  taken along the line A-A′ of  FIG. 7 . 
     A gate insulating film  42 , a semiconductor film  48  (a-Si), an n +  semiconductor film  49  (n + Si), an interlevel insulating film  43 , and a protective film  44  which are stacked in a display region are also located in the seal region  37 ′ of the thin film transistor substrate  32 . The stacked layers are notched in the seal region  37 ′ so that notches  47 ′ are formed, and a glass substrate  40  is exposed at the notches  47 ′. Each of the notches  47 ′ is formed to have a circular column shape, for example, having a height of about 400 nm and a diameter of about 400 nm. However, the shape of the notches  47 ′ is not limited to the above example, but may be a rectangular column shape, a tapered shape, an inverse tapered shape, and the like. 
     Structures  45  made of the same material as that of the gate insulating film  42  are provided on a part of the glass substrate  40  located in the seal region  37 ′ so as to be located adjacent to the notches  47 ′, and are arranged in the direction in which the seal region  37 ′ extends along the entire circumference of the seal region  37 ′. 
     An eave portion  46  is formed over the structures  45 . The eave portion  46  protrudes in a direction along a surface of the glass substrate  40  to provide voids  47  under the eave portion  46 . Each of the voids  47  is a side portion of an associated one of the notches  47 ′. The eave portion  46  is made of the same material as that of the semiconductor film  48  provided in the display region  36 . 
     A sealant  37 , which is provided between the thin film transistor substrate  32  and a color filter substrate and in the seal region  37 ′ to surround a liquid crystal layer  41 , is located over the eave portion  46  to adhere to the eave portion  46 , and is filled in the voids  47  formed in the gate insulating film  42  to adhere to the structure  45 . 
     Similar to the first embodiment, the structures  45  and the eave portion  46  provided in the seal region  37 ′ can be formed simultaneously with forming corresponding components of the thin film transistor substrate  32 . Specifically, first, a glass substrate  40  to serve as a base of the thin film transistor substrate  32  is prepared. Then, a base coating layer and gate electrodes are formed on the glass substrate  40 . Next, a SiN film, a-Si, and n + Si are continuously formed as a gate insulating film  42 , a semiconductor film  48 , and an n +  semiconductor film  49 , and subsequently, a-Si and n + Si are patterned into islands using photolithography. At the same time, a part of the semiconductor film  48  located in the seal region  37 ′ is also pattered using the same mask so that a plurality of circular holes are formed to be arranged in the direction in which the seal region  37 ′ extends along the entire circumference of the seal region  37 ′. 
     Next, a Ti film is formed by sputtering over parts of the gate insulating film  42 , the semiconductor film  48 , and the n +  semiconductor film  49  located in the display region  36  to have a thickness of about 200 nm, and then, patterning is performed using photolithography to form source electrodes and drain electrodes. 
     Subsequently, an interlevel insulating film  43  and a protective film  44  are formed using a SiNx layer and the like, and then, etching is performed to form contact holes in the interlevel insulating film  43  and the protective film  44  so that each of the contact holes extends from a surface of the protective film  44  to an associated one of the drain electrodes. At the same time, etching is performed to remaining parts of the semiconductor film  48  and the gate insulating film  42  in the seal region  37 ′ using the same mask. In this case, an etching speed of etching of the gate insulating film  42  (SiN) is higher than an etching speed of etching of the semiconductor film  48  (a-Si), and thus, parts of the gate insulating film  42  corresponding to the plurality of circular holes formed in the semiconductor film  48  are etched faster. By further performing etching, a large part of the gate insulating film  42  is etched, and the gate insulating film  42  becomes narrow. Thus, structures  45  are formed, and an eave portion  46  is made of the semiconductor film  48  over the structures  45  so that the eave portion  46  protrudes in the direction along the surface of the glass substrate  40  to provide voids  47  under the eave portion  46 . During this step, a plurality of notches  47 ′ are formed so that each of the notches  47 ′ has a circular column shape whose side portion is an associated one of the voids  47 . 
     Next, pixel electrodes are formed on the protective film  44  so that each of the pixel electrodes is electrically coupled to an associated one of the drain electrodes through an associated one of the contact holes, and subsequently, an orientation film is formed, thus forming a thin film transistor substrate  32 . 
     Next, similar to the first embodiment, a color filter substrate is formed, and subsequently, a sealant  37  is applied to one the thin film transistor substrate  32  and the color filter substrate at a part thereof located closer to an associated one of the orientation films and in a seal region  37 ′ so as to have a substantially frame shape. Thus, the sealant  37  is located over the eave portion  46  to adhere to the eave portion  46 , and is filled in the voids  47  formed in the gate insulating film  42  to adhere to the structures  45 . 
     Next, a polarizing plane is bonded to each of surfaces of the thin film transistor substrate  32  and the color filter substrate each of which is located at an opposite side to a liquid crystal layer  41  to form a liquid crystal display panel. Then, a back light is provided to the liquid crystal display panel to complete a liquid crystal display device  30 . 
     Third Embodiment 
     Next, a third embodiment of the present invention will be described.  FIG. 9  is an enlarged plan view of a seal region  57 ′ and its periphery in a liquid crystal display device  50  according to a third embodiment of the present invention.  FIG. 10  is a cross-sectional view of a thin film transistor substrate  52  taken along the line A-A′ of  FIG. 9 . 
     A gate insulating film  62 , a semiconductor film  68  (a-Si), an n +  semiconductor film  69  (n + Si), an interlevel insulating film  63 , and a protective film  64  which are stacked in a display region  56  are also located in the seal region  57 ′ of the thin film transistor substrate  52 . The stacked layers are notched in the seal region  57 ′ so that notches  67 ′ are formed, and a glass substrate  60  is exposed at the notches  67 ′. Each of the notches  67 ′ is formed to have a circular column shape, for example, having a height of about 400 nm and a diameter of about 400 nm. However, the shape of the notches  67 ′ is not limited to the above example, but may be a rectangular column shape, a tapered shape, an inverse tapered shape, and the like. 
     Structures  65  made of the same material as that of the gate insulating film  62  are provided on a part of the glass substrate  60  located in the seal region  57 ′ so as to be located adjacent to the notches  67 ′, and are arranged in the direction in which the seal region  57 ′ extends along the entire circumference of the seal region  57 ′. 
     An eave portion  66  is formed over the structures  65 . The eave portion  66  protrudes in a direction along a surface of the glass substrate  60  to provide voids  67  under the eave portion  66 . Each of the voids  67  is a side portion of an associated one of the notches  67 ′. The eave portion  66  is made of the same material as that of the semiconductor film  68  provided in the display region  56 . 
     Upper structures  90  each having a raised shape are formed on the eave portion  66 , and upper eave portions  91  are formed on the upper structures  90  so as to protrude in the direction along the glass substrate  60  and provide voids  92 . 
     The upper structures  90  are made of the same material as that of the n +  semiconductor film  69  (n + Si) provided in the display region  56 . Each of the upper structures  90  is formed to have a circular column shape having, for example, a height of about 100 nm and a diameter of about 100 nm. 
     The upper eave portions  91  are made of the same metal thin film as the metal thin film of which source electrodes and drain electrodes are formed. Each of the upper eave portions  91  is formed to have a circular column shape having, for example, a height of about 200 nm and a diameter of about 200 nm. 
     A sealant  57 , which is provided between the thin film transistor substrate  52  and the color filter substrate and in the seal region  57 ′ to surround a liquid crystal layer  61 , is located over the eave portion  66  and the upper eave portions  91  to adhere to the eave portion  66  and the upper eave portions  91 , and is filled in the voids  67  and  92  formed in the gate insulating film  62  and the n +  semiconductor film  69  to adhere to the structures  65  and the upper structures  90 . 
     Similar to the first embodiment, the structures  65 , the eave portion  66 , the upper structures  90 , and the upper eave portions  91  in the seal region  57  can be formed simultaneously with forming corresponding components of the thin film transistor substrate  52 . Specifically, first, a glass substrate  60  to serve as a base of a thin film transistor substrate  52  is prepared. Then, a base coating layer and gate electrodes are formed on the glass substrate  60 . Next, a SiN film, a-S, and n + Si are continuously formed as a gate insulating film  62 , a semiconductor film  68 , and an n +  semiconductor film  69 , and subsequently, a-Si and n + Si are patterned into islands using photolithography. At the same time, a part of the semiconductor film  68  located in the seal region  57 ′ is also pattered using the same mask so that a plurality of circular holes are formed to be arranged in the direction in which the seal region  57 ′ extends along the entire circumference of the seal region  57 ′. Furthermore, patterning is performed to the n +  semiconductor film  69  to form a plurality of upper structures  90  each having a circular column shape in other parts of the n +  semiconductor film  69  than parts thereof corresponding to the circular holes in the semiconductor film  68 . 
     Next, a Ti film is formed by sputtering over parts of the gate insulating film  62 , the semiconductor film  68 , and the n +  semiconductor film  69  located in the display region  56  to have a thickness of about 200 nm, and then, patterning is performed using photolithography to form source electrodes and drain electrodes. At the same time, a part of the Ti film located in the seal region  57 ′ is patterned using the same patterning mask to form upper eave portions  91  each having a circular column shape on the upper structures  90 . 
     Subsequently, an interlevel insulating film  63  and a protective film  64  are formed using the SiNx layer and the like, and etching is performed to form contact holes in the interlevel insulating film  63  and the protective film  64  so that each of the contact holes extends from a surface of the protective film  64  to an associated one of the drain electrodes. At the same time, etching is performed to remaining parts of the semiconductor film  68  and the gate insulating film  62  in the seal region  57 ′ using the same mask. In this case, an etching speed of etching of the gate insulating film  62  (SiN) is higher than an etching speed of etching of the semiconductor film  68  (a-Si), and thus, parts of the gate insulating film  62  corresponding to the plurality of circular holes formed in the semiconductor film  68  are etched faster. By further performing etching, a large part of the gate insulating film  62  is etched, and the gate insulating film  62  becomes narrow. Thus, structures  65  are formed, and an eave portion  66  is made of the semiconductor film  68  on the structures  65  so that the eave portion  66  protrudes in the direction along the surface of the glass substrate  60  to provide voids  67  under the eave portion  66 . During this step, a plurality of notches  67 ′ are formed so that each of the notches  67 ′ has a circular column shape whose side portion is an associated one of the voids  67 . 
     Next, pixel electrodes are formed on the protective film  64  so that each of the pixel electrodes is electrically coupled to an associated one of the drain electrodes through an associated one of the contact holes, and subsequently, an orientation film is formed, thus forming a thin film transistor substrate  52 . 
     Next, similar to the first embodiment, a color filter substrate is formed, and subsequently, a sealant  57  is applied to one of the thin film transistor substrate  52  and the color filter substrate at a part thereof located closer to an associated one of the orientation films and in a seal region  57 ′ so as to have a substantially frame shape. Thus, the sealant  57  is located over the eave portions  66  and the upper eave portions  91  to adhere to the eave portion  66  and the upper eave portions  91 , and is filled in the voids  67  and  92  formed in the gate insulating film  62  and the n +  semiconductor film  69  to adhere to the structures  65  and the upper structures  90 . 
     Next, a polarizing plane is bonded to each of surfaces of the thin film transistor substrate  52  and the color filter substrate each of which is located at an opposite side to a liquid crystal layer  61  to form a liquid crystal display panel. Then, a back light is provided to the liquid crystal display panel to complete a liquid crystal display device  50 . 
     Note that in this embodiment, a liquid crystal display device (LCD) has been described as a display device, but the present invention is not limited thereto. A display device according to the present invention may be, for example, an organic electro luminescence (organic EL) display, an inorganic electro luminescence (inorganic EL) display, an electrophoretic display, a plasma display (PD), a plasma addressed liquid crystal display (PALC), a field emission display (FED), a surface-conduction electron-emitter display (SED), and the like. 
     (Operational Advantages) 
     Next, operational advantages of embodiments of the present invention will be described. 
     In the liquid crystal display devices  10 ,  30 , and  50 , the plurality of structures  25 ,  45 , and  65  are formed in the seal region  17 ′,  37 ′, and  57 ′ of the thin film transistor substrates  12 ,  32 , and  52  so as to be arranged in the direction in which the seal regions  17 ′,  37 ′, and  57 ′ extend, and the eave portions  26 , the eave portion  46 , and the eave portion  66  are formed on the plurality of structures  25 ,  45 , and  65  to protrude in the direction along the surfaces of the glass substrates  20 ,  40 , and  60  and provide the voids  27 ,  47 , and  67  thereunder. The sealants  17 ,  37 , and  57  are provided on the eave portions  26 , the eave portion  46 , and the eave portion  66  to adhere to the eave portions  26 , the eave portion  46 , and the eave portion  66 , and is filled in the voids  27 ,  47 , and  67  to adhere to the structures  25 ,  45 , and  65 . 
     In such configurations, an adhered area of each of the sealants  17 ,  37 , and  57  is increased because the structures  25 ,  45 , and  65  to which the sealants  17 ,  37 , and  57  respectively adhere, and the eave portions  26 , the eave portion  46 , and the eave portion  66  provided on the structures  25 ,  45 , and  65  are formed respectively in the seal region  17 ′,  37 ′, and  57 ′, and thus, each of the thin film transistor substrates  12 ,  32 , and  52  can be bonded to a color filter substrate in a good state. Also, the eave portions  26 , the eave portion  46 , and the eave portion  66  which are provided on the plurality of the structures  25 ,  45 ,  65  to protrude in the direction along the surface of the glass substrate  20 ,  40 , and  60  and provide the voids  27 ,  47 , and  67  thereunder serve as catching portions to catch the sealants  17 ,  37 , and  57 , respectively, and thus, the adhesive strength between the substrates can be further improved. Accordingly, the cell thickness between the substrates can be reliably controlled. Furthermore, the plurality of structures  25 ,  45 , and  65  are formed to be arranged in the direction in which the seal regions  17 ′,  37 ′, and  57 ′ extend, and thus, moisture and a foreign matter can be preferably prevented from entering the display regions  16 ,  36 , and  56  from the outside, so that the liquid crystal display devices  10 ,  30 , and  50  with good display quality can be achieved. 
     In the liquid crystal display device  10 , each of the structures  25  is formed into a raised shape. 
     In such a configuration, the adhered area with the sealant  17  can be increased by providing more structures  25 , so that the thin film transistor substrate  12  and the color filter substrate  13  can be well bonded together. 
     Furthermore, in the liquid crystal display devices  10 ,  30 , and  50 , the structures  25 ,  45 , and  65  are made of the same gate insulating films as the gate insulating films  22 ,  42 , and  62  provided in the display regions  16 ,  36 , and  56  on the insulating base materials, and the eave portions  26 , the eave portion  46 , and the eave portion  66  are made of the same semiconductor films as the semiconductor films  29 ,  48 , and  68  on the gate insulating films  22 ,  42 , and  62  provided in the display regions  16 ,  36 , and  56 . 
     In such configurations, the structures  25 ,  45 , and  65 , and the eave portions  26 , the eave portion  46 , and the eave portion  66  can be formed simultaneously with forming corresponding components of the liquid crystal display devices  10 ,  30 , and  50  forming of the display regions  16 ,  36 , and  56 , using the same method. Thus, the structures  25 ,  45 , and  65 , and the eave portions  26 , the eave portion  46 , and the eave portion  66  can be formed simultaneously with corresponding components in a known production line without requiring additional steps. Therefore, the liquid crystal display devices  10 ,  30 , and  50  can be fabricated with improved fabrication efficiency and reduced fabrication cost. 
     In the liquid crystal display device  50 , the upper structures  90  each having a raised shape are formed on the eave portion  66 , and the upper eave portions  91  are further formed on the upper structures  90  to protrude in the direction along the surface of the glass substrate  60  and provide the voids  92  under the upper eave portions  91 . 
     In such a configuration, the upper structures  90  to which the sealant  57  adheres is provided in the seal region  57 ′, and the upper eave portions  91  are further formed on the upper structures  90 . Thus, the adhered area of the sealant  57  is further increased, so that the thin film transistor substrate  52  and the color filter substrate can be bonded together in a good state. Also, the upper eave portions  91  provided on the upper structures  90  to protrude in the direction along the surface of the glass substrate  60  and provide the voids  92  under the upper eave portions  91  serve as catching portions to catch the sealant  57 , and thus, the adhesive strength between the substrates can be further improved. 
     Furthermore, in the liquid crystal display device  50 , the upper structures  90  are made of the same n +  semiconductor film  69  as the n +  semiconductor film  69  provided in the display region  56 , and the upper eave portions  91  are made of the same metal thin film as a metal film of which the source electrodes and the drain electrodes are made. 
     In such a configuration, the upper structures  90  and the upper eave portions  91  can be formed simultaneously with corresponding components of the liquid crystal display device  50  forming the display region  56 , using the same method. Thus, the upper structures  90  and the upper eave portions  91  can be formed simultaneously with corresponding components in a known production line without requiring additional steps. Therefore, the liquid crystal display device  50  can be fabricated with improved fabrication efficiency and reduced fabrication cost. 
     Furthermore, in the liquid crystal display devices  10 ,  30 , and  50 , the structures  25 ,  45 , and  65  are formed to be arranged along the entire circumferences of the seal regions  17 ′,  37 ′, and  57 ′ surrounding the liquid crystal layers  21 ,  41 , and  61 . 
     In such configurations, since the structures  25 ,  45 , and  65  are formed to be arranged along the entire circumferences of the seal regions  17 ′,  37 ′, and  57 ′ surrounding the liquid crystal layers  21 ,  41 , and  61 , each of the thin film transistor substrates  12 ,  32 , and  52  can be bonded to an color filter substrate in a good state along the entire circumferences of the seal region  17 ′,  37 ′, and  57 ′. 
     INDUSTRIAL APPLICABILITY 
     As described above, the present invention is useful for a display device.