Patent Publication Number: US-2012044450-A1

Title: Liquid crystal display apparatus and method for manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2010-184768, filed on Aug. 20, 2010, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiment discussed herein is related to a liquid crystal display apparatus and a method for manufacturing the liquid crystal display apparatus. 
     BACKGROUND 
     In a known method for manufacturing a liquid crystal display element for use in electronic paper, after two substrates have been bonded together with a sealant, a liquid crystal is injected into a space between the substrates. For example, in a method for manufacturing a liquid crystal display element disclosed in Japanese Laid-open Patent Publication No. 05-127176, after a liquid crystal has been injected through an inlet into a space between two substrates, portions of the substrates corresponding to the inlet are heat-pressed to seal the liquid crystal space. 
     In the liquid crystal space of the liquid crystal display element, the portions of the substrates corresponding to the inlet are filled with the liquid crystal. Thus, the heat press bonding of the portions of the substrates corresponding to the inlet heats the liquid crystal in the vicinity of the inlet, possibly generating air bubbles in the liquid crystal space. Air bubbles in the liquid crystal space can degrade image quality and hinder the drive of the liquid crystal. Thus, elements thus manufactured must be checked for the presence of air bubbles. Once a liquid crystal display element is heat-pressed, however, air bubbles in the liquid crystal cannot be removed. Liquid crystal display elements containing air bubbles must therefore be disposed of as defective products. 
     SUMMARY 
     According to an aspect of an embodiment, a liquid crystal display apparatus includes a first substrate and a second substrate facing each other, a liquid crystal disposed between the first substrate and the second substrate, a sealant provided between the first substrate and the second substrate, the sealant defining a space in which the liquid crystal is contained and an opening in communication with the space in association with the first substrate and the second substrate, and a sealing film covering the opening and including a first portion bonded to a surface of the first substrate and a second portion bonded to a surface of the second substrate. Portions of the first substrate and the second substrate are welded together. The portions are located on an opposite side to the opening with respect to the opening and being covered with the sealing film. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a partly cutaway plan view of a liquid crystal display apparatus according to a first embodiment. 
         FIG. 2  is a plan view of a liquid crystal display element according to the first embodiment. 
         FIG. 3  is a partly cutaway plan view of the liquid crystal display element according to the first embodiment. 
         FIG. 4  is a plan view of a liquid crystal inlet portion according to the first embodiment. 
         FIG. 5  is a cross-sectional view taken along the line V-V in  FIG. 4 . 
         FIG. 6  is a plan view of a liquid crystal inlet portion according to a modification of the first embodiment. 
         FIG. 7  is a plan view of a liquid crystal inlet portion according to another modification of the first embodiment. 
         FIG. 8  is an explanatory drawing of a process for manufacturing the liquid crystal display element according to the first embodiment. 
         FIG. 9  is an explanatory drawing of a process for manufacturing the liquid crystal display element according to the first embodiment. 
         FIG. 10  is an explanatory drawing of a process for manufacturing the liquid crystal display element according to the first embodiment. 
         FIG. 11  is an explanatory drawing of a process for manufacturing the liquid crystal display element according to the first embodiment. 
         FIG. 12  is an explanatory drawing of a process for sealing a liquid crystal inlet according to the first embodiment. 
         FIG. 13  is a cross-sectional view of the liquid crystal inlet portion in the process for sealing a liquid crystal inlet according to the first embodiment. 
         FIG. 14  is a cross-sectional view of a liquid crystal inlet portion according to another modification of the first embodiment. 
         FIG. 15  is a perspective view of welding heads according to a modification of the first embodiment. 
         FIG. 16  is a partly cutaway plan view of a liquid crystal display element according to a second embodiment. 
         FIG. 17  is a plan view of a liquid crystal inlet portion according to the second embodiment. 
         FIG. 18  is a cross-sectional view taken along the line XVIII-XVIII in  FIG. 17 . 
         FIG. 19  is a plan view of a liquid crystal inlet portion according to a modification of the second embodiment. 
         FIG. 20  is a plan view of a liquid crystal inlet portion according to another modification of the second embodiment. 
         FIG. 21  is a cross-sectional view of the liquid crystal inlet portion according to that other modification of the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A first embodiment will be described below with reference to  FIGS. 1 to 15 . 
     Structure of Liquid Crystal Display Apparatus 
       FIG. 1  is a partly cutaway plan view of a liquid crystal display apparatus according to the first embodiment. The liquid crystal display apparatus may be electronic paper. The liquid crystal display apparatus includes a liquid crystal display element  10 , a circuit board  20 , and a housing  30 . Although the liquid crystal display apparatus according to the present embodiment includes only one liquid crystal display element  10 , color liquid crystal display apparatuses may include three liquid crystal display elements for red, green, and blue. 
     The liquid crystal display element  10  is connected to the circuit board  20  through a flexible printed circuit (not shown). As viewed from the top, the liquid crystal display element  10  overlaps with the circuit board  20  with a backlight (not shown) interposed therebetween. The housing  30  contains the liquid crystal display element  10 , the circuit board  20 , and the backlight. The housing  30  has an opening  30 A, which faces the liquid crystal display element  10  and defines the display screen. 
     Structure of Liquid Crystal Display Element 
       FIG. 2  is a plan view of the liquid crystal display element  10  according to the first embodiment. The liquid crystal display element  10  includes a liquid crystal display portion  10 A and a liquid crystal inlet portion  10 B, which has a smaller width than the liquid crystal display portion  10 A. The liquid crystal display portion  10 A drives a liquid crystal L (not shown) in a liquid crystal space S to display information. The liquid crystal inlet portion  10 B protrudes from the liquid crystal display portion  10 A. The liquid crystal L is injected through the liquid crystal inlet portion  10 B into the liquid crystal space S of the liquid crystal display portion  10 A. 
       FIG. 3  is a partly cutaway plan view of the liquid crystal display element  10  according to the first embodiment. The liquid crystal display element  10  includes a first film substrate  11  and a second film substrate  12 . For example, the first film substrate  11  and the second film substrate  12  are made of poly(ethylene terephthalate) (PET), polycarbonate (PC), poly(ethylene naphthalate) (PEN), or polyethersulfone (PES). These materials may have a melting point in the range of 130° C. to 150° C. The first film substrate  11  and the second film substrate  12  are bonded together with a sealant  13  so as to be a predetermined distance from each other. The distance between the first film substrate  11  and the second film substrate  12  depends on the dimensions of columnar spacers  14  and spherical spacers  15  described below. For example, the distance ranges from approximately 4 to 5 μm. 
     A plurality of transparent electrodes (not shown) and alignment films (not shown) are disposed on the surfaces of the first film substrate  11  and the second film substrate  12  facing the liquid crystal L. A driving voltage can be applied to the liquid crystal L through the transparent electrodes. The alignment films allow the liquid crystal L to be oriented. The transparent electrodes may be made of indium tin oxide (ITO). 
     The alignment films cover the first film substrate  11 , the second film substrate  12 , and the transparent electrodes. The surfaces of the alignment films have been subjected to a rubbing process to facilitate the orientation of the liquid crystal L in the vicinity of the first film substrate  11  and the second film substrate  12 . The alignment films may be made of polyimide. 
     The columnar spacers  14  and the spherical spacers (for example, bead spacers)  15  are disposed between the first film substrate  11  and the second film substrate  12 . The liquid crystal space S between the first film substrate  11  and the second film substrate  12  is filled with the liquid crystal L. 
     The columnar spacers  14  are shaped like a cross as viewed from the top and are disposed between the transparent electrodes. The columnar spacers  14  may have a height in the range of approximately 4 to 5 μm. The columnar spacers  14  are sticky and can adhere to the first film substrate  11  and the second film substrate  12 . Thus, the columnar spacers  14  prevent an increase and a decrease in the distance between the first film substrate  11  and the second film substrate  12 . The columnar spacers  14  may be made of an acrylic photoresist. 
     The spherical spacers  15  are dispersed between the first film substrate  11  and the second film substrate  12 . The spherical spacers  15  may have a diameter in the range of 4 to 5 μm. The spherical spacers  15  may be made of a vitreous material or an acrylic resin material. The material of the liquid crystal L has a decomposition temperature or a temperature at which the thermal decomposition of the liquid crystal L causes gas evolution higher than the melting points of the materials of the first film substrate  11  and the second film substrate  12 . The liquid crystal L may be a cholesteric liquid crystal. The cholesteric liquid crystal may have a decomposition temperature in the range of approximately 170° C. to 180° C. 
     The columnar spacers  14 , the spherical spacers  15 , and the liquid crystal L are uniformly disposed in not only the liquid crystal display portion  10 A, but also the liquid crystal inlet portion  10 B. Thus, also in the liquid crystal inlet portion  10 B, there is a space between the first film substrate  11  and the second film substrate  12 , and the space is filled with the liquid crystal L. 
     The sealant  13  is disposed along the peripheries of the first film substrate  11  and the second film substrate  12  and defines the liquid crystal space S to be filled with the liquid crystal L. A first end  13   a  and a second end  13   b  of the sealant  13  extend from the liquid crystal display portion  10 A to the liquid crystal inlet portion  10 B and define a liquid crystal inlet O 1  through which the liquid crystal L can be injected into the liquid crystal space S. For example, the sealant  13  can be formed by the application of an adhesive with a dispenser. The adhesive may be an acrylic resin material. 
     The sealant  13  is disposed slightly away from the peripheries of the first film substrate  11  and the second film substrate  12 . Thus, the first film substrate  11  and the second film substrate  12  have a first substrate outer-area  11 A and a second substrate outer-area  12 A, respectively, outside the sealant  13 . 
     The first substrate outer-area  11 A and the second substrate outer-area  12 A are disposed along the entire peripheries of the first film substrate  11  and the second film substrate  12 , forming a gap G between the first film substrate  11  and the second film substrate  12 . The gap G has approximately the same thickness as the liquid crystal space S. The formation of the first substrate outer-area  11 A and the second substrate outer-area  12 A depends on the method for manufacturing the liquid crystal display element  10 . 
     In the manufacture of the liquid crystal display element  10 , two large sheets are bonded together with the sealant  13  to form a large-size sheet. The large-size sheet is then cut, for example, by a punching method into the liquid crystal display element  10 . The contact between a blade used in the punching method and the sealant  13  may produce undesired asperities on the surface of the sealant  13 . Furthermore, the sealant  13  may become detached from the large-size sheet. The large-size sheet is therefore cut at a position sufficiently away from the sealant  13 . This forms blank spaces of the first film substrate  11  and the second film substrate  12  outside the sealant  13 , that is, the first substrate outer-area  11 A and the second substrate outer-area  12 A, thereby forming the gap G. The width of the gap G corresponds to the distance between the sealant  13  and the edges of the first film substrate  11  and the second film substrate  12 , that is, the widths of the first substrate outer-area  11 A and the second substrate outer-area  12 A and may be approximately 200 μm. 
       FIG. 4  is a plan view of the liquid crystal inlet portion  10 B according to the first embodiment.  FIG. 5  is a cross-sectional view taken along the line V-V in  FIG. 4 . As illustrated in  FIG. 4  or  5 , the first film substrate  11  and the second film substrate  12  have a first substrate inlet portion  11 B and a second substrate inlet portion  12 B, respectively, corresponding to the liquid crystal inlet portion  10 B. 
     The first substrate inlet portion  11 B and the second substrate inlet portion  12 B are bent such that the distance therebetween decreases in the vicinity of the sealant  13 . The inner surfaces of the first substrate inlet portion  11 B and the second substrate inlet portion  12 B adhere closely to the surface of the sealant  13  opposite the liquid crystal L, that is, an outer side surface  13 S. Portions of the first substrate inlet portion  11 B and the second substrate inlet portion  12 B extending outside the sealant  13  are welded together to form welded portions P 1 . Thus, at least in the liquid crystal inlet portion  10 B, the gap G between the first substrate outer-area  11 A and the second substrate outer-area  12 A is sealed. In each of the welded portions P 1 , an end face  11 S of the first substrate inlet portion  11 B and an end face  12 S of the second substrate inlet portion  12 B continuously form a side surface  10 S. The hatched areas in  FIG. 4  indicate the welded portions P 1  between the first film substrate  11  and the second film substrate  12 . 
     The liquid crystal inlet portion  10 B of the liquid crystal display element  10  is provided with a sealing member  16  for sealing the liquid crystal inlet O 1 . The sealing member  16  includes two resin films and has a holding portion  16 A and a peripheral portion  16 B. The holding portion  16 A surrounds the first substrate inlet portion  11 B and the second substrate inlet portion  12 B so as to include the liquid crystal inlet O 1  and the welded portions P 1 . The peripheral portion  16 B includes two resin films welded together and extends from the holding portion  16 A. 
     The inner surface of the holding portion  16 A is welded to the outer surface of the first substrate inlet portion  11 B, the outer surface of the second substrate inlet portion  12 B, and the side surfaces  10 S of the welded portions P 1  and hermetically seals the liquid crystal inlet O 1 . This can prevent the leakage of the liquid crystal L from the liquid crystal space S and the flow of the outside air into the liquid crystal space S. 
     The material of the resin films of the sealing member  16  has a lower melting point than the materials of the first film substrate  11  and the second film substrate  12 . For example, the material is low-density polyethylene (LDPE) or poly(vinyl chloride) (PVC). These materials may have a melting point in the range of 100° C. to 115° C. 
     Although the welded portions P 1  are formed within the holding portion  16 A of the sealing member  16  in the present embodiment, the present embodiment is not limited to this structure.  FIG. 6  is a plan view of a liquid crystal inlet portion  10 B according to a modification of the first embodiment. As illustrated in  FIG. 6 , the welded portions P 1  may extend from the inside to the outside of the holding portion  16 A of the sealing member  16 . In this case, an increased welded area between the first film substrate  11  and the second film substrate  12  allows securer sealing of the gap G between the first substrate outer-area  11 A and the second substrate outer-area  12 A. Alternatively, the welded portions P 1  may be partly formed within the holding portion  16 A of the sealing member  16 .  FIG. 7  is a plan view of a liquid crystal inlet portion  10 B according to another modification of the first embodiment. As illustrated in  FIG. 7 , the welded portions P 1  may be partly formed within the sealing member  16 . In this case, a decreased welded area between the first film substrate  11  and the second film substrate  12  can shorten the welding time with welding heads described below. 
     Method for Manufacturing Liquid Crystal Display Element 
     A method for manufacturing the liquid crystal display element  10  according to the first embodiment will be described below.  FIGS. 8 to 11  are explanatory drawings of a process for manufacturing the liquid crystal display element  10  according to the first embodiment. 
     As illustrated in  FIG. 8 , a first sheet  17  and a second sheet  18  are prepared. Transparent electrodes (not shown) and alignment films (not shown) are formed on the first sheet  17  and the second sheet  18 , respectively. The first sheet  17  and the second sheet  18  have been subjected to half-cut pretreatment in a predetermined shape. The “half-cut” pretreatment forms a portion having a reduced thickness in the first sheet  17  and the second sheet  18 , for example, by laser beam irradiation. 
     An adhesive is then applied to areas of elements in the first sheet  17  with a dispenser to form sealants  13 . Although not shown, a plurality of columnar spacers  14  and spherical spacers  15  are formed on the second sheet  18 . For example, the columnar spacers  14  are formed by the application of an acrylic photoresist to the second sheet  18  and the exposure and development of the photoresist (photolithography). For example, the spherical spacers  15  are formed using a spray nozzle located above the second sheet  18 . Although the sealants  13  are applied to the first sheet  17  in the present embodiment, the sealants  13  may be applied to the second sheet  18 . The first sheet  17  and the second sheet  18  are then bonded together with the sealants  13  to produce a large-size sheet  19 . In  FIGS. 8 and 9 , the sealants  13  are disposed on the back side of the first sheet  17  and should therefore be indicated by a broken line. For convenience in drawing, however, the sealants  13  are indicated by solid lines. 
     As illustrated in  FIG. 9 , the large-size sheet  19  is then punched out with a cutter C to form liquid crystal display elements  10 . The cutter C is positioned such that the sections of the large-size sheet  19  are apart from the sealants  13 . In other words, the cutter C is positioned such that the sections of the large-size sheet  19  do not interfere with the sealants  13 . After the large-size sheet  19  is divided into the liquid crystal display elements  10 , unnecessary portions of the first sheet  17  and the second sheet  18  along the half-cut line are removed. 
     Through these processes, the liquid crystal display element  10  containing no liquid crystal L as illustrated in  FIG. 10  is completed in which the first film substrate  11  and the second film substrate  12  are bonded together. In  FIG. 10 , the first film substrate  11  and the second film substrate  12  are different in shape because the half-cut lines on the first film substrate  11  and the second film substrate  12  are different. 
     The liquid crystal display element  10  containing no liquid crystal L is then placed in a vacuum chamber (not shown) to evacuate air between the first film substrate  11  and the second film substrate  12 . 
     As illustrated in  FIG. 11 , the liquid crystal inlet O 1  of the liquid crystal display element  10  is then immersed in the liquid crystal L in a liquid crystal tank T. The vacuum chamber is then opened to the atmosphere. This pressurizes the liquid crystal L in the liquid crystal tank T to the atmosphere, allowing the liquid crystal L to be injected into the liquid crystal space S between the first film substrate  11  and the second film substrate  12  (a vacuum pumping method). The columnar spacers  14  and the spherical spacers  15  disposed on the liquid crystal inlet portion  10 B can provide a gap between the first substrate inlet portion  11 B and the second substrate inlet portion  12 B, allowing the liquid crystal L to be smoothly injected. 
     After the liquid crystal space S of the liquid crystal display element  10  is filled with the liquid crystal L, the liquid crystal inlet O 1  of the liquid crystal display element  10  is sealed with the sealing member  16 . Through these processes, the liquid crystal display element  10  according to the first embodiment is manufactured. 
     Method for Sealing Liquid Crystal Inlet 
     A method for sealing the liquid crystal inlet O 1  of the liquid crystal display element  10  will be described below.  FIG. 12  is an explanatory drawing of a process for sealing the liquid crystal inlet O 1  according to the first embodiment. 
     As illustrated in  FIG. 12 , four welding heads are used to seal the liquid crystal inlet O 1  of the liquid crystal display element  10  in the present embodiment. The four welding heads are a first upper welding head  101 , a second upper welding head  102 , a first lower welding head  103 , and a second lower welding head  104 . The first upper welding head  101  and the first lower welding head  103  can be used to weld the first substrate inlet portion  11 B to the second substrate inlet portion  12 B, forming the welded portions P 1 . The second upper welding head  102  and the second lower welding head  104  can be used to weld a first resin film F 1  to a second resin film F 2 , thereby sealing the liquid crystal inlet O 1 . 
     The first upper welding head  101  includes a head main body  101   a  and two pressure blocks  101   b  disposed on the undersurface of the head main body  101   a . For example, the distance d1 between the two pressure blocks  101   b  satisfies the equation d1=d2+2×d3, wherein d2 denotes the distance between the sealants  13  in the liquid crystal inlet portion  10 B of the liquid crystal display element  10 , and d3 denotes the diameter of the sealant  13 . 
     The second upper welding head  102  has a pressure surface  102   a , which has a larger area than each of the first resin film F 1  and the second resin film F 2 . 
     The first lower welding head  103  has a shape and dimensions corresponding to those of the first upper welding head  101  and includes a head main body  103   a  and two pressure blocks  103   b  fixed to the top surface of the head main body  103   a.    
     The second lower welding head  104  has a shape and dimensions corresponding to those of the second upper welding head  102  and includes a pressure surface  104   a , which has a larger area than each of the first resin film F 1  and the second resin film F 2 . 
     The first upper welding head  101  and the first lower welding head  103  are connected to a first oscillator (not shown). The first oscillator provides the pressure blocks  101   b  and  103   b  of the first upper welding head  101  and the first lower welding head  103  with ultrasonic vibrations. 
     The second upper welding head  102  and the second lower welding head  104  are connected to a second oscillator (not shown). The second oscillator provides the pressure surfaces  102   a  and  104   a  of the second upper welding head  102  and the second lower welding head  104  with ultrasonic vibrations. The amplitude or frequency of ultrasonic vibrations generated by the first oscillator is different from the amplitude or frequency of ultrasonic vibrations generated by the second oscillator. 
     In the present embodiment, the amplitudes or frequencies of ultrasonic vibrations generated by the first oscillator and the second oscillator are determined such that the temperature at which the first substrate inlet portion  11 B and the second substrate inlet portion  12 B are welded together to form the welded portions P 1  is higher than the temperature at which the first resin film F 1  and the second resin film F 2  are welded together to seal the liquid crystal inlet O 1 . 
     When the liquid crystal inlet O 1  of the liquid crystal display element  10  is sealed using the welding heads  101  to  104 , the liquid crystal display element  10  is first placed on a table (not shown). The table is then moved to locate the liquid crystal display element  10  at a predetermined position. 
     The first upper welding head  101  and the first lower welding head  103  are then moved to position the pressure blocks  101   b  and the pressure blocks  103   b  along the outsides of the sealants  13  in the liquid crystal inlet portion  10 B of the liquid crystal display element  10 . The first resin film F 1  and the second resin film F 2  are then placed above and below the liquid crystal inlet portion  10 B of the liquid crystal display element  10 , respectively. The first resin film F 1  and the second resin film F 2  are rectangular and can sufficiently cover the liquid crystal inlet portion  10 B. 
     The first resin film F 1 , the second resin film F 2 , the first substrate inlet portion  11 B, and the second substrate inlet portion  12 B are then pressurized with the first upper welding head  101  and the first lower welding head  103 . The first oscillator is then operated to apply ultrasonic vibrations to the pressure blocks  101   b  and  103   b.    
     Friction generated by the ultrasonic vibrations heats the first substrate inlet portion  11 B and the second substrate inlet portion  12 B to a temperature in the range of approximately 180° C. to 200° C., locally welding parts of the first substrate inlet portion  11 B and the second substrate inlet portion  12 B corresponding to the pressure blocks  101   b  and  103   b . Thus, as illustrated in  FIG. 13 , the welded portions P 1  are formed in the liquid crystal inlet portion  10 B. This is hereinafter referred to as first welding. The friction also locally fuses the portions of the first resin film F 1  and the second resin film F 2  corresponding to the pressure blocks  101   b  and  103   b , thereby welding these portions to the outer surfaces of the first substrate inlet portion  11 B and the second substrate inlet portion  12 B. 
     Thus, in the welding process described above, the parts of the first substrate inlet portion  11 B and the second substrate inlet portion  12 B extending along the outsides of the sealants  13 , that is, the parts containing no liquid crystal L are locally heated. This can reduce heating of the liquid crystal L, thereby preventing the generation of air bubbles in the liquid crystal L. The welded portions P 1  of the first substrate inlet portion  11 B and the second substrate inlet portion  12 B are sometimes cloudier than their surrounding area because of the influence of heating. 
     After the first upper welding head  101  is removed from the liquid crystal inlet portion  10 B, the second upper welding head  102  is placed above the liquid crystal inlet portion  10 B. Likewise, after the first lower welding head  103  has been removed from the liquid crystal inlet portion  10 B, the second lower welding head  104  is placed under the liquid crystal inlet portion  10 B. 
     The first resin film F 1 , the second resin film F 2 , the first substrate inlet portion  11 B, and the second substrate inlet portion  12 B are then pressurized with the second upper welding head  102  and the second lower welding head  104 . The second oscillator is then operated to apply ultrasonic vibrations to the pressure surfaces  102   a  and  104   a . Friction generated by the ultrasonic vibrations heats the first resin film F 1  and the second resin film F 2  to a temperature in the range of approximately 120° C. to 130° C., fusing the portions of the first resin film F 1  and the second resin film F 2  corresponding to the pressure surfaces  102   a  and  104   a , that is, the entire resin films F 1  and F 2 . 
     Thus, the first resin film F 1  and the second resin film F 2  are welded together to cover the liquid crystal inlet portion  10 B, forming the sealing member  16  sealing the liquid crystal inlet O 1 , as illustrated in  FIG. 5 . This is hereinafter referred to as second welding. 
     The portions of the first resin film F 1  and the second resin film F 2  corresponding to the liquid crystal inlet portion  10 B are welded to the outer surface of the first substrate inlet portion  11 B, the outer surface of the second substrate inlet portion  12 B, and the side surfaces  10 S of the liquid crystal inlet portion  10 B, forming the holding portion  16 A of the sealing member  16 . The portions of the first resin film F 1  and the second resin film F 2  outside the liquid crystal inlet portion  10 B are welded together to form the peripheral portion  16 B of the sealing member  16 . 
     Since the first substrate inlet portion  11 B and the second substrate inlet portion  12 B have a melting point in the range of approximately 130° C. to 150° C., the first substrate inlet portion  11 B and the second substrate inlet portion  12 B are not fused. Furthermore, since the liquid crystal L has a decomposition temperature in the range of approximately 170° C. to 180° C., no air bubble is generated in the liquid crystal L. Through these processes, the liquid crystal inlet O 1  of the liquid crystal display element  10  is hermetically sealed. 
     In the present embodiment, the first resin film F 1  and the second resin film F 2  are placed above and below the liquid crystal inlet portion  10 B before the first welding. However, the present embodiment is not particularly limited to this. For example, the first resin film F 1  and the second resin film F 2  may be placed above and below the liquid crystal inlet portion  10 B after the first welding. 
     Alternatively, the first upper welding head  101  and the second lower welding head  104  may be used in combination in the first welding. In this case, the flat pressure surface  104   a  of the second lower welding head  104  is used in place of the first lower welding head  103 . Thus, as illustrated in  FIG. 14 , the first substrate inlet portion  11 B is mainly deformed. 
     Alternatively, the second upper welding head  102  and the first lower welding head  103  may be used in the first welding. In this case, the flat pressure surface  102   a  of the second upper welding head  102  is used in place of the first upper welding head  101 . Thus, as opposed to the deformation illustrated in  FIG. 14 , the second substrate inlet portion  12 B is mainly deformed. The sealing member  16  is omitted in  FIG. 14 . 
     An upper welding head according to a modification of the first embodiment will be described below.  FIG. 15  is a perspective view of an upper welding head  105  according to a modification of the first embodiment. 
     The upper welding head  105  includes first upper pressure blocks  105   a  and a second upper pressure block  105   b . The first upper pressure blocks  105   a  can be used to weld the first substrate inlet portion  11 B to the second substrate inlet portion  12 B, forming the welded portions P 1 . The second upper pressure block  105   b  can be used to weld the first resin film F 1  to the second resin film F 2 , thereby sealing the liquid crystal inlet O 1 . 
     The first upper pressure blocks  105   a  have a shape and dimensions corresponding to those of the two pressure blocks  101   b  of the first upper welding head  101 . The second upper pressure block  105   b  has a quadrilateral hole in which the first upper pressure blocks  105   a  are disposed. The first upper pressure blocks  105   a  are connected to a first oscillator (not shown), and the second upper pressure block  105   b  is connected to a second oscillator (not shown). 
     A lower welding head  106  includes first lower pressure blocks  106   a  and a second lower pressure block  106   b . The first lower pressure blocks  106   a  can be used to weld the first substrate inlet portion  11 B to the second substrate inlet portion  12 B, forming the welded portions P 1 . The second lower pressure block  106   b  can be used to weld the first resin film F 1  to the second resin film F 2 , thereby sealing the liquid crystal inlet O 1 . The first lower pressure blocks  106   a  have a shape and dimensions corresponding to those of the two pressure blocks  103   b  of the first lower welding head  103 . The second lower pressure block  106   b  has a quadrilateral hole in which the first lower pressure blocks  106   a  are disposed. The first lower pressure blocks  106   a  are connected to a first oscillator (not shown), and the second lower pressure block  106   b  is connected to a second oscillator (not shown). 
     When the liquid crystal inlet O 1  of the liquid crystal display element  10  is sealed using the upper welding head  105  and the lower welding head  106 , the first resin film F 1 , the second resin film F 2 , the first substrate inlet portion  11 B, and the second substrate inlet portion  12 B are first pressurized with the upper welding head  105  and the lower welding head  106 . 
     The first oscillator is then operated to apply ultrasonic vibrations to the first upper pressure blocks  105   a  and the first lower pressure blocks  106   a . Friction generated by the ultrasonic vibrations heats the first substrate inlet portion  11 B and the second substrate inlet portion  12 B to a temperature in the range of approximately 180° C. to 200° C., locally welding parts of the first substrate inlet portion  11 B and the second substrate inlet portion  12 B corresponding to the first upper pressure blocks  105   a  and the first lower pressure blocks  106   a . Thus, as illustrated in  FIG. 13 , the welded portions P 1  are formed in the liquid crystal inlet portion  10 B. 
     After the first oscillator is stopped, the second oscillator is operated to apply ultrasonic vibrations to the second upper pressure block  105   b  and the second lower pressure block  106   b . More specifically, after the first oscillator has been stopped, the second oscillator is operated while the first resin film F 1 , the second resin film F 2 , the first substrate inlet portion  11 B, and the second substrate inlet portion  12 B are pressurized with the upper welding head  105  and the lower welding head  106 . Friction generated by the ultrasonic vibrations heats the first resin film F 1  and the second resin film F 2  to a temperature in the range of approximately 120° C. to 130° C., fusing the portions corresponding to the second upper pressure block  105   b  and the second lower pressure block  106   b . Thus, as illustrated in  FIG. 5 , the first resin film F 1  and the second resin film F 2  are welded together to cover the liquid crystal inlet portion  10 B, forming the sealing member  16  sealing the liquid crystal inlet O 1 . 
     Thus, using the upper welding head  105  and the lower welding head  106 , the liquid crystal inlet O 1  can be sealed only by switching between the first oscillator and the second oscillator. This obviates the necessity of changing the upper welding head between the first welding and the second welding. 
     Although the upper welding head  105  and the lower welding head  106  are used in this modification, the upper welding head  105  and the first lower welding head  103 , the upper welding head  105  and the second lower welding head  104 , the first upper welding head  101  and the lower welding head  106 , or the second upper welding head  102  and the lower welding head  106  may be used in combination. 
     Furthermore, although ultrasonic vibrations are utilized in the present embodiment, laser welding may also be used. In this case, a colored irradiation target may be provided on a material to be welded. 
     Second Embodiment 
     A second embodiment will be described below with reference to  FIGS. 16 to 21 . Like reference numerals designate like parts and will not be further described. 
       FIG. 16  is a partly cutaway plan view of a liquid crystal display element  50  according to the second embodiment. A liquid crystal inlet portion  50 B of the liquid crystal display element  50  does not protrude from a liquid crystal display portion  50 A. A peripheral region of a liquid crystal inlet O 2  in the liquid crystal display portion  50 A functions as the liquid crystal inlet portion  50 B. A first film substrate  51  and a second film substrate  52  according to the second embodiment therefore do not have the first substrate inlet portion  11 B and the second substrate inlet portion  12 B described in the first embodiment. 
     A first end  53   a  and a second end  53   b  of a sealant  53  in the liquid crystal inlet portion  50 B extend to edges of the first film substrate  51  and the second film substrate  52 , thereby forming the liquid crystal inlet O 2  through which the liquid crystal L is injected into a liquid crystal space S. 
       FIG. 17  is a plan view of the liquid crystal inlet portion  50 B according to the second embodiment.  FIG. 18  is a cross-sectional view taken along the line XVIII-XVIII in  FIG. 17 . A sealing member  56  is omitted in  FIG. 18 . As illustrated in  FIG. 17  or  18 , portions of the first film substrate  51  and the second film substrate  52  outside the sealant  53  are partly bent such that the first film substrate  51  comes close to the second film substrate  52 . Thus, the inner surfaces of the first film substrate  51  and the second film substrate  52  adhere closely to the surface of the sealant  53  opposite the liquid crystal L, that is, an outer side surface  53 S. 
     Portions of the first film substrate  51  and the second film substrate  52  extending outside the sealant  53  are welded together to form welded portions P 2 . Thus, at least in the liquid crystal inlet portion  50 B, a gap G between a first substrate outer-area  51 A and a second substrate outer-area  52 A is sealed. The hatched areas in  FIG. 17  indicate the welded portions P 2  between the first substrate outer-area  51 A and the second substrate outer-area  52 A. 
     The liquid crystal inlet portion  50 B of the liquid crystal display element  50  is provided with a sealing member  56  for sealing the liquid crystal inlet O 2 . The sealing member  56  includes a first resin film F 1  and a second resin film F 2  and has covering portions  56 A and a peripheral portion  56 B. 
     The covering portions  56 A cover the outer surfaces of the first film substrate  51  and the second film substrate  52  so as to contain at least the liquid crystal inlet O 2  and the welded portions P 2 . The covering portions  56 A do not form a pocket and only cover the first film substrate  51  and the second film substrate  52 . The peripheral portion  56 B is formed by welding the first resin film F 1  to the second resin film F 2  and surrounds the covering portions  56 A. 
     The inner surfaces of the covering portions  56 A are welded to the outer surface of the first film substrate  51  and the outer surface of the second film substrate  52 , hermetically sealing the liquid crystal inlet O 2 . This can prevent the leakage of the liquid crystal L from the liquid crystal space S and the flow of the outside air into the liquid crystal space S. 
     Although the welded portions P 2  are formed inside the covering portions  56 A of the sealing member  56  in the present embodiment, the present embodiment is not limited to this structure.  FIG. 19  is a plan view of a liquid crystal inlet portion  50 B according to a modification of the second embodiment. As illustrated in  FIG. 19 , the welded portions P 2  may extend from the inside to the outside of the covering portions  56 A of the sealing member  56 . The welded portions P 2  are not necessarily formed throughout the whole area covered with the covering portions  56 A of the sealing member  56 . 
       FIG. 20  is a plan view of a liquid crystal inlet portion  50 B according to another modification of the second embodiment. As illustrated in  FIG. 20 , the welded portions P 2  may be partly formed in the area covered with the covering portions  56 A of the sealing member  56 . 
     Also in the present embodiment, depending on the combination of welding heads, the first film substrate  51  may be mainly deformed as illustrated in  FIG. 21 . Alternatively, as opposed to the deformation illustrated in  FIG. 21 , the second film substrate  52  may be mainly deformed. The sealing member  56  is omitted in  FIG. 21 . 
     Although electronic paper has been described, the present embodiments are not limited to electronic paper. Provided that two substrates for containing a liquid crystal are made of a weldable resin, such as a thermoplastic resin, these embodiments may be applied to any liquid crystal display element including the two substrates. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.