Patent Publication Number: US-2009237352-A1

Title: Electrophoretic display unit

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to an electrophoretic display unit. 
     2. Related Art 
     In recent years, electrophoretic display units have been used as display sections of displays such as electronic paper displays. The electrophoretic display units each contain an electrophoretic dispersion containing a liquid dispersion medium and electrophoretic particles dispersed therein and use that the distribution of the electrophoretic particles is varied by the application of an electric field to the electrophoretic dispersion and therefore optical properties of the electrophoretic dispersion are varied. Japanese Unexamined Patent Application Publication No. 2007-72127 discloses an electrophoretic display unit including an electrophoretic display panel and a protective member. The electrophoretic display panel includes an element board having a display region, an electrophoretic sheet attached to the display region, a moisture barrier sheet, and an impact-absorbing film. These components are retained in the protective member. The moisture barrier sheet and the impact-absorbing film are disposed on or above the electrophoretic sheet. 
     The protective member includes a support plate, a frame, and a surface protector. The frame laterally surrounds the electrophoretic display panel. The support plate supports the front surface of the element board. The surface protector covers the front surface of the electrophoretic sheet. The frame and the electrophoretic display panel are spaced from each other with a gap therebetween. The gap contains a cushion. 
     If a side portion of the electrophoretic display panel is subjected to shock, the electrophoretic display panel moves in a space in the protective member. Therefore, the shock applied to the electrophoretic display panel is less than the shocks applied to electrophoretic display panels abutting frames. The presence of the cushion prevents the electrophoretic display panel from colliding with the frame. This allows the electrophoretic display panel to have high impact resistance. 
     In the electrophoretic display unit, the front and rear surfaces of the electrophoretic display panel have different coefficients of friction. That is, the friction between the surface protector and the impact-absorbing film is higher than the friction between the element board and the support plate. Therefore, when the electrophoretic display panel is moved toward a side portion of the protective member, the element board and the electrophoretic sheet are subjected to different friction forces and therefore stresses are generated between layers disposed in the electrophoretic display panel. There is a problem in that the layers are stripped off by the stresses. 
     SUMMARY 
     An advantage of an aspect of the invention is to provide an electrophoretic display unit having high impact resistance. 
     An electrophoretic display unit according to the present invention includes a first protective substrate, a second protective substrate, and an electrophoretic display panel disposed between the first and second protective substrates. The electrophoretic display panel includes an electrophoretic sheet which includes an electrophoretic layer and which faces the first protective substrate, an element board having a display region attached to the electrophoretic sheet, and a friction-reducing member which is the outermost layer located on the side of the electrophoretic sheet. The friction-reducing member is made of a material that allows the coefficient of friction between the friction-reducing member and the first protective substrate to be less than or equal to the coefficient of friction between the element board and the second protective substrate. 
     According to the present invention, the electrophoretic display panel includes the friction-reducing member, which is the outermost layer located on the side of the electrophoretic sheet, and the friction-reducing member is made of such a material that allows the coefficient of friction between the friction-reducing member and the first protective substrate to be less than or equal to the coefficient of friction between the element board and the second protective substrate; hence, when the electrophoretic display panel is moved in a protective member by shock, the friction between the electrophoretic display panel and the protective member can be reduced. The reduction of the friction therebetween allows the friction force applied to the electrophoretic display panel to be reduced. This prevents the breakage of the electrophoretic display panel and allows the electrophoretic display unit to have high impact resistance. 
     In the electrophoretic display unit, the friction-reducing member is disposed between the electrophoretic sheet and the first protective substrate. 
     Conventional electrophoretic display units have a problem that the friction against element boards is higher than the friction against electrophoretic sheets. On the other hand, in the electrophoretic display unit, the friction-reducing member is disposed between the electrophoretic sheet and the first protective substrate; hence, unlike the conventional electrophoretic display units, the friction against the electrophoretic sheet can be reduced. Therefore, the breakage of the electrophoretic display panel can be securely prevented. 
     In the electrophoretic display unit, the friction-reducing member overlies the electrophoretic sheet. 
     If the electrophoretic layer is partly broken, a broken portion of the electrophoretic layer cannot be used for display; hence, a measure for preventing the breakage of the electrophoretic layer has been demanded. According to the present invention, the friction-reducing member overlies the electrophoretic sheet; hence, friction force can be prevented from being applied to the electrophoretic sheet and therefore the breakage of the electrophoretic layer can be securely prevented. 
     In the electrophoretic display unit, the electrophoretic display panel further includes a third protective substrate overlying the electrophoretic sheet and the friction-reducing member overlies the third protective substrate. 
     The electrophoretic layer is susceptible to moisture changes and is readily damaged by impact. In the present invention, the friction-reducing member overlies the third protective substrate and has high moisture barrier properties and high impact resistance; hence, the electrophoretic sheet can be protected. In addition, the presence of the friction-reducing member, which overlies the third protective substrate, is effective in preventing friction force from being applied to the third protective substrate; hence, the electrophoretic sheet can be stably protected. 
     In the electrophoretic display unit, the friction-reducing member is positioned in contact with the first protective substrate. 
     According to the present invention, friction force can be prevented from being applied to all members disposed between the first protective substrate and the electrophoretic sheet because the friction-reducing member is positioned in contact with the first protective substrate. 
     In the electrophoretic display unit, the friction-reducing member is fixed to the electrophoretic display panel. 
     According to the present invention, the friction-reducing member and the electrophoretic display panel can be prevented from being misaligned with each other because the friction-reducing member is fixed to the electrophoretic display panel. Therefore, the electrophoretic display panel can be securely protected. 
     The electrophoretic display unit further includes a frame member laterally surrounding the electrophoretic display panel and a shock-absorbing member disposed between the electrophoretic display panel and the frame member. 
     According to the present invention, the shock applied to the electrophoretic display panel can be reduced when the electrophoretic display panel is laterally moved, because the electrophoretic display unit further includes the frame member, which laterally surrounds the electrophoretic display panel, and the shock-absorbing member, which is disposed between the electrophoretic display panel and the frame member. This allows the electrophoretic display unit to have enhanced impact resistance. 
     In the electrophoretic display unit, the shock-absorbing member abuts a side portion of the electrophoretic display panel. 
     According to the present invention, the transverse motion of the electrophoretic display panel is restricted because the shock-absorbing member abuts a side portion of the electrophoretic display panel. This allows the electrophoretic display unit to have enhanced impact resistance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a schematic plan view of an electrophoretic display unit according to an embodiment of the present invention. 
         FIG. 2  is a sectional view of the electrophoretic display unit taken along the line II-II of  FIG. 1 . 
         FIG. 3  is a sectional view of an electrophoretic display unit which includes no friction-reducing member and which hits a floor. 
         FIG. 4  is a sectional view of the electrophoretic display unit, according to the present invention, hitting a floor. 
         FIG. 5  is a modification of the electrophoretic display unit according to the present invention. 
         FIG. 6  is another modification of the electrophoretic display unit according to the present invention. 
         FIG. 7  is another modification of the electrophoretic display unit according to the present invention. 
         FIG. 8  is a sectional view of an electrophoretic display unit hitting something. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Embodiments of the present invention will now be described with reference to the accompanying drawings. 
       FIG. 1  is a schematic plan view of an electrophoretic display unit  1  according to an embodiment of the present invention.  FIG. 2  is a sectional view taken along the line II-II of  FIG. 1 . 
     With reference to  FIGS. 1 and 2 , the electrophoretic display unit  1  includes an electrophoretic display panel  10  and protective member  11 . The front surface of the electrophoretic display panel  10  is entirely covered with the electrophoretic display panel  10 . 
     The electrophoretic display panel  10  includes an element board  2  and an electrophoretic sheet  3  attached thereto. 
     The electrophoretic display panel  10  has a display region  5  for displaying an image such as a still image or a video image. The display region  5  contains a plurality of pixels arranged in a matrix pattern. The pixels are independently addressable. The electrophoretic display panel  10  further has a non-display region  6  which extends around the display region  5  and on which no image is displayed. The non-display region  6  contains no pixel and has a first driving circuit element  22 , a second driving circuit element  23 , and terminals  24 . 
     The element board  2  includes a substrate  20  and a driving layer  21  disposed thereon. The substrate  20  has a rectangular shape in plan view. Examples of the substrate  20  include inorganic substrates such as glass substrates, quartz substrates, silicon substrates, and gallium arsenide substrates; plastic substrates (resin substrates) such as polyimide substrates, polyethylene terephthalate (PET) substrates, polyethylene naphthalate (PEN) substrates, polymethyl methacrylate (PMMA) substrates, polycarbonate (PC) substrates, polyethersulfon (PES) substrates, and aromatic polyester (liquid crystal polymer) substrates; and similar substrates. 
     The substrate  20  has a region corresponding to the display region  5 . The driving layer  21  overlies the region. The driving layer  21  includes pixel electrodes  25 , switching elements  26 , data lines (not shown), and scanning lines (not shown). The pixel electrodes  25  and the switching elements  26  are each connected to a corresponding one of the pixels. The data and scanning lines are connected to the switching elements  26 . The driving layer  21  substantially overlaps with the display region  5  in plan view. The first and second driving circuit element  22  and  23  are disposed in the non-display region  6 , which surrounds the driving layer  21 . The first and second driving circuit element  22  and  23  are electrically connected to the data and scanning lines and supply signals to the driving layer  21 . The terminals  24  are arranged on an end portion (a right end portion) of the element board  2  and are connected to the first and second driving circuit element  22  and  23  through wires extending on the element board  2 . The terminals  24  are connected to an external circuit substrate, which is not shown. The substrate  20  slidably abuts the protective member  11 . 
     The electrophoretic sheet  3  includes a transparent substrate  30 , a common electrode  35 , an electrophoretic layer  31 , and an adhesive layer  33 . 
     The transparent substrate  30  supports the electrophoretic layer  31 . The transparent substrate  30  has a rectangular shape and is made of a material, such as PET, PES, or PC, having high light transmittance. The transparent substrate  30  has an outer surface  30   a  serving as a screen of the electrophoretic display unit  1 . 
     The transparent substrate  30  has an inner surface  30   b . The common electrode  35  extends over the inner surface  30   b  thereof. The common electrode  35  is made of a conductive material, such as indium tin oxide (ITO), having high light transmittance and is connected to the element board  2  through a through conductive member  9 . 
     The electrophoretic layer  31  contains a plurality of microcapsules  32 . 
     The microcapsules  32  are substantially spherical, contain an electrophoretic dispersion, and have a uniform diameter of about 50 to 100 μm. Examples of a material for forming the walls of the microcapsules  32  include Arabic gum-gelatin composites and polymers such as urethane resins and urea resins. The electrophoretic dispersion is sealed in the microcapsules  32  and contains a plurality of electrophoretic particles and a liquid dispersion medium for dispersing the electrophoretic particles. 
     Examples of the liquid dispersion medium include water, alcohol solvents, esters, ketones, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halohydrocarbons, carboxylates, and oils. These compounds may be used alone or in combination or used in combination with a surfactant. 
     The electrophoretic particles may be organic or inorganic particles (polymer or colloid particles) that migrate electrophoretically in the liquid dispersion medium under the influence of an electric potential. In particular, the electrophoretic particles may contain a black pigment such as carbon black or aniline black, a white pigment such as titanium dioxide, an azo pigment such as monoazo pigments, a yellow pigment such as isoindolinone, a red pigment such as quinacridone red, a blue pigment such as phthalocyanine blue, or a green pigment such as phthalocyanine green. These pigments may be used alone or in combination. These pigments may contain a charge control agent containing particles of an electrolyte, a surfactant, metal soap, resin, rubber, oil, varnish, or compound; a dispersant such as a titanium coupling agent, an aluminum coupling agent, or a silane coupling agent; a lubricant; an stabilizer; and/or the like as required. 
     The microcapsules  32  preferably contain two types of electrophoretic particles made of carbon black, which is a black pigment, or titanium dioxide, which is a white pigment: one type of electrophoretic particles are negatively charged and the other type of electrophoretic particles are positively charged. The microcapsules  32  may contain another type of electrophoretic particles. Alternatively, the microcapsules  32  may contain only one type of electrophoretic particles such that an image or the like can be displayed in such a manner that these electrophoretic particles are caused to migrate electrophoretically to the common electrode  35  or the pixel electrodes  25 . 
     The adhesive layer  33  is made from a heat-curable adhesive acting as a binder. The adhesive preferably has high affinity to the walls of the microcapsules  32 , high adhesion to the common electrode  35  and the pixel electrodes  25 , and high insulating properties. The cured adhesive is preferably elastic. 
     The transparent substrate  30  is overlaid with a moisture barrier sheet  40 . The moisture barrier sheet  40  has substantially the same size as that of the transparent substrate  30  in plan view, has a thickness of about 0.1 mm, and is light-transmissive. The moisture barrier sheet  40  may include a light-transmissive film made of, for example, polyethylene terephthalate or polyethylene naphthalate and an inorganic barrier layer disposed thereon. The moisture barrier sheet  40  is attached to the electrophoretic sheet  3  with, for example, a double-faced adhesive tape or a highly light-transmissive adhesive layer (not shown) made from a photocurable adhesive. 
     The moisture barrier sheet  40  is overlaid with a shock-absorbing film  41 . The shock-absorbing film  41  has substantially the same size as that of the transparent substrate  30  and that of the moisture barrier sheet  40  in plan view and is a highly light-transmissive film made of, for example, an acrylic or silicone-based shock-absorbing material. The shock-absorbing film  41  is fixed to the moisture barrier sheet  40  with, for example, a double-faced adhesive tape or a transparent adhesive layer (not shown). A sealing member  7  is disposed between the shock-absorbing film  41  and the element board  2 . The sealing member  7  surrounds the electrophoretic sheet  3 , the moisture barrier sheet  40 , and the shock-absorbing film  41  when viewed from above. Examples of a material for forming the sealing member  7  include epoxy resins, acrylic resins, and silicone resins. 
     The shock-absorbing film  41  is overlaid with a friction-reducing member  17 . The friction-reducing member  17  is made of a material, such as polyethylene terephthalate, polycarbonate, or an acrylic resin, having high light-transmittance such that a surface  17   a  of the friction-reducing member  17  has a coefficient of friction less than or equal to that between the electrophoretic sheet  3  and a support plate  13  described below. The friction-reducing member  17  is fixed on the shock-absorbing film  41 . Therefore, the element board  2 , the electrophoretic sheet  3 , the moisture barrier sheet  40 , the shock-absorbing film  41 , and the friction-reducing member  17  are unified. 
     The surface  17   a  of the friction-reducing member  17  slidably abuts the protective member  11 . The substrate  20  of the element board  2  also slidably abuts the protective member  11 . Therefore, the friction-reducing member  17  and the above members unified with the friction-reducing member  17  can be moved in the protective member  11  in such a state that the surface  17   a  of the friction-reducing member  17  is in contact with the protective member  11 . 
     The protective member  11  includes a surface-protecting sheet  12 , the support plate  13 , a frame member  14 , and a shock-absorbing member  15 . 
     The surface-protecting sheet  12  is located on the side of the electrophoretic sheet  3 , which is disposed in the electrophoretic display panel  10 , and is in contact with the surface  17   a  of the friction-reducing member  17 . The surface-protecting sheet  12  is not fixed to the friction-reducing member  17 . The surface-protecting sheet  12  contains an acrylic or silicone-based shock-absorbing material and has a thickness of about 0.5 mm. The surface-protecting sheet  12  has high impact resistance, is resistant to bending stress, and is flexible because of the presence of this shock-absorbing material. 
     The support plate  13  is located on the side of the element board  2 , which is disposed in the electrophoretic display panel  10 , and is positioned so as to overlap with the surface-protecting sheet  12  in plan view. The support plate  13 , as well as the surface-protecting sheet  12 , contains an acrylic or silicone-based shock-absorbing material and has a thickness of about 0.5 mm. 
     The frame member  14  laterally surrounds the electrophoretic display panel  10 . A marginal portion of the frame member  14  is sandwiched between the surface-protecting sheet  12  and the support plate  13 . The frame member  14  is made of an organic material such as an acrylic resin or PET and is tightly bonded to a marginal portion of the surface-protecting sheet  12  and a marginal portion of the support plate  13  so as to fix these marginal portions. The frame member  14  may be fixed to the surface-protecting sheet  12  and the support plate  13  by laser welding or with an adhesive, which is not shown. If this adhesive is used, this adhesive preferably contains a highly moisture-proof material and has high moisture barrier properties. 
     The shock-absorbing member  15  is disposed between the electrophoretic display panel  10  and the frame member  14  and is in contact with an inner surface of the frame member  14 . Examples of a material for forming the shock-absorbing member  15  include acrylic resins and silicone resins. The shock-absorbing member  15  can absorb the shock applied to a portion surrounding the electrophoretic display panel  10 . A gap is present between the electrophoretic display panel  10  and the shock-absorbing member  15  in plan or sectional view. In this embodiment, the gap is an air layer (air gap). The presence of the gap allows the electrophoretic display unit  1  to have increased impact resistance. 
     The electrophoretic layer  31  is sandwiched between the element board  2  and the transparent substrate  30  and is sealed with the surface-protecting sheet  12 , the support plate  13 , and the frame member  14 . The electrophoretic layer  31  is sensitive to moisture. Since the electrophoretic layer  31  is sealed as described above, moisture can be securely prevented from entering the electrophoretic layer  31 . The electrophoretic display panel  10  is in contact with the surface-protecting sheet  12  and the support plate  13 . This allows the electrophoretic display panel  10  to have increased impact resistance. 
     The operation of the electrophoretic display unit  1  is briefly described below. 
     When voltages are applied between the common electrode  35  and the pixel electrodes  25  such that the voltage of the common electrode  35  is relatively high, positively charged black electrophoretic particles are moved in the microcapsules  32  toward the pixel electrodes  25  by Coulomb&#39;s force and negatively charged white electrophoretic particles are moved in the microcapsules  32  toward the common electrode  35  by Coulomb&#39;s force. This results in that the white electrophoretic particles gather at portions of the microcapsules  32  that are close to the transparent substrate  30 , thereby displaying white, which is the color of the white electrophoretic particles, on the display region  5  of the electrophoretic display unit  1 . 
     In contrast, when voltages are applied between the common electrode  35  and the pixel electrodes  25  such that the voltage of the pixel electrodes  25  is relatively high, negatively charged white electrophoretic particles are attracted toward the pixel electrodes  25  by Coulomb&#39;s force and positively charged black electrophoretic particles are attracted toward the common electrode  35  by Coulomb&#39;s force. This results in that the black electrophoretic particles gather at portions of the microcapsules  32  that are close to the transparent substrate  30 , thereby displaying black, which is the color of the black electrophoretic particles, on the display region  5  of the electrophoretic display unit  1 . 
     When the friction-reducing member  17  is not present in the electrophoretic display unit  1 , the friction between the surface-protecting sheet  12  and the shock-absorbing film  41  is higher than the friction between the element board  2  and the support plate  13 . If a side portion of the electrophoretic display unit  1  hits a floor, the electrophoretic display panel  10  is moved toward the side portion thereof by the shock caused by hitting the floor as shown in  FIG. 3 . In this moment, the element board  2  and electrophoretic sheet  3  of the electrophoretic display panel  10  are subjected to different friction forces and therefore a stress is caused between layers of the electrophoretic display panel  10  or in, for example, the electrophoretic layer  31 , which contains the microcapsules  32 . Hence, there is a problem in that the electrophoretic layer  31  is broken by the stress. 
     According to this embodiment, the electrophoretic display panel  10 , however, includes the friction-reducing member  17 . The friction-reducing member  17  is the outermost layer located on the side of the electrophoretic sheet  3 , which faces the surface-protecting sheet  12 , and is made of the above-mentioned material, which allows the coefficient of friction between the friction-reducing member  17  and the surface-protecting sheet  12  to be less than or equal to that between the element board  2  and the support plate  13 . Therefore, when the electrophoretic display panel  10  is moved in the protective member  11  by a shock or the like as shown in  FIG. 4 , the friction between the electrophoretic display panel  10  and the protective member  11  is low. The low friction therebetween allows the electrophoretic display panel  10  to slide in the protective member  11 , because the surface  17   a  of the friction-reducing member  17  and a surface of the element board  2  serve as sliding surfaces. Therefore, the friction force applied to the electrophoretic display panel  10  can be reduced and stresses caused between layers of the electrophoretic display panel  10  can be also reduced. This prevents the breakage of the electrophoretic display panel  10  and allows the electrophoretic display unit  1  to have high impact resistance. 
     In this embodiment, the friction-reducing member  17  is disposed between the electrophoretic sheet  3  and the surface-protecting sheet  12 ; hence, the electrophoretic sheet  3  has reduced friction as compared to a conventional one. This is effective in preventing the breakage of the electrophoretic display panel  10 . 
     The microcapsules  32 , which are contained in the electrophoretic layer  31 , are susceptible to moisture changes and are readily damaged by a shock. In this embodiment, the moisture barrier sheet  40 , which has high moisture barrier properties, and the shock-absorbing film  41 , which has high impact resistance, are arranged on the electrophoretic sheet  3  in that order and the friction-reducing member  17  is disposed on the shock-absorbing film  41 ; hence, friction stresses can be prevented from being applied to the moisture barrier sheet  40  and the shock-absorbing film  41 . This allows the electrophoretic sheet  3  to be stably protected. The friction-reducing member  17  is positioned in contact with the surface-protecting sheet  12 ; hence, friction stresses can be prevented from being applied to all the members disposed between the surface-protecting sheet  12  and the electrophoretic sheet  3 . 
     According to this embodiment, the friction-reducing member  17  is fixed to the shock-absorbing film  41 , which is included in the electrophoretic display panel  10 ; hence, the friction-reducing member  17  and the electrophoretic display panel  10  can be prevented from being misaligned with each other. This allows the electrophoretic display panel  10  to be securely protected. 
     The technical scope of the present invention is not limited to this embodiment. Various modifications can be made within the scope of the present invention. 
     The friction-reducing member  17 , which is a characteristic element in this embodiment, can be modified as described below. 
       FIG. 5  is a sectional view of a modification of the electrophoretic display unit  1  and corresponds to  FIG. 2 , which is used to describe the above embodiment. 
     The coefficient of friction between the friction-reducing member  17  and the surface-protecting sheet  12  may be reduced in such a manner that the surface  17   a  of the friction-reducing member  17  is treated as shown in  FIG. 5 . The surface  17   a  may be treated with, for example, Teflon® or the like such that a surface layer  17   b  is formed. Alternatively, the surface  17   a  may be smoothed by polishing. 
       FIG. 6 , as well as  FIG. 5 , is a sectional view of another modification of the electrophoretic display unit  1 . 
     In the above embodiment, the friction-reducing member  17  is disposed on the shock-absorbing film  41 . The present invention is not limited to this configuration. As shown in  FIG. 6 , the shock-absorbing film  41  may be used to reduce friction instead of the friction-reducing member  17  in such a manner that the shock-absorbing film  41  is surface-treated with, for example, Teflon® or the like such that a surface layer  17   b  is formed thereon or in such a manner that a surface  41   a  of the shock-absorbing film  41  is smoothed by polishing. Alternatively, the moisture barrier sheet  40  or the transparent substrate  30  may be surface-treated in the same manner as above so as to serve as a friction-reducing member. 
       FIG. 7 , as well as  FIGS. 5 and 6 , is a sectional view of another modification of the electrophoretic display unit  1 . 
     In the above embodiment, the friction-reducing member  17  is disposed on the shock-absorbing film  41  as described above. The present invention is not limited to this configuration. As shown in  FIG. 7 , the friction-reducing member  17  may be disposed between the shock-absorbing film  41  and the moisture barrier sheet  40 . In this configuration, the friction-reducing member  17  is fixed to the moisture barrier sheet  40  and is not fixed to the shock-absorbing film  41 . Therefore, the element board  2 , the electrophoretic sheet  3 , the moisture barrier sheet  40 , and the friction-reducing member  17  are unified. 
     For this configuration, if a side portion of the electrophoretic display unit  1  hits a floor, the unified members move in the protective member  11  toward the floor because the friction between the surface  17   a  of the friction-reducing member  17  and the shock-absorbing film  41  is low. Therefore, stresses can be prevented from being applied to portions between the unified members and in particular, a stress can be prevented from being applied to the electrophoretic layer  31 . 
     The friction-reducing member  17  may be disposed between the electrophoretic sheet  3  and the moisture barrier sheet  40 . In this configuration, the friction-reducing member  17  is fixed to the transparent substrate  30  of the electrophoretic sheet  3  and is not fixed to the moisture barrier sheet  40 . For this configuration, even if a side portion of the electrophoretic display unit  1  hits a floor, stresses can be prevented from being applied to portions between the unified members including the electrophoretic layer  31 . 
     In the above embodiment, the friction-reducing member  17  is located on the side of the electrophoretic sheet  3 , which is disposed in the electrophoretic display panel  10 . Another friction-reducing member  17  may be placed on the side of element board  2 . This friction-reducing member  17 , which is locate on the side of the element board  2 , is made of the same material as that used to form that friction-reducing member  17 , which is located on the side of the electrophoretic sheet  3 . Therefore, when electrophoretic display panel  10  is moved in the protective member  11 , the friction generated on that friction-reducing member  17 , which is located on the side of the electrophoretic sheet  3 , is substantially equal to the friction generated on this friction-reducing member  17 , which is located on the side of the element board  2 . This securely prevents stresses from being generated between layers in the electrophoretic display panel  10 . 
     In the above embodiment, the air layer (air gap) is disposed between the electrophoretic display panel  10  and the shock-absorbing member  15 . The present invention is not limited to this configuration. The shock-absorbing member  15  may be directly bonded to the electrophoretic display panel  10 . In this case, even if a side portion of the electrophoretic display unit  1  hits a floor, the shock-absorbing member  15  restricts the motion of the electrophoretic display panel  10  and therefore can securely prevent a stress from being applied to the electrophoretic display panel  10  in cooperation with the friction-reducing member  17 . 
     The entire disclosure of Japanese Patent Application No.2008-076014, filed Mar. 24, 2008 is expressly incorporated by reference herein.