Patent Publication Number: US-11657771-B2

Title: Display device substrate, display device, electronic apparatus, and method for manufacturing display device substrate

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application having Ser. No. 16/826,374 filed on Mar. 23, 2020 (Publication No. 2020/0218125), which is a continuation of U.S. patent application Ser. No. 15/259,165 filed on Sep. 8, 2016 (Publication No. 2017/0082904) now U.S. Pat. No. 10,599,004 issued on Mar. 24, 2020. The entire disclosures of the prior applications are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to a display device substrate, a display device, an electronic apparatus, and a method for manufacturing a display device substrate. 
     Related Art 
     Electrophoretic display devices in which particles having charges move in a dispersion medium are widely used. The electrophoretic display device has less screen flicker, and therefore is used as a display device for viewing an electronic book, or the like. This type of electrophoretic display device is disclosed in JP-A-2007-240679. According to JP-A-2007-240679, the electrophoretic display device includes a pair of substrates disposed with electrodes. A dispersion medium containing colored charged particles is disposed between the electrodes. A partition wall is disposed in a grid shape between the substrates, and rooms are partitioned by the partition wall. A distance between the substrates is kept by the partition wall. 
     In the room, the colored charged particles are charged. By applying voltages to a pair of electrodes disposed in the substrates facing each other, the colored charged particles are attracted to one of the electrodes. Next, by changing the voltages of the electrodes, the position of the colored charged particles is changed. 
     Pixel electrodes are disposed in one of the substrates, and the pixel electrode serves as one pixel. By controlling the position of the colored charged particles for each of the pixels, a predetermined figure can be displayed. 
     In JP-A-2007-240679, an insulating film covered by an inorganic material is disposed on a surface of the one substrate. The partition wall is disposed on the insulating film. The material of the partition wall is a cardo polymer, which is one kind of resin materials. After the dispersion medium is disposed in the room within the partition wall, the pair of substrates are combined together. When the pair of substrate are combined together, a load is applied between the substrates. In this case, since the partition wall and the insulating film are made of the materials having different properties, the partition wall and the insulating film are not securely bonded together. Thus, when a load is applied to the partition wall, the partition wall and the insulating film may peel from each other or may be shifted to each other. In this case, the partition wall collapses or crushes, and therefore, there is a need for a display device substrate, in which the partition wall is inhibited from collapsing or crushing even when a load is applied between the substrates. 
     SUMMARY 
     An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples. 
     Application Example 1 
     A display device substrate according to this application example includes: a substrate including an insulating layer, and a partition wall disposed on the insulating layer, wherein the insulating layer and the partition wall are formed of a resin material, and the partition wall has a higher hardness than the insulating layer. 
     According to this application example, the display device substrate includes the substrate, and the substrate is disposed with the insulating layer. The partition wall is disposed on the insulating layer. The insulating layer and the partition wall are formed of a resin material. Thus, compared with the case where one of the insulating layer and the partition wall is an inorganic material, the insulating layer and the partition wall can be fixed together at high strength. Further, the partition wall has a higher hardness than the insulating layer, and therefore has strength. As a result, even when a load is applied to the partition wall, it is possible to inhibit the partition wall from collapsing or crushing. 
     Application Example 2 
     In the display device substrate according to the application example, it is preferable that a protective film that protects the insulating layer is disposed on a surface of the insulating layer. 
     According to this application example, the protective film protecting the insulating layer is disposed on the surface of the insulating layer. Thus, since the insulating layer and a chemical liquid constituting a display device do not come in contact with each other, the chemical liquid or the insulating layer can be prevented from being damaged. 
     Application Example 3 
     In the display device substrate according to the application example, it is preferable that the protective film includes an opening, and that the partition wall is disposed so as to close the opening. 
     According to this application example, the partition wall is disposed so as to close the opening of the protective film, so that a chemical liquid constituting a display device is inhibited from coming in contact with the insulating layer by the protective film, and also that the partition wall made of resin and the insulating layer made of resin can be fixed together while being in contact with each other. 
     Application Example 4 
     In the display device substrate according to the application example, it is preferable that the substrate includes one pixel electrode corresponding to one pixel, and that the partition wall is disposed to surround the pixel electrode. 
     According to this application example, the substrate is disposed with one pixel electrode corresponding to one pixel. The partition wall is disposed to surround the pixel electrode. In this case, compared with the case where the partition wall surrounds a plurality of pixel electrodes, the area surrounded by the partition wall is reduced. Thus, since the area within the partition wall is small, the strength of the partition wall can be increased. As a result, even when a load is applied to the partition wall, it is possible to inhibit the partition wall from collapsing or crushing. 
     Application Example 5 
     In the display device substrate according to the application example, it is preferable that a circuit portion that is electrically connected to the pixel electrode is disposed between the substrate and the insulating layer. 
     According to this application example, the circuit portion electrically connected to the pixel electrode is provided between the substrate and the insulating layer. Thus, it is possible to inhibit the circuit portion from being eroded by a chemical liquid or the like constituting a display device. 
     Application Example 6 
     In the display device substrate according to the application example, it is preferable that the insulating layer is a planarizing layer. 
     According to this application example, since the insulating layer is a planarizing layer, the pixel electrode can be formed into a flat shape, and thus display quality can be improved. 
     Application Example 7 
     A display device according to this application example includes: the display device substrate described above, a transparent sealing member supported by the partition wall, a counter electrode disposed on the transparent sealing member; a circuit portion located between the substrate and the insulating layer and connected to a pixel electrode; and an electrophoretic dispersion liquid sealed in a space formed by the partition wall, the transparent sealing member, and the substrate. 
     According to this application example, the display device includes the display device substrate, and the transparent sealing member is supported by the partition wall. The counter electrode is disposed on the transparent sealing member. The display device substrate is disposed with the partition wall, and the electrophoretic dispersion liquid is disposed in a pixel region surrounded by the partition wall. Thus, the partition wall is located between the display device substrate and the counter electrode. Since the partition wall is less likely to collapse or crush even when a load is applied, the display device substrate, and the transparent sealing member and the counter electrode can be easily assembled. 
     Application Example 8 
     An electronic apparatus according to this application example includes: the display device described above; and a control unit that controls the display device. 
     According to this application example, the control unit controls the display device in the electronic apparatus. Since the display device is less likely to collapse or crush even when a load is applied to the partition wall, the display device is a device in which the display device substrate and the transparent sealing member can be easily assembled. Thus, the electronic apparatus can be a device including the display device in which the display device substrate and the transparent sealing member can be easily assembled. 
     Application Example 9 
     A method for manufacturing a display device substrate according to this application example includes: disposing an insulating layer of a resin material on a substrate; disposing a protective film on the insulating layer; removing a portion of the protective film; and disposing a partition wall of a resin material to cover the insulating layer at a place where the portion of the protective film is removed. 
     According to this application example, the insulating layer of a resin material is disposed on the substrate. Then, the protective film is disposed on the insulating layer, and a portion of the protective film is removed. Thus, a portion of the insulating layer is exposed. The partition wall of a resin material is disposed to cover the exposed insulating layer. Thus, since the insulating layer of a resin material and the partition wall of a resin material are connected to each other, the insulating layer and the partition wall can be securely connected. As a result, even when a load is applied to the partition wall in a later step, it is possible to inhibit the partition wall from collapsing or crushing. 
    
    
     
       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 perspective view showing the structure of an electrophoretic display device according to a first embodiment. 
         FIG.  2    is a schematic plan view showing the structure of the electrophoretic display device. 
         FIG.  3    is a partial schematic exploded perspective view showing the structure of the electrophoretic display device. 
         FIG.  4    is a schematic sectional side elevation showing the structure of the electrophoretic display device. 
         FIG.  5    is a schematic plan view of a main portion for explaining the relationship between a pixel and a partition wall. 
         FIG.  6    is an electrical control block diagram of the electrophoretic display device. 
         FIG.  7    is a schematic sectional side elevation showing the structure of the electrophoretic display device. 
         FIG.  8    is a schematic sectional side elevation showing the structure of the electrophoretic display device. 
         FIG.  9    is a flowchart of a method for manufacturing the electrophoretic display device. 
         FIG.  10    is a schematic view for explaining the method for manufacturing the electrophoretic display device. 
         FIG.  11    is a schematic view for explaining the method for manufacturing the electrophoretic display device. 
         FIG.  12    is a schematic view for explaining the method for manufacturing the electrophoretic display device. 
         FIG.  13    is a schematic view for explaining the method for manufacturing the electrophoretic display device. 
         FIG.  14    is a schematic view for explaining the method for manufacturing the electrophoretic display device. 
         FIG.  15    is a schematic view for explaining the method for manufacturing the electrophoretic display device. 
         FIG.  16    is a schematic view for explaining the method for manufacturing the electrophoretic display device. 
         FIG.  17    is a schematic view for explaining the method for manufacturing the electrophoretic display device. 
         FIG.  18    is a schematic view for explaining the method for manufacturing the electrophoretic display device. 
         FIG.  19    is a schematic sectional side elevation showing the structure of an electrophoretic display device according to a second embodiment. 
         FIG.  20    is a schematic perspective view showing the structure of an electronic book according to a third embodiment. 
         FIG.  21    is a schematic perspective view showing the structure of a wristwatch. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In embodiments, an electrophoretic display device and a distinct example of manufacturing the electrophoretic display device will be described according to the drawings. Members in the drawings are illustrated on different scales for each of the members in order to show the members in recognizable sizes on the drawings. 
     First Embodiment 
     An electrophoretic display device according to a first embodiment will be described according to  FIGS.  1  to  18   .  FIG.  1    is a schematic perspective view showing the structure of the electrophoretic display device.  FIG.  2    is a schematic plan view showing the structure of the electrophoretic display device. 
     As shown in  FIG.  1   , the electrophoretic display device  1  as a display device has a structure in which a first substrate  2  as a display device substrate and a second substrate  3  are stacked on top one another. The thickness direction of the first substrate  2  and the second substrate  3  is defined as a Z direction, and directions along the side surfaces of the first substrate  2  are defined as an X direction and a Y direction. The second substrate  3  is located on the +Z direction side. When viewing the electrophoretic display device  1 , a viewer views the electrophoretic display device  1  from the +Z direction side. A surface of the second substrate  3  on the +Z direction side is an image display surface  3   a . The first substrate  2  has a shape longer in the −Y direction than the second substrate  3 . On the −Y direction side of the first substrate  2 , a flexible cable  4  is disposed on a surface of the first substrate  2  on the +Z direction side. The flexible cable  4  is connected to a drive circuit (not shown), from which a power source and a drive signal are supplied through the flexible cable  4 . 
     As shown in  FIG.  2   , a partition wall  5  is disposed between the first substrate  2  and the second substrate  3  in the electrophoretic display device  1 . The partition wall  5  has a grid shape and defines pixel regions  6 . The dimensions of the partition wall  5  are not particularly limited; however, for example, the width thereof is 3 to 5 μm, and the height thereof is 30 μm in the embodiment. 
     In the drawing, 15 pixel regions  6  in the X direction and 10 pixel regions  6  in the Y direction are arranged side by side for clarity of illustration. The number of the pixel regions  6  is not particularly limited; however, for example, 320 pixel regions in the X direction and 250 pixel regions in the Y direction are arranged side by side in the embodiment. 
     The size of the pixel region  6  is not particularly limited; however, for example, the length thereof in the X direction is 50 to 100 μm, and the length thereof in the Y direction is 50 to 100 μm, in the embodiment. Also the size of the electrophoretic display device  1  is not particularly limited; however, for example, the length of the first substrate  2  in the X direction is 30 to 50 mm, and the length thereof in the Y direction is 20 to 40 mm, in the embodiment. 
     In the first substrate  2 , a first semiconductor element  7  as a circuit portion is disposed in each of the pixel regions  6 . The first semiconductor element  7  is an element that performs switching, and changes a voltage to be applied to the pixel region  6 . Since the first semiconductor element  7  exists in each of the pixel regions  6 , the number of the first semiconductor elements  7  is the same as the number of the pixel regions  6 . When a predetermined pattern is displayed on the image display surface  3   a , one pixel region  6  serves as one pixel  8 . On a surface of the first substrate  2  on the +Z direction side, a signal distributing unit  9  is disposed between the second substrate  3  and the flexible cable  4 . The signal distributing unit  9  changes a signal to be output to the first semiconductor element  7 . 
       FIG.  3    is a partial schematic exploded perspective view showing the structure of the electrophoretic display device, in which some portions of the electrophoretic display device  1  are separated in the Z direction. As shown in  FIG.  3   , the first substrate  2  includes a first base material  10 . Examples of materials used for the first base material  10  can include glass, plastic, ceramic, and silicon. The first base material  10  is arranged on the side opposite to the image display surface  3   a , which can be seen from the +Z direction, and therefore, the material of the first base material  10  may be opaque. 
     An element layer  11  is disposed on the first base material  10 . In the element layer  11 , voltage supply lines  7   a , control signal lines  7   b , the first semiconductor elements  7 , first through-electrode  7   d , and the like are disposed. The first semiconductor element  7  is a thin film transistor (TFT) element, and is an element that performs switching. An insulating layer  12  is disposed on the element layer  11 , and a protective film  13  and pixel electrodes  14  are stacked in this order on the insulating layer  12 . The insulating layer  12  is a layer that insulates the element layer  11  from the pixel electrodes  14 . The protective film  13  is a layer that protects the insulating layer  12 . The first through-electrode  7   d  in the element layer  11  is connected with the pixel electrode  14 . The pixel electrode  14  is separated in each of the pixel regions  6 . The first substrate  2  is configured of the partition wall  5 , the first base material  10 , the element layer  11 , the insulating layer  12 , the protective film  13 , the pixel electrodes  14 , and the like. 
     The material of the element layer  11  is not particularly limited as long as the material can form semiconductor, and examples thereof can include silicon, germanium, gallium arsenide, gallium arsenide phosphide, gallium nitride, and silicon carbide. The material of the insulating layer  12  is not particularly limited as long as the material has an insulating property and is readily formable, and a resin material can be used. In the embodiment, for example, a positive photosensitive acrylic resin is used as the material of the insulating layer  12 . By using a positive type, an opening to expose a portion of the insulating layer  12  can be easily formed. Moreover, the insulating layer  12  has the function of a planarizing layer so as not to reflect irregularities of the element layer  11  on the pixel region  6 . 
     The material of the pixel electrode  14  is not particularly limited as long as the material has conductivity, and examples thereof can include, in addition to copper, aluminum, nickel, gold, silver, and indium-tin oxide (ITO), a material obtained by stacking a nickel film or gold film on copper foil, and a material obtained by stacking a nickel film or gold film on aluminum foil. In the embodiment, for example, the material of the pixel electrode  14  is ITO. 
     The partition wall  5  is disposed on the protective film  13  and the insulating layer  12 , and an electrophoretic dispersion liquid  15  is filled in the pixel regions  6  defined by the partition wall  5 . The material of the partition wall  5  is not particularly limited as long as the material has proper strength, is readily formable, and is not eluted into the electrophoretic dispersion liquid  15 . A material obtained by adding a cross-linking agent to a resin material such as polyester resin, polyolefin resin, acrylic resin, or epoxy resin can be used. In the embodiment, for example, a negative photosensitive epoxy resin is used as the material of the partition wall  5 . By using a negative type, a convex shape can be easily formed. The partition wall  5  is disposed so as to close an opening of the protective film  13 . As can be seen from  FIG.  3   , the width of the opening of the protective film  13  is narrower than the width of the bottom portion of the partition wall  5 . With this configuration, a portion where the partition wall  5  and the insulating layer  12  are joined together without the protective film  13  can be formed, and the partition wall  5  and the insulating layer  12  can be securely joined. Moreover, the partition wall  5  and the insulating layer  12  are joined together through the protective film  13  on both sides of the opening, so that the insulating layer  12  can be prevented from being damaged by the electrophoretic dispersion liquid  15  through the opening. 
     The material of the protective film  13  is not particularly limited as long as the material has an insulating property and is not eluted into the electrophoretic dispersion liquid  15 . In the embodiment, for example, silicon nitride is used as the material of the protective film  13 . The protective film  13  prevents the insulating layer  12  from being eluted into the electrophoretic dispersion liquid  15 . With this configuration, the alteration of the electrophoretic dispersion liquid  15  is prevented, and the degradation of the insulating layer  12  is prevented. 
     The electrophoretic dispersion liquid  15  includes white charged particles  16  as charged particles and black charged particles  17  as charged particles. The white charged particles  16  and the black charged particles  17  are dispersed in a dispersion medium  18 . The material of the white charged particles  16  is not particularly limited as long as the material is white and chargeable and can be formed into fine particles. Examples of materials used for the white charged particles  16  can include, for example, particles, high polymer, or colloid made of a white pigment such as titanium dioxide, hydrozincite, or antimony trioxide. In the embodiment, for example, positively charged titanium dioxide particles are used as the white charged particles  16 . 
     The material of the black charged particles  17  is not particularly limited as long as the material is black and chargeable and can be formed into fine particles. Examples of materials used for the black charged particles  17  can include, for example, particles, high polymer, or colloid made of a black pigment such as aniline black, carbon black, or titanium oxynitride. In the embodiment, for example, negatively charged titanium oxynitride is used as the black charged particles  17 . For the white charged particles  16  and the black charged particles  17 , a charge control agent such as an electrolyte, a surfactant, metal soap, resin, rubber, oil, varnish, or a compound can be added to the particles as necessary. In addition, a dispersant such as a titanium coupling agent, an aluminum coupling agent, or a silane coupling agent, a lubricant, a stabilizer, or the like can be added to the white charged particles  16  and the black charged particles  17 . 
     The material of the dispersion medium  18  is not particularly limited as long as the material has fluidity and is less alterable Examples of materials used for the dispersion medium  18  can include water; alcohol solvents such as methanol, ethanol, isopropanol, butanol, octanol, and methyl cellosolve; esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aliphatic hydrocarbons such as pentane, hexane, and octane; and alicyclic hydrocarbons such as cyclohexane and methyl cyclohexane. In addition, examples of materials used for the dispersion medium  18  can include aromatic hydrocarbons such as benzene, toluene, xylene, and long-chain alkyl group-containing benzenes. As the long-chain alkyl group-containing benzenes, hexylbenzene, heptylbenzene, octylbenzene, nonylbenzene, decylbenzene, undecylbenzene, dodecylbenzene, tridecylbenzene, tetradecylbenzene, or the like can be used. In addition, as the dispersion medium  18 , halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, and 1,2-dichloroethane can be used. In addition, examples of materials used for the dispersion medium  18  can include oils and a silicone oil. These substances can be used alone or as a mixture, and further, a surfactant such as a carboxylate, or the like may be mixed. 
     The second substrate  3  is disposed on the partition wall  5  and the electrophoretic dispersion liquid  15 . The second substrate  3  includes a second base material  21 . A common electrode  22  as a counter electrode is disposed on the second base material  21 . A sealing layer  23  as a transparent sealing member that seals the electrophoretic dispersion liquid  15  is disposed on the common electrode  22 . The common electrode  22  is a common electrode that is disposed over the plurality of pixel regions  6 . Thus, the common electrode  22  faces the plurality of pixel electrodes  14 . The second substrate  3  is joined, on the sealing layer  23  side, with the partition wall  5 . Further, the sealing layer  23  has the function of insulating the partition wall  5  from the common electrode  22 . 
     The material of the second base material  21  is not particularly limited as long as the material has a light transmitting property, strength, and an insulating property Examples of materials used for the second base material  21  can include glass and a resin material. In the embodiment, for example, a glass plate is used as the material of the second base material  21 . 
     The common electrode  22  is not particularly limited as long as the common electrode is a transparent conductive film. For example, MgAg, indium-gallium oxide (IGO), indium-tin oxide (ITO), indium-cerium oxide (ICO), indium-zinc oxide (IZO), or the like can be used as the common electrode  22 . In the embodiment, for example, ITO is used as the common electrode  22 . 
     The material of the sealing layer  23  is not particularly limited as long as the material can be joined with the partition wall  5 , has a light transmitting property and an insulating property, and does not cause the alteration of the electrophoretic dispersion liquid  15 . For example, examples of materials used for the sealing layer  23  can include polyurethane, polyurea, polyurea-polyurethane, urea-formaldehyde resin, melamine-formaldehyde resin, polyamide, polyester, polysulfonamide, polycarbonate, polysulfinate, epoxy resin, acrylic resin such as polyacrylic acid ester, polymethacrylic acid ester, polyvinyl acetate, gelatin, phenol resin, and vinyl resin. In the embodiment, for example, an ultraviolet-curable acrylic resin or epoxy resin is used. 
       FIG.  4    is a schematic sectional side elevation showing the structure of the electrophoretic display device. As shown in  FIG.  4   , the electrophoretic display device  1  is used by applying a voltage between the pixel electrode  14  and the common electrode  22 . Then, the voltage is changed in use between the pixel electrode  14  and the common electrode  22 . 
     The common electrode  22  is set at a low voltage relative to the pixel electrode  14 . In this case, since the black charged particles  17  are charged to a negative voltage, the black charged particles  17  are attracted to the pixel electrode  14 . Since the white charged particles  16  are charged to a positive voltage, the white charged particles  16  are attracted to the common electrode  22 . As a result, the black charged particles  17  gather at the first substrate  2 , while the white charged particles  16  gather at the second substrate  3 . When the electrophoretic display device  1  is viewed from the second substrate  3  side, the white charged particles  16  can be seen through the second substrate  3 . Thus, white display is achieved in the pixel region  6 . 
     The first semiconductor element  7  is disposed in the element layer  11 . The first semiconductor element  7  includes a semiconductor film  7   e . In the semiconductor film  7   e , a source region  7   h , a channel forming region  7   k , and a drain region  7   j  are formed side by side in this order. A gate insulating film  7   f  is disposed on the semiconductor film  7   e , and a gate electrode  7   g  is disposed on the gate insulating film  7   f  A source electrode  7   n  is connected to the source region  7   h , and the voltage supply line  7   a  is connected to the source electrode  7   i . A first drain electrode  7   p  is disposed to be connected with the drain region  7   j , and the first through-electrode  7   d  is disposed to be connected with the first drain electrode  7   p . Since the first through-electrode  7   d  is connected with the pixel electrode  14 , the first semiconductor element  7  is electrically connected with the pixel electrode  14 . The control signal line  7   b  is connected to the gate electrode  7   g.    
     The main material of the partition wall  5  is epoxy resin, and the main material of the insulating layer  12  is acrylic resin. The insulating layer  12  and a portion of the partition wall  5  are joined together. Thus, the joining of the insulating layer  12  and the partition wall  5  is the joining of the resin materials that are the same as each other, which makes it possible to fix the insulating layer  12  and the partition wall  5  together at high strength compared with the case where one of the insulating layer  12  and the partition wall  5  is an inorganic material. The hardness of the partition wall  5  is 2 GPa, and the hardness of the insulating layer  12  is 0.5 GPa. The partition wall  5  has a higher hardness than the insulating layer  12 , and therefore has strength. For this reason, even when a load is applied to the partition wall  5  in a step of assembling the first substrate  2  and the second substrate  3  together, the deformation or the like of the partition wall  5  is prevented, and the partition wall  5  is less likely to peel from the insulating layer  12  because the partition wall  5  bites into the insulating layer  12  side. As a result, it is possible to inhibit the partition wall  5  from collapsing or crushing. 
     The hardness of the insulating layer  12  before curing is approximately 15 mPa/s, and the hardness of the partition wall  5  before curing is approximately 2000 mPa/s. Because of this, the material of the insulating layer  12  can be easily formed into a thin film compared with the material of the partition wall  5 . However, since the insulating layer  12  is likely to be eluted into the electrophoretic dispersion liquid  15  compared with the partition wall  5 , the protective film  13  is disposed to cover the insulating layer  12 . Since the insulating layer  12  and the electrophoretic dispersion liquid  15  are not in contact with each other due to the protective film  13 , the electrophoretic dispersion liquid  15  or the insulating layer  12  can be prevented from being damaged. 
     A portion of the protective film  13  is located between the partition wall  5  and the insulating layer  12 . Specifically, the width of the partition wall  5  on the insulating layer  12  side is defined as a first width  5   a . The partition wall  5  is joined to the insulating layer  12  at the center of the partition wall  5  in the width direction of the partition wall  5 . The width of a portion of the partition wall  5  joined to the insulating layer  12  is defined as a second width  5   b . For example, the length of the second width Sb is % that of the first width  5   a . The protective film  13  enters between the partition wall  5  and the insulating layer  12  from the both side surfaces of the partition wall  5 . The length of a portion of the protective film  13  entering between the partition wall  5  and the insulating layer  12  from the side surface of the partition wall  5  is defined as a third width  5   c . For example, the length of the third width  5   c  is V; that of the first width Sa. In this case, the protective film  13  is located on the insulating layer  12 , and a portion of the partition wall  5  is located on the protective film  13 . Thus, since the insulating layer  12  is covered by the partition wall  5  and the protective film  13 , the insulating layer  12  is not exposed in a surface to be in contact with the electrophoretic dispersion liquid  15 . As a result, it is possible to inhibit the insulating layer  12  from coming in contact with the electrophoretic dispersion liquid  15 . 
       FIG.  5    is a schematic plan view of a main portion for explaining the relationship between the pixel and the partition wall, as the first substrate  2  is viewed from the image display surface  3   a  side. As shown in  FIG.  5   , the first substrate  2  includes one pixel electrode  14  corresponding to one pixel  8 . The partition wall  5  is disposed to surround the pixel electrode  14  for one pixel  8 . The partition wall  5  may not surround the entire periphery of the pixel electrode  14  and may be partially removed. Then, through the removed place, the electrophoretic dispersion liquid  15  may move between the pixels  8 . The partition wall  5  is disposed to surround the pixel electrode  14 . In this case, compared with the case where the partition wall  5  surrounds a plurality of pixel electrodes  14 , the area surrounded by the partition wall  5  can be narrowed. Then, the strength of the partition wall  5  can be increased. Thus, even when a load is applied to the partition wall  5 , it is possible to inhibit the partition wall  5  from collapsing or crushing. 
       FIG.  6    is an electrical control block diagram of the electrophoretic display device. As shown in  FIG.  6   , the electrophoretic display device  1  is connected in use to a controller  24 . The controller  24  includes an input unit  25 . The input unit  25  is connected to a device that outputs an image signal representing an image to be displayed on the electrophoretic display device  1 , and receives the image signal. The input unit  25  is connected with a control unit  26 . The control unit  26  is connected with a storage unit  27 , a first waveform forming unit  28 , a second waveform forming unit  29 , and the signal distributing unit  9 . 
     The control unit  26  is a portion that controls the first waveform forming unit  28 , the second waveform forming unit  29 , and the signal distributing unit  9 . The storage unit  27  stores, in addition to the image signal, information used when forming, from the image signal, a signal to be output to the electrophoretic display device  1 . The first waveform forming unit  28  is connected with the first semiconductor element  7  through the flexible cable  4 , the signal distributing unit  9 , and the control signal line  7   b , and outputs a data signal for each pixel to the first semiconductor element  7 . The first semiconductor element  7  is connected with the pixel electrode  14 , and outputs a voltage corresponding to the data signal to the pixel electrode  14 . The second waveform forming unit  29  is connected with the common electrode  22  through the flexible cable  4  and the signal distributing unit  9 , and outputs a voltage waveform to the common electrode  22 . 
     The signal distributing unit  9  distributes a drive signal to the first semiconductor element  7  to change a voltage waveform to be output to the pixel electrode  14 . Further, the signal distributing unit  9  transmits a voltage waveform to be output to the common electrode  22 . 
       FIGS.  7  and  8    are schematic sectional side elevations showing the structure of the electrophoretic display device. As shown in  FIG.  7   , the common electrode  22  is set at a low voltage relative to the pixel electrode  14 . In this case, since the black charged particles  17  are charged to a negative voltage, the black charged particles  17  are attracted to the pixel electrode  14 . Since the white charged particles  16  are charged to a positive voltage, the white charged particles  16  are attracted to the common electrode  22 . As a result, the black charged particles  17  gather at the first substrate  2 , while the white charged particles  16  gather at the second substrate  3 . When the electrophoretic display device  1  is viewed from the second substrate  3  side, the white charged particles  16  can be seen through the second substrate  3 . Thus, white display is achieved in the pixel region  6 . 
     As shown in  FIG.  8   , the common electrode  22  is set at a high voltage relative to the pixel electrode  14 . In this case, since the black charged particles  17  are charged to a negative voltage, the black charged particles  17  are attracted to the common electrode  22 . Since the white charged particles are charged to a positive voltage, the white charged particles  16  are attracted to the pixel electrode  14 . As a result, the white charged particles  16  gather at the first substrate  2 , while the black charged particles  17  gather at the second substrate  3 . When the electrophoretic display device  1  is viewed from the second substrate  3  side, the black charged particles  17  can be seen through the second substrate  3 . Thus, black display is achieved in the pixel region  6 . 
     Next, a method for manufacturing the electrophoretic display device  1  described above will be described with reference to  FIGS.  9  to  18   .  FIG.  9    is a flowchart of the method for manufacturing the electrophoretic display device.  FIGS.  10  to  18    are schematic views for explaining the method for manufacturing the electrophoretic display device. In the flowchart of  FIG.  9   , Step S 1  corresponds to an upper electrode disposing step. This step is a step of disposing the common electrode  22  and the sealing layer  23  on the second base material  21 . 
     Next, the method proceeds to Step S 2 . Step S 2  is an element disposing step. This step is a step of disposing the element layer  11  on the first base material  10 . 
     Next, the method proceeds to Step S 3 . Step S 3  is an insulating layer disposing step. This step is a step of disposing the insulating layer  12  on the element layer  11 . 
     Next, the method proceeds to Step S 4 . Step S 4  is a protective film disposing step. This step is a step of disposing the protective film  13  on the insulating layer  12 . 
     Next, the method proceeds to Step S 5 . Step S 5  is a lower electrode disposing step. This step is a step of disposing the first through-electrode  7   d  and the pixel electrode  14  on the protective film  13 . 
     Next, the method proceeds to Step S 6 . Step S 6  is a partition wall disposing step. This step is a step of disposing the partition wall  5  on the first substrate  2 . 
     Next, the method proceeds to Step S 7 . Step S 7  is a dispersion liquid filling step. This step is a step of filling the pixel region  6  with the electrophoretic dispersion liquid  15 . 
     Next, the method proceeds to Step S 8 . Step S 8  is a substrate assembling step. This step is a step of bonding the partition wall  5  and the second substrate  3  together. 
     Through the steps described above, the steps of manufacturing the electrophoretic display device  1  are finished. 
     Next, the manufacturing method will be described in detail using  FIGS.  10  to  18    in correspondence with the steps shown in  FIG.  9   . 
     First, the second substrate  3  is manufactured.  FIG.  10    is a diagram corresponding to the upper electrode disposing step of Step S 1 . As shown in  FIG.  10   , the second base material  21  is prepared. As the second base material  21 , a plate obtained by grinding a glass plate to a predetermined thickness and polishing the plate to reduce a surface roughness is used. Next, the common electrode  22  is disposed on the second base material  21 . An ITO film with a film thickness of approximately 100 nm is formed on the second base material  21  using a deposition method such as a sputtering method. Next, the ITO film is patterned by a photolithography method and an etching method to form the common electrode  22 . 
     Next, the sealing layer  23  is disposed on the common electrode  22 . The sealing layer  23  can be disposed using an ink jet method and various kinds of printing methods such as offset printing, screen printing, relief printing including flexographic printing, and intaglio printing including gravure printing. In addition, a spin coating method, a roll coating method, a die coating method, a slit coating method, a curtain coating method, a spray coating method, a dip coating method, or the like may be used. 
     Subsequently, the first substrate  2  is manufactured.  FIG.  11    is a diagram corresponding to the element disposing step of Step S 2 . As shown in  FIG.  11   , in Step S 2 , the first base material  10  is prepared. Also as the first base material  10 , a plate obtained by grinding a glass plate to a predetermined thickness and polishing the plate to reduce a surface roughness is used. The element layer  11  is formed on the first base material  10 . Since the method for forming the element layer  11  is publicly known, a detailed description is omitted, and the manufacturing method will be roughly described. There are multiple methods for forming the element layer  11 , and the forming method is not particularly limited. 
     First, a foundation insulating film  30  of SiO 2  is formed on the first base material  10  by a chemical vapor deposition (CVD) method. Next, an amorphous silicon film with a film thickness of approximately 50 nm is formed on the foundation insulating film by a CVD method or the like. The amorphous silicon film is crystallized by a laser crystallization method or the like to form a polycrystalline silicon film. Thereafter, the semiconductor film  7   e  as an island-like polycrystalline silicon film is formed by a photolithography method and an etching method or the like. 
     Next, SiO 2  with a film thickness of approximately 100 nm is formed so as to cover the semiconductor film  7   e  and the foundation insulating film by a CVD method or the like to serve as the gate insulating film  7   f . A Mo film with a film thickness of approximately 500 nm is formed on the gate insulating film  7   f  by a sputtering method or the like, and the gate electrode  7   g  having an island-like shape is formed by a photolithography method and an etching method. Impurity ions are implanted into the semiconductor film by an ion implantation method to form the source region  7   h , the drain region  7   j , and the channel forming region  7   k . A SiO 2  film with a film thickness of approximately 800 nm is formed so as to cover the gate insulating film  7   f  and the gate electrode  7   g  to serve as a first inter-layer insulating film  11   n.    
     Next, a contact hole reaching the source region  7   h  and a contact hole reaching the drain region  7   j  are formed in the first inter-layer insulating film  11   m . Thereafter, a Mo film with a film thickness of approximately 500 nm is formed on the first inter-layer insulating film  11   m  and in the contact holes by a sputtering method or the like, and patterned by a photolithography method and an etching method, to form the source electrode  7   n , the first drain electrode  7   p , and wires (not shown). 
     A Si 3 N 4  film with a film thickness of approximately 800 nm is formed so as to cover the first inter-layer insulating film  11   i , the source electrode  7   n , the first drain electrode  7   p , and the wires to serve as a second inter-layer insulating film  11   r . The second inter-layer insulating film  11   r  is patterned by a photolithography method and an etching method to form a contact hole therein. 
       FIG.  12    is a diagram corresponding to the insulating layer disposing step of Step S 3  As shown in  FIG.  12   , in Step S 3 , the insulating layer  12  is disposed on the second inter-layer insulating film  11   r . First, a resin film serving as the material of the insulating layer  12  is disposed. A solution with the acrylic resin dissolved therein is coated on the element layer  11 , and then dried and solidified. The resin film can be disposed using an ink jet method and various kinds of printing methods such as offset printing, screen printing, relief printing including flexographic printing, and intaglio printing including gravure printing. In addition, a spin coating method, a roll coating method, a die coating method, a slit coating method, a curtain coating method, a spray coating method, a dip coating method, or the like may be used. 
     Next, the resin film is patterned by a photolithography method and an etching method. With this configuration, the outer shape of the insulating layer  12  and the shape of a through-hole  12   a  are patterned. Subsequently, the insulating layer  12  is etched using an etchant to form the through-hole  12   a.    
       FIGS.  13  and  14    are diagrams corresponding to the protective film disposing step of Step S 4  As shown in  FIG.  13   , in Step S 4 , a SiN film with a film thickness of approximately 500 nm is formed on the insulating layer  12  and in the through-hole  12   a  using a deposition method such as vapor deposition or a CVD method. Next, as shown in  FIG.  14   , the SiN film is patterned and etched to form the protective film  13 . In the through-hole  12   a , the first drain electrode  7   p  is exposed. Further, the insulating layer  12  is exposed in a place where the partition wall  5  is disposed. The etching method is not particularly limited, but a dry etching method is used in the embodiment. 
       FIG.  15    is a diagram corresponding to the lower electrode disposing step of Step S 5 . As shown in  FIG.  15   , in Step S 5 , an ITO film with a film thickness of approximately 500 nm is formed on the insulating layer  12  and the protective film  13  and in the through-hole  12   a  using a deposition method such as a sputtering method. Further, the ITO film is etched by a photolithography method and an etching method to form the pixel electrode  14  and the first through-electrode  7   d  The insulating layer  12  and the protective film  13  are exposed in the place where the partition wall  5  is to be disposed. The etching method is not particularly limited, but a dry etching method is used in the embodiment. 
       FIG.  16    is a diagram corresponding to the partition wall disposing step of Step S 6 . As shown in  FIG.  16   , in Step S 6 , the partition wall  5  is disposed on the exposed insulating layer  12  and the exposed protective film  13 . First, a photosensitive resin material serving as the material of the partition wall  5  is coated on the pixel electrode  14 . As the coating method, various kinds of printing methods such as offset printing, screen printing, and relief printing can be used. In addition, a coating method such as a spin coating method or a roll coating method may be used Subsequently, the photosensitive resin material is heated, dried, and solidified. Next, the photosensitive resin material is patterned by a photolithography method and then etched to shape the partition wall  5 . The partition wall  5  of the resin material is disposed to cover the insulating layer  12  in the place where a portion of the protective film  13  is removed. In this step, the first substrate  2  is completed. 
       FIG.  17    is a diagram corresponding to the dispersion liquid filling step of Step S 7  As shown in  FIG.  17   , in Step S 7 , the first substrate  2  with the partition wall  5  disposed thereon is placed in a container (not shown). Then, the white charged particles  16  and the black charged particles  17  are added to the dispersion medium  18  and then stirred to prepare the electrophoretic dispersion liquid  15 . Next, the electrophoretic dispersion liquid  15  is supplied to the pixel region  6  using a supply tool such as a syringe. As the method for supplying the electrophoretic dispersion liquid  15 , various kinds of printing methods or an ink jet method may be used. The electrophoretic dispersion liquid  15  is supplied to such an extent that the electrophoretic dispersion liquid  15  overflows the pixel region  6 . 
       FIG.  18    is a diagram corresponding to the substrate assembling step of Step S 8 . As shown in  FIG.  18   , in Step S 8 , the second substrate  3  is disposed on the partition wall  5 . First, the first substrate  2  supplied with the electrophoretic dispersion liquid  15  is placed in a reduced pressure chamber. Next, the second substrate  3  is mounted on the partition wall  5 . Subsequently, the pressure in the reduced pressure chamber is reduced to pressurize the second substrate  3  against the first substrate  2 . With this state maintained, the sealing layer  23  is irradiated with ultraviolet rays. The sealing layer  23  is ultraviolet-curable and functions also as an adhesive, so that the partition wall  5  and the second substrate  3  are temporarily fixed together. Next, by heating the first substrate  2 , on which the second substrate  3  is disposed, to solidify the sealing layer  23 , the second substrate  3  is fixed to the partition wall  5 . Through the steps described above, the electrophoretic display device  1  is completed. 
     As described above, the embodiment has the following advantageous effects. 
     (1) According to the embodiment, the first base material  10  is disposed with the insulating layer  12 . The partition wall  5  is disposed on the insulating layer  12 . Both the insulating layer  12  and the partition wall  5  are formed of a resin material. Thus, compared with the case where one of the insulating layer  12  and the partition wall  5  is an inorganic material and the other is a resin material, the insulating layer  12  and the partition wall  5  can be fixed together at high strength. Further, the partition wall  5  has a higher hardness than the insulating layer  12 , and therefore has high strength. As a result, even when a load is applied to the partition wall  5 , it is possible to inhibit the partition wall  5  from collapsing or crushing due to peeling-off from the insulating layer  12 . 
     (2) According to the embodiment, the protective film  13  protecting the insulating layer  12  is disposed on the surface of the insulating layer  12 . Thus, the electrophoretic dispersion liquid  15  is prevented from coming in contact with the insulating layer  12 . Then, it is possible to prevent the electrophoretic dispersion liquid  15  and the insulating layer  12  from being damaged by each other. 
     (3) According to the embodiment, a portion of the protective film  13  is located between the partition wall  5  and the insulating layer  12 . That is, the partition wall  5  closes the opening of the protective film  13 . Thus, the insulating layer  12  is not exposed in the pixel region  6 . As a result, it is possible to inhibit the electrophoretic dispersion liquid  15  from coming in contact with the insulating layer  12 . 
     (4) According to the embodiment, the first substrate  2  is disposed with one pixel electrode  14  corresponding to one pixel  8 . The partition wall  5  is disposed to surround the pixel electrode  14 . In this case, compared with the case where the partition wall  5  surrounds a plurality of pixel electrodes  14 , the area of the place surrounded by the partition wall  5  is narrow, and therefore, the strength of the partition wall  5  can be increased. Thus, even when a load is applied to the partition wall  5 , it is possible to inhibit the partition wall  5  from collapsing or crushing. 
     (5) According to the embodiment, the insulating layer  12  and the partition wall  5  are made of a resin material, and the values of the thermal expansion coefficients thereof are close to each other. Thus, even when the temperature changes greatly in the manufacturing steps of the electrophoretic display device  1 , the partition wall  5  can be less likely to peel from the insulating layer  12 . 
     (6) According to the embodiment, the force of adhesion between the insulating layer  12  and the partition wall  5  is high. Thus, even when the electrophoretic dispersion liquid  15  expands on heating, it is possible to inhibit the partition wall  5  from peeling from the insulating layer  12 . 
     Second Embodiment 
     Next, an electrophoretic display device according to a second embodiment will be described using  FIG.  19   .  FIG.  19    is a schematic sectional side elevation showing the structure of the electrophoretic display device. The second embodiment differs from the first embodiment in that the protective film  13  is not located between the insulating layer  12  and the partition wall  5 . Parts that are the same as those of the first embodiment are not described. 
     That is, in the embodiment as shown in  FIG.  19   , the electrophoretic display device  33  includes a first substrate  34  and the second substrate  3 , and has a structure in which the first substrate  34  and the second substrate  3  interpose the electrophoretic dispersion liquid  15  therebetween. In the first substrate  34 , a protective film  35  is disposed on the insulating layer  12 , the top of the partition wall  5 , and the side surfaces of the partition wall  5 . It is sufficient, for the protective film  35  on the side surface of the partition wall  5 , to be disposed to such an extent that the insulating layer  12  is not exposed in the boundary between the partition wall  5  and the insulating layer  12 , and thus, it is not necessary for the protective film  35  to be disposed on the entire side surface of the partition wall  5 . The protective film  35  is not interposed between the insulating layer  12  and the partition wall  5 . Thus, the entire bottom surface of the partition wall  5  is in contact with and fixed to the insulating layer  12 . Thus, since the contact area of the bottom surface of the partition wall  5  with the insulating layer  12  is wide compared with the first substrate  2  of the first embodiment, the partition wall  5  can be still less likely to peel from the insulating layer  12 . 
     The protective film  35  is formed by a CVD method or the like after the partition wall  5  is disposed on the insulating layer  12 . Thereafter, the first drain electrode  7   p  in the contact hole is exposed, and then, the pixel electrode  14  is formed. In  FIG.  19   , the protective film  35  is also disposed on the top of the partition wall  5 ; however, the protective film  35  on the top of the partition wall  5  may be removed. 
     Third Embodiment 
     Next, an electronic apparatus including the electrophoretic display device mounted therein according to a third embodiment will be described using  FIGS.  20  and  21   .  FIG.  20    is a schematic perspective view showing the structure of an electronic book.  FIG.  21    is a schematic perspective view showing the structure of a wristwatch. As shown in FIG.  20 , the electronic book  38  as the electronic apparatus includes a plate-like case  39 . The case  39  is disposed with a lid portion  41  through hinges  40 . Further, the case  39  is disposed with operation buttons  42  and a display unit  43  as a display device. An operator can operate the contents to be displayed on the display unit  43  by operating the operation buttons  42 . 
     Inside the case  39 , a control unit  44  and a signal drive unit  45  that drives a data signal to the display unit  43  are disposed. The control unit  44  outputs display data to the signal drive unit  45 , and also outputs a timing signal when converting the display data into the data signal. The signal drive unit  45  generates the data signal from the display data, and outputs the data signal to the display unit  43 . Moreover, the control unit  44  outputs a display control signal that is synchronized with the data signal output by the signal drive unit  45  to the display unit  43 . The display unit  43  generates a signal necessary for electrophoretic display, from the display control signal and data signal input thereto, in a signal distributing circuit inside the display unit  43 , so that it is possible to perform display according to the display data output by the control unit  44  to the display unit  43 . The operation of the operator through the operation buttons  42  is converted into a signal at the appropriate time, and the signal is transmitted to the control unit  44  and reflected in the output signal of the control unit  44 . As the display unit  43 , any of the electrophoretic display device  1  and the electrophoretic display device  33  is used. Thus, the electronic book  38  can be a device using, as the display unit  43 , the electrophoretic display device in which the partition wall  5  is less likely to collapse and thus which has an easy-to-assemble structure. 
     As shown in  FIG.  21   , the wristwatch  48  as the electronic apparatus includes a plate-like case  49 . The case  49  includes a band  50 , and the operator can wrap the band  50  around the arm to secure the wristwatch  48  to the arm. Further, the case  49  is disposed with operation buttons  51  and a display unit  52  as a display device. The operator can operate the contents to be displayed on the display unit  52  by operating the operation buttons  51 . 
     Inside the case  49 , a control unit  53  that controls the wristwatch  48  and a signal drive unit  54  that drives a signal to the display unit  52  are disposed. The control unit  53  outputs display data and a necessary timing signal to the signal drive unit  54 . The necessary timing signal may include a signal directly output from the control unit  53  to the display unit  52 . The signal drive unit  54  outputs the signal necessary for display to the display unit  52 , so that the contents corresponding to the display data can be displayed on the display unit  52 . As the display unit  52 , any of the electrophoretic display device  1  and the electrophoretic display device  33  is used. Thus, the wristwatch  48  can be a device using, as the display unit  52 , the electrophoretic display device in which the partition wall  5  is less likely to collapse and thus which has an easy-to-assemble structure. 
     The invention is not limited to the embodiments described above, and various modifications or improvements can be added within the technical idea of the invention by a person ordinarily skilled in the art. Modified examples will be described below. 
     Modified Example 1 
     In the first embodiment, the white charged particles  16  and the black charged particles  17  are disposed in the electrophoretic dispersion liquid  15 . Instead of the white charged particles  16  and the black charged particles  17 , charged particles of red, green, blue, and other colors may be used. According to this configuration, color display can be performed by displaying the red, green, blue, and other colors. In addition, only charged particles of one color may be used in the electrophoretic dispersion liquid  15 . 
     Modified Example 2 
     In the first embodiment, one pixel electrode  14  is disposed in one pixel region  6 . A plurality of pixel electrodes  14  may be disposed in one pixel region  6 . Display can be subdivided. 
     Modified Example 3 
     In the first embodiment, the white charged particles  16  are positively charged, while the black charged particles  17  are negatively charged. The white charged particles  16  may be negatively charged, while the black charged particles  17  may be positively charged. An easy-to-control charged state may be employed. 
     Modified Example 4 
     In the first embodiment, the shape of the pixel region  6  is quadrilateral. The shape of the pixel region  6  may be a circle, an ellipse, a polygon, or a shape including an arc and a line. In this case, since the partition wall  5  is formed of a resin material, the shape of the partition wall  5  can be easily matched to the shape of the pixel region  6 . 
     Modified Example 5 
     In the first embodiment, after the electrophoretic dispersion liquid  15  is disposed in the pixel regions  6  of the first substrate  2 , the first substrate  2  and the second substrate  3  are joined together. In addition, after the pixel regions  6  are communicated with each other and the first substrate  2  and the second substrate  3  are joined together, the electrophoretic dispersion liquid  15  may be disposed in the pixel regions  6 . An easy-to-manufacture step order may be employed. 
     Modified Example 6 
     In the first embodiment, the first semiconductor element  7  is disposed in the first substrate  2 . A structure may be employed in which the first semiconductor element  7  is not disposed in the first substrate  2  but only the pixel electrode  14  is disposed therein. Then, a drive circuit that directly applies a voltage to the pixel electrode  14  may be provided. Since the structure of the first substrate  2  is simplified, the first substrate  2  can be easily manufactured. 
     The entire disclosure of Japanese Patent Application No. 2015-184810, filed Sep. 18, 2015 is expressly incorporated by reference herein.