Patent Publication Number: US-2015087093-A1

Title: Method and system for manufacturing display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-195063, filed on Sep. 20, 2013; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a method and a system for manufacturing display device. 
     BACKGROUND 
     There is known a display device based on electroluminescence (EL) elements. The display device based on electroluminescence elements is required to be lightweight and large-scale. In addition, there are high requirements such as long-term reliability, high freedom of shape, and capability of curved surface display. Thus, as a substrate used in the display device, a resin layer such as a transparent plastic layer is drawing attention instead of a glass substrate, which is heavy, fragile, and difficult to form in large area. In a method for manufacturing the display device, a resin layer is provided on a support substrate such as a glass substrate. A circuit and a display layer are formed on the resin layer. Then, the support substrate is peeled from the resin layer to form the display device. In such a method for manufacturing the display device, improvement in reliability is desired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view schematically showing a display device according to a first embodiment; 
         FIGS. 2A to 2C  are sectional views schematically showing a sequential process for manufacturing a display device according to the first embodiment; 
         FIGS. 3A and 3B  are sectional views schematically showing a sequential process for manufacturing a display device according to the first embodiment; 
         FIG. 4  is a flow chart schematically showing the method for manufacturing a display device according to the first embodiment; 
         FIG. 5  is a sectional view schematically showing a display device according to a second embodiment; 
         FIGS. 6A to 6C  are sectional views schematically showing a sequential process for manufacturing a display device according to the second embodiment; 
         FIG. 7  is a sectional view schematically showing a sequential process for manufacturing a display device according to the second embodiment; and 
         FIG. 8  is a block diagram schematically showing a manufacturing system according to a third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a method is disclosed for manufacturing a display device. The method can include forming a first resin layer on a substrate. The method can include forming a display layer on the first resin layer. The display layer includes a plurality of pixels arranged in a direction perpendicular to a stacking direction of the first resin layer and the display layer. Each of the pixels includes a first electrode provided on the first resin layer, an organic light emitting layer provided on the first electrode, and a second electrode provided on the organic light emitting layer. The method can include bonding a second resin layer onto the display layer via a bonding layer. The method can include removing the substrate. The method can include increasing a density of the bonding layer. 
     According to another embodiment, a system for manufacturing a display device includes a first processing unit, a second processing unit, a third processing unit, a fourth processing unit, and a fifth processing unit. The first processing unit is configured to form a first resin layer on a substrate. The second processing unit is configured to form a display layer on the first resin layer. The display layer includes a plurality of pixels arranged in a direction perpendicular to a stacking direction of the first resin layer and the display layer. Each of the pixels includes a first electrode provided on the first resin layer, an organic light emitting layer provided on the first electrode, and a second electrode provided on the organic light emitting layer. The third processing unit is configured to bond a second resin layer onto the display layer via a bonding layer. The fourth processing unit is configured to remove the substrate. The fifth processing unit is configured to increase a density of the bonding layer. 
     Various embodiments will be described hereinafter with reference to the accompanying drawings. 
     The drawings are schematic or conceptual. The relationship between the thickness and the width of each portion, and the size ratio between the portions, for instance, are not necessarily identical to those in reality. Furthermore, the same portion may be shown with different dimensions or ratios depending on the figures. 
     In the present description and the drawings, components similar to those described previously with reference to earlier figures are labeled with like reference numerals, and the detailed description thereof is omitted appropriately. 
     First Embodiment 
       FIG. 1  is a sectional view schematically showing a display device according to a first embodiment. 
     As shown in  FIG. 1 , the display device  110  includes a first resin layer  11 , a second resin layer  12 , a display layer  13 , and a bonding layer  14 . In the display device  110 , for instance, the display layer  13  is supported by the first resin layer  11  and the second resin layer  12 . The display device  110  has e.g. flexibility. The display device  110  is e.g. a flexible display device. 
     The display layer  13  is provided on the first resin layer  11 . The second resin layer  12  is provided on the display layer  13 . The bonding layer  14  is provided between the display layer  13  and the second resin layer  12 . The second resin layer  12  is bonded onto the display layer  13  by the bonding layer  14 . 
     In this example, the display device  110  further includes a first sealing layer  21  and a second sealing layer  22 . The first sealing layer  21  and the second sealing layer  22  are provided as necessary, and can be omitted. The first sealing layer  21  is provided on the first resin layer  11 . In this example, the display layer  13  is provided on the first sealing layer  21 . The second sealing layer  22  is provided on the display layer  13 . In this example, the bonding layer  14  is provided on the second sealing layer  22 . That is, in this example, the second resin layer  12  is bonded to the second sealing layer  22  via the bonding layer  14 . 
     The first resin layer  11  has flexibility. In this example, the first resin layer  11  further has optical transmissivity. The first resin layer  11  has a thermal characteristic that is not substantially changed in e.g. the formation of the display layer  13 . The first resin layer  11  is made of e.g. polyimide. 
     The first sealing layer  21  suppresses e.g. penetration of moisture and impurities. The first sealing layer  21  protects e.g. the display layer  13  from moisture, impurities and the like. The first sealing layer  21  is made of e.g. a material having flexibility, optical transmissivity, and gas barrier property. The first sealing layer  21  is made of e.g. silicon oxide film, silicon nitride film, or silicon oxynitride film. 
     The display layer  13  includes a plurality of pixels  30 . The plurality of pixels  30  are arranged in directions perpendicular to the stacking direction of the first resin layer  11  and the display layer  13 . 
     Here, the direction parallel to the stacking direction of the first resin layer  11  and the display layer  13  is referred to as Z-axis direction. One direction perpendicular to the Z-axis direction is referred to as X-axis direction. The direction perpendicular to the X-axis direction and the Z-axis direction is referred to as Y-axis direction. 
     The plurality of pixels  30  are arranged in e.g. the X-axis direction and the Y-axis direction. The plurality of pixels  30  are arranged in e.g. a two-dimensional matrix in the plane (X-Y plane) perpendicular to the stacking direction. 
     Each of the plurality of pixels  30  includes a first electrode  31 , a second electrode  32 , and an organic light emitting layer  33 . The first electrode  31  is provided on the first resin layer  11 . The organic light emitting layer  33  is provided on the first electrode  31 . The second electrode  32  is provided on the organic light emitting layer  33 . The first electrode  31  has e.g. optical transmissivity. The second electrode  32  has e.g. optical reflectivity. The optical reflectance of the second electrode  32  is higher than the optical reflectance of the first electrode  31 . 
     The organic light emitting layer  33  is electrically connected to each of the first electrode  31  and the second electrode  32 . Thus, a current flows in the organic light emitting layer  33  by applying a voltage between the first electrode  31  and the second electrode  32 . Accordingly, a current is passed in the organic light emitting layer  33  through the first electrode  31  and the second electrode  32 . Thus, light is emitted from the organic light emitting layer  33 . 
     In this example, the light emitted from the organic light emitting layer  33  is transmitted through the first electrode  31  and emitted outside from the first resin layer  11 . That is, in this example, the display device  110  is of what is called the bottom emission type. For instance, the first electrode  31  may be optically reflective, the second electrode  32  may be optically transmissive, and light may be emitted outside from the second resin layer  12 . That is, the display device  110  may be of what is called the top emission type. 
     The pixel  30  is e.g. a portion of the display device  110  where light is emitted from the organic light emitting layer  33 . In the display device  110 , light emission of each of the pixels  30  arranged in a two-dimensional matrix is controlled. Thus, an image can be displayed in the display device  110 . 
     In this example, the display layer  13  includes a plurality of thin film transistors  35 . The plurality of thin film transistors  35  are provided respectively corresponding to the plurality of pixels  30 . In this example, light emission of the pixels  30  is controlled by the respective thin film transistors  35 . The pixels  30  and the thin film transistors  35  are combined and arranged in a matrix. That is, in this example, the display device  110  is an active matrix display device based on organic EL. 
     The driving scheme of the pixels  30  is not limited to the active matrix scheme. For instance, the driving scheme may be the passive matrix scheme or other driving schemes. For instance, in the passive matrix scheme, there is no need to provide a thin film transistor  35  for each pixel  30 . That is, the thin film transistor  35  is provided as necessary, and can be omitted. 
     The thin film transistors  35  are arranged on the first resin layer  11 . In this example, the thin film transistors  35  are provided on the first sealing layer  21 . 
     The thin film transistor  35  includes e.g. a first conductive part  41 , a second conductive part  42 , a gate electrode  43 , a gate insulating film  44 , a semiconductor layer  45 , and a channel protective film  46 . 
     The gate electrode  43  is provided on the first sealing layer  21 . The gate electrode  43  is made of e.g. aluminum, copper, molybdenum, tantalum, titanium, or tungsten. 
     The gate insulating film  44  is provided on the gate electrode  43 . In this example, the respective gate insulating films  44  of the plurality of thin film transistors  35  are continuous with each other. In other words, in this example, one gate insulating film is provided entirely on the first sealing layer  21  so as to cover each of the plurality of gate electrodes  43 . The gate insulating film  44  is made of e.g. a material having insulating property and optical transmissivity. The gate insulating film  44  is made of e.g. one of silicon oxide film, silicon nitride film, and silicon oxynitride film. 
     The semiconductor layer  45  is provided on the gate insulating film  44 . The gate insulating film  44  is provided between the gate electrode  43  and the semiconductor layer  45 , and insulates the gate electrode  43  from the semiconductor layer  45 . The semiconductor layer  45  is made of e.g. amorphous silicon. The semiconductor layer  45  may be made of e.g. polysilicon crystallized by laser annealing and the like, an oxide semiconductor such as ZnO and InGaZnO, or an organic semiconductor such as pentacene. 
     The first conductive part  41  is electrically connected to the semiconductor layer  45 . The second conductive part  42  is electrically connected to the semiconductor layer  45 . The first conductive part  41  and the second conductive part  42  are made of e.g. Ti, Al, and Mo. The first conductive part  41  and the second conductive part  42  may be made of e.g. a stacked body including at least one of Ti, Al, and Mo. The first conductive part  41  is one of the source electrode and the drain electrode of the thin film transistor  35 . The second conductive part  42  is the other of the source electrode and the drain electrode of the thin film transistor  35 . 
     The channel protective film  46  is provided on the semiconductor layer  45 . The channel protective film  46  protects the semiconductor layer  45 . The channel protective film  46  is made of e.g. silicon oxide film, silicon nitride film, or silicon oxynitride film. 
     The first conductive part  41  covers part of the semiconductor layer  45 . The second conductive part  42  covers another part of the semiconductor layer  45 . The semiconductor layer  45  includes a portion not covered with the first conductive part  41  and the second conductive part  42 . The gate electrode  43  overlaps the portion between the first conductive part  41  and the second conductive part  42  as projected on the plane parallel to the X-Y plane. Thus, a channel is generated in the semiconductor layer  45  by applying a voltage to the gate electrode  43 . Accordingly, a current flows between the first conductive part  41  and the second conductive part  42 . 
     This example is based on the thin film transistor  35  of the bottom gate type in which the semiconductor layer  45  is provided on the gate electrode  43 . The thin film transistor  35  is not limited to the bottom gate type. For instance, the thin film transistor  35  may be of the top gate type in which the gate electrode  43  is provided on the semiconductor layer  45 . 
     In this example, the display layer  13  further includes a passivation film  50 , a color filter  52 , and a bank layer  54 . 
     The passivation film  50  is provided between the thin film transistor  35  and the first electrode  31 . The passivation film  50  is made of e.g. a material having insulating property and optical transmissivity. The passivation film  50  is made of e.g. one of silicon oxide film, silicon nitride film, and silicon oxynitride film. 
     The color filter  52  is provided between the first electrode  31  and the passivation film  50 . The color filter  52  has e.g. a different color for each pixel  30 . The color filter  52  is made of e.g. a color resin film (e.g., color resist) of one of red, green, and blue. For instance, red, green, and blue color filters  52  are arranged in a prescribed pattern in the respective pixels  30 . The light emitted from the organic light emitting layer  33  is transmitted through the color filter  52  and emitted outside from the first resin layer  11  side. Thus, light of a color corresponding to the color filter  52  is emitted from each pixel  30 . The color filter  52  is provided as necessary. The color filter  52  can be omitted. 
     The first electrode  31  is electrically connected to one of the first conductive part  41  and the second conductive part  42 . In this example, the first electrode  31  is electrically connected to the first conductive part  41  (e.g., source). 
     The first electrode  31  is provided on the color filter  52 . The first electrode  31  is made of e.g. a material having conductivity and optical transmissivity. The first electrode  31  is made of e.g. ITO (indium tin oxide). 
     The passivation film  50  and the color filter  52  are each provided with an opening for exposing part of the first conductive part  41 . Part of the first electrode  31  is inserted into the respective openings of the passivation film  50  and the color filter  52 . The first electrode  31  is electrically connected to the first conductive part  41  in e.g. the portion exposed in the opening of the first conductive part  41 . The first electrode  31  is e.g. in contact with the portion exposed in the opening of the first conductive part  41 . 
     The bank layer  54  is provided on the first electrode  31  and the color filter  52 . The bank layer  54  is made of e.g. a material having insulating property. The bank layer  54  is made of e.g. an organic resin material. The bank layer  54  is provided with an opening for exposing part of the first electrode  31 . For instance, the opening of the bank layer  54  defines the region of each pixel  30 . 
     The organic light emitting layer  33  is provided on the bank layer  54 . The organic light emitting layer  33  is e.g. in contact with the first electrode  31  in the opening of the bank layer  54 . The organic light emitting layer  33  is made of e.g. a stacked body in which a hole transport layer, a light emitting layer, and an electron transport layer are stacked. In this example, the organic light emitting layers  33  of the respective pixels  30  are continuous with each other. The organic light emitting layer  33  may be provided only in the portion in contact with the first electrode  31 . That is, the organic light emitting layer  33  may be provided only in the opening of the bank layer  54 . 
     The second electrode  32  is provided on the organic light emitting layer  33 . The second electrode  32  is made of a material having conductivity. The second electrode  32  is made of e.g. Al. In this example, the second electrodes  32  of the respective pixels  30  are continuous with each other. For instance, the second electrodes  32  may be spaced from each other for each pixel  30 . For instance, in the case of the passive matrix scheme, the second electrodes  32  of the pixels  30  of a given column are continuous with each other, whereas the second electrodes  32  of different columns are spaced from each other. 
     The second sealing layer  22  covers the organic light emitting layer  33  and the second electrode  32 . The second sealing layer  22  protects e.g. the organic light emitting layer  33  and the second electrode  32 . The second sealing layer  22  is made of e.g. one of silicon oxide film, silicon oxynitride film, silicon nitride film, alumina, and tantalum oxide film. The second sealing layer  22  is made of e.g. a stacked film thereof. 
     The second resin layer  12  can be made of e.g. substantially the same material as the first resin layer  11 . The second resin layer  12  is made of e.g. polyimide. The material of the second resin layer  12  may be different from the material of the first resin layer  11 . In this example, the second resin layer  12  does not need to have optical transmissivity. For instance, in the case of a display device of the top emission type, the second resin layer  12  is made of an optically transmissive material. The bonding layer  14  is made of e.g. a photosetting resin material or thermosetting resin material. 
     Next, a method for manufacturing the display device  110  is described. 
       FIGS. 2A to 2C ,  3 A, and  3 B are sectional views schematically showing a sequential process for manufacturing a display device according to the first embodiment. 
     As shown in  FIGS. 2A and 2B , in the manufacturing of the display device  110 , first, a first resin layer  11  is formed on a substrate  5 . 
     In forming the first resin layer  11 , for instance, a material layer  11   m  including the raw material of the first resin layer  11  is formed on the substrate  5 . Subsequently, the material layer  11   m  is heated. Thus, a first resin layer  11  is formed from the material layer  11   m . The substrate  5  is e.g. a glass substrate. 
     Formation of polyimide film as an example of the first resin layer  11  is now briefly described. In the case where the first resin layer  11  is made of polyimide film, a heat-resistant resin including a polymer having an imide group in its structure is used. Examples of the polyimide resin include polyamide-imide, polybenzimidazole, polyimide ester, polyether imide, and polysiloxane-imide. 
     The polyimide resin can be produced by reaction of known diamine and acid anhydride in the presence of a solvent. For instance, a resin solution of polyamic acid, which is a precursor of the polyimide resin, can be obtained by reaction of diamine and acid anhydride. 
     The substrate  5  functions as e.g. a support body for applying a polyamic acid solution. The moisture permeability of the substrate  5  affects the peelability of the polyimide resin being formed. For instance, the organic solvent in the step for drying and imidizing the polyamic acid solution and the moisture associated with the progress of imidization concentrate at the interface between the substrate  5  and the first resin layer  11  and hamper the adherence therebetween. In this state, for instance, the substrate  5  is easily peeled from the first resin layer  11 . That is, high moisture permeability of the substrate  5  prevents moisture from remaining at the interface and enhances the adherence. On the other hand, if the moisture permeability is too low, the moisture is insufficiently eliminated and tends to cause unexpected floating of the first resin layer  11  during the process. 
     Imidization is a step for advancing cyclodehydration of polyamic acid by heat treatment to form polyimide. That is, imidization is the step for forming the first resin layer  11  from the material layer  11   m . As described above, the peelability of the substrate  5  is significantly affected by how much amount of imidization water generated in the imidization is left at the interface between the substrate  5  and the first resin layer  11 . If the liquid component at the interface is completely removed, the adherence becomes robust and causes peeling failure. In the case of lowering the adhering strength by inserting a peeling layer, it is supposed that, for instance, the peeling layer is made of a material such that imidization moisture remains at the interface with the peeling layer. 
     As shown in  FIG. 2C , a first sealing layer  21  is formed on the first resin layer  11 . Then, a display layer  13  is formed on the first sealing layer  21 . In this embodiment, for instance, the display layer  13  can be manufactured in the same way as the existing process on the glass substrate. For instance, a display including an array of the active matrix display can be fabricated on the first resin layer  11  using the existing technique. 
     For instance, a metal layer may be formed on the first resin layer  11 , and a first sealing layer  21  may be formed on the metal layer. A contact with the metal layer is formed by forming a through hole in the first sealing layer  21  before forming the gate electrode  43 . Thus, for instance, mounting from the back side is enabled by the laser peeling process performed later. Subsequently, an active matrix basically similar to the conventional one may be formed. For instance, a method for forming an active matrix based on amorphous TFT (thin film transistor) is now illustrated. 
     First, a gate electrode  43  is formed. The gate electrode is made of e.g. at least one of aluminum, copper, molybdenum, tantalum, titanium, and tungsten. The gate electrode  43  is electrically connected to e.g. the driver IC through a contact hole and a wiring. 
     Next, a gate insulating film  44  is formed. The gate insulating film  44  is formed by e.g. CVD technique or sputtering technique. The gate insulating film  44  is made of e.g. SiO, SiN, or SiON. 
     Next, a semiconductor layer  45  is formed. The semiconductor layer  45  is formed by e.g. CVD technique. The semiconductor layer  45  is made of e.g. hydrogenated amorphous silicon (a-Si:H). Next, a channel protective film  46  is formed. The channel protective film  46  is formed by e.g. CVD technique or sputtering technique. The channel protective film  46  is made of e.g. SiO, SiN, or SiON. Then, a first conductive part  41  and a second conductive part  42  are formed. Thus, a thin film transistor  35  is formed. 
     Subsequently, formation of a passivation film  50 , formation of a contact hole, formation of a first electrode  31 , formation of a bank layer  54 , formation of an organic light emitting layer  33 , and formation of a second electrode  32  are sequentially performed. Thus, a display layer  13  is formed. Then, a second sealing layer  22  is formed on the second electrode  32 . The second sealing layer  22  is made of e.g. a stacked film including SiN or AlO. The method for forming the thin film transistor  35  and the structure of the thin film transistor  35  are not limited to the foregoing. For instance, the channel protective film  46  may be omitted in the thin film transistor. 
     In the formation of the organic light emitting layer  33 , for instance, a hole transport layer is evaporated, and a light emitting layer is deposited. An electron transport layer is formed on the light emitting layer. The second electrode  32  is made of e.g. a stacked film of LiF and Al. The second sealing layer  22  may be made of e.g. SiN x  formed by PE-CVD technique, SiO x  formed by sputtering technique, or an organic resin film (parylene) including polyparaxylene. 
     As shown in  FIG. 3A , a second resin layer  12  is bonded onto the display layer  13  via a bonding layer  14 . In this example, the second resin layer  12  is bonded to the second sealing layer  22 . This can improve e.g. the sealing performance. Furthermore, the second resin layer  12  also functions as a support body for the display layer  13  and the like when the substrate  5  is removed by laser peeling or the like. 
     As shown in  FIG. 3B , the substrate  5  is removed. The substrate  5  is removed by e.g. laser peeling. In laser peeling, laser light is applied from the substrate  5  side to cause the first resin layer  11  or an absorption layer (not shown) to absorb the light. Thus, heat is generated in a very small region. Accordingly, the substrate  5  is peeled from the first resin layer  11 . 
     The laser light is restricted in terms of wavelength. It is necessary to select laser light having a center wavelength transmitted through the substrate  5  (e.g., glass) and absorbed in the first resin layer  11  (e.g., polyimide). Candidates include e.g. XeCl excimer laser (center wavelength 308 nm) and YAG:THG laser (center wavelength 355 nm). 
     In another scheme, light is absorbed in an absorption layer even if there is no absorption in the first resin layer  11 . In this case, a metal film used as the absorption layer has absorption in a wide wavelength range. This expands the range of choices for available lasers. For instance, the metal film is made of Ti, and an infrared fiber laser is used as the laser. The XeCl excimer laser is very expensive in the apparatus cost and running cost. Thus, in view of reducing the process cost in the future, it is considered that the manufacturing cost can be suppressed even with an additional process for providing an absorption layer. 
     The removal of the substrate  5  is not limited to laser peeling. For instance, the substrate  5  may be peeled from the first resin layer  11  by heating the first resin layer  11  with a lamp or the like. Alternatively, for instance, the substrate  5  may be removed by grinding the substrate  5 . Alternatively, for instance, the substrate  5  may be removed by dissolving the adhesive between the substrate  5  and the first resin layer  11  with a chemical agent or the like. 
     After removing the substrate  5 , the step for increasing the density of the bonding layer  14  is performed. The “step for increasing the density of the bonding layer  14 ” is, in other words, the step for decreasing the intermolecular distance of the material of the bonding layer  14 . For instance, it can also be referred to as the process of increasing the elasticity. More specifically, for instance, it is the step for curing the bonding layer  14  by heat or light. For instance, in the case where the bonding layer  14  is made of a photosetting resin material, the density of the bonding layer  14  is increased by irradiating the bonding layer  14  with light. That is, the bonding layer  14  is cured by irradiation with light. For instance, in the case where the bonding layer  14  is made of a thermosetting resin material, the density of the bonding layer  14  is increased by heating the bonding layer  14 . That is, the bonding layer  14  is cured by heating. 
     Thus, the display device  110  is completed. 
     After removing the substrate  5 , the bonding layer  14  is cured by heat or light. Thus, for instance, the bonding layer  14  develops barrier property. In this embodiment, the bonding layer  14  is not cured before removing the substrate  5 . In contrast, the bonding layer  14  is cured after removing the substrate  5 . This can avoid e.g. stress concentration on the organic light emitting layer  33 . The organic light emitting layer  33  has low interlayer adhesiveness. Thus, film peeling occurs in the organic light emitting layer  33  under concentration of force. The pixel  30  subjected to film peeling lacks EL light emission and results in a dark spot. Thus, it is very important to suppress the film stress applied to the organic light emitting layer  33 . 
     For instance, a film may be laminated on the surface of the first resin layer  11  on the side opposite from the display layer  13  to strike a balance between the second resin layer  12  and the second sealing layer  22 . Thus, the organic light emitting layer  33  may be positioned as close to the neutral plane as possible. That is, the position in the Z-axis direction of the organic light emitting layer  33  is placed near the center of thickness in the Z-axis direction of the display device  110 . Thus, the stress applied to the organic light emitting layer  33  can be decreased e.g. when the flexible display device  110  is warped. For instance, the display device  110  can be provided with a structure resistant to bending. 
     The foregoing has described only the process characteristic of the display device  110  according to this embodiment. However, this does not exclude processes other than the foregoing, but any process can be included. 
     The inventor formed the display layer  13  on a polyimide film (10 μm) applied on a glass substrate (film thickness 700 μm). Samples laminated with a PEN substrate as the second resin layer  12  were fabricated, and evaluation of peeling using XeCl excimer laser was performed. 
     In the peeling evaluation, three samples different in the type of the bonding layer  14  were fabricated. In the first sample, the bonding layer  14  was made of a material serving only for bonding. In the second sample, the bonding layer  14  was made of a material subjected to thermosetting after bonding. In the third sample, the bonding layer  14  was made of a thermoplastic adhesive. 
     The first sample and the third sample were not affected by the overlap ratio even under the peeling condition of laser irradiation. EL light emission was achieved in both samples. Here, the overlap ratio refers to the proportion of the overlapping area of the portion subjected to the first laser shot and the portion subjected to the second laser shot versus the area of the portion subjected to the first laser shot. On the other hand, the second sample was significantly affected by the overlap ratio in the case where laser peeling was performed after curing the bonding layer  14 . 
     Thus, in the case of high overlap ratio, the organic light emitting layer  33  of the pixel  30  was subjected to film peeling, and exhibited high residual stress. Normal lighting of the pixel  30  was confirmed before peeling. For instance, by the removal of the glass substrate serving as a support body, the first resin layer  11  constitutes the outermost surface, and the residual stress is relaxed. Thus, in the process in which the first resin layer  11  changes its own shape, a large stress is applied to the edge of the bank structure part of the organic light emitting layer  33 . It is considered that this causes film peeling. 
     Irrespective of whether peeling is performed mechanically by hands or tools, or by laser irradiation, a large stress occurs at the interface between the peeled region and the adhering region yet to be peeled. This continuously moves with the progress of peeling. Thus, whether film peeling occurs at the moment of peeling is determined by the balance between the structure and the stress. From the foregoing, it turns out that the influence of residual stress of the second resin layer  12  and the bonding layer  14  is significant. Thus, it is important to remove the substrate  5  when the residual stress of the bonding layer  14  is made as small as possible. 
     Thus, the inventor has found that the residual stress of the bonding layer  14  affects the film peeling of the organic light emitting layer  33  in the step for removing the substrate  5 . This is a technical problem that has first been found by the inventor&#39;s investigation. 
     Furthermore, the inventor evaluated the above samples also in terms of gas barrier property. As a result, it has turned out that the gas barrier property of the first sample and the third sample is lower than the gas barrier property of the second sample. 
     Thus, in the case where the bonding layer  14  is made of a material serving only for bonding, and in the case where the bonding layer  14  is made of a thermoplastic material, film peeling of the organic light emitting layer  33  can be suppressed, but the gas barrier property is low. On the other hand, in the method of peeling the bonding layer  14  from the substrate  5  after curing the bonding layer  14 , a good gas barrier property is achieved, but film peeling of the organic light emitting layer  33  is likely to occur. 
     In contrast, in the method for manufacturing the display device  110  according to this embodiment, the substrate  5  is removed when the bonding layer  14  has low density. Specifically, the substrate  5  is removed before curing the bonding layer  14 . Thus, the stress applied to the organic light emitting layer  33  in the step for removing the substrate  5  can be made smaller than in the case of removing the substrate  5  after curing the bonding layer  14 . This can suppress e.g. film peeling of the organic light emitting layer  33  in the step for removing the substrate  5 . Furthermore, a good gas barrier property can also be achieved by increasing the density of the bonding layer  14  after removing the substrate  5 . 
     Thus, the method for manufacturing the display device  110  according to this embodiment can achieve high reliability. For instance, suppression of film peeling of the organic light emitting layer  33  can be made compatible with high gas barrier property. For instance, the display device  110  can be manufactured with higher yield. For instance, the manufacturing cost can be suppressed. 
       FIG. 4  is a flow chart schematically showing the method for manufacturing a display device according to the first embodiment. 
     As shown in  FIG. 4 , the method for manufacturing a display device according to the embodiment includes a step S 110  for forming a first resin layer  11 , a step S 120  for forming a display layer  13 , a step S 130  for bonding a second resin layer  12 , a step S 140  for removing the substrate  5 , and a step S 150  for increasing the density of the bonding layer  14 . The method for manufacturing a display device according to the embodiment may further include other steps. For instance, the step S 110  for forming the first resin layer  11  may include a step for forming a material layer  11   m  and a step for forming the first resin layer  11  from the material layer  11   m.    
     The step S 110  performs e.g. the processing described with reference to  FIGS. 2A and 2B . The step S 120  performs e.g. the processing described with reference to  FIG. 2C . The step S 130  performs e.g. the processing described with reference to  FIG. 3A . The step S 140  and the step S 150  perform e.g. the processing described with reference to  FIG. 3B . 
     Thus, a method for manufacturing a display device with high reliability can be obtained. 
     Second Embodiment 
       FIG. 5  is a sectional view schematically showing a display device according to a second embodiment. 
     As shown in  FIG. 5 , in the display device  120 , a color filter layer  60  is provided between the second resin layer  12  and the bonding layer  14 . Furthermore, the display device  120  further includes a planarization layer  61  provided between the second resin layer  12  and the color filter layer  60 , and a barrier layer  62  provided between the bonding layer  14  and the color filter layer  60 . In the display device  120 , the color filter layer  60 , the planarization layer  61 , and the barrier layer  62  are provided as necessary, and can be omitted. The members similar to those in the above first embodiment are labeled with like reference numerals, and the detailed description thereof is omitted. 
     In the display device  120 , the second electrode  32  has optical transmissivity. In the display device  120 , the second electrode  32  is e.g. a transparent electrode. The first electrode  31  is e.g. optically reflective. The first electrode  31  may be optically transmissive. That is, the display device  120  is of the top emission type in which the light emitted from the organic light emitting layer  33  is transmitted through the second electrode  32  and emitted outside from the second resin layer  12  side. Thus, in the display device  120 , each of the second sealing layer  22 , the bonding layer  14 , the barrier layer  62 , the color filter layer  60 , the planarization layer  61 , and the second resin layer  12  also has optical transmissivity. 
     In this example, the first electrode  31  is made of e.g. LiF/AI, Al, or Ag. The second electrode  32  is made of e.g. ITO or MgAg. The planarization layer  61  is made of e.g. silicon oxide film, silicon nitride film, silicon oxynitride film, or aluminum oxide film. The barrier layer  62  is made of e.g. silicon oxide film, silicon nitride film, silicon oxynitride film, or aluminum oxide film. 
     The color filter layer  60  includes e.g. a plurality of color filters  60   a . The color filters  60   a  are placed at e.g. positions overlapping the respective pixels  30  as projected on the plane parallel to the X-Y plane. Thus, the light emitted from the organic light emitting layer  33  is transmitted through the color filter  60   a . Accordingly, light of a color corresponding to the color filter  60   a  is emitted outside. 
     The color filter layer  60  further includes e.g. a light blocking part  60   b . The light blocking part  60   b  has no optical transmissivity. The light blocking part  60   b  is shaped like e.g. a frame surrounding each of the color filters  60   a . For instance, the light blocking part  60   b  overlaps each of the thin film transistors  35  as projected on the plane parallel to the X-Y plane. This can suppress e.g. incidence of external light on the thin film transistors  35 . Thus, characteristics variation of the thin film transistors  35  can be suppressed. The light blocking part  60   b  is made of e.g. a black resin material. 
     Next, a method for manufacturing the display device  120  is described. 
       FIGS. 6A to 6C , and  7  are sectional views schematically showing a sequential process for manufacturing a display device according to the second embodiment. 
     As shown in  FIG. 6A , in the manufacturing of the display device  120 , first, a first resin layer  11  is formed on a substrate  5  as in the above first embodiment. A first sealing layer  21  is formed on the first resin layer  11 . A display layer  13  is formed on the first sealing layer  21 . Then, a second sealing layer  22  is formed on the display layer  13 . 
     As shown in  FIG. 6B , besides the display layer  13  and the like, a second resin layer  12  is formed on a support body  6 . The support body  6  is made of e.g. a glass substrate. The step for forming the second resin layer  12  on the support body  6  may be performed before the step for forming the first resin layer  11  on the substrate  5 . Alternatively, the step for forming the first resin layer  11  on the substrate  5  and the step for forming the second resin layer  12  on the support body  6  may be performed substantially at the same time. 
     A color filter layer  60  is formed on the second resin layer  12 . In this example, a planarization layer  61  is formed on the second resin layer  12 , and a color filter layer  60  is formed on the planarization layer  61 . Then, a barrier layer  62  is formed on the color filter layer  60 . 
     As shown in  FIG. 6C , the second resin layer  12  is bonded onto the display layer  13  via a bonding layer  14 . In this example, the color filter layer  60  and the second resin layer  12  are bonded onto the display layer  13  via the bonding layer  14  so that the color filter layer  60  is placed between the display layer  13  and the second resin layer  12 . In this example, the barrier layer  62  is bonded to the second sealing layer  22  by the bonding layer  14 . 
     As shown in  FIG. 7 , the substrate  5  is removed by e.g. irradiation with laser light. Then, in this example, the support body  6  is further removed. The removal of the support body  6  can be based on e.g. a method similar to the removal of the substrate  5 . Subsequently, the step for increasing the density of the bonding layer  14  is performed as in the first embodiment. Thus, the display device  120  is completed. 
     Thus, in the display device  120  of the top emission type, the step for increasing the density of the bonding layer  14  is performed after removing the substrate  5  and removing the support body  6 . This can suppress e.g. film peeling of the organic light emitting layer  33  in the step for removing the substrate  5  and the step for removing the support body  6 . Furthermore, a good gas barrier property can also be achieved by increasing the density of the bonding layer  14  after removing the substrate  5  and the support body  6 . 
     Third Embodiment 
       FIG. 8  is a block diagram schematically showing a manufacturing system according to a third embodiment. 
     As shown in  FIG. 8 , the manufacturing system  200  includes a first processing unit  201 , a second processing unit  202 , a third processing unit  203 , a fourth processing unit  204 , and a fifth processing unit  205 . 
     The first processing unit  201  performs the processing for forming a first resin layer  11  on a substrate  5 . The first processing unit  201  performs e.g. the processing described with reference to  FIGS. 2A and 2B . 
     The second processing unit  202  performs the processing for forming a display layer  13  on the first resin layer  11 . The second processing unit  202  performs e.g. the processing described with reference to  FIG. 2C . 
     The third processing unit  203  performs the processing for bonding a second resin layer onto the display layer  13  via a bonding layer  14 . The third processing unit  203  performs e.g. the processing described with reference to  FIG. 3A . 
     The fourth processing unit  204  performs the processing for removing the substrate  5 . The fourth processing unit  204  performs e.g. the processing described with reference to  FIG. 3B . 
     The fifth processing unit  205  performs the processing for increasing the density of the bonding layer  14 . The fifth processing unit  205  performs e.g. the processing described with reference to  FIG. 3B . 
     The first to fifth processing units  201 - 205  may be configured in a single apparatus, or may be configured in separate apparatuses. Each of the first to fifth processing units  201 - 205  may include a plurality of apparatuses. For instance, the first processing unit  201  may include an apparatus for forming a material layer  11   m  and an apparatus for forming the first resin layer  11  from the material layer  11   m.    
     The manufacturing system  200  may further include e.g. a transport apparatus for transporting a workpiece such as the substrate  5  among the first to fifth processing units  201   205 . The transport of the workpiece among the first to fifth processing units  201 - 205  may be performed e.g. manually by an operator or the like. 
     The embodiments provide a method and system for manufacturing a display device having high reliability. 
     In this specification, “perpendicular” and “parallel” mean not only being exactly perpendicular and exactly parallel, but include e.g. variations in the manufacturing process, and only need to mean being substantially perpendicular and substantially parallel. In this specification, the state of being “provided on” includes not only the state of being provided in direct contact, but also the state of being provided with another element interposed in between. The state of being “stacked” includes not only the state of being stacked in contact with each other, but also the state of being stacked with another element interposed in between. The state of being “opposed” includes not only the state of directly facing, but also indirectly facing with another element interposed in between. In this specification, “electrically connected” includes not only the case of being connected by direct contact, but also the case of being connected via another conductive member and the like. 
     The embodiments of the invention have been described above with reference to examples. 
     However, the embodiments of the invention are not limited to these examples. For instance, any specific configurations of various components such as the substrate, first resin layer, display layer, pixel, first electrode, organic light emitting layer, second electrode, bonding layer, and material layer included in the display device, and the first to fifth processing units included in the manufacturing system are encompassed within the scope of the invention as long as those skilled in the art can similarly practice the invention and achieve similar effects by suitably selecting such configurations from conventionally known ones. 
     Furthermore, any two or more components of the examples can be combined with each other as long as technically feasible. Such combinations are also encompassed within the scope of the invention as long as they fall within the spirit of the invention. 
     Moreover, all manufacturing methods and manufacturing systems for display device practicable by an appropriate design modification by one skilled in the art based on the manufacturing methods and the manufacturing systems for display device described above as embodiments of the invention also are within the scope of the invention to the extent that the spirit of the invention is included. 
     Various other variations and modifications can be conceived by those skilled in the art within the spirit of the invention, and it is understood that such variations and modifications are also encompassed within the scope of the invention. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.