Patent Publication Number: US-11038141-B2

Title: Semiconductor device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/113,478, filed on Aug. 27, 2018, which, in turn, is a continuation of U.S. patent application Ser. No. 15/891,458 (now U.S. Pat. No. 10,084,151), filed on Feb. 8, 2018, which, in turn, is a continuation of U.S. patent application Ser. No. 15/629,876 (now U.S. Pat. No. 9,929,371), filed on Jun. 22, 2017, which, in turn, is a continuation of U.S. patent application Ser. No. 14/984,905 (now U.S. Pat. No. 9,722,204), filed on Dec. 30, 2015. Further, this application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2015-006786, filed on Jan. 16, 2015, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present application is related to a display device. The embodiments disclosed by the present application are related to a sealing structure of a display device. 
     BACKGROUND 
     An organic electroluminescence (referred to below as “organic EL”) display device is arranged with a light emitting element in each pixel and an image is displayed by individually controlling the emitted light. A light emitting element includes a structure in which a layer (referred to below as “light emitting layer”) including an organic EL material is sandwiched between a pair of electrodes wherein one is an anode and the other is a cathode. In an organic EL display device, one electrode is arranged as an individual pixel electrode for each pixel and the other electrode is arranged as a common pixel electrode applied with a common potential across a plurality of pixels. The organic EL display device controls light emitted by a pixel by applying a potential of the individual pixel electrode for each pixel with respect to the potential of the common pixel electrode. 
     An organic EL display device has been pointed out as being vulnerable to moisture after a period of time. Pixels which do not emit light occur when the organic EL material which forms the light emitting layer deteriorates due to moisture. In an organic EL display device, display defects due to non-light emitting pixels are referred to as dark spots. 
     For example, a structure is disclosed in the organic EL display device in Japanese Laid Open Patent No. 2005-164818 in which a region is arranged for dividing a planarized film formed in order to cover and smooth an upper side of a substrate in order to prevent the infiltration of water to the light emitting layer. A component called a bank which sections a pixel is arranged in a pixel region of the organic EL display device. For example, a structure is disclosed in Japanese Laid Open Patent No. 2005-302707 in which an aperture part is arranged in this bank layer and water is prevented from infiltrating due the aperture part being covered by a common pixel electrode. 
     SUMMARY 
     One embodiment of a display device according to the present invention includes a display region arranged with a plurality of pixels, and a first sealing region arranged in an exterior periphery part of the display region, the display region includes an individual pixel electrode arranged in each of the plurality of pixels, a common pixel electrode arranged in upper layer of the individual pixel electrode and in succession to the plurality of pixels, and a light emitting layer arranged between the individual pixel electrode and the common pixel electrode, and the first sealing region includes a sealing layer arranged on a lower layer than the common pixel electrode and a region stacked with the common pixel electrode extending from the display region, the stacked region being enclosed by the display region. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view diagram showing a structure of a display device related to one embodiment of the present invention; 
         FIG. 2  is a planar view diagram showing a structure of a display device related to one embodiment of the present invention; 
         FIG. 3  is a cross-sectional diagram showing a structure of a display device related to one embodiment of the present invention; 
         FIG. 4  is a planar view diagram showing a structure of a display device related to one embodiment of the present invention; 
         FIG. 5  is a cross sectional diagram showing a structure of a display device related to one embodiment of the present invention; 
         FIG. 6  is a planar view diagram showing a structure of a display device related to one embodiment of the present invention; 
         FIG. 7  is a cross sectional diagram showing a structure of a display device related to one embodiment of the present invention; 
         FIG. 8  is a planar view diagram showing a structure of a display device related to one embodiment of the present invention; 
         FIG. 9  is a cross sectional diagram showing a structure of a display device related to one embodiment of the present invention; and 
         FIG. 10  is a cross sectional diagram showing a structure of a display device related to one embodiment of the present invention; 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The embodiments of the present invention are explained below while referring to the drawings. However, the present invention can be carried out using many different variations and should not be interpreted as being limited to the contents described in the embodiments exemplified below. In addition, although the width, thickness and shape etc of each component are represented schematically compare to the actual components in order to clarify the explanation, these are merely examples and should not limit an interpretation of the present invention. Furthermore, the same reference symbols are attached to the same or similar elements that have already appeared previously in the specification and each drawing and an explanation of such elements may be omitted as appropriate. 
     In the present specification, when certain components or regions are described as [above (or below)] other components or regions, unless specified otherwise, this includes not only being directly above [or directly below] other components or regions, but also above [or below] other components or regions, that is, other structural components may be included therebetween. 
     An organic EL display device includes a complex structure in which a plurality of coating films are stacked and patterned. As a result, as is the organic EL display device disclosed in the patent document 1, in the case where a light emitting layer extends from a display region, there is a problem wherein an end part the light emitting layer contacts a bank layer which includes water even if a side surface and upper surface of a planarized film are covered by a conductive film. In addition, a problem occurs wherein water encapsulated in the bank layer infiltrates the light emitting layer even if waterproof properties of a panel periphery are improved using the bank layer. 
     One embodiment of the present invention aims to provide a display device having a structure in which a light emitting layer is protected from both moisture infiltrating from the exterior of the display device and moisture encapsulated within a display region. 
     Embodiment 1 
     The structure of a display device  100  related to the present embodiment is explained while referring to  FIG. 1 . The display device  100  is arranged with a display region  106  in a first substrate  102 . The display region  106  is formed by arranging a plurality of pixels  108 . A second substrate  104  is arranged as a sealing material on an upper surface of the display region  106 . The second substrate  104  is fixed to the first substrate  102  by a third sealing region  110  which encloses the display region  106 . The display region  106  formed in the first substrate  102  is sealed using a sealing material so that is not exposed to air by the second substrate  104  which is a sealing material and the third sealing region  110 . Deterioration of a light emitting element  124  arranged in each pixel  108  is suppressed by adopting this type of sealing structure. 
     One end of the first substrate  102  is arranged with a terminal region  114 . The terminal region  114  is arranged on the exterior side of the second substrate  104 . The terminal region  114  is formed using a plurality of connection terminals  116 . A connection terminal  116  forms a connection point between devices which output a video signal or power sources and the like, and a wiring substrate connecting a display panel. This connection point in the connection terminal  116  is exposed to the exterior. A driver circuit  112  which outputs a video signal input from the terminal region  114  to the display region  106  may be arranged in the first substrate  102 . 
     The structure of the display device  100  related to the present embodiment is explained further while referring to  FIG. 2  and  FIG. 3 .  FIG. 2  is a planar view diagram showing the structure of the display device  100  related to the present embodiment.  FIG. 3  is a cross-sectional diagram showing the structure of the display device  100  related to the present embodiment. 
     As is shown in  FIG. 2 , a plurality of pixels are arranged in a matrix shape in the display region  106  which forms a display screen above the substrate  102 , and an individual pixel electrode  126  of each electrode is shown in a planar view. In addition, in the present embodiment, a sealing layer  142  is arranged so as to enclose a plurality of individual pixel electrodes  126 . A plurality of cathode contacts  118  and a second sealing region  120  are arranged in a periphery edge part. A perpendicular scanning circuit or horizontal circuit which input signals to the display region  106  may be further added as other components. 
       FIG. 3  is a cross-sectional structure along the line A-B in the display device  100  shown in  FIG. 2 . As is shown in  FIG. 3 , each of the plurality of pixels  108  in the display region  106  includes a transistor  122  and light emitting element  124 . In the case of an organic EL element, the light emitting element  124  includes a structure in which a light emitting layer  130  formed from an organic EL material is sandwiched by the individual pixel electrode  126  and a common pixel electrode  128  arranged facing the individual pixel electrode  126 . The individual pixel electrode  126  is independent in each pixel and is connected to each transistor  122  respectively. 
     In the present embodiment, the sealing layer  142  is arranged so as to enclose the periphery of a plurality of pixels  108  arranged in a matrix shape. The sealing layer  142  and common pixel electrode  128  include a region where they contact (first sealing region), the first sealing region forms a closed periphery shape in an upper surface view and encloses the plurality of pixels  108  arranged in a matrix shape. The sealing layer  142  is arranged further to the interior than the sealing region  120 . In this way, the light emitting layer  130  and bank  135  outside of the display region  106  are separated. It is preferred that the light emitting layer  130  avoid contact as much as possible with an organic element such as the bank  135  outside of the display region  106 , and it is preferred that as much as possible an end part of the interior side of the sealing layer  142  is arranged in the vicinity of the most exterior periphery pixel  108 . In addition, it is preferred that an end part on the exterior side of the sealing layer  142  is arranged as much as possible in the vicinity of the sealing region  120 . 
     The sealing layer  142  may be formed above an insulation layer  136  as is shown in  FIG. 3 . That is, the sealing layer  142  can be formed using the same material and in the same process as the individual pixel electrode  126  in the manufacturing process of the display device. In this case, it is possible to form the sealing layer  142  just by a structural change without any large change in processes. However, the material and method for forming the sealing layer  142  are not limited to these. The sealing layer  142  may be a material with high water blocking properties, a metal material other than the individual pixel electrode  126  or an insulation material. In the case an insulation material, it is possible to use a nitride silicon film with high water blocking properties. 
     Since the individual pixel electrode  126  reflects light generated by the light emitting layer  130  to the common pixel electrode  128  side, it is preferred that the individual pixel electrode  126  is formed from a metal film with high reflectance. Alternatively, the individual pixel electrode  126  may be formed from a stacked structure of a metal film and transparent conductive film or a structure including a light reflective surface. Although it is possible to also form the sealing layer  142  using the same material and in the same process as the individual pixel electrode  126 , the material and method used is not limited to this as mentioned previously. 
     A bank  132  is arranged between two adjacent pixels  108 . The bank  132  is arranged so that an end part covers a periphery edge part of the individual pixel electrode  126 . In the present embodiment, the bank  132  is further arranged so as to cover an end part of the sealing layer  142 . 
     Since the bank  132  prevents shorting with the common pixel electrode  128  without the light emitting layer  130  being sufficiently covered by an end part of the individual pixel electrode  126  and insulates the space between adjacent pixels, it is preferred that the bank  132  is formed using an insulation material. For example, it is preferred to use an organic material such as polyimide or acryl or an inorganic material such as silicon oxide when forming the bank  132 . 
     The light emitting layer  130  is arranged in common with a plurality of pixels  108  and is arranged so as to cover the bank  132  between the individual pixel electrode  126  and pixel  108 . In addition, the light emitting layer  130  may extend from the display region  106  exceeding the most exterior periphery pixel  108  to cover a part of the sealing layer  142 . 
     In the case where the light emitting layer  130  is formed from an organic EL layer for example, the light emitting layer  130  is formed using a low molecular or high molecular organic material. In the case where a low molecular organic material is used, in addition to including an organic material with light emitting properties, a hole injection layer or electron injection layer, or a hole transport layer or electron transport layer may be included to sandwich the light emitting layer  130 . In the present embodiment, the light emitting layer  130  uses an element which displays white light emitting properties and a full color can be realized using a color filter. 
     The common pixel electrode  128  arranged above the light emitting layer  130  includes a region which contacts with the common pixel electrode  128  above the sealing layer  142  as described previously. The region has a closed periphery shape and encloses a plurality of pixels arranged in a matrix shape. In the case where the light emitting layer  130  extends as far as the sealing layer  142 , the common pixel electrode  128  and sealing layer  142  covers an end part of the light emitting layer  130 . By adopting this type of structure, the light emitting layer  130  and the bank  135  extending from the exterior side of the display region  106  are separated. 
     Since the common pixel electrode  128  allows light generated by the light emitting layer  130  to pass through, it is preferred that the common pixel electrode  128  is formed from a transparent conductive film such as ITO (indium doped with tin oxide) or IZO (indium doped with zinc oxide) having translucent properties and conduction properties. Alternatively, a metal film with a thickness which allows emitted light to pass through may be formed as the common pixel electrode  128 . 
     It is possible to effectively block moisture from infiltrating the light emitting layer  130  by arranging a first sealing region as in the present embodiment. As a result, it is possible to improve resistance to moisture and provide a display device  100  with a high level of reliability. Furthermore, by arranging double structure in which a moisture infiltration path is blocked together with a second sealing region, it is possible to further effectively block the infiltration of moisture. 
     The common pixel electrode  128  is arranged in common with a plurality of pixels  108  and extends to the periphery edge part of the substrate  102 . The common pixel electrode  128  and a low potential power supply wire  129  are conductive in a cathode contact  118  arranged in the periphery edge part of the substrate. As is shown in  FIG. 2 , the cathode contact  118  may also be arranged in a plurality of places of the periphery edge part. In addition, in the present embodiment, although the cathode contact  118  is shown being arranged in a periphery edge part, the present embodiment is not limited to this arrangement, the cathode contact  118  may also be arranged within the display region  106  or both the display region  106  and a periphery edge part. 
     Although not shown in the diagram, in the case where the sealing layer  142  is formed from a metal material, the low potential power source  129  may be extended to below the sealing layer  142  and arranged to conduct with the cathode contact  118 . In this case, the sealing layer  124  operates as a dummy electrode. When the resistance of a wire itself or the contact resistance between wires becomes high, the potential difference between the individual pixel electrode  126  and common pixel electrode  128  becomes smaller compared to a voltage which should originally be applied due to a drop in voltage which leads to a problem where the amount of light emitted by the light emitting element  124  drops (shading). However, by adopting this type of structure, it is possible to reduce the space between the display region  106  and cathode contact  118 , improve control of a potential of the common pixel electrode  128  and suppress shading. 
     Auxiliary electrodes  135  may be arranged below the individual pixel electrode  126  via the insulation layer  136 . It is possible to form a capacitances holding a video signal by using the individual pixel electrode  126 , insulation layer  136  and auxiliary electrode  134 . Furthermore, if a structure in which the auxiliary electrode  134  covers a planarizing film  133  is adopted, it is possible to suppress moisture from the planarizing firm  133  from infiltrating the light emitting layer  130 , Furthermore, moisture blocking properties are further improved since it is possible to completely cover the bank  135  extending from the exterior side of the display region  106  using the auxiliary electrode  13 , sealing layer  142  and common pixel electrode  128 . 
     The second sealing region  120  is arranged so as to enclose the display region  106 . As can be seen from the cross-sectional view shown in  FIG. 3 , the bank  135  and planarizing film  133  are removed within the second sealing region  120 , and the planarizing film  133  and bank  135  are divided with the second sealing region  120  as the boundary. When an organic element is used for the bank  135  or planarizing film  133 , the organic element becomes a path for propagating moisture, moisture which has infiltrated from the exterior reaches as far as the light emitting element  124  which is likely to degrade the display device  100 . As a result, the second sealing region  120  is arranged for opening both the bank  135  and planarizing film  133 , and an organic film is divided by the interior and exterior which is effective for breaking a propagation path for moisture. An inorganic insulation film is suitable for an insulation film  198  which covers a gate insulation film  196  of the transistor  122  and a gate electrode of the transistor  122 . In the sealing region  120 , the insulation layer  136 , auxiliary electrode  134 , gate insulation film  196 , insulation film  198 , common pixel electrode  128  and sealing film  138  have a form so that an inorganic insulation film, metal material or organic metal compound material mutually contact. Moisture infiltration from the exterior of the sealing region  120  is prevented by adopting this structure. A material basically formed using an organic insulation film such as the bank  135  and planarizing film  133  prevents the infiltration of moisture by being removed from the sealing region  120 . 
     The sealing film  138  is arranged above the common pixel electrode  128 . It is preferred that the sealing film  138  is an insulation film which can block the infiltration of moisture. An inorganic insulation film can be used as the insulation film. The sealing film may also have a multilayer structure or a structure in which an organic insulation film is sandwiched by inorganic insulation films. 
     For example, in the case of using an inorganic insulation film as the insulation film, it is possible to use silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy), nitride oxide silicon (SiNxOy), aluminum oxide (AlOx), aluminum nitride (AlNx), aluminum oxynitride (AlOxNy), aluminum nitride oxide (may use a film of AlNxOy) and the like (x, y are arbitrary). A structure in which these films are stacked may also be used. It is possible to use a plasma CVD method or sputtering method as a film formation method. 
     In the case where an organic insulation film is used as the insulating film, it is possible to use a polyimide resin, an acrylic resin, an epoxy resin, a silicone resin, a fluorine resin and a siloxane resin and the like. It is also possible to use a stacked structure of these materials, A vapor deposition method or vapor deposition polymerization method may be used as the film forming method. 
     Furthermore, a stacked structure in which the inorganic insulation films and organic insulation films described above are combined may be used as the sealing film  138 . 
     A transparent opposing substrate  104  is covered while maintaining a gap with the first substrate  102  by the third sealing region  110  in the first substrate  102 . A filler  140  comprised from a transparent epoxy resin is filled in the space which is enclosed by the opposing substrate  104 , third sealing region  110  and sealing film  138 . 
     The display device  100  shown in the present embodiment has what is called a top emission type structure in which light emitted by the light emitting element  124  is emitted to the common pixel electrode  128  side. Although a top emission type structure is exemplified in the present embodiment, the present invention is not limited to a top emission type structure. It is also possible to apply a bottom emission type structure in which light is emitted to the individual pixel electrode  126  side. 
     The display device  100  according to the present embodiment is characterized by arranging the sealing layer  142  in the periphery of a pixel  108  in addition to the individual pixel electrode  126  which forms a pixel  108 . It is possible to separate the light emitting layer  130  and bank  135  or planarizing film  133  which are organic films by covering the light emitting layer  130  which is arranged between the sealing layer  142  and common pixel electrode  128  arranged on an upper layer, block a moisture infiltration path to the light emitting layer  130 , and provide the display device  100  with a high level of reliability. In addition, moisture blocking properties and reliability of the display device  100  are further improved by arranging the second sealing region  120 . 
     Furthermore, in the manufacturing process of the display device  100  related to the present embodiment, it is possible to separate the light emitting layer  130  from bank  135  and planarizing film  133  which are organic films just using a structural change without a large process change. For example, it is possible to form the sealing layer  142  in the same process as the individual pixel electrode  126  and a deposition range of the light emitting layer  130  may be changed by changing an opening region of a film formation mask. 
     Modified Example 1 
     A schematic structure of a display device  200  related to a modified example of the present embodiment is explained while referring to  FIG. 4  and  FIG. 5 .  FIG. 4  is a planar view diagram showing a schematic structure of the display device  200  related to a modified example of the present embodiment.  FIG. 5  is a cross-sectional diagram showing a schematic structure of the display device  200  related to a modified example of the present embodiment. 
     The display device  200  according to the present modified example is different only in the layout of sealing layer  142  and the layout of the light emitting layer  130  compared to the display device  100  of the present embodiment. In the display device  200  according to the present modified example, the sealing layer  142  extends more to the vicinity of the second sealing region  120  and the light emitting layer also extends in a similar manner compared to the display device  100  according to the present embodiment. The sealing layer  142  has a closed periphery shape and the width is preferred to be 250 μm or more and 500 μm or less. However, the width is preferred to be set according to the positional accuracy of the light emitting layer  130 , and it is possible to set the width to a position and width which encompasses the entire range of positional variation of an end part of the light emitting layer  130 . The end part of the light emitting layer  130  is preferred to extend within a region of 20 μm or more and 250 μm or les to the exterior side of the display region  106  from a pixel arranged on the outermost periphery among the plurality of pixels arranged in a matrix shape. In this way, it is possible to secure a wide design margin with respect to positional accuracy when patterning the light emitting layer  130 . 
     Modified Example 2 
     A schematic structure of a display device  300  related to a modified example of the present embodiment is explained while referring to  FIG. 6  and  FIG. 7 .  FIG. 6  is a planar view diagram showing a schematic structure of the display device  300  related to a modified example of the present embodiment.  FIG. 7  is a cross-sectional diagram showing a schematic structure of the display device  300  related to a modified example of the present embodiment. 
     The display device  300  according to the present modified example is different compared to the display device  100  of the present embodiment in that a separation region  210  which separates the bank  135  is included between the sealing layer  142  and second sealing region  120 . In this way, it is possible to break a propagation path of moisture triply, further improve moisture blocking properties and provide a display device with a high level of reliability. 
     Modified Example 3 
     A schematic structure of a display device  400  related to a modified example of the present embodiment is explained while referring to  FIG. 8  and  FIG. 9 .  FIG. 8  is a planar view diagram showing a schematic structure of the display device  400  related to a modified example of the present embodiment.  FIG. 9  is a cross-sectional diagram showing a schematic structure of the display device  400  related to a modified example of the present embodiment. 
     The display device  400  according to the present modified example is different to the display device  100  of the present embodiment in that it includes the second sealing region  120 . Since it is possible to secure moisture blocking properties by a structure in which the light emitting layer  130  is separated from the bank  135  outside the display region  106  and the planarizing film  133  using the sealing layer  142  and common pixel electrode  128 , the second sealing region  120  is not always required. In addition, it is possible to break a water propagation path by including the separation region  120  which separates the bank  135 . In this way, it is possible to secure a wide display region  106  compared to the display devices  100 ,  200  and  300  described previously and achieve a narrow framed display device  400 . 
     Modified Example 4 
     A schematic structure of a display device  500  related to a modified example of the present embodiment is explained while referring to  FIG. 10 .  FIG. 10  is a cross-sectional diagram showing a schematic structure of the display device  500  related to a modified example of the present embodiment. 
     Compared to the display device  100  of the present embodiment the display device  500  related to the present modified example is different in that the structure of the light emitting layer  130  is different. The display devices  100  to  400  described above use a method for realizing a full color by arranging a light emitting layer which emits white light and a color filter. In the present modified example, an individual light emitting layer of a red light emitting layer, green light emitting layer, blue light emitting layer and white light emitting layer are coated in a sub-pixel of each pixel  108 . The individual light emitting layer extends as far as above the sealing layer  142  arranged outside the display region  106 . An end part of the individual light emitting layer is covered by the sealing layer  142  and common pixel electrode  128  and thereby becomes separated from the bank  135  or planarizing film  133  outside of the display region  106 . 
     Furthermore, the present modified example is obviously not limited to the display device and the display devices  200  to  400  may be combined. 
     The preferred forms of the present invention were explained above using the display devices  100  to  500 . However, these are merely examples and the technical scope of the present invention should not be limited to these embodiments. A person ordinarily skilled in the art could carry out various modifications without departing from the gist of the present invention. Therefore, those modifications should also be interpreted as belonging to the technical scope of the present invention.