Patent Publication Number: US-10332920-B2

Title: Hollowed electronic display

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of a U.S. utility patent application Ser. No. 15/625,686, filed on Jun. 16, 2017, which is a continuation of the U.S. utility patent application Ser. No. 15/233,818, filed Aug. 10, 2016, now U.S. Pat. No. 9,735,185, which claims priority to U.S. provisional patent application Ser. No. 62/348,421, filed Jun. 10, 2016, all of which are incorporated herein in their entirety and by this reference thereto. 
    
    
     TECHNICAL FIELD 
     The present application is related to manufacturing of electronic displays and, more specifically, to methods and systems to manufacture hollowed electronic displays. 
     BACKGROUND 
     Electronic displays disposed on a side of mobile devices of today do not occupy the full side of the mobile device because certain areas of the mobile device are reserved for various sensors, such as a camera, ambient light sensor, proximity sensor, etc. The areas containing the sensors are considerably larger than the sensors, and those areas do not function as a part of the display. As a result, the size of the electronic display is reduced. Further, the manufacturing techniques used in the creation of the electronic displays are optimized for manufacture of rectangular electronic displays. 
     SUMMARY 
     Presented here are manufacturing techniques to create an irregularly shaped electronic display, including a hollow within which a sensor, such as a camera, can be placed. The manufacturing techniques enable the creation of the hollow anytime during the manufacturing process. The resulting electronic display occupies the full side of the mobile device, with the sensors placed within and surrounded by the display. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a flowchart of a method to create a hollowed electronic display and place a sensor, such as a camera, an ambient light sensor, and/or a proximity sensor, inside the hollow, according to one embodiment. 
         FIG. 1B  shows the distribution pattern associated with the plurality of row and column electrodes, according to one embodiment. 
         FIG. 2A  is a flowchart of a method to create a hollowed electronic display and place a sensor, such as a camera, an ambient light sensor, and/or a proximity sensor, inside the hollow, according to another embodiment. 
         FIG. 2B  shows an exposure of a substrate to light using a photomask, according to one embodiment. 
         FIG. 2C  shows the modified photomask, according to one embodiment. 
         FIG. 3  shows a sensor disposed within a hollow associated with an electronic display, according to one embodiment. 
         FIG. 4  shows a side view of the sensor disposed within the hollow associated with the electronic display, according to one embodiment. 
         FIG. 5  shows a circular hollow associated with the electronic display, according to one embodiment. 
         FIG. 6  shows a rectangular hollow associated with the electronic display, according to one embodiment. 
         FIG. 7  shows a sealant disposed on a layer associated with the electronic display, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Technology 
     Presented here are manufacturing techniques to create an irregularly shaped electronic display, including a hollow within which a sensor, such as a camera, can be placed. The manufacturing techniques enable the creation of the hollow anytime during the manufacturing process. The resulting electronic display occupies the full side of the mobile device, with the sensors placed within and surrounded by the display. 
     The process of making electronic displays, such as liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, and micro-electromechanical system (MEMS) displays, involves the creation of multiple layers. Multiple layers include a thin film transistor (TFT) layer, a color filter (CF) layer, and a display layer, which includes display elements such as liquid crystals, OLEDs, MEMS, etc. Each TFT in the TFT layer is connected to an intersection of rows and columns of electrodes. The rows of electrodes are connected to a first integrated circuit, called the row driver, which determines which electrode rows to activate by applying voltage to the ends of the row electrode. The columns of electrodes are connected to a second integrated circuit, the column driver, which determines which electrode columns to activate by applying voltage to the ends of the column electrode. The TFT is activated when both the row and the column electrode are activated. When the TFT is activated, the TFT in turn activates a corresponding display element which transmits light. The light, transmitted by the display element, is colored by a corresponding color region in the CF layer to produce any color in the visible spectrum. In addition, the light transmitted by the display element can include a frequency outside of the visible spectrum, such as infrared (IR). A group of one TFT, a corresponding display element, and a corresponding color region associated with the CF layer form a sub pixel. 
     Creating the TFT layer includes multiple steps. First, thin film transistors (TFTs) are deposited onto a substrate, such as a glass substrate or a plastic substrate. Afterwards, a photoresist coating is placed on the TFT coating. 
     In the photo development step, the photoresist coating is exposed to light, such as ultraviolet (UV) light. A photomask is used to selectively shade the photoresist coating from the light. The pattern on the photomask is transferred onto the photoresist coating. The photo development step varies based on the type of the photoresist coating. Photoresist coating can be either positive or negative. When the photoresist coating is positive, the photo development process removes the photoresist coating that was exposed to the light. When the photoresist coating is negative, the photo development process removes the photoresist coating that was not exposed to the light. 
     The etching step removes the TFT coating that is not protected by the photoresist. The stripping step removes the remaining photoresist coating from the TFTs by spraying organic solvent onto the substrate, thus leaving only the TFTs on the substrate in the areas that were protected by the photoresist coating during the etching step. 
     Creation of the TFT layer can include steps in addition to the steps described herein. Further, one or more of the steps described herein can be repeated multiple times. 
     Creating the CF layer involves multiple steps, some of which are described herein. First, a black photoresist is deposited on a substrate, such as a glass substrate. Next, the black photoresist on the substrate is treated with heat to remove solvents. The black photoresist is exposed to light through a photomask. The shape of the photomask can be grid-like, or a modified grid with various shapes added to the grid. The black photoresist is exposed to light, such as the UV light, through the photomask. In the photo development step, either the photoresist that was exposed to the light (positive photoresist) or the photoresist that was not exposed to the light (negative photoresist) is removed. 
     Next, the color regions, such as red, green, blue, cyan, magenta, yellow, white, infrared (IR), etc., are added to the substrate with the remaining black photoresist. The substrate is coated with a single color photoresist, such as a red photoresist, and prebaked to remove solvents. The red photoresist is exposed to light through a photomask. The photomask can take on various shapes. In the photo development step, either the red photoresist that was exposed to the light (positive photoresist) or the red photoresist that was not exposed to the light (negative photoresist) is removed from the substrate. To add additional colors, such as green, blue, cyan, magenta, yellow, white, infrared (IR), etc., the substrate is coated with a green photoresist and a blue photoresist, and the steps of exposure and photo development are repeated. 
     Creating the display layer includes depositing sealant on either the TFT layer or the CF layer. The shape of the sealant defines the perimeter of the electronic display. Inside the sealant, display elements are deposited, such as liquid crystals, OLEDs, MEMS, etc. 
       FIG. 1A  is a flowchart of a method to create a hollowed electronic display and place a sensor, such as a camera, an ambient light sensor, and/or a proximity sensor, inside the hollow, according to one embodiment. In this method, a hollow is created in the electronic display before depositing the various elements such as color regions, the TFTs, the display elements, etc. on various substrates. 
     In step  100 , a mask associated with a plurality of layers in an electronic display is provided. The electronic display can be a flat panel display and include a color filter (CF) layer, a thin film transistor (TFT) layer, and a display layer. Each layer in the plurality of layers can have substantially the same shape. The mask can be shaped like a circle, an ellipse, a square, a rectangle, a square with one or more rounded corners, a rectangle with one or more rounded corners, etc. The mask can be disposed anywhere on the electronic display, such as proximate to a top edge associated with the electronic display, in the middle of the electronic display, in a corner associated with electronic display, along the sides of the electronic display, etc. 
     In one embodiment, the edge of the mask traces a sub pixel boundary. Given that the size of a sub pixel is significantly smaller than the size and curvature of the mask, the edge of the mask appears smooth, and no sub pixel outline is visible along the mask edge. In another embodiment, shown in  FIG. 1B , the edge of the mask does not align with the sub pixel boundary. 
     In step  110 , a hollow corresponding to the mask is removed from a CF substrate associated with the CF layer and from a TFT substrate associated with the TFT layer to create a hollowed substrate. The hollowed substrate includes a CF substrate and a hollowed TFT substrate. Removing the hollow corresponding to the mask can be done in various ways, including cutting and/or etching. Cutting the hollow can be done with a laser or a diamond saw. The laser can be a Corning Laser Technologies laser, which cuts the glass with ultra-short laser pulses lasting several picoseconds. Etching can be done by coating the CF substrate and the TFT substrate with an etching-resistant coating. The etching-resistant coating is distributed everywhere on the CF substrate and the TFT substrate, except for the hollow corresponding to the mask. The coated CF substrate and the coated TFT substrate are submerged in the etcher, which removes the substrate in the uncoated areas. In the next step, the etching-resistant coating is removed from both the CF substrate and the TFT substrate. 
     In step  120 , a plurality of colors are distributed on the hollowed CF substrate. The CF substrate can be made out of various materials, such as glass, plastic, etc. The plurality of colors are distributed to follow the outline of the hollowed CF substrate, without depositing any colors in the substrate hollow corresponding to the mask. The colors are filters that pass various frequency bands of the electromagnetic spectrum, such as red, green, blue, white, infrared (IR), cyan, magenta, yellow, etc. 
     In step  130 , a plurality of thin film transistors is disposed on the hollowed TFT substrate. The TFT substrate can be made out of various materials, such as glass, plastic, etc. The plurality of TFTs are distributed to follow the outline of the hollowed TFT substrate, without depositing any TFTs in the substrate hollow corresponding to the mask. 
     In step  140 , a plurality of row and column electrodes corresponding to the plurality of thin film transistors are distributed such that each row and column electrode in the plurality of row and column electrodes interrupted by the hollow partially follows a perimeter associated with the hollow. The distribution pattern is further explained in  FIG. 1B . Step  140  can be performed before the plurality of TFTs are deposited on the TFT substrate, and/or after the plurality of TFTs are deposited on the TFT substrate. 
     In step  150 , the CF layer and the TFT layer are combined to obtain the electronic display. The electronic display comprises a hollow corresponding to the mask. The hollow can have the same shape as the mask. Combining the CF layer and the TFT layer includes depositing a sealant on either the CF layer or the TFT layer. Depositing the sealant includes tracing the perimeter of the hollowed substrate. Once the sealant is deposited, the display elements are deposited inside the area enclosed by the sealant. The display elements can be liquid crystals, OLEDs, or MEMS. 
     In step  160 , a sensor, such as a camera, an ambient light sensor, and/or a proximity sensor, is disposed inside the hollow such that the top of the sensor is aligned with the top of the electronic display. For example, the top of the camera comprises a lens associated with the camera. The camera lens is aligned with the top of the electronic display and placed beneath a cover glass associated with an electronic device. 
       FIG. 1B  shows the distribution pattern associated with the plurality of row and column electrodes, according to one embodiment. The plurality of row electrodes  170  (only one row electrode labeled for brevity) and the plurality of column electrodes  180  (only one column electrode labeled for brevity) are distributed on the substrate in a modified grid-like pattern circumventing the hollow  190  corresponding to the mask. A thin film transistor  105  is disposed at an intersection of a row electrode and a column electrode (only one thin film transistor is labeled for brevity). Segment  125  of the row electrode  115  interrupted by the hollow  190  partially follows the perimeter associated with the hollow  190 . There can be multiple row electrodes interrupted by the hollow  190 . Similarly, segments  165 ,  175 ,  185  of the respective column electrodes  135 ,  145 ,  155  interrupted by the hollow  190  partially follow the perimeter associated with the hollow  190 . 
     The mask corresponding to the hollow  190  does not follow a sub pixel boundary, and the formation of the hollow  190  creates an area  195  of partially formed pixels. The area  195  is bounded by the sub pixel boundary  197 . The area  195  comprising the partially formed sub pixels is not part of the electronic display, and is used to layout the row electrode segment  125  and the plurality of column electrode segments  165 ,  175 ,  185  to circumvent the hollow  190 . 
       FIG. 2A  is a flowchart of a method to create a hollowed electronic display and place a sensor, such as a camera, an ambient light sensor, and/or a proximity sensor, inside the hollow, according to another embodiment. In this method, a hollow is created in the electronic display after depositing the various elements such as color regions, the TFTs, the display elements, etc. on various substrates. In this method, there is no need to modify the manufacturing machinery to avoid depositing the various elements inside the hollow formed within the substrates. Even though depositing the various elements inside the hollow increases the amount of discarded material, the low cost of the discarded material, and the lack of need to modify the manufacturing machinery make this method cost-efficient. 
     In step  200 , a mask corresponding to a plurality of layers in the electronic display is provided. The electronic display can be a flat panel display and include a color filter (CF) layer, a thin film transistor (TFT) layer, a polarizer layer, and a display layer. Each layer in the plurality of layers can have substantially the same shape. The mask can be shaped like a circle, an ellipse, a square, a rectangle, a square with one or more rounded corners, a rectangle with one or more rounded corners, etc. The mask can be disposed anywhere on the electronic display, such as proximate to a top edge associated with the electronic display, in the middle of the electronic display, in a corner associated with electronic display, along the sides of the electronic display, etc. 
     In one embodiment, the edge of the mask traces a sub pixel boundary. Given that the size of a sub pixel is significantly smaller than the size and curvature of the mask, the edge of the mask appears smooth, and no sub pixel outline is visible along the mask edge. When the edge of the mask traces the sub pixel boundary, only regions corresponding to whole sub pixels are removed, and no partially formed sub pixels remain. 
     In another embodiment, the edge of the mask does not trace the sub pixel boundary. Once a hollow corresponding to the mask is removed from the substrate, the partially formed sub pixels do not function as part of the display. Instead, the area  195  in  FIG. 1B  comprising the partially formed sub pixels is used to layout the plurality of row and column electrodes in a pattern circumventing the hollow, as shown in  FIG. 1B . 
     In step  210 , the CF layer is provided. The CF layer includes a CF substrate and a plurality of color regions disposed on the CF substrate. The substrate can be made out of various materials such as glass, plastic, etc. The color regions are filters that pass various bands of the electromagnetic spectrum such as red, green, blue, white, infrared (IR), cyan, magenta, yellow, etc. 
     Providing the CF substrate includes depositing a colored photoresist coating onto the CF substrate. The colored photoresist coating includes filters that pass various bands of the electromagnetic spectrum such as red, green, blue, white, infrared (IR), cyan, magenta, yellow, black, etc. 
     The colored photoresist is exposed to light, such as the UV light, through a photomask.  FIG. 2B  shows an exposure of a substrate to light using a photomask, according to one embodiment. A light source  245  transmits light, such as the UV light, and illuminates the substrate  265  through the photomask  255 . The substrate  265  can be the CF substrate, the TFT substrate, etc. The pattern on the photomask  255  is transferred onto the photoresist coating to form a pattern  275 . 
     The photomask can take on various shapes. In one embodiment, the photomask is modified based on the provided mask.  FIG. 2C  shows the modified photomask, according to one embodiment. Element  270  is the unmodified photomask, including the plurality of protected areas  280  (only one of which is labeled in the figure for brevity), and the plurality of unprotected areas  290  (only one of which is labeled in the figure for brevity). Element  205  corresponds to the mask used in modifying the photomask  270 . The modified mask  215  includes a plurality of protected areas  225  (only one of which is labeled in the figure for brevity), and a plurality of unprotected areas  235  (only one of which is labeled in the figure for brevity), where the plurality of unprotected areas  235  include the mask  205 . 
     Finally, the plurality of unprotected areas  235  are removed from the substrate using a photo development process. In the photo development step, if the photoresist is positive, the photoresist that is exposed to the light is removed from the substrate, and if the photo is negative, the photoresist that is not exposed to the light is removed from the substrate. To add additional colors, such as green, blue, yellow, magenta, black, white, cyan, IR, etc., the substrate is coated with an appropriately colored photoresist, and the steps of exposure and photo development are repeated. 
     In step  220  of  FIG. 2A , a display layer is provided, which includes a plurality of display elements disposed between the CF layer and the TFT layer. The plurality of display elements are configured to transmit light and can include liquid crystals, OLEDs, MEMS, etc. Providing the display layer includes depositing a sealant, and depositing a plurality of display elements inside the sealant. The sealant is deposited on a layer in the plurality of layers, such as the CF layer or the TFT layer. The shape of the sealant traces at least a partial outline associated with the electronic display, element  730  in  FIG. 7 , and an outline associated with the mask, element  740  in  FIG. 7 . The display elements are deposited inside the outline defined by the sealant. 
     In step  230  of  FIG. 2A , the TFT layer is provided, which includes a TFT substrate and a plurality of transistors disposed on the TFT substrate. The TFT substrate can be made out of various materials such as glass, plastic, etc. Providing the TFT layer includes depositing TFTs, depositing a photoresist coating, modifying a photomask, and removing a plurality of unprotected areas from the substrate. Initially, TFTs are deposited onto the TFT substrate. A photoresist coating is deposited on the thin film transistors. The photoresist is exposed to light, such as the UV light, through a photomask, as shown in  FIG. 2B  and described herein. The photomask can take on various shapes. In one embodiment, the photomask is modified based on the provided mask, as shown in  FIG. 2C  and described herein. The photomask includes a plurality of protected areas and a plurality of unprotected areas. 
     Finally, the plurality of unprotected areas are removed to leave TFTs disposed on the TFT substrate in the plurality of protected areas. The removal of the unprotected areas can be done using photo development, etching and stripping. In the photo development step, either the photoresist that was exposed to the light (positive photoresist) or the photoresist that was not exposed to the light (negative photoresist) is removed from the substrate. In the etching step, the TFTs in the areas where the photoresist was removed are etched away, leaving only TFTs and the photoresist coating in the plurality of protected areas. In the stripping step, the photoresist is removed from the substrate, leaving only TFTs in the plurality of protected areas. 
     In addition, providing the TFT layer includes distributing a plurality of row and column electrodes corresponding to the plurality of thin film transistors such that each row and column electrode in the plurality of row and column electrodes interrupted by the hollow partially follows a perimeter associated with the hollow. The distribution pattern is further explained in  FIG. 1B . Distributing the plurality of row and column electrodes can be performed before the plurality of TFTs are deposited on the TFT substrate, and/or after the plurality of TFTs are deposited on the TFT substrate. 
     In step  240 , a hollow is removed from the CF layer, the display layer, the polarizer layer, and the TFT layer, wherein the removed hollow corresponds to the provided mask. Since the edge of the mask traces the sub pixel boundary, only regions corresponding to whole sub pixels are removed, and no partially formed sub pixels remain. Removing the hollow corresponding to the mask can be done in various ways, including cutting and/or etching. Cutting the hollow can be done with a laser or a diamond saw. The laser can be a Corning Laser Technologies laser, which cuts the glass with ultra-short laser pulses lasting several picoseconds. Etching can be done by coating the CF substrate, the display layer, the polarizer layer, and the TFT substrate with an etching-resistant coating. The etching-resistant coating is distributed everywhere on the CF layer, the display layer, the polarizer layer, and the TFT layer, except for the hollow corresponding to the mask. The coated CF layer, the coated display layer, the coated polarizer layer, and the coated TFT layer are submerged in the etcher, such as a chemical etcher, which removes the substrate in the uncoated areas. In the next step, the etching-resistant coating is removed from the CF substrate, the display layer, the polarizer layer, and the TFT substrate. In one embodiment, the polarizer layer is specially manufactured to be stamped with a polarizing material, where the stamp is in the shape of the hollowed substrate. By stamping the polarizer to exclude the mask, the amount of polarizing material discarded is reduced. 
     In step  250 , the CF layer, the display layer, and the TFT layer are combined to obtain a combined layer. Step  240  can be performed before step  250 . That is, the hollow can be removed from each layer in the electronic display separately. Alternatively, step  240  can be performed after step  250 , meaning that the hollow can be removed once from the combined layer. 
     In step  260 , a sensor, such as a camera, an ambient light sensor, and/or a proximity sensor, is disposed inside the removed hollow, with the top of the sensor aligned with the top of the electronic display. For example, the top of the camera comprises a lens associated with the camera. The camera lens is aligned with the top of the electronic display and placed beneath a cover glass associated with an electronic device. 
       FIG. 3  shows a sensor disposed within a hollow associated with an electronic display, according to one embodiment. An electronic display  300 , such as a flat panel display, includes a color filter (CF) layer  310 , a display layer  320 , a thin film transistor (TFT) layer  330 , and a sensor  340 , such as a camera, an ambient light sensor, and/or a proximity sensor. The electronic display  300  can include additional layers, such as a polarizer layer, a light guide plate, a diffuser layer, etc. The display layer  320  can include liquid crystals, organic light emitting diodes, or micro-electromechanical system (MEMS) devices. The sensor  340  is disposed within a hollow  350  formed in the electronic display  300 . The hollow  350  can take on different shapes, such as a rectangular shape with one or more rounded corners, as shown in  FIG. 3 . In addition, the hollow  350  can take on a rectangular shape with sharp corners, an elliptical shape, a circular shape, a square shape, etc. A top surface of the sensor  340  can be disposed at the same height as the top surface of the electronic display  300 . Also, the top surface of the sensor  340  can be slightly recessed from the top surface of the electronic display  300 . The sensor  340  is optically isolated from the electronic display  300  so that light from the electronic display  300  does not reach the sensor  340 . The sensor  340  can be isolated using an optically opaque material surrounding the sensor  340  and extending to the cover glass. 
       FIG. 4  shows a side view of the sensor disposed within the hollow associated with the electronic display, according to one embodiment. Cover glass  400  is disposed above the electronic display  410  and the sensor  340 . The top surface of the sensor  340  and the top surface of the electronic display  410  can be at the same height. Also, the top surface of the sensor  340  can be slightly recessed from the top surface of the electronic display  410 , thus forming an air gap  490  between the top surface of the sensor  340  and the cover glass  400 . In another embodiment, the electronic display  410  includes a top polarizer layer  420 , a CF layer  430 , a display layer  440 , a TFT layer  450 , a bottom polarizer layer  460 , a diffuser  470 , a light guide plate  480 , and the sensor  340 . The display layer  440  can include liquid crystals, organic light emitting diodes, or micro-electromechanical system (MEMS) devices. The sensor  340  is optically isolated from the electronic display  410  so that light from the electronic display  410  does not reach the sensor  340 . The sensor  340  can be isolated using an optically opaque material surrounding the sensor  340  and extending to the cover glass  400 . 
       FIG. 5  shows a circular hollow associated with the electronic display, according to one embodiment. The circular hollow  500  is formed inside an electronic display  510 . The circular hollow  500  can be placed anywhere on the electronic display  510 , such as the forehead  520  associated with the electronic display  510 , as shown in  FIG. 5 , as well as the middle of the electronic display  510 , middle left portion of the electronic display  510 , middle right portion of the electronic display  510 , bottom portion of the electronic display  510 , etc. The sensor  340  is placed inside the circular hollow  500 . The hollow on all sides is surrounded by the active electronic display  510 . 
       FIG. 6  shows a rectangular hollow associated with the electronic display, according to one embodiment. The rectangular hollow  600  with two round angles is formed inside the electronic display  610 . The rectangular hollow  600  can be placed anywhere on the electronic display  610 , such as the forehead of the electronic display  610 , the bottom left corner, the bottom right corner, middle left side, mid-right side, etc. When the rectangular hollow  600  is placed close to one edge associated with the electronic display  610 , such as the edge  620 , a thin portion  630  of the electronic display  610  formed between the rectangular hollow  600  and the edge  620  does not include active display elements. Instead, the thin portion  630  serves as a structural support for the electronic display  610 . In one embodiment, a plurality of glue beads  640  are placed on the surface of the thin portion  630  to further provide structural support for the electronic display  610 . In another embodiment, a sealant is placed on the surface of the thin portion  630  to further provide structural support for the electronic display  610 . 
       FIG. 7  shows a sealant disposed on a layer associated with the electronic display, according to one embodiment. The dispenser  720  disposes the sealant  700  on a layer  710  associated with the electronic display, such as the CF layer or the TFT layer. The shape of the sealant  700  traces the contour  730  of the electronic display and the contour  740  of the hollow. The sealant section  750  is optional and can be removed in some embodiments. When added, the sealant section  750  provides additional structural support to the electronic display. Display elements, such as liquid crystals, organic light emitting diodes, or MEMS, are deposited inside area  760 . In other embodiments, the display elements are deposited inside the contour  730  of the electronic display, including the area defined by the contour  740  of the hollow. 
     Remarks 
     The language used in the specification has been principally selected for readability and instructional purposes, and it may not have been selected to delineate or circumscribe the inventive subject matter. It is therefore intended that the scope of the invention be limited, not by this Detailed Description but rather by any claims that issue on an application based hereon. Accordingly, the disclosure of various embodiments is intended to be illustrative, but not limiting, of the scope of the embodiments, which is set forth in the following claims.