PATENT DOCUMENT

Publication Number: US-9964820-B2
Application Number: US-201414491248-A
Country: US
Kind Code: B2

Title: Displays with flipped panel structures

Abstract:
A display may have a thin-film transistor layer and a color filter layer. The display may include light blocking structures formed on a transparent substrate. In one arrangement, a clear planarization layer may be formed over the light blocking structures. The thin-film transistor layer may be formed over the planarization layer. The color filter layer may be integrated with the thin-film transistor layer. At least light blocking structures and the planarization layer should be formed from high temperature resistance material. In another arrangement, the color filter layer may be formed on the light blocking structures. A clear planarization layer may then be formed over the color filter layer. The thin-film transistor layer may be formed on the planarization layer. In this arrangement, the color filter layer also needs to be formed from thermal resistance material.

Claims:
What is claimed is: 
     
       1. Display circuitry, comprising:
 a transparent substrate; 
 light blocking structures formed on the transparent substrate; 
 a display pixel having a thin-film transistor coupled to associated pixel electrodes, wherein the display pixel is formed over the light blocking structures, and wherein the thin-film transistor has a bottom gate; 
 color filter structures interposed between the thin-film transistor and the pixel electrodes; and 
 additional light blocking structures formed over the color filter structures. 
 
     
     
       2. The display circuitry defined in  claim 1 , wherein the light blocking structures comprise a patterned black masking layer formed on the transparent substrate. 
     
     
       3. The display circuitry defined in  claim 1 , wherein the color filter layer is formed from low-k color filter material. 
     
     
       4. The display circuitry defined in  claim 1 , further comprising:
 a planarization layer that is formed on the transparent substrate and that is interposed between the light blocking structures and the thin-film transistor. 
 
     
     
       5. The display circuitry defined in  claim 4 , wherein the light blocking structures and the planarization layer are formed from material able to withstand at least 350° C. without degrading. 
     
     
       6. The display circuitry defined in  claim 1 , wherein the light blocking structures comprise high temperature resistant material. 
     
     
       7. The display circuitry defined in  claim 1 , further comprising:
 liquid crystal material formed over the pixel electrodes. 
 
     
     
       8. The display circuitry defined in  claim 1 , wherein the light blocking structures comprises black masking material. 
     
     
       9. The display circuitry defined in  claim 8 , wherein the black masking material comprises black photoresist. 
     
     
       10. An electronic device, comprising:
 a transparent substrate; 
 light blocking structures formed on the transparent substrate; 
 liquid crystal material; 
 color filter elements interposed between the liquid crystal material and the light blocking structures, wherein the color filter elements and the light blocking structures are formed in different layers; and 
 a backlight unit that emits backlight, wherein the emitted backlight travels through the color filter elements before travelling through the transparent substrate. 
 
     
     
       11. The electronic device defined in  claim 10 , wherein the emitted backlight travels through the liquid crystal material before travelling through the color filter elements. 
     
     
       12. The electronic device defined in  claim 10 , further comprising:
 a thin-film transistor that is interposed between the color filter elements and the light blocking structures. 
 
     
     
       13. The electronic device defined in  claim 10 , further comprising:
 a thin-film transistor layer that is interposed between the color filter elements and the liquid crystal material. 
 
     
     
       14. The electronic device defined in  claim 13 , wherein the emitted backlight travels through the thin-film transistor layer before travelling through the color filter elements. 
     
     
       15. The electronic device defined in  claim 10 , further comprising:
 additional light blocking structures that are formed between the transparent substrate and the liquid crystal material and that are at least partially overlapping with the light blocking structures formed on the transparent substrate.

Description:
This application claims the benefit of provisional patent application No. 61/935,734, filed Feb. 4, 2014, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays. 
     Electronic devices often include displays. For example, cellular telephones, computers, and televisions have displays. 
     A display such as a liquid crystal display has an active area filled with an array of display pixels. The active area is surrounded by an inactive border area. It may be desirable to minimize or eliminate the use of unsightly bezel structures in the inactive border area. In displays with small bezels or no bezels, there is a risk that backlight can leak through the inactive border area. If care is not taken, stray backlight will undesirably lighten the inactive area. 
     It would therefore be desirable to be able to provide improved light blocking structures in displays such as liquid crystal displays. 
     SUMMARY 
     An electronic device having a liquid crystal display (LCD) is provided. The liquid crystal display may include display pixel circuitry formed on a glass substrate. Light blocking structures such as black masking material may be patterned on the glass substrate to prevent stray light from propagating in undesired directions. 
     In one suitable arrangement, a planarization layer may be formed on the glass substrate over the light blocking structures. Thin film transistor structures such as thin-film transistors and associated pixel electrodes may be formed over the planarization layer. A color filter layer may be interposed between the thin-film transistors and the pixel electrodes (e.g., color filter elements may be integrated with the thin-film transistor structures). If desired, additional light blocking structures may be embedded with the color filter layer (e.g., additional light blocking structures may be formed directly on respective color filter elements). Liquid crystal material may be formed over the color filter layer. Formed in this way, at least the light blocking structures formed on the glass substrate and the planarization layer may be formed from high temperature resistant material (e.g., material that can withstand temperatures of at least 300° C. without degrading). 
     Display circuitry of this type may be assembled in a flipped orientation. Configured in the flipped orientation, a backlight unit in the LCD display may emit backlight that travels through the liquid crystal material, the color filter layer, the thin-film transistor structures, the planarization layer, and the glass substrate in that order to a user of the electronic device. 
     In another suitable arrangement, a color filter array may be formed directly on the glass substrate over the light blocking structures. A planarization layer may be formed on the color filter array. A thin-film transistor (TFT) layer may then be formed on the planarization layer. If desired, additional light blocking structures may be embedded within the thin-film transistor layer (e.g., additional black mask material may be formed directly on one or more dielectric layers directly above thin-film transistors in the TFT layer). Liquid crystal material may be formed over the thin-film transistor layer. Formed in this way, at least the light blocking structures formed on the glass substrate, the color filter array, and the planarization layer may be formed from high thermal resistant material (e.g., material that can withstand temperatures of at least 300° C. without degradation). 
     Display circuitry of this type may also be assembled in a flipped orientation. Configured in the flipped/inverted orientation, a backlight unit in the LCD display may emit backlight that travels through the liquid crystal material, the thin-film transistor layer, the planarization layer, the color filter array, and the glass substrate in that order to a user of the electronic device. 
     Further features of the present invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a laptop computer with a display in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a handheld electronic device with a display in accordance with an embodiment. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer with a display in accordance with an embodiment. 
         FIG. 4  is a perspective view of an illustrative electronic device such as a display for a computer or television with a display in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative display in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of a portion of an illustrative electronic device showing how an edge of a display in the device may be free of overlapping housing structures in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of display circuitry having color filter elements interposed between thin-film transistor structures and liquid crystal material in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of display circuitry having thin-film transistor structures interposed between liquid crystal material and color filter elements in accordance with an embodiment. 
         FIG. 9  is a more detailed view of the display circuitry of  FIG. 7  in accordance with an embodiment. 
         FIG. 10  is a more detailed view of the display circuitry of  FIG. 8  in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative electronic devices of the types that may be provided with displays are shown in  FIGS. 1, 2, 3, and 4 . 
     Electronic device  10  of  FIG. 1  has the shape of a laptop computer and has upper housing  12 A and lower housing  12 B with components such as keyboard  16  and touchpad  18 . Device  10  has hinge structures  20  (sometimes referred to as a clutch barrel) to allow upper housing  12 A to rotate in directions  22  about rotational axis  24  relative to lower housing  12 B. Display  14  is mounted in housing  12 A. Upper housing  12 A, which may sometimes be referred to as a display housing or lid, is placed in a closed position by rotating upper housing  12 A towards lower housing  12 B about rotational axis  24 . 
       FIG. 2  shows an illustrative configuration for electronic device  10  based on a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device  10 , housing  12  has opposing front and rear surfaces. Display  14  is mounted on a front face of housing  12 . Display  14  may have an exterior layer that includes openings for components such as button  26  and speaker port  28 . Device  10  may, if desired, be a compact device such as a wrist-mounted device or pendant device (as examples). 
     In the example of  FIG. 3 , electronic device  10  is a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  has opposing planar front and rear surfaces. Display  14  is mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  has an opening to accommodate button  26 . 
       FIG. 4  shows an illustrative configuration for electronic device  10  in which device  10  is a computer display, a computer that has an integrated computer display, or a television. Display  14  is mounted on a front face of housing  12 . With this type of arrangement, housing  12  for device  10  may be mounted on a wall or may have an optional structure such as support stand  30  to support device  10  on a flat surface such as a table or desk. 
     Display  14  may be a liquid crystal display or a display formed using other suitable display technologies. A cross-sectional side view of an illustrative configuration for display  14  of device  10  (e.g., a liquid crystal display for the devices of  FIG. 1 ,  FIG. 2 ,  FIG. 3 ,  FIG. 4  or other suitable electronic devices) is shown in  FIG. 5 . As shown in  FIG. 5 , display  14  may include backlight structures such as backlight unit  42  for producing backlight  44 . During operation, backlight  44  travels outwards (vertically upwards in dimension Z in the orientation of  FIG. 5 ) and passes through display pixel structures in display layers  46 . This illuminates any images that are being produced by the display pixels for viewing by a user. For example, backlight  44  may illuminate images on display layers  46  that are being viewed by viewer  48  in direction  50 . 
     Display layers  46  may be mounted in chassis structures such as a plastic chassis structure and/or a metal chassis structure to form a display module for mounting in housing  12  or display layers  46  may be mounted directly in housing  12  (e.g., by stacking display layers  46  into a recessed portion of housing  12 ). 
     Display layers  46  may include a liquid crystal layer such a liquid crystal layer  52 . Liquid crystal layer  52  may be sandwiched between display layers such as display layers  58  and  56 . Layers  56  and  58  may be interposed between lower (innermost) polarizer layer  60  and upper (outermost) polarizer layer  54 . 
     Layers  58  and  56  may be formed from transparent substrate layers such as clear layers of glass or plastic. Layers  56  and  58  may be layers such as a thin-film transistor layer and/or a color filter layer. Conductive traces, color filter elements, transistors, and other circuits and structures may be formed on the substrates of layers  58  and  56  (e.g., to form a thin-film transistor layer and/or a color filter layer). Touch sensor electrodes may also be incorporated into layers such as layers  58  and  56  and/or touch sensor electrodes may be formed on other substrates. 
     With one illustrative configuration, outer substrate layer  56  may be a thin-film transistor layer that includes an array of thin-film transistors and associated electrodes (display pixel electrodes) for applying electric fields to liquid crystal layer  52  and thereby displaying images on display  14 . Inner substrate layer  58  may be a color filter layer that includes an array of color filter elements for providing display  14  with the ability to display color images. 
     In another suitable arrangement, inner substrate layer  58  may be a thin-film transistor layer that includes an array of thin-film transistors and associated electrodes (display pixel electrodes) for applying electric fields to liquid crystal layer  52 , whereas outer substrate layer  56  may be a color filter layer that includes an array of color filter elements for providing display  14  with the ability to display color images. 
     Backlight structures  42  may include a light guide plate such as light guide plate  78 . Light guide plate  78  may be formed from a transparent material such as clear glass or plastic. During operation of backlight structures  42 , a light source such as light source  72  may generate light  74 . Light source  72  may be, for example, an array of light-emitting diodes. 
     Light  74  from light source  72  may be coupled into edge surface  76  of light guide plate  78  and may be distributed in dimensions X and Y throughout light guide plate  78  due to the principal of total internal reflection. Light guide plate  78  may include light-scattering features such as pits or bumps. The light-scattering features may be located on an upper surface and/or on an opposing lower surface of light guide plate  78 . 
     Light  74  that scatters upwards in direction Z from light guide plate  78  may serve as backlight  44  for display  14 . Light  74  that scatters downwards may be reflected back in the upwards direction by reflector  80 . Reflector  80  may be formed from a reflective material such as a layer of white plastic or other shiny materials. 
     To enhance backlight performance for backlight structures  42 , backlight structures  42  may include optical films  70 . Optical films  70  may include diffuser layers for helping to homogenize backlight  44  and thereby reduce hotspots, compensation films for enhancing off-axis viewing, and brightness enhancement films (also sometimes referred to as turning films) for collimating backlight  44 . Optical films  70  may overlap the other structures in backlight unit  42  such as light guide plate  78  and reflector  80 . For example, if light guide plate  78  has a rectangular footprint in the X-Y plane of  FIG. 5 , optical films  70  and reflector  80  may have a matching rectangular footprint. 
     Display  14  may have an array of display pixels (e.g., a rectangular array having rows and columns) for displaying images to a viewer. Vertical signal lines called data lines may be used to carry display data to respective columns of display pixels. Horizontal signal lines called gate lines may be used to carry gate line signals (sometimes referred to as gate control signals or gate signals) to respective rows of display pixels. The outline of the array of display pixels in display  14  defines an active area for display  14 . The active area may have a rectangular shape and may be surrounded by an inactive border region. An inactive border area may, for example, run along one edge, two edges, three edges, or all four edges of the active area. 
     A cross-sectional side view of an illustrative electronic device having a display such as display  14  of  FIG. 5  is shown in  FIG. 6 . As shown in  FIG. 6 , images may be displayed on central active area AA of display  14 . Inactive area IA may have a rectangular ring shape that runs around the rectangular periphery of active area AA. To avoid unsightly bezel structures in device  10 , it may be desirable to keep inactive area IA free of overlapping housing structures, bezels, or other potentially unattractive border structures. 
     To avoid light leakage in inactive area IA (e.g., to prevent stray light from escaping in the absence of a bezel or other overlapping structure), display  14  may be provided with border masking structures in inactive area IA. The border masking structures may help block stray backlight from backlight unit  42  and thereby ensure that border IA does not allow excess light to escape. Backlight from backlight unit  42  will therefore be confined to active area AA. 
     To provide satisfactory light blocking capabilities, light blocking structures can be formed in two parts (e.g., two layers). A first part of the light blocking structures may be formed from a black masking layer on the underside of thin-film transistor layer  56 . The black masking layer may be patterned to form a black mask. The black mask is a grid-shaped series of intersecting black lines that define a rectangular array of clear display pixel openings in the thin-film transistor layer. Each of the openings in the black mask is aligned with a respective color filter element in a corresponding array of color filter elements on color filter layer  58 . The grid-shaped black mask on the thin-film transistor layer may sometimes be referred to as a black matrix. A second part of the light blocking structures may be formed from opaque structures that are integrated with color filter layer  58 . The first and second parts of the light blocking structures may be at least partly overlapping to ensure that light emitted from each image pixel does not leak into undesired regions on the display (e.g., to ensure that the light associated with a given display pixel does not leak into an adjacent pixel location or into the inactive area). 
       FIG. 7  shows a cross-sectional side view of illustrative display circuitry  100  that can be formed as part of device  10 . As shown in  FIG. 7 , display circuitry  100  may include a first transparent substrate such as substrate  102 - 1 . Substrate  102 - 1  may be formed from a clear planar structure such as a sheet of transparent plastic, transparent glass, or other clear substrate layer. Black masking layer  106  may be patterned to form part of a black matrix in active area AA of the display and may be patterned to form part of a light-blocking black mask border in inactive area IA. 
     Black masking material  106  may be formed from a photoimageable material such as black photoresist. The black photoresist may be formed from a polymer such as polyimide. To withstand the elevated temperatures involved in subsequent thin-film transistor fabrication steps, the polymer that is used in forming black masking material  106  preferably can withstand elevated temperatures (e.g., temperatures of 350° C. or higher or other suitable elevated temperatures). Opaque filler materials such as carbon black and/or titanium black may be incorporated into the polyimide or other polymer of layer  106  so that layer  106  is opaque. 
     Planarization layer  104  is used to planarize black masking layer  106  so that thin-film transistor circuitry  106  can be formed over black masking layer  106  (e.g., so that thin-film transistors can overlap black mask  106 ). As an example, planarization layer  104  is formed from a black mask compatible material having a low dielectric constant such as a spin-on glass (SOG). For example, planarization layer  104  may be formed from a spin-on glass such as a silicon oxide based spin-on glass (e.g., a silicate spin-on glass). During thin-film transistor formation, the structures of  FIG. 7  may be subjected to elevated processing temperatures (e.g., temperatures of 350° C. or higher). Polyimide black mask layer  106  and spin-on glass planarization layer  104  are preferably able to withstand processing at these elevated temperatures (i.e., spin-on glass layer  104  will not experience diminished transparency and polyimide layer  106  will not degrade). 
     Thin-film transistor (TFT) structures  110  may be formed on planarization layer  104 . For example, one or more thin-film transistors and/or transistors associated with gate driver circuitry may be formed on planarization layer  104  as part of layer  110 . As described above, it may be desirable to form the thin-film transistors at locations overlapping with black masking layer  106 . In general, regions in layer  110  that are not overlapping with any black mask material  106  should be devoid of thin-film transistors. 
     An array of color filter elements  108  may be formed over the TFT structures  110 . Color filter elements  108  may include red color filter elements R, blue color filter elements B, and green color filter elements G. Color filter elements  108  may be formed from low-k colored photoimageable polymers. In other words, color filter elements  108  may be formed from organic material having a dielectric constant K less than that of silicon dioxide. The use of low-k color filter elements eliminates the need for an additional clear overcoat layer to be disposed directly on the thin-film transistors, which can help improve backlight transmittance. 
     Each color filter element  108  in the array of color filter elements may be laterally aligned with a respective opening in the array of openings in the black matrix formed from material  106  within the planarization layer  104  (e.g., each display pixel in the display may have a transparent opening, an associated display pixel electrode, and an associated aligned color filter element  108  through which backlight can pass). In the example of  FIG. 7 , black mask material  116  may also be embedded within the array of color filter elements  108 . Black mask material  116  may be at least partially aligned with black mask material  106 . 
     Color filter elements  108  formed in this way may be considered to be integrated with the thin-film transistor structures. Configured in this way, color filter elements  108  merely serve as one of the dielectric layers that are formed over the thin-film transistors. Other display pixel structures such as the pixel electrode, the common electrode, and other pixel interconnect routing structure can actually be formed over color filter elements  108 . Integrating the color filter elements with the formation of the thin-film transistors enables both the thin-film transistor structures and the color filter elements to be manufacturing at the same fabrication facility without the need for an additional color filter to TFT assembly process. Moreover, the required width of black mask material  116  can also be reduced, since the distance between materials  106  and  116  is minimized by forming the color filter elements directly on the thin-film transistors. 
     This arrangement in which the color filter elements are integrated with the thin-film transistor layer is sometimes referred to as the color-filter-on-array or “COA” configuration. The thin-film transistor structures  110  and the integrated color filter elements  108  may therefore sometimes be referred to collectively as a COA layer  112 . Still referring to  FIG. 7 , liquid crystal (LC) material  114  may be formed on COA layer  112 . A second transparent substrate such as substrate  102 - 2  (e.g., a sheet of transparent plastic, transparent glass, or other clear substrate layer) may be formed over the liquid crystal material  114 . 
     The orientation of circuitry  100  in  FIG. 7  is actually inverted for illustrative purposes. During operation of device  10 , the backlight travels in direction Z and passes through display pixel structures and color filter elements in circuitry  100 . From a users perspective (e.g.,  FIG. 5  a user  48  that looks at display  14  from the top), the COA layer is formed over the liquid crystal material  114  (i.e., the color filter elements  108  are formed over LC material  114 , whereas the thin-film transistors are formed over the color filter elements  108 ). Display circuitry  100  oriented in this way may sometimes be referred to as a flip-over display panel or a flipped TFT panel (sometimes abbreviated as FTP). 
     The example of  FIG. 7  in which the color filter elements are interposed between the liquid crystal material and the thin-film transistors is merely illustrative and does not serve to limit the scope of the present invention.  FIG. 8  shows another suitable arrangement in which the thin-film transistors are interposed between the liquid crystal material and the color filter elements. As shown in  FIG. 8 , display circuitry such as display circuitry  200  may include a first transparent substrate such as substrate  202 - 1 . Substrate  202 - 1  may be formed from a clear planar structure such as a sheet of transparent plastic, transparent glass, or other clear substrate layer. Black masking layer  206  may be patterned to form part of a black matrix in active area AA of the display and may be patterned to form part of a light-blocking black mask border in inactive area IA. 
     Black masking material  206  may be formed from a photoimageable material such as black photoresist (e.g., polyimide). To withstand the elevated temperatures involved in subsequent thin-film transistor fabrication steps, the polymer that is used in forming black masking material  206  preferably can withstand elevated temperatures (e.g., temperatures of 300° C. or higher or other suitable elevated temperatures). Opaque filler materials such as carbon black and/or titanium black may be incorporated into the polyimide or other polymer of layer  206  so that layer  206  is opaque. 
     In particular, an array of color filter elements  208  may be formed on substrate  202 - 1  over black masking material  206 . Color filter elements  208  may include red color filter elements R, blue color filter elements B, and green color filter elements G. Color filter elements  208  may be formed from colored photoimageable polymers. 
     Planarization layer  208  is used to planarize color filter elements  204  so that thin-film transistor circuitry  210  can be formed over color filter layer  204  (e.g., so that thin-film transistors can overlap black mask  206 ). As an example, planarization layer  204  is formed from a black mask compatible material having a low dielectric constant such as a spin-on glass (SOG). For example, planarization layer  204  may be formed from a spin-on glass such as a silicon oxide based spin-on glass (e.g., a silicate spin-on glass). During thin-film transistor formation, the structures of  FIG. 8  may be subjected to elevated processing temperatures (e.g., temperatures of 350° C. or higher). Polyimide black mask layer  206 , color filter elements  204 , and spin-on glass planarization layer  208  are preferably able to withstand processing at these elevated temperatures (i.e., spin-on glass layer  208  will not experience diminished transparency, and color filter elements  204  and polyimide layer  206  will not degrade). 
     Thin-film transistor (TFT) structures  210  may be formed on planarization layer  208 . For example, one or more thin-film transistors and/or transistors associated with gate driver circuitry may be formed on planarization layer  208  as part of layer  210 . As described above, it may be desirable to form the thin-film transistors at locations overlapping with black masking layer  206 . In general, regions in layer  210  that are not overlapping with any black mask material  206  should be devoid of thin-film transistors and should be laterally aligned with a respective opening in the array of openings in the black matrix formed from material  206  and with each respective color filter element  204 . 
     In the example of  FIG. 8 , black mask material  212  may also be embedded within the TFT layer  210 . Black mask material  212  may be at least partially aligned with black mask material  206 . The required width of black mask material  212  can be minimized by reducing the distance between materials  206  and  212  (e.g., by forming the black mask material  212  on dielectric layers relatively close to the thin-film transistors). 
     Forming display circuitry  200  in this way allows the thin-film transistor layer and the color filter array to be manufacturing at the same fabrication facility without the need for an additional color filter to TFT assembly process. This arrangement in which the thin-film transistor layer is formed on the color filter layer is sometimes referred to as the array-on-color-filter or “AOC” configuration. Still referring to  FIG. 8 , liquid crystal (LC) material  214  may be formed on TFT layer  210 . A second transparent substrate such as substrate  202 - 2  (e.g., a sheet of transparent plastic, transparent glass, or other clear substrate layer) may be formed over the liquid crystal material  214 . 
     The orientation of circuitry  200  in  FIG. 8  is actually flipped for illustrative purposes. During operation of device  10 , the backlight travels in direction Z and passes through display pixel structures and color filter elements in circuitry  200 . From a users perspective (e.g.,  FIG. 5  a user  48  that looks at display  14  from the top), the color filter elements  204  are formed over the thin-film transistors, whereas the thin-film transistors are formed over the LC material  214 . Display circuitry  200  oriented in this way may also be considered an FTP display. 
       FIG. 9  shows a more detailed cross-sectional side view of display circuitry  100  described in connection with  FIG. 7 . As shown in  FIG. 9 , display circuitry  100  may include a transparent thin-film transistor substrate such as substrate  300  (similar to substrate  102 - 1  of  FIG. 7 ). Substrate  300  may be formed from a clear planar structure such as a sheet of transparent plastic, transparent glass, or other clear substrate layer. Black masking layer  302  may be patterned to form a black matrix in active area AA of display  14  and may be patterned to form part of a light-blocking black mask border in inactive area IA. 
     As shown in  FIG. 9 , black masking layer  302  may be patterned to form display pixel openings such as opening  304  that are aligned with patterned display pixel electrodes  310 . Electrodes  310  may be separated from common electrode (Vcom) trace  312  by dielectric layer  314 . Color filter element material  350  may be formed on top of thin-film transistor  324  from a photoimageable polymer or other dielectric (e.g., a color filter layer may be interposed between thin-film transistor  324  and associated electrodes  310 ). Additional black masking material  352  (similar to BM material  116  in  FIG. 7 ) may be formed on top of color filter layer  350  directly over transistor  324 . 
     Patterned metal  318  may be used to form transistor terminals such as source S, drain D, and gate G. Gate insulator  320  may be formed from dielectric materials such as silicon nitride and/or silicon oxide and may separate gate G from semiconductor region  322 . Semiconductor region  322 , which is used in forming the channel region for thin-film transistor  324 , may be formed from semiconductor materials such as amorphous silicon, polysilicon, indium gallium zinc oxide, or other semiconductors. Passivation layer  326  may be formed on top of gate insulator  320 . 
     As described above in connection with  FIG. 7 , black masking material  302  may be formed from a photoimageable material such as black photoresist (e.g., polyimide). Planarization layer  306  (e.g., a spin-on glass layer) may be used to planarize black masking layer  302 . During thin-film transistor formation, the structures of  FIG. 9  may be subjected to elevated processing temperatures (e.g., temperatures of 350° C. or higher). Polyimide black mask layer  302  and spin-on glass planarization layer  306  are preferably able to withstand processing at these elevated temperatures (i.e., spin-on glass layer  306  will not experience diminished transparency and polyimide layer  302  will not degrade). 
     In some embodiments, a buffer layer such as inorganic buffer layer  307  may be formed at the interface between planarization layer  306  and TFT layer  308 . Buffer layer  307  may be a thin layer of silicon nitride, silicon oxide, and/or other inorganic materials having a thickness of 250-3000 angstroms (as an example). Formed in this way, inorganic buffer layer  307  may serve to prevent chemicals such as etching solution from being injected into spin-on glass planarization layer  306  during formation of the TFT circuitry in layer  308 . 
       FIG. 10  shows a more detailed cross-sectional side view of display circuitry  200  described in connection with  FIG. 8 . As shown in  FIG. 10 , display circuitry  200  may include a transparent thin-film transistor substrate such as substrate  400  (similar to substrate  102 - 1  of  FIG. 8 ). Substrate  400  may be formed from a clear planar structure such as a sheet of transparent plastic, transparent glass, or other clear substrate layer. Black masking layer  402  may be patterned to form a black matrix in active area AA of display  14  and may be patterned to form part of a light-blocking black mask border in inactive area IA. 
     As shown in  FIG. 10 , black masking layer  402  may be patterned to form display pixel openings such as opening  404  that are aligned with patterned display pixel electrodes  410 . Electrodes  410  may be separated from common electrode (Vcom) trace  412  by dielectric layer  414 . Dielectric material  416  may be formed on top of thin-film transistor  424  from a photoimageable polymer or other dielectric. Additional black masking material  452  (similar to BM material  212  in  FIG. 8 ) may be formed on top of dielectric material  416  directly over transistor  424 . 
     Patterned metal  418  may be used to form transistor terminals such as source S, drain D, and gate G. Gate insulator  420  may be formed from dielectric materials such as silicon nitride and/or silicon oxide and may separate gate G from semiconductor region  422 . Semiconductor region  422 , which is used in forming the channel region for thin-film transistor  424 , may be formed from semiconductor materials such as amorphous silicon, polysilicon, indium gallium zinc oxide, or other semiconductors. Passivation layer  426  may be formed on top of gate insulator  420 . 
     As described above in connection with  FIG. 8 , black masking material  402  may be formed from a photoimageable material such as black photoresist (e.g., polyimide). Color filter material  450  (e.g., a first color filter element  450 - 1  of a first color, a second color filter element of a second color that is different than the first color, etc.) may be formed over black masking material  402 . Planarization layer  406  (e.g., a spin-on glass layer) may be used to planarize color filter layer  450 . In other words, the color filter layer may be interposed between the TFT layer and light blocking structures  402 . 
     During thin-film transistor formation, the structures of  FIG. 10  may be subjected to elevated processing temperatures (e.g., temperatures of 350° C. or higher). Polyimide black mask layer  402 , color filter array  450 , and spin-on glass planarization layer  406  are preferably high thermal resistant material that is able to withstand processing at these elevated temperatures. 
     In some embodiments, a buffer layer such as inorganic buffer layer  407  may be formed at the interface between planarization layer  406  and TFT layer  408 . Buffer layer  407  may be a thin layer of silicon nitride, silicon oxide, and/or other inorganic materials having a thickness of 250-3000 angstroms (as an example). Formed in this way, inorganic buffer layer  407  may serve to prevent chemicals such as etching solution from being injected into spin-on glass planarization layer  406  during formation of the TFT circuitry in layer  408 . 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20140919
Publication Date: 20180508
Grant Date: 20180508
Priority Date: 20140204
Inventors: YANG, BYUNG DUK
KIM, KYUNG-WOOK
CHANG, SHIH-CHANG
OSAWA, HIROSHI
ZHONG, JOHN Z.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/136209", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F2001/136222", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F2001/133357", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/136209", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/136222", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/136209", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/136222", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133357", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133357", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 53754735