Patent Application
20160170247
This relates generally to electronic devices with displays, and, more particularly, to processing edges in displays to enhance display strength.
Electronic devices often include displays. A display may have glass substrates. For example, a liquid crystal display may have a glass color filter layer substrate and a glass thin-film transistor layer substrate. During manufacturing, the edges of a glass substrate may be ground using a grinding tool. The grinding tool may create microcracks along the edges of the display that can weaken the display. To strengthen the display, it may be desirable to remove the microcracks. If care is not taken, however, liquids that are used during microcrack removal may penetrate the edges of the display and cause damage to metal traces and other display structures.
It would therefore be desirable to be able to provide improved methods of forming displays with ground edges for use in electronic devices.
An electronic device may have a display. The display may have an upper layer such as a color filter layer and a lower layer such as a thin-film transistor layer. A liquid crystal layer may be interposed between the upper and lower layers. A ring of adhesive sealant may surround the liquid crystal layer to retain the liquid crystal layer between the upper and lower layers. Columns spacers may extend between the upper and lower layers through the liquid crystal layer to help ensure that the upper and lower layers are separated from each other by a desired distance.
A ring-shaped polymer spacer may surround the ring of adhesive sealant. The spacer may form a seal with the color filter layer and thin-film transistor layer when compressed between the color filter layer and the thin-film transistor layer. The presence of the spacer may help prevent etchant or other materials form entering the edge of the display. The etchant may be used to smooth peripheral edges of glass layers in the display to help minimize grinding microcracks that might otherwise weaken the display.
The spacer may be formed from the same layer of material that forms the column spacers. For example, the column spacers and the ring-shaped spacer may be formed from a photoimageable polymer such as photoimageable acrylic and may be patterned using photolithography.
A black masking layer may be formed on the underside of the color filter layer using techniques that prevent the formation of unsightly protruding black masking layer portions. The black masking layer may be formed from a photoimageable polymer. If desired, an edge portion of the masking layer may be formed from metal. The metal may have a ring shape that runs along the edges of the display. Dielectric may be interposed between the metal and a layer of black masking polymer to prevent electrostatic charge from disrupting display operation.
During processing, a portion of a color filter layer may be retained on a display panel to protect metal traces in a thin-film transistor ledge region of the thin-film transistor layer during acid etching of the display edges. Following etching, the portion of the color filter layer in the ledge region may be removed from the display panel using techniques such as scribing and breaking techniques.
An illustrative electronic device of the type that may be provided with a display is shown in
Input-output circuitry in device 10 such as input-output devices 12 may be used to allow data to be supplied to device 10 and to allow data to be provided from device 10 to external devices. Input-output devices 12 may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device 10 by supplying commands through input-output devices 12 and may receive status information and other output from device 10 using the output resources of input-output devices 12.
Input-output devices 12 may include one or more displays such as display 14. Display 14 may be a touch screen display that includes a touch sensor for gathering touch input from a user or display 14 may be insensitive to touch. A touch sensor for display 14 may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements.
Control circuitry 16 may be used to run software on device 10 such as operating system code and applications. During operation of device 10, the software running on control circuitry 16 may display images on display 14.
Device 10 may be a tablet computer, laptop computer, a desktop computer, a television, a cellular telephone, a media player, a wristwatch device or other wearable electronic equipment, or other suitable electronic device.
Display 14 may be a liquid crystal display, an organic light-emitting diode display, an electrophoretic display, an electrowetting display, or any other suitable type of display. Configurations in which display 14 is a liquid crystal display are sometimes described herein as an example. This is, however, merely illustrative. Any suitable type of display may be used, if desired.
Display 14 may have a rectangular shape (i.e., display 14 may have a rectangular footprint and a rectangular peripheral edge that runs around the rectangular footprint) or may have other suitable shapes. A cross-sectional side view of an illustrative liquid crystal display is shown in
During operation of display 14, backlight unit 20 may produce backlight illumination 22. Backlight 22 travels through display layers 24 to illuminate images that are being produced by layers 24 for a viewer such as viewer 26 who is viewing display 14 in direction 28. Display layers 24 may include lower polarizer 34 and upper polarizer 36. Substrate layers 30 and 32 and liquid crystal layer 48 may be sandwiched between lower polarizer 34 and upper polarizer 36. A peripheral ring of sealant such as sealant 46 may be used to retain liquid crystal material 48 within display 14. Sealant 46 may be formed from an adhesive such as epoxy or other suitable material.
Display layers 24 may contain color filter elements that allow display 14 to display color images for viewer 26. Thin-film transistor circuitry may be used to control how electric fields are applied to pixels of liquid crystal material in the display. The thin-film transistor circuitry may have an array of electrodes associated with an array of respective pixel circuits for the pixels of display 14. The thin-film transistor circuitry and color filter elements may be provided on a single substrate layer or on separate substrate layers. With one suitable arrangement, which is sometimes described herein is an example, upper substrate layer 32 is a color filter layer and lower substrate layer 30 is a thin film transistor layer. Other configurations may be used for display 14 if desired.
Color filter layer 32 may include glass substrate 38. Color filter element layer 40 may include color filter elements 44. Color filter elements 44 may include red color filter elements, green color filter elements, and blue color filter elements or may include color filter elements of other colors. Color filter element layer 40 may also include opaque masking material such as black masking material 42. Display 14 may have a central active region which black masking layer 42 is patterned to form a black matrix. The black matrix may have a grid shape with openings that receive respective color filter elements. Display 14 may also have a peripheral rectangular-ring-shaped inactive region in which black masking layer 42 forms an opaque border for display 14. Thin-film transistor layer 30 may include glass substrate 52.
If desired, display 14 may have a thin-film transistor ledge region such as region 54 of
As shown in the cross-sectional side view of display 14 in
The glass substrate layers of display 14 may be formed from large motherglass panels. During manufacturing, scribing and breaking techniques, laser-based cutting techniques, or other cutting techniques may be used to divide the motherglass panels into smaller individual display panels. Grinding techniques may be used to smooth and to impart a desired edge profile to the scribed-and-broken display edges. The scribing and breaking process and the edge grinding process may create small cracks along the edge of the glass layers. These cracks, which may sometimes be referred to as microcracks, may weaken the glass substrate layers of display 14. Chemical and/or mechanical polishing techniques may be used to remove or at least blunt the microcracks so that the display is strengthened sufficiently to withstand impacts during drop events and other stresses during use for device 10. For example, the edges of the display may be exposed to a glass etchant such as hydrofluoric acid (HF).
There is potential for damage to exposed metal traces and other structures around the edge of a display if these structures are exposed to an acid such as HF. To prevent damage from HF exposure, display 14 may be provided with a peripheral ring-shaped spacer structure that surrounds ring-shaped sealing structure 46.
An illustrative configuration for display 14 in which display 14 has been provided with a spacer is shown in
Thin-film transistor layer 30 may have coating layers such as inorganic buffer layer 70 and passivation layer 72. Buffer layer 70 may be a layer of inorganic material such as silicon nitride. Passivation layer 72 may be formed from an organic layer of material such as a layer of acrylic or other polymer.
The upper surface of color filter layer 32 may be coated with an electrostatic discharge protection layer such as indium tin oxide layer 68. The lower surface of color filter layer 32 may be coated with an opaque masking material such as black masking layer 42. Layer 42 may be coated with acrylic overcoat layer 74. Black masking layer 42 may be formed from an opaque photoimageable polymer such as a polymer containing a black material such as carbon black.
To ensure that an appropriate distance is maintained between color filter layer 32 and thin-film transistor layer 30, display 14 may be provided with column spacers such as column spacer 80. Column spacers 80 may be patterned from a layer of photoimageable polymer such as a layer of photoimageable acrylic. An array of column spacers 80 may pass through liquid crystal layer 48 and may help separate layers 30 and 32 from each other.
Spacer 78 may be formed from the same layer of material that is used to form column spacers 80. Spacer 78 may have the shape of a rectangular ring that runs around the edge of display 14 between layers 32 and 30. Sealant 46 is preferably an adhesive and forms adhesive bonds between layers 30 and 32. In contrast, spacer 78 need not be an adhesive material. Rather, spacer 78 may be patterned on layer 32 using photolithography and may form a seal with layer 30 due to compressive force between layers 30 and 32. The presence of spacer 78 helps prevent HF and other corrosive processing liquids from intruding into the edge region of display 14 while the HF is being used to etch the glass layers display 14 and thereby remove microcracks from the edge of display 14. In particular, spacer 78 prevents HF and other liquids from reaching edge region 66 of display 14 and sealant 46. This helps protect traces and other structures on the surfaces of the layers of display 14 in region 66 from damage. Column spacers 80 and peripheral spacer 78 may be patterned simultaneously using photolithographic processing techniques. As a result, no additional processing steps are needed to create spacer 78. Because photolithographic processing techniques are used, spacer 78 may be accurately positioned along the edge of display 14. In a rectangular display, seal 46 and spacer 78 may have concentric rectangular ring shapes.
At step 82, a thin-film transistor motherglass layer may be formed. The thin-film transistor motherglass may contain sufficient thin-film transistor circuitry to form multiple displays. The thin film transistor circuitry may include polysilicon thin-film transistors, semiconducting-oxide thin-film transistors, metal traces, dielectric layers, buffer layers, passivation layers, and other thin film transistor circuit structures.
At step 84, a color filter layer motherglass layer may be formed. The color filter motherglass may contain color filter elements 44, black masking material 42, and other color filter layer structures such as acrylic overcoat layer 74. As part of the process of forming the color filter layer motherglass, photolithographic processing techniques may be used to simultaneously form column spacers 80 and peripheral spacers 78.
At step 86, a ring of sealant 46 may be dispensed around each panel location within the motherglass and liquid crystal material 48 may be dispensed within each ring of sealant 46. The thin-film transistor motherglass and the color filter motherglass may then be pressed together. Sealant 46 may be cured (e.g., by exposure to ultraviolet light, etc.).
At step 88, scribing and breaking techniques and/or laser cutting techniques or other cutting techniques may be used to singulate the motherglass into individual display panels. During singulation, the portion of color filter layer 32 in ledge region 54 in each panel may be retained. This portion of color filter layer 32 will cover metal traces 56 on thin-film transistor layer 30 during subsequent processing in HF or other processing substances. Because this portion of color filter layer 32 is present, traces 56 on ledge 54 may be protected without using additional masking materials.
At step 90, a grinding tool may be used to grind edges of each display panel. The grinding tool may use a curved bit so that the edges of the display have a rounded appearance or bits of other shapes may be used to smooth the edges of the display. The display may have glass substrate layers (e.g., the color filter layer and/or the thin-film transistor layer may be formed from glass substrates) or substrate materials of other types may be used. If desired, features such as opening 58 of
The grinding processes of steps 90 and 92 create microcracks along the edges of the display glass layers such as color filter layer 32 and create microcracks within opening 58. The presence of microcracks may weaken display 14. Accordingly, at step 94, HF etching or other chemical or mechanical smoothing techniques may be used to remove or modify the microcracks to strength display 14. Because a portion of color filter layer 32 is present in ledge region 54, traces 56 are not exposed to HF or other potentially corrosive materials during the processing operations of step 94. Electrostatic discharge protection layer 68 is preferably not present during the processing of step 94 so that the indium tin oxide or other material used to form layer 68 is not exposed to HF. The presence of spacer 78 ensures that HF will not penetrate into region 66 and thereby ensures that display structures in region 66 will not be damaged during microcrack removal.
Following processing at step 94, color filter layer 32 may be coated with electrostatic discharge protection layer 68 (step 96). For example, a layer of indium tin oxide may be deposited as a coating on top of color filter layer 32. The electrostatic discharge protection layer helps dissipate static charge that might otherwise build up on the surface of display 14 during use.
At step 98, laser cutting techniques, scribing and breaking techniques, or other techniques may be use to remove the portion of color filter layer 32 in thin-film transistor ledge region 54. This exposes traces 56 in thin-film transistor ledge region 54 and allows display 14 to be electrically coupled to other components in device 10.
There is a potential for the coating layers on color filter layer 32 in display 14 to protrude from the edge of display 14 following chemical etching of the glass substrates with HF. For example, HF may not remove black masking layer 42 and acrylic overcoat layer 74 along the edge of color filter layer 32 while the HF is etching away the glass substrate of color filter layer 32. Unsightly coating protrusions can be avoided by patterning the coating layers so that the coating layers do not extend all the way to the edge of color filter layer substrate 32 before HF exposure. Consider, as an example, the illustrative configuration of display 14 in
Layers 42 and 74 may be formed from a photoimageable polymer that allows layers 42 and 74 to be patterned using photolithography. For example, overcoat layer 74 may be formed from a photoimageable acrylic material. The size of gap G may be 20 μm or any other suitable size (i.e., an amount equal to the expected amount of glass to be removed from layer 32 during HF etching). Following exposure to HF (e.g., during step 94 of
In the illustrative configuration
To prevent electrostatic charge from disrupting operation of display 14, it may be desirable to place an intervening dielectric layer between metal layer 102 and black masking layer 42. For example, dielectric layer 104 may overlap metal layer 102 and black masking layer 42 may be formed from a black polymer layer that overlaps dielectric layer 104 without contacting metal layer 102. With this type of configuration, electrostatic charge that is deposited on layer 102 (e.g., due to contact with a user's finger or other source of static electricity), will not be conducted from metal layer 102 to black masking layer 42 and will therefore not disrupt electric fields within liquid crystal layer 48.
Dielectric layer 104 may be formed from an inorganic dielectric such as silicon nitride, silicon oxide, or silicon oxynitride, or may be formed from other dielectric material. To prevent portions of metal layer 120 from protruding out from under color filter layer 32 following etching at step 94 (
Another illustrative arrangement for preventing portions of the opaque masking layer from protruding out from under the edge of the glass of color filter 32 is shown in
In the configuration of
If desired, spacer 78 may be incorporated into displays of the type shown in
The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.
This application claims priority to U.S. provisional patent application No. 62/091,278 filed Dec. 12, 2014, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62091278 | Dec 2014 | US |
