Patent Application
20140098332
This relates generally to electronic devices, and more particularly, to electronic devices with displays.
Electronic devices often include displays. For example, cellular telephones and portable computers often include displays for presenting information to a user.
It can be challenging to form displays for electronic devices. Displays such as liquid crystal displays typically include color filter layers for allowing the displays to display color images. Arrays of color filter element are formed on color filter layer substrates. If care is not taken, layers of material in a display such as the layers on a color filter layer substrate may be improperly aligned, may be overly complex to fabricate, or may exhibit performance shortcomings.
It would therefore be desirable to be able to provide improved displays for electronic devices.
An electronic device may be provided with a display mounted within a housing. The display may include a color filter layer, a liquid crystal layer, and a thin-film transistor layer. Other display layers such as layers associated with backlight structures may also be included in the display.
The color filter layer may form the outermost layer of the display. A color filter layer substrate in the color filter layer may have opposing inner and outer surfaces. The outer surface may be viewed by a user of the electronic device. The inner surface may face the liquid crystal layer.
A layer of patterned metal on the inner surface of the color filter layer may be used in forming metal alignment marks. The metal alignment marks may be used to ensure alignment between layers of material that are patterned on the inner surface and the color filter layer substrate.
The metal alignment marks may include alignment marks for color filter elements, alignment marks for a black matrix layer that is formed on top of the color filter elements, and post spacer alignment marks.
The layer of patterned metal may also form structures such as logo structures that are visible on the outer surface in an inactive border region of the display.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.
Electronic devices may include displays. The displays may be used to display images to a user. Illustrative electronic devices that may be provided with displays are shown in
The illustrative configurations for device 10 that are shown in
Housing 12 of device 10, which is sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device 10 may be formed using a unibody construction in which most or all of housing 12 is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures).
Display 14 may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors for display 14 may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components.
Display 14 for device 10 includes display pixels formed from liquid crystal display (LCD) components or other suitable image pixel structures.
A display cover layer may cover the surface of display 14 or a display layer such as a color filter layer or other portion of a display may be used as the outermost (or nearly outermost) layer in display 14. The outermost display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member.
A cross-sectional side view of an illustrative configuration for display 14 of device 10 (e.g., for display 14 of the devices of
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 in housing 12). Display layers 46 may form a liquid crystal display or may be used in forming displays of other types.
In a configuration in which display layers 46 are used in forming a liquid crystal display, 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 polarizer layer 60 and upper 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, 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 and thereby displaying images on display 14. 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. If desired, layer 58 may be a color filter layer and layer 56 may be a thin-film transistor layer.
During operation of display 14 in device 10, control circuitry (e.g., one or more integrated circuits on a printed circuit) may be used to generate information to be displayed on display 14 (e.g., display data). The information to be displayed may be conveyed to a display driver integrated circuit such as circuit 62A or 62B using a signal path such as a signal path formed from conductive metal traces in a rigid or flexible printed circuit such as printed circuit 64 (as an example).
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
As shown in
Logo structures such as illustrative logo 100 of
Structures such as logo 100 may be formed (in reverse) on the inner surface of a layer in display 14 such as color filter layer 56. A cross-sectional side view of a portion of display 14 showing how color filter layer 56 may include a substrate layer covered with color filter elements is shown in
Color filter layer 56 may have a substrate layer such as substrate 104. Substrate 104 may be formed from a sheet of glass, plastic, or other transparent dielectric. Substrate 104 may have an outer surface such as surface 116 facing viewer 48 and an inner surface such as surface 118. An array of color filter elements 106 may be formed on inner surface 118 (e.g., in a rectangular array shape having rows and columns associated with respective rows and columns of display pixels 102). Color filter elements 106 may include, for example, red color filter elements R, green color filter elements G, and blue color filter elements B. The array of color filter elements in color filter layer 56 may be used to provide display 14 with the ability to display color images.
Opaque masking material 108 may be formed on top of color filter elements 106. Opaque masking material 108 may be formed from a dark substance such as a polymer that contains a black pigment and may therefore sometimes be referred to as a black mask, black masking layer, black pigmented layer, or black masking material. Illustrative polymeric materials for forming black masking layer 108 include acrylic-based and polyimide-based photoresists. An illustrative black pigment that may be used for black masking layer 108 is amorphous carbon (carbon black).
Black mask 108 may be patterned to form a grid of relatively thin lines (sometimes referred to as a black matrix) on top of color filter elements 108 in active area AA. The black matrix may have an array of rectangular openings bordered by the thin lines. The openings in the black matrix may overlap respective color filter elements 106 to help optically delineate the separation between adjacent color filter elements and thereby reduce color bleeding effects. Portions of color filter elements 106 that are aligned with display pixels 102 (
Placing opaque masking material 108 above the layer of color filter element on substrate 104 as shown in
To ensure that photolithographic processing operations are performed satisfactorily when patterning the structures of color filter layer 56, alignment marks may be formed on surface 118.
In inactive region IA, black masking material such as the material of structures 108 in
Display 14 may include layers on outer surface 116 of substrate 104 or on a display cover layer. These layers, which may sometimes be referred to as coatings, may include layers such as polarization structures, layers for reducing fingerprints (e.g., a smudge-resistant coating in a touch-sensitive display), anti-scratch coatings, antireflection coatings, one or more shielding layers for reducing the impact of static electricity such as an indium tin oxide electrostatic discharge protection layer, or other layers of material.
Layers of material such as color filter material (e.g., red color filter material, green color filter material, and blue color filter material) may be deposited on inner surface 118 of color filter layer substrate 104. Black masking material 108 may be deposited on color filter elements 106. Color filter material and black masking material may be deposited by screen printing, spin-on coating, spray coating, physical vapor deposition, chemical vapor deposition, or other suitable deposition techniques. Photosensitive materials may be used for elements 106 and structures 108. Photolithographic patterning techniques may be used in patterning photosensitive layers.
Color filter elements 106 of each color (e.g., red R, green G, and blue G) may be formed by depositing color filter material of that color on inner surface 118 (and over any previously deposited and/or patterned materials) and by etching or otherwise patterning (e.g., using photolithographic equipment) the color filter material of that color to form the color filter elements. Photolithographic patterning may also be used in forming black mask 108. Following formation of elements 106 and black mask 108, overcoat layer 110 may be formed. Overcoat layer 110 may be formed from a clear polymer such as acrylic. Layer 110 may be used as a blocking layer to prevent impurities from color filter elements 106 from reaching liquid crystal layer 52. Layer 110 may also serve as a planarization layer.
Post spacer structures such as post spacers 114 may be patterned onto the surface of layer 110 (e.g., using photolithography). Post spacers 114 may be formed from a material such as metal and may be used to establish desired size for gap G between thin-film transistor layer 58 and color filter layer 56. A roller printed liquid crystal alignment layer of polyimide or other suitable material such as layer 112 may be formed on top of post spacers 114 and overcoat 110. When assembled to form display 14 as shown in
A view of color filter layer 56 from the interior of display 14 is shown in
Alignment structures such as alignment marks 120 may be formed from metal or other suitable material. As an example, alignment mark structures 120 and structures such as logo 100 may be formed as different portions of the same patterned layer of metal. The patterned layer of metal may be a layer of chromium, a multilayer stack formed from a layer of aluminum capped with a layer of molybdenum, a multilayer stack formed from a layer of aluminum capped with a layer of titanium, a layer of molybdenum, a layer of titanium, a layer of copper, a layer of aluminum coated with optional clear protective dielectric coatings such as silicon dioxide or silicon nitride coatings, a layer of copper, or other metal. When fabricating displays such as display 14 from a common large panel, it may be desirable to divide the panel into smaller displays using scribe-and-break techniques. A scribing tool may be used to form scribe lines in a layer of display glass. Color filter layers such as color filer layer 56 can then be separated from the larger display panel by breaking the panel along the scribe lines. Alignment marks 120 may be formed inside or outside of the rectangular color filter layer area formed by the scribe lines.
By forming alignment structures 120 from a shiny material such as metal, structures 120 may be visible during manufacturing, even when covered by dark layers of material such as the layer of material used in forming black mask 108 or other layers of material that are not highly transparent. To ensure that the layers of material that are deposited on substrate 104 during fabrication of color filter layer 56 do not interfere with the alignment marks, alignment marks 120 may include separate sets of alignment marks for each of the layers of colored or opaque material in
For example, a set of five alignment marks may be included in each cluster of marks 120. The set of alignment marks may include red-layer metal alignment marks 120R for aligning a red-layer photolithographic mask with respect to substrate 104 when patterning red color filter elements 106, green-layer metal alignment marks 120G for aligning a green-layer photolithographic mask with respect to substrate 104 when patterning green color filter elements 106, blue-layer metal alignment marks 120B for aligning a blue-layer photolithographic mask with respect to substrate 104 when patterning blue color filter elements 106, black-mask-layer metal alignment marks 120BM for aligning a black-mask-layer photolithographic mask with respect to substrate 104 when patterning black mask 108, and post-spacer-layer metal alignment marks 120PS for aligning a post-spacer-layer photolithographic mask with respect to substrate 104 when patterning post spacers 114.
In the example of
Photolithographic mask 130 has corresponding alignment marks such as alignment mark 122 on mask substrate 124. During mask alignment operations, a mask aligner or other equipment may be used to adjust the position of mask 130 laterally (i.e., in directions 136) so that alignment mark 122 is centered with respect to alignment mark 120R of
Alignment marks such as mark 122 of
Following exposure through the photolithographic mask (and associated alignment marks 122 of
Subsequent layers of material may be patterned on substrate 104 using additional masks, as described further in connection with
Red, green, and blue color filter elements can be formed using marks 120R, 120G, and 120B. Initially, a layer of red photoresist (color filter material) may be patterned on substrate 104 using alignment marks 120R, thereby forming an array of red color filter elements 106R in alignment with substrate 104, as shown in
After forming red color filter elements 106R, an array of green color filter elements 106G may be formed in alignment with substrate 104 and therefore in alignment with red color filter elements 106R, as shown in
After forming red color filter elements 106R and green color filter elements 106G, an array of blue color filter elements 106B may be formed in alignment with substrate 104 and therefore in alignment with red color filter elements 106R and green color filter elements 106G, as shown in
Once an array of red, blue, and green color filter elements 106 has been formed, black mask 108 (i.e., a grid-shaped black matrix) may be formed on color elements 106 using metal alignment mark structures 120BM for alignment. Black mask material 132BM may cover alignment structures 120BM during the alignment process and after patterning, as shown in
After patterning black mask 108 on color filter elements 106, post spacer alignment mark structures 120PS can be used to fabricate post spacer structures 114 in alignment with substrate 104, color filter elements 106, and black mask 108, as shown in
Illustrative steps involved in forming device 10 and display 14 with logo structures or other metal structures 100 and metal alignment structures 120 of the type shown in
At step 200, a blank color filter substrate such as substrate 104 may be provided with alignment marks 120 and structures 100. Substrate 104 may be, for example, a layer of clear glass, a transparent plastic layer, or other transparent substrate. Alignment marks 120 may be formed along one or more of the edges of substrate 104. Alignment marks 120 may include individual alignment marks for each of the respective layers of
Alignment marks 120 and structures 100 may be formed from a material such as metal. Metal alignment marks exhibit satisfactory visibility through dark material layers such as black mask photoresist during fabrication. Metal is also sufficiently shiny to create readily visible logos or other structures 100. During step 200, alignment marks 120 and structures 100 are preferably formed using the same metal patterning operations. For example, a blanket metal layer for both alignment marks 120 and structures 100 may be deposited using physical vapor deposition equipment or other suitable metal deposition equipment. The metal layer may then be patterned to form alignment marks 120 and structures 100 using a common layer of photoresist, a common photolithographic mask, and common development and etching operations. By forming alignment marks 120 and structures 100 from a common layer of metal, the number of masks and fabrication operations used in forming display 14 may be minimized.
After forming alignment marks 120 and structures 100 on substrate 104, additional processing steps may be used to form color filter elements 106 (step 202). During the operations of step 202, alignment marks such as red-layer alignment marks 120R, green-layer alignment marks 120G, and blue-layer alignment marks 120B may be used in forming an array of color filter elements on substrate 106.
At step 204, black mask 108 may be deposited and patterned on top of the array of color filter elements. In forming the black mask layer, alignment marks 120BS may be used to ensure that the grid lines in the black matrix pattern are aligned with respect to substrate 104 and the color filter elements. Portions of black mask 108 may cover inactive border region IA (
Once the black matrix has been formed over the color filter elements, the operations of step 206 may be performed to form overcoat 110, post spacers 114, and layer 112. Color filter layer 56 may then be assembled with liquid crystal layer 52 and thin-film transistor layer 58 and the other display layers of display 14 (
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.
