Patent Publication Number: US-2021166895-A1

Title: Keycaps having reduced thickness

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/283,148, filed Feb. 22, 2019, and titled “Keycaps Having Reduced Thickness,” which is a continuation of U.S. patent application Ser. No. 15/640,249, filed Jun. 30, 2017, now U.S. Pat. No. 10,224,157, issued Mar. 5, 2019 and titled “Keycaps Having Reduced Thickness,” which is a continuation of U.S. patent application Ser. No. 14/502,788, filed Sep. 30, 2014, now U.S. Pat. No. 9,704,670, issued Jul. 11, 2017 and titled “Keycaps Having Reduced Thickness,” which is a non-provisional of and claims the benefit to U.S. Provisional Patent Application No. 61/884,259, filed Sep. 30, 2013 and titled “Keycaps Having Reduced Thickness,” the disclosures of which are hereby incorporated by reference herein in their entireties. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to input apparatuses for computing devices or other similar information processing devices and, in particular, to thin profile keyboards. 
     BACKGROUND 
     A pleasing exterior appearance of an electronic device is often difficult to pair with the market demand for advanced functionality, improved durability, and reduced thickness and weight. Some aesthetically pleasing materials may not be sufficiently durable to include in a device housing and other aesthetically pleasing materials may interfere with the advance functionality of the electronic device. Further, for certain input components such as buttons and keys, a user may physically engage the selected material several hundred thousand times, if not millions of times, over the life of a device. 
     Many visually pleasing solutions lack the durability for such extended function. This can be especially true when electronic devices and/or associated input devices are made smaller, thinner or otherwise reduced in dimension. Reduced dimensions of keycaps, for example, may lead to those keycaps being less structurally sound and so breaking or otherwise failing earlier during a use cycle than would thicker keycaps made of the same material. 
     Accordingly, there may be a present need for a durable and aesthetically pleasing external surface for an input device. 
     SUMMARY 
     This application provides techniques for forming and manufacturing an illuminated glass keycap for use with a key or keyboard as an input apparatus to an electronic computing device. In certain embodiments, an input apparatus may include a plurality of keys, each key of the plurality of keys including a transparent glass keycap having a top surface, a background layer comprising a glyph window, a glyph diffuser layer, a compressible scissor mechanism configured to activate electrical switch circuitry, and a light source having an on state and an off state. The light source may be oriented to transmit light through the transparent glass keycap. In certain embodiments, the transparent glass keycap is comprised of glass. In certain cases the glass may be a material such as sapphire, a ceramic or another scratch resistant material. Accordingly, the term “glass” may encompass such materials. The perimeter of the glass keycap may be beveled or otherwise polished. 
     Certain embodiments may relate to or take the form of an illuminated input apparatus having a glyph diffuser layer that may diffuse light through a glyph window. In these embodiments, the background layer may be opaque and the glyph window may be transparent. In other embodiments, the background layer may be translucent and the glyph window may be transparent. In further embodiments, the light source may be a light emitting diode, a light emitting polymer, or a light pipe or other visible light waveguide oriented to direct light through the transparent glass keycap. 
     Other embodiments described herein may relate to or take the form of an illuminated input apparatus having a light source including at least an on state and an off state. In certain cases, the on state may include a keycap perimeter illumination mode in which the light source may emit visible light proximate or otherwise adjacent to the perimeter of the keycap. In further embodiments, the on state may include a background illumination mode in which the light source may transmit light through the background layer. In this case, the background layer may diffuse the transmitted light before it exits the top surface of the transparent glass keycap. In further embodiments, the on state may include a glyph illumination mode in which the light source may transmit light through a glyph diffuser layer and further through the glyph window. 
     In other embodiments, the glyph diffuser layer is disposed partially within the glyph window, such that at least a portion of the glyph diffuser layer is coplanar with the background layer. In such an embodiment, or in similar embodiments, the glyph window may be etched from the background layer. 
     Other embodiments described herein may relate to or take the form of a method for manufacturing a light transmissive keycap for illuminating a keyboard, including the acts of selecting a transparent glass keycap, depositing a background ink layer on a bottom surface of the transparent glass keycap, etching a symbol aperture into the background ink layer, depositing a translucent glyph diffuser layer on the background ink over at least the symbol aperture, and aligning the transparent glass keycap along a vertical axis with a compressible scissor mechanism positioned above electrical switch circuitry. The method may also include beveling the perimeter edges of the transparent glass keycap. 
     Further embodiments may include positioning a light emitting element below the transparent glass keycap such that light emitted from the light emitting element transmits through the translucent glyph diffuser layer and through the symbol aperture. In certain cases the symbol aperture may be etched in a laser etching process or, in other embodiments, the symbol aperture may be formed by etching in a chemical process. 
     Other embodiments described herein may relate to or take the form of a keyboard with a plurality of keys, each of the plurality of keys having a keycap. Each keycap may include a glass top layer having at least four beveled edges along the perimeter of a top surface of the keycap, an ink layer disposed along a bottom surface of the glass top layer, a glyph window within the ink layer, and a diffuser fill within the glyph window. The keyboard may also include a light emissive layer, such as a layer of light emitting diodes, positioned below the keys. The keyboard can also include an electrical switch layer that has a number of electrical switches, each associated with an individual key. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference will now be made to representative embodiments illustrated in the accompanying figures. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the described embodiments as defined by the appended claims. 
         FIG. 1  is a perspective view of a sample embodiment of a sample keyboard for use with an electronic device. 
         FIG. 2  is a partially exploded side cross-sectional view of a keycap and supporting structure of the sample keyboard of  FIG. 1 , taken along line  2 - 2  of  FIG. 1 . 
         FIG. 3A  is a top plan view of a keycap showing a symbol as a portion of the embodiment as shown in  FIG. 1 . 
         FIG. 3B  is a side view of the embodiment shown in  FIG. 3A  taken along line  3 B- 3 B. 
         FIG. 3C  is a side view of the embodiment shown in  FIG. 3A  taken along line  3 C- 3 C. 
         FIG. 3D  is a side view of the embodiment shown in  FIG. 3A  taken along line  3 D- 3 D. 
         FIG. 3E  is a side view of the embodiment shown in  FIG. 3A  taken along line  3 E- 3 E. 
         FIG. 4A  is an inverted side view of an embodiment showing a sample cross section of a keycap after a background layer is applied. 
         FIG. 4B  is an inverted side view of the embodiment shown in  FIG. 4A  showing a sample cross section of a keycap after a background layer has been etched to expose portions of a glyph window. 
         FIG. 4C  is an inverted side view of the embodiment shown in  FIG. 4B  showing a sample cross section of a keycap after a glyph diffuser layer is applied over the background layer and the exposed portions of a glyph window. 
         FIG. 4D  is an inverted side view of the embodiment shown in  FIG. 4C  showing a sample cross section of a keycap after a glyph diffuser layer is drawn in to occupy the area of the glyph window. 
         FIG. 4E  is an inverted side view of the embodiment shown in  FIG. 4D  showing a sample cross section of a keycap with the glyph diffuser layer finished to a smooth plane, parallel with the planes of the keycap and the background layer. 
         FIG. 4F  is an inverted side view of the embodiment shown in  FIG. 4D  showing a sample cross section of a keycap with the glyph diffuser layer finished to a smooth plane, coplanar with a surface of a background layer. 
         FIG. 5A  is a top plan view of a keycap showing illumination of a perimeter portion, a glyph portion, and a background portion in an off state. 
         FIG. 5B  is a top plan view of a keycap showing illumination of a perimeter portion and a background portion in an off state with the illumination of a glyph portion in an on state. 
         FIG. 5C  is a top plan view of a keycap showing illumination of a background portion in an off state with the illumination of a perimeter portion and a glyph portion in an on state. 
         FIG. 5D  is a top plan view of a keycap showing illumination of a perimeter portion, a glyph portion, and a background portion in an on state. 
         FIG. 5E  is a top plan view of a keycap showing illumination of a glyph portion in an off state with the illumination of a perimeter portion and a background portion in an on state. 
         FIG. 5F  is a top plan view of a keycap showing illumination of a glyph portion and a perimeter portion in an off state with the background portion in an on state. 
         FIG. 6  is a flow chart illustrating operations of a sample method for manufacturing an illuminated input apparatus. 
     
    
    
     The use of the same reference numerals in different drawings indicates similar, corresponding, or identical items. 
     DETAILED DESCRIPTION 
     Embodiments described herein may relate to or take the form of light-transmissive and power efficient input apparatuses with low-profile, durable external surfaces. In particular, certain embodiments may take the form of a fully or partially illuminated keyboard or keypad or individual key having glass keycaps. Such input apparatuses may be used in conjunction with personal computing devices such as laptop computers, tablet computers, or desktop computers as either integrated or peripheral devices. Certain other embodiments may take the form of a fully or partially illuminated button with a glass outer surface for use with other electronic devices, such as televisions, portable media players, cellular telephones, tablet computers, and the like. 
     One embodiment may be a back-illuminated key associated with a keyboard. The embodiment may include a glass keycap. The glass keycap can have beveled or otherwise polished edges along a top surface. Disposed immediately below the glass keycap may be a background layer formed of ink or another pigment, and may translucent, semi-transparent or opaque. In certain embodiments, the background layer may be applied to the glass keycap in a printing process, a screening process, an immersion process or any other suitable process. 
     Etched into the background layer may be a glyph, symbol, window, or aperture (collectively, a “glyph window”). The glyph window may take the form of any numeral, symbol or letter of any language, or any information-conveying symbol, appropriately suited to the input device as used. For example, the glyph window may take the form of an English letter or letters or symbols in one embodiment. In another embodiment, the glyph window may take the form of a simplified Chinese character or characters. The glyph window may be etched through the background layer by a laser scribing process, for example. In other embodiments, the glyph window may be etched via a mask and immerse chemical etching process. In still further embodiments, the glyph window may not be etched at all, but may instead be provided by selectively applying a background layer. For example, the background layer may be printed on a surface, such as a top or bottom surface, of the glass keycap in all areas except those reserved for the glyph window. In further embodiments, the glyph window may be formed within the background layer before the background layer is applied to the glass keycap. 
     A glyph diffuser layer may be disposed below the background layer. The glyph diffuser layer may be formed of a semi-transparent or translucent material that is doped with glass beads or another diffusion dopant. In certain embodiments, the glyph diffuser layer may also include a pigment or ink of a particular color. For example, in certain embodiments titanium oxide may be used to give the glyph diffuser layer a white color when light is transmitted through it. In certain further embodiments, the glyph diffuser layer may be disposed over the background layer with, and/or within the glyph window in a screening, printing, immersion, or any other suitable process. During the application of the glyph diffuser layer to the background layer, unwanted pockets of air may form within the glyph window, trapped by the application of the glyph diffuser layer. In order to remove the unwanted pockets of air, the keycap (with background layer and glyph diffuser layer formed) may be placed in a vacuum chamber such that differential pressure between the pockets and the vacuum cause the glyph diffuser layer to remove the air pockets. In another embodiment, the keycap with background layer and glyph diffuser layer may be placed within an autoclave or other high pressure chamber to facilitate a pressure differential to remove the air pockets. 
     The glyph diffuser layer may be smoothed or polished to a plane in a subsequent process such that a bottom surface of the glyph diffuser layer is substantially parallel with the top surface of the glass keycap. Once smoothed, the keycap may be attached to a scissor mechanism and other elements of a key, in order to assemble the key. In certain embodiments, the glyph diffuser layer may be polished such that the bottom surface of the layer is coplanar with the bottom of the background layer. In other embodiments, the glyph diffuser layer may be polished such that the bottom surface of the layer is parallel to, but separated by, a specified depth from the bottom surface of the background layer. 
     Included within, below, or adjacent to the scissor mechanism may be one or more light sources positioned to emit light through the keycap. In certain embodiments, the light source may include or be coupled to a light source such as an organic light-emitting diode (OLED), a light-emitting diode (LED), or any other suitable light source. In a first embodiment, the light source may be positioned to transmit light through the glyph diffuser layer and through the glyph window. In such an embodiment, the background layer may not transmit any of the light emitted by the light source. In this way, when viewing the keycap from above, a glyph may be illuminated. 
     In a further embodiment, the light source may be positioned to transmit light around the perimeter of the keycap. In this way, when viewing the keycap from above the perimeter of the key (or an area around the key perimeter) may be illuminated. In other words, the keycap may appear to have a halo surrounding its periphery. 
     In a further embodiment, the light source may be positioned to transmit light through the background layer. In such an embodiment, light may not necessarily pass through the glyph window. In this way, when viewing the keycap from above the background of a glyph may appear illuminated while the glyph itself remains dark. 
       FIG. 1  is a perspective view of a sample embodiment of an illuminated keyboard  100  for use with an electronic device (not shown). The illuminated keyboard  100  may be a peripheral component of a computing system, or in other embodiments, it may be an integral portion of a computing system. In further embodiments, the illuminated keyboard  100  may have a greater number of keys or a fewer number of keys. The keys may be arranged in various orders or configurations. The illuminated keyboard  100  may have one or more keys  110  and a housing  120  that fully or partially encases the internal components of the keyboard. Each of the one or more keys  110  may have a glyph window  130  associated with it (e.g., visible on the keycap). As illustrated, the one or more keys  110  may be of different sizes and/or positioned at different locations along the top surface of the illuminated keyboard  100 . 
       FIG. 2  is a close-up and exploded side cross-sectional view of a key  200  of an embodiment of the illuminated keyboard  100  of  FIG. 1  taken along line  2 - 2 . The key  200  may be positioned at least partially within the housing  220  of the illuminated keyboard  100 . A key aperture  225  may be defined through the housing  220 . The key aperture  225  may be sized so that a perimeter gap  230  exists between the key  200  and the housing  220 . The perimeter gap  230  may be selectively sized based on the size of the key  200 . In certain embodiments, the key aperture  225  may not be present. Instead, one or more keys  110  (not shown in  FIG. 2 ) may be arranged substantially adjacent to one another such that the perimeter gap  230  of each key is defined by its neighboring keys. 
     The term “horizontal” as used herein and except as otherwise noted, is defined as the plane parallel to the upper surface of the housing  220  of the illuminated keyboard  100 . The term “vertical” as used herein and except as otherwise noted, is defined as the direction perpendicular to the horizontal plane. Similar directional terminology as used herein (e.g., “above” or “below” or “top” or “bottom”) is defined with respect to the orientation of the keyboard shown in  FIG. 1 . 
     The key  200  may have a keycap  240 . In certain embodiments, the keycap  240  may be composed of silica glass (which may be chemically treated), sapphire, or another similar substantially transparent and scratch resistant material. The keycap  240  may have a substantially flat top surface. In certain embodiments, the keycap  240  may have a slightly concave shape so as to enhance the feel of the key when depressed by a user. The top surface of the keycap  240  may have one or more beveled edges  242 . A beveled edge  242  may be angled at a  45  degree angle as shown, or in some embodiments, the beveled edge  242  may be machined such that it takes another shape that reduces or increases the angle formed by the top and sidewalls of the keycap  240  along its perimeter. 
     A substantially opaque background layer  250  may be formed on an underside of the keycap  240 . The background layer  250  may define a glyph window  260  extending through the background layer. Although shown in cross section, one may appreciate that the glyph window  260  may, when viewed from above, take the form of any numeral, symbol or letter of any language or symbol set appropriately suited to the illuminated keyboard  100  (not shown in  FIG. 2 ). Essentially, the portions of the underside of the keycap  240  that are not coated, treated, or otherwise covered with the background layer may form the glyph window  260 . As the glyph window may correspond to a letter, symbol, character, number and the like, it may vary in size, shape and cross-section from keycap to keycap. Further, some keycaps may lack any glyph window at all; the space bar is one example of this. 
     A glyph diffuser layer  270  may be formed on the underside of the background layer  250  and may fill (either partially or fully) the glyph window  260 . The glyph diffuser layer  270  may be composed of a semi-transparent or translucent material that is doped with a diffusion dopant. In certain embodiments, the glyph diffuser layer  270  may also be doped with a colored pigment to color the layer. As one example, titanium oxide may be used to give the glyph diffuser layer a white appearance. The glyph diffuser layer  270  may also include complementary geometry to the glyph window  260 . In this way, the glyph diffuser layer  270  may occupy the volume of the glyph window  260  within the background layer  250 . 
     A mechanical support may be positioned beneath and attached to the keycap. For example, a scissor mechanism  284  or butterfly mechanism may be affixed to a keycap receiving pad  280 . The receiving pad  280  may be adhered or otherwise bonded to the glyph diffuser layer  270 . The keycap receiving pad  280  may include a structure such as a detent, ledge or aperture to accept one or more top crossbars forming part of a scissor mechanism  284 . 
     In more detail, the keycap receiving pad  280  may have a substantially flat top surface and may be adhered or attached to the bottom surface of the glyph diffuser layer  270 . 
     A membrane  282  of a dome switch may be positioned below the keycap receiving pad  280 . In some embodiments, the membrane  282  may contact the bottom surface of the keycap receiving pad  280  when the key is in a neutral (e.g., unpressed) state, while in other embodiments the membrane  282  and keycap receiving pad  280  may be separated by an air gap when the key is in a neutral state. The membrane  282  may be constructed of a deformable material such as rubber, silicone, or any suitable polymer and may include one or more electrical contacts (not shown in the cross-section of  FIG. 2 ). In some embodiments the membrane  282  may be substantially transparent, while in others the membrane may be translucent or opaque. In some embodiments, light may be transmitted to or through the keycap from a light source located to a side of the key, such as an LED or a light pipe connected to an LED. 
     Adjacent to the membrane  282  may be a compressible scissor mechanism  284 . Below the membrane  282  may be a first contact wiring layer  286 . Electrical contacts (not shown in the cross-section view of  FIG. 2 ) may be disposed on the top surface of the first contact wiring layer  286  such that when the membrane  282  and the compressible scissor mechanism  284  compress beyond a selected threshold, the electrical contacts of the membrane  282  and the electrical contacts of the first contact wiring layer  286  complete an electrical circuit and thereby signal that the key  200  has been depressed. 
     The first contact wiring layer  286  may be disposed upon a first substrate layer  288  to provide structural support to the key  200 . The substrate layer  288  may be composed of a transparent or substantially transparent material. Below the substrate layer  288  may be an illumination layer  290  including a light emitting element  292  which is centered below the keycap  240 . The light emitting element  292  may be an LED, OLED, or any other suitable light source. Although shown as a single light source, one may appreciate that multiple light sources may be used. For example, a light emitting element  292  may be positioned on the illumination layer  290  so as to direct or transmit light through the perimeter gap  230 . In this manner, the light emitting element  292  may illuminate the perimeter of the key  200 , creating a halo effect about the key  200  when viewed from above. 
     In another embodiment, a light emitting element  292  may be positioned to direct light only through the glyph window  260 . In this manner, the light emitting element  292  may illuminate the glyph window  260 , creating an illuminated glyph effect on the surface of the key  200  when viewed from above. 
     In another embodiment, a light emitting element may be positioned to direct light only through the background layer  250 . In this manner, the light emitting element  292  may illuminate the background area around the glyph window, leaving the glyph window area unilluminated. In such an embodiment, one may appreciate that the background layer  250  may be composed of a semi-transparent or translucent material. For example, in this embodiment the background layer  250  may be composed of a semi-transparent or translucent material that is doped with glass beads or other diffusion dopant. 
     One may further appreciate that a plurality of light emitting elements  292  may be disposed upon or within the light emissive layer  290 . In this manner, multiple portions of the key  200  may be selectively or jointly illuminated. Below the light emissive layer  290  may be disposed a second substrate layer  294 , providing structural support to the key  200 . 
     One may appreciate that  FIG. 2  is not necessarily drawn to scale. For clarity, the relative height of each illustrated item has in some cases been exaggerated to show the relationship between each of the several layers forming key  200 . For example, the background layer  250  and the glyph diffuser layer  270  may only be a few microns in height. Further, one may appreciate the keycap  240  may be less than a millimeter in height. 
       FIG. 3A  is a top plan view of a keycap  300  showing a glyph as a portion of the embodiment as shown in  FIG. 1 . The keycap may include at least background area  310  and a glyph area  315 , which as illustrated shows the English letter “A.” The keycap  300  may be situated within the housing  320  of an illuminated keyboard  100  (now shown, see  FIG. 1 ). The keycap  300  may be positioned within a key aperture  325 . The horizontal surface area of the key aperture  325  may be slightly larger than the horizontal surface area of the keycap  300  such that a keycap perimeter gap  380  is exposed. 
       FIGS. 3B-3E  are close up side views of the embodiment shown in  FIG. 3A  taken along cross sections  3 B- 3 E respectively. Visible in all four cross sections shown in  FIGS. 3B-3E  is the keycap  340 . The keycap  340  sits within a key aperture (not labeled) formed in the keyboard housing  320 . A perimeter gap  330  is formed between the edges of the key aperture and the keycap. As noted with respect to the embodiment illustrated by  FIG. 2 , the keycap  340  may be composed of glass and may have beveled or polished edges. 
     Visible in all four cross sections shown in  FIGS. 3B-3E  is the background layer  350 . Also as noted with respect to the embodiment shown in  FIG. 2 , the background layer  350  may be disposed directly below the glass keycap  340 . Disposed below the background layer  350  is the glyph diffusion layer  370 . 
     One may appreciate that line  3 B- 3 B of  FIG. 3A  may not intersect any portion of the glyph area  315  of  FIG. 3A . Accordingly, in the cross-section shown in  FIG. 3B , no portion of a glyph window is present or illustrated. However, line  3 C- 3 C of  FIG. 3A  does intersect a portion of the glyph area  315  of  FIG. 3A . Specifically, line  3 C- 3 C intersects the crest of the “A” glyph as illustrated in  FIG. 3A . Accordingly, within the cross section shown in  FIG. 3C , a portion of a glyph window  360  is shown. Because line  3 C- 3 C intersects the glyph window only once,  FIG. 3C  illustrates only a single portion of the glyph window  360 . 
       FIG. 3D  is a close up side view of the embodiment shown in  FIG. 3A  taken along line  3 D- 3 D, which intersects both legs of the letter “A,” illustrated as the glyph area  315  in FIG.  3 A. Accordingly, in cross section  FIG. 3D  illustrates two portions of the glyph window  360  separated by a portion of the background layer  350 . 
     Similar to  FIG. 3B ,  FIG. 3E  does not intersect any portion of the glyph area  315  of  FIG. 3A  and accordingly, no portion of a glyph window is present or illustrated. 
     With respect to  FIGS. 4A-4D , the term “horizontal” is defined as the plane parallel to the surface of the glass keycap. The term “vertical” as with respect to  FIGS. 4A-4D  is defined as the direction perpendicular to the horizontal plane. Similar directional terminology as used herein (e.g., “above” or “below” or “on” or “under”) is defined with respect to the horizontal plane. 
       FIG. 4A  is an inverted close up side view of an embodiment showing a sample cross section of a keycap  440  after a background layer  450  is applied. The background layer  450  may be composed of ink or pigment, and may be translucent, semi-transparent or opaque. In certain embodiments, the background layer  450  may be applied to the glass keycap  440  in a printing process, a screening process, an immersion process or any other suitable process. 
       FIG. 4B  is an inverted close up side view of the embodiment shown in  FIG. 4A  showing a sample cross section of a keycap  440  after a background layer  450  has been etched to expose portions of a glyph window  460 . The glyph window  460  may be etched through the background layer in a laser-scribing process. For example, a laser may ablate the background layer  450  in order to expose the glyph window  460 . In certain cases, the laser may be sufficiently powerful to ablate or otherwise remove the material of the background layer  450  while being insufficiently powerful to ablate or otherwise etch or damage the material selected for the keycap  440 . 
     In other embodiments, the glyph window  460  may be etched with a chemical etching process. For example, a mask may be applied over the background layer  450 . The mask may cover portions of the background layer  450  that will remain after etching, but may expose all portions of the background layer  450  that should be removed in order to expose the glyph window  460 . After the mask is applied, the keycap  440  and background layer  450  may be immersed in or exposed to an etching solution that dissolves or otherwise reacts with the material selected for the background layer  450  but not the material selected for the mask or the material selected for the keycap  440 . After a proscribed period of time, the keycap  440  may be removed from the etching solution and the mask may be removed from the background layer  450 . 
     In still further embodiments, the glyph window  460  may not be etched at all, but may instead be formed by selectively applying background layer  450 . For example, the background layer  450  may be printed along the surface of the glass keycap  440  in all areas except those reserved for the glyph window  460 . 
       FIG. 4C  is an inverted close-up side view of the embodiment shown in  FIG. 4B , showing a sample cross section of a keycap  440  after a glyph diffuser layer  470  is applied over the background layer  450  and the exposed portions of a glyph window  460 . In certain embodiments, during the application of the glyph diffuser layer  470  to the background layer  450 , unwanted pockets of air  490  may remain within the glyph window  460 . The unwanted pockets of air  490  may cause undesirable visual artifacts in the keycap  440 . 
     In order to remove the unwanted pockets of air  490 , the keycap  440  (with background layer  450  and glyph diffuser layer  470  already formed) may be placed in a vacuum chamber (not shown) such that a negative pressure differential forms to eliminate the air pockets  490 . Generally, air pockets  490  may be created at or near atmospheric pressure. Accordingly, when placed in a vacuum environment, the pressure of the air pockets  490  may equalize with the vacuum, which may pull the diffuser layer  470  in to fill the entire volume of the glyph window  460 , as shown in  FIG. 4D . 
     In another embodiment, the keycap  440 , with background layer  450  and glyph diffuser layer  470 , may be placed within an autoclave or other high pressure chamber to facilitate a positive pressure differential to remove the air pockets  490 . As noted above, the air pockets  490  may be created at or near atmospheric pressure. When placed in a high pressure environment, the difference in pressure may push the diffuser layer  470  to fill the entire volume of the glyph window  460 , as shown in  FIG. 4D . 
       FIG. 4E  is an inverted close up side view of the embodiment shown in  FIG. 4D  showing a sample cross section of a keycap  440  with the glyph diffuser layer  470  finished to a smooth plane, parallel with the planes of the keycap  440  and the background layer  450 . Once polished or otherwise smoothed, the glyph diffuser layer  470  may be attached to a scissor mechanism (not shown) or other button mechanism positioned to activate electrical switch circuitry when depressed. The glyph diffuser layer  470  may be smoothed in order to provide a substantially parallel relationship between the scissor mechanism and the top surface of the keycap  440 . 
       FIG. 4F  is an inverted close-up side view of the embodiment shown in  FIG. 4D  showing a sample cross section of a keycap  440  with the glyph diffuser layer  470  finished to a smooth plane that is coplanar with a surface of a background layer  450 . In certain embodiments, smoothing the glyph diffuser layer in this manner may provide for an exceptionally thin overall key thickness. 
     One may appreciate that  FIGS. 3A-4F  are not drawn to scale. For clarity, the relative height of each illustrated item has in some cases been substantially exaggerated to show the relationship between each of the several layers forming the illustrated key. For example, one may appreciate that the background layer  350  and  450  and the glyph diffuser layer  370  and  470  may only be a few microns in height. Further, one may appreciate the keycap  340  and  440  may be less than a millimeter in height. 
       FIGS. 5A-5F  illustrate various configurations of selective a joint illumination of individual portions of a key according to one embodiment of the invention. 
       FIG. 5A  is a top plan view of a keycap showing the selective illumination of a perimeter gap portion  580 , a glyph area portion  515  (not shown), and a background area portion  510  in an off state. One may note that in the illustrated embodiment, a glyph portion  515  is not visible. In certain embodiments, the boundaries between the background portion  510  and the glyph area portion  515  are not distinguishable. Accordingly,  FIG. 5A  is illustrated without the glyph area visible. 
       FIG. 5B  is a top plan view of a keycap showing illumination of a perimeter gap portion  580  and a background area portion  510  in an off state with the illumination of a glyph area portion  515  in an on state. 
       FIG. 5C  is a top plan view of a keycap showing illumination of a background area portion  510  in an off state with the illumination of a perimeter gap portion  580  and a glyph area portion  515  in an on state. In this manner,  FIG. 5C  illustrates a glyph illumination mode of the keycap. 
       FIG. 5D  is a top plan view of a keycap showing illumination of a perimeter gap portion  580 , a glyph area portion  515  (not shown), and a background area portion  510  in an on state. As noted above with respect to  FIG. 5A , the glyph portion  515  is not visible. In certain embodiments, the boundaries between the background portion  510  and the glyph area portion  515  are not distinguishable. Accordingly,  FIG. 5D  is also illustrated without the glyph area visible. In this manner,  FIG. 5D  illustrates a perimeter illumination mode of the keycap. 
       FIG. 5E  is a top plan view of a keycap showing illumination of a glyph area portion  515  in an off state with the illumination of a perimeter gap portion  580  and a background area portion  510  in an on state. In this embodiment, the glyph area  515  may visible to a user as a shadow and the background area portion  510  and the perimeter gap portion  580  may appear as a singular or substantially singular illuminated area. 
       FIG. 5F  is a top plan view of a keycap showing illumination of a glyph area portion  515  and a perimeter gap portion  580  in an off state with the background area portion  510  in an on state. In this embodiment, the glyph area  515  may visible to a user as a shadow within the illuminated background area portion  510 . The darkened perimeter gap portion  580  may provide enhanced contrast with the background area  510 . In this manner,  FIG. 5F  illustrates a background illumination mode of the keycap. 
     Although  FIGS. 5A-5F  illustrate various combinations of illuminated portions of a keycap, one may appreciate that additional or fewer combinations are contemplated. One may appreciate further that individual keys on the same keyboard may be illuminated separately, sequentially, with differing brightness, for varying durations, etc. 
       FIG. 6  is a flow chart illustrating operations of a sample method for manufacturing an illuminated input apparatus. At  610 , a glass keycap may be selected. In certain embodiments, the glass keycap may be singulated from a larger sheet or, in other embodiments a large mother sheet containing a plurality of individual glass keycaps to be singulated in a later process. 
     At  620 , a background layer may be deposited on the glass keycap. In certain embodiments, the background layer may be applied to the glass keycap in a printing process, a screening process, an immersion process or any other suitable process. In certain embodiments, the background layer may be cured before other operations continue. 
     At  630 , a glyph window may be etched into the background layer. The glyph window may be etched in a laser etching process, or in other embodiments, the glyph window may be formed by etching in a chemical process. The glyph window may take the form of any numeral, symbol or letter of any language appropriately suited to the keycap. One may further appreciate that in certain embodiments, operations  620  and  630  may be accomplished simultaneously if the background layer is applied in a printing process. 
     At  640 , a diffuser layer may be applied to the background layer. The diffuser layer may be composed of a semi-transparent or translucent material that is doped with glass beads or other diffusion dopant. The diffuser layer may be disposed over the background layer with glyph window in a screening, printing, immersion, or any other suitable process. 
     At  650 , the glass keycap, background layer, and diffuser layer may be placed in curing conditions in order to solidify or otherwise bond the layers together. Curing conditions may include but are not limited to an ultraviolet oven, a heated oven, a vacuum chamber, or an autoclave chamber. The curing process may include processes to remove unwanted air pockets from either the background layer or the diffuser layer. 
     At  660 , the diffuser layer may be polished or otherwise finished to a plane substantially parallel to the top surface of the glass keycap. The process may conclude at  670 . 
     One may appreciate that although many embodiments are disclosed above, that the operations presented in  FIG. 6  are meant as exemplary and accordingly are not exhaustive. One may further appreciate that alternate step order, or additional or fewer steps may be used to accomplish methods contemplated here. 
     Where components or modules of the invention are implemented in whole or in part using software, in one embodiment, these software elements can be implemented to operate with a computing or processing module capable of carrying out the functionality described with respect thereto. 
     Embodiments have been described herein with respect to glass keycaps, but it should be appreciated that structures, methods, processes, apparatuses and the like may employ, operate with, be incorporated into or otherwise associated with keycaps and/or keys made from other materials. For example, certain embodiments may use a metal keycap, a ceramic keycap, a polymer keycap, and so on. 
     Although the disclosure above is described in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied alone or in various combinations to one or more of the other embodiments of the invention, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments but is instead defined by the claims herein presented.