Patent ID: 12204135

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention mainly involves the complex application of the adhesion function and the optical properties of adhesives (e.g. light-permeable glue layer) in a sophisticated optical system (e.g. an illuminated keyboard and an illuminated keyswitch with a backlit module). The invention is designed to modulate the glue layer and the associated optical elements to achieve the ultimate luminous effect for a single keyswitch or even the entire keyboard and to promote the luminance uniformity. Therefore, it is necessary to understand the invention concept in the embodiments of the invention, and how to optimize the backlit module, the illuminated keyswitch structure, and the illuminated keyboard of the invention in consideration of multiple variables and restriction will be described in detail.

In pursuit of extremely thin electronic devices, such as laptop computer and keyboard, the illuminated keyswitch and the backlit module thereof are intensively integrated in a small space. With the miniaturization of light sources, reduction of luminous efficacy, modification of optical materials year by year, a slight change of different optical elements will cause a significant change in the luminous effect. Therefore, the backlit design for keyswitch must consider complex technical issues, which cannot be solved by simple design choices.

At first, light sources of different light input positions, different sizes, or different numbers/locations of light-emitting surfaces have height differences when cooperating with the light guide sheet, which may easily cause the optical film to float and cause light leakage. Moreover, when the relative position between the light source and the optical film (mask film, light guide sheet, reflective layer, and light source circuit board) is not fixed, the optical coupling will also be unstable. However, simply fixing the relative position between the light source and the optical film by glue will fall into a technical trap that seriously affects the optical effect. For example, if the refractive index of the light-permeable glue layer is closer to that of the light guide sheet than the air, the glue layer will more easily destroy the total reflection of the light guide sheet. Consequently, light will be easily emitted out of the light guide sheet from where the glue layer is disposed. For example, when a dedicated light source is provided to the keyswitch with the keycap having an area of 1 square centimeter, the ultra-thin key height of 2 mm, and the 1.8 mm backlit module, providing the glue layer on the light guide sheet around the light source with the mask film and the reflective layer/light source (driving) circuit board for reflecting light inwards will cause a large amount of light that just comes out of the light source to directly or indirectly pass through the glue layer. As such, the light is repeatedly in and out of the light guide sheet at the periphery inside and outside the light source hole of the light guide sheet and between the mask film and the reflective layer/light source circuit board, resulting in unnecessary loss of light, reduction of light flux transmitted toward the transverse (horizontal) direction. This will have a huge impact on the backlit applications with the light source of low illuminance because the keycap halo and the corner characters will become very dim. If the glue layer is only arranged on the outline of the keycap and not around the light source, the tolerance of thickness, hole position, glue printing for each optical film before and after the rolling, punching, and heating processes will cause problems, such as light source shift, extrusion, or falling off. In addition, the distance between the glue and the light source, the distance between the glue and the light source hole of the light guide sheet, the distance between the light source and the light source hole, the relative position between the glue and the mask/reflective optical element will also cause differences in the optical effect.

On the other hand, whether the glue is applied to the heat dissipation hole or the structure hole (closed hole or open hole) or not, the application location of glue, and the cooperation with optical element the (absorption/reflection/total reflection/diffusion/refraction, etc.) will have different modifications and effects from the glue applied to the neighborhood of the light source. For example, the mask film and the reflective layer/light source circuit board of the backlit module are adhered in the heat dissipation hole or the structural hole, i.e., the glue is applied outside the edge of the light guide sheet, it may cause serious light leakage due to the optical coupling effect of the glue. If the edges are not adhered by the glue, allowing the light to be directly emitted from the hole wall of the light guide sheet will cause serious light leakage. In other words, the relative position between the glue and the optical element must be optimized to reduce the light leakage from the heat dissipation hole or structure hole.

Referring toFIG.1A,FIG.1Ais a schematic view of the stack of the illuminated keyboard in an embodiment of the invention. In an embodiment, the illuminated keyboard KB of the invention includes a plurality of keyswitches KS (such as square keyswitches SK or multiple keyswitches MK) and a backlit module BL. Each keyswitch KS includes a keycap12, an up-down lift structure14, a portion of a membrane circuit board16, a restoring member18, and a portion of a baseplate10. For the illuminated keyboard KB, the backlit module BL includes a mask film210, a light guide sheet220and a driving circuit board240, and the driving circuit board240can include a reflective layer230and a light-emitting element250disposed thereon.

Referring toFIG.1BandFIG.2,FIG.1Bis a schematic exploded view of the illuminated keyswitch structure in an embodiment of the invention, andFIG.2is a schematic cross-sectional view of the illuminated keyswitch structure in an embodiment of the invention. For a single keyswitch structure, in an embodiment, the illuminated keyswitch structure1of the invention includes the baseplate10, the keycap12, the up-down lift structure14, the membrane circuit board16, the restoring member18, the mask film210, the light guide sheet220, the reflective layer230, the driving circuit board240, and the light-emitting element250. The keycap12is disposed over the baseplate10and has a light permeable portion122(e.g. one or more light permeable characters). The up-down lift structure14is connected between the baseplate10and the keycap12and configured to support the up-down movement of the keycap12relative to the baseplate10. The membrane circuit board16is disposed under the keycap12and preferably above the baseplate10. The membrane circuit board16has a switch162(represented by a circle inFIG.1B). The membrane circuit board16has a multi-layered structure, and the switch circuit is formed on one or more layers thereof. When the keycap12is pressed, the switch162of the membrane circuit board16will be conducted. The restoring member18is disposed between the keycap12and the baseplate10and configured to provide a restoring force to enable the keycap12to move upward relative to the baseplate10to the non-pressed position when the pressing force is released. In this embodiment, the restoring member18can be embodied as an elastic member (e.g. rubber dome) and disposed corresponding to the switch162. When the keycap12is pressed and moves downward to compress the restoring member18, the restoring member18can trigger the switch162, but not limited thereto, The switch162can be triggered by a triggering portion, which can be disposed on the restoring member18, the up-down lift structure14, or the keycap12, but not limited thereto. According to practical applications, the restoring member18can be embodied as any suitable element, which can provide the restoring force to enable the keycap12to return the non-pressed position, such as spring, magnetic member. The switch of the illuminated keyswitch structure1is not limited to the switch162of the membrane circuit board16and can be any suitable switch, which is triggered in response to the pressing of the keycap12, such as mechanical switch, magnetic switch, optical switch. In this embodiment, the up-down lift structure14can be embodied as a scissors-like up-down lift structure, which has two frames pivotally coupled with each other, and two ends of each frame are movably coupled to the baseplate10and the keycap12, respectively, but not limited thereto. According to practical applications, the up-down lift structure14can be embodied as a butterfly up-down lift structure, a cantilever up-down lift structure, etc. The baseplate10, the keycap12, the up-down lift structure14, the membrane circuit board16, and the restoring member18constitute the keyswitch unit of the illuminated keyswitch structure1.

As shown inFIG.2, the mask film210is disposed below the baseplate10, and the mask film210preferably has a first coating212and a second coating214. The first coating212is configured to substantially reflect light, such as the light emitted from the light-emitting element250), and the second coating214is configured to substantially block light. The light guide sheet220is disposed at one side of the mask film210opposite to the baseplate10(e.g. the lower side), and the light guide sheet220has a light source hole222corresponding to the central hole102of the baseplate10. The reflective layer230is disposed at one side of the light guide sheet220opposite to the mask film210(e.g. the lower side), and the reflective layer230has an opening232, which communicates with the light source hole222. The light-emitting element250is fixed on the driving circuit board240by an adhesive layer252and is electrically coupled to the light source circuit of the driving circuit board240. The adhesive layer252can be a non-conductive adhesive layer, which is configured to fix the light-emitting element250on the driving circuit board240, instead of the solder paste or other conductive layer, which is configured to fix and electrically connect the light-emitting element250to the driving circuit board240. The driving circuit board240is disposed below the light guide sheet220, so the light-emitting element250can extend upward into the light source hole222of the light guide sheet220from below the opening232of the reflective layer230. In an embodiment, the light-emitting element250can be a micro light-emitting diode (LED), which can have a light-emitting pattern from five surfaces, mainly top-lighting, such as 80% of light emitting from the top surface, and the rest of light from four side surfaces, but not limited thereto. The mask film210, the light guide sheet220, the reflective layer230, the driving circuit board240, and the light-emitting element250constitute the backlit unit (or module) of the illuminated keyswitch structure1. Moreover, the adhesive layer252can be light permeable, and a portion of the reflective layer230, which surrounds the light-emitting element250, can be disposed in the light source hole222, so the reflected light can enter the light guide sheet220from the sidewall of the light source hole222via the adhesive layer252and/or the reflective layer230disposed in the light source hole222, and then travels along the transverse (or horizontal) direction.

Referring toFIG.3andFIG.3AtoFIG.3D,FIG.3is a schematic plan view of the stack of certain components (e.g. the baseplate10, the mask film210, the light guide sheet220, the driving circuit board240including the reflective layer230) of the illuminated keyswitch structure in an embodiment of the invention, andFIG.3AtoFIG.3Dare schematic plan views of the components ofFIG.3, respectively. As shown inFIG.3andFIG.3A, the baseplate10can be formed by metal stamping, so the baseplate10has a plurality of ribs connected to each other (such as inner rib104, bridge rib106, and peripheral rib108) to define a plurality of holes (such as central hole102and peripheral hole102′). Specifically, the peripheral rib108of the baseplate10is disposed at the outermost of the baseplate10, and the peripheral rib108can be a frame-like rib or a plurality of ribs connected to each other in a head-to-tail manner to form a ring shaped configuration. As such, the baseplate10can have a frame structure, but not limited thereto. When a plurality of keyswitches are integrated into the keyboard, the baseplate10of each keyswitch can be connected by the peripheral rib108, so as to form a single integral baseplate. The inner rib104is disposed at the center or in the neighborhood of the center of the baseplate10and configured to define the central hole102, so the inner rib104encloses the central hole102, and the central hole102substantially corresponds to the center or in the neighborhood of the center of the keycap12. A plurality of the bridge ribs106is configured to connect the inner rib104and the peripheral rib108. The bridge ribs106are disposed between the inner rib104and the peripheral rib108to define a plurality of peripheral holes102′, so the peripheral holes102′ substantially correspond to the peripheral portion or corners of the keycap12. The central hole102and the peripheral holes102′ allow the light emitted from the light-emitting element250to pass therethrough, so as to illuminate the keycap12and thereout of from the light permeable portion122.

Specifically, as shown inFIG.3andFIG.3B, the mask film210can be a light permeable film (such as polyethylene terephthalate (PET) film) with the first coating212and the second coating214formed by light-blocking materials thereon. In this embodiment, the first coating212and the second coating214have different light transmittances. As such, the first coating212can reflect a major portion of light and allow a small portion of light to pass therethrough (or absorb the small portion of light), and the second coating214can substantially block or absorb a major portion of light and allow a small portion of light to pass therethrough (or reflect the small portion of light). For example, in an embodiment, the first coating212can be a white ink coating, the second coating214can be a black ink coating, and both can be formed by the printing technology, but not limited thereto. Moreover, the second coating214is closer to the baseplate10than the first coating212is (i.e., the first coating212is closer to the light guide sheet220than the second coating214is). As such, a major portion of the upward light can be firstly reflected from the first coating212, and a small portion of the upward light passing through the first coating212is then absorbed by the second coating214, effectively directing the upward light from the vertical (upward) direction to propagate along the transverse (or horizontal) direction. In an embodiment, as shown inFIG.2, the first coating212and the second coating214are preferably disposed on different surfaces of the mask film210. For example, the first coating212is disposed on the lower surface of the mask film210(i.e., closer to the light guide sheet220), and the second coating214is disposed on the upper surface of the mask film210(i.e., closer to the baseplate10), but not limited thereto. In another embodiment (not shown), the first coating212and the second coating214can be disposed on the same surface of the mask film210. For example, the first coating212is disposed on the upper surface of the mask film210, and the second coating214is disposed on the upper surface of the mask film210and/or on the upper surface of the first coating212. Alternatively, the second coating214can be disposed on the lower surface of the mask film210, and the first coating212is disposed on the lower surface of the mask film210and/or on the lower surface of the second coating214. As such, the upward light is mostly reflected from the first coating212and less passes through the first coating212to be absorbed by the second coating214.

It is noted that in the figures (such asFIG.3.FIG.3B,FIG.4,FIG.5orFIG.7), the region with left-shaded lines is where the first coating212(or212′) is disposed, and the region with the right-shaded line is where the second coating214is disposed. When a region exhibits both of left-shaded lines and right-shaded lines, the region is where the first coating212(or212′) and the second coating214are overlappingly disposed, and the first coating212is closer to the light guide sheet220than the second coating214is.

In an embodiment, the first coating212and the second coating214are disposed corresponding to the central hole102, so the vertical projection of the first coating212on the baseplate10preferably overlaps the central hole102and extends to the inner rib104. The vertical projection of the second coating214on the baseplate10is preferably located within the central hole102. For example, the first coating212preferably has a first central coating portion212a, and the second coating214preferably has a second central coating portion214a. The first central coating portion212aand the second central coating portion214apreferably overlap with each other and correspond to the central hole102of the baseplate10. As shown inFIG.3andFIG.3B, taking the circled central hole102as an example, the diameter of the first central coating portion212ais preferably larger than the diameter of the central hole102, and the diameter of the central hole102is preferably larger than the diameter of the second central coating portion214a. In practical applications, the first coating212(or the second coating214) can have a distribution pattern corresponding to the arrangement of ribs of the baseplate10. When the baseplate10and the mask film210are disposed in a stacked manner, the shape of the light permeable region218of the mask film210(i.e., the portion of the light permeable film without the first coating212and the second coating214disposed thereon) and the shape of the peripheral holes102′ of the baseplate10are preferably substantially identical. As shown inFIG.3B, in addition to the second central coating portion214a, which is located within the central hole102, the second coating214can further have a coating portion partially corresponding to the peripheral ribs108of the baseplate10. In addition to the first central coating portion212a, which covers below the central hole102, the first coating212can further have a coating portion overlapping (or corresponding to) the peripheral rib108, the bridge ribs106, and the inner rib104of the baseplate10, so as to define the plurality of light permeable portions218, which correspond to the peripheral holes102′ in number and shape, but not limited thereto. According to practical applications, the vertical projection of the first coating212(or the second coating214) on the baseplate10preferably overlaps at least one of the bridge ribs106, but not limited thereto. As shown inFIG.4, in another embodiment, the arrangement of the second coating214of the mask film210′ is similar to that ofFIG.3B, i.e., the second coating214includes the second central coating portion214alocated within the central hole102and the coating portion corresponding to the peripheral rib108. In the embodiment ofFIG.4, the first coating212′ includes the first central coating portion212aand a coating portion corresponding to the peripheral rib108, so the light permeable region218′ becomes a single continuous region, and the vertical projection of the light permeable region218′ on the baseplate10overlaps the bridge ribs106and the peripheral holes102′. As shown in the figures, the coating portion of the first coating212′ corresponding to the peripheral rib108preferably extends beyond the coating portion of the second coating214corresponding to the peripheral rib108to be closer to the central hole102(i.e., the width thereof is wider), but not limited thereto. In another embodiment, the coating portion of the first coating212′ corresponding to the peripheral rib108can be the same as the coating portion of the second coating214corresponding to the peripheral rib108or retreats with respect to the central hole102(i.e., the width thereof is narrower).

As shown inFIG.3andFIG.3C, the light guide sheet220can be a film-like or sheet-like plate, which can be made of any suitable optical materials, such as optical polymers. The light source hole222is a through hole penetrating through the light guide sheet220in the thickness direction (i.e., Z-axis direction), so the light-emitting element250can be located in the light source hole222. The first central coating portion212aof the first coating212and the second central coating portion214aof the second coating214are located right above the light source hole222. The light guide sheet220can further have a plurality of light-exit portions228configured to destroy the total reflection of light to emit light upward. The plurality of light-exit portions228is preferably disposed corresponding to the peripheral holes102′, but not limited thereto. The light-exit portions228can be disposed at any positions for light output as appropriate. As shown inFIG.3C, a top glue262is disposed on the top surface of the light guide sheet220and located around the light source hole222. Specifically, the top glue262is configured to connect the mask film210and the light guide sheet220and located around the central hole102, so the mask film210, the light guide sheet220, and the light-emitting element250can be positioned by the top glue262to enhance the optical coupling stability. Moreover, the top glue262can be formed by optical materials, which are light permeable and have a refractive index closer to that of the light guide sheet220than the air. As such, light reflected from the first central coating portion212acan enter the light guide sheet220at a relatively higher proportion and then propagates in the light guide sheet220by total reflection. Moreover, the top glue262is spaced apart from the edge of the light source hole222of the light guide sheet220to form a top clearance region272therebetween, i.e., the region around the light source hole222without the top glue262.

As shown inFIG.3andFIG.3D, the reflective layer230is disposed at one side of the light guide sheet220opposite to the mask film210(e.g. the lower side) and configured to reflect light leaking from the bottom surface of the light guide sheet220back to the light guide sheet220. Specifically, the reflective layer230can be a reflective film made of reflective materials (e.g. metal foil), a layer of reflective material coated on a non-reflective film, or a plastic film doped with reflective particles (e.g. PET film doped with reflective particles), but not limited thereto. In an embodiment, the reflective layer230can be a reflective coating (such as a white ink coating) coated on the upper surface of the driving circuit board240, and the reflectivity of the reflective layer230is preferably larger than 80%, but not limited there. The opening232of the reflective layer230can be a through hole penetrating through the layer body of the reflective layer230or can be a portion of the upper surface of the driving circuit board240on which the light-emitting element250is disposed without the reflective coating. As shown inFIG.3D, a bottom glue264is disposed on the top surface of the reflective layer230(or the bottom surface of the light guide sheet220) and located around the light source hole222. Specifically, the bottom glue264is configured to connect the light guide sheet220and the reflective layer230and located around the central hole102, so the light guide sheet220, the reflective layer230, and the light-emitting element250can be positioned by the bottom glue264to enhance the optical coupling stability. Moreover, the bottom glue264can be formed by optical materials, which are light permeable and have a refractive index closer to that of the light guide sheet220than the air. As such, light reflected from the reflective layer230can enter the light guide sheet220at a relatively higher proportion and then propagates in the light guide sheet220by total reflection. Moreover, the top glue262and the bottom glue264can be formed by the same or different adhesive materials, such as water-based glues, but not limited thereto. The bottom glue264is spaced apart from the edge of light source hole222of the light guide sheet220(or the opening232) to form a bottom clearance region274therebetween, i.e., the region around the light source hole222without the bottom glue264. As shown inFIG.3D, when the reflective layer230is the reflective coating formed on the upper surface of the driving circuit board240, the opening232can be a portion of the upper surface of the driving circuit board240without the bottom glue264and without the reflective layer230. The driving circuit board240further includes one or more main wirings242and one or more sub-wirings244. For example, two main wirings242respectively provide high/low potentials, and two sub-wirings244respectively extend from the two main wirings242, so the light-emitting element250is electrically connected to the main wirings242via the sub-wirings244. Moreover, a light absorption layer (not shown) can be disposed under the reflective layer230and configured to absorb the light passing through the reflective layer230.

Referring toFIG.2again, the layout design of the top glue262and the bottom glue264will be further described. As shown inFIG.2, in a stacked direction of the baseplate10, the mask film210, the light guide sheet220, and the reflective layer230(e.g. Z-axis direction), at least one of the top glue262and the bottom glue264overlaps the first coating212. For example, only the top glue262, only the bottom glue264, or both of the top glue262and the bottom glue264overlaps the first coating212in the stacked direction. In an embodiment, as shown in the figure, the vertical projection of the top glue262or the bottom glue264on the mask film210can fall within the first coating212. As described above, the top glue262or the bottom glue264is disposed surrounding the light source hole222, so the top clearance region272is formed between the top glue262and the edge2222of the light source hole222of the light guide sheet220, and the bottom clearance region274is formed between the bottom glue264and the edge2222of the light source hole222of the light guide sheet220. In this embodiment, the top clearance region272is the top surface portion of the light guide sheet220around the light source hole222without the top glue262, and the bottom clearance region274is the bottom surface portion of the light guide sheet220around the light source hole222without the bottom glue264. From another aspect, the top clearance region272can be the lower surface portion of the mask film210around the light source hole222of the light guide sheet220without the top glue262, and the bottom clearance region274can the upper surface portion of the reflective layer230(or the driving circuit board240) without the bottom glue264. As such, the top glue262or the bottom glue264can be prevented from entering the light source hole222to interfere with light output or from overlapping the adhesive layer252which fixes the light-emitting element250to unnecessarily increase the stacked height. In other words, with the arrangement of the top clearance region272and/or the bottom clearance region274, at least one of the top glue262and the bottom glue264does not overlap the adhesive layer252(which fixes the light-emitting element250) in the stacked direction (such as Z-axis direction), so as to effectively prevent the unnecessary increase of the stacked height. Preferably, the top glue262and the bottom glue264both do not overlap the adhesive layer252in the stacked direction.

In an embodiment, the bottom clearance region274is preferably larger than the top clearance region272. For example, the distance between the bottom glue264and the edge2222of the light source hole222is larger than the distance between the top glue262and the edge2222of the light source hole222to prevent the bottom glue264and/or the reflective layer230from outputting light upward, so as to reduce the amount and chance of light outputting from the central region (e.g. the central hole102), to increase the recycle of light from the central region, and increase the proportion of light traveling along the transverse (or horizontal) direction.

Moreover, since the first central coating portion212aof the first coating212, which overlaps the central hole102and extends to the inner rib104, overlaps the top glue262and/or the bottom glue264, so the top clearance region272and the bottom clearance region274, which are adjacent to the light source hole222, also overlap the first central coating portion212aof the first coating212and even further overlaps the inner rib104. In other words, at least one of the top glue262and the bottom glue264(preferably both of them) overlaps the first central coating portion212aand the inner rib104in the stacked direction (such as Z-axis direction), so the top clearance region272and the bottom clearance region274also overlap the first central coating portion212a. In an embodiment, the diameter of the coating portion of the first coating212covering right above the light source hole222(i.e., the first central coating portion212a) is preferably larger than the diameter of the top glue262. Specifically, as shown inFIG.2A, the first central coating portion212apreferably substantially extends under the whole inner rib104, so the first central coating portion212ahas a larger reflective area to effectively direct the central light to the transverse (horizontal) direction, but not limited thereto.

As shown inFIG.2, the light guide sheet220has a plurality of light-exit portions228, which is configured to direct the light upward out of the light guide sheet220. For example, the plurality of light-exit portions228is disposed on the bottom surface of the light guide sheet220and preferably corresponds to the peripheral holes102′. The light-exit portion228can be any suitable optical microstructure, so when the light encounters the light-exit portion228, the light will scatter upward out of the light guide sheet220. Specifically, the vertical projection of the plurality of light-exit portions228on the baseplate10preferably does not overlap the inner rib104to form an exit-free region226. In this embodiment, the exit-free region226preferably corresponds to the vertical projections of the inner rib104and the central hole102on the light guide sheet220. From another aspect, the plurality of light-exit portions228is preferably not disposed in the top clearance region272and the bottom clearance region274to reduce the chance and amount of light outputting from the central hole102, increase the recycle of light from the central region, and increase the proportion of light traveling along the transverse (horizontal) direction.

Referring toFIG.2andFIG.2A, the transverse propagation and recycle of the light of the illuminated keyswitch structure of the invention will be further described. As shown inFIG.2andFIG.2A, since the first coating212is closer to the light guide sheet220than the second coating214is and covers right above the light source hole222, when the light emitted from the light-emitting element250toward the central hole102encounters the first coating212(i.e., the first central coating portion212a), most of the light will be reflected from the first coating212into the light guide sheet220due to the presence of the top clearance region272. Since the light-exit portions228are not disposed in the exit-free region226of the light guide sheet220(e.g. the region corresponding to the central hole102and the inner rib104), the light entering the light guide sheet220will be repeatedly reflected in the light guide sheet220along the transverse direction. Even when a portion of light is reflected to the top glue262(or the bottom glue264) and emitted out of the light guide sheet220, because the top glue262(or the bottom glue264) overlaps the first coating212and the reflective layer230in the stacked direction, the light can be reflected back to the light guide sheet220to effectively achieve the light recycle and transverse propagation, not only reducing the amount of light output from the central hole102(i.e., preventing the central character of the keycap12from being too bright), but also promoting the light output from the peripheral portion of the keycap12(i.e., enhancing the luminance uniformity). Moreover, the size of the portion of the second coating214located in the central hole102(i.e., the second central coating portion214a) can be modified based on the desired light output from the central hole102to at least partially block the light that passes through the first coating212, so as to further modulate the luminance uniformity. In addition, since the light-exit portions228are disposed corresponding to the peripheral holes102′, and the first coating212can be further disposed corresponding to the bridge ribs106, the light emitted from the light guide sheet220toward the bridge ribs106can be reflected from the first coating212back into the light guide sheet220and propagate to the light-exit portions228to be emitted out of the peripheral holes102′. As such, the amount of light output from the peripheral holes102′ can be increased to enhance the luminance uniformity.

Moreover, as shown inFIG.2A, the reflective layer230can be provided with microstructures238, which are disposed further away from the light-emitting element250and configured to guide the light upward. When the microstructures238are disposed to overlap the light-exit portions228of the light guide sheet220in the stacked direction, the light output can be increased. When the microstructures238are disposed to overlap the non-light exit portion of the light guide sheet220in the stacked direction, such as overlapping the bridge rib106of the baseplate10, the recycle of light can be facilitated.

Referring toFIG.5,FIG.5is a schematic plan view of the stack of certain components of the illuminated keyswitch structure in another embodiment of the invention. As shown inFIG.5, the illuminated keyswitch structure (or the backlit module) further includes at least one side glue268, and the side glue268is preferably disposed along the side of the keycap12. The vertical projection of the plurality of light-exit portions on the mask film210is preferably located between the top glue262and the side glue268or between the bottom glue264and the side glue268. Specifically, the light-exit portions are located between the light guide sheet220and the reflective layer230. For example, the plurality of light-exit portions can be the light-exit portions228formed on the bottom surface of the light guide sheet220or the microstructures230formed on the upper surface of the reflective layer230, and configured to guide the light upward. The side glue268can be disposed between the mask film210and the driving circuit board240, between the mask film210and the light guide sheet220, between the driving circuit board240and the light guide sheet220, and/or between the mask film210and the reflective layer230, and configured to enhance the adhesion between thereof. In this embodiment, the side glue268is preferably disposed parallel to the side of the keycap12and located outside of the vertical projection of the keycap12, but not limited thereto.

Referring toFIG.6andFIG.7,FIG.6is a schematic cross-sectional view of the illuminated keyswitch structure in another embodiment of the invention, andFIG.7is a schematic plan view of the stack of certain components of the illuminated keyswitch structure in another embodiment of the invention. As shown inFIG.6andFIG.7, the illuminated keyswitch structure further has a through hole103. The through hole103penetrates through the baseplate10, the mask film210, the light guide sheet220, the reflective layer230, and the driving circuit board240and functions as a dissipation hole or a structural hole of the illuminated keyswitch structure. Corresponding to the disposition of the through hole103, the illuminated keyswitch structure further includes a through-hole top glue262aand a through-hole bottom glue264a. The through-hole top glue262ais disposed over the light guide sheet220around the through hole103. The through-hole bottom glue264ais disposed under the light guide sheet220around the through hole103. For example, the through hole103is preferably disposed adjacent to the outer side of the keycap12or in the key gap between adjacent keyswitches. The first coating212(such as the first peripheral coating portion212b) and the second coating214(such as the second peripheral coating portion214b) are disposed surrounding the through hole103. The first coating212preferably retreats from the through hole103with respect to the second coating214to form a modulation region216.

Specifically, the first coating212can include the first central coating portion212aand the first peripheral coating portion212b, which can be simultaneously formed by the printing process on the lower surface of the mask film210at locations corresponding to the central hole102and the through hole103, respectively. The second coating214can include the second central coating portion214aand the second peripheral coating portion214b, which can be formed simultaneously by the printing process on the upper surface of the mask film210at locations corresponding to the central hole102and the through hole103, respectively, but not limited thereto. The second peripheral coating portion214bpreferably extends to the edge of the through hole103. As shown inFIG.7, the edge214b1of the second peripheral coating portion214bis aligned with the edge of the through hole103. The first peripheral coating portion212bis spaced apart from the edge of the through hole103at the mask film210to form the modulation region216. As shown inFIG.7, the edge212b1of the first peripheral coating portion212band the edge of the through hole103(or the edge214b1of the second peripheral coating portion214b) has a gap therebetween, and the first peripheral coating portion212bfurther retreats with respect to the edge105of the through hole103at the baseplate10. In other words, the first peripheral coating portion212bdoes not extend to the edge of the through hole103(e.g. the edge214b1) and does not extend to the edge105of the baseplate10. That is, the first peripheral coating portion212bis not disposed in the modulation region216. Accordingly, the second peripheral coating portion214bextends closer to the through hole103than the first peripheral coating portion212b. In other words, the aperture of the second peripheral coating portion214bis smaller than that of the first peripheral coating portion212b. With such configurations, the modulation region216provided without the first peripheral coating portion212bcan reduce the chance of reflecting light into the through hole103, and the second peripheral coating portion214bcan block the light emitting upward from the modulation region216, so as to reduce the light leakage from the through hole103. Moreover, the illuminated keyswitch structure can optionally include a third coating (not shown). The third coating is disposed in the modulation region216and configured to substantially block or absorb light. For example, the third coating can be disposed on the lower surface of the mask film210between the first peripheral coating portion212band the edge of the through hole103. Specifically, according to practical applications, the modulation region216can be provided with the third coating having a lower transmittance to reduce the upward light that passes through the modulation region216, further reducing the light leakage from the through hole103. The transmittance of the third coating is preferably smaller than the transmittance of the first coating212, and the third coating can be the same or different light-blocking materials as the second coating214. For example, the third coating can be a black ink coating. Similarly, the reflective layer230can retreat with respect to the edge of the through hole103, so a modulation region234can be formed between the reflective layer230and the edge of the through hole103. The modulation region234can be provided with a fourth coating (not shown), which has a lower reflectivity (or higher absorptivity), to reduce the upward light reflected from the modulation region234and reduce the light that is inclinedly reflected forward, further reducing the light leakage of the through hole103. The reflectivity of the fourth coating is preferably smaller than the reflectivity of the reflective layer230, and the fourth coating can be the same or different light-blocking materials as the second coating214. For example, the fourth coating can be a black ink coating on the upper surface of the driving circuit board240between the reflective layer230and the edge of the through hole103. With such configurations, the modulation region234provided without the reflective layer230(or with the fourth coating) can reduce the chance of reflecting the light into the through hole103, so as to reduce the light leakage from the through hole103. In another embodiment, the fourth coating can be a light-absorbing cladding material (such as the cladding layer280) on the backside (the lower side) of the driving circuit board240and exposed upward for absorbing light due to the modulation region234formed by retreating the reflective layer230. Alternatively, the modulation region234is not necessarily formed by retreating the reflective layer230, the fourth coating can be directly disposed on the reflective layer230around the through hole103to function as the modulation region234for absorbing light. In other words, no matter the fourth coating is disposed on the reflective layer230or on the driving circuit board240, the light leakage from the through hole103can be effectively reduced. Moreover, if necessary, the edge portions of the mask film210and the driving circuit board240around the through hole103can be attached to each other in the through hole103by glue (not shown).

At least one of the through-hole top glue262aand the through-hole bottom glue264aoverlaps the first coating212(i.e., the first peripheral coating portion212b) in the stacked direction (such as Z-axis direction). The through-hole top glue262aand the through-hole bottom glue264aare preferably spaced apart from the edge of the through hole103at the light guide sheet220to form a top through-hole clearance region276and a bottom through-hole clearance region278therebetween, respectively. Specifically, the through-hole top glue262aand the through-hole bottom glue264aare disposed around the through hole103and configured to direct a certain proportion of light to the vertical direction (i.e., the stacked direction), reducing the amount of light leaking from the through hole103. Moreover, the vertical projection of the first coating212(i.e., the first peripheral coating portion212b) on the light guide sheet220preferably completely covers (overlaps) the through-hole top glue262a(and the through-hole bottom glue264a). The through-hole top glue262a(and the through-hole bottom glue264a) is preferably completely located within the vertical projections of the first coating212(i.e., the first peripheral coating portion212b) and the second coating214(i.e., the second peripheral coating portion214b). As such, the amount of light entering the through hole103via the through-hole top glue262a(and the through-hole bottom glue264a) can be effectively reduced, so as to reduce the light leakage from the through hole103.

The top through-hole clearance region276and the bottom through-hole clearance region278are the top surface portion and the bottom surface portion of the light guide sheet220around the through hole103, which are provided without the through-hole top glue262aand the through-hole bottom glue264a, respectively. The top through-hole clearance region276and the bottom through-hole clearance region278preferably correspond to each other in the stacked direction (such as Z-axis direction). As such, the through-hole top glue262aor the through-hole bottom glue264acan be prevented from entering the through hole103to interfere with heat dissipation or positioning and also reduce the amount of light entering the through hole103via the through-hole top glue262a(the through-hole bottom glue264a), so as to effectively reduce the light leakage from the through hole103. In an embodiment, the top through-hole clearance region276and the bottom through-hole clearance region278can be optionally provided with a fifth coating (not shown), which has a lower reflectivity (or higher absorptivity), to reduce the light entering the through hole103, further reducing the light leakage from the through hole103. The fifth coating can be the same or different light-blocking materials as the second coating214. For example, the fifth coating can be a black ink coating.

As shown inFIG.6, in this embodiment, the illuminated keyswitch structure can further include the cladding layer280. The cladding layer280is disposed under the driving circuit board240and extends to the projection of the through hole103. The cladding layer280can extend flatly to at least cover under the through hole103and can be processed to further extend into the through hole103. The cladding layer280preferably has a higher absorptivity to absorb the light in the through hole103, so as to reduce the light leakage from the through hole103. In an embodiment, the cladding layer280can extend into the through hole103and can be further attached or adhered to the second coating214(i.e., the second peripheral coating portion214b). In an embodiment, the aperture of the second peripheral coating portion214b(such as the length of the edge214b1in the X-axis direction) is preferably smaller than the aperture of the through hole103at the baseplate10(such as the length of the edge105in the X-axis direction), the aperture of the through hole103at the light guide sheet220, and the aperture of the through hole103at the driving circuit board240. Corresponding to the through hole103, the aperture of the cladding layer280is preferably smaller than the aperture of the through hole103at the baseplate10(such as the length of the edge105in the X-axis direction), the aperture of the through hole103at the light guide sheet220, the aperture of the through hole103at the driving circuit board240, and the aperture of the through hole103at the reflective layer230.

It is noted that when the illuminated keyswitch structure of the invention is applied to the keycap with characters mostly located at corners, only small amount of light (or even no light) directly emitted upward from the light-emitting element250is required, so the size of the central hole102of the baseplate10can be reduced, or the central hole102can even be omitted, but not limited thereto. In another embodiment, by increasing the size of the portion of the first coating212that covers right above the light-emitting element250(such as the first central coating portion212a) or by forming the first coating212with metal materials, the reflectivity can be promoted, the amount of light propagating along the transverse direction can be increased, and the brightness at the peripheral portion (e.g. corners) of the keycap can be enhanced.

FIG.8AtoFIG.8Dare schematic plan views of the layout of glue layers in various embodiments of the invention, wherein the right hatched region represents the distribution region of the top glue262, and the left hatched region represents the distribution region of the bottom glue264. As shown inFIG.8A, in a first embodiment, each of the top glue262and the bottom glue264surrounds the light source hole222to form a closed-ring coating region. As shown inFIG.8B, in a second embodiment, the top glue262surrounds the light source hole222to form a closed-ring coating region, and the bottom glue264partially surrounds the light source hole222to form an open-ring coating region. For example, in the sector region263, only the top glue262is disposed on the top surface of the light guide sheet220, and the bottom glue264is not disposed on the bottom surface of the light guide sheet220. As shown inFIG.80, in a third embodiment, the top glue262surrounds the light source hole222to form a closed-ring coating region, and the bottom glue264partially surrounds the light source hole222to form an open-ring coating region with an auxiliary coating region at the opening of the open-ring coating region. For example, in the sector region263, only the top glue262is disposed on the top surface of the light guide sheet220, and only an auxiliary portion of the bottom glue264is disposed on the bottom surface of the light guide sheet220. For example, the bottom glue264is disposed on the bottom surface of the light guide sheet220in the enhancement region266as the auxiliary portion, and the enhancement region266partially overlaps the section region263. As shown inFIG.8D, in a fourth embodiment, each of the top glue262and the bottom glue264surrounds the light source hole222to form a closed-ring coating region. In this embodiment, the top glue262is spaced apart from the edge of the light source hole222to form the top clearance region272with no glue, and the bottom glue264is spaced apart from the edge of the light source hole222to form the bottom clearance region274with no glue.

Although the preferred embodiments of the invention have been described herein, the above description is merely illustrative. The preferred embodiments disclosed will not limit the scope of the invention. Further modification of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.