Patent Publication Number: US-2023138295-A1

Title: Keyboard backlight module and applications thereof

Description:
This is a Continuation of U.S. application Ser. No. 17/521,525, filed Nov. 8, 2021, which is a Continuation of U.S. application Ser. No. 16/904,276, filed Jun. 17, 2020 (now U.S. Pat. No. 11,170,950), which claims the benefits of U.S. provisional application Ser. No. 62/863,251, filed Jun. 18, 2019, and People&#39;s Republic of China application Serial No. 202010510100.4, filed Jun. 8, 2020, the subject matters of which are incorporated herein by reference. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a backlight module, and more particularly to a keyboard backlight module and a backlit keyboard applying the same. 
     Description of Background 
     An input device is often used as a communication medium between users and electronic devices. A common input device, such as a keyboard, includes a plurality of key switches arranged in a block. The users can access the electronic device to perform corresponding functions by pressing different key switches. In order to enable the human eye to clearly see the symbols on each key switch in a low-light environment, backlight module technology is introduced into the keyboard, in which light generated by a keyboard backlight module is project to the backside of each keycap of the keyboard; then a portion of the light passes through the keycaps and emits outwards resulting in a backlight effect, so that the users can clearly see the symbols on the key switches during operation. 
     SUMMARY 
     The object of the present disclosure is to provide a keyboard backlight module and a backlit keyboard applying the same to improve the light-emitting uniformity thereof. 
     One aspect of the present disclosure is to provide a keyboard backlight module, wherein the keyboard backlight module includes a light guide plate, a reflector, a light-emitting device and a first microstructure. The light guide plate has an output surface, a light guide pattern and a bottom surface disposed on an opposite side of the output surface. The light guide pattern is arranged on at least one of the bottom surface and the output surface. The reflector has a reflecting surface facing the bottom surface. The light-emitting device is disposed on one side of the light guide plate and configured to provide an incident light to the reflecting surface. The first microstructure is disposed on the reflecting surface, at least partially overlaps with the light guide pattern, wherein a first reflected light is formed by a portion of the incident light via the first microstructure. 
     In one embodiment of the present disclosure, the reflecting surface has a first region and a second region, the distance between the first region and the light-emitting element is smaller than the distance between the second region and the light-emitting element; and the portion of the first microstructure disposed in the first region has a configuration different from that of the portion of the first microstructure disposed in the second region. 
     In one embodiment of the present disclosure, the first microstructure is a light-absorbing feature, the reflecting surface has a first region and a second region with substantially equal areas, the first region is closer to the light-emitting device than the second region, and a first area occupied by a portion of the first microstructure disposed in the first region is larger than a second area occupied by another portion of the first microstructure disposed in the second region. 
     In one embodiment of the present disclosure, the first microstructure has at least one first reflective surface facing the light-emitting device, and the first reflective surface and the reflecting surface form a first angle less than or equal to 90°. 
     In one embodiment of the present disclosure, the reflecting surface has a first region and a second region with substantially equal areas, the first region is closer to the light-emitting device than the second region, there is a first number of the first reflective surfaces disposed in the first region and a second number of the first reflecting surfaces disposed in the second region, and the first number is smaller than the second number. 
     In one embodiment of the present disclosure, the keyboard backlight module further includes a second microstructure configured to transform the incident light into a second reflected light, wherein the reflecting surface has a first region and a second region with substantially equal areas; the first region is closer to the light-emitting device than the second region; the first microstructure is disposed in the first region and the second microstructure is disposed in the second region; the second microstructure has at least one second reflective surface facing the light-emitting device, and the second reflective surface and the reflecting surface form a second angle smaller than the first angle. 
     In one embodiment of the present disclosure, the keyboard backlight module further includes a second microstructure configured to transform the incident light into a second reflected light, wherein the reflecting surface has a first region and a second region with substantially equal areas; the first region is closer to the light-emitting device than the second region; the first microstructure is disposed in the first region and has a first light-shielding area; and the second microstructure is disposed in the second region and has a second light-shielding area smaller than the first light-shielding area. 
     In one embodiment of the present disclosure, the light guide pattern has a first number of at least one light-guiding dot corresponding to the first region and a second number of at least one light-guiding dot corresponding to the second region, and the first number is smaller than the second number. 
     In one embodiment of the present disclosure, the first microstructure includes at least one protruding portion convexly protruding outwards from the reflecting surface, or at least one concave portion concavely recessed inwards to the reflector from the reflecting surface. 
     In one embodiment of the present disclosure, the keyboard backlight module further includes at least one light-absorbing material at least partially overlapping the protruding portion or the concave portion. 
     In one embodiment of the present disclosure, the light guide pattern has at least one light-guiding dot; and a single unit of the first microstructure has an area larger than an area of a single unit of the light-guiding dot. 
     Another aspect of the present disclosure is to provide a backlit keyboard, wherein the backlit keyboard includes a key switch module having at least one key switch and the keyboard backlight module as described above. The key switch module of the backlit keyboard is disposed on one side of the keyboard backlight module. 
     In one embodiment of the present disclosure, a portion of the light guide pattern and a portion of the first microstructure are correspondingly arranged below the at least one key switch. 
     In accordance with the embodiments of the present disclosure, a keyboard backlight module and a backlit keyboard applying the same are provided, wherein the keyboard backlight module includes a light guide, a reflector and at least one light-emitting device. It is characterized in that at least one microstructure is formed on a reflecting surface of the reflector to make it at least partially overlapping with a light guide pattern disposed on the light guide plate. A portion of the light that is provided by the light-emitting device, passing through the light guide plate and projected to the reflecting surface are lock and absorbed, or changed in the reflection direction by the microstructure, such that the intensity of the reflected light that comes from different regions of the reflecting surface can be adjusted, meanwhile the intensity of backlight that exits through different positions on the output surface of the light guide plate can be changed. 
     In one embodiment of the present disclosure, the reflecting surface of the reflector can be divided into a first region and a second region with substantially equal areas, and a first microstructure and a second microstructure with different sizes, patterns, materials, colors or structures are formed on these two regions respectively. The incident light emitted by the light-emitting device can be reflected by the first region and the second region to obtain two different kinds of reflected light having different intensities respectively passing through different regions of the output surface of the light guide plate. Thus, after these two different kinds of reflected light mixing with other light emitted from the output surface of the light guide plate, the uneven light emission phenomenon of the light guide plate both occurring on the region (corresponding to the first region) close to the light-emitting device and on the region (corresponding to the second region) far from the light-emitting device can be effectively neutralized. Whereby, the backlight uniformity of the keyboard backlight module can be significantly improved. 
     In one embodiment of the present disclosure, the first microstructure and the second microstructure may be a light-absorbing feature, and the area covered by the first microstructure is larger than the area covered by the second microstructure. In one embodiment of the present disclosure, the first microstructure and the second microstructure respectively have a reflective surface that can form a first angle and a second angle both less than or equal to 90° with the reflecting surface. Two different kinds of reflected light can be obtained when an incident light is respectively reflected with the first angle and the second angle; and these two different kinds of reflected light have lower intensity when they pass through the output surface of the light guide plate. By applying the above embodiments, the uneven light emission phenomenon of the light guide plate both occurring on the region close to the light-emitting device and on the region far from the light-emitting device can be effectively neutralized; the optical design of the keyboard backlight module can be optimized, and the light emitting uniformity of the keyboard backlight module can be increased. Whereby, the display effect of the backlit keyboard applying the above keyboard backlight module can be improved. 
     The above objects and advantages of the present disclosure will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a top view illustrating the structure of a keyboard backlight module according to one embodiment of the present disclosure; 
         FIG.  1 B  is a cross-sectional view of the keyboard backlight module take along the cutting line S 1  depicted in  FIG.  1 A ; 
         FIGS.  2 A- 2 C  are top views illustrating partial structures of a plurality of keyboard backlight modules according to some embodiments of the present disclosure; 
         FIG.  3    is a cross-sectional view illustrating the structure a keyboard backlight module according to another embodiment of the present disclosure; 
         FIG.  4 A  is a top view illustrating the structure of a keyboard backlight module according to yet another embodiment of the present disclosure; 
         FIG.  4 B  is a cross-sectional view of the keyboard backlight module take along the cutting line S 4  depicted in  FIG.  4 A ; 
         FIG.  5    is a cross-sectional view illustrating the structure a keyboard backlight module according to further embodiment of the present disclosure; 
         FIGS.  6 A- 6 B  are top views illustrating partial structures of a plurality of keyboard backlight modules according to some embodiments of the present disclosure; 
         FIG.  7    is a cross-sectional view illustrating the structure a keyboard backlight module according to still another embodiment of the present disclosure; and 
         FIG.  8    is a prospective view illustrating the structure of a backlit keyboard applying the keyboard backlight module as described above according to one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments as illustrated below provide a keyboard backlight module and a backlit keyboard applying the same, which can improve the light emitting uniformity of the keyboard backlight module. The present disclosure will now be described more specifically with reference to the following embodiments illustrating the structure and arrangements thereof. 
     It is to be noted that the following descriptions of preferred embodiments of this disclosure are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. Also, it is important to point out that there may be other features, elements, steps, and parameters for implementing the embodiments of the present disclosure which are not specifically illustrated. Thus, the descriptions and the drawings are to be regard as an illustrative sense rather than a restrictive sense. Various modifications and similar arrangements may be provided by the persons skilled in the art within the spirit and scope of the present disclosure. In addition, the illustrations may not be necessarily drawn to scale, and the identical elements of the embodiments are designated with the same reference numerals. 
       FIG.  1 A  is a top view illustrating the structure of a keyboard backlight module  100  according to one embodiment of the present disclosure; and  FIG.  1 B  is a cross-sectional view of the keyboard backlight module  100  take along the cutting line S 1  depicted in  FIG.  1 A . The keyboard backlight module  100  includes a light guide plate  101 , a reflector  102 , at least one light-emitting device  103 , at least one microstructure  104 , and a light-shielding layer  107 . 
     The light guide plate  101  has an output surface  101   a  and a bottom surface  101   b  disposed on an opposite side of the output surface  101   a.  In some embodiments of the present disclosure, the light guide plate  101  may be an optical sheet made of an optical material with high reflectivity that does not absorb light, such as polymethyl methacrylate (PMMA), polycarbonate (PC), or cyclo-olefin polymer (COP). And the light guide plate  101  may include a light guide pattern protruding upwards or recessed inwards from the bottom surface  101   b  or the light-emitting surface  101   a  or both using a screen-printing technology. For example, in some embodiments of the present disclosure, the light guide pattern may include a plurality of light-guiding dots  101   c  that are circular, square, triangular, polygonal, or other shapes. In one embodiment, the light-guiding points  101   c  of the light guide plate  101  can be formed by a continuous roll to roll fabrication process, in which a plurality of light scattering dots and/or V-cutting pattern may be directly pressed to imprint on the light guide plate  101 , when the material is hot pressed for forming the light guide plate  101 . Since the continuous roll to roll fabrication process has technical limits on size shrinkage and pattern complexity, thus the light guide pattern corresponding to different key switches may be designed, for example, as having a plurality of light guide dots  101   c  with the same pitch. 
     The incident light L 1  emitted by the light-emitting device  103  propagates inside the light guide plate  101  by total internal reflection of light. When the incident light L 1  is projected onto light-guiding dots  101   c,  the conditions of refraction can no longer be satisfied, thereby lights diffused to various angles may be generated and then pass through the output surface  101   a  to form the backlight of the keyboard backlight module  100 . Wherein a portion of the incident light L 1 ′ diffused downward through the bottom surface  101   b  of the light guide plate  101  will be reflected by the reflector  102  to form the reflected light L 1   r  returning to the light guide plate  101 , and then exiting through the output surface  101   a  to form a portion of the backlight projecting to the keyboard backlight module  100 . 
     The light-shielding layer  107  is disposed outside the light-emitting surface  101   a  of the light guide plate  101 , and includes a patterned light-shielding portion, such as a black matrix, and a plurality of light-transmitting portions  107   a  that allows the light that passes through the light-emitting surface  101   a  projecting outwards from define the predetermined positions. Each of the light-transmitting portions  107   a  can be arranged corresponding to a key switch to make the light selectively passing through the light-transmitting portion  107   a  projecting to the backside of the corresponding key switch and to shield the positions where do not require light (such as the positions between two adjacent key switches) to avoid light leakage. In the present embodiment, the light-shielding layer  107  may include a transparent or white substrate (not shown) that can transmit light, a patterned white reflective layer (not shown) coated on the substrate, and a black matrix (not shown), wherein the white reflective layer is disposed, for example, on the side (the lower side of the substrate) facing the output surface  101   a  of the light guide plate  101 , and the black matrix is located, for example, on the opposite side (upper side of the substrate) of the patterned white reflective layer. 
     The reflector  102  is disposed below the light guide plate  101  and has a reflecting surface  102   c  facing the bottom surface  101   b,  which can reflect the incident light L 1 ′ diffused downward through the bottom surface  101   b  of the light guide plate  101  to form the reflected lights Li r retuning back to the light guide plate  101 . In some embodiments of the present disclosure, the material constituting the reflector  102  may include polyethylene terephthalate (PET). Alternatively, the reflector  102  may be made by a polyethylene terephthalate-based substrate coated with other higher reflectivity materials (such as metal) on the reflecting surface  102   c  by performing a post-treatment. The reflector  102  generally has a reflectivity greater than 95%. 
     The light-emitting device  103  is disposed on a circuit layer  106  and located on one side of the light guide plate  101 . In some embodiments of the present disclosure, the light-emitting device  103  may be a light emitting diode (LED) device that can emit red colored light (R), green colored light (G), or blue colored light (B); or a LED device that can emit white light. In the present embodiment, the circuit layer  106  that has a plurality of light-emitting devices  103  disposed thereon is located one side of the light guide plate  101  and adjacent to a sidewall  101   d  of the light guide plate  101 . Wherein, the sidewall  101   d  of the light guide plate  101  is perpendicular to and connected to (but not limited thereto) both the output surface  101   a  and the bottom surface  101   b.  In one embodiment, the circuit layer  106  can be a flexible circuit board disposed under the light-shielding layer  107 , and the light-emitting devices  103  electrically connected to the flexible circuit board can pass through the light-shielding layer  107  to be adjacent to the sidewall  101   d  of the light guide plate  101 , so that the light emitted by the light-emitting devices  103  can come into the light guide plate  101  from the sidewall  101   d.  In another embodiment, the light guide plate  101  may alternatively have an opening (not shown) formed on the sidewall  101   d,  the inner sidewall of the opening may serve as the light incident surface, and one of the light-emitting devices  103  is disposed in the opening of the light guide plate  101 , so that the light emitted by the light-emitting device  103  can come into the light guide plate  101  from the inner side wall of the opening. In other words, the light incident surface of the light guide plate  101  may be, for example, located on the vertical sidewall  101   d  of the light guide plate  101  or the inner wall of the opening formed on the vertical sidewall  101   d.    
     In recent years, as the light guide plate  101  becomes thinner, the diffusion effect (total internal reflection) of the light guide plate  101  becomes worse. Therefore, more diffused light usually passes through the region of the output surface  101   a,  close to the light-emitting device  103 , which causes the problem of uneven light output (emission). In some embodiments of the present disclosure, by adjusting the number or area ratio of the light-guiding dots  101   c  in different regions of the bottom surface  101   b  of the light guide plate  101 , the intensity of the backlight emitted outward from the region close to the light-emitting devices  103  can be reduced after the diffusion light L 1  passing through the output surface  101   a.  However, due to the technical limitation in the process accuracy and size shrinkage of the light-guiding dots  101   c,  the problem of uneven light output of the keyboard backlight module  100  cannot be completely solved by adjusting the number or area ratio of the light-guiding dots  101   c.    
     In some embodiments of the present disclosure, the problem of uneven light output of the keyboard backlight module  100  can be further improved by providing a plurality of microstructures  104  on the reflecting surface  102   c  of the reflector  102 . For example, in the present embodiment, the microstructures  104  can be a light-absorbing feature covering the reflecting surface  102   c  of the reflector  102  and overlapping at least a portion of the light-guiding dots  101   c  of the light guide plate  101 , and can be used to block or absorb a portion of the incident light L 1 ′ that diffuses downward and passes through the bottom surface  101   b  of the light guide plate  101 . Such that, the portion of the incident light L 1   r  reflected by the reflector  102  and returning to the light guide plate  101  can be reduced. 
     The reflector  102  has a first region  102 A and a second region  102 B, wherein the first region  102 A is relatively close to the light-emitting devices  103 . The distance between the first region  102 A and the light-emitting devices  103  is smaller than the distance between the second region  102 B and the light-emitting devices  103 . Therefore, under the condition without applying the microstructure  104 , the keyboard backlight module  100  may have a light output corresponding to the first region  102 A with a stronger intensity than that corresponding to the second region  102 B. In other words, the problem of uneven light output from the keyboard backlight module  100  can be improved by adjusting the distribution density of the microstructures  104  in different regions of the reflecting surface  102   c  of the reflector  102  (corresponding to different regions of the bottom surface  101   b  of the light guide plate  101 ). For example, larger number and denser microstructures  104  are provided in the first region  102 A of the reflecting surface  102   c  of the reflector  102  near the light-emitting devices  103 , and less and sparse microstructures  104  are provided in the second region  102 B of the reflecting surface  102   c  of the reflector  102  far from the light-emitting devices  103  (as shown in  FIG.  1 B ). 
     In one embodiment of the present disclosure, the areas of the first region  102 A and the second region  102 B are equal, and the area of the first region  102 A covered by the microstructures  104  is larger than the area of the second region  102 B covered by the microstructures  104 . In another embodiment of the present disclosure, the densities of the microstructures  104  in the first region  102 A and the second region  102 B are exactly opposite to the numbers or area ratios of the light-guiding dots  101   c  arranged in different regions of the bottom surface  101   b  of the light guide plate  101  that are corresponding to the first region  102 A and the second region  102 B respectively. In other words, the number of light-guiding dots  101   c  disposed on the region of the bottom surface  101   b  corresponding to the first regions  102 A is smaller than the number of light-guiding dots  101   c  disposed on the region of the bottom surface  101   b  corresponding to the second regions  102 B. In the present embodiment, there may not have any microstructure  104  formed in the second region  102 B of the reflecting surface  102   c  of the reflector  102  far away from the light-emitting devices  103 . 
     In addition, the shape of the microstructures  104  is not limited. On a top view of the microstructures  104 , the shape of the microstructures  104  may be circular, square, triangular, polygonal, circular, or various patterns with regular or irregular arc sides; and one single unit of the microstructures  104  may have an area larger than that of one single unit of the light-guiding dots  101   c.  The material constituting the microstructure  104  is not limited, and any material that can prevent reflection or absorption of light does not exceed the spiritual scope of the material. For example, in some embodiments of the present disclosure, the microstructure  104  may be made of a black opaque material or a semi-transparent material with single or multiple gray levels, such as printing ink. 
     It should be appreciated that adjusting the distribution density of the microstructures  104  in different regions of the reflecting surface  102   c  of the reflector  102  does not limit to use the distance to the light-emitting devices  103  as a reference standard. It is also not limited to use the coverage ratio of the microstructures  104  to reflecting surface  102   c  of the reflector  102  as a reference to adjust the light uniformity of the key backlight module  100 . Those with ordinary knowledge in the art can adjust the distribution density, shape, area or light absorption characteristics of the microstructures  104  disposed in different regions of the reflecting surface  102   c  of the reflector  102  (or other factors that can affect the reflective characteristics of the microstructures  104 ) according to any parameters that affect the light uniformity of the keyboard backlight module  100  to solve the problem of uneven light output of the keyboard backlight module  100 . 
       FIGS.  2 A- 2 C  are top views illustrating partial structures of a plurality of keyboard backlight modules  200 ,  200 ′ and  200 ″ according to some embodiments of the present disclosure. For the purpose of clear description, the light-shielding layer  107  and the light-emitting devices  103  are omitted, and only the arrangement and distribution of the microstructures  204  on the reflector  202  and their relative positions with the light-guiding dots  101   c  of the light guide plate  101  are shown. 
     As shown in  FIG.  2 A , both the microstructures  204  and the light-guiding dots  101   c  may be circular, and the number and density of the microstructure  204  and the light-guiding dots  101   c  may be approximately the same. The structure of the keyboard backlight module  200 ′ shown in  FIG.  2 B  is substantially similar as that of the keyboard backlight module  200  shown in  FIG.  2 A , the main difference is that the distribution density of the microstructures  204 ′ disposed on the reflector  202 ′ is smaller than the distribution density of the light-guiding dots  101   c.  In addition, the shape of the microstructure  204 ″ is not limited to a circle. As shown in  FIG.  2 C , the microstructure  204 ″ disposed on the reflector  202 ″ may be elongated. 
       FIG.  3    is a cross-sectional view illustrating the structure a keyboard backlight module  300  according to another embodiment of the present disclosure. The structure of the keyboard backlight module  300  is substantially similar as that of the keyboard backlight module  100  as shown in  FIG.  1 B , the main difference is that the keyboard backlight module  300  further includes another microstructure  304  disposed on the reflecting surface  102   c  of the reflector  102 . In the present embodiment, the microstructures  304  and the microstructures  104  are both light-absorbing features. The only difference therebetween is that a single unit of the microstructures  304  has an area different from that of a single unit of the microstructures  104 , and these two have different distribution densities. The microstructure  304  is disposed in the second region  102 B away from the light-emitting devices  103 , and a single microstructure  304  has an area larger than that of a single microstructure  104 . The area of the first region  102 A occupied (overlapped) by the microstructure  104  is substantially larger than the area of the second region  102 B occupied by the microstructure  304 . In other words, the density of the microstructures  104  disposed in the first region  102 A is significantly greater than the density of microstructures  304  with different sizes disposed in the second region  102 B. By disposing different microstructures  104  and  304  on the reflecting surface  102   c  of the reflector  102 , the uneven light output of the keyboard backlight module  300  can be further improved. 
     However, it should be appreciated that the shape, size, number, and pattern distribution of the microstructure  104  and  304  are not limited thereto. Any of the light-shielding/light-absorbing structures that meet the requirements for solving the problems of uneven light output does not exceed the spirit of the microstructures  104  and  304  described in the present disclosure. Those with skilled in the art can arbitrarily adjust the shape, size, color, material or graphic distribution of the microstructures  104  and  304  according to the design requirements of the keyboard backlight module  300 . 
     After the incident light L 1  emitted by the light-emitting devices passes through the bottom surface  101   b  of the light guide plate  101 , a portion of the incident light L 1 ′ may be partially blocked or absorbed by the microstructures  104  and  304 , thus merely a remaining portion of the incident light L 1 ′ can be reflected by the reflector  102  to return the light guide plate  101 . By the blocking or absorption of the microstructure  104  and  304 , a portion of the incident light L 1 ′ diffused downward through the bottom surface  101   b  of the light guide plate  101  can be prevented from being reflected by the first region  102 A and the second region  102 B of the reflecting surfaces  102   c  to form the reflected light L 3   r,  such that the backlight passing through the output surface  101   a  of the light guide plate  101  to exit outward can be reduced. The intensity of the backlight respectively emitted outward from the regions of the output surface  101   a  corresponding to the first region  102 A and the second region  102 B can be reduced. However, because the area of the microstructure  104  shielding the first region  102 A is larger than the area of the microstructure  304  shielding the second region  102 B, the intensity of the backlight emitted from the region of the output surface  101   a  of the light guide plate  101  corresponding to the first region  102 A is less than that of the backlight emitted from the region of the output surface  101   a  corresponding to the second region  102 B. Therefore, the problem of uneven light output (emission) of the keyboard backlight module  300  can be improved. 
       FIG.  4 A  is a top view illustrating the structure of a keyboard backlight module  400  according to yet another embodiment of the present disclosure; and  FIG.  4 B  is a cross-sectional view of the keyboard backlight module  400  take along the cutting line S 4  depicted in  FIG.  4 A . The structure of the keyboard backlight module  400  is substantially similar as that of the keyboard backlight module  100 , except that the keyboard backlight module  400  has a different arrangement in the light-emitting devices  403 . In the present embodiment, the keyboard backlight module  400  includes a light guide plate  401 , a reflector  102 , a plurality of light-emitting devices  403 , and a microstructure  404 . 
     The plurality of light-emitting devices  403  are disposed on a circuit layer  406  and penetrate through the light guide plate  401 . In detail, the light guide plate  401  has at least one opening  401   d  penetrating through the output surface  401   a  and the bottom surface  401   b;  at least one of the plurality of light-emitting devices  403  (e.g. light-emitting devices  403   a  and  403   b ) has on end connecting to the wiring of the circuit layer  406  and the other end extending into the opening  401   d.    
     The plurality of light-emitting devices  403  are, for example, disposed at the relatively center of the keyboard backlight module  400 , and the light emitted by the light-emitting devices  403   a  and  403   b  respectively propagates to the opposite sides of the keyboard backlight module  400  in the longitudinal direction. The incident light L 41  emitted by the light-emitting device  403   a  can come into the light guide plate  401  through the sidewall  401   e  of the opening  401   d  and propagate inside the light guide plate  401  by total internal reflection. When the incident light L 41  is projected to each of the light-guiding dots  401   c , the conditions of refraction can no longer be satisfied, thereby the incident light L 41  cab be diffused to various angles. Wherein, a portion of the incident light L 41 ′ that is diffused downward and passes through the bottom surface  401   b  of the light guide plate  401  can be reflected by the first region  402 A of the reflector  102  to form a reflected light L 41   r  returning to the light guide plate  401 , and the reflected light L 41   r  then exits outward through the output surface  401   a  to form part of the backlight of the keyboard backlight module  400 . The incident light L 42  emitted by the light-emitting device  403   b  can come into the light guide plate  401  through the sidewall  401   f  of the opening  401   d  and propagate inside the light guide plate  401  by total internal reflection. When the incident light L 42  is projected to each of the light-guiding dots  401   c,  the conditions of refraction can no longer be satisfied, thereby the incident light L 41  cab be diffused to various angles. Wherein, a portion of the incident light L 42 ′ that is diffused downward and passes through the bottom surface  401   b  of the light guide plate  401  can be reflected by the second region  402 B of the reflector  102  to form a reflected light L 42   r  returning to the light guide plate  401 , and the reflected light L 42   r  then exits outward through the output surface  401   a  to form part of the backlight of the keyboard backlight module  400 . 
     The microstructure  404  covers the reflecting surface  102   c  of the reflector  102  and overlaps at least a portion of the light-guiding dots  401   c  of the light guide plate  401 . In the present embodiment, the microstructure  404  can be a light-absorbing feature both cover the first region  402 A and the second region  402 B of the reflecting surface  102   c  of the reflector  102  to block or absorb the portion of the incident light L 41 ′ and L 42 ′ diffused downward and passing through the bottom surface  401   b  of the light guide plate  401 , so as to reduce the reflected light L 41   r  and L 42   r  reflected by the reflector  102  retuning to the light guide plate  401 . The distribution density and coverage area of the microstructures  404  in the first area  402 A and the second area  402 B can be adjusted according to the aforementioned method for improving the backlight uniformity of the keyboard backlight module  400 . For example, a densely distributed microstructure  404  is disposed on the region of the reflecting surface  102   c  closer to the light-emitting devices  403 . Since the adjusting method has been described above, thus it will not be redundantly repeated here. By the blocking or absorption of the microstructure  404 , a portion of the incident light L 41 ′ and L 42 ′ diffused downward through the bottom surface  401   b  of the light guide plate  401  can be prevented from being reflected by the first region  402 A and the second region  402 B of the reflecting surfaces  402   c  to form the reflected light L 41   r  and L 42   r,  such that the backlight passing through the output surface  101   a  of the light guide plate  101  to exit outward can be reduced. The intensity of the backlight respectively emitted outward from the regions of the output surface  401   a  corresponding to the first region  402 A and the second region  402 B can be adjusted or reallocated to achieve the purpose of improving the problem of uneven light output of the keyboard backlight module  400 . 
       FIG.  5    is a cross-sectional view illustrating the structure a keyboard backlight module  500  according to further embodiment of the present disclosure. The structure of the keyboard backlight module  500  is substantially similar as that of the keyboard backlight module  100 , except that the keyboard backlight module  500  has a different arrangement in the microstructure  504 . 
     In the present embodiment, the microstructure  504  can be a concave/convex pattern, which is disposed on the reflecting surface  502   c  of the reflector  502  and overlaps at least a portion of the light-guiding dots  101   c  of the light guide plate  101 . The microstructure  504  is, for example, a micro-prism protruding from the reflecting surface  502   c  of the reflector  502 . The microstructure  504  has at least one reflective surface  504   r  facing the light-emitting devices  103 , and the reflective surface  504   r  and the reflecting surface  502   c  of the reflector  502  form an angle θ1 of less than or equal to 90°. 
     In detail, the microstructure  504  includes at least one protruding portion  504   a,  such as a bar-shaped wedge, a pyramid, or a hairline structure, convexly protruding from the reflecting surface  502   c.  Taking wedge-shaped stripe structures as an example of the protruding portion  504   a,  each of the wedge-shaped stripe structure (protruding portion  504   a ) has a triangular or trapezoid-shaped cross-sectional profile, by which a plurality of trenches  504   b  (formed between two adjacent wedge-shaped stripe structures) can be defined on the reflecting surface  502   c  of the reflector  502 . Wherein, the inclined sidewall of the wedge-shaped strip structures (protruding portion  504   a ) can serve as the reflective surface  504   r,  and it can form the angle θ1 less than or equal to 90° with the reflecting surface  502   c.  In other words, the reflective surface  504   r  is also a sidewall of the trenches  504   b.  In the present embodiment, the protruding portion  504   a  of the microstructure  504  has a triangular cross-sectional profile; and this triangular cross-sectional profile has an apex angle θ2 away from the reflecting surface  502   c  and between 87° and 
     After the incident light L 1  emitted by the light-emitting devices  103  is projected to each light guide point  101   c,  the portion incident light L 1 ′ that is diffused downward and passes through the bottom surface  101   b  of the light guide plate  101  to the reflector  502   be  can be reflected by the reflector  502  to form the reflected light L 5   r  returning to the light guide plate  101 . The reflected light L 5   r  is then projected outward passing through the output surface  101   a  of the light guide plate  101  to serve as a portion of the backlight of the keyboard backlight module  500 . By providing the microstructure  504  on the reflecting surface  502   c  of the reflector  502 , the protruding portion  504   a  can be used to adjust the reflection direction of the portion of the incident light L 1 ′ that is diffused downward through the bottom surface  101   b  of the light guide plate  101 . Thereby, the reflected light L 5   r  has directivity; and the amount of light emitted by the keyboard backlight module  500  and perpendicular to the keycap surface can be increased to improve the performance of the backlit keyboard applying the keyboard backlight module  500 . 
     In addition, by adjusting the angle et the reflection angle of the reflected light L 5   r  can be changed. For example, by adjusting the angle θ1 to be greater than 45°, the reflected light L 5   r  can be mainly shifted away from the direction perpendicular to the output surface  101   a  of the light guide plate  101 , thereby the amount of the reflected light L 5   r  passing through the output surface  101   a  can be reduced, and the backlight intensity of the keyboard backlight module  500  is the decreased. Alternatively, by adjusting the angle θ1 to be less than 45° allows the reflected light L 5   r  to be mainly directed toward the direction perpendicular to the output surface  101   a  of the light guide plate  101 , thereby the amount of the reflected light L 5   r  passing through the output surface  101   a  can be increased; and the backlight intensity of the keyboard backlight module  500  can be thus also increased. 
     The distance between the first region  502 A and the light-emitting devise  103  is smaller than the distance between the second region  502 B and the light-emitting devices  103 . Those skilled in the art can adjust the distribution density of the microstructures  504  in the first region  502 A and the second region  502 B according to the actual light emitting state of keyboard backlight module  500  to further change the intensity of the light L 5   r  emitted outward from different positions of the light guide plate  101  corresponding to the first region  502 A and the second region  502 B. Therefore, the problem of uneven light output of the keyboard backlight module  500  can be improved. In some other embodiments of the present disclosure, the keyboard backlight module  500  may include at least one light-absorbing material  508  at least partially covering the one of the wedge-shaped stripe structures (protruding portion  504   a ) of the microstructure  504  or one of the trenches  504   b.    
       FIGS.  6 A- 6 B  are top views illustrating partial structures of a plurality of keyboard backlight modules  600  and  600 ′ according to some embodiments of the present disclosure. For the purpose of clear description, the light-shielding layer  107  and the light-emitting devices  103  are omitted, and only the arrangement and distribution of the microstructures  604  on the reflector  602  and their relative positions with the light-guiding dots  101   c  of the light guide plate  101  are shown. As shown in  FIG.  6 A , the light-guiding dots  101   c  can be circular, and the microstructure  604  is a wedge-shaped stripe or hairline structure  604   a;  the pitch  604   b  of the wedge-shaped stripe or hairline  604   a  is equal; and the number and density of the microstructure  604  may be greater than the number and density of the light-guiding dots  101   c.  In the microstructure  604 ′ as shown in  FIG.  6 B , the pitch  604   b ′ and the size of the wedge-shaped stripe or hairline structures  604   a ′ can be different, and the distribution density of the microstructure  604 ′ can be smaller than the number and density of the light-guiding dots  101   c.    
       FIG.  7    is a cross-sectional view illustrating the structure a keyboard backlight module  700  according to still another embodiment of the present disclosure. The structure of the keyboard backlight module  500  is substantially similar as that of the keyboard backlight module  100 , except that the keyboard backlight module  700  has a different arrangement in the microstructure  704 . In the present embodiment, the microstructure  704  is a microprism pattern concavely recessed on the reflecting surface  702   c  of the reflector  702 . In other words, the microstructure  704  includes a plurality of concave portions  704   a  recessed inwards the reflector  702  from the reflecting surface  702   c,  and the microstructure  704  may have at least one reflective surface (not shown) facing the light-emitting devices  103 . Since the fabricating method, structure and function of the microstructure  704  are similar to the microstructure  604  of the keyboard backlight module  600  and have been described in detail above, thus they will not be redundantly repeated here. 
     In another embodiment of the present disclosure, the micro structure of the keyboard backlight module can also be a combination of the above-mentioned concave and convex patterns, that is, the reflecting surface of the reflector can be provided with a pattern convexly protruding from the reflecting surface (such as microstructure  504 ) and a pattern concavely recessed downward from the reflecting surface (such as microstructure  704 ). 
       FIG.  8    is a prospective view illustrating the structure of a backlit keyboard  80  applying the keyboard backlight module  100  as described above according to one embodiment of the present disclosure. In the present embodiment, the backlit keyboard  80  includes the keyboard backlight module  100  and a key switch module  81 . The key switch module  81  is composed of a plurality of key switches  801 , disposed on one side of the keyboard backlight module  100 , and facing the output surface  101   a  of the light guide plate  100  of the keyboard backlight module  100 . 
     In accordance with the embodiments of the present disclosure, a keyboard backlight module and a backlit keyboard applying the same are provided, wherein the keyboard backlight module includes a light guide, a reflector and at least one light-emitting device. It is characterized in that at least one microstructure is formed on a reflecting surface of the reflector to make it at least partially overlapping with a light guide pattern disposed on the light guide plate. A portion of the light that is provided by the light-emitting device, passing through the light guide plate and projected to the reflecting surface may be block and absorbed, or changed in the reflection direction by the microstructure, such that the intensity of the reflected light that comes from different regions of the reflecting surface can be adjusted, meanwhile the intensity of backlight that exits through different positions on the output surface of the light guide plate can be changed. 
     In one embodiment of the present disclosure, the reflecting surface of the reflector can be divided into a first region and a second region with substantially equal areas, and a first microstructure and a second microstructure with different sizes, patterns, materials, colors or structures are formed on these two regions respectively. The incident light emitted by the light-emitting device can be reflected by the first region and the second region to obtain two different kinds of reflected light having different intensities respectively passing through different regions of the output surface of the light guide plate. Thus, after these two different kinds of reflected light mixing with other light emitted from the output surface of the light guide plate, the uneven light emission phenomenon of the light guide plate both occurring on the region (corresponding to the first region) close to the light-emitting device and on the region (corresponding to the second region) far from the light-emitting device can be effectively neutralized. Whereby, the backlight uniformity of the keyboard backlight module can be significantly improved. 
     In one embodiment of the present disclosure, the first microstructure and the second microstructure may be a light-absorbing feature, and the area covered by the first microstructure is larger than the area covered by the second microstructure. In one embodiment of the present disclosure, the first microstructure and the second microstructure respectively have a reflective surface that can form a first angle and a second angle both less than or equal to 90° with the reflecting surface. Two different kinds of reflected light can be obtained when an incident light is respectively reflected with the first angle and the second angle; and these two different kinds of reflected light have lower intensity when they pass through the output surface of the light guide plate. By applying the above embodiments, the uneven light emission phenomenon of the light guide plate both occurring on the region close to the light-emitting device and on the region far from the light-emitting device can be effectively neutralized; the optical design of the keyboard backlight module can be optimized, and the light emitting uniformity of the keyboard backlight module can be increased. Whereby, the display effect of the backlit keyboard applying the above keyboard backlight module can be improved. 
     While the disclosure has been described by way of example and in terms of the exemplary embodiment(s), it is to be understood that the disclosure is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation, so as to encompass all such modifications and similar arrangements and procedures.