Patent Publication Number: US-2019170328-A1

Title: Energy efficient communication and display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of co-pending U.S. patent application Ser. No. 15/173,231, filed Jun. 3, 2016, which is hereby incorporated herein by reference. 
    
    
     FIELD 
     Embodiments of the disclosure generally relate to an adaptive backlight module for a display and a method and system for fabricating the same. 
     BACKGROUND 
     Backlight units for display devices are often one of the largest draws on power consumption, causing battery endurance to be limited in mobile electronics. Often a large portion of the light exiting a display screen is not needed for a single user, and is vulnerable to being viewed by non-users in the line of sight. Many current privacy filters and films for laptops, monitors, and some mobile devices absorb light, thereby reducing energy efficiency of the device. Additionally, these current privacy filters and films are expensive, and are cumbersome in that they interfere with touch screen functionality and must be physically removed to enable wide-angle viewing of the display. 
     Thus, a need exists for techniques to reduce power consumption from the emission of excess light, and to provide privacy for a user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  is a system for producing an adaptive backlight module according to one embodiment. 
         FIG. 2  is a schematic side cross-sectional view of a chemical vapor deposition processing chamber according to one embodiment of the system in  FIG. 1 . 
         FIG. 3A  is a schematic side cross-sectional view of a physical vapor deposition processing chamber according to one embodiment of the system in  FIG. 1 . 
         FIG. 3B  is a schematic side cross-sectional view of a roll-to-roll physical vapor deposition processing chamber according to one embodiment of the system in  FIG. 1 . 
         FIG. 3C  is a schematic side cross-sectional view of a rotatable target assembly of a physical vapor deposition processing chamber according to one embodiment of the system in  FIG. 1 . 
         FIGS. 4A-4B  are schematic views of an adaptive backlight module according to different embodiments. 
         FIG. 5  is a schematic view of a switchable diffuser stack in an adaptive backlight module according to one embodiment. 
         FIG. 6  is a flow chart depicting a method of forming an adaptive backlight module according to one embodiment. 
         FIG. 7A  illustrates frequency levels of an alternating electric field that may be applied in a display device to a switchable diffuser in an adaptive backlight module according to one embodiment. 
         FIG. 7B  illustrates the viewing angles corresponding to the frequencies of an electric field that may be applied in a display device to a diffuser in an adaptive backlight module according to one embodiment. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     SUMMARY 
     An adaptive backlight module and method and system for producing an adaptive backlight module are described herein. In one embodiment, an adaptive backlight module includes a light source, a polarizer, at least one enhancement film disposed between the light source and the polarizer, and a diffuser disposed between the light source and the enhancement film. The diffuser includes a first electrode coupled to a first substrate and a second electrode coupled to a second substrate. A liquid crystal layer is disposed between the first electrode and the second electrode of the diffuser. 
     In another embodiment, a method of producing an adaptive backlight module is provided that includes forming at least one enhancement film on a first substrate, forming a polarizer on the enhancement film, forming a diffuser by forming a liquid crystal layer between a first electrode on the first substrate and a second electrode on a second substrate, and connecting the diffuser to a light source. 
     In another embodiment, a system for producing an adaptive backlight module includes a first chamber, configured to form a first electrode on a first substrate and a second electrode on a second substrate, and a second chamber, configured to form a diffuser by forming a liquid crystal layer between the first electrode on the first substrate and the second electrode on the second substrate. 
     DETAILED DESCRIPTION 
     Embodiments of the disclosure generally include an adaptive backlight module for a display and a method and system for fabricating the same. 
       FIG. 1  is a system for producing an adaptive backlight module according to one embodiment. The system  100  may include a physical vapor deposition (PVD) chamber  102 , a chemical vapor deposition (CVD) chamber  104 , an embossing/printing chamber  108 , and a liquid crystal deposition chamber  106 . According to one embodiment, for production of an adaptive backlight module, substrates may first enter either the PVD chamber  102  for processing, as described with respect to  FIGS. 3A-3C  below, or the CVD chamber  104  for processing, as described with respect to  FIG. 2  below. In one embodiment, if the substrate first enters the CVD chamber  104 , the substrate will then directly enter the liquid crystal deposition chamber  106  for processing. If the substrate first enters a PVD chamber  102 , the substrate might next enter the embossing/printing chamber  108  for processing, before it then enters the liquid crystal deposition chamber  106  for processing, or alternatively, the substrate may directly enter the liquid crystal deposition chamber  106  from the PVD chamber  102  for processing. In an alternative embodiment, pre-formed substrates may enter the liquid crystal deposition chamber without first entering any other chambers. The substrates may then be removed from the liquid crystal deposition chamber  106  to be connected to a light guide plate, a reflector, and a light source to form an adaptive backlight module. In alternative embodiments, the system  100  may not include a PVD chamber  102 , the system may not include an embossing/printing chamber  108 , and/or the system may not include a CVD chamber  104 . 
       FIG. 2  is a schematic side cross-sectional view of a CVD processing chamber  104  according to one embodiment. A plasma enhanced chemical vapor deposition (PECVD) system, such as a PECVD system available from Applied Materials, Inc., located in Santa Clara, Calif. is described. However, it should be understood that other chemical vapor deposition chambers could be utilized. 
     The CVD chamber  104  is suitable for performing PECVD processes for fabricating circuitry on a large area substrate  214 . The large area substrate  214  may be made of glass, a polymer, or other suitable substrate. The CVD chamber  104  is configured to form structures and devices on the large area substrate  214  for use in the fabrication of liquid crystal displays (LCD&#39;s) or flat panel displays, photovoltaic devices for solar cell arrays, or other structures. The structures may include thin film transistors and p-n junctions utilized to form diodes for photovoltaic cells, among other structures. 
     The CVD chamber  104  includes a chamber sidewall  230 , a bottom  232 , and a substrate support  224 . The substrate support  224 , such as a susceptor, supports the substrate  214  during processing. A heater element  226 , such as a resistive heater, disposed in the substrate support  224 , is coupled to plasma source  202  and is utilized to controllably heat the substrate support  224  and large area substrate  214  positioned thereon to a predetermined temperature. The CVD chamber  104  also includes a lid structure  208 , a backing plate  212 , a cover plate  210 , and a gas distribution showerhead  218 . The gas distribution showerhead  218  is positioned opposite the substrate support  224  and the large area substrate  214 . 
     The CVD chamber  104  has a gas inlet  204  that is coupled to a gas source  206  and a plasma source  202 . The plasma source  202  may be a direct current power source, a radio frequency (RF) power source, or a remote plasma source. The gas inlet  204  delivers process and/or cleaning gases from the gas source  206  to a processing region  216  defined in an area below the gas distribution showerhead  218  and above the substrate support  224 . Gases present in the processing region  216  may be energized by the plasma source  202  to form a plasma. The plasma is utilized to deposit a layer of material on the substrate  214 . Although the plasma source  202  is shown coupled to the gas inlet  204  in this embodiment, the plasma source  202  may be coupled to the gas distribution showerhead  218  or other portions of the CVD chamber  104 . 
       FIG. 3A  is a schematic side cross-sectional view of a PVD processing chamber  102  from  FIG. 1  according to a first embodiment. The first embodiment shown in  FIG. 3A  is a PVD processing chamber  102   a . One example of the PVD chamber  102   a  that may be adapted to benefit from the disclosure is a physical vapor deposition (PVD) process chamber, available from Applied Materials, Inc., located in Santa Clara, Calif. However, it should be understood that other physical vapor deposition chambers could be utilized. 
     The PVD chamber  102   a  includes a chamber body  308  and a lid assembly  304 , defining a process volume  336 . The chamber body  308  is typically fabricated from a unitary block of aluminum or welded stainless steel plates. The chamber body  308  generally includes sidewalls  310  and a bottom  314 . The sidewalls  310  and/or bottom  314  generally include a plurality of apertures, such as an access port  318  and a pumping port (not shown). The pumping port is coupled to a pumping device (also not shown) that evacuates and controls the pressure within the process volume  336 . The pumping device is able to maintain the pressure of the PVD chamber  102   a  to a certain vacuum level. 
     The lid assembly  304  generally includes a target  334  and a ground shield assembly  322  coupled thereto. The target  334  provides a material source that can be deposited onto the surface of a substrate  340  during a PVD process. The target  334  or target plate may be fabricated of a material that will become the deposition species or it may contain a coating of the deposition species. To facilitate sputtering, a high voltage power supply, such as a power source  316  is connected to the target  334 . 
     The target  334  generally includes a peripheral portion  324  and a central portion  338 . The peripheral portion  324  is disposed over the sidewalls  310  of the chamber. The central portion  338  of the target  334  may protrude, or extend in a direction towards a substrate support  328 . The substrate support  328  is generally disposed on the bottom  314  of the chamber body  308  and supports the substrate  340  thereupon during substrate processing within the PVD chamber  102   a . The substrate support  328  may include one or more electrodes and/or heating elements imbedded within the plate-like body support. 
     During a sputtering process to deposit a material on the substrate  340 , the target  334  and the substrate support  328  are biased relative each other by the power source  316 . A process gas, such as inert gas and other gases, e.g., argon, and nitrogen, is supplied to the process volume  336  from a gas source  320  through one or more apertures (not shown), typically formed in the sidewalls  310  of the PVD chamber  102   a . The process gas is ignited into a plasma and ions within the plasma are accelerated toward the target  334  to cause target material being dislodged from the target  334  into particles. The dislodged material or particles are attracted towards the substrate  340  through the applied bias, depositing a film of material onto the substrate  340 . 
       FIG. 3B  is a schematic side cross-sectional view of a PVD processing chamber  102  according to a second embodiment. The second embodiment shown in  FIG. 3B  is an in-line, roll-to-roll PVD processing chamber  102   b . However, it should be understood that other in-line physical vapor deposition chambers could be 
     The roll-to-roll PVD chamber  102   b  is configured for depositing material  378  on a flexible substrate  344 . The roll-to-roll PVD chamber  102   b  may include at least a first vacuum processing region  366  and a second vacuum processing region  368  which may be separated from each other by at least one gas separation unit  370 , wherein a gas separation passage  376  configured as a passageway for the flexible substrate  344  is provided therebetween. 
     The roll-to-roll PVD chamber  102   b  includes a vacuum chamber  372 . Various vacuum deposition techniques can be used to deposit material on the flexible substrate  344 . The flexible substrate  344  is guided, as indicated by arrow X, into the vacuum chamber  372 . For example, the flexible substrate  344  can be guided into the vacuum chamber  372  from an unwinding station. The flexible substrate  344  is directed by rollers  358  to a substrate support configured for supporting the flexible substrate  344  during processing and/or deposition. As shown in  FIG. 3B , particularly for roll-to-roll deposition apparatuses, the substrate support can be a coating drum  354 , which is rotatable around a rotation axis  356 . From the coating drum  354 , the flexible substrate  344  is guided to a further roller  360  and out of the vacuum chamber  372 , as indicated by the second arrow X. 
     The embodiment depicted in  FIG. 3B  includes a first deposition source  362  provided in the first vacuum processing region  366 , and a second deposition source  364  provided in the second vacuum processing region  368 . In the vacuum processing regions  366 ,  368 , the flexible substrate  344  is supported by the coating drum  354  while being processed. Yet, it is to be understood that according to further embodiments, which can be combined with other embodiments described herein, more than two deposition sources can be provided. For example, four, five, six, or even more deposition sources can be provided. 
     The flexible substrate  344  has a self-adhesive first main surface  348  which can be covered with a protection layer  342  configured as a release liner. The flexible substrate  344  may be guided on the support surface  352  of the rotatable coating drum  354 , wherein the first main surface  348  is directed toward the rotatable coating drum  354 . However, as the first main surface  348  may be covered with the protection layer  342 , the first main surface  348  does not directly come into contact with the support surface  352 . 
     The deposited material  378  is vacuum deposited on the second main surface  350  of the flexible substrate  344  which is directed away from the rotatable coating drum  354  via the first deposition source  362  in the first vacuum processing region  366  and via the second deposition source  364  in the second vacuum processing region  368 . After vacuum deposition, the protection layer  342  covering the first main surface  348  may be removed, and the multilayer substrate  346  may be ready for use. 
       FIG. 3C  is a schematic view of a rotatable target assembly of a PVD processing chamber  102  according to a third embodiment. However, it should be understood that other rotatable target assemblies or cathodes could be utilized in a physical vapor deposition chamber. 
       FIG. 3C  is a schematic view of a rotatable target assembly  382 .  FIG. 3C  shows the distribution of released particles  384  as arrows. The rotatable target assembly  382  has a target support  386  and several target elements  388 ,  390 . The target assembly  382  and the target support  386  are rotatable. 
     The distribution field of deposition material can be understood as including substantially all particles  384  released from the target elements  388 ,  390 . Arrows denote the direction of the released particles  384  of the target elements  388 ,  390 . For instance, the distribution field of deposition material of target element  388  includes all particles  384  originating from the target element  388 . According to some embodiments, the distribution field may have substantially the shape of a cosine function. The length of arrows indicates approximately the number of particles  384  released in the direction of the arrow. For instance, the arrow going straight upwards presents the direction of a defined number of released particles  384 , whereas the arrow to the left or right of the straight arrow presents a smaller number of particles  384 . The target-substrate-distance  392  reaches from the target elements  388  and  390  to a plane  394  of a substrate surface. 
     According to some embodiments, the target support  386  and the substrate support of a deposition chamber may be adapted to be movable with respect to each other. For instance, the target support  386  and/or the substrate support may be adapted to adjust the distance between the plane  394  of the substrate surface and the target elements  388 ,  390 . Typically, the distance between the plane  394  of the substrate surface and the target elements  388 ,  390  of the rotatable target assembly  382  may be adjusted dependent on the gap  396  between the target elements  388 ,  390  of the rotatable target assembly  382  before using the rotatable target assembly  382  in a deposition process. 
       FIG. 4A  is a schematic view of an adaptive backlight module  400 A according to one embodiment. The adaptive backlight module  400 A has a reflector  410 . A light source and light guide plate  408  are on the reflector  410 . The light source may be one or more cold cathode fluorescent lamps (CCFL), one or more light-emitting diodes (LED), one or more organic light-emitting diodes (OLED), or any other suitable point source for a display device. 
     A switchable diffuser  406  is on the light source and light guide plate  408 . At least one enhancement film  404  is on the switchable diffuser  406 . For example, the enhancement film  404  may be a light recycling film, or any other brightness enhancing film tailored to a particular device&#39;s optical emission pattern. A polarizer  402  is on the enhancement film  404 . For example, in one embodiment, the polarizer may be a wire grid polarizer. 
       FIG. 4B  is a schematic view of an adaptive backlight module  400 B according to a different embodiment. The adaptive backlight modules  400 A,  400 B may be utilized in a display device, such as a laptop, monitor, or a mobile device. The adaptive backlight module  400 B has the polarizer  402 , the enhancement film  404 , and the switchable diffuser  406  of the embodiment of an adaptive backlight module  400 A shown in  FIG. 4A . However, adaptive backlight module  400 B has a high efficiency light guide comprising a light source  412  instead of having the light source and light guide plate  408  and the reflector  410  of the adaptive backlight module  400 A. For example, the high efficiency light guide comprising a light source  412  may be a single molded part with LEDs embedded in a light guide material, such as polymethyl-methacrylate (PMMA), ZEONOR™ or polycarbonate (PC). The high efficiency light guide  412  may also have a reflector integrated into the single molded part. For example, the reflector may be formed using a PVD process on the high efficiency light guide  412 . 
       FIG. 5  includes a schematic view of a switchable diffuser stack  500  in an adaptive backlight module according to one embodiment. The switchable diffuser stack  500  may comprise the switchable diffuser  406  in adaptive backlight module  400 A from  FIG. 4A  or in adaptive backlight module  400 B from  FIG. 4B . The switchable diffuser stack  500  has a first substrate  502  with an electrode  504  thereon, and a second substrate  510  with an electrode  508  thereon. The electrodes  504 ,  508  may each be a substantially transparent electrode, such as an indium tin oxide (ITO) film. The electrode  504  on the first substrate  502  faces the electrode  508  on the second substrate  510 . A liquid crystal layer  506  is disposed between the electrode  504  on the first substrate  502  and the electrode  508  on the second substrate  510 . In some embodiments, a dielectric barrier layer may be disposed between the electrode  504  and the first substrate  502 , and between the electrode  508  and the second substrate  510 . For example, the dielectric barrier layers may be comprised of silicon oxynitride, silicon oxide, silicon nitride, tin oxide, titanium oxide, or zirconium oxide. The liquid crystal layer  506  may be comprised of liquid crystals and spacer elements. In one embodiment, the material for the spacer elements may be selected to match the refractive index of the liquid crystal as closely as possible to prevent light from scattering off the spacer elements. In one embodiment, the spacer elements may be between 5-200 micron spacer beads. The liquid crystals may be any liquid crystals that scatter upon application of an electric field of a different frequency. In one embodiment, the liquid crystals may be smectic phase liquid crystals, such as smectic A (SmA) phase liquid crystals, which can preserve transmissivity for a wide range of haze. For example, in one embodiment, the smectic phase liquid crystals may allow for 95% or greater transmissivity for a haze of anywhere from 3% to 95%. 
       FIG. 6  is a flow chart depicting a method  600  of forming an adaptive backlight module according to one embodiment. The method  600  begins at operation  602  by forming an electrode on each of two substrates. The electrodes may be formed on a lower surface of the first substrate, and on an upper surface of the second substrate. The electrodes may be formed planar to or patterned on the substrates. In some embodiments, a dielectric barrier layer may be formed on each substrate before the electrodes are formed thereon, such that the dielectric barrier layer is between each substrate and the electrode formed thereon. The electrodes may be formed using a PVD process as described above with respect to  FIGS. 3A-3C . For example, on a glass substrate, the electrodes may be formed using the PVD process described above with respect to  FIG. 3A  or  FIG. 3C . In another example, on a plastic substrate, the electrodes may be formed using a roll-to-roll PVD process as described above with respect to  FIG. 3B . For example, each electrode may comprise an ITO film coated on polyethylene terephthalate (PET). Alternatively, the electrodes may be formed using a CVD process as described above with respect to  FIG. 2 . If a dielectric barrier layer is formed, the dielectric barrier layer may be formed using the same CVD or PVD process used to form the electrodes. Alternatively, the dielectric barrier layer may be formed using a different CVD or PVD process than the process used to form the electrodes. Accordingly, operation  602  may occur in a PVD chamber, such as the PVD chamber  102  shown in  FIG. 1 , in a CVD chamber, such as the CVD chamber  104  shown in  FIG. 1 , or in both (in the case that the dielectric layers are formed using a different process from the process used to form the electrodes). In an alternative embodiment, pre-formed substrates having an electrode already formed thereon may be used to form the adaptive backlight module. In this alternative embodiment, the method  600  would begin at operation  604 , using the pre-formed substrates having an electrode layer pre-formed thereon. 
     In operation  604 , at least one enhancement film may be formed on the first substrate on which the electrode is formed in operation  602 . The enhancement film may be formed on the upper surface of the first substrate, opposite from the lower surface of the first substrate on which the electrode is formed in operation  602 . The enhancement film may be formed on the substrate using an embossing, printing, or any other patterning process. Alternatively, the enhancement film may be formed using a CVD process as described above with respect to  FIG. 2 . Accordingly, operation  604  may occur in an embossing/printing chamber, such as the chamber  108  shown in  FIG. 1 , or in a CVD chamber, such as the CVD chamber  104  shown in  FIG. 1 . 
     In operation  606 , after the enhancement film has been formed on the first substrate in operation  604 , a polarizer may be formed on the enhancement film. The polarizer may be formed on the enhancement film using an embossing, printing, or any other patterning process. Alternatively, the polarizer may be formed on the enhancement film using a wire grid process, in which wires are placed into the enhancement film. Alternatively, the polarizer may be formed on the enhancement film using a CVD process as described above with respect to  FIG. 2 . Accordingly, operation  606  may occur in an embossing/printing chamber, such as the chamber  108  shown in  FIG. 1 , a metallization chamber (not shown in  FIG. 1 ), or in a CVD chamber, such as the CVD chamber  104  shown in  FIG. 1 . 
     If a roll-to-roll or sheet-to-sheet PVD process is used to form the electrodes on the substrates in operation  602 , the substrates may be rolls or sheets of substrates that are ultimately cut to form multiple individual substrates. The electrodes formed in operation  602 , the enhancement film formed in operation  604 , and/or the polarizer formed in operation  606  may all be formed on one substrate roll or sheet. The roll or sheet may then be cut to the sizes of individual displays before operation  608 . In an alternative embodiment the polarizer formed in operation  606  may be formed on a substrate independent from the substrates on which the electrodes are formed in operation  602 . In another alternative embodiment, the enhancement film formed in operation  604  may also be formed on a substrate independent from the substrates on which the electrodes are formed in operation  602 . 
     In operation  608 , a liquid crystal layer is formed between the two substrates on which the electrodes are formed in operation  602  to form a diffuser. In operation  608 , the lower surface of the first substrate (having the electrode thereon) faces the upper surface of the second substrate (having the electrode thereon) when the liquid crystal layer is formed. The liquid crystal layer is formed between the electrode on the first substrate and the electrode on the second substrate. To form the liquid crystal layer, a plurality of spacer elements, such as spacer beads, is placed between the electrodes. The spacer elements are used so that liquid crystals may be uniformly deposited between the electrodes. Liquid crystals are deposited between the electrodes to surround the spacer elements and to bond the two substrates to each other, thus forming one diffuser element. The liquid crystals may be deposited using an inkjet printing process, a slot die coating process, a screen printing process, a stamp transfer process, a vacuum filling process, or any other suitable liquid or solid injection or deposition process. The liquid crystal layer may be formed in a chamber independent from the CVD chamber  104 , the PVD chamber  102 , and the embossing/printing chamber  108 , as is shown by the liquid crystal deposition chamber  106  in the embodiment of the system shown in  FIG. 1 . 
     After the diffuser is formed in operation  608 , a light source is connected to the diffuser to form an adaptive backlight module in operation  610 . For example, the adaptive backlight module may be the adaptive backlight module  400 A shown in  FIG. 4A  or the adaptive backlight module  400 B shown in  FIG. 4B . In one embodiment, the diffuser is connected to a light source, a light guide plate, and a reflector using a lamination assembly process in operation  610 . In an alternative embodiment, the diffuser is connected a high efficiency light guide comprising a light source using a lamination assembly process in operation  610 . In the alternative embodiments in which the enhancement film and/or the polarizer are formed on substrates independent from the substrates having the electrodes thereon that form the diffuser, the diffuser is connected to the substrate having the enhancement film and/or the substrate having the polarizer using a lamination assembly process in operation  610 . 
     The adaptive backlight module described herein and the method and system for producing the same may allow for increased power efficiency when used in a display device, such as a liquid crystal display device. Electrodes on the diffuser of the adaptive backlight module may be electrically connected to a power source in a display device. For example, the electrodes  504 ,  508  in the switchable diffuser stack  500  shown in  FIG. 5  may be electrically connected to a power source. An alternating electric field may be applied to the electrodes to alter the appearance of the diffuser and the viewing angle of the device display. 
       FIG. 7A  illustrates the frequency levels of the alternating electric field that may be applied to the electrodes on a switchable diffuser in an adaptive backlight module used in a display device, according to one embodiment. For example, an alternating current electric field with the frequency levels shown in  FIG. 7A  may be applied to the switchable diffuser stack  500  implemented in the adaptive backlight module  400 A or  400 B to switch the appearance of the diffuser.  FIG. 7A  illustrates the range of frequencies that may be applied from a low frequency F 1  at a first end of the range, to a high frequency F 2  at a second end of the range. When an electric field of a low frequency F 1  is applied to a diffuser, the diffuser will appear translucent. When an electric field of a high frequency F 2  is applied to the diffuser, the diffuser will appear transparent. In one embodiment, an alternating current field of +/−55V or approximate field of strength 100-400 V/m, cycled at 180 degrees phase, may be applied with the low frequency F 1  in the range of 5-60 Hz, or with the high frequency F 2  in the range of 500-5000 Hz. In one embodiment, the time required for switching to the high frequency F 2  is 0-1 seconds, and the time required for switching to the low frequency F 1  is 0-3 seconds. 
       FIG. 7B  illustrates the range of viewing angles of the display on a device  700  when an electric field with a frequency within the range shown in  FIG. 7A  is applied to a diffuser. When the electric field of the low frequency F 1  is applied, and the diffuser appears translucent, the display may be seen from a first viewing angle V 1 . When an electric field of the high frequency F 2  is applied, and the diffuser appears transparent, the display may be seen from a second viewing angle V 2  that is narrower than the first viewing angle V 1 . The second, narrower viewing angle V 2  may be used when a single user is using the device  700  to limit the amount of light emitted that is not needed for the single user, and to provide privacy for the single user by limiting the ability of non-users to see the display. The first, wider viewing angle V 1  may be used when multiple viewers are viewing the display of the device  700 . The second viewing angle V 2  may have the same apparent brightness as the first viewing angle V 1 , but will require less power. For example, in one embodiment, there may be greater than 95% transmissivity of the diffuser when an electric field of either the low frequency F 1  or the high frequency F 2  is applied, but applying an electric field of the low frequency F 1  results in greater than 90% haze, and applying an electric field of the low frequency F 2  results in less than 5% haze. Thus, when only a single user is viewing the device, power can be saved and privacy can be obtained by applying an electric field of the high frequency F 2 , having the narrower viewing angle V 2 . However, if multiple viewers need to view the display, an electric field of the low frequency F 1  can be applied to set a wider viewing angle V 1 . The viewing angle may be configured to switch automatically, or the viewing angle may be configured to switch upon user selection. 
     Additionally, as shown in  FIG. 7A , an electric field of any frequency Fx between the low frequency F 1  and the high frequency F 2  may be applied to the diffuser, which results in the diffuser appearing somewhere between the translucent and transparent states. The viewing angle when an electric field of frequency Fx is applied to the diffuser will be between the first viewing angle V 1  and the second viewing angle V 2 , as shown in the hatched region in  FIG. 7B . In one embodiment, the intermediate frequency Fx range may be between 60-500 Hz, and the time required for switching to an intermediate frequency Fx may be less than the time required to switch to the low frequency F 1  and/or the high frequency F 2 . 
     In the embodiments of the switchable diffuser  406  shown in  FIGS. 4A and 4B , the switchable diffuser  406  is the only diffuser in each switchable diffuser module  400   a ,  400   b . As such, when the high frequency F 2  is applied to the switchable diffuser  406 , and the switchable diffuser  406  appears transparent, there will be substantially no diffusion of the light. By contrast, if the switchable diffuser  406  were used in addition to a typical passive diffuser, the passive diffuser would still diffuse the light even when the switchable diffuser appears transparent. When only a single viewer is viewing the display, an electric field of the high frequency F 2  can be applied, such that the switchable diffuser  406  is in the transparent state, with no other diffuser causing unnecessary diffusion or waste of light. 
     According to embodiments, which can be combined with other embodiments described, herein an adaptive backlight module is provided. The adaptive backlight module includes a light source; a polarizer; at least one enhancement film disposed between the light source and the polarizer; and a diffuser disposed between the light source and the enhancement film. The diffuser includes a first electrode coupled to a first substrate, a second electrode coupled to a second substrate, and a liquid crystal layer disposed between the first electrode and the second electrode. 
     According to embodiments, which can be combined with other embodiments described herein, the light source includes one of: one or more cold cathode fluorescent lamps (CCFL), one or more light-emitting diodes (LED), and one or more organic light-emitting diodes (OLED). 
     According to embodiments, which can be combined with other embodiments described herein, the adaptive backlight module further includes a light guide plate and a reflector. 
     According to embodiments, which can be combined with other embodiments described herein, the liquid crystal layer includes smectic phase liquid crystals and a plurality of spacer elements. 
     According to embodiments, which can be combined with other embodiments described herein, the first electrode is disposed on a lower surface of the first substrate and includes a first indium tin oxide (ITO) film. The second electrode is disposed on an upper surface of the second substrate and comprises a first indium tin oxide (ITO) film. The lower surface of the first substrate faces the upper surface of the second substrate. 
     According to further embodiments, which can be combined with other embodiments described herein, a system for producing an adaptive backlight module is provided. The system includes a first chamber, configured to form a first electrode on a first substrate and a second electrode on a second substrate. Additionally, the system includes a second chamber, configured to form a diffuser by forming a liquid crystal layer between the first electrode on the first substrate and the second electrode on the second substrate. 
     According to embodiments, which can be combined with other embodiments described herein, the liquid crystal layer is formed in the second chamber using one of: an inkjet printing process, a slot die coating process, a screen printing process, a stamp transfer process, and a vacuum filling process. 
     According to embodiments, which can be combined with other embodiments described herein, the first chamber comprises a chemical vapor deposition (CVD) chamber. 
     According to embodiments, which can be combined with other embodiments described herein, the system further includes a third chamber configured to form an enhancement film on the diffuser. 
     According to embodiments, which can be combined with other embodiments described herein, the first chamber includes a physical vapor deposition (PVD) chamber. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.