Abstract:
The present disclosure provides a color filter substrate used in an organic light-emitting diode (OLED) or liquid crystal (LC) display structure for improving a contrast ratio and light output. The color filter substrate includes a substrate; a color filter layer comprising a plurality of pixel units; and a reflective metallic matrix comprising a plurality of reflective metallic matrix elements surrounding each pixel unit.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to the display technologies and, more particularly, relates to a color filter substrate, and a fabrication method thereof, OLED structure, related display panels, and related display devices. 
       BACKGROUND 
       [0002]    OLED display devices, with advantages such as low energy consumption, high luminance, short response time, wide viewing angle, and light weight, have been broadly used in devices such as mobile communication terminals, personal digital assistants (PDAs) and tablet computers. OLED display devices are classified into the passive matrix type and active matrix type. The active matrix type OLED display devices utilize thin film transistors (TETs) to drive OLEDs. 
         [0003]    A white organic light emitting diode (WOLED) device provides high resolution and large scale displays, and can be used in a backlight of a liquid crystal display (LCD) device or a full color display device employing color filters. White OLED and other top-emitting display devices have relatively high aperture ratios, but the light output and viewing angles of these display devices are not ideal. To output colored light, a color filter substrate is used to filter white light generated by the OLED layer. The color filter substrate includes color filters and a black matrix formed on a glass substrate of the display panel. When the emitted light enters the glass substrate, the black matrix structure would absorb part of the light to reduce the reflection and improve the contrast ratio of the OLED display. 
         [0004]    However, a conventional black matrix absorbs light, including the diffused light generated by many pixels, which may reduce the brightness levels of the display panels. Further, conventional black matrix is often made of heavy metals, such as chromium. Such materials pollute the environment. In addition, the processes implemented to clean up manufacturing wastes containing heavy metals are often burdensome and costly. 
         [0005]    It is therefore desirable to improve the designs of OLED/LC structures to reduce pollution in the manufacturing processes, and to improve contrast ratios and view angles of the display panels. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0006]    The present disclosure provides an OLED/LC structure and fabrication method thereof, and related display panels and display devices. By using the disclosed color filter substrate, the light output and the contrast ratio of an OLED/LC display panel can be improved. Further, the manufacturing process according to the embodiments of the present disclosure is cleaner and therefore more economical. 
         [0007]    One aspect of the present disclosure provides a color filter substrate. The color filter substrate includes a substrate; a color filter layer comprising a plurality of pixel units; and a reflective metallic matrix comprising a plurality of reflective metallic matrix elements surrounding each pixel unit. 
         [0008]    Optionally, each reflective metallic matrix element includes a reflective surface facing each adjacent pixel unit. The reflective surface forms an acute angle with the substrate. 
         [0009]    Optionally, the reflective surface may form an acute angle of about 30 to 60° with a bottom surface of the metal matrix element contacting the substrate. 
         [0010]    Optionally, the reflective metallic matrix elements comprise pyramid shaped metallic elements with reflective surfaces. 
         [0011]    Optionally, the reflective metallic elements comprise frustum shaped metallic elements with reflective surfaces. 
         [0012]    Optionally, the color filter layer is thinner than the reflective metallic matrix. 
         [0013]    Optionally, the color filter substrate includes a protection layer covering the reflective metallic matrix and the color filter layer. 
         [0014]    Optionally, a thickness of the protection layer is about 2 um to 4 um. 
         [0015]    Optionally, the color filter substrate includes light diffusers dispensed on the protection layer. 
         [0016]    Optionally, the light diffusers may be transparent. The light diffusers may be light scattering particles with diameters of about 20 nm to 80 nm. The light diffusers are selected from one or a combination of SiO2 and TiO2. 
         [0017]    The pixel units include blue pixel units, red pixel units, green pixel units, and white pixel units. 
         [0018]    Another aspect of the present disclosure provides an OLED structure for improving a contrast ratio and light output. The OLED structure includes an OLED array substrate. The OLED array substrate includes a thin-film transistor (TFT) substrate with a TFT layer; and an OILED layer formed on the TFT substrate, the OLED layer emitting light. The OLED structure further includes a color filter substrate. The color filter substrate includes a substrate; a color filter layer comprising a plurality of pixel units; arid a reflective metallic matrix comprising a plurality of reflective metallic elements surrounding each pixel unit. 
         [0019]    Optionally, each reflective metallic matrix element includes a reflective surface facing each adjacent pixel unit. The reflective surface forms an acute angle with the substrate. 
         [0020]    Optionally, the reflective surface may form an acute angle of about 30° to 60° with a bottom surface of the metal matrix element contacting the substrate. 
         [0021]    Optionally, the reflective metallic matrix elements comprise pyramid shaped metallic elements with reflective surfaces. 
         [0022]    Optionally, the reflective metallic elements comprise frustum shaped metallic elements with reflective surfaces. 
         [0023]    Optionally, the color filter layer is thinner than the reflective metallic matrix. 
         [0024]    Optionally, the color filter substrate includes a protection layer covering the reflective metallic matrix and the color filter layer. 
         [0025]    Optionally, a thickness of the protection layer is about 2 μm to 4 μm. 
         [0026]    Optionally, the color filter substrate includes light diffusers dispensed on the protection layer. 
         [0027]    Optionally, the light diffusers may be transparent. The light diffusers may be light scattering particles with diameters of about 20 nm to 80 nm. The light diffusers are selected from one or a combination of SiO2 and TiO2. 
         [0028]    The pixel units include blue pixel units, red pixel units, green pixel units, and white pixel units. 
         [0029]    Another aspect of the present disclosure provides a method for fabricating a color filter substrate. 
         [0030]    The method for fabricating the color filter substrate includes forming a reflective metallic matrix in an active region of a cover glass, wherein each metallic matrix element is of a pyramid shape; forming pixel units in the active region of the cover glass; forming a protection layer on the pixel units and the reflective metallic matrix; and dispensing light diffusers on the protection layer. 
         [0031]    Further, each reflective metallic matrix element includes a reflective surface facing each adjacent pixel unit. The reflective surface forms an acute angle with a bottom surface of the metal matrix element contacting the substrate. Optionally, the reflective surface may form an acute angle of about 30° to 60° with the substrate. 
         [0032]    Optionally, the reflective metallic matrix elements comprise pyramid shaped metallic elements with reflective surfaces. 
         [0033]    Optionally, the reflective metallic elements comprise frustum shaped metallic elements with reflective surfaces. 
         [0034]    Further, the color filter layer is thinner than the reflective metallic matrix. 
         [0035]    Another aspect of the present disclosure provides a display panel including the color filter substrate described above. 
         [0036]    Another aspect of the present disclosure provides a display device including the above-mentioned display panel. 
         [0037]    Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0038]    The following drawings are merely examples for illustrative purposes according to various disclosed embodiments and are not intended to limit the scope of the present disclosure. 
           [0039]      FIG. 1 a    is a top view of an exemplary cover glass according to embodiments of the present disclosure; 
           [0040]      FIG. 1 b    illustrates a cross sectional view of an exemplary display panel according to embodiments of the present disclosure; 
           [0041]      FIG. 2  illustrates an exemplary process flow for fabricating OLED/LC structure according to embodiments of the present disclosure; and 
           [0042]      FIG. 3  illustrates exemplary components described in the process flow of  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    For those skilled in the art to better understand the technical solution of the invention, reference will now be made in detail to exemplary embodiments of the invention, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
         [0044]    Color filters in OLED/LC structures need to have a high degree of color purity, optical transmittance, and optical tolerance, with little or no discoloration or fading over time, as well as high thermal stability and chemical resistance. A color filter may also be referred to as a pixel unit. The two terms are used interchangeably in the present disclosure. To reduce pixel light crosstalk, pixel units are often interposed with a black matrix. 
         [0045]    Instead of a conventional black matrix, embodiments of the present disclosure provide a color filter substrate with a highly reflective metallic matrix that can be used with pixel units. The metallic matrix forms a pattern of lines on the color filter substrate that shields bus lines and TFTs from the viewable area of the display. These lines distinguish red, green, or blue (ROB) pixels to prevent pixel crosstalk and light leakage, thus improving the contrast ratio. Further, the metallic matrix is a layer only a few microns thick. Thus, it has little impact on the aperture ratio. 
         [0046]    The metallic matrix may be formed by reflective metallic materials, such as certain metals including copper (Cu), silver (Ag), etc. The metallic matrix is highly reflective also because each element of the metallic matrix is of a pyramid shape or similar shapes. The shape of the metallic matrix elements further enables the metallic matrix to reflect scattered light to the adjacent pixel units, increasing the light output of the display panel. Moreover, the metallic matrix is thicker than the pixel units on the color filter substrate, which prevents light mixings between light going through different pixel units. 
         [0047]    In addition, the color filter substrate according to embodiments of the present disclosure further includes a layer of light diffusers dispensed on top of the pixel units and the metallic matrix. The light diffusers scatter light emitted by the luminescent layer. The diffused light is then reflected by the metallic matrix and transmitted out of the display panel through the pixel units, 
         [0048]    One aspect of the present disclosure provides a color filter substrate that is used in an OLED/LC structure. 
         [0049]      FIGS. 1 a  and 1 b    illustrate an exemplary OLED/LC structure  100  according to various embodiments of the present disclosure. As shown in  FIG. 1   b,  the OLED/LC structure  100  includes a cover glass  2  bonded with the TFT substrate  1 , encapsulating a number of functional layers. Specifically,  FIG. 1 a    shows a top/front view of the cover glass  2 . The cover glass  2  includes an active region  21 , in which an image is displayed on the display panel during operation. The cover glass  2  also includes a peripheral region  22 , in which no image is displayed during operation. 
         [0050]    As shown in  FIG. 1   b,  the OLED/LC structure  100  includes an OLED array substrate  3  according to embodiments of the present disclosure. The OLED array substrate  3  includes a TFT substrate  1  with TFTs disposed on it and an OLED/LC layer formed over the TFTs. 
         [0051]    The OLED/LC layer is a luminescent layer. In some embodiments, the OLED/LC layer may be disconnected by certain barriers. In other embodiments, the OLED/LC layer may be formed integrally in one layer. In one example, the OLED/LC layer may be an OLED layer sandwiched by a cathode layer and an anode layer. The array of electrodes may be controlled by the TFT circuitry in the TFT layer. 
         [0052]    The OLED/LC structure  100  further includes a color filter substrate  4 . The color filter substrate  4  includes a cover glass  2 . The cover glass  2  includes an active region  21  and a peripheral region  22 . The active region  21  maybe, for example, a rectangular region in the center of the cover glass  2  in which display pixels are actively used to display images. The peripheral region  22  may be devoid of active display pixels. In the example of  FIG. 1   a,  the peripheral region  22  has the shape of a rectangular ring, surrounding the periphery of active region  21 . Circuitry and other components may sometimes be formed in the peripheral region  22 . To hide the circuitry and other components from view by a user of the display device, the peripheral region  22  may sometimes be provided with an opaque mask. The opaque mask can be formed from an opaque material such as a black material or may be formed from opaque masking materials of other colors. 
         [0053]    The color filter substrate  4  further includes pixel units  24 . The pixel units  24  may be red (R), green (G), blue (B), and/or white (W). The pixel units  24  may form a color filter layer. The array of pixel units  24  in the color filter layer may be used to provide the display panel with the ability to display color images. 
         [0054]    The color filter substrate  4  further includes a reflective metallic matrix  23 . The metallic matrix  23  is interposed between the pixel units  24 . The metallic matrix  23  masks light leaked from the space between the pixel units  24 . To enhance reflectance, the metallic matrix  23  may be made of metallic materials that have a high reflectance, such as aluminum (Al), aluminum alloy, copper (Cu), silver (Ag), titanium (Ti), etc., and/or a combination of the metallic materials. 
         [0055]    In the active region  21 , metallic matrix  23  may be formed from a grid of relatively thin lines. The metallic matrix  23  may have a pattern of openings such as an array of rectangular holes for receiving pixel units  24 . In some embodiments, in the peripheral region  22 , metallic matrix material may be used in forming a peripheral metallic matrix that serves as a black border for the display. For example, the metallic matrix in the peripheral region  22  may have a rectangular ring shape that surrounds a central rectangular active region  21 . In some embodiments, in the peripheral region  22 , black matrix material may be used in forming a peripheral black matrix that serves as a black border for the display. 
         [0056]    In one embodiment of the present disclosure, each element of the metallic matrix  23  may be pyramid shaped, as shown in  FIG. 1   b.  Compared to other shapes, the pyramid shaped metallic matrix  23  may reflect more light into the pixel units  24  and thus enables more light emitted by the OLED/LC layer to be transmitted through the pixel units  24 . The elements of metallic matrix  23  may be of a right pyramid shape, a non-right pyramid shape, square pyramid shape, triangular prism shape, etc. In some embodiments, the metallic matrix  23  elements may be frustums. In  FIG. 1   b,  the arrows pointing down from the cover glass  2  indicate the direction of the light output of the display panel. 
         [0057]    As shown in  FIG. 1   b,  each metallic matrix  23  element provides reflective surfaces  30  that reflect light into the adjacent pixel units  24 . In one embodiment, the metallic matrix  23  element may he a square pyramid with four reflective surfaces  30 . Each reflective surface  30  faces one pixel unit  24 . Each reflective surface  30  may form an acute angle with the cover glass  2 . For example, each reflective surface  30  may form an angle of about 30°-60° with the cover glass  2 . 
         [0058]    In one embodiment, as shown in  FIG. 1   b,  the thickness of the pixel units  24  may be thinner than the thickness of the metallic matrix  23 . In one embodiment, the thickness of the pixel units  24  may be thinner than the thickness of the metallic matrix  23  by 1 μm to 2 μm. Such a configuration enables the metallic matrix  23  to reflect scattered light into pixel units  24 , therefore increases light output of the display panel. 
         [0059]    The shape of the metallic matrix  23  element according to the present disclosure is not limited to those disclosed in the present disclosure. The angle formed by the reflective surfaces of the metallic matrix  23  elements with the cover glass, according to the present disclosure, is not limited to those disclosed in the present disclosure. Embodiments of the present disclosure provide metallic matrix  23  with elements of the metallic matrix  23  being of any shape that may improve the light transmission rate or contrast ratio of the display panel. The shape of the metallic matrix  23  elements and the angles formed between the reflective surfaces  30  of the metallic matrix  23  and the cover glass  2  may be adjusted to achieve various design objectives in light transmission rate, contrast ratio, manufacturing cost, etc. 
         [0060]    The size of the elements of the metallic matrix  23  according to the present disclosure is not limited to those disclosed in the present disclosure. In embodiments of the present disclosure, any size of the metallic matrix  23  elements that can be properly interposed between the pixel units  24  may be appropriate for the color filter substrate. The thickness of the metallic matrix  23  elements can he adjusted to achieve different design objectives in light transmission rate, manufacturing cost, etc. 
         [0061]    The composition of the metallic matrix  23  may also be adjusted according to various designs and applications. Embodiments of the present disclosure provide metallic matrix with elements of the metallic matrix he made of any metal or other materials, or a combination thereof, that may improve the light transmission rate or the contrast ratio of the display panel. 
         [0062]    The color filter substrate  4  further includes a protection layer  25 . For example, the protection layer  25  is substantially transparent and can be formed of a resin. The protection layer  25  encapsulates the pixel units  24  and the metallic matrix  23  on the surface of the cover glass  2 , protects the pixel units  24  and the metallic matrix  23  from the external environment, and thus limits damages caused by environmental factors such as oxygen and moisture. 
         [0063]    The protection layer  25  should be of an appropriate thickness. If the protection layer  25  is too thin, it may not provide sufficient insulation to the external environment. If the protection layer  25  is too thick, it may lead to increased opacity and deterioration of light transmission efficiency. In some embodiments, the protection layer  25  may be around 2 um-4 um thick. 
         [0064]    In addition, the color filter substrate  4  further includes light diffusers  26 . In one embodiment, the light diffusers  26  may be dispensed onto the protection layer  25 . Light generated by the OLED/LC layer may be scattered by the light diffusers  26  to reach the color filter substrate  4  and be transmitted through the pixel units  24 . The light diffusers  26  are another element for effectively improving the light output and viewing angle of the display panel. 
         [0065]    The light diffusers  26  may be light scattering particles, each having a diameter of about 30 nm to about 80 nm. The light diffusers  26  may be transparent. If light is incident to fine particles, such as the light diffusers  26 , light is generally scattered. In a case where a diameter of a particle is less than 1/10 of a light wavelength, forward scattering and backward scattering similarly occur. Forward scattering refers to when light scatters in a direction in which light travels. Backward scattering refers to when light scatters in a direction in which light is reflected. This is referred to as Rayleigh scattering. 
         [0066]    However, in a case where the diameter of the particle is greater than 1/10 of the light wavelength, Mie scattering, in which the forward scattering overwhelmingly occurs compared to the backward scattering, is induced. In some embodiments, the light diffusers  26  induce Mie scattering to allow the forward scattering to overwhelmingly occur, which improves the viewing angle characteristics due to more light scattering, while not impairing light transmission efficiency. 
         [0067]    To induce Mie scattering, the light diffusers  26  need to have diameters greater than 1/10 of a corresponding light wavelength. In consideration of a wavelength of light generated by the OLED/LC layer, the light diffusers  26  may need to have diameters greater than 4 nm-70 nm. 
         [0068]    As described above, the different sizes of the light diffusers  26  may cause various light scattering effect. In some embodiments of the present disclosure, the light diffusers  26  may have diameters of about 20 mn-80 nm. The light diffusers  26  may be made of polystyrene (PS), silicon dioxide (SiO2), titanium dioxide (TiO2), etc. The light diffusers  26  may be dispensed on top of the protection layer  25  by a sol-gel method or a microemulsion method. The composition and diameters of the light diffusers  26  may be adjusted according to various designs and applications to achieve different light transmitting effects. 
         [0069]    As shown in  FIG. 1   b,  the OLED array substrate is bonded with the color filter substrate  4  through a sealant  27 . In some embodiments, the sealant  27  may be a UV-curing sealant  27 . The UV-curing sealant  27  may be applied in the peripheral region  22  of the cover glass  2 . The OLED array substrate  3  and color filter substrate  4  may subsequently be pressed together. The UV-curing sealant  27  may then be cured by applying UV light to the sealant. 
         [0070]    Another aspect of the present disclosure provides a method for fabricating art color filter substrate that is used in an OLED/LC structure according to various embodiments of the present disclosure. 
         [0071]      FIG. 2  illustrates an exemplary process for fabricating the OLED/LC structure discussed in relation to  FIGS. 1 a    and  1   b.  The process may include steps S 1  to S 7 .  FIG. 3  further illustrates exemplary components that are fabricated through each step of the exemplary process described in  FIG. 2 . 
         [0072]    In step S 1 , a TFT substrate  1 , i.e., a substantially transparent substrate with a TFT layer formed on the substrate, is provided. Further, as shown in  FIG. 3 , an OLED/LC layer is formed on top of the TFT layer. The OLED/LC layer is a luminescent layer. In some embodiments, the OLED/LC layer may be disconnected by certain barriers. In other embodiments, the OLED/LC layer may be formed integrally in one layer. 
         [0073]    In step S 2 , a cover glass  2  is provided. The cover glass  2  includes an active region  21  and a peripheral region  22 . A metallic matrix  23  may be formed in the active region  21 . 
         [0074]    Further, in step S 2 , as shown in  FIG. 3 , a reflective metallic matrix  23  is formed in the active region  21  of cover glass  2 . In some embodiments, a metallic matrix may be formed in the peripheral region  22 . In other embodiments, a conventional black matrix may be formed in the peripheral region  22 . 
         [0075]    A metallic matrix  23  may be formed by a photolithography process. First, a pattern comprising a metallic matrix  23  is formed in the active region  21  of cover glass  2 . Then, a protection layer is deposited on the cover glass  2 . The protection layer may be, for example, silicon nitride (SiNx) or silicon oxide (SiOx) (e.g., SiN 2  or SiO 2 ). The part of the protection layer corresponding to the metallic matrix  23  is then etched by a patterning process. The metallic matrix  23  is then formed over the active region  21 . 
         [0076]    In one example, to enhance reflectance, the metallic matrix  23  may be formed with metallic materials that has a high reflectance, such as aluminum (Al), aluminum alloy, copper (Cu), silver (Ag), silver alloy, titanium (Ti), etc. 
         [0077]    In one embodiment of the present disclosure, each element of the metallic matrix  23  may be pyramid shaped, as shown in  FIG. 3 . The pyramid shaped metallic matrix  23  reflects more light into the pixel units  24  and thus enables more light emitted by the OLED/LC layer to be transmitted through the pixel units  24 . 
         [0078]    The shape of the elements of the metallic matrix  23  according to the present disclosure is not limited to those disclosed in the present disclosure. Embodiments of the present disclosure provide a metallic matrix with elements of the metallic matrix  23  that can be of any shape that may improve the light transmission rate or contrast of the display panel. The shape of the metallic matrix  23  elements may be adjusted to achieve various design objectives in light transmission rate, contrast ratio, manufacturing cost, etc. 
         [0079]    In step S 3 , pixel units  24  are disposed in the active region  21  of the cover glass  2 . As shown in  FIG. 3 , the pixel units  24  may he red (R), green (G), blue (B), and white (W) pixels. The metallic matrix  23  is interposed between the pixel units  24 . The metallic matrix  23  masks light leaked from spaces disposed between the pixel units  24 . 
         [0080]    In one embodiment, as shown in  FIG. 3 , the thickness of the pixel units  24  may be thinner than the thickness of the metallic matrix  23 . Such a configuration enables the metallic matrix  23  to reflect more scattered light into pixel units  24 , therefore increases the light output of the display panel. 
         [0081]    In step S 4 , a protection layer  25 , such as a resin layer, is formed to cover and protect the pixel units  24  and metallic matrix  23  from the external environment. In one embodiment, a thickness of the protection layer  25  may be around 2 μm-4 μm. The protection layer  25  may be formed using a screen printing method, a drip coating method, a lamination coating method, etc. 
         [0082]    In step S 5 , light diffusers  26  may be dispensed on top of the protection layer  25 . The light diffusers  26  may need to have diameters greater than 40 nm-70 nm. In one embodiment, the light diffusers  26  may have diameters of about 20 nm-80 nm. The light diffusers  26  may be made of polystyrene (PS), silicon dioxide (SiO2), titanium dioxide (TiO2), etc. The light diffusers  26  may be dispensed on top of the protection layer  25  by a sol-gel method or a microemulsion method. 
         [0083]    In step S 6 , a sealant  27 , such as a UV-curing sealant  27 , is applied around the edge of the cover glass  2 , in the peripheral region  22 . As shown in  FIG. 3 , the color filter substrate  4  is then pressed together with the OLED array substrate  3 . In some embodiments, sealant  27  may be applied along the edges of the OLED array substrate  3  before the color filter substrate  4  and the OLED array substrate  3  are pressed together. 
         [0084]    In step S 7 , a light, such as a UV light is applied on the UV-curing sealant  27  to cure the sealant. The OLED array substrate  3  and the color filter substrate  4  are then bonded. 
         [0085]    Another aspect of the present disclosure provides a display panel. 
         [0086]    The disclosed color filter substrate and the related OLED/LC structure may be used in a display panel. In some embodiments, the display panel may be an LCD display panel. In some embodiments, the display panel may be an OLED display panel. In some embodiments, the display panel may include the OLED array substrate  3  and the color filter substrate  4 . The color filter substrate  4  may include pixel units  24  with interposed reflective metallic matrix  23 . 
         [0087]    Another aspect of the present disclosure provides a display device, 
         [0088]    The display device may incorporate the display panel described above. The display device according to the embodiments of the present disclosure may be used in any product with display functions such as a television, an LCD display, an OLED display, an electronic paper, a digital photo frame, a mobile phone, a tablet computer, a navigation device, etc. 
         [0089]    For descriptive purposes, only certain elements of the OLED/LC structure are illustrated and describe in the embodiments described in the present disclosure. Certain elements of the OLED/LC structure, such as certain circuits, are known in the art and not repeated herein. It should be understood that other elements of the OLED/LC structure that are understood by and known to a person of ordinary skill in the art are within the scope of the present disclosure. 
         [0090]    Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” “some embodiments,” etc., indicates that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases throughout the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is noted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments. 
         [0091]    It should be understood that the above embodiments disclosed herein are exemplary only and not limiting the scope of this disclosure. Without departing from the spirit and scope of this invention, other modifications, equivalents, or improvements to the disclosed embodiments are obvious to those skilled in the art and are intended to be encompassed within the scope of the present disclosure.