The disclosure relates generally to backlight units and display devices comprising such backlight units, and more particularly to backlight units comprising a thin light guide plate and a light coupling unit for increasing optical coupling efficiency.
Liquid crystal displays (LCDs) are commonly used in various electronics, such as cell phones, laptops, electronic tablets, televisions, and computer monitors. Increased demand for thinner, larger, high-resolution flat panel displays drives the need for high-quality substrates for use in the display, e.g., as light guide plates (LGPs). As such, there is a desire in the industry for thinner LGPs with higher light coupling efficiency and/or light output, which may allow for a decrease in the thickness and/or an increase in the screen size of various display devices.
Plastic materials such as polymethylmethacrylate (PMMA) may be used to manufacture LGPs. However, PMMA has a relatively high coefficient of thermal expansion (e.g., approximately one order of magnitude greater than that of glass), which may necessitate a larger space between the light source, e.g., LED, and the light guide when designing an LCD device. This gap can decrease the efficiency of light coupling from the light source to the light guide and/or necessitate a larger bezel to conceal the edges of the display. Moreover, due to its relatively weak mechanical strength, it can be difficult to make light guides from PMMA that are both sufficiently large and thin to meet current consumer demands. PMMA light guides can thus limit the light emitting surface area available to display an image, either due to concealment by a bezel or inability to manufacture sheets large enough for the desired display size.
Glass light guides have been proposed as alternatives to PMMA due to their low light attenuation, low coefficient of thermal expansion, and high mechanical strength at relatively low thicknesses. However, while glass can be used to produce relatively thin LGPs, such LGPs may also have various drawbacks. For instance, reducing the thickness of the LGP may necessitate the use of smaller light sources (e.g., LEDs) to promote efficient optical coupling. Decreasing the size of the light source can, in turn, decrease light output luminance and/or efficiency and/or increase the overall cost of the backlight unit (BLU). It may therefore be desirable from economic and/or design standpoints to use larger light sources even in the case of thinner LGPs. Various efforts have been made to more efficiently couple light injected into an edge-lit LGP by an adjacent light source, particularly as the distance between the light source and the LGP increases. However, coupling apparatuses currently may have one or more drawbacks, such as increased manufacturing expense and/or complexity and/or low effectiveness.
It would therefore be advantageous to provide devices for coupling light from a larger light source into a thinner light guide plate, and to reduce the overall thickness of the display device without sacrificing brightness and/or energy efficiency. It would also be advantageous to provide improved methods and apparatuses for increasing the light coupling efficiency between a light source and a light guide plate that do not substantially increase the cost and/or complexity of manufacture.
The disclosure relates, in various embodiments, to backlight units comprising a light guide plate comprising a light emitting major surface, an opposing major surface, and a first light incident edge surface; a light coupling unit comprising a second light incident edge surface, an opposing light reflecting edge surface, a first surface, and an opposing second surface; and a light source optically coupled to the first and second light incident edge surfaces, wherein at least a portion of the first surface of the light coupling unit is in physical contact with at least a portion of the light emitting major surface or opposing major surface of the light guide plate. Also disclosed herein are backlight units comprising a light guide plate comprising a light emitting major surface, an opposing major surface, and a first light incident edge surface; a light coupling unit in physical contact with at least a portion of the light emitting major surface or opposing major surface of the light guide plate, the light coupling unit comprising a second light incident edge surface and an opposing light reflecting edge surface; a light source optically coupled to the first and second light incident edge surfaces; and a light recycling cavity defined by the light reflecting edge surface of the light coupling unit and a reflective film on each of a top, bottom, and back surface of the light source. Electronic, display, and lighting devices comprising such BLUs are further disclosed herein.
In certain embodiments, the light reflecting edge surface of the light coupling unit can comprise a reflective film or coating and/or at least one of the top, bottom, and/or back surfaces of the light source can comprise a reflective film or coating. According to various embodiments, a height of the at least one light source may be less than or equal to a combined thickness of the light guide plate and light coupling unit. The first and second surfaces of the light coupling unit can, in non-limiting embodiments, be parallel with the light emitting major surface of the light guide plate or, in other embodiments, may not be parallel and the second surface may have a tilt angle ranging from −10° to 10°. In a further embodiment, the first light incident edge surface of the light guide plate may be chamfered, e.g., at an angle ranging from about 10° to about 60°.
According to various embodiments, the refractive index of the light guide plate (np) can be different from a refractive index of the light coupling unit (nc), for example, np may be greater than nc, e.g., about 5% to about 20% greater than nc. In certain embodiments, 0.25np+0.77≤nc≤0.25np+1.18. According to further embodiments, a difference between a coefficient of thermal expansion of the light coupling unit and a coefficient of thermal expansion of the light guide plate is less than 30%. In still further embodiments, a modulus of elasticity of at least one of the light guide plate or light coupling unit is less than 5 GPa. According to yet further embodiments, at least one of the light guide plate and the light coupling unit comprises a glass, glass-ceramic, plastic, or polymeric material and/or has an optical transmission of at least about 80% at a visible wavelength ranging from about 420 nm to about 750 nm.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the methods as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description present various embodiments of the disclosure, and are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure and together with the description serve to explain the principles and operations of the disclosure.
The following detailed description can be further understood when read in conjunction with the following drawings, wherein, when possible, like numerals refer to like components, it being understood that the appended figures are not necessarily drawn to scale.
Disclosed herein are backlight units comprising a light guide plate comprising a light emitting major surface, an opposing major surface, and a first light incident edge surface; a light coupling unit comprising a second light incident edge surface, an opposing light reflecting edge surface, a first surface, and an opposing second surface; and a light source optically coupled to the first and second light incident edge surfaces, wherein at least a portion of the first surface of the light coupling unit is in physical contact with at least a portion of the light emitting major surface or opposing major surface of the light guide plate. Also disclosed herein are backlight units comprising a light guide plate comprising a light emitting major surface, an opposing major surface, and a first light incident edge surface; a light coupling unit in physical contact with at least a portion of the light emitting major surface or opposing major surface of the light guide plate, the light coupling unit comprising a second light incident edge surface and an opposing light reflecting edge surface; a light source optically coupled to the first and second light incident edge surfaces; and a light recycling cavity defined by the light reflecting edge surface of the light coupling unit and a reflective film on each of a top, bottom, and back surface of the light source. Electronic, display, and lighting devices comprising such BLUs are further disclosed herein.
Various embodiments of the disclosure will now be discussed with reference to
As used herein, the term “optically coupled” is intended to denote that a light source is positioned relative to the LGP so as to introduce or inject light into the LGP. A light source may be optically coupled to a LGP even though it is not in physical contact with the LGP. As shown in
Referring again to
One or more components of the backlight unit 100 may be provided with a reflective surface to promote light recycling and further increase light coupling efficiency. For example, the light reflecting edge surface 124 of the LCU may reflect light incident on its surface, for instance, using a reflective film or coating 140 or any other device or composition capable of reflecting light. One or more surfaces of the light source 130 may also comprise a reflecting film or coating, e.g., one or more films 150a, 150b, and/or 150c, which may be positioned in contact with a top surface, back surface, or bottom surface of the light source 130, respectively.
In some embodiments, as depicted in
With reference to
Similar to
With reference to
The angle of the second surface 322 with respect to the normal is referred to herein as the “tilt angle” (θ). The tilt angle θ of the second surface 322 with the normal can range, in some embodiments, from about −10° to about 10°, such as from about −8° to about 8°, from about −6° to about 6°, from about −5° to about 5°, from about −4° to about 4°, from about −3° to about 3°, from about −2° to about 2°, from about −1° to about 1°, or 0°, including all ranges and subranges therebetween.
As shown in
With general reference to each of
The light source can also have a height HL, which may, in some embodiments, be greater than a thickness TP of the LGP. For example, HL may be at least about 10% greater than TP, such as ranging from about 1.1*TP to about 2*TP, from about 1.2*TP to about 1.9*TP, from about 1.3*TP to about 1.8*TP, from about 1.4*TP to about 1.7*TP, or from about 1.5*TP to about 1.6*TP. Of course, the light source may have any other height relative to the LGP, including heights less than the thickness of the LGP, as appropriate for a desired configuration. In additional embodiments, the thickness of the LGP and/or LCU may be chosen such that TC+TP≥HL. For instance, as shown in
According to certain embodiments, the thickness of the LGP, TP, and/or the thickness of the LCU, TC, can be less than or equal to about 3 mm, for example, ranging from about 0.1 mm to about 2 mm, from about 0.3 mm to about 1.5 mm, from about 0.5 mm to about 1.1 mm, or from about 0.7 mm to about 1 mm, including all ranges and subranges therebetween. In some embodiments, the length of the LCU, LC, can be less than a length of the LGP. For instance, it may be desirable to decrease the length of the LCU such that it is not visible in a device comprising the BLU, e.g., it can be concealed behind a bezel or otherwise hidden from the user's view. Furthermore, it may be desirable to decrease the length of the LCU to limit coupling of light back into the LCU from the LGP.
Light injected into the LCU by the light source can couple into the LGP by way of physical contact (e.g., between the first surface of the LCU and the light emitting major surface of the LGP). However, at longer LCU lengths, the potential for light to couple back into the LCU from the LGP increases. As such, in various non-limiting embodiments, a length of the LCU, LC, may be less than 5mm, such as ranging from about 0.3 mm to about 3 mm, from about 0.5 mm to about 2.5 mm, from about 0.8 mm to about 2 mm, from about 1 mm to about 1.8 mm, from about 1.2 mm to about 1.6 mm, or from about 1.4 mm to about 1.5 mm, including all ranges and subranges therebetween. A ratio of LCU length to LGP length may range, in some embodiments from about 1:100 to about 1:2, from about 1:50 to about 1:3, from about 1:20 to about 1:4, or from about 1:10 to about 1:5, including all ranges and subranges therebetween. Alternatively, a ratio of LCU length to LCU height may range from about 20:1 to about 1:1, from about 15:1 to about 2:1, from about 10:1 to about 3:1, or from about 5:1 to about 4:1, including all ranges and subranges therebetween.
As shown in
The surfaces of the LGP and/or LCU may, in certain embodiments, be planar or substantially planar, e.g., substantially flat. The light emitting major surface and opposing major surface of the LGP may, in various embodiments, be parallel or substantially parallel. Similarly, the first and second surfaces of the LCU may be parallel or substantially parallel. By way of a non-limiting example, the LGP and/or LCU may comprise a rectangular or square sheet having four edges, although other shapes and configurations, including surfaces having one or more curvilinear portions, are envisioned and are intended to fall within the scope of the disclosure. In some embodiments, a rectangular glass or plastic LGP may be coupled to a rectangular LCU waveguide. In further embodiments, as depicted in
BLUs disclosed herein may have improved light coupling efficiency as compared to similar BLUs not comprising an LCU. For example, light coupling efficiency may be as high as 95%, such as ranging from about 65% to about 90%, from about 70% to about 85%, or from about 75% to about 80%, including all ranges and subranges therebetween. As previously discussed, the LCU may comprise a reflecting edge surface (124, 224, 324) opposite the light incident edge surface, which may be coated with a reflective film or coating (140, 240, 340). In some embodiments, the second surface may also be coated with a reflective film. However, in other embodiments, such a reflective film may not be present, as the majority of the light incident upon the second surface of the LCU will likely be confined in the LCU due to TIR.
Light coupling efficiency can be further enhanced, in some embodiments, by including a reflective film or coating on one or more surfaces of the light source (130, 230, 240), e.g., on the back surface (film 150a, 250a, 350a), top surface (film 150b, 250b, 350b), and/or bottom surface (film 150c, 250c, 350c) to form a recycle cavity (160, 260, 360). It is noted that the front or light emitting surface of the light source may be sufficiently reflective (at visible wavelengths, ˜420-750 nm) without the presence of a film, e.g., at least 50% reflective, such as at least 60% reflective, or at least 70% reflective, including all ranges and subranges therebetween.
Suitable reflective films and coatings may include, for instance, reflective tapes such as diffuse (Lambertian) reflector films or enhanced specular reflector (ESR) films commercially available from WhiteOptics (e.g., White98™), 3M (e.g., Vikuiti™), and Labsphere (e.g., Spectralon®, Spectraflect®, or Permaflect) or metallic films, such as aluminum, gold, silver, copper, platinum, and the like. In certain embodiments, the reflective film on the LCU may be a specular reflector, whereas the reflective film(s) on the light source may be Lambertian reflectors. The reflectivity of any of these films (at visible wavelengths, ˜420-750 nm) may vary as desired for a particular application and can range, for example, from greater than 50% to greater than 98%, such as from 60% to 99%, from 70% to 96%, or from 80% to 90%, including all ranges and subranges therebetween.
Light coupling efficiency may also be affected by the refractive index of the LGP and/or LCU. According to various embodiments, the LGP and/or LCU may have a refractive index ranging from about 1.3 to about 1.8, such as from about 1.35 to about 1.7, from about 1.4 to about 1.65, from about 1.45 to about 1.6, or from about 1.5 to about 1.55, including all ranges and subranges therebetween. In some embodiments, the refractive index of the LCU may be substantially similar to (e.g., within 5% of) the index of refraction of the LGP. In other embodiments, the refractive index of the LCU may be less than that of the LGP. For instance, nc can be less than 0.95*np, such as 0.85*np, 0.8*np, 0.75*np, or 0.70*np, including all ranges and subranges therebetween. According to certain embodiments, nc can be greater than np, e.g., less than or equal to 1.1*np, or less than or equal to 1.05*np. In various non-limiting embodiments, a relationship between nc and np can be expressed as: 0.25np+0.77≤nc≤0.25np+1.18, or 0.25np+0.82≤nc0.25nLGP+1.12, or 0.25np+0.87≤nc0.25np+1.08, or 0.25np+0.92≤nc0.25np+1.02.
According to various embodiments, the materials of construction for the LGP and/or LCU may be chosen to withstand various working conditions during continuous operation, such as the heat and/or light emitted by the light source, without exhibiting aging effects such as discoloration, deformation, cracking, and/or delamination. As the gap between the light source and the LGP decreases, the ability to withstand heat may become more important. Alternatively, it may be possible to increase the gap between the light source and the LGP by utilizing an LGP and LCU that have a combined thickness in excess of the height of the light source (e.g., if TP+TC>>HL).
While improved coupling efficiency can be obtained by decreasing the gap between the light source and the LGP, the temperature changes associated with the proximity of the light source can be significant, e.g., as high as 20-40° C. It may therefore be desirable to choose LGP and/or LCU materials with the same or similar coefficient of thermal expansion (CTE) and/or modulus of elasticity. For instance, if the CTE of the LCU (CTEC) greatly differs from the CTE of the LGP (CTEP), stress at the interface of the two materials may be generated due to elevated temperatures during operation of the BLU. In particular, a large CTE mismatch combined with a high elastic modulus could result in stress that may exceed the adhesive forces holding the LCU and LGP together or, if this does not occur, the stress may produce out of plane bending that might interfere with light coupling. It may therefore be desirable to choose the materials of construction for the LGP and/or LCU such that there is a sufficient CTE match between the LCU and LGP, or to choose at least one material that has an elastic modulus lower than that of the other material such that it produces an easily managed level of stress during operation. In some embodiments, the LGP and LCU may be chosen such that their CTEs are within 30% of one another, e.g., 0.7*CTEP≤CTEC≤1.3*CTEP, or 0.8*CTEP≤CTEC≤1.2*CTEP, or 0.9*CTEP≤CTEC≤1.1*CTEP, or 0.95*CTEP≤CTEC≤1.05*CTEP.
Exemplary CTEs (measured over a temperature range of about 25-300° C.) for glass materials can range, for example, from about 3×10−6/° C. to about 11×10−6/° C., such as from about 4×10−6/° C. to about 10×10−6/° C., from about 5×10−6/° C. to about 8×10−6/° C., or from about 6×10−6/° C. to about 7×10−6/° C., including all ranges and subranges therebetween. Exemplary elastic moduli for glass materials can range from about 50 GPa to about 90 GPa, such as from about 60 GPa to about 80 GPa, or from about 70 GPa to about 75 GPa, including all ranges and subranges therebetween. CTEs for plastic or polymeric materials may range from about 50×10−6/° C. to about 80×10−6/° C., such as from about 55×10−6/° C. to about 75×10−6/° C., from about 60×10−6/° C. to about 70×10−6/° C., including all ranges and subranges therebetween. Exemplary elastic moduli for plastic/polymeric materials can be lower than those of glass, e.g., ranging from about 1.5 GPa to about 3 GPa, such as from about 2 GPa to about 2.5 GPa, including all ranges and subranges therebetween. As such, while the CTE of plastic/polymeric materials may be high as compared to that of glass, a suitable coupling between such materials may still be possible due to the low elastic modulus of the plastic/polymer. In some instances, at least one of the LGP or LCU has an elastic modulus of less than 5 GPa.
With continued reference to
Some non-limiting glass compositions can include between about 50 mol % to about 90 mol % SiO2, between 0 mol % to about 20 mol % Al2O3, between 0 mol % to about 20 mol % B2O3, and between 0 mol % to about 25 mol % RxO, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2, or Zn, Mg, Ca, Sr or Ba and x is 1, and wherein the glass produces less than or equal to 2 dB/500 mm absorption. In some embodiments, the glass comprises less than 1 ppm each of Co, Ni, and Cr. In some embodiments, the concentration of Fe is <about 50 ppm, <about 20 ppm, or <about 10 ppm. In other embodiments, Fe+30Cr+35Ni<about 60 ppm, Fe+30Cr+35Ni<about 40 ppm, Fe+30Cr+35Ni<about 20 ppm, or Fe+30Cr+35Ni<about 10 ppm. In other embodiments, the composition sheet comprises between about 60 mol % to about 80 mol % SiO2, between about 0.1 mol % to about 15 mol % Al2O3, 0 mol % to about 12 mol % B2O3, and about 0.1 mol % to about 15 mol % R2O and about 0.1 mol % to about 15 mol % RO, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2, or Zn, Mg, Ca, Sr or Ba and x is 1, and wherein the glass produces less than or equal to 2 dB/500 mm absorption. In some embodiments, the glass produces a color shift less than 0.006, less than 0.005, less than 0.004, or less than 0.003.
In other embodiments, the glass composition can comprise between about 65.79 mol % to about 78.17 mol % SiO2, between about 2.94 mol % to about 12.12 mol % Al2O3, between about 0 mol % to about 11.16 mol % B2O3, between about 0 mol % to about 2.06 mol % Li2O, between about 3.52 mol % to about 13.25 mol % Na2O, between about 0 mol % to about 4.83 mol % K2O, between about 0 mol % to about 3.01 mol % ZnO, between about 0 mol % to about 8.72 mol % MgO, between about 0 mol % to about 4.24 mol % CaO, between about 0 mol % to about 6.17 mol % SrO, between about 0 mol % to about 4.3 mol % BaO, and between about 0.07 mol % to about 0.11 mol % SnO2. In some embodiments, the glass can produce a color shift<0.015. In some embodiments, the glass can produce a color shift<0.008, less than 0.005, or less than 0.003.
In additional embodiments, the glass composition can comprise an RxO/Al2O3 ratio between 0.95 and 3.23, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2. In further embodiments, the glass composition may comprise an RxO/Al2O3 ratio between 1.18 and 5.68, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2, or Zn, Mg, Ca, Sr or Ba and x is 1. In yet further embodiments, the glass composition can comprise an RxO—Al2O3—MgO between −4.25 and 4.0, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2. In still further embodiments, the glass composition may comprise between about 66 mol % to about 78 mol % SiO2, between about 4 mol % to about 11 mol % Al2O3, between about 4 mol % to about 11 mol % B2O3, between about 0 mol % to about 2 mol % Li2O, between about 4 mol % to about 12 mol % Na2O, between about 0 mol % to about 2 mol % K2O, between about 0 mol % to about 2 mol % ZnO, between about 0 mol % to about 5 mol % MgO, between about 0 mol % to about 2 mol % CaO, between about 0 mol % to about 5 mol % SrO, between about 0 mol % to about 2 mol % BaO, and between about 0 mol % to about 2 mol % SnO2.
In additional embodiments, the glass composition can comprise between about 72 mol % to about 80 mol % SiO2, between about 3 mol % to about 7 mol % Al2O3, between about 0 mol % to about 2 mol % B2O3, between about 0 mol % to about 2 mol % Li2O, between about 6 mol % to about 15 mol % Na2O, between about 0 mol % to about 2 mol % K2O, between about 0 mol % to about 2 mol % ZnO, between about 2 mol % to about 10 mol % MgO, between about 0 mol % to about 2 mol % CaO, between about 0 mol % to about 2 mol % SrO, between about 0 mol % to about 2 mol % BaO, and between about 0 mol % to about 2 mol % SnO2. In certain embodiments, the glass composition can comprise between about 60 mol % to about 80 mol % SiO2, between about 0 mol % to about 15 mol % Al2O3, between about 0 mol % to about 15 mol % B2O3, and about 2 mol % to about 50 mol % RxO, wherein R is any one or more of Li, Na, K, Rb, Cs and x is 2, or Zn, Mg, Ca, Sr or Ba and x is 1, and wherein Fe+30Cr+35Ni<about 60 ppm.
The LGP and/or LCU may also comprise a glass that has been chemically strengthened, e.g., by ion exchange. During the ion exchange process, ions within a glass sheet at or near the surface of the glass sheet may be exchanged for larger metal ions, for example, from a salt bath. The incorporation of the larger ions into the glass can strengthen the sheet by creating a compressive stress in a near surface region. A corresponding tensile stress can be induced within a central region of the glass sheet to balance the compressive stress.
Ion exchange may be carried out, for example, by immersing the glass in a molten salt bath for a predetermined period of time. Exemplary salt baths include, but are not limited to, KNO3, LiNO3, NaNO3, RbNO3, and combinations thereof. The temperature of the molten salt bath and treatment time period can vary. It is within the ability of one skilled in the art to determine the time and temperature according to the desired application. By way of a non-limiting example, the temperature of the molten salt bath may range from about 400° C. to about 800° C., such as from about 400° C. to about 500° C., and the predetermined time period may range from about 4 to about 24 hours, such as from about 4 hours to about 10 hours, although other temperature and time combinations are envisioned. By way of a non-limiting example, the glass can be submerged in a KNO3 bath, for example, at about 450° C. for about 6 hours to obtain a K-enriched layer which imparts a surface compressive stress.
The LGP and/or LCU can, in certain embodiments be transparent or substantially transparent. As used herein, the term “transparent” is intended to denote that the LGP and/or LCU, at a thickness of approximately 1 mm, has a transmittance of greater than about 80% in the visible region of the spectrum (420-750 nm). For instance, an exemplary transparent LGP and/or LCU may have greater than about 85% transmittance in the visible light range, such as greater than about 90%, greater than about 92%, or greater than about 95% transmittance, including all ranges and subranges therebetween. According to various embodiments, the LCU may have a transmittance of less than about 80% in the visible region, such as less than about 70%, less than about 60%, or less than about 50%, including all ranges and subranges therebetween.
In some embodiments, an exemplary transparent LGP and/or LCU can comprise less than 1 ppm each of Co, Ni, and Cr. In some embodiments, the concentration of Fe is <about 50 ppm, <about 20 ppm, or <about 10 ppm. In other embodiments, Fe+30Cr+35Ni<about 60 ppm, Fe+30Cr+35Ni<about 40 ppm, Fe+30Cr+35Ni<about 20 ppm, or Fe+30Cr+35Ni<about 10 ppm. According to additional embodiments, an exemplary transparent LGP and/or LCU can comprise a color shift <0.015 or, in some embodiments, a color shift <0.008.
Color shift may be characterized by measuring the variation in chromaticity coordinate y along length L of a sample using the CIE 1931 standard for color measurements. For glass LGPs, the value of color shift can be reported as Δy=y(L2)−y(L1) where L2 and L1 are Z positions along the panel or substrate direction away from the source launch and where L2-L1=0.5 meters.
According to various embodiments, one or more surfaces of the LGP may be patterned with a plurality of light extraction features, e.g., the light emitting major surface and/or the opposing major surface of the LGP. As used herein, the term “patterned” is intended to denote that the plurality of elements and/or features are present on the surface of the LGP in any given pattern or design, which may, for example, be random or arranged, repetitive or non-repetitive. For instance, in the case of light extraction features, such features may be distributed across the second surface, e.g. as textural features making up a roughened surface.
In various embodiments, the light extraction features present on the surface(s) of the LGP may comprise light scattering sites. For example, the light emitting major surface or opposing major surface of the LGP may be textured, etched, coated, damaged and/or roughened to produce the light extraction features. Non-limiting examples of such methods include, for instance, laser damaging the surface, acid etching the surface, and coating the surface with TiO2. In certain embodiments, a laser can be used both to cut holes into the LGP and to damage the first and/or second surface to create light extraction features. According to various embodiments, the extraction features may be patterned in a suitable density so as to produce a substantially uniform illumination. The light extraction features may produce surface scattering and/or volumetric scattering of light, depending on the depth of the features in the glass surface. The optical characteristics of these features can be controlled, e.g., by the processing parameters used when producing the extraction features. The LGP may be treated to create light extraction features according to any method known in the art, e.g., the methods disclosed in co-pending and co-owned International Patent Application No. PCT/US2013/063622, incorporated herein by reference in its entirety.
The LCU may be manufactured using any method known in the art of waveguide or light guide processing. For instance, a sheet of material with length LC can be coated with a reflective film on one face and cut into a strip of thickness TC using any variety of apparatuses, e.g., a dicing saw, a wire saw, a laser, to name a few. The cut edges can optionally be polished or any rough surfaces may be filled with an index matching polymer, such as Accuglass T-11 from Honeywell Corp. The LCU and LGP may then be brought into contact and adhered or bonded to each other, e.g., by applying an adhesive between the LGP and LCU, such as a polymer or other conformable material, and/or by heating the materials at a low temperature to form a bond.
The BLUs disclosed herein may be used in various display devices including, but not limited to LCDs or other displays used in the television, advertising, automotive, and other industries. The BLUs disclosed herein may also be used in any suitable lighting applications such as, but not limited to, luminaires or the like.
It will be appreciated that the various disclosed embodiments may involve particular features, elements or steps that are described in connection with that particular embodiment. It will also be appreciated that a particular feature, element or step, although described in relation to one particular embodiment, may be interchanged or combined with alternate embodiments in various non-illustrated combinations or permutations.
It is also to be understood that, as used herein the terms “the,” “a,” or “an,” mean “at least one,” and should not be limited to “only one” unless explicitly indicated to the contrary. Thus, for example, reference to “a light source” includes examples having two or more such light sources unless the context clearly indicates otherwise. Likewise, a “plurality” is intended to denote “more than one.” As such, a “plurality of light sources” includes two or more such light sources, such as three or more, etc.
Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, examples include from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
The terms “substantial,” “substantially,” and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. As used herein, the term “substantially similar” is intended to denote that two values are approximately equal, e.g., within about 5% of each other, or within about 2% of each other in some cases. For example, in the case of a refractive index of 1.5, a substantially similar refractive index may range from about 1.425 to about 1.575.
Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that any particular order be inferred.
While various features, elements or steps of particular embodiments may be disclosed using the transitional phrase “comprising,” it is to be understood that alternative embodiments, including those that may be described using the transitional phrases “consisting” or “consisting essentially of,” are implied. Thus, for example, implied alternative embodiments to an apparatus that comprises A+B+C include embodiments where an apparatus consists of A+B+C and embodiments where an apparatus consists essentially of A+B+C.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the spirit and scope of the disclosure. Since modifications combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the disclosure may occur to persons skilled in the art, the disclosure should be construed to include everything within the scope of the appended claims and their equivalents.
The following Examples are intended to be non-restrictive and illustrative only, with the scope of the invention being defined by the claims.
Exemplary backlight units having a configuration similar to that depicted in
The reflecting surface of the LCU was coated with a specular reflect with 96% reflectivity. The refractive index of the LCU was varied from 1.2 to 1.6, the thickness was varied from 0.56 mm to 0.68 mm, and the length was varied from 0.1 mm to 5 mm. The effect of these variations on light coupling efficiency was studied using a ray-tracing model based on Zemax optical modeling software. The light coupled to the LGP was detected at the edge of the LGP opposite the coupler to ensure that only the injected or guided light was detected. The reflectivity of the LED surface itself was determined by measuring a commercial 7040 LED using three lasers with red, green, and blue wavelengths, respectively. Measurement results indicated that the LED surface reflectivity was approximately 60% for all three wavelengths and was unrelated to the LED drive voltage.
Exemplary backlight units having a configuration similar to that depicted in
Exemplary backlight units having a configuration similar to that depicted in
This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 62/320052 filed on Apr. 8, 2016, the content of which is relied upon and incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/US2017/025864 | 4/4/2017 | WO | 00 |
Number | Date | Country | |
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62320052 | Apr 2016 | US |