TWI772501B - Multilayer reflector for direct lit backlights - Google Patents

Abstract

Disclosed herein are light guide assemblies comprising a backlight unit having a substrate comprising a light emitting first major surface and an opposing second major surface, at least one light source optically coupled to the substrate, and a reflector positioned proximate first or second major surface of the substrate, the reflector comprising two or more layers of a reflective material with each of the layers having a first area and a second area, the first area being more reflective than the second area, and the second area being more transmissive than the first area.

Description

Multilayer reflectors for direct-emitting backlights

This application claims the benefit of priority under the patent law from US Provisional Patent Application No. 62/551,491, filed on August 29, 2017, the entire contents of which are hereby incorporated by reference herein. middle.

The present disclosure generally relates to backlight units and display or lighting apparatus including such backlight units, and more particularly to backlight units including patterned glass light guide plates and patterned reflective layers.

Liquid crystal displays (LCDs) are commonly used in various electronic devices such as cell phones, laptops, electronic tablets, televisions, and computer monitors. The LCD can include a backlight unit (BLU) for generating light, which can then be converted, filtered, and/or polarized to produce the desired image. The BLU may be edge-lit (eg, including a light source coupled to the edge of a light guide plate (LGP)) or back-lit (eg, including a two-dimensional array of light sources disposed behind the LCD panel).

An LCD can also be considered a light valve based display, where the display panel includes an array of individually addressable light valves using a pair of polarizers and an electrically controlled liquid crystal layer. The BLU is required to generate the emission image from the LCD. Due to the high efficiency and small size of state-of-the-art light emitting diodes (LEDs), most modern BLUs utilize LEDs. BLU is divided into two variants. An edge-lit BLU includes a linear LED array edge-coupled to a light guide plate (LGP) that emits light from the surface of the light guide plate. The direct-emitting BLU includes a 2D LED array directly behind the LCD panel. Direct-emitting BLUs may have the advantage of improved dynamic contrast compared to edge-emitting BLUs. For example, a display with a direct-emitting BLU can independently adjust the brightness of each LED to optimize the dynamic range of brightness across the image. This is often referred to as local dimming. However, to achieve the desired light uniformity and/or to avoid hot spots in direct-emitting BLUs, the light source may be positioned at a distance from the LGP and/or diffuser film, thus making the overall display thickness greater than that of edge-emitting BLUs display thickness. Lenses positioned over the LEDs have also been proposed to improve the lateral propagation of light in direct-emitting BLUs, but in such configurations, the optical distance between the LEDs and the diffuser film (eg, from about 15-20 mm) still causes The undesirably high overall display thickness and/or these components may result in undesirably light loss as the BLU thickness is reduced. While edge-lit BLUs may be thinner, light from individual LEDs may spread across large areas of the LGP, so that turning off individual LEDs or groups of LEDs may have only minimal impact on dynamic contrast. Direct-emitting BLUs are also advantageous as they can allow for improved dynamic contrast by employing 2D local dimming where LEDs in dark areas of the screen can be turned off.

Therefore, it would be advantageous to provide a thin BLU with improved local dimming efficiency without negatively affecting the uniformity of the light emitted by the BLU.

In various embodiments, the present disclosure is related to a design and method of making a multilayer patterned reflector comprising two or more layers, wherein each of the layers is designed such that the layer has a first region and A second area, the first area is more reflective than the second area, and the second area is more transmissive than the first area.

The multilayer patterned reflector can be optimized for use in thin direct emitting LCD backlights, where the multilayer patterned reflector is used to reflect the The light from the discrete LED sources is propagated on the backlight plane and thereby provides illumination of uniform brightness to the LCD panel.

A method of making a multilayer patterned reflector may include the steps of using a reflective white paint or ink, and applying the paint or ink to a suitable glass or plastic substrate by successively printing multiple layers using digital printing techniques. The patterned reflector can have several layers, each layer being patterned with a relatively low resolution, which can be simply and inexpensively fabricated by printing using highly reflective inks. When such reflectors are used in direct-lit backlights, this allows for smaller thicknesses, better light utilization efficiency, and better brightness uniformity than prior art direct-lit backlights using variable reflectors sex.

In one embodiment where the patterned reflector is fabricated on the top surface of the light guide plate, the same printing process can also be used to create the light extraction features.

Additional features and advantages of the present disclosure will be set forth in the detailed description that follows, and some of those features and advantages will be readily understood by those skilled in the art from this description, or by practicing the methods as described herein. To appreciate some of these features and advantages, the methods include the following detailed description, claims, and drawings.

It is to be appreciated that 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 nature of the claimed items. The accompanying drawings are included to provide a further understanding of the present 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 operation of the disclosure.

Disclosed herein are backlight units comprising: a light guide plate having a first major face that emits light, a second opposite major face, and a plurality of light extraction features; at least one light source optically coupled to the light guide plate the second main face of the light guide plate; a rear reflector positioned near the second main face of the light guide plate; and a patterned reflective layer positioned near the first main face of the light guide plate, the patterned reflective layer comprising at least An optically reflective element and at least one optically transmissive element. Display and lighting devices including such backlight units are also disclosed herein.

Also disclosed herein are devices that include such backlights, such as displays, lighting, and electronic devices, such as televisions, computers, phones, tablets, and other display panels, lighting fixtures, solid-state lighting, sign boards, and other building components, only To name a few.

Various embodiments of the present disclosure will now be discussed with reference to FIGS. 1-8B , which illustrate exemplary elements and aspects of the backlight units disclosed herein. The following general description is intended to provide an overview of the claimed apparatus, and various aspects will be discussed in more detail throughout this disclosure with reference to non-limiting depicted embodiments, which may be used throughout this disclosure. interchangeable within the context of each other.

FIG. 1 shows a top view of an exemplary light guide plate (LGP) 100 and an array of light sources 110 optically coupled to the LGP 100 . For illustrative purposes, light source 110 may be seen through LGP 100 in FIG. 1 , although in some embodiments this may not be the case. Alternative configurations are also within the scope of this disclosure, including different light source positions, sizes, shapes, and/or spacings. For example, while the depicted embodiment includes periodic or regular arrays of light sources 110 having the same size, shape, and spacing, other embodiments in which the array is irregular or aperiodic are also contemplated.

LGP 100 may have any dimensions, such as length L and width W , which may vary depending on the display or lighting application. In certain embodiments, the length L may range from about 0.01 m to about 10 m, such as from about 0.1 m to about 5 m, from about 0.5 m to about 2.5 m, or from about 1 m to about 2 m, All ranges and subranges in between are included. Similarly, width W may range from about 0.01 m to about 10 m, such as from about 0.1 m to about 5 m, from about 0.5 m to about 2.5 m, or from about 1 m to about 2 m, including all therebetween Ranges and subranges. Each light source 110 in the light source array may also define a block of cells (represented by dashed lines) having an associated cell length L ₀ and cell width W ₀ , which may depend on the dimensions of the LGP 100 and the width of the light source 110 . varies with the number and/or spacing of LGPs 100 . In non-limiting examples, cell width _W0 and/or cell length _L0 may be less than or equal to about 150 mm, eg, ranging from about 1 mm to about 120 mm, from about 5 mm to about 100 mm, from about 10 mm to about 80 mm, from about 20 mm to about 70 mm, from about 30 mm to about 60 mm, or from about 40 mm to about 50 mm, including all ranges and subranges therebetween. In some embodiments, the length L and width W of the LGP are substantially equal, or they may be different. Similarly, cell length L ₀ and cell width W ₀ may be substantially equal, or they may be different.

Of course, although a rectangular LGP 100 is depicted in FIG. 1 , it is to be understood that the LGP may have any regular or irregular shape as appropriate to produce the desired light distribution for the selected application. LGP 100 may include four edges as shown in FIG . 1 , or may include more than four edges, such as polygons. In other embodiments, LGP 100 may include less than four edges, such as triangles. By way of non-limiting example, LGPs may include rectangular, square, or diamond-shaped sheets having four edges, although other shapes and configurations are also intended to fall within the scope of this disclosure, including having one or more curves their shapes and configurations of parts or edges.

According to various embodiments, the LGP may include any transparent material known in the art for lighting and display applications. As used herein, the term "transparent" is intended to indicate that the LGP has a light transmission of greater than about 80% over a length of 500 mm in the visible spectral region (~420-750 nm). For example, an exemplary transparent material may have a transmittance in the visible light range of greater than about 85%, such as greater than about 90%, greater than about 95%, or greater than about 99% transmittance over a length of 500 mm, including all ranges therebetween and sub-ranges. In certain embodiments, an exemplary transparent material may have a light transmittance in the ultraviolet (UV) region (~100-410 nm) of greater than about 50% over a length of 500 mm, eg, greater than about 55%, greater than about 60%, greater than about 65%, greater than about 70%, greater than about 75%, greater than about 80%, greater than about 85%, greater than about 90%, greater than about 95%, or greater than about 99% transmittance, including all therebetween Ranges and subranges. According to various embodiments, the LGP may include at least 98% optical transmission over a path length of 75 mm for wavelengths ranging from about 450 nm to about 650 nm.

The optical properties of LGP may be affected by the refractive index of the transparent material. According to various embodiments, the LGP can have an index of refraction 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 in between. In other embodiments, the LGP may have relatively low levels of light attenuation (eg, due to absorption and/or scattering). The optical attenuation (α) of the LGP may be, for example, less than about 5 dB/m for wavelengths ranging from about 420 to 750 nm. For example, a may be less than about 4 dB/m, less than about 3 dB/m, less than about 2 dB/m, less than about 1 dB/m, less than about 0.5 dB/m, less than about 0.2 dB/m, or even less , including all ranges and subranges therebetween, eg, from about 0.2 dB/m to about 5 dB/m.

The LGP 100 may include polymeric materials such as plastics such as polymethyl methacrylate (PMMA), methyl methacrylate styrene (MS), polydimethylsiloxane (PDMS), or other similar materials. LGP 100 may also include glass materials such as aluminosilicate, alkali aluminosilicate, borosilicate, alkali borosilicate, aluminoborosilicate, alkali aluminoborosilicate, soda lime, or other suitable Glass. Non-limiting examples of commercially available glasses suitable for use as glass light guides include, for example, EAGLE XG ^® , Lotus ^™ , Willow ^® , Iris ^™ and Gorilla ^® glasses from Corning Incorporated.

Certain non-limiting glass compositions may include between about 50 mole percent and about 90 mole percent SiO ₂ , between 0 mole percent and about 20 mole percent Al ₂ O ₃ , 0 mole percent to between about ₂₀ mol percent B2O3 and between 0 mol percent and about 25 mol percent RxO, wherein _{R is} any one or more of Li, Na, K, Rb, Cs and x is 2, or R is any one or more of Zn, Mg, Ca, Sr, or Ba and x is 1. In certain embodiments, R _x O - Al ₂ O ₃ >0; 0 < R _x O - Al ₂ O ₃ <15; x = 2 and R ₂ O - Al ₂ O ₃ <15; R ₂ O - Al ₂ O ₃ <2; x=2 and R ₂ O - Al ₂ O ₃ - MgO >-15; 0 < (R _x O - Al ₂ O ₃ ) < 25, -11 < (R ₂ O - Al ₂ O ₃ ) < 11 and -15 < (R ₂ O - Al ₂ O ₃ - MgO) <11; and/or -1 < (R ₂ O - Al ₂ O ₃ ) < 2 and -6 < (R ₂ O – Al ₂ O ₃ – MgO) < 1. In certain embodiments, the glass includes less than 1 ppm of each of Co, Ni, and Cr. In certain 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 glass includes between about 60 mole percent and about 80 mole percent SiO ₂ , between about 0.1 mole percent and about 15 mole percent Al ₂ O ₃ , 0 mole percent to about ₁₂ molar percent B2O3 and about 0.1 molar percent to about ₁₅ molar percent RxO, wherein R _is any one or more of Li, Na, K, Rb, Cs and x is 2, or R is any one or more of Zn, Mg, Ca, Sr, or Ba and x is 1.

In other embodiments, the glass composition may include between about 65.79 mole percent and about 78.17 mole percent SiO ₂ , between about 2.94 mole percent and about 12.12 mole percent Al ₂ O ₃ , about 0 mole percent Between about 11.16 mole percent _B2O3 , between about ₀ mole percent and about 2.06 mole percent _Li2O , between about 3.52 mole percent and about 13.25 mole percent _Na2O , K2O between about ₀ mole percent and about 4.83 mole percent, ZnO between about 0 mole percent and about 3.01 mole percent, MgO between about 0 mole percent and about 8.72 mole percent , between about 0 mole percent and about 4.24 mole percent CaO, between about 0 mole percent and about 6.17 mole percent SrO, between about 0 mole percent and about 4.3 mole percent BaO, and about SnO ₂ between 0.07 mole percent and about 0.11 mole percent.

In additional embodiments, the glass may include 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 can include 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 R is any one or more of Zn, Mg, Ca, Sr, or Ba and x is 1. In yet other embodiments, the glass may include RxO _{- Al2O3} -MgO between -4.25 and 4.0, where R _is any one or more of Li, Na, K, Rb, Cs and x is 2. In yet other embodiments, the glass can include between about 66 mole percent and about 78 mole percent SiO ₂ , between about 4 mole percent and about 11 mole percent Al ₂ O ₃ , about 4 mole percent B ₂ O ₃ between about 1 mol % and about 11 mol %, Li ₂ O between about 0 mol % and about 2 mol %, Na ₂ between about 4 mol % and about 12 mol % O, K2O between about 0 mol% and about ₂ mol%, ZnO between about 0 mol% and about 2 mol%, between about 0 mol% and about 5 mol% MgO, between about 0 mole percent and about 2 mole percent CaO, between about 0 mole percent and about 5 mole percent SrO, between about 0 mole percent and about 2 mole percent BaO, and SnO ₂ between about 0 mole percent to about 2 mole percent.

In additional embodiments, the glass may include between about 72 mole percent and about 80 mole percent SiO ₂ , between about 3 mole percent and about 7 mole percent Al ₂ O ₃ , about 0 mole percent between about 0 and about 2 mole percent of B ₂ O ₃ , between about 0 and about 2 mole percent of Li ₂ O, between about 6 and about 15 mole percent of Na ₂ O , K2O between about 0 mole percent and about ₂ mole percent, ZnO between about 0 mole percent and about 2 mole percent, MgO between about 2 mole percent and about 10 mole percent , between about 0 mol% and about 2 mol% CaO, between about 0 mol% and about 2 mol% SrO, between about 0 mol% and about 2 mol% BaO, and about SnO ₂ between 0 mole percent and about 2 mole percent. In certain embodiments, the glass may include between about 60 mole percent and about 80 mole percent SiO ₂ , between about 0 mole percent and about 15 mole percent Al ₂ O ₃ , 0 mole percent to about ₁₅ mole percent B2O3 and about ₂ mole percent to about 50 mole percent RxO, wherein R _is any one or more of Li, Na, K, Rb, Cs and x is 2, or R is any one or more of Zn, Mg, Ca, Sr, or Ba and x is 1, and wherein Fe + 30Cr + 35Ni < about 60 ppm.

In certain embodiments, LGP 100 may include a color shift Δy less than 0.015, eg, ranging from about 0.005 to about 0.015 (eg, about 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.011, 0.012, 0.013, 0.014, or 0.015). In other embodiments, the LGP may include a color shift of less than 0.008. Color shift can be characterized by measuring the change in the x and y chromaticity coordinates along the length L using the CIE 1931 standard for color measurement. For LGP, the color shift Δy can be reported as Δy=y(L ₂ )-y(L ₁ ), where L ₂ and L ₁ are the Z positions along the panel or substrate direction away from the source of the emission, and where L ₂ -L ₁ =0.5 meters. Exemplary LGPs have Δy < 0.01, Δy < 0.005, Δy < 0.003, or Δy < 0.001. According to certain embodiments, for wavelengths ranging from about 420 to 750 nm, the LGP may have an optical attenuation α ₁ (eg, due to absorption and/or scattering losses) of less than about 4 dB/m, eg, less than about 3 dB /m, less than about 2 dB/m, less than about 1 dB/m, less than about 0.5 dB/m, less than about 0.2 dB/m, or even less, eg, ranging from about 0.2 dB/m to about 4 dB/m.

In certain embodiments, LGP 100 may comprise chemically strengthened (eg, ion exchanged) glass. During the ion exchange process, ions within the glass sheet at or near the surface of the glass sheet can be exchanged for larger metal ions, eg, from a salt bath. Incorporation of larger ions into the glass can strengthen the sheet by creating compressive stress in nearby surface regions. A corresponding tensile stress can be induced in the central region of the glass sheet to balance the compressive stress.

Ion exchange can be accomplished, 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 the time period of treatment can vary. Determining the time and temperature depending on the desired application is within the capabilities of those skilled in the art. By way of non-limiting example, the temperature of the molten salt bath can range from about 400 ºC to about 800 ºC, such as from about 400 ºC to about 500 ºC, and the predetermined time period can 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 also contemplated. By way of non-limiting example, the glass can be immersed, for example, at about 450 ^° C. in a KNO ₃ bath for about 6 hours to obtain a K-rich layer that imparts compressive stress to the surface.

2 , which depicts a top view of an exemplary patterned reflective layer 120 , the reflective layer can have at least two regions with different optical properties. For example, the patterned reflective layer may include optically reflective elements 120A (represented by white dots), which may have higher optical reflectivity than optical transmissive elements 120B (represented by black dots), and/or transmissive Element 120B may have an optical transmittance greater than that of reflective element 120A . Again, for illustrative purposes, the two exemplary light sources 110 may be seen through the patterned reflective layer 120 in FIG. 2 , although in some embodiments this may not be the case.

In some embodiments, the first region 125A may have denser reflective elements 120A in the region corresponding to the at least one light source 110 , as depicted in FIG . 2 . The second region 125B may similarly have denser transmissive elements 120B in the region between the light sources 110 , as depicted in FIG . 2 . After assembly, the first regions 125A with high reflectivity and/or low transmittance can be distributed over each discrete light source 110 in the light source array with a higher density, and a higher density can be used with low reflectivity and/or low transmittance Or second regions 125B of high transmittance are distributed in regions near or between the light sources.

The patterned reflective layer 120 may include any material capable of at least partially modifying the light output from the LGP 100 . In certain embodiments, the patterned reflective layer 120 may include a patterned metal film, a multilayer dielectric film, or any combination thereof. In some examples, the reflective elements 120A and transmissive elements 120B and/or the first and second regions 125A and 125B of the patterned reflective layer 120 may have different diffuse or specular reflectivity. In other embodiments, the patterned reflective layer 120 can adjust the amount of light transmitted by the LGP 100 . For example, the reflective element 120A and the transmissive element 120B and/or the first region 125A and the second region 125B of the patterned reflective layer 120 may have different transmittances.

According to various embodiments, the first reflectivity of the first region 125A may be about 50% or more, and the second reflectivity of the second region 125B may be about 20% or less. For example, the first reflectivity may be at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, or at least about 92%, eg, ranging from about 50% to 100%, inclusive All scopes and subscopes of . The second reflectivity can be about 20% or less, about 15% or less, about 10% or less, or about 5% or less, eg, ranging from 0% to about 20%, including all ranges therebetween and sub-ranges. In certain embodiments, the first reflectivity may be at least about 2.5 times greater than the second reflectivity, eg, about 3 times greater, about 4 times greater, about 5 times greater, about 10 times greater, about 15 times greater, or about 20 times greater, eg, from about 2.5 times greater to about 20 times greater, including all ranges and subranges therebetween. The reflectivity of the patterned reflective layer 120 can be measured, for example, by a UV/Visible (UV/Vis) spectrometer available from Perkin Elmer Corporation.

In additional non-limiting examples, the first transmittance of the first region 125A may be about 50% or less, and the second transmittance of the second region 125B may be about 80% or greater. For example, the first transmittance may be about 50% or less, about 40% or less, about 30% or less, about 20% or less, or about 10% or less, eg, ranging from 0% to About 50%, including all ranges and subranges therebetween. The second transmittance can be about 80% or greater, about 85% or greater, about 90% or greater, or about 95% or greater, eg, ranging from 80% to 100%, including all ranges therebetween and sub range. In certain embodiments, the second transmittance may be at least about 1.5 times greater than the first transmittance, such as about 2 times greater, about 3 times greater, about 4 times greater, about 5 times greater, about 10 times greater, about 15 times greater or about 20 times greater, such as from about 1.5 times greater to about 20 times greater, including all ranges and subranges therebetween. The transmittance of the patterned reflective layer 120 can be measured, for example, by a UV/Visible (UV/Vis) spectrometer available from Perkin Elmer Corporation.

Reflective elements 120A and/or transmissive elements 120B may be positioned in reflective layer 120 to create any given pattern or design, which may, for example, be random or arranged, repeating or non-repeating, uniform or non-uniform of. As such, while FIG. 2 depicts an exemplary repeating pattern of reflective elements 120A and transmissive elements 120B , it is to be understood that other patterns (both regular and irregular) may be used and are intended to fall within the scope of this within the scope of the disclosure. In some embodiments, the elements may form a gradient, such as decreasing from the first region 125A to the second region 125B , decreasing from the light source to the region between the light sources, or from the center of each cell block to the edge of each cell block and/or corner-reduced reflectivity gradients. In additional embodiments, the reflective and transmissive elements may be formed to increase from the first area 125A to the second area 125B , from the light source to the area between the light sources, or from the center of each unit block to the edge of each unit block and /or increased transmittance gradient at the corners, etc.

Referring to FIG. 3 , which depicts a cross-sectional view of an exemplary BLU, LGP 100 may include a first major surface 100A that emits light and an opposing second major surface 100B . In certain embodiments, the major faces may be flat or substantially flat and/or parallel or substantially parallel. In certain embodiments, LGP 100 may have a thickness t extending between the first and second major faces that is less than or equal to about 3 mm, eg, ranging from about 0.1 mm to about 2.5 mm, from From about 0.3 mm to about 2 mm, from about 0.5 mm to about 1.5 mm, or from about 0.7 mm to about 1 mm, including all ranges and subranges therebetween.

The patterned reflective layer 120 may be positioned near the first major face 100A of the LGP 100 . As used herein, the term "positioned near" and variations thereof is intended to indicate that an element or layer is positioned near a particular surface or recited element, but is not necessarily directly physical with that surface or element touch. For example, in the non-limiting embodiment depicted in Figure 3 , the patterned reflective layer 120 is not in direct physical contact with the first major face 100A , eg, an air gap exists between the two elements. However, in some embodiments, the patterned reflective layer 120 may be integrally integrated with the LGP 100 , eg, disposed on the first major face 100A of the LGP 100 . As used herein, the phrase "disposed on" and variations thereof is intended to indicate that an element or layer is in direct physical contact with a particular surface or recited element. In other embodiments, one or more layers or films, such as adhesive layers, may be present between the two elements. As such, element A positioned near the surface of element B may or may not be in direct physical contact with element B.

Although FIG. 3 depicts a single patterned reflective layer 120 , it is to be understood that the reflective layer 120 may comprise multiple sheets, films or layers. For example, the patterned reflective layer 120 may be a multilayer composite film or coating, such as a dielectric coating. In other embodiments, the portion of the reflective layer corresponding to the first region 125A may be applied to the LGP 100 first, and the portion of the reflective layer corresponding to the second region 125B may be subsequently applied to the LGP, or vice versa. Alternatively, a first film or layer having a first optical property can be positioned over one or more portions of LGP 100 and a second film or layer having a second optical property can be coated to cover substantially all of LGP 100 part, including the part covered by the first film. In such embodiments, the first region 125A of the multilayer reflective layer may have the combined optical properties of the first and second films, while the second region 125B may have only the optical properties of the second film, or vice versa. The patterned reflective layer 120 may thus comprise a single film or composite film, a single layer, or multiple layers, as appropriate, to produce the desired optical effect.

Regardless of the configuration of the patterned reflective layer, it is to be understood that the embodiments disclosed herein may include a patterned reflective layer having at least one optical property that is lower in reflection than the second region 125B (eg, lower reflection) (eg, higher reflectance and/or lower transmittance) in the first region 125A . The areal density of reflective elements 120A and transmissive elements 120B may vary across reflective layer 120 such that higher density reflective elements 120A are present in first region 125A positioned above light source 110 , while higher density transmissive elements 120B are present in Positioned in the second region 125B between the light sources 110 . Also, embodiments of the BLU disclosed herein produce substantially uniform light, eg, light emitted from regions corresponding to light sources may have an illuminance substantially equal to that of light emitted from regions between light sources.

As shown in FIG. 3 , the at least one light source 110 may be optically coupled to the second major face 100B of the LGP 100 . Non-limiting exemplary light sources may include light emitting diodes (LEDs), such as LEDs that emit blue, UV, near UV light (eg, light having wavelengths ranging from about 100 nm to about 500 nm). As used herein, the term "optically coupled" is to be used to indicate that a light source is positioned at the surface of the LGP so as to direct light into the LGP such that the light propagates at least in part due to total internal reflection. The light source 110 may be in direct physical contact with the LGP 100 as shown in FIG . 3 . However, the light source can be optically coupled to the LGP even if the light source is not in direct physical contact with the LGP. For example, the optical adhesive layer 150 may be used to adhere the light source 110 to the second major face 110B of the LGP 100 as depicted in FIG . 4 . In certain embodiments, the optical adhesion layer may be index matched to LGP 100 , eg, having an index of refraction within 10% of the index of refraction of LGP, eg, within 5%, within 3%, within 2%, within 1%, or Has the same refractive index as LGP.

Referring again to FIG. 3 , the BLU may further include a rear reflector 130 positioned near the second main face 100B of the LGP 100 . The optical distance OD for light to travel between two reflectors can thus be defined as the distance between the patterned reflective layer 120 and the back reflector 130 . Exemplary back reflectors 130 may, for example, include metal foils such as silver, platinum, gold, copper, and the like. As further depicted in FIG. 4 , the backlight unit may include one or more additional films or elements, such as one or more auxiliary optical films and/or structural elements. Exemplary auxiliary optical films 170 may include, but are not limited to, diffuser films, diaphanous films, such as brightness enhancement films (BEF), or reflective polarizing films, such as dual brightness enhancement films (DBEF), to name a few. In some embodiments, the light source 110 and/or the back reflector 130 may be disposed on the printed circuit board 140 . Auxiliary optical elements (eg, diffuser film 160 , color conversion layer 170 (eg, including quantum dots and/or phosphors), fluorine film 180 , and/or reflective polarizer film 190 ) may be positioned between patterned reflective layer 120 and the display panel between 200 . Although not shown in Figure 4 , the BLUs disclosed herein may include other elements commonly found in display or lighting devices such as thin film transistor (TFT) arrays, liquid crystal (LC) layers, and color filters, only to name a few exemplary elements) or may be combined with such other elements.

Referring back to FIG. 3 , the light rays emitted from the light source 110 are depicted by dashed arrows, dashed-dotted arrows, and solid arrows. For illustrative purposes only, transmissive elements 120B are depicted as dots with varying dimensions representing the density of the transmissive elements along the light guide plate, eg, having a low density above the light source 110 and increasing the density further away from the light source 110 . high. The density of reflective elements 120A and/or transmissive elements 120B can be increased or decreased by increasing the number and/or size of the elements. Also, the reflective element 120A and/or the transmissive element 120B may have any shape or combination of shapes, including circles, ovals, squares, rectangles, triangles, or any other regular or irregular polygons, including those with straight and/or curved edges shape.

The first ray (dashed arrow) injected into the LGP 100 may directly proceed through the LGP without propagating laterally within the LGP 100 , and may also pass through the second region 120B of the patterned reflective layer 120 without being retroreflected therethrough LGP, resulting in the first transmitted light T ₁ . The second ray (dash-dotted arrow) injected into LGP 100 may proceed directly through the LGP without propagating laterally within LGP 100 , but may strike reflective element 120A in patterned reflective layer 120 and travel back through LGP 100 to Rear reflector 130 . The second light ray may thus traverse the optical distance OD one or more times while being reflected between the patterned reflective layer 120 and the back reflector 130 . Finally, the second light will pass through the transmissive element 120B of the patterned reflective layer 120 , resulting in a second transmitted light _T2 .

A third ray (solid arrow) may be injected into the LGP 100 and may propagate within the LGP due to total internal reflection (TIR) until the third ray hits the light extraction feature or otherwise with an angle of incidence less than the critical angle hits the surface of the LGP and transmits through the LGP. The optical distance traveled by the third ray can thus be reduced to the thickness t of the LGP 100 . While the third ray may experience some light losses during TIF due to absorption by the LGP 100 , such light losses may be relatively small compared to those of the second ray traveling the optical distance OD because The third rays travel a short vertical and/or horizontal distance. Specifically, light tends to travel only about half the distance (pitch) between the traveling light sources before being extracted out of the LGP 100 . In certain embodiments, the light source spacing may correspond to a cell width W0 ₍ shown) or a cell length (not shown), which may be less than or equal to about 150 mm, or even less than about 80 mm, such as As discussed with reference to FIG. 1 . Finally, the third ray will also pass through the transmissive element 120B of the patterned reflective layer, resulting in a third transmissive ray T ₃ .

Total Internal Reflection (TIR) is the means by which light propagating in a first material (eg glass, plastic, etc.) comprising a first refractive index can interact with a second material comprising a second refractive index lower than the first refractive index (eg glass, plastic, etc.) Such as air, etc.) the phenomenon of complete reflection at the interface of the joint. TIR can be explained using Snell's law: n ₁ sin( θ _i ) = n ₂ sin( θ _r ) which describes the refraction of light at the interface between two materials with different indices of refraction. According to Snell's law, n ₁ is the refractive index of the first material, n ₂ is the refractive index of the second material, θ _i is the angle of light incident at the interface with respect to the interface normal (angle of incidence), and Θ _r is the angle of refraction of the refracted light relative to the normal. When the angle of refraction (Θ _r ) is 90 ^o (eg sin(Θ _r ) = 1), Snell's law can be expressed as:

The angle of incidence Θ _i under these conditions may also be referred to as the critical angle Θ _c . Light with an angle of incidence greater than the critical angle (Θ _i > Θ _c ) will be totally internally reflected within the first material, while light with an angle of incidence equal to or less than the critical angle (Θ _i ≤ Θ _c ) will be reflected by the first material transmission.

In the case of an exemplary interface between air ( n ₁ =1) and glass ( n ₂ =1.5), the critical angle (Θ _c ) can be calculated as 41 ^o . Therefore, if light propagating in glass strikes an air-glass interface with an angle of incidence greater than 41 ^° , all incident light will be reflected from the interface at an angle equal to the angle of incidence. If the reflected light encounters a second interface comprising the same refractive index relationship as the first interface, light incident on the second interface will again be reflected with a reflection angle equal to the angle of incidence.

According to various embodiments, the first major face 100A and/or the second major face 100B of the LGP 100 may be patterned to have a plurality of light extraction features. As used herein, the term "patterned" is intended to indicate that the plurality of light-extracting features are present on or under the surface of the LGP in any given pattern or design, which may, for example, be random or Arranged, repeated or not, uniform or non-uniform. In other embodiments, light extraction features may be positioned within a matrix of LGPs near the surface (eg, below the surface). For example, light extraction features may be distributed across a surface (eg, as textured features that make up a rough or raised surface), or may be distributed within and throughout an LGP or a portion of an LGP (eg, as a location or feature of laser damage) ). Suitable methods for creating such light extraction features may include printing (eg, inkjet printing, screen printing, microprinting, etc.), texturing, mechanical roughening, etching, injection molding, coating, laser damage , or any combination thereof. Non-limiting examples of such methods include, for example, acid etching the surface, coating the surface with _TiO2 , and laser-damaging the substrate by focusing the laser on the surface or within the substrate matrix.

Each application may be prepared according to any method known in the art (such as the methods disclosed in co-pending and co-owned international patent applications of PCT/US2013/063622 and PCT/US2014/070771). The entire contents of which are incorporated herein by reference) process LGP to generate light extraction features. For example, the surface of the LGP can be ground and/or polished to achieve a desired thickness and/or surface quality. The surface may then optionally be cleaned and/or the surface to be etched may be subjected to a process for removing contaminants (eg, exposing the surface to ozone). By way of non-limiting example, the surface to be etched may be exposed to an acid bath such as glacial acetic acid (GAA) and ammonium fluoride (NHF) in a ratio (eg, ranging from about 1:1 to about 9:1). ₄ F) mixture). The etching time can range, for example, from about 30 seconds to about 15 minutes, and the etching action can occur at room temperature or at elevated temperature. Process parameters such as acid concentration/ratio, temperature and/or time may affect the size, shape and distribution of the resulting extraction features. Varying these parameters to achieve desired surface extraction characteristics is within the capabilities of those skilled in the art.

While the pattern of light extraction features may be selected to improve light extraction uniformity along the length and width of the LGP 100 , it is possible that areas of the LGP corresponding to individual light sources may emit light with higher intensities (eg, the overall LGP's overall light output may not be uniform). The patterned reflective layer 120 can thus be engineered to have regions with varying optical properties to further homogenize the light output. For example, the patterned reflective layer 120 may provide increased reflectivity and/or reduced transmittance in the first regions 125A corresponding to the light sources and increased transmittance and/or reduced transmittance in the second regions 125B between the light sources reflectivity. Such a configuration may allow a diffusing film or other optical film to be placed closer to the light source, and thus allow for a thinner overall BLU and resulting illumination or display screen.

In conventional direct lighting assemblies, as the optical distance between the back reflector and the patterned reflective film becomes smaller, the number of light reflections increases, which results in increased light loss. However, in the BLUs disclosed herein, incorporating an LGP optically coupled to the light source may allow for reduced light loss along the Propagating light sideways along the length of the LGP.

In a reference device that propagates light sideways only by a reflector (eg, the device of FIG. 3 without LGP), light with an angle of incidence (θ) can pass through one or more of the reflective layers between the two reflective layers. Each reflection travels a lateral distance (X) over a vertical distance (d). The number (N) of reflections can be represented by N=X/d*tan(θ). Assuming both reflectors have 98% reflectivity, after N reflections, the light will have 98%^N remaining energy. Table 1 below shows the number of reflections and Table 2 shows the remaining percentage of light energy for different combinations of the angle of incidence (θ) and the ratio X/d.

As the ratio X/d increases, the light loss due to multiple reflections between the reflectors becomes strikingly apparent. As mentioned above, the spacing between the light sources can be up to 150 mm. As the vertical distance decreases, the ratio X/d can increase rapidly and will exceed 50 in many cases. At X/d = 50, the residual energy of light with an angle of incidence Θ = 10 ^° is less than 1%.

Referring to FIG. 5A , light is emitted from the light source 110 with an emission angle Θ _LED and delivered to the LGP 100 . Light is incident on the light emitting face of the LGP with an angle of incidence Θ _LGP that does not exceed the critical angle Θ _C and thus does not cause TIR within the LGP 100 . A portion of the light travels a lateral distance X ₁ (expressed as X ₁ = t*tan(sin ^-1 (sin(Θ)/n)), where n is the index of refraction of the LGP and t is the thickness of the LGP 100 ), And the transmission becomes the first transmission T ₁ . The smaller portion of the light travels a second lateral distance X ₂ (denoted as X ₂ = 3X ₁ ), and the transmission becomes the second transmission T ₂ . Table 3 below lists the percentages of the luminous flux of the first reflection R ₁ , the second reflection R ₂ , the first transmission T ₁ and the second transmission T ₂ for different emission angles _ΘLED = 20 ^° , 41 ^° and 60 ^° , assuming that the index of refraction (n) of the LGP is 1.5. The higher order reflection _R3 and transmission _T3 (see Figure 5B ) are negligible since the total flux is less than 1%. Regardless of the angle of emission, the majority of the light may only travel a lateral distance X1 and be transmitted as _T1 , while less than ₁ % of the light is transmitted as _T2 . Even light transmitted _T2 can only travel a maximum lateral distance X2 _{= 3X1} in the depicted configuration. Table 3 : Luminous Flux Percentage

5B , light is emitted from the light source 110 optically coupled to the _LGP 100 such that the emission angle ΘLED is substantially equal to the incident angle ΘLG _. Optical coupling (eg, using an index-matching optical adhesive) allows at least a portion of the light to travel laterally along the length of the LGP due to TIR. A portion of the light travels a lateral distance X ₁ (expressed as X ₁ = t*tan(Θ), where t is the thickness of the LGP 100 ), and the transmission is the first transmission T ₁ . A portion of the light travels a second lateral distance X ₂ (denoted as X ₂ = 3X ₁ ) due to reflections between, and is transmitted as a second transmission T ₂ . Once the angle of incidence exceeds the critical angle (eg, greater than about 42 ^° in the depicted configuration), light rays may experience TIR, which allows the light to travel significantly larger lateral distances within the LGP before being extracted. As such, a portion of the light may travel a lateral distance _X3 due to TIR and be transmitted as a third transmission _T3 .

Table 4 below lists the first reflection R ₁ , the second reflection R ₂ , the first transmission T ₁ , the second transmission T ₂ , the third reflection R ₃ and the third transmission for emission angles _ΘLED = 20 ^° and 41 ^° T ₃ percent of the luminous flux, assuming that the index of refraction (n) of the LGP is 1.5. In both Tables 3 and 4, for an emission angle _ΘLED = 20 ^° , the majority of the light is transmitted as T ₁ . However, in Table 3 (no optical coupling), X ₁ = 0.23t, and in Table 4 (optical coupling), X ₂ = 0.36t, indicating that light with the same emission angle (20 ^o ) is in the optical coupling A longer lateral distance travels in the LGP connected to the light source. For the emission angle _ΘLED = ^41o , the light travels a longer lateral distance in the optically coupled LGP (Table 4) compared to the uncoupled LGP (Table 3), as shown in Table 4. implied by the high _T2 and _T3 values. Table 4 : Luminous Flux Percentage

6A-D, the effect of TIR on lateral light propagation can be further demonstrated by comparing backlight assemblies including a rear reflector, a patterned reflector, at least one LED, and an LGP positioned between the reflectors. Four cases were investigated where: (a) the bottom reflector had 98% Lambertian reflectance and 2% absorptivity; (b) the LED had 60% Lambertian reflectance and 40% absorptivity; (c) ) LGP includes glass with an index of refraction of 1.5 and a thickness varying from 0.1 mm to 5 mm, the glass optically coupled to the LED; and (d) the patterned reflector has one of four different properties: (i) Case I: 98% specular reflectance and 2% absorptivity ( Fig. 6A ); (ii) Case II: 92% specular reflectance and 8% absorptivity ( Fig. 6B ); (iii) Case III: 98 % Lambertian reflectance and 2% absorptivity ( FIG. 6C ); or (iv) Case IV: 92% Lambertian reflectance and 8% absorptivity ( FIG. 6D ).

The above-described components including LGP were compared to identical components that did not have LGP and instead included an air gap with a distance corresponding to the thickness of the LGP.

Referring to Figures 6A-D , which are plotted as light extraction efficiency as a function of LGP/air gap thickness, in all four cases, the light extraction efficiency of a component including an air gap decreases with decreasing thickness t . In contrast, the light extraction efficiency of components including LGP increased as the thickness t decreased from 5 mm to about 0.7 mm. In all cases, for thicknesses of about 2 mm and below, the light extraction efficiency of components comprising LGP is significantly higher than that of components with air gaps. As customer demand for thinner display devices increases, variants to reduce the overall thickness of the BLU are equally desirable. By positioning the optically coupled LGP between the patterned reflective layer and the back reflector, light losses that might otherwise occur as the distance between the reflectors decreases, and the overall thickness of the BLU can be effectively reduced.

In additional embodiments, such as the configuration depicted in FIG. 7 , it may be desirable to include one or more microstructures 105 on the first major face 100A of the LGP 100 . In certain embodiments, the microstructures 105 may be used to redirect normally incident light toward off-axis angles to further facilitate side propagation of light from the light source and/or reduce light loss caused by absorption by the light source (eg, LEDs). In such embodiments, the light extraction efficiency can be improved by up to 5% compared to configurations without microstructures on the LGP, eg, ranging from about 1% to about 4%, or from about 2% to about 3% %, including all ranges and subranges in between.

In some embodiments, the microstructures 105 may have a pyramid shape. The pyramid shape may be individual raised features (as shown) or straight grooves. The raised microstructures can be formed, for example, from the same or different materials as the LGP, such as glass and plastic. The raised microstructures can be made, for example, by molding or microprinting the microstructures on the first major face 100A . In further embodiments, the microstructures may be stamped or etched into the first major face 100A . According to further embodiments, the base angle Θ _M formed by the microstructures and the first major face 100A may range from about 20 ^° to about 40 ^° , such as from about 25 ^° to about 35 ^° , or about 30 ^° , inclusive. All scopes and subscopes.

8A-8B illustrate certain embodiments of multilayer variable reflectors in accordance with certain embodiments of the present disclosure. Referring to Figure 8A, a non-limiting embodiment is depicted having an LED size of about 1 mm x 1 mm and an LGP thickness of about 1 mm. In this non-limiting example, the spacing of the LEDs (distance between centers) is 100 mm, where the size of an individual 2D dimmed area or the size of an area illuminated by one LED is 100 mm x 100 mm. As depicted in Figure 8A , light rays emitted by LEDs outside the escape cone having an angle of about 42 degrees or higher with respect to the surface normal (for an LGP index of 1.5) will be totally internally reflected And thus captured by LGP. If the top reflector is not present, the light in the cone will escape. In this non-limiting example, the intersection of the escape cone and the top surface of the LGP is about 3 mm x 3 mm or about 1000 times smaller than the size of the dimmed area. Meanwhile, for emitters with a Lambertian angle light distribution, about 45% of the total emitted flux is within the escape cone. Thus, if a reflector as shown in Figure 8A happens to cover the escape cone, in order to achieve uniform illumination over the LGP, between about 0.1% and 0.2% of the light impinging on the reflector would need to be transmitted (depending on the reflection rate and exact values of other design parameters that determine backlight efficiency). Therefore, for a 3 mm x 3 mm square, if a single pattern feature or "hole" is made in the reflector, the feature size will be between about 95 µm x 95 µm and about 134 µm x 134 µm . Having only one feature will inevitably produce brighter areas above the feature (hot spots) and darker areas around the feature (cold spots). Indeed, in order to improve brightness uniformity over an area exceeding 3 mm x 3 mm, it may be necessary in some embodiments to fabricate a plurality of pattern features with correspondingly smaller dimensions. Such small features typically require some form of photolithography process to produce. If a highly reflective paint or ink is used to make the variable reflector, it may also be necessary to build a thickness of 100 µm or more before high reflectivity is achieved.

Referring to Figure 8B , another non-limiting embodiment having a reflector comprising two or more layers is shown. In certain embodiments, an exemplary reflective paint can transmit about 95% of the input light, and if the first layer of the reflector only lets 5% of the light out, the second layer should transmit between 2% and 4% input light. In embodiments where the second layer is fully opaque, this would correspond to a pattern feature size in the second layer between about 0.42 mm by 0.42 mm and 0.6 mm by 0.6 mm. Such feature sizes are easier to manufacture than the embodiment depicted in Figure 8A, and more uniform brightness is easier to achieve.

Figures 8A and 8B thus illustrate that the size of two features (one being a pattern feature (eg "holes" or "islands") and the other being a reflective layer can be varied in an exemplary embodiment transmittance/reflectance of each of the ) to keep the ratio of feature size to layer thickness within an easily accessible range for printing. Depending on the type of reflective ink or lacquer available, any suitable digital printing technique may be used, such as ink jet printing, screen printing, flexographic printing, and the like. In some embodiments, the advantage of using white paint or ink as the reflector material in thin backlight designs is that the paint generally has diffuse rather than specular reflectivity, which will help avoid too much reflected light back to the LED source, and The backlight efficiency is further increased.

If used in the thin backlight designs disclosed herein, exemplary variable reflectors can be printed on the top surface of the LGP and any other suitable surface above the LGP (eg, an optical diffuser, diffuser, or on the underside of the Brightness Enhancement Film (BEF). If the exemplary variable reflector is printed on the LGP, an additional advantage provided to the corresponding display is that the light extraction features can be printed in the same operation as the first layer of the variable reflector, since the white paint is in this It is well known in the art for use as an efficient light extractor.

In some embodiments, if the exemplary variable reflector is printed on the underside of the BEF, diffuser, or other element of the backlight other than the LGP, the presence of the LGP may not be necessary, but may still provide ease of manufacture and The advantage of higher luminance uniformity.

To illustrate certain examples, multiple samples with different thicknesses d were prepared by printing the commercially available white ink LH-100 on glass with a Mimaki UJF7151 plus printer. One sample had d = 0, ie no white ink; the second sample had d = d0 = 0.025 mm; and the other samples had ink thicknesses between 0 and 6xd0. Using an Imaging Sphere for Scatter and Appearance (IS-SA) detector (available from Radiant Imaging) and a light source at normal incidence and a wavelength of 550 nm, each sample was analyzed using an Imaging Sphere for Scatter and Appearance (IS-SA) detector. Measure the cosine-corrected bidirectional transmission distribution function (ccBTDF) above (ccBTDF(0) at zero degrees has been determined to be a good measure for transmitted intensity). The same instrument was also used to measure the cosine-corrected bidirectional reflectance distribution function (ccBRDF). Since, in the case of normal incidence, the reflected beam and the incident beam overlap spatially, ccBRDF(0) cannot be obtained; however, it has been determined that total integrated scattering (TIS_R) from the ccBRDF is the quantified reflected light good measure.

Table 5 below provides a table of TIS_R and ccBTDF(0) at zero degrees versus relative ink thickness d/d0 for a wavelength of 550 nm. Form 5

Referring to Table 5, it can be observed that the transmitted light intensity at normal incidence, quantified by ccBTDF(0), can be varied by more than 3 orders of magnitude by controlling the thickness of the white ink. It should be noted that when the ink thickness is 2xd0 or more, the transmitted light intensity may be too small to be accurately measured. The total product scattering of reflected light can vary from about 21% to about 93%. Thus, these experimental results illustrate an exemplary variable reflector with different reflection and transmission effects and spatially varying white ink thickness.

The BLUs disclosed herein may be used in a variety of display devices including, but not limited to, televisions, computers, telephones, handheld devices, billboards, or other display screens. The BLUs disclosed herein may also be used in various lighting devices, such as lighting fixtures or solid state lighting devices.

Certain embodiments provide a backlight unit comprising: a substrate including a light emitting first major surface and an opposing second major surface; at least one light source optically coupled to the substrate; and a reflector positioned on the substrate Near the first or second major surface of the reflector, the reflector includes two or more layers of reflective material, wherein each of the layers has a first area and a second area, the first area being larger than the The second area is more reflective and the second area is more transmissive than the first area. In certain embodiments, the substrate includes glass. The glass may include a composition having on an _oxide molar percent basis: 50-90 molar percent _SiO2 , 0-20 molar percent _Al2O3 , 0-20 molar percent B _2O3 , and 0-25 mole percent _RxO , wherein _x is 2 and R is selected from Li, Na, K, Rb, Cs, and combinations thereof, or wherein x is 1 and R is selected from Zn, Mg, Ca, Sr, Ba and combinations thereof. In certain embodiments, the substrate includes a color shift Δy of less than about 0.015. In other embodiments, the substrate includes a thickness ranging from about 0.1 mm to about 2 mm. In certain embodiments, the reflective material is white ink, and wherein the total integrated scattering of reflections from the white ink varies between 4% and 93%. In certain embodiments, the substrate is a volume diffuser, surface diffuser, light guide, brightness enhancement film, or reflective polarizer. In certain embodiments, the at least one light source is optically coupled to the second major face of the light guide plate through an optical adhesive layer.

Further embodiments provide a backlight unit comprising: a substrate including a light-emitting first major surface and an opposing second major surface; a plurality of discrete light sources; a reflector positioned adjacent the second major surface; and Multilayer patterned reflectors positioned near the first major surface, each layer having a first area and a second area, the first area being more reflective than the second area, and the second area being more reflective than the first area more transmissive. In certain embodiments, the discrete light sources are positioned below the multilayer patterned reflector and above the bottom reflector, and light emitted by the light sources is due to the bottom reflector and the reflective surfaces of the patterned reflector multiple reflections at and travel laterally between the bottom reflector and the patterned reflector. In certain embodiments, the substrate includes glass. The glass may include a composition having on an _oxide molar percent basis: 50-90 molar percent _SiO2 , 0-20 molar percent _Al2O3 , 0-20 molar percent B _2O3 , and 0-25 mole percent _RxO , wherein _x is 2 and R is selected from Li, Na, K, Rb, Cs, and combinations thereof, or wherein x is 1 and R is selected from Zn, Mg, Ca, Sr, Ba and combinations thereof. In certain embodiments, the substrate includes a color shift Δy of less than about 0.015. In other embodiments, the substrate includes a thickness ranging from about 0.1 mm to about 2 mm. In certain embodiments, the substrate is a volume diffuser, surface diffuser, light guide, brightness enhancement film, or reflective polarizer. In certain embodiments, the at least one light source is optically coupled to the second major face of the light guide plate through an optical adhesive layer.

Additional embodiments provide a backlight unit comprising: a substrate including a light emitting first major surface, an opposing second major surface, and a plurality of patterned features on either the first major surface or the second major surface a plurality of discrete light sources; a reflector positioned adjacent the second major face; and a multilayer patterned reflector positioned adjacent the first major face, each of the layers having a first region and a second region , the first area is more reflective than the second area, and the second area is more transmissive than the first area. In certain embodiments, the discrete light sources are positioned directly behind the patterned substrate, and wherein light from the discrete light sources is optically coupled to the patterned glass light guide such that the first portion of the light is due to the full internal reflected to travel sideways in the patterned glass light guide and extracted by the pattern of light extractors, and a second portion of the light due to multiple reflections at the bottom reflector and the reflective surface of the patterned reflector Advance laterally between the bottom reflector and the patterned reflector. In certain embodiments, the substrate includes glass. The glass may include a composition having on an _oxide molar percent basis: 50-90 molar percent _SiO2 , 0-20 molar percent _Al2O3 , 0-20 molar percent B _2O3 , and 0-25 mole percent _RxO , wherein _x is 2 and R is selected from Li, Na, K, Rb, Cs, and combinations thereof, or wherein x is 1 and R is selected from Zn, Mg, Ca, Sr, Ba and combinations thereof. In certain embodiments, the substrate includes a color shift Δy of less than about 0.015. In other embodiments, the substrate includes a thickness ranging from about 0.1 mm to about 2 mm. In certain embodiments, the substrate is a volume diffuser, surface diffuser, light guide, brightness enhancement film, or reflective polarizer. In certain embodiments, the at least one light source is optically coupled to the second major face of the light guide plate through an optical adhesive layer. In certain embodiments, the substrate is a patterned glass light guide plate with light extractor patterns on both the first major side and the second major side.

It will be appreciated that various disclosed embodiments may involve specific features, components or steps described in connection with the specific embodiment. It will also be understood that although described in association with one particular embodiment, the particular features, components or steps may be interchanged or combined with alternative embodiments in various unillustrated combinations or permutations.

It is also to be understood that, as used herein, the terms "the", "one (a)" or "an (an)" refer to "at least one" and should not be limited to "only one" unless expressly Indicate the opposite. Thus, for example, reference to "a light source" includes instances with two or more such light sources, unless the context clearly dictates otherwise. Likewise, "plural" or "array" is intended to indicate "more than one". Thus, "light scattering features" includes two or more such features, such as three or more such features, etc., and "array of holes" includes two or more such holes, such as three or more such holes, etc.

Ranges may be expressed herein as from "about" one particular value and/or to "about" another particular value. When expressing such ranges, examples include from that one particular value and/or to another particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be appreciated that the particular value forms another aspect. It will be further understood that an endpoint of each of the ranges is significant relative to and independent of the other endpoint.

As used herein, the terms "substantially," "substantially," and variations thereof are intended to describe that the feature is equal or nearly equal to a value or description. For example, a "substantially flat" surface is intended to indicate a flat or nearly flat surface. Also, "substantially similar" is meant to indicate that two values are equal or nearly equal. In certain embodiments, "substantially similar" may indicate values within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

Although the conjunctive phrase "comprising" may be used to disclose various features, components, or steps of a particular embodiment, it is to be understood that alternative embodiments (including the conventional phrase "consisting of" or "substantially consisting of" may be used ...composition" to describe those embodiments) are implied. Thus, for example, alternative embodiments implied for a device comprising A+B+C include embodiments where the device consists of A+B+C and embodiments where the device consists essentially of A+B+C.

Those skilled in the art will understand that various modifications and variations can be made in the present disclosure without departing from the spirit and scope of the disclosure. As modifications, combinations, sub-combinations, and variations of the disclosed embodiments that incorporate the spirit and essence of the present disclosure may occur to those skilled in the art, the present disclosure should be deemed to include the appended claims and their equivalents everything within range.

100‧‧‧Light Guide Plate (LGP) 100A‧‧‧First Major Surface 100B‧‧‧Second Major Surface 105‧‧‧Microstructure 110‧‧‧Light Source 120‧‧‧Patterned Reflective Layer 120A‧‧‧Optical Reflection Element 120B‧‧‧Optical Transmitting Element 125A‧‧‧First Area 125B‧‧‧Second Area 130‧‧‧Rear Reflector 140‧‧‧Printed Circuit Board 150‧‧‧Optical Adhesive Layer 160‧‧‧Diffusing Film 170‧‧‧Auxiliary Optical Film/Color Conversion Layer 180‧‧‧Electrical Film 190‧‧‧Reflecting Polarizing Film 200‧‧‧Display Panel L‧‧‧Length L ₀ ‧‧‧Unit Length OD‧‧‧Optical Distance R ₁ ‧‧‧First reflection R ₂ ‧‧‧Second reflection R ₃ ‧‧‧Third reflection t‧‧‧Thickness T ₁ ‧‧‧First transmission T ₂ ‧‧‧Second transmission T ₃ ‧‧‧Third Three Transmission W‧‧‧Width W ₀ ‧‧‧Cell Width X ₁ ‧‧‧Side Distance X ₂ ‧‧‧Side Distance X ₃ ‧‧‧Side Distance Θ _LED ‧‧‧Emitting Angle Θ _LGP ‧‧‧ Incidence angle

The following detailed description can be further understood when read in conjunction with the following drawings.

1 illustrates a light guide plate and an array of light sources optically coupled to the light guide plate;

2 illustrates an exemplary patterned reflective layer in accordance with certain embodiments of the present disclosure;

3-4 illustrate cross-sectional views of exemplary BLUs in accordance with various embodiments of the present disclosure;

5A-B illustrate lateral propagation of light within a light guide;

6A-D are plots of light extraction efficiency for exemplary BLUs with various patterned reflective layers;

7 illustrates LGP patterned with microstructures in accordance with additional embodiments of the present disclosure;

8A-8B illustrate certain embodiments of multilayer variable reflectors in accordance with certain embodiments of the present disclosure.

Domestic storage information (please note in the order of storage institution, date and number) None

Foreign deposit information (please note in the order of deposit country, institution, date and number) None

100‧‧‧Light Guide Plate (LGP)

100A‧‧‧First main side

100B‧‧‧Second main aspect

110‧‧‧Light source

120‧‧‧Patterned reflective layer

120A‧‧‧Optical Reflector

120B‧‧‧Optical transmission element

130‧‧‧Rear reflector

OD‧‧‧Optical distance

t‧‧‧Thickness

T ₁ ‧‧‧First transmission

T ₂ ‧‧‧Second Transmission

T ₃ ‧‧‧Third transmission

W ₀ ‧‧‧Unit width

Claims (28)

A backlight unit comprising: a substrate including a light-emitting first major surface and an opposite second major surface; a plurality of discrete light sources optically coupled to the substrate; and a reflector positioned on the substrate of the substrate Near the light emitting first major surface or the opposite second major surface, the reflector includes two or more layers of a reflective material, wherein each of the layers has a first area and a second area, the The first area corresponds to an area around each of the plurality of discrete light sources, and the second area is defined between a plurality of areas around each of the plurality of discrete light sources, the first area is larger than the The second area is more reflective and the second area is more transmissive than the first area. The backlight unit of claim 1, wherein the substrate comprises glass. The backlight unit of claim 2, wherein the glass comprises a composition, and the composition includes the following components on the basis of monoxide molar percentage: 50-90 molar percentage of SiO ₂ , 0-20 molar percentage % Al ₂ O ₃ , 0-20 mol % B ₂ O ₃ , and 0-25 mol % R _x O, where x is 2 and R is selected from Li, Na, K, Rb, Cs, and the like combination, or wherein x is 1 and R is selected from Zn, Mg, Ca, Sr, Ba, and combinations thereof. The backlight unit of claim 1, wherein the substrate includes a color shift Δy of less than 0.015. The backlight unit of claim 1, wherein the substrate includes a thickness ranging from 0.1 mm to 2 mm. The backlight unit of claim 1, wherein the reflective material is a white ink, and wherein a total integrated scattering of reflections from the white ink varies between 4% and 93%. The backlight unit of claim 1, wherein the substrate is selected from the group consisting of: a volume diffuser plate, a surface diffuser plate, a light guide plate, a brightness enhancement film, and a Reflective polarizer. The backlight unit of claim 1, wherein the substrate is a light guide plate, and the plurality of discrete light sources are optically coupled to the opposite second main surface of the light guide plate through an optical adhesive layer. A display or lighting device comprising the backlight unit of claim 1. A backlight unit, comprising: a substrate including a first main surface for light emission and an opposite second main surface; a plurality of discrete light sources; a reflector positioned adjacent the opposing second major face of the substrate; and a multilayer patterned reflector positioned adjacent the light emitting first major face, each of the multilayer patterned reflectors The layer has a first area and a second area, the first area is more reflective than the second area and corresponds to an area around each of the plurality of discrete light sources, and the second area is more reflective than the first area The regions are more transmissive and are defined between regions around each of the plurality of discrete light sources. The backlight unit of claim 10, wherein the plurality of discrete light sources are positioned between the multilayer patterned reflector and the reflector, and light emitted by the plurality of light sources is due to the reflector and the multilayer pattern The multiple reflections at the reflecting surface of the reflector travel laterally between the reflector and the multilayer patterned reflector. The backlight unit of claim 10, wherein the substrate comprises glass. The backlight unit of claim 12, wherein the glass comprises a composition comprising the following components on a molar percentage basis of monoxide: 50-90 molar SiO ₂ , 0-20 molar % Al ₂ O ₃ , 0-20 mol % B ₂ O ₃ , and 0-25 mol % R _x O, wherein x is 2 and R is selected from Li, Na, K, Rb, Cs, and the like combination, or wherein x is 1 and R is selected from Zn, Mg, Ca, Sr, Ba, and combinations thereof. The backlight unit of claim 10, wherein the substrate includes a color shift Δy of less than 0.015. The backlight unit of claim 10, wherein the substrate includes a thickness ranging from 0.1 mm to 2 mm. The backlight unit of claim 10, wherein the substrate is selected from the group consisting of: a volume diffuser plate, a surface diffuser, a light guide plate, a brightness enhancement film, and a Reflective polarizer. The backlight unit of claim 10, wherein the substrate is a light guide plate, and the plurality of discrete light sources are optically coupled to the opposite second main surface of the light guide plate through an optical adhesive layer. A display or lighting device comprising a backlight unit as claimed in claim 10. A backlight unit, comprising: a substrate including a first light-emitting main surface, an opposite second main surface, and a plurality of patterned features on the light-emitting first main surface or the opposite second main surface; a plurality of patterned features discrete light source; a reflector positioned adjacent the opposite second major face of the substrate; and a multilayer patterned reflector positioned adjacent the light emitting first major face of the substrate, each layer of the multilayer patterned reflector having a first area and a second area, the first area is more reflective than the second area and corresponds to an area around each of the plurality of discrete light sources, and the second area is more reflective than the first area Transmissive and defined between regions around each of the plurality of discrete light sources. The backlight unit of claim 19, wherein the plurality of discrete light sources are positioned between the substrate and the reflector, and wherein light from the plurality of discrete light sources is optically coupled to the substrate such that the light is A first portion travels laterally in the substrate due to total internal reflection and is extracted by patterned features of the substrate, and a second portion of the light travels laterally in the substrate due to total internal reflection, and a second portion of the light due to reflections at the reflector and the multi-layer patterned reflector Multiple reflections travel laterally between the reflector and the multilayer patterned reflector. The backlight unit of claim 19, wherein the substrate comprises glass. The backlight unit of claim 21, wherein the glass comprises a composition, the composition comprises the following components based on the molar percentage of monoxide: 50-90 molar SiO ₂ , 0-20 molar % Al ₂ O ₃ , 0-20 mol % B ₂ O ₃ , and 0-25 mol % R _x O, wherein x is 2 and R is selected from Li, Na, K, Rb, Cs, and the like combination, or wherein x is 1 and R is selected from Zn, Mg, Ca, Sr, Ba, and combinations thereof. The backlight unit of claim 19, wherein the substrate includes a color shift Δy of less than 0.015. The backlight unit of claim 19, wherein the substrate includes a thickness ranging from 0.1 mm to 2 mm. The backlight unit of claim 19, wherein the substrate is selected from the group consisting of: a volume diffuser plate, a surface diffuser plate, a light guide plate, a brightness enhancement film, and a Reflective polarizer. The backlight unit of claim 19, wherein the substrate is a light guide plate, and the plurality of discrete light sources are optically coupled to the opposite second main surface of the light guide plate through an optical adhesive layer. A display or lighting device comprising a backlight unit as claimed in claim 19. The backlight unit of claim 19, wherein the substrate is a patterned glass light guide plate having a light extractor pattern on both the light emitting first major surface and the opposite second major surface.

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