BACKGROUND OF THB INVENTION

Field of (he invention

{6601J The present invention relates to display systems comprising light- emitting diodes (LEDs), suitably blue light LEDs, which demonstrate increased optics! power output In embodiments, the display systems include compositions comprising phosphors, including luminescent nanocrysta!s.

Background of the Invention fO0O2] In liquid crystal display (LCD) backlights, white LEDs are typically utilized as a light source, in one configuration, (he LEDs are arranged around the edge or perimeter of the display. In such the case of edge-lit backlights, light emanating from the LEDs enters a light guide plate which distributes white light uniformly across the display. White LED package designs have been optimized to enable high extraction efficiency and coupling efficiency into the light guide plate.

f O803| LCD backlights often utilize phosphors, such as YAG phosphors.

Traditionally, these phosphors have been situated inside the LED package itself Luminescent nanocrystals represent a new, alternative class of phosphors often used in. remote-phosphor configurations where the phosphor is no longer inside the LED package. For example, luminescent nanocrystals can be embedded in a flexible film/sheet that is placed above a light guide plate (see, e.g., Published U.S. Pstent Application Nos, 2010/01 10728 and 2012/0113672, the disclosures of each of which are incorporated by reference herein in their entireties), in other examples, luminescent nanocrystals are encapsulated in a container, for example a capillar)', which is placed between the LEDs and the light guide plate (see, e.g., Published U.S. Patent Application No 20 ί 0/0 i 10/28). 000 1 Blue LED light .extraction efficiency and coupling efficiency into the light guide plate play a critical role in the overall display efficiency. Blue light extraction efficiency is poor in current blue LED designs, This is most likely a result of the reflection from the eaeapsu!ation-pdyuier/sir interface. A significant amount of the blue light is reflected from this interface back toward the blue die of the LED, whic in turn absorbs the blue light.

6005) Disclosed herein, are embodiments that overcome this deficiency with blue LED-based display devices, thereby increasing the optical power output of such devices.

SUMMARY OF PREFERRED EMBODIMENTS

[0006] In embodiments, the present application provides display systems, suitably comprising one or more blue Sight emitting dsode(s) (LED), a light guide plate, optically coupled to the blue LED, a display and a composition, comprising a plurality of phosphors, the composition oriented between the light guide plate and the display. Suitably, the display system exhibits increased optical power output as compared to a display system where the light guide plate not optically coupled to fee blue LED,

[000?] In embodiments, the light guide plate is optically coupled to the blue

LED with a tape or an adhesive. In embodiments, the light guide plate is optically coupled to the blue LED via an encapsulate protruding from the .LED,

fOitOS] Suitably, the phosphors are YAG phosphors, silicate phosphors, garnet phosphors, alurninale phosphors, nitride phosphors, YAG phosphors, SiAiON phosphors and CASK phosphors. In further embodiments, the phosphors are luminescent nanocrysrais, for example luminescent .nanocrystals comprising CdSe or ZnS, including for example, luminescent nanocrystals comprising CdSe/ZnS, MVZoS,. foP/ZnSe, PbSe/PbS ₅ CdSe/CdS, CdTe/CdS or CdTe/ZnS.

βΜ9] !rt exemplary embodiments, the composition is a film. {00810] Suitably, the display is a liquid crystal module.

008! 1] In additional embodiments, the -systems further comprise one or more of a diff ser. one or more brightness enhancement films (BEFs) and a reflector.

(.00012} in embodiments, the display system suitably exhibit at least a 10% increase in optical power output as compared to a display system where the light guide plate is not optically coupled to the blue LED.

OOl 3] Also provided are display systems, suitably comprising one or more blue light emitting, diodefs) (LED) a light guide piste, optically coupled to the blue LED a display and a film comprising a plurality of phosphors, the composition oriented between the light guide plate and the display. Suitably, the display system exhibits at least a 10% increase in optical power output as compared to a display system where the light guide plate is .not optically coupled to the blue LED.

|t> 4| Exemplary methods for optical coupling are described herein, as are suitable phosphors, including luminescent nanocrys als.

1 _. 000! -S| Also provided are display systems, suitably comprising one or more blue light emitting diode(s) (LED), a light guide piste, optically coupled to the blue LED, a polymeric film comprising a plurality of phosphors, the polymeric film oriented above the light guide plate, one or more brightness enhancement .films (BEFs) oriented above the polymeric film, a top di fuses- oriented above the BEFs and a liquid crystal module oriented above the top dii!user, Suitably, the display systems exhibit at least a 10% increase in optical power output as compared to a display system where the light guide plate is not. optically coupled to the blue LED.

(000!$] Exemplary methods for optical coupling are described herein, as are suitable phosphors. Including luminescent nanocrystafs.

[0001?) Also provided are methods of increasing the optical power output of a blue LED in a display system, comprising optically coupling the blue LED to a light guide plate of the display system. [00018} In embodiments of the methods, the optical coupling comprises coupling the blue LED to the light guide plate with tape .or m adhesive, in embodiments of the methods, the light, guide plate is optically coupled to the blue LED via an encapsulant protruding from the LED.

[00019] Suitably, the methods increase the optical power output of the blue LED by at least 10% as compared to a display system that does not comprise the bine LEO optically coupled to the light guide.

[00020} Further embodiments, features, and advantages of the embodiments, as well as the structure and operation of the various embodiments, are described in detail below with reference to accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

[00021] FIG. I A. shows an exemplary display system as described herein,00022] FIG. IB shows an additional exemplary display system as described herein.

00023} FlGs. 2A-2C show schematics illustrating the source of loss of optical power output in blue LEDs and the effect of optical coupling between an LED and a light guide plate,

| _. 0OO24| FIGs. 3.A-38 show theoretical calculations of spectral power density and .integrated spectral power density for blue and white LEDs,

100025] FIGs. 4A-4C show images of backlights in three different LED/optieai coupling configurations,

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[00026] It should be appreciated that the particular .implementations shown and described herein are examples and are not intended to otherwise limit the scope of the application in any way.

fO0O27] The published patents, patent applications, websites, company names, and scientific literature referred to herein are hereby Incorporated by -reference in their entirety to the same extent as if each was specifically and individually indicated to be incorporated by reference. Any conflict between any reference cited herein and the specific teachings of this specification shall be resolved in favor of the latter. Likewise, any conflict between an art-understood definition of s word or phrase and a definition of the word or phrase as specifically taught in this specification shall be resolved in favor of the latter. {000281 As used in this specification, the singular icons ^s "a " and "t e" specifically also encompass the plural forms of the terms to which they refer, unless the content clearly dictates otherwise. The term "about" is used herein to mean approximately, in the region of, roughly, or around. When referring to any numerical value, "about" means a value of - / ^» !0% of the stated value (e.g. "about 100 nm" encompasses a range of sizes from 90 nm to 1 10 am, Inclusive).

0 029) Technical and scientific terms used herein have the meaning commonly understood by one of skill in the art to which the present application pertains, unless otherwise defined. Reference is made herein to various methodologies and materials wn to those of skill in the art.

Luminescent Nanocrystal Phosphors

|0Ο03β| Described herein are various compositions comprising nanoctystsls, including luminescent nanocrystals. The various properties of the luminescent nanocrystals, including their absorption properties, emission properties and refractive index properties, can be tailored and adjusted for various applications. As used herein, the term "nanocrystal" refers to nanostructores that are substantially monocrystallme. A. nanocrystal has at least one region or characteristic dimension with a dimension of less than about 500 ran, and down to on the order of less than about Ϊ mn. The terms "nanocrystal," "nanodot," "dot," "quantum dot" and "QD" are readily understood by the ordinarily skilled artisan to represent like structures and are used herein interchangeably. The present invention also encompasses the use of polyerystaH!ne or amorphous nanocrystals. As used herein, the term "nanocrystal" also encompasses "luminescent nanocrystals." As used herein, the term "luminescent nanocrystats" mesas sianoerystals that emit, light when excited by an extents! energy source (suitably light).

0Οβ311 The material properties of nanoerystais can be substantially homogenous, or in certain embodiments, can he heterogeneous. The optical properties of nanocrystaJs can be determined by their particle size, chemical or surface composition. The ability to tailor the luminescent nanocrysiai ske in the range between about I nm and about 15 nm enables photoemmion coverage in the -entire optical spectrum to offer great versatility in color rendering. Particle encapsulation offers robustness against chemical and IN deteriorating agents,

[O0O32J Nanoerysiais, including luminescent nanoerystais, for use in embodiments described herein can be produced using any method known to those skilled in the art. Suitable methods and exemplary nanoerysiais are disclosed in U.S. Patent No. 7,374,80?; U.S. patent application Ser. No. ! 0/796,832, filed Mar. 10, 2004; U.S. Pat. No. 6, 9,206; and U.S. Provisional Patent Application o, 60/578,236, filed inn. 8, 2004. the disclosures of each of which are incorporated by reference herein in their entireties.

|00O33| Luminescent nanoerysta!s for use in embodiments described herein can be produced from any suitable material, including an Inorganic material, and more suitably an inorganic conductive or sernieondnctive material Suitable semiconductor materials include those disclosed in U.S. patent application Ser. No. 10/796,832, and Include any type of semiconductor, including group 11- VL group ΪΗ-V, group IV-VI and group IV semiconductors. Suitable semiconductor materials include, but are not limited to, Si, Ge, Sn, Se. Te, B, C (including diamond), P _s BK BP. BAs, A IN, A!P, AlAs, ASSh, GaN, GaP, GaAs, GaSb, ϊηΝ, InP, CnAs, InSb, AiN, A IP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe _; HgS, HgSe, HgTe, BeS, BeSe, BeTe, gS, MgSe ₅ GeS, GeSe, GeTe, SnS _s SnSe, SnTe, PbO, PbS, PbSe, Pol e, Cuf , CuCI, Cu t, Cut, $½ ¾ _> Ge ₃ N , Ai. ₂ 0 _3> (At Ga, lm ₂ (S, Se, Te)3 ₅ AbCO. and an appropriate combination of two or more such semiconductors,

(00034] In certain embodiments, the nanocrysta!s may comprise a dopant from the group consisting of a p ype dopant or an n-type dopant. The nanocrystals useful herein can also comprise lf~Vl or 0.1-V semiconductors. Examples of II- YI or ll V semiconductor nanocrystals include any combination of an element from Group 1 such as 2n, Cd and Hg, with any element from Group VI, snch as S, Se, Te and Po, of the Periodic Table; and any combination of an element from Group 111, such as B, A I, Oa< In, and XL with any element from Group V, snch as R P, As, Sb and BL of the Periodic Table,

[06035) The nanocrystals, including luminescent nanocrystals, use&l in embixliments described herein can also further comprise Iigands conjugated, cooperated, associated or attached to their surface. Suitable Uganda include any group known. to those skilled .in the art. Including those disclosed In U.S. patent application Ser. No. 12/79,813, filed Feb. 4, 2000; U.S. patent application Ser, No. 12/076,530, filed Mar. 19, 2008: U.S. patent application Ser. No. 12/609,736, filed Oct.. 30, 2009; U.S. patent application Ser. No. 1 1/299,299, filed Dec. 9, 2005; U.S. Pat. No. 7,645,397; U.S. Pat, No, 7J74J07; U.S. Pat. No, 6,949,206; U.S. Pat. No. 7,572,393; and U.S. Pat, No, 7,267,875, the disclosures of each of which are incorporated herein by reference. Use of such iigands can enhance the ability of the nanocrystals to Incorporate into various solvents and matrixes,, including polymers. Increasing the raiseibsHty (re., the ability to be mixed without separation) of the nanocrystals in various solvents and matrixes allows them to be distributed throt!ghont a polymeric composition such that the nanocrystals do not aggregate together and therefore do not scatter light Such Iigands are described as "miseibility-eohancing^ Iigands herein.

(00036] In certain embodiments, compositions comprising nanoerystais disiributed or embedded In a matrix material are provided. Suitable matrix materials can fee any material known to the ordinarily skilled artisan, including polymeric materials, organic and inorganic oxides. Compositions described ~ $ ~ herein can be layers, encapsulants, coatings, sheets or films. It should be understood that In embodiments described herein where reference Is made to a layer, polymeric layer, matrix, sheet or film, these terms are used interchangeably, and the embodiment so described is not limited to any one type of composition, but encompasses any matrix material or layer described herein or known In the art.

(060371 Down-converting nanocrysiais (for example, as disclosed in U.S.

Patent Ho. 7,374.80?) utilize the emission properties of luminescent nanocrysiais that are tailored to absorb light of a particular wavelength and then emit at a second wavelength, thereby providing enhanced performance and efficiency of active sources (e.g., LEDs).

(O0O3SJ While any method known to the ordinarily skilled artisan can be used to create nanocrysiais {luminescent nanocrysta!s), suitably, a solution-phase, colloidal method for controlled growth of inorganic nanomaterial phosphors is used. See Alivisatos, A. P., "Semiconductor clusters, nanoerystais, and quantum dots," Science 271 :933 (1996): X.. Peng, M. Sch!amp, A, Kadavsnlch. A. P. Alivisatos. "Epitaxial growth of highly luminescent CdSe/CdS Core/Shell nanocrysiais with photosiabllity and electronic accessibility^ ¹ J Am. Chem. S c, Jd:70S -?029 (1997); and C. S. Murray, D, j. orris, M. G, Bawendi, "Synthesis and characterization of nearly tnooodisperse CdE (E~sulfur _s selenium, tellurium) semiconductor nanocrysialhtes ' Am. Chem. 115: 8706 (1993), the disclosures of which are incorporated by reference herein in their entireties. This manufacturing process technology leverages low cost processability without the need for clean rooms and expensive manulaciuring equipment. In these methods, metal precursors thai undergo pyroiysis at high temperature are rapidly injected into a hot solution of organic surfactant molecules. These precursors break apart at elevated temperatures and react to nucleate nanocrysiais. After this initial nucleatlon phase, a growth phase begins by the addition of monomers to the growing crystal. The result is freestanding crystalline nanopanieles in solution that have an organic surfactant molecule coating their surface.

[060391 Utilizing this approach, synthesis occurs as an Initial nuefcation event that takes place over seconds, followed by crystal growth at elevated temperature for several minutes. Parameters such as d e temperature, types of surfactants present, precursor materials, and ratios of surfactants to monomers can be modified so as to change the nature and progress of the reaction. The temperature controls the structural phase of the nuoleation event, rate of decomposition of precursors, and rate of growth. The organic- surfactant molecules mediate both solubility and control of the nanocrystai shape. The ratio of surfactants to monomer, surfactants to each other, monomers to each other, and the individual concentrations of monomers strongly influence the kinetics of growth.

^' 600401 in suitable embodiments, CdSe is used as the nanocrystai material, in one- example, for visible light down-conversion, due to the .relative maturity of the synthesis of this material. Due to the nse of a generic surface chemistry, it is also possible to substitute non-cadmium-confaining nanocrysfals.

Core/Shell Luminescent Nanocrystals

00041] J ^' n semiconductor nanoerystals, photo-induced emission arises from the band edge states of the nanocrystai. The band-edge emission from luminescent nanoerystals competes with radiative and non-radiative decay channels originating from surface electronic stales, X. Feng, i al, J. Am, Ghent Soc. 30:7019-7029 ( 1.99?}. As a result, the presence of surface defects such as dangling bonds provide non-radiative recombination centers and contribute to lowered emissio efficiency. An efficient and permanent method to passivate and remove the surface trap states is to epitaxial ty grow an inorganic shell material on the surface of the aanocrysta-l. X, Peng, -ei J. Am. Che . Soc. 3ft 701 -7029 (1 97). The shell material ears he chosen such that the electronic levels are type 1 with respect to the core material {e.g., with a larger bandgap - io ~ to provide a potential step localizing the electron and hole to the core). As a result, the probability of non-radiative ^combin t n can be red need,

[00042J Core-shell structures are obtained by adding organornetallic precursors containing the shell materials to a reaction mixture containing the core iiaoocrvslsl In this ease, rather than a mscleaUon event followed by .growth, the cores act as the n cle , and the shells grow from their surface. The temperature of the reaction is kept low to favor the addition of shell material monomers to the core surface, while preventing independent nueleation of nanocrystals of the shell materials. Surfactants in the reaction mixture are present to direct the controlled growth of shell material, and to ensure solubility, A uniform and epitaxlally grown shell is obtained when there is a low lattice mismatch between the two materials.

£06043] Exemplary materials for preparing core-shell luminescent nanocrystals include, bu are not limited to. Si, Ge, Sn, Se, Te, B, C (including diamond), P, Co, An, B ^' N _S BP, BAs, A IN, AIP, AlAs, AlSb, GaN. GaP, GaAs, GaSb, In , Ιίχ , InAs, inSb, AIM, AIP, AIAs, AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZoSe, ZnTe, CdS, CdSe, CdXe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe, GeTe, SnS, SnSe, Snl ^' e, PbO, PbS, PhSe, PbTe, CuF, CnCl, CuBr, Cut Si ₃ N _4s Ge _s N _;!; AhO¾ (Al, Ga, In) ₃ (S, Se, Te) _¾ AICO, and an appropriate combination, of two or more such materials. Exemplary core- shell luminescent «anoery¾tais for use in the practice of the present invention include, hut are not limited to, (represented as Core/Shell). CdSe ZnS, InP/ZnS, InP/2n.Se, PbSe/FbS, CdSe/CdS, CdTe/CdS, Cd ^' Te/ZnS, as well as others..

|O0044J As used throughout, a plurality of phosphors or a plurality of luminescent nanocrystals means more than one phosphor or luminescent nanoerystal (Le„ 2, 3, 4, 5, 10, 100, 1,000, 1 ,000,000, etc., nanocrystals). The compositions will suitably comprise phosphors or luminescent nanocrystals having the same composition, though, in further embodiments, the plurality of phosphors or luminescent nanocrystals can be various different compositions. For example, the luminescent nanocrystals can ail emit at the same wavelength, or in further embodiments, the compositions can comprise luminescent .nanocrystals that emit at different wavelengths,

| ^β( Μ ⁾ 45| Luminescent nanocrystals for use in the embodiments described herein will suitably be less than about 100 nm hi size, and down to less than about 2 •ran in size. In suitable embodiments, the luminescent Mnocrystals of the present invention absorb visible light As used herein, visible, light is electromagnetic radiation with wavelengths between about 380 and about 780 nanometers that is visible to the human eye. Visible light can be separated into the various colors of the spectrum, such as red, orange, yellow, gree s blue, indigo and violet As used herein, blue light comprises light between about 435 nm and about 500 nm,. green light comprises light between about 520 am and 565 nm and red light comprises light between about 625 nm and about 740 nm in wavelength,

|fHH 46| In embodiments, me luminescent nanocrystals have a size and a composition such thai they absorb photons that are in the ultraviolet, near* infrared, and/or Infrared spectra. As used herein, the ultraviolet spectrum comprises light between about 100 nm to about 400 nm, the near-infrared spectrum comprises light between about 750 nm to about 100 um in wavelength and the infrared spectrum comprises light between about 750 nm to about 300 um in wavelength,

{00047] While luminescent nanocrystaSs of any suitable materia! can be used in the various embodiments described herein, in certain embodiments, the nanocrystals can. be ZnS, in As or CdSe nanocrystals,, or the nanocrystaSs can comprise various combinations to form a population of nanocrystals for use in the practice of the present invention. As discussed above, in further embodiments, the luminescent nanocrystals are core/shell nanocrystals, such as CdSe/ZuS, InP/ZnSe, CdSe/CdS or inP/ZnS,

{00048} In embodiments, the luminescent nanocrystals will include at least one population of luminescent nanocrystals capable of emitting red light and at least one population of luminescent nanocrystals capable of emitting green light upon excitation by a blue light source. The luminescent nanoerystal wavelengths and concentrations can be adjusted to meet the optical performance required. In still other embodiments, the luminescent nanocrystals phosphor material can comprise a population of luminescent nanocrystals which absorb wavelengths of light having undesirable emission wavelengths, and reemit secondary light having a desirable emission wavelength. In this ma ner, the luminescent nanocrystal films described herein comprise at least one population of color-filtering, luminescent nanocrystals t further time the lighting device emission and to reduce or eliminate the need for color filtering.

£08049} Suitable luminescent nanocrystals _. , methods of preparing luminescent nanocrystals, including the addition of various solubility-enhancing ligands, can be found in Published U.S. Patent Application No, 2012/01 13672, the disclosure of which is incorporated by reference herein in its entirety.

Display Systems

[00959] In embodiments, various display systems are provided herein that are suitably used in any number of applications. As used herein, a "display system" refers an arrangement of elements that allow for the visible representation of data on a display. Suitable displays include various flat, curved or otherwise-shaped screens, films, sheets or other structures for displaying information visually to a user. Display systems described herein can be included in. for example, devices encompassing a liquid crystal display (LCD), televisions, computers, mobile phones, smart phones, personal digital assistants (PDAs), gaming devices, electronic reading devices, digital cameras, and the !ike.

[00051] An exemplary display system 100 is shown in FIG. 1A. In embodiments, display system 100 comprises one or more blue light emitting diode(s) (LED) 102, Various orientations and components of LEDs are well known to those of ordinary skill in the art. Blue LEDs described herein suitably emit in the range of 440-470 nm. For example, the blue LEDs can be GaN LEDs such as a GaN LED which emits blue fight at a wavelength of 450 am,

|O0OS2] As shown in FIG. J A, display system 100 also comprises light guide plate 104, Suitably, light guide plate 104 is optically coupled to the one Of more bios LEDs in the display systems described throughout.

(06053) As used herein the following terms are used interchangeably, "light guide plate," "light guide," or "Sight guide panel," and refer to an optical component that is suitable for directing electromagnetic radiation (light) from one position to another. Exemplary light guide plates include fiber optic cables, polymeric or glass solid bodies such as plates, films, containers, or other structures. The s&e of the light guide plate will depend on the ultimate application sod characteristics of the LED. In general, the thickness of the light guide plate will be compatible with thickness of the LED. The other dimensions of the light guide plate arc generally designed to extend beyond the dimensions of the LED, and are suitably on the order of 10s of millimeters, to IDs to 100s of centimeters. While the light guide plates illustrated in the Figures represent embodiments suitable for use in display systems and the like, other light guides, including fiber optic cables, etc., can also be utilized.

|0O S4| Suitable light guide plate materials include polycarbonate (PC), poly methyl methacrylate (PMM.A), methyl methaerylate, styrene, acrylic polymer resin, glass, or any suitable light guide piste materials known in the art. Suitable manufacturing methods for the light guide plate include injection molding, extrusion, or other suitable embodiments known in the art. In exemplary embodiments, the light guide plate provides uniform primary light emission from the top surface of the light guide plate, such that primary light entering the luminescent nanocrystai film is of uniform color and brightness. The light guide plate can include any thickness or shape known in the art. For example, the light guide plate thickness can be uniform over the entire light guide piate surface. Alternatively,, the light guide plate can have a wedge-like shape. {08055} As used ^' herein, "optically coupled" means thai components (eg., a light guide piste and an LED) are positioned so that light is able to pass from one component to another component without substantial interference. Optical coupling includes embodiments in which components such as a light guide plate and an LED are direct physical contact or as shown in FIG. 1 A, the light guide plats 104 and the LED 102 are each in contact with an optically transparent element 118. The optically transparent element may comprise tape or adhesive, including various glues, polymeric compositions such as silicones, etc. placed between the light guide plate 104 and the LED 102 to optically couple the elements, Additional optically transparent adhesives ^' that can be used in embodiments described herein include various polymers, including, but not limited to, polyvinyl butyml):poIy( vinyl acetate); epoxies; urethanes; silicone and derivatives of silicone, including, hut not limited to, polyphenylmethyisiloxans, polyphenylalkylsiloxane, pol.ydiphenyls.ilox.ane, polydialkylsiloxane, fluoriuaied silicones and vinyl and hydride substituted silicones; acrylic polymers and copolymers formed from monomers including, but not limited to, methylmethaerylate, hutyhnethacrylate and laurylmeihaorylate; siyrene based polymers; and polymers that are cross linked with difunctional monomers, such as divh yi benzene,

{880S6J In further embodiments, optical coupling can be accomplished, for example, by utilizing a polymeric light guide plate, that when heated, melts or deforms such that an LED can be contacted to the light guide plate, and then the light guide plate cooled, thereby facilitating the formation of a physical adhesion or contact between the two elements. In further embodiments, optical coupling can be achieved with blue- LEDs that have an encapsuSant protruding from the LED, for example a protruding polymer surface tilled with a compliant encapsulation polymer having a .refractive index, similar to the refractive index of the light guide plate. In such embodiments,, when the light guide plate i pressed against the blue LED, an optical coupling is formed directly between the light guide plate and the LED via the protruding eneapsolant, i.e., the encapsulation polymer. 100057} It should he noted that while optical coupling does not require physical interaction between the components, suitably physical interaction, does occur, nd suitably involves contact mid is facilitated by s¾n adhering composite (eg., tape or polymer) connecting the two components. So long as light is able to pass between the components they are considered optically coupled.

I OO SS) Display system 100, shown in FIG. I A. also suitably further comprises a display, for example, liquid crystal module 1 14. As used herein,, the "display" or "display panel" of the display systems is the portion of the display- output seen, by the user or observer of the display systems.

{00059] Display system 100 also suitably further comprises composition 106 comprising a plurality of phosphors 122 _» the composition oriented between the light guide piste and the display. As described herein, in embodiments, display system 100 exhibits increased optical power output as compared to a display system where the light .guide plate is not optically coupled to the blue LED,

{ 60 j In embodiments, the display systems described herein suitably comprise one or more additional, elements traditionally found in LED-based display systems. Such elements, as shown in FIG, 1 A, include, hut are not limited to, one or .more of ditfuser(s) 1 12 {top or bottom), horizontal brightness enhancement fiimis) (BEF) 110, vertical BEF(s) 108, and refiector(s) 1 16. Suitably orientations of these elements, their manufacture a«d incorporation in display systems are well known in the art.

000611 Diff users, or diffuse? films, are distinct from and supplemental to the scattering features described herein. Diffusers 1 12 can include any diffuser film known in the art. Including gain diffuser -films, and can be disposed above or below the one or .more BEFs 108, Π0 or other optical films of the display systems. In exemplary embodiments, the composition, comprising phosphors (suitably a film comprising luminescent naaocrystals) eliminates the need for a conventional bottom diffuser film in the display systems, thereby minimizing the thickness of the lighting device. The compositions comprising phosphors can also include one or more scattering or diffuser features associated therewith, which can serve the purpose of traditional diffuses in addition to increasing secondary emission of the phosphors in the compositions.

{(MM)62| The BEFs and brightness enhancing features can include reflective and/or refractive films, reflective polarizer films, prism films, groove films, grooved prism films, prisms, pitches, grooves, or any suitable BEFs or brightness enhancement features known in the art. For example, the BEFs cm include conventional BEFs such as Vikufci™. BEFs available from 3M™.

|¾0063| in exemplary embodiments, the display systems comprise at least one BEF, more suitably at least two BEFs, Suitably, the display systems can comprise at least three BEFs, In exemplary embodiments- at least one BEF comprises a reflective polarizer BEF, e.g., for recycling light which would otherwise be absorbed by the bottom polarizer iihvs. live brightness-enhancing features and BEFs can include reflectors and/or refractors, polarizers, reflective polarizers, light extraction features, light recycling features, or any brightness-enhancing features known in the art The BEFs and brightness- enhancing features can include conventional BEFs. For example, the BEFs can include a first layer having pitche or prisms having a first pitch angle, and at least a second layer having pitches or prisms having a second pitch angle,

(00064) Reflectors 1 1 are suitably positioned so as to increase the amount of light that is emitted from the light guide plate. Reflectors can comprise any suitable material, such as a reflective mirror, a film of reflector particles, a reflective .metal film, or any suitable conventional reflectors. In embodiments, reflectors are suitably a white film, in certain embodiments, the reflectors can comprise additional functionality or features, such as scattering, diffbser, or brightness-enhancing features.

(00065) in still further embodiments, as shown in FIG. I A, the display systems comprise one or more blue LED 102, light guide plate 104, optically coupled to bine LED 102, a display (e.g., liquid crystal module 1 14) and a film (e,g„ 106) comprising a plurality of phosphors (122), the composition oriented between the light guide plate and the liquid crystal module. Suitably, the display systems described herein exhibit Increased optical power output and luminous output as compared to a display system where the light guide plate is not optically coupled to the blue LED.

PMMl6 ^' 6f As used herein, when describing elements of he various display systems provided, "oriented between" is meant to indicate that various elements are positioned relative to one anothe such that one element, e.g., a composition comprising phosphors, is above one element, but below another, in a configuration in which the elements are in a stack or layered orientation, it should be understood that other orientations can be utilize , in the embodiments described herein, and. cars be readily -determined by a person of ordinary skill in the art.

(08β6?| Exemplary tapes and adhcsives for optically coupling light guide 1 4 to blue LED 1 02 are described herein, In additional embodiments, the blue LED is coupled to the ligh guide via an encapsuiant protruding from the LED. in addition, exemplary phosphors, including various luminescent nanocrysfals are described throughout.

fh0068) As described herein, in suitable embodiments, film 106 is a polymeric film, comprising luminescent nanoerystals. Exemplary polymers for use in preparing film 106, and methods of preparing polymeric films comprising luminescent nanoerystals are described herein.

|00 69) Additional elements that can be included in display systems described herein are described throughout.

|00070) In an additional, embodiment of display system 100, shown in FIG. i.A, described herein are display systems comprising one or more blue LED 102, a light guide plate, optically coupled to the blue LED 104, a polymeric film (e.g., 106} comprising a plurality of phosphors (122), the polymeric film oriented above the l ght guide piste 104, a vertical BEF 1.08 oriented above the polymeric f lm, a horizontal BEF 1 10 oriented above the vertical BEF 108, a top dif!hser 1. 1.2 oriented above the horizontal BEF 1 1 0, and a liquid crystal module 1 14 oriented above the top diffuse.r 1 12,

[0007.1.1 Suitably, the display systems described herein exhibit increased optical power output as compared to a display system where the light guide plate is not optically coupled to the blue LED. In embodiments, display systems described herein exhibit an optical power output of at least 26 mW/LED, more suitably at least 28 mW/LED, or at least 29 mW/I D at a driving current: of 20 MA.

$8972 f Exemplary methods and compositions for preparing the optical coupling are described herein, as ate exemplary phosphors including luruineseem nanocrystals,

|0Θ073| The display systems described herein can comprise one or more medium materials between adjacent elements of the systems. The system can include one or more medium material disposed between any of the adjacent elements in the systems, including the LED and the light guide plate the light guide plate and the composition comprising phosphors; between any different layers or regions within the composition comprising phosphors; the composition comprising phosphors and one or more barrier layers; the composition comprising phosphors and the light guide plate; the composition comprising phosphors and one or more 8EF, diffbser, reflector, or other features; and between multiple barrier layers, or between any other elements of the display systems. The one or more media can include any suitable materials, including, but not limited to, a vacuum, air, gas, optical materr&Is, adhesives, optical adhesives, glass, polymers, solids,, liquids, gels, cured materials, optical coupling materials, index-matching or index-mismatching materials, index-gradient materials, cladding or anti-cladding materials,, spacers, epoxy, silica gel, silicones, any matrix materials described herein, brightness-erthatvcirig materials,, scattering or diffuser materials, reflective or auti-reflectsve materials, wavelength-selective materials, wavelength-selective anti-reflective materials,, colo filters, or other suitable media known in the art. Suitable media materials include optically transparent, non-yeliowiog, pressure-sensitive optical adhesives. Suitable materials include silicones, silicone gels, silica gel, epoxies (e.g., Loetite™ Epoxy B-30CL), acryiatcs (e.g., Μ ^1Μ Adhesive 2175), and matrix materials mentioned herein. The one or more media materials can be applied as a curable, gel or liquid and cured during or after deposition, or pre-tormed and pre-c red prior to deposition. Suitable curing methods include liV curing, thermal curing, chemical curing, or other suitable curing methods known in the art. Suitably, index-matching media materials can be chosen to minimize optical losses between elements of the lighting device.

(06074! in additional embodiments, display systems are provided in which a container comprising a plurality of phosphors is optically coupled to a blue LED. For example, as shown in display system 160 .in FIG. I B, blue LED 1 2 is optically coupled at 182, to container 17$ that contains a plurality of phosphors 184, for example a plurality of luminescent nanoerysials as disclosed herein. In exemplary embodiments, container 178 is a capillary, as described throughout

{000 5! As shows in FIG. I B, light guide plate 164 is optically coupled to container 1 78 at 182, via glue, mechanical alignment alone, various adhesives as described throughout, or the like,, and combinations thereof. This can also be accomplished, for example, by utilizing a polymeric light guide plate, that when heated, melts or deforms such tha hermetically sealed container can he contacted, to the light guide plate, and then the light guide plate cooled, thereby !acihtatmg the formation of a physical adhesion or contact between elements (e.g., between LED, light guide plate and container comprising phosphors). In additional embodiments, the blue LED is coupled to the light guide via an eneapsulani protruding from the LED.

(00076) in exemplary embodiments, display systems 160 as shown in FIG. IB, can further comprise bottom diffuser 166 oriented above light guide plate 164, vertical BEF 168 oriented above bottom diffuser .166, horizontal BEF 170 oriented above vertical BEF 168, top diffuser 172 oriented above horizontal BEF 170, and liquid crystal module 174 (be., display) oriented above top diffuser 1 72. The display systems can also further comprise reflector 1 76, as described herein. Compositions of Phosphors

{ _. 86877! s used herein, the term "phosphors'- refers to a synthetic fluorescent or phosphorescent substance. Exemplary phosphors include traditional materials such as ceri.u.m(ll>doped YAG phosphors (YAG:CV\ or YjAfiOi as well as luminescent nanocryst& as described herein.

Additional phosphors that can be utilized in the devices described herein include, but are noi. limited to, silicate phosphors, garnet phosphors, a!uminate phosphors, nitride phosphors, NY AG phosphors, SiAlON phosphors and CaA!SINrbased (CASN) phosphors, as well as other phosphors known in the art

100078] As described throughout,, compositions comprising phosphors for use in embodiments provided can take numerous shapes, including for example, films or sheets (e.g. composition 106 of FIG, IA}< In further embodiments, the compositions can be various containers or receptacles for receiving the phosphors, suitably luminescent nanocrystais.

{00079} Suitably, phosphors, and specifically luminescent naoocrystais, are dispersed or embedded in suitable polymeric materials to create films or sheets, also called quantum dot enhancement film (QDEFs), Such films are described, for example, In Published U.S. Patent Application Nos. 2010/0110728 and 2012/01 13672, the disclosures of each of which are incorporated by reference herein in their entireties,

{00080} The luminescent nanocrystais are suitably coated with one or more iigand coatings, embedded in one or more films or sheets, and/or sealed by one or more barrier layers. Such Hgands, films, and barriers can provide photostahilit to the luminescent nanocrystais and protect, the luminescent nanocrystais from environmental conditions including elevated temperatures, high, intensity light, external gases, moisture, and other harmful environmental conditions. Additional effects can be achieved with these materials, including a desired index of .refraction in the host film material, a desired viscosity or luminescent nanocrystal dsspersiomndscibiiity In the host film material and other desired effects, in suitable embodiments, the !igand and film materials ili be chosen to have a sufficiently low thermal expansion coefficient, such that thermal curing does not substantially affect the luminescent nanocrystal phosphor material

100081 J The luminescent nanocrystals useful herein, suitably . comprise ligands conjugated to, cooperated with, associated with, or attached to their surface. In preferred embodiments, the luminescent nanocrystals include a coating layer comprising !igands to protect the luminescent nanocrystals from external moisiure and oxidation, control aggregation, and allow for dispersion of the luminescent nanocrystals in the matrix material Suitable Ugands and matrix materials, as well as methods for ro iding such materials, are described herein, Additional suitable Hgands and film materials, as well as methods for providing such materials, include any group known to those skilled in the art, including those disclosed in Published U.S. Patent Application No. 2012/O i 13672; U.S. patent application Ser. No. 12/79,8 } 3, filed Feb. <t 2000; U.S. patent application Ser. No. 12/076,330, filed Mar, 19, 2008; U.S. patent application Ser. No. 12/609,736, filed Oct, 30, 2009; U.S. patem application Ser. No. 1 1 /299,299, filed Dec. 9, 2005; U.S. Pal. No. 7,645,397; US. Pat. No. 7374,807; U.S. Pat. No. 6,949,206; U.S. Pat. No. 7,572393; and U.S. Pat. No. 7,267,875, the disclosure of each of which is incorporated herein by reference in its entirety. Additionally, suitable ligand and matrix materials include any suitable materials in the art.

[60 821 Dispersing luminescent nanocrystals in a polymeric material provides a method to sea! the nanocrystals and provide a mechanism for mixing various compositions and sizes of luminescent nanocrystals. As used throughout "dispersed" includes uniform (i.e., substantially homogeneous) as well as nonuniform (i.e., substantially heterogeneous) distribution or placement of luminescent nanocrystals.

88883] Suitable materials for use in the compositions comprising the luminescent nanocrystals include polymers and organic and Inorganic oxides. Suitable polymers include any polymer known to the ordinarily skilled artisan that can be used for such a purpose, in suitable embodiments, the polymer will be substantially translucent or substantially transparent. Suitable matrix materials include, but are net limited to, epoxies; aerySates: norhorene; polyethylene; polyvinyl butyral ):poiy{vmyl acetate); polyurea; polyurethanes; silicones and silicone derivatives including, but not limited to, amino silicone (AMS), polyphenylmethylsiloxane, polyphenylalkylsiloxane, poiydiphenylsi!oxane, polydislky!siloxane, sdsesquioxanes, fiiior ated silicones, and vinyl and hydride substituted silicones; acrylic polymers and copolymers .formed from monomers including, but not limited to, tnethyimethacrylate, bntylrnethacryia.te, and latrrylmethaerylate; st rene-hased polymers such as polystyrene, amino polystyrene (APS), and poly(aeryk>mtrHe ethylene styrene) (AES); polymers that are erosslinked with difunctional monomers, such as divmyibenzene; cross-linkers suitable for cross-linking ligand materials; epoxides which combine with ligand amines (e.g., APS or FBI figand amines) to form epoxy, and the like.

¾0 S4| The luminescent nanocrystais as described herein can be embedded in a polymeric (or other suitable material, e.g., waxes, oils) matrix using any suitable method, for example, mixing the luminescent nanocrystais m a polymer and easting a film; mixing the luminescent nanocrystais with monomers and polymerizing them together; mixing the luminescent nanocrystais in a sol-gel, or any other method known to those skilled in the art. As used herein, the term "embedded" is used to indicate that the luminescent nanocrystais are enclosed or encased within the polymer. It should be noted that luminescent nanocrystais are suitably uniformly distributed throughout the composition, though in further embodiments they can be distributed according to an application-specific uniformity distribution function,

110085) The thickness of the compositions comprising luminescent .nanocrystais as described herein can be controlled by any method known in the art, such as spin coating and screen printing. The luminescent nanocrystal compositions as described herein can be any desirable size, shape, configuration and thickness. For example, the compositions can be in the form of layers, as well as other shapes, for example, discs, spheres, cubes or blocks. tubular configurations and the like. While the various compositions can he any thickness required or desired, suitably, she compositions are on the order of about 100 mm in thickness (i.e., in one dimension), and down to on the order of less than about 1 mm in thickness. In other embodiments, the polymeric films can be on the order of 10's to 100's of microns in thickness. The luminescent nanoerystals can be embedded in the various compositions at any loading ratio that is appropriate for the desired function. Suitably, the luminescent nanoerystals will be loaded at a ratio of between about 0,001% and about 75% by volume depending upon the application, polymer and type of nanoerystals used. The appropriate loading ratios can readily be determined by the ordinarily skilled artisan and are described ^' herein further with regard to specific applications. In exemplary embodiments the amount of nanocrystais loaded in a luminescent nanoerysiai composition are on the order of about 10% by volume, to parts-per-mihlon (pprn) levels.

Containers Comprising Phosphors

08886] in further embodiments, the compositions comprising phosphors are containers comprising a plurality of !eminescent nanoerystals. As used herein, a "container" refers to a carrier, .receptacle or preformed article into which luminescent nanoerystals are introduced (often a composition of luminescent nanoerystals, e.g., a polymeric matrix comprising luminescent, nanoerystals). Examples of containers include, but are not limited to, polymeric or glass structures such as tubes, molded or formed vessels, or receptacles, in exemplary embodiments, a container can be formed by extruding a polymeric or glass substance into a desired shape, such as a tube (circular, rectangular, triangular, oval or other desired cross-section) or similar structure. Any polymer can. he used to form the containers for use in the embodiments described herein. Exemplary polymers for preparation of containers for use in the practice of the present invention include, but are not limited to, acrylics, polyCmethyl methacryiate) (PM A), and various silicone derivatives. Additional materials can also be used to form the containers for use in the practice of the present invention. For example, the containers ears be prepared from metals, various glasses, ceramics and the like,

{00887] in embodiments, a polymeric of glass to be can be used as a container.

A solution of luminescent nanocrystals can then he drawn into the container by simply applying a reduced pressure to an end of the container. The container can then be sealed by heating and "pinching" the container at variou sealing positions or seals throughout the length of the container, or by using other sealing mechanisms as described throughout. In this way, the container can be separated into various individual sections. These sections can either be retained together as a single, sealed container, or the sections can be separated into individual pieces. Hermetic sealing of the container can be performed such that each individual seal separates solutions of the same nanoerystals. In other embodiments, seals can be created such that separate sections of the container each contain a different nanocrystal solution (i.e., different nanocrystal composition, ske or density),

[00088| in embodiments, the container is suitably a plastic or glass container, in suitable embodiments, the sealed container is a plastic or glass (e.g., borosiiicate) capillary. As used herein ''capillary ^" refers to an elongated container having a length dimension that is longer than both Its width and height dimension.. Suitably, a capillary Is a tube or similar structure having a circular, rectangular, square, triangular, irregular, or other cross-section. •Suitably, a capillary for use in the display devices described herein can be configured so as to match the shape and orientation of the LED to which it is optically coupled. l.n exemplary embodiments, a capillary has at least one dimension of about 100 μι« to about 1 mm. In embodiments in which a plastic capillary it utilized, a coating such as SiCb, Ai(¾ or T ¾. as well as others described herein, can be added so as to provide an additional hermetic seal to the capillary.

fWI08#f Suitably, capillaries described herein have a thickness of about 50 μχη to about 10 mm, about 100 pm to about 1 mm, or about 100 μ rn to about 500 μη\. Thickness refers to dimension of the capillary into the plane of the light guide piste. Suitably, a capillary .has a height (in the plane of the light guide plate} of about 50 μιη to about 10 mm, about 100 pm to about 1 mm, or about 100 μΐϊί to about: 500 pr Suitably, a capillary has a length (in the plane of the light, guide) of about 1 mm to about 50 rnm, about I mm to about 40 mm, about i mm to about 30 mm, about 1 mm to about 20 sum. or about 1 mm to about 10 nun.

iOtMI&ej The concentration of luminescent nanoerysiais in the containers described herein depends on the application, sixe of the luminescent nanocrystals composition of the luminescent nanocrystals. the composition of polymeric matrix in which the luminescent nanocrystais are dispersed, and other factors, and can be optimized using routine methods is the art. Suitably, the luminescent nanoerystais are present at a concentration of about 0,01% to about 50%, about 0.1% to about 50% _s about 1 % to about 50%.. about 1 % to about 40%, about 1% to about 30%, about 1% to about 20%, about 1 % to about 10%, about 1 % to about 5%, or about 1% to about 3% _: by weight.

Display Systems Exhibit Increased Optical Power Output and increased Luminous Output

OO091| As described herein and particularly in the Examples, display systems described herein exhibit increased optical power output and increased .luminous output as compared to a display system where the light guide plate is not optically coupled to the blue LED. As used ^' herein "optical power output" is defined to be the total power emitted by an LED per unit time, per LED, when driven at a constant current Optical power output is suitably expressed as W tts/LED (suitably /LBD}, A person of ordinary skil l in the art will readily understand that optical power output can also be calculated at various dri ing currents, so long as comparative measurements are appropriately made at the same drivin current. ^' 0O92J As used herein "luminous output" is defined to be the total amount of visible Sight emitted by a display system. Lis ubio s output, as described herein, is measured in lumens,

06093] As used herein "increased optical power output' ^' when referring to the display systems described herein, is used to indicate that the display systems demonstrate greater than at least 3% more optical power as compared to a display system where the light guide plate is not optically coupled to the blue LED. More suitably, the disclosed display systems provide at least 4%, at least 5%, at least 6% _f at least 7%, at least 8%, at least 9%, ai least 10%, at least 1 1% at least 12%, at least 1.3%, at least 14%, at least 15%, at least 16%, at least 17%, at least I 8%, at least 19%, or at least 20% more optical power as compared to a display system where the light guide plate is not optically coupled to the blue LED. In other embodiments, the disclosed display systems demonstrate an increased optical power output of about 3% to about 20%, about 5% to about 20%, about 5% to about 1 5%, about 5% to about 1:2%, about 5% to about 1 .1 %, about 6% to about 14%, about ?% to about 13%, about 8% to about 12%, about 9% to about I 1 %, about 7%, about 8%, about 9%, about 10%, about 1 1%,. about 12%, about 13%, abou 14% or about 15%, as compared to a display system where the light guide plate is not optically coupled to the blue LED, including any values and ranges within the recited values.

00094J As used herein "'increased luminous output' ⁵ when referring to the display systems described herein, is used to indicate that the display systems demonstrate, greater than at least 3% more luminous output as compared to a display system where the light guide plate is not optically coupled to the blue LED. More suitably, the disclosed display systems provide at least 4%, at least 5%, at least 6%, at least 7%, at least 8%, at least 9%, at least 10%, at least i 1%, at least 12%, at least 1 %, at least I4% _; at least 15%, ai least 16%, at least 17%, at least 18%, at least 19%, or at least 20% more luminous output as compared to a display system where the light guide plate is not optically coupled to the blue LED, In other embodiments, the disclosed display systems demonstrate an increased luminous output of about 3% to about 20%, about 5% to about 20% _s about 5% to about 15%, about 5% to about 12%, about $% to about 1 1 %, about 6% to about 14%. about 7% to about 13%, about 8% to about .12%, about 9% to about 1 1 %, about 7%, about 8%, about 9%, about 10%, about 1 !%, about 12%, about 13%, about 14% or about 15%, as compared io a display system where the light guide plate is not optically coupled to the blue LED, including any values and ranges within the recited values,

j 08095] In further embodiments, the disclosed display systems In which a container comprising a plurality of phosphors is optically coupled to a blue LED and optically coupled to a light guide plate provide at least 4%. at least 5%, at least 6%, at least 7%. at least 8%, at least 9%, at least 10%, at least 1 1%, at least 12%, at least 1.3%, at least 14%, at least 15%, at least 16%, at least 17%, at least 18%, at least 1 %, or at least 20% more optical power as compared to a display system where & container comprising a plurality of phosphors is not optically coupled to a blue LED and is not optically coupled to. a light guide plate. In other embodiments, the disclosed display systems demonstrate an increased optical power output of about 3% to about 20%, about 5% to about 20% about 5% to about 15%, abou 5% to about 12%, about 5% to about 11 %, about 6% to about 14%, about 7% to about 13%, about 8% to about 12%, about 9% to about 1 1 %, about 7%, about 8%, about 9%, about 10%, about 1 1%, about 12%, abou 13%, about 14% or about 15%, as compared to a display system where a container comprising a plurality of phosphors is no optically coupled to a blue LED and is not optically coupled to a light guide plate, including any values and ranges within the recited values.

jlMM>%] In further embodiments, the disclosed display systems in which, a container comprising a plurality of phosphors is optically coupled to a blue LED and optically coupled to a light, guide plate provide at least 4%, at. least 5%, at least 6%. at least 7%, at least 8%, at least 9%, at least 10%, at least i i.%, at least 12%, at least 1.3%, at least 14%, at least 15%, at (east 16%, at least 17% _: , at least 18%, at least 1 %. or at least 20% more luminous output as compared to a display system where a container comprising a plurality of phosphors is not optically coupled to a blue LED and is not optically coupled to a light guide plate, In other embodiments, the disclosed display systems demonstrate an increased luminous output of about 3% to about 20%, about 5% to about 20% about 5% to about 15%. about 3% to about 12%, about 5 to about 1 1 %, about 6% to about 14%, about 7% to about i 3%, about 8% to about 12%:, about We to about 1 1%, about 7%. about 8% ₅ about 9%, about 10%, about l i.%, about: 12% _s about 13%, about 14% or about ! 5% _f as compared to a display system where a container comprising a plurality of phosphors is not optically coupled to a blue LED and is not optically coupled to a light guide plate, including any values and ranges within the recited values.

Methods of Increasing Optical Power Output and Luminous Output

[00097] As described herein, display systems are provided thai improve blue light extraction efficiency from blue LEDs. In embodiments, the blue LEDs are optically coupled to a light guide plate. Such optical coupl ing removes the po!ynier/air interfaces, thereby suitably preventing blue light from back- reflection and subsequent absorption by the blue die (1.20 of FIG. l Aj. Improvements in optical power output and luminous output are described throughout,

[00098] Reduction or elimination of blue light reflection brings the additional benefit of lowering the bine flux on LED package sidewalls. which extends the lifetime of the LED package. In addition, reduction of blue light absorption by the LED die can reduce the die temperature, which can further increase its efficiency and extend the LED lifetime.

[00099] In still further embodiments, methods of increasing the optical power output and luminous output of a blue LED in a display system are provided. Such method suitably comprise optically coupling the blue LED to a light guide plate of the display system. Exemplary methods and compositions for use in optical coupling, including tape and various adhesbves; arc provided herein, In additional embodiments, the blue LED is coupled to the light guide via an enca sulate protruding from the LED,

000.10») As described herein, the methods suitably increase the optical power output of a blue LED In a display system by greater than at least 3% as compared t a display system where the Sight guide plate is not. optically coupled to the blue LED. More suitably, the methods increase the optical power by at least 4%, at least 5% _; at least 6%, at least ?%, at feast 8%, at least 9%, at least 10%, at least 1 1%, at least 12%, at least 13%, at least 14%, at least I S%, at least 16%, at least 17%, at least 18%, at least 19%, or at least 20% as compared to a display system where the light guide plate is not optically coupled to the blue LED. in other embodiments, the methods described herein provide an increased optical power output of about 3% to about 20%, about 5% to about 20%, about 5% to about 15%, about 5% to about 12%, about 5% to about 1 1 %, about 6% to about 14%, about 7% to about 13%, about 8% to about 12%, about 9% to about 1 1%, about ?%, about 8%, about 9%, about 10%, about 1 1 %, about 12%, about 13%, about 14% or about 15%, as compared to a display system where the light guide plate is not optically coupled to the blue LED, including any values and ranges within the recited values.

[600101] As described herein, the methods suitably increase the luminous output of a blue LED in a display system by greater than at least 3% as compared to a display system where the light guide plate is not opticall coupled to the blue LED. More suitably, the methods increase the luminous output by at least 4%, at least 5%, at least 6%, at least 7%. at least 8%, at least 9%, at least 10%, at least 1 1%, at least 12%, at least 13%, at least 14%, at least 15%, at least 16%, at least 17%, at least 1.8%, at least 19%, or at least 20% as compared to a display system where the light guide plate is not optically coupled to the blue LED, In other embodiments, the methods described herein, provide at? increased luminous output of about 3% to about 20%, about 5% to about 20%, about 5% to about 15%, about 3% to about 12%, about 5% to about 1 1 %. about 6% to about 1 %, about ?% to about 13%, about 8% to about 12%, about 9% to about 1 1 %, abotn 7%, about 8%, about. 9%, about .10%, about 1 1 %, about 12%, about 13%, about 14% or about 15%, as compared to a display system where the light guide plate is not optically coupled to the blue LED, including any values and ranges within the recited values.

[00010.2] It will be readily apparent to one of ordinary skill, in the .relevant arts that other suitable modifications and adaptations to the methods and applications described herein can be made without departing from the scope of any of the embodiments. The following examples are included herewith for purposes of illustration only and are not intended to be limiting.

Examples

Example I: increased Power Output f m Blue LEDs by Optical Coupling to a Light Guide Plate

[000103] Generally, liquid crystal displays utilize white LEDs as the light source in the backlight. Most backlights are edge-lit - the white LEDs are placed on the edge(s) of the backlight. The white LEDs are mounted on a flex strip and placed in close proximity to a light guide plate. White light coming out of the LEDs enters the light guide plate from the edge and, through total internal reflections, is guided across the light guide plate. Extraction features are molded on the surface of the light guide plates to extract light from the light guide plate to enable a uniform distribution, of light across the display, Phosphors are often introduced thai offer better system efficiency and/or higher color gamut

[00011)4] As described herein,, luminescent sanoerystals (quantum dots) are dispersed/embedded lu a. polymeric film or sheet (quantum dot enhancement film (QDEF)) and placed on top of a light guide plate. White LEDs are replaced by blue LEDs (FIG 1 A). {See Published U.S. Patent Application No. 2012/01 13672. the disclosure of which is incorporated by reference herein in its entirety.) When color gamut is matched at 72% National Television System Committee (NTSC). for example, luminescent nanocrystals plus blue- LEDs deliver 15-20% higher power efficiency compared to white LEDs as a result of better spectral distribution of the backlight of the Q ^' DEF that matches the color filters, which enables the use of higher transmission color filters.

[000105] To convert from white LEDs to blue LEDs, a clear encapsulation polymer is utilized inside the LED package Instead of using YAG- impregnated encapsulation polymer. Doing s , however, has an unintended consequence of lowering the out-coupling efficiency of the LED. As shown in FIGs, 2A-2C, tor white LEDs (FIG. 2A), much of the blue light is converted to yellow by the YAG phosphor in the encapsulation polymer. When the yellow photons are reflected back towards the LED die, the yellow photons are not absorbed since they are below the band gap of the die materia L

[000*06] In the ease of blue LED (FIG. 2B), in contrast, the blue photons that are reflected off the encapsulation polymer and air interface can re-enter the die 120 and can be absorbed. As a result, the blue out-coopbng efficiency is lower than that of the white LED,

[000.107] To estimate the oui-coupling efficiency loss, the total optical output of a white LED and a blue LED using nominally the same efficiency blue die were determined. From theoretical calculations (FIGs 3A-3B), if the YAG quantum efficiency is at the theoretical limit of 100%, the total optical power of a white LED should be close to 85% of a blue LED if the out-coupling efficiencies are the same in both cases. This is because the yellow photons are lower in energy (SSOnm corresponds to 2,25eV) than a blue photon (450nm corresponds to 2.76 ^' eV). To convert from blue to white, the majority of the blue photons (higher energy) need to be down-shifted to yellow photons (lower energy) where the energy difference is dissipated as heat, In reality,, current YAG phosphor material has quantum efficiency of close to 90%, The expected power output from a white LED should be close to 80% that of the blue. ffiOul ] In the measurements conducted on white LEDs and blue LEDs coming from the same vendor, using the same ranked dies, arid using the same packages, the surprising result was observed that the white LED power output is actually almost the same as that of the blue (Table !}.

TABLE 1

integrated optical power output (snW)

White LED driven at 20mA 24,5

Blue LED driven at 20mA 25. ?

Table 1 ; Experimental measurements of total optical power from white LEDs and blue LEDs from the same vendor, using the same rank die. same package, and driven, at the same current Measurements were done in an integrating sphere.

^' 8δ(11β$] Similar results were obtamed on LEDs from different vendors. Thi indicates that the light extraction efficiency from the blue LED package is significantly worse than that of the white LED package. This lower extraction efficiency is likely a result of the reflection of the blue light from the encapsulation/air interface and absorption of the blue light from the die (as shown in FIG. 2B). These results suggest that improving the out-coupling of the blue LEDs can increase the power output by close to 20%, for example up to 29-30 raW/LED or more (at a driving current of 20 mA),

C!6f!i i0] To improve light extraction efficiency .from blue LEDs and coupling efficiency to the light guide plate, blue LEDs are optically coupled, to the light gnide plate using a thin optically clear adhesive (e.g.. silicone).

O iilj As illustrated in FIG. 2C, this optically clear adhesive, when index- matched to the LED encapsulation polymer and light guide plate, eliminates the reflections from two interfaces: the LED encapxulatlos/asr interface and air/light-guide-pate interface. As a result, the blue light emitted by the blue die directly enters the light guide plate without suffering from reflection losses and absorption, losses (i.e., from the blue die), 000112) Optically coupling a white LED and a light guide plate was found to reduce brightness, Hkeiy due to the white LED's higher light extraction efficiency. See FIG. 2A, This is illustrated in the results tor coupled and uncoupled brightness as demonstrated in Table 2.

TABLE 2

1000.113] in. the coupled case, the brightness is actually lower and the white point is cooler. The reason for this is that the blue light is able to escape the package out of the first pass when coupled to the light-guide plate. In the uncoupled case, which is the intended use configuration, some of the blue light Is reflected off the encapsulation/air interface and goes back into the package. This reflection enables more of the blue light to be absorbed by the yellow phosphors in the LED cup, which makes the white -point warmer.

E00GM4] However, with blue LEDs, a 14% total increase In efficiency by optical coupling is demonstrated by the following set of experiments {see Table 3). A surprising and unexpected result of the embodiments described herein that has heretofore not been necessary or beneficial when using white LED for display systems which did not utilize films comprising luminescent nanoesy stsls.

|060.115| I case I , a fle strip with 25 blue LEDs is placed in an integrating sphere. When driven with 20 raA per LED. a total optical power of 673 ra is measured. In case 2. a light guide plate (LOP) is abutted against the LED strip (as In a back light) without use of an adhesive to provide the optical coupling. The integrated optical power in case 2 is 645 mW, a 4% reduction compared to case ^' !. with the bare flex. This reduction is likely a result of the reflection from the air/LGP interface sending same of the blue light back towards the LED and the flex strip leading to losses. In case 3, the LEDs are optically coupled to the light guide plate using an optically clear adhesive. The total integrated blue light is 737 mW, which is 9% higher than case 1 with the bare flex and 1 % higher than ease 2 with the LGP uncoupled to the LEDs. In case 3, the optical power output of 29,5 mW LED is achieved.

TABLE 3

I Power Flex/LET) Ratio to flex Ratio to LGP (mW) w/o coupling

Flex w/o LGP 673/26.9 100%

LGP w/o adhesive- 645/25,8 96% 100% based optical coupling

LGP w/ coupling 737/29.5 109% ! I4%

Table 3: Measured optical power output in an integrating sphere of a flex strip h 25 blue LEDs driven at 20mA.

000116) in order t achieve good optical coupling when the blue LE s and the light guide plate were joined with the adhesive layer, their surfaces were prepared as follows. First, a small amount of silicone was added to the encapsulation polymer of each blue LED package. This treatment reduced the possibility of air gaps at the adhesive/EED interface. The possibility of air gaps in currently manufactured LEDs is increased due to the fact that they have concave surfaces. The possibility of air gaps ould be reduced if a convex LED encapsulation surface were used and such a convex surface Is preferred. Second, the edge of the light guide plate was polished to a flat surface from its original lenticular surface to enable good optical coupling with minimal air gaps. A thin strip of optically-clear adhesive was applied between the modified blue LED strip and the polished light guide plate to provide an adhesive-based optical coupling. The particular adhesive used in thi experiment was a 3M optically clear adhesive 8146-x with SQ thickness.

|Ο001 ί?Ί Comparison of optically-coupled and non-coupled (i.e., without adhesive coupling) configurations demonstrated that eliminating the original lenticular surface form the edge of the light guide plate did not significantly change the light mixing distance, {See F!Gs. 4A and 4B), Furthermore, the backlight appeared homogeneous without any noticeable .streaks close to the LEDs in a fully assembled backlight assembly that included QDEF and horizontal and vertical BEFs placed on top of the light guide plate, (FIG. 4Q.

[00011.8] By combining the benefits of a high-efficiency QDEF and better out- coupled blue LEDs, the next generation LCD backlights can enable >30% energy savings compared to the current generation LCDs at the same color gamut e.g., sRGB. Even for high-color gamut displays, e.g., Adobe-RGB and DCI-P3, higher efficiency LCDs can be achieved compared to today's sRGB LCDs, in addition to other benefits, such increases can enable the use of smaller batteries in various mobile devices.

[000119] It is to be understood that while certain, embodiments have been illustrated and described herein, the claims are not to be limited to the specific forms or arrangement of parts described and shown. In the specification, there have been disclosed illustrative embodiments and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation. Modifications and variations of the embodiments are possible in light of the above teachings. It is therefore to be understood that the embodiments may be practiced otherwise than as specifically described.