QUANTUM DOT-CONTAINING COMPOSITIONS HAVING SUPERIOR RESISTANCE TO DEGRADATION FROM EXPOSURE TO ENVIRONMENTAL CONTAMINANTS WHILE MAINTAINING THEIR LIGHT GENERATING CAPABILITIES

BACKGROUND

Field

[0001] Quantum dot-containing compositions and methods of forming quantum dot-containing compositions and assemblies fabricated therewith, all of which having superior resistance to degradation from environmental contaminants, such as air and/or moisture, are provided.

Brief Description of Related Technology

[0002] Quantum dot-containing compositions, such as in a film format, and elements made with such films are used in display devices and other optical

applications. In these applications, the quantum dots need to be shielded from air and moisture in order to ensure that performance is not compromised. In many instances, quantum dot-containing compositions are provided in a film format, composed of a top barrier film, a bottom barrier film, and a middle layer of a film adhesive within which are dispersed quantum dots.

[0003] US Patent Application Publication No. 2015/0368553 is an example of such a structure, where a quantum dot-containing film is described as a first barrier film; a second barrier film; and a quantum dot layer separating the first barrier film from the second barrier film, the quantum dot layer comprising quantum dots dispersed in a polymer matrix.

[0004] During the formation of quantum dot-containing films, the polymeric matrices throughout which quantum dots are dispersed may be formed from a two-part adhesive. The so-formed films have a higher tendency to be defective because increased temperature is often used to cure the adhesive, which leads to an initial decrease in viscosity of the adhesive. The lower viscosity enables migration of the adhesive within the structure, as does responses to stresses caused by barrier film shrinkage, line tension mismatch and non-uniform heating, for example. [0005] Quantum dots are typically sensitive to degradation by exposure to environmental contaminants, such as air and moisture. When constructed in a format as described in the US '553 patent publication, the top and bottom barrier films serve to protect the quantum dots against air and moisture from the environment. However, at the edges of the film, in the direction perpendicular to the barrier films, the quantum dots have only the polymer matrix serving as a barrier from exposure to environmental contaminants. The penetration of air and moisture leads to degradation of the quantum dots, particularly those proximate to the edge of the film. Such quantum dot

degradation results in an inactive edge area that fails to provide color, thereby leading to poor and uneven performance of the display device in which the quantum dot- containing film is used.

[0006] International Patent Publication No. WO2015/095296 recognized this phenomena by noting that "[s]ome currently available matrix materials provide only minimal barrier properties, which can lead to a phenomenon called edge ingress. If water and/or oxygen enter the edge regions of the quantum dot article, the quantum dots on or adjacent to the exposed edge of the laminate construction can degrade and ultimately fail to emit light when excited by ultraviolet or blue light irradiation. This quantum dot degradation can cause a dark line around a cut edge of the film article, which can be detrimental to performance of a display in which the quantum dot article forms a part." [Page 1 , lines 16-22.] The '296 PCT publication also noted the

desirability of addressing the phenomena:

[s]lowing or eliminating quantum dot degradation along the

laminate edges is particularly important to extend the service life of the displays in smaller electronic devices such as

those utilized in, for example, handheld devices and tablets.

[Page 1 , lines 22-24.]

[0007] The '296 PCT publication answered the issue by providing matrix formulations for use in quantum dot articles, which are reported to resist ingress from air and/or moisture and thus can slow the degradation of the quantum dots on or adjacent to the edges of the quantum dot articles. The '296 PCT publication claimed that such benefits may be realized with a quantum dot film article including a first barrier layer; a second barrier layer; and a quantum dot layer between the first barrier layer and the second barrier layer, the quantum dot layer including quantum dots dispersed in a matrix comprising a cured adhesive composition, where the adhesive composition includes: an epoxide; a di-amino-functional compound and a radiation curable

methacrylate compound.

[0008] Notwithstanding the '296 PCT publication, it would be desirable to provide alternative approaches to address the issue so that the end user has multiple choices of approach and supplier.

[0009] It would thus be desirable to create a quantum dot-containing composition, particularly in a film format, having a superior ability to withstand the deleterious effects on performance that results from exposure to environmental contaminants.

SUMMARY

[0010] Quantum dot-containing compositions, such as in the form of films, and methods of forming such quantum dot-containing compositions and assemblies fabricated therewith, all of which having superior resistance to degradation from exposure to environmental contaminants, such as air and/or moisture, are thus provided.

[0011] Here, the present invention uses desiccants and/or oxygen scavengers in the quantum dot-containing compositions to minimize degradation of the quantum dots. The benefits and advantages of the present invention are particularly evident at the edge of the composition when it is disposed in film form.

[0012] Quantum dot-containing compositions may be used in film form and used in manufacturing using appropriate coating and laminating techniques to create quantum dot-containing display devices, for instance. Desiccants and/or oxygen scavengers are added to the composition during formulation of the matrix in which the quantum dots are dispersed. The type, loading and particle size of the desiccant and/or oxygen scavenger can be tailored to achieve the edge protection desired by the application at hand.

[0013] In a first aspect, quantum dot-containing compositions in film form may be used as a layer disposed between a first barrier film and a second barrier film. The layer of quantum dot-containing film composition includes quantum dots dispersed in a curable matrix, which itself includes a curable component and in some embodiments a photoinitiator. Of course, the curable matrix also includes at least one of a desiccant and an oxygen scavenger.

[0014] The penetration of moisture and/or air at or around the edge of a quantum dot film results in quantum dot degradation and the formation of an inactive edge area in the film. Such an inactive area can no longer perform wavelength conversion function in the display. To prevent color distortion in the viewable area of a display, the quantum dot film is ordinarily dimensioned to be larger than the display size and the inactive edge is confined within a bezel area, toward the periphery of a display. In order to improve aesthetic considerations and the consumer's viewing experience, it is desirable to minimize the bezel width. However, against this desire is the recognized issue of degradation of quantum dots along the outer edge of quantum dot films and the attendant failure of that area to color.

[0015] The inventive compositions greatly retard quantum dot degradation after exposure to environmental contaminants, such as moisture and/or air. In so doing, quantum dots maintain their light and color generating abilities. The inventive

compositions may prove useful in display device applications where quantum dot degradation is known to be problematic near the edge of a quantum dot film, which reduces the width of the inactive edge area after a given aging time. Among other things, a reduced, or desirably eliminated, inactive edge of a quantum dot film can enable displays with a bezel of a minimum wjdth.

BRIEF DESCRIPTION OF THE DRAWING

[0016] FIG. 1 is a schematic side elevation view of an illustrative quantum dot- containing composition in the form of a film between two barrier films.

DETAILED DESCRIPTION

[0017] As noted above, quantum dot-containing compositions in film form may be used as a layer disposed between a first barrier film and a second barrier film, such as for use in a backlighting unit. The layer of quantum dot-containing film composition in film form includes quantum dots dispersed in a curable matrix, which itself includes a curable component and a curative, such as a photoinitiator. Desiccants and/or oxygen scavengers are added to the composition, oftentimes during formulation of the matrix in which the quantum dot are dispersed.

[0018] The quantum dot-containing compositions thus include a plurality of quantum dots; a curable matrix; and at least one of a desiccant and an oxygen scavenger. The plurality of quantum dots are ordinarily dispersed in a carrier.

[0019] The curable matrix may be chosen from one of a (meth)acrylate

component, an epoxy component, an oxazine component (such as a benzoxazine component), an oxazoline component, a maleimide component, a silicone component, and combinations thereof.

[0020] The curable matrix may also include a curative or an initiator, the latter of which may be a photoinitiator. The former material desirably is a nitrogen-containing curative, such as an amine like an aliphatic amine. The nitrogen-containing curative may be selected from a cyclic amidine; a tertiary amine; a secondary amine; a substituted cyclic amidine, substituted tertiary amine, substituted secondary amine; or a combination thereof The catalyst can comprise one or more of imidazole, imidazoline, pyrrolidine, a substituted imidazole compound, a substituted imidazoline compound, 1 ,4,5,6- tetrahydropyrimidine, a substituted 1 ,4,5,6-tetrahydropyrimidine compound, a substituted pyrrolidine compound, a substituted piperidine compound, and combinations thereof The catalyst can also comprise an unsubstituted piperidine, an acyclic amidine or a substituted acyclic amidine. Examples of acyclic amidines that may be acceptable catalysts according to the present invention include NN ¹ - dialkylalkylamidines, such as Ν,Ν'-dimethylalkylamidine and NN'diethylmethylamidine.

[0021] The (meth)acrylate component may be selected from a host of

(meth)acrylates, including monofunctional (meth)acrylates, difunctional (meth)acrylates, trifunctional (meth)acrylates, polyfunctional (meth)acrylates, and the like. Epoxy-based (meth)acrylates and urethane (meth)acrylates may also be included.

[0022] Examples of monofunctional (meth)acrylates include phenylphenol (meth)acrylate, methoxypolyethylene (meth)acrylate, acryloyloxyethyl succinate, fatty acid (meth)acrylates, (meth)acryloyloxyethylphthalic acid, phenoxyethylene glycol (meth)acrylate, β-carboxyethyl (meth)acrylate, isobornyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, dihydrocyclopentadiethyl (meth)acrylate, cyclohexyl (meth)acrylate, t- butyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl

(meth)acrylate, t-butylaminoethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, ethylcarbitol (meth)acrylate, phenoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate,

monopentaerythritol (meth)acrylate, dipentaerythritol (meth)acrylate, tripentaerythritol (meth)acrylate, polypentaerythritol (meth)acrylate, and the like.

[0023] Examples of difunctional (meth)acrylates include hexanediol

di(meth)acrylate, hydroxyacryloyloxypropyl (meth)acrylate, hexanediol di(meth)acrylate, urethane (meth)acrylate, epoxy(meth)acrylate, bisphenol A-type epoxy(meth)acrylate, modified epoxy(meth)acrylate, fatty acid-modified epoxy(meth)acrylate, amine-modified bisphenol F-type epoxy(meth)acrylate, allyl (meth)acrylate, ethylene glycol

di(meth)acrylate, diethylene glycol di(meth)acrylate, ethoxylated bisphenol A

di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, glycerin di(meth)acrylate, polypropylene glycol di(meth)acrylate, propoxylated ethoxylated bisphenol A

di(meth)acrylate, 9,9-bis(4-(2-(meth)acryloyloxyethoxy)phenyl) fluorene, tricyciodecane di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol

di(meth)acrylate, PO-modified neopentyl glycol di(meth)acrylate,

tricyclodecanedimethanol di(meth)acrylate, 1 ,12-dodecanediol di(meth)acrylate, and the like.

[0024] Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxy tri(meth)acrylate, polyether

tri(meth)acrylate, glycerin propoxy tri(meth)acrylate, and the like.

[0025] Examples of polyfunctional (meth)acrylates include dipentaerythritol poly(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol

tetra(meth)acrylate, pentaerythritolethoxy tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and the like.

[0026] The epoxy component may be selected from a wide variety of epoxy- functionalized resins. For instance, liquid-type epoxy resins based on bisphenol A, solid-type epoxy resins based on bisphenol A, liquid-type epoxy resins based on bisphenol F (e.g., EPICLON EXA-835LV), multifunctional epoxy resins based on phenol-novolac resin, dicyclopentadiene-type epoxy resins (e.g., EPICLON HP-7200L), naphthalene-type epoxy resins, and the like, as well as mixtures of any two or more thereof may be useful herein.

[0027] Examples of epoxy-functionalized resins include the diepoxide of the cycloaliphatic alcohol, hydrogenated bisphenol A (commercially available as EPALLOY 5000), a difunctional cycloaliphatic glycidyl ester of hexahydrophthallic anhydride (commercially available as EPALLOY 5200), EPICLON EXA-835LV, EPICLON HP- 7200L, and the like, as well as mixtures of any two or more thereof.

[0028] In certain embodiments, the epoxy component may include the

combination of two or more different bisphenol based epoxies. These bisphenol based epoxies may be selected from bisphenol A, bisphenol F, or bisphenol S epoxies, or combinations thereof. In addition, two or more different bisphenol epoxies within the same type of resin (such A, F or S) may be used.

[0029] Commercially available examples of the bisphenol epoxies include bisphenol-F-type epoxies (such as RE-404-S from Nippon Kayaku, Japan, and

EPICLON 830 (RE1801), 830S (RE1815), 830A (RE1826) and 830W from Dai Nippon Ink & Chemicals, Inc., and RSL 1738 and YL-983U (from Resolution) and bisphenol-A- type epoxies (such as YL-979 and 980 from Resolution).

[0030] These bisphenol epoxies available commercially from Dai Nippon and noted above are promoted as liquid undiluted epichlorohydrin-bisphenol F epoxies having much lower viscosities than conventional epoxies based on bisphenol A epoxies and have physical properties similar to liquid bisphenol A epoxies. The EEW of these four bisphenol F epoxies is between 165 and 180; the viscosity at 25°C is between 3,000 and 4,500 cps (except for RE1801 whose upper viscosity limit is 4,000 cps); and the hydrolyzable chloride content is reported for RE1815 and 830W as 200 ppm, and for RE1826 as 100 ppm.

[0031] The bisphenol epoxies available commercially from Resolution and noted above are promoted as low chloride containing liquid epoxies. The bisphenol A epoxies have a EEW (g/eq) of between 180 and 195 and a viscosity at 25°C of between 100 and 250 cps. The total chloride content for YL-979 is reported as between 500 and 700 ppm, and that for YL-980 as between 100 and 300 ppm. The bisphenol F epoxies have a EEW (g/eq) of between 165 and 180 and a viscosity at 25°C of between 30 and 60. The total chloride content for RSL-1738 is reported as between 500 and 700 ppm, and that for YL-983U as between 150 and 350 ppm.

[0032] Cycloaliphatic epoxies, such as 3,4-epoxycyclohexylmethyl-3,4- epoxycyclohexylcarbonate, can also be used. Reactive diluents ones, such as monofunctional, difunctional or multifunctional reactive diluents may be used to adjust the viscosity and/or lower the Tg of the resulting resin material. The monofunctional epoxy coreactant diluents should have an epoxy group with an alkyl group of about 6 to about 28 carbon atoms, examples of which include Ce-28 alkyl glycidyl ethers, C6-28 fatty acid glycidyl esters, Ce-28 alkylphenol glycidyl ethers, and the like. Examples of the reactive diluents include butyl glycidyl ether, cresyl glycidyl ether, polyethylene glycol glycidyl ether, polypropylene glycol glycidyl ether, and the like.

[0033] Polyglycidyl derivatives of phenolic compounds, such as those available commercially under the tradename EPON, such as EPON 828, EPON 1001 , EPON 1009, and EPON 1031 from Resolution; DER 331 , DER 332, DER 334, and DER 542 from Dow Chemical Co.; and BREN-S from Nippon Kayaku may be used. Other suitable epoxies include polyepoxides prepared from polyols and the like and

polyglycidyl derivatives of phenol-formaldehyde novolacs, the latter of such as DEN 431 , DEN 438, and DEN 439 from Dow Chemical. Cresol analogs are also available commercially under the tradename ARALDITE, such as ARALDITE ECN 1235, ARALDITE ECN 1273, and ARALDITE ECN 1299 from Ciba Specialty Chemicals Corporation. SU-8 is a bisphenol-A-type epoxy novolac available from Resolution. Polyglycidyl adducts of amines, aminoalcohols and polycarboxylic acids are also useful in this invention, commercially available resins of which include GLYAMINE 135, GLYAMINE 125, and GLYAMINE 1 15 from F.I.C. Corporation; ARALDITE MY-720, ARALDITE 0500, and ARALDITE 0510 from Ciba Specialty Chemicals and PGA-X and PGA-C from the Sherwin-Williams Co.

[0034] Appropriate monofunctional epoxy coreactant diluents for optional use herein include those that have a viscosity which is lower than that of the epoxy component, ordinarily, less than about 250 cps. [0035] The oxazine component ma be selected from

where o is 1-4, X is selected from a direct bond (when o is 2), alkyl (when o is 1), alkylene (when o is 2-4), carbonyl (when o is 2), thiol (when o is 1), thioether (when o is 2), sulfoxide (when o is 2), and sulfone (when o is 2), and Ri is selected from hydrogen, alkyl and aryl.

[0036] More specifically, the oxazine may be embraced by the following structure:

where X is selected from of a direct bond, CH2, C(CH ₃ )2, C=0, S, S=0 and 0=S=0, and Ri and R2 are the same or different and are selected from hydrogen, alkyl, such as methyl, ethyl, propyls and butyls, and aryl.

[0037] The oxazine thus may be selected from any of the following exemplified structures:

where Ri and R2 are as defined above.

[0038] Though not embraced by either of oxazine structures I or II additional oxazines may be embraced by the following structures:

11

V

where Ri are R2 are as defined above, and R3 is defined as Ri or R2.

[0039] Specific examples of these oxazines therefore include:



[0040] The oxazine component may include the combination of multifunctional oxazines and monofunctional oxazines.

[0041] Examples of monofunctional oxazines may be embraced by the following structure:

where R is alkyl, such as methyl, ethyl, propyls and butyls.

[0042] As the oxazoline, compounds embraced by the following structure are suitable

where R , R ² , R ³ , R ⁴ , and X are hydrogen or as regards x a direct bond to a divalent organic radical, and m is 1.

[0043] Exemplary compounds have the structure

in which k is 0-6; m and n are each independently 1 or 2 provided that at least one of m or n is 1 ; X is a monovalent or polyvalent radical selected from branched chain alkyl, alkylene, alkylene oxide, ester, amide, carbamate and urethane species or linkages, having from about 12 to about 500 carbon atoms; and R ¹ to R ⁸ are each independently selected from C1-40 alkyl, C2-40 alkenyl, each of which being optionally substituted or interrupted by one or more— O— ,— NH— ,— S— ,—CO—,— C(O)O— ,— NHC(O)— , and C6-2o aryl groups.

[0044] The oxazoline compounds include 4,4',5,5'-tetrahydro-2,2'-bis-oxazole, 2,2'-bis(2-oxazoline); a 2,2'-(alkanediyl) bis [4,4-dihydrooxazole], e.g., 2,2'-(2,4- butanediyl) bis [4,5-dihydrooxazole] and 2,2'-(1 ,2-ethanediyl) bis [4,5-dihydrooxazole]; a 2,2'-(arylene) bis [4,5-dihydrooxazole]; e.g., 2,2'-(1 ,4-phenylene)bis (4,5- dihydrooxazole], 2,2'-(1 ,5-naphthalenyl) bis (4,5-dihydrooxazole], 2,2'-(1 ,3-phenylene) bis [4,5-dihydrooxazole), and 2,2'-(1 ,8-anthracenyl) bis [4,5-dihydrooxazole]; a sulfonyl, oxy, thio or alkylene bis 2-(arylene) [4,5-dihydrooxazole], e.g., sulfonyl bis 2-(1 ,4- phenylene) [4,5-dihydrooxazole], thio bis 2,2'-(1 ,4-phenylene) [4,5-dihydrooxazole] and methylene bis 2,2'-(1 ,4-phenylene) [4,5-dihydrooxazole]; a 2,2',2"-(1 ,3,5-arylene) tris [4,5-dihydrooxazole], e.g., 2,2',2"-tris (4,5-dihydrooxazole]1 ,3,5-benzene; a poly [(2- alkenyl) 4,5-hydrooxazole], e.g., poly[2-(2-propenyl)4,5-dihydrooxazole], and others and mixtures thereof.

[0045] In some embodiments, the oxazoline compounds will have the following structures.

[0046] The maleimide component may be selected from maleimides, nadimides or itaconimides. For instance, maleimides, nadimides or itaconimides include those having the structure:

respectively, where:

m is 1-15,

p is 0-15,

each R ² is independently selected from hydrogen or lower alkyl (such as C1-5), and

J is a monovalent or a polyvalent radical comprising organic or organosiloxane radicals, and combinations of two or more thereof.

[0047] J is a monovalent or polyvalent radical selected from:

■ hydrocarbyl or substituted hydrocarbyl species typically having in the range of about 6 up to about 500 carbon atoms, where the hydrocarbyl species is selected from alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, alkylaryl, arylalkyl, aryalkenyl, alkenylaryl, arylalkynyl or alkynylaryl, provided, however, that X can be aryl only when X comprises a combination of two or more different species;

■ hydrocarbylene or substituted hydrocarbylene species typically having in the range of about 6 up to about 500 carbon atoms, where the hydrocarbylene species are selected from alkylene, alkenylene, alkynylene, cycloalkylene, cycloalkenylene, arylene, alkylarylene, arylalkylene, arylalkenylene,

alkenylarylene, arylalkynylene or alkynylarylene, ^■ heterocyclic or substituted heterocyclic species typically having in the range of about 6 up to about 500 carbon atoms,

^■ polysiloxane, or

^■ polysiloxane-polyurethane block copolymers, as well as

combinations of one or more of the above with a linker selected from covalent bond, -O- , -S-, -NR-, -NR-C(O)-, -NR-C(O)-O-, -NR-C(0)-NR-, -S-C(O)-, -S-C(0)-0-, -S-C(0)-NR- , -0-S(0)2-, -O-S(0)2-0-, -0-S(O)2-NR-, -O-S(O)-, -0-S(0)-0-, -0-S(0)-NR- , -O-NR-C(O)-, -0-NR-C(0)-0-, -0-NR-C(0)-NR

, -NR-O-C(O)-, -NR-0-C(0)-0-, -NR-0-C(0)-NR-, -O-NR-C(S)-, -0-NR-C(S)-0-, -O-NR- C(S)-NR-, -NR-O-C(S)-, -NR-0-C(S)-0-, -NR-0-C(S)-NR-, -O-C(S)-, -0-C(S)-0- , -0-C(S)-NR-, -NR-C(S)-, -NR-C(S)-0-, -NR-C(S)-NR-, -S-S(O) ₂ -, -S-S(O) ₂ -0-, -S- S(0) ₂ -NR-, -NR-O-S(O)-, -NR-O-S(O)-0-, -NR-0-S(0)-NR-, -NR-0-S(0) ₂ -, -NR-O- S(0) ₂ -0-, -NR-0-S(0) ₂ -NR-, -O-NR-S(O)-, -0-NR-S(0)-0-, -0-NR-S(0)-NR-, -O-NR- S(0) ₂ -0-, -0-NR-S(0) ₂ -NR-, -O-NR-S(0) ₂ -, -0-P(0)R ₂ -, -S-P(0)R ₂ -, or -NR-P(0)R ₂ -; where each R is independently hydrogen, alkyl or substituted alkyl.

[0048] J thus may be oxyalkyl, thioalkyl, aminoalkyl, carboxylalkyl, oxyalkenyl, thioalkenyl, aminoalkenyl, carboxyalkenyl, oxyalkynyl, thioalkynyl, aminoalkynyl, carboxyalkynyl, oxycycloalkyl, thiocycloalkyl, aminocycloalkyl, carboxycycloalkyl, oxycloalkenyl, thiocycloalkenyl, aminocycloalkenyl, carboxycycloalkenyl, heterocyclic, oxyheterocyclic, thioheterocyclic, aminoheterocyclic, carboxyheterocyclic, oxyaryl, thioaryl, aminoaryl, carboxyaryl, heteroaryl, oxyheteroaryl, thioheteroaryl,

aminoheteroaryl, carboxyheteroaryl, oxyalkylaryl, thioalkylaryl, aminoalkylaryl, carboxyalkylaryl, oxyarylalkyl, thioarylalkyl, aminoarylalkyl, carboxyarylalkyl,

oxyaryialkenyl, thioarylalkenyl, aminoarylalkenyl, carboxyarylalkenyl, oxyalkenylaryl, thioalkenylaryl, aminoalkenylaryl, carboxyalkenylaryl, oxyarylalkynyl, thioarylalkynyl, aminoarylalkynyl, carboxyarylalkynyl, oxyalkynylaryl, thioalkynylaryl, aminoalkynylaryl or carboxyalkynylaryl, oxyalkylene, thioalkylene, aminoalkylene, carboxyalkylene, oxyalkenylene, thioalkenylene, aminoalkenylene, carboxyalkenylene, oxyalkynylene, thioalkynylene, aminoalkynylene, carboxyalkynylene, oxycycloalkylene,

thiocycloalkylene, aminocycloalkylene, carboxycycloalkylene, oxycycloalkenylene, thiocycloalkenylene, aminocycloalkenylene, carboxycycloalkenylene, oxyarylene, thioarylene, aminoarylene, carboxyarylene, oxyalkylarylene, thioalkylarylene, aminoalkylarylene, carboxyalkylarylene, oxyarylalkylene, thioarylalkylene,

aminoarylalkylene, carboxyarylalkylene, oxyarylalkenylene, thioarylalkenylene, aminoarylalkenylene, carboxyarylalkenylene, oxyalkenylarylene, thioalkenylarylene, aminoalkenylarylene, carboxyalkenylarylene, oxyarylalkynylene, thioarylalkynylene, aminoarylalkynylene, carboxy arylalkynylene, oxyalkynylarylene, thioalkynylarylene, aminoalkynylarylene, carboxyalkynylarylene, heteroarylene, oxyheteroarylene, thioheteroarylene, aminoheteroarylene, carboxyheteroarylene, heteroatom-containing di- or polyvalent cyclic moiety, oxyheteroatom-containing di- or polyvalent cyclic moiety, thioheteroatom-containing di- or polyvalent cyclic moiety, aminoheteroatom-containing di- or polyvalent cyclic moiety, or a carboxyheteroatom-containing di- or polyvalent cyclic moiety.

[0049] The silicone component may be selected from (meth)acrylate- functionalized silcones.

[0050] Desirably, the curable matrix comprises a (meth)acrylate component and an epoxy component, where the epoxy component is present in an amount of 40 percent by weight to 90 percent by weight (such as about 50 percent by weight to about 80 weight by weight), and the (meth)acrylate component is present in an amount of about 10 percent by weight to about 60 percent by weight (such as about 20 percent by weight to about 40 percent by weight). The relative percentages here are based on the total composition. And the relative percentage of the epoxy component also includes the nitrogen-containing curative.

[0051] Desirably, but alternatively, the curable matrix comprises the combination of an epoxy-based (meth)acry!ate, an urethane (meth)acrylate and an alkyl

(meth)acrylate, where the epoxy-based (meth)acrylate is present in an amount of 10 percent by weight to 50 percent by weight (such as about 20 percent by weight to about 40 weight by weight), the urethane (meth)acrylate may or may not be present, but when present it is used in an amount of greater than 0 to about 30 percent by weight (such as about 10 percent by weight to about 20 percent by weight) and the alkyl (meth)acrylate is present in an amount of about 20 percent by weight to about 60 percent by weight (such as about 30 percent by weight to about 50 percent by weight). The relative percentages here are based on the total composition.

[0052] The quantum dots used in the inventive quantum dot-containing

compositions may be of a variety of constructions. One such construction involves a core and at least one ligand.

[0053] In some cases, the ligand on or associated with the quantum dots may be molecules, oligomers, or polymers bound to their surfaces, resulting in a desirable local ligand environment for atoms at the surfaces of the quantum dots. Generally, certain ligands are present during the growth process used to synthesize the quantum dots. Often, these ligands are replaced or exchanged at a later time to provide a new ligand environment selected to optimize properties. Ligands perform several functions. They help prevent quantum dots from clustering and quenching, they can improve the chemical stability of the quantum dot surface, and they can improve the emission efficiency of the quantum dots. Ligand systems can include several forms. In general, they can include molecules or functional groups directly bound to quantum dots, and optionally, additional material. In some embodiments the functional silicone provides the requisite ligand functional groups.

[0054] In some embodiments, the ligands on or associated with the quantum dots may be represented by the following formula:

R ⁸ -(X)p

where here R ⁸ is (hetero)hydrocarbyl group having C2 to C30 carbon atoms; preferably a linear or branched alkyl of 10 to 30 carbon atoms or a polysiloxane; p is at least one; preferably at least two; and X is an electron-donating group. Preferably X is an amino group or a thiol.

[0055] Generally, where a ligand is present on or with the quantum dot, there are many ligand molecules per quantum dots.

[0056] In some embodiments, the quantum dot materials can include quantum dots dispersed in a liquid carrier. For example, the liquid carrier can include an oil such as an amino-silicone oil. Desirably, the liquid carrier is chosen to match the

transmissivity of the curable matrix. To increase the optical path length through the quantum dot layer and improve quantum dot absorption and efficiency, the difference in the refractive indices of the carrier liquid and the curable matrix is greater than 0.05, such as greater than 0.1.

[0057] The liquid carrier for the quantum dots may be an amino-functionalized silicone, such as is shown

III

where each R ⁶ is independently an alkyl or aryl; R ^NH2 is a n amine-substituted

(hetero)hydrocarbyl group; x is 1 to 2000; such as 3 to 100; y may be zero; x+y is at least one; R ⁷ is alkyl, aryl or R ^NH2 , where the amine-functional silicone has at least two RNH2 g _r0U p _S

[0058] Useful amino-functionalized silicones are described in US Patent

Application Publication No. 2013/0345458 (Freeman et al.); and Lubkowsha et al., "Aminoalkyl Functionalized Siloxanes," Polimery, 59, pp 763-68 (2014). Amino- functionalized silicones are available commercially from Gelest Inc, Morrisville, PA; from Dow Corning under the Xiameter tradename, including Xiameter OFX-0479, OFX-8040, OFX-8166, OFX-8220, OFX-8417, OFX-8630, OFX-8803, and OFX-8822; from Siletech under the tradename Silamine; and from Momentive under the trade designations ASF3830, SF4901 , RPS-1 16, XF40-C3029 and TSF4707, and the tradenames

Magnasoft, such as Magnasoft PlusTSF4709, and Baysilone OF-TP3309.

[0059] In some embodiments, the ligand may be a thiol, such as a polythiol selected from primary polythiols, secondary polythiols and combinations thereof, desirably any one or more of pentaerythritol tetrakis (3-mercaptobutylate),

pentaerythritol tetra-3-mercaptopropionate, trimethylolpropane tri(3- mercaptopropionate), tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate,

dipentaerythritol hexakis(3-mercaptopropionate), ethoxilated-trimethylolpropane tri-3- mercaptopropionate, mercapto-functional methylalkyl silicone polymers and

combinations thereof.

[0060] When the quantum dots are constructed with polythiol ligands, the ligands should have a functionality of at least 2, desirably 3 to 4. [0061] In some embodiments, the ligand system can be a liquid initially, and then rendered a solid by curing, polymerization, or solvent removal. In some embodiments the ligand system may remain liquid to provide droplets of quantum dots dispersed in a carrier liquid, which in turn becomes dispersed in a curable matrix.

[0062] In some embodiments the amount of ligand and carrier liquid (ligand functional or non-functional) is greater than 60 percent by weight, such as greater than 70 percent by weight, desirably greater than 80 percent by weight, relative to the total composition.

[0063] In some cases, the ligand of the quantum dots is embraced by:

R -(X)n

where here R ¹ here is an alkyl group having Ci to C30 carbon atoms, an alkenyl group having C2 to C30 carbon atoms, or an alkynyl group having C2 to C30 carbon atoms, any of which may be linear, branched or cyclic, provided the appropriate number of carbon atoms is present, or may be substituted or interrupted with a heteroatom; n is an integer of at least one; and X is an electron donating group, such as amines, carboxylic acids and thiols.

[0064] The core of the quantum dots here is constructed of a metal or a semiconductive compound or a mixture thereof. In some embodiments, each core is surrounded by at least one ligand, such as a polythiol ligand, which may be crosslinked with at least one other ligand surrounding another core.

[0065] The inventive quantum dot-containing compositions can include a single quantum dot type or a single quantum dot binding-ligand type, or a plurality of quantum dot types or a plurality of quantum dot binding-ligand types. For example, an inventive quantum dot-containing composition can include a Cd quantum dot, such as CdS, CdTe, CdSe, CdSe/CdS, CdTe/CdS, CdTe/ZnS, CdSe/CdS/ZnS, CdSe/ZnS,

CdSeZn/CdS/ZnS, or CdSeZn/ZnS, or a Cd quantum dot binding ligand having amine binding groups. The inventive quantum dot-containing composition can also include an InP quantum dot, such as InP or InP/ZnS, and an InP quantum dot binding ligand having carboxy binding groups.

[0066] In all embodiments, the metal or semiconductive compound used to form the core is a combination of one or more elements selected from Group IV of the Periodic Table; one or more elements selected from Groups II and VI of the Periodic Table; one or more elements selected from Groups III and V of the Periodic Table; one or more elements selected from Groups IV and VI of the Periodic Table; and one or more elements selected from Groups I and III and VI of the Periodic Table; or

combinations thereof.

[0067] Desirably, the metal or semiconductive compound is a combination of one or more elements selected from Groups I and III and VI of the Periodic Table. For instance, the metal or semiconductive compound is a combination of one or more of Cd, Zn, In, Cu, S and Se.

[0068] Examples of materials for preparing core-shell quantum dots include Si, Ge, Sn, Se, Te, B, C (including diamond), P, Co, Au, BN, BP, BAs, AIN, AIP, AIAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, In As, InSb, AIN, AIP, AIAs, AlSb, GaN, GaP, GaAs, GaSb, ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe, CdSeZn, CdTe, HgS, HgSe, HgTe, BeS, BeSe, BeTe, MgS, MgSe, GeS, GeSe, GeTe, SnS, SnSe, SnTe, PbO, PbS, PbSe, PbTe, CuF, CuCI, CuBr, Cul Si ₃ N ₄ , Ge ₃ N ₄ , AI2O3, (Al, Ga, ln) ₂ (S, Se, Te) ₃ , AI2CO3, and appropriate combinations of two or more such materials. Exemplary core- shell luminescent quantum dots include CulnS, CulnSeS, CuZnlnSeS, CuZnlnS, Cu:ZnlnS, CulnS/ZnS, Cu:ZnlnS/ZnS, CulnSeS/ZnS, CdSe/ZnS, InP/ZnS, PbSe/PbS, CdSe/CdS, CdTe/CdS, CdTe/ZnS, among others.

[0069] In some embodiments, the quantum dots may be sourced from Nanosys, Inc., Milpitas, CA, which supplies quantum dots in the form of quantum dots and quantum dot concentrates, where the quantum dots may or may not have ligands associated therewith. Nanosys supplies for instance GP-988 and Green Nanocrystal Paste. (Nanocrystals and quantum dots are used herein interchangeably.) These quantum dots may be prepared with reference to Alivisatos, A. P., "Semiconductor clusters, quantum dots, and quantum dots," Science, 271 :933 (1996); X. Peng, M.

Schlamp, A. Kadavanich, A. P. Alivisatos, "Epitaxial growth of highly luminescent CdSe/CdS Core/Shell quantum dots with photostability and electronic accessibility," J. Am. Chem. Soc, 30:7019-7029 (1997); and C. B. Murray, D. J. Norris, M. G. Bawendi, "Synthesis and characterization of nearly monodisperse CdE (E=sulfur, selenium, tellurium) semiconductor nanocrystallites," J. Am. Chem. Soc, 1 15:8706 (1993), X. Peng, et al., J. Am. Chem. Soc, 30:7019-7029 (1997). For instance, 1.5 g GP-988 was added to green nanocrystal paste (from 15 mL washed nanocrystal, which was decanted of its wash solvent), stirred well with a spatula, and then a stir bar while heating to a temperature of about 90°C for a period of time 2 hours. The solution was cooled to room temperature and decanted to another vial. A typical weight ratio would be 0.8 g paste in 8.0 g GP-988. Quantum yield measurements of exchanged green polymer 323-13E measured 86.8%.

[0070] The quantum dots can be produced using any method known to those skilled in the art. For example, see U.S. Patent Nos. 6,225,198; 6,207,229; 6,322,901 ; 6,872,249; 6,949,206; 7,572,393; 7,267,865 and 7,374,807, each of which is

incorporated by reference herein in its entirety.

[0071] The optical properties of quantum dots can be determined by their particle size, chemical or surface composition and/or by suitable optical testing available in the art. The ability to tailor the quantum dot size in the range between about 1 nm and about 15 nm enables photoemission coverage in the entire optical spectrum to offer great versatility in color rendering.

[0072] After formation or as they are formed, the quantum dots may be dispersed in a carrier for use in a pre-mix.

[0073] The quantum dots emit green light and red light upon down-conversion of blue primary light, such as from a blue LED, to secondary light emitted by the quantum dots. The respective portions of red, green, and blue light can be controlled to achieve a desired white point for the white light emitted by a display device incorporating a quantum dot film article.

[0074] The quantum dot concentrate may be used in the quantum dot-containing composition in an amount of about 0.05 percent by weight to about 10 percent by weight.

[0075] The quantum dots may be dispersed in the curable matrix in an amount of about 0.2 to about 1 percent by weight, such as about 0.3 percent by weight to about 0.6 percent by weight.

[0076] Once formed, the thickness of the quantum dot layer is about 40 microns to about 250 microns. [0077] The curable matrix of the quantum dot-containing composition adheres to the barrier layers to form a laminate construction, and also forms a protective matrix for the quantum dots. However, known quantum dot layers have shown the tendency to degrade at the periphery over time due at least in part to penetration of environmental contaminants.

[0078] Such penetration, or ingress, including edge ingress, is defined by a loss in quantum dot performance due to ingress of moisture and/or oxygen into the matrix 24. In various embodiments, the edge ingress of moisture and oxygen into the cured matrix 24 is less than about 1.0 mm after 1 week at 85°C, or about less than 0.75 mm after 1 week at 85°C, or less than about 0.5 mm after 1 week at 85°C or less than 0.25 mm after 1 week at 85°C. In various embodiments the matrix has a moisture and oxygen ingress of less than about 0.5 mm after 500 hours at 65°C and 95% relative humidity.

[0079] In various embodiments, oxygen transmission rate the cured matrix is less than about 150 (cc.mil)/(m ² day), or less than about 100 (cc.mil)/(m ² day). In various embodiments, the water vapor transmission rate of the cured matrix should be less than about 50 g/m ² .mil.day, such as less than about 30 g/m ² .mil.day.

[0080] The inventive compositions may also include a desiccant, such as one selected from calcium oxide, anhydrous calcium sulfate, molecular sieves, and zeolite.

[0081] The desiccant should have a particle size within the range of about 0.1 urn to about 500 urn, such as about 0.1 urn to about 10 urn.

[0082] The desiccant should be present in an amount within the range of about 0.5 to about 15 percent by weight, such as about 1 to about 8 percent by weight.

[0083] The inventive compositions may include an oxygen scavenger, such as one selected from sodium sulfite, sodium bisulfite, triphenyl phosphine, ascorbic acid derivatives, and thiourea derivatives.

[0084] The chosen oxygen scavenger should have a particle size within the range of about 1 urn to about 500 urn, and should be present in an amount within the range of about 1 to about 8 percent by weight. [0085] Desirably, in some embodiments, the desiccant and the oxygen scavenger may be present. However, at least one of the desiccant and oxygen scavenger must be present in the quantum dot-containing compositions.

[0086] The desiccant and/or the oxygen scavenger assist to maintain the integrity of the quantum dot layer. By so doing, the color changing ability is preserved. In various embodiments, the color change observed upon aging is defined by a change of less than 0.02 on the 1931 CIE (x,y) Chromaticity coordinate system following an aging period of 1 week at 85°C. In certain embodiments, the color change upon aging is less than 0.005 on the following an aging period of 1 week at 85°C. In certain embodiments the matrix has a color shift d(x,y) using the CIE 1931 (x,y) convention of less than about 0.02 after 100 hours at 65°C and 95% relative humidity.

[0087] In many embodiments, the method of forming a quantum dot film article includes forming a partially cured quantum dot material having a viscosity after partial cure of the polymeric curable matrix at least 10 times greater or at least 20 times greater than the viscosity prior to partial cure of the curable matrix. In one or more embodiments the first viscosity is less than 10,000 centipoise and the second viscosity is greater than 100,000 centipoise. The viscosity of the quantum dot-containing composition prior to cure is of at least 200 centipoise, and up to 15,000 centipoise, preferably 500 to 10,000 centipoise and most preferably between 1000 and 3000 centipoise.

[0088] A method of forming a quantum dot film article includes coating a quantum dot-containing composition on a first barrier layer and disposing a second barrier layer on or over the quantum dot-containing composition in a mating relationship with the first barrier layer.

[0089] In one or more embodiments the method of forming a quantum dot film article includes exposing the curable matrix to condition effective to initiate cure to form a partially cured quantum dot film.

[0090] FIG. 1 is a schematic side elevation view of an illustrative quantum dot film 10.

[0091] In one or more embodiments, a quantum dot film article 10 includes a first barrier film 32, a second barrier film 34, and a quantum dot layer 20 separating the first barrier 32 from the second barrier film 34. The quantum dot layer 20 includes quantum dots 22 dispersed in a curable matrix 24.

[0092] In one or more embodiments, a method of forming a quantum dot film article 10 includes coating a quantum dot-containing composition 20 on a first barrier film 32 and disposing a second barrier film 34 on the quantum dot-containing

composition 20.

[0093] Barrier films 32, 34 can be formed of any useful film material that can protect the quantum dots from environmental conditions, such as air and moisture.

Suitable barrier films include polymers, such as polyethylene terephthalate, glass, oxides (such as silicon oxide, titanium oxide, or aluminum oxide) or other dielectric materials. In many embodiments each barrier layer of the quantum dot film includes at least two layers of different materials or compositions, such that the multi-layered barrier eliminates or reduces pinhole defect alignment in the barrier layer, providing an effective barrier to air and moisture reading.

[0094] The identity, thickness, and number of barrier layers will depend on the particular application, and will suitably be chosen to maximize barrier protection and brightness of the quantum dot while minimizing thickness of the quantum dot film. In many embodiments each barrier layer is a laminate film, such as a dual laminate film, where the thickness of each barrier layer is sufficiently thick to eliminate wrinkling in roll- to-roll or laminate manufacturing processes. In one illustrative embodiment the barrier films are polyester films having an oxide layer.

[0095] The barrier protection discussed above refers to that offered in the vertical direction. Protection afforded in the horizontal or lateral direction, particularly at the distil edges of the quantum dot films, comes from the added desiccant and/or moisture scavenger.

[0096] Some of the advantages of the inventive quantum dot-containing composition and films formed therefrom are illustrated by the following examples.

EXAMPLES

Example 1 : [0097] As a comparative example, a formulation (Sample A) was prepared by mixing the following components.

Table 1

[0098] To the four components were added with mixing 5% by weight of Green Gen 2 QD Concentrate from Nanosys Inc. The quantum dot-containing composition so formed (Sample A) was then laminated between two barrier films (each from Vitriflex) and cured by exposure to 2 J/cm ² UVA dosage from a 365nm UV LED lamp, and then by exposure to an additional 1J/cm ² from a mercury vapor UV lamp. The thickness of the quantum dot film article was about 00 microns.

[0099] The resulting quantum dot film article was punched into 19 mm diameter circles and placed in a humidity chamber at 60°C/90%RH for aging study. Periodically, the film samples were removed from the humidity chamber and observed by an optical microscope on a blue LED backlight. The quantum dots in the film articles were excited by the blue light and emitted green light, as was determined by virtual observation. At the peripheral edge of the film articles, air and moisture penetration caused quantum dot degradation and the formation of an inactive area. The width of this inactive edge area was measured and monitored as a function of aging time (in weeks). After 1 week, the inactive edge was measured as 1.6 mm; after 2 weeks it was measured as 1.66 mm; and after 3 weeks it was measured at 2.61 mm.

Example 2: [00100] Calcium oxide as a desiccant was added into the formulation of Table 1 (Sample A) at 1 %, 3%, 5%, 8% and 10% wt loading.

Table 2

[00101] Quantum dot film articles were then prepared following the same procedure described in Sample A. These quantum dot film articles were aged in a humidity chamber at 60°C/90%RH. The width of the inactive edge area at different aging times was observed and recorded below. Sample 5 showed delamination. No proper evaluation was performed on Sample 5 as the quantum dot film showed local delamination upon punching.

Table 3

[00102] As can be seen, the addition of calcium oxide as a desiccant reduced the width of the inactive edge area of the quantum dot film article that formed after heat and humidity aging.

[00103] The effect of calcium oxide as a desiccant on the optical properties of the quantum dot films was also measured. The luminance and color coordinates of the quantum dot films were measured by a Photo Research PR655 spectroradiometer. The quantum dot films were illuminated by a blue LED backlight and the emitted light from the quantum dot film was measured by the PR655 spectroradiometer. The luminance and color coordinates of the quantum dot films of Sample Nos. 1 to 3 was observed and recorded below in Table 4.

Table 4

[00104] The luminance and y color coordinates are indicative of the amount of green light being emitted by the quantum dot film. The presence of the desiccant in the quantum dot films increased the amount of green light emitted by the film. Thus, more blue light can be converted to green light with the same loading of quantum dots. In other words, with calcium oxide as a desiccant it seems that a lower concentrate of quantum dot is needed to convert the same amount of blue light to green light.

Example 3:

[00105] Sodium sulfite and sodium bisulfite as oxygen scavengers were added to Sample A at the weight percent loading shown below in Table 5 (3 percent by weight for Sample Nos. 6 and 8; 5 percent by weight for Sample Nos. 7 and 9).

Table 5

[00106] Quantum dot film articles were then prepared following the same procedure described in Example . These quantum dot film articles were also aged in a humidity chamber at 60°C/90%RH. The width of the inactive edge area at different aging times was observed and recorded below in Table 6.

Table 6

[00107] As can be seen, the addition of sodium sulfite and sodium bisulfite as oxygen scavenger reduced the width of inactive edge area during heat and humidity aging.

Example 4:

[00108] As a comparative example (Sample B), a two-part adhesive formulation was prepared by mixing the following components listed in Parts A and B. Table 7a -- Part A

[00109] The components of Part A and those of Part B were mixed and thereafter Part A and Part B were brought together to form a quantum dot-containing composition which was then laminated between two barrier films (each from Vitriflex) and cured by exposure to 1 J/cm ² UVA dosage from a 365nm UV LED lamp. The laminated film was then cured at a temperature of 100°C for a period of time of 5 minutes.

[00110] The resulting quantum dot film was evaluated using the same method outlined in Example 1. Result from observations are recorded for Sample B in Table 9.

Example 5:

[00111] Micronized calcium oxide was mixed into the Part A formulation of the previous example.

Table 8a -- Part A

Table 8b - Part B

[00112] The noted components were mixed together to form a Part B formulation, which was mixed with Part A and a quantum dot film was prepared and evaluated following the same process as in the previous example.

[00113] Table 9 below shows the results of the evaluation.

Table 9

Example 6:

[00114] Here, a desiccant and an oxygen scavenger in combination were prepare quantum dot-containing formations at different but equal, low levels.

Table 10

[00115] Quantum dot film articles were then prepared following the same procedure described in Example 1. The quantum dot film articles were aged in a humidity chamber at 60°C/90%RH. The width of the inactive edge area at different aging times was observed and recorded below in Table 1 1.

Table 11

[00116] The results shown in Table 1 1 indicate that the combination of a desiccant and an oxygen scavenger can also be used to effectively reduce the width of inactive edge of a quantum dot film.