BORON-CONTAINING CYCLIC EMISSIVE COMPOUNDS AND COLOR CONVERSION FILM CONTAINING THE SAME

Inventors: Shijun Zheng, Jeffrey R. Flammaker, Hiep Luu, Peng Wang, and Jie Cai

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 63/152,664, filed February 23, 2021 , which is incorporated by reference in its entirety.

BACKGROUND

In color reproduction the gamut, or color gamut, is a certain complete subset of colors available on a device such as a television or monitor. For example, Adobe™ Red Green Blue (RGB), a wide-gamut color space achieved by using pure spectral primary colors, was developed to provide a broader color gamut and offer a more realistic representation of visible colors viewed through a display. It is believed that a device which could provide a wider gamut could enable the display to portray more vibrant colors.

As high-definition large screen displays become more common, the demand for higher performance, slimmer and highly functional displays have increased. Current light emitting diode (LEDs) are obtained by a blue light source exciting a green phosphor, a red phosphor or a yellow phosphor to obtain a white light source. Flowever, the full width half maximum (FWFIM) of the emission peak of the current green and red phosphors are quite large, usually greater than 40 nm, resulting in the green and red color spectrums overlapping and rendering colors that are not fully distinguishable from one another. This overlap leads to poor color rendition and the deterioration of the color gamut.

To correct the deterioration in the color gamut, methods have been developed using films containing quantum dots in combination with LEDs. Flowever, there are problems with the use of quantum dots. First, cadmium-based quantum dots are extremely toxic and are banned from use in many countries due to health safety issues. Second, non-cadmium-based quantum dots have a very low efficiency in converting blue LED light to green and red light. Third, quantum dots require expensive encapsulating processes for protection against moisture and oxygen. Last, the cost of using quantum dots is high, because of the difficulties in controlling size uniformity during the production process. Therefore, there exists a need for improving performance in color conversion films, backlight units, and display devices.

SUMMARY

Photoluminescent compounds described herein may be used to improve the contrast between distinguishable colors in televisions, computer monitors, smart devices and many other devices that utilize color displays. The photoluminescent complexes of the present disclosure provide novel color converting complexes with good blue light absorbance and narrow emissions bandwidths, with the full width half maximum [FWHM] of emission band of less than 40 nm. In some embodiments, a photoluminescent complex absorbs light of a first wavelength and emits light of a second wavelength higher than the first wavelength. The photoluminescent complexes disclosed herein can be utilized with a color conversion film for use in light emitting apparatuses. The color conversion films of the present disclosure reduce color deterioration by reducing overlap within the color spectrum, resulting in high quality color rendition.

In some embodiments, a photoluminescent complex is described, the photoluminescent complex may comprise:

In some embodiments, a color conversion film can comprise the photoluminescent complex described herein. Some embodiments include a method for preparing a BODIPY analogue, the method may comprise condensing a substituted 2,4-dimethyl-1 H-pyrrole-3 carboxylate analogue with a hydroxyalkylbenzaldehyde, e.g., 4-hydroxy-2,6-dimethylbenzaldehyde, and BF ₃ to form a BODIPY analogue. In some embodiments, the substituted 2,4-dimethyl-1 H-pyrrole-3 carboxylate analogue can be 2,4-dimethyl-1 H-pyrrole-3 carboxylic acid ethyl ester. In some embodiments, the substituted 2, 4-dimethyl-1 H-pyrrole-3 carboxylate analogue can be 2, 4-dimethyl-1 H-pyrrole-3 carboxylic acid methyl ester. In some embodiments, the hydroxyalkylbenzaldehyde can be 4- hydroxy-2,6-dimethylbenzaldehyde.

Some embodiments include a method for preparing the color conversion film, wherein the method comprises: dissolving at least one photoluminescent complex, described herein and a binder resin within a solvent; and applying the mixture on one of the transparent substrate’s opposing surfaces.

Some embodiments include a backlight unit including a color conversion film described herein.

Some embodiments include a display device including the backlight unit described herein.

The present application provides photoluminescent complexes having excellent color gamut and luminescent properties, a method for manufacturing color conversion films using the photoluminescent complexes, and a backlight unit including the color conversion film. The present application provides a less expensive method for preparing a photoluminescent complex described herein. These and other embodiments are described in greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph depicting the absorption and emission spectra of one embodiment of a photoluminescent complex.

DETAILED DESCRIPTION

The present disclosure is related to photoluminescent compounds for use in color conversion films, backlight units, and display devices including the same.

A novel approach to address the issues presented with the use of quantum dots involves the use of a boron-dipyrromethene (BODIPY) compounds as the emissive materials to replace the quantum dots. BODIPY complexes have a narrow FWHM, high fluorescent efficiency, stability to both moisture and oxygen, and low production cost. However, BODIPY materials can have some drawbacks, such as very low absorption of blue LED light, e.g., 450 nm, resulting in inefficient conversion of blue LED light to green and red light. Another drawback of current BODIPY compounds is the FWHM tend to be broad when used in color converting films.

The current disclosure describes photoluminescent complexes and their uses in color conversion films. The photoluminescent complex may be used to improve and enhance the transmission of one or more desired emissive bandwidths within a color conversion film. In some embodiments, the photoluminescent complex can both enhance the transmission of a desired first emissive bandwidth and decrease the transmission of a second emissive bandwidth. For example, a color conversion film can enhance the contrast or intensity between two or more colors, increasing the distinction from one another. The present disclosure includes a photoluminescent complex that can enhance the contrast or intensity between two colors, increasing their distinction from one another.

As used herein, when a compound or chemical structure is referred to as being optionally substituted, it may be unsubstituted, or it may be substituted, meaning it can include one or more substituents. A substituted group is related to the unsubstituted parent structure in that one or more hydrogen atoms on the parent structure have been independently replaced by one or more substituent groups. In one or more forms, the substituent groups may independently be F, Cl, Br, I, C0-7H1-15O1-2N0-2, C0-7H1-15O0-2N1-2, optionally substituted alkyl (including unsubstituted alkyl, such as methyl, ethyl, C3 alkyl, C4 alkyl, etc., fluoroalkyl, e.g. CF _3, etc.), alkenyl, or a C3-C7 heteroalkyl.

An alkyl moiety may be branched, straight chain (i.e., unbranched), or cyclic. In some embodiments, the alkyl moiety may have 1 to 8 carbon atoms. The alkyl group of the compounds designated herein may be designated as “CrCg alkyl” or similar designations. By way of example only, “CrCg alkyl” indicates that there are 1 , 2, 3, 4, 5, 6, 7, or 8 carbon atoms in the alkyl chain, i.e., the alkyl chain is methyl, ethyl, propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, and any isomers thereof. Thus, CrCg alkyl includes C1-C2 alkyl, C1-C3 alkyl, C1-C4 alkyl, C1-C5 alkyl, C1-C6 alkyl, C1-C7 alkyl, and CrCg alkyl. Alkyl groups can be substituted or unsubstituted. Typical alkyl groups include, but are in no way limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tertiary butyl, pentyl, hexyl, ethenyl, propenyl, butenyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. The term “halogen” as used herein means fluorine, chlorine, bromine, and iodine.

The term “aryl” as used herein refers to an aromatic ring wherein each of the atoms forming the ring is a carbon atom. Aryl rings can be formed by five, six, seven, eight, or more than eight carbon atoms. Aryl groups can be substituted or unsubstituted. Examples of aryl groups include, but are not limited to phenyl, naphthalenyl, phenanthrenyl, etc.

The term “bond”, “bonded”, “direct bond” or “single bond” as used herein means a chemical bond between two atoms or to two moieties when the atoms joined by the bond are considered to be part of a larger structure.

The term “moiety” as used herein refers to a specific segment or functional group of a molecule. The term “cyano” or “nitrile” as used herein refers to any organic compound that contains a -CN functional group.

The term “ester” refers to a chemical moiety with the formula -COOR, where R is alkyl, cycloalkyl, aryl, heteroaryl (bonded through a ring carbon) or heterocyclic (bonded through a ring carbon). Any hydroxy or carboxyl side chain on the compounds described herein can be esterified. The procedures and specific groups to make such may be any suitable method that can readily be found in reference sources.

As used herein the term “ether” refers to a chemical moiety that contains an oxygen atom connected to two alkyl groups, two aryl groups, or one alkyl group and one aryl group; with the general formula of R-O-R’, wherein R and R’ are independently alkyl and/or aryl.

As used herein the term “ketone” refers to the chemical moiety that contains a carbonyl group (a carbon-oxygen double bond) connected to two alkyl groups, two aryl groups, or one alkyl group and one aryl group; with the general formula of RC(=0)R’, wherein R and R’ are independently alkyl and/or aryl.

The term “BODIPY” as used herein, refers to a chemical moiety with the formula:

The BODIPY may be composed of dipyrromethene complexed with a di-substituted boron atom, typically a BF ₂ unit. The lUPAC name for the BODIPY core is 4,4-difluoro-4-bora-3a,4a-diaza-s- indacene.

The present disclosure is related to photoluminescent complexes that absorb light energy of a first wavelength and emit light energy of a second higher wavelength. The photoluminescent complexes of the present disclosure comprise an absorbing luminescent moiety and an emitting luminescent moiety that are coupled through a linker such that their distance is adjusted for the absorbing luminescent moiety to transfer its energy to the acceptor luminescent moiety, wherein the acceptor luminescent moiety then emits energy at a second wavelength that is larger than the absorbed first wavelength. In some embodiments, the photoluminescent complex may be described by the following formulae: Some photoluminescent complexes comprise: a blue light absorbing moiety; a linker moiety; and a boron-dipyrromethene (BODIPY) moiety. In some embodiments, the linker moiety may covalently link the blue light absorbing moiety to the BODIPY moiety. In some embodiments, the blue light absorbing moiety may be selected from an optionally substituted perylene. In some embodiments, the blue light absorbing optionally substituted perylene can be represented as in Formula A. In some embodiments, the luminescent BODIPY moiety can be represented as in Formula B. In some embodiments, the linker moiety can be represented as in Formula C. In some embodiments, the blue light absorbing moiety absorbs light of a first excitation wavelength and transfers energy to the BODIPY moiety, and then the BODIPY moiety then emits a light energy of a second wavelength, wherein the light energy of the second wavelength is higher than the first wavelength. It is believed that energy transfer from the excited blue light absorbing moiety to the BODIPY moiety occurs through a Forster resonance energy transfer (FRET). This belief is due to the absorbance/emission spectra of the photoluminescent complexes where there are two major absorption bands, one at the blue light absorbing moiety absorption band and one at the BODIPY absorption band, and only one emission band located at the BODIPY moiety’s emission wavelength (see FIG. 1).

In an embodiment, the photoluminescent complex can have a high emission quantum yield. In some embodiments, the emission quantum yield can be greater than 50%, 60%, 70%, 80%, or 90%. In some embodiments, the emission quantum yield can be greater than 50%, or 55%, or 60%, or 65%, or 70%, or 75%, or 80%, or 85%, or 90%, or 95%. Emission quantum yield can be measured by dividing the number of photons emitted by the number of photons absorbed, which is equivalent to the emission efficiency of the luminescent moiety. In some embodiments, the absorbing luminescent moiety, may have an emission quantum yield greater than 80%. In some embodiments, the quantum yield can be greater than 0.8 (80%), 0.81 (81%), 0.82 (82%), 0.83 (83%), 0.84 (84%), 0.85 (85%), 0.86 (86%), 0.87 (87%), 0.88 (88%), 0.89 (89%), 0.9 (90%), 0.91 (91%), 0.92 (92%), 0.93 (93%), 0.94 (94%), or 0.95 (95%), and may be up to nearly 1 (100%). Quantum yield measurements in film can be made by spectrophotometer, e.g., Quantaurus-QY spectrophotometer (Humamatsu, Inc., Campbell, CA, USA).

In some embodiments, the photoluminescent complex has an emission band, wherein the emission band can have a full width half maximum (FWHM) of less than 40 nm. The FWHM is the width of the emission band in nanometers at the emission intensity that is half of the maximum emission intensity for the band. In some embodiments, the photoluminescent complex has an emission band FWHM value that is less than or equal to about 35 nm, less than or equal to about 30 nm, less than or equal about 25 nm, less than or equal to about 20 nm. In some embodiments, the FWHM is about 40 nm to about 35 nm, about 35 nm to about 30 nm, about 30 nm to about 25 nm, about 25 nm to about 20 nm, or less than about 20 nm.

In some embodiments, the photoluminescent complex can have a Stokes shift that is equal to or greater than 45 nm. As used herein, the term “Stokes shift” means the distance between the excitation peak of the blue light absorbing moiety and the emission peak of the BODIPY moiety. In some embodiments, the Stokes shift is at least 45 nm. In some embodiments, the Stokes shift of photoluminescent complex can be about 45 nm to about 50 nm, about 50 nm to about 55 nm, about 55 nm to about 60 nm, about 60 nm to about 65 nm, about 65 nm to about 70 nm, about 70 nm to about 75 nm, about 75 nm to about 80 nm, about 80 nm to about 85 nm, about 85 to about 90 nm, about 90 nm to about 95 nm, about 95 nm to about 100 nm, or greater than about 100 nm, or any number bound by this range.

The photoluminescent complex of the current disclosure can have a tunable emission wavelength. By modifying the substituents of the BODIPY moiety, the emission wavelength can be tuned between 510 nm to about 560 nm, between about 610 nm to about 645 nm, or any wavelength in a range bounded by any of these values.

In some embodiments, the blue light absorbing moiety may have a peak absorption maximum wavelength between about 400 nm to about 470 nm. In some embodiments, the peak absorption wavelength may be between about 400 nm to about 405 nm, about 405-410 nm, about 410-415 nm, about 415-420 nm, about 420-425 nm, about 425-430 nm, about 430-435 nm, about 435-440 nm, about 440-445 nm, about 445-450 nm, about 450-455 nm, about 455-460 nm, about 460-465 nm, about 465-470 nm, or any wavelength in a range bounded by any of these values.

In some embodiments, the photoluminescent complex can have an emission peak between 510 nm and 560 nm. In some embodiments, the emission peak can be between about 510-515 nm, about 515-520 nm, about 520-525 nm, about 525-530 nm, about 530-535 nm, about 535-540 nm, about 540-545 nm, about 545-550 nm, about 550-555 nm, about 555-560 nm, or any wavelength in a range bounded by any of these values.

In another embodiment, the photoluminescent complex can have an emission peak between 610 nm to 645 nm. In some embodiments, the emission peak can be between 610-615 nm, about 615-620 nm, about 620-625 nm, about 625-630 nm, about 630-635 nm, about 635 nm- 640 nm, about 640 nm-645 nm, or any wavelength in a range bounded by any of these values.

Other embodiments include the photoluminescent complex wherein the blue light absorbing moiety and the BODIPY derivative luminescent moiety’s spatial distance is adjusted through the linker moiety, for transfer of the blue light absorbing moiety’s energy to be transferred to the BODIPY derivative luminescent moiety.

In some embodiments, the optionally substituted perylene can comprise a structure represented by Formula A:

In some embodiments, the BODIPY derivative can comprise a structure of Formula B:

wherein R may be CrCg alkyl. Some embodiments include a BODIPY derivative wherein R is ethyl. Some embodiments include a BODIPY derivative wherein R is methyl. In some embodiments, the BODIPY derivative may comprise:

In some embodiments, a substituted phenyl group may be positioned between a BODIPY and a linker moiety, wherein the substituted phenyl group may be of the following structure:

In some embodiments, the distance separating the blue light absorbing moiety and the BODIPY moiety can be about 8 A or greater. The linker moiety can maintain a distance between the blue light absorbing moiety and the BODIPY moiety. In some embodiments, the photoluminescent complex comprises a linker moiety. In some embodiments, the linker moiety (L) can be of the following Formula C: , wherein n is 1 , 2, 3, 4, or 5.

In some embodiments, a photoluminescent complex comprises a blue light absorbing moiety. The blue light absorbing moiety can comprise an organic lumiphore. In some embodiments, the absorbing luminescent moiety may have a maximum absorbance in the light in the range of 400 nm to about 480 nm, about 400 nm to about 410 nm, about 410 nm to about 420 nm, about 420 nm to about 430 nm, about 430 nm to about 440 nm, about 440 nm to about 450 nm, about 450 nm to about 460 nm, about 460 nm to about 470 nm, about 470 nm to about 480 nm, or any wavelength that is in a range bounded by any of these values. In some embodiments, the photoluminescent complex can have an absorbance maximum peak of about 450 nm. In other embodiments, the blue light absorbing moiety can have a maximum peak absorbance of about 405 nm. In still other embodiments, the blue light absorbing moiety can have a maximum peak absorbance of about 480 nm. In some embodiments, the photoluminescent complex of Formulae A, B and C, may be represented by the following examples, but the present disclosure is not limited by these examples: ll

Some embodiments include a color conversion film, wherein the color conversion film comprises: a color conversion layer wherein the color conversion layer includes a resin matrix and a photoluminescent complex, described above, dispersed within the resin matrix. In some embodiments, the color conversion film can be described as comprising one or more of the photoluminescent complexes described herein.

Some embodiments include the color conversion film which may be about 1 pm to about 200 pm thick. In some embodiments, the color conversion film can have a thickness of about 1-

5 pm, about 5-10 pm, about 10-15 pm, about 15-20 pm, about 20-40 pm, about 40 pm-80 pm, about 80-120 pm, about 120-160 pm, about 160-200 pm, or about 1-2 pm, about 2-3 pm, about 3-4 pm, about 4-5 pm, about 5-6 pm, about 6-7 pm, about 7-8 pm, about 8-9 pm, about 9-10 pm, about 10-11 pm, about 11-12 pm, about 12-13 pm, about 13-14 pm, about 14-15 pm, about 15- 16 pm, about 16-17 pm, about 17-18 pm, about 18-19 pm, about 19-20 pm, or about 1-10 pm, about 10-20 mhi, about 20-30 mhi, about 30-40 mhi, about 40-50 mhi, about 50-60 mhi, about 60- 70 mhi, about 70-80 mhi, about 80-90 mhi, about 90-100 mhi, about 100-110 mhi, about 110-120 mhi, about 120-130 mhi, about 130-140 mhi, about 140-150 mhi, about 150-160 mhi, about 160- 170 mhi, about 170-180 mhi, about 180-190 mhi, about 190-200 mhi thick, or any thickness in a range bounded by any of these values.

In some embodiments, the color conversion film can absorb light in the 400 nm to about 480 nm wavelength and can emit light in the range of about 510 nm to about 560 nm and/or about 610 nm to about 645 nm. In other embodiments, color conversion film can emit light in the 510 nm to about 560 nm range, the 610 nm to about 645 nm range, or any combination thereof.

In some embodiments, the color conversion film can further comprise a transparent substrate layer. The transparent substrate layer has two opposing surfaces, wherein the color conversion layer can be disposed on and in physical contact with the surfaces of the transparent layer that will be adjacent to a light emitting source. The transparent substrate is not particularly limited and one skilled in the art would be able to choose a transparent substrate from those used in the art. Some non-limiting examples of transparent substrates include PE (polyethylene), PP (polypropylene), PEN (polyethylene naphthalate), PC (polycarbonate), PMA (polymethylacrylate), PMMA (Polymethylmethacrylate), CAB (cellulose acetate butyrate), PVC (polyvinylchloride), PET (polyethyleneterephthalate), PETG (glycol modified polyethylene terephthalate), PDMS (polydimethylsiloxane), COC (cycloolefin copolymer), PGA (polyglycolide or polyglycolic acid), PLA (polylactic acid), PCL (polycaprolactone), PEA (polyethylene adipate), PHA (polyhydroxy alkanoate), PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)), PBE (polybutylene terephthalate), PTT (polytrimethylene terephthalate). Any of the aforedescribed resins can be corresponding/respective monomers and/or polymers.

In some embodiments, the transparent substrate may have two opposing surfaces. In some embodiments, the color conversion film may be disposed on and in physical contact with one of the opposing surfaces. In some embodiments, the side of the transparent substrates without color conversion film disposed thereon may be adjacent to a light source. The substrate may function as a support during the preparation of the color conversion film. The type of substrates used are not particularly limited, and the material and/or thickness is not limited, as long as it is transparent and capable of functioning as a support. A person skilled in the art could determine which material and thickness to use as a supporting substrate. Some embodiments include a method for synthesizing a luminescent complex described above. In some embodiments, the method can comprise condensing a substituted 2,4-dimethyl- 1 H-pyrrole-3 carboxylate analogue (e.g., an ester of 2,4-dimethyl-1 H-pyrrole-3-carboxylic acid) with a hydroxyalkylbenzaldehyde (e.g., 4-hydroxy-2,6-dimethylbenzaldehyde) and BF ₃ to form a BODIPY analogue. In some embodiments, the substituted 2,4-dimethyl-1 H-pyrrole-3 carboxylate analogue can be commercially available, for example ,4-dimethyl-1 H-pyrrole-3 carboxylic acid (Sigma Aldrich, St. Louis, MO, USA). It is believed the use of this particular starting material and the described condensation reaction will lower production costs.

In some embodiments the condensation reaction can be combining the substituted 2,4- dimethyl-1 H-pyrrole-3 carboxylate analogue with an organic solvent, e.g., 1 ,2-dichloroethane (DCE). In some embodiment, the pyrrole derivative condenses at least once, e.g., twice, to form dipyrrole-methane in the presence of an acid catalyst (e.g., para-toluenesulfonic acid)( p-TsOH). the first condensation step can be performed over 8 to 12 hours, e.g., overnight.

In some embodiments, the condensing reaction can comprise oxidizing the dipyrrole- methane to dipyrrole-methene. In some embodiments, the oxidizing agent, oxidizing the dipyrrole-methane to dipyrrole-methene can be 2,3-dichloro-5,6-dicyano-1 ,4-benzoquinone (DDQ). In some embodiments, the oxidizing can occur at room temperature for between 10 minutes and 1 hour, e.g., for about 20 minutes.

In some embodiments the condensing reaction can comprise cyclizing the dipyrrole- methene to form the BODIPY structure. In some embodiments, cyclizing the dipyrrole-methane can be performed by adding a cyclizing agent. In some embodiments, the cyclizing agent can be trifluoroboron-diethylether (BF ₃ -OEt2) and / or triethylamine. In some embodiments, the condensation reacting can comprise reacting the dipyrrole-methene with a cyclizing agent, e.g., at a temperature between room temperature and 75 °C, e.g., 50 °C.

Some embodiments include a method for preparing the color conversion film, wherein the method comprises: dissolving a photoluminescent compound, described herein, and a binder resin within a solvent; and applying the mixture on to the surface of the transparent substrate.

The binder resin which can be used with the photoluminescent complex includes resins such as acrylic resins, polycarbonate resins, ethylene-vinyl alcohol copolymer resins, ethylene- vinyl acetate copolymer resins and saponification products thereof, AS resins, polyester resins, vinyl chloride-vinyl acetate copolymer resins, polyvinyl butyral resins, polyvinylphosphonic acid (PVPA), polystyrene resins, phenolic resins, phenoxy resins, polysulfone, nylon, cellulosic resins, and cellulose acetate resins. In some embodiments, the binder resin can be a polyester resin and/or acrylic resin. In some embodiments, the word resin is equivalent to the word polymeric resin, or polymer.

The solvent which can be used for dissolving or dispersing the complex and the resin can include an alkane, such as butane, pentane, hexane, heptane, and octane; cycloalkanes, such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; alcohols, such as ethanol, propanol, butanol, amyl alcohol, hexanol, heptanol, octanol, decanol, undecanol, diacetone alcohol, and furfuryl alcohol; Cellosolves™, such as Methyl Cellosolve™, Ethyl Cellosolve™, Butyl Cellosolve™, Methyl Cellosolve™ acetate, and Ethyl Cellosolve™ acetate; propylene glycol and its derivatives, such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, and dipropylene glycol dimethyl ether; ketones, such as acetone, methyl amyl ketone, cyclohexanone, and acetophenone; ethers, such as dioxane and tetrahydrofuran; esters, such as butyl acetate, amyl acetate, ethyl butyrate, butyl butyrate, diethyl oxalate, ethyl pyruvate, ethyl 2-hydroxybutyrate, ethyl acetoacetate, methyl lactate, ethyl lactate, and methyl 3-methoxypropionate; halogenated hydrocarbons, such as chloroform, methylene chloride, and tetrachloroethane; aromatic hydrocarbons, such as benzene, toluene, xylene, and cresol; and highly polar solvents, such as dimethyl formamide, dimethyl acetamide, and N-methylpyrrolidone.

Some embodiments include a backlight unit, wherein the backlight unit may include the color conversion film described herein.

Other embodiments may include a display device, wherein the device may include the backlight unit described herein.

Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and embodiments are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the specification and attached embodiments are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents. To the scope of the embodiments, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. For the processes and/or methods disclosed, the functions performed in the processes and methods may be implemented in differing order, as may be indicated by context. Furthermore, the outlined steps and operations are only provided as examples and some of the steps and operations may be optional, combined into fewer steps and operations, or expanded into additional steps and operations.

This disclosure may sometimes illustrate different components contained within, or connected with, different other components. Such depicted architectures are merely examples, and many other architectures can be implemented which achieve the same or similar functionality.

The terms used in this disclosure and in the appended embodiments, (e.g., bodies of the appended embodiments) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including, but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes, but not limited to,” etc.). In addition, if a specific number of elements is introduced, this may be interpreted to mean at least the recited number, as may be indicated by context (e.g., the bare recitation of “two recitations,” without other modifiers, means at least two recitations of two or more recitations). As used in this disclosure, any disjunctive word and/or phrase presenting two or more alternative terms should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phase “A or B”: will be understood to include the possibilities of “A or B” or “A and B.”

The terms “a,” “an,” “the” and similar referents used in the context of describing the present disclosure (especially in the context of the following embodiments) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of any and all examples, or related language (e.g., “such as”) provided herein is intended merely to better illuminate the present disclosure and does not pose a limitation on the scope of any embodiments. No language in the specification should be construed as indicating any non-embodied element essential to the practice of the present disclosure.

Groupings of alternative elements or embodiments disclosed herein are not to be construed as limitations. Each group member may be referred to and embodied individually or in any combination with other members of the group or other elements found herein. It is anticipated that one or more members of a group may be included in, or deleted from, a group for reasons of convenience or to expedite prosecution. When any such inclusion or deletion occurs, the specification is deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended embodiments. Certain embodiments are described herein, including the best mode known to the inventors for carrying out the present disclosure. Of course, variations on these described embodiments, will become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventor expects skilled artisans to employ such variations as appropriate, and the inventors intend for the present disclosure to be practiced otherwise than specifically described herein. Accordingly, the embodiments include all modifications and equivalents of the subject matter recited in the embodiments as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is contemplated unless otherwise indicated herein or otherwise clearly contradicted by context. In closing, it is to be understood that the embodiments disclosed herein are illustrative of the principles of the embodiments. Other modifications that may be employed are within the scope of the embodiments. Thus, by way of example, but not of limitation, alternative embodiments may be utilized in accordance with the teachings herein. Accordingly, the embodiments are not limited to the embodiments precisely as shown and described.

EMBODIMENTS

Embodiment 1 A photoluminescent complex comprising: Embodiment 2 A color conversion film comprising the photoluminescent complex of

Embodiment 1 .

Embodiment 3 A backlight unit including a color conversion film of Embodiment 2. Embodiment 4 A display device including the backlight unit of Embodiment 3. Embodiment 5 A method for preparing a BODIPY analogue comprising: providing a substituted 2,4-dimethyl-1 H-pyrrole-3 carboxylate analogue; and condensing the substituted 2, 4-dimethyl-1 H-pyrrole-3 carboxylate analogue with a hydroxyalkylbenzaldehyde to form a BODIPY analogue. Embodiment 6 The method of Embodiment 5, wherein the substituted 2,4-dimethyl-1 H- pyrrole-3 carboxylate analogue is 2, 4-dimethyl-1 H-pyrrole-3 carboxylic acid.

Embodiment 7 The method of Embodiment 5, wherein the hydroxyalkylbenzaldehyde is 4- hydroxy-2,6-dimethylbenzaldehyde.

Embodiment 8 A method for preparing the color conversion film, comprising: dissolving at least one photoluminescent complex, described herein and a binder resin within a solvent; and applying the mixture on one of the transparent substrate’s opposing surfaces.

EXAMPLES

It has been discovered that embodiments of the photoluminescent complexes described herein have improved performance as compared to other forms of dyes used in color conversion films. These benefits are further demonstrated by the following examples, which are intended to be illustrative of the disclosure only but are not intended to limit the scope or underlying principles in any way.

Example 1.1 Comparative example 1 (CE-1):

CE-1 : 0.75 g of 4-hydoxyl-2,6-dimethylvenzaldehyde (5 mmol) and 1.04 g of 2,4- dimethylpyrrole (11 mmol) was dissolved in 100 mL of anhydrous dichloromethane (DCM). The solution was degassed for 30 minutes. Then one drop of trifluoroacetic acid (TFA) was added. The solution was stirred overnight under argon gas atmosphere at room temperature. To the resulting solution, DDQ (2.0g) was added and the mixture was stirred overnight. The next day the solution was filtered and then washed with dichloromethane (DCM) resulting in a dipyrrolemethane. Next, 1 .0 g of dipyrrolemethane was dissolved in 60 mL of THF. 5 mL of trimethylamine was added to the solution and then degassed for 10 minutes. After degassing, 5 mL of trifluoroboron-diethylether (BF ₃ OEt2 _0r ) was added slowly followed by heating for 30 minutes at 70° C. The resulting solution was loaded on a silica gel and purified by flash chromatography using dichloromethane as the eluent. The desired fraction was collected and dried under reduced pressure to yield 0.9 g or an orange solid (76% yield). LCMS (APCI+): calculated for C21H24BF2N2O (M+H) = 369; found: 369. ¹ H NMR (400 MHz, Chloroform-d) d 6.64 (s, 2H), 5.97 (s, 2H), 4.73 (s, 1 H), 2.56 (s, 6H), 2.09 (s, 6H), 1.43 (s, 6H).

Example 2: Synthesis of Photoluminescent Complexes Example 2.1 : PLC-1

Compound PLC-1.2

AICI3 (78.0 g, 585 mmol, 31.9 mL, 1.80 eq) was added to anhydrous DCM (1.50 L) at 0- 10 °C. The mixture was stirred at 0 °C for 30 mins. A mixture of compound 1 A (88.1 g, 585 mmol,

72.2 mL, 1.80 eq) in anhydrous DCM (100 mL) was added to the mixture at 0-10 °C under N ₂ . PLC-1.1 (82 g, 325 mmol, 1.00 eq) was added to the mixture in portions and the mixture was stirred at 25-30 °C for 30 mins. The mixture was stirred at 50 °C for 12 hrs. Thin layer chromatography (TLC) (Petroleum ether/Ethyl acetate = 10/1) showed that the reaction was completed. The mixture was cooled to 25-30 °C and poured into water (1.00 L). The mixture was separated, and the aqueous phase was extracted with DCM (500 mL ^* 2). The combine organic layer was dried over Na2SC>4 and concentrated. The product was purified by MPLC (100-200 mesh silica gel, DCM). Compound 2 (82.0 g, 223 mmol, 68.8% yield) was obtained as orange solid. LCMS (APCI+), calcd for Formula: C25H18O3; found: 366.1 H NMR (400 MHz, Chloroform-d) d 8.57 (dd, J = 8.6, 1.0 Hz, 1 H), 8.30 - 8.17 (m, 4H), 7.97 (d, J = 8.1 Hz, 1 H), 7.78 (d, J = 8.1 Hz,

1 H), 7.73 (d, J = 8.1 Hz, 1 H), 7.64 - 7.48 (m, 3H), 3.75 (s, 3H), 3.41 (t, J = 6.5 Hz, 2H), 2.86 (t, J = 6.5 Hz, 2H). Compound PLC-1.3

PLC-1.2 PLC-1.3

TFA (231 g, 2.03 mol, 150 mL, 9.90 eq) was added to a mixture of PLC1 .2 (75.0 g, 204 mmol, 1 .00 eq) in anhydrous DCM (600 mL) at 0-10 °C. The mixture was stirred at 0-10°C for 30 mins. Triethylsilane (Et3SiH) (71 .4 g, 614 mmol, 98.1 mL, 3.00 eq) was added to the mixture at 0-10 °C and the mixture was stirred at 25 °C for 16 hrs. TLC (Petroleum ether/Ethyl acetate = 3/1 ) showed that the reaction was completed. The mixture was concentrated to give the crude product. The crude product was triturated with methyl tert-butylether (MTBE) (400 mL) at 25-30 °C for 30 mins. The mixture was filtered, and the filtrate cake was washed by MTBE (100 mL). The filtrate cake was dried under vacuum. The mother liquid was concentrated and purified by silica gel chromatography (100-200 mesh silica gel, Petroleum ether/Ethyl acetate = 100/1-2/1). PLC 1 .3 (62.0 g, 176 mmol, 85.9% yield) was obtained as yellow solid. 1 H NMR (400MHz, CDCI ₃ ) d 8.27 - 8.08 (m, 4H), 7.91 (d, J = 8.3 Hz, 1 H), 7.68 (dd, J = 5.5, 7.9 Hz, 2H), 7.53 (t, J = 8.0 Hz, 1 H), 7.48 (dt, J = 1.5, 7.9 Hz, 2H), 7.34 (d, J = 7.7 Hz, 1 H), 3.71 (s, 3H), 3.07 (t, J = 7.8 Hz, 2H), 2.47 (t, J = 7.2 Hz, 2H), 2.12 (quin, J = 7.5 Hz, 2H)

Compound PLC 1.4

PLC-1.3 PLC-1.4

N-bromosuccinimide (NBS) (88.4 g, 496 mmol, 3.40 eq) was added to a mixture of PLC- 1.3 (51.5 g, 146 mmol, 1.00 eq) in chloroform (CHCI3) (2.00 L) at 25 °C in portions. The mixture was stirred at 25 °C for 16 hrs and keeping in darkness. The mixture was washed by Na2SC>3 (1 N, 1 .00 L). The mixture was separated, and the aqueous phase was extracted with DCM (200 ml_). The combine organic layer was concentrated to give the crude product. The product was purified by silica gel chromatography (100-200 mesh silica gel, Petroleum ether/Ethyl acetate = 1/0-1/1 ). PLC-1.4 (69.2 g, 102 mmol, 69.9% yield, 87.0% purity) was obtained as red brown oil. LCMS (APCI+), calculated for Formula: C25Hi ₇ Br ₃ C>2; found: 589. Compound PLC-1.6

PLC-1 .5 (228 g, 1.19 mol, 151 mL, 10.0 eq) was added to a mixture of PLC-1.4 (70.0 g, 119 mmol, 1.00 eq) and Cul (113 g, 594 mmol, 5.00 eq) in N,N-dimethylacetamide (DMA) (490 mL) at 25 °C. The mixture was stirred at 160 °C for 3 hrs under N2. LCMS (ET39890-26-P1 A) showed that the reaction was completed. The mixture was cooled to 25-30°C and diluted with water (1 .50 L) and ethyl acetate (EtOAc) (1 .00 L). The mixture was filtered through a Celite pad. The filtrate cake was washed by EtOAc (500 mL ^* 2). The combine filtrate was separated, and the aqueous phase was extracted with EtOAc (500 mL ^* 2). The combine organic layer was concentrated to give the crude product. The product was purified by silica gel chromatography (100-200 mesh silica gel, Petroleum ether/Ethyl acetate = 1/0-1/1). PLC-1.6 (40.0 g, 71.9 mmol, 60.5% yield) was obtained as red brown oil.

Compound PLC-1.7

PLC-1.6 PLC-1.7 NaOH (8.63 g, 215 mmol, 3.00 eq) was added to a mixture of PLC-1 .6 (40.0 g, 71 .9 mmol,

1.00 eq) in THF (200 mL), methanol (MeOH) (200 mL) and H ₂ 0 (200 mL) at 25 °C. The mixture was stirred at 25 °C for 2 hrs. TLC (Petroleum ether/Ethyl acetate = 10/1) showed that the reaction was completed. The mixture was acidified to pH = 1-2 by HCI solution (1 N). The mixture was concentrated to move the solvent. The residue was diluted with water (150 mL) and extracted with EtOAc (100 mL ^* 2). The combine organic layer was concentrated. The crude product was purified by silica gel chromatography (100-200 mesh silica gel, Petroleum ether/Ethyl acetate = 1/0-0/1 ). PLC-1.7 (26.2 g, 48.1 mmol, 66.9% yield, 99.6% purity) was obtained as yellow solid. 1 HNMR (400MHz, CDCI ₃ ). d 8.37 - 7.93 (m, 6H), 7.91 - 7.50 (m, 2H), 3.47 - 3.13 (m, 2H), 2.68 - 2.53 (m, 2H), 2.26 - 2.13 (m, 2H)

Compound PLC-1 : PLC-1.8 PLC-1

Compound PLC-1.8: 1st step: A mixture of ethyl 2,4-dimethyl-1 H-pyrrole-3-carboxylate (1.0g, 6.0 mmol), 4- hydroxy-2,6-dimethylbenzaldehyde (0.449g, 3.0 mmol) and para-toluenesulfonic acid (p-TsOH) (50 mg, 0.29mmol) in 50 ml. 1 ,2-dichloroethane (DCE) was degassed and stirred at room temperature overnight. LCMS analysis shows that reaction completed with main leak of m/e+=467.

2nd step: To the mixture obtained above, 2,3-dichloro-5,6-dicyano-1 ,4-benzoquinone (DDQ) (0.817g, 3.6 mmol) was added and the whole was stirred at room temperature for 30 min. LCMS analysis indicates that reaction completed with main peak of m/e+ = 465.

3rd step: With ice-batch cooling, to the mixture obtained above, triethylamine (1 .7 mL, 19 mmol) and BF ₃ OEt ₂ (2.2 mL, 18 mmol) was added, and the resulting mixture was stirred at 50 °C for one hour. Additional 1 mL triethylamine and 1 mL BF ₃ OEt ₂ were added, and the whole was heated for additional one hour. LCMS analysis indicates that all dipyrrolemethine starting material was converted to BODIPY product with m/e+ = 513. After being cooled to room temperature, the reaction mixture was submitted to silica gel and purified by flash chromatography using eluents of hexanes/ethyl acetate (0% □ 30% ethyl acetate). The desired fraction was collected. After removal of solvents, the desired product was obtained as orange solid (1.0g, in 65% yield). 1 H NMR (400 MHz, Chloroform-d) d 6.68 (s, 2H), 4.29 (q, J = 7.1 Hz, 4H), 2.84 (s, 6H), 2.05 (s, 6H), 1 .34 (t, J = 7.1 Hz, 6H). LCMS (APCI+): calcd for C ₂₇ H ₃₂ BF ₂ N ₂ 0 ₅ (M+H) = 513.2; Found: 513.

Compound PLC-1 :

A mixture of Compound PLC-1.8 (100mg, 0.195mmol), tris(trifluoromethyl)perylen-3- yl)butanoic acid (120 mg, 0.221 mmol), N,N’-diisopropylcarbodiimide (DIC) (80 mg, 0.634 mmol) and 4-(N,N-dimethylamino)pyridine/ para-toluenesulfonic acid salt (DMAP/p-TsOH) (118 mg, 0.4 mmol) in DCM (6mL) was stirred at room temperature overnight, then loaded on silica gel and purified by flash chromatography using eluents of DCM/ethyl acetate (0%-> 15% ethyl acetate). The main desired fraction was collected. After removal of solvents, the resulting orange solid was reprecipitated in DCM/MeOH. The desired product was collected after filtration and dried in air as an orange solid (155mg, in 77% yield). 1 H NMR (400 MHz, d2-TCE) d 8.51 - 7.48 (m, 8H), 6.98 - 6.82 (m, 2H), 4.18 (qd, J = 7.2, 3.2 Hz, 4H), 3.40 - 3.15 (m, 2H), 2.74 (m, 7H), 2.63 - 2.46 (m, 1 H), 2.22 (d, J = 9.0 Hz, 1 H), 2.11 - 1 .90 (m, 7H), 1.67 - 1 .58 (m, 6H). LCMS (APCI-): calcd for C ₅₄ H44BF11N2O ₆ (M-) = 1036.3; Found: 1036. Example 2.2: PLC-2

PLC-2.1 -

Compound PLC-2.1 :

1st step: A mixture of methyl 2,4-dimethyl-1 H-pyrrole-3-carboxylate (0.919 g, 6.0 mmol), 4-hydroxy-2,6-dimethylbenzaldehyde (0.449g, 3.0 mmol) and para-toluenesulfonic acid (p-TsOH) (50 mg, 0.29mmol) in 50 mL 1 ,2-dichloroethane (DCE) was degassed and stirred at room temperature overnight. LCMS analysis shows that reaction completed with main leak of m/e+=439.

2nd step: To the mixture obtained above, 2,3-dichloro-5,6-dicyano-1 ,4-benzoquinone (DDQ) (0.817g, 3.6 mmol) was added and the whole was stirred at room temperature for 30 min. LCMS analysis indicates that reaction completed with main peak of m/e+ = 437.

3rd step: With ice-batch cooling, to the mixture obtained above, triethylamine (1 .7 mL, 19 mmol) and BF ₃ OEt2 (2.2 mL, 18 mmol) was added, and the resulting mixture was stirred at 50 °C for one hour. Additional 1 mL triethylamine and 1 mL BF ₃ OEt2 were added, and the whole was heated for additional one hour. LCMS analysis indicates that all dipyrrolemethine starting material was converted to BODIPY product with m/e- = 483. After cooling to room temperature, the reaction mixture was submitted to silica gel and purified by flash chromatography using eluents of DCM/ethyl acetate (0% to 30% ethyl acetate). The desired fraction was collected. After removal of solvents, the desired product was obtained as orange solid (0.77g, in 53% yield). LCMS (APCI- ): Calcd for C25H26BF2N205 (M-H): 483.2; Found: 483. ¹ H NMR (400 MHz, d2-TCE) d 6.61 (s, 2H), 5.16 (s, 1 H), 3.73 (s, 6H), 2.74 (s, 6H), 1 .97 (s, 6H), 1 .65 (s, 6H).

Compound PLC-2:

A mixture of Compound PLC-2.1 (50mg, 0.1 mmol), tris(trifluoromethyl)perylen-3-yl)butanoic acid (PLC-1.7, 100 mg, 0.17 mmol), N,N’-diisopropylcarbodiimide (DIC) (80 mg, 0.634 mmol) and 4-(N,N-dimethylamino)pyridine/ para-toluenesulfonic acid salt (DMAP/p-TsOH) (29 mg, 0.1 mmol) in DCM (8mL) was stirred at room temperature overnight, then loaded on silica gel and purified by flash chromatography using eluents of DCM/ethyl acetate (0%--> 10% ethyl acetate). The main desired fraction was collected. After removal of solvents, the resulting orange solid was reprecipitated in DCM/MeOH. The desired product was collected after filtration and dried in air as an orange solid (85mg, in 80% yield). LCMS (APCI-): Calcd for C52H40BF11 N206:

1008.28; Found: 1008. ¹ H NMR (400 MHz, d2-TCE) d 8.38 - 7.50 (m, 8H), 6.91 (multiple singlet, 2H), 3.73 (s, 6H), 3.25 (m, 2H), 2.75 (s, 6H), 2.69 (m, 2H), 2.21 (m, 2H), 2.09 (s, 6H), 1.64 (s, 6H).

Example 3 Fabrication of Color Conversion Film

A glass substrate was prepared in substantially the following manner. A 1.1 mm thick glass substrate measuring 1 -inch X 1 -inch was cut to size. The glass substrate was then washed with detergent and deionized (Dl) water, rinsed with fresh Dl water, and sonicated for about 1 hour. The glass was then soaked in isopropanol (IPA) and sonicated for about 1 hour. The glass substrate was then soaked in acetone and sonicated for about 1 hour. The glass was then removed from the acetone bath and dried with nitrogen gas at room temperature.

A 20 wt% solution of poly(methylmethacrylate) (PMMA) (average M.W. 120,000 by GPC from MilliporeSigma, Burlington, MA, USA) copolymer in cyclopentanone (99.9% pure) was prepared. The prepared copolymer was stirred overnight at 40 °C. [PMMA] CAS: 9011-14-7; [Cyclopentanone] CAS: 120-92-3

The 20% PMMA solution prepared above (4 g) was added to 3 mg of the photoluminescent complex made as described above in a sealed container and mixed for about 30 minutes. The PMMA/lumiphore solution was then spin coated onto a prepared glass substrate at 1000 RPM for 20 s and then 500 RPM for 5 s. The resulting wet coating had a thickness of about 10 pm. the samples were covered with aluminum foil before spin coating to protect them from exposure to light. Three samples each were prepared in this manner for each for Emission/FWHM and quantum yield. The spin coated samples were baked in a vacuum oven at 80 °C for 3 hours to evaporate the remaining solvent.

The 1 -inch X 1-inch sample was inserted into a Shimadzu, UV-3600 UV-VIS- NIR spectrophotometer (Shimadzu Instruments, Inc., Columbia, MD, USA). All device operations were performed inside a nitrogen-filled glove-box. The resulting absorption/emission spectrum for PLC-1 is shown in FIG.1 . The fluorescence spectrum of a 1-inch X 1-inch film sample prepared as described above was determined using a Fluorolog spectrofluorometer (Horiba Scientific, Edison, NJ, USA) with the excitation wavelength set at the respective maximum absorbance wavelength. The maximum emission and FWHM are shown in Table 1. The quantum yield of a 1-inch X 1-inch sample prepared as described above were determined using a Quantarus-QY spectrophotometer (Hamamatsu Inc., Campbell CA, USA) was excited at the respective maximum absorbance wavelength. The results are reported in Table 1.

The results of the film characterization (absorbance peak wavelength, FWHM, and quantum yield) are shown in Table 1 , below. Example 4 Photostability

Photostability tests of the photoluminescent complexes were performed on 1-inch X 1- inch samples; comprising PMMA as described above herein. The photoluminescent complexes were individually included with PMMA film samples at a concentration of 2 X10 ³ M. The samples were then exposed to a blue LED light source (Inspired LED, Tempe, AZ, USA) with an emission peak of 465 nm, at room temperature. The Blue LED light was incorporated into a 1-inch X 12- inche U channel with commercial diffuser film placed on top of the U channel to give a uniform light distribution. The 1-inch X 1-inch samples were placed on top of the diffuser. The average irradiance at the sample was - 1.5mW/cm ² .

Absorption at peak absorption wavelength was measured before and after film had been exposed to the LED light for 165 h, 330 h, 500 h respectively. The samples absorption was measured using a UV-vis 3600 (Shimadzu Manufacturing Company, Kyoto, Japan) Photostability was measured by dividing the absorption remaining after exposure by the absorption before exposure time. The results are shown in Table 2, below.

Table 1.

Table 2. : loading 21 wt%