Diazobiphenyl dyes, polarizers containing them, and methods for preparing diazobiphenyl dyes.

Abstract

This invention provides a diazobiphenyl dye for thin-film polarizers, which is an analog of AD1. Thin-film polarizers prepared using this dye exhibit good optical quality, such as low light scattering, high dichroism ratio, broadband absorption, and / or stability to heat and light irradiation. This invention also provides a method for preparing the diazobiphenyl dye from two different monoazo dyes via a cross-coupling reaction. This method is eco-friendly because it does not use toxic benzidine as a raw material. The product (diazobiphenyl dye) obtained by this method can be purified in a simple and convenient manner, and the diazobiphenyl dye prepared by this method can have a symmetrical or asymmetrical structure. Furthermore, this invention provides a thin-film polarizer comprising the diazobiphenyl dye and an apparatus for display applications comprising the thin-film polarizer.

Description

Technical Field

[0001] This invention relates to a diazobiphenyl dye, and more specifically, to a diazobiphenyl dye for use in thin-film polarizers, a method for preparing the diazobiphenyl dye, a thin-film polarizer comprising the aforementioned diazobiphenyl dye, and an apparatus for display applications comprising the thin-film polarizer. Background Technology

[0002] Display technology is evolving towards thin, flexible, and foldable displays, which require polarizers, typically thin-film polarizers. Currently, several methods exist for manufacturing thin-film polarizers. For absorptive polarizers, the manufacturing method involves coating a substrate with a dichroic dye and aligning it using photo-alignment technology. This method can produce polarizers with a thickness of less than 0.5 micrometers and a high dichroic ratio (DR).

[0003] Among the many dichroic dyes, one is a diazo derivative of benzidine—4,4'-(biphenyl-4,4'-diylbis(diazetenyl-2,1-diyl))bis(N,N-dibutylaniline), named AD1, which has the structure shown in the following formula:

[0004]

[0005] This dichroic dye is characterized by a uniquely high dichroic ratio (DR up to 90) in photo-aligned films. Chemically modified, such as protonated, AD1 films exhibit increased absorption in the visible and near-infrared regions as well as resistance to light exposure, thus these modified films can be used to manufacture broadband polarizers.

[0006] However, thin-film polarizers based on protonated or basic AD1 have several drawbacks. Optically oriented AD1 films exhibit a considerably high level of light scattering, which increases further after chemical modification, thus reducing the optical quality of the polarizer. Adding plasticizers during film preparation has little effect on light scattering but significantly reduces the dichroism ratio. Furthermore, changes in solvent and / or temperature during film preparation do not lead to the desired improvement in film quality.

[0007] Furthermore, the dichroic ratio of the AD1 film is primarily dependent on the chemical purity of AD1. The highest dichroic ratio can only be achieved by using materials with a purity exceeding 99%. However, even with impurities as low as 3% (e.g., impurities inherent in the synthesis of AD1 via benzidine, which are difficult to remove), the dichroic ratio of the resulting AD1 film can drop below 10. Therefore, the purification of dichroic dyes, or the development of new synthetic methods to avoid difficult-to-remove impurities, is crucial for the manufacture of polarizing films.

[0008] Conventional AD1 synthesis involves diazotization of benzidine (1,1'-biphenyl-4,4'-diamine) followed by azo coupling with N,N-dibutylaniline. The crude product isolated from the reaction mixture contains a large number of various colored impurities with similar physical properties to the target product AD1. Purification methods are typically used, involving multiple recrystallizations and / or rapid chromatography, but these methods yield AD1 with a purity <97% and a dichroism ratio <10. Only preparative column chromatography can provide the desired purity and high dichroism ratio for AD1. However, preparative column chromatography is expensive in terms of both materials and processing time.

[0009] More importantly, we note that benzidine, the starting material used in the synthesis of AD1, is a hazardous chemical because it is a human carcinogen. Therefore, the use of benzidine in commercial processes has decreased significantly in recent years. Consequently, there is a need to find alternatives to benzidine for the preparation of dichroic dyes.

[0010] However, among dichroic dyes with structures fundamentally different from AD1, none offer the benefits of AD1 without its drawbacks. Furthermore, it has been established that even minor modifications to the core structure of the AD1 molecule (e.g., introducing side substituents into the benzene ring or replacing the benzene ring with naphthalene) significantly worsen the dichroism of the new dyes. Therefore, finding new dye structures similar to AD1 (AD1-like dyes) that combine photoorientation capabilities with lower crystallinity is a challenge.

[0011] Therefore, there is an urgent need in the field for an AD1 alternative that is similar in structure to AD1 but does not have the above-mentioned disadvantages, namely, a new "AD1-like" material. Summary of the Invention

[0012] In view of this, the present invention provides a novel diazobiphenyl dye, a method for preparing a diazobiphenyl dye, a thin-film polarizer comprising the above-mentioned diazobiphenyl dye, and an apparatus for display applications comprising the thin-film polarizer.

[0013] According to a first aspect of the present invention, a diazobiphenyl dye is provided having the structure shown in formula (I):

[0014]

[0015] In this group, at least one of the substituents R1, R2, R3, and R4 is different from the other substituents, and each is independently C1. n H 2n+1 , where n = 1 - 18.

[0016] According to a second aspect of the present invention, a method for preparing a diazobiphenyl dye having the structure shown in formula (I) is provided, the method comprising subjecting a first monoazo dye and a second monoazo dye to a cross-coupling reaction, wherein the first monoazo dye is a haloazobenzene and the second monoazo dye is a borate ester derivative of azobenzene:

[0017]

[0018] Among them, R1, R2, R3, and R4 may be the same or different, and each is independently C. n H 2n+1 , where n = 1 - 18.

[0019] According to a third aspect of the present invention, a diazobiphenyl dye is provided, wherein the diazobiphenyl dye is prepared by the method of the second aspect of the present invention.

[0020] According to a fourth aspect of the present invention, a thin-film polarizer is provided, wherein the thin-film polarizer comprises: a substrate; and a first dye layer oriented by light, the first dye layer comprising a diazobiphenyl dye as described in the first aspect of the present invention or a diazobiphenyl dye as described in the third aspect of the present invention.

[0021] According to a fifth aspect of the present invention, the present invention provides an apparatus for a display application, wherein the apparatus comprises the thin-film polarizer described in the fourth aspect of the present invention.

[0022] The beneficial effects of this invention are:

[0023] This invention has one or more of the following technical effects:

[0024] The diazo biphenyl dye of the present invention is easily affected by photoorientation. Therefore, a high dichroic ratio can be produced by irradiating the film deposited by the dye with polarized ultraviolet or blue light. Furthermore, the film has good optical quality after chemical modification, such as low light scattering, high dichroic ratio, broadband absorption, and / or stability to heat and light irradiation.

[0025] The method of this invention provides a safe and eco-friendly method for preparing diazo biphenyl dyes by forming a central biphenyl fragment of a diazo biphenyl dye from two different monoazo dyes through a cross-coupling reaction, thereby avoiding the use of toxic benzidine. Furthermore, compared to methods based on azo coupling with benzidine, the impurities formed in the preparation method provided by this invention are easier to remove due to significant differences in solubility between them and the target product. Therefore, a simpler and more convenient purification process can be used to produce high-purity diazo biphenyl dyes. The diazo biphenyl dyes prepared by the method provided by this invention can have symmetrical or asymmetrical structures. In asymmetrical structures, alkyl or alkenyl substituents of varying lengths on the amino group result in thin-film polarizers with high optical quality, such as low light scattering, high dichroism ratio, broadband absorption, and / or stability to heat and light irradiation.

[0026] The high dichroism thin-film polarizer provided by this invention can be widely used in display devices, such as organic light-emitting diode (OLED) displays or liquid crystal displays (LCDs). Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other implementation schemes can be obtained based on these drawings without creative effort.

[0028] Figure 1 Flowcharts of the conventional method and the method of the present invention are shown.

[0029] Figure 2 A- Figure 2 D shows the UV-VIS spectra of thin-film polarizers made of diazobiphenyl dyes AD45, AD46, AD4455 and AD55 before protonation (dashed line) and after protonation (solid line), respectively.

[0030] Figure 3 SEM images of the AD1 dye layer before protonation (A and B) and after protonation (C and D) are shown.

[0031] Figure 4 SEM images of the AD45 dye layer before protonation (AC) and after protonation (DF) are shown.

[0032] Figure 5 SEM images of dye AD4455 before (A) and after (B) protonation are shown.

[0033] Figure 6SEM images of the AD46 dye layer before protonation (A) and after protonation (B) are shown. Detailed Implementation

[0034] The present invention will now be clearly and completely described in conjunction with its embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments that can be obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0035] All terms and phrases in this invention should be interpreted according to their ordinary meaning as understood by those skilled in the art, unless their meaning is obviously different depending on the context. Unless otherwise specified, the terms mentioned in this invention have the same meaning. In this invention, only the terms mentioned for the first time, the materials used, and the properties of the materials are described in detail. Unless otherwise specified, when mentioned again in this invention, the meaning of the terms, the types of materials used, the properties of the materials, etc., are the same as when they were first mentioned, and therefore will not be repeated.

[0036] Those skilled in the art know that photo-oriented AD1 dye layers have a high dichroic ratio (DR up to 90), but also a high light scattering level, which increases further after chemical modification. Therefore, polarizers made from AD1 dyes have low optical quality. Furthermore, we have found that even minor modifications to the core structure of the AD1 molecule significantly worsen the dichroic properties of the new dye. However, the inventors unexpectedly discovered that by modifying the AD1 molecule while retaining its core structure, a novel class of diazobiphenyl dyes with a structure similar to AD1 can be obtained, namely, derivatives of 4,4'-bis(4-N,N-dialkylaminophenylazo)-biphenyl. This dye has dichroic properties comparable to or even higher than AD1, and the dye layers made from it exhibit a high dichroic ratio after photo-orientation. Moreover, after chemical modification, the thin-film polarizers prepared from it still possess good optical quality, such as low light scattering, low haze, high dichroic ratio, broadband absorption, and / or stability to heat and light irradiation. This completes the present invention.

[0037] Therefore, according to a first aspect of the present invention, a diazobiphenyl dye is provided having the structure shown in formula (I):

[0038]

[0039] In this group, at least one of the substituents R1, R2, R3, and R4 is different from the other substituents, and each is independently C1. n H 2n+1 , where n = 1 - 18.

[0040] Those skilled in the art will know that structural C n H 2n+1 This represents an alkyl group. In some embodiments, in the structure shown in formula (I), n can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. In some specific embodiments, n is 4, 5, or 6.

[0041] As described above, the diazobiphenyl dye of the present invention, because at least one of the substituents R1, R2, R3 and R4 is different from the other substituents, can make the thin film polarizer have higher optical quality, such as lower light scattering, higher dichroism ratio and / or lower haze, when used to prepare thin film polarizers.

[0042] In some implementations, R1≠R2, R2=R3=R4; or R1=R3, R2=R4, R1≠R2; or R1=R2, R3=R4, R1≠R3; or R1≠R2≠R3≠R4.

[0043] In some implementations, in the structure shown in formula (I), R1 is C4H9 and R2 is C5H 11 R3 is C4H9, R4 is C5H 11 This yields compound 1 (abbreviated as AD45).

[0044] In some implementations, in the structure shown in formula (I), R1 is C4H9 and R2 is C6H 13 R3 is C4H9, R4 is C6H 13 This yields compound 2 (abbreviated as AD46).

[0045] In some implementations, in the structure shown in formula (I), R1 is C4H9, R2 is C4H9, and R3 is C5H9. 11 R4 is C5H 11 This yields compound 3 (abbreviated as AD44-55).

[0046] In this invention, compounds 1-3 are merely examples, and other compounds having the structure shown in formula (I) can also be formed, including compounds in which R1, R2, R3 and R4 are different from each other.

[0047] As described above, the diazo biphenyl dye of the present invention is easily affected by photoorientation. Therefore, a high dichroism ratio can be produced by irradiating the film deposited by the dye with polarized ultraviolet or blue light. Furthermore, the film has good optical quality after chemical modification, such as low light scattering, low haze, high dichroism ratio, broadband absorption, and / or stability to heat and light irradiation.

[0048] Those skilled in the art will know that conventional methods for synthesizing diazo dyes involve diazotizing benzidine (1,1'-biphenyl-4,4'-diamine) followed by an azo coupling reaction with N,N-dialkylaniline, as shown in the following reaction procedure:

[0049]

[0050] This method has been extensively studied and widely applied in the manufacture of azo dyes. However, this traditional method has various limitations. For example, it can only synthesize symmetrical molecules where the left and right halves of the parent structure are identical, i.e., R1 = R3, R2 = R4, R1 ≠ R2, or R1 = R2 = R3 = R4. Therefore, asymmetric diphenyl diazo dyes with different left and right halves cannot be prepared from benzidine precursors. Furthermore, this traditional method requires benzidine, a human carcinogen, as a starting material, and the resulting dyes have reduced purity due to the presence of numerous difficult-to-remove impurities. This necessitates complex additional processes, such as preparative chromatography, for purification of the azo dyes prepared by this method, leading to increased time and economic costs.

[0051] Based on this, in a second aspect of the present invention, a novel method for preparing a diazo biphenyl dye having the structure shown in formula (I) is proposed, the method comprising: performing a cross-coupling reaction between a first monoazo dye and a second monoazo dye, wherein the first monoazo dye is a haloazobenzene, and the second monoazo dye is a borate ester derivative of azobenzene:

[0052]

[0053] Among them, R1, R2, R3, and R4 may be the same or different, and each is independently C. n H 2n+1 , where n = 1 - 18.

[0054] As understood by those skilled in the art, a "monoazo dye" refers to an organic compound containing only one diazoxide group in its molecule. Furthermore, as understood by those skilled in the art, the "haloazobenzene" mentioned in this invention refers to a substituted azobenzene formed by replacing one hydrogen atom (particularly the hydrogen atom at the para position of the benzene ring connected to the azooxide group) with chlorine (Cl), bromine (Br), iodine (I), or trifluoromethanesulfonate. In a further embodiment, the first monoazo dye is a haloazobenzene having the structure shown in formula (II):

[0055]

[0056] Wherein, X is Cl, Br, I or trifluoromethanesulfonate, preferably Br, and R3 and R4 are each independently C. n H 2n+1 , where n = 1 - 18.

[0057] In some embodiments, the second monoazo dye is a borate ester derivative of azobenzene having the structure shown in formula (Ⅲ):

[0058]

[0059] in,

[0060] R1 and R2 can each be independently C n H 2n+1 Where n = 1 - 18;

[0061] R is H or C m H 2m+1 Where m is 1-6, or

[0062] The B(OR)2 group is a 5-membered ring, such as dioxacyclopentaborane. Or a 6-membered ring such as dioxane

[0063] In some embodiments, the first monoazo dye is synthesized by diazotizing 4-haloaniline and then coupling it with N,N-dialkylaniline.

[0064] As understood by those skilled in the art, "diazotization" refers to the reaction of a primary amine with a nitrite, such as sodium nitrite, at low temperature to form a diazonium salt. In one specific embodiment of the present invention, p-bromoaniline can be dissolved in an HCl solution, and then a sodium nitrite solution can be added dropwise to the p-bromoaniline solution while stirring to carry out a diazotization reaction. After mixing, sodium acetate is added, and the reaction is allowed to proceed overnight. After precipitation, washing, and crystallization, the first monoazo dye can be obtained.

[0065] As understood by those skilled in the art, a "coupling reaction" is a process in which two organic chemical units undergo a chemical reaction to obtain an organic molecule. In a narrow sense, a coupling reaction refers to a carbon-carbon bond formation reaction involving an organometallic catalyst. In one specific embodiment of the invention, the solution obtained after the above-described diazotization reaction is added dropwise to an N,N-dialkylaniline solution.

[0066] In some embodiments, the second monoazo dye (III) is synthesized by boronizing a haloazobenzene.

[0067] As understood by those skilled in the art, borylation refers to a class of reactions that utilize the coupling reaction of aryl or alkenyl halides or trifluorosulfonate derivatives with pinacol borate in the presence of a palladium catalyst to prepare the corresponding pinacol borate ester. In one embodiment of the invention, under an inert (e.g., nitrogen) atmosphere, a dry... PdCl2 is added to a mixture of bromoazobenzene, pinacol diboronic acid ester, and anhydrous potassium acetate in an alkane. After the reaction, the product is washed, purified, and recrystallized to obtain the second monoazo dye.

[0068] In one specific embodiment of the present invention, the cross-coupling reaction is a Suzuki cross-coupling reaction. As understood by those skilled in the art, the Suzuki cross-coupling reaction is a cross-coupling reaction between coupling ligands such as organoboronic acids and organoboronic acids under the action of palladium catalysts. Generally, organoboronic acids can be arylboronic acids, alkenylboronic acids, alkynylboronic acids, etc.; organohalides can be aryl, sulfonate esters, etc. Specifically, in the present invention, the organoboronic acid can be a borate ester derivative of azobenzene having the structure shown in formula (III), and the organohalide can be a haloazobenzene having the structure shown in formula (II). Of course, other organoboronic acids and haloalkanes that can generate the structure shown in formula (I) can also be used, and the present invention does not further limit them.

[0069] As Figure 1 As shown, traditional methods for preparing diazobiphenyl dyes can only produce symmetrical diazobiphenyl dyes in which R1 and R3 are the same and R2 and R4 are the same, but cannot produce asymmetrical diazobiphenyl dyes in which the four substituents R1-R4 can be arbitrarily combined; in contrast, the method of the present invention can not only prepare symmetrical diazobiphenyl dyes, but also asymmetrical diazobiphenyl dyes in which the four substituents R1-R4 can be arbitrarily combined.

[0070] Therefore, in some embodiments, at least one of the substituents R1, R2, R3, and R4 is different from the other substituents. Such diazobiphenyl dyes can be symmetrical or asymmetrical, depending on the choice of substituents R1, R2, R3, and R4.

[0071] In some embodiments, the synthesized diazobiphenyl dyes are symmetrical, and wherein R1 = R3, R2 = R4, R1 ≠ R2, or R1 = R2 = R3 = R4. In this invention, as an example, compounds AD45, AD46, AD55, and AD1 are symmetrical.

[0072] In some implementations, in the structure shown in formula (I), R1 is C4H9 and R2 is C5H 11 R3 is C4H9, R4 is C5H 11 Thus, compound 1 (abbreviated as AD45) is obtained. In compound 1, R1 and R3 are the same, and R2 and R4 are the same, so the diazobiphenyl dye AD45 has a symmetrical structure.

[0073] In some implementations, in the structure shown in formula (I), R1 is C4H9 and R2 is C6H 13 R3 is C4H9, R4 is C6H 13 This yields compound 2 (abbreviated as AD46). In compound 2, R1 and R3 are the same, and R2 and R4 are the same, thus the diazobiphenyl dye AD46 has a symmetrical structure.

[0074] In some implementations, in the structure shown in formula (I), R1 is C4H9, R2 is C4H9, and R3 is C5H9. 11 R4 is C5H 11 Thus, compound 3 (abbreviated as AD44-55) was obtained. In compound 3, R1 is the same as R2, R3 is the same as R4, and R1 and R2 are different from R3 and R4. Therefore, the diazobiphenyl dye AD44-55 has an asymmetric structure.

[0075] In some implementations, in the structure shown in formula (I), R1 is C5H 11 R2 is C5H 11 R3 is C5H 11 R4 is C5H 11 This yields compound 4 (abbreviated as AD55). In compound 4, R1, R2, R3, and R4 are all identical, thus the diazobiphenyl dye AD55 has a symmetrical structure.

[0076] In some embodiments, R1, R2, R3, and R4 are all C4H9 in the structure shown in formula (I), thus yielding compound 5 (abbreviated as AD1). In compound 5, R1, R2, R3, and R4 are all identical, therefore the diazobiphenyl dye AD1 has a symmetrical structure.

[0077] In this invention, compounds 1-5 are merely examples, and other compounds having the structure shown in formula (I) can be formed, including one, two, three or four different compounds of R1, R2, R3 and R4.

[0078] In this invention, residual impurities from the chemical reaction in the above-described preparation method have significantly different solubilities than the desired diazo dye product. Therefore, to obtain the target diazo dye with acceptable high purity, a simple purification technique can be used to purify the dye product. For example, the diazo dye can be purified by rapid chromatography on a short silica gel column followed by recrystallization with a suitable solvent. Therefore, in some embodiments, purification can be performed by a combination of rapid chromatography and recrystallization. Purification yields a diazo dye with a purity of at least 99%.

[0079] The yield of purified diazo dyes is in the range of 35-40%. In the case of symmetrical diazo dyes (R1=R3, R2=R4, R1≠R2, or R1=R2=R3=R4), such yields are close to those obtained by the conventional benzidine method. However, the method of the present invention can also be used to produce asymmetrical diazo dyes (by using two different monoazo precursors). Furthermore, the method of the present invention requires fewer resources because high-purity substances can be obtained through a simple purification procedure without the need for preparative column chromatography purification used in conventional AD1 synthesis. The preparation method of the present invention can be used not only for the formation of asymmetrical diazo dyes but also for the synthesis of existing symmetrical diazo dyes such as AD1. Advantageously, the method of the present invention does not involve the toxic raw material benzidine.

[0080] According to a third aspect of the present invention, a diazobiphenyl dye is provided, wherein the diazobiphenyl dye is prepared by the method of the second aspect of the present invention.

[0081] As can be seen from the above description of the second aspect of the present invention, the method of the second aspect of the present invention can prepare diazo biphenyl dyes with the same or similar structure, properties and performance as those of the first aspect of the present invention. Therefore, for the sake of brevity, it will not be described in detail here.

[0082] Secondly, the method of the second aspect of the present invention can also prepare other diazo biphenyl dyes other than those of the first aspect of the present invention, such as diazo biphenyl dyes in which R1, R2, R3, and R4 are the same as each other, such as AD1 as in the prior art, or AD55 synthesized by the inventors, wherein R1, R2, R3, and R4 are all linear pentyl groups.

[0083] According to a fourth aspect of the present invention, a thin-film polarizer is provided, wherein the thin-film polarizer comprises: a substrate; and a first dye layer oriented by light, the first dye layer comprising a diazobiphenyl dye as described in the first aspect of the present invention or a diazobiphenyl dye as described in the third aspect of the present invention.

[0084] In this invention, diazobiphenyl dyes can be coated onto a substrate using various thin-film deposition techniques, such as spin coating. Taking spin coating as an example, the dye can be dispersed in a suitable solvent, typically an organic solvent, and then the dye-laden solvent is deposited onto a substrate, which is then rotated by centrifugal force to form a uniform coating layer. Of course, other techniques known to those skilled in the art can also be used, such as spraying, roller coating, dip coating, brush coating, evaporation, sputtering, and printing, such as slot die printing, aerosol jet printing, or inkjet printing, as long as the objective of this invention is achieved. Those skilled in the art can choose according to actual needs.

[0085] In some embodiments, the coating of the diazobiphenyl dye is carried out under controlled temperature and humidity conditions. Regarding temperature, coating is preferably carried out at temperatures below 25°C, for example at 25°C, 20°C, 15°C, 10°C, and 5°C; more preferably, coating is carried out at temperatures in the range of 15°C to 25°C, for example at 25°C, 20°C, and 15°C. The temperature should not be too high, as excessively high temperatures will cause the solvent to evaporate too quickly, resulting in rapid crystallization and high haze. Regarding humidity, coating is preferably carried out at medium to high humidity levels above 50%, for example at relative humidity levels of 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, and 90%; more preferably, coating is carried out at relative humidity levels in the range of 50% to 80%, for example at 50%, 55%, 60%, 65%, 70%, 75%, and 80%. Controlling the humidity within the above range can make the resulting hybrid film layer more uniform and smooth.

[0086] It should be understood that in this application, the term "thin film" in relation to "thin film polarizer" refers to the layer structure other than the substrate. In this invention, "thin film polarizer" refers to a polarizer in which the layer structure other than the substrate has a thickness of ≤1000nm.

[0087] As understood by those skilled in the art, "substrate" refers to a material that supports other substances coated thereon, such as the photo-oriented first dye layer of this invention. In some embodiments, the substrate may be a flexible substrate such as a polymer substrate, thereby enabling the polarizer to be used in foldable displays. In some embodiments, the substrate may be selected from glass, polymers, various liquid crystal layers, color filters, etc. Of course, other materials known to those skilled in the art as substrates for polarizers may also be used, as long as the objectives of this invention are achieved, and those skilled in the art may choose according to actual needs.

[0088] In some embodiments, the photo-oriented first dye layer is formed by coating the diazobiphenyl dye described in the first aspect of the present invention onto the substrate and photo-orienting the diazobiphenyl dye. In some embodiments, the photo-oriented first dye layer can be a dye layer prepared from a single diazobiphenyl dye described in the first aspect of the present invention, or it can be a dye layer prepared from multiple, such as two, three, or more diazobiphenyl dyes described in the first or third aspect of the present invention. When using multiple diazobiphenyl dyes, the dye layer can be prepared by coating the diazobiphenyl dyes onto the substrate one by one, or by first preparing the diazobiphenyl dyes into a mixture in a certain proportion and then coating the mixture onto the substrate.

[0089] As understood by those skilled in the art, "photoorientation" refers to the orientation of a material when exposed to polarized light (e.g., with a total energy of 100 J / cm²). 2The photoalignment process is performed under linearly polarized light irradiation. In this invention, a diazobiphenyl dye can be deposited on a substrate, and the dye layer is photoaligned after the solvent is evaporated. The photoalignment technique used can be the technique disclosed by Pan et al. in "High performance coatable polarizer by photoalignment", SID Digest, pp. 1866-1868, 2017, the disclosure of which is incorporated herein by reference. In this photoalignment technique, the dye layer is exposed to polarized light so as to reorient the dye molecules in a direction perpendicular to the coatable polarized light. In some embodiments, the polarizing light source can be a polarizing layer with a center wavelength of 442 nm, but other light sources can also be used. The contrast ratio of the two polarizations of the coatable polarizer is 500. Thin film polarizers containing the diazobiphenyl dye of this invention are susceptible to the influence of photoalignment, and high dichroism ratios are produced when the deposited thin film polarizer is irradiated with polarized UV or blue light. In this invention, the dichroic ratio (DR) of the dye layer after photo-orientation is in the range of 40-70, for example, 45, 50, 60, 70, which is much higher than the required DR≥10, even after chemical treatment.

[0090] In some embodiments, the thickness of the photo-oriented first dye layer is about 40 nm to 1000 nm.

[0091] In this invention, after the first dye layer is photo-oriented, the photo-oriented dye layer can be further chemically modified to produce a broadband thin-film polarizer that is stable under visible or UV light irradiation. Chemical modification includes acid treatment or protonation treatment. In this invention, chemical modification has the same meaning as "chemical modification" in the PCT patent application with international publication number WO 2021 / 051258 A1, the entire contents of which are incorporated herein by reference. Specifically, chemical modification / protonation is achieved by treatment with an acid or its derivative (which can produce an acid, such as an anhydride), simultaneously or sequentially with water, typically carried out in the gas phase. Examples of acids that can be used include hydrohalic acids, nitric acid, sulfuric acid, phosphoric acid, aryl sulfonic acids, alkyl sulfonic acids, halosulfonic acids, trifluoromethanesulfonic anhydride, and halogenated carboxylic acids. Before chemical modification such as protonation, the first dye layer exhibits relatively narrow absorption in the blue spectral region, while after chemical modification such as protonation, the photo-oriented first dye layer exhibits broad absorption and redshift absorption in the visible spectral region.

[0092] Following chemical modification, such as protonation, an additional protective layer can be formed on the photo-oriented first dye layer. In some embodiments, the thin-film polarizer further includes a protective layer located above the photo-oriented first dye layer. In some preferred embodiments, the protective layer comprises a polymer such as polyacrylate, polyacrylonitrile, epoxy resin, or silicone resin, or combinations thereof, and may be, for example, a NOA-61 protective layer. In this invention, the polymer used in the protective layer can be a polymerized material that can be deposited and reacted in situ. After coating the chemically modified, such as protonated, photo-oriented first dye layer with the deposited protective layer, the thin-film polarizer of this invention still exhibits high dichroism, low light scattering, and / or stability to radiation, humidity, and heating, demonstrating excellent optical properties.

[0093] In this invention, additional layers can be formed on top of the protective layer. In some embodiments, the thin-film polarizer further includes an additional dye layer that covers the additional protective layer located on top of the protective layer 1. By adding these additional layers, the polarizer provided by this invention can form a multilayer polarizer.

[0094] The thin-film polarizer of the present invention has an optical haze of ≤10%, preferably ≤4%, ≤3%, or ≤2%. As understood by those skilled in the art, "haze" refers to the ratio of scattered light flux deviating from the incident light direction through the sample to the transmitted light flux, as defined in GB / T2410-2008 (the same as ASTM D1003), expressed as a percentage (for this method, only scattered light flux deviating from the incident light direction by more than 2.5° is used to calculate haze).

[0095] In the field of polarizers, the thin-film polarizer of the third aspect of this invention can be used in display applications. Therefore, according to a fourth aspect of this invention, an apparatus for display applications is provided, wherein the apparatus includes the thin-film polarizer described in the third aspect of this invention. In some embodiments, the apparatus is an organic light-emitting diode (OLED) display or a liquid crystal display (LCD). Of course, it can also be used in other display applications.

[0096] The present invention will now be described in further detail with reference to specific embodiments.

[0097] In the following embodiments, glass is used as the substrate for all thin-film coatings, unless otherwise stated.

[0098] Example

[0099] Example 1: Synthesis of the precursor (dialkylaniline)

[0100] Example 1-1: Synthesis of N-Butyl-N-pentylaniline

[0101] A mixture of N-butylaniline (5 mL, 31.1 mmol), n-pentyl bromide (4.6 mL, 37.4 mmol), anhydrous K₂CO₃ (12.9 g, 93.4 mmol), and KI (0.64 g, 3.4 mmol) in 50 mL DMF and 100 mL toluene was refluxed for 24 hours using a Dean-Stark separator. The reaction progress was monitored by GC-MS. After the reaction was complete, 200 mL of water was added to the mixture. The organic layer was separated, and the aqueous layer was extracted twice with 30 mL of toluene. The combined organic extracts were washed with brine and evaporated to dryness. The residue was purified by rapid chromatography (silica gel-hexane) to give N-butyl-N-n-pentylaniline as a pale yellow oil, 6.6 g, 97% yield; purified by GC-MS alone. GC-MS (m / z (I rel. ,%):219(52,M + ),176(91),162(98),120(100),106(85),91(20),77(37).

[0102] Examples 1-2: Synthesis of N-butyl-N-hexylaniline

[0103] N-Butyl-N-hexylaniline was prepared from n-hexyl bromide (4.7 mL, 37.4 mmol) according to the procedure used for N-butyl-N-pentylaniline. N-Butyl-N-hexylaniline was obtained as a pale yellow oil, 8 g, yield 89%, by GC-MS alone. GC-MS (m / z (I rel. ,%):233(12,M + ),190(32),162(51),120(100),106(63),91(10),77(26).

[0104] Examples 1-3: Synthesis of N,N-dipentylaniline

[0105] A mixture of aniline (10 mL, 109.7 mmol), n-pentyl bromide (34 mL, 274.3 mmol), and anhydrous potassium carbonate (92 g, 660 mmol) in 100 mL DMF and 200 mL toluene was refluxed overnight using a Dean-Stark apparatus. Then, another portion of n-pentyl bromide (5 mL, 40 mmol) was added, and the mixture was refluxed until the reaction was complete. The reaction was monitored by GC-MS. After the reaction was complete, 300 mL of water was added to the mixture, and the toluene was separated. The aqueous layer was extracted twice with 50 mL of toluene. The toluene extract was washed with brine and evaporated. The residue was purified by rapid chromatography (silica gel-hexane) to give N,N-dipentylaniline, a pale yellow oil, 24 g, 96% yield, by GC-MS alone. GC-MS (m / z (I rel.,%):233(44,M + ),176(100),120(98),106(63),91(12),77(26).

[0106] Example 2: Synthesis of Bromoazobenzene – Azo Coupling of Bromoaniline and Dialkylaniline

[0107] General procedure: Dissolve p-bromoaniline (4.8 g, 28 mmol) in 200 mL of 1 N HCl and cool to 0 °C. Cool a solution of sodium nitrite (1.93 g, 28 mmol) in 40 mL of water to 5 °C, then add it dropwise to the p-bromoaniline solution at 0–2 °C, stirring for 40 minutes after addition. Then, add this solution dropwise to an ice-cold solution of N,N-dialkylaniline (28 mmol) in a mixture of 150 mL of ethanol and 50 mL of water. After mixing, add a solution of 5 g of sodium acetate in 10 mL of water and stir the mixture overnight. Filter out the precipitate, wash with water, dry, and recrystallize twice with ethanol.

[0108] In the above preparation method, the specific reaction process is as follows:

[0109]

[0110] Example 2-1: Synthesis of 4-((4-bromophenyl)diazenin)-N,N-dibutylaniline

[0111] 4-((4-bromophenyl)diazeninyl)-N,N-dibutylaniline was synthesized from 6.4 mL of N,N-dibutylaniline (28 mmol) as described in the general procedure; the yield of orange crystals was 5.8 g, representing a yield of 53%.

[0112] 1 H NMR (400MHz, CDCl3) δ, ppm: 7.86 (d, J = 9.1Hz, 2H), 7.72 (d, J = 8.5Hz, 2H), 7.61 (d, J = 8.7Hz, 2H), 6.69 (d,J=9.1Hz,2H),3.42(t,J=7.8Hz,4H),1.72-1.59(m,4H),1.40-1.36(m,4H),0.99(t,J=7.3Hz,6H).

[0113] Example 2-2: Synthesis of 4-((4-bromophenyl)diazenin)-N,N-dipentylaniline

[0114] 4-((4-bromophenyl)diazeninyl)-N,N-dipentylaniline was synthesized from 6.5 mL of N,N-dipentylaniline (28 mmol) as described in the general procedure, yielding 5.6 g of orange crystals in 51% yield.

[0115] 1 H NMR (400MHz, CDCl3) δ, ppm: 7.85 (d, J = 9.0Hz, 2H), 7.71 (d, J = 8.4Hz, 2H), 7.58 (d, J = 8.7Hz, 2H), 6.72 (d, J=9.0Hz, 2H), 3.41 (t, J=7.6Hz, 4H), 1.70-1.57 (m, 4H), 1.40-1.36 (m, 8H), 0.99 (t, J=7.3Hz, 6H).

[0116] Examples 2-3: Synthesis of 4-((4-bromophenyl)diazenin)-N-butyl-N-pentylaniline

[0117] 4-((4-bromophenyl)diazeninyl)-N-butyl-N-pentylaniline was synthesized from 6.4 mL of N-butyl-N-pentylaniline (28 mmol) as described in the general procedure, yielding 5.3 g of orange crystals in 47% yield.

[0118] 1 H NMR (400MHz, CDCl3) δ, ppm: 7.84 (d, J = 9.2Hz, 2H), 7.72 (d, J = 8.5Hz, 2H), 7.61 (d, J = 8.8Hz, 2H), 6.71 (d, J = 9.0 Hz,2H),3.39–3.35(m,4H),1.67-1.59(m,4H),1.44-1.36(m,6H),0.99(t,J=7.1Hz,3H),0.92(t,J=6.9Hz,3H).

[0119] Examples 2-4: Synthesis of 4-((4-bromophenyl)diazenin)-N-butyl-N-hexylaniline

[0120] 4-((4-bromophenyl)diazeninyl)-N-butyl-N-hexylaniline was synthesized from 6.5 mL of N-butyl-N-hexylaniline (28 mmol) as described in the general procedure, yielding 5.9 g of orange crystals in 53% yield.

[0121] 1 H NMR (400MHz, CDCl3) δ, ppm: 7.85 (d, J = 9.0Hz, 2H), 7.71 (d, J = 8.4Hz, 2H), 7.58 (d, J = 8.7Hz, 2H), 6.72 (d, J = 9.1 Hz,2H),3.38–3.35(m,4H),1.66-1.59(m,4H),1.39-1.33(m,8H),0.98(t,J=6.5Hz,3H),0.92(t,J=6.5Hz,3H).

[0122] Example 3: Boration of bromoazobenzene

[0123] General procedure: Under an inert (nitrogen) atmosphere, apply the following to dry carbon dioxide. PdCl2 (dppf) (0.02 equivalents) was added to a mixture of bromoazobenzene (1 equivalent), bis(pinacolato)diborane (1.5 equivalents), and anhydrous potassium acetate (3 equivalents). The mixture was heated to 85°C and stirred for 10 hours. The mixture was then diluted with ethyl acetate and washed with brine. The resulting mixture, after solvent evaporation, was purified by rapid chromatography (eluent: hexane, or a 9 / 1 mixture of hexane and ethyl acetate) and recrystallized from methanol.

[0124] In the above preparation method, the specific reaction process is as follows:

[0125]

[0126] Example 3-1: Synthesis of N,N-dipentyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)diazenin)aniline

[0127] N,N-Dipentyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)diazepine)aniline was prepared by 140 mL of diphenyl ether as described in the general procedure. The synthesis was carried out using 7 g (16.9 mmol) of 4-((4-bromophenyl)diazeninyl)-N,N-dipentylaniline, 6.4 g (25.3 mmol) pinacol diboronic acid ester, 5 g (50.6 mmol) potassium acetate, and 0.25 g (0.34 mmol) PdCl2 (dppf) from alkane, yielding 6.6 g of orange precipitate in 84% yield.

[0128] 1 H NMR (400MHz, CDCl3) δ, ppm: 7.91 (d, J = 7.8Hz, 2H), 7.86 (d, J = 9.3Hz, 2H), 7.81 (d, J = 7.5Hz, 2H), 6.71 (d,J=9.3Hz,2H),3.53(t,J=8.0Hz,4H),1.69-1.61(m,4H),1.42-1.33(m,8H),0.94(t,J=6.7Hz,6H).

[0129] Example 3-2: Synthesis of N,N-dibutyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)diazenin)aniline

[0130] N,N-Dibutyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)diazepine)aniline, as described in the general procedure, is prepared from 40 mL of dibutyl... The synthesis was carried out using 2 g (5.2 mmol) of 4-((4-bromo-phenyl)diazetenyl)-N,N-dibutylaniline, 2 g (7.7 mmol) of pinacol diboronate, 1.5 g (15.5 mmol) of potassium acetate, and 0.075 g (0.1 mmol) of PdCl2 (dppf) from an alkane. 2 g of an orange oil was obtained, which crystallized slowly at low temperature in 91% yield.

[0131] 1 H NMR (400MHz, CDCl3) δ, ppm: 7.87 (d, J = 7.5Hz, 2H), 7.84 (d, J = 9.0Hz, 2H), 7.73 (d, J = 8.2Hz, 2H), 6.67 ( d,J=9.0Hz,2H),3.36(t,J=8.0Hz,4H),1.67-1.58(m,4H),1.42-1.34(m,16H),0.99(t,J=7.3Hz,6H).

[0132] Example 3-3: Synthesis of N-butyl-N-hexyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)-diazepine)aniline

[0133] The synthesis of N-butyl-N-hexyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)phenyl)-diazepine)aniline was performed as described in the general procedure using 40 mL of dioxane. The synthesis was carried out using 2 g (4.86 mmol) of 4-((4-bromophenyl)-diazetenyl)-N-butyl-N-hexylaniline, 1.9 g (7.3 mmol) of pinacol diboronate, 1.4 g (14.5 mmol) of potassium acetate, and 0.070 g (0.097 mmol) of PdCl2 (dppf) from an alkane. 3.9 g of fine orange crystals were obtained in 87% yield.

[0134] 1H NMR (400MHz, CDCl3) δ, ppm: 7.92 (d, J = 7.5Hz, 2H), 7.87 (d, J = 9.2Hz, 2H), 7.82 (d, J = 8.3Hz, 2H), 6.69 (d, J = 9.0H z,2H),3.38–3.35(m,4H),1.66-1.59(m,4H),1.39-1.33(m,20H),0.98(t,J=6.5Hz,3H),0.92(t,J=6.5Hz,3H).

[0135] Examples 3-4: Synthesis of N-butyl-N-pentyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)phenyl)-diazepine)aniline

[0136] N-Butyl-N-pentyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)phenyl)-diazepine)aniline is prepared as per the general procedure from 40 mL of di The synthesis was carried out using 1 g (2.49 mmol) of 4-((4-bromophenyl)-diazetenyl)-N-butyl-N-pentylaniline, 0.95 g (3.74 mmol) of pinacol diboronate, 0.75 g (7.5 mmol) of potassium acetate, and 0.040 g (0.05 mmol) of PdCl2 (dppf) from an alkane. 1.0 g of fine orange crystals was obtained in 90% yield.

[0137] 1 H NMR (400MHz, CDCl3) δ, ppm: 7.90 (d, J = 8.5Hz, 2H), 7.87 (d, J = 8.5Hz, 2H), 7.75 (d, J = 8.8Hz, 2H), 6.69 (d, J = 9.0H z,2H),3.39–3.35(m,4H),1.67-1.59(m,4H),1.44-1.36(m,18H),0.99(t,J=7.3Hz,3H),0.92(t,J=7.1Hz,3H).

[0138] Example 4: Synthesis of diazo dyes via cross-coupling reaction

[0139] General procedure: A mixture of pinacol borate (1 equivalent), bromoazobenzene (1 equivalent), sodium dodecyl sulfate (1%, soluble in water), toluene, water, and butanol was degassed and purged with nitrogen. Then, PdCl2 (dppf) (0.03 equivalent) was added under nitrogen, and the degassed process was repeated. The resulting emulsion was heated to reflux with stirring, and an aqueous solution of Na2CO3 (4 equivalent) was added dropwise over 5–10 minutes. The reaction mixture was refluxed until HPLC indicated completion. The reaction mixture was cooled, diluted with isopropanol, evaporated to dryness, suspended in dichloromethane, filtered through a short silica gel sieve, washed with dichloromethane, and evaporated to dryness. The product was purified by thermal extraction and / or crystallization from a suitable solvent.

[0140] The specific reaction process in the above synthesis method is as follows:

[0141]

[0142] In summary, the overall preparation process of the diazo dye provided by this invention is as follows:

[0143]

[0144] Example 4-1: Synthesis of 4,4'-([1,1'-biphenyl]-4,4'-diylbis(diazetenyl-2,1-diyl))bis(N,N-dipentylaniline) (AD55)

[0145] 4,4'-([1,1'-biphenyl]-4,4'-diylbis(diazenin-2,1-diyl))bis(N,N-dipentylaniline) (AD55) was synthesized as described in the general procedure from a solution of 1 g (2.16 mmol) N,N-dipentyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxaneborane-2-yl)phenyl)diazenin)aniline, 0.9 g (2.16 mmol) 4-((4-bromophenyl)-diazenin)-N,N-dipentylaniline, 0.25 g sodium dodecyl sulfate (SDS), 20 mL toluene, 20 mL water, 5 mL butanol, 0.05 g (0.065 mmol) PdCl2 (dppf), and 0.9 g (8.64 mmol) Na2CO3 in 5 mL water. The product was purified by thermal extraction on silica gel with a mixture of hexane and then 10% DCE in heptane (major fraction). The residue after evaporation of the major fraction was recrystallized with acetonitrile to give 0.8 g of fine red needle-like material in 62% yield (HPLC purity >99%).

[0146] 1H NMR (400MHz, CDCl3) δ, ppm: 7.94 (d, J = 9.2Hz, 4H), 7.89 (d, J = 9.2Hz, 4H), 7.78 (d, J = 9Hz, 4H), 6.71 (d, J = 9.3Hz, 4H ),3.67(t,J=7.7Hz,8H),1.69-1.61(m,8H),1.42-1.33(m,16H),0.94(t,J=6.5Hz,12H).HRMS(CI-TOF,m / z)calcd for C 44 H 60 N6[M+H] + 673.4879, found 673.4822.

[0147] Example 4-2: Synthesis of 4,4'-([1,1'-biphenyl]-4,4'-diylbis(diazetenyl-2,1-diyl))bis(N-butyl-N-hexylaniline) (AD 46)

[0148] 4,4'-([1,1'-biphenyl]-4,4'-diylbis(diazenin-2,1-diyl))bis(N-butyl-N-hexylaniline) (AD 46) was synthesized as described in the general procedure from 1.6 g (3.45 mmol) N-butyl-N-hexyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)diazenin)aniline, 1.45 g (3.45 mmol) 4-((4-bromophenyl)diazenin)-N-butyl-N-hexylaniline, 0.25 g SDS, 20 mL toluene, 20 mL water, 5 mL butanol, 0.080 g (0.1 mmol) PdCl2 (dppf) and 1.0 g (13.8 mmol) Na2CO3 in 5 mL water. The product was purified by thermal extraction on silica gel with a mixture of hexane and then 10% DCE in heptane (major fraction). The residue after evaporation of the major fraction was recrystallized with acetonitrile to give 1.2 g of fine red crystals in 57% yield (HPLC purity >99%).

[0149] 1H NMR (400MHz, CDCl3) δ, ppm: 7.94 (d, J = 9.2Hz, 4H), 7.89 (d, J = 9.2Hz, 4H), 7.79 (d, J = 9.2Hz, 4H), 6.72 (d, J = 9.2Hz, 4H), 3.40 –3.36(m,8H),1.66-1.61(m,8H),1.44-1.36(m,16H),0.99(t,J=7.3Hz,6H),0.92(t,J=6.5Hz,6H).HRMS(CI-TOF,m / z)calcd forC 44 H 60 N6[M+H] + 673.4879, found 673.4932.

[0150] Example 4-3: Synthesis of 4,4'-([1,1'-biphenyl]-4,4'-diylbis(diazetenyl-2,1-diyl))bis(N-butyl-N-pentylaniline) (AD45)

[0151] 4,4'-([1,1'-biphenyl]-4,4'-diylbis(diazenin-2,1-diyl))bis(N-butyl-N-pentylaniline) (AD45) was synthesized as described in the general procedure from 1 g (2.22 mmol) N-butyl-N-pentyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)diazenin)aniline, 0.9 g (2.22 mmol) 4-((4-bromophenyl)diazenin)-N-butyl-N-pentylaniline, 0.25 g SDS, 20 mL toluene, 20 mL water, 5 mL butanol, 0.050 g (0.7 mmol) PdCl2 (dppf) and 0.9 g (8.88 mmol) Na2CO3 in 5 mL water. The product was purified by thermal extraction on silica gel with heptane followed by a mixture of 10% dichloroethane in n-heptane (major fraction). The residue after evaporation of the major fraction was recrystallized with acetonitrile to give 0.8 g of small, dark red crystals in 56% yield (HPLC purity >99%).

[0152] 1H NMR(400MHz, CDCl3)δ,ppm:7.92(d,J=8.5Hz,4H),7.88(d,J=8.2Hz,4H),7.77(d,J=8.6Hz,4H),6.70(d,J=9Hz,4H),3.39– 3.35(m,8H),1.67-1.59(m,8H),1.44-1.36(m,16H),0.99(t,J=7.3Hz,6H),0.92(t,J=7.1Hz,6H).HRMS(CI-TOF,m / z)calcd forC 42 H 56 N6[M+H] + 645.4566, found 645.4613.

[0153] Example 4-4: Synthesis of N,N-dibutyl-4-((4'-((4-(dipentylamino)phenyl)diazeninyl)-[1,1'-biphenyl]-4-yl)-diazeninyl)aniline (AD44-55)

[0154] N,N-Dibutyl-4-((4'-((4-(dipentylamino)phenyl)diazenoyl)-[1,1'-biphenyl]-4-yl)-diazenoyl)aniline was synthesized from 6.6 g (14.2 mmol) N,N-dipentyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)diazenoyl)aniline, 5.5 g (14.2 mmol) 4-((4-bromophenyl)diazenoyl)-N,N-dibutylaniline, 1 g SDS, 100 mL toluene, 80 mL water, 15 mL butanol, 0.310 g (0.426 mmol) PdCl2 (dppf) and 6 g (56.6 mmol) Na2CO3 in 20 mL water, as per the general procedure. The product was crystallized sequentially with isopropanol, heptane, and acetonitrile to obtain lustrous, dark red crystals. The yield was 6.8 g, with a yield of 74% (HPLC purity >99%).

[0155] 1 H NMR (400MHz, CDCl3) δ, ppm: 7.93 (d, J = 7.8Hz, 4H), 7.88 (d, J = 8.3Hz, 4H), 7.77 (d, J = 9.3Hz, 4H), 6.70 (d, J = 7.8Hz, 4H), 3.39 –3.34(m,8H),1.67-1.60(m,8H),1.42-1.32(m,12H),0.99(t,J=9.3Hz,6H),0.94(t,J=7.3Hz,6H).HRMS(CI-TOF,m / z)calcd forC 42 H56 N6[M+H] + 645.4566, found 646.4689.

[0156] Examples 4-5: Synthesis of 4,4'-([1,1'-biphenyl]-4,4'-diylbis(diazetenyl-2,1-diyl))bis(N,N-dibutylaniline) (AD1)

[0157] 4,4'-([1,1'-biphenyl]-4,4'-diylbis(diazenin-2,1-diyl))bis(N,N-dibutylaniline) was synthesized from 1 g (2.30 mmol) N,N-dibutyl-4-((4-(4,4,5,5-tetramethyl-1,3,2-dioxacyclopentaborane-2-yl)phenyl)diazenin)aniline, 0.9 g (2.3 mmol) 4-((4-bromophenyl)-diazenin)-N,N-dibutylaniline, 0.25 g SDS, 20 mL toluene, 20 mL water, 5 mL butanol, 0.05 g (0.065 mmol)) PdCl2 (dppf), and 0.9 g (8.64 mmol) Na2CO3 in 5 mL of water. The product was crystallized sequentially from isopropanol, n-octane, and acetonitrile to give lustrous red crystals. The yield was 1.1g, with a yield of 78% (HPLC purity >99%).

[0158] 1 H NMR (400MHz, CDCl3) δ, ppm: 7.93 (d, J = 8.5Hz, 4H), 7.90 (d, J = 9.0Hz, 4H), 7.77 (d, J = 8.4Hz, 4H), 6.71 (d, J = 9.0Hz, 4H),3.37(t,J=8.0Hz,8H),1.66-1.58(m,8H),1.42-1.37(m,8H),0.99(t,J=7.3Hz,12H).HRMS(CI-TOF,m / z)calcd for C 40 H 52 N6[M+H] + 617.4253, found 617.4332.

[0159] Example 5 (Comparative Example): Synthesis of AD1 via benzidine diazotization and diazo coupling reaction

[0160] Add 200 mL of 1N HCl to benzidine (6.5 g, 35.28 mmol) and stir at 50 °C until completely dissolved. Then, cool the mixture to 0 °C (to obtain a slurry) and add a solution of NaNO2 (5.1 g, 73.9 mmol) in 40 mL of water dropwise at 0–2 °C for 10–15 minutes (to dissolve the precipitate), followed by stirring for another 30 minutes. Over 15 minutes, add the diazotized solution dropwise to a solution of N,N-dibutylaniline diazonium salt (18 mL, 79.5 mmol) in 150 mL of 1N HCl. Then, add a solution of 30 g of sodium acetate in 40 mL of water and stir the mixture for 10 hours. Filter out the precipitate, wash with water and acetone, and dry (yield of crude product approximately 20 g).

[0161] Crude AD1 was purified by rapid chromatography and recrystallization. The crude AD1 was dissolved in 600 mL of dichloromethane (DCM) and filtered through a silica gel layer (6 cm in diameter and 6 cm in height). The solution was then washed with 1200 mL of DCM and evaporated to dryness. The residue was then recrystallized twice with 700 mL of acetonitrile and once with 800 mL of heptane to obtain 16 g of AD1 with an HPLC purity of 94%.

[0162] Fine purification was performed using preparative column chromatography. A column (6 cm in diameter, 80 cm in length) was packed with 600 mL of silica gel (particle size 40-63 μm). AD1 was dissolved in 600 mL of a heptane-toluene mixture (20:80 v / v), packed into the column, and eluted with a heptane-toluene mixture, gradually increasing the toluene content to 90%, for a total eluent of 9 L. The first yellow fraction was discarded, and the red fraction was collected and monitored by thin-layer chromatography (TLC). The fraction obtained by TLC was collected, evaporated to dryness, and recrystallized from acetonitrile and heptane to give 8.2 g of AD1 as large, lustrous red crystals, in a yield of 38% (HPLC purity >99%).

[0163] Example 6: Preparation of diazo dye thin films by spin coating

[0164] The glass substrate was washed with water and a surfactant, dried, and activated in an ozone chamber for 20 minutes. A drop of a suitable diazo dye solution (5%) in toluene was spin-coated onto the substrate at 3000 rpm and further spin-coated for 30 seconds. The film was then dried at 70°C for 5 minutes. As described above, the resulting film was photo-oriented using linearly polarized light. The light source wavelength was 420 nm.

[0165] Example 7: Chemical modification and performance characterization of thin films

[0166] Protonation: As described above, the photo-oriented diazo dye film sample was protonated by continuous treatment with trifluoro anhydride and water vapor in a vapor deposition chamber.

[0167] Performance characterization:

[0168] (1) Determination of dichroic ratio (DR):

[0169] The dichroic ratio (DR) is calculated according to the prior art described in Optical System Design, R. Kingslake, 1983, Elsevier Inc., 398p, as follows:

[0170] DR=A || / A ⊥ ,

[0171] Where A || and A ⊥ It refers to the absorbance (optical density) of the sample when its orientation is parallel or perpendicular to the polarizer.

[0172] (2) Determination of fog: The fog value was measured according to ASTM D1003 using the HZ-V3 instrument of Suga Testing Machine Co., Ltd., Japan.

[0173] (3) Determination of thermal stability: The thermal stability of diazo biphenyl dyes AD45, AD46, AD4455 and AD55 after protonation and covered with NOA-61 protective layer on thin film polarizers exposed to 65°C and 90% relative humidity for 20 hours was studied using a Bench Top Type Temperature & Humidity Chamber SH-222 instrument (ESPEC, Japan).

[0174] The dichroic ratio (DR), thermal stability test results, and haze data of films prepared by spin coating from diazo dyes AD45, AD46, AD4455, AD55, and AD1 are listed in Table 1 below.

[0175] Table 1: DR and haze of films prepared by various diazo dyes

[0176]

[0177] As can be seen from Table 1, all dyes, including the existing AD1 diazo dyes, exhibited high DR values ​​(range 45-70) before protonation, and the DR values ​​decreased significantly by about 50% after protonation.

[0178] In all cases, the haze of the film also increased by approximately three times. However, it is important to note that dyes with all four alkyl groups on the terminal nitrogen atom being identical (i.e., dyes AD55 and AD1) consistently exhibited higher haze than dyes with alkyl groups of varying lengths on the terminal nitrogen atom (i.e., dyes AD45, AD46, and AD44-55). Specifically, dyes AD55 and AD1 showed a haze increase from 3-4% before protonation to 10-12% after protonation. In contrast, dyes AD45, AD46, and AD44-55 showed a haze increase from 0.5-1% before protonation to 2-3% after protonation.

[0179] As can also be seen from Table 1, for all dyes, including the existing AD1 diazo dye, the DR did not decrease significantly after the thermal stability test.

[0180] Therefore, the diazo dyes provided by this invention produce polarizers with higher optical quality, such as high dichroism ratio, good thermal stability, and low haze, regardless of the length of the alkyl substituents, before and after protonation.

[0181] 3) UV-VIS spectral characterization: Ultraviolet spectra were recorded using a Perkin Elmer UV / Vis spectrometer (model Lambda 45).

[0182] Figure 2 A- Figure 2 Figure D shows the UV-VIS spectra of thin-film polarizers made from diazobiphenyl dyes AD45, AD46, AD4455, and AD55 before and after protonation. As can be seen from the figures, the thin-film polarizers with protonated dye layers exhibit a broader absorption spectrum compared to the unprotonated version, which is highly advantageous for visible light polarizer applications.

[0183] 4) SEM characterization:

[0184] Figure 3 A-3B shows a SEM image of the AD1 dye layer before protonation. Figure 3 C-3D shows a SEM image of the AD1 dye layer after protonation. (By...) Figure 3 As can be seen from A-3D, the AD1 dye layer has a considerable surface roughness both before and after protonation, which results in reduced optical performance of the thin-film polarizer, such as increased haze.

[0185] Figure 4-6SEM images of each new dye layer before and after protonation are presented. These SEM images show that the dye layers deposited using the new dyes of this invention are smoother than AD1 before and after protonation, thus exhibiting lower light scattering. This improves the optical properties of the thin-film polarizers made from these new dyes, such as lower haze.

[0186] Although the invention has been described and illustrated with reference to specific embodiments thereof, such descriptions and illustrations are not limiting. Those skilled in the art will understand that various changes and equivalent substitutions can be made without departing from the true spirit and scope of the invention as defined by the appended claims. The drawings are not necessarily drawn to scale. Due to manufacturing processes and tolerances, artistic representations of the invention may differ from actual devices. Other embodiments of the invention may also be possible, which are not specifically described herein. The specification and drawings are intended to be illustrative rather than limiting. Modifications can be made to adapt particular circumstances, materials, composition of substances, methods, or processes to the purpose, spirit, and scope of the invention. All such modifications are intended to fall within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations can be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not limiting.

[0187] As used herein, the terms “approximately,” “generally,” “substantially,” and “about” are used to describe and explain small variations. When used in conjunction with an event or situation, the term can refer to the exact occurrence of the event or situation, or the approximate occurrence of the event or situation. As used herein, with respect to a given value or range, the term “about” generally refers to a range within ±10%, ±5%, ±1%, or ±0.5% of the given value or range. This range can be expressed herein as from one endpoint to another or between two endpoints. Unless otherwise stated, all ranges disclosed in this invention include endpoints. The term “substantially coplanar” can refer to two surfaces located within a few micrometers (μm) along the same plane, such as within 10 micrometers, 5 micrometers, 1 micrometer, or 0.5 micrometers along the same plane. When referring to “substantially” identical values ​​or characteristics, the term can refer to values ​​within ±10%, ±5%, ±1%, or ±0.5% of the average of these values.

[0188] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bis-azo-biphenyl dye having the structure shown in formula (I) below: Formula (I), wherein at least one of R1, R2, R3, and R4 is different from the others and is each independently C n H 2n+1 where n = 1-18.

2. The bis-azo biphenyl dye according to claim 1, wherein R1 R2, R2= R3= R4; or R1= R3, R2= R4, R1≠ R2; or R1= R2, R3= R4, R1≠ R3; or R1≠ R2≠ R3≠ R4.

3. The bis-azo-biphenyl dye of any one of claims 1-2, wherein, R1is C4H9, R2is C5H 11 , R3is C4H9, R4is C5H 11 ; R1is C4H9, R2is C6H 13 R3is C4H9, R4is C6H 13 ; or R1 is C4H9, R2 is C4H9, R3 is C5H 11 , R4 is C5H 11 .

4. A method of preparing a bis-azo-biphenyl dye having the structure shown in formula (I) below, the method comprising subjecting a first mono-azo dye and a second mono-azo dye to a cross-coupling reaction, wherein, the first mono-azo dye is a halogenated azobenzene and the second mono-azo dye is a boronic acid ester derivative of azobenzene: Formula (I), wherein R1, R2, R3and R4are the same or different and each independently is C n H 2n+1 wherein n = 1-18.

5. The method of claim 4, wherein, the cross-coupling reaction is a Suzuki cross-coupling reaction.

6. The method of claim 4, wherein, the first mono-azo dye is a halogenated azobenzene having the structure shown in formula (II): Formula (II), wherein X is CI, Br, I or triflate, each of R3and R4is independently C n H 2n+1 wherein n = 1-18.

7. The method of claim 6, wherein, X is Br.

8. The method of any one of claims 4-7, wherein, the second mono-azo dye is a boronic acid ester derivative of azobenzene having the structure shown in formula (III): Formula (Ⅲ), wherein, R1and R2are each independently C n H 2n+1 where n = 1-18, R is H or C m H 2m+1 wherein m is 1-6, or the B(OR)2group is a 5-membered ring or a 6-membered ring.

9. The method of claim 8, wherein, The 5-membered ring is a dioxaborolane , or .

10. The method of claim 8, wherein, The 6-membered ring is dioxaborinane .

11. The method of any one of claims 4-7, wherein, at least one of R1, R2, R3, and R4is different from the others and the bis-azo-biphenyl dye is asymmetric; or the bis-azo-biphenyl dye is symmetric and wherein R1= R3, R2= R4, R1≠ R2, or R1= R2= R3= R4.

12. The method of any one of claims 4-7, wherein, R1is C4H9, R2is C5H 11 R3is C4H9, R4is C5H 11 ; R1is C4H9, R2is C6H 13 R3is C4H9, R4is C6H 13 ; R1 is C4H9, R2 is C4H9, R3 is C5H 11 , R4 is C5H 11 ; R1is C5H 11 R2is C5H 11 R3is C5H 11 R4is C5H 11 ; or R1is C4H9, R2is C4H9, R3is C4H9, and R4is C4H9.

13. The method of any one of claims 4-7, wherein, the product of the cross-coupling reaction is purified by a combination of flash chromatography and recrystallization.

14. A thin film polarizer, wherein, The thin film polarizer comprises: a substrate; and a photo-oriented first dye layer comprising the bis-azo-biphenyl dye of any one of claims 1-3.

15. The thin film polarizer of claim 14, wherein, The substrate is a flexible substrate.

16. The thin film polarizer of claim 15, wherein, The flexible substrate is a polymeric substrate.

17. The thin film polarizer of claim 14, wherein, The photo-oriented first dye layer has a thickness of 40 nm to 1000 nm.

18. The thin film polarizer of claim 14, wherein, The thin film polarizer further comprises a protective layer on top of the photo-oriented first dye layer.

19. The thin film polarizer of claim 18, wherein, The protective layer comprises a polymer.

20. The thin film polarizer of claim 19, wherein, The polymer is a polyacrylate, a polyacrylonitrile, an epoxy resin, or a silicone resin.

21. The thin film polarizer of claim 18, wherein, The thin film polarizer further comprises a photo-oriented second dye layer on top of the protective layer.

22. The thin film polarizer of claim 21, wherein, The first and second dye layers are chemically modified photo-oriented dye layers.

23. The thin film polarizer of claim 22, wherein, The chemical modification is protonation.

24. The thin film polarizer of claim 14, wherein, The thin film polarizer has a dichroic ratio of 40-70.

25. The film polarizer according to any one of claims 14 to 24, wherein, The thin film polarizer has a haze of < 10%.

26. The thin film polarizer of claim 25, wherein, The thin film polarizer has a haze of < 3%.

27. The film polarizer according to claim 26, wherein The thin film polarizer has a haze of < 2%.

28. An apparatus for display applications, wherein, The device comprises the thin film polarizer of any one of claims 14-27.

29. The apparatus of claim 28, wherein, The device is an organic light emitting diode (OLED) display or a liquid crystal display (LCD).

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