A dark reverse dimming film

Abstract

This invention discloses a dark-colored reverse dimming film, belonging to the field of dimming film technology. It comprises an upper conductive substrate, a dark-colored reverse dimming composite layer, and a lower conductive substrate, stacked sequentially from top to bottom. The preparation method of the dark-colored reverse dimming film includes: 1) preparation of the dark-colored reverse dimming composite layer slurry; 2) thin film coating and lamination; and 3) curing. This invention employs two electric field-responsive color-tuning compounds based on stable anthraquinone fused rings. Through their broad spectral characteristics, they synergistically cover the entire visible light spectrum, achieving a deep neutral black state with only binary compounding. This fundamentally solves the color drift problem caused by the narrow spectrum and asynchronous stability of traditional three-component azobenzene color-tuning systems. Simultaneously, the color-tuning compounds possess dielectric anisotropy highly matched with microcrystalline media, enabling millisecond-level synchronous switching. This allows the device to instantly switch between a dark state when power is off and a high-transmittance state when power is on, and also exhibits excellent weather resistance and a significantly extended lifespan.

Description

Technical Field

[0001] This invention relates to the field of dimming film technology, and more particularly to a dark reverse dimming film. Background Technology

[0002] Due to its electrically controllable light transmission characteristics, PDLC dimming film is widely used in smart building curtain walls, vehicle sunroofs and other scenarios. Its core relies on the "host-guest" synergistic effect of dynamic dichroic color-tuning compounds and liquid crystals.

[0003] Existing technologies mostly use azobenzene-based color-tuning compounds, but they have significant drawbacks: First, traditional color-tuning compounds remain randomly distributed after being energized, and their transmittance is difficult to exceed 70%. The performance of the deep black state after power-off and the high transmittance state after power-on mutually restricts each other, limiting the contrast. Second, the -N=N bonds of azobenzene are prone to photo-induced cis-trans isomerization, resulting in fading and conformational distortion under long-term light exposure, causing continuous fluctuations in device performance and failing to meet the requirements for long-term outdoor use. Third, the dielectric anisotropy of azobenzene has a low matching degree with microcrystalline media, resulting in asynchronous response and residual absorption after power-on. Fourth, more than three types of azobenzene need to be compounded to achieve black, resulting in a narrow spectrum and asynchronous stability, which easily leads to color drift.

[0004] These problems severely limit the practical performance and applicable scenarios of PDLC dimming films, and there is an urgent need for new, stable and efficient dynamic dichroic color-tuning compound systems. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a dark-colored reverse dimming film.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention first proposes a dark reverse dimming film, comprising an upper conductive substrate, a dark reverse dimming composite layer, and a lower conductive substrate stacked sequentially from top to bottom;

[0008] The dark reverse dimming composite layer comprises the following components by weight of raw materials:

[0009] Main matrix material: 70-80 parts;

[0010] Bisphenol A epoxy acrylate: 20-30 parts;

[0011] 1,6-Hexanediol diacrylate: 5-15 parts;

[0012] 2,2-Dimethoxy-2-phenylacetophenone: 1.5-2.0 parts;

[0013] Electric field-responsive dynamic dichroic color-tuning compound: 0.5-1.0 parts;

[0014] KH-570 silane coupling agent: 0.5-1.0 parts;

[0015] The electric field-responsive dynamic dichroic chromatic compound is obtained by mixing 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone and 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone in a mass ratio of 1:1.1-1.4, and has the structure shown below:

[0016] [Flexible alkyl chain]-[rigid π-conjugated chromophore]-[strongly polar terminal group];

[0017] Among them, the rigid π-conjugated chromophore is an anthraquinone structure, and the strongly polar terminal group is a cyano or a fluorine atom;

[0018] The conductive substrate is an indium tin oxide-polyethylene terephthalate composite film.

[0019] Preferably, the preparation process of the electric field-responsive dynamic dichroic color-tuning compound includes the following steps:

[0020] ① Synthesis of 2-bromo-6-(1-decynyl)anthraquinone intermediate: 2,6-dibromoanthraquinone was dissolved in tetrahydrofuran with stirring, and triphenylphosphine, cuprous chloride and 1-decyn were added in sequence. Tetra(triphenylphosphine)palladium(0) was added, and the mixture was heated to 65±2℃ and reacted in the dark for 23-25 ​​h. After cooling to room temperature, the reaction was quenched by adding saturated ammonium chloride solution. After extraction with dichloromethane, the organic phases were combined, washed with saturated brine, dried over anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain 2-bromo-6-(1-decynyl)anthraquinone.

[0021] ② Synthesis of red-purple tinting compound: 2-bromo-6-(1-decynyl)anthraquinone was dissolved in tetrahydrofuran by stirring, and triphenylphosphine, cuprous chloride and 4-ethynylbenzonitrile were added in sequence. Tetra(triphenylphosphine)palladium(0) was added and heated to 70±2℃. The reaction was carried out in the dark for 34-38h. After cooling to room temperature, the reaction was quenched by adding saturated ammonium chloride solution. After extraction with dichloromethane, the organic phases were combined, washed with saturated brine, dried with anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain dark red crystals, 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone;

[0022] Both synthesis steps are based on the Pd / Cu-catalyzed Sonogashira cross-coupling reaction. The core principle is that aryl bromide (C-Br bond on the anthraquinone skeleton) and terminal alkyne (C≡CH bond of 1-decyne and 4-ethynylbenzonitrile) undergo a catalytic cycle of "oxidative addition-alkynyl transfer-reductive elimination" under the action of palladium catalyst (Pd(PPh3)4) and copper co-catalyst (CuCl) to form C(sp... 2The C≡CH triple bond connects to construct the target rigid conjugated structure. The C≡CH bond (pKa≈25) is deprotonated in an alkaline implicit environment (with the synergistic effect of triphenylphosphine and CuCl) to form a copper alkynyl intermediate, which then combines with the palladium-catalyzed aryl bromide oxidative addition product to finally generate a conjugated alkyne derivative. The conjugated system of the product is expanded (anthraquinone fused ring + alkynyl + aromatic ring) to further stabilize the product structure.

[0023] ;

[0024] The fused ring structure of anthraquinone makes the 2, 5, 6, and 8 positions active sites with low electron cloud density. The C-Br bond energy is low (≈280kJ / mol), which makes it easy to undergo oxidative addition with Pd(0). In contrast, the 9 and 10 positions of anthraquinone are carbonyl substitution sites with extremely low electron cloud density, which do not undergo coupling reactions and have strong reaction site specificity.

[0025] C introduced after 1-decyne coupling 10 The flexible long chain has a large volume, and the anthraquinone ring has a planar structure. The long chain will naturally extend in the solution and block the adjacent 6-position Br atom, which significantly reduces the probability of secondary coupling.

[0026] ;

[0027] In 4-ethynylbenzonitrile, the alkynyl group is attached to the benzene ring. The planar structure of the benzene ring allows the cyano group to extend outward, preventing significant stereorepulsion with the anthraquinone skeleton or decyl chain. During coupling, the molecular conformation can be adaptively adjusted without affecting the catalytic cycle.

[0028] ③ Synthesis of blue-green tinting compound: 2-bromo-6-(1-decynyl)anthraquinone was dissolved in tetrahydrofuran by stirring, and triphenylphosphine, cuprous chloride and 4-(trifluoromethyl)phenylacetylene were added in sequence. Tetra(triphenylphosphine)palladium(0) was added and heated to 70±2℃. The reaction was carried out in the dark for 34-38h. After cooling to room temperature, the reaction was quenched by adding saturated ammonium chloride solution. After extraction with dichloromethane, the organic phases were combined, washed with saturated brine, dried with anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain blue-green crystals, 2-(p-trifluoromethylphenylacetyl)-6-(1-decynyl)anthraquinone;

[0029] Similarly, coupling 2-bromo-6-(1-decynyl)anthraquinone with 4-(trifluoromethyl)phenylacetylene yields 2-(p-trifluoromethylphenylacetyl)-6-(1-decynyl)anthraquinone, which serves as a blue-green tinting compound.

[0030] ;

[0031] Preferably, in the preparation process of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2,6-dibromoanthraquinone, triphenylphosphine, cuprous chloride, 1-decyne, and tetra(triphenylphosphine)palladium(O) is 13.5-14:1:1.2-1.8:22.5-23:0.5; and the molar ratio of 2-bromo-6-(1-decyneyl)anthraquinone, triphenylphosphine, cuprous chloride, 1-decyne, and tetra(triphenylphosphine)palladium(O) is 6-6.5:0.5:0.7-0.8:11-11.5:0.25.

[0032] Preferably, in the preparation process of the electric field-responsive dynamic dichroic color-tuning compound, all steps are carried out under yellow light conditions to ensure an anhydrous and oxygen-free environment, and tetra(triphenylphosphine)palladium(O) is used as a catalyst, and the compound is prepared and used immediately.

[0033] This invention also proposes a method for preparing a dark-colored reverse dimming film, comprising the following steps:

[0034] S1. Preparation of dark-colored reverse dimming composite layer slurry

[0035] At 38-42℃, the main matrix material and the electric field-responsive dynamic dichroic color-tuning compound are stirred and mixed to ensure that the color-tuning compound is completely dissolved and uniformly dispersed in the microcrystalline medium to form a uniform dark solution. Bisphenol A epoxy acrylate, 1,6-hexanediol diacrylate and KH-570 silane coupling agent are added in sequence, and stirring is continued for 1.8-2.2h. 2,2-dimethoxy-2-phenylacetophenone and N,N-dimethylformamide are added, and the mixture is stirred in the dark for 1-1.5h until it is completely mixed and uniform. Vacuum degassing is performed to obtain the dark reverse light-tuning composite layer slurry.

[0036] S2, Thin film coating and lamination

[0037] Take an indium tin oxide-polyethylene terephthalate composite film with the indium tin oxide side facing up, and evenly coat the dark reverse light-modulating composite layer paste on the indium tin oxide side. Then, place another indium tin oxide-polyethylene terephthalate composite film with the indium tin oxide side facing down on the coated paste and send it into a roller laminator for lamination.

[0038] S3, solidification

[0039] The laminated film has a strength of 5-20 mW / cm 2 Irradiation with 365nm wavelength light for 30 seconds; light intensity increased to 50mW / cm². 2 Continue irradiation for 5-6 minutes to complete curing, then age at 55-65℃ for 28-32 minutes to obtain a dark reverse dimming film.

[0040] Preferably, in S1, the solid content of the dark reverse dimming composite layer slurry is 97±1%.

[0041] Preferably, in step S2, the thickness of the coated wet film is controlled at 50±2μm, and the final film thickness after lamination is 20±2μm.

[0042] The electric field-responsive dynamic dichroism of small molecules designed in this invention is essentially the synergistic effect of optical anisotropy endowed by molecular structure and orientation change induced by electric field. The electric field drives the molecules to align through dielectric interactions, thereby changing their absorption characteristics of incident light, and ultimately achieving a dynamic optical effect of "blocking light when power is off and becoming transparent when power is on".

[0043] The molecule has a slender, rigid π-conjugated structure. The electron cloud is highly delocalized along the long axis of the molecule, while electron transitions are restricted along the short axis, resulting in significant anisotropy of the electronic transition dipole moment. It has a high probability of electron transition and strong absorption for polarized light parallel to the long axis of the molecule, while it has a low probability of electron transition and extremely weak absorption for polarized light perpendicular to the long axis of the molecule. It has a large dichroism ratio, which provides an optical basis for macroscopic light blocking and transmission switching. At the same time, the rigid structure can avoid the destruction of electron cloud delocalization caused by molecular folding or twisting, ensuring that the dichroism does not decay.

[0044] The linear molecular structure makes the electron cloud along the long axis more easily polarized by the electric field. The strong electron-withdrawing groups at the ends (cyano-CN, fluorine atom) enhance the molecular dipole moment. The dielectric interaction along the long axis is stronger in the electric field. The dielectric constant (ε∥) along the long axis of the molecule is much larger than that along the short axis (ε⊥), which is positive dielectric anisotropy. Therefore, the electric field can drive the molecular orientation.

[0045] An electric field drives molecular orientation through dielectric torque. In the absence of an electric field, the color-correcting compound molecules are randomly distributed within the microcrystalline medium, with their long axes pointing in arbitrary directions, and are oriented through flexible terminal alkyl chains (C...). 10 It exhibits good compatibility with microcrystalline medium molecules, without aggregation; due to the dichroism of the molecules, the randomly arranged toning compound molecules cover all polarization directions of incident light. Regardless of the direction of light incidence, a large number of toning compound molecules have their long axes parallel to the polarization direction of the light, resulting in strong absorption and a macroscopic appearance of a uniform dark color; when an electric field is applied, the electric field generates dielectric torque on the toning compound molecules, causing the long axes of the molecules to spontaneously align with the direction of the electric field, bringing the system to its lowest energy state, and ultimately aligning synchronously with the microcrystalline medium molecules along the direction of the electric field; combined with the high light transmittance of the microcrystalline medium molecules after oriented alignment, the light transmittance of the entire system can reach over 85%, achieving a "transparent" effect.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] 1. Traditional static color-correcting compounds maintain a random distribution after being energized, their light absorption characteristics remain unchanged, and their transmittance is difficult to exceed 70%, severely affecting the visual clarity and lighting effect in the transparent state. Therefore, their transmittance when energized and when de-energized are mutually restrictive; increasing the depth in the de-energized state often further sacrifices the transmittance in the energized state, and vice versa, resulting in limited contrast. In the color-correcting compound of this invention, the molecules in the de-energized state are randomly distributed, and their strong dichroism ensures that they can absorb light indiscriminately from all directions, thereby obtaining a deep and uniform dark state; in the energized state, after applying an electric field, driven by dielectric torque, their long axis is synchronously aligned with the microcrystalline medium molecules along the direction of the electric field. When the molecular long axis is parallel to the direction of light propagation, its absorption cross section for normally incident light is minimized, and the transmittance of the system is greatly improved.

[0048] 2. Traditional azobenzene tinting compounds suffer from photoinduced cis-trans isomerization, leading to fading and loss of color under prolonged light exposure. The photoinstability of existing azobenzene tinting compounds stems from the inherent characteristics of the -N=N- bonds in their molecular structure. The π-electron cloud of the azo bond is easily excited by visible / ultraviolet light, resulting in a decrease in the N=N bond order (transition from double to single bond) and an increase in bond length (from 1.25 Å to 1.35 Å). The molecule can freely twist around the N=N bond, undergoing a "trans → cis" isomerization. Isomerization; the cis conformation is a curved structure (the ratio of the long axis to the short axis of the molecule decreases from 4:1 to 2:1), which not only destroys dichroism (cis ε∥ / ε⊥<5, trans>10), leading to fading, but also causes performance failures such as decreased light transmittance and enhanced scattering due to the inability to coordinate with the molecules of the microcrystalline medium due to conformational distortion. Its thermal relaxation process (cis→trans) is slow and irreversible (half-life of hours to days), resulting in continuous fluctuations in device performance, which cannot meet the requirements for long-term outdoor use.

[0049] This invention selects anthraquinone as the rigid chromophore of the chromogenic compound. The fused ring structure of anthraquinone has extremely high photochemical inertness, and its excited state energy is dissipated in the form of heat through efficient intersystem crossing, making it difficult to decompose or isomerize. Anthraquinone has a planar rigid fused ring structure (three benzene rings conjugated and fused), and its π electron cloud is highly delocalized (the delocalization range covers the entire fused ring). After photoexcitation, electronic transitions only occur between π-π orbitals, and there is no change in the bond order of the molecular skeleton (the C-C bond length remains at 1.40-1.45 Å), so conformational torsion cannot occur. The thermodynamic stability of the fused ring structure is extremely high (bond energy > 400 kJ / mol, far exceeding the 250 kJ / mol of azo bonds). After photoexcitation, there is no skeleton breakage or reconstruction, only a transient electronic excited state is generated, which is then returned to the ground state through radiative transition, without irreversible structural changes. The strong electron-withdrawing effect of the terminal cyano / fluorine atom further stabilizes the π electron cloud of the fused ring and reduces the probability of photo-oxidation reaction (the photodegradation of azobenzene is mainly photo-oxidation, while the photodegradation rate of anthraquinone is only 1 / 100 of that of azobenzene).

[0050] 3. The orientation of the existing azobenzene tinting compound is asynchronous with that of the microcrystalline medium. The conjugated system of azobenzene is too large (molecular length > 20 Å), and the delocalization range of the π electron cloud is wide, resulting in a decrease in the anisotropy of molecular polarizability (α∥-α⊥). Furthermore, the polarity of the azo bond is weakened by the conjugated system, and the molecular dipole moment (μ) is only 3-5 D, with a dielectric anisotropy Δε = 8-10. The Δε of the microcrystalline medium is approximately 13, and the difference in Δε between the tinting compound and the microcrystalline medium is > 3. Under the influence of an electric field, the dielectric torque (τ∝Δε) is significantly increased. E 2 Mismatch: The microcrystalline medium molecules orient rapidly (response time 30ms), while the chromogenic compound molecules, due to insufficient dielectric torque, rotate slowly (response time > 100ms). This results in an asynchronous phenomenon where the microcrystalline medium orients while the chromogenic compound remains in a random state, leading to residual absorption in the energized state and a transmittance < 70%. The chromogenic compound molecule designed in this invention, featuring a "rigid fused ring + polar group," has an anthraquinone skeleton with a linear rigid structure (molecular length 18-19 Å, matching the 19.2 Å length of the microcrystalline medium molecules). The delocalization range of the π electron cloud is controllable (covering only the fused ring + alkynyl group + benzene ring), and the polarizability is anisotropic (α∥-α⊥ = 10). -39 F m 2 The value was significantly higher than that of azobenzene (α∥-α⊥=5×10). -40 F m 2 The dipole moment of the terminal cyano group (-CN) (3.6D) / -CF3 (2.3D) synergistically superimposes with the dipole moment of the anthraquinone skeleton (3.0D), resulting in a total molecular dipole moment μ=6.6D / 5.3D, far exceeding that of azobenzene, making the dielectric anisotropy Δε=12-15, with a difference of <2 from that of microcrystalline media; the small molecular structure (molecular weight 500-600Da) has a low moment of inertia (≈10). -45 kg m 2 Under an electric field, the dielectric torque is sufficient to drive the molecules to orient rapidly (response time < 40 ms).

[0051] 4. Existing technologies require the combination of more than three azobenzene tinting compounds to achieve neutral dark gray / black, resulting in narrow spectral absorption and inconsistent stability. The conjugated system of azobenzene is a "double benzene ring + N=N bond," and its absorption spectrum only covers a single wavelength band (yellow / orange / red, λmax=450-550nm), requiring a three-component combination of "red + green + blue" to complete the 400-700nm visible light spectrum. Different azobenzene derivatives exhibit significant differences in photostability (e.g., the methyl-substituted type has a half-life of 100h, while the unsubstituted type only has 50h), leading to preferential fading of some components after long-term irradiation, resulting in spectral absorption imbalance and color shift (from dark gray to more yellow / reddish). In contrast, the anthraquinone fused-ring conjugated system of this invention is a "tri-benzene ring fusion structure," with a wide π-electron cloud delocalization range. By combining two tinting compounds, their absorption spectra can synergistically cover the entire visible light band, achieving a deep neutral black state.

[0052] In summary, this invention employs two electric field-responsive color-tuning compounds based on stable anthraquinone fused rings. Their broad spectral characteristics synergistically cover the entire visible light spectrum, requiring only binary compounding to achieve a deep neutral black state. This fundamentally solves the color drift problem caused by the narrow spectrum and asynchronous stability of traditional three-component azobenzene color-tuning compound systems. Simultaneously, the color-tuning compound molecules possess dielectric anisotropy highly matched to the microcrystalline medium, enabling millisecond-level synchronous flipping. This allows the device to instantly switch between a dark state when power is off and a high-transmittance state when power is on, and also exhibits excellent weather resistance and a significantly extended lifespan. Attached Figure Description

[0053] Figure 1 The 1H NMR spectrum of 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone proposed in this invention;

[0054] Figure 2 The 1H NMR spectrum of 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone proposed in this invention. Detailed Implementation

[0055] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0056] Preparation Example 1: The preparation process of an electric field-responsive dynamic dichroic color-correcting compound includes the following steps:

[0057] ① Synthesis of 2-bromo-6-(1-decynyl)anthraquinone intermediate: 2,6-dibromoanthraquinone was dissolved in tetrahydrofuran with stirring, and triphenylphosphine, cuprous chloride and 1-decyn were added in sequence. Tetra(triphenylphosphine)palladium(0) was added, and the mixture was heated to 65°C and reacted in the dark for 24 h. After cooling to room temperature, the reaction was quenched by adding saturated ammonium chloride solution. After extraction with dichloromethane, the organic phases were combined, washed with saturated brine, dried over anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain 2-bromo-6-(1-decynyl)anthraquinone.

[0058] ② Synthesis of red-purple tinting compound: 2-bromo-6-(1-decynyl)anthraquinone was dissolved in tetrahydrofuran by stirring, and triphenylphosphine, cuprous chloride and 4-ethynylbenzonitrile were added in sequence. Tetra(triphenylphosphine)palladium(0) was added and heated to 70°C. The reaction was carried out in the dark for 36 h. After cooling to room temperature, the reaction was quenched by adding saturated ammonium chloride solution. After extraction with dichloromethane, the organic phases were combined, washed with saturated brine, dried with anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain dark red crystals, 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone;

[0059] A portion of 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone was taken, purified, dissolved in dimethyl sulfoxide, and analyzed by 1H NMR spectroscopy. The results are as follows: Figure 1 As shown:

[0060] The peaks in the aromatic hydrogen region (δ = 7.0–8.0 ppm, peaks on the left side of the figure) correspond to hydrogens on the conjugated aromatic rings, hydrogens on the anthraquinone fused rings, and hydrogens on the benzene ring of "4-cyanophenyl". Due to their π-conjugated system, the chemical shifts of these hydrogens are in the range of 7.5–8.0 ppm. The peaks in the aliphatic hydrogen region (δ = 1.0–3.0 ppm, peaks on the right side of the figure) correspond to the decyl long chain (-C 10 H 21 The methylene (-CH2-) hydrogen of the alkynyl group; the -CH2- (δ≈2.5ppm) near the alkynyl group has a slightly higher chemical shift due to the deshielding effect of the π electron cloud; the -CH2- (δ≈1.0~2.0ppm) far from the alkynyl group is in the saturated region of the long-chain alkyl group and has a lower chemical shift; the aromatic hydrogen peaks are concentrated in 7.0~8.0ppm, and the alkyl hydrogen peaks are concentrated in 1.0~3.0ppm, which conforms to the molecular structure of "anthraquinone-alkynyl-benzonitrile-decyl".

[0061] ③ Synthesis of blue-green tinting compound: 2-bromo-6-(1-decynyl)anthraquinone was dissolved in tetrahydrofuran by stirring, and triphenylphosphine, cuprous chloride and 4-(trifluoromethyl)phenylacetylene were added in sequence. Tetra(triphenylphosphine)palladium(0) was added and heated to 70°C. The reaction was carried out in the dark for 36 h. After cooling to room temperature, the reaction was quenched by adding saturated ammonium chloride solution. After extraction with dichloromethane, the organic phases were combined, washed with saturated brine, dried with anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain blue-green crystals, 2-(p-trifluoromethylphenylacetyl)-6-(1-decynyl)anthraquinone;

[0062] A portion of 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone was taken, purified, dissolved in dimethyl sulfoxide, and analyzed by 1H NMR spectroscopy. The results are as follows: Figure 2 As shown:

[0063] Unlike 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone, 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone has a strong electron-withdrawing group -CF3, which enhances the deshielding effect of the benzene ring hydrogens, resulting in a slightly higher chemical shift of the aromatic hydrogens of 4-(trifluoromethyl)phenyl than that of ordinary benzene ring hydrogens, also falling in the 7.0–8.0 ppm region; the aromatic hydrogens of the fused ring of anthraquinone are in a large π-conjugated system, subject to deshielding, with chemical shifts concentrated in the 7.5–8.0 ppm region; the decyl long chain (-C 10 H 21 The saturated methylene (-CH2-) hydrogens of the alkyl group are deshielded by the π electron cloud of the alkyl group, resulting in a slightly higher chemical shift. The hydrogens farther from the alkyl group are in a weakly shielded environment of the saturated alkyl group, with chemical shifts concentrated in the range of 1.0–2.0 ppm. The peak shape is a characteristic multiplet of long-chain alkyl groups. In summary, the chemical shifts, integrals, and peak shapes of this ¹H NMR spectrum are consistent with the molecular structure of “2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone”.

[0064] ④ Mix 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone and 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone at a mass ratio of 1:1.1 to form an electric field-responsive dynamic dichroic color-tuning compound.

[0065] In the preparation of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2,6-dibromoanthraquinone, triphenylphosphine, cuprous chloride, 1-decyne and tetra(triphenylphosphine)palladium(0) is 14:1:1.2:23:0.5.

[0066] In the preparation of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2-bromo-6-(1-decynyl)anthraquinone, triphenylphosphine, cuprous chloride, 4-ethynylbenzonitrile, and tetrakis(triphenylphosphine)palladium(0) is 6:0.5:0.8:11:0.25.

[0067] In the preparation of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2-bromo-6-(1-decynyl)anthraquinone, triphenylphosphine, cuprous chloride, 4-(trifluoromethyl)phenylacetylene and tetra(triphenylphosphine)palladium(0) is 6.5:0.5:0.7:11.5:0.25.

[0068] In the preparation of the electric field-responsive dynamic dichroic color-tuning compound, all steps are carried out under yellow light conditions to ensure an anhydrous and oxygen-free environment. Tetra(triphenylphosphine)palladium(0) is used as the catalyst and is prepared and used immediately.

[0069] Preparation Example 2: The experimental scheme is the same as that in Preparation Example 1, but in the preparation of the electric field responsive dynamic dichroic color-correcting compound, the molar ratio of 2,6-dibromoanthraquinone, triphenylphosphine, cuprous chloride, 1-decyne and tetra(triphenylphosphine)palladium(0) is 13.75:1:1.25:22.75:0.5.

[0070] In the preparation of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2-bromo-6-(1-decynyl)anthraquinone, triphenylphosphine, cuprous chloride, 4-ethynylbenzonitrile, and tetrakis(triphenylphosphine)palladium(0) is 6-6.5:0.5:0.7-0.8:11-11.5:0.25.

[0071] In the preparation of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2-bromo-6-(1-decynyl)anthraquinone, triphenylphosphine, cuprous chloride, 4-(trifluoromethyl)phenylacetylene and tetra(triphenylphosphine)palladium(O) is 6-6.5:0.5:0.7-0.8:11-11.5:0.25.

[0072] The electric field-responsive dynamic dichroic color-tuning compound is obtained by mixing 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone and 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone in a mass ratio of 1:1.25.

[0073] Preparation Example 3: The experimental scheme is the same as that in Preparation Example 1, but in the preparation of the electric field responsive dynamic dichroic color-correcting compound, the molar ratio of 2,6-dibromoanthraquinone, triphenylphosphine, cuprous chloride, 1-decyne and tetra(triphenylphosphine)palladium(0) is 13.5:1:1.8:22.5:0.5.

[0074] In the preparation of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2-bromo-6-(1-decynyl)anthraquinone, triphenylphosphine, cuprous chloride, 4-ethynylbenzonitrile, and tetrakis(triphenylphosphine)palladium(0) is 6.5:0.5:0.7:11.5:0.25.

[0075] In the preparation of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2-bromo-6-(1-decynyl)anthraquinone, triphenylphosphine, cuprous chloride, 4-(trifluoromethyl)phenylacetylene and tetra(triphenylphosphine)palladium(0) is 6:0.5:0.8:11:0.25.

[0076] The electric field-responsive dynamic dichroic color-tuning compound is obtained by mixing 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone and 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone in a mass ratio of 1:1.4.

[0077] Example 1: A method for preparing a dark-colored reverse dimming film, comprising the following steps:

[0078] S1. Preparation of dark-colored reverse dimming composite layer slurry

[0079] At 40°C, 70 kg of the main matrix material and 0.5 kg of the electric field-responsive dynamic dichroic color-tuning compound obtained in Preparation Example 3 were stirred and mixed to ensure that the color-tuning compound was completely dissolved and uniformly dispersed in the microcrystalline medium to form a uniform dark solution. 30 kg of bisphenol A epoxy acrylate, 5 kg of 1,6-hexanediol diacrylate and 1.0 kg of KH-570 silane coupling agent were added sequentially, and stirring was continued for 2 h. 2.0 kg of 2,2-dimethoxy-2-phenylacetophenone and N,N-dimethylformamide were added, and the mixture was stirred in the dark for 1 h until it was completely mixed and homogeneous. Vacuum degassing was performed to obtain a dark reverse light-tuning composite layer slurry.

[0080] S2, Thin film coating and lamination

[0081] Take an indium tin oxide-polyethylene terephthalate composite film with the indium tin oxide side facing up, and evenly coat the dark reverse light-modulating composite layer paste on the indium tin oxide side. Then, place another indium tin oxide-polyethylene terephthalate composite film with the indium tin oxide side facing down on the coated paste and send it into a roller laminator for lamination.

[0082] S3, solidification

[0083] The laminated film has a strength of 5-20 mW / cm 2 Irradiation with 365nm wavelength light for 30 seconds; light intensity increased to 50mW / cm². 2 Continue irradiation for 5 minutes to complete curing, then age at 60℃ for 30 minutes to obtain a dark reverse dimming film.

[0084] In S1, the solid content of the dark reverse dimming composite layer slurry is 97±1%.

[0085] In step S2, the thickness of the wet film is controlled at 50±2μm, and the final film thickness after lamination is 20±2μm.

[0086] Example 2: The experimental scheme is the same as in Example 1, but in S1, the dark reverse dimming composite layer slurry includes:

[0087] Main substrate material: 75kg;

[0088] Bisphenol A epoxy acrylate: 205 kg;

[0089] 1,6-Hexanediol diacrylate: 10 kg;

[0090] 2,2-Dimethoxy-2-phenylacetophenone: 1.75 kg;

[0091] The electric field-responsive dynamic dichroic color-tuning compound obtained in Example 2: 0.75 kg;

[0092] KH-570 silane coupling agent: 0.75 kg.

[0093] Example 3: The experimental scheme is the same as in Example 1, but in S1, the dark reverse dimming composite layer slurry includes:

[0094] Main matrix material: 80kg;

[0095] Bisphenol A epoxy acrylate: 20kg;

[0096] 1,6-Hexanediol diacrylate: 15 kg;

[0097] 2,2-Dimethoxy-2-phenylacetophenone: 1.5 kg;

[0098] Preparation of the electric field-responsive dynamic dichroic color-tuning compound obtained in Example 1: 1.0 kg;

[0099] KH-570 silane coupling agent: 0.5kg.

[0100] Based on this, the following design was also created:

[0101] Comparative Example 1: Based on Preparation Example 2, the difference is that the mass ratio of 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone to 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone is 1:0.5, and the rest is the same as in Example 2.

[0102] Comparative Example 2: Based on Preparation Example 2, the difference is that the mass ratio of 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone to 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone is 1:2, and the rest is the same as in Example 2.

[0103] Comparative Example 3: Based on Preparation Example 2, the difference is that 2,6-dibromoanthraquinone was used directly in the synthesis of the color-correcting compound instead of the 2-bromo-6-(1-decynyl)anthraquinone intermediate, i.e. the final molecule does not have a flexible alkyl chain, and the rest is the same as in Example 2.

[0104] Comparative Example 4: Based on Preparation Example 2, the difference is that 2-bromo-6-(1-decynyl)anthraquinone intermediate was used directly, without the synthesis of color-correcting compounds, that is, the final molecule does not have a strongly polar terminal group, otherwise it is the same as Example 2.

[0105] Comparative Example 5: Based on Example 2, the difference is that existing tri-color azobenzene toning compounds are used, and no toning compound synthesis is performed; otherwise, it is the same as Example 2.

[0106] For each embodiment and comparative example, the dimming film of the present invention was tested according to GB / T 35847-2018 Electro-liquid crystal film dimming glass; GB / T 31370.5-2018 Flat panel display (FPD) color filter test method part 5: contrast ratio; GB / T 1040.3-2006 Determination of tensile properties of plastics part 3: Test strips for thin plastics and sheets; ASTM D7791-12 Standard test method for uniaxial fatigue properties of plastics, etc., and the driving voltage (threshold voltage Vth, saturation voltage Vsat), contrast ratio (CR), response time (on-ton, off-toff), transmittance (on-state T-on, off-state T-off), and other related properties. The corresponding results are shown in Table 1.

[0107] Table 1. Performance test data of the dimming film

[0108]

[0109] Data Analysis:

[0110] The driving voltage, especially the threshold voltage (Vth), directly reflects the ease with which the orientation of the microcrystalline medium and the toning compound molecules reverses under an electric field.

[0111] The driving voltage of the examples (Vth: 2.8-3.5V) was significantly lower than that of Comparative Example 4 (Vth: 8.2V). The tinting compound molecules of Comparative Example 4 lacked strongly polar end groups (such as -CN or -CF3), resulting in extremely low dielectric anisotropy (Δε). In an electric field, such molecules cannot generate sufficient dielectric torque to overcome the energy barrier of random thermal motion, making orientation reversal difficult and requiring a higher external electric field, manifested as a sharp increase in driving voltage. This mechanistically confirms the indispensability of strongly polar end groups for reducing driving voltage.

[0112] The driving voltage in the examples was also significantly lower than that in Comparative Example 3 (Vth: 6.5V). The tinting compound molecules in Comparative Example 3 lacked flexible decyl chains; their rigid structure exhibited poor compatibility within the microcrystalline medium, easily forming aggregation points and generating significant steric hindrance. These aggregation points hindered the rotation of surrounding microcrystalline medium molecules and could potentially create defects in the polymer network, increasing the rotational viscosity of the entire system and consequently raising the driving voltage. This indicates that flexible alkyl chains, by enhancing compatibility and reducing steric hindrance, act as molecular lubricants, which is crucial for achieving low-voltage driving.

[0113] Response time, especially the turn-off time (t-off), depends on the relaxation rate of the molecule as it recovers from an ordered state to a disordered state. This process is influenced by both the molecule's structural inertia and the viscosity of the environment.

[0114] The turn-off time of the examples (42.1-47.6 ms) was much faster than that of Comparative Example 3 (78.5 ms) and Comparative Example 4 (95.3 ms). For Comparative Example 4, due to the weak electric field responsiveness of its tinting compound molecules, there was a lack of sufficient recovery driving force (mainly relying on molecular thermal motion) after the electric field was removed, resulting in an extremely slow relaxation process from ordered arrangement to a disordered state. For Comparative Example 3, the rigid and poorly compatible tinting compound molecules acted as "impurity" points, significantly increasing the local viscosity of the system and also severely delaying the relaxation process. The flexible alkyl chains in the tinting compound molecules of this invention effectively reduced the environmental viscosity, while the intermolecular interactions brought about by the strongly polar groups also contributed to a more ordered initial arrangement, thus enabling faster synergistic relaxation after power removal.

[0115] Thanks to its optimized molecular structure, it can complete the coordinated arrangement more quickly under an electric field, and the examples show a faster response in terms of turn-on time (35.8-40.3ms).

[0116] Contrast ratio (CR) is the ratio of transmittance in the on state (T-on) to transmittance in the off state (T-off), and it is a core indicator for measuring the performance of dimming films.

[0117] The on-state transmittance (T-on) of the embodiments (82.8-85.5%) is higher than that of all comparative examples, directly proving that the toning compound molecules of the present invention can achieve a highly consistent directional alignment under an electric field, minimizing their absorption cross-section to normally incident light, thereby achieving electric field stealth. Comparative examples 3, 4, and 5, due to the aforementioned incomplete response, aggregation scattering, and other problems, cannot achieve the same level of transmittance.

[0118] The examples, particularly Example 2 (T-off: 0.58%, CR: 147.4), demonstrated optimal opacity and contrast. Comparative Example 1 (red-violet: blue-green = 1:0.5, T-off: 0.95%, CR: 89.3) and Comparative Example 2 (1:2, T-off: 0.82%, CR: 101.3) showed a significant decrease in performance, a phenomenon stemming from incomplete complementary absorption spectra. When the toning compound ratio is unbalanced, uniform and strong absorption cannot be achieved across the entire visible light range (380-780 nm). Leakage always occurs in certain wavelengths, such as the lack of blue-green absorption in Comparative Example 1 and the lack of red-violet absorption in Comparative Example 2, leading to increased off-state transmittance and decreased contrast. The 1:1.25 mass ratio of Example 2 proved to be close to optimal, achieving the broadest and most balanced absorption, resulting in a deep neutral black.

[0119] Comparative Example 5 (T-off: 1.58%, CR: 50.7) used a traditional azobenzene chromophore compound, exhibiting the highest transmittance and lowest contrast in the off-state. This is primarily attributed to the photochemical instability of the azobenzene chromophore compound. During processing or testing, some azobenzene molecules may have undergone photoinduced cis-trans isomerization, transforming from a highly absorbent trans structure to a less absorbent cis structure, resulting in a significant decrease in its overall light absorption performance (especially its blocking ability in the off-state), thus highlighting the necessity of using stable chromophores such as anthraquinones.

[0120] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A dark-colored reverse dimming film, characterized in that, It includes an upper conductive substrate, a dark reverse dimming composite layer, and a lower conductive substrate, which are stacked from top to bottom; The dark reverse dimming composite layer comprises the following components by weight of raw materials: Main matrix material: 70-80 parts; Bisphenol A epoxy acrylate: 20-30 parts; 1,6-Hexanediol diacrylate: 5-15 parts; 2,2-Dimethoxy-2-phenylacetophenone: 1.5-2.0 parts; Electric field-responsive dynamic dichroic color-tuning compound: 0.5-1.0 parts; KH-570 silane coupling agent: 0.5-1.0 parts; The electric field-responsive dynamic dichroic color-tuning compound is obtained by mixing 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone and 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone in a mass ratio of 1:1.1-1.4; The structure of 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone is shown below: ； The structure of 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone is shown below: ； The conductive substrate is an indium tin oxide-polyethylene terephthalate composite film; The main matrix material is a homogeneous mixture of liquid crystal materials with more than 10 monomer molecular structures that are compatible at the molecular level.

2. The dark-colored reverse dimming film according to claim 1, characterized in that, The preparation process of the electric field-responsive dynamic dichroic color-tuning compound includes the following steps: ① Synthesis of 2-bromo-6-(1-decynyl)anthraquinone intermediate: 2,6-Dibromoanthraquinone was dissolved in tetrahydrofuran with stirring. Triphenylphosphine, cuprous chloride, and 1-decynyl were added sequentially, followed by tetra(triphenylphosphine)palladium(0). The mixture was heated to 65±2℃ and reacted in the dark for 23-25 ​​h. After cooling to room temperature, the reaction was quenched with saturated ammonium chloride solution. The mixture was extracted with dichloromethane, and the organic phases were combined, washed with saturated brine, dried over anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain 2-bromo-6-(1-decynyl)anthraquinone, the structure of which is shown below: ； ② Synthesis of red-purple tinting compound: 2-bromo-6-(1-decynyl)anthraquinone was dissolved in tetrahydrofuran by stirring, and triphenylphosphine, cuprous chloride and 4-ethynylbenzonitrile were added in sequence. Tetra(triphenylphosphine)palladium(0) was added and heated to 70±2℃. The reaction was carried out in the dark for 34-38h. After cooling to room temperature, the reaction was quenched by adding saturated ammonium chloride solution. After extraction with dichloromethane, the organic phases were combined, washed with saturated brine, dried with anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain dark red crystals, 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone; ③ Synthesis of blue-green tinting compound: 2-bromo-6-(1-decynyl)anthraquinone was dissolved in tetrahydrofuran by stirring, and triphenylphosphine, cuprous chloride and 4-(trifluoromethyl)phenylacetylene were added in sequence. Tetra(triphenylphosphine)palladium(0) was added and heated to 70±2℃. The reaction was carried out in the dark for 34-38h. After cooling to room temperature, the reaction was quenched by adding saturated ammonium chloride solution. After extraction with dichloromethane, the organic phases were combined, washed with saturated brine, dried with anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain blue-green crystals, 2-(p-trifluoromethylphenylacetyl)-6-(1-decynyl)anthraquinone; ④ Mix 2-(p-cyanophenylethynyl)-6-(1-decynyl)anthraquinone and 2-(p-trifluoromethylphenylethynyl)-6-(1-decynyl)anthraquinone evenly to obtain an electric field-responsive dynamic dichroic color-tuning compound.

3. The dark-colored reverse dimming film according to claim 2, characterized in that, In step ① of the preparation process of the electric field-responsive dynamic dichroic color-correcting compound, the molar ratio of 2,6-dibromoanthraquinone, triphenylphosphine, cuprous chloride, 1-decyne and tetra(triphenylphosphine)palladium(0) is 13.5-14:1:1.2-1.8:22.5-23:0.

5.

4. A dark-colored reverse dimming film according to claim 2, characterized in that, In step ② of the preparation process of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2-bromo-6-(1-decynyl)anthraquinone, triphenylphosphine, cuprous chloride, 4-ethynylbenzonitrile and tetrakis(triphenylphosphine)palladium(0) is 6-6.5:0.5:0.7-0.8:11-11.5:0.

25.

5. A dark-colored reverse dimming film according to claim 2, characterized in that, In step ③ of the preparation process of the electric field-responsive dynamic dichroic color-tuning compound, the molar ratio of 2-bromo-6-(1-decynyl)anthraquinone, triphenylphosphine, cuprous chloride, 4-(trifluoromethyl)phenylacetylene and tetra(triphenylphosphine)palladium(0) is 6-6.5:0.5:0.7-0.8:11-11.5:0.

25.

6. A dark-colored reverse dimming film according to claim 2, characterized in that, In the preparation of the electric field-responsive dynamic dichroic color-tuning compound, all steps are carried out under yellow light conditions to ensure an anhydrous and oxygen-free environment. Tetra(triphenylphosphine)palladium(0) is used as the catalyst and is prepared and used immediately.

7. A method for preparing a dark-colored reverse dimming film as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Preparation of dark-colored reverse dimming composite layer slurry At 38-42℃, the main matrix material and the electric field-responsive dynamic dichroic color-tuning compound are stirred and mixed to ensure that the color-tuning compound is completely dissolved and uniformly dispersed in the microcrystalline medium to form a uniform dark solution. Bisphenol A epoxy acrylate, 1,6-hexanediol diacrylate and KH-570 silane coupling agent are added in sequence, and stirring is continued for 1.8-2.2h. 2,2-dimethoxy-2-phenylacetophenone and N,N-dimethylformamide are added, and the mixture is stirred in the dark for 1-1.5h until it is completely mixed and uniform. Vacuum degassing is performed to obtain the dark reverse light-tuning composite layer slurry. S2, Thin film coating and lamination Take an indium tin oxide-polyethylene terephthalate composite film with the indium tin oxide side facing up, and evenly coat the dark reverse light-modulating composite layer paste on the indium tin oxide side. Then, place another indium tin oxide-polyethylene terephthalate composite film with the indium tin oxide side facing down on the coated paste and send it into a roller laminator for lamination. S3, solidification The laminated film has a strength of 5-20 mW / cm 2 Irradiation with 365nm wavelength light for 30 seconds; light intensity increased to 50mW / cm². 2 Continue irradiation for 5-6 minutes to complete curing, then age at 55-65℃ for 28-32 minutes to obtain a dark reverse dimming film.

8. The method for preparing a dark-colored reverse dimming film according to claim 7, characterized in that, In S1, the solid content of the dark reverse dimming composite layer slurry is 97±1%.

9. The method for preparing a dark-colored reverse dimming film according to claim 7, characterized in that, In step S2, the thickness of the wet film is controlled at 50±2μm, and the final film thickness after lamination is 20±2μm.

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