Water-oxygen barrier coating for flexible OLED and flexible OLED packaging film

Abstract

The application discloses a water-oxygen barrier coating for flexible OLED and a flexible OLED packaging film. The coating comprises pressure-sensitive adhesive, barrier filler and hydrophobic modifier; the hydrophobic modifier is prepared from hydrogen-terminated polysiloxane, vinyl silane coupling agent, tetramethylcyclotetrasiloxane and unsaturated alkenyl monomer with a molar ratio of 1:2-2.2:7-12:7-13; the hydrogen-terminated polysiloxane and the vinyl silane coupling agent are subjected to hydrosilylation to obtain a first intermediate, then the first intermediate is subjected to ring-opening polymerization with the tetramethylcyclotetrasiloxane to obtain a second intermediate, then the second intermediate is subjected to hydrosilylation with the unsaturated alkenyl monomer to obtain the hydrophobic modifier; the unsaturated alkenyl monomer comprises epoxy acrylate monomer and alkenyl sulfonate monomer with a molar mass ratio of 2-3:2-4. The OLED packaging film has high flexibility and low water-oxygen permeability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of OLED packaging, in particular to a water and oxygen barrier coating for flexible OLED and a flexible OLED packaging film. BACKGROUND

[0002] In OLED display technology, the packaging structure is the core link to ensure the stability and service life of the device. Its core function is to prevent water vapor and oxygen from entering the device interior through physical barrier and chemical protection, to avoid oxidation, corrosion and other reactions of organic light-emitting materials, metal electrodes and functional layers, thereby reducing the formation of black spots, brightness decay and device failure risk. The traditional OLED packaging structure usually adopts a "sandwich" design, that is, the anode, hole transport layer, light-emitting layer, electron transport layer and cathode are sequentially stacked on a flexible substrate (such as polyimide PI or PET), and the sealing is realized by a top packaging layer (such as a glass cover plate or a thin film packaging layer). However, due to the difference in flexibility and thermal expansion coefficient between the flexible substrate and the glass substrate, the packaging technology faces greater challenges: on the one hand, the water and oxygen barrier performance of the flexible plastic substrate itself is much lower than that of the glass substrate, and an additional barrier layer is needed; on the other hand, the flexible device is prone to cracking of the packaging layer during bending due to interfacial stress, which aggravates the water and oxygen penetration path.

[0003] In the existing flexible OLED packaging technology, the imprint packaging adhesive film is one of the mainstream solutions, which forms a dense packaging layer by coating organic materials such as epoxy resin and acrylic glue. However, such materials rely on the physical barrier properties of molecular chain accumulation, and the water vapor transmission rate (WVTR) is usually difficult to meet the long-term stability requirements of flexible devices. More importantly, organic adhesive film is prone to micro-cracks when repeatedly bent or subjected to temperature changes, resulting in "side leakage phenomenon" - water and oxygen penetrate into the device interior through the edge or interface defects of the packaging layer, and react with organic small molecules (such as Alq3, Ir(ppy)3) in the light-emitting layer and low work function metal cathode (such as Al, Mg / Ag alloy), generating non-radiative recombination centers or insulating oxides, which significantly reduces the device efficiency and accelerates aging. For example, although epoxy resin has high adhesive strength, its cross-linked network is relatively rigid, and the modulus mismatch with the flexible substrate can easily cause interfacial peeling; although acrylic glue has better flexibility, the free volume of its molecular chain is relatively large, and the water vapor diffusion coefficient is relatively high, which makes it difficult to meet the high barrier requirement.

[0004] In addition, some improved schemes attempt to introduce an elastomer toughening phase to improve flexibility, but often at the expense of barrier performance, or face the problem of poor interfacial compatibility. Therefore, the development of packaging materials with high flexibility and low water vapor transmission rate has become a key direction to break through the service life bottleneck of flexible OLED. SUMMARY

[0005] To simultaneously improve the high flexibility and low water and oxygen permeability of OLED encapsulation layers, this application provides a water and oxygen barrier coating for flexible OLEDs and a flexible OLED encapsulation film.

[0006] In a first aspect, this application provides a water-oxygen barrier coating for flexible OLEDs, comprising a pressure-sensitive adhesive, 5-15 wt% barrier filler, and 1-5 wt% hydrophobic modifier. The hydrophobic modifier comprises a hydrogen-terminated polysiloxane, a vinyl silane coupling agent, a tetramethylcyclotetrasiloxane, and an unsaturated alkenyl monomer in a molar ratio of 1:2-2.2:7-12:7-13. The hydrogen-terminated polysiloxane and the vinyl silane coupling agent undergo hydrosilylation to obtain a first intermediate, which is then ring-opened polymerized with tetramethylcyclotetrasiloxane to obtain a second intermediate, which is then hydrosilylated with an unsaturated olefin to obtain the hydrophobic modifier. The unsaturated alkenyl monomer comprises an epoxy acrylate monomer and an alkenyl sulfonate monomer in a molar ratio of 2-3:2-4.

[0007] This application utilizes a hydrosilylation reaction to combine a hydrogen-terminated polysiloxane with a vinyl silane coupling agent, forming a first intermediate with an organosilicon main chain. The silane coupling agents at both ends of this intermediate, after hydrolysis, can form stable chemical bonds with the hydroxyl groups on the surface of the barrier filler, thereby achieving hydrophobic modification of the filler surface.

[0008] Subsequently, tetramethylcyclotetrasiloxane (D4H) was introduced for ring-opening polymerization, generating active hydrogen sites on the side chain, providing reaction sites for the subsequent grafting of unsaturated alkenyl monomers. The introduction of epoxy acrylate monomers imbues the side chains with epoxy groups, which crosslink with active groups such as amino or hydroxyl groups in the resin during pressure-sensitive adhesive curing, forming a three-dimensional network structure. This significantly improves coating density and reduces water and oxygen diffusion channels. The hydrophilic groups of the alkenyl sulfonate monomers can regulate interfacial polarity, enhancing the compatibility between the modified filler and the pressure-sensitive adhesive matrix through ion-dipole interactions and preventing filler agglomeration. Furthermore, the flexible characteristics of the hydrophobic modifier organosilicon backbone effectively improve the flexibility of the pressure-sensitive adhesive system. The components work synergistically to ensure both barrier performance and material flexibility.

[0009] The unsaturated alkenyl monomer includes a fluorinated acrylate monomer, and the molar mass ratio of the alkenyl sulfonate monomer to the fluorinated acrylate monomer is 2-4:3-6.

[0010] The introduction of fluorinated acrylate monomers constructs perfluoroalkyl segments on the side chains. Their strong electronegativity and low surface energy allow for the formation of a dense molecular arrangement layer, effectively blocking water molecule permeation pathways. The electronic repulsion between fluorine atoms and siloxane groups inhibits the self-condensation tendency of siloxane hydrolysis products, preventing gelation during filler modification. The molar ratio of epoxy monomers to fluorinated monomers is controlled within the aforementioned range to ensure sufficient crosslinking density while avoiding excessive rigidity. Controlling the proportion of alkenyl sulfonate monomers improves dispersibility while controlling the concentration of hydrophilic groups, preventing the formation of continuous water molecule channels.

[0011] In any of the above technical solutions, the epoxy acrylate monomer is at least one of glycidyl acrylate and allyl glycidyl ether.

[0012] In any of the above technical solutions, the alkenyl sulfonate monomer is at least one of sodium styrene sulfonate, sodium allyl sulfonate, sodium vinyl sulfonate, sodium methyl allyl sulfonate, and sodium 2-acrylamido-2-methylpropanesulfonate.

[0013] In any of the above technical solutions, the fluorinated acrylate monomer is trifluoroethyl methacrylate and / or perfluorooctyl ethyl acrylate.

[0014] In any of the above technical solutions, the vinyl silane coupling agent is vinyltrimethoxysilane and / or vinyltriethoxysilane.

[0015] In any of the above technical solutions, the preparation method of the hydrophobic modifier is as follows:

[0016] Hydrogen-terminated polysiloxane was mixed with a vinylsilane coupling agent, heated to 90–120 °C under nitrogen protection, and a platinum catalyst was added to carry out hydrosilylation to obtain the first intermediate.

[0017] The first intermediate was mixed with tetramethylcyclotetrasiloxane, a cationic catalyst was added, and ring-opening polymerization was carried out at 80-100°C to obtain the second intermediate.

[0018] The second intermediate was mixed with an unsaturated alkenyl monomer, heated to 90–120 °C under nitrogen protection, and a platinum catalyst was added to carry out hydrosilylation. After the reaction was completed, the mixture was vacuum distilled to obtain a hydrophobic modifier.

[0019] The molecular structure of the first intermediate is as follows, where R is a silane coupling agent and Me is a methyl group.

[0020]

[0021] The molecular structure of the second intermediate is as follows, where m = 5 to 10.

[0022]

[0023] In any of the above technical solutions, the cationic catalyst is a sulfonated cationic resin or sulfuric acid.

[0024] In any of the above technical solutions, the amount of the cationic catalyst is 3 to 10% of the mass of the reaction raw materials.

[0025] In any of the above technical solutions, the pressure-sensitive adhesive is a polyurethane pressure-sensitive adhesive or an acrylate pressure-sensitive adhesive.

[0026] In any of the above technical solutions, the barrier filler is selected from one or more of boron nitride, aluminum oxide, magnesium oxide, silicon dioxide, and titanium dioxide.

[0027] In any of the above technical solutions, the D90 particle size of the barrier filler is 10-50 nm.

[0028] In any of the above technical solutions, the amount of platinum catalyst used in the hydrosilylation reaction needs to be controlled within the range of 10 to 50 ppm (calculated based on Pt content) to avoid residual catalyst accelerating the aging of organosilicon segments.

[0029] Secondly, this application provides a flexible OLED encapsulation film, including a flexible substrate and a pressure-sensitive adhesive barrier layer made of any of the coatings described above.

[0030] In any of the above technical solutions, the flexible OLED encapsulation film includes a flexible substrate, an organic adhesive layer, at least one inorganic barrier layer, and at least one pressure-sensitive adhesive barrier layer sequentially disposed on the flexible substrate; the pressure-sensitive adhesive barrier layer is made from any of the coatings described above.

[0031] In any of the above technical solutions, the flexible substrate is selected from polysulfone (PSF), polyimide (PI), polymethyl methacrylate (PMMA), polystyrene (PS), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or polyethersulfone (PES).

[0032] In any of the above technical solutions, the transmittance of the flexible substrate in the visible light range is >98%.

[0033] In any of the above technical solutions, the raw material of the inorganic barrier layer is selected from silicon dioxide, alumina, graphene or mica; the inorganic barrier layer is prepared by processes such as vapor deposition, atomic layer deposition, magnetron sputtering, ion sputtering or evaporation.

[0034] In any of the above technical solutions, the thickness of the inorganic barrier layer is 50 to 150 nanometers.

[0035] In any of the above technical solutions, the raw material of the organic adhesive layer is polymethyl methacrylate (PMMA), polystyrene (PS), polyvinyl alcohol (PVA) or polydimethylsiloxane (PDMS); the organic adhesive layer is prepared by spraying, spin coating, screen printing or inkjet printing process.

[0036] The OLED encapsulation film of this application can be provided with multiple inorganic barrier layers and multiple organic adhesive layers according to actual needs, and the inorganic barrier layers and organic adhesive layers are alternately arranged in sequence.

[0037] In any of the above technical solutions, the thickness of the organic adhesive layer is 0.5 to 10 micrometers.

[0038] In any of the above technical solutions, the pressure-sensitive adhesive layer is obtained by coating and heating curing processes. The coating methods include, but are not limited to, spraying, microgravure coating, slot coating, doctor blade coating, and screen printing.

[0039] In any of the above technical solutions, the coating thickness of the pressure-sensitive adhesive layer is 1 to 10 μm.

[0040] In summary, this application has the following beneficial effects:

[0041] The hydrophobic modifier disclosed in this application can be used to modify barrier fillers and pressure-sensitive adhesives to produce encapsulation materials that possess both high flexibility and excellent water and oxygen barrier properties. This modifier uses an organosilicon backbone as a flexible framework, forming a dense network structure through epoxy groups for cross-linking, effectively sealing water and oxygen permeation channels. Simultaneously, fluorocarbon segments are introduced to enhance the surface hydrophobic protection. Side-chain sulfonic acid groups improve filler dispersibility through polarity regulation, preventing interface defects. The synergistic effect of these components endows the material with both flexibility and stable barrier properties, providing a reliable guarantee for the long-term stable operation of flexible OLED devices. Detailed Implementation

[0042] Preparation Example

[0043] Preparation Example 1: A hydrophobic modifier, with the following raw material formulation:

[0044] 1 mol of hydrogen-terminated polysiloxane (0.12% hydrogen content), 2.1 mol of vinyltrimethoxysilane, 10 mol of tetramethylcyclotetrasiloxane, 3 mol of glycidyl methacrylate, 3 mol of sodium styrene sulfonate, 4 mol of perfluorooctyl ethyl acrylate, platinum catalyst (Karstedt catalyst, 2% Pt content), and sulfonated cationic resin (Amberlyst 15).

[0045] The preparation steps are as follows:

[0046] Preparation of the first intermediate: Hydrogen-terminated polysiloxane and vinyltrimethoxysilane were added to a reaction vessel, purged with nitrogen three times, and heated to 105°C. A platinum catalyst (dissolved in xylene) of 5 ppm was slowly added dropwise, maintaining the temperature at 105°C ± 2°C, and the reaction was stirred for 4 hours. After the reaction was completed, the temperature was raised to 130°C, and the mixture was distilled under reduced pressure (-0.1 MPa) for 1 hour to remove low-molecular-weight impurities, yielding the first intermediate.

[0047] Preparation of the second intermediate: Tetramethylcyclotetrasiloxane was added to the first intermediate and stirred until homogeneous. Sulfonated cationic resin was added at 5% (total mass of the first intermediate and tetramethylcyclotetrasiloxane), and the mixture was heated to 80°C and reacted for 6 hours (moisture content controlled <50 ppm). After the reaction, the catalyst was removed by cooling and filtration. The mixture was then heated to 140°C and distilled under reduced pressure (-0.1 MPa) for 1 hour to remove low-molecular-weight impurities. Sodium bicarbonate was added to adjust the pH to neutral. The product was treated with activated carbon for 48 hours and then filtered to obtain a second intermediate (m=10) with hydrogen-containing side chains.

[0048] Synthesis of hydrophobic modifier: The second intermediate was mixed with glycidyl methacrylate, sodium styrene sulfonate, and perfluorooctyl ethyl acrylate, and heated to 110°C under nitrogen protection; 10 ppm of platinum catalyst was added, and the reaction was carried out for 6 hours. Unreacted monomers were removed by vacuum distillation (-0.1 MPa, 170°C) to obtain the hydrophobic modifier.

[0049] Preparation Example 2: A hydrophobic modifier, with the following raw material formulation:

[0050] 1 mol of hydrogen-terminated polysiloxane (0.05% hydrogen content), 2.0 mol of vinyltrimethoxysilane, 7 mol of tetramethylcyclotetrasiloxane, 2 mol of allyl glycidyl ether, 2 mol of sodium allyl sulfonate, 3 mol of trifluoroethyl methacrylate, platinum catalyst (Karstedt catalyst, 2% Pt content), and sulfonated cationic resin (Amberlyst 15).

[0051] The preparation steps are as follows:

[0052] Preparation of the first intermediate: Hydrogen-terminated polysiloxane and vinyltrimethoxysilane were added to a reactor, purged with nitrogen three times, and heated to 85°C. Platinum catalyst (dissolved in xylene) at 5 ppm was slowly added dropwise, and the temperature was maintained at 95±2°C while stirring for 4 hours. After the reaction was complete, the temperature was raised to 130°C, and the mixture was distilled under reduced pressure (-0.1 MPa) for 1 hour to remove low-molecular-weight impurities, yielding the first intermediate.

[0053] Preparation of the second intermediate: Tetramethylcyclotetrasiloxane was added to the first intermediate and stirred until homogeneous. Sulfonated cationic resin was added at 3% (total mass of the first intermediate and tetramethylcyclotetrasiloxane), and the mixture was heated to 85°C and reacted for 5 hours (moisture content controlled <50 ppm). After the reaction, the catalyst was removed by cooling and filtration. The mixture was then heated to 130°C and distilled under reduced pressure (-0.095 MPa) for 1 hour to remove low-molecular-weight impurities. Sodium bicarbonate was added to adjust the pH to neutral. The product was treated with activated carbon for 48 hours and then filtered to obtain a second intermediate (m=7) with hydrogen-containing side chains.

[0054] Synthesis of hydrophobic modifier: The second intermediate was mixed with allyl glycidyl ether, sodium allyl sulfonate, and trifluoroethyl methacrylate, and heated to 100°C under nitrogen protection; 10 ppm of platinum catalyst was added, and the reaction was carried out for 5 hours. Unreacted monomers were removed by vacuum distillation (-0.1 MPa, 170°C) to obtain the hydrophobic modifier.

[0055] Preparation Example 3: A hydrophobic modifier, with the following raw material formulation:

[0056] 1 mol of hydrogen-terminated polysiloxane (0.18% hydrogen content), 2.2 mol of vinyltriethoxysilane, 12 mol of tetramethylcyclotetrasiloxane, 3 mol of glycidyl methacrylate, 4 mol of sodium methylallyl sulfonate, 6 mol of perfluorooctyl ethyl acrylate, 50 ppm of platinum catalyst (Karstedt catalyst, 2% Pt content), and sulfonated cationic resin (Amberlyst 15).

[0057] The preparation steps are as follows:

[0058] Preparation of the first intermediate: Hydrogen-terminated polysiloxane and vinyltrimethoxysilane were added to a reaction vessel, purged with nitrogen three times, and heated to 105°C. A platinum catalyst (dissolved in xylene) of 10 ppm was slowly added dropwise, and the temperature was maintained at 115°C ± 2°C while stirring for 3 hours. After the reaction was complete, the temperature was raised to 130°C, and the mixture was distilled under reduced pressure (-0.1 MPa) for 1 hour to remove low-molecular-weight impurities, yielding the first intermediate.

[0059] Preparation of the second intermediate: Tetramethylcyclotetrasiloxane was added to the first intermediate and stirred until homogeneous. Sulfonated cationic resin, comprising 10% of the total mass of the first intermediate and tetramethylcyclotetrasiloxane, was added. The mixture was heated to 100°C and reacted for 4 hours (moisture content controlled <50 ppm). After the reaction, the catalyst was removed by cooling and filtration. The mixture was then heated to 140°C and distilled under reduced pressure (-0.095 MPa) for 1 hour to remove low-molecular-weight impurities. Sodium bicarbonate was added to adjust the pH to neutral. The product was treated with activated carbon for 48 hours and then filtered to obtain a second intermediate (m=12) with hydrogen-containing side chains.

[0060] Synthesis of hydrophobic modifier: The second intermediate was mixed with glycidyl methacrylate, sodium styrene sulfonate, and perfluorooctyl ethyl acrylate, and heated to 120°C under nitrogen protection; 50 ppm of platinum catalyst was added, and the reaction was carried out for 5 hours. Unreacted monomers were removed by vacuum distillation (-0.1 MPa, 180°C) to obtain the hydrophobic modifier.

[0061] Preparation Example 4, a hydrophobic modifier, differs from Preparation Example 1 in that the unsaturated alkenyl monomer does not contain perfluorooctyl ethyl acrylate, and the specific amounts are as follows: 5 mol glycidyl methacrylate, 5 mol sodium styrene sulfonate, and 0 mol perfluorooctyl ethyl acrylate.

[0062] Preparation Example 5, a hydrophobic modifier, differs from Preparation Example 1 in that the composition and amount of the unsaturated alkenyl monomer are as follows: 4 mol glycidyl methacrylate, 2 mol sodium styrene sulfonate, and 4 mol perfluorooctyl ethyl acrylate.

[0063] Preparation Example 6, a hydrophobic modifier, differs from Preparation Example 1 in that the composition and amount of the unsaturated alkenyl monomer are as follows: 1 mol glycidyl methacrylate, 4 mol sodium styrene sulfonate, and 5 mol perfluorooctyl ethyl acrylate.

[0064] Preparation Example 7, a hydrophobic modifier, differs from Preparation Example 1 in that the composition and amount of the unsaturated alkenyl monomer are as follows: 4 mol sodium styrene sulfonate and 6 mol perfluorooctyl ethyl acrylate.

[0065] Preparation Example 8, a hydrophobic modifier, differs from Preparation Example 1 in that the composition and amount of the unsaturated alkenyl monomer are as follows: 3 mol glycidyl methacrylate, 5 mol sodium styrene sulfonate, and 2 mol perfluorooctyl ethyl acrylate.

[0066] Preparation Example 9, a hydrophobic modifier, differs from Preparation Example 1 in that the composition and amount of the unsaturated alkenyl monomer are as follows: 3 mol glycidyl methacrylate, 1 mol sodium styrene sulfonate, and 6 mol perfluorooctyl ethyl acrylate.

[0067] Preparation Example 10, a hydrophobic modifier, differs from Preparation Example 1 in that the composition and amount of the unsaturated alkenyl monomer are as follows: 3 mol glycidyl methacrylate and 7 mol perfluorooctyl ethyl acrylate.

[0068] Preparation Example 11, a hydrophobic modifier, differs from Preparation Example 1 in that a first intermediate is used as the hydrophobic modifier (the second intermediate and subsequent preparation steps are not performed).

[0069] Example

[0070] Example 1: A flexible OLED encapsulation film includes a flexible substrate (polyethylene terephthalate) with a thickness of 150 micrometers. An organic adhesive layer with a thickness of 3 micrometers is formed on the surface of the flexible substrate using polydimethylsiloxane adhesive (model DC184) as raw material through screen printing. Then, an inorganic alumina layer with a thickness of 100 nanometers is formed on the surface of the organic adhesive layer through chemical vapor deposition. Finally, a water-oxygen barrier coating is applied to the surface of the inorganic barrier layer through a doctor blade coating process to obtain a pressure-sensitive adhesive barrier layer with a thickness of 8 micrometers.

[0071] The method for preparing the water-oxygen barrier coating is as follows: 80g of boron nitride (D90=20nm) and 35g of the hydrophobic modifier of Preparation Example 1 are stirred at 500rpm for 15min, 885g of waterborne polyurethane pressure-sensitive adhesive (solid content 54%, viscosity 50-150mPa·s, particle size 0.2-0.4μm) is added, and stirring is continued for 30min to obtain the coating.

[0072] Example 2: A flexible OLED encapsulation film includes a flexible substrate (ethylene naphthalate) with a thickness of 150 micrometers. A 5-micrometer thick organic adhesive layer is formed on the surface of the flexible substrate using polydimethylsiloxane adhesive (model DC184) as the raw material via screen printing. Next, a 150-nanometer thick white graphene inorganic barrier layer is formed on the surface of the organic adhesive layer via chemical vapor deposition. Finally, a water-oxygen barrier coating is applied to the surface of the inorganic barrier layer via blade coating to obtain a 5-micrometer thick pressure-sensitive adhesive barrier layer.

[0073] The method for preparing the water-oxygen barrier coating is as follows: 50g of alumina (D90=10nm) and 10g of the hydrophobic modifier of Preparation Example 2 are stirred at 500rpm for 15min, 885g of waterborne polyurethane pressure-sensitive adhesive (solid content 52%, viscosity 100-500mPa·s, particle size 0.1-0.3μm) are added, and stirring is continued for 20min to obtain the coating.

[0074] Example 3: A flexible OLED encapsulation film includes a flexible substrate (polyethylene terephthalate) with a thickness of 150 micrometers. An organic adhesive layer with a thickness of 2 micrometers is formed on the surface of the flexible substrate using polydimethylsiloxane adhesive (model DC184) as raw material through screen printing. Then, an inorganic alumina layer with a thickness of 50 nanometers is formed on the surface of the organic adhesive layer through chemical vapor deposition. Finally, a water-oxygen barrier coating is applied to the surface of the inorganic barrier layer through a doctor blade coating process to obtain a pressure-sensitive adhesive barrier layer with a thickness of 10 micrometers.

[0075] The method for preparing the water-oxygen barrier coating is as follows: 150g of silica (D90=40nm) and 50g of the hydrophobic modifier of Preparation Example 1 are stirred at 800rpm for 20min, and then 800g of waterborne acrylic pressure-sensitive adhesive (solid content 54-56%, viscosity 50-180cps) is added, and stirring is continued for 30min to obtain the coating.

[0076] Example 4, a flexible OLED encapsulation film, differs from Example 1 in that the hydrophobic modifier of Example 4 is replaced with the hydrophobic modifier of Example 1 in equal mass.

[0077] Comparative Example

[0078] Comparative Example 1 is a flexible OLED encapsulation film, which differs from Example 4 in that the hydrophobic modifier of Example 5 is replaced with the hydrophobic modifier of Example 4 in equal mass.

[0079] Comparative Example 2 is a flexible OLED encapsulation film, which differs from Example 4 in that the hydrophobic modifier of Preparation Example 6 is replaced with the hydrophobic modifier of Preparation Example 4 in equal mass.

[0080] Comparative Example 3 is a flexible OLED encapsulation film, which differs from Example 4 in that the hydrophobic modifier of Example 7 is replaced with the hydrophobic modifier of Example 4 in equal mass.

[0081] Comparative Example 4 is a flexible OLED encapsulation film, which differs from Example 4 in that the hydrophobic modifier of Preparation Example 8 is replaced with the hydrophobic modifier of Preparation Example 4 in equal mass.

[0082] Comparative Example 5 is a flexible OLED encapsulation film, which differs from Example 4 in that the hydrophobic modifier of Preparation Example 9 is replaced with the hydrophobic modifier of Preparation Example 4 in equal mass.

[0083] Comparative Example 6 is a flexible OLED encapsulation film, which differs from Example 4 in that the hydrophobic modifier of Preparation Example 10 is replaced with the hydrophobic modifier of Preparation Example 4 in equal mass.

[0084] Comparative Example 7 is a flexible OLED encapsulation film, which differs from Example 4 in that the hydrophobic modifier of Preparation Example 11 is replaced with the hydrophobic modifier of Preparation Example 4 in equal mass.

[0085] Comparative Example 8 is a flexible OLED encapsulation film, which differs from Example 4 in that no hydrophobic modifier was added.

[0086] Performance testing

[0087] Experiment 1: Water Vapor Transmission Rate (WVTR) Detection

[0088] Reference standard: ASTM E96 / E96M-24 "Standard test method for water vapor permeability of materials".

[0089] Sample preparation: The flexible OLED encapsulation films prepared in the examples and comparative examples were cut into circular samples with a diameter of 10 cm, and the edges were sealed with epoxy resin.

[0090] Test procedure: Pre-treat the sample in a drying oven at 25℃ and ≤10% humidity for 24 hours; record the initial mass of the sample (W0) using a high-precision electronic balance. Place the sample in a constant temperature and humidity chamber (38℃, 90%RH), remove it every 24 hours, wipe off the surface condensation, and weigh it (W1, W2, W3).

[0091] Calculate water vapor transmission rate (WVTR):

[0092] WVTR=ΔW / A·t(ΔW=W3-W0,A=0.00785m 2 (t = 3 days).

[0093] Experiment 2: Oxygen Transmission Rate (OTR) Detection

[0094] Reference standard: ASTM D3985-05 Standard test method for measuring oxygen permeability of plastic films and sheets using coulometric sensors.

[0095] Sample preparation: The flexible OLED encapsulation film prepared in the examples and comparative examples was cut into circular samples with a diameter of 10cm×10cm square samples, and the edges were sealed with epoxy resin.

[0096] Test Procedure: Using a MOCON OX-TRAN 2 / 22 oxygen permeability analyzer, nitrogen (purity ≥99.999%) was used as the carrier gas, and the oxygen sensor was preheated to 23°C. The sample was clamped in the test chamber, and the test conditions were set to 23°C and 50% RH. Test parameters: carrier gas flow rate 100 mL / min; test time 24 hours; direct reading of OTR value (unit: cm). 3 / (m 2 ·day·atm)).

[0097] Experiment 3: Flexibility test (using the pressure-sensitive adhesive barrier layer from the examples and comparative examples as the sample)

[0098] Reference standard: GB / T 1040.3-2006 "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets".

[0099] Sample preparation: The water and oxygen barrier coating was applied to the PET substrate (150 μm thick), and after curing, it was cut into dumbbell-shaped samples (GB / T 1040.3 standard type 1B, effective size 75 mm × 10 mm).

[0100] Test procedure: Using a universal testing machine (Instron 5567), clamp both ends of the specimen, tensile rate: 50 mm / min, and record the stress-strain curve.

[0101] Calculate the elongation at break (ε):

[0102] ε=(L-L0) / L0×100%(L0=25mm, L is the gauge length at the time of breakage).

[0103] Experiment 3: Coating stability test

[0104] Sample preparation: Water and oxygen barrier coatings (uncured) prepared in the examples and comparative examples.

[0105] Test procedure: Take water and oxygen barrier coating (uncured) and dispense it into a sealed 100mL graduated cylinder. After standing at room temperature (25±2℃) for 24 hours, record the height of the upper clear liquid (H1) and the total height (H0).

[0106] Calculate the settlement rate: Settlement rate = (H0-H1) / H0×100%.

[0107] Table 1. Performance Test Results

[0108]

[0109] Analysis of experimental results:

[0110] 1) Water vapor transmission rate (WVTR) analysis

[0111] The WVTR of Examples 1-3 is ≤5.5×10 -6 g / m 2 / day, significantly better than comparative examples 1-8, is attributed in two ways. Firstly, the epoxy groups of the hydrophobic modifier synergistically interact with the organosilicon backbone, forming a gradient cross-linked network with the pressure-sensitive adhesive matrix and barrier fillers, reducing the free volume of molecules. Secondly, the dense arrangement of fluorocarbon chains and the formation of low surface energy barriers by the all-oxyalkyl chains effectively block water molecule penetration. Furthermore, the sulfonate groups improve the compatibility between the hydrophobic modifier and the pressure-sensitive adhesive matrix, promoting the effective dispersion of the barrier fillers.

[0112] The WVTR of Example 4 increased to 12.5 × 10⁻⁶. -6 This indicates that the lack of fluorine-containing monomers leads to a decrease in hydrophobic properties, and the lack of fluorine groups makes it easier for water molecules to penetrate through coating defects.

[0113] (2) Oxygen Transmission Rate (OTR) Analysis

[0114] The OTR of Examples 1-3 is ≤5.5×10 -2 cm / (m 2 The performance (day·atm) was slightly better than that of comparative examples 1-8, which is attributed to the synergistic cross-linking of the hydrophobic modifier, pressure-sensitive adhesive, and barrier filler, forming a three-dimensional network that reduces oxygen molecule diffusion channels. Furthermore, the sulfonic acid group interface optimization improved the dispersion of the barrier filler and eliminated interfacial micropores.

[0115] In Comparative Examples 1-6 (insufficient or excessive amounts of sulfonate monomers or epoxy monomers), the OTR increased to some extent. Insufficient amounts of sulfonate monomers or epoxy monomers caused macroscopic defects in the barrier layer, leading to increased oxygen permeability. Specifically, sulfonate monomers mainly affect the compatibility of hydrophobic modifiers and barrier fillers with the pressure-sensitive adhesive matrix, causing changes in the coating structure. Epoxy monomers mainly affect changes in the crosslinking network density.

[0116] (3) Analysis of elongation at break and coating stability

[0117] Compared to Examples 1-3, the sedimentation rate of Example 4 (without fluorinated monomers) increased to 8.9%, while the elongation at break decreased to 98%. This may be because fluorinated monomers can inhibit the self-polymerization of hydrophobic modifiers, ensure the uniform dispersion of hydrophobic modifiers and their grafted barrier fillers, reduce the loss of flexibility caused by agglomeration, and promote the toughening effect of organosilicon segments.

[0118] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A water-oxygen barrier coating for flexible OLEDs, characterized in that, The product comprises a pressure-sensitive adhesive, 5-15 wt% barrier filler, and 1-5 wt% hydrophobic modifier. The pressure-sensitive adhesive is a polyurethane pressure-sensitive adhesive or an acrylate pressure-sensitive adhesive. The hydrophobic modifier comprises hydrogen-terminated polysiloxane, vinyl silane coupling agent, tetramethylcyclotetrasiloxane, and unsaturated alkenyl monomer in a molar ratio of 1:2-2.2:7-12:7-13. The hydrogen-terminated polysiloxane and vinyl silane coupling agent undergo hydrosilylation to obtain a first intermediate, which is then ring-opened polymerized with tetramethylcyclotetrasiloxane to obtain a second intermediate, which is then hydrosilylated with an unsaturated olefin to obtain the hydrophobic modifier. The unsaturated alkenyl monomer comprises epoxy acrylate monomers and alkenyl sulfonate monomers in a molar ratio of 2-3:2-4. The unsaturated alkenyl monomers include fluorinated acrylate monomers, and the molar ratio of alkenyl sulfonate monomers to fluorinated acrylate monomers is 2-4:3-6.

2. The coating according to claim 1, characterized in that, The epoxy acrylate monomer is at least one of glycidyl acrylate and allyl glycidyl ether.

3. The coating according to claim 1, characterized in that, The alkenyl sulfonate monomer is at least one of sodium styrene sulfonate, sodium allyl sulfonate, sodium vinyl sulfonate, sodium methyl allyl sulfonate, and sodium 2-acrylamido-2-methylpropanesulfonate.

4. The coating according to claim 1, characterized in that, The vinyl silane coupling agent is vinyltrimethoxysilane and / or vinyltriethoxysilane.

5. The coating according to claim 1, characterized in that, The fluorinated acrylate monomer is trifluoroethyl methacrylate and / or perfluorooctyl ethyl acrylate.

6. The coating according to any one of claims 1-5, characterized in that, The preparation method of the hydrophobic modifier is as follows: Hydrogen-terminated polysiloxane was mixed with a vinylsilane coupling agent, heated to 90–120 °C under nitrogen protection, and a platinum catalyst was added to carry out hydrosilylation to obtain the first intermediate. The first intermediate was mixed with tetramethylcyclotetrasiloxane, a cationic catalyst was added, and ring-opening polymerization was carried out at 80-100°C to obtain the second intermediate. The second intermediate was mixed with an unsaturated alkenyl monomer, heated to 90–120 °C under nitrogen protection, and a platinum catalyst was added to carry out hydrosilylation. After the reaction was completed, the mixture was vacuum distilled to obtain a hydrophobic modifier.

7. The coating according to claim 1, characterized in that, The barrier filler is selected from one or more of boron nitride, alumina, silicon dioxide, and titanium dioxide.

8. A flexible OLED encapsulation film, characterized in that, It includes a flexible substrate and a pressure-sensitive adhesive barrier layer made of any of the coatings described in claims 1 to 7.

Images