UV-crosslinkable rubber pressure-sensitive adhesive, support film and preparation method of UV-crosslinkable rubber pressure-sensitive adhesive

Abstract

The invention discloses a UV cross-linkable rubber pressure-sensitive adhesive, a support film and a preparation method of the UV cross-linkable rubber pressure-sensitive adhesive. The pressure-sensitive adhesive comprises the following raw material components in parts by weight: 50-100 parts of (methyl) acrylate modified rubber, 5-25 parts of tackifying resin, 0.01-1 part of a first initiator, 0.01-1 part of a photosensitizer, 0.1-10 parts of an antioxidant and 50-150 parts of a first organic solvent. The support film prepared by the invention has the characteristics of high viscosity, high transmittance, low low-temperature modulus, high high-temperature modulus, low dielectric constant and high surface impedance, and is favorable for well supporting a protective substrate to prevent the protective substrate from curling and deforming; due to the characteristics of high modulus at a high-temperature section (more than 150 DEG C) and difficulty in falling at a high temperature, the phenomena of glue overflow and bubbles of a product in an actual high-temperature die cutting process can be effectively avoided, and the modulus at a low-temperature section (less than-10 DEG C) is lower than that of a conventional acrylate support film, so that the bonding force to a substrate at a low temperature can be ensured.

Description

Technical Field

[0001] This invention relates to the field of support membrane materials, and in particular to a UV crosslinkable rubber pressure-sensitive adhesive, a support membrane, and a method for preparing the same. Background Technology

[0002] In recent years, with the rapid development of curved / foldable phones, the application of OLED displays has become increasingly widespread. Compared to traditional LCD screens, OLED displays offer greater flexibility, more design flexibility, lighter weight, and lower power consumption. As OLED replaces LCD as the trend in the display industry, display panels also need to be replaced by flexible materials instead of rigid ones. Currently, flexible printed circuit boards are typically made using polyimide or polyester film as the substrate, offering advantages such as high wiring density, light weight, and good heat resistance. However, polyimide, as a substrate for flexible screens, is very thin and easily curled, lacking stiffness. This poses a risk of damage or breakage during assembly or transportation. Therefore, a support film (Black Plate Film, BP) needs to be attached to the back of the screen to provide adhesion and support, extending the lifespan of the flexible screen.

[0003] In the OLED manufacturing process, static electricity is generated when the support film and release film are peeled off. When the support film is bonded to the PI substrate, friction occurs with the production equipment, resulting in static electricity accumulation. Static discharge can cause irreversible damage to the screen material, leading to dark spots or bright lines. This requires the pressure-sensitive adhesive layer of the support film to have a low dielectric constant and a high surface resistance, making both the adhesive surface of the support film and the PI substrate a perfect insulator, thereby greatly limiting charge movement and avoiding irreversible damage to the OLED screen caused by static discharge. In addition, in existing processes, conventional support films are prone to adhesive pull or air bubbles during high-temperature die-cutting, leading to a decrease in adhesion and long-term slippage and detachment. Therefore, it is necessary to develop a new type of support film tape with high transmittance, high adhesion stability, high high-temperature modulus, low dielectric constant, and high surface resistance as a support module for flexible displays.

[0004] Currently, support films designed to address the aforementioned issues have emerged in the market. For example, Chinese patent CN118853031A discloses an acrylic pressure-sensitive adhesive, a support film, and a method for preparing the same for flexible OLED support films. The support film comprises a protective film layer, a PET substrate layer, a pressure-sensitive adhesive layer, and a release layer, layered sequentially. By controlling the ratio of hydroxypropyl acrylate to 5-methyl-3-vinyl-2-oxazolinone at 2:1, the resulting acrylic pressure-sensitive adhesive, after coating, exhibits both high viscosity and high modulus, thus avoiding issues such as adhesive overflow or bubbles during high-temperature die-cutting in the production process.

[0005] This invention uses a pure acrylic system. Because it contains a large number of polar groups, the surface resistivity is usually lower than 10^14, and the dielectric constant cannot be made very low. Static electricity is easily accumulated during the screen production process, which can easily damage the screen, resulting in dark spots or bright lines and reducing the production yield.

[0006] For example, Chinese patent CN119570408A discloses a high-resistivity support film used to support a display screen body. The high-resistivity support film includes: a release layer, an SBS modified adhesive layer, a substrate layer, and a protective film layer disposed on the substrate layer. The surface resistance of the adhesive surface is increased by using a rubber elastomer adhesive layer, and the crosslinking density is increased after thermosetting by grafting acrylate containing crosslinking sites, thereby increasing the modulus of the support film body at high temperature.

[0007] This invention uses SBS elastomer as the main body to improve the surface resistivity of the adhesive layer. However, SBS usually has high hardness, which results in a high modulus of the adhesive at room temperature and weakened pressure sensitivity. In addition, SBS has low transparency, and the transmittance of the adhesive film made of SBS is lower than that of ordinary acrylic support film.

[0008] Acrylic-based support films can achieve both high high-temperature modulus and high high-temperature viscosity by controlling the ratio of hydroxyl-containing monomers and polar monomers. However, their low surface resistivity makes it difficult to effectively eliminate static electricity during the screen production process.

[0009] While SBS elastomer-based support film solutions achieve high surface resistance in the adhesive layer, SBS typically has high hardness, resulting in a high room temperature modulus and reduced pressure sensitivity. Additionally, SBS has low transparency, meaning that films made with SBS have lower transmittance than those made with conventional acrylic support films.

[0010] In summary, there is a need to develop a support film with high transparency, low low temperature modulus, high high temperature modulus, low dielectric constant, and high surface impedance to improve the production yield of OLED modules. Summary of the Invention

[0011] The technical problem to be solved by this invention is to address the issues in the prior art, such as easy glue overflow during high-temperature die-cutting of the support film and the tendency to generate static electricity when bonding to the PI substrate, leading to a decrease in screen production yield. This invention provides a UV-crosslinkable rubber pressure-sensitive adhesive, a support film, and a method for preparing the same. The support film in this invention effectively protects and supports the flexible substrate, possessing not only excellent mechanical and optical properties but also high high-temperature modulus, low dielectric constant, and high surface resistivity.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In the first aspect, the present invention provides a UV-crosslinkable rubber pressure-sensitive adhesive, comprising the following raw material components by weight: 50-100 parts of (meth)acrylate modified rubber, 5-25 parts of tackifying resin, 0.01-1 parts of a first initiator, 0.01-1 parts of a photosensitizer, 0.1-10 parts of an antioxidant, and 50-150 parts of a first organic solvent; The (meth)acrylate modified rubber is mainly composed of styrene-isoprene-styrene (SIS), which is obtained by thermally initiating polymerization with a free radical initiator after mixing with (meth)acrylate monomers. The (meth)acrylate monomer is a (meth)acrylate monomer containing an epoxy group.

[0013] Preferably, the raw materials for preparing the (meth)acrylate modified rubber include, by weight, 80-120 parts of styrene-isoprene-styrene, 5-20 parts of (meth)acrylate monomer, 150-300 parts of a second organic solvent, and 0.1-0.4 parts of a free radical initiator.

[0014] Preferably, the (meth)acrylate modified rubber is prepared by the following method: According to the weight ratio, styrene-isoprene-styrene copolymer, (meth)acrylate monomer, and organic solvent are added to the reactor and stirred for 3-12 hours. The system temperature is raised to 78-83℃, and nitrogen is purged under stirring for 20-40 minutes. The initiator is added under nitrogen, and the reaction is carried out for 2-4 hours. The temperature is raised to 90-95℃ and the reaction is maintained for 2-3 hours. The mixture is then cooled to room temperature to obtain (meth)acrylate modified rubber.

[0015] Preferably, the (meth)acrylate monomer is one or two of glycidyl methacrylate and glycidyl acrylate, the free radical initiator is one or more of azobisisobutyronitrile, azobisisobutyronitrile, dimethyl azobisisobutyrate, and benzoyl peroxide, and the second organic solvent is toluene.

[0016] Preferably, the tackifying resin is one or more of the following: C5 aliphatic petroleum resin, C9 aromatic petroleum resin, aromatic hydrocarbon modified aliphatic resin, rosin, hydrogenated rosin, and terpene resin. The first initiator is one or more of the following: diazonium salt, diaryliodomonium salt, triarylthionium salt, alkylthionium salt, iron aromatic salt, sulfonyloxy ketone, and triarylsiloxane; The photosensitizer is at least one of alkyl phenyl ketones, benzophenones, acylphosphine oxides, and thioxanthones. The antioxidant is any one or a combination of dilaurate thiodipropionate, antioxidant 1010, antioxidant 4020, and antioxidant 1076. The first organic solvent is one or a combination of more of the following: methylcyclohexane, cyclohexane, hexane, toluene, or xylene.

[0017] Preferably, the first initiator is one or two of 4,4'-di-tert-butylphenyliodonium hexafluorophosphate, 4,4'-bis(dodecylphenyliodonium)hexafluoroantimonate, 4,4'-xylyliodonium hexafluorophosphate, mixed thionium hexafluorophosphate, and mixed thionium hexafluoroantimonate. The photosensitizer is any one or a combination of 819, 651, 184, TPO, ITX, and benzophenone; A second aspect of the present invention provides a method for preparing the UV-crosslinkable rubber pressure-sensitive adhesive as described above, comprising the following steps: By weight, 50-100 parts of (meth)acrylate modified rubber, 5-25 parts of tackifying resin, 0.01-1 part of first initiator, 0.01-1 part of photosensitizer, 0.1-10 parts of antioxidant, and 50-150 parts of first organic solvent are mixed evenly to obtain UV crosslinkable rubber pressure-sensitive adhesive.

[0018] A third aspect of the present invention provides a support film for a flexible OLED display, comprising a protective film layer, a substrate layer, a pressure-sensitive adhesive layer and a release layer stacked sequentially; the pressure-sensitive adhesive layer is obtained by coating the UV-crosslinkable rubber pressure-sensitive adhesive as described above onto the substrate layer and then curing it.

[0019] Preferably, the protective film layer comprises an antistatic transparent PET film and a polyurethane adhesive layer bonded to the antistatic transparent PET film, and the thickness of the protective film layer is 25-75 μm; The substrate layer is a PET substrate layer with an antistatic coating on the first side, and the thickness of the substrate layer is 25-80μm.

[0020] Preferably, the support film for flexible OLED displays is prepared by the following method: the UV-crosslinkable rubber pressure-sensitive adhesive described above is uniformly coated on the second side of the substrate layer, baked at 100-120°C for 3-5 minutes to form a pressure-sensitive adhesive layer, a release film is bonded to the other side of the pressure-sensitive adhesive layer to form a release layer, irradiated with a mercury lamp, and finally the polyurethane adhesive layer of the protective film layer is bonded to the first side of the substrate layer to obtain the support film for flexible OLED displays.

[0021] The beneficial effects of this invention are: This invention provides a UV-crosslinkable rubber pressure-sensitive adhesive and support film for flexible OLED displays. The flexible OLED support film prepared by this invention has the characteristics of high adhesion, high transmittance, low low-temperature modulus, high high-temperature modulus, low dielectric constant, and high surface impedance. This is beneficial for providing good support and protection for the substrate, preventing it from curling and deforming. The high modulus at high temperatures (>150℃) and the characteristic of not easily detaching at high temperatures can also effectively avoid the phenomenon of adhesive overflow and bubbles in the actual high-temperature die-cutting process. The modulus at low temperatures (<-10℃) is lower than that of conventional acrylic support films, which can ensure the adhesion to the substrate at low temperatures. The high impedance and low dielectric constant help to suppress static electricity accumulation, reduce the damage of static electricity to the screen material, avoid the risk of green lines on the screen caused by static electricity, and greatly improve the production yield and the aging resistance of the product. This support film also has excellent mechanical and optical properties, ensuring the support and protection of the polyimide flexible substrate, increasing the overall structural strength of the flexible display, and has wide applications in flexible electronic devices.

[0022] The UV crosslinkable rubber pressure-sensitive adhesive formulation of the present invention uses SIS rubber elastomer with low hardness and high transparency as the main chain structure. Glycidyl acrylate containing epoxy structure is grafted onto the SIS main chain by thermal polymerization. The resulting film has a high transmittance (≥90). Under the influence of UV light and cationic initiators, a large number of epoxy groups in the polymer chain undergo ring-opening reactions, initiating cross-linking of the epoxy groups and forming a network structure. This significantly increases the cross-linking density of the colloidal material, contributing to the improvement of the storage modulus at high temperatures and achieving a storage modulus of 82 kPa at 200°C. Simultaneously, with the appropriate combination of a high-softening-point tackifying resin, the rubber pressure-sensitive adhesive balances high viscosity and high modulus, allowing the product to adhere well to the surface of the polyimide film for support and reinforcement. This also avoids issues such as adhesive overflow or bubbles during high-temperature production. Furthermore, the main polymer chain is composed of SIS rubber, giving it a lower dielectric constant (2-2.5) and a higher surface resistance (>10^15 Ω) than acrylic pressure-sensitive adhesives. This helps suppress static electricity accumulation, reducing damage to the screen material and preventing green lines on the screen caused by static electricity. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0024] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0026] This invention provides a UV-crosslinkable pressure-sensitive rubber adhesive, comprising the following raw material components by weight: 50-100 parts of (meth)acrylate modified rubber, 5-25 parts of tackifying resin, 0.01-1 part of first initiator, 0.01-1 part of photosensitizer, 0.1-10 parts of antioxidant, and 50-150 parts of first organic solvent; Among them, the (meth)acrylate modified rubber is mainly composed of styrene-isoprene-styrene (SIS), which is obtained by thermally initiating polymerization with a free radical initiator after mixing with (meth)acrylate monomers.

[0027] In a preferred embodiment, the styrene content in the styrene-isoprene-styrene (SIS) is preferably 0-30%, and its Shore A hardness is preferably 50 or less. The weight-average molecular weight (Mw) of the styrene-isoprene-styrene (SIS) is preferably 100,000 or more, more preferably 150,000 or more, and particularly preferably 200,000 or more. Furthermore, the upper limit of the weight-average molecular weight is not particularly limited, but is preferably 500,000 or less. By setting the weight-average molecular weight of the styrene-isoprene-styrene (SIS) to 100,000 or more, a rubber-like adhesive composition with a higher storage modulus at high temperatures can be prepared.

[0028] The content of styrene-isoprene-styrene (SIS) is not particularly limited, but it is preferably 50% by weight or more, more preferably 60% by weight or more, and even more preferably 70% by weight or more in the total solids component of the UV-crosslinkable rubber composition. The upper limit of the styrene-isoprene-styrene (SIS) content is not particularly limited, but it is preferably 90% by weight or less, more preferably 88% by weight or less. By including styrene-isoprene-styrene (SIS) within the above range, the colloidal dielectric constant is low and the surface resistivity is high, which is therefore preferred.

[0029] In a preferred embodiment, the (meth)acrylate monomer is an epoxy-containing (meth)acrylate monomer. Further, it may be one or both of glycidyl methacrylate (GMA) and glycidyl acrylate; the content of the epoxy-containing (meth)acrylate monomer is not particularly limited, but is preferably 0.2-20% by weight in the total solids of the UV-crosslinkable rubber composition. By including epoxy-containing (meth)acrylate monomers within the above range, a large number of epoxy groups as crosslinking sites can be provided, which can greatly increase the crosslinking density of the colloid after UV treatment and improve the modulus of the colloid at high temperatures, thus making it preferred.

[0030] The free radical initiator used in the thermal polymerization grafting reaction is an azo or peroxide initiator, preferably one or more of azobisisoheptanenitrile, azobisisobutyronitrile, dimethyl azobisisobutyrate, and benzoyl peroxide.

[0031] In a preferred embodiment, the raw materials for preparing (meth)acrylate modified rubber include, by weight, 80-120 parts of styrene-isoprene-styrene, 5-20 parts of (meth)acrylate monomer, 150-300 parts of a second organic solvent, and 0.1-0.4 parts of a free radical initiator.

[0032] In a preferred embodiment, the (meth)acrylate modified rubber is prepared by the following method: According to the weight ratio, styrene-isoprene-styrene copolymer, (meth)acrylate monomer, and organic solvent are added to the reactor and stirred for 3-12 hours. The system temperature is raised to 78-83℃, and nitrogen is purged under stirring for 20-40 minutes. The initiator is added under nitrogen, and the reaction is carried out for 2-4 hours. The temperature is raised to 90-95℃ and the reaction is maintained for 2-3 hours. The mixture is then cooled to room temperature to obtain (meth)acrylate modified rubber.

[0033] In a preferred embodiment, the (meth)acrylate monomer is glycidyl methacrylate, the free radical initiator is benzoyl peroxide, and the second organic solvent is toluene.

[0034] In a preferred embodiment, the tackifying resin is one or more of C5 aliphatic petroleum resin, C9 aromatic petroleum resin, aromatic hydrocarbon modified aliphatic resin, rosin, hydrogenated rosin, and terpene resin; by including a tackifier in the rubber adhesive composition, a rubber adhesive layer with high adhesion to various adherends and high durability even at high temperatures can be formed, which is therefore preferred.

[0035] The softening point (softening temperature) of the tackifying resin is not particularly limited, but is preferably about 80°C or higher, and more preferably about 100°C or higher. Since the tackifier has a softening point of 80°C or higher, it does not soften even at high temperatures and can maintain its adhesive properties, which is therefore preferred. The upper limit of the softening point of the tackifier is not particularly limited. However, if the softening point becomes too high, the molecular weight becomes higher, compatibility deteriorates, and sometimes adverse conditions such as whitening occur. Therefore, it is preferably about 200°C or lower, and more preferably about 150°C or lower.

[0036] The amount of tackifying resin added relative to 100 parts by weight of (meth)acrylate modified rubber is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, and even more preferably 30 parts by weight or less. Furthermore, there is no particular limitation on the lower limit of the amount of tackifying resin added, but it is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 5 parts by weight or more. By setting the amount of tackifying resin used within the above range, the adhesive properties can be improved while ensuring the high-temperature modulus, and therefore this is preferred. However, when the amount of tackifying resin used exceeds the above range and is added in large quantities, the high-temperature modulus of the supporting film adhesive layer tends to decrease, which can lead to adhesive pulling or air bubbles during high-temperature die cutting, resulting in decreased bonding strength and long-term slippage and detachment, and is therefore undesirable.

[0037] The first initiator is a cationic initiator, which, upon irradiation with ultraviolet light, can initiate ring-opening and chain extension of the epoxy groups in the modified rubber, forming a cross-linked network. The cationic initiator can be one or more of diazonium salts, diaryliodomonium salts, triarylthionium salts, alkylthionium salts, iron aromatic salts, sulfonyloxyketones, and triarylsiloxanes. Preferably, the cationic initiator is one or two of 4,4'-di-tert-butylphenyliodomonium hexafluorophosphate, 4,4'-bis(dodecylphenyliodomonium)hexafluoroantimonate, 4,4'-xylyliodomonium hexafluorophosphate, mixed thionium hexafluorophosphate, and mixed thionium hexafluoroantimonate. The content of the first initiator relative to 100 parts by weight of (meth)acrylate modified rubber is preferably 0.01 parts by weight to 1 part by weight, more preferably 0.01 parts by weight to 0.5 parts by weight. Within this range, the crosslinking reaction can proceed to the target density, and therefore is preferred.

[0038] The photosensitizer is at least one of alkyl phenyl ketones, benzophenones, acylphosphine oxides, and thioxanthones; more preferably, the photosensitizer can be any one or more combinations of 819, 651, 184, TPO, ITX, and benzophenone.

[0039] The photosensitizer content is preferably 0.01 to 1 part by weight, more preferably 0.01 to 0.5 parts by weight, relative to 100 parts by weight of glycidyl methacrylate modified rubber. Including the photosensitizer within the above range improves the efficiency of the cationic initiator ring-opening polymerization, and is therefore preferred.

[0040] The antioxidant is any one or a combination of dilaurate thiodipropionate, antioxidant 1010, antioxidant 4020, and antioxidant 1076. The antioxidant content is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 1 part by weight, relative to 100 parts by weight of (meth)acrylate modified rubber. Including antioxidants within the above range effectively improves the aging resistance of the colloid, and is therefore preferred.

[0041] The first organic solvent is one or a combination of methylcyclohexane, cyclohexane, hexane, toluene, or xylene, more preferably toluene. The amount of the first organic solvent added is 50-200 parts relative to 100 parts by weight of (meth)acrylate modified rubber.

[0042] The present invention also provides a method for preparing the above-mentioned UV-crosslinkable rubber pressure-sensitive adhesive, comprising the following steps: mixing 50-100 parts of (meth)acrylate modified rubber, 5-25 parts of tackifying resin, 0.01-1 parts of first initiator, 0.01-1 parts of photosensitizer, 0.1-10 parts of antioxidant, and 50-150 parts of first organic solvent evenly to obtain the UV-crosslinkable rubber pressure-sensitive adhesive.

[0043] The present invention also provides a support film for flexible OLED displays, comprising a protective film layer, a substrate layer, a pressure-sensitive adhesive layer and a release layer stacked sequentially; the pressure-sensitive adhesive layer is obtained by coating the above-mentioned UV-crosslinkable rubber pressure-sensitive adhesive onto the substrate layer and then curing it.

[0044] The formation of the pressure-sensitive adhesive layer requires SIS crosslinking by irradiating the UV-crosslinkable rubber pressure-sensitive adhesive with ultraviolet light. The irradiation conditions are not particularly limited and can be set to any suitable condition depending on the composition of the rubber adhesive composition to be crosslinked; for example, the cumulative irradiation intensity is preferably 100 mJ / cm² to 2000 mJ / cm². Before irradiation with ultraviolet light, organic solvents need to be removed by heating or drying. The heating and drying temperature is not particularly limited, but from the viewpoint of reducing residual solvents, it is preferably about 30°C to about 130°C, more preferably about 60°C to about 110°C. The drying time can be appropriately chosen. The drying time is preferably about 5 seconds to about 20 minutes, more preferably 30 seconds to 10 minutes, and even more preferably 1 minute to 5 minutes.

[0045] The gel fraction of the pressure-sensitive adhesive layer is not particularly limited, but is preferably about 10% to about 98%, more preferably about 25% to about 98%, further preferably about 45% to about 90%, and particularly preferably about 55% to about 70%. A gel fraction within the above range can balance durability and adhesion, and is therefore preferred.

[0046] The thickness of the pressure-sensitive adhesive layer is preferably 5-20 μm, and more preferably 10-16 μm.

[0047] The surface resistance of the pressure-sensitive adhesive layer of the present invention is preferably 10^15Ω or higher. The higher the surface resistance value of the adhesive layer, the better it is to suppress static electricity accumulation, reduce the damage of static electricity to the screen material, avoid the problem of green lines on the screen caused by static electricity, and improve the yield.

[0048] The dielectric constant of the pressure-sensitive adhesive layer of the present invention is preferably 3.5 or less, more preferably 3 or less, more preferably 2.5 or less, and the lower limit is preferably 2 or more. The storage modulus of the pressure-sensitive adhesive layer of the present invention at 200°C is preferably 30 kPa or more, more preferably 50 kPa or more, and even more preferably 60 kPa or more. Furthermore, there is no particular limitation on the upper limit of the storage modulus. If the storage modulus of the pressure-sensitive layer at 200°C is within the above range, then when the pressure-sensitive layer is applied to a support film, the phenomena of adhesive overflow and bubble peeling in the product during actual high-temperature processes can be effectively avoided.

[0049] In a preferred embodiment, the protective film layer includes an antistatic transparent PET film and a polyurethane adhesive layer bonded to the antistatic transparent PET film, and the thickness of the protective film layer is 25-75 μm.

[0050] In a preferred embodiment, the substrate layer is a PET substrate layer with an antistatic coating on the first side, and the thickness of the substrate layer is 25-80 μm.

[0051] In a preferred embodiment, the release layer is a double-sided antistatic release film.

[0052] In a preferred embodiment, the support film for flexible OLED displays is prepared by the following method: the UV-crosslinkable rubber pressure-sensitive adhesive is uniformly coated on the second side of the substrate layer and baked at 100-120°C for 3-5 minutes to form a pressure-sensitive adhesive layer. A release film is then bonded to the other side of the pressure-sensitive adhesive layer to form a release layer. The film is then irradiated with a mercury lamp. Finally, the polyurethane adhesive layer of the protective film layer is bonded to the first side of the substrate layer to obtain the support film for flexible OLED displays.

[0053] The UV-crosslinkable rubber pressure-sensitive adhesive formulation of this invention uses SIS rubber elastomer, which has low hardness, high transparency, low dielectric constant, and high surface resistance, as the main chain structure. Glycidyl methacrylate containing an epoxy structure is grafted onto the SIS main chain using thermal polymerization. Utilizing the large number of epoxy groups introduced into the rubber chain segments, a cationic initiator is activated by ultraviolet irradiation, causing the epoxy groups to open rings and extend the chain, thus achieving SIS crosslinking. Simultaneously, the storage modulus at high temperatures is controlled by adjusting the amount of light irradiation energy. Furthermore, by rationally combining high-softening-point tackifying resins, the resulting UV-crosslinkable rubber pressure-sensitive adhesive achieves a balance between high viscosity and high modulus.

[0054] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0055] Example 1 A (meth)acrylate modified rubber, the preparation method of which includes the following steps: By weight, 100 parts of SIS (trade name: 1178, hardness 30, manufactured by Jusheng Technology Co., Ltd.) with a styrene content of 22% and 233 parts of toluene were added to the reactor and mixed. After stirring thoroughly for 6 hours until the mixture was homogeneous, 10 parts of glycidyl methacrylate were added. The system temperature was raised to 80°C, and nitrogen gas was purged for 30 minutes under stirring. Benzoyl peroxide initiator was added under nitrogen atmosphere. The reaction was carried out for 4 hours, the temperature was raised to 95°C, and the reaction was maintained for 2 hours. The mixture was then cooled to room temperature to obtain (meth)acrylate modified rubber, namely glycidyl methacrylate modified rubber (solution).

[0056] A support film for flexible OLED displays includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer, and a release layer stacked sequentially. Its preparation method includes the following steps: S1. By weight, 100 parts of the glycidyl methacrylate modified rubber, 9 parts of terpene tackifying resin (trade name: 3115, softening point 115℃, manufactured by KRATON), 0.12 parts of cationic initiator (trade name: 1176, manufactured by Guangyi Chemical Company), 0.12 parts of photosensitizer (trade name: 819, manufactured by BASF), 0.4 parts of antioxidant (trade name: 1010, manufactured by Changzhou Jiatong Chemical Company), and 65 parts of toluene are mixed and stirred evenly to obtain a UV crosslinkable pressure-sensitive rubber with a mass fraction of 22%. S2. Apply a UV-crosslinkable rubber pressure-sensitive adhesive to the second surface of a 75μm PET substrate layer, bake at 110℃ for 3 minutes to form a 15μm thick pressure-sensitive adhesive layer, and then attach a 50μm thin release film to the adhesive surface on the other side of the pressure-sensitive adhesive layer. Irradiate with ultraviolet light at room temperature (light energy 1000mJ / cm²).2 (The wavelength is in the UVA region). Finally, a protective film layer (the polyurethane adhesive layer of the protective film layer is bonded to the antistatic coating) is applied to the antistatic coating of the PET substrate layer to obtain a support film for flexible OLED displays.

[0057] Examples 2-4, Comparative Examples 1 and 2, prepared glycidyl methacrylate modified rubber in the same manner as in Example 1.

[0058] Example 2 A support film for flexible OLED displays includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer, and a release layer stacked sequentially. Its preparation method includes the following steps: S1. By weight, 100 parts of the glycidyl methacrylate modified rubber, 9 parts of terpene tackifying resin (trade name: 3115, softening point 115℃, manufactured by KRATON), 0.12 parts of cationic initiator (trade name: 1176, manufactured by Guangyi Chemical Company), 0.12 parts of photosensitizer (trade name: 819, manufactured by BASF), 0.4 parts of antioxidant (trade name: 1010, manufactured by Changzhou Jiatong Chemical Company), and 65 parts of toluene are mixed and stirred evenly to obtain a UV crosslinkable pressure-sensitive rubber with a mass fraction of 22%. S2. Apply a UV-crosslinkable rubber pressure-sensitive adhesive to the second surface of a 75μm PET substrate layer, bake at 110℃ for 3 minutes to form a 15μm thick pressure-sensitive adhesive layer, and then attach a 50μm thin release film to the adhesive surface on the other side of the pressure-sensitive adhesive layer. Irradiate with ultraviolet light at room temperature (light energy 500mJ / cm²). 2 (The wavelength is in the UVA region). Finally, a protective film layer (the polyurethane adhesive layer of the protective film layer is bonded to the antistatic coating) is applied to the antistatic coating of the PET substrate layer to obtain a support film for flexible OLED displays.

[0059] Example 3 A support film for flexible OLED displays includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer, and a release layer stacked sequentially. Its preparation method includes the following steps: S1. By weight, 100 parts of the glycidyl methacrylate modified rubber, 13.5 parts of terpene tackifying resin (trade name: 3115, softening point 115℃, manufactured by KRATON), 0.12 parts of cationic initiator (trade name: 1176, manufactured by Guangyi Chemical Company), 0.12 parts of photosensitizer (trade name: 819, manufactured by BASF), 0.4 parts of antioxidant (trade name: 1010, manufactured by Changzhou Jiatong Chemical Company), and 65 parts of toluene are mixed and stirred evenly to obtain a UV crosslinkable pressure-sensitive rubber with a mass fraction of 24.7%. S2. Apply a UV-crosslinkable rubber pressure-sensitive adhesive to the second surface of a 75μm PET substrate layer, bake at 110℃ for 3 minutes to form a 15μm thick pressure-sensitive adhesive layer, and then attach a 50μm thin release film to the adhesive surface on the other side of the pressure-sensitive adhesive layer. Irradiate with ultraviolet light at room temperature (light energy 1000mJ / cm²). 2 (The wavelength is in the UVA region). Finally, a protective film layer (the polyurethane adhesive layer of the protective film layer is bonded to the antistatic coating) is applied to the antistatic coating of the PET substrate layer to obtain a support film for flexible OLED displays.

[0060] Example 4 A support film for flexible OLED displays includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer, and a release layer stacked sequentially. Its preparation method includes the following steps: S1. By weight, 100 parts of the glycidyl methacrylate modified rubber, 9 parts of rosin ester tackifying resin (trade name: RE 85, softening point 81℃, manufactured by KRATON), 0.12 parts of cationic initiator (trade name: 1176, manufactured by Guangyi Chemical Company), 0.12 parts of photosensitizer (trade name: 819, manufactured by BASF), 0.4 parts of antioxidant (trade name: 1010, manufactured by Changzhou Jiatong Chemical Company), and 65 parts of toluene are mixed and stirred evenly to obtain a UV crosslinkable pressure-sensitive rubber with a mass fraction of 22%. S2. Apply a UV-crosslinkable rubber pressure-sensitive adhesive to the second surface of a 75μm PET substrate layer, bake at 110℃ for 3 minutes to form a 15μm thick pressure-sensitive adhesive layer, and then attach a 50μm thin release film to the adhesive surface on the other side of the pressure-sensitive adhesive layer. Irradiate with ultraviolet light at room temperature (light energy 1000mJ / cm²). 2 (The wavelength is in the UVA region). Finally, a protective film layer (the polyurethane adhesive layer of the protective film layer is bonded to the antistatic coating) is applied to the antistatic coating of the PET substrate layer to obtain a support film for flexible OLED displays.

[0061] Comparative Example 1 A support film for flexible OLED displays includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer, and a release layer stacked sequentially. Its preparation method includes the following steps: S1. By weight, 100 parts of the glycidyl methacrylate modified rubber, 9 parts of terpene tackifying resin (trade name: 3115, softening point 115℃, manufactured by KRATON), 0.12 parts of cationic initiator (trade name: 1176, manufactured by Guangyi Chemical Company), 0.4 parts of antioxidant (trade name: 1010, manufactured by Changzhou Jiatong Chemical Company), and 65 parts of toluene are mixed and stirred evenly to obtain a UV crosslinkable pressure-sensitive rubber with a mass fraction of 22%. S2. Apply a UV-crosslinkable rubber pressure-sensitive adhesive to the second surface of a 75μm PET substrate layer, bake at 110℃ for 3 minutes to form a 15μm thick pressure-sensitive adhesive layer, and then attach a 50μm thin release film to the adhesive surface on the other side of the pressure-sensitive adhesive layer. Irradiate with ultraviolet light at room temperature (light energy 1000mJ / cm²). 2 (The wavelength is in the UVA region). Finally, a protective film layer (the polyurethane adhesive layer of the protective film layer is bonded to the antistatic coating) is applied to the antistatic coating of the PET substrate layer to obtain a support film for flexible OLED displays.

[0062] Comparative Example 2 A support film for flexible OLED displays includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer, and a release layer stacked sequentially. Its preparation method includes the following steps: S1. By weight, 100 parts of the glycidyl methacrylate modified rubber, 9 parts of terpene tackifying resin (trade name: 3115, softening point 115℃, manufactured by KRATON), 0.12 parts of photosensitizer (trade name: 819, manufactured by BASF), 0.4 parts of antioxidant (trade name: 1010, manufactured by Changzhou Jiatong Chemical Co., Ltd.), and 65 parts of toluene are mixed and stirred evenly to obtain a UV crosslinkable pressure-sensitive rubber with a mass fraction of 22%. S2. Apply a UV-crosslinkable rubber pressure-sensitive adhesive to the second surface of a 75μm PET substrate layer, bake at 110℃ for 3 minutes to form a 15μm thick pressure-sensitive adhesive layer, and then attach a 50μm thin release film to the adhesive surface on the other side of the pressure-sensitive adhesive layer. Irradiate with ultraviolet light at room temperature (light energy 1000mJ / cm²). 2 (The wavelength is in the UVA region). Finally, a protective film layer (the polyurethane adhesive layer of the protective film layer is bonded to the antistatic coating) is applied to the antistatic coating of the PET substrate layer to obtain a support film for flexible OLED displays.

[0063] Comparative Example 3 A support film for flexible OLED displays includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer, and a release layer stacked sequentially. Its preparation method includes the following steps: S1. By weight, 30 parts of SIS (trade name: 1178, hardness 30, manufactured by Jusheng Technology Co., Ltd.), 9 parts of terpene tackifying resin (trade name: 3115, softening point 115℃, manufactured by KRATON), 0.12 parts of cationic initiator (trade name: 1176, manufactured by Guangyi Chemical Co., Ltd.), 0.12 parts of photosensitizer (trade name: 819, manufactured by BASF), 0.4 parts of antioxidant (trade name: 1010, manufactured by Changzhou Jiatong Chemical Co., Ltd.), and 135 parts of toluene are mixed and stirred evenly to obtain a UV crosslinkable pressure-sensitive rubber with a mass fraction of 22%. S2. Apply a UV-crosslinkable rubber pressure-sensitive adhesive to the second surface of a 75μm PET substrate layer, bake at 110℃ for 3 minutes to form a 15μm thick pressure-sensitive adhesive layer, and then attach a 50μm thin release film to the adhesive surface on the other side of the pressure-sensitive adhesive layer. Irradiate with ultraviolet light at room temperature (light energy 1000mJ / cm²). 2 (The wavelength is in the UVA region). Finally, a protective film layer (the polyurethane adhesive layer of the protective film layer is bonded to the antistatic coating) is applied to the antistatic coating of the PET substrate layer to obtain a support film for flexible OLED displays.

[0064] Comparative Example 4 A support film for flexible OLED displays includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer, and a release layer stacked sequentially. Its preparation method includes the following steps: S1. By weight, mix 100 parts of acrylic pressure-sensitive adhesive, 0.05 parts of HDI, and 50 parts of ethyl acetate, and stir until homogeneous to obtain acrylic pressure-sensitive adhesive. S2. Apply acrylic pressure-sensitive adhesive to the second side of a 75μm PET substrate layer and bake at 120℃ for 3 minutes to form a 15μm thick pressure-sensitive adhesive layer. Then, attach a 50μm light release film to the adhesive surface on the other side of the pressure-sensitive adhesive layer and bake at 70℃ for 2 days. Finally, attach a protective film layer (the polyurethane adhesive layer of the protective film layer is bonded to the antistatic coating) to the antistatic coating of the PET substrate layer to obtain a support film for flexible OLED displays.

[0065] Comparative Example 5 A glycidyl methacrylate modified rubber pressure-sensitive adhesive, the preparation method of which includes the following steps: By weight, 100 parts of styrene-butadiene-styrene copolymer SBS (trade name: 1177, hardness 63, manufactured by Jusheng Technology Co., Ltd.) with a styrene content of 23% and 233 parts of toluene were added to the reactor and mixed. After stirring thoroughly for 6 hours until the mixture was homogeneous, 5 parts of glycidyl methacrylate were added. The system temperature was raised to 80°C, and nitrogen gas was purged for 30 minutes under stirring. Benzoyl peroxide initiator was added under nitrogen atmosphere. The reaction was carried out for 4 hours, the temperature was raised to 95°C, and the reaction was maintained for 2 hours. The mixture was then cooled to room temperature to obtain glycidyl methacrylate modified rubber pressure-sensitive adhesive.

[0066] A support film for flexible OLED displays includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer, and a release layer stacked sequentially. Its preparation method includes the following steps: S1. By weight, 100 parts of the glycidyl methacrylate modified rubber, 9 parts of terpene tackifying resin (trade name: 3115, softening point 115℃, manufactured by KRATON), 0.12 parts of cationic initiator (trade name: 1176, manufactured by Guangyi Chemical Company), 0.12 parts of photosensitizer (trade name: 819, manufactured by BASF), 0.4 parts of antioxidant (trade name: 1010, manufactured by Changzhou Jiatong Chemical Company), and 65 parts of toluene are mixed and stirred evenly to obtain a UV crosslinkable rubber pressure-sensitive adhesive with a mass fraction of 22%. S2. Apply UV-crosslinkable rubber pressure-sensitive adhesive to the second surface of a 75μm PET substrate layer, bake at 110℃ for 3 minutes to form a 15μm thick pressure-sensitive adhesive layer. Then, attach a 50μm lightweight release film to the adhesive surface on the other side of the pressure-sensitive adhesive layer and irradiate with ultraviolet light at room temperature (light energy 1000mJ / cm²). 2 (The wavelength is in the UVA region). Finally, a protective film layer (the polyurethane adhesive layer of the protective film layer is bonded to the antistatic coating) is applied to the antistatic coating of the PET substrate layer to obtain a support film for flexible OLED displays.

[0067] The support films prepared in Examples 1-4 and Comparative Examples 1-5 for use in flexible OLED displays were subjected to the following performance tests. (1) Peel strength: The support film samples in the examples and comparative examples were cut into samples with a width of 25.4 mm and a length of 300 mm. The light release film was peeled off, and the sample was rolled onto the Glass with a 2 KG roller at a speed of 600 mm / min. After standing for 20 min, the 180° peel adhesion was tested using a tensile testing machine. The specific test method refers to the ASMTD3330 international standard.

[0068] (2) Storage modulus: Samples for measurement were obtained by laminating each pressure-sensitive adhesive film layer to a thickness of approximately 1 mm. Dynamic viscoelasticity was measured using an ARES instrument manufactured by TA Instruments under the following conditions. The storage modulus G' at -20℃ / 25℃ / 200℃ was read from the measurement results.

[0069] (3) Transmittance: The data can be read using a transmittance tester.

[0070] (4) Surface resistivity: The surface resistivity test performance was carried out in accordance with GB / T1410-2006.

[0071] (5) Dielectric constant: The dielectric constant Dk of the plate was determined at 100 kHz using the plate capacitance method.

[0072] (6) Gel fraction: The mass of the porous membrane (Wa (mg)) was determined. 1g of the adhesive layer was taken from the obtained adhesive sheet and wrapped in a purse-string liner within the porous membrane, then sealed with staples. The purse-string liner was placed in 50mL of toluene. It was left at room temperature for one day, then the purse-string liner was removed, and the membrane was dried at 130℃ for 2 hours. The weight of the purse-string liner (Wb (mg)) was determined, and the gel fraction was calculated using the following formula: Gel fraction (%) = (Wb - Wa) / 1 × 100.

[0073] The test results are shown in Table 1 below: Table 1 The test results show that the flexible OLED support films prepared in Examples 1-4 have the characteristics of high viscosity, high transmittance, low low-temperature modulus, high high-temperature modulus, low dielectric constant, and high surface impedance. A comparison between the comparative examples and the embodiments further illustrates this. Examples 1-4 and Comparative Examples 1-3 used SIS rubber modified with glycidyl methacrylate, Comparative Example 4 used acrylate resin, and Comparative Example 5 used SBS rubber modified with glycidyl methacrylate. Using SIS as a raw material, the dielectric constant of the support film adhesive layer was found to be below 2.5. Comparative Example 4 used acrylate resin, which has many colloidal polar groups, leading to an increased dielectric constant. Comparative Example 5 used SBS rubber as the modifying material. Because SBS rubber has fewer branches than SIS, the support film adhesive layer made with SBS rubber has smaller air gaps between the molecules and the substrate, resulting in an increased dielectric constant of the adhesive layer in Comparative Example 5. Therefore, when using a support film mainly composed of SIS rubber, the probability of the screen being damaged by static electricity during the manufacturing process is lower. Comparative Example 4 uses acrylate resin, which has more polar groups in its molecular chain segments. Therefore, its surface resistance is lower than that of other examples that use SIS / SBS ​​rubber as the main body. It is easier to accumulate static electricity in the screen manufacturing process, resulting in a higher probability of screen damage. In Example 1, when irradiated with ultraviolet light at an energy of 1000 mJ, the epoxy groups in the system reacted fully, resulting in a gel fraction of 65%. In contrast, in Example 2, with an irradiation energy of 500 mJ, only a portion of the epoxy groups reacted, resulting in a colloidal gel fraction of 30% and a lower high-temperature modulus than Example 1. Therefore, Example 1 exhibits superior high-temperature resistance. Example 3 increased the amount of tackifying resin added compared to Example 1. Under the same light energy, the gel fraction of Example 3 decreased, resulting in a decrease in high-temperature modulus. Example 4: Based on Example 1, the terpene tackifying resin with a softening point of 115℃ was replaced with a rosin ester tackifying resin with a softening point of 81℃. After ultraviolet radiation, a colloid with the same gel fraction was obtained. However, due to the smaller molecular weight of the tackifying resin with lower softening point, the high temperature modulus decreased from 82 kPa to 23 kPa, which increased the risk of high temperature process. Compared with Example 1, Comparative Example 1 did not add photosensitizer. Under the same radiation energy, the reaction efficiency decreased and the gel fraction of the obtained film was only 35%. Therefore, the high temperature modulus was lower than that of Example 1, and the risk of peeling and bubble formation at high temperature increased. Compared with Example 1, Comparative Example 2 did not add a cationic initiator, so under the same radiation energy conditions, it could not initiate the ring-opening crosslinking of epoxy groups, and the resulting film had a gel fraction of 0 and a low high-temperature modulus. Compared with Example 1, Comparative Example 3 used unmodified SIS as the rubber matrix. Since the system does not have epoxy groups, it cannot undergo cross-linking reaction after being irradiated by ultraviolet light. Therefore, the gel fraction of the obtained film is 0 and the high temperature modulus is low. Comparative Example 4 used acrylic resin. Although the high temperature modulus and adhesion properties met the requirements, compared with Example 1, Comparative Example 4 had a higher dielectric constant and lower surface resistance. Therefore, it was more likely to be damaged by static electricity during the manufacturing process. Comparative Example 5 used glycidyl methacrylate-modified SBS rubber, which had lower transmittance and higher dielectric constant compared to Example 1. The test results show that the flexible OLED support film prepared in Example 1 has the characteristics of high viscosity, high transmittance, low low temperature modulus, high high temperature modulus, low dielectric constant, and high surface impedance. Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A UV-crosslinkable rubber pressure-sensitive adhesive, characterized in that, It includes the following raw material components by weight: 50-100 parts of (meth)acrylate modified rubber, 5-25 parts of tackifying resin, 0.01-1 part of first initiator, 0.01-1 part of photosensitizer, 0.1-10 parts of antioxidant, and 50-150 parts of first organic solvent; The (meth)acrylate modified rubber is mainly composed of styrene-isoprene-styrene (SIS), which is obtained by thermally initiating polymerization with a free radical initiator after mixing with (meth)acrylate monomers. The (meth)acrylate monomer is a (meth)acrylate monomer containing an epoxy group.

2. The UV-crosslinkable rubber pressure-sensitive adhesive according to claim 1, characterized in that, The raw materials for preparing the (meth)acrylate modified rubber include, by weight, 80-120 parts of styrene-isoprene-styrene, 5-20 parts of (meth)acrylate monomer, 150-300 parts of second organic solvent, and 0.1-0.4 parts of free radical initiator.

3. The UV-crosslinkable rubber pressure-sensitive adhesive according to claim 2, characterized in that, The (meth)acrylate modified rubber was prepared by the following method: According to the weight ratio, styrene-isoprene-styrene copolymer, (meth)acrylate monomer, and organic solvent are added to the reactor and stirred for 3-12 hours. The system temperature is raised to 78-83℃, and nitrogen is purged under stirring for 20-40 minutes. The initiator is added under nitrogen, and the reaction is carried out for 2-4 hours. The temperature is raised to 90-95℃ and the reaction is maintained for 2-3 hours. The mixture is then cooled to room temperature to obtain (meth)acrylate modified rubber.

4. The UV-crosslinkable rubber pressure-sensitive adhesive according to claim 2, characterized in that, The (meth)acrylate monomer is one or two of glycidyl methacrylate and glycidyl acrylate, the free radical initiator is one or more of azobisisobutyronitrile, azobisisobutyronitrile, dimethyl azobisisobutyrate, and benzoyl peroxide, and the second organic solvent is toluene.

5. The UV-crosslinkable rubber pressure-sensitive adhesive according to claim 1, characterized in that, The tackifying resin is one or more of the following: C5 aliphatic petroleum resin, C9 aromatic petroleum resin, aromatic hydrocarbon modified aliphatic resin, rosin, hydrogenated rosin, and terpene resin. The first initiator is one or more of the following: diazonium salt, diaryliodomonium salt, triarylthionium salt, alkylthionium salt, iron aromatic salt, sulfonyloxy ketone, and triarylsiloxane; The photosensitizer is at least one of alkyl phenyl ketones, benzophenones, acylphosphine oxides, and thioxanthones. The antioxidant is any one or a combination of dilaurate thiodipropionate, antioxidant 1010, antioxidant 4020, and antioxidant 1076. The first organic solvent is one or a combination of more of the following: methylcyclohexane, cyclohexane, hexane, toluene, or xylene.

6. The UV-crosslinkable rubber pressure-sensitive adhesive according to claim 5, characterized in that, The first initiator is one or two of the following: 4,4'-di-tert-butylphenyliodonium hexafluorophosphate, 4,4'-bis(dodecylphenyliodonium)hexafluoroantimonate, 4,4'-xylyliodonium hexafluorophosphate, mixed thionium hexafluorophosphate, and mixed thionium hexafluoroantimonate. The photosensitizer is any one or a combination of 819, 651, 184, TPO, ITX, and benzophenone.

7. A method for preparing a UV-crosslinkable rubber pressure-sensitive adhesive as described in any one of claims 1-6, characterized in that, Includes the following steps: By weight, 50-100 parts of (meth)acrylate modified rubber, 5-25 parts of tackifying resin, 0.01-1 part of first initiator, 0.01-1 part of photosensitizer, 0.1-10 parts of antioxidant, and 50-150 parts of first organic solvent are mixed evenly to obtain UV crosslinkable rubber pressure-sensitive adhesive.

8. A support film for use in flexible OLED displays, characterized in that, It includes a protective film layer, a substrate layer, a pressure-sensitive adhesive layer and a release layer stacked in sequence; the pressure-sensitive adhesive layer is obtained by coating the UV-crosslinkable rubber pressure-sensitive adhesive according to any one of claims 1-6 onto the substrate layer and then curing it.

9. The support film for a flexible OLED display according to claim 8, characterized in that, The protective film layer includes an antistatic transparent PET film and a polyurethane adhesive layer bonded to the antistatic transparent PET film, and the thickness of the protective film layer is 25-75μm. The substrate layer is a PET substrate layer with an antistatic coating on the first side, and the thickness of the substrate layer is 25-80μm.

10. The support film for a flexible OLED display according to claim 9, characterized in that, It is prepared by the following method: the UV crosslinkable rubber pressure-sensitive adhesive described in any one of claims 1-6 is uniformly coated on the second side of the substrate layer, baked at 100-120°C for 3-5 minutes to form a pressure-sensitive adhesive layer, a release film is bonded to the other side of the pressure-sensitive adhesive layer to form a release layer, irradiated with a mercury lamp, and finally the polyurethane adhesive layer of the protective film layer is bonded to the first side of the substrate layer to obtain the support film used in flexible OLED displays.

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