Bending-resistant high-light-transmittance protective film for folding screen and preparation process of bending-resistant high-light-transmittance protective film

Abstract

The invention belongs to the technical field of protective films, and particularly relates to a bending-resistant high-light-transmittance protective film for a folding screen and a preparation process of the bending-resistant high-light-transmittance protective film. The bending-resistant high-light-transmittance protective film sequentially comprises a release layer, an OCA optical adhesive layer, a flexible base material layer A, a flexible base material layer B, a silica gel layer and a protective layer from top to bottom, wherein raw materials of the flexible base material layer A and the flexible base material layer B both contain organic and inorganic hybrid particles, and the content of the organic and inorganic hybrid particles in the raw materials of the flexible base material layer A is larger than that of the organic and inorganic hybrid particles in the raw materials of the flexible base material layer B. The bending-resistant high-light-transmittance protective film for the folding screen is excellent in bending resistance, especially low-temperature bending resistance, light transmittance and hardness.

Description

Technical Field

[0001] The present invention belongs to the technical field of protective films, and specifically relates to a bending-resistant and high-transmittance protective film for folding screens and a preparation process thereof. Background Art

[0002] With the rapid development of flexible display technology, foldable smartphones, tablets, and rollable display devices are becoming a key development direction in the consumer electronics sector. Compared to traditional rigid screens, foldable screens offer portability while maintaining a large display. However, their unique mechanical structure also places higher demands on screen protection materials. The core of foldable screen devices lies in the screen's reusable bendability, which generally requires the following conditions: high bending resistance, high light transmittance, low-temperature adaptability, and surface hardness.

[0003] Existing screen protective films mainly fall into the following categories: 1. Tempered glass-like protective films, which offer high hardness and scratch resistance, but are brittle and cannot withstand repeated bending, making them suitable only for traditional candy-bar phones. 2. PET films, which offer high light transmittance but are prone to permanent creases after bending and have a narrow temperature resistance range. 3. PI films, which offer excellent high-temperature resistance and high mechanical strength and were initially used in flexible screen substrates, have low light transmittance and a high yellowness index, which affects display quality. 4. TPU films, which offer excellent flexibility and bending resistance but are prone to scratching due to their low surface hardness. 5. Composite films, typically consisting of OCA adhesive + PI + hardened coating, offer increased hardness but limited low-temperature bendability. There are also silicone layer + PET composite films, which offer improved adhesion but reduced light transmittance. Existing protective films also contain high-hardness materials (such as inorganic nanoparticles), which often increase light scattering, reduce light transmittance, and increase modulus sharply at low temperatures, making them prone to microcracks when bent. That is, the existing protective film technology cannot meet the comprehensive requirements of folding screens for high light transmittance, bending resistance, low temperature stability and hardness. Therefore, there is an urgent need for a bending-resistant, high-transmittance protective film for folding screens that has bending resistance, especially low-temperature bending resistance, transmittance and hardness, and a preparation process thereof. Summary of the Invention

[0004] The object of the present invention is to provide a bending-resistant and high-transmittance protective film for a folding screen, which has excellent bending resistance, especially low-temperature bending resistance, transmittance and hardness.

[0005] In order to achieve the above object, the present invention provides the following technical solutions: In a first aspect, the present invention provides a bending-resistant and high-transmittance protective film for a foldable screen, wherein the bending-resistant and high-transmittance protective film comprises, from top to bottom, a release layer, an OCA optical adhesive layer, a flexible substrate layer A, a flexible substrate layer B, a silicone layer, and a protective layer; The raw materials of both the flexible substrate layer A and the flexible substrate layer B contain organic-inorganic hybrid particles, and the content of the organic-inorganic hybrid particles in the raw materials of the flexible substrate layer A is greater than that in the raw materials of the flexible substrate layer B.

[0006] The traditional flexible base and silicone layer solution produce stress concentration, especially at low temperatures, due to different material shrinkage rates, resulting in interface peeling or cracking, which reduces the bending resistance of the bend-resistant and high-transmittance protective film at low temperatures. In the present invention, the gradient design of organic-inorganic hybrid particles in the flexible substrate layer A and the flexible substrate layer B can better buffer the flexible substrate layer and the silicone layer, reduce the internal stress caused by low-temperature temperature changes, and enable the bend-resistant and high-transmittance protective film to maintain better stability.

[0007] Preferably, the thickness of the protective layer is 15-80 microns, preferably 40-60 microns.

[0008] Preferably, the protective layer is made of PET material.

[0009] The protective layer in the present invention can be obtained commercially. Preferably, the protective layer is purchased from Shanghai Jiri Electronics Co., Ltd. with a brand name of AR-N and a thickness of 50 μm.

[0010] Preferably, the thickness of the silica gel layer is 20-80 microns, preferably 30-35 microns.

[0011] Preferably, the silicone layer is obtained by subjecting silicone glue to a step including thermal curing.

[0012] Preferably, the silicone glue is addition-type liquid silicone rubber glue, preferably model Kanglibang KL-2620.

[0013] Preferably, the thickness of the flexible substrate layer B is 10-60 microns, preferably 20-25 microns.

[0014] Preferably, the thickness of the flexible substrate layer A is 30-100 microns, preferably 70-80 microns.

[0015] Preferably, the flexible substrate layer B is obtained from a flexible adhesive B through a step including thermal curing.

[0016] Preferably, the flexible substrate layer A is obtained from a flexible adhesive material A through a step including thermal curing.

[0017] Preferably, the raw materials of the flexible rubber material B include, by weight: 100 parts of hydroxy acrylic resin, 50-65 parts of hyperbranched polyester polyol, 10-15 parts of polyketone resin, 50-55 parts of organic-inorganic hybrid particles, 4-5 parts of leveling agent, 8-15 parts of curing agent, and 200-235 parts of diluent.

[0018] Preferably, the preparation method of the flexible rubber material B comprises: adding a polyketone resin to a diluent at 70-80° C. according to the corresponding weight parts of the raw materials of the flexible rubber material B; after the polyketone resin is dissolved, adding a hydroxyl acrylic resin, a hyperbranched polyester polyol, organic-inorganic hybrid particles, a leveling agent and a curing agent and mixing for 20-60 minutes to obtain the flexible rubber material B.

[0019] Preferably, the raw materials of the flexible rubber material A include, by weight: 100 parts of hydroxy acrylic resin, 50-65 parts of hyperbranched polyester polyol, 10-15 parts of polyketone resin, 15-20 parts of organic-inorganic hybrid particles, 4-5 parts of leveling agent, 8-15 parts of curing agent, and 180-200 parts of diluent.

[0020] Preferably, the preparation method of the flexible rubber material A comprises: adding a polyketone resin to a diluent at 70-80° C. according to the corresponding weight parts of the raw materials of the flexible rubber material A; after the polyketone resin is dissolved, adding a hydroxyl acrylic resin, a hyperbranched polyester polyol, organic-inorganic hybrid particles, a leveling agent and a curing agent and mixing for 20-60 minutes to obtain the flexible rubber material A.

[0021] The flexible substrate layer A and the flexible substrate layer B in the present invention can better achieve excellent flexibility and bending resistance, especially low-temperature bending resistance. It is speculated that the reason is that the hydroxyl acrylic resin matrix is ​​combined with the flexible cross-linked network of the hyperbranched polyester polyol, which can ensure that the molecular chain segments can still maintain their mobility at low temperatures and avoid embrittlement. At the same time, the organic-inorganic hybrid particles are combined to form microscopic reinforcement points in the system to inhibit crack initiation and expansion, especially effectively preventing brittle fracture at low temperatures. The polyketone resin can enhance the intermolecular force, increase the cohesive energy, and prevent interlayer peeling during bending.

[0022] Preferably, the viscosity of the hydroxy acrylic resin at 23° C. is 1700-1900 mPa·s, preferably 1800 mPa·s.

[0023] The hydroxy acrylic resin in the present invention can be obtained commercially. Preferably, the hydroxy acrylic resin is Covestro hydroxy acrylic resin Desmophen A160X.

[0024] Hyperbranched polyester polyols are a type of polyester polymer with a highly branched structure and polyhydroxyl functional groups at the ends. Preferably, the hydroxyl value of the hyperbranched polyester polyol is 200-300 mg KOH / g, preferably 270 mg KOH / g.

[0025] The hyperbranched polyester polyol in the present invention can be obtained commercially. Preferably, the model of the hyperbranched polyester polyol is BASF Basonol-HPE 1170 B.

[0026] Polyketone resins are a class of high-performance polymers formed by the alternating copolymerization of carbon monoxide and olefins. Their molecular chains typically contain regular ketone structural units. The polyketone resins used in the present invention are commercially available, preferably PolySource Integra™ POK 9060 from the United States.

[0027] Preferably, the preparation method of the organic-inorganic hybrid particles comprises: (1) Ethanol, water and ammonia water are first mixed, and then ethyl orthosilicate is added dropwise. After the addition is completed, a first reaction is carried out to obtain a silica sol; (2) Tetrabutyl titanate and ethanol are mixed for a second time to obtain a dispersion, and then silica sol is added dropwise to the dispersion. After the addition is complete, a second reaction is performed, and then centrifugation, washing, and drying are performed to obtain inorganic particles; (3) The inorganic particles, ethanol and water are mixed for a third time, and then a coupling agent KH-570 is added for a third reaction, centrifuged, washed and dried to obtain modified inorganic particles; (4) The modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier and water are mixed for the fourth time, and then the temperature is raised to 70-75°C under nitrogen protection, and a potassium persulfate aqueous solution with a concentration of 5-8 wt% is added dropwise. After the addition is completed, the mixture is kept warm for 5-6 hours, and then cooled to room temperature, filtered, dried, and ground through a 1200 mesh sieve to obtain organic-inorganic hybrid particles.

[0028] The organic-inorganic hybrid particles in the present invention can better increase the transmittance, low-temperature bending resistance and hardness of the bending-resistant and high-transmittance protective film. The reason is that the high refractive index of titanium dioxide and the low refractive index of silicon dioxide in the composite inorganic core formed by silicon dioxide and titanium dioxide can be matched with the refractive index of the polymer system through proportion control, thereby reducing interface light scattering. At the same time, the organic-inorganic hybrid structure formed by chemical bonding can enhance the interface bonding force, avoid the defects of transmittance caused by macroscopic phase separation and interface debonding at low temperatures; in addition, the organic-inorganic hybrid particles can enable the system to form a three-dimensional network structure through polymerization, thereby further improving the rigidity.

[0029] Preferably, in step (1), the volume ratio of ethanol, water and ammonia water is 100: (20-25): (5-6).

[0030] Preferably, in step (1), the concentration of the ammonia water is 28 wt %.

[0031] Preferably, in step (1), the volume ratio of ethyl orthosilicate to ethanol is 1:(6-7).

[0032] Preferably, in step (1), the first mixing conditions include: temperature of 40-45°C and time of 5-10 minutes.

[0033] Preferably, in step (1), the dripping speed of the ethyl orthosilicate is 1-2 mL / min.

[0034] Preferably, in step (1), the conditions of the first reaction include: temperature of 40-45°C and time of 2-3h.

[0035] Preferably, in step (2), the volume ratio of tetrabutyl titanate to ethanol is (15-20):100.

[0036] Preferably, in step (2), the volume ratio of the dispersion to the silica sol is 1:(6-7).

[0037] Preferably, in step (2), the silica sol is added at a rate of 0.5-1 mL / min.

[0038] Preferably, in step (2), the conditions of the second reaction include: reaction temperature of 60-70°C, and reaction time of 4-5h.

[0039] The centrifugation, washing and drying methods in step (2) of the present invention are conventional methods in the present invention. Preferably, in step (2), the centrifugation conditions include: a rotation speed of 5000-6000 rpm and a time of 5-10 min; the washing method includes: washing with ethanol 3-5 times; and the drying conditions include: vacuum drying at 60-70°C for 8-24 h.

[0040] Preferably, in step (3), the mass ratio of the inorganic particles, ethanol and water is (10-15): (90-95): (5-10).

[0041] Preferably, in step (3), the mass ratio of the coupling agent KH-570 to the inorganic particles is (1-1.5):10.

[0042] Preferably, in step (3), the third mixing conditions include: ultrasonication at room temperature for 10-30 minutes.

[0043] Preferably, in step (3), the conditions of the third reaction include: reflux reaction at 80-85°C for 6-7h.

[0044] Preferably, in step (3), the centrifugation, washing and drying methods are conventional methods of the present invention. Preferably, in step (3), the centrifugation conditions include: a rotation speed of 5000-6000 rpm and a time of 5-10 min; the washing method includes: washing with ethanol 3-5 times; and the drying conditions include: vacuum drying at 60-70°C for 8-24 h.

[0045] Preferably, in step (4), the mass ratio of the modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier, potassium persulfate aqueous solution and water is (0.5-0.6): (1-1.5): (2.5-3): (0.05-0.06): (0.6-0.7): 100.

[0046] Preferably, in step (4), the fourth mixing conditions include: mixing at a rotation speed of 8000-12000 rpm for 20-40 min at room temperature.

[0047] Preferably, in step (4), the potassium persulfate aqueous solution is added dropwise within 1 hour.

[0048] In step (4), the filtering and drying methods are conventional methods in the present invention. Preferably, in step (4), the drying conditions include: vacuum drying at 75-80°C for 8-24h.

[0049] Preferably, the leveling agent is selected from at least one of leveling agent BYK-381, leveling agent BYK-310, leveling agent BYK-358, leveling agent Tego FLOW 425 and leveling agent TEGO 432.

[0050] Preferably, the curing agent is selected from cyanate curing agents.

[0051] Preferably, the cyanate curing agent is selected from at least one of Desmodur N75, Desmodur Z4470, Desmodur N3390 and BASF HI100ap, preferably Desmodur N3390.

[0052] Preferably, the diluent is selected from a combination of dimethylformamide and cyclohexanone.

[0053] Preferably, the weight ratio of dimethylformamide to cyclohexanone is 1:(3-4).

[0054] [OCA optical adhesive layer] Preferably, the thickness of the OCA optical adhesive layer is 30-100 microns, preferably 40-50 microns.

[0055] Preferably, the OCA optical adhesive layer is obtained by subjecting OCA adhesive to a step including photocuring.

[0056] Preferably, the viscosity of the OCA glue at 25° C. is 1500-2500 mPa·s, preferably 2500 mPa·s.

[0057] The OCA glue in the present invention can be obtained commercially. Preferably, the OCA glue is purchased from Shenzhen Haoli New Material Technology Co., Ltd. and the model number is HL3010.

[0058] [Release layer] In the present invention, the release layer can protect the bending-resistant and high-transmittance protective film from dust, scratches, or accidental adhesion with other materials during storage and transportation. Preferably, the release layer is a PET release film.

[0059] Preferably, the thickness of the release layer is 20-80 microns.

[0060] The PET release film in the present invention can be obtained commercially. Preferably, the PET release film is purchased from Suzhou Amberley Electronic Materials Co., Ltd., with a model number of ABL75TM1-3 and a thickness of 75 μm.

[0061] In a second aspect, the present invention provides a method for preparing the bending-resistant, high-transmittance protective film for a foldable screen according to the first aspect of the present invention, the preparation method comprising: Silicone glue is applied on the protective layer, and a silicone layer with a thickness of 30-35 microns is formed through a first thermal curing process; flexible substrate layer B is applied on the silicone layer, and a flexible substrate layer B with a thickness of 20-25 microns is formed through a second thermal curing process; flexible adhesive material A is applied on flexible substrate layer B, and a flexible substrate layer A with a thickness of 70-80 microns is formed through a third thermal curing process; OCA glue is applied on flexible substrate layer A, and a OCA optical adhesive layer with a thickness of 40-50 microns is formed through light curing; a release layer is applied on the OCA optical adhesive layer to obtain a bending-resistant and high-transmittance protective film.

[0062] Preferably, the conditions for the first thermal curing include: a temperature of 130-135° C. and a time of 50-70 seconds.

[0063] Preferably, the conditions for the second thermal curing include: a temperature of 120-125° C. and a time of 5-8 minutes.

[0064] Preferably, the conditions of the third thermal curing include: a temperature of 120-125° C. and a time of 5-8 minutes.

[0065] Preferably, the light curing conditions include: a wavelength of 356 nm of ultraviolet light, a temperature of 90-100° C., and a time of 10-15 seconds.

[0066] Compared with the prior art, the advantages and beneficial effects of the present invention are: 1. The present invention utilizes a gradient design of organic-inorganic hybrid particles in flexible substrate layer A (high content) and flexible substrate layer B (low content), which can enhance flexibility and buffer stress, thereby synergistically improving overall bending resistance. Furthermore, the organic-inorganic hybrid particles can inhibit the embrittlement of the material at low temperatures, resulting in a bend-resistant, high-transmittance protective film for foldable screens with excellent bending resistance (especially in low-temperature environments). 2. The present invention uses organic-inorganic hybrid particles with matching refractive indices to reduce interfacial light scattering, achieving a transmittance of over 90%, thus avoiding blurry screen displays or rainbow patterns. Furthermore, the refractive index of the OCA optical adhesive layer is similar to that of the flexible substrate layer, which reduces interlayer reflection losses. This results in a bend-resistant, high-transmittance protective film for foldable screens with excellent optical properties. DETAILED DESCRIPTION The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0067] The information of the raw materials used in the Examples and Comparative Examples is as follows: The release layer is a PET release film purchased from Suzhou Amberley Electronic Materials Co., Ltd., model ABL75TM1-3, with a thickness of 75 μm; The material of the protective layer is PET material, purchased from Shanghai Jiri Electronics Co., Ltd., brand AR-N, with a thickness of 50 μm; The silicone glue is an addition-type liquid silicone rubber glue, model Kanglibang KL-2620; The model of the hydroxylated acrylic resin is Covestro's hydroxylated acrylic resin Desmophen A160X, with a viscosity of 1800 mPa·s at 23°C; The model of hyperbranched polyester polyol is BASF Basonol-HPE 1170 B, with a hydroxyl value of 270 mg KOH / g; The model of polyketone resin is PolySource Integra™ POK 9060 from the United States; The leveling agent is selected from the leveling agent BYK-381; The curing agent is selected from cyanate curing agent, specifically Desmodur N3390; The diluent is selected from a combination of dimethylformamide and cyclohexanone in a weight ratio of 1:3.

[0068] Example 1 This embodiment provides a bend-resistant, high-transmittance protective film for a foldable screen. The bend-resistant, high-transmittance protective film comprises, from top to bottom, a release layer, an OCA optical adhesive layer, a flexible substrate layer A, a flexible substrate layer B, a silicone layer, and a protective layer. The raw materials of both flexible substrate layer A and flexible substrate layer B contain organic-inorganic hybrid particles, and the content of the organic-inorganic hybrid particles in the raw material of flexible substrate layer A is greater than the content of the organic-inorganic hybrid particles in the raw material of flexible substrate layer B. The thickness of the silicone layer is 35 microns, and the silicone layer is obtained by applying silicone glue through a process including heat curing; The flexible substrate layer A has a thickness of 70 microns and is obtained from a flexible adhesive material A through a process including thermal curing. The raw materials for the preparation include, by weight, 100 parts of a hydroxylated acrylic resin, 50 parts of a hyperbranched polyester polyol, 10 parts of a polyketone resin, 15 parts of organic-inorganic hybrid particles, 4 parts of a leveling agent, 8 parts of a curing agent, and 180 parts of a diluent. The preparation method comprises: adding the polyketone resin to the diluent at 70° C. according to the corresponding parts by weight of the raw materials of the flexible adhesive material A; after the polyketone resin is dissolved, adding the hydroxylated acrylic resin, hyperbranched polyester polyol, organic-inorganic hybrid particles, the leveling agent, and the curing agent and mixing for 30 minutes to obtain the flexible adhesive material A. The flexible substrate layer B has a thickness of 20 microns and is obtained from a flexible adhesive material B through a step including thermal curing. The raw materials for the preparation include, by weight, 100 parts of a hydroxylated acrylic resin, 50 parts of a hyperbranched polyester polyol, 10 parts of a polyketone resin, 50 parts of organic-inorganic hybrid particles, 4 parts of a leveling agent, 8 parts of a curing agent, and 200 parts of a diluent. The preparation method comprises: adding the polyketone resin to the diluent at 70° C. according to the corresponding weight parts of the raw materials of the flexible adhesive material B; after the polyketone resin is dissolved, adding the hydroxylated acrylic resin, hyperbranched polyester polyol, organic-inorganic hybrid particles, leveling agent, and curing agent and mixing for 30 minutes to obtain the flexible adhesive material B. The preparation method of organic-inorganic hybrid particles includes: (1) Ethanol, water and ammonia water are first mixed, and then ethyl orthosilicate is added dropwise. After the addition is completed, a first reaction is carried out to obtain a silica sol; (2) Tetrabutyl titanate and ethanol are mixed for a second time to obtain a dispersion, and then silica sol is added dropwise to the dispersion. After the addition is complete, a second reaction is performed, and then centrifugation, washing, and drying are performed to obtain inorganic particles; (3) The inorganic particles, ethanol and water are mixed for a third time, and then a coupling agent KH-570 is added for a third reaction, centrifuged, washed and dried to obtain modified inorganic particles; (4) The modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier and water were mixed for the fourth time, and then the temperature was raised to 70°C under nitrogen protection, and a 6 wt% potassium persulfate aqueous solution was added dropwise. After the addition was completed, the mixture was kept warm for 5 hours, and then cooled to room temperature, filtered, dried, and ground through a 1200 mesh sieve to obtain organic-inorganic hybrid particles; In step (1), the volume ratio of ethanol, water and ammonia water is 100:20:5; the concentration of ammonia water is 28 wt%; the volume ratio of ethyl orthosilicate to ethanol is 1:6; the first mixing conditions include: temperature of 40°C and time of 10 min; the dripping rate of ethyl orthosilicate is 1 mL / min; the first reaction conditions include: temperature of 40°C and time of 3 h; In step (2), the volume ratio of tetrabutyl titanate to ethanol is 15:100; the volume ratio of the dispersion to the silica sol is 1:6; the drop rate of the silica sol is 0.5 mL / min; the conditions for the second reaction include: a reaction temperature of 60° C. and a reaction time of 5 h; the conditions for centrifugation include: a speed of 5000 rpm and a time of 10 min; the washing method includes: washing with ethanol three times; and the drying conditions include: vacuum drying at 60° C. for 12 h. In step (3), the mass ratio of inorganic particles, ethanol and water is 10:90:10; the mass ratio of coupling agent KH-570 to inorganic particles is 1:10; the third mixing conditions include: ultrasonication at room temperature for 20 minutes; the third reaction conditions include: reflux reaction at 80°C for 7 hours; the centrifugation conditions include: speed of 6000 rpm, time for 10 minutes; the washing method includes: washing with ethanol 3 times; the drying conditions include: vacuum drying at 60°C for 12 hours; In step (4), the mass ratio of the modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier, potassium persulfate aqueous solution and water is 0.5:1:2.5:0.05:0.6:100; the fourth mixing conditions include: mixing at a speed of 10,000 rpm at room temperature for 30 minutes; the potassium persulfate aqueous solution is controlled to be added dropwise within 1 hour; the drying conditions include: vacuum drying at 80°C for 12 hours; The thickness of the OCA optical adhesive layer is 50 μm. The OCA optical adhesive layer is obtained by a process including light curing of OCA adhesive. The OCA adhesive is purchased from Shenzhen Haoli New Material Technology Co., Ltd., model HL3010, and has a viscosity of 2500 mPa·s at 25°C. The method for preparing the bending-resistant and high-transmittance protective film for a folding screen in this embodiment includes: Silicone glue is applied to the protective layer and subjected to a first thermal curing step to form a 35-micron thick silicone layer. Flexible substrate layer B is applied to the silicone layer and subjected to a second thermal curing step to form a 20-micron thick flexible substrate layer B. Flexible adhesive material A is applied to flexible substrate layer B and subjected to a third thermal curing step to form a 70-micron thick flexible substrate layer A. OCA adhesive is applied to flexible substrate layer A and subjected to light curing to form a 50-micron thick OCA optical adhesive layer. A release layer is applied to the OCA optical adhesive layer to obtain a bend-resistant, high-transmittance protective film. The conditions for the first thermal curing include: temperature of 130°C and time of 60 seconds; the conditions for the second thermal curing include: temperature of 120°C and time of 8 minutes; the conditions for the third thermal curing include: temperature of 120°C and time of 8 minutes; the conditions for light curing include: wavelength of ultraviolet lamp of 356nm, temperature of 90°C and time of 15 seconds.

[0069] Example 2 The specific implementation of this embodiment is the same as that of Example 1, except that: The thickness of the silicone layer is 30 microns; the silicone layer is obtained by a step including heat curing of silicone glue; The flexible substrate layer A has a thickness of 80 microns and is obtained from a flexible adhesive material A through a step including thermal curing. The raw materials include, by weight, 100 parts of a hydroxylated acrylic resin, 65 parts of a hyperbranched polyester polyol, 15 parts of a polyketone resin, 20 parts of organic-inorganic hybrid particles, 5 parts of a leveling agent, 15 parts of a curing agent, and 200 parts of a diluent. The preparation method comprises: adding the polyketone resin to the diluent at 80° C. according to the corresponding weight parts of the raw materials of the flexible adhesive material A; after the polyketone resin is dissolved, adding the hydroxylated acrylic resin, hyperbranched polyester polyol, organic-inorganic hybrid particles, the leveling agent, and the curing agent and mixing for 40 minutes to obtain the flexible adhesive material A; The flexible substrate layer B has a thickness of 25 microns and is obtained from a flexible adhesive material B through a step including thermal curing. The raw materials of the flexible adhesive material B include, by weight, 100 parts of a hydroxylated acrylic resin, 65 parts of a hyperbranched polyester polyol, 15 parts of a polyketone resin, 55 parts of organic-inorganic hybrid particles, 5 parts of a leveling agent, 15 parts of a curing agent, and 235 parts of a diluent. The preparation method comprises: adding the polyketone resin to the diluent at 80° C. according to the corresponding parts by weight of the raw materials of the flexible adhesive material B; after the polyketone resin is dissolved, adding the hydroxylated acrylic resin, the hyperbranched polyester polyol, the organic-inorganic hybrid particles, the leveling agent, and the curing agent and mixing for 40 minutes to obtain the flexible adhesive material B; In step (1) of the method for preparing organic-inorganic hybrid particles, the volume ratio of ethanol, water and ammonia water is 100:25:6; the concentration of ammonia water is 28 wt%; the volume ratio of ethyl orthosilicate to ethanol is 1:7; the first mixing conditions include: temperature of 45°C and time of 5 minutes; the dripping rate of ethyl orthosilicate is 1 mL / min; the first reaction conditions include: temperature of 45°C and time of 2 hours; In step (2), the volume ratio of tetrabutyl titanate to ethanol is 20:100; the volume ratio of the dispersion to the silica sol is 1:7; the drop rate of the silica sol is 0.5 mL / min; the conditions for the second reaction include: a reaction temperature of 70° C. and a reaction time of 4 h; the conditions for centrifugation include: a speed of 6000 rpm and a time of 5 min; the washing method includes: washing with ethanol three times; and the drying conditions include: vacuum drying at 60° C. for 12 h. In step (3), the mass ratio of inorganic particles, ethanol and water is 15:95:5; the mass ratio of coupling agent KH-570 to inorganic particles is 1.5:10; the third mixing conditions include: ultrasonication at room temperature for 30 minutes; the third reaction conditions include: reflux reaction at 85°C for 6 hours; the centrifugation conditions include: speed of 6000 rpm, time for 10 minutes; the washing method includes: washing with ethanol 3 times; the drying conditions include: vacuum drying at 60°C for 12 hours; In step (4), the mass ratio of the modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier, potassium persulfate aqueous solution and water is 0.6:1.5:3:0.06:0.7:100; the fourth mixing conditions include: mixing at a speed of 12000 rpm at room temperature for 20 minutes; the potassium persulfate aqueous solution is controlled to be added dropwise within 1 hour; the drying conditions include: vacuum drying at 80°C for 12 hours; The thickness of the OCA optical adhesive layer is 40 μm. The OCA optical adhesive layer is obtained by a process including light curing of OCA adhesive. The OCA adhesive is purchased from Shenzhen Haoli New Material Technology Co., Ltd., model HL3010, and has a viscosity of 2500 mPa·s at 25°C. The method for preparing the bending-resistant and high-transmittance protective film for a folding screen in this embodiment includes: Silicone glue is applied to the protective layer and subjected to a first thermal curing step to form a 30-micron thick silicone layer. Flexible substrate layer B is applied to the silicone layer and subjected to a second thermal curing step to form a 25-micron thick flexible substrate layer B. Flexible adhesive material A is applied to flexible substrate layer B and subjected to a third thermal curing step to form an 80-micron thick flexible substrate layer A. OCA adhesive is applied to flexible substrate layer A and subjected to light curing to form a 40-micron thick OCA optical adhesive layer. A release layer is applied to the OCA optical adhesive layer to obtain a bend-resistant, high-transmittance protective film. The conditions for the first thermal curing include: temperature of 130°C and time of 60 seconds; the conditions for the second thermal curing include: temperature of 125°C and time of 5 minutes; the conditions for the third thermal curing include: temperature of 125°C and time of 5 minutes; the conditions for light curing include: wavelength of ultraviolet lamp of 356nm, temperature of 100°C and time of 10 seconds.

[0070] Example 3 The specific implementation of this embodiment is the same as that of Example 1, except that: The thickness of the silicone layer is 33 microns; the silicone layer is obtained by applying silicone glue through a process including heat curing; Flexible substrate layer A has a thickness of 77 microns and is obtained from flexible adhesive material A through a step including thermal curing. The raw materials, in parts by weight, include: 100 parts of hydroxy acrylic resin, 54 parts of hyperbranched polyester polyol, 12 parts of polyketone resin, 18 parts of organic-inorganic hybrid particles, 4.4 parts of leveling agent, 12 parts of curing agent, and 188 parts of diluent. The preparation method comprises: adding the polyketone resin to the diluent at 75° C. according to the corresponding parts by weight of the raw materials of flexible adhesive material A; after the polyketone resin is dissolved, adding the hydroxy acrylic resin, hyperbranched polyester polyol, organic-inorganic hybrid particles, leveling agent, and curing agent and mixing for 30 minutes to obtain flexible adhesive material A; The flexible substrate layer B has a thickness of 23 microns and is obtained from a flexible adhesive material B through a step including thermal curing. The raw materials of the flexible adhesive material B include, by weight, 100 parts of a hydroxylated acrylic resin, 54 parts of a hyperbranched polyester polyol, 12 parts of a polyketone resin, 54 parts of organic-inorganic hybrid particles, 4.4 parts of a leveling agent, 12 parts of a curing agent, and 223 parts of a diluent. The preparation method includes: adding the polyketone resin to the diluent at 75° C. according to the corresponding parts by weight of the raw materials of the flexible adhesive material B; after the polyketone resin is dissolved, adding the hydroxylated acrylic resin, the hyperbranched polyester polyol, the organic-inorganic hybrid particles, the leveling agent, and the curing agent and mixing for 30 minutes to obtain the flexible adhesive material B; In step (1) of the method for preparing organic-inorganic hybrid particles, the volume ratio of ethanol, water and ammonia water is 100:23:5.2; the concentration of ammonia water is 28 wt%; the volume ratio of ethyl orthosilicate to ethanol is 1:6.4; the first mixing conditions include: temperature of 42°C and time of 8 minutes; the dripping rate of ethyl orthosilicate is 1 mL / min; the first reaction conditions include: temperature of 42°C and time of 2.5 hours; In step (2), the volume ratio of tetrabutyl titanate to ethanol is 18:100; the volume ratio of the dispersion to the silica sol is 1:6.5; the drop rate of the silica sol is 0.5 mL / min; the conditions for the second reaction include: a reaction temperature of 65° C. and a reaction time of 4.5 h; the conditions for centrifugation include: a rotation speed of 5500 rpm and a time of 8 min; the washing method includes: washing with ethanol three times; and the drying conditions include: vacuum drying at 60° C. for 12 h. In step (3): the mass ratio of inorganic particles, ethanol and water is 12:94:6; The mass ratio of coupling agent KH-570 to inorganic particles is 1.3:10; the third mixing conditions include: ultrasonication at room temperature for 20 minutes; the third reaction conditions include: reflux reaction at 85° C. for 6 hours; the centrifugation conditions include: speed of 6000 rpm for 10 minutes; the washing method includes: washing with ethanol three times; the drying conditions include: vacuum drying at 60° C. for 12 hours; In step (4), the mass ratio of the modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier, potassium persulfate aqueous solution and water is 0.55:1.2:2.8:0.052:0.65:100; the fourth mixing conditions include: mixing at a speed of 10,000 rpm at room temperature for 30 minutes; the potassium persulfate aqueous solution is controlled to be added dropwise within 1 hour; the drying conditions include: vacuum drying at 80°C for 12 hours; The thickness of the OCA optical adhesive layer is 44 μm. The OCA optical adhesive layer is obtained by a process including light curing of OCA adhesive. The OCA adhesive is purchased from Shenzhen Haoli New Material Technology Co., Ltd., model HL3010, and has a viscosity of 2500 mPa·s at 25°C. The method for preparing the bending-resistant and high-transmittance protective film for a folding screen in this embodiment includes: Silicone glue is applied on the protective layer, and a silicone layer with a thickness of 33 microns is formed through a first thermal curing process; flexible substrate layer B is applied on the silicone layer, and a flexible substrate layer B with a thickness of 23 microns is formed through a second thermal curing process; flexible adhesive material A is applied on flexible substrate layer B, and a flexible substrate layer A with a thickness of 77 microns is formed through a third thermal curing process; OCA glue is applied on flexible substrate layer A, and a OCA optical adhesive layer with a thickness of 44 microns is formed through light curing; a release layer is applied on the OCA optical adhesive layer to obtain a bending-resistant and high-transmittance protective film.

[0071] The conditions for the first thermal curing include: temperature of 130°C and time of 60 seconds; the conditions for the second thermal curing include: temperature of 123°C and time of 6 minutes; the conditions for the third thermal curing include: temperature of 123°C and time of 6 minutes; the conditions for light curing include: wavelength of ultraviolet lamp of 356nm, temperature of 100°C and time of 10 seconds.

[0072] Comparative Example 1 The difference between this comparative example and Example 1 is: There is no flexible substrate layer B, and the thickness of the flexible substrate layer A is 90 μm; When preparing a bending-resistant and high-transmittance protective film for a folding screen, the preparation method includes: Silicone glue is applied to the protective layer and subjected to a first thermal curing step to form a 35-micron-thick silicone layer. Flexible adhesive A is applied to the silicone layer and subjected to a third thermal curing step to form a 90-micron-thick flexible substrate layer A. OCA glue is applied to the flexible substrate layer A and subjected to light curing to form a 50-micron-thick OCA optical adhesive layer. A release layer is applied to the OCA optical adhesive layer to obtain a bending-resistant, high-transmittance protective film.

[0073] Comparative Example 2 The difference between this comparative example and Example 1 is: There is no flexible substrate layer A, and the thickness of the flexible substrate layer B is 90 μm; When preparing a bending-resistant and high-transmittance protective film for a folding screen, the preparation method includes: Silicone glue is applied to the protective layer and subjected to a first thermal curing step to form a 35-micron thick silicone layer. Flexible adhesive B is applied to the silicone layer and subjected to a third thermal curing step to form a 90-micron thick flexible substrate layer B. OCA glue is applied to the flexible substrate layer A and subjected to light curing to form a 50-micron thick OCA optical adhesive layer. A release layer is applied to the OCA optical adhesive layer to obtain a bending-resistant, high-transmittance protective film.

[0074] Comparative Example 3 The difference between this comparative example and Example 1 is: The preparation method of organic-inorganic hybrid particles includes: (1) Ethanol, water and ammonia water are first mixed, and then ethyl orthosilicate is added dropwise. After the addition is completed, a first reaction is carried out to obtain silica sol, which is then centrifuged, washed and dried to obtain inorganic particles; (2) The inorganic particles, ethanol and water are mixed for a second time, and then a coupling agent KH-570 is added for a second reaction, centrifuged, washed and dried to obtain modified inorganic particles; (3) The modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier and water were mixed for the third time, and then the temperature was raised to 70°C under nitrogen protection, and a 6 wt% potassium persulfate aqueous solution was added dropwise. After the addition was completed, the mixture was kept warm for 5 hours, and then cooled to room temperature, filtered, dried, and ground through a 1200 mesh sieve to obtain organic-inorganic hybrid particles; In step (1), the volume ratio of ethanol, water and ammonia water is 100:20:5; the concentration of ammonia water is 28wt%; the volume ratio of tetraethyl orthosilicate to ethanol is 1:6; the first mixing conditions include: temperature of 40°C and time of 10 minutes; the dripping rate of tetraethyl orthosilicate is 1 mL / min; the first reaction conditions include: temperature of 40°C and time of 3 hours; the centrifugation conditions include: speed of 5000 rpm and time of 10 minutes; the washing method includes: washing with water 3 times; the drying conditions include: vacuum drying at 60°C for 12 hours; In step (2), the mass ratio of inorganic particles, ethanol and water is 10:90:10; the mass ratio of coupling agent KH-570 to inorganic particles is 1:10; the second mixing conditions include: ultrasonication at room temperature for 20 minutes; the second reaction conditions include: reflux reaction at 80°C for 7 hours; the centrifugation conditions include: speed of 6000 rpm for 10 minutes; the washing method includes: washing with ethanol 3 times; the drying conditions include: vacuum drying at 60°C for 12 hours; In step (3), the mass ratio of the modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier, potassium persulfate aqueous solution and water is 0.5:1:2.5:0.05:0.6:100; the third mixing conditions include: mixing at a speed of 10,000 rpm at room temperature for 30 minutes; the potassium persulfate aqueous solution is controlled to be added dropwise within 1 hour; and the drying conditions include: vacuum drying at 80°C for 12 hours.

[0075] Comparative Example 4 The difference between this comparative example and Example 1 is: The preparation method of organic-inorganic hybrid particles includes: (1) Tetrabutyl titanate and ethanol are first mixed to obtain a dispersion, followed by a first reaction, and finally centrifuged, washed, and dried to obtain inorganic particles; (2) The inorganic particles, ethanol and water are mixed for a second time, and then a coupling agent KH-570 is added for a second reaction, centrifuged, washed and dried to obtain modified inorganic particles; (3) The modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier and water were mixed for the third time, and then the temperature was raised to 70°C under nitrogen protection, and a 6 wt% potassium persulfate aqueous solution was added dropwise. After the addition was completed, the mixture was kept warm for 5 hours, and then cooled to room temperature, filtered, dried, and ground through a 1200 mesh sieve to obtain organic-inorganic hybrid particles; In step (1), the volume ratio of tetrabutyl titanate to ethanol is 15:100; the conditions for the first reaction include: a reaction temperature of 60° C. and a reaction time of 5 h; the conditions for centrifugation include: a rotation speed of 5000 rpm and a time of 10 min; the washing method includes: washing with water 3 times; and the drying conditions include: vacuum drying at 60° C. for 12 h. In step (2), the mass ratio of inorganic particles, ethanol and water is 10:90:10; the mass ratio of coupling agent KH-570 to inorganic particles is 1:10; the second mixing conditions include: ultrasonication at room temperature for 20 minutes; the second reaction conditions include: reflux reaction at 80°C for 7 hours; the centrifugation conditions include: speed of 6000 rpm for 10 minutes; the washing method includes: washing with ethanol 3 times; the drying conditions include: vacuum drying at 60°C for 12 hours; In step (3), the mass ratio of the modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier, potassium persulfate aqueous solution and water is 0.5:1:2.5:0.05:0.6:100; the third mixing conditions include: mixing at a speed of 10,000 rpm at room temperature for 30 minutes; the potassium persulfate aqueous solution is controlled to be added dropwise within 1 hour; and the drying conditions include: vacuum drying at 80°C for 12 hours.

[0076] Performance Testing 1. Bending resistance test The release layers of the bending-resistant and high-transmittance protective films for folding screens prepared in Examples 1-3 and Comparative Examples 1-4 were torn off respectively, and the OCA optical adhesive layer was attached to the flexible tempered film to obtain a test sample. The test sample was fixed on a folding screen test instrument and a LW-102W folding screen bending life tester was used for the bendability test. The bending radius R = 2 mm, the bending angle 180 °, and the bending-resistant and high-transmittance protective films for folding screens were tested in both unfolded and folded states. The protective film was bent for 150,000, 200,000, 250,000 and 300,000 times respectively. The experiment was stopped at 150,000, 200,000, 250,000 and 300,000 times respectively, and the protective film was observed to see if there were any bubbling, cracking, falling off or creases. If so, the subsequent bending test was stopped and the number of bending times was recorded. If there were no such phenomena, the bending test was continued. If there were no bubbling, cracking, falling off or creases after 300,000 times, the bending number was recorded as being greater than 300,000 times.

[0077] The above bending resistance test was carried out at room temperature (25±3℃) and low temperature (-30℃).

[0078] 2. Light transmittance test The release layers of the bending-resistant, high-transmittance protective films for folding screens prepared in Examples 1-3 and Comparative Examples 1-4 were respectively torn off to obtain test samples. The transmittance of the test samples was measured by the transmitted light method using a NDH2000N haze meter produced by Japan Denshoku in accordance with the JISK-7105 standard.

[0079] 3. Hardness test The release layers of the bending-resistant and high-transmittance protective films for folding screens prepared in Examples 1-3 and Comparative Examples 1-4 were respectively torn off to obtain test samples. The hardness of the test samples was measured using a Shore LHA200 hardness tester with reference to GB / T531-2008 standard.

[0080] The test results of the bending-resistant and high-transmittance protective films in Examples 1-3 and Comparative Examples 1-4 are shown in Table 1.

[0081] Table 1 Test results of the bending-resistant high-transmittance protective films in Examples 1-3 and Comparative Examples 1-4

[0082] It can be seen from the above performance test results that the bending-resistant and high-transmittance protective films for folding screens of Examples 1-3 have excellent bending resistance, especially low-temperature bending resistance, transmittance and hardness. It is speculated that the protective films achieve a balance between transmittance, bending resistance and hardness through the gradient distribution of organic-inorganic hybrid particles and multi-layer functional design.

[0083] The comparative examples, however, lacked the necessary technical solutions, resulting in significantly lower performance than the examples. In Comparative Example 1, flexible substrate layer B was removed, leaving only flexible substrate layer A (thickness increased to 90 μm). This significantly reduced light transmittance and bending resistance. In Comparative Example 2, flexible substrate layer A was removed, leaving only flexible substrate layer B (thickness increased to 90 μm). This significantly reduced hardness and bending resistance. In Comparative Example 3, the silica sol and tetrabutyl titanate compounding step was omitted (using only pure SiO2). This significantly reduced hardness and light transmittance. In Comparative Example 4, the silica sol step was omitted (using only pure TiO2). This significantly reduced bending resistance and light transmittance. These experimental results further demonstrate the importance of the technical solutions defined in the present invention for its technical effectiveness.

[0084] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A bending-resistant and high-transmittance protective film for a folding screen, characterized in that: The bending-resistant high-transmittance protective film comprises, from top to bottom, a release layer, an OCA optical adhesive layer, a flexible substrate layer A, a flexible substrate layer B, a silicone layer and a protective layer; The raw materials of both the flexible substrate layer A and the flexible substrate layer B contain organic-inorganic hybrid particles, and the content of the organic-inorganic hybrid particles in the raw materials of the flexible substrate layer A is greater than that in the raw materials of the flexible substrate layer B.

2. The bending-resistant and high-transmittance protective film for foldable screens according to claim 1, characterized in that: The thickness of the protective layer is 15-80 microns; the material of the protective layer is PET material.

3. The bending-resistant and high-transmittance protective film for foldable screens according to claim 2, characterized in that: The thickness of the flexible substrate layer A is 30-100 microns; the thickness of the flexible substrate layer B is 10-60 microns.

4. The bending-resistant and high-transmittance protective film for foldable screens according to claim 3, characterized in that: The flexible substrate layer A is obtained from a flexible adhesive material A through a step including thermal curing; the raw materials of the flexible adhesive material A include, by weight, 100 parts of hydroxy acrylic resin, 50-65 parts of hyperbranched polyester polyol, 10-15 parts of polyketone resin, 15-20 parts of organic-inorganic hybrid particles, 4-5 parts of leveling agent, 8-15 parts of curing agent, and 180-200 parts of diluent.

5. The bending-resistant and high-transmittance protective film for foldable screens according to claim 4, characterized in that: The flexible substrate layer B is obtained by a process including heat curing of a flexible rubber material B; In parts by weight, the raw materials of the flexible rubber material B include: 100 parts of hydroxy acrylic resin, 50-65 parts of hyperbranched polyester polyol, 10-15 parts of polyketone resin, 50-55 parts of organic-inorganic hybrid particles, 4-5 parts of leveling agent, 8-15 parts of curing agent, and 200-235 parts of diluent;.

6. The bending-resistant and high-transmittance protective film for foldable screens according to claim 5, characterized in that: The preparation method of the organic-inorganic hybrid particles comprises: (1) Ethanol, water and ammonia water are first mixed, and then ethyl orthosilicate is added dropwise. After the addition is completed, a first reaction is carried out to obtain a silica sol; (2) Tetrabutyl titanate and ethanol are mixed for a second time to obtain a dispersion, and then silica sol is added dropwise to the dispersion. After the addition is complete, a second reaction is performed, and then centrifugation, washing, and drying are performed to obtain inorganic particles; (3) performing a third mixing of the inorganic particles, ethanol, and water, and then adding a coupling agent for a third reaction, centrifuging, washing, and drying to obtain modified inorganic particles; (4) The modified inorganic particles, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, OP-10 emulsifier and water are mixed for the fourth time, and the potassium persulfate aqueous solution is added dropwise after heating. After the addition is completed, the mixture is kept warm for reaction, cooled, filtered, dried, ground and sieved to obtain organic-inorganic hybrid particles.

7. The bending-resistant and high-transmittance protective film for foldable screens according to claim 6, characterized in that: The leveling agent is selected from at least one of leveling agent BYK-381, leveling agent BYK-310, leveling agent BYK-358, leveling agent Tego FLOW 425 and leveling agent TEGO 432; the curing agent is selected from cyanate curing agent; and the diluent is selected from a combination of dimethylformamide and cyclohexanone.

8. The bending-resistant and high-transmittance protective film for foldable screens according to claim 7, characterized in that: The thickness of the OCA optical adhesive layer is 30-100 microns; the OCA optical adhesive layer is obtained by OCA adhesive through a step including light curing; the release layer is a PET release film; the thickness of the release layer is 20-80 microns.

9. A method for preparing a bending-resistant, high-transmittance protective film for a foldable screen according to any one of claims 1 to 8, characterized in that: The preparation method comprises: Silicone glue is applied on the protective layer, and a silicone layer with a thickness of 30-35 microns is formed through a first thermal curing process; flexible substrate layer B is applied on the silicone layer, and a flexible substrate layer B with a thickness of 20-25 microns is formed through a second thermal curing process; flexible adhesive material A is applied on flexible substrate layer B, and a flexible substrate layer A with a thickness of 70-80 microns is formed through a third thermal curing process; OCA glue is applied on flexible substrate layer A, and a OCA optical adhesive layer with a thickness of 40-50 microns is formed through light curing; a release layer is applied on the OCA optical adhesive layer to obtain a bending-resistant and high-transmittance protective film.

10. The method for preparing a bending-resistant and high-transmittance protective film for a foldable screen according to claim 9, characterized in that: The conditions for the first thermal curing include: temperature of 130-135°C and time of 50-70s; the conditions for the second thermal curing include: temperature of 120-125°C and time of 5-8min; the conditions for the third thermal curing include: temperature of 120-125°C and time of 5-8min; the conditions for the light curing include: wavelength of ultraviolet lamp of 356nm, temperature of 90-100°C and time of 10-15s.

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