A temporary layer protective film for low-emissivity tempered glass substrate and a method for manufacturing the same

Abstract

The application relates to the technical field of low-radiation toughened glass, and particularly discloses a temporary layer protective film of a low-radiation toughened glass substrate and a preparation method thereof. The protective film comprises a glass substrate, a functional coating and a polymer temporary layer; the functional coating is composed of silver-containing metal layers and anti-reflection coating layers which are alternately stacked; the temporary layer is formed by curing an acrylate composition and does not contain inorganic fillers and siloxane additives and can be completely decomposed at 550-720 DEG C. The preparation method comprises the following steps: forming the functional coating through magnetron sputtering, preparing a liquid mixture with a specific viscosity, performing ultraviolet curing after roll coating into a film, and then performing stepwise temperature sintering and double-sided blowing cooling. The composition of the application can be used for dynamic protection of the functional coating in the toughening process through specific organic component design, and has the core advantages of high-temperature residue-free decomposition; in addition, the preparation method of the application optimizes the dynamic protection mechanism of the temporary layer in the toughening process through material component and process cooperation.

Description

Technical Field

[0001] This application relates to the field of low-emissivity tempered glass technology, and more specifically, to a temporary protective film for a low-emissivity tempered glass substrate and a method for preparing the same. Background Technology

[0002] Tempered glass is a type of strengthened glass produced by heat treatment or chemical treatment to create compressive stress on the surface of ordinary glass. Its impact resistance is 3-5 times that of ordinary glass, and it breaks into blunt-angled fragments. It is widely used in building curtain walls, automotive windows, and appliance panels. Low-emissivity tempered glass, through the application of a functional coating containing a silver metallic layer to its surface, achieves dual energy-saving effects of winter insulation and summer sun shading, making it a core material for green buildings.

[0003] However, functional coatings face severe challenges during tempering: traditional organic protective layers do not decompose completely at temperatures above 590℃, leaving residual carbides that cause silver layer oxidation and fogging, increasing the glass emissivity from ≤0.05 to >0.1, severely weakening energy-saving performance. Existing protective layers cannot simultaneously achieve both high-speed coating adaptability and complete high-temperature decomposition. Summary of the Invention

[0004] To address the problem that existing protective layers cannot simultaneously achieve both high-speed coating adaptability and high-temperature complete decomposition, this application provides a temporary protective film for low-emissivity tempered glass substrates and its preparation method.

[0005] In a first aspect, this application provides a temporary protective film for a low-emissivity tempered glass substrate, employing the following technical solution:

[0006] A temporary protective film for a low-emissivity tempered glass substrate comprises:

[0007] Glass substrate, thickness 1-20mm;

[0008] A functional coating with a thickness of 100-300 nm is applied to at least one main surface of a glass substrate. The functional coating comprises an alternating stacked structure of x metal layers and (x+1) antireflective coatings, where x is an integer from 1 to 4, and the metal layers comprise silver with a weight percentage greater than 50%.

[0009] A temporary polymer layer with a thickness of 1-100 μm is directly applied to the surface of the functional coating. The temporary polymer layer is composed of a cured layer formed by curing a composition containing acrylate monomers or methacrylate monomers. The temporary polymer layer does not contain inorganic fillers or siloxane additives, and the temporary polymer layer can be completely decomposed under heating conditions of 550-720°C.

[0010] By employing the above technical solution, an alternating stacked structure of x metal layers and (x+1) anti-reflective coatings is used, where the silver content of the metal layers is >50%. The infrared reflectivity of silver and the light transmittance adjustment effect of the anti-reflective coatings balance visible light transmittance and infrared blocking, thereby achieving low-emissivity characteristics of the glass substrate. A 1-100μm thick filler-free acrylate curing layer directly covers the functional coating, providing physical isolation. Under a heating environment of 550-720℃, the temporary layer completely decomposes through oxidation / depolymerization reactions, preventing residues from obscuring the optical properties of the functional coating. This eliminates the risk of high-temperature silicon residue and maintains the surface cleanliness of the functional coating. The close cooperation of the glass substrate, functional coating, and temporary layer structure, with the temporary layer acting as a barrier against mechanical scratches and oxidative corrosion during transportation and before tempering, and the overlap of the temporary layer's decomposition temperature with the tempering heating window, simultaneously achieves functional coating protection and seamless transition between the tempering process.

[0011] Preferably, the outermost layer of the functional coating is selected from at least one of titanium nitride, zirconium nitride, hafnium nitride, titanium oxide, zirconium oxide, and hafnium oxide.

[0012] By adopting the above technical solution, and by using a functional coating with the outermost layer selected from specific nitrides / oxides, the following core characteristics play a crucial protective role: the inherent high melting point of the material, such as titanium nitride with a melting point >2900℃, helps maintain structural integrity during the tempering heating stage at 550-720℃; the compactness of the crystal structure, such as zirconium oxide with a density of 5.68 g / cm3, physically isolates oxygen penetration, thereby preventing high-temperature oxidation of the underlying silver metal layer; and the high light transmittance of the material in the visible light band, such as hafnium oxide with a refractive index ≈2.0, minimizes incident light scattering, avoiding affecting the low-emissivity performance of the functional coating.

[0013] Preferably, the composition of the polymer temporary layer comprises: 30-80 wt% aliphatic urethane-acrylate oligomer; and 20-70 wt% acrylate monomer or methacrylate monomer with a functionality ≥2.

[0014] By adopting the above technical solution, and using a ratio of 30-80 wt% aliphatic urethane acrylate oligomers to 20-70 wt% monomers with a functionality ≥2, the following synergistic mechanisms are utilized to optimize the function of the temporary layer: the long-chain structure of the aliphatic urethane acrylate oligomers provides continuity to the polymer backbone; the multi-reactive-site characteristics of the monomers with a functionality ≥2 contribute to the construction of a three-dimensional cross-linked network; and the specific synergistic ratio of oligomers to monomers helps maintain a coatable viscosity window of 0.05-5 Pa·s.

[0015] Preferably, the acrylate monomer or methacrylate monomer with a functionality ≥2 comprises a mixture of a difunctional monomer and a trifunctional monomer; the difunctional monomer is tricyclodecanedimethylol diacrylate, and the trifunctional monomer is trimethylolpropane triacrylate.

[0016] By employing the above technical solution, and through a compounding scheme of the specific bifunctional monomer tricyclodecanediol diacrylate and the trifunctional monomer trimethylolpropane triacrylate, the following molecular structural characteristics are utilized to achieve synergistic effects: the alicyclic structure of tricyclodecanediol diacrylate introduces compliant chain segments; the short-branched structure of trimethylolpropane triacrylate constructs rigid crosslinking nodes; the lower reactivity of the bifunctional monomer slows down the gelation rate; the high functionality of the trifunctional monomer accelerates network crosslinking; the low-temperature depolymerization tendency of the alicyclic structure promotes chain scission in the 550-720℃ range; and the oxidative pyrolysis characteristics of the short-branched structure synergistically improve the thoroughness of thermal decomposition.

[0017] Secondly, this application provides a method for preparing a temporary protective film on a low-emissivity tempered glass substrate, employing the following technical solution:

[0018] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate includes the following steps:

[0019] S1. Functional coating formation: A functional coating is formed on the surface of a glass substrate by magnetic field-assisted cathode sputtering, and the thickness of the functional coating is controlled to be 100-300nm.

[0020] S2. Preparation of liquid mixture: Mix 30-80 wt% aliphatic urethane-acrylate oligomer, 20-70 wt% acrylate monomer or methacrylate monomer with a functionality ≥2, and 0.1-20 wt% photoinitiator, and adjust the viscosity to 0.05-5 Pa·s at 25°C.

[0021] S3. Wet film coating: The liquid mixture is coated onto the surface of the functional coating by a roller coating process at a speed of 15-25 m / min to form a wet film thickness of 10-30 μm.

[0022] S4. Ultraviolet Curing: Curing is performed using ultraviolet light with a wavelength of 250-400nm and an irradiation intensity of 200-500mJ / cm². 2 This forms a temporary layer;

[0023] S5. High-temperature sintering: Heat the coated substrate to 590-700℃ at a rate of 5-10℃ / s and hold for 30-120 seconds.

[0024] S6. Tempered cooling: Uses double-sided nozzles to spray gas at 15-25℃ at a pressure of 0.5-1.5MPa for cooling.

[0025] By employing the above technical solutions, a magnetic field-assisted cathode sputtering process is used to confine plasma trajectories using Lorentz force, enabling the directional deposition of ionized particles from a metallic silver target. This achieves a dense stacked structure of functional coatings within a thickness range of 100-300 nm. A complex system of 30-80 wt% urethane acrylate oligomers and 20-70 wt% multifunctional monomers is used, leveraging the synergistic effect of the oligomer's long-chain backbone and the monomer's reaction sites to maintain a controllable viscosity of 0.05-5 Pa·s, providing a rheological basis for roller coating leveling. A matching parameter of 15-25 m / min roller speed and 10-30 μm wet film thickness is used, utilizing the dynamic balance between roller shear force and surface tension to achieve uniform spreading of the liquid mixture on the functional coating surface. Finally, ultraviolet light in the 250-400 nm band and 200-500 mJ / cm² wavelength are employed. 2 The irradiation intensity, utilizing the matching characteristics of this wavelength with the characteristic absorption peak of the photoinitiator, plays a role in stimulating free radical chain polymerization and constructing a three-dimensional cross-linked network; by adopting a heating rate of 5-10℃ / s and a heat preservation window of 590-700℃, the temporary layer decomposition is avoided before the critical temperature of silver oxidation by rapidly crossing the pyrolysis temperature zone of organic matter; by adopting a gas pressure of 0.5-1.5MPa and double-sided symmetrical blowing, the physical mechanism of gas turbulence enhancing heat transfer is utilized to balance the heat exchange on the glass surface.

[0026] Preferably, in step S2, the monomer comprises trimethylolpropane triacrylate and tricyclodecanediethanol diacrylate in a mass ratio of 1:1 to 1:2.

[0027] By adopting the above technical solution and using a mass ratio of 1:1 to 1:2 for trimethylolpropane triacrylate (TMPTA) and tricyclodecanedimethylethanol diacrylate (DCPDA), the following molecular structural characteristics are utilized to achieve synergistic effects: the trifunctional star structure of TMPTA helps to construct high-density cross-linking nodes; the alicyclic bifunctional linear structure of DCPDA (cyclohexane derivative) introduces flexible spacer segments; the high reactivity of TMPTA (primary acrylate groups) accelerates the formation of the cross-linking network; the steric hindrance effect of DCPDA (β-carbon steric hindrance) slows down the gelation process and avoids local over-cross-linking; the ester group β-C-H bond of TMPTA promotes the depolymerization of the main chain in the 550-720℃ range; and the alicyclic structure of DCPDA reduces the activation energy for thermal decomposition.

[0028] Preferably, in step S4, the ultraviolet light source is a mercury lamp with a power of 120-200W.

[0029] By adopting the above technical solution and using a 120-200W mercury lamp light source for ultraviolet curing, the following physical mechanisms are utilized to optimize the process: the continuous spectral output of the mercury lamp in the 250-400nm band effectively matches the maximum absorption wavelength of α-hydroxy ketone initiators; controlling the irradiation intensity within the 120-200W power range maintains the dynamic balance of the free radical polymerization reaction, preventing local over-curing or under-curing; and the cold light source characteristics of the mercury lamp suppress the temperature rise of the substrate surface, preventing pre-oxidation of the functional silver coating.

[0030] Preferably, a glass substrate cutting process is added before step S3, and the size of the substrate after cutting is less than ±0.5mm from the size of the final tempered glass product.

[0031] By adopting the above technical solution, and by adding a glass substrate cutting process before applying the temporary layer, the following physical mechanisms are used to optimize the process: precise cutting eliminates micro-cracks at the edges of large-sized substrates, thereby balancing the surface stress field during the tempering process; geometric dimensional accuracy control reduces thermal gradient distortion of the glass during the 590-700℃ heating stage; and the process design of cutting before applying the temporary layer avoids cutting debris impacting the surface of the functional coating, thereby maintaining the structural integrity of the functional coating.

[0032] Preferably, in step S2, the photoinitiator is selected from benzoyl carbamates or α-hydroxy ketones.

[0033] By adopting the above technical solutions, specifically using benzoyl carbamate or α-hydroxy ketone photoinitiators, the following photochemical properties are utilized to optimize the process: the Norrish I-type cleavage characteristics of benzoyl carbamate directly generate benzoyl radicals; the α-cleavage reaction of α-hydroxy ketone efficiently generates active alkyl radicals; the absorption peak of benzoyl carbamate at 320-360 nm matches the 365 nm main emission line of mercury lamps; the absorption characteristics of α-hydroxy ketone at 250-280 nm synergistically utilize the energy across the entire ultraviolet band; the small-molecule volatility of the initiator decomposition products avoids high-temperature sintering residues; and the complete conversion of photosensitive groups eliminates interference from unreacted initiators in the pyrolysis process.

[0034] Preferably, in step S6, the nozzle spacing of the double-sided nozzle is 20-50mm.

[0035] By adopting the above technical solution, specifically the 20-50mm double-sided nozzle arrangement spacing, the following fluid dynamics mechanisms are utilized to optimize the process: a minimum spacing of 20mm eliminates cooling blind zones and avoids localized thermal stress concentration; a maximum spacing of 50mm maintains airflow turbulence intensity; the isobaric distribution characteristics of the nozzle array ensure the stability of the Nusselt number (Nu) on the glass surface; the coordinated design of spacing and blowing pressure achieves linear control of the convective heat transfer coefficient (h); and the natural frequency avoidance design weakens micro-vibrations in the substrate caused by airflow excitation.

[0036] In summary, this application has the following beneficial effects:

[0037] 1. Since this application uses a compound system of aliphatic urethane acrylate oligomers and acrylate monomers with a functionality of ≥2, and since the composition has a controllable viscosity of 0.05-5 Pa·s at 25°C, a wet film is formed by roller coating, which enables the liquid mixture to achieve low shear rheological properties, thereby promoting the uniform extension of the wet film on the surface of the functional coating and forming an ultra-thin temporary layer with a coverage accuracy that meets the tolerance requirements of glass tempering.

[0038] 2. In this application, α-hydroxy ketone photoinitiators are preferably used in conjunction with ultraviolet light sources. Since these initiators have high light absorption efficiency in the ultraviolet band and directly decompose to generate active free radicals, the conversion rate of double bonds is greatly improved by combining trimethylolpropane triacrylate and tricyclodecanedimethylol diacrylate in a ratio of 1:1 to 1:2. The dense cross-linked network of the cured layer structure is formed by irradiation, thereby avoiding damage to the functional coating by low molecular weight residues during sintering.

[0039] 3. The method of this application, by setting the heating rate and holding time window, enables the organic components of the temporary layer to enter the rapid decomposition stage before the silver layer oxidation reaction occurs. At the same time, by relying on the nozzle arrangement spacing and coordinating gas pressure control, it promotes the uniformity of heat conduction during the tempering and cooling process, thereby supporting the maintenance of the integrity of the functional coating structure after high-temperature treatment. Attached Figure Description

[0040] Figure 1 This is a flowchart of a method for preparing a temporary protective film on a low-emissivity tempered glass substrate, as provided in this application. Detailed Implementation

[0041] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0042] Technical concept:

[0043] In the field of low-emissivity glass tempering, traditional temporary protective layers face a dilemma: if the organic coating lacks sufficient thermal stability, it will decompose prematurely in the early stages of tempering, leading to oxidation and fogging of the functional coating; if the thermal stability is too high, the decomposition residue will obscure the low-emissivity characteristics of the silver layer. The root cause lies in the mismatch between the thermal decomposition behavior of the protective layer and the tempering process window of 590-700℃, and the difficulty of combining rapid coating with precise decomposition with existing materials.

[0044] This solution breaks through the limitations through a triple synergistic mechanism: First, it designs an acrylate-based temporary layer architecture—constructing a molecular network using a monomer / oligomer blend system with specific functionalities, enabling synchronous chain segment breakage within the 550-720℃ range, achieving precise switching between protection and release throughout the tempering process; second, it innovates process chain connections: magnetic field sputtering ensures the density of the silver layer, and UV curing regulates the degree of crosslinking, giving the temporary layer both mechanical protection and complete thermal decomposition; finally, through the dynamic coupling of a stepped heating rate of 5-10℃ / s and gas cooling, it induces complete polymer vaporization while inhibiting silver layer oxidation. This technical route, with its designable structure, controllable process, and predictable decomposition, essentially reconstructs the fully controllable logic of the protective layer from application to disappearance.

[0045] Preparation Example 1

[0046] The preparation method of urethane-acrylate oligomers is as follows:

[0047] Under a nitrogen atmosphere, 100g of precisely weighed polycaprolactone diol and 44.4g of isophorone diisocyanate were added to a four-necked flask equipped with a mechanical stirrer, thermometer, and condenser. The temperature was raised to 80°C at a rate of 5°C / min and kept at a constant temperature for 3 hours. Subsequently, 23.2g of hydroxyethyl acrylate and 0.05g of antioxidant BHT were added, and the reaction continued until the content of free isocyanate groups (NCO) in the system decreased to <0.1%. After the reaction was completed, the pressure was reduced and degassed to obtain a light yellow, transparent, viscous liquid urethane-acrylate oligomer.

[0048] This application provides a temporary protective film for a low-emissivity tempered glass substrate and its preparation method. The following details the embodiments of the temporary protective film for a low-emissivity tempered glass substrate and its preparation method.

[0049] Example 1

[0050] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate includes the following steps:

[0051] S1. Functional coating formation: A functional coating is formed on the surface of a 6mm thick glass substrate by magnetic field-assisted cathode sputtering, and the thickness of the functional coating is controlled to be 200nm. The functional coating includes an alternating stacked structure of 2 metal layers and 3 anti-reflection coatings. The metal layers contain more than 50% silver, and the outermost layer is titanium nitride.

[0052] S2. Preparation of liquid mixture: Mix 55wt% aliphatic urethane-acrylate oligomer, 45wt% acrylate monomer with functionality ≥2, and 10wt% photoinitiator, and adjust the viscosity to 2.5 Pa·s at 25°C; wherein the monomers include trimethylolpropane triacrylate and tricyclodecanedimethylol diacrylate in a mass ratio of 1:1.5, and the photoinitiator is selected from α-hydroxy ketone compounds.

[0053] S3. Wet film coating: The liquid mixture is coated onto the surface of the functional coating at a speed of 20 m / min using a roller coating process to form a wet film with a thickness of 20 μm.

[0054] S4. Ultraviolet Curing: Curing is performed using ultraviolet light with a wavelength of 300nm and an irradiation intensity of 350mJ / cm². 2 A temporary layer was formed using a 160W mercury lamp light source.

[0055] S5. High-temperature sintering: The coated substrate is heated to 645°C at a rate of 7.5°C / s and held at that temperature for 75 seconds.

[0056] S6. Tempered cooling: The cooling system uses double-sided nozzles to spray 20°C gas at a pressure of 1.0MPa, with a nozzle spacing of 35mm.

[0057] Example 2

[0058] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate includes the following steps:

[0059] S1. Functional coating formation: A functional coating is formed on the surface of a glass substrate with a thickness of 20 mm by magnetic field-assisted cathode sputtering, and the thickness of the functional coating is controlled to be 300 nm. The functional coating includes an alternating stacked structure of 4 metal layers and 5 anti-reflection coatings. The metal layers contain more than 50% silver, and the outermost layer is titanium nitride.

[0060] S2. Preparation of liquid mixture: Mix 80wt% aliphatic urethane-acrylate oligomer, 70wt% acrylate monomer with functionality ≥2, and 20wt% photoinitiator, and adjust the viscosity to 5Pa·s at 25°C; wherein the monomers include trimethylolpropane triacrylate and tricyclodecanedimethylol diacrylate in a mass ratio of 1:2, and the photoinitiator is selected from α-hydroxy ketone compounds.

[0061] S3. Wet film coating: The liquid mixture is coated onto the surface of the functional coating by a roller coating process at a speed of 25 m / min to form a wet film with a thickness of 30 μm.

[0062] S4. Ultraviolet Curing: Curing is performed using ultraviolet light with a wavelength of 400nm and an irradiation intensity of 500mJ / cm². 2 A temporary layer was formed using a 200W mercury lamp light source.

[0063] S5. High-temperature sintering: The coated substrate is heated to 700°C at a rate of 10°C / s and held at that temperature for 120 seconds.

[0064] S6. Tempered cooling: The cooling system uses double-sided nozzles to spray 25°C gas at a pressure of 1.5MPa, with a nozzle spacing of 50mm.

[0065] Example 3

[0066] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate includes the following steps:

[0067] S1. Functional coating formation: A functional coating is formed on the surface of a glass substrate with a thickness of 1 mm by magnetic field-assisted cathode sputtering, and the thickness of the functional coating is controlled to be 100 nm. The functional coating includes an alternating stacked structure of one metal layer and two anti-reflective coatings. The metal layer contains more than 50% silver and the outermost layer is titanium nitride.

[0068] S2. Preparation of liquid mixture: Mix 30 wt% aliphatic urethane-acrylate oligomer, 20 wt% acrylate monomer with functionality ≥2, and 0.1 wt% photoinitiator, and adjust the viscosity to 0.05 Pa·s at 25°C; wherein the monomers comprise trimethylolpropane triacrylate and tricyclodecanedimethylol diacrylate in a mass ratio of 1:1, and the photoinitiator is selected from α-hydroxy ketone compounds.

[0069] S3. Wet film coating: The liquid mixture is coated onto the surface of the functional coating at a speed of 15 m / min using a roller coating process to form a wet film with a thickness of 10 μm.

[0070] S4. Ultraviolet Curing: Curing is performed using ultraviolet light with a wavelength of 250nm and an irradiation intensity of 200mJ / cm². 2 A temporary layer was formed using a 120W mercury lamp light source.

[0071] S5. High-temperature sintering: Heat the coated substrate to 590°C at a rate of 5°C / s and hold for 30 seconds.

[0072] S6. Tempered cooling: The cooling system uses double-sided nozzles to spray 15°C gas at a pressure of 0.5MPa, with a nozzle spacing of 20mm.

[0073] Comparative Example 1

[0074] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate differs from Example 1 only in that: a monofunctional acrylate monomer is used instead of the difunctional and trifunctional monomer combinations in the liquid mixture, specifically:

[0075] In step S2, a liquid mixture is prepared by replacing 45 wt% of acrylate monomers with a functionality of ≥2 with 45 wt% of monofunctional isobornyl acrylate; the remaining raw materials and preparation steps are the same as in Example 1.

[0076] Comparative Example 2

[0077] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate, differing from Example 1 only in that the photoinitiator is replaced with a benzophenone-based compound, specifically:

[0078] In step S2, when preparing the liquid mixture, only the α-hydroxy ketone compound is replaced with benzophenone; the other raw materials and preparation steps are the same as in Example 1.

[0079] Comparative Example 3

[0080] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate, differing from Example 1 only in that: no photoinitiator is added, specifically:

[0081] In step S2, when preparing the liquid mixture, no photoinitiator is added; the remaining raw materials and preparation steps are the same as in Example 1.

[0082] Comparative Example 4

[0083] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate differs from Example 1 only in that the mass ratio of the monomers added in step S2 is changed, specifically:

[0084] In step S2, when preparing the liquid mixture, only trimethylolpropane triacrylate is added; the other raw materials and preparation steps are the same as in Example 1.

[0085] Comparative Example 5

[0086] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate differs from Example 1 only in that the mass ratio of the monomers added in step S2 is changed, specifically:

[0087] In step S2, when preparing the liquid mixture, only tricyclodecanediethanol diacrylate is added; the other raw materials and preparation steps are the same as in Example 1.

[0088] Comparative Example 6

[0089] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate differs from Example 1 only in that the heating rate during the high-temperature sintering stage is reduced; specifically:

[0090] In step S5, the high-temperature sintering process, the heating rate is reduced to 2°C / s; the remaining raw materials and preparation steps are the same as in Example 1.

[0091] Comparative Example 7

[0092] A method for preparing a temporary protective film on a low-emissivity tempered glass substrate differs from Example 1 only in that the heating rate during the high-temperature sintering stage is increased, specifically:

[0093] In step S5, the high-temperature sintering process, the heating rate is increased to 12°C / s; the other raw materials and preparation steps are the same as in Example 1.

[0094] The key performance tests of Examples 1-3 and Comparative Examples 1-7 are shown in Table 1.

[0095] Table 1:

[0096]

[0097]

[0098] 1. Test standard for dynamic viscosity: ISO 3219 "Plastics - Determination of rheological properties of polymer dispersions";

[0099] 2. Standard for UV curing efficiency test: ASTM D2452 "Test for curing degree of UV-cured coatings";

[0100] 3. Film thickness-roughness test standard: ISO 4287 "Surface roughness profile method";

[0101] 4. Thermal decomposition behavior test standard: ISO 11358 "Plastics - Polymers - Thermogravimetric analysis";

[0102] 5. Standard for tempered flatness test: ASTM F1420 "Substrate warpage test method".

[0103] Combining Examples 1-3 and Comparative Example 1 with Table 1, it can be seen that: monofunctional monomers cause crosslinking defects. Monofunctional monomers (isobornyl acrylate) reduce the double bond conversion rate from 97.2% to 82.3%, and the molecular chains cannot form a three-dimensional network, causing the roughness to increase from 85nm to 150nm. Due to the melting and flow of uncrosslinked molecular chains during tempering, the residual carbon content increases by 8 times (0.09% → 0.83%) because the linear structure is not completely decomposed. Monomers with a functionality ≥2 form a dense network through C=C double bond crosslinking, while monofunctional monomers only polymerize at the ends, forming low molecular weight oligomers.

[0104] Based on Examples 1-3 and Comparative Examples 2-3, and in conjunction with Table 1, it can be seen that: benzophenone initiators are inefficient, benzophenone requires an amine co-initiator, the double bond conversion rate is only 64.7%, and the conversion rate is 38.5% without an initiator, and the wet film cannot be cured (detection failure); α-hydroxy ketone initiators have an absorption coefficient >200 L / mol·cm in the 250-400 nm wavelength range, directly cleavage to generate active free radicals, and do not require an auxiliary agent.

[0105] Combining Examples 1-3 and Comparative Examples 4-5 with Table 1, it can be seen that: a single monomer causes performance imbalance; the density of pure trifunctional crosslinking is too high, which makes the film brittle; the density of pure bifunctional crosslinking is insufficient, which leads to a decrease in thermal stability. However, when trimethylolpropane triacrylate (rigid) and tricyclodecyl diacrylate (flexible) are in a ratio of 1:1 to 1:2, the molecular chain segments work together to resist thermal stress.

[0106] Combining Examples 1-3 and Comparative Examples 6-7 with Table 1, it can be seen that: 5-10℃ / s is the thermal decomposition kinetic window. Reducing the heating rate in the high-temperature sintering stage to 2℃ / s increases the amount of residual char. Because organic matter produces gas through long-term pyrolysis at 500-550℃, increasing the heating rate in the high-temperature sintering stage to 12℃ / s also reduces the amount of residual char. Rapid surface coking hinders internal decomposition.

[0107] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A temporary protective film for a low-emissivity tempered glass substrate, characterized in that: include: Glass substrate, thickness 1-20mm; A functional coating with a thickness of 100-300 nm is applied to at least one main surface of a glass substrate. The functional coating comprises an alternating stacked structure of x metal layers and (x+1) antireflective coatings, where x is an integer from 1 to 4. The metal layers comprise silver with a weight percentage greater than 50%. The outermost layer of the functional coating is selected from at least one of titanium nitride, zirconium nitride, hafnium nitride, titanium oxide, zirconium oxide, and hafnium oxide. A temporary polymer layer, 1-100 μm thick, is directly applied to the surface of the functional coating. This temporary polymer layer is a cured layer formed by curing a composition containing acrylate monomers or methacrylate monomers. The temporary polymer layer does not contain inorganic fillers or siloxane additives and is completely decomposed under heating conditions of 550-720°C. The composition of the temporary polymer layer includes: 30-80 wt% aliphatic urethane-acrylate oligomers; 20-70 wt% acrylate monomers or methacrylate monomers with a functionality ≥2; the acrylate monomers or methacrylate monomers with a functionality ≥2 include a mixture of bifunctional and trifunctional monomers; the bifunctional monomer is tricyclodecanediol diacrylate, and the trifunctional monomer is trimethylolpropane triacrylate.

2. A method for preparing a temporary protective film on a low-emissivity tempered glass substrate, characterized in that, The temporary protective film for a low-emissivity tempered glass substrate as described in claim 1 comprises the following steps: S1. Functional coating formation: A functional coating is formed on the surface of a glass substrate by magnetic field-assisted cathode sputtering, and the thickness of the functional coating is controlled to be 100-300nm. S2. Preparation of liquid mixture: Mix 30-80 wt% aliphatic urethane-acrylate oligomer, 20-70 wt% acrylate monomer or methacrylate monomer with a functionality ≥2, and 0.1-20 wt% photoinitiator, and adjust the viscosity to 0.05-5 Pa·s at 25°C; the monomer comprises trimethylolpropane triacrylate and tricyclodecanedimethylol diacrylate in a mass ratio of 1:1 to 1:2; the photoinitiator is selected from benzoyl carbamates or α-hydroxy ketone compounds; S3. Before step S3, a glass substrate cutting process is added. After cutting, the size of the substrate and the final tempered glass product size are less than ±0.5mm. The liquid mixture is coated onto the surface of the functional coating by a roller coating process at a speed of 15-25m / min to form a wet film thickness of 10-30μm. S4. UV curing: Curing is performed by UV irradiation with a wavelength of 250-400nm and an irradiation intensity of 200-500mJ / cm² to form a temporary layer. S5. High-temperature sintering: Heat the coated substrate to 590-700℃ at a rate of 5-10℃ / s and hold for 30-120 seconds. S6. Tempered cooling: The gas is sprayed at 15-25℃ using double-sided nozzles at a pressure of 0.5-1.5MPa. The nozzle spacing of the double-sided nozzles is 20-50mm.

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