Polycarbonate composite, display screen mask and outdoor led display

Abstract

The application relates to a polycarbonate composite material, a display screen mask and an outdoor LED display screen. The polycarbonate composite material comprises the following components in mass fractions: 30-75% of polycarbonate, 0-45% of high-temperature-resistant resin, 5-20% of reinforcing fiber, 8-12% of flame retardant, 1-3% of synergistic flame retardant, 1-3% of toughening agent and 0.3-0.6% of weather-resistant agent; wherein the high-temperature-resistant resin satisfies the conditions of a melting point greater than or equal to 260 DEG C or a glass transition temperature greater than or equal to 185 DEG C; the reinforcing fiber comprises one or more of surface-modified glass fiber and surface-modified carbon fiber; and the mass fractions of the high-temperature-resistant resin and the surface-modified carbon fiber are not both 0. The display screen mask made of the polycarbonate composite material has very excellent heat deformation resistance and rarely or even does not have the phenomenon of bulging when working for more than 4 hours under the condition of a temperature of 100 DEG C and a brightness of 5000 cd / m 2 2.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, and in particular to a polycarbonate composite material, a display screen mask and an outdoor LED display screen. BACKGROUND

[0002] A light emitting diode (LED) is a kind of semiconductor electronic element that converts electrical energy into light energy, which has the advantages of energy saving, high efficiency, rich color, fast response speed and long service life, and is widely used in lighting devices, display screens and electronic indicator lights and other fields. Among them, large-screen display screens made of LEDs are mostly used in outdoor scenes such as shopping malls, high-rise buildings and squares. In order to be suitable for long-distance viewing, a point spacing (i.e. the distance between the centers of two adjacent pixel points) of P6.0 or more is generally adopted. With the development of application fields such as new infrastructure, intelligent transportation and Internet of Things and the widening of application scenarios, outdoor LED display screens have begun to develop towards small pitch below P4.0 in order to provide clearer and more delicate images.

[0003] The display screen mask is a kind of component installed on the surface of the LED display screen module, which can play the roles of anti-glare, improving contrast, improving color uniformity and protection. For outdoor LED display screens, the protection of the display screen mask is particularly important. Traditional display screen masks mostly adopt polycarbonate (PC) composite materials modified by glass fiber reinforcement. However, such polycarbonate composite materials are prone to deformation when applied to small-pitch outdoor LED display screens, such as local bulging under heat, display picture being blocked, abnormal situations such as black blocks or shadows, etc., which brings very bad experience to users. SUMMARY

[0004] Therefore, it is necessary to provide a polycarbonate composite material, a display screen mask and an outdoor LED display screen to solve the problem that the traditional polycarbonate composite material is prone to deformation when applied to small-pitch outdoor LED display screens.

[0005] The above-mentioned purpose of the present application is realized by the following technical solutions:

[0006] In a first aspect of the present application, a polycarbonate composite material is provided, which comprises the following components by mass fraction:

[0007] ;

[0008] The high-temperature-resistant resin satisfies: melting point ≥ 260℃, or glass transition temperature ≥ 185℃;

[0009] The reinforcing fiber comprises one or more of surface-modified glass fiber and surface-modified carbon fiber.

[0010] The mass fraction of the high-temperature-resistant resin and the surface-modified carbon fiber is not 0.

[0011] In one embodiment, the polycarbonate composite material comprises the following mass fractions of components:

[0012] .

[0013] In one embodiment, the polycarbonate composite material comprises the following mass fractions of components:

[0014] ;

[0015] The mass fraction of the surface-modified carbon fiber in the polycarbonate composite material is ≥5%.

[0016] In one embodiment, the high-temperature-resistant resin comprises one or more of liquid crystal polymer, polyphenylamide, polyether ether ketone, polyetherimide, polysulfone, polyphenyl sulfone, and polyether sulfone.

[0017] In one embodiment, the surface-modified carbon fiber comprises carbon fiber coated with a polymer on the surface.

[0018] In one embodiment, the polymer comprises one or more of polyurethane, epoxy resin, and acrylic acid.

[0019] In one embodiment, the mass ratio of the polymer to the carbon fiber is (1.5-6):100.

[0020] In one embodiment, the length of the carbon fiber is 4-8 mm, and the diameter is 4-9 μm.

[0021] In one embodiment, the surface-modified glass fiber comprises glass fiber modified by a silane coupling agent.

[0022] In one embodiment, the mass ratio of the silane coupling agent to the glass fiber is (0.5-2.5):100.

[0023] In one embodiment, the length of the glass fiber is 3-5 mm, and the diameter is 8-12 μm.

[0024] In one embodiment, the toughening agent comprises one or more of ethylene-methyl acrylate copolymer, methyl methacrylate-acrylate copolymer, methyl methacrylate-butadiene-styrene copolymer, ethylene-acrylate-glycidyl methacrylate terpolymer, acrylic acid-based toughening agent, and acrylic acid-silicone rubber-based toughening agent.

[0025] In one embodiment, the flame retardant includes one or more of a nitrogen-based flame retardant, a phosphorus-based flame retardant, and an organic sulfonate-based flame retardant.

[0026] In one embodiment, the synergistic flame retardant includes one or more of an organosiloxane, an organosilicon resin, a silicate, and a silicon micro powder.

[0027] In one embodiment, the weathering agent includes a light stabilizer.

[0028] In one embodiment, the polycarbonate composite further includes one or more of an antioxidant, a lubricant, and an anti-dripping agent.

[0029] In one embodiment, the antioxidant includes one or more of a hindered phenol antioxidant and a phosphite antioxidant.

[0030] In one embodiment, the lubricant includes one or more of an organosiloxane polymer, a fatty acid salt, a fatty acid amide, pentaerythritol stearate, erucic acid amide, oleic acid amide, ethylene bis-stearamide, and a polyolefin wax.

[0031] In one embodiment, the anti-dripping agent includes one or more of polytetrafluoroethylene, polyvinylidene fluoride, and silicone.

[0032] In a second aspect, the present application provides a display screen mask made of the polycarbonate composite as described above.

[0033] In a second aspect, the present application provides an outdoor LED display screen including the display screen mask as described above.

[0034] The present application has at least the following beneficial effects:

[0035] The melting point of the high-temperature resistant resin selected in the present application is greater than or equal to 260 DEG C or the glass transition temperature is greater than or equal to 185 DEG C, which can significantly improve the strength, rigidity and heat resistance of the polycarbonate composite material, thereby reducing the thermal deformation phenomenon thereof in a high-temperature environment. The glass fiber and carbon fiber in the reinforcing fiber are subjected to surface modification treatment, so that the reinforcing fiber has good compatibility with the resin; at the same time, compared with the glass fiber, the mechanical properties and heat resistance of the carbon fiber are better, and the introduction of an appropriate amount of surface-modified carbon fiber can compensate for the defects of insufficient strength, rigidity and heat resistance of the composite material. The present application uses high-temperature resistant resin and polycarbonate for alloy modification or adds surface-modified carbon fiber for reinforcement modification, and cooperates with flame retardants, synergistic flame retardants, toughening agents and weathering agents and other components in a specific ratio, which greatly improves the comprehensive performance of the composite material, such as strength, rigidity, heat resistance, high-temperature creep resistance, flame retardancy and weather resistance. The display mask made of the polycarbonate composite material provided by the present application has very excellent heat deformation resistance, and has very few or even no bulging phenomenon when working at a temperature of 100 DEG C and a brightness of 5000 cd / m 2 for more than 4 hours, and has very excellent heat deformation resistance. DETAILED DESCRIPTION

[0036] In order to facilitate the understanding of the present application, the present application will be further described in detail in combination with specific examples. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0038] In the present application, the meaning of "and / or" is any and all combinations of one or more related listed items. The meaning of "at least one" is more than one, such as one, two and more than two. The meaning of "multiple" or "several" is at least two, such as two, three, etc. The meaning of "several" is at least one, such as one, two, etc. unless otherwise specifically defined. In the description of the present application, the meaning of "several" is at least one, such as one, two, etc. unless otherwise specifically defined.

[0039] When a range of values is disclosed, the disclosure is to be construed to include each and every value and sub-range within the range. Further, where a range of values is provided, it is to be understood that each intervening value, to the minimum and maximum value of the range, is also contemplated, unless the context clearly indicates otherwise. Further, it is intended that every combination of individual values of those listed candidates for the ranges is to be considered disclosed. For example, where a range of values is provided, it is intended to include every possible combination of the range, including every integer and fraction within the range. Also, it is intended to include all ranges including endpoints unless otherwise indicated.

[0040] Unless otherwise indicated, all steps of the application can be performed in sequence or randomly. For example, the method comprises steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0041] In the present application, "above" or "below" includes the number itself. For example, 1 below includes 1.

[0042] In the present application, the temperature parameter, unless otherwise specified, allows for constant temperature treatment, and also allows for fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within a range such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0043] In the present application, room temperature refers to indoor temperature, normal temperature or general temperature. Generally, the range of room temperature can be any of the following temperature ranges: 23°C ± 2°C, 25°C ± 5°C or 20°C ± 5°C.

[0044] Polycarbonate (PC) is a high-performance thermoplastic engineering plastic with high light transmission, good weather resistance and excellent impact resistance, which can be used to prepare LED display screen covers. At present, the LED display screen cover is commonly reinforced and modified by adding 10wt.% glass fiber in PC, and this PC composite material can withstand high temperature of 40°C~60°C. For LED display screen covers with point spacing P6.0 or more, the traditional PC composite material does not produce obvious thermal deformation when used in outdoor scenes for a long time due to the relatively large size and thickness of the product. However, for LED display screen covers with point spacing P4.0 or less, the display brightness exceeds 4500cd / m 2When the limit condition occurs, the surface temperature of the display screen will exceed 60℃, and even reach above 80℃. At this time, if the display mask continues to use the traditional PC composite material, obvious thermal deformation will occur, which directly manifests as local bulging due to heat, display screen being blocked, abnormal conditions such as black blocks or shadows, and the like, thereby bringing very poor user experience.

[0045] There is a reported method for manufacturing a small-pitch mask for an outdoor LED display screen, which uses 70wt.%~80wt.% polyphenylene sulfide as a base material, and adds 20wt.%~30wt.% glass fiber for blending modification. Although this composite material can improve the mask bulging problem, the material cost is high, and the detailed structure of the mask needs to be optimized, further increasing the cost. Therefore, it is necessary to develop a composite material with high strength, high modulus, excellent heat resistance and low cost, which can effectively solve the problem of thermal deformation of the small-pitch outdoor LED display screen mask under the condition that the product structure remains unchanged.

[0046] Based on this, the first aspect of the present application provides a polycarbonate composite material.

[0047] In some embodiments, the polycarbonate composite material comprises the following mass fractions of components:

[0048] ;

[0049] The high-temperature-resistant resin satisfies: melting point ≥ 260℃, or glass transition temperature ≥ 185℃;

[0050] The reinforcing fiber comprises one or more of surface-modified glass fiber and surface-modified carbon fiber;

[0051] The mass fractions of the high-temperature-resistant resin and the surface-modified carbon fiber are not both 0.

[0052] The melting point of the high-temperature-resistant resin selected in the application is greater than or equal to 260 DEG C or the glass transition temperature is greater than or equal to 185 DEG C, which can significantly improve the strength, rigidity and heat resistance of the polycarbonate composite material, thereby reducing the thermal deformation phenomenon of the polycarbonate composite material in a high-temperature environment. The glass fiber and carbon fiber in the reinforcing fiber are both subjected to surface modification treatment, so that the reinforcing fiber has good compatibility with the resin; at the same time, compared with the glass fiber, the carbon fiber has better mechanical properties and heat resistance, and the introduction of an appropriate amount of surface-modified carbon fiber can compensate for the defects of the insufficient strength, rigidity and heat resistance of the composite material. The application uses the high-temperature-resistant resin and polycarbonate to perform alloy modification or add surface-modified carbon fiber to perform reinforcing modification, and combines with the flame retardant, synergistic flame retardant, toughening agent and weathering agent and other components in a specific ratio, which greatly improves the comprehensive performance of the composite material such as strength, rigidity, heat resistance, high-temperature creep resistance, flame retardancy and weather resistance. The display mask made of the polycarbonate composite material provided by the application has very excellent heat deformation resistance, and has very few or even no bulging phenomenon when working at a temperature of 100 DEG C and a brightness of 5000 cd / m 2

[0053] As an example, the mass fraction of the polycarbonate (PC) in the PC composite material can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%.

[0054] As an example, the mass fraction of the high-temperature-resistant resin in the PC composite material can be 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or 45%.

[0055] As an example, the mass fraction of the reinforcing fiber in the PC composite material can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0056] As an example, the mass fraction of the flame retardant in the PC composite material can be 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5% or 12%.

[0057] As an example, the mass fraction of the synergistic flame retardant in the PC composite material can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8% or 3%.

[0058] As an example, the mass fraction of the toughening agent in the PC composite material can be 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8% or 3%.

[0059] ​As an example, the mass fraction of the weather-resistant agent in the PC composite material can be 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, or 0.6%.

[0060] Optionally, the polycarbonate composite material comprises the following mass fractions of components:

[0061] .

[0062] In the present application, if a high-temperature-resistant resin with a mass fraction of 40% to 45% is added to PC for blending modification, the strength, rigidity, and heat resistance of the PC composite material can be greatly improved, regardless of whether the reinforcing fibers contain surface-modified carbon fibers or not. When the content of the high-temperature-resistant resin is the same, replacing part or all of the surface-modified glass fibers with surface-modified carbon fibers can achieve higher strength, rigidity, and heat resistance.

[0063] As an example, the mass fraction of the PC in the PC composite material can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%.

[0064] As an example, the mass fraction of the high-temperature-resistant resin in the PC composite material can be 40%, 40.5%, 41%, 41.5%, 42%, 42.5%, 43%, 43.5%, 44%, 44.5%, or 45%.

[0065] Optionally, the polycarbonate composite material comprises the following mass fractions of components:

[0066] ;

[0067] wherein the mass fraction of the surface-modified carbon fiber in the polycarbonate composite material is ≥ 5%.

[0068] In the present application, adding a surface-modified carbon fiber with a mass fraction of ≥ 5% without adding a high-temperature-resistant resin can also significantly improve the strength, rigidity, and heat resistance of the PC composite material.

[0069] As an example, the mass fraction of the PC in the PC composite material can be 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, or 75%.

[0070] As an example, the mass fraction of the surface-modified carbon fiber in the PC composite material is 5% to 20%, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%.

[0071] As an example, the mass fraction of the surface-modified glass fiber in the PC composite material is 0% to 15%, such as 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%.

[0072] Optionally, the synthesis process of the PC includes one or more of a non-phosgene method, a semi-phosgene method, and a phosgene method. Among them, the main raw materials of the phosgene method are bisphenol A and phosgene, and the process is relatively mature, which is conducive to producing PC with a high molecular weight. Therefore, the phosgene method PC with a higher molecular weight is selected in the present application.

[0073] Optionally, the PC satisfies the following conditions: the number average relative molecular weight is 20,000 to 50,000; and the melt flow index (MFI) is greater than or equal to 10 g / 10 min under the condition of a temperature of 300°C and a load of 1.2 kg.

[0074] In the present application, the high-temperature-resistant resin can be divided into three types, i.e., a crystalline state, a semi-crystalline state, and a non-crystalline state, according to different resin compositions. For the high-temperature-resistant resin in the crystalline state and the semi-crystalline state, the melting point (T m ) should be above 260°C. For the high-temperature-resistant resin in the non-crystalline state, the glass transition temperature (T g ) should be above 185°C.

[0075] Optionally, the high-temperature-resistant resin includes one or more of a liquid crystal polymer, polyphenylenediamide, polyether ether ketone, polyetherimide, polysulfone, polyphenyl sulfone, and polyether sulfone. Further optionally, the high-temperature-resistant resin includes one or more of polyetherimide, polysulfone, polyphenyl sulfone, and polyether sulfone.

[0076] The high-temperature-resistant resin selected by the present application has a similar bisphenol A structure as PC, so that the high-temperature-resistant resin has certain compatibility with PC at different use amounts, thereby showing good alloy modification effect. The liquid crystal polymer (LCP) is a kind of polymer material with special performance, which not only has the characteristics of high strength and modulus, good tensile and bending resistance, but also has excellent heat resistance and can maintain stable performance at high temperature. The polyphthalamide (PPA) has two forms of semi-crystalline and non-crystalline, and the melting point of the semi-crystalline is about 310℃, which has excellent heat resistance and performs well in high-temperature creep resistance, fatigue resistance and chemical resistance. The polyether ether ketone (PEEK) has excellent high-temperature resistance, and the long-term use temperature can reach 260℃, and also has high strength, high modulus and good chemical corrosion resistance. The polyetherimide (PEI) is an amorphous high-performance thermoplastic plastic, which has excellent heat resistance, a glass transition temperature of 217℃, a long-term use temperature of more than 170℃, high strength, high rigidity, excellent flame retardance and excellent chemical corrosion resistance. The polysulfone (PSU) is a high-performance thermoplastic plastic, which has good heat resistance, a long-term use temperature of 150℃-174℃, high strength, high rigidity, high transparency, good chemical corrosion resistance and good dimensional stability, and the size change is small under different temperature and humidity conditions. The polyphenylsulfone (PPSU) is a high-performance special engineering plastic, which has excellent high-temperature resistance, can maintain stable performance in a wide temperature range, and has a long-term use temperature of more than 180℃, excellent mechanical strength, excellent chemical corrosion resistance and good dimensional stability. The polyethersulfone (PES) is a high-performance special engineering plastic, which has excellent heat resistance, a long-term use temperature of 180℃, a short-term use temperature of more than 220℃, high strength and rigidity, excellent chemical corrosion resistance, good dimensional stability and high transparency.

[0077] It can be understood that the particle size of the high-temperature-resistant resin is not particularly limited. Generally, the high-temperature-resistant resin exists in the form of sheet or powder, and can be made into granular form, and then blended with PC for alloy modification. However, it is difficult to process PEEK powder into granular form.

[0078] Optionally, the surface-modified carbon fiber includes a carbon fiber coated with a polymer on the surface.

[0079] Optionally, the polymer comprises one or more of polyurethane, epoxy resin and acrylic acid. Further optionally, the polymer coated on the surface of the carbon fiber is epoxy resin; or the polymer coated on the surface of the carbon fiber is acrylic acid and polyurethane, and the mass ratio of the acrylic acid and the polyurethane is (1-2):(2-1). As an example, the mass ratio of the acrylic acid and the polyurethane can be 1:1, 1:1.5, 1:2, 2:1 or 2:1.5, and further optionally 1:2.

[0080] In the present application, the polymer such as polyurethane, epoxy resin and acrylic acid coated on the surface of the carbon fiber can enhance the compatibility between the carbon fiber and the resin, avoid the defect that the reinforcing modification effect is not ideal due to poor compatibility, and play an important role in improving the strength, rigidity and heat resistance of the composite material.

[0081] Optionally, the mass ratio of the polymer and the carbon fiber is (1.5-6):100, and further optionally (2.5-4.5):100. As an example, the mass ratio of the polymer and the carbon fiber can be 1.5:100, 2:100, 2.5:100, 3:100, 3.5:100, 4:100, 4.5:100, 5:100, 5.5:100 or 6:100.

[0082] Optionally, the length of the carbon fiber is 4mm-8mm, and the diameter is 4pm-9pm. Further optionally, the length of the carbon fiber is 5mm-7mm, and the diameter is 6pm-8pm. As an example, the length of the carbon fiber can be 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm or 8mm, and the diameter can be 4pm, 4.5pm, 5pm, 5.5pm, 6pm, 6.5pm, 7pm, 7.5pm, 8pm, 8.5pm or 9pm.

[0083] Optionally, the surface modified glass fiber comprises a glass fiber modified by a silane coupling agent.

[0084] In the present application, the surface of the glass fiber is modified by the silane coupling agent, which can enhance the compatibility between the glass fiber and the resin, avoid the defect that the reinforcing modification effect is not ideal due to poor compatibility, and play an important role in improving the strength, rigidity and heat resistance of the composite material.

[0085] Optionally, the mass ratio of the silane coupling agent and the glass fiber is (0.5-2.5):100. As an example, the mass ratio of the silane coupling agent and the glass fiber can be 0.5:100, 0.8:100, 1:100, 1.2:100, 1.5:100, 1.8:100, 2:100, 2.2:100, 2.4:100 or 2.5:100.

[0086] Optionally, the glass fiber is selected from long glass fiber or chopped glass fiber, the length of the glass fiber is 3mm-5mm, and the diameter of the glass fiber is 8μm-12μm. For example, the length of the glass fiber can be 3mm, 3.2mm, 3.8mm, 3.8mm, 4mm, 4.2mm, 4.5mm, 4.8mm or 5mm, and the diameter can be 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm or 12μm.

[0087] Optionally, the toughening agent includes one or more of ethylene-methyl acrylate copolymer, methyl methacrylate-acrylate copolymer, methyl methacrylate-butadiene-styrene copolymer, ethylene-acrylate-glycidyl methacrylate terpolymer, acrylic toughening agent and acrylic-silicone rubber-based toughening agent, and is further optionally one or more of methyl methacrylate-butadiene-styrene copolymer, ethylene-acrylate-glycidyl methacrylate terpolymer and acrylic-silicone rubber-based toughening agent.

[0088] The toughening agent selected in the application has acrylic functional groups or acrylate functional groups, has certain polarity and active functional groups, can play a role at the interface of polymers with different polarities, enhance the interfacial bonding force, improve the compatibility, reduce phase separation and improve the performance of the alloy modified material.

[0089] Optionally, the flame retardant includes one or more of nitrogen-based flame retardant, phosphorus-based flame retardant and organic sulfonate-based flame retardant, and is further optionally phosphorus-based flame retardant. The nitrogen-based flame retardant includes one or more of melamine, melamine cyanurate, melamine phosphate, dicyandiamide and guanidine compounds; the phosphorus-based flame retardant includes one or more of triphenyl phosphate, bisphenol A-bis(diphenyl phosphate) and resorcinol-bis(diphenyl phosphate); and the organic sulfonate-based flame retardant includes one or more of 2,4,5-trichlorobenzenesulfonic acid sodium, benzenesulfonyl benzenesulfonic acid potassium and potassium perfluorobutyl sulfonate.

[0090] Optionally, the synergistic flame retardant includes one or more of organosiloxane, organosilicon resin, silicate and silicon powder, and is further optionally organosiloxane.

[0091] In the application, the synergistic flame retardant refers to an auxiliary agent that can significantly improve the flame retardant effect and reduce the amount of main flame retardant when used in combination with the main flame retardant in the flame retardant system. The organosiloxane-based synergistic flame retardant can assist in flame retardation by promoting charring and releasing inert gas, has good thermal stability, low smoke and low toxicity, and can improve the processability and flowability of the composite material. The use of organosiloxane-based synergistic flame retardant and phosphorus-based flame retardant can achieve good flame retardant effect of PC composite material, and maintain good mechanical strength and high transparency.

[0092] Optionally, the weathering agent comprises a light stabilizer.

[0093] It can be understood that the light stabilizer is a kind of additive that can inhibit or slow down the degradation and aging of high polymer materials under the action of light (mainly ultraviolet light), which usually includes one or more of ultraviolet absorbers, free radical capturing agents and quenching agents. Among them, the ultraviolet absorber is a kind of additive that can absorb ultraviolet light to protect the material from ultraviolet damage, and common ones are benzophenone, benzotriazole and triazine. The free radical capturing agent is a kind of substance that can effectively capture and terminate the free radical chain reaction, which plays an important role in preventing material aging and degradation, and common ones are hindered amine compounds such as piperidine derivatives and imidazoline derivatives, and phenolic compounds such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). The quencher is a kind of substance that can make the molecule in the excited state return to the ground state through energy transfer or charge transfer, thereby reducing the probability of photochemical reaction, and common ones are metal ion quenchers and aromatic quenchers.

[0094] Optionally, the weathering agent comprises an ultraviolet absorber and a free radical capturing agent. Among them, the ultraviolet absorber comprises one or more of benzotriazole ultraviolet absorbers and triazine ultraviolet absorbers; the free radical capturing agent comprises a hindered amine free radical capturing agent; the mass ratio of the ultraviolet absorber to the free radical capturing agent is (1-3):(1-3), for example 1:1, 2:1, 3:1, 1:2, 3:2, 1:3 or 2:3.

[0095] Optionally, the polycarbonate composite material further comprises one or more of an antioxidant, a lubricant and an anti-dripping agent.

[0096] Optionally, the polycarbonate composite material further comprises the following components in the following mass fractions:

[0097] .

[0098] As an example, the mass fraction of the antioxidant in the PC composite material can be 0.3%, 0.4%, 0.5%, 0.6%; the mass fraction of the lubricant in the PC composite material is 0.4%, 0.5%, 0.6%, 0.7% or 0.8%; the mass fraction of the anti-dripping agent in the PC composite material is 0%, 0.1%, 0.2%, 0.3%, 0.4% or 0.5%.

[0099] Optionally, the antioxidant comprises one or more of hindered phenolic antioxidants and phosphite antioxidants. Further optionally, the mass ratio of the hindered phenolic antioxidant to the phosphite antioxidant is (1-2):(1-4), for example 1:1, 2:1, 1:2, 1:3, 2:3 or 1:4.

[0100] Optionally, the lubricant comprises one or more of organosiloxane polymer, fatty acid salt, fatty acid amide, pentaerythritol stearate, erucamide, oleamide, ethylene bis-stearamide, and polyolefin wax, further optionally one or more of organosiloxane polymer, pentaerythritol stearate, and ethylene bis-stearamide.

[0101] Optionally, the anti-dripping agent comprises one or more of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and silicone, further optionally polytetrafluoroethylene (PTFE).

[0102] In some embodiments, the method for preparing the PC composite material comprises the following steps:

[0103] S100: mixing PC, high-temperature-resistant resin, flame retardant, synergistic flame retardant, toughening agent, and weather-resistant agent to prepare a blend;

[0104] S200: mixing the blend and the reinforcing fiber, and performing an extrusion molding process to prepare a molding material;

[0105] S300: performing a granulation process on the molding material to prepare the PC composite material.

[0106] Optionally, the blend further comprises one or more of an antioxidant, a lubricant, and an anti-dripping agent.

[0107] Optionally, in the mixing process of step S100, a high-speed mixing stirrer is used as the mixing device, the stirring speed is 400 rpm to 800 rpm, and the stirring time is 2 min to 3 min.

[0108] Optionally, in the extrusion process of step S200, a screw extruder is used as the extrusion device, the blend enters the extruder through a hopper, and the reinforcing fiber enters the extruder through a side feeder, the main machine feeding speed is 15 rpm to 25 rpm, the side feeder feeding speed is 8 rpm to 15 rpm, the extrusion temperature is 250°C to 290°C, the screw rotation speed is 350 rpm to 450 rpm, and the vacuum degree is -0.02 MPa to -0.04 MPa.

[0109] Optionally, the granulation process of step S300 comprises a die, a draw bar, and a cutting process.

[0110] Optionally, the particle size of the PC composite material is 1.5 mm to 4.0 mm, for example, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm, 3 mm, 3.2 mm, 3.5 mm, 3.8 mm, or 4 mm.

[0111] Optionally, the tensile strength of the PC composite material is ≥72 MPa, further optionally 100 MPa to 120 MPa.

[0112] Optionally, the flexural modulus of the PC composite material is ≥ 3700 MPa, further optionally 4600 MPa ~ 7000 MPa.

[0113] Optionally, the notched Izod impact strength of the PC composite material is ≥ 6 kJ / m 2 , further optionally 6.4 kJ / m 2 ~ 10 kJ / m 2 .

[0114] Optionally, the heat distortion temperature of the PC composite material is ≥ 150℃, further optionally 153℃ ~ 160℃.

[0115] Optionally, the flame retardant rating of the PC composite material at a thickness of 1.6 mm is V0 level.

[0116] In the second aspect of the present application, a display screen mask is provided, which is made of the polycarbonate composite material as described above.

[0117] Optionally, the display screen mask can continuously work for more than 4h under the environment of a temperature of 100℃ and a brightness of 5000 cd / m 2 , and the number of bulges or shadows on the surface is not more than 3.

[0118] In the third aspect of the present application, an outdoor LED display screen is provided, which comprises the display screen mask as described above.

[0119] The following will be further described in combination with specific examples and comparative examples. The raw materials involved in the following specific examples and comparative examples, if not specifically stated, can be sourced from the market. The instruments used, if not specifically stated, can be sourced from the market. The processes involved, if not specifically stated, are the routine choices of those skilled in the art.

[0120] Example 1

[0121] Please refer to Table 1. The PC composite material of the present embodiment is composed of the following components with mass fractions as follows: .

[0122] Wherein, the high-temperature-resistant resin is selected from polyether sulfone (PES); the surface-modified glass fiber is a glass fiber modified by a silane coupling agent, the length of the glass fiber is 3mm-5mm, and the fiber diameter is 8μm-12μm; the flame retardant is selected from bisphenol A bis-diphenyl phosphate, the synergistic flame retardant is selected from polysiloxane, the toughening agent is selected from ethylene-acrylic ester-glycidyl methacrylate terpolymer, the weathering agent is selected from benzotriazole UV234, the antioxidant is selected from a combination of hindered phenol 1076 as a main antioxidant and phosphite 168 as an auxiliary antioxidant, the lubricant is selected from pentaerythritol stearate, and the anti-dripping agent is selected from polytetrafluoroethylene powder.

[0123] In the embodiment, the preparation method of the PC composite material is as follows:

[0124] (1) The PC, the high-temperature-resistant resin, the flame retardant, the synergistic flame retardant, the toughening agent, the weathering agent, the antioxidant, the lubricant, and the anti-dripping agent are put into a high-speed mixing stirrer, and are stirred at a uniform speed under a stirring speed of 400rpm-800rpm for 2min-3min to obtain a uniformly mixed blend.

[0125] (2) The blend is fed into an extruder through a hopper, and the feeding speed is controlled at 15rpm-25rpm; the reinforcing fiber is fed into the extruder through a side feeder, and the feeding speed is 8rpm-15rpm; the extrusion temperature is set to 250℃-290℃, the screw rotation speed is 350rpm-450rpm, and the vacuum degree is-0.02MPa--0.04MPa, and the extrusion molding is performed to obtain a molded material.

[0126] (3) The molded material is granulated through a die, a draw bar, and a granulating process to obtain a PC composite material with a particle size of 1.5mm-4.0mm.

[0127] Examples 2~6

[0128] The formulations of the PC composite materials of Examples 2-6 are shown in Table 1, and the preparation method is the same as that of Example 1.

[0129] In the examples, the high-temperature-resistant resin polyether sulfone (PES) is added in Examples 1-4, no surface-modified carbon fiber is added in Examples 1-2, and the surface-modified carbon fiber is added in Examples 3-4; no high-temperature-resistant resin is added in Examples 5-6, but the surface-modified carbon fiber is added.

[0130] Comparative Examples 1~4

[0131] The formulations of the PC composite materials of Comparative Examples 1-4 are shown in Table 1, and the preparation method is the same as that of Example 1.

[0132] In the comparative examples, no high-temperature-resistant resin and no surface-modified carbon fiber are added in Comparative Example 1.

[0133] Comparative Example 2 is substantially the same as Example 4, except that no toughening agent is added;

[0134] Comparative Example 3 is substantially the same as Example 3, except that the surface-modified carbon fiber is replaced by carbon fiber without surface modification;

[0135] Comparative Example 4 is substantially the same as Example 2, except that the surface-modified glass fiber is replaced by glass fiber without surface modification.

[0136] Test Example

[0137] The PC composite materials in each example and each comparative example are injection molded to prepare standard samples and display covers according to the standard requirements. The performance of the PC composite materials is tested according to the standard test method, and the results are shown in Table 2. The display covers are assembled into LED boxes, and the LED boxes are tested as follows, and the results are shown in Table 3.

[0138] (1) Tensile strength: refer to GB / T 1040.1-2018 Plastics-Determination of tensile properties;

[0139] (2) Elongation at break: refer to GB / T 1040.1-2018 Plastics-Determination of tensile properties;

[0140] (3) Flexural modulus: refer to GB / T 9341-2000 Plastics-Determination of flexural properties;

[0141] (4) Notched Izod impact strength: refer to GB / T 1843-2008 Plastics-Determination of Izod impact strength;

[0142] (5) Heat distortion temperature: refer to GB / T 1634.1-2019 Plastics-Determination of heat distortion temperature under load;

[0143] (6) Flame retardant level: refer to UL 94 flame retardant level standard.

[0144] (7) LED box temperature aging test: the LED box is placed in an oven, and the box is lit and aged at 40℃, 50℃, 60℃, 70℃, 80℃, 90℃ and 100℃, respectively. Under the serial condition, at each temperature, the luminance of 5000cd / m 2 is used, and the box is lit for at least 4h. When the number of blisters or shadows exceeds 15 per box, the verification is stopped, and the temperature at which the verification is stopped is recorded. The results are shown in Table 3.

[0145] As can be seen from Tables 1-3, the PC composite materials of Examples 1-2 are alloyed with high-temperature resistant resin, the PC composite materials of Examples 5-6 are reinforced with surface-modified carbon fibers, and the PC composite materials of Examples 3-4 are both alloyed with high-temperature resistant resin and reinforced with surface-modified carbon fibers, all of which can greatly improve the strength, rigidity and heat resistance of the PC composite materials. In the temperature aging test of the LED box, the face shield made of the PC composite material of Examples 1-6 has few or even no bulging defect, indicating that it has very excellent heat deformation resistance and is very suitable for long-term use in small-pitch outdoor LED display screens.

[0146] Table 1. Formulation of PC composite material (unit: wt. %)

[0147]

[0148] Table 2. Performance comparison of PC composite material

[0149]

[0150] Table 3. Temperature aging test results of LED box

[0151]

[0152] Note: “--” in Table 3 means that the verification has been stopped.

[0153] The technical features of the above-described embodiments can be combined in any manner. For brevity, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not contradict each other, they should be considered within the scope of the present disclosure.

[0154] The above-described embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the protection scope of the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A polycarbonate composite material, characterized by, Comprise the following components by mass fraction: Polycarbonate 30%~40%, High temperature resistant resin 40%~45%, Reinforcing fiber 5%~15%, Flame retardant 8%~10%, Synergistic flame retardant 1%~3%, Toughening agent 1%~3%, and Weathering agent 0.3~0.6%; or, Polycarbonate 67%~75%, Reinforcing fiber 10%~20%, Flame retardant 10%~12%, Synergistic flame retardant 1%~3%, Toughening agent 1%~3%, and Weathering agent 0.3~0.6%, the mass fraction of surface modified carbon fiber in the reinforcing fiber in the polycarbonate composite material is ≥5%; The polycarbonate composite material further comprises the following components by mass fraction: Antioxidant 0.3%~0.6%, Lubricant 0.4%~0.8%, and Anti-dripping agent 0%~0.5%; Wherein, the high temperature resistant resin satisfies: melting point ≥ 260℃, or, glass transition temperature ≥ 185℃; The high temperature resistant resin comprises one or more of liquid crystal polymer, polyphenylamide, polyether ether ketone, polyetherimide, polysulfone, polyphenyl sulfone, polyether sulfone; The number average relative molecular mass of the polycarbonate is 20000~50000; The reinforcing fiber comprises surface modified glass fiber and surface modified carbon fiber, or, the reinforcing fiber comprises surface modified carbon fiber; The surface modified carbon fiber comprises carbon fiber coated with polymer, the polymer comprises one or more of polyurethane and epoxy resin; The surface modified glass fiber comprises glass fiber modified by silane coupling agent, the length of the glass fiber is 3mm~5mm; The toughening agent comprises one or more of ethylene-methyl acrylate copolymer, methyl methacrylate-acrylate copolymer, methyl methacrylate-butadiene-styrene copolymer, ethylene-acrylate-glycidyl methacrylate terpolymer, acrylic toughening agent and acrylic-silicone rubber toughening agent; The weathering agent comprises ultraviolet absorber.

2. The polycarbonate composite of claim 1, wherein, The mass fraction of the surface modified carbon fiber in the polycarbonate composite material is 5%~20%.

3. The polycarbonate composite of claim 1, wherein, The mass fraction of the surface modified glass fiber in the polycarbonate composite material is 0%~15%.

4. The polycarbonate composite of claim 1, wherein, The toughening agent is one or more of methyl methacrylate-butadiene-styrene copolymer, ethylene-acrylate-glycidyl methacrylate terpolymer and acrylic-silicone rubber toughening agent.

5. The polycarbonate composite of claim 1, wherein, The surface modified carbon fiber satisfies one or more of the following conditions: (1) The mass ratio of the polymer to the carbon fiber is (1.5~6):100; (2) The length of the carbon fiber is 4mm~8mm, and the diameter is 4μm~9μm.

6. The polycarbonate composite of claim 1, wherein, The surface modified glass fiber satisfies one or more of the following conditions: (1) The mass ratio of the silane coupling agent to the glass fiber is (0.5~2.5):100; (2) The diameter of the glass fiber is 8μm~12μm.

7. The polycarbonate composite of claim 1, wherein, Satisfy one or more of the following conditions: (1) The flame retardant comprises one or more of nitrogen-based flame retardant, phosphorus-based flame retardant and organic sulfonate-based flame retardant; (2) the synergistic flame retardant comprises one or more of organosiloxane, organosilicon resin, silicate and silicon micro powder.

8. The polycarbonate composite of claim 1, wherein, The polycarbonate composite further comprises one or more of antioxidant, lubricant and anti-dripping agent, satisfying one or more of the following conditions: (1) the antioxidant comprises one or more of hindered phenol antioxidant and phosphite antioxidant; (2) the lubricant comprises one or more of organosiloxane polymer, fatty acid salt, fatty acid amide, pentaerythritol stearate, erucic acid amide, oleic acid amide, ethylene bis-stearamide and polyolefin wax; (3) the anti-dripping agent comprises one or more of polytetrafluoroethylene, polyvinylidene fluoride and silicone.

9. A display screen visor, characterized in that The polycarbonate composite is made of any one of claims 1-8.

10. An outdoor LED display screen, characterized by The display screen mask comprises claim 9.

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