Innovative application of PC in LED field (Part 2)
Innovative application of PC in LED field (Part 2)[Introduction] Because of its unique advantages, LED has developed rapidly since its birth. However, in the field of ultra-thin and light-weight LEDs, the thickness of products has fallen below 0.7 mm. PCs have shortcomings such as low strength and linear expansion coefficient. Products are prone to soft deformation and bending problems. In order to solve the problems in this aspect of PC, nano-reinforced tube PC materials have been developed in the industry.
3.2 Nano-reinforced PC material
3.2.1 Background introduction:
Because of its unique advantages, LED has developed rapidly since its birth. However, in the field of ultra-thin and light-weight LEDs, the thickness of products has fallen below 0.7 mm. PCs have shortcomings such as low strength and linear expansion coefficient. Products are prone to soft deformation and bending problems. In order to solve the problems in this aspect of PC, nano-reinforced tube PC materials have been developed in the industry.
Nano-reinforced PC material refers to a material that reinforces PC with inorganic or organic nano-materials (at least one dimension of which is in the nano-size in three-dimensional space). Conventional reinforcement materials often have problems such as excessive filler size and uneven dispersion, which leads to a significant decrease in toughness while the strength and modulus of the reinforcement material increase, manifested by a significant decrease in impact strength and elongation at break. Compared with general reinforcement materials, nano-reinforcement materials use unique particle miniaturization technology and surface treatment technology to treat fillers, improve the compatibility of fillers and polymers, and increase the strength and modulus of polymers while improving polymerization The impact strength, elongation at break, UV resistance and other properties. Not only the comprehensive performance of the material is comprehensively improved, but also the molding shrinkage rate of the material is reduced, the cost is reduced, and the application field of the material is expanded [5].
Patent No. CN 104725816 A discloses the use of ordinary glass fiber reinforced modified PC, but because ordinary glass fiber is cylindrical, the reinforcement effect is relatively limited, resulting in the improvement effect of bending and expansion is not obvious. In addition, the material The refractive index is about 1.45, the light transmittance is greatly reduced, the lighting effect is worse than that of ordinary light diffusion PC, and the uniformity of light is poor; therefore, using glass fiber alone, the addition amount is large, the enhancement effect is not obvious, and the apparent effect is poor [6]. Nano-reinforced tube materials provide a low-expansion and flame-retardant light-diffusing PC composite material for LED lamps to meet the shortcomings of the existing technology. It has low expansion and flame-retardant properties, and has good light transmittance, haze, and mechanical properties And other characteristics, it can be used in the field of large size and ultra-thin lamps.
3.2.2 Nano-reinforced PC material properties
Nano-reinforced tube material is a low-expansion and flame-retardant light-diffusing PC composite material for LED lamps. It has low expansion and flame-retardant properties, and has good light transmittance, haze, mechanical properties, etc. , Used in the field of ultra-thin lamps.
Nano-reinforced tube materials have the following innovative features:
(1), while increasing the strength and modulus of the material, increase the elongation at break and impact strength of the material by 5-10%;
(2). Because the PC molecule contains a rigid benzene ring structure, it is difficult to deorient the molecular chains oriented during molding, which ultimately leads to problems such as stress cracking and warpage deformation during the use of the product. The technology can reduce the residual stress of the product, so that the cracking, warping and deformation of the product after molding can be well suppressed;
(3), reduce the molding shrinkage of the material, can widen the processing window, so that the material is suitable for more complex shape design;
(4). To a certain extent, improve the fluidity of the material to solve the problem of welding marks of complex flow channels.
Figure 7 The comparison between nano-reinforced tube materials and ordinary PC materials can reduce the thickness of the product, reduce the loss, and greatly reduce the cost of the product:
Figure 5 Comparison of nano-reinforced tube materials and ordinary PC materials
3.2.3 Nano-reinforced tube PC material industry progress
The industry uses at least one of nano-alumina crystal grains or whiskers, and a PC material composition that uses enhanced LED lamps. The material itself has more excellent light transmittance and light diffusion properties, and can eliminate the dispersion. Halo or dark spots and other phenomena also have more excellent mechanical properties [7].
3.2.4 Market application
Nano-reinforced tube materials are widely used in ultra-thin LED lamp tubes, bulb lampshades, shaped tubes and other product fields due to their advantages of high strength, good toughness, high light transmittance, light and durable, and soft eye protection.
Figure 6 Application of nano-reinforced tube materials
3.3 High permeability and high fog PC material
3.3.1 Introduction:
PC is characterized by its unique high transmittance, high refractive index, high impact resistance, excellent dimensional stability, and ease of processing and molding in engineering plastics, occupying an increasingly important position in the LED field. Various optical materials made with optical grade PC, whether it is impact resistance or molding performance, are unmatched by traditional inorganic glass. Nonetheless, due to the structural characteristics itself, PC as an LED material still lacks in performance, so researching its optical performance and improving it through various means has become an important issue in the PC field. High-performance light diffusion PC is to add light diffusing agent, flame retardant and other additives to the PC resin. The two main indicators for evaluating light scattering materials are light transmittance and haze [8]. Therefore, it is very important to develop some high-performance light diffusion PCs. In order to break through the current common technical problems of high light transmittance and high haze, Jubilee Optoelectronics has solved the following key technologies:
High light transmittance and high haze: At present, the light transmittance is up to 90% and the haze is 96%. It is currently close to the performance of the products of international companies such as Idemitsu and Teijin.
3.3.2 High permeability and high fog PC material characteristics
Use special treatment methods to improve the dispersion of the light diffusing agent in the PC matrix, investigate the characteristics of different light diffusing agents on the transmittance and haze of the final PC resin, and establish a single factor variable (light diffusing agent dosage) The parameters affecting the final characteristics (transmittance, haze), and then find the amount of light diffusing agent that matches the high transmittance and high haze characteristics of PC [10].
3.3.3 Progress of high permeability and high fog PC industry
The industry adopts the method of melting and blending the components including PC resin, silicone resin microspheres and crosslinked copolymer microspheres at a time. In the composition thus obtained, the silicone resin microspheres and crosslinks Copolymer microspheres Two types of microspheres are evenly distributed in the continuous phase PC. Both microspheres are in a monodispersed state. The crosslinked copolymer microspheres have acid anhydride groups on the surface of the crosslink, so they can be linked to the PC molecular chain. The carbonyl group of the ester undergoes a transesterification reaction, which further contributes to its dispersion in the PC. When light passes through the composition, the incident light can be dispersed under the joint action of the two microspheres in the dispersed phase, turning the point light source into a surface light source It can greatly improve the haze of the PC resin composition, at the same time it can have a higher light transmittance, can save a lot of energy, at the same time save the use of materials, and greatly reduce the cost of materials [11].
3.3.4 Market application
At present, the products with high light transmittance and high haze have passed the certification of the chemical industry synthetic material aging quality supervision and inspection center, and are entering the field of rail transit and household lighting.
Figure 7 Application of high-transparent high-fog PC on LED
High-performance light-diffusion PC materials vigorously promote the promotion and application of plastic materials in LED lamps. As shown in Figure 7, LED lamps have a power saving efficiency of 70% higher than ordinary lamps, and their life span is more than 10 times that of ordinary lamps. There is no problem of frequent replacement of lamps, ballasts, and starters. The green and environmentally friendly semiconductor electric light source has soft light and pure colors, which is conducive to people's vision protection and physical health. The implementation of this project can not only greatly reduce the cost of use, but also save secondary energy, which has a significant positive impact on the environment and energy, and is conducive to the realization of China's goal of building an environmentally friendly and harmonious society.
3.4 Development and application of 3D printed PC in the field of lighting
3.4.1 Introduction
3D printing, also known as additive manufacturing, is a type of rapid prototyping technology. It is based on a computer three-dimensional design model and builds three-dimensional objects by layering the printed materials in layers. It is used in aerospace, automotive, medical, construction, consumer products And other fields have good potential application value. With the in-depth study of 3D printing technology, the application of 3D printing in the field of lighting has also been rapidly developed. The customization of lighting product parts and components and innovative lamp design are the main reasons for the combination of lighting and 3D printing. . Brooklyn designer Robert Debbane used a 3D printer to create a set of exquisitely carved decorative lamps and appeared at the Wanted Design Expo 2015 during New York Design Week (Figure 8). At the 2018 Milan Design Week, the Amethyst Cube, founded by Tsinghua students, carried a 3D printed moon lamp at the exhibition, making the 3D printed moon lamp a dazzling "one" at the exhibition (Figure 9). All these illustrate the important application value of 3D printing materials in the field of lighting.
3.4.2. 3D printing PC material characteristics
The 3D printing technologies used in the lighting field mainly include fused deposition modeling (FDM), selective laser sintering (SLS) and stereo photocuring molding (SLA). FDM has the advantages of extensive molding materials, simple molding equipment, simple operation, and low cost. The disadvantages are low accuracy, poor surface quality, support for cantilever parts, and complex components that are not easy to manufacture. The material printed by the FDM method is PC. The original PC has the characteristics of transparency, high gloss and high heat resistance (more than 120 ° C). It is suitable for lighting tubes and lampshades in the lighting field. However, the printing temperature of PC is high. Printed products are easily warped. The advantages of SLS technology are high material utilization rate, short production cycle, low development cost, molded parts without supporting structure, can print complex products, but need to be preheated and cooled, toxic gases and dust are generated during the molding process, and the surface is rough. The working system of SLA technology is stable, the workpiece has high dimensional accuracy, and the surface quality is good. It can build workpieces with complex structures, but the choice of materials is limited. It must be photosensitive resin. The resin will absorb water, causing the soft and thin parts to bend. Design the support structure of the workpiece, the production cost is relatively high.
3.4.3 3D printing PC materials industry progress
Chengdu Xinkeli Chemical Technology Co., Ltd.'s three-dimensional printed dipped PC wire material is characterized in that the outer layer of PC wire material is wrapped with fast-melting hot-melt adhesive, which is prepared by the following raw materials in parts by weight and passed on the surface of the PC filament Wrapped with a layer of composite hot-melt adhesive, through the carbon powder and aluminum powder in the hot-melt adhesive, the PC filament is quickly and evenly melted. The added reinforcing agent can enhance the toughness and thermal stability of the PC material, making the PC material in use It has excellent melt fluidity when it is rapidly melted in 3D printing, and it has a very wide range of applications in 3D printing [12].
3.4.4 Lighting application case
3D printing materials have been applied in the field of lighting. The FDM method is mainly used to print lampshades and bases of lamps in the lighting field.
Picture 8 Feitz lamp (left) and Sidon lamp (right) at the "wanted design fair"
Figure 9 3D printed moon lights at Milan Design Week 2018
3.5 Green environmental protection spray-free materials
3.5.1 Definition and introduction of spray-free materials:
The spray-free material is added with different display effects by melt blending plastic materials: metal powder, pearl powder, ceramic powder, high-gloss color powder, etc., to bring its own special color effect, through direct injection molding, while forming, Obtaining a surface effect close to painting, removing high-pollution and high-cost spraying links, can reduce the use of solvents and heavy metals, reduce environmental pollution, reduce the risk of illness for related practitioners, improve production efficiency, and reduce production costs.
3.5.2 Development trend of spray-free materials at home and abroad
With the enhancement of national and public awareness of environmental protection, spray-free technology is increasingly gaining attention in the industry. Li Zheng and Liu Yongqiang of Shanghai Automobile Group Co., Ltd. [13] made an in-depth analysis of the development of piano black high-gloss injection molded parts on automotive interior parts from the injection molding process, mold structure, and material selection, using steam heating equipment, mold temperature Instantly heated to 180 ℃ and instant cooled to 40 ℃, prepared piano black parts, comparable to the appearance of sprayed parts. Zhao Ying et al. [14-15] of the Pan-Asian Automotive Technology Research Center conducted a large number of comparative tests on the application of different piano black spray-free materials in the automotive grille, which provided a technical basis for automotive material selection. Hu Gang [16-17] investigated the effect of the addition of pearl powder and metal powder in conventional spray-free materials on the mechanical properties and appearance of the materials.
3.5.3 Advantages, disadvantages and solutions of spray-free:
Spraying can achieve colorful and colorful colors, highlights, smooth texture, reduce surface friction, but also brings adverse effects on the environment and health, if you can achieve the same function and effect, spray-free plastics will replace sprayed plastics.
Spray-free polymer material is to add metal powder, pearl powder, ceramic powder, high-gloss powder, etc. with different display effects to the PC by melt blending to make it bring its own special color effect. Compared with spray products, spray-free products are easy to form and have a high yield rate. The parts can be recycled 100%, and no pollutants such as gas and dust that are harmful to the environment are generated [18-19]. In addition, its beautiful colors can help customers respond to diversified and differentiated market needs.
With the rapid development of various industries, it has greatly promoted the development of China's coating industry. From the annual output of 1,000 tons in the 1970s to 16 million tons in 2014, the output value is about 200 billion yuan, and its growth rate Amazing, growing at a rate of 10% every year. However, while the coating industry is developing rapidly, the lethality of organic solvents and heavy metals to the environment and human health should not be underestimated. The introduction of spray-free plastic products will mainly have a great impact on automobile, coil and industrial protective coating production enterprises. If spray-free polymer materials replace 20% of the paint market, a new market capacity of 40 billion yuan will be added. . As a new type of environmentally friendly material, spray-free polymer materials, Jubilee Optoelectronics actively carries out spray-free related technology and process research from raw materials, formulations, mold design to injection molding process, and the upstream and downstream of the industrial chain, and the market demand grows at a rate of 20% per year , Has broad market prospects in the fields of automobiles, home appliances and electrical and electronic.
From environmental protection and healthFrom the perspective of Kang management, there is no doubt that spray-free polymer materials have an overwhelming advantage. Eliminating the painting process can effectively control the generation of VOC, which is beneficial to the environment and human health.
From the cost point of view, although the price of spray-free products is relatively high, in the molding process, the paint spraying process is eliminated, and it can be recycled 100%. Overall, compared with spray-painted products, the cost is reduced by 20-30% .
From raw materials, formulations, mold design to injection molding process, upstream and downstream of the industrial chain actively carry out spray-free related technology and process research, which greatly promotes the application and popularity of spray-free technology in various fields.
However, in the replacement of coatings using special effect pigments, large-scale applications have not yet been achieved. The main technical difficulties have not yet been well resolved:
(1) Metal pigments are shredded, bent, and gloss is reduced during the extrusion process, resulting in darker products and poor metal texture, which cannot match the color appearance effect of painting.
(2) During the injection molding process, due to the poor compatibility and dispersion of the metal pigment and resin, and the influence of the flow field on the arrangement of the metal pigment, the surface of the product is dark or flow marks appear.
(3) The bond line is dark due to the unreasonable product structure and mold gate arrangement.
Solving the above three major technical difficulties is a prerequisite for promoting large-scale application of spray-free materials. The industry mainly studies to overcome the above technical difficulties, and has achieved some results. The above technical problems are solved by methods such as multi-layer coating treatment on the pigment surface, functional modification technology and advanced extrusion technology.
3.5.5 Application examples
At present, spray-free plastics include spray-free PC, spray-free PC / ABS, etc. The application fields cover household appliances, electronic appliances, automobiles, 3C, and lighting. Spray-free polymer materials can be used for rice cookers, washing machines, air-conditioning panels, mobile phone housings, auto parts, etc. As shown in Figure 10, the application of spray-free materials of different materials in the field of lighting.
Figure 10 Application of spray-free materials in the field of lighting
IV. Conclusion
Due to the rapid development of optoelectronic technology, various transparent materials for optics are gradually developing in the direction of replacing inorganic glass with polymer materials. Among them, PC's unique and excellent comprehensive performance makes its application in this field continue to expand. With the continuous deepening of the research on the relationship between its optical performance, structure and molding process, the current development and application of optical-grade PCs in China is still in its infancy, and it will further show its wider application field and greater Economic prospects.
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