Innovative Application Of PC In The Field Of LED (Part II)

- Dec 20, 2018-

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 lightweight LED, the thickness of the product is reduced to less than 0.7mm. PC has the disadvantage of low strength and linear expansion coefficient, and the product is prone to soft deformation and bending. In order to solve the problem of PC, nanotube PC materials have been developed in the industry.

Nano-reinforced PC materials refer to the materials reinforced with inorganic or organic nanomaterials (at least one dimension in three-dimensional space is nano-sized). Conventional reinforcing materials often have the problems of too large filler size and uneven dispersion, which lead to the increase of strength and modulus of reinforcing materials, but at the same time, the toughness of reinforcing materials decreases greatly, which is manifested by the decrease of impact strength and elongation at break. Compared with general reinforcing materials, nano-reinforcing materials use unique particle refinement technology and surface treatment technology to treat fillers, improve the compatibility between fillers and polymers, improve the strength and modulus of polymers, but also improve the impact strength, elongation at break, ultraviolet resistance and other properties of polymers. It not only improves the comprehensive properties of materials, but also reduces the shrinkage rate of materials, reduces the cost and enlarges the application fields of materials.

The invention patent No. CN 104725816A discloses the use of ordinary glass fibers to reinforce and modify PC. However, due to the cylindrical shape of ordinary glass fibers and the limited reinforcement effect, the improvement effect of curvature and expansion is not obvious. In addition, the refractive index of materials is about 1.45, the transmittance decreases greatly, the lighting effect is worse than that of ordinary light diffusion PC, and the uniformity of light is better. Poor; therefore, the single use of glass fiber, adding a large amount, the strengthening effect is not obvious, the apparent effect is poor [6]. In view of the shortcomings of the existing technology, nano-reinforced tube material provides a low-expansion flame-retardant light-diffusion PC composite material for LED lamp. It has low expansion and flame-retardant characteristics, and has good transmittance, mist and mechanical properties. It can be used in the field of large-size and ultra-thin lamp tubes.

Properties of 3.2.2 Nano-reinforced PC Material

Nano-reinforced tube material is a kind of low-expansion flame-retardant light-diffusion PC composite material for LED lamp tube. It has low expansion and flame-retardant properties, and has good transmittance, mist and mechanical properties. It can be used in large-scale and ultra-thin lamp tube field.

The nanotube materials have the following innovative characteristics:

(1) While increasing the strength and modulus of the material, the elongation at break and impact strength of the material are increased by 5-10%.

(2) Due to the rigid benzene ring structure of PC molecule, it is difficult to dissolve the orientation of the molecular chains in the forming process, which eventually leads to the problems of stress cracking and warping deformation in the use of the products. The technology can reduce the residual stress of the products, so that the cracking, warping and deformation of the products after forming can be well suppressed.

(3) Reducing the shrinkage of material forming can widen the processing window and make the material suitable for more complex shape design.

(4) To some extent, improving material fluidity can solve the problem of weld marks in complex runners.

Progress of 3.2.3 Nanotube PC Material Industry

At least one of the nano-alumina grains or whiskers is used in the industry, and the PC material composition of the enhanced LED lamp tube is used. The material itself has better transmittance and light diffusion performance, and can eliminate the halo or dark spot caused by dispersion, as well as better mechanical properties [7].

3.2.4 Market Applications

Because of its high strength, good toughness, high transmittance, light weight, durability, soft eye protection and other advantages, nanotube materials are widely used in ultra-thin LED lamps, bulb lampshades, special-shaped tubes and other products.

3.3 High Permeability and High Fog PC Material

3.3.1 Background Introduction:

PC occupies an increasingly important position in the field of LED because of its unique characteristics in engineering plastics, such as high transmittance, high refractive index, high impact resistance, excellent dimensional stability and easy processing and forming. All kinds of optical materials fabricated by optical grade PC are incomparable to traditional inorganic glass in terms of impact resistance and processing performance. Nevertheless, due to the structural characteristics of PC itself, there are still some shortcomings in the performance of PC as an LED material. Therefore, it has become an important topic in the field of PC to study its optical properties and improve them by various means. High performance light diffusive PC (PDPC) is used to evaluate light scattering materials by adding light diffusives, flame retardants and other additives in PC resins. The two main indicators for evaluating light scattering materials are transmittance and mist [8]. Therefore, it is particularly important to develop some high-performance optical diffusion PCs. In order to break through the key common technical problems of high transmittance and high fog, the key technologies of Jubilee Optoelectronics have been solved as follows:

High transmittance and high fog: At present, the transmittance is as high as 90%, and the fog is 96%. At present, it is similar to the performance of the products of big international companies such as Luminous and Emperor, and has been used in some products.

Material Properties of 3.3.2 High Permeability and High Fog PC

A special treatment method was used to improve the dispersion of light diffuser in PC matrix. The effects of different dosages of light diffuser on the transmittance and mist of the final PC resin were investigated. The influence parameters of single variable (the dosage of light diffuser) on the final properties (transmittance and mist) were established, and then the amount of light diffuser [10], which matched the high transmittance and mist characteristics of PC, was found.

3.3.3 Progress of High Permeability and High Fog PC Industry

In the industry, PC resin, silicone resin microspheres and cross-linked copolymer microspheres were prepared by melting and blending at one time. In the compositions, silicone resin microspheres and cross-linked copolymer microspheres were evenly distributed in continuous phase PC. Both microspheres were monodispersed, and acid anhydride existed on the cross-linked surface of the cross-linked copolymer microspheres. As a result, the group can transesterify with carbonyl groups on PC molecular chains, which further contributes to the dispersion of light in PC. When light passes through the composite, the incident light can be dispersed under the combined action of dispersed phase microspheres, and the point light source can be turned into a surface light source, thus greatly improving the mist of PC resin compositions, and at the same time, making it have higher transmittance. It can save a lot of energy, save the use of materials and greatly reduce the cost of materials [11].

3.3.4 Market Application

At present, the products with high transmittance and fog have passed the certification of the Aging Quality Supervision and Inspection Center of Chemical Industry Synthetic Materials, and are entering the field of rail transit and household lighting.

Figure 7 Application of High Permeability and High Fog PC in LED

High-performance light-diffusion PC materials vigorously promote the popularization and application of plastic materials in LED lamps. As shown in Figure 7, compared with ordinary lamps, LED lamps have 70% higher energy-saving efficiency and 10 times longer life than ordinary lamps. It is almost maintenance-free. There is no need to replace lamps, ballasts and starters frequently. Green and environmentally friendly semiconductor light sources have soft light, pure color and have the following advantages: It is good for people's eyesight protection and health. The implementation of this project can not only greatly reduce the cost of use, but also save secondary energy, which is of great positive significance to the environment and energy, and is conducive to the realization of the goal of building an environment-friendly and harmonious society in China.

Development and Application of 3.4 3D Printing PC in Lighting Field

3.4.1 Background Introduction

3D printing, also known as add-on manufacturing, is a kind of rapid prototyping technology. Based on the three-dimensional design model of computer, it constructs three-dimensional objects by stacking printing materials layer by layer. It has good potential application value in aerospace, automobile, medical, construction, consumer goods and other fields. With the in-depth study of 3D printing technology, the application of 3D printing in the field of lighting has also developed rapidly. The main reason why lighting and 3D printing can be combined is the customization of parts and components of lighting products and the innovative design of lamps and lanterns. Robert Debane, a Brooklyn designer, created a set of elaborate decorative lamps with a 3D printer and appeared at the "Wanted Design Exposition" during the 2015 New York Design Week (Figure 8). During the Milan Design Week in 2018, the Amethyst Cube, created by Tsinghua students, brought a 3-D printed lunar lamp to the exhibition, making the 3-D printed lunar lamp a bright "one" (fig. 9). All these show that 3D printing materials have important application value in the field of lighting.

3.4.2. Material Characteristics of 3D Printing PC

The main 3D printing technologies used in lighting field are fused deposition moulding (FDM), selective laser sintering (SLS) and stereo light curing moulding (SLA). FDM has the advantages of wide range of forming materials, simple forming equipment, simple operation and low cost. Its disadvantages are low accuracy, poor surface quality, cantilever parts need support, and complex components are not easy to manufacture. The material printed by FDM is PC, which has the characteristics of transparency, high gloss and high heat resistance (over 120 C). It is suitable for lamp tube and lampshade in lighting field. However, the printing temperature of PC is higher and the printing products are easy to warp. The advantages of SLS technology are high material utilization, short production cycle, low cost of development, no need for supporting structure, printing complex products, but need preheating and cooling, toxic gases and dust generated in the forming process, rough surface. SLA technology has stable working system, high dimensional accuracy and good surface quality. It can construct workpieces with complex structure. However, the choice of materials is limited. It must be photosensitive resin, which absorbs water and causes bending of soft and thin parts. At the same time, it needs to design the support structure of workpieces, and the production cost is relatively high.

Progress of 3.4.3 3D Printing PC Material Industry

The three-dimensional printing impregnated PC filament material of Chengdu Xinkeli Chemical Technology Co., Ltd. is characterized in that the outer layer of PC filament is coated with fast melting hot melt adhesive, which is prepared by weight of the following raw materials. A composite hot melt adhesive is coated on the surface of PC filament. The rapid and uniform melting of PC filament is realized by carbon powder and aluminium powder in the hot melt adhesive. The toughness of PC material can be enhanced by adding reinforcing agent. PC material has excellent melting fluidity when it is used in rapid melting of three-dimensional printing because of its thermal stability. It is widely used in three-dimensional printing [12].

3.4.4 Illumination Application Cases

3D printing materials have been used in lighting field. FDM method is mainly used for printing lamp shade and base in lighting field.

Figure 8: Jade Lamp (left) and Sidon Lamp (right) on "Wanted Design Expo"

Figure 9 3D Printed Lunar Lamp on Milan Design Week 2018

3.5 Green Environment-friendly Non-spraying Material

3.5.1 Definition and introduction of spray-free materials:

Non-spraying materials have different display effects by melt blending of plastic raw materials: metal powder, pearlescent powder, ceramic powder, high-gloss color powder, etc., so that they have special color effects. By direct injection moulding and forming, they can achieve near-coating surface effect, remove high-pollution and high-cost spraying links, reduce the use of solvents and heavy metals, and reduce the use of solvents and heavy metals. Environmental pollution, reduce the risk of illness, improve production efficiency and reduce production costs.

3.5.2 Development Trend of Non-spraying Materials at Home and Abroad

With the enhancement of national and public awareness of environmental protection, spray-free technology has been paid more and more attention by the industry. Li Zheng and Liu Yongqiang of Shanghai Automobile Group Co., Ltd. [13] Aiming at the development of piano black highlight injection parts in automotive interior decorations, the injection process, die structure and material selection are analyzed in depth. The piano black parts are prepared by steam heating equipment, instantaneous heating to 180 C and instantaneous cooling to 40 C, which can be comparable to the appearance effect of spraying parts. Zhao Ying and others of Pan-Asian Automobile Technology Research Center [14-15] have done a lot of comparative experiments on the application of different piano black non-spraying materials in automobile grille, which provides a technical basis for the selection of automobile materials. Hu Gang [16-17] investigated the effects of pearlescent powder and metal powder addition on mechanical properties and appearance of conventional spray-free materials.

3.5.3 Advantages, Disadvantages and Solutions of Non-spraying:

Spraying can achieve colorful, high-gloss, smooth texture, reduce surface friction, but it also brings adverse effects on the environment and health. If the same function and effect can be achieved, spraying-free plastic will replace spraying plastic.

Non-spraying polymer materials are made of metal powder, pearlescent powder, ceramic powder and high gloss powder which have different display effects by melt blending in PC to bring special color effect. Compared with spraying products, non-spraying products are easy to form, and the yield of finished products is high. The products can be recycled and reused by 100%, without producing toxic and harmful gases, dust and other pollutants [18-19]. In addition, its beautiful color can help customers cope with diversified and differentiated market demand.

With the rapid development of various industries, the development of China's paint industry has been greatly promoted. From the annual production of 1000 tons in the 1970s to the annual production of 16 million tons in 2014, the output value is about 200 billion RMB. Its growth rate is astonishing, with an annual growth rate of 10%. However, with the rapid development of the coating industry, the harmfulness of organic solvents and heavy metals to the environment and human health can not be underestimated. The appearance of non-spraying plastic products will bring great impact to automobile, coil and industrial protective coatings manufacturers. If the non-spraying polymer materials replace 20% of the coatings market, it will increase the market capacity of 40 billion RMB. As a new type of environmental protection material, non-spraying polymer materials have been actively studied in the upstream and downstream of the industrial chain from raw materials, formulation, mould design to injection molding process. The market demand of non-spraying polymer materials is growing at a rate of 20% annually, and it has broad market prospects in the fields of automobile, household appliances, electronics and electrical appliances.

From the point of view of environmental protection and health management, there is no doubt that spray-free polymer materials have overwhelming advantages. Without spraying process, VOC can be effectively controlled, 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, the cost of spray-free products is reduced by 20-30% compared with spray-painted products because of the free spray process and 100% recycling in the forming process.

From raw materials, formulation, mold design to injection process, the upstream and downstream of the industrial chain actively carry out spray-free related technology and process research, which greatly promotes the application and popularization of spray-free technology in various fields.

However, large-scale application of special effect pigments has not yet been achieved in the painting process. The following technical difficulties have not been well solved:

(1) Metal pigments are cut, bended and glossy in the extrusion process, which results in darkening of the product color and poor metal texture, which can not match the appearance of the color of the coating.

(2) In the process of injection moulding, due to the poor compatibility and dispersion of metal pigments and resins, and the influence of flow field on the arrangement of metal pigments, the surface of the product becomes darker or runs.

(3) Darkening of bonding line caused by unreasonable product structure and die gate arrangement.

Solving the above three main technical difficulties is the precondition to promote the large-scale application of spray-free materials. In this industry, we mainly study and overcome the technical difficulties mentioned above, and have achieved some results. Through multi-layer coating treatment of the surface of pigments, functional modification technology and advanced extrusion technology are used to solve the technical problems mentioned above.

3.5.5 Application Example

At present, spray-free plastics include spray-free PC, spray-free PC/ABS and so on. The application fields include household appliances, electronic appliances, automobiles, 3C, lighting fields. Non-spraying polymer materials can be used in rice cookers, washing machines, air conditioning panels, mobile phone shells, automobile accessories, etc. As shown in Figure 10, the application of non-spraying materials of different materials in lighting field.

Figure 10 Application of spray-free materials in lighting field

Four, conclusion

With the rapid development of optoelectronic technology, various transparent optical materials are gradually developing towards polymer materials instead of inorganic glass. PC, with its unique and excellent comprehensive properties, has been widely used in this field. With the deepening of the research on the relationship between its optical properties, structure and forming process, the development and application of optical PC in China is still in its infancy, which will further show its wider application fields and greater economic prospects.

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