By analyzing the difference in performance found in various trials of various water-soluble film-forming resins, and the effects of various light-diffusing agents in coatings, the film-forming resins and light-diffusing agents for the preparation of straight-tube type glass LED light-diffusing coatings Selection and application for research.
The glass tube led lamp has high requirements on the uniformity, light transmittance, haze, safety, adhesion, stability, pollution-free, and price of the light-diffusing coating. To meet these requirements, the selection of the resin and the light diffusing agent must be Research on various aspects such as manufacturing processes. The application of water-based LED light-diffusing coatings avoids environmental pollution caused by low organic volatiles (VOC) emissions, and is safe and convenient to use, and has been rapidly developed under the large-scale development of straight-tube glass LED lamps.
1. Selection of water-soluble film-forming resin
Membrane resins that meet the process requirements of the equipment are the key to the harmless aqueous light diffusion coating technology. At present, the film-forming resins that can be used as the diffusion coating of LED light are water-based alkyd resin, water-based polyacrylic resin, water-based polyurethane resin, etc. [1]. These three types of resins can be formed separately or in combination in a certain ratio to avoid performance defects when a certain type of resin is used alone. The performance differences of the three types of water-soluble film-forming resins are separately described below.
1.1 Waterborne alkyd resin - the first developed film former
Waterborne alkyd resin is an early development of waterborne coatings. Its film formation mechanism is similar to that of traditional solvent-based alkyd resins. It is formed by oxidative crosslinking of unsaturated fatty acids to form a film without adding a cosolvent (filming aid). Sexual organic matter. In addition, the water-based alkyd resin has good wettability to the light diffusing agent, strong bearing capacity, good permeability, leveling and fullness, easy coating, and good coating effect. However, the polymer chain is more easily hydrolyzed, the durability of the coating film is poor, and the ignition time is too long, and the color is slightly discolored. However, the resin is self-emulsified and modified by acrylic acid or polyurethane, and the durability is improved to be used for the light diffusion layer.
1.2 Water-based polyacrylic resin - the most ideal film former
The water-based acrylic resin includes three types of acrylic resin emulsion, aqueous acrylic resin dispersion and aqueous acrylic resin solution. The aqueous polyacrylic resin used as a water diffusion coating is one of the emulsions, and is usually classified into a pure acrylic emulsion, a styrene-acrylic emulsion, a vinegar-acrylic emulsion, a silicone-acrylic emulsion, and a tertiary vinegar (tert-carbonate-vinyl acetate) according to the monomer composition. Emulsion, tert-propyl (tert-carbonate-acrylate) emulsion, fluorocarbon emulsion, fluoropropene emulsion, and the like. Acrylic resin emulsion has high drying speed, high hardness, low cost, good weather resistance (flame point is not easy to change color), and it is used for LED light diffusion coating to avoid poor film formation, low gloss, solvent resistance and hot sticky And so on. Comprehensive performance and cost performance, water-based polyacrylic resin is currently the most ideal light diffusion coating film former.
1.3 Water-soluble polyurethane resin - the first choice for high-end coating
The water-based polyurethane coating utilizes water-based polyurethane resin and is configured with water as a medium. It has the advantages of low toxicity, non-flammability, environmental pollution, energy saving and safety, and has high coating hardness, strong adhesion and good flexibility. The one-component polyurethane coating polymer has a relatively large molecular weight, and does not undergo a crosslinking reaction during film formation, and is convenient to use. Two-component waterborne polyurethane coatings must be mixed before use, and cross-linking reaction occurs during film formation, and the coating performance is better. However, most of this resin is produced abroad, with high cost and unsatisfactory cost performance, and is only used for some high-end products.
2. Comparative analysis of light diffusing agents
2.1 Technical parameters of light diffusion coating
(1) Light transmittance - the ratio of the luminous flux passing through the tube coated with the light diffusing layer to the luminous flux passing through the glass tube through the non-light diffusing coating, expressed as a percentage. However, the straight tube lamp has the problem of thickness difference between the upper and lower layers in the process of manufacturing. Now many manufacturers use the comparison of the luminous flux before and after the light-diffusing layer of the glass tube measured under the same conditions in the integrating sphere.
(2) Haze - the ratio of the flux of transmitted light through the glass tube (from the direction of the incident light) to the flux of transmitted light, expressed as a percentage (this method uses a scattered light flux of more than 2.5° from the direction of the incident light for haze calculation) ), commonly used haze meter for measurement.
(3) Anti-aging time - the rate of light decay caused by the coating during the specific ignition time at the working temperature. It is usually expressed by the light decay rate of 1000h or 10000h.
Both light transmittance and haze are important indicators for measuring the transparency of LED lamps. The challenge of the light diffusing agent is to ensure high light transmittance while obtaining high haze, and to obtain a uniform and soft lighting effect. The key criterion for the excellent light diffusing agent is to minimize the resulting light decay during the process of efficiently performing light diffusion.
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