In order to ensure the three-dimensional effect of three-dimensional printing, when considering the material of the grating, it is also necessary to select the grating with different parameters in combination with the image effect. 1. The material of the grating The material of the grating should have high transparency, high refractive index, good gloss, strong plasticity, stability and other properties. The materials used for making toys and food packaging also require non-toxic and harmless. At present, three kinds of grating plates made of polystyrene (PET), polypropylene (PP) and polyvinyl chloride (PVC) are mainly used in the market. ①Polystyrene resin (PET) Polystyrene (PET) is used to make hard plastic gratings and can be printed directly with ordinary ink. The polystyrene raw material is processed by injection molding to form a concave-convex cylindrical mirror grating. Polystyrene is colorless and transparent (transparency is 88% -92%), refractive index is 1.59-1.6, non-ductile and flammable. Because of such a high refractive index, it has good gloss. Its tensile strength is 3.52-6.33MPa, its bending strength is 6.12-9.84MPa, and its thermal deformation temperature is 70-98 ° C. The chemical properties of polystyrene are resistant to certain mineral oils, organic acids, alkalis, salts, lower alcohols and their aqueous solutions. It is softened after being eroded by hydrocarbons, ketones, higher fatty esters, etc. It is soluble in aromatic hydrocarbons and toluene, ethylbenzene and styrene monomers. In some cases, the degree of erosion of polystyrene by chemical reagents can be reduced by annealing, stress relief and other measures. Polystyrene has good stability, high picture quality, non-toxic raw materials, and high chemical resistance, but it is more difficult to bond and process. Mostly used in toys, fine advertising, etc. ② Polypropylene (PP) Polypropylene is softer than polystyrene and harder than polyvinyl chloride. The stability is high, but the image quality is average. The raw materials are non-toxic, low chemical resistance, easy to bond processing, mostly used in packaging, stationery, etc. Polyvinyl chloride (PVC) is used to make soft plastic cylindrical lens grating. A hot oil press is required to press and shape the picture and the PVC film base through a metal grating drum or grating plate. Polyvinyl chloride has low stability and rough picture quality. In addition, because the PVC grating is toxic and not environmentally friendly, it is generally not used in toys and food packaging products in European and American countries. 2. Choose the grating material according to the final effect of the picture According to the principle of stereo vision, if we can allow our left and right eyes to see two images taken at different positions, the brain can synthesize the two images and feel a three-dimensional space. Different images can be seen from different angles by using the split-image effect of the grating plate, so if we place the grating perpendicular to the two eyes, the two eyes will see two different angles due to the different viewing angles of the grating on the two eyes The image, resulting in a three-dimensional sense. In order to obtain a better stereoscopic effect, it is usually not made with two images, but with a sequence of stereoscopic images to construct. In such a case, according to the different observation positions, as long as you see two pairs in this sequence at the same time Image, you can feel the three-dimensional effect. Stereo gratings require delicate images and sharp changes, so the viewing angle range is smaller, so that the visual effect is real and the stereoscopic effect is strong. The variable grating places the grating flat between the two eyes. Note that the line angles of the two eyes to the grating must be parallel, so the two eyes see the same image. If the image is composed of a series of continuous animations, then when the eyes are up and down When you move or flip the grating up and down, the angle between the eyes and the grating will change, and we will also see successive images one after another, that is, see the effect of a change. The variable grating requires a larger viewing angle range, so that the image conversion range is larger, and there is less crossover between different images, and the image conversion can be clearly felt. According to the analysis, it can be known that this type of grating requires a smaller ratio of thickness to pitch, so that a larger viewing angle range can be obtained. 3. Method for precise measurement of grating pitch The grating pitch is generally matched precisely by using a series of grating test strips with a nominal pitch. There are many types of grating pitch test strips. Different software vendors use different test strips, but the basic principles are basically similar. It is to use the split-image characteristics of the grating plate and load different grating pitch parameters to create a series of black and white patterns, so that when the grating plate is in accordance with the nominal grating pitch, it will show a specific angle when viewed at a certain angle. pattern. Before the 1990s, paper products, packaging, printing adhesives, varnishes, and laminating adhesives were mostly formulated with solvent-based polymer as the base material. Due to the large amount of organic solvents used as the diluent in the base material, with the application of the products, the organic solvents will eventually evaporate and pollute the air, wasting resources, and the organic solvents are mostly flammable and explosive substances, which poses serious fire hazards. After the 1990s, with the continuous strengthening of foreign environmental regulations, western industrialized countries have continuously developed water-based adhesives and water-based varnishes for packaging and printing that use water instead of organic solvents. The products developed by American National Starch Chemical Co., Ltd., Fuller Chemicals, Aksu Nobel, Henkel Chemicals, etc., due to their excellent performance and moderate price, are an environmentally friendly and environmentally friendly water-based material. Favored by the market. According to the literature, the output of these water-based products has been increasing from 20% to 30% annually from 1991 to 2005. In 2005, 1.5 million tons of products were produced, accounting for 15% of the global annual output of water-based adhesives and water-based varnishes for packaging and printing. Domestic packaging and printing water-based adhesives and water-based varnishes started late. Five years before and after the beginning of this century, although a few manufacturers introduced water-based products to the market, most of them have low technical content and poor application performance, compared with foreign products. There is still a big gap. The technical route of some manufacturers' products is generally achieved by blending and blending some domestic non-specialized latex with other general water-soluble polymers, or based on starch modification, and adding a small amount of non-specialized latex. Multiple performance defects, it is difficult to meet the development needs of the printing industry. In recent years, some water-based latexes have been prepared by synthetic means, but the technology is outdated, the technical starting point is not high, and the products lack market competitiveness. Therefore, among the middle and high products, foreign products still occupy 70% of the domestic market share. Since the beginning of this century, the application of water-based adhesives and water-based varnishes for packaging and printing is in the ascending development stage. This is because water-based products are not only in line with international trends, but also in line with China ’s current sustainable development policies. In 2005, the total output value of the domestic packaging and printing industry was about 300 billion yuan, and the consumption of adhesives (including adhesives, varnishes and laminating adhesives) was about 4.5 million tons. In the Pearl River Delta region, each accounted for about two-fifths of the market share, and other domestic regions accounted for about one-fifth of the market share. The market demand ratio of water-based adhesives to water-based varnishes and water-based laminating adhesives (including aluminum-plated film transfer adhesives) is about 2.5: 0.5: 1. That is, the market demand for water-based adhesives is about 2.8 million tons, water-based varnish is about 560,000 tons, and water-based film adhesive is about 1.1 million tons. You may like,High Quality You may like,You may like Details, CN WENZHOU HAGO HOUSEHOLD GOODS CO., LTD. , https://www.wzhago.com
Polypropylene (PP) can be printed directly with ordinary ink, but the surface should be treated with sparks, and the ink dries faster than polystyrene.
â‘¢ Polyvinyl chloride (PVC)
Polyvinyl chloride is a polymer compound formed by polymerizing chlorinated olefins and is difficult to burn. Although polyvinyl chloride and polyethylene are both milky white, polyvinyl chloride can be made into a colorless, transparent and shiny film, and can produce various softness films according to the content of plasticizer. The fastness of this material after pulse heat sealing and high frequency heat sealing is also large. The chemical properties of PVC have good chemical resistance, but poor thermal stability and light resistance. Hydrogen chloride begins to decompose at 140 ° C, and stabilizers need to be added during manufacturing. Polyvinyl chloride has a chlorine content of 56% -58%. Low molecular weight is easily soluble in ketones, esters and chlorinated hydrocarbon solvents; high molecular weight is difficult to dissolve.
If the stereoscopic grating is used to produce the aberration effect, it often leads to incomplete extinction; while the stereoscopic grating is used to produce the stereoscopic effect, the stereoscopic effect will not be strong. Therefore, the appropriate grating plate should be selected according to the desired performance.
As shown in Figure 1, it is composed of a series of black and white stripes. When testing, a grating is pressed against the grating test strip. When one of them can be observed at a certain angle, it shows a completely white pattern. When an all-black pattern can be displayed when viewed from an angle, the grid pitch value under the test strip is the actual grid pitch of the grating plate.