The gloss of the paper is determined by the smoothness of the surface of the paper, which is related to the type of fiber, the degree of beating and calendering, the content ratio of fillers and rubber compounds, and the sizing method. The main factors that affect the gloss of printed matter are the surface smoothness, ink absorption and gloss of the paper. 1. The surface smoothness of the paper The surface smoothness of the paper, which means the time required to pass a certain amount of air in the gap between the paper and the glass under a certain pressure under a certain area of ​​paper, in seconds (S) as the unit of calculation . The surface smoothness of various papers is different. Ordinary paper with a smoothness below 80S is a low-smoothness paper, above 80S is a medium-smoothness paper, and 300-600S is a high-smoothness paper, such as coated paper with a smoothness of 800S, and the paper surface gap is about 2.5μm. The smoothness of domestic 150g / m2 special-grade double-sided coated paper is 500S, and the smoothness of coated paper of the same weight abroad is more than 1000S. The domestically produced 150g / m2 high-quality art coated paper with a smoothness of 1000 ～ 1500S is the paper that reaches the highest standard of smoothness in China. The smoothness of the paper is actually expressed as the size of the gap on the surface of the paper. Therefore, the smoothness has a great influence on the gloss of the finished product. The paper with high smoothness has good contact with the ink, which can ensure the complete reproduction of the dots and make the finished product have better gloss. After the ink is transferred to the paper surface. The surface flatness of the ink film formed on the paper is also relatively high. After being irradiated with light, a certain "specular reflection" is formed, which shows a certain brightness. On the contrary, the paper with poor smoothness, rough surface, and uneven ink film can only form diffuse reflection to the light, and the finished product lacks gloss. 2. Ink absorption of paper The ink absorption of paper refers to the absorption performance of paper to the ink binder. The rougher the paper, the larger the fiber gap and the stronger the absorption ability of the binder. The ink absorption of different types of paper is different. The ink absorption of the paper is too large. When the ink layer is dried on the paper surface, after the ink binder is absorbed in large amounts, particles such as pigments float on the imprinted surface and form diffuse reflection, so they cannot produce gloss. The ink absorption of the paper is too small, and the penetration of the linking material is small, which can obtain printed products with bright colors and high gloss, but at the same time, it is easy to produce slow drying, easy sticking, crystallization and other undesirable phenomena. For coated paper (coated paper), there are two main reasons that affect ink absorption: the first is the variety and amount of adhesive used in the coating. The lower the ratio of adhesive to pigment, the paper absorbs ink The higher the concentration of the coating is, the adhesive and water in the coating can easily penetrate into the thick paper, reducing the amount of adhesive in the coating, thereby increasing the absorption of ink. Second, the variety of pigments and the fineness of particles in the coating are also related to the absorption of ink. The lower the particle size of the pigment, the less easily the rubber in the coating is transferred to the paper base: the thicker the pigment particles, the larger the gap between The greater the absorbency of the ink, the worse the gloss effect of the printed matter. The determination of paper ink absorption is to use a graduated ink absorption tube, apply a quantitative amount of test ink on the test sample, and after a specified time, quickly wipe off the remaining ink on the paper with cotton or a clean soft cloth. In this way, the depth of the ink varies with the strength of the paper absorption, and then use the reflectometer to measure the ink on the paper. Low reflectivity and strong absorption; otherwise, weak. Usually expressed as a percentage A. 3. The gloss of the paper The quality of the gloss of the paper itself also determines the size of the gloss of the printed matter. The gloss of the coated paper surface mainly depends on the glossing materials used in papermaking and the processing accuracy of the paper. Brightening materials include aluminum stearate and paraffin. The finishing method is super calendering. The paper processed by the above method has a smooth surface. The combined effect of the glossiness and ink absorption of the paper is expressed as the surface efficiency of the paper. Specifically, the surface efficiency of the paper can be expressed by the average value of glossiness and ink absorption. which is: Among them: A is the ink absorption of paper, C is the gloss of the paper. The surface efficiency of the paper can be calculated by the above formula. As shown in the table. Different papers have different surface efficiencies. The coated paper is larger than the offset paper, and the imported coated paper is a big dry domestic coated paper. The absorption of coated paper is smaller, in order to allow the blot to dry on the paper surface by the way of oxidative conjunctiva, to avoid the large amount of joining material infiltrating into the paper, and the adverse consequences such as poor gloss, powdering and unbearable blotting. Use highly absorbent paper, increase the amount of ink when printing, and increase the pressure to increase the density value, so it is easy to cause tonal compression, gradation and gradation. The four-color machine is slightly more absorbent than the paper printed by the single-color machine, because the wet press wet printing hopes that the ink penetration can be slightly faster, which is helpful to improve the viscosity of the ink layer on the paper (especially the ink color printed first), so that the post-printing Overprint rate increased. Generally speaking, in order to get a bright and colorful picture, it is necessary to use paper with high surface efficiency.
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Surface efficiency: [(100-A)] + G / 2