Optical properties and standards of the most popul

2022-09-23
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Optical properties and standards of publishing and printing paper

in recent years, China's paper industry has developed rapidly. The total output and consumption of paper and paperboard have ranked second in the world, and a complete standardization system has been formed. Among them, the national standardization method, measurement method and product quality method are the three basic creep testing machine methods that must be followed in the production and sales of paper products

China's paper industry standards include national standards, light industry standards and enterprise standards. In terms of application fields, there are product standards, product performance test method standards and product test environmental atmospheric conditions standards. At the same time, there are also paper quality supervision and inspection, special measuring instruments for paper making, and metrological verification regulations of the Ministry of light industry. According to the standardization system table of China's paper industry, publishing and printing paper is divided into two categories: uncoated paper and coated paper. The paper used in large quantities in the publishing and printing industry, such as paper, offset printing paper, offset books and periodicals paper, relief printing paper, etc., belongs to uncoated printing paper; Coated printing paper, such as coated paper, low weight coated paper, cast coated paper, etc. Optical properties of paper from the optical principle of the test basis, whiteness, chromaticity, opacity and so on belong to the diffuse reflection characteristics of paper, while glossiness and printing glossiness belong to the specular reflection characteristics of paper. This paper mainly introduces the optical properties of publishing and printing paper, such as whiteness, chromaticity, opacity and their test standards

optical properties

1, whiteness

as we all know, white paper can truly and objectively reflect all the colors of printed pictures and texts, improve the contrast and clarity of words, and make reproductions colorful, achieving the effect of both pictures and texts. The higher the whiteness of the paper, the more significant this effect is. However, the whiteness should not be too high, otherwise the reflected light is strong, the stimulation to the visual nerve is too strong, and it is easy to cause visual fatigue. Therefore, the higher the whiteness of printing paper is, the better. Moreover, the whiteness values of printing paper for different purposes are also different. It is reported that the development of new materials industry in China has also become a major way to implement the supply side structural reform. China children's publishing house, from the perspective of protecting children's vision, Many textbooks use low whiteness paper, and some books even use bean green and light yellow writing paper. Heilongjiang children's Publishing House has also reduced the whiteness of teaching auxiliary books to 76% - 85%. The Ministry of education stipulates that the whiteness of textbook paper for children is 75% - 76%

although the paper used for publishing and printing is basically white or near white, there are color biases, some blue and some red, in order to make the visual judgment appear whiter, but it also varies from person to person. In any case, the paper supplied in the same batch should have the same whiteness, uniform hue and no obvious color difference, so as to avoid the delamination of the cut tone of the bound printed matter

2. Opacity

the opacity value of printing paper directly affects the through printing condition of prints. Printing paper for various purposes must have sufficient opacity, otherwise it is easy to cause through printing failure

3, glossiness

the glossiness of printed matter is closely related to the specular reflection characteristics of paper. The printing gloss of paper refers to the field printing with standard bright ink on the paper sample under the condition of, and the gloss of the imprinted area is measured with 1 straight line after drying, which is expressed as a percentage. Generally, the gloss of paper is high, while that of printed matter is high. The graphic and graphic levels of printed matter are bright and colorful. For example, the glossiness of coated paper and printing should be at least 60% and 88%

optical performance standards for all kinds of paper

1. Paper

international gb/t divides paper products into excellent products, first-class products and qualified products

a) brightness. Brightness is also called whiteness, and the whiteness value of the three grades of products specified in the standard is not less than 52%, 50% and 48% respectively

b) hue energy test value. It is stipulated that l* ≥ 80.0, a* = - 2.0 ~ +2.0 and b* <10.0 are used as the basis for each factory to control the hue of the three grades of products

c) color difference △ e*. Color difference of the same batch of paper △ e*. Superior products and first-class products shall be no more than 2.5 and 3.0 respectively, and there is no requirement for qualified products

d) opacity value. The opacity value of the three grades of 45g/m2 paper is 86.0%; 47g/m2 paper, 88.0% for superior products, 86.0% for first-class products and qualified products; ≥ 49g/m2 paper, 90.0% for superior products, 87.0% for first-class products and qualified products

in addition, the material supply and Celebration Committee of China Newspaper Association formulated the "domestic paper (user) quality standard" in June 2002 with reference to gb/t1910-1999 and the paper delivery standards of relevant paper manufacturers. Among them, the technical index calibration related to optical performance is set at 45g/m2 and 48.8g/m2, the whiteness of paper is ≥ 56.0%, and the opacity is ≥ 90.0%

2. Coated paper

national standard gb/t stipulates that coated paper is divided into a, B-I, b-II, C, etc, Except that the whiteness value of grade C is 80.0%, the other three grades are 85.0%. The opacity value varies according to different quantities, 70 ~ 90g/m2 is not less than 85.0%, 90 ~ 130g/m2 is not less than 90.0%, and the paper greater than 130g/m2 is not less than 95.0%. The opacity value of products with the same quantity and different grades is the same. There are no specific international requirements for the chromaticity value of coated paper, but the color of the same batch of paper should not be significantly different

3. offset printing paper

the publishing and printing industry calls offset printing paper double offset paper, which is popularly known in commerce as forest paper. It is specially used for multicolor offset printing. The light industry standard qb/t divides dishes into three grades: A, B and C. The specified whiteness value is not less than 87.0%, 82.0% and 77.0% respectively, and the opacity varies with different quantities. The opacity value of offset paper of 60g/m2, 79 g/m2, 80 g/m2, 90 g/m2, 100 g/m2, 120 g/m2 and 150g/m2 stipulates that grade A is 84.0%, 86.0%, 87.0%, 89.0%, 91.0%, 93.0% and 95.0% respectively, and grade B and C are correspondingly lower than Grade A. There are no specific requirements for chromaticity, only that the color of each batch of paper should be consistent, and there should be no obvious difference

4. Offset book paper

light industry standard qb/t stipulates that offset book paper is divided into three grades: A, B and C, and the whiteness value is a:70.0% - 75.0%, B: ≥ 60.0%, C: ≥ 55.0%. The opacity value of three grades of products stipulates that 52g/m2 is not less than 78.0%, 60g/m2 is not less than 80.0%; 70g/m2 paper, grade a not less than 82.0%, grade B and C not less than 80.0%. The color should be consistent, and there should be no significant difference between each batch of paper

5. Low weight coated paper

also known as lightweight coated paper, LWC paper. At present, there is no unified national standard or industry standard, and the finished product inspection is generally carried out according to the enterprise standard or contract standard. In view of the fact that this kind of paper is suitable for color printing and has low freight, which greatly reduces the printing cost, it has been widely used in the world. Shandong Huatai, Quanlin, Chenming, Luohe Yinge, Yueyang paper, Guangzhou Zao paper and other paper-making enterprises produce light coated paper, which not only meets domestic demand, but also has some exports. It is reported that the new national standard for coated printing paper that is being developed will make corresponding provisions and specifications for the deterioration of material properties caused by the performance indicators of low weight coated paper

among the relevant standards for optical performance test methods of publishing and printing paper: the national standards gb/t7973 "pulp, paper and board Determination of diffuse reflectance factor (diffuse/vertical method)", gbt7974 "paper and board whiteness determination method (diffuse/vertical method)", gb/t7975 "paper and board color determination method (diffuse/vertical method)" and gb/t8940.1 "paper and board whiteness determination method (45/0 directional reflection method)" have been promulgated and implemented for more than 10 years. The promulgation and implementation of these methods and standards are of great significance to unify the testing operation of paper performance, improve the testing technology of paper optical performance, popularize the basic knowledge of colorimetry theory, and guide production. These standards are applicable to the optical performance test of publishing and printing paper related to diffuse reflection factors

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