Printing quality includes the reproducibility and quality stability of the original. Print quality is the comprehensive effect of various appearance characteristics of printed matter, mainly divided into image quality and text quality. Image quality characteristic parameters can be divided into gradient and color reproduction, image resolution, moire and other fault patterns and surface characteristics. The definition of the best text quality is very clear, they must be free from the following physical defects: blocking ink, character damage, white spots, unclear edges, redundant ink marks, etc. This paper mainly from the printing quality related factors and printing quality parameters two aspects to explain. 1、 Factors related to the quality of printed matter in printing production, the factors that may affect the quality of printed matter can be classified into three main categories. They are aesthetic factors, technical factors and consistency factors. 1. Aesthetic factor because printed matter is visual product in the final analysis, so when people evaluate the quality of printed matter, the first feeling is the aesthetic effect of printed matter. The aesthetic effect of printed matter is mainly related to the design level of craftsmen. The font selection, color design, art pattern, image position and layout style are all related to the aesthetic effect of printed matter. Good design can make printed matter show good aesthetic characteristics, but it is difficult to describe the excellent degree of design with quantity. Sometimes, "good" design does not conform to the rules of typesetting, color combination and image synthesis. Some people think that the design is not good, it may be appropriate to use on the cover of some commemorative album, but it is not appropriate to use it in the advertisement of high-grade cosmetics. It can be seen that the aesthetic factors of print quality are actually the embodiment of designers' imagination and creativity. An excellent designer should be familiar with the aesthetic design criteria, and should be aware of the technical constraints existing in the printing materials, ink and printing technology, so as to make the printed matter produce excellent aesthetic effect. 2. Technical factors the technical characteristics of print quality include image clarity, color and gradient reproduction, glossiness and texture. Among these characteristic factors, some can be expressed by quantity, such as color and tone reproduction. These factors can be controlled in various processes of the replication process; some technical factors can not be expressed in quantity, but can be described by language. For example, in order to obtain the best printing quality, it is necessary to reduce the possibility of Moire to the minimum, which is the form of language description; and some changes according to different uses. For example, glossiness property, in order to improve the legibility of printed text, low gloss paper is needed, but high gloss paper is needed to achieve the best contrast in the reproduction of photographic originals. ① Color and tone reproduction. The degree of tone and color reproduction refers to the consistency between the color appearance and tone balance of the screen and the original. For black-and-white photos and black-and-white copies, density value is usually used to express the degree of tone reproduction; for color copies, hue, saturation and lightness are more practical, which can be measured by colorimeter. Because the reproduction quality of black and white tone is limited by the maximum density of black ink that can be transferred to the paper, the reproduction quality of tone in three primary color reproduction is limited by the comprehensive density of yellow, magenta, cyan and black. Therefore, it is impossible for a printed copy to have the same density range as the original. For example, the density range of black-and-white original is 0 – 2.00, however, the maximum density printed on coated paper is rarely more than 1.50. Therefore, to achieve high-quality reproduction, some method should be used to balance. Color gamut (basically saturation) is limited by ink, paper, printing color sequence and ink overprint quality. For example, the color gamut of non coated paper is smaller than that of coated paper. At the same time, the use of additional printing ink can expand the color gamut and improve the quality of tone reproduction.At the same time, the change of dot size, ink layer thickness, and ink overprint fastness on the printing machine will lead to the change of tone and color reproduction quality. The change of field density is related to each of the above factors. The data show that: even if the offset press is in a stable state, there will be a density change of 0.02; the difference in the structure of the ink transfer device will make the density change as high as 0.12 between the mouth and the tip. Because the printing press can not always be in a stable state of operation, coupled with the changes in the chemical and physical properties of raw materials, environmental conditions and the impact of the mechanical movement and structural characteristics of the press, changes in the quality of printed matter are inevitable. Only by measuring the image with instrument and controlling the spot density, dot enlargement, background color removal, gray balance and dot transfer, can the change be as small as possible. Therefore, what we mean by the best reproduction is that within the limits of various constraints and capabilities of the printing equipment, we can synthesize the subject matter and various requirements of the original to produce the printed matter that most people regard as high-quality. It is generally believed that tone reproduction is the most important aspect of color reproduction quality. Although there is no quality standard for the best hue and saturation, people have realized that how to match the saturation is the key problem in color reproduction, and a lot of research has been done on the issue of optimal saturation reproduction. In order to keep the saturation of all colors in balance, some people think that it is better to compress all kinds of colors in an equal amount; some people, in order to emphasize a particular color, adopt the method of strengthening another color separation on the basis of losing one part of the color. ② Image resolution. Image resolution includes resolution and definition. In monochrome printing, the resolution is mainly determined by the number of screen lines and limited by the thickness of ink layer. In a certain range, the thinner ink layer can obtain higher resolution, otherwise, the resolution is lower. The results show that: in offset printing, the smallest detail that can be distinguished is about 8pm. From a practical point of view, human eyes can distinguish the number of network cables up to 2501pi. In color printing, image resolution is also affected by the accuracy of overprint between different colors. The actual printing results show that: for the printing press in good working condition, the error between each other is not more than 0.075m when conveying all single sheets of paper; the registration change between ink colors depends on the design of printing operation, and the random change is about 0.05mm. In practice, to obtain satisfactory printing effect, the registration error of all ink colors should be kept within 0.1 mm. Sharpness refers to the contrast on the edge of the tone, that is, the contrast between the combination of darker and brighter tones. Image definition is mainly affected by the thickness of ink layer. The thicker the ink layer, the higher the definition. Because it is difficult to strike a balance between various types of printed matter, it is still difficult to determine the optimal definition. For example, enhancing the image clarity will make the printed matter of fabric or machinery produce better effect, but it will also make the scenery or portrait photos look inconsistent with the actual situation.③ Spots and fault patterns. The spots and faults in the quality of printed matter refer to moire, bar, particle size, water marks, spots and other fault graphics. The results show that the fewer spots and fault patterns, the better the reproduction effect. ④ Surface characteristics. The surface characteristics of printing quality mainly include gloss, texture and smoothness. The glossiness of printed matter is related to the gloss of substrate, ink absorption and the thickness of printing ink layer. The requirements for glossiness vary with the nature of the original and the end use of the printed image. Generally speaking, high gloss paper and glossy ink should be used when copying photo originals, because the high gloss will reduce the light scattering on the surface of the printed matter, thus enhancing the color saturation; when copying watercolor or pencil drawings, non coated paper or matte coated paper should be used, because the original texture of this paper will make the printed matter produce a copy effect closer to the original. Flatness refers to the concave convex degree of paper surface caused by factors such as blistering and fuzzing. The results show that the better the smoothness, the better the printing effect. 3. How to make the images of all products have ideal appearance is an important aspect to evaluate the quality of printed products. Consistency factor mainly refers to: within the scope of the best reproduction, how much variation can be allowed between the printing sheets? This paper mainly explains from the following points: first, the visual resolution. For example, in the standard observation distance, when the number of screen lines is 150 lines / inch, the maximum allowable value of registration change is 0.05mm. Beyond this range, changes in the image can be observed visually. Second, the inherent characteristics of production equipment will produce uncontrollable image variation. For example, the existing ink delivery mechanism of offset printing or embossing machine can not guarantee the same density from front to back, and the density variation on the same sheet can reach 0.15. Third, the allowable limit of deviation. This needs to be determined according to the product type and customer requirements. For example, newspaper printing can have a large color change, while cosmetics or food packaging products are not allowed to have large color difference.
Dongguan Beite packaging materials Co., Ltd. - located in Dongguan City, the world's manufacturing city, is a subsidiary of Beite packaging (China) Co., Ltd., with a plant area of 6000 square meters. It is a flexible packaging enterprise integrating R & D, production and sales. It has a complete set of domestic advanced production equipment, a scientific and humanized management system and a group of experienced technical personnel For backing, to provide customers with quality products and first-class service.
The company produces composite bags, roll film, fruit bags, aluminum foil bags, suction mouth bags, self-supporting bags, zipper bags, anti-static bags, special-shaped bags, etc., which are suitable for the internal and external packaging of food, daily chemicals, electronics, toys, medicine, cosmetics, industrial products and other industries.
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