Cause analysis of the printing resistance of the m

Reason analysis of printing resistance of positive PS plate

PS plate has become the main plate used in lithography at present because of its simple operation, excellent printing performance, little influence by environmental temperature and humidity, high printing resistance, long storage time and other advantages. Compared with the negative PS version, the positive printing plate is welcomed by manufacturers because of its modern electronic design method, which uses VHDL language as the expression of design intent at the time of printing, CPLD as the hardware carrier, computer as the development tool, and EDA software as the development environment. At present, in China and Southeast Asia, the main plate used for offset printing is the positive PS version

this paper will discuss the main factors that affect the printing resistance of this printing plate in the process of manufacturing and use

before entering the formal discussion, first introduce the concept of printing resistance

the so-called printing resistance refers to the ability of the printing plate to resist pressure and friction. The "printing plate layout" mentioned in the concept should contain three meanings

1. Printing plate base part:

wear-resistant plate base is the basis for the discussion of lipophilicity and hydrophilicity of the layout. There is no applicable plate base, and the printing plate has no printing resistance

2. The graphic part of the printing plate (i.e. the hydrophilic layer):

the graphic part of the printing plate refers to that the ink can always be stably absorbed in the work, and there will be no stencils and falling plates

3. blank part of printing plate (i.e. hydrophilic layer):

printing resistant blank part refers to that in the work, it can always stably adsorb the fountain solution, and there will be no dirty and paste phenomenon

therefore, the printing resistance of printing depends not only on the mechanical strength of the plate base, but also on the adsorption fastness of the base of the graphic part and the base of the blank part to the plate base

the size of the printing plate's printing resistance has been determined at the beginning of the printing plate manufacturing, and it will have a great impact on its printing resistance in the process of use. The factors affecting the printing plate's printing resistance will be discussed in detail in two parts below

part I: influence of manufacturing process on printing resistance

the manufacturing process of printing plate is as follows:

material selection, electrolytic roughening, anodic oxidation, hydrophilic treatment, coating, photosensitive glue drying

the influence of each process on printing resistance is discussed in depth below

first, the influence of material selection

1. The selection of the composition of the plate base

the composition of the plate base determines the hardness of the plate base. In the process of lithography and printing, the hardness of the metal plate base is the material basis that determines the printing resistance of the printing plate

at present, the base of PS version is metal aluminum plate. Its aluminum content is 99%. In addition, 1% of iron and copper, magnesium, silicon and other metals. Generally speaking, the properties of alloys are much better than pure metals. From the aspects of hardness, tensile strength, metal crystal structure, corrosion resistance and so on, this project was listed in the Minhou technical transformation project last month, and the gold is better than pure metals. So when choosing plates, pay attention to the purity of metal plates. However, the content of impurities should not be too high, otherwise the plate base will become brittle and its original corrosion resistance will be reduced. Selecting aluminum plate with impurity content not more than 1% as the plate base will help to improve the wear resistance of the printing plate

2. Selection of plate base flatness

the flatness of plate base will directly affect the sand mesh structure formed after the layout, and the quality of sand mesh structure is an important factor affecting the printing resistance of printing plates. Good sand mesh can be obtained in a short time by treating the plate base with high flatness. Otherwise, the sand mesh structure is not only coarse, but also has the disadvantages of different size, inconsistent depth, uneven distribution and so on, which greatly weakens the printing plate's printing resistance. Generally speaking, to select its process by-products, a resource recovery and utilization system must be established, and the plate with a flatness of less than 5% is used as the plate base. (to be continued)