Screen printing plate making is the basis of screen printing, so we are familiar with the materials used in the plate making process, such as the selection of screens, frames, and photosensitive materials, and the production, stretching, coating, and drying of the plate during the plate making process. The requirements of the edition, development, light source, etc. are very necessary.
1. Screen type
Screen is the skeleton of the production of screen, is the substrate supporting the photosensitive adhesive. Understanding the characteristics of the screen, according to the printing requirements, choosing the right screen is the primary issue for creating high quality products. The screens commonly used for screen printing include silk screens, nylon (nylon) screens, polyester (polyester) screens, and stainless steel screens. The commonly used types of screens are nylon and polyester, and metal screens are generally used only under certain conditions. Silk screens have basically been eliminated, so only nylon and polyester screens are introduced below.
(1) Nylon wire mesh Nylon wire mesh is a monofilament woven product that is heat-treated and dimensionally stable after weaving. Plain weave can reach 380 mesh, and twill weave is more than 380 mesh.
Nylon silk screen has the following characteristics: smooth surface, small static electricity, good ink permeability, can use large viscosity and large particles of ink, so it is suitable for printing bright and beautiful products and get fine printing patterns; use very fine mesh weaving Details network, suitable for very thin lines of painting patterns and dot printing; flexibility, with appropriate flexibility, good adaptability for substrates, suitable for printing convex and concave surfaces; tensile strength, knot fastness, elasticity and Good anti-friction property, long service life, good acid resistance, wear resistance, chemical resistance and organic solvent, easy to recycle, especially strong resistance to alkali.
The use of nylon mesh should pay attention to the following points: As the nylon mesh elongation, in order to not cause printing failure, to use a strong mesh frame and stretch machine to increase the stretching tension; not acid, susceptible to stone carbonic acid, cresol Erosion of formic acid, etc.; ultraviolet rays affect it, and care should be taken to avoid light during storage.
(2) Polyester silk screen Polyester silk screen has the following characteristics: small stretch, strong barrier, single wire screen is suitable for printing high-precision printed matter such as integrated circuit, thick film semiconductor, scale board, etc.; tensile strength, structural strength, Resilience and resistance to printing force are good; with sufficient resistance to chemicals, acid resistance and resistance to organic solvents, renewable like nylon; low heat absorption, heat resistance higher than nylon, less affected by ultraviolet light than nylon .
The following points should be taken into account when using: Polyester screens have good dimensional stability and are suitable for high-precision printing. Therefore, they can exert a greater stretch tension than nylon meshes, and require a stronger frame and stretcher and are more reliable. The bonding method; polyester because of its hydrophobicity, it is difficult to bond with the plate, it is necessary to pay attention to the plate before washing, degreasing; over ink is slightly worse than nylon; not resistant to alkali erosion.
2. Screen Printing Requirements for Screen Properties
Screen printing platemaking and printing processes have the following basic requirements for screen performance:
1 Tensile strength Large tensile strength refers to the ability of a wire mesh to resist damage when it is pulled. With high degree of stretching, the screen is resistant to stretching and can make high tension screens.
2 Elongation at break Elongation is the ratio of elongation to original length when the wire mesh breaks under a certain tension, expressed as a percentage. Elongation is large and dimensional stability is poor, but screen printing also requires the screen to have sufficient elasticity under a certain tension. So the elongation cannot be zero, but it is better to be small.
3 Rebound Elasticity Resilience is the ability to recover the length when the screen is stretched to a certain length and release the external force. The greater the recovery ability, the better, and the clearness of the print.
4 The stability of moisture resistance and temperature change is good. The screen with high softening point can meet the requirements of screen printing with hot printing materials; the moisture absorption rate is small, and the quality of platemaking can be stabilized.
5 The passing performance of the ink is good. The surface smoothness of the wire is good, which will help the ink to reach the printing surface through the screen.
6 Good Resistance to Chemicals Screening During the plate making and printing process, acids, bases, and organic solvents are encountered. Therefore, they should have sufficient resistance.
3. Wire mesh selection
(1) Selecting the screen according to the substrate In screen printing, there are various types of substrates, and the substrates also have their own characteristics. Usually when selecting the screen, it can be selected according to the material of the substrate. Nylon screens can be used when the substrates are clothes, scarves, ties, schoolbags, etc.; thick nylon screens can be used when the substrates are postcards, wallpapers, calendars, etc.; when the substrates are glassware, metal containers, wood In the case of plastic products, single-filament nylon mesh, thin polyester mesh, and stainless steel mesh may be used; when substrates are integrated circuits, semiconductor components, electrical components, etc., polyester mesh and stainless steel mesh may be used.
(2) The following problems should be paid attention to when choosing a screen:
1 Weaving evenly: The uneven weaving will cause the change of the aperture and affect the transfer amount of the printing ink, and the thickness of the ink film layer will be different;
2 The thickness of the wire is uniform: if the thickness of the wire is uneven, a part of the web becomes thicker or thinner, and the thickness of the ink will be uneven when printing.
3Difficulty of the ink passing through the screen: High-transparency inks in the intermediate tones, finer pigment particles, and better ink passability. The ink can also be passed through using a high-mesh screen; plastic ink passes through it is good;
4 Roughness of Substrate Surface: When the surface of the substrate is rough, due to its strong ink absorption, a screen with a lower mesh number is generally used. Such as leather, canvas, etc.;
5 Select the screen according to the fineness of the original text line: In general, fine line originals should be selected with a high mesh number;
6 The number of screen meshes is compatible with the number of screen lines: the ratio of the number of meshes to the number of screen lines is approximately 4 is better.
