Screen printing plate making

First, the characteristics of screen printing 1. Printing for a wide range of screen printing plate soft and flexible, the printing pressure is very small, so the substrate is not subject to the restrictions of the area and shape, both in the plane printing, but also in the Printed on curved surface; can be printed on film, paper and on hard plastic sheet, hard plastic product, metal, wood, glass, fabric; size can be arbitrary; can be directly printed or transfer printing.
2. The printing ink layer is thick, and the image has strong three-dimensional effect. Compared with other printing methods, the printing ink layer has the thickest thickness of 30-100 μm. The thickness of the lithographic ink layer is only 5 μm, the embossing is about 10 μm, and the gravure is 12-15 μm. Thick ink layer, strong three-dimensional image, colorful, strong light resistance, strong hiding power, so you can color printing on a variety of materials. For this purpose, it is also used for the printing of printed circuit boards.
3. Screen printing investment is less, faster, and quicker.

Second, the screen printing plate making method 1. The carve plate making method has two kinds of manual engraving method and computer engraving method, suitable for printing lines, patterns, text, color blocks and a simple type of print.
(1) Manual engraving method. Apply a layer of paraffin on the original, lay a piece of clear paint paper (or film) on it, and carefully dig along the contour of the graphic to remove the paint paper inside the graphic. Then, the carved film paper (or film) is affixed to the frame, and it is hot-pressed at about 100° C., and then the original (ink draft) is peeled off. The printing plate is completed. Each color is printed separately.
(2) computer engraving method. It is currently a more advanced screen printing method. The manuscript image is input through an overscan device, and is edited by a computer (information processing). Finally, a computer-controlled automatic film cutting machine performs film cutting on the film (film film). The film cutting device consists of a scanner, a microcomputer, a printer, a plotter (a film cutting machine), and the like.
2. The photolithography method utilizes the cause of the photocuring effect of the photosensitive resin upon irradiation with light. After developing and rinsing, the non-photosensitive resin is removed, and an ink blocking portion and an ink penetrating portion are formed on the screen to make a plate. There are three types: direct, indirect, and hybrid.
(1) Direct method. The process flow is as follows:
Stretching → Washing → Drying → Applying photosensitive resin → Drying → Printing → Developing (flushing) → Drying → Correcting → Printing
Positive picture negative 1 frame. There are two kinds of wood and metal, metal mesh frame is mainly aluminum alloy frame, light weight, high strength, water resistance, solvent resistance, deformation and other advantages, widely used in manual printing and mechanical printing. The size of the frame should be selected based on the print area and taking into account the distance the squeegee travels.
2 wire mesh. Materials include stencil nets, nylon nets, polyester nets, and stainless steel wire mesh. The net is made of raw silk, which has strong water resistance, certain moisture absorption, good adhesion to the photosensitive resin, elasticity, easy to stretch the net, and easy operation. The disadvantages are that the wear resistance, chemical resistance, and weather resistance are all relatively poor, easy to age, brittle, and costly. Nylon mesh is woven from nylon yarn, and its characteristics are smooth surface, good ink performance, good heat resistance, good dimensional stability, high tensile strength, good abrasion resistance, chemical resistance, elasticity, and long service life. . The disadvantage is that after a long time of tension, the tension will relax, affecting the quality of the plate printing. Polyester line network is characterized by high strength, good elasticity, high stretching tension, good dimensional stability and high temperature resistance, water resistance, chemical resistance, and can be used for high-precision printing. The disadvantage is that the abrasion resistance and overinking are inferior to nylon mesh. Stainless steel wire mesh is characterized by high strength, good abrasion resistance, almost no stretching, and can print high-precision products; good over ink property, good mechanical properties, chemical resistance, and high temperature resistance. Disadvantages are poor elasticity, can not be bent, can not be restored after elongation, the price is high.
The mesh size of the screen is 80-150 mesh/cm (200-400 mesh/in). The following factors should be taken into consideration when selecting the mesh size: A. The thick text pattern can be 80 meshes/cm, and fine text patterns can be used with meshes of 100 mesh/cm or more. B. For the thickness of printed ink, the higher the mesh size, the smaller the mesh, the less the amount of ink, and the thinner the ink.
3 photosensitive adhesive and photosensitive film. Early emulsions were formulated with dichromate and gelatin. Recently, gelatin has been replaced by polyvinyl alcohol, and dichromate has also been replaced by a double emulsion. Photosensitive film, also known as film, is a transparent polyester film for the film base, coated with a layer of screen sensitive adhesive layer. The adhesive layer consists of a film-forming resin, a binder, a plasticizer, a sensitizer, and the like. The screen film is a pink or blue translucent film. The ability of pink to absorb ultraviolet light is weaker than blue, and for this reason, the exposure time should be appropriately increased. There are 1, 2, 3, and 4 photosensitive films, and the thickness of No. 1 photosensitive film is 0.01-0.014mm, which is mainly used for screen printing of fine products; the thickness of No. 2 photosensitive film is 0.018-0.022mm, used to make lines. Screen printing with a width of 0.02mm; Photosensitive film No. 3 with a thickness of 0.035-0.040mm for screen printing with a line width of 0.25mm; Photosensitive film No. 4 with a thickness of 0.05-0.06mm for the production of printed circuit boards Wire mesh.
4 Sealing slurry and stripping agent. Sealing paste is specially used to block empty mesh material. It has the same characteristics as screen printing film. The film stripping agent is specially used for stripping the solvent of the screen printing plate photosensitive film and the sealing paste, and the screen after stripping the film can be reused. The requirement of film stripping agent is not to harm the screen, it is easy to use, harmless to the human body and does not pollute the environment.
(2) Indirect method. The process flow is as follows:
Film film→printing→activation treatment→development
↑ │
Positive Photo Films│
│
↓
Stretching → Screening → Drying → Transferring film film → Drying
For printing ← peeling film base ← closure net ← ┘
Film film used in indirect method is made of transparent plastic film base diazo photosensitive adhesive. The film was first printed, activated by hydrogen peroxide soaking, developed and rinsed, and then transferred to a screen that had been pretreated. The photosensitive film layer of the film is attached to the screen (base upwards), and it should be firm and secure, with no bubbles in the middle. After drying, the screen around the photosensitive film is screened with a sealing paste, and the plastic film base can be printed after drying.
(3) mixing method. The process flow is as follows:
Printing plate
Stretching → screen treatment → drying → paste film → coating emulsion → drying → remove film base → │ → development rinse → drying → correction → for printing
Positive plate film, the film will be flat on the platform, the adhesive layer up, with a stretch net flat on the film, and then poured into the photosensitive adhesive, with a pressure coating blade, blow dry, from the reverse side Go to the plastic film base, and then print, rinse, dry and correct for printing.
The positive film negative film production process is as follows:
Color Originals → Photographic Screening or Electronic Color Screening → Imposition → Copy Positives
Text, line ink draft → photo negative film
The formulas for various chemicals for silk screen making are as follows:
(1) Polyvinyl alcohol photosensitive resin adhesive formulation formula 1: A solution: polyvinyl alcohol 8.3%
Industrial ethanol 8.5%
83.2% of water
Solution B: ammonium dichromate 1%
Water 99%
Method of preparation: The PVA is heated and dissolved in water in a water bath to form a slurry, which is cooled and then added to industrial ethanol. When the liquid B is used, it is added to the A liquid under stirring, and the mixture can be evenly stirred.
Formulation 2: PVA (saponification degree 88%, average degree of polymerization 1400) 10 parts of vinyl acetate latex (solid content 50%) 30 parts of water 50 parts of ammonium dichromate (10% aqueous solution) 10 parts (2) gelatin-based photosensitive resin formulation Formula one: gelatin 180g
Citric acid 10g
Ethanol 20mL
Water 1000mL
Potassium red 30g
Ammonium dichromate 10g
Barium Sulfate 10g
Ammonia 55mL
Preparation method: The above substances were heated and dissolved and filtered, kept at 70° C., and coated on the back of the screen plate in a dark room.
Recipe II: Water 74%
13.3% gelatin
Barium sulphate 4.5%
Citric acid 0.4%
Red quinone potassium 3.5%
Ammonium dichromate 11%
Ammonia (25%) 3.3%
Preparation method: Soak gelatin for 2-3 hours, dissolve in water bath at about 70°C, and cool to 60°C. The 120-mesh sieved barium sulphate is added with citric acid and potassium citrate, stirred well, then added in hot gelatin maintained at about 60°C, and finally filtered into a plastic coating box and homogenized, and maintained at 60-65°C for use. Suitable for spring applications.
(3) Nylon sensitized plastic formula three yuan nylon 200g
Methylene bisacrylamide 50g
Benzoin Ether 2g
Benzophenone 5g
Ethanol 1000mL
Active K Blue dye 2g
Diethanolamine 0.4mL
Phthalic anhydride 0.8mL
Preparation method: Dissolve three-way nylon with 700 mL of ethanol; Dissolve other additives with 250 mL of ethanol. When dissolved, heat with water bath and continue stirring. Mix until the above two solutions are fully dissolved. Use a small amount of hot water to dissolve the active K blue dye into the mixture, stir and filter it.
(4) wax gram paper production formula formula one: translucent nitro soft varnish 200mL
Nitro color paint (blue green) 40mL
Castor oil 4mL
Banana water amount formula two: transparent nitrocellulose varnish 200mL
Alkaline green 4mL
Castor oil 5-10mL
Banana water amount (5) paint film engraving plate paint formula nitro lacquer 32%
Waste film solution (made up of 20% waste film + 80% acetone) 8%
Castor oil 5%
Ethyl acetate 55%
Blue Dye Trace (6) Wire Mesh Tension Photosensitive Resin Adhesive Formula Epoxy Phenolic Methacrylate 300mL
Benzoyl Butyl Ether 11g
Anhydrous 150mL
(7) Washing solution (except oil) formula NaOH 20g
Water 80mL