In the label production process, the decisive role is the screen printing plate and substrate pretreatment process technology and printing points and screen printing ink selection.
First, screen printing plate:
1, the film carving method:
It's a handmade plate making method. It's simpler. It can print generally not very exquisite monochrome patterns and characters.
(1) Spray engraving coated paper: stick the tracing paper with paste on the flat board, adjust the rubber water part (volume ratio) and the gasoline part with a row pen, spray the soft varnish on the paper evenly, spray it 3-5 times after drying. After each spraying, dry it in the oven with 40-50 degrees, and spray the film thickness to 5-6 mm. The paint film should be bright. Uniform, no bubbles, no stains.
(2) Carving graphics: paste the paint film paper on the graphics, carve with carving knife, compass knife, ruler according to the graphics, gently remove the paint film.
(3) post paste: after carving the graphics, it can be posted on the silk screen frame. The method is to press the carved film under the mesh frame and rub it gently with cotton dipped with a little thin material until the film is firmly adhered to the mesh. After drying for a few minutes, remove the tracing paper. If the paper is not fully removed, wipe it off with cotton. The blank part is coated with nitrocellulose lacquer, and the mesh of the screen is blocked. After drying, it can be printed.
2, carbon paper printing process:
It is also a relatively simple manual plate making method.
(1) Photosensitive paper: Photosensitive paper is a kind of carbon paper made of a mixture of thicker coated with barium oxygenate base paper. It is cut to reserve according to the size of the pattern.
(2) sensitization: soak for 3-5 minutes in a solution of 500 millimetres and 20 grams of ammonium dichromate, remove the carbon paper and drain the water.
(3) Exposure: Carbon paper flat pasted on clean glass, film upward, on the top of the cover positive polyester film substrate, exposure with a plate machine, exposure time 8-12 minutes.
(4) Development: After exposure, soak in 40-50 degree warm water for several minutes, so that the film and positive plate and zinc oxide base paper naturally separate, with warm water carefully developed until the force text is clear.
(5) Transfer paste: Put the finished plate under the wire mesh frame, cover several layers of newspaper on the wire mesh, press the glass plate, and press it with a weight of 1-2 kg/square centimeter. At this time, the adhesive film is firmly attached to the screen, remove the weight and newspaper, dry the adhesive film with an electric oven, and then remove the base paper. The adhesive film pattern is transferred to the wire mesh. Carefully inspect the drawings to see if they are defective. After passing, coat the silk screen around the drawings with a layer of nitro-magnetic paint to protect them. Place the screen printing plate on the printing table for printing. This plate making method has the same application scope as the film carving method.
3. Photosensitive plate-making method: Silk-screen marking plate used by the higher precision requirements, generally using advanced direct, indirect, straight three kinds of photosensitive plate-making method.
A, direct plate making:
(1) Aluminum frame is used for the post frame, and the air pressure is 5-6 kg/square centimeter. The tension is measured by tension. The tension is 5-7 kg and the sinking size should be less than 2 mm.
(2) Screen cleaning: use detergent powder, detergent, ethanol and other detergents, clean both sides of the screen, and wash with clean water, after drying by hot air to be used. The purpose is to make the mesh better adhesive with photosensitive adhesive.
(3) scraper (coating bucket, coating device): the scraper coated with photosensitive adhesive can be made of stainless steel, but also can be made of plexiglass board scraper. The length is usually slightly smaller than the inner diameter of the screen frame (matching several scrapers with different lengths) to B. The edge of the scraper must be thin but not edged, smooth and straight, not allowed to have convex, burr, scars and other defects, in order to affect the quality of plate making. When coating screen photosensitive adhesive, drying every three times, need to be done 3-4 times continuously until the film reaches the desired thickness, and then exposure.
(4) the temperature of the drying box is ideal for drying boxes with adjustable temperatures. The drying temperature of the photosensitive adhesive is generally controlled at about 40 degrees. If the baking time is too long or the temperature is too high, the quality of the photosensitive layer will be affected.
(5) Safety lighting: the lighting source of the studio, generally using orange, yellow or red light as safety lighting, but from the visual point of view, orange light source more comfortable. Its brightness should be able to clearly see all objects.
(6) Inspection of the plate: Before printing, the plate must be carefully checked, including the dust on the plate, the blackness of the plate, line breakage, sand hole defects and other items and whether the positive and negative images and characters meet the requirements.

B, indirect method:
(1) Prepare the mesh frame and photosensitive film: the stretched mesh frame (nylon wire with 220-260 purposes) with 10% sodium phosphate solution cleaning, remove oil stains.
Film film is a kind of photosensitive adhesive with polyenol glue as the main body. Film film is the main photosensitive agent of gelatin coated on 0.12-0.06mm transparent plastic sheet. The size of the front pattern is used, each side is 20 mm wide, and the powder dirt on the film is wiped clean with cloth.
(2) exposure: press the film and the base plate in the printer and expose it with carbon or xenon lamp. The distance between the net frame and the light source is 50-60 cm, and the exposure time is 2-6 minutes.
(3) Development: After exposure, the film is placed on a flat plate, soaked in warm water for 1-2 minutes, sprayed with a water sprinkler, dissolve the non-photosensitive part (graphical part) of the film, after development, until the graphics are clear.
(4) Film film: the exposed film is pasted on the silk screen, the back of the film is scraped with rubber or other straight plates, so that the film and the screen contact firmly, immediately placed in the oven, baked at a temperature of 55 + 2 degrees for 8-12 minutes, after drying, the screen frame fixed on the printing table for trial printing.
(5) film removal method: in the exposure, development process, found that the plate is not up to standard, immediately with warm water can be brushed off the film to re-create. If the plate has been dried or produced for a period of time after the film removal, you can use industrial sodium hypochlorite and water each one, soak for 10-20 minutes. A 5% sodium hydroxide solution can be used to heat the screen to remove the adhesive film.