Silk screen printing technology and key printing s

2022-08-07
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Label silk screen printing technology and printing key points standard

plays a decisive role in the label production process, which is the process technology, printing key points and the selection of screen printing ink for the pretreatment of screen printing plate and substrate

I. silk printing plate making:

1. Paint film carving method:

is a kind of manual plate making method, which is relatively simple. It can print monochrome patterns and words that are not usually exquisite

(1) spray engraving paint film paper: paste the tracing paper on the flat wood plate with paste, adjust 1 part of rubber water (volume ratio) and 1 part of gasoline with a pencil, and evenly paint it on the paper. After drying, spray the soft varnish for 35 times to improve the development level of the new material industry. After each spraying, dry it in the oven at 40 ~50 degrees, and spray the paint film thickness to 5~6 mm. The paint film should be bright, uniform, free of bubbles and stains

(2) carving graphics: stick the paint film paper on the graphics, carve according to the graphics with a carving knife, compass knife and ruler, and gently remove the paint film

(3) transfer: after carving the figure, you can transfer it on the previously made silk frame. The method is to put the carved paint film under the frame and press it tightly, and gently re wipe it with cotton dipped with a little thinner until the paint film is firmly adhered to the silk. After drying for several minutes, remove the tracing paper. If the paper is not all gone, wipe it with cotton. The blank part is coated with nitrocellulose paint to block the silk eye. It can be printed after drying

2. Carbon paper plate printing method:

is also a relatively simple manual plate making method

(1) cut photosensitive paper: photosensitive paper is a kind of carbon paper made by coating oxygen barium base paper with a thick mixture, which is cut according to the size of the figure for standby

(2) sensitization: soak in the solution prepared by 500 milliliters and 20 grams of ammonium dichromate for minutes, take out the carbon paper and drain the water

(3) exposure: stick the carbon paper flat on the clean glass, with the adhesive film upward, cover the positive polyester film bottom plate on the top, and expose it with a plate printer for minutes

(4) development: after exposure, immerse in 40~50 ℃ warm water for several minutes to naturally separate the adhesive film and positive plate from the zinc oxide base paper, and carefully develop with warm water until the force shape text is clear

(5) transfer: put the prepared version under the frame with the silk stretched in advance, cover several layers of newspapers on the silk, press the glass plate with the weight of kg/cm2, at this time, the adhesive film is firmly attached to the silk, remove the weight and the newspaper, dry the adhesive film with an electric stove, and then remove the base paper, and the adhesive film figure is transferred to the silk. Carefully check whether the graphics have defects. After the graphics are qualified, apply a layer of nitro enamel on the wires around the graphics for protection, and install the silk screen printing plate on the printing plate table for printing. The application scope of this plate making method is the same as that of the paint film carving method

3. Photosensitive plate making method: the plate printing accuracy used for silk screen signs is required to be high. Generally, advanced direct, indirect and direct photosensitive plate making methods are used

a. direct plate making method:

(1) aluminum frame is used for the post frame, which does not need to be stretched flexibly. The air pressure is kg/cm2, acetal adhesive is used, and the tension degree is measured by tension. The tension is kg, and the sinking size should be less than 2mm

(2) cleaning silk: use washing powder, detergent, ethanol, etc. as detergent, clean both sides of silk, rinse with clean water, and dry with hot air before use. The purpose is to better bond with the photosensitive adhesive

(3) scraper (coating bucket and applicator): the scraper for coating photosensitive adhesive can be made of stainless steel or plexiglass plate. Its length is generally slightly less than the inner diameter of the wire frame (several scrapers with different lengths are configured into a set for standby) B. The edge of the scraper must be thin without edge, smooth and straight, without concave convex, burr, scar and other defects, so as to affect the plate making quality. When coating the silk photosensitive adhesive, dry it every three times, and then expose it until the adhesive film reaches the required thickness

(4) the temperature of the drying oven. It is ideal to use the drying oven with adjustable temperature. The drying temperature of photosensitive adhesive is generally controlled at about 40 ℃. Too long baking time or too high temperature will affect the quality of photosensitive layer

(5) safety light: orange, yellow or red light is generally used as the safety light for the lighting source of the studio, but from the visual point of view, the orange light source is more comfortable. Its brightness should be able to clearly see all objects

(6) inspection of the base plate: before printing, the base plate must be carefully inspected, including whether the dust, base plate blackness, broken lines, sand hole defects and other items on the plate and the positive and negative of the image text meet the requirements

b. indirect preparation method:

(1) preparation of frame and photosensitive film: clean the stretched frame (for nylon wire) with 10% sodium phosphate aqueous solution to remove oil stains

line sensitive film film is a kind of photosensitive adhesive with polyvinyl alcohol adhesive as the main body. The film is Apply gelatin as the main photosensitive agent on the 06mm transparent plastic film base. Before use, connect the size of the figure with a width of 20mm on each side. Wipe the powder dirt on the film with a cloth

(2) exposure: press the film film and the bottom plate in the plate printer, and expose them with a carbon lamp or xenon lamp. The distance between the frame and the light source is cm, and the exposure time is minutes

(3) development: after exposure, place the phenanthrene film on the flat plate, soak the film with warm water for minutes, spray with water nozzle, and dissolve the non photosensitive part (graphic part) with water after printing and development until the graphic is clear

(4) pasting film film: paste the exposed film surface on the silk, gently scrape and paste the back of the human film with a rubber plate or other straight plate to make the film contact firmly, immediately put it in the oven and bake it for minutes at a temperature of 552 degrees. After drying, fix the frame on the plate bench for trial printing

(6) film removal method: in the process of exposure and development, if the plate is found to be unqualified, immediately brush off the adhesive film with warm water to make it again. If the plate has been dried or the film is removed after production for a period of time, one part of industrial sodium hypochlorite and one part of water can be used for soaking for minutes. Or there is 5% sodium hydroxide solution heating treatment version, which can remove the adhesive film

c. direct plate making method:

direct plate making method is a mixed plate making method of direct method and indirect method. The difference between indirect method and indirect method is that the image is first made on the film film and then transferred to the silk, while the direct method is that the film is first transferred to the silk and then exposed to make the image

II. Pretreatment of printing materials:

the printing materials of signs mainly include aluminum, copper, stainless steel and aluminum, and the amount of plexiglass is the most. In addition, there are plastic, polyester, paper, etc

aluminum signs are widely used among the types of signs, which are characterized by beauty, brightness, high hardness, good wear resistance, wide application and large dosage. For machinery, electronics, instruments, meters, household appliances, daily hardware, clocks, daily cosmetics packaging, etc

there are many methods for pretreatment of aluminum substrate, mainly including oil removal, sand blasting, wire drawing, polishing and oxygen grease

1. Oil removal: to make 2 The surface of the aluminum base material on which the power line is installed has a certain inkiness. The oil layer and oil stain on the surface should be removed, and the cotton yarn can be dipped in gasoline for wiping. The alkaline solution can also be used for chemical oil removal, such as g/l sodium sulfate, g/l sodium phosphate and g/l sodium silicate. The oil can be removed by soaking in the temperature for minutes

2. Sandblasting: sandblasting is to improve the adhesion between ink and metal materials. Usually, a special sandblasting machine is used for spraying. If 0 Mm thick aluminum plate, sand diameter for sand blasting is 0 15mm, river sand can also be used after sieving

3. Wire drawing: also known as twisting, it is to process fine linear lines on the surface of aluminum plate by mechanical friction. It is a relatively new surface decorative treatment process, which can overcome the defects such as scratches on the aluminum surface. Improve the utilization rate of materials. There are two kinds of wire drawing: coarse wire and fine wire. Generally, stainless steel wire brush with a diameter of 0.1mm or cleaning cloth belt brush can be used, and nylon abrasive belt can also be used for processing

4. Polishing: to overcome the surface defects of aluminum based materials and improve the surface smoothness. Polishing includes mechanical polishing and chemical polishing. Mechanical polishing adopts cloth wheel polishing machine. Chemical polishing is mostly carried out in acid solution, such as sulfuric acid 15%, nitric acid 10%, temperature and time of minutes

5. Oxidation: there is residual polishing soap on the polished surface of the aluminum plate, which shall be wiped off with the plate yarn dipped in gasoline, then chemically degreased, and then immersed in nitric acid solution (nitric acid and water 1:1 ratio), which shall be taken out after 10 minutes, and then put into the oxidation tank for electrochemical oxidation. Oxidation solution formula: nitric acid g/ml, temperature ℃, time 30 minutes

the oxidized aluminum plate is fully washed and dried, and a layer of oxide layer with uniform pores is formed on the surface, i.e. oxide film. Dirt pollution should be avoided. The oxidized aluminum plate should be printed immediately. If it cannot be printed immediately, it should be wrapped with soft paper or directly placed on the air drying rack. The storage time should not exceed one week

the oxide layer on the surface of aluminum plate can adsorb dyes, water and other salts, so there is no need to touch the surface with hands or things with oil stains during silk screen printing. When the ink is printed on the oxide layer, the ink penetrates into the pores. The heating of the next process is to accelerate the penetration of the ink into the pores until all the surface pores covered by the ink are filled

the ink printed on the surface rarely diffuses or does not diffuse, which well ensures the accuracy and clarity of words and patterns

6. Sealing: its function is to firmly seal the ink in the pores and never overflow or spread. For the parts not covered by the ink, the sealing function is to fill the gap of the oxide film, make it impervious, and strengthen the corrosion resistance of the surface. Nickel sulfate solution is generally used for sealing. Formula: nickel hexanoate ml, temperature degrees, minutes. After sealing the hole, touch the surface with hands or other oily things, and wash it off with general detergent

III. silk screen printing ink (coating):

in today's metal signs or non-metal standard plate silk screen printing, there are many printing inks that can be used, but it is not easy to select the appropriate ink (coating). The commonly used inks for label screen printing are as follows:

1. Baking enamel:

is a single liquid formula, which is crosslinked when heated and has good storage performance. It can be stored for 6 months to one year. It has good finish, wear resistance, chemical resistance and weather resistance, so it is most commonly used. Alkyd, acrylic acid and polyester have these characteristics. Epoxy resin has the tendency of fracture and pulverization. It is generally not used outdoors, but it dries quickly and has good chemical corrosion resistance. Alkyd enamel is the most widely used because of its balanced physical properties, such as chemical and weather resistance, formability, hardness and gloss

2. Air dried enamel:

it is usually made of drunk acid. It can be cured with oxygen in the air through reaction. The performance of inebriated enamel depends on the type and quantity of oil used. The longer the oil dries, the longer the enamel dries. When the drying speed is taken as the condition, the experimental data will now be taken as part of bigmax. Paints with long drying time generally have good surface durability. These paints are mostly used for outdoor metal signs

3. Dissolving and volatilizing ink:

only rely on solvent volatilization to achieve drying. The final performance of the coating depends on the inherent material properties in the polymer before it is formulated into a liquid. These polymers contain thermoplastic acrylic acid. Silk printing inks, which are mainly volatile, are often damaged by dissolution. There are some propylene insoluble in gasoline and alcohol

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