(III) Method for Making Screen Printing Plates
Photopolymer coating method is usually used. Photosensitive adhesive coating plate-making is the direct coating on the screen, drying, printing plate, development and other processes, made of film, the specific production process shown in Figure 4.
1, making positive negatives
Positive printing negatives are required for screen printing. There are two ways to make positive negatives: one is manual rendering and the other is photographic printing.
(1) Hand-drawing method Use a writing brush, pen, etc. to draw a picture on a transparent film or tracing paper. This is a positive image negative film. In order to prevent the ink on the negative film from cracking after drying, a small amount of sugar may be added to the ink, and a small amount of beer may be added for defoaming. The hand-drawing method is mainly used to produce positive negatives with low requirements and relatively simple pictures and drawings. If you need to make negative positive film, you should adopt a photo-taking method.
(2) The photographic method uses a photographic device to take the original as a negative image, and then turns the negative image into a positive negative. If it is a manuscript with shades of change, it is necessary to make a picture with a net added, and then turn it into a net-yang picture. If it is a color manuscript, you need to make a color separation picture first, and then flip the color negative positive picture.
2. Pretreatment of wire mesh
Screen pretreatment mainly includes degreasing and dyeing.
(1) The degreasing treatment screen has grease and dirt, which will reduce the combined fastness of the plate and the screen and affect the quality of the plate. Degreasing treatment is required for this purpose. The following three kinds of commonly used degreasing treatment:
1 Degreasing of the decontamination powder Wet the screen first, then place it on a flat surface. Use a brush to pick up the dirt. Scrub on the screen, wash it off with clean water, dry naturally or at low temperatures.
2 solvent degreasing Use cotton cloth to soak up acetone, alcohol, banana water and other solvents, scrub on the screen, and dry it for later use.
3 Dilute alkali solution skimming with 10% sodium hydroxide solution, then rinse with water, dry naturally or at low temperature. Metal mesh frame should not use this method.
(2) Dyeing treatment The purpose of the dyeing treatment is to absorb the light shining on the screen to eliminate the diffuse reflection of the light during the printing, thereby improving the clarity of the plate-making graphic. The method of dyeing is to coat the dyeing liquid evenly on the screen with a brush, and after drying, the photosensitive adhesive can be coated. Staining solution is made by adding cresol or red alcohol soluble dye in ethanol solution. If it is a colored wire mesh, there is no need for dyeing.
3, the deployment and coating of photosensitive adhesive
(1) Preparation of Photosensitive Adhesives Photosensitive adhesives are generally classified into solvent-resistant and water-resistant types. Solvent-resistant photosensitive adhesive, suitable for printing water-based ink. The former screen can be stripped and recycled; the latter can not be stripped and recovered. Dedicated water resistance photosensitive adhesives include nylon and diazo photosensitive adhesives. The user must select the appropriate photosensitive adhesive with reference to the relevant manual according to the specific conditions of the steel drum.
Here are some formulations of photosensitive adhesives:
1 polyvinyl alcohol emulsion
Formula one: S silk adhesive 100g, 8% ammonium dichromate solution 25g. S-silk gel is produced by Kanto Chemical Co., Ltd., Japan.
The preparation method is as follows: 10g of ammonium dichromate is dissolved in 100g of water, and then mixed with S-silk glue in proportion, and the mixture is evenly mixed. Just adjust the good emulsion can not be used immediately, generally need to place 8h in cold and dark place. This is because a lot of bubbles in the photosensitive adhesive just adjusted will produce pinholes on the screen, and the photographic performance of the just-imparted photosensitive adhesive is still poor.
Recipe II: Meinung 100# Wire Mesh or 200# Mesh Glue 100g, 4% Dichromium Ammonium 20g. Meinung 100# and 200# silk screen adhesives are manufactured by Japan Fuji Pharmaceutical Company. 100# is a thick film type and 200# is a solvent resistant type.
The preparation method is the same as Formula One.
Formula 3: 32# EZ wire mesh adhesive 100g, 10% ammonium dichromate solution 20g. 32#EZ silk screen adhesive is produced by the United States Na Zdar. The preparation method is the same as Formula One.
2 gelatin emulsion
Formula: 180 g of gelatin, 10 g of citric acid, 20 mL of alcohol, 1000 mL of water, 30 g of potassium citrate, 10 g of ammonium dichromate, 10 g of strontium sulfate, and 55 mL of ammonia water.
The preparation method is as follows: the above substances are dissolved and filtered by heating, and the glue is easy to freeze, so it is kept at a relatively high temperature (for example, 70° C.) and is applied behind the screen in a dark room.
3 nylon photosensitive adhesive
Formulation 1: three-way nylon 200g, methylenebisacrylamide 50g, benzoin ether 2g, diethanolamine 0.4mL, benzophenone 5g, ethanol 1000mL, active K blue dye 2g, phthalic anhydride 0.8mL.
The preparation method is as follows: dissolve ternary nylon with 750 mL of ethanol; dissolve other additives with 250 mL of ethanol; dissolve with water bath and continue stirring; until the above two liquids are fully dissolved and mixed, dissolve the active K blue dye with a small amount of hot water, add The mixture was stirred thoroughly and filtered until use.
Formula two: three yuan nylon 100g, methylene diacrylamide ammonium 30 ~ 40g, benzophenone 6 ~ 7g, active K blue dye 1g, ethanol 400 ~ 500mL.
Formula 3: three yuan nylon 100g, ammonium dichromate 20 ~ 40g, ethanol 400 ~ 500mL. The three-way nylon is dissolved in ethanol; ammonium dichromate is dissolved in a small amount of hot water, and the above two solutions are mixed, stirred well, and filtered for use.
The easiest way is to purchase sensitized plastic from the market. For example, the high-strength nylon sensitizer made by Shanghai Zhonghua Printing Co., Ltd. is made of multi-nylon as a film former and is made of auxiliary materials such as cross-linking agent and sensitizer. The following features:
a. Resistant to water, acid and alkali, resistant to organic solvents, resistant to solvents such as toluene, xylene, cyclohexanone, acetophenone, ethyl acetate, banana water, gasoline, and flame oil.
b. Photo-sensitive latitude, high resolution, minimum line width up to 0.025mm, and can be made cable version.
c. Can make thick film screen printing plate, the coating film can be up to 0.20mm.
d. Easy to operate, nylon emulsion is a single liquid type, can be bright room operation (can be operated under fluorescent lamp, but do not operate under sunlight); printing plate light source is ultraviolet (printing under sunlight), developing With industrial ethanol, it can be cleaned with a brush.
e. High print rate, up to 100,000 prints.
f. A prefabricated plate can be made. After the glue is ready, the screen plate is stored and used for printing.
g. glue storage period is long, protected from light and room temperature, valid for up to 2 years.
h. Suitable for a variety of screen printing plate making.
Its disadvantage is that it cannot be removed from the net and it cannot be used repeatedly. If the screen can be used repeatedly, you can buy Italian A38 (oily) emulsion or Dutch-made Autosal Plus II emulsion. Use it for plate making. If the pattern is not ideal, it can be removed with a release powder and re-plated until it is satisfactory. Its coating thickness is easy to grasp, and its photosensitivity is large; resolution, printability, and graphic clarity are all better than domestic ones.
(2) Photosensitive adhesive coating A variety of coating methods for photosensitive adhesives are available, including stainless steel bath coating, brush coating, cast coating, plastic film coating, and machine coating. Among them, stainless steel tank coating method is more commonly used. When coating, the film surface must be free of spots, uniform in thickness, and glossy after drying. The coating thickness is generally 10-30 μm. If the coating layer is too thin, the edge of the printed image is likely to produce a rough jagged shape; if the coating layer is too thick, the amount of ink permeation will be affected.
Stainless steel tank coating operation is as follows:
a. Pour the photoresist into the stainless steel tank to half the tank capacity.
b. Place the screen plate at an angle of 70°.
c. The stainless steel tank is in contact with the lower end of the screen, and while the tank is tilted out of the photoresist, slowly lift the tank up and apply it along the screen surface. It should be noted that the coating should be slow, otherwise it will produce bubbles.
d. Turn the screen frame upside down and apply it again as described above.
e. Use 32-36°C hot air to dry the membrane.
f. Follow the above steps and apply 2~4 times until the film surface is shiny.
4, drying
In the coating process, although the photosensitive film has been dried, further drying is required before the printing. Hot air drying is generally used. The drying temperature is suitable at about 35°C, and it is not allowed to exceed 40°C. Do not allow the dust to fall on the film surface when it is dry, otherwise pinholes, etc. will occur. After drying, print as soon as possible to ensure plate quality.
5, printing version
First, use a soft-bristled brush to clean the screen-printing film, printing plate glass, and positive-working film. Then put the positive film and stretched wire mesh frame into the printing box. Look through the glass plate to see the positive film on the film. Position in the frame, and place it in the correct position, and finally expose it.
In order to make positive negatives fit tightly on the photosensitive film of the screen, it is best to use a cassette with a vacuum device. It can use arc lights, fluorescent lamps, high pressure mercury lamps, xenon lamps, incandescent lamps, and daylight. The exposure time varies greatly depending on the type of photoresist, the thickness of the photosensitive film, the type of light source, the distance between the light source and the screen, and the specific exposure time is best determined by test methods. The specific operation is as follows: In the parts that need to be mapped, the light blocking plate is first covered, exposed to 1000W/220V high-pressure mercury lamp for 5 minutes, and then the positive film is covered on the screen and exposed for 10-20 minutes. During the exposure process, the frame is about 30cm away from the high-pressure mercury lamp and is cooled by a fan (eg, it can be cooled without a fan using a cold light source).
6, development
The immersed printing plate is immersed in water for 1~2min. After the unexposed part is swollen, it is rinsed with water. The photosensitive film with good solvent resistance should be developed with warm water (35°C) for 1~2min and then rinsed with warm water of about 42°C. Nylon photosensitive films need to be soaked in ethanol or brush developed. The development time of the printing plate should be as short as possible.
7, then dry
Drain the plate first, then use a sponge to dry the water at the corners of the plate, and finally dry it with hot air or dry naturally. If hot air drying is used, the temperature of hot air should not exceed 40°C. Otherwise, the printed text will be out of shape, otherwise the screen will be loose.
8, repair and release film
(1) After the revised plate is dried, it is generally necessary to perform minor trimming such as plugging of pinholes in the plate. Clogging the pinhole can be coated with photosensitive resin, and then exposed to light for 5 minutes.
(2) When the plate is removed from the plate, or when the old plate needs to be replaced, the plate on the screen may be removed. The screen after removing the film can continue to be used,
Method of removing the printing film: first remove the residual ink from the screen printing plate, then wipe the two sides of the screen printing plate with the plate removing agent or stripping powder, or soak it in the removing plate printing agent. After 5 to 10 minutes, the printing film is made White, then rinse with water (or scrub with sponge). After removing the plate, dry the screen. The release film includes hydrogen peroxide, hypochlorous acid solution, sodium hydroxide solution, ammonia, and lactic acid.
Photosensitive adhesive coating plate making method has high quality, good effect, economical and practical, so this plate making method is the most important plate making method in modern screen printing. Other plate making methods include manual engraving plate making method, non-photosensitive adhesive coating method, carbon Plain paper making method, photosensitive film making method, infrared plate making method, and electronic plate making method.
1. Correct selection of teeth
1) Before use, confirm whether the mechanical properties of the product meet the customer's requirements (such as the tensile strength of the Bolt and the safe load of the nut).
2) The length of the bolt should be selected properly, with 1-2 pitch exposed after tightening.
3) Before use, the thread should be kept clean.
2. How to use dental strips correctly
1) When tightening the teeth, pay attention to that the direction of force applied by the wrench should coincide with the axis of the screw, and do not tilt.
2) In the process of tightening, the force should not exceed the safety torque, and should be uniform. Try to use the torque wrench or socket.
3) Locking too fast will lead to locking, it is recommended not to use electric or pneumatic wrench.
4) Keep the thread clean. In order to ensure the smooth fit of screw and nut, it is recommended to put the product in a clean container and do not place it at will.
3. Standard of tooth bar maintenance
1) If there is slight damage to the removed tooth, screw and nut, the die and tap shall be used for repair.
2) The removed and repaired teeth, Screws and Nuts shall be maintained by means of oil bubble or lubricating oil, and shall be placed in order according to specifications, models and purposes.
4. Scrap standard
The bolts with obvious crack, broken thread, sliding, disorderly thread, screw tensile deformation, shear trace, etc. which can not be repaired by the on-site leader can be scrapped.
5. Specification parameters of tooth strips
Texture of material:
304/316
Product standard:
DIN975
Surface treatment:
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