How to screen print the logo?

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Preparing for screen printing is the first and most important step in the process of screen printing. If the screen is not selected properly, you can't make a good printing effect. Screen printing workers must choose the correct screen printing system and equipment in order to reproduce the true color of the manuscript. Screen printing is widely used to meet different quality requirements. Modern screen printing system can produce all kinds of drawings, but it must be selected properly. Even the best screen printing system will not succeed if it cannot be used and operated correctly. This paper introduces most modern screen materials and how to use them correctly.

1. Screen requirements: No matter what materials are printed, you must confirm the screen requirements before selecting the screen. These requirements include:

(1) resistant to ink and other chemical materials.

(2) Resistance to mechanical action

(3) Edge resolution

(4) Bridging property of silk screen

(5) Resolution

Raw materials and production technology determine the quality of screen products, and in the application process, the best printing quality depends on the operation method and exposure and development equipment.

2. Chemical resistance: Chemical resistance is the basis for being able to use different inks and cleaning chemicals. According to the screen printing system and its own chemistry, each system has certain chemical resistance, and the chemical resistance of different products is different, which can be determined according to the chemical composition of the products. Screen printing system is based on the requirements of ink.

3. Mechanical property: By selecting suitable raw materials, the hardness and elasticity of the materials can be balanced, and the mechanical resistance of the screen can be achieved. The factors affecting mechanical resistance are: screen tension and mechanical strength. The mechanical strength may include the number of printing times. To achieve the maximum tension, correct operation is needed.

4. Edge sharpness: high-quality photosensitive paste particles are small and smooth. The poor quality screen graphics have uneven edges, and the reasons why the edges cannot be clearly displayed are: overexposure or underexposure. Poor edge resolution will affect the penetration and resolution of ink on the screen, and the image cannot be displayed completely. Edge sharpness can be observed with a microscope of 50X60.

5. photosensitive material bridging: the screen system bridged by photosensitive material makes a straight line; However, the lines printed by photosensitive materials with poor bridging performance are curved or jagged. The bridging property of photosensitive materials can be checked with a magnifying glass of 50 times or 60 times. The best effect is that the thread passes through the silk thread at a certain small angle. In printing, any deviation from the original can be found in the bridge of photosensitive materials. Too thin screen, underexposure and overexposure are all related to the bridging property of photosensitive materials.

6. Resolution: Good resolution means that the screen can accurately display the thin lines of the manuscript, so it requires high screen material. The resolution of screen is affected by screen thickness (including screen), screen color, exposure lamp quality, unexposed and overexposed. Similarly, the resolution is also affected by the particle size, edge sharpness and screen shape of photosensitive materials.

The above six requirements determine the printing quality. Different screen materials have their own advantages and disadvantages; Choose the right material, be sure to choose according to the requirements.

Screen printing system and features:

There are many ways to make printing screen. Up to now, there are still hand-carved templates or direct drawings on the sealing net. These methods can achieve certain results, but in industrial printing, modern screen printing system can achieve good results.

Early screen printing system: hand-carved template film colloid direct film

Direct/indirect (size+non-photosensitive film) diazo capillary film

Synthesis of direct film with dichromate sensitized slurry

Diazo sensitized slurry

Modern screen system: direct, direct/indirect photosensitive system of diazo photosensitive polymer paste

Diazo photosensitive polymer capillary membrane

Modern screen printing system has many advantages over the early screen printing system, and its notable features are good printing quality and less coating. The water resistance and solvent resistance of diazo photosensitive polymerization system are better than those of early screen printing system.

Diazonium system: Diazonium photosensitive adhesive appeared in 1950s, and has a great market. Chemical resistance and mechanical resistance are moderate, and the printing effect is good.

Characteristic diazo photosensitive system

Low, medium and high water resistance

Medium-high-low-high solvent resistance

Screen bridging is low-medium-high.

Low-medium-high resolution

The exposure time is slow-medium fast.

Exposure latitude high school

The average cost is low.

Suggested scope of fabric graphic printing, high-quality printing in all fields (including four-color printing)

Diazo photosensitive system: binary curing, that is, the combination of diazo photosensitive and UV curing resin. Its biggest advantage is excellent printing effect and chemical resistance, which is 5-8 times faster than ordinary diazo screen printing system and has higher solid content. The photosensitive paste with high solid content can reach a certain thickness with few coating times; Another advantage is that the exposure latitude is wide, the exposure time of fine lines does not need to be shortened when the screen is correctly exposed, and the diazo photosensitive system has good quality, excellent performance and reasonable price.

Screen:

Screen selection: according to different application requirements, screen selection is different, and the following points need to be considered when selecting a screen:

* screen tension should be greater than 15-20 N/cm.

* The thinner the screen, the better the resolution.

* Screen determines the ink quantity (the number of printing lines is greater than 300-500 microns).

* Maximum resolution: the width of silk thread is not less than the opening+the diameter of silk thread.

The development of modern technology can provide higher tension screen and finer screen, so the printing quality is better.

Screen preparation: When preparing screen materials, it is recommended to clean the screen first to reduce pinholes and fisheye during coating. New filters and reused filters should be degreased with degreaser. When using the straight membrane system, special screen grinding paste should be used to increase the binding force between the screen membrane and the screen; Direct photographic paste does not need grinding. After degreasing, wetting agent is used to increase the wettability of capillary film and screen, but direct photosensitive paste does not need this step.

Application technology of capillary membrane;

There are four basic methods of capillary film. Two for small frames and two for large frames.

Application method 1 (small screen frame):

* Cut the film into appropriate sizes.

* Place the film horizontally, with the photosensitive surface facing up.

* With the wet screen version, first contact a corner of the capillary membrane with the screen, and then gradually stick the membrane on the Internet, and the membrane will react when it meets water.

* Scrape off excess water with a scraper and dry the screen.

Application Method 2 (Small Screen Framework):

* Cut the film into appropriate size, and place the film horizontally with the photosensitive surface facing up.

* Put the film on a dry screen frame.

* Wet the screen with water, and the film will react when it meets water.

* Before drying the screen, use a scraper to scrape off the water.

Application method 3 (large mesh frame):

* Roll the film into a circular test tube with the photosensitive surface facing outward.

* Wet the screen with mild water and immediately dry the screen frame to prevent the water on the screen frame from flowing into the screen.

* Slowly unfold the curled film on the screen.

* Scrape off excess water with a scraper and thoroughly dry the screen.

Application method 4 (large mesh frame):

* This method is automatic printing rather than manual printing. The machine will wet the screen and open the curled film for cutting. Through the combination of machines and various technologies.

If the capillary membrane is applied correctly and the thickness is appropriate, high-quality screen can be made. If the film is too thin, there should be serrations and tooth edges. To avoid the above problems, we must follow the principles of film thickness and mesh number.

Application technology of direct photographic paste: direct film can make high-quality screens. The evaluation method is to test the thickness of the screen and the roughness of the screen and the substrate surface.

Coating: coating affects the coating effect. The amount of photosensitive paste applied each time depends on the design of the sizing machine. The thickness of photosensitive adhesive will vary by several microns, and uneven coating and pinholes are also related to the design of sizing machine.

* Sizer should be loaded with as much photosensitive pulp as possible.

* After each coating, the classifier should be cleaned.

* The scraping edge is round and blunt, with a diameter of 1.5-2 microns.

* The diameter of sharp edge scraping groove is less than 65438 0 micron.

* Scraping groove material is stainless steel or aluminum.

* Scraping groove is at least 5.0CM smaller than the mesh frame.

Wet-wet coating is a common method, which can be used in 90% printing fields. Fast and resistant to screen printing.

* Step 1: Wet coat the screen printing surface twice or more, and use a blunt scraper. Photosensitive paste needs to penetrate the surface of the scraper.

* Step 2: Apply at least 1 time on the surface of the scraper to make the photosensitive paste penetrate from the surface of the scraper to the printing surface.

* Dry the screen.

Dry and wet coating method can be used for screen with mesh number greater than 140 mesh/cm, and only a thin layer of photosensitive adhesive is needed.

If printed with UV ink, the mesh number is greater than 140tpc(355tpi). The opening area of the screen is small, and if wet-wet coating method is adopted, only a small part of photosensitive paste can penetrate. The thinner the screen, the more difficult it is for the photosensitive coating to penetrate. Dry-wet alternation technology can improve printing effect without increasing screen thickness.

* Step 1: Wet-wet coating method: coat the printed surface twice or more with a circular scraper, and the fine screen can reach 3-4 times.

* Step 2: Apply 1 time to the surface of the scraper, which can scrape off the excess photosensitive paste and scrape a part of the photosensitive paste onto the printing surface.

* Step 3: Dry the screen.

* Step 4: Apply 1 time on the printed surface with a thin edge scraper.

* Repeat steps 3 and 4 twice each.

Most wet and dry coating methods can achieve the effect of smoothing the screen. Each shoe coating can increase the screen thickness by 1-2 microns. If the photosensitive layer is allowed to be slightly higher, 1 time can be coated on the surface of the scraper, which can reduce the coating times of the front shoes. This technology is suitable for T-screen (33-35 microns). Because the S-screen is thinner, 2+2 wet-wet coating is enough; High-definition screens need more shoe painting.

Shoe brushing guide:

Provide the following screen guides with different mesh numbers. The direct photosensitive paste has medium viscosity (10000-16000 mpas/1000-1600 cps) and medium solid content (35-40%). Shoes with low solid content have more coating times, while shoes with high solid content have fewer coating times; High-density photosensitive paste painted shoes more times, low-density photosensitive paste painted shoes less times. Others such as leveling, different screen characteristics, etc. You can change coated shoes.

Screen wet-wet coating wet-dry coating

34tpc/86tpi 1+ 1 0

43-54 TPC/110-137 tpi2+1or 2+2 0.

61-78/156-197 2+2 or 2+3 0

9 1-110/230-280 2+3 or 2+3 0 or1

120-130/305-330 2+2 or 2+3 1 or 2

140-154/355-390 2+1or 2+2 2 or 3

165-185/420-470 2+1or 2+2 2 or 3

Rules for making screen boards:

* The width of the thinnest graphic is greater than the thickness of the screen (screen+photosensitive paste).

* The thickness of photosensitive adhesive is 20-25% higher than that of screen, and the height of printing thread is 15-20%.

* The thinner the photosensitive adhesive, the more times the shoes are painted.

* The thickness of the photosensitive glue is at least 5 microns higher than the screen.

* The smaller the wire diameter, the higher the resolution.

Conclusion: Many factors will affect the screen quality and print results. This paper introduces the most basic problems, and following these rules is the basis of printing high-quality products.