Magnetic Printing Process and Mechanical Discussion--Screen Printing (3)

(1) Mesh Frame The frame is the frame of the support mesh and is made of metal, wood or other materials. Divided into fixed and adjustable two. The most commonly used is a frame made of aluminum material. Various network frames have their own characteristics. When selecting, different materials should be selected according to different situations. The materials used to make the frame should meet the needs of stretching tension, and they should be strong, durable, lightweight, and inexpensive. Under conditions of high temperature and humidity, the performance should be stable, and should have a certain degree of water resistance, solvent resistance, and resistance. Chemicals, acid, alkali and other properties.

(2) stretch net before the first stretch net according to the size of the appropriate selection of the appropriate network box, the net frame and the screen side of the adhesive clean. If the frame is used for the first time, it needs to be lightly rubbed with sandpaper to make the surface of the frame rough, so that it is easy to improve the adhesion of the frame and the screen. If it is a used frame, it must be rubbed with sandpaper to remove residual glue and other substances. The cleaned frame is pre-coated on the surface that is in contact with the screen and dried before it is stretched.

When stretching the net, manually or mechanically stretch the net. After the screen is stretched, the screen and the net frame are tightly adhered, and then the adhesive is applied on the contact portion of the screen and the net frame, and then dried. Note that the adhesive should not be coated. If it is too thick or too thin, when it is dry, a rubber sheet or a soft cloth may be used to wipe the adhesive part while applying a certain pressure to make the screen and the frame more securely. After the adhesive is dry, loosen the external tension, cut off the screen around the outside of the frame, and then use a single adhesive tape on the screen and the frame to adhere to the site, so as to protect the wire The function of the net and the frame can also prevent the solvent or water from dissolving the adhesive when printing, so as to ensure the effective use of the screen plate.

Finally, rinse the screen with clean water or detergent. After the screen is air-dry, it can be coated with photosensitive adhesive (plate making). The process flow of the stretch cloth is as follows:

Check box→Clean net frame→Pre-applied adhesive→Chodding→Drying→Stretching→Coating adhesive→Drying→Finishing→Adhesive paper tape→Wash net

5. Screen printing sensitive adhesive

Screen-printing plate-making photosensitive materials are classified according to their forms of photosensitive adhesive and photosensitive film (also known as film film, film paper), according to the composition of the material quality divided by dichromate, diazonium salt, iron salt Departments, etc., according to the use of a distinction between a screen sensitive adhesive, screen photosensitive film, sealing net adhesive, hardener, stripping agent, developer and so on.

(1) The requirements of stencil plate making on photographic materials are better than that of plate-making, and there is an appropriate range of sensitization spectrum, generally 340-440nm, high sensitivity; good developing performance; high resolution; good stability.

(2) Requirements for screen printing on photosensitive materials Plates formed from photosensitive webs should be adapted to the performance requirements of different types of inks: they have considerable resistance to printing and can withstand considerable scraping pressure of the scraper; combined with screens Good ability, no stripping failure during printing, easy to peel, conducive to the regeneration of screen plate material.

6. Make the bottom plate

The bottom plate, also known as the original plate, is the basis for the stencil printing screen. The bottom plate of the screen printing plate printing plate is generally a positive printing plate. The bottom plate manufacturing methods include the manual drawing method, the manual engraving method, and the manual pressure-sensitive printing method. , manual painting, photographic production, electronic color separation and color desktop system production.

7. Screen printing plate production

According to the relationship between the film and the screen, the printing plate production can be divided into three kinds: direct method, indirect method and interim method. The plate-making method of directly coating the film on the screen is called direct method; the other photosensitive film is first imaged, and then the plate-making method transferred to the screen on the screen is called the indirect method; the film is coated on the film base and imaged on the screen. The platemaking method is called the straight method.

Screen printing platemaking methods can be divided into manual plate method, metal plate plate making method and photosensitive plate making method. Because the high quality and good effect of photolithography are commonly used, the following only describes the photolithography method.

Photographic plate making method is to make the positive plate base plate that has been prepared and is sealed on the screen sensitive adhesive. When the image is exposed, the part of the image is shielded from light, the film does not undergo chemical changes, and the through hole is formed by washing with water or other developer to form a through hole. In some cases, sensitized adhesives are used to produce cross-linked hardened films that are firmly bonded to screens to form stencils.

Photographic platemaking methods are divided into three methods: direct method, indirect method, and straight method. Essentially, the technical requirements of these three methods are the same.

(1) Direct method This method is to apply photosensitive liquid directly on the screen to form a photosensitive film. The process flow is:

(2) Indirect method A transparent or translucent plastic film base with a thickness of about 0.12 to 0.20 μm is coated with a sensitizing film mainly composed of gelatin to form a photosensitive film, and the positive plate and the photosensitive film are sealed together. After exposure and development, a gelatinous image is formed, the image is transferred to a stretched screen, and the film base is dried to remove the film.

The indirect method is more precise than the direct method, and does not require the use of special printing equipment. The process flow is as follows:

(3) Straight-line method This is a combination of direct plate-making method and indirect plate-making method. That is, the photosensitive film is first applied to the screen with water, alcohol or photosensitive adhesive. After drying, the polyester film base on the photosensitive film is peeled off, the positive plate is sealed, exposed, developed, and dried to form a printing plate. The transfer film is the same as the direct method before exposure. The process is as follows:

8. Screen printing operation

(1) Test printing Before every opening, you should make a test and check the reproducibility and hue of the image on the test print. If the reproducibility is poor, the screen pitch, doctor blade, printing pressure, ink viscosity, etc. should be slightly adjusted. For multi-color overprinting, after the inspection of the first color version is qualified, the position marking of the loading plate should be drawn on the printing table, and the distance between the screens should be recorded.

(2) Overprinting When the next color is to be overprinted, the loading version shall be based on the position marking device of the previous color version; the netting distance and the flatness of the screen shall be the same as the pre-colored version. The upper and lower version of the alignment positioning is to align the previous color school template with the gauge and fix it. Put the screen plate with the same color plate mark in the frame clamp, observe the graphic pattern of the screen plate and the school board, and slowly move the frame to align the two. At this time, tighten the clamps. The squeegee angle and ink knife pressure remain the same as the previous color version. Then try to print, and check the impression on the school board. Under normal circumstances, the overlay error is between 1 and 2 mm. After 2 to 3 trials, the error is basically stable, and then the adjustment method is determined to fine-tune the stamp pad or screen clamp. In manual printing, regardless of the printing version, the same direction of squeegee should be maintained. You can refer to the related works for the detailed operation steps of manual, flat, and curved screen printing.