Selection of Photographic Emulsion for Screen Printing

Screen printing is a method of printing by tightly stretch the silk printing polyester mesh onto a screen frame. This method utilizes hand-engraved lacquer films or photochemical plate-making techniques to create screen printing plates that enable efficient, low-cost printing on a variety of materials.

Modern screen printing technology is more advanced. It uses photoresist emulsion, through the way of photographic plate making elaborate screen printing plate. In this process, the screen holes in the graphic portion of the screen printing plate are treated as through holes, while the holes in the non-graphic portion of the screen are skillfully blocked. During printing, the screen printing polyurethane squeegee applies pressure to force the screen printing oil or pigment ink to pass through the graphic portion of the screen holes only, and then transfer it to the substrate with precision, resulting in a beautiful graphic that is exactly the same as the original.

The selection and application of photographic materials is crucial. Among the many choices, how to find the most suitable photographic material for you has become a topic that every printing practitioner needs to face. In the process of screen printing plate making, the choice of photoresist emulsion has an important impact on the printing effect and efficiency. No matter which method is used, photoresist emulsion is indispensable.

In the plate making process, photographic emulsion need to have good photographic properties, physical and chemical properties, as well as environmental protection to meet the needs of modern printing processes. At the same time, its environmental protection is also a modern printing process can not be ignored in the consideration of factors. The photographic emulsion should have good developing performance, high resolution, stability and easy long-term storage to minimize waste; finally, from the economic, health and environmental protection point of view, the selected photoresist emulsion should be non-toxic, harmless and environmentally friendly.

Photoresist emulsion is generally categorized into single-component(one-part) photoresist emulsion and dual-component(two-part) photoresist emulsion types. The single-component type is used directly, while the dual-component type needs to be mixed with photosensitizer. The new diazonium salt photoresist emulsion is gradually replacing dichromate, because of its non-toxic, print-resistant and environmentally friendly advantages. Single-component photoresist emulsion has been fully mixed with photosensitizer into the colloid during the production process, and there is no need for additional preparation when using it; while dual-component photoresist emulsion needs to dissolve the photosensitizer according to a specific formula before using it, and then mix with the latex to be used after mixing and stirring.

In addition, the photoresist emulsion used for screen printing plates also includes dichromate-based photoresist emulsion, diazonium-based photoresist emulsion and single-components photoresist emulsion. Among them, diazonium salt photoresist emulsion, formulated with a specific ratio of diazonium resin, vinyl acetate and polyvinyl alcohol is the commonly used photoresist emulsion for screen printing plates.

In the process of screen printing plate making, how to evenly apply the photoresist emulsion on the screen printing machine is an important part to ensure the printing quality. As there are many different types of photoresist emulsion, the method of application can vary. However, no matter which type of photoresist emulsion is used, certain procedures need to be followed to ensure print quality.

There are two methods of applying photoresist emulsion: mechanical and manual. Mechanical coating is more uniform, while manual coating offers greater flexibility. First, you can choose to use mechanical coating. An appropriate amount of photoresist emulsion is poured onto a thick steel plate, which is then placed on a rotary applicator. When the switch is turned on, the steel plate will be evenly coated with photoresist emulsion by centrifugal force. It is important to note that the speed of rotation affects the thickness of the coating; the faster the speed, the thinner the coating, and vice versa.

In addition, spray-on coating is also an option. This method results in a highly uniform coating. The photoresist emulsion is held in a spray gun, and after adjusting the appropriate pressure, the coating is applied against the surface of the steel plate.

Finally, if you prefer to apply the coating by hand, there are a couple of different methods available. One method is to use a sizing applicator for screen coating, which wraps a piece of high mesh screen around the outside to apply the coating. Another method is to manually rotate the coater to mimic a rotary coater. Another method uses a wide brush with fine bristles to apply the coating. Whichever method you choose, you need to make sure that you maintain an even force and speed during the operation to get the desired coating results.

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For the products out of stock or with your own design, we're able to send out the sample within 15 days.

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