What do you need to learn about screen printing plate making?

In the screen printing process, the plate making process is a key link. In this article, we will introduce some basic skills in the process of screen plate making, I hope to help you.

One, the preparatory work

In the selection of screen, we must pay attention to the screen mesh and printing product quality match; screen stretch to be as small as possible; screen organization should be close, otherwise it is impossible to make a high quality screen.

If the screen is previously used, first of all for the screen to oil, dust, but also need to wash away the residual ink and so on. Cleaning screen with detergent, you should choose the newly acquired concentrated screen washing agent, it is best not to use household detergent or laundry detergent, because it contains flavor, hand care agent (detergent) and bleach (laundry detergent) and other additional ingredients, and the particles in it will block the network.

When cleaning the screen with a screenwashing detergent, coat both sides of the screen evenly and wipe it repeatedly with a sponge. Then rinse the screen with water and dry it to ensure that there is no residual foam on the screen, and the screen should never be touched by hand again after cleaning.

After cleaning, the screen should be dried in a dust-free environment. Now there are still many people using a fan blowing against the screen drying method, but this is dusty, it is best to do a drying box, so that the airflow flows evenly over the surface of the screen. At the same time, try to do the same day to wash the screen, the same day coating photopolymer, which can prevent the coating of glue before the screen and then fall on the dust. If the operating site of the humidity is very large, it is best to install a dehumidifier to speed up the screen drying.

There are still people who use roughing agent to polish the edges of the silk thread, this method is suitable for indirect plate making method, which can improve the bonding fastness between the photopolymer film and the screen. If we use the coated photopolymer method to make screen printing plate, there is no need for roughing, otherwise it will reduce the strength of the screen.

Second, the plate method

Screen production methods are most commonly used in the direct photopolymer plate method and direct film plate method, the following mainly introduces the two methods of the emergence of new photopolymer materials and plate process.

Direct photopolymer plate making method

1. Photopolymer type and performance

Simply put, the photopolymer is a chemical reaction of the gelatinous liquid, with a scraper in the clean and completely dry screen uniformly coated with a scraper, you can get a photopolymer performance of the screen.

Photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer photopolymer. Double sulfide photopolymer photopolymer photopolymer compared to the diazo compound photopolymer, containing less water, shrinkage in the drying process is small, the advantage of this can make the graphics on the screen to get sharp edges, but also can speed up the speed of plate making. When water-based inks are used, their durability is better. As a result, bisulfide photopolymer photopolymer photopolymer is gradually replacing diazo compound photopolymer.

2. Preparation of photopolymer photopolymer

Whether it is bisulfide photopolymer photopolymer photopolymer or general diazo photopolymer, the finished product includes two parts, part of the adhesive base, the other part is to see the light reactive photopolymer. When preparing the photopolymerized photopolymer glue, first add some warm water to dissolve the powdered photopolymer in the bottle (some photopolymer is a dark brown liquid rather than a powder). Since the photopolymerized photopolymer may react with minerals in the water, it is best to use distilled water to dissolve the photopolymerized photopolymer. The temperature of the water should be no higher than 38°C, otherwise the performance of the photopolymer will be affected; if the water temperature is too low, the powder will not be easily dissolved. Shaking the bottle or stirring it properly will help dissolve the photoconductor.

The next step is to add the photopolymer solution to the glue base to go, and non-metallic stick (such as wooden spoon, etc.) for stirring, it takes about 10 minutes or so, do not pull back and forth when stirring, it is best to "∞" shape. Then the matching photopolymer placed for a few hours, to be one of the air bubbles escape, you can use.

3. Advantages of photopolymerized adhesive for making screens

1) The photopolymerized adhesive has a long-lasting performance and can be used for a variety of screen frames. It is suitable for a variety of inks, including water-based fabric dye inks. Since the photopolymer can exist on the inside of the screen by coating, this type of plate can express the details of the image.

2) Screens made with photopolymer can be recycled without affecting image quality. In most cases (except for photopolymer with added hardener), the used screen can be reused as long as it is cleaned with solvent.

4. Coating environment

Photopolymer is quite sensitive to light, but this does not mean that it must work in total darkness, in the 50W yellow light can work. Remember not to be near windows or places with UV light. Bisulfide photopolymer photopolymer photopolymer photopolymer and pure photopolymer photopolymer photopolymer are even more sensitive to light than heavy nitrogen photopolymer, and it is best to operate in a light-free environment.

5. Applying Photopolymer Adhesive

The main tool for applying photopolymer adhesive is the sizing device, also known as a squeegee. There are many specifications for the length of the scraper, the standard size of the scraper used for printing T-shirts with a screen is 14 inches or 16 inches, the length of the scraper should be smaller than the size of the inner frame of the screen, so that it does not touch the blank part of the screen. Some squeegees have one blunt edge and one sharp edge; others have rounded edges. Coating to use the sharp edge of the squeegee, because the sharp edge of the photopolymer layer scraped thin, the screen can reproduce the image details, help to get a high-quality screen printing plate.

6. Drying of the screen plate

The drying process should be carried out under safe light. It is best to use a drying box (homemade can also be), fitted with a fan, so that the screen surface air flow to speed up the drying. Note that the fan should not be blown against the screen, so easy to blow up the dust adhering to the surface of the photopolymer layer. Generally speaking, screen drying takes 30 to 60 minutes, if the humidity is large, it takes 1 day to completely dry. At this time, if there is a dehumidifier, will play a big role.

After the screen is dried, it can be stored in a light-free box for up to 2 months at room temperature. For efficiency, you can apply a batch of screens at a time and save them for when they are needed.

Direct Film Platemaking

Another method of platemaking for screen printing, called direct film platemaking, is what we traditionally call the hybrid method. Simply put, the film used is a transparent acetate film coated with photopolymer.

The direct-film method is easier to use than the direct-photopolymer method because it eliminates the need to formulate photopolymer, and there are many fewer steps involved in making a plate. The main advantage of the direct film platemaking method is the print line is clean, because the plate is dry, no shrinkage, only the film adsorption on the blank screen can be. Direct film plate method, suitable for self-adhesive labels, posters and other printing quality requirements of high printing products.

1. Selection of film

Film is sold in the form of rolls or sheets, with a variety of thicknesses. General T-shirt printing, it is best to use the thickness of 38μm film; for screen mesh number is higher (such as 230 ~ 350 mesh / inch) screen, you can choose a thinner film (18μm), and screen mesh number is lower (such as 86 mesh / inch), to choose a 60μm thick film; if it is in the black fabric color printing, the need for a larger amount of ink, you need to choose a thicker film.

Film and photopolymer with the same light-sensitive properties, should be operated under soft light or yellow light, and storage, the temperature is not too high. The screen plate made by direct film plate making method can be stored for about 1 month.

2. Film

The process of film is to make the water in the screen rely on "capillary action" will be adsorbed on the screen film. The photographic film is firmly attached to the screen depends on the degree of cleanliness. There is a chemical reagent called "wetting agent", which helps the screen in the process of adhering to the film to absorb water, film as long as the screen to spray some of the "wetting agent", and sponge it evenly, water will be "wetting agent" and then rinsed clean. When there is still a lot of water on the screen, it is necessary to spread the film to the screen (rough face to the screen), and then use the rubber roller, respectively, rolled on the inside and outside of the screen. If there are still some places that are not adhered, then spray a little water on the inner part of the screen that is not adhered, and roll with the rubber roller, while spraying to the parts that are not adhered to the film sheet.

Each type of film has its own operation method, we only need to operate according to the instructions. After the attachment is completed, it takes about 30 minutes to dry. Then, remove the backing film of the film sheet and it is ready for exposure. Before removing the backing film, make sure that the screen and the film are completely dry. If the bottom film is quite difficult to remove, it means that the screen is not completely dry, if it is because of the high humidity of the environment, after removing the bottom film, you can put the film screen to dry for a period of time.

Many manufacturers prefer to use direct film plate making method, because this method of plate making fast, simple plate making steps. However, if you use the direct film plate making method, always can not get satisfied with the printing plate, you have to check whether the mesh number of the screen is higher than 200 mesh / inch.

In the use of high mesh screen to produce color mesh toned plate, the use of direct photopolymer platemaking method, is still dominant.