Silk screen printing plate making process (1)

Photolithography is the main method of modern silkscreening. It is through the camera equipment, the text, pattern to be copied in accordance with the requirements on the photosensitive film, in order to obtain a positive version of the silk screen plate.

As the photographic technology is applied to silk screen printing, the application scope of screen printing and screen printing is expanded. Photographing the bottom plate can not only provide very fine lines, text bottom plates, but also can reproduce colors and gradations of complex patterns to produce a color separation bottom plate that meets the requirements of silk screen printing. Therefore, photolithography plays an important role in the silk screen platemaking process.

Screen printing photographic platemaking process can be divided into lines, text draft photography; monochrome screen tone photography, color screen color separation photography three categories.

The following is a brief introduction of the specific contents of each process link in photolithography:

1 full text. Organize the originals, determine the proportion of spring style, and determine the rules.

2 photos. Using a photographic device, equipment, take a monochrome or color separation of the original.

3 development. The exposed film is placed in developer and developed. After exposing the photographic film, the silver halide of the emulsion layer is exposed to light to form a latent image. After the chemical treatment of the developer, the latent image becomes a visible and clear image. The commonly used developer consists of the developer Mituol (also known as Irun), Nuonanni (also known as Hydra, scientific name hydroquinone), the protective agent sodium sulfite, the accelerator sodium carbonate, and the inhibitor potassium bromide.

4Fixing. Fixing is to keep the developed silver image unchanged for a long time. The principle is to dissolve and remove the unsensitized residual silver halide on the photographic film to obtain a fixed image. The fixing solution is generally sodium thiosulfate (soda soda) solution. In order to prevent the development reaction of the photosensitive film in the fixing solution, a certain amount of weak acid may be added to the ordinary fixing solution to make the acidic fixing solution. The pH value of the acid fixing solution should be maintained between 4 and 6. In order to strengthen the mechanical strength of the photo-resist, a certain amount of potassium rhenium, chrome tanning, and other hardeners can be added to the acid fixative to make a firm fixing solution.

5 washed. Washing is divided into intermediate washing and final washing. The intermediate water washing is performed after the development and before the fixing, and can play a role of stopping and protecting the fixing liquid; the final water washing is performed after the fixing, and the function thereof is to wash away the soluble double salt formed on the photosensitive film during the fixing process. Washing water is better with running water. The water temperature should be maintained at 16~24°C.

Photographic preparation of the bottom plate is easy and fast. In recent years, with the advent of automatic developing machines and automatic fixing machines, the photoengraving process has gradually become mechanized and standardized.

1. Production of lines and texts.

The basic features of lines and text manuscripts are black and white, and there are no tone changes. Such manuscripts include tables, text, line drawings, patch patterns, and the like. By copying such originals by screen printing, in addition to the manual method of preparing the master, photographs are often used to obtain the master.

1 process. The production process of lines and texts is roughly as follows:

Full manuscript (process design, inspection of originals, calculation of scaling, etc.) → Placing originals → Light adjustment → Adjust aperture → Calculate exposure time → Place photographic film → Exposure → Development → Fixing → Washing → Drying → Inspection → Retouching → Duplicator

The problem to pay attention to during the full manuscript is: first check the quality of the original document, and do not miss the pen and ink. The ink should be black and the document surface should be cleaned. If you do not meet the requirements, if you can repair it and then take a picture and it is difficult to repair it, you can propose a change of draft. Second is to identify the color of the original. If the original is color-tagged, it is necessary to find out what color the original is sensitive to, and what color is not sensitive to it, so that a suitable photosensitive material can be used for photographing.

When placing the original, it must be placed in the center of the original holder. If there are too many scrapbooks, it is best to make the direction of the light source shine parallel to the long side of the clip strip to avoid too many shades and reduce the man-hours of the plate.

After washing and drying, the underneath version must be checked carefully. The inspection contents are usually whether the dimensions are correct, whether the layout image is complete (with or without omissions and omissions), whether the density meets the requirements, whether the layout is consistent, lines, text, and color blocks. Is it clear and transparent and meets the requirements of the original?

Checked and corrected negative film negatives can be delivered for copying and printing, which can be used for screen printing plates.

There are two methods for copying the positive image. One is to reprint the negative version on the original holder of the camera. This copying method can enlarge or reduce the size of the negative image of the negative; the other is the contact copy method. This method can only get the original large image.

The contact copy method is used to make the positive image. To use the copying machine, the film surface of the photosensitive film must be matched with the film surface of the negative plate at the time of copying.

2 workroom. The most important workroom for photogrammetry is the darkroom, which usually requires a large work space in the dark.

The darkroom area should be based on the size of the camera. The workroom of the darkroom camera should take into account the opening and closing of the focusing glass and the cassette, the development work, the sink, the workbench, the work table, the net frame, and the like, and leave room for it. If the camera uses a 50 cm square focusing glass, the standard area occupied by the camera should be 3 x 8 meters. If the machine is equipped with a sealed printing machine or a magnifying machine, it will need a correspondingly larger site.

Darkroom entrances and entrances can cause harmful light when only one door is set. Therefore, two doors should be set up. There should be a certain distance between the door and the door, and there must be a black curtain, as shown in Figure 2-62.

Since the darkroom operation is performed under a long-term closed condition, attention should be paid to the ventilation of the darkroom, and ventilation should be done so as not to leak outdoor light. A dust filter should be installed outside the ventilation hole.

The temperature difference between winter and summer is large, so it is very important to control the temperature. The development of the film is affected by the temperature, not only to maintain the constant temperature during the flushing, but also to keep the temperature of the entire room.

The darkroom equipment mainly includes a sink. The sink is provided with plates for developing, fixing, and washing. Since the temperature of each step must be maintained at 18 to 20°C, it is necessary to maintain a constant temperature of the water. The material of the thermostatic bath is stainless steel, but due to its high price, plastic and wood can also be used. Some of the baths are in the sink and some are located elsewhere to facilitate their use. However, no matter which one is used, water supply must be continuously used during use. Therefore, to place a water leveler in the water tank, all the developing plates used for phase washing should be immersed in the same water level.

The developing plate should be compatible with the size of the photosensitive material, at least three kinds of large, medium and small. And have a certain amount. Its materials are made of stainless steel, plastic, and glass. For ease of storage and use, they should be placed neatly on the shelf (see Figure 2-64).

Photosensitive films, contact screens, color filters, etc., except for those used on the day, should not be placed in a dark room. The amount of film stored in the dark room should not be too much, just put enough amount for the day. Put it in a very shallow film storage table (see Figure 2-65). The various drugs used in the darkroom include developer, neutralizing acetic acid, fixer, and Hypobar. The developer and fixer should be filled with the bottle in advance according to the regulations. When preparing, use warm water to make it in the dark outside. The temperature of the water should reach above 20°C, so it should be dissolved and cooled on the previous day. Due to the large amount of warm water, it should be made in dark outdoor areas.

Two 10 litre capped bottles are to be provided in the darkroom as containers for liquid A and liquid B. In addition, prepare 5 liters and 1 litre vials for proper placement.

The equipment in the darkroom shall also be equipped with: 1 clock in a darkroom; 2 thermometer (100°C for mercury or 60°C for photography); 3 cups (1L, 500ml, 100ml, 50ml); 4 safety lights (Figure 2) -66) and other major appliances, in addition to a full set of tables and chairs.

Dark desks should be provided with a lighting table for checking and correcting negatives. It is very busy to take corrective actions in the darkroom when taking pictures.