Velvet coating screen printing screen production (four)

<

(7) Relationship between light source and exposure time and distance

The distance between the light source and the photosensitive film and the exposure time should be determined according to the requirements of the photosensitive material and the requirements of the light source used in the printing machine. Under normal circumstances, if the light source is placed at a distance of 50 cm and the exposure time is 3 minutes, if the distance is 2 times, ie 100 cm, the exposure time should be 12 minutes, which is four times the original. However, it is actually 9 minutes, which is 3 times the original number. When the exposure time and the distance from the light source to the photoreceptor surface are fixed, the higher the light source irradiation intensity, the shorter the exposure time, the lower the irradiation intensity of the light source, and the longer the exposure time. If the illumination intensity of the light source is constant, the longer the distance from the light source to the photoreceptor surface, the longer the exposure time, and vice versa, the shorter the exposure time.

In the actual plate making, the distance from the light source to the surface of the photoconductor is determined according to the light source, photosensitive material, etc. used to determine a reasonable exposure time.

(8) Light irradiation method.

The light should be parallel rays perpendicular to the photosensitive surface. If daylight is used, the screen should be placed directly in the sun, but not all the light from time to time. At the same time, the light changes strongly due to the seasons.

When using a point light source such as an arc, the exposure time may be prolonged, and it is advisable to set the distance to be longer than the allowable condition. The worst is cross light from different angles. In this case, a glass of frost can be placed between the light source and the photosensitive surface to diffuse the light and the light source conditions can be improved.

(9) Development.

The exposed plate is immersed in water for a minute or two. The unexcited part of the screen, such as the frame, is constantly shaken and swollen. After washing, it can be developed. Development should be completed as soon as possible. Sometimes spray water from both sides with a 3.5 to 5.5 kg/cm2 spray gun. Due to the different types of photosensitive liquids, some are easily developed and some are not easily developed, but in any case, the unexposed areas must be completely dissolved away. When the pattern is fine, use 8-10 times the magnifying glass to check if the subtle part is completely air-permeable. After developing, use a sponge or hair dryer to quickly remove the moisture and dry.

Due to the difference in the type of the photosensitive liquid, the polyvinyl alcohol emulsion film having a high degree of polymerization and the emulsion film having a large solvent resistance are applied with warm water. Nylon photographic film is mostly developed with industrial alcohol until the finest image can be fully displayed. After careful inspection, all images can be clearly displayed and rinsed with clean water. The developing alcohol can be retained and used multiple times.

Due to the different properties of the photosensitive material, the plate-making requirements and the development requirements are also different, and the plate-making methods and the developing methods commonly used for different photosensitive materials are shown in the table. Table 17

Photosensitive materials, plate making methods and developing methods Photosensitive materials nameplate making method Developing methods Dichromate emulsions Diazonium emulsions Dichromate films Diazonium salts Film iron salts Films Direct methods Direct methods Indirect methods Indirect methods Indirect methods Water Development Water Development Water Development Water Development

(10) Drying.

The developed screen plate should be placed in a dust-free dry box and blown with warm air.

Silk screen version drying box is a plate-making equipment. It is used for low-temperature drying after screen cleaning and coating of photo-sensitive adhesive. Drying temperature can generally be controlled at 40 °C ± 5 °C.

Screen drying box can be divided into vertical and horizontal two.

Drying box should be equipped with automatic temperature control system and timing device, and keep the inside of the box clean. The vertical drying oven has a small footprint and is suitable for screen plates with large areas and low precision requirements. Horizontal drying oven covers a large area and is suitable for screen plates with small area and high precision. Two kinds of drying boxes are multi-row and multi-layer, which can ensure that multiple screen plates are dried simultaneously.

When drying, the moisture on the surface of the screen should be blown off in advance so as to prevent the moisture from flowing under the screen surface during the drying process to generate residual adhesive, which affects the sharpness of the line edges. If a solid film is used to treat the layout, it can be carried out after the water is washed. Pay attention to uniform cloth flow. After the screen plate is dry, it can be checked on the translucent inspection table, whether there are stains such as bubbles, sand holes, etc., and the edge of the line can be trimmed with glue solution.

(11) Reinforcement and correction of the film.

Before or after the printing plate is dried, in order to strengthen the printing plate and improve the water resistance and the solvent resistance, an anhydrous dilute chromate solution may be applied. However, from the perspective of preventing public hazards, it is not appropriate to use chromic acid-based drugs.

Recently, there has been a market for less-strength plate enhancers sold.

Secondly, in order to block the pinholes or openings that should not be on the plate, block the blockage with a blocking liquid or a photosensitive liquid for plate making. In the printing process, the ink and ink leakage may sometimes occur at the junction of the net and the frame. Especially when fixing with an adhesive, ink leakage is more likely to occur. This should be blocked with proper materials to prevent the ink solvent from leaking out of contact with the adhesive. In order to enhance the imprint resistance of the printing film, the retouched printing plate can be re-exposed (double exposure) for a period of time depending on the light intensity. The film remaining on the screen can be sturdy by being exposed to ultraviolet rays again. Resist printing.

Screen inspection is the final process of the entire plate making work and it is also an extremely important process. Exposure to small defects after development can be corrected by revision. If major defects occur, they must be re-plated.

In the quality inspection of the screen, at least the following issues should be emphasized.

A, whether the exposure time is correct

In addition to the use of a density ladder to check whether the exposure time for film hardening is reached, it is also possible to see how the fineness of the bottom plate is reproduced on the screen, whether the lines are complete, whether the edges are clear, and whether the zigzag is severe.

B. Whether the mesh is completely transparent Check the quality of the screen printing plate, including whether the picture and text are all developed, whether there are burrs, broken lines, broken pens, and dead mesh in the graphic and dot lines. If the above conditions are found, the time should be timely. Various methods can be used to remedy the situation and re-plates can be considered to ensure the quality of future printing. Only very transparent mesh can make screen printing ink pass through smoothly. If it is found that the perforated mesh on the screen plate is still sealed by the film, it should be developed again. If there is still no effect, it should be re-plated.

C. Testing the adaptability of various photosensitive materials The different photosensitive films have different adaptability. For printing materials using organic solvents as diluents, solvent-resistant photosensitive films should be used. When water-soluble paint is used as the printing material, a water-resistant photosensitive film should be used, and the two should not be confused. This inspection work should be combined with the use of manuals, and understanding of the substrate can only be correctly grasped.

Check for omentum, blisters, and unsealed mesh on the four sides near the frame. Bubbles and trachoma should be promptly remedied. The four-sided screen is screened to avoid ink leakage during printing. Use adhesive tape to attach the screen to the adhesive part of the frame. Check the printing orientation markings for compliance with printing requirements.

CZ Jewelry Sets

Jewelry Set,Fashion Jewelry,Silver Jewelry

Charming Times Jewelry Co., Ltd , http://www.gz-bracelets.com