Copper plate etching technology (on)

Copper plate making plays a decisive role in letterpress printing, packaging printing, and electro-aluminum hot stamping. The plate making process is more complex than the inside. To make a printing plate that meets the printing requirements, one must be familiar with its lack of workmanship and strict control over each link. Otherwise, it is easy to produce quality accidents. The process operations are briefly described as follows:

First, mesh copper etching plate

1. Plate selection

The plate used for copper plate making requires a thickness of 0.8 to 2.0 mm, and a common copper plate of 1.0 to 1.6 mm. Copper plates for plate making are special plates. They contain metals such as cadmium, tellurium and silver. When corroded, they are easier than pure copper. Generally, they are required to be free from impurities, streaks, and have a smooth surface and moderate hardness.

2. Preparation of etching solution (ferric chloride solution)

The main component of the etching solution is ferric chloride, which is a compound of iron oxide and hydrochloric acid. It is a yellow solid or black-brown crystal that is easily deliquescent.

In the etching process, the water dissolves into a golden yellow liquid and copper produces a displacement redox effect.

Corrosion solution preparation: Dissolve ferric chloride with water to the required concentration. One concentration is 35 to 40 degrees, and filtered and clarified.

The prepared ferric chloride solution has a sweet taste. If odoriferous hydrochloric acid is smelled, it indicates that the acidity in the ferric chloride solution is too large, and the old corrosive solution or the slightly acidic trichlorm solution is required. Iron solution reconciliation.

3. Cleaning liquid preparation

The role of the cleaning liquid is to clean the impurities of the copper plate, so that the copper and the ferric chloride contact well to get a better corrosion effect. The copper plate is treated with a cleaning solution to treat the plate before and after etching. Cleaning liquid preparation:

Acetic acid 50cc

Salt 150g

25cc hydrochloric acid

Water 500cc

The various drugs mentioned above may be appropriately increased or decreased, but it should be noted that hydrochloric acid should not be too much, so as not to affect the film.

4. Printing

Stencil printing is the exposure treatment of a copper plate surface coated photosensitive film, which is a mixture of animal glue or resin and other polymer compounds and dichromate. After being exposed to light, the photosensitive plastics do not dissolve in water, and the unexposed areas are soluble in water, so that the copperplate layout will show the lines and dots of the original, and then it will be turned into a corrosion-resistant enamel by heating and baking, and it will reach the letterpress plate. Claim.

Shaiban is an important process of copperplate plate making process. It requires very strict requirements for the photographs of the meshes. Generally, it requires the high-profile parts of the image (highlights) to be transparent, and it is appropriate to photograph 3.5 to 4.5. More than 30% of the outlets, the low-key parts of the image (shade) black spots to shoot 0.5 ~ 1 is appropriate, the idea is to black to be round, must follow a small solid reflective spot, so that the layout can be displayed after the corrosion layer.

(1) Abrasive plate: Choose good quality, moderate hardness, no scarring, rough grain hardwood charcoal milling, grinding plate should be careful, the milled plate has no carbon scratch lines, smooth and clean, no grease, Can make the photosensitive liquid coating evenly attached firmly.

(2) Coating Bakeplate: Set the temperature and rotation speed of the baking plate in advance, clamp the plated plate on the plate, and turn it on. After flushing the plate with clean water, the plate surface is coated with a photo-sensitive liquid under weak light. The photo-sensitive liquid must flow uniformly, without streaks, without bubbles, and without dust inclusions. The rotation speed during drying should be determined by the concentration of the photosensitive liquid, and the film should not be too thin or too thick. The drying platen temperature should not exceed 70°C to avoid dark reaction of the photosensitive film and accelerate hardening, resulting in failure after the printing. Coating baking temperature is generally 50 °C, speed 60 ~ 80 rotation, time 5 to 10 minutes.

Photographic solution preparation

A liquid

PVA (degree of polymerization 500, water soluble 85°C～90°C) 100g

Water 1000 cc

After cooking for one and a half hours, it is filtered (about 4 degrees).

Liquor

Water 100 cc

Ammonium dichromate 10~14g

When the liquid is cooled to 45°C, the two liquids are mixed.

If the PVA polymerization degree is too high, it is easy to paste the plates during printing, and a small amount of sodium sulfonate, ethanol, glacial acetic acid, etc. can be added during cooking.

(3) Exposure: After the film is dried, the film is relatively densely packed with the film of the film on the vacuum stencil and compacted for exposure. The exposure time should be determined according to the temperature, the temperature, and the intensity of the light source. The light source uses a xenon lamp or other lamps as the light source. Under normal circumstances, the lamp distance is 0.5 to 1 meters and the exposure time is 3 to 5 minutes.

(4) Development: After exposure, rinse the unprinted film on the plate surface with clean water. Use a 1% methyl violet dye for easy observation to make the plate show a clear image. Rinse the plate with water. After rinsing, if there is still a small amount of residue on the plate, it can be wiped off with cotton, and then rinsed with water.

(5) Hard film: immersed in 10% chromic acid solution for 20 to 30 seconds. Immediately flush with water. Rinse and place it on the plate holder to allow it to dry naturally.

The chromic acid in the hardener is a strong oxidizer that can make the film astringent and dehydrated to become more sturdy.

(6) Bakeware

The copper plate after the chromic acid hardening is baked on an electric furnace or a constant temperature oven. The copper-plate adhesive film is baked to change from yellow to strong brown-red enamel corrosion-resistant film. Baking temperature 180 °C ~ 190 °C, baking time about 10 minutes.