Offset Printing Plate
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offset printing plate
Offset Printing Plate
Offset printing plate, or also named as presensitized plate, PS plate, lithographic plate, or aluminum printing plate, is our leading product with distribution in many countries in the world, and well accepted by customers of offset printing with advantages such as:
- Short Exposure Time
- Superior Resolution
- Excellent Dot Reproduction
- Long Run Impression
- Exceptional Processing Latitude
- High Contrast after Exposure and Development
High quality aluminum coil made in China, Japan and Germany, prepared specially for PS plate production.
- Production method:
By continuous coil production system with advanced and dependable technology
- Standard thickness:
Available in 0.15mm, 0.20mm, 0.25mm and 0.30mm.
Equivalent version of gauge at 7, 8, 10, and 12.
- Standard sizes:
Readily available for widely used offset machine:
Heidelberg, Roland, Solnar, KBA, Adast, Ryobi, Komori, Multilith, Goss, Gestetner, Hamada, Rotaprint, AB Dick, Crabtree, CATU, and so on.
Also available in any sizes required by customers
Punching perforation acceptable on gripper side in standard style including pb-1, pb-2 and SL, meeting the requirement of printing machines from Multilith and Rotaprint to CATU made in Brazil.
- Conforming standard:
ISO 9000 for manufacturing and ISO 12635 for plate specifications.
- Color of coating:
Dark green, and turns to blue after exposure.
- Dots reproduction:
At least 2% - 98% with 7 5 line shown *
- Exposure time:
50-60 seconds under 3,000W iodine gallium light at the distance of one meter. *
- Development time:
20-30 seconds. *
- Printing runs:
Maximum above 100,000 impressions *
- Also acceptable:
Negative PS plate with same features on order basis
Producing PS plates by aluminum coil or sheets provided by customers and charge only for the processing.
Re-generate (recycle) used PS plates provided by customers and charge only for the processing.
* May change according to different printing conditions related to machine, ink, paper and other factors
1. Light source
The spectral sensitivity of Demoprint positive PS plate falls within the blue and UV light range. Iodine-gallium lamp is recommended as the best light source. Other UV light such as high pressure mercury lamp or pulsed-xenon lamp is also suitable.
2. Exposure volume
As an example, the exposure volume for a 5000W iodine-gallium lamp is between 20-40 pulses (around 30-60 seconds) at a distance about one meter.
3. Exposure time
Place the 15-step gray scale (step difference 0.15) in the printing-down frame and expose the PS plate under perfect vacuum condition. The first 3 steps of gray scale are clear after exposure and development and will not accept ink.
- Keep the glass on the exposure unit clean and clear. Either dust or scratches may effect graphic quality.
- The original graphic arts film must be clean without any scratches, and its density should not be lower than 2.5.
2. 2. Development
Demoprint positive PS plate can be developed with our own DPX-1 developing powder and diluted liquid developer, or any other developer available in customers local market.
- When developed with DPX-1 developing powder:
1. Dissolving the whole bottle of DPX-1 developing powder with 5 liters of warm water to form concentrated solution.
2. Diluting concentrated developer with water by the ratio of 1:5. Store the concentrated and diluted developer properly.
3. Developing temperature is suggested at 25 0.
4. Monitoring the consistency of developing solution, and add new solution whenever it is necessary.
- When developed with other developing powder or liquid solution:
Always follow the diluting instruction of each different solution, and keep watching the final developed result.
- Although Demoprint PS plate is designed with wide alkaline latitude to work with different developer, too weak developer may result in poor image quality and insufficient development, while too strong developer may destroy the oxidized layer of the PS plate, and result in scum and less printing runs during printing.
3. 3. Image Removing and Correction
Remove the unwanted spots on the developed plate with the retouching solution such as Demoprint DRV-1 Image Remover.
After inking the developed PS plate, always evenly apply Demoprint DGM-1 Protection Gum or other similar finishing gum on the surface during the time of short storage before printing.
5. 5. Baking
Baking is necessary to give the plate a longer printing runs, though it is not a must according to our plate feature. When baking, Demoprint DBK-1 baking solution or any other similar baking solution can be applied on PS plate. After baking under a constant temperature at 230-2500 for 5-7 minutes, the color of the plate turned from green to brown-red. With the second development, rinsing and gumming, impression will be 3-4 times longer.