Offset printing size CTP thermal CTP plate
Offset printing remains a stalwart in the high-quality, high-volume print industry. With continual technological advancements, the Computer-to-Plate (CTP) photographic process has revolutionized traditional plate making methods. Particularly, thermal CTP plates, selectable in various offset printing sizes, is know as robust enablers of print fidelity and durability.
The photopolymer or silver halide emulsions traditionally used in plates have increasingly been replaced by thermal CTP plates, entailing a photosensitive layer atop an aluminium alloy substrate. The substrate's alloy selection is essential for plate longevity and resistance to typical print pressures and chemical wear.
Aluminium Alloy Substrate
Typical alloys: 1050A and 3003 H14 are widely employed for thermal CTP plate substrates.
Chemical composition:| Alloy | Al (%) | Si (%) | Fe (%) | Cu (%) | Mn (%) | Mg (%) | Rest (%) ||-------|--------|---------|---------|---------|--------|----------|----------|| 1050A | 99.5+ | 0.25 max | 0.4 max | 0.05 max | 0.05 max | 0.03 max | Trace || 3003 | 97.0+ | 0.6 max | 0.7 max | 0.1 max |1.0-1.5 | 0.1 max | Trace |
These alloys offer an ideal alloy temper ('H14' work-hardened and partially annealed) delivering balanced hardness (56 - 69 Brinell HB) and formability.
Aluminium provides an optimal flush, flat plate but inherently requires surface modification—microetching and anodizing—to promote emulsion adherence and chemical resistance during high-speed press runs.
Features of Offset Printing Size Thermal CTP Plates
1. Thermal Sensitivity and Fast Imaging
Thermal CTP plates, responsive within 830 nm-wavelength LASER exposure, initiate crosslinking rather than requiring chemical developers (in most cases), enabling dry, fast plate formation. Research confirm sub-micron coherent laser energy synergy with ultrapure alloy surface peaks advancing precision.
2. Precise Offset Printing Sizes
CTP plates are delivered in standard offset sizes (e.g., Europe: 52 x 74 cm; Asia: 610 x 1016 mm; or custom sizes), solution compatibility with platesetter machinery ensures waste minimization and streamlined plate mounting in press cylinders. The dimensional stability imparted by high-grade aluminium QUESTION facilities consistent spatial replication.
3. Surface Microstructure Engineering
The substrate’s anodized layer (~5-20 microns thick), formed through sulfuric or phosphoric acid anodizing, is tailored for dot stability under print pressure and repeat cycling. Recent innovation involves particulate mineral additives or thermally formed oxides protests enhancing chemical resistivity, particularly under alcohol-substituted fountain solutions.
4. Durability and Run-Length Performance
Heat-treated forged alloy bases with optimal surface hardeness minimize "plate swell" — a deleterious swelling causing print distortion. Therefore, thermal plates sized with attention to alloy temper underpin runs exceeding 300,000 impressions under rigorous smoothness and dot gain tolerance constraints.
5. Eco-Sustainable Operation Mode
Thermal CTP plates typically minimize or eliminate need for chemical developing (chemical-free processors), reducing environmental toxicants accumulation. Aluminium recycling post-use with negligible contaminant variance sustains ecological print margins.
Applications and Niche Suitability
Commercial Web Presses utilize thermal plates sized meticulously to match press cylinders (typical web width between 50-78 cm) ensuring stronger registration for long run adverts, catalogues, magazines.
Packaging and Label Offset Fringing, including folding cartons and labels, require heftier substrate gauge with treated alloy to resist higher ink lay densities and multiple coating appliqués.
Security Document Printing employs fine-grained, disturbance-resistant thermal layers facilitating microtext and anti-counterfeiting micro-patterning – necessitating precision thermal exposure at target lithographic offset scale.
Short-run Digital-to-offset Hybrid Printers—smaller sized thermal CTP plates with ready-to-run fast exposure systems optimize turnaround and mediate costs without sacrificing homogenous print quality.
Technical Implementation Insights
1. Plate Shape & Offset Size Specification
- Standard up to 520 mm × 740 mm (Europe) or larger sheets proportionate:
| Application Type | Plate Size (mm) | Alloy Temper | Surface Finish |
|---|---|---|---|
| Standard Commercial | 520 × 740 | 3003 H14 | Anodized & Microetched |
| High-Volume Web | 610 × 1016 | 1050A H14 | Phosphated Anodized |
| Special Packaging | Custom (variable) | 3003 H24 | Anodized + Ceramic modifier |
2. Surface Treatments
- Microetching in NaOH or alkaline solution achieving controlled roughness ~0.5-1.5 microns depth.
- Anodizing to increase aluminium oxide thickness influencing adhesion trapping cross links in thermal exposure.
3. Heat Treatment
Maintaining mechanical strength through aging (330 - 370°C for 4 hours conf Cerrium logarithmic increases wear resistance)
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