PCT-550 - Ultra-Bright Metallic Varnish Base
1. Overview & Applications
The PCT-550 Series is a specialized ultra-bright varnish explicitly engineered for custom-mixing premium silver and pearl screen printing inks. Compared to standard clear varnishes, PCT-550 delivers an exceptionally bright, ultra-smooth, and highly reflective metallic texture.
Primary Applications: Large-area metallic backgrounds on membrane switch overlays, nameplates, and graphic panels.
Applicable Substrates: Excellent adhesion on PC (Polycarbonate) sheets and print-treated PET sheets. (Note: Adhesion is poor on untreated PET).
Environmental Compliance: Formulated with low-odor, eco-friendly solvents. Fully compliant with EU RoHS 6 standards (free of Lead, Mercury, Cadmium, Hexavalent Chromium, PBB, and PBDE).
2. Metallic Pigment Selection & Preparation
Critical Pigment Selection Rules
- Non-Leafing Paste ONLY: You MUST use non-leafing (sinking) silver paste. Utilizing leafing (floating) silver paste will severely compromise the ink's adhesion to the substrate.
- Particle Size Limits: For silver paste, the particle size should ideally be ≤ 10 microns. For pearl powder, it should be ≤ 25 microns.
- Maximum Loading Ratio: The maximum addition of silver paste must not exceed 16% of the varnish weight. For pearl powder, the maximum is 10%. Exceeding these limits will degrade adhesion. If the silver paste particle size exceeds 10 microns, its addition must be strictly kept under 10%.
Preparation / Mixing Process
| PCT-550 Varnish Base | 100 Parts |
|---|---|
| Silver Paste / Pearl Powder | 1 - 16 Parts (depending on opacity requirements) |
| A1001 Thinner | Add moderately to adjust to proper mixing viscosity. |
| Mechanical Dispersion | Use a mechanical mixer at 1,000 - 1,500 RPM for 10 to 20 minutes until the pigment is perfectly dispersed. |
*Color Matching: To create colored metallics (e.g., champagne silver, coffee silver, light blue silver), tint the mixture using our 3D-TM Transparent Color Paste series.
3. Printing Formulation & Curing Guidelines
Printing Formulation
Once the metallic ink has been properly dispersed, it must be formulated with a specific binder before printing to guarantee substrate adhesion.
| Prepared Metallic Ink | 100 Parts |
|---|---|
| C-660 Binder | 2 Parts (MANDATORY) - Failure to add this binder will result in severe adhesion failure. |
| Thinner | A1001 Standard Thinner. Add only if viscosity adjustment is needed. |
| Pot Life | While the mixed ink remains usable for 2-3 days, it is highly recommended to use the entire batch on the same day to ensure absolute color and brilliance consistency. |
Processing & Curing Parameters
- Screen Mesh Count: If using ≤ 10-micron silver paste, a 200 mesh/inch screen is appropriate to allow the metallic flakes to pass through smoothly without clogging.
- MANDATORY Forced Baking: This ink cannot be air-dried at room temperature. It requires a mandatory forced-drying process at 70°C - 90°C for 30 minutes.
- Substrate-Specific Backing Protection: To prevent the brilliant metallic layer from being scratched during subsequent processing, it must be overprinted (backed) with a protective ink layer.
- For PET Sheets: You must use PET-5900 Ink as the backing layer.
- For PC Sheets: You must use PS-Ink as the backing layer. - Shelf Life: Store in a cool, dry place. Shelf life is 1 year from the date of manufacture.
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