Industry: New‑Display Technology

Application Scenario： Solvent removal and structural protection of quantum‑dot nanomaterials (for 12.9‑inch iPad Pro Mini‑LED backlight modules).

 I. Core Pain Points

A display‑panel manufacturer encountered the following problems when drying quantum‑dot ink with conventional hot‑air drying:

- **Quantum‑dot agglomeration**: High temperature (>80 °C) causes collapse of CdSe/ZnS core‑shell structures. Particle size increases from 5 nm to 20 nm, and NTSC color gamut drops from 120% to 90%.
- **Solvent residue**: Toluene / chlorobenzene residue exceeds 200 ppm, inducing bubble defects after encapsulation, with panel yield merely 75%.
- **Oxidation failure**: Surface ligands (TOP/TOPO) of quantum dots are oxidized under high temperature. The photoluminescence quantum yield (QY) falls from 95% to 60%.

II. Solution

1. High‑precision Vacuum Freeze Dryer

**Equipment Parameters**

- Plate area: 5 m²; ultimate vacuum: 0.01 Pa
- Temperature range: ‑80 °C ~ +50 °C; cooling rate: 3 °C/min (direct liquid‑nitrogen cooling)
- Solvent recovery rate: 99.8% (three‑stage cold trap plus activated‑carbon adsorption)

**Special Design**

- UV‑shielded viewing window: prevents photo‑oxidation of quantum dots (light transmittance <0.1% for wavelengths below 450 nm).
- Nano‑level material spreading system: aerosol‑spray technology for uniform coating of quantum‑dot films (thickness ≤100 nm).

 2. Three‑Stage Freeze‑Drying Process

1. **Ultra‑fast deep freezing**: Rapid freezing at ‑75 °C for 10 min to form nano‑sized ice crystals.
2. **Gradient sublimation**:
- Stage 1: ‑50 °C / 2 h (vacuum 10 Pa), removing 90% of toluene.
- Stage 2: ‑30 °C / 4 h (vacuum 0.1 Pa), chlorobenzene residue reduced below 5 ppm.
3. **In‑situ encapsulation**: Direct transfer to ALD (Atomic Layer Deposition) equipment under argon atmosphere at 40 °C for 1 h, with oxygen content kept <1 ppm.

 III. Operation Results

**Performance Improvements**

- Quantum‑dot particle‑size distribution D90 ≤6 nm; color gamut raised to 138% NTSC (top‑tier industry level).
- Photoluminescence quantum yield stably maintained at 92‑94%; panel brightness uniformity >98%.