I. Manufacturing Steps of the Protective Layer
1. Material Preparation
- Base Material Preparation:
- The support layer (BOPET film) needs to undergo corona treatment (voltage 30-50 kV, time 1-2 seconds) to increase the surface tension to 42-46 mN/m and enhance adhesion.
- Static Electricity Elimination: Surface static electricity is eliminated using an ion wind stick (surface resistivity ≤ 10⁸ Ω/sq). 

2. Coating Solution Preparation
- Main Components:
- Film-forming Agent: Polyvinyl Alcohol (PVA, alcohol degree 88%) or Gelatin (peptide of animal or plant collagen protein).
- Additives: Silica (SiO₂) particles (particle size 0.5 - 1 μm, hydrophobic anti-fouling), Calcium Stearate (lubricant, addition amount 0.5 - 1%).
- Solvents: Deionized water (conductivity ≤ 1 μS/cm), pH adjusted to 5.0 - 6.5 (PVA requires alkaline conditions for dissolution, gelatin requires acidic conditions for dissolution).
- Viscosity Control: By adjusting the solid content (PVA solution concentration 5 - 8%, gelatin solution 3 - 5%) or adding thickeners (such as Sodium Carboxymethyl Cellulose). 

3. Coating Process
- Coating Method: Scrape coating (suitable for PVA) or slit coating (suitable for gelatin).
- Wet Film Thickness: 8 - 12 μm.
- Coating Speed: 1.5 - 2.5 m/min.
- Drying Conditions:
- Gradient Heating: 60°C (pre-drying) → 80°C (main drying) → 100°C (final drying), total time 2 - 3 minutes.
- Humidity Control: Environmental humidity ≤ 30% RH, to prevent the coating from absorbing moisture. 

4. Post-processing
- Surface polishing: By using soft rollers for rolling (pressure 0.2 - 0.5 MPa), the surface smoothness is enhanced (Ra ≤ 10nm).
- Cooling and setting: The material is cooled to room temperature to prevent curling caused by thermal stress. 

5. Quality Inspection
- Thickness Measurement: Coulomb thickness gauge (tolerance ±1μm).
- Adhesion Test: Tape剥离 method (ASTM D3359, rating ≥ 4B).
- Transmittance: UV-Visible spectrophotometer (≥92% @ 550nm).

II. Manufacturing Steps of the Sensitizing Agent Layer
1. Preparation of Silver Bromide Emulsion
- Raw material preparation:
- Silver Bromide: Nano-sized AgBr microcrystals (particle size 0.1 - 0.3 μm, cubic crystal form), produced by the reaction of silver nitrate and sodium bromide.
- Dispersing medium: Gelatin solution (concentration 5 - 8%, pH 4.5 - 5.5).
- Emulsification process:
- High-speed stirring: Slowly add the silver bromide powder into the gelatin solution, at a speed of 2000 - 3000 rpm, for 30 minutes.
- Ultrasonic dispersion: 10 minutes of ultrasonic treatment at 20 kHz, to break up aggregated particles. 

2. Add functional additives
- Fixing agent precursor: Sodium thiosulfate (Na₂S₂O₃, addition amount 1-2%), used for fixing the image after development.
- Anti-graininess agent: Lead stearate (0.1-0.3%), inhibits darkroom exposure.
- Plasticizer: Diisononyl phthalate (1-2%), enhances the flexibility of the emulsion. 

3. Coating Process
- Coating Method: Narrow slit coating (suitable for high viscosity emulsions).
- Wet Film Thickness: 15-20 μm.
- Coating Speed: 2-3 m/min.
- Drying Conditions:
- Infrared Heating: 60-80℃, avoid high temperature causing AgBr decomposition.
- Time: 1-2 minutes, dry until moisture content ≤ 0.5%. 

4. Post-processing
- Surface hardening: UV-cured coating (UV LED irradiation, wavelength 365nm, power 500mW/cm², duration 10 seconds).
- Edge trimming and positioning: Laser cutting of the edges (precision ±0.1mm), compatible with the camera paper feeding mechanism. 

5. Quality Inspection
- Particle Uniformity: Dynamic Light Scattering (DLS) is used to measure the particle size distribution (CV value ≤ 10%).
- Sensitivity Test: ISO standard exposure test (DIN 5034, sensitivity range ISO 100 - 400).
- Adhesion Strength: Spot test (ASTM D3359, rating ≥ 4B).

     3. Development Layer System​​

Inorganic Developer​​

Components: Hydroquinone derivatives (e.g., Metol), Phenidone.

Organic Developer​​

Components: Ascorbic acid (Vitamin C), Sodium borohydride.

Carrier & Stabilizer​​

Components: Gelatin, Antioxidants (e.g., Sodium sulfite), pH adjusters (e.g., Borax).

Manufacturing Method​​

Mix inorganic developer with gelatin solution and uniformly coat onto the PET substrate using a coating machine.

Drying: Infrared heating or hot-air drying to remove solvents.

Disperse organic developer in gelatin solution and prepare microcapsules via emulsion-coacervation method.

Dispersion: Apply spray drying or coacervation method to uniformly distribute microcapsules in another gelatin layer.

Bond the microcapsule-containing gelatin layer with the pre-coated inorganic developer layer via hot pressing lamination.

      4.Back Membrane Layer​​

Antistatic Polyester Film​

Composition: Polyethylene terephthalate (PET) synthesized from terephthalic acid and ethylene glycol.

Ink-Absorbing Layer​​

Composition: Hydrophilic polymers (e.g., polyvinyl alcohol, PVA), silica gel particles, surfactants.

Manufacturing Method​​

Polymerization: Condensation polymerization of terephthalic acid and ethylene glycol to produce PET resin.

Biaxial Stretching: Melt extrusion followed by longitudinal and transverse stretching to enhance mechanical strength and flatness.

Ink-Absorbing Layer Coating: Dissolve ink-absorbing components (polymers + additives) in water or organic solvents.

Coat via reverse-roll coating or doctor blade coating.

Drying: Hot-air oven drying to control residual solvent content below 1%.

     5.Support Layer (PET Substrate)​​

Composition: PET (polyethylene terephthalate).

Manufacturing Method​​

Polymerization →Melt Extrusion→Cast Film→Biaxial Stretching →Heat Setting→ ​​Winding.

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