Measure optical haze
Transparent coated films are widely used in display devices, packaging materials, and optical components, and their optical haze directly affects light scattering and visual clarity. This method is based on the international standards ISO 14782 and ASTM D1003, combined with laboratory practice, to develop a unified haze meter measurement process. The following is the operating specification and key parameters.
Instrument preparation and calibration
Choose a haze meter that meets the standard configuration, and its light source is C light source or D65 light source, and the observation conditions are 0°/d (vertical incidence, diffuse reflection collection) or d/0° (diffuse illumination, vertical reception). The instrument should be warmed up before each use until the light source is stable. Calibration uses a standard reference plate, usually zeroed in air, and the haze value is calibrated on a standard transparent plate. The sample should be a flat film without scratches and contamination, and the size should cover at least the measurement caliber.
Sample handling and placement
The film sample should be kept at a constant temperature and humidity for at least 4 hours at a temperature of 23°C and a relative humidity of 50%. When measuring, the sample is snug against the incident window of the integrating sphere, avoiding wrinkling or warping. For the direction of the coating surface, indicate the incident side of the light (e.g., the coating side facing the light source), and measure the two directions separately and record the difference if necessary.
Measurement steps
The steps include:
1. Without placing the sample, the measuring instrument is zeroed in the air to obtain the scattered luminous flux T0 and the total transmitted luminous flux T1.
2. Place the sample and measure the total transmitted light flux T2. The geometry of the sphere must be kept free of contamination.
3. Remove the sample, add a light catcher, and measure the scattered light flux T3 of the device itself.
4. Calculate the haze value T: T = [(T2/T1) - (T3/T0)] × 100. The instrument handles this operation automatically.
Example of result calculation
Suppose a single measurement is obtained: T0=1000, T1=995, T2=850, T3=12. Substitution Formula:
T = [850/995 - 12/1000] × 100 = [0.8543 - 0.0120] × 100 = 84.23 %
This value indicates that the optical haze of the film is approximately 84%. The actual measurement needs to be repeated three times to take the mean.
Key influencing factors
| factors | Description |
|---|---|
| Film thickness | Uneven thickness leads to fluctuations in haze, which requires multi-point measurement. |
| Coating surface roughness | Rough surfaces enhance light scattering, affecting haze values. |
| Light source stability | Insufficient preheating causes light intensity drift and reduces repeatability. |
| Environmental cleanliness | Dust adheres to the inner wall of the film or integrating sphere, introducing stray light. |
Results report
The report should include: sample identification, coating direction, measurement conditions (light source type, observation geometry, temperature and humidity), haze value per time, average and standard deviation. If there are any outliers, the reason should be indicated. It is recommended to attach a photo of the film's appearance for easy traceability.
References
1. ISO 14782:1999, Method for determination of haze in transparent materials.
2. ASTM D1003-13, Standard Test Method for Haze and Light Transmittance of Transparent Plastics.
3. Industry technical circular, optical performance measurement specification of transparent coated film.