Optical Density Measurement of Aluminized Film with Densitometer

Aluminized film is a composite flexible packaging material formed by coating a very thin layer of aluminum on a plastic film using a special process. Commonly aluminized films include PET aluminized film, CPP aluminized film, OPP aluminized film and so on. The packaging material with aluminum coating has both the characteristics of metal and plastic film. The aluminum coating on the vacuum aluminum coating is very thin. The optical density value can be detected by a densitometer. The larger the optical density value, the thicker the aluminum layer. 

1. What is optical density?

The optical density is also called the absorbance value, which represents the optical density absorbed by the detected object. It can also be understood as the light-shielding ability of the material. OD (short for optical density value) = log10 (1 / light transmittance), that is, the material is transparent. Logarithm of the reciprocal of light. Light transmittance refers to the percentage of the transmitted light intensity through the material to the incident light intensity.

2. The optical density value of aluminum coating

If the aluminum coating thickness is different, the hiding power will be reduced and the color difference will also appear. Non-uniform aluminized films can be measured at different positions to obtain different light transmittance and optical density values. Therefore, we often use optical densitometers to check the uniformity of aluminized films. The thicker the aluminum plating film, the lower the light transmittance and the larger the optical density value.

3. Measuring the optical density of aluminized film with a densitometer

Linshang LS117 densitometer is a portable aluminum-plated film optical density detection instrument, which uses the principle of diffuse transmission. The instrument is suitable for measuring the optical density values of various translucent materials, such as aluminized film, opalescent diffuser and zirconia.

When using the LS117 densitometer to measure the aluminum coating film, it can get its light transmittance and optical density value at the same time. Through this data, the uniformity of the aluminum coating film can be well judged. You can also refer to the comparison table of the aluminum coating film optical density value to determine the thickness of the aluminized film.
        If you need to measure the optical density of aluminized film in real time on the production line of vacuum aluminized film, you can also learn about our LS152 vacuum coating thickness measuring system. For more product information, please contact Linshang engineer at sales21@linshangtech.com.