Surface Characteristics
An explanation of the meaning behind and the measurement method for the main physical properties measured.
Friction (Slip) Coefficient
| Unit |
µs/µd |
| Purpose / Details |
This is a measurement of the amount of sliding and friction between films. There is a resistance immediately after beginning to slide (µs: static friction coefficient), and a resistance in the stable region after sliding has begun (µd: dynamic friction coefficient). |
| Measurement Method / Standards |
In accordance with ASTM-D-1894. |
| Specific Measurement Method |
The values are measured using a slip tester, measuring the film-to-film friction coefficient. Values are obtained using the following formula.
Friction Coefficient = Resistance Value / Load |
Wetting Tension
| Unit |
mN/m |
| Purpose / Details |
This represents the surface tension of the film. The higher the value, the more hydrophilic it is, while lower values denote the film being more hydrophobic. |
| Measurement Method / Standards |
In accordance with JIS-K-6768. |
| Specific Measurement Method |
A cotton swab is immersed in a JIS standard solution and applied to the sample. The value is obtained from the shape of the applied liquid film after 2 seconds and is represented by the surface tension of the liquid. |
Gloss
| Unit |
% |
| Purpose / Details |
This is a numerical value representing the matt tone. The lower the gloss, the greater the roughness of the surface and the more matt it is. |
| Measurement Method / Standards |
In accordance with JIS-Z-8741 and ASTM-D-2457. |
| Specific Measurement Method |
Using a gloss meter, the reflectance when light is projected on to the film surface at an incident angle of 60° is measured at a light receiving angle of 60°. |
Surface Roughness (Ra)
| Unit |
nm |
| Purpose / Details |
Arithmetic mean roughness. A reference length is extracted from the roughness curve in the direction of the average line, and the absolute value of the deviation from that average line to the roughness curve for the extracted portion is summed and averaged to obtain the value. |
| Measurement Method / Standards |
In accordance with JIS-B-0601. |
| Specific Measurement Method |
Using a surface roughness tester, the film surface is traced with a stylus having a diameter of 2 to 5 µm to measure any irregularities. |
