User`s guide

Label Requirements
LABEL AND LINER OPTICAL DENSITY
If liner paper transmits 2% of the light which is incident on it, the optical density is
log
10
(100/2) = 1.7
If the light transmitted through the liner is 3 times the light transmitted through the liner and label,
the relative optical densities are:
Optical Density of Liner + Label = log
10
(100 / X)
Optical Density of Liner Only = log
10
(100 / 3X)
= log
10
(0.3333X)
= log
10
0.3333 + log10 (X)
= log
10
(X) – 0.48
Therefore, if the liner must transmit 3 times the light that the liner and label transmits, the
transmission optical density of the liner must be 0.48 less than the transmission optical density of
the liner and label.
BLACK STRIPE OPTICAL DENSITY
If only 0.5 % of incident light is transmitted through the black stripe, the optical density is:
log
10
(100 / 0.5) = log
10
(200) = 2.3
The purpose of specifying a transmission optical density of at least 2.3 for the printed black stripe
on the back of the label is to minimize any variation in light transmission as a result of black pre-
printing on the front of the label. This variation due to black preprinting can cause the gap sensor to
give gap detection errors.
UC-ST User’s Guide
5-9