21 Applications of NIR Techniques in Polymer Coatings …
497
0
1 0
2 0
3 0
4 0
0
1
2
3
4
5
6
7
Opening: 15 %
Opening: 10 %
Speed 100 %
Speed 100 %
Speed 75 %
Speed 50 %
Gravimetric Coating Weight
Predicted Coating Weight
Coating Weight [g m
-2
]
Sheet Number
Fig. 21.12 In-line monitoring of the coating weight of a UV-curable printing varnish on paper in
a sheet-fed offset printing press (printing speed 8000 sheets/h). For comparison, coating weights
determined off-line by gravimetry are shown. Explanation of other labels is given in the text.
Reprinted with permission by SAGE Publications Ltd. from Ref. [31]
printing press that control the amount of ink or varnish on the printing plate. An
increase of these values corresponds to higher coating weights. The results demonstrate that the applied coating weight can be determined with very high precision.
The prediction error was found to be about 150 mg/m
2 .
Further studies on both printing inks and clear varnishes were directed toward
the investigation of the influence of different printing speeds [32], the recipe of the
varnish formulation [32], the color of the ink, the use of different paper and cardboard
materials as substrate [33] as well as different gloss levels of the printed layers [34]
on the accuracy of the prediction results. Complex calibration procedures including
multistage and universal calibration models were developed, which were adapted to
the requirements of each specific problem. Despite the rather low thickness of printed
layers, the precision of the predictions from NIR reflection spectra recorded in-line
is rather high: RMSEP values for the determination of the coating weight were found
to be in the order between 120 and 200 mg/m
2 .
21.2.5.2 Conversion of UV-Cured Printed Layers
Similar to UV-cured coatings, numerous factors in the printing process may influence the conversion of printed layers. This includes the characteristics of the ink or
varnish (e.g., its composition and viscosity), the ambient conditions (e.g. temperature, humidity), and technical factors such as UV irradiance, printing speed and the
497
0
1 0
2 0
3 0
4 0
0
1
2
3
4
5
6
7
Opening: 15 %
Opening: 10 %
Speed 100 %
Speed 100 %
Speed 75 %
Speed 50 %
Gravimetric Coating Weight
Predicted Coating Weight
Coating Weight [g m
-2
]
Sheet Number
Fig. 21.12 In-line monitoring of the coating weight of a UV-curable printing varnish on paper in
a sheet-fed offset printing press (printing speed 8000 sheets/h). For comparison, coating weights
determined off-line by gravimetry are shown. Explanation of other labels is given in the text.
Reprinted with permission by SAGE Publications Ltd. from Ref. [31]
printing press that control the amount of ink or varnish on the printing plate. An
increase of these values corresponds to higher coating weights. The results demonstrate that the applied coating weight can be determined with very high precision.
The prediction error was found to be about 150 mg/m
2 .
Further studies on both printing inks and clear varnishes were directed toward
the investigation of the influence of different printing speeds [32], the recipe of the
varnish formulation [32], the color of the ink, the use of different paper and cardboard
materials as substrate [33] as well as different gloss levels of the printed layers [34]
on the accuracy of the prediction results. Complex calibration procedures including
multistage and universal calibration models were developed, which were adapted to
the requirements of each specific problem. Despite the rather low thickness of printed
layers, the precision of the predictions from NIR reflection spectra recorded in-line
is rather high: RMSEP values for the determination of the coating weight were found
to be in the order between 120 and 200 mg/m
2 .
21.2.5.2 Conversion of UV-Cured Printed Layers
Similar to UV-cured coatings, numerous factors in the printing process may influence the conversion of printed layers. This includes the characteristics of the ink or
varnish (e.g., its composition and viscosity), the ambient conditions (e.g. temperature, humidity), and technical factors such as UV irradiance, printing speed and the