Paper, the Fifth Color
Current Classifications
Optical Brighteners
By Trish Wales
Sappi Fine Paper
March 15,2006
April 9, 2006
First Segmentation
U.S. vs. EU
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•
•
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Coated
Supercalendered
Newsprint
Uncoated
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•
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Coated
Supercalendered
Newsprint
Uncoated
U.S. Coated Paper Classification
Classification
Brightness
[Tappi T452]
Classification
Brightness
[Tappi T452}
Premium
94+
Premium
N/A
No. 1 Coated
91-94
No. 1 Coated
N/A
No. 2 Coated
87-91
No. 2 Coated
87+
No. 3 Coated
82-87
No. 3 Coated
82-87
No. 4 Coated
75-82
No. 4 Coated
75-82
No 5 Coated ]
N/A
No. 5 Coated
Under 75
Coated Free Sheet
Classification
Coated Groundwood
Classification
Supercalendered Classification
GE Brightness
750 Gloss
SC-A++
> 73
> low 50's
SC-A+
70-72
High 40's - low 50's
SC-A
67-69
High 30's - low 40's
SC-B
64-66
Low 30's
SC-C
60-64
Low 30's or <
Uncoated Paper Classification
• Quality and Use
– Offset
Utility Opaque
Premium Opaque
Copy Paper
– Text and cover
• Writing Papers
• Bristols
– Newsprint
• Finish
– Smooth
– Vellum
– Embossed
• Laid
• Wove
Brightness
Brightness
Illuminant
Ink Film
Paper
Brightness is measured at one wave length
457 nm
Test Methods
Brightness
TAPPI - Paper
(GE Brightness)
ISO - Paper
Standard ID
TAPPI T452
ISO 2469, 2470
Geometry
Directional
Diffuse
Illuminant
C
D65 [C]
Test Comparison
BRIGHTNESS
110
105
100
95
ISO C
ISO D65
90
85
TAPPI C
80
75
0
1
2
Paper Grades
3
4
European Classification
• Related to paper manufacturing process
• Separated by fiber type
• Number of coating layers considered
European Papers
Art
Chemical Pulp
Std WFC
UWF
HWC
MWC
Mechanical Pulp
Std. LWC
Relative
FCO
MFC
Price
SC
Newsprint
Relative Quality
ISO 12647-2
• Five types
• Optical characterization
• Shade/Gloss
ISO 12647-2 Categories
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•
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1. Gloss Coated, woodfree
2. Matte Coated, woodfree
3. Gloss Coated, web
4. Uncoated, white
5. Uncoated, slightly yellowish
Paper Types
Type
L*
Black
L*
White
a*
Black
a*
White
b*
Black
b*
White
Gloss/
ISO BRT
1
93
95
0
0
-3
-2
65/89
2
92
94
0
0
-3
-2
38/89
3
87
92
-1
0
3
5
55/70
4
92
95
0
0
-3
-2
6/93
5
88
90
0
0
6
9
6/73
+/-3
+/-2
+/-2
+/-2 +/-2
Toler +/-3
ance
+/-5
Fluorescence
Optical Brighteners
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Prevalent
Increasing
Measurement nightmare
Visual Matching challenge
What are they?
• Chemical additives
– Textiles
– Paints
– Paper
Paper OBA Properties
• Absorb light in UV
More UV, more absorbed, more emitted
• Emit in blue region
No UV, no emission
• Unstable in light
– Paper goes from white to yellow
Re-Emission
Optical Brighteners
Absorption
300
100
50
350
0
400
-50
-100
450
500
550
600
Wavelength in nm
650
700
OBA affects Print
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•
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See effect in the white spaces
See effect through cyan ink
Effect blocked by magenta and black ink
Yellow ink effect depends on ink
transparency
• On-line measurements give false reading
– Pulsed Xenon
– White point compensation
Optical Brighteners
2/27/04 Spectral Curves
Control
95
Value
90
85
80
400
500
600
700
Wavelength
2/27/04 Spectral Curves
Appearance
105
100
Value
95
90
85
80
400
500
600
Wavelength
700
Questions????