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EVALUATION OF THE SCRATCH RESISTANT LAYER (UHC) ON AN ABRASER |
Introduction
This report compares the scratch-resistant qualities of a standard DVD-R and a DVD-R with a “UHC” scratch-resistant layer.
DESCRIPTION OF THE EXPERIMENT
The 5135 abraser used in this experiment applied a uniform abrasive pressure to the surface of the disc. The discs were then studied with the aid of a microscope, in order to observe the state of their surface and to view the scratching.
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Photo 1: 5135 abraser used for this test.This is a device commonly used in the optical disc industry to evaluate the hardness of materials.
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| Photo 2: Result after testing on the 5135 abraser of a standard DVD-R and a DVD-R with a “UHC” scratch-resistant layer |
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| DVD-R with no "UHC" layer after ten cycles of abrasion |
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| DVD-R with "UHC" layer after ten cycles of abrasion |
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Results
The consequences of the scratches for the reading of the two types of disc were analysed after various numbers of abrasion cycles on a CATS DVD device (an industrial quality control system for CD/DVDs). The PiSum 8 method which counts the number of errors measured per second of reading of a recorded disc was used as the comparison criterion. This standard allows 280 read errors per second as the upper limit acceptable but in reality discs are readable up to 560 errors.
Tests were carried out, varying the number of abrasion cycles. The discs without the “UHC” scratch-resistant protective layer gave mediocre results. Actually, even after just a single abrasion cycle, the discs showed numerous read errors.
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Discs with “UHC” layer
(max PiSum 8) |
Standard discs without “UHC” layer
(max PiSum 8) |
| 1 cycle |
not tested |
1050
(Read errors) |
| 5 cycles |
90 |
1050
(Read errors) |
| 10 cycles |
140 |
1050
(Read errors) |
| 20 cycles |
195 |
1050
(Read errors) |
| 30 cycles |
300 |
1050
(Read errors) |
| 40 cycles |
420 |
1050
(Read errors) |
| 50 cycles |
600 |
1050
(Read errors) |
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Photo 3:Test result for a DVD-R with a UHC surface after ten abrasion cycles on the 5135 abraser. |
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Table 1 :Number of read errors between a standard DVD-R and a DVD-R with a “UHC” scratch-resistant layer, varying the number of abrasion cycles. The figures relate to the average value of PiSum 8 measured on three discs in the area between 24 and 45 mm radii. |
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Photo 4 : Résultat du test d’abrasion entre DVD-R standard et DVD-R comprenant la couche anti-rayures « UHC » en faisant varier le nombre de cycles d’abrasion. Les chiffres correspondent à la valeur moyenne du PiSum 8 mesurée sur 3 disques sur la zone allant de 24 à 45 mm de rayon.
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The surface of the discs was looked at under a microscope The findings were that the scratches present on the discs without a scratch-resistant surface were more numerous and deeper than those counted on discs with the “UHC” surface coating. |
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| Without “UHC” layer after 10 cycles |
Without “UHC” layer after 50 cycles |
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| With “UHC” layer after 10 cycles |
With “UHC” layer after 50 cycles |
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Figure 5: Microscopic views of scratched discs after 10 and 50 cycles. Enlarged five times under a microscope
Conclusion
“UHC” surface coating provides excellent protection against scratches. Actually, discs coated with a scratch-resistant layer withstood up to 40 or 50 abrasion cycles while the discs without protection already showed evidence of problems after the first abrasion cycle.
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