| OHARA's GD-FHT is a glass disk for use in flying height testers. It contributes to the decrease of static breaking in the magnetic head, both in manufacturing and R&D. This obvious advantage is due to the superior electrical properties of GD-FHT compared to conventional products, such as S-BSL7 and Synthetic Fused Silica. As the glide height of the magnetic head is lowered, we offer our "smooth type" GD-FHT which is an extremely precise, super smooth and ultra-clean disk. OHARA's GD-FHT is transparent with the same mechanical strength as conventional products. |
|
 |
We offer ex-stock "GD-FHT smooth type" and disks with improved mechanical properties.
Please do not hesitate to contact us.
GD-FHT
| Properties |
GD-FHT |
Conventional Materials |
| S-BSL7 (BK7) |
Synthetic
Fused Silica |
Electrical
Properties |
Volume Resistivity* (Ω·cm) |
1.1×1011 |
1.0×1015 |
1.0×1019 |
| Surface Resistivity*** (Ω·□) |
4.4×1012 |
1.0×1015 |
8.6×1014 |
| Charging Voltage*** kV |
0.05 |
2.6 |
3.1 |
| Half Decay Period*** (s) |
8.9 |
>30min |
>30min |
Mechanical
Properties |
Knoop Hardness** Hk |
590 (6) |
570 (6) |
640 (6) |
| Abrasion** |
53 |
94 |
59 |
| Young's Modulus (GPa) |
82 |
80 |
71 |
| Rigidity Modulus (GPa) |
33 |
33 |
31 |
| Bending Strength (MPa) |
107 |
64 |
69 |
| Poisson's Ratio |
0.22 |
0.21 |
0.17 |
Thermal
Properties |
CTE (10-7/K) |
33 |
72 |
5.5 |
*Measured at 20°C and Humidity of 60% according to JIS K 6911.
**Measured according to Japanese Optical Glass Industrial Standards (JOGIS).
***Measured referring to JIS L 1094 (OHARA's original method).
·Half decay period is the time required for the charging voltage of the surface to half of its initial value. |
Transmittance
(%) |
Wavelength nm |
400 |
500 |
600 |
700 |
| 2.45mmt |
89.8 |
91.4 |
91.6 |
92.0 |
| 2.76mmt |
89.8 |
91.3 |
91.6 |
92.0 |
| 4.35mmt |
88.5 |
90.9 |
91.3 |
91.6 |
| 6.44mmt |
87.4 |
90.7 |
91.3 |
91.6 |
| Refractive Indices |
436nm |
1.539 |
| 486nm |
1.534 |
| 546nm |
1.530* |
| 588nm |
1.528 |
| 633nm |
1.526* |
| 656nm |
1.525 |
| *Calculated Value n=0.00482/λ2+1.51362 n: Refractive Index λ: Wavelength μm) |
| Specifications |
Outer Diameter mm |
48-133 |
| Inner Diameter mm |
5-10 |
| Thickness mm |
2-8 |
| Concentricity μm |
5-10 |
Roundness of Inner
Diameter μm |
≤5-10 |
| Parallelism μm |
≤5-10 |
| Flatness μm |
≤0.5 |
| Roughness Rmax nm |
≤2.5-4.0 |
Properties subject to change along development.
