A sapphire watch crystal is a watch screen that is fabricated using sapphire crystal. Sapphires are used due to their resistance and toughness as well as their aesthetic appearance.
Sapphire is the second strongest jewel on the Mohs mineral hardness scale, second only to the diamond. The crystal is usually made up of a sapphire-quartz combination. The screens are not completely shatter proof since strength is different than hardness, but it does mean that almost nothing other than diamond is able to scratch the face. This means that those who like to keep their watch faces completely scratch-free often go with this watch crystal.
There are many modern examples of using sapphire crystals as screens in watches and other devices. The Richard Mille watch series, including the Tourbillion, is one such example. Sapphire is tough, but it takes delicate work during machining. Such watches often take 1,000 hours of machining with up to 430 hours pre-forming case components and another 350 just for watch case polishing. Watches with sapphire crystals can often cost between $100 and $300 or more depending on the watch. They are also a common addition to diving watches due to their clearness and toughness despite water pressure of 50 meters or more.
| GENERAL | |||||
| Chemical Formula | Al2O3 | ||||
| Crystal Stucture | Hexagonal System ((hk o 1) | ||||
| Unit Cell Dimension | a=4.758 Å,Å c=12.991 Å, c:a=2.730 | ||||
| PHYSICAL | |||||
| Metric | English (Imperial) | ||||
| Density | 3.98 g/cc | 0.144 lb/in3 | |||
| Hardness | 1525 – 2000 Knoop, 9 mhos | 3700° F | |||
| Melting Point | 2310 K (2040° C) | ||||
| STRUCTURAL | |||||
| Tensile Strength | 275 MPa to 400 MPa | 40,000 to 58,000 psi | |||
| at 20° | 400 MPa | 58,000 psi (design min.) | |||
| at 500° C | 275 MPa | 40,000 psi (design min.) | |||
| at 1000° C | 355 MPa | 52,000 psi (design min.) | |||
| Flexural Stength | 480 MPa to 895 MPa | 70,000 to 130,000 psi | |||
| Compression Strength | 2.0 GPa (ultimate) | 300,000 psi (ultimate) | |||
| MODULUS | |||||
| Young’s Modulus, E | 345 GPa | 50 x 106 psi | |||
| (Modulus of Elasticity) | |||||
| Bulk Modulus, k | 250 GPa | 36 x 106 psi | |||
| (Modulus of Compression) | |||||
| Shear Modulus, G | 145 GPa | 21 x 106 psi | |||
| (Modulus of Rigidity) | |||||
| MOR | 350 MPa to 690 MPa | 50,000 to 100,000 psi | |||
| (Modulus of Rupture) | |||||
| Poisson’s Ratio | Sapphire is anisotropic. It is orientation dependent. | ||||
| THERMAL | |||||
| Thermal Conductivity | at 0° C | 46.06 W/(m • K) | 319.4 BTU in/hr ft2 °F | ||
| (60° orientation) | at 100° C | 25.12 W/(m • K) | 174.2 BTU in/hr ft2 °F | ||
| at 400° C | 12.56 W/(m • K) | 87.1 BTU in/hr ft2 °F | |||
| Specific Heat at 20° C | 0.187 cal/(g • °C) | 0.1827 BTU/lb °F | |||
| Heat Capacity | at 20° C | 18.63 cal/ (mole • °C) | 18.6 BTU/lb mole °F | ||
| at 1000° C | 29.86 cal/ (mole • °C) | 29.9 BTU/lb mole °F | |||
| Thermal Expansion Coefficient | 20° to 50° C | 5.8 x 10-6/ °C | 3.2 x 10-6/ °F | ||
| (60 degree orientation) | 20° to 500°C | 7.7 x 10-6/ °C | 4.3 x 10-6/ °F | ||
| ELECTRICAL | |||||
| Frequency | E l to C axis | E ll to C axis | |||
| DielectricConstant | Loss Tangent | DielectricConstant | Loss Tangent | ||
| 1 MHz | 9.39 | 0.0001 | 11.58 | 0.0001 | |
| 3 GHz | 9.39 | <0.0001 | 11.58 | <0.0001 | |
| 8.5 GHz | 9.39 | <0.00002 | 11.58 | <0.00002 | |
| Volume Resistivity at 25 °C | 1014 ohm • cm |
Sapphire is, as stated above, an anisotropic crystal, and the values given above are average values. Please remember that this engineering data is representative only, and should not be considered absolute or warrantable.
Sapphire Features:
- Transmits Wavelengths Ranging From UV to Mid-Infrared
- Extreme Surface Hardness Chemical Resistance
- Thinner and Stronger than Standard Glass Windows
- High thermal conductivity
- High bulk damage threshold
Sapphire Applications
- Aircraft windows
- Submarine windows
- FLIR
- Medical/Life Sciences
- Industrial OEM
- Intelligence, surveillance & reconnaissance(ISR)
FAQ:
Q1. Are you a factory?
A1. Yes, we have a professional optical lens manufactruer in China.
Q2. What is the MOQ of optical lens?
A2. No MOQ for customer if optical lens is in stock. customized watch glass size is for 10pcs.
Q3: Can I customize the products based on my need?
A3.Yes, we can customize the material, specifications and optical coating for your optical components based on your needs.
Q4. How many days will samples be finished? How about mass products?
A4. Generally, we need 1~10 days to finish the sample production. As for the mass products, it depends on your order quantity.
Q5 What’s the deliver time?
A5. (1) For inventory: the delivery time is 5 workdays.
(2) For customized products: the delivery time is 7 to 25 workdays. According to the quantity.
Q6. How do you control lens quality?
A6. Producing process is in vacuum dust-free shop, like prepare material, mixed material and take out . Four times quality checking during production process.
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