Charge control agent for fluid dynamic bearing motor lubricant
Embodiments disclosed herein generally relate to magnetic recording systems having a spindle motor and, more particularly, to an optimized lubricant for bearings within the spindle motor. A lubricant used in a fluid dynamic bearing motor has an antioxidant additive and a charge control agent dissolved in a diester base oil. The charge control agent is chemically attached to the same diacid reactant used in the diester lubricant base oil, and is prepared through an esterification reaction. The charge control agent is then dissolved in the lubricant base oil. The charge control agent is soluble in the lubricant, and is resistant to free radical oxidation. The charge control agent effectively controls the charge of the lubricant by creating electron donor/acceptor sites in the lubricant, facilitating an independent electronic pathway through the lubricant.
1. A solution, comprising:
a lubricant that includes a first acid reactant;
a soluble charge control agent including a second acid reactant; and
an antioxidant additive, wherein the first acid reactant and the second acid reactant are the same.
2. The solution of claim 1 , wherein the first and second acid reactants are sebacic acid.
3. The solution of claim 2 , wherein the soluble charge control agent is chemically attached to the lubricant through an esterification reaction.
4. The solution of claim 3 , wherein the soluble charge control agent is dibenzyl sebacate.
5. The solution of claim 4 , wherein one reactant used in the esterification reaction is benzyl alcohol.
6. The solution of claim 3 , wherein the soluble charge control agent is dinaphthyl sebacate.
7. The solution of claim 6 , wherein one reactant used in the esterification reaction is naphthyl alcohol.
8. The solution of claim 3 , wherein one reactant used in the esterification reaction is anthracene methanol.
9. The solution of claim 3 , wherein one reactant used in the esterification reaction is pyrene methanol.
10. The solution of claim 1 , wherein the soluble charge control agent is an asymmetric aryl ester.
11. The solution of claim 1 , wherein the first and second acid reactants are a poly-acid.
12. The solution of claim 1 , wherein the first and second acid reactants are a mono-acid.
13. The solution of claim 1 , wherein the relative permittivity of the lubricant and soluble charge control agent solution is between about 2.5 and 200.
14. The solution of claim 1 , wherein the relative permittivity of the lubricant and soluble charge control agent solution is less than 100.
15. The solution of claim 1 , wherein the conductivity of the lubricant and soluble charge control agent solution is between about 1 and 100 nS/m.
16. The solution of claim 1 , wherein the conductivity of the lubricant and soluble charge control agent solution is greater than 4 nS/m.
17. The solution of claim 1 , wherein the soluble charge control agent is an aryl ester, the concentration of the aryl ester charge control agent being 0.1 to 10% by weight.
18. The solution of claim 17 , wherein the concentration of the aryl ester charge control agent is between 1 and 5% by weight.
19. The solution of claim 1 , wherein the soluble charge control agent is an asymmetric aryl ester or an asymmetric alkyl ester that is liquid at room temperature.
20. The solution of claim 19 , wherein the asymmetric aryl ester or asymmetric alkyl ester is used as a base oil of the lubricant with a concentration of 90 to 100% by weight.