Polycarbonate and method of preparing the same

A polycarbonate containing about 1˜50 mol % of repeating units of Formula 4 based on the whole repeating units, and having a glass transition temperature of about 130 to about 190° C., a flame retardancy of V-0, as measured on a 3.2 mm thick specimen according to the UL-94, a notched IZOD impact strength of about 25 to about 120 kg·cm/cm, as measured on a ⅛″ thick specimen at room temperature according to ASTM D256, and a transmittance difference (ΔT) of about 12% or less, as calculated by the following Equation 1:

• wherein R1 and R2 are each independently substituted or unsubstituted C1 to C6 alkyl group, substituted or unsubstituted C3 to C6 cycloalkyl group, substituted or unsubstituted C6 to C12 aryl group or halogen atom;
• R3 is substituted or unsubstituted C1 to C6 alkyl group, substituted or unsubstituted C6 to C12 aryl group, substituted or unsubstituted C7 to C20 aralkyl group, a and b are each independently an integer from 0 to 4, and n is 0 or 1,
• Δ
• ⁢
• ⁢
• T
• =
• T
• 0
• -
• T
• 1
• T
• 0
• ×
• 100
• [
• Equation
• ⁢
• ⁢
• 1
• ]
• wherein, T0 is initial visible light transmittance of a 2.5 mm thick sample, and T1 is visible light transmittance of the sample obtained by immersing the sample in a solution consisting of methyl isobutyl ketone, cyclohexanone and 2-ethoxy ethanol for 2 minutes and then drying the sample at 80° C. for 30 minutes.

A method of preparing polycarbonate, comprising transesterifying diols comprising Formula 1-1 and Formula 2-1 with carbonate ester and phosphate ester:

• wherein R1 and R2 are each independently substituted or unsubstituted C1 to C6 alkyl group, substituted or unsubstituted C3 to C6 cycloalkyl group, substituted or unsubstituted C6 to C12 aryl group or halogen atom, and a and b are each independently an integer from 0 to 4;
• and
• wherein R1 and R2 are each independently substituted or unsubstituted C1 to C6 alkyl group, substituted or unsubstituted C3 to C6 cycloalkyl group, substituted or unsubstituted C6 to C12 aryl group or halogen atom;
• and a and b are each independently an integer from 0 to 4.