Following the merger agreement by the firms, SB Acquisition Company, which owns nearly 75% of the outstanding shares of common stock of Pacific Capital Bancorp also approved the agreement by written consent.

Union Bank president and chief executive officer Masashi Oka said the acquisition allows it to extend its community-focused banking services to customers in Santa Barbara and Central Coast regions.

"As a responsible California-based bank that has provided services to Californians for nearly 150 years, our approach and focus on long-term customer and community relationships will be a perfect fit with Pacific Capital Bancorp," Oka said.

The deal is expected to close in the fourth quarter of 2012, which is subject to approval from banking regulators and other customary closing conditions.

Upon completion of the transaction of Pacific Capital Bancorp and its primary bank operations including Santa Barbara Bank & Trust, Union Bank will be able to expand its geographic footprint to important areas of the Central Coast, said the bank.

The deal will strengthen Union Bank’s ability to serve customers through community banking, consumer, commercial and small business lending and wealth management, claims UNBC.

UnionBanCal Corporation obtained financial advice form Morgan Stanley & Company, while Sullivan & Cromwell provided legal counseling.

As on 31 December 2011, UnionBanCal owned assets of $89.7bn and is a wholly-owned subsidiary of The Bank of Tokyo-Mitsubishi UFJ, which is a subsidiary of Mitsubishi UFJ Financial Group.