One of the largest corporate design firms on the West Coast has been purchased by Los Angeles-based Chiat/Day. Bright & Associates, a Los Angeles company that has created new corporate designs for such clients as National Car Rental, Ryder Systems and L'Ermitage Hotels, was purchased for an undisclosed sum by the ad firm. The purchase takes effect Nov. 1. Bright & Associates, which posted billings of about $3 million last year, will operate as an independent subsidiary of Chiat/Day. Eventually, the design firm may be asked to help design a new corporate logo for Nissan, Chiat/Day's recently acquired account. "That's not why we were purchased," said Keith Bright, who will remain president of the 10-year-old design firm, "but I suspect down the road we'll be asked to take a look at Nissan's logo." The design firm, which employs 40 workers, also developed a series of designs that were used in signs to identify the various athletic events for the 1984 Los Angeles Olympics, like the ones above.