Everton chief Robert Elstone says their £12 million shirt deal with Chang will go to manager David Moyes' transfer kitty.
Moyes is believed to be on the look-out for a centre forward and a right-sided midfielder in January, and has been linked with a fresh loan move for USA captain Landon Donovan.
Elstone said: "It is a big increase on the current deal and allows us to flow that into our financial forecast and can only really strengthen our resolve to continue to strengthen the playing squad.
"There were other brands out there who were interested in sponsoring us, but it's a partnership that works for us and for them. We are proud that we will have had 12 years as commercial partners at the end of this new deal.
"It is the longest standing sponsorship in the league and it really is a great deal. It is important to have the security of a new deal on the table for the next three years, especially during these volatile economic times.
"I am sure all businesses in the world are looking where they should spend their money or cut back, and value for money will be massively important to them.
"It says a lot about what Chang think about is that they have agreed to this deal and all it entails."