It appears that Apple is investing in Toshiba as either an exclusive or additional iPhone 4 LCD panel supplier. Reuters has reported that Toshiba will "mainly" being supplying Apple. Leaving the door open to supply Android or Window devices I'd assume.
"The company’s wholly owned unit, Toshiba Mobile Display Co, will construct the facility in Ishikawa prefecture and the plant will churn out low-temperature polysilicon LCD panels, which allow for high-resolution images. Work on the plant will start by early next year, with the production due to begin in the second half of 2011"