UPDATE 1-Merck extends AZ offer again over Chinese antitrust issues
* Offer period extended for sixth time
* Now runs until May 2
* Merck says 67.5 pct of shares tendered (Adds more comment from Merck, background on deal)
FRANKFURT, April 18 (Reuters) - German liquid crystal maker Merck KGaA extended the offer period for its planned takeover of AZ Electronic Materials for a sixth time on Friday as it continues to seek Chinese antitrust approval.
The offer period has been extended to until 1200 GMT on May 2, Merck said in a statement.
It said China's Ministry of Commerce had "raised certain specific concerns that Merck is working with the Chinese authorities to address".
"Merck is confident that there will be a satisfactory explanation or solution to these concerns," it added.
The world's largest maker of liquid crystals used in TVs and tablet and smartphone screens agreed in December to buy AZ for $2.6 billion to expand its range of specialist chemicals for hi-tech gadgets.
AZ Electronic generates the bulk of its revenue in Asia. China's new-found clout in regulating global mergers is causing headaches for some companies seeking deals that need Beijing's approval.
Merck said it had received valid acceptances of the offer representing approximately 67.53 percent of AZ by 1200 GMT on April 18.
Merck in March lowered the minimum acceptance threshold among AZ shareholders to 75 percent from 95 percent once the deal had been approved in China.