Demand for the bookbuild segment came in at about S$4.4 billion versus the S$230 million worth of shares being offered, said one of the sources who declined to be named as the information is not public.

"This is a total blow out. We had to stop taking orders early," said another source.

The IPO is set to be the largest on the Singapore Exchange in recent years, excluding those from real estate investment trusts for which the exchange has become a global hub over the past decade.

Nanofilm, which is set to have a market value of about S$1.7 billion, is expected to list on Oct 30.

A spokeswoman for Nanofilm, which makes coating materials for smartphones, televisions and smartwatches among others, declined to comment on subscription levels.

Nanofilm said last week it had secured 13 cornerstone investors, including subsidiaries of state investor Temasek Holdings, marking a rare move by Temasek firms to invest in local IPOs recently. Cornerstone investors are taking up just over 50% of Nanofilm's total offering. [L4N2H72GM]

Founded in 1999 as a technology spin-off from Singapore's Nanyang Technological University by Shi Xu, a professor, Nanofilm counts Canon and Microsoft among its 300-plus customers. Xu is the company's executive chairman.

Citi, Credit Suisse and OCBC Bank are joint global coordinators and bookrunners on the IPO with investment bank CLSA.

($1 = 1.3582 Singapore dollars)

(Reporting by Anshuman Daga; editing by Jason Neely and Emelia Sithole-Matarise)

By Anshuman Daga