* Idemitsu and Showa Shell jump after merger news
* Exporters lifted as yen drops to 1-week low vs dollar
* Yahoo Japan up, SoftBank Group to buy its shares via subsidiary
By Shinichi Saoshiro and Ayai Tomisawa
TOKYO, July 10 (Reuters) - Japan's Nikkei share average rose to a 1-1/2-week high on Tuesday as deals news added to a solid Wall Street performance, with oil refiners Idemitsu Kosan and Showa Sekiyu jumping after they said they had agreed to merge in April next year.
Shares of the two firms rallied 12.6 percent and 9.7 percent, respectively, after the announcement. They plan to merge via a share swap, and Showa Shell will be delisted on March 29.
Yahoo Japan was in the spotlight as well, surging 11 percent on news that SoftBank Group would buy roughly $2 billion worth of its shares through a subsidiary.
The Nikkei ended 0.7 percent higher at 22,196.89, its loftiest closing level since June 29.
Equities were boosted after the Dow and the S&P 500 posted their biggest gains in over a month overnight, with focus steadily turning away from U.S.-China trade angst that buffeted financial markets last week.
"Other markets are leaning towards 'risk on' and this is supportive for Japanese shares. There are also expectations that trade frictions won't worsen," said Chihiro Ohta, equity general manager at SMBC Nikko Securities, tipping the Nikkei to stretch its recent highs.
Exporters such as high-techs and automakers were buoyed by the yen's retreat to a one-week low against the dollar, with Tokyo Electron gaining 1.8 percent and Advantest Corp up 0.9 percent.
Honda Motor Co rose 1.0 percent and Nissan Motor Co gained 3.8 percent, despite the automaker's admission on Monday that it had improperly measured exhaust emissions and fuel economy for 19 vehicle models sold in Japan.
The broader Topix advanced 0.3 percent to 1,716.13. (Additional reporting by the Tokyo markets team Editing by Shri Navaratnam)