I did a little research on the Japanese wikipedia page for the stadium and got my answer. To fully explain it though, I need to give a little background about the home stadiums of the Kintetsu Buffaloes. I've been confused for a while about what stadium actually was the home of the Buffaloes up until the late 1980's as I had seen things that indicated both Fujiidera and Nippon Life Stadiums were the Buffaloes home park. It turns out that they both were. They apparently used Nippon Life Stadium during the week as it only sat around 20,000 fans and used Fujiidera Stadium on weekends and holidays as it sat 30,000 fans. Kintetsu decided to renovate the stadium in 1973 to add more seating to the outfield and to add lights. The people living around the ballpark, however, were concerned about the light and noise that having night games at the stadium would cause and went to court to prevent the team from adding the lights. The case took 10 years to get resolved in Kintetsu's favor and Fujiidera Stadium hosted its first night game in April of 1984. I'm not positive but I think they stopped playing weekday games at Nippon Life Stadium after that.
Here's some photos I scanned from the book. First here's a shot showing the ballpark right before the renovations in 1973:
I think this is a protest by the local residents:
Here's the light-less light towers:
The lack of lights had forced the Buffaloes to host their Nippon Series games in 1979 and 1980 in nearby Osaka Stadium but now that they had lights, they were able to play at Fujiidera Stadium when they reached the Series again in 1989.
Here's what the ballpark looked like in 1991, just a few years before the Buffaloes would move to the Osaka Dome in 1996:
|1992 BBM #109|