Tape cassette with tape tension controlled by grease of a specified range of viscosity

A tape cassette comprising:

• a pair of reels mounted side by side, on which tape is wound;
• a cassette casing for rotatably enclosing said pair of reels therein;
• a driven roller being rotated by a drive device of a recording and/or reproducing apparatus, associated with said tape cassette, said driven roller rotatably supported by an upstanding roller shaft fixed on the wall of said casing;
• a pair of idle rollers, each rotatably supported by an upstanding roller shaft fixed on the wall of said casing;
• a endless flexible drive belt for drivingly engaging said driven roller and said idle rollers to rotate said reels, such that a portion of said drive belt between said driven roller and each idle roller pressingly contacts a portion of the outermost peripheral surface of the tape wound on each reel, said drive belt being driven according to rotation of said driven roller;
• means for controlling tape tension of the tape during operation of said tape cassette, said means including grease disposed between said associated rollers and shafts for lubricating the contacting surfaces therebetween, with a predetermined viscous drag;
• said grease including a viscosity coefficient of 50 to 500 P (poise) within a grease temperature range of -10.degree. to 60.degree. C.