Not to say 的 用法?

问题描述:

Not to say 的 用法?
大家好,我想请教一下not to say 的用法,请解释下面这个句子中not to say 的意思,并且再给我举一两个例子好嘛?谢谢了!
In Japan today throw-away tissues are so universal that cloth handkerchiefs are regarded as old fashioned, not to say unsanitary. 这个句子属于什么从句?句子成分是?

上句中Not to say意思为“更不要说”之意.