Scan time is a parameter of measurement performed in spectrophotometer. Here you can learn more.
Depending on the spectrophotometer scan time, acquisition time or integration time can be the same thing or each of them can be considered as separate parameter of the measurement. This mostly depends on the detector used in spectrophotometer.
Acquisition time (sampling time) is the time required for the Analog-to-Digital Converter (ADC) to capture the input voltage during measurement. Acquisition time is distinguished as separate parameter of the measurement mostly if in the spectrophotometer a CCD camera is used as detector.
Similarly, integration time determine the period of time over which the light detected by the CCD is summed (like setting the shutter speed of a film camera). The longer the integration time, the more light is absorbed and the larger the peaks in the spectra will appear.
Scan time dictate the time over which the scan of the full spectrum should be performed. It is also directly connected with the scan speed, which depends on data interval and resolution of the spectrophotometer.