The 231E1SB has a maximum contrast ratio of 25000:1. That's 100% less contrast ratio than the most common dynamic contrast ratio of 20000000:1. Across all PC monitors of a similar spec and age to the 231E1SB the contrast ratio ranges from Mega Contrast (worst) to 100000000:1 (best).
Alternative PC screens that have a 25000:1 dynamic contrast ratio currently available which you might want to look at include the MultiSync EA234 (£234.00), or the MultiSync EA244WMI (£331.93) both from NEC which has a better Rating.
If the contrast ratio of this PC screen is too low for you then you might also want to consider the E2442TC (500000:1), or the 32WL30 (£521.80) (500000:1) both from LG.