The highest contrast ratio of the LS23C350 is 1000:1. That's 100% less contrast ratio than a 20000000:1 LCD screen, which is the most common contrast ratio. The best contrast ratio of all medium monitors that are a comparable age to the LS23C350 is 100000000:1 and the worst is Mega Contrast.
There are a number of alternative PC screens that have a 1000:1 dynamic contrast ratio currently available that you might want to consider including the LG 23M45 (£106.58) which is cheaper; or the LG 24M45 (£115.81), or the Viewsonic VA2246 (£122.40) which has a better Rating.
If the contrast ratio of this LCD screen is not high enough for you then you might want to look at the iiyama X2485WS (£220.36) (3000:1 and higher rated), or the Benq BL2410 (£172.11) (3000:1 and higher rated).