The highest contrast ratio of the ES240d Slim is 10000:1. That's 100% less contrast ratio than a 20000000:1 PC monitor, which is the most common contrast ratio. Flatpanel monitors of a similar type and age to the ES240d Slim dynamic contrast ratios range from Mega Contrast (worst) to 100000000:1 (best).
Alternative PC screens that have a 10000:1 dynamic contrast ratio currently available which you might also want to consider include cheaper LCD screens such as the EB220H (£112.83), or the ET220a both from Edge10.
If the contrast ratio of this LCD screen is not high enough for you then you might also want to consider the LG E2442TC (500000:1), the Benq GW2460HM (£129.43) (2000000:1), or the Lenovo LT2423 (£60.00) (2000000:1).