Fully dispersible silicalite nanocrystals have been prepared by a newly developed method that leads to higher than 90% crystalline yield after a short hydrothermal treatment of a transparent semi-crystalline aged precursor sol. A coating sol could be prepared by the proper combination of these nanocrystals, the aged precursor sol and non-ionic surfactant with solvent. The resulted coating on glass substrate showed a broadband antireflection (AR) effect with less than 1% average reflection over the visible range. With proper control of the film thickness, one can shift the reflection minimum to achieve neutral colour. The same type of AR coating sol was further applied to transparent plastic web in a continuous fashion, which will be important to the future flexible display industry.