X-ray emission in the water window spectral region (2.3-4.4 nm) from materials (carbon, aluminum, titanium, copper, and molybdenum) irradiated by a 5 J/35 ns slab glass laser was recorded with a grazing-incidence spectrometer for microscopy application. Carbon was determined to be the suitable source material for an x-ray microscopy experiment. The absolute spectral brightness of the CVI ls-2p line and CV 1s2-1s2p line emitted from the carbon plasmas was estimated to be approximately 1.0 X 10(16) photons/s/mm2/mrad2 in 0.1% bandwidth. The electron density and electron temperature of the carbon plasmas were derived from the x-ray spectra and the conditions for intense emission are also discussed.