We present results of optical identifications of the X-ray sources detected in the ASCA Large Sky Survey .
Optical spectroscopic observations were done for 34 X-ray sources which were detected with the SIS in the 2–7 keV band above 3.5 \sigma .
The flux limit corresponds to \sim 1 \times 10 ^ { -13 } { erg } { cm } ^ { -2 } { s } ^ { -1 } in the 2–10 keV band .
The sources are identified with 30 AGNs , 2 clusters of galaxies , and 1 galactic star .
Only 1 source is still unidentified .

All of the X-ray sources that have a hard X-ray spectrum with an apparent photon index of smaller than 1 in the 0.7–10 keV band are identified with narrow-line or weak-broad-line AGNs at redshifts smaller than 0.5 .
This fact supports the idea that absorbed X-ray spectra of narrow-line and weak-broad-line AGNs make the Cosmic X-ray Background ( CXB ) spectrum harder in the hard X-ray band than that of a broad-line AGN , which is the main contributor in the soft X-ray band .
Assuming their intrinsic spectra are same as a broad-line AGN ( a power-law model with a photon index of 1.7 ) , their X-ray spectra are fitted with hydrogen column densities of \log N _ { H } ( { cm } ^ { -2 } ) = 22 \sim 23 at the object ’ s redshift .
On the other hand , X-ray spectra of the other AGNs are consistent with that of a nearby type 1 Seyfert .
In the sample , four high-redshift luminous broad-line AGNs show a hard X-ray spectrum with an apparent photon index of 1.3 \pm 0.3 .
The hardness may be explained by the reflection component of a type 1 Seyfert .
The hard X-ray spectra may also be explained by absorption with \log N _ { H } ( { cm } ^ { -2 } ) = 22 \sim 23 at the object ’ s redshift , if we assume an intrinsic photon index of 1.7 .
The origin of the hardness is not clear yet .

Based on the logN-logS relations of each population , contributions to the CXB in the 2–10 keV band are estimated to be 9 % for less-absorbed AGNs ( \log N _ { H } ( { cm } ^ { -2 } ) < 22 ) including the four high-redshift broad-line AGNs with a hard X-ray spectrum , 4 % for absorbed AGNs ( 22 < \log N _ { H } ( { cm } ^ { -2 } ) < 23 , without the four hard broad-line AGNs ) , and 1 % for clusters of galaxies in the flux range from 3 \times 10 ^ { -11 } { erg } { cm } ^ { -2 } { s } ^ { -1 } to 2 \times 10 ^ { -13 } { erg } { cm } ^ { -2 } { s } ^ { -1 } .
If the four hard broad-line AGNs are included in the absorbed AGNs , the contribution of the absorbed AGNs to the CXB is estimated to be 6 % .

In optical spectra , there is no high-redshift luminous cousin of a narrow-line AGN in our sample .
The redshift distribution of the absorbed AGNs are limited below z = 0.5 excluding the four hard broad-line AGNs , in contrast to the existence of 15 less-absorbed AGNs above z = 0.5 .
The redshift distribution of the absorbed AGNs suggests a deficiency of AGNs with column densities of \log N _ { H } ( { cm } ^ { -2 } ) = 22 to 23 in the redshift range between 0.5 and 2 , or in the X-ray luminosity range larger than 10 ^ { 44 } erg s ^ { -1 } , or both .
If the large column densities of the four hard broad-line AGNs are real , they could complement the deficiency of X-ray absorbed luminous high-redshift AGNs .