8. An image reader, comprising: a reading unit configured to receive light reflected from a document; and an automatic document feeder configured to supply the document to the reading unit, the automatic document feeder having defined therein a document transfer channel along which the document travels within the automatic document feeder, the document transfer channel including an automatic document feeder (ADF) window through which the reading unit receives the light reflected from the document and a reference bar for positioning the document on the ADF window, wherein at least one of the reference bar and the ADF window comprises a surface having a surface tension that is less than or equal to about 40 dyne-per-centimeter, and wherein the at least one of the reference bar and the ADF window includes a base material and a surface material disposed on a surface of the base material, the surface material having a surface tension that is less than or equal to about 40 dyne-per-centimeter.
8. An image reader, comprising: a reading unit configured to receive light reflected from a document; and an automatic document feeder configured to supply the document to the reading unit, the automatic document feeder having defined therein a document transfer channel along which the document travels within the automatic document feeder, the document transfer channel including an automatic document feeder (ADF) window through which the reading unit receives the light reflected from the document and a reference bar for positioning the document on the ADF window, wherein at least one of the reference bar and the ADF window comprises a surface having a surface tension that is less than or equal to about 40 dyne-per-centimeter, and wherein the at least one of the reference bar and the ADF window includes a base material and a surface material disposed on a surface of the base material, the surface material having a surface tension that is less than or equal to about 40 dyne-per-centimeter. 10. The image reader according to claim 8 , wherein the surface material includes one or more of a PP-based resin, a PE resin, a PVC resin, a PVB-based resin, an F-based resin, silicon, EVA and amide.