Hard edge painting
A term descriptive of paintings whose surfaces are treated as a single flat unit with emphasis on symmetry and geometry and limited areas of color that are separated from one another by 'hard edges'. The phrase was first used as a formal description in Los Angeles in 1958 by critic Jules Langsner to describe West Coast painting by artists rebelling against the prevalent East-Coast subjective styles of Expressionism and Gesturalism, exemplified in New York by Jackson Pollock and other Abstract Expressionists. Hard-Edge Painting was popular through the 1950s, and was practiced by such painters as Kenneth Noland, Ellsworth Kelly, and Karl Benjamin, Ad Reinhardt, Leon Polk Smith, Barnett Newman, Mark Rothco and Alexander Liberman. Source: Robert Atkins, "Art Speak"; "Phaidon Dictionary of Twentieth Century Art"