Liquid crystal compound and liquid crystal composition

A compound as represented by formula I,

• in said formula I, R1 represents an alkyl having a carbon atom number of 1-9, a fluoro-substituted alkyl having a carbon atom number of 1-9, an alkoxy having a carbon atom number of 1-9, a fluoro-substituted alkoxy having a carbon atom number of 1-9, an alkenyl having a carbon atom number of 2-9, a fluoro-substituted alkenyl having a carbon atom number of 2-9, an alkenyloxy having a carbon atom number of 3-8, or an alkenyloxy having a carbon atom number of 3-8;
• represents 1,4-phenylene, fluoro-substituted 1,4-phenylene, 1,4-cyclohexylidene, 1,4-cyclohexenylene, or 1,4-cyclohexylidene with one or two —CH2-being substituted by oxygen atoms;
• X1 and X3 each independently represent hydrogen or fluorine;
• and
• X2 represents hydrogen, fluorine, an alkyl having a carbon atom number of 1-9, an alkoxy having a carbon atom number of 1-9, a fluoro-substituted alkyl having a carbon atom number of 1-9, a fluoro-substituted alkoxy having a carbon atom number of 1-9, or an alkenyl having a carbon atom number of 2-9;
• wherein said fluoro-substituted 1,4-phenylene in said
• and
• wherein said 1,4-cyclohexylidene with one or two —CH2— being substituted by oxygen atoms in said