Liquid crystal compounds containing a difluoromethyleneoxy linking group that hydrogen substituted by deuterium, their preparation and application

A liquid-crystalline compound comprising:

• a compound of formula I:
• wherein, R1, R2 are selected from the group consisting of H, Cl, F, CN, OCN, OCF3, CF3, CHF2, CH2F, OCHF2, SCN, NCS, SF5 or alkyl having 1 to 15 carbons, fluorinated alkyl having 1 to 15 carbons, chlorinated alkyl having 1 to 15 carbons, deuterated alkyl having 1 to 15 carbons, alkoxy having 1 to 15 carbons, fluorinated alkoxy having 1 to 15 carbons, chlorinated alkoxy having 1 to 15 carbons, deuterated alkoxy having 1 to 15 carbons, alkenyl having 2 to 15 carbons, fluorinated alkenyl having 2 to 15 carbons, chlorinated alkenyl having 2 to 15 carbons, deuterated alkenyl having 2 to 15 carbons, alkenoxy having 1 to 15 carbons, fluorinated alkenoxy having 1 to 15 carbons, chlorinated alkenoxy having 1 to 15 carbons, deuterated alkenoxy having 1 to 15 carbons, cyclopropane, cyclobutane, cyclopentane, cyclohexane, and cycloheptane wherein one or more —CH2— independently of one another are replaced by —CH═CH—, —C≡C—, —COO—, —OOC—, —O— or —S—;
• wherein rings A1, A2 and A3 are independently selected from the group consisting of:
• wherein ring B is selected from the group consisting of:
• which may be monosubstituted or polysubstituted by fluorine, deuterium, chlorine;
• wherein l is 0, 1;
• m is 0, 1;
• n is 0, 1;
• wherein Z1, Z2 and Z3 are selected from the group consisting of —CH2—, —CH2—CH2—, —(CH2)3—, —(CH2)4—, —CH═CH—, —C≡C—, —COO—, —OOC—, —CF2O—, —OCH2—, —CH2O—, —OCF2—, —CF2CH2—, —CH2CF2—, —C2F4—, —CF═CF— and single bond;
• and
• wherein L1, L2 and L3 are selected from the group consisting of H, F, Cl and D.