Smectic liquid crystal composition and liquid crystal display

A smectic liquid crystal composition having a layer construction in a liquid crystal molecular arrangement, which comprises a mixed composition of at least one type of first smectic liquid crystal compound,

• wherein a difference between a maximum value and a minimum value of a layer spacing of the layer construction in a temperature range from a temperature which gives the minimum value for the layer spacing to -20.degree. C. or a crystallization temperature for compounds which have a crystallization temperature higher than -20.degree. C., is not greater than 0.1 nm, and
• at least one type of second smectic liquid crystal compound with variable temperature dependency of the layer spacing, the proportion of said first smectic liquid crystal compound to said mixed composition being at least 45 wt %,
• wherein said first and second smectic liquid crystal compounds are antiferroelectric liquid crystal compounds, the molecular structures of the antiferroelectric liquid crystal compounds being represented by the following structural formula (2) or (3):
• ##STR28## wherein R.sub.1 and R.sub.2 represent alkyl groups, alkoxy groups, alkylcarbonyl groups or alkylcarbonyloxy groups of 2 to 20 carbon atoms, and Z.sub.1, Z.sub.2 and Z.sub.3 each independently represent a hydrogen atom or halogen atom, and at least one thereof is a halogen atom;
• and ##STR29## wherein CH.sub.2 .dbd.R'.sub.1 represent alkenyl groups, alkenyloxy groups, alkenylcarbonyl groups or alkenylcarbonyloxy groups of 3 to 21 carbon atoms, R.sub.2 represents alkyl alkylcarbonyloxy groups of 2 to 20 carbon atoms, and Z.sub.4, Z.sub.5 and Z.sub.6 each independently represent a hydrogen atom or a halogen atom.

A smectic liquid crystal composition having a layer construction in a liquid crystal molecular arrangement, which comprises a mixed composition of at least one type of first smectic liquid crystal compound,

• wherein a difference between a maximum value and a minimum value of a layer spacing of the layer construction in a temperature range from a temperature which gives the minimum value for the layer spacing to -20.degree. C. or a crystallization temperature for compounds which have a crystallization temperature higher than -20.degree. C., is not greater than 0.1 nm, and at least one type of second smectic liquid crystal compound with variable temperature dependency of the layer spacing, the proportion of said first smectic liquid crystal compound to said mixed composition being at least 45 wt %,
• wherein the values for the layer spacing of said second smectic liquid crystal compound in the temperature range from the temperature which gives the minimum value for the layer spacing to the crystallization temperature, the difference between the maximum value and the minimum value is greater than 0.1 nm and not greater than 0.4 nm,
• wherein the first smectic liquid crystal compound is represented by the following chemical structural formula (2) and the second smectic liquid crystal compound is represented by the following chemical structural formula (1):
• ##STR30## wherein R.sub.1 and R.sub.2 represent alkyl groups, alkoxy groups, alkylcarbonyl groups or alkylcarboxy groups of 2 to 20 carbon atoms;
• and Z.sub.1, Z.sub.2 and Z.sub.3 each independently represent a hydrogen atom or halogen atom, and at least one thereof is a halogen atom.

A liquid crystal display comprising a smectic liquid crystal composition having a layer construction in the liquid crystal molecular arrangement,

• wherein said smectic liquid crystal composition comprises a mixed composition of at least one type of first smectic liquid crystal compound,
• wherein the difference between a maximum value and a minimum value of a layer spacing of the layer construction in a temperature range from a temperature which gives the minimum value for the layer spacing to -20.degree. or crystallization temperature for compounds which have a crystallization temperature higher than -20.degree., is not greater than 0.1 nm, and
• at least one type of second smectic liquid crystal compound with variable temperature dependency of the layer spacing, wherein of the values for the layer spacing of said second smectic liquid crystal compound in the temperature range from the temperature which gives the minimum value for the layer spacing in the crystallization temperature, the difference between the maximum value and the minimum value is greater than 0.1 nm and not greater than 0.4 nm,
• and wherein the proportion of said first smectic liquid crystal compound in said mixed composition is a proportion such that when said liquid crystal cell is subjected to a cold/hot temperature cycle wherein the temperature is lowered from the temperature which gives the minimum value for the layer spacing of said smectic liquid crystal composition to -20.degree. or crystallization temperature for compounds which have a crystallization temperature higher than -20.degree. and then raised again to the temperature which gives the minimum value for the layer spacing of said smectic liquid crystal composition, the relative change (T.sub.2 -T.sub.1) between a dark luminance T.sub.1 (%) during periods of dark indication of said liquid crystal cell at said temperature prior to said cold/hot temperature cycle and a dark luminance T.sub.2 (%) during dark indication of said liquid crystal cell at said temperature after said cold/hot temperature cycle is no greater than 0.1%,
• wherein said first and second smectic liquid crystal compounds are antiferroelectric liquid crystal compounds, molecular structures of the antiferroelectric liquid crystal compounds being represented by the following structural formula (2) or (3):
• ##STR31## wherein R.sub.1 and R.sub.2 represent alkyl groups, alkoxy groups, alkylcarbonyl groups or alkylcarbonyloxy groups of 2 to 20 carbon atoms, Z.sub.1, Z.sub.2, and Z.sub.3 each independently represent a hydrogen atom or halogen atom, and at least one thereof is a halogen atom;
• and ##STR32## wherein CH.sub.2 .dbd.R'.sub.1 represent alkenyl groups, alkenyloxy groups, alkenylcarbonyl groups or alkenylcarbonyloxy groups of 3 to 21 carbon atoms, R.sub.2 represent alkyl groups, alkoxy groups, alkycarbonyl groups or alkylcarbonyloxy groups of 2 to 20 carbon atoms, and Z.sub.4, Z.sub.5 and Z.sub.6 each independently represent a hydrogen atom or a halogen atom.

A smectic liquid crystal composition having a layer construction in a liquid crystal molecular arrangement, which comprises a mixed composition of at least two types of compounds, each compound of said composition having a difference between a maximum value and a minimum value for the layer spacing in a temperature range from a temperature which gives the minimum value for the layer spacing to -20.degree. C. or a crystallization temperature for compounds which have a crystallization temperature higher than -20.degree. C., being not greater than 0.1 nm,

• wherein said two types of smectic liquid crystal compounds are antiferroelectric liquid crystal compounds, molecular structures of the antiferroelectric liquid crystal compounds being represented by the following structural formula (2) or (3):
• ##STR33## wherein R.sub.1 and R.sub.2 of structural formula (2) represent alkyl groups, alkoxy groups, alkylcarbonyl groups or alkylcarbonyloxy groups of 2 to 20 carbon atoms, Z.sub.1, Z.sub.2, and Z.sub.3 each independently represent a hydrogen atom or a halogen atom, and at least one thereof is a halogen atom;
• and ##STR34## wherein CH.sub.2 .dbd.R'.sub.1 represent alkenyl groups, alkenyloxy groups, alkenylcarbonyl groups of alkenylcarbonyloxy groups of 3 to 21 carbon atoms, R.sub.2 represent alkyl groups, alkoxy groups, alkylcarbonyl groups or alkylcarbonyloxy groups of 2 to 20 carbon atoms, and Z.sub.4, Z.sub.5, and Z.sub.6 each independently represent a hydrogen atom or a halogen atom.