Liquid crystal display and its manufacturing method

A liquid crystal display comprising:

• two opposed substrates and
• a liquid crystal layer sandwiched between the substrates,
• the liquid crystal layer comprising liquid crystal molecules whose orientation is changed from a splay orientation to a bend orientation for display by applying a voltage of not less than a threshold voltage to the liquid crystal layer,
• wherein a difference in absolute value between a pretilt angle of the liquid crystal molecules in the vicinity of one substrate and a pretilt angle of the liquid crystal molecules in the vicinity of the other substrate is not more than 0.7 degrees.

A liquid crystal display comprising:

• two opposed substrates and
• a liquid crystal layer sandwiched between the substrates,
• the liquid crystal layer comprising liquid crystal molecules whose orientation is changed from a splay orientation to a bend orientation for display by applying a voltage of not less than a threshold voltage to the liquid crystal layer,
• wherein both absolute values of pretilt angles of the liquid crystal molecules in the vicinity of one substrate and in the vicinity of the other substrate are not more than 4 degrees.

A method for manufacturing a liquid crystal display, the liquid crystal display comprising two opposed substrates and a

• liquid crystal layer sandwiched between the substrates, the liquid crystal layer comprising liquid crystal molecules whose orientation is changed from a splay orientation to a bend orientation for display by applying a voltage of not less than a threshold voltage to the liquid crystal layer,
• the method comprising:
• rubbing surfaces of the substrates to be in contact with the liquid crystal layer,
• wherein a rubbing density of the rubbing process is not less than 20000 mm2.

A method for manufacturing a liquid crystal display,

• the liquid crystal display comprising two opposed substrates and a liquid crystal layer sandwiched between the substrates, the liquid crystal layer comprising liquid crystal molecules whose orientation is changed from a splay orientation to a bend orientation for display by applying a voltage of not less than a threshold voltage to the liquid crystal layer;
• the method comprising:
• forming an alignment film precursor on surfaces of the substrates to be in contact with the liquid crystal layer;
• and
• firing the alignment film precursor to produce an alignment film,
• wherein the alignment film can reduce a variation in pretilt angle of the liquid crystal molecules in contact with the alignment film to not more
• than 0.5 degrees when a firing temperature is changed by 20%.

A method for manufacturing a liquid crystal display,

• the liquid crystal display comprising two opposed substrates and a liquid crystal layer sandwiched between the substrates, the liquid crystal layer comprising liquid crystal molecules whose orientation is changed from a splay orientation to a bend orientation for display by applying a voltage of not less than a threshold voltage to the liquid crystal layer;
• the method comprising:
• an inspection process after producing the liquid crystal display,
• wherein the inspection process is performed by applying a voltage of less than the threshold voltage to the liquid crystal layer and evaluating an area ratio of a region where the liquid crystal molecules having a molecular axis parallel to the substrates predominantly lie on one substrate side with respect to a central portion of the liquid crystal layer to a region where those liquid crystal molecules predominantly lie on the other substrate side with respect to the central portion.

A liquid crystal display comprising:

• a first substrate;
• a second substrate;
• and
• a liquid crystal layer sandwiched between the first substrate and the second substrate,
• the first substrate and the second substrate being opposed to each other, and the liquid crystal layer comprising liquid crystal molecules whose orientation is changed from a splay orientation to a bend orientation for display by applying a voltage of not less than a threshold voltage to the liquid crystal layer,
• wherein an absolute value of a pretilt angle of the liquid crystal molecules in the vicinity of the first substrate differs from an absolute value of a pretilt angle of the liquid crystal molecules in the vicinity of the second substrate, and at least one of the first substrate and the second substrate is provided with a bend transition nucleus induction means.

A liquid crystal display comprising:

• a first substrate;
• a second substrate;
• and
• a liquid crystal layer sandwiched between the first substrate and the second substrate,
• the first substrate and the second substrate being opposed to each other, and the liquid crystal layer comprising liquid crystal molecules whose orientation is changed from a splay orientation to a bend orientation for display by applying a voltage to the liquid crystal layer,
• wherein an absolute value of a pretilt angle of the liquid crystal molecules in the vicinity of the first substrate differs from an absolute value of a pretilt angle of the liquid crystal molecules in the vicinity of the second substrate, and a twist elastic constant k22 of a liquid crystal material for the liquid crystal layer is not more than 10 pN.

A liquid crystal display comprising:

• a first substrate;
• a second substrate;
• a liquid crystal layer sandwiched between the first substrate and the second substrate;
• a first alignment film formed on a surface of the first substrate to be in contact with the liquid crystal layer;
• and
• a second alignment film formed on a surface of the second substrate to be in contact with the liquid crystal layer,
• the first substrate and the second substrate being opposed to each other,
• wherein the first alignment film and the second alignment film are formed with the same material, and an absolute value of a pretilt angle of liquid crystal molecules in the vicinity of the first substrate differs from an absolute value of a pretilt angle of liquid crystal molecules in the vicinity of the second substrate.

A method for manufacturing a liquid crystal display,

• the liquid crystal display comprising opposed first and second substrates and a liquid crystal layer sandwiched between the first substrate and the second substrate, wherein an absolute value of a pretilt angle of liquid crystal molecules in the vicinity of the first substrate differs from an absolute value of a pretilt angle of liquid crystal molecules in the vicinity of the second substrate,
• the method comprising:
• forming a first alignment film on a surface of the first substrate to be in contact with the liquid crystal layer and a second alignment film made of the same material as that of the first alignment film on a surface of the second substrate to be in contact with the liquid crystal layer;
• and
• performing an alignment process on at least one of the first alignment film and the second alignment film so as to make a difference in pretilt angle control characteristics between the first alignment film and the second alignment film.

A method for manufacturing a liquid crystal display, the liquid crystal display comprising opposed first and second substrates and a liquid crystal layer sandwiched between the first substrate and the second substrate, wherein an absolute value of a pretilt angle of liquid crystal molecules in the vicinity of the first substrate differs from an absolute value of a pretilt angle of liquid crystal molecules in the vicinity of the second substrate,

• the method comprising:
• forming a first alignment film by forming a polyimide alignment film precursor on a surface of the first substrate to be in contact with the liquid crystal layer and firing the polyimide alignment film precursor;
• and
• forming a second alignment film by forming a precursor made of the same material as that of the polyimide alignment film precursor on a surface of the second substrate to be in contact with the liquid crystal layer and firing the precursor,
• wherein a firing temperature for the first alignment film differs from a firing temperature for the second alignment film.

A liquid crystal display comprising:

• a first substrate;
• a second substrate;
• a liquid crystal layer sandwiched between the first substrate and the second substrate;
• a first alignment film formed on a surface of the first substrate to be in contact with the liquid crystal layer;
• and
• a second alignment film formed on a surface of the second substrate to be in contact with the liquid crystal layer,
• the first substrate and the second substrate being opposed to each other,
• wherein the first alignment film and the second alignment film are formed with different materials, a dielectric constant of the first alignment film is larger than a dielectric constant of the second alignment film, and a thickness of the first alignment film is smaller than a thickness of the second alignment film.

A liquid crystal display comprising:

• a first substrate;
• a second substrate;
• a liquid crystal layer sandwiched between the first substrate and the second substrate;
• a first alignment film formed on a surface of the first substrate to be in contact with the liquid crystal layer;
• and
• a second alignment film formed on a surface of the second substrate to be in contact with the liquid crystal layer,
• the first substrate and the second substrate being opposed to each other,
• wherein the first alignment film and the second alignment film are formed with different materials, and an insulating film is provided below at least one of the first alignment film and the second alignment film.