Production of gradient density liquid crystal filter

Claim 2

A process for producing a gradient density light transmissive filter wherein a solvent solution of dichroic substance capable of existing in the nemaTic liquid crystal phase is applied to the directionally oriented surface of a light transmissive substrate to form a light transmissive film thereon, the substrate being non-absorptive with respect to the solvent solution, the improvement which comprises the step of changing the concentration of the dichroic substance in the solvent solution as it is applied to different portions of the substrate, whereby to vary the optical density of the film being formed in accordance with a predetermined pattern, and thereafter drying the applied solution to evaporate the solvent and thereby form a discrete film on the oriented surface of the substrate which consists essentially of said dichroic substance.

Claim 3

The process claimed in claim 1 wherein said solvent solution contains a single dichroic substance.

Claim 4

The process claimed in claim 1 wherein said solvent solution contains a mixture of dichroic substances.

Claim 5

The process claimed in claim 1 wherein said solvent solution includes a non-polarizing die.

Claim 6

The process claimed in claim 1 including the steps of forming a plurality of substrates each having a dried film of dichroic substance defining a different predetermined density pattern, and juxtaposing said substrates to form a laminated filter having a density pattern which is a composite of the density patterns of the films carried by the individual substrates.

Claim 7

In a process for producing a gradient density light transmissive filter wherein a solvent solution of a dichroic substance capable of existing in the nematic liquid crystal phase is applied to a directionally oriented surface of a light transmissive substrate to form a light transmissive film thereon, the substrate being non-absorptive with respect to the applied solvent solution, the improvement which comprises the steps of: positioning the substrate in an essentially upright position, applying the solvent solution progressively along the uppermost edge of the directionally oriented surface of the substrate in a quantity sufficient to flow downwardly to completely cover the said surface of the substrate, including the step of changing the concentration of the dichroic substance in the solvent solution as the solvent solution is being progressively applied to the substrate, whereby to vary the optical density of the film being formed in accordance with changes in the concentration of the dichroic substance, and thereafter evaporating the solvent from the applied solution to form a film consisting essentially of said dichroic substance.

Claim 8

In a process for producing a gradient density light transmissive filter wherein a solvent solution of a dichroic substance capable of existing in the nematic liquid crystal phase is applied to a directionally oriented surface of a light transmissive substrate to form a light transmissive film thereon, the substrate being non-absorptive with respect to the applied solvent solution, the improvement which comprises the steps of: positioning the substrate in an essentially upright position, applying the solvent solution progressively along the uppermost edge of the directionally oriented surface of the substrate in a quantity sufficient to flow downwardly to completely cover the said surface of the substrate, including the step of changing the concentration of the dichroic substance in the solvent solution as the solvent solution is being progressively applied to the substrate, whereby to vary the optical density of the film being formed in accordance with changes in the concentration of the dichroic substance, and thereafter evaporating the solvent from the applied solution to form a film consisting essentially of said dichroic substance.

Claim 9

The process claimed in claim 6 including the step of providing an applicator for applying the solvent solution to the substrate, and progressively applying the solution to the substrate by effecting relative movement between the substrate and the applicator.

Claim 10

The process claimed in claim 6 including the step of moving the substrate in a horizontal path of travel, and applying the solvent solution from a fixed point overlying the path of travel of the substrate.

Claim 11

The process claimed in claim 7 including the step of maintaining the substrate in a stationary position during the application of the solvent solution, and moving the applicator for applying the solvent solution in a horizontal path of travel overlying and following the upper edge of the substrate.

Claim 12

A gradient density light transmissive filter comprising a light transmissive substrate having a directionally oriented surface, a light transmissive film on the directionally oriented surface of the substrate, said film consisting of dichroic substance having a nematic liquid crystal phase, the optical density of the dichroic substance varying in a smooth gradient from area to area of said substrate in a predetermined density pattern, the substrate being non-absorptive with respect to the dichroic substance, said film being characterized by having been formed by applying a solvent solution of the dichroic substance to the substrate in a coating of substantially uniform thickness in which the Concentration of the dichroic substance is varied from area to area in accordance with the predetermined density pattern and the applied coating dried to eliminate the solvent, the optical density of the dry film directly corresponding to the concentration of the solvent solution.

Claim 13

A gradient density light transmissive filter comprising a light transmissive substrate having a directionally oriented surface, a light transmissive film on the directionally oriented surface of the substrate, said film consisting of dichroic substance having a nematic liquid crystal phase, the optical density of the dichroic substance varying in a smooth gradient from area to area of said substrate in a predetermined density pattern, the substrate being non-absorptive with respect to the dichroic substance, said film being characterized by having been formed by applying a solvent solution of the dichroic substance to the substrate in a coating of substantially uniform thickness in which the Concentration of the dichroic substance is varied from area to area in accordance with the predetermined density pattern and the applied coating dried to eliminate the solvent, the optical density of the dry film directly corresponding to the concentration of the solvent solution.

Claim 14

The gradient density filter claimed in claim 10 wherein said filter comprises at least two juxtaposed substrates each having a dichroic film defining a different optical density pattern, the optical density of the filter comprising a composite of the optical density patterns of the juxtaposed substrates.

Claim 15

The gradient density filter claimed in claim 11 wherein the directionally oriented surfaces of the juxtaposed substrates are parallel.

Claim 16

The gradient density filter claimed in claim 11 wherein the directionally oriented surfaces of the juxtaposed substrates are angularly disposed relative to each other.

Claim 17

The gradient density filter claimed in claim 10 wherein the light transmissive film is composed of a mixture of dichroic substances.