# US 9,040,229 B2 · Maskless process for pre-tilting liquid crystal molecules

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- Number: US 9,040,229 B2
- Document ID: US9040229B2
- Status: Granted
- Kind: B2
- Application number: 13/750,833
- Filed: 2013-01-25
- Published: 2014-07-31
- Granted: 2015-05-26
- Earliest claimed: 2013-01-25
- Assignees: Kent State University
- Applicants: Kent State University
- Inventors: Hiroshi Yokoyama
- Web page: https://patentgrep.com/patent/US9040229B2

## CPC

- G02F 1/133788: {by light irradiation, e.g. linearly polarised light photo-polymerisation}
- G03F 7/0005: {Production of optical devices or components in so far as characterised by the lithographic processes or materials used therefor}
- G03F 7/2051: {Exposure without an original mask, e.g. using a programmed deflection of a point source, by scanning, by drawing with a light beam, using an addressed light or corpuscular source (G03F7/70 takes precedence)}
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)

## Abstract

A method of tilting liquid crystal molecules is presented. The method entails providing a substrate including a photoalignment layer on top of a layer of liquid crystal molecules. The photoalignment layer is exposed to patterned light that is incident on the substrate at a substantially normal angle. The patterned light is polarized in a polarization direction that is non-parallel to an incident surface of the substrate.

## Claims

### Claim 1

A method of tilting liquid crystal molecules, the method comprising:
providing a substrate including a photoalignment layer on top of a layer of liquid crystal molecules;
apportioning the photoalignment layer into a plurality of longitudinal regions; and
exposing the photoalignment layer to a patterned light one longitudinal region at a time such that the patterned light moves across a longitudinal region in a first direction along its length, then moves to an adjacent longitudinal region in a second direction perpendicular to the first direction, and then moves across the adjacent horizontal region in a direction opposite to the first direction,
wherein the patterned light has a pattern including dark areas and bright areas, the patterned light being polarized in a polarization direction that is non-parallel to an incident surface of the substrate, wherein the patterned light is incident on the substrate at a substantially normal angle.

### Claim 2 (depends on 1)

The method of claim 1, wherein the pattern comprises alternating lines of dark areas and bright areas.

### Claim 3 (depends on 2)

The method of claim 2 further comprising controlling a pretilt angle of the liquid crystal molecules by adjusting a pitch of the pattern.

### Claim 4 (depends on 1)

The method of claim 1, wherein the photoalignment layer is a photoreactive polymer.

### Claim 5 (depends on 1)

The method of claim 1, wherein the patterned light is polarized in a polarization direction that is perpendicular to a boundary between the dark areas and bright areas.

### Claim 6 (depends on 1)

The method of claim 1, further comprising moving the patterned light on the photoalignment layer repetitively until the boundary between the bright areas and the dark areas passes on a section of the photoalignment layer a selected number of times.

### Claim 7 (depends on 1)

The method of claim 1 further comprising controlling a pretilt angle of the liquid crystal molecules by adjusting a speed at which the patterned light is moved across the photoalignment layer.

### Claim 8 (depends on 1)

The method of claim 1, wherein the polarization direction of the patterned light is non-parallel and non-perpendicular to the main propagation direction of the patterned light.

### Claim 9 (depends on 1)

The method of claim 1 further comprising creating the pattern with a digital micro-mirror device and a computer.

### Claim 10 (depends on 1)

The method of claim 1, wherein the patterned light is ultraviolet light.

### Claim 11 (depends on 1)

A method of claim 1, wherein a width of the pattern light in the second direction is equal to a width of each of the longitudinal regions.

### Claim 12

A method of tilting liquid crystal molecules, the method comprising:
providing a substrate including a photoalignment layer on top of a layer of liquid crystal molecules; and
exposing the photoalignment layer to a patterned light, wherein the patterned light has a pattern including dark areas and bright areas, the patterned light being polarized in a polarization direction that is non-parallel to an incident surface of the substrate, wherein the patterned light is incident on the substrate at a substantially normal angle, and wherein the light is an extended Laguerre beam.

### Claim 13

A method of tilting liquid crystal molecules, the method comprising:
providing a substrate including a photoalignment layer on top of a layer of liquid crystal molecules;
apportioning the photoalignment layer into a plurality of longitudinal regions; and
directing light at the photoalignment layer at a substantially normal angle of incidence and non-continuously such that light and absence of light alternate on a spot of the photoalignment layer, wherein the light is polarized in a polarization direction that is non-parallel to an incident surface of the substrate, and
wherein the light moves across a longitudinal region in a first direction along its length, then moves to an adjacent longitudinal region in a second direction perpendicular to the first direction, and then moves across the adjacent horizontal region in a direction opposite to the first direction.

### Claim 14 (depends on 13)

The method of claim 13, wherein directing the light non-continuously comprises scanning a patterned light across the photoalignment layer, the patterned light having bright portions and dark portions.

### Claim 15 (depends on 13)

A method of claim 13, wherein a width of the light in the second direction is equal to a width of each of the longitudinal regions.

### Claim 16

A method of tilting liquid crystal molecules, the method comprising:
providing a substrate including a photoalignment layer on top of a layer of liquid crystal molecules; and
directing light at the photoalignment layer at a substantially normal angle of incidence and non-continuously such that light and absence of light alternate on a spot of the photoalignment layer, wherein the light is polarized in a polarization direction that is non-parallel to an incident surface of the substrate, and wherein the light is an extended Laguerre beam.