Empty Liquid Crystal Cells
- Seven Different Cell Gaps
- Two Liquid Crystal Inject Holes
- AR Coating (350 - 700 nm) on Both Sides
Filled Cell with Wires Attached
- Models with Seven Different Cell Gaps Available
- Anti-Reflective Coating (350 - 700 nm) on Both Sides
- High Resistance Indium Tin Oxide (ITO) Conductive Layer (300 - 350 Ω/sq Resistance)
- All Models Except 20 µm Cell Feature an Anti-Parallel PI Alignment Layer
- Custom Cells Available Upon Request to Tech Support
Thorlabs’ empty liquid crystal cells are designed for testing liquid crystal compounds and materials. These cells are coated with an Indium Tin Oxide (ITO) conductive layer and a Polyimide (PI) alignment layer (20 µm version has no PI layer). Seven cells are available with various sized spacers to provide cell gaps from 3 µm to 20 µm, and all are designed for simple filling in the lab (See the Filling and ITO tab).
Our empty cells are optimized for high transmission in the visible range, using UV Fused Silica glass, a broadband anti-reflective coating, and thin film, high resistance ITO. If your application requires liquid crystal cells for other wavelength ranges, please contact us for such a custom cell.
Empty cells with cell gaps from 3 to 10 µm are rubbed and assembled for anti-parallel alignment of the liquid crystal. The LCC1324-A has a 20 µm gap and no polyimide alignment layer. This cell is designed for use with materials that do not require an alignment layer, such as Polymer Dispersed Liquid Crystal (PDLC) materials. Thorlabs can also provide cells with different alignment methods such as 90° twist, parallel alignment, or with custom PI material.
|Cell Gap||3 ± 0.3 µm||4 ± 0.4 µm||5 ± 0.5 µm||6 ± 0.6 µm||8 ± 0.8 µm||10 ± 1 µm||20 ± 2 µm|
|Cell Gap Uniformity||5% over the Entire Clear Aperture|
|ITO Resistance (See Below)||350 - 450 Ω/sq|
|AR Coating||Ravg <0.5%, 350 nm – 700 nm|
|External Dimensions||17 ± 0.1 mm x 12 ± 0.1 mm x 6 ± 0.2 mm|
|Clear Aperture||10 mm x 10 mm|
|Surface Quality||40 -20 Scratch Dig|
|Surface Flatness||λ/10 @ 633 nm|
|Glass Material||UV Grade Fused Silica|
The resistance of a thin film is usually described using the sheet resistance (Rs) instead of the resistivity (ρ). Sheet resistance is defined as the ratio between the resistivity (ρ) and the film thickness (t), with units of ohms per square (Ω/sq). It is a more convenient parameter for users because the film thickness has been taken into account and only two dimensions (the length L and the width W) are needed to calculate the resistance of the thin film, which is R = Rs*L/W. Since a square has L = W, the resistance of a square of the thin film is constant and equal to the sheet resistance, regardless of the size of the square. Our liquid crystal cells are 12 mm x 15 mm, so the actual resistance is 15/12 times the sheet resistance.
Click to Enlarge
Transmission of Unpolarized Light in a Liquid Crystal Cell Filled with a Typical Nematic LC Material
Recommended Filling Procedures
Filling Using the Capillary Effect
- In a clean environment, remove the cell from the packaging. Place a drop of liquid crystal material on one of the filling ports and wait for the LC material to completely fill the cell. Note: Depending on the LC material and cell gap, this can take anywhere from 10 minutes to several hours.
- After the cell is completely full, seal the two holes with UV glue (such as the NOA68) and cure the glue. Note: If you are using nematic LC material you will need to bake the filled cell for two hours at a temperature above the clearing temperature (i.e., the temperature at which the liquid crystal becomes isotropic) to get a homogenous alignment of the LC material.
Filling Using a Vacuum Chamber
- In a clean environment, remove the cell from the package. Using UV glue (such as the NOA68), seal one hole and cure the UV glue.
- Insert the cell into a vacuum chamber, place the liquid crystal material in a container under the cell (but not touching the cell), and hold the cell with a device that can later be lowered.
- Evacuate the vacuum chamber to a level of 10 Pa, and heat the chamber to a temperature above the LC clearing point.
- After the chamber has reached the required vacuum level and temperature, lower the cell so that the filling hole touches the LC.
- Release the pressure in the chamber and the LC will fill the cell.
- Slowly reduce the temperature back to room temperature.
- Remove the cell from the chamber, seal the second hole with UV glue, and cure the glue.
After completing the filling using either method, use conductive epoxy such as EG58 to connect wires to the two ITO strips.