Coatable Polarizers for Rollable, Flexible & Folding Display Applications

Light Polymers has used our proprietary lyotropic liquid crystal technology to create a Direct-Coatable Circular Polarizer for Foldable OLED displays. Other display applications include Curved LCD, Privacy Displays, and Micro and Mini LED.

Direct-Coatable Polarizer for Flexible, Foldable & Rollable Displays

Borderless displays with an edge-to-edge screen, one of the major advances in Apple’s iPhone X and Xs, use what is called a “Flexible Display,” as it can wrap around the edge of the smartphone, and it is widely used in Samsung’s Galaxy smartphone offering as well. Flexible display components were just the first step on the path to fully foldable displays. Light Polymers is now perfecting the foldable version of this circular polarizer that is thinner than any current competitive offerings. This technology pushed the industry one step closer to making the foldable displays being introduced today. Light Polymers’ thin and durable coatable polarizer for foldable mobile devices is expected to be introduced in October 2019. 

When testing films for Flexible or Folding displays, the film must meet the static bending test with no deformation. Directly coating our polarizer on PI cover film or retarder film solves the deformation issues that PVA based polarizer films experience after the bending test. Light Polymers’ Grey Polarizer sample has passed initial bend tests and meets the minimum contrast ratio after successfully being directly coated onto customer’s compensation film.

Problem: PVA Based Polarizers

Current traditional PVA-based polarizers are not fit for the next generation of foldable and flexible displays. They are:

  • Too thick (latest non-commercial technology is >15 µm thick)
  • Not durable (not able to meet the folding requirement of 200,000 folds at 3.0 mm bend radius)
  • Cost-prohibitive (based on non-value added films and complicated process)

Solution: Direct Coated Polarizers

Light Polymers’ Direct-Coatable Polarizer chemistry solves these issues:

  • Thinner because it is direct-coated on panel substrates and other functional layers (less than 1.0 µm coated layer)
  • More durable due to proprietary water-based chemistry and the elimination of fragile plastic substrates (customer confirmed ability to meet the folding requirement of 200,000 folds at 1.5 mm bend radius) – Updated
  • Cost-effective (by eliminating costly films and simplifying the overall manufacturing process)

Self-aligning via p-p interaction

Gray Polarizer

E-type: absorption axis perpendicular to coating direction. 

Small molecule units undergo face-to-face aggregation into stacks, then stacks are aligned by sheer force.

Covalent bonding

Polymer Polarizer

O-type: absorption axis parallel to coating direction. 

Rigid polymers are aligned by sheer force. Chromophores diffuse into polymer coating layer and are aligned by neighboring polymer chains.

Chemistry Menu

  • GP005 (Gray Polarizer) – Small molecule-based linear polarizer chemistry
  • PP001 (Polymer Polarizer) – Polymer-based linear polarizer chemistry
  • CR010 – Reverse Dispersion – QWP chemistry on any isotropic substrate (glass, TAC, etc.)
  • Circular Polarizer – QWP – Linear polarizer stack

Light Polymers Advantage

  • Lower price
  • Less than 0.8 um thickness (PVA – 12um)
  • Coatable polarizer without stretchable process
  • Roll to roll manufacturing process
  • Direct coating process on any film substrate
  • Direct coating process on-cell OLED and in-cell LCD

Linear Polarizer

Linear Polarizer PP01 Process

  • Sheer-coating of lyotropic liquid crystal solution of PP01 polymer to form aligned polymer, transparent in visible wavelength range.
  • Doping step results in diffusion of chromophores into polymer layer. Chromophores are aligned by neighboring polymer chains. Certain salts in doping solution stabilize the coating.

Sub- µm Coatable Linear Polarizer: GP005

  • Approximately 0.75 µm thick GP005 coating
  • Currently capable of coating at +/- 3 % thickness variation over G2 size (400 mm x 500 mm)

Sub- µm Coatable Linear Polarizer: PP01

  • Approximately 0.8 µm thick PP01 coating

Circular Polarizer

Circular polarizers used today are made of two films: a standard linear polarizer and a “1⁄4 wave plate” compensation film with reverse dispersion of retardation properties. Light Polymers’ patented films are more durable during fold tests due to proprietary water-based chemistry and the elimination of fragile plastic substrates. Polarizers developed by Light Polymers also eliminate costly extra film components while simplifies the overall manufacturing process. Transparent, high refractive index polarizer materials enable next-generation display technologies with higher light efficiency at a lower cost. Other applications for this technology include flexible and foldable displays, curved LCD, and privacy displays.

Circular Polarizer is an optical film or coatings to cancel the reflected light so the user can see the image. The technical development objectives or Light Polymers’ Polarizer is to have the thinnest total stack by integrating the cover film, retardant film, polarizer film and adhesive for an all-in-one film solution.

Circular Polarizer Features

  • Laminated sample
  • Average reflectivity (400 nm – 700 nm) is less than 4%
  • Reflectivity at 550 nm is less than 3%
  • Direct coat thickness < 5 µm
  • Color Tunability
  • Black off-state
  • Formulation is tunable to OLED color
  • Circular polarizer passes 200,000 folding-unfolding test
  • GP-CR010 circular polarizer has RTh close to 0
  • GP has RTh > 0
  • CR010 has RTh < 0
  • RTh of GP and CR010 layers almost cancel out
  • Do not need additional +C plate
  • PVA-type conventional polarizer has large negative RTh
  • No photo-alignment
  • Cost effective

Light Polymers Direct Coated Solutions

  • Thickness < 5 microns
  • Cost is a fraction of current competitors
  • Can pass the 200,000 bend test
  • Two coated solutions
  • State of the art technology

Current Circular Polarizer Problems

  • Thickness > 60 microns
  • Cost is >$100 Sq./Meter
  • Doesn’t pass 200,000 bend test
  • Two expensive films
  • 60-year-old polarizer technology

Circular Polarizer - Laminated Sample

  • Technology demonstration, by laminating polarizer coated on quarter wave plate film.
  • Reflectance measured by placing sample on mirror.
  • Actual reflectance in OLED will be < 5 %

Circular Polarizer - Direct Coat

* Passivation to render the coating insoluble in water.

Conventional circular polarizers use a polarizer film laminated with an adhesive layer to both the ¼ wave retarder film on one side and the cover film/glass on the other. Light Polymers’ coatable polarizers enable two new solutions, only possible with direct-coatable polarizers: one where the polarizer layer is coated directly on the cover film/glass to then be laminated to the retarder film, and another where the polarizer layer is coated directly on the retarder film to then be laminated to the cover film/glass. Both new solutions are thinner than the conventional stack, and allow freedom to design manufacturing processes to suit the specific needs of the customer.

Sub-4 µm Reverse Dispersion ¼ Wave Plate: CR010

  • In-plane retardation R0 and out-of-plane retardation Rth for 3.7 mm thick CR010 coating shown below. R0(550nm) = 137.1 nm.
  • In-plane retardation R0 exhibits reverse dispersion.
  • R0(450nm)/R0(550nm) = 0.75
  • R0(650nm)/R0(550nm) = 1.08
  • Coating thickness can be adjusted up or down. R0 and Rth depend linearly on thickness.
  • Can be coated on an LCD panel or OLED panel.
  • CR010 (3.7 mm)
  • Primer (0.03 mm)
  • Substrate (Glass, TAC)