FPD manufacturing processes Flexible OLED displays

The OLED (Organic Light Emitting Diodes) display emits light by conducting electricity to the RGB organic light emitting materials that are sandwiched between the electrodes.
Since OLEDs are self-emissive displays, they don't require backlight units like LCD displays. OLEDs have many outstanding characteristics such as thin and flexible form factor, lightweight, high image quality.
In particular, flexible OLED displays, which use flexible substrates such as polyimide instead of glass, are foldable or rollable, so demand is increasing mainly for mobile devices.

Flexible substrate formation

Varnish * is coated on the carrier glass and heat treated to form a flexible substrate (PI).
＊Varnish: Polyamic acid solution (precursor of PI)
Coater Line (SK-P Series)

Backplane formation

A backplane consisting of TFTs (thin film transistor circuit) and banks (partition wall for an organic light emitting layer) is formed on a flexible substrate.

TFT formation process

　Cleaning

Substrates, which will serve as the base material, are cleaned to remove adhered micron-sized particles (dust) and organic residues.
Cleaning Processor (TS Series)

　Deposition

A thin film is formed (deposited) on the substrate as a layer of circuit material.

　Resist Coating

Resist (photosensitive solution) is dispensed from the slit nozzle to uniformly coat the substrate.
Coater Developer (SK-E Series)

　Exposure

Light is projected onto the substrates to expose the circuit pattern. Only areas of the resist layer that are exposed to the light undergo a structural change.

　Development

The areas that were exposed to the light are dissolved to reveal the thin film.
Coater Developer (SK-E Series)

　Etching

The thin film not covered with resist is dissolved and removed to form the transistor circuit.
Wet Etcher (TE Series)

　Resist Stripping

The resist layer is stripped off as it is no longer needed for masking.
Resist Stripper (TR Series)

Bank formation process

　Resist Coating

Resist (photosensitive solution) is dispensed from the slit nozzle to uniformly coat the substrate.

Transparent PDL
Coater Developer (SK-E Series)
Black PDL formation
Coater Developer (SK-B Series)

　Exposure

Light is projected onto the substrates to expose the circuit pattern. Only areas of the resist layer that are exposed to the light undergo a structural change.

　Development

The areas that were exposed to the light are dissolved to reveal the thin film.
Coater Developer (SK-E Series)

Photolithography and etching processes are repeated multiple times to form a backplane.

Organic light emitting layer formation

The light-emitting material of red, green, and blue (RGB) colors is heated in a vacuum chamber and vaporized to form a light-emitting layer through a metal mask. * Other methods are also being developed.

Thin film encapsulation (TFE)

In order to protect the organic light emitting layer from moisture and oxygen in the atmosphere, a encapsulating film is formed by vapor deposition and inkjet printing.

Touch sensor panel formation

An on-cell touch sensor is formed on the TFE layer.

Touch sensor panel formation process

　Cleaning

Substrates, which will serve as the base material, are cleaned to remove adhered micron-sized particles (dust) and organic residues.
Cleaning Processor (TS Series)

　Deposition

Layers of the material that will become the circuit material are formed (deposited) as thin films on the substrates.

　Resist Coating

Resist (photosensitive chemical) is dispensed from the slit nozzle to uniformly coat the substrates.
Coater/Developer (SK-EH Series)

　Exposure

Light is projected onto the substrates to expose the circuit pattern. Only areas of the resist layer that are exposed to the light undergo a structural change.

　Development

The areas that were exposed to the light are dissolved to reveal the thin film.
Coater/Developer (SK-EH Series)

　Etching

The thin film not covered with resist is dissolved and removed to form the transistor circuit.
Wet Etcher (TE Series)

　Resist Stripping

The resist layer is stripped off as it is no longer needed for masking.
Resist Stripper (TR Series)

Photolithography and etching processes are repeated multiple times to form the on-cell touch sensor.

Formation of Color filter film with anti-reflection function

A color filter (CF) film with anti-reflection function is formed on the on-cell touch sensor.
Coater Developer (SK-F Series)

Flexible substrate delamination

After pre-treatment to improve the peelability of the flexible substrate, a carrier glass is removed from flexible devices.