LCD cell making

In LCD cell-making the back plate, either passive or active (TFT) is combined with the color filter front plate.
The principle of the LCD is based on the fact that orientated Liquid Crystal molecules can interact with the light passing through it, e.g. when the LC molecules are twisted 90 ° by applying an electrical field, the polarization of the light also twists by the same amount.In order to obtain this twist, the glass plate is coated with polyimide which is oriented by rubbing with a cloth or alternatively by photoalignment using UV light.
This PI layer is applied by spincoating or flexprinting techniques.

Principle TN LCD Display

 

 

 

 

Exploded view of an LCD device

 

To create the cell the two glassplates need to be combined at a separation of around 5 µm but depending on the application and type of LC material. To keep the distance of the glass plate at the desired value plastic or glass spheres are deposited with the dry-spacerbox or by spincoat techniques.
After spacering the two glassplates are glued together in a process called Coupling. This UV sensitive glue is applied with a plotter (dispensing).
The glue-pattern dispensed on one of the two glassplates is called the seal.
In the seal there is a seal-opening left to be able to fill the cell with LC later-on in the process.
Coupling is performed with a coupling machine and can be done within a few microns accuracy.
After coupling the glue is cured under pressure with UV or heat. Next step is LC-filling, done in a vacuum chamber.
The cell is put in the chamber with the seal opening downwards. Underneath this opening there is a small quantity of LC material.
The chamber is evacuated and after the right vacuum is reached, the cell-opening is dipped into the LC.
Due to capillary forces the LC will flow into the cell. After a while the chamber is slowly backfilled with
air (N2). The pressure difference between the inside and outside of the cell will enhance the flow of the LC into the cell so it fills the cell faster.
After completion, the cell is taken out of the vacuum chamber. The now overpressured filled cell is pressed back onto its spacers with a pressure tool. The opening in the seal used for filling is then closed with a UV glue.
The cell making is finished and a working display has been made!

 

42”-2D/3D line

Philips’ 3D lenticular technology enhances the 3D feeling by generating multiple views.
However, as all views are generated and displayed simultaneously, the multi-view principle compromises the effective resolution per view. To overcome this resolution loss in 2D mode, we have developed a display with a switchable lenticular structure. By filling the negative replicated lenticular structure of the lenses with LC material and covering the cell with electrodes, we can electrically influence the orientation of the molecules (fig. 1).
Hence the index of refraction for the light passing the lens is either (n(e) is larger than n(0)) or zero. The former lens state is the 3D mode and the latter state is the 2D mode.

Fig. 1

In our cleanroom equipment is available for making complete switchable lenticular structures of up to 42”. In order to realize this, roughly the following process steps have been installed:

Cutting

Glass substrates can be cutted (by hand) in dimensions of roughly 100 x 70 cm.

Cleaning
Cleaning equipment QSP-350-2500-40 Qualitys Sonic Products b.v. - Soest
UV-Ozon built in house
Oven Binder Hielkema Testequipment b.v. - Uden
In the cleaning equipment substrates can be cleaned by ultrasonic vibration in a surface active waterbased solution at elevated temperature.

Orientation layer (for L.C.-material)
Dipcoating equipment built in house fig. 2

Fig. 2

By dipcoating a LC-orientationlayer can be applied to the substrates.

Rubbing of the orientation layer
Rubbing equipment built in house fig. 3

 
Fig. 3

After rubbing the LC-material can be orientated later on in the right direction.

Gluing
Gluing equipment built in house fig. 4

Fig. 4

A seal line is applied on one of the glass plates in such a way that later on an LC-cell with filling-openings can be formed.

Coupling and filling with LC-material
After the two glass plates are coupled the glue has to be cured (by UV-light in the case of UV-cureable glue or otherwise.)

Filling the cell with LC-material
Filling equipment built in house fig. 5

Fig. 5

In this equipment the sealed cell will be filled with LC-material before closing the filling openings.

OLED line

Another example of a more or less structural specific device realisation line is the OLED line (OLED = Organic Light Emitting Diode).
In a dedicated clean room a complete infrastructure for the realisation of OLEDs is available.
Both SMOLEDs (Small Molecule OLEDs) and PolyLEDs (based on solution processable polymers) can be processed.
Applications of these devices are in the display, lighting and sensor area. The infrastructure allows for the use of both glass substrates and flexible substrates.
The infrastructure consists of a whole range of equipment varying from specially developed inkjet printers which can accommodate for many different types of print heads, spin coating and laser ablation equipment, surface treatment equipment, many cathode evaporation and encapsulation set-ups, which allow for the use of many different cathode materials and for metal lid and glass cover encapsulation.
Next to this a special very flexible integrated research system is available consisting of a combination
of glove boxes for device manipulation, evaporation tools and a PECVD tool for the application of thin film
encapsulation.

Thin Film Encapsulation Device This device is special built to evaporate materials like Ba, Al, . (max. size 450*250mm). and/or to cover surfaces  with SiN, SiON or SiOx layer in a very dust free environment. The main field of application area is all kinds of surfaces which needs to be protected against moisture and/or oxygen.