Computer graphics processing and selective visual display system – Plural display systems
Reexamination Certificate
1998-05-13
2003-06-24
Shankar, Vijay (Department: 2673)
Computer graphics processing and selective visual display system
Plural display systems
C345S001200, C345S003100
Reexamination Certificate
active
06583770
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a display arrangement with display to two directions comprising a first display displaying to a first direction and a second display displaying to an essentially opposite second direction. The invention also relates to a terminal device comprising such a display arrangement.
BACKGROUND OF THE INVENTION
Liquid crystal displays (LCD, Liquid Crystal Display) are at present very common especially in small size devices. They are displays thin in construction, consisting of transparent electrodes, a medium containing liquid crystals and polarization filters. One of the most common constructions is the so called twisted nematic (TN, Twisted Nematic) LCD-display. In it the molecules of a layer of liquid arranged between glass plates are directed in a desired direction using control voltages, at which the optical properties of the display elements change and create the desired pattern in the display.
FIG. 1
presents a cross section of the most commonly used twisted nematic liquid crystal display
12
. Liquid crystal display
12
consists of transparent electrodes
3
, liquid crystal layer
5
containing liquid crystal molecules
15
and polarization filters
1
and
9
. Closest to the viewer (topmost in the figure) there is polarization filter
1
, which is located on top of glass plate
2
protecting liquid crystal layer
5
. Under glass plate
2
electrodes
3
(figures seen in the display) have been arranged using a conductive, transparent layer (for example indiumtinoxide, ITO). The glass plates can also be replaced with plastics, if a lighter and more robust construction is desired. The disadvantages of plastics are the high price and so far difficulties in manufacturing. A so called orientation layer
4
has been integrated on the surface of electrode
3
. Liquid crystal molecules
15
in liquid crystal layer
5
which touch it are oriented and thus orient the whole liquid crystal layer
5
(the layer between orientation layers
4
and
6
containing liquid crystal molecules
15
) in the desired way. On the other side of liquid crystal layer
5
there is orientation layer
6
, and as next transparent electrode
7
alike electrode
3
. The next layer is protective glass layer
8
, in the bottom surface of which polarization filter
9
has been arranged. On the other side of polarization filter
9
there is reflector
10
which in the figure is reflecting light upwards.
The electric field controlling the display is arranged by connecting an electric field between display elements, or electrodes
3
, arranged in a desired form, and electrode
7
using voltage supply
13
and switch
11
. The operation of a liquid crystal display is based upon the fact that when there is no electric field in the display, light passes through layers
1
-
9
and is reflected back by reflector
10
. In this case the background of the display seems light. When controlling control voltage
13
is connected between electrodes
3
and
7
, the electric field generated by it twists liquid crystal molecules
15
in medium
5
in such a way that the light polarized using polarization filters
1
and
9
cannot pass through the construction but is absorbed in the construction. In this case the background of electrode
3
seems black. Different shades of darkness can be obtained by adjusting the control voltage level. The crossing of electrodes
3
and
7
forms a pixel. A multi-color liquid crystal display is manufactured by adding a color filter in each pixel. All colors can be produced with pixels provided with red, green and blue filters. In practice the color filter is a single layer, placed for example between lower glass plate
8
and electrode
7
(or between upper glass plate
2
and electrode
3
), in which case the desired color is obtained when light is reflected upwards (in FIG.
1
). The display can further be provided with a background light placed under reflector
10
, in which case light passes through the reflector upwards in the figure and illuminates the display. The background light can be realized as an electroluminescense layer (a so-called EL-background light), which is illuminated when a voltage is brought over it.
Other kinds of prior known liquid crystal displays are a display based on dynamic scattering and a display based upon induced rotation (guest-host). Even if a liquid crystal display is flat and as such requires little space, space can be a problem in small size devices, such as mobile telephones, in which it is striven for devices with as small outer dimensions as possible and which are as light as possible. At present there are devices with several displays. An example of these is Nokia 9000 Communicator, with two displays opposite to each other, one display of the telephone section towards the outside of the device and a second display of computer/organizer section towards the inside of the device. The display of the telephone section is smaller and thus requires less surface area. Both displays however have the same thickness and they thus increase the thickness of the device when folded against each other. The situation has been illustrated in more detail in
FIG. 2
, in which telephone section display D
1
is topmost with the viewing direction from top downwards in the figure, and in which computer/organizer section display D
2
is lower with the viewing direction from bottom upwards in the figure. The structure of the displays has been simplified a little here. In telephone section display D
1
there are top- and bottom polarizers
1
′ and
9
′, and glass plates
2
′ and
8
′, between which there is structure
14
′ (presented in
FIG. 1
with reference
14
), which has been omitted here because of simplicity, and reflector
10
′. In computer/organizer section display D
2
there are respectively top- and bottom polarizers
1
″ and
9
″, and the glass plates
2
″ and
8
″, between which there is structure
14
″ (presented in
FIG. 1
with reference
14
), which has been omitted here because of simplicity, and reflector
10
″. Displays D
1
and D
2
have been fixed in printed circuit boards PCB
1
and PCB
2
, which in the device have been fixed to each other. In the printed circuit board it has preferably been fixed display driver circuits Dr′ and Dr″, which control the display (realizing the functions
11
and
13
in
FIG. 1
for each pixel). The solution presented in
FIG. 2
is vertically rather thick in the figure and thus significantly increases the size of the device in the direction in question. In a more advanced version of Nokia 9000 Communicator -device, which will be released in the summer of 1997, the construction has been made smaller by using only one printed circuit board and by fixing displays D
1
and D
2
on both sides of the printed circuit board.
SUMMARY OF THE INVENTION
Now a two-sided display element has been invented, by using which a display to two opposite directions can be realized and the thickness of said display construction can be reduced compared with previous solutions. In the invention the one and same display component or display material element is utilized in the realization of a first display displaying in a first direction and of a second display displaying in a second opposite direction. In this way a part of said display component (display material element) is used for the realizing of a first display displaying in a first direction and a second part of said component is utilized in the realization of a second display displaying in a second opposite direction. The common Display Material Element is preferably such a part of the display the direction of which as to the direction of viewing has no importance. Other parts (layers) of the display, the direction of which as to the direction of viewing has importance, are arranged in such a way that they are in the first and second display in reversed order and turned into opposite directions if required. The displays are formed next to each other di
Antila Mika
Rönkkä Risto
Nokia Mobile Phones Ltd.
Perman & Green LLP
Shankar Vijay
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