Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-04-23
2003-12-09
Wu, Xiao (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S033000, C345S045000
Reexamination Certificate
active
06661396
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a display device used in electronic equipment and for displaying various character information and characters, in particular to a display device for displaying pictures by using organic electroluminescent (EL) elements in the display section.
2. Description of Related Art
As a flat-type display device based on the dot matrix display system, there is a display device in which luminescent elements such as organic electroluminescent (EL) elements are used. A luminescent element based on organic electroluminescent (EL) elements (hereinafter referred to as “organic EL element”) is an element composed basically of a luminescent layer made of laminated fluorescent material in which electrodes of a small work function (electrodes for injection of electrons) are formed. Such organic EL elements are characterized by their ability to provide a very high luminance for a small voltage.
As shown in
FIG. 6
, a display device in which organic EL element is used
21
(hereinafter referred to simply as “the display device”) has organic layers (luminescent layers)
22
a
and
22
b
sandwiched between a plurality of common line electrodes
23
serving as negative poles and a plurality of segment line electrodes
24
serving as positive electrodes, and disposed between the transparent (glass) substrates
25
and
26
. Any potential difference given between the common line electrodes
23
and the segment line electrodes
24
creates an electric field between the organic layers
22
a
and
22
b
, and electrons accelerated by this electric field creates electron-hole pairs. Alternatively, the application of an electric field may result in the disappearance of electron-hole pairs. The area of the part radiating at this time (hereinafter referred to as the “luminescent surface”) will be the area of individual electrodes for injection of electrons sandwiching the organic layers
22
a
and
22
b.
Display devices developed in recent years adopted the dot matrix system for chronologically changing pictures and figures specifically formed for each character for fixed pictures. As figures specifically formed for each character are used for fixed pictures, curves can be used freely and freedom of display may be enhanced. A display device including both a display section based on a prior dot matrix system and a display section for displaying a figure formed into a specific character will be explained with reference to
FIGS. 6 and 7
.
The display device
21
includes a dot display portion
27
based on the dot matrix system, which is connected with a line electrode drive circuit
28
and a column electrode drive circuit
29
providing a potential difference to the organic layer
22
a
. Line electrode drive circuit
28
and column electrode drive circuit
29
are connected with the control section
30
. Similarly, the display device
21
includes a figure display portion
31
for displaying a figure formed into a character, which is connected with a line electrode drive circuit
32
and a column electrode drive circuit
33
providing a potential difference to the organic layer
22
b
. The line electrode drive circuit
32
and column electrode drive circuit
33
are connected with the control section
34
. Control sections
30
and
34
are designed to receive inputs of image signals and based on these image signals each of these control sections
30
and
34
control the line electrode drive circuits
28
and
32
and column electrode drive circuits
29
and
33
to change the potential differences given to the organic layers
22
a
and
22
b
of the dot display portion
27
and the figure display portion
31
.
In case where the dot matrix system is used for displaying any picture, the reduction of each dot or radiating surface to a small area produces clearer pictures. On the other hand, where a figure formed into a specific character is to be displayed, the enlargement of the figure itself for display makes it easier to view. Thus, a figure formed into a character tends to grow far larger than a dot adopted for the dot matrix system. In other words, the area of electrodes into which electrons are injected to radiate a figure formed into a character on the organic layer
22
b
grows larger than the area of an electrode into which electrons are injected to radiate according to the dot matrix system. Therefore, even if the same potential difference is given to both of the organic layers
22
a
and
22
b
, the amount of electric current flowing into the latter organic layer
22
b
grows smaller. As a result, in comparison with the luminescent area of each dot according to the dot matrix system, the luminescent surface of the figure formed into a character grows darker.
For the above reason, in order to maintain the luminosity of the luminescent surface of the figure formed into a character at a level of luminosity similar to that of the luminescent surface of each dot displayed according to the dot matrix system, the potential difference between the common line electrodes and the segment line electrodes must be kept at a higher level than the potential difference applied to the organic layer
22
a
radiating according to the dot matrix system. Therefore, apart from the common line electrodes, the segment line electrodes, the line electrode drive circuit and the column electrode drive circuit for supplying electric current to the organic layer
22
a
radiating according to the dot matrix system, new common line electrodes, segment line electrodes, line electrode drive circuit and column electrode drive circuit must be created to provide for further potential difference, which resulted in additional components, further complication of the control section and added up the cost.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a display device by which a figure formed into a character can radiate with an even luminosity as that of the luminescent surface according to the dot matrix system without increasing the number of components.
In order to solve the above problem, the display device according to one embodiment of the present invention includes the first luminescent section of a prescribed area and the second luminescent section forming a picture of an area larger than the first luminescent section, the first and the second luminescent sections being formed by a luminescent body radiating as electrons move and a pair of electrodes sandwiching this luminescent body, at least one of the electrodes determining the area of radiation, and at least the second luminescent section being formed by a plurality of divided electrodes.
In another embodiment, the display device according to the present invention includes a drive circuit for driving the segment line electrodes and common line electrodes for supplying electric current to the first luminescent section, and the drive circuit drives the second luminescent section.
In still another embodiment, the display device according to the present invention includes electrodes forming the second luminescent section divided so that each of them would take the same area as that of the first luminescent section.
In still another embodiment, the present invention provides a display device in which the electrodes of the second luminescent section are disposed in such a way as to form at least a character and the electrodes are divided by slits crossing with characters.
In another embodiment, the present invention provides a display device in which slits are formed by a line smaller than characters.
The presently preferred embodiment includes a first luminescent section of a prescribed area, i.e. a dot of the dot display portion
2
, and a second luminescent section displaying a figure of an area larger than that of said first luminescent section, i.e. a figure display portion
3
. As electrons move between the pair of electrodes sandwiching the first or second luminescent sections, the luminescent body radiates. The area of luminescence is determined by at least
Alpine Electronics Inc.
Brinks Hofer Gilson & Lione
Wu Xiao
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