Electro-optical flat-design display device, in particular LCD area

The invention relates to an electro-optical flat-design display device, in particular to an LCD area, comprising a flat-design housing 1 having at least one line of display elements 10 forming the front 8 of the housing 1, and comprising a backlighting device disposed inside the housing 1 and assigned to the line of display elements 10. For reducing the heat load of the LCD display elements 10 and for simplifying the construction of the housing 1, it is provided, according to the invention, that the backlighting device includes a light-guide tube 12, 17 disposed inside the housing 1 and a light source 18 disposed at a light entrance opening of the light-guide tube 12, 17, that the light-guide tube 12 is made from transparent material and surrounded by a reflector material 14, and that the reflector material 14 comprises cutouts 15 assigned to the individual display elements 10 and serving as light-exit openings FIG. 2.

FIELD OF THE INVENTION 
The invention relates to an electro-optical flat-design display device, in 
particular to an LCD area display which is preferably backlit. 
BACKGROUND OF THE INVENTION 
An electro-optical flat-design display device formed as an LCD area of the 
mentioned species is known in the art from EP No. 0.146.285. Herein, five 
horizontal lines having several side-by-side display elements each are 
provided, each of the display elements being built-up by a 5.times.3 
matrix. The five lines of LCD display elements form the front of the 
housing. Two light sources are installed in the housing extending in the 
longitudinal direction of the lines, as backlighting devices. 
The considerable generation of heat by the light sources within the 
flat-design housing has been found to be disadvantageous. It is 
disadvantageous, further, that the two light sources have to be replaced 
after a certain operating time. For this purpose the individual lines of 
LCD display elements are arranged in a hinged manner on the front side of 
the housing, in order that the light sources provided with a reflector on 
the rear side of the housing can be replaced from the front of the 
housing. 
It is also disadvantageous that the LCD display elements are continuously 
exposed to u.v. and heat irradiation. This will lead to degregation, 
disintegration and destruction of the dye pigments inside the LCD display 
elements, such that these have to be replaced after a certain operating 
time. Further, there is a disadvantage in that electrical installation 
equipment has to be assigned to the light sources inside the housing or on 
its rear side such electrical equipment also generates heat and is heavy 
in weight. Finally, another disadvantage resides in the necessitated 
hinged arrangement of the LCD display element, dust is capable of entering 
through a plurality of housing openings, such that the dust deposits both 
on the light sources and on the inner sides of the LCD display element 
thereby, causing a premature damping of light. 
SUMMARY AND OBJECT OF THE INVENTION 
It is an object of the invention to improve an electro-optical flat-design 
display, in particular an LCD area, of the abovementioned type such that 
the backlighting device is considerably simplified, in order to obtain a 
more compact flat-design display device, the display elements of which are 
affected neither by u.v. nor by heat irradiation nor by dust ingress, and 
which is particularly maintenance-friendly. 
According to the invention, backlighting of the display elements, in 
particular of the LCD display elements, is effected by a light-guide tube 
disposed inside the housing, the light source of which is disposed at one 
end of the light-guide tube, in particular outside the housing. The 
light-guide tube is made from transparent material and is surrounded by a 
reflector, such that the total light irradiation generated by the light 
source is continuously reflected inside the light-guide tube and can 
emerge only through the cutouts of the reflector immediately in the area 
of the individual display elements. By this arrangement complete usage is 
made of the light radiation of the light source. Additionally, there is no 
u.v. or heat irradiation load of the display elements, in particular LCD 
display elements. Further, replacing the components disposed inside the 
housing in the area of the display elements is no longer necessary, such 
that the individual display elements can be fixed to the front side of the 
housing. The housing can, thereby, be encapsulated in a dust-tight manner. 
Further, there is no need for electrical equipment inside the housing. 
Even blower equipment is not required anymore. 
In another embodiment of the invention, the light source is disposed at the 
end of the light-guide tube disposed outside the housing and there are 
mounted heat and color filters in front of the light source. This 
arrangement improves both the ease of maintenance of the flat-design 
display device, and reduces the heat irradiation on the display elements 
in the housing. 
Further, for an arrangement of several lines of LCD display elements having 
assigned each a light-guide tube, there can be disposed electronic 
components in the free spaces formed therebetween for controlling the LCD 
display elements 
Light-guide tubes are per se known in the art from DE Pat. No. 34 30 191. 
They serve, however, exclusively as lighting bodies for room lighting 
purposes. According to the invention, the usage of such light-guide tubes 
is provided for electro-optical flat-design display devices, in particular 
for LCD areas. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects obtained by its uses, reference 
is made to the accompanying drawings and descriptive matter in which a 
preferred embodiment of the invention is illustrated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings in particular the LCD area consists of a 
flat-design housing 1 with rear wall 2, top wall 3, bottom wall 4, side 
walls 5 and with intermediate walls 6 extending between the side walls 5 
in parallel to the top wall 3 and the bottom wall 4 and forming individual 
chambers 7. The front side 8 of the housing is substantially formed by 
rows 9 of LCD display elements 10, which, in the embodiment shown, are 
formed as known-in-the-art 7-segment display elements. Instead of the 
7-segment elements, 3.times.5 matrix elements or the like can also be 
employed. The construction of such LCD elements is described in more 
detail in EP No. 0.146.285. The LCD elements 10 are received by profiled 
sections 11 extending on the front side 8, the profiled sections 11 being 
fixed to the top wall 3 and to the bottom wall 4 as well as to the 
intermediate walls 6. The electronic components 23 assigned to the 
individual LCD elements 10 are mounted on the intermediate walls 6. On the 
inner side diffuser disks 24 are assigned to the LCD elements 10. The 
total housing 1 is encapsulated in dust-tight manner. 
Within the individual chambers 7 of the housing 1, light-guide tubes 12 are 
disposed, which, in the embodiment shown, are U-shaped, the open side of 
the U-shape being formed by a strip-type wall 13. The light-guide U-shaped 
tubes 12 and the strip-type walls 13 are surrounded by reflector material 
14. In the area of the LCD elements 10 the material 14 is provided with 
cutouts 15 which serve as light-exit openings and correspond in their area 
dimensions accurately to those of the LCD elements 10 to be lighted and 
being assigned thereto. Within the light-guide tubes 12, in the curved 
rear section of the U-shape, concentrators 16 are supported. The 
concentrators 16 direct the light, which has been reflected in the 
light-guide tubes 12, in the direction of the opposed cutouts 15 of the 
reflector material 14. 
Each light-guide tube 12 is connected to a light-guide tube 17 arranged 
outside the housing 1. The light-guide tube 17 comprises at its one end a 
light source 18 directing its total light radiation by means of a suitable 
reflector 25 into the light-guide tube 17. At the bendings of the 
light-guide tube 17 and at the entrance locations of the light-guide tubes 
12, deflector mirrors 19, 20 are disposed, the deflector mirror 19 
deflecting the total light radiation and the deflector mirrors 20 
deflecting each part only of the radiation into the respective light-guide 
tubes 17 or 12, respectively. Finally, a heat filter 21 formed as a glass 
disk and a color filter 22 are mounted in front of the light source 18. 
The color filter 22 is formed as an electrically controllable, doubly 
refracting color filter using liquid crystal technology (ECB-LC filter). 
The light radiation emerging from the light source 18 passes through color 
filter 22 and through heat filter 21 and is guided totally over the 
light-guide tube 17 and the deflector mirrors 19, 20 into the individual 
light-guide tubes 12. Here, continuous total reflection of the entering 
light radiation is effected at the walls of the light-guide tubes 12, 
including the flat walls 13 assigned to the light-guide tubes 12. At the 
end opposite to the light source 18, (at an end of each light-guide tube 
12), additional mirrors are arranged (not shown) for a substantially 
loss-free reflection of the light radiation. The light radiation being, 
thus, continuously reflected inside the light-guide tubes 12 can only exit 
through the light exit openings 15 assigned to the respective LCD elements 
10. By means of the concentrators 16, the intensity of the light radiation 
emerging here is further increased. 
As material for the light-guide tube 12 and for the wall 13 limiting the 
latter, a per se known reflector foil is employed. In particularly 
advantageous manner, a reflector foil is employed, which is described in 
more detail in DE Pat. No. 34 30 191 A1 following the example of a 
lighting body having prismatic light guiding for room illumination. 
Herein, a special shape of the outside contour of the light-guide foil 
serves for total reflection of the light radiation inside the light-guide 
tube 12, an exit of the radiation being only possible within the cutouts 
15. 
While a specific embodiment of the invention has been shown and described 
in detail to illustrate the application of the principles of the invention 
it will be understood that the invention may be embodied otherwise without 
departing from such principles.