ELECTRONIC DISPLAY AND/OR APPARATUS HAVING SUCH A DISPLAY

Abstract: An electronic display (2) for displaying signs or the like, for example for use in an electronic apparatus (1) within a cabinet (4) and with a keyboard (3) or similar control means. Behind the display there is arranged a radiation-sensitive power generator, for example a solar cell or a solar cell panel. Between the display and the solar cell there is arranged a filter which ensures the desired transmission and reflection of incident radiation.

Description: ELECTRONIC DISPLAY AND/OR APPARATUS HAVING SUCH A DISPLAY State of the art The invention relates to an electronic display for display¬ ing signs, graphics, pictures, symbols etc. Such displays are for example used in connection with vari¬ ous types of electric or electronic apparatuses such as measuring apparatuses, calculators etc. where the power supply to the apparatus and the display function by the use of radiation-sensitive power generators, for example in the form of one or more solar cells or solar cell panels. Such apparatuses are often small and portable. The term solar cells will at all times be used in the present application of any type of radiation-sensitive power generators which convert radiation, for example light, into electric power. The combination of solar cells and one or more displays is usually applied in connection with a store for electric energy, for example a condenser battery or a rechargeable battery, which in a known manner will operate as a buffer so that the apparatus will also operate during periods of less or no radiation on the solar cells. The term display is used in the present application as a common term of any type of electronic, controllable display panel or display screen for displaying signs, graphics, pictures, symbols etc. In the known apparatuses the display and the solar cells are arranged in respective openings which must both be pro¬ tected against the surroundings with protective glass or the like. This has economic as well as design-related drawbacks, will increase the production costs of the cab- inet, may cause space problems inside and outside the ap¬ paratus and may result in the application of an unnecessar- ily big cabinet for the apparatus in order to accomodate the solar cells, the display and what must otherwise be accessible on the cabinet. Display and solar cells are also seen to be arranged imme¬ diately next to each other in a cabinet and protected by one and the same cover glass to reduce space consumption. Since a display and the cover glass of a solar cell do not require quite the same optical properties, there may be a number of technical and economical drawbacks in arranging them side by side and under a common cover glass. The specification of US patent no. 4,882,471 describes an electronic apparatus with a display which is supplied with power from one or more solar cells. It is suggested therein that space may be saved by arranging the solar cells on the rear of the housing of the apparatus, namely under the dis¬ play. Such a structure is of no particularly great prac¬ tical importance since by normal use of the apparatus the solar cells will not generate sufficient power because the cells are not exposed when the apparatus is for example placed on a support. This structure will also necessitate an opening for the solar cells on the rear of the housing of the apparatus which has many drawbacks both technically and designwise. Advantages of the invention An electronic display according to the invention and with the features stated in the characterising part of claim 1 is advantageous in that it is possible to place the display and the solar cell on the same side of the housing of the apparatus and immediately over each other thereby avoiding many of the known drawbacks and providing a far higher de- gree of freedom when designing the cabinet of the appar¬ atus. The cabinet will become cheaper to produce with only one opening for the display and may usually be designed smaller which will also reduce costs. Another important ad¬ vantage is that it is possible to apply a solar cell area which is just as big as the display without additional space consumption which will usually amount to an increase of the solar cell area and provide increased and improved power supply of the circuit of the apparatus. An increase of the solar cell area will also permit extended working time without exposure since an energy store with a higher capacity may be applied. By designing the display according to the invention as disclosed in the characterising part of claims 2-4, there is obtained a simple and efficiently operating display sys- tem which can be used everywhere. The display system takes up less space than the known ones and provides increased freedom designwise. By designing the display according to the invention as disclosed in the characterising part of claim 5, there is obtained a unit which is very compact and of small thick¬ ness and which may be used instead of the known displays. If the display according to the invention is designed as disclosed in the characterising part of claim 6 or claim 7, there is obtained a quite new and highly compact component available to manufacturers and designers of electronic and electric apparatuses. The display according to the invention will not only pro¬ vide design-related and space-related advantages but will also permit simplified mounting since the supply lines to the display and to the solar cells may be designed as known contact plugs, soldered joints etc. The display according to the invention is preferably, but not exclusively, adapted for use in connection with electronic apparatuses as disclosed in the characterising part of claim 8. Such apparatuses are very often portable but may also be stationary, for example in places without electricity supply or in places with unstable electricity supply. The drawing An embodiment of the invention will now be explained further with reference to the drawing wherein fig. 1 is an electronic apparatus with a display accord¬ ing to the invention, fig. 2 is a schematic drawing of the display in fig. 1, but shown at a larger scale, and fig. 3 is a cross section of an integrated display with a solar cell according to another embodiment of the invention. Description of the embodiments Fig. 1 shows an electronic apparatus 1 which may for ex¬ ample be a calculator, a measuring apparatus or the like arranged in a cabinet 4 with a keyboard 3 and display 2 according to the invention. The invention will now be explained in connection with a display 2 in the form of an LCD (Liquid Crystal Display) display. From the following explanation it will be obvious to a person skilled in the art that also other display types may be used without departing from the basic idea of the invention and obtaining the advantages of the invention but that there are particular additional advantages in using an LCD display. The display 2 comprises a solar cell panel (not immediately visible in fig. 1) arranged behind the display face and which supply power to the display and the electronic cir¬ cuit in the apparatus. In order to improve the power supply the apparatus also comprises some form of store for electricity, for example a condenser battery, a recharge¬ able battery or the like, designed and dimensioned in a generally known manner. The cabinet 4 has thus only one opening for the display with solar cells and one cover glass therefor. Fig. 2 shows in greater detail the principles of a display according to the invention. The plate 5 is an LCD display provided at its rear face with a plate 6 which is a com¬ bined filter/reflector layer. In a common LCD display the incident daylight is reflected by a reflector, usually a silver foil or the like, which is attached to the rear face of the display. When a digit or a sign is activated electrically, the reflector effect of the crystal in front of the reflector is removed whereby the digit or the sign becomes visible. The filter/reflector 6 has among other things this function. Additionally, the layer 6 also has the function of allowing radiation to penetrate same to a solar cell or a solar cell panel 7, for example a silicon- planar solar cell with maximum sensitivity at about 900nm (nanometre) wavelength. A radiation Bl, for example infrared light from the day¬ light, within the range of 750-1100nm may thus penetrate the diplay 5 and the filter/reflector layer 6 to the solar cell panel 7 so that the solar cell panel may generate electric power. The damping here should be less than 20% so as to ensure that the solar cell 7 can produce the required energy. A radiation B2, for example daylight, in the range of 300- 750nm will be reflected from the filter/reflector layer 6, and it is this reflection which is prevented when a digit or the like in the LCD display is activated. The reflection from the layer 6 for the wave range in question should be higher than 80% to achieve a good contrast. If, for example, the filter/reflector layer 6 is designed as a so-called cold mirror, for example of gallium arsenide coated on a glass plate, it is possible to achieve a re¬ flection efficiency close to 99% for wavelengths within the range of 300-750nm and a transmission loss of max. 7-10% within the range of 750-llOOnm. Fig. 2 moreover shows that it is possible to apply a solar cell panel 7 with the same physical extent as the LCD layer 5 and thereby allow a larger solar cell area which will result in a higher production of electric power. Modified properties, including improved optical properties may also be achieved by inserting further layers between the LCD layer 5 and the solar cell 7 for improving the contrast of the display if the contrast is not sufficient. Fig. 3 shows a plane cross section of an integrated unit comprising an LCD display 5 and a solar cell panel 7. In front of the unit there is arranged a cover glass 12 may form one side of the LCD display. The layer 11 at the centre of the unit is likewise a glass plate carrying the crystal layer 13 on one side and the other side thereof carrying the coated filter 6'. Commonly known supply lines 9 at a sufficient number to form the symbols or signs de- sired lead to the crystal layer, and the solar cell panel 7 likewise comprises connecting parts 10. The unit shown in fig. 3 is therefore an integrated unit with display, power supply and contact plugs or the like ready for mounting in an electronic apparatus. The construction of the LCD unit itself is not further ex¬ plained since it is designed in a generally known manner, for example as further explained in Basic Guide, Liquid Crystal Displays, 1989, by LXD, Inc., 24500 Highpoint Road, Beachwood, Ohio 44122. The solar cell or solar cell panel 7 is not further ex¬ plained either, either regarding construction or function, since they are designed according to generally known technology within the area, , for example as described in data sheets from Kodenshi Corp., Japan, for example the types SSC-8-85LH and SSC-D8-85LH. Practical tests with known LCD crystal displays and known solar cells where between the display and the solar cell there is inserted a filter, for example solar filter film type P18 from 3M, have shown that the combined display- solar cell operates as desired with useful contrast as well as sufficient light transmission to the solar cell. By the test there was used a display from LXD, Inc. where the re- flector was removed and replaced by a piece of P18 solar filter film and immediately behind same there was arranged a common solar cell from a small pocket calculator. The test showed that the contrast on the display was sufficient and that there is achieved an acceptable transmission to the solar cell even though the filter material in question is not directly intended for such application.

Claims: C L A I M S 1. Electronic display (2, 5) and/or apparatus having such display for displaying signs, graphics, pictures, symbols etc. and a radiation-sensitive power generator, for example in the form of at least one solar cell arranged behind the display, which is at least partially translucent, charac¬ terised in that between the display (2, 5) and the solar cell or cells (7) there is arranged a radiation filter (6, 6'). 2. Display according to claim 1, characterised in that the display is an LCD display (5) and that the filter is a plane filter (6, 6' ) arranged behind the display and having a wavelength-dependent radiation-reflecting surface, pre¬ ferably on the side facing the display. 3. Display according to claim 1 or 2, characterised in that the solar cell or cells (6, 6') is/are plate-shaped and has/have an area which is smaller than or equal to the area of the display. 4. Display according to claim 1 or 2, characterised in that the filter is a semi-conducting radiation filter with a transmission loss which is less than 20% within the wave range of 750-llOOnm and a reflection of more than 80% with¬ in the wave range of 300-750nm. 5. Display according to any one of claims 1-4, character- ised in that the filter (6') has been directly applied, for example vapour-deposited, on the rear side of the display (2, 5) or a translucent plate behind the display. 6. Display according to any one of claims 1-5, character- ised in that the display (2, 5) and the solar cell or cells (7) are designed as one integral unit (fig. 3). 7. Display according to claim 6, characterised in that the integral unit (fig. 3) comprises a wavelength-dependent radiation filter (6') arranged between the display (2, 5) and the solar cell or cells (7). 8. Electronic apparatus according to claim 1, characterised in that it further comprises a store for electric energy, for example a condenser battery or a rechargeable battery.

Inventors: PEDERSEN KJELD, RASMUSSEN HENRIK FIND LINDSKOV, PEDERSEN, KJELD, RASMUSSEN, HENRIK, FIND, LINDSKOV
Applicants: PEDERSEN KJELD, RASMUSSEN HENRIK FIND LINDSKOV, PEDERSEN, KJELD, RASMUSSEN, HENRIK, FIND, LINDSKOV
Application year: 1993
Main classification: G09F9
IPC codes: G02F1, G09F9