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Patent Searching and Data


Title:
ILLUMINATING DISPLAY DEVICE
Document Type and Number:
WIPO Patent Application WO/1994/025950
Kind Code:
A1
Abstract:
There is disclosed an illuminating display device (11) comprising a legend-bearing face layer (13) which is part of a deep transparent member (14) in a lamp housing, the deep transparent member (14) being of uniform or substantially uniform refractive index throughout ist depth whereby to avoid internal reflections.

Inventors:
ROWLEY DAVID MICHAEL (GB)
Application Number:
PCT/GB1994/000927
Publication Date:
November 10, 1994
Filing Date:
April 29, 1994
Export Citation:
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Assignee:
UNIV LOUGHBOROUGH (GB)
ROWLEY DAVID MICHAEL (GB)
International Classes:
B60Q3/04; G09F13/04; (IPC1-7): G09F13/04; B60Q3/04
Foreign References:
GB2156292A1985-10-09
US4012632A1977-03-15
FR1523677A1968-05-03
EP0547943A11993-06-23
US3609023A1971-09-28
US4829407A1989-05-09
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Claims:
CLAIMS
1. An illuminating display device comprising a legendbearing face layer which is part of a deep transparent member in a lamp housing, the deep transparent member being of uniform or substantially uniform refractive index throughout its depth whereby to avoid internal reflections.
2. A device according to claim 1, in which the legendbearing face layer is a layer of photographic film.
3. A device according to claim 2, in which the film is of polyester.
4. A device according to claim 2 or claim 3, in which the film is bonded to a block of transparent material of the same refractive index as the film.
5. A device according to claim 4, in which the transparent material of a block is an acrylic plastic such as Perspex (RTM) .
6. A device according to claim 4 or claim 5, in which the film is bonded to the block using a cyano¬ acrylate bond.
7. A device according to any one of claims 2 to 6, in which the layer of film is arranged emulsionside down.
8. A device according to any one of claims 1 to 7, in which the face layer is coated with a matt overspray.
9. A device according to any one of claims 1 to 8, comprising an optical filter.
10. A device according to claim 9, in which the filter is part of the deep transparent member.
11. A device according to claim 10, in which the filter is bonded at the end of the deep transparent member opposite the face.
12. A device according to claim 11, in which the filter is bonded using a cyanoacrylate bond.
13. A device according to claim 11 or claim 12, in which the filter is of the same material as or a material having the same refractive index as the rest of the deep transparent member.
14. A device according to any one of claims 1 to 13, the lamp housing having lamp means directing illumination at the deep transparent member such that the angle of incidence of any ray is less than 45°.
15. A device according to claim 14, in which the lamp means are shrouded.
16. A device according to any one of claims 1 to 15, in which the lamp means are at such depth behind the face layer that light rays incident on the face layer at angles of incidence greater than 45° do not strike the lamp means or any reflector thereof.
Description:
ILLUMINATING DISPLAYDEVICE

This invention relates to illuminating display devices.

Illuminating display devices are used in control panels such as aircraft cockpit instrument panels.

Problems arise in conditions of high ambient illumination in that the display device legend is illuminated by the ambient illumination to such an extent that it gives a spurious indication. A device is required which will present a dark, matt, uniform surface under high ambient illumination, with no spurious indication, but will present a bright, clear and readable indication when illuminated, even under high ambient illumination.v.

The present invention provides such a device.

The invention comprises an illuminating display device comprising a legend-bearing face layer which is part of a deep transparent member in a lamp housing, the deep transparent member being of uniform or substantially uniform refractive index throughout its depth whereby to avoid internal reflections.

The legend-bearing face layer may be a layer of photographic film, such as a polyester film, which may be bonded, emulsion side down, to a block of transparent material of the same refractive index as the film - a material such as an acrylic plastic, such as Perspex (RTM) . The film may be bonded using a cyanoacrylate bond which has a similar refractive index.

The face layer may be coated with a matt overspray.

The device may comprise an optical filter, which may be part of the deep transparent member and which may be bonded at the end of the deep transparent member opposite the face, using, again, an acrylocyanate bond. The filter may be of the same material or a material having the same refractive-- index as the rest of the deep transparent member.

The lamp housing may have lamp means directing illumination at the deep transparent member such that the angle of incidence of any ray is less than 45°. The lamp means may be shrouded.

The lamp means may be at such depth behind the face layer that light rays incident on the face layer at angles of incidence greater than 45° do not strike the lamp means or any reflector thereof.

An illuminating display device according to the invention will now be described with reference to the accompanying drawings, in which :-

Figure 1 is a face-on view of the display device;

and Figure 2 is an axial section.

The drawings illustrate an illuminated display device 11 of the sort that might be used for example in control panels such as instrument panels in aircraft cockpits and bears a legend visible when the device is illuminated by internal lamp means 12.

Conventional such display means - and this is despite measures -taken -against this happening - tend to reveal the legend in bright ambient lighting conditions such as will be frequently encountered in aircraft flying above the weather, making it difficult to see if the device is illuminated or not. It will be appreciated that this is particularly unsatisfactory in aircraft.

The display device 11 comprises a legend-bearing face layer 13 which is part of a deep transparent member 14 in a lamp housing 15, the deep transparent member 14 being of uniform or substantially uniform refractive

index throughout its depth whereby to avoid internal reflections.

The legend-bearing face layer 13 is a layer of polyester photographic film, bonded by a cyanoacrylate bond (Loctite (RTM) Superglue 3) to a block 16 of acrylic plastic (Perspex (RTM)) which is transparent and has the same or substantially the same refractive index as the film 13. The bond material also has the same or substan¬ tially the same refractive index and this means that there is no or effectively no interface at which reflection could take place.

The film 13 is arranged emulsion-side down on the block 16 and its upper face is coated with a matt overspray 17.

The device 11 also comprises an optical filter 18 - it is desired to facilitate identification e.g. in cluttered cockpit conditions by colour coding. The filter 18 is part of the deep transparent member 14 and is bonded at the end thereof opposite the face - to the end of the block 16 - again using a cyanoacrylate (Superglue) bond. The filter 18 is also of Perspex (RTM).

In a particular case, the photographic emulsion was Agfa Gavaert 10E75 Holotest, 35 mm format on 100 um

polyester base. After exposure to image the desired legend, the film was processed at 20°C in developer Neofin Red (Tetenal) at dilution 1:5, 5 minutes constant agitation, fixed with G334 (Agfa) dilution 1:5, 5 minutes constant agitation, followed by a 5 minute wash and final rinse in 1:100 photoflo (Kodak).

The cyanoacrylate bond was applied as one drop on the Perspex base, to which the film was then applied, emulsion side down, and a pressure of 1 kg (9.8 N) applied over the area of the display which was 2 x 2 cm.

The matt overspray was Letracote (RTM) 103 Matt. Two layers of this cellulose nitrate spray were applied to a processed strip of exposed film, and allowed to dry for 24 hours before being cut up into individual legends.

The lamp housing 15 has lamp means 12 in the form of incandescent bulbs 21 - usually provided in pairs to survive filament failure. The bulbs 21 direct illumination at the deep transparent member 14 such that the angle of incidence of any ray is less than 45° - the spread of illumination is indicated in Figure 2. The lamp means 12 - the bulbs 21 - are shrouded in lamp holders 22 with reflectors 23, to achieve this.

The lamp means 12 are at such depth behind the face layer that light rays incident on the face layer at angles of incidence greater than 45° do not strike the lamp means 12, neither the bulbs 21 nor the reflectors 22 thereof - this further cuts down the tendency of ambient illumination to give spurious indications.

The depth of the block 16 for a 2 x 2 cm display is typically 5 mm.