PHOTOLUMINOUS SIGNS

Abstract

An aircraft emergency sign comprising a plurality of layers, the plurality of layers comprising a base layer (2) comprising a photoluminescent material (4) designed to be charged by electromagnetic wavelengths in a first range and designed to emit electromagnetic emissions in a second range; a barrier layer (6); and a printing layer (10), the printing layer (10) being printed with at least one of a color or pattern, the printing layer being above the barrier layer (6) and on a side distant from the base layer (2), and the printing layer being at least semi-transparent to wavelengths in the first and second ranges, the sign further comprising a masking layer (14) situated between the barrier layer and the printing layer. Figure to be published with the abbreviation: Figure 1

Description

Title of the invention: PHOTOLUMINESCENT SIGNS

[0001] The present invention relates to photoluminescent signs. The invention has particular but not exclusive application to signs used in transportation vehicles such as boats, aircraft, buses, trains and the like to identify an exit and / or to indicate a path or route to an exit or to provide emergency information. Such signs may be used to assist people in exiting vehicles and the like in an emergency situation. It will be appreciated that the signs may also be used in buildings or other locations where emergency signaling is required. Such signs may also be located at or near an exit so as to facilitate identification of the exit. Such signs may also be provided as part of an evacuation system designed to guide people to and identify an exit.

[0002] Equipping signs with electrical lighting to enable them to be more easily visible is known. In an emergency, the electrical supply may be lost and emergency signs relying on electrical lighting then lack illumination and may not be visible. In passenger vehicles in particular it is important to provide signs that are visible even in the event of a loss of electrical supply. This is particularly important in passenger vehicles such as aircraft and boats.

[0003] In a particular aircraft there are usually safety rules and requirements. The safety rules may specify that an emergency power system may be provided and this may include a battery-powered lighting system. The safety requirements specify that the battery in an emergency system must power the lighting system for at least ten minutes. However, it is also known that evacuation of a cabin may take more than 10 minutes and if the battery fails before the evacuation is complete, the remaining passengers and staff may have difficulty locating the exit. In addition, if an aircraft or other vehicle is disabled then the lighting system circuits may be broken and the electric lighting may fail completely.

[0004] The use of photoluminescent signs and markers in passenger vehicles such as boats and particularly aircraft is known. The photoluminescent signs and markers comprise a photoluminescent material. When exposed to a light source, the photoluminescent material is activated and provides a low level light source which is normally invisible in daylight but is visible in dark or Low illumination from other light sources, for example, where smoke from a fire blocks the overhead lights that normally illuminate the passenger cabin. The level of illumination provided by the photoluminescent material under these conditions is sufficient to guide passengers to an exit to evacuate the aircraft and eliminates the problems associated with electrically powered systems that are prone to failure just when needed.

[0005] Commonly photoluminescent material usually has a pale yellow color. Conventional colors of photoluminescent material tend to be highly visible even under normal ambient lighting conditions. In some situations, it may be undesirable to have a sign that is highly visible under normal ambient lighting conditions. Some passengers do not like to see safety equipment or safety information because it can increase awareness of obvious hazards and cause a feeling of concern or unease. Accordingly, the presence of visible safety signs can have a detrimental effect on a passenger's experience in an aircraft. In addition, the presence of obvious emergency signs in an aircraft can also detract from an aesthetic appearance of a cabin environment.

[0006] According to a first aspect of the invention there is provided an aircraft emergency sign comprising a plurality of layers, the plurality of layers comprising a base layer comprising a photoluminescent material adapted to be charged by electromagnetic wavelengths in a first range and adapted to emit electromagnetic emissions in a second range; a barrier layer; and a print layer, the print layer being printed with at least one of a color or a pattern, the print layer being above the barrier layer and on a side spaced from the base layer, and the print layer being at least semi-transparent to wavelengths in the first range and the second range, the sign further comprising a mask layer located between the barrier layer and the print layer.

[0007] The aircraft emergency sign according to the present invention may also have one or more of the following characteristics, taken in isolation or in any technically possible combination: • the mask layer is a neutral color. • the sign includes a protective layer and the protective layer is a top layer. • the photoluminescent material is selected from Sr4Ali4O25Eu, Dy emitting blue and SrAlO4Eu, Dy emitting green. • the first range goes from 250 nm to 470 nm. • the second range goes from 450 nm to 500 nm or from 501 nm to 540 nm.

[0008] Another subject matter of the invention is an aircraft comprising a cabin having at least one emergency sign comprising a plurality of layers, the plurality of layers comprising a base layer comprising a photoluminescent material adapted to be charged by electromagnetic wavelengths in a first range and adapted to emit electromagnetic emissions in a second range; a barrier layer; and a print layer, the print layer being above the barrier layer and on a side remote from the base layer, the print layer being printed with at least one of a color or a pattern and the print layer being at least semi-transparent to wavelengths in the first range and the second range, the sign further comprising a mask layer located between the barrier layer and the print layer.

[0009] The aircraft according to the present invention may also have one or more of the following characteristics, taken in isolation or in any technically possible combination: • the sign is mounted in a portion of a wall or trim in the cabin and the print layer of the sign has a pattern corresponding to a surface of the wall or trim. • the barrier layer includes symbology or words in positive or negative form. • the symbology or words are visible in low ambient light level and where the pattern on the print layer is visible in high ambient light level.

[0010] The emergency sign comprises a plurality of layers, the plurality of layers comprising a base layer comprising a photoluminescent material configured to be charged by electromagnetic wavelengths in a first range and configured to emit electromagnetic emissions in a second range; a barrier layer; and a print layer, the print layer being above the barrier layer and on a side spaced from the base layer, and the print layer being at least semi-transparent to wavelengths in the first range and the second range.

[0011] In some embodiments, the barrier layer is dark. In some embodiments, the barrier layer may be black. The barrier layer is adapted and arranged such that at least a portion of the layer prevents light, such as visible light or light emitted by the photoluminescent material, in the second range, from passing through that portion of the layer. In some embodiments, the barrier layer is typically provided with apertures forming words or illustrations or images that may be referred to as text or symbology. Photoluminescent light may pass through the apertures. The barrier layer may include a film layer. The barrier layer may include a colored film. In other embodiments, the barrier layer may include a film having a color printed on at least one side of the film. The color printed on the film may be opaque or at least substantially opaque to light emitted from the photoluminescent material. In a preferred embodiment, a dark color printed on the film may include unprinted areas through which the emitted light may pass. In other embodiments, the barrier layer may include printed words or symbology forming a barrier to the emitted light. The remainder of the barrier layer may be configured to allow the emitted light to pass such that the words or symbology are formed in negative. The text or symbology may be formed by apertures in the film.

[0012] According to preferred embodiments the text or symbology is formed by printing a dark color directly onto the photoluminescent material, as a positive or negative image. According to some embodiments the barrier layer may form a negative image of the desired words, illustrations or images by having the text or symbology printed as a barrier layer on at least a portion of the photoluminescent material such that photoluminescent light cannot pass through the print forming the barrier layer.

[0013] It has been found that providing a printed layer over the barrier layer does not provide a satisfactory appearance in ambient light. In prior art solutions it is found that the presence of emergency signage is under normal ambient lighting. It is believed, at least in part, that this arises from a contrast between dark areas of the barrier layer through which the emitted photoluminescent light cannot pass and lighter areas where an opening in the film or in the print allows light from the photoluminescent material to pass.

[0014] In the sign according to the invention a mask layer is disposed between the barrier layer and the printing layer. The mask layer may comprise a film. The mask layer film may comprise a colored film. More preferably the mask layer may comprise a film on which an ink coating has been printed. Ideally the mask layer comprises a layer of ink or other pigment printed on or applied to the barrier layer. The mask layer may be printed over the entire sign. The mask layer may be printed over the dark portions and over the openings or unprinted portions of the barrier layer to provide a background for the printing layer.

[0015] Applicant has found that providing a mask layer improves the appearance of the printed layer. The mask layer may comprise a neutral color. In some embodiments, the mask layer has a uniform color. Desirably, a color of the mask layer is selected to provide a smooth background to the printed layer. The mask layer may be configured to at least partially obscure the barrier layer and to provide a smooth background to the print layer. Typically, the mask layer may be a light color or tint or may be another neutral color and is preferably uniform. The mask layer may be white in some embodiments.

[0016] It has been found that the mask layer provides a smooth and even background to the print layer and thus obscures the image of the text or symbology in the barrier layer when the sign is viewed under ambient lighting conditions.

[0017] It is desirable that the mask layer is transparent, or at least partially transparent, to wavelengths in the first range and in the second range. The first range allows wavelengths that are absorbed by the photoluminescent material to charge the photoluminescent materials. The second range allows emitted wavelengths to pass through the other layer. The first range may be UV or blue light wavelengths. The second range of emitted light is typically in the blue to green wavelength range. The second range is preferably visible light. The barrier layer may, according to some embodiments, be at least partially transparent to electromagnetic radiation in the first range.

[0018] The sign may have a surface area. Desirably the mask layer is disposed over substantially the entire surface area of ​​the sign.

[0019] According to some embodiments the sign may be used in a cabin of an aircraft. The sign may be adapted to be attached to a wall in the cabin. According to another embodiment the sign may be adapted to be attached to a trim in the cabin of the aircraft. The wall of the aircraft may have a color or a pattern. According to some embodiments the wall or trim may include a pattern such as a wood effect.

[0020] Desirably the print layer is printed with at least one of a color or a pattern. The print layer may comprise a color. The color of the print layer may be selected to correspond to an area on a surface of the aircraft cabin on which the sign may be mounted in use. In some embodiments the sign may be mounted on a wall and the selected color corresponds to the color of the wall. In other embodiments the sign has a print layer having a pattern printed thereon. The printed pattern may be selected or designed to correspond to the surface of the surrounding area.

[0021] Desirably the sign is provided with a protective layer. The protective layer may be arranged to cover at least a portion of the layer printing. The protective layer is desirably arranged to cover substantially the entire printing layer.

[0022] Desirably the photoluminescent material exhibits persistent luminescence. In some embodiments the photoluminescent material comprises a strontium aluminate. The photoluminescent material may be selected from blue-emitting Sr4Ali4O25Eu, Dy and blue-emitting SrA104Eu, Dy. Typically the photoluminescent material is excited, or charged, by electromagnetic wavelengths in the first range. The excitation wavelengths in the first range may be from 250 nm to 470 nm. In some embodiments the photoluminescent material may be excited by wavelengths in the range of 400 nm to 470 nm.

[0023] According to some embodiments the photoluminescent material emits electromagnetic wavelengths in the range of 400 to 800 nm. The second range may be from 400 nm to 600 nm or from 450 nm to 500 nm or substantially be at 490 nm. According to other embodiments the second range may be from 450 nm to 700 nm or from 500 nm to 600 nm or more preferably from 500 nm to 550 nm or from 500 nm to 540 nm or substantially be at 520 nm. According to a preferred embodiment the wavelengths emitted in the second range are in the visible light range.

[0024] As described above a barrier layer may be disposed adjacent to the base photoluminescent layer and between the base layer and the print layer. The barrier layer may comprise symbology or words in positive or negative form. Where the symbology or words are provided in positive form in the barrier layer the symbology or wording will appear as a dark area on an illuminated background in the sign in a high light level scenario.Where symbology or words are provided in negative form in the mask, the symbology or wording will appear as a lit area on a dark background in the sign in a low light level scenario.

[0025] An important aspect of the invention is that in a low ambient light scenario the light emission from the photoluminescent material passes through the apertures in the barrier layer, where the words or symbology are provided or vice versa, the mask layer and the print layer and the emergency signage or symbols is visible to the passengers and crew of the vehicle. Typically a low light scenario is one in which normal electrical lighting in the vehicle has failed.

[0026] In a normal lighting scenario ambient light is reflected by the print layer which corresponds to that of a surrounding surface of a wall or trim on which the sign is mounted. The intensity of emissions from the photoluminescent material is relatively much lower than the light reflected and thus the emitted photoluminescent light is not perceived by passengers or crew. As a result the sign is perceived as part of the surrounding surface and the symbology or words in the barrier layer are not visible to passengers or crew in a normal ambient light scenario.

[0027] It will be appreciated that as ambient light levels decrease, the light emission from the photoluminescent material becomes more visible. It will also be appreciated that the emergency sign provides luminance but not illumination. Providing luminance means that the sign can be seen. On the other hand, illumination means that a surrounding area is lit. By providing luminance but not illumination, the sign can be used to provide emergency guidance but without disturbing passengers who may be sleeping. In addition, it will be appreciated that the color of the light emitted from the photoluminescent material can be important. In low light levels the human eye uses scotopic vision in which the eye uses rods to detect light. Scotopic vision is particularly sensitive to light emitted in the blue wavelengths of 450 nm to 500 nm.In scotopic vision the eye perceives light and dark. In scotopic vision the eye does not perceive color. Therefore if signs emit light having wavelengths in this region of 450 to 500 nm then the sign will be able to provide sufficient luminance at lower light output levels. In high light levels the human eye uses photopic vision which uses cones in the retina to detect objects and color. In medium light levels the human eye uses mesopic vision which is a combination of photopic vision and mesopic vision.

[0028] Accordingly the emergency sign emitting in the range of 450 nm to 500 nm is not visible under normal operating light level conditions but becomes visible in an emergency scenario in which the electrical lighting has failed or is obscured. The safety requirements to enable guidance of passengers and crew are met by the sign in an emergency scenario but the passenger experience is not reduced by the visibility of the emergency signage in normal use. In addition the aesthetic appearance of a cabin is not reduced by the intrusion of emergency signage in normal use but the safety requirements are met in an emergency.

[0029] According to a second aspect, the invention relates to an aircraft comprising a cabin comprising at least one sign in accordance with the first aspect of the invention.

[0030] It will be appreciated that the cabin may have a wall and the sign may be mounted in a portion of the wall. In other embodiments the cabin may be provided with a trim and the sign may be mounted in a portion of the trim in the cabin. The portion of the wall or trim may have a surface having a color or pattern. Desirably the print layer of the sign has a pattern corresponding to the surface of the portion of the wall or trim on which the sign is mounted. The color may be a solid color. In some embodiments the portion of the wall or trim has a pattern such as a wood effect. The pattern on the print layer may be designed to have the same pattern as the pattern on the portion of the wall or trim on which the sign is mounted.

[0031] The invention will now be further described by way of example only with reference to the appended Figures in which:

[0032] [Fig.l], [Fig.l] is an exploded view of the structure of a sign in accordance with the invention;

[0033] [Fig.2], [Fig.2] is a view of the sign of [Fig.l] under normal ambient lighting conditions;

[0034] [Fig.3], [Fig.3] is a view of the sign of [Fig.l] in dark conditions;

[0035] [Fig.4], [Fig.4] is one of an alternative embodiment of the sign;

[0036] [Fig.5], [Fig.5] is a view of a cabin of an aircraft in accordance with the invention; And

[0037] [Fig.6], [Fig.6] is a schematic view of an aircraft in accordance with the invention.

[0038] As best illustrated in [Fig.l] an emergency sign 1 is proposed comprising a plurality of layers. The emergency sign comprises a base layer 2. The base layer 2 comprises a photoluminescent material 4 adapted to be charged by electromagnetic wavelengths in a first range and adapted to emit electromagnetic emissions in a second range. A barrier layer 6 is disposed adjacent to the base photoluminescent layer 2. The barrier layer 6 comprises text or information symbology 8. A print layer 10 is disposed above the barrier layer 6 and on one side of the barrier layer 6 spaced from the photoluminescent base layer 2. The print layer 10 is at least semi-transparent to wavelengths in the first range and the second range.

[0039] The base layer 2 comprises a photoluminescent material 4. The photoluminescent material 4 may be disposed on a substrate 12. According to certain embodiments, the photoluminescent material 4 may be provided as a suspension of photoluminescent pigments in a resin.

[0040] The barrier layer 6 is disposed adjacent to the photoluminescent base layer 2 and between the base layer 2 and the printing layer 10. The barrier layer 6 may be a film. Alternatively, the barrier layer may be directly printed onto the photoluminescent layer. The barrier layer 6 is desirably at least partially opaque to at least electromagnetic emissions. in the second range. It is preferred that the barrier layer be substantially opaque to at least electromagnetic emissions in the second range. In some embodiments the barrier layer may comprise a colored film such as a black film. In some embodiments the barrier layer may comprise a film, transparent or colored, on which dark or black ink has been printed. The barrier layer 6 may comprise symbology or words in positive or negative form. In preferred embodiments the symbology or words may be printed on a barrier film or more preferably in other embodiments printed directly onto the photoluminescent material. The symbology or words may be a statement such as EXIT or arrows to indicate direction or other symbols such as a running man.Where the symbology or words 8 are provided in positive form in the barrier layer 6 the desired words or symbology may be printed on the barrier layer 6. The printed portion 8 of the barrier layer is selected to block the transmission of light emitted from the photoluminescent material. In the final product the symbology or statement will appear as a dark area on an illuminated background in the sign in a low light level scenario as illustrated in [Fig. 3]. In some embodiments the barrier layer may comprise black or red printing on a film. The printing may be the statement or symbology. The black or red printing may be a layer provided with the words or symbology in negative.

[0041] Where the symbology or words are provided in negative form in the barrier layer, the symbology or statement 8 will appear as an illuminated area on a dark background in the emergency sign in a low light level scenario as illustrated in [Fig. 4]. In some embodiments a print may be comprised of an opaque material over an area of ​​the barrier layer with unprinted areas on the layer forming the symbology words. In other arrangements the words or symbology could be formed by a cut(s) in an opaque film. The words or symbology may be provided by an aperture in the film or in another embodiment by a portion of the layer where there is no print on the photoluminescent material.

[0042] A mask layer 14 is disposed between the barrier layer 6 and the printing layer 10. According to this embodiment the mask layer may comprise a film. The mask layer film may be a colored film. More preferably the mask layer 14 is a film on which an ink coating has been printed. According to another preferred embodiment the mask layer comprises a layer of printed ink or other coating applied over the barrier layer.

[0043] The mask layer 14 is designed to be a neutral color. Preferably the mask layer has a homogeneous color. The color of the mask layer 14 may be selected to provide a smooth and homogeneous background to the printed layer 10 which at least partially obscures and neutralizes the contrast in the barrier layer 6 between an aperture and the printed barrier layer.

[0044] In some embodiments, the mask layer 14 has a uniform color. In some embodiments, the mask layer 14 is white. In other embodiments, another neutral color may be selected. The mask layer 14 provides a consistent tone as a background for the print layer. In some embodiments, the print layer 10 may be disposed on a film layer and superimposed on the mask layer. In other embodiments, a printed pattern may be printed directly onto the mask layer to provide a print layer 10.

[0045] It is desirable that the mask layer 14 be transparent, or at least partially transparent, to wavelengths in the first range and in the second range. The first range allows wavelengths that are absorbed by the photoluminescent material to charge the photoluminescent materials. The second range allows emitted wavelengths to pass through the mask layer.

[0046] Desirably the mask layer 14 is disposed over substantially the entire surface area of ​​the sign.

[0047] As illustrated in [Fig. 5], it is intended that the sign 1 be used in a cabin 20 in an aircraft 22. The sign 1 may be adapted to be attached to a wall 24 of the cabin 20 or to be attached to a trim 26 of the cabin 20 of the aircraft 22. Typically a wall 24 of an aircraft has a color or pattern. The wall 24 or trim 26 may have a solid color or may have a pattern such as a wood effect.

[0048] It will be appreciated that the sign 1 may indicate the location of an emergency exit 28 or may be informative. [Fig. 6] is a schematic indication of an aircraft in accordance with the invention in which the location of emergency exits 28 is indicated by the location of signs 1 on the cabin walls 20 and internal walls 24 of the cabin 20.

[0049] In a normal lighting scenario ambient light is reflected by the print layer which corresponds to that of a surrounding surface of a wall or trim on which the sign is mounted as illustrated in [Fig.2]. Emissions from the photoluminescent material are relatively much lower in intensity than the reflected light and are not perceived by passengers or crew. As a result the sign is perceived as part of the surrounding surface and the symbology or words in the barrier layer are not visible to passengers or crew in a normal ambient light scenario.

[0050] The printing layer is printed with at least one of a color or a pattern to match the wall or trim to which the sign is intended to be affixed. It is intended that the printed pattern or color be such that under normal ambient light levels the location of the sign is not identifiable and the words or symbology are not visible. The sign blends into the surface on which it is mounted under normal ambient lighting conditions.

[0051] According to some embodiments the sign is provided with a protective layer that is configured to cover at least a portion of the print layer. The protective layer is desirably configured to cover substantially all of the print layer and to protect the sign from wear and tear. The protective layer may have a finish selected from matte, glossy, or anti-reflective.

[0052] The photoluminescent material in the base layer exhibits persistent luminescence. Typically the photoluminescent material comprises strontium aluminate. According to a preferred embodiment the photoluminescent material may be selected from blue-emitting Sr4Ali4O25Eu, Dy and green-emitting SrA104Eu, Dy. The photoluminescent material is excited, or charged, by electromagnetic wavelengths in the first range. The excitation wavelengths in the first range may range from 250 nm to 470 nm.

[0053] According to some embodiments the photoluminescent material emits electromagnetic wavelengths in the range of 400 to 800 nm. The second range may be from 400 nm to 600 nm or from 450 nm to 500 nm. The photoluminescent material may be emission wavelengths in the second range that are blue and may be substantially 490 nm. According to other embodiments the second range may be from 450 nm to 700 nm or from 500 nm to 600 nm or more preferably from 500 nm to 550 nm. According to some embodiments the photoluminescent material may be emission wavelengths in the second range that are green and may be designed to be around 520 nm.

[0054] An important aspect of the invention is that in a low ambient light scenario the light emitted from the photoluminescent material passes through a portion of the barrier layer, the mask layer and the print layer and the emergency signage or symbols are visible to the passengers and crew of the vehicle. Typically a low light scenario is one in which normal electric lighting in the vehicle has failed and the cabin is dark. It will be appreciated that the emitted light may be in the range to which the human eye is sensitive in scotopic vision. A level or intensity of light output from the photoluminescent material may then be lower than would be required if the light output were in a different wavelength range.

[0055] In a normal lighting scenario ambient light is reflected by the layer printing that matches that of a surrounding surface of a wall or trim on which the sign is mounted. The emissions from the photoluminescent material are relatively much lower than reflected light and are not perceived by passengers or crew. As a result, the sign is perceived as part of the surrounding surface and the symbology or words in the barrier layer are not visible to passengers or crew in a normal ambient light scenario.

[0056] Therefore, the emergency sign is not visible under normal operating light level conditions but becomes visible in an emergency scenario in which the electrical lighting has failed or is obscured. The safety requirements for guiding passengers and crew are met by the sign in an emergency scenario but the passenger experience is not reduced by the visibility of an emergency sign in normal use. Furthermore, the aesthetic appearance of a cabin is not reduced by the intrusion of an emergency sign in normal use but the safety requirements are met in an emergency.

[0057] Preferably the emergency sign is used in an aircraft or aircraft cabin.

[0058] It will be realized that the product must meet aerospace requirements. These include DO-160 for environmental requirements such as the effects of temperature, altitude, humidity, shock and crash safety, vibration, water and fluid sensitivity, flammability, etc. Signs must meet the requirements of CS / FAR25.853 for fire resistance.

[0059] The luminance of the sign must also meet the requirements of CS 25.812 and CS23.2315 for large aircraft or CS 29.812 for large rotorcraft for safety critical signage, particularly where the signs are used for emergency exit signs. In small aircraft or rotorcraft the sign may need to meet the requirements of CS27.805 and CS27.807.

[0060] It will be appreciated that the sign may be mounted in a portion of a wall of the aircraft cabin. In other embodiments the cabin may be provided with trim and the sign may be mounted in a wall of the trim in the cabin. The sign is provided with a pattern or color that corresponds to the portion of the wall or trim on which the sign is to be mounted or secured.

Claims

Claims

1. An aircraft emergency sign comprising a plurality of layers, the plurality of layers comprising a base layer comprising a photoluminescent material configured to be charged by electromagnetic wavelengths in a first range and configured to emit electromagnetic emissions in a second range; a barrier layer; and a print layer, the print layer being printed with at least one of a color or a pattern and the print layer being above the barrier layer and on a side spaced from the base layer, and the print layer being at least semi-transparent to wavelengths in the first range and the second range, the sign further comprising a mask layer located between the barrier layer and the print layer.

2. The sign of claim 1 wherein the color of the mask layer is selected to provide a smooth background to the printed layer that at least partially obscures the barrier layer.

3. An aircraft emergency sign according to any preceding claim wherein the sign comprises a protective layer and wherein the protective layer is a top layer.

4. An aircraft emergency sign according to any preceding claim wherein the photoluminescent material is selected from blue emitting Sr4Ali4O25Eu, Dy and green emitting SrA104Eu, Dy.

5. An aircraft emergency sign according to any preceding claim wherein the first range is from 250 nm to 470 nm.

6. A sign according to any preceding claim wherein the second range is from 450 nm to 500 nm or from 501 nm to 540 nm.

7. An aircraft comprising a cabin having at least one emergency sign comprising a plurality of layers, the plurality of layers comprising a base layer comprising a photoluminescent material adapted to be charged by electromagnetic wavelengths in a first range and adapted to emit electromagnetic emissions in a second range; a barrier layer; and a print layer, the print layer being above the barrier layer and on a side spaced from the base layer, the print layer being printed with at least one of a color or a pattern and the print layer being at least semi- transparent to wavelengths in the first range and the second range, the sign further comprising a mask layer located between the barrier layer and the printing layer.

8. An aircraft according to claim 7 wherein the sign is mounted in a portion of a wall or trim in the cabin and wherein the print layer of the sign has a pattern corresponding to a surface of the wall or trim.

9. An aircraft according to claim 7 or claim 8 wherein the barrier layer comprises symbology or words in positive or negative form.

10. An aircraft according to claim 9 wherein the symbology or words are visible in a low ambient light level and the pattern on the print layer is visible in a high ambient light level.

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