A key pad according to the invention may be used for display of information on a permanent or intermittent basis. When the information is required for display only on an intermittent basis it is considered advantageous if the presence of information graphics is not visible to an observer until the information becomes relevant to a particular situation and is to be displayed.

In such an arrangement, in addition to the information conveyed to the viewer by the hidden graphics, there may be provided further information conveniently printed upon the obverse surface of a key of the key pad which remains visible under all lighting conditions.

According to a first aspect of the present invention there is provided a key pad having one or more keys, the or at least one of the keys having an obverse side and a reverse side, and wherein, in use, when viewed from the obverse side the or the at least one of the keys has a first appearance when not lit from the reverse side, but has a second appearance when lit from the reverse side.

According to a second aspect of the present invention, there is provided a key pad having one or more keys, wherein at least one of the one or more keys comprise a

plurality of layers, said layers including s. first at least partially transparent layer, and a second layer, at least selected areas of said second layer having a degree of contrast in opacity and/or colour, said first and second layers being associated with a substrate layer having an obverse surface and a reverse surface, wherein means are provided for furnishing said substrate layer with a partially transparent tinted appearance, and wherein said first layer comprises a coating comprising a transparent carrier in which are supported non-opaque particulate light splitting or light frequency modifying materials, said materials being capable of causing light splitting effects when viewed in light falling in a direction of the obverse surface of said substrate layer, and wherein further said second layer provides said at least selected areas rearwardly of said first layer which are of pre-determined size and shape, the construction and arrangement being such that the light-splitting or modifying effects caused by said particulate material in said first layer and visible in ambient light, is suppressed by the passage of light from a source located at the reverse side of the at least one key so that the presence of said at least selected areas become visible from the obverse side of the key.

Advantageously, the light-splitting or modifying effects caused by said particulate material in said first material in said first layer and visible in ambient light in said keys is in a pattern which matches with a pattern in a key pad body.

Advantageously, a suitable first layer may be provided by comprising at least a substantially transparent carrier containing particulate semi-transparent colour producing materials. A suitable material may be a flaked iridescent material of the kind exemplified by mica. Mica flakes may be pre-coated with ultra-thin layers of pigment, for example, oxides of metals such as titanium or iron.

Advantageously, the visual effect of the presence of the pigment may be varied according to the thickness of the pre-coating. Variations may also be observed in accordance with a base colour of the substrate layer and degree of translucency thereof.

Advantageously, said second layer may be provided as graphics in the form of information symbols applied in a discontinuous layer of an opaque or a substantially opaque pigment. Conveniently, said pigmented material may be printed pigmented ink or the like.

Alternatively, said second layer may by colour tinted in a contrasting hue so that the colour tint is visible only on the passage of light from a source located at a reverse side of the at least one key.

According to a third aspect of the present invention there is provided a key pad having one or more keys, wherein at least one of the one or more keys comprise a substrate layer and a coating layer applied to an obverse surface of the layer, said coating comprising non-opaque particulate light frequency modifying materials entrained in a carrier therefor, said particulate materials being

capable of causing light splitting effects when viewed in light falling upon the coated obverse surface, wherein said substrate layer is non-opaque except where provided with a layer comprising opaque or substantially opaque areas which are of pre-determined size and shape, the construction and arrangement being such that the light-splitting or modifying effect caused by the particulate material and visible in ambient light is suppressed by the passage of light from a source located at a reverse side of the at least one key so that the presence of the opaque areas become visible from an obverse side of the key.

In examples of key pads according to the invention and their use, the at least one key (s) may be comprised of a partially transparent panel substrate which is of the kind referred to as smoke coloured. The colour may, if preferred, be imparted to the keys (s) in a third layer which may be applied by a printing technique, but if preferred, may be obtained by the inclusion of pigment in the plastics film or other material of the key (s) substrate. It may be found that high quality visual effects are obtained with the use of pigments of a relatively dark hue.

The first layer may be provided by coating the substrate with a layer including ultra-thin flakes of mica that in the present example has been pre-coated with titanium dioxide. The coated flakes are capable of splitting light into its visible component colours, the apparent colour depending upon the thickness of the

titanium dioxide layer on the mica. This. varies in the present examples from 40 to 160 nm giving a range of colour from silver-white through copper-red, lilac, vivid blue, turquoise and finally green, the colour sequence being repeated as additional thickness is imparted to the titanium dioxide layer.

It should be noted that in addition to the effect described above, colour changes may be seen according to an angle from which the coated mica flakes are observed, the so-called interference colour being visible only at the glancing angle. Colours seen at other angles will differ.

For example, if a blue"interference"layer of pigmented material forms a coating on a white background, then the light reflected at the glancing angle is blue and masks the complementary colour yellow which is seen at other angles.

On a coloured background, the transparency of the coating permits the background colour to be visible through the coating, but at the glancing angle the interference colour predominates. On a curved key both colour effects may be observed at the same time on differing areas of the key to give a visually pleasing effect.

In a key pad in accordance with the invention, the positioning of a light source behind the key (s) will allow light from that source to penetrate the key (s) and the pigmented coating of the first layer. If the light from behind the key (s) is of greater intensity than ambient light falling on the obverse surface of the facia key (s) the colour effect visible in the first layer will be

suppressed and the colours of the second layers will predominate as the keys"lights up". The provision of graphics if present in the second layer will permit symbols to be visible, eg. as dark or darker areas against the back-lit key (s).

According to a fourth aspect of the present invention there is provided a key pad assembly adapted to provide a variable visual appearance and including a key (s) according to the first aspect of the invention.

The key pad assembly may comprise a facia having one or more apertures, each aperture being adapted to receive a key of the key pad.

The facia may be made from an opaque material.

Alternatively, the facia may also be formed from a plurality of layers in a similar manner to the key (s).

The key pad and facia are advantageously mounted relative to one another.

The assembly may further comprise a light source such that, in use, light from the source falls on a reverse surface of the key (s).

Advantageously, patterning on and or colouring of the facia matches one of the appearances of the key (s).

According to a fifth aspect of the present invention there is provided a key for use in a key pad according to the first to third aspects of the invention.

According to a sixth aspect of the present invention there is provided an apparatus including a key pad according to the first to third aspects.

The apparatus may be a telephone apparatus, such as a cordless or mobile telephone. Alternatively the apparatus may be a commercial or domestic electrical appliance, e. g. white goods.

Advantageously, the light-splitting or modifying effects caused by said particulate material in said first material in said first layer and visible in ambient light in said keys is in a pattern which matches with a pattern in a key pad body.

There will now be described a number of embodiments of the present invention, by way of example only. It will be understood that the description, which is to be read with reference to the accompanying drawings, is given by way of example only, and not by way of limitation. In the drawings: Figure 1 is a fragmentary perspective view of a portion of a key according to an embodiment of the invention; Figure 2 is a schematic side view illustrating layers of the key of Figure 1 and directions of light falling thereon; Figures 3 to 6 are schematic side views illustrating four alternative arrangements of layers of a key according to further embodiments of the invention; Figure 7 is a side view of a key pad including a plurality of keys according to Figure 1; Figures 8 to 12 are front views of a number of key pads according to embodiments of the present

invention; Figures 13 and 14 are front views of a key pad assembly according to an embodiment of the present invention ; and Figures 15 and 16 are front views of a mobile phone apparatus according to an embodiment of the present invention.

A key, generally designated 1 according to an embodiment of the present invention is illustrated in Figure 1 in which a substrate layer 2 is provided which is of plastics material-in the present example a transparent polycarbonate sheet. It will be understood that the substrate may be of any transparent material-e. g. glass or plastic-and may be flexible or rigid, and contoured, e. g. by a forming technique, or flat, as desired.

Applied to an obverse surface 4 of the substrate layer 2 is a layer 6 of smoky or similarly tinted material which introduces a degree of opacity to the substrate 2 to the extent that when viewed in ambient light or daylight falling on said obverse surface 4, the key 1'provides a dense appearance.

The layer 6 may be provided with a layer 8 comprising a transparent coating of acrylic varnish or other suitable carrier in which is entrained a quantity of flaked mica particles which have been pre-coated with a titanium oxide pigment to give a desired colour effect by means of the light modifying properties of mica (iridescence). In the present example, the layer 8 is discontinuous but if preferred, it may comprise a continuous coating.

On the reverse surface 10 of the substrate 2 is provided a discontinuous applied layer 12 of an opaque or substantially opaque pigmented ink or the like in a pre- determined pattern. This may comprise letters or graphics.

The effect of light on the key 1 of Figure 1 is shown diagrammatically in Figure 2.

Ambient light or daylight is shown by arrows A falling on the obverse side of the key 1 (the left-hand side in the Figure). The light reflects from the particles in the layer 8 and tends to be absorbed by layer 6 (smoked) so that the eye is aware only of the colour effect of the layer 8 which is at least partially iridescent.

However, a source of illumination is provided to produce light rays (arrows B) from the rear of the key 1 to fall on the reverse side thereof as required. These rays B pass through the substrate 2 and the layer 6 and 8 and are of sufficient intensity that the colour effects are suppressed and indeed it is no longer possible to see the pattern or decoration afforded by the pigmented layer 8.

However, some of the rays B do not penetrate layer 12 and therefore the pattern of the pigmented ink comprising the layer 12 becomes visible to the eye through the other layers.

It will be understood that in an alternative arrangement, the layer 12 may comprise one or more contrasting colour hue (s) which predominate over the layer 8 when back illumination is present (rays B).

It will be understood that the layers may be in direct and intimate contact with each other or it may if convenient be preferred to provide a gap between any adjacent pair of layers.

Figures 3 to 6 show variations in the arrangements of the layers which are possible within the scope of the invention.

Figure 3 shows an arrangement which the layers run from left to right as follows: (a) layer 8 (b) layer 6 (c) layer 12 (d) substrate 12 Figure 4 has the arrangement; (a) layer 8 (b) substrate (c) layer 6 (d) layer 12 Figure 5 has the arrangement: (a) substrate (b) layer 8 (c) layer 6 (d) layer 12 In Figure 5 however, the layer 6 (smoked) is replaced by the provision of a smoky dye effect in the plastics material of the substrate itself. Therefore the arrangement is: (a) layer 8

(b) substrate (with smoky effect) (c) layer 12 If a light source is switched on and the back light level predominates, the appearance changes on the key 1.

Referring now to Figure 7 there is shown an assembly, generally designated 100, including a key pad 105 having a key pad body in the form of facia 110 carrying a plurality of keys 1 through apertures formed therein. As can be seen the keys 1 are formed on a common sheet form member. The assembly 100 also includes a light source 115 capable of back illuminating the key (s) 1. The assembly may comprise part of an electrical apparatus, such as a mobile phone.

It should also be stated that the facia 110 may be made from an opaque material-e. g. a rigid plastics material. Alternatively the facia 110 may also be made from a plurality of layers as hereinbefore described regarding the key (s) 1. In this way the facia may also provide variable visual effects.

Referring now to Figures 8 and 10 there are illustrated a number of embodiments of key pads, generally designated 105a, 105b, 106c with keys designated as iOla, lOlb, lOlc, according to the present invention, particularly adapted for use in mobile telephone apparatus.

The Figures show the key pads 105a, 105b, 105c in a back illuminated state, wherein all keys 101a, 101b, lOlc, lOld are illuminated for use. However, without back illumination, in a quiescent mode, the information on one or more of the keys 101a, 101b, lOlc, 101d, is not visible.

Referring now to Figure 11 there is-illustrated an embodiment of a key pad 105d with keys 101d for use, for example, on white goods such as washing machines or the like.

Referring to Figure 12 there is illustrated a facia 110e suitable for use with a key pad 105e (not shown) for example, as part of a mobile telephone apparatus.

Referring to Figure 13, there is illustrated a key pad assembly 200f providing a key pad 105f including a facia 110f and a number of keys 101f comprising part of an apparatus such as a mobile phone 116f. With no back illumination keys 101f and key pad 105f together appear as a substantially continous decorative pattern of the flag of the United States of America. However, with back illumination, as shown in Figure 14, the keys 101f show their respective numbers (or graphics).

Finally, Figures 15 and 16 illustrate a mobile phone apparatus 200g including a key pad 105g, a facia 110f and a number of keys 101g. As can be seen from Figure 15 in a first (quiescent) mode the key pad 105g is hidden.

However, upon pressing of a relevant key 101g, the phone 200g adopts a second (active) mode, where illumination means (not shown) back illuminate the key pad 105g thereby allowing use of the phone 200g.

It will be understood by those skilled in the art that the embodiments of the invention hereinbefore described are given by way of example only, and are not meant to limit the scope thereof in any way, Particularly, it should be

appreciated that the present invention is of particular benefit in apparatus employing alpha-numeric keys. The invention allows provision of a quiescent mode where keys are not illuminated from behind, and an active mode where keys are back illuminated and information displayed thereupon. Switching between the two modes may be done by pressing a single"on-off"button.

In examples of keys according to the invention it will be understood that a variety of materials may be chosen for the substrate and for the layers. Moreover, the thicknesses of the various layers may be selected as required for the purpose concerned.

For example, the thickness of substrate layer 2 may be from say 0.075 mm up to 10 mm, or if appropriate, up to 15 or 20 mm. In providing the layer the pigmented carrier may be an acrylic varnish or a blending base and may for instance be water-based if preferred. The size and shape of the particles is determined by that of the mica flakes from 5 to 60ßm being suitable although flakes up to 180Um in size may be used and maybe present on the carrier varnish in the proportions 1-10, typically 3-5k. The thicknesses of the layer 8 may be between 3 and 30ßm although a range from 6-15ßm may be preferred, typically 6- 7 ; m.

The decorative features of the layers 8 and 12 may be purely informative, and may be in the form of a layer which is continuous except for shaped gaps or comprised by "islands"of pigmented carrier.