This invention relates to an assembly method.

Background of the Invention

Typically, solid-state light sources are, by design, practically point sources and produce a high glare effect if not appropriately lensed or diffused. As a result, conventional general purpose, or decorative, lighting solutions for use in buildings and the like, typically use a semiconductor- based Light-emitting diode (LED), Organic LED, Electroluminescent wire or a substantially similar light source together with either an assembly of optical parts, such as lenses and waveguides, a diffusion layer or an arrangement of reflectors to alter the distribution of light. These manufactured conventional general purpose, or decorative, lighting solutions suffer from a variety of problems.

Leaving a light source exposed will result in the light source producing a high glare effect, which is undesirable. A short distance between a light source and diffuser suffers from uneven light distribution due to the short throw distance between the source and diffuser. It will often be necessary to align the light source with the surrounding optics which typically requires additional mechanical fixings; this increases assembly complexity and cost. The requirement for further fixings and/or heatsinking restricts the control of the directionality of the light from the light source. The geometry of manufactured conventional general purpose, or decorative, lighting solutions is restricted by the manufacturing limitations of existing methods.

The present invention aims to overcome or at least ameliorate one or more of the problems set out above.

Summary of the Invention

In a first aspect of the invention, there is provided apparatus for a light unit comprising a light source and an optical assembly, the optical assembly comprising at least a first and second layer of light transmissive material, wherein the first layer is proximate to the light source and the second layer is further away from the light source than the first layer; wherein the first layer has a smaller scattering coefficient with respect to the second layer; and wherein the light source is affixed to the optical assembly without the use of mechanical fixings.

In a second aspect of the invention, there is provided a method of manufacturing a light unit comprising a light source and an optical assembly, the optical assembly comprising at least a first and second layer of a light transmissive material, the method comprising: extruding a first light transmissive material to form the first layer of the optical assembly; extruding a second light transmissive material to form the second layer of the optical assembly; affixing the first layer within the second layer such that the outer surface of the first layer is in contact with the inner surface of the second layer to form the optical assembly; wherein the first layer has a smaller scattering coefficient with respect to the second layer; and affixing the light source within the optical assembly such that the inner surface of the first layer is in contact with the light source.

In a third aspect of the invention, there is provided a method of manufacturing a light unit comprising a light source and an optical assembly, the optical assembly comprising at least a first and second layer of a light transmissive material, the method comprising: extruding a first light transmissive material to form the first layer of the optical assembly; extruding a second light transmissive material to form the second layer of the optical assembly; affixing the first layer within the second layer such that the outer surface of the first layer is in contact with the inner surface of the second layer to form the optical assembly; wherein the first layer has a smaller scattering coefficient with respect to the second layer; and affixing the light source within the optical assembly such that the inner surface of the first layer is in contact with the light source.

Preferably, the layers are arranged to coaxially align with the light source. The coaxial alignment of the light transmissive layers with the light source 4 allows an improved even distribution of light within the light unit 2 to be achieved.

Favourably, the first layer is pliable and the second layer is rigid. The pliable inner material is able to be mechanically manipulated into its final intended geometry before the rigid outer layer is formed such that the rigid material provides structural support to the pliable inner material, and therefore, to the light unit.

Preferably, the light transmissive material is arranged to positionally align the light source in a pre-determined spatial relationship with the transmissive material without the use of mechanical fixings. The removal of additional mechanical fixings required to secure the light source within the optical assembly reduces the cost, time and complexity of both the design and manufacturing process of a light unit. Advantageously, the light source comprises a source mounted onto a substrate, wherein the source is an LED, and the substrate is flexible such that the substrate can be mechanically manipulated into a non-linear shape during the assembly of the light unit. Here, the flexible substrate does not mechanically fail under mechanical manipulation allowing the light unit to be mechanically manipulated into its desired final geometrical shape.

Favourably, the substrate may comprise a plurality of LED’s to provide an increase in the amount of light the light unit is able to produce.

Preferably, the optical assembly may comprise a plurality of materials of differing optical and mechanical properties such as the optical assembly can be further optically and mechanically tuned to maximise both the alignment of the light source and the light distribution achieved within the light unit.

Advantageously, the light source is embedded within the optical assembly using an optically suitable material to provide ancillary positioning and/or thermal support to the light source.

Favourably, the light transmissive material can be modified using a chemical or mechanical process to alter, at least one of, the mechanical or optical properties of the transmissive material such that the mechanical and/or optical properties of the light transmissive material can be fine-tuned to the desired effect

Preferably, the diffusion of the light transmissive material can be improved by adjusting the thickness of the transmissive material depending on the light distribution characteristics of the light source. In this way, it is possible to manufacture a variety of light units that are compatible with a variety of light sources.

Brief Description of the Drawings

The description will now be described by way of example and by reference to specific embodiments with reference to the attached drawing in which-:

Figure 1 is a front cross-sectional view of a light unit.

Detailed Description

With reference to Figure 1 , apparatus for a light unit 2 comprises a light source 4 and an optical assembly (6,8). The optical assembly (6,8) comprises a first layer 6 and a second layer 8 whereby, the first layer 6 is proximate to the light source 4 and the second layer 8 is bonded to the first layer 6 via the layer boundary 10 such that the second layer 8 is further away from the light source 4 and both layers coaxially align with the light source 4. In other embodiments, the second layer 8 is not bonded to the first layer 6 and there is a gap between layers. The coaxial alignment of the light transmissive layers with the light source 4 allow for an improved even distribution of light within the light unit 2 to be achieved.

Regions of the light source outer surface 12 are in physical contact with regions of the first layer inner surface 14 such that the light source 4 is affixed within the first layer 6 of the optical assembly (6,8) using a predetermined fit via the contact points 16; the light source 4 is held in position by frictional contact with the first layer 6. In this way, the light source 4 is secured within the optical assembly (6,8) without the requirement for additional mechanical fixings, or adhesive measures, to secure the light source 4 to, or within, the optical assembly (6,8) reducing the cost, time and complexity of both the design and manufacturing process of a light unit 2.

Typical examples of mechanical fixings include extruded rails to hold a rigid light source 4 or the use of screws and/or clips to fix a light source 4 to another part. Examples of adhesive measures include thermally conductive adhesive and/or two sided tape to affix the light source 4 to the optical assembly (6,8).

The predetermined fit may be an interference, location or clearance fit, whereby a different type of fit can be used when manufacturing the light unit 2 according to the desired specifications for the light unit 2, and the properties and dimensions of the light source 4 to be affixed within the optical assembly (6,8).

The first layer 6 and second layer 8 of the optical assembly (6,8) comprise a light transmissive material whereby, the scattering coefficient of the second layer 8 is greater than the scattering coefficient of the first layer 6:

As ^*2 ^ As^l whereby m ₃ is the scattering coefficient of the material and L _n is the layer number ordered radially from the light source 4 outwards. Additionally, the first layer 6 has a different refractive index to that of the second layer 8. The light source 4 is affixed and optimally positioned within the first layer 6 of the optical assembly (6,8) due to the pre-defined geometrical structure of the first layer 6 such that a pre determined spatial relationship between the first layer 6 and the light source 4 can be defined without the need for additional mechanical fixings, or adhesive measures, to secure the light source 4 to, or within, the optical assembly (6,8). The pre-determined spatial relationship between the first layer 6 and the light source 4 maximises the distribution of light within the light unit 2 before subsequently being emitted, radially, from the light unit 2.

With the light source 4 affixed within the optical assembly (6,8), the assembly (6,8) is able to receive transmitted light 18 from the light source 4. Upon entering the first layer 6, the transmitted light 18 is partially refracted producing refracted light 20; the refracted light 20 increases the distribution of the transmitted light 18 throughout the second layer 8. The transmitted light 18 and refracted light 20 continue through the first layer 6 and reach the second layer 8 where the light is partially reflected and/or diffused to produce reflected light 22 and diffused light 24.

The internally reflected light 22 is created due to the difference in index of refraction between the first layer 6 and the second layer 8 of the optical assembly (6,8); reflection and refraction occur in varying proportions at the layer boundary 10. As described above, in other embodiments, a gap exists, introducing air, between the first layer 6 and the second layer 8 such that additional reflection and reduced refraction can take place at the second layer 8 to improve the polar distribution of light throughout the light unit 2 at the cost of luminous efficacy.

The difference in scattering coefficient between the multilayer design of the optical assembly (6,8), particularly by having the scattering coefficient of the second layer 8 greater than the scattering coefficient of the first layer 6, allows the majority of the diffusion of the transmitted light 18 to occur at a further distance from the light source 4 with respect to using a single layer design. Here, the increased distance between the created diffused light 24 and the light source 4 allows for an increase in the amount of internally reflected light 22 created.

The reflected light 22 further increases the photometric distribution of transmitted light 18 throughout the first layer 8; this results in a more even distribution of diffused light at the second layer 8 to allow an improved uniformity of illumination of the light unit 2. This design allows for a light unit 2 with a less directional light output with respect to what the light source 4 would typically produce without the proposed optical assembly design (6,8). In this case, the emitted light from the light unit 2 has much a wider angular photometric distribution. On entering the second layer 8, the transmitted light 18 diffuses such that the diffused light 24 aids in removing the high glare effect from the transmitted light 18 seen exiting the light unit 2; the light appears to be coming from the entire surface of the second layer 8 of the light unit 2, rather than as a point source from the light source 4. In this way, the light unit 2 provides a wider angular photometric distribution of the emitted light from the light source 4, with respect to conventional general purpose or decorative lighting solutions, which allows for a cheaper, less complex and reduced depth optical assembly design.

For the first layer 6, primarily, the mechanical properties are optimised such that the positioning and affixing of the light source 4 results in the optimum pre-determined spatial relationship between the light source 4 and first layer 6 to ensure improved light distribution is achieved throughout the light unit 2. In addition, the optical properties of the first layer 6 are also optimised such that, as described above, an increase in the amount of refracted light 20 is produced in the first layer 6.

For the second layer 8, primarily, the optical properties are optimised such that, as described above, an increase in the amount of both reflected light 22 and diffused light 24 is produced in the second layer 8 to improve the directionality and reduce the glaring effects of the emitted light from the light unit 2. In addition, the mechanical properties of the second layer 8 are also optimised such that the thickness of the layer 8 is as thin as feasibly possible while maintaining a maximum distance between the second layer 8 and the light source 4 for a given a total distance between the light source 4 and the outer surface of the second layer 8. The aforementioned optimisations allow the overall size of the light unit 2 to be reduced. The mechanical properties of the second layer can be further optimised to achieve the desired external visual appearance, tactility and durability of the light unit 2.

Overall, diffuse illumination is achieved by taking advantage of the internal reflections 22 and refractions 20 within the light unit 2 and by maximising the distance between the light source 4 and the layer with the higher scattering coefficient, i.e. the second layer 8.

The light source 4 is ideally, but not restricted to, a semiconductor-based LED mounted onto a substrate (not shown); the LED may be an OLED or other such suitable LED. In other embodiments, the light source 4 may be any such suitable light source which produces a non- uniform distribution pattern, for example an electroluminescent wire. The light source 4 may further comprise a plurality of LED’s mounted onto a substrate to provide an increase in the amount of light the light unit 2 is able to produce.

The substrate is a flexible plastic structure, such as polyimide, PEEK or transparent conductive polyester film, such that the substrate, and LED, can be mechanically manipulated into a non linear shape during the manufacturing and assembly of the light unit 2. The substrate can be mechanically manipulated into a variety of different shapes and is not entirely geometrically restricted by the material of the substrate. The substrate may further comprise strain relief within the material to aid in the ease of mechanically manipulating the substrate without the substrate mechanically failing. In other embodiments, the material of the substrate may be any such suitable flexible material, for example metallic and/or fibreglass.

The optical assembly (6,8) may further comprise a pliable inner material, whereby the inner surface of the inner material is proximate to the light source 4, and a rigid outer material. The pliable material can undergo a stiffening process by the application of heat, a chemical and/or UV light to the pliable material such that it becomes non-pliable. In some embodiments, the pliable inner material is the first layer 6 and the rigid outer material is the second layer 8 of the optical assembly (6,8). Here, the second layer 8 can under the stiffening process separately from the first layer 6 before being joined with the first layer 6 to form the optical assembly (6,8). Alternately, the first layer 6 may undergo the stiffening process such that the second layer 8 is formed and bonded to the first layer 6 to form a similar optical assembly (6,8).

In other embodiments, the optical assembly may comprise a plurality of layers, each layer comprising differing optical and mechanical properties such that the optical assembly (6,8) can be further optically and mechanically tuned to maximise both the alignment of the light source 4 and the light distribution achieved within the light unit 2. The plurality of layers may also contribute to altering other desired mechanical properties of the light unit 2, for example the external visual appearance and/or durability of the light unit 2 as mentioned previously. One example of an additional layer that may be added to the optical assembly (6,8) is a UV protective lacquer that would offer protection to the internal layers of the assembly (6,8) from discolouration if made using PMMA.

The process of manufacturing the light unit 2 begins by first manufacturing the optical assembly (6,8). A first coating of a light transmissive material is applied to a substrate such that the coating adheres to the substrate to form the first layer 6 of the optical assembly (6,8). After the first coating has chemically stabilised, a second coating of light transmissive material can then be applied to the first layer 6, whereby the second coating adheres and bonds to the first layer 6 and, subsequently, chemically stabilises to form the second layer 8 of the optical assembly (6,8). Here, the substrate forms part of the first layer 6. Alternatively, the substrate outlined above may begin as the first layer 6 whereby, the second layer 8 and/or additional layers may be added the first layer 6 by the coating process also described above. In other embodiments, the substrate may not be or form part of the first layer 6 and may be removed from the first layer 6 after the first layer 6 has chemically stabilised.

Alternatively, the optical assembly (6,8) can be manufactured by extruding a first light transmissive material such that a first tube of the first layer 6 is formed. A second light transmissive material is then extruded in a similar fashion to that of the first extrusion to form a second tube of the second layer 8. Here, the extrusions of the first layer 6 and the second layer 8 are done such that a particular fit can be achieved between the outer surface of the first tube and the inner surface of the second tube when the first tube is affixed within the second tube. To affix the tubes in this manner, the first tube is fed into the second tube to form the optical assembly (6.8) using a pre-determined particular fit in the manner described above. As before, the particular fit may be an interference, location or clearance fit. A surface finish may be applied to the second layer 8 before the first layer 6 is fed into the second layer 8 to form the optical assembly (6,8).

The light transmissive material used for the first layer 6 differs from that used for the second layer 8 in that the scattering coefficient of the first coating material is lower than the scattering coefficient of the second coating material.

To complete the manufacturing process of the light unit 2, the light source 4 is then affixed within the body of the optical assembly (6,8) via a predetermined fit, as previously described. The optical assembly (6,8) undergoes a deforming process to allow plastic deformation of the assembly (6,8) such that the assembly (6,8) can be mechanically manipulated into the intended geometrical structure of the light unit 2. The deforming process is typically a thermal or chemical process, for example, in the case of a thermal deforming process, the optical assembly is subjected to heat to allow plastic deformation to occur.

The light unit 2 may be manufactured in the same fashion as the methods described above with the variation of affixing the light source 4 within the optical assembly (6,8) after the assembly (6,8) has been mechanically manipulated into its final geometrical structure. Here, the light source 4 is affixed within the geometrically finalised optical assembly (6,8) by splitting the optical components of the assembly (6,8) into multiple pieces and reassembling the same pieces together with the light source 4 affixed within the optical assembly (6,8). Alternately, the light source 4 is affixed within the optical assembly (6,8) using an assembly fixture. Here, the assembly fixture comprises utilising a pulsed, high-pressure air hose to manipulate the light source 4 into the optical assembly (6,8).

The light transmissive material of the optical assembly (6,8) can be modified using a chemical or mechanical process to alter the mechanical and/or optical properties of the transmissive material. Here, it is possible to fine-tune the mechanical and/or optical properties of the light transmissive material of the optical assembly (6,8) to the desired effect; these modifications include modifying the surface and/or chemical properties of the light transmissive material.

The diffusion of light within the light transmissive material can be improved by adjusting the thickness of the transmissive material according to the light distribution characteristics of the intended light source. In this way, it is possible to manufacture a variety of light units that are compatible with a variety of light sources.

The overall efficiency, positioning and thermal support of the light unit 2 may be enhanced by first embedding the light source 4 within a material with optical properties that are similar to the material of the encapsulation method of the light source 4, i.e. the optical properties of the embedding material would broadly match the optical properties of the first layer of the optical assembly (6,8).

From the manner described above, a light unit 2 can be manufactured that has a reduced size with respect to the size of conventional general purpose, or decorative, lighting solutions; this, along with the removal of additional mechanical fixtures required to affix a light source within a light unit, allows for a reduction in the time, complexity and cost of the manufacture of the light unit 2 whilst, as described above, improving the even light distribution of the affixed light source 4 and minimising the depth of the optics required for the improved level of even light distribution.

The light unit 2 may be mounted within structural housing and electrically coupled to an electrical driver to create a lamp. In this way, the light unit 2 can be used as a light source for conventional general purpose, or decorative, lighting solutions, for example lamps.