Patent Application
20140340920
This application is based upon and claims the benefit of prior German Application No. 10 2013 008 433.4, filed on May 17, 2013, the entire contents of which are incorporated herein by reference.
The disclosure relates to a flat device for illuminating an assembly that is installed in the interior of a vehicle. Such devices are needed in particular in vehicles in the automotive field, in aviation, in rail-bound transport, and in shipping.
DE 10 2012 215 801, for example, discloses illuminating an interior of a vehicle with a light guide. The light guide is used either to generate visible light lines or an indirect illumination, which is also referred to as ambient lighting. The illumination is intended at very specific places and should not have any fluctuations in brightness.
In such a light guide, the principle of the guiding of light is based on a reflection at a boundary between the light guide and surroundings. If the light guide has a refractive index of 1.5, for example, and is surrounded by air with a refractive index of 1.0, the total reflection occurs at the transition from an optically denser medium, i.e., the light guide, toward an optically thinner medium, in the present case the medium air.
However, when used in vehicles, light guides or contacts between the light guides and the surrounding materials may become contaminated, which has a negative effect on the luminous behavior. In particular, if light guides are used for backlighting assemblies, contacts to other materials, which are often connected by adhesives, can be avoided only at higher costs.
An object of the disclosed embodiments is to ensure a homogenous illumination of an assembly in an interior of a vehicle, which overcomes the disadvantages described above.
This problem is solved with a device having the characteristics consistent with embodiments of the disclosure.
The device according to the disclosure includes a flat light guide that is at least partially covered by an optical lacquer coat. Because of the flat development of the light guide, it is easier to homogenously illuminate larger areas. The optical lacquer coat protects the light guide in particular at the places where contamination may occur or where a contact to other assemblies is planned. The optical lacquer coat has a defined refractive index and therefore controls the emergence of light rays at the surface of the light guide.
Furthermore, the lacquer coat is at least partially connected to a first adhesive coat that establishes the contact to a cover element. This results in a mechanically secure fastening of the light guide to the cover element to be backlit, which barely raises the surface and can have any refractive indices. This means that conventional adhesives can be used for the cover element.
In some embodiments, the cover element includes a spacer fabric and a lining made of, e.g., leather, synthetic leather, or fabric, which are interconnected by a second adhesive coat. The spacer fabric results in a pleasantly soft haptic appearance of the cover element, onto which optically appealing and, if necessary, very thin linings can be applied with an additional adhesive. Because of the lacquer coat, selection of the materials of the cover element may not be limited, because they do not influence the optical reflection behavior. Alternately, the light guide can also be lined with a decorative sheet. In some embodiments, the decorative sheet is at least partially transparent. This can be achieved with the selection of material for the sheet or by printing color motives on a transparent sheet. Printing the sheet on both sides would create an additional depth effect. In some embodiments, the sheet is pulled down low, i.e., is produced by deep drawing, and therefore can be prepared for the form of the surface of the light guide, which also allows for three-dimensional flat interior equipment components. The sheet is glued to the lacquer coat that covers the light guide.
In some embodiments, the light guide is formed by injected molding or injection compression molding. These technologies allow for a simple and economic production of the flat light guide.
In some embodiments, the lacquer coat for a light guide made of polymethylmethacrylate (PMMA) has a refractive index of less than 1.49, and the lacquer coat for a light guide made of polycarbonate (PC) has a refractive index of less than 1.57. This means that PMMA and PC are two favorable light guide materials and there may be a sufficiently large selection of optical lacquers available.
In some embodiments, a thickness of the lacquer coat is greater than 1 μm to ensure a secure reflection, such as between 8 and 12 μm to compensate production tolerances. Lacquer coats that are too thick may be brittle.
According to the disclosure, the optical lacquer coat is essentially transparent, with an absorption spectrum independent of the wavelength in the visible spectral range (380-780 nm) so as not to effect any color changes of the radiated light.
In some embodiments, the lacquer coat has a damping independent of wavelength. This means that light effects that are not monochrome and support a multi-color illumination or an illumination that changes color can be used as well.
According to the disclosure, the light guide has a surface structure to evenly couple out light. This can achieve even large-area illuminations where a weakening of a luminous power is compensated over the length of the light guide and a largely homogenous luminous intensity can be achieved. In some embodiments, the surface structure includes a large number of dot-shaped notches. The notches are easy to apply and barely impact the mechanical strength of the light guide. In some embodiments, the dot-shaped notches increase in size starting at a coupling in spot so that the largest notches at the end of the light guide then couple out from the lesser luminous intensity a light quantity that is similar in size to that at the beginning of the light guide. Alternately to notches, scatter particles can be used as well to couple out light. For example, PMMA by Evonik, manufacturer's reference LD12, LD24, LD48, LD96, and/or “Endlighten” can be applied to the light guide. In the production of the light guide, structural elements such as stiffeners and hooks for later fastening can be already applied in the light guide. Such a one-piece development of the light guide simplifies the assembly of the interior equipment parts.
According to the disclosure, light-emitting diodes (LED) or laser diodes may be used to couple light into the light guide. In some embodiments, a plurality of LEDs are used. LED light is coupled into the light guide along an edge of the light guide over a large number of coupling spots. Single-color or RGB LED maybe used.
The device can be used in vehicle doors, cockpit, or central consoles where the optical effects are well visible to the driver without interfering with the view of the road.
In addition, the description of certain embodiments below reveals other advantages and characteristics of the disclosure. The characteristics described there can be implemented alone or in combination with one or more of the characteristics described above. Below, embodiments consistent with the disclosure will be described with reference to the drawings.
The light guide 3 is surface-treated to ensure that the light is coupled out of the light guide 3 evenly and in a directed fashion. In the direction of the coupling out of the light, the surface has notches 10 that are arranged in one line from the coupling-in location at the edge 13 at the start of the light guide 3 to the end of the light guide 3. In some embodiments, the first notch 10a has a smaller diameter than the last notch 10b. However, other means can be used here as well to adjust the relative portion of light coupled out from the total light passing the coupling-out spot, so that the portion of the light is small at the start of the light guide 3 and large at the end of the light guide 3.
A reflection coat 15 is applied on the side opposite the light guide 3. At the notch 10 that forms the coupling-out spot, the reflection coat 15 reflects refractive light that refracts into the direction of the reflection coat 15 back to the side where the light is coupled out. Alternately, the reflection coat 15 can also be formed by an optical lacquer, with the reflection effect then being a lesser one.
A refractive index of the lacquer coat 4 is adjusted according to the light guide 3, and is smaller than a refractive index of a synthetic material that forms the light guide 3. For example, if polymethylmethacrylate PMMA is used to form the light guide 3, the refractive index of the lacquer coat 4 is less than 1.49. If polycarbonate PC with a refractive index of approximately 1.57 is used to form the light guide 3, the refractive index of the lacquer coat 4 is correspondingly smaller than the specific refractive number of the PC, i.e., is in a range up to 1.56.
The lacquer coat 4 may cover the light guide 3 on an entire surface area of the light guide 3, including narrow sides (which is not absolutely necessary), but not on the side of the reflection coat 15. However, if a reflection coat 15 is to be glued on as a sheet, this side can be lacquered as well. Alternately, the lacquer coat 4 covers only the places of the light guide 3 that are sensitive to soiling or need to fasten the cover element 6, which includes a spacer fabric 7 and a lining 8. The spacer fabric 7 has a thickness of a few millimeters to generate a soft, supple surface of the cover element 6. A structure without a spacer fabric 7, i.e., a hard lining, is also possible. The remaining coat thicknesses are substantially smaller.
The connection between the lacquer coat 4 and spacer fabric 7 is effected by a first adhesive coat 5. A second adhesive coat 9 connects the spacer fabric 7 and the lining coat 8. For a robust connection that avoids trapped air, the adhesive coats 5 and 9 are applied to nearly the entire surface of the coats 4, 7, and 8. A suitable adhesive includes Alexit-HighGloss-Clearcoat 460-13 by Mankiewicz.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed embodiments herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosed embodiments being indicated by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 008 433.4 | May 2013 | DE | national |
