Method for producing an optical module having a polymer optical system

Abstract

A method is provided for production of a module, including the steps of: providing a substrate (1) having a first surface (5) in the form of a translucent carrier; providing an open casting mold (6), wherein the formation of at least one optical element (4, 4) is provided in the casting mold (6); covering the surface (5) with a polymeric casting compound (3) in the open casting mold, while forming the optical element from the casting compound (3); and curing the casting compound in the casting mold, wherein the translucent carrier and the casting compound (3) together form an optical system (10).

Claims

1. A method for producing an optical module comprising the following steps: (a) providing a translucent carrier having a first surface; (b) providing an open casting mold, wherein a molding for at least one optical element is formed in the open casting mold, the open casting mold including supports for supporting the translucent carrier and an overflow region; (c) coating the first surface with an adhesion promoter, the adhesion promoter comprising a mixture of reactive siloxanes and silicon resins; (d) after the first surface is coated with the adhesion promoter, positioning the translucent carrier on the supports and covering the first surface with a polymeric casting compound in the open casting mold while forming the at least one optical element from the polymeric casting compound, such that excess polymeric casting compound displaced by the translucent carrier flows into the overflow region, the polymeric casting compound comprising at least predominantly a silicone; and (e) curing the casting compound in the casting mold, wherein the translucent carrier and the at least one optical element together form an optical system.

2. The method according to claim 1, wherein the polymeric casting compound contains no admixture of adhesion promoter.

3. The method according to claim 1, wherein the polymeric casting compound contains a catalyst for initiation of a curing process.

4. The method according to claim 1, further comprising the following step: heating the polymeric casting compound in the casting mold to a defined temperature to initiate and/or accelerate the curing step.

5. The method according to claim 1, wherein the adhesion promoter is applied onto the first surface as a layer having a mean thickness of less than 100 nm.

6. The method according to claim 1, wherein the polymeric casting compound has a viscosity before curing of less than 1,000 mPa.Math.s.

7. The method according to claim 1, wherein the cured casting compound possesses a hardness in a range of 10 to 90 Shore A.

8. The method according to claim 1, wherein the at least one optical element formed from the polymeric casting compound possesses a UV resistance for irradiation intensities in excess of 1 W/cm.sup.2 in a wavelength range below 400 nm.

9. The method according to claim 1, wherein the silicone is provided as a mixture of at least two silicones right before placing it into the casting mold.

10. The method according to claim 1, wherein the silicone contains less than 100 ppm of foreign substances.

11. The method according to claim 1, further comprising the following step: coating a second surface after step (e), wherein the coating of the second surface also comprises procedural steps (a) to (e).

12. The method according to claim 1, wherein the open casting mold is reusable, the method further comprising the following steps: (f) releasing the optical system from the casting mold; and (g) re-using the casting mold to produce a second optical system.

13. The method according to claim 1, wherein the first surface of the translucent carrier is completely wetted.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:

(2) FIG. 1 is a series of schematic, sectional views of three variants of an optical module according to embodiments of the invention.

(3) FIG. 2 is two schematic, sectional views of an open casting mold and a substrate during the production of an optical module according to an embodiment of the invention.

(4) FIG. 3 is a schematic, sectional view of a variant of the casting mold from FIG. 2.

(5) FIG. 4 is a schematic, sectional view of a first refinement of a module according to FIG. 1.

(6) FIG. 5 is a schematic, sectional view of a second refinement of a module according to FIG. 1.

(7) FIG. 6 is a schematic, sectional view of an example of a use of a module according to FIG. 1.

(8) FIG. 7 is a schematic, sectional view of an example of a combined use of various exemplary embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) An optical module according to FIG. 1 comprises a substrate 1 onto which a layer of an adhesion promoter 2 has been applied. A shaped layer 3 of a polymeric casting compound has been applied onto the adhesion promoter 2 and comprises, in the present case, a plurality of optical elements 4 in the form of collecting lenses. Silicone is the casting compound in each of the exemplary embodiments described in the following. In general, though, other polymeric casting compounds are suitable just as well.

(10) In this context, the substrate consists of a translucent carrier 1, a glass plate in the present case. The carrier 1 and one or more silicone layers 3, 3 (see FIG. 4, FIG. 5), which have been applied analogously to the first example and have optical elements 4, 4 provided therein, jointly form an optical system 10. In the present case, the substrates and/or translucent carriers 1 each are shown as plates having plane-parallel surfaces. Depending on the existing requirements, the carrier can just as well comprise optical elements, such as lenses.

(11) In the example on the top according to FIG. 1, the optical elements 4 are provided as collecting lenses.

(12) In the example in the middle according to FIG. 1, the optical elements 4 are provided as Fresnel lenses.

(13) In the example on the bottom according to FIG. 1, the optical element 4 is provided as a quasi-random collection of light-diffracting structures and/or formations by which a scattering effect is attained.

(14) The layers 3, 3 each consist of a highly pure silicone having a hardness of approx. 65 Shore A. The silicone is colorless and transparent. The silicone is highly translucent in the wavelength range from approx. 300 nm to approx. 1,000 nm. The silicone is UV-resistant to long-lasting irradiation with wavelengths below 400 nm and an energy density in excess of 10 Watt/cm.sup.2.

(15) Each of the optical modules described above is produced according to the following method:

(16) First, an open casting mold 6 (see FIG. 2) is provided that contains the negative molds of the formations for the optical elements 4. Moreover, supports 6a in the form of fins or lugs supporting the substrate 1 in a certain position are provided in the mold 6.

(17) Then, the surface 5 of the substrate 1 to be coated is coated with an adhesion promoter 2, possibly after a cleaning step. The coating then proceeds, for example, by applying droplets of the substance and blowing-off any excess of the substance, which also dries the remaining adhesion promoter. In the ideal case, the thickness of the adhesion promoter applied is equal to just one monolayer, in any case it is preferred to be less than 100 nm.

(18) As soon as the substrate is prepared as described, a silicone mixture of two components is produced and placed in the open casting mold. One of the components contains a catalyst and the other component contains a cross-linker. The mixture has a viscosity of less than 50 mPa.Math.s in the present case. As a matter of principle, mixing the components initiates the curing process, though this process proceeds quite slowly at low temperatures such as room temperature.

(19) Subsequently, the substrate is placed in the casting mold in a controlled manner, with the coated surface 5 facing downwards and immersed into the silicone mixture (see left side of FIG. 2).

(20) In particular, an overflow 7 can be provided on the casting mold in this context, as shown schematically in FIG. 3. The overflow and the low viscosity of the silicone jointly ensure that the depth of immersion of the substrate is well-defined and, in particular, that any silicone displaced by the substrate can flow off. By this means, it can be ensured, if necessary, that not only the surface 5 of the substrate, but also the front sides of the substrate get covered by a circumferential rim 8 of layer 3, whereas a back side 9 of the substrate is not being coated. Complete enveloping of the substrate may be desirable in other embodiments, though.

(21) The rim 8 has not only a protective function for the carrier substrate 1, if the same is supported on its rim or upon a number of the modules being arranged edge to edge, but it also enables direct, gap-less, transparent arrangement of the substrates and thus minimization of the deviation of light at the optical boundaries between two carrier substrates.

(22) Once the substrate is positioned on the supports 6a, it is checked, if necessary, whether the surface 5 is wetted completely and, in particular, without forming bubbles. In a possible refinement of the invention, the immersion of the substrate can just as well proceed in a vacuum in order to prevent the air bubble issue. However, due to the viscosity being low, bubble-free coating can generally be attained in the absence of a vacuum as well.

(23) After the positioning, the silicone is cured and/or cross-linked. This is accelerated significantly in expedient manner by increasing the temperature. Typically, curing can be completed in half an hour at a temperature of approx. 100 C. At temperatures in the range of 150 C., curing can typically be completed in just a few minutes. The selection of the temperature for this thermal curing process must also take into consideration the properties of the respective substrate.

(24) Once the silicone is cured, the substrate, now coated, can be taken out of the re-usable casting mold as shown on the right side in FIG. 2.

(25) Since highly pure silicone without any admixture of adhesion promoter in the silicone is used in the present case, no further measures aimed at releasing the silicone 3 from the mold 6 are required. In particular, the casting mold is not being lined with a release film or the like. This simplifies the production and enables very exact reproduction of the structures of the casting mold.

(26) The method described above can be applied repeatedly to the same object, if required. FIG. 4 and FIG. 5 show embodiments of the invention, which each show such refinements of examples from FIG. 4. In each case, after producing a first layer 3 having optical elements 4, a second layer 3 having optical elements 4 was produced.

(27) In the case of the example according to FIG. 4, the second layer 3 was applied onto the back side and/or opposite sides of the substrate 1, which is provided as a planar plate in the present case. For this purpose, the substrate simply needs to be provided with an adhesion promoter 2 on the yet uncoated side 9 and then inserted forward in a corresponding casting mold 6. The further procedural steps correspond to the procedure described above.

(28) In the example shown in FIG. 4, the first surface 5, which is the front side of the substrate 1, has been coated with a plurality of collecting lenses 4, for purposes of illustration. The second surface 9, which is the back side of the substrate 1, has been coated with Fresnel lenses 4, which each are aligned with the collecting lenses 4.

(29) In the example shown in FIG. 5, first, a layer 3 having Fresnel lenses in the present case, was applied to the first surface 5, which is the front side of the substrate. Subsequently, an adhesion promoter 2 was applied onto the layer 3 and a second layer 3 having collecting lenses 4 was then applied onto the first layer 3. In this case, the first layer 3 applied is the substrate according to the scope of the invention and its external surface is the second surface 9.

(30) As a matter of principle, the number and design of such multiple layers are not limited in any way.

(31) The layers can just as well differ in composition of the casting material, in particular can be different casting materials and/or admixtures to the casting materials. Accordingly, different properties thus can be combined, or the optical properties obtained by application of many layers can be influenced nearly gradually, e.g. by slightly changing the refractive index of the casting material used. Likewise, the final current boundary layer can be influenced and changed before applying the next layer, e.g. by silanizing a silicone boundary layer, dielectric or metallic coating by sputtering, spraying, wetting, or any other customary surface coating procedures.

(32) The use of particularly pure silicone is specified above as being preferred in order to optimize high degrees of transmission and material resistance in critical wavelength ranges. As a matter of principle, the casting material can be filled with optically effective materials in order to thus generate further optical functionalities, such as conversion of the wavelength of light by introducing phosphorescent and fluorescent substances, such as rare earth elements, or for affecting the opacity of the optical system by introducing scattering substances, such as transparent or translucent particles (e.g., made of glass or ceramic materials) or metallic particles.

(33) FIG. 6 shows a preferred use of an optical system 10, as described above, in combination with a two-dimensional light source. The light source is provided in this case as LED module 11 having a number of LEDs arranged in an array. The optical system is situated at a distance in front of the light source and refracts the light of the individual LEDs in a desired manner, by collecting lenses that are each assigned to one LED.

(34) FIG. 7 shows another preferred use, in which an LED module 11 is combined with a module according to the embodiment of the invention according to FIG. 1. In this context, the LED module 11 is provided to have a primary optical system 12. An optical module that is provided as optical system 10 is arranged upstream of the first optical module. Preferably, both modules comprise multiple collecting lenses, each correlated to the LEDs, which act in concert to transport a large opening angle of the LEDs.

(35) The LED module 11 having the primary optical system 12 can be manufactured, for example, according to the teaching of WO 2012/031703 A1.

(36) It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.