AU2015271916B2

AU2015271916B2 - Illumination apparatus for aquatic environment

Info

Publication number: AU2015271916B2
Application number: AU2015271916A
Authority: AU
Inventors: Christian Guillet; Patrick Pellaton
Original assignee: SIELED
Current assignee: SIELED
Priority date: 2015-12-17
Filing date: 2015-12-17
Publication date: 2022-03-24
Anticipated expiration: 2035-12-17
Also published as: AU2015271916A1

Abstract

The present invention provides a lighting apparatus for aquatic environments which comprises an electronic board (such as a printed circuit board) with an upper face, light emitting means mounted on the upper face of the electronic board, a protective cover arranged for protecting the electronic board and the light emitting (or illumination) means, heat transfer means arranged for transferring the heat generated by the light emitting means to the aquatic environment, the heat transfer means having a layer of heat-conductive resin on a heat transfer surface thereof in direct contact with the aquatic environment and arranged relative to the electronic board for transferring the heat generated by the light emitting means towards the heat exchange surface, the resin layer being formed to ensure the protective cover maintains a tight fit on the heat exchange surface, the resin layer having a contact surface in direct contact with the upper face of the electronic board, and further comprising lenses arranged on the upper face of the electronic board for focusing the light emitted by the light emitting means, and wherein the resin layer has a thickness that is smaller over the locations of the lenses than elsewhere. 11/8 31 311 310 4 Fig. 1 310 -31 1 1 1 11 4 Fig. 2

Description

11/8 31 311

310

4 Fig. 1

310 -31 1 1

1

11

4 Fig. 2

UNDERWATER LIGHTING DEVICE

Technical Field The present invention relates to an underwater lighting device.

Background Art Underwater lighting devices are known in the state of the art. For example, document EP 2 594 245 Al discloses an underwater lighting device which comprises: - an electronic board (a printed circuit board) having a front surface and a rear surface, opposite the front surface, - light-emitting means assembled on the front surface of the electronic board, - a protective cover arranged to protect the electronic board and the light-emitting means arranged thereon, - heat transfer means arranged to transfer heat generated by the light-emitting means to an aquatic underwater environment when immersed therein. The heat transfer means comprise a metal plate assembled on the rear surface of the electronic board. The metal plate is intended to be submerged in the aquatic environment to benefit from a heat exchange with the aquatic medium of that environment in order to be cooled. The metal plate thus enables to dissipate the heat essentially generated by the light-emitting means, such as light emitting diodes, particularly power diodes. Indeed, in the absence of heat transfer means, it can be observed that the temperature of the electronic board strongly increases, which may deteriorate the electronic board and the light-emitting means in case of an extended operation of the device. However, such a device of the state of the art is not fully satisfactory since it requires a conical seal, typically made of rubber, arranged between the metal plate and the protective cover, to prevent the coming into contact of the electronic board and of the light-emitting means with the aquatic medium. Now, such a conical seal requires the forming of shoulders in the protective cover to create support surfaces for the seal. The forming of shoulders in the protective cover also results in the forming of shoulders in the metal plate. Indeed, the metal plate partly rests on the rear surface of the electronic board, and partly on the shoulders of the protective cover. Accordingly, such a device of the state of the art introduces a complexity in the manufacturing thereof, by requiring congruent machining of the protective cover and of the metal plate. Further, the metal plate is submitted to external pressure when immersed in the aquatic environment. As such, the metal plate, which is rigid, transmits high stress to the seal. The seal undergoes compressive losses due to differential expansions with respect to the metal plate, which adversely affects the lifetime of the seal, and thereby of the device.

Summary of the Invention The present invention seeks to make available an underwater lighting device which ameliorates and/or addresses all or part of the above-mentioned disadvantages. For this purpose, the present invention provides an underwater lighting device, comprising: - a printed circuit board having a front surface; - light-emitting means comprising at least one light emitter assembled on the front surface of the printed circuit board; - a protective cover configured to protect the printed circuit board and the at least one light emitter when in an aquatic environment; - heat transfer means comprising at least one thermally-conductive resin layer configured to transfer heat generated by the at least one light emitter to the aquatic environment when immersed therein, wherein the at least one thermally conductive resin layer has a heat exchange surface in direct contact with the aquatic environment and is arranged with respect to the printed circuit board so as to transfer the heat generated by the at least one light emitter to the heat exchange surface, wherein the at least one thermally-conductive resin layer is shaped with respect to the protective cover to ensure sealing of the protective cover with the heat exchange surface, and wherein the at least one thermally conductive resin layer has a first direct contact surface in direct contact with the front surface of the printed circuit board, a ratio of an area of the first direct contact surface to an area of the front surface being greater than or equal to 5%; - collimators arranged on the front surface of the printed circuit board and configured to collimate light emitted by the at least one light emitter, wherein the at least one thermally-conductive resin layer has a thickness smaller than a height of the collimators so as not to cover the collimators; and

- through holes arranged in the printed circuit board facing the collimators, the through holes arranged to remove air trapped between the collimators and the printed circuit board. "Resin layer" means a layer made of a resin-based material. Said material may be a one-component or multicomponent material. Said material may be used for coating or potting operations. Said material may be glue. "Thermally conductive" means a resin layer which has a heat conductivity adapted to dissipate the heat generated by the light-emitting means, the resin layer being likely to have a ratio of conductivity to the conductivity of air greater than or equal to 5. It should be noted that a resin layer should not be confused with a foam. Thus, such a resin layer enables to provide both: - the transfer of the heat generated by the light-emitting means to the heat exchange surface, and - the sealing of the protective cover with the heat exchange surface to prevent the coming into contact of the electronic board and of the light-emitting means with the aquatic environment. Such a device according to the invention can thus be easily manufactured in the absence of a dedicated seal and of specific machining requirements to accommodate such seal, particularly of the protective cover. Further, such a resin layer enables to better absorb the outer pressure of the aquatic environment than a metal plate, which enables to improve the lifetime of the device. As noted, the device comprises collimators arranged on the front surface of the electronic board to collimate the light emitted by the light-emitting means, and the resin layer has a thickness smaller than the height of the collimators. It is thus possible to obtain a long distance underwater lighting device, which is compact and simple to manufacture. Such a resin thickness enables to do away with the presence of translation locking means on the collimators to prevent a translation of the resin along a direction perpendicular to the front surface in the case of an overmolding above the collimators. Advantageously, the collimators may comprise a shoulder extending on the front surface of the electronic board, and the resin layer extending on the shoulder.

Thus, such a shoulder enables to significantly improve the adherence and the sealing of the resin layer with the collimators. Advantageously, the thickness of the resin layer and the height of the colli mators have a ratio greater than 0.7, preferably in the range from 0.85 to 0.95. Thus, such a ratio enables to combine a good heat conductivity of the resin layer and a good sealing between the resin layer and the collimators. Advantageously, there is an interface between the resin layer and the collimators, and the collimators are adapted so that the interface has a surface tension in the range from 65 dyn to 80 dyn. Thus, such a surface tension enables to obtain an interface with an excel lent tightness. The collimators are preferably adapted by means of a surface treatment such as flame treatment. In accordance with the invention, the resin layer further has a first direct contact surface in direct contact with the front surface of the electronic board, wherein a ratio of an area of the first direct contact surface to an area of the front surface is greater than or equal to 5%. In one embodiment, the stated ratio is preferably greater than or equal to 10%, and more preferably still, greater than or equal to 20%. Thus, the fact for the resin layer to be in direct contact with the front surface of the electronic board enables to suppress air between the electronic board and the protective cover and, thereby, to improve the heat dissipation since air is a poor heat conductor. The area of the direct contact surface is adapted to the power of the light-emitting means. In an embodiment, the resin layer extends all over the front surface of the electronic board in direct contact. Thus, the heat dissipation generated by the light-emitting means is facili tated by increasing the heat exchange surface area. In an embodiment, the electronic board has a rear surface, opposite to the front surface, and the resin layer has a second direct contact surface in direct contact with the rear surface of the electronic board, wherein a ratio of an area of said direct contact surface to the rear surface area is greater than or equal to 5%. In another embodiment, said ratio is preferably greater than or equal to 10%, and more preferably still, greater than or equal to 20%.

Thus, for certain electronic boards, for example, of IMS (Insulated Metal Substrate) type, the heat generated by the light-emitting means mainly accumu lates at the rear surface of the electronic board. The fact for the resin layer to be in direct contact with the rear surface of the electronic board allows the transfer of said heat to the heat exchange surface. In another embodiment, the resin layer extends all over the rear surface of the electronic board and is in direct contact therewith. Thus, the heat dissipation generated by the light-emitting means is facilitated by increasing the heat exchange surface area. In an embodiment, the heat transfer means comprise a heat exchanger interposed between the electronic board and the resin layer, the heat exchanger being preferably selected from the group comprising a metal plate or a U-tube exchanger. Thus, interposing a heat exchanger between the electronic board and the resin layer enables to decrease the resin layer thickness necessary to obtain a heat exchange surface meant to be in direct contact with the aquatic environment. Advantageously, the resin layer can be arranged to cover the heat exchanger. Thus, such a resin layer ensures the additional function of protecting the heat exchanger, particularly against corrosion. The collimators of the device are arranged to collimate the light emitted by the light-emitting means. It is thus possible to obtain a long-distance underwater lighting. As already noted above, the device comprises through openings made in the electronic board opposite the collimators. Thus, such through openings enable to avoid the forming of air bubbles in the resin layer originating from the air trapped between the collimators and the electronic board. Such through openings enable to exhaust the air. Advantageously, the resin layer comprises a metal filler. Thus, the presence of a metal filler enables to increase the heat conductiv ity of the resin layer, and thereby to improve the transfer of the heat generated by the light-emitting means to the heat exchange surface. In an embodiment, the resin layer has an expansion coefficient adapted with respect to the expansion coefficient of the electronic board and to the temperature of the aquatic environment, particularly to avoid the tearing-off of the light-emitting means when the device is submerged in the aquatic environment. Thus, such a resin layer enables to protect the electronic board from deformations linked to the outer pressure of the aquatic environment. According to an embodiment, the resin layer is formed from a casting resin selected from the group comprising polyepoxides, polyurethanes, polyesters, and polysiloxanes, acrylics, and methyl methacrylates. Thus, such resins are selected, in particular, for their flexibility and their heat conductivity, which is much greater than that of air.

The foregoing and other features and advantages of the invention will be discussed in detail in the following non-limiting description of different embodiments of a device according to the invention, in connection with the accompanying drawings.

Brief Description of the Drawings - Figure 1 is an exploded perspective view of a first device according to the invention before the forming of the resin layer, - Figure 2 is a perspective view of the device illustrated in Figure 1, - Figure 3 is a perspective view of the device illustrated in Figure 1 after the forming of the resin layer, - Figure 4 is a perspective detail view of the device illustrated in Figure 3, - Figure 5 is a partial cross-section view at an enlarged scale of a second device according to the invention, - Figure 6 is a partial cross-section view of a third device according to the invention, - Figure 7 is a partial cross-section view of a fourth device according to the invention, - Figure 8 is a cross-section view of a fifth device according to the invention, - Figure 9 is a cross-section view of a sixth device according to the invention, - Figure 10 is a cross-section view of a variation of the sixth device according to the invention,

- Figure 11 is a cross-section view of a seventh device according to the invention, - Figure 12 is a cross-section view of an eighth device according to the invention, - Figure 13 is a cross-section view of a ninth device according to the invention, - Figure 14 is a cross-section view of a tenth device according to the invention, - Figure 15 is a partial cross-section view of an eleventh device according to the invention, - Figure 16 is a cross-section view of a twelfth device according to the invention, - Figure 17 is a cross-section view of a thirteenth device according to the invention, - Figure 18 is a cross-section view of a variation of the ninth device illustrated in Figure 13, - Figure 19 is a cross-section view of a fourteenth device according to the invention, - Figure 20 is a partial cross-section view of a device according to the invention.

Detailed Description of Embodiments of the Invention For the different embodiments, the same references will be used for identical elements or elements performing the same function, to simplify the description. The technical characteristics described hereafter for different embodiments are to be considered separately or according to any technically possible combination. The first device illustrated in Figures 1 to 4 is an underwater lighting device, comprising: - an electronic board 1 comprising a surface, called front surface 11, - light-emitting means 2, preferably of light-emitting diode type, assembled on front surface 11 of electronic board 1, - a protective cover 4 arranged to protect electronic board 1 and light emitting means 2,

- heat transfer means for transferring the heat generated by light-emitting means 2 to the aquatic environment. Electronic board 1 comprises a circuit for controlling light-emitting means 2. Electronic board 1 preferably is in the shape of a disk. As a non-limiting example, electronic board 1 may also be parallelepiped-shaped. Front surface 11 of elec tronic board 1 is advantageously planar. Front surface 11 of electronic board 1 is preferably circular. Electronic board 1 may be made of a material which is a good heat conductor to uniformly distribute the heat generated by light-emitting means 2 at front surface 11 of electronic board 1. Front surface 11 of electronic board 1 may comprise a coating adapted to reflect light and/or heat so as to increase the heat transfer to heat exchange surface 30. Light-emitting means 2 may be distributed at front surface 11 of electronic board 1 to avoid a local heat concentration. Thus, the distances between two neighboring areas of front surface 11 occupied by light-emitting means 2 may be substantially identical. The device comprises collimators 310 arranged on front surface 11 of electronic board 1 to collimate the light emitted by light-emitting means 2. Colli mators 310 may be interconnected by branches 311 to form a network 31 of collimators 310. Such collimators 310 in a network are simple to install. Network 31 of collimators 310 is preferably made of a plastic material. Network 31 of colli mators 310 may be equipped with an adapted lens to allow interplays of light such as color mixing. Network 31 of collimators 310 occupies an area of front surface 11 of electronic board 1. Protective cover 4 is a half-shell in the shape of a half-sphere which may be made of a plastic material. Other shapes are of course possible for protective cover 4. Protective cover 4 delimits an enclosure within which electronic board 1 is arranged. The heat transfer means comprise a thermally-conductive resin layer 3 having a heat exchange surface 30 meant to be in direct contact with the aquatic environ ment. Resin layer 3 is arranged relatively to electronic board 1 to transfer the heat generated by light-emitting means 2 to heat exchange surface 30. More specifi cally, resin layer 3 extends on the area complementary to front surface 11 of electronic board 1 in direct contact. "Complementary" is used in the mathematical meaning of the term; front surface 11 of the electronic board is a set, the area occupied by network 31 of collimators 310 is a subset and the complementary of said occupied area (called complementary area) is the assembly of the elements of front surface 11 of electronic board 1 which do not belong to said occupied area. Resin layer 3 is shaped relatively to protective cover 4 to ensure the sealing of protective cover 4 with heat exchange surface 30. Resin layer 3 may comprise a metal filler. Resin layer 3 advantageously has an expansion coefficient adapted with respect to the expansion coefficient of electronic board 1 and to the temperature of the aquatic environment, particularly to avoid the tearing of light emitting means 2 when the device is submerged in the aquatic environment. Resin layer 3 may be transparent, translucent, or opaque in the visible range. Resin layer 3 is preferably formed from a cast resin selected from the group comprising polyepoxides, polyurethanes, polyesters, polysiloxanes, acrylics, and methyl methacrylates. Resin layer 3 advantageously has a thickness smaller than the height of collimators 310. An experiment has been conducted when resin layer 3 is based on poly urethane, the results thereof being gathered in the following table. The table shows the intensity (a.u.) consumed by light-emitting means 2 according to the temperature of the aquatic environment and to the thickness of the resin layer. Light-emitting means 2 are equipped with a temperature probe which enables to inform a control unit to decrease the consumed intensity as soon as there is a significant heating of electronic board 1. Light-emitting means 2 should conventionally operate up to a 400 C temperature. Thickness of resin layer 3 (mm) Temperature (°C) 3.5 mm 4 mm 5mm 6 mm 28 0 C 3.55 3.4 32 0 C 3.5 3.5 3.55 3.25 36 0 C 3.5 3.5 3.4 2.95 40 0 C 3.3 3.4 3.15-3.3 2.75

The table shows that the thickness of polyurethane resin layer 3 should be smaller than 5 mm. Above this value, the heat conduction of resin layer 3 is not sufficient to provide an efficient heat transfer to the aquatic environment. As an example, the thickness of resin layer 3 may be in the order of 4.5 mm and the height of collimators 310 may be in the order of 5 mm with a ratio in the order of 0.9. In the embodiment illustrated in Figure 5, the second device differs from the first device in that it comprises through openings 12 formed in electronic board 1 opposite collimators 310 to exhaust air A trapped between collimators 310 and electronic board 1. Through openings 12 advantageously have a sufficiently large size to avoid creating a pressure drop for air A, which should easily flow therethrough. A plurality of through openings 12 are advantageously formed in electronic board 1 opposite each collimator 310. As a non-limiting example, four circular through openings 12, having a 2.5-mm diameter, may be distributed around light-emitting means 2, opposite each collimator 310.

In the embodiment illustrated in Figure 6, the third device differs from the first device in that it comprises no collimators, and in that resin layer 3 extends all over front surface 11 of electronic board 1 in direct contact. Resin layer 3 may be transparent or translucent in the visible range. Resin layer 3 is preferably formed from a cast resin selected from the group comprising polyurethanes and polysiloxanes. Thus, such resins enable to combine an excellent light trans mission and a heat conductivity much greater than that of air, the ratio being greater than 7.

In the embodiment illustrated in Figure 7, the fourth device differs from the first device in that it comprises no collimators. Protective cover 4 comprises lenses 40 which may be made of glass or of a plastic material transparent or translucent in the visible range. Lenses 40 are arranged opposite light-emitting means 2. Lenses 40 of protective cover 4 occupy an area of front surface 11 of electronic board 1. Resin layer 3 extends on the area complementary to front surface 11 of electronic board 1 in direct contact. "Complementary" is used in the mathematical meaning of the term; front surface 11 of the electronic board is a set, the area occupied by lenses 40 of protective cover 4 is a subset, and the complementary of said occupied area (called complementary area) is the assembly of the elements of front surface 11 of electronic board 1 which do not belong to said occupied area. The complementary area forms a central area between lenses 40 and a peripheral area between protective cover 4 and lenses 40.

In the embodiment illustrated in Figure 8, the fifth device differs from the fourth device in that protective cover 4 comprises a lens 40 arranged opposite light-emitting means 2. Lens 40 occupies a central area of front surface 11 of electronic board 1. Resin layer 3 extends on the peripheral area complementary to front surface 11 of electronic board 1 in direct contact.

In the embodiment illustrated in Figure 9, the sixth device differs from the first device in that protective cover 4 comprises a lens 40 which may be made of glass or of a plastic material transparent or translucent in the visible range. Lens 40 is arranged opposite light-emitting means 2. Electronic board 1 comprises a surface, called rear surface 13, opposite to front surface 11, and resin layer 3 extends all over rear surface 13 of electronic board 1 in direct contact. Electronic board 1 comprises circuits 6 for controlling light-emitting means 2. Control circuits 6 are arranged on front surface 11 of electronic board 1. Figure 9 also shows a wire 7 of connection to electronic board 1. This embodiment is particularly adapted to an electronic board 1 of IMS (Insulated Metal Substrate) type, the heat generated by light-emitting means 2 mainly accumulating at rear surface 13 of electronic board 1.

In the embodiment illustrated in Figure 10, control circuits 6 are arranged on rear surface 13 of electronic board 1 and are encapsulated in resin layer 3.

In the embodiment illustrated in Figure 11, the seventh device differs from the embodiments illustrated in Figures 9 and 10 in that the heat transfer means comprise a heat exchanger 5 interposed between electronic board 1 and resin layer 3. Heat exchanger 5 is a metal plate extending all over rear surface 13 of electronic board 1 in direct contact. Resin layer 3 is arranged to cover the metal plate.

In the embodiment illustrated in Figure 12, the eighth device differs from the first device in that protective cover 4 comprises a lens 40 which may be made of glass or of a plastic material transparent or translucent in the visible range. Lens 40 is arranged opposite light-emitting means 2. Electronic board 1 comprises a surface, called rear surface 13, opposite to front surface 11. Elec tronic board 1 comprises circuits 6 for controlling light-emitting means 2. Control circuits 6 are arranged on front surface 11 of electronic board 1. Protective cover 4 comprises portions occupying peripheral areas of rear surface 13 of electronic board 1. Control circuits 6 may also be arranged on said peripheral areas of rear surface 13 of electronic board 1. The heat transfer means comprise a heat exchanger 5, of metal plate type, extending over a central portion of rear surface 13 of electronic board 1. Resin layer 3 is arranged to cover the metal plate. Resin layer 3 is shaped to interpose between the metal plate and said portions of protective cover 4 to ensure the sealing of protective cover 4 with heat exchange surface 30 of resin layer 3. Heat exchange surface 30 is flush with said portions of protective cover 4.

In the embodiment illustrated in Figure 13, the ninth device differs from the first device in that protective cover 4 comprises lenses 40 which may be made of glass or of a plastic material transparent or translucent in the visible range. Lenses 40 are arranged opposite light-emitting means 2. Lenses 40 of protective cover 4 occupy a peripheral area of front surface 11 of electronic board 1. The heat transfer means comprise a heat exchanger 5, of metal plate type, extending on a central portion of front surface 11 of electronic board 1. Resin layer 3 is arranged to cover the metal plate. Resin layer 3 is shaped to interpose between the metal plate and said lenses 40 of protective cover 4 to ensure the sealing of protective cover 4 with heat exchange surface 30 of resin layer 3. Heat exchange surface 30 is flush with said lenses 40 of protective cover 4.

In the embodiment illustrated in Figure 14, the tenth device differs from the first device in that protective cover 4 comprises a lens 40 which may be made of glass or of a plastic material transparent or translucent in the visible range. Lens 40 is arranged opposite light-emitting means 2. Lens 40 entirely occupies front surface 11 of electronic board 1. The heat transfer means comprise a heat exchanger 5, of metal plate type, assembled on protective cover 4 to extend all over rear surface 13 of electronic board 1 in direct contact. Resin layer 3 rests on the metal plate. Resin layer 3 is shaped to interpose between lens 40 and protec tive cover 4 to provide the sealing of protective cover 4 with heat exchange surface 30 of resin layer 3.

In the embodiment illustrated in Figure 15, the eleventh device differs from the first device in that protective cover 4 comprises lenses 40 which may be made of glass or of a plastic material transparent or translucent in the visible range. Lenses 40 are arranged opposite light-emitting means 2. The heat transfer means comprise a heat exchanger 5, of metal plate type, assembled on protective cover 4 to extend all over rear surface 13 of electronic board 1 in direct contact. Resin layer 3 rests on the metal plate in its central portion. Resin layer 3 is shaped to interpose between lenses 40 to provide the sealing of protective cover 4 with heat exchange surface 30 of resin layer 3.

In the embodiment illustrated in Figure 16, the twelfth device differs from the first device in that a resin layer 3 extends all over rear surface 13 of electronic board 1 in direct contact.

In the embodiment illustrated in Figure 17, the thirteenth device differs from the sixth device illustrated in Figure 9 in that protective cover 4 comprises a half shell having lens 40 assembled thereon. The half-shell is arranged opposite resin layer 3. The half-shell is provided with openings 8 capable of allowing the entering of water from the aquatic environment into enclosure 9 defined by the half-shell. Thus, resin layer 3 has a heat exchange surface 30 meant to be in direct contact with the aquatic environment.

In the embodiment illustrated in Figure 18, which is a variation of the ninth device illustrated in Figure 13, heat exchanger 5 is of U-tube exchanger type.

In the embodiment illustrated in Figure 19, the fourteenth device differs from the thirteenth device illustrated in Figure 17 in that a heat exchanger 5, of U tube exchanger type, is interposed between a central area of rear surface 13 of electronic board 1 and resin layer 3. According to an alternative embodiment of the fourteenth device (not shown), heat exchanger 5 is a metal plate interposed between rear surface 13 of the electronic board and resin layer 3.

In the embodiment illustrated in Figure 20, the device differs from the first device in that collimators 310 comprise a shoulder 32 extending on front surface 11 of electronic board 1. Resin layer 3 extends on shoulder 32. Shoulder 32 has a substantially L-shaped cross-section. A method of manufacturing the first device comprises a step of overmolding based on the thermally-conductive resin on the complementary area of front surface 11 of electronic board 1. Collimators 310 may comprise means for preventing a translation of the resin along the direction perpendicular to said front surface 11 in case of an overmolding above collimators 310. It may be advanta geous to form a resin thickness smaller than the height of collimators 310.

Claims

1. An underwater lighting device, including: - a printed circuit board having a front surface; - light-emitting means comprising at least one light emitter assembled on the front surface of the printed circuit board; - a protective cover configured to protect the printed circuit board and the at least one light emitter; - heat transfer means comprising at least one thermally-conductive resin layer configured to transfer heat generated by the at least one light emitter to an aquatic environment, wherein the at least one thermally-conductive resin layer has a heat exchange surface in direct contact with the aquatic environment when the lighting device is immersed therein, wherein the at least one thermally conductive resin layer is configured with respect to the printed circuit board so as to transfer the heat generated by the at least one light emitter to the heat exchange surface, wherein the at least one thermally-conductive resin layer is shaped with respect to the protective cover to ensure sealing of the protective cover with the heat exchange surface, and wherein the at least one thermally conductive resin layer has a first contact surface in direct contact with the front surface of the printed circuit board, a ratio of an area of the first contact surface to an area of the front surface being greater than or equal to 5%; - collimators arranged on the front surface of the printed circuit board and configured to collimate light emitted by the at least one light emitter, wherein the at least one thermally-conductive resin layer has a thickness smaller than a height of the collimators so as not to cover the collimators; and - through holes in the printed circuit board facing the collimators and arranged to remove air trapped between the collimators and the printed circuit board.

2. The device according to claim 1, wherein the collimators comprise a shoulder extending on the front surface of the printed circuit board, and wherein the at least one thermally-conductive resin layer extends on the shoulder.

3. The device according to claim 1 or 2, wherein the thickness of the at least one thermally-conductive resin layer and the height of the collimators have a ratio greater than 0.7.

4. The device according to claim 3, wherein the ratio is in the range from 0.85 to 0.95.

5. The device according to any one of claims 1 to 4, wherein the at least one thermally-conductive resin layer and the collimators have an interface, the collimators configured so that the interface has a surface tension in a range from 65 dyn to 80 dyn.

6. The device according to any one of claims 1 to 5, wherein the ratio of the area of said first direct contact surface to the front surface area is greater than or equal to 10%.

7. The device according to anyone of claims 1 to 6, wherein the printed circuit board has a rear surface, opposite to the front surface, wherein the at least one thermally-conductive resin layer has a second contact surface in direct contact with the rear surface of the printed circuit board, and wherein a ratio of an area of said second contact surface to the rear surface area is greater than or equal to 5%.

8. The device according to any one of claims 1 to 6, wherein the printed circuit board has a rear surface, opposite to the front surface, and wherein the at least one thermally-conductive resin layer extends all over the rear surface of the printed circuit board in direct contact with the rear surface.

9. The device according to any one of claims 1 to 8, wherein the heat transfer means further comprise a heat exchanger interposed between the printed circuit board and the at least one thermally-conductive resin layer.

10. The device according to claim 9, wherein the heat exchanger is a metal plate or a U-tube exchanger.

11. The device according to claim 9, wherein the at least one thermally conductive resin layer covers the heat exchanger.

12. The device according to any one of claims 1 to 11, wherein the at least one thermally-conductive resin layer comprises a metal filler.

13. The device according to any one of claims 1 to 12, wherein the at least one thermally-conductive resin layer is formulated to have a coefficient of expansion adapted with respect to a coefficient of expansion of the printed circuit board and to a temperature of the aquatic environment, in particular so as to prevent the at least one light emitter from being torn-off when the device is submerged in the aquatic environment.

14. The device according to any one of claims 1 to 13, wherein the at least one thermally-conductive resin layer is made from a casting resin selected from the group comprising polyepoxides, polyurethanes, polyesters, polysiloxanes, acrylics and methyl methacrylates.