The present invention relates to a lighting device. More specifically, a device of this kind comprises:

- at least one LED element emitting light radiation at a wavelength in the range from 400 to 800 nm, and

- a layer of transparent resin for protection against dust and water.

The protective layer must enable the device to achieve a grade from 66 to 68 of the IP (Index of Protection) class according to the UNI EN 60529 standard.

The light emitted by the LED element is primarily blue, and is then changed towards a yellow tonality by means of light- emitting substances (also called "phosphors") associated with the LED element.

According to a technique known to the applicant, the aforesaid layer of transparent resin is applied directly to the LED element. In this case, owing to the "wetting" of the phosphors by the liquid resin, it has been found that there is a change from warm light to cold light during passage through the transparent resin, resulting in an increase in what is known as the "colour temperature" of the device. As is known, this expression signifies the temperature of a black body emitting the radiation most similar in chromatic terms to the radiation in question. According to the aforesaid prior art, there is thus an undesired increase in the "colour temperature" from values of 2700 - 3000 K to 3300 - 3700 K.

On the other hand, DE-20 2009 002127 Ul describes a lighting device, in one embodiment of which LED elements are separated by a gap from a protective layer.

The object of the present invention is therefore to overcome this drawback of the prior art.

According to the invention, this object is achieved by means of a device of the type indicated at the beginning of the present description, wherein the aforesaid resin layer is spaced apart by a gap from said LED element, and wherein the surface of said resin layer facing said at least one LED element is covered with a transparent film.

In the device according to the invention, phenomena of change from warm light to cold light are substantially absent, and therefore the corresponding "colour temperature" remains substantially unchanged at values corresponding to warm tonalities.

Typically, the "colour temperature" of the device according to the invention is within the range from 2700 to 3000 K, and is preferably about 2800 K.

Other advantages and characteristics of the present invention will be apparent from the following detailed description which is given by way of non-limiting example with reference to the attached drawing, in which the single figure is a schematic representation of a device according to the invention viewed in section.

A lighting device comprises a housing 10 shaped in the form of a channel of variable length, on the bottom of which an LED element 14 is placed on a base 12. The LED element emits light radiation 18 at a wavelength in the range from 400 to 800 nm.

The mouth of the housing 10 is closed by a layer 16 of transparent resin, of the polyure- thane or epoxy type for example.

The resin layer 16 is spaced apart from the LED element 14 by a gap 20 occupied by air.

The surface of the resin layer 16 facing the LED element 14 is covered by a transparent film 22, made for example of a material of the polycarbonate (PC), polymethyl methacry- late (PMMA), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF) or aliphatic poly- urethane type, or any combination thereof. More generally, it is possible to use any materials which are transparent to visible light, and which do not tend to become yellow when exposed to UV light.

The attached figure also clearly shows that the surface of the resin layer 16 facing the LED element 14 and covered with the transparent film 22 is not completely flat, and in particular has lateral portions inclined with respect to a central portion. The film 22 may be shaped by thermoforming a sheet, or by casting a liquid in a mould as desired: for example, in embodiments which are not illustrated, it may copy the profile of the LED element 14.

The overall light emitted by the LED element 14 is yellow and remains so, although it passes through the resin layer 16 and the film 22. The "colour temperature" of the device remains substantially unchanged over a desired range, preferably within the range from 2700 to 3000 K.

Naturally, the principle of the invention remaining the same, the details of construction and the forms of embodiment may be varied widely with respect to those described, which have been given purely by way of example, without thereby departing from the scope of the invention as defined in the attached claims.