Display device and light source module having high color conversion efficiency thereof

A light source module includes a lighting structure, a light diffusing layer, a wavelength converting layer, and a cover plate. The lighting structure includes a plurality of light emitting elements that are all blue-light emitting elements. The light diffusing layer is disposed on the lighting structure, the wavelength converting layer is disposed on the light diffusing layer, and the cover plate is disposed on the wavelength converting layer.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of priority to Taiwan Patent Application No. 106144003, filed on Dec. 14, 2017. The entire content of the above identified application is incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to a light source module, and more particularly to a light source module that uses blue-light emitting elements to produce varying color lights and a display device using the same.

BACKGROUND OF THE DISCLOSURE

Light-emitting diodes (LEDs) have many advantages including small size, high luminous efficiency and low energy consumption. Nowadays, displace devices are developed with the trend toward thinness and high efficiency, and thus have begun to employ LED light sources.

The conventional LED light source used in the displace devices generally arranges red, green and blue LED chips in a package so as to mix red, green and blue lights into a white light. However, the at least three types of LED chips in the LED light source have different aging speeds and brightness decaying speeds that may result in the shift of the color temperature in a long-term operation. In addition, the conventional LED light source needs to apply different powers to the at least three types of LED chips respectively and thus has a complicated design of the driving circuit.

SUMMARY OF THE DISCLOSURE

In response to the above-referenced technical inadequacies, the present disclosure provides a light source module and a display device using the same.

In one aspect, the present disclosure provides a light source module which includes a lighting structure, a light diffusing layer, a wavelength converting layer, and a cover plate. The lighting structure includes a substrate and at least three blue-light emitting elements, wherein the substrate has a first region, a second region adjacent to the first region, and a third region adjacent to the second region, and the blue-light emitting elements are respectively disposed in the first region, the second region, and the third region. The light diffusing layer is disposed on the lighting structure. The wavelength converting layer is disposed on the light diffusing layer, wherein the wavelength converting layer includes a first converting layer disposed in the first region, a second converting layer disposed in the second region, and a transparent layer disposed in the third region. A blue light generated from one of the blue-light emitting elements and emitted from the first region is converted to a red light via the first converting layer. A blue light generated from another one of the blue-light emitting elements and emitted from the second region is converted to a green light via the second converting layer. The cover plate is disposed on the wavelength converting layer. The blue-light reflecting layer is disposed on the cover plate and covers the first converting layer and the second converting layer.

In one aspect, the present disclosure provides a display device which includes a plurality of light source modules described above.

In certain embodiments, the light diffusing layer is formed from a silicone resin with light diffusing particles dispersed therein.

In certain embodiments, the content of the light diffusing particles is 5% by weight to 25% by weight based on the total weight of the light diffusing layer. The light diffusing particles are titanium dioxide particles having a mean particle size between 20 nm and 70 nm.

In certain embodiments, the first converting layer contains red phosphors, the second converting layer contains green phosphors, and the transparent layer is formed from a silicone resin.

In certain embodiments, the cover plate is a glass cover plate.

In certain embodiments, the glass cover plate has a first surface proximate to the wavelength converting layer and a second surface opposite to the first surface, and the blue-light reflecting layer is formed on the first surface.

In certain embodiments, the glass cover plate has a first surface proximate to the wavelength converting layer and a second surface opposite to the first surface, and the blue-light reflecting layer is formed on the second surface.

In certain embodiments, each of the blue-light emitting elements is a blue LED chip for generating a blue light having a wavelength between 360 nm and 450 nm.

In certain embodiments, the wavelength converting layer further includes a first light shielding layer and a second light shielding layer. The first light shielding layer is disposed between the first converting layer and the second converting layer. The second light shielding layer is disposed between the second converting layer and the transparent layer. The first light shielding layer and the second light shielding layer jointly form a black matrix.

One of the advantages of the present disclosure is that the light source module of the present disclosure includes a lighting structure, in which the light emitting elements of the lighting structure are all blue-light emitting elements, a light diffusing layer disposed on the lighting structure and a wavelength converting layer disposed on the light diffusing layer, and therefore the product cost and the complexity of the driving circuit can be reduced. Furthermore, the product defects caused by different brightness decaying speeds and driving voltages of the light emitting elements can be avoided.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

First Embodiment

Referring toFIG. 1toFIG. 3, a first embodiment of the present disclosure provides a light source module Z1which includes a lighting structure1, a light diffusing layer2, a wavelength converting layer3, and a cover plate4.

As shown inFIG. 1, the lighting structure1includes a substrate11and a plurality of blue-light emitting elements12a,12b,12c. The substrate11is provided with a driving circuit (now shown) for applying power signals to the blue-light emitting elements12a,12b,12c. The blue-light emitting elements12a,12b,12care disposed on the substrate11and electrically connected to the driving circuit. The blue-light emitting elements12a,12b,12cgenerate blue lights when they receive the power signals. In the present embodiment, the substrate11has a first region111, a second region112adjacent to the first region111, and a third region113adjacent to the second region112. The first region111, the second region112, and third region113respectively serve as a red light region, a green light region, and a blue light region, wherein the first region111and the second region112are spaced apart at a predetermined distance, and the second region112and the third region113are spaced apart at a predetermined distance.

In practice, the substrate11can be a printed circuit board (PCB), metal core printed circuit board (MCPCB), metal printed circuit board (MPCB) or flexible printed circuit board (FPCB), but is not limited thereto. Each of the blue-light emitting elements12a,12b,12ccan be a blue LED chip for generating a blue light having a wavelength between 360 and 450 nm, and be directly mounted onto the substrate11using chip-on-board (COB) techniques. Although, in the present embodiment, the number of the blue-light emitting elements12a,12b,12cof the lighting structure1is three, in other embodiments, the number of the blue-light emitting elements12a,12b,12cof the lighting structure1can be more than three. For example, each of the first, second, and third regions of the substrate11can have two blue-light emitting elements12a,12b,12cdisposed therein to meet different brightness requirements.

It should be noted that, the light emitting elements of the lighting structure1are all blue LED chips that are common in the market and relatively inexpensive. Therefore, the product cost and the complexity of the driving circuit can be reduced, and the product defects caused by different brightness decaying speeds and driving voltages of the light emitting elements can be avoided.

As shown inFIG. 1andFIG. 2, the light diffusing layer2is stacked on the lighting structure1to uniformly diffuse the lights emitted from the blue-light emitting elements12a,12b,12c. The composition of the light diffusing layer2includes a transparent resin21and light diffusing particles22dispersed in the transparent resin21. Specifically speaking, the light diffusing layer2is formed from the transparent resin21mixed with the light diffusing particles22. Although, in the present embodiment, the light diffusing layer2is adjoining to the blue-light emitting elements12a,12b,12c, in other embodiments as shown inFIG. 3, the light diffusing layer2can be disposed above the lighting structure1and over the light emission paths of the blue-light emitting elements12a,12b,12c. That is to say, the light diffusing layer2and the blue-light emitting elements12a,12b,12chave a predetermined optical path L therebetween.

The transparent resin21may consist of silicone, polycarbonate (PC), polymethylmethacrylate (PMMA), methacrylate-styrene copolymer (MS), polystyrene (PS), or polyethylene terephthalate (PET). The light diffusing particles22may include organic particles, inorganic particles, and/or combinations thereof. The organic particles may consist of polystyrene, polymethylmethacrylate, silicone, polyethylene terephthalate, or polyamide (PA). The inorganic particles may consist of zinc oxide (ZnO), silicon dioxide (SiO2), titanium dioxide (TiO2), zirconium oxide (ZrO2), aluminum oxide (Al2O3), zinc sulfide (ZnS), or barium sulfate (BaSO4). However, the aforesaid materials for the transparent resin21and the light diffusing particles22are merely examples and are not meant to limit the present disclosure.

In the present embodiment, the thickness of the light diffusing layer2is preferably between 0.1 μm and 0.6 μm and the transparent resin21thereof is preferably a silicone resin. The content of the light diffusing particles22is preferably 5% by weight to 25% by weight based on the total weight of the light diffusing layer2, and the light diffusing particles22are preferably titanium dioxide particles having a mean particle size between 20 nm and 70 nm. However, there is no limitation to the shape of the light diffusing particles22.

The wavelength converting layer3is stacked on the light diffusing layer2and includes a first converting layer31, a second converting layer32, and a transparent layer33. The first converting layer31is disposed in the first region111for converting a blue light emitted from the blue-light emitting element12ato a red light. The second converting layer32is disposed in the second region112for converting a blue light emitted from the blue-light emitting element12bto a green light. The transparent layer33is disposed in the third region113for transmission of a blue light emitted from the blue-light emitting element12c. Therefore, red, green and blue lights can be produced respectively in the first, second and third regions to output white lights.

In the present embodiment, the first converting layer31contains red phosphors, the second converting layer32contains green phosphors, and the transparent layer33is formed from a silicone resin, but the present disclosure is not limited thereto. For example, the first converting layer31may contain quantum dots, phosphors, or other wavelength converting materials that are capable of being excited by a blue light to produce a red light. The second converting layer32may contain quantum dots, phosphors, or other wavelength converting materials that are capable of being excited by a blue light to produce a green light. The transparent layer33may be formed from the aforesaid transparent resins.

It should be noted that, before entering the wavelength converting layer3, the lights emitted from the blue-light emitting elements12a,12b,12ccan be uniformly diffused by the light diffusing layer2and the energy density thereof can be reduced. Therefore, the proportion of the wavelength converting materials such as red and green phosphors can be reduced, and the color conversion efficiency can be improved.

As shown inFIG. 1, the cover plate4is stacked on the wavelength converting layer3for protecting the lighting structure1, light diffusing layer2, and the wavelength converting layer3from being crushed and damage and uniformly outputting the produced white lights. In the present embodiment, the cover plate4is a glass cover plate having a thickness between 0.1 μm and 2 μm. In other embodiments, the cover plate4can be a plastic cover plate with high light transmittance, and the thickness thereof can be adjusted according to particular requirements. The plastic cover plate may consist of polyethylene, polycarbonate, polymethylmethacrylate, or polyethylene terephthalate.

Second Embodiment

Referring toFIG. 4toFIG. 6, a second embodiment of the present disclosure provides a light source module Z2which includes a lighting structure1, a light diffusing layer2, a wavelength converting layer3, a cover plate4, and a blue-light reflecting layer5. The technical details and implementations of the lighting structure1, the light diffusing layer2, the wavelength converting layer3, and the cover plate4have been described in the first embodiment and will not be reiterated herein.

In the present embodiment, the blue-light reflecting layer5can be formed on the cover plate4and the coverage thereof relative to the lighting structure1includes the first and second regions111,112. The blue-light reflecting layer5is configured to totally reflect blue lights emitted from the first region111and allow the transmission of red lights, and totally reflect blue lights emitted from the second region112and allow the transmission of green lights. Furthermore, the blue-light reflecting layer5can further guide the reflected blue lights from the first and second regions111,112into the third region113, so that the reflected blue lights can project outwardly from the third region113. Therefore, the color purity and color conversion efficiency of red, green and blue lights can be improved. Specifically speaking, as shown inFIG. 4andFIG. 5, the cover plate4has a first surface41proximate to the wavelength converting layer3and a second surface42opposite to the first surface41. The blue-light reflecting layer5can be disposed on the first surface41or the second surface42and cover the first converting layer31and the second converting layer32.

The blue-light reflecting layer5can be a DBR (Distributed Bragg Reflector, DBR) layer. For example, the blue-light reflecting layer5can consist of a plurality of first oxide layers and a plurality of second oxide layers alternately stacked with each other, wherein each of the first oxide layers has a refractive index different from that of each of the second oxide layers. Each of the first oxide layers can be a silicon dioxide layer and each of the second oxide layers can be a titanium dioxide or niobium pentoxide (Nb2O5) layer, but the present disclosure is not limited thereto.

Third Embodiment

Referring toFIG. 7, a third embodiment of the present disclosure provides a light source module Z3having the same main components as that of the second embodiment. The main difference between the second and third embodiments is that the wavelength converting layer3further includes a first light shielding layer34and a second light shielding layer35that jointly form a black matrix. The first light shielding layer34is disposed between the first converting layer31and the second converting layer32for preventing the red lights produced via the first converting layer31and the green lights produced via the second converting layer32from color-mixing. The second light shielding layer35is disposed between the second converting layer32and the transparent layer33for preventing the green lights produced via the second converting layer32and the blue light passing through the transparent layer33from color-mixing.

Referring toFIG. 8, the aforesaid light source modules Z1, Z2, Z3can be applied to a display device D such as an LED display device. For example, the display device D can includes a predetermined number of the light source modules Z1that are arranged in a matrix, but the present disclosure is not limited thereto.

In conclusion, the light source module of the present disclosure includes a lighting structure, in which the light emitting elements of the lighting structure are all blue-light emitting elements, a light diffusing layer disposed on the lighting structure and a wavelength converting layer disposed on the light diffusing layer. Therefore, the product cost and the complexity of the driving circuit can be reduced, and the product defects caused by different brightness decaying speeds and driving voltages of the light emitting elements can be avoided.

Furthermore, the light source module can further include a blue-light reflecting layer disposed on a cover plate and covering the first and second converting layers of the wavelength converting layer. Therefore, the color purity and color conversion efficiency of red, green and blue lights can be improved.