POLARISING PHOTOVOLTAIC MODULE BUILT INTO THE SCREEN OF AN ELECTRONIC DISPLAY DEVICE

Abstract

A display device provided with a polarising photovoltaic module includes (a) a plurality of polarisers; (b) a plurality of pixels which emit or transmit light referred to as image light; (c) a plurality of photovoltaic active zones and a plurality of openings, two adjacent photovoltaic active zones forming an opening and said photovoltaic active zones being arranged between the pixels and the polarisers; wherein said polarisers are semi-reflective and are made up of one or more surfaces selected among planar surfaces, which are concave or convex, and have parabolic, conical, pyramidal, tetrahedral, semi-cylindrical or cylindrical-parabolic shapes, said polarisers being arranged so as to concentrate, by reflection, a first linear polarised component of the ambient light onto said photovoltaic active zones, as well as to transmit, through the polarising photovoltaic module, a second linear polarised component of the ambient light or of the image light.

Claims

1. A display device provided with a polarizing photovoltaic module including at least: (a) a plurality of polarizers; (b) a plurality of pixels which emit or transmit light referred to as image light; (c) a plurality of photovoltaic active zones and a plurality of openings, two neighboring photovoltaic active zones forming an opening and said photovoltaic active zones being positioned between the pixels and the polarizers; wherein said polarizers are semi-reflective and consist of one or more surfaces chosen from among planar, concave or convex surfaces which are parabolic, conical, pyramidal, tetrahedral, semicylindrical or cylindro-parabolic in shape, said polarizers being arranged so as both to concentrate, by reflection, a first linearly polarized component of the ambient light onto said photovoltaic active zones and to transmit, through said polarizing photovoltaic module, a second linearly polarized component of the ambient light or of the image light.

2. The display device as claimed in claim 1, wherein said polarizers are composed of an array of reflective strips, the widths of which and the distances separating them are advantageously less than 400 nanometers.

3. The display device as claimed in claim 1, wherein said photovoltaic active zones are positioned in the vicinity of the plane of maximum concentration of said polarizers.

4. The display device as claimed in claim 1, wherein the plurality of pixels are separated from one another by an inter-pixel matrix and in that said photovoltaic active zones are aligned with the inter-pixel matrix.

5. The display device as claimed in claim 1, wherein said photovoltaic active zones and said polarizers are organized into a continuous or discontinuous array of elementary patterns, defining any type of shape, in particular curved shapes, for example circular shapes, and/or planar shapes, for example polygonal, prismatic or hexagonal shapes.

6. The display device as claimed in claim 1, wherein said pixels consist of electro-optical modulators, optionally combined with color filters, or of electroluminescent materials.

7. The display device as claimed in claim 1, wherein said image light corresponds to a portion of the ambient light that is fully or partially reflected in the device and/or a portion of the light emitted by the device.

8. The display device as claimed in claim 1, wherein it additionally includes one or more other polarizers and/or a quarter-wave plate being used to polarize the image light.

9. The display device as claimed in claim 1, wherein it additionally includes a functional surface, for example an antireflective, anti-UV or touch-sensitive surface.

10. A method for manufacturing a portion of the display device as claimed in claim 1 composed of concentrators (4) and photovoltaic active zones, wherein it successively includes steps consisting of: (a) providing a semitransparent photovoltaic module composed of a plurality of photovoltaic active zones and a plurality of openings, said photovoltaic active zones consisting of a plurality of thin films deposited on a transparent substrate; (b) depositing a first transparent resist layer then structuring said resist so as to form the geometry of the concentrators; (c) depositing a conformal layer of a reflective material on the structured face of said resist; (d) etching the entire surface of the reflective layer in the form of strips and etching the surface at the tops of the concentrators; (e) depositing a second, planarizing layer of transparent resist.

11. A fixed or portable, rigid or flexible electronic unit, wherein it comprises a display device according to claim 1.

Description

FIGURES

[0034] The invention will be better understood from its detailed description, provided with reference to the figures in which:

[0035] FIGS. 1a and 1b are schematic representations in cross section of a portion of the display device according to the invention and illustrate its operation;

[0036] FIG. 2 is a schematic representation in cross section of the structure of an emissive LCD display device according to the invention;

[0037] FIG. 3 is a schematic representation in cross section of the structure of a reflective LCD display device according to the invention;

[0038] FIG. 4 is a schematic representation in cross section of the structure of an OLED display device according to the invention.

[0039] The figures are not to scale, the relative thicknesses of the components of the device being intentionally exaggerated in order to provide a clearer representation of its structure.

DETAILED DESCRIPTION

[0040] Reference is made to FIGS. 1a and 1b, which are schematic representations in cross section of a portion of the display device according to the invention, referred to as a polarizing photovoltaic module 18. Said polarizing photovoltaic module 18 includes a plurality of photovoltaic active zones 1, two neighboring photovoltaic active zones 1′, 1″ forming an opening 2, and a plurality of semi-reflective polarizers 4 that are parabolic in shape. Generally consisting of a set of metal strips of controlled size, said polarizers 4 are arranged at the interface between two layers of transparent materials 7, 8 which ideally have identical, or nearly identical, refractive indices so as to limit the phenomena of total reflection of the light passing through this interface.

[0041] As shown in FIG. 1a, the polarizers 4 reflect a first linearly polarized component 5′ of the ambient light 5 emitted by natural or artificial light sources that are external to the device (hence not polarized before reaching the device) and transmit a second linearly polarized component 5″, orthogonal to the first, through the polarizing photovoltaic module 18. By virtue of their parabolic shape, the polarizers 4 act as concentrators of a portion of the ambient light 5 by way of multiple reflections of its first linearly polarized component 5′. They are positioned with respect to the photovoltaic active zones 1 so that said first linearly polarized component 5′ of the ambient light 5 is directed by the light concentrators 4 onto said photovoltaic active zones 1.

[0042] FIG. 1b illustrates the operation of the polarizing photovoltaic module 18 with respect to the image light 6 emitted by the display device, which light is generally polarized at the output of emissive or reflective LCD and OLED devices. It is assumed here that the components allowing the display are oriented such that the image light 6 corresponds to the second linearly polarized component P2. In the case of an ideal interface, all of the polarized image light 6 is transmitted through the semi-reflective polarizers 4. In practice, reflection or absorption loss phenomena occurring successively in the layers 8, 4, 7 limit the amount of transmitted light 6′ to around 90% of the amount of light 6 arising from the image. Furthermore, a portion of the image light 6 is reflected or absorbed by the back face of the photovoltaic active zones 1. However, for a given level of production of electricity, the surface fraction of said photovoltaic active zones 1 is smaller with respect to a standard device without light concentrators 4, thereby allowing the total quantity of transmitted image light 6′ to be increased.

[0043] The polarizing photovoltaic module 18 may be incorporated into a display device, either in addition to the components allowing an image to be displayed or by replacing the last linear polarizer through which the image light 6 passes. The cases of use described in FIGS. 2 to 4 make reference to three different display devices in which the polarizing photovoltaic module 18 replaces the last linear polarizer that is usually incorporated into such devices.

[0044] FIG. 2 is a schematic representation in cross section of the structure of an emissive LCD display device according to the invention. Said device consists, inter alia, of a backlight 12 allowing light to be produced via LED illumination and a first linear polarizer 11 that polarizes the light arising from the backlight 12. The plane of polarization of the light may be altered by means of an electro-optical modulator 10 (a liquid-crystal electro-optical modulator in the present case) controlled by means of two transparent electrodes that are deposited on glass substrates 9′, 9″. The pixels 3 alternately consist of three color filters, typically red, green and blue, and are separated by an inter-pixel matrix 13. The polarizing photovoltaic module 18 acts as the upper polarizer. In order to maximize transmission and to limit the moire phenomena known to those skilled in the art as far as possible, a pitch of the array of photovoltaic active zones 1 is chosen so as to accord with the pitch of the inter-pixel matrix 13.

[0045] FIG. 3 is a schematic representation in cross section of the structure of a reflective LCD display device according to the invention. The composition of such a device differs from that described in FIG. 2 in that the backlight and the first polarizer are replaced by a mirror 14. The image light 6 corresponds to the ambient light that is reflected by the mirror 14 and passes through the pixels 3. Again in this case, the polarizer that is positioned as standard above the upper electrode 9″ of such a device is replaced by the polarizing photovoltaic module 18.

[0046] A concrete exemplary embodiment is described below. On the basis of a display device containing an array of pixels 3 of 150 μm in width separated from one another by an inter-pixel distance 13 of 30 μm, a photovoltaic module formed from an array of photovoltaic active strips 1 of 10 μm in width, separated by openings of 20 μm, is provided. The structured transparent substrate 8 has a refractive index close to 1.5. The polarizers 4 are in the shape of truncated parabolas with an entrance surface of 30 μm in width and a height of between 20 and 40 μm. In the case of the planarizing transparent resist 7 having a refractive index close to 1.5, the angle of acceptance of ambient light incident on the surface of said device is 60°.

[0047] FIG. 4 is a schematic representation in cross section of the structure of an OLED display device according to the invention. The electroluminescent pixels 3, typically alternately composed of three different organic materials that emit in the blue, green and red are positioned on an electronic panel 17 for controlling said electroluminescent pixels 3, then encapsulated using a transparent material 16. The encapsulating layer 16 makes it possible to improve the stability of the materials used in manufacturing the pixels 3, in particular by forming a barrier to oxygen and water. The image light 6 is directly emitted by the electroluminescent pixels 3. In such a device, the upper polarizer is generally combined with a quarter-wave plate 15 that makes it possible to prevent the reflection of ambient light. This polarizer is replaced by the photovoltaic module according to the invention.

Advantages of the Invention

[0048] It follows from the above that the invention achieves its stated goals. The invention describes an electronic display device including transflective polarizers that are capable of effectively concentrating a first component of the ambient light onto an array of photovoltaic active zones while being transparent to the second polarization of the image light at the openings of the photovoltaic module. Thus, the energy of the first component of the ambient light, usually lost through absorption in standard display devices, is converted to electrical energy.

[0049] Moreover, one advantage of the device that is a subject of the invention is that it produces energy independently of the light or dark state of the image.

[0050] Lastly, the surface fraction of photovoltaic active zones may be optimized so as to limit the reflection of the ambient light of the polarizing photovoltaic module toward the user.

LIST OF THE REFERENCES USED IN THE FIGURES

[0051]

TABLE-US-00001 1 Photovoltaic active zone 2 Opening 3 Pixel 4 Semi-reflective polarizer 5 Ambient light 6 Image light 7 First transparent dielectric material layer 8 Second transparent dielectric material layer 9 Glass for protecting and controlling the electro-optical module 10 Electro-optical modulator 11 First polarizer 12 Backlight 13 Inter-pixel 14 Mirror 15 Quarter-wave plate 16 Encapsulating layer 17 Electronic control panel 18 Polarizing photovoltaic module