WO2008107588A2

WO2008107588A2 - Projection and rear projection screen, chemical composition, method for making a projection and rear projection screen, and projection and rear projection method

Info

Publication number: WO2008107588A2
Application number: PCT/FR2008/050055
Authority: WO
Inventors: Laurent Heddebaux
Original assignee: Laurent Heddebaux
Priority date: 2007-01-11
Filing date: 2008-01-11
Publication date: 2008-09-12
Also published as: FR2911405A1; WO2008107588A3; FR2911405B1

Abstract

The invention relates to a projection and rear projection screen (10) that comprises first (12) and second (14) surfaces separated by a layer (E) of a transparent material (16). The first surface (12) is coated with a first coating (18) containing an acrylic resin, mica, titanium dioxide and a colloidal silica. The second surface (14) is coated with a second coating (20) containing an encapsulated photochromic ink as well as an ultraviolet filter for filtering wavelengths preferably in a range of between 390 and 420 nm.

Description

Projection and retroprojection screen, chemical composition, method of manufacturing a projection and overhead projection screen, and projection and overhead projection method

The present invention relates to a projection screen and backprojection, a chemical composition, a method of manufacturing a projection screen and backprojection and a method of projection and rear projection.

It is known to simultaneously project and backproject, for example, a film from a single source on a transparent screen. This source is a projector, for example a video projector.

Thus, there is already known in the state of the art a projection screen and rear projection type comprising first and second surfaces separated by a thickness of a transparent material.

Thus the screen has, for example, a general form of plate in which the first and second surfaces are substantially flat and parallel to each other. It can be made, for example, of polymethyl methacrylate or a copolymer of polymethylmethacrylate.

When a film is backprojected, by means of a video projector, on one of the first and second surfaces of the screen, a person looking at that surface sees the film in place. At the same time, as the screen is transparent, the film is projected onto the other of the first and second surfaces of the screen. A person looking at this other surface then sees the film upside down.

Similarly, the film can be projected to the spot by means of a projector on one of the first or second surfaces of the screen so that a person looking at that surface sees the film upside down. Simultaneously, the film is back-projected on the other of the first and second surfaces of the screen. A person looking at this other surface then sees the film in place.

In both cases, the projected or retro-projected film has different brightness and contrast on both surfaces. In particular, the surface on which the film is projected or retroprojected directly has a higher contrast and brightness than on the other surface.

The object of the invention is to provide a projection and back projection screen in which the film or a projected or retroprojected image has a similar luminosity and contrast on both surfaces.

The subject of the invention is a projection and retroprojection screen of the aforementioned type, characterized in that the first surface is coated with a first coating comprising an acrylic resin, a mica, titanium dioxide and a colloidal silica. Such a first coating on the first surface makes it possible to obtain substantially equal luminosities and contrasts on the first and second surfaces.

In addition, the acrylic resin is particularly suitable for optical use because of the excellent optical properties in the visible range of this type of resin. In addition, the impact resistance of the acrylic resin provides a durable coating.

Surprisingly, this first coating makes it possible to avoid a so-called "hot spot" phenomenon. A "hot spot" is a superlumeness that appears in the center of the screen or in front of a projector lens or video projector. Thus, the first coating according to the invention makes it possible to impart perfect homogeneity to the image.

It is also surprising to note that such a screen does not have a projection angle constraint. Indeed, to obtain a picture or a film projected or backprojected of good quality (absence of reflections, good color definition, etc.) with a screen of the state of the art, it is common to be forced to position precisely the objective of the projector or the video projector emitting the light radiation with respect to a central normal of the screen, this central normal being concurrent with a point located at the center of the screen. Thus, the light radiation and this normal must in particular form small angles, generally less than 30 °. With a screen according to the invention and a projector or a video projector equipped with the standard functions of angle corrections, it is possible to project or to project back, for example a film, regardless of the position of the projector or the video projector with respect to the normal of the screen.

Another advantage of such a screen is to allow to see the image or film without any degradation regardless of the position of an observer relative to the screen. Examples of such degradations are a moire of the image or reflections. Thus, the image or the film can be viewed correctly from a very large number of positions around the screen, ie a horizontal and vertical vision of 180 ° per face of the screen.

Finally, the simplicity of manufacture of the screen makes it possible to produce a screen having any size and format. Thus, it will be possible to achieve a very large screen, for example for advertising use. On the other hand, it will be possible to use the screen for private use.

According to the invention, the second surface is coated with a second coating comprising an encapsulated photochromic ink.

With known state-of-the-art screens, when the ambient brightness increases, contrast and brightness decrease sharply on both surfaces. This This decrease is especially amplified on the surface on which the film is not directly projected or retroprojected. The screen according to the invention makes it possible, thanks to the photochromic ink, to obtain an improved contrast and brightness compared to the screens of the state of the art. Indeed, when the brightness increases, the screen darkens so that the black rendering is improved compared to a screen of the state of the art. Conversely, when the brightness decreases, the screen regains its original clarity. The encapsulation of the photochromic ink allows the ink component pigments to exhibit increased reversibility of the ink over non-encapsulated pigments.

Advantageously, the second coating comprises an ultraviolet filter for filtering, preferably, a range of wavelengths between 390 and 420 nanometers.

Such an ultraviolet filter makes it possible to avoid the degradation of the encapsulated photochromic ink. Indeed, such an ink is sensitive to certain wavelengths, in particular those in the range 390 and 420 nanometers.

According to other optional features of the screen according to the invention:

The first and second surfaces are substantially planar and parallel to one another.

The screen is a showcase. It can be a shop window with many variations in brightness, for example because it is exposed in daylight. The invention is, in this case, particularly advantageous. According to other optional features of the screen according to the invention:

The mass fraction of acrylic resin of the first coating is between 25 and 95%, or between 45 and 95%, and preferably between 70 and 95%.

The mica mass fraction of the first coating is between 5 and 40%, even between 5 and 30%, and preferably between 5 and 20%. The mass fraction of titanium dioxide of the first coating is between 2 and 10%, even between 2 and 8%, and preferably between 2 and 6%.

The mass fraction of colloidal silica of the first coating is between 1 and 10%, even between 1 and 8%, and preferably between 2 and 6%. The invention also relates to a chemical composition, characterized in that it comprises an acrylic resin, a mica, titanium dioxide and a colloidal silica. -AT-

Such a composition has excellent optical properties and allows, when used on a transparent surface, to obtain perfectly equal luminosities and contrasts on the first and second surfaces of the screen.

The composition is therefore particularly suitable for use in the manufacture of a projection screen and a rear projection screen.

Resin plays the role of binder in the chemical composition. Colloidal silica acts as a tixotropic agent and allows to suspend the mica present in particulate form.

Mica is, for example, a muscovite mica. The particles have an average particle size generally between 2 micrometers and 50 micrometers.

Advantageously, the acrylic resin is a self-crosslinkable resin that does not require additives for polymerization, as certain additives can degrade the optical properties of the composition.

Such a resin makes it possible to obtain polymerization without additives.

According to other optional characteristics of the composition according to the invention:

The mass fraction of acrylic resin is between 25 and 95%, even between 45 and 95%, and preferably between 70 and 95%. The mass fraction of mica is between 5 and 40%, even between 5 and 30%, and preferably between 5 and 20%.

The mass fraction of titanium dioxide is between 2 and 10%, even between 2 and 8%, and preferably between 2 and 6%. The mass fraction of colloidal silica is between 1 and 10%, even between 1 and 8%, and preferably between 2 and 6%.

The invention furthermore relates to a method of manufacturing a projection and rear projection screen comprising first and second surfaces separated by a thickness of a transparent material, characterized in that the composition is deposited. defined above by spraying this composition on the first surface.

The nature of the composition makes it possible to deposit this composition on the first surface of the screen by spraying. Such a deposition process is very effective because it allows a homogeneous distribution of the composition, as well as a good control of the thickness of the coating of the screen. Indeed, a coating too thick decreases the brightness of the projected film or retroprojected.

In addition, such a manufacturing method makes it possible to deposit an isotropic coating on the first surface, which avoids, on both surfaces of the screen, any degradation in brightness and contrast of the film projected or backprojected, this degradation from anisotropy coating.

According to another optional feature of the method according to the invention, a layer of a photochromic ink is deposited on the second surface and optionally a layer of an ultraviolet filter making it possible to filter, preferably, a range of wavelengths. between 390 and 420 nanometers.

The ultraviolet filter and the photochromic ink can be mixed and deposited simultaneously on the second surface. Such a deposit is very easy to achieve. The deposition of the second coating is, for example, made by screen printing.

In a variant, it is possible to deposit either, firstly a first layer of the photochromic ink and then a second layer of the ultraviolet filter, firstly a first layer of the ultraviolet filter and then a second layer of the photochromic ink.

Finally, a subject of the invention is a method for projecting and retroprojecting a film or an image, characterized in that the film or image is projected onto the first or second surface of a film or film. screen as defined above.

Surprisingly, it is possible to indifferently project the film or image onto the surface comprising the first coating or onto the surface comprising the second coating. The contrast and brightness of the films or images projected or backprojected are then substantially similar on both surfaces of the screen. Such a method has the advantage of not requiring attention to the positioning of the projector or the projector on one side or the other of the screen.

According to an optional feature of the projection and rear projection method according to the invention, the screen is a showcase.

The invention will be better understood on reading the description which follows, given solely by way of nonlimiting example and with reference to the drawings in which: FIG. 1 is a sectional view of a screen according to a first Embodiment of the invention, FIGS. 2 and 3 are schematic perspective representations of a projection method according to the invention FIG. 4 is a sectional view of a screen according to a second embodiment of FIG. invention.

FIG. 1 shows a screen according to a first embodiment of the invention, designated by the general reference 10. The projection and rear projection screen 10 comprises first and second surfaces 12 and 14.

These two surfaces 12 and 14 are substantially flat and parallel to each other. The first and second surfaces 14 are separated by a thickness E of a transparent material 16. The thickness E generally varies from 0.5 mm to 20 mm.

The screen 10 is made of a plastic material, for example polymethyl methacrylate, or in glass. The screen can be isotropic, but also anisotropic.

In the example described in Figure 1, the screen may, for example, be a storefront. This window can be exposed in broad daylight, possibly outdoors.

The first surface is coated with a first coating comprising an acrylic resin, a mica, titanium dioxide and a colloidal silica.

The second surface 14 is coated with a second coating 20 comprising an encapsulated photochromic ink and an ultraviolet filter for filtering, preferably, a wavelength range of between 390 and 20 nanometers.

The first coating 18 comprises a mass fraction of acrylic resin of between 25 and 95%, even between 45 and 95%, and preferably between 70 and 95%. The first coating 18 also comprises a mass fraction of mica of between 5 and 40%, even between 5 and 30%, and preferably between 5 and 20%. In addition, the mass fraction of titanium dioxide of the first coating 18 is between 2 and 10%, even between 2 and 8%, and preferably between 2 and 6%. Finally, the mass fraction of colloidal silica of the first coating 18 is between 1 and 10%, even between 1 and 8%, and preferably between 2 and 6%.

The screen 10 is manufactured by a manufacturing method which will be specified below certain aspects.

In such a process, a chemical composition is sprayed onto the first surface 12, which is then dried.

The chemical composition comprises acrylic resin, mica, titanium dioxide and colloidal silica. In the example illustrated in Figure 1, the acrylic resin is a self-crosslinkable resin.

The chemical composition comprises a mass fraction of acrylic resin of between 25 and 95%, even between 45 and 95%, and preferably between 70 and 95%. The acrylic resin may in particular be non-styrenated.

The chemical composition also comprises a mass fraction of mica of between 5 and 40%, even between 5 and 30%, and preferably between 5 and 20%. The mica generally used is muscovite. In addition, the mass fraction of titanium dioxide of the chemical composition according to the invention is between 2 and 10%, even between 2 and 8%, and preferably between 2 and 6%. The titanium used in the example of Figure 1 is anatase titanium dioxide.

Finally, the mass fraction of colloidal silica is between 1 and 10%, even between 1 and 8%, and preferably between 2 and 6%.

The chemical composition is supplemented, in the example, by a complementary mass fraction of demineralized water.

An exemplary procedure for preparing the composition is given hereinafter by way of example.

Example of procedure for preparing the composition

30g of acrylic resin (NUPLEX, Setalux 6756) are introduced into a beaker. 5g of demineralized water are added. 1 g of titanium dioxide (Warwick, WX98P) and 6 g of mica (CMMP, Biomica 325) are introduced simultaneously to the mixture. Finally, 2 g of colloidal silica (DEGUSS, Aerosil 200) are added to the mixture to support the aqueous solution.

In the method of manufacturing the screen 10 shown in Fig. 1, a second coating comprising the encapsulated photochromic ink and the ultraviolet filter is also deposited on the second surface 14. The deposition of this second coating can be indifferently made before or after the deposition of the chemical composition.

The screen 10 makes it possible to implement a method of projecting and retroprojecting a film or an image, of which certain aspects will be specified below.

FIGS. 2 and 3 show a projection method according to the invention.

In Figure 2, a projector 22 projects an image composed by the numbers "123" on the screen 10. An observer is positioned on the other side of the screen. The observer 24 therefore sees the image at the location on the first face 12 covered by the coating 18. In FIG. 3, the observer 24 is this time positioned on the side of the projector and sees the image "123 Inverted on the second surface 14 covered by the coating 20.

FIG. 4 shows a screen according to a second embodiment of the invention. In this figure 4, elements similar to those shown in the previous figure are designated by identical references.

The screen 10 comprises, on the second surface 14, a layer 26 of an encapsulated photochromic ink and a layer 28 of an ultraviolet filter.

In this second embodiment, the screen 10 is manufactured by a manufacturing process, details of which will be specified below. After or before having deposited the first coating on the first surface 12, a layer 26 of a photochromic ink is deposited on the second surface 14, then the layer 28 is deposited with an ultraviolet filter making it possible to filter, preferably, a range wavelengths between 390 and 420 nanometers.

It should be noted that, alternatively, a layer 26 of ultraviolet filter may first be deposited and then a layer 28 of photochromic ink deposited.

Among the advantages of the invention, it will be noted that this makes it possible to simply and inexpensively produce a projection and rear projection screen.

The invention is not limited to the previously described embodiments.

Indeed, the screen may have a shape other than flat. Thus, the screen may be manufactured by thermoforming and have a concave or convex shape. The screen may also have a general shape of cylinder or sphere. The image or film projected or retroprojected is then previously processed by a correction program called "mapping program" to account for the non-flat surface of the screen.

Claims

1. Screen (10) projection and rear projection type comprising first (12) and second (14) surfaces separated by a thickness (E) of a transparent material (16), characterized in that the first surface (12) ) is coated with a first coating (18) comprising an acrylic resin, a mica, titanium dioxide and a colloidal silica.

The screen (10) of claim 1, wherein the second surface (14) is coated with a second coating (20) comprising an encapsulated photochromic ink.

The screen (10) of claim 2, wherein the second coating (20) comprises an ultraviolet filter for filtering, preferably, a range of wavelengths between 390 and 420 nm.

4. Screen (10) according to any one of the preceding claims, wherein the first (12) and second (14) surfaces are substantially flat and parallel to each other.

5. Screen (10) according to any one of the preceding claims, wherein the screen (10) is a showcase.

6. Screen (10) according to any one of the preceding claims, wherein the mass fraction of acrylic resin of the first coating is between 25 and 95%, or between 45 and 95%, and preferably between 70 and 95%.

7. Screen (10) according to any one of the preceding claims, wherein the mica mass fraction of the first coating is between 5 and 40%, or between 5 and 30%, and preferably between 5 and 20%.

8. Screen (10) according to any one of the preceding claims, wherein the mass fraction of titanium dioxide of the first coating is between 2 and 10%, or between 2 and 8%, and preferably between 2 and 6%.

9. Screen (10) according to any one of the preceding claims, wherein the mass fraction of colloidal silica of the first coating is between 1 and 10%, even between 1 and 8%, and preferably between 2 and 6%.

10. Use of a chemical composition comprising an acrylic resin, a mica, titanium dioxide and a colloidal silica for the manufacture of a projection screen and a rear projection screen.

The use of claim 10, wherein the acrylic resin is a self-crosslinkable resin.

12. Use according to claim 11, wherein the mass fraction of acrylic resin is between 25 and 95%, or between 45 and 95%, and preferably between 70 and 95%.

13. Use according to claim 1 1 or 12, wherein the mica mass fraction is between 5 and 40%, even between 5 and 30%, and preferably between 5 and 20%.

14. Use according to any one of claims 10 to 13, wherein the mass fraction of titanium dioxide is between 2 and 10%, or between 2 and 8%, and preferably between 2 and 6%.

15. Use according to any one of claims 10 to 14, wherein the mass fraction of colloidal silica is between 1 and 10%, even between 1 and 8%, and preferably between 2 and 6%.

A method of manufacturing a projection and back projection screen (10) comprising first (12) and second (14) surfaces separated by a thickness (E) of a transparent material (16), characterized in that a chemical composition comprising an acrylic resin, a mica, titanium dioxide and a colloidal silica is deposited on the first surface (12) by spraying.

The method of claim 16, wherein: a layer of an encapsulated photochromic ink is deposited on the second surface (14), and optionally a layer of an ultraviolet filter for filtering, preferably, a range of wavelengths between 390 and 420 nm.

18. A method of projecting and retroprojecting a film or an image, characterized in that the film or image is projected onto the first (12) or second (14) surface of a film or image. screen (10) according to any one of claims 1 to 9.

19. The method of claim 18, wherein the screen (10) is a showcase.