WO2008040857A1

WO2008040857A1 - Device for displaying renewable images

Info

Publication number: WO2008040857A1
Application number: PCT/FR2007/000945
Authority: WO
Inventors: Jean Pierre Lazzari; Jean Marc Lazzari
Original assignee: Jean Pierre Lazzari; Jean Marc Lazzari
Priority date: 2006-10-05
Filing date: 2007-06-08
Publication date: 2008-04-10
Also published as: FR2906923A1; FR2906923B1

Abstract

The invention relates to a device for displaying renewable images that comprises a transparent surface as well as painted sub-pixels of the three fundamental colours (401), (402), (403), said colours being transparent. Light generating means generate a light that passes through the sub-pixels and transparent surface assembly. A monochrome recoverable and recyclable opaque gel (404) applied on the surface of the sub-pixels blocks more or less the light passing through the sub-pixels and the transparent surface, thus forming the levels of grey of an image. Application in wide-surface public displays of fixed and electronically renewable images.

Description

DEVICE FOR DISPLAYING RENEWABLE IMAGES

DESCRIPTION OF THE FIELD OF THE INVENTION

The present invention aims at a device for displaying renewable images. It finds applications including advertising screens, preferably large, installed for example in public places. The invention more particularly relates to display devices for still images, which are electronically renewable.

State of the prior art: Some large screens use LEDs according to the Anglo-Saxon term which means "Light Emission Diode". These screens produce animated images. Their use is nevertheless restricted because of the low image quality, the high cost, and also the maintenance. Plasma or liquid crystal displays produce excellent image quality, but would be extremely expensive if they were to be manufactured in very large areas. In addition, it is difficult to implement outdoors. This is how other techniques have been developed. A first category uses mechanical devices, as described in patents WO0101378, WO03042966. A ramp that sweeps the screen, moves micro-shutters of different colors, constituting the pixels of the screen. Patent US4742632 proposes microvolts that obstruct more or less the passage of light that backlit the screen. These devices are extremely complex because to obtain a acceptable image resolution, it is necessary to mount on the screen, a very large number of these components which is very expensive, and difficult to achieve. In addition, for the renewal of the image is fast, it is necessary that the movement of the ramp that sweeps the screen is carried out in about ten seconds, involving a great complexity of moving the micro-shutters by the ramp. This problem greatly affects the reliability of the whole. A second category of devices uses magnetic recording, as described for example in JP 4199181 or JP 8016115. An endless magnetic tape is recorded by magnetic heads. The band passes near a magnetic powder which constitutes the toner. The latter is attracted by the points recorded on the tape, thus forming a latent image. To erase the image, the tape passes in front of a magnetic head that demagnetizes it, allowing a scraper or vacuum cleaner to recover the toner thus released. If this method is more reliable than the previous one, it nevertheless has the disadvantage of producing only two-color images, with low contrast compared to the magnetic tape, because there is only a very limited choice of color of the toners magnetic and recording layers. In addition, it is impossible to backlight the image, because there is no transparent magnetic tape having the properties required for this application. A third category, more recent, has been developed, as described in patents JP6046225, and JP2003337548 and JP2002251150 for example. This technique involves printing an image on an endless band, using jet printing techniques ink. These techniques have the advantage in comparison with the previous ones, the simplicity, the high quality of the image, in terms of color and resolution. Nevertheless, they have certain disadvantages. To renew the image, you must erase the previous image. As it is composed of inks of several colors, the inks mix with the erasing, which makes impossible their recycling. It is therefore necessary to store the inks after erasure, in a container called "trash". The storage of the rejected ink causes many problems. In addition to the toxic gases that emerge, the cleaning of the container is made difficult by the drying of the ink. Patent JP2002251150, moreover describes an ultraviolet process for decomposing the organic substances of these inks in the trash. In these devices, the ink consumption is a blocking factor, drastically limiting the size of the screen, and the number of images. The volume of ink used can reach several tens of liters of ink per day. Moreover, the use of an endless belt is poorly suited to large screens, guiding the band becoming very difficult, especially for horizontal movement.

The object of the present invention is to remedy these drawbacks by proposing an electronically renewable image display device of great size and of high quality in terms of resolution, gray levels and colors produced on a flat surface. preferably rigid. This surface is uniformly covered with small areas called subpixels, coated with the fundamental colors, these colors being transparent. The sub pixels are totally or partially covered with a gelatinous substance, pasty appearance, similar to grease, which will be called later "gel". This monochrome gel is opaque to light. The gel deposited on the sub-pixels is recyclable. The screen is backlit. The generation of the image is fast. The device according to the invention makes it possible to produce large screens. Finally the device by its simplicity can be manufactured at low cost.

This object is achieved by the invention, thanks to a preferably rigid and transparent plane constituting the plane of the screen. At the rear of this plane with respect to the observer, there are small colored areas with the three basic colors that form the sub-pixels of the screen, a pixel consisting of three of these sub-pixels. Each subpixel has a fundamental color that is transparent. The sub-pixels are uniformly distributed on the plane constituting the screen. The gray levels of the image are obtained by depositing a monochrome and opaque gel on the back of the surface of the sub-pixels. The opaque gel covers a larger or smaller surface of the sub-pixel, depending on the desired gray level. The viscosity and surface tension of the gel are such that the gel remains attached to the surface of the subpixels without flowing, drying or curing during the exposure time of the image. When it is appropriate to erase the image to expose another, the gel is recovered and recycled. According to one embodiment of the invention, the inkjet techniques known to those skilled in the art are proposed for depositing the gel at the rear of the surface of the sub-pixels. A ramp with a large number of nozzles of ejection of gel droplets, moves to the back of the screen, to cover its entire surface. As the gel after exposure of the image, is recovered, and recycled, there is no consumption of gel according to the invention.

More precisely, the subject of the invention is an electronically renewable image display device of large size that can reach several meters in length or height. The screen consists of a plane preferably rigid and transparent, preferably mounted in a vertical position, comprising sub-pixels in the fundamental colors (red, green and blue), these colors being transparent so that the screen can be backlit. Subpixels are simply small, colored and transparent areas. The sub-pixels receive opaque gel droplets, produced by gel ejection nozzles, according to known inkjet techniques. A large number of nozzles are aligned under a ramp which sweeps at the rear of the screen its surface preferably in the direction of its largest dimension. The number of opaque gel droplets more or less obstructs the passage of light passing through the sub-pixels, thus making it possible to achieve the gray levels of the image. The sub-pixels of square or rectangular shape, are uniformly distributed on the plane. In another mode, the sub-pixels are in the form of narrow bands, each having a fundamental color. These strips are parallel to the movement of the ramp comprising the nozzles for ejecting the gel droplets. In this second mode, the length of the sub-pixel is only fixed by the deposition of the gel droplets, and its width by the width of the narrow band. The size of the sub-pixels is between a few tenths of a square millimeter to a few tens of square millimeters depending on the size of the screen and its resolution. The sub-pixels are totally or partially covered with an opaque and monochrome gel. Once deposited on the surface of the sub-pixels, the gel remains in the latent state, without flowing or drying or hardening during the exposure of the image, which is between a few seconds, and a few hours. In the case where the same image must remain exposed for a longer period, the invention provides that the same image is nevertheless erased and periodically renewed. Various gel deposition techniques may be used, including inkjet techniques known to those skilled in the art. In this case, the viscosity of the gel at the passage of the ejection nozzles, is close to that of standard inks, ie of the order of 15 mPa.S. When a higher viscosity is required, which would prohibit the use of the ink jet nozzles, then the gel is heated in the reservoir feeding the ejection nozzles, to achieve the viscosity adequate for the proper ejection of the droplets. In contact with the rear surface of the sub-pixels, the gel regains its original viscosity. These heating techniques are known to those skilled in the art under the name Anglo-Saxon "hot melt ink jet printing", ie printing ink jet liquefied by heating. Indeed, according to the applications, these techniques use a solid ink, which is melted by heating, so that it can be ejected through the ink jet nozzles. According to the invention, these techniques allow simply to make the gel more fluid if necessary to be ejected by conventional inkjet nozzles. Once the exposure of the image is complete, the gel is recovered, which has the effect of erasing the existing image, so that a new image is formed. The recovered gel is filtered and reused for subsequent images. According to one embodiment of the invention, the diameter of the deposited gel drops is adjusted so that the sub-pixel can be completely covered with gel by a projection of up to 256 gel droplets, which allows, according to this mode, to achieve, depending on the number of droplets deposited, up to 256 gray levels per sub-pixel. According to another embodiment of the invention, nozzles called "greyscale ink jet" according to the Anglo-Saxon term are proposed. These nozzles make it possible to eject droplets of variable volume. For example, to reach the 256 levels of gray, only 16 droplets of 16 variable volumes are enough. The ramp that sweeps the screen at the back of it, preferably moves along its long length, to minimize the number of nozzles that are aligned according to the width of the screen. On either side of the line of the ejection nozzles are installed on the same ramp means for removing the gel. During the movement of the ramp, the removal of the gel, ie the erasure of the existing image, is done just before production by the ejection nozzles of the next image. Thus, the observer, during the duration of erasure of the existing image, and the generation of the next image, sees only a dark line, of width equal to that of the ramp, which sweeps the screen. According to the direction of movement of the ramp, at the front of this line, the existing image disappears, and at the back of this line, the new image appears. In order not to erase the new image that is being deposited, the gel removal means located after the ink jet nozzles, depending on the direction of movement of the ramp, are inactive. Various means for recovering the gel are provided, such as mechanical means, which use brushes or flexible rubber blades, means by suction, by blowing, by magnetic or electrostatic attraction, or a combination of these means. According to one embodiment of the invention, the ramp supports the electronic and computer means for controlling the ejection nozzles, in particular the multiplexing of the nozzles, the heating of the gel if necessary, the means for removing the gel, the means for controlling the quality of the removal, as well as the means of filtration. The ramp is guided by two rails located on either side of the rigid plane constituting the screen, preferably along the long sides of the screen. The rails have means for moving the ramp, as well as means for locating the ramp at any time, with respect to the screen, and for controlling its speed of movement. The screen has a back light, the light passes through the sub-pixels, and the main plane transparent, between the drops of gel, which obstruct more or less the passage of light to achieve the gray levels. Radio or wired reception means coded graphic information, are installed at the back of the screen, and after processing, transmitted to the means electronic control of nozzles installed on the mobile ramp.

In any case, the features and advantages of the invention will appear better after the description which follows, given for explanatory purposes and in no way limiting. This description refers to the accompanying drawings, in which:

- Figure 1 shows the general plan, seen from the rear, of the device according to the invention. FIG. 2 shows the section according to A of the device

FIGS. 3A and 3B show two subpixel geometry modes

FIGS. 4A and 4B show examples of gray levels according to the two modes of geometry of the sub-pixels of FIGS. 3A and 3B

FIG. 5 shows in section the implantation of the various means of the ramp, in particular the ejection nozzles, and the gel recovery elements. FIG. 6 shows in section an example of a device for removing the deposited gel.

- Figure 7 shows a section of the gel recovery means.

Figure 1 shows a general view of the device according to the invention, seen from the rear relative to the observer. The plane (100) generally in a vertical position constitutes the surface of the screen. It consists of a rigid preference plan. This plane is transparent, like a plane of glass for example. At the rear of this plane, the sub-pixels are represented by small areas uniformly distributed over the plan (100) coated with a transparent color, among the fundamental colors like red, green and blue. Figure 1 shows a portion of these sub-pixels represented by small squares (101). Near the plane (100), and parallel to its surface, a ramp (102), guided by the rails (103) and (104) moves from left to right, and vice versa, generating each time a new image while erasing the previous one. The movement means of the ramp (102) not shown here, and known to those skilled in the art, are mounted in the rails (103) and (104). Means for controlling the position of the ramp at all times, also known to those skilled in the art, are included in the movement means of the ramp (102). Figure 2 shows a section along the axis (A) of Figure 1. At the rear of the transparent plane (100) is the sub-pixels (101). These sub-pixels, which are simply transparent colored surfaces, are printed on the plane (100), or on a transparent flexible sheet attached to the rear of the plane (100). The ramp (102) supports the erasing means and of generating the image. It moves parallel to the plane (100) at a fixed distance from the plane. At the back of the screen is the lighting means (201) which produces light rays that pass through the sub-pixels and appear to the observer (202) colored according to the fundamental color of each pixel. The light passing through each sub-pixel is partially or completely stopped by the opaque gel deposited by the ejection nozzles at the rear of the surface of each sub-pixel.

FIG. 3A represents a form of the invention, in which the sub-pixels have the shape of rectangles or squares, each having a color fundamental. The sub-pixels in this first mode, are therefore physically determined by their geometry, in both directions (x) and (y) of the plane (100).

FIG. 3B represents, according to another form of the invention, the sub-pixels which have the shape of narrow strips (300) covering all or part of the length of the plane (100), along the direction (x) of this plane. According to this mode, the sub-pixels are geometrically defined only in the direction (y) of the plane (100). In the direction (x), the sub-pixels may have a variable length, depending on the needs of the image, their length being determined by the distribution of the gel drops in the direction (x).

FIG. 4A shows sub-pixels (401) (402) and (403) according to the form of the invention, of FIG. 3A. As an illustration, we will determine, according to the invention, the size of these sub-pixels for a high quality image. The drops of gel are represented by the points (404). According to the state of the art of inkjet techniques, the density of the deposited dots measured in dot per inch (dpi) or dot per inch, is between 100 dpi and more than 1000 dpi .A 360 dpi by for example, the average diameter of the drops deposited is 70.5 microns. It is necessary that the points are secant and not tangent with each other, in order to obstruct the passage of light. A superimposition coefficient of 70% is necessary, which gives a distance between the axes of the points of 70.5 μm x 0.7 = 49.35 μm. For a high-quality image, with 15.7 million colors, or 256 greyscales per fundamental color, each of these gray levels being represented by a drop of gel, each sub-pixel could be covered at most by 16 x 16 = 256 drops of gel. The sub-pixel would then have the shape of a square of 49.35 μm x 16 = 789.6 μm on the side. Suppose a screen of 3000 x 8000 sub-pixels is 3000 by 2660 pixels, a resolution of 8 million pixels would be obtained. The size of this screen would then be 2.37 meters x 6.32 meters.

Figure 4B shows the pixels according to the other embodiment of the invention of Figure 3B. Like the ramp

(102) moves horizontally, it may be advantageous not to fix the length of the pixels in the direction of movement of the ramp, but to use the projection of the drops of gel to define the gray levels in the same fundamental color, along the movement of the ramp. Thus, the images produced could have a very high horizontal resolution. The pixels, according to this mode of the invention, would be narrow bands, monochrome, of length equal to that of the screen in the direction of movement of the ramp (102)

Figure 5 shows a section of the ramp (102). Opposite the plane (100) behind which the sub-pixels (101) are located, the nozzles for ejecting the drops of gel (500) are maintained at a suitable distance from the plane (100) by the ramp (102). The gel drops (404) are projected onto the surface of the sub-pixels (101), and form small opaque surfaces (506). According to the example of FIG. 5, the ramp (102) moves from right to left according to the arrow (507), erasing the previous image which is in front of the movement of the ramp (102) and generating a new image that appears after the passage of the ramp (102). The means for recovering the gel are represented by a flexible blade (501) described below. A second means (502) for recovering the gel located on the other side of the nozzle line (500) is not activated, as shown in FIG. 5, since it is located at the rear of the nozzles ejection, relative to the movement of the ramp (102), so as not to erase the new image that the ejection nozzles are producing. The gel removed by the means (501) is filtered in order to eliminate any dust or dirt that could stick to the gel during exposure of the image. These filtering operations are known to those skilled in the art. The gel is then stored in the reservoir (503) located just behind the ejection nozzles, ready to be reused. In the case where the chosen gel has a viscosity greater than that for which the ejection nozzles have been optimized, then the gel must be heated to reduce its viscosity. To do this, the tank (503) is heated to the necessary temperature, which is around 150 ⁰ C depending on the type of gel. These heating means are known to those skilled in the art. In order to verify the quality of the erasing of the existing image, means (505) are installed on either side of the ejection nozzles (500) between the means (501) and (502) for recovering the gel. . These means of control

(505) are activated together with the gel recovery means associated therewith. These means using optical techniques are known to those skilled in the art. All of the means described in FIG. 5 are controlled by electronics (504) on the ramp (102). This set includes in particular the management and the multiplexing of the ejection nozzles (500), the recovery means (501) and (502), the control means (505) of the erasing of the existing image, the chain of recovery of the gel, its filtration, levels and temperature of the gel contained in the reservoir (503).

FIG. 6 shows the view from above of a gel removal means (506) constituting the image at wipe off. On the plane (100) coated behind the sub-pixels (101), a brush (601) in the form of a moving belt sweeps the plane (101) of the sub-pixels, moving the gel towards the bottom of the screen. A flexible blade (600) preferably of rubber finishes recovering the gel which would not have been swept by the brush (601). The latter also sweeps the tip of the flexible blade (600) to remove the gel that would have accumulated on this blade. The brush (601) is guided by a groove (602) dug in a guide attached to the ramp (102).

Figure 7 shows the section along B of Figure 6 of the gel recovery means. The bottom of the plane (100) coated with the sub-pixels (101) is indicated by the index (700) in FIG. 7. The brush (601) wraps around the wheel (701) at the bottom of the screen, the wheel (701) being driving. The belt (601) circulates in the direction of the arrows (704), returning the gel to the bottom of the screen (700). The bristles of the brush (601) are rotated on the grid (702). The gel is deposited on this grid and is sucked through this grid into the container (703) connected to the filter station not shown here, which feeds the storage tank (503) above the line of nozzles (500 ) of Figure 5.

Claims

1. Renewable image display device comprising a transparent surface, sub-pixels painted in the three basic colors, these colors being transparent, light generating means, the light passing through all the sub-pixels and the surface transparent, characterized in that a gel, opaque, monochrome, recoverable and recyclable deposited on the surface of the sub-pixels more or less obstructs the passage of light through the sub-pixels and the transparent surface, thus forming the levels of gray of an image.

Renewable image display device according to claim 1, characterized in that the recoverable and recyclable monochrome opaque gel is deposited on the surface of the sub-pixels in the form of droplets projected by ejection nozzles, according to inkjet techniques.

Renewable image display device according to claim 1, characterized in that the opaque, monochrome, recoverable and recyclable gel adheres to the surface of the sub-pixels without flowing, drying or hardening during the period of time. exposure of the image.

4. Device for displaying renewable images, according to claim 2, characterized in that the opaque gel, monochrome, recoverable and recyclable, passing through the ejection nozzle has a viscosity of the order of 15 mPa. s.

5. Renewable image display device according to claims 1 and 2, characterized in that the ejection nozzles are mounted on a ramp (102) which sweeps the surface of the screen.

6. Device for displaying renewable images, according to one of the claims 1 to 5, characterized in that the ramp (102) comprises means for recovering the gel (505) and (502) located on both sides. other ejection nozzles only the means located upstream of the nozzles relative to the movement of the ramp being activated.

7. Device for displaying renewable images, according to any one of claims 1 to 6, characterized in that the ramp (102) supporting the ejection nozzles and the recovery means, during its displacement, erases the image upstream of its displacement, and generates a new image downstream of its displacement, the transition between the two images appearing to the observer as a dark line.

8. Image produced according to the device of claim 7 characterized in that it consists of sub-pixels painted on the surface (100), or on a flexible sheet attached to the surface (100), these sub-pixels may consist of narrow monochrome strips (300) according to the direction of movement of the ramp (102).