WO2004023438A1

WO2004023438A1 - Information panel with changing contents

Info

Publication number: WO2004023438A1
Application number: PCT/FI2003/000640
Authority: WO
Inventors: Miikka Ahola; Pekka Orava
Original assignee: Techsign Oy
Priority date: 2002-09-03
Filing date: 2003-09-02
Publication date: 2004-03-18
Also published as: AU2003258746A1; FI20021572A0; FI113501B

Abstract

The invention relates to a traffic sign provided with a variable display. The invention is implemented in such a way that the variable display (2-2) is of electric paper comprising capsules that contain pigment particles. The pigment particles are electrically charged in such a way that for instance dark pigment particles have a positive charge and light pigment particles have a negative charge, or vice versa. Thus, a figure (2-3) in the traffic sign can be modified by exposing the capsules to an electric field of an appropriate shape, whereby the pigment particles are positioned either at the bottom or on the surface of the display, forming a desired figure.

Description

INFORMATION PANEL WITH CHANGING CONTENTS

BACKGROUND OF THE INVENTION

[0001] The invention relates to applying digital display techniques to information panels, such as traffic signs. [0002] Digital displays have been applied to traffic signs when the aim has been to create a sign that can be modified according to seasons or times of day, for example. A typical example of a traffic sign provided with a digital display is a variable speed-limit sign. Presently, variable traffic signs apply LED (Light Emitting Diode) technology or displays based on turnable lamellas. A LED, i.e. a light emitting diode, is a semiconductive component emitting visible light when an electric current is conducted through it. The light emitting diodes can radiate infrared, red, yellow, green and blue colours, but the light emitted by them is not particularly bright. Light emitting diodes can form a dot matrix display or, stretched into a bar-like shape, a segment display. In the case of turnable lamellas, a segment display is formed.

[0003] US 6,317,108 B1 discloses an updatable traffic sign display based on electrostatically actuated electrode shutters, the position of which can be moved from a light-transmitting position into a light-blocking position. According to the publication, high resolution can be achieved with such a display both during the day and at night, while the costs remain low.

[0004] However, a problem with the above arrangements is that the installation and running costs of a traffic sign based on the LED technology are significantly high. Such a traffic sign is relatively cumbersome and the technology requires a lot of maintenance, because it is sensitive to faults. Furthermore, the contrast of a LED display is poor in bright weather. The selection of signs on a segment display is restricted. For instance, a 7-segment display allows implementation of all numbers, but does not allow implementation of all letters. A problem with the arrangement described in US 6,317,108 B1 is that the display based on static electricity is sensitive to faults and updating the large display takes a long time.

BRIEF DESCRIPTION OF THE INVENTION

[0005] An object of the invention is to provide a variable traffic sign and electric paper in such a way that the above problems can be solved. This is achieved with a traffic sign and electric paper that are characterized in what is stated in the independent claims. Preferred embodiments of the invention are described in the dependent claims.

[0006] The invention is based on the display of the variable traffic sign being implemented with what is called electric paper. Electric paper comprises encapsulated pigment particles that have, depending on the colour, a positive or negative electric charge. When the electric paper is exposed to an electric field, the charged particles are positioned according to the electric field in the capsules. A desired figure can be formed on the display with an electric field of a suitable shape. The figure can be modified by changing the electric field, in which case the charged particles in the capsules are repositioned. Thus, the figure or text in the traffic sign can be modified when required. The cold resistance of the electric paper used according to the invention can be improved with an anti-freeze agent added to the capsules.

[0007] An advantage of the traffic sign according to the invention is that when the traffic sign is implemented with an electric paper display, its installation and running costs are low. The display can be attached to existing traffic signs like a sticker. The text on the display can be seen clearly also in bright sunlight. The current consumption of the electric paper display is low, because it requires current only when the display is updated, and updating does not take a long time. Existing telecommunication links can be utilized in the implementation of the invention.

BRIEF DESCRIPTION OF THE FIGURES

[0008] The invention will now be described in greater detail in connection with preferred embodiments, referring to the attached drawings, of which

Figure 1 shows a simplified structure of electric paper;

Figure 2 shows a simplified traffic sign according to the invention.

DETAILED DESCRPTION OF THE INVENTION

[0009] Electric paper is a display technique based on electrically charged pigment particles and arranging them according to the electric field.

The applications of electric paper include advertising signs, for example.

Modifiable information can be changed for signs from the mainframe computer.

Colour contrasts in the electric paper are achieved with "electric ink", which comprises transparent capsules having a diameter of a few micrometers and containing polymer solution. The solution contains, for example, black and white pigment particles having different electric charges. The pigment particles appropriately exposed to an electric field can be caused to swim either to the surface or the bottom of the capsule, whereby the surface colour of the capsule can be modified for instance from dark to light, and vice versa. The text or figure on the electric paper is visible without separate background illumination, and maintenance of the image does not require continuous electric current.

[0010] The operating temperature of electric paper is +5°C at the lowest. At temperatures lower than this the electric paper may be destroyed so that it cannot be used any longer, and therefore it is not suitable for use in a cold climate.

[0011] Figure 1 illustrates the operating principle of electric paper. Electric paper is manufactured of a plastic film 1-2, inside which there are capsules 1-1 containing pigment particles 1-3, 1-4. The pigment particles of the electric paper are positively or negatively charged, for instance in such a way that the light particles 1-3 have a positive electric charge, whereas the dark particles 1-4 have a negative electric charge, or vice versa. When the electric paper is exposed to an electric field by means of bottom electrodes 1-5 and a transparent surface electrode 1-6, the charged particles 1-3, 1-4 are positioned, according to the electric field, either on the surface or at the bottom of the capsule 1-1. The colour visible to the outside depends on which pigment matter is positioned on the surface of the capsule 1-1 and which at the bottom of the capsule 1-1. A desired figure is formed on the display with a suitably shaped electric field. The operating principle of electric paper is described in more detail in US 6,422,687 B1 , for example.

[0012] Figure 2 shows a simplified variable traffic sign according to a first preferred embodiment of the invention, provided with an electric paper display 2-2. The display 2-2 is mounted in the background part 2-1 of the traffic sign, for instance like a sticker. The electric field directed at the display capsules containing pigment is preferably implemented with a voltage of 5 V, obtained from a current supply. The figure 2-3 formed of the capsules can be modified by changing the electric field of the electric paper, in which case the charged pigment particles in the capsules are repositioned according to the new electric field. In this way, the figure or text of the traffic sign can be changed when required. The sign is controlled from a signal obtained from a monitoring unit, which signal controls the electric field to be directed at the display. The sign may also operate independently, in which case it is preferably pre-programmed to modify the figure on the display on the basis of the date, for instance.

[0013] According to a preferred embodiment of the invention, a heating element is connected to the electric paper used in a traffic sign, which element comprises a temperature-measuring sensor and a heater with which the display temperature can be kept within an appropriate temperature range, which depends on the properties of the electric paper used. This means typically a temperature of at least 10°C to keep the electric paper operational. The heater is a heating film of a type of a defroster, the operation of which is based on the heating of a thin resistance wire net. To prevent the magnetic field generated by the operation of the heating element from disturbing the operation of the electric paper of the display, a transparent insulating plate or the like having low electric conductivity is preferably mounted between the display and the heating element.

[0014] According to yet another preferred embodiment of the invention, the cold resistance of the electric paper used is improved by adding anti-freeze agent, such as an alcohol, to the pigment capsules of the display. Examples of typical anti-freeze agents are ethylene glycol and propene glycol. [0015] According to yet another preferred embodiment of the invention, the electric paper display is protected against the effects of the weather and against vandalism or other wearing. This is done by placing over the display a transparent plexiglass or the like, which is preferably manufactured of a material having high impact resistance and/or low reflectivity. For protection against the detrimental effect of the ultraviolet radiation of the sun the plexiglass used has preferably an ultraviolet-ray filtering property. To prevent the plexiglass from increasing the heating effect of the sun, directed at the display, in warm weather and, on the other hand, the cooling effect of the cold weather, the plexiglass used is preferably made of a material having low thermal conductivity.

[0016] According to still another preferred embodiment of the invention, the electric paper used contains some light-reflecting matter in order to improve the visibility of the electric paper display in the dark. The reflectivity may be based on phosphorescence, for instance, in such a way that a phosphorescent pigment, such as alkali earth sulphide or zinc sulphide, is used in the electric paper. [0017] Although the invention has been described above with reference to an exemplary implementation utilizing electric paper that comprises two pigments of different colours, the intention is not to restrict the invention to this embodiment, but the traffic sign according to the invention can be implemented with electric paper comprising one pigment or three or more pigments of different colours. Further, the intention is not to restrict the embodiments of the invention to be used only in traffic signs, but they can be applied to any object where better cold resistance and/or, when there is little light, better visibility is/are required of electric paper. Outdoor advertisements are an example of such an object of application for electric paper.

[0018] It will be obvious to a person skilled in the art that as the technology advances, the basic idea of the invention can be implemented in a plurality of ways. The invention and its embodiments are thus not confined to the above examples but can vary within the scope of the claims.

Claims

1. A traffic sign provided with a variable display, comprising a background part (2-1) on which a variable display (2-2) is mounted, characterized in that the variable display (2-2) is of electric paper comprising pigment capsules (1-1) containing at least one pigment (1-3, 1-4), whereby a figure (2-3) seen on the variable display (2-2) can be modified by changing the position of the pigment (1-3, 1-4) in the capsule (1-1) by means of an electric field.

2. A traffic sign according to claim 1, characterized in that it comprises a heating element for controlling the temperature of the variable display (2-2).

3. A traffic sign according to claim 1 or 2, characterized in that said pigment capsules (1-1) contain anti-freeze agent for improving the cold resistance of the variable display (2-2).

4. A traffic sign according to claim 1,2 or 3, characterized in that the variable display (2-2) is coated with a protective plate.

5. A traffic sign according to any one of preceding claims 1 to 4, characterized in that said pigment capsules (1 -1 ) contain at least one phosphorescent and/or reflecting agent for improving the visibility of the traffic light when there is little light.

6. Electric paper comprising pigment capsules (1-1) containing at least one pigment (1-3, 1-4), whereby the figure seen on the electric paper can be modified by changing the position of the pigment (1-3, 1-4) in the capsules (1-1) by means of an electric field, characterized in that the pigment capsules (1 -1 ) contain anti-freeze agent for improving cold resistance.

7. Electric paper according to claim 6, characterized in that the pigment capsules (1-1) contain at least one phosphorescent and/or reflecting agent for improving the visibility of the figure seen on the electric paper when there is little light.

8. Use of the electric paper according to claim 6 or 7 in an information panel.