WO2001079031A1

WO2001079031A1 - Rearview display mirror

Info

Publication number: WO2001079031A1
Application number: PCT/SE2001/000829
Authority: WO
Inventors: Bo Norell
Original assignee: Norells Sweden Ab
Priority date: 2000-04-14
Filing date: 2001-04-12
Publication date: 2001-10-25
Also published as: AU2001248973A1; SE0001437D0

Abstract

A rearview display mirror comprises a pattern of transparent windows (7) that are formed in a light reflective coating (6) of the mirror. The pattern of windows defines symbols of information addressed to the driver of a vehicle. An additional material layer (8) of high reflectivity is arranged behind the mirror coating to be exposed by incident light (L) through the windows, and being operative for illuminating the pattern by passively returning the incident light (L) through the windows at a reflex angle not less than 20° relative to the incident light.

Description

TITLE

Rearview display mirror

TECHNICAL FIELD OF INVENTION

The present invention relates to a rearview display mirror for a vehicle, wherein patterns conveying information such as text, markings or symbols on the mirror, are made visible to the driver during driving in darkness by incident light emitted from external light sources, notably following vehicles, without the need for energy supply from the own vehicle.

PRIOR ART

It is known in the art to include patterns conveying information such as texts, markings or symbols, in a rearview mirror of a vehicle. Such patterns may permanently or dynamically provide status information on the vehicle's operational conditions, or they may be designed to provide warning and alert symbols that are addressed to the driver of the vehicle, or a driver of a following vehicle. Electric power supplied from a battery or a generator is conventionally required to activate such patterns in darkness.

In addition to the obvious primary function of external vehicle rearview mirrors to supply the driver with an image of the traffic situation behind the own vehicle, several supplementary uses of the mirror as a message conveying medium are known. For such purposes, the mirror's overall specular reflector coating is locally reduced or removed in patterns representing text or symbols, or minor openings that are void, or backed by, LCD patterns (all of these features are here called "windows"). Means to improve the visibility of such windows have been published, as have contrary means to hide windows when to be ignored. Such measures are sometimes combined with means to electrochromically control the reflectance of the entire mirror surface and with means of clearing the mirror surface from frost or mist by heating. The following categorization is intended to facilitate an overview: A. Target of information

Aa) The own vehicle's driver. (Examples: Warning texts, demarcation lines, symbols signaling the function of various operational units) Ab) Persons outside the own vehicle, notably the driver of a following ve- hide. (Example: Turn signals in the mirror)

B. Means of increasing or reducing visibility of mirror portions

Ba) Light sources inside the mirror housing. (Examples: Incandescent lamps, LEDs, electroluminescent (EL) foils) Bb) Means enhancing visibility, generally or in certain directions. (Examples: Louvres, interference devices, etc.)

Be) Means reducing visibility, generally or in selected locations and directions. (Examples: Louvres, electro-optical filters)

Specific combinations in the patent literature are embodied as follows:

WO 96/ 14222: Both Ab+Ba+Bb - an internally illuminated turn sign visible outside the vehicle but not for the driver, and Aa+Ba+Bb - internally illuminated symbols in the mirror visible to the driver but not outside the vehicle:

US 6,005,724: Ab+Ba+Bb - a mirror with a turn sign internally illuminated by LEDs, and means ensuring satisfactory mirror reflectance;

DE-A 1-37 20 848: Aa+Ba+Bb - a mirror with a display area for the driver illuminated by an incandescent lamp or LED with a light diffusor;

DE-A 1- 198 43 189: Aa+Ba - a mirror with windows backed by EL foils for illumination;

DE-A 1- 196 31 409: Aa+Ab+Bb+Bc - passive or electro-optical light-filters to improve or to hide internally, in the driver's or the passenger's direction, illuminated message windows in the mirror; US 5,689,370: Aa+Bb - an electrochromically dimmed mirror with display windows that are arranged not to dim when the mirror dims;

US 4,906,085: Ab+Ba+Bc - a mirror with a semi-reflecting layer illuminated from the rear by a light source, or solar radiation through openings in the mirror housing, with light deflecting or attenuating means such that the mirror image of the interior of the own car, especially its driver, cannot be discerned by the driver of a following car, whereas the mirror supplies the own car's driver with a clear image of outside objects.

Of these publications, a part only deals with the object of the present invention to make messages in the mirror's windows visible to the driver when driving in darkness. Those that do accomplish this task by means of internal light sources in the mirror housing. Such means add considerably to the mirror assembly's cost, notably in the case of EL foils that need a special voltage supply (e.g. 120 N, 1000 Hz). In heated mirrors such devices (EL foils, light diffusors with LED or incandescent lamps), when located in the path of the heat flow, impair the defrosting or de-misting function of the mirror.

OBJECT OF THE INVENTION

The present invention aims to provide a low cost solution for a passive signal mirror that is able to display information, addressed to the driver, on a rearview mirror of a vehicle during the most critical conditions of night driving.

This object is met in a rearview display mirror according to the appended claims.

SUMMARY OF THE INVENTION Briefly, the invention suggests a rearview mirror provided with patterns conveying information that by suitable means are made visible during night driving by incident light from following vehicles. The patterns in question may include permanent warning texts, markings and alert signals addressed to the operator or driver of the vehicle, and may also include static status information.

According to the invention, a rearview display mirror comprises transparent windows by locally removing metal in a light reflective coating of the mirror and so creating a transparent pattern. Said windows define patterns addressed to the driver of a vehicle. Further, an additional material layer of high reflectivity is disposed adjacent to and behind said reflective coating, and formed at least to cover the windows, said additional layer being ar- ranged to be exposed by incident light and operative for illumination of the symbols by reflecting the incident light from a following vehicle through the windows and directing the reflected light towards the driver.

In a modified embodiment, the additional reflective layer is carried on a heater foil that is attached to a backside of the mirror.

The invention is preferably applied in an external rearview mirror of a vehicle, but may also be applied in an internal rearview mirror or in any other application where incident light may be utilized to render a pattern of messages, markings and symbols clearly visible in darkness when activated by incident light.

In yet a modified embodiment, the patterns may also include dynamic or condition triggered status information in association with a liquid-crystal layer that is operative as a controllable screen for incident light. In this em- bodiment, a liquid crystal layer is introduced in front of the transparent windows, or in front of the additional reflective layer, in order to control the intensity of the reflected light, generally or in a programmed pattern.

DRAWINGS The invention is more closely described below, reference being made to the attached drawings. In the schematic drawings, showing an embodiment of the invention, Fig. 1 is a front elevation view of a rearview display mirror on a motor vehicle, illustrating symbols for warning or alerting of the driver;

Fig. 2 is a sectional view of a rearview mirror according to the invention;

Fig. 3 is a corresponding view of a second embodiment of the mirror, and

Fig. 4 is another front elevation view, showing schematically a modified em- bodiment of the mirror.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows schematically a rearview mirror 1 for a motor vehicle. In the mirror 1 , the patterns 2, 3 and 4 are introduced for alerting the driver or operator of the vehicle. Required by law in certain countries, the text 2 is intended to make the driver aware of the distance distortion that is inherent in the mirror image. The line 3 separates the wide-angle field of the mirror from the planar or substantially planar field. The borderline 4 is introduced in order to define the outline of the mirror image when driving in darkness. Naturally, the shown and mentioned patterns are only exemplifying.

In daylight driving, these and other patterns on the mirror 1 are visible due to their contrast to adjacent areas. In darkness driving, these patterns be- come clearly visible when illuminated through incident light, emitted from an external light source as is further explained below. Thus it is believed, in darkness driving, that the warning or alerting symbols are most important only when another vehicle is closing up from behind.

Fig. 2 shows a section of an embodiment of the inventive mirror. A glass plate 5 carries, on one side thereof, a first reflective coating 6 arranged as a light reflective coating or mirror coating 6. Said mirror coating 6 may be applied to either side of the glass plate, i.e. to the exposed front side or first side, or the opposite second side or back side of the mirror glass. Transparent windows 7 in the mirror coating 6 define patterns as desired, e.g. the above mentioned symbols or other patterns. Said windows 7 are conveniently formed by subjecting the coating 6 to an etching or laser abrasion op- eration. The coating 6 may be a metal coating as conventional.

Adjacent to and behind the glass plate 5 and mirror coating 6, as seen in the direction of the incident light L, is arranged a layer 8 of highly reflective material. The reflective material 8 is arranged to be exposed by the incident light L through the windows 7 and is able to efficiently reflect the incident light towards the driver by returning and directing the incident light through the windows. Thus, the incident light is passively directed through the windows for alerting the driver, and informing him about a vehicle that is closing up from behind.

The reflective material 8 is preferably a material having directive light reflection properties. In this context, this should be interpreted as a material from which incident light is directed towards the driver. The reflective material 8 may advantageously be a reflex material incorporating a plurality of light reflecting surfaces, that are obliquely oriented relative to the orientation of the mirror in a saw-tooth formation. The incident light, reaching the mirror from a vehicle that is closing up from behind, is thus reflected by the reflective material 8 and directed towards the driver through the windows 7. The reflective material 8 is chosen to direct the reflected light at a reflex angle α relative to the incident light, as seen in a horizontal plane. For optimal visibility, said reflex angle may preferably be in the range of α=20° - α=75°.

As used herein, the expression "reflectivity" is considered to be the ratio of energy of the reflected light beam to that of the incident beam. The expres- sion "transparent window" should be understood to include also a window that is translucent, i.e. substantially transparent or semi-transparent. The highly reflective material 8 is arranged at least to cover the windows 7, and may be carried by an adhesive-coated foil or carrier member 9 that is arranged to adhere to the backside of the metalized glass 5,6, at least outside the periphery of the opening 7. The reflective material 8 may be realized as particles or pigments mixed with a binding medium to be printed on the carrier 9.

In an alternative embodiment of the mirror, illustrated in fig. 3, the reflective material 8 is carried by a heater foil 10, arranged to adhere to the backside of the metalized glass 5,6. Also in the embodiment of fig. 3, the reflective material 8 may be realized as printed areas on the heater foil 10.

In yet another embodiment, not shown in the drawings, the reflective material 8 may be integrated as particles or pigments in the adhesive, applied for attaching the carrier member 9 or the heater foil 10 to the backside of the metalized glass.

In still another embodiment, also not shown in the drawings, the reflective material 8 may carry an adhesive for direct attachment to the mirror glass 5, exposed by the opening 7 that is formed in the mirror coating 6.

The highly reflective material may be arranged to return the incident light with or without color filtering as desired for providing symbols of a specific color.

Thus there is suggested a rearview display mirror for a vehicle, the mirror being provided with patterns that are visible in daylight, while in darkness these patterns are rendered luminous when illuminated by incident light preferentially from behind the vehicle, for alerting the driver of the vehicle. The disclosed mirror is a low cost, zero-energy solution for providing a display mirror carrying the most adequate security information addressed to the driver, both at day-light driving and in darkness. In a modified embodiment, the mirror may be structured also to display an operational condition or dynamic status information.

Fig. 4 illustrates schematically a mirror, substantially arranged as the men- tioned mirror 1. An electrically supplied layer 1 1 , which may be a liquid crystal layer 1 1 , is introduced in front of the reflective material 8, as seen in the direction of the incident light. In the drawing, layer 1 1 is schematically illustrated by hatch lines 1 1. The layer 1 1 presents a screen 1 1 by which the intensity of the returned light may be controlled. The screen 1 1 may be ap- plied to cover one or several of the symbols formed in the reflective coating, or to cover a partial area of the mirror carrying the pattern. Thus, when the screen 1 1 is electrically associated with a turn signal, e.g., the screen may be controlled to be transparent and allow the full intensity of the reflected light to be received by the driver only when the turn signal is on. Thus, the passive symbols of the display mirror may also be arranged to dynamically display conditional status information 12, e.g. in a sideview signal mirror.

In the disclosure, the invention is explained with reference to exemplary embodiments from which modifications are possible without departing from the scope of invention, as defined in the appended claims.

Claims

1. A rearview display mirror for a motor vehicle, wherein a pattern of transparent windows (7) are formed in a light reflective coating (6) of the mirror, said pattern defining symbols of information addressed to the driver of the vehicle, characterized by an additional reflective layer (8) of high reflectivity arranged behind the mirror coating (6) to be exposed by incident light (L) through said windows, said reflective layer (8) being a reflex material operative for illuminating said pattern by passively returning, through said win- dows, the incident light from external light sources behind the vehicle and directing the reflected light towards the driver of the vehicle at a reflex angle not less than 20° relative to the incident light in a horizontal plane.

2. The mirror of claim 1 , characterized in that the reflex angle relative to the incident light is at least 20° and not more than 75°, in the horizontal plane.

3. The mirror of claim 2, characterized in that the reflex material layer (8) is carried by a carrier member (9), that adheres to a backside of the metalized mirror glass (5,6).

4. The mirror of claim 2, characterized in that said reflex material layer (8) is attached to a heater foil (10) that adheres to the backside of the metalized mirror glass (5,6).

5. The mirror of claim 4, characterized in that the reflex material layer (8) is printed on the heater foil.

6. The mirror of claim 4, characterized in that the reflex material layer (8) is integrated in an adhesive coating applied for attaching the heater foil to the metalized mirror glass (5,6).

7. The mirror of any previous claim, characterized in that the reflex material (8) incorporates a plurality of reflective surfaces that are angularly oriented relative to the mirror in a saw-tooth formation.

8. The mirror of any previous claim, characterized in that the reflex material layer (8) is a colored reflective material layer.

9. The mirror of any previous claim, characterized in that the windows (7) are formed to define one or several from the art of warning symbols, alert symbols, outline border symbols and other symbols of information addressed to the driver of the vehicle.

10. The mirror of any previous claim, characterized by an electrically controlled screen (1 1) introduced for controlling the intensity of reflected light through the windows (7).

1 1. The mirror of claim 10, characterized in that the electrically controlled screen is a liquid crystal layer ( 1 1).

12. The mirror of claim 10, characterized in that the screen (1 1) is electrically associated with an operational function of the vehicle in order to provide conditional information about said function.

13. The mirror of claim 10, characterized in that the screen (11) is electri- cally associated with a turn signal of the vehicle.