WO2007122427A1

WO2007122427A1 - Head-up display

Info

Publication number: WO2007122427A1
Application number: PCT/GB2007/050203
Authority: WO
Inventors: Michael Robert Greenall; Jonathan Peter Voss
Original assignee: Pilkington Group Limited
Priority date: 2006-04-20
Filing date: 2007-04-20
Publication date: 2007-11-01
Also published as: JP2009534246A; GB0607744D0

Abstract

A laminated automotive glazing comprising a head-up display (HUD) display area (4) is disclosed. The display area is a switchable liquid crystal display (LCD). The laminated glazing comprises two plies of glass having an interlayer structure laminated therebetween, wherein the interlayer structure comprises a first sheet of an interlayer material framing the LCD film which is incorporated therein. Preferably, the interlayer material does not contain plasticizer, or contains a plasticizer which does not diffuse into the LCD film structure.

Description

HEAD-UP DISPLAY

The present invention relates to a head-up display, in particular, to a glazing for viewing a head-up display in an automotive vehicle.

Although the instruments present on the dashboard of a vehicle provide vital information to a driver, when looking at the instruments, the driver is distracted from the road. Research has shown that the repetitive change in focus between the instrument panel and the road ahead is a major factor in increased driver fatigue on long journeys. One approach to eliminating the need to repeatedly look at the instrument panel is to employ a head-up display, or HUD. Head-up displays were originally developed for military uses, such as in fighter aircraft, to minimise distraction, and comprised a means of displaying information in a pilot's or driver's field of view. HUDs were first included in automotive vehicles in the late 1980's, and offered a way of displaying information on the glazing of a vehicle, allowing the driver to focus easily on the road ahead whilst viewing information usually shown on the instrument panel or dashboard.

In a vehicle, a HUD works by reflecting an image off the glazing into the driver's field of view. The image is generated below the glazing, by a unit positioned on or in the dashboard, and projected upwards towards the glazing. The unit typically comprises at least one light source, such as an LED (light-emitting diode), illuminating a thin film transistor display, for example, an LCD (liquid crystal display). If coloured light sources are used, the HUD may display coloured information or indicia onto the glazing. To create the display, an image is generated on the LCD, illuminated from behind and projected onto the glazing. The projection may be direct onto the glazing, or via mirrors and/or polarizers to produce a sharp and clear image.

Although displaying the image in the main vision area of the glazing ensures that the driver is not constantly looking away from the road, the image displayed needs to be bright, particularly in daylight conditions. This may result in the display becoming distracting for the driver, who has no choice but to look at it, unless the HUD is turned on and off constantly. This may be irritating, rather than distracting, but fails to avoid the problems inherent in traditional dashboard displays.

It is therefore important to find a way in which vital information can be displayed to a driver, without causing undue distraction or irritation.

The present invention aims to address these problems by providing a laminated automotive glazing comprising a head-up display (HUD) display area, wherein the display area is a switchable liquid crystal display.

By providing a dedicated display area within the glazing, the intensity of the head-up display image displayed can be reduced compared with traditional head-up display systems, resulting in reduced driver distraction and fatigue.

Preferably, in use, an image is projected onto the display area for a selected time period. Preferably, the HUD display area is located at the periphery of the glazing.

Preferably, the laminated glazing comprises first and second plies of glass having an interlayer structure laminated therebetween, the interlayer structure comprising a first sheet of an interlayer material framing the liquid crystal display film which is incorporated therein.

Preferably, the interlayer material is chosen to minimise the migration of the components of the interlayer material into the liquid crystal display film and/or minimises the migration of mobile liquid crystal display film components into the interlayer material. More preferably, the components of the interlayer material do not contain plasticizer. Alternatively, it is preferable that the components of the interlayer material contain a plasticizer which does not migrate into the liquid crystal film.

Preferably, the interlayer structure comprises a second and a third sheet of an interlayer material, each in contact with and co-extensive with a ply of glass. The first sheet of interlayer material may be one of ethylene vinyl acetate copolymer, polyurethane, polycarbonate, poly vinyl chloride or a copolymer of ethylene and methacrylic acid. At least one of the second and third sheets of interlayer material may be one of ethylene vinyl acetate copolymer, polyurethane, polycarbonate, poly vinyl chloride or a copolymer of ethylene and methacrylic acid.

Preferably, the laminated glazing further comprises a heat reflective solar control coating. Alternatively, the laminated glazing may further comprise a poly ethylene terephthalate substrate having a heat reflective solar control coating and a fourth sheet of an interlayer material, interposed between the third sheet of interlayer material and the second ply of glass. Preferably, the fourth sheet of interlayer material is poly vinyl butyral or ethylene vinyl acetate copolymer.

The present invention will now be described by way of example only, and with reference to the accompanying drawings in which:

Figure 1 is a schematic side view of a head-up display employing a glazing in accordance with the present invention;

Figure 2 is a schematic perspective view of a glazing in accordance with the present invention;

Figure 3 is a schematic plan view of a display area in accordance with the present invention;

Figure 4 is a schematic view of a head-up display in use, displaying an image;

Figure 5 is schematic showing the areas of a glazing in which a head-up display may utilise the glazing of the present invention; and

Figure 6 is a schematic side view of a further glazing in accordance with the present invention.

In the present invention, it has been appreciated that rather than providing a head-up display which relies on a ply of glass in a glazing as a display area, it is possible to provide a display area within a glazing, specifically for displaying head-up display information. By providing a specific display area, it is possible to use less intense illumination whilst retaining the quality of the displayed image. Figure 1 is a schematic side view of a head-up display employing a glazing in accordance with the present invention. The head-up display 1 comprises a projection system 2, for projecting images onto a glazing 3. The projection system 2 may be any suitable system for projecting a head-up display image. The images are displayed on a specific display area 4 within the glazing 3 to the driver 5 (and/or passengers) of a vehicle in which the glazing 3 is fitted.

Figure 2 is a schematic perspective view showing a portion of the glazing 3 in greater detail. The glazing 3 comprises a first 6a and second 6b ply of glass, such as annealed glass, having an interlayer system 7 laminated in between, forming a laminated glazing construction. The interlayer system 7 comprises three layers of interlayer material: a first interlayer 8a, a second interlayer 8b and a third interlayer 8c, which is laminated between the first 8a and second 8b interlayers. The display area 4 comprises a thin film liquid crystal device (LCD) 9, incorporated into the interlayer structure 7 within a "picture frame" structure formed from the third interlayer 8c. This "picture frame" extends around at least two sides of the LCD 9, depending upon the required position of the display area 4 in the finished glazing. The first 8a and second 8b interlayers are co-extensive with the first 6a and second 6b plies of glass, and the third interlayer 8c/LCD 9, such that the thickness of the interlayer structure 7 in the region where the LCD 9 is laminated is the same as, or substantially similar to, the total thickness of the first 8a, second 8b and third 8c interlayers. This construction reduces stress within the laminated structure, decreasing the likelihood of delamination, cracking or damage to the LCD 9. The thickness of the third interlayer 8c is therefore chosen to be of the same order as that of the LCD 9.

Figure 3 is a schematic plan view of the display area 4, showing the "picture frame" construction and electrical connections. The LCD 9 is supplied with electrical power from the vehicle in which the glazing 3 is fitted. Two electrical connections 10a, 10b run from the LCD 9, through the laminated structure to the edge of the glazing 3. A terminal 10a, 10b is provided at the end of each connector 1 Ia, 1 Ib, to allow the display area 4 to be connected into the wiring harness of the vehicle. Preferably, the LCD 9 is a thin film liquid crystal device formed from a mixture of a polymer and liquid crystals (polymer dispersed liquid crystal), which is transparent when a current is applied. Such a liquid crystal device is described for use as a display in US 6.997,592. When power is supplied to the film, the liquid crystal molecules become aligned, allowing incident light to be transmitted through the film. When the power supply is off, the liquid crystal molecules relax, resuming a non-aligned orientation, and the film appears to be opaque, as incident light is dispersed therein. In this opaque state, the liquid crystal device may be used as a display area for projected images.

When incorporated into a glazing, the LCD film forms the display area for a head-up display. When power is provided, the LCD film transmits incident light, allowing vehicle passengers to look through the display area. When the power to the LCD film is turned off, and the display area rendered opaque, images forming the head-up display are projected onto the glazing.

Figure 4 is a schematic view of a head-up display, employing a glazing containing a display area 4 in accordance with the present invention, in use. To illustrate the general principle of the invention, an image 12 (an indicator arrow) is displayed in the corner of a glazing 3. The image may flash (as the indicator light on a dashboard would do) or remain constant, depending on its purpose. In particular, images may be displayed for a selected time period only. This reduces the distraction to a driver in comparison with traditional head-up displays. Images such as warning indicia and signs, maps or text can be displayed.

Preferably, the display area 4 is included in an edge region of a glazing 3. This is because when viewed at an angle (non-vertical position), when no power is applied, the LCD forming the viewing area appears hazy (off-angle haze). This is an issue for glazings which are installed as windscreens, (and therefore generally viewed at an angle). Windscreens are subject to ECE R43, which stipulates the optical transmission, dimensions and position of vision areas A, B and C. Figure 5 illustrates the regions 13, around the edge of a windscreen, where the display are 4 can be provided, which are within vision area C. For head-up displays which are required to be within either vision area A or B of a windscreen, it may be desirable to use an LCD which is specifically designed to avoid off-angle haze, such as that disclosed in EP 1 619 541. For vertical or near vertical glazings, such as sidelights and bus and truck windscreens, the issue of off- angle haze does not arise to such an extent.

Preferably, the interlayer materials used to make the interlayer structure 7 are polymer interlayer materials such as EVA (ethylene vinyl acetate copolymer), PU (polyurethane), PC (polycarbonate), PVC (poly vinyl chloride) or a copolymer of ethylene and methacrylic acid. More preferably, the interlayer materials have a low or zero plasticizer content, or a plasticizer with low mobility in the LCD matrix polymer. In particular, it is preferred that the interlayer material used is EVA. Migration of the plasticizer used in the interlayer material into the LCD film, and diffusion of liquid crystal molecules out of the LCD film and into the polymer matrix of the interlayer material can lead to damage of the LCD film. A clear border region appears around the edge of the film, which gives an unacceptable visual appearance when the display area is in use.

Laminated glazings incorporating such a display area can be made by the following process. Firstly, the electrical connectors are prepared. A busbar may be applied to the LCD film, or the film may come provided with pre-applied busbars. Electrical connectors for joining the display area into the wiring harness of a vehicle are soldered to the busbars.

Secondly, once the soldering is completed, the glazing components are laid up for lamination. Three sheets of interlayer material (for example, 0.76mm, 0.38mm and 0.76mm thick respectively for a PVB interlayer and 0.40mm thick for each EVA interlayer) are placed between the two plies of glass to be used to form the sample, and trimmed to the external size of the plies of glass. By trimming the three sheets of interlayer material to size before cutting the "picture frame" for the LCD film prevents the frame from being tugged out of the assembled laminate during trimming, which would create a large gap between the LCD film and the frame. The LCD film is then used as a template to mark a hole in the sheet of 0.38mm/0.40mm thick interlayer material, and a hole cut to form the "picture frame" in which the LCD film is placed. The sheets of interlayer material and LCD film are then laid up on the glass to create the structure shown in Figure 2. Thirdly, the assembled glazings are laminated. Each is then vacuum bagged and held under vacuum overnight, before being heated in an autoclave at 105°C for 90 minutes under atmospheric pressure.

In addition, the electrical connectors 10a, 10b, may be hidden by an obscuration band. This is a band of fired, black ceramic ink around the edge of the upper ply of glass, which acts to cover the adhesive holding the glazing into a vehicle, and electrical connections. The purpose of the band is two-fold, firstly aesthetic, and secondly, to prevent damage of adhesive or other components from UV exposure. The obscuration band, or cowling provided at the bottom of a glazing, may also hide the edges of the display area 4, depending on its position within the glazing 3.

It may also be desirable to provide a solar reflective film on the inner surface of an outer ply of clear glass in a glazing containing a display area 4 as described above. Heat reflective coatings, which have an element of solar control, for example, a two-layer silver coating, may be used. Typically, the solar heat reflected by such coatings is greater than 23%, measured in accordance with ISO9050:E(2003), air mass 1.5.

Rather than provide a coating on one of the plies of glass, it may be desirable to include a solar reflective, in particular, a double-layered silver coating, on a PET substrate included within an interlayer structure in a laminated glazing. Figure 6 is a schematic side view of a glazing 14 comprising a five-layer interlayer structure 15 laminated between two plies of glass 16a, 16b. Preferably, the upper ply of glass 16a is clear. The interlayer structure 15 comprises a first interlayer 17, a second interlayer 18, having an LCD film 19 incorporated therein, a third interlayer 20, a first PET substrate 21, a fourth interlayer 22, a second PET substrate 23, coated with a heat reflective solar control coating, and a fifth interlayer 24. Preferably, the first 17, second 18 and third 20 interlayers are formed of EVA or other suitable interlayer material, as discussed above. The fourth interlayer may be a PVB interlayer, and may be clear or tinted. The fifth interlayer is preferably also PVB. In particular, the LCD film 19 may be included in an upper region of the glazing where a tinted portion of a PVB interlayer forms a shadeband. In addition, the PVB interlayer may have acoustic or solar/thermal control properties. By using a five-layered interlayer structure, a barrier is provided between the LCD film 19 and a PVB interlayer, removing any issues due to interlayer component migration.

Further embodiments within the scope of the appended claims will be apparent to those skilled in the art. In particular, although the invention has been described with reference to head-up displays, it is possible to use a glazing of the present invention as a display area for any projected image, requiring a screen, in a vehicle.

Claims

1 A laminated automotive glazing comprising a head-up display (HUD) display area, wherein the display area is a switchable liquid crystal display.

2 The laminated glazing of claim 1, wherein in use, an image is projected onto the display area for a selected time period.

3 The laminated glazing of claim lor 2 wherein the HUD display area is located at the periphery of the glazing.

4 The laminated glazing of any of claims 1 to 3, comprising first and second plies of glass having an interlayer structure laminated therebetween, the interlayer structure comprising a first sheet of an interlayer material framing the liquid crystal display film which is incorporated therein.

5 The laminated glazing of claim 4, wherein the interlayer material is chosen to minimise the migration of the components of the interlayer material into the liquid crystal display film and/or minimise the migration of mobile liquid crystal display film components into the interlayer material.

6 The laminated glazing of claim 4 or 5, wherein the components of the interlayer material do not contain plasticizer.

7 The laminated glazing of claim 4 or 5, wherein the components of the interlayer material contain a plasticizer which does not migrate into the liquid crystal film.

8 The laminated glazing of any of claims 4 to 7, wherein the interlayer structure comprises a second and a third sheet of an interlayer material, each in contact with and co-extensive with a ply of glass. The laminated glazing of any of claims 4 to 8, wherein the first sheet of interlayer material is one of ethylene vinyl acetate copolymer, polyurethane, polycarbonate, poly vinyl chloride or a copolymer of ethylene and methacrylic acid.

The laminated glazing of claim 8 or 9 wherein at least one of the second and third sheets of interlayer material is one of ethylene vinyl acetate copolymer, polyurethane, polycarbonate, poly vinyl chloride or a copolymer of ethylene and methacrylic acid.

The laminated glazing of any of claims 8 to 10, wherein the glazing further comprises a heat reflective solar control coating.

The laminated glazing of any of claims 8 to 11, wherein the glazing further comprises a poly ethylene terephthalate substrate having a heat reflective solar control coating and a fourth sheet of an interlayer material, interposed between the third sheet of interlayer material and the second ply of glass.

The laminated glazing of claim 12, wherein the fourth sheet of interlayer material is poly vinyl butyral.

The laminated glazing of claim 12, wherein the fourth sheet of interlayer material is ethylene vinyl acetate copolymer.

A laminated glazing comprising a head-up display (HUD) display area, substantially as herein described, with reference to Figures 1 to 6 of the accompanying drawings.