The present invention is a Nonprovisional Application under 35 USC 111(a), claiming priority to Serial No. GB 1904482.5, filed on 29 Mar. 2019 the entirety of which is incorporated herein by reference.
The present disclosure relates to a display device for off-axis viewing, in particular to a liquid crystal display (LCD) for off-axis viewing.
A variety of display devices have been developed. Examples thereof include liquid crystal display (LCD) devices and organic light emitting display (OLED) devices. These displays are generally used in various electronic devices such as a mobile telephones, televisions, digital signage etc.
LCDs are usually optimised for wide horizontal viewing angles, and to some extent vertical viewing angles. This means that off-axis brightness and contrast quality is reduced, in particular when viewed in a viewing cone at approximately 45° to the normal. This is especially a problem for installations, such as A-pillar displays in cars, where display when mounted to the A-pillar is always viewed at 45° due to the shape and position of the A-pillar.
According to one aspect of the present invention there is provided a display device, the device comprising: a plurality of pixels, wherein each pixel comprises: a first encapsulation layer; a second encapsulation layer; a display medium disposed between the first and second encapsulation layers, wherein the first encapsulation layer is disposed above an upper surface of the display medium and the second encapsulation layer is disposed below a lower surface of the display medium; and a plurality of electrodes extending laterally through the display medium, wherein the plurality of electrodes are oriented at an oblique angle relative to an axis extending between two opposing edges of the pixel.
This has the advantage that the contrast of the display is improved when viewing the display off-axis. For example, in applications where the display has to be mounted so that it is always viewed off-axis then display performance is improved. Furthermore, rotation of the electrodes is simple to manufacture and allows the viewer to see high contrast.
The display device may further comprise a first polariser and a second polariser, wherein a polarisation axis of the first polariser is oriented at an oblique angle relative to said axis extending between two opposing edges of the pixel.
The first polariser may be disposed over the first encapsulation layer, and the second polariser may be disposed below the second encapsulation layer, so that the encapsulation layers are between the first polariser and the second polariser.
Alternatively, the first polariser may be disposed below the first encapsulation layer, and the second polariser may be disposed above the second encapsulation layer, so that the first polariser and the second polariser are between the encapsulation layers.
The polarizers may have to be aligned with the electrodes. Therefore aligning the polarizers at an oblique angle relative to the axis between the two opposing edges of the pixels improves contrast for viewers viewing the display off-axis.
A polarisation axis of the first polariser may be oriented parallel to the plurality of electrodes.
A polarisation axis of the second polariser may be oriented perpendicular to the polarisation axis of the first polariser.
The plurality of electrodes may form a grating of electrodes.
Each electrode of the plurality of electrodes may extend in a straight line.
Alternatively, each electrode of the plurality of electrodes may have a chevron shape. This is advantageous in FFS and IPS type LCD displays based on in-plane switching
An axis extending between two opposing ends of one of the plurality of electrodes may be oriented at an oblique angle relative to an axis extending between two opposing edges of the pixel. This is advantageous in cases where the electrodes have a chevron shape, however also applies where the electrodes extend in a straight line. When the electrodes have a chevron shape, the average angle of the chevron is oblique relative to the axis between two opposing edges of the pixel, however each side of the chevron is oriented at a different angle due to the shape of the chevron. This accounts for the difference in angles between two sides of the chevron shape, caused by the inherent shape of the chevron. In other words, overall the electrodes are rotated at an oblique angle relative to an axis extending between two opposing edges of the pixel.
The display device may further comprise: a first set of conductive lines connected to the plurality of pixels; and a second set of conductive lines connected to the plurality of pixels; wherein the first set of conductive lines and the second set of conductive lines are arranged to define a shape of each of the plurality of pixels.
The shape of each of the pixels may be square, wherein the plurality of electrodes are oriented such that at least one electrode of the plurality of electrodes extends laterally from a first side of a pixel to a second side of the pixel, wherein the first side of the pixel is oriented perpendicular to the second side of the pixel.
Alternatively, the shape of each of the pixels may be a parallelogram and has a pair of equal opposing angles, and the plurality of electrodes are oriented such that at least one electrode of the plurality of electrodes extends laterally from a first side of a pixel to a second side of a pixel, wherein the first side of the pixel is oriented at an oblique angle relative to the second side of the pixel. This has the advantage that the pixels appear to a viewer to extend horizontally or vertically across the display, when the display is conformally mounted a curved surface.
The shape of each of the plurality of pixels may be a rhombus or rhomboid.
The first set of conductive lines and the second set of conductive lines may form an active matrix array.
Alternatively, the first set of conductive lines and the second set of conductive lines may form a passive matrix array.
The display medium may be a liquid crystal display medium.
Advantageously, the display device may be flexible. This allows the device to be conformally mounted on a curved surface.
The display device may be for conformal mounting on a curved surface.
The display device may further comprise at least one contrast enhancing film. Contrast enhancing films reduce light leakage of dark parts of the display, therefore improving off-axis viewing quality.
The at least one contrast enhancing film may be oriented parallel to the polarisation axis of the first polariser.
At least one contrast enhancing film may be oriented parallel to the polarisation axis of the second polariser. This may be perpendicular to the polarisation axis of the first polariser. This may be in addition or as an alternative to the contrast enhancing film oriented parallel to the polarisation axis of the first polariser.
At least one contrast enhancing film may be integrated in the same layer as the first polariser or the second polariser. This has the advantage that manufacture of the display device is easier.
The oblique angle relative to an axis extending between two opposing edges of the pixel may be within a range of 0 degrees to 90 degrees.
Preferably, the oblique angle relative to an axis extending between two opposing edges of the pixel may be within a range of 15 degrees to 75 degrees.
Preferably, the oblique angle relative to an axis extending between two opposing edges of the pixel may be within a range of 30 degrees to 60 degrees.
More preferably, the oblique angle relative to an axis extending between opposing edges of the pixel may be 45 degrees. This improves contrast of the display when viewed at 45°.
The oblique angle relative to an axis extending between two opposing edges of the pixel may be uniform for the plurality of pixels. This has the advantage that the contrast is optimised for all pixels when all viewed from the same angle.
The display device may comprise n pixels, wherein n represents the total number of pixels of the display device. In embodiments, each of the n pixels is oriented at the oblique angle relative to an axis extending between two opposing edges of the pixel. That is, all of the pixels within the display device may be oriented at the same oblique angle between two opposing edges of the pixels.
According to a further aspect of the present disclosure, we provide a method of manufacturing a display device, the method comprising: forming a first encapsulation layer; forming a second encapsulation layer; forming a display medium between the first and second encapsulation layers, wherein the first encapsulation layer is disposed above an upper surface of the display medium and the second encapsulation layer is disposed below a lower surface of the display medium; forming a plurality of electrodes extending laterally through the display medium, wherein the plurality of electrodes are oriented at an oblique angle relative to an axis extending between two opposing edges of the pixel.
These and other aspects will be apparent from the embodiments described in the following. The scope of the present disclosure is not intended to be limited by this summary nor to implementations that necessarily solve any or all of the disadvantages noted.
The invention is diagrammatically illustrated, by way of example, in the accompanying drawings, in which:
Embodiments will now be described by way of example only.
In both passive and active matrix display devices, the arrangement of the conductive lines defines the shape of pixels of the display device to be square or rectangle (due to the grid structure of the conductive lines).
The display device in embodiments described below, advantageously provides improved display quality when the display device is viewed off-axis, from an angle of approximately 45° (in embodiments the display device can be modified to optimise viewing at viewing angles other than 45° in dependence on the application).
A display device has a horizontal axis 402 and a vertical axis 404. A viewing direction is defined by an angle of inclination θ measured from the surface normal 406 of the display, and an azimuth angle Φ which is the angle that the projection of the viewing direction onto the surface of the display makes with the horizontal axis 402.
As shown in
Furthermore as shown in
The dashed line 412 represents the series of positions with varying angles of inclination θ having an azimuth angle Φ of 135° or 315°. The dashed line 414 represents the series of positions with varying angles of inclination θ having an azimuth angle Φ of 45° or 225°. A viewer viewing the display at the central point, where 412 and 414 intersect, would not be viewing the display off-axis as at this point the angle of inclination θ=0°. Similarly, at the ends of 412 and 414, the viewer is not viewing the display off-axis as the angle of inclination θ=90° or 270°.
In other words, the viewer is viewing the display off-axis when neither the angle of inclination θ or the azimuth angle Φ are 0°, 90°, 180°, or 270°.
On this plot, the straight line between points where Φ=90° and 270° (from top to bottom on the display) represents the line 410 in
As shown in
Embodiments of the present disclosure address these issues.
Generally in LCD displays, one of the polarization axes of the polarizers is approximately aligned with the electrodes, and the polarization axes of the two polarizers are perpendicular to each other. The polarizers do not have omnidirectional performance, and in particular have poor quality performance when viewed off-axis. In the display of
The electrodes 805 are oriented at an oblique angle relative to an axis, A, extending between two opposing edges 802, 804 of a pixel 800. This also applies to an axis extending between the other two edges of the pixel, in a perpendicular direction to A in this example. In this figure, the pixel electrodes 805 are provided with 6 to 16 degree shift forming the chevron shape; however they may also be straight lines.
The line A′ illustrates an axis extending between opposing ends of an electrode. A′ is oriented at an oblique angle relative to A. Therefore the chevron shaped electrode, on average, is oriented at an oblique angle relative to axis A.
In this embodiment all of the pixels 800 are oriented at the same oblique angle relative to the axis A between two opposing edges of the pixels 802, 804, so that none of the pixels 800 are parallel or perpendicular to the axis A between two opposing edges of the pixels 802, 804.
The electrodes within the pixels, and the polarizers, are rotated to improve contrast and viewing quality for a viewer viewing the display off axis. The electrodes 905 are oriented at an oblique angle relative to an axis, B, extending between two opposing edges of a pixel 900. This also applies to an axis extending between the other two edges of the pixel. In this figure, the pixel electrodes 905 are provided with 6 to 16 degree shift forming the chevron shape; however they may also be straight lines.
The line B′ illustrates an axis extending between opposing ends of a pixel. B′ is oriented at an oblique angle relative to B. Therefore the chevron shaped electrode, on average, is oriented at an oblique angle relative to axis B.
The display device 900 may be conformally mounted to the curved surface of the A-frame of a car which is tilted at an oblique angle. The pixels in the display device 900 have a rhombus or parallelogram shape to appear to a viewer to extend vertically across the display device or to extend horizontally across the display device, which improves image quality.
Conductive row electrodes and the conductive column electrodes are arranged to define a shape and size of each of the plurality of pixels that is uniform across the display. In this embodiment, each of the plurality of pixels is a parallelogram having a pair of equal opposing angles corresponding to the oblique angle of inclination of the curved surface onto which the display device is to be mounted.
Each of the equal opposing angles between adjacent sides of the pixel may be the same as the angle between the pixel electrodes and the axis extending between two opposing sides. Alternatively, each of the equal opposing angles between adjacent sides of the pixel may be different to the angle between the pixel electrodes and the axis extending between two opposing sides.
The first encapsulation layer, display medium, and second encapsulation layer form the display cell. The display electrodes (not shown) are formed extending through the display medium. These are rotated to improve contrast at an off axis viewing angle, for example at 45°.
The first polarizer is located above the display cell. The orientation of the first polarizer is also rotated to compliment the display electrodes within the display cell.
The second polarizer is located below the display cell, on the opposite side of the display cell to the first polarizer. The orientation of the second polarizer is also rotated to compliment the display electrodes within the display cell, and generally the second polarizer is perpendicular to the first polarizer to provide opposite polarization to the first polarizer.
The display may also include brightness enhancing and/or contrast enhancing films. In general, these are aligned with the polarization axes. The brightness enhancing films may also have reduced viewing quality when viewed off-axis, therefore rotating this in line with the polarisers improves off-axis viewing quality. Contrast enhancing films reduce light leakage of dark parts of the display; therefore rotating the contrast enhancing films in line with the polarisers improves off-axis viewing quality. This would be done by rotating the brightness or contrast enhancing film by the same oblique angle as the chevron and/or polariser rotation. The display device may be an LCD display device (the pixels having a first and second substrate) whereby the display medium is a liquid crystal display medium. The LCD display device may operate in accordance with one of a plurality of known technologies for example the LCD display device may be a twisted nematic (TN) display device, a fringe-field switching (FFS) display device, an in-plane switching (IPS) display device, a plane-to-line switching (PLS) display device, or operate in accordance with another known LCD technology not described herein.
The display device of the embodiments described above may be flexible, that is, the whole of the active area defined by the pixels of the display device exhibits flexibility i.e. can be bent multiple times without breaking. In particular the first and second encapsulation layers referred to above may be made of a deformable plastic substrate e.g. Cellulose triacetate (TAC), Polyethylene terephthalate (PET), Polyethylene naphthalate (PEN), Polyimide (PI), or acrylic based etc. (replacing the conventional glass substrate) such that the display device has flexibility and can be rolled, folded, bent, etc. In alternative embodiments, the first and second encapsulation layers referred to above are made of glass such that the active area defined by the pixels of the display device does not exhibit such flexibility however are shaped for conformal mounting to a curved surface. Alternatively, the display device could be a non-flexible type which could be merely comfortable to bend one time only.
Although the disclosure has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in the disclosure, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.