GB2239342A - Liquid crystal display - Google Patents

Abstract

In a liquid crystal display the segments a to g of the display have a main body portion 27 and a defined edge region 29 of contrasting shade to the main body portion 27, the edge region 29 being shaped to give a three-dimensional appearance to the segments a to g. The segments a to g may also be shaped to have the appearance of perspective, for example by tapering from the bottom to the top of the display. The perspective effect may be used without the border regions 29. <IMAGE>

Description

Liquid Crystal Display The present invention relates to a liquid crystal display.

The structure of liquid crystal displays is well known in the art. The common form of twisted nematic liquid crystal display cell comprises two flat glass sheets which are sealed together around their periphery. The facing surfaces of the glass sheets have transparent electrodes printed on them, and prior to assembly have typically been rubbed to cause the liqud crystal material at the surfaces to adopt a particular alignment. The twisted nematic liquid crystal material fills the cell. The electrodes are exposed at an edge of the cell for power to be supplied to the electrodes.The cell is sandwiched between polarizers and the arrangement, which may work using transmitted light (a back lit display) or reflected light is such that when two facing electrodes are energised the overlapping area of the electrodes, hereinafter called a segment, appears dark against a light background, or, less commonly, light against a dark background.

The displayed pattern is two dimensional in appearance. The contrast between the energised segment area and the background may change with viewing angle, and very close inspection of a reflected light display may reveal a shadow cast on the reflector at the back of the display.

A first aspect of the present invention provides a liquid crystal display in which a displayed segment includes at an edge thereof a defined region of contrasting shade to a main body part of the segment, the region being shaped to impart a three-dimensional appearance to the segment.

The region of contrasting shade may be defined by providing an energised border line which encompasses an area of the display background. Other ways of providing the region may include providing a plurality of relatively narrow lines which provide a cross-hatching effect in the defined region.

A second aspect of the invention provides a liquid crystal display comprising two transparent sheets of material which are sealed together to define a cell volume which contains liquid crystal material, facing surfaces of the sheets having transparent electrodes thereupon, areas of overlap of the electrodes each defining a segment, wherein a segment includes a main body portion having at at least part of its edge a defined border region which, in use, is of contrasting appearance to the main body portion.

A third aspect of the invention provides a liquid crystal display in which the displayed pattern is configured to have the appearance of perspective.

The provision of perspective is particularly suitable for numeric displays.

Other, preferred, features and advantages of the invention will be apparent from the following description and the accompanying claims.

The invention will be further described by way of example with reference to the accompanying drawings, in which: Figures la and lb illustrate a prior art form of seven segment display for displaying digits 0 to 9; Figure 2 is a cross-section along the line II-II of figure la; Figures 3a and 3b illustrate upper and lower electrode patterns for the display of Figure 1; Figures 4a and 4b illustrate a display forming a first embodiment of the invention; Figure 5 illustrates a display forming a second embodiment of the invention; Figure 6 illustrates a display forming a third embodiment of the invention; Figure 7 illustrates a display forming a fourth embodiment of the invention; Figure 8 illustrates a display forming a fifth embodiment of the invention; and Figure 9 illustrates a display forming a sixth embodiment of the invention.

Referring to figures 1 to 3, the construction of liquid crystal displays and in particular of a prior art 7-segment numeric display will be described briefly. Such a display comprises a cell 1 having upper and lower flat transparent glass sheets 3, 5.

The sheets are sealed together about their periphery by a bead of sealant 7 to define a volume 9 which is filled with liquid crystal material. The facing surfaces 11, 13 of the sheets 3, 5 have transparent electrode patterns printed on them. The pattern on each surface 11, 13 is shown in Figure 3a and 3b respectively, both being viewed from above as in Figures 1 and 2.

The upper surface has four electrodes 15, 17, 19, 21 and the lower surface has two electrodes 23, 25. The upper glass sheet overlaps the lower sheet at an edge 27 to form an exposed surface 29 carrying the electrodes 15, 17, 19, 21. Also, electrodes 23, 25 are connected by conductive contacts (not shown) to electrodes 23a, 25a on the exposed surface.

To operate the display, the electrodes are energised in multiplexed fashion as is well known in the art.

To display the numeral 1, electrodes 15, 23 and 25 are energised so that the overlapping area of the electrodes, i.e. the two segments a, b (Figure lb) of electrode 15, is displayed. To show a figure 8, all electrodes are energised, to display segments a to g.

Figure lb shows the appearance of a seven segment display in which the energised segments form a dark area against a light background, but the appearance can be the inverse of this as indicated previously.

Figure 4 shows the appearance of a seven segment display forming a first embodiment of the invention, which is energised to show the numeral 8. Each segment a through g has a border 29 formed on the edges of a main body portion 27 near the bottom of the display. Each border 29 is defined by thin lines 31 formed on the respective upper and lower electrode portions (refer to figures 1 to 3) which serve to define each segment. As can be seen clearly in Figure 4, the effect of this is to give a three dimensional appearance to each display segment, and hence a displayed numeral. In the embodiment of figure 2, the number appears to be viewed from the "6 o'clock" position. Figure 4b shows the same embodiment with the electrodes energised to display the numeral "2".

Figure 5 shows a second embodiment of the invention similar to the embodiment of Figure 4, but in which the defined border areas 29 are filled with vertical (as seen in the drawing) cross-hatching lines 33 formed by using thin electrode lines, to impart a 'grey' appearance to contrast more with both the segment body portion 27 and the surrounding inactive area of the display.

Figure 6 shows a third embodiment, similar to the embodiment of Figure 5, but in which the laterally extending border lines 31 have been omitted.

Figure 7 shows a fourth embodiment, similar to the embodiment of Figure 4, but with the segment pattern skewed off the vertical so that the segments are viewed from below and one side.

In order to enhance the three dimensional appearance of the displayed numeral , the numeral can be "drawn" with perspective. Figure 8 illustrates this particularly advantageous embodiment, with each segment being tapered in the vertical direction, from the bottom of the numeral to the top, and the relative height of the horizontal segments c, f, g being varied accordingly.

Figure 9 illustrates a sixth embodiment of the invention, in which the displayed numeral has perspective, but the border areas 29 are omitted. It can be seen that providing perspective, without the border areas, also provides a significantly enhanced visual effect.

In the embodiments of figures 8 and 9, the electrode patterns (cf. figures 3a and 3b) are laid out to have perspective, thus the resultant display numeral has perspective.

Preferably the electrode patterns which define the border areas are contiguous with the electrode patterns for the respective main body portions of the segments. An electrically separate electrode pattern could be provided, to enable the three dimensional effect to be switched off, i.e. by not activating the electrodes which correspond to the border.

The displays illustrated by Figure 4 to 9 are fabricated and driven in the usual way.

It can be seen that by providing a three dimensional effect to the displayed segments and/or perspective, the appearance of the display is enhanced.

A typical liquid crystal display will have several numerals or characters and may also include dots or symbols.

Various modifications may be made to the described embodiments, and it is desired to include all such modifications as fall within the scope of the accompanying claims.

Claims (15)

Claims

1. A liquid crystal display in which a displayed segment includes at an edge thereof a defined region of contrasting shade to a main body part of the segment, the region being shaped to impart a three-dimensional appearance to the segment.

2. A display as claimed in claim 1, in which the region of contrasting shade is defined by a line border.

3. A display as claimed in claim 1 or 2, in which the region of contrasting shade is defined at least in part by a plurality of generally parallel lines.

4. A display as claimed in claim 1, 2 or 3, in which the electrode patterns for the defined region are contiguous with the electrode patterns for the main body part of the segment.

5. A display as claimed in any one of claims 1 to 4, wherein the displayed segment is configured to have the appearance of perspective.

6. A liquid crystal display comprising two transparent sheets of material which are sealed together to define a cell volume which contains liquid crystal material, facing surfaces of the sheets having transparent electrode patterns thereupon, areas of overlap of the electrode patterns each defining a segment, wherein a segment includes a main body portion having at at least part of its edge a defined border region which, in use, is of contrasting appearance to the main body portion.

7. A liquid crystal display in which segments of the display have a three dimensional appearance.

8. A liquid crystal display as claimed in any one of claims 1 to 7, which displays numerals.

9. A liquid crystal display in which the displayed pattern is configured to have the appearance of perspective.

10. A liquid crystal display as claimed in claim 9, which displays numerals.

11. A liquid crystal display as claimed in claim 10, in which segments of the display are tapered from the bottom of the display, relative to the normal viewing position, towards the top of the display.

12. A liquid crystal display comprising two transparent sheets of material which are sealed together to define a cell volume which contains liquid crystal material, facing surfaces of the sheets having transparent electrodes thereupon, areas of overlap of the electrodes each defining a segment, wherein the electrodes of the display are shaped in the plane of the display so as to have the appearance of perspective.

13. A liquid crystal display substantially as hereinbefore described with reference to figure 4, 5, 6, 7 or 8 of the accompanying drawings.

14. A liquid crystal display substantially as hereinbefore described with reference to figure 9 of the accompanying drawings.

15. A liquid crystal cell for a display as defined in any one of claims 1 to 14.