GB2118349A

GB2118349A - Liquid crystal character display

Info

Publication number: GB2118349A
Application number: GB08308150A
Authority: GB
Inventors: Geoffrey John Boughton
Original assignee: Fujitsu Services Ltd
Current assignee: Fujitsu Services Ltd
Priority date: 1982-04-08
Filing date: 1983-03-24
Publication date: 1983-10-26
Also published as: GB8308150D0; GB2118349B

Abstract

In a character display, liquid crystal elements 1 displaying a single character include two groups of transparent electrodes 4, 5 disposed one on each side of liquid crystal material. Co- extending portions of the electrodes 4, 5 define character segments 6. Each character segment 6 is selected by energising one of the electrodes 4 in conjunction with one of the electrodes 5, the liquid crystal material 2 situated between the co-extending portions of the two electrodes 4, 5 thereby being activated to provide a visual indication of the selected segment 6 visible through the transparent electrodes 4, 5. <IMAGE>

Description

SPECIFICATION Character display arrangements The present invention relates to character display arrangements and in particular to such arrangements which include liquid crystal character representing elements.

Liquid crystal elements for representing alphanumerical characters are known and typically comprise sixteen character forming segments. The segments are fabricated from a transparent conductive material and overlie a liquid crystal material. Liquid crystal materials have the property that their light transmitting characteristics are changed by the application of an electrical potential. This property, therefore, is utilised to provide a visual indication of any induced change. A common electrode is positioned beneath the liquid crystal material and, by introducing a potential difference between the common electrode and selected character segments the liquid crystal material under each selected character segment is activated to provide a visual representation of a required character visible through the transparent segments.

It will be realised that, in order to select individual character segments, an electrical connection must be provided to each segment and to the common electrode. As a typical character display arrangement may comprise a large number of liquid crystal display elements situated in a very small viewing area, it will be appreciated that the provision of electrical connections to all of the character segments of each element presents a problem.

According to the present invention a character display arrangement includes: at least one character representing element comprising first and second groups of electrodes disposed on opposite sides of a quantity of liquid material whose light transmitting properties are changeable by the application of an electrical potential, the electrodes of at least one of the groups being transparent, and each electrode being shaped so that portions of the electrodes of the first group co-extend with portions of the electrodes of the second group, the co-extensive portions defining areas representing character forming segments, whereby application of a potential difference between pairs of electrodes selected one from each of the first and second groups causes the light transmitting properties of said liquid material situated between co-extensive portions of the selected pairs of electrodes to be changed to thereby provide a visual indication of the associated character forming segments visible through said transparent electrodes.

Preferably said liquid material is a liquid crystal material.

Preferably the electrodes of the first and second groups extend across the liquid crystal element between opposite edges of the element.

Preferably end portions of the electrodes of the first and second groups lying at the edges of the liquid crystal elements are shaped so that when a plurality of the elements are arranged in abutment in rows and columns, corresponding electrodes of adjacent elements are electrically connected.

Additional segments may be provided in the liquid crystal elements for extra character features.

A character display arrangement will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a section through a liquid crystal element at line 1-1 of Figure 4.

Figure 2 is a plan view showing the arrangement of one of two groups of electrodes, Figure 3 is a plan view showing the arrangement of the other of the two groups of electrodes, Figure 4 shows the two groups of electrodes in superimposed relationship, and Figure 5 is a block diagram showing a matrix of elements and means for energising the elements.

Referring to Figure 1 of the drawings, a liquid crystal character representing element 1 comprises an enclosure in which a quantity of liquid crystal material 2 is sandwiched between two spaced apart glass layers 3. A group of electrodes 4 is formed on an inner surface of one of the glass layers 2 and a further group of electrodes 5, overlying the group of electrodes 4, is formed on an inner surface of the other glass layer 2. The electrodes 4 and 5 are formed from a transparent conductive material such as, for example, tin oxide and may be deposited on the glass in conventional manner.

A plan view of the group of electrodes 4 is shown in Figure 2. The group comprises five electrodes designated 4a to 4e. It will be noted that the electrodes extend generally in a vertical direction.

Figure 3 shows a plan view of the group of electrodes 5. The group comprises four electrodes designated 5a to 5d. It will be noted that the electrodes extend generally in a horizontal direction.

Figure 4 shows the group of electrodes 5a to 5d overlying the group of electrodes 4a to 4e, the electrodes 4 being shown in broken lines. The inter-relationship of the two groups of electrodes is such that twenty areas of overlap or co-extension which are shown shaded, occur between the electrodes 4 and 5. Sixteen of these areas of overlap, designated 6a to 6p, define the conventional sixteen character segments required to reproduce alphanumeric characters and the remaining four areas designated 7a to 7dform segments which may be used simply or in combination to provide extra character features such as, for example, punctuation symbols or qualifying indicators.

In operation, the electrodes 4a to 4e, and the electrodes 5a to Sdform a 4 x 5 matrix and thus any one of the twenty character segments may be selected by energising one of the electrodes 4 in conjunction with one of the electrodes 5. For example, if the character segment 6a is required to be displayed, vertical electrode 4c and horizontal electrode 5a is energised to produce a potential differ encetherebetween. The liquid crystal material situated between the overlapping portions of the two electrodes is thereby activated to provide a visual indication of the segment 6a.It will be realised that the groups of electrodes 4 and 5 are shaped in such manner as to avoid overlap anywhere other than those areas defining character segments, unwanted overlap, of course, producing spurious indications.

It will also be realised that the levels of energisation are such that a character segment is only displayed when both a vertical and horizontal electrode is energised and is not displayed if only a single electrode is energised.

Opposite ends W and X of the electrodes 4a to 4e are in vertical alignment so that when two or more of the character elements 1 are arranged in a vertical column, the ends W of the electrodes 4 of one element abut the ends X of corresponding electrodes 4 of an adjacent element to electrically connect together all the corresponding electrodes 4.

Similarly ends Y and Z of the electrodes 5a to 5d are arranged so that when the elements 1 are aligned in a horizontal row abutment occurs between the Y ends of the electrodes 5 of one element and the X ends of the corresponding electrodes 5 of an adjacent element to thereby electrically connect together all the corresponding electrodes 5. Thus, a character display arrangement may be formed from rows and columns of character elements, the abutted elements 4 and 5 forming conductor lines extending vertically and horizontally across the display arrangement to provide a matrix of conductors by which any segment of any element may be selectively activated by coincidently energising one of the conductor lines 4 and one of the conductor lines 5.

A typical character display arrangement consists of four horizontal rows, each comprising eighty elements to provide a total of three hundred and twenty elements 1. The three hundred and twenty character elements form a display having dimensions in the order to 0.6 x 7.0 ins. It will be realised that four horizontal rows of elements 1 will result in 4x4 or 16 lines of electrodes 5 and eighty vertical columns of elements will produce 80 x 5 or 400 lines of electrodes 4.

Figure 5 shows such a display arrangement. For the sake of clarity only seven of the elements 1 are shown. In operation a multiplexor 8 is employed to cyclically energise each of the sixteen lines 9 connected to the electrodes 5. The lines 10 connected to the electrodes 4 are selectively energised by outputs from a buffer register 11 which contains information entered into it via an input 12. Atiming control unit 13 controls the timing of the energisation of the lines 10 in relation to the cycling of the multiplexor so that during the energisation of each electrode line 9 all those electrode lines 10 which, in conjunction with the currently energised lines 9 define required character segments, are energised.Thus, after energisation of all the electrodes lines 9 in sequence, all required character segments of the display will have been activated. It will be realised that the multiplexer cycles at a speed sufficient to produce a substantially flicker free display.

It will be seen that the number of external electrical connections required for the operation of the described character display arrangement has been considerably reduced when compared with a display using conventional character representing elements each requiring, for example, seventeen connections.

In practice the density of the 400 connections to the electrodes 4 may be reduced by providing connections to alternate ones of the electrodes at the top and bottom edges of the display area. In the case of the horizontal electrodes 5, however, it has been found preferable, because the larger number of elements in a row produces a high electrical resistance, to provide connections at both ends off each row.

Claims

1. A character display arrangement including at least one character representing element comprising first and second groups of electrodes disposed on opposite sides of a quantity of liquid material whose light transmitting properties are changeable by the application of an electrical potential, the electrodes of at least one of the groups being transparent, and each electrode being shaped so that portions of the electrodes of the first group co-extend with portions of the electrodes of the second group, the coextensive portions defining areas representing character forming segments, whereby application of a potential difference between pairs of electrodes selected one from each of the first and second groups causes the light transmitting properties of said liquid material situated between co-extensive portions of the selected pairs of electrodes to be changed to thereby provide a visual indication of the association character forming segments visible through said transparent electrodes.

2. A character display arrangement as claimed in Claim 1, in which each electrode of the first and second groups includes a plurality of portions which co-extend with the electrodes of the other group, the arrangement of the electrodes being such that the character forming segments can each be selected by energisation of one electrode from each group.

3. A character display arrangement as claimed in Claim 1 or 2, in which the liquid material is a liquid crystal material.

4. A character display arrangement as claimed in Claim 1,2 or 3, in which the electrodes of the first group extend between a pair of opposite edges of the character representing element and the electrodes of the second group extend between a further pair of opposite edges.

5. A character display arrangement as claimed in Claim 4, in which the ends of the electrodes of the first and second groups lying at the edges of the character representing element are shaped so that, when a plurality of the elements are arranged in abutment in rows and columns, corresponding electrodes of adjacent elements are electrically connected.

6. A character display arrangement as claimed in any preceding claim including a plurality of elements arranged so that corresponding electrodes of the first group of the elements are interconnected; means to cyclically energise the electrodes of the first group of all of the elements; and means selectively operated to energise the electrodes of the second group of all of the elements at selected times coincident with energisation of the electrodes of the first group so that desired segments of the elements are selected.

7. A character display arrangement as claimed in Claim 6 in which the elements are arranged in rows and columns and in which all of the corresponding electrodes of the second group are interconnected.

8. A character display arrangement constructed and arranged to operate substantially as herein described with reference to the accompanying drawing.