CA1129530A - Programmable key utilizing a liquid-crystal display and methods for operating the key - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A programmable key for displaying messages to an operator so as to draw the operator's attention actively to the key is presented. The key comprises a liquid-crystal display for showing at least one message on the key according to the program chosen, components for creating messages on the liquid-crystal display, and a device for enabling the liquid-crystal display to be translated from one position to another position. In typical operation, the liquid-crystal display is initially activated to show a message at the key's neutral position. When the key is depressed the liquid-crystal display automatically reactivates to show a second message. At either position, the key may show a blank screen by appropriate energization or deenergization of the liquid-crystal display.

Description

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This invention relates to liquid-crystal electronic technology and more particularly to devices and methods for using liquid-crystal displays to present messages.
A number of techniques and devices exist in the prior art for pre-senting a message to an operator in such a way as to assist the operator in making a decision to use or not to use a certain key from among a group of keys where only a fraction of the group are of specific interest to the operator for the decision at hand. Of concern herein are those techniques and devices in which the message is displayed on the key or very near the key.
One simple prior art device of this nature is the standard type- -writer key. In a relatively unsophisticated manner, the alphanumeric or punctuation symbol on the key helps the operator in deciding whether to press the key. The typewriter key may be classified as an unlighted key.
Another relatively simple message-carrying key is the telephone push button which lights up when a call is being placed to the telephone.
In this case, the message is conveyed to the operator by the lighting of tne key rather than by a specific message printed on the key. The lighting of the key helps to inform the operator that a call is coming through and also causes the operator to focus attention on that particular push button among other push buttons that usually exist on such telephones.
A somewhat more advanced message-carrying key is the translucent lightable key having a symbol printed on the key. When the key is in the unlighted state, the symbol does not stand out to the operator. With appropriate color contrast, the translucent key may almost seem blank to the operator. When the key lights up, the operator can easily read the symbol. The lighting of the key serves to focus the operator's attention on that particular key among other unlighted keys that exist near the lighted key and to carry a specific message across to the operator.
There are a number of disadvantages with the foregoing message-presentation devices used to assist an operator in deciding whether to engage a certain key or not from a group of keys in which only part of the 3~

group is of direct interest to the operator. The unlighted key provides minimal assistance to the operator in making the decision. While the unlighted key does carry a specific message, the key essentially looks like all the other keys on the keyboard. No active mechanism exists to cause the operator to focus attention on that fraction of the group of keys relevant to the immediate decision. In addition, an unlighted key provides no direct feedback to the operator indicating that the desired key function has been initiated after the key is hit.
The lightable keys in the prior art have different disadvantages.
Whereas lightable keys attract the operator's attention and act to narrow the range of choice to those keys that are lighted up, the lightable keys utilize incandescent bulbs to provide the light and, consequently, experience the problems inherent with incandescent bulbs. Lightable keys typically require a relatively high amount of power. For instance, only one or two lightable keys usually may be operated from the internal power of a telephone.
If more lightable keys are desired, an external power source must be provided ~;
for the keys on the telephone. Lightable keys have a usage lifetime of only about 5000 hours per bulb. A lightable key is a relatively bulky device.
It typically goes to a depth of 1-1.25 inches into its mounting structure.
Since a lightable key requires several mechanical parts including a bulb ;~
and bulb-mounting hardware, the key may incur problems in reliability. ~!' ~urthermore, lightable keys are normally limited to one function per key because no convenient way to ~ndicate other functions has been found that ~`
is consistent with the lighting concept.
Unlighted keys within the prior art may be programmed to perform multiple functions. For example, the standard typewriter key may be utilized to print either of two symbols printed on the key depending on whether an auxiliary program-selecti~ key is pressed. Some of the recent calculators ~;
available in the market permit an operator to use keys on the calculators for multiple functions. In one versionJ a primary function is printed on a key and secondary functions are printed near the key. The operator usually engages the secondary functions with an auxiliary program-selection device.

:, In this version, the total number of functions per key is usually no morethan two or three due to the limited amount of space around each key. In another version, the operator inserts a program-selection card into a slot near certain keys. The functional symbols appropriate to these keys are printed on the card and are visible to the operator. This version enables each key to perform a greater number of functions than with the first version but requires an external device -- the program-selection card -- to display the message symbols.
The unlighted programmable keys in the prior art have all the deficiencies of the standard unlighted keys. Furthermore, the technique of printing two or more message symbols on or near each key tends to con-fuse the operator even more than where only one symbol is associated with each key. Although the technique of using a program-selection card with the symbol for each key printed on the card reduces the operator-confusion level to that of an unlighted keyboard, this technique is more complex mechanically. An efficient programmable key which conveys a message to the operator in such a manner as to draw the operator's attention actively to that key does not exist in the prior art.
The liquid-crystal display, hereafter referred to as LCD, has been in existence for over ten years. For example, see Goldmacher et al in U.S.
Patent No. 3,499,702.
The LCD is essentially a light valve controlled by an electric field impressed across the LCD. Depending on the arrangement of the com-ponents of an LCD and on the strength of the applied electric field, light impinging on one face of the LCD is largely transmitted, partially transmitted, or largely not transmitted through the LCD. This characteristic can be employed in many useful ways. By arranging the LCD so that light is trans-mitted through certain parts of the LCD but is not transmitted through other parts, the LCD can be utilized to show various types of messages such as pictures or alphanumeric characters. As an example, LCD's are employed in watches to show the time of day.
LCD's may be operated in either of two general modes. In the -- 'I --transmissive mode, light passing into one side of an LCD creates a picture or message viewable on the other side of the LCD. In the reflective mode, a light reflector is placed behind one side -- the back side -- of the LCD.
Light passing into the front side of the LCD is reflected back through the LCD, permitting a picture or message to be viewed on the front side. The reflective LCD is particularly useful because the natural light of the surroundings can be used to produce a message on the LCD when the back side of the LCD is situated against or near an opaque backdrop.
A programmable key for displaying messages to an operator so as to draw the operator's attention actively to the key at the precise time when the operator must decide whether to use the key is presented. The key comprises a liquid-crystal display (LCD) J means for creating at least one message symbol on said LCD, and means for enabling said LCD to be translated from a first position, the translation causing said message creating means to change the message on said LCD. In a preferred embodiment, electro-conductive coating formed over parts of the inside face of the glass front plate of the LCD in the shapes of the desired messages are used in creating the messages. In another preferred embodiment, a spring mechanism is utilized to control the translation of the key in a direction perpendicular to the ;
plane of the LCD.
In typical operation, the LCD is initially activated through an externai circuit to show a message at the key's neutral or undepressed posi- ~
tion. ~hen the key is depressed or otherwise translated to a second posi- ~ i tion~ the LCD de-activates and then automatically reactivates after the second position is reached to show a second message. At either position, a blank screen may be shown on thelkey through appropriate energization or deenergization of the LCD.
One advantage of the present invention is that it can be used so as effectively to limit the operator's range of choice to only those keys relevant to the key selection decision. In particular, messages can `
be displayed on the relevant keys and blanks can be shown on all the rest of the keys. The operator then effectively "sees" only those keys actually necessary to the decision at hand. This feature reduces the likelihood of operator confusion, especially in comparison with unlighted keys of the prior art.
Another advantage is that this invention can be programmed to show different messages at different times. For example, on a signal from an external source an LCD key might initially show the message "PRESS ME".
After the key has been pressed, it might change to display the message "ON".
If the operator mis-strikes the key, it continues to display the original message. In one embodiment, this invention can also be used with different programs to show different messages for each program. The programming flexibility of the present invention is far greater than the flexibility of any of the programmable keys in the prior art.
A further advantage of the invention disclosed herein is that an LCD key employing a reflective LCD is much more efficient than a lightable key using an incandescent bulb. The LCD key using a reflective LCD con-sumes about one microampere of current at 5 volts, which is less than one-thousandth of the power used by the incandescent bulb in a lightable key.
The LCD key is typically one-tenth to one-fifth as heavy as a lightable key and is far more compact, going only about one-fourth as deep into the mounting structure as a lightable key. The LCD has a normal lifetime of 50,000 hours; this is ten times the life of an incandescent bulb. The present invention is more reliable than a lightable key because the LCD
key has fewer movable parts. In short, the programmable LCD key utilizing a reflective LCD represents a milestone improvement in efficiency over lightable keys in the prior art.
According to the present invention, then, there is provided a key for message display in which said key comprises: a liquid-crystal display (LCD); means for creating at least one message symbol on said LCD; and means for enabling said LCD to be translated from a first position, the `
translation causing said message-creating means to change the message on said LCD.
According to the present invention, there is also provided a s ~

method for controlling the message display on a liquid-crystal display (LCD) comprising the steps of: displaying a first message on the LCD while the LCD is at a first position; translating the LCD from the first position; and changing the first message in response to a signal caused by the translation.
Other advantages and features to this invention will becomes apparent from the following description of the preferred embodiments.
Like reference numbers are employed in the following drawings to represent the same item or items in the various drawings.
Figure 1 is an exploded cross-sectional schematic view of a reflective LCD utilized in the present invention.
Figure 2 shows a top view of the inside face of a glassplate in an LCD.
Figure 3 shows a side view of one embodiment of the LCD key disclosed herein.
Figure 4 shows a schematic view of another embodiment of the present invention.
The invention disclosed herein employs an LCD for presenting messages to an operator. In one embodiment, the LCD is of the reflective type.
Reflective LCD's are known in the prior art. Nonetheless, to comprehend the LCD key fully, it is necessary to review the principal components of a reflective LCD. ~;
Referring to the drawings, Figure 1 shows an exploded cross-sectional schematic view of a reflective LCD suitable for use in this invention. The reflective LCD 10 is constructed by sandwiching liquid- ~' crystal material 11 between a front plate 12 and a back plate 13. A
sealant ring 14 keeps the liquid-crystal material 11 between the glass plates 12 and 13.
In one type of LCD, the glass plates 12 and 13 are so treated that the liquid-crystal molecules establish preferred orientations relative to the plates 12 and 13 in the absence of an electric field. In particular, the liquid-crystal molecules align their dipole axes in directions parallel to the general plane of the LCD. The molecules nearest the front plate 12 all align their dipole axes in one direction parallel to the plane of the LCD. The molecules nearest the back plate 13 all align their dipole axes in a second direction parallel to the plane of the LCD. Between the plates 12 and 13, the directions of the dipole axes of the liquid-crystal molecules gradually "twist" from the first direction to the second direction when no electric field is applied. The angle of twist is usually chosen to be 90 degrees to obtain maximum contrast. Treatments of the glass plates 12 and 13 to obtain the desired angle of twist are known in the prior art.
Transparent electroconductive coatings 15 and 16 are formed on the inside faces of the glass plates 12 and 13 -- i.e., the faces directly adjacent to the liquid-crystal material. These electroconductive coatings 15 and 16 comprise part of the means for creating message symbols on the LCD.
Depending on the particular embodiment, the electroconductive caatings 16 and 16 may cover the entire inside faces of the glass plates 12 and 13 or only certain regions of the inside faces. For illustrative purposes only, the electroconductive coating 15 is depicted in Figure 1 as covering the area on the inside face of the front plate 12 which corresponds to the dashed `~
star 17 shown on the outside face of the front pla~e 12. Similarly, another electroconductive coating, which is not shown for convenience in illustrating the reflective LCD 10, covers the area on the inside face of the front plate ~ ;
12 that corresponds to the dashed arrow 18 shown on the outside face of the front plate 12. Also, for illustrative purposes only, the electroconductive coating 16 covers the entire active area of the inside face of the back plate 13. The active area of a glass plate 12 or 13 is that area enclosed by the sealant ring 14.
Another part of the means for creating message symbols on ~he LCD
are the electrical leads 19 and 20 which are connected to the electro-conductive coatings-15 and 16 for the two plates 12 and 13 and the electrical contacts 21 and 22 whlch in turn are connected to the leads 19 and 20.
The contacts 21 and 22 in Figure 1 are shown as being located on the back plate 13. This location is for illustrative purposes only. The 3q~

contacts 21 and 22 may be located at other convenient sites on the LCD key.
The electrical contacts 21 and 22 are not essential to the LCD key. In some embodiments, the leads 19 and 20 may be connected directly to an exter-nal electric power source without employing electrical contacts as an inter-mediate connèctive device.
An external electric power source, as known in the prior art but not depicted in the drawings, is needed to complete the electrical circuit with the LCD. I~lhen the external power source is connected to the leads 19 and 20, an electric field can be applied across parts or all of the liquid-crystal material 11 in the reflective LCD 10. To create the necessary black and white contrast between the areas of the LCD through which light is large-ly transmitted and those areas through which light is largely not transmitted, light polarizers 23 and 24 are placed over the outside faces of the glass plates 12 and 13. The light polarizers 23 and 24 are termed the front polarizer 23 and the back polarizer 24. The two polarizers 23 and 24 may be arranged so as to have their polarization directions perpendicular to each other, parallel to each other, or at some intermediate angle in rela-tion to each other. For illustrative purposes only~ the polarizers 23 and

2~ in Figure 1 are depicted as being crossed.

The final basic component to the reflective LCD 10 is the light reflector 25 which is placed behind the back polarizer 24. The reflector 25 is normally of the diffuse type.
The present invention employs means for creating message symbols on the LCD. The terminology "means for creating message symbols on the LCD" or equivalent terminology is intended to include only those devices, components, mechanisms, and materials that are physically situated on the LCD key or directly form part of the LCD key. The message-creating means do not include external logic circuitry which selects the precise messages to be shown on the LCD key or the external electric power source which provides curre~t to the LCD.
The means for creating message symbols on the LCD key may be embodied in a number of ways. In general, the embodiments of message-creating means _ g _ described herein are known in the prior art.
In one embodiment, the electroconductive coating is formed on one of the glass plates in discrete patterns for each of the message symbols to be shown. Each pattern is located in a different area of the LCD. There is one electrical lead to the electroconductive coating pattern for each discrete pattern. On the other glass plate an electroc~nductive coating is normally deposited over the entire active area of the inside face of that plate. One electrical lead to the electroconductive pattern is provided for this plate. An example of this embodiment is illustrated in Figure 1 using the dashed star 17 and the dashed arrow 18. In this example, the discrete patterns are formed with electroconductive coating 15 on the front plate 12, whereas electroconductive coating 16 is formed over the entire active area of the inside face of the back plate 13. Alternatively, electroconductive coatings may be formed in discrete patterns on both glass plates.
In another embodiment, the electroconductive coating on one of the ;
glass plates is patterned in a series of thick "lines" which are used to generate different messages by energizing appropriate lines. There is one lead for each electroconductive coating line. The remainder of this embo-diment is fabricated in the same manner as for the previous embodiment.
An example of this embodiment is illustrated in Figure 2. The inside face of a glass plate 26 has seven electroconductive coating lines 27 formed on it. Seven electrical leads 28 are connected to the lines 27. The darkened lines 29 indicate the lines that would have to be activated to create the symbol "3".
In a further embodiment, decals having patterns in the shapes of desired message symbols are placed on the front polarizer. The decals block the transmission of reflected light impinging on the back sides of the decal areas where the symbol patterns are located. An electroconductive coating is deposited over discrete segments of the inside face of one of the glass plates at one segment for each discrete message. Each discrete message falls completely within the segment associated with that message when the

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LCD is viewed from the front. The separation distance between coating seg-ments is normally no greater than needed to avoid electrically shorting one segment to another. One electrical lead is provided for each coating seg-ment. The remainder of this embodiment is constructed in the same manner as the first embodiment for message-creating means described herein. In this embodiment, the LCD key acts essentially as a light shutter.
To construct the present invention, means are needed for enabling an LCD to be translated from one position to another position in such a manner that the means for creating message symbols are activated to display, or terminate the display of, a message on the LCD. In some cases, the LCD
automatically returns to the first position.
Figure 3 shows one embodiment of the LCD key wherein a spring mechanism 30 is utilized in translating a reflective LCD 10 from a neutral position to a depressed position and then back to the neutral position.
The spring mechanism may comprise a mechanical spring, an elastomeric material, or another mechanism or material which can be compressed a small distance with moderate fingertip pressure and which automatically returns to the neutral position immediately after fingertip pressure is removed. A com-pression distance of .020 inch is usually adequate. Not indicated in Figure 3 are guide brackets and other hardware needed to restrict the translation to a specified direction and to keep the LCD key properly centered in the mounting structure 31 and 32. Methods for fabricating spring mechanisms of the type shown in Figure 3 are well known to persons skilled in making push-button keys.
The LCD key may be translated in any convenient direction relative to the key and mounting structure. The direction of translation in Figure 3 is perpendicular to the approximate plane of the reflective LCD 10. Al-ternatively, an LCD might move in a direction approximately parallel to the plane of the LCD so that the LCD slides back and forth. This invention is intended to encompass translation-enabling means in which translation of the LCD key is at an arbitrary direction relative to the LCD.

In Figure 3, a message is displayed on the LCD key only when the , . . .

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spring mechanism 30 is at its neutral posltion and the LCD contacts 21 and 22 are touching the external electrical contacts 33 and 34 located on the front panel 31 of the mounting structure. As the LCD key is depressed, the contacts are broken and a signal is generated to the external power source and logic circuit to allow the message on the LCD to be changed. The LCD
key of Figure 3 can be conveniently employed with any of the specific message-creating means previously described. In these situations, the logic circuit causes the electric power source to energize only those external contacts that are necessary to create the desired message.
Figure 4 shows another embodiment of the LCD key. In this embodi-ment, a reflective LCD 10 is situated on a sheet of conductive elastomer 35 which is in turn situated over the contact pattern 36 of a printed circuit board 37. The printed circuit board 37 forms part of the back panel 32 of the mounting structure. Translation of the LCD is controlled by the con-ductive elastomer 35 and two or more leaf springs 38 and 39 attached to the LCD near the ends of the back plate 13. The leaf springs 38 and 39 are connected to the electroconductive coatings or the glass plates 12 and 13 through LCD leads which are not shown. The leaf springs 38 and 39 are ;
connected to the external power source through the external leads 40 and 41. ;
In this embodiment, the leaf springs 38 and 39 serve both as part of the message-creating means and as part of the translation-enabling means for the LCD.
As the reflective LCD 10 is depressed, the conductive elastomer 35 touches the contact pattern 36 of the circuit board 37 causing the logic circuit to initiate operation. The external power source then activates the LCD through the leaf springs 38 and 39 to display the desired message on the LCD. Any of the previously described means for creating message symbols on the LCD may be conveniently utilized with the embodiment illustrated in Figure 4.
The theory and modes of operation for an LCD are known in the prior art. For example, see the discussion by Goldmacher et al. in U.S. Patent No. 3,499,702.

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In the case of a reflective LCD of the type illustrated in Figure 1, operation is basically as follows. Light passing through the front polarizer 23 is plane polarized. In the absence of an electric field, the plane of polarization of the light rotates through the previously discussed twist angle as the light passes through the liquid-crystal material 11. This rotation results from the birefringement properties of the liquid-crystal materi~ 11. As the light reaches the back polarizer 24 the light is largely transmitted, partially transmitted, or largely absorbed by the back polarizer 24, depending on the twist angle and the orientation of the 12 two polarizers 23 and 24 relative to each other. For a 90 degree twist angle, the light is largely transmitted if the polarizer 23 and 24 are crossed. If the polarizers 23 and 24 have their polarization directions parallel to each other, the light is largely absorbed by the back polarizer 24 in the absence of an electric field.
If an electric field of sufficient strength is applied across certain regions of the liquid-crystal material 11, the liquid-crystal molecules in the vicinity of the field reorient their dipole axes in the direction of the electric field -- i.e., perpendicular to the direction of alignment in the absence of an electric field. Light passing through the front polarizer 23 now maintains the same-plane of polarization as the light passes through the liquid-crystal molecules in the vicinity of the electric field. Light reaching the back polarizer 24 is then trans-mitted or absorbed in different amounts than the amounts transmitted or absorbed when no electric field is applied. The light is largely absorbed if the polarizers 23 and 24 are crossed. If the polarizers 23 and 24 are parallel to each other, the light is largely transmitted in the presence of a sufficiently strong electric field. ;
Essentially the same transmission-absorption phenomenon occurs with light that has passed through the LCD once and has been turned back toward the LCD by the reflector 25. Reflected light reaching the front polarizer 23 is largely transmitted, partially transmitted, or largely absorbed by the front polarizer 23 depending on the twist angle, the orien-;3~
tation of the polarizers 23 and 24 relative to each other, and whether the reflected light passes through a region of the LCD where the electric field exists. In fact, application of the reflective LCD 10 to show message symbols is based principally on light reflected back through the LCD. By applying an`electric field across some certain regions of the reflective LCD 10 but not across other regions a time-varying picture can be displayed in which some areas of the LCD are dark and other areas are light.
From the foregoing discussion it follows that a patterned electro-conductive coating can be used to present a message on an LCD in any one of at least four distinct modes. By employing a 90-degree tvist angle, crossing the polarizers 23 and 24, and forming the electroconductive coating on one of the plates in the shape of the desired symbol, the message appears as a dark symbol on a light background when an electric field is established `-across the coated area by energizing the leads to that area. For parallel polarizers, the message becomes visible as a light symbol on a dark back-ground when the LCD is energized to create an electric field across the coated area. In either of these two modes, the background usually remains the same color. The message appears as a change in the color of the area of the symbol.
Alternatively, electroconductive coating can be deposited over an entire segment of one of the plates except over the region of the message ` symbol -- i.e., precisely opposite to what is done for the first two modes.
For a 90-degree twist angle and crossed polarizers, the message appears as a light symbol on a dark background when the LCD is activated. With the polarizers parallel to each other, the message becomes visible as a dark symbol on a light background upon energization of the LCD to establish an electric field across the coated area. In each of these two modes, the area of the message symbol usually remains the same color. The message appears when the background changes color. -The preceding four modes apply to patterned electroconductive coatings in which different messages are presented in separate areas of an LCD and to patterned electroconductive coatings wherein messages overlie each other on the LCD.
Using these four modes, the LCD key having patterned electro-conductive coatings operates in the following manner. The LCD is initially activated through the external power source and logic circuit to show a first message on the key by energizing the leads appropriate for the first message. The LCD is translated from one position to another position.
Typically, this translation is accomplished by the operator pushing the key with his/her finger, using the translation-enabling means to guide the translation. In some cases, the translation-enabling means automatically returns the LCD to the first position. The translation acts in such a man-ner as to cause the first message to be cleared by deactivation of the LCD.
For instance, in the embodiment of Figure 3, the LCD contacts 19 and 20 separate from the external contacts 33 and 34, breaking the electrical cir-cuit to deactivate the LCD and clear the message. The translation causes a signal to be supplied to the external power supply and logic circuit.
Again, for example, in the embodiment in Figure 3, the signal is caused by the separation of the LCD contacts 19 and 20 from the external contacts 33 and 34. As the result of this signal~ the LCD is reactivated to display `!
a second message on the key by energization of the leads appropriate to the second message. Depending on the particular embodiment of the key, the second message may appear at some point during the translation or immediately after the key has reached its final position~ ;~
If no message is to be displayed when the key reaches its final position, the step involving supplying a signal to the external power supply and reactivation of the LCD is not performed. After the key reaches its final position, it remains in the non-activated state and displays a blank screen. Conversely, if no message is to be displayed initially, the steps involving initial activation of the LCD and deactivation as the re-sult of the translation are not performed.
An LCD may operate in at least four distinct modes where decals !
are utilized in creating messages. In these four modes, the area of the message symbol on the decal usually stays the same color on the I.CD. The ,. . . .

,i7 message appears as the background changes color. Using 90-degree twist angle, crossed polarizers, and a light-colored symbol on the decal, the message becomes visible as a light symbol on a dark background when the LCD
is activated. With parallel polarizers and a dark-colored symbol, the message appèars as a dark symbol on a light background upon activating the LCD. For parallel polarizers and a light-colored symbol, the message is visible as a light symbol on a dark background when the leads to the area of the symbol are not energized. Similarly, using crossed polariæers and a dark-colored symbol, the message is visible as a dark symbol on a light backgro~md when the leads to the area of the decal are not energized.
In these last two modes, the message disappears as the appropriate leads are energized and reappears as these leads are deenergized.
Using these four modes, the LCD key having decals operates in one of two ways. When one of the first two modes is employed such that a message appears when the LCD is activated, the key operates in precisely the same manner as a key having patterned electroconductlve coatings.
With one of the last two modes, the LCD key having decals operates in the following manner. The LCD is initially activated to show a first message by energizing the leads for all other messages except the leads for the first message. The LCD is translated from one position ~o another position. Again, in some cases, the LCD is translated back to the first position. The translation causes a signal to be supplied to the external power source and logic circuit. As the result of this signal, the first message is cleared by energization of the lead or leads appropriate to the first message and a second message appears on the LCD by deenergization .
of the lead or leads appropTiate to the second message.
If no message is to be displayed when the key reaches its final position, the step involving deenergization of the lead or leads for the second message is not performed. Conversely, if no message is to be displayed initially, the lead or leads appropriate to the first message are energized when the leads to all the other messages are enerigized. ;~
The programmable LCD key acts to draw the operator's attention ~'2~

actively to the key and thus greatly reduces operator confusion and saves operator time.
~ Vhile the invention has been described with reference to particular embodiments, the description is solely for the purpose of illustration and is not to be construed as limiting the scope of the invention claimed below. For example, a transmissive LCD may be utilized as well as a reflective LCD in the LCD key~

Claims (19)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A key for message display in which said key comprises:
a liquid-crystal display (LCD);
means for creating at least one message symbol on said LCD; and means for enabling said LCD to be translated from a first posi-tion, the translation causing said message-creating means to change the message on said LCD.

2. A key according to Claim 1 in which said LCD includes:
a region of liquid-crystal material;
two transparent plates sandwiched about said liquid-crystal material, the inside faces of said plates being the faces nearest said liquid-crystal material;
means for keeping said liquid-crystal material between said plates;
means for establishing preferred orientations of the molecules of said liquid-crystal material in the absence of an electric field; and two polarizers sandwiched about said plates.

3. A key according to Claim 2 in which said LCD further includes a light reflector behind and adjacent to one of said polarizers.

4. A key according to Claim 3 in which said message-creating means comprises:
electroconductive coatings on the inside faces of said plates;
and electrical lead means connected to said coatings for supplying electrical signals to said coatings at selected times;

5. A key according to Claim 4 in which the coating on at least one of said plates includes a discrete pattern in the shape of a desired message symbol.

6. A key according to Claim 4 in which the coating on at least one of said plates includes at least one discrete pattern selectively utilizable to form at least one desired message symbol.

7. A key according to Claim 4 in which said message-creating means further includes a decal having a discrete pattern in the shape of a desired message symbol, said decal located on said LCD outside said liquid-crystal material.

8. A key according to Claim 4 in which said message-creating means further includes at least one decal having at least one discrete pattern selectively utilizable to form at least one desired message symbol, each decal located on said LCD outside said liquid-crystal material.

9. A key according to Claim 8 in which light which has passed through said liquid-crystal material is substantially not transmitted through each discrete pattern.

10. A key according to Claim 8 in which said translation-enabling means comprises a spring mechanism attached to said LCD to control and facilitate translation of said LCD between the first position and at least one other position.

11. A key according to Claim 10 in which said translation-enabling means further includes guide means to restrict translation of said LCD
to at least one specified trajectory between the first position and said at least one other position.

12. A key according to Claim 11 in which said guide means restricts translation of said LCD to a direction substantially perpendicular to the plane tangent to the center of the inside face of one of said plates.

13. A key according to Claim 6, 7, or 8 in which said electrical lead means includes at least one electrical lead per each of said coatings; and said message-creating means includes at least two electrical contacts situated on said key and selectively connected to said electrical leads whereby said electrical contacts are caused to touch external electrical contacts for supplying the electrical signals to a selected number of said electrical leads when said LCD is at the first position.

14. A key according to Claim 8 in which said translation-enabling means comprises:
at least two leaf springs attached to said LCD and connected selectively to said electrical leads for supplying the electrical signals to a selected number of said electrical leads; and a sheet of conductive elastomer located behind and contiguous to said LCD, the combination of said leaf springs and said sheet of con-ductive elastomer acting to control and facilitate translation of said LCD
between said first position and at least one other position, whereby said sheet of conductive elastomer contacts a printed circuit board when said LCD reaches said at least one other position to change the message display.

15. A key according to Claim 14 in which said combination restricts translation of said LCD to a direction substantially perpendicular to a plane tangent to the center of the inside face of one of said plates.

16. A method for controlling the message display on a liquid-crystal display (LCD) comprising the steps of:
displaying a first message on the LCD while the LCD is at a first position;
translating the LCD from the first position; and changing the first message in response to a signal caused by the translation.

17. A method according to Claim 16 in which said step of changing comprises clearing said LCD to show a blank screen on said LCD;

18. A method according to Claim 16 in which said step of changing comprises clearing the first message from said LCD and displaying a second message on said LCD.

19. A method according to Claim 16, 17, or 18 including the step of returning said LCD to the first position.