CH712577B1 - Liquid crystal display device with touch keys. - Google Patents

Abstract

A liquid crystal display device includes a front substrate (2) and a back substrate (6) that extends parallel to and away from the front substrate (2), the front (2) and rear substrates (6) being joined together by means of a sealing frame (8) which delimits a sealed enclosure (10) for the confinement of a liquid crystal, at least a first electrode (12) being structured on a lower face ( 14) of the front substrate (2), and at least one second opposite electrode (16) being structured on an upper face (18) of the rear substrate (6), the optical properties of the liquid crystal being modified by applying a voltage appropriate at the point of intersection of the first and second electrodes (12, 16) considered, the at least one first electrode (12) and the at least one second electrode (16) being made of an electrically conductive transparent material ur and being extended towards the outside of the liquid crystal display device (1) by a first, respectively a second electrically conductive tracks structured on the lower face (14) of the front substrate (2), at least one third electrode ( 26) defining a capacitive touch zone being structured on an upper face (28) of the front substrate (2), said third electrode (26) being made of an electrically conductive transparent material and being extended by a third electrically conductive track (32) with which a connection pin (40) is in electrical contact to connect the third electrode (26) with an external control device (30), at least one protective layer or polarizer (34) being fixed on the upper face (28). ) of the front substrate (2) and covering the third electrode (26).

Description

Description

TECHNICAL FIELD OF THE INVENTION [0001] The present invention relates to a display device provided with tactile keys. The present invention particularly relates to a display device of the liquid crystal type comprising such tactile keys.

BACKGROUND OF THE INVENTION [0002] In its simplest sense, a liquid crystal display cell comprises a front substrate oriented toward the observer and a rear substrate that extends parallel to and at a distance. of the front substrate. The front and rear substrates are joined together by means of a sealing frame which delimits a sealed enclosure for the confinement of a liquid crystal. A lower surface of the front substrate carries at least one electrode and an upper surface of the rear substrate carries at least one corresponding counter electrode. By applying a suitable voltage between the electrode and the counter-electrode, it is possible to modify the optical properties of the liquid crystal at the crossing point of the electrodes in question.

It is already known to associate with a liquid crystal display device of the type briefly described above a control data input device of the touch-sensitive type. Such a data input device typically comprises a flexible or rigid film on a lower surface of which are structured touch control keys which are made by means of a conductive material such as tin-indium oxide, also known under its name Anglo-Saxon Indium-Tin Oxide or ITO. Each of these tactile keys forms an armature of a capacitor whose other armature is formed by the portion of an upper surface of the flexible or rigid film that faces the touch key. By placing a finger on one of these touch keys, the user modifies the value of the capacity detected by this touch key, which causes the introduction of a control signal in a microcontroller to which the touch keys of the data input device are conventionally connected by means of a flexible connection cable. Once fabricated, the touch-sensitive data input device is typically laminated to the upper surface of the front substrate of the liquid crystal display device.

One of the interests of the above assembly is that it provides a set of display and monobloc control that can easily be integrated for example in the volume of the box of a portable object such than a wristwatch. However, the manufacturing costs of such a set of display and control are relatively high. It is indeed necessary to separately manufacture the liquid crystal display device and the touch-sensitive control device, and then assemble these two elements.

Moreover, on its own, the touch-sensitive control device which requires, on the one hand, a flexible or rigid film on which the tactile control keys are structured, and on the other hand a flexible connection cable, is expensive.

Finally, the electrical connection of such a display and one-piece control unit must be in two distinct steps which consist for one to connect the liquid crystal display cell to an external control device, and for the other to connect the touch-sensitive controller to the same external control device or a second external control device separate from the first. These electrical connection operations are time consuming. SUMMARY OF THE INVENTION [0007] The object of the present invention is to overcome the disadvantages mentioned above as well as others by providing a liquid crystal display device provided with tactile keys whose cost price is substantially lowered. .

For this purpose, the present invention relates to a liquid crystal display device comprising a front substrate and a rear substrate which extends parallel to and away from the substrate before, the front and rear substrates being joined together to means of a sealing frame which delimits a sealed enclosure for the confinement of a liquid crystal, at least a first electrode being structured on a lower face of the front substrate, and at least a second opposite electrode being structured on an upper face of the rear substrate, the optical properties of the liquid crystal being modified by applying an appropriate voltage at the point of intersection of the first and second electrodes in question, the at least one first electrode and the at least one second electrode being made in one electrically conductive transparent material and being extended outward of the liquid crystal display device by a first, respectively a second electrically conductive tracks structured on the lower face of the front substrate, at least a third electrode defining a capacitive touch zone being structured on an upper face of the front substrate, this third electrode being made of an electrically conductive transparent material and being extended by a third electrically conductive track with which a connection pin is in electrical contact for connecting the third electrode with an external control device, at least one protective layer or a polarizer being fixed on the upper face of the front substrate and covering the third electrode.

According to an additional characteristic of the invention, first and second connection pins in electrical contact with the first and the second electrically conductive track, respectively, make it possible to connect the first and second electrodes to the same external control device as the third electrode or to a separate external control device.

With these features, the present invention provides a liquid crystal display device with capacitive touch keys that can be manufactured in a reduced number of steps and the cost is very advantageous.

Indeed, the first electrodes which, in cooperation with the second electrodes, make it possible to modify the optical properties of the liquid crystal of the display device, and the third electrodes which define the tactile keys are all structured on the front substrate, respectively on the lower face and on the upper face of the latter. Therefore, all of these electrodes can be made using the same manufacturing techniques such as photolithography, and preferably using the same electrically conductive material. It is understood that such rationalization of the production operations of the liquid crystal display device according to the invention saves time and achieve economies of scale which have a positive impact on the final cost of this device. display. In particular, it is not necessary to separately manufacture a device for inputting control data with tactile keys, which makes it possible to economize the flexible or rigid film on which the electrodes were structured and the flexible connection cable associated.

Furthermore, thanks to the presence of the connecting pins, the liquid crystal display device according to the invention can be very easily connected to an external control device by simply pushing the pins in corresponding holes in a printed circuit board, also known under the name Anglo-Saxon Printed Circuit Board or PCB.

BRIEF DESCRIPTION OF THE FIGURES [0013] Other features and advantages of the present invention will emerge more clearly from the following detailed description of an exemplary embodiment of a liquid crystal display device according to the invention, this example being given purely for illustrative and not limiting purposes only in connection with the appended drawing in which: FIG. 1 is a top view in perspective of a liquid crystal display device provided with tactile keys according to the invention; fig. 2 is a sectional view along the line 11-11 of FIG. 1 which illustrates the electrical connection between a connecting pin and a first electrically conductive track for connecting a first structured electrode on a lower face of the front substrate with an external control device, and FIG. 3 is a sectional view along the line III-III of FIG. 1 which illustrates the electrical connection between a connecting pin and a third electrically conductive track for connecting a third electrode structured on an upper face of the front substrate with the external control device.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION [0014] The present invention proceeds from the general inventive idea which consists in structuring on one and the same transparent substrate on one side one or more electrodes necessary for controlling the optical properties of a liquid crystal, and on the other side one or more electrodes which form as capacitive touch keys allowing a user to introduce commands into a control device outside the liquid crystal display device according to the invention. Thanks to these features, the present invention makes it possible to produce a device that is able both to display information and to take into account instructions from a user in a limited number of manufacturing steps, using a same material and on the same element. Savings in manufacturing costs and components required for manufacturing are sensitive. On the other hand, it is sufficient to push the connection pins into corresponding holes in a printed circuit board to be able to connect the liquid crystal display device according to the invention to an external control device. The electrical connection operations of the liquid crystal display device according to the invention are therefore reduced to the maximum, which also allows savings on the manufacturing time.

The invention will be described in part with reference to FIGS. 1 and 2 attached to this patent application. As is apparent from the examination of these two figures, the liquid crystal display device according to the invention, generally designated by the general reference numeral 1, comprises a front substrate 2 situated on the side of an observer 4, and a rear substrate 6, disposed parallel to and away from the front substrate 2. The front substrate 2 and the rear substrate 6 are joined to each other by means of a sealing frame 8 which delimits a sealed enclosure 10 for the confinement of a liquid crystal. A plurality of first electrodes 12 is structured on a lower face 14 of the front substrate 2, and a plurality of second electrodes 16 is structured on an upper face 18 of the rear substrate 6. These first and second electrodes 12 and 16 are made of a material transparent conductor of electricity, for example tin-indium oxide, by means of etching techniques such as photolithography, and control the optical properties of the liquid crystal contained in the sealed enclosure 10.

The first electrodes 12 are extended towards the outside of the liquid crystal display device 1 by first conductive tracks 20 which are structured on the lower face 14 of the front substrate 2. The second electrodes 16 which are structured on the upper face 18 of the rear substrate 6 are returned to the lower face 14 of the front substrate 2 and are extended towards the outside of the liquid crystal display device 1 by second conductive tracks 24. Preferably, these first and second conductive tracks 20, 24 are produced using the same material and the same etching techniques as the first and second electrodes 12, 16. These first and second conductive tracks 20, 24 extend close to the edge or to the edge of the front substrate 2.

A plurality of third electrodes 26 which define capacitive touch zones are structured on an upper face 28 of the front substrate 2. These third electrodes 26 are made of an electrically conductive transparent material which is preferably the same as the one used. to produce the first and second electrodes 12, 16. Preferably, these third electrodes 26 are made by the same manufacturing techniques as those used for the first and second electrodes 12, 16. These third electrodes 26 define contact zones whose capacitance changes when the user places a finger on it, which makes it possible to send a control signal to an external control device 30. These third electrodes 26 are extended towards the edge of the front substrate 2 by third conductive tracks 32 which are structured at the same time as the third electrodes 26.

By way of purely illustrative and in no way limiting example, the liquid crystal used in the liquid crystal display device 1 according to the invention is of the helical nematic type, also well known by its Anglo-Saxon name Twisted Nematic liquid crystal or liquid crystal TN. This implies that the liquid crystal display device 1 is provided with a front polarizer 34 secured to the upper face 28 of the front substrate 2 and covering the third electrodes 26, as well as at least one rear polarizer 36 secured to a bottom face 38 of the rear substrate 6. Depending on whether a positive or negative display contrast is desired, the polarization directions of the forward polarizer 34 and the rear polarizer 36 are crossed or parallel to one another. Alternatively, it is possible to replace the rear polarizer 36 by a reflector, that is to say a polarizer provided with a reflective layer on its rear face, or by a transflector, that is to say say a polarizer associated with a semi-transparent reflective layer.

An examination of FIG. 2 reveals that a first (or second) conductive track 20 or 24, structured on the lower face 14 of the front substrate 2, is flush with the lower edge of the front substrate 2. Through the use of a connection pin 40 it is possible to electrically connect the first (or the second) electrode 12 or 16 corresponding to an external control device 30. This connection pin 40 consists of a rod 42 whose free end is intended to be driven into a hole formed in a printed circuit board 44, and a head 46 comprising two arms 48 which enclose the edge of the front substrate 2 and which make electrical contact with the first (or second) conductive track 20 or 24. Preferably, the maintenance of the connection pins 40 is provided by the elasticity of the arms 48 and can be reinforced by deposition of an adhesive layer.

Similarly, an examination of FIG. 3 reveals that a third conductive track 32, structured on the upper face 28 of the front substrate 2, is flush with the upper edge of the front substrate 2. Thanks to the use of a connection pin 40, it is possible to connect electrically the third electrode 26 to which the third conductive track 32 is connected to the external control device 30. The rod 42 of this connection pin 40 is intended to be depressed by its free end into a hole in the printed circuit board 44, and its two arms 48 enclose the edge of the front substrate 2 and make electrical contact with the third conductive track 32.

It goes without saying that the present invention is not limited to the embodiment which has just been described and that various modifications and simple variants can be envisaged by those skilled in the art without departing from the scope of the invention. as defined by the appended claims. In particular, the present invention has been described in connection with a liquid crystal display device 1 comprising several first, second and third electrodes 12, 16 and 26. It goes without saying that in its simplest sense, the device liquid crystal display 1 may comprise only first and second electrodes 12, 16 for modifying, by application of an electrical voltage at the point of intersection of these two electrodes 12 and 26, the optical properties of the liquid crystal, and a single third electrode 26 to define a single contact zone.

Similarly, the present invention has been described in connection with a liquid crystal display device 1 comprising a nematic-type liquid crystal helix, also well known by its Anglo-Saxon name Twisted Nematic liquid crystal or liquid crystal TN. It goes without saying, however, that other liquid crystals such as Super Twisted Nematic (STN) or guest-host liquid crystal may be considered. In the case of a liquid crystal of the guest-host type, it is possible to dispense with any polarizer.

Similarly, in the above description, it was envisaged the case where the first and the second electrodes 12, 16 which allow to modify the optical properties of the liquid crystal, and the third electrodes 26 which allow the However, it is possible to envisage that the electrodes making it possible to control the liquid crystal on the one hand, and the capacitive touch electrodes on the other hand, are connected to the same external control device 30. connected to two separate external control devices.

It is also conceivable that only the third electrodes 26 which allow the user to input data into the external control device 30 are connected by means of connection pins 40, while

Claims (2)

the first and second electrodes 12, 16 which make it possible to control the optical properties of the liquid crystal can be connected with the external environment for example by means of a Zébra® type connector formed of a succession of insulating sheets, for example made of elastomer and conductive sheets of electricity, for example copper. Nomenclature [0025] A liquid crystal display device comprising a front substrate (2) and a rear substrate (6) which extends parallel to and away from the front substrate (2), the front (2) and back (6) substrates being joined to each other by means of a sealing frame (8) which delimits a sealed enclosure (10) for the confinement of a liquid crystal, at least a first electrode (12) being structured on a lower face (14) of the front substrate (2), and at least one second opposite electrode (16) being structured on an upper face (18) of the rear substrate (6), the optical properties of the liquid crystal being modified by application of a voltage appropriate to the point crossing the first and second electrodes (12, 16) considered, the at least one first electrode (12) and the at least one second electrode (16) being made of a transparent electrically conductive material and being extended s outwardly of the liquid crystal display device (1) by a first, respectively a second electrically conductive tracks (20, 24) structured on the underside (14) of the front substrate (2), at least a third electrode (26) defining a capacitive touch zone being structured on an upper face (28) of the front substrate (2), this third electrode (26) being made of an electrically conductive transparent material and being extended by a third electrically conductive track (32). ) with which a connection pin (40) is in electrical contact for connecting the third electrode (26) with an external control device (30), at least one protective layer or a polarizer (34) being fixed on the upper face (28) of the front substrate (2) and covering the third electrode (26). 1. Liquid crystal display device 2. Substrate before 4. Observer 6. Rear substrate 8. Sealing frame 10. Waterproof enclosure 12. First electrodes 14. Bottom face 16. Second electrodes 18. Top face 20. First conductive tracks 24. Second conductive tracks 26. Third electrodes 28. Upper face 30. External control device 32. Third conductive tracks 34. Front polarizer 36. Rear polarizer 38. Bottom face 40. Connection pin 42. Stem 44. Printed circuit board 46. Head 48. Arms Claims 2. Display device according to claim 1, characterized in that connection pins (40) in electrical contact with the first, respectively the second electrically conductive track (20, 24), to connect the first and second electrode (12, 16) to the external control device (30) or to a separate external control device.