Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-02-19
2003-03-18
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S160000, C349S151000
Reexamination Certificate
active
06535262
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a display unit in which the activation or driver electronics are disposed on the rear side of a display element.
Flat displays based on LED or LCD technology are increasingly being used in the area of data processing equipment or communication and entertainment electronics. In the process, LCD (liquid crystal diode) technologies are especially becoming widely accepted, on the basis of their contrast, low necessary current and favorable production costs. A customary LCD display in this case includes a top plate that covers the actual liquid crystal element with the liquid crystals and a bottom plate on which the liquid crystal element with the actual liquid crystals is mounted. This sandwich method achieves good protection for the sensitive liquid crystals.
For the electrical activation of the individual liquid crystals, the bottom plate is made larger than the actual liquid crystal, to allow contacts for leading away signal lines to be attached to it. It is customary to use what is known as a flex circuit, that is to say a flat ribbon cable with numerous individual signal lines, to allow the signals to be led to the bottom plate. The actual activation or driver electronics is/are consequently separate from the display unit.
It has also been proposed to dispose the control electronics directly on the protruding part of the bottom plate or bottom glass sheet. Both configurations, known in the prior art, have the disadvantage, however, that the bottom plate must be significantly larger than the actual display area, to allow the flat ribbon cable or the activation electronics to be fastened on it.
Integration of displays, such as LCD displays, in what are known as chip cards has so far not been possible at all on account of the confined lateral space, but in particular on account of the small thickness of chip cards of only at most 0.84 mm (according to ISO 7816, 10373). However, on account of the growing significance of chip cards and the increasing functionality accommodated on them, it would be advantageous also to provide a display capability on chip cards. This applies in particular when a capability of recharging with data or a monetary value is to be used for the purpose of repeated usability.
In the case of customary displays, moreover, the separation of the actual display area and the control electronics involves additional expenditure and further possible sources of faults. It would therefore be advantageous to have a display unit that is more compact, involves lower expenditure to produce and assemble and could possibly be included in chip cards.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a display unit and a method for manufacturing a display unit that overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a display unit for chip cards. The display unit includes a display element having a front side, a rear side, and a liquid crystal layer for the front side of the display unit. The display unit also includes a control element being electrically connected to the display element and disposed as an integrated circuit on the rear side of the display unit opposite from the front side.
With the objects of the invention in view, there is also provided a method of producing an LCD display element for chip cards. The first step of the method is providing a display element having a liquid crystal layer. The next step is providing a control element. The next step is providing a bottom sheet with a side having conductor tracks and a region extending beyond the liquid crystal layer. The next step is attaching the display element on the side of the bottom sheet. The next step is attaching the control element on the side of the bottom sheet in the region extending beyond the liquid crystal layer. The next step is folding the bottom sheet between the display element and the control element to form an edge on the bottom sheet, a face facing toward the liquid crystal layer, and a face facing away from the liquid crystal layer that holds the control element. The next step is leading the conductor tracks around the edge of the bottom sheet.
In one aspect, the invention is directed at a display unit in which a control element is positioned directly behind a display element.
In a further aspect, the invention is directed at a display unit of which the base area corresponds substantially to the base area of the liquid crystal.
In another aspect, the invention is directed at a display unit in which it has been possible for fault-prone plug-in connections largely to be minimized.
Accordingly, the invention is directed at a display unit with a front region with at least one display element, a rear region facing away from the front region, with at least one control element for the activation of the at least one display element and electrical lines for the connection of the at least one display element to the at least one control element.
A control element is to be understood here as meaning any electronic device that is capable of making the respectively used display elements display informational contents. For example, the control element may have a driver circuit or a number of circuits that convert the signals coming from an information-representing device into electric currents suitable for the display element.
The control element may in this case be disposed directly on the rear region or be encapsulated by a package. The package improves the control element stability with respect to external influences. A display element for the purposes of the present invention is understood here as meaning any substantially flat element that is suitable for the display of information, for example multi-element LED display modules, multi-element LCD display modules, which are suitable for the representation of numeric or alphanumeric information, matrix-based LED, LCD or plasma screens, mechanically displaying elements, etc. In this case, one or a number of the display elements respectively used may actually be used, for example a number of LED modules, which are respectively suitable for the display of a figure or a letter.
It is particularly preferred for the display element to have an LCD display. A display element that includes different types of individual elements is also conceivable.
When an LCD display is used, it is preferred for it to have a top layer, a liquid crystal layer, a bottom sheet, and for at least one control element to be disposed on the bottom sheet. The configuration of the control element on the bottom sheet may take place by techniques familiar to a person skilled in the art, for example by adhesive attachment, solder, fixing by common frame, etc. The top layer may, in the way already customary in the case of today's LCD displays, include glass. It may, however, also include a plastic sheet to reduce the thickness of the LCD display and increase the mechanical flexibility, as is necessary for example for use in chip cards. To avoid the absorption of moisture, the plastic sheet may be additionally provided with at least one water-vapor barrier layer.
Also, when other display elements are used as an LCD display, it is preferred for the control element to be disposed directly on the rear side of the at least one display element. In this case, the display element also may have a bottom sheet or bottom plate, which forms its rear side, it then being possible for the control element to be fastened to the bottom sheet or to the bottom plate.
The control element may have a package with a socket. The socket may be connected directly to the bottom sheet or bottom plate. In the case of driver circuits, which have a higher power demand, and as a result greater heat dissipation, this configuration improves cooling. Moreover, it is possible to comply exactly with specifications with respect to the desired depth of a di
Greenberg Laurence A.
Infineon - Technologies AG
Locher Ralph E.
Schechter Andrew
Stemer Werner H.
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