Patent Application
20060197442
This application claims priority from European Patent Application No. 05004551.7 filed Mar. 2, 2005, the entire disclosure of which is incorporated herein by reference
The invention concerns an electro-optical matrix display device such as a liquid crystal cell (LCD) comprising an overall rectangular substrate plate and a control circuit.
The invention concerns in particular a “chip on glass” type display device, i.e. a device wherein the control circuit is arranged directly on one face of the substrate plate, and more specifically of the type which is fitted with a single control circuit for addressing lines and columns.
This type of display device is well known and is widely used, in particular in portable electronic apparatus such as portable telephones, watches, remote controls . . . All of these apparatus are tending to be miniaturised, such that the surface dimension of the display device can be inconvenient. This is particularly true in the case of a narrow rectangular display device whose longitudinal dimension is several times larger than the transverse dimension.
One example of this type of display device is disclosed and shown in US A 2002/075439.
Another example is schematically shown in
In order to minimise the surface dimension of display device 10, the connection pads 26 arranged on the main edge 28 of control circuit 22, on the matrix side, are connected to the closest and most numerous electrodes, i.e. transverse electrodes 16 which thus form the columns. The other connection pads 26 of control circuit 22 are thus connected to longitudinal electrodes 18 which form the lines.
It will be noted that the electrodes forming the lines, addressed by dedicated connection pads of the control circuit, can be designated by the term “common”, and the electrodes forming the columns, addressed by dedicated connection pads of the control circuit, can be designated by the term “segments”.
The control circuits are designed in accordance with this connection mode, i.e. the connection pads located on the main edge are dedicated to addressing the columns, and the connection pads located on either side of the main edge are dedicated to addressing the lines.
This is of non-negligible importance since, because of the design of the control signals, the electronic circuits used for addressing a line, or common, must be much more powerful than those used for addressing a column, or segment. The control circuit is thus chosen as a function of the number of lines that it is capable of addressing, so as to minimise its complexity, cost and power consumption.
However, certain new applications necessitating display devices that are particularly narrow transversely, require the control circuit to be mounted at the longitudinal end of the display device. The connection pads addressing the columns are then connected to the longitudinal electrodes, and the connection pads addressing the lines are connected to the transverse electrodes.
This type of assembly is expensive since, as the number of transverse electrodes is much greater than the number of longitudinal electrodes, the control circuit has to be oversized, i.e. include a large number of dedicated line addressing connection pads, which leave a large number of unused dedicated column addressing connection pads. The silicon surface necessary to make this control circuit is larger thus, in addition to the higher cost, this causes an encumbrance for the top circuit.
It is an object of the invention to overcome these drawbacks by proposing a display device having a reduced surface dimension while minimising cost price thereof.
Thus, the invention proposes an electro-optical matrix display device including at least one bottom substrate plate of overall rectangular shape carrying an electro-optical layer, a series of transverse N electrodes and a series of longitudinal M electrodes forming a display matrix, and including a control circuit which is fixed to the bottom substrate plate and which includes connection pads connected to the two series of electrodes by conductive paths, one part of the connection pads being dedicated to the addressing the matrix columns and another part of the connection pads being dedicated to addressing the matrix lines, characterized in that the control circuit is arranged on a longitudinal end portion of the bottom substrate plate, and in that the connection pads addressing the columns are connected to the transverse electrodes and the connection pads addressing the lines are connected to the longitudinal electrodes.
The display device thereby formed minimises the number of dedicated line addressing connection pads on the control circuit, which means that that a more economical control circuit consuming less energy can be used.
According to another feature of the invention, the control circuit includes a transverse edge provided with dedicated column addressing connection pads, the dedicated line addressing connection pads being arranged on at least one side of the dedicated column addressing connection pads.
This feature enables the display device to use a conventional display circuit which minimises the cost thereof.
According to another feature of the invention, part of the line addressing connection pads are connected to the corresponding longitudinal electrodes via a vertical connection zone which extends along a longitudinal direction.
This feature enables the addressing order of the line addressing connection pads to correspond to the physical order of the longitudinal electrodes, to facilitate the control circuit programming operations.
According to another feature of the invention, the control circuit package includes a transverse edge provided with dedicated line addressing connection pads, the dedicated column addressing connection pads being arranged on at least one side of the dedicated line addressing connection pads.
This feature enables a more compact display device to be obtained along the transverse and longitudinal directions.
The invention also proposes a control circuit designed to be fitted to the aforementioned display device.
Other features and advantages of the present invention will appear more clearly upon reading the following detailed description, made with reference to the annexed drawings, given by way of non-limiting example and in which:
In the following description, similar or identical elements will be designated by the same references.
In the following description vertical, longitudinal and transverse orientations will be used, in a non-limiting manner, in accordance with the marks V, L, T shown in the Figures.
Display device 10 includes a bottom substrate plate 12 and a top substrate plate 14 of overall rectangular shape, which are bonded to each other so as to trap an electro-optical layer formed here by a layer of liquid crystals. The lengths of plates 12, 14 extend here along the longitudinal direction and the widths of plates 12, 14 extend here along the transverse direction.
The inner faces 32, 34, i.e. the faces oriented towards electro-optical layer 30, of bottom plate 12 and top plate 14 respectively carry a series of N transverse electrodes 16 and a series of M longitudinal electrodes 18 which form a display matrix 11.
Of course, according to an alternative embodiment (not shown), the transverse electrodes 16 could be carried by top plate 14 and the longitudinal electrodes 18 by bottom plate 12.
Moreover, display matrix 11 could be designed to be seen, either from above, through top plate 14, or from below, through bottom plate 12.
By way of example, the display matrix 11 shown includes N=100 transverse electrodes 16 and M=20 longitudinal electrodes 18.
Each intersection of a transverse electrode 16 with a longitudinal electrode 18, in matrix 11, corresponds here to a pixel, such that display matrix 11 forms an active display zone formed of a pixel matrix. However, the invention also applies to a display matrix 11 including one or several physical icons addressed in a similar way to a pixel, i.e. by the intersection of at least one transverse electrode 16 with one longitudinal electrode 18.
In accordance with “chip on glass” (COG) technology, a control circuit 22 is directly fixed to a portion 36 of bottom substrate plate 12, here on its inner face 32, and its connection pads 26 are connected to the two series of electrodes 16, 18 by conductive paths 24. Portion 36 of bottom plate 12 which carries control circuit 22 is not covered by top plate 14.
In accordance with the teaching of the invention, control circuit 22 is arranged on a longitudinal end portion 36 of bottom plate 12, here the left end in
Control circuit 22 has the overall shape of a rectangular plate comprising a main, generally transverse, edge 40 which is arranged on the side of display matrix 11. Main edge 40 is provided with a series SC of connection pads 26 dedicated to addressing columns C.
Control circuit 22 comprises, on either side of main edge 40, a first series S1L and a second series S2L of connection pads 26 dedicated to addressing lines L. According to the embodiment shown here, the connection pads 26 of the first series S1L, at the top of
It will be noted that it is possible to use only the first series S1L of connection pads 26 if it comprises a sufficient number of connection pads 26 to address all of lines L of display matrix 11.
According to another feature of the invention, connection pads 26 addressing columns C are connected to transverse electrodes 16 and connection pads 26 addressing lines L are connected to longitudinal electrodes 18.
Transverse electrodes 16 are electrically connected to series SC of connection pads 26 addressing columns C by conductive paths 41 arranged on inner face 32 of bottom plate 12.
According to the embodiment shown here, a first series S1C of connection pads 26 addressing half of columns C is connected to transverse electrodes 16 of one side of matrix 11, at the bottom of
This type of connection enables the transverse space requirement due to conductive paths 41 to be distributed on either side of matrix 11.
In order to allow connection pads 26 addressing lines L, which are carried by bottom plate 12, to be electrically connected to longitudinal electrodes 18, which are carried by top plate 14, first Z1 and second Z2 vertical connection zones are provided, arranged in proximity to the peripheral edge of top plate 14. These vertical connection zones Z1, Z2 comprise here an anisotropic conductive adhesive material which conducts the electrical current vertically only. This adhesive material is deposited over the entire peripheral edge of top plate 14 to fix top plate 14 onto bottom plate 12. The adhesive material is made anisotropically conductive for example by means of conductive balls. This connection technology can be called “contact in seal”.
Of course, vertical connection zones Z1, Z2 could be achieved by other means, for example by contact points arranged in a suitable manner.
Each of vertical connection zones Z1, Z2 extend here over a transverse segment of the peripheral edge of top plate 14, at the border between top plate 14 and the longitudinal end portion 36 that is not covered by bottom plate 12.
A first series of bottom conductive paths 42 is arranged on inner face 32 of bottom plate 12 so as to electrically connect the first series S1L of connection pads 26 addressing lines L to the first vertical connection zone Z1.
A second series of bottom conductive paths 44 is arranged on inner face 32 of bottom plate 12 so as to electrically connect the second series S2L of connection pads 26 addressing lines L to the second vertical connection zone Z2.
Likewise, a first series of top conductive paths 46 is arranged on inner face 34 of top plate 14 so as to electrically connect the longitudinal electrodes 18 corresponding to lines M/2 to first vertical connection zone Z1
A second series of top conductive paths 48 is arranged on inner face 34 of top plate 14 so as to electrically connect the longitudinal electrodes 18 corresponding to lines M/2+1 to M to second vertical connection zone Z2.
It should be noted that in order to facilitate comprehension of the diagrams, conductive paths 41, 42, 44, 46, 48 and connection pads 26 have been partially shown.
It will be noted that conductive paths 41 connected to columns C intersect connective paths 46, 48 connected to lines L outside display matrix 11. These intersections are possible, without any short-circuit problems, since they occur in a zone where conductive paths 46, 48 connected to lines L are carried by top plate 14. These intersections can cause pixels to be activated in the active crystals, outside display matrix 11. However, this activation is not detrimental since it occurs outside the active display zone formed by matrix 11.
The display device 10 obtained according to the first embodiment has the advantage of being particularly compact widthways, here along the transverse direction. Moreover, it is compatible with a conventional control circuit 22, i.e. of the type used in display devices according to the state of the art, which minimises the manufacturing and referencing costs.
Other embodiments of display device 10 according to the invention will now be presented. These embodiments will be described mainly as a function of their differences as regards the first embodiment.
Referring to
The second embodiment of display device 10 according to the invention, which is shown in
Thus, the first series S1L of bottom conductive paths 42 extends under top plate 14 so as to reach the closest longitudinal edge 50 of conductive plate 14, where the first vertical connection zone Z1 is located. The associated top conductive paths 46 go from this longitudinal edge 50 towards the corresponding longitudinal electrodes 18, with a reverse order relative to the first embodiment.
Owing to this configuration, the connection pads 26 addressing lines 1 to M/2 are connected in ascending order to longitudinal electrodes 18, from the outside of display matrix 11 inwards.
According to a third embodiment (not shown) of the invention, control circuit 22 includes an reversal device which is operated for reversing the order of the first series S1L of connection pads 26 addressing lines 1 to M/2, which enables the order of connection pads 26 addressing lines L to be made to match the physical order of longitudinal electrodes 18 in matrix 11.
Advantageously, control circuit 22 also includes an inverting device which is operated to invert the order of connection pads 26 addressing columns N/2+1 to N, which also enables the order of connection pads 26 addressing columns C to be made to match the physical order of transverse electrodes 16 in matrix 11.
Preferably, these inverting devices are achieved by means of electronic components integrated in control circuit 22 and can be controlled in a reversed mode and in a normal mode, which enables control circuit 22 to be used in a display device 10 that does not require reversal of the order of connection pads 26.
The conductive paths 41 connect connection pads 26 of the first series S1C to a third vertical connection zone Z3 which extends transversely. This third vertical connection zone Z3 is connected, by conductive paths 43 carried by top plate 14, to a fourth vertical connection zone Z4, which extends longitudinally and which returns addressing data down to bottom plate 12, where conductive paths 45 form the connection with the corresponding transverse electrodes 16.
The reversal of the addressing order of connection pads 26 of the first series S1C is achieved along the same principle as that used in the second embodiment (
Of course, connection pads 26 of the second series S2C addressing columns C are connected to the corresponding transverse electrodes 16 as in the embodiments previously described, without passing through top plate 14.
According to this fourth embodiment, matrix 11 has only ten lines L which are addressed by a single series SL of connection pads 26 addressing lines L, located on only one side of connection pads 26 addressing columns C. These connection pads 26 are connected to longitudinal electrodes 18 via a single vertical connection zone Z1, such that it is not necessary to reverse the addressing order as in the second embodiment (
According to a fifth embodiment of display device 10 according to the invention, which is shown in
As for the preceding embodiments, the connection pads 26 addressing columns C are connected to transverse electrodes 16 and the connection pads 26 addressing lines L are connected to longitudinal electrodes 18.
It will be noted that bottom conductive paths 42, 44 could be connected to top conductive paths 46, 48 at the heart of the same vertical connection zone Z1, Z2.
This embodiment provides a display device 10 that is even more compact, both in the longitudinal direction and in the transverse direction, owing to a simpler conductive path connection diagram, which avoids intersections of conductive paths 41, 42, 44, 46, 48 outside display matrix 11.
Moreover, this embodiment enables the order of all of connection pads 26 to be made to match the physical order of transverse electrodes 16 and longitudinal electrodes 18 in matrix 11.
According to a variant of this fifth embodiment, control circuit 22 includes electronic means that make the connection pads 26 arranged on the main edge 40 able to address columns C of matrix 11 and which make the connection pads 26 arranged on the longitudinal edges able to address lines L of matrix 11. Moreover, control circuit 22 includes selection means which are operated to assign a determined type of dedicated addressing to each series of connection pads 26.
The selection means include for example two states: a first state in which the connection pads 26 of main edge 40 are dedicated to addressing columns C, the other connection pads 26 addressing lines L, and a second state in which the connection pads 26 of main edge 40 are dedicated to addressing columns L, the other connection pads 26 addressing lines C.
In order to make display device 10 of
| Number | Date | Country | Kind |
|---|---|---|---|
| 05004551.7 | Mar 2005 | EP | regional |
