Projective capacitive touch sensor

A projective capacitive touch sensor includes a substrate, a plurality of electrode layers and a plurality of dielectric layers. The electrode layers are arranged on the substrate along a first direction. At least one dielectric layer is formed on each electrode layer and the dielectric layer has different widths along a second direction.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan Patent Application Serial Number 098136810, filed on Oct. 30, 2009, the full disclosure of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

This invention generally relates to a touch control device and, more particularly, to a projective capacitive touch sensor.

2. Description of the Related Art

With the popularity of the portable device, human-machine interface devices have been broadly adapted to portable devices, such as PDAs, cell phones and note books so as to humanize the operation thereof. And the touch screen plays an important role in humanize operation.

Presently, touch screens can mainly be divided into resistive, capacitive, infrared and SAW touch screens. Because the projective capacitive touch screen will not be deteriorated by moisture and the material of its touch surface has no function in touch detection mechanism, it is more suitably adapted to portable devices operated outdoors.

The projective capacitive touch screen mainly detects the capacitance variation of a touch-sensor pad induced by a conductive object approaching thereto so as to detect a position of the conductive object with respect to the touch screen. For exampleFIG. 1shows a sensor array9of a conventional touch-sensor pad that includes a plurality of first sensor elements91coupled together, a plurality of second sensor elements92coupled together and a processing device93, wherein the first sensor elements91and the second sensor elements92are coupled to the processing device93through conductive traces. The first sensor elements91and the second sensor elements92are disposed in a repetitive sequence on the sensor array9along a moving direction of the conductive object. The processing device93respectively calculates capacitance variations of the first sensor elements91and the second sensor elements92so as to identify a two-dimensional position of the conductive object approaching the sensor array9. However, the sensor array9has a double layer structure thereby requiring more complicated process during manufacturing. Details of the sensor array 9 above can be referred to U.S. Patent Publication No. 2008/0007534.

Accordingly, it is necessary to provide a projective capacitive touch sensor having a single layer of sensing units so as to simplify the manufacturing process thereof.

SUMMARY

The present invention provides a projective capacitive touch sensor that has a single layer of sensing units thereby having a simpler manufacturing process.

The present invention provides a projective capacitive touch sensor that changes the capacitance variation of an electrode layer induced by a conductive object approaching thereto by means of changing areas of dielectric layers or the width of a dielectric layer along a predetermined direction thereby detecting a contact position of the conductive object in that direction.

The present invention provides a projective capacitive touch sensor including a subject, a plurality of electrode layers and a plurality of dielectric layers. The electrode layers are arranged on the substrate along a first direction. A plurality of dielectric layers are formed on each electrode layer and the plurality of dielectric layers formed on each electrode layer have different areas along a second direction.

The present invention further provides a projective capacitive touch sensor including a substrate, a plurality of electrode layers and a plurality of dielectric layers. The electrode layers are arranged on the substrate along a first direction. A dielectric layer is formed on each electrode layer and the dielectric layer formed on each electrode layer has different widths along a second direction.

The present invention further provides a projective capacitive touch sensor including a substrate, a plurality of electrode layers and a plurality of dielectric layers. The electrode layers are arranged on the substrate along a first direction. A dielectric layer is formed on each electrode layer and the dielectric layer formed on each electrode layer includes through openings with different areas along a second direction.

In the projective capacitive touch sensor of the present invention, each electrode has a substantially identical width along the second direction. The plurality of dielectric layers formed on each electrode layer have different areas along the second direction, or the dielectric layer formed on each electrode layer has different widths along the second direction, or the dielectric layer formed on each electrode layer includes through openings with different areas along the second direction. In addition, a plurality of slits may further be formed on the electrode layer so as to increase resolution of the position identification, e.g. more silts may be formed surrounding the dielectric layer with a smaller area, outside the section of the dielectric layer with a smaller width or inside the through opening with a larger area.

The projective capacitive touch sensor of the present invention further includes a plurality of conductive traces and a processing unit coupled to all electrode layers through the conductive traces. The processing unit identifies the position of a conductive object with respect to the projective capacitive touch sensor along the first and second directions according to a capacitance variation of the electrode layers induced by the conductive object approaching thereto.

DETAILED DESCRIPTION OF THE EMBODIMENT

Please refer toFIG. 2, it shows a projective capacitive touch sensor1according to an embodiment of the present invention. The projective capacitive touch sensor1includes a substrate11, a plurality of sensing units12, a processing unit13and a plurality of conductive traces141-144. The substrate11may be formed of glass, polymer film or other suitable material. The sensing units12include an electrode layer120that may be, for example, but not limited to, a patterned Indium Tin Oxide (ITO) layer, Antimony Tin Oxide (ATO) layer or Fluorine Tin Oxide (FTO) layer. The sensing units12may be patterned as a plurality of separated sensing units12arranged on the substrate11along a first direction (e.g. Y direction) so as to divide a touch zone15into different regions along the first direction. The electrode layers120preferably have a fixed width along a second direction (e.g. X direction). It is appreciated that, although the sensing units12are shown as two columns inFIG. 2, the present invention is not limited to this. The column number of the sensing units12may be determined according to the resolution actually required.

The processing unit13is coupled to the electrode layer120of a sensing unit12through the conductive traces141-144and is configured to identify the position of a conductive object, e.g. a finger or a touch pen, with respect to the touch zone15along a first direction (e.g. Y direction) and a second direction (e.g. X direction) according to a capacitance variation of the electrode layer120induced by the conductive object approaching (or contacting) a sensing unit12. The processing unit13may be coupled to an electronic device2, e.g. a display. The processing unit13may control the electronic device2to execute corresponding actions according to the identified position of the conductive object. It is appreciated that, numbers of the sensing units12and the conductive traces inFIG. 2are only exemplary and not to limit the present invention.

A plurality of dielectric layers121, e.g. dielectric layers121a-121e, with different areas are formed along the second direction on the surface of the electrode layers120, wherein an area of the dielectric layer121ais larger than that of the dielectric layer121b, an area of the dielectric layer121bis larger than that of the dielectric layer121c, . . . ; wherein areas of the dielectric layers121a-121eare preferably monotonically decreasing or increasing along the second direction. Preferably, the dielectric layers121are made of materials having relatively larger dielectric constant, e.g. dielectric constant of 3-4. In this manner, no capacitance (the stray capacitance is ignored herein) is inducted on the electrode layer120of any sensing unit12when a conductive object does not approach thereto, i.e. the capacitance is zero. When the conductive object approaches different positions of a sensing unit12along the second direction, as dielectric layers121with different equivalent dielectric constants exist between the conductive object and the electrode layer120at different positions, different capacitance variations will be induced.

Please refer toFIG. 3a, for example when a conductive object8approaches (or contacts) the dielectric layer121a, a capacitor of value C1=∈1A1/d is generated, wherein ∈1is an equivalent dielectric constant of the dielectric layer121aand the air in the capacitor C1. As the dielectric layer121has a relatively larger dielectric constant (e.g. 3-4) herein, the equivalent dielectric constant C1is relatively larger such that the capacitor C1has a relatively larger capacitance. In this case, the processing unit13is able to detect a relatively larger capacitance variation. Please refer toFIG. 3b, when a conductive object8approaches (or contacts) the dielectric layer121e, a capacitor of value C2=∈2A1/d is generated, wherein ∈2is an equivalent dielectric constant of the dielectric layer121eand the air in the capacitor C2. As the dielectric constant of the air is much smaller than that of the dielectric layer121e, the equivalent dielectric constant ∈2is relatively smaller such that the capacitor C2has a relatively smaller capacitance. In this case, the processing unit13will detect a relatively smaller capacitance variation, where A1is an area of the conductive object8relative to the electrode layer120.

In another embodiment, in order to increase resolution of the processing unit13in identifying position, a plurality of slits122may further be formed on the electrode layer120surrounding the dielectric layers121, and more slits122may be formed surrounding the dielectric layer with a smaller area as shown inFIG. 2, so as to reduce the relative area between the conductive object8and the electrode layer120. Please refer toFIG. 3c, for example when the conductive object8approaches (or contacts) the dielectric layer121a, as the slits122are formed on the electrode layer120, a capacitor of value C3=∈1A2/d is generated. Herein, as A2<A1, the capacitance C3is smaller than the capacitance C1shown inFIG. 3a. Please refer toFIG. 3d, when the conductive object8approaches (or contacts) the dielectric layer121e, as the slits122are formed on the electrode layer120, a capacitor of value C4=∈2A3/d is generated. Herein, as A3<A1, the capacitance C4is smaller than the capacitance C2shown inFIG. 3b. In this manner, a larger range of the capacitance variation can be induced between the conductive object8and the electrode layer120, such that it is able to increase resolution of the position identification.

It is appreciated that, although the dielectric layers121inFIG. 2are shown as a square shape, the present invention is not limited to this. The dielectric layers121may be formed as different shapes, e.g. a rectangular shape, a circular shape, a diamond shape or non-canonical shapes.

Please refer toFIGS. 4a-4c, they show sectional views of the sensing unit12taken along the line A-A′ ofFIG. 2, wherein no slit122is formed on the electrode layer120. InFIG. 4a, the electrode layer120is formed on the substrate11and the dielectric layers121a-121eare formed on the electrode layer120. In another embodiment, the electrode layer120may further include a protective layer to protect the electrode layer120and/or the dielectric layer121. For example inFIG. 4b, the sensing unit12further includes a protective layer123formed between the electrode layer120and the dielectric layers121a-121eso as to protect the electrode layer120, wherein the material of the protective layer123may be identical to or different from the dielectric layer121. Please refer toFIG. 4c, a protective layer123′ covers over the electrode layer120and the dielectric layers121a-121eso as to protect the electrode layer120and the dielectric layers121a-121e. In this embodiment, a difference of dielectric constant between the dielectric layer121and the protective layer123′ is preferably at least larger than 4, such that the protective layer123′ does not significantly degrade the degree of capacitance variation on the electrode layer120when a conductive object approaches (or contacts) the electrode layer120.

Please refer toFIGS. 5a-5c, they show other sectional views of the sensing unit12taken along the line A-A′ ofFIG. 2, where a plurality of slits122are formed on the electrode layer120herein. InFIG. 5a, the electrode layer120is formed on the substrate11, the dielectric layers121a-121eare formed on the electrode layer120, and the slits122are formed on the electrode layer120surrounding the dielectric layers121a-121e. InFIG. 5b, the sensing unit12further includes a protective layer123formed between the electrode layer120and the dielectric layers121a-121eso as to protect the electrode layer120. InFIG. 5c, a protective layer123′ covers over the electrode layer120and the dielectric layers121a-121eso as to protect the electrode layer120and the dielectric layers121a-121e.

In a sensing unit12of the present invention, the dielectric layer121may not be formed as a plurality of separated dielectric layers121a-121eas shown inFIG. 2but be formed as a whole dielectric layer whose width changes along the first direction or the second direction. Please refer toFIGS. 6a-6b, they show upper views of the sensing unit12according to another embodiment of the present invention, wherein the width of the dielectric layers121′-121″ may change continuously along the second direction (for example X direction), e.g. monotonically increasing or decreasing. In an alternative embodiment, the width of the dielectric layers121′-121″ may change non-continuously along a direction. In addition, in order to increase resolution of the position identification, a plurality of slits122may further be formed outside the electric layers121′-121″ on each electrode layer120, and more slits may be formed outside the section of dielectric layers121′-121″ with a smaller width as shown inFIGS. 6a-6b. It is appreciated that,FIGS. 6a-6bare only exemplary but not to limit the present invention.

In an alternative embodiment, the dielectric layer121may be formed complementary to that shown inFIG. 2, i.e. the dielectric layer121formed on each electrode layer120may include through openings O with different areas along the second direction (e.g. X direction), such that the electrode layer120is exposed outside the dielectric layer through the through openings O. Areas of the through openings O within the dielectric layer121on each electrode layer120monotonically decrease or increase along the second direction. For example,FIG. 7ashows an upper view of the sensing unit12according to another embodiment of the present invention whileFIG. 7bshows a sectional view taken alone the line B-B′ ofFIG. 7a, wherein the electrode layer120has no slit. By forming the through openings, when a conductive object approaches different positions of a sensing unit12along a direction (e.g. X direction), the processing unit13is able to detect different capacitance variations since a dielectric layer with different dielectric constants (an equivalent dielectric value of the air and the dielectric layer) exists between the conductive object and the electrode layer120along the direction. In addition, in order to increase resolution of the position identification, a plurality of slits122may further be formed inside the through openings O on each electrode layer120, and more slits may be formed inside the through opening O with a larger area. For example,FIG. 8ashows an upper view of the sensing unit12according to another embodiment of the present invention whileFIG. 8bshows a sectional view taken along the line C-C′ ofFIG. 8a, wherein the electrode layer120includes a plurality of slits122.

It is appreciated that, although aforementioned descriptions disclose the embodiment of changing the area of the dielectric layers121, the width of the dielectric layer121or the area of the through openings O in a second direction (e.g. X direction), but a person skilled in the art may implement this feature in a first direction (e.g. Y direction) or simultaneously in the first and second directions. It is appreciated that, the slits122are not limited to specific shapes.

It should be understood that, the structure of the projective capacitive touch sensor1is not limited to the above embodiments. The spirit of the present invention is to change a capacitance variation of the electrode layer induced by an approached conductive layer through changing an equivalent dielectric constant of the dielectric layer at different positions between the conductive object and the electrode layer. In addition, it is able to increase resolution of the position identification by changing the relative area (i.e. forming slits) between the electrode layer and the conductive object.

As mentioned above, as conventional projective capacitive touch screens have multilayer sensor array structure to increase the manufacturing complexity, the present invention provides a projective capacitive touch sensor (FIG. 2) that has a single layer of sensing units thereby having simpler manufacturing process.

Although the invention has been explained in relation to its preferred embodiment, the present invention is not limited to this. It is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the invention as hereinafter claimed.