Display device

According to one embodiment, a lateral-electric-field liquid crystal display device includes a light-emitting display layer including OLEDs and a driving circuit controlling light emission of the OLEDs, a moisture impermeable film provided to be laminated on the light-emitting display layer to prevent infiltration of moisture into the light-emitting display layer, an optical substrate provided separately from the moisture impermeable film and subjecting light from the light-emitting display region to optical processing, a first touch electrode group serving as one electrode group of touch electrodes and provided on a back surface of the optical substrate, and an extraction electrode group formed to be laminated on the moisture impermeable film, the extraction electrode group and the optical substrate have an overlapping part in plan view, and electrodes of the first touch electrode group being electrically connected to electrodes of the extraction electrode group in the overlapping part.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2013-209238, filed Oct. 4, 2013, the entire contents of which are incorporated herein by reference.

FIELD

BACKGROUND

Electronic apparatuses such as mobile phones, personal digital assistants, and personal computers have been developed. Such electronic apparatuses are equipped with a display device including a touch panel function as a form of user interface. These electronic apparatuses usually include a capacitive touch panel function. In a capacitive touch panel, conductive electrodes are disposed on the panel, and a contact position of a finger or a pen on the surface of the panel is sensed based on change in capacity between the electrode and the finger or the like.

An electronic apparatus having the above touch panel function is known as having a structure in which a touch panel board is separately bonded to a display device such as a liquid crystal display device and an organic EL display device, to add a touch panel function.

In the meantime, in electronic apparatuses using a liquid crystal device (LCD), an in-cell structure is being generalized. In the in-cell structure, a touch panel function is formed inside the LCD device. Adopting the in-cell structure produces the merit that the thickness and the weight of the devices are reduced, because it becomes unnecessary to use a dedicated touch panel.

On the other hand, in OLED display devices using organic light emitting diodes (OLED), it is difficult to provide a touch panel function inside in the same form as LCD devices, because a cathode provided on the whole light-emitting display surface thereof serves as an electromagnetic shield.

DETAILED DESCRIPTION

In general, according to one embodiment, a display device includes a light-emitting display layer including a light-emitting display region formed of OLEDs and a driving circuit controlling light emission of the OLEDs, a moisture impermeable film provided to be laminated on the light-emitting display layer to prevent infiltration of moisture into the light-emitting display layer, an optical substrate provided separately from the moisture impermeable film and subjecting light from the light-emitting display region to optical processing, a first touch electrode group serving as one electrode group of touch electrodes and provided on a back surface of the optical substrate, and an extraction electrode group formed to be laminated on the moisture impermeable film, the extraction electrode group and the optical substrate have an overlapping part in plan view, and electrodes of the first touch electrode group being electrically connected to electrodes of the extraction electrode group in the overlapping part.

First Embodiment

FIG. 1is a cross-sectional view illustrating a structure of a display device discussed prior to the present invention.

The display device illustrated inFIG. 1comprises an OLED display device1, an adhesive layer2, and a touch panel3. Specifically, the touch panel3is bonded onto the OLED display device1via the adhesive layer2.

The touch panel3includes first touch electrodes3aand second touch electrodes3bthat are placed on a touch panel substrate3c.The touch panel substrate3cis formed of transparent glass or plastic. The first touch electrodes3aand the second touch electrodes3bare transparent electrodes using a material such as ITO (Indium Tin Oxide) and a silver nanowire, and are arranged on the touch panel substrate3cas, for example, a number of mosaic electrode patterns formed of columns and rows. Each of the first touch electrodes3aand the second touch electrodes3bis electrically connected to a touch signal controlling circuit11via an FPC (Flexible Print Circuit) serving as a touch connection component. The touch panel3senses an approaching (contact) position of a dielectric such as a finger by change in capacitance of the touch electrodes3aand3b.

The OLED display device1includes an array substrate4, an OLED light-emitting display layer5, a moisture impermeable film (sealing layer)6, a seal material7, a filler8, and an optical substrate9that are provided on the array substrate4.

The array substrate4is an insulating substrate formed of glass, quartz, ceramics, or plastic. The OLED light-emitting display layer5is provided with a light-emitting layer including organic light-emitting diodes (OLED), and a driving circuit to control light-emitting operations of the OLEDs. The light-emitting layer is a thin film including luminescent organic compound that emits light of red, green, blue, or an achromatic color. A TFT (thin-film transistor) that forms the driving circuit is formed of low-temperature polysilicon. The driving circuit is supplied with a driving signal from a display panel controlling circuit10that is electrically connected via an FPC.

The colors of light emitted from the OLEDs are not necessarily divided into red, green, blue, and an achromatic color, but may be only an achromatic color. In such a case, the OLEDs may be used in combination with red, green, and blue color filters to emit light of red, green, blue, or an achromatic color.

The moisture impermeable film6seals the OLEDs and the thin-film transistor to prevent moisture from infiltrating from the outside. The seal material7serving as a holding member is provided between the moisture impermeable film6and the optical substrate9. The seal material7is provided in a frame shape in peripheral regions of the moisture impermeable film6and the optical substrate9, and a space surrounded by the moisture impermeable film6, the optical substrate9, and the seal material7is filled with the filler8. The filler8is, for example, a thermosetting resin that prevents moisture from infiltrating from the outside and enhances impact resistance.

The optical substrate9is properly provided with a member that subjects light from the OLEDs to optical processing, such as an optical element such as a color filter and a polarizer, and a black matrix. Although a color filter is required in the case where the OLEDs emit light of an achromatic color as described above, a color filter is not always required in the case where the OLEDs emit light of red, green, or blue color. A polarizer is provided in the case of reducing reflected light.

FIG. 2is a schematic diagram illustrating a structure of the touch panel3.

The touch panel3is provided with a plurality of transparent first touch electrodes3a(line1, line2, . . . ) extending in the horizontal direction and a plurality of transparent second touch electrodes3b(line A, line B, . . . ) extending in the vertical direction in a lattice shape. The first touch electrodes3aand the second touch electrodes3bare arranged in different layers via a transparent insulating film (not illustrated).

FIG. 2illustrates the state where the finger touches a point close to an intersection point between the first touch electrode3ain line2and the second touch electrode3bin line A. In this state, the finger serving as a dielectric changes the mutual capacitance between the first touch electrode3ain line2and the second touch electrode3bin line A. Thus, the position where the finger is located can be sensed by measuring the mutual capacitance between the first touch electrode3aand the second touch electrode3b.

The finger serving as a dielectric changes the self capacitance of the first touch electrode3aof line2or the self capacitance of the second touch electrode3bof line A. The term “self capacitance” indicates capacitance that exists between each first touch electrode3aor second touch electrode3band the ambient conductor. Thus, it is possible to sense the position where the finger is located, by measuring change in self capacitance with the first touch electrode3aor the second touch electrode3bcaused by touch of the finger.

For example, the sensing operation is executed as follows.

The touch signal controlling circuit11supplies a signal to the first touch electrode3aof line1and reads signals of the respective second touch electrodes3b(line A, line B, . . . ). Each of the read signals includes information relating to the mutual capacitance between the first touch electrode3aand the second touch electrode3b.Next, the touch signal controlling circuit11supplies a signal to the first touch electrode3aof line2and reads signals of the respective second touch electrodes3b(line A, line B, . . . ). This operation is performed with the first touch electrode3asuccessively switched, and thereby the position where the finger is present (the position of the first touch electrode3aand the position of the second touch electrode3b) can be sensed. The operation can be achieved by outputting, by the touch signal controlling circuit11, an alternative-current waveform signal (such as a square wave signal), switching the first touch electrode3ato be supplied with a signal in synchronization with the alternative-current waveform signal, and reading signals of the respective second touch electrodes3b(line A, line B, . . . ).

In the process of manufacturing the display device illustrated inFIG. 1, first, the moisture impermeable film6, the filler8, and the optical substrate9are laminated on the array substrate4provided with the OLED light-emitting display layer5, to form the OLED display device1. In addition, the touch panel3in which the touch electrodes3aand3bare provided on the touch panel substrate3cis formed separately. Then, at the final step of the display device, the touch panel3is bonded via the adhesive layer2.

As described above, the display device having the structure illustrated inFIG. 1requires a step of adding the touch panel3separately from the process of manufacturing the OLED display device1. This structure complicates the process, and increases the cost. In addition, this structure has demerits such as increase in size in the thickness direction of the display device.

FIG. 3is a cross-sectional view illustrating a structure of a display device100according to the first embodiment. Constituent elements having the same functions as those of the display device ofFIG. 1are denoted by same reference numerals, and detailed explanation thereof are omitted.

The display device100illustrated inFIG. 3has a structure in which a moisture impermeable film6, a seal material7, a filler8, and an optical substrate9are laminated on an array substrate4provided with an OLED light-emitting display layer5. In addition, a back surface (a surface opposed to the array substrate) of the optical substrate9is provided with first touch electrodes3a,and a front surface of the optical substrate9is provided with second touch electrodes3b.

The second touch electrodes3bare electrically connected to a touch signal controlling circuit11via an FPC at an end part of the optical substrate9. On the other hand, an end part of the first touch electrodes3ais not provided with an FPC to electrically connect to the touch signal controlling circuit11.

In the first embodiment, part of the region of the moisture impermeable film6is extended toward the side on which a signal line is drawn out, in comparison with the structure illustrated inFIG. 1. Then, an external extraction electrode20is formed on an upper layer of the extended region, and an end of the external extraction electrode20is electrically connected to the touch signal controlling circuit11via an FPC. The other end of the external extraction electrode20is held between the seal material7and the moisture impermeable film6.

The seal material7includes conductive particulates such as Au-plated pearl material. Thus, by pressing the optical substrate9and the moisture impermeable film6, electrodes at an end part of the first touch electrodes3aare electrically connected with electrodes at an end part of the external extraction electrode20via the conductive particulates. A connecting part21illustrated inFIG. 3indicates the electrically connected region. The connecting part21is an electric circuit that is formed by pressing the optical substrate9and the moisture impermeable film6.

Next, the process of manufacturing the display device100according to the first embodiment will be explained hereinafter.

FIG. 4AandFIG. 4Bare diagrams for explaining a method for forming the moisture impermeable film in the display device according to the first embodiment.

As illustrated inFIG. 4A, the OLED light-emitting display layer5including OLED light-emitting devices, a driving circuit, and a display driving external terminal23is formed on the array substrate4. The formation is performed with a step similar to that of a conventional method. Then, as illustrated inFIG. 4B, the moisture impermeable film6that covers the OLED light-emitting display layer5is formed on the whole surface of the array substrate4.

FIG. 5AandFIG. 5Bare diagrams for explaining a method for forming an extraction terminal in the display device according to the first embodiment.

As illustrated inFIG. 5A, a pattern of the external extraction terminal20is formed using a dry process such as mask deposition. A dry process is used to prevent deterioration of the OLED light-emitting devices due to moisture. As illustrated inFIG. 6, a plurality of connection pads24are arranged on the external extraction electrode20. InFIG. 5A, for example, a plurality of connection pads24are provided in a range indicated by a region25.

FIG. 6is a diagram illustrating arrangement of connection pads in the display device according to the first embodiment.

As illustrated inFIG. 6, n extraction lines included in the external extraction electrode20are extended into the region25, and connected with n connection pads (24-1,24-2, . . . ,24-n) provided at positions corresponding to end parts of the n first touch electrodes3a.The connection pads24are electrically connected with the first touch electrodes3avia the connecting part21.FIG. 6only illustrates an example, and arrangement positions of the connection pads24in the seal material can be properly determined in consideration of the structure of the first touch electrodes3aand the size of the frame region.

Then, inFIG. 5B, resin serving as a material of the seal material7is disposed in a frame shape. As described above, the seal material7includes conductive particulates such as Au-plated pearl material. Next, the filler8is filled into a space enclosed by the seal material7. Thereafter, the optical substrate9on which the first touch electrodes3aare formed is positioned such that the first touch electrodes3aare opposed to the array substrate4, and the optical substrate9is bonded to the array substrate4. In the bonding, the optical substrate9and the array substrate4are pressed to hold the seal material and the filler8therebetween, to form the connecting part21.

[Peeling the Moisture Impermeable Film and Exposing Driving Terminal]

FIG. 7AandFIG. 7Bare diagrams for explaining a method for peeling the moisture impermeable film and a method for exposing and extracting a driving terminal in the display device according to the first embodiment.

First, as illustrated inFIG. 7A, the whole panel manufactured is put into a sealing-layer-peeling gas to peel the moisture impermeable film6. This treatment removes the moisture impermeable film6in a region other than the region covered with the optical substrate9and the external extraction electrode20in the plan view. As a result, the external extraction electrode20is formed at a position that is higher than the array substrate4by the thickness of the moisture impermeable film6. However, the difference in height between the moisture impermeable film6and the array substrate4is minute.

Then, as illustrated inFIG. 7B, patterns of the second touch electrodes3band the external extraction electrode26are formed on the front surface of the optical substrate9by a dry process such as mask deposition.

[Connection to External Driving Circuit]

FIG. 8is a diagram for explaining a method for connection to the external driving circuit in the display device according to the first embodiment. The upper part ofFIG. 8is a plan view of the display device, and the lower part ofFIG. 8is a cross-sectional view of the display device.

An FPC to connect to the display panel controlling circuit10is attached to the display driving external circuit23connected to the OLED light-emitting display layer5. In addition, an FPC connected to the touch signal controlling circuit11is attached to the external extraction electrode20that is electrically connected to the first touch electrode3a,and another FPC connected to the touch signal controlling circuit11is attached to the external extraction electrode26connected to the second touch electrode3b.

Both the two FPCs connected to the touch signal controlling circuit11are attached in the same direction from the front surface of the display device100toward the back surface of the display device100. In addition, the FPC connected to the display panel controlling circuit10is also attached in the same direction. Thus, the display device100according to the present embodiment has an advantage of easier attachment of FPCs. Besides, because the difference in height between the surface of the moisture impermeable film6and the surface of the array substrate4is minute as described above, FPCs can be attached to the display panel controlling circuit10and the touch signal controlling circuit11simultaneously.

In the first embodiment, a signal is supplied to the first touch electrode3aprovided on the back surface of the optical substrate9to read signals of the respective second touch electrodes3b.In consideration of attenuation of the signal in the connecting part21, a sense signal with a good S/N ratio is obtained by the above structure. However, the display device may have a structure in which a signal is supplied to the second touch electrode3bprovided on the front surface of the optical substrate9to read signals of the respective first touch electrodes3a.

With the display device according to the first embodiment explained above, it is possible to reduce the thickness and the weight of the display device.

Second Embodiment

The second embodiment is different from the first embodiment in that a black matrix BM of an optical substrate9also serves as first touch electrodes3a.Constituent elements having functions that are the same as or similar to those of the first embodiment are denoted by same reference numerals, and detailed explanation thereof are omitted.

FIG. 9is a diagram illustrating a structure of touch electrodes in a display device according to the second embodiment. The lower part ofFIG. 9shows a cross-sectional view of the display device according to the second embodiment. Because the cross-sectional view is the same as the cross-sectional view of the display device shown in the lower part ofFIG. 8, detailed explanation thereof is omitted. The upper left part ofFIG. 9shows a plan view of the back surface of the optical substrate9as viewed from inside. The upper right part ofFIG. 9shows an enlarged view of the back surface.

In the second embodiment, the black matrix BM is formed of low-resistance conductors that are arranged to extend in parallel at predetermined pitches, and low-resistance conductors that are electrically connected to and cross the conductors and extend in parallel at other predetermined pitches. The black matrix BM is provided with cutoff parts to form a plurality of electrodes that extend in a predetermined direction (the vertical direction inFIG. 9). The width of each cutoff part is shorter than an interval (a pitch) between the adjacent low-resistance conductors extending in the predetermined direction. The cutoff parts are provided at intervals of a plurality of pitches in the horizontal direction. Thus, the influence of light leakage from the cutoff parts on the display image is small enough not to cause any problem.

The first touch electrodes3acan be formed by drawing a plurality of electrodes formed by processing the black matrix BM as described above to be brought into contact with the connecting part21. Although each cutoff part is provided on a vertical straight line in the upper right part ofFIG. 9, the cutoff part is not limited to this form, but may be provided to form a plurality of electrodes that extend in a desired direction.

The second touch electrodes3bmay be formed in the same form as that of the first embodiment, or may be formed of low-resistance conductors in the same manner as the first touch electrodes3aof the second embodiment. Forming both the touch electrodes3aand3bof low-resistance conductors suppresses attenuation of the touch signal.

According to the second embodiment, it is possible to further reduce the thickness and the weight of the display device.

Variation of the Second Embodiment

In a variation of the second embodiment, first touch electrodes3aare laminated on a black matrix BM of an optical substrate9.

FIG. 10is a diagram illustrating a structure of touch electrodes in the display device according to the variation of the second embodiment.

The lower part ofFIG. 10shows a cross-sectional view of the display device of the variation. Because the cross-sectional view is the same as the cross-sectional view of the display device shown in the lower part ofFIG. 8, detailed explanation thereof is omitted. The upper left part ofFIG. 10shows a plan view of the back surface of the optical substrate9as viewed from inside. The upper right part ofFIG. 10shows an enlarged view of the back surface.

In the variation, low-resistance conductors are formed and laminated on the black matrix BM. Because the conductors are laminated on the black matrix BM, the conductors are not required to be light-transmitting material, such as ITO indicated in the first embodiment. Thus, it is possible to use a material having low electric resistance even if it is a non-light-transmitting material.

The conductors are provided with cutoff parts to form a plurality of electrodes that extend in a predetermined direction (the vertical direction inFIG. 10). The width of each cutoff part is shorter than an interval (a pitch) between the adjacent low-resistance conductors extending in the predetermined direction.

The electrodes formed as described above are drawn to the frame side and brought into contact with a connecting part21, and thereby the electrodes can be functioned as first touch electrodes3a.Although each cutoff part is provided on a vertical straight line in the upper right part ofFIG. 10, the cutoff part is not limited to this form, but may be provided to form a plurality of electrodes that extend in a desired direction.

Second touch electrodes3bmay be formed in the same form as that of the first embodiment, or may be formed of low-resistance conductors in the same manner as the first touch electrodes3aof the second embodiment. Forming both the touch electrodes3aand3bof low-resistance conductors suppresses attenuation of the touch signal, and produces a touch signal with high sensitivity.

According to the variation of the second embodiment, it is possible to obtain a touch sensor electrode with high sensitivity.

[Comparison with Other Structures]

The embodiments explained above have the structure provided with the touch electrodes3aand3bwithout the touch panel substrate illustrated inFIG. 1. However, various forms exist as the structure provided with the touch electrodes3aand3bwithout a touch panel substrate. The following is explanation of advantages of the present application as compared with these various structures.

FIG. 11is a cross-sectional view illustrating a structure of a display device discussed to be compared with the display device of the present embodiment. In the display device illustrated inFIG. 11, touch electrodes3aand3bare provided on the front surface of the optical substrate9.

In the structure illustrated inFIG. 11, the touch electrodes3aand3bare formed after forming an array substrate4, an OLED light-emitting display layer5, a moisture impermeable film6, a filler8, and an optical substrate9in a laminated manner. In the formation, because two electrode layers are provided, the manufacturing process is more complicated than the case of providing one electrode layer. For example, although one electrode layer can be simply formed by mask deposition, providing two electrode layers requires repeatedly executing processing (metal patterning, etching, and interlayer film formation) with a photo mask. However, the processing steps are executed after formation of the OLED light-emitting display layer5that must be protected from infiltration of moisture, and protection from water is indispensable. Thus, forming the touch electrodes of two layers on the surface of the optical substrate9greatly complicates the manufacturing process.

FIG. 12is a cross-sectional view illustrating a structure of a display device discussed to be compared with the display device according to the present embodiment. In the display device illustrated inFIG. 12, the touch electrodes3aand3bare provided on the front surface and the back surface of the optical substrate9, respectively.

In the structure illustrated inFIG. 12, an optical substrate9having a back surface provided with the touch electrodes3bin advance is bonded to the filler8, and thereafter touch electrodes3aof a single layer can be formed on the front surface of the optical substrate9. Thus, this structure simplifies the manufacturing process in comparison with the structure ofFIG. 11. However, this structure requires increase of the step of attaching an FPC to extract a signal from the touch electrodes3bformed on the back surface, and increase in size of the optical substrate9. Thus, this structure has demerits in both the cost and the module size.

FIG. 13is a cross-sectional view illustrating a structure of a display device discussed to be compared with the display device according to the present embodiment. In the display device illustrated inFIG. 13, the touch electrodes3aand3bare provided on the front surface and the back surface of the optical substrate9, respectively. In addition, a signal of the touch electrodes3aon the back surface is extracted onto the array substrate4via the seal material7and the moisture impermeable film6.

However, in the structure illustrated inFIG. 13, it is difficult to extract a signal of the touch electrodes3aonto the array substrate4. Specifically, in the case where a signal is extracted via the seal material7, the signal can be extracted using conductive particulates such as Au-plated pearl spacers. However, it is impossible to use conductive particulates for the moisture impermeable film6, and it is also difficult to process the moisture impermeable film6. Thus, it is impossible to construct any process that can be put into practice.

However, the structure illustrated inFIG. 13can be constructed with a practical process, when it becomes possible to process the moisture impermeable film6, or when it is possible to receive and transmit signals by, for example, capacity coupling, without processing the moisture impermeable film6. Thus, the structure illustrated inFIG. 13is not excluded from the present application, but claimed as the third embodiment.

For example, although the external extraction electrode20is connected with the first touch electrodes3avia conductive particulates in the above embodiments, signals may be transmitted and received between the electrodes via capacitive elements (parasitic capacitance) formed between the electrodes, when the interval between the electrodes can be shortened and the areas of the electrodes can be increased. Signals may also be transmitted and received between the external extraction electrode20and the second touch electrodes3bvia capacitive elements (parasitic capacitance).

Various inventions can be made by proper combinations of a plurality of constituent elements disclosed in the above embodiments. For example, some constituent elements may be deleted from the constituent elements disclosed in the embodiment. In addition, constituent elements of different embodiments may be used in combination.