U.S. patent application number 14/725205 was filed with the patent office on 2015-12-03 for touch panel.
The applicant listed for this patent is Semiconductor Energy Laboratory Co., Ltd.. Invention is credited to Koji KUSUNOKI, Hiroyuki MIYAKE, Kazunori WATANABE.
Application Number | 20150346866 14/725205 |
Document ID | / |
Family ID | 54481743 |
Filed Date | 2015-12-03 |
United States Patent
Application |
20150346866 |
Kind Code |
A1 |
KUSUNOKI; Koji ; et
al. |
December 3, 2015 |
TOUCH PANEL
Abstract
To increase the detection sensitivity of a touch panel, provide
a thin touch panel, provide a foldable touch panel, or provide a
lightweight touch panel. A display element and a capacitor forming
a touch sensor are provided between a pair of substrates.
Preferably, a pair of conductive layers forming the capacitor each
have an opening. The opening and the display element are provided
to overlap each other. A light-blocking layer is provided between a
substrate on the display surface side and the pair of conductive
layers forming the capacitor.
Inventors: |
KUSUNOKI; Koji; (Kawasaki,
JP) ; MIYAKE; Hiroyuki; (Atsugi, JP) ;
WATANABE; Kazunori; (Atsugi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Semiconductor Energy Laboratory Co., Ltd. |
Atsugi-shi |
|
JP |
|
|
Family ID: |
54481743 |
Appl. No.: |
14/725205 |
Filed: |
May 29, 2015 |
Current U.S.
Class: |
345/174 |
Current CPC
Class: |
G06F 2203/04111
20130101; G06F 2203/04102 20130101; Y02E 10/549 20130101; G06F
3/04166 20190501; G06F 3/045 20130101; G06F 3/0445 20190501; G06F
2203/04808 20130101; H01L 51/0097 20130101; G06F 2200/1633
20130101; G06F 1/1618 20130101; G06F 1/1652 20130101; G06F 1/1677
20130101; G06F 15/0216 20130101; G06F 2203/04104 20130101; H01L
27/323 20130101; G06F 3/0446 20190501; G06F 2203/04112 20130101;
G06F 3/0412 20130101; G06F 2203/04101 20130101; G06F 3/0488
20130101 |
International
Class: |
G06F 3/044 20060101
G06F003/044; G06F 3/0488 20060101 G06F003/0488; G06F 15/02 20060101
G06F015/02; G06F 3/041 20060101 G06F003/041; G06F 3/045 20060101
G06F003/045 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2014 |
JP |
2014-112316 |
Jun 23, 2014 |
JP |
2014-128409 |
Dec 1, 2014 |
JP |
2014-242912 |
Claims
1. A touch panel comprising: a first substrate; a second substrate;
a first conductive layer having a first opening; a second
conductive layer having a second opening; and a first
light-emitting element and a second light-emitting element between
the first substrate and the second substrate, wherein the first
conductive layer and the second conductive layer form a capacitor,
wherein the first opening and whole of the first light-emitting
element overlap with each other, wherein the second opening and
whole of the second light-emitting element overlap with each other,
and wherein the first conductive layer and the second conductive
layer are positioned between the second substrate and at least one
of the first light-emitting element and the second light-emitting
element.
2. The touch panel according to claim 1, wherein a time constant of
at least one of the first conductive layer and the second
conductive layer is greater than 0 s and less than or equal to
1.times.10.sup.-4 s.
3. The touch panel according to claim 1, wherein an aperture ratio
of at least one of the first conductive layer and the second
conductive layer is greater than or equal to 20% and less than
100%.
4. The touch panel according to claim 1, further comprising: a
third conductive layer provided closer to the first substrate than
at least one of the first conductive layer and the second
conductive layer, wherein at least one of a first distance between
the first conductive layer and the third conductive layer and a
second distance between the second conductive layer and the third
conductive layer is greater than or equal to 25 nm and less than or
equal to 50 nm.
5. The touch panel according to claim 1, further comprising: a
first insulating layer, wherein the first conductive layer and the
second conductive layer overlap with each other, and wherein the
first insulating layer is positioned between the first conductive
layer and the second conductive layer.
6. The touch panel according to claim 1, further comprising: a
fourth conductive layer; and a second insulating layer having a
third opening, wherein the fourth conductive layer and the second
conductive layer overlap with each other, wherein the second
insulating layer is positioned between the first conductive layer
and the fourth conductive layer, wherein the second insulating
layer is positioned between the second conductive layer and the
fourth conductive layer, and wherein the first conductive layer and
the fourth conductive layer are electrically connected to each
other through the third opening.
7. The touch panel according to claim 1, further comprising: a
light-blocking layer between the second substrate and at least one
of the first conductive layer and the second conductive layer,
wherein the first conductive layer and the light-blocking layer
overlap with each other, and wherein the second conductive layer
and the light-blocking layer overlap with each other.
8. A module comprising: the touch panel according to claim 1; and
at least one of a flexible printed circuit and a tape carrier
package.
9. An electronic appliance comprising: the touch panel according to
claim 1; and at least one of a battery, an antenna, a housing, an
operation button, an external connection port, a speaker, and a
microphone.
10. A touch panel comprising: a first substrate; a second
substrate; a first conductive layer having a first opening; a
second conductive layer having a second opening; and a first
light-emitting element and a second light-emitting element between
the first substrate and the second substrate, wherein the first
conductive layer and the second conductive layer form a capacitor,
wherein the first opening and both of whole of the first
light-emitting element and whole of the second light-emitting
element overlap with each other, and wherein the first conductive
layer and the second conductive layer are positioned between the
second substrate and at least one of the first light-emitting
element and the second light-emitting element.
11. The touch panel according to claim 10, wherein a time constant
of at least one of the first conductive layer and the second
conductive layer is greater than 0 s and less than or equal to
1.times.10.sup.-4 s.
12. The touch panel according to claim 10, wherein an aperture
ratio of at least one of the first conductive layer and the second
conductive layer is greater than or equal to 20% and less than
100%.
13. The touch panel according to claim 10, further comprising: a
third conductive layer provided closer to the first substrate than
at least one of the first conductive layer and the second
conductive layer, wherein at least one of a first distance between
the first conductive layer and the third conductive layer and a
second distance between the second conductive layer and the third
conductive layer is greater than or equal to 25 nm and less than or
equal to 50 .mu.m.
14. The touch panel according to claim 10, further comprising: a
first insulating layer, wherein the first conductive layer and the
second conductive layer overlap with each other, and wherein the
first insulating layer is positioned between the first conductive
layer and the second conductive layer.
15. The touch panel according to claim 10, further comprising: a
fourth conductive layer; and a second insulating layer having a
third opening, wherein the fourth conductive layer and the second
conductive layer overlap with each other, wherein the second
insulating layer is positioned between the first conductive layer
and the fourth conductive layer, wherein the second insulating
layer is positioned between the second conductive layer and the
fourth conductive layer, and wherein the first conductive layer and
the fourth conductive layer are electrically connected to each
other through the third opening.
16. The touch panel according to claim 10, further comprising: a
light-blocking layer between the second substrate and at least one
of the first conductive layer and the second conductive layer,
wherein the first conductive layer and the light-blocking layer
overlap with each other, and wherein the second conductive layer
and the light-blocking layer overlap with each other.
17. A module comprising: the touch panel according to claim 10; and
at least one of a flexible printed circuit and a tape carrier
package.
18. An electronic appliance comprising: the touch panel according
to claim 10; and at least one of a battery, an antenna, a housing,
an operation button, an external connection port, a speaker, and a
microphone.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] One embodiment of the present invention relates to a touch
panel.
[0003] Note that one embodiment of the present invention is not
limited to the above technical field. One embodiment of the
invention disclosed in this specification and the like relates to
an object, a method, or a manufacturing method. One embodiment of
the present invention relates to a process, a machine, manufacture,
or a composition of matter. Specifically, examples of the technical
field of one embodiment of the present invention disclosed in this
specification include a semiconductor device, a display device, a
light-emitting device, a power storage device, a memory device, an
electronic appliance, a lighting device, an input device, an
input/output device, a method for driving any of them, and a method
for manufacturing any of them.
[0004] In this specification and the like, a semiconductor device
generally means a device that can function by utilizing
semiconductor characteristics. A semiconductor element such as a
transistor, a semiconductor circuit, an arithmetic device, and a
memory device are each an embodiment of a semiconductor device. An
imaging device, a display device, a liquid crystal display device,
a light-emitting device, an electro-optical device, a power
generation device (including a thin film solar cell, an organic
thin film solar cell, and the like), and an electronic appliance
may each include a semiconductor device.
[0005] 2. Description of the Related Art
[0006] Recent display devices are expected to be applied to a
variety of uses and become diversified. For example, a smartphone
and a tablet with a touch panel are being developed as portable
information terminals.
[0007] Patent Document 1 discloses a flexible active matrix
light-emitting device in which an organic EL element and a
transistor serving as a switching element are provided over a film
substrate.
REFERENCE
Patent Document
[0008] [Patent Document 1] Japanese Published Patent Application
No. 2003-174153
SUMMARY OF THE INVENTION
[0009] What is desirable is a touch panel in which a display panel
is provided with a function of inputting data with a finger, a
stylus, or the like touching a screen as a user interface.
[0010] Furthermore, it is demanded that an electronic appliance
using a touch panel is reduced in thickness and weight. Therefore,
a touch panel itself is required to be reduced in thickness and
weight.
[0011] For example, in a touch panel, a touch sensor can be
provided on the viewer side (the display surface side) of a display
panel.
[0012] In a touch panel where a capacitive touch sensor is provided
so as to overlap with the display surface side of a display panel,
when the distance between a pixel or a wiring of the display panel
and an electrode or a wiring of the touch sensor is reduced, the
touch sensor is likely to be influenced by noise caused when the
display panel is driven by the touch sensor, which results in a
reduction of the detection sensitivity of the touch panel in some
cases.
[0013] One object of one embodiment of the present invention is to
improve detection sensitivity of a touch panel. Another object is
to provide a thin touch panel. Another object is to provide a
foldable touch panel. Another object is to provide a lightweight
touch panel. Another object is to provide a touch panel with high
reliability.
[0014] Another object is to provide a novel input device. Another
object is to provide a novel input/output device.
[0015] Note that the descriptions of these objects do not disturb
the existence of other objects. In one embodiment of the present
invention, there is no need to achieve all the objects. Other
objects will be apparent from and can be derived from the
description of the specification, the drawings, the claims, and the
like.
[0016] One embodiment of the present invention is a touch panel
including a first substrate, a second substrate, a first conductive
layer, a second conductive layer, a first light-emitting element, a
second light-emitting element, and a light-blocking layer. The
first conductive layer has a first opening, and the second
conductive layer has a second opening. The first conductive layer
and the second conductive layer form a capacitor. The first opening
and the first light-emitting element overlap with each other in a
region. The second opening and the second light-emitting element
overlap with each other in a region. The first conductive layer and
the light-blocking layer overlap with each other in a region. The
second conductive layer and the light-blocking layer overlap with
each other in a region. The first light-emitting element and the
second light-emitting element are positioned between the first
substrate and the second substrate in a region. The first
conductive layer and the second conductive layer are positioned
between the first light-emitting element or the second
light-emitting element and the second substrate in a region. The
light-blocking layer is positioned between the first conductive
layer or the second conductive layer and the second substrate in a
region.
[0017] In the above embodiment, a CR value of the first conductive
layer or the second conductive layer is preferably greater than 0 s
and less than or equal to 1.times.10.sup.-4 s.
[0018] In the above embodiment, an aperture ratio of the first
conductive layer or the second conductive layer is preferably
greater than or equal to 20% and less than 100% in a region.
[0019] In the above embodiment, it is preferable that the touch
panel include a third conductive layer, the third conductive layer
be provided closer to the first substrate than the first conductive
layer or the second conductive layer, and a distance between the
first conductive layer and the third conductive layer or a distance
between the second conductive layer and the third conductive layer
be greater than or equal to 25 nm and less than or equal to 50
.mu.m in a region.
[0020] In the above embodiment, it is preferable that the touch
panel include a third light-emitting element, the third
light-emitting element is positioned between the first substrate
and the second substrate in a region, and the third light-emitting
element and the first opening overlap with each other in a
region.
[0021] In the above embodiment, it is preferable that the touch
panel include a fourth light-emitting element, the fourth
light-emitting element is positioned between the first substrate
and the second substrate in a region, and the fourth light-emitting
element and the second opening overlap with each other in a
region.
[0022] In the above embodiment, it is preferable that the touch
panel include an insulating layer, the first conductive layer and
the second conductive layer overlap with each other in a region,
and the insulating layer is positioned between the first conductive
layer and the second conductive layer in a region.
[0023] In the above embodiment, it is preferable that the touch
panel include a fourth conductive layer, a fifth conductive layer,
and an insulating layer. Here, the fourth conductive layer and the
light-blocking layer overlap with each other in a region, the fifth
conductive layer and the light-blocking layer overlap with each
other in a region, the fifth conductive layer and the second
conductive layer overlap with each other in a region, the
insulating layer is positioned between the first conductive layer
and the fifth conductive layer in a region, the insulating layer is
positioned between the second conductive layer and the fifth
conductive layer in a region, and the insulating layer is
positioned between the fourth conductive layer and the fifth
conductive layer in a region. The insulating layer has a third
opening and a fourth opening. The first conductive layer and the
fifth conductive layer are electrically connected to each other
through the third opening. It is preferable that the fourth
conductive layer and the fifth conductive layer be electrically
connected to each other through the fourth opening.
[0024] It is preferable that the touch panel further include a
fifth light-emitting element. At this time, it is preferable that
the fourth conductive layer have a fifth opening, the fifth
light-emitting element is positioned between the first substrate
and the second substrate in a region, and the fifth opening and the
fifth light-emitting element overlap with each other in a
region.
[0025] One embodiment of the present invention can improve the
detection sensitivity of a touch panel. Alternatively, a thin touch
panel can be provided. Alternatively, a foldable touch panel can be
provided. Alternatively, a lightweight touch panel can be provided.
Alternatively, a touch panel with high reliability can be
provided.
[0026] Alternatively, a novel input device can be provided.
Alternatively, a novel input/output device can be provided. Note
that the description of these effects does not disturb the
existence of other effects. One embodiment of the present invention
does not necessarily achieve all the effects listed above. Other
effects will be apparent from and can be derived from the
description of the specification, the drawings, the claims, and the
like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIGS. 1A and 1B show a structure example of a touch panel
module of an embodiment.
[0028] FIGS. 2A to 2C show a structure example of a touch sensor of
an embodiment.
[0029] FIGS. 3A to 3C show structure examples of a touch sensor of
an embodiment.
[0030] FIGS. 4A and 4B show structure examples of a touch sensor of
an embodiment.
[0031] FIGS. 5A and 5B show structure examples of a touch sensor of
an embodiment.
[0032] FIG. 6 shows a structure example of a touch sensor of an
embodiment.
[0033] FIGS. 7A to 7G show structure examples of a touch panel of
an embodiment.
[0034] FIG. 8 shows a structure example of a touch panel of an
embodiment.
[0035] FIGS. 9A to 9E show structure examples of a touch panel of
an embodiment.
[0036] FIGS. 10A and 10B show a structure example of a touch panel
of an embodiment.
[0037] FIGS. 11A and 11B show a structure example of a touch panel
of an embodiment.
[0038] FIGS. 12A and 12B show a structure example of a touch panel
of an embodiment.
[0039] FIG. 13 shows a structure example of a touch panel of an
embodiment.
[0040] FIG. 14 shows a structure example of a touch panel of an
embodiment.
[0041] FIG. 15 shows a structure example of a touch panel of an
embodiment.
[0042] FIGS. 16A and 16B are a block diagram and a timing chart of
a touch sensor of an embodiment.
[0043] FIG. 17 is a circuit diagram of a touch sensor of an
embodiment.
[0044] FIGS. 18A to 18G each illustrate an electronic appliance of
an embodiment.
[0045] FIGS. 19A to 19I illustrate electronic appliances of an
embodiment.
[0046] FIG. 20 shows a structure of a touch panel of an
example.
[0047] FIGS. 21A to 21C are photographs of a touch panel of an
example.
[0048] FIG. 22 shows measurement results of parasitic capacitance
and parasitic resistance of a touch panel of an example.
DETAILED DESCRIPTION OF THE INVENTION
[0049] Embodiments will be described in detail with reference to
drawings. Note that the present invention is not limited to the
description below, and it is easily understood by those skilled in
the art that various changes and modifications can be made without
departing from the spirit and scope of the present invention.
Accordingly, the present invention should not be interpreted as
being limited to the content of the embodiments below.
[0050] Note that in the structures of the invention described
below, the same portions or portions having similar functions are
denoted by the same reference numerals in different drawings, and
description of such portions is not repeated. Further, the same
hatching pattern is applied to portions having similar functions,
and the portions are not especially denoted by reference numerals
in some cases.
[0051] Note that in each drawing described in this specification,
the size, the layer thickness, or the region of each component is
exaggerated for clarity in some cases. Therefore, embodiments of
the present invention are not limited to such a scale.
[0052] Note that in this specification and the like, ordinal
numbers such as "first", "second", and the like are used in order
to avoid confusion among components and do not limit the
number.
[0053] Note that the terms "film" and "layer" can be interchanged
with each other depending on the case or circumstances. For
example, the term "conductive layer" can be changed into the term
"conductive film" in some cases. Also, the term "insulating film"
can be changed into the term "insulating layer" in some cases.
Embodiment 1
[0054] In this embodiment, a structure example of a touch panel of
one embodiment of the present invention will be described with
reference to drawings. In the description below, a capacitive touch
sensor is used as a touch sensor of a touch panel.
[0055] Note that in this specification and the like, a touch panel
has a function of displaying or outputting an image or the like on
or to a display surface and a function of a touch sensor capable of
sensing contact or proximity of an object such as a finger or a
stylus on or to the display surface. Therefore, the touch panel is
an embodiment of an input/output device.
[0056] In this specification and the like, a structure in which a
connector such as a flexible printed circuit (FPC) or a tape
carrier package (TCP) is attached to a substrate of a touch panel,
or a structure in which an integrated circuit (IC) is directly
mounted on a substrate by a chip on glass (COG) method is referred
to as a touch panel module or simply referred to as a touch panel
in some cases.
[0057] A capacitive touch sensor that can be used for one
embodiment of the present invention includes a capacitor. The
capacitor can have a structure in which a dielectric is provided
between a first conductive layer and a second conductive layer. At
this time, part of the first conductive layer and part of the
second conductive layer each function as an electrode of the
capacitor. The other part of the first conductive layer and the
other part of the second conductive layer may each function as a
wiring.
[0058] Examples of the capacitive touch sensor are a surface
capacitive touch sensor and a projected capacitive touch sensor.
Examples of the projected capacitive touch sensor are a
self-capacitive touch sensor, a mutual capacitive touch sensor, and
the like, which differ mainly in the driving method. The use of a
mutual capacitive type is preferable because multiple points can be
sensed simultaneously.
[0059] A touch panel of one embodiment of the present invention
includes, between a pair of substrate, a display element and a
capacitor included in a touch sensor. Thus, a thin and lightweight
touch panel can be obtained.
[0060] It is preferable that a pair of conductive layers included
in the capacitor each have an opening. It is preferable that the
opening and the display element overlap with each other. Such a
structure enables extraction of light emitted from the display
element to the outside through the opening, and therefore, the pair
of conductive layers included in the capacitor do not necessarily
have a light-transmitting property. That is, a material such as
metal or alloy that has lower resistance than a light-transmitting
conductive material can be used as a material for the pair of
conductive layer included in the capacitor. This reduces the
influence of detection signal delay or the like and increases the
detection sensitivity of the touch panel. Furthermore, such a
structure can be applied to large-sized display devices such as
televisions as well as portable devices.
[0061] Since the pair of conductive layers can be formed of a
low-resistance material, each of the conductive layers can have an
extremely small line width. That is, a surface area of each of the
conductive layers when seen from the display surface side (in a
plan view) can be reduced. As a result, the influence of noise
caused by driving a pixel is suppressed, which increases detection
sensitivity. Furthermore, even when the capacitor included in the
touch sensor and the display element included in the pixel are
provided close to each other and between the two substrates, a
reduction in detection sensitivity can be suppressed. Thus, the
thickness of the touch panel can be reduced. In particular, in the
case where a flexible material is used for the pair of substrates,
a flexible touch panel that is thin and lightweight can be
obtained.
[0062] In the case of using a projected capacitive type, the
product of resistance and capacitance (also referred to as a CR
value or a time constant) of the first conductive layer is
preferably as small as possible. Similarly, the CR value of the
second conductive layer is preferably as small as possible.
[0063] For example, in the case of using a projected mutual
capacitive type, a pulse voltage is supplied to one of the
conductive layers, and a current flowing in the other conductive
layer is sensed. At this time, as the CR value of the conductive
layer where current sensing is performed is smaller, a change in
current due to the presence or absence of a touch motion can be
increased more. Furthermore, as the CR value of the conductive
layer supplied with the pulse voltage is smaller, delay in the
waveform of the pulse voltage is suppressed more and detection
sensitivity can be increased more.
[0064] In the case of using a projected self-capacitive type, a
pulse voltage is applied to each of the pair of conductive layers,
and a current flowing in each of the conductive layers is sensed.
Therefore, as the CR value of each of the conductive layers is
smaller, detection sensitivity can be increased more.
[0065] For example, the CR value of the first conductive layer or
the second conductive layer is greater than 0 s and less than or
equal to 1.times.10.sup.-4 s, preferably greater than 0 s and less
than or equal to 5.times.10.sup.-5 s, more preferably greater than
0 s and less than or equal to 5.times.10.sup.-6 s, still more
preferably greater than 0 s and less than or equal to
5.times.10.sup.-7 s, still more preferably greater than 0 s and
less than or equal to 2.times.10.sup.-7 s. In particular, when the
CR value is 1.times.10.sup.-6 s or less, high detection sensitivity
can be achieved while the influence of noise is suppressed.
[0066] The first conductive layer or the second conductive layer
preferably has a mesh shape having a plurality of openings. At this
time, the aperture ratio of the first conductive layer or the
second conductive layer (the proportion of the opening area of the
first conductive layer or the second conductive layer per unit
area) is preferably higher than at least the aperture ratio of the
pixel included in the touch panel. When the aperture ratio of the
first conductive layer or the second conductive layer is higher
than the aperture ratio of the pixel, blocking of light emitted
from the pixel by the first conductive layer or the second
conductive layer can be suppressed. When the aperture ratio is
increased by increasing the size of the opening, the area where the
object overlaps with the first conductive layer or the second
conductive layer is reduced, and therefore, detection sensitivity
is reduced in some cases. In view of this, the aperture ratio and
an opening pattern are preferably set so that the opening area is
smaller than the area of the object.
[0067] For example, the aperture ratio of the first conductive
layer or the second conductive layer is preferably higher than or
equal to 20% and lower than 100%, more preferably higher than or
equal to 30% and lower than 100%, still more preferably higher than
or equal to 50% and lower than 100%.
[0068] The touch panel of one embodiment of the present invention
has high detection sensitivity and is less influenced by noise
caused when a display panel is driven. Therefore, the thickness of
the touch panel itself can be reduced. For example, the distance
between the pair of substrates included in the touch panel can be
reduced to 50 nm or more and 100 .mu.m or less, preferably 200 nm
or more and 50 .mu.m or less, more preferably 500 nm or more and 20
.mu.m or less. When a flexible substrate is used for the pair of
substrates at this time, a flexible touch panel strong against
bending can be obtained.
[0069] In particular, the distance between the first conductive
layer or the second conductive layer and a conductive layer closer
to the substrate provided with the display element than the first
conductive layer or the second conductive layer is set to, for
example, greater than or equal to 25 nm and less than or equal to
50 .mu.m, preferably greater than or equal to 50 nm and less than
or equal to 10 .mu.m, more preferably greater than or equal to 50
nm and less than or equal to 5 .mu.m.
[0070] Furthermore, a light-blocking layer is preferably provided
between the substrate on the display surface side and the pair of
electrodes included in the capacitor. The light-blocking layer may
have a function of suppressing color mixing between adjacent
pixels. When the light-blocking layer is closer to the display
surface than the pair of electrodes, reflection of external light
by the pair of electrodes is prevented, and the pair of electrodes
is prevented from being visually recognized from the display
surface side. Thus, the touch panel can have high display
quality.
[0071] The light-blocking layer and the pair of electrodes included
in the capacitor are preferably provided between adjacent pixels
when seen from the display surface side (in a plan view).
Furthermore, the width of each of the pair of electrodes included
in the capacitor is preferably smaller than the width of the
light-blocking layer or the interval between the two adjacent
pixels.
[0072] A more specific structure example of one embodiment of the
present invention is described below with reference to
drawings.
Structure Example
[0073] FIG. 1A is a schematic perspective view of a touch panel
module 10 of one embodiment of the present invention. FIG. 1B is a
developed view of the schematic perspective view of the touch panel
module 10. In the touch panel module, a touch sensor module 20 and
a display panel 30 are provided to overlap with each other.
[0074] In the touch sensor module 20, a substrate 21 is provided
with an FPC 41. Furthermore, a touch sensor 22 is provided on a
surface on the display panel 30 side of the substrate 21. The touch
sensor 22 includes a conductive layer 23, a conductive layer 24,
and a conductive layer 25. Furthermore, the touch sensor module 20
includes a wiring 29 which electrically connects these conductive
layers to the FPC 41. The FPC 41 has a function of supplying a
signal from the outside to the touch sensor 22. Furthermore, the
FPC 41 has a function of outputting a signal from the touch sensor
22 to the outside. Note that the substrate without the FPC 41 is
also simply referred to as a touch sensor, or referred to as a
touch sensor substrate or a touch sensor panel.
[0075] The touch sensor 22 includes a plurality of conductive
layers 23, a plurality of conductive layers 24, and a plurality of
conductive layers 25. Each of the conductive layers 23 has a shape
extending in one direction. The plurality of conductive layers 23
are arranged in a direction crossing the extending direction. Each
of the conductive layers 24 is positioned between two adjacent
conductive layers 23. Each of the conductive layer 25 electrically
connects two conductive layers 24 adjacent in the direction
crossing the extending direction of the conductive layers 23. That
is, the plurality of conductive layers 24 arranged in the direction
crossing the extending direction of the conductive layers 23 are
electrically connected to each other with the plurality of
conductive layers 25.
[0076] Here, there is a region where the conductive layer 23 and
the conductive layer 25 overlap with each other. The conductive
layer 23, the conductive layer 25, and an insulating layer which is
provided therebetween and functions as a dielectric form a
capacitor 11. Therefore, the conductive layer 23 and the conductive
layer 25 partly function as the pair of electrodes of the capacitor
11.
[0077] Note that here, the plurality of conductive layers 24 are
electrically connected to each other with the conductive layer 25.
Alternatively, it is possible to employ a structure in which the
conductive layer 24 has a shape extending in one direction like the
conductive layer 23, an insulating layer is provided between the
conductive layer 23 and the conductive layer 24, and the conductive
layer 25 is not provided. In this case, part of the conductive
layer 24 functions as one electrode of the capacitor 11.
[0078] Note that, for example, a low-resistance material is
preferably used as a material of conductive films such as the
conductive layer 23, the conductive layer 24, and the conductive
layer 25, i.e., a wiring and an electrode in the touch panel. As an
example, metal such as silver, copper, or aluminum may be used.
Alternatively, a metal nanowire including a number of conductors
with an extremely small width (for example, a diameter of several
nanometers) may be used. Examples of such a metal nanowire include
an Ag nanowire, a Cu nanowire, and an Al nanowire. In the case of
using an Ag nanowire, light transmittance of 89% or more and a
sheet resistance of 40 ohm/square or more and 100 ohm/square or
less can be achieved. Note that because such a metal nanowire
provides high transmittance, the metal nanowire may be used for an
electrode of the display element, e.g., a pixel electrode or a
common electrode.
[0079] In the display panel 30, a display portion 32 is provided
over a substrate 31. The display portion 32 includes a plurality of
pixels 33 arranged in a matrix. Each pixel 33 preferably includes a
plurality of sub-pixels. Each sub-pixel includes a display element.
A circuit 34 electrically connected to the pixel 33 in the display
portion 32 is preferably provided over the substrate 31. For
example, a circuit functioning as a gate driver circuit can be used
for the circuit 34. An FPC 42 has a function of supplying a signal
from the outside to at least one of the display portion 32 and the
circuit 34. An IC functioning as a source driver circuit is
preferably mounted on the substrate 31 or the FPC 42. The IC can be
mounted on the substrate 31 by a COG method or a COF method.
Alternatively, the FPC 42, a TAB, a TCP, or the like on which an IC
is mounted can be attached to the substrate 31. Note that an object
in which an IC or a connector such as an FPC is mounted on the
display panel 30 can be referred to as a display panel module.
[0080] The touch panel module of one embodiment of the present
invention can output positional information based on the change in
capacitance by the touch sensor 22 at the time of a touch motion.
Furthermore, the display portion 32 can display an image.
[Structural Example of Touch Sensor]
[0081] FIG. 2A is a schematic top view (schematic plan view) of
part of the touch sensor 22. FIG. 2B is an enlarged schematic top
view of a region surrounded by dashed-dotted line in FIG. 2A.
[0082] As shown in FIGS. 2A and 2B, it is preferable that the
conductive layer 23 be partly narrowed so that the width of a
portion crossing the conductive layer 25 is small. Thus, the
capacitance of the capacitor 11 can be reduced. In the case of
using a self-capacitive touch sensor, the detection sensitivity can
be increased more as the capacitance of the capacitor 11 is
smaller.
[0083] Furthermore, it is preferable to provide, between the
conductive layer 23 and the conductive layer 24 which are adjacent
to each other, a conductive layer 26 which is electrically
insulated from these conductive layers 23 and 24. The conductive
layer 26 can suppress the formation of a thin portion of the touch
sensor 22. For example, in the case where the conductive layer 23
and the conductive layer 24 are formed over the same flat surface,
the conductive layer 26 formed in a manner similar to that of the
conductive layer 23 and the conductive layer 24 can increase
coverage of a thin film formed after the formation of these
conductive layers; thus, a surface can be planarized. Furthermore,
owing to the uniform thickness of the touch sensor 22, luminance
unevenness of light emitted from the pixels through the touch
sensor 22 can be reduced, so that the touch panel can achieve high
display quality.
[0084] FIG. 2C shows the case where the conductive layer 23 and the
conductive layer 24 are formed over different flat surfaces and the
conductive layer 25 is not provided. At this time, the conductive
layer 26 may be formed over the flat surface over which the
conductive layer 23 or the conductive layer 24 is formed, or may be
formed over a flat surface different from the flat surface over
which the conductive layer 23 or the conductive layer 24 are
formed. Note that the conductive layer 26 is not necessarily
provided if not necessary.
[0085] FIG. 3A shows an example of a circuit diagram of the touch
sensor 22 including a plurality of conductive layers 23 and a
plurality of conductive layers 24. In FIG. 3A, six conductive
layers 23 and six conductive layers 24 are shown for simplicity,
but the number of the conductive layers 23 and the number of the
conductive layers 24 are not limited thereto.
[0086] One capacitor 11 is formed between one of the conductive
layers 23 and one of the conductive layers 24. Therefore,
capacitors 11 are arranged in a matrix.
[0087] In the case of a projected self-capacitive type, a pulse
voltage is applied to each of the conductive layers 23 and 24 so
that the conductive layers 23 and 24 are scanned, and the value of
a current flowing in the conductive layer 23 or the conductive
layer 24 at this time is sensed. The amount of current is changed
when an object approaches, and therefore, positional information of
the object can be obtained by sensing the difference between the
values. In the case of a projected mutual-capacitive type, a pulse
voltage is applied to one of the conductive layers 23 and 24 so
that one of the conductive layers 23 and 24 is scanned, and a
current flowing in the other is sensed to obtain positional
information of the object.
[0088] The CR value of the conductive layer 23 or the conductive
layer 24 is greater than 0 s and less than or equal to
1.times.10.sup.-4 s, preferably greater than 0 s and less than or
equal to 5.times.10.sup.-5 s, more preferably greater than 0 s and
less than or equal to 5.times.10.sup.-6 s, still more preferably
greater than 0 s and less than or equal to 5.times.10.sup.-7 s,
still more preferably greater than 0 s and less than or equal to
2.times.10.sup.-7 s.
[0089] Each of the conductive layers 23 and 24 preferably has a
lattice shape or a mesh shape having a plurality of openings. FIG.
3B shows an example of a top surface shape of part of the
conductive layer 23.
[0090] The conductive layer 23 shown in FIG. 3B has a lattice shape
in which a distance P1 is provided in a lateral direction and a
distance P2 is provided in a longitudinal direction. The distance
P1 and the distance P2 are almost the same in FIG. 3B, but may be
different from each other. For example, the distance P2 in a
longitudinal direction may be larger than the distance P1 in a
lateral direction as shown in FIG. 3C, or the distance P2 in a
longitudinal direction may be smaller than the distance P1 in a
lateral direction. The same can be said for the conductive layer
24.
[0091] The aperture ratio of the conductive layer 23 or the
conductive layer 24 (the proportion of the opening area in the
conductive layer 23 or the conductive layer 24 per unit area) is
preferably higher than or equal to 20% and lower than 100%, more
preferably higher than or equal to 30% and lower than 100%, still
more preferably higher than or equal to 50% and lower than 100% in
a region.
[0092] The aperture ratio can be easily calculated from the
distance P1, the distance P2, and the width of the conductive
layer. Alternatively, when a region R is assumed to be a periodic
unit in FIG. 3B, the aperture ratio can be calculated from the
ratio of the area of the region R to the area of the conductive
layer 23 included in the region R. Here, the region R is a periodic
unit of a periodic pattern of the conductive layer 23. By arranging
regions R longitudinally and laterally in a periodic manner, the
pattern of the conductive layer 23 can be formed.
[0093] In each of the conductive layer 23 and the conductive layer
24, the line width of a lattice is preferably greater than or equal
to 50 nm and less than or equal to 100 .mu.m, more preferably
greater than or equal to 1 .mu.m and less than or equal to 50
.mu.m, still more preferably greater than or equal to 1 .mu.m and
less than or equal to 20 .mu.m. The lattice having such a narrow
line width allows adjacent pixels to be close to each other in the
case where the opening overlaps with the pixel as described later.
Consequently, the touch panel can have higher resolution and higher
aperture ratio.
[0094] FIG. 4A is an enlarged schematic top view of a region
indicated by a dashed-dotted line in FIG. 2B.
[0095] As shown in FIG. 4A, each of the conductive layers 23 and 24
preferably has a lattice shape (also referred to as a mesh shape).
That is, each of the conductive layers 23 and 24 preferably has a
plurality of openings (an opening 23a and an opening 24a). When the
opening and the pixel are provided to overlap with each other as
described later, light emitted from the display element in the
pixel is not blocked by the conductive layer 23 and the conductive
layer 24, or a reduction in the luminance of light due to the
transmission through the conductive layer 23 and the conductive
layer 24 does not occur. As a result, the touch sensor 22 can be
used in the touch panel without a reduction in the aperture ratio
of the pixel and the light extraction efficiency. It is preferable
that the conductive layer 25 similarly have a shape not overlapping
with the pixel.
[0096] In the structure shown in FIG. 4A, the conductive layer 24
and the conductive layer 25 are electrically connected to each
other through openings 27 formed in an insulating layer positioned
between the conductive layer 24 and the conductive layer 25. The
capacitor 11 is formed in a portion where the conductive layer 23
and the conductive layer 25 overlap with each other.
[0097] As shown in FIG. 4A, the shape of the conductive layer 25
crossing the conductive layer 23 preferably has two or more
portions shaped like strips whose long sides extend in a direction
crossing the conductive layer 23. The plurality of strip-like
portions can reduce contact resistance between the conductive layer
24 and the conductive layer 25. Furthermore, electrical connection
between the conductive layer 25 and the conductive layer 24 can be
kept even when part of the conductive layer 25 is broken or a
contact failure occurs in a portion where the conductive layer 25
and the conductive layer 24 are connected to each other. Defects
like the break and the contact failure might occur particularly
when the touch panel is used while being bent; therefore, the
conductive layer 25 preferably has the above-described shape.
[0098] FIG. 4B shows an example of increasing the area where the
conductive layer 23 and the conductive layer 25 overlap with each
other. In the example, the conductive layer 25 overlaps with the
conductive layer 23 not only in the portion where the conductive
layer 23 and the conductive layer 25 cross each other but also in
another portion, whereby the capacitance of the capacitor 11 can be
increased. The capacitance of the capacitor 11 can be changed as
appropriate by adjusting the area where the conductive layer 23 and
the conductive layer 25 overlap with each other or the dielectric
constant or the thickness of the insulating layer, for example.
[0099] Furthermore, in the example shown in FIG. 4B, the conductive
layer 26 shown in FIGS. 2A to 2C is provided. As shown in FIG. 4B,
a plurality of island-like patterns may be provided as the
conductive layer 26.
[0100] FIG. 5A shows an example where the conductive layer 25 is
not provided in the structure shown in FIG. 4A. In FIG. 5A, the
conductive layer 23 and the conductive layer 24 are provided to
overlap with each other. FIG. 5B shows an example where the
conductive layer 25 is not provided in the structure shown in FIG.
4B.
[0101] FIG. 6 shows an example of a boundary portion between the
conductive layer 23 and the conductive layer 24. As shown in FIG.
6, an opening 22a surrounded by part of the conductive layer 23 and
part of the conductive layer 24 may be formed in the boundary
portion. Such a structure can significantly reduce the distance
between the conductive layer 23 and the conductive layer 24 and can
increase mutual capacitance therebetween. In particular, in the
case of using a mutual capacitive type, the distance between the
two conductive layers is preferably reduced to increase mutual
capacitance.
[Arrangement Example of Opening of Conductive Layer and Pixel]
[0102] FIGS. 7A to 7G, FIG. 8, and FIGS. 9A to 9E are schematic
views each showing the positional relationship between a pixel,
sub-pixels included in the pixel, and the conductive layer 23 which
are seen from the display surface side. Note that although the
conductive layer 23 is shown in FIGS. 7A to 7G, FIG. 8, and FIGS.
9A to 9E as an example, the same applies to the conductive layer 24
and the conductive layer 25.
[0103] In the example shown in FIG. 7A, the pixel 33 includes a
sub-pixel 33R, a sub-pixel 33G, and a sub-pixel 33B. For example,
the sub-pixel 33R, the sub-pixel 33G, and the sub-pixel 33B have a
function of expressing red color, green color, and blue color,
respectively. Note that the number and the colors of the sub-pixels
included in the pixel 33 are not limited thereto.
[0104] The sub-pixels included in the pixel 33 each have a display
element. Typical examples of the display element include
light-emitting elements such as organic EL elements; liquid crystal
elements; display elements (electronic ink) that perform display by
an electrophoretic method, an electronic liquid powder (registered
trademark) method, or the like; MEMS shutter display elements; and
optical interference type MEMS display elements. The sub-pixel may
have a transistor, a capacitor, a wiring that electrically connects
the transistor and the capacitor, and the like in addition to the
display element.
[0105] Furthermore, this embodiment can be used in a transmissive
liquid crystal display, a transflective liquid crystal display, a
reflective liquid crystal display, a direct-view liquid crystal
display, or the like. In the case of a transflective liquid crystal
display or a reflective liquid crystal display, some or all of
pixel electrodes function as reflective electrodes. For example,
some or all of pixel electrodes are formed to contain aluminum,
silver, or the like. In such a case, a memory circuit such as an
SRAM can be provided under the reflective electrodes, leading to
lower power consumption. A structure suitable for employed display
elements can be selected from among a variety of structures of
pixel circuits.
[0106] In the structure shown in FIG. 7A, one opening 23a in the
conductive layer 23 is provided to overlap with three sub-pixels,
i.e., the sub-pixel 33R, the sub-pixel 33G, and the sub-pixel 33B.
In this manner, the opening 23a in the conductive layer 23 is
preferably provided to overlap with one pixel 33. In other words,
the pixels 33 and the openings in the lattice of the conductive
layer 23 are preferably provided at the same intervals. Such a
structure allows the peripheral portions of the pixels 33 to have
the same structures (e.g., the structures of films in the pixels
and in the periphery of the pixels, the thicknesses of the films,
and the unevenness of surfaces thereof), leading to a reduction in
display unevenness.
[0107] Note that two or more pixels 33 and one opening 23a may
overlap with each other as shown in FIG. 8, for example.
[0108] FIG. 7B shows an example where one opening 23a and one
sub-pixel overlap with each other. When the conductive layer 23 is
provided between two sub-pixels in one pixel 33 in a plan view, the
wiring resistance of the conductive layer 23 can be reduced.
Consequently, the detection sensitivity of the touch panel can be
increased.
[0109] FIG. 7C shows an example where the pixel 33 further includes
a sub-pixel 33Y in the structure shown in FIG. 7A. For example, a
pixel capable of expressing yellow color can be used for the
sub-pixel 33Y. Instead of the sub-pixel 33Y, a pixel capable of
expressing white color may be used. When the pixel 33 includes
sub-pixels of more than three colors, power consumption can be
reduced.
[0110] FIG. 7D shows an example where one opening 23a and one
sub-pixel overlaps with each other, i.e., an example where the
conductive layer 23 is provided between two adjacent sub-pixels in
a plan view. Note that a structure in which two of the four
sub-pixels overlap with one opening 23a may be employed, although
not shown.
[0111] In the examples shown in FIGS. 7A to 7D, sub-pixels of each
color are arranged in a stripe pattern. Alternatively, as shown in
FIGS. 7E to 7G, sub-pixels of two colors may be alternated in one
direction, for example. In a structure shown in FIG. 7E, the pixel
33 including four sub-pixels and one opening 23a overlap with each
other. In a structure shown in FIG. 7F, two adjacent sub-pixels and
one opening 23a overlap with each other. In a structure shown in
FIG. 7G, one sub-pixel and one opening 23a overlap with each
other.
[0112] Furthermore, the sub-pixels included in the pixel 33 may
differ in size (e.g., the area of a region contributing to
display). For example, the size of the sub-pixel of blue color with
a relatively low luminosity factor can be set large, whereas the
size of the sub-pixel of green or red color with a relatively high
luminosity factor can be set small.
[0113] FIGS. 9A and 9B each show an example where the size of the
sub-pixel 33B is larger than the size of the sub-pixel 33R and the
size of the sub-pixel 33G. In the examples shown here, the
sub-pixel 33R and the sub-pixel 33G are alternated. However,
sub-pixels of each color may be arranged in a stripe pattern as
shown in FIG. 7A and other drawings, and may have different sizes
from each other.
[0114] FIG. 9A shows a structure in which the pixel 33 including
three sub-pixels and one opening 23a overlap with each other. FIG.
9B shows a structure in which one opening 23a and one sub-pixel 33B
overlap with each other and another opening 23a and two sub-pixels
(the sub-pixel 33R and the sub-pixel 33G) overlap with each
other.
[0115] Alternatively, pixel structures as those shown in FIGS. 9C
to 9E can be employed. Here, a column of the sub-pixels 33B
arranged in a stripe pattern is provided between columns in each of
which sub-pixels 33R and 33G are alternated. Furthermore, one
sub-pixel 33B is provided between one sub-pixel 33R and one
sub-pixel 33G.
[0116] In the structure shown in FIG. 9C, six sub-pixels (using two
sub-pixels for each color) overlap with one opening 23a. In a
structure shown in FIG. 9D, three sub-pixels (using one sub-pixel
for each color) overlap with one opening 23a. In a structure shown
in FIG. 9E, one sub-pixel and one opening 23a overlap with each
other. Note that the pixel structure is not limited to the
structures described here, and a structure in which two or more
adjacent sub-pixels and one opening 23a overlap with each other may
be employed.
[0117] Note that although the positional relationship between the
conductive layer 23 and the sub-pixels is described here, the same
applies to the conductive layer 24 and the conductive layer 25.
That is, in the touch panel of one embodiment of the present
invention, the opening 23a in the conductive layer 23 overlaps with
one or more sub-pixels in a region and the opening 24a in the
conductive layer 24 overlaps with one or more of the other
sub-pixels in a region. Since each sub-pixel includes the display
element as described above, it can be said that the opening 23a and
the opening 24a each have a region overlapping with one or more
display elements.
[Stacked-Layer Structure Included in Touch Panel]
[0118] FIG. 10A is a schematic top view of part of the touch panel
when seen from the display surface side. In FIG. 10A, the
conductive layer 23, the conductive layers 24, the conductive layer
25, a light-blocking layer 53, coloring layers 52R, 52G, and 52B,
and the like are shown.
[0119] FIG. 10B is a developed schematic view of a stacked-layer
structure of FIG. 10A. As shown in FIG. 10B, the light-blocking
layer 53, the conductive layer 23, the conductive layers 24, an
insulating layer 28, the conductive layer 25, the coloring layers
52R, 52G, and 52B, and display elements 51 are provided between the
substrate 21 and the substrate 31.
[0120] Note that hereinafter, each of the coloring layers 52R, 52G,
and 52B is also simply referred to as a coloring layer 52 in the
case of describing common points of the coloring layers 52R, 52G,
and 52B without distinguishing them.
[0121] Each coloring layer 52 has a function of transmitting light
in a particular wavelength range. Here, the coloring layer 52R
transmits red light, the coloring layer 52G transmits green light,
and the coloring layer 52B transmits blue light. One of the display
elements 51 and one of the coloring layers 52 are provided to
overlap with each other, whereby only light in a particular
wavelength range in light emitted from the display element can be
transmitted to the substrate 21 side.
[0122] The light-blocking layer 53 has a function of blocking
visible light. The light-blocking layer 53 is provided to overlap
with a region between two adjacent coloring layers 52. In the
example shown in FIGS. 10A and 10B, the light-blocking layer 53 has
an opening provided to overlap with the display element 51 and the
coloring layer 52.
[0123] As shown in FIG. 10B, the light-blocking layer 53 is
preferably provided closer to the substrate 21 than the conductive
layer 23, the conductive layers 24, and the conductive layer 25.
That is, the light-blocking layer 53 is preferably provided closer
to the display surface than these conductive layers. Furthermore,
the light-blocking layer 53, the conductive layer 23, the
conductive layers 24, and the conductive layer 25 preferably
overlap with each other in a region. Such a structure allows the
conductive layer 23, the conductive layers 24, and the conductive
layer 25 to be less recognized visually by a user because these
conductive layers are hidden by the light-blocking layer 53 when
seen from the display surface side. Such a structure is effective
particularly when the conductive layer 23, the conductive layers
24, and the conductive layer 25 are formed using a material
reflecting visible light such as metal or alloy.
[0124] In the structure shown in FIG. 10B, the conductive layer 23,
the conductive layer 25, and the insulating layer 28 provided
therebetween form the capacitor 11. Furthermore, the two conductive
layers 24 between which the conductive layer 23 is provided are
electrically connected to the conductive layer 25 through the
openings 27 formed in the insulating layer 28.
[0125] Each of the conductive layer 23, the conductive layer 24,
and the conductive layer 25 is preferably provided between two
adjacent display elements 51 in a plan view. Furthermore, each of
the conductive layer 23, the conductive layer 24, and the
conductive layer 25 is preferably provided between two adjacent
coloring layers 52 in a plan view. Note that in the case where the
area of the coloring layer 52 or the area of the display element 51
is larger than the opening area in the light-blocking layer 53,
part of the conductive layer 23, the conductive layer 24, or the
conductive layer 25 may overlap with the display element 51 or the
coloring layer 52 in a region.
[0126] Note that in the example shown here, the coloring layer 52
is provided closer to the substrate 31 than the conductive layer 23
or the like; however, the coloring layer 52 may be provided closer
to the substrate 21 than the conductive layer 23 or the like.
[0127] In the example shown in FIGS. 10A and 10B, the two
conductive layers 24 between which the conductive layer 23 is
provided are electrically connected to each other with the
conductive layer 25. However, the conductive layer 25 is not
necessarily provided as described above.
[0128] FIGS. 11A and 11B show a structure example of the case where
the conductive layer 25 and the opening 27 are not provided in
FIGS. 10A and 10B. As shown in FIG. 11B, the conductive layer 23,
the conductive layer 24, and the insulating layer 28 provided
therebetween form the capacitor 11.
[0129] The above is the description of the stacked-layer
structure.
[Cross-Sectional Structure Example]
[0130] A cross-sectional structure example of the touch panel
module 10 is described below.
[Cross-Sectional Structure Example 1]
[0131] FIG. 12A is a schematic cross-sectional view of a touch
panel module of one embodiment of the present invention. In the
touch panel module shown in FIG. 12A, a capacitor of a touch sensor
and a display element are provided between a pair of substrates,
and therefore, the thickness of the touch panel module can be
reduced.
[0132] The touch panel module has a structure in which the
substrate 21 and the substrate 31 are bonded to each other with an
adhesive layer 220. The conductive layer 23, the conductive layer
24, the conductive layer 25, and the insulating layer 28 which form
a touch sensor, a contact portion 253, the coloring layer 52, the
light-blocking layer 53, and the like are provided on the substrate
31 side of the substrate 21. A transistor 201, a transistor 202, a
transistor 203, a light-emitting element 204, a contact portion
205, and the like are provided on the substrate 21 side of the
substrate 31.
[0133] An insulating layer 212, an insulating layer 213, an
insulating layer 214, an insulating layer 215, an insulating layer
216, an insulating layer 217, an insulating layer 218, a spacer
219, a conductive layer 225, and the like are provided over the
substrate 31 with an adhesive layer 211 provided therebetween.
[0134] The light-emitting element 204 is provided over the
insulating layer 217. The light-emitting element 204 includes a
first electrode 221, an EL layer 222, and a second electrode 223
(see FIG. 12B). An optical adjustment layer 224 is provided between
the first electrode 221 and the EL layer 222. The insulating layer
218 is provided to cover end portions of the first electrode 221
and the optical adjustment layer 224.
[0135] In FIG. 12A, the transistor 201 for controlling current and
the transistor 202 for controlling switching are provided in the
pixel 33. One of a source and a drain of the transistor 201 is
electrically connected to the first electrode 221 through the
conductive layer 225.
[0136] In FIG. 12A, the transistor 203 is provided in the circuit
34.
[0137] In the example illustrated in FIG. 12A, the transistors 201
and 203 each have a structure in which a semiconductor layer where
a channel is formed is provided between two gate electrodes. Such
transistors can have a higher field-effect mobility and thus have
higher on-state current than other transistors. Consequently, a
circuit capable of high-speed operation can be obtained.
Furthermore, the area occupied by a circuit portion can be reduced.
The use of the transistor having high on-state current can reduce
signal delay in wirings and can suppress display unevenness even in
a display panel or a touch panel in which the number of wirings is
increased because of increase in size or resolution.
[0138] Note that the transistor included in the circuit 34 and the
transistor included in the pixel 33 may have the same structure.
Transistors included in the circuit 34 may have the same structure
or different structures. Transistors included in the pixel 33 may
have the same structure or different structures.
[0139] The light-emitting element 204 has a top-emission structure
and emits light to the second electrode 223 side. The transistors
201 and 202, a capacitor, a wiring, and the like are provided to
overlap with the light-emitting region of the light-emitting
element 204. Thus, an aperture ratio of the pixel 33 can be
increased.
[0140] The spacer 219 is provided over the insulating layer 218 and
has a function of adjusting the distance between the substrate 31
and the substrate 21. In FIG. 12A, the spacer 219 and an overcoat
267 of the substrate 21 are provided with a gap therebetween.
Alternatively, as shown in FIG. 13, components such as the overcoat
267 on the substrate 21 side may be in contact with the second
electrode 223 over the spacer 219 in a region. Furthermore, as
shown in FIG. 13, the spacer 219 may also be provided outside the
pixel 33, e.g., in a region overlapping with the circuit 34 or in a
peripheral portion of the substrate 21 or the substrate 31.
Although the spacer 219 is formed on the substrate 31 side in the
structure described here, the spacer 219 may be formed on the
substrate 21 side. For example, the spacer 219 may be provided on
an insulating layer 266, the overcoat 267, the coloring layer 52,
or the like.
[0141] As shown in FIG. 14, a spherical spacer 226 may be used
instead of the spacer 219. A light-transmitting material or a
light-absorbing material may be used for the spherical spacer 226.
Although a material such as silica can be used for the spacer 226,
an elastic material such as an organic resin or rubber is
preferably used. In FIG. 14, the spacer 226 having elasticity is
deformed and seems to be pressed from above and below.
[0142] An insulating layer 262, the light-blocking layer 53, an
insulating layer 264, the conductive layer 23, the conductive layer
24, the insulating layer 28, the conductive layer 25, the
insulating layer 266, the coloring layer 52, and the like are
provided on the substrate 31 side of the substrate 21 with an
adhesive layer 261 provided between the substrate 21 and them.
Furthermore, the overcoat 267 covering the coloring layer 52 may be
provided.
[0143] The light-blocking layer 53 is provided closer to the
substrate 31 than the insulating layer 262. The light-blocking
layer 53 has the opening, and the opening is provided to overlap
with the light-emitting region of the light-emitting element
204.
[0144] As examples of a material that can be used for the
light-blocking layer 53, carbon black, a metal oxide, and a
composite oxide containing a solid solution of a plurality of metal
oxides can be given. Stacked films containing the material of the
coloring layer 52 are preferably used for the light-blocking layer
53. For example, a material containing an acrylic resin can be used
for each coloring layer, and a stacked-layer structure of a film
containing the material of the coloring layer 52R transmitting red
light and a film containing the material of the coloring layer 52B
transmitting blue light can be employed. Formation of the coloring
layer 52 and the light-blocking layer 53 using the same material
can reduce a manufacturing cost because the same manufacturing
apparatus can be used.
[0145] As examples of a material that can be used for the coloring
layer 52, a metal material, a resin material, and a resin material
containing a pigment or dye can be given.
[0146] The insulating layer 264 is provided to cover the
light-blocking layer 53. The insulating layer 264 may have a
function of a planarization film. In the case where a material with
low heat resistance is used for the light-blocking layer 53, an
organic insulating material is preferably used for the insulating
layer 264 because a layer with high planarity can be formed at a
low temperature. Alternatively, an inorganic insulating material is
preferably used for the insulating layer 264 because the insulating
layer 264 can function as an etching stopper at the time of
processing the conductive layer 23 and the conductive layer 24.
[0147] Each of the conductive layer 23 and the conductive layer 24
is provided to cover part of the insulating layer 264. Each of the
conductive layer 23 and the conductive layer 24 overlaps with the
light-blocking layer 53 in a region. In FIG. 12A, the example where
the conductive layer 24 is provided in part of a region of the
pixel 33 is shown. The opening 24a in the conductive layer 24
overlaps with the light-emitting element 204 in a region. In the
pixel 33, the conductive layer 24 is provided to surround the
light-emitting region of the light-emitting element 204. Therefore,
the conductive layer 24 may overlap with, for example, the spacer
219, the insulating layer 218, the conductive layer 225, the
transistor 201, the transistor 202, or a wiring electrically
connected to the transistor 201 or 202 in a region. The same
applies to the conductive layer 23 and the conductive layer 25.
[0148] In the example shown in FIG. 12A, the conductive layer 23
and the conductive layer 24 are processed using the same conductive
film. Since the conductive layer 23 and the conductive layer 24 are
formed over the entire display region, formation of the conductive
layers in the same step can reduce display unevenness.
[0149] The insulating layer 28 has a function of a dielectric of
the capacitor 11. In the example shown in FIG. 12A, an inorganic
insulating material is used for the insulating layer 28. When the
insulating layer 28 is formed using an inorganic insulating
material, the insulating layer 28 having a uniform thickness can be
formed easily, and furthermore, the insulating layer 28 can be
thinner than the case of using an organic insulating material.
Therefore, variation in the capacitances of the capacitors 11 can
be reduced. Like the insulating layer 264, the insulating layer 28
can function as an etching stopper at the time of processing the
conductive layer 25. Note that the insulating layer 28 may be
formed using an organic insulating material. In this case, a
material with low heat resistance can be used for components
between the substrate 21 and the insulating layer 28, and
therefore, the range of choices of materials thereof can be
expanded.
[0150] The conductive layer 25 is provided to cover part of the
insulating layer 28. The conductive layer 25 is provided to overlap
with the light-blocking layer 53. Part of the conductive layer 25
overlaps with the conductive layer 23 in a region. The conductive
layer 25 has a function of electrically connecting the two
conductive layers 24 between which the conductive layer 23 is
provided, through the openings formed in the insulating layer
28.
[0151] The insulating layer 266 is provided to cover the conductive
layer 25 and the insulating layer 28, and the coloring layer 52 is
provided to cover part of the insulating layer 266. The overcoat
267 may be provided to cover the coloring layer 52.
[0152] It is preferable that the insulating layer 266 have a
function of a planarization layer and be formed using an organic
insulating material. Alternatively, an inorganic insulating
material having high planarity may be used. A flat surface provided
by the insulating layer 266 can reduce a variation in the thickness
of the coloring layer 52. Thus, the touch panel can have high
display quality.
[0153] When a flexible substrate is used for at least one of the
substrates 21 and 31, the touch panel can be thin and lightweight.
When a flexible substrate is used for each of the substrates 21 and
31, the touch panel can be flexible.
[0154] A color filter method is employed in the touch panel shown
in FIGS. 12A and 12B. For example, a structure where pixels of
three colors of red (R), green (G), and blue (B) express one color
can be employed for the coloring layer 52. In addition, a pixel of
white (W) or yellow (Y) may be used for the structure.
[0155] An EL layer that emits white light is preferably used as the
EL layer 222 of the light-emitting element 204. By using the
light-emitting element 204, it is not necessary to separately form
the EL layers 222 expressing different colors in pixels. Therefore,
the cost can be reduced, and the high resolution is achieved
easily. Furthermore, by varying the thickness of the optical
adjustment layer 224 in pixels, light with a wavelength suitable
for each pixel can be extracted, which increases color purity. Note
that the EL layers 222 expressing different colors may be
separately formed in pixels, in which case the optical adjustment
layer 224 is not necessarily used.
[0156] An opening is provided in the insulating layers and the like
in a region overlapping with the contact portion 205 provided over
the substrate 31, and the contact portion 205 and the FPC 41 are
electrically connected to each other with a connection layer 260
provided in the opening. Furthermore, an opening is provided in the
insulating layers and the like in a region overlapping with the
substrate 21, and the contact portion 253 and the FPC 42 are
electrically connected to each other through a connection layer 210
provided in the opening.
[0157] Note that as shown in FIG. 13 or FIG. 14, a structure in
which the FPC 41 and the connection layer 260 do not overlap with
the substrate 21 and the insulating layer and the like provided for
the substrate 21 may be employed. Similarly, in the structures
shown in FIG. 13 and FIG. 14, the FPC 42 and the connection layer
210 do not overlap with the substrate 31 and the insulating layer
and the like provided for the substrate 31.
[0158] In the structure shown in FIG. 12A, the contact portion 205
has a conductive layer formed by processing a conductive film that
is also used for the source electrode and the drain electrode of
the transistor. Furthermore, the contact portion 253 has a
stacked-layer structure of a conductive layer formed by processing
a conductive film that is also used for the conductive layer 23 and
the conductive layer 24, and a conductive layer formed by
processing a conductive film that is also used for the conductive
layer 25. The contact portion preferably has a stacked-layer
structure of a plurality of conductive layers as described above
because electric resistance can be reduced and mechanical strength
can be increased.
[0159] Furthermore, FIG. 12A shows a cross-sectional structure of a
crossing portion 206 where a wiring formed by processing the
conductive film used for forming the gate electrode of the
transistor and a wiring formed by processing the conductive film
used for forming the source electrode and the drain electrode of
the transistor cross each other.
[0160] As the connection layer 210 and the connection layer 260,
any of various anisotropic conductive films (ACF), anisotropic
conductive pastes (ACP), or the like can be used.
[0161] A material in which impurities such as water or hydrogen do
not easily diffuse is preferably used for the insulating layer 212
and the insulating layer 262. That is, the insulating layer 212 and
the insulating layer 262 can each function as a barrier film. Such
a structure can effectively suppress diffusion of the impurities to
the light-emitting element 204 and the transistors even in the case
of using a material permeable to moisture for the substrate 21 and
the substrate 31, and a highly reliable touch panel can be
achieved.
[0162] Here, the distance between one of the conductive layer 23
and the conductive layer 24 (or the conductive layer 25) which is
positioned closer to the display panel (i.e., the substrate side on
which the display element is provided) than the other and a
conductive layer which is the closest to the one of the conductive
layer 23 and the conductive layer 24 (or the conductive layer 25)
of the conductive layers provided closer to the display panel than
the one of the conductive layer 23 and the conductive layer 24 (or
the conductive layer 25) is preferably greater than or equal to 25
nm and less than or equal to 100 .mu.m, more preferably greater
than or equal to 50 nm and less than or equal to 10 .mu.m, still
more preferably greater than or equal to 50 nm and less than or
equal to 5 .mu.m.
[0163] In the example shown in FIG. 12A, the second electrode 223
of the light-emitting element 204 corresponds to the conductive
layer which is the closest to the conductive layer 24 in a region
of the pixel 33 of the conductive layers provided closer to the
display panel than the conductive layer 24. Here, the distance
between the conductive layer 24 and the second electrode 223 is
denoted by D. As the distance D is shorter, a distance between the
pair of substrates can be reduced more, and the thickness of the
touch panel can be reduced more. In particular, when flexible
substrates are used as the pair of substrates, the touch panel can
be flexible and strong against bending.
[0164] Note that the conductive layer which is the closest to the
conductive layer 23 or 24 of the conductive layers provided closer
to the display panel than the conductive layer 23 or 24 is not
limited to the second electrode 223 and may be a conductive layer
other than the second electrode 223. For example, in the case where
another conductive layer is provided between the second electrode
223 and the conductive layer 23 or 24, the distance between the
conductive layer and the conductive layer 23 or 24 is set within
the above-described range. For example, a conductive layer can be
provided on the insulating layer 266 so that the adhesive layer 220
can be formed on a surface with higher wettability of higher
adhesion.
[Components]
[0165] The above components are described below.
[0166] The transistor includes a conductive layer functioning as
the gate electrode, the semiconductor layer, a conductive layer
functioning as the source electrode, a conductive layer functioning
as the drain electrode, and an insulating layer functioning as a
gate insulating layer. FIG. 12A shows the case where a bottom-gate
transistor is used.
[0167] Note that there is no particular limitation on the structure
of the transistor included in the touch panel of one embodiment of
the present invention. For example, a forward staggered transistor
or an inverted staggered transistor may be used. A top-gate
transistor or a bottom-gate transistor may be used. A semiconductor
material used for the transistor is not particularly limited, and
for example, an oxide semiconductor, silicon, or germanium can be
used.
[0168] There is no particular limitation on the crystallinity of a
semiconductor material used for the transistor, and an amorphous
semiconductor or a semiconductor having crystallinity (a
microcrystalline semiconductor, a polycrystalline semiconductor, a
single-crystal semiconductor, or a semiconductor partly including
crystal regions) may be used. It is preferable that a semiconductor
having crystallinity be used, in which case deterioration of the
transistor characteristics can be suppressed.
[0169] As a semiconductor material for the semiconductor layer of
the transistor, an element of Group 14, a compound semiconductor,
or an oxide semiconductor can be used, for example. Typically, a
semiconductor containing silicon, a semiconductor containing
gallium arsenide, an oxide semiconductor containing indium, or the
like can be used.
[0170] An oxide semiconductor is preferably used as a semiconductor
in which a channel of the transistor is formed. In particular, an
oxide semiconductor having a wider band gap than silicon is
preferably used. A semiconductor material having a wider band gap
and a lower carrier density than silicon is preferably used because
off-state current of the transistor can be reduced.
[0171] For example, the oxide semiconductor preferably contains at
least indium (In) or zinc (Zn). The oxide semiconductor more
preferably contains an In--M-Zn-based oxide (M is a metal such as
Al, Ti, Ga, Ge, Y, Zr, Sn, La, Ce, or Hf).
[0172] As the semiconductor layer, it is particularly preferable to
use an oxide semiconductor film including a plurality of crystal
parts whose c-axes are aligned substantially perpendicular to a
surface on which the semiconductor layer is formed or the top
surface of the semiconductor layer and having no grain boundary
between adjacent crystal parts.
[0173] There is no grain boundary in such an oxide semiconductor;
thus, generation of a crack in an oxide semiconductor film which is
caused by stress when a display panel is bent is prevented.
Therefore, such an oxide semiconductor can be preferably used for a
flexible touch panel which is used in a bent state, or the
like.
[0174] Moreover, the use of such an oxide semiconductor for the
semiconductor layer makes it possible to provide a highly reliable
transistor in which a change in the electrical characteristics is
suppressed.
[0175] Charge accumulated in a capacitor through a transistor can
be held for a long time because of the low off-state current of the
transistor. When such a transistor is used for a pixel, operation
of a driver circuit can be stopped while a gray scale of an image
displayed in each display region is maintained. As a result, a
display device with an extremely low power consumption can be
obtained.
[0176] Alternatively, silicon is preferably used as a semiconductor
in which a channel of a transistor is formed. Although amorphous
silicon may be used as silicon, silicon having crystallinity is
particularly preferable. For example, microcrystalline silicon,
polycrystalline silicon, single crystal silicon, or the like is
preferably used. In particular, polycrystalline silicon can be
formed at a lower temperature than single crystal silicon and has
higher field effect mobility and higher reliability than amorphous
silicon. When such a polycrystalline semiconductor is used for a
pixel, the aperture ratio of the pixel can be improved. Even in the
case where pixels are provided at extremely high resolution, a gate
driver circuit and a source driver circuit can be formed over a
substrate over which the pixels are formed, and the number of
components of an electronic appliance can be reduced.
[0177] As conductive layers such as a gate, a source, and a drain
of the transistor and a wiring and an electrode in the touch panel,
a single-layer structure or a stacked-layer structure using any of
metals such as aluminum, titanium, chromium, nickel, copper,
yttrium, zirconium, molybdenum, silver, tantalum, and tungsten, or
an alloy containing any of these metals as its main component can
be used. For example, a single-layer structure of an aluminum film
containing silicon, a two-layer structure in which an aluminum film
is stacked over a titanium film, a two-layer structure in which an
aluminum film is stacked over a tungsten film, a two-layer
structure in which a copper film is stacked over a
copper-magnesium-aluminum alloy film, a two-layer structure in
which a copper film is stacked over a titanium film, a two-layer
structure in which a copper film is stacked over a tungsten film, a
three-layer structure in which a titanium film or a titanium
nitride film, an aluminum film or a copper film, and a titanium
film or a titanium nitride film are stacked in this order, a
three-layer structure in which a molybdenum film or a molybdenum
nitride film, an aluminum film or a copper film, and a molybdenum
film or a molybdenum nitride film are stacked in this order, and
the like can be given. Note that a transparent conductive material
containing indium oxide, tin oxide, or zinc oxide may be used.
Copper containing manganese is preferably used because
controllability of a shape by etching is increased.
[0178] As a light-transmitting conductive material, a conductive
oxide such as indium oxide, indium tin oxide, indium zinc oxide,
zinc oxide, or zinc oxide to which gallium is added, or graphene
can be used. Alternatively, a metal material such as gold, silver,
platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron,
cobalt, copper, palladium, or titanium, or an alloy material
containing any of these metal materials can be used. Alternatively,
a nitride of the metal material (e.g., titanium nitride) or the
like may be used. In the case of using the metal material or the
alloy material (or the nitride thereof), the thickness is set small
enough to be able to transmit light. Alternatively, a stack of any
of the above materials can be used as the conductive layer. For
example, a stack of indium tin oxide and an alloy of silver and
magnesium is preferably used because the conductivity can be
increased.
[0179] Examples of an insulating material that can be used for the
insulating layers, the overcoat 267, the spacer 219, and the like
include a resin such as acrylic or epoxy resin, a resin having a
siloxane bond, and an inorganic insulating material such as silicon
oxide, silicon oxynitride, silicon nitride oxide, silicon nitride,
or aluminum oxide.
[0180] As described above, the light-emitting element is preferably
provided between a pair of insulating films with low water
permeability. Thus, an impurity such as water can be prevented from
entering the light-emitting element, leading to prevention of a
decrease in the reliability of the light-emitting device.
[0181] As an insulating film with low water permeability, a film
containing nitrogen and silicon (e.g., a silicon nitride film or a
silicon nitride oxide film), a film containing nitrogen and
aluminum (e.g., an aluminum nitride film), or the like can be used.
Alternatively, a silicon oxide film, a silicon oxynitride film, an
aluminum oxide film, or the like can be used.
[0182] For example, the water vapor transmittance of the insulating
film with low water permeability is lower than or equal to
1.times.10.sup.-5 [g/(m.sup.2day)], preferably lower than or equal
to 1.times.10.sup.-6 [g/(m.sup.2day)], further preferably lower
than or equal to 1.times.10.sup.-7 [g/(m.sup.2day)], still further
preferably lower than or equal to 1.times.10.sup.-8
[g/(m.sup.2day)].
[0183] For the adhesive layers, a curable resin such as a heat
curable resin, a photocurable resin, or a two-component type
curable resin can be used. For example, a resin such as an acrylic
resin, a urethane resin, an epoxy resin, or a resin having a
siloxane bond can be used.
[0184] The EL layer 222 includes at least a light-emitting layer.
In addition to the light-emitting layer, the EL layer 222 may
further include one or more layers containing any of a substance
with a high hole-injection property, a substance with a high
hole-transport property, a hole-blocking material, a substance with
a high electron-transport property, a substance with a high
electron-injection property, a substance with a bipolar property (a
substance with a high electron- and hole-transport property), and
the like.
[0185] For the EL layer 222, either a low molecular compound or a
high molecular compound can be used, and an inorganic compound may
be used. Each of the layers included in the EL layer 222 can be
formed by any of the following methods: an evaporation method
(including a vacuum evaporation method), a transfer method, a
printing method, an inkjet method, a coating method, and the
like.
[0186] In the case where a light-emitting element emitting white
light is used as the light-emitting element 204, the EL layer 222
preferably contains two or more kinds of light-emitting substances.
For example, light-emitting substances are selected so that two or
more light-emitting substances emit complementary colors to obtain
white light emission. Specifically, it is preferable to contain two
or more selected from light-emitting substances emitting light of
red (R), green (G), blue (B), yellow (Y), orange (0), and the like
and light-emitting substances emitting light containing two or more
of spectral components of R, G, and B. The light-emitting element
204 preferably emits light with a spectrum having two or more peaks
in the wavelength range of a visible light region (e.g., 350 nm to
750 nm). An emission spectrum of a material emitting light having a
peak in the wavelength range of a yellow light preferably includes
spectral components also in the wavelength range of a green light
and a red light.
[0187] More preferably, a light-emitting layer containing a
light-emitting material emitting light of one color and a
light-emitting layer containing a light-emitting material emitting
light of another color are stacked in the EL layer 222. For
example, the plurality of light-emitting layers in the EL layer 222
may be stacked in contact with each other or may be stacked with a
separation layer therebetween. For example, a separation layer may
be provided between a fluorescent layer and a phosphorescent
layer.
[0188] The separation layer can be provided to prevent an energy
transfer by the Dexter mechanism (particularly triplet energy
transfer) from a phosphorescent material or the like in an excited
state which is generated in the phosphorescent layer to a
fluorescent material or the like in the fluorescent layer. The
thickness of the separation layer may be approximately several
nanometers, specifically 0.1 nm or more and 20 nm or less, 1 nm or
more and 10 nm or less, or 1 nm or more and 5 nm or less. The
separation layer contains a single material (preferably a bipolar
material) or a plurality of materials (preferably, a hole-transport
material and an electron-transport material).
[0189] The separation layer may be formed using a material
contained in the light-emitting layer in contact with the
separation layer. This facilitates the manufacture of the
light-emitting element and reduces the drive voltage. For example,
in the case where the phosphorescent layer contains a host
material, an assist material, and the phosphorescent material (a
guest material), the separation layer may contain the host material
and the assist material. In other words, the separation layer
includes a region which does not contain the phosphorescent
material, while the phosphorescent layer includes a region
containing the phosphorescent material. Thus, the separation layer
and the phosphorescent layer can be separately deposited depending
on the presence of the phosphorescent material. Furthermore, such a
structure enables the separation layer and the phosphorescent layer
to be deposited in the same chamber, which leads to a reduction in
manufacturing cost.
[0190] The light-emitting element 204 may be a single element
including one EL layer or a tandem element in which a plurality of
EL layers are stacked with a charge generation layer
therebetween.
[Manufacturing Method Example]
[0191] Here, a method for manufacturing a flexible touch panel is
described.
[0192] For convenience, a structure including a pixel and a
circuit, a structure including an optical member such as a color
filter, or a structure including a touch sensor is referred to as
an element layer. An element layer includes a display element, for
example, and may include a wiring electrically connected to the
display element or an element such as a transistor used in a pixel
or a circuit in addition to the display element.
[0193] Here, a support body (e.g., the substrate 21 or the
substrate 31) with an insulating surface where an element layer is
formed is referred to as a base material.
[0194] As a method for forming an element layer over a flexible
base material provided with an insulating surface, there are a
method in which an element layer is formed directly over a base
material, and a method in which an element layer is formed over a
supporting base material that has stiffness and then the element
layer is separated from the supporting base material and
transferred to the base material.
[0195] In the case where a material of the base material can
withstand heating temperature in a process for forming the element
layer, it is preferable that the element layer be formed directly
over the base material, in which case a manufacturing process can
be simplified. At this time, the element layer is preferably formed
in a state where the base material is fixed to the supporting base
material, in which case transfer thereof in an apparatus and
between apparatuses can be easy.
[0196] In the case of employing the method in which the element
layer is formed over the supporting base material and then
transferred to the base material, first, a separation layer and an
insulating layer are stacked over the supporting base material, and
then the element layer is formed over the insulating layer. Next,
the element layer is separated from the supporting base material
and then transferred to the base material. At this time, a material
is selected that would causes separation at an interface between
the supporting base material and the separation layer, at an
interface between the separation layer and the insulating layer, or
in the separation layer.
[0197] For example, it is preferable that a stacked layer of a
layer including a high-melting-point metal material, such as
tungsten, and a layer including an oxide of the metal material be
used as the separation layer, and a stacked layer of a plurality of
layers, such as a silicon nitride layer and a silicon oxynitride
layer be used over the separation layer. The use of the
high-melting-point metal material is preferable because the degree
of freedom of the process for forming the element layer can be
increased.
[0198] The separation may be performed by application of mechanical
power, by etching of the separation layer, by dripping of a liquid
into part of the separation interface to penetrate the entire
separation interface, or the like. Alternatively, separation may be
performed by heating the separation interface by utilizing a
difference in thermal expansion coefficient.
[0199] The separation layer is not necessarily provided in the case
where separation can occur at an interface between the supporting
base material and the insulating layer. For example, glass is used
as the supporting base material and an organic resin such as
polyimide is used as the insulating layer, a separation trigger is
formed by locally heating part of the organic resin by laser light
or the like, and separation is performed at an interface between
the glass and the insulating layer. Alternatively, a metal layer
may be provided between the supporting base material and the
insulating layer formed of an organic resin, and separation may be
performed at the interface between the metal layer and the
insulating layer by heating the metal layer by feeding a current to
the metal layer. In that case, the insulating layer formed of an
organic resin can be used as a base material.
[0200] Examples of such a base material having flexibility include
polyester resins such as polyethylene terephthalate (PET) and
polyethylene naphthalate (PEN), a polyacrylonitrile resin, a
polyimide resin, a polymethyl methacrylate resin, a polycarbonate
(PC) resin, a polyethersulfone (PES) resin, a polyamide resin, a
cycloolefin resin, a polystyrene resin, a polyamide imide resin,
and a polyvinyl chloride resin. In particular, it is preferable to
use a material with a low thermal expansion coefficient, and for
example, a polyamide imide resin, a polyimide resin, PET, or the
like with a thermal expansion coefficient lower than or equal to
30.times.10.sup.-6/K can be suitably used. A substrate in which a
fibrous body is impregnated with a resin (also referred to as
prepreg) or a substrate whose thermal expansion coefficient is
reduced by mixing an inorganic filler with an organic resin can
also be used.
[0201] In the case where a fibrous body is included in the above
material, a high-strength fiber of an organic compound or an
inorganic compound is used as the fibrous body. The high-strength
fiber is specifically a fiber with a high tensile elastic modulus
or a fiber with a high Young's modulus. Typical examples thereof
include a polyvinyl alcohol based fiber, a polyester based fiber, a
polyamide based fiber, a polyethylene based fiber, an aramid based
fiber, a polyparaphenylene benzobisoxazole fiber, a glass fiber,
and a carbon fiber. As the glass fiber, glass fiber using E glass,
S glass, D glass, Q glass, or the like can be used. These fibers
may be used in a state of a woven fabric or a nonwoven fabric, and
a structure body in which this fibrous body is impregnated with a
resin and the resin is cured may be used as the flexible substrate.
The structure body including the fibrous body and the resin is
preferably used as the flexible substrate, in which case the
reliability against bending or breaking due to local pressure can
be increased.
[0202] Alternatively, glass, metal, or the like that is thin enough
to have flexibility can be used as the base material.
Alternatively, a composite material where glass and a resin
material are attached to each other may be used.
[0203] In the structure shown in FIG. 12A, for example, a first
separation layer and the insulating layer 262 are formed in this
order over a first supporting base material, and then components in
a layer over the first separation layer and the insulating layer
262 are formed. Separately, a second separation layer and the
insulating layer 212 are formed in this order over a second
supporting base material, and then upper components are formed.
Next, the first supporting base material and the second supporting
base material are bonded to each other using the adhesive layer
220. After that, separation at an interface between the second
separation layer and the insulating layer 212 is conducted so that
the second supporting base material and the second separation layer
are removed, and then the substrate 31 is bonded to the insulating
layer 212 using the adhesive layer 211. Further, separation at an
interface between the first separation layer and the insulating
layer 262 is conducted so that the first supporting base material
and the first separation layer are removed, and then the substrate
21 is bonded to the insulating layer 262 using the adhesive layer
261. Note that either side may be subjected to separation and
attachment first.
[0204] The above is the description of a manufacturing method of a
flexible touch panel.
[Cross-Sectional Structure Example 2]
[0205] FIG. 15 is a cross-sectional structure example whose
structure is partly different from that of FIG. 12A. Note that
descriptions of the portions already described are omitted and
different portions are described below.
[0206] In the example shown in FIG. 15, the conductive layer 25 is
not provided. The conductive layer 24 is provided to cover part of
the insulating layer 28. The conductive layer 23 and the conductive
layer 24 overlap with each other in a region, and the capacitor 11
is formed in the region.
[0207] FIG. 15 also shows a cross-sectional structure of a
connection portion 272 in which the conductive layer 24 is
electrically connected to a wiring formed by processing the
conductive film used for forming the conductive layer 23 through an
opening formed in the insulating layer 28.
[0208] In the example shown in FIG. 15, the EL layer 222 is
separately formed in each pixel. The EL layer 222 can include a
light-emitting layer containing a light-emitting material emitting
light of one color. In the light-emitting element 204 shown in FIG.
15, the optical adjustment layer 224 shown in FIG. 12B is not
included. Furthermore, the coloring layer 52 is not provided in
FIG. 15. In this manner, the structure of the light-emitting
element can be simplified in the case where the EL layer 222 of the
light-emitting element 204 is separately formed in each pixel to
obtain light emission with high color purity from the
light-emitting element 204.
[0209] Here, the distance between one of the conductive layer 23
and the conductive layer 24 which is positioned closer to the
display panel than the other and a conductive layer which is the
closest to the one of the conductive layers 23 and 24 of the
conductive layers provided closer to the display panel than the one
of the conductive layers 23 and 24 is preferably greater than or
equal to 25 nm and less than or equal to 100 .mu.m, more preferably
greater than or equal to 50 nm and less than or equal to 10 .mu.m,
still more preferably greater than or equal to 50 nm and less than
or equal to 5 .mu.m.
[0210] In the example shown in FIG. 15, the second electrode 223 of
the light-emitting element 204 corresponds to the conductive layer
which is the closest to the conductive layer 24 of the conductive
layers provided closer to the display panel than the conductive
layer 24. Here, as the distance D between the conductive layer 24
and the second electrode 223 is shorter, a distance between the
pair of substrates can be reduced more, and the thickness of the
touch panel can be reduced more. In particular, when a flexible
substrate is used as the pair of substrates, the touch panel can be
flexible and strong against bending.
[0211] The above is the description of the cross-sectional
structure example 2.
[0212] Though this embodiment shows the structure including two
substrates, i.e., the substrate supporting the touch sensor and the
substrate supporting the display element, the structure is not
limited thereto. For example, a structure with three substrates
where a display element is sandwiched between two substrates and
the substrate supporting a touch sensor is bonded thereto can be
employed. Alternatively, a structure with four substrates where a
display element sandwiched between two substrates and a touch
sensor sandwiched between two substrates are bonded to each other
can be employed.
[0213] This embodiment can be combined with any of the other
embodiments disclosed in this specification as appropriate.
Embodiment 2
[0214] In this embodiment, an example of a method for operating the
touch panel of one embodiment of the present invention is described
with reference to drawings.
[Example of Sensing Method of Sensor]
[0215] FIG. 16A is a block diagram illustrating the structure of a
mutual capacitive touch sensor. FIG. 16A illustrates a pulse
voltage output circuit 601 and a current sensing circuit 602. Note
that in FIG. 16A, six wirings X1 to X6 represent the electrodes 621
to which a pulse voltage is applied, and six wirings Y1 to Y6
represent the electrodes 622 that detect changes in current. FIG.
16A also illustrates a capacitor 603 that is formed where the
electrodes 621 and 622 overlap with each other. Note that
functional replacement between the electrodes 621 and 622 is
possible.
[0216] The pulse voltage output circuit 601 is a circuit for
sequentially applying a pulse voltage to the wirings X1 to X6. By
application of a pulse voltage to the wirings X1 to X6, an electric
field is generated between the electrodes 621 and 622 of the
capacitor 603. When the electric field between the electrodes is
shielded, for example, a change occurs in the capacitor 603 (mutual
capacitance). The approach or contact of a sensing target can be
sensed by utilizing this change.
[0217] The current sensing circuit 602 is a circuit for detecting
changes in current flowing through the wirings Y1 to Y6 that are
caused by the change in mutual capacitance in the capacitor 603. No
change in current value is detected in the wirings Y1 to Y6 when
there is no approach or contact of a sensing target, whereas a
decrease in current value is detected when mutual capacitance is
decreased owing to the approach or contact of a sensing target.
Note that an integrator circuit or the like is used for sensing of
current values.
[0218] FIG. 16B is a timing chart showing input and output
waveforms in the mutual capacitive touch sensor illustrated in FIG.
16A. In FIG. 16B, sensing of a sensing target is performed in all
the rows and columns in one frame period. FIG. 16B shows a period
when a sensing target is not sensed (not touched) and a period when
a sensing target is sensed (touched). Sensed current values of the
wirings Y1 to Y6 are shown as the waveforms of voltage values.
[0219] A pulse voltage is sequentially applied to the wirings X1 to
X6, and the waveforms of the wirings Y1 to Y6 change in accordance
with the pulse voltage. When there is no approach or contact of a
sensing target, the waveforms of the wirings Y1 to Y6 change in
accordance with changes in the voltages of the wirings X1 to X6.
The current value is decreased at the point of approach or contact
of a sensing target and accordingly the waveform of the voltage
value changes.
[0220] By detecting a change in mutual capacitance in this manner,
the approach or contact of a sensing target can be sensed.
[0221] It is preferable that the pulse voltage output circuit 601
and the current sensing circuit 602 be mounted on a substrate in a
housing of an electronic appliance or on the touch panel in the
form of an IC. In the case where the touch panel has flexibility,
parasitic capacitance might be increased in a bent portion of the
touch panel, and the influence of noise might be increased. In view
of this, it is preferable to use an IC to which a driving method
less influenced by noise is applied. For example, it is preferable
to use an IC to which a driving method capable of increasing a
signal-noise ratio (S/N ratio) is applied.
[0222] Although FIG. 16A is a passive matrix type touch sensor in
which only the capacitor 603 is provided at the intersection of
wirings as a touch sensor, an active matrix type touch sensor
including a transistor and a capacitor may be used. FIG. 17 is a
sensor circuit included in an active matrix type touch sensor.
[0223] The sensor circuit includes the capacitor 603 and
transistors 611, 612, and 613. A signal G2 is input to a gate of
the transistor 613. A voltage VRES is applied to one of a source
and a drain of the transistor 613, and one electrode of the
capacitor 603 and a gate of the transistor 611 are electrically
connected to the other of the source and the drain of the
transistor 613. One of a source and a drain of the transistor 611
is electrically connected to one of a source and a drain of the
transistor 612, and a voltage VSS is applied to the other of the
source and the drain of the transistor 611. A signal G1 is input to
a gate of the transistor 612, and a wiring ML is electrically
connected to the other of the source and the drain of the
transistor 612. The voltage VSS is applied to the other electrode
of the capacitor 603.
[0224] Next, the operation of the sensor circuit will be described.
First, a potential for turning on the transistor 613 is supplied as
the signal G2, and a potential with respect to the voltage VRES is
thus applied to the node n connected to the gate of the transistor
611. Then, a potential for turning off the transistor 613 is
applied as the signal G2, whereby the potential of the node n is
maintained.
[0225] Then, mutual capacitance of the capacitor 603 changes owing
to the approach or contact of a sensing target such as a finger,
and accordingly the potential of the node n is changed from
VRES.
[0226] In reading operation, a potential for turning on the
transistor 612 is supplied as the signal G1. A current flowing
through the transistor 611, that is, a current flowing through the
wiring ML is changed in accordance with the potential of the node
n. By sensing this current, the approach or contact of a sensing
target can be sensed.
[0227] It is preferred that the transistors 611, 612, and 613 each
include an oxide semiconductor in a semiconductor layer where a
channel is formed. In particular, by using an oxide semiconductor
in a semiconductor layer where a channel of the transistor 613 is
formed, the potential of the node n can be held for a long time and
the frequency of operation (refresh operation) of resupplying VRES
to the node n can be reduced.
[0228] At least part of this embodiment can be implemented in
combination with any of the embodiments described in this
specification as appropriate.
Embodiment 3
[0229] In this embodiment, electronic appliances and lighting
devices that can be fabricated according to one embodiment of the
present invention will be described with reference to FIGS. 18A to
18G and FIGS. 19A to 19I.
[0230] The touch panel of one embodiment of the present invention
has flexibility. Therefore, a touch panel of one embodiment of the
present invention can be used in electronic appliances and lighting
devices having flexibility. Furthermore, according to one
embodiment of the present invention, electronic appliances and
lighting devices having high reliability and resistance against
repeated bending can be manufactured.
[0231] Examples of electronic appliances include a television set
(also referred to as a television or a television receiver), a
monitor of a computer or the like, a digital camera, a digital
video camera, a digital photo frame, a mobile phone (also referred
to as a mobile phone device), a portable game machine, a portable
information terminal, an audio reproducing device, a large game
machine such as a pinball machine, and the like.
[0232] The touch panel of one embodiment of the present invention
has flexibility and therefore can be incorporated along a curved
inside/outside wall surface of a house or a building or a curved
interior/exterior surface of a car.
[0233] An electronic appliance of one embodiment of the present
invention may include a touch panel and a secondary battery. It is
preferable that the secondary battery is capable of being charged
by contactless power transmission.
[0234] As examples of the secondary battery, a lithium ion
secondary battery such as a lithium polymer battery (lithium ion
polymer battery) using a gel electrolyte, a lithium ion battery, a
nickel-hydride battery, a nickel-cadmium battery, an organic
radical battery, a lead-acid battery, an air secondary battery, a
nickel-zinc battery, and a silver-zinc battery can be given.
[0235] The electronic appliance of one embodiment of the present
invention may include a touch panel and an antenna. When a signal
is received by the antenna, the electronic appliance can display an
image, data, or the like on a display portion. When the electronic
appliance includes a secondary battery, the antenna may be used for
contactless power transmission.
[0236] FIG. 18A illustrates an example of a mobile phone. The
mobile phone 7400 is provided with a display portion 7402
incorporated in a housing 7401, operation buttons 7403, an external
connection port 7404, a speaker 7405, a microphone 7406, and the
like. Note that the mobile phone 7400 is manufactured by using the
touch panel of one embodiment of the present invention for the
display portion 7402. In accordance with one embodiment of the
present invention, a highly reliable mobile phone having a curved
display portion can be provided at a high yield.
[0237] When the display portion 7402 of the mobile phone 7400
illustrated in FIG. 18A is touched with a finger or the like, data
can be input into the mobile phone 7400. Further, operations such
as making a call and inputting a letter can be performed by touch
on the display portion 7402 with a finger or the like.
[0238] With the operation buttons 7403, power ON or OFF can be
switched. In addition, types of images displayed on the display
portion 7402 can be switched; switching images from a mail creation
screen to a main menu screen.
[0239] FIG. 18B illustrates an example of a wrist-watch-type
portable information terminal A portable information terminal 7100
includes a housing 7101, a display portion 7102, a band 7103, a
buckle 7104, an operation button 7105, an input/output terminal
7106, and the like.
[0240] The portable information terminal 7100 is capable of
executing a variety of applications such as mobile phone calls,
e-mailing, reading and editing texts, music reproduction, Internet
communication, and a computer game.
[0241] The display surface of the display portion 7102 is bent, and
images can be displayed on the bent display surface. Furthermore,
the display portion 7102 includes a touch sensor, and operation can
be performed by touching the screen with a finger, a stylus, or the
like. For example, by touching an icon 7107 displayed on the
display portion 7102, an application can be started.
[0242] With the operation button 7105, a variety of functions such
as time setting, power ON/OFF, ON/OFF of wireless communication,
setting and cancellation of manner mode, and setting and
cancellation of power saving mode can be performed. For example,
the functions of the operation button 7105 can be set freely by
setting the operating system incorporated in the portable
information terminal 7100.
[0243] The portable information terminal 7100 can employ near field
communication that is a communication method based on an existing
communication standard. In that case, for example, mutual
communication between the portable information terminal 7100 and a
headset capable of wireless communication can be performed, and
thus hands-free calling is possible.
[0244] Moreover, the portable information terminal 7100 includes
the input/output terminal 7106, and data can be directly
transmitted to and received from another information terminal via a
connector. Charging through the input/output terminal 7106 is
possible. Note that the charging operation may be performed by
wireless power feeding without using the input/output terminal
7106.
[0245] The display portion 7102 of the portable information
terminal 7100 includes the touch panel of one embodiment of the
present invention. According to one embodiment of the present
invention, a highly reliable portable information terminal having a
curved display portion can be provided with a high yield.
[0246] FIGS. 18C to 18E illustrate examples of a lighting device.
Lighting devices 7200, 7210, and 7220 each include a stage 7201
provided with an operation switch 7203 and a light-emitting portion
supported by the stage 7201.
[0247] The lighting device 7200 illustrated in FIG. 18C includes a
light-emitting portion 7202 having a wave-shaped light-emitting
surface, and thus has good design.
[0248] A light-emitting portion 7212 included in the lighting
device 7210 illustrated in FIG. 18D has two convex-curved
light-emitting portions symmetrically placed. Thus, all directions
can be illuminated with the lighting device 7210 as a center.
[0249] The lighting device 7220 illustrated in FIG. 18E includes a
concave-curved light-emitting portion 7222. This is suitable for
illuminating a specific range because light emitted from the
concave-curved light-emitting portion 7222 is collected to the
front of the lighting device 7220.
[0250] The light-emitting portion included in each of the lighting
devices 7200, 7210, and 7220 are flexible; thus, the light-emitting
portion may be fixed on a plastic member, a movable frame, or the
like so that an emission surface of the light-emitting portion can
be bent freely depending on the intended use.
[0251] Note that although the lighting device in which the
light-emitting portion is supported by the stage is described as an
example here, a housing provided with a light-emitting portion can
be fixed on a ceiling or suspended from a ceiling. Since the
light-emitting surface can be curved, the light-emitting surface is
curved to have a depressed shape, whereby a particular region can
be brightly illuminated, or the light-emitting surface is curved to
have a projecting shape, whereby a whole room can be brightly
illuminated.
[0252] Here, the light-emitting portions each include the touch
panel of one embodiment of the present invention. In accordance
with one embodiment of the present invention, a highly reliable
lighting device having a curved light-emitting portion can be
provided at a high yield.
[0253] FIG. 18F illustrates an example of a portable touch panel. A
touch panel 7300 includes a housing 7301, a display portion 7302,
operation buttons 7303, a display portion pull 7304, and a control
portion 7305.
[0254] The touch panel 7300 includes a rolled flexible display
portion 7302 in the cylindrical housing 7301.
[0255] The touch panel 7300 can receive a video signal with the
control portion 7305 and can display the received video on the
display portion 7302. In addition, a battery is included in the
control portion 7305. Moreover, a terminal portion for connecting a
connector may be included in the control portion 7305 so that a
video signal or power can be directly supplied from the outside
with a wiring.
[0256] By pressing the operation buttons 7303, power ON/OFF,
switching of displayed videos, and the like can be performed.
[0257] FIG. 18G illustrates a touch panel 7300 in a state where the
display portion 7302 is pulled out with the display portion pull
7304. Videos can be displayed on the display portion 7302 in this
state. Further, the operation buttons 7303 on the surface of the
housing 7301 allow one-handed operation. The operation buttons 7303
are provided not in the center of the housing 7301 but on one side
of the housing 7301 as illustrated in FIG. 18F, which makes
one-handed operation easy.
[0258] Note that a reinforcement frame may be provided for a side
portion of the display portion 7302 so that the display portion
7302 has a flat display surface when pulled out.
[0259] Note that in addition to this structure, a speaker may be
provided for the housing so that sound is output with an audio
signal received together with a video signal.
[0260] The display portion 7302 includes the touch panel of one
embodiment of the present invention. According to one embodiment of
the present invention, a lightweight and highly reliable touch
panel can be provided with a high yield.
[0261] FIGS. 19A to 19C illustrate a foldable portable information
terminal 310. FIG. 19A illustrates the portable information
terminal 310 that is opened. FIG. 19B illustrates the portable
information terminal 310 that is being opened or being folded. FIG.
19C illustrates the portable information terminal 310 that is
folded. The portable information terminal 310 is highly portable
when folded. When the portable information terminal 310 is opened,
a seamless large display region is highly browsable.
[0262] A display panel 316 is supported by three housings 315
joined together by hinges 313. By folding the portable information
terminal 310 at a connection portion between two housings 315 with
the hinges 313, the portable information terminal 310 can be
reversibly changed in shape from an opened state to a folded state.
The touch panel according to one embodiment of the present
invention can be used for the display panel 316. For example, a
touch panel that can be bent with a radius of curvature of greater
than or equal to 1 mm and less than or equal to 150 mm can be
used.
[0263] Note that in one embodiment of the present invention, a
sensor that senses whether the touch panel is in a folded state or
an unfolded state and supplies sensing data may be used. The
operation of a folded portion (or a portion that becomes invisible
by a user by folding) of the touch panel may be stopped by a
control device through the acquisition of data indicating the
folded state of the touch panel. Specifically, display of the
portion may be stopped, and furthermore, sensing by the touch
sensor may be stopped.
[0264] Similarly, the control device of the touch panel may acquire
data indicating the unfolded state of the touch panel to resume
displaying and sensing by the touch sensor.
[0265] FIGS. 19D and 19E each illustrate a foldable portable
information terminal 320. FIG. 19D illustrates the portable
information terminal 320 that is folded so that a display portion
322 is on the outside. FIG. 19E illustrates the portable
information terminal 320 that is folded so that the display portion
322 is on the inside. When the portable information terminal 320 is
not used, the portable information terminal 320 is folded so that a
non-display portion 325 faces the outside, whereby the display
portion 322 can be prevented from being contaminated or damaged.
The touch panel in one embodiment of the present invention can be
used for the display portion 322.
[0266] FIG. 19F is a perspective view illustrating an external
shape of the portable information terminal 330. FIG. 19G is a top
view of the portable information terminal 330. FIG. 19H is a
perspective view illustrating an external shape of a portable
information terminal 340.
[0267] The portable information terminals 330 and 340 each function
as, for example, one or more of a telephone set, a notebook, and an
information browsing system. Specifically, the portable information
terminals 330 and 340 each can be used as a smartphone.
[0268] The portable information terminals 330 and 340 can display
characters and image information on its plurality of surfaces. For
example, three operation buttons 339 can be displayed on one
surface (FIGS. 19F and 19H). In addition, information 337 indicated
by dashed rectangles can be displayed on another surface (FIGS.
19F, 19G, and 19H). Examples of the information 337 include
notification from a social networking service (SNS), display
indicating reception of an e-mail or an incoming call, the title of
an e-mail or the like, the sender of an e-mail or the like, the
date, the time, remaining battery, and the reception strength of an
antenna. Alternatively, the operation buttons 339, an icon, or the
like may be displayed in place of the information 337. Although
FIGS. 19F and 19G illustrate an example in which the information
337 is displayed at the top, one embodiment of the present
invention is not limited thereto. The information may be displayed,
for example, on the side as in the portable information terminal
340 illustrated in FIG. 19H.
[0269] For example, a user of the portable information terminal 330
can see the display (here, the information 337) with the portable
information terminal 330 put in a breast pocket of his/her
clothes.
[0270] Specifically, a caller's phone number, name, or the like of
an incoming call is displayed in a position that can be seen from
above the portable information terminal 330. Thus, the user can see
the display without taking out the portable information terminal
330 from the pocket and decide whether to answer the call.
[0271] A touch panel of one embodiment of the present invention can
be used for a display portion 333 mounted in each of a housing 335
of the portable information terminal 330 and a housing 336 of the
portable information terminal 340. According to one embodiment of
the present invention, a highly reliable touch panel having a
curved display portion can be provided with a high yield.
[0272] As in a portable information terminal 345 illustrated in
FIG. 19I, data may be displayed on three or more surfaces. Here,
data 355, data 356, and data 357 are displayed on different
surfaces.
[0273] The touch panel of one embodiment of the present invention
can be used for a display portion 358 included in a housing 354 of
the portable information terminal 345. According to one embodiment
of the present invention, a highly reliable touch panel having a
curved display portion can be provided with a high yield.
[0274] At least part of this embodiment can be implemented in
combination with any of the embodiments described in this
specification as appropriate.
Example
[0275] In this example, a foldable touch panel of one embodiment of
the present invention was fabricated. This example also describes
the results of performing evaluation of a time constant and
performing a folding test on the touch panel.
[Fabrication of Touch Panel]
[0276] In this example, an in-cell touch panel in which a touch
sensor was formed in a counter substrate (a substrate on the
display surface side) of a flexible display panel was fabricated.
An electrode of the touch sensor had a metal-mesh structure to
reduce the load capacitance formed between the touch sensor and the
display panel. Thus, the whole touch panel can be thin enough to be
freely folded by a user. In addition, because of the small load
capacitance, the influence of noise from the display panel to the
touch sensor can be suppressed, so that defects such as false
detection and detection failure can be suppressed.
[0277] As a method for driving the in-cell touch panel fabricated
in this example, a projected mutual capacitive type was
employed.
[0278] The touch panel having the cross-sectional structure shown
in FIGS. 12A and 12B was fabricated in this example. As the mesh
pattern of the touch sensor, the pattern shown in FIG. 6 was
used.
[0279] FIG. 20 shows a structure of the touch panel fabricated in
this example. A schematic view of the touch panel is shown in the
center of FIG. 20, a cross-sectional structure of the touch panel
is shown in the left side thereof, and an enlarged view of a bent
portion of the touch panel is shown in the right side thereof. The
touch panel includes a display portion (denoted by Display) having
flexibility and an FPC. In the structure of the touch panel, two
flexible substrates were bonded to each other with an adhesive
layer, and a passivation layer was provided on each of the facing
surfaces of the flexible substrates. An FET layer (denoted by FET)
and an organic EL element (denoted by OLED) were formed over the
passivation layer over one of the flexible substrates. A touch
sensor and a color filter were formed over the passivation layer
over the other of the flexible substrates. As shown in FIG. 20, the
touch panel fabricated in this example can be folded so that its
display surface has a convex curve and a concave curve.
[0280] First, a separation layer, the passivation layer, the FET
layer, and the organic EL element were formed over a glass
substrate.
[0281] As a transistor (e.g., the transistor 201) included in the
FET layer, a transistor including an oxide semiconductor as a
semiconductor where a channel is formed was used. Here, a
crystalline oxide semiconductor having c-axis alignment in a
direction perpendicular to a film surface (CAAC-OS: c-axis aligned
crystalline-oxide semiconductor) was used as the oxide
semiconductor in this example.
[0282] A CAAC-OS is a crystalline oxide semiconductor having c-axis
alignment of crystals in a direction substantially perpendicular to
the film surface. It has been found that oxide semiconductors have
a variety of crystal structures other than a single-crystal
structure. An example of such structures is a nano-crystal (nc)
structure, which is an aggregate of nanoscale microcrystals. The
crystallinity of a CAAC-OS structure is lower than that of a
single-crystal structure and higher than that of an nc structure.
Moreover, since the CAAC-OS does not have a grain boundary, a
stable and uniform film can be formed over a large area, and stress
that is caused by bending a flexible light-emitting device does not
easily make a crack in a CAAC-OS film.
[0283] In--Ga--Zn-based oxide was used as the oxide semiconductor
material in this example.
[0284] As a pixel electrode (the first electrode 221), alloy
containing silver with extremely high reflectivity was used. A
transparent electrode layer (the optical adjustment layer 224) was
formed over the pixel electrode and the thickness thereof varied as
appropriate depending on the structure of the sub-pixel to produce
a microcavity effect.
[0285] As the organic EL element, a top-emission white EL element
was used. The organic EL element had a tandem structure in which a
blue light-emitting unit and a yellow light-emitting unit were
stacked.
[0286] Furthermore, a separation layer, the passivation layer, a
light-blocking layer, a touch sensor electrode, and the color
filter were formed over another glass substrate. In order to
suppress reflection of light by the touch sensor electrode, the
light-blocking layer was provided between the touch sensor
electrode and the passivation layer.
[0287] Then, the two substrates were bonded to each other with the
adhesive layer. The distance (cell gap) between the substrates was
set to approximately 5 .mu.m. Then, separation of each substrate
was made to occur between the separation layer and the passivation
layer, and the flexible substrates were attached. The flexible
substrates were plastic substrates each having a thickness of
approximately 20 .mu.m.
[0288] In this manner, the touch panel was fabricated. Table 1
shows the specifications of a display device, and Table 2 shows the
specifications of the touch sensor.
TABLE-US-00001 TABLE 1 Specifications of 8.67 inch OLED Display
Screen diagonal 8.67 inch Driving method Active Matrix Number of
effective pixels 1080 .times. RGBY .times. 1920 Pixel pitch 0.100
mm .times. 0.100 mm Pixel density 254 ppi Aperture ratio 0.46%
Pixel arrangement RGBY checker Pixel circuit 6Tr + 1C/cell Source
driver COF Scan driver Integrated
TABLE-US-00002 TABLE 2 Specifications of 8.67 inch Touch Sensor
Screen diagonal 8.67 inch Driving method Projection capacitance
(Mutual capacitance) Sensor structure Metal mesh Number of sensor
units 48(T) .times. 27(R) Sensor unit pitch 4.00 mm .times. 4.00
mm
[0289] The pixel included in the touch panel fabricated in this
example included four RGBY sub-pixels. The use of the Y (yellow)
sub-pixel increased current efficiency and reduced chromaticity
variation depending on the viewing angle more than the case of
using a white sub-pixel.
[0290] For the touch sensor, 48 transmitting electrodes were
arranged in the longitudinal direction of the display portion and
27 receiving electrodes were arranged in the lateral direction
thereof with 4 mm pitches. A matrix of 40.times.40 pixels in the
display portion corresponds to one unit of the touch sensor.
[Touch Panel]
[0291] FIGS. 21A to 21C are photographs of the fabricated touch
panel. FIG. 21A shows a state where the display panel is unfolded.
FIG. 21B shows a state where the display panel is folded in three.
FIG. 21C shows a state where the display panel is touched while
folded. It was demonstrated that a touch on each of a flat surface
portion, a convex curved portion, and a concave curved portion of
the surface of the touch panel was detected appropriately.
[0292] Since the pixels are arranged in the openings in the mesh of
the touch sensor electrode, providing the touch sensor does not
significantly affect the light extraction efficiency.
[Evaluation of Time Constant]
[0293] Next, the parasitic capacitance and resistance between the
receiving electrode of the fabricated touch panel and the display
panel were measured with varying frequency. An LCR meter (4275A
manufactured by Agilent Technologies, Inc.) was used for the
measurement.
[0294] FIG. 22 shows the measurement results. The vertical axis on
the left side, the vertical axis on the right side, and the
horizontal axis in FIG. 22 represent parasitic capacitance,
parasitic resistance, and frequency, respectively. The number of
measurements was six. As shown in FIG. 22, with 10 kHz measurement
frequency, the parasitic capacitance was approximately 910 pF, and
the parasitic resistance was approximately 1.3 k.OMEGA.. The time
constant was calculated to be approximately 1.2 .mu.s. This value
is small but not so small as to cause failure of touch
detection.
[Folding test]
[0295] Next, the results of performing a folding test on the
fabricated touch panel are described. In the folding test, an
operation of folding and unfolding the touch panel with a curvature
radius of 5 mm or 3 mm was performed once every two seconds, and
the operation was repeated 100,000 times. The folding and unfolding
operation was performed under two different conditions: inward
folding (the display surface faces inward) and outward folding (the
display surface faces outward). Even after the folding and
unfolding operation was performed 100,000 times, normal display and
touch detection were achieved.
[0296] These results show that the touch panel of one embodiment of
the present invention is a foldable touch panel with high
reliability, high visibility, and low power consumption. This touch
panel will lead to a novel mobile device.
[0297] This application is based on Japanese Patent Application
serial no. 2014-112316 filed with Japan Patent Office on May 30,
2014, Japanese Patent Application serial no. 2014-128409 filed with
Japan Patent Office on Jun. 23, 2014, and Japanese Patent
Application serial no. 2014-242912 filed with Japan Patent Office
on Dec. 1, 2014, the entire contents of which are hereby
incorporated by reference.
* * * * *