U.S. patent application number 14/444799 was filed with the patent office on 2015-02-05 for display device.
This patent application is currently assigned to Semiconductor Energy Laboratory Co., Ltd.. The applicant listed for this patent is Semiconductor Energy Laboratory Co., Ltd.. Invention is credited to Yoshiharu HIRAKATA, Seiko INOUE, Hiroyuki MIYAKE, Shunpei YAMAZAKI.
Application Number | 20150035777 14/444799 |
Document ID | / |
Family ID | 52427219 |
Filed Date | 2015-02-05 |
United States Patent
Application |
20150035777 |
Kind Code |
A1 |
HIRAKATA; Yoshiharu ; et
al. |
February 5, 2015 |
DISPLAY DEVICE
Abstract
A display device with low power consumption is provided.
Furthermore, a display device in which an image is displayed in a
region that can be used in a folded state is provided. The
conceived display device includes a display portion that can be
opened and folded, a sensing portion that senses a folded state of
the display portion, and an image processing portion that
generates, when the display portion is in the folded state, an
image in which a black image is displayed in part of the display
portion.
Inventors: |
HIRAKATA; Yoshiharu; (Ebina,
JP) ; MIYAKE; Hiroyuki; (Atsugi, JP) ; INOUE;
Seiko; (Isehara, JP) ; YAMAZAKI; Shunpei;
(Setagaya, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Semiconductor Energy Laboratory Co., Ltd. |
Atsugi-shi |
|
JP |
|
|
Assignee: |
Semiconductor Energy Laboratory
Co., Ltd.
|
Family ID: |
52427219 |
Appl. No.: |
14/444799 |
Filed: |
July 28, 2014 |
Current U.S.
Class: |
345/173 ;
345/156 |
Current CPC
Class: |
G06F 3/0412 20130101;
G06F 3/0446 20190501; G06F 1/1652 20130101; G06F 3/041 20130101;
G06F 2203/04102 20130101 |
Class at
Publication: |
345/173 ;
345/156 |
International
Class: |
G06F 1/16 20060101
G06F001/16; G06F 3/041 20060101 G06F003/041 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 2, 2013 |
JP |
2013-161577 |
Claims
1. A display device comprising: a display portion having a
flexibility, the display portion comprising: a first region exposed
outward when the display device is folded; and a second region
folded inward when the display device is folded; a first driver
circuit electrically connected to the display portion; a sensing
portion configured to sense a state of the display portion and
supply data on whether the display device is folded; and a control
portion configured to control the first driver circuit so that,
when the sensing portion detects that the display device is folded,
the first driver circuit supplies an image signal for displaying an
image to the first region while the first driver circuit supplies a
signal for displaying a black image to the second region.
2. The display device according to claim 1, wherein the display
portion comprises a light-emitting element.
3. The display device according to claim 1, wherein the display
portion comprises a transistor comprising an oxide semiconductor
layer.
4. The display device according to claim 3, wherein the oxide
semiconductor layer comprises indium and zinc.
5. The display device according to claim 1, comprising a touch
sensor over the display portion.
6. The display device according to claim 1, comprising a sign
operationally coupled to the sensing portion.
7. The display device according to claim 6, wherein the sign is a
magnet.
8. A display device comprising: a display portion having a
flexibility, the display portion comprising: a first region exposed
outward when the display device is folded; and a second region
folded inward when the display device is folded; a first driver
circuit electrically connected to the first region of the display
portion; a second driver circuit electrically connected to the
second region of the display portion; a sensing portion configured
to sense a state of the display portion and supply data on whether
the display device is folded; and a control portion configured to
control the first driver circuit so that, when the sensing portion
detects that the display device is folded, the first driver circuit
supplies an image signal for displaying an image to the first
region while the second driver circuit supplies a signal for
displaying a black image to the second region.
9. The display device according to claim 8, wherein the display
portion comprises a light-emitting element.
10. The display device according to claim 8, wherein the display
portion comprises a transistor comprising an oxide semiconductor
layer.
11. The display device according to claim 10, wherein the oxide
semiconductor layer comprises indium and zinc.
12. The display device according to claim 8, comprising a touch
sensor over the display portion.
13. The display device according to claim 8, comprising a sign
operationally coupled to the sensing portion.
14. The display device according to claim 13, wherein the sign is a
magnet.
15. A display device comprising: a display portion having a
flexibility, the display portion comprising: a first region exposed
outward when the display device is folded; and a second region
folded inward when the display device is folded; a first driver
circuit electrically connected to the first region of the display
portion; a second driver circuit electrically connected to the
second region of the display portion; a power supply portion
connected to the first driver circuit and the second driver
circuit; a sensing portion configured to sense a state of the
display portion and supply data on whether the display device is
folded; and a control portion configured to control the power
supply portion so that the power supply portion stops supplying a
power supply potential when the sensing portion detects that the
display device is folded.
16. The display device according to claim 15, wherein the display
portion comprises a light-emitting element.
17. The display device according to claim 15, wherein the display
portion comprises a transistor comprising an oxide semiconductor
layer.
18. The display device according to claim 17, wherein the oxide
semiconductor layer comprises indium and zinc.
19. The display device according to claim 15, comprising a touch
sensor over the display portion.
20. The display device according to claim 15, comprising a sign
operationally coupled to the sensing portion.
21. The display device according to claim 20, wherein the sign is a
magnet.
Description
TECHNICAL FIELD
[0001] The present invention relates to an object, a method, or a
manufacturing method. In addition, the present invention relates to
a process, a machine, manufacture, or a composition of matter. In
particular, the present invention relates to, for example, a human
interface, a semiconductor device, a display device, a
light-emitting device, a power storage device, a driving method
thereof, or a manufacturing method thereof. For example, the
present invention particularly relates to a display device. In
particular, one embodiment of the present invention relates to a
foldable display device.
BACKGROUND ART
[0002] The social infrastructures relating to means for
transmitting information have advanced. This has made it possible
to acquire, process, and send out many pieces and various kinds of
information with the use of an information processor not only at
home or office but also at other visiting places.
[0003] With this being the situation, portable information
processors are under active development.
[0004] For example, portable information processors are often used
outdoors, and force might be accidentally applied by dropping to
the information processors and display devices included in them. As
an example of a display device that is not easily broken, a display
device having high adhesiveness between a structure body by which a
light-emitting layers are partitioned and a second electrode layer
is known (Patent Document 1).
[0005] A multi-panel electronic device including the following
functions is known. First acceleration data is received from a
first sensor coupled to a first portion of an electronic device. In
addition, second acceleration data is further received from a
second sensor coupled to a second portion of the electronic device,
and a position of the first portion is movable with respect to a
position of the second portion. Moreover, a structure of the
electronic device is further determined at least on the basis of
part of the first acceleration data and part of the second
acceleration data (Patent Document 2).
REFERENCE
Patent Document
[0006] [Patent Document 1] Japanese Published Patent Application
No. 2012-190794 [0007] [Patent Document 2] Japanese Published
Patent Application No. 2012-502372
DISCLOSURE OF INVENTION
[0008] An object of one embodiment of the present invention is to
provide a display device with low power consumption. Another object
is to provide a display device in which an image is displayed in a
region that can be used in a folded state. Another object is to
provide a novel display device.
[0009] 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.
[0010] One embodiment of the present invention is a display device
including: a foldable display portion including a first region and
a second region; a sensing portion that senses an opened state or a
folded state of the display portion and supplies a fold signal; a
control portion that receives the fold signal and supplies an image
control signal; an image processing portion that receives the image
control signal and generates and supplies an image signal; and a
driver circuit that receives the image signal and drives the
display portion. The control portion supplies the image control
signal that makes the image processing portion generate an image in
which a black image is displayed in the second region of the
display portion in a folded state.
[0011] Another embodiment of the present invention is the above
display device in which the control portion includes an arithmetic
unit and a storage unit that stores a program to be executed by the
arithmetic unit. The program includes a first step of allowing
interrupt processing; a second step of proceeding to a third step
when the display portion is in an opened state and proceeding to a
fourth step when the display portion is in a folded state; the
third step of generating an image to be displayed in the first
region and the second region; the fourth step of generating an
image in which a black image is displayed in the second region; a
fifth step of displaying an image on the display portion; a sixth
step of proceeding to a seventh step when a termination instruction
has been supplied in the interrupt processing and returning to the
second step when the termination instruction has not been supplied
in the interrupt processing; and the seventh step of terminating
the program. The interrupt processing includes an eighth step of
allowing operation and a ninth step of recovering from the
interrupt processing.
[0012] The above display device of one embodiment of the present
invention includes a display portion that can be opened and folded,
a sensing portion that senses a folded state of the display
portion, and an image processing portion that generates, when the
display portion is in the folded state, an image in which a black
image is displayed in part of the display portion. Thus, a region
where display is unnecessary when part of the display portion is
folded can display a black image. Consequently, a display device
with low power consumption can be provided. Furthermore, a display
device in which an image is displayed in a region that can be used
in a folded state can be provided.
[0013] Another embodiment of the present invention is a display
device including: a foldable display portion including a first
region and a second region; a sensing portion that senses an opened
state or a folded state of the display portion and supplies a fold
signal; a control portion that receives the fold signal and
supplies an image control signal and a synchronization control
signal; an image processing portion that receives the image control
signal and generates and supplies a first image signal and a second
image signal; a synchronization signal supply portion that receives
the synchronization control signal and supplies a first
synchronization signal and a second synchronization signal; a first
driver circuit that receives the first image signal and the first
synchronization signal and drives the first region; and a second
driver circuit that receives the second image signal and the second
synchronization signal and drives the second region. The control
portion supplies the image control signal that makes the image
processing portion generate an image in which a black image is
displayed in the second region of the display portion in a folded
state and the synchronization control signal that stops selection
of a scan line in the second region of the display portion in a
folded state.
[0014] Another embodiment of the present invention is the above
display device in which the control portion includes an arithmetic
unit and a storage unit that stores a program to be executed by the
arithmetic unit. The program includes a first step of allowing
interrupt processing; a second step of proceeding to a third step
when the display portion is in an opened state and proceeding to a
fourth step when the display portion is in a folded state; the
third step of proceeding to a fifth step when the opened state has
not changed and proceeding to a sixth step when the opened state
has changed to the folded state; the fourth step of proceeding to a
seventh step when the folded state has not changed and proceeding
to an eighth step when the folded state has changed to the opened
state; the fifth step of executing processing 1; the sixth step of
executing processing 2; the seventh step of executing processing 3;
the eighth step of executing processing 4; a ninth step of
proceeding to a tenth step when a termination instruction has been
supplied in the interrupt processing and returning to the second
step when the termination instruction has not been supplied in the
interrupt processing; and the tenth step of terminating the
program. The interrupt processing includes an eleventh step of
allowing operation and a twelfth step of recovering from the
interrupt processing.
[0015] Another embodiment of the present invention is the above
display device in which the program includes the following four
types of processing. The processing 1 includes a first step of
making the synchronization signal supply portion supply
synchronization signals to the first driver circuit and the second
driver circuit; a second step of making the image processing
portion generate an image to be displayed in the first region and
the second region; a third step of making the display portion
display the image; and a fourth step of recovering from the
processing 1. The processing 2 includes a first step of making the
synchronization signal supply portion supply synchronization
signals to the first driver circuit and the second driver circuit;
a second step of making the image processing portion generate an
image in which a black image is displayed in the second region; a
third step of making the display portion display the image; a
fourth step of making the synchronization signal supply portion
sequentially stop supply of synchronization signals to the second
driver circuit; and a fifth step of recovering from the processing
2. The processing 3 includes a first step of making the
synchronization signal supply portion supply synchronization
signals to the first driver circuit; a second step of making the
image processing portion generate an image to be displayed in the
first region; a third step of making the display portion display
the image in the first region; and a fourth step of recovering from
the processing 3. The processing 4 includes a first step of making
the synchronization signal supply portion sequentially supply
synchronization signals to the second driver circuit; a second step
of making the image processing portion generate an image to be
displayed in the first region and the second region; a third step
of making the display portion display the image; and a fourth step
of recovering from the processing 4.
[0016] The above display device of one embodiment of the present
invention includes a display portion that can be opened and folded,
a sensing portion that senses a folded state of the display
portion, an image processing portion that generates, when the
display portion is in the folded state, an image in which a black
image is displayed in part of the display portion, and a
synchronization signal supply portion that can stop the supply of a
synchronization signal used for a portion where a black image is to
be displayed. Thus, the display in a region where display is
unnecessary when part of the display portion is folded can be
stopped. Consequently, a display device with low power consumption
can be provided. Furthermore, a display device in which an image is
displayed in a region that can be used in a folded state can be
provided.
[0017] Another embodiment of the present invention is the above
display device further including a first power supply that supplies
a power supply potential to the first driver circuit and a second
power supply that supplies a power supply potential to the second
driver circuit. The control portion supplies a power supply control
signal to the second power supply in accordance with the fold
signal. The second power supply stops supply of a power supply
potential in accordance with the power supply control signal.
[0018] The above display device of one embodiment of the present
invention includes a display portion that can be opened and folded,
a synchronization signal supply portion that can stop the supply of
a synchronization signal used for a portion where a black image is
to be displayed, and a power supply that can stop the supply of a
power supply potential used for a portion where a black image is to
be displayed. Thus, the display in a region where display is
unnecessary when part of the display portion is folded can be
stopped. Consequently, a display device with low power consumption
can be provided. Furthermore, a display device in which an image is
displayed in a region that can be used in a folded state can be
provided.
[0019] Another embodiment of the present invention is the above
display device which further includes a magnet and in which the
sensing portion includes a magnetic sensor. The magnet is placed at
a position such that the magnetic sensor can sense an opened state
or a folded state of the display portion.
[0020] The above display device of one embodiment of the present
invention includes a display portion that can be opened and folded,
a magnet and a sensing portion including a magnetic sensor that are
placed to sense a folded state of the display portion, and an image
processing portion that generates, when the display portion is in
the folded state, an image in which a black image is displayed in
part of the display portion. Thus, a region where display is
unnecessary when part of the display portion is folded can display
a black image. Moreover, the folded state can be maintained by a
magnetic force of the magnet. Consequently, a display device with
low power consumption can be provided. Furthermore, a display
device in which an image is displayed in a region that can be used
in a folded state can be provided.
[0021] According to one embodiment of the present invention, a
display device with low power consumption can be provided.
Furthermore, a display device in which an image is displayed in a
region that can be used in a folded state can be provided.
BRIEF DESCRIPTION OF DRAWINGS
[0022] FIGS. 1A, 1B1, and 1B2 are a block diagram and schematic
views illustrating a structure of a display device of an
embodiment.
[0023] FIGS. 2A and 2B are a block diagram and a circuit diagram
illustrating a structure of a display portion in a display device
of an embodiment.
[0024] FIGS. 3A and 3B are flow charts illustrating the operation
of a control portion in a display device of an embodiment.
[0025] FIG. 4 is a block diagram illustrating a structure of a
display device of an embodiment.
[0026] FIGS. 5A and 5B are flow charts illustrating the operation
of a control portion in a display device of an embodiment.
[0027] FIGS. 6A to 6D are flow charts each illustrating a
processing performed by a control portion in a display device of an
embodiment.
[0028] FIGS. 7A to 7C are external views illustrating a structure
of a display device of an embodiment.
[0029] FIGS. 8A to 8D illustrate a structure of a display device of
an embodiment.
[0030] FIGS. 9A and 9B illustrate a structure of a display panel
that can be used for a display device of an embodiment.
[0031] FIGS. 10A to 10C illustrate a structure of a transistor that
can be used in a display device of an embodiment.
[0032] FIGS. 11A to 11C illustrate a structure of a display panel
that can be used for a display device of an embodiment.
[0033] FIGS. 12A and 12B illustrate a structure of a display panel
that can be used for a display device of an embodiment.
[0034] FIG. 13 illustrates a structure of a display panel that can
be used for a display device of an embodiment.
[0035] FIG. 14 is a block diagram illustrating a structure of a
display portion in a display device of an embodiment.
[0036] FIGS. 15A and 15B are a block diagram and a circuit diagram
illustrating a structure of a display portion in a display device
of an embodiment.
[0037] FIG. 16 is a block diagram illustrating a structure of a
display device of an embodiment.
[0038] FIG. 17 is a block diagram illustrating a structure of a
display device of an embodiment.
[0039] FIG. 18 is a block diagram illustrating a structure of a
display device of an embodiment.
BEST MODE FOR CARRYING OUT THE INVENTION
[0040] 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.
Therefore, the present invention should not be construed as being
limited to the description in the following embodiments. 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.
Embodiment 1
[0041] In this embodiment, a structure of a display device of one
embodiment of the present invention is described with reference to
FIGS. 1A, 1B1, and 1B2, FIGS. 2A and 2B, and FIGS. 3A and 3B.
[0042] FIGS. 1A, 1B1, and 1B2 are a block diagram and schematic
views illustrating the structure of the display device of one
embodiment of the present invention.
[0043] FIGS. 2A and 2B illustrate a display portion that can be
used in the display device of one embodiment of the present
invention. FIG. 2A is a block diagram illustrating the structure of
the display portion, and FIG. 2B is a circuit diagram illustrating
a pixel circuit in which an electroluminescent (EL) element is used
as a display element.
[0044] FIGS. 3A and 3B are flow charts illustrating the operation
of a control portion of the display device of one embodiment of the
present invention. FIG. 3A is a flow chart illustrating main
processing, and FIG. 3B is a flow chart illustrating interrupt
processing.
[0045] A display device 200 described in this embodiment includes a
foldable display portion 230 including a first region 230(1) and a
second region 230(2); a sensing portion 240 that senses an opened
state or a folded state of the display portion 230 and supplies a
fold signal F; a control portion 210 that receives the fold signal
F and supplies an image control signal VC; an image processing
portion 220 that receives the image control signal VC and supplies
an image signal VIDEO; and driver circuits 232 that receive the
image signal VIDEO and drive the display portion 230 (see FIG. 1A).
Note that the first region 230(1) refers to a region seen from a
user regardless of an opening state and a folded state. Further,
the second region 230(2) refers to a region that is inside in a
folded sate and is not seen from a user.
[0046] The control portion 210 supplies the image control signal VC
that makes the image processing portion 220 generate an image in
which a black image is displayed in the second region 230(2) of the
display portion 230 in a folded state.
[0047] The control portion 210 of the display device 200 described
in this embodiment includes an arithmetic unit and a storage unit
that stores a program to be executed by the arithmetic unit. The
program includes the following steps.
[0048] In a first step, the interrupt processing is allowed (FIG.
3A (Q1)). Note that when the interrupt processing is allowed, the
arithmetic unit can receive an instruction to execute the interrupt
processing. The arithmetic unit that has received the instruction
to execute the interrupt processing stops the main processing and
executes the interrupt processing. For example, the arithmetic unit
that has received an event associated with the instruction stops
the main processing, executes the interrupt processing, and stores
the execution result of the interrupt processing in the storage
unit. Then, the arithmetic unit that has recovered from the
interrupt processing can resume the main processing on the basis of
the execution result of the interrupt processing.
[0049] In a second step, the operation proceeds to a third step
when the display portion 230 is in an opened state and proceeds to
a fourth step when the display portion 230 is in a folded state
(FIG. 3A (Q2)). Specifically, a fold signal F is acquired and is
used to determine whether the display portion 230 is in an opened
state or in a folded state.
[0050] In the third step, an image to be displayed in the first
region 230(1) and the second region 230(2) is generated (FIG. 3A
(Q3)). Note that since the display portion 230 is opened, an image
can be displayed using the entire display portion 230, that is, the
first region 230(1) and the second region 230(2).
[0051] In the fourth step, an image in which a black image is
displayed in the second region 230(2) is generated (FIG. 3A (Q4)).
Note that since the display portion 230 is folded, an image can be
displayed using part of the display portion 230, that is, only the
first region 230(1).
[0052] In a fifth step, an image is displayed in the display
portion 230 (FIG. 3A (Q5)).
[0053] In a sixth step, the operation proceeds to a seventh step
when a termination instruction has been supplied in the interrupt
processing and returns to the second step when the termination
instruction has not been supplied in the interrupt processing (FIG.
3A (Q6)).
[0054] In the seventh step, the program is terminated (FIG. 3A
(Q7)).
[0055] The interrupt processing includes an eighth step of allowing
operation and a ninth step of recovering from the interrupt
processing (FIGS. 3B (R8) and (R9)). Note that a variety of
operations can be performed in the interrupt processing. For
example, a user of the display device 200 can give an instruction
to select an image to be displayed or an instruction to terminate
the program.
[0056] The above display device 200 of one embodiment of the
present invention includes the display portion 230 that can be
opened and folded, the sensing portion 240 that senses a folded
state of the display portion 230, and the image processing portion
220 that generates, when the display portion 230 is in the folded
state, an image in which a black image is displayed in part of the
display portion 230. Thus, a region where display is unnecessary
when part of the display portion 230 is folded can display a black
image. Consequently, a display device with low power consumption
can be provided. Furthermore, a display device in which an image is
displayed in a region that can be used in a folded state can be
provided.
[0057] In addition, the display device 200 described as an example
in this embodiment includes a power supply portion 214 that
supplies power supply potential to the driver circuits 232 and a
synchronization signal supply portion 212 that supplies a
synchronization signal SYNC to the driver circuits 232.
[0058] The driver circuits 232 include a scan line driver circuit
232G and a signal line driver circuit 232S. Note that as shown in
FIG. 14, the scan line driver circuit 232G and the signal line
driver circuit 232S in FIG. 1A may be replaced with each other.
Similarly, as shown in FIG. 15A, the scan line driver circuit 232G
and the signal line driver circuit 232S in FIG. 2A may be replaced
with each other. In that case, as shown in FIG. 15B, a pixel 631p
is rotated by 90.degree..
[0059] The sensing portion 240 senses a sign 239 and senses a
folded state of the display portion 230.
[0060] The sign 239 is placed, for example, in the vicinity of the
display portion 230 so that the positional relation between the
sign 239 and the sensing portion 240 changes in accordance with the
opened state or the folded state of the display portion 230. Thus,
the sensing portion 240 can sense the opened state or the folded
state of the display portion 230 and supply a fold signal F.
[0061] Elements included in the display device 200 of one
embodiment of the present invention are described below.
<<Foldable Display Portion>>
[0062] The foldable display portion 230 includes the first region
230(1) and the second region 230(2). The display portion 230
includes a display panel provided with display elements and a
housing supporting the display panel.
[0063] The display panel includes a pixel portion in the first
region 230(1) and the second region 230(2). Pixels are arranged
such that a continuous image is displayed in the first region
230(1) and the second region 230(2). For example, pixels are
arranged at regular intervals throughout the first and second
regions so that a user does not recognize a boundary 230b(1)
between the first region 230(1) and the second region 230(2) (see
FIG. 1A).
[0064] The pixel portion includes a plurality of pixels, a
plurality of scan lines, and a plurality of signal lines.
[0065] Each of the pixels includes a pixel circuit electrically
connected to one scan line and one signal line and a display
element electrically connected to the pixel circuit.
[0066] A display panel that can be used for the foldable display
portion 230 includes, for example, a flexible substrate and display
elements over the substrate. For example, the display panel can be
bent with a curvature radius of greater than or equal to 1 mm and
less than or equal to 100 mm with one surface on which an image can
be displayed facing either inward or outward. Specifically, the
display panel can have a structure in which an inorganic film
provided with pixels is sandwiched between flexible films.
[0067] A housing that can be used for the foldable display portion
230 includes a hinge that can be folded at, for example, the
boundary 230b(1) (see FIGS. 1B1 and 1B2).
[0068] The display portion 230 described in this embodiment is
foldable in three parts; however, one embodiment of the present
invention is not limited to such a structure. Specifically, the
display portion 230 may be foldable in two parts or in four or more
parts. A larger foldable number leads to a smaller external shape
in a folded state, resulting in higher portability.
[0069] The display portion 230 can be folded at the boundary
230b(I) between the first region 230(1) and the second region
230(2).
[0070] FIG. 1B1 illustrates a state where the display portion 230
is opened flat.
[0071] FIG. 1B2 schematically illustrates a state where the display
portion 230 is bent, specifically, a state where the display
portion 230 is bent outward at the boundary 230b(1) and bent inward
at a boundary 230b(2) so as to be folded in three parts.
[0072] In particular, in a folded state of the display device 200,
the first region 230(1) is preferably placed on the outer side of
the display device 200. In that case, a user can see an image
displayed in the first region 230(1) in a folded state.
[0073] Note that an example of a structure of the foldable display
portion 230 is described in detail in Embodiment 3.
<<Driver Circuit>>
[0074] The driver circuits 232 include the scan line driver circuit
232G and the signal line driver circuit 232S. The driver circuits
232 can be formed using, for example, any of a variety of
sequential circuits such as a shift register. In the case where a
driver circuit that is formed using an LSI is placed in a flexible
display portion, the driver circuit is placed in a portion other
than a bendable portion. Note that a driver circuit that can be
formed in the same process as the pixel circuit is preferable
because it can be placed in a bendable portion of a flexible
display portion and therefore has a small limit in its
position.
[0075] The scan line driver circuit 232G receives power supply
potential and a synchronization signal SYNC and supplies a scan
line selection signal.
[0076] The signal line driver circuit 232S receives power supply
potential, a synchronization signal SYNC, and an image signal VIDEO
and supplies an image signal.
[0077] A scan line selection signal is supplied to the display
portion 230, whereby one scan line and pixels connected to the scan
line are selected.
[0078] Image signals are supplied to pixels to which a scan line
selection signal is supplied, and pixel circuits in the pixels
store the image signals. In addition, display elements in the
pixels perform display in accordance with the image signals.
<<Synchronization Signal Supply Portion>>
[0079] The synchronization signal supply portion 212 supplies a
synchronization signal SYNC. The synchronization signal SYNC is
used for synchronous operation of the driver circuits 232. Examples
of the synchronization signal SYNC include a vertical
synchronization signal and a horizontal synchronization signal, a
start pulse signal SP, a latch signal LP, a pulse width control
signal PWC, and a clock signal CLK.
<<Power Supply Portion>>
[0080] The power supply portion 214 supplies power supply
potential. As the power supply potential, at least one of a high
power supply potential (e.g., VDD) and a low power supply potential
(e.g., VSS or GND) can be supplied. There is also a case where a
plurality of high power supply potentials (e.g., VDD1 and VDD2) are
supplied.
<<Image Processing Portion>>
[0081] The image processing portion 220 receives an image control
signal VC, generates an image, and supplies an image signal VIDEO
of the generated image.
[0082] The image signal VIDEO includes data on an image to be
displayed in the first region 230(1) and the second region 230(2)
of the display portion 230.
[0083] For example, the image processing portion 220 can generate,
in accordance with the image control signal VC, one image to be
displayed in the first region 230(1) and the second region 230(2).
Moreover, the image processing portion 220 can generate, in
accordance with the image control signal VC, one image in which a
black image, for example, is displayed in the second region 230(2).
For example, an image with the darkest gray level among gray levels
that can be displayed by display elements is referred to as a black
image.
[0084] When display elements display a black image, power
consumption can be made lower than that for displaying other images
(e.g., a white image or a gray image), resulting in a reduction in
the power consumption of the display device 200.
[0085] Specifically, power consumed by the second region 230(2)
that is folded so that display cannot be seen can be reduced.
[0086] A light-emitting element is an example of a display element
that consumes less power when displaying a black image than when
displaying other images. Note that in the case where display
elements consume the least power at a gray level different from the
darkest gray level that can be displayed by the display elements,
an image with that gray level may be displayed instead of a black
image.
<<Sensing Portion and Sign>>
[0087] The sensing portion 240 senses an opened state or a folded
state of the display portion 230 and supplies a fold signal F. Note
that the fold signal F includes data indicating an opened state or
data indicating a folded state.
[0088] The sensing portion 240 is provided with a sensor that
senses the sign 239 that is close thereto. The sensor senses the
sign 239 placed in the vicinity of the display portion 230, whereby
the sensing portion 240 can supply a fold signal F corresponding to
the folded state of the display portion 230.
[0089] For example, the shape or place of an object such as a
protrusion, an electromagnetic wave such as light, an electric
wave, or a magnetic force, or the like can serve as the sign 239.
Specifically, the above serving as the sign 239 may have different
polarities (e.g., the N- and S-poles of a magnet) or different
signals (e.g., electromagnetic waves which are modulated by
different methods), for example.
[0090] A sensor that can identify the sign 239 is selected as the
sensor included in the sensing portion 240.
[0091] Specifically, in the case where a structure having different
shapes or in different places (e.g., a protrusion) is used as the
sign 239, a switch or the like having different shapes or in
different places can be used for the sensor so that the structure
can be identified. Alternatively, in the case where light is used
as the sign 239, a photoelectric conversion element or the like can
be used for the sensor. In the case where an electric wave is used
as the sign 239, an antenna or the like can be used for the sensor.
In the case where a magnet is used as the sign 239, a magnetic
sensor or the like can be used for the sensor.
[0092] Note that the sensing portion 240 may sense acceleration, a
direction, a global positioning system (GPS) signal, temperature,
humidity, or the like and supply data thereon in addition to the
fold signal F.
[0093] A structure in which a magnet is used as the sign 239 and a
magnetic sensor that senses a magnetic force of the magnet is used
for the sensing portion 240 will be described.
[0094] The display device 200 includes a magnet as the sign 239,
and the sensing portion 240 includes a magnetic sensor. The magnet
is placed at a position such that the magnetic sensor can sense an
opened state or a folded state of the display portion 230.
[0095] The display device 200 described in this embodiment includes
the display portion 230 that can be opened and folded, a magnet
(the sign 239) and the sensing portion 240 including a magnetic
sensor that are placed to sense a folded state of the display
portion 230, and the image processing portion 220 that generates,
when the display portion is in the folded state, an image in which
a black image is displayed in part of the display portion 230
(specifically, the second region). Thus, a region (specifically,
the second region) where display is unnecessary when part of the
display portion 230 is folded can display a black image. Moreover,
the folded state can be maintained by a magnetic force of the
magnet. Consequently, a display device with low power consumption
can be provided. Furthermore, a display device in which an image is
displayed in a region that can be used in a folded state can be
provided. Furthermore, a display device that is prevented from
being changed from a folded state to an opened state
unintentionally can be provided.
<<Control Portion>>
[0096] The control portion 210 can receive a fold signal F and
supply an image control signal VC. The control portion 210 may also
supply signals for controlling the power supply portion 214 and the
synchronization signal supply portion 212.
[0097] The image control signal VC is a signal for controlling the
image processing portion 220. Examples of the image control signal
VC include a signal that makes the image processing portion 220
generate different images in accordance with the opened state or
the folded state of the display portion 230.
<<Timing Generator>>
[0098] A timing generator generates and supplies a reference clock
signal or the like that the display device 200 needs.
<<Structure of Display Portion 230>>
[0099] The display portion 230 includes a plurality of pixels 631p
and wirings that connect the plurality of pixels 631p (see FIG. 2A
and FIG. 15A). Note that the kinds and number of the wirings are
determined as appropriate depending on the structure, number, and
arrangement of the pixels 631p.
[0100] Each of the pixels 631p is electrically connected to at
least one scan line and one signal line.
[0101] For example, in the case where the pixels 631p are arranged
in a matrix of x columns and y rows in the display portion 230,
signal lines S1 to Sx and scan lines G1 to Gy are provided in the
display portion 230 (see FIG. 2A and FIG. 15A). The scan lines G1
to Gy can supply scan line selection signals to the respective
rows. The signal lines S1 to Sx can supply image signals to pixels
to which a scan line selection signal is supplied.
<<Structure of Pixel 631p>>
[0102] The pixel 631p includes a display element and a pixel
circuit including the display element.
[0103] The pixel circuit holds the supplied image signal and makes
the display element display a gray level corresponding to the image
signal. Note that the structure of the pixel circuit is selected as
appropriate in accordance with the kind or the driving method of
the display element.
[0104] As the display element, an EL element, electronic ink
utilizing electrophoresis, a liquid crystal element, or the like
can be used.
[0105] FIG. 2B and FIG. 15B each illustrate, as an example of the
pixel circuit, a structure in which an EL element is used as the
display element.
[0106] A pixel circuit 634EL includes a first transistor 634t_1
including a gate electrode electrically connected to a scan line G
through which a scan line selection signal can be supplied, a first
electrode electrically connected to a signal line S through which
an image signal can be supplied, and a second electrode
electrically connected to a first electrode of a capacitor
634c.
[0107] The pixel circuit 634EL also includes a second transistor
634t_2 including a gate electrode electrically connected to a
second electrode of the first transistor 634t_1, a first electrode
electrically connected to a second electrode of the capacitor 634c,
and a second electrode electrically connected to a first electrode
of an EL element 635EL.
[0108] The second electrode of the capacitor 634c and the first
electrode of the second transistor 634t_2 are electrically
connected to a wiring A through which power supply potential and a
potential needed for light emission of the EL element 635EL can be
supplied. Note that the potential of the wiring A may be constant
or may change in a pulsed manner every certain period. A second
electrode of the EL element 635EL is electrically connected to a
wiring C through which a common potential can be supplied. Note
that the difference between the power supply potential and the
common potential is larger than the emission start voltage of the
EL element 635EL.
[0109] The EL element 635EL includes a layer containing a
light-emitting organic compound between a pair of electrodes.
<<Transistor>>
[0110] The second transistor 634t_2 supplies a current
corresponding to the potential of the signal line S to control the
light emission of the EL element 635EL. The second transistor
634t_2 includes silicon, an oxide semiconductor, or the like in a
region where a channel is formed.
[0111] As an example of a transistor that can be suitably used as
the first transistor 634t_1 or the second transistor 634t_2, a
transistor including an oxide semiconductor can be given.
[0112] A transistor including an oxide semiconductor film can have
leakage current between a source and a drain in an off state
(off-state current) much lower than that of a conventional
transistor including silicon. An example of a structure of the
transistor that can be suitably used as the first transistor 634t_1
or the second transistor 634t_2 is described in Embodiment 4.
[0113] This embodiment can be combined with any of the other
embodiments in this specification as appropriate.
Embodiment 2
[0114] In this embodiment, a structure of a display device of one
embodiment of the present invention is described with reference to
FIG. 4, FIGS. 5A and 5B, and FIGS. 6A to 6D.
[0115] FIG. 4 is a block diagram illustrating the structure of the
display device of one embodiment of the present invention.
[0116] FIGS. 5A and 5B are flow charts illustrating the operation
of a control portion of the display device of one embodiment of the
present invention. FIG. 5A is a flow chart illustrating main
processing, and FIG. 5B is a flow chart illustrating interrupt
processing.
[0117] FIGS. 6A to 6D are flow charts illustrating processing 1,
processing 2, processing 3, and processing 4 performed by the
control portion of the display device of one embodiment of the
present invention.
[0118] A display device 200B described in this embodiment includes
the foldable display portion 230 including the first region 230(1)
and the second region 230(2); the sensing portion 240 that senses
an opened state or a folded state of the display portion 230 and
supplies a fold signal F; a control portion 210B that receives the
fold signal F and supplies an image control signal VC and a
synchronization control signal SC; the image processing portion 220
that receives the image control signal VC and supplies a first
image signal VIDEO(1) and a second image signal VIDEO(2); the
synchronization signal supply portion 212 that receives the
synchronization control signal SC and supplies a first
synchronization signal SYNC(1) and a second synchronization signal
SYNC(2); a first driver circuit 232(1) that receives the first
image signal VIDEO(1) and the first synchronization signal SYNC(1)
and drives the first region 230(1); and a second driver circuit
232(2) that receives the second image signal VIDEO(2) and the
second synchronization signal SYNC(2) and drives the second region
230(2).
[0119] The control portion 210B supplies the image control signal
VC that makes the image processing portion 220 generate an image in
which a black image is displayed in the second region 230(2) of the
display portion 230 in a folded state and the synchronization
control signal SC that stops selection of a scan line in the second
region 230(2) of the display portion 230 in a folded state.
[0120] The control portion 210B of the display device 200B
described in this embodiment includes an arithmetic unit and a
storage unit that stores a program to be executed by the arithmetic
unit. The program includes the following steps.
[0121] In a first step, the interrupt processing is allowed (FIG.
5A (S1)).
[0122] In a second step, the operation proceeds to a third step
when the display portion 230 is in an opened state and proceeds to
a fourth step when the display portion 230 is in a folded state
(FIG. 5A (S2)). Specifically, a fold signal F is acquired and is
used to determine whether the display portion 230 is in an opened
state or in a folded state.
[0123] In the third step, the operation proceeds to a fifth step in
the case where the opened state of the display portion 230 has not
changed, and proceeds to a sixth step in the case where the opened
state of the display portion 230 has changed to the folded state
(FIG. 5A (S3)). Note that a fold signal F that was acquired in the
second step just prior to this step is compared with a fold signal
F that was stored in the storage unit previously, whereby it is
determined whether or not there has been a change in the state. In
the case where the opened state of the display portion 230 has
changed, a new fold signal F is stored to update the storage
unit.
[0124] In the fourth step, the operation proceeds to a seventh step
in the case where the folded state of the display portion 230 has
not changed, and proceeds to an eighth step in the case where the
folded state of the display portion 230 has changed to the opened
state (FIG. 5A (S4)). Note that a fold signal F that was acquired
in the second step just prior to this step is compared with a fold
signal F that was stored in the storage unit previously, whereby it
is determined whether or not there has been a change in the
state.
[0125] In the case where the folded state of the display portion
230 has changed, a new fold signal F is stored to update the
storage unit.
[0126] In the fifth step, the processing 1 is executed (FIG. 5A
(S5)).
[0127] In the sixth step, the processing 2 is executed (FIG. 5A
(S6)).
[0128] In the seventh step, the processing 3 is executed (FIG. 5A
(S7)).
[0129] In the eighth step, the processing 4 is executed (FIG. 5A
(S8)).
[0130] In a ninth step, the operation proceeds to a tenth step when
a termination instruction has been supplied in the interrupt
processing and returns to the second step when the termination
instruction has not been supplied in the interrupt processing (FIG.
5A (S9)).
[0131] In the tenth step, the program is terminated (FIG. 5A
(S10)).
[0132] The interrupt processing includes an eleventh step of
allowing operation and a twelfth step of recovering from the
interrupt processing (FIGS. 5B (T11) and (T12)).
[0133] The control portion 210B of the display device 200B
described in this embodiment includes the storage unit that stores
a program for execution of four types of processing. The program
for execution of the four types of processing includes the
following steps.
<<Processing 1>>
[0134] In a first step of the processing 1, the arithmetic unit
makes the synchronization signal supply portion 212 supply a first
synchronization signal SYNC(1) to the first driver circuits 232(1)
and a second synchronization signal SYNC(2) to the second driver
circuits 232(2) (FIG. 6A (U1)).
[0135] In a second step, the arithmetic unit makes the image
processing portion 220 generate an image to be displayed in the
first region 230(1) and the second region 230(2) (FIG. 6A
(U2)).
[0136] In a third step, the arithmetic unit makes the display
portion 230 display the image (FIG. 6A (U3)).
[0137] In a fourth step, the operation recovers from the processing
1 (FIG. 6A (U4)).
<<Processing 2>>
[0138] In a first step of the processing 2, the arithmetic unit
makes the synchronization signal supply portion 212 supply a first
synchronization signal SYNC(1) to the first driver circuits 232(1)
and a second synchronization signal SYNC(2) to the second driver
circuits 232(2) (FIG. 6B (V1)).
[0139] In a second step, the arithmetic unit makes the image
processing portion 220 generate an image in which a black image is
displayed in the second region 230(2) (FIG. 6B (V2)).
[0140] In a third step, the arithmetic unit makes the display
portion 230 display the image (FIG. 6B (V3)).
[0141] In a fourth step, the arithmetic unit makes the
synchronization signal supply portion 212 sequentially stop the
supply of the second synchronization signals SYNC(2) to the second
driver circuits 232(2) (FIG. 6B (V4)).
[0142] For example, the supply of synchronization signals is
sequentially stopped in the following order: the potential of a
start pulse signal is fixed at "Low", the potential of a clock
signal is fixed at "Low", and then the power supply potential is
fixed at "Low".
[0143] In a fifth step, the operation recovers from the processing
2 (FIG. 6B (V5)).
<<Processing 3>>
[0144] In a first step of the processing 3, the arithmetic unit
makes the synchronization signal supply portion 212 supply a first
synchronization signal SYNC(1) to the first driver circuits 232(1)
(FIG. 6C (W1)).
[0145] In a second step, the arithmetic unit makes the image
processing portion 220 generate an image to be displayed in the
first region 230(1) (FIG. 6C (W2)).
[0146] In a third step, the arithmetic unit makes the display
portion 230 display the image in the first region 230(1) (FIG. 6C
(W3)).
[0147] In a fourth step, the operation recovers from the processing
3 (FIG. 6C (W4)).
<<Processing 4>>
[0148] In a first step of the processing 4, the arithmetic unit
makes the synchronization signal supply portion 212 sequentially
resume the supply of the second synchronization signals SYNC(2) to
the second driver circuits 232(2) (FIG. 6D (X1)).
[0149] For example, the supply of synchronization signals is
sequentially resumed in the following order: a predetermined power
supply potential is supplied, a clock signal is supplied, and then
a start pulse signal is supplied.
[0150] In a second step, the arithmetic unit makes the image
processing portion 220 generate an image to be displayed in the
first region 230(1) and the second region 230(2) (FIG. 6D
(X2)).
[0151] In a third step, the arithmetic unit makes the display
portion 230 display the image (FIG. 6D (X3)).
[0152] In a fourth step, the operation recovers from the processing
4 (FIG. 6D (X4)).
[0153] The above display device 200B of one embodiment of the
present invention includes the display portion 230 that can be
opened and folded, the sensing portion 240 that senses a folded
state of the display portion 230, the image processing portion 220
that generates, when the display portion 230 is in the folded
state, an image in which a black image is displayed in part of the
display portion 230, and the synchronization signal supply portion
212 that can stop the supply of a second synchronization signal
SYNC(2) used for a portion where a black image is to be displayed.
Thus, the display in a region where display is unnecessary when
part of the display portion is folded can be stopped. Consequently,
a display device with low power consumption can be provided.
Furthermore, a display device in which an image is displayed in a
region that can be used in a folded state can be provided.
[0154] Elements included in the display device 200B of one
embodiment of the present invention are described below. For
elements that can be similar to those in the display device 200
described in Embodiment 1, the description in Embodiment 1 can be
referred to.
<<Foldable Display Portion>>
[0155] The display portion 230 that can be used in the display
device 200B can be similar to the display portion 230 described in
Embodiment 1 except that the first region 230(1) is driven by the
first driver circuits 232(1) and the second region 230(2) is driven
by the second driver circuits 232(2).
[0156] Scan lines provided in the first region 230(1) and scan
lines provided in the second region 230(2) are electrically
insulated from each other at the boundary 230b(1) between the first
region 230(1) and the second region 230(2). Note that in the case
where the scan line driver circuit 232G is placed on only one side
as shown in FIG. 16, the scan lines in the first region 230(1) and
the scan lines in the second region 230(2) may be connected to each
other. In that case, since the scan lines in the second region
230(2) are also selected when the scan lines in the first region
230(1) are selected, if black display is to be performed in the
second region 230(2), signals for black display need to be supplied
from the signal line driver circuit 232S(2). However, since keeping
black display requires only supply of a constant voltage, power
consumption can be reduced.
<<Driver Circuit>>
[0157] The display device 200B includes the first driver circuits
232(1) and the second driver circuits 232(2).
[0158] The first driver circuits 232(1) include a scan line driver
circuit 232G(1) and a signal line driver circuit 232S(1).
[0159] The second driver circuits 232(2) include a scan line driver
circuit 232G(2) and a signal line driver circuit 232S(2).
[0160] Like FIG. 14 and FIGS. 15A and 15B, FIG. 17 illustrates the
case where the scan line driver circuits and the signal line driver
circuits in FIG. 4 are replaced with each other. In this case,
signal lines provided in the first region 230(1) and signal lines
provided in the second region 230(2) are electrically insulated
from each other at the boundary 230b(1) between the first region
230(1) and the second region 230(2). Note that in the case where
the signal line driver circuit 232S is placed on only one side as
shown in FIG. 18, the signal lines in the first region 230(1) and
the signal lines in the second region 230(2) may be connected to
each other. In that case, since image signals are supplied also to
the signal lines in the second region 230(2) when image signals are
supplied to the signal lines in the first region 230(1), if black
display is to be performed in the second region 230(2), signals for
not selecting pixels need to be supplied from the scan line driver
circuit 232G(2). However, since keeping a non-selection state
requires only supply of a constant voltage, power consumption can
be reduced.
[0161] The scan line driver circuit 232G(1) receives power supply
potential and a first synchronization signal SYNC(1) and supplies
scan line selection signals to scan lines provided in the first
region 230(1).
[0162] The scan line driver circuit 232G(2) receives power supply
potential and a second synchronization signal SYNC(2) and supplies
scan line selection signals to scan lines provided in the second
region 230(2).
[0163] The signal line driver circuit 232S(1) receives power supply
potential, a first synchronization signal SYNC(1), and a first
image signal VIDEO(1) and supplies an image signal.
[0164] The signal line driver circuit 232S(2) receives power supply
potential, a second synchronization signal SYNC(2), and a second
image signal VIDEO(2) and supplies an image signal.
[0165] A scan line selection signal is supplied to the first region
230(1) of the display portion 230, whereby one scan line and pixels
connected to the scan line are selected. In addition, a scan line
selection signal is supplied to the second region 230(2) of the
display portion 230, whereby one scan line and pixels connected to
the scan line are selected.
[0166] Image signals are supplied to pixels to which a scan line
selection signal is supplied, and pixel circuits in the pixels
store the image signals. In addition, display elements in the
pixels perform display in accordance with the image signals.
<<Synchronization Signal Supply Portion>>
[0167] The synchronization signal supply portion 212 receives a
synchronization control signal SC and supplies a first
synchronization signal SYNC(1) and a second synchronization signal
SYNC(2).
[0168] The first synchronization signal SYNC(i) is used for
synchronous operation of the first driver circuits 232(1). The
second synchronization signal SYNC(2) is used for synchronous
operation of the second driver circuits 232(2). Examples of the
synchronization signal include a vertical synchronization signal
and a horizontal synchronization signal, a start pulse signal SP, a
latch signal LP, a pulse width control signal PWC, and a clock
signal CLK.
[0169] The synchronization signal supply portion 212 supplies the
second synchronization signal SYNC(2) or stops the supply in
accordance with the supplied synchronization control signal SC. By
stopping the supply of the second synchronization signal SYNC(2),
the operation of the second region 230(2) can be stopped. Note that
"operation is stopped" refers to the case where wirings in the
portion are in a high-impedance state (or floating state) or to the
case where a predetermined potential is supplied to the wirings and
the potential remains constant so that the portion is kept in the
same state.
<<Image Processing Portion>>
[0170] The image processing portion 220 receives an image control
signal VC, generates an image, and supplies a first image signal
VIDEO(1) and a second image signal VIDEO(2) of the generated
image.
[0171] The first image signal VIDEO(1) includes data on an image to
be displayed in the first region 230(1) of the display portion 230.
The second image signal VIDEO(2) includes data on an image to be
displayed in the second region 230(2) of the display portion
230.
[0172] For example, the image processing portion 220 can generate,
in accordance with the image control signal VC, one image to be
displayed in the first region 230(1) and the second region
230(2).
[0173] Moreover, the image processing portion 220 can generate, in
accordance with the image control signal VC, one image in which a
black image, for example, is displayed in the second region
230(2).
[0174] Furthermore, in accordance with the image control signal VC,
the image processing portion 220 can generate only one image to be
displayed in the first region 230(1).
[0175] Accordingly, the power consumption of the display device
200B can be reduced.
[0176] Specifically, power consumed by the second region 230(2)
that is folded so that display cannot be seen can be reduced.
[0177] A light-emitting element is an example of a display element
that consumes less power when displaying a black image than when
displaying other images.
<<Sensing Portion and Sign>>
[0178] The sensing portion 240 senses an opened state or a folded
state of the display portion 230 and supplies a fold signal F. Note
that structures similar to those in Embodiment 1 can be used for
the sensing portion and the sign.
<<Control Portion>>
[0179] The control portion 210B can receive a fold signal F and
supply an image control signal VC, a synchronization control signal
SC, and a power supply control signal PC.
[0180] The image control signal VC is a signal for controlling the
image processing portion 220. Examples of the image control signal
VC include a signal that makes the image processing portion 220
generate different images in accordance with the opened state or
the folded state of the display portion 230.
<<Timing Generator>>
[0181] A timing generator generates and supplies a reference clock
signal or the like that the display device 200B needs.
<<Power Supply Portion>>
[0182] The power supply portion 214 receives a power supply control
signal PC and supplies power supply potential.
[0183] The power supply portion 214 supplies power supply potential
or stops the supply in accordance with the supplied power supply
control signal PC. By stopping the supply of the power supply
potential to the second driver circuits 232(2), power consumed by
the second driver circuits 232(2) can be reduced.
[0184] Note that "supply of power supply potential is stopped"
sometimes refers to the following case: impedance to at least one
of a high power supply potential (e.g., VDD) and a low power supply
potential (e.g., VSS or GND) is made high so that energy is not
supplied, and energy of the other power supply potential is
supplied. In that case, only the other power supply potential is
supplied from the driver circuit. As a result, a predetermined
potential is supplied to wirings in the portion connected to the
driver circuit and the potential remains constant so that the
portion is kept in the same state.
[0185] For example, in the case where only a non-selection signal
is to be supplied from the scan line driver circuit 232G(2), only a
power supply potential corresponding to the potential of the
non-selection signal is supplied to the scan line driver circuit
232G(2) from the power supply portion 214. Consequently, current
hardly flows in the scan line driver circuit 232G(2); thus, power
consumption can be reduced. Alternatively, in the case where only a
potential needed for black display is to be supplied from the
signal line driver circuit 232S(2), only a power supply potential
corresponding to the potential needed for black display is supplied
to the signal line driver circuit 232S(2) from the power supply
portion 214. Consequently, current hardly flows in the signal line
driver circuit 232S(2); thus, power consumption can be reduced.
[0186] Furthermore. "supply of power supply potential is stopped"
sometimes refers to the following case: impedance to both a high
power supply potential (e.g., VDD) and a low power supply potential
(e.g., VSS or GND) is made high so that energy is not supplied. In
that case, energy is not supplied from the driver circuit. As a
result, wirings in the portion connected to the driver circuit are
put in a high-impedance state (or floating state). Thus, in the
case where black display has been performed, the black display
state is maintained, so that power consumption can be reduced. In
addition, since current does not flow in the driver circuit, power
consumption can be reduced.
[0187] Note that the power supply portion 214 may include a
plurality of power supplies, specifically a first power supply and
a second power supply.
[0188] A modification example of the display device 200B described
in this embodiment includes a first power supply that supplies
power supply potential to the first driver circuit 232(1) and a
second power supply that supplies power supply potential to the
second driver circuit 232(2). The control portion 210B supplies a
power supply control signal PC to the second power supply in
accordance with the fold signal F. The second power supply stops
supply of power supply potential in accordance with the power
supply control signal PC.
[0189] The above display device of one embodiment of the present
invention includes a display portion that can be opened and folded,
a synchronization signal supply portion that can stop the supply of
a synchronization signal used for a portion where a black image is
to be displayed, and a power supply that can stop the supply of a
power supply potential used for a portion where a black image is to
be displayed. Thus, the display in a region where display is
unnecessary when part of the display portion is folded can be
stopped. Consequently, a display device with low power consumption
can be provided. Furthermore, a display device in which an image is
displayed in a region that can be used in a folded state can be
provided.
Modification Example
[0190] A display device 200D described as a modification example in
this embodiment will be described with reference to FIG. 4; the
display device 200B in FIG. 4 is replaced with the display device
200D.
[0191] In the display device 200D described as a modification
example in this embodiment, the frequency of rewriting images in
the display portion can be varied.
[0192] Specifically, description is given on a display device which
has a first mode in which a scan line selection signal for
selecting a pixel is output at a frequency of more than or equal to
30 Hz (30 times per second), preferably more than or equal to 60 Hz
(60 times per second) and less than 960 Hz (960 times per second)
and a second mode in which the scan line selection signal is output
at a frequency of more than or equal to 11.6 .mu.Hz (once per day)
and less than 0.1 Hz (0.1 times per second), preferably more than
or equal to 0.28 mHz (once per hour) and less than 1 Hz (once per
second).
[0193] When a still image is displayed with the display device 200D
described as a modification example in this embodiment, the refresh
rate can be set to less than 1 Hz, preferably less than or equal to
0.2 Hz. This enables display with reduced eye strain on a user.
Further, a display image can be refreshed at an optimal frequency
in accordance with the quality of the image displayed on the
display portion. Specifically, in displaying a still image, the
refresh rate can be set lower than that in displaying a smooth
moving image; thus, a still image with less flicker can be
displayed. In addition, power consumption can be reduced.
[0194] Note that the display device 200D described as a
modification example in this embodiment has the same structure as
the display device 200B except for the structures of the control
portion, the driver circuits, and the display portion.
<<Driver Circuit>>
[0195] The scan line driver circuit 232G(1) and the scan line
driver circuit 232G(2) each supply scan line selection signals at
different frequencies in accordance with the supplied first
synchronization signal SYNC(1) and second synchronization signal
SYNC(2).
[0196] For example, the driver circuit supplies scan line selection
signals in the following modes: a first mode of outputting a scan
line selection signal at a frequency of more than or equal to 30 Hz
(30 times per second), preferably more than or equal to 60 Hz (60
times per second) and less than 960 Hz (960 times per second) and a
second mode of outputting a scan line selection signal at a
frequency of more than or equal to 11.6 .mu.Hz (once per day) and
less than 0.1 Hz (0.1 times per second), preferably more than or
equal to 0.28 mHz (once per hour) and less than 1 Hz (once per
second).
<<Synchronization Signal Supply Portion>>
[0197] The synchronization signal supply portion 212 supplies, in
accordance with the supplied synchronization control signal SC, a
first synchronization signal SYNC(1) and a second synchronization
signal SYNC(2) that make the driver circuits each supply scan line
selection signals at different frequencies.
[0198] For example, the synchronization signal supply portion 212
controls the output frequency of a start pulse signal supplied to
the scan line driver circuit, whereby scan line selection signals
can be supplied at different frequencies.
<<Control Portion>>
[0199] A control portion 210D supplies a synchronization control
signal SC to the synchronization signal supply portion 212 and
makes the driver circuit supply scan line selection signals at
different frequencies. For example, when a moving image is
displayed, the control portion 210D supplies a synchronization
control signal SC for supplying scan line selection signals at a
high frequency, and when a still image is displayed, the control
portion 210D supplies a synchronization control signal SC for
supplying scan line selection signals at a low frequency.
<<Transistor>>
[0200] The second transistor 634t_2 supplies a current
corresponding to the potential of the signal line S to control the
light emission of the EL element 635EL.
[0201] As an example of a transistor that can be suitably used as
the first transistor 634t_1 or the second transistor 634t_2, a
transistor including an oxide semiconductor can be given.
[0202] A transistor including an oxide semiconductor film can have
leakage current between a source and a drain in an off state
(off-state current) much lower than that of a conventional
transistor including silicon.
[0203] When a transistor with extremely low off-state current is
used in a pixel portion of a display portion, frame frequency can
be lowered while flicker is reduced.
[0204] Furthermore, in the processing 2 in this embodiment, pixels
in the second region 230(2) in each of which a transistor with
extremely low off-state current including an oxide semiconductor is
used can hold image signals for a black image supplied to the
second region 230(2) for a long time, as compared to the case where
a transistor including silicon is used. Thus, the display in a
region where display becomes unnecessary can be stopped.
Consequently, a display device with low power consumption can be
provided. Furthermore, a display device in which an image is
displayed in a region that can be used in a folded state can be
provided.
[0205] An example of a structure of the transistor that can be
suitably used as the first transistor 634t 1 or the second
transistor 634t 2 is described in Embodiment 4.
[0206] This embodiment can be combined with any of the other
embodiments in this specification as appropriate.
Embodiment 3
[0207] In this embodiment, a structure of a display device 200C of
one embodiment of the present invention is described with reference
to FIGS. 7A to 7C, FIGS. 8A to 8D, and FIGS. 9A and 9B.
[0208] FIGS. 7A to 7C are perspective views illustrating the
structure of the display device 200C of one embodiment of the
present invention. FIG. 7A illustrates the display device 200C in
an opened state, FIG. 7B illustrates the display device 200C in a
bent state, and FIG. 7C illustrates the display device 200C in a
folded state.
[0209] FIGS. 8A to 8D illustrate the structure of the display
device 200C of one embodiment of the present invention. FIG. 8A is
a top view of the display device 200C that is opened, and FIG. 8B
is a bottom view of the display device 200C that is opened. FIG. 8C
is a side view of the display device 200C that is opened, and FIG.
8D is a cross-sectional view taken along dashed-dotted line A-B in
FIG. 8A.
[0210] FIGS. 9A and 9B illustrate the structure of a display panel
of the display device 200C of one embodiment of the present
invention. FIG. 9A is a cross-sectional view of the center of the
display device 200C in a folded state, and FIG. 9B is a top view of
the display panel in an opened state.
[0211] The display device 200(C described in this embodiment
includes a foldable display portion including the first region
230(1) and the second region 230(2); driver circuits that drive the
display portion; an image processing portion that supplies an image
signal to the driver circuits; the sensing portion 240 that senses
an opened state or a folded state of the display portion and
supplies a fold signal; and a control portion that receives the
fold signal (FIG. 7A).
[0212] The control portion supplies an image control signal in
accordance with the fold signal, and the image processing portion
generates, in accordance with the image control signal, an image in
which a black image is displayed in the second region 230(2).
[0213] Note that the driver circuits, the image processing portion,
and the control portion are provided between support panels 15a and
support panels 15b.
[0214] The display device 200C includes a strip-like high
flexibility region E1 and a strip-like low flexibility region E2
that are arranged alternately, in other words, form stripes (FIG.
8A). Note that the regions are not necessarily arranged in parallel
to each other.
[0215] A connecting member 13a is partly exposed between two
support panels 15a apart from each other. In addition, a connecting
member 13b is partly exposed between two support panels 15b apart
from each other (FIGS. 8A and 8B).
[0216] The display device 200C can be folded by bending the high
flexibility region E1 (see FIGS. 7B and 7C).
<<High Flexibility Region>>
[0217] The high flexibility region E1 serves as a hinge. The high
flexibility region E1 includes at least a flexible display
panel.
[0218] The high flexibility region E1 includes the connecting
member 13a on the image display side of the display panel and the
connecting member 13b on the opposite side (see FIGS. 8A and 8B).
The display panel is held between the connecting member 13a and the
connecting member 13b (see FIG. 7A and FIGS. 8C and 8D).
<<Low Flexibility Region>>
[0219] The low flexibility region E2 includes the support panel 15a
on the image display side of the display panel and the support
panel 15b on the opposite side. The display panel is held between
the support panel 15a and the support panel 15b.
[0220] A stacked body in which the support panel 15a and the
support panel 15b overlap with each other has a lower flexibility
than that of the display panel.
[0221] The support panels 15a and the support panels 15b support
the display panel to increase its mechanical strength and can
prevent breakage of the display panel.
[0222] The scan line driver circuit 232G(1), the scan line driver
circuit 232G(2), and the signal line driver circuit 232S(1) are
held between the support panels 15a and the support panels 15b.
Thus, the driver circuits can be protected from external stress
(see FIGS. 9A and 9B).
[0223] Note that the support panels may be placed on only one of
the display surface side and the side opposite to the display
surface side of the display panel. For example, a display device
that includes the plurality of support panels 15b and does not
include the plurality of support panels 15a may be employed. Thus,
the display device can be made thin and/or lightweight.
<<Connecting Member and Support Panel>>
[0224] For the connecting member 13a, the connecting member 13b,
the support panels 15a, and the support panels 15b, for example,
plastic, a metal, an alloy, and/or rubber can be used.
[0225] Plastic, rubber, or the like is preferably used because it
can form a connecting member or a support panel that is lightweight
and less likely to be broken. For example, silicone rubber may be
used for the connecting member and stainless steel or aluminum may
be used for the support panel.
[0226] In the case where a connecting member or a support panel is
placed on the display surface side of the display panel, a
light-transmitting material is used for a portion that overlaps
with a region where display is performed on the display panel,
i.e., the first region 230(1) and the second region 230(2).
[0227] To fix two of the connecting member, the support panel, and
the display panel, for example, an adhesive, a screw or pin that
penetrates them, or a clip that holds them can be used.
<<Sensing Portion and Sign>>
[0228] The sign 239 and the sensing portion 240 are provided on the
support panels 15a to sense an opened state or a folded state of
the display portion 230 (see FIGS. 7A and 7B and FIGS. 8A and
8C).
[0229] When the display portion 230 is in an opened state, the sign
239 is away from the sensing portion 240 (see FIG. 7A).
[0230] When the display portion 230 is bent at the connecting
member 13a, the sign 239 gets close to the sensing portion 240 (see
FIG. 7B).
[0231] When the display portion 230 is folded at the connecting
member 13a, the sign 239 faces the sensing portion 240 (see FIG.
7C). The sensing portion 240 senses the sign 239 facing it,
recognizes a folded state, and supplies a fold signal F indicating
a folded state.
<<Display Panel>>
[0232] The display panel includes the display portion, first driver
circuits, and second driver circuits (see FIGS. 9A and 9B).
[0233] The display portion includes the first region 230(1) and the
second region 230(2).
[0234] The first driver circuits include the scan line driver
circuit 232G(1) and the signal line driver circuit 232S(1). The
second driver circuits include the scan line driver circuit
232G(2), a signal line driver circuit 232S(2a), and a signal line
driver circuit 232S(2b).
[0235] The first driver circuits drive the first region 230(1). The
second driver circuits drive the second region 230(2). The signal
line driver circuit 232S(2a) and the signal line driver circuit
232S(2b) supply image signals to pixels to which the scan line
driver circuit 232G(2) supplies a selection signal.
[0236] There is the boundary 230b(1) between the first region
230(1) and the second region 230(2). In addition, there is a region
230(1)S that is close to the boundary 230b(1) and is in the first
region 230(1) (see FIG. 9B). The region 230(1)S is on a side
surface of the display device 200C in a folded state (see FIG.
9A).
[0237] The first region 230(1) includes the region 230(1)S. Even
when driving of the second region 230(2) of the display device 200C
is stopped in a folded state, an image can be displayed in the
region 230(1)S by driving the first region 230(1). In this manner,
an image can be displayed on the side surface of the display device
200C; thus, the side surface can be effectively utilized.
[0238] Structures of the flexible display panel are described in
Embodiments 6 and 7.
[0239] The display device 200C in a folded state is highly
portable. It is possible to fold the display device 200C such that
the first region 230(1) of the display portion is on the outer side
and use only the first region 230(1) for display (see FIG. 7C). For
example, when the display portion is provided with a touch panel
and has a size such that it can be supported with one hand in a
folded state, the touch panel can be operated with the thumb of the
hand supporting it. Thus, a display device that can be operated
with one hand in a folded state can be provided.
[0240] When the second region 230(2) that is hidden from a user in
a folded state is not driven in a folded state, the power
consumption of the display device 200C can be reduced. Moreover,
folding the display device 200C such that the second region 230(2)
is on the inner side can prevent damage and attachment of dirt to
the second region 230(2).
[0241] The display device 200C can display an image on a seamless
large region in an opened state. Thus, highly browsable display is
possible.
[0242] This embodiment can be combined with any of the other
embodiments in this specification as appropriate.
Embodiment 4
[0243] In this embodiment, a structure of a transistor 151 that can
be used in a display device of one embodiment of the present
invention is described with reference to FIGS. 10A to 10C.
[0244] FIGS. 10A to 10C are a top view and cross-sectional views of
the transistor 151. FIG. 10A is a top view of the transistor 151,
FIG. 10B is a cross-sectional view taken along dashed-dotted line
A-B in FIG. 10A, and FIG. 10C is a cross-sectional view taken along
dashed-dotted line C-D in FIG. 10A. Note that in FIG. 10A, some
components are not illustrated for clarity.
[0245] Note that in this embodiment, the first electrode refers to
one of a source and a drain of a transistor, and the second
electrode refers to the other.
[0246] The transistor 151 is a channel-etched transistor and
includes a gate electrode 104a provided over a substrate 102, a
first insulating film 108 that includes insulating films 106 and
107 and is formed over the substrate 102 and the gate electrode
104a, an oxide semiconductor film 110 overlapping with the gate
electrode 104a with the first insulating film 108 provided
therebetween, and a first electrode 112a and a second electrode
112b in contact with the oxide semiconductor film 110. In addition,
over the first insulating film 108, the oxide semiconductor film
110, the first electrode 112a, and the second electrode 112b, a
second insulating film 120 including insulating films 114, 116, and
118 and a gate electrode 122c formed over the second insulating
film 120 are provided. The gate electrode 122c is connected to the
gate electrode 104a in openings 142d and 142e provided in the first
insulating film 108 and the second insulating film 120. In
addition, a conductive film 122a serving as a pixel electrode is
formed over the insulating film 118. The conductive film 122a is
connected to the second electrode 112b through an opening 142a
provided in the second insulating film 120.
[0247] Note that the first insulating film 108 serves as a first
gate insulating film of the transistor 151, and the second
insulating film 120 serves as a second gate insulating film of the
transistor 151. Furthermore, the conductive film 122a serves as a
pixel electrode.
[0248] In the channel width direction of the transistor 151 of one
embodiment of the present invention, the oxide semiconductor film
110 is provided between the gate electrode 104a and the gate
electrode 122c with the first insulating film 108 provided between
the gate electrode 104a and the oxide semiconductor film 110 and
with the second insulating film 120 provided between the gate
electrode 122c and the oxide semiconductor film 110. In addition,
as illustrated in FIG. 10A, the gate electrode 104a overlaps with
side surfaces of the oxide semiconductor film 110 with the first
insulating film 108 provided therebetween, when seen from the
above.
[0249] A plurality of openings is provided in the first insulating
film 108 and the second insulating film 120. Typically, as
illustrated in FIG. 10B, the opening 142a through which part of the
second electrode 112b is exposed is provided. Furthermore, in the
channel width direction, the openings 142d and 142e are provided
with the oxide semiconductor film 110 provided therebetween as
illustrated in FIG. 10C. In other words, the openings 142d and 142e
are provided on outer sides of the side surfaces of the oxide
semiconductor film 110.
[0250] In the opening 142a, the second electrode 112b is connected
to the conductive film 122a.
[0251] In addition, in the openings 142d and 142e, the gate
electrode 104a is connected to the gate electrode 122c. This means
that the gate electrode 104a and the gate electrode 122c surround
the oxide semiconductor film 110 in the channel width direction
with the first insulating film 108 and the second insulating film
120 provided between the oxide semiconductor film 110 and each of
the gate electrode 104a and the gate electrode 122c. Furthermore,
the gate electrode 122c on the side surfaces of the openings 142d
and 142e faces the side surfaces of the oxide semiconductor film
110.
[0252] The gate electrode 104a and the gate electrode 122c are
included, the same potential is applied to the gate electrode 104a
and the gate electrode 122c, the side surface of the oxide
semiconductor film 110 faces the gate electrode 122c, and the gate
electrode 104a and the gate electrode 122c surround the oxide
semiconductor film 110 in the channel width direction with the
first insulating film 108 and the second insulating film 120
provided between the oxide semiconductor film 110 and each of the
gate electrode 104a and the gate electrode 122c; thus, carriers
flow not only at the interfaces between the oxide semiconductor
film 110 and each of the first insulating film 108 and the second
insulating film 120 but also in a wide region in the oxide
semiconductor film 110, which results in an increase in the amount
of carriers that move in the transistor 151.
[0253] As a result, the on-state current of the transistor 151 is
increased, and the field-effect mobility is increased to greater
than or equal to 10 cm.sup.2/Vs or to greater than or equal to 20
cm.sup.2/Vs, for example. Note that here, the field-effect mobility
is not an approximate value of the mobility as the physical
property of the oxide semiconductor film but is the apparent
field-effect mobility in a saturation region of the transistor,
which is an indicator of current drive capability. Note that an
increase in field-effect mobility becomes significant when the
channel length (also referred to as L length) of the transistor is
longer than or equal to 0.5 .mu.m and shorter than or equal to 6.5
.mu.m, preferably longer than 1 .mu.m and shorter than 6 .mu.m,
further preferably longer than 1 .mu.m and shorter than or equal to
4 .mu.m, still further preferably longer than 1 .mu.m and shorter
than or equal to 3.5 .mu.m, yet still further preferably longer
than 1 .mu.m and shorter than or equal to 2.5 .mu.m. Furthermore,
with a short channel length longer than or equal to 0.5 .mu.m and
shorter than or equal to 6.5 .mu.m, the channel width can also be
short.
[0254] Thus, even if a plurality of regions to be connection
portions between the gate electrode 104a and the gate electrode
122c is provided, the area of the transistor 151 can be
reduced.
[0255] Defects are formed at the end portion of the oxide
semiconductor film 110, which is processed by etching or the like,
because of damage due to the processing, and the end portion is
polluted by attachment of impurities or the like. For this reason,
in the case where only one of the gate electrode 104a and the gate
electrode 122c is formed in the transistor 151, even when the oxide
semiconductor film 110 is intrinsic or substantially intrinsic, the
end portion of the oxide semiconductor film 110 is easily activated
to be an n-type region (a low-resistance region) by application of
stress such as an electric field.
[0256] In the case where the n-type end portions overlap with
regions between the first electrode 112a and the second electrode
112b, the n-type regions serve as carrier paths, resulting in
formation of a parasitic channel. As a result, drain current with
respect to the threshold voltage is gradually increased, so that
the threshold voltage of the transistor shifts in the negative
direction. However, as illustrated in FIG. 10C, the gate electrode
104a and the gate electrode 122c having the same potentials are
included and the gate electrode 122c faces the side surfaces of the
oxide semiconductor film 110 in the channel width direction at the
side surfaces of the second insulating film 120, whereby an
electric field from the gate electrode 122c affects the oxide
semiconductor film 110 also from the side surfaces of the oxide
semiconductor film 110. As a result, a parasitic channel is
prevented from being generated at the side surface of the oxide
semiconductor film 110 or the end portion including the side
surface and its vicinity. Thus, the transistor having favorable
electrical characteristics of a sharp increase in drain current
with respect to the threshold voltage is obtained.
[0257] The transistor includes the gate electrode 104a and the gate
electrode 122c, each of which has a function of blocking an
external electric field; thus, charges such as a charged particle
between the substrate 102 and the gate electrode 104a and over the
gate electrode 122c do not affect the oxide semiconductor film 110.
Thus, degradation due to a stress test (e.g., a negative gate bias
temperature (-GBT) stress test in which a negative potential is
applied to a gate electrode) can be reduced, and changes in the
rising voltages of on-state current at different drain voltages can
be suppressed.
[0258] The BT stress test is one kind of accelerated test and can
evaluate, in a short time, change in characteristics (i.e., a
change over time) of transistors, which is caused by long-term use.
In particular, the amount of change in threshold voltage of a
transistor between before and after the BT stress test is an
important indicator when examining the reliability of the
transistor. If the amount of change in the threshold voltage
between before and after the BT stress test is small, the
transistor has higher reliability.
[0259] Elements included in the transistor 151 are described
below.
<<Substrate 102>>
[0260] For the substrate 102, a glass material such as
aluminosilicate glass, aluminoborosilicate glass, or barium
borosilicate glass is used. In the mass production, for the
substrate 102, a mother glass with any of the following sizes is
preferably used: the 8-th generation (2160 mm.times.2460 mm), the
9-th generation (2400 mm.times.2800 mm or 2450 mm.times.3050 mm),
the 10-th generation (2950 mm.times.3400 mm), and the like. High
process temperature and a long period of process time drastically
shrink the mother glass. Thus, in the case where mass production is
performed with the use of the mother glass, it is preferable that
the heat process in the manufacturing process be performed at a
temperature lower than or equal to 600.degree. C., preferably lower
than or equal to 450.degree. C., further preferably lower than or
equal to 350.degree. C.
<<Gate Electrode 104a>>
[0261] As a material used for the gate electrode 104a, a metal
element selected from aluminum, chromium, copper, tantalum,
titanium, molybdenum, and tungsten, an alloy containing any of
these metal elements as a component, an alloy containing these
metal elements in combination, or the like can be used. The gate
electrode 104a may have a single-layer structure or a stacked-layer
structure of two or more layers. For example, a two-layer structure
in which a titanium film is stacked over an aluminum film, a
two-layer structure in which a titanium film is stacked over a
titanium nitride film, a two-layer structure in which a tungsten
film is stacked over a titanium nitride film, a two-layer structure
in which a tungsten film is stacked over a tantalum nitride film or
a tungsten nitride film, a three-layer structure in which a
titanium film, an aluminum film, and a titanium film are stacked in
this order, and the like can be given. Alternatively, a film, an
alloy film, or a nitride film which contains aluminum and one or
more elements selected from titanium, tantalum, tungsten,
molybdenum, chromium, neodymium, and scandium may be used. The gate
electrode 104a can be formed by a sputtering method, for
example.
<<First Insulating Film 108>>
[0262] An example in which the first insulating film 108 has a
two-layer structure of the insulating film 106 and the insulating
film 107 is illustrated. Note that the structure of the first
insulating film 108 is not limited thereto, and for example, the
first insulating film 108 may have a single-layer structure or a
stacked-layer structure including three or more layers.
[0263] The insulating film 106 is formed with a single-layer
structure or a stacked-layer structure using, for example, any of a
silicon nitride oxide film, a silicon nitride film, an aluminum
oxide film, and the like with a PE-CVD apparatus. In the case where
the insulating film 106 has a stacked-layer structure, it is
preferable that a silicon nitride film with fewer defects be
provided as a first silicon nitride film, and a silicon nitride
film from which hydrogen and ammonia are less likely to be released
be provided over the first silicon nitride film, as a second
silicon nitride film. As a result, hydrogen and nitrogen contained
in the insulating film 106 can be inhibited from moving or
diffusing into the oxide semiconductor film 110 to be formed
later.
[0264] The insulating film 107 is formed with a single-layer
structure or a stacked-layer structure using any of a silicon oxide
film, a silicon oxynitride film, and the like with a PE-CVD
apparatus.
[0265] The first insulating film 108 can have a stacked-layer
structure, for example, in which a 400-nm-thick silicon nitride
film used as the insulating film 106 and a 50-nm-thick silicon
oxynitride film used as the insulating film 107 are formed in this
order. The silicon nitride film and the silicon oxynitride film are
preferably formed in succession in a vacuum, in which case entry of
impurities is suppressed. The first insulating film 108 in a
position overlapping with the gate electrode 104a serves as a gate
insulating film of the transistor 151. Note that silicon nitride
oxide refers to an insulating material that contains more nitrogen
than oxygen, whereas silicon oxynitride refers to an insulating
material that contains more oxygen than nitrogen.
<<Oxide Semiconductor Film 110>>
[0266] The oxide semiconductor film 110 preferably includes a film
represented by an In-M-Zn oxide that contains at least indium (In),
zinc (Zn), and M (M is a metal such as Al, Ga, Ge, Y, Zr, Sn, La,
Ce, or Hf). Alternatively, both In and Zn are preferably contained.
In order to reduce fluctuations in electrical characteristics of
the transistors including the oxide semiconductor, the oxide
semiconductor preferably contains a stabilizer in addition to In
and Zn.
[0267] As a stabilizer, gallium (Ga), tin (Sn), hafnium (Hf),
aluminum (Al), zirconium (Zr), and the like can be given. As
another stabilizer, lanthanoid such as lanthanum (La), cerium (Ce),
praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu),
gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho),
erbium (Er), thulium (Tm), ytterbium (Yb), or lutetium (Lu) can be
given.
[0268] As the oxide semiconductor included in the oxide
semiconductor film 110, any of the following can be used: an
In--Ga--Zn-based oxide, an In--Al--Zn-based oxide, an
In--Sn--Zn-based oxide, an In--Hf--Zn-based oxide, an
In--La--Zn-based oxide, an In--Ce--Zn-based oxide, an
In--Pr--Zn-based oxide, an In--Nd--Zn-based oxide, an
In--Sm--Zn-based oxide, an In--Eu--Zn-based oxide, an
In--Gd--Zn-based oxide, an In--Tb--Zn-based oxide, an
In--Dy--Zn-based oxide, an In--Ho--Zn-based oxide, an
In--Er--Zn-based oxide, an In--Tm--Zn-based oxide, an
In--Yb--Zn-based oxide, an In--Lu--Zn-based oxide, an
In--Sn--Ga--Zn-based oxide, an In--Hf--Ga--Zn-based oxide, an
In--Al--Ga--Zn-based oxide, an In--Sn--Al--Zn-based oxide, an
In--Sn--Hf--Zn-based oxide, and an In--Hf--Al--Zn-based oxide.
[0269] Note that here, for example, an "In--Ga--Zn-based oxide"
means an oxide containing In, Ga, and Zn as its main components and
there is no limitation on the ratio of In:Ga:Zn. The
In--Ga--Zn-based oxide may contain another metal element in
addition to In, Ga, and Zn.
[0270] The oxide semiconductor film 110 can be formed by a
sputtering method, a molecular beam epitaxy (MBE) method, a CVD
method, a pulse laser deposition method, an atomic layer deposition
(ALD) method, or the like as appropriate. In particular, the oxide
semiconductor film 110 is preferably formed by the sputtering
method because the oxide semiconductor film 110 can be dense.
[0271] In the formation of an oxide semiconductor film as the oxide
semiconductor film 110, the hydrogen concentration in the oxide
semiconductor film is preferably reduced as much as possible. To
reduce the hydrogen concentration, for example, in the case of a
sputtering method, a deposition chamber needs to be highly
evacuated and also a sputtering gas needs to be highly purified. As
an oxygen gas or an argon gas used for a sputtering gas, a gas
which is highly purified to have a dew point of -40.degree. C. or
lower, preferably -80.degree. C. or lower, further preferably
-100.degree. C. or lower, or still further preferably -120.degree.
C. or lower is used, whereby entry of moisture or the like into the
oxide semiconductor film can be minimized.
[0272] In order to remove moisture remaining in the deposition
chamber, an entrapment vacuum pump, such as a cryopump, an ion
pump, or a titanium sublimation pump, is preferably used. A turbo
molecular pump provided with a cold trap may be alternatively used.
When the deposition chamber is evacuated with a cryopump, which has
a high capability in removing a hydrogen molecule, a compound
including a hydrogen atom such as water (H.sub.2O), a compound
including a carbon atom, and the like, the concentration of an
impurity to be contained in a film formed in the deposition chamber
can be reduced.
[0273] When the oxide semiconductor film as the oxide semiconductor
film 110 is formed by a sputtering method, the relative density
(filling factor) of a metal oxide target that is used for the film
formation is greater than or equal to 90% and less than or equal to
100%, preferably greater than or equal to 95% and less than or
equal to 100%. With the use of the metal oxide target having high
relative density, a dense oxide semiconductor film can be
formed.
[0274] Note that to reduce the impurity concentration of the oxide
semiconductor film, it is also effective to form the oxide
semiconductor film as the oxide semiconductor film 110 while the
substrate 102 is kept at high temperature. The heating temperature
of the substrate 102 may be higher than or equal to 150.degree. C.
and lower than or equal to 450.degree. C., and preferably the
substrate temperature is higher than or equal to 200.degree. C. and
lower than or equal to 350.degree. C.
[0275] Next, first heat treatment is preferably performed. The
first heat treatment may be performed at a temperature higher than
or equal to 250.degree. C. and lower than or equal to 650.degree.
C., preferably higher than or equal to 300.degree. C. and lower
than or equal to 500.degree. C., in an inert gas atmosphere, an
atmosphere containing an oxidizing gas at 10 ppm or more, or a
reduced pressure state. Alternatively, the first heat treatment may
be performed in such a manner that heat treatment is performed in
an inert gas atmosphere, and then another heat treatment is
performed in an atmosphere containing an oxidizing gas at 10 ppm or
more, in order to compensate for desorbed oxygen. By the first heat
treatment, the crystallinity of the oxide semiconductor that is
used as the oxide semiconductor film 110 can be improved, and in
addition, impurities such as hydrogen and water can be removed from
the first insulating film 108 and the oxide semiconductor film 110.
The first heat treatment may be performed before the oxide
semiconductor film 110 is processed into an island shape.
<<First Electrode and Second Electrode>>
[0276] The first electrode 112a and the second electrode 112b can
be formed using a conductive film 112 having a single-layer
structure or a stacked-layer structure with 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. In particular, one or
more elements selected from aluminum, chromium, copper, tantalum,
titanium, molybdenum, and tungsten are preferably included. For
example, a two-layer structure in which a titanium film is stacked
over an aluminum film, a two-layer structure in which a titanium
film is stacked over a tungsten film, a two-layer structure in
which a copper film is formed over a copper-magnesium-aluminum
alloy 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. The
conductive film can be formed by a sputtering method, for
example.
<<Insulating Films 114, 116, and 118>>
[0277] An example in which the second insulating film 120 has a
three-layer structure of the insulating films 114, 116, and 118 is
illustrated. Note that the structure of the second insulating film
120 is not limited thereto, and for example, the second insulating
film 120 may have a single-layer structure or a stacked-layer
structure including two layers or four or more layers.
[0278] For the insulating films 114 and 116, an inorganic
insulating material containing oxygen can be used in order to
improve the characteristics of the interface with the oxide
semiconductor used for the oxide semiconductor film 110. As
examples of the inorganic insulating material containing oxygen, a
silicon oxide film, a silicon oxynitride film, and the like can be
given. The insulating films 114 and 116 can be formed by a PE-CVD
method, for example.
[0279] The thickness of the insulating film 114 can be greater than
or equal to 5 nm and less than or equal to 150 nm, preferably
greater than or equal to 5 nm and less than or equal to 50 nm, more
preferably greater than or equal to 10 nm and less than or equal to
30 nm. The thickness of the insulating film 116 can be greater than
or equal to 30 nm and less than or equal to 500 nm, preferably
greater than or equal to 150 nm and less than or equal to 400
nm.
[0280] Further, the insulating films 114 and 116 can be formed
using insulating films formed of the same kinds of materials; thus,
a boundary between the insulating films 114 and 116 cannot be
clearly observed in some cases. Thus, in this embodiment, the
boundary between the insulating films 114 and 116 is shown by a
dashed line. Although a two-layer structure of the insulating films
114 and 116 is described in this embodiment, the present invention
is not limited to this. For example, a single-layer structure of
the insulating film 114, a single-layer structure of the insulating
film 116, or a stacked-layer structure including three or more
layers may be used.
[0281] The insulating film 118 is a film formed using a material
that can prevent an external impurity, such as water, alkali metal,
or alkaline earth metal, from diffusing into the oxide
semiconductor film 110, and that further contains hydrogen.
[0282] For example, a silicon nitride film, a silicon nitride oxide
film, or the like having a thickness of greater than or equal to
150 nm and less than or equal to 400 nm can be used as the
insulating film 118. In this embodiment, a 150-nm-thick silicon
nitride film is used as the insulating film 118.
[0283] The silicon nitride film is preferably formed at a high
temperature to have an improved blocking property against
impurities or the like; for example, the silicon nitride film is
preferably formed at a temperature in the range from the substrate
temperature of 100.degree. C. to the strain point of the substrate,
more preferably at a temperature in the range from 300.degree. C.
to 400.degree. C. When the silicon nitride film is formed at a high
temperature, a phenomenon in which oxygen is released from the
oxide semiconductor used for the oxide semiconductor film 110 and
the carrier concentration is increased is caused in some cases;
therefore, the upper limit of the temperature is a temperature at
which the phenomenon is not caused.
<<Conductive Film 122a and Gate Electrode 122c>>
[0284] For the conductive film used as the conductive film 122a and
the gate electrode 122c, an oxide containing indium may be used.
For example, a light-transmitting conductive material such as
indium oxide containing tungsten oxide, indium zinc oxide
containing tungsten oxide, indium oxide containing titanium oxide,
indium tin oxide containing titanium oxide, indium tin oxide
(hereinafter referred to as ITO), indium zinc oxide, or indium tin
oxide to which silicon oxide is added can be used. The conductive
film that can be used as the conductive film 122a and the gate
electrode 122c can be formed by a sputtering method, for
example.
[0285] Note that the structures, methods, and the like described in
this embodiment can be used as appropriate in combination with any
of the structures, methods, and the like described in the other
embodiments.
Embodiment 5
[0286] In this embodiment, an example of an oxide semiconductor
film that can be used in the transistor 151 in Embodiment 4 is
described.
<Crystallinity of Oxide Semiconductor Film>
[0287] A structure of the oxide semiconductor film is described
below.
[0288] An oxide semiconductor film is classified roughly into a
single-crystal oxide semiconductor film and a non-single-crystal
oxide semiconductor film. The non-single-crystal oxide
semiconductor film includes any of a c-axis aligned crystalline
oxide semiconductor (CAAC-OS) film, a polycrystalline oxide
semiconductor film, a microcrystalline oxide semiconductor film, an
amorphous oxide semiconductor film, and the like.
[0289] First, a CAAC-OS film is described.
[0290] The CAAC-OS film is one of oxide semiconductor films
including a plurality of crystal parts, and most of the crystal
parts each fit inside a cube whose one side is less than 100 nm.
Thus, there is a case where a crystal part included in the CAAC-OS
film fits inside a cube whose one side is less than 10 nm, less
than 5 nm, or less than 3 nm.
[0291] In a transmission electron microscope (TEM) image of the
CAAC-OS film, a boundary between crystal parts, that is, a grain
boundary is not clearly observed. Thus, in the CAAC-OS film, a
reduction in electron mobility due to the grain boundary is less
likely to occur.
[0292] According to the TEM image of the CAAC-OS film observed in a
direction substantially parallel to a sample surface
(cross-sectional TEM image), metal atoms are arranged in a layered
manner in the crystal parts. Each metal atom layer has a morphology
reflected by a surface over which the CAAC-OS film is formed
(hereinafter, a surface over which the CAAC-OS film is formed is
referred to as a formation surface) or a top surface of the CAAC-OS
film, and is arranged in parallel to the formation surface or the
top surface of the CAAC-OS film.
[0293] In this specification, the term "parallel" indicates that
the angle formed between two straight lines is greater than or
equal to -10.degree. and less than or equal to 100, and accordingly
also includes the case where the angle is greater than or equal to
-5.degree. and less than or equal to 5.degree.. The term
"perpendicular" indicates that the angle formed between two
straight lines is greater than or equal to 80.degree. and less than
or equal to 1000, and accordingly includes the case where the angle
is greater than or equal to 85.degree. and less than or equal to
95.degree..
[0294] On the other hand, according to the TEM image of the CAAC-OS
film observed in a direction substantially perpendicular to the
sample surface (plan TEM image), metal atoms are arranged in a
triangular or hexagonal configuration in the crystal parts.
However, there is no regularity of arrangement of metal atoms
between different crystal parts.
[0295] From the results of the cross-sectional TEM image and the
plan TEM image, alignment is found in the crystal parts in the
CAAC-OS film.
[0296] A CAAC-OS film is subjected to structural analysis with an
X-ray diffraction (XRD) apparatus. For example, when the CAAC-OS
film including an InGaZnO.sub.4 crystal is analyzed by an
out-of-plane method, a peak appears frequently when the diffraction
angle (2.theta.) is around 31.degree.. This peak is derived from
the (009) plane of the InGaZnO.sub.4 crystal, which indicates that
crystals in the CAAC-OS film have c-axis alignment, and that the
c-axes are aligned in a direction substantially perpendicular to
the formation surface or the top surface of the CAAC-OS film.
[0297] On the other hand, when the CAAC-OS film is analyzed by an
in-plane method in which an X-ray enters a sample in a direction
substantially perpendicular to the c-axis, a peak appears
frequently when 2.theta. is around 56.degree.. This peak is derived
from the (110) plane of the InGaZnO.sub.4 crystal. Here, analysis
(.phi. scan) is performed under conditions where the sample is
rotated around a normal vector of a sample surface as an axis
(.phi. axis) with 2.theta. fixed at around 56.degree.. In the case
where the sample is a single-crystal oxide semiconductor film of
InGaZnO.sub.4, six peaks appear. The six peaks are derived from
crystal planes equivalent to the (110) plane. On the other hand, in
the case of a CAAC-OS film, a peak is not clearly observed even
when .phi. scan is performed with 2.theta. fixed at around
56.degree..
[0298] According to the above results, in the CAAC-OS film having
c-axis alignment, while the directions of a-axes and b-axes are
different between crystal parts, the c-axes are aligned in a
direction parallel to a normal vector of a formation surface or a
normal vector of a top surface. Thus, each metal atom layer
arranged in a layered manner observed in the cross-sectional TEM
image corresponds to a plane parallel to the a-b plane of the
crystal.
[0299] Note that the crystal part is formed concurrently with
deposition of the CAAC-OS film or is formed through crystallization
treatment such as heat treatment. As described above, the c-axis of
the crystal is aligned in a direction parallel to a normal vector
of a formation surface or a normal vector of a top surface. Thus,
for example, in the case where a shape of the CAAC-OS film is
changed by etching or the like, the c-axis might not be necessarily
parallel to a normal vector of a formation surface or a normal
vector of a top surface of the CAAC-OS film.
[0300] Further, the degree of crystallinity in the CAAC-OS film is
not necessarily uniform. For example, in the case where crystal
growth leading to the CAAC-OS film occurs from the vicinity of the
top surface of the film, the degree of the crystallinity in the
vicinity of the top surface is higher than that in the vicinity of
the formation surface in some cases. Further, when an impurity is
added to the CAAC-OS film, the crystallinity in a region to which
the impurity is added is changed, and the degree of crystallinity
in the CAAC-OS film varies depending on regions.
[0301] Note that when the CAAC-OS film with an InGaZnO.sub.4
crystal is analyzed by an out-of-plane method, a peak of 2.theta.
may also be observed at around 36.degree., in addition to the peak
of 2.theta. at around 31.degree.. The peak of 2.theta. at around
36.degree. indicates that a crystal having no c-axis alignment is
included in part of the CAAC-OS film. It is preferable that in the
CAAC-OS film, a peak of 2.theta. appear at around 31.degree. and a
peak of 2.theta. do not appear at around 36.degree..
[0302] In this specification, trigonal and rhombohedral crystal
systems are included in a hexagonal crystal system.
[0303] The CAAC-OS film is an oxide semiconductor film having a low
impurity concentration. The impurity is an element other than the
main components of the oxide semiconductor film, such as hydrogen,
carbon, silicon, or a transition metal element. In particular, an
element that has higher bonding strength to oxygen than a metal
element included in the oxide semiconductor film, such as silicon,
disturbs the atomic arrangement of the oxide semiconductor film by
depriving the oxide semiconductor film of oxygen and causes a
decrease in crystallinity. Further, a heavy metal such as iron or
nickel, argon, carbon dioxide, or the like has a large atomic
radius (molecular radius), and thus disturbs the atomic arrangement
of the oxide semiconductor film and causes a decrease in
crystallinity when it is contained in the oxide semiconductor film.
Note that the impurity contained in the oxide semiconductor film
might serve as a carrier trap or a carrier generation source.
[0304] The CAAC-OS film is an oxide semiconductor film having a low
density of defect states.
[0305] With the use of the CAAC-OS film in a transistor, variation
in the electrical characteristics of the transistor due to
irradiation with visible light or ultraviolet light is small.
[0306] Next, a microcrystalline oxide semiconductor film is
described.
[0307] In an image obtained with the TEM, crystal parts cannot be
found clearly in the microcrystalline oxide semiconductor film in
some cases. In most cases, the size of a crystal part in the
microcrystalline oxide semiconductor film is greater than or equal
to 1 nm and less than or equal to 100 nm, or greater than or equal
to 1 nm and less than or equal to 10 nm. A microcrystal with a size
greater than or equal to 1 nm and less than or equal to 10 nm, or a
size greater than or equal to 1 nm and less than or equal to 3 nm
is specifically referred to as nanocrystal (nc). An oxide
semiconductor film including nanocrystal is referred to as a
nanocrystalline oxide semiconductor (nc-OS) film. In an image
obtained with TEM, a grain boundary cannot be found clearly in the
nc-OS film in some cases.
[0308] In the nc-OS film, a microscopic region (for example, a
region with a size greater than or equal to 1 nm and less than or
equal to 10 nm, in particular, a region with a size greater than or
equal to 1 nm and less than or equal to 3 nm) has a periodic atomic
order. Note that there is no regularity of crystal orientation
between different crystal parts in the nc-OS film. Thus, the
orientation of the whole film is not observed. Accordingly, in some
cases, the nc-OS film cannot be distinguished from an amorphous
oxide semiconductor film depending on an analysis method. For
example, when the nc-OS film is subjected to structural analysis by
an out-of-plane method with an XRD apparatus using an X-ray having
a diameter larger than that of a crystal part, a peak which shows a
crystal plane does not appear. Furthermore, a halo pattern is shown
in an electron diffraction pattern (also referred to as a
selected-area electron diffraction pattern) of the nc-OS film
obtained by using an electron beam having a probe diameter (e.g.,
greater than or equal to 50 nm) larger than the diameter of a
crystal part. Meanwhile, spots are shown in a nanobeam electron
diffraction pattern of the nc-OS film obtained by using an electron
beam having a probe diameter (e.g., greater than or equal to 1 nm
and smaller than or equal to 30 nm) close to, or smaller than or
equal to a diameter of a crystal part. Further, in a nanobeam
electron diffraction pattern of the nc-OS film, regions with high
luminance in a circular (ring) pattern are observed in some cases.
Also in a nanobeam electron diffraction pattern of the nc-OS film,
a plurality of spots are shown in a ring-like region in some
cases.
[0309] The nc-OS film is an oxide semiconductor film that has high
regularity as compared to an amorphous oxide semiconductor film.
Therefore, the nc-OS film has a lower density of defect states than
an amorphous oxide semiconductor film. Note that there is no
regularity of crystal orientation between different crystal parts
in the nc-OS film. Therefore, the nc-OS film has a higher density
of defect states than the CAAC-OS film.
[0310] Note that an oxide semiconductor film may be a stacked film
including two or more kinds of an amorphous oxide semiconductor
film, a microcrystalline oxide semiconductor film, and a CAAC-OS
film, for example.
<Method for Forming CAAC-OS Film>
[0311] For example, a CAAC-OS film is deposited by a sputtering
method using a polycrystalline oxide semiconductor sputtering
target. When ions collide with the sputtering target, a crystal
region included in the sputtering target may be separated from the
target along an a-b plane; in other words, a sputtered particle
having a plane parallel to an a-b plane (flat-plate-like sputtered
particle or pellet-like sputtered particle) may flake off from the
sputtering target. In that case, the flat-plate-like or pellet-like
sputtered particle reaches a substrate while maintaining its
crystal state, whereby the CAAC-OS film can be formed.
[0312] The flat-plate-like or pellet-like sputtered particle has,
for example, an equivalent circle diameter of a plane parallel to
the a-b plane of greater than or equal to 3 nm and less than or
equal to 10 nm, and a thickness (length in the direction
perpendicular to the a-b plane) of greater than or equal to 0.7 nm
and less than 1 nm. Note that in the flat-plate-like or pellet-like
sputtered particle, the plane parallel to the a-b plane may be a
regular triangle or a regular hexagon. Here, the term "equivalent
circle diameter of a plane" refers to the diameter of a perfect
circle having the same area as the plane.
[0313] For the deposition of the CAAC-OS film, the following
conditions are preferably used.
[0314] By increasing the substrate temperature during the
deposition, migration of sputtered particles is likely to occur
after the sputtered particles reach a substrate surface.
Specifically, the substrate temperature during the deposition is
higher than or equal to 100.degree. C. and lower than or equal to
740.degree. C., preferably higher than or equal to 200.degree. C.
and lower than or equal to 500.degree. C. By increasing the
substrate temperature during the deposition, when the
flat-plate-like or pellet-like sputtered particles reach the
substrate, migration occurs on the substrate surface, so that a
flat plane of the sputtered particles is attached to the substrate.
At this time, the sputtered particle is charged positively, whereby
sputtered particles are attached to the substrate while repelling
each other; thus, the sputtered particles do not overlap with each
other randomly, and a CAAC-OS film with a uniform thickness can be
deposited.
[0315] By reducing the amount of impurities entering the CAAC-OS
film during the deposition, the crystal state can be prevented from
being broken by the impurities. For example, the concentration of
impurities (e.g., hydrogen, water, carbon dioxide, or nitrogen)
which exist in the deposition chamber may be reduced. Furthermore,
the concentration of impurities in a deposition gas may be reduced.
Specifically, a deposition gas whose dew point is -80.degree. C. or
lower, preferably -100.degree. C. or lower is used.
[0316] Furthermore, it is preferable that the proportion of oxygen
in the deposition gas be increased and the power be optimized in
order to reduce plasma damage at the deposition. The proportion of
oxygen in the deposition gas is higher than or equal to 30 vol %,
preferably 100 vol %.
[0317] Alternatively, the CAAC-OS film is formed by the following
method.
[0318] First, a first oxide semiconductor film is formed to a
thickness of greater than or equal to 1 nm and less than 10 nm. The
first oxide semiconductor film is formed by a sputtering method.
Specifically, the substrate temperature is set to higher than or
equal to 100.degree. C. and lower than or equal to 500.degree. C.,
preferably higher than or equal to 150.degree. C. and lower than or
equal to 450.degree. C., and the proportion of oxygen in a
deposition gas is set to higher than or equal to 30 vol %,
preferably 100 vol %.
[0319] Next, heat treatment is performed so that the first oxide
semiconductor film becomes a first CAAC-OS film with high
crystallinity. The temperature of the heat treatment is higher than
or equal to 350.degree. C. and lower than or equal to 740.degree.
C., preferably higher than or equal to 450.degree. C. and lower
than or equal to 650.degree. C. The heat treatment time is longer
than or equal to 1 minute and shorter than or equal to 24 hours,
preferably longer than or equal to 6 minutes and shorter than or
equal to 4 hours. The heat treatment may be performed in an inert
atmosphere or an oxidation atmosphere. It is preferable to perform
heat treatment in an inert atmosphere and then perform heat
treatment in an oxidation atmosphere. The heat treatment in an
inert atmosphere can reduce the concentration of impurities in the
first oxide semiconductor film in a short time. At the same time,
the heat treatment in an inert atmosphere may generate oxygen
vacancies in the first oxide semiconductor film. In such a case,
the heat treatment in an oxidation atmosphere can reduce the oxygen
vacancies. Note that the heat treatment may be performed under a
reduced pressure, such as 1000 Pa or lower, 100 Pa or lower, 10 Pa
or lower, or 1 Pa or lower. The heat treatment under the reduced
pressure can reduce the concentration of impurities in the first
oxide semiconductor film in a shorter time.
[0320] The first oxide semiconductor film with a thickness of
greater than or equal to 1 nm and less than 10 nm can be easily
crystallized by heat treatment as compared to the case where the
first oxide semiconductor film has a thickness of greater than or
equal to 10 nm.
[0321] Next, a second oxide semiconductor film having the same
composition as the first oxide semiconductor film is formed to a
thickness of greater than or equal to 10 nm and less than or equal
to 50 nm. The second oxide semiconductor film is formed by a
sputtering method. Specifically, the substrate temperature is set
to higher than or equal to 100.degree. C. and lower than or equal
to 500.degree. C., preferably higher than or equal to 150.degree.
C. and lower than or equal to 450.degree. C., and the proportion of
oxygen in a deposition gas is set to higher than or equal to 30 vol
%, preferably 100 vol %.
[0322] Next, heat treatment is performed so that solid phase growth
of the second oxide semiconductor film is performed using the first
CAAC-OS film, thereby forming a second CAAC-OS film with high
crystallinity. The temperature of the heat treatment is higher than
or equal to 350.degree. C. and lower than or equal to 740.degree.
C., preferably higher than or equal to 450.degree. C. and lower
than or equal to 650.degree. C. The heat treatment time is longer
than or equal to 1 minute and shorter than or equal to 24 hours,
preferably longer than or equal to 6 minutes and shorter than or
equal to 4 hours. The heat treatment may be performed in an inert
atmosphere or an oxidation atmosphere. It is preferable to perform
heat treatment in an inert atmosphere and then perform heat
treatment in an oxidation atmosphere. The heat treatment in an
inert atmosphere can reduce the concentration of impurities in the
second oxide semiconductor film in a short time. At the same time,
the heat treatment in an inert atmosphere may generate oxygen
vacancies in the second oxide semiconductor film. In such a case,
the heat treatment in an oxidation atmosphere can reduce the oxygen
vacancies. Note that the heat treatment may be performed under a
reduced pressure, such as 1000 Pa or lower, 100 Pa or lower, 10 Pa
or lower, or 1 Pa or lower. The heat treatment under the reduced
pressure can reduce the concentration of impurities in the second
oxide semiconductor film in a shorter time.
[0323] In the above manner, a CAAC-OS film with a total thickness
of greater than or equal to 10 nm can be formed. The CAAC-OS film
can be favorably used as the oxide semiconductor film in an oxide
stack.
[0324] Next, a method for forming an oxide film in the case where a
formation surface has a low temperature because, for example, the
substrate is not heated is described (for example, the temperature
is lower than 130.degree. C., lower than 100.degree. C. lower than
70.degree. C. or at room temperatures (20.degree. C. to 25.degree.
C.)).
[0325] In the case where the formation surface has a low
temperature, sputtered particles fall irregularly to the formation
surface. For example, migration does not occur; therefore, the
sputtered particles are randomly deposited on the formation surface
including a region where other sputtered particles have been
deposited. That is, an oxide film obtained by the deposition might
have a non-uniform thickness and a disordered crystal alignment.
The oxide film obtained in the above manner maintains the
crystallinity of the sputtered particles to a certain degree and
thus has a crystal part (nanocrystal).
[0326] For example, in the case where the pressure at the
deposition is high, the frequency with which the flying sputtered
particle collides with another particle (e.g., an atom, a molecule,
an ion, or a radical) of argon or the like is increased. When the
flying sputtered particle collides with another particle
(resputtered), the crystal structure of the sputtered particle
might be broken. For example, when the sputtered particle collides
with another particle, the flat-plate-like or pellet-like shape of
the sputtered particle cannot be kept, and the sputtered particle
might be broken into parts (e.g., atomized). At this time, when
atoms obtained from the sputtered particle are deposited on the
formation surface, an amorphous oxide film might be formed.
[0327] In the case where not a sputtering method using a target
including a polycrystalline oxide but a deposition method using
liquid or a method for depositing a film by vaporizing a solid such
as a target is used, the atoms separately fly to be deposited on
the formation surface; therefore, an amorphous oxide film might be
formed. Furthermore, for example, by a laser ablation method,
atoms, molecules, ions, radicals, clusters, or the like released
from the target flies to be deposited on the formation surface;
therefore, an amorphous oxide film might be formed.
[0328] An oxide semiconductor film included in a resistor and a
transistor in one embodiment of the present invention may have any
of the above crystal states. Further, in the case of stacked oxide
semiconductor films, the crystal states of the oxide semiconductor
films may be different from each other. Note that a CAAC-OS film is
preferably used as the oxide semiconductor film functioning as a
channel of the transistor. Further, the oxide semiconductor film
included in the resistor has a higher impurity concentration than
that of the oxide semiconductor film included in the transistor;
thus, the crystallinity is lowered in some cases.
[0329] The structures, the methods, and the like described in this
embodiment can be combined as appropriate with any of the
structures, the methods, and the like described in the other
embodiments.
Embodiment 6
[0330] In this embodiment, a structure of a display panel that can
be used in the display device of one embodiment of the present
invention is described with reference to FIGS. 11A to 11C. Note
that the display panel described in this embodiment includes a
touch sensor (a contact sensor device) that overlaps with a display
portion; thus, the display panel can be called a touch panel (an
input/output device).
[0331] FIG. 11A is a plan view illustrating the structure of a
display panel that can be used in the display device of one
embodiment of the present invention.
[0332] FIG. 11B is a cross-sectional view taken along line A-B and
line C-D in FIG. 11A.
[0333] FIG. 11C is a cross-sectional view taken along line E-F in
FIG. 11A.
<Top View>
[0334] An input/output device 300 described as an example in this
embodiment includes a display portion 301 (see FIG. 11A).
[0335] The display portion 301 includes a plurality of pixels 302
and a plurality of imaging pixels 308. The imaging pixels 308 can
sense a touch of a finger or the like on the display portion 301.
Thus, a touch sensor can be formed using the imaging pixels
308.
[0336] Each of the pixels 302 includes a plurality of sub-pixels
(e.g., a sub-pixel 302R). In addition, in the sub-pixels,
light-emitting elements and pixel circuits that can supply electric
power for driving the light-emitting elements are provided.
[0337] The pixel circuits are electrically connected to wirings
through which selection signals are supplied and wirings through
which image signals are supplied.
[0338] Furthermore, the input/output device 300 is provided with a
scan line driver circuit 303g(1) that can supply selection signals
to the pixels 302 and an image signal line driver circuit 303s(1)
that can supply image signals to the pixels 302. Note that when the
image signal line driver circuit 303s(1) is placed in a portion
other than a bendable portion, malfunction can be inhibited.
[0339] The imaging pixels 308 include photoelectric conversion
elements and imaging pixel circuits that drive the photoelectric
conversion elements.
[0340] The imaging pixel circuits are electrically connected to
wirings through which control signals are supplied and wirings
through which power supply potentials are supplied.
[0341] Examples of the control signals include a signal for
selecting an imaging pixel circuit from which a recorded imaging
signal is read, a signal for initializing an imaging pixel circuit,
and a signal for determining the time it takes for an imaging pixel
circuit to detect light.
[0342] The input/output device 300 is provided with an imaging
pixel driver circuit 303g(2) that can supply control signals to the
imaging pixels 308 and an imaging signal line driver circuit
303s(2) that reads out imaging signals. Note that when the imaging
signal line driver circuit 303s(2) is placed in a portion other
than a bendable portion, malfunction can be inhibited.
<Cross-Sectional View>
[0343] The input/output device 300 includes a substrate 310 and a
counter substrate 370 that faces the substrate 310 (see FIG.
11B).
[0344] The substrate 310 is a stacked body in which a substrate
310b having flexibility, a barrier film 310a that prevents
diffusion of unintentional impurities to the light-emitting
elements, and an adhesive layer 310c that attaches the barrier film
310a to the substrate 310b are stacked.
[0345] The counter substrate 370 is a stacked body including a
substrate 370b having flexibility, a barrier film 370a that
prevents diffusion of unintentional impurities to the
light-emitting elements, and an adhesive layer 370c that attaches
the barrier film 370a to the substrate 370b (see FIG. 11B).
[0346] A sealant 360 attaches the counter substrate 370 to the
substrate 310. The sealant 360, also serving as an optical adhesive
layer, has a refractive index higher than that of air. The pixel
circuits and the light-emitting elements (e.g., a first
light-emitting element 350R) and the imaging pixel circuits and
photoelectric conversion elements (e.g., a photoelectric conversion
element 308p) are provided between the substrate 310 and the
counter substrate 370.
<<Structure of Pixel>>
[0347] Each of the pixels 302 includes the sub-pixel 302R, a
sub-pixel 302G, and a sub-pixel 302B (see FIG. 11C). The sub-pixel
302R includes a light-emitting module 380R, the sub-pixel 302G
includes a light-emitting module 380G, and the sub-pixel 302B
includes a light-emitting module 380B.
[0348] For example, the sub-pixel 302R includes the first
light-emitting element 350R and the pixel circuit that can supply
electric power to the first light-emitting element 350R and
includes a transistor 302t (see FIG. 11B). Furthermore, the
light-emitting module 380R includes the first light-emitting
element 350R and an optical element (e.g., a first coloring layer
367R).
[0349] The first light-emitting element 350R includes a first lower
electrode 351R, an upper electrode 352, and a layer 353 containing
a light-emitting organic compound between the first lower electrode
351R and the upper electrode 352 (see FIG. 11C).
[0350] The layer 353 containing a light-emitting organic compound
includes a light-emitting unit 353a, a light-emitting unit 353b,
and an intermediate layer 354 between the light-emitting units 353a
and 353b.
[0351] The light-emitting module 380R includes the first coloring
layer 367R on the counter substrate 370. The coloring layer
transmits light of a particular wavelength and is, for example, a
layer that selectively transmits light of red, green, or blue
color. A region that transmits light emitted from the
light-emitting element as it is may be provided as well.
[0352] The light-emitting module 380R, for example, includes the
sealant 360 that is in contact with the first light-emitting
element 350R and the first coloring layer 367R.
[0353] The first coloring layer 367R is positioned in a region
overlapping with the first light-emitting element 350R.
Accordingly, part of light emitted from the first light-emitting
element 350R passes through the sealant 360 that also serves as an
optical adhesive layer and through the first coloring layer 367R
and is emitted to the outside of the light-emitting module 380R as
indicated by arrows in FIGS. 11B and 11C.
<<Structure of Input/Output Device>>
[0354] The input/output device 300 includes a light-blocking layer
367BM on the counter substrate 370. The light-blocking layer 367BM
is provided so as to surround the coloring layer (e.g., the first
coloring layer 367R).
[0355] The input/output device 300 includes an anti-reflective
layer 367p positioned in a region overlapping with the display
portion 301. As the anti-reflective layer 367p, a circular
polarizing plate can be used, for example.
[0356] The input/output device 300 includes an insulating film 321.
The insulating film 321 covers the transistor 302t. Note that the
insulating film 321 can be used as a layer for planarizing
unevenness caused by the pixel circuits. An insulating film on
which a layer that can prevent diffusion of impurities to the
transistor 302t and the like is stacked can be used as the
insulating film 321.
[0357] The input/output device 300 includes the light-emitting
elements (e.g., the first light-emitting element 350R) over the
insulating film 321.
[0358] The input/output device 300 includes, over the insulating
film 321, a partition wall 328 that overlaps with an end portion of
the first lower electrode 351R (see FIG. 11C). In addition, a
spacer 329 that controls the distance between the substrate 310 and
the counter substrate 370 is provided on the partition wall
328.
<<Structure of Image Signal Line Driver Circuit>>
[0359] The image signal line driver circuit 303s(1) includes a
transistor 303t and a capacitor 303c. Note that the image signal
line driver circuit 303s(1) can be formed in the same process and
over the same substrate as those of the pixel circuits.
<<Structure of Imaging Pixel>>
[0360] The imaging pixels 308 each include a photoelectric
conversion element 308p and an imaging pixel circuit for sensing
light received by the photoelectric conversion element 308p. The
imaging pixel circuit includes a transistor 308t.
[0361] For example, a PIN photodiode can be used as the
photoelectric conversion element 308p.
<<Other Structures>>
[0362] The input/output device 300 includes a wiring 311 through
which a signal can be supplied. The wiring 311 is provided with a
terminal 319. Note that an FPC 309(1) through which a signal such
as an image signal or a synchronization signal can be supplied is
electrically connected to the terminal 319. The FPC 309(1) is
preferably placed in a portion other than a bendable portion of the
input/output device 300. Moreover, the FPC 309(1) is preferably
placed at almost the center of one side of a region surrounding the
display portion 301, especially a side which is folded (a longer
side in FIG. 11A). Accordingly, the distance between an external
circuit for driving the input/output device 300 and the
input/output device 300 can be made short, resulting in easy
connection. Furthermore, the center of gravity of the external
circuit can be made almost the same as that of the input/output
device 300. As a result, an information processor can be treated
easily and mistakes such as dropping can be prevented.
[0363] Note that a printed wiring board (PWB) may be attached to
the FPC 309(1).
[0364] This embodiment can be combined with any of the other
embodiments in this specification as appropriate.
Embodiment 7
[0365] In this embodiment, a structure of a display panel that can
be used in the display device of one embodiment of the present
invention is described with reference to FIGS. 12A and 12B and FIG.
13. Note that the display panel described in this embodiment
includes a touch sensor (a contact sensor device) that overlaps
with a display portion; thus, the display panel can be called a
touch panel (an input/output device).
[0366] FIG. 12A is a schematic perspective view of a touch panel
500 described as an example in this embodiment. Note that FIGS. 12A
and 12B illustrate only main components for simplicity. FIG. 12B is
a developed view of the schematic perspective view of the touch
panel 500.
[0367] FIG. 13 is a cross-sectional view of the touch panel 500
taken along line X1-X2 in FIG. 12A.
[0368] The touch panel 500 includes a display portion 501 and a
touch sensor 595 (see FIG. 12B). Furthermore, the touch panel 500
includes a substrate 510, a substrate 570, and a substrate 590.
Note that the substrate 510, the substrate 570, and the substrate
590 each have flexibility.
[0369] The display portion 501 includes the substrate 510, a
plurality of pixels over the substrate 510, and a plurality of
wirings 511 through which signals are supplied to the pixels. The
plurality of wirings 511 is led to a peripheral portion of the
substrate 510, and part of the plurality of wirings 511 forms a
terminal 519. The terminal 519 is electrically connected to an FPC
509(1).
[0370] <Touch Sensor>
[0371] The substrate 590 includes the touch sensor 595 and a
plurality of wirings 598 electrically connected to the touch sensor
595. The plurality of wirings 598 is led to a peripheral portion of
the substrate 590, and part of the plurality of wirings 598 forms a
terminal for electrical connection to an FPC 509(2). Note that in
FIG. 12B, electrodes, wirings, and the like of the touch sensor 595
provided on the back side of the substrate 590 (the side opposite
to the viewer side) are indicated by solid lines for clarity.
[0372] As a touch sensor used as the touch sensor 595, a capacitive
touch sensor is preferably used. 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 and a mutual capacitive
touch sensor, which differ mainly in the driving method. The use of
a mutual capacitive touch sensor is preferable because multiple
points can be sensed simultaneously.
[0373] An example of using a projected capacitive touch sensor is
described below with reference to FIG. 12B. Note that a variety of
sensors that can sense the closeness or the contact of a sensing
target such as a finger can be used.
[0374] The projected capacitive touch sensor 595 includes
electrodes 591 and electrodes 592. The electrodes 591 are
electrically connected to any of the plurality of wirings 598, and
the electrodes 592 are electrically connected to any of the other
wirings 598.
[0375] The electrode 592 is in the form of a series of quadrangles
arranged in one direction as illustrated in FIGS. 12A and 12B. Each
of the electrodes 591 is in the form of a quadrangle. A wiring 594
electrically connects two electrodes 591 arranged in a direction
intersecting with the direction in which the electrode 592 extends.
The intersecting area of the electrode 592 and the wiring 594 is
preferably as small as possible. Such a structure allows a
reduction in the area of a region where the electrodes are not
provided, reducing unevenness in transmittance. As a result,
unevenness in luminance of light from the touch sensor 595 can be
reduced.
[0376] Note that the shapes of the electrodes 591 and the
electrodes 592 are not limited to the above-mentioned shapes and
can be any of a variety of shapes. For example, the plurality of
electrodes 591 may be provided so that space between the electrodes
591 are reduced as much as possible, and a plurality of electrodes
592 may be provided with an insulating layer sandwiched between the
electrodes 591 and the electrodes 592 and may be spaced apart from
each other to form a region not overlapping with the electrodes
591. In that case, between two adjacent electrodes 592, it is
preferable to provide a dummy electrode which is electrically
insulated from these electrodes, whereby the area of a region
having a different transmittance can be reduced.
[0377] The structure of the touch panel 500 is described with
reference to FIG. 13.
[0378] The touch sensor 595 includes the substrate 590, the
electrodes 591 and the electrodes 592 provided in a staggered
arrangement on the substrate 590, an insulating layer 593 covering
the electrodes 591 and the electrodes 592, and the wiring 594 that
electrically connects the adjacent electrodes 591 to each
other.
[0379] An adhesive layer 597 attaches the substrate 590 to the
substrate 570 so that the touch sensor 595 overlaps with the
display portion 501.
[0380] The electrodes 591 and the electrodes 592 are formed using a
light-transmitting conductive material. 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 can be used.
[0381] The electrodes 591 and the electrodes 592 may be formed by
depositing a light-transmitting conductive material on the
substrate 590 by a sputtering method and then removing an
unnecessary portion by any of various patterning techniques such as
photolithography.
[0382] The insulating layer 593 covers the electrodes 591 and the
electrodes 592. Examples of a material for the insulating layer 593
are 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, or aluminum oxide.
[0383] Furthermore, openings reaching the electrodes 591 are formed
in the insulating layer 593, and the wiring 594 electrically
connects the adjacent electrodes 591. The wiring 594 is preferably
formed using a light-transmitting conductive material, in which
case the aperture ratio of the touch panel can be increased.
Moreover, the wiring 594 is preferably formed using a material that
has higher conductivity than those of the electrodes 591 and the
electrodes 592.
[0384] One electrode 592 extends in one direction, and a plurality
of electrodes 592 is provided in the form of stripes.
[0385] The wiring 594 intersects with the electrode 592.
[0386] Adjacent electrodes 591 are provided with one electrode 592
provided therebetween and are electrically connected by the wiring
594.
[0387] Note that the plurality of electrodes 591 is not necessarily
arranged in the direction orthogonal to one electrode 592 and may
be arranged to intersect with one electrode 592 at an angle of less
than 90 degrees.
[0388] One wiring 598 is electrically connected to any of the
electrodes 591 and 592. Part of the wiring 598 serves as a
terminal. For the wiring 598, a metal material such as aluminum,
gold, platinum, silver, nickel, titanium, tungsten, chromium,
molybdenum, iron, cobalt, copper, or palladium or an alloy material
containing any of these metal materials can be used.
[0389] Note that an insulating layer that covers the insulating
layer 593 and the wiring 594 may be provided to protect the touch
sensor 595.
[0390] Furthermore, a connection layer 599 electrically connects
the wiring 598 to the FPC 509(2).
[0391] As the connection layer 599, any of various anisotropic
conductive films (ACF), anisotropic conductive pastes (ACP), or the
like can be used.
[0392] The adhesive layer 597 has a light-transmitting property.
For example, a thermosetting resin or an ultraviolet curable resin
can be used; specifically, a resin such as an acrylic resin, an
urethane resin, an epoxy resin, or a resin having a siloxane bond
can be used.
<Display Portion>
[0393] The touch panel 500 includes a plurality of pixels arranged
in a matrix. Each of the pixels includes a display element and a
pixel circuit for driving the display element.
[0394] In this embodiment, an example of using an organic
electroluminescent element that emits white light as a display
element will be described; however, the display element is not
limited to such element.
[0395] As the display element, for example, in addition to organic
electroluminescent elements, any of a variety of display elements
such as display elements (electronic ink) that perform display by
an electrophoretic method, an electronic liquid powder method, or
the like; MEMS shutter display elements; and optical interference
type MEMS display elements can be used. Note that a structure
suitable for employed display elements can be selected from among a
variety of structures of pixel circuits.
[0396] The substrate 510 is a stacked body in which a flexible
substrate 510b, a barrier film 510a that prevents diffusion of
unintentional impurities to the light-emitting elements, and an
adhesive layer 510c that attaches the barrier film 510a to the
substrate 510b are stacked.
[0397] The substrate 570 is a stacked body in which a flexible
substrate 570b, a barrier film 570a that prevents diffusion of
unintentional impurities to the light-emitting elements, and an
adhesive layer 570c that attaches the barrier film 570a to the
substrate 570b are stacked.
[0398] A sealant 560 attaches the substrate 570 to the substrate
510. The sealant 560, also serving as an optical adhesive layer,
has a refractive index higher than that of air. The pixel circuits
and the light-emitting elements (e.g., a first light-emitting
element 550R) are provided between the substrate 510 and the
substrate 570.
<<Structure of Pixel>>
[0399] A pixel includes a sub-pixel 502R, and the sub-pixel 502R
includes a light-emitting module 580R.
[0400] The sub-pixel 502R includes the first light-emitting element
550R and the pixel circuit that can supply electric power to the
first light-emitting element 550R and includes a transistor 502t.
Furthermore, the light-emitting module 580R includes the first
light-emitting element 550R and an optical element (e.g., a first
coloring layer 567R).
[0401] The first light-emitting element 550R includes a lower
electrode, an upper electrode, and a layer containing a
light-emitting organic compound between the lower electrode and the
upper electrode.
[0402] The light-emitting module 580R includes the first coloring
layer 567R on the counter substrate 570. The coloring layer
transmits light of a particular wavelength and is, for example, a
layer that selectively transmits light of red, green, or blue
color. A region that transmits light emitted from the
light-emitting element as it is may be provided as well.
[0403] The light-emitting module 580R includes the sealant 560 that
is in contact with the first light-emitting element 550R and the
first coloring layer 567R.
[0404] The first coloring layer 567R is positioned in a region
overlapping with the first light-emitting element 550R.
Accordingly, part of light emitted from the first light-emitting
element 550R passes through the sealant 560 that also serves as an
optical adhesive layer and through the first coloring layer 567R
and is emitted to the outside of the light-emitting module 580R as
indicated by an arrow in FIG. 13.
<<Structure of Display Portion>>
[0405] The display portion 501 includes a light-blocking layer
567BM on the counter substrate 570. The light-blocking layer 567BM
is provided so as to surround the coloring layer (e.g., the first
coloring layer 567R).
[0406] The display portion 501 includes an anti-reflective layer
567p positioned in a region overlapping with pixels. As the
anti-reflective layer 567p, a circular polarizing plate can be
used, for example.
[0407] The display portion 501 includes an insulating film 521. The
insulating film 521 covers the transistor 502t. Note that the
insulating film 521 can be used as a layer for planarizing
unevenness caused by the pixel circuits. An insulating film on
which a layer that can prevent diffusion of impurities to the
transistor 502t and the like is stacked can be used as the
insulating film 521.
[0408] The display portion 501 includes the light-emitting elements
(e.g., the first light-emitting element 550R) over the insulating
film 521.
[0409] The display portion 501 includes, over the insulating film
521, a partition wall 528 that overlaps with an end portion of the
lower electrode. In addition, a spacer that controls the distance
between the substrate 510 and the substrate 570 is provided on the
partition wall 528.
<<Structure of Image Signal Line Driver Circuit>>
[0410] An image signal line driver circuit 503s(1) includes a
transistor 503t and a capacitor 503c. Note that the image signal
line driver circuit 503s(1) can be formed in the same process and
over the same substrate as those of the pixel circuits.
<<Other Structures>>
[0411] The display portion 501 includes the wirings 511 through
which signals can be supplied. The wirings 511 are provided with
the terminal 519. Note that the FPC 509(1) through which a signal
such as an image signal or a synchronization signal can be supplied
is electrically connected to the terminal 519.
[0412] Note that a printed wiring board (PWB) may be attached to
the FPC 509(1).
[0413] This embodiment can be combined with any of the other
embodiments in this specification as appropriate.
EXPLANATION OF REFERENCE
[0414] 13a: connecting member, 13b: connecting member, 15a: support
panel, 15b: support panel, 102: substrate, 104a: gate electrode,
106: insulating film, 107: insulating film, 108: insulating film,
110: oxide semiconductor film, 112: conductive film, 112a: first
electrode, 112b: second electrode, 114: insulating film, 116:
insulating film, 118: insulating film. 120: insulating film, 122a:
conductive film. 122b: conductive film. 122c: gate electrode, 142a:
opening, 142d: opening, 142e: opening. 151: transistor, 200:
display device, 200B: display device, 200C: display device, 200D:
display device, 210: control portion. 210B: control portion, 212:
synchronization signal supply portion, 214: power supply portion,
220: image processing portion, 230: display portion. 230(1): first
region, 230(2): second region, 230(1)S: region, 230b(1): boundary,
230b(2): boundary, 232: driver circuit, 232G: scan line driver
circuit, 232S: signal line driver circuit, 239: sign. 240: sensing
portion, 300: input-output device, 301: display portion, 302:
pixel, 302B: sub-pixel, 302G: sub-pixel, 302R: sub-pixel, 302t:
transistor, 303c: capacitor, 303g(1): scan line driver circuit,
303g(2): imaging pixel driver circuit, 303s(1): image signal line
driver circuit, 303s(2): imaging signal line driver circuit, 303t:
transistor, 308: imaging pixel, 308p: photoelectric conversion
element, 308t: transistor, 309: FPC, 310: substrate, 310a: barrier
film, 310b: substrate. 310c: adhesive layer, 311: wiring, 319:
terminal, 321: insulating film, 328: partition wall, 329: spacer,
350R: light-emitting element, 351R: lower electrode. 352: upper
electrode, 353: layer. 353a: light-emitting unit, 353b:
light-emitting unit, 354: intermediate layer, 360: sealant, 367BM:
light-blocking layer, 367p: anti-reflective layer, 367R: coloring
layer, 370: counter substrate, 370a: barrier film, 370b: substrate,
370c: adhesive layer, 380B: light-emitting module, 380G:
light-emitting module, 380R: light-emitting module, 500: touch
panel, 501: display portion, 502R: sub-pixel. 502t: transistor,
503c: capacitor, 503s: image signal line driver circuit, 503t:
transistor, 509: FPC, 510: substrate, 510a: barrier film, 510b:
substrate, 510c: adhesive layer, 511: wiring, 519: terminal, 521:
insulating film, 528: partition wall, 550R: light-emitting element.
560: sealant, 567BM: light-blocking layer, 567p: anti-reflective
layer, 567R: coloring layer, 570: substrate. 570a: barrier film,
570b: substrate, 570c: adhesive layer, 580R: light-emitting module,
590: substrate, 591: electrode, 592: electrode, 593: insulating
layer, 594: wiring, 595: touch sensor. 597: adhesive layer. 598:
wiring, 599: connection layer, 631p: pixel, 634c: capacitor, 634EL:
pixel circuit, 634t: transistor. 634t_1: transistor, 634t_2:
transistor, 635EL: EL element, E1: high flexibility region, E2: low
flexibility region.
[0415] This application is based on Japanese Patent Application
serial no. 2013-161577 filed with Japan Patent Office on Aug. 2,
2013, the entire contents of which are hereby incorporated by
reference.
* * * * *