U.S. patent application number 15/642573 was filed with the patent office on 2018-01-11 for electronic 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 Yoshiaki Oikawa, Kensuke Yoshizumi.
Application Number | 20180011447 15/642573 |
Document ID | / |
Family ID | 60910744 |
Filed Date | 2018-01-11 |
United States Patent
Application |
20180011447 |
Kind Code |
A1 |
Yoshizumi; Kensuke ; et
al. |
January 11, 2018 |
Electronic Device
Abstract
A convenient electronic device is provided. An electronic device
from which a user can easily read the displayed data is provided.
The user can read data with a small motion. A housing of the
electronic device includes a first portion positioned on a front
surface of the housing, a second portion positioned on a side
surface of the housing, a first band attachment portion, and a
second band attachment portion. The second portion is configured to
display an image. The first band attachment portion is positioned
on the side surface on the top side when seen from the front
surface side of the housing. The second portion and the second band
attachment portion are positioned on the side surface on the bottom
side when seen from the front surface side of the housing. The
first portion is configured to display an image or includes at
least one of an hour hand, a minute hand, and a second hand.
Inventors: |
Yoshizumi; Kensuke;
(Isehara, JP) ; Oikawa; Yoshiaki; (Atsugi,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Semiconductor Energy Laboratory Co., Ltd. |
Kanagawa-ken |
|
JP |
|
|
Assignee: |
Semiconductor Energy Laboratory
Co., Ltd.
Kanagawa-ken
JP
|
Family ID: |
60910744 |
Appl. No.: |
15/642573 |
Filed: |
July 6, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G04B 47/00 20130101;
G06F 3/041 20130101; G06F 3/044 20130101; H01L 27/3267 20130101;
H01L 27/3262 20130101; G02F 1/133305 20130101; H01L 27/3213
20130101; H01L 27/3232 20130101; G02F 1/1333 20130101 |
International
Class: |
G04B 47/00 20060101
G04B047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 8, 2016 |
JP |
2016-135870 |
Claims
1. An electronic device comprising a housing, the housing
comprising: a first portion; a second portion; a first band
attachment portion; and a second band attachment portion, wherein
the first portion is on a front surface of the housing, wherein the
second portion is configured to display an image, wherein the
second portion, the first band attachment portion, and the second
band attachment portion are on a side surface of the housing,
wherein the first band attachment portion is on the side surface on
a top side when seen from the front surface side of the housing,
and wherein the second portion and the second band attachment
portion are on the side surface on a bottom side when seen from the
front surface side of the housing.
2. The electronic device according to claim 1, wherein the first
portion comprises at least one of an hour hand, a minute hand, and
a second hand.
3. The electronic device according to claim 1, wherein the first
portion is configured to display an image.
4. The electronic device according to claim 3, wherein the first
portion and the second portion are connected seamlessly.
5. The electronic device according to claim 3, further comprising a
first display panel inside the housing, the first display panel
overlapping with the first portion, wherein the first display panel
comprises one or more elements selected from a liquid crystal
element, an organic electroluminescent element, an inorganic
electroluminescent element, a light-emitting diode element, a
microcapsule, an electrophoretic element, an electrowetting
element, an electrofluidic element, an electrochromic element, and
a micro electro mechanical system element.
6. The electronic device according to claim 3, further comprising a
second display panel inside the housing, the second display panel
overlapping with the first portion, wherein the second display
panel comprises a first substrate, a second substrate, a first
liquid crystal element, a first light-emitting element, and a first
insulating layer, wherein the first liquid crystal element is
between the second substrate and the first insulating layer,
wherein the first light-emitting element is between the first
substrate and the first insulating layer, wherein the first liquid
crystal element is configured to reflect light to the second
substrate side, and wherein the first light-emitting element is
configured to emit light to the second substrate side.
7. The electronic device according to claim 1, further comprising a
third display panel inside the housing, the third display panel
overlapping with the second portion, wherein the third display
panel comprises one or more elements selected from a liquid crystal
element, an organic electroluminescent element, an inorganic
electroluminescent element, a light-emitting diode element, a
microcapsule, an electrophoretic element, an electrowetting
element, an electrofluidic element, an electrochromic element, and
a micro electro mechanical system element.
8. The electronic device according to claim 1, further comprising a
fourth display panel inside the housing, the fourth display panel
overlapping with the second portion, wherein the fourth display
panel comprises a third substrate, a fourth substrate, a second
liquid crystal element, a second light-emitting element, and a
second insulating layer, wherein the second liquid crystal element
is between the fourth substrate and the second insulating layer,
wherein the second light-emitting element is between the third
substrate and the second insulating layer, wherein the second
liquid crystal element is configured to reflect light to the fourth
substrate side, and wherein the second light-emitting element is
configured to emit light to the fourth substrate side.
9. The electronic device according to claim 4, further comprising a
fifth display panel in the housing, the fifth display panel
overlapping with the first portion and the second portion and being
partly curved, wherein the fifth display panel comprises one or
more elements selected from a liquid crystal element, an organic
electroluminescent element, an inorganic electroluminescent
element, a light-emitting diode element, a microcapsule, an
electrophoretic element, an electrowetting element, an
electrofluidic element, an electrochromic element, and a micro
electro mechanical system element.
10. The electronic device according to claim 4, further comprising
a sixth display panel in the housing, the sixth display panel
overlapping with the first portion and the second portion and being
partly curved, wherein the sixth display panel comprises a fifth
substrate, a sixth substrate, a third liquid crystal element, a
third light-emitting element, and a third insulating layer, wherein
the third liquid crystal element is between the sixth substrate and
the third insulating layer, wherein the third light-emitting
element is between the fifth substrate and the third insulating
layer, wherein the third liquid crystal element is configured to
reflect light to the sixth substrate side, and wherein the third
light-emitting element is configured to emit light to the sixth
substrate side.
11. An electronic device comprising a housing, the housing
comprising: a first portion; a second portion; a first band
attachment portion; and a second band attachment portion, wherein
the first portion is on a front surface of the housing, wherein the
second portion is configured to display an image, wherein the
second portion, the first band attachment portion, and the second
band attachment portion are on a side surface of the housing,
wherein the first band attachment portion and the second band
attachment portion are positioned to face each other on a first
straight line penetrating the side surface of the housing, and
wherein the second portion overlaps with a first point on the
second band attachment portion side of intersection points where
the first straight line and the side surface of the housing
intersect each other.
12. The electronic device according to claim 11, wherein the second
portion overlaps with a second point, the second point being one of
two intersection points of the side surface of the housing and a
second straight line penetrating the side surface and intersecting
the first straight line when seen from the front surface side, and
wherein an angle formed by the first point, an intersection point
of the first straight line and the second straight line, and the
second point is more than or equal to 45 degrees and less than or
equal to 270 degrees.
13. The electronic device according to claim 11, wherein the first
portion comprises at least one of an hour hand, a minute hand, and
a second hand.
14. The electronic device according to claim 11, wherein the first
portion is configured to display an image.
15. The electronic device according to claim 14, further comprising
a first display panel inside the housing, the first display panel
overlapping with the first portion, wherein the first display panel
comprises one or more elements selected from a liquid crystal
element, an organic electroluminescent element, an inorganic
electroluminescent element, a light-emitting diode element, a
microcapsule, an electrophoretic element, an electrowetting
element, an electrofluidic element, an electrochromic element, and
a micro electro mechanical system element
16. The electronic device according to claim 14, further comprising
a second display panel inside the housing, the second display panel
overlapping with the first portion, wherein the second display
panel comprises a first substrate, a second substrate, a first
liquid crystal element, a first light-emitting element, and a first
insulating layer, wherein the first liquid crystal element is
between the second substrate and the first insulating layer,
wherein the first light-emitting element is between the first
substrate and the first insulating layer, wherein the first liquid
crystal element is configured to reflect light to the second
substrate side, and wherein the first light-emitting element is
configured to emit light to the second substrate side.
17. The electronic device according to claim 11, further comprising
a third display panel inside the housing, the third display panel
overlapping with the second portion, wherein the third display
panel comprises one or more elements selected from a liquid crystal
element, an organic electroluminescent element, an inorganic
electroluminescent element, a light-emitting diode element, a
microcapsule, an electrophoretic element, an electrowetting
element, an electrofluidic element, an electrochromic element, and
a micro electro mechanical system element.
18. The electronic device according to claim 11, further comprising
a fourth display panel inside the housing, the fourth display panel
overlapping with the second portion, wherein the fourth display
panel comprises a third substrate, a fourth substrate, a second
liquid crystal element, a second light-emitting element, and a
second insulating layer, wherein the second liquid crystal element
is between the fourth substrate and the second insulating layer,
wherein the second light-emitting element is between the third
substrate and the second insulating layer, wherein the second
liquid crystal element is configured to reflect light to the fourth
substrate side, and wherein the second light-emitting element is
configured to emit light to the fourth substrate side.
19. The electronic device according to claim 14, further comprising
a fifth display panel in the housing, the fifth display panel
overlapping with the first portion and the second portion and being
partly curved, wherein the first portion and the second portion are
connected seamlessly, and wherein the fifth display panel comprises
one or more elements selected from a liquid crystal element, an
organic electroluminescent element, an inorganic electroluminescent
element, a light-emitting diode element, a microcapsule, an
electrophoretic element, an electrowetting element, an
electrofluidic element, an electrochromic element, and a micro
electro mechanical system element.
20. The electronic device according to claim 14, further comprising
a sixth display panel in the housing, the sixth display panel
overlapping with the first portion and the second portion and being
partly curved, wherein the first portion and the second portion are
connected seamlessly, wherein the sixth display panel comprises a
fifth substrate, a sixth substrate, a third liquid crystal element,
a third light-emitting element, and a third insulating layer,
wherein the third liquid crystal element is between the sixth
substrate and the third insulating layer, wherein the third
light-emitting element is between the fifth substrate and the third
insulating layer, wherein the third liquid crystal element is
configured to reflect light to the sixth substrate side, and
wherein the third light-emitting element is configured to emit
light to the sixth substrate side.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] One embodiment of the present invention relates to an
electronic device including a display device.
[0002] Note that one embodiment of the present invention is not
limited to the above technical field. Examples of the technical
field of one embodiment of the present invention disclosed in this
specification and the like include a semiconductor device, a
display device, a light-emitting device, a power storage device, a
memory device, an electronic device, a lighting device, an input
device, an input/output device, a driving method thereof, and a
manufacturing method thereof.
2. Description of the Related Art
[0003] Portable information terminals typified by smartphones and
tablet terminals have been actively developed. These portable
information terminals are required to be lightweight and small, for
example.
[0004] In particular, development of a wearable electronic device
(also referred to as a wearable device) has been actively carried
out recently. Examples of the wearable device include a watch-type
device worn on an arm, a glasses-like device worn on a head, and a
necklace-type device worn on a neck. For example, a watch-type
device includes a small-sized display instead of a conventional
watch dial to provide the user with various information in addition
to the time. Such wearable devices have attracted attention to the
medical use, the use for self-health management, or the like and
have been increasingly put into practical use.
[0005] Examples of the display device include, typically, a
light-emitting device including a light-emitting element such as an
organic electroluminescent (EL) element or a light-emitting diode
(LED), a liquid crystal display device, and an electronic paper
performing display by an electrophoretic method or the like.
[0006] Patent Document 1 discloses a flexible light-emitting device
including an organic EL element.
REFERENCE
Patent Document
[0007] [Patent Document 1] Japanese Published Patent Application
No. 2014-197522
SUMMARY OF THE INVENTION
[0008] An object of one embodiment of the present invention is to
provide a convenient electronic device. Another object of one
embodiment of the present invention is to provide an electronic
device from which a user can easily read the displayed data.
Another object of one embodiment of the present invention is to
enable the user to read data with a small motion.
[0009] Another object of one embodiment of the present invention is
to provide an electronic device having high visibility regardless
of the brightness of external light. Another object of one
embodiment of the present invention is to provide an electronic
device with low power consumption. Another object of one embodiment
of the present invention is to provide an electronic device which
can display both a smooth moving image and an eye-friendly still
image. Another object of one embodiment of the present invention is
to provide a novel electronic device.
[0010] One embodiment of the present invention is an electronic
device including a housing. The housing includes a first portion, a
second portion, a first band attachment portion, and a second band
attachment portion. The first portion is positioned on a front
surface of the housing. The second portion is configured to display
an image. The second portion, the first band attachment portion,
and the second band attachment portion are positioned on a side
surface of the housing. The first band attachment portion is
positioned on the side surface on the top side when seen from the
front surface side of the housing, and the second portion and the
second band attachment portion are positioned on the side surface
on the bottom side when seen from the front surface side of the
housing.
[0011] Another embodiment of the present invention is an electronic
device including a housing. The housing includes a first portion, a
second portion, a first band attachment portion; and a second band
attachment portion. The first portion is positioned on a front
surface of the housing. The second portion is configured to display
an image. The second portion, the first band attachment portion,
and the second band attachment portion are positioned on a side
surface of the housing. The first band attachment portion and the
second band attachment portion are positioned to face each other on
a first straight line penetrating the side surface of the housing.
The second portion overlaps with a first point on the second band
attachment portion side of intersection points where the first
straight line and the side surface of the housing intersect each
other.
[0012] In the above-described electronic device, the second portion
preferably overlaps with a second point which is one of two
intersection points of the side surface of the housing and a second
straight line penetrating the side surface and intersecting the
first straight line when seen from the front surface side. In this
case, an angle formed by the first point, an intersection point of
the first straight line and the second straight line, and the
second point is preferably more than or equal to 45 degrees and
less than or equal to 270 degrees.
[0013] The first portion preferably includes at least one of an
hour hand, a minute hand, and a second hand.
[0014] The first portion is preferably configured to display an
image.
[0015] Furthermore, it is preferable to include a display panel
overlapping with the first portion and a display panel overlapping
with the second portion in the housing.
[0016] The first portion and the second portion may be each
configured to display an image and may be configured to be
connected seamlessly. In this case, a display panel overlapping
with the first portion and the second portion and being partly
curved is preferably included.
[0017] A display panel provided over the first portion, the second
portion or both the first portion and second portion preferably
includes one or more elements selected from a liquid crystal
element, an organic EL element, an inorganic EL element, an LED
element, a microcapsule, an electrophoretic element, an
electrowetting element, an electrofluidic element, an
electrochromic element, and a MEMS element.
[0018] Alternatively, the display panel provided over the first
portion, the second portion or both the first portion and second
portion preferably includes a first substrate, a second substrate,
a first liquid crystal element, a first light-emitting element, and
a first insulating layer. The first liquid crystal element is
preferably positioned between the second substrate and the first
insulating layer. The first light-emitting element is preferably
positioned between the first substrate and the first insulating
layer. The first liquid crystal element is preferably configured to
reflect light to the second substrate side. The first
light-emitting element is preferably configured to emit light to
the second substrate side.
[0019] With one embodiment of the present invention, a convenient
electronic device can be provided. Furthermore, an electronic
device from which a user can easily read the displayed data can be
provided. Furthermore, the user can read data with a small
motion.
[0020] Moreover, with one embodiment of the present invention, an
electronic device having high visibility regardless of the
brightness of external light can be provided. Furthermore, an
electronic device with low power consumption can be provided.
Furthermore, an electronic device which can display both a smooth
moving image and an eye-friendly still image can be provided.
Furthermore, a novel electronic device can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In the accompanying drawings:
[0022] FIGS. 1A and 1B illustrate an electronic device;
[0023] FIGS. 2A to 2C each illustrate an electronic device;
[0024] FIGS. 3A and 3B illustrate an electronic device;
[0025] FIGS. 4A and 4B illustrate an electronic device;
[0026] FIGS. 5A and 5B each illustrate an electronic device;
[0027] FIGS. 6A1, 6A2, 6B, 6C, 6D, and 6E each illustrate an
electronic device;
[0028] FIGS. 7A and 7B each illustrate an electronic device;
[0029] FIG. 8 is a block diagram of an electronic device;
[0030] FIG. 9 is a block diagram illustrating an example of a
display device;
[0031] FIGS. 10A to 10C illustrate an example of a pixel unit;
[0032] FIGS. 11A to 11C illustrate examples of a pixel unit;
[0033] FIGS. 12A to 12C illustrate examples of a pixel unit;
[0034] FIGS. 13A, 13B1, 13B2, 13B3, and 13B4 illustrate an example
of a display device and examples of pixels;
[0035] FIG. 14 is a circuit diagram illustrating an example of a
pixel circuit of a display device;
[0036] FIG. 15A is a circuit diagram illustrating an example of a
pixel circuit of a display device, and FIG. 15B illustrates an
example of a pixel;
[0037] FIG. 16 is a perspective view illustrating an example of a
display device;
[0038] FIG. 17 is a cross-sectional view illustrating an example of
a display device;
[0039] FIG. 18 is a cross-sectional view illustrating an example of
a display device;
[0040] FIGS. 19A and 19B are cross-sectional views each
illustrating an example of a display device;
[0041] FIGS. 20A to 20E are cross-sectional views illustrating
examples of a transistor;
[0042] FIGS. 21A to 21D are cross-sectional views illustrating an
example of a manufacturing method of a display device;
[0043] FIGS. 22A to 22C are cross-sectional views illustrating an
example of a manufacturing method of a display device;
[0044] FIGS. 23A and 23B are cross-sectional views illustrating an
example of a manufacturing method of a display device; and
[0045] FIGS. 24A and 24B are cross-sectional views illustrating an
example of a manufacturing method of a display device.
DETAILED DESCRIPTION OF THE INVENTION
[0046] Embodiments will be described in detail with reference to
drawings. Note that the present invention is not limited to the
following description, and it is easily understood by those skilled
in the art that various changes and modifications can be made
without departing from the spirit and scope of the present
invention. Accordingly, the present invention should not be
interpreted as being limited to the description of the embodiments
below.
[0047] Note that in the structures of the invention described
below, the same portions or portions having similar functions are
denoted by the same reference numerals in different drawings, and
description of such portions is not repeated. Further, the same
hatching pattern is applied to portions having similar functions,
and the portions are not denoted by reference numerals in some
cases.
[0048] Note that in each drawing described in this specification,
the size, the layer thickness, or the region of each component is
exaggerated for clarity in some cases. Therefore, embodiments of
the present invention are not limited to such scales.
[0049] Note that in this specification and the like, ordinal
numbers such as "first", "second", and the like are used in order
to avoid confusion among components and do not limit the
number.
Embodiment 1
[0050] In this embodiment, an electronic device of one embodiment
of the present invention will be described.
[0051] One embodiment of the present invention is an electronic
device including a housing and a display portion located on a side
surface of the housing. The housing is provided with a pair of band
attachment portions to which bands (belt or strap) for a user to
wear the electronic device is attached. One embodiment of the
present invention can be used as a wearable device, preferably as a
watch-type information terminal device that can be worn on a user's
arm.
[0052] A dial of the watch or a display portion (also referred to
as a first display portion) that can display an image is provided
on a front surface of the housing. In the case where a display
portion is provided on the front surface of the housing, the
display portion preferably functions as a touch panel.
[0053] One embodiment of the present invention further includes a
display portion (also referred to as a second display portion),
which displays an image, along a side surface of the housing. The
display portion provided on the side surface of the housing can
display various types of data, whereby the convenience of the user
can be increased.
[0054] The second display portion preferably functions as a touch
panel. Thus, the side surface of the housing can be used as an
input device. A user can operate the electronic device by touching
the side surface of the housing.
[0055] For example, in the watch-type device intended to be worn on
the arm, the two band attachment portions are positioned on the top
and bottom sides when seen from the front surface side.
Specifically, the two band attachment portions are arranged to face
each other on the straight line that penetrates the side surface of
the housing. The band (first band) attached to the band attachment
portion positioned on the top side (first band attachment portion)
is positioned on the little finger side when worn on the arm, and
the band (second band) attached to the band attachment portion
(second band attachment portion) positioned on the bottom side is
positioned on the thumb side (on the side near the user) when worn
on the aim.
[0056] In particular, the second display portion preferably
includes a portion located on the second band attachment portion
side in the side surface of the housing. This portion in the
housing easily comes into user's sight without a motion of
intentionally looking at the electronic device. For example, it is
a portion coming within sight of a user when he or she turns his or
her eyes to the arm in walking or when he or she looks down in
doing desk work (the state in which the user put his or her arm on
the desk). In the case where the second display portion is located
in this portion, the user can naturally obtain data displayed on
the second display portion of the electronic device only by turning
his or her eyes upon the electronic device without turning his or
her wrist and looking at the front surface of the housing.
[0057] Furthermore, the second display portion is preferably
provided from the bottom side surface of the housing to the left
side surface or the right side surface. The second display portion
may be provided from the bottom side surface of the housing through
the left side surface or the right side surface to the top side
surface. Thus, the display area of the second display portion can
be increased, and more data can be provided to the user.
[0058] For example, in the case where the electronic device is
designed to be worn on the left arm (preferably, the left wrist),
the second display portion is preferably provided from the bottom
side surface to the left side surface of the housing when seen from
the front surface side. In the case where the electronic device is
worn on the left aim, part of the left side surface of the housing
is also a portion that easily comes into the user's sight without a
motion of intentionally looking at the electronic device.
[0059] While in the case where the electronic device is designed to
be worn on the right arm, the second display portion is preferably
provided from the bottom side surface to the right side surface of
the housing when seen from the front surface side.
[0060] Moreover, the second display portion may be provided from
the right side surface through the bottom side surface to the left
side surface of the housing. Thus, universal design for use on both
the right and left arms can be achieved.
[0061] A button, an operation switch, a winding crown, or the like
may be provided on a portion that is not provided with the second
display portion in the left side surface or the right side surface
of the electronic device. For example, they may be provided on the
right side surface of the housing in the case where the electronic
device is designed to be worn on the left arm, and provided on the
left side surface of the housing in the case where the electronic
device is designed to be worn on the right arm.
[0062] Providing a button, an operation switch, a winding crown, or
the like on the top side surface of the housing enables universal
design for use on both the right and left arms.
[0063] The first display portion and the second display portion
preferably include one or more elements selected from a liquid
crystal element, an organic EL element, an LED element, a
microcapsule, an electrophoretic element, an electrowetting
element, an electrofluidic element, an electrochromic element, and
a MEMS element. As the liquid crystal element, a transmissive
liquid crystal element, a reflective liquid crystal element, a
transflective liquid crystal element, or the like can be used. In
particular, a reflective liquid crystal element can reduce power
consumption because it does not need a light source. When an
element that uses a memory liquid crystal material, such as a
nematic liquid crystal element, a cholesteric liquid crystal
element, or a ferroelectric liquid crystal element, is used as the
liquid crystal element, the rewriting frequency can be reduced in
displaying a still image, so that power consumption can be
reduced.
[0064] It is particularly preferable to employ a display device in
which a reflective element and a light-emitting element are both
included, in the first display portion. In this case, image display
can be performed by the reflective element with low power
consumption in bright external light, while image display can be
performed vividly by the light-emitting element in poor external
light. The combination display of the reflective element and the
light-emitting element can reduce power consumption and allows an
image to be displayed vividly.
[0065] Furthermore, it is also preferable to employ the
above-described display device in which a reflective element and a
light-emitting element are both included, in the second display
portion.
[0066] By using the above-described display device in which a
reflective element and a light-emitting element are both included
in at least one of the first display portion and the second display
portion, an electronic device which displays an image that can be
easily viewed by the user regardless of the brightness of external
light can be provided.
[0067] Here, the display devices included in the first display
portion and the second display portion may have the same structure
or different structures.
[0068] For example, when a display device in which a reflective
element and a light-emitting element are both included is used in
each of the first display portion positioned on the front surface
of the housing and the second display portion positioned on the
side surface of the housing, the electronic device can have low
power consumption and high visibility.
[0069] For example, the first display portion positioned on the
front surface of the housing may use a display device in which a
reflective element and a light-emitting element are both included
for low power consumption, and the second display portion may use a
display device including a light-emitting element for vivid display
of images. In this case, if the second display portion positioned
on the side surface of the housing is used as a sub display which
is smaller than the first display portion, the display area can be
reduced, and thereby power consumption can be reduced.
[0070] Furthermore, the housing may include a windshield, a bezel,
a winding crown, a push button, a lug, or the like.
[0071] More specific examples of the electronic device of one
embodiment of the present invention are described below with
reference to the drawings.
Structure Example 1
[0072] FIGS. 1A and 1B are perspective views of an electronic
device 10 described below. FIG. 1A illustrates a front surface
(main surface), a right side surface, and a bottom surface (bottom
side surface) of the electronic device 10, and FIG. 1B illustrates
the front surface, a left side surface, and the bottom side surface
of the electronic device 10.
[0073] The electronic device 10 includes a housing 11. The housing
11 includes a display portion 21, a display portion 22, a band
attachment portion 31, a band attachment portion 32, a winding
crown 25, buttons 26, and the like. In the example illustrated in
FIGS. 1A and 1B, the electronic device 10 is provided with a band
41 and a band 42.
[0074] The display portion 21 is positioned on the front surface
side of the housing 11 and has a function of showing data such as
the time to the user. For example, a dial of a watch or a display
device capable of displaying a moving image or a still image may be
used in the display portion 21.
[0075] In the case where a display device is used in the display
portion 21, a segment display device may be used. In this way, the
electronic device 10 can function as a digital watch.
[0076] In particular, an active matrix display device or a passive
matrix display device is preferably used in the display portion 21.
In particular, in the case where a display device is used in the
display portion 21, a display device functioning as a touch panel
is preferably used.
[0077] In the case where a dial of an analog watch is provided in
the display portion 21 positioned on the front surface side of the
housing 11, at least one of the hour hand, the minute hand, and the
second hand is included. Furthermore, the watch is preferably a
quartz watch but may be a mechanical watch. When a quartz watch is
employed, a battery can be shared between the display portion 21
and electronic components (e.g., display panel) inside the housing.
Furthermore, when a mechanical watch is employed, electric power is
not necessary for operation of the watch; accordingly, even when
the electronic device is in short of remaining battery, it can
function as a watch. Note that the watch may be a hybrid watch of a
quartz watch and a mechanical watch, capable of employing two
dynamic sources. The quartz watch operates with a battery, and a
mechanical watch operates with restoring force of a spring.
[0078] The display portion 22 is provided on part of a side surface
of the housing 11 and has a function of displaying an image. The
display portion 22 may be provided with a segment display device
but is preferably provided with an active matrix display device or
a passive matrix display device. In particular, the display portion
22 is preferably provided with a display device functioning as a
touch panel.
[0079] The band attachment portion 31 is positioned on the side
surface on the top side of the housing 11 and the band attachment
portion 32 is positioned on the side surface on the bottom side
(bottom surface) of the housing 11. The band attachment portion 31
and the band attachment portion 32 are provided to face each other
with the display portion 21 sandwiched therebetween. Although the
band attachment portion 31 and the band attachment portion 32 each
being a hollow provided in the housing 11 are illustrated in FIGS.
1A and 1B, the present invention is not limited to this embodiment
as long as a mechanism for fixing the band 41 or the band 42 is
included. For example, when the band 41 and the band 42 are
connected to the housing 11 with spring bars, the band attachment
portion 31 and the band attachment portion 32 can each have at
least a pair of bearings to which the spring bar is attached.
[0080] Note that the housing 11 and the band 41 may be configured
to be undetachable from each other, and the housing 11 and the band
42 may be configured to be undetachable from each other.
Furthermore, the band 41, the band 42, and the housing 11 may be
united with unclear boundary therebetween. In such a case, at least
a bendable portion serves as the band 41 or the band 42.
[0081] In this specification and the like, when the electronic
device 10 is seen from the front surface side (the display portion
21 side), the direction on the band 41 side is the top side and the
direction on the band 42 side is the bottom side.
[0082] Note that the direction of the image, the dial, or the like
displayed on the display portion 21 is not limited to the top or
bottom direction and may be inclined. For example, in the case
where a display device is used in the display portion 21 and the
electronic device 10 has a function of measuring the attitude, such
as the inclination, of the housing 11, the direction of the
displayed image may be changed depending on the attitude of the
housing 11.
[0083] The winding crown 25 and the buttons 26 each function as one
user interface. For example, the user can push, pull, turn, or
slide up and down or back and forth the winding crown 25 or the
buttons 26. In response to such operation, a power-on/off
operation, an application startup operation, an application
switching operation, or other operations can be performed in the
electronic device 10. Although the housing 11 is provided with one
winding crown 25 and two buttons 26 in the example shown here, a
switch or the like may be included as well.
[0084] When the band 41 and the band 42 are worn on the user's arm,
the band 41 is positioned on the little finger side, and the band
42 is positioned on the thumb side (on the side near the user).
[0085] The display portion 22 is positioned on the band 42 side
(i.e., the band attachment portion 32 side) on the side surface of
the housing 11. Thus, the user can view the display portion 22 only
by turning his or her eyes upon the electronic device 10 without a
motion of, for example, turning the wrist for looking at the front
surface (e.g., the display portion 21) of the electronic device 10.
Thus, an extremely convenient electronic device can be
achieved.
[0086] FIG. 2A is a schematic view of the electronic device 10 seen
from the front surface side. In the display portion 21 in FIG. 2A,
a dial of an analog watch is used.
[0087] The display portion 21 includes an hour hand 51, a minute
hand 52, a second hand 53, and an index 54. Note that at least one
of the hour hand 51, the minute hand 52, and the second hand 53 is
included. Furthermore, the index 54 is not limited to the example
illustrated in FIG. 2A and may be selected from a variety of
designs. Moreover, the display portion 21 may have a date indicator
(calendar), a moon age indicator (moon phase), a power reserve
indicator, or the like.
[0088] FIG. 2B illustrates an example of an image that can be
displayed in the case where a display device is used in the display
portion 21.
[0089] FIG. 2B illustrates an example of displaying date and time
data 55, notification data 56, and a plurality of icons 57 on the
display portion 21. As the notification data 56, an image notifying
the reception of a message, an image notifying the reception status
of data communication electric waves, and an image notifying the
reception status of telephone communication electric waves are
illustrated from the left as an example. Note that the data
displayed on the display portion 21 is not limited to the example
illustrated here, and various data can be displayed.
[0090] FIG. 2C is a schematic view of the electronic device 10 seen
from the display portion 22 side.
[0091] In the example illustrated in FIG. 2C, data notifying the
reception of a message and the sender of the message and data
notifying the reception status of electric waves are displayed on
the display portion 22. Note that the data displayed on the display
portion 22 is not limited to the example illustrated here, and
various data can be displayed.
[0092] In the case where a still image is mainly displayed on the
display portion 21 and the display portion 22, a display device
including a memory display element is preferably used in each of
the display portion 21 and the display portion 22; in this way,
power consumption can be reduced.
[0093] Here, a memory display element is a display element which
can retain a displayed still image without rewriting. Examples of
the memory display element include a display element which retains
a displayed still image after the stop of power supply, a display
element which retains a displayed still image under the supply of a
constant voltage, and a display element which retains a displayed
still image without a refresh operation.
[0094] The period the memory display element can retain an image
without a refresh or rewriting operation is preferably as long as
possible. For example, the retention period is one second or more,
preferably one minute or more, further preferably one hour or more,
still further preferably one day or more, and one year or less.
Here, the displayed image retention state is, for example, the
state in which luminance variation is within 5%, preferably within
3%, further preferably within 1% with respect to the luminance
dynamic range. Note that in the case of a reflective display
element, the above-described luminance is read as reflectivity.
[0095] As the memory display element, any of display elements to
which various approaches of bistable display technology are applied
can be used. As a typical example of this kind of display element,
electronic paper can be given. The electronic paper may be a
particle-movement type element with a microcapsule method, an
electrophoretic display (EPD) method, or an electronic liquid
powder (registered trademark) method, for example. A display
element having a bistable liquid crystal such as a nematic liquid
crystal element, a cholesteric liquid crystal element, or a
ferroelectric liquid crystal element can also be used.
[0096] Other than the above, an electrowetting (EW) element, an
electrofluidic (EF) element, an electrochromic (EC) element, a
micro electro mechanical system (MEMS) element, or the like can be
used as the memory display element. As the MEMS element, a MEMS
element utilizing optical interference, a MEMS shutter element, or
the like can be used.
[0097] Display elements selected from those of various types can be
used in the display portion 21 and the display portion 22 in
accordance with uses of the electronic device 10.
[0098] Furthermore, in the case where a smooth moving image needs
to be displayed on the display portion 21 and the display portion
22, the display element can be a self-luminous light-emitting
element such as an organic EL (OLED; organic light-emitting diode)
element, a light-emitting diode (LED) element, or a quantum-dot
light-emitting diode (QLED) element, for example. Alternatively, a
transmissive, reflective, or transflective liquid crystal element
may be used.
[0099] Using a display panel which includes a display element
utilizing reflected light and a light-emitting element is
particularly preferable in the display portion 21 and the display
portion 22. More specifically, a display panel which includes a
reflective liquid crystal element, a transistor for driving the
liquid crystal element, an organic EL element, and a transistor for
driving the organic EL element between a pair of substrates is
preferably used. This display panel achieves excellent visibility
and low power consumption by using the reflective liquid crystal
element to display an image in bright external light. Furthermore,
the display panel is capable of vivid display by using the organic
EL element to display an image in poor external light. Moreover,
displaying an image with a combination of the reflective liquid
crystal element and the organic EL element allows both low power
consumption and vivid display.
[0100] Furthermore, it is preferable that the electronic device 10
can be configured so that the display portion 21 or the display
portion 22 does not display an image depending on the situation.
Specifically, it is preferable that the electronic device 10 can be
configured so that pixels in the display portion 21 or the display
portion 22 are not driven. In the case where a display device
including a backlight like a transmissive liquid crystal display
device is used in the display portion 21 or the display portion 22,
it is preferable that the electronic device 10 can be configured so
that the backlight is not driven. By making the display portion 21
or the display portion 22 in a non-displaying (non-operating) state
temporarily, power consumption can be significantly reduced.
[0101] Note that the display portion 21 and the display portion 22
can display various data other than the above. Examples of the
displayed data include notification of an incoming e-mail, call,
social networking service (SNS) message, or the like, the subject
of an e-mail, an SNS message, or the like, the sender of an e-mail,
an SNS message, or the like, the message, the date, the time,
information on playing music or voice, the volume, the temperature,
the battery level, the communication status, the reception strength
of an antenna, and the status of downloading a file or the like.
The display portion 21 and the display portion 22 may display icons
associated with applications, icons associated with functions,
operation buttons, a slider, or the like. Examples of the icons are
icons associated with a function of adjusting the volume, a
fast-forward function, and a fast-backward function during the
replay of voice or music. Furthermore, icons associated with a
function of answering the call or placing the call on hold or a
function of awaking the operation invalid state (the lock state) of
the electronic device 10 may be displayed.
[0102] Note that a transistor including an oxide semiconductor in
its channel formation region thereby to have an extremely low
off-state current is preferably used in pixels, driver circuits, or
the like of the display portion 21 and the display portion 22. A
transistor including an oxide semiconductor whose band gap is
larger than the band gap of silicon can hold charges stored in a
capacitor that is series-connected to the transistor for a long
time, owing to the low off-state current of the transistor. For
example, even when a memory display element is not used, using such
a transistor in a pixel enables a driver circuit to stop while
keeping the grayscale level of the displayed image. As a result, an
electronic device with extremely low power consumption can be
obtained.
Structure Example 2
[0103] FIGS. 3A and 3B are perspective views illustrating an
electronic device 10a described below. The electronic device 10a
illustrated in FIGS. 3A and 3B is different from the structure
illustrated in FIGS. 1A and 1B and the like in the shape of the
display portion 22.
[0104] The display portion 22 is provided from the bottom side
surface to the left side surface of the housing 11. The display
portion 22 curves along a corner on the side surface of the housing
11. The display portion 22 can display a continuous image from the
bottom side surface to the left side surface of the housing 11.
[0105] For example, in the case where the electronic device 10a is
designed to be worn on the left arm, the left side surface of the
housing 11 as well as the bottom side surface of the housing 11 is
a portion that easily comes into the user's sight without a motion
of intentionally looking at the electronic device 10a. Thus, the
user can view the display portion 22 only by turning his or her
eyes upon the electronic device 10a without a motion of, for
example, turning the wrist for looking at the front surface (e.g.,
the display portion 21) of the electronic device 10a.
[0106] With this structure, the area of the display region of the
display portion 22 can be increased; accordingly, more data can be
displayed to the user. Thus, a more convenient electronic device
can be achieved.
[0107] In the case where the electronic device 10a is designed to
be worn on the right arm, the structure in FIGS. 3A and 3B is
inverted horizontally. In other words, when seen from the front
surface side, the display portion 22 is provided from the bottom
side surface to the right side surface of the housing 11, and the
winding crown 25, the buttons 26, and the like are provided on the
left side surface of the housing 11.
Structure Example 3
[0108] FIGS. 4A and 4B are perspective views illustrating an
electronic device 10b described below. The electronic device 10b
illustrated in FIGS. 4A and 4B is different from the structure
illustrated in FIGS. 3A and 3B and the like in the shape of the
housing 11.
[0109] The housing 11 has a circular shape when seen from the front
surface side. The display portion 21 also has a circular shape.
[0110] The side surface of the housing 11 forms a cylindrical
shape. The display portion 22 curves along the side surface. The
display portion 22 is evenly curved from the bottom side surface to
the left side surface of the housing 11. The display portion 22 can
display a continuous image from the bottom side surface to the left
side surface of the housing 11.
[0111] For example, in the case where the electronic device 10b is
designed to be worn on the left arm, the region from the bottom
side surface to the left side surface of the housing 11 is a
portion that easily comes into the user's sight without a motion of
intentionally looking at the electronic device 10b. Thus, the user
can view the display portion 22 only by turning his or her eyes
upon the electronic device 10b without a motion of, for example,
turning the wrist for looking at the front surface (e.g., the
display portion 21) of the electronic device 10b.
[0112] With this structure, the area of the display region of the
display portion 22 can be increased; accordingly, more data can be
displayed to the user. Thus, a more convenient electronic device
can be achieved.
[0113] In the case where the electronic device 10b is designed to
be worn on the right arm, the structure in FIGS. 4A and 4B is
inverted horizontally. In other words, when seen from the front
surface side, the display portion 22 is provided from the bottom
side surface to the right side surface of the housing 11, and the
winding crown 25, the buttons 26, and the like are provided on the
left side surface of the housing 11.
Structure Example 4
[0114] FIG. 5A is a perspective view illustrating an electronic
device 10c described below. The electronic device 10c illustrated
in FIG. 5A is different from the structure illustrated in FIGS. 1A
and 1B and the like in that the display portion 21 and the display
portion 22 are seamlessly connected.
[0115] The display portion 21 and the display portion 22 are
provided from the front surface to the bottom side surface of the
housing 11. The display portion 21 and the display portion 22 can
display a continuous image from the front surface to the bottom
side surface of the housing 11.
[0116] The display portion 21 and the display portion 22 are
preferably formed by one display device. For example, a display
device that partly or entirely has flexibility can be used.
[0117] In FIG. 5A, a boundary between the display portion 21 and
the display portion 22 is indicated by dotted lines for
convenience. For example, in the case where the housing on the
front surface side is flat, of the display portion in the
electronic device 10c, a region positioned on the front surface
side and being flat can be regarded as the display portion 21 and
the other region including the curved portion can be regarded as
the display portion 22. Alternatively, a region which can be seen
from the front surface side can be regarded as the display portion
21 and the region which cannot be seen from the front surface side
can be regarded as the display portion 22.
[0118] <Variation Example>
[0119] FIG. 5B illustrates an example including a display portion
22a positioned on the bottom side surface of the housing 11 and a
display portion 22b positioned on the left side surface of the
housing 11. The display portion 21, the display portion 22a, and
the display portion 22b are connected seamlessly. The display
portion 21 and the display portion 22a can display a continuous
image, and the display portion 21 and the display portion 22b can
display a continuous image.
[0120] [Placement of Display Portion 22]
[0121] Next, the placement of the display portion 22 is
described.
[0122] FIG. 6A1 is a schematic view of the electronic device 10
illustrated in FIG. 1A and the like, seen from the front surface
side. FIG. 6A2 is a perspective view of the electronic device 10
seen from the left side surface side and the bottom side surface
side.
[0123] In FIG. 6A1, a region where the display portion 22 is
provided is indicated by broken lines. Note that although the
display portion 22 forms part of the side surface of the housing,
the thickness of the display portion 22 is illustrated in FIG. 6A1
for clarity.
[0124] In FIGS. 6A1 and 6A2, a virtual straight line 15 which
penetrates the side surface of the housing 11 is shown. The
straight line 15 is parallel to the surface of the display portion
21. In the case where the surface of the display portion 21 is
curved, the straight line 15 is a straight line which is orthogonal
to a perpendicular passing through the center of gravity of the
display portion 21.
[0125] Furthermore, the straight line 15 is orthogonal to a
symmetry line or a symmetry plane of the band attachment portion 31
and the band attachment portion 32 which are symmetric with respect
to the line or the plane. In other words, the band attachment
portion 31 and the band attachment portion 32 are each provided on
the straight line 15.
[0126] In the case where the band 41, the band 42, and the housing
11 are formed as one piece and the clear band attachment portions
31 and 32 do not exist, the band attachment portions 31 and 32 can
be replaced by the bands 41 and 42. In other words, the straight
line 15 is orthogonal to a symmetry line or a symmetry plane of the
band 41 and the band 42 which are symmetric with respect to the
line or the plane, and the band 41 and the band 42 are each
provided along the straight line 15.
[0127] Because the straight line 15 penetrates the side surface of
the housing 11, two intersection points exist between the straight
line 15 and the side surface of the housing 11. Of the two
intersection points, the intersection point on the top side (the
band attachment portion 31 side) is referred to as an intersection
point 15a, and the intersection point on the bottom side (the band
attachment portion 32 side) is referred to as an intersection point
15b.
[0128] The display portion 22 is preferably provided in at least a
position overlapping with the intersection point 15b. Because the
intersection point 15b is a point that easily comes into the user's
sight without a motion of intentionally looking at the electronic
device 10, providing the display portion 22 in such a position
allows the user to view the display portion 22 only by turning his
or her eyes upon the electronic device 10 without a motion of, for
example, turning the wrist for looking at the front surface (e.g.,
the display portion 21) of the electronic device 10.
[0129] FIG. 6B illustrates the electronic device 10a illustrated in
FIGS. 3A and 3B.
[0130] In FIG. 6B, a straight line 16 intersecting the straight
line 15 is shown. The straight line 16 is a straight line
penetrating the side surface of the housing 11 like the straight
line 15, and two intersection points between the straight line 16
and the housing 11 are referred to as an intersection point 16a and
an intersection point 16b. Here, the straight line 16 is a straight
line intersecting the straight line 15 at a midpoint between the
intersection point 15a and the intersection point 15b.
[0131] Of the two intersection points, the intersection point
overlapping with the display portion 22 is referred to as the
intersection point 16a. In the case where both of the two
intersection points overlap with the display portion 22, the
intersection point farther from the intersection point 15b is
referred to as the intersection point 16a, and the intersection
point closer to the intersection point 15b is referred to as the
intersection point 16b.
[0132] FIGS. 6B to 6E each illustrate a case in which the display
portion 22 overlaps with the intersection point 16a and the
intersection point 16a is positioned at an edge of the display
portion 22.
[0133] Here, an angle between the straight line 15 and the straight
line 16 is referred to as angle .theta.. The angle .theta. is
formed by the intersection point 15b, an intersection point of the
straight lines 15 and 16, and the intersection point 16a.
[0134] The angle .theta. between the straight lines 15 and 16 is,
for example, more than or equal to 30 degrees and less than or
equal to 300 degrees, preferably more than or equal to 45 degrees
and less than or equal to 270 degrees, further preferably more than
or equal to 90 degrees and less than or equal to 270 degrees. The
more the angle .theta. becomes, the area of the display region of
the display portion 22 is increased.
[0135] For example, FIG. 6C illustrates a case in which the angle
.theta. is more than 180 degrees. In this case, the display portion
22 is positioned from the bottom side surface through the left side
surface to part of the top side surface of the housing 11.
[0136] FIG. 6D illustrates the electronic device 10b illustrated in
FIGS. 4A and 4B.
[0137] In FIG. 6D, the display portion 22 is provided so as to be
curved along the cylindrical side surface of the housing 11. FIG.
6D illustrates a case in which .differential. is less than 180
degrees. In this case, the display portion 22 is positioned from
the bottom side surface to part of the left side surface of the
housing 11.
[0138] Furthermore, FIG. 6E illustrates an example of a case in
which the angle .theta. is more than 180 degrees. In this case, the
display portion 22 is positioned from the bottom side surface
through the left side surface to part of the top side surface of
the housing 11.
[0139] Described so far is the placement of the display portion
22.
[0140] [Internal Structure Example of Electronic Device]
[0141] An example of an internal structure of an electronic device
according to one embodiment of the present invention is described
below.
[0142] FIG. 7A is a schematic cross-sectional view of the
electronic device 10. FIG. 7A corresponds to a cross section taken
along line A1-A2 in FIG. 2B.
[0143] The electronic device 10 includes, inside the housing 11, a
display device 61, a display device 62, a battery 71, a printed
board 72, a vibration module 74, an antenna 75, and the like.
[0144] A plurality of ICs 73 are mounted on the printed board 72.
The display device 61 and the printed board 72 are electrically
connected to each other by an FPC 63a. The display device 62 and
the printed board 72 are electrically connected to each other by an
FPC 63b.
[0145] The electronic device 10 includes a light-transmitting
member 64a in a region overlapping with the display device 61 on
the front surface side of the housing 11. The user can view an
image displayed on the display region of the display device 61
through the light-transmitting member 64a. A region where the
light-transmitting member 64a is provided in the housing 11
corresponds to the display portion 21.
[0146] The electronic device 10 includes a light-transmitting
member 64b in a region overlapping with the display device 62 on
the side surface of the housing 11. The user can view an image
displayed on the display device 62 through the light-transmitting
member 64b. A region where the light-transmitting member 64b is
provided in the housing 11 corresponds to the display portion
22.
[0147] As the light-transmitting member 64a and the
light-transmitting member 64b, glass, crystal glass, plastic, or
the like can be used, for example.
[0148] FIG. 7B illustrates a cross-sectional structure example of
the electronic device 10c illustrated in FIG. 5A.
[0149] The electronic device 10c includes the display device 61.
The display device 61 is provided from the front surface to the
side surface of the housing 11 so as to be partly curved. The
display device 61 and the printed board 72 are electrically
connected to each other through an FPC 63.
[0150] Furthermore, the housing 11 includes a light-transmitting
member 64. The light-transmitting member 64 is provided from the
front surface to the side surface of the housing 11 so as to be
partly curved.
[0151] Described so far is an example of an internal structure of
an electronic device.
[0152] At least part of this embodiment can be implemented in
combination with any of the other embodiments described in this
specification as appropriate.
Embodiment 2
[0153] [Hardware Structure Examples of Electronic Device]
[0154] A structural example of hardware of the electronic device 10
will be described below.
[0155] FIG. 8 is a block diagram illustrating a structural example
of the electronic device 10.
[0156] Although a block diagram attached to this specification
shows elements classified according to their functions in
independent blocks, it may be practically difficult to completely
separate the elements according to their functions and, in some
cases, one element may be involved in a plurality of functions, or
a plurality of elements may be involved in one function.
[0157] Note that the structure of the electronic device 10
illustrated in FIG. 8 is an example, and the electronic device 10
does not need to include all the components. The electronic device
10 includes necessary components among the components illustrated
in FIG. 8 and may include a component other than the components in
FIG. 8.
[0158] The electronic device 10 includes the housing 11.
[0159] The housing 11 includes an arithmetic portion (CPU) 661, a
touch panel 651, a touch panel 652, a memory device 664, a display
controller 671, a touch sensor controller 672, a battery controller
673, a power receiving portion 674, a battery module 675, a sound
controller 676, an audio input portion 677, an audio output portion
678, a communication module 681, an antenna 682, an attitude
measurement portion 683, an external interface 685, a camera module
686, a vibration module 687, a sensor module 688, and the like.
[0160] The memory device 664, the display controller 671, the touch
sensor controller 672, the battery controller 673, the sound
controller 676, the communication module 681, the attitude
measurement portion 683, the external interface 685, the camera
module 686, the vibration module 687, the sensor module 688, and
the like are connected to the arithmetic portion 661 via a bus line
662.
[0161] The touch panel 651 corresponds to the display device
included in the display portion 21. The touch panel 652 corresponds
to the display device included in the display portion 22.
[0162] The arithmetic portion 661 can, for example, function as a
central processing unit (CPU), and has a function of controlling
components such as the memory device 664, the display controller
671, the touch sensor controller 672, the battery controller 673,
the sound controller 676, the communication module 681, the
attitude measurement portion 683, the external interface 685, the
camera module 686, the vibration module 687, and the sensor module
688.
[0163] Signals are transmitted between the arithmetic portion 661
and the components via the bus line 662. The arithmetic portion 661
has a function of processing signals input from the components
which are connected to the arithmetic portion 661 via the bus line
662, a function of generating signals to be output to the
components, and the like, so that the components connected to the
bus line 662 can be controlled comprehensively.
[0164] Note that a transistor which includes an oxide semiconductor
in a channel formation region and has an extremely low off-state
current can be used in an IC included in the arithmetic portion 661
and the other components, and the like. With the use of the
transistor having an extremely low off-state current as a switch
for holding electric charge (data) which flows into a capacitor
functioning as a memory element, a long data retention period can
be ensured. By utilizing this characteristic for a register or a
cache memory of the arithmetic portion 661, normally off computing
is achieved where the arithmetic portion 661 operates only when
needed and information on the previous processing is stored in the
memory element in the rest of time; thus, power consumption of the
electronic device 10 can be reduced.
[0165] The arithmetic portion 661 interprets and executes
instructions from various programs with a processor to process
various kinds of data and control programs. The programs executed
by the processor may be stored in a memory region of the processor
or in the memory device 664.
[0166] As an example of the arithmetic portion 661 other than the
CPU, a microprocessor, such as a digital signal processor (DSP) or
a graphics processing unit (GPU), can be used alone or in
combination. Furthermore, such a microprocessor may be obtained
with a programmable logic device (PLD) such as a field programmable
gate array (FPGA) or a field programmable analog array (FPAA).
[0167] The arithmetic portion 661 may include a main memory. The
main memory can include a volatile memory, such as a random access
memory (RAM), and a nonvolatile memory, such as a read only memory
(ROM).
[0168] For example, a dynamic random access memory (DRAM) is used
for the RAM included in the main memory, in which case a memory
space as a workspace for the arithmetic portion 661 is virtually
allocated and used. An operating system, an application program, a
program module, program data, and the like which are stored in the
memory device 664 are loaded into the RAM and executed. The data,
program, and program module which are loaded into the RAM are
directly accessed and operated by the arithmetic portion 661.
[0169] In the ROM, a basic input/output system (BIOS), firmware,
and the like for which rewriting is not needed can be stored. As
the ROM, a mask ROM, a one-time programmable read only memory
(OTPROM), an erasable programmable read only memory (EPROM), or the
like can be used. As an EPROM, an ultra-violet erasable
programmable read only memory (UV-EPROM) which can erase stored
data by irradiation with ultraviolet rays, an electrically erasable
programmable read only memory (EEPROM), a flash memory, and the
like can be given.
[0170] Examples of the memory device 664 are a memory device
including a nonvolatile memory element, such as a flash memory, a
magnetoresistive random access memory (MRAM), a phase change RAM
(PRAM), a resistive RAM (ReRAM), or a ferroelectric RAM (FeRAM),
and a memory device including a volatile memory element, such as a
dynamic RAM (DRAM) or a static RAM (SRAM). Alternatively, a storage
media drive such as a hard disk drive (HDD) or a solid state drive
(SSD) may be used, for example.
[0171] As the memory device 664, a memory device which can be
connected to and disconnected from the external interface 685 with
a connector, such as an HDD or an SSD, or a storage media drive,
such as a flash memory, a Blu-ray disc, or a DVD can be used. Note
that the memory device 664 is not necessarily incorporated in the
electronic device 10, and a memory device outside the electronic
device 10 may be used as the memory device 664. In this case, the
memory device may be connected through the external interface 685,
or data transmission and reception may be wirelessly performed
using the communication module 681.
[0172] The touch panel 651 and the touch panel 652 are each
connected to the display controller 671 and the touch sensor
controller 672. The display controller 671 and the touch sensor
controller 672 are connected to the arithmetic portion 661 via the
bus line 662.
[0173] The display controller 671 controls the touch panel 651 and
the touch panel 652 according to drawing instructions input from
the arithmetic portion 661 via the bus line 662 so that a
predetermined image is displayed on the display surface of these
touch panels.
[0174] The touch sensor controller 672 controls touch sensors of
the touch panels 651 and 652 according to requests from the
arithmetic portion 661 via the bus line 662. In addition, the touch
sensor controller 672 outputs a signal received by the touch
sensors to the arithmetic portion 661 via the bus line 662. Note
that the function of calculating touch position information from a
signal received by the touch sensors may be given to the touch
sensor controller 672 or the arithmetic portion 661.
[0175] The touch panels 651 and 652 can display an image on the
basis of a signal supplied from the display controller 671. In
addition, the touch panels 651 and 652 are capable of sensing the
proximity or touch of an object such as a finger or a stylus on the
basis of a signal supplied from the touch sensor controller 672 and
outputting the positional information of the object to the touch
sensor controller 672.
[0176] The touch panel 651, the touch panel 652, and the touch
sensor controller 672 preferably have a function of obtaining the
distance between a sensing surface and the object in the height
direction, a function of obtaining the magnitude of pressure
applied to the sensing surface by the object, and a function of
obtaining the area where the sensing surface is in contact with the
object.
[0177] In the touch panels 651 and 652, a module including a touch
sensor is provided on the display surface side of the display panel
so as to overlap with the display panel. At this time, at least
part of the module including a touch sensor is preferably flexible
to follow the bending of the display panel. The module including a
touch sensor can be bonded to the display panel with an adhesive or
the like. A polarizing plate or a cushion material (e.g., a
separator) may be provided between the module and the display
panel. The thickness of the module including a touch sensor is
preferably smaller than or equal to that of the display panel.
[0178] A touch panel in which a display panel and a touch sensor
are combined may be used as each of the touch panels 651 and 652.
For example, the touch panels 651 and 652 are preferably on-cell
touch panels or an in-cell touch panels. The on-cell or in-cell
touch panel has a small thickness and therefore can be lightweight.
In addition, the number of components of the on-cell or in-cell
touch panel can be reduced, so that cost can be reduced.
[0179] A variety of sensors capable of sensing the proximity or
touch of an object such as a finger can be used as the touch
sensors included in the touch panels 651 and 652. For example, a
sensor of a capacitive type, a resistive type, a surface acoustic
wave type, an infrared type, an electromagnetic induction type, or
an optical type can be used. In addition, an optical sensor using a
photoelectric conversion element, a pressure-sensitive sensor using
a pressure-sensitive element, or the like may be used. Two or more
sensors of different types may be used, or two or more sensors of
the same type may be used.
[0180] For example, a capacitive touch sensor includes a pair of
conductive layers. The pair of conductive layers is capacitively
coupled. The capacitance between the pair of conductive layers
changes when an object touches, presses, or approaches the pair of
conductive layers. Utilizing this effect, sensing can be
conducted.
[0181] 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 the mutual
capacitive touch sensor is preferable because simultaneous sensing
of multiple points can be performed easily.
[0182] Instead of the touch panel 651 and the touch panel 652, a
display panel which does not have a function of a touch sensor may
be used.
[0183] For example, a flexible substrate is used as a substrate
that supports a display element, a circuit for driving the display
element, a circuit included in a touch sensor, and the like,
whereby the touch panel 651, the touch panel 652, the display
panel, the touch sensor, and the like can have flexibility. Using a
flexible substrate in the touch panel 651 and the touch panel 652
is preferable because the electronic device 10 can become
lightweight.
[0184] A typical example of a material of a flexible substrate is
an organic resin. In addition, glass, metal, alloy, a
semiconductor, or the like that is thin enough to have flexibility,
or a composite material or a stacked material containing two or
more of an organic resin, glass, metal, alloy, a semiconductor, and
the like can be used.
[0185] The battery controller 673 can manage a charge state of the
battery module 675. In addition, the battery controller 673
supplies power from the battery module 675 to the components. The
power receiving portion 674 has a function of receiving power
supplied from the outside and charging the battery module 675. The
battery controller 673 can control the operation of the power
receiving portion 674 depending on the charge state of the battery
module 675.
[0186] The battery module 675 includes one or more primary
batteries or secondary batteries, for example. Examples of the
secondary battery which can be used for the battery module 675
include a lithium ion secondary battery and a lithium ion polymer
secondary battery. In addition to such a battery, a protection
circuit for preventing overcharge, overdischarge, and the like of
the battery may be provided in the battery module 675.
[0187] In the case of indoor use or the like, an
alternating-current (AC) power supply may be used as an external
power supply. Particularly in the case of using the electronic
device 10 separately from the external power supply, it is
favorable that the battery module 675 have a large charge/discharge
capacity which allows the electronic device 10 to be used for a
long time. The battery module 675 may be charged using a battery
charger capable of supplying power to the electronic device 10. At
this time, charging may be performed through wires using a
universal serial bus (USB) connector, an AC adaptor, or the like;
alternatively, charging may be performed by a wireless power
feeding method such as an electric field coupling method, an
electromagnetic induction method, or an electromagnetic resonance
(electromagnetic resonant coupling) method.
[0188] The battery controller 673 may include a battery management
unit (BMU), for example. The BMU collects data on cell voltage or
cell temperatures of the battery, monitors overcharge and
overdischarge, controls a cell balancer, handles a deterioration
state of the battery, calculates the remaining battery power level
(state of charge: SOC), and controls detection of a failure, for
example.
[0189] The battery controller 673 controls power transmission from
the battery module 675 to the components through a power supply
line (not shown). The battery controller 673 can include a power
converter with a plurality of channels, an inverter, a protection
circuit, and the like.
[0190] The battery module 675 preferably overlaps with the touch
panel 651 or the touch panel 652. When the housing 11 incorporating
the battery module 675 is flexible and can be used in a bent state,
it is preferable that at least part of the battery module 675 be
also flexible. Examples of the secondary battery which can be used
for the battery module 675 include a lithium ion secondary battery
and a lithium ion polymer secondary battery. It is preferable that
a laminate pouch be used as an external package of the battery so
that the battery has flexibility.
[0191] A film used for the laminate pouch is a single-layer film
selected from a metal film (e.g., an aluminum film, a stainless
steel film, and a nickel steel film), a plastic film made of an
organic material, a hybrid material film containing an organic
material (e.g., an organic resin or fiber) and an inorganic
material (e.g., ceramic), and a carbon-containing inorganic film
(e.g., a carbon film or a graphite film), or a stacked-layer film
including two or more of the above films. A metal film can be
easily embossed. Forming depressions or projections by embossing
increases the surface area of the film exposed to outside air,
achieving efficient heat dissipation.
[0192] It is particularly preferable that a laminate pouch
including a metal film having depressions and projections by
embossing be used, in which case a strain caused by stress applied
to the laminate pouch can be relieved, leading to an effective
decrease of defects such as a break of the laminate pouch due to
bending of a secondary battery.
[0193] In addition, the battery controller 673 preferably has a
function of reducing power consumption. For example, after
detection of no input to the electronic device 10 for a given
period, the battery controller 673 lowers clock frequency or stops
input of clocks of the arithmetic portion 661, stops operation of
the arithmetic portion 661 itself, stops operation of the auxiliary
memory, or reduces power supplied to the components in order to
reduce power consumption. Such a function is performed with the
battery controller 673 alone or the battery controller 673
interlocking with the arithmetic portion 661.
[0194] The audio input portion 677 includes a microphone, an audio
input connector, or the like. The audio output portion 678 includes
a speaker, an audio output connector, or the like. The audio input
portion 677 and the audio output portion 678 are connected to the
sound controller 676, and are connected to the arithmetic portion
661 via the bus line 662. Audio data input to the audio input
portion 677 is converted into a digital signal in the sound
controller 676 and then processed in the sound controller 676 and
the arithmetic portion 661. The sound controller 676 generates an
analog audio signal audible to a user according to instructions
from the arithmetic portion 661 and outputs the analog audio signal
to the audio output portion 678. To the audio output connector of
the audio output portion 678, an audio output device such as
earphones, headphones, or a headset can be connected and a sound
generated in the sound controller 676 is output to the device.
[0195] The communication module 681 can communicate via the antenna
682. For example, the communication module 681 controls a control
signal for connecting the electronic device 10 to a computer
network according to instructions from the arithmetic portion 661
and transmits the signal to the computer network. Accordingly,
communication can be performed by connecting the electronic device
10 to a computer network such as the Internet, which is an
infrastructure of the World Wide Web (WWW), an intranet, an
extranet, a personal area network (PAN), a local area network
(LAN), a campus area network (CAN), a metropolitan area network
(MAN), a wide area network (WAN), or a global area network (GAN).
When a plurality of communication methods are used, the electronic
device 10 may have a plurality of antennas 682 for the
communication methods.
[0196] For example, a high frequency circuit (RF circuit) is
included in the communication module 681 for receiving and
transmitting an RF signal. The RF circuit performs conversion
between an electromagnetic signal and an electric signal in a
frequency band which is set by a national law, and performs
communication with another communication device wirelessly with the
use of the electromagnetic signal. Several tens of kilohertz to
several tens of gigahertz are a practical frequency band which is
generally used. The RF circuit connected to the antenna 682
includes an RF circuit portion compatible with a plurality of
frequency bands. The RF circuit portion can include an amplifier, a
mixer, a filter, a DSP, an RF transceiver, or the like. The
following communication protocol or communication technology for
wireless communication can be used: a communications standard such
as Long Term Evolution (LTE), Global System for Mobile
Communication (GSM) (registered trademark), Enhanced Data Rates for
GSM Evolution (EDGE), Code Division Multiple Access 2000
(CDMA2000), or Wideband Code Division Multiple Access (W-CDMA)
(registered trademark), or a communications standard developed by
IEEE such as Wi-Fi (registered trademark), Bluetooth (registered
trademark), or ZigBee (registered trademark).
[0197] The communication module 681 may have a function of
connecting the electronic device 10 to a telephone line. In the
case of a telephone call through the telephone line, the
communication module 681 controls a connection signal for
connecting the electronic device 10 to the telephone line according
to instructions from the arithmetic portion 661 and transmits the
signal to the telephone line.
[0198] The communication module 681 may include a tuner generating
an image signal from airwaves received by the antenna 682. The
image signal is output to the touch panel 651 and the touch panel
652. The tuner can include a demodulation circuit, an
analog-digital (AD) converter circuit, a decoder circuit, and the
like. The demodulation circuit has a function of demodulating a
signal received by the antenna 682. The AD converter circuit has a
function of converting the demodulated analog signal into a digital
signal. The decoder circuit has a function of decoding image data
contained in the digital signal and generating a signal to be
transmitted to the display controller 671.
[0199] Alternatively, a decoder may include a dividing circuit and
a plurality of processors. The dividing circuit has a function of
dividing the input image data spatiotemporally and outputting it to
the processors. The plurality of processors decode the input image
data and generate signals to be transmitted to the display
controller 671. Since the decoder includes the plurality of
processors which perform parallel data processing, image data
containing enormous amounts of information can be decoded.
Particularly in the case of displaying an image with resolution
higher than the full high definition, a decoder circuit capable of
decoding compressed data preferably includes a processor having
extremely high-speed processing capability. The decoder circuit
preferably includes a plurality of processors capable of performing
4 or more, preferably 8 or more, further preferably 16 or more
parallel operations. The decoder may include a circuit for
classifying an image signal contained in the input signal from
other signals (e.g., text information, broadcast program
information, and certification information).
[0200] The antenna 682 can receive airwaves such as a ground wave
and a satellite wave. The antenna 682 can receive airwaves for
analog broadcasting, digital broadcasting, and the like, and
image-sound-only broadcasting, sound-only broadcasting, and the
like. For example, the antenna 682 can receive airwaves transmitted
in a certain frequency band, such as a UHF band (about 300 MHz to 3
GHz) or a VHF band (30 MHz to 300 MHz). When a plurality of pieces
of data received in a plurality of frequency bands is used, the
transfer rate can be increased, and thus, more information can be
obtained. Accordingly, the touch panel 651 and the touch panel 652
can display an image with resolution higher than the full high
definition, such as 4K2K, 8K4K, 16K8K, or higher.
[0201] Alternatively, the tuner may generate a signal using the
broadcasting data transmitted with data transmission technology
through a computer network. The signal is transmitted to the
display controller 671. In the case where the tuner receives a
digital signal, the tuner does not necessarily include the
demodulation circuit and the AD converter circuit.
[0202] The attitude measurement portion 683 has a function of
measuring a tilt, an attitude, and the like of the electronic
device 10. For example, an acceleration sensor, an angular velocity
sensor, a vibration sensor, a pressure sensor, a gyroscope sensor,
or the like can be used for the attitude measurement portion 683.
Alternatively, these sensors may be used in combination.
[0203] Examples of the external interface 685 include one or more
buttons or switches (also referred to as housing switches) and an
external port to which another input component can be connected
which are provided on the housing 11. The external interface 685 is
connected to the arithmetic portion 661 via the bus line 662.
Examples of the housing switches include a switch associated with
powering on/off, a button for adjusting volume, and a camera
button.
[0204] The external port of the external interface 685 can be
connected to an external device such as a computer or a printer
through a cable. A USB terminal is a typical example. As the
external port, a local area network (LAN) connection terminal, a
digital broadcasting reception terminal, an AC adaptor connection
terminal, or the like may be provided. A transceiver for optical
communication, without limitation to wire communication, using
infrared rays, visible light, ultraviolet rays, or the like, may be
provided.
[0205] The camera module 686 is connected to the arithmetic portion
661 via the bus line 662. The camera module 686 can take a still
image or a moving image in synchronization with pushing a switch
provided on the housing or touching the touch panel 651 and the
touch panel 652. The camera module 686 may include a light source
for taking images. For example, a lamp such as a xenon lamp, and a
light-emitting element such as an LED or an organic EL element can
be used. Alternatively, the touch panel 651 and the touch panel 652
may be used as the light sources for taking images, in which case
light of a variety of colors in addition to white may be used for
taking images.
[0206] The vibration module 687 includes a vibrating element for
vibrating the electronic device 10 and a vibration controller for
controlling the vibrating element. As the vibrating element, an
element capable of converting an electric signal or a magnetic
signal into vibration, such as a vibration motor (eccentric motor),
a resonant actuator, a magnetostrictive element, or a piezoelectric
element can be used.
[0207] The vibration module 687 can vibrate the electronic device
10 with a variety of vibration patterns by controlling the number
of vibrations, the amplitude, vibration time, and the like of the
vibrating element according to instructions from the arithmetic
portion 661. The vibration module 687 can generate vibration with a
variety of vibration patterns based on operation executed by a
variety of applications. Examples of such vibration include
vibration linked with operation of the housing switch or the like,
vibration linked with startup of the electronic device 10,
vibration linked with a moving image or audio reproduced by an
application for reproducing a moving image, vibration linked with
reception of an e-mail, and vibration linked with input operation
to the touch panels 651 and 652.
[0208] The sensor module 688 includes a sensor and a sensor
controller. The sensor controller supplies electric power from the
battery module 675 or the like to a sensor unit. Moreover, the
sensor controller converts the input from the sensor unit into a
control signal and outputs it to the arithmetic portion 661 via the
bus line 662. The sensor controller may handle errors made by the
sensor unit or may calibrate the sensor unit. Note that the sensor
controller may include a plurality of controllers which control the
sensor unit.
[0209] The sensor module 688 may include any of a variety of
sensors which measure force, displacement, position, speed,
acceleration, angular velocity, rotational frequency, distance,
light, liquid, magnetism, temperature, a chemical substance, a
sound, time, hardness, electric field, current, voltage, electric
power, radiation, flow rate, humidity, gradient, oscillation,
smell, and infrared rays.
[0210] The above is the description of the hardware structure
examples of the electronic device 10.
[0211] At least part of this embodiment can be implemented in
combination with any of the other embodiments described in this
specification as appropriate.
Embodiment 3
[0212] An example of a display panel which can be used for a
display portion or the like in the electronic device of one
embodiment of the present invention is described below. The display
panel described below as an example includes both a reflective
liquid crystal element and a light-emitting element and can display
an image in both the transmissive mode and the reflective mode.
[0213] FIG. 9 is a block diagram of a display device 500. The
display device 500 includes a display portion 501.
[0214] The display portion 501 includes a plurality of pixel units
530 arranged in a matrix. The pixel units 530 each include a first
pixel 531p and a second pixel 532p.
[0215] FIG. 9 shows an example where the first pixel 531p and the
second pixel 532p each include display elements corresponding to
three colors of red (R), green (G), and blue (B).
[0216] The display elements included in the first pixel 531p are
each a display element that utilizes reflection of external light.
The first pixel 531p includes a first display element 531R
corresponding to red (R), a first display element 531G
corresponding to green (G), and a first display element 531B
corresponding to blue (B).
[0217] The display elements included in the second pixel 532p are
each a light-emitting element. The second pixel 532p includes a
second display element 532R corresponding to red (R), a second
display element 532G corresponding to green (G), and a second
display element 532B corresponding to blue (B).
[0218] FIGS. 10A to 10C are schematic views illustrating a
structure example of the pixel unit 530.
[0219] The first pixel 531p includes the first display element
531R, the first display element 531G, and the first display element
531B. The first display element 531R reflects external light and
emits red light Rr to the display surface side. Similarly, the
first display element 531G and the first display element 531B emit
green light Gr and blue light Br, respectively, to the display
surface side.
[0220] The second pixel 532p includes the second display element
532R, the second display element 532G, and the second display
element 532B. The second display element 532R emits red light Rt to
the display surface side. Similarly, the second display element
532G and the second display element 532B emit green light Gt and
blue light Bt, respectively, to the display surface side.
[0221] FIG. 10A corresponds to a display mode (third mode) in which
both the first pixel 531p and the second pixel 532p are driven. The
pixel unit 530 can emit light 535tr of a predetermined color to the
display surface side using the reflected light (the light Rr, the
light Gr, and the light Br) and the transmitted light (the light
Rt, the light Gt, and the light Bt).
[0222] FIG. 10B corresponds to a display mode (first mode) using
reflected light in which only the first pixel 531p is driven. For
example, when the intensity of external light is high enough, the
pixel unit 530 can emit light 535r to the display surface side
using only the light from the first pixel 531p (the light Rr, the
light Gr, and the light Br), without driving the second pixel 532p.
Thus, driving with extremely low power consumption can be
performed.
[0223] FIG. 10C corresponds to a display mode (second mode) using
generated light (transmitted light) in which only the second pixel
532p is driven. For example, when the intensity of external light
is extremely low, the pixel unit 530 can emit light 535t to the
display surface side using only the light from the second pixel
532p (the light Rt, the light Gt, and the light Bt), without
driving the first pixel 531p. Thus, a vivid image can be displayed.
Furthermore, by lowering the luminance in a dark environment, a
user can be prevented from feeling glare and power consumption can
be reduced.
[0224] The color and number of display elements included in the
first pixel 531p and the second pixel 532p are not limited.
[0225] FIGS. 11A to 11C and FIGS. 12A to 12C each illustrate a
structure example of the pixel unit 530. Although FIGS. 11A to 11C
and FIGS. 12A to 12C are schematic views corresponding to the
display mode (third mode) in which both the first pixel 531p and
the second pixel 532p are driven, display can also be performed in
the mode (first mode or second mode) in which only the first pixel
531p or the second pixel 532p is driven, like the above-described
structure example.
[0226] The second pixel 532p illustrated in FIGS. 11A and 11C and
FIG. 12B includes a second display element 532W emitting white (W)
light in addition to the second display element 532R, the second
display element 532G, and the second display element 532B.
[0227] The second pixel 532p illustrated in FIG. 11B and FIG. 12C
includes a second display element 532Y emitting yellow (Y) light in
addition to the second display element 532R, the second display
element 532G, and the second display element 532B.
[0228] Power consumption in the display mode using the second pixel
532p (second mode and third mode) can be lower in the structures
illustrated in FIGS. 11A to 11C and FIGS. 12B and 12C than in the
structure not including the second display element 532W or the
second display element 532Y.
[0229] The first pixel 531p illustrated in FIG. 11C includes a
first display element 531W emitting white (W) light in addition to
the first display element 531R, the first display element 531G, and
the first display element 531B.
[0230] Power consumption in the display mode using the first pixel
531p (first mode and third mode) can be lower in the structure
illustrated in FIG. 11C than in the structure illustrated in FIG.
10A.
[0231] The first pixel 531p illustrated in FIGS. 12A to 12C
includes only the first display element 531W emitting white (W)
light. In this structure, a black and white image or a grayscale
image can be displayed in the display mode (first mode) using only
the first pixel 531p, and a color image can be displayed in the
display mode (second mode and third mode) using the second pixel
532p.
[0232] This structure can increase the aperture ratio of the first
pixel 531p and thus increase the reflectivity of the first pixel
531p; accordingly, a brighter image can be displayed.
[0233] The first mode is suitable for displaying data that need not
be displayed in color such as text data.
[0234] At least part of this embodiment can be implemented in
combination with any of the other embodiments described in this
specification as appropriate.
Embodiment 4
[0235] In this embodiment, more specific examples of the display
device described in
[0236] Embodiment 2 will be described with reference to
drawings.
[0237] FIG. 13A is a block diagram of a display device 400. The
display device 400 includes a display portion 362, a circuit GD,
and a circuit SD. The display portion 362 includes a plurality of
pixels 410 arranged in a matrix.
[0238] The display device 400 includes a plurality of wirings G1, a
plurality of wirings G2, a plurality of wirings ANO, a plurality of
wirings CSCOM, a plurality of wirings 51, and a plurality of
wirings S2. The plurality of wirings G1, the plurality of wirings
G2, the plurality of wirings ANO, and the plurality of wirings
CSCOM are each electrically connected to the circuit GD and the
plurality of pixels 410 arranged in a direction indicated by an
arrow R. The plurality of wirings Si and the plurality of wirings
S2 are each electrically connected to the circuit SD and the
plurality of pixels 410 arranged in a direction indicated by an
arrow C.
[0239] Although the structure including one circuit GD and one
circuit SD is illustrated here for simplicity, the circuit GD and
the circuit SD for driving liquid crystal elements and the circuit
GD and the circuit SD for driving light-emitting elements may be
provided separately.
[0240] The pixels 410 each include a reflective liquid crystal
element and a light-emitting element.
[0241] FIGS. 13B1, 13B2, 13B3, and 13B4 illustrate structure
examples of an electrode 311 included in the pixel 410. The
electrode 311 serves as a reflective electrode of the liquid
crystal element. An opening 451 is provided in the electrode 311 in
FIGS. 13B1 and 13B2.
[0242] In FIGS. 13B1 and 13B2, a light-emitting element 360
positioned in a region overlapping with the electrode 311 is
indicated by a broken line. The light-emitting element 360 overlaps
with the opening 451 included in the electrode 311. Thus, light
from the light-emitting element 360 is emitted to the display
surface side through the opening 451.
[0243] In FIG. 13B1, the pixels 410 which are adjacent in the
direction indicated by the arrow R are pixels emitting light of
different colors. As illustrated in FIG. 13B1, the openings 451 are
preferably provided in different positions in the electrodes 311 so
as not to be aligned in two adjacent pixels provided in the
direction indicated by the arrow R. This allows two light-emitting
elements 360 to be apart from each other, thereby preventing light
emitted from the light-emitting element 360 from entering a
coloring layer in the adjacent pixel 410 (such a phenomenon is
referred to as crosstalk). Furthermore, since two adjacent
light-emitting elements 360 can be arranged apart from each other,
a high-resolution display device is achieved even when EL layers of
the light-emitting elements 360 are separately formed with a shadow
mask or the like.
[0244] In FIG. 13B2, the pixels 410 which are adjacent in a
direction indicated by the arrow C are pixels emitting light of
different colors. Also in FIG. 13B2, the openings 451 are
preferably provided in different positions in the electrodes 311 so
as not to be aligned in two adjacent pixels provided in the
direction indicated by the arrow C.
[0245] As the ratio of the total area of the opening 451 to the
total area except for the opening is smaller, display performed
using the liquid crystal element can be brighter. Furthermore, as
the ratio of the total area of the opening 451 to the total area
except for the opening is larger, display performed using the
light-emitting element 360 can be brighter.
[0246] The opening 451 may have a polygonal shape, a quadrangular
shape, an elliptical shape, a circular shape, a cross-like shape, a
stripe shape, a slit-like shape, or a checkered pattern, for
example. The opening 451 may be provided close to the adjacent
pixel. Preferably, the opening 451 is provided close to another
pixel emitting light of the same color, in which case crosstalk can
be suppressed.
[0247] As illustrated in FIGS. 13B3 and 13B4, a light-emitting
region of the light-emitting element 360 may be positioned in a
region where the electrode 311 is not provided, in which case light
emitted from the light-emitting element 360 is emitted to the
display surface side.
[0248] In FIG. 13B3, the light-emitting elements 360 are not
aligned in two adjacent pixels 410 provided in the direction
indicated by the arrow R. In FIG. 13B4, the light-emitting elements
360 are aligned in two adjacent pixels 410 provided in the
direction indicated by the arrow R.
[0249] The structure illustrated in FIG. 13B3 can, as mentioned
above, prevent crosstalk and increase the resolution because the
light-emitting elements 360 included in two adjacent pixels 410 can
be apart from each other. The structure illustrated in FIG. 13B4
can prevent light emitted from the light-emitting element 360 from
being blocked by the electrode 311 because the electrode 311 is not
positioned along a side of the light-emitting element 360 which is
parallel to the direction indicated by the arrow C. Thus, high
viewing angle characteristics can be achieved.
[0250] As the circuit GD, any of a variety of sequential circuits
such as a shift register can be used. In the circuit GD, a
transistor, a capacitor, and the like can be used. A transistor
included in the circuit GD can be formed in the same steps as the
transistors included in the pixels 410.
[0251] The circuit SD is electrically connected to the wirings S1.
For example, an integrated circuit can be used as the circuit SD.
Specifically, an integrated circuit formed on a silicon substrate
can be used as the circuit SD.
[0252] For example, a chip on glass (COG) method, a COF method, or
the like can be used to mount the circuit SD on a pad electrically
connected to the pixels 410. Specifically, an anisotropic
conductive film can be used to mount an integrated circuit on the
pad.
[0253] FIG. 14 is an example of a circuit diagram of the pixels
410. FIG. 14 shows two adjacent pixels 410.
[0254] The pixels 410 each include a switch SW1, a capacitor C1, a
liquid crystal element 340, a switch SW2, a transistor M, a
capacitor C2, the light-emitting element 360, and the like. The
pixel 410 is electrically connected to the wiring G1, the wiring
G2, the wiring ANO, the wiring CSCOM, the wiring S1, and the wiring
S2. FIG. 14 illustrates a wiring VCOM1 electrically connected to
the liquid crystal element 340 and a wiring VCOM2 electrically
connected to the light-emitting element 360.
[0255] FIG. 14 illustrates an example in which a transistor is used
as each of the switches SW1 and SW2.
[0256] A gate of the switch SW1 is connected to the wiring Gl. One
of a source and a drain of the switch SW1 is connected to the
wiring S1, and the other is connected to one electrode of the
capacitor C1 and one electrode of the liquid crystal element 340.
The other electrode of the capacitor C1 is connected to the wiring
CSCOM. The other electrode of the liquid crystal element 340 is
connected to the wiring VCOM1.
[0257] A gate of the switch SW2 is connected to the wiring G2. One
of a source and a drain of the switch SW2 is connected to the
wiring S2, and the other is connected to one electrode of the
capacitor C2 and gates of the transistor M. The other electrode of
the capacitor C2 is connected to one of a source and a drain of the
transistor M and the wiring ANO. The other of the source and the
drain of the transistor M is connected to one electrode of the
light-emitting element 360. Furthermore, the other electrode of the
light-emitting element 360 is connected to the wiring VCOM2.
[0258] FIG. 14 illustrates an example where the transistor M
includes two gates between which a semiconductor is provided and
which are connected to each other. This structure can increase the
amount of current flowing through the transistor M.
[0259] The wiring G1 can be supplied with a signal for changing the
on/off state of the switch SW1. A predetermined potential can be
supplied to the wiring VCOM1. The wiring S1 can be supplied with a
signal for changing the orientation of liquid crystals of the
liquid crystal element 340. A predetermined potential can be
supplied to the wiring CSCOM.
[0260] The wiring G2 can be supplied with a signal for changing the
on/off state of the switch SW2. The wiring VCOM2 and the wiring ANO
can be supplied with potentials having a difference large enough to
make the light-emitting element 360 emit light. The wiring S2 can
be supplied with a signal for changing the conduction state of the
transistor M.
[0261] In the pixel 410 of FIG. 14, for example, an image can be
displayed in the reflective mode by driving the pixel with the
signals supplied to the wiring G1 and the wiring Si and utilizing
the optical modulation of the liquid crystal element 340. In the
case where an image is displayed in the transmissive mode, the
pixel is driven with the signals supplied to the wiring G2 and the
wiring S2 and the light-emitting element 360 emits light. In the
case where both modes are performed at the same time, the pixel can
be driven with the signals supplied to the wiring G1, the wiring
G2, the wiring S1, and the wiring S2.
[0262] Although FIG. 14 illustrates an example in which one liquid
crystal element 340 and one light-emitting element 360 are provided
in one pixel 410, one embodiment of the present invention is not
limited thereto. FIG. 15A illustrates an example in which one
liquid crystal element 340 and four light-emitting elements 360
(light-emitting elements 360r, 360g, 360b, and 360w) are provided
in one pixel 410. The pixel 410 illustrated in FIG. 15A differs
from that in FIG. 14 in being capable of performing full-color
display with the use of the light-emitting elements by one
pixel.
[0263] In FIG. 15A, in addition to the wirings in FIG. 14, a wiring
G3 and a wiring S3 are connected to the pixel 410.
[0264] In the example in FIG. 15A, light-emitting elements emitting
red light (R), green light (G), blue light (B), and white light (W)
can be used as the four light-emitting elements 360, for example.
Furthermore, as the liquid crystal element 340, a reflective liquid
crystal element emitting white light can be used. Thus, in the case
of performing display in the reflective mode, white display with
high reflectivity can be performed. In the case of performing
display in the transmissive mode, images can be displayed with a
higher color rendering property at low power consumption.
[0265] FIG. 15B illustrates a structure example of the pixel 410
corresponding to FIG. 15A. The pixel 410 includes the
light-emitting element 360w overlapping with the opening included
in the electrode 311 and the light-emitting element 360r, the
light-emitting element 360g, and the light-emitting element 360b
which are arranged in the periphery of the electrode 311. It is
preferable that the light-emitting elements 360r, 360g, and 360b
have almost the same light-emitting area.
[0266] At least part of this embodiment can be implemented in
combination with any of the other embodiments described in this
specification as appropriate.
Embodiment 5
[0267] In this embodiment, specific structure examples of the
display device described in Embodiments 2 and 3 will be described
with reference to drawings.
[0268] [Structure Example 1]
[0269] FIG. 16 is a schematic perspective view of a display device
300. In the display device 300, the substrate 351 and the substrate
361 are bonded to each other. In FIG. 16, the substrate 361 is
denoted by a dashed line.
[0270] The display device 300 includes a display portion 362, a
circuit 364, a wiring 365, and the like. FIG. 16 illustrates an
example in which the display device 300 is provided with an
integrated circuit (IC) 373 and an FPC 372. Thus, the structure
illustrated in FIG. 16 can be regarded as a display module
including the display device 300, the IC, and the FPC.
[0271] As the circuit 364, for example, a scan line driver circuit
can be used.
[0272] The wiring 365 has a function of supplying a signal and
power to the display portion 362 and the circuit 364. The signal
and power are input to the wiring 365 from the outside through the
FPC 372 or from the IC 373.
[0273] FIG. 16 illustrates an example in which the IC 373 is
provided over the substrate 351 by a chip on glass (COG) method, a
chip on film (COF) method, or the like. An IC including a scan line
driver circuit, a signal line driver circuit, or the like can be
used as the IC 373, for example. Note that the display device 300
and the display module are not necessarily provided with an IC. The
IC may be provided over the FPC by a COF method or the like.
[0274] FIG. 16 illustrates an enlarged view of part of the display
portion 362. Electrodes 311b included in a plurality of display
elements are arranged in a matrix in the display portion 362. The
electrode 311b has a function of reflecting visible light, and
serves as a reflective electrode of the liquid crystal element
180.
[0275] As illustrated in FIG. 16, the electrode 311b includes an
opening 451. In addition, the display portion 362 includes the
light-emitting element 170 that is positioned closer to the
substrate 351 than the electrode 311b. Light from the
light-emitting element 170 is emitted to the substrate 361 side
through the opening 451 in the electrode 311b. The area of the
light-emitting region of the light-emitting element 170 may be
equal to the area of the opening 451. One of the area of the
light-emitting region of the light-emitting element 170 and the
area of the opening 451 is preferably larger than the other because
a margin for misalignment can be increased. It is particularly
preferable that the area of the opening 451 be larger than the area
of the light-emitting region of the light-emitting element 170.
When the area of the opening 451 is small, part of light from the
light-emitting element 170 is blocked by the electrode 311b and
cannot be extracted to the outside, in some cases. The opening 451
with a sufficiently large area can reduce waste of light emitted
from the light-emitting element 170.
[0276] FIG. 17 illustrates an example of cross-sections of part of
a region including the FPC 372, part of a region including the
circuit 364, and part of a region including the display portion 362
of the display device 300 illustrated in FIG. 16.
[0277] The display device 300 illustrated in FIG. 17 includes a
transistor 201, a transistor 203, a transistor 205, a transistor
206, the liquid crystal element 180, the light-emitting element
170, the insulating layer 220, a coloring layer 131, a coloring
layer 134, and the like, between the substrate 351 and the
substrate 361. The substrate 361 and the insulating layer 220 are
bonded to each other with an adhesive layer 141. The substrate 351
and the insulating layer 220 are bonded to each other with the
adhesive layer 142.
[0278] The substrate 361 is provided with the coloring layer 131, a
light-blocking layer 132, an insulating layer 121, the electrode
113 functioning as a common electrode of the liquid crystal element
180, the alignment film 133b, an insulating layer 117, and the
like. A polarizing plate 135 is provided on an outer surface of the
substrate 361. The insulating layer 121 may have a function of a
planarization layer. The insulating layer 121 enables the electrode
113 to have an almost flat surface, resulting in a uniform
alignment state of a liquid crystal layer 112. The insulating layer
117 serves as a spacer for holding a cell gap of the liquid crystal
element 180. In the case where the insulating layer 117 transmits
visible light, the insulating layer 117 may be positioned to
overlap with a display region of the liquid crystal element
180.
[0279] The liquid crystal element 180 is a reflective liquid
crystal element. The liquid crystal element 180 has a stacked-layer
structure of an electrode 311a, the liquid crystal layer 112, and
the electrode 113. The electrode 311b that reflects visible light
is provided in contact with a surface of the electrode 311a on the
substrate 351 side. The electrode 311b includes the opening 451.
The electrode 311a and the electrode 113 transmit visible light.
The alignment film 133a is provided between the liquid crystal
layer 112 and the electrode 311a. The alignment film 133b is
provided between the liquid crystal layer 112 and the electrode
113.
[0280] In the liquid crystal element 180, the electrode 311b has a
function of reflecting visible light, and the electrode 113 has a
function of transmitting visible light. Light entering from the
substrate 361 side is polarized by the polarizing plate 135,
transmitted through the electrode 113 and the liquid crystal layer
112, and reflected by the electrode 311b. Then, the light is
transmitted through the liquid crystal layer 112 and the electrode
113 again to reach the polarizing plate 135. In this case,
alignment of a liquid crystal can be controlled with a voltage that
is applied between the electrode 311b and the electrode 113, and
thus optical modulation of light can be controlled. In other words,
the intensity of light emitted through the polarizing plate 135 can
be controlled. Light excluding light in a particular wavelength
region is absorbed by the coloring layer 131, and thus, emitted
light is red light, for example.
[0281] As illustrated in FIG. 17, the electrode 311a that transmits
visible light is preferably provided across the opening 451.
Accordingly, liquid crystals in the liquid crystal layer 112 are
aligned in a region overlapping with the opening 451 as in the
other regions, in which case an alignment defect of the liquid
crystals is prevented from being generated in a boundary portion of
these regions and undesired light leakage can be suppressed.
[0282] At a connection portion 207, the electrode 311b is
electrically connected to a conductive layer 222a included in the
transistor 206 via a conductive layer 221b. The transistor 206 has
a function of controlling the driving of the liquid crystal element
180.
[0283] A connection portion 252 is provided in part of a region
where the adhesive layer 141 is provided. In the connection portion
252, a conductive layer obtained by processing the same conductive
film as the electrode 311a is electrically connected to part of the
electrode 113 with the connector 243. Accordingly, a signal or a
potential input from the FPC 372 connected to the substrate 351
side can be supplied to the electrode 113 formed on the substrate
361 side through the connection portion 252.
[0284] As the connector 243, for example, a conductive particle can
be used. As the conductive particle, a particle of an organic
resin, silica, or the like coated with a metal material can be
used. It is preferable to use nickel or gold as the metal material
because contact resistance can be decreased. It is also preferable
to use a particle coated with layers of two or more kinds of metal
materials, such as a particle coated with nickel and further with
gold. A material capable of elastic deformation or plastic
deformation is preferably used for the connector 243. As
illustrated in FIG. 17, the connector 243, which is the conductive
particle, has a shape that is vertically crushed in some cases.
With the crushed shape, the contact area between the connector 243
and a conductive layer electrically connected to the connector 243
can be increased, thereby reducing contact resistance and
suppressing the generation of problems such as disconnection.
[0285] The connector 243 is preferably provided so as to be covered
with the adhesive layer 141. For example, the connectors 243 are
dispersed in the adhesive layer 141 before curing of the adhesive
layer 141.
[0286] The light-emitting element 170 is a bottom-emission
light-emitting element. The light-emitting element 170 has a
stacked-layer structure in which the electrode 191, the EL layer
192, and the electrode 193 are stacked in this order from the
insulating layer 220 side. The electrode 191 is connected to a
conductive layer 222b included in the transistor 205 through an
opening provided in the insulating layer 214. The transistor 205
has a function of controlling the driving of the light-emitting
element 170. The insulating layer 216 covers an end portion of the
electrode 191. The electrode 193 includes a material that reflects
visible light, and the electrode 191 includes a material that
transmits visible light. The insulating layer 194 is provided to
cover the electrode 193. Light is emitted from the light-emitting
element 170 to the substrate 361 side through the coloring layer
134, the insulating layer 220, the opening 451, the electrode 311a,
and the like.
[0287] The liquid crystal element 180 and the light-emitting
element 170 can exhibit various colors when the color of the
coloring layer varies among pixels. The display device 300 can
display a color image using the liquid crystal element 180. The
display device 300 can display a color image using the
light-emitting element 170.
[0288] The transistor 201, the transistor 203, the transistor 205,
and the transistor 206 are formed on a plane of the insulating
layer 220 on the substrate 351 side. These transistors can be
fabricated through the same process.
[0289] The transistor 203 is used for controlling whether the pixel
is selected or not (such a transistor is also referred to as a
switching transistor or a selection transistor). The transistor 205
is used for controlling a current flowing to the light-emitting
element 170 (such a transistor is also referred to as a driving
transistor).
[0290] Insulating layers such as an insulating layer 211, an
insulating layer 212, an insulating layer 213, and the insulating
layer 214 are provided on the substrate 351 side of the insulating
layer 220. Part of the insulating layer 211 functions as a gate
insulating layer of each transistor. The insulating layer 212 is
provided to cover the transistor 206 and the like. The insulating
layer 213 is provided to cover the transistor 205 and the like. The
insulating layer 214 functions as a planarization layer. Note that
the number of insulating layers covering the transistor is not
limited and may be one or two or more.
[0291] A material through which impurities such as water or
hydrogen do not easily diffuse is preferably used for at least one
of the insulating layers that cover the transistors. This is
because such an insulating layer can serve as a barrier film. Such
a structure can effectively suppress diffusion of the impurities
into the transistors from the outside, and a highly reliable
display device can be provided.
[0292] Each of the transistors 201, 203, 205, and 206 includes a
conductive layer 221a functioning as a gate, the insulating layer
211 functioning as the gate insulating layer, the conductive layer
222a and the conductive layer 222b functioning as a source and a
drain, and a semiconductor layer 231. Here, a plurality of layers
obtained by processing the same conductive film are shown with the
same hatching pattern.
[0293] The transistor 201 and the transistor 205 each include a
conductive layer 223 functioning as a gate, in addition to the
components of the transistor 203 or the transistor 206.
[0294] The structure in which the semiconductor layer where a
channel is formed is provided between two gates is used as an
example of the transistors 201 and 205. Such a structure enables
the control of the threshold voltages of transistors. The two gates
may be connected to each other and supplied with the same signal to
operate the transistors. Such transistors can have higher
field-effect mobility and thus have higher on-state current than
other transistors. Consequently, a circuit capable of high-speed
operation can be obtained. Furthermore, the area occupied by a
circuit portion can be reduced. The use of the transistor having
high on-state current can reduce signal delay in wirings and can
reduce display unevenness even in a display device in which the
number of wirings is increased because of increase in size or
definition.
[0295] Alternatively, by supplying a potential for controlling the
threshold voltage to one of the two gates and a potential for
driving to the other, the threshold voltage of the transistors can
be controlled.
[0296] There is no limitation on the structure of the transistors
included in the display device. The transistor included in the
circuit 364 and the transistor included in the display portion 362
may have the same structure or different structures. A plurality of
transistors included in the circuit 364 may have the same structure
or a combination of two or more kinds of structures. Similarly, a
plurality of transistors included in the display portion 362 may
have the same structure or a combination of two or more kinds of
structures.
[0297] It is preferable to use a conductive material containing an
oxide for the conductive layer 223. A conductive film used for the
conductive layer 223 is formed under an atmosphere containing
oxygen, whereby oxygen can be supplied to the insulating layer 212.
The proportion of an oxygen gas in a deposition gas is preferably
higher than or equal to 90% and lower than or equal to 100%. Oxygen
supplied to the insulating layer 212 is then supplied to the
semiconductor layer 231 by later heat treatment; as a result,
oxygen vacancies in the semiconductor layer 231 can be reduced.
[0298] It is particularly preferable to use a low-resistance oxide
semiconductor for the conductive layer 223. In that case, an
insulating film that releases hydrogen, such as a silicon nitride
film, is preferably used for the insulating layer 213, for example,
because hydrogen can be supplied to the conductive layer 223 during
the formation of the insulating layer 213 or by heat treatment
performed after the formation of the insulating layer 213, which
leads to an effective reduction in the electric resistance of the
conductive layer 223.
[0299] The coloring layer 134 is provided in contact with the
insulating layer 213. The coloring layer 134 is covered with the
insulating layer 214.
[0300] A connection portion 204 is provided in a region where the
substrate 351 does not overlap with the substrate 361. In the
connection portion 204, the wiring 365 is electrically connected to
the FPC 372 via a connection layer 242. The connection portion 204
has a similar structure to the connection portion 207. On the top
surface of the connection portion 204, a conductive layer obtained
by processing the same conductive film as the electrode 311a is
exposed. Thus, the connection portion 204 and the FPC 372 can be
electrically connected to each other via the connection layer
242.
[0301] As the polarizing plate 135 provided on the outer surface of
the substrate 361, a linear polarizing plate or a circularly
polarizing plate can be used. An example of a circularly polarizing
plate is a stack including a linear polarizing plate and a
quarter-wave retardation plate. Such a structure can reduce
reflection of external light. The cell gap, alignment, drive
voltage, and the like of the liquid crystal element used as the
liquid crystal element 180 are controlled depending on the kind of
the polarizing plate so that desirable contrast is obtained.
[0302] Note that a variety of optical members can be arranged on
the outer surface of the substrate 361. Examples of the optical
members include a polarizing plate, a retardation plate, a light
diffusion layer (e.g., a diffusion film), an anti-reflective layer,
and a light-condensing film. Furthermore, an antistatic film
preventing the attachment of dust, a water repellent film
suppressing the attachment of stain, a hard coat film suppressing
generation of a scratch caused by the use, or the like may be
arranged on the outer surface of the substrate 361.
[0303] For each of the substrates 351 and 361, glass, quartz,
ceramic, sapphire, an organic resin, or the like can be used. When
the substrates 351 and 361 are formed using a flexible material,
the flexibility of the display device can be increased.
[0304] A liquid crystal element having, for example, a vertical
alignment (VA) mode can be used as the liquid crystal element 180.
Examples of the vertical alignment mode include a multi-domain
vertical alignment (MVA) mode, a patterned vertical alignment (PVA)
mode, and an advanced super view (ASV) mode.
[0305] A liquid crystal element having a variety of modes can be
used as the liquid crystal element 180. For example, a liquid
crystal element using, instead of a VA mode, a twisted nematic (TN)
mode, an in-plane switching (IPS) mode, a fringe field switching
(FFS) mode, an axially symmetric aligned micro-cell (ASM) mode, an
optically compensated birefringence (OCB) mode, a ferroelectric
liquid crystal (FLC) mode, an antiferroelectric liquid crystal
(AFLC) mode, or the like can be used.
[0306] The liquid crystal element is an element that controls
transmission or non-transmission of light utilizing an optical
modulation action of the liquid crystal. The optical modulation
action of the liquid crystal is controlled by an electric field
applied to the liquid crystal (including a horizontal electric
field, a vertical electric field, and an oblique electric field).
As the liquid crystal used for the liquid crystal element, a
thermotropic liquid crystal, a low-molecular liquid crystal, a
high-molecular liquid crystal, a polymer dispersed liquid crystal
(PDLC), a ferroelectric liquid crystal, an anti-ferroelectric
liquid crystal, or the like can be used. Such a liquid crystal
material exhibits a cholesteric phase, a smectic phase, a cubic
phase, a chiral nematic phase, an isotropic phase, or the like
depending on conditions.
[0307] As the liquid crystal material, a positive liquid crystal or
a negative liquid crystal may be used, and an appropriate liquid
crystal material can be used depending on the mode or design to be
used.
[0308] To control the alignment of the liquid crystal, the
alignment films can be provided. In the case where a horizontal
electric field mode is employed, a liquid crystal exhibiting a blue
phase for which an alignment film is unnecessary may be used. The
blue phase is one of liquid crystal phases, which is generated just
before a cholesteric phase changes into an isotropic phase while
the temperature of a cholesteric liquid crystal is increased. Since
the blue phase appears only in a narrow temperature range, a liquid
crystal composition in which several weight percent or more of a
chiral material is mixed is used for the liquid crystal in order to
improve the temperature range.
[0309] The liquid crystal composition that includes a liquid
crystal exhibiting a blue phase and a chiral material has a short
response time and has optical isotropy. In addition, the liquid
crystal composition that includes a liquid crystal exhibiting a
blue phase and a chiral material does not need alignment treatment
and has small viewing angle dependence. An alignment film does not
need to be provided and rubbing treatment is thus not necessary;
accordingly, electrostatic discharge damage caused by the rubbing
treatment can be prevented and defects and damage of the liquid
crystal display device in the manufacturing process can be
reduced.
[0310] In the case where the reflective liquid crystal element is
used, the polarizing plate 135 is provided on the display surface
side. In addition, a light diffusion plate is preferably provided
on the display surface side to improve visibility.
[0311] A front light may be provided on the outer side of the
polarizing plate 135. As the front light, an edge-light front light
is preferably used. A front light including a light-emitting diode
(LED) is preferably used to reduce power consumption.
[0312] As the adhesive layer, any of a variety of curable adhesives
such as a reactive curable adhesive, a thermosetting adhesive, an
anaerobic adhesive, and a photocurable adhesive such as an
ultraviolet curable adhesive can be used. Examples of these
adhesives include an epoxy resin, an acrylic resin, a silicone
resin, a phenol resin, a polyimide resin, an imide resin, a
polyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB) resin,
and an ethylene vinyl acetate (EVA) resin. In particular, a
material with low moisture permeability, such as an epoxy resin, is
preferred. Alternatively, a two-component-mixture-type resin may be
used. Further alternatively, an adhesive sheet or the like may be
used.
[0313] As the connection layer 242, an anisotropic conductive film
(ACF), an anisotropic conductive paste (ACP), or the like can be
used.
[0314] The light-emitting element 170 may be a top emission, bottom
emission, or dual emission light-emitting element, or the like. A
conductive film that transmits visible light is used as the
electrode through which light is extracted. A conductive film that
reflects visible light is preferably used as the electrode through
which light is not extracted.
[0315] The EL layer 192 includes at least a light-emitting layer.
In addition to the light-emitting layer, the EL layer 192 may
further include one or more layers containing any of a substance
with a high hole-injection property, a substance with a high
hole-transport property, a hole-blocking material, a substance with
a high electron-transport property, a substance with a high
electron-injection property, a substance with a bipolar property (a
substance with a high electron- and hole-transport property), and
the like.
[0316] Either a low molecular compound or a high molecular compound
can be used for the EL layer 192, and an inorganic compound may
also be included. The layers included in the EL layer 192 can be
formed by any of the following methods: an evaporation method
(including a vacuum evaporation method), a transfer method, a
printing method, an inkjet method, a coating method, and the
like.
[0317] The EL layer 192 may contain an inorganic compound such as
quantum dots. When quantum dots are used for the light-emitting
layer, quantum dots can function as light-emitting materials, for
example.
[0318] With the use of the combination of a color filter (coloring
layer) and a microcavity structure (optical adjustment layer),
light with high color purity can be extracted from the display
device. The thickness of the optical adjustment layer varies
depending on the color of the pixel.
[0319] As materials of a gate, a source, and a drain of a
transistor, and a conductive layer such as a wiring or an electrode
included in a display device, any of metals such as aluminum,
titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum,
silver, tantalum, and tungsten, or an alloy containing any of these
metals as its main component can be used. A single-layer structure
or multi-layer structure including a film containing any of these
materials can be used.
[0320] As a light-transmitting conductive material, a conductive
oxide such as indium oxide, indium tin oxide, indium zinc oxide,
zinc oxide, or zinc oxide to which gallium is added, or graphene
can be used. Alternatively, a metal material such as gold, silver,
platinum, magnesium, nickel, tungsten, chromium, molybdenum, iron,
cobalt, copper, palladium, or titanium, or an alloy material
containing any of these metal materials can be used. Alternatively,
a nitride of the metal material (e.g., titanium nitride) or the
like may be used. In the case of using the metal material or the
alloy material (or the nitride thereof), the thickness is set small
enough to be able to transmit light. Alternatively, a stacked film
of any of the above materials can be used for the conductive
layers. For example, a stacked film of indium tin oxide and an
alloy of silver and magnesium is preferably used because the
conductivity can be increased. They can also be used for conductive
layers such as a variety of wirings and electrodes included in a
display device, and conductive layers (e.g., conductive layers
serving as a pixel electrode or a common electrode) included in a
display element.
[0321] Examples of an insulating material that can be used for the
insulating layers include a resin such as acrylic or epoxy resin,
and an inorganic insulating material such as silicon oxide, silicon
oxynitride, silicon nitride oxide, silicon nitride, or aluminum
oxide.
[0322] Examples of a material that can be used for the coloring
layers include a metal material, a resin material, and a resin
material containing a pigment or dye.
[0323] [Structure Example 2]
[0324] A display device 300A illustrated in FIG. 18 is different
from the display device 300 mainly in that a transistor 281, a
transistor 284, a transistor 285, and a transistor 286 are included
instead of the transistor 201, the transistor 203, the transistor
205, and the transistor 206.
[0325] Note that the positions of the insulating layer 117, the
connection portion 207, and the like in FIG. 18 are different from
those in FIG. 17. FIG. 18 illustrates an end portion of a pixel.
The insulating layer 117 is provided so as to overlap with an end
portion of the coloring layer 131 and an end portion of the
light-blocking layer 132. As in this structure, the insulating
layer 117 may be provided in a region not overlapping with a
display region (or in a region overlapping with the light-blocking
layer 132).
[0326] Two transistors included in the display device may partly
overlap with each other like the transistor 284 and the transistor
285. In that case, the area occupied by a pixel circuit can be
reduced, leading to an increase in resolution. Furthermore, the
light-emitting area of the light-emitting element 170 can be
increased, leading to an improvement in aperture ratio. The
light-emitting element 170 with a high aperture ratio requires low
current density to obtain necessary luminance; thus, the
reliability is improved.
[0327] Each of the transistors 281, 284, and 286 includes the
conductive layer 221a, the insulating layer 211, the semiconductor
layer 231, the conductive layer 222a, and the conductive layer
222b. The conductive layer 221a overlaps with the semiconductor
layer 231 with the insulating layer 211 positioned therebetween.
The conductive layer 222a and the conductive layer 222b are
electrically connected to the semiconductor layer 231. The
transistor 281 includes the conductive layer 223.
[0328] The transistor 285 includes the conductive layer 222b, an
insulating layer 217, a semiconductor layer 261, the conductive
layer 223, the insulating layer 212, the insulating layer 213, a
conductive layer 263a, and a conductive layer 263b. The conductive
layer 222b overlaps with the semiconductor layer 261 with the
insulating layer 217 positioned therebetween. The conductive layer
223 overlaps with the semiconductor layer 261 with the insulating
layers 212 and 213 positioned therebetween. The conductive layer
263a and the conductive layer 263b are electrically connected to
the semiconductor layer 261.
[0329] The conductive layer 221a functions as a gate. The
insulating layer 211 functions as a gate insulating layer. The
conductive layer 222a functions as one of a source and a drain. The
conductive layer 222b included in the transistor 286 functions as
the other of the source and the drain.
[0330] The conductive layer 222b shared by the transistor 284 and
the transistor 285 has a portion functioning as the other of a
source and a drain of the transistor 284 and a portion functioning
as a gate of the transistor 285. The insulating layer 217, the
insulating layer 212, and the insulating layer 213 function as gate
insulating layers. One of the conductive layer 263a and the
conductive layer 263b functions as a source and the other functions
as a drain. The conductive layer 223 functions as a gate.
[0331] [Structure Example 3]
[0332] FIG. 19A is a cross-sectional view illustrating a display
portion of a display device 300B.
[0333] The display device 300B is different from the display device
300 in that the coloring layer 131 is not provided. Other
components are similar to those of the display device 300 and thus
are not described in detail.
[0334] The liquid crystal element 180 emits white light. Since the
coloring layer 131 is not provided, the display device 300B can
display a black and white image or a grayscale image using the
liquid crystal element 180.
[0335] [Structure Example 4]
[0336] A display device 300C illustrated in FIG. 19B is different
from the display device 300B in that the EL layer 192 is separately
provided for each color (the EL layer 192 is provided for each
light-emitting element 170) and the coloring layer 134 is not
provided. Other components are similar to those of the display
device 300B and thus are not described in detail.
[0337] In the light-emitting element 170 employing a separate
coloring method, at least one layer (typified by the light-emitting
layer) included in the EL layer 192 is separately provided for each
color. All layers included in the EL layer may be separately
provided for each color.
[0338] There is no particular limitation on the structure of the
transistor included in the display device of one embodiment of the
present invention. For example, a planar transistor, a staggered
transistor, or an inverted staggered transistor may be used. A
top-gate transistor or a bottom-gate transistor may be used. Gate
electrodes may be provided above and below a channel.
[0339] FIGS. 20A to 20E illustrate structure examples of
transistors.
[0340] A transistor 110a illustrated in FIG. 20A is a top-gate
transistor.
[0341] The transistor 110a includes a conductive layer 221, the
insulating layer 211, the semiconductor layer 231, the insulating
layer 212, the conductive layer 222a, and the conductive layer
222b. The semiconductor layer 231 is provided over an insulating
layer 151. The conductive layer 221 overlaps with the semiconductor
layer 231 with the insulating layer 211 positioned therebetween.
The conductive layer 222a and the conductive layer 222b are
electrically connected to the semiconductor layer 231 through
openings provided in the insulating layer 211 and the insulating
layer 212.
[0342] The conductive layer 221 functions as a gate. The insulating
layer 211 functions as a gate insulating layer. One of the
conductive layer 222a and the conductive layer 222b functions as a
source and the other functions as a drain.
[0343] In the transistor 110a, the conductive layer 221 can be
physically distanced from the conductive layer 222a or 222b easily;
thus, the parasitic capacitance between the conductive layer 221
and the conductive layer 222a or 222b can be reduced.
[0344] A transistor 110b illustrated in FIG. 20B includes, in
addition to the components of the transistor 110a, the conductive
layer 223 and an insulating layer 218.
[0345] The conductive layer 223 is provided over the insulating
layer 151. The conductive layer 223 overlaps with the semiconductor
layer 231. The insulating layer 218 covers the conductive layer 223
and the insulating layer 151.
[0346] The conductive layer 223 functions as one of a pair of
gates. Thus, the on-state current of the transistor can be
increased and the threshold voltage can be controlled.
[0347] FIGS. 20C to 20E each illustrate an example of a
stacked-layer structure of two transistors. The structures of the
two stacked transistors can be independently determined, and the
combination of the structures is not limited to those illustrated
in FIGS. 20C to 20E.
[0348] FIG. 20C illustrates a stacked-layer structure of a
transistor 110c and a transistor 110d. The transistor 110c includes
two gates. The transistor 110d has a bottom-gate structure. Note
that the transistor 110c may have a structure including one gate
(top-gate structure). The transistor 110d may include two
gates.
[0349] The transistor 110c includes the conductive layer 223, the
insulating layer 218, the semiconductor layer 231, the conductive
layer 221, the insulating layer 211, the conductive layer 222a, and
the conductive layer 222b. The conductive layer 223 is provided
over the insulating layer 151. The conductive layer 223 overlaps
with the semiconductor layer 231 with the insulating layer 218
positioned therebetween. The insulating layer 218 covers the
conductive layer 223 and the insulating layer 151. The conductive
layer 221 overlaps with the semiconductor layer 231 with the
insulating layer 211 positioned therebetween. Although FIG. 20C
illustrates an example where the insulating layer 211 is provided
only in a region overlapping with the conductive layer 221, the
insulating layer 211 may be provided so as to cover an end portion
of the semiconductor layer 231, as illustrated in FIG. 20B and
other drawings. The conductive layer 222a and the conductive layer
222b are electrically connected to the semiconductor layer 231
through openings provided in the insulating layer 212.
[0350] The transistor 110d includes the conductive layer 222b, the
insulating layer 213, the semiconductor layer 261, the conductive
layer 263a, and the conductive layer 263b. The conductive layer
222b includes a region overlapping with the semiconductor layer 261
with the insulating layer 213 positioned therebetween. The
insulating layer 213 covers the conductive layer 222b. The
conductive layer 263a and the conductive layer 263b are
electrically connected to the semiconductor layer 261.
[0351] The conductive layer 221 and the conductive layer 223 each
function as a gate of the transistor 110c. The insulating layer 218
and the insulating layer 211 each function as a gate insulating
layer of the transistor 110c. The conductive layer 222a functions
as one of a source and a drain of the transistor 110c.
[0352] The conductive layer 222b has a portion functioning as the
other of the source and the drain of the transistor 110c and a
portion functioning as a gate of the transistor 110d. The
insulating layer 213 functions as a gate insulating layer of the
transistor 110d. One of the conductive layer 263a and the
conductive layer 263b functions as a source of the transistor 110d
and the other functions as a drain of the transistor 110d.
[0353] The transistor 110c and the transistor 110d are preferably
applied to a pixel circuit of the light-emitting element 170. For
example, the transistor 110c can be used as a selection transistor
and the transistor 110d can be used as a driving transistor.
[0354] The conductive layer 263b is electrically connected to the
electrode 191 that functions as a pixel electrode of the
light-emitting element through an opening provided in the
insulating layer 217 and the insulating layer 214.
[0355] FIG. 20D illustrates a stacked-layer structure of a
transistor 110e and a transistor 110f. The transistor 110e has a
bottom-gate structure. The transistor 110f includes two gates. The
transistor 110e may include two gates.
[0356] The transistor 110e includes the conductive layer 221, the
insulating layer 211, the semiconductor layer 231, the conductive
layer 222a, and the conductive layer 222b. The conductive layer 221
is provided over the insulating layer 151. The conductive layer 221
overlaps with the semiconductor layer 231 with the insulating layer
211 positioned therebetween. The insulating layer 211 covers the
conductive layer 221 and the insulating layer 151. The conductive
layer 222a and the conductive layer 222b are electrically connected
to the semiconductor layer 231.
[0357] The transistor 110f includes the conductive layer 222b, the
insulating layer 212, the semiconductor layer 261, the conductive
layer 223, the insulating layer 218, the insulating layer 213, the
conductive layer 263a, and the conductive layer 263b. The
conductive layer 222b includes a region overlapping with the
semiconductor layer 261 with the insulating layer 212 positioned
therebetween. The insulating layer 212 covers the conductive layer
222b. The conductive layer 263a and the conductive layer 263b are
electrically connected to the semiconductor layer 261 through
openings provided in the insulating layer 213. The conductive layer
223 overlaps with the semiconductor layer 261 with the insulating
layer 218 positioned therebetween. The insulating layer 218 is
provided in a region overlapping with the conductive layer 223.
[0358] The conductive layer 221 functions as a gate of the
transistor 110e. The insulating layer 211 functions as a gate
insulating layer of the transistor 110e. The conductive layer 222a
functions as one of a source and a drain of the transistor
110e.
[0359] The conductive layer 222b has a portion functioning as the
other of the source and the drain of the transistor 110e and a
portion functioning as a gate of the transistor 110f. The
conductive layer 223 functions as another gate of the transistor
110f. The insulating layer 212 and the insulating layer 218 each
function as a gate insulating layer of the transistor 110f. One of
the conductive layer 263a and the conductive layer 263b functions
as a source of the transistor 110f and the other functions as a
drain of the transistor 110f.
[0360] The conductive layer 263b is electrically connected to the
electrode 191 that functions as a pixel electrode of a
light-emitting element through an opening provided in the
insulating layer 214.
[0361] FIG. 20E illustrates a stacked-layer structure of a
transistor 110g and a transistor 110h. The transistor 110g has a
top-gate structure. The transistor 110h includes two gates. The
transistor 110g may include two gates.
[0362] The transistor 110g includes the semiconductor layer 231,
the conductive layer 221, the insulating layer 211, the conductive
layer 222a, and the conductive layer 222b. The semiconductor layer
231 is provided over the insulating layer 151. The conductive layer
221 overlaps with the semiconductor layer 231 with the insulating
layer 211 positioned therebetween. The insulating layer 211
overlaps with the conductive layer 221. The conductive layer 222a
and the conductive layer 222b are electrically connected to the
semiconductor layer 231 through openings provided in the insulating
layer 212.
[0363] The transistor 110h includes the conductive layer 222b, the
insulating layer 213, the semiconductor layer 261, the conductive
layer 223, the insulating layer 218, the insulating layer 217, the
conductive layer 263a, and the conductive layer 263b. The
conductive layer 222b includes a region overlapping with the
semiconductor layer 261 with the insulating layer 213 positioned
therebetween. The insulating layer 213 covers the conductive layer
222b. The conductive layer 263a and the conductive layer 263b are
electrically connected to the semiconductor layer 261 through
openings provided in the insulating layer 217. The conductive layer
223 overlaps with the semiconductor layer 261 with the insulating
layer 218 positioned therebetween. The insulating layer 218 is
provided in a region overlapping with the conductive layer 223.
[0364] The conductive layer 221 functions as a gate of the
transistor 110g. The insulating layer 211 functions as a gate
insulating layer of the transistor 110g. The conductive layer 222a
functions as one of a source and a drain of the transistor
110g.
[0365] The conductive layer 222b has a portion functioning as the
other of the source and the drain of the transistor 110g and a
portion functioning as a gate of the transistor 110h. The
conductive layer 223 functions as another gate of the transistor
110h. The insulating layer 212 and the insulating layer 218 each
function as a gate insulating layer of the transistor 110h. One of
the conductive layer 263a and the conductive layer 263b functions
as a source of the transistor 110h and the other functions as a
drain of the transistor 110h.
[0366] The conductive layer 263b is electrically connected to the
electrode 191 that functions as a pixel electrode of a
light-emitting element through an opening provided in the
insulating layer 214.
[0367] [Manufacturing Method Example]
[0368] Hereinafter, the method for manufacturing the display device
of this embodiment will be specifically described with reference to
FIGS. 21A to 21D, FIGS. 22A to 22C, FIGS. 23A and 23B, and FIGS.
24A and 24B.
[0369] Note that thin films included in the display device (e.g.,
insulating films, semiconductor films, or conductive films) can be
formed by any of a sputtering method, a chemical vapor deposition
(CVD) method, a vacuum evaporation method, a pulsed laser
deposition (PLD) method, an atomic layer deposition (ALD) method,
and the like. As the CVD method, a plasma-enhanced chemical vapor
deposition (PECVD) method or a thermal CVD method may be used. As
the thermal CVD method, for example, a metal organic chemical vapor
deposition (MOCVD) method may be used.
[0370] Alternatively, thin films included in the display device
(e.g., insulating films, semiconductor films, or conductive films)
can be formed by a method such as spin coating, dipping, spray
coating, ink-jetting, dispensing, screen printing, or offset
printing, or with a doctor knife, a slit coater, a roll coater, a
curtain coater, or a knife coater.
[0371] When thin films included in the display device are
processed, a lithography method or the like can be used for the
processing. Alternatively, island-shaped thin films may be formed
by a film formation method using a blocking mask. A nanoimprinting
method, a sandblasting method, a lift-off method, or the like may
be used for the processing of thin films. Examples of a
photolithography method include a method in which a resist mask is
formed over a thin film to be processed, the thin film is processed
by etching or the like, and the resist mask is removed, and a
method in which a photosensitive thin film is formed and exposed to
light and developed to be processed into a desired shape.
[0372] In the case of using light in the lithography method, any of
an i-line (light with a wavelength of 365 nm), a g-line (light with
a wavelength of 436 nm), and an h-line (light with a wavelength of
405 nm), or combined light of any of them can be used for exposure.
Alternatively, ultraviolet light, KrF laser light, ArF laser light,
or the like can be used. Exposure may be performed by liquid
immersion exposure technique. As the light for the exposure,
extreme ultra-violet (EUV) light or X-rays may be used. Instead of
the light for the exposure, an electron beam can be used. It is
preferable to use EUV, X-rays, or an electron beam because
extremely minute processing can be performed. Note that in the case
of performing exposure by scanning of a beam such as an electron
beam, a photomask is not needed.
[0373] For etching of thin films, a dry etching method, a wet
etching method, a sandblast method, or the like can be used.
[0374] An example of a manufacturing method of the display device
300 illustrated in FIG. 17 will be described below. The
manufacturing method will be described with reference to FIGS. 21A
to 21D, FIGS. 22A to 22C, FIGS. 23A and 23B, and FIGS. 24A and 24B,
focusing on the display portion 362 of the display device 300.
[0375] First, the coloring layer 131 is formed over the substrate
361 (FIG. 21A). The coloring layer 131 is formed using a
photosensitive material, in which case the processing into an
island shape can be performed by a photolithography method or the
like. Note that in the circuit 364 and the like illustrated in FIG.
17, the light-blocking layer 132 is provided over the substrate
361.
[0376] Then, the insulating layer 121 is formed over the coloring
layer 131 and the light-blocking layer 132.
[0377] The insulating layer 121 preferably functions as a
planarization layer. A resin such as acrylic or epoxy is suitably
used for the insulating layer 121.
[0378] An inorganic insulating film may be used for the insulating
layer 121. For example, an inorganic insulating film such as a
silicon nitride film, a silicon oxynitride film, a silicon oxide
film, a silicon nitride oxide film, an aluminum oxide film, or an
aluminum nitride film can be used for the insulating layer 121.
Alternatively, a hafnium oxide film, an yttrium oxide film, a
zirconium oxide film, a gallium oxide film, a tantalum oxide film,
a magnesium oxide film, a lanthanum oxide film, a cerium oxide
film, a neodymium oxide film, or the like may be used. Further
alternatively, a stack including two or more of the above
insulating films may be used.
[0379] Next, the electrode 113 is formed. The electrode 113 can be
formed in the following manner: a conductive film is formed, a
resist mask is formed, the conductive film is etched, and the
resist mask is removed. The electrode 113 is formed using a
conductive material that transmits visible light.
[0380] After that, the insulating layer 117 is formed over the
electrode 113. An organic insulating film is preferably used for
the insulating layer 117.
[0381] Subsequently, the alignment film 133b is formed over the
electrode 113 and the insulating layer 117 (FIG. 21A). The
alignment film 133b can be formed in the following manner: a thin
film is formed using a resin or the like, and then, rubbing
treatment is performed.
[0382] Note that steps illustrated in FIGS. 21B to 21D, FIGS. 22A
to 22C, FIGS. 23A and 23B, and FIG. 24A are performed independently
of the steps described with reference to FIG. 21A.
[0383] First, a separation layer 382 is formed over a formation
substrate 381, and an insulating layer 383 is formed over the
separation layer 382 (FIG. 21B).
[0384] In this step, a material is selected that would cause
separation at the interface between the formation substrate 381 and
the separation layer 382, the interface between the separation
layer 382 and the insulating layer 383, or in the separation layer
382 when the formation substrate 381 is peeled. In this embodiment,
an example in which separation occurs at the interface between the
insulating layer 383 and the separation layer 382 is described;
however, one embodiment of the present invention is not limited to
such an example and depends on a material used for the separation
layer 382 or the insulating layer 383.
[0385] The formation substrate 381 has stiffness high enough for
easy transfer and has resistance to heat applied in the
manufacturing process. Examples of a material that can be used for
the formation substrate 381 include glass, quartz, ceramics,
sapphire, a resin, a semiconductor, a metal, and an alloy. Examples
of the glass include alkali-free glass, barium borosilicate glass,
and aluminoborosilicate glass.
[0386] The separation layer 382 can be formed using an organic
material or an inorganic material.
[0387] Examples of an inorganic material that can be used for the
separation layer 382 include a metal containing an element selected
from tungsten, molybdenum, titanium, tantalum, niobium, nickel,
cobalt, zirconium, zinc, ruthenium, rhodium, palladium, osmium,
iridium, and silicon; an alloy containing any of the above
elements; and a compound containing any of the above elements. A
crystal structure of a layer containing silicon may be amorphous,
microcrystal, or polycrystal.
[0388] In the case of using an inorganic material, the thickness of
the separation layer 382 is greater than or equal to 1 nm and less
than or equal to 1000 nm, preferably greater than or equal to 10 nm
and less than or equal to 200 nm, and further preferably greater
than or equal to 10 nm and less than or equal to 100 nm.
[0389] In the case of using an inorganic material, the separation
layer 382 can be formed by a sputtering method, a CVD method, an
ALD method, or an evaporation method, for example.
[0390] Examples of an organic material that can be used for the
separation layer 382 include an acrylic resin, an epoxy resin, a
polyamide resin, a polyimide-amide resin, a siloxane resin, a
benzocyclobutene-based resin, and a phenol resin.
[0391] In the case of using an organic material, the thickness of
the separation layer 382 is preferably greater than or equal to
0.01 .mu.m and less than 10 .mu.m, further preferably greater than
or equal to 0.1 .mu.m and less than or equal to 3 .mu.m, and still
further preferably greater than or equal to 0.5 .mu.m and less than
or equal to 1 .mu.m. The separation layer 382 whose thickness is
within the above range can lead to a reduction in manufacturing
cost. The thickness of the separation layer 382 is not necessarily
within the above range and may be greater than or equal to 10
.mu.m: for example, greater than or equal to 10 .mu.m and less than
or equal to 200 .mu.m.
[0392] In the case of using an organic material, the separation
layer 382 can be formed by a method such as spin coating, dipping,
spray coating, ink-jetting, dispensing, screen printing, or offset
printing, or with a doctor knife, a slit coater, a roll coater, a
curtain coater, or a knife coater, for example.
[0393] An inorganic insulating film is preferably formed using the
insulating layer 383. For example, an inorganic insulating film
such as a silicon nitride film, a silicon oxynitride film, a
silicon oxide film, a silicon nitride oxide film, an aluminum oxide
film, or an aluminum nitride film can be used for the insulating
layer 383. Alternatively, a hafnium oxide film, an yttrium oxide
film, a zirconium oxide film, a gallium oxide film, a tantalum
oxide film, a magnesium oxide film, a lanthanum oxide film, a
cerium oxide film, a neodymium oxide film, or the like may be used.
Further alternatively, a stack including two or more of the above
insulating films may be used.
[0394] For example, a stacked-layer structure of a layer containing
a high-melting-point metal material such as tungsten and a layer
containing an oxide of the metal material may be used for the
separation layer 382, and a stacked-layer structure of a plurality
of inorganic insulating films containing silicon nitride, silicon
oxynitride, silicon nitride oxide, or the like may be used for the
insulating layer 383. When a high-melting-point metal material is
used for the separation layer 382, layers formed after the
separation layer 382 can be formed at higher temperatures; thus,
impurity concentration can be reduced and a highly reliable display
device can be fabricated. A step for removing a layer unnecessary
for the display device (e.g., the separation layer 382 or the
insulating layer 383) may be performed after the peeling. The
separation layer 382 or the insulating layer 383 is not necessarily
removed and may be used as a component of the display device.
[0395] Next, the electrode 311a is formed over the insulating layer
383, and the electrode 311b is formed over the electrode 311a (FIG.
21C). The electrode 311b includes the opening 451 over the
electrode 311a. Each of the electrodes 311a and 311b can be formed
in the following manner: a conductive film is formed, a resist mask
is formed, the conductive film is etched, and the resist mask is
removed. The electrode 311a is formed using a conductive material
that transmits visible light. The electrode 311b is formed using a
conductive material that reflects visible light.
[0396] After that, the insulating layer 220 is formed (FIG. 21D).
Then, an opening that reaches the electrode 311b is formed in the
insulating layer 220.
[0397] The insulating layer 220 can be used as a barrier layer that
prevents diffusion of impurities contained in the separation layer
382 into the transistor and the display element formed later. In
the case of using an organic material for the separation layer 382,
the insulating layer 220 preferably prevents diffusion of moisture
or the like contained in the separation layer 382 into the
transistor and the display element when the separation layer 382 is
heated. Thus, the insulating layer 220 preferably has a high
barrier property.
[0398] The insulating layer 220 can be formed using the inorganic
insulating film, the resin, or the like that can be used for the
insulating layer 121.
[0399] Next, the transistor 205 and the transistor 206 are formed
over the insulating layer 220.
[0400] There is no particular limitation on a semiconductor
material used for the semiconductor layer of the transistor, and
for example, a Group 14 element, a compound semiconductor, or an
oxide semiconductor can be used. Typically, a semiconductor
containing silicon, a semiconductor containing gallium arsenide, an
oxide semiconductor containing indium, or the like can be used.
[0401] Described here is the case where a bottom-gate transistor
including an oxide semiconductor layer as the semiconductor layer
231 is fabricated as the transistor 206. The transistor 205
includes the conductive layer 223 and the insulating layer 212 in
addition to the components of the transistor 206, and has two
gates.
[0402] An oxide semiconductor is preferably used for the
semiconductor layer of the transistor. The use of a semiconductor
material having a wider band gap and a lower carrier density than
silicon can reduce the off-state current of the transistor.
[0403] Specifically, first, the conductive layer 221a and the
conductive layer 221b are formed over the insulating layer 220. The
conductive layer 221a and the conductive layer 221b can be formed
in the following manner: a conductive film is formed, a resist mask
is formed, the conductive film is etched, and the resist mask is
removed. At this time, the conductive layer 221b and the electrode
311b are connected to each other through an opening in the
insulating layer 220.
[0404] Next, the insulating layer 211 is formed.
[0405] For the insulating layer 211, for example, an inorganic
insulating film such as a silicon nitride film, a silicon
oxynitride film, a silicon oxide film, a silicon nitride oxide
film, an aluminum oxide film, or an aluminum nitride film can be
used. Alternatively, a hafnium oxide film, an yttrium oxide film, a
zirconium oxide film, a gallium oxide film, a tantalum oxide film,
a magnesium oxide film, a lanthanum oxide film, a cerium oxide
film, a neodymium oxide film, or the like may be used. Further
alternatively, a stack including two or more of the above
insulating films may be used.
[0406] An inorganic insulating film is preferably formed at high
temperatures because the film can have higher density and a higher
barrier property as the deposition temperature becomes higher. The
substrate temperature during the deposition of the inorganic
insulating film is preferably higher than or equal to room
temperature (25.degree. C.) and lower than or equal to 350.degree.
C., and further preferably higher than or equal to 100.degree. C.
and lower than or equal to 300.degree. C.
[0407] Then, the semiconductor layer 231 is formed. In this
embodiment, an oxide semiconductor layer is formed as the
semiconductor layer 231. The oxide semiconductor layer can be
formed in the following manner: an oxide semiconductor film is
formed, a resist mask is formed, the oxide semiconductor film is
etched, and the resist mask is removed.
[0408] The substrate temperature during the deposition of the oxide
semiconductor film is preferably lower than or equal to 350.degree.
C., further preferably higher than or equal to room temperature and
lower than or equal to 200.degree. C., and still further preferably
higher than or equal to room temperature and lower than or equal to
130.degree. C.
[0409] The oxide semiconductor film can be formed using one or both
of an inert gas and an oxygen gas. Note that there is no particular
limitation on the percentage of oxygen flow rate (partial pressure
of oxygen) at the time of forming the oxide semiconductor film. To
fabricate a transistor having high field-effect mobility, however,
the percentage of oxygen flow rate (partial pressure of oxygen) at
the time of forming the oxide semiconductor film is preferably
higher than or equal to 0% and lower than or equal to 30%, further
preferably higher than or equal to 5% and lower than or equal to
30%, and still further preferably higher than or equal to 7% and
lower than or equal to 15%.
[0410] The oxide semiconductor film preferably contains at least
indium or zinc. It is particularly preferable to contain indium and
zinc.
[0411] The energy gap of the oxide semiconductor is preferably 2 eV
or more, further preferably 2.5 eV or more, and still further
preferably 3 eV or more. The use of such an oxide semiconductor
having a wide energy gap leads to a reduction in off-state current
of a transistor.
[0412] The oxide semiconductor film can be formed by a sputtering
method. Alternatively, a PLD method, a PECVD method, a thermal CVD
method, an ALD method, a vacuum evaporation method, or the like may
be used.
[0413] Note that an example of an oxide semiconductor is described
in Embodiment 4.
[0414] Next, the conductive layer 222a and the conductive layer
222b are formed. The conductive layer 222a and the conductive layer
222b can be formed in the following manner: a conductive film is
formed, a resist mask is formed, the conductive film is etched, and
the resist mask is removed. Each of the conductive layers 222a and
222b is connected to the semiconductor layer 231. Here, the
conductive layer 222a included in the transistor 206 is
electrically connected to the conductive layer 221b. As a result,
the electrode 311b and the conductive layer 222a can be
electrically connected to each other at the connection portion
207.
[0415] Note that during the processing of the conductive layer 222a
and the conductive layer 222b, the semiconductor layer 231 might be
partly etched to be thin in a region not covered by the resist
mask.
[0416] In the above manner, the transistor 206 can be fabricated
(FIG. 21D). In the transistor 206, part of the conductive layer
221a functions as a gate, part of the insulating layer 211
functions as a gate insulating layer, and the conductive layer 222a
and the conductive layer 222b function as a source and a drain.
[0417] Next, the insulating layer 212 that covers the transistor
206 is formed, and the conductive layer 223 is formed over the
insulating layer 212.
[0418] The insulating layer 212 can be formed in a manner similar
to that of the insulating layer 211.
[0419] The conductive layer 223 included in the transistor 205 can
be formed in the following manner: a conductive film is formed, a
resist mask is formed, the conductive film is etched, and the
resist mask is removed.
[0420] In the above manner, the transistor 205 can be fabricated
(FIG. 21D). In the transistor 205, part of the conductive layer
221a and part of the conductive layer 223 function as gates, part
of the insulating layer 211 and part of the insulating layer 212
function as gate insulating layers, and the conductive layer 222a
and the conductive layer 222b function as a source and a drain.
[0421] Next, the insulating layer 213 is formed (FIG. 21D). The
insulating layer 213 can be formed in a manner similar to that of
the insulating layer 211.
[0422] It is preferable to use an oxide insulating film formed in
an atmosphere containing oxygen, such as a silicon oxide film or a
silicon oxynitride film, for the insulating layer 212. An
insulating film with low oxygen diffusibility and oxygen
permeability, such as a silicon nitride film, is preferably stacked
as the insulating layer 213 over the silicon oxide film or the
silicon oxynitride film. The oxide insulating film formed in an
atmosphere containing oxygen can easily release a large amount of
oxygen by heating. When a stack including such an oxide insulating
film that releases oxygen and an insulating film with low oxygen
diffusibility and oxygen permeability is heated, oxygen can be
supplied to the oxide semiconductor layer. As a result, oxygen
vacancies in the oxide semiconductor layer can be filled and
defects at the interface between the oxide semiconductor layer and
the insulating layer 212 can be repaired, leading to a reduction in
defect levels. Accordingly, an extremely highly reliable display
device can be fabricated.
[0423] Next, the coloring layer 134 is formed over the insulating
layer 213 (FIG. 21D), and then, the insulating layer 214 is formed
(FIG. 22A). The coloring layer 134 is positioned so as to overlap
with the opening 451 in the electrode 311b.
[0424] The coloring layer 134 can be formed in a manner similar to
that of the coloring layer 131. The display element is formed on
the insulating layer 214 in a later step; thus, the insulating
layer 214 preferably functions as a planarization layer. For the
insulating layer 214, the description of the resin or the inorganic
insulating film that can be used for the insulating layer 121 can
be referred to.
[0425] After that, an opening that reaches the conductive layer
222b included in the transistor 205 is formed in the insulating
layer 212, the insulating layer 213, and the insulating layer
214.
[0426] Subsequently, the electrode 191 is formed (FIG. 22A). The
electrode 191 can be formed in the following manner: a conductive
film is formed, a resist mask is formed, the conductive film is
etched, and the resist mask is removed. Here, the conductive layer
222b included in the transistor 205 and the electrode 191 are
connected to each other. The electrode 191 is formed using a
conductive material that transmits visible light.
[0427] Then, the insulating layer 216 that covers the end portion
of the electrode 191 is formed (FIG. 22B). For the insulating layer
216, the description of the resin or the inorganic insulating film
that can be used for the insulating layer 121 can be referred to.
The insulating layer 216 includes an opening in a region
overlapping with the electrode 191.
[0428] Next, the EL layer 192 and the electrode 193 are formed
(FIG. 22B). Part of the electrode 193 functions as the common
electrode of the light-emitting element 170. The electrode 193 is
formed using a conductive material that reflects visible light.
[0429] The EL layer 192 can be formed by an evaporation method, a
coating method, a printing method, a discharge method, or the like.
In the case where the EL layer 192 is formed for each individual
pixel, an evaporation method using a shadow mask such as a metal
mask, an ink-jet method, or the like can be used. In the case of
sharing the EL layer 192 by some pixels, an evaporation method not
using a metal mask can be used.
[0430] Either a low molecular compound or a high molecular compound
can be used for the EL layer 192, and an inorganic compound may
also be included.
[0431] Steps after the formation of the EL layer 192 are performed
such that temperatures higher than the heat resistant temperature
of the EL layer 192 are not applied to the EL layer 192. The
electrode 193 can be formed by an evaporation method, a sputtering
method, or the like.
[0432] In the above manner, the light-emitting element 170 can be
formed (FIG. 22B). In the light-emitting element 170, the electrode
191 part of which functions as the pixel electrode, the EL layer
192, and the electrode 193 part of which functions as the common
electrode are stacked. The light-emitting element 170 is formed
such that the light-emitting region overlaps with the coloring
layer 134 and the opening 451 in the electrode 311b.
[0433] Although an example where a bottom-emission light-emitting
element is formed as the light-emitting element 170 is described
here, one embodiment of the present invention is not limited
thereto.
[0434] The light-emitting element may be a top emission, bottom
emission, or dual emission light-emitting element. A conductive
film that transmits visible light is used as the electrode through
which light is extracted. A conductive film that reflects visible
light is preferably used as the electrode through which light is
not extracted.
[0435] Next, the insulating layer 194 is formed so as to cover the
electrode 193 (FIG. 22B). The insulating layer 194 functions as a
protective layer that prevents diffusion of impurities such as
water into the light-emitting element 170. The light-emitting
element 170 is sealed with the insulating layer 194. After the
electrode 193 is formed, the insulating layer 194 is preferably
formed without exposure to the air.
[0436] The inorganic insulating film that can be used for the
insulating layer 121 can be used for the insulating layer 194, for
example. It is particularly preferable that the insulating layer
194 include an inorganic insulating film with a high barrier
property. A stack including an inorganic insulating film and an
organic insulating film can also be used.
[0437] The insulating layer 194 is preferably formed at substrate
temperature lower than or equal to the heat resistant temperature
of the EL layer 192. The insulating layer 194 can be formed by an
ALD method, a sputtering method, or the like. An ALD method and a
sputtering method are preferable because a film can be formed at
low temperatures. An ALD method is preferable because the coverage
of the insulating layer 194 is improved.
[0438] Then, the substrate 351 is bonded to a surface of the
insulating layer 194 with the adhesive layer 142 (FIG. 22C).
[0439] As the adhesive layer 142, any of a variety of curable
adhesives such as a reactive curable adhesive, a thermosetting
adhesive, an anaerobic adhesive, and a photocurable adhesive such
as an ultraviolet curable adhesive can be used. Alternatively, an
adhesive sheet or the like may be used.
[0440] For the substrate 351, a polyester resin such as
polyethylene terephthalate (PET) or polyethylene naphthalate (PEN),
a polyacrylonitrile resin, an acrylic resin, a polyimide resin, a
polymethyl methacrylate resin, a polycarbonate (PC) resin, a
polyethersulfone (PES) resin, a polyamide resin (e.g., nylon or
aramid), a polysiloxane resin, a cycloolefin resin, a polystyrene
resin, a polyamide-imide resin, a polyurethane resin, a polyvinyl
chloride resin, a polyvinylidene chloride resin, a polypropylene
resin, a polytetrafluoroethylene (PTFE) resin, an ABS resin, or
cellulose nanofiber can be used, for example. Any of a variety of
materials such as glass, quartz, a resin, a metal, an alloy, and a
semiconductor can be used for the substrate 351. The substrate 351
formed using any of a variety of materials such as glass, quartz, a
resin, a metal, an alloy, and a semiconductor may be thin enough to
be flexible.
[0441] After that, the formation substrate 381 is peeled (FIG.
23A).
[0442] The position of the separation surface depends on the
materials, the formation methods, and the like of the insulating
layer 383, the separation layer 382, the formation substrate 381,
and the like.
[0443] FIG. 23A illustrates an example where the separation occurs
at the interface between the separation layer 382 and the
insulating layer 383. By the separation, the insulating layer 383
is exposed.
[0444] Before the separation, a separation trigger may be formed in
the separation layer 382. For example, part of or the entire
separation layer 382 may be irradiated with laser light, in which
case the separation layer 382 can be embrittled or the adhesion
between the separation layer 382 and the insulating layer 383 (or
the formation substrate 381) can be reduced.
[0445] The formation substrate 381 can be peeled by applying a
perpendicular tensile force to the separation layer 382, for
example. Specifically, the formation substrate 381 can be peeled by
pulling up the substrate 351 by part of its suction-attached top
surface.
[0446] The separation trigger may be formed by inserting a sharp
instrument such as a knife between the separation layer 382 and the
insulating layer 383 (or the formation substrate 381).
Alternatively, the separation trigger may be formed by cutting the
separation layer 382 from the substrate 351 side with a sharp
instrument.
[0447] Next, the insulating layer 383 is removed. The insulating
layer 383 can be removed by a dry etching method, for example.
Accordingly, the electrode 311a is exposed (FIG. 23B).
[0448] Subsequently, the alignment film 133a is formed on the
exposed surface of the electrode 311a (FIG. 24A). The alignment
film 133a can be formed in the following manner: a thin film is
formed using a resin or the like, and then, rubbing treatment is
performed.
[0449] Then, the substrate 361 obtained from the steps described
using FIG. 21A and the substrate 351 obtained from the steps up to
the step illustrated in FIG. 24A are bonded to each other with the
liquid crystal layer 112 provided therebetween (FIG. 24B). Although
not illustrated in FIG. 24B, the substrate 351 and the substrate
361 are bonded to each other with the adhesive layer 141 as
illustrated in FIG. 17 and other drawings. For materials of the
adhesive layer 141, the description of the materials that can be
used for the adhesive layer 142 can be referred to.
[0450] In the liquid crystal element 180 illustrated in FIG. 24B,
the electrode 311a (and the electrode 311b) part of which functions
as the pixel electrode, the liquid crystal layer 112, and the
electrode 113 part of which functions as the common electrode are
stacked. The liquid crystal element 180 is formed so as to overlap
with the coloring layer 131.
[0451] Through the above steps, the display device 300 can be
fabricated.
[0452] The display device of this embodiment includes two types of
display elements as described above; thus, switching between a
plurality of display modes is possible. Accordingly, the display
device can have high visibility regardless of the ambient
brightness, leading to high convenience.
[0453] In the case where a plurality of structure examples are
described in one embodiment in this specification, some of the
structure examples can be combined as appropriate.
[0454] At least part of this embodiment can be implemented in
combination with any of the other embodiments described in this
specification as appropriate.
Embodiment 6
[0455] In this embodiment, described below is the composition of a
cloud-aligned composite oxide semiconductor (CAC-OS) applicable to
a transistor disclosed in one embodiment of the present
invention.
[0456] The CAC-OS refers to, for example, a composition of a
material in which elements included in an oxide semiconductor are
unevenly distributed. The material including unevenly distributed
elements has a size of greater than or equal to 0.5 nm and less
than or equal to 10 nm, preferably greater than or equal to 1 nm
and less than or equal to 2 nm, or a similar size. Note that in the
following description of an oxide semiconductor, a state in which
one or more metal elements are unevenly distributed and regions
including the metal element(s) are mixed is referred to as a mosaic
pattern or a patch-like pattern. The region has a size of greater
than or equal to 0.5 nm and less than or equal to 10 nm, preferably
greater than or equal to 1 nm and less than or equal to 2 nm, or a
similar size.
[0457] Note that an oxide semiconductor preferably contains at
least indium. In particular, indium and zinc are preferably
contained. In addition, one or more of aluminum, gallium, yttrium,
copper, vanadium, beryllium, boron, silicon, titanium, iron,
nickel, germanium, zirconium, molybdenum, lanthanum, cerium,
neodymium, hafnium, tantalum, tungsten, magnesium, and the like may
be contained.
[0458] For example, of the CAC-OS, an In--Ga--Zn oxide with the CAC
composition (such an In--Ga--Zn oxide may be particularly referred
to as CAC-IGZO) has a composition in which indium oxide (InO.sub.n,
where X1 is a real number greater than 0) or indium zinc oxide
(In.sub.X2Zn.sub.Y2O.sub.Z2, where X2, Y2, and Z2 are real numbers
greater than 0) forming a mosaic pattern is evenly distributed in
the film (this composition is also referred to as a cloud-like
composition). The mosaic pattern is formed by separating the
materials into InO.sub.X1 or In.sub.X2Zn.sub.Y2O.sub.Z2 and gallium
oxide (GaO.sub.X3, where X3 is a real number greater than 0) or
gallium zinc oxide (Ga.sub.X4Zn.sub.Y4O.sub.Z4, where X4, Y4, and
Z4 are real numbers greater than 0), for example.
[0459] That is, the CAC-OS is a composite oxide semiconductor with
a composition in which a region including GaO.sub.X3 as a main
component and a region including In.sub.X2Zn.sub.Y2O.sub.Z2 or
InO.sub.X1 as a main component are mixed. Note that in this
specification, for example, when the atomic ratio of In to an
element M in a first region is greater than the atomic ratio of In
to an element M in a second region, the first region is described
as having higher In concentration than the second region.
[0460] Note that a compound including In, Ga, Zn, and O is also
known as IGZO. Typical examples of IGZO include a crystalline
compound represented by InGaO.sub.3(ZnO).sub.m1 (m1 is a natural
number) and a crystalline compound represented by
In.sub.(1+X0Ga(.sub.1-X0)O.sub.3(ZnO).sub.m0(-1.ltoreq.X0.ltoreq.1;
m0 is a given number).
[0461] The above crystalline compounds have a single crystal
structure, a polycrystalline structure, or a CAAC structure. Note
that the CAAC structure is a crystal structure in which a plurality
of IGZO nanocrystals have c-axis alignment and are connected in the
a-b plane direction without alignment.
[0462] The CAC-OS relates to the material composition of an oxide
semiconductor. In a material composition of a CAC-OS including In,
Ga, Zn, and O, nanoparticle regions including Ga as a main
component are observed in part of the CAC-OS and nanoparticle
regions including In as a main component are observed in part
thereof. These nanoparticle regions are randomly dispersed to form
a mosaic pattern. Therefore, the crystal structure is a secondary
element for the CAC-OS.
[0463] Note that in the CAC-OS, a stacked-layer structure including
two or more films with different atomic ratios is not included. For
example, a two-layer structure of a film including In as a main
component and a film including Ga as a main component is not
included.
[0464] A boundary between the region including GaO.sub.X3 as a main
component and the region including In.sub.X2Zn.sub.Y2O.sub.Z2 or
InO.sub.X1 as a main component is not clearly observed in some
cases.
[0465] In the case where one or more of aluminum, yttrium, copper,
vanadium, beryllium, boron, silicon, titanium, iron, nickel,
germanium, zirconium, molybdenum, lanthanum, cerium, neodymium,
hafnium, tantalum, tungsten, magnesium, and the like are contained
instead of gallium in a CAC-OS, nanoparticle regions including the
selected element(s) as a main component(s) are observed in part of
the CAC-OS and nanoparticle regions including In as a main
component are observed in part of the CAC-OS, and these
nanoparticle regions are randomly dispersed to form a mosaic
pattern in the CAC-OS.
[0466] The CAC-OS can be formed by a sputtering method under a
condition where a substrate is not heated intentionally. In the
case where the CAC-OS is formed by a sputtering method, one or more
of an inert gas (typically, argon), an oxygen gas, and a nitrogen
gas are used as a deposition gas. Furthermore, the flow rate of the
oxygen gas to the total flow rate of the deposition gas in
deposition is preferably as low as possible, for example, the flow
rate of the oxygen gas is higher than equal to 0% and lower than
30%, preferably higher than equal to 0% and lower than or equal to
10%.
[0467] The CAC-OS is characterized in that a clear peak is not
observed when measurement is conducted using a .theta./2.theta.
scan by an out-of-plane method with an X-ray diffraction (XRD).
That is, it is found by the XRD that there are no alignment in the
a-b plane direction and no alignment in the c-axis direction in the
measured areas.
[0468] In the CAC-OS, an electron diffraction pattern that is
obtained by irradiation with an electron beam with a probe diameter
of 1 nm (also referred to as nanobeam electron beam) has regions
with high luminance in a ring pattern and a plurality of bright
spots appear in the ring-like pattern. Thus, it is found from the
electron diffraction pattern that the crystal structure of the
CAC-OS includes a nanocrystalline (nc) structure that does not show
alignment in the plane direction and the cross-sectional
direction.
[0469] For example, energy dispersive X-ray spectroscopy (EDX) is
used to obtain EDX mapping, and according to the EDX mapping, the
CAC-OS of the In--Ga--Zn oxide has a composition in which the
regions including GaO.sub.X3 as a main component and the regions
including In.sub.X2Zn.sub.Y2O.sub.Z2 or InO.sub.X1 as a main
component are unevenly distributed and mixed.
[0470] The CAC-OS has a structure different from that of an IGZO
compound in which metal elements are evenly distributed, and has
characteristics different from those of the IGZO compound. That is,
in the CAC-OS, regions including GaO.sub.X3 or the like as a main
component and regions including In.sub.X2Zn.sub.Y2O.sub.Z2 or
InO.sub.X1 as a main component are separated to form a mosaic
pattern.
[0471] The conductivity of a region including
In.sub.X2Zn.sub.Y2O.sub.Z2 or InO.sub.X1 as a main component is
higher than that of a region including GaO.sub.X3 or the like as a
main component. In other words, when carriers flow through regions
including In.sub.X2Zn.sub.Y2O.sub.Z2 or InO.sub.X1 as a main
component, the conductivity of an oxide semiconductor is generated.
Accordingly, when regions including In.sub.X2Zn.sub.Y2O.sub.Z2 or
InO.sub.X1 as a main component are distributed in an oxide
semiconductor like a cloud, high field-effect mobility (.mu.) can
be achieved.
[0472] In contrast, the insulating property of a region including
GaO.sub.X3 or the like as a main component is higher than that of a
region including In.sub.X2Zn.sub.Y2O.sub.Z2 or InO.sub.X1 as a main
component. In other words, when regions including GaO.sub.X3 or the
like as a main component are distributed in an oxide semiconductor,
leakage current can be suppressed and favorable switching operation
can be achieved.
[0473] Accordingly, when a CAC-OS is used in a semiconductor
element, the insulating property derived from GaO.sub.X3 or the
like and the conductivity derived from In.sub.X2Zn.sub.Y2O.sub.Z2
or InO.sub.X1 complement each other, whereby high on-state current
(I.sub.on) and high field-effect mobility (.mu.) can be
achieved.
[0474] A semiconductor element including a CAC-OS has high
reliability. Thus, the CAC-OS is suitably used in a variety of
semiconductor devices typified by a display.
[0475] At least part of this embodiment can be implemented in
combination with any of the other embodiments described in this
specification as appropriate.
[0476] This application is based on Japanese Patent Application
serial no. 2016-135870 filed with Japan Patent Office on Jul. 8,
2016, the entire contents of which are hereby incorporated by
reference.
* * * * *