U.S. patent application number 12/731482 was filed with the patent office on 2010-10-07 for liquid crystal display device and manufacturing method thereof.
This patent application is currently assigned to SEMICONDUCTOR ENERGY LABORATORY CO., LTD.. Invention is credited to Tetsuji ISHITANI, Shunpei YAMAZAKI.
Application Number | 20100253902 12/731482 |
Document ID | / |
Family ID | 42825916 |
Filed Date | 2010-10-07 |
United States Patent
Application |
20100253902 |
Kind Code |
A1 |
YAMAZAKI; Shunpei ; et
al. |
October 7, 2010 |
LIQUID CRYSTAL DISPLAY DEVICE AND MANUFACTURING METHOD THEREOF
Abstract
Disclosed is a liquid crystal display device which can be used
in a variety of situations and applications. The liquid crystal
display device comprises: a first substrate comprising a first
display region, a second display region, and a third display region
wherein the first display region, the second display region, and
the third display region are continuously formed; a second
substrate having a form which fits the first substrate; and a
liquid crystal interposed between the first substrate and the
second substrate. The second display region is interposed between
the first display region and the second display region. The second
display region is curved, and the first display region and the
second display region are substantially flat.
Inventors: |
YAMAZAKI; Shunpei;
(Setagaya, JP) ; ISHITANI; Tetsuji; (Atsugi,
JP) |
Correspondence
Address: |
Robinson Intellectual Property Law Office, P.C.
3975 Fair Ridge Drive, Suite 20 North
Fairfax
VA
22033
US
|
Assignee: |
SEMICONDUCTOR ENERGY LABORATORY
CO., LTD.
Kanagawa-ken
JP
|
Family ID: |
42825916 |
Appl. No.: |
12/731482 |
Filed: |
March 25, 2010 |
Current U.S.
Class: |
349/158 ;
257/E21.535; 438/30 |
Current CPC
Class: |
H01L 27/1218 20130101;
H01L 27/1266 20130101; G02F 1/1303 20130101; G02F 1/133305
20130101 |
Class at
Publication: |
349/158 ; 438/30;
257/E21.535 |
International
Class: |
G02F 1/1333 20060101
G02F001/1333; H01L 21/50 20060101 H01L021/50 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 7, 2009 |
JP |
2009-093392 |
Claims
1. A manufacturing method for a liquid crystal display device
comprising: forming an element layer comprising a thin film
transistor over a supporting substrate; shaping a first substrate
into a form having a curved region and a flat region by attaching
the first substrate to a first support which has a curved portion
and a flat portion; transferring the element layer from the
supporting substrate to the first substrate; shaping a second
substrate into a form having a curved region and a flat region by
attaching the second substrate to an inside of a second support
which has a curved portion and a flat portion; and attaching the
first substrate to the second substrate so that the element layer
is interposed therebetween.
2. The manufacturing method according to claim 1, wherein the first
substrate and the second substrate are flexible.
3. The manufacturing method according to claim 1, further
comprising: forming a spacer over the second substrate before
shaping the second substrate, wherein the first substrate is
attached to the second substrate so that the spacer is interposed
therebetween.
4. The manufacturing method according to claim 1, further
comprising: bonding the first substrate to the second substrate
with a sealant.
5. The manufacturing method according to claim 1, further
comprising: providing a backlight in a concave which is formed by
the curved region and the flat region of the first substrate.
6. The manufacturing method according to claim 1, wherein the
formation of the element layer is performed by transferring the
element layer provided over a manufacturing substrate to the first
substrate.
7. The manufacturing method according to claim 1, further
comprising dripping a liquid crystal on one of the first substrate
and the second substrate prior to attaching the first substrate and
the second substrate.
8. The manufacturing method according to claim 1, further
comprising: injecting a liquid crystal between the first substrate
and the second substrate after the first substrate is attached to
the second substrate.
9. A manufacturing method for a liquid crystal display device
comprising: forming an element layer comprising a thin film
transistor over a supporting substrate; shaping a first substrate
into a form having a curved region and a flat region by attaching
the first substrate to a first support which has a curved portion
and a flat portion; forming a first protective film over the first
substrate so that the first protective film covers the curved
region and the flat region of the first substrate; transferring the
element layer over the first protective film; shaping a second
substrate into a form having a curved region and a flat region by
attaching the second substrate to an inside of a second support
which has a curved portion and a flat portion; and attaching the
first substrate to the second substrate so that the element layer
and the first protective film are interposed therebetween.
10. The manufacturing method according to claim 9, wherein the
first substrate and the second substrate are flexible.
11. The manufacturing method according to claim 9, further
comprising: forming a spacer over the second substrate before
shaping the second substrate, wherein the first substrate is
attached to the second substrate so that the spacer is interposed
therebetween.
12. The manufacturing method according to claim 9, further
comprising: bonding the first substrate to the second substrate
with a sealant.
13. The manufacturing method according to claim 9, further
comprising: providing a backlight in a concave which is formed by
the curved region and the flat region of the first substrate.
14. The manufacturing method according to claim 9, wherein the
formation of the element layer is performed by transferring the
element layer provided over a manufacturing substrate to the first
substrate.
15. The manufacturing method according to claim 9, further
comprising: dripping a liquid crystal on one of the first substrate
and the second substrate prior to attaching the first substrate and
the second substrate.
16. The manufacturing method according to claim 9, further
comprising: injecting a liquid crystal between the first substrate
and the second substrate after the first substrate is attached to
the second substrate.
17. The manufacturing method according to claim 9, further
comprising: forming a second protective layer over the second
substrate after shaping the second substrate.
18. A liquid crystal display device comprising: a first substrate
comprising a first display region, a second display region, and a
third display region wherein the first display region, the second
display region, and the third display region are continuously
formed; a second substrate having a form which fits the first
substrate; and a liquid crystal layer interposed between the first
substrate and the second substrate, wherein the second display
region is interposed between the first display region and the third
display region, wherein the second display region is curved, and
wherein the first display region and the third display region are
substantially flat.
19. The liquid crystal display device according to claim 18,
wherein a plane of the first display region is substantially
perpendicular to a plane of the third display region.
20. The liquid crystal display device according to claim 18,
further comprising a backlight, wherein the backlight is placed in
a concave which is formed by the first display region, the second
display region, and the third display region.
21. The liquid crystal display device according to claim 18,
further comprising a touch screen over the first display
region.
22. The liquid crystal display device according to claim 18,
wherein the first substrate and the second substrate are
flexible.
23. A liquid crystal display device comprising: a first substrate
comprising a first display region, a second display region, and a
third display region wherein the first display region, the second
display region, and the third display region are continuously
formed; an element layer comprising a thin film transistor formed
over the first display region, the second display region, and the
third display region; a pixel electrode layer over the element
layer; a liquid crystal layer over the pixel electrode layer; a
counter electrode layer over the liquid crystal layer; and a second
substrate over the counter electrode layer, the second substrate
having a form which fits the first substrate; wherein the second
display region is interposed between the first display region and
the third display region, wherein the second display region is
curved, and wherein the first display region and the third display
region are substantially flat.
24. The liquid crystal display device according to claim 23,
wherein a plane of the first display region is substantially
perpendicular to a plane of the third display region.
25. The liquid crystal display device according to claim 23,
further comprising a backlight, wherein the backlight is placed in
a concave which is formed by the first display region, the second
display region, and the third display region.
26. The liquid crystal display device according to claim 23,
further comprising a touch screen over the first display
region.
27. The liquid crystal display device according to claim 23,
wherein the first substrate and the second substrate are flexible.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a liquid crystal display
device and a method for manufacturing the same.
[0003] 2. Description of the Related Art
[0004] In recent years, display devices have been used in a variety
of places for a variety of applications and therefore have been
required to have diverse characteristics and shapes. Accordingly,
display devices serving their intended purposes have been actively
developed.
[0005] For example, a liquid crystal panel using a plastic
substrate has been produced to reduce the weight thereof (e.g., see
Non-Patent Document 1).
REFERENCE
[0006] [Non-Patent Document 1] Akihiko ASANO and Tomoatsu
KINOSHITA, SID DIGEST, 2002, pp. 1196-1199
SUMMARY OF THE INVENTION
[0007] Thus, an object of one embodiment of the present invention
is to provide a more convenient liquid crystal display device which
can be used for a variety of applications. Another object of one
embodiment of the present invention is to manufacture, without
complicating the process, a liquid crystal display device having a
shape suitable for its intended purpose.
[0008] In the manufacturing process of the liquid crystal display
device, the liquid crystal display device is shaped after the
manufacture of an electrode layer and an element layer, thereby
having a more useful function.
[0009] The shape of the liquid crystal display device can be freely
determined by selecting the shape of a mold used for shaping the
liquid crystal display device. Accordingly, it is possible to
manufacture various kinds of liquid crystal display devices capable
of being used in a variety of places for a variety of applications,
which allows a convenient liquid crystal display device to be
provided.
[0010] One embodiment of the invention disclosed in this
specification includes: a supporting member that is at least partly
curved; and a liquid crystal display panel that includes a liquid
crystal material sealed between a pair of flexible substrates and
is provided in contact with an inner surface of the supporting
member.
[0011] Another embodiment of the invention disclosed in this
specification includes: a supporting member that has a curved
portion and has a first surface and a second surface with the
curved portion therebetween; and a liquid crystal display panel
that includes a liquid crystal material sealed between a pair of
flexible substrates and is provided in contact with an inner
surface of the supporting member. The liquid crystal display panel
has a first display area, a second display area, and a third
display area which are formed continuously, and the first display
area is faces the first surface of the supporting member, the
second display area faces the second surface of the supporting
member, and the third display area faces the curved portion of the
supporting member.
[0012] A still another embodiment of the invention disclosed in
this specification includes: a first substrate that is at least
partly curved; a second substrate fitting into the first substrate
with a spacer interposed therebetween; and a liquid crystal
material filling a space between the first substrate and the second
substrate.
[0013] A further embodiment of the invention disclosed in this
specification includes: a first substrate that is at least partly
curved; a second substrate fitting into the first substrate with a
spacer interposed therebetween; and a liquid crystal material
filling a space between the first substrate and the second
substrate. A first display area is formed on one of the surfaces
holding the curved portion therebetween, and a second display area
is formed on the other surface. A third display area is formed on
the curved surface. The first display area and the second display
area may be substantially flat, and a plane of the first display
area may be perpendicular to a plane of the second display
area.
[0014] A manufacturing method of a liquid crystal display having
the above-mentioned structure is also included in an embodiment of
the invention.
[0015] In the above structures, the liquid crystal display device
may be provided with a protective film. The protective film may be
formed to cover the outside of the liquid crystal display panel, or
may be formed between a liquid crystal layer and each of the first
substrate and the second substrate. The liquid crystal display
device may include a sensor portion. For example, a touch sensor (a
touch screen) can be provided in a supporting member on the viewer
side.
[0016] In the case of a transmissive liquid crystal display device,
a backlight may be provided to light a display area. The backlight
is preferably curved in accordance with the shape of the liquid
crystal display device.
[0017] Note that the ordinal numbers such as "first" and "second"
are used for convenience and do not denote the order of steps and
the stacking order of layers. In addition, the ordinal numbers in
this specification do not denote particular names which specify the
present invention.
[0018] Note that a semiconductor device in this specification
refers to all the devices that can operate by using semiconductor
characteristics, and an electro-optical device, a semiconductor
circuit, and an electronic appliance are all included in the
semiconductor device.
[0019] The shape of the liquid crystal display device can be freely
determined by selecting the shape of the mold used for shaping the
liquid crystal display device. Accordingly, it is possible to
manufacture various kinds of liquid crystal display devices capable
of being used in a variety of places for a variety of applications,
which allows a convenient liquid crystal display device to be
provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In the accompanying drawings:
[0021] FIGS. 1A to 1D are diagrams illustrating a method for
manufacturing a liquid crystal display device;
[0022] FIGS. 2A to 2C are diagrams illustrating a method for
manufacturing a liquid crystal display device;
[0023] FIGS. 3A to 3C are diagrams illustrating a method for
manufacturing a liquid crystal display device;
[0024] FIGS. 4A to 4D are diagrams illustrating a method for
manufacturing a liquid crystal display device;
[0025] FIGS. 5A to 5C are diagrams illustrating a method for
manufacturing a liquid crystal display device;
[0026] FIGS. 6A to 6C are diagrams illustrating a method for
manufacturing a liquid crystal display device;
[0027] FIGS. 7A to 7F are diagrams illustrating a method for
manufacturing a liquid crystal display device;
[0028] FIGS. 8A and 8B are diagrams illustrating a method for
manufacturing a liquid crystal display device;
[0029] FIGS. 9A and 9B are diagrams each illustrating a liquid
crystal display device;
[0030] FIGS. 10A and 10B are diagrams each illustrating a liquid
crystal display module;
[0031] FIGS. 11A1 to 11C2 are diagrams illustrating a method for
manufacturing a liquid crystal display device;
[0032] FIG. 12 is a diagram illustrating a liquid crystal display
module;
[0033] FIGS. 13A to 13D are diagrams each illustrating a
semiconductor element that can be used for a liquid crystal display
device;
[0034] FIGS. 14A to 14D are diagrams illustrating an example of a
cellular phone using a liquid crystal display device; and
[0035] FIG. 15 is a diagram illustrating an example of a cellular
phone using a liquid crystal display device.
DETAILED DESCRIPTION OF THE INVENTION
[0036] Embodiments of the present invention will be described in
detail with reference to drawings. Note that the present invention
is not limited to the description below, and it is apparent to
those skilled in the art that modes and details can be modified in
various ways without departing from the spirit and scope of the
present invention. Accordingly, the present invention should not be
construed as being limited to the description of the embodiments
given below. Note that in the structures of the present invention
described below, like portions or portions having a similar
function are denoted by the same reference numerals, and the
description thereof is omitted.
Embodiment 1
[0037] A liquid crystal display device will be described with
reference to FIGS. 1A to 1D, FIGS. 2A to 2C, and FIGS. 3A to
3C.
[0038] FIGS. 1A to 1D, FIGS. 2A to 2C, and FIGS. 3A to 3C are
cross-sectional views illustrating a method for manufacturing a
liquid crystal display device.
[0039] The liquid crystal display device includes at least a liquid
crystal layer, a pair of substrates holding the liquid crystal
layer therebetween, and an electrode layer for applying voltage to
the liquid crystal layer. The liquid crystal display device may
also be provided with a semiconductor element, preferably a thin
film transistor. In the case of an active matrix liquid crystal
display device, a driving thin film transistor is provided in each
pixel.
[0040] Although an active matrix liquid crystal display device is
shown as an example in this embodiment, this embodiment can also be
applied to a passive matrix liquid crystal display device.
[0041] In a manufacturing process of the liquid crystal display
device in this embodiment, the liquid crystal display device is
shaped after the manufacture of the electrode layer and an element
layer, thereby having a more useful function.
[0042] An element layer 101 is formed over a manufacturing
substrate 100 (see FIG. 1A). The element layer 101 includes a thin
film transistor. Next, the element layer 101 is transferred to a
supporting substrate 102 (see FIG. 1B).
[0043] A first substrate 110 is provided along a curved surface of
a first support 111 serving as a mold for the liquid crystal
display device (see FIG. 1C). The first substrate 110 may be
attached to the first support 111 with an adhesive layer or the
like. By this step, the first substrate 110 is processed to a form
having a curved region and a flat region.
[0044] The supporting substrate 102 and the first support 111 are
arranged so that the element layer 101 faces the first substrate
110, then, the element layer 101 is transferred to the first
substrate 110 side in a direction indicated by arrows (see FIG.
1D). That is, the element layer 101 is transferred from the
supporting substrate 102 to a surface of the first substrate which
is opposite to a surface contacting with the first support 111.
[0045] The manufacturing substrate 100 may be selected as
appropriate depending on the manufacturing process of the element
layer 101. For example, a glass substrate, a quartz substrate, a
sapphire substrate, a ceramic substrate, or a metal substrate
having an insulating layer on its surface can be used as the
manufacturing substrate 100. It is also possible to use a plastic
substrate which is heat resistant to a processing temperature.
[0046] Spacers 121 are formed on a second substrate 120 (see FIG.
2A). The spacers 121 may be formed on another manufacturing
substrate and then transferred to the second substrate 120.
[0047] As the supporting substrate 102, the first substrate 110,
and the second substrate 120, a substrate having flexibility (a
flexible substrate) is used. However, the first substrate 110 and
the second substrate 120 that have been shaped and fixed do not
need to have flexibility. The supporting substrate 102, the first
substrate 110, and the second substrate 120 can be made of an
aramid resin, a poly(ethylene naphthalate) (PEN) resin, a
poly(ether sulfone) (PES) resin, a poly(phenylene sulfide) (PPS)
resin, a polyimide (PI) resin, or the like.
[0048] Next, the second substrate 120 provided with the spacers 121
and a second support 123 which has a curved surface at least in a
portion thereof are arranged so that a surface of the second
substrate 120 on which the spacers 121 are not formed faces the
inside of the second support 123 (see FIG. 2B). The second support
123 may have a U-shape.
[0049] When the second substrate 120 is attached to the inside of
the second support 123 in a direction indicated by arrows, the
second substrate 120 provided with the spacers 121 is made into a
shape similar to that of the second support 123 (see FIG. 2C). By
this step, the second substrate 120 is processed to a form having a
curved region and a flat region.
[0050] The first support 111 provided with the element layer 101
and the first substrate 110 and the second support 123 provided
with the spacers 121 and the second substrate 120 are arranged so
that the element layer 101 faces the spacers 121 (see FIG. 3A).
[0051] The first support 111 and the second support 123 fit into
each other (are combined to each other) in a direction indicated by
arrows. Then, with use of a sealant 124, the first substrate 110 is
bonded to the second substrate 120 with a liquid crystal layer 125
and the element layer 101 interposed therebetween (see FIG. 3B).
This attachment step may be performed under reduced pressure.
[0052] As the sealant 124, it is typically preferable to use a
visible light curable resin, an ultraviolet light curable resin, or
a thermosetting resin. Typically, an acrylic resin, an epoxy resin,
an amine resin, or the like can be used. The sealant 124 may
include a photopolymerization initiator (typically, an ultraviolet
light polymerization initiator), a thermosetting agent, a filler,
or a coupling agent.
[0053] The liquid crystal layer 125 is formed by filling a space
with a liquid crystal material. The liquid crystal layer 125 may be
formed by a dispenser method (a dripping method) in which a liquid
crystal is dripped before the attachment of the first substrate 110
to the second substrate 120, or by an injection method in which a
liquid crystal is injected by using a capillary phenomenon after
the attachment of the first substrate 110 to the second substrate
120. There is no particular limitation on the kind of liquid
crystal material, and a variety of materials can be used. If a
material exhibiting a blue phase is used as the liquid crystal
material, an orientation film does not need to be provided.
[0054] The first support 111 and the second support 123 are
removed, whereby a curved liquid crystal display panel 150 that
reflects the shape of the first support 111 and the second support
123 can be manufactured (see FIG. 3C).
[0055] Although not illustrated in this embodiment, a color filter
(a coloring layer), a black matrix (a light-shielding layer), an
optical member (an optical substrate) such as a polarizing member,
a retardation member, or an anti-reflection member, and the like
are provided as appropriate. For example, circular polarization may
be obtained by using a polarizing substrate and a retardation
substrate. In addition, a backlight, a sidelight, or the like may
be used as a light source.
[0056] When the first substrate 110 and the second substrate 120
are shaped by the first support 111 and the second support 123,
they may be subjected to fixing treatment such as heat treatment or
light irradiation treatment so that the obtained shape is fixed.
Alternatively, the substrate may be shaped by heat treatment and
cooled maintaining the obtained shape, so that the shape of the
substrate can be fixed.
[0057] The element layer 101 may be directly formed on the
supporting substrate 102 or the first substrate 110. For example,
an electrode layer may be directly formed on the supporting
substrate 102 or the first substrate 110 by printing.
[0058] There is no particular limitation on the method for
transferring the element layer 101 from the manufacturing substrate
100 to another substrate as shown in this embodiment, and a variety
of methods can be used. For example, a separation layer may be
formed between the manufacturing substrate 100 and the element
layer 101.
[0059] By sputtering, plasma CVD, coating, printing, or the like,
the separation layer is formed with a single layer or staked layers
made of an element selected from tungsten (W), molybdenum (Mo),
titanium (Ti), tantalum (Ta), niobium (Nb), nickel (Ni), cobalt
(Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium (Rh),
palladium (Pd), osmium (Os), iridium (Ir), and silicon (Si); or an
alloy or a compound containing any of these elements as its main
component. A layer containing silicon may have any crystalline
structure: an amorphous structure, a microcrystalline structure, or
a polycrystalline structure. Note that the coating method includes
here a spin coating method, a droplet discharging method, and a
dispensing method.
[0060] In the case where the separation layer has a single-layer
structure, it is preferable to form a tungsten layer, a molybdenum
layer, or a layer containing a mixture of tungsten and molybdenum.
Alternatively, the separation layer may be a layer containing an
oxide or oxynitride of tungsten, a layer containing an oxide or
oxynitride of molybdenum, or a layer containing an oxide or
oxynitride of a mixture of tungsten and molybdenum. Note that the
mixture of tungsten and molybdenum corresponds to, for example, a
tungsten, molybdenum alloy.
[0061] In the case where the separation layer has a multi-layer
structure, it is preferable that a tungsten layer, a molybdenum
layer, or a layer containing a mixture of tungsten and molybdenum
be formed as a first layer, and a layer containing an oxide,
nitride, oxynitride, or nitride oxide of tungsten, molybdenum, or a
mixture of tungsten and molybdenum is formed as a second layer.
[0062] In the case where the separation layer has a multi-layer
structure of a layer containing tungsten and a layer containing an
oxide of tungsten, it may be formed in the following manner: a
layer containing tungsten is formed and an insulating layer
containing an oxide is formed thereover, so that a layer containing
an oxide of tungsten can be formed at the interface between the
tungsten layer and the insulating layer. Alternatively, a surface
of the layer containing tungsten may be subjected to thermal
oxidation treatment, oxygen plasma treatment, treatment with a
highly oxidizing solution such as ozone-containing water, or the
like, so that a layer containing an oxide of tungsten can be
formed. The plasma treatment and the thermal treatment may be
performed in an atmosphere of oxygen, nitrogen, or dinitrogen
monoxide alone, or a mixed gas of any of these gasses and another
gas. A layer containing a nitride, oxynitride, or nitride oxide of
tungsten may be formed in a manner similar to that used for forming
the layer containing an oxide of tungsten: after a layer containing
tungsten is formed, a silicon nitride layer, a silicon oxynitride
layer, or a silicon nitride oxide layer is formed thereover.
[0063] Note that the element layer can be transferred to another
substrate by any of the following methods: a method in which a
separation layer is formed between a substrate and the element
layer and a metal oxide film is formed between the separation layer
and the element layer and then weakened by crystallization so that
the element layer can be separated; a method in which an amorphous
silicon film containing hydrogen is formed between a high
heat-resistant substrate and the element layer and then removed by
laser light irradiation or etching so that the element layer can be
separated; a method in which a separation layer is formed between a
substrate and the element layer and a metal oxide film is formed
between the separation layer and the element layer and then
weakened by crystallization, and after part of the separation layer
is etched away using a solution or a halogen-containing gas such as
NF.sub.3, BrF.sub.3, or ClF.sub.3, the element layer is separated
at the weakened metal oxide film; and a method in which a substrate
over which the element layer is formed is mechanically removed or
etched away using a solution or a halogen-containing gas such as
NF.sub.3, BrF.sub.3, or ClF.sub.3. It is also possible to use a
method in which a film containing nitrogen, oxygen, hydrogen, or
the like (e.g., an amorphous silicon film containing hydrogen, an
alloy film containing hydrogen, or an alloy film containing oxygen)
is formed as a separation layer, and the separation layer is
irradiated with laser light so that nitrogen, oxygen, hydrogen, or
the like contained in the separation layer is released as gas to
promote separation.
[0064] A combination of the above separation methods further
facilitates the transferring step. That is, laser light
irradiation, etching of a separation layer with a gas or a
solution, and mechanical removal of a portion of the element layer
with a sharp knife, scalpel, or the like may be performed so that
the separation layer and the element layer can be easily separated
from each other, then, the separation step can be achieved by
physical force (with a machine or the like).
[0065] Alternatively, the interface between the separation layer
and the element layer may be soaked with a liquid, whereby the
element layer is separated from the substrate.
[0066] The shape of the liquid crystal display panel 150 can be
freely determined by selecting the shape of the first support 111
and the second support 123. Accordingly, it is possible to
manufacture various kinds of liquid crystal display devices capable
of being used in a variety of places for a variety of applications,
which allows a convenient liquid crystal display device to be
provided.
Embodiment 2
[0067] In this embodiment, an example of a method for manufacturing
the liquid crystal display device shown in Embodiment 1, which is
additionally provided with a protective film, will be described
with reference to FIGS. 4A to 4D, FIGS. 5A to 5C, and FIGS. 6A to
6C. Therefore, the liquid crystal display device of this
embodiment, except the protective film, can be manufactured in a
manner similar to that shown in Embodiment 1; thus, description of
the same components or components having the same functions as
those in Embodiment 1, and the manufacturing process thereof will
be omitted.
[0068] FIGS. 4A to 4D, FIGS. 5A to 5C, and FIGS. 6A to 6C are
cross-sectional views illustrating a method for manufacturing the
liquid crystal display device.
[0069] In a manufacturing process of the liquid crystal display
device in this embodiment, the liquid crystal display device is
shaped after the manufacture of an electrode layer and an element
layer, thereby having a more useful function. Furthermore, the
provision of a protective film increases the reliability of the
liquid crystal display device.
[0070] The element layer 101 is formed over the manufacturing
substrate 100 (see FIG. 4A). In this embodiment, the element layer
101 includes spacers. Next, the element layer 101, which includes a
thin film transistor, is transferred to the supporting substrate
102 (see FIG. 4B).
[0071] With use of the first support 111 serving as a mold for the
liquid crystal display device, the first substrate 110 is provided
along a curved surface of the first support 111. The first
substrate 110 may be attached to the first support 111 with an
adhesive layer or the like.
[0072] A protective film 103 is formed on the first substrate 110
attached to the first support 111 (see FIG. 4C). The protective
film 103 is formed to cover the first substrate 110 that has been
bent along the shape of the first support 111. Since the first
substrate 110 is not shaped after the formation of the protective
film 103, it is possible to prevent defects such as damage of the
protective film 103 due to the shaping of the first substrate 110.
As a result, the protective film 103 which is a dense film blocks
moisture or other impurities from the first substrate 110, and the
contamination of the element layer or the liquid crystal layer can
be efficiently prevented.
[0073] The supporting substrate 102 and the first support 111 are
arranged so that the protective film 103 and the first substrate
110 are interposed therebetween, then, the element layer 101 is
transferred to the protective film 103 and first substrate 110 side
in a direction indicated by arrows (see FIG. 4D).
[0074] Next, the second substrate 120 and the second support 123
which has a curved surface at least in a portion thereof are
arranged (see FIG. 5A).
[0075] When the second substrate 120 is attached to the inside of
the second support 123 in a direction indicated by arrows, the
second substrate 120 is made into a shape similar to that of the
second support 123 (see FIG. 5B).
[0076] A protective film 122 is formed on the second substrate 120
attached to the second support 123 (see FIG. 5C). The protective
film 122 is formed to cover the second substrate 120 that has been
bent along the shape of the second support 123. Since the second
substrate 120 is not shaped after the formation of the protective
film 122, it is possible to prevent defects such as damage of the
protective film 122 due to the shaping of the second substrate 120.
As a result, the protective film 122 which is a dense film blocks
moisture or other impurities from the second substrate 120, and the
contamination of the element layer or the liquid crystal layer can
be efficiently prevented.
[0077] The protective film 103 and the protective film 122 can be
formed by sputtering using an inorganic insulating material.
Examples of the inorganic insulating material include silicon
oxide, silicon nitride, silicon oxynitride, aluminum oxide,
aluminum nitride, and aluminum oxynitride.
[0078] The first support 111 provided with the element layer 101,
the protective film 103, and the first substrate 110, and the
second support 123 provided with the protective film 122 and the
second substrate 120 are arranged so that the element layer 101
faces the protective film 122 (see FIG. 6A).
[0079] The first support 111 and the second support 123 are
combined to each other in a direction indicated by arrows. Then,
with use of the sealant 124, the element layer 101, the protective
film 103, and the first substrate 110 are attached to the
protective film 122 and the second substrate 120 with the liquid
crystal layer 125 interposed therebetween (see FIG. 6B).
[0080] Although the spacers formed on the element layer 101 are
shown as an example in this embodiment, spherical spacers may be
dispersed on the protective film 122.
[0081] The liquid crystal layer 125 may be formed by a dispenser
method (a dripping method) in which a liquid crystal is dropped
before the attachment of the first substrate 110 to the second
substrate 120, or by an injection method in which a liquid crystal
is injected by using a capillary phenomenon after the attachment of
the first substrate 110 to the second substrate 120.
[0082] The first support 111 and the second support 123 are
removed, whereby the curved liquid crystal display panel 150 that
reflects the shape of the first support 111 and the second support
123 can be manufactured (see FIG. 6C).
[0083] The shape of the liquid crystal display panel 150 can be
freely determined by selecting the shape of the first support 111
and the second support 123. Accordingly, it is possible to
manufacture various kinds of liquid crystal display devices capable
of being used in a variety of places for a variety of applications,
which allows a convenient liquid crystal display device to be
provided.
[0084] In addition, the protective film protects the element layer
and the liquid crystal layer from impurities and thus increases the
reliability of the liquid crystal display device.
Embodiment 3
[0085] In this embodiment, a method for manufacturing a liquid
crystal display device, which is different from that shown in
Embodiments 1 and 2, will be described with reference to FIGS. 7A
to 7F and FIGS. 8A and 8B. Therefore, the liquid crystal display
device of this embodiment, except a different part, can be
manufactured in a manner similar to that shown in Embodiment 1;
thus, description of the same components or components having the
same functions as those in Embodiment 1, and the manufacturing
process thereof will be omitted.
[0086] FIGS. 7A to 7F and FIGS. 8A and 8B are cross-sectional views
illustrating a method for manufacturing the liquid crystal display
device.
[0087] In a manufacturing process of the liquid crystal display
device in this embodiment, the liquid crystal display device is
shaped after the attachment of a pair of substrates with a liquid
crystal layer interposed therebetween, thereby having a more useful
function.
[0088] The element layer 101 is formed over the manufacturing
substrate 100 (see FIG. 7A). The element layer 101 includes a thin
film transistor. Next, the element layer 101 is transferred to the
supporting substrate 102 (see FIG. 7B).
[0089] The element layer 101 is transferred from the supporting
substrate 102 to the first substrate 110 (see FIG. 7C).
[0090] The spacers 121 and the sealant 124 are formed on the second
substrate 120. The spacers 121 may be formed on another
manufacturing substrate and then transferred to the second
substrate 120.
[0091] Next, the second substrate 120 provided with the spacers 121
and the first substrate 110 are arranged so that a surface of the
second substrate 120 on which the spacers 121 and the sealant 124
are formed faces the element layer 101 (see FIG. 7D).
[0092] The first substrate 110 is attached to the second substrate
120 with the liquid crystal layer 125 interposed therebetween (see
FIG. 7E). Through the above steps, a flexible liquid crystal
display panel 155 can be obtained.
[0093] The flexible liquid crystal display panel 155, which is a
structure body in which the first substrate 110 faces the second
substrate 120 with the liquid crystal layer 125 interposed
therebetween, is shaped to be bent, whereby the curved liquid
crystal display panel 150 can be manufactured (see FIG. 7F). The
liquid crystal display panel may be shaped using the supports 111
and 123 shown in Embodiment 1.
[0094] The liquid crystal display panel 155 may be attached to a
light-transmitting supporting member so that the liquid crystal
display panel 155 can be shaped and fixed.
[0095] FIG. 8A illustrates an example in which the flexible liquid
crystal display panel 155 manufactured in FIG. 7E is attached to a
light-transmitting supporting member 127 and then formed into a
curved shape and fixed. The supporting member 127 has a curved
portion on a side, and includes a first surface and a second
surface with the curved portion therebetween. The liquid crystal
display panel 155 is provided in contact with an inner side of the
supporting member 127, whereby a first display area and a second
display area can be formed respectively on the first surface and
the second surface of the supporting member 127. A third display
area is also formed in the curved surface of the supporting member
127 and is interposed between the first display area and the second
display area. The liquid crystal display panel 155 may be attached
to the supporting member 127 with a light-transmitting adhesive
layer.
[0096] The liquid crystal display panel 150 illustrated in FIG. 7F
may be additionally provided with a protective film.
[0097] A protective film 126 is formed to surround the liquid
crystal display panel 150 (see FIG. 8B).
[0098] Since the protective film 126 is formed on the liquid
crystal display panel 150 that has been formed into a curved shape,
it is possible to prevent defects such as damage of the protective
film 126 due to the shaping of the liquid crystal display panel
150. As a result, the protective film 126 which is a dense film
blocks moisture or other impurities from the outside, and the
contamination of the liquid crystal display panel 150 can be
efficiently prevented.
[0099] The protective film 126 can be formed by sputtering using an
inorganic insulating material. Examples of the inorganic insulating
material include silicon oxide, silicon nitride, silicon
oxynitride, aluminum oxide, aluminum nitride, and aluminum
oxynitride.
[0100] The shape of the liquid crystal display panel 150 can be
freely determined by selecting the shape of the supporting member
127. Accordingly, it is possible to manufacture various kinds of
liquid crystal display devices capable of being used in a variety
of places for a variety of applications, which allows a convenient
liquid crystal display device to be provided.
[0101] In addition, the protective film protects the element layer
and the liquid crystal layer from impurities and thus increases the
reliability of the liquid crystal display device.
Embodiment 4
[0102] In this embodiment, an example of the liquid crystal display
device shown in Embodiments 1 to 3, which is additionally provided
with an optical member, will be described with reference to FIGS.
9A and 9B. Therefore, the liquid crystal display device of this
embodiment, except the optical member, can be manufactured in a
manner similar to that shown in Embodiments 1 to 3; thus,
description of the same components or components having the same
functions as those in Embodiments 1 to 3, and the manufacturing
process thereof will be omitted.
[0103] The liquid crystal display device shown in Embodiments 1 to
3 can be provided with an optical member. As the optical member, it
is possible to use a light source such as a backlight or a
sidelight, an optical film (such as a polarizing film, a
retardation film, or an anti-reflection film), or the like.
[0104] The optical film may be provided on the outside of the first
substrate and the second substrate (on the side opposite to the
liquid crystal layer) or on the inside thereof (between the liquid
crystal layer and each of the first substrate and the second
substrate).
[0105] For the backlight, a light source such as a cold cathode
fluorescent lamp or a light-emitting diode (LED) can be used. A
planar light source may be formed using a plurality of LED light
sources or a plurality of electroluminescent (EL) light sources.
The planar light source may be formed using three or more kinds of
LEDs or an LED emitting white light.
[0106] FIGS. 9A and 9B each illustrate an example of the liquid
crystal display device provided with a backlight. Note that the
liquid crystal display panel 150 shown in Embodiments 1 to 3 is
also referred to as a liquid crystal display device. The backlight
is placed in a concave formed by the curved region and the flat
region of the first substrate 110.
[0107] FIG. 9A is the liquid crystal display panel 150 provided
with a backlight 130. The backlight 130 includes a cold cathode
fluorescent lamp 131a as a light source. The cold cathode
fluorescent lamp 131a is disposed in a housing 132 that is curved
along the shape of the liquid crystal display panel.
[0108] FIG. 9B is also the liquid crystal display panel 150
provided with the backlight 130. The backlight 130 includes an LED
131b as a light source. The LED 131b is disposed in the housing 132
that is curved along the shape of the liquid crystal display
panel.
[0109] The backlight 130 illustrated in FIGS. 9A and 9B may include
a light guide member (component) such as a light-diffusing member
(film) or a light-reflecting member (film). The housing 132
includes a light-transmitting portion in a region through which
light from the light source passes.
[0110] As shown in this embodiment, the optical member is also
shaped and arranged so as to be curved in accordance with the shape
of the curved liquid crystal display device.
[0111] The shape of the liquid crystal display device can be freely
determined by selecting the shape of the mold used for shaping the
liquid crystal display device. Accordingly, it is possible to
manufacture various kinds of liquid crystal display devices capable
of being used in a variety of places for a variety of applications,
which allows a convenient liquid crystal display device to be
provided.
Embodiment 5
[0112] In this embodiment, an example in which a plurality of
element layers for the liquid crystal display devices shown in
Embodiments 1 to 4 are manufactured over a large substrate (a
so-called multi-panel technology) will be described with reference
to FIGS. 11A1 to 11C2. Therefore, the liquid crystal display device
of this embodiment can be manufactured in a manner similar to that
shown in Embodiments 1 to 4; thus, description of the same
components or components having the same functions as those in
Embodiments 1 to 4, and the manufacturing process thereof will be
omitted.
[0113] As described in the above embodiments, the element layer 101
is formed over the manufacturing substrate 100 and then transferred
from the manufacturing substrate 100 to the supporting substrate
102 that is a flexible substrate.
[0114] FIGS. 11A1 to 11C2 illustrate a method for transferring a
plurality of element layers from a large manufacturing substrate to
a supporting substrate. FIGS. 11A2, 11B2, and 11C2 are plan views
and FIGS. 11A1, 11B1, and 11C1 are cross-sectional views along line
X-Y of FIGS. 11A2, 11B2, and 11C2, respectively.
[0115] Element layers 101a, 101b, and 101c are formed over a large
manufacturing substrate 180 (see FIGS. 11A1 and 11A2).
[0116] A supporting substrate 182 is arranged so as to face the
element layers 101a, 101b, and 101c, and the element layers 101a,
101b, and 101c are transferred from the manufacturing substrate 180
to the supporting substrate 182 in a direction indicated by arrows
(see FIGS. 11B1 and 11B2).
[0117] The supporting substrate 182 is divided into supporting
substrates 102a, 102b, and 102c respectively for the element layers
101a, 101b, and 101c (see FIGS. 11C1 and 11C2). There is no
particular limitation on a dividing method as long as the
supporting substrate can be cut off physically. For example, the
supporting substrate 182 can be divided with a dicer or a scriber,
or by laser light irradiation.
[0118] The element layers 101 (101a, 101b, and 101c) formed over
the supporting substrates 102 (102a, 102b, and 102c) for panels are
used for manufacturing liquid crystal display devices. The
subsequent steps may be performed in a manner similar to those
shown in Embodiments 1 to 4.
[0119] Such a step of simultaneously transferring a plurality of
element layers with use of a large substrate allows a plurality of
liquid crystal display devices to be provided at a higher
productivity.
Embodiment 6
[0120] The invention disclosed in this specification can be applied
to a passive matrix liquid crystal display device as well as an
active matrix liquid crystal display device.
[0121] Thin film transistors are manufactured and used for a pixel
portion and further a driver circuit, so that a liquid crystal
display device having a display function can be manufactured. In
addition, when part or whole of the driver circuit is formed over
the same substrate as the pixel portion with use of the thin film
transistors, a system-on-panel can be obtained.
[0122] The liquid crystal display device includes a liquid crystal
element (also referred to as a liquid crystal display element) as a
display element.
[0123] Furthermore, the liquid crystal display device includes a
panel in which the display element is sealed, and a module in which
an IC or the like including a controller is mounted on the panel.
In this embodiment, liquid crystal display device modules will be
illustrated in FIGS. 10A and 10B and FIG. 12.
[0124] Note that a liquid crystal display device in this
specification refers to an image display device, a display device,
or a light source (including a lighting device). Furthermore, the
liquid crystal display device also includes the following modules
in its category: a module to which a connector such as a flexible
printed circuit (FPC), a tape automated bonding (TAB) tape, or a
tape carrier package (TCP) is attached; a module having a TAB tape
or a TCP at the tip of which a printed wiring board is provided;
and a module in which an integrated circuit (IC) is directly
mounted on a display element by the chip on glass (COG)
technique.
[0125] The appearance and cross section of a liquid crystal display
panel, which is one embodiment of the liquid crystal display
device, will be described with reference to FIGS. 10A and 10B and
FIG. 12. FIGS. 10A and 10B and FIG. 12 are examples of liquid
crystal display modules in which an FPC 4018 is attached to a
liquid crystal display panel 4000. Thin film transistors 4010 and
4011 and a liquid crystal element 4013 are sealed between a first
substrate 4001 and a second substrate 4006 with a sealant 4005.
FIGS. 10A and 10B are perspective views of the liquid crystal
display modules, and FIG. 12 is a cross-sectional view along line
M-N of FIG. 10A.
[0126] The liquid crystal display module of FIG. 10B shows an
example in which the liquid crystal display panel 4000 is attached
to a light-transmitting supporting member 4040. The liquid crystal
display panel 4000 is provided in contact with an inner surface of
the light-transmitting supporting member 4040.
[0127] As illustrated in FIGS. 10A and 10B, a pixel portion 4002
serving as a display area is continuously provided on the side
surfaces and bottom surface of the liquid crystal display panel
that is curved, so that a first display area can be provided on the
bottom surface and a second display area can be provided on the
side surfaces.
[0128] The sealant 4005 is provided to surround the pixel portion
4002 and a scan line driver circuit 4004 that are provided over the
first substrate 4001. The second substrate 4006 is provided over
the pixel portion 4002 and the scan line driver circuit 4004.
Therefore, the pixel portion 4002 and the scan line driver circuit
4004 are sealed together with a liquid crystal layer 4008, by the
first substrate 4001, the sealant 4005, and the second substrate
4006.
[0129] A signal line driver circuit 4003 is formed using a single
crystal semiconductor film or a polycrystalline semiconductor film
over a substrate separately prepared, and is mounted by TAB in a
region different from the region surrounded by the sealant.
[0130] Further, a variety of signals and potentials are supplied
from an FPC 4018 to the signal line driver circuit 4003 that is
formed separately, and the scan line driver circuit 4004 or the
pixel portion 4002.
[0131] Note that there is no particular limitation on the
connection method of the driver circuit separately formed, and the
driver circuit may be connected by COG, wire bonding, TAB, or the
like.
[0132] The pixel portion 4002 and the scan line driver circuit 4004
that are provided over the first substrate 4001 each include a
plurality of thin film transistors. FIG. 12 illustrates the thin
film transistor 4010 included in the pixel portion 4002 and the
thin film transistor 4011 included in the scan line driver circuit
4004. Insulating layers 4020 and 4021 are provided over the thin
film transistors 4010 and 4011. Note that an insulating film 4023
is an insulating film serving as a base film.
[0133] Various kinds of thin film transistors can be applied to the
thin film transistors 4010 and 4011 without particular limitation.
FIG. 12 illustrates an example in which inverted-staggered thin
film transistors having a bottom-gate structure are used as the
thin film transistors 4010 and 4011. Although the thin film
transistors 4010 and 4011 are channel-etched thin film transistors,
they may be channel-protective inverted-staggered thin film
transistors in which a channel protective film is provided over a
semiconductor layer.
[0134] A pixel electrode layer 4030 is provided over the first
substrate 4001 and electrically connected to the thin film
transistor 4010. The liquid crystal element 4013 includes the pixel
electrode layer 4030, a counter electrode layer 4031, and the
liquid crystal layer 4008. Insulating films 4032 and 4033 serving
as orientation films are provided so that the liquid crystal layer
4008 is interposed therebetween. The counter electrode layer 4031
is provided on the second substrate 4006 side and stacked over the
pixel electrode layer 4030 with the liquid crystal layer 4008
interposed therebetween.
[0135] The first substrate 4001 and the second substrate 4006 can
be made of plastic having light-transmitting properties. A plastic
substrate may be a fiberglass-reinforced plastics (FRP) plate, a
poly(vinyl fluoride) (PVF) film, a polyester film, or an acrylic
resin film. Alternatively, a sheet with a structure in which an
aluminum foil is sandwiched between PVF films or polyester films
can be used.
[0136] Reference numeral 4035 denotes a columnar spacer obtained by
selectively etching an insulating film and is provided to control
the thickness of the liquid crystal layer 4008 (a cell gap).
Alternatively, a spherical spacer may be used.
[0137] Although FIG. 12 illustrates an example of a transmissive
liquid crystal display device, an embodiment of the present
invention can also be applied to a transflective liquid crystal
display device.
[0138] FIG. 12 illustrates an example of the liquid crystal display
device in which a polarizing films 4040a and 4040b are provided on
the outside of the substrates; however, the polarizing films may be
provided on the inside of the substrates. The polarizing films may
be provided inside or outside the substrate as appropriate
depending on materials of the polarizing film or conditions of
manufacturing steps. Furthermore, a light-shielding layer serving
as a black matrix may be provided.
[0139] The insulating layer 4020 serves as a protective film of the
thin film transistors.
[0140] The protective film (insulating layer 4020) is provided to
prevent entry of impurities floating in the air, such as organic
substances, metal substances, or moisture, and is preferably a
dense film. The protective film (insulating layer 4020) may be
formed by sputtering with a single layer or stacked layers of a
silicon oxide film, a silicon nitride film, a silicon oxynitride
film, a silicon nitride oxide film, an aluminum oxide film, an
aluminum nitride film, an aluminum oxynitride film, and/or an
aluminum nitride oxide film.
[0141] The insulating layer 4021 serving as a planarizing
insulating film can be made of an organic material having heat
resistance, such as polyimide, an acrylic resin, a
benzocyclobutene-based resin, polyamide, or an epoxy resin. Other
than such organic materials, it is also possible to use a
low-dielectric constant material (a low-k material), a
siloxane-based resin, PSG (phosphosilicate glass), BPSG
(borophosphosilicate glass), or the like. Note that the insulating
layer 4021 may be formed by stacking a plurality of insulating
films made of these materials.
[0142] There is no particular limitation on the method for forming
the insulating layer 4021, and the insulating layer 4021 can be
formed, depending on the material, by sputtering, spin coating,
dipping, spray coating, droplet discharging (e.g., ink-jet, screen
printing, or offset printing), roll coating, curtain coating, knife
coating, or the like. In the case where the insulating layer 4021
is formed using a material solution, the semiconductor layer may be
annealed (at 200.degree. C. to 400.degree. C.) at the same time as
a baking step. The baking step of the insulating layer 4020 also
serves as the annealing step of the semiconductor layer, whereby a
liquid crystal display device can be manufactured efficiently.
[0143] In this specification, in the case where the liquid crystal
display device is a transmissive liquid crystal display device (or
a transflective liquid crystal display device) performing display
by transmitting light from a light source, light needs to pass
through at least a pixel region. Accordingly, the substrates and
the thin films such as insulating films and conductive films
existing in the pixel region through which light passes have
light-transmitting properties in the visible wavelength range.
[0144] The electrode layer (such as a pixel electrode layer, a
common electrode layer, or a counter electrode layer) for applying
voltage to the liquid crystal layer may have light-transmitting
properties or light-reflecting properties depending on the place
where the electrode layer is provided or the pattern structure of
the electrode layer.
[0145] The pixel electrode layer 4030 and the counter electrode
layer 4031 can be made of a light-transmitting conductive material
such as indium oxide containing tungsten oxide, indium zinc oxide
containing tungsten oxide, indium oxide containing titanium oxide,
indium tin oxide containing titanium oxide, indium tin oxide
(hereinafter referred to as ITO), indium zinc oxide, or indium tin
oxide to which silicon oxide is added.
[0146] The pixel electrode layer 4030 and the counter electrode
layer 4031 can also be made of one or more kinds of materials
selected from a metal such as tungsten (W), molybdenum (Mo),
zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum
(Ta), chromium (Cr), cobalt (Co), nickel (Ni), titanium (Ti),
platinum (Pt), aluminum (Al), copper (Cu), and silver (Ag); an
alloy of these metals; and a nitride of these metals.
[0147] Alternatively, a conductive composition containing a
conductive high molecule (also referred to as a conductive polymer)
can be used for the pixel electrode layer 4030 and the counter
electrode layer 4031. As the conductive high molecule, a so-called
.pi.-electron conjugated conductive polymer can be used. For
example, it is possible to use polyaniline or a derivative thereof,
polypyrrole or a derivative thereof, polythiophene or a derivative
thereof, or a copolymer of two or more kinds of them.
[0148] Since the thin film transistors are easily damaged by static
electricity or the like, a protective circuit for protecting the
driver circuits is preferably provided over the same substrate as a
gate line or a source line. It is preferable to use a non-linear
element for the protective circuit.
[0149] In FIG. 12, a connecting terminal electrode 4015 is formed
using the same conductive film as that of the pixel electrode layer
4030, and a terminal electrode 4016 is formed using the same
conductive film as that of source and drain electrode layers of the
thin film transistors 4010 and 4011.
[0150] The connecting terminal electrode 4015 is electrically
connected to a terminal included in the FPC 4018 through an
anisotropic conductive film 4019.
[0151] FIGS. 10A and 10B illustrate an example in which the signal
line driver circuit 4003 is formed separately and mounted on the
FPC 4018; however, this embodiment is not limited to this
structure. The scan line driver circuit may be separately formed
and then mounted, or only part of the signal line driver circuit or
part of the scan line driver circuit may be separately formed and
then mounted.
[0152] This embodiment can be implemented in an appropriate
combination with the structures described in the other
embodiments.
Embodiment 7
[0153] There is no particular limitation on the kind of thin film
transistor included in the liquid crystal display device disclosed
in this specification. Therefore, a variety of structures and
materials can be used for the thin film transistor.
[0154] Examples of the structure of the thin film transistor will
be described with reference to FIGS. 13A to 13D. FIGS. 13A to 13D
illustrate examples of the thin film transistor that can be applied
to the thin film transistor 4010 in Embodiment 6, and FIGS. 13A to
13D correspond to FIG. 12.
[0155] In FIGS. 13A to 13D, the insulating film 4023 is formed over
the first substrate 4001, and thin film transistors 4010a, 4010b,
4010c, and 4010d are provided over the insulating film 4023. The
insulating layers 4020 and 4021 are formed over each of the thin
film transistors 4010a, 4010b, 4010c, and 4010d, and the pixel
electrode layer 4030 is provided thereover to be electrically
connected to the thin film transistors 4010a, 4010b, 4010c, and
4010d.
[0156] The thin film transistor 4010a is an example of the thin
film transistor 4010 illustrated in FIG. 12, in which wiring layers
405a and 405b serving as source and drain electrode layers are in
contact with a semiconductor layer 403 without an n.sup.+ layer
interposed therebetween.
[0157] The thin film transistor 4010a is an inverted-staggered thin
film transistor in which a gate electrode layer 401, a gate
insulating layer 402, the semiconductor layer 403, and the wiring
layers 405a and 405b serving as source and drain electrode layers
are provided over the first substrate 4001 having an insulating
surface, and over the insulating film 4023.
[0158] The thin film transistor 4010b is a bottom-gate thin film
transistor in which the gate electrode layer 401, the gate
insulating layer 402, the wiring layers 405a and 405b serving as
source and drain electrode layers, n.sup.+ layers 404a and 404b
serving as source and drain regions, and the semiconductor layer
403 are provided over the first substrate 4001 having an insulating
surface, and over the insulating film 4023. In addition, an
insulating film 4020 is provided in contact with the semiconductor
layer 403 so as to cover the thin film transistor 4010b. The
n.sup.+ layers 404a and 404b are semiconductor layers each having a
lower resistance than the semiconductor layer 403.
[0159] The n.sup.+ layers 404a and 404b may be provided between the
gate insulating layer 402 and the wiring layers 405a and 405b.
Alternatively, the n.sup.+ layers may be provided both between the
gate insulating layer and the wiring layers and between the wiring
layers and the semiconductor layer.
[0160] The gate insulating layer 402 exists in the entire region
including the thin film transistor 4010b, and the gate electrode
layer 401 is provided between the gate insulating layer 402 and the
first substrate 4001 having an insulating surface. The wiring
layers 405a and 405b and the n.sup.+ layers 404a and 404b are
provided over the gate insulating layer 402. Then, the
semiconductor layer 403 is provided over the gate insulating layer
402, the wiring layers 405a and 405b, and the n.sup.+ layers 404a
and 404b. Although not illustrated, a wiring layer is provided over
the gate insulating layer 402 in addition to the wiring layers 405a
and 405b, and the wiring layer extends beyond the perimeter of the
semiconductor layer 403.
[0161] The thin film transistor 4010c has another structure of the
thin film transistor 4010b, in which source and drain electrode
layers are in contact with a semiconductor layer without an n.sup.+
layer interposed therebetween.
[0162] The gate insulating layer 402 exists in the entire region
including the thin film transistor 4010c, and the gate electrode
layer 401 is provided between the gate insulating layer 402 and the
first substrate 4001 having an insulating surface. The wiring
layers 405a and 405b are provided over the gate insulating layer
402. Then, the semiconductor layer 403 is provided over the gate
insulating layer 402 and the wiring layers 405a and 405b. Although
not illustrated, a wiring layer is provided over the gate
insulating layer 402 in addition to the wiring layers 405a and
405b, and the wiring layer extends beyond the perimeter of the
semiconductor layer 403.
[0163] The thin film transistor 4010d is a top-gate thin film
transistor and an example of a planar thin film transistor. The
semiconductor layer 403 including the n.sup.+ layers 404a and 404b
serving as source and drain regions is formed over the first
substrate 4001 having an insulating surface, and over the
insulating film 4023. The gate insulating layer 402 is formed over
the semiconductor layer 403, and the gate electrode layer 401 is
formed over the gate insulating layer 402. In addition, the wiring
layers 405a and 405b serving as source and drain electrode layers
are formed in contact with the n.sup.+ layers 404a and 404b. The
n.sup.+ layers 404a and 404b are semiconductor regions each having
a lower resistance than the semiconductor layer 403.
[0164] The thin film transistor may be a top-gate forward-staggered
thin film transistor.
[0165] Although a single-gate transistor is described in this
embodiment, a multi-gate transistor such as a double-gate
transistor may also be used. In that case, a gate electrode layer
may be provided above and below the semiconductor layer, or a
plurality of gate electrode layers may be provided only on one side
of (above or below) the semiconductor layer.
[0166] There is no particular limitation on the semiconductor
material used for the semiconductor layer. Examples of the material
used for the semiconductor layer of the thin film transistor will
be described below.
[0167] As a material for the semiconductor layer included in the
semiconductor element, it is possible to use an amorphous
semiconductor (hereinafter, also referred to as an AS) that is
formed by sputtering or vapor-phase growth using a semiconductor
material gas typified by silane or germane, a polycrystalline
semiconductor that is obtained by crystallizing the amorphous
semiconductor by utilizing light energy or thermal energy, a
microcrystalline semiconductor (also referred to as a
semi-amorphous or microcrystal semiconductor, and hereinafter, also
referred to as an SAS), or the like. The semiconductor layer can be
deposited by sputtering, LPCVD, plasma CVD, or the like.
[0168] Considering Gibbs free energy, the microcrystalline
semiconductor film is in a metastable state that is intermediate
between an amorphous state and a single crystal state. That is, the
microcrystalline semiconductor is in a third state that is
thermodynamically stable, and has short-range order and lattice
distortion. Columnar or needle-like crystals grow in the direction
of the normal to the surface of the substrate. The Raman spectrum
of microcrystalline silicon, which is a typical example of a
microcrystalline semiconductor, is shifted to a lower wavenumber
side than 520 cm.sup.-1 that represents single crystal silicon. In
other words, the Raman spectrum of microcrystalline silicon has a
peak between 520 cm.sup.-1 that represents single crystal silicon
and 480 cm.sup.-1 that represents amorphous silicon. Furthermore,
the microcrystalline semiconductor film contains 1 atomic % or more
of hydrogen or halogen to terminate dangling bonds. The
microcrystalline semiconductor film may further contain a rare gas
element such as helium, argon, krypton, or neon to further promote
lattice distortion, whereby a favorable microcrystalline
semiconductor film with improved stability can be obtained.
[0169] This microcrystalline semiconductor film can be formed by a
high-frequency plasma CVD method with a frequency of several tens
of megahertz to several hundreds of megahertz, or a microwave
plasma CVD apparatus with a frequency of 1 GHz or more. Typically,
the microcrystalline semiconductor film can be formed using silicon
hydride, such as SiH.sub.4, Si.sub.2H.sub.6, SiH.sub.2Cl.sub.2, or
SiHCl.sub.3, or silicon halide such as SiCl.sub.4 or SiF.sub.4,
which is diluted with hydrogen. Furthermore, the microcrystalline
semiconductor film can be formed with a gas containing silicon
hydride and hydrogen which is diluted by one or more kinds of rare
gas elements selected from helium, argon, krypton, and neon. In
such a case, the flow rate ratio of hydrogen to silicon hydride is
set to 5:1 to 200:1, preferably, 50:1 to 150:1, and more
preferably, 100:1.
[0170] The amorphous semiconductor is typified by hydrogenated
amorphous silicon, and the crystalline semiconductor is typified by
polysilicon or the like. Polysilicon (polycrystalline silicon)
includes so-called high-temperature polysilicon that contains
polysilicon formed at a process temperature of 800.degree. C. or
higher as its main component, so-called low-temperature polysilicon
that contains polysilicon formed at a process temperature of
600.degree. C. or lower as its main component, and polysilicon
formed by crystallizing amorphous silicon by using, for example, an
element that promotes crystallization. It is needless to say that a
microcrystalline semiconductor or a semiconductor partially
including a crystalline phase can also be used as described
above.
[0171] As a semiconductor material, a compound semiconductor such
as GaAs, InP, SiC, ZnSe, GaN, or SiGe as well as silicon (Si) or
germanium (Ge) alone can be used.
[0172] In the case of using a crystalline semiconductor film for
the semiconductor layer, the crystalline semiconductor film may be
manufactured by various methods (e.g., laser crystallization,
thermal crystallization, or thermal crystallization using an
element such as nickel that promotes crystallization).
Alternatively, a microcrystalline semiconductor, which is an SAS,
may be crystallized by laser irradiation to increase crystallinity.
In the case where an element that promotes crystallization is not
introduced, before being irradiated with laser light, an amorphous
semiconductor film is heated at 500.degree. C. for one hour in a
nitrogen atmosphere, whereby hydrogen contained in the amorphous
semiconductor film is eliminated to allow its concentration to be
1.times.10.sup.20 atoms/cm.sup.3 or less. This is because, if the
amorphous semiconductor film contains much hydrogen, the amorphous
semiconductor film is broken by laser irradiation.
[0173] In the case of the crystallization of the amorphous
semiconductor film using the element that promotes crystallization,
it is possible to use one or more kinds of metal elements selected
from iron (Fe), nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium
(Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt),
copper (Cu), and gold (Au). There is no particular limitation on a
method for introducing the metal element into the amorphous
semiconductor film as long as the metal element can exist on the
surface of or inside the amorphous semiconductor film. For example,
sputtering, CVD, plasma processing (including plasma CVD), an
adsorption method, or a method of applying a metal-salt solution
can be employed. Among them, the method using a solution is simple
and easy, and is useful in terms of easy concentration adjustment
of the metal element. At this time, an oxide film may be deposited
at the surface of the amorphous semiconductor film by UV light
irradiation in an oxygen atmosphere, thermal oxidation, treatment
with ozone-containing water or hydrogen peroxide including a
hydroxyl radical, or the like in order to improve its wettability
and to spread the solution containing the metal salt on the entire
surface of the amorphous semiconductor film.
[0174] In the crystallization of the amorphous semiconductor film
using the element that promotes crystallization, heat treatment (at
550.degree. C. to 750.degree. C. for 3 minutes to 24 hours) may be
performed.
[0175] In order to remove or reduce the element that promotes
crystallization of the crystalline semiconductor film, a
semiconductor film containing an impurity element is formed in
contact with the crystalline semiconductor film so as to function
as a gettering sink. As the impurity element, an impurity element
imparting n-type conductivity, an impurity element imparting p-type
conductivity, a rare gas element, or the like can be used. For
example, it is possible to use one or more kinds of elements
selected from phosphorus (P), nitrogen (N), arsenic (As), antimony
(Sb), bismuth (Bi), boron (B), helium (He), neon (Ne), argon (Ar),
krypton (Kr), and xenon (Xe). A semiconductor film containing a
rare gas element is formed in contact with the crystalline
semiconductor film containing the element that promotes
crystallization, and then heat treatment is performed (at
550.degree. C. to 750.degree. C. for 3 minutes to 24 hours). The
element promoting crystallization that is contained in the
crystalline semiconductor film moves into the semiconductor film
containing a rare gas element, and thus the element promoting
crystallization that is contained in the crystalline semiconductor
film is removed or reduced. After that, the semiconductor film
containing a rare gas element, which has functioned as a gettering
sink, is removed.
[0176] The amorphous semiconductor film may be crystallized by a
combination of thermal treatment and laser light irradiation.
Alternatively, either thermal treatment or laser light irradiation
may be performed plural times.
[0177] A crystalline semiconductor film can also be formed directly
over the substrate by a plasma method. Alternatively, a crystalline
semiconductor film may be selectively formed over the substrate by
a plasma method.
[0178] It is also possible to use an oxide semiconductor such as
zinc oxide (ZnO) or tin oxide (SnO.sub.2) for the semiconductor
layer. In the case of using ZnO for the semiconductor layer, a gate
insulating layer is formed of Y.sub.2O.sub.3, Al.sub.2O.sub.3,
TiO.sub.2, a stack thereof, or the like, and a gate electrode
layer, a source electrode layer, and a drain electrode layer can be
formed of ITO, Au, Ti, or the like. In addition, In, Ga, or the
like may be added to ZnO.
[0179] As the oxide semiconductor, a thin film represented by
InMO.sub.3 (ZnO).sub.m (m>0) can be used. Note that M denotes
one or more of metal elements selected from gallium (Ga), iron
(Fe), nickel (Ni), manganese (Mn), and cobalt (Co). For example, M
is gallium (Ga) in some cases, and in other cases, M contains other
metal elements in addition to Ga, such as Ga and Ni or Ga and Fe.
Furthermore, the above oxide semiconductor may contain another
transition metal or an oxide of the transition metal as an impurity
element. For example, an In--Ga--Zn--O-based non-single-crystal
film can be used as the oxide semiconductor layer.
[0180] An oxide semiconductor layer (InMO.sub.3(ZnO).sub.m film
(m>0)) in which M is another metal element may be used instead
of the In--Ga--Zn--O-based non-single-crystal film.
[0181] This embodiment can be implemented in an appropriate
combination with the structures described in the other
embodiments.
Embodiment 8
[0182] A liquid crystal display device disclosed in this
specification can be applied to a variety of electronic appliances
(including an amusement machine). Examples of electronic appliances
include a television set (also referred to as a television or a
television receiver), a monitor of a computer or the like, a camera
such as a digital camera or a digital video camera, a digital photo
frame, a cellular phone (also referred to as a mobile phone or a
mobile phone set), a portable game console, a portable information
terminal, an audio reproducing device, and a large-sized game
machine such as a pachinko machine.
[0183] In this embodiment, an example of a cellular phone using the
liquid crystal display device disclosed in this specification will
be described with reference to FIGS. 14A to 14D and FIG. 15.
[0184] FIG. 14C is a front view of the cellular phone; FIG. 14D, a
side view; and FIG. 14B, a top view. The cellular phone includes a
housing 1411a and a housing 1411b, which include a
light-transmitting supporting member at least in a region where
display is performed. FIG. 14A is a cross-sectional view of the
inside of the housing 1411a and the housing 1411b. The front of the
housing 1411a has a rectangular shape with a longer side and a
shorter side, which may have a round corner. In this embodiment,
the direction parallel to the longer side of the rectangle that is
the front shape is referred to as a longitudinal direction, and the
direction parallel to the shorter side is referred to as a lateral
direction.
[0185] The sides of the housing 1411a and the housing 1411b also
have a rectangular shape with a longer side and a shorter side,
which may have a round corner. In this embodiment, the direction
parallel to the longer side of the rectangle that is the side shape
is referred to as a longitudinal direction, and the direction
parallel to the shorter side is referred to as a depth
direction.
[0186] The cellular phone illustrated in FIGS. 14A to 14D includes
a display area 1413, operating buttons 1404, and a touch screen
1423, and the housings 1411a and 1411b include a liquid crystal
display panel 1421, a backlight 1424, and a wiring board 1425. The
touch screen 1423 may be provided as needed.
[0187] As the liquid crystal display panel 1421, the liquid crystal
display panel and the liquid crystal display module described in
Embodiments 1 to 7 may be used.
[0188] As illustrated in FIGS. 14B and 14C, the liquid crystal
display panel 1421 is arranged along the shape of the housing 1411a
so as to cover not only the front area on the viewer side but also
parts of the top area and the bottom area. Accordingly, a display
area 1427 can be formed on the top of the cellular phone in the
lateral direction to be connected to the display area 1413. That
is, the display area 1427 is provided on the top surface of the
cellular phone, which makes it possible to see the display area
1427 without taking out the cellular phone from, for example, the
breast pocket.
[0189] On the display areas 1413 and 1427, incoming mails or calls,
dates, phone numbers, personal names, and the like may be
displayed. Display may be performed only in the display area 1427
and not be performed in the other regions as needed, resulting in
saving of energy.
[0190] FIG. 15 is a cross-sectional view of FIG. 14D. As
illustrated in FIG. 15, the liquid crystal display panel 1421 is
continuously provided on the top, front, and bottom of the inside
of the housing 1411a. The backlight 1424, the wiring board 1425
electrically connected to the liquid crystal display panel 1421,
and a battery 1426 are provided on the back side of the liquid
crystal display panel 1421. Furthermore, the touch screen 1423 is
provided on the outside of the housing 1411a (on the viewer
side).
[0191] Images and letters can be displayed on the cellular phone of
this embodiment, whether it is placed horizontally or vertically
for a landscape mode or a portrait mode.
[0192] The liquid crystal display panel 1421 is not manufactured
separately in the front area and the top area, but manufactured to
cover both the front display area 1413 and the top display area
1427, resulting in a reduction in manufacturing cost and time.
[0193] The touch screen 1423 is provided on the housing 1411a, and
buttons 1414 on the touch screen are displayed on the display area
1413. By touching the buttons 1414 with a finger or the like,
contents displayed on the display area 1413 can be changed.
Furthermore, making calls or composing mails can also be performed
by touching the buttons 1414 on the display area 1413 with a finger
or the like.
[0194] The buttons 1414 on the touch screen 1423 may be displayed
when needed, and when the buttons 1414 are not necessary, images or
letters can be displayed on the entire display area 1413.
[0195] A longer side of the top cross section of the cellular phone
may have a radius of curvature. When the top cross section has a
longer side with a radius of curvature, each of the liquid crystal
display panel 1421 and the touch screen 1423 also has a top cross
section having a longer side with a radius of curvature.
Furthermore, the housing 1411a is also curved. That is, the display
area 1413 is curved outwards when seen from the front.
[0196] This application is based on Japanese Patent Application
serial No. 2009-093392 filed with Japan Patent Office on Apr. 7,
2009, the entire contents of which are hereby incorporated by
reference.
* * * * *