U.S. patent application number 14/164912 was filed with the patent office on 2014-08-21 for display device.
This patent application is currently assigned to Japan Display Inc.. The applicant listed for this patent is Japan Display Inc.. Invention is credited to Arichika ISHIDA, Yasushi Kawata.
Application Number | 20140232962 14/164912 |
Document ID | / |
Family ID | 51310798 |
Filed Date | 2014-08-21 |
United States Patent
Application |
20140232962 |
Kind Code |
A1 |
ISHIDA; Arichika ; et
al. |
August 21, 2014 |
DISPLAY DEVICE
Abstract
According to one embodiment, a display device includes a first
substrate including a first resin substrate having a first thermal
expansion coefficient, and a first barrier layer having a second
thermal expansion coefficient which is lower than the first thermal
expansion coefficient, a second substrate including a second resin
substrate having a third thermal expansion coefficient which is
equal to the first thermal expansion coefficient, and a second
barrier layer having a fourth thermal expansion coefficient which
is lower than the third thermal expansion coefficient and is equal
to the first thermal expansion coefficient, and a display element
located between the first resin substrate and the second resin
substrate.
Inventors: |
ISHIDA; Arichika; (Tokyo,
JP) ; Kawata; Yasushi; (Minato-ku, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Japan Display Inc. |
Minato-ku |
|
JP |
|
|
Assignee: |
Japan Display Inc.
Minato-ku
JP
|
Family ID: |
51310798 |
Appl. No.: |
14/164912 |
Filed: |
January 27, 2014 |
Current U.S.
Class: |
349/42 ;
257/40 |
Current CPC
Class: |
Y02P 70/50 20151101;
G02F 1/1333 20130101; H01L 2924/0002 20130101; H01L 51/0097
20130101; G02F 2001/133354 20130101; G02F 2001/133302 20130101;
G02F 1/133305 20130101; Y02E 10/549 20130101; G02F 2201/54
20130101; G02F 1/133351 20130101; H01L 2924/0002 20130101; H01L
2924/00 20130101 |
Class at
Publication: |
349/42 ;
257/40 |
International
Class: |
G02F 1/1333 20060101
G02F001/1333; H01L 25/16 20060101 H01L025/16 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2013 |
JP |
2013-030997 |
Claims
1. A display device comprising: a first substrate including a first
resin substrate having a first thermal expansion coefficient, a
first barrier layer which covers an inner surface of the first
resin substrate and has a second thermal expansion coefficient
which is lower than the first thermal expansion coefficient, and a
switching element formed above the first barrier layer; a second
substrate including a second resin substrate which is formed of a
material different from a material of the first resin substrate and
has a third thermal expansion coefficient which is equal to the
first thermal expansion coefficient, a second barrier layer which
covers an inner surface of the second resin substrate and has a
fourth thermal expansion coefficient which is lower than the third
thermal expansion coefficient and is equal to the first thermal
expansion coefficient; and a display element located between the
first resin substrate and the second resin substrate and including
a pixel electrode which is electrically connected to the switching
element.
2. The display device of claim 1, wherein a thickness of the first
resin substrate and a thickness of the second resin substrate are
equal.
3. The display device of claim 1, wherein the display element is an
organic electroluminescence element, and the display device further
comprises a sealing film covering the display element.
4. The display device of claim 1, wherein the display element is a
liquid crystal element.
5. The display device of claim 1, wherein a difference between the
first thermal expansion coefficient and the second thermal
expansion coefficient is equal to a difference between the third
thermal expansion coefficient and the fourth thermal expansion
coefficient.
6. The display device of claim 1, wherein each of the first thermal
expansion coefficient and the third thermal expansion coefficient
is 20 to 50 ppm/.degree. C.
7. The display device of claim 1, wherein each of the second
thermal expansion coefficient and the fourth thermal expansion
coefficient is 0.5 to 3.0 ppm/.degree. C.
8. The display device of claim 1, wherein each of the first resin
substrate and the second resin substrate is formed of a material
including polyimide as a main component.
9. The display device of claim 1, wherein each of the first barrier
layer and the second barrier layer is formed of an inorganic
material including silicon as a main component.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2013-030997, filed
Feb. 20, 2013, the entire contents of which are incorporated herein
by reference.
FIELD
[0002] Embodiments described herein relate generally to a display
device.
BACKGROUND
[0003] Display devices including organic electroluminescence (EL)
elements or liquid crystal elements have been used in various
fields. A display device is constructed by stacking a plurality of
members. In such a display device, there is a concern that a warp
occurs due to a difference in thermal expansion coefficient between
the respective members.
[0004] For example, as regards an optical sheet in which a
plurality of optical elements, which are formed of materials with
different thermal expansion coefficients, are adhered or attached,
there is known a technique of reducing a warp by providing a warp
prevention layer having a thermal expansion coefficient which is
equal to a thermal expansion coefficient of an optical functional
member. In addition, as regards an organic EL device configured
such that a warp-reducing substrate, which is opposed to a light
emission element provided on a substrate body formed of glass, and
a warp-reducing substrate disposed on that surface of the substrate
body, which is not opposed to the light emission element, are
attached, there is also known a technique in which the two
warp-reducing substrates are formed of materials having an equal
thermal expansion coefficient, and the thermal expansion
coefficient of the materials is close to the thermal expansion
coefficient of the substrate body, thereby reducing a warp.
Furthermore, as regards a semiconductor device in which a
semiconductor chip is bonded on a substrate, there is known a
technique in which a warp prevention sheet, which is bonded to the
other surface of the semiconductor chip, and the substrate have
substantially equal thermal expansion coefficients, thereby
preventing a warp of the semiconductor device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1A is a cross-sectional view which schematically
illustrates a structure example of a display device 1 of an
embodiment.
[0006] FIG. 1B is a cross-sectional view which schematically
illustrates another structure example of the display device 1 of
the embodiment.
[0007] FIG. 1C is a cross-sectional view which schematically
illustrates another structure example of the display device 1 of
the embodiment.
[0008] FIG. 2 schematically illustrates a state in which a stress
occurs in each of an array substrate AR and a counter-substrate CT
in the display device 1 of the embodiment.
[0009] FIG. 3 is a view for describing a manufacturing method of
the display device 1 of the embodiment, illustrating a step of
preparing a first mother substrate M1.
[0010] FIG. 4 is a view for describing the manufacturing method of
the display device 1 of the embodiment, illustrating a step of
preparing a second mother substrate M2.
[0011] FIG. 5 is a view for describing a step of coating a sealant
SE and an adhesive 40.
[0012] FIG. 6 is a view for describing the manufacturing method of
the display device 1 of the embodiment, illustrating a step of
attaching the first mother substrate M1 and the second mother
substrate M2.
[0013] FIG. 7 is a view for describing the manufacturing method of
the display device 1 of the embodiment, illustrating a step of
peeling a first support substrate 100 of the first mother substrate
M1 and a second support substrate 200 of the second mother
substrate M2.
[0014] FIG. 8 is a view for describing the manufacturing method of
the display device 1 of the embodiment, illustrating a step of
cutting a first resin substrate 10.
DETAILED DESCRIPTION
[0015] In general, according to one embodiment, a display device
includes: a first substrate including a first resin substrate
having a first thermal expansion coefficient, a first barrier layer
which covers an inner surface of the first resin substrate and has
a second thermal expansion coefficient which is lower than the
first thermal expansion coefficient, and a switching element formed
above the first barrier layer; a second substrate including a
second resin substrate which is formed of a material different from
a material of the first resin substrate and has a third thermal
expansion coefficient which is equal to the first thermal expansion
coefficient, a second barrier layer which covers an inner surface
of the second resin substrate and has a fourth thermal expansion
coefficient which is lower than the third thermal expansion
coefficient and is equal to the first thermal expansion
coefficient; and a display element located between the first resin
substrate and the second resin substrate and including a pixel
electrode which is electrically connected to the switching
element.
[0016] FIG. 1A is a cross-sectional view which schematically
illustrates a structure example of a display device 1 of the
embodiment. A description is given of a cross-sectional structure
of an organic EL display device as an example of the display device
1.
[0017] The illustrated organic EL display device 1 adopts an active
matrix driving method, and includes an array substrate AR and a
counter-substrate CT. The array substrate AR is formed by using a
first resin substrate 10. The array substrate AR includes, on an
inner surface 10A side of the first resin substrate 10, a first
insulation film 11, a second insulation film 12, a third insulation
film 13, a fourth insulation film 14, ribs 15, switching elements
SW1 to SW3, and organic EL elements OLED1 to OLED3 functioning as
display elements.
[0018] The first resin substrate 10 is an insulative substrate,
which is formed of, for example, a material consisting mainly of
polyimide (PI). The first resin substrate 10 has a thickness of,
e.g. 5 to 30 .mu.m. As the material for forming the first resin
substrate 10, a material with a high heat resistance, such as
polyamide-imide or polyaramide, as well as polyimide, is selected.
Specifically, the first resin substrate 10 is often exposed to a
high-temperature process in the formation of various insulation
films, the formation of switching elements, and the formation of
organic EL elements. Thus, the most important property, which is
required for the first resin substrate 10, is a high heat
resistance. As will be described later, the organic EL element is
of a so-called top emission type which emits light via the
counter-substrate CT. Accordingly, it is not always necessary that
the first resin substrate 10 have high transparency, and the first
resin substrate 10 may be colored.
[0019] The inner surface 10A of the first resin substrate 10 is
covered with the first insulation film 11. The first insulation
film 11 functions as a first barrier layer for suppressing entrance
of ionic impurities from the first resin substrate 10 or entrance
of moisture via the first resin substrate 10. The first insulation
film 11 is formed of an inorganic material including silicon as a
main component, such as silicon nitride (SiN), silicon oxide (SiO)
or silicon oxynitride (SiON), and is composed of a single layer or
a multilayer. For example, the first insulation film 11 is formed
of a multilayer body in which silicon nitride and silicon oxide are
alternately stacked. Incidentally, the first insulation film 11 may
be formed of some other material which can ensure a barrier
capability.
[0020] The switching elements SW1 to SW3 are formed on the first
insulation film 11. The switching elements SW1 to SW3 are, for
example, thin-film transistors (TFTs) each including a
semiconductor layer SC. The switching elements SW1 to SW3 have the
same structure. In the description below, attention is paid to the
switching element SW1, and the structure thereof is described more
specifically.
[0021] In the example illustrated, the switching element SW1 is of
a top gate type, but may be of a bottom gate type. The
semiconductor layer SC is formed of a silicon-based material such
as amorphous silicon or polysilicon, or an oxide semiconductor
which is an oxide including at least one of indium (In), gallium
(Ga) and zinc (Zn).
[0022] The semiconductor layer SC is formed on the first insulation
film 11, and is covered with a second insulation film 12. The
second insulation film 12 is also disposed on the first insulation
film 11. A gate electrode WG of the switching element SW1 is formed
on the second insulation film 12. The gate electrode WG is covered
with a third insulation film 13. The third insulation film 13 is
also disposed on the second insulation film 12.
[0023] A source electrode WS and a drain electrode WD of the
switching element SW1 are formed on the third insulation film 13.
The source electrode WS is put in contact with a source region of
the semiconductor layer SC. The drain electrode WD is put in
contact with a drain region of the semiconductor layer SC. The
source electrode WS and drain electrode WD are covered with a
fourth insulation film 14. The fourth insulation film 14 is also
disposed on the third insulation film 13.
[0024] The organic EL elements OLED1 to OLED3 are formed on the
fourth insulation film 14. In the example illustrated, the organic
EL element OLED1 is electrically connected to the switching element
SW1, the organic EL element OLED2 is electrically connected to the
switching element SW2, and the organic EL element OLED3 is
electrically connected to the switching element SW3. The color of
emission light of each of the organic EL elements OLED1 to OLED3 is
white. The organic EL elements OLED1 to OLED3 have the same
structure.
[0025] The organic EL element OLED1 includes a pixel electrode PE1
which is formed on the fourth insulation film 14. The pixel
electrode PE1 is in contact with the drain electrode WD of the
switching element SW1 and is electrically connected to the
switching element SW1. Similarly, the organic EL element OLED2
includes a pixel electrode PE2 which is electrically connected to
the switching element SW2, and the organic EL element OLED3
includes a pixel electrode PE3 which is electrically connected to
the switching element SW3. The pixel electrodes PE1 to PE3 function
as, for example, anodes. The pixel electrodes PE1 to PE3 may be
formed of a transparent, electrically conducive material such as
indium tin oxide (ITO) or indium zinc oxide (IZO), or may be formed
of a metallic material such as aluminum (Al), magnesium (Mg),
silver (Ag), titanium (Ti), or an alloy thereof. In the case of the
top emission type, it is desirable that the pixel electrodes PE1 to
PE3 include reflective layers formed of a metallic material with a
high reflectivity.
[0026] The organic EL elements OLED1 to OLED3 further include an
organic light emission layer ORG and a common electrode CE. The
organic light emission layer ORG is located on the pixel electrodes
PE1 to PE3. In addition, the organic light emission layer ORG is
continuously formed, without a break, over the organic EL elements
OLED1 to OLED3. The common electrode CE is located on the organic
light emission layer ORG. In addition, the common electrode CE is
continuously formed, without a break, over the organic EL elements
OLED1 to OLED3. The common electrode CE is formed of, for example,
a transparent, electrically conductive material such as ITO or
IZO.
[0027] Specifically, the organic EL element OLED1 is composed of
the pixel electrode PE1, organic light emission layer ORG and
common electrode CE. The organic EL element OLED2 is composed of
the pixel electrode PE2, organic light emission layer ORG and
common electrode CE. The organic EL element OLED3 is composed of
the pixel electrode PE3, organic light emission layer ORG and
common electrode CE.
[0028] In the meantime, in the organic EL elements OLED1 to OLED3,
a hole injection layer or a hole transport layer may be further
provided between each of the pixel electrodes PE1 to PE3 and the
organic light emission layer ORG, and an electron injection layer
or an electron transport layer may be further provided between the
organic light emission layer ORG and the common electrode CE.
[0029] The organic EL elements OLED1 to OLED3 are partitioned by
the ribs 15. The ribs 15 are formed on the fourth insulation film
14 and cover the edges of the pixel electrodes PE1 to PE3. The ribs
15 are formed, for example, in a grid shape or in a stripe shape on
the fourth insulation film 14. The ribs 15 are covered with the
organic light emission layer ORG. Specifically, the organic light
emission layer ORG extends over not only the pixel electrodes PE1
to PE3 but also over the ribs 15.
[0030] In the example illustrated, the organic EL elements OLED1 to
OLED3 are sealed by a sealing film 20. The sealing film 20
functions as a barrier film which protects the organic EL elements
OLED1 to OLED3 from contaminants such as moisture, oxygen and
hydrogen. The sealing film 20 is formed of an inorganic material
including silicon as a main component, such as silicon nitride
(SiN), silicon oxide (SiO) or silicon oxynitride (SiON), and is
composed of a single layer or a multilayer.
[0031] The counter-substrate CT is formed by using a transparent
second resin substrate 30. The counter-substrate CT includes a
fifth insulation film 31, a blue color filter 32B, a green color
filter 32G and a red color filter 32R on an inner surface 30A side
of the second resin substrate 30.
[0032] The second resin substrate 30 is a transparent resin
substrate, which is formed of, for example, a material consisting
mainly of polyimide (PI). The second resin substrate 30 has a
thickness which is equal to the thickness of the first resin
substrate 10, for example, a thickness of 5 to 30 .mu.m. As the
material for forming the second resin substrate 30, a material with
high transparency is selected. Specifically, light emitted from the
organic EL elements OLED1 to OLED3 of the top emission type passes
through the second resin substrate 30. Thus, the most important
property, which is required for the second resin substrate 30, is a
high transparency. In this manner, the property that is required is
different between the first resin substrate 10 and the second resin
substrate 30. Thus, the second resin substrate 30 is formed of a
material which is different from the material of the first resin
substrate 10. For example, the first resin substrate 10 is formed
by using an opaque polyimide with good heat resistance, and the
second resin substrate 30 is formed by using a transparent
polyimide.
[0033] The inner surface 30A of the second resin substrate 30 is
covered with a fifth insulation film 31. The fifth insulation film
31 functions as a second barrier layer for suppressing entrance of
ionic impurities from the second resin substrate 30 or entrance of
moisture via the second resin substrate 30. The fifth insulation
film 31 is formed of an inorganic material including silicon as a
main component, such as silicon nitride (SiN), silicon oxide (SiO)
or silicon oxynitride (SiON), and is composed of a single layer or
a multilayer. For example, the fifth insulation film 31 has the
same structure as the first insulation film 11, and is formed of a
multilayer body in which silicon nitride and silicon oxide are
alternately stacked.
[0034] The thermal expansion coefficient of the second resin
substrate 30 is substantially equal to the thermal expansion
coefficient of the first resin substrate 10. In addition, the
thermal expansion coefficient of the fifth insulation film 31 is
substantially equal to the thermal expansion coefficient of the
first insulation film 11. Besides, the thermal expansion
coefficients of the fifth insulation film 31 and first insulation
film 11 are lower than the thermal expansion coefficients of the
first resin substrate 10 and second resin substrate 30. For
example, each of the thermal expansion coefficients of the fifth
insulation film 31 and first insulation film 11 is 0.5 to 3
ppm/.degree. C., and each of the thermal expansion coefficients of
the first resin substrate 10 and second resin substrate 30 is 20 to
50 ppm/.degree. C. The thermal expansion coefficients of the first
resin substrate 10, second resin substrate 30, fifth insulation
film 31 and first insulation film 11 are so set as to meet the
above-described relationship, and thereby a warp of the display
device 1 can be prevented.
[0035] The blue color filter 32B is opposed to the organic EL
element OLED1 and passes a light component of a blue wavelength of
white light. The green color filter 32G is opposed to the organic
EL element OLED2 and passes a light component of a green wavelength
of white light. The red color filter 32R is a red color filter
which is opposed to the organic EL element OLED3 and passes a light
component of a red wavelength of white light. Boundaries between
the neighboring color filters are located above the ribs 15.
[0036] The above-described array substrate AR and counter-substrate
CT are attached by a sealant which attaches the array substrate AR
and counter-substrate CT on an outside of a display section which
displays an image. A transparent filler 40 is sealed between the
array substrate AR and counter-substrate CT. Specifically, the
organic EL elements OLED1 to OLED3 are located between the first
resin substrate 10 and second resin substrate 30. In the example
illustrated, the sealing film 20 and filler 40 are interposed
between the organic EL element OLED1 and blue color filter 32B,
between the organic EL element OLED2 and green color filter 32G and
between the organic EL element OLED3 and red color filter 32R. It
is desirable that the filler 40 be formed of a material having a
moisture-absorbing capability. Thereby, even if a defect occurs in
the sealing film 20, the filler 40 enters the defect of the sealing
film 20, and can block a moisture entrance path.
[0037] Incidentally, the array substrate AR and counter-substrate
CT may be attached by an adhesive having a moisture-absorbing
capability, in place of the filler.
[0038] According to the above-described organic EL display device
that is an example of the display device 1, when each of the
organic EL elements OLED1 to OLED3 has emitted light, this radiated
light (white light) is emitted to the outside via the blue color
filter 32B, green color filter 32G or red color filter 32R. At this
time, a light component of a blue wavelength of the white light,
which has been radiated from the organic EL element OLED1, passes
through the blue color filter 32B. In addition, a light component
of a green wavelength of the white light, which has been radiated
from the organic EL element OLED2, passes through the green color
filter 32G. A light component of a red wavelength of the white
light, which has been radiated from the organic EL element OLED3,
passes through the red color filter 32R. Thereby, color display is
realized.
[0039] Next, other structure examples of the display device 1 of
the embodiment will be described.
[0040] FIG. 1B is a cross-sectional view which schematically
illustrates another structure example of the display device 1 of
the embodiment.
[0041] The illustrated structure example differs from the structure
example shown in FIG. 1A in that the color filter of the
counter-substrate CT is omitted, and the organic EL elements OLED1
to OLED3 emit lights of different colors. The same structure as in
the structure example shown in FIG. 1A is denoted by like reference
numerals, and a detailed description thereof is omitted.
[0042] Specifically, the array substrate AR includes a first resin
substrate 10, a first insulation film 11, a second insulation film
12, a third insulation film 13, a fourth insulation film 14, ribs
15, switching elements SWl to SW3, organic EL elements OLED1 to
OLED3, and a sealing film 20. The thermal expansion coefficient of
the first insulation film 11 is lower than the thermal expansion
coefficient of the first resin substrate 10.
[0043] The organic EL element OLED1 is composed of a pixel
electrode PE1 which is connected to the switching element SW1, an
organic light emission layer ORG(B) which is located above the
pixel electrode PE1, and a common electrode CE which is located
above the organic light emission layer ORG(B). The organic EL
element OLED2 is composed of a pixel electrode PE2 which is
connected to the switching element SW2, an organic light emission
layer ORG(G) which is located above the pixel electrode PE2, and
the common electrode CE which is located above the organic light
emission layer ORG(G). The organic EL element OLED3 is composed of
a pixel electrode PE3 which is connected to the switching element
SW3, an organic light emission layer ORG(R) which is located above
the pixel electrode PE3, and the common electrode CE which is
located above the organic light emission layer ORG(R).
[0044] The organic light emission layer ORG(B) emits blue light,
the organic light emission layer ORG(G) emits green light, and the
organic light emission layer ORG(R) emits red light. The organic
light emission layer ORG(B), the organic light emission layer
ORG(G) and the organic light emission layer ORG(R) are made
discontinuous at locations above the ribs 15. The common electrode
CE is continuously formed, without a break, over the organic EL
elements OLED1 to OLED3, and also covers the ribs 15.
[0045] The counter-substrate CT includes a second resin substrate
30 and a fifth insulation film 31. The second resin substrate 30 is
formed of, for example, a transparent polyimide, and the first
resin substrate 10 is formed of, for example, an opaque polyimide
with good heat resistance.
[0046] The thermal expansion coefficient of the first resin
substrate 10 is substantially equal to the thermal expansion
coefficient of the second resin substrate 30, and the thermal
expansion coefficient of the first insulation film 11 is
substantially equal to the thermal expansion coefficient of the
fifth insulation film 31. In addition, the thermal expansion
coefficients of the first insulation film 11 and fifth insulation
film 31 are lower than the thermal expansion coefficients of the
first resin substrate 10 and second resin substrate 30. For
example, each of the thermal expansion coefficients of the first
insulation film 11 and fifth insulation film 31 is 0.5 to 3
ppm/.degree. C., and each of the thermal expansion coefficients of
the first resin substrate 10 and second resin substrate 30 is 20 to
50 ppm/.degree. C. As has been described above, the thermal
expansion coefficients of the first resin substrate 10, second
resin substrate 30, first insulation film 11 and fifth insulation
film 31 are so set as to meet the above-described relationship, and
thereby a warp of the display device 1 can be prevented.
[0047] The above-described array substrate AR and counter-substrate
CT are attached.
[0048] FIG. 1C is a cross-sectional view which schematically
illustrates another structure example of the display device 1 of
the embodiment. A description is given of a cross-sectional
structure of a liquid crystal display device as an example of the
display device 1.
[0049] The illustrated structure example differs from the structure
example shown in FIG. 1A in that this illustrated structure example
includes liquid crystal elements as display elements. The same
structure as in the structure example shown in FIG. 1A is denoted
by like reference numerals, and a detailed description thereof is
omitted.
[0050] Specifically, the array substrate AR includes a first resin
substrate 10, a first insulation film 11, a second insulation film
12, a third insulation film 13, a fourth insulation film 14,
switching elements SW1 to SW3, pixel electrodes PE1 to PE3, and a
first alignment film AL1. The thermal expansion coefficient of the
first insulation film 11 is lower than the thermal expansion
coefficient of the first resin substrate 10.
[0051] The pixel electrode PE1 is connected to the switching
element SW1, the pixel electrode PE2 is connected to the switching
element SW2, and the pixel electrode PE3 is connected to the
switching element SW3. The first alignment film AL1 covers the
pixel electrodes PE1 to PE3.
[0052] The counter-substrate CT includes a second resin substrate
30, a fifth insulation film 31, a blue color filter 32B, a green
color filter 32G, a red color filter 32R, a common electrode CE,
and a second alignment film AL2. The second resin substrate 30 is
formed of a material which is different from the material of the
first resin substrate 10. For example, the second resin substrate
30 is formed of a transparent polyimide, and the first resin
substrate 10 is formed of an opaque polyimide with good heat
resistance.
[0053] The thermal expansion coefficient of the first resin
substrate 10 is substantially equal to the thermal expansion
coefficient of the third resin substrate 30, and the thermal
expansion coefficient of the first insulation film 11 is
substantially equal to the thermal expansion coefficient of the
fifth insulation film 31. In addition, the thermal expansion
coefficients of the first insulation film 11 and fifth insulation
film 31 are lower than the thermal expansion coefficients of the
first resin substrate 10 and second resin substrate 30. For
example, each of the thermal expansion coefficients of the first
insulation film 11 and fifth insulation film 31 is 0.5 to 3
ppm/.degree. C., and each of the thermal expansion coefficients of
the first resin substrate 10 and second resin substrate 30 is 20 to
50 ppm/.degree. C. As has been described above, the thermal
expansion coefficients of the first resin substrate 10, second
resin substrate 30, first insulation film 11 and fifth insulation
film 31 are so set as to meet the above-described relationship, and
thereby a warp of the display device 1 can be prevented.
[0054] The blue color filter 32B is located above the pixel
electrode PE1, the green color filter 32G is located above the
pixel electrode PE2, and the red color filter 32R is located above
the pixel electrode PE3. The common electrode CE is opposed to each
of the pixel electrodes PE1 to PE3. The second alignment film AL2
covers the common electrode CE.
[0055] The array substrate AR and counter-substrate CT are attached
by an adhesive (or sealant) in the state in which a predetermined
cell gap is created by spacers (not shown). A liquid crystal layer
LQ is held in the cell gap between the array substrate AR and
counter-substrate CT. The liquid crystal layer LQ includes liquid
crystal molecules, the alignment state of which is controlled by an
electric field between the pixel electrodes PE and the common
electrode CE.
[0056] A liquid crystal element LC1 is composed of the pixel
electrode PE1, liquid crystal layer LQ and common electrode CE. A
liquid crystal element LC2 is composed of the pixel electrode PE2,
liquid crystal layer LQ and common electrode CE. A liquid crystal
element LC3 is composed of the pixel electrode PE3, liquid crystal
layer LQ and common electrode CE.
[0057] In the example illustrated, the case has been described that
the pixel electrodes PE1 to PE3, which constitute the respective
liquid crystal elements, are provided on the array substrate AR and
the common electrode CE is provided on the counter-substrate CT.
Alternatively, both the pixel electrodes PE1 to PE3 and the common
electrode CE may be provided on the array substrate Ar.
[0058] According to the present embodiment, the display device 1 is
configured such that the first resin substrate 10 and second resin
substrate 30 are applied. Thus, compared to a display device to
which glass substrates are applied, the reduction in thickness and
weight can be realized, the flexibility is high, and the degree of
freedom in shape is high. In addition, although the first resin
substrate 10 and second resin substrate 30 have relatively high
moisture absorption properties, the inner surface 10A of the first
resin substrate 10 is covered with the first insulation film 11
that is the first barrier layer, and the inner surface 30A of the
second resin substrate 30 is covered with the fifth insulation film
31 that is the second barrier layer. Thus, the entrance of
moisture, etc. via the first resin substrate 10 or second resin
substrate 30 can be suppressed. Thereby, it is possible to suppress
degradation due to moisture, etc. of the display elements located
between the first resin substrate 10 and second resin substrate
30.
[0059] In addition, the first resin substrate 10, which constitutes
the array substrate AR, is formed of, for example, an opaque
polyimide with good heat resistance, and the second resin substrate
30, which constitutes the counter-substrate CT, is formed of, for
example, a transparent polyimide, which is different from the
material of the first resin substrate 10. Moreover, the thermal
expansion coefficient of the first resin substrate 10 is equal to
the thermal expansion coefficient of the second resin substrate 30.
Thus, even if the display device 1 is thermally expanded, there is
little difference in thermal expansion coefficient between the
first resin substrate 10 and the second resin substrate 30.
Therefore, the occurrence of a warp of the display device 1 can be
suppressed.
[0060] Furthermore, the first insulation film (first barrier layer)
11, which covers the inner surface 10A of the first resin substrate
10, has a lower thermal expansion coefficient than the first resin
substrate 10. In addition, the fifth insulation film (second
barrier layer) 31, which covers the inner surface 30A of the second
resin substrate 30, has a lower thermal expansion coefficient than
the second resin substrate 30. The difference in thermal expansion
coefficient between the first resin substrate 10 and first
insulation film 11 is equal to the difference in thermal expansion
coefficient between the second resin substrate 30 and fifth resin
substrate 31. Thus, although stresses occur in both the array
substrate AR and counter-substrate CT, these stresses are balanced
and therefore the occurrence of a warp of the display device 1 can
be suppressed. Hence, the shape of the display device 1 can stably
be maintained.
[0061] Besides, since the thickness of the first resin substrate 10
is equal to the thickness of the second resin substrate 30, the
variation in dimension due to thermal expansion is equal between
the first resin substrate 10 and second resin substrate 30, and the
shape of the display device 1 can further be stabilized.
[0062] In FIG. 2, arrows schematically illustrate a relationship
between the thermal expansion coefficients of the first resin
substrate 10, first insulation film 11, second resin substrate 30
and fifth insulation film 31 in the array substrate AR and
counter-substrate CT in the display device 1 of the embodiment.
[0063] In the manufacturing process of the display device 1 of the
embodiment, the first resin substrate 10, first insulation film 11,
second resin substrate 30 and fifth insulation film 31 are formed
in a state of relatively high temperatures. At this time, since the
thermal expansion coefficients of the first resin substrate 10 and
second resin substrate 30 are higher than the thermal expansion
coefficients of the first insulation film 11 and fifth insulation
film 31, the first resin substrate 10 and second resin substrate 30
are, at a time immediately after the display device 1 has been
formed at high temperatures, are formed with a predetermined size
in the state in which the first resin substrate 10 and second resin
substrate 30 are expanded to a greater degree than the first
insulation film 11 and fifth insulation film 31. The ratio of
contraction of the first resin substrate 10 and second resin
substrate 30 at a time when the display device 1 has been cooled
from the high-temperature state is greater than the ratio of
contraction of the first insulation film 11 and fifth insulation
film 31. Accordingly, as the display device 1 which was formed at
high temperatures is cooled, a stress occurs in the peripheral part
of the array substrate AR such that the peripheral part of the
array substrate AR warps toward the outside of the first resin
substrate 10 (i.e. to a side away from the counter-substrate CT).
On the other hand, a stress similarly occurs in the
counter-substrate CT such that the peripheral part of the
counter-substrate CT warps toward the outside of the second resin
substrate 30 (i.e. to a side away from the array substrate AR). In
addition, the thermal expansion coefficients of the first resin
substrate 10 and second resin substrate 30 are equal, and the
thermal expansion coefficients of the first insulation film 11 and
fifth insulation film 31 are equal. Thus, such a stress as to cause
an outward warp on the array substrate AR side is substantially
equal to such a stress as to cause an outward warp on the
counter-substrate CT side.
[0064] As has been described above, although stresses occur in both
the array substrate AR and counter-substrate CT, these stresses
substantially equally act in such direction as to make the array
substrate AR and counter-substrate CT closer to each other, and
therefore the shape of the display device 1 can be maintained. In
addition, when the temperature of the environment of use of the
display device 1 is low, since such stresses as to cause outward
warps equally occur in both the array substrate AR and
counter-substrate CT, the shape of the display device 1 can be
maintained. Even when the temperature of the environment of use of
the display device 1 is high, stresses have been acting to cause
outward warps since before. Thus, the shape of the display device 1
can be maintained as long as the temperature of use exceeds the
temperature in the manufacturing process. As regards the organic EL
display device as shown in FIG. 1A and FIG. 1B, even when the
adhesion force of the adhesive for attaching the array substrate AR
and counter-substrate CT is weak, the shape of the display device 1
can be maintained since the stresses occurring in both the array
substrate AR and counter-substrate CT act in such directions as to
make the array substrate AR and counter-substrate CT closer to each
other. As regards the liquid crystal display device as shown in
FIG. 1C, the shape of the display device 1 can be maintained and
the cell gap can be kept since the stresses occurring in both the
array substrate AR and counter-substrate CT act in such directions
as to press the spacers lying between the array substrate AR and
counter-substrate CT, and therefore degradation in display quality
can be suppressed.
[0065] In the meantime, a comparative example will now be examined,
in which the thermal expansion coefficient of the first resin
substrate 10 is lower than the thermal expansion coefficient of the
first insulation film 11, and the thermal expansion coefficient of
the second resin substrate 30 is lower than the thermal expansion
coefficient of the fifth insulation film 31. In this comparative
example, in the array substrate AR after fabrication, such a stress
occurs that the central part of the array substrate AR warps toward
the outside of the first resin substrate 10. On the other hand, in
the counter-substrate CT after fabrication, such a stress occurs
that the central part of the counter-substrate CT warps toward the
outside of the second resin substrate 30. In this manner, the
stresses occurring in both the array substrate AR and
counter-substrate CT act in such directions as to make the array
substrate AR and counter-substrate CT away from each other at the
central part of the display device 1.
[0066] Thus, as regards the organic EL display device as shown in
FIG. 1A and FIG. 1B, when the adhesion force between the array
substrate AR and counter-substrate CT is weak, the shape of the
display device 1 can hardly be maintained. As regards the liquid
crystal display device as shown in FIG. 1C, there is a concern that
the degradation in display quality or the occurrence of bubbles
will occur, since the stresses occurring in both the array
substrate AR and counter-substrate CT act in such directions as to
increase the cell gap between the array substrate AR and
counter-substrate CT.
[0067] As has been described above, according to the display device
1 of the present embodiment, the shape can be maintained more
stably than in the comparative example, and the degradation in
display quality can be suppressed.
[0068] Next, a description is given of an example of a method of
manufacturing the display device 1 according to the embodiment. In
the description below, an example of the manufacturing method of
the display device with the structure example shown in FIG. 1A will
be described.
[0069] To begin with, as illustrated in FIG. 3, a first mother
substrate Ml is prepared. Specifically, a film of a resin material
with a desired thickness is formed on a first support substrate 100
such as a glass substrate. Then, this film is cured, and a first
resin substrate 10 is formed. At this time, the first resin
substrate 10 extends over a region corresponding to the display
section, this region being a part of the region which becomes an
individual array substrate after a cutting step (to be described
later). In the example illustrated, the first resin substrate 10
extends over regions corresponding to three display sections,
namely a first region A1, a second region A2 and a third region A3.
Thereafter, on the first resin substrate 10, a thin film of an
inorganic material is formed and, where necessary, a multilayer of
thin films is formed. Thereby, a first insulation film 11 is
formed. The first insulation film 11 extends over the first region
A1, second region A2 and third region A3.
[0070] Subsequently, a display element part 121 is formed in the
first region A1 on the first insulation film 11, a display element
part 122 is formed in the second region A2 on the first insulation
film 11, and a display element part 123 is formed in the third
region A3 on the first insulation film 11. In addition, mounting
portions 131 to 133 for mounting signal supply sources, such as
driving IC chips and flexible circuit boards, are formed on the
first insulation film 11. The display element parts 121 to 123 have
the same structure, and each of the display element parts 121 to
123 includes a plurality of display elements, for example, organic
EL elements, which are arranged in a matrix.
[0071] The display element parts 121 to 123 are formed in the
following manner. Specifically, switching elements SW1 to SW3, a
second insulation film 12, a third insulation film 13 and a fourth
insulation film 14 are formed on the first insulation film 11. At
the same time, various wirings are formed. Subsequently, pixel
electrodes PE1 to PE3 are formed on the fourth insulation film 14,
and then ribs 15 are formed. Thereafter, an organic light emission
layer ORG is formed, and a common electrode CE is formed. Through
these steps, organic EL elements OLED1 to OLED3 are formed. Then,
where necessary, a sealing film 20, which covers the organic EL
elements OLED1 to OLED3, is formed.
[0072] Subsequently, as illustrated in FIG. 4, a second mother
substrate M2 is prepared. Specifically, a film of a resin material
with a desired thickness is formed on a second support substrate
200 such as a glass substrate. Thereafter, the film of resin
material is cured and then patterned by using a photolithography
process or the like. Thereby, transparent second resin substrates
30 are formed. The individual second resin substrates 30 are spaced
apart from each other. Specifically, each of the second resin
substrates 30 is formed in an island shape on the second support
substrate 200.
[0073] A thin film of an inorganic material is formed on each of
the second resin substrates 30 and, where necessary, a multilayer
of thin films is formed. Thus, fifth insulation films 31 are
formed.
[0074] A color filter layer CF is formed on each of the fifth
insulation films 31. The color filter layers CF have the same
structure, and each color filter layer includes a blue color filter
32B, a green color filter 32G and a red color filter 32R.
[0075] Subsequently, as illustrated in FIG. 5, a frame-shaped
sealant SE is formed in each of the first region A1, second region
A2 and third region A3, and then a filler (or an adhesive) 40 is
coated in an inside surrounded by the sealant SE.
[0076] Thereafter, as illustrated in FIG. 6, the first mother
substrate M1 and second mother substrate M2 are attached.
Specifically, the respective display element parts 121 to 123 are
attached to the color filter layers CF by the sealant SE and
adhesive 40.
[0077] Subsequently, as illustrated in FIG. 7, with respect to the
second mother substrate M2, the second support substrate 200 is
peeled from the second resin substrate 30, and the second support
substrate 200 is removed. Similarly, with respect to the first
mother substrate M1, the first support substrate 100 is peeled from
the first resin substrate 10, and the first support substrate 100
is removed. As regards the peeling and removal of the first support
substrate 100 and second support substrate 200, for example, a
technology called "laser ablation" is applicable. The laser
ablation is a technique in which a laser beam is radiated on the
support substrate, whereby local energy absorption occurs at the
interface between the support substrate and the resin substrate and
the support substrate is made separable from the resin substrate.
An excimer laser, for example, is applicable as the light source
for emitting the laser beam.
[0078] Subsequently, as illustrated in FIG. 8, the first resin
substrate 10 is cut. In the example illustrated, the first resin
substrate 10 is cut between the first region A1 and second region
A2 and between the second region A2 and third region A3. Thereby,
chips C1 to C3 are separated. The chip C1 includes the display
element part 121 in the first region A1, and includes the mounting
portion 131 on the outside of the first region A1. The chip C2
includes the display element part 122 in the second region A2, and
includes the mounting portion 132 on the outside of the second
region A2. The chip C3 includes the display element part 123 in the
third region A3, and includes the mounting portion 133 on the
outside of the third region A3.
[0079] Subsequently, a signal supply source is mounted on each of
the mounting portions 131 to 133.
[0080] Thereby, the display device (organic EL display device) 1 of
the present embodiment is manufactured.
[0081] During the above-described manufacturing process, the
display device (organic EL display device) 1 of the present
embodiment is exposed in a high-temperature state. However, as
described above, the thermal expansion coefficients of the first
resin substrate 10, second resin substrate 30, fifth insulation
film 31 and first insulation film 11 are so set as to meet the
above-described relationship. Thereby, a warp of the display device
1 can be prevented.
[0082] As has been described above, according to the present
embodiment, a display device, which can stably maintain the shape
thereof, can be provided.
[0083] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *