U.S. patent application number 17/403665 was filed with the patent office on 2021-12-02 for method and device for manufacturing flexible light emission device.
The applicant listed for this patent is SAKAI DISPLAY PRODUCTS CORPORATION. Invention is credited to KATSUHIKO KISHIMOTO, KAZUNOBU MAMENO, KOHICHI TANAKA.
Application Number | 20210375844 17/403665 |
Document ID | / |
Family ID | 1000005779703 |
Filed Date | 2021-12-02 |
United States Patent
Application |
20210375844 |
Kind Code |
A1 |
KISHIMOTO; KATSUHIKO ; et
al. |
December 2, 2021 |
METHOD AND DEVICE FOR MANUFACTURING FLEXIBLE LIGHT EMISSION
DEVICE
Abstract
According to a flexible light-emitting device production method
of the present disclosure, after an intermediate region (30i) and
flexible substrate regions (30d) of a plastic film (30) of a
multilayer stack (100) are divided from one another, the interface
between the flexible substrate regions (30d) and a glass base (10)
is irradiated with lift-off light. The multilayer stack (100) is
separated into a first portion (110) and a second portion (120)
while the multilayer stack (100) is in contact with a stage (210).
The first portion (110) includes a plurality of light-emitting
devices (1000) which are in contact with the stage (210). The
light-emitting devices (1000) include a plurality of functional
layer regions (20) and the flexible substrate regions (30d). The
second portion (120) includes the glass base (10) and the
intermediate region (30i). The step of irradiating with the
lift-off light includes the first light scanning for scanning the
interface in a first direction with the light in the form of a line
beam, and the second light scanning for scanning the interface in a
second direction with the light. In each of the first and second
light scanning, the irradiation intensity is modulated such that
the intensity for at least part of the interface between the
intermediate region (30i) and the glass base (10) is lower than the
irradiation intensity for the interface between the flexible
substrate regions (30d) and the glass base (10).
Inventors: |
KISHIMOTO; KATSUHIKO;
(Osaka, JP) ; MAMENO; KAZUNOBU; (Osaka, JP)
; TANAKA; KOHICHI; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAKAI DISPLAY PRODUCTS CORPORATION |
Osaka |
|
JP |
|
|
Family ID: |
1000005779703 |
Appl. No.: |
17/403665 |
Filed: |
August 16, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16967705 |
Oct 7, 2020 |
11127726 |
|
|
PCT/JP2018/017900 |
May 9, 2018 |
|
|
|
17403665 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2227/326 20130101;
H01L 51/56 20130101; H01L 25/167 20130101; H01L 27/3244 20130101;
H01L 33/005 20130101; H01L 51/0097 20130101; H01L 2251/566
20130101; B32B 17/10 20130101 |
International
Class: |
H01L 25/16 20060101
H01L025/16; H01L 27/32 20060101 H01L027/32; H01L 33/00 20060101
H01L033/00; H01L 51/00 20060101 H01L051/00; H01L 51/56 20060101
H01L051/56; B32B 17/10 20060101 B32B017/10 |
Claims
1. A method for producing a flexible light-emitting device,
comprising: providing a multilayer stack which has a first surface
and a second surface, the multilayer stack including a glass base
which defines the first surface, a plurality of functional layer
regions each including a TFT layer and a light-emitting device
layer, a synthetic resin film provided between the glass base and
the plurality of functional layer regions and bound to the glass
base, the synthetic resin film including a plurality of flexible
substrate regions respectively supporting the plurality of
functional layer regions and an intermediate region surrounding the
plurality of flexible substrate regions, and a protection sheet
which covers the plurality of functional layer regions and which
defines the second surface; dividing the intermediate region and
respective ones of the plurality of flexible substrate regions of
the synthetic resin film from one another; irradiating an interface
between the synthetic resin film and the glass base with lift-off
light; and separating the multilayer stack into a first portion and
a second portion by increasing a distance from a stage to the glass
base while the second surface of the multilayer stack is kept in
contact with the stage, wherein the first portion of the multilayer
stack includes a plurality of light-emitting devices which are in
contact with the stage, and the plurality of light-emitting devices
respectively include the plurality of functional layer regions and
include the plurality of flexible substrate regions of the
synthetic resin film, the second portion of the multilayer stack
includes the glass base and the intermediate region of the
synthetic resin film, irradiating the interface between the
plurality of flexible substrate regions of the synthetic resin film
and the glass base with the lift-off light includes first light
scanning for scanning the interface in a first direction parallel
to the interface with the lift-off light in the form of a line beam
which is transverse to the first direction, and second light
scanning for scanning the interface in a second direction which is
parallel to the interface and different from the first direction
with the lift-off light in the form of a line beam which is
transverse to the second direction, and in each of the first and
second light scanning, an irradiation intensity of the lift-off
light is modulated such that an irradiation intensity of the
lift-off light for at least part of an interface between the
intermediate region of the synthetic resin film and the glass base
is lower than an irradiation intensity of the lift-off light for
the interface between the plurality of flexible substrate regions
of the synthetic resin film and the glass base, wherein the
light-emitting device layer includes a plurality of arrayed micro
LEDs, and the lift-off light is laser light.
2. The method of claim 1, wherein in each of the first and second
light scanning, an irradiation intensity of the lift-off light is
lower than a threshold level which is necessary for delaminating
the plurality of flexible substrate regions of the synthetic resin
film from the glass base through a single scanning cycle, and a sum
of irradiation intensities of the lift-off light in the first and
second light scanning is higher than the threshold level.
3. The method of claim 1, wherein providing the multilayer stack
includes providing a delamination layer between the glass base and
the synthetic resin film.
4. The method of claim 3, wherein the delamination layer is made of
a metal or a semiconductor.
5. The method of claim 1, wherein the lift-off light is a line beam
extending in a direction parallel to a peripheral edge of the glass
base, and irradiating the interface between the synthetic resin
film and the glass base with the lift-off light includes moving an
irradiation region on the interface which is to be irradiated with
the lift-off light in another direction which is transverse to an
extending direction of the line beam.
6. The method of claim 5, wherein the at least part of the
interface between the intermediate region of the synthetic resin
film and the glass base includes two parallel stripe regions
extending along the peripheral edge of the glass base.
7. The method of claim 6, wherein the at least part of the
interface between the intermediate region of the synthetic resin
film and the glass base includes at least one middle stripe region
which is parallel to the stripe regions.
8. The method of claim 1, wherein the at least part of the
interface between the intermediate region of the synthetic resin
film and the glass base has a width which is not less than 50% of a
width of the intermediate region.
9. The method of claim 1, wherein the at least part of the
interface between the intermediate region of the synthetic resin
film and the glass base has a width which is not less than 1
mm.
10. The method of claim 1 further comprising, after separating the
multilayer stack into the first portion and the second portion,
sequentially or concurrently performing a process on the plurality
of light-emitting devices which are in contact with the stage.
11. The method of claim 10, wherein the process includes any of
attaching a dielectric and/or electrically-conductive film to each
of the plurality of light-emitting devices, cleaning or etching
each of the plurality of light-emitting devices, and mounting an
optical part and/or an electronic part to each of the plurality of
light-emitting devices.
12. An apparatus for producing a flexible light-emitting device,
comprising: a stage for supporting a multilayer stack which has a
first surface and a second surface, the multilayer stack including
a glass base which defines the first surface, a plurality of
functional layer regions each including a TFT layer and a
light-emitting device layer, a synthetic resin film provided
between the glass base and the plurality of functional layer
regions and bound to the glass base, the synthetic resin film
including a plurality of flexible substrate regions respectively
supporting the plurality of functional layer regions and an
intermediate region surrounding the plurality of flexible substrate
regions, and a protection sheet which covers the plurality of
functional layer regions and which defines the second surface, the
intermediate region and respective ones of the plurality of
flexible substrate regions of the synthetic resin film being
divided from one another; and a lift-off light irradiation unit for
irradiating with lift-off light an interface between the synthetic
resin film and the glass base in the multilayer stack supported by
the stage, wherein the lift-off light irradiation unit configured
to performing: first light scanning for scanning the interface in a
first direction parallel to the interface with the lift-off light
in the form of a line beam which is transverse to the first
direction, and second light scanning for scanning the interface in
a second direction which is parallel to the interface and different
from the first direction with the lift-off light in the form of a
line beam which is transverse to the second direction, and wherein,
in each of the first and second light scanning, an irradiation
intensity of the lift-off light is modulated such that an
irradiation intensity of the lift-off light for at least part of an
interface between the intermediate region of the synthetic resin
film and the glass base is lower than an irradiation intensity of
the lift-off light for the interface between the plurality of
flexible substrate regions of the synthetic resin film and the
glass base, wherein the lift-off light irradiation unit comprises
an incoherent light source.
13. An apparatus for producing a flexible light-emitting device,
comprising: a stage for supporting a multilayer stack which has a
first surface and a second surface, the multilayer stack including
a glass base which defines the first surface, a plurality of
functional layer regions each including a TFT layer and a
light-emitting device layer, a synthetic resin film provided
between the glass base and the plurality of functional layer
regions and bound to the glass base, the synthetic resin film
including a plurality of flexible substrate regions respectively
supporting the plurality of functional layer regions and an
intermediate region surrounding the plurality of flexible substrate
regions, and a protection sheet which covers the plurality of
functional layer regions and which defines the second surface, the
intermediate region and respective ones of the plurality of
flexible substrate regions of the synthetic resin film being
divided from one another; and a lift-off light irradiation unit for
irradiating with lift-off light an interface between the synthetic
resin film and the glass base in the multilayer stack supported by
the stage, wherein the lift-off light irradiation unit configured
to performing: first light scanning for scanning the interface in a
first direction parallel to the interface with the lift-off light
in the form of a line beam which is transverse to the first
direction, and second light scanning for scanning the interface in
a second direction which is parallel to the interface and different
from the first direction with the lift-off light in the form of a
line beam which is transverse to the second direction, and wherein,
in each of the first and second light scanning, an irradiation
intensity of the lift-off light is modulated such that an
irradiation intensity of the lift-off light for at least part of an
interface between the intermediate region of the synthetic resin
film and the glass base is lower than an irradiation intensity of
the lift-off light for the interface between the plurality of
flexible substrate regions of the synthetic resin film and the
glass base, wherein the light-emitting device layer includes a
plurality of arrayed micro LEDs, and the lift-off light irradiation
unit comprises a laser light source.
14. The apparatus of claim 12, wherein in each of the first and
second light scanning, an irradiation intensity of the lift-off
light is lower than a threshold level which is necessary for
delaminating the plurality of flexible substrate regions of the
synthetic resin film from the glass base through a single scanning
cycle, and a sum of irradiation intensities of the lift-off light
in the first and second light scanning is higher than the threshold
level.
15. The apparatus of claim 12, further comprising an actuator for
increasing a distance from the stage to the glass base while the
stage is kept in contact with the second surface of the multilayer
stack, thereby separating the multilayer stack into a first portion
and a second portion, wherein the first portion of the multilayer
stack includes a plurality of light-emitting devices which are in
contact with the stage, and the plurality of light-emitting devices
respectively include the plurality of functional layer regions and
include the plurality of flexible substrate regions of the
synthetic resin film, and the second portion of the multilayer
stack includes the glass base and the intermediate region of the
synthetic resin film.
16. The apparatus of claim 13, wherein in each of the first and
second light scanning, an irradiation intensity of the lift-off
light is lower than a threshold level which is necessary for
delaminating the plurality of flexible substrate regions of the
synthetic resin film from the glass base through a single scanning
cycle, and a sum of irradiation intensities of the lift-off light
in the first and second light scanning is higher than the threshold
level.
17. The apparatus of claim 13, further comprising an actuator for
increasing a distance from the stage to the glass base while the
stage is kept in contact with the second surface of the multilayer
stack, thereby separating the multilayer stack into a first portion
and a second portion, wherein the first portion of the multilayer
stack includes a plurality of light-emitting devices which are in
contact with the stage, and the plurality of light-emitting devices
respectively include the plurality of functional layer regions and
include the plurality of flexible substrate regions of the
synthetic resin film, and the second portion of the multilayer
stack includes the glass base and the intermediate region of the
synthetic resin film.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a method and apparatus for
producing a flexible light-emitting device.
BACKGROUND ART
[0002] A typical example of the flexible display includes a film
which is made of a synthetic resin such as polyimide (hereinafter,
referred to as "plastic film"), and elements supported by the
plastic film, such as TFTs (Thin Film Transistors) and OLEDs
(Organic Light Emitting Diodes). The plastic film functions as a
flexible substrate. The flexible display is encapsulated with a gas
barrier film (encapsulation film) because an organic semiconductor
layer which is a constituent of the OLED is likely to deteriorate
due to water vapor.
[0003] Production of the above-described flexible display is
carried out using a glass base on which a plastic film is formed
over the upper surface. The glass base functions as a support
(carrier) for keeping the shape of the plastic film flat during the
production process. TFT devices, light-emitting devices such as
OLEDs, a gas barrier film, and the other constituents are formed on
the plastic film, whereby the structure of a flexible display is
realized while it is supported by the glass base. Thereafter, the
flexible display is delaminated from the glass base and gains
flexibility. The entirety of a portion in which TFT devices and
light-emitting devices such as OLEDs are arrayed can be referred to
as "functional layer region".
[0004] According to the prior art, a sheet-like structure including
a plurality of flexible displays is delaminated from a glass base,
and thereafter, optical parts and other constituents are mounted to
this sheet-like structure. Thereafter, the sheet-like structure is
divided into a plurality of flexible devices. This dividing is
realized by, for example, laser beam irradiation.
[0005] Patent Document No. 1 discloses the method of irradiating
the interface between each flexible display and the glass base with
laser light in order to delaminate each flexible display from the
glass base (supporting substrate). According to the method
disclosed in Patent Document No. 1, after irradiation with the
lift-off light, respective flexible displays are divided from one
another, and each of the flexible displays is delaminated from the
glass base.
CITATION LIST
Patent Literature
[0006] Patent Document No. 1: Japanese Laid-Open Patent Publication
No. 2014-48619
SUMMARY OF INVENTION
Technical Problem
[0007] According to the conventional production method, the
dividing by means of laser beam irradiation is carried out after
expensive parts, for example, encapsulation film, polarizer, and/or
heat radiation sheet, are mounted to a sheet-like structure
including a plurality of flexible displays. Therefore, unnecessary
portions divided by laser beam irradiation, i.e., portions which
are not to be constituents of a final display, are quite useless.
Also, there is a problem that, after being delaminated from the
glass base, it is difficult to handle a plurality of flexible
displays which have no rigidity.
[0008] Such a problem is not limited to flexible displays which
include OLEDs as light-emitting devices but can arise in producing
a flexible light-emitting device which includes a micro LED (PLED)
formed as a light-emitting device using inorganic semiconductor
materials.
[0009] The present disclosure provides a method and apparatus for
producing a flexible light-emitting device which are capable of
solving the above-described problems.
Solution to Problem
[0010] A flexible light-emitting device production method of the
present disclosure includes, in an exemplary embodiment, providing
a multilayer stack which has a first surface and a second surface,
the multilayer stack including a glass base which defines the first
surface, a plurality of functional layer regions each including a
TFT layer and a light-emitting device layer, a synthetic resin film
provided between the glass base and the plurality of functional
layer regions and bound to the glass base, the synthetic resin film
including a plurality of flexible substrate regions respectively
supporting the plurality of functional layer regions and an
intermediate region surrounding the plurality of flexible substrate
regions, and a protection sheet which covers the plurality of
functional layer regions and which defines the second surface,
dividing the intermediate region and respective ones of the
plurality of flexible substrate regions of the synthetic resin film
from one another, irradiating an interface between the synthetic
resin film and the glass base with lift-off light, and separating
the multilayer stack into a first portion and a second portion by
increasing a distance from a stage to the glass base while the
second surface of the multilayer stack is kept in contact with the
stage, wherein the first portion of the multilayer stack includes a
plurality of light-emitting devices which are in contact with the
stage, and the plurality of light-emitting devices respectively
include the plurality of functional layer regions and include the
plurality of flexible substrate regions of the synthetic resin
film, the second portion of the multilayer stack includes the glass
base and the intermediate region of the synthetic resin film,
irradiating the interface between the plurality of flexible
substrate regions of the synthetic resin film and the glass base
with the lift-off light includes first light scanning for scanning
the interface in a first direction parallel to the interface with
the lift-off light in the form of a line beam which is transverse
to the first direction, and second light scanning for scanning the
interface in a second direction which is parallel to the interface
and different from the first direction with the lift-off light in
the form of a line beam which is transverse to the second
direction, and in each of the first and second light scanning, an
irradiation intensity of the lift-off light is modulated such that
an irradiation intensity of the lift-off light for at least part of
an interface between the intermediate region of the synthetic resin
film and the glass base is lower than an irradiation intensity of
the lift-off light for the interface between the plurality of
flexible substrate regions of the synthetic resin film and the
glass base.
[0011] In one embodiment, the lift-off light is incoherent
light.
[0012] In one embodiment, the light-emitting device layer includes
a plurality of arrayed micro LEDs, and the lift-off light is laser
light.
[0013] In one embodiment, in each of the first and second light
scanning, an irradiation intensity of the lift-off light is lower
than a threshold level which is necessary for delaminating the
plurality of flexible substrate regions of the synthetic resin film
from the glass base through a single scanning cycle, and a sum of
irradiation intensities of the lift-off light in the first and
second light scanning is higher than the threshold level.
[0014] In one embodiment, providing the multilayer stack includes
providing a delamination layer between the glass base and the
synthetic resin film.
[0015] In one embodiment, the delamination layer is made of a metal
or a semiconductor.
[0016] In one embodiment, the lift-off light is a line beam
extending in a direction parallel to a peripheral edge of the glass
base, and irradiating the interface between the synthetic resin
film and the glass base with the lift-off light includes moving an
irradiation region on the interface which is to be irradiated with
the lift-off light in another direction which is transverse to an
extending direction of the line beam.
[0017] In one embodiment, the at least part of the interface
between the intermediate region of the synthetic resin film and the
glass base includes two parallel stripe regions extending along the
peripheral edge of the glass base.
[0018] In one embodiment, the at least part of the interface
between the intermediate region of the synthetic resin film and the
glass base includes at least one middle stripe region which is
parallel to the stripe regions.
[0019] In one embodiment, the at least part of the interface
between the intermediate region of the synthetic resin film and the
glass base has a width which is not less than 50% of a width of the
intermediate region.
[0020] In one embodiment, the at least part of the interface
between the intermediate region of the synthetic resin film and the
glass base has a width which is not less than 1 mm.
[0021] In one embodiment, the method further includes, after
separating the multilayer stack into the first portion and the
second portion, sequentially or concurrently performing a process
on the plurality of light-emitting devices which are in contact
with the stage.
[0022] In one embodiment, the process includes any of attaching a
dielectric and/or electrically-conductive film to each of the
plurality of light-emitting devices, cleaning or etching each of
the plurality of light-emitting devices, and mounting an optical
part and/or an electronic part to each of the plurality of
light-emitting devices.
[0023] A flexible light-emitting device production apparatus of the
present disclosure includes, in an exemplary embodiment, a stage
for supporting a multilayer stack which has a first surface and a
second surface, the multilayer stack including a glass base which
defines the first surface, a plurality of functional layer regions
each including a TFT layer and a light-emitting device layer, a
synthetic resin film provided between the glass base and the
plurality of functional layer regions and bound to the glass base,
the synthetic resin film including a plurality of flexible
substrate regions respectively supporting the plurality of
functional layer regions and an intermediate region surrounding the
plurality of flexible substrate regions, and a protection sheet
which covers the plurality of functional layer regions and which
defines the second surface, the intermediate region and respective
ones of the plurality of flexible substrate regions of the
synthetic resin film being divided from one another, and a lift-off
light irradiation unit for irradiating with lift-off light an
interface between the synthetic resin film and the glass base in
the multilayer stack supported by the stage, wherein the lift-off
light irradiation unit includes first light scanning for scanning
the interface in a first direction parallel to the interface with
the lift-off light in the form of a line beam which is transverse
to the first direction, and second light scanning for scanning the
interface in a second direction which is parallel to the interface
and different from the first direction with the lift-off light in
the form of a line beam which is transverse to the second
direction, and in each of the first and second light scanning, an
irradiation intensity of the lift-off light is modulated such that
an irradiation intensity of the lift-off light for at least part of
an interface between the intermediate region of the synthetic resin
film and the glass base is lower than an irradiation intensity of
the lift-off light for the interface between the plurality of
flexible substrate regions of the synthetic resin film and the
glass base.
[0024] In one embodiment, the lift-off light irradiation unit
comprises an incoherent light source.
[0025] In one embodiment, the light-emitting device layer includes
a plurality of arrayed micro LEDs, and the lift-off light
irradiation unit comprises a laser light source.
[0026] In one embodiment, in each of the first and second light
scanning, an irradiation intensity of the lift-off light is lower
than a threshold level which is necessary for delaminating the
plurality of flexible substrate regions of the synthetic resin film
from the glass base through a single scanning cycle, and a sum of
irradiation intensities of the lift-off light in the first and
second light scanning is higher than the threshold level.
[0027] In one embodiment, the apparatus further includes an
actuator for increasing a distance from the stage to the glass base
while the stage is kept in contact with the second surface of the
multilayer stack, thereby separating the multilayer stack into a
first portion and a second portion, wherein the first portion of
the multilayer stack includes a plurality of light-emitting devices
which are in contact with the stage, and the plurality of
light-emitting devices respectively include the plurality of
functional layer regions and include the plurality of flexible
substrate regions of the synthetic resin film, and the second
portion of the multilayer stack includes the glass base and the
intermediate region of the synthetic resin film.
Advantageous Effects of Invention
[0028] According to an embodiment of the present invention, a novel
method for producing a flexible light-emitting device which is
capable of solving the above-described problems is provided.
BRIEF DESCRIPTION OF DRAWINGS
[0029] FIG. 1A is a plan view showing a configuration example of a
multilayer stack used in a flexible light-emitting device
production method of the present disclosure.
[0030] FIG. 1B is a cross-sectional view of the multilayer stack
taken along line B-B of FIG. 1A.
[0031] FIG. 1C is a cross-sectional view showing another example of
the multilayer stack.
[0032] FIG. 1D is a cross-sectional view showing still another
example of the multilayer stack.
[0033] FIG. 2 is a cross-sectional view schematically showing the
dividing positions in the multilayer stack.
[0034] FIG. 3A is a diagram schematically showing a state
immediately before a stage supports a multilayer stack.
[0035] FIG. 3B is a diagram schematically showing a state where the
stage supports the multilayer stack.
[0036] FIG. 3C is a diagram schematically showing that the
interface between a glass base and a plastic film of the multilayer
stack with lift-off light.
[0037] FIG. 4A is a perspective view schematically showing
irradiation of the multilayer stack with a line beam emitted from a
line beam source of a delaminating apparatus.
[0038] FIG. 4B is a perspective view schematically showing the
position of the stage at the start of the first light scanning.
[0039] FIG. 4C is a perspective view schematically showing the
position of the stage at the end of the first light scanning.
[0040] FIG. 4D is a perspective view schematically showing a
multilayer stack with its orientation being rotated by 90.degree.
on an axis parallel to the Z-axis.
[0041] FIG. 4E is a perspective view schematically showing the
position of the stage at the end of the second light scanning.
[0042] FIG. 5A is a perspective view schematically showing the
first light scanning.
[0043] FIG. 5B is a perspective view schematically showing the
first light scanning.
[0044] FIG. 5C is a perspective view schematically showing the
first light scanning.
[0045] FIG. 5D is a perspective view schematically showing the
second light scanning.
[0046] FIG. 6 is a diagram schematically showing an example of the
distribution in the Y-axis direction of the irradiation intensity
of the lift-off light in the first light scanning.
[0047] FIG. 7 is a diagram schematically showing another example of
the distribution in the Y-axis direction of the irradiation
intensity of the lift-off light in the first light scanning.
[0048] FIG. 8 is a diagram schematically showing an example of the
distribution in the X-axis direction (scanning direction) of the
irradiation intensity of the lift-off light in the first light
scanning.
[0049] FIG. 9 is a diagram schematically showing another example of
the distribution in the X-axis direction of the irradiation
intensity of the lift-off light in the first light scanning.
[0050] FIG. 10A is a diagram schematically showing still another
example of the distribution in the X-axis direction of the
irradiation intensity of the lift-off light.
[0051] FIG. 10B is a diagram schematically showing still another
example of the distribution in the X-axis direction of the
irradiation intensity of the lift-off light.
[0052] FIG. 11 is a diagram schematically showing an example of the
distribution in the Y-axis direction of the irradiation intensity
of the lift-off light in the second light scanning.
[0053] FIG. 12 is a diagram schematically showing another example
of the distribution in the Y-axis direction of the irradiation
intensity of the lift-off light in the second light scanning.
[0054] FIG. 13 is a diagram schematically showing an example of the
distribution in the X-axis direction (scanning direction) of the
irradiation intensity of the lift-off light in the second light
scanning.
[0055] FIG. 14 is a diagram schematically showing another example
of the distribution in the X-axis direction of the irradiation
intensity of the lift-off light in the second light scanning.
[0056] FIG. 15A is a plan view schematically showing low
irradiation regions by the first light scanning.
[0057] FIG. 15B is a plan view schematically showing low
irradiation regions by the second light scanning.
[0058] FIG. 15C is a plan view schematically showing the entire
shape of a low irradiation region after the first and second light
scanning.
[0059] FIG. 16A is a cross-sectional view schematically showing the
multilayer stack before the multilayer stack is separated into the
first portion and the second portion after irradiation with
lift-off light.
[0060] FIG. 16B is a cross-sectional view schematically showing the
multilayer stack separated into the first portion and the second
portion.
[0061] FIG. 17 is a perspective view showing the glass base
separated from the multilayer stack by a delaminating
apparatus.
[0062] FIG. 18 is a perspective view showing removal of the glass
base from the stage.
[0063] FIG. 19 is a perspective view showing the stage from which
the glass base has been removed.
[0064] FIG. 20 is a cross-sectional view showing the stage from
which the glass base has been removed.
[0065] FIG. 21 is a cross-sectional view showing flexible
light-emitting devices detached from the stage.
[0066] FIG. 22 is a cross-sectional view showing another protection
sheet bound to a plurality of light-emitting devices which are in
contact with the stage.
[0067] FIG. 23 is a cross-sectional view showing a carrier sheet
carrying a plurality of parts which are to be mounted to the
plurality of light-emitting devices.
[0068] FIG. 24A is a cross-sectional view illustrating a step of
the flexible light-emitting device production method in an
embodiment of the present disclosure.
[0069] FIG. 24B is a cross-sectional view illustrating a step of
the flexible light-emitting device production method in an
embodiment of the present disclosure.
[0070] FIG. 24C is a cross-sectional view illustrating a step of
the flexible light-emitting device production method in an
embodiment of the present disclosure.
[0071] FIG. 24D is a cross-sectional view illustrating a step of
the flexible light-emitting device production method in an
embodiment of the present disclosure.
[0072] FIG. 25 is an equivalent circuit diagram of a single
sub-pixel in a flexible light-emitting device.
[0073] FIG. 26 is a perspective view of the multilayer stack in the
middle of the production process.
[0074] FIG. 27A is a diagram schematically showing the upper
surface of a line beam source 214 which includes a single column of
light emitting diode devices arrayed in Y-axis direction.
[0075] FIG. 27B is a cross-sectional view of the line beam source
shown in FIG. 27A taken along line B-B.
[0076] FIG. 27C is a diagram showing the moving direction of the
line beam source relative to the multilayer stack 100.
[0077] FIG. 28A is a diagram schematically showing the upper
surface of a line beam source 214 which includes a plurality of
columns of light emitting diode devices arrayed in Y-axis
direction.
[0078] FIG. 28B is a cross-sectional view of the line beam source
shown in FIG. 28A taken along line B-B.
[0079] FIG. 28C is a diagram showing the moving direction of the
line beam source relative to the multilayer stack.
[0080] FIG. 28D is a plan view schematically showing irradiation
regions the line beam source of FIG. 28A is forming.
[0081] FIG. 28E is a plan view showing an example of irradiation
regions formed by temporarily modulating the electric current
flowing through each of the light emitting diode devices during
scanning by the line beam source.
DESCRIPTION OF EMBODIMENTS
[0082] An embodiment of a method and apparatus for producing a
flexible light-emitting device of the present disclosure is
described with reference to the drawings. Examples of the
"light-emitting device" include displays and illumination devices.
In the following description, unnecessarily detailed description
will be omitted. For example, detailed description of well-known
matter and repetitive description of substantially identical
elements will be omitted. This is for the purpose of avoiding the
following description from being unnecessarily redundant and
assisting those skilled in the art to easily understand the
description. The present inventors provide the attached drawings
and the following description for the purpose of assisting those
skilled in the art to fully understand the present disclosure.
Providing these drawings and description does not intend to limit
the subject matter recited in the claims.
[0083] <Multilayer Stack>
[0084] See FIG. 1A and FIG. 1B. In a flexible light-emitting device
production method of the present embodiment, firstly, a multilayer
stack 100 illustrated in FIG. 1A and FIG. 1B is provided. FIG. 1A
is a plan view of the multilayer stack 100. FIG. 1B is a
cross-sectional view of the multilayer stack 100 taken along line
B-B of FIG. 1A. In FIG. 1A and FIG. 1B, an XYZ coordinate system
with X-axis, Y-axis and Z-axis, which are perpendicular to one
another, is shown for reference.
[0085] The multilayer stack 100 includes a glass base (motherboard
or carrier) 10, a plurality of functional layer regions 20 each
including a TFT layer 20A and a light-emitting device layer 20B, a
synthetic resin film (hereinafter, simply referred to as "plastic
film") 30 provided between the glass base 10 and the plurality of
functional layer regions 20 and bound to the glass base 10, and a
protection sheet 50 covering the plurality of functional layer
regions 20. The multilayer stack 100 further includes a gas barrier
film 40 provided between the plurality of functional layer regions
20 and the protection sheet 50 so as to cover the entirety of the
functional layer regions 20. The multilayer stack 100 may include
another unshown layer, such as a buffer layer.
[0086] In the present embodiment, the light-emitting device layer
20B includes, for example, a plurality of OLED devices which are
two-dimensionally arrayed. In the present disclosure, the
"light-emitting device layer" refers to a two-dimensional array of
light-emitting devices. Each of the light-emitting devices is not
limited to an OLED device but may be a micro LED device. In the
present embodiment, a typical example of the flexible
light-emitting device is a "flexible display" but may be a
"flexible illumination device".
[0087] The first surface 100a of the multilayer stack 100 is
defined by the glass base 10. The second surface 100b of the
multilayer stack 100 is defined by the protection sheet 50. The
glass base 10 and the protection sheet 50 are materials temporarily
used in the production process but are not constituents of a final
flexible light-emitting device.
[0088] The plastic film 30 shown in the drawings includes a
plurality of flexible substrate regions 30d respectively supporting
the plurality of functional layer regions 20, and an intermediate
region 30i surrounding each of the flexible substrate regions 30d.
The flexible substrate regions 30d and the intermediate region 30i
are merely different portions of a single continuous plastic film
30 and do not need to be physically distinguished. In other words,
regions of the plastic film 30 lying immediately under respective
ones of the functional layer regions 20 are the flexible substrate
regions 30d, and the other region of the plastic film 30 is the
intermediate region 30i.
[0089] Each of the plurality of functional layer regions 20 is a
constituent of a final flexible light-emitting device (e.g.,
display panel). In other words, the multilayer stack 100 has such a
structure that a plurality of flexible light-emitting devices which
are not yet divided from one another are supported by a single
glass base 10. Each of the functional layer regions 20 has such a
shape that, for example, the thickness (size in Z-axis direction)
is several tens of micrometers, the length (size in X-axis
direction) is about 12 cm, and the width (size in Y-axis direction)
is about 7 cm. These sizes can be set to arbitrary values according
to the required largeness of the display screen or emission surface
region. The shape in the XY plane of each of the functional layer
regions 20 is rectangular in the example illustrated in the
drawings but is not limited to this example. The shape in the XY
plane of each of the functional layer regions 20 may include a
square, a polygon, or a shape which includes a curve in the
contour.
[0090] As shown in FIG. 1A, the flexible substrate regions 30d are
two-dimensionally arrayed in rows and columns according to the
arrangement of the flexible light-emitting devices. The
intermediate region 30i consists of a plurality of stripes
perpendicular to one another and forms a grid pattern. The width of
the stripes is, for example, about 1-4 mm. The flexible substrate
region 30d of the plastic film 30 functions as the "flexible
substrate" in each flexible light-emitting device which is in the
form of a final product. Meanwhile, the intermediate region 30i of
the plastic film 30 is not a constituent of the final product.
[0091] In an embodiment of the present disclosure, the
configuration of the multilayer stack 100 is not limited to the
example illustrated in the drawings. The number of functional layer
regions 20 supported by a single glass base 10 is arbitrary.
[0092] The size or proportion of each component illustrated in
respective drawings is determined from the viewpoint of
understandability. The actual size or proportion is not necessarily
reflected in the drawings.
[0093] The multilayer stack 100 which can be used in the production
method of the present disclosure is not limited to the example
illustrated in FIG. 1A and FIG. 1B. FIG. 1C and FIG. 1D are
cross-sectional views showing other examples of the multilayer
stack 100. In the example illustrated FIG. 1C, the protection sheet
50 covers the entirety of the plastic film 30 and extends outward
beyond the plastic film 30. In the example illustrated FIG. 1D, the
protection sheet covers the entirety of the plastic film 30 and
extends outward beyond the glass base 10. As will be described
later, after the glass base 10 is separated from the multilayer
stack 100, the multilayer stack 100 is a thin flexible sheet-like
structure which has no rigidity. The protection sheet 50 serves to
protect the functional layer regions 20 from impact and abrasion
when the functional layer regions 20 collide with or come into
contact with external apparatuses or instruments in the step of
delaminating the glass base 10 and the steps after the
delaminating. Since the protection sheet 50 is peeled off from the
multilayer stack 100 in the end, a typical example of the
protection sheet 50 has a laminate structure which includes an
adhesive layer of a relatively small adhesive force (a layer of an
applied mold-releasing agent) over its surface. The more detailed
description of the multilayer stack 100 will be described
later.
[0094] <Dividing of Light-Emitting Devices>
[0095] According to the flexible light-emitting device production
method of the present embodiment, after the step of providing the
above-described multilayer stack 100, the step of dividing an
intermediate region 30i and respective ones of a plurality of
flexible substrate regions 30d of the plastic film 30 from one
another is carried out.
[0096] FIG. 2 is a cross-sectional view schematically showing the
positions for dividing the intermediate region 30i and respective
ones of the plurality of flexible substrate regions 30d of the
plastic film 30 from one another. The positions of irradiation
extend along the periphery of each of the flexible substrate
regions 30d. In FIG. 2, the positions indicated by arrows are
irradiated with a laser beam for cutting. Part of the multilayer
stack 100 exclusive of the glass base 10 is cut into a plurality of
light-emitting devices (e.g., display panels) 1000 and the
remaining unnecessary portions. By cutting, a gap of several tens
of micrometers to several hundreds of micrometers is formed between
each of the light-emitting devices 1000 and a portion surrounding
the light-emitting device 1000. The cutting can also be realized by
a cutter which has a fixed blade or a rotary blade instead of the
laser beam irradiation. After the cutting, the light-emitting
devices 1000 and the remaining unnecessary portions are still bound
to the glass base 10.
[0097] When the cutting is realized by a laser beam, the wavelength
of the laser beam may be in any of the infrared, visible and
ultraviolet bands. From the viewpoint of reducing the effect of the
cutting on the glass base 10, the laser beam desirably has a
wavelength in the range of green to ultraviolet. For example, when
a Nd:YAG laser apparatus is used, the cutting can be carried out
using a second harmonic wave (wavelength: 532 nm) or a third
harmonic wave (wavelength: 343 nm or 355 nm). In such a case, the
laser power is adjusted to 1 to 3 watts, and the scanning rate is
set to about 500 mm per second, so that the multilayer structure
supported by the glass base 10 can be cut (divided) into
light-emitting devices and unnecessary portions without damaging
the glass base 10.
[0098] According to the embodiment of the present disclosure, the
timing of the above-described cutting is earlier than in the prior
art. Since the cutting is carried out while the plastic film 30 is
bound to the glass base 10, alignment for the cutting can be made
with high precision and accuracy even if the gap between adjoining
light-emitting devices 1000 is narrow. Thus, the gap between
adjoining light-emitting devices 1000 can be shortened, and
accordingly, useless portions which are unnecessary for a final
product can be reduced. In the prior art, after the delaminating
from the glass base 10, a polarizer, a heat radiation sheet, and/or
an electromagnetic shield can be adhered to the plastic film 30 so
as to cover the entirety of the surface (delaminated surface) of
the plastic film 30. In such a case, the polarizer, the heat
radiation sheet, and/or the electromagnetic shield are also divided
by cutting into portions covering the light-emitting devices 1000
and the remaining unnecessary portions. The unnecessary portions
are disposed of as waste. On the other hand, according to the
production method of the present disclosure, production of such
waste can be suppressed as will be described later.
[0099] <Lift-Off Light Irradiation>
[0100] After the intermediate region 30i and respective ones of the
plurality of flexible substrate regions 30d of the plastic film 30
are divided from one another, the step of irradiating the interface
between the flexible substrate regions 30d of the plastic film 30
and the glass base 10 with laser light is carried out using a
lift-off light irradiation unit.
[0101] FIG. 3A schematically shows a state immediately before the
stage 210 supports the multilayer stack 100. In the present
embodiment, the stage 210 is a chuck stage which has a large number
of pores in the surface for suction. The multilayer stack 100 is
arranged such that the second surface 100b of the multilayer stack
100 faces the surface 210S of the stage 210, and is supported by
the stage 210.
[0102] FIG. 3B schematically shows a state where the stage 210
supports the multilayer stack 100. The arrangement of the stage 210
and the multilayer stack 100 is not limited to the example
illustrated in the drawing. For example, the multilayer stack 100
may be placed upside down such that the stage 210 is present under
the multilayer stack 100.
[0103] In the example illustrated in FIG. 3B, the multilayer stack
100 is in contact with the surface 210S of the stage 210, and the
stage 210 holds the multilayer stack 100 by suction.
[0104] Then, as shown in FIG. 3C, the interface between the plastic
film 30 and the glass base 10 is irradiated with lift-off light
216. FIG. 3C schematically illustrates irradiation of the interface
between the glass base 10 and the plastic film 30 of the multilayer
stack 100 with the lift-off light 216 in the shape of a line
extending in a direction vertical to the sheet of the drawing. A
part of the plastic film 30 at the interface between the glass base
10 and the plastic film 30 absorbs the lift-off light 216 and
decomposes (disappears). By scanning the above-described interface
with the lift-off light 216, the degree of binding of the plastic
film 30 to the glass base 10 is reduced. The wavelength of the
lift-off light 216 is typically in the ultraviolet band. The
wavelength of the lift-off light 216 is selected such that the
lift-off light 216 is hardly absorbed by the glass base 10 but is
absorbed by the plastic film 30 as much as possible. The light
absorption by the glass base 10 is, for example, about 10% in the
wavelength range of 343-355 nm but can increase to 30-60% at 308
nm.
[0105] Hereinafter, lift-off light irradiation according to the
present embodiment is described in detail.
[0106] <Lift-Off Light Irradiation Unit 1>
[0107] In the present embodiment, the lift-off light irradiation
unit includes a line beam source for emitting the lift-off light
216. The line beam source includes a laser apparatus and an optical
system for shaping laser light emitted from the laser apparatus
into a line beam. In the present disclosure, the lift-off light
irradiation unit is referred to as "delaminating apparatus".
[0108] FIG. 4A is a perspective view schematically showing
irradiation of the multilayer stack 100 with a line beam (lift-off
light 216) emitted from a line beam source 214 of a delaminating
apparatus 220. For the sake of understandability, the stage 210,
the multilayer stack 100 and the line beam source 214 are shown as
being spaced away from one another in the Z-axis direction of the
drawing. During irradiation with the lift-off light 216, the second
surface 100b of the multilayer stack 100 is in contact with the
stage 210.
[0109] The delaminating apparatus 220 includes a controller 300 for
controlling the operation of the line beam source 214 and the stage
210. The controller 300 changes the irradiation intensity of
lift-off light emitted from the line beam source 214 according to
the position of the stage 210. The controller 300 can be a
general-purpose computer which has a known configuration. The
controller 300 includes, for example, a microprocessor and a
nonvolatile memory. In the nonvolatile memory, a program is stored
which includes instructions to the microprocessor.
[0110] FIG. 4B schematically shows the position of the stage 210
during irradiation with the lift-off light 216 (at the start of the
first light scanning). Although not shown in FIG. 4B, the
multilayer stack 100 is supported by the stage 210.
[0111] Examples of the laser apparatus that emits the lift-off
light 216 include gas laser apparatuses such as excimer laser,
solid state laser apparatuses such as YAG laser, semiconductor
laser devices, and other types of laser apparatuses. A XeCl excimer
laser apparatus can generate laser light at the wavelength of 308
nm. When yttrium orthovanadate (YVO.sub.4) doped with neodymium
(Nd) or YVO.sub.4 doped with ytterbium (Yb) is used as a lasing
medium, the wavelength of laser light (fundamental wave) emitted
from the lasing medium is about 1000 nm. Therefore, the fundamental
wave can be converted by a wavelength converter to laser light at
the wavelength of 340-360 nm (third harmonic wave) before it is
used. Laser light in the shape of a spot beam emitted from these
laser apparatuses is combined with an optical system consisting of
lenses and prisms for reshaping the light into the shape of a line
beam, whereby lift-off light 216 in the shape of a line beam is
produced.
[0112] In the embodiment of the present disclosure, as will be
described later, light scanning is carried out multiple times in
different directions (first direction and second direction)
relative to the multilayer stack 100. A sacrificial layer or
delamination layer (a thin layer of a metal or amorphous silicon)
may be provided at the interface between the plastic film 30 and
the glass base 10. From the viewpoint of suppressing generation of
ashes, using laser light at the wavelength of 308 nm from the
excimer laser apparatus, rather than laser light at the wavelength
of 340-360 nm, is more effective. Providing the sacrificial layer
is highly effective in suppressing generation of ashes.
[0113] The position of irradiation with the lift-off light 216
moves relative to the glass base 10 for scanning with the lift-off
light 216. In the delaminating apparatus 220, the multilayer stack
100 may be movable while the light source 214 from which the
lift-off light is to be emitted and an optical unit (not shown) are
stationary. Alternatively, the light source 214 may be movable
while the multilayer stack 100 is stationary. In the present
embodiment, irradiation with the lift-off light 216 is carried out
during a period where the stage 210 moves from the position shown
in FIG. 4B to the position shown in FIG. 4C. That is, scanning with
the lift-off light 216 is carried out by movement of the stage 210
in the X-axis direction (first light scanning).
[0114] Then, as illustrated in FIG. 4D, the stage 210 rotates by
90.degree. on an axis parallel to the Z-axis. Thereafter, as shown
in FIG. 4E, the stage 210 is irradiated with the lift-off light 216
while moving in the negative direction of the X-axis (second light
scanning). In each of the first and second light scanning, the
irradiation intensity of laser light is modulated such that the
irradiation intensity of laser light for at least part of the
interface between the intermediate region 30i of the plastic film
30 and the glass base 10 is lower than the irradiation intensity of
laser light for the interface between the plurality of flexible
substrate regions 30d of the plastic film 30 and the glass base 10.
In each of the first and second light scanning, the irradiation
intensity of laser light is lower than a threshold level which is
necessary for delamination at the interface between the plurality
of flexible substrate regions 30d of the plastic film 30 and the
glass base 10 through a single scanning cycle. However, the sum of
the irradiation intensities of laser light in the first and second
light scanning is higher than the threshold level. Hereinafter,
details of these two light scanning cycles are described.
[0115] First, see FIG. 5A to FIG. 5D. FIG. 5A to FIG. 5D are
perspective views schematically showing the scanning with the
lift-off light 216. In these drawings, the direction of the Z-axis
is opposite to the direction of the Z-axis of FIG. 4A to FIG.
4C.
[0116] In FIG. 5A, the rays of the lift-off light 216 are
represented by broken line arrows. In FIG. 5B to FIG. 5D, the rays
of the lift-off light 216 are represented by solid line arrows. The
broken line arrows represent rays whose irradiation intensity is
relatively low as compared with the solid line arrows. The state of
FIG. 5D corresponds to the state of FIG. 4D. The stage 210 of FIG.
5D results from rotation of the stage 210 of FIG. 5C by 90.degree.
on an axis parallel to the Z-axis. In the present embodiment,
scanning with the lift-off light 216 is first carried out along the
longer side of the multilayer stack 100 and then carried out along
the shorter side of the multilayer stack 100. Such an order is
arbitrary.
[0117] In the present embodiment, the lift-off light 216 is a line
beam extending in a direction parallel to the peripheral edge of
the glass base 10 (in this example, the Y-axis direction). This
line beam is emitted from the line beam source 214 shown in FIG. 4A
and other drawings. The irradiation position of the lift-off light
216 on the multilayer stack 100 can be moved not only in the
positive direction of the X-axis but also in the negative direction
of the X-axis with the passage of time as shown in FIG. 5A, FIG.
5B, FIG. 5C and FIG. 5D.
[0118] Next, see FIG. 6. FIG. 6 is a diagram schematically showing
an example of the distribution in the Y-axis direction of the
irradiation intensity of the lift-off light 216. In the graph of
FIG. 6, the horizontal axis represents the Y-axis coordinate of the
irradiation region, and the vertical axis represents the
irradiation intensity. The irradiation intensity is expressed by
the energy density per unit area (e.g., [mJ/cm.sup.2]). In the
graph of FIG. 6, specific values of the irradiation intensity are
not shown. The irradiation intensity refers to a value in the range
of, for example, not less than 0 mJ/cm.sup.2 and not more than 500
mJ/cm.sup.2. In the graph of FIG. 6, a solid line represents the
Y-axis direction distribution I(Y) of the irradiation intensity,
and a dot-chain line represents threshold level Th of the
irradiation intensity which is necessary for delamination. In the
present disclosure, the "threshold level" means a level at which
the plastic film 30 sufficiently delaminates from the glass base
10. Threshold level Th is, for example, 250-300 mJ/cm.sup.2. When a
sacrificial layer is provided between the plastic film 30 and the
glass base 10, threshold level Th can be increased to, for example,
300-600 mJ/cm.sup.2. Finally, in a region irradiated with lift-off
light at an irradiation intensity lower than this threshold level
Th, the amount of lift-off light absorbed by the plastic film 30 is
insufficient. Therefore, the plastic film 30 in that region remains
bound, without being delaminated from the glass base 10.
[0119] According to the present embodiment, the irradiation
intensity does not exceed threshold level Th at any position
through a single light scanning cycle.
[0120] In FIG. 6, a cross section of the multilayer stack 100 which
is parallel to the YZ plane is shown above the graph for reference.
The glass base 10 extends from position Y0 to position Y5. The
light-emitting device 1000 on the left-hand side resides in the
region extending from position Y1 to position Y2. The
light-emitting device 1000 on the right-hand side resides in the
region extending from position Y3 to position Y4. In other words,
the flexible substrate regions 30d of the plastic film 30
correspond to the region extending from position Y1 to position Y2
and the region extending from position Y3 to position Y4.
Meanwhile, the intermediate region 30i of the plastic film 30
corresponds to the region extending from position Y0 to position
Y1, the region extending from position Y2 to position Y3, and the
region extending from position Y4 to position Y5.
[0121] In the example of FIG. 6, the irradiation intensity
distribution I(Y) of the lift-off light is, for example, in a range
of 50% to 98% of threshold level Th in a region larger than the
region extending from position Y0 to position Y5. In the present
embodiment, the lift-off light is a line beam which is longer than
the size in the Y-axis direction of the glass base 10. The
irradiation intensity of the line beam achieved through a single
scanning cycle is insufficient for delamination. The smallest value
of the irradiation intensity distribution I(Y) of the lift-off
light during the scanning is, for example, 0 mJ/cm.sup.2 but may be
greater than 0 mJ/cm.sup.2 (e.g., 20-130 mJ/cm.sup.2). It is only
required that the sum of the irradiation intensities achieved
through two lift-off light irradiation cycles does not reach a
level which is necessary for delaminating the intermediate region
30i of the plastic film 30 from the glass base 10.
[0122] In the example of FIG. 6, the irradiation intensity
distribution I(Y) of the lift-off light is linear although the
embodiment of the present disclosure is not limited to such an
example. For example, as in the example illustrated in FIG. 7, a
part or the entirety of the irradiation intensity distribution I(Y)
of the lift-off light may be curved. When an amorphous
semiconductor is heated and crystallized by irradiation with laser
light in the shape of a line beam, the irradiation intensity
distribution is desired to be uniform in order to achieve uniform
crystallinity. On the other hand, when the delamination in the
present embodiment is carried out, the line beam does not need to
be uniform so long as the irradiation intensity of the lift-off
light at the interface which needs delamination exceeds threshold
level Th after two scanning cycles.
[0123] Next, see FIG. 8. FIG. 8 is a diagram schematically showing
an example of the distribution in the X-axis direction (scanning
direction) of the irradiation intensity of the lift-off light 216.
In the graph of FIG. 8, the horizontal axis represents the X-axis
coordinate of the irradiation position, and the vertical axis
represents the irradiation intensity. In the graph of FIG. 8, a
solid line represents the X-axis direction distribution I(X) of the
irradiation intensity, and a dot-chain line represents threshold
level Th of the irradiation intensity which is necessary for
delamination.
[0124] In FIG. 8, a cross section of the multilayer stack 100 which
is parallel to the XZ plane is shown above the graph for reference.
This cross section is perpendicular to the cross section of FIG. 6.
The glass base 10 extends from position X0 to position X5. The
light-emitting device 1000 on the left-hand side in the drawing
resides in the region extending from position X1 to position X2.
The light-emitting device 1000 on the right-hand side resides in
the region extending from position X3 to position X4. In other
words, the flexible substrate regions 30d of the plastic film
correspond to the region extending from position X1 to position X2
and the region extending from position X3 to position X4.
Meanwhile, the intermediate region 30i of the plastic film 30
corresponds to the region extending from position X0 to position X1
(width: W1), the region extending from position X2 to position X3
(width: W3), and the region extending from position X4 to position
X5 (width: W2). The intermediate region 30i at the left edge of the
plastic film in FIG. 8 (width: W1) includes a region in which the
irradiation intensity is sufficiently lower than threshold level Th
(width: S1). Meanwhile, the intermediate region 30i at the right
edge of the plastic film 30 in FIG. 8 (width: W2) includes another
region in which the irradiation intensity is sufficiently lower
than threshold level Th (width: S2). Here, W1>S1 and W2>S2
hold. It is preferred that width S1 is not less than 50% of width
W1 and width S2 is not less than 50% of width W2.
[0125] The X-axis direction distribution I(X) of the irradiation
intensity represents the whole (total or integral value) of a
single scanning cycle with the lift-off light. For example, while
the irradiation position of the lift-off light (the position of the
center line of the line beam) moves from position X0 to position
X5, the region extending from position X4 to position X5 is not
irradiated with the lift-off light. In this period, the irradiation
intensity of the lift-off light in the region extending from
position X4 to position X5 is, as a matter of course, zero.
[0126] The line width (the short axis dimension, the size in the
X-axis direction) of the lift-off light 216 can be, for example,
about 0.2 mm (=200 .mu.m). This dimension defines the largeness of
the irradiation region at the interface between the plastic film 30
and the glass base 10 at a certain time. The lift-off light 216 can
be emitted in the form of a pulsed or continuous wave. Irradiation
with the pulsed wave can be carried out at the frequency (the
number of shots in one second) of, for example, about 200 times per
second. When the lift-off light 216 is a pulsed wave, the scanning
speed is determined such that two consecutive shots form
partially-overlapping irradiation regions. If, for example, the
line width (the short axis dimension, the size in the X-axis
direction) of the lift-off light 216 is 0.2 mm and the irradiation
position moves at 20 mm per second in the X-axis direction, a gap
can occur between neighboring shots so long as the number of shots
per second is less than 100. Therefore, the number of shots per
second needs to exceed 100.
[0127] The positioning accuracy of the irradiation position depends
on the mechanical forwarding accuracy of the stage 210. When a YAG
laser apparatus is used, the line width (the short axis dimension,
the size in the X-axis direction) of the lift-off light 216 can be
set to, for example, 40 .mu.m. When the stage 210 is moved stepwise
at intervals of 20 .mu.m, the overlap of irradiation regions formed
by two consecutive shots can be 50%. When the stage 210 is moved
stepwise at intervals of 30 .mu.m, the overlap of irradiation
regions formed by two consecutive shots can be 75%. Although, in
general, the line width (the short axis dimension, the size in the
X-axis direction) of the lift-off light 216 depends on the type of
the laser light source and the optical system, the irradiation
intensity can be changed without modulating the power of the laser
light source by controlling the overlap of irradiation regions.
[0128] When the irradiation position of the lift-off light is
forwarded stepwise, "stepwise movement of the line beam source 214"
and "pulsed irradiation with the lift-off light" can be repeated.
In this case, irradiation with the lift-off light can be carried
out while movement of the line beam source 214 relative to the
stage 210 is stopped. In irradiation of a stationary object with
laser light, adjustment of the irradiation intensity to a target
value is easier than in irradiation of a moving object with laser
light. For example, the irradiation intensity can be adjusted by
increasing or decreasing the number of irradiation pulses or the
irradiation duration at a stationary position.
[0129] When the moving speed (scanning speed) of the irradiation
position is fixed to a predetermined value, the irradiation
intensity can be modulated by increasing or decreasing the number
of shots per second. On the contrary, when the number of shots per
second is fixed, the irradiation intensity can be modulated by
increasing or decreasing the moving speed (scanning speed) of the
irradiation position. The irradiation intensity can be modulated by
changing the other parameters, e.g., the power of the line beam
source 214 or the optical distance from the line beam source 214 to
the multilayer stack 100. Also, a low irradiation region can be
formed by providing a mechanical shutter between the line beam
source 214 and the glass base 10 such that this shutter blocks the
optical path of the lift-off light.
[0130] As seen from FIG. 8, in this example, the irradiation
intensity of lift-off light for at least part of the interface
between the intermediate region 30i of the plastic film 30 and the
glass base 10 is lower than the irradiation intensity of lift-off
light for the interface between the flexible substrate regions 30d
of the plastic film 30 and the glass base 10. The region of this
"at least part" may be referred to as "low irradiation region". In
the example of FIG. 8, the low irradiation region includes two
parallel stripe regions extending along the peripheral edge of the
glass base 10 (a region of width S1 and a region of width S2). The
two stripe regions can be formed by irradiation with weak lift-off
light 216 shown in FIG. 5A.
[0131] FIG. 9 shows an example where the irradiation intensity is
temporarily lower than threshold level Th in the middle of the
scanning with the lift-off light 216. Specifically, the irradiation
intensity is lower than threshold level Th in part of the region
extending from position X2 to position X3 (width: S3). In this
example, the "low irradiation region" at the interface between the
intermediate region 30i of the plastic film 30 and the glass base
10 includes not only the two stripe regions but also a single
middle stripe region (width: S3) which is parallel to the two
stripe regions. Each of widths S1, S2, S3 of these stripe regions
is, for example, not less than 1 mm and, in a certain example, not
less than 3 mm.
[0132] In the examples of FIG. 8 and FIG. 9, two light-emitting
devices 1000 are arranged in the direction of the X-axis. When N is
an integer not less than 3 and N light-emitting devices 1000 are
arranged in the direction of the X-axis, the total number of
stripes formed by the intermediate region 30i lying between two
adjoining light-emitting devices 1000 is N-1. It is not necessary
to provide a low irradiation region in all of the N-1 stripes.
Alternatively, a plurality of low irradiation regions may be
provided for an intermediate region 30i which forms a single
stripe.
[0133] In the examples of FIG. 8 and FIG. 9, the low irradiation
region of width S1 and the low irradiation region of width S2 each
reach the peripheral edge of the plastic film 30, although the
embodiment of the present disclosure is not limited to this
example. For example, the low irradiation region can be in various
forms as shown in FIG. 10A and FIG. 10B. FIG. 10A and FIG. 10B are
diagrams schematically showing still other examples of the
distribution in the X-axis direction of the irradiation intensity
of the lift-off light. In these drawings, examples of the
modulation pattern of the irradiation intensity at the interface
between the intermediate region 30i surrounding the light-emitting
device 1000 on the left-hand side of FIG. 8 and the glass base 10
are shown.
[0134] In the example shown in FIG. 10A, the striped low
irradiation regions (width: S1) extending along the peripheral edge
of the plastic film 30 do not reach the peripheral edge of the
plastic film 30. The irradiation intensity of the lift-off light
may exceed threshold level Th before the glass base 10 is
irradiated with the lift-off light. As in the region extending from
position X1 to position X3 shown in FIG. 10A, the irradiation
intensity may gradually change. When the irradiation intensity
gradually changes, the width (the size in the scanning direction)
of the "low irradiation region" can be defined as the width of a
region in which the irradiation intensity in a single light
scanning cycle is lower than threshold level Th.
[0135] In the example shown in FIG. 10B, the low irradiation region
consists of a plurality of stripes which have a relatively narrow
width. When the lift-off light is, for example, pulsed light, such
a low irradiation region can be realized by applying consecutive
shots such that irradiation regions do not overlap each other.
[0136] Next, the second light scanning is described with reference
to FIG. 11 to FIG. 14. The second light scanning is carried out in
a direction different from the direction of the first light
scanning.
[0137] FIG. 11 and FIG. 12 correspond to FIG. 6 and FIG. 7. A
difference in the drawings resides in the difference in the cross
section of the multilayer stack 100. To meet the cross section of
the multilayer stack 100, position Y0 to position Y5 of FIG. 6 and
FIG. 7 are shifted to position Y0' to position Y5',
respectively.
[0138] FIG. 13 and FIG. 14 correspond to FIG. 8 and FIG. 9 and show
the irradiation intensity in the second light scanning. The first
difference in the drawings resides in the difference in the cross
section of the multilayer stack 100. To meet the cross section of
the multilayer stack 100, position X0 to position X5 of FIG. 8 and
FIG. 9 are shifted to position X0' to position X5', respectively.
Widths W1, W2, W3 are represented by widths W1', W2', W3'. The
waveform of the X-axis direction distribution I(X) of the
irradiation intensity of the lift-off light in the second light
scanning does not need to be identical with the X-axis direction
distribution I(X) of the irradiation intensity of the lift-off
light in the second light scanning. The highest value and/or the
lowest value of the irradiation intensity also do not need to be
identical between the first and second light scanning.
[0139] FIG. 15A is a plan view showing the outline of the first
light scanning and an example of the shape and arrangement of low
irradiation regions S1, S2, S3 to be formed. The low irradiation
regions S1, S2, S3 are formed at positions not overlapping the
functional layer regions 20. Also in the other regions than the low
irradiation regions S1, S2, S3, the irradiation intensity of the
lift-off light in the first light scanning does not reach threshold
level Th.
[0140] FIG. 15B is a plan view showing the outline of the second
light scanning and an example of the shape and arrangement of low
irradiation regions S1', S2', S3' to be formed. The low irradiation
regions S1', S2', S3' are also formed at positions not overlapping
the functional layer regions 20. In the other regions than the low
irradiation regions S1', S2', S3', the irradiation intensity of the
lift-off light in the second light scanning does not reach
threshold level Th, but the accumulated value of the irradiation
intensity of the lift-off light in the first and second light
scanning exceeds threshold level Th.
[0141] FIG. 15C is a plan view showing an example of the entire
shape of a low irradiation region S after the two light scanning
cycles. In the example illustrated in FIG. 15C, the four
rectangular regions represent regions in which the total
irradiation intensity of the lift-off light sufficiently exceeds
threshold level Th through the two light scanning cycles. In the
hatched region S, the total irradiation intensity of the lift-off
light is lower than threshold level Th even through the two light
scanning cycles. In a region which is a low irradiation region at
least once in the two light scanning cycles, the irradiation
intensity of the lift-off light is determined such that the
irradiation intensity does not finally reach threshold level
Th.
[0142] According to the present embodiment, light scanning which is
carried out while modulating the irradiation intensity is performed
twice in different directions (directions transverse to each other,
typically directions perpendicular to each other), whereby a low
irradiation region S of a shape such as shown in FIG. 15C can be
formed. Therefore, the intermediate region 30i of the plastic film
30 can be selectively kept bound to the glass base 10.
[0143] In the present embodiment, the moving direction of the stage
210 in the second light scanning is opposite to the moving
direction of the stage 210 in the first light scanning, although
these moving directions may be identical.
[0144] <Lift-Off Light Irradiation Unit 2>
[0145] The lift-off light irradiation unit according to the present
disclosure does not necessary to comprise the above-described light
sources. The lift-off light may be radiated from an incoherent
light source instead of a coherent light source such as laser light
source. In the example described in the following paragraphs, the
interface between the plastic film and the glass base is irradiated
with lift-off light radiated from a plurality of light emitting
diode devices.
[0146] As the light source for radiating the lift-off light, light
emitting diode devices are available at a lower cost than coherent
light sources such as semiconductor laser devices, and designing
and operation of the apparatus are easier from the viewpoint of
eye-safety. Light emitting diode (UV-LED) devices which are capable
of radiating ultraviolet light have the size of, for example, 3.5
mm (longitudinal).times.3.5 mm (transverse).times.1.2 mm
(thickness). The technique of enlarging and shaping a spot beam
laser light into a line beam laser (lift-off light) by an optical
system is difficult to apply to a substrate having a G8 size (2400
mm.times.2200 mm) or more. The reason for this is that the optical
system becomes huge, so that the manufacturing cost is too high and
the quality (uniformity) of the line beam is deteriorated. When
using line-beam-shaped laser light, the limit was practically up to
the G6H substrate size (1800 mm.times.750 mm short side). Unlike
such a conventional laser lift-off equipment, a lift-off light
source in which a plurality of light emitting diode are arrayed
makes it possible to process a G8 substrate or a super-large
substrate larger.
[0147] The emission intensity of the light emitting diode device is
controlled by adjusting the magnitude of the driving current.
Therefore, a plurality of light emitting diode devices, by
modulating the driving current flowing through each of the light
emitting diode devices, the irradiation intensity of the lift-off
light can be modulated.
[0148] The array pitch of the light emitting diode devices is in
the range of, for example, not less than 3 mm and not more than 10
mm. The light radiated from the light emitting diode devices is
incoherent (non-coherent) light, which is different from laser
light. The wavelength of the light radiated from the light emitting
diode devices is in the range of, for example, not less than 300 nm
and not more than 380 nm. The irradiation energy of the lift-off
light radiated from the plurality of light emitting diode devices
is in the range of not less than 100 mJ/cm.sup.2 and not more than
300 mJ/cm.sup.2.
[0149] Light radiated from each of the light emitting diode devices
diverges around the Z-axis direction at the center. This light
represents the distribution (directivity) of the relative radiation
intensity which depends on the radiation angle .theta. that is the
gradient from the Z-axis. In one example, the relative radiation
intensity of the light emitting diode devices can be about 75% at
0=45.degree., and about 50% at 0=65.degree.. The directivity of the
light emitting diode devices can be adjusted by providing a lens
and/or reflector.
[0150] Commercially-available light emitting diode devices are
capable of radiating ultraviolet light at 365 nm with the power of
1450 milliwatts on the driving conditions that, for example, the
electric voltage is 3.85 volts and the electric current is 1000
milliamperes.
[0151] An example of a line beam light source in which a plurality
of light emitting diode devices are arrayed is described with
reference to FIG. 27A, FIG. 27B and FIG. 27C.
[0152] FIG. 27A schematically shows the upper surface of a line
beam light source 214 which includes a plurality of light emitting
diode devices 400 arrayed in Y-axis direction. FIG. 27B is a
cross-sectional view of the line beam light source 214 shown in
FIG. 27A taken along line B-B. FIG. 27B also shows a multilayer
stack 100. FIG. 27C is a diagram showing the moving direction of
the line beam light source 214 relative to the multilayer stack
100.
[0153] As shown in FIG. 27A, the line beam light source 214 can be
coupled with a driving circuit 280A. The driving circuit 280A can
modulate the magnitude of the electric current flowing through each
of the light emitting diode devices 400. The driving circuit 280A
can be coupled with a controller 260. The controller 260 controls
the operation of the driving circuit 280A, thereby temporally
and/or spatially modulating the irradiation intensity of the
lift-off light radiated from the line beam light source 214.
[0154] In this example, the ultraviolet light radiated from the
light emitting diode devices 400 travels through a cylindrical lens
410 and enters the glass base 10 of the multilayer stack 100 in
order to increase the irradiation energy per unit area (irradiation
intensity expressed in joule/cm.sup.2). Since the ultraviolet light
is focused in X-axis direction, the width (the size in X-axis
direction) of the irradiation region in the interface at which
delamination is to occur (delamination plane) can be decreased to,
for example, about 0.2 mm or smaller. Since the cylindrical lens
410 does not focus the light in X-axis direction, the size in
Y-axis direction of the irradiation region is not shortened.
[0155] The irradiation intensity of the lift-off light can be
increased by decreasing the array pitch of the light emitting diode
devices 400 such that the number density of the light emitting
diode devices 400 increases. For example, when each of the light
emitting diode devices 400 has the above-described size, several
tens of light emitting diode devices 400 or 100 or more light
emitting diode devices 400 may be arrayed with the intervals of 3.5
mm to 10 mm (array pitch: the distance between the centers of
adjoining light sources). When smaller light emitting diode devices
400 are used, they can be arrayed with the intervals of, for
example, 2.0 mm to 10 mm. The array pitch of the light emitting
diode devices 400 is preferably not more than 5 mm.
[0156] When light emitting diode devices 400 of high directivity
are arrayed at a high density and the distance from the light
emitting diode devices 400 to the delamination plane is, for
example, 1.5-5 mm, the irradiation intensity can be modulated at
the spatial resolution of 2 mm to 10 mm even without an optical
element such as cylindrical lens.
[0157] The electric current flowing through each of the light
emitting diode devices is modulated while the line beam light
source 214 is moved relative to the multilayer stack 100 as shown
in FIG. 27C. As a result, lift-off light irradiation can be
realized in the same way as the embodiment with the use of the line
beam light source 214.
[0158] To increase the spatial resolution of the line beam light
source 214, the light emitting diode devices 400 may be arrayed in
a plurality of columns.
[0159] FIG. 28A schematically shows the upper surface of the line
beam light source 214 which includes a plurality of columns of
light emitting diode devices 400 arrayed in Y-axis direction. FIG.
28B is a cross-sectional view of the line beam light source 214
shown in FIG. 28A taken along line B-B. FIG. 28B also shows the
multilayer stack 100. FIG. 28C is a diagram showing the moving
direction of the line beam light source 214 relative to the
multilayer stack 100.
[0160] This line beam light source 214 can also be coupled with the
driving circuit 280A. The controller 260 controls the operation of
the driving circuit 280A, thereby modulating the lift-off light
radiated from the line beam light source 214.
[0161] In this example, the line beam light source 214 includes
five columns of light emitting diode devices 400 each extending in
Y-axis direction. The positions in Y-axis direction of the five
columns of light emitting diode devices 400 are different from one
another. The positions of the light emitting diode columns are
shifted by P/5 in Y-axis direction between adjoining columns where
P is the array pitch.
[0162] This line beam light source 214 includes a lens sheet 420
for converging light such that one side of the irradiation region
formed by each of the light emitting diode devices 400 has the
length of about P/5. Ultraviolet light transmitted through the lens
sheet 420 can form irradiation regions in the form of dots over the
delamination plane.
[0163] As shown in FIG. 28C, when the line beam light source 214 is
moved relative to the multilayer stack 100, a plurality of
irradiation regions overlap so that the entire delamination plane
can be irradiated with the ultraviolet light. By modulating the
electric current flowing through each of the light emitting diode
while the line beam light source 214 is moved relative to the
multilayer stack 100, spatial and temporal modulation can be
carried out.
[0164] FIG. 28D is a diagram schematically showing irradiation
regions 218 the line beam source 214 of FIG. 28A is forming. By
turning off some of the light emitting diode devices 400 during
scanning by the line beam light source 214, non-irradiation regions
whose width is smaller than the size of the light emitting diode
devices 400 can be formed.
[0165] FIG. 28E is a plan view showing an example of irradiation
regions formed by temporarily modulating the electric current
flowing through each of the light emitting diode devices 400 during
scanning by the line beam source 214. It is seen that a pattern of
irradiation regions and non-irradiation regions can be formed with
high spatial resolution.
[0166] Thus, according to the array of the light emitting diode
devices 400 illustrated in FIG. 28A, modulation with high spatial
resolution is possible as compared with the array of the light
emitting diode devices 400 illustrated in FIG. 27A.
[0167] As such a light source is used for performing the first
light scanning and the second light scanning, the above-described
irradiation intensity distribution for delamination can be achieved
at a lower cost than the expensive laser light source. Furthermore,
since laser light is not used, it is also advantageous from the
viewpoint of safety for human eyes (eye-safe).
[0168] <Lift-Off>
[0169] FIG. 16A illustrates a state where the multilayer stack 100
is in contact with the stage 210 after irradiation with the
lift-off light. While this state is maintained, the distance from
the stage 210 to the glass base 10 is increased. At this point in
time, the stage 210 of the present embodiment holds a
light-emitting device portion of the multilayer stack 100.
[0170] An unshown actuator holds the glass base 10 and moves the
entirety of the glass base 10 in the direction of arrow L, thereby
carrying out delaminating (lift-off). The glass base 10 can be
moved together with an unshown chuck stage while being adhered by
suction to the chuck stage. The direction of movement of the glass
base 10 does not need to be vertical, but may be diagonal, to the
first surface 100a of the multilayer stack 100. The movement of the
glass base does not need to be linear but may be rotational.
Alternatively, the stage 210 may be moved upward in the drawing
while the glass base 10 is secured by an unshown holder or another
stage.
[0171] FIG. 16B is a cross-sectional view showing the
thus-separated first portion 110 and second portion 120 of the
multilayer stack 100. FIG. 17 is a perspective view showing the
second portion 120 of the multilayer stack 100. The first portion
110 of the multilayer stack 100 includes a plurality of
light-emitting devices 1000 which are in contact with the stage
210. The respective light-emitting devices 1000 include the
functional layer regions 20 and the plurality of flexible substrate
regions 30d of the plastic film 30. Meanwhile, the second portion
120 of the multilayer stack 100 includes the glass base 10 and the
intermediate region 30i of the plastic film 30. The intermediate
region 30i of the plastic film 30 is bound to the glass base 10 in
at least some low-irradiation regions. Thus, the entirety of the
intermediate region 30i of the plastic film 30 separates from the
stage 210 while the entirety of the intermediate region 30i is kept
adhered to the glass base 10.
[0172] In the example of FIG. 17, both the irradiation process with
the lift-off light and the delaminating process are carried out
using the delaminating apparatus 220 that includes the stage 210.
The embodiment of the present disclosure is not limited to this
example. The irradiation process with the lift-off light may be
carried out using a lift-off light irradiation unit (delaminating
apparatus) which includes the stage 210, while the delaminating
process is carried out using a different apparatus that includes
another stage which is different from the stage 210. In this case,
after irradiation with the lift-off light, it is necessary to
transfer the multilayer stack 100 from the stage 210 to another
unshown stage. When the same stage is used for carrying out both
the irradiation process with the lift-off light and the
delaminating process, the step of transferring the multilayer stack
between the stages can be omitted.
[0173] As described above, in the present embodiment, the step of
separating the multilayer stack 100 into the first portion 110 and
the second portion 120 is carried out while the stage 210 holds the
second surface 100b of the multilayer stack 100 by suction. The
essence of this separation step resides in that an unnecessary part
of the multilayer stack 100 which is not a constituent of the
light-emitting device 1000 separates together with the glass base
10 from the stage 210. In the present embodiment, the cutting step
illustrated in FIG. 2, i.e., the step of cutting a part of the
multilayer stack 100 exclusive of the glass base 10 into the
plurality of light-emitting devices 1000 and the remaining
unnecessary portions, is carried out before irradiation with the
lift-off light. Carrying out the cutting step before the lift-off
light irradiation step is effective in realizing the separation
illustrated in FIG. 16B and FIG. 17. In order that an unnecessary
portion which is not a constituent of the light-emitting device
1000 remains on the glass base 10, the irradiation intensity of the
lift-off light is modulated such that part of that unnecessary
portion is kept bound to the glass base 10.
[0174] <Steps after Delaminating>
[0175] FIG. 18 is a perspective view showing the first portion 110
(light-emitting devices 1000) of the multilayer stack 100 adhered
by suction to the stage 210 and the second portion 120 (the glass
base 10 and objects bound thereto) at a position distant from the
stage 210. Unnecessary portions of the multilayer stack 100 which
are not constituents of the light-emitting devices 1000 are bound
to the glass base 10.
[0176] FIG. 19 is a perspective view showing the first portion 110
of the multilayer stack 100 adhered by suction to the stage 210.
The first portion 110 of the multilayer stack 100 supported by the
stage 210 includes a plurality of light-emitting devices 1000
arrayed in rows and columns. In the example of FIG. 19, a part of
the plastic film 30, specifically the surface (delaminated surface)
30s of the flexible substrate regions 30d, is exposed.
[0177] FIG. 20 is a cross-sectional view showing that the stage 210
holds the light-emitting devices 1000 by suction. This cross
section is parallel to the ZX plane. The direction of the Z-axis of
FIG. 20 is opposite to the direction of the Z-axis of FIG. 18 and
FIG. 19.
[0178] Various processes can be sequentially or concurrently
performed on the plurality of light-emitting devices 1000 which are
in contact with the stage 210.
[0179] The "processes" to be performed on the light-emitting
devices 1000 can include attaching a dielectric and/or
electrically-conductive film to each of the plurality of
light-emitting devices 1000, cleaning or etching each of the
plurality of light-emitting devices 1000, and mounting an optical
part and/or an electronic part to each of the plurality of
light-emitting devices 1000. Specifically, a part such as, for
example, a polarizer, encapsulation film, touchscreen, heat
radiation sheet, electromagnetic shield, driver integrated circuit,
or the like, can be mounted to the flexible substrate region 30d of
each of the light-emitting devices 1000. The sheet-like part
includes a functional film which can add an optical, electrical or
magnetic function to the light-emitting devices 1000.
[0180] The plurality of light-emitting devices 1000 are supported
by the stage 210 such that the light-emitting devices 1000 are
adhered by suction to the stage 210. The various processes which
are to be performed on each of the light-emitting devices 1000 can
be efficiently carried out.
[0181] The surface 30s of the plastic film 30 delaminated from the
glass base 10 is active. Therefore, the surface 30s may be covered
with a protection film or subjected to a surface treatment for
conversion to a hydrophobic surface before various parts are
mounted to the surface 30s.
[0182] FIG. 21 is a cross-sectional view schematically showing the
light-emitting devices 1000 detached from the stage 210 after the
sheet-like part (functional film) 60 is mounted to the
light-emitting devices 1000.
[0183] According to the prior art, the plastic film is delaminated
from the glass base before the light-emitting devices 1000 are
divided from one another. Therefore, when a subsequent process is
carried out, a large number of light-emitting devices 1000 are
bound to a single plastic film. Thus, it is difficult to carry out
an efficient process on each of the light-emitting devices 1000.
When the light-emitting devices 1000 are divided from one another
after the sheet-like part is attached, a portion of the sheet-like
part which is present in an intermediate region between adjoining
two of the light-emitting devices 1000 is useless.
[0184] On the other hand, according to the embodiment of the
present disclosure, a large number of light-emitting devices 1000
are still orderly arrayed on the stage 210 after being delaminated
from the glass base 10. Therefore, various processes can be
efficiently performed on the light-emitting devices 1000
sequentially or concurrently.
[0185] After the step of separating the multilayer stack 100 into
the first portion 110 and the second portion 120, the step of
adhering another protection sheet (second protection sheet) 70 to
the plurality of light-emitting devices 1000 which are in contact
with the stage 210 may be further performed as shown in FIG. 22.
The second protection sheet 70 can perform the function of
temporarily protecting the surface of the flexible substrate
regions 30d of the plastic film 30 delaminated from the glass base
10. The second protection sheet 70 can have the same laminate
structure as that of the previously-described protection sheet 50.
The protection sheet 50 can be referred to as "first protection
sheet 50".
[0186] The second protection sheet 70 may be adhered to the
plurality of light-emitting devices 1000 after various processes
which have previously been described are performed on the plurality
of light-emitting devices 1000 which are in contact with the stage
210.
[0187] When suction of the light-emitting devices 1000 by the stage
210 is stopped after the second protection sheet 70 is adhered, the
plurality of light-emitting devices 1000 which are bound to the
second protection sheet 70 can be detached from the stage 210.
Thereafter, the second protection sheet 70 can function as a
carrier for the plurality of light-emitting devices 1000. This is
transfer of the light-emitting devices 1000 from the stage 210 to
the second protection sheet 70. Various processes may be
sequentially or concurrently performed on the plurality of
light-emitting devices 1000 which are bound to the second
protection sheet 70.
[0188] FIG. 23 is a cross-sectional view showing a carrier sheet 90
carrying a plurality of parts (functional films) 80 which are to be
mounted to the plurality of light-emitting devices 1000. By moving
this carrier sheet 90 in the direction of arrow U, the respective
parts 80 can be attached to the light-emitting devices 1000. The
upper surface of the parts 80 has an adhesive layer which is
capable of strongly adhering to the light-emitting devices 1000.
Meanwhile, the adhesion between the carrier sheet 90 and the parts
80 is relatively weak. Using such a carrier sheet 90 enables a
simultaneous "transfer" of the parts 80. Such a transfer is readily
realized because the plurality of light-emitting devices 1000 are
regularly arrayed on the stage 210 while the light-emitting devices
1000 are supported by the stage 210.
[0189] Hereinafter, the configuration of the multilayer stack 100
before the dividing of FIG. 2 is described in more detail.
[0190] First, see FIG. 24A. FIG. 24A is a cross-sectional view
showing the glass base 10 with the plastic film 30 provided on the
surface of the glass base 10. The glass base 10 is a supporting
substrate for processes. The thickness of the glass base 10 can be,
for example, about 0.3-0.7 mm.
[0191] In the present embodiment, the plastic film 30 is a
polyimide film having a thickness of, for example, not less than 5
.mu.m and not more than 100 .mu.m. The polyimide film can be formed
from a polyamide acid, which is a precursor of polyimide, or a
polyimide solution. The polyimide film may be formed by forming a
polyamide acid film on the surface of the glass base 10 and then
thermally imidizing the polyamide acid film. Alternatively, the
polyimide film may be formed by forming, on the surface of the
glass base 10, a film from a polyimide solution which is prepared
by melting a polyimide or dissolving a polyimide in an organic
solvent. The polyimide solution can be obtained by dissolving a
known polyimide in an arbitrary organic solvent. The polyimide
solution is applied to the surface 10s of the glass base 10 and
then dried, whereby a polyimide film can be formed.
[0192] In the case of a bottom emission type flexible display, it
is preferred that the polyimide film realizes high transmittance
over the entire range of visible light. The transparency of the
polyimide film can be represented by, for example, the total light
transmittance in accordance with JIS K7105-1981. The total light
transmittance can be set to not less than 80% or not less than 85%.
On the other hand, in the case of a top emission type flexible
display, it is not affected by the transmittance.
[0193] The plastic film 30 may be a film which is made of a
synthetic resin other than polyimide. Note that, however, in the
embodiment of the present disclosure, the process of forming a thin
film transistor includes a heat treatment at, for example, not less
than 350.degree. C., and therefore, the plastic film 30 is made of
a material which will not be deteriorated by this heat
treatment.
[0194] The plastic film 30 may be a multilayer structure including
a plurality of synthetic resin layers. In one form of the present
embodiment, in delaminating a flexible display structure from the
glass base 10, laser lift-off is carried out such that the plastic
film 30 is irradiated with ultraviolet laser light transmitted
through the glass base 10. A part of the plastic film 30 at the
interface with the glass base 10 needs to absorb the ultraviolet
laser light and decompose (disappear). Alternatively, for example,
a sacrificial layer which is to absorb laser light of a certain
wavelength band and produce a gas may be provided between the glass
base 10 and the plastic film 30. In this case, the plastic film 30
can be easily delaminated from the glass base 10 by irradiating the
sacrificial layer with the laser light. Providing the sacrificial
layer also achieves the effect of suppressing generation of
ashes.
[0195] <Polishing>
[0196] When there is an object (target) which is to be polished
away, such as particles or protuberances, on the surface 30x of the
plastic film 30, the target may be polished away using a polisher
such that the surface becomes flat. Detection of a foreign object,
such as particles, can be realized by, for example, processing of
an image obtained by an image sensor. After the polishing process,
a planarization process may be performed on the surface 30x of the
plastic film 30. The planarization process includes the step of
forming a film which improves the flatness (planarization film) on
the surface 30x of the plastic film 30. The planarization film does
not need to be made of a resin.
[0197] <Lower Gas Barrier Film>
[0198] Then, a gas barrier film may be formed on the plastic film
30. The gas barrier film can have various structures. Examples of
the gas barrier film include a silicon oxide film and a silicon
nitride film. Other examples of the gas barrier film can include a
multilayer film including an organic material layer and an
inorganic material layer. This gas barrier film may be referred to
as "lower gas barrier film" so as to be distinguishable from a gas
barrier film covering the functional layer regions 20, which will
be described later. The gas barrier film covering the functional
layer regions 20 can be referred to as "upper gas barrier
film".
[0199] <Functional Layer Region>
[0200] Hereinafter, the process of forming the functional layer
regions 20, including the TFT layer 20A and the light-emitting
device layer 20B, and the upper gas barrier film 40 is
described.
[0201] First, as shown in FIG. 24B, a plurality of functional layer
regions 20 are formed on a glass base 10. There is a plastic film
30 between the glass base 10 and the functional layer regions 20.
The plastic film 30 is bound to the glass base 10.
[0202] More specifically, the functional layer regions 20 include a
TFT layer 20A (lower layer) and a light-emitting device layer 20B
(upper layer). The TFT layer 20A and the light-emitting device
layer 20B are sequentially formed by a known method. When the
light-emitting device is a display, the TFT layer 20A includes a
circuit of a TFT array which realizes an active matrix. The
light-emitting device layer 20B includes an array of light-emitting
devices (OLED devices and/or micro LED devices), each of which can
be driven independently.
[0203] The chip size of the micro LED devices is, for example,
smaller than 100 .mu.m.times.100 .mu.m. The micro LED devices can
be made of different inorganic semiconductor materials according to
the color or wavelength of light to be radiated. Identical
semiconductor chips may include a plurality of semiconductor
multilayer stacks of different compositions such that light of
different colors, R (red), G (green) and B (blue), are radiated
from the respective semiconductor multilayer stacks. As well known
in the art, a semiconductor chip which radiates ultraviolet light
or a semiconductor chip which radiates blue light may be combined
with various phosphor materials such that light of R, G and B are
radiated.
[0204] The thickness of the TFT layer 20A is, for example, about 4
.mu.m. The thickness of the light-emitting device layer 20B
including the OLED devices is, for example, 1 .mu.m. The thickness
of the light-emitting device layer 20B including the micro LED
devices can be, for example, not less than 10 .mu.m.
[0205] FIG. 25 is a basic equivalent circuit diagram of a sub-pixel
in a display which is an example of the light-emitting device. A
single pixel of the display can consist of sub-pixels of different
colors such as, for example, R, G, and B. The example illustrated
in FIG. 25 includes a selection TFT element Tr1, a driving TFT
element Tr2, a storage capacitor CH, and a light-emitting device
EL. The selection TFT element Tr1 is connected with a data line DL
and a selection line SL. The data line DL is a line for
transmitting data signals which define an image to be displayed.
The data line DL is electrically coupled with the gate of the
driving TFT element Tr2 via the selection TFT element Tr1. The
selection line SL is a line for transmitting signals for
controlling the ON/OFF state of the selection TFT element Tr1. The
driving TFT element Tr2 controls the state of the electrical
connection between a power line PL and the light-emitting device
EL. When the driving TFT element Tr2 is ON, an electric current
flows from the power line PL to a ground line GL via the
light-emitting device EL. This electric current allows the
light-emitting device EL to emit light. Even when the selection TFT
element Tr1 is OFF, the storage capacitor CH maintains the ON state
of the driving TFT element Tr2.
[0206] The TFT layer 20A includes a selection TFT element Tr1, a
driving TFT element Tr2, a data line DL, and a selection line SL.
The light-emitting device layer 20B includes a light-emitting
device EL. Before formation of the light-emitting device layer 20B,
the upper surface of the TFT layer 20A is planarized by an
interlayer insulating film that covers the TFT array and various
wires. A structure which supports the light-emitting device layer
20B and which realizes active matrix driving of the light-emitting
device layer 20B is referred to as "backplane".
[0207] The circuit elements and part of the lines shown in FIG. 25
can be included in any of the TFT layer 20A and the light-emitting
device layer 20B. The lines shown in FIG. 25 are connected with an
unshown driver circuit.
[0208] In the embodiment of the present disclosure, the TFT layer
20A and the light-emitting device layer 20B can have various
specific configurations. These configurations do not limit the
present disclosure. The TFT element included in the TFT layer 20A
may have a bottom gate type configuration or may have a top gate
type configuration. Emission by the light-emitting device included
in the light-emitting device layer 20B may be of a bottom emission
type or may be of a top emission type. The specific configuration
of the light-emitting device is also arbitrary.
[0209] The material of a semiconductor layer which is a constituent
of the TFT element includes, for example, crystalline silicon,
amorphous silicon, and oxide semiconductor. In the embodiment of
the present disclosure, part of the process of forming the TFT
layer 20A includes a heat treatment step at 350.degree. C. or
higher for the purpose of improving the performance of the TFT
element.
[0210] <Upper Gas Barrier Film>
[0211] After formation of the above-described functional layer, the
entirety of the functional layer regions 20 is covered with a gas
barrier film (upper gas barrier film) 40 as shown in FIG. 24C. A
typical example of the upper gas barrier film 40 is a multilayer
film including an inorganic material layer and an organic material
layer. Elements such as an adhesive film, another functional layer
which is a constituent of a touchscreen, polarizers, etc., may be
provided between the upper gas barrier film 40 and the functional
layer regions 20 or in a layer overlying the upper gas barrier film
40. Formation of the upper gas barrier film 40 can be realized by a
Thin Film Encapsulation (TFE) technique. From the viewpoint of
encapsulation reliability, the WVTR (Water Vapor Transmission Rate)
of a thin film encapsulation structure is typically required to be
not more than 1.times.10.sup.-4 g/m.sup.2/day. According to the
embodiment of the present disclosure, this criterion is met. The
thickness of the upper gas barrier film 40 is, for example, not
more than 1.5 .mu.m.
[0212] FIG. 26 is a perspective view schematically showing the
upper surface side of the multilayer stack 100 at a point in time
when the upper gas barrier film 40 is formed. A single multilayer
stack 100 includes a plurality of light-emitting devices 1000
supported by the glass base 10. In the example illustrated in FIG.
26, a single multilayer stack 100 includes a larger number of
functional layer regions 20 than in the example illustrated in FIG.
1A. As previously described, the number of functional layer regions
20 supported by a single glass base 10 is arbitrary.
[0213] <Protection Sheet>
[0214] Next, refer to FIG. 24D. As shown in FIG. 24D, a protection
sheet 50 is adhered to the upper surface of the multilayer stack
100. The protection sheet 50 can be made of a material such as, for
example, polyethylene terephthalate (PET), polyvinyl chloride
(PVC), or the like. As previously described, a typical example of
the protection sheet 50 has a laminate structure which includes a
layer of an applied mold-releasing agent at the surface. The
thickness of the protection sheet 50 can be, for example, not less
than 50 .mu.m and not more than 200 .mu.m.
[0215] After the thus-formed multilayer stack 100 is provided, the
production method of the present disclosure can be carried out
using the above-described production apparatus (delaminating
apparatus 220).
INDUSTRIAL APPLICABILITY
[0216] An embodiment of the present invention provides a novel
flexible light-emitting device production method. A flexible
light-emitting device is broadly applicable to smartphones, tablet
computers, on-board displays, and small-, medium- and large-sized
television sets. The flexible light-emitting device can also be
used as an illumination device.
REFERENCE SIGNS LIST
[0217] 10 . . . glass base, 20 . . . functional layer region, 20A .
. . TFT layer, 20B . . . light-emitting device layer, 30 . . .
plastic film, 30d . . . flexible substrate region of plastic film,
30i . . . intermediate region of plastic film, 40 . . . gas barrier
film, 50 . . . protection sheet, 100 . . . multilayer stack, 210 .
. . stage, 220 . . . lift-off light irradiation unit (delaminating
apparatus), 1000 . . . light-emitting device
* * * * *