U.S. patent application number 16/748110 was filed with the patent office on 2020-05-21 for organic electroluminescent display device.
The applicant listed for this patent is Sakai Display Products Corporation. Invention is credited to Takuji KATO, Katsuhiko KISHIMOTO.
Application Number | 20200161596 16/748110 |
Document ID | / |
Family ID | 62635813 |
Filed Date | 2020-05-21 |
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United States Patent
Application |
20200161596 |
Kind Code |
A1 |
KISHIMOTO; Katsuhiko ; et
al. |
May 21, 2020 |
ORGANIC ELECTROLUMINESCENT DISPLAY DEVICE
Abstract
An organic EL display device including a plurality of pixels
includes an element substrate including a substrate, and a
plurality of organic EL elements supported by the substrate and
respectively located in the plurality of pixels; and a thin film
encapsulation structure covering the plurality of pixels. The thin
film encapsulation structure includes a first inorganic barrier
layer, an organic barrier layer in contact with a top surface of
the first inorganic barrier layer, the organic barrier layer
including a plurality of solid portions distributed discretely, and
a second inorganic barrier layer in contact with the top surface of
the first inorganic barrier layer and top surfaces of the plurality
of solid portions of the organic barrier layer. The organic barrier
layer is black.
Inventors: |
KISHIMOTO; Katsuhiko;
(Osaka, JP) ; KATO; Takuji; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sakai Display Products Corporation |
Osaka |
|
JP |
|
|
Family ID: |
62635813 |
Appl. No.: |
16/748110 |
Filed: |
January 21, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15780298 |
May 31, 2018 |
10581028 |
|
|
PCT/JP2017/042912 |
Nov 29, 2017 |
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16748110 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/02288 20130101;
H01L 51/0001 20130101; H05B 33/10 20130101; G09G 3/00 20130101;
H01L 21/0234 20130101; H01L 21/02348 20130101; H01L 22/20 20130101;
H01L 21/02315 20130101; H01L 51/50 20130101; H01L 27/3279 20130101;
H01L 51/0097 20130101; H05B 33/22 20130101; H01L 27/32 20130101;
H01L 27/3276 20130101; H01L 21/02359 20130101; H01L 27/3246
20130101; G09F 9/30 20130101; H01L 21/0231 20130101; H01L 51/5253
20130101; H05B 33/04 20130101; H05B 33/12 20130101; H01L 51/56
20130101 |
International
Class: |
H01L 51/56 20060101
H01L051/56; H01L 51/52 20060101 H01L051/52; H01L 51/00 20060101
H01L051/00; H01L 27/32 20060101 H01L027/32; H01L 21/66 20060101
H01L021/66; H01L 21/02 20060101 H01L021/02 |
Claims
1. An organic electroluminescent display device including a
plurality of pixels, comprising: an element substrate including a
substrate, and a plurality of organic electroluminescent elements
supported by the substrate and respectively located in the
plurality of pixels; and a thin film encapsulation structure
covering the plurality of pixels, wherein the thin film
encapsulation structure includes a first inorganic barrier layer,
an organic barrier layer in contact with a top surface of the first
inorganic barrier layer, the organic barrier layer including a
plurality of solid portions distributed discretely, and a second
inorganic barrier layer in contact with the top surface of the
first inorganic barrier layer and top surfaces of the plurality of
solid portions of the organic barrier layer, wherein the organic
barrier layer is formed of a photosensitive resin and is black,
wherein the organic electroluminescent display device comprises a
bank layer defining each of the plurality of pixels, wherein the
bank layer has an inclining surface enclosing each of the plurality
of pixels, wherein the plurality of solid portions include a pixel
periphery solid portion extending on the first inorganic barrier
layer from an inclining surface thereof to a peripheral area in the
pixel, wherein the inclining surface of the first inorganic barrier
layer is lyophilic to the photosensitive resin, and wherein a flat
portion of the surface of the first inorganic barrier layer in a
region enclosed by the bank layer is repelling against the
photosensitive resin.
2. The organic electroluminescent display device of claim 1,
wherein the organic barrier layer contains a dye or a pigment.
3. The organic electroluminescent display device of claim 1,
wherein the inclining surface of the bank layer has an inclination
angle smaller than, or equal to, 60 degrees.
Description
TECHNICAL FIELD
[0001] The present invention relates to an organic EL display
device and a method for producing the same.
BACKGROUND ART
[0002] Organic EL (Electro-Luminescence) display devices start
being put into practical use. One feature of an organic EL display
device is being flexible. An organic EL display device includes, in
each of pixels, at least one organic EL element (Organic Light
Emitting Diode: OLED) and at least one TFT (Thin Film Transistor)
controlling an electric current to be supplied to each of the at
least one OLED. Hereinafter, an organic EL display device will be
referred to as an "OLED display device". Such an OLED display
device including a switching element such as a TFT or the like for
each of OLEDs is called an "active matrix OLED display device". A
substrate including the TFTs and the OLEDs will be referred to as
an "element substrate".
[0003] An OLED (especially, an organic light emitting layer and a
cathode electrode material) is easily influenced by moisture to be
deteriorated and to cause display unevenness. One technology
developed in order to provide an encapsulation structure that
protects the OLED against moisture while not spoiling the
flexibility of the OLED display device is a thin film encapsulation
(TFE) technology. According to the thin film encapsulation
technology, an inorganic barrier layer and an organic barrier layer
are stacked alternately to provide a sufficient level of barrier
property against water vapor with these thin films. From the point
of view of the moisture-resistance reliability of the OLED display
device, such a thin film encapsulation structure is typically
required to have a WVTR (Water Vapor Transmission Rate) lower than,
or equal to, 1.times.10.sup.-4 g/m.sup.2/day.
[0004] A thin film encapsulation structure used in OLED display
devices commercially available currently includes an organic
barrier layer (polymer barrier layer) having a thickness of about 5
.mu.m to about 20 .mu.m. Such a relatively thick organic barrier
layer also has a role of flattening a surface of the element
substrate. However, such a thick organic barrier layer involves a
problem that the bendability of the OLED display device is
limited.
[0005] Patent Document No. 1 discloses a thin film encapsulation
structure including a first inorganic material layer, a first resin
member and a second inorganic material layer provided on the
element substrate in this order, with the first inorganic material
layer being closest to the element substrate. In this thin film
encapsulation structure, the first resin member is present locally,
more specifically, around a protruding portion of the first
inorganic material layer (first inorganic material layer covering a
protruding portion). According to Patent Document No. 1, the first
resin member is present locally, more specifically, around the
protruding portion, which may not be sufficiently covered with the
first inorganic material layer. With such a structure, entrance of
moisture or oxygen via the non-covered portion is suppressed. In
addition, the first resin member acts as an underlying layer for
the second inorganic material layer. Therefore, the second
inorganic material layer is properly formed and properly covers a
side surface of the first inorganic material layer with an expected
thickness. The first resin member is formed as follows. An organic
material heated and vaporized to be mist-like is supplied onto an
element substrate maintained at a temperature lower than, or equal
to, room temperature. The organic material is condensed and put
into liquid drops on the substrate. The organic material in liquid
drops moves on the substrate by a capillary action or a surface
tension to be present locally, more specifically, at a border
between a side surface of the protruding portion of the first
inorganic material layer and a surface of the substrate. Then, the
organic material is cured to form the first resin member at the
border. Patent Documents Nos. 2 and 3 also disclose an OLED display
device including a similar thin film encapsulation structure.
[0006] The thin film encapsulation structure, described in each of
Patent Documents Nos. 1 and 2, including an organic barrier layer
formed of a resin member that is present locally does not include a
thick organic barrier layer, and therefore, is considered to
improve the bendability of the OLED display device.
CITATION LIST
Patent Literature
[0007] Patent Document No. 1: WO2014/196137
[0008] Patent Document No. 2: Japanese Laid-Open Patent Publication
No. 2016-39120
[0009] Patent Document No. 3: Japanese Laid-Open Patent Publication
No. 2015-50022
SUMMARY OF INVENTION
Technical Problem
[0010] The OLED display device, produced by the method described in
each of Patent Documents Nos. 1 and 2, including a thin film
encapsulation structure including an organic barrier layer that
includes a plurality of solid portions distributed discretely is
not necessarily considered to be provided at a high yield.
[0011] As described above, in the case where an organic barrier
layer is formed by the method described in Patent Document No. 1 or
2, if a surface of the first inorganic material layer includes a
protruding portion, the organic barrier layer (solid portion) may
be formed only around the protruding portion of the surface of the
first inorganic material layer. However, the method for forming the
organic barrier layer described in Patent Document No. 1 or 2
merely uses a surface tension of the resin in a liquid state to
form the organic barrier layer locally. Therefore, the organic
barrier layer may not be formed with certainty in a region where
the organic barrier layer needs to be formed. Oppositely, the
organic barrier layer may be formed in a region where the organic
barrier layer does not need to be formed. The organic barrier layer
in the thin film encapsulation structure described in Patent
Document No. 1 or 2 is formed of a transparent photocurable resin.
Therefore, it is not easily checked whether or not the organic
barrier layer is properly formed around the protruding portion of
the surface of the first inorganic material layer. In other words,
it requires time and/or cost to inspect whether or not the organic
barrier layer is formed in a region where the organic barrier layer
needs to be formed.
[0012] The protruding portion of the surface of the first inorganic
material layer is formed by a stepped portion reflecting a line
such as, for example, a gate bus line, a source bus line, a lead
wire connected with the gate bus line or the source bus line, or
the like. Also in the case where a particle (microscopic dust
particle) is present above or below the first inorganic material
layer, the protruding portion is formed at the surface of the first
inorganic material layer.
[0013] The present invention, made to solve the above-described
problems, has an object of providing an organic EL display device
including a thin film encapsulation structure, and a method for
producing the same, that improve the yield.
Solution to Problem
[0014] An organic EL display device according to an embodiment of
the present invention is an organic EL display device including a
plurality of pixels. The organic EL display device comprises an
element substrate including a substrate, and a plurality of organic
EL elements supported by the substrate and respectively located in
the plurality of pixels; and a thin film encapsulation structure
covering the plurality of pixels. The thin film encapsulation
structure includes a first inorganic barrier layer, an organic
barrier layer in contact with a top surface of the first inorganic
barrier layer, the organic barrier layer including a plurality of
solid portions distributed discretely, and a second inorganic
barrier layer in contact with the top surface of the first
inorganic barrier layer and top surfaces of the plurality of solid
portions of the organic barrier layer. The organic barrier layer is
black.
[0015] In an embodiment, the organic barrier layer contains a dye
or a pigment.
[0016] In an embodiment, the organic EL display device further
includes a bank layer defining each of the plurality of pixels. The
bank layer has an inclining surface enclosing each of the plurality
of pixels, and the plurality of solid portions include a pixel
periphery solid portion extending on the first inorganic barrier
layer from an inclining surface thereof to a peripheral area in the
pixel.
[0017] In an embodiment, the inclining surface of the bank layer
has an inclination angle smaller than, or equal to, 60 degrees.
[0018] A production method according to an embodiment of the
present invention is a method for producing any one of the
above-described organic EL display devices. A step of forming the
thin film encapsulation structure includes step A of preparing the
element substrate having the first inorganic barrier layer formed
thereon, step B of forming a liquid film containing a
photosensitive resin on the first inorganic barrier layer, step C
of irradiating the liquid film with light to form a resin layer,
and step D of forming the organic barrier layer, the step D
including the step of partially removing the resin layer by a dry
process.
[0019] In an embodiment, the inclining surface of the first
inorganic barrier layer is lyophilic to the liquid film, and a
region enclosed by the bank layer is repelling against the liquid
film.
[0020] In an embodiment, the step D further includes the step of
performing a plasma process and/or a corona process.
[0021] In an embodiment, the step of forming the thin film
encapsulation structure further includes the step of, after the
step A and before the step B, performing asking on a surface of the
first inorganic barrier layer.
[0022] In an embodiment, the step of forming the thin film
encapsulation structure further includes the step of, after the
step A and before the step B, supplying a silane coupling agent
onto the surface of the first inorganic barrier layer.
[0023] In an embodiment, the liquid film contains a photocurable
resin and a dye or a pigment.
[0024] In an embodiment, the liquid film contains a
photopolymerizable dye monomer.
[0025] In an embodiment, the step B is performed by spraying,
spin-coating, slit-coating, screen printing or inkjet printing.
[0026] In an embodiment, the step B includes the steps of, after
the step A, putting the element substrate into a chamber and
supplying a vapor-like or mist-like photocurable resin into the
chamber, and condensing the photocurable resin on the first
inorganic barrier layer to form the liquid film.
[0027] In an embodiment, the production method further includes the
steps of, after the step of forming the thin film encapsulation
structure, optically acquiring a pattern of the organic barrier
layer, and determining whether the thin film encapsulation
structure is good or not based on the pattern.
Advantageous Effects of Invention
[0028] An embodiment of the present invention provides an organic
EL display device including a thin film encapsulation structure,
and a method for producing the same, that improve the yield.
BRIEF DESCRIPTION OF DRAWINGS
[0029] FIG. 1(a) is a schematic partial cross-sectional view of an
active region of an OLED display device 100 according to an
embodiment of the present invention, and FIG. 1(b) is a partial
cross-sectional view of a TFE structure 10 formed on an OLED 3.
[0030] FIG. 2 is a plan view schematically showing a structure of
the OLED display device 100 according to an embodiment of the
present invention.
[0031] FIG. 3(a) through FIG. 3(c) are each a schematic
cross-sectional view of the OLED display device 100; FIG. 3(a) is a
cross-sectional view taken along line 3A-3A' in FIG. 2, FIG. 3(b)
is a cross-sectional view taken along line 3B-3B' in FIG. 2, and
FIG. 3(c) is a cross-sectional view taken along line 3C-3C' in FIG.
2.
[0032] FIG. 4(a) is an enlarged view of a portion including a
particle P shown in FIG. 3(a), FIG. 4(b) is a schematic plan view
showing the size relationship among the particle P, a first
inorganic barrier layer (SiN layer) covering the particle P, and an
organic barrier layer, and FIG. 4(c) is a schematic cross-sectional
view of the first inorganic barrier layer covering the particle
P.
[0033] FIG. 5 is a plan view schematically showing a plurality of
pixels and a bank layer 48 included in the OLED display device
100.
[0034] FIG. 6(a) and FIG. 6(b) are each a schematic cross-sectional
view of the OLED display device 100; FIG. 6(a) is a cross-sectional
view taken along line 6A-6A' in FIG. 5, and FIG. 6(b) is a
cross-sectional view taken along line 6B-6B' in FIG. 5.
[0035] FIG. 7 is a schematic view showing a foreign object
detection device 50 usable for a method for producing an OLED
display device according to an embodiment of the present
invention.
[0036] FIG. 8 is a schematic view showing an inkjet device 60
usable for the method for producing an OLED display device
according to an embodiment of the present invention.
[0037] FIG. 9(a) and FIG. 9(b) show schematic views provided to
describe a preferred range of volume of an organic barrier layer to
be formed around the particle P in an OLED display device according
to an embodiment of the present invention; FIG. 9(a) is a schematic
view of a cross-section including a diameter of the particle P
(cross-section taken along line 9A-9A' in FIG. 9(b)), and FIG. 9(b)
is a plan view as seen in the normal direction.
DESCRIPTION OF EMBODIMENTS
[0038] Hereinafter, an organic EL display device and a method for
producing the same according to an embodiment of the present
invention will be described with reference to the drawings. The
embodiments of the present invention are not limited to the
embodiments described below as an example.
[0039] First, with reference to FIG. 1(a) and FIG. 1(b), a basic
structure of an OLED display device 100 according to an embodiment
of the present invention will be described. FIG. 1(a) is a
schematic partial cross-sectional view of an active region of the
OLED display device 100 according to an embodiment of the present
invention. FIG. 1(b) is a partial cross-sectional view of a TFE
structure 10 formed on an OLED 3.
[0040] The OLED display device 100 includes a plurality of pixels,
and each of the pixels includes at least one organic EL element
(OLED). Herein, a structure corresponding to one OLED will be
described for the sake of simplicity.
[0041] As shown in FIG. 1(a), the OLED display device 100 includes
a flexible substrate (hereinafter, may be referred to simply as a
"substrate") 1, a circuit (back plane) 2 formed on the substrate 1
and including a TFT, the OLED 3 formed on the circuit 2, and the
TFE structure 10 formed on the OLED 3. The OLED 3 is, for example,
of a top emission type. An uppermost portion of the OLED 3 is, for
example, an upper electrode or a cap layer (refractive index
adjusting layer). An optional polarizing plate 4 is located on the
TFE structure 10.
[0042] The substrate 1 is, for example, a polyimide film having a
thickness of 15 .mu.m. The circuit 2 including the TFE has a
thickness of, for example, 4 .mu.m. The OLED 3 has a thickness of,
for example, 1 .mu.m. The TFE structure 10 has a thickness that is,
for example, less than, or equal to, 1.5 .mu.m.
[0043] FIG. 1(b) is a partial cross-sectional view of the TFE
structure 10 formed on the OLED 3. The TFE structure 10 includes a
first inorganic barrier layer (e.g., SiN layer) 12, an organic
barrier layer (e.g., acrylic resin layer) 14, and a second
inorganic barrier layer (e.g., SiN layer) 16. The first inorganic
barrier layer 12 is formed immediately on the OLED 3. The organic
barrier layer 14 is in contact with a top surface of the first
inorganic barrier layer 12, and includes a plurality of solid
portions distributed discretely. The second inorganic barrier layer
16 is in contact with the top surface of the first inorganic
barrier layer 12 and top surfaces of the plurality of solid
portions of the organic barrier layer 14. The organic barrier layer
is black. The organic barrier layer 14 contains, for example, a
dye.
[0044] Since the organic barrier layer 14 is black, it may be
inspected in a short time and/or at low cost whether or not the
organic barrier layer 14 is formed in a region where the organic
barrier layer 14 needs to be formed. This improves the yield of the
OLED display device 100. A method for producing the OLED display
device 100 and a method for performing the inspection will be
described below.
[0045] The organic barrier layer 14 merely needs to be sufficiently
colored black to be visually recognizable in an inspection process
described below, and does not need to be light-blocking.
[0046] The first inorganic barrier layer 12 and the second
inorganic barrier layer 16 are each, for example, an SiN layer
(e.g., Si.sub.3N.sub.4 layer) having a thickness of, for example,
400 nm. The first inorganic barrier layer 12 and the second
inorganic barrier layer 16 each have a thickness of 200 nm or
greater and 1000 nm or less independently. The thickness of the TFE
structure 10 is preferably 400 nm or greater and less than 2 .mu.m,
and more preferably 400 nm or greater and less than 1.5 .mu.m. The
thickness of the organic barrier layer (solid portion) 14, which
depends on the size of the protruding portion of the surface of the
first inorganic barrier layer 12 or the size of the particle, may
be 1 .mu.m at the maximum. The thickness of the organic barrier
layer (solid portion) 14 is typically 200 nm or greater and 500 nm
or less.
[0047] The TFE structure 10 is formed so as to protect an active
region (see the active region R1 in FIG. 2) of the OLED display
device 100. As described above, the TFE structure 10 includes, in
at least the active region, the first inorganic barrier layer 12,
the organic barrier layer 14 and the second inorganic barrier layer
16 in this order, with the first inorganic barrier layer 12 being
closest to the OLED 3. The organic barrier layer 14 is not present
as a film covering the entirety of the active region, but has
openings. Portions of the organic barrier layer 14 where an organic
film is actually present, namely, portions except for the openings,
will be referred to as "solid portions". The "openings" (may also
referred to as "non-solid portions") do not need to be enclosed by
the solid portions and may include a cutout portion and the like.
In the openings, the first inorganic barrier layer 12 and the
second inorganic barrier layer 16 are in direct contact with each
other. The openings of the organic barrier layer 14 include at
least an opening formed so as to enclose the active region, and the
active region is fully enclosed by the portion in which the first
inorganic barrier layer 12 and the second inorganic barrier layer
16 are in direct contact with each other (hereinafter, such a
portion will be referred to as an "inorganic barrier layer joint
portion").
[0048] With reference to FIG. 2 through FIG. 6, a structure of, and
a method for producing, an OLED display device according to an
embodiment of the present invention will be described.
[0049] FIG. 2 is a schematic plan view of the OLED display device
100 according to an embodiment of the present invention.
[0050] The OLED display device 100 includes the flexible substrate
1, the circuit (back plane) 2 formed on the substrate 1, a
plurality of the OLEDs 3 formed on the circuit 2, and the TFE
structure 10 formed on the OLEDs 3. A layer including the plurality
of OLEDs 3 may be referred to as an "OLED layer 3". The circuit 2
and the OLED layer 3 may share a part of components. The optional
polarizing plate (see reference numeral 4 in FIG. 1) may further be
located on the TFE structure 10. In addition, for example, a layer
having a touch panel function may be located between the TFE
structure 10 and the polarizing plate. Namely, the OLED display
device 100 may be altered to a display device including an on-cell
type touch panel.
[0051] The circuit 2 includes a plurality of TFTs (not shown), and
a plurality of gate bus lines (not shown) and a plurality of source
bus lines (not shown) each connected with either one of the
plurality of TFTs (not shown). The circuit 2 may be a known circuit
that drives the plurality of OLEDs 3. The plurality of OLEDs 3 are
each connected with either one of the plurality of TFTs included in
the circuit 2. The OLEDs 3 may be known OLEDs.
[0052] The OLED display device 100 further includes a plurality of
terminals 38 located in a peripheral region R2 outer to the active
region R1 (region enclosed by the dashed line in FIG. 2), where the
plurality of OLEDs 3 are located, and also includes a plurality of
lead wires 30 connecting each of the plurality of terminals 38 and
either one of the plurality of gate bus lines or either one of the
plurality of source bus lines to each other. The TFE structure 10
is formed on the plurality of OLEDs 3 and on a portion of the
plurality of lead wires 30 that is close to the active region R1.
Namely, the TFE structure 10 covers the entirety of the active
region R1 and is also selectively formed on the portion of the
plurality of lead wires 30 that is close to the active region R1.
Neither a portion of the plurality of lead wires 30 that are closer
to the terminals 38, nor the terminals 38, is covered with the TFE
structure 10.
[0053] Hereinafter, an example in which the lead wires 30 and the
terminals 38 are integrally formed in the same conductive layer
will be described. Alternatively, the lead wires 30 and the
terminals 38 may be formed in different conductive layers
(encompassing stack structures).
[0054] Now, with reference to FIG. 3(a) through FIG. 3(c), the TFE
structure 10 of the OLED display device 100 will be described. FIG.
3(a) is a cross-sectional view taken along line 3A-3A' in FIG. 2.
FIG. 3(b) is a cross-sectional view taken along line 3B-3B' in FIG.
2. FIG. 3(c) is a cross-sectional view taken along line 3C-3C' in
FIG. 2.
[0055] As shown in FIG. 3(a) and FIG. 3(b), the TFE structure 10
includes the first inorganic barrier layer 12 formed on the OLED 3,
the organic barrier layer 14, and the second inorganic barrier
layer 16 in contact with the first inorganic barrier layer 12 and
the organic barrier layer 14. The first inorganic barrier layer 12
and the second inorganic barrier layer 16 are each, for example, an
SiN layer, and are selectively formed in a predetermined region so
as to cover the active region R1 by plasma CVD by use of a mask. In
general, a surface of a layer formed by a thin film deposition
method (e.g., CVD, sputtering, vacuum vapor deposition) reflects a
stepped portion in an underlying layer. The organic barrier layer
(solid portion) 14 is formed only around the protruding portion of
the surface of the first inorganic barrier layer 12.
[0056] FIG. 3(a) is a cross-sectional view taken along line 3A-3A'
in FIG. 2, and shows a portion including a particle P. The particle
P is a microscopic dust particle generated during the production of
the OLED display device, and is, for example, a microscopic piece
of broken glass, a metal particle or an organic particle. Such a
particle is especially easily generated in the case where mask
vapor deposition is used.
[0057] As shown in FIG. 3(a), the organic barrier layer (solid
portion) 14 includes a portion 14b formed around the particle P. A
reason for this is that an acrylic monomer supplied after the first
inorganic barrier layer 12 is formed is condensed and present
locally, namely, around a surface of a first inorganic barrier
layer 12a on the particle P (the surface has a tapering angle
larger than 90 degrees). The organic barrier layer 14 includes the
opening (non-solid portion) on a flat portion of the first
inorganic barrier layer 12.
[0058] Now, with reference to FIG. 4(a) through FIG. 4(c), a
structure of the portion including the particle P will be
described. FIG. 4(a) is an enlarged view of the portion including
the particle P shown in FIG. 3(a). FIG. 4(b) is a schematic plan
view showing the size relationship among the particle P, the first
inorganic barrier layer (SiN layer) 12 covering the particle P and
the organic barrier layer 14. FIG. 4(c) is a schematic
cross-sectional view of the first inorganic barrier layer covering
the particle P.
[0059] In the case where the particle P (having a diameter that is,
for example, longer than, or equal to, 1 .mu.m) is present, a crack
(defect) 12c may be formed in the first inorganic barrier layer as
shown in FIG. 4(c). As described below, this is considered to be
caused by impingement of the SiN layer 12a growing from a surface
of the particle P and an SiN layer 12b growing from a flat portion
of a surface of the OLED 3. In the case where such a crack 12c is
present, the level of barrier property of the TFE structure 10 is
decreased.
[0060] In the TFE structure 10 of the OLED display device 100, as
shown in FIG. 4(a), the organic barrier layer 14 is formed to fill
the crack 12c of the first inorganic barrier layer 12, and a
surface of the organic barrier layer 14 couples a surface of the
first inorganic barrier layer 12a on the particle P and a surface
of the first inorganic barrier layer 12b on the flat portion of the
OLED 3 to each other continuously and smoothly. The organic barrier
layer 14, which is formed by curing a photocurable resin in a
liquid state as described below, has a recessed surface by a
surface tension. In this state, the photocurable resin exhibits a
high level of wettability to the first inorganic barrier layer 12.
If the level of wettability of the photocurable resin to the first
inorganic barrier layer 12 is low, the surface of the organic
barrier layer 14 may protrude. The organic barrier layer 14 may
also be formed with a small thickness on the first inorganic
barrier layer 12a on the particle P.
[0061] The organic barrier layer (solid portion) 14 having the
recessed surface connects the surface of the first inorganic
barrier layer 12a on the particle P and the surface of the first
inorganic barrier layer 12b on the flat portion to each other
continuously and smoothly. Therefore, the second inorganic barrier
layer 16 formed thereon is a fine film with no defect. As can be
seen, even if the particle P is present, the organic barrier layer
14 keeps high the level of barrier property of the TFE structure
10.
[0062] As shown in FIG. 4(b), the organic barrier layer 14 (solid
portion) is formed in a ring shape around the particle P. Where the
particle P has a diameter (equivalent circle diameter) of about 1
.mu.m as seen in a direction normal to the surface of the OLED 3,
the ring-shaped solid portion has a diameter Do (equivalent circle
diameter) that is, for example, longer than, or equal to, 2
.mu.m.
[0063] In this example, the organic barrier layer 14 is formed only
in a discontinuous portion in the first inorganic barrier layer 12
formed on the particle P, and the particle P is already present
before the first inorganic barrier layer 12 is formed on the OLED
3. The particle P may be present on the first inorganic barrier
layer 12. In this case, the organic barrier layer 14 is formed only
at the border, namely, in a discontinuous portion, between the
first inorganic barrier layer 12 and the particle P on the first
inorganic barrier layer 12, and thus maintains the barrier property
of the TFE structure 10 like in the above-described case. The
organic barrier layer 14 may also be formed with a small thickness
on the surface of the first inorganic barrier layer 12a on the
particle P, or on the surface of the particle P. In this
specification, the expression that "the organic barrier layer is
present around the particle P" encompasses all these forms.
[0064] The organic barrier layer (solid portion) 14 is not limited
to being formed as in the example of FIG. 3(a), and may be formed
only around the protruding portion of the surface of the first
inorganic barrier layer 12 for substantially the same reason.
Examples of the other regions where the organic barrier layer
(solid portion) 14 may be formed will be described below.
[0065] Now, with reference to FIG. 3(b), a structure of the TFE
structure 10 on the lead wires 30 will be described. FIG. 3(b) is a
cross-sectional view taken along line 3B-3B' in FIG. 2; more
specifically, is a cross-sectional view of portions 32, of the lead
wires 30, close to the active region R1.
[0066] As shown in FIG. 3(b), the organic barrier layer (solid
portions) 14 includes portions 14c formed around the protruding
portions of the surface of the first inorganic barrier layer 12.
The protruding portions reflect the cross-sectional shape of the
portions 32 of the lead wires 30.
[0067] The lead wires 30 are patterned by the same step as that of,
for example, the gate bus lines or the source bus lines. Thus, in
this example, the gate bus lines and the source bus lines formed in
the active region R1 also have the same cross-sectional structure
as that of the portion 32, of each of the lead wires 30, close to
the active region R1 shown in FIG. 3(b). It should be noted that
typically, a flattening layer is formed on the gate bus lines and
the source bus lines formed in the active region R1, and thus no
stepped portion is formed at the surface of the first inorganic
barrier layer 12 on the gate bus lines and the source bus
lines.
[0068] The portion 32 of the lead wire 30 may have, for example, a
forward tapering side surface portion (inclining side surface
portion) having a tapering angle smaller than 90 degrees. In the
case where the lead wire 30 includes the forward tapering side
surface portion, formation of defects in the first inorganic
barrier layer 12 and the second inorganic barrier layer 16 formed
on the lead wire 30 is prevented. Namely, the moisture-resistance
reliability of the TFE structure 10 is improved. The tapering angle
of the forward tapering side surface portion is preferably smaller
than, or equal to, 70 degrees.
[0069] The active region R1 of the OLED display device 100 is
substantially covered with the inorganic barrier layer joint
portion, in which the first inorganic barrier layer 12 and the
second inorganic barrier layer 16 are in direct contact with each
other, except for the regions where the organic barrier layer 14 is
selectively formed. Therefore, it does not occur that the organic
barrier layer 14 acts as a moisture entrance route to allow the
moisture to reach the active region R1 of the OLED display
device.
[0070] The OLED display device 100 according to an embodiment of
the present invention is preferably usable for, for example,
medium- to small-sized high-definition smartphones and tablet
terminals. In a medium- to small-sized (e.g., 5.7-inch)
high-definition (e.g., 500 ppi) OLED display device, it is
preferred that lines (encompassing the gate bus lines and the
source bus lines) in the active region R1 have a cross-sectional
shape, taken in a direction parallel to a line width direction,
close to a rectangle (side surfaces of the lines have a tapering
angle of about 90 degrees) in order to allow the lines to have a
sufficiently low resistance with a limited line width. In order to
form the lines having a low resistance, the tapering angle of the
forward tapering side surface portion TSF may be larger than 70
degrees and smaller than 90 degrees, or the tapering angle may be
about 90 degrees in the entire length of the lines with no forward
tapering side surface portion TSF being provided.
[0071] Now, FIG. 3(c) will be referred to. FIG. 3(c) is a
cross-sectional view of a region where the TFE structure 10 is not
formed. In this region, a terminal portion 38 has the same
cross-sectional structure as that of portions 36 of the lead wires
30 shown in FIG. 3(c). The portions 36 of the lead wires 30 shown
in FIG. 3(c) may have a tapering angle of, for example, about 90
degrees.
[0072] Now, with reference to FIG. 5 and FIG. 6, the organic
barrier layer 14 formed around a bank structure BS will be
described. The organic barrier layer (solid portion) 14 is also
formed around a protruding portion of the surface of a portion, of
the first inorganic barrier layer 12, that is used to form the bank
structure BS. FIG. 5 is a plan view schematically showing the
plurality of pixels and a bank layer 48 included in the OLED
display device 100. FIG. 6(a) and FIG. 6(b) are each a schematic
cross-sectional view of the OLED display device 100. FIG. 6(a) is a
cross-sectional view taken along line 6A-6A' in FIG. 5, and FIG.
6(b) is a cross-sectional view taken along line 6B-6B' in FIG.
5.
[0073] As shown in FIG. 5 and FIG. 6(a), the OLED display device
100 further includes the bank layer 48 defining each of the
plurality of pixels. The bank layer 48 has an inclining surface
enclosing each of the plurality of pixels. The plurality of solid
portions of the organic barrier layer 14 each include a pixel
periphery solid portion 14a extending on the first inorganic
barrier layer 12 from an inclining surface S12 to a peripheral area
in the pixel.
[0074] As shown in FIG. 6(a), the bank structure BS includes the
bank layer 48 formed of an insulating material (the bank layer may
be referred to also as a "PDL (Pixel Defining Layer)"). The bank
layer 48 is formed between a lower electrode 42 and an organic
layer 44 of the OLED 3. As shown in FIG. 6(a), the OLED 3 includes
the lower electrode 42, the organic layer 44 formed on the lower
electrode 42, and an upper electrode 46 formed on the organic layer
44. In this example, the lower electrode 42 and the upper electrode
46 respectively act as an anode and a cathode of the OLED 3. The
upper electrode 46 is a common electrode formed for the entirety of
the pixels in the active region. By contrast, the lower electrode
(pixel electrode) 42 is formed for each of the pixels. In the
structure in which the bank layer 48 is present between the lower
electrode 42 and the organic layer 44, no holes are injected from
the lower electrode 42 into the organic layer 44. Therefore, the
region where the bank layer 48 is present does not act as a pixel
Pix. Thus, the bank layer 48 defines an outer perimeter of the
pixel Pix.
[0075] As shown in FIG. 5, each pixel Pix is defined by an opening
in the bank layer 48. The bank layer 48 is formed to be, for
example, lattice-shaped. A side surface of the opening of the bank
layer 48 has an inclining surface including the forward tapering
side surface portion TSF. The inclining surface of the bank layer
48 encloses each pixel. The bank layer 48 is formed of, for
example, a photosensitive resin (e.g., polyimide or acrylic resin).
The bank layer 48 has a thickness of, for example, 1 .mu.m to 2
.mu.m. The inclining surface of the bank layer 48 is inclined at an
inclination angle .theta.b that is, for example, smaller than, or
equal to, 60 degrees. If the inclination angle .theta.b of the
inclining surface of the bank layer 48 is larger than 60 degrees, a
defect may be caused in layers located on the bank layer 48. The
layers located on the bank layer 48 (including, for example, the
organic layer 44, the upper electrode 46, the first inorganic
barrier layer 12 and the second inorganic barrier layer 16) may be
included in the bank structure BS. The layers included in the bank
structure BS may each have an inclining surface enclosing each of
the plurality of pixels. In the case where each of the layers
formed on the bank layer 48 is thinner than the bank layer 48, the
inclination angle of the inclining surface of the bank structure BS
is considered to be substantially equal to the inclination angle of
the inclining surface of the bank layer 48. The first inorganic
barrier layer 12 is included in the bank structure BS, and has the
inclining surface S12 enclosing each of the plurality of pixels.
The organic barrier layer (solid portion) 14 includes the pixel
periphery solid portion 14a extending on the first inorganic
barrier layer 12 from the inclining surface S12 to a peripheral
area in the pixel.
[0076] As shown in, for example, FIG. 6(a), in a central area of
the pixel, the organic barrier layer 14 is formed only in a
discontinuous portion formed in the first inorganic barrier layer
12 by the particle P. Namely, as shown in FIG. 6(b), the organic
barrier layer 14 is not present in a central area, of the pixel,
where no particle P is present. The OLED display device with no
particle P does not include the organic barrier layer in the
central area of the pixel. A particle P having a size (equivalent
spherical diameter) of approximately 0.3 .mu.m or longer and 5
.mu.m or shorter declines the moisture-resistance reliability of
the TFE structure 10. It should be noted that a particle P having a
size of 0.2 .mu.m or longer and shorter than 0.3 .mu.m may also
decline the moisture-resistance reliability. A particle P having a
size shorter than 0.2 .mu.m is considered to have substantially no
possibility of declining the moisture-resistance reliability. A
particle having a size longer than 5 .mu.m is removed by cleaning
or the like.
[0077] A board of G4.5 (730 mm.times.920 mm) may have, for example,
several tens to about 100 particles each having a size of
approximately 0.3 .mu.m or longer and 5 .mu.m or shorter. One OLED
display device (active region) may have approximately several
particles. Needless to say, there are OLED display devices with no
particle P. The organic barrier layer 14 is formed of, for example,
a cured photocurable resin. A portion where the photocurable resin
is actually present is referred to as a "solid portion". As
described above, the organic barrier layer 14 (solid portion) is
selectively formed only around a protruding portion of the surface
of the first inorganic barrier layer 12.
[0078] As shown in, for example, FIG. 6(a), in the case where there
is a particle P in the central area of the pixel, the organic
barrier layer 14 is formed in a discontinuous portion formed by the
particle P. As described above with reference to FIG. 4(b), the
organic barrier layer (solid portion) 14 is formed in a ring shape
around the particle P. Where the particle P has a diameter
(equivalent circle diameter) of, for example, about 1 .mu.m as seen
in a direction normal to the surface of the OLED 3, the ring-shaped
solid portion has a diameter Do (equivalent circle diameter) that
is, for example, longer than, or equal to, 2 .mu.m. In the case of,
for example, a 5.7-inch display device having 2560.times.1440
pixels (about 500 ppi), the pixel pitch is 49 .mu.m. The size of
the particle P and the size of the organic barrier layer (solid
portion) 14 formed around the particle P are sufficiently smaller
than the pixel pitch. Therefore, a change in the transmittance
caused by the barrier layer 14 (solid portion) formed around the
particle P does not have a significant influence on the
display.
[0079] Now, with reference to FIG. 6(a) and FIG. 6(b), a further
advantage provided by the black organic barrier layer 14 included
in the OLED display device 100 will be described.
[0080] Patent Document No. 3 discloses a thin film encapsulation
structure including an organic barrier layer (may be referred to as
a "flattening layer"; for example, an acrylic resin layer) formed
selectively around an inclining surface of a bank structure. Patent
Document No. 3 does not disclose a colored organic barrier layer.
According to the studies made by the present inventors, unless the
colored organic barrier layer is formed, the luminous intensity
distribution (viewing angle dependence) of light output from the
pixel may be changed by the formation of the organic barrier layer
(solid portion) around the inclining surface of the bank structure.
When the size, shape or the like of the organic barrier layer is
different, the intensity or the luminous intensity distribution of
the light output from a periphery of the pixel is different. As a
result, a problem that the luminous intensity distribution of light
is different among the pixels is caused.
[0081] By contrast, as shown in FIG. 6(a) and FIG. 6(b), the OLED
display device 100 according to an embodiment of the present
invention includes the organic barrier layer (solid portion) 14
colored black and extending from the inclining surface of the bank
structure BS to a peripheral area in the pixel. Therefore, the
light output from the periphery of the pixel is decreased. This
uniformizes the luminous intensity distributions of the light
output from the pixels. As shown in FIG. 6(a), the OLED display
device 100 also includes the organic barrier layer (solid portion)
14 around the particle P. Therefore, the light is suppressed from
leaking from the vicinity of the particle P.
[0082] The organic barrier layer 14 merely needs to effectively
absorb light output in an oblique direction (e.g., absorb 70% or
greater of the light) in order to provide the above-described
effect. The organic barrier layer 14 may be formed of, for example,
a black resist usable for a black matrix of a color filter layer of
a known display device. However, the organic barrier layer 14 does
not necessarily need to have a level of light-blocking property
required of a black matrix (e.g., OD value of about 3 to
4/.mu.m).
[0083] Now, a method for producing an OLED display device according
to an embodiment of the present invention will be described.
[0084] A step of forming the TFE structure 10 in the OLED display
device according to an embodiment of the present invention includes
the following steps.
[0085] Step A: step of preparing an element substrate having the
first inorganic barrier layer 12 formed thereon
[0086] Step B: step of forming a liquid film containing a
photosensitive resin on the first inorganic barrier layer 12
[0087] Step C: step of irradiating the liquid film with light to
form a resin layer
[0088] Step D: step of forming the organic barrier layer 14,
including a step of partially removing the resin layer by a dry
process
[0089] Step D is optional and may be omitted. For example, as
described below, mask exposure may be performed at the time of
curing the photocurable resin to form the organic barrier layer
14.
[0090] As an example, a method for forming the organic barrier
layer 14 by use of the method described in Patent Document No. 1 or
2 will be described. Regarding the method for forming the organic
barrier layer, the disclosures of Patent Documents Nos. 1 and 2 are
incorporated herein by reference.
[0091] Step B includes a step of, after step A, putting the element
substrate into a chamber and supplying a vapor-like or mist-like
photocurable resin (e.g., acrylic monomer) into the chamber, and a
step of condensing the photocurable resin on the first inorganic
barrier layer 12 to form the liquid film. Namely, a vapor-like or
mist-like organic material is supplied onto the element substrate
maintained at a temperature lower than, or equal to, room
temperature in the chamber, and is condensed on the element
substrate. Thus, the organic material put into a liquid state is
located locally, more specifically, at the border between the side
surface of the protruding portion and the flat portion of the
surface of the first inorganic barrier layer 12 by a capillary
action or a surface tension of the organic material.
[0092] In the case where step B is performed by the method
described in Patent Document No. 1 or 2, the liquid film formed in
step B contains, for example, a photocurable resin (e.g.,
ultraviolet-curable resin) and a black dye. The black dye may be a
known dye. The black dye may contain a photopolymerizable dye
monomer. The black dye is generally a mixture of a plurality of
dyes (compounds) of different colors.
[0093] Next, step C is performed. More specifically, the organic
material is irradiated with, for example, ultraviolet rays to form
the photocurable resin layer (e.g., acrylic resin layer). The
photocurable resin layer formed in this step typically includes a
plurality of solid portions distributed discretely. Substantially
no solid portion is present on the flat portion of the surface of
the first inorganic barrier layer 12. Even if the organic material
is present on the flat portion of the surface of the first
inorganic barrier layer 12, the amount (e.g., thickness) thereof is
smaller than the amount around the protruding portion of the
surface of the first inorganic barrier layer 12. Therefore, the
resin layer, once formed, may be asked in, for example, a
subsequent step (step D) to remove the organic material from the
flat portion of the surface of the first inorganic barrier layer
12. As a result, the organic barrier layer (solid portion) 14 is
formed locally, more specifically, only around the protruding
portion of the surface of the first inorganic barrier layer 12. In
order to form the organic barrier layer 14 in this manner, the
thickness of the liquid film to be formed and/or the asking
conditions (including time) may be appropriately adjusted when
necessary, in addition to the above.
[0094] Alternatively, selective exposure such as mask exposure or
the like may be performed at the time of curing the photocurable
resin. For example, mask exposure may be performed, so that the
inorganic barrier layer joint portion, where the first inorganic
barrier layer 12 and the second inorganic barrier layer 16 are in
direct contact with each other, is formed. An opening of the
organic barrier layer 14 is formed in a region corresponding to a
light-blocking portion of the photomask. Therefore, for example,
the photocurable resin layer may be exposed via a photomask
including a light-blocking portion formed so as to enclose the
active region, so that the organic barrier layer 14 having an
opening formed so as to enclose the active region is provided.
[0095] Then, step D is performed when necessary to form the organic
barrier layer (solid portion) 14 located locally, more
specifically, only around the protruding portion of the surface of
the first inorganic barrier layer 12. Step D includes a step of
partially removing the photocurable resin layer by a dry process.
For example, a relatively thick portion of the photocurable resin
layer is left without being fully removed. The expression "remove
an organic material by a dry process" indicates removing an organic
material from the surface by ashing or by a dry process other than
ashing (e.g., by sputtering). The expression "remove an organic
material by a dry process" encompasses removing the organic
material entirely and removing the organic material partially
(e.g., from the surface to a certain depth). The "dry process"
refers to a process that is not a wet process using a liquid such
as a release liquid, a solvent or the like.
[0096] Patent Document No. 1 or 2 does not disclose or suggest a
step of partially removing a photocurable resin layer by a dry
process. This step enlarges a margin for the formation of the
organic barrier layer. Namely, an organic barrier layer
(photocurable resin layer) is once formed in a region larger
(wider) than the region where the organic barrier layer needs to be
formed, and the resultant organic barrier layer is partially
removed. In this manner, the organic barrier layer is formed only
in the region where the organic barrier layer needs to be formed.
This improves the yield.
[0097] Ashing oxidizes and thus removes an organic material. Ashing
is used also to remove an organic material attached to a surface of
an inorganic film. Ashing is used to remove the organic material
entirely and also to remove the organic material partially (e.g.,
from a surface to a certain depth). Ashing may be performed in, for
example, an atmosphere containing at least one of N.sub.2O, O.sub.2
and O.sub.3. Ashing is roughly classified into plasma ashing (or
corona discharge) using plasma generated by treating any one of the
above-described types of atmospheric gas at a high frequency, and
photo-excited ashing of irradiating atmospheric gas with light such
as ultraviolet rays or the like. Ashing may be performed by use of,
for example, a known plasma ashing device, a known ashing device
using corona discharge, a known photo-excited ashing device, a
known UV ozone ashing device or the like. In the case where an SiN
film is formed by CVD as each of the first inorganic barrier layer
12 and the second inorganic barrier layer 16, N.sub.2O is used as
material gas. Therefore, use of N.sub.2O for ashing provides an
advantage of simplifying the ashing device.
[0098] Ashing results in shaving the surface the organic barrier
layer 14 substantially uniformly, and also oxidizing the surface
the organic barrier layer 14 to modify the surface of the organic
barrier layer 14 to be hydrophilic. Ashing also results in forming
extremely tiny concaved and convexed portions to increase the
surface area size of the organic barrier layer 14. The effect of
ashing of increasing the surface area size is greater for the
surface of the organic barrier layer 14 than for the first
inorganic barrier layer 12 formed of an inorganic material. Since
the surface of the organic barrier layer 14 is modified to be
hydrophilic and the surface area size thereof is increased, the
adhesiveness between the organic barrier layer 14 and the second
inorganic barrier layer 16 is improved.
[0099] In order to improve the adhesiveness between the first
inorganic barrier layer 12 and the organic barrier layer 14, the
surface of the first inorganic barrier layer 12 may be exposed to
plasma ashing (e.g., plasma process and/or corona process) or to
photo-excited ashing before the organic barrier layer 14 is formed.
Namely, the step of forming the TFE structure 10 may further
include a step of, after step A and before step B, performing
plasma ashing (e.g., plasma process and/or corona process) or
photo-excited ashing. Such a step provides an advantage that the
side surface of the protruding portion of the surface of the first
inorganic barrier layer 12 is modified to be lyophilic to the
liquid film formed in step B, or that the degree of the lyophilic
property of the side surface is improved. Alternatively, the
surface of the flat portion of the first inorganic barrier layer 12
may be modified to be repelling against the liquid film formed in
step B. For example, the inclining surface S12 of the first
inorganic barrier layer 12 of the bank structure BS (see FIG. 6(a)
and FIG. 6(b)) may be lyophilic to the liquid film formed in step
B, whereas the region enclosed by the bank structure BS may be
repelling against the liquid film formed in step B.
[0100] The above-described modification of the surface may also be
realized by, for example, a silane coupling agent (hydrophilic or
hydrophobic). Namely, the step of forming the TFE structure 10 may
further include a step of, after step A and before step B,
supplying a silane coupling agent onto the surface of the first
inorganic barrier layer 12. Either the step of supplying the silane
coupling agent or the step of asking may be performed.
Alternatively, after the surface of the first inorganic barrier
layer 12 is asked, the silane coupling agent may be supplied.
Supply of the silane coupling agent may modify the surface of the
first inorganic barrier layer 12 to be hydrophilic or
hydrophobic.
[0101] Still alternatively, for example, a photolithography process
may be used to modify a particular region of the surface to be
hydrophilic or hydrophobic by use of a silane coupling agent. For
example, the inclining surface S12 of the first inorganic barrier
layer 12 of the bank structure BS may be modified to be lyophilic
to the liquid film, whereas the region enclosed by the bank
structure BS may be modified to be repelling against the liquid
film.
[0102] Step D may further include a step of performing plasma
ashing (e.g., plasma process and/or corona process) or
photo-excited ashing. This step removes the organic material from
the surface of the flat portion of the first inorganic barrier
layer 12 more certainly.
[0103] As described above, the active region of the OLED display
device 100 according to an embodiment of the present invention is
fully enclosed by the inorganic barrier layer joint portion, where
the first inorganic barrier layer 12 and the second inorganic
barrier layer 16 are in direct contact with each other. With such a
structure, the OLED display device 100 has a higher level of
moisture-resistance reliability than an OLED display device
including an organic barrier layer formed by the method described
in Patent Document No. 1 or 2.
[0104] According to the studies made by the present inventors, in
the case where the organic barrier layer is formed by the method
described in Patent Document No. 1 or 2, there may be a problem
that a sufficiently high level of moisture-resistance reliability
is not provided. This problem has been found to be caused by water
vapor in the air reaching the active region (may also be referred
to as an "element formation region" or a "display region") on the
element substrate via the organic barrier layer.
[0105] In the case where an organic barrier layer is formed by
printing such as inkjet printing or the like, the organic barrier
layer may be adjusted to be formed only in the active region (may
also be referred to as an "element formation region" or a "display
region") on the element substrate but not in a region other than
the active region. Therefore, there is a region where the first
inorganic barrier layer and the second inorganic barrier layer are
in direct contact with each other around the active region (outer
to the active region). The organic barrier layer is fully enclosed
by the first inorganic barrier layer and the second inorganic
barrier layer and is isolated from the outside of the first
inorganic material layer and the second inorganic material
layer.
[0106] By contrast, with the method for forming the organic barrier
layer described in Patent Document 1 or 2, a resin (organic
material) is supplied onto the entire surface of the element
substrate, and the surface tension of the resin in a liquid state
is used to locate the resin locally, more specifically, at the
border between the surface of the substrate and the side surface of
the protruding portion on the surface of the element substrate.
Therefore, the organic barrier layer may also be formed in a region
other than the active region (the region other than the active
region may also be referred to as a "peripheral region"), namely,
in a terminal region, where the plurality of terminals are located,
and in a lead wire region, where the lead wires extending from the
active region to the terminal region are formed. Specifically, the
resin is present locally, more specifically, at, for example, the
border between the side surfaces of the lead wires and the
terminals and the surface of the substrate. In this case, an end of
the organic barrier layer formed along the lead wires is not
enclosed by the first inorganic barrier layer or the second
inorganic barrier layer, but is exposed to the air (ambient
atmosphere). The organic barrier layer is lower in the barrier
property against water vapor than the inorganic material layers
(inorganic barrier layers). Therefore, the organic barrier layer
formed along the lead wires acts as a route that leads the water
vapor in the air to the active region.
[0107] With the production method according to an embodiment of the
present invention, as described above, the openings of the organic
barrier layer 14 include an opening formed so as to enclose at
least the active region, and the active region is fully enclosed by
the inorganic barrier layer joint portion, where the first
inorganic barrier layer 12 and the second inorganic barrier layer
16 are in direct contact with each other. Therefore, the organic
barrier layer does not act as a route that leads the water vapor in
the air to the active region.
[0108] The organic barrier layer 14 of the OLED display device 100
according to an embodiment of the present invention is not limited
to being formed by the above-described method, and may be formed
by, for example, spraying, spin-coating, slit-coating, screen
printing or inkjet printing. Namely, step B may be performed by
spraying, spin-coating, slit-coating, screen printing or inkjet
printing. In the case where such a method is used, a photosensitive
resin (positive or negative) may be used as well as a photocurable
resin (negative). In the case where a positive photosensitive resin
is used, a photomask having an opening corresponding to a region
where the inorganic barrier layer joint portion is to be formed is
used.
[0109] In the case where any of such methods is used, the liquid
film (a material containing a photosensitive resin used to form the
liquid film may be referred to as a "coating liquid") is not
limited to a dye and may contain a pigment. A known black pigment,
for example, carbon black, may be used. Usable as a photosensitive
resin (e.g., photocurable resin) having black pigment dispersed
therein is, for example, a black resist usable for a black matrix
of a color filter layer of a liquid crystal display device. The
organic barrier layer merely needs to be sufficiently colored black
to be visually recognizable in an inspection process described
below, and does not necessarily need to have a light-blocking
property require of a black matrix (e.g., OD value of about 3 to
4/.mu.m). As described above, the thickness of the organic barrier
layer 14 is less than, or equal to, 1 .mu.m, typically, 200 nm or
greater and 500 nm or less. Therefore, even a usual photosensitive
resist for a black matrix may be sufficiently exposed to light
(e.g., cured) with an exposure amount of, for example, 150
mJ/cm.sup.2 or less. As the black pigment, a mixture of a plurality
of pigments of different colors may be used.
[0110] In the case where the organic barrier layer 14 is formed by
inkjet printing, the organic barrier layer (solid portion) may be
selectively formed only in a particular region. Therefore, the
inorganic barrier layer joint portion is formed with no mask
exposure. Even with printing such as screen printing, inkjet
printing or the like, the resultant organic barrier layer 14 is
thinner than a relatively thick organic barrier layer having a
thickness of about 5 .mu.m to about 20 .mu.m, which is used for a
thin film encapsulation structure of an OLED display device
currently commercially available. In this case, the photosensitive
resin to be used is photo-curable (i.e., negative).
[0111] In the case where the organic barrier layer is formed by
inkjet printing, a region to which the coating liquid is to be
supplied needs to be specified. Therefore, the method for producing
the OLED display device in an embodiment includes a foreign object
detection step and an inkjet printing step.
[0112] FIG. 7 is a schematic view showing a foreign object
detection device 50 usable for the method for producing an OLED
display device according to an embodiment of the present invention.
FIG. 8 is a schematic view showing an inkjet device 60 usable for
the method for producing an OLED display device according to an
embodiment of the present invention.
[0113] The foreign object detection device 50 shown in FIG. 7
includes a controller 52 and a detection head 54. The controller 52
controls an operation of the detection head 54 and also controls an
operation of a stage 70. The stage 70 is capable of receiving a
substrate 100M and transporting the substrate 100M in an x-axis
direction and a y-axis direction. The stage 70 is capable of, for
example, attracting and securing the substrate 100M, and/or
transporting the substrate 100M in a floating state (contactless
transportation). The substrate 100M is an element substrate formed
by use of a G4.5 mother board, and includes the components up to
the first inorganic barrier layer.
[0114] The controller 52 includes a memory and a processor (neither
is shown), and controls the operation of the detection head 54
and/or the stage 70 in accordance with information stored on the
memory, such that the detection head scans on the substrate 100M. A
signal to control the detection head 54 and/or the stage 70 to
operate is generated by the processor and supplied to the detection
head 54 and/or the stage 70 via an interface (represented by the
arrow in the figure).
[0115] The detection head 54 includes, for example, a laser light
source (e.g., semiconductor laser element), an image-forming
optical system, and an image-capturing element (none of these
components is shown). Laser light is directed toward a
predetermined position on the substrate 100M, and the light
scattered by the substrate 100M is caused, by the image-forming
optical system, to form an image on a light receiving surface of
the image-capturing element. Regarding the result of
image-capturing performed by the image-capturing element, the
processor finds whether or not there is a particle, the size of the
particle, and the like in accordance with a predetermined
algorithm, and stores the obtained results on the memory. Such a
foreign object inspection device is described in, for example,
Japanese Laid-Open Patent Publication No. 2016-105052. The entirety
of the disclosure of Japanese Laid-Open Patent Publication No.
2016-105052 is incorporated herein by reference. As the foreign
object inspection device 50, for example, HS-930 produced by Toray
Engineering Co., Ltd. is preferably usable. HS-930 is capable of
detecting a foreign object having a size of 0.3 .mu.m (evaluation
performed by scattering standard particles). HS-930 is capable of
inspecting a G4.5 board in a time period shorter than 60
seconds.
[0116] The standard particles are true sphere polystyrene latex
particles. The actual particle P is a microscopic piece of broken
glass, a metal particle or an organic particle (organic EL
material), and is covered with an SiN layer (refractive index:
about 1.8; second inorganic barrier layer). Therefore, the actual
particle P is more easily detectable than the standard particle.
With the above-described foreign object inspection device using
scattered laser light, a foreign object having an equivalent
spherical diameter of 0.2 .mu.m or longer is detected.
[0117] The inkjet device 60 shown in FIG. 8 includes a controller
62, an inkjet head 64, and a UV (ultraviolet) irradiation head
66.
[0118] The controller 62 includes a memory and a processor (neither
is shown), and controls the operation of the inkjet head 64, the
irradiation head 66 and/or the stage 70 in accordance with
information stored on the memory, such that the inkjet head 64 and
the UV irradiation head 66 move to a desired position on the
substrate 100M.
[0119] A signal to control the inkjet head 64, the UV irradiation
head 66 and/or the stage 70 to operate is generated by the
processor and supplied to the inkjet head 64, the UV irradiation
head 66 and/or the stage 70 via interfaces (represented by the
arrows in the figure). For example, position information (e.g., xy
coordinates), on the position at which the particle is present,
stored on the memory of the controller 52 of the foreign object
detection device 50 is received by the controller 62. Based on the
position information, microscopic liquid drops of the coating
liquid containing the photocurable resin are supplied from the
inkjet head 64. The amount of the coating liquid (the number of the
microscopic liquid drops, namely, the number of shots) supplied
from the inkjet head 64 is, for example, found by the processor
based on size information on the particle stored on the memory of
the controller 52 of the foreign object detection device 50 and
received by the controller 62.
[0120] Then, the UV irradiation head 66 directs ultraviolet rays
to, and thus cures, the supplied photocurable resin to form the
organic barrier layer. This operation is performed on each of the
particles.
[0121] FIG. 8 shows the inkjet head 64 and the UV irradiation head
66 as being separate from each other. Alternatively, the inkjet
head 64 and the UV irradiation head 66 may be provided as one head.
An LED or a semiconductor laser element may be used as an
ultraviolet source, so that the UV irradiation device 66 is
realized as a compact device including a light source itself.
Alternatively, the UV irradiation device 66 may include only an
output end of an optical fiber and a lens unit provided when
necessary. In this case, as an ultraviolet source that emits
ultraviolet rays toward an input end of the optical fiber, an LED,
a semiconductor laser or any of various other ultraviolet sources
(e.g., lamp sources such as, for example, a mercury xenon lamp, a
super-high pressure mercury lamp and the like) is usable. In
consideration of the combining efficiency, it is preferred to use a
light source capable of oscillating laser light, for example, an
LED, a semiconductor laser element or the like. In the case where
the UV irradiation head 66 and an ultraviolet source are located
separately from each other, there is an advantage that in a series
of steps including the detection of a foreign object, the supply of
a coating liquid and the irradiation with ultraviolet rays, the
influence exerted by heat generation caused by the light source on
the OLED 3 in the substrate 100M is decreased.
[0122] Alternatively, for example, a plurality of inkjet heads may
be prepared. For example, two or more inkjet heads generating
different sizes of microscopic liquid drops may be prepared, so
that different inkjet heads are used for particles of different
sizes.
[0123] For example, the inkjet head 64 preferably usable may
generate microscopic liquid drops each having a volume of the order
of 1 fL (1 fL or larger and smaller than 10 fL) or may generate
microscopic liquid drops each having a volume smaller than 1 fL. 1
fL corresponds to a volume of a sphere having a diameter of about
1.2 .mu.m, and 0.1 fL corresponds to a volume of a sphere having a
diameter of about 0.6 .mu.m. For example, the inkjet device (Super
Inkjet (registered trademark)) produced by SIJ Technology Inc.,
capable of injecting 0.1 fL microscopic liquid drops, is preferably
usable.
[0124] Now, with reference to FIG. 9(a) and FIG. 9(b), the volume
of the organic barrier layer (solid portion) to be formed around
the particle P and a preferred size of the microscopic liquid drops
used to form the organic barrier layer will be described. FIG. 9(a)
and FIG. 9(b) are schematic views provided to describe a preferred
range of the volume of the organic barrier layer to be formed
around the particle P in the OLED display device according to an
embodiment of the present invention. FIG. 9(a) is a cross-sectional
view taken along line 9A-9A' in FIG. 9(b), and is a schematic view
of a cross-section including a diameter of the particle P. FIG.
9(b) is a plan view as seen in a direction normal to the surface of
the OLED.
[0125] Now, it is assumed that the particle P or the first
inorganic barrier layer 12a formed to cover the particle P (the
particle P and the first inorganic barrier layer 12a formed to
cover the particle P may be collectively referred to as a
"protruding portion by the particle P") is spherical. An organic
barrier layer 14v around the particle P may be formed to cover the
particle P and/or the inorganic barrier layer 12a on the particle
P. However, if the organic barrier layer 14v is too thick, the
protruding portion by the particle P may be visually recognized by
a refraction function (lens effect) of the organic barrier layer
14v. Therefore, it is preferred that as shown in FIG. 9(a), the
organic barrier layer 14v is formed only in a region of a radius R
of the protruding portion by the particle P, namely, from the
bottom to the center of the protruding portion. The organic barrier
layer 14v provided in this manner may be formed by adjusting the
volume of the coating liquid to be supplied (in the case where the
coating liquid contains a solvent, the volume of the solid content)
and/or by adjusting the asking conditions (e.g., time). Ashing will
be described below.
[0126] Assuming that a recessed surface of the organic barrier
layer 14v is a curved surface having a radius of curvature that is
the same as the radius R of the protruding portion by the particle
P, the volume V.sub.0 of the organic barrier layer 14v shown in
FIG. 9(a) and FIG. 9(b) is represented by the following expression
(1).
V.sub.0=(4-.pi.).pi.R.sup.3 (1)
[0127] When the radius R of the protruding portion by the particle
P is 0.15 .mu.m, V.sub.0 is about 0.009 fL. When the radius R is
0.25 .mu.m, V.sub.0 is about 0.04 fL. When the radius R is 2.5
.mu.m, V.sub.0 is about 42 fL.
[0128] It is preferred that the volume of the organic barrier layer
14v is larger than, or equal to, about a half of V.sub.0. If the
volume of the organic barrier layer 14v is smaller than this range,
the formation of the organic barrier layer 14v may prevent
formation of the second inorganic barrier layer 16 with a fine film
with no defect. The upper limit of the volume of the organic
barrier layer 14v may be a level at which the protruding portion by
the particle P is not visually recognized by the refraction
function (lens effect). The upper limit preferably does not exceed
five times of V.sub.0, and preferably does not exceed twice of
V.sub.0. In the case where the radius R of the protruding portion
by the particle P is shorter than 2.5 .mu.m (in the case where
V.sub.0 is smaller than about 42 fL), the volume of the organic
barrier layer 14v is not limited to the above-described range. The
volume of the organic barrier layer 14v is merely required not to
exceed about 200 fL, and is preferably smaller than, or equal to,
about 100 fL.
[0129] It is preferred that the size of the microscopic liquid
drops is appropriately set in accordance with the radius R of the
protruding portion by the particle P. It is preferred that, for
example, the size of the microscopic liquid drops is set such that
one to three drops satisfy V.sub.0. A solvent may be incorporated
into the coating liquid, so that the microscopic liquid drops are
made large with respect to the solid content in the coating liquid
(amount left as the organic barrier layer 14v in a final state)
(the size of the microscopic liquid drops may be increased to, for
example, a range from a size exceeding 1 time the original size to
a size 10 times the original size).
[0130] A protruding portion, by the particle P, having a diameter
shorter than 0.2 .mu.m (having a radius R shorter than 0.1 .mu.m)
is considered to have substantially no influence on the
moisture-resistance reliability even if the organic barrier layer
14v is not provided. Therefore, it is merely needed to detect
protruding portions, by the particle P, having a diameter of 0.2
.mu.m or longer (having a radius R of 0.1 .mu.m or longer) and form
the organic barrier layer 14v in corresponding portions.
[0131] It is not efficient to supply a microscopic liquid drop of
0.1 fL a great number of times for a particle P having a diameter
of 5 .mu.m (having a radius R of 2.5 .mu.m). Therefore, for
example, an inkjet head generating microscopic liquid drops smaller
than 1 fL (e.g., 0.1 fL) and an inkjet head generating microscopic
liquid drops of 10 fL or larger and smaller than 0.5 pL (e.g., 50
fL) may be prepared, so that one of the inject heads is selected in
accordance with the size of the particle P. The UV irradiation head
66 is commonly usable. Needless to say, three or more inkjet heads
generating microscopic liquid drops of different sizes may be
prepared.
[0132] As described above, the portion 14b of the organic barrier
layer 14 may be formed around the particle P. By contrast, the
pixel periphery solid portion 14a, of the organic barrier layer 14,
extending on the first inorganic barrier layer 12 from the
inclining surface S12 to a peripheral area in the pixel, is more
efficiently formed by use of an inkjet head that generates
microscopic liquid drops of 10 fL or larger and smaller than 100 pL
(e.g., 200 fL). The position of the pixel periphery solid portion
14a is determined in advance. Therefore, an inkjet device may be
separately prepared, and the pixel periphery solid portion 14a may
be formed in accordance with the design data.
[0133] A coating liquid containing a photocurable resin (monomer)
contains a photoinitiator (radical polymerization initiator or
cationic polymerization initiator) and also a small amount of
additive such as a surfactant or the like. The photocurable resin
is contained in the coating liquid at a content of about 80% by
mass to about 90% by mass, and the photoinitiator is contained at a
content of about 5% by mass to about 10% by mass. A pigment or a
dye may be incorporated into the coating liquid. In the case of a
pigment is incorporated, a dispersant may also be incorporated. A
preferred viscosity is, for example, about 0.5 mPa or higher and 10
Pas. In the case where a dye or a pigment is incorporated, it is
easily checked whether or not the organic barrier layer (solid
portion) has been formed at a desired position. The pigment needs
to be put into microscopic pieces, which raises the viscosity.
Therefore, it is preferred to use a dye. In the case where, for
example, microscopic liquid drops of 0.1 fL are to be generated, it
is preferred that the coating liquid does not contain a pigment or
a dye. In order to adjust the viscosity or the size (volume) of the
microscopic liquid drops, a solvent (e.g., an organic solvent such
as alcohol or the like) may be incorporated.
[0134] Usable as the photocurable resin may be a radical
polymerizable monomer containing a vinyl group such as an acrylic
resin (acrylate monomer), or a cationic polymerizable monomer
containing an epoxy group. An appropriate photoinitiator is
selected in accordance with the type of the resin to be used and
the wavelength range of the UV light to be directed. Instead of
using the UV irradiation head 66, an ultraviolet irradiation device
such as a high pressure mercury lamp, a super-high pressure mercury
lamp or the like may be used to, for example, irradiate the
entirety of the photocurable resin on the substrate 100M with
ultraviolet rays at the same time. The amount of the ultraviolet
rays to be directed (exposure amount), which depends on the
thickness of the organic barrier layer 14 to be formed, is, for
example, 50 mJ/cm.sup.2 or larger and 200 mJ/cm.sup.2 or smaller,
preferably 100 mJ/cm.sup.2 or larger and 150 mJ/cm.sup.2 or
smaller, with i line of 365 nm.
[0135] The production method described above includes a step in
which a photocurable resin (organic material) heated and vaporized
to be vapor-like or mist-like is supplied onto an element substrate
maintained at a temperature lower than, or equal to, room
temperature and is condensed on the element substrate, so that the
organic material put into a liquid state is located locally, more
specifically, at the border between the side surface of the
protruding portion and the flat portion of the surface of the first
inorganic barrier layer by use of a capillary action or a surface
tension of the organic material. With this production method, the
photocurable resin needs to be once vaporized. In this case, it is
preferred that the photocurable resin does not contain a pigment.
The viscosity of the photocurable resin, at room temperature (e.g.,
25.degree. C.) before the photocurable resin is cured, preferably
does not exceed 10 Pas, and especially preferably is 1 to 100 mPas.
If the viscosity is too high, it may be difficult to form a thin
film having a thickness of 500 nm or less.
[0136] The production method may further include a step of
partially ashing the photocurable resin layer formed by curing the
photocurable resin. Ashing may be performed by use of a known
plasma ashing device, a known ashing device using corona discharge,
a known photo-excited ashing device, a known UV ozone ashing device
or the like. Ashing may be performed, for example, by plasma ashing
using at least one type of gas among N.sub.2O, O.sub.2 and O.sub.3,
or by a combination of plasma ashing and ultraviolet irradiation.
In the case where an SiN film is formed by CVD as each of the first
inorganic barrier layer 12 and the second inorganic barrier layer
16, N.sub.2O is used as material gas. Therefore, use of N.sub.2O
for ashing provides an advantage of simplifying the ashing
device.
[0137] Ashing results in oxidizing the surface the organic barrier
layer 14 to modify the surface the organic barrier layer 14 to be
hydrophilic. In addition, ashing results in shaving the surface the
organic barrier layer 14 substantially uniformly and forming
extremely tiny concaved and convexed portions to increase the
surface area size of the organic barrier layer 14. The effect of
ashing of increasing the surface area size is greater for the
surface of the organic barrier layer 14 than for the first
inorganic barrier layer 12 formed of an inorganic material. Since
the surface of the organic barrier layer 14 is modified to be
hydrophilic and the surface area size thereof is increased, the
adhesiveness between the organic barrier layer 14 and the second
inorganic barrier layer 16 is improved.
[0138] In order to improve the adhesiveness between the first
inorganic barrier layer 12 and the organic barrier layer 14, the
surface of the first inorganic barrier layer 12 may be exposed to
plasma ashing before the organic barrier layer 14 is formed.
[0139] Ashing results in, for example, removing the photocurable
resin formed on the protruding portion by the particle P to adjust
the location and/or the volume of the organic barrier layer 14 left
in a final state, and also results in improving the adhesiveness
between the organic barrier layer 14 and the second inorganic
barrier layer 16.
[0140] The method for producing the OLED display device according
to an embodiment of the present invention may further include,
after the step of forming the thin film encapsulation structure, a
step of optically acquiring a pattern of the organic barrier layer
14 and a step of determining whether the thin film encapsulation
structure is good or not based on the pattern. Since the black
organic barrier layer 14 is formed, it may be determined whether
the thin film encapsulation structure is good or not based on the
pattern of the organic barrier layer optically acquired. Such an
inspection process may be easily inlined. This improves the
yield.
[0141] Specifically, a pattern of a region, of the element
substrate having the first inorganic barrier layer formed thereon,
on which the organic barrier layer (solid portions) is to be formed
(such a pattern is also referred to as a "design pattern" or a
"target pattern") is prepared. From the element substrate having
the organic barrier layer 14 formed thereon, the pattern of the
organic barrier layer (solid portions) is optically acquired by use
of, for example, an image capturing device. The acquired pattern of
the organic barrier layer (solid portions) is compared against the
design pattern (target pattern), and thus it is determined whether
or not the organic barrier layer (solid portions) has been formed
in the predetermined region. With the method for producing the
organic EL display device according to an embodiment of the present
invention, the organic barrier layer is black. Therefore, the
pattern of the organic barrier layer may be acquired optically with
high precision. Naturally, the design pattern does not include a
pattern of the organic barrier layer (solid portions) to be formed
in correspondence with the particles. However, in the case where a
pattern matching the design pattern is formed, if the particles are
present, it is presumed that the organic barrier layer (solid
portions) corresponding to the particles has also been formed.
Therefore, the yield is improved as compared with a case where no
inspection is made regarding the state of formation of the organic
barrier layer. The determination is made with higher precision or
in a shorter time as compared with a case where a transparent
organic barrier layer is formed.
[0142] It may also be inspected whether or not an organic barrier
layer corresponding to the particles has been formed. For example,
foreign objects on the element substrate are detected by the
foreign object detection device before the organic barrier layer is
formed, and data including position information on the foreign
objects (mapping) and image information on a microscopic region
including each of the foreign objects (light intensity
distribution) is acquired. After the organic barrier layer is
formed on the element substrate, a foreign object inspection is
performed in substantially the same manner by use of the foreign
object detection device, and substantially the same type of data is
acquired. The data before the formation of the organic barrier
layer and the data after the formation of the organic barrier layer
may be compared against each other to determine whether or not the
organic barrier layer corresponding to each of the particles has
been formed. With the method for producing the organic EL display
device according to an embodiment of the present invention, the
organic barrier layer is black. Therefore, the image information
(light intensity distribution) is significantly changed by the
formation of the organic barrier layer. For this reason, the
determination is made with higher precision or in a shorter time as
compared with a case where a transparent organic barrier layer is
formed.
INDUSTRIAL APPLICABILITY
[0143] Embodiments of the present invention are applicable to an
organic EL display device, especially, a flexible organic EL
display device, and a method for producing the same.
REFERENCE SIGNS LIST
[0144] 1 flexible substrate [0145] 2 back plane (circuit) [0146] 3
organic EL element [0147] 4 polarizing plate [0148] 10 thin film
encapsulation structure (TFE structure) [0149] 12 first inorganic
barrier layer [0150] 14 organic barrier layer [0151] 16 second
inorganic barrier layer [0152] 30 lead wire [0153] 42 lower
electrode [0154] 44 organic layer [0155] 46 upper electrode [0156]
48 bank layer [0157] 50 foreign object detection device [0158] 52
controller [0159] 54 detection head [0160] 60 inkjet device [0161]
62 controller [0162] 64 inkjet head [0163] 66 UV irradiation head
[0164] 100 organic EL display device
* * * * *