U.S. patent application number 14/379443 was filed with the patent office on 2015-02-05 for optical-device surface-sealing composition, optical-device surface-sealing sheet, display, and display manufacturing method.
The applicant listed for this patent is MITSUI CHEMICALS, INC.. Invention is credited to Setsuko Oike, Masatoshi Takagi, Yugo Yamamoto.
Application Number | 20150034928 14/379443 |
Document ID | / |
Family ID | 49005429 |
Filed Date | 2015-02-05 |
United States Patent
Application |
20150034928 |
Kind Code |
A1 |
Yamamoto; Yugo ; et
al. |
February 5, 2015 |
OPTICAL-DEVICE SURFACE-SEALING COMPOSITION, OPTICAL-DEVICE
SURFACE-SEALING SHEET, DISPLAY, AND DISPLAY MANUFACTURING
METHOD
Abstract
The purpose of the present invention is to provide the
following: an optical-device surface-sealing composition that makes
it possible to fabricate an optical-device-using display with a low
amount of warpage even if there is a large difference between the
coefficients of linear expansion of substrates used in said
display; a display with a low amount of warpage; and a
manufacturing method therefor. The storage modulus of elasticity
(G'(80)) of this optical-device surface-sealing composition,
measured at 80.degree. C. after said composition is heated from
40.degree. C. to 80.degree. C. at 5.degree. C./min and then held at
80.degree. C. for 30 minutes, is between 1.0.times.10.sup.3 and
2.0.times.10.sup.6 Pa.
Inventors: |
Yamamoto; Yugo; (Chiba-shi,
JP) ; Oike; Setsuko; (Yokohama-shi, JP) ;
Takagi; Masatoshi; (Yokohama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUI CHEMICALS, INC. |
Tokyo |
|
JP |
|
|
Family ID: |
49005429 |
Appl. No.: |
14/379443 |
Filed: |
February 21, 2013 |
PCT Filed: |
February 21, 2013 |
PCT NO: |
PCT/JP2013/001001 |
371 Date: |
August 18, 2014 |
Current U.S.
Class: |
257/40 ; 438/28;
525/314; 525/323; 525/324; 528/87 |
Current CPC
Class: |
H01L 51/56 20130101;
C08G 59/245 20130101; B32B 15/20 20130101; B32B 27/302 20130101;
B32B 27/40 20130101; B32B 27/325 20130101; B32B 27/308 20130101;
B32B 27/32 20130101; C08L 63/00 20130101; H01L 27/32 20130101; H01L
51/5246 20130101; B32B 2457/20 20130101; B32B 27/36 20130101; B32B
2255/06 20130101; B32B 2307/51 20130101; H01L 51/0035 20130101;
C08G 59/56 20130101; B32B 27/365 20130101; C08G 59/5073 20130101;
B32B 2274/00 20130101; B32B 2307/412 20130101; C08L 2205/03
20130101; C09J 163/00 20130101; B32B 15/08 20130101 |
Class at
Publication: |
257/40 ; 438/28;
528/87; 525/324; 525/323; 525/314 |
International
Class: |
H01L 51/52 20060101
H01L051/52; H01L 51/56 20060101 H01L051/56; C09J 163/00 20060101
C09J163/00; H01L 27/32 20060101 H01L027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 24, 2012 |
JP |
2012-038838 |
Claims
1. An optical device surface-sealing composition comprising a
flexible epoxy resin (A) having two or more epoxy groups in a
molecule, and a curing accelerator (B), the composition having a
storage elastic modulus G' (80) of 1.0.times.10.sup.3 to
2.0.times.10.sup.6 Pa at 80.degree. C. measured after temperature
increase from 40.degree. C. to 80.degree. C. at 5.degree. C./min
and subsequent temperature retention at 80.degree. C. for 30
minutes.
2. (canceled)
3. The optical device surface-sealing composition according to
claim 1, wherein the component (A) is at least one resin selected
from the group consisting of an aliphatic epoxy resin, a thiol
epoxy resin, a butadiene epoxy resin, a polyol-modified epoxy
resin, an .epsilon.-caprolactone-modified epoxy resin, a
rubber-modified epoxy resin, a dimer acid-modified epoxy resin, a
urethane-modified epoxy resin, and an amine-modified epoxy
resin.
4. The optical device surface-sealing composition according to
claim 1, wherein the component (A) is an epoxy resin having a hard
segment including a fluorene structure or a bisphenol structure and
a soft segment including a structure derived from a compound
selected from the group consisting of C.sub.2-20 alkylene glycol,
polybutadiene, and a butadiene-acrylic copolymer or a C.sub.2-20
alkylene group.
5. The optical device surface-sealing composition according to
claim 1, wherein 10 to 70 parts by weight of the component (A) is
contained in 100 parts by weight of the entire composition.
6. An optical device surface-sealing composition comprising one or
more thermoplastic elastomers selected from the group consisting of
a polystyrene-based elastomer, a polyolefin-based elastomer, a
polyurethane-based elastomer, and a polyester-based elastomer, the
composition having a storage elastic modulus G' (80) of
1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa at 80.degree. C.
measured after temperature increase from 40.degree. C. to
80.degree. C. at 5.degree. C./min and subsequent temperature
retention at 80.degree. C. for 30 minutes.
7. The optical device surface-sealing composition according to
claim 1, wherein the composition is used for surface-sealing an
organic EL device.
8. An optical device surface-sealing sheet comprising a layer
formed of a composition according to claim 1.
9. The optical device surface-sealing sheet according to claim 8,
wherein the composition is used for surface-sealing an organic EL
device.
10. A display comprising, in order: a substrate (H); a
surface-sealing material having a storage elastic modulus G' (80)
of 1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa at 80.degree. C.;
and a substrate (L), wherein an optical device is disposed on the
substrate (H) or on the substrate (L), wherein a linear expansion
coefficient of the substrate (L) is smaller than a linear expansion
coefficient of the substrate (H), and a difference between the
linear expansion coefficient of the substrate (H) and the linear
expansion coefficient of the substrate (L) is 5.times.10.sup.-6
cm/cm/.degree. C. or more.
11. The display according to claim 10, wherein the linear expansion
coefficient of the substrate (H) is 20.times.10.sup.-6 to
200.times.10.sup.-6 cm/cm/.degree. C.
12. The display according to claim 10, wherein the substrate (H) is
a metal plate containing aluminum or a resin plate containing one
or more selected from the group consisting of an ester (co)polymer,
a cyclic olefin (co)polymer, a 4-methyl-1-pentene (co)polymer, an
acrylic (co)polymer, and polycarbonate.
13. The display according to claim 10, wherein the linear expansion
coefficient of the substrate (L) is 1.times.10.sup.-6 to
100.times.10.sup.-6 cm/cm/.degree. C.
14. The display according to claim 10, wherein the substrate (L) is
an inorganic substrate containing glass or silicon, or a resin
plate containing one or more selected from the group consisting of
an ester (co)polymer, polyimide, polycarbonate, and polyamide.
15. The display according to claim 10, wherein the optical device
is an organic EL device.
16. A method of manufacturing a display comprising: obtaining a
laminate having, in order, a first substrate on which an optical
device is disposed, a layer formed of an optical device
surface-sealing composition according to claim 1 laminated on the
optical device, and a second substrate; and heating the laminate at
50 to 110.degree. C.
17. The method according to claim 16, wherein a linear expansion
coefficient of the second substrate is smaller than a linear
expansion coefficient of the first substrate, and a difference
between the linear expansion coefficient of the one substrate and
the linear expansion coefficient of the other substrate is
5.times.10.sup.-6 cm/cm/.degree. C. or more.
18. The method according to claim 16, wherein the optical device is
an organic EL device.
19. The display according to claim 10, wherein the surface-sealing
material is a cured product of an optical device surface-sealing
composition comprising a flexible epoxy resin (A) having two or
more epoxy groups in a molecule, and a curing accelerator (B), the
composition having a storage elastic modulus G' (80) of
1.0.times.10.sup.3 to 2.0.times.10.sup.8 Pa at 80.degree. C.
measured after temperature increase from 40.degree. C. to
80.degree. C. at 5.degree. C./min and subsequent temperature
retention at 80.degree. C. for 30 minutes.
20. The display according to claim 10, wherein the surface-sealing
material is a thermocompressed material of an optical device
surface-sealing composition comprising one or more thermoplastic
elastomers selected from the group consisting of a
polystyrene-based elastomer, a polyolefin-based elastomer, a
polyurethane-based elastomer, and a polyester-based elastomer, the
composition having a storage elastic modulus G' (80) of
1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa at 80.degree. C.
measured after temperature increase from 40.degree. C. to
80.degree. C. at 5.degree. C./min and subsequent temperature
retention at 80.degree. C. for 30 minutes.
Description
TECHNICAL FIELD
[0001] The present invention relates to an optical device
surface-sealing composition, an optical device surface-sealing
sheet, a display, and a method of manufacturing a display.
BACKGROUND ART
[0002] Displays having optical devices, particularly organic EL
displays having organic EL devices have been expected as flat panel
displays because of their advantages such as wide view angle, fast
response speed, and low power consumption. Each organic EL device
that constitutes an organic EL display includes two electrodes (one
of which is transparent) and an organic light-emitting medium layer
disposed between the electrodes. Current is injected from both of
the electrodes so that the organic light-emitting medium layer
emits light.
[0003] Since optical devices, particularly the organic
light-emitting medium layer of the organic EL devices, are degraded
by moisture or the like, a method for surface-sealing an organic EL
device has been investigated to prevent the moisture or the like
from coming in contact with the organic EL device (PTL 1). In other
words, an organic EL display has been investigated that includes a
pair of substrates and a surface-sealing material disposed between
the substrates for surface-sealing the organic EL device. A member
for surface-sealing an organic EL device (surface-sealing material)
may be in general a cured product of a composition including a
thermosetting resin such as epoxy resin curable under conditions
which hardly cause deterioration of an organic EL device.
[0004] The total thickness of an organic EL device (total thickness
of the two electrodes and the organic light-emitting medium layer
disposed between the electrodes) is particularly small: about
several hundred nanometers thick. As a result, the thickness of an
organic EL display is determined substantially by the sum of the
thickness of the substrates and the thickness of the
surface-sealing material for surface-sealing an organic EL device.
An organic EL device is expected for use in a compact and thin
display or a backlight member for a cell-phone or the like which is
expected to be thinner or more lightweight, and a flexible display
or the like having a substrate of flexible plastic.
[0005] A problem of a thinned substrate for thinning a display,
however, is that warpage occurs in the display due to, for example,
the heat imparted when surface-sealing an optical device,
particularly an organic EL device. In order to prevent the warpage
of a display, it has been proposed in the art to dispose a warpage
prevention layer or an anti-curl layer on the substrate of the
display with an adhesive layer interposed in between (refer to PTLs
2 and 3).
CITATION LIST
Patent Literature
[0006] PTL 1 [0007] Japanese Patent Application Laid-Open No.
2006-070221 [0008] PTL 2 [0009] Japanese Patent Application
Laid-Open No. 2003-317937 [0010] PTL 3 [0011] Japanese Patent
Application Laid-Open No. 2009-81123
SUMMARY OF INVENTION
Technical Problem
[0012] A display including optical devices, particularly an organic
EL display, includes a pair of substrates (e.g. a circuit substrate
and a display substrate) and a surface-sealing material disposed
between the substrates for surface-sealing the organic EL devices.
The difference in linear expansion coefficient between the circuit
substrate and the display substrate may be large in some cases.
When manufacturing such a display, the difference caused in
expansion and contraction between the substrates, for example,
during heat curing of a surface-sealing composition has in some
cases caused warpage or strain in the resultant display.
[0013] An object of the present invention is to provide an optical
device surface-sealing composition for manufacturing an organic EL
display having less warpage even with a large difference in linear
expansion coefficient between a pair of substrates (e.g. a circuit
substrate and a display substrate) for constituting a display using
an optical device, a display having little warpage, and a
manufacturing method thereof.
Solution to Problem
[0014] A first aspect of the present invention relates to optical
device surface-sealing compositions given below.
[0015] [1] An optical device surface-sealing composition having a
storage elastic modulus G' (80) of 1.0.times.10.sup.3 to
2.0.times.10.sup.6 Pa at 80.degree. C. measured after temperature
increase from 40.degree. C. to 80.degree. C. at 5.degree. C./min
and subsequent temperature retention at 80.degree. C. for 30
minutes.
[0016] [2] The optical device surface-sealing composition according
to [1], including a flexible epoxy resin (A) having two or more
epoxy groups in a molecule, and a curing accelerator (B).
[0017] [3] The optical device surface-sealing composition according
to [2], wherein the component (A) is at least one resin selected
from the group consisting of an aliphatic epoxy resin, a thiol
epoxy resin, a butadiene epoxy resin, a polyol-modified epoxy
resin, an .epsilon.-caprolactone-modified epoxy resin, a
rubber-modified epoxy resin, a dimer acid-modified epoxy resin, a
urethane modified epoxy resin, and an amine-modified epoxy
resin.
[0018] [4] The optical device surface-sealing composition according
to [2] or [3], wherein the component (A) is an epoxy resin having a
hard segment including a fluorene structure or a bisphenol
structure and a soft segment including a structure derived from a
compound selected from the group consisting of C.sub.2-20 alkylene
glycol, polybutadiene, and a butadiene-acrylic copolymer or a
C.sub.2-20 alkylene group.
[0019] [5] The optical device surface-sealing composition according
to any one of [2] to [4], wherein 10 to 70 parts by weight of the
component (A) is contained in 100 parts by weight of the entire
composition.
[0020] [6] The optical device surface-sealing composition according
to [1], including a thermoplastic elastomer.
[0021] [7] The optical device surface-sealing composition according
to any one of [1] to [6], wherein the composition is used for
surface-sealing an organic EL device.
[0022] [8] An optical device surface-sealing sheet including a
layer formed of the composition according to any one of [1] to
[6].
[0023] [9] The optical device surface-sealing sheet according to
[8], wherein the composition is used for surface-sealing an organic
EL device.
[0024] A second aspect of the present invention relates to displays
and methods of manufacturing a display given below.
[0025] [10] A display including, in order: [0026] a substrate (H);
[0027] a surface-sealing material having a storage elastic modulus
G' (80) of 1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa at
80.degree. C.; and [0028] a substrate (L), [0029] wherein an
optical device is disposed on the substrate (H) or on the substrate
(L), wherein [0030] a linear expansion coefficient of the substrate
(L) is smaller than a linear expansion coefficient of the substrate
(H), and a difference between the linear expansion coefficient of
the substrate (H) and the linear expansion coefficient of the
substrate (L) is 5.times.10.sup.-6 cm/cm/.degree. C. or more.
[0031] [11] The display according to [10], wherein the linear
expansion coefficient of the substrate (H) is 20.times.10.sup.-6 to
200.times.10.sup.-6 cm/cm/.degree. C.
[0032] [12] The display according to [10] or [11], wherein the
substrate (H) is a metal plate containing aluminum or a resin plate
containing one or more selected from the group consisting of an
ester (co)polymer, a cyclic olefin (co)polymer, a
4-methyl-1-pentene (co)polymer, an acrylic (co)polymer, and
polycarbonate.
[0033] [13] The display according to any one of [10] to [12],
wherein the linear expansion coefficient of the substrate (L) is
1.times.10.sup.-6 to 100.times.10.sup.-6 cm/cm/.degree. C.
[0034] [14] The display according to any one of [10] to [13],
wherein the substrate (L) is an inorganic substrate containing
glass or silicon, or a resin plate containing one or more selected
from the group consisting of an ester (co)polymer, polyimide,
polycarbonate, and polyamide.
[0035] [15] The display according to any one of [10] to [14],
wherein the optical device is an organic EL device.
[0036] [16] A method of manufacturing a display including:
obtaining a laminate having, in order, a first substrate on which
an optical device is disposed, a layer formed of the optical device
surface-sealing composition according to any one of [1] to [7]
laminated on the optical device, and a second substrate; and
heating the laminate at 50 to 110.degree. C.
[0037] [17] The method according to [16], wherein a linear
expansion coefficient of the second substrate is smaller than a
linear expansion coefficient of the first substrate, and a
difference between the linear expansion coefficient of the one
substrate and the linear expansion coefficient of the other
substrate is 5.times.10.sup.-6 cm/cm/.degree. C. or more.
[0038] [18] The manufacturing according to [16] or [17], wherein
the optical device is an organic EL device.
Advantageous Effects of Invention
[0039] The optical device surface-sealing composition of the
present invention can limit, even in the case of a display
including an optical device (e.g. an organic EL display including
an organic EL device) having a pair of substrates (e.g. a display
substrate and a circuit substrate) of which the difference in
linear expansion coefficient is equal to or above a certain value,
the occurrence of warpage of the display when sealing an optical
device such as an organic EL device by heating the composition.
BRIEF DESCRIPTION OF DRAWINGS
[0040] FIG. 1 is a cross-sectional diagram illustrating an optical
device surface-sealing composition according to an embodiment of
the present invention;
[0041] FIG. 2 is a cross-sectional diagram illustrating an organic
EL display according to an embodiment of the present invention;
[0042] FIG. 3A illustrates a laminate before heat curing during the
manufacturing process of an organic EL display;
[0043] FIG. 3B illustrates the state of a heat-cured layer formed
of a surface-sealing composition by heating the laminate in FIG.
3A; and
[0044] FIG. 3C illustrates the cooled state of a conventional
laminate heated in FIG. 3B.
DESCRIPTION OF EMBODIMENTS
1. Optical Device Surface-Sealing Composition
[0045] The optical device surface-sealing composition of the
present invention may be preferably a composition for
surface-sealing an organic EL device (organic EL device
surface-sealing composition). The optical device surface-sealing
composition of the present invention has a storage elastic modulus
G' (80) of 1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa at
80.degree. C. measured after temperature increase of the
composition from 40.degree. C. to 80.degree. C. at 5.degree. C./min
and subsequent temperature retention at 80.degree. C. for 30
minutes.
[0046] In Embodiment 1 of the present invention, the optical device
surface-sealing composition may contain a flexible epoxy resin (A)
and a curing accelerator (B) on an as-needed basis. The optical
device surface-sealing composition which contains the components
may further contain a high molecular weight epoxy resin (C), a low
molecular weight epoxy resin (D), a silane coupling agent having an
epoxy group or a functional group capable of reacting with an epoxy
group (E), a solvent (F), and other component(s) (G).
[0047] In Embodiment 2 of the present invention, the optical device
surface-sealing composition may contain a thermoplastic elastomer
on an as-needed basis. The optical device surface-sealing
composition according to Embodiment 2 which contains a
thermoplastic elastomer may contain no component other than the
thermoplastic elastomer, or may further contain any one or all of
the components (A) to (G) on an as-needed basis.
[0048] The shape of the optical device surface-sealing composition
of the present invention is not limited and may be in liquid form
or sheet form. The sheet-like optical device surface-sealing
composition of the present invention may be a laminate. The
laminate may be formed of a layer including the components (A) and
(B) and a layer not including the components (A) and (B). The
composition which contains a thermoplastic elastomer may be a
laminate formed of a layer of thermoplastic elastomer and a layer
which is disposed on one or both sides of the layer and contains an
epoxy resin and no thermoplastic elastomer.
[0049] The optical device surface-sealing composition of the
present invention has a storage elastic modulus G' (80) of
1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa at 80.degree. C.
measured after temperature increase from 40.degree. C. to
80.degree. C. at 5.degree. C./min and subsequent temperature
retention at 80.degree. C. for 30 minutes. In the case that a
display is manufactured using a pair of substrates (e.g. a circuit
substrate and a display substrate) having a difference equal to or
above a certain value in linear expansion coefficient and an
optical device surface-sealing composition having a storage elastic
modulus G' (80) that is larger than the upper limit of the
above-described range, the stress caused by the difference in the
expansion or contraction between the two substrates cannot be
relaxed with the cured product or the thermocompressed material of
the composition. Consequently, the display is likely to be
significantly warped. In contrast, an optical device
surface-sealing composition having a storage elastic modulus G'
(80) of smaller than the lower limit of the above-described range
has excessively high flowability. Consequently, the handling
ability in surface-sealing an optical device such as an organic EL
device is likely to be reduced. Furthermore, the sealing
performance of the surface-sealing material is reduced, with
difficulty in preventing infiltration by moisture or the like
causing possible degradation of an optical device such as an
organic EL device, in particular, resulting in possible reduction
in reliability of the display. In the case of an optical device
surface-sealing composition having thermosetting properties (e.g.
an optical device surface-sealing composition according to
Embodiment 1), the surface-sealing material means a cured product
of the composition. In the case of the composition having no
thermosetting properties (e.g. an optical device surface-sealing
composition according to Embodiment 2), the surface-sealing
material means the composition itself.
[0050] In the case of the optical device surface-sealing
composition of the present invention with thermosetting properties
including the component (A) and the like to be described later
(e.g. an optical device surface-sealing composition according to
Embodiment 1), the composition is heated from 40.degree. C. to
80.degree. C. at 5.degree. C./min and maintained at 80.degree. C.
for 30 minutes for heat curing to form into a cured product. In
other words, the phrase "the optical device surface-sealing
composition of the present invention has a storage elastic modulus
G' (80) of 1.0.times.10.sup.3 to 2.0.times.10.sup.6 at 80.degree.
C. measured after temperature increase from 40.degree. C. to
80.degree. C. at 5.degree. C./min and subsequent temperature
retention at 80.degree. C. for 30 minutes" means that, in the case
of the composition of the present invention being a thermosetting
composition, a cured product which is obtained by heating the
composition from 40.degree. C. to 80.degree. C. at 5.degree. C./min
and then maintained at 80.degree. C. for 30 minutes has a storage
elastic modulus of 1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa
measured at 80.degree. C.
[0051] On the other hand, in the case of the optical device
surface-sealing composition of the present invention which contains
a thermoplastic elastomer to be described later and no
thermosetting properties (e.g. an optical device surface-sealing
composition according to Embodiment 2), the composition heated from
40.degree. C. to 80.degree. C. at 5.degree. C./min and then
maintained at 80.degree. C. for 30 minutes results in no heat
curing. It means that the composition itself containing the
thermoplastic elastomer to be described later has a storage elastic
modulus of 1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa measured at
80.degree. C.
[0052] Examples of a method for obtaining a storage elastic modulus
G' (80) that falls within the above-described range at 80.degree.
C. include adjusting the type and the content (relative to all the
components of a composition) of the flexible epoxy resin (A) in an
optical device surface-sealing composition according to Embodiment
1. The increase in the ratio of the component (A) allows the
storage elastic modulus G' (80) to be reduced.
[0053] In an optical device surface-sealing composition according
to Embodiment 2, the storage elastic modulus G' (80) of the
composition of the present invention may be adjusted by selecting
the type of thermoplastic elastomer.
[0054] Optical Device Surface-Sealing Composition According to
Embodiment 1
[0055] The optical device surface-sealing composition according to
Embodiment 1 may contain a flexible epoxy resin (A) and a curing
accelerator (B).
[0056] (A) Flexible Epoxy Resin
[0057] The optical device surface-sealing composition of the
present invention may contain a flexible epoxy resin for adjustment
of the storage elastic modulus G' (80). The flexible epoxy resin is
an epoxy resin having both rubber elasticity and strength. The
flexible epoxy resin is preferably an epoxy resin having two or
more epoxy groups in a molecule, more preferably a two-functional
epoxy resin having two epoxy groups in a molecule. From the
viewpoint of manufacturing a display with little warpage, the
flexible epoxy resin is also preferably one that exhibits
flexibility in the temperature range within which the optical
device surface-sealing composition (also referred to as an organic
EL device surface-sealing composition when manufacturing an organic
EL display) is heated during the manufacturing process of a display
to be described later.
[0058] A flexible epoxy resin may be specifically defined as
follows.
[0059] 1) A varnish of a flexible epoxy resin composition is
prepared by mixing 70 parts by weight of a flexible epoxy resin, 30
parts by weight of acid anhydride (e.g. RIKACID MH700G (main
component: methylhexahydrophthalic anhydride, made by New Japan
Chemical Co., Ltd.)), 1 part by weight of a curing accelerator
(e.g. IBMI12 (1-isobutyl-2-methylimidazole, made by Mitsubishi
Chemical Corporation)), and 1 part by weight of a curing
accelerator (e.g. 2E4MZ (1-cyanoethyl-2-ethyl-4-methylimidazole,
made by Shikoku Chemicals Corporation)).
[0060] 2) Meanwhile, a laminate of a glass plate/a mold-releasing
film/a spacer (500-.mu.m thick)/a mold-releasing film/a glass plate
spacer is made. The center part of the laminate is hollowed out so
as to form a 1.5 cm by 1.5 cm square recess to fabricate an
instrument for curing.
[0061] 3) The recess of the instrument is filled with the varnish
and the thickness is adjusted to 500 .mu.m by the own weight of the
glass plate. The varnish is heated for curing at 80.degree. C. for
1 hour to 3 hours until stickiness to the mold-releasing films
disappears.
[0062] 4) The produced cured product of the flexible epoxy resin
composition is measured by the method described in "(3) storage
elastic modulus method" to be described later. An epoxy resin
having a storage elastic modulus G'E (80) in the range of
1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa measured at 80.degree.
C. by the method can be used as a "flexible epoxy resin."
[0063] The flexible epoxy resin of the present invention may be:
.alpha.) an epoxy resin such as an aliphatic epoxy resin, a
butadiene epoxy resin, and a thiol epoxy resin; or .beta.) a
modified epoxy resin such as a polyol-modified epoxy resin, an
.epsilon.-caprolactone-modified epoxy resin, a rubber-modified
epoxy resin, a dimer acid-modified epoxy resin, a urethane-modified
epoxy resin, and an amine-modified epoxy resin.
[0064] .alpha.) Epoxy Resin
[0065] The aliphatic epoxy resin is not specifically limited, and
examples include a two-functional epoxy resin which is commonly
manufactured and sold such as a diglycidyl ether including
1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl
ether, polypropylene glycol diglycidyl ether, and neopentyl glycol
diglycidyl ether. Examples of the thiol epoxy resin include a
dithioether-modified epoxy resin. Examples of the butadiene epoxy
resin include polybutadiene-modified epoxy resin.
[0066] .beta.) Modified Epoxy Resin
[0067] Preferably the modified epoxy resin is either a modified
epoxy resin produced from the reaction of bisphenol or
bisphenolfluorene with epichlorohydrin, or an epoxy resin produced
from the reaction of a modified bisphenol or bisphenolfluorene with
epichlorohydrin.
[0068] Examples of the polyol-modified epoxy resin include
bisphenol A bis(triethylene glycol glycidyl ether)ether and
bisphenol A bis(propylene glycol glycidyl ether)ether.
[0069] Examples of the .epsilon.-caprolactone-modified epoxy resin
include an .epsilon.-caprolactone modified two functional epoxy
resin such as an .epsilon.-caprolactone modified bisphenol A epoxy
resin and .epsilon.-caprolactone modified
(3,4-3',4'-epoxycyclohexyl)methylhexane carboxylate.
[0070] Examples of the rubber-modified epoxy resin include a
modified product obtained by carboxylation of a diglycidyl
etherified product of bisphenol A by epichlorohydrin with a
butadiene-acrylonitrile copolymer. Examples of the rubber-modified
epoxy resin commercially available include EPDX-MK SR35K and
EPDX-MK SR3542.
[0071] Examples of the dimer acid-modified epoxy resin include
YD-171 and YD-172 made by Nippon Steel & Sumikin Chemical Co.,
Ltd.
[0072] Examples of the urethane-modified epoxy resin include a
urethane cross-linked bisphenol epoxy resin having a structure for
cross-linking two or more molecules of bisphenol epoxy resin (e.g.
a bisphenol A epoxy resin, a bisphenol F epoxy resin, and a
bisphenol AD epoxy resin) with a urethane polymer. Examples of the
urethane-modified epoxy resin commercially available include
EPU-78-135 (urethane cross-linked bisphenol epoxy resin) made by
Adeka Corporation.
[0073] Among the foregoing, a polyol-modified epoxy resin and an
aliphatic epoxy resin are preferred in view of the rubber
elasticity and strength. The flexible epoxy resins may be used
singly or in combination.
[0074] In order to obtain a cured product having sufficient
moisture permeability and transparency with a storage elastic
modulus in the required range, the flexible epoxy resin preferably
has a hard segment including a fluorene structure or a bisphenol
structure and a soft segment including a structure derived from a
compound selected from the group consisting of a C.sub.2-20
(preferably C.sub.2-5)alkylene glycol, polybutadiene, and a
butadiene-acrylic copolymer, or a C.sub.2-20 (preferably
C.sub.2-5)alkylene group.
[0075] Examples of the C.sub.2-20 alkylene glycol include ethylene
glycol, propylene glycol, HO--(CH.sub.2CH.sub.2--O).sub.m--H (where
m represents an integer of 1 to 10) which includes an ethylene
glycol unit as a repeating unit, and
HO--(CH.sub.2CH(CH.sub.3)--O).sub.n--H (where n represents an
integer of 1 to 6) which includes a propylene glycol unit as a
repeating unit. Examples of the butadiene-acrylic copolymer include
an acrylonitrile-butadiene copolymer. Examples of the C.sub.2-20
alkylene group include a pentylene group.
[0076] The hard segment is a segment which includes a fluorene
structure or a bisphenol structure. The soft segment is a segment
which is present between two hard segments or between a hard
segment and an epoxy group in one molecule of the flexible epoxy
resin.
[0077] For example, in an epoxy resin represented by the following
formula, the hard segment may be a bisphenol structure
(--C.sub.6H.sub.4--C(CH.sub.3).sub.2--C.sub.6H.sub.4--), and the
soft segment may be (--OCH.sub.2CH(CH.sub.3)--O--).sub.nd1 or
(--OCH.sub.2CH(CH.sub.3)--O--).sub.nd2 sandwiched between a hard
segment and an epoxy group (where n.sub.d1 and n.sub.d2 each
independently represent an integer of 1 to 6).
##STR00001##
[0078] The content of the flexible epoxy resin (A) is preferably 10
to 70 parts by weight relative to 100 parts by weight of the entire
composition, more preferably 20 to 50 parts by weight. When the
content falls within the above-described range, it easily limits
the warpage of a display made using the composition of the present
invention. In the case that a high molecular weight epoxy resin (C)
to be described later is added to the composition of the present
invention so as to be formed into a sheet form, the sheet shape is
easily maintained. In the case that the sheet-like composition is
formed on a mold-releasing film, the sheet-like composition is
easily separated from the mold-releasing film while maintaining the
shape.
[0079] (B) Curing Accelerator
[0080] Preferably the optical device surface-sealing composition of
the present invention which includes the component (A) contains a
curing accelerator (B). The curing accelerator has a function of
initiating and accelerating curing of an epoxy resin.
[0081] Examples of the curing accelerator include imidazole
compounds and amine compounds. Examples of the imidazole compounds
include 2-ethyl-4-methylimidazole. Examples of the amine compounds
include tris-dimethylaminomethylphenol. The curing accelerator (B)
may be a Lewis base compound.
[0082] The curing accelerator has a molecular weight of, preferably
70 to 800, more preferably 80 to 500, and further more preferably
90 to 250. A curing accelerator (B) having a molecular weight less
than 70 results in high volatility, which may cause gas bubbles in
the optical device surface-sealing composition during thermal
compression of the optical device surface-sealing composition. In
contrast, a curing accelerator having a molecular weight more than
800 may reduce flowability of the optical device surface-sealing
composition during thermal compression of the optical device
surface-sealing composition, and may result in insufficient
curability in some cases due to reduction in diffusibility of the
curing accelerator in the optical device surface-sealing
composition.
[0083] In the case that the composition of the present invention
contains an epoxy resin, the content of the curing accelerator (B)
is preferably 0.01 to 10 parts by mass relative to the total 100
parts by mass of the epoxy resins contained.
[0084] (C) High Molecular Weight Epoxy Resin
[0085] The high molecular weight epoxy resin (C) of the present
invention is an epoxy resin other than the flexible epoxy resin
(A), which is added to the composition of the present invention
including the component (A) in some cases, so that the composition
can be formed into a sheet form.
[0086] The component (C) is an epoxy resin having a weight-average
molecular weight of 2.times.10.sup.3 to 1.times.10.sup.5,
preferably 3.times.10.sup.3 to 8.times.10.sup.4, more preferably
4.times.10.sup.3 to 6.times.10.sup.4. The weight-average molecular
weight may be measured under the following conditions by gel
permeation chromatography (GPC) with polystyrene as a standard
material.
[0087] Apparatus: GPC-101 made by SHODEX;
[0088] Developing solvent: tetrahydrofuran; and
[0089] Standard polystyrene: PS-1 made by Varian Inc. (molecular
weight: 580 to 7,500,000), and PS-2 made by Varian Inc. (molecular
weight: 580 to 377,400).
[0090] The component (C) blended in the composition allows the
shape stability to be improved when the composition of the present
invention is formed into a sheet form or the like. The epoxy resin
having the weight-average molecular weight allows for relatively
low temperature dependency of the storage elastic modulus.
Consequently, the blending of the high molecular weight epoxy resin
(C) having the weight-average molecular weight in a predetermined
amount or more produces a composition having small variation in
storage elastic module G' with temperature.
[0091] Preferably the high molecular weight epoxy resin has an
epoxy equivalent of 500 to 1.times.10.sup.4 g/eq in view of the
cros slink density of the cured product of the composition and the
like, more preferably 600 to 9,000 g/eq.
[0092] Preferred examples of the high molecular weight epoxy resin
(C) include a resin having a bisphenol skeleton in the main chain
because low moisture permeability and the like can be achieved,
more preferably a resin which contains bisphenol and
epichlorohydrin as monomer components, further more preferably an
oligomer thereof.
[0093] All of the monomer components of the high molecular weight
epoxy resin (C) may be bisphenol and epichlorohydrin.
Alternatively, some of the monomer components may be a compound
(comonomer component) other than bisphenol and epichlorohydrin.
Examples of the comonomer component include a divalent or
higher-valent polyalcohol (e.g. divalent phenol and glycol). With
some of the monomer components being a compound other than
bisphenol (comonomer component) and epichlorohydrin, it is possible
to control the molecular weight to a desired value.
[0094] Preferred examples of the high molecular weight epoxy resin
include a resin having a repeating structural unit represented by
the following general formula (1).
##STR00002##
[0095] In the general formula (1), X represents a single bond, a
methylene group, an isopropylidene group, --S--, or --SO.sub.2--.
In the general formula (1), the structural unit whose X is
methylene group is a structural unit of bisphenol F type, and the
structural unit whose X is isopropylidene group is a structural
unit of bisphenol A type. Further, n represents the repeating
number of the structural unit represented by the general formula
(1), being an integer of 2 or more.
[0096] In the general formula (1), P represents the substitution
number of a substituent R.sub.1, being an integer of 0 to 4. In
view of the heat resistance and the low moisture permeability, P is
preferably 0. R.sub.1 each independently represents a C.sub.1-5
alkyl group, preferably being a methyl group.
[0097] In the present invention, in particular, an oligomer which
includes the repeating structural unit of bisphenol F type whose X
is methylene group in the general formula (1) and the repeating
structural unit of bisphenol A type whose X is isopropylidene group
in the general formula (1) in a molecule is preferred. The oligomer
which contains the repeating structural unit of bisphenol A type
allows the high molecular weight epoxy resin composition to have a
high viscosity. On the other hand, the oligomer which contains the
repeating structural unit of bisphenol F type allows the steric
barrier to be reduced. Consequently a plurality of phenylene groups
is easily oriented, so that the moisture permeability of the cured
product of the optical device surface-sealing composition can be
reduced.
[0098] The ratio of the number (F) of repeating structural unit of
bisphenol F type in a molecule to the sum of the number (A) of
repeating structural unit of bisphenol A type and the number (F) of
repeating structural unit of bisphenol F type in a oligomer
molecule {(F/A+F).times.100} is preferably 50% or more, more
preferably 55% or more. Including the large amount of repeating
structural units of bisphenol F type allows the cured product of
the optical device surface-sealing composition to have sufficiently
low moisture permeability.
[0099] The content of the high molecular weight epoxy resin (C) is
preferably 100 to 2,000 parts by mass, more preferably 210 to 2,000
parts by mass, further more preferably 250 to 1,200 parts by mass
relative to the total 100 parts by mass of the curing accelerator
(B), the low molecular weight epoxy resin (D) to be described
later, the flexible epoxy resin (A), and the silane coupling agent
(E) to be described later. The content ratio of the high molecular
weight epoxy resin (C) in the above-described range allows the
sheet-like composition of the present invention to easily maintain
the sheet shape. An excessively high content ratio of the high
molecular weight epoxy resin (C) reduces the flowability of the
composition when sealing an optical device such as an organic EL
device, which may cause a gap between the composition and the
optical device such as an organic EL device.
[0100] For the optical device surface-sealing composition which
contains the low molecular weight epoxy resin (D) to be described
later and the flexible epoxy resin (A), the content of the high
molecular weight epoxy resin (C) is preferably 50 to 1,200 parts by
mass, more preferably 80 to 1,000 parts by mass relative to the
total 100 parts by mass of the low molecular weight epoxy resin (D)
and the flexible epoxy resin (A). The content ratio of the high
molecular weight epoxy resin (C) in the range relative to the total
of the low molecular weight epoxy resin (D) and the flexible epoxy
resin (A) improves the shape stability of the optical device
surface-sealing composition and produces a cured product having low
moisture permeability, without reduction in flowability in
surface-sealing an organic EL device. In processing into a sheet
form, the content ratio of the high molecular weight epoxy resin
(C) of 100 to 800 parts by mass relative to the total of the low
molecular weight epoxy resin (D) and the flexible epoxy resin (A)
allows the sheet shape to be easily maintained.
[0101] (D) Low Molecular Weight Epoxy Resin
[0102] The optical device surface-sealing composition of the
present invention may contain a low molecular weight epoxy resin
(D). The low molecular weight epoxy resin is an epoxy resin other
than the flexible epoxy resin (A), having a weight-average
molecular weight of 100 to 1,200, preferably 200 to 1,100. The
weight-average molecular weight is measured in the same way as
described above. The blending of the epoxy resin (C) having the
weight-average molecular weight in the above-described range in an
optical device surface-sealing composition allows the flowability
of the optical device surface-sealing composition to be increased
when sealing an optical device such as an organic EL device with
the optical device surface-sealing composition, resulting in
improved adhesion to the optical device such as an organic EL
device.
[0103] The low molecular weight epoxy resin (D) has an epoxy
equivalent of preferably 80 to 300 g/eq, more preferably 100 to 200
g/eq. Blending the low molecular weight epoxy resin having an epoxy
equivalent in the above-described range in an optical device
surface-sealing composition allows the amount of hydrogen bonds in
the optical device surface-sealing composition to be increased, so
that the storage elastic modulus at 80.degree. C. in a
predetermined range may be obtained.
[0104] The low molecular weight epoxy resin (D) is preferably a
phenol type epoxy resin, more preferably a divalent or
higher-valent phenol type epoxy resin, or an oligomer including a
phenol derivative and epichlorohydrin as monomer components.
[0105] Examples of the divalent or higher-valent phenol type epoxy
resin include a bisphenol epoxy compound, a phenol novolac type
epoxy compound, and a cresol novolac type epoxy compound. Examples
of the bisphenol epoxy compound include a compound represented by
the general formula (2). In the general formula (2), X, R.sub.1,
and P are the same as X, R.sub.1, and P in the general formula
(1).
##STR00003##
[0106] Examples of the phenol derivative of the oligomer including
a phenol derivative and epichlorohydrin as monomer components
include bisphenol, hydrogenated bisphenol, phenol novolac, and
cresol novolac.
[0107] Preferred examples of the low molecular weight epoxy resin
(D) include a bisphenol epoxy compound and an oligomer including
bisphenol and epichlorohydrin as monomer components, more
preferably an oligomer having a repeating number n of 2 to 4 in the
general formula (1). Such an oligomer has high compatibility with a
high molecular weight epoxy resin.
[0108] The repeating structural unit included in the low molecular
weight epoxy resin (D) may be the same as or different from the
repeating structural unit included in the high molecular weight
epoxy resin (C).
[0109] The content of the low molecular weight epoxy resin (D) is
preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by
mass, relative to the total 100 parts by mass of the high molecular
weight epoxy resin (C), the curing accelerator (B), and the silane
coupling agent (E) to be described later. The content of the low
molecular weight epoxy resin (D) in the above-described range
allows the optical device surface-sealing composition to have
sufficient flowability during sealing an optical device such as an
organic EL device with the composition, and enhances the
thermosetting properties in the case of an optical device
surface-sealing composition having thermosetting properties.
[0110] (E) Silane Coupling Agent Having Epoxy Group or Functional
Group Capable of Reacting with Epoxy Group
[0111] The optical device surface-sealing composition of the
present invention may contain a silane coupling agent having an
epoxy group 1), and a silane coupling agent having a functional
group 2) capable of reacting with an epoxy group. The reaction with
an epoxy group includes an addition reaction with the epoxy group.
In the case that an optical device surface-sealing composition
which contains a silane coupling agent is used, for example, as an
optical device surface-sealing sheet for an organic EL, the
adhesion to a substrate is enhanced. In the case that an epoxy
resin is present in an optical device surface-sealing composition,
the silane coupling agent having an epoxy group or a functional
group capable of reacting with an epoxy group reacts with the
resin. As a result, the silane coupling agent conveniently allows
no low molecular weight component to remain in the cured product of
the optical device surface-sealing composition.
[0112] The silane coupling agent having an epoxy group 1) is a
silane coupling agent including an epoxy group such as a glycidyl
group, and examples include .gamma.-glycidoxypropyltrimethoxysilane
and .beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.
[0113] Examples of the functional group 2) capable of reacting with
an epoxy group include an amino group such as a primary amino group
and a secondary amino group, a carboxyl group, and a group to be
converted into a functional group capable of reacting with an epoxy
group (e.g. methacryloyl group and isocyanate group). Examples of
the silane coupling agent having a functional group capable of
reacting with an epoxy group include
N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane,
N-2-(aminoethyl)-3-aminopropylmethyltrimethoxysilane,
N-2-(aminoethyl)-3-aminopropylmethyltriethoxysilane,
3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane,
3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine,
N-phenyl-3-aminopropyltrimethoxysilane or
3-(4-methylpiperazino)propyltrimethoxysilane, trimethoxysilyl
benzoate, .gamma.-methacryloxypropyltrimethoxysilane, and
.gamma.-isocyanato propyltriethoxysilane.
[0114] In combination with the silane coupling agent, an other
silane coupling agent may be used. Examples of the other silane
coupling agent include vinyltriacetoxysilane and
vinyltrimethoxysilane. Such silane coupling agents may be used
singly or in combination.
[0115] Preferably the silane coupling agent has a molecular weight
of 80 to 800. A silane coupling agent having a molecular weight
more than 800 may cause reduction in adhesion in some cases due to
insufficient flowability when sealing an optical device such as an
organic EL device with the optical device surface-sealing
composition.
[0116] The content of the silane coupling agent is preferably
0.0001 to 30 parts by mass, more preferably 0.0005 to 20 parts by
mass, furthermore preferably 0.0008 to 10 parts by mass, relative
to 100 parts by mass of the optical device surface-sealing
composition.
[0117] (F) Solvent
[0118] The optical device surface-sealing composition of the
present invention may contain a solvent from the perspective of
homogenous mixing of the components (A) to (E) and the like. The
solvent has a function for uniformly dispersing or dissolving a
high molecular weight epoxy resin, in particular. Examples of the
solvent may include various kinds of organic solvents including an
aromatic solvent such as toluene and xylene; a ketone-based solvent
such as acetone, methyl ethyl ketone, and methyl isobutyl ketone;
ethers such as ether, dibutyl ether, tetrahydrofuran, dioxane,
ethylene glycol monoalkyl ether, ethylene glycol dialkyl ether, and
propylene glycol dialkyl ether; an aprotic polar solvent such as
N-methylpyrrolidone, dimethyl imidazolidinone, and
dimethylformamide; and esters such as ethyl acetate and butyl
acetate. The ketone-based solvent (solvent having a keto group)
such as methyl ethyl ketone is more preferred particularly due to
the easy dissolution of a high molecular weight epoxy resin.
[0119] (G) Other Optional Components
[0120] The optical device surface-sealing composition of the
present invention may further contain optional components such as
other resin components, fillers, modifiers, and stabilizers in
amounts that do not impair the effect of the invention. Examples of
other resin components include polyamide, polyamideimide,
polyurethane, polybutadiene, polychloroprene, polyether, polyester,
styrene-butadiene-styrene block copolymer, petroleum resin, xylene
resin, ketone resin, cellulose resin, fluorine-based oligomer,
silicone-based oligomer, and polysulfide-based oligomer. One of
these may be contained alone or a plurality of these may be
contained in combination.
[0121] Examples of the fillers include glass beads, styrene-based
polymer particles, methacrylate-based polymer particles,
ethylene-based polymer particles, and propylene-based polymer
particles. A plurality of the fillers may be used in
combination.
[0122] Examples of the modifier include a polymerization initiating
aid, an antiaging agent, a leveling agent, a wettability improver,
a surfactant, and a plasticizer. A plurality of these may be used
in combination. Examples of the stabilizer include an ultraviolet
absorber, a preserving agent, and an antimicrobial agent. A
plurality of modifiers may be used in combination.
[0123] The optical device surface-sealing composition of the
present invention has a water content of preferably 0.1% or less,
more preferably 0.06% or less, in view of prevention of the effect
of moisture on a material to be sealed.
[0124] An Optical Device Surface-Sealing Composition According to
Embodiment 2
[0125] Examples of the thermoplastic elastomer which may be
contained in an optical device surface-sealing composition
according to Embodiment 2 of the present invention include a
polystyrene-based elastomer, a polyolefin-based elastomer, a
polyurethane-based elastomer, and a polyester-based elastomer.
Among them, a polystyrene-based elastomer and a polyolefin-based
elastomer are preferred in view of the easy adjustment of adhesion
and flexibility.
[0126] Examples of the polystyrene-based elastomer include a
styrene-isoprene-styrene block copolymer (SIS), a
styrene-ethylene/butylene-styrene block copolymer (SEBS), a
styrene-ethylene/propylene-styrene block copolymer (SEPS), and an
other styrene-diene-based block copolymer and a hydrogenated
product thereof (e.g. hydrogenated styrene-butadiene rubber
(HSBR)). Examples of the styrene-based elastomer include DYNARON
(registered trade mark) made by JSR Corporation.
[0127] Examples of the polyolefin-based elastomer include a block
copolymer composed of polyolefin blocks which exhibit crystalline
characteristics and monomer copolymer blocks which exhibit
non-crystalline characteristics. Specific examples thereof include
an olefin-ethylene-butylene-olefin copolymer, a
polypropylene-polyethylene oxide-polypropylene block copolymer, and
a polypropylene-polyolefin-polypropylene block copolymer. Examples
of the commercially available polyolefin-based elastomer include
NOTIO (registered trade mark) made by Mitsui Chemicals, Inc.
[0128] The content of the thermoplastic elastomer in the optical
device surface-sealing composition according to Embodiment 2 is
preferably 10 mass % or more, more preferably 30 mass % or more,
relative to the entire composition.
[0129] Curability of Optical Device Surface-Sealing Composition
[0130] In the case of an optical device surface-sealing composition
of the present invention having thermosetting properties (e.g. an
optical device surface-sealing composition according to Embodiment
1), the curing rate of the optical device surface-sealing
composition is preferably high to some extent, for increasing the
workability in bonding to a material to be thermocompressed. Curing
in a rapid manner means, for example, curing within 120 minutes
under heating conditions (80 to 100.degree. C.).
[0131] Whether or not the optical device surface-sealing
composition has been cured may be determined by confirming, with a
figer, whether or not the optical device surface-sealing
composition thermally cured on a hot plate has been gelated.
Alternatively, whether or not the optical device surface-sealing
composition has been cured may be determined from the conversion
ratio of epoxy groups. The conversion ratio of epoxy groups may be
obtained from the reduction rate of epoxy groups in the measurement
of IR spectra before and after the curing reaction of the optical
device surface-sealing composition. The curability of the optical
device surface-sealing composition is controlled by adjustment of
the content of a curing accelerator.
[0132] Method of Producing Optical Device Surface-Sealing
Composition
[0133] The optical device surface-sealing composition of the
present invention may be manufactured by any method as long as the
effect of the present invention is not impaired. For example, the
manufacturing method of a sheet formed of the optical device
surface-sealing composition according to Embodiment 1 may include:
step 1) of preparing components (A) to (E); step 2) of dissolving
the components (A) to (E) in component (F) and mixing at 30.degree.
C. or lower; step 3) of applying the mixture on a substrate into a
sheet form; and step 4) of drying the applied mixture in the sheet
form.
[0134] In step 2), the components (A) to (E) may be mixed at a
time, or the component (A) may be dissolved in the component (F)
and mixed and then the other components may be added and mixed.
Examples of the mixing method include stirring the components
placed in a flask, and kneading using a triple roll mill.
[0135] The mixture obtained in step 2) has a viscosity at
25.degree. C. of preferably 0.01 to 100 Pas. The viscosity of the
mixture in the above-described range allows for improved coating
properties and easy forming into a sheet. The viscosity is a
measured value at 25.degree. C. by an E-type viscometer (RC-500
made by Toki Sangyo Co., Ltd.). The viscosity of the mixture may be
adjusted for example by the amount of the component (E).
[0136] The application method in step 3) is not specifically
limited, and examples include screen printing, dispensing, and a
method using various types of coating rolls. The type of substrate
film for use is not specifically limited, and examples include a
known mold-releasing film. The coating thickness of the mixture is
properly selected depending on the film thickness of the intended
optical device surface-sealing composition, and may be set such
that the optical device surface-sealing composition has a film
thickness of, for example, 1 to 100 .mu.m after drying.
[0137] The drying temperature and the drying time in step 4) may be
set such that the solvent (F) is removed by drying to a desired
level or less without curing of the high molecular weight epoxy
resin (C) and the low molecular weight epoxy resin (D) contained in
the optical device surface-sealing composition. The drying
temperature is, for example, 20 to 70.degree. C., and the drying
time is, for example, about 10 minutes to about 3 hours. More
specifically, it is preferred that the coating film be dried at 30
to 60.degree. C. under inert gas atmosphere such as nitrogen
atmosphere for about 10 minutes and then further dried by vacuum
for about 2 hours. The additional vacuum drying allows the solvent
and moisture included in the sheet to be removed at a relatively
low drying temperature. The drying method is not specifically
limited, and examples include hot-air drying and vacuum drying.
[0138] The sheet formed of the optical device surface-sealing
composition according to Embodiment 2 of the present invention may
be obtained from a composition which contains a predetermined
thermoplastic elastomer by a commonly used method (e.g. melt
extrusion method).
[0139] 2. Sealing Sheet
[0140] The sheet which includes the optical device surface-sealing
composition of the present invention is referred to as a sealing
sheet. The sealing sheet of the present invention includes a
substrate film, a layer formed of the optical device
surface-sealing composition formed on the substrate film, and an
optional protective film formed on the layer formed of the optical
device surface-sealing composition. In a preferred embodiment, a
thermosetting resin layer of epoxy resin or the like is further
disposed on the surface of the layer formed of optical device
surface-sealing composition of the present invention so as to
improve the adhesion force between a substrate (H) and a substrate
(L) to be described later. In other words, in a preferred
embodiment, a thermosetting resin layer/a layer formed of the
optical device surface-sealing composition of the present
invention/a thermosetting resin layer may be disposed between the
substrate film and the protective film.
[0141] The layer formed of the optical device surface-sealing
composition of the present invention has a water content of
preferably 0.1% or less, more preferably 0.06% or less, in view of
limiting the effect of the moisture on the material to be sealed.
In particular, an optical device such as an organic EL device is
easily deteriorated by the moisture. In the case that an optical
device such as an organic EL device is sealed with the composition
of the present invention, it is therefore preferred that the water
content be reduced as much as possible. The water content of the
optical device surface-sealing composition can be reduced, for
example, by heat drying the optical device surface-sealing
composition under vacuum.
[0142] The water content of the optical device surface-sealing
composition of the present invention may be obtained by, for
example, weighing about 0.1 g of sample piece of the sheet, heating
the sample piece to 150.degree. C. with a Karl Fischer moisture
meter, and measuring the water content generated on the occasion
(sublimation method).
[0143] The thickness of the layer formed of the optical device
surface-sealing composition of the present invention is, for
example, 1 to 100 .mu.m, preferably 10 to 30 .mu.m, more preferably
20 to 30 .mu.m, depending on the type of material to be sealed.
[0144] Preferably the layer formed of the optical device
surface-sealing composition of the present invention has proper
flowability at the temperature for surface-sealing an optical
device such as an organic EL device. The reason for this is that
when sealing the optical device such as an organic EL device,
irregularities on the device surface are smoothed out by the sheet
which has been thermally made flowable so as to fill the recesses
of the irregularities. The flowability during thermocompression may
be determined from the melting point. The melting point is a
temperature at which flowability is exhibited when the layer formed
of the optical device surface-sealing composition is heated, which
is preferably 30 to 100.degree. C. In the case that the optical
device surface-sealing composition of the present invention
contains the solvent (E), the melting point is for the dried
material after drying the composition for substantially removing
the solvent (E).
[0145] The melting point is obtained by finding the setting
temperature for initiation of melting of the sheet (thickness: 100
.mu.m) pressed against a glass plate on a hot plate. With a melting
point lower than 30.degree. C., the layer formed of the optical
device surface-sealing composition easily causes sagging due to the
excessively large flowability in thermal transferring
(thermocompression) or when sealing by heat curing, resulting in
difficulty in control of the film thickness of the cured product.
In contrast, with a melting point higher than 100.degree. C., a gap
is likely to be easily formed between the layer formed of the
optical device surface-sealing composition and an optical device
such as an organic EL device due to worsened workability during
thermal transferring, and adversely affects the optical device such
as an organic EL device due to heating.
[0146] The layer formed of the optical device surface-sealing
composition of the present invention has proper flowability when
laminated with an optical device such as an organic EL device for
thermocompression. Consequently formation of a gap between the
layer formed of the optical device surface-sealing composition of
the present invention and an optical device such as an organic EL
device is limited, resulting in excellent adhesion.
[0147] As described above, the sealing sheet of the present
invention may include a layer formed of the optical device
surface-sealing composition of the present invention, a substrate
film, and a protective film. Examples of the substrate film and the
protective film include known mold-releasing films, preferably
films having moisture barrier properties or gas barrier properties,
more preferably polyethylene terephthalate films. The thickness of
the substrate film or the protective film is, for example, about 50
.mu.m in view of having followability to a material to be sealed
such as an organic EL device, depending on a film material.
[0148] The sealing sheet of the present invention may further have
a gas barrier layer on an as-needed basis. The gas barrier layer
may limit permeation of moisture and gas such as moisture in
ambient air which degrades the optical device such as an organic EL
device in the display. The gas barrier layer may be disposed at any
location other than the surface in contact with an optical device
such as an organic EL device, preferably disposed between the
substrate film and the layer formed of the optical device
surface-sealing composition of the present invention.
[0149] The material for constituting the gas barrier layer is not
specifically limited, and examples include Al, Cr, Ni, Cu, Zn, Si,
Fe, Ti, Ag, Au, and Co; oxides of these metals; nitrides of these
metals; and oxynitrides of these metals. These materials may be
used singly or in combination. The gas barrier layer of a sealing
sheet used when sealing a bottom emission organic EL device is
preferably formed of a material having high light reflectivity such
as Al and Cu. The gas barrier layer of a sealing sheet used when
sealing a top emission organic EL device is preferably formed of a
material having high light transmission such as polyethylene
terephthalate (PET), polycarbonate (PC), and cyclic polyolefin
(COP). The thickness of the gas barrier layer may be about 100
.mu.m to about 3,000 .mu.m.
[0150] The sealing sheet having a gas barrier layer may be
manufactured by forming a gas barrier layer on a substrate film and
then forming the layer of the optical device surface-sealing
composition of the present invention. The forming method of the gas
barrier layer is not specifically limited, including as dry process
various PVD methods such as vacuum deposition, sputtering, and ion
plating and CVD methods such as plasma CVD, and as wet process
plating and coating.
[0151] Preferably a protective film is further laminated on the
layer formed of the optical device surface-sealing composition.
Preferably the lamination is performed at about 60.degree. C.,
using, for example, a laminator. The thickness of the protective
film is, for example, about 20 .mu.m.
[0152] FIG. 1 illustrates a preferred example of the sealing sheet.
As shown in FIG. 1 sealing sheet 10 includes substrate film 12,
layer 16 formed of the optical device surface-sealing composition
formed on substrate film 12, and protective film 18 disposed on
layer 16 formed of the optical device surface-sealing
composition.
[0153] Sealing sheet 10 may be used, for example, as an organic EL
device surface-sealing sheet by peeling protective film 18 and then
disposing exposed layer 16 formed of the optical device
surface-sealing composition in contact with a display substrate on
which an organic EL device is disposed.
[0154] Preferably the sealing sheet of the present invention is
stored together with a drying agent such as silica gel, so that the
water content is maintained at a certain level or less.
[0155] 3. Application of Optical Device Surface-Sealing
Composition
[0156] The optical device surface-sealing composition and sealing
sheet of the present invention are cured for use as a
surface-sealing material, in the case of the optical device
surface-sealing composition having thermosetting properties. In
contrast, in the case of the optical device surface-sealing
composition having no thermosetting properties, the composition
itself may be used as a surface-sealing material. The object to be
sealed (also referred to as a material to be sealed) is not
specifically limited, preferably including, for example, an optical
device. Examples of the optical device include an organic EL
device, a liquid crystal, and an LED, preferably an organic EL
device.
[0157] Preferably the optical device surface-sealing composition
and sealing sheet of the present invention are used as a
surface-sealing material for a display using an optical device
(organic EL display, in particular), i.e. as an organic EL device
surface-sealing composition or an organic EL device surface-sealing
sheet. In view of the coupling-out efficiency of a top emission
organic EL display, transparency is required for the
surface-sealing material. Since an organic EL device is easily
deteriorated by moisture, low moisture permeability in particular
is required for the surface-sealing material.
[0158] The cured product of the optical device surface-sealing
composition of the present invention has a moisture permeability of
preferably 60 (g/m.sup.224 h) or less, more preferably 30
(g/m.sup.224 h) or less. The moisture permeability is obtained by
measuring a 100-.mu.m cured product of the optical device
surface-sealing composition under conditions of 60.degree. C./90%
RH according to JIS Z0208.
[0159] The adhesion force between the cured product of the optical
device surface-sealing composition of the present invention and a
material to be sealed is preferably 100 gf/15 mm or more.
[0160] The adhesion force between the cured product and the
material to be sealed is measured by the following method. On the
aluminum foil-side of a lamination film of an aluminum foil and PET
(product name: AL-PET), the optical device surface-sealing
composition is applied and dried to form a thickness of about 15
.mu.m. The surface of the optical device surface-sealing
composition is thermocompressed onto a glass substrate (glass plate
according to JIS R3202, 100 mm by 25 mm by 2 mm) with a roll
laminator (MRK-650Y type, made by MCK Co., Ltd.) under conditions
with a velocity of 0.3 m/min, an air cylinder pressure of 0.2 MPa,
a roller temperature of 90.degree. C., and top and bottom heating.
The laminate is heated at 80.degree. C. for 30 minutes in an oven,
so that the optical device surface-sealing composition is cured.
The laminate is then cut into a width of 15 mm, and the 90-degree
peeling strength of the bond between the glass substrate and the
optical device surface-sealing composition is measured with a
peeling testing machine (apparatus name: STOROGRAPH E-S, range: 50
mm/min). The 90-degree peeling strength is regarded as the adhesion
force in the present invention.
[0161] Preferably the cured product of the optical device
surface-sealing composition of the present invention has a Tg of
40.degree. C. or higher in view of maintaining the adhesion force.
An excessively low Tg allows the adhesion force with a substrate to
be reduced, which may decrease the water vapor barrier properties.
Tg of the cured product is obtained from the inflexion point in
measurement of the linear expansion coefficient with a TMA
(TMA/SS6000 made by Seiko Instruments Inc.) under conditions with a
rate of temperature increase of 5.degree. C./min.
[0162] The optical device surface-sealing composition of the
present invention has a solvent content of preferably 50,000 ppm by
mass or less, more preferably 30,000 ppm by mass or less relative
to the total composition components. A large content of the solvent
in the optical device surface-sealing composition may have an
effect on a material to be sealed. The amount of the solvent in the
optical device surface-sealing composition may be measured with,
for example, an IR absorption spectrometer (FT/IR-4100 made by
JASCO Corporation). The method for measuring the amount of solvent
will be described below for the composition containing methyl ethyl
ketone (MEK) as a solvent.
[0163] A reference sample (optical device surface-sealing
composition) the amount of the solvent of which is quantitatively
determined by gas chromatography/mass spectrometry (GC-MS) in
advance is prepared. The IR absorption spectrum of the reference
sample is measured. The intensity ratio of the absorption peak of
C.dbd.O of MEK (about 1,710 cm.sup.-1) to the absorption peak of
C.dbd.C of epoxy resin (about 1,609 cm.sup.-1) is calculated from
the IR absorption spectrum of the reference sample. Subsequently,
the IR absorption spectrum of the measurement sample (optical
device surface-sealing composition) is measured, and the intensity
ratio of the absorption peak of C.dbd.O of MEK (about 1,710
cm.sup.-1) to the absorption peak of C.dbd.C of epoxy resin (about
1,609 cm.sup.-1) is calculated. The proportion of the peak
intensity ratio of the measurement sample relative to the peak
intensity ratio of the reference sample is obtained, so that the
amount of solvent contained in the measurement sample is
calculated.
[0164] 4. Display
[0165] A display includes: a substrate on which an optical device
such as an organic EL device is disposed (display substrate); a
counter substrate to make a pair with the display substrate; and a
surface-sealing material which is disposed between the display
substrate and the counter substrate for sealing the optical device
such as an organic EL device. As described above, a display that
includes a surface-sealing material filling a part of space formed
between the optical device such as an organic EL device and a
sealing substrate is called a surface-sealing type display
[0166] By way of example, use of the optical device surface-sealing
composition of the present invention for sealing an organic EL
device in an organic EL display will be described below. However,
the display of the present invention is not limited to an organic
EL display. Use of the optical device surface-sealing composition
of the present invention for sealing an organic EL device in a top
emission structure is also described, but the display of the
present invention is not limited to a top emission structure.
Examples of the display in the present invention include not only
an output apparatus of a computer or the like but also an
illumination apparatus such as a lighting apparatus.
[0167] FIG. 2 is a schematic cross-sectional diagram, illustrating
a surface-sealing type organic EL display having a top emission
structure. As shown in FIG. 2, organic EL display 20 includes
display substrate 22, organic EL device 24, counter substrate
(transparent substrate) 26, which are laminated in the order
presented. Surface-sealing material 28 is filled between the
periphery of organic EL device 24 and counter substrate
(transparent substrate) 26. In the organic EL display of the
present invention, surface-sealing material 28 in FIG. 2 can be the
cured product or thermocompressed material of the optical device
surface-sealing composition of the present invention.
[0168] Organic EL device 24 includes cathode reflecting electrode
layer 30 (formed of aluminum, silver, or the like), organic EL
layer 32, and anode transparent electrode layer 34 (formed of ITO,
IZO, or the like), which are laminated in the order presented from
the display substrate 22 side. Cathode reflecting electrode layer
30, organic EL layer 32, and anode transparent electrode layer 34
may be formed as a film by vacuum vapor deposition, sputtering, or
the like.
[0169] The substrate for use in an organic EL display is described
in the following. A substrate (H) and a substrate (L) to be
described later may be the display substrate and the counter
substrate, respectively. Both of the substrates are used as the
substrates of the organic EL display of the present invention. More
specifically, a combination of the substrate (H) as display
substrate and the substrate (L) as counter substrate, or a
combination of the substrate (H) as counter substrate and the
substrate (L) as display substrate constitutes the organic EL
display of the present invention.
[0170] Substrate (H)
[0171] The substrate (H) is a member with a surface on which an
organic EL device may be disposed. The substrate (H) may be
transparent or non-transparent. In the case that light is extracted
from an organic light-emitting layer through the substrate (H), the
substrate (H) is transparent.
[0172] The substrate (H) has a linear expansion coefficient larger
than that of the substrate (L). More specifically the coefficient
may be larger than the linear expansion coefficient of the
substrate (L) by 5.times.10.sup.-6 cm/cm/.degree. C. or more.
[0173] The linear expansion coefficient of the substrate (H) may be
20.times.10.sup.-6 cm/cm/.degree. C. to 200.times.10.sup.-6
cm/cm/.degree. C., preferably 20.times.10.sup.-6 cm/cm/.degree. C.
to 180.times.10.sup.-6 cm/cm/.degree. C. The linear expansion
coefficient of the substrate (H) may be measured, for example, by
TMA method, based on ASTM E-831. The linear expansion coefficient
of the substrate (H) is the average of linear expansion
coefficients in the range of 25 to 100.degree. C.
[0174] The thickness of the substrate (H) is preferably 5 to 300
.mu.m. The modulus of elongation of the substrate (H) is preferably
10 to 500 MPa.
[0175] The material of the substrate (H) is not specifically
limited, preferably is a metal including aluminum (preferably
aluminum) or a resin. Examples of the preferred resin include one
or more polymers selected from the group consisting of an ester
(co)polymer, a cyclic olefin (co)polymer, a 4-methyl-1-pentene
(co)polymer, an acrylic (co)polymer, and polycarbonate.
[0176] A "(co)polymer" as used herein encompasses both homopolymer
and copolymer. More specifically, 4-methyl-1-pentene (co)polymer
encompasses poly4-methyl-1-pentene, a homopolymer of
4-methyl-1-pentene, and a copolymer of 4-methyl-1-pentene and a
compound copolymerizable with 4-methyl-1-pentene, such as an
.alpha.-olefin. A cyclic olefin (co)polymer encompasses both a
polymer (homopolymer) of a cyclic olefin and a copolymer of a
cyclic olefin and a polymerizable compound copolymerizable with the
cyclic olefin.
[0177] In order to improve the water vapor barrier properties and
the adhesion force of the substrate (H), a film formed of an
inorganic material such as SiO.sub.2 may be laminated on the
substrate (H).
[0178] Substrate (L)
[0179] In an organic EL display, the substrate (L) is laminated on
the surface-sealing material. The substrate (L) has a linear
expansion coefficient lower than that of the substrate (H). More
specifically the coefficient may be lower than the linear expansion
coefficient of the substrate (H) by 5.times.10.sup.-6
cm/cm/.degree. C. or more. The linear expansion coefficient of the
substrate (L) may be preferably in the range of 1.times.10.sup.-6
cm/cm/.degree. C. to 100.times.10.sup.-6 cm/cm/.degree. C., more
preferably in the range of 5.times.10.sup.-6 cm/cm/.degree. C. to
10.times.10.sup.-6 cm/cm/.degree. C.
[0180] The material of the substrate (L) is not specifically
limited, including inorganic materials such as glass and silicon
and resins such as an ester copolymer (PET, PEN, PBT, or the like),
polyimide, polycarbonate, and polyamide. The inorganic material
such as glass and silicon is preferred.
[0181] The thickness of the substrate (L) is preferably 0.1 to 1
mm, in view of thinning and durability of an organic EL
display.
[0182] 5. Method of Manufacturing Display
[0183] A display having a surface-sealing material formed of the
cured product of the optical device surface-sealing composition of
the present invention (also referred to as an organic EL device
surface-sealing composition for use in an organic EL device) or
formed of the composition itself may be manufactured by any method.
The display having an optical device may be manufactured by a
method including at least step 1) of obtaining a laminate having a
substrate on which an optical device such as an organic EL device
is disposed, a layer formed of the optical device surface-sealing
composition of the present invention which is laminated on the
optical device, and another substrate in the order presented, and
step 2) of heating the laminate at, for example, 50 to 110.degree.
C.
[0184] In the manufacturing method of the display of the present
invention, the form of the optical device surface-sealing
composition of the present invention is not specifically limited,
which may be in a liquid form or in a sheet form. The optical
device surface-sealing composition of the present invention may or
may not have thermosetting properties.
[0185] The method for manufacturing an organic EL display using the
optical device surface-sealing composition of the present invention
having thermosetting properties will be described in the
following.
[0186] More specifically, the manufacturing method includes: step
1) of obtaining a laminate of display substrate 22 on which organic
EL device 24 as an optical device is disposed, an optical device
surface-sealing composition of the present invention, and counter
substrate (transparent substrate) 26; step 2A) of thermocompressing
the optical device surface-sealing composition in a sheet form of
the obtained laminate; and step 2B) of curing the thermocompressed
optical device surface-sealing composition in a sheet form. Step
2A) and step 2B) may be performed in one step at a time on an
as-needed basis. Each of the steps is performed according to a
known method.
[0187] In step 1), a laminate may be obtained by placing (or
transferring) the sheet-like optical device surface-sealing
composition on display substrate 22 on which organic EL device 24
is disposed and then laminating counter substrate (transparent
substrate) 26 to make a pair on the composition (method (i)).
[0188] On this occasion, in the case of the sealing sheet of the
present invention having a protective film, the protective film may
be peeled to expose the layer formed of the optical device
surface-sealing composition, which is then placed on organic EL
device 24 to peel the substrate film for transfer. Alternatively,
the sheet-like optical device surface-sealing composition having no
protective film may be directly placed on organic EL device 24 with
a roll laminator or the like.
[0189] Alternatively, counter substrate 26 on which a layer formed
of the optical device surface-sealing composition of the present
invention is disposed in advance may be prepared, which is then
laminated on display substrate 22 on which organic EL device 24 is
formed so as to form a laminate (method (ii)). This method is
effective, for example, when the optical device surface-sealing
composition is directly incorporated in an organic EL display
without peeling of the substrate film.
[0190] In step 2A), the sheet-like optical device surface-sealing
composition is thermocompressed, for example, at 50 to 110.degree.
C. with a vacuum laminator apparatus, so that thermocompression of
the sheet-like optical device surface-sealing composition and
organic EL device 24 and thermocompression of the sheet-like
optical device surface-sealing composition and display substrate 22
or counter substrate 26 are performed. On this occasion, preferably
the organic EL device-side is heated to 50 to 110.degree. C. in
advance for lamination of organic EL device 24 and the optical
device surface-sealing composition.
[0191] In step 2B), the sheet-like optical device surface-sealing
composition is thoroughly cured, for example, at 80 to 100.degree.
C. in many cases. Preferably the heat curing is performed at 80 to
100.degree. C. for 0.1 to 2 hours. The temperature for heat curing
is set at 110.degree. C. or lower, so that no damage is imparted to
organic EL device 24.
[0192] Limitation of Warpage of Display of Present Invention
[0193] Even though the display of the present invention has a large
difference in linear expansion coefficient between the substrate
(H) and the substrate (L), the warpage of the display to be caused
by formation of the surface-sealing material by heat curing of a
surface-sealing composition having thermosetting properties or by
thermocompressing a surface-sealing composition having no
thermosetting properties can be limited.
[0194] The mechanism by which warpage is limited will now be
described with reference to FIGS. 3A to 3C. FIG. 3A illustrates a
laminate having a substrate (H), a layer 302 formed of a
surface-sealing composition having thermosetting properties, and a
substrate (L) before heat curing in the manufacturing process of a
display. In FIGS. 3A to 3C, an optical device such as an organic EL
device is omitted.
[0195] FIG. 3A illustrates a laminate having a substrate (H), a
layer 302 formed of a surface-sealing composition, and a substrate
(L) as described above. The thickness of the layer 302 formed of a
surface-sealing composition is represented by D1. The width of the
laminate is represented by L1.
[0196] FIG. 3B illustrates the state of cured layer 302 formed of a
surface-sealing composition by heating the laminate shown in FIG.
3A. Since the substrate (H) has a large expansion coefficient, the
substrate (H) expands to have a width of L2 during heating. On the
other hand, since the substrate (L) has a low expansion
coefficient, the substrate (L) hardly expands during heating, so
that the width L1' is not much changed from L1. The thickness of
cured product 306 of the surface-sealing composition becomes D2
(D2<D1), and the length of the side of cured product 306 of the
surface-sealing composition becomes D3 (D1<D3).
[0197] FIG. 3C illustrates the cooled state of a conventional
laminate heated in FIG. 3B. Since the cured product 306 of a
conventional surface-sealing composition usually has a high storage
elastic modulus at the temperature for surface-sealing, it attempts
to maintain its shape. Consequently a recess is formed in the
center part of the substrate (H), so that warpage occurs in the
laminate. Warpage thus occurred in a conventional display,
particularly in an organic EL display, in some cases.
[0198] In the present invention, an optical device surface-sealing
composition having a storage elastic modulus G' (80) of
1.0.times.10.sup.3 to 2.0.times.10.sup.6 Pa at 80.degree. C.
measured after temperature increase from 40.degree. C. to
80.degree. C. at 5.degree. C./min and subsequent temperature
retention at 80.degree. C. for 30 minutes is used. The cured
product of the surface-sealing composition of the present invention
thus has a reduced storage elastic modulus at the temperature for
surface-sealing. In other words, a certain degree of flexibility
can be imparted to the cured product of the composition
(surface-sealing material) at the temperature for surface-sealing
an organic EL device, so that the stress caused between the
substrate (H) having a large linear expansion coefficient and the
substrate (L) having a small linier expansion coefficient can be
appropriately relaxed. The display to be obtained thus can prevent
from being warped due to the mechanism described above.
EXAMPLES
[0199] The present invention is further described with reference to
Examples and Comparative Examples, which however shall not be
construed as limiting the scope of the present invention.
[0200] 1. Material of Surface-Sealing Composition
[0201] Firstly, the components used in Examples and Comparative
Examples are described. The weight-average molecular weight of the
component (A) is a measured value measured by the method described
above. Although a sheet-like optical device surface-sealing
composition is used in Examples, the composition of the present
invention may be in a liquid form, not limited to a sheet form.
[0202] The storage elastic modulus G'E (80) of the raw material
epoxy resin is the storage elastic modulus G'E (80) of a cured
product made by the following method measured by the method
described in (3) Storage elastic modulus to be described later.
[0203] (Method for Measuring the Storage Elastic Modulus G'E
(80))
[0204] 1) As raw materials, 70 parts by weight of epoxy resin, 30
parts by weight of acid anhydride (e.g. RIKACID MH700G (main
component: methylhexahydrophthalic anhydride, made by New Japan
Chemical Co., Ltd.)), 1 part by weight of a curing accelerator
(e.g. IBMI12 (1-isobutyl-2-methylimidazole, made by Mitsubishi
Chemical Corporation)), and 1 part by weight of a curing
accelerator (e.g. 2E4MZ (1-cyanoethyl-2-ethyl-4-methylimidazole),
made by Shikoku Chemicals Corporation) were mixed to prepare a
varnish.
[0205] 2) Meanwhile, a laminate of a glass plate/a mold-releasing
film/a spacer (500-.mu.m thick)/a mold-releasing film/a glass plate
spacer was made. The center part of the laminate was hollowed out
so as to form a 1.5 cm by 1.5 cm square recess for use as a curing
instrument.
[0206] 3) The recess of the obtained instrument was filled with the
varnish prepared in the 1) and the thickness of the varnish was
adjusted to 500 .mu.m by the own weight of the glass plate. The
instrument filled with the varnish was heated at 80.degree. C. for
1 hour to 3 hours until stickiness to the mold-releasing film
disappeared, so that the varnish was cured.
[0207] 4) The storage elastic modulus G'E (80) at 80.degree. C. of
the produced cured product of flexible epoxy resin composition was
measured by the "(3) storage elastic modulus method" to be
described later.
[0208] (A) Flexible Epoxy Resin
[0209] EG-250 (made by Osaka Gas Chemicals Co., Ltd.): epoxy
equivalent of 417 g/eq, viscosity of 36,500 mPas, storage elastic
modulus G'E (80) of 3.4.times.10.sup.5 Pa, fluorene
skeleton-containing epoxy resin;
[0210] EG-280 (made by Osaka Gas Chemicals Co., Ltd.): epoxy
equivalent of 467 g/eq, viscosity of 7,440 mPas, storage elastic
modulus G'E (80) of 1.2.times.10.sup.5 Pa, fluorene
skeleton-containing epoxy resin;
[0211] BPO-20E (made by New Japan Chemical Co., Ltd.): bisphenol A
bis(triethylene glycol glycidyl ether)ether, molecular weight of
457, epoxy equivalent of 310 to 340 g/eq, viscosity of 3,500 to
5,500 mPas, storage elastic modulus G'E (80) of 2.8.times.10.sup.4
Pa.
##STR00004##
[0212] In the formula, n.sub.d1 and n.sub.d2 each represent an
integer of 0 or more, with a total of 2.
[0213] BPO-60E (made by New Japan Chemical Co., Ltd.): bisphenol A
bis(propylene glycol glycidyl ether)ether, molecular weight of 541,
epoxy equivalent of 345 to 385 g/eq, viscosity of 800 to 1,600
mPas, storage elastic modulus G'E (80) of 5.4.times.10.sup.4
Pa.
##STR00005##
[0214] In the formula, n.sub.d3 and n.sub.d4 each represent an
integer of 0 or more, with a total of 6.
[0215] (B) Curing Accelerator [0216] IBMI12
(1-isobutyl-2-methylimidazole) (made by Mitsubishi Chemical
Corporation)
[0217] (C) High Molecular Weight Epoxy Resin
[0218] <Bisphenol F Type Epoxy Resin> [0219] jER4010 (made by
Mitsubishi Chemical Corporation): weight-average molecular weight
of 39,102, epoxy equivalent of 4,400 g/eq. [0220] jER4005 (made by
Mitsubishi Chemical Corporation): weight-average molecular weight
of 7,582, epoxy equivalent of 1,070 g/eq. [0221] jER4007 (made by
Mitsubishi Chemical Corporation): epoxy equivalent of 2,270
g/eq.
[0222] (D) Low Molecular Weight Epoxy Resin
[0223] <Bisphenol F Type Epoxy Resin>
[0224] YL983U (made by Mitsubishi Chemical Corporation):
weight-average molecular weight of 398, epoxy equivalent of 170
g/eq, storage elastic modulus G'E (80) of 2.2.times.10.sup.6
Pa.
[0225] jER807 (made by Mitsubishi Chemical Corporation):
weight-average molecular weight of 229, epoxy equivalent of 175
g/eq, storage elastic modulus G'E (80) of 2.1.times.10.sup.6
Pa.
[0226] (E) Silane Coupling Agent [0227] KBM-403
(3-glycidoxypropyltrimethoxysilane, molecular weight of 236) (made
by Shin-Etsu Chemical Co., Ltd.)
[0228] (F) Solvent [0229] Methyl ethyl ketone
Example 1
[0230] Into a flask, 0.3 parts by mass of EG-280 as flexible epoxy
resin (A), 0.6 parts by mass of jER4010 as high molecular weight
epoxy resin (C), and 0.1 parts by mass of jER807 as low molecular
weight epoxy resin (D) were fed, to which 0.67 parts by mass of
methyl ethyl ketone as solvent (F) was added and stirred for
dissolution at room temperature. To the solution, 0.06 parts by
mass of IBMI12 as curing accelerator (B) and 0.001 parts by mass of
KBM-403 as silane coupling agent (E) were added and stirred at room
temperature to prepare a varnish of epoxy resin composition.
[0231] The prepared varnish was applied to a mold release treated
PET film (PUREX A53, 38 .mu.m, made by Teijin DuPont Films Japan
Ltd.) with a coater so as to have a dried thickness of about 20
.mu.m, which was dried under vacuum at 40.degree. C. for 2 hours.
An optical device surface-sealing composition which is solid at
room temperature (about 25.degree. C.) was thus obtained. The
composition had an amount of the remaining solvent of 212 ppm.
Further, a mold-releasing treated PET film (PUREX A31, made by
Teijin DuPont Films Japan Ltd.) as a protective film was
thermocompressed on the optical device surface-sealing composition,
so that an optical device surface-sealing sheet was obtained. The
protective film is properly peeled to expose the surface of the
optical device surface-sealing composition for use.
Examples 2 to 7 and Comparative Examples 1 and 2
[0232] Except that the composition ratio (mass ratio) was changed
as shown in Table 1, the varnish of epoxy resin composition was
prepared in the same way as in Example 1 so as to prepare an
optical device surface-sealing sheet.
Example 8
[0233] A thermoplastic elastomer (TAFMER A4085, made by Mitsui
Chemicals, Inc.) was melted at 220.degree. C. and extrusion molded
from a T-die so as to form into a sheet with a thickness of 400
.mu.m. A sheet-like optical device surface-sealing composition
(thickness: 40 .mu.m) in Comparative Example 1 was thermocompressed
to both surfaces of the obtained sheet at 65.degree. C. so as to
form into a laminated sheet of optical device surface-sealing
composition (total thickness: 480 .mu.m). The storage elastic
modulus G' (80) of the obtained laminated sheet was
1.0.times.10.sup.5 Pas, measured by the method to be described
later in (3) Storage elastic modulus. The amount of warpage was
evaluated to be 1.6 mm, by the method to be described later in (4)
Warpage evaluation method.
[0234] For the optical device surface-sealing compositions obtained
in Examples 1 to 7 and Comparative Examples 1 and 2, the amount of
remaining MEK, melting point, Tg of the cured product, storage
elastic modulus of the cured product, and warpage of a panel were
evaluated by the following method. The results are shown in Table
1.
[0235] (1) Melting Point
[0236] The varnish was applied to a substrate film (trade name:
A53, thickness: 38 made by Teijin DuPont Films Japan Ltd.) with an
applicator so as to have a dried thickness of about 15 .mu.m. The
produced film was kept in an inert oven (30.degree. C.) for 10
minutes, and then in a vacuum oven (40.degree. C.) for 2 hours, so
that MEK in the applied varnish film was removed by drying. A
sealing sheet having a layer formed of optical device
surface-sealing composition was thus obtained.
[0237] A strip specimen with a length of about 40 mm and a width of
about 5 mm was cut out from the dried sealing sheet. The layer
formed of the optical device surface-sealing composition of the
strip specimen is disposed to come in contact with a heated glass
plate on a hot plate. The strip specimen was gripped at one end in
the length direction so as to be gradually peeled from the surface
of the glass plate in the 180.degree. direction for the evaluation
of adhesion peelability. The operation was initiated at a setting
temperature of the hot plate of 35.degree. C. and performed up to
70.degree. C. (temperature at which the melting point can be
confirmed) with a temperature increment of 1.degree. C. Every time
the setting temperature is increased by 1.degree. C., a new strip
specimen was used. The temperature at which the adhesion
peelability of the optical device surface-sealing composition layer
reached the highest during peeling was defined as the melting
point.
[0238] (2) Tg
[0239] A cut out optical device surface-sealing composition in a
sheet form (thickness: 12 .mu.m) having a predetermined size was
sandwiched with two glass plates and then bonded by heat curing at
100.degree. C. for 30 minutes. Subsequently the glass plates were
peeled, so that the sheet-like cured product of the optical device
surface-sealing composition was taken out. The linear expansion
coefficient of the cured product was measured with a TMA
(TMA/SS6000 made by Seiko Instruments Inc.) under conditions with a
rate of temperature increase of 5.degree. C./min. The Tg was
obtained from the inflexion point thereof.
[0240] (3) Storage Elastic Modulus
[0241] A plurality sheets of optical device surface-sealing
composition were laminated on a PET film disposed on a hot plate
set at 60.degree. C., and then thermocompressed to form into a
sheet-like optical device surface-sealing composition having a film
thickness of 300 to 500 .mu.m. The obtained sheet-like optical
device surface-sealing composition was measured with a rheometer
made by Haake, Inc. (RS150 type) at a measurement frequency of 1
Hz, at a temperature increase rate of 5.degree. C./min, in a
measurement temperature range of 40 to 80.degree. C., so that the
storage elastic modulus G' (80) at 80.degree. C. was obtained.
[0242] (4) Warpage of Laminate
[0243] A glass substrate (cover glass made by Matsunami,
50.times.70 mm, thickness No. 1 (150 .mu.m)) was used as the
substrate (L). MELINEX S (PET made by Teijin DuPont Films Japan
Ltd., 100 .mu.m) was used as the substrate (H). The glass
substrate, i.e. substrate (L), had a linear expansion coefficient
of 8.5.times.10.sup.-6 cm/cm/.degree. C.
[0244] A laminate of the substrate (L) (glass substrate, thickness:
150 .mu.m)/a layer formed of an optical device surface-sealing
composition (thickness: 40 .mu.m)/the substrate (H) (trade name:
MELINEX S, made by Teijin DuPont Films Japan Ltd., thickness: 100
.mu.m), which are laminated in the order presented, was
obtained.
[0245] After measurement of the thickness T1 of the obtained
laminate, the laminate was heated at 80.degree. C. for 3 hours, so
that the optical device surface-sealing composition was thermally
cured. Subsequently the laminate was cooled to 25.degree. C., and
placed on a horizontal plate. One of the sides of the glass with a
width of 50 mm was fixed to the horizontal plate with a tape, and
each of the distance between the two corners of the other side of
the glass with a width of 50 mm and the upper face of the plate was
measured to obtain the average T2. The amount of warpage T3 was
then calculated by subtracting T1 from T2.
TABLE-US-00001 TABLE 1 Compar- Compar- Exam- Exam- Exam- Exam-
Exam- Exam- Exam- ative ative ple ple ple ple ple ple ple Exam-
Exam- 1 2 3 4 5 6 7 ple 1 ple 2 Varnish (A) Flexible epoxy EG-250
Comp- resin EG-280 0.3 osition BPO-20E 0.3 BPO-60E 0.3 0.3 0.3 0.3
0.3 (C) High molecular jER-4010 0.6 0.6 0.6 0.6 0.6 0.6 0.6 weight
epoxy resin jER-4005 0.8 jER-4007 0.6 (D) Low molecular jER-807 0.1
0.1 0.1 0.4 weight epoxy resin YL-983U 0.1 0.1 0.1 0.1 0.2 (B)
Curing agent IBMI12 0.06 0.06 0.06 0.06 0.06 0.03 0.03 0.06 0.06
(E) Silane coupling KBM-403 0.001 0.001 0.001 0.001 0.001 0.001
0.04 0.001 0.001 agent (F) Solvent MEK 0.67 0.67 0.67 0.67 0.67
0.67 0.67 0.67 0.67 Evalu- Amount of remaining MEK in 212 0 91 42
11 6289 ation sheet-like composition (ppm) (1) Melting point of
sheet-like 51 45 43 42 45 46 40 composition (.degree. C.) (2)
Physical property Tg of cured 54 53 78 product (.degree. C.) (3)
Storage elastic modulus 4 8 8 5 6 6 1 75 64 G (80) of cured product
(.times.10.sup.5 Pa) (4) Warpage evaluation (amount of 3.8 2.4 3.7
4.3 2.5 1.6 2.7 9 5.9 warpage T3(mm))
[0246] As shown in Table 1, the surface-sealing composition in each
of Examples 1 to 7 has less warpage in the obtained laminate, since
the cured product has a storage elastic modulus G' (80) of a
certain value or lower. On the other hand, it is shown that the
surface-sealing composition in each of Comparative Examples 1 and 2
has large warpage in the obtained laminate, since the cured product
has an excessively high storage elastic modulus G' (80).
[0247] The present application claims the priority based on
Japanese Patent Application No. 2012-038838 filed on Feb. 24, 2012,
the entire content described in the specification and drawings of
which is incorporated herein by reference.
INDUSTRIAL APPLICABILITY
[0248] Since the display of the present invention has a limited
amount of warpage, damages to optical devices such as organic EL
devices is reduced, allowing for further thinning of a display.
REFERENCE SIGNS LIST
[0249] 10 Organic EL device surface-sealing sheet [0250] 12
Substrate film [0251] 16 Layer formed of optical device
surface-sealing composition [0252] 18 Protective film [0253] 20
Organic EL display [0254] 22 Display substrate [0255] 24 Organic EL
device [0256] 26 Counter substrate (transparent substrate) [0257]
28 Surface-sealing material [0258] 30 Cathode reflecting electrode
layer [0259] 32 Organic EL layer [0260] 34 Anode transparent
electrode layer
* * * * *