U.S. patent application number 15/798054 was filed with the patent office on 2018-08-16 for polyamic acid, polyimide film and fabrication method of the polyimide film.
The applicant listed for this patent is Samsung Display Co., Ltd., University-Industry Cooperation Group of Kyung Hee University. Invention is credited to Chaungi CHOI, Seulgi KIM, Jangju LEE, Sang-hyon PAEK.
Application Number | 20180230271 15/798054 |
Document ID | / |
Family ID | 60582395 |
Filed Date | 2018-08-16 |
United States Patent
Application |
20180230271 |
Kind Code |
A1 |
CHOI; Chaungi ; et
al. |
August 16, 2018 |
POLYAMIC ACID, POLYIMIDE FILM AND FABRICATION METHOD OF THE
POLYIMIDE FILM
Abstract
A polyamic acid according to an embodiment is formed by a
polymerization reaction of a dianhydride compound, a first diamine
compound represented by the following Formula 1, and a second
diamine compound, which is different from the first diamine
compound. A polyimide film derived from the polyamic acid may
exhibit excellent heat resistance and improved optical properties:
##STR00001##
Inventors: |
CHOI; Chaungi; (Suwon-si,
KR) ; PAEK; Sang-hyon; (Seongnam-si, KR) ;
KIM; Seulgi; (Suwon-si, KR) ; LEE; Jangju;
(Hwaseong-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Display Co., Ltd.
University-Industry Cooperation Group of Kyung Hee
University |
Yongin-si
Yongin-si |
|
KR
KR |
|
|
Family ID: |
60582395 |
Appl. No.: |
15/798054 |
Filed: |
October 30, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G 73/1057 20130101;
C08G 73/1042 20130101; C08J 2379/08 20130101; C08G 73/1067
20130101; C08J 5/18 20130101 |
International
Class: |
C08G 73/10 20060101
C08G073/10; C08J 5/18 20060101 C08J005/18 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2017 |
KR |
10-2017-0018866 |
Claims
1. A polyamic acid being a polymerization product of: a dianhydride
compound; a first diamine compound represented by the following
Formula 1; and a second diamine compound different from the first
diamine compound: ##STR00021## wherein in Formula 1, R.sub.1 and
R.sub.2 are each independently selected from a hydrogen atom, a
deuterium atom, a halogen atom, and a substituted or unsubstituted
alkyl group of 1 to 20 carbon atoms, and n.sub.1 and n.sub.2 are
each independently an integer of 0 to 4.
2. The polyamic acid of claim 1, wherein the second diamine
compound is represented by the following Formula 2: ##STR00022##
wherein in Formula 2, Ar is a substituted or unsubstituted phenyl
group, and m is an integer of 1 to 4.
3. The polyamic acid of claim 1, wherein the second diamine
compound is represented by the following Formula 2-1:
##STR00023##
4. The polyamic acid of claim 1, wherein in Formula 1, n.sub.1 and
n.sub.2 are each independently an integer of 1 or more, and R.sub.1
and R.sub.2 are each independently an alkyl group of 1 to 20 carbon
atoms substituted with at least one fluorine atom.
5. The polyamic acid of claim 1, wherein the first diamine compound
Formula 1 is represented by the following Formula 1-1: ##STR00024##
wherein in Formula 1-1, definitions of R.sub.1, R.sub.2, n.sub.1
and n.sub.2 are the same as those in Formula 1.
6. The polyamic acid of claim 1, wherein the first diamine compound
of Formula 1 is represented by the following Formula 1-2:
##STR00025##
7. The polyamic acid of claim 1, wherein a molar ratio of a sum of
the first diamine compound and the second diamine compound with
respect to the dianhydride compound is from 1:0.9 to 1:1.1.
8. The polyamic acid of claim 7, wherein a molar ratio of the first
diamine compound to the second diamine compound is from 0.01:0.99
to 0.99:0.01.
9. The polyamic acid of claim 1, wherein the dianhydride compound
comprises at least one selected from
4,4'-(hexafluoroisopropylidene)diphthalic anhydride,
3,3',4,4'-biphenyltetracarboxylic dianhydride,
cyclobutane-1,2,3,4-tetracarboxyl dianhydride and pyromellitic
dianhydride.
10. The polyamic acid of claim 1, wherein the dianhydride compound
is 3,3',4,4'-biphenyltetracarboxylic dianhydride, the first diamine
compound is 2,2'-bis(trifluoromethyl)benzidine, and the second
diamine compound is 3,5-diaminobenzoic acid.
11. The polyamic acid of claim 1, wherein the polyamic acid
comprises a repeating unit represented by the following Formula 3:
##STR00026## wherein in Formula 3, X and Y are each independently
an integer of 1 or more.
12. A polyimide film comprising a repeating unit derived from the
polyamic acid according to claim 1.
13. The polyimide film of claim 12, wherein a thermal expansion
coefficient of the polyimide film is from 10 ppm/.degree. C. to 20
ppm/.degree. C.
14. The polyimide film of claim 12, wherein a glass transition
temperature of the polyimide film is from 300.degree. C. to
420.degree. C.
15. The polyimide film of claim 12, wherein a thermal decomposition
temperature of the polyimide film is from 400.degree. C. to
500.degree. C., wherein the thermal decomposition temperature is a
temperature at which a weight reduction ratio of the polyimide film
reaches 1%.
16. The polyimide film of claim 12, wherein a light transmittance
of the polyimide film is 95% or more.
17. The polyimide film of claim 12, wherein a yellow index of the
polyimide film is from 1 to 10.
18. The polyimide film of claim 12, wherein the polyimide film has
a light transmittance of 95% or more, a thermal expansion
coefficient of 10 ppm/.degree. C. to 20 ppm/.degree. C., and a
glass transition temperature of 300.degree. C. to 420.degree.
C.
19. The polyimide film of claim 12, wherein the polyimide film
comprises a repeating unit represented by the following Formula 4:
##STR00027## wherein in Formula 4, A and B are each independently
an integer of 1 or more.
20. A fabrication method of a polyimide film, the method
comprising: preparing a polyamic acid according to claim 1 by a
polymerization reaction of a dianhydride compound and at least two
kinds of diamine compounds; providing the polyamic acid on a
substrate to form a polyamic acid layer; and heat treating the
polyamic acid layer.
21. The fabrication method of a polyimide film of claim 20, wherein
the preparing of the polyamic acid is performed at a temperature
range of -10.degree. C. to 80.degree. C.
22. The fabrication method of a polyimide film of claim 20, wherein
the heat treating of the polyamic acid layer comprises heat
treating at a temperature range of 250.degree. C. to 550.degree.
C.
23. The fabrication method of a polyimide film of claim 22, further
comprising cooling after the heat treating of the polyamic acid
layer.
24. The fabrication method of a polyimide film of claim 20, wherein
the heat treating of the polyamic acid layer comprises: first heat
treating at a first temperature; and second heat treating at a
second temperature higher than the first temperature.
25. The fabrication method of a polyimide film of claim 24, wherein
the first temperature is from 250.degree. C. to less than
300.degree. C., and the second temperature is from 300.degree. C.
to 550.degree. C.
26. The fabrication method of a polyimide film of claim 20, wherein
the heat treating of the polyamic acid layer is conducted in a
vacuum state.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This patent application claims priority to and the benefit
of Korean Patent Application No. 10-2017-0018866, filed on Feb. 10,
2017, the entire content of which is hereby incorporated by
reference.
BACKGROUND
[0002] One or more aspects of embodiments of the present disclosure
herein relate to a polyamic acid, a polyimide film formed using the
same, and a fabrication method of the polyimide film, and more
particularly, to a polyamic acid utilized for attaining a polyimide
film having excellent optical properties and heat resistance and a
fabrication method of the polyimide film.
[0003] Polyimide is a polymer material capable of having excellent
heat resistance and chemical resistance and exhibiting good
mechanical properties, and may be used (utilized) in various
industrial fields. For example, polyimide has been developed as an
alignment material of a liquid crystal display, an insulating
material, and/or a material for a flexible substrate, and it may be
utilized for diverse applications in a display apparatus.
[0004] Recently, in order to use a polyimide film as a replacement
of a glass substrate in a flexible display apparatus, a portable
display apparatus, etc., developments on improving the optical
properties and heat resistance of the polyimide film are being
conducted.
SUMMARY
[0005] One or more aspects of embodiments of the present disclosure
are directed toward a polyamic acid for obtaining a polyimide that
maintains optical properties of high transparency and has high
dimensional stability and heat resistance, a polyimide film formed
using the polyamic acid, and a fabrication method of the polyimide
film.
[0006] An embodiment of the inventive concept provides a polyamic
acid being a polymerization product of a dianhydride compound, a
first diamine compound represented by the following Formula 1, and
a second diamine compound different from the first diamine
compound:
##STR00002##
[0007] wherein in Formula 1, R.sub.1 and R.sub.2 may each
independently be a hydrogen atom, a deuterium atom, a halogen atom,
or a substituted or unsubstituted alkyl group of 1 to 20 carbon
atoms, and n.sub.1 and n.sub.2 may each independently be an integer
of 0 to 4.
[0008] In an embodiment, the second diamine compound may be
represented by the following Formula 2:
##STR00003##
[0009] wherein in Formula 2, Ar may be a substituted or
unsubstituted phenyl group, and m may be an integer of 1 to 4.
[0010] In an embodiment, the second diamine compound may be
represented by the following Formula 2-1:
##STR00004##
[0011] In an embodiment, in Formula 1, n.sub.1 and n.sub.2 may be
each independently an integer of 1 or more, and R.sub.1 and R.sub.2
may each independently be an alkyl group of 1 to 20 carbon atoms
substituted with at least one fluorine atom.
[0012] In an embodiment, the first diamine compound of Formula 1
may be represented by the following Formula 1-1:
##STR00005##
[0013] wherein R.sub.1, R.sub.2, n.sub.1 and n.sub.2 are the same
as defined above.
[0014] In an embodiment, the first diamine compound of Formula 1
may be represented by the following Formula 1-2:
##STR00006##
[0015] In an embodiment, a molar ratio of a sum of the first
diamine compound and the second diamine compound with respect to
the dianhydride compound may be from about 1:0.9 to about
1:1.1.
[0016] In an embodiment, a molar ratio of the first diamine
compound to the second diamine compound may be from about 0.01:0.99
to about 0.99:0.01.
[0017] In an embodiment, the dianhydride compound may include at
least one selected from 4,4'-(hexafluoroisopropylidene)diphthalic
anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride,
cyclobutane-1,2,3,4-tetracarboxyl dianhydride and pyromellitic
dianhydride.
[0018] In an embodiment, the dianhydride compound may be
3,3',4,4'-biphenyltetracarboxylic dianhydride, the first diamine
compound may be 2,2'-bis(trifluoromethyl)benzidine, and the second
diamine compound may be 3,5-diaminobenzoic acid.
[0019] In an embodiment, the polyamic acid may include a repeating
unit represented by the following Formula 3:
##STR00007##
[0020] wherein, in Formula 3, X and Y may each independently be an
integer of 1 or more.
[0021] In an embodiment of the inventive concept, there is provided
a polyimide film including a repeating unit derived from the
polyamic acid according to the above-described embodiment.
[0022] In an embodiment, a thermal expansion coefficient of the
polyimide film may be from about 10 ppm/.degree. C. to about 20
ppm/.degree. C.
[0023] In an embodiment, a glass transition temperature of the
polyimide film may be from about 300.degree. C. to about
420.degree. C.
[0024] In an embodiment, a thermal decomposition temperature of the
polyimide film may be from about 400.degree. C. to about
500.degree. C., where the thermal decomposition temperature may
refer to a temperature at which a weight reduction ratio of the
polyimide film reaches about 1%.
[0025] In an embodiment, a light transmittance of the polyimide
film may be about 95% or more.
[0026] In an embodiment, a yellow index of the polyimide film may
be from about 1 to about 10.
[0027] In an embodiment, the polyimide film may have a light
transmittance of about 95% or more, a thermal expansion coefficient
of about 10 ppm/.degree. C. to about 20 ppm/.degree. C., and a
glass transition temperature of about 300.degree. C. to about
420.degree. C.
[0028] In an embodiment, the polyimide film may include a repeating
unit represented by the following Formula 4:
##STR00008##
[0029] wherein, in Formula 4, A and B are each independently an
integer of 1 or more.
[0030] In an embodiment of the inventive concept, there is provided
a fabrication method of a polyimide film, the method including
preparing a polyamic acid according to the above-described
embodiment by a polymerization reaction of a dianhydride compound
and at least two kinds of diamine compounds, providing the polyamic
acid on a substrate to form a polyamic acid layer, and heat
treating the polyamic acid layer.
[0031] In an embodiment, the preparing of the polyamic acid may be
performed at a temperature range of about -10.degree. C. to about
80.degree. C.
[0032] In an embodiment, the heat treating of the polyamic acid
layer may include heat treating at a temperature range of about
250.degree. C. to about 550.degree. C.
[0033] In an embodiment, the fabrication method of a polyimide film
may further include cooling after the heat treating of the polyamic
acid layer.
[0034] In an embodiment, the heat treating of the polyamic acid
layer may include first heat treating at a first temperature, and
second heat treating at a second temperature higher than the first
temperature.
[0035] In an embodiment, the first temperature may be from about
250.degree. C. to less than about 300.degree. C., and the second
temperature may be from about 300.degree. C. to about 550.degree.
C.
[0036] In an embodiment, the heat treating of the polyamic acid
layer may be conducted in a vacuum state.
BRIEF DESCRIPTION OF THE FIGURES
[0037] The accompanying drawings are included to provide a further
understanding of the inventive concept, and are incorporated in and
constitute a part of this specification. The drawings illustrate
example embodiments of the inventive concept and, together with the
description, serve to explain principles of the inventive
concept.
[0038] In the drawings:
[0039] FIG. 1 is a flowchart showing a fabrication method of a
polyimide film according to an embodiment; and
[0040] FIG. 2 is a flowchart showing a fabrication method of a
polyimide film according to an embodiment.
DETAILED DESCRIPTION
[0041] The inventive concept may be embodied in different forms and
may have various modifications, and example embodiments of the
inventive concept will be described below in more detail with
reference to the accompanying drawings. The inventive concept,
however, should not be construed as limited to the embodiments set
forth herein. Rather, these embodiments should be understood to
include modifications, equivalents, or substitutes within the
spirit and scope of the inventive concept.
[0042] In the drawings, like reference numerals refer to like
elements throughout. The dimensions of structures may be
exaggerated for clarity of illustration. It will be understood
that, although the terms first, second, etc. may be used herein to
describe various elements, these elements should not be limited by
these terms. These terms are only used to distinguish one element
from another element. For example, a first element could be termed
a second element without departing from the teachings of the
present invention. Similarly, a second element could be termed a
first element. As used herein, the singular forms are intended to
include the plural forms as well, unless the context clearly
indicates otherwise.
[0043] It will be further understood that the terms "comprises" or
"comprising," when used in this specification, specify the presence
of stated features, numerals, tasks, operations, elements, parts,
or the combination thereof, but do not preclude the presence or
addition of one or more other features, numerals, tasks,
operations, elements, parts, or the combination thereof. It will
also be understood that when a layer, a film, a region, a plate,
etc. is referred to as being `on` another part, it can be directly
on the other part, or intervening layers may also be present.
[0044] Hereinafter, a polyamic acid according to an embodiment will
be explained in more detail.
[0045] The polyamic acid according to an embodiment may be formed
by including a dianhydride compound and at least two kinds of
diamine compounds. The polyamic acid according to an embodiment may
be a polymerization product obtained by the polymerization reaction
of a dianhydride compound, a first diamine compound represented by
the following Formula 1, and a second diamine compound, which is
different from the first diamine compound.
[0046] The first diamine compound may be represented by the
following Formula 1:
##STR00009##
[0047] In Formula 1, R.sub.1 and R.sub.2 may be each independently
a hydrogen atom, a deuterium atom, a halogen atom, or a substituted
or unsubstituted alkyl group of 1 to 20 carbon atoms. In addition,
n.sub.1 and n.sub.2 may be each independently an integer of 0 to
4.
[0048] In Formula 1, R.sub.1 and R.sub.2 may be the same or
different from each other. In addition, n.sub.1 and n.sub.2 may be
the same or different from each other.
[0049] In some embodiments, in the first diamine compound
represented by Formula 1, n.sub.1 and n.sub.2 may be each
independently an integer of 1 or more. For example, n.sub.1 and
n.sub.2 may be the same integer of 1 or more. In some embodiments,
n.sub.1 and n.sub.2 may be different from each other (e.g., n.sub.1
and n.sub.2 may be different integers of 1 or more). For example,
both n.sub.1 and n.sub.2 may be 1. In another example, one of
n.sub.1 and n.sub.2 may be 0, and the remaining one of n.sub.1 and
n.sub.2 may be an integer of 1 or more.
[0050] When n.sub.1 and n.sub.2 are each independently an integer
of 2 or more, a plurality of R.sub.1 may be the same or different
from each other, and a plurality of R.sub.2 may be the same or
different from each other.
[0051] In an embodiment, in the case where n.sub.1 and n.sub.2 are
each independently an integer of 1 or more, R.sub.1 and R.sub.2 of
the first diamine compound represented by Formula 1 may be each
independently an alkyl group of 1 to 20 carbon atoms substituted
with at least one fluorine atom. In embodiments where n.sub.1 is an
integer of 2 or more, at least one R.sub.1 may be an alkyl group of
1 to 20 carbon atoms substituted with at least one fluorine atom,
or two or more R.sub.1 may be alkyl groups of 1 to 20 carbon atoms
substituted with at least one fluorine atom. In embodiments where
n.sub.2 is an integer of 2 or more, at least one R.sub.2 may be an
alkyl group of 1 to 20 carbon atoms substituted with at least one
fluorine atom, or two or more R.sub.2 may be alkyl groups of 1 to
20 carbon atoms substituted with at least one fluorine atom.
[0052] R.sub.1 and R.sub.2 may each independently be a hydrogen
atom, a deuterium atom, a halogen atom, an unsubstituted alkyl
group of 1 to 20 carbon atoms, or a substituted alkyl group of 1 to
20 carbon atoms. For example, R.sub.1 and R.sub.2 may be each
independently an alkyl group of 1 to 20 carbon atoms substituted
with at least one fluorine atom. For example, R.sub.1 and R.sub.2
may be represented by *--CF.sub.3, *--CF.sub.2CF.sub.3,
*--CH.sub.2CF.sub.3, *--CH.sub.2CF.sub.2CF.sub.3, and/or
*--CF.sub.2CF.sub.2CF.sub.3. However, an embodiment of the
inventive concept is not limited thereto.
[0053] For example, in the first diamine compound represented by
Formula 1 for forming the polyamic acid according to an embodiment,
both n.sub.1 and n.sub.2 may be 1, and both R.sub.1 and R.sub.2 may
be trifluoromethyl. Heat resistance may be improved by using the
first diamine compound represented by Formula 1, in which at least
one of R.sub.1 and R.sub.2 is an alkyl group of 1 to 20 carbon
atoms substituted with at least one fluorine atom, when forming the
polyamic acid according to an embodiment.
[0054] As used in the present disclosure, the term "substituted or
unsubstituted" may refer to the corresponding group being either
unsubstituted or substituted with at least one substituent selected
from a deuterium atom, a halogen atom, a cyano group, a nitrile
group, a nitro group, an amino group, a silyl group, a boron group,
a phosphine oxide group, an alkyl group, an alkenyl group, a
fluorenyl group, an aryl group and a heteroaryl group. In addition,
each of the substituent groups above may be substituted or
unsubstituted. For example, a biphenyl group may be described as an
aryl group, or as a phenyl group substituted with a phenyl
group.
[0055] In the present disclosure, examples of the halogen atom may
include a fluorine atom, a chlorine atom, a bromine atom, and an
iodine atom.
[0056] In the present disclosure, the alkyl group may refer to a
carbohydrate group having a linear or branched chain or a cyclic
shape. Non-limiting examples of the alkyl group may include methyl,
ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, i-butyl,
2-ethylbutyl, 3,3-dimethylbutyl, n-pentyl, i-pentyl, neopentyl,
t-pentyl, cyclopentyl, 1-methylpentyl, 3-methylpentyl,
2-ethylpentyl, 4-methyl-2-pentyl, n-hexyl, 1-methylhexyl,
2-ethylhexyl, 2-butylhexyl, cyclohexyl, 4-methylcyclohexyl,
4-t-butylcyclohexyl, n-heptyl, 1-methylheptyl, 2,2-dimethylheptyl,
2-ethylheptyl, 2-butylheptyl, n-octyl, t-octyl, 2-ethyloctyl,
2-butyloctyl, 2-hexyloctyl, 3,7-dimethyloctyl, cyclooctyl, n-nonyl,
n-decyl, adamantyl, 2-ethyldecyl, 2-butyldecyl, 2-hexyldecyl,
2-octyldecyl, n-undecyl, n-dodecyl, 2-ethyldodecyl, 2-butyldodecyl,
2-hexyldodecyl, 2-octyldodecyl, n-tridecyl, n-tetradecyl,
n-pentadecyl, n-hexadecyl, 2-ethylhexadecyl, 2-butylhexadecyl,
2-hexylhexadecyl, 2-octylhexadecyl, n-heptadecyl, n-octadecyl,
n-nonadecyl, n-eicosyl, 2-ethyl eicosyl, 2-butyl eicosyl, 2-hexyl
eicosyl, 2-octyl eicosyl, n-henicosyl, n-docosyl, n-tricosyl,
n-tetracosyl, n-pentacosyl, n-hexacosyl, n-heptacosyl, n-octacosyl,
n-nonacosyl, and n-triacontyl.
[0057] In the present disclosure, * may refer to a bonding
site.
[0058] The first diamine compound represented by Formula 1 may be
represented by the following Formula 1-1:
##STR00010##
[0059] In Formula 1-1, R.sub.1, R.sub.2, n.sub.1 and n.sub.2 may be
defined as in Formula 1.
[0060] In some embodiments, the first diamine compound of Formula
1-1 may be a biphenyl compound in which the two amine groups
(*--NH.sub.2) are bonded at the para position thereof. For example,
the first diamine compound according to an embodiment may be a
benzidine compound.
[0061] In Formula 1-1, n.sub.1 and n.sub.2 may be each
independently an integer of 1 or more, and R.sub.1 and R.sub.2 may
be each independently an alkyl group of 1 to 20 carbon atoms
substituted with at least one fluorine atom. For example, in
Formula 1-1, both n.sub.1 and n.sub.2 may be 1, and both R.sub.1
and R.sub.2 may be trifluoromethyl.
[0062] In some embodiments, the first diamine compound represented
by Formula 1 may be represented by the following Formula 1-2:
##STR00011##
[0063] In some embodiments, the first diamine compound may be a
diamine compound represented by the following Formula 1-3:
##STR00012##
[0064] In an embodiment, the first diamine compound may be
2,2'-bis(trifluoromethyl)benzidine (TFMB).
[0065] The polyamic acid according to embodiments of the present
disclosure may be a polymer formed by the polymerization reaction
of at least two kinds (types) of diamine compounds and at least one
dianhydride compound. For example, one diamine compound may be the
first diamine compound represented by Formula 1 and at least one
other diamine compound may be different from the first diamine
compound. For example, the polyamic acid according to embodiments
of the present disclosure may be formed by the polymerization
reaction of two kinds (types) of diamine compounds including the
first diamine compound of the present embodiments and further
including a second diamine compound, which is different from the
first diamine compound, with at least one dianhydride compound.
[0066] In some embodiments, the second diamine compound may be
represented by the following Formula 2:
##STR00013##
[0067] In Formula 2, Ar may be a substituted or unsubstituted
phenyl, and m may be an integer of 1 to 4. In the second diamine
compound represented by Formula 2, Ar may be phenyl, or phenyl
substituted with phenyl. For example, Ar may be phenyl or
biphenyl.
[0068] In an embodiment, the second diamine compound may have at
least one carboxyl group.
[0069] In the polyamic acid of the present embodiments, the second
diamine compound represented by Formula 2 may inhibit
intermolecular interaction during a thermal imidization process via
heat treatment, and increase the distance between chains, thereby
restraining the formation of a charge transfer complex. In
addition, the second diamine compound may play the role of a cross
linker in the polymerization reaction. For example, the second
diamine compound may play the role of a cross linking agent for
connecting polyamic acid units that are formed by the
polymerization reaction, may increase the formation of a polyamic
acid network, and may improve the mechanical properties and
increase the heat resistance of the resulting polyimide film.
[0070] The second diamine compound represented by Formula 2 may be
represented by the following Formula 2-1:
##STR00014##
[0071] In the second diamine compound represented by Formula 2-1,
two amine groups (*--NH.sub.2) may be bonded ortho or meta to the
phenyl group. For example, the second diamine compound may be
3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid,
2,3-diaminobenzoic acid, or 2,6-diaminobenzoic acid. However, an
embodiment of the inventive concept is not limited thereto.
[0072] In some embodiments, the second diamine compound may be
represented by the following Formula 2-2:
##STR00015##
[0073] The dianhydride compound for forming the polyamic acid
according to an embodiment of the present disclosure may include at
least one selected from 4,4'-(hexafluoroisopropylidene)diphthalic
anhydride (6FDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride
(BPDA), cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA), and
pyromellitic dianhydride (PMDA). In an embodiment, the dianhydride
compound may be one selected from 6FDA, BPDA, CBDA, and PMDA, or
may include at least two selected therefrom.
[0074] The polyamic acid of an embodiment may be a polymer product
prepared by the polymerization reaction of at least one dianhydride
compound selected from 6FDA, BPDA, CBDA, and PMDA, the first
diamine compound represented by Formula 1, and the second diamine
compound represented by Formula 2. For example, the polyamic acid
of an embodiment may be a polymerization product of
3,3',4,4'-biphenyltetracarboxylic dianhydride,
2,2'-bis(trifluoromethyl)benzidine (TFMB), and 3,5-diaminobenzoic
acid (DABA).
[0075] The polyamic acid of an embodiment may be formed by the
reaction of the dianhydride compound with the first diamine
compound and the second diamine compound, where the first and
second diamine compounds are in a molar ratio of about 1:0.9 to
about 1:1.1. For example, at least two kinds (types) of the diamine
compounds including the first diamine compound and the second
diamine compound may be included in a molar ratio of about 0.9 to
about 1.1, based on 1 mole of the dianhydride compound. For
example, the dianhydride compound may react with at least two kinds
(types) of the diamine compounds including the first diamine
compound and the second diamine compound in a molar ratio of about
1:1 to produce the polyamic acid of an embodiment of the present
disclosure.
[0076] In an embodiment, the first diamine compound and the second
diamine compound may be included in a molar ratio of about
0.01:0.99 to about 0.99:0.01. For example, the first diamine
compound and the second diamine compound may be included in a molar
ratio of about 0.5:0.5 to about 0.9:0.1. For example, the first
diamine compound and the second diamine compound may be included in
a molar ratio of about 0.6:0.4 to about 0.8:0.2. In this case, all
of the first diamine compound and the second diamine compound may
react with the dianhydride compound in a molar ratio of about 1:0.9
to about 1:1.1.
[0077] In an embodiment, the first diamine compound and the second
diamine compound may be included in a molar ratio of about
0.75:0.25. In this case, all of the first diamine compound and the
second diamine compound may react with the dianhydride compound in
a molar ratio of about 1:0.9 to 1:1.1.
[0078] The polyamic acid of an embodiment may include a polyamic
acid unit represented by the following Formula 3:
##STR00016##
[0079] In Formula 3, X and Y may be each independently an integer
of 1 or more. The number average molecular weight (Mn) of the
polyamic acid according to an embodiment, which may include the
polyamic acid unit represented by Formula 3, may be from about
10,000 to about 1,000,000.
[0080] The polyamic acid of an embodiment is a polymer that may be
obtained by simultaneously reacting a dianhydride compound and at
least two different kinds (types) of diamine compounds that include
the first diamine compound represented by Formula 1 and the second
diamine compound, which is different from the first diamine
compound. Accordingly, a polyimide precursor for preparing
polyimide having good heat resistance, and excellent optical
properties, including high transparency and low yellow index, may
be obtained.
[0081] The polyamic acid of an embodiment may be obtained by
polymerizing the dianhydride compound, the first diamine compound
represented by Formula 1, and the second diamine compound
represented by Formula 2, and from the resulting polyamic acid, a
polyimide film exhibiting good heat resistance and optical
properties may be fabricated.
[0082] The polyimide film of an embodiment may include a repeating
unit derived from the polyamic acid of an embodiment. For example,
the polyimide film of an embodiment may be fabricated to include a
repeating unit obtained by the imidization of the polyamic acid of
an embodiment.
[0083] The polyimide film of an embodiment may be formed from a
polyamic acid, which in turn may be obtained by the polymerization
reaction of the dianhydride compound with at least two kinds
(types) of diamine compounds including the first diamine compound
represented by Formula 1. For example, the polyimide film of an
embodiment may be fabricated by including the repeating unit
derived from the polyamic acid, where the polyamic acid may be a
polymerization product of the dianhydride compound, the first
diamine compound represented by Formula 1, and the second diamine
compound represented by Formula 2.
[0084] Hereinafter, a fabrication method of a polyimide film of an
embodiment of the present disclosure will be explained by referring
to attached drawings.
[0085] Each of FIGS. 1 and 2 is a flowchart showing tasks of a
fabrication method of a polyimide film according to one or more
embodiments of the present disclosure. Referring to FIG. 1, the
fabrication method of a polyimide film of an embodiment may include
a task of preparing a polyamic acid by a polymerization reaction of
a dianhydride compound with at least two kinds (types) of diamine
compounds (S100), a task of supplying the polyamic acid on a
substrate to form a polyamic acid layer (S200), and a task of heat
treating the polyamic acid layer (S300).
[0086] In the task of preparing a polyamic acid by the
polymerization reaction of a dianhydride compound and at least two
kinds (types) of diamine compounds (S100), the polyamic acid of the
present embodiments may be prepared. The polyamic acid thus
prepared may be a polyamic acid copolymer obtained by the
polymerization reaction of the dianhydride compound and at least
two kinds (types) of diamine compounds. In the task of preparing
the polyamic acid (S100), the dianhydride compound, the first
diamine compound represented by Formula 1 and the second diamine
compound, which is different from the first diamine compound, may
be added to an organic solvent, and a polymerization reaction may
be performed in the organic solvent to produce the polyamic
acid.
[0087] In the task of preparing a polyamic acid (S100), the organic
solvent may be N,N-dimethyl acetamide (DMAc), dimethylformamide
(DMF), N-methyl-2-pyrrolidone (NMP), m-cresol, tetrahydrofuran
(THF), chloroform, or a mixture solvent thereof. For example, the
organic solvent may be N,N-dimethylacetamide (DMAc),
N-methyl-2-pyrrolidone (NMP), or a mixture solvent of the two
solvents. However, the organic solvent used in the task of
preparing a polyamic acid (S100) is not limited to the suggested
organic solvents, and any organic solvent capable of dissolving the
dianhydride compound and the diamine compound may be used, without
limitation.
[0088] In the task of preparing a polyamic acid (S100), a
dianhydride compound and at least two kinds (types) of diamine
compounds may be included in a molar ratio of about 1:0.9 to about
1:1.1 and may be mixed with the organic solvent to perform a
polymerization reaction. The at least two kinds (types) of diamine
compounds may include a first diamine compound represented by
Formula 1 and a second diamine compound represented by Formula 2.
The first diamine compound and the second diamine compound may be
mixed in a molar ratio of about 0.01:0.99 to about 0.99:0.01 and
polymerized. For example, the first diamine compound and the second
diamine compound may be mixed in a molar ratio of about 0.5:0.5 to
about 0.9:0.1 and polymerized. For example, the dianhydride
compound and at least two kinds (types) of diamine compounds may be
mixed in a molar ratio of about 1:1, and among the at least two
kinds (types) of diamine compounds, the first diamine compound and
the second diamine compound may be mixed in a molar ratio of about
0.5:0.5 to about 0.9:0.1, to prepare the polyamic acid via an
imidization reaction.
[0089] The task of preparing a polyamic acid (S100) may include a
task of preparing a diamine compound solution by first dissolving
at least two kinds (types) of diamine compounds in an organic
solvent. Here, the diamine compound solution may be without a
dianhydride compound. The task of preparing a polyamic acid (S100)
may further include a task of preparing a dianhydride compound
solution by dissolving a dianhydride solution in an organic
solvent, separately from the diamine compound solution.
[0090] For example, in the task of fabricating a polyimide film of
an embodiment, at least two kinds (types) of diamine compounds may
be first mixed in the organic solvent in a suitable molar ratio to
prepare the diamine compound solution, and then, the dianhydride
compound may be separately dissolved in the organic solvent to
prepare the dianhydride compound solution. Then, the diamine
compound solution and the dianhydride compound solution may be
mixed in a molar ratio of the diamine compound to the dianhydride
compound of about 1:0.9 to about 1:1.1, to perform a polymerization
reaction and to prepare a polyamic acid.
[0091] In an alternative embodiment, a dianhydride compound, a
first diamine compound and a second diamine compound may be mixed
in a suitable molar ratio in one task and may be polymerized to
prepare a polyamic acid.
[0092] The task of preparing a polyamic acid (S100) may be
performed in an inert gas atmosphere. For example, the task of
preparing a polyamic acid (S100) may be performed in a nitrogen gas
atmosphere.
[0093] The task of preparing a polyamic acid (S100) may be
performed in a temperature range of about -10.degree. C. to about
80.degree. C. In an embodiment, the task of preparing a polyamic
acid (S100) may be performed in a temperature range of about
-10.degree. C. to about 80.degree. C. for about 10 minutes to about
24 hours.
[0094] The polyamic acid prepared by the polymerization reaction of
the present embodiments may be included in an organic solvent in an
amount of about 5 wt % to about 80 wt %. For example, the polyamic
acid thus prepared may be included in the organic solvent in an
amount of about 10 wt % to about 50 wt % by the solid content.
[0095] For example, the polyamic acid prepared by the
polymerization reaction may have a repeating unit represented by
the following Formula 3:
##STR00017##
[0096] In Formula 3, X and Y may be each independently an integer
of 1 or more. The number average molecular weight (Mn) of the
polyamic acid according to an embodiment, which may include a
polyamic acid unit represented by Formula 3, may be from about
10,000 to about 1,000,000.
[0097] The fabrication method of a polyimide film of an embodiment
may include a task of providing (e.g., supplying) a polyamic acid
on a substrate to form a polyamic acid layer (S200), following the
task of preparing a polyamic acid (S100), as shown in FIG. 1.
[0098] The polyamic acid prepared according to the method of the
present embodiments may be provided on a substrate as a support for
forming a film. However, a coating method for providing the
polyamic acid thus prepared on the substrate is not limited
thereto, and any suitable method for uniformly (or substantially
uniformly) providing the polyamic acid on the substrate to form a
film layer may be used, without limitation. For example, the
polyamic acid thus prepared may be provided on the substrate by a
coating method.
[0099] The substrate on which the polyamic acid is supplied may be
any suitable substrate for providing a support for fabrication of a
polyimide film, without limitation. For example, the substrate may
be a glass substrate, a substrate formed of a metal material, or a
substrate formed of a polymer material, and the surface of the
substrate may be substantially smooth, for uniformly (or
substantially uniformly) coating the polyamic acid.
[0100] The polyamic acid provided on the substrate may include an
organic solvent. After providing the polyamic acid on the
substrate, a task of drying the organic solvent may be performed.
The task of drying the polyamic acid provided on the substrate may
be performed at a temperature of about 30.degree. C. to about
140.degree. C. for about 10 to about 180 minutes. For example, the
task of drying the organic solvent after coating the polyamic acid
may be performed at a temperature of about 40.degree. C. to about
80.degree. C. for about 30 to about 120 minutes.
[0101] The polyamic acid layer formed after drying may be a coated
layer having a thickness of about 5 .mu.m to about 150 .mu.m. For
example, the polyamic acid layer formed after drying may be a
coated layer having a thickness of about 10 .mu.m to about 100
.mu.m.
[0102] After the task of forming a polyamic acid layer by providing
the polyamic acid on the substrate (S200), a task of heat treating
the polyamic acid layer (S300) may be performed. The task of heat
treating the polyamic acid layer (S300) may be a task of forming a
polyimide layer by applying heat to the polyamic acid for the
reaction by a thermal imidization method.
[0103] The task of heat treating the polyamic acid layer (S300) may
include a heat treating task performed at a temperature of about
250.degree. C. to about 550.degree. C. For example, the task of
heat treating the polyamic acid layer (S300) may be performed at a
temperature of about 300.degree. C. to about 500.degree. C.
[0104] In the case where the heat treating is performed at about
250.degree. C. or more, the imidization degree of the resulting
polyamic acid may be increased and the hysteresis of the polyimide
thus formed may be improved when compared with a case where the
heat treating of the polyamic acid is performed at less than about
250.degree. C. In the case where the task of heat treating the
polyamic acid layer (S300) is performed at greater than about
500.degree. C., thermal decomposition phenomenon of the polyamic
acid layer may be generated, and the yellow index may be increased
in a film formed by the imidization of the polyamic acid according
to the present embodiments.
[0105] In an embodiment, the task of heat treating a polyamic acid
layer (S300) may be performed at high temperature conditions, for
example, at a temperature of about 250.degree. C. to about
550.degree. C., for about 5 to about 180 minutes. For example, the
task of heat treating a polyamic acid layer (S300) may be performed
for about 5 to about 120 minutes, for example, for about 30 to
about 120 minutes. In the case where the heat treating time is less
than about 5 minutes, the imidization of the polyamic acid layer
may be insufficiently performed, and in the case where the heat
treating time is longer than about 180 minutes, the polyamic acid
layer and the film formed by the imidization of the polyamic acid
layer may be thermally decomposed, and thus the mechanical
properties of the resulting polyimide film may be deteriorated, and
the yellow index thereof may be increased.
[0106] For example, the task of heat treating a polyamic acid layer
(S300) may be performed at about 300.degree. C. for about 30 to
about 120 minutes. However, an embodiment of the inventive concept
is not limited thereto. In the case where the heat treating
temperature is greater than about 300.degree. C. during the heat
treating task of a polyamic acid layer (S300), the heat treating
time may decrease to about 30 minutes.
[0107] In the fabrication method of a polyimide film of an
embodiment, by performing the task of heat treating a polyamic acid
layer (S300) at high temperature conditions of about 250.degree. C.
to about 550.degree. C., the imidization degree of the polyamic
acid may be increased, the glass transition temperature (T.sub.g)
and thermal decomposition temperature (T.sub.d) of the resulting
polyimide film may be increased to improve heat resistance, and a
thermal expansion coefficient (CTE) may be decreased to increase
dimensional stability. In addition, by performing the task of heat
treating a polyamic acid layer (S300) at high temperature
conditions of about 250.degree. C. to about 550.degree. C., the
yellow index of the polyimide film thus fabricated may be decreased
to improve optical properties.
[0108] In an embodiment, the task of heat treating a polyamic acid
layer (S300) may be performed in a vacuum state. For example, the
task of heat treating a polyamic acid layer (S300) may be performed
at temperature conditions of about 250.degree. C. to about
550.degree. C. and in a vacuum state. For example, the vacuum state
may be a quasi-vacuum state.
[0109] The task of heat treating a polyamic acid layer (S300) may
be performed in isothermal conditions within a certain temperature
range. Alternatively, the task of heat treating a polyamic acid
layer (S300) may be performed by a plurality of heat treating
tasks, where the heat treating tasks are performed in a plurality
of temperature conditions, respectively, in a temperature range of
about 250.degree. C. to about 550.degree. C.
[0110] In the fabrication method of a polyimide film of an
embodiment as shown in FIG. 1, a task of cooling a heat treated
polyamic acid layer (see e.g., S400, FIG. 2) is not illustrated.
However, in the fabrication method of a polyimide film of an
embodiment, the task of cooling a heat treated polyamic acid layer
may be further included after the task of heat treating a polyamic
acid layer (S300).
[0111] The polyimide film of an embodiment fabricated on a
substrate may be used as a supporting substrate of a display
apparatus, after the initial substrate acting as a support is
removed, or as a transparent substrate of an electronic information
material. In an embodiment, the polyimide film and the substrate on
which the polyimide film is provided may be used together as the
supporting substrate of a display apparatus.
[0112] FIG. 2 is a flowchart schematically illustrating a
fabrication method of a polyimide film according to an embodiment
of the present disclosure and is different from the fabrication
method of a polyimide film shown in FIG. 1 in the task of heat
treating a polyamic acid layer.
[0113] In the fabrication method of a polyimide film according to
an embodiment as shown in FIG. 2, a task of heat treating the
polyamic acid layer at a first temperature (S310) and a task of
heat treating the polyamic acid layer at a second temperature
(S320) may be sequentially included after the task of forming a
polyamic acid layer (S200) by supplying the polyamic acid on a
substrate.
[0114] In the fabrication method of a polyimide film according to
an embodiment as shown in FIG. 2, descriptions of a task of
preparing a polyamic acid by a polymerization reaction of a
dianhydride compound with at least two kinds (types) of diamine
compounds (S100) and a task of forming a polyamic acid layer by
supplying the polyamic acid on a substrate (S200) may be the same
as those provided in connection with the fabrication method of a
polyimide film according to an embodiment shown in FIG. 1.
[0115] In the fabrication method of a polyimide film according to
an embodiment as shown in FIG. 2, the task of heat treating the
polyamic acid layer at the first temperature (S310) may be a first
heat treating task, the task of heat treating the polyamic acid
layer at a second temperature (S320) may be a second heat treating
task, following the first heat treating task, and the second
temperature may be higher than the first temperature. For example,
the first temperature may be from about 250.degree. C. to less than
about 300.degree. C., and the second temperature may be from about
300.degree. C. to about 550.degree. C.
[0116] Referring to the fabrication method of a polyimide film
according to an embodiment as shown in FIG. 2, the task of heat
treating, at a high temperature, the polyamic acid layer formed on
the substrate may be performed in two or more tasks. For example,
the task of heat treating the polyamic acid layer may include at
least two heat treating tasks with different temperature conditions
for heat treating. The fabrication method of a polyimide film
according to an embodiment may be performed by at least two heat
treating tasks of the polyamic acid layer, so as to improve the
imidization degree of the polyamic acid and the mechanical
properties of the polyimide film. Accordingly, a polyimide film
having good heat resistance and optical properties may be
obtained.
[0117] In FIG. 2, the task of cooling the heat treated polyamic
acid layer (S400) may be a task of cooling an imidized film to room
temperature, after heat treating the film at a high temperature. In
an embodiment, the task of cooling the heat treated polyamic acid
layer (S400) may be a task of cooling an imidized film to a
temperature below room temperature, after heat treating the film at
a high temperature.
[0118] In the fabrication method of a polyimide film according to
an embodiment, the arrangement of polyimide polymer chains forming
the polyimide film may be controlled by controlling the cooling
rate in the task of cooling the polyamic acid layer (S400), and
thus the heat resistance and optical properties of the resulting
polyimide film may be improved. For example, by performing the task
of cooling the heat treated polyamic acid layer (S400) in a chamber
so as to slowly cool the heat treated polyamic acid layer, the
packing degree of polymer chains may be increased, and a polyimide
film having improved mechanical properties and heat resistance may
be fabricated.
[0119] The polyamic acid used in the fabrication method of a
polyimide film according to an embodiment of FIGS. 1 and 2 may be
the polyamic acid of the present embodiments. In the polyamic acid
prepared by the polymerization reaction of a dianhydride compound
and at least two diamine compounds, the dianhydride compound may
include at least one selected from
4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA),
3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA),
cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) and
pyromellitic dianhydride (PMDA).
[0120] In some embodiments, the at least two kinds (types) of
diamine compounds may include the first diamine compound
represented by Formula 1, and the second diamine compound
represented by Formula 2:
##STR00018##
[0121] In Formula 1, R.sub.1 and R.sub.2 may be each independently
a hydrogen atom, a deuterium atom, a halogen atom, or a substituted
or unsubstituted alkyl group of 1 to 20 carbon atoms. In addition,
n.sub.1 and n.sub.2 may be each independently an integer of 0 to
4.
##STR00019##
[0122] In Formula 2, Ar may be a substituted or unsubstituted
phenyl group, and m may be an integer of 1 to 4.
[0123] Description of the dianhydride compound, the first diamine
compound, the second diamine compound and the polyamic acid
produced by the polymerization reaction of the compounds, may be
the same as the description of the polyamic acid of the
above-described embodiment. The polyamic acid of the present
embodiment may correspond to the polyamic acid prepared by the
polymerization reaction of the dianhydride compound and at least
two kinds (types) of diamine compounds in the fabrication method of
a polyimide film described with reference to FIGS. 1 and 2.
[0124] The polyimide film fabricated by the fabrication method of
the present embodiment may simultaneously (or concurrently) have
excellent optical properties and heat resistance.
[0125] The polyimide film of the present embodiment may be
fabricated by the fabrication method of the polyimide film of the
above-described embodiment. The polyimide film of the present
embodiment may include a repeating unit derived from the polyamic
acid of the present embodiment.
[0126] For example, the repeating unit of the polyimide derived
from the polyamic acid may be represented by the following Formula
4:
##STR00020##
[0127] In Formula 4, A and B may each independently be an integer
of 1 or more. The number average molecular weight (Mn) of the
polyimide according to an embodiment, which may include the
polyimide repeating unit represented by Formula 4, may be from
about 10,000 to about 1,000,000.
[0128] The polyimide film of an embodiment may have a thermal
expansion coefficient of about 10 ppm/.degree. C. to about 20
ppm/.degree. C. The polyimide film may have a thermal expansion
coefficient of about 10 ppm/.degree. C. to about 20 ppm/.degree.
C., while maintaining dimensional stability even at high
temperature conditions.
[0129] In addition, the glass transition temperature of the
polyimide film of an embodiment may be from about 300.degree. C. to
about 420.degree. C. Meanwhile, the thermal decomposition
temperature of the polyimide film of an embodiment may be from
about 400.degree. C. to about 500.degree. C. In this case, the
thermal decomposition temperature may refer to the temperature at a
point when the weight reduction ratio of the polyimide film reaches
about 1%. For example, the thermal decomposition temperature may
refer to the temperature at the moment when the weight of the
polyimide film after heating reduces to 1% based on the weight of
an initial polyimide film before heating.
[0130] The polyimide film of an embodiment may have a high glass
transition temperature of about 300.degree. C. to about 420.degree.
C. and a high thermal decomposition temperature of about
400.degree. C. to about 500.degree. C., and thus may have high
stability and reliability at high temperature conditions.
[0131] Light transmittance of the polyimide film of an embodiment
may be about 95% or more, and the yellow index thereof may be from
1 to 10. In this case, the light transmittance of the polyimide
film may refer to the light transmittance in a visible light
region. In the present disclosure, the light transmittance may
refer to a relative transmittance, when the transmittance of a
glass substrate is set to about 100%. That is, the light
transmittance of the polyimide film may refer to a relative
transmittance based on the transmittance of a glass substrate.
[0132] The light transmittance of the polyimide film of an
embodiment may represent light transmittance at about 550 nm. For
example, the polyimide film of an embodiment may have a high light
transmittance of about 95% or more and a low yellow index of about
1 to about 10, and may be used as an optical film requiring
transparency or a substrate of a display apparatus.
[0133] The polyimide film of an embodiment may simultaneously (or
concurrently) have a light transmittance of about 95% or more, and
a thermal expansion coefficient of about 10 ppm/.degree. C. to
about 20 ppm/.degree. C. For example, the polyimide film of an
embodiment may simultaneously (or concurrently) have a light
transmittance of about 95% or more, a thermal expansion coefficient
of about 10 ppm/.degree. C. to about 20 ppm/.degree. C., and a
glass transition temperature of about 300.degree. C. to about
420.degree. C.
[0134] In an embodiment, the polyimide film may simultaneously (or
concurrently) have a light transmittance of about 95% or more, a
yellow index of about 1 to about 10, and a glass transition
temperature of about 300.degree. C. to about 420.degree. C.
[0135] The polyimide film of an embodiment may be fabricated from
the polyamic acid of an embodiment, which in turn may represent a
polymerization reaction product of a dianhydride compound and at
least two kinds (types) of diamine compounds, and the polyimide
film may have high heat resistance and excellent optical
properties.
[0136] The polyimide film of an embodiment may have a high light
transmittance and a low yellow index, and in addition, a high glass
transition temperature and a high thermal decomposition
temperature, and may be used as a substrate of a display apparatus
requiring excellent optical properties, heat resistance and
mechanical strength. In addition, the polyimide film of an
embodiment is a polymer film having dimensional stability and
excellent mechanical properties, and may be used as a supporting
substrate of a flexible display apparatus, etc.
[0137] The polyimide film of an embodiment may be fabricated using
a polyamic acid prepared by polymerizing a dianhydride compound and
the combination of at least two diamine compounds, and the
polyimide film may have high heat resistance and good optical
properties. Accordingly, the polyimide film may be used as a
material for a transparent substrate of a display apparatus
requiring a manufacturing process at a high temperature.
[0138] Hereinafter, a polyamic acid according to an embodiment, and
a polyimide film of an embodiment, fabricated by a fabrication
method of a polyimide film of an embodiment will be explained with
reference to example embodiments and comparative embodiments. The
following embodiments are provided only for illustration and to
assist the understanding of the inventive concept, however, and the
scope of the inventive concept is not limited thereto.
Examples
1. Preparation of Polyamic Acid
[0139] A polyamic acid of an embodiment was prepared by a
condensation polymerization method in a solution phase using a
dianhydride compound, and two kinds (types) of diamine compounds
including a first diamine compound and a second diamine compound,
while maintaining a molar ratio of about 1:1, through the following
tasks.
[0140] In this case, the dianhydride compound was
3,3',4,4'-biphenyltetracarboxyl dianhydride (BPDA), the first
diamine compound was 2,2'-bis(trifluoromethyl)benzidine (TFMB), and
the second diamine compound was 3,5-diaminobenzoic acid (DABA).
[0141] The mixing molar ratios of the dianhydride compound, the
first diamine compound, and the second diamine compound used in
embodiments are listed in Table 1 below. In the following Examples,
the diamine compound, including the first diamine compound and the
second diamine compound, and the dianhydride were mixed in a molar
ratio of about 1:1 (diamine compound:dianhydride), while a molar
ratio of the first diamine compound to the second diamine compound
was varied from about 0.5:0.5 to about 0.9:0.1.
TABLE-US-00001 TABLE 1 Diamine compound (mole %) First diamine
Second diamine Dianhydride compound Example compound compound (mole
%) 1 90 10 100 2 80 20 100 3 75 25 100 4 65 35 100 5 50 50 100
[0142] First, nitrogen (99.99%) was injected into a flask at a rate
of about 100 ml/min for about 10 minutes to fill the interior of
the flask with nitrogen. Then, a nitrogen injector including a 0.2
.mu.m separator membrane filter was installed in the flask, and
nitrogen was injected at a rate of about 20 ml/min, so that the
interior of the flask maintained a nitrogen-charged state during
the polymerization reaction of a polyamic acid.
[0143] N,N-dimethyl acetamide (DMAc, Duksan Pure Chemicals Co.,
Ltd., Korea) with purity of about 95% was injected into the flask
as an organic solvent, and a first diamine compound and a second
diamine compound were mixed in a molar ratio shown in Table 1 with
the organic solvent to prepare a diamine compound solution with a
concentration of 2 m (molality, molal concentration). Then, the
solution thus prepared was left at room temperature (about
25.degree. C.) for about 5 to about 20 minutes under a nitrogen
atmosphere to completely dissolve the diamine compounds to prepare
a diamine compound solution.
[0144] In addition, DMAc was injected into a separate flask, and
3,3',4,4'-biphenyltetracaroxylic acid dianhydride (BPDA) was
injected thereto to prepare a solution of 2 m concentration. Then,
the solution thus prepared was left at room temperature (about
25.degree. C.) for about 5 to about 20 minutes under a nitrogen
atmosphere to completely dissolve the dianhydride compound to
prepare a dianhydride compound solution.
[0145] After that, the dianhydride compound solution was added to
the flask including the diamine compound solution, and DMAc was
added thereto, so that a polyamic acid solid content was about 20
wt %, followed by mixing the resulting product at a temperature
range of room temperature (about 25.degree. C.) to a low
temperature (about -10.degree. C.) under a nitrogen atmosphere for
about 22 hours at a speed of about 60 rpm to about 100 rpm, to
prepare a polyamic acid polymer solution via a polymerization
reaction. The resulting polyamic acid polymer solution included
about 20 wt % of the polyamic acid polymer in a solid content, and
synthesis conditions were controlled to obtain the viscosity of a
solution of about 5000.+-.300 cps.
2. Fabrication of Polyimide Film
[0146] The polyamic acid prepared by the above-described method was
applied to a glass substrate. In this case, the glass substrate
included soda-lime glass (MATSUNAMI (Japan)) and/or borosilicate
glass (MATSUNAMI (Japan)). In order to remove foreign substances
and/or impurities from the glass substrate, the glass substrate was
cleaned in acetone for about 10 minutes using an ultrasonicator and
then in isopropyl alcohol (IPA) for about 10 minutes. Then, the
resulting glass substrate was sufficiently and repeatedly cleaned
in de-ionized water with 17 MO or more for about 30 minutes, and
dried in a convection-type drying oven at about 120.degree. C. for
about 60 minutes.
[0147] On the glass substrate thus cleansed and dried, the polyamic
acid solution prepared by the above-described method was coated,
and a thin film was formed using a spin-coater or a slit-die
coater. The coated layer of the polyamic acid solution was
pre-dried using a hot plate at about 50.degree. C. for about 60
minutes, and then additionally dried at about 70.degree. C. for
about 120 minutes to remove organic solvents and to form a polyamic
acid layer. After drying the organic solvents, the thickness of the
polyamic acid layer was measured using a surface profiler (Dektak
150, Veeco Instruments, Inc., USA), and the thickness of the
polyamic acid layer thus measured was about 18.+-.2 .mu.m.
[0148] The glass substrate on which the polyamic acid layer was
formed was injected into a self-designed reactor, and the polyamic
acid layer was heat treated. In this case, the self-designed
reactor was kept in a vacuum state.
[0149] The heat treating of the polyamic acid layer was conducted
in two tasks. In the first heat treating task, the temperature of
the reactor was elevated at a rate of about 4.degree. C. per minute
to about 270.degree. C., and then an isothermal state was
maintained at about 270.degree. C. for about 120 minutes. After
that, the temperature was elevated at a rate of 5.degree. C. per
minute to a final temperature of about 400.degree. C., and an
isothermal state was maintained at about 400.degree. C. for about
60 minutes to conduct the second heat treating task.
[0150] By conducting the above-described heat treating tasks, the
polyamic acid layer was thermally imidized to fabricate a polyimide
film.
3. Evaluation of Properties of the Polyimide Film
[0151] The optical properties and heat resistance of the polyimide
film fabricated by the above-described method were evaluated, and
the results are shown in Table 2. The evaluation results were
compared to those obtained in comparative embodiments. In
comparative embodiments, polyimide films were fabricated by the
same method as the one described above, except for using only one
kind (type) of a diamine compound.
[0152] In Comparative Example 1, only
2,2'-bis(trifluoromethyl)benzidine (TFMB) was used as the diamine
compound, and in Comparative Example 2, only 3,5-diaminobenzoic
acid (DABA) was used as the diamine compound.
[0153] In order to evaluate optical properties, light transmittance
(total transmittance) was measured at a wavelength of about 550 nm
and yellow index (Y.I.) was measured by an ASTM D1925 method using
a measurement apparatus of chromaticity and brightness (Array
spectrometer MCPD-3000, Otsuka Electronics, JAPAN). The light
transmittance was evaluated as relative transmittance on the basis
of the transmittance of a glass substrate. That is, the light
transmittance in Table 2 represents a relative transmittance of a
polyimide film obtained when the transmittance of the glass
substrate was set to 100%.
[0154] In order to evaluate heat resistance, a glass transition
temperature (T.sub.g) and a thermal expansion coefficient (CTE)
were measured using Thermomechanical Analyzer (TMA Q400 TA
Instruments). A sample was taken by cutting a polyimide film
fabricated by the above-described method into a size of 2
mm.times.16 mm, and fixed with a load of about 0.03 N under a
nitrogen environment to stabilize, and the length change of the
sample polyimide film was measured. A thermal expansion coefficient
was evaluated by measuring the expansion degree of the sample
polyimide film in a length direction on a plane. In order to
minimize (reduce) the influence of external factors such as
humidity and dusts, the sample polyimide film was heated at a rate
of about 10.degree. C./min to about 150.degree. C., cooled
naturally to about 40.degree. C., and heated again at a rate of
about 10.degree. C./min to about 500.degree. C., before obtaining
final measurements. The thermal expansion coefficient was measured
in a temperature range of about 50.degree. C. to about 250.degree.
C.
[0155] A thermal decomposition temperature (T.sub.d) was measured
by measuring weight reduction according to the temperature, using
Thermogravimetric Analyzer (TGA Q600 TA Instruments). The weight of
a specimen was 4 mg (.+-.0.2 mg). The thermal decomposition
temperature was measured by the same method as the one used for
measuring the thermal expansion coefficient (using TMA under
nitrogen environment by a two-task heat treatment and by taking
final measurements). First, in the first heat treating task, the
temperature of the specimen was elevated at a rate of about
20.degree. C. per minute to about 250.degree. C., and then
naturally cooled to about 150.degree. C., and in the second heat
treating task, the temperature was elevated at the same rate to
about 700.degree. C. Thermal stability was evaluated by measuring
the thermal decomposition temperature, which refers to a
temperature at which the weight of the specimen is decreased due to
thermal decomposition. In Table 2, T.sub.d, 1% refers to a
temperature at which the weight of the specimen was decreased by
about 1% due to thermal decomposition, and T.sub.d, 0.5% refers to
a temperature at which the weight of the specimen was decreased by
about 0.5% due to thermal decomposition. In this case, a weight of
about 100% was based on the weight at about 200.degree. C. after
the first heat treating.
TABLE-US-00002 TABLE 2 Trans- CTE mittance T.sub.d, 1% T.sub.d,
0.5% (ppm/ T.sub.g (%) Y.I. (.degree. C.) (.degree. C.) .degree.
C.) (.degree. C.) Example 1 96.8 5.9 469 438 14.7 322 2 96.7 5.9
457 430 15.5 340 3 96.1 6.1 458 438 16.0 361 4 95.6 6.1 456 429
18.0 382 5 95.6 6.2 436 375 19.2 383 Comparative 1 87.4 30.6 491
425 19.5 318 Example 2 92.0 9.3 429 391 31.5 400
[0156] Referring to the results shown in Table 2, it was found that
the polyimide films of Examples 1 to 5 exhibited a high optical
transmittance and a low yellow index when compared with the
polyimide films of Comparative Examples 1 and 2. That is, the
polyimide films fabricated in Examples 1 to 5 by including at least
two kinds (types) of diamine compounds exhibited better optical
properties when compared with the polyimide films fabricated in the
Comparative Examples by including only one kind (type) of a diamine
compound.
[0157] In addition, the polyimide films of Examples 1 to 5
exhibited a lower thermal expansion coefficient when compared with
the polyimide films of Comparative Examples 1 and 2. That is, the
polyimide films of the Examples formed by including at least two
kinds (types) of diamine compounds may have a lower thermal
expansion coefficient and higher dimensional stability when
compared with the polyimide films of the Comparative Examples
formed by including only one kind of a diamine compound.
[0158] Further referring to Table 2, it may be found that the
polyimide films of Examples 1 to 5 exhibited a higher thermal
decomposition temperature, T.sub.d, 1%, when compared with the
polyimide film of Comparative Example 2. That is, the polyimide
films of the Examples formed by including at least two kinds
(types) of diamine compounds had improved heat resistance when
compared with the polyimide film using only 3,5-diaminobenzoic acid
(DABA) as the diamine compound.
[0159] In addition, it may be found that the polyimide films of
Examples 1 to 5 had a remarkably improved optical transmittance and
yellow index when compared with the polyimide film of Comparative
Example 1. That is, the polyimide films of the Examples formed by
including at least two kinds (types) of diamine compounds had
significantly improved optical properties when compared with the
polyimide film using only 2,2'-bis(trifluoromethyl)benzidine (TFMB)
as the diamine compound.
[0160] The polyamic acid of an embodiment, and the polyimide film
of an embodiment fabricated using the polyamic acid may have a high
glass transition temperature, a high thermal decomposition
temperature, and a low thermal expansion coefficient, and thus, a
polyimide film with improved heat resistance may be attained. In
addition, the polyamic acid of an embodiment, and the polyimide
film of an embodiment fabricated using the polyamic acid may have
excellent (or suitable) heat resistance properties, while
maintaining a high optical transmittance and a low yellow index,
and thus, a polyimide film having excellent (or suitable) optical
properties may be attained.
[0161] The polyamic acid of the present embodiments may be
polymerized using at least two different kinds (types) of diamine
compounds, and may be used for the fabrication of a polyimide film
having high heat resistance and excellent optical properties. In
addition, according to the fabrication method of the present
embodiments, the polyimide film of the present embodiments may be
fabricated by using the polyamic acid (polymerized by using at
least two different kinds (types) of diamine compounds), and by
treating the polyamic acid thus prepared under high temperature
heat treating conditions, to carry out an imidization reaction of
the polyamic acid. The resulting polyimide film may have high heat
resistance and excellent optical properties.
[0162] The polyamic acid according to an embodiment of the present
disclosure may include two different kinds (types) of diamine
compounds and may be utilized as a material for forming a polyimide
film having excellent optical properties and high heat
resistance.
[0163] The polyimide film according to an embodiment of the present
disclosure may use the polyamic acid (formed by including two
different kinds (types) of diamine compounds), and may have
excellent optical properties and heat resistance.
[0164] The fabrication method of a polyimide film according to an
embodiment of the present disclosure may use the polyamic acid
(formed by including two different kinds (types) of diamine
compounds) and by heat treating the polyamic acid at a high
temperature, to provide a polyimide film having excellent optical
properties and heat resistance.
[0165] As used herein, the terms "use," "using," and "used" may be
considered synonymous with the terms "utilize," "utilizing," and
"utilized," respectively.
[0166] In addition, the terms "substantially," "about," and similar
terms are used as terms of approximation and not as terms of
degree, and are intended to account for the inherent deviations in
measured or calculated values that would be recognized by those of
ordinary skill in the art.
[0167] Also, any numerical range recited herein is intended to
include all subranges of the same numerical precision subsumed
within the recited range. For example, a range of "1.0 to 10.0" is
intended to include all subranges between (and including) the
recited minimum value of 1.0 and the recited maximum value of 10.0,
that is, having a minimum value equal to or greater than 1.0 and a
maximum value equal to or less than 10.0, such as, for example, 2.4
to 7.6. Any maximum numerical limitation recited herein is intended
to include all lower numerical limitations subsumed therein and any
minimum numerical limitation recited in this specification is
intended to include all higher numerical limitations subsumed
therein. Accordingly, Applicant reserves the right to amend this
specification, including the claims, to expressly recite any
sub-range subsumed within the ranges expressly recited herein.
[0168] Although the example embodiments of the present invention
have been described herein, it will be understood that the present
invention should not be limited to these example embodiments, but
various changes and modifications can be made by one of ordinary
skill in the art within the spirit and scope of the present
invention, as defined by the following claims and equivalents
thereof.
[0169] The technical scope of the present inventive concept should
therefore be determined not by the description in the specification
but by the attached claims.
* * * * *