U.S. patent application number 13/728565 was filed with the patent office on 2014-05-22 for amorphous copolyester, substrate, and optical film.
This patent application is currently assigned to INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE. The applicant listed for this patent is INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE. Invention is credited to Cheng-Hsing FAN, Li-Cheng JHENG, Ming-Tsong LEU, Kuo-Chen SHIH.
Application Number | 20140142247 13/728565 |
Document ID | / |
Family ID | 50728538 |
Filed Date | 2014-05-22 |
United States Patent
Application |
20140142247 |
Kind Code |
A1 |
FAN; Cheng-Hsing ; et
al. |
May 22, 2014 |
AMORPHOUS COPOLYESTER, SUBSTRATE, AND OPTICAL FILM
Abstract
Disclosed is an amorphous copolyester polymerized of a diacid
and diols. The diacid is selected from a group consisting of
terephthalic acid, 5-tert-butylisophthalic acid, and dimethyl
2,6-naphthalenedicarboxylate. The diols are selected at least two
from a group consisting of ethylene glycol,
2,2-dimethyl-1,3-propanediol, and tricyclodecanedimethanol. The
molar ratio of the tricyclodecanedimethanol is 30% to 95% of the
diols.
Inventors: |
FAN; Cheng-Hsing; (Taichung
City, TW) ; SHIH; Kuo-Chen; (Kaohsiung City, TW)
; LEU; Ming-Tsong; (Qishan Town, TW) ; JHENG;
Li-Cheng; (Kaohsiung City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE |
Chutung |
|
TW |
|
|
Assignee: |
INDUSTRIAL TECHNOLOGY RESEARCH
INSTITUTE
Chutung
TW
|
Family ID: |
50728538 |
Appl. No.: |
13/728565 |
Filed: |
December 27, 2012 |
Current U.S.
Class: |
524/787 ;
524/789; 528/298 |
Current CPC
Class: |
C08K 3/26 20130101; C08K
3/36 20130101; C08K 3/36 20130101; C08K 2003/265 20130101; G02B
1/04 20130101; C08G 63/199 20130101; C08K 3/26 20130101; C08K 3/34
20130101; C08G 63/181 20130101; C08L 67/02 20130101; C08K 3/013
20180101; C08L 67/02 20130101; C08L 67/02 20130101; C08L 67/02
20130101; G02B 1/04 20130101; C08K 3/013 20180101 |
Class at
Publication: |
524/787 ;
528/298; 524/789 |
International
Class: |
C08G 63/181 20060101
C08G063/181; C08K 3/26 20060101 C08K003/26; C08K 3/34 20060101
C08K003/34 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 21, 2012 |
TW |
101143374 |
Claims
1. An amorphous copolyester, polymerized of a diacid and diols,
wherein the diacid is selected from a group consisting of
terephthalic acid and 5-tert-butylisophthalic acid, wherein the
diols are tricyclodecanedimethanol and at least one diol selected
from the group consisting of ethylene glycol and
2,2-dimethyl-1,3-propanediol, and the molar ratio of the
tricyclodecanedimethanol is 30% to 95% of the diols.
2. The amorphous copolyester as claimed in claim 1, comprising: an
A molar ratio of a repeating unit ##STR00007## and a B molar ratio
of a repeating unit ##STR00008## wherein A+B=1, and
0.3.ltoreq.A.ltoreq.0.95.
3. The amorphous copolyester as claimed in claim 1, comprising: a C
molar ratio of a repeating unit ##STR00009## and a D molar ratio of
a repeating unit ##STR00010## wherein C+D=1, and
0.3.ltoreq.C.ltoreq.0.95.
4. An amorphous copolyester, comprising: an E molar ratio of a
repeating unit ##STR00011## and an F molar ratio of a repeating
unit ##STR00012## wherein E+F=1, and 0.7.ltoreq.E.ltoreq.0.95.
5. The amorphous copolyester as claimed in claim 1, wherein the
amorphous copolyester has an intrinsic viscosity of about 0.5 dL/g
to 0.8 dL/g.
6. A substrate, comprising the amorphous copolyester as claimed in
claim 1.
7. The substrate as claimed in claim 6, further comprising
inorganic nano powders mixed into the amorphous copolyester,
wherein the inorganic nano powders comprise silicon oxide, titanium
oxide, calcium carbonate, strontium carbonate, barium sulfate,
aluminum oxide, or combinations thereof, and the inorganic nano
powders and the amorphous copolyester have a weight ratio of larger
than 0:100 and less than or equal to 1:100.
8. An optical film, comprising the amorphous copolyester as claimed
in claim 1.
9. The optical film as claimed in claim 8, further comprising
inorganic nano powders mixed into the amorphous copolyester,
wherein the inorganic nano powders comprise silicon oxide, titanium
oxide, calcium carbonate, strontium carbonate, barium sulfate,
aluminum oxide, or combinations thereof, and the inorganic nano
powders and the amorphous copolyester have a weight ratio of larger
than 0:100 and less than or equal to 1:100.
10. The optical film as claimed in claim 8, comprising an optical
protective film of a liquid crystal display, a release film, a
brightness enhancement film, a retardation film, a polarizer
protective film, or an anti-reflection film.
11. A substrate, comprising the amorphous copolyester as claimed in
claim 2.
12. A substrate, comprising the amorphous copolyester as claimed in
claim 3.
13. A substrate, comprising the amorphous copolyester as claimed in
claim 4.
14. A substrate, comprising the amorphous copolyester as claimed in
claim 5.
15. An optical film, comprising the amorphous copolyester as
claimed in claim 2.
16. An optical film, comprising the amorphous copolyester as
claimed in claim 3.
17. An optical film, comprising the amorphous copolyester as
claimed in claim 4.
18. An optical film, comprising the amorphous copolyester as
claimed in claim 5.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is based on, and claims priority
from, Taiwan Application Serial Number 101143374, filed on Nov. 21,
2012, the disclosure of which is hereby incorporated by reference
herein in its entirety
TECHNICAL FIELD
[0002] The technical field relates to a copolyester, and in
particular, to an amorphous copolyester.
BACKGROUND
[0003] Polyester film is an excellent plastic film, which can be
applied as a peripheral material of a computer, e.g. keyboard,
panel protection film, electrical insulative material for a panel
back light module, or a magnetic substrate such as a computer
magnetic tape. Alternately, the polyester film can be applied as
food package, plated metal film, electrical insulative material,
stationery, another livelihood industry, or another industry.
[0004] In general, the polyester film has excellent properties,
e.g. high tensile strength, good impact resistance, high melting
point for being used at a higher temperature. As such, the
polyester film may serve as a protective material or a substrate
material. Next, the polyester film has high transmittance,
brightness, and smooth surface for being used in tag, adhering,
printing, or the likes. The polyester film also withstand a high
voltage, thereby being an electrical insulative material for
wrapping wire, an insulative tape, a motor transformer, a
capacitor, or the likes. The polyester film is not dissolved in
organic solvents. Moreover, the polyester film has excellent acid
resistance and oil resistance.
[0005] Since 1953, biaxial oriented polyester film is developed for
various fields. The biaxial oriented polyester film is widely
applied in electronics, equipments, magnetic records, packages,
plate making printings, photosensitive materials due to its
excellent physical and chemical properties.
[0006] The biaxial oriented polyester film is the major packaging
material for high performance application or higher level products.
For example, the biaxial oriented polyester film may serve as a
brightness enhancement film substrate of a backlight module in a
panel flat display (PFD), a protection film of optical degree and
release film for a polarizer plate, an ITO substrate of a touch
panel, and the likes.
[0007] The biaxial oriented polyester film for the PFD should
simultaneously meet the requirements of high transmittance and low
birefringence. In other words, a novel biaxial oriented polyester
film is still called-for.
SUMMARY
[0008] One embodiment of the disclosure provides an amorphous
copolyester, polymerized of a diacid and diols, wherein the diacid
is selected from a group consisting of terephthalic acid,
5-tert-butylisophthalic acid, and dimethyl
2,6-naphthalenedicarboxylate, wherein the diols are selected at
least two from a group consisting of ethylene glycol,
2,2-dimethyl-1,3-propanediol, and tricyclodecanedimethanol, and the
molar ratio of the tricyclodecanedimethanol is 30% to 95% of the
diols.
[0009] One embodiment of the disclosure provides a substrate
comprising the described amorphous copolyester.
[0010] One embodiment of the disclosure provides an optical film
comprising the described amorphous copolyester.
[0011] A detailed description is given in the following embodiments
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The disclosure can be more fully understood by reading the
subsequent detailed description and examples with references made
to the accompanying drawings, wherein:
[0013] FIG. 1 shows heat flow versus temperature curves of several
copolyesters analyzed by a differential scanning calorimeter in one
embodiment of the disclosure;
[0014] FIG. 2 shows heat flow versus temperature curves of several
copolyesters analyzed by a differential scanning calorimeter in one
embodiment of the disclosure;
[0015] FIG. 3 shows heat flow versus temperature curves of several
copolyesters analyzed by a differential scanning calorimeter in one
embodiment of the disclosure;
[0016] FIG. 4 shows birefringence (.DELTA.Nx-y) versus biaxial
stretching ratio curves of several copolyesters in one embodiment
of the disclosure;
[0017] FIG. 5 shows birefringence (.DELTA.Nx-y) versus biaxial
stretching ratio curves of several copolyesters in one embodiment
of the disclosure;
[0018] FIG. 6 shows birefringence (.DELTA.Nx-y) versus biaxial
stretching ratio curves of several copolyesters in one embodiment
of the disclosure;
[0019] FIG. 7 shows birefringence (.DELTA.Nx-y) versus biaxial
stretching ratio curves of several copolyesters in one embodiment
of the disclosure; and
[0020] FIG. 8 shows heat flow versus temperature curves of several
copolyesters analyzed by a differential scanning calorimeter in one
embodiment of the disclosure.
DETAILED DESCRIPTION
[0021] In the following detailed description, for purposes of
explanation, numerous specific details are set forth in order to
provide a thorough understanding of the disclosed embodiments. It
will be apparent, however, that one or more embodiments may be
practiced without these specific details. In other instances,
well-known structures and devices are schematically shown in order
to simplify the drawing.
[0022] In embodiments of the disclosure, different monomers are
condensation polymerized to form a thin plate of a random amorphous
copolyester. The thin plate is then biaxial stretched to form a
copolyester film.
[0023] In one embodiment, the diacid is selected from a group
consisting of terephthalic acid (TPA), 5-tert-butylisophthalic acid
(5tBIA), and dimethyl 2,6-naphthalenedicarboxylate (NDC) which is
copolymerized to form the amorphous copolyester. The diols are
selected at least two from a group consisting of ethylene glycol
(EG), 2,2-dimethyl-1,3-propanediol (DMPD), and
tricyclodecanedimethanol (TCD) which is copolymerized to form the
amorphous copolyester. Note that the molar ratio of
tricyclodecanedimethanol is about 30% to 95% of the diols (which
means the tricyclodecanedimethanol occupies a molar ratio of 30% to
95% of the diols). In one embodiment, an overly high molar ratio of
the tricyclodecanedimethanol may make the copolyester too brittle
to form a film. In another embodiment, an overly low molar ratio of
the tricyclodecanedimethanol may make the copolyester crystallize,
such that the copolyester has an overly high birefringence and an
overly low thermal resistance. In one embodiment, the amorphous
copolyester has an intrinsic viscosity of about 0.5 dL/g to 0.8
dL/g.
[0024] In one embodiment, the diacid and the diols are
esterificated and then condensation polymerized by two steps to
form the amorphous copolyester. The copolyester has an A molar
ratio of a repeating unit as shown in Formula 1, and a B molar
ratio of a repeating unit as shown in Formula 2. A+B=1, and
0.3.ltoreq.A.ltoreq.0.95. The molar ratios of A and B are
determined by the DMPD and TCD amounts. In one embodiment, a
condensation polymerization catalyst such as an antimony-based
catalyst, a titanium-based catalyst, a germanium-based catalyst, a
tin-based catalyst, a gallium-based catalyst, an aluminum-based
catalyst, or combinations thereof can be added during
polymerization. In one embodiment, the catalyst is antimony acetate
or tetra-butyl titanate. The catalyst content is of about 25 ppm to
500 ppm.
##STR00001##
[0025] In one embodiment, the amorphous copolyester composed of the
repeating units as shown in Formulae 1 and 2 has an intrinsic
viscosity of about 0.5 dL/g to 0.8 dL/g. In one embodiment, the
amorphous copolyester composed of the repeating units as shown in
Formulae 1 and 2 having an overly high intrinsic viscosity cannot
be easily processed due to low flowability. In another embodiment,
the amorphous copolyester composed of the repeating units as shown
in Formulae 1 and 2 having an overly low intrinsic viscosity cannot
form a film due to low mechanical properties.
[0026] In addition, the repeating unit as shown in Formula 1 may
have the chemical structure of Formulae 3 to 8 or combinations
thereof, which is determined by the TCD structure.
##STR00002##
[0027] In one embodiment, the diacid and the diols are
esterificated and then condensation polymerized by two steps to
form the amorphous copolyester. The copolyester has a C molar ratio
of a repeating unit as shown in Formula 9, and a D molar ratio of a
repeating unit as shown in Formula 10. C+D=1, and
0.3.ltoreq.C.ltoreq.0.95. The molar ratios of C and D are
determined by the EG and TCD amounts. In one embodiment, a
condensation polymerization catalyst such as an antimony-based
catalyst, a titanium-based catalyst, a germanium-based catalyst, a
tin-based catalyst, a gallium-based catalyst, an aluminum-based
catalyst, or combinations thereof can be added during
polymerization. In one embodiment, the catalyst is antimony acetate
or tetra-butyl titanate. The catalyst content is of about 25 ppm to
500 ppm.
##STR00003##
[0028] In one embodiment, the amorphous copolyester composed of the
repeating units as shown in Formulae 9 and 10 has an intrinsic
viscosity of about 0.5 dL/g to 0.8 dL/g. In one embodiment, the
amorphous copolyester composed of the repeating units as shown in
Formulae 9 and 10 having an overly high intrinsic viscosity cannot
be easily processed due to low flowability. In another embodiment,
the amorphous copolyester composed of the repeating units as shown
in Formulae 9 and 10 having an overly low intrinsic viscosity
cannot form a film due to low mechanical properties.
[0029] In addition, the repeating unit as shown in Formula 9 may
have the chemical structure of Formulae 11 to 16 or combinations
thereof, which is determined by the TCD structure.
##STR00004##
[0030] In one embodiment, the diacid and the diols are
esterificated and then condensation polymerized by two steps to
form the amorphous copolyester. The copolyester has E molar ratio
of a repeating unit as shown in Formula 17, and F molar ratio of a
repeating unit as shown in Formula 18. E+F=1, and
0.3.ltoreq.E.ltoreq.0.95. The molar ratios of E and F are
determined by the EG and TCD amounts. In one embodiment, a
condensation polymerization catalyst such as an antimony-based
catalyst, a titanium-based catalyst, a germanium-based catalyst, a
tin-based catalyst, a gallium-based catalyst, an aluminum-based
catalyst, or combinations thereof can be added during
polymerization. In one embodiment, the catalyst is antimony acetate
or tetra-butyl titanate. The catalyst content is of about 25 ppm to
500 ppm.
##STR00005##
[0031] In one embodiment, the amorphous copolyester composed of the
repeating units as shown in Formulae 17 and 18 has an intrinsic
viscosity of about 0.5 dL/g to 0.8 dL/g. In one embodiment, the
amorphous copolyester composed of the repeating units as shown in
Formulae 17 and 18 having an overly high intrinsic viscosity cannot
be easily processed due to low flowability. In another embodiment,
the amorphous copolyester composed of the repeating units as shown
in Formulae 17 and 18 having an overly low intrinsic viscosity
cannot form a film due to low mechanical properties.
[0032] In addition, the repeating unit as shown in Formula 17 may
have the chemical structure of Formulae 19 to 24 or combinations
thereof, which is determined by the TCD structure.
##STR00006##
[0033] As described above, different monomers can be introduced
into the polymer by condensation polymerization, thereby forming
the random amorphous copolyester. In one embodiment, inorganic nano
powders can be added into the diacid and the diols, and the diacid
and the diols are then polymerized. The inorganic nano powders
mixed in the amorphous copolyester may reduce the birefringence of
the amorphous copolyester. The inorganic nano powders can be
silicon oxide, titanium oxide, calcium carbonate, strontium
carbonate, barium sulfate, aluminum oxide, or combinations thereof.
The inorganic nano powders can be layered structure with a high
aspect ratio, such as modified clay with different aspect ratios.
The inorganic nano powders and the amorphous polyester have a
weight ratio of larger than 0:100 and less than or equal to 1:100
(0:100<w/w.ltoreq.1:100). An overly high amount of the inorganic
nano powders may reduce the light transmittance of the copolyester
film. The copolyester (or mixed with the inorganic nano powders) is
then molten and processed by a twin screw extruder with a screw
rotation rate of about 200 rpm to 800 rpm at a temperature of
220.degree. C. to 300.degree. C. Thereafter, the molten copolyester
is extruded by a T-die to form a plate. The plate then passes
through a casting drum to achieve a uniform thickness. The casting
temperature is usually lower than the glass transition temperature
(Tg) of the copolyester, such that the molten copolyester is
quickly cooled.
[0034] Subsequently, the extruded amorphous copolyester plate is
biaxial stretched to form a film. For example, the plate can be
stretched by one step or step by step in a hot air circulating
oven. Alternatively, the biaxial stretching is a continuous
two-step stretching process. First, the plate is stretched
according to a longitudinal direction of the plate by a heated
roll, thereby increasing the tensile strength in the machine
direction (MD) of the film. Next, the stretched plate is heated by
circulating hot air and then stretched according to a transverse
direction (TD) of the plate in an oven. If the plate is
simultaneously biaxially stretched in one step by a biaxial
stretching machine (Bruckner KARO IV), the copolyester molecules in
the plate will be orientated during the stretching, thereby forming
an anisotropic film. The plate can be simultaneously biaxially
stretched to form the film at a stretching temperature of about
90.degree. C. to 160.degree. C., a hot air circulating motor
rotation rate of 1400 rpm to 1800 rpm, and a stretching rate of 1
mm/sec to 100 mm/sec for a stretching times (length.times.width) of
1.times.1 to 6.5.times.6.5.
[0035] The film was then thermal treated at a specific temperature
for a period. The biaxially stretched polymer chains of the film
are straightened by external stress, such that the polymer
molecules move to largely deform. If the film is directly cooled to
a temperature lower than the Tg of the film when molded, internal
stress will remain in molecules. As such, the dimension of the
directly cooled film was unstable. In other words, thermal setting
treatment is for the film to have low thermal contraction. The
thermal setting treatment may relax short chains or branch chains
of the stretched polymer, thereby eliminating the internal stress
and thermal contraction of the film. In one embodiment, the thermal
treatment is performed at a temperature of about 80.degree. C. to
130.degree. C. for a period of about 3 seconds to 180 seconds.
[0036] A single layered and non-stretched plate composed of the
polymer can be directly extruded by a twin screw extruder.
Alternatively, the polymer can be extruded to form strips and then
cut to form pellets. The pellets are thermal pressed to form the
single layered and non-stretched plate.
[0037] Because the copolyester has a low retardation variation and
an excellent light transmittance after being stretched, it may
serve as a substrate of a flexible electronic device. Furthermore,
the copolyester may serve as a substrate (e.g. light guide plate,
diffusion film, or touch panel) of a display device, or an optical
film (e.g. an optical protective film of a liquid crystal display,
a release film, a brightness enhancement film, a retardation film,
a polarizer protective film, or an anti-reflection film) on the
substrate.
[0038] Below, exemplary embodiments will be described in detail
with reference to accompanying drawings so as to be easily realized
by a person having ordinary knowledge in the art. The inventive
concept may be embodied in various forms without being limited to
the exemplary embodiments set forth herein. Descriptions of
well-known parts are omitted for clarity, and like reference
numerals refer to like elements throughout.
EXAMPLES
Comparative Example 1
[0039] PET pellets were vibration sieved by a screen mesh to remove
fine dust and fragments thereon. The sieved PET pellets were then
dried by a hot air circulating oven at 70.degree. C. for 24 hours
to ensure that the PET pellets were completely dried. The physical
properties of the dried PET pellets were tested as shown in Table
1.
[0040] 100 parts by weight of PET was molten and processed by a
twin screw extruder with a screw rotation rate of about 300 rpm to
500 rpm at a temperature of 270.degree. C. to 280.degree. C.
Thereafter, the molten PET was extruded by a T-die to form a
transparent plate. The transparent plate was then passed through a
casting drum at a temperature of 60.degree. C. to 70.degree. C. to
achieve a uniform thickness. The plate was cut to 117 mm.times.117
mm, and then simultaneously biaxially stretched at a stretching
temperature of 90.degree. C. to 100.degree. C., a hot air
circulating motor rotation rate of 1700 rpm, and a stretching rate
of 10 mm/sec to 100 mm/sec for a biaxially stretching times
(length.times.width) of 1.25.times.1.25 to 4.times.4 for forming
films. The films were thermal treated at a temperature of
190.degree. C. to 210.degree. C. for 3 seconds to 9 seconds, and
the physical properties of the films were measured and tabulated in
Table 2.
Comparative Example 2
[0041] 166 g of TPA serving as diacid and 93.6 g of DMPD (90 mol %)
and 19.6 g of TCD (10 mol %) serving as diols were esterificated at
240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.1 molar ratio of the repeating unit in Formula
1 and 0.9 molar ratio of the repeating unit in Formula 2 (A=0.1,
B=0.9) was obtained. The intrinsic viscosity (0.69 dL/g) of the
amorphous copolyester was measured by the Ubbelohde viscometer.
Comparative Example 3
[0042] 222 g of 5tBIA serving as diacid and 74.4 g of EG (90 mol %)
and 19.6 g of TCD (10 mol %) serving as diols were esterificated at
240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.1 molar ratio of the repeating unit in Formula
9 and 0.9 molar ratio of the repeating unit in Formula 10 (C=0.1,
D=0.9) was obtained. The intrinsic viscosity (0.70 dL/g) of the
amorphous copolyester was measured by the Ubbelohde viscometer.
Comparative Example 4
[0043] 244 g of NDC serving as diacid and 74.4 g of EG (90 mol %)
and 19.6 g of TCD (10 mol %) serving as diols were esterificated at
240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.1 molar ratio of the repeating unit in Formula
17 and 0.9 molar ratio of the repeating unit in Formula 18 (E=0.1,
F=0.9) was obtained. The intrinsic viscosity (0.65 dL/g) of the
amorphous copolyester was measured by the Ubbelohde viscometer.
Example 1
[0044] 166 g of TPA serving as diacid and 72.8 g of DMPD (70 mol %)
and 58.8 g of TCD (30 mol %) serving as diols were esterificated at
240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.3 molar ratio of the repeating unit in Formula
1 and 0.7 molar ratio of the repeating unit in Formula 2 (A=0.3,
B=0.7) was obtained. The intrinsic viscosity (0.70 dL/g) of the
amorphous copolyester was measured by the Ubbelohde viscometer.
Example 2
[0045] 166 g of TPA serving as diacid and 31.2 g of DMPD (30 mol %)
and 137.2 g of TCD (70 mol %) serving as diols were esterificated
at 240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.7 molar ratio of the repeating unit in Formula
1 and 0.3 molar ratio of the repeating unit in Formula 2 (A=0.7,
B=0.3) was obtained. The intrinsic viscosity (0.69 dL/g) of the
amorphous copolyester was measured by the Ubbelohde viscometer.
Example 3
[0046] 166 g of TPA serving as diacid and 5.2 g of DMPD (5 mol %)
and 186.2 g of TCD (95 mol %) serving as diols were esterificated
at 240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.95 molar ratio of the repeating unit in
Formula 1 and 0.05 molar ratio of the repeating unit in Formula 2
(A=0.95, B=0.05) was obtained. The intrinsic viscosity (0.68 dL/g)
of the amorphous copolyester was measured by the Ubbelohde
viscometer.
Example 4
[0047] 166 g of TPA serving as diacid, 31.2 g of DMPD (30 mol %)
and 137.2 g of TCD (70 mol %) serving as diols, and 0.5 wt % (based
on the diacid and the diols) of silicon oxide serving as inorganic
nano powders were mixed to form a mixture. The diacid and the diols
of the mixture were esterificated at 240.degree. C. to 250.degree.
C. for about 4 hours, and then condensation polymerized with 350
ppm of antimony acetate at 280.degree. C. to 290.degree. C. for
about 4 hours. After two steps of esterification and condensation
polymerization, an amorphous copolyester having 0.7 molar ratio of
the repeating unit in Formula 1 and 0.3 molar ratio of the
repeating unit in Formula 2 (A=0.7, B=0.3) was obtained. The
intrinsic viscosity (0.68 dL/g) of the amorphous copolyester was
measured by the Ubbelohde viscometer.
Example 5
[0048] 166 g of TPA serving as diacid, 31.2 g of DMPD (30 mol %)
and 137.2 g of TCD (70 mol %) serving as diols, and 0.5 wt % (based
on the diacid and the diols) of strontium carbonate serving as
inorganic nano powders were mixed to form a mixture. The diacid and
the diols of the mixture were esterificated at 240.degree. C. to
250.degree. C. for about 4 hours, and then condensation polymerized
with 350 ppm of antimony acetate at 280.degree. C. to 290.degree.
C. for about 4 hours. After two steps of esterification and
condensation polymerization, an amorphous copolyester having 0.7
molar ratio of the repeating unit in Formula 1 and 0.3 molar ratio
of the repeating unit in Formula 2 (A=0.7, B=0.3) was obtained. The
intrinsic viscosity (0.69 dL/g) of the amorphous copolyester was
measured by the Ubbelohde viscometer.
Example 6
[0049] 222 g of 5tBIA serving as diacid and 62 g of EG (70 mol %)
and 58.8 g of TCD (30 mol %) serving as diols were esterificated at
240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.3 molar ratio of the repeating unit in Formula
9 and 0.7 molar ratio of the repeating unit in Formula 10 (C=0.3,
D=0.7) was obtained. The intrinsic viscosity (0.69 dL/g) of the
amorphous copolyester was measured by the Ubbelohde viscometer.
Example 7
[0050] 222 g of 5tBIA serving as diacid and 37.2 g of EG (30 mol %)
and 137.2 g of TCD (70 mol %) serving as diols were esterificated
at 240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.7 molar ratio of the repeating unit in Formula
9 and 0.3 molar ratio of the repeating unit in Formula 10 (C=0.7,
D=0.3) was obtained. The intrinsic viscosity (0.71 dL/g) of the
amorphous copolyester was measured by the Ubbelohde viscometer.
Example 8
[0051] 222 g of 5tBIA serving as diacid and 21.7 g of EG (5 mol %)
and 186.2 g of TCD (95 mol %) serving as diols were esterificated
at 240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.95 molar ratio of the repeating unit in
Formula 9 and 0.05 molar ratio of the repeating unit in Formula 10
(C=0.95, D=0.05) was obtained. The intrinsic viscosity (0.70 dL/g)
of the amorphous copolyester was measured by the Ubbelohde
viscometer.
Example 9
[0052] 222 g of 5tBIA serving as diacid, 37.2 g of EG (30 mol %)
and 137.2 g of TCD (70 mol %) serving as diols, and 0.5 wt % (based
on the diacid and the diols) of silicon oxide serving as inorganic
nano powders were mixed to form a mixture. The diacid and the diols
of the mixture were esterificated at 240.degree. C. to 250.degree.
C. for about 4 hours, and then condensation polymerized with 350
ppm of antimony acetate at 280.degree. C. to 290.degree. C. for
about 4 hours. After two steps of esterification and condensation
polymerization, an amorphous copolyester having 0.7 molar ratio of
the repeating unit in Formula 9 and 0.3 molar ratio of the
repeating unit in Formula 10 (C=0.7, D=0.3) was obtained. The
intrinsic viscosity (0.70 dL/g) of the amorphous copolyester was
measured by the Ubbelohde viscometer.
Example 10
[0053] 222 g of 5tBIA serving as diacid, 37.2 g of EG (30 mol %)
and 137.2 g of TCD (70 mol %) serving as diols, and 0.5 wt % (based
on the diacid and the diols) of strontium carbonate serving as
inorganic nano powders were mixed to form a mixture. The diacid and
the diols of the mixture were esterificated at 240.degree. C. to
250.degree. C. for about 4 hours, and then condensation polymerized
with 350 ppm of antimony acetate at 280.degree. C. to 290.degree.
C. for about 4 hours. After two steps of esterification and
condensation polymerization, an amorphous copolyester having 0.7
molar ratio of the repeating unit in Formula 9 and 0.3 molar ratio
of the repeating unit in Formula 10 (C=0.7, D=0.3) was obtained.
The intrinsic viscosity (0.69 dL/g) of the amorphous copolyester
was measured by the Ubbelohde viscometer.
Example 11
[0054] 244 g of NDC serving as diacid and 62 g of EG (70 mol %) and
58.8 g of TCD (30 mol %) serving as diols were esterificated at
240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.3 molar ratio of the repeating unit in Formula
17 and 0.7 molar ratio of the repeating unit in Formula 18 (E=0.3,
F=0.7) was obtained. The intrinsic viscosity (0.66 dL/g) of the
amorphous copolyester was measured by the Ubbelohde viscometer.
Example 12
[0055] 244 g of NDC serving as diacid and 37.2 g of EG (30 mol %)
and 137.2 g of TCD (70 mol %) serving as diols were esterificated
at 240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.7 molar ratio of the repeating unit in Formula
17 and 0.3 molar ratio of the repeating unit in Formula 18 (E=0.7,
F=0.3) was obtained. The intrinsic viscosity (0.65 dL/g) of the
amorphous copolyester was measured by the Ubbelohde viscometer.
Example 13
[0056] 244 g of NDC serving as diacid and 21.7 g of EG (5 mol %)
and 186.2 g of TCD (95 mol %) serving as diols were esterificated
at 240.degree. C. to 250.degree. C. for about 4 hours, and then
condensation polymerized with 350 ppm of antimony acetate at
280.degree. C. to 290.degree. C. for about 4 hours. After two steps
of esterification and condensation polymerization, an amorphous
copolyester having 0.95 molar ratio of the repeating unit in
Formula 17 and 0.05 molar ratio of the repeating unit in Formula 18
(E=0.95, F=0.05) was obtained. The intrinsic viscosity (0.63 dL/g)
of the amorphous copolyester was measured by the Ubbelohde
viscometer.
Example 14
[0057] 244 g of NDC serving as diacid, 37.2 g of EG (30 mol %) and
137.2 g of TCD (70 mol %) serving as diols, and 0.5 wt % (based on
the diacid and the diols) of silicon oxide serving as inorganic
nano powders were mixed to form a mixture. The diacid and the diols
of the mixture were esterificated at 240.degree. C. to 250.degree.
C. for about 4 hours, and then condensation polymerized with 350
ppm of antimony acetate at 280.degree. C. to 290.degree. C. for
about 4 hours. After two steps of esterification and condensation
polymerization, an amorphous copolyester having 0.7 molar ratio of
the repeating unit in Formula 17 and 0.3 molar ratio of the
repeating unit in Formula 18 (E=0.7, F=0.3) was obtained. The
intrinsic viscosity (0.65 dL/g) of the amorphous copolyester was
measured by the Ubbelohde viscometer.
Example 15
[0058] 244 g of NDC serving as diacid, 37.2 g of EG (30 mol %) and
137.2 g of TCD (70 mol %) serving as diols, and 0.5 wt % (based on
the diacid and the diols) of strontium carbonate serving as
inorganic nano powders were mixed to form a mixture. The diacid and
the diols of the mixture were esterificated at 240.degree. C. to
250.degree. C. for about 4 hours, and then condensation polymerized
with 350 ppm of antimony acetate at 280.degree. C. to 290.degree.
C. for about 4 hours. After two steps of esterification and
condensation polymerization, an amorphous copolyester having 0.7
molar ratio of the repeating unit in Formula 17 and 0.3 molar ratio
of the repeating unit in Formula 18 (E=0.7, F=0.3) was obtained.
The intrinsic viscosity (0.66 dL/g) of the amorphous copolyester
was measured by the Ubbelohde viscometer.
[0059] The copolyesters of Comparative Examples 1 to 7 and Examples
1 to 15 were analyzed by the DSC to measure their Tg, as tabulated
in Table 1.
TABLE-US-00001 TABLE 1 Composition Tg (.degree. C.) Comparative PET
78 Example 1 Comparative Formula 1 + Formula 2 (A/B = 0.1/0.9) 84
Example 2 Comparative Formula 9 + Formula 10 (C/D = 0.1/0.9) 94
Example 3 Comparative Formula 17 + Formula 18 (E/F = 0.1/0.9) 119
Example 4 Comparative Formula 1 (A/B = 1.0/0) 121 Example 5
Comparative Formula 9 (C/D = 1.0/0) 128 Example 6 Comparative
Formula 17 (E/F = 1.0/0) 144 Example 7 Example 1 Formula 1 +
Formula 2 (A/B = 0.3/0.7) 96 Example 2 Formula 1 + Formula 2 (A/B =
0.7/0.3) 111 Example 3 Formula 1 + Formula 2 (A/B = 0.95/0.05) 120
Example 4 Formula 1 + Formula 2 (A/B = 0.7/0.3) + 112 SiO.sub.2
Example 5 Formula 1 + Formula 2 (A/B = 0.7/0.3) + 113 SrCO.sub.3
Example 6 Formula 9 + Formula 10 (C/D = 0.3/0.7) 104 Example 7
Formula 9 + Formula 10 (C/D = 0.7/0.3) 118 Example 8 Formula 9 +
Formula 10 (C/D = 0.95/0.05) 126 Example 9 Formula 9 + Formula 10
(C/D = 0.7/0.3) + 119 SiO.sub.2 Example 10 Formula 9 + Formula 10
(C/D = 0.7/0.3) + 120 SrCO.sub.3 Example 11 Formula 17 + Formula 18
(E/F = 0.3/0.7) 124 Example 12 Formula 17 + Formula 18 (E/F =
0.7/0.3) 137 Example 13 Formula 17 + Formula 18 (E/F = 0.95/0.05)
143 Example 14 Formula 17 + Formula 18 (E/F = 0.7/0.3) + 138
SiO.sub.2 Example 15 Formula 17 + Formula 18 (E/F = 0.7/0.3) + 138
SrCO.sub.3
[0060] Physical Properties of the Copolyesters
[0061] The copolyesters of Comparative Example 1 and Examples 1 to
5 were analyzed by a differential scanning calorimeter (DSC), as
shown in FIG. 1. Accordingly, the copolyesters in Examples 1 to 5
had the glass transition temperatures (Tg, 96.degree. C. to
120.degree. C.) which were higher than the Tg (78.degree. C.) of
PET in the Comparative Example 1. The copolyesters of Examples 6 to
10 were analyzed by the DSC, as shown in FIG. 2. Accordingly, the
copolyesters in Examples 6 to 10 had the Tg (104.degree. C. to
126.degree. C.) which was higher than the Tg (78.degree. C.) of the
PET in the Comparative Example 1. The copolyesters of Examples 11
to 15 were analyzed by the DSC, as shown in FIG. 3. Accordingly,
the copolyesters in Examples 11 to 15 had the Tg (124.degree. C. to
143.degree. C.) which was higher than the Tg (78.degree. C.) of the
PET in the Comparative Example 1.
[0062] Preparation and Tests for the Copolyesters Film
[0063] Copolyester pellets in Examples 1 to 15 were vibration
sieved by a screen mesh to remove fine dust and fragments thereon.
The sieved copolyester pellets were then dried by a hot air
circulating oven at 70.degree. C. for 24 hours to ensure that the
copolyester pellets were completely dried. The dried copolyester
pellets were molten and processed by a twin screw extruder with a
screw rotation rate of about 300 rpm to 500 rpm at a temperature of
220.degree. C. to 270.degree. C. Thereafter, the molten copolyester
was extruded by a T-die to form a transparent plate. The
transparent plate then passed through a casting drum at a
temperature of 60.degree. C. to 70.degree. C. to achieve a uniform
thickness. The plate was cut to 117 mm.times.117 mm, and then
simultaneously biaxially stretched at a stretching temperature of
90.degree. C. to 160.degree. C., a hot air circulating motor
rotation rate of 1700 rpm, and a stretching rate of 10 mm/sec for a
biaxially stretching times (length.times.width) of 1.25.times.1.25
to 3.times.3 for forming films. The films were thermal treated at a
temperature of 80.degree. C. to 100.degree. C. for 10 seconds to 50
seconds. The physical properties such as total transmittances and
birefringence coefficients of the amorphous copolyester films
(having different molecular structure) stretched by different
biaxially stretching times were measured and tabulated in Table
2.
TABLE-US-00002 TABLE 2 Biaxial stretching Total times transmittance
Birefringence coefficient (550 nm) Composition (length .times.
width) (%) .DELTA.Nx-y .DELTA.Ny-z .DELTA.Nx-z Comparative PET 1.25
.times. 1.25 88.6 3.88 .times. 10.sup.-4 4.22 .times. 10.sup.-3
4.61 .times. 10.sup.-3 Example 1-1 Comparative 1.5 .times. 1.5 88.9
7.60 .times. 10.sup.-4 8.76 .times. 10.sup.-3 9.52 .times.
10.sup.-3 Example 1-2 Comparative 2 .times. 2 89.3 1.77 .times.
10.sup.-3 8.87 .times. 10.sup.-3 1.06 .times. 10.sup.-2 Example 1-3
Comparative 3 .times. 3 89.5 1.07 .times. 10.sup.-2 6.62 .times.
10.sup.-2 7.69 .times. 10.sup.-2 Example 1-4 Comparative 4 .times.
4 89.6 1.74 .times. 10.sup.-2 7.78 .times. 10.sup.-2 9.51 .times.
10.sup.-2 Example 1-5 Example 2-1 Formula 1 + Formula 2 1.5 .times.
1.5 89.8 5.88 .times. 10.sup.-5 2.74 .times. 10.sup.-4 3.02 .times.
10.sup.-4 Example 2-2 (A/B = 0.7/0.3) 2 .times. 2 90.4 9.07 .times.
10.sup.-5 4.53 .times. 10.sup.-4 4.77 .times. 10.sup.-4 Example 2-3
3 .times. 3 90.7 3.44 .times. 10.sup.-4 6.02 .times. 10.sup.-4 6.74
.times. 10.sup.-4 Example 4-1 Formula 1 + Formula 2 1.5 .times. 1.5
89.6 4.55 .times. 10.sup.-5 2.23 .times. 10.sup.-4 2.34 .times.
10.sup.-4 Example 4-2 (A/B = 0.7/0.3) + SiO.sub.2 2 .times. 2 89.9
8.11 .times. 10.sup.-5 4.37 .times. 10.sup.-4 4.43 .times.
10.sup.-4 Example 4-3 3 .times. 3 90.2 2.33 .times. 10.sup.-4 5.88
.times. 10.sup.-4 6.22 .times. 10.sup.-4 Example 5-1 Formula 1 +
Formula 2 1.5 .times. 1.5 89.5 4.05 .times. 10.sup.-5 1.06 .times.
10.sup.-4 2.05 .times. 10.sup.-4 Example 5-2 (A/B = 0.7/0.3) +
SrCO.sub.3 2 .times. 2 89.8 7.59 .times. 10.sup.-5 3.55 .times.
10.sup.-4 3.98 .times. 10.sup.-4 Example 5-3 3 .times. 3 90.2 2.21
.times. 10.sup.-4 5.25 .times. 10.sup.-4 5.83 .times. 10.sup.-4
Example 7-1 Formula 9 + Formula 1.5 .times. 1.5 89.7 6.47 .times.
10.sup.-5 4.03 .times. 10.sup.-4 3.54 .times. 10.sup.-4 Example 7-2
10 (C/D = 0.7/0.3) 2 .times. 2 90.3 1.08 .times. 10.sup.-4 8.63
.times. 10.sup.-4 6.71 .times. 10.sup.-4 Example 7-3 3 .times. 3
90.5 6.23 .times. 10.sup.-4 1.49 .times. 10.sup.-3 9.63 .times.
10.sup.-4 Example 9-1 Formula 9 + Formula 1.5 .times. 1.5 89.5 5.01
.times. 10.sup.-5 3.55 .times. 10.sup.-4 3.22 .times. 10.sup.-4
Example 9-2 10 (C/D = 0.7/0.3) + SiO.sub.2 2 .times. 2 89.9 9.22
.times. 10.sup.-5 7.05 .times. 10.sup.-4 6.08 .times. 10.sup.-4
Example 9-3 3 .times. 3 90.1 4.85 .times. 10.sup.-4 1.01 .times.
10.sup.-3 8.57 .times. 10.sup.-4 Example 10-1 Formula 9 + Formula
1.5 .times. 1.5 89.6 4.87 .times. 10.sup.-5 3.35 .times. 10.sup.-4
2.99 .times. 10.sup.-4 Example 10-2 10 2 .times. 2 89.9 9.01
.times. 10.sup.-5 6.88 .times. 10.sup.-4 5.88 .times. 10.sup.-4
Example 10-3 (C/D = 0.7/0.3) + SrCO.sub.3 3 .times. 3 90.2 4.21
.times. 10.sup.-4 9.95 .times. 10.sup.-4 8.12 .times. 0.sup.-4
Example 12-1 Formula 17 + Formula 1.5 .times. 1.5 89.5 1.94 .times.
10.sup.-4 9.46 .times. 10.sup.-4 1.14 .times. 10.sup.-3 Example
12-2 18 (E/F = 0.7/0.3) 2 .times. 2 89.7 3.13 .times. 10.sup.-4
2.08 .times. 10.sup.-3 2.40 .times. 10.sup.-3 Example 12-3 3
.times. 3 90.0 1.08 .times. 10.sup.-3 2.47 .times. 10.sup.-3 3.59
.times. 10.sup.-3 Example 14-1 Formula 17 + Formula 1.5 .times. 1.5
89.4 1.68 .times. 10.sup.-4 8.79 .times. 10.sup.-4 1.05 .times.
10.sup.-3 Example 14-2 18 (E/F = 0.7/0.3) + SiO.sub.2 2 .times. 2
89.5 2.57 .times. 10.sup.-4 1.82 .times. 10.sup.-3 2.08 .times.
10.sup.-3 Example 14-3 3 .times. 3 89.7 6.50 .times. 10.sup.-4 2.14
.times. 10.sup.-3 2.39 .times. 10.sup.-3 Example 15-1 Formula 17 +
Formula 1.5 .times. 1.5 89.3 1.42 .times. 10.sup.-4 8.03 .times.
10.sup.-4 9.89 .times. 10.sup.-4 Example 15-2 18 (E/F = 0.7/0.3) +
2 .times. 2 89.6 2.33 .times. 10.sup.-4 1.64 .times. 10.sup.-3 1.78
.times. 10.sup.-3 Example 15-3 SrCO.sub.3 3 .times. 3 89.7 6.01
.times. 10.sup.-4 2.02 .times. 10.sup.-3 2.21 .times. 10.sup.-3
[0064] As shown in Table 2, all the copolyester films in Examples
2, 4, 5, 7, 9, 10, 12, 14, and 15 stretched by different biaxial
stretching times had a higher transmittance than the copolyester
film in the Comparative Example 1.
[0065] The PET is a crystalline material, and it should be
biaxially stretched to at least 4.times.4 to achieve sufficient
thermal resistance as an optical film in practice. The PET film
biaxially stretched to 4.times.4 had a birefringence coefficient
(.DELTA.Nx-y) of 1.74.times.10.sup.-2, and the birefringence
coefficient of the PET film obviously increased with the increase
of the biaxially stretching times.
[0066] As shown in FIG. 4, the copolyester films in Examples 2, 7,
and 12 stretched by the biaxial stretching times of 3.times.3 had
birefringence coefficients (.DELTA.Nx-y) of 3.44.times.10.sup.-4,
6.23.times.10.sup.-4, and 1.08.times.10.sup.-3, respectively, and
the birefringence coefficients of the copolyester films in Examples
2, 7, and 12 are slightly increased with the increase of the
biaxially stretching times. Compared to the PET film in the
Comparative Example 1, the copolyester films in Examples 2, 7, and
12 stretched by the same biaxially stretching times had lower
birefringence coefficients.
[0067] As shown in FIG. 5, the copolyester films in Examples 2, 4,
and 5 stretched by the biaxial stretching times of 3.times.3 had
birefringence coefficients (.DELTA.Nx-y) of 3.44.times.10.sup.-4,
2.33.times.10.sup.-4, and 2.21.times.10.sup.-4, respectively, and
the birefringence coefficients of the copolyester films in Examples
2, 4, and 5 are slightly increased with the increase of the
biaxially stretching times. Compared to the copolyester film in
Example 2, the copolyester film including 0.5 wt % of silicon oxide
in Example 4 and the copolyester film including 0.5 wt % of
strontium carbonate in Example 5 stretched by the same biaxially
stretching times had lower birefringence coefficients.
[0068] As shown in FIG. 6, the copolyester films in Examples 7, 9,
and 10 stretched by the biaxial stretching times of 3.times.3 had
birefringence coefficients (.DELTA.Nx-y) of 6.23.times.10.sup.-4,
4.85.times.10.sup.-4, and 4.21.times.10.sup.-4, respectively, and
the birefringence coefficients of the copolyester films in Examples
7, 9, and 10 are slightly increased with the increase of the
biaxially stretching times. Compared to the copolyester film in
Example 7, the copolyester film including 0.5 wt % of silicon oxide
in Example 9 and the copolyester film including 0.5 wt % of
strontium carbonate in Example 10 stretched by the same biaxially
stretching times had lower birefringence coefficients.
[0069] As shown in FIG. 7, the copolyester films in Examples 12,
14, and 15 stretched by the biaxial stretching times of 3.times.3
had birefringence coefficients (.DELTA.Nx-y) of
1.08.times.10.sup.-3, 6.50.times.10.sup.-4, and
6.01.times.10.sup.-4, respectively, and the birefringence
coefficients of the copolyester films in Examples 12, 14, and 15
are slightly increased with the increase of the biaxially
stretching times. Compared to the copolyester film in Example 12,
the copolyester film including 0.5 wt % of silicon oxide in Example
14 and the copolyester film including 0.5 wt % of strontium
carbonate in Example 15 stretched by the same biaxially stretching
times had lower birefringence coefficients.
[0070] As shown in FIG. 8, the copolyesters in Comparative Examples
2 to 4 were analyzed by the DSC to measure their Tg. Accordingly,
the copolyesters in Examples 1 to 5 had Tg (96.degree. C. to
120.degree. C.) which was higher than the Tg (84.degree. C.) of the
copolyester in the Comparative Example 2, the copolyesters in
Examples 6 to 10 had the Tg (104.degree. C. to 126.degree. C.)
which was higher than the Tg (94.degree. C.) of the copolyester in
the Comparative Example 3, and the copolyesters in Examples 11 to
15 had the Tg (124.degree. C. to 143.degree. C.) which was higher
than the Tg (119.degree. C.) of the copolyester in the Comparative
Example 4.
Comparative Example 5
[0071] 166 g of TPA serving as diacid and 196 g of TCD serving as
diols were esterificated at 240.degree. C. to 250.degree. C. for
about 4 hours, and then condensation polymerized with 350 ppm of
antimony acetate at 280.degree. C. to 290.degree. C. for about 4
hours. After two steps of esterification and condensation
polymerization, an amorphous copolyester having 1.0 molar ratio of
the repeating unit in Formula 1 and 0 molar ratio of the repeating
unit in Formula 2 (A=1.0, B=0) was obtained. The intrinsic
viscosity (0.67 dL/g) of the amorphous copolyester was measured by
the Ubbelohde viscometer.
Comparative Example 6
[0072] 222 g of 5tBIA serving as diacid and 196 g of TCD serving as
diols were esterificated at 240.degree. C. to 250.degree. C. for
about 4 hours, and then condensation polymerized with 350 ppm of
antimony acetate at 280.degree. C. to 290.degree. C. for about 4
hours. After two steps of esterification and condensation
polymerization, an amorphous copolyester having 1.0 molar ratio of
the repeating unit in Formula 9 and 0 molar ratio of the repeating
unit in Formula 10 (C=1.0, D=0) was obtained. The intrinsic
viscosity (0.69 dL/g) of the amorphous copolyester was measured by
the Ubbelohde viscometer.
Comparative Example 7
[0073] 244 g of NDC serving as diacid and 196 g of TCD serving as
diols were esterificated at 240.degree. C. to 250.degree. C. for
about 4 hours, and then condensation polymerized with 350 ppm of
antimony acetate at 280.degree. C. to 290.degree. C. for about 4
hours. After two steps of esterification and condensation
polymerization, an amorphous copolyester having 1.0 molar ratio of
the repeating unit in Formula 17 and 0 molar ratio of the repeating
unit in Formula 18 (E=1.0, F=0) was obtained. The intrinsic
viscosity (0.66 dL/g) of the amorphous copolyester was measured by
the Ubbelohde viscometer.
[0074] The copolyesters of Comparative Examples 5 to 7 were
analyzed by the DSC to measure their Tg, as tabulated in Table
1.
[0075] Copolyester pellets in Comparative Examples 5 to 7 were
vibration sieved by a screen mesh to remove fine dust and fragments
thereon. The sieved copolyester pellets were then dried by a hot
air circulating oven at 70.degree. C. for 24 hours to ensure the
copolyester pellets being completely dried. The dried copolyester
pellets were molten and processed by a twin screw extruder with a
screw rotation rate of about 300 rpm to 500 rpm at a temperature of
220.degree. C. to 270.degree. C. Thereafter, the molten copolyester
was extruded by a T-die. However, the copolyesters in Comparative
Examples 5 to 7 had too low of a toughness to be extruded as a
transparent plate.
[0076] In the Examples of the disclosure, different monomers were
condensation polymerized to form a thin plate of a random amorphous
copolyester with low birefringence, thereby overcoming the high
birefringence problem of the conventional PET film. The
copolyesters of specific compositions in the Examples had low haze,
high transmittance, and low birefringence. The copolyester plate
can be further biaxially stretched to form a film having high
mechanical properties and uniform thickness. The film can be widely
utilized as a substrate or optical film.
[0077] It will be apparent to those skilled in the art that various
modifications and variations can be made to the disclosed methods
and materials. It is intended that the specification and examples
be considered as exemplary only, with a true scope of the
disclosure being indicated by the following claims and their
equivalents.
* * * * *