U.S. patent application number 09/792626 was filed with the patent office on 2001-11-22 for composition and article for optical data storage devices.
This patent application is currently assigned to General Electric Co.. Invention is credited to Dris, Irene, Gallucci, Robert R., Hariharan, Ramesh, Hoefflin, Frank A., Hubbard, Steven F..
Application Number | 20010044003 09/792626 |
Document ID | / |
Family ID | 23001391 |
Filed Date | 2001-11-22 |
United States Patent
Application |
20010044003 |
Kind Code |
A1 |
Gallucci, Robert R. ; et
al. |
November 22, 2001 |
Composition and article for optical data storage devices
Abstract
Disclosed is an article for the optical storage of data having
low birefringence prepared from a mixture of a polycarbonate and a
cycloaliphatic polyester. The article may optionally have
stabilization and mold release additives that retain transparency,
color and processability.
Inventors: |
Gallucci, Robert R.; (Mt.
Vernon, IN) ; Hoefflin, Frank A.; (Evansville,
IN) ; Hubbard, Steven F.; (Mt. Vernon, IN) ;
Hariharan, Ramesh; (Guilderland, NY) ; Dris,
Irene; (Clifton Park, NY) |
Correspondence
Address: |
Robert E. Walter
GE Plastics
One Plastics Avenue
Pittsfield
MA
01201
US
|
Assignee: |
General Electric Co.
|
Family ID: |
23001391 |
Appl. No.: |
09/792626 |
Filed: |
February 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09792626 |
Feb 23, 2001 |
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09263341 |
Mar 5, 1999 |
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6221556 |
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Current U.S.
Class: |
428/64.7 ;
264/1.1; 264/1.33; 430/270.11; 525/146; 525/147; G9B/7.172 |
Current CPC
Class: |
G11B 7/2533 20130101;
C08L 67/02 20130101; C08L 67/02 20130101; C08L 69/00 20130101; G11B
7/2595 20130101; Y10S 430/146 20130101; C08L 69/00 20130101; G11B
7/2585 20130101; G11B 7/259 20130101; G11B 7/2534 20130101; C08L
67/02 20130101; C08L 69/00 20130101; G11B 7/2535 20130101 |
Class at
Publication: |
428/64.7 ;
264/1.33; 264/1.1; 525/146; 525/147; 430/270.11 |
International
Class: |
C08L 069/00; B29D
011/00; G11B 007/24 |
Claims
What is claimed is:
1. An article for optical storage of information comprising a blend
of cycloaliphatic polyester and polycarbonate with in plane
birefringence from -100 to +100 nm.
2. An article for optical storage of information comprising a blend
of cycloaliphatic polyester and polycarbonate with vertical
birefringence less than or equal to 300.times.10-6.
3. An article for optical storage of information comprising a blend
of cycloaliphatic polyester and polycarbonate with stress optical
coefficient (Cg) less than or equal to 70 Brewesters.
4. An article of claim 1 where the blend has % transmittance of
greater than or equal to 75%.
5. An article of claim 1 where the blend has a glass transition
temperature of from about 90 to 150.degree. C.
6. An article of claim 1 where the blend further contains an
effective amount of a stabilizer to prevent color formation.
7. An article of claim 6 where stabilizer is chosen from the group
consisting of: phosphorus oxo acids, acid organo phosphates, acid
organo phosphites, acid phosphate metal salts, acidic phosphite
metal salts or mixture thereof giving an article with greater than
or equal to about 75% transmittance.
8. An article of claim 6 where the yellowness index is less than or
equal to about 5 YI units.
9. An article of claim 1 further comprising an effective amount of
a mold release wherein the transmittance of the polycarbonate
cycloaliphatic polyester blend is greater than or equal to about
75%.
10. Article of claim 9 wherein the mold release is pentaerythritol
tetrastearate.
11. An article of claim 1 where the cycloaliphatic polyester is
comprised of cycloaliphatic diacid and cycloaliphatic diol
units.
12. An article of claim 11 where the polyester is polycyclohexane
dimethanol cyclohexane dicarboxylate (PCCD).
13. An article of claim 1 where the polycarbonate is composed
primarily of the following structural units: bisphenol A, spiro
biindane bisphenol, an aryl substituted bisphenol, a cycloaliphatic
bisphenol or mixtures thereof.
14. An article of claim 1 where the polycarbonate is BPA-PC and the
cycloaliphatic polyester is PCCD.
15. An article of claim 1 where the ratio of cycloaliphatic
polyester to polycarbonate in the blend is 40:60 to 5:95
16. An article of claim 1 which is a metal coated optical disc.
17. An article of claim 1 wherein the stored information can be
read by a laser.
18. An article for optical storage of information comprising a
blend of a cycloaliphatic polyester and a polycarbonate wherein
said polycarbonate comprises a spiro biindane bisphenol.
19. An article for optical storage of information of claim 18
wherein the cycloaliphatic polyester is comprised of cycloaliphatic
diacid and cycloaliphatic diol units.
20. A resin for molding optical quality articles comprising a blend
of cycloaliphatic polyester and polycarbonate, wherein said resin
blend has properties suitable for molding an optical quality
article having in plane birefringence from -100 to +100 nm.
21. A resin for molding optical quality articles comprising a blend
of cycloaliphatic polyester and polycarbonate, wherein said resin
blend has properties suitable for molding an optical quality
article having vertical birefringence less than or equal to
300.times.10-6.
22. A resin for molding optical quality articles comprising a blend
of cycloaliphatic polyester and polycarbonate, wherein said resin
blend has properties suitable for molding an optical quality
article having a stress optical coefficient of less than or equal
to 70 Brewsters.
23. A resin for molding optical quality articles of claim 20
wherein said blend has a glass transition temperature of from about
90 to 150.degree. C.
24. A resin for molding optical quality articles of claim 20
wherein said blend further contains an effective amount of a
stabilizer to prevent color formation.
25. A resin for molding optical quality articles of claim 24
wherein said stabilizer is chosen from the group consisting of:
phosphorus oxo acids, acid organo phosphates, acid organo
phosphites, acid phosphate metal salts, acidic phosphite metal
salts or mixture thereof for making a molded article with greater
than or equal to about 75% transmittance.
26. A resin for molding optical quality articles of claim 20
wherein said cycloaliphatic polyester is comprised of
cycloaliphatic diacid and cycloaliphatic diol units.
27. A resin for molding optical quality articles of claim 20
wherein said polycarbonate is composed primarily of the following
structural units: bisphenol A, spiro biindane bisphenol, an aryl
substituted bisphenol, a cycloaliphatic bisphenol or mixtures
thereof.
28. A process for molding optical articles comprising the steps of
forming a resin blend of a blend of cycloaliphatic polyester and
polycarbonate and molding an optical quality article having in
plane birefringence from -100 to +100 nm.
29. A process for molding optical articles comprising the steps of
forming a resin blend of a blend of cycloaliphatic polyester and
polycarbonate and molding an optical quality article having
vertical birefringence less than or equal to 300.times.10-6.
30. A process for molding optical articles comprising the steps of
forming a resin blend of a blend of cycloaliphatic polyester and
polycarbonate and molding an optical quality article having a
stress optical coefficient less than or equal to 70 Brewsters.
31. A process for molding optical articles of claim 28 wherein said
molding is carried out above the glass transition temperature of
said resin blend, said resin blend having a glass transition
temperature of from about 90 to 150.degree. C.
32. A process for molding optical articles of claim 31 wherein said
molding is carried out by injection molding.
33. An article of claim 1 which is an optical disc comprising at
least one optical quality layer and means for encoding information
from a signal, said optical quality layer comprising a blend of
cycloaliphatic polyester and polycarbonate.
34. A process for reading stored information on a disc of the type
having at least one optical quality layer comprising transmitting a
signal to said optical quality layer to read said stored
information, said storing means being operably associated with said
optical quality layer, said optical quality layer comprising a
blend of cycloaliphatic polyester and polycarbonate with in plane
birefringence from -100 to +100 nm.
35. A process for reading stored information on a disc of the type
having at least one optical quality layer comprising transmitting a
signal to said optical quality layer to read said stored
information, said storing means being operably associated with said
optical quality layer, said optical quality layer comprising a
blend of cycloaliphatic polyester and polycarbonate with vertical
birefringence less than or equal to 300.times.10-6.
36. A process for reading stored information on a disc of the type
having at least one optical quality layer comprising transmitting a
signal to said optical quality layer to read said stored
information, said storing means being operably associated with said
optical quality layer, said optical quality layer comprising a
blend of cycloaliphatic polyester and polycarbonate with a stress
optical coefficient of less than or equal to 70 Brewsters.
37. A process for reading stored information on a disc according to
claim 34 wherein said signal comprises electromagnetic radiation
from a laser.
38. A process for reading stored information on a disc according to
claim 34 wherein said storage means comprises a plurality of
surface depressions on said layer.
Description
FIELD OF THE INVENTION
[0001] This invention relates to transparent thermoplastic molding
compositions and articles made from them suitable for the optical
storage of information.
BACKGROUND OF THE INVENTION
[0002] Use of optical storage devices has become common since the
advent of the compact disc (CD) widely used for the storage of
music, video and other information. Optical storage devices of this
type require a transparent substrate with excellent optical
properties. This substrate is encoded with information often by
molding in a series of pits or depressions. Suitably coated this
substrate can be read by a laser to give a series of signals
recovering the information stored on the disc. With storage devices
of this type, there is a growing need to store more and more
information in a smaller space.
[0003] Bisphenol A Polycarbonate (BPA-PC) has been widely used for
optical storage media applications, however, BPA-PC has some
limitations. It is rather difficult to process by injection molding
which limits the speed with which discs can be made and the quality
and amount of information that can be stored on them. In these
applications BPA-PC and optical data storage devices made from it
are limited by their birefringence. Birefringence, resulting from
the inherent properties of the resin and also from how it was
processed (influenced by its rheological properties) can interfere
with the recovery of information stored on the device (i.e.
disc).
[0004] In the further development of optical discs, particularly
read-write discs and discs which are capable of storing larger
amounts of data, various physical factors become increasingly
important. One such factor, which is closely related to the storage
capacity of the disc, is birefringence, i.e., the difference
between indices of refraction for light polarized in perpendicular
directions. Birefringence leads to phase retardation between
different polarization components of the laser beam (i.e., a
polarization-dependent effect), thereby reducing readability of the
disc.
[0005] Birefringence has several sources including the chemical
nature of the raw material from which the disc is fabricated, the
degree of molecular orientation therein, and thermal stresses in a
fabricated plastic optical disc. The observed birefringence of a
disc is therefore determined by the molecular structure, which
determines the intrinsic birefringence, and the processing
conditions, which can create thermal stresses and orientation of
the polymer chains. Specifically, the observed birefringence is
typically a function of the intrinsic birefringence plus the
birefringence introduced upon molding articles such as optical
discs.
[0006] Structural variations of BPA-PC have been made to deal with
the birefringence limitations of BPA-PC but many of them do not
fully meet the other requirements for a successful optical data
storage device material. They are either too brittle, have poor
optical properties (low transmittance and/or high haze), or are
difficult to process due to their high glass transition temperature
(Tg). High processing temperature can also lead to degradation of
the polymer chain leading to loss of mechanical properties, color
formation (especially yellowing) and generation of gaseous
by-products impairing optical properties. Other potential optical
materials of low birefringence do not meet the needs of an optical
storage device because they are too floppy (have a flex modulus
below about 150,000 psi) or have a low thermal capability (Tg below
about 80.degree. C).
[0007] Therefore, there is a need to prepare resin compositions and
articles made from them that are transparent, have low
birefringence and good melt processability.
[0008] There are several patents describing specific types of
aromatic polycarbonate with improved optical properties or higher
thermal capability. Polycarbonates of a specific molecular weight
range with at least one pendant aromatic group and an optical disc
substrate made thereof are claimed by M. Hasuo et al. in U.S. Pat.
No. 4,734,488. These materials are shown to have superior heat
resistance (higher Tg) than polycarbonate along with good optical
properties.
[0009] U.S. Pat. No. 4,680,374 claims an optical substrate with
double refraction not greater than 5.times.10-5 made of a
polycarbonate copolymer of aliphatic substituted bisphenols.
[0010] Polycarbonate polymers and copolymers of spiro dihydric
phenols and their preparation are disclosed by V. Mark in U.S. Pat.
No. 4,552,949 as exhibiting improved heat distortion and retaining
transparency. The chain stiffness of these types of polycarbonates
is discussed by R. Wimberger-Friedl, M. G. T. Hut and H. F. M.
Schoo in Macromolecules, 29, 5453-5458 (1996).
[0011] Specific spiro biindane aliphatic diacid copolymers are
disclosed as having low birefringence in published EP 846711-A2
entitled Optical Disk grade Copolyestercarbonates Derived from
Hydroxyphenyl Indanols.
[0012] There are references to transparent blends of aromatic
polycarbonates with specific cycloaliphatic polyesters but none
address birefringence or the requirements of optical storage
devices.
[0013] U.S. Pat. No. 4,188,314 describes shaped articles (such as
sheet and helmets) of blends of 25-98 parts by weight (pbw) of an
aromatic polycarbonate and 2-75 pbw of a poly cyclohexane
dimethanol phthalate where the phthalate is from 5-95% isophthalate
and 95-10% terephthalate. Articles with enhanced solvent resistance
and comparable optical properties and impact to the base
polycarbonate resin and superior optical properties to an article
shaped from a polycarbonate and an aromatic polyester, such as
polyalkylene terephthalate, are disclosed.
[0014] There are other patents that deal with polycarbonate
polycyclohexane dimethanol phthalate blends for example; U.S. Pat.
No. 4,125,572; U.S. Pat. Nos. 4,391,954; 4,786,692; 4,897,453 and
5,478,896. U.S. Pat. No. 5,478,896 relates to transparent
polycarbonate blends with 10-99% polyester of CHDM with some minor
amount of aliphatic diol and iso and terephthalic acid. U.S. Pat.
No. 4,786,692 relates to a 2-98% aromatic polycarbonate blend with
a polyester made of cyclohexane dimethanol (CHDM) and ethylene
glycol (EG) in a 1:1 to 4:1 ratio with iso and terephthalic acid.
U.S. Pat. No. 4,391,954 describes compatible compositions of non
halogen polycarbonate (PC) and amorphous polyesters of CHDM and a
specific iso/tere phthalate mixture. U.S. Pat. No. 4,125,572
relates to a blend of 40-95% PC, 5-60% polybutylene terephthalate
(PBT) 1-60% and 1-60% an aliphatic/cycloaliphatic iso/terephthalate
resin. U.S. Pat. No. 4,897,453 describes blends of 10-90% PC,
10-90% of a polyester of 0.8-1.5 IV, comprised of 1,4-cyclohexane
dicarboxylic acid, 70% trans isomer, CHDM and 15-50 wt. % poly
oxytetramethylene glycol with 0-1.5 mole % branching agent. Also
claimed are molded or extruded articles of the composition. None of
these references raise, suggest, or address the question of
birefringence and the special needs for an optical data storage
material.
SUMMARY OF THE INVENTION
[0015] There is a need for resins and articles made from them for
the optical storage of data, that are transparent, easy to process
in the melt and have low birefringence. Typically, optical resin
materials for articles of low birefringence do not fully meet the
needs of optical storage devices because the resulting articles are
too floppy (have a flex modulus below about 150,000 psi), have a
low thermal capability (Tg below about 80.degree. C.), have low
light transmission, poor color, are difficult to mold, or have high
birefringence.
[0016] In accordance with the present invention there is provided
an article for optical storage of information comprising a blend of
a cycloaliphatic polyester and a polycarbonate with low
birefringence. Also described are optical storage media comprising
a resin blend of a cycloaliphatic polyester and a polycarbonate for
molding optical quality articles, a process for molding optical
quality articles, and a process for reading information stored on
optical media.
[0017] Blends of poly cycloaliphatic polyesters and polycarbonates
give transparent compositions which have reduced Tgs compared to
the polycarbonate (indicative of improved processability) and
articles made from them have low birefringence, as measured by IBR,
VBR or Cg as hereinafter explained in detail.
[0018] Poly cycloaliphatic polyesters generally have low Tgs and
high birefringence however, their blends with polycarbonates give
transparent articles with reduced birefringence (compared to the
base polyester). The blends have Tgs suitable for easy processing
yet having sufficient heat resistance for practical use.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Birefringence is an important property of molded optical
parts of the present invention. The in-plane birefringence (IBR) is
critical to the performance of an optical disc and is defined as
the phase retardation experienced by light as it travels through an
optical part. IBR is influenced by the optical and Theological
properties of the material. IBR is measured by illuminating a part
of thickness d with polarized light with wavelength l at normal
incidence and using a variable phase retarder, such as a
Soliel-Babinet compensator, with a linear polarizer to determine
the phase shift, D, experienced by the light as it travels through
the part. The IBR is the phase shift expressed in units of
nanometers and is related to the refractive index difference in the
radial (nr) and tangential (nt) directions. 1 IBR 2 = d ( n r - n t
)
[0020] Another key property in optical data storage, particularly
magneto-optical storage, is vertical birefringence (VBR). VBR is
defined as the difference between the refractive index in the plane
of the part (nr) and that perpendicular to the plane (nz). VBR of
an optical substrate is influenced by the optical properties of the
material. It is measured by finding the retardation experienced by
a laser beam as it traverses a part at normal incidence and the
retardation at non-normal (but known) incidence. Comparison of the
two numbers allows calculation of nr-nz. VBR is dimensionless and
is typically expressed on a scale of 10-6.
[0021] A third parameter for optical materials is Cg which is the
stress-optical coefficient of material in the glassy state. It can
be measured with a molded part such as a small bar or disc.
Birefringence can be measured by the methods described above. When
a stress (s) is applied to the bar, the birefringence will change
by an amount, B. The stress-optical coefficient, which has units of
Brewsters, is given by:
B=C.sub.g.sigma.
[0022] Taken together or separately lower IBR, VBR and Cg values
indicate superior optical properties. These properties are
especially important in the storage and retrieval of information
using optical methods. As these storage and retrieval methods move
to increasingly finer scale, the birefringence properties of a
material and an article made from it become very important.
[0023] Low birefringence is defined as : In-Plane Birefringence
(IBR) from -100 to +100 nanometers (nm); Vertical Birefringence
(VBR) less than or equal to 300.times.10-6 and a stress optical
coefficient (Cg) less than or equal to 70 Brewsters.
[0024] In cases where the polycarbonate has a high Tg and is
difficult to process the cycloaliphatic polyester acts to lower the
PC Tg while the blend maintains low birefringence and has excellent
melt flow. This is especially true of polycarbonates based on
spirobiindane (SBI) units. The cup shaped SBI units reduce the
birefringence associated with the PC but make the polymer chain
very stiff resulting in a high Tg and difficult processing. A blend
with a cycloaliphatic polyester reduces Tg making melt processing
easier while the blend has excellent optical properties
overall.
[0025] In order to further enhance performance in optical storage
devices, acidic phosphorus based stabilizers are useful to retard
melt reaction of the cycloaliphatic polyester and polycarbonate
resin and improve color.
[0026] In addition specific mold release agents that retain
transparency while allowing easy de-bonding of the formed part from
the mold are also desirable. Since the discs have such high surface
area, due to the textured nature of the disc needed for information
storage, easy release from the molding tool is quite important.
High molecular weight aliphatic esters like pentaerythritol tetra
stearate (PETS) are especially useful.
[0027] The most preferred materials will be blends where the
polyester has both cycloaliphatic diacid and cycloaliphatic diol
components specifically polycyclohexane dimethanol cyclohexyl
dicarboxylate (PCCD).
[0028] The preferred polycarbonate will be composed of units of
BPA, SBI bis phenol, aryl substituted bisphenols, cycloaliphatic
bisphenols and mixtures thereof.
[0029] The ratio of cycloaliphatic polyester to polycarbonate in
the range of 40:60 to 5:95% by weight of the entire mixture is
preferred. Blends from 50:50 to 30:70 are most preferred.
[0030] The cycloaliphatic polyester resin comprises a polyester
having repeating units of the formula I: 1
[0031] where at least one R or R1 is a cycloalkyl containing
radical.
[0032] The polyester is a condensation product where R is the
residue of an aryl, alkane or cycloalkane containing diol having 6
to 20 carbon atoms or chemical equivalent thereof, and Ri is the
decarboxylated residue derived from an aryl, aliphatic or
cycloalkane containing diacid of 6 to 20 carbon atoms or chemical
equivalent thereof with the proviso that at least one R or R1 is
cycloaliphatic. Preferred polyesters of the invention will have
both R and R1 cycloaliphatic.
[0033] The present cycloaliphatic polyesters are condensation
products of aliphatic diacids, or chemical equivalents and
aliphatic diols, or chemical equivalents. The present
cycloaliphatic polyesters may be formed from mixtures of aliphatic
diacids and aliphatic diols but must contain at least 50 mole % of
cyclic diacid and/or cyclic diol components, the remainder, if any,
being linear aliphatic diacids and/or diols. The cyclic components
are necessary to impart good rigidity to the polyester and to allow
the formation of transparent blends due to favorable interaction
with the polycarbonate resin.
[0034] The polyester resins are typically obtained through the
condensation or ester interchange polymerization of the diol or
diol equivalent component with the diacid or diacid chemical
equivalent component.
[0035] R and R1 are preferably cycloalkyl radicals independently
selected from the following formula: 2
[0036] The preferred cycloaliphatic radical R1 is derived from the
1,4-cyclohexyl diacids and most preferably greater than 70 mole %
thereof in the form of the trans isomer. The preferred
cycloaliphatic radical R is derived from the 1,4-cyclohexyl primary
diols such as 1,4-cyclohexyl dimethanol, most preferably more than
70 mole % thereof in the form of the trans isomer.
[0037] Other diols useful in the preparation of the polyester
resins of the present invention are straight chain, branched, or
cycloaliphatic alkane diols and may contain from 2 to 12 carbon
atoms. Examples of such diols include but are not limited to
ethylene glycol; propylene glycol, i.e., 1,2- and 1,3-propylene
glycol; 2,2-dimethyl-1,3-propane diol; 2-ethyl, 2-methyl,
1,3-propane diol; 1,3- and 1,5-pentane diol; dipropylene glycol;
2-methyl-1,5-pentane diol; 1,6-hexane diol; dimethanol decalin,
dimethanol bicyclo octane; 1,4-cyclohexane dimethanol and
particularly its cis- and trans-isomers; triethylene glycol;
1,10-decane diol; and mixtures of any of the foregoing. Preferably
a cycloaliphatic diol or chemical equivalent thereof and
particularly 1,4-cyclohexane dimethanol or its chemical equivalents
are used as the diol component.
[0038] Chemical equivalents to the diols include esters, such as
dialkylesters, diaryl esters and the like.
[0039] The diacids useful in the preparation of the aliphatic
polyester resins of the present invention preferably are
cycloaliphatic diacids. This is meant to include carboxylic acids
having two carboxyl groups each of which is attached to a saturated
carbon. Preferred diacids are cyclo or bicyclo aliphatic acids, for
example, decahydro naphthalene dicarboxylic acids, norbornene
dicarboxylic acids, bicyclo octane dicarboxylic acids,
1,4-cyclohexanedicarboxylic acid or chemical equivalents, and most
preferred is trans-1,4-cyclohexanedicarboxylic acid or chemical
equivalent. Linear dicarboxylic acids like adipic acid, azelaic
acid, dicarboxyl dodecanoic acid and succinic acid may also be
useful.
[0040] Cyclohexane dicarboxylic acids and their chemical
equivalents can be prepared, for example, by the hydrogenation of
cycloaromatic diacids and corresponding derivatives such as
isophthalic acid, terephthalic acid or naphthalenic acid in a
suitable solvent such as water or acetic acid using a suitable
catalysts such as rhodium supported on a carrier such as carbon or
alumina. See, Friefelder et al., Journal of Organic Chemistry, 31,
3438 (1966); U.S. Pat. Nos. 2,675,390 and 4,754,064. They may also
be prepared by the use of an inert liquid medium in which a
phthalic acid is at least partially soluble under reaction
conditions and with a catalyst of palladium or ruthenium on carbon
or silica. See, U.S. Pat. Nos. 2,888,484 and 3,444,237.
[0041] Typically, in the hydrogenation, two isomers are obtained in
which the carboxylic acid groups are in cis- or trans-positions.
The cis- and trans-isomers can be separated by crystallization with
or without a solvent, for example, n-heptane, or by distillation.
The cis-isomer tends to blend better; however, the trans-isomer has
higher melting and crystallization temperatures and may be
preferred. Mixtures of the cis- and trans-isomers are useful herein
as well.
[0042] When the mixture of isomers or more than one diacid or diol
is used, a copolyester or a mixture of two polyesters may be used
as the present cycloaliphatic polyester resin.
[0043] Chemical equivalents of these diacids include esters, alkyl
esters, e.g., dialkyl esters, diaryl esters, anhydrides, salts,
acid chlorides, acid bromides, and the like. The preferred chemical
equivalents comprise the dialkyl esters of the cycloaliphatic
diacids, and the most favored chemical equivalent comprises the
dimethyl ester of the acid, particularly
dimethyl-1,4-cyclohexane-dicarboxylate.
[0044] A preferred cycloaliphatic polyester is
poly(cyclohexane-1,4-dimeth- ylene cyclohexane-1,4-dicarboxylate)
also referred to as
poly(1,4-cyclohexane-dimethanol-1,4-dicarboxylate) (PCCD) which has
recurring units of formula II: 3
[0045] With reference to the previously set forth general formula,
for PCCD, R is derived from 1,4 cyclohexane dimethanol; and R1 is a
cyclohexane ring derived from cyclohexanedicarboxylate or a
chemical equivalent thereof. The favored PCCD has a cis/trans
formula.
[0046] The polyester polymerization reaction is generally run in
the melt in the presence of a suitable catalyst such as a tetrakis
(2-ethyl hexyl) titanate, in a suitable amount, typically about 50
to 200 ppm of titanium based upon the final product.
[0047] The preferred aliphatic polyesters used in the present
transparent molding compositions have a glass transition
temperature (Tg) which is above 50.degree. C., more preferably
above 80.degree. C. and most preferably above about 100.degree.
C.
[0048] Also contemplated herein are the above polyesters with from
about 1 to about 50 percent by weight, of units derived from
polymeric aliphatic acids and/or polymeric aliphatic polyols to
form copolyesters. The aliphatic polyols include glycols, such as
poly(ethylene glycol) or poly(butylene glycol). Such polyesters can
be made following the teachings of, for example, U.S. Pat. Nos.
2,465,319 and 3,047,539.
[0049] Polycarbonates useful in the invention comprise the divalent
residue of dihydric phenols, Ar', bonded through a carbonate
linkage and are preferably represented by the general formula III:
4
[0050] wherein A is a divalent hydrocarbon radical containing from
1 to about 15 carbon atoms or a substituted divalent hydrocarbon
radical containing from 1 to about 15 carbon atoms; each X is
independently selected from the group consisting of hydrogen,
halogen, and a monovalent hydrocarbon radical such as an alkyl
group of from 1 to about 8 carbon atoms, an aryl group of from 6 to
about 18 carbon atoms, an arylalkyl group of from 7 to about 14
carbon atoms, an alkoxy group of from 1 to about 8 carbon atoms;
and m is 0 or 1 and n is an integer of from 0 to about 5. Ar' may
be a single aromatic ring like hydroquinone or resorcinol, or a
multiple aromatic ring like biphenol or bisphenol A.
[0051] The dihydric phenols employed are known, and the reactive
groups are thought to be the phenolic hydroxyl groups. Typical of
some of the dihydric phenols employed are bis-phenols such as
bis(4-hydroxyphenyl)met- hane, 2,2-bis(4-hydroxyphenyl)propane
(also known as bisphenol-A),
2,2-bis(4-hydroxy-3,5-dibromo-phenyl)propane; dihydric phenol
ethers such as bis(4-hydroxyphenyl)ether,
bis(3,5-dichloro-4-hydroxyphenyl)ether; p,p'-dihydroxydiphenyl and
3,3'-dichloro-4,4'-dihydroxydiphenyl; dihydroxyaryl sulfones such
as bis(4-hydroxyphenyl)sulfone,
bis(3,5-dimethyl-4-hydroxyphenyl)sulfone, dihydroxy benzenes such
as resorcinol, hydroquinone, halo- and alkyl-substituted
dihydroxybenzenes such as 1,4-dihydroxy-2,5-dichlorobenzene,
1,4-dihydroxy-3-methylbenzene; and dihydroxydiphenyl sulfides and
sulfoxides such as bis(4-hydroxyphenyl)sulfide,
bis(4-hydroxy-phenyl)sulfoxide and
bis(3,5-dibromo-4-hydroxyphenyl)sulfoxide. A variety of additional
dihydric phenols are available and are disclosed in U.S. Pat. Nos.
2,999,835, 3,028,365 and 3,153,008; all of which are incorporated
herein by reference. It is, of course, possible to employ two or
more different dihydric phenols or a combination of a dihydric
phenol with a glycol.
[0052] The carbonate precursors are typically a carbonyl halide, a
diarylcarbonate, or a bishaloformate. The carbonyl halides include,
for example, carbonyl bromide, carbonyl chloride, and mixtures
thereof. The bishaloformates include the bishaloformates of
dihydric phenols such as bischloroformates of
2,2-bis(4-hydroxyphenyl)-propane, hydroquinone, and the like, or
bishaloformates of glycol, and the like. While all of the above
carbonate precursors are useful, carbonyl chloride, also known as
phosgene, and diphenyl carbonate are preferred.
[0053] The aromatic polycarbonates can be manufactured by any
processes such as by reacting a dihydric phenol with a carbonate
precursor, such as phosgene, a haloformate or carbonate ester in
melt or solution. U.S. Pat. No. 4,123,436 describes reaction with
phosgene and U.S. Pat. No. 3,153,008 describes a
transesterification process.
[0054] Preferred polycarbonate will be made of dihydric phenols
that result in resins having low birefringence for example dihydric
phenols having pendant aryl or cup shaped aryl groups like:
[0055] Phenyl-di(4-hydroxyphenyl) ethane (acetophenone
bisphenol):
[0056] Diphenyl-di(4-hydroxyphenyl) methane (benzophenone
bisphenol):
[0057] 2,2-bis(3-phenyl-4-hydroxyphenyl) propane
[0058] 2,2-bis-(3,5-diphenyl-4-hydroxyphenyl) propane;
[0059] bis-(2-phenyl-3-methyl-4-hydroxyphenyl) propane;
[0060] 2,2'-bis(hydroxyphenyl)fluorene;
[0061] 1,1-bis(5-phenyl-4-hydroxyphenyl)cyclohexane;
[0062] 3,3'-diphenyl4,4'-dihydroxy diphenyl ether;
[0063] 2,2-bis(4-hydroxyphenyl)-4,4-diphenyl butane;
[0064] 1,1-bis(4-hydroxyphenyl)-2-phenyl ethane;
[0065] 2,2-bis(3-methyl-4-hydroxyphenyl)-1-phenyl propane;
[0066]
6,6'-dihdyroxy-3,3,3',3'-tetramethyl-1,1'-spiro(bis)indane;
[0067] (hereinafter "SBI"), or dihydric phenols derived from spiro
biindane of formula IV: 5
[0068] Units derived from SBI and its 5-methyl homologue are
preferred, with SBI being most preferred.
[0069] Other dihydric phenols which are typically used in the
preparation of the polycarbonates are disclosed in U.S. Pat. Nos.
2,999,835, 3,038,365, 3,334,154 and 4,131,575. Branched
polycarbonates are also useful, such as those described in U.S.
Pat. Nos. 3,635,895 and 4,001,184. Polycarbonate blends include
blends of linear polycarbonate and branched polycarbonate.
[0070] It is also possible to employ two or more different dihydric
phenols or a copolymer of a dihydric phenol with an aliphatic
dicarboxylic acids like; dimer acids, dodecane dicarboxylic acid,
adipic acid, azelaic acid in the event a carbonate copolymer or
interpolymer rather than a homopolymer is desired for use in the
preparation of the polycarbonate mixtures of the invention. Most
preferred are aliphatic C5 to C12 diacid copolymers.
[0071] The preferred polycarbonates are preferably high molecular
weight aromatic carbonate polymers have an intrinsic viscosity (as
measured in methylene chloride at 25.degree. C.) ranging from about
0.30 to about 1.00 dl/gm. Polycarbonates may be branched or
unbranched and generally will have a weight average molecular
weight of from about 10,000 to about 200,000, preferably from about
20,000 to about 100,000 as measured by gel permeation
chromatography. It is contemplated that the polycarbonate may have
various known end groups.
[0072] In the thermoplastic compositions which contain a
cycloaliphatic polyester resin and a polycarbonate resin it is
preferable to use a stabilizer or quencher material. Catalyst
quenchers are agents which inhibit activity of any catalysts which
may be present in the resins. Catalyst quenchers are described in
detail in U.S. Pat. No. 5,441,997. It is desirable to select the
correct quencher to avoid color formation and loss of clarity to
the polyester polycarbonate blend.
[0073] A preferred class of stabilizers including quenchers are
those which provide a transparent and colorless product. Typically,
such stabilizers are used at a level of 0.001-10 weight percent and
preferably at a level of from 0.005-2 weight percent. The favored
stabilizers include an effective amount of an acidic phosphate
salt; an acid, alkyl, aryl or mixed phosphite having at least one
acidic hydrogen; a Group IB or Group IIB metal phosphate salt; a
phosphorus oxo acid, a metal acid pyrophosphate or a mixture
thereof. The suitability of a particular compound for use as a
stabilizer and the determination of how much is to be used as a
stabilizer may be readily determined by preparing a mixture of the
polyester resin component and the polycarbonate and determining the
effect on melt viscosity, gas generation or color stability or the
formation of interpolymer. The acidic phosphate salts include
sodium dihydrogen phosphate, mono zinc phosphate, potassium
hydrogen phosphate, calcium dihydrogen phosphate and the like. The
phosphites may be of the formula V: 6
[0074] where R1, R2 and R3 are independently selected from the
group consisting of hydrogen, alkyl and aryl with the proviso that
at least one of R1, R2 and R3 is hydrogen.
[0075] The phosphate salts of a Group IB or Group IIB metal include
zinc phosphate and the like. The phosphorus oxo acids include
phosphorous acid, phosphoric acid, polyphosphoric acid or
hypophosphorous acid.
[0076] The polyacid pyrophosphates may be of the formula VI:
MzxHyPnO3n+1
[0077] wherein M is a metal, x is a number ranging from 1 to 12 and
y is a number ranging 1 to 12, n is a number from 2 to 10, z is a
number from 1 to 5 and the sum of (xz)+y is equal to n+2. The
preferred M is an alkaline or alkaline earth metal.
[0078] The most preferred quenchers are oxo acids of phosphorus or
acidic organo phosphorus compounds. Inorganic acidic phosphorus
compounds may also be used as quenchers, however they may result in
haze or loss of clarity. Most preferred quenchers are phosphoric
acid, phosphorous acid or their partial esters.
[0079] Preferred polycarbonate cycloaliphatic polyester blends with
low birefringence will further comprise a mold release. The mold
release composition will retain clarity and color while allowing
easy de-bonding of the optical data storage device from the forming
mold. This will be especially important for devices that are
injection molded. Preferred mold release compounds will be of low
molecular weight most preferably below 2000. The preferred mold
release can be chosen from the group consisting of low molecular
weight polyolefins, esters and amides. Mold release agents will
generally be use at 0.01 to 0.5% by weight of the whole
formulation.
[0080] The most preferred mold releases are pentaerythritol tetra
esters, especially the stearate esters. Also preferred are
carboxylic acid esters of other polyols like glycerol; for example
glycerol mono stearate.
[0081] The preferred articles of the invention will produce optical
storage devices having the following characteristics:
[0082] Visible light transmission as measured by ASTM method D1003,
will be greater than or equal to 75%, most preferred above 85%.
[0083] In-Plane Birefringence (IBR) will be from -100 to +100
nanometers (nm)
[0084] Vertical Birefringence (VBR) will be less than or equal to
300.times.10-6.
[0085] The stress optical coefficient (Cg) will be less than or
equal to 70 Brewsters.
[0086] The glass transition temperature of the preferred blend will
be from 80 to 180.degree. C. with the range of 90-150.degree. C.
most preferred.
[0087] A flexural modulus (as measured by ASTM method D790) at room
temperature of greater than or equal to 150,00 psi is preferred,
with a flexural modulus of greater than or equal to 250,000 psi
being more preferred.
[0088] The yellowness index (YI) will be less than 10, preferably
less than 5 as measured by ASTM method D1925.
[0089] Haze, as measured by ASTM method D1003, will be below 1% in
the preferred composition.
[0090] Articles of the invention for optical storage of data can be
of any type with compact discs (CD), digital video disc (DVD),
magneto optical discs being most preferred. Devices can also be
recordable and rewritable optical data storage media. In the most
preferred devices a reflective metal layer is attached directly to
the resin blend substrate where the metal is aluminum, gold or
silver.
[0091] The substrate will have a plurality of pits or depressions
to encode data.
[0092] The data will be read from the optical recording device by a
laser.
EXAMPLES
[0093] The following examples serve to illustrate the invention but
are not intended to limit the scope of the invention. Control
experiments are designated by letters, examples of the invention
are designated by numbers.
[0094] Blends were prepared by tumbling all ingredients together
for 1-5 min at room temperature followed by extrusion at
250-300.degree. C. on a co-rotating 30 mm vacuum vented twin screw
extruder. Blends were run at 300 rpm. The output was cooled as a
strand in a water bath and pelletized.
[0095] The resultant materials were dried at 100-130.degree. C. for
3-6 h and injection molded in discs or sections of discs (fans) for
evaluation of optical properties.
[0096] In this work Bisphenol A Polycarbonate (BPA-PC) was molded
into the test parts under the same conditions as the examples of
the invention and was used as a basis for comparison. BPA-PC is
widely used for the production of laser read compact discs for
optical storage of information.
[0097] IBR, VBR and Cg were measured on injection molded center
gated 120 mm.times.2 mm discs at 40 mm radius from the center or on
130 mm.times.2 mm fan shaped parts at 50 or 65 mm radius from the
gate (which was located at the narrow end of the fan).
[0098] The glass transition temperature of the blends (Tg) was
measured by Differential Scanning Calorimetery (DSC) and will
reflect the processability of the resin; a lower Tg being easier to
melt and process. However a Tg which is too low will indicate an
inability to hold shape under normal environmental heating. For
practical heat resistance a Tg above 80.degree. C. is preferred. To
have better processability than BPA-PC, a Tg below 150.degree. C.
is preferred but any relative reduction in PC Tg is beneficial
depending on the overall balance of optical and thermal properties
desired.
1 Materials BPA-PC Bisphenol A (BPA) Polycarbonate SBI-BPA-PC 72:28
(mole %) Spirobiindane bisphenol: BPA Polycarbonate PC-Bis AP
Polycarbonate of the bisphenol adduct of acetophenone SBI-DDDA-
Polycarbonate copolymer of spirobiindane bisphenol: BPA-PC 1,12
dodceyl dicarboxylic acid: BPA (18:7:75 mole %) PCCD
Polycyclohexane dimethanol cyclohexyl dicarboxylate PCT
Polycyclohexane dimethanol terephthalate PCCD-PBO Block copolymer
of PCCD with poly butylene oxide (l7 wt. %)
Examples 1-2
[0099] Table 1 shows blends of PCCD with BPA-PC or SBI-BPA-PC
(Examples 1 & 2).
[0100] Compared to BPA-PC alone (Ex. B) the blends show lower IBR
or VBR.
[0101] The blends also have reduced Tg vs. BPA-PC or
SBI-BPA-PC.
[0102] Note the SBI-BPA-PC (Ex. C) has very small VBR and IBR
values but its high Tg (210.degree. C.) makes it difficult to mold.
PCCD (Ex . A) has a very low Tg which limits its heat
resistance.
[0103] The blends also maintain excellent optical clarity which is
critical for optical data storage devices. Percent transmission was
>75% for all samples.
2TABLE 1 Birefringence from Fan- Gated Plaque of PCCD Blends
Example A B C 1 2 PCCD 100 0 0 50 70 BPA-PC 0 100 0 50 0 SBI-BPA-PC
0 0 100 0 30 Tg .degree. C. 62 145 210 102 108 IBR 50 mm 790 237 5
58 235 radius IBR 65 mm 648 158 * -20 186 radius VBR 50 mm 463 527
65 523 373 radius VBR 65 mm 717 598 * 432 419 radius
[0104] Blends 1 & 2 contained 0.10% of 45% aqueous phosphorous
acid.
Examples 3-5
[0105] Table 2 shows various levels of SBI-BPA-PC blended with PCCD
(Examples 3-5). All blends are transparent and show reduced Tg vs.
the parent polycarbonate (SBI-BPA-PC; Ex. E) and have reduced VBR,
IBR and Cg vs. the PCCD control (Ex. D).
3TABLE 2 Birefringence from Discs of PCCD Blends Example D E F 3 4
5 PCCD 100 0 0 30 50 70 BPA-PC 0 0 100 0 0 0 SBI-BPA-PC 0 100 0 70
50 30 Tg .degree. C. 62 210 145 163 148 * IBR 50 mm 392 5 146 36 *
211 radius VBR 50 mm 403 65 530 129 * 353 radius Cg Brewesters 58
37 82 37 43 45
[0106] Examples 3,4 & 5 of Table 2 additionally contained: 0.1%
45% aqueous phosphorous acid, 0.2% tris (di-tertbutylphenyl)
phosphite, 0.2% Irganox.RTM.1076 hindered phenol ester antioxidant
from Ciba Geigy Co., and 0.27% pentaerythritol tetrastearate; based
on wt % of the whole blend.
Examples 6-12
[0107] Table 3 shows blends of PCCD with BPA-PC, PC-Bis AP,
SBI-DDDA-BPA-PC and SBI-BPA-PC. All blends were transparent and
show improved birefringence properties.
4TABLE 3 Birefringence from Discs of PCCD Blends Example 6 7 8 9 10
11 12 PCCD 50 50 50 50 30 15 5 BPA-PC 50 0 0 0 0 0 0 SBI-BPA-PC 0 0
0 50 70 85 95 PC-Bis AP 0 50 0 0 0 0 0 SBI-DDDA-BPA- 0 0 50 0 0 0 0
PC Tg oC 95 113 97 148 163 183 195 IBR 40 mm radius -20 -46 -4 4 12
27 27 VBR 40 mm 209 286 252 168 170 110 97 radius Cg Brewsters 49
46 * 38 33 35 31
[0108] All blends of Table 3 additionally contained: 0.1% 45%
aqueous phosphorous acid, 0.2% tris (di-tertbutylphenyl) phosphite,
0.2% Irganox.RTM.1076 hindered phenol ester antioxidant from Ciba
Geigy Co., and 0.27% pentaerythritol tetrastearate; based on wt %
of the whole blend.
Examples 13-14
[0109] Table 4 shows examples of the invention using other cyclo
aliphatic polyesters PCT and the copolymer PCCD-PBO with
SBI-BPA-PC
[0110] The blends show reduced Tg vs. SBI-BPA-PC and low IBR, VBR
and Cg values.
5TABLE 4 Discs of PCT and PCCD copolymers Blends Example 13 14 PCT
50 0 PCCD-PBO 0 50 SBI-BPA-PC 50 50 Tg .degree. C. 95 90 IBR 40 mm
radius 10 -96 VBR 40 mm 72 156 radius Cg Brewesters * 33
[0111] All blends of Table 4 additionally contained: 0.1% 45%
aqueous phosphorous acid, 0.2% tris (di-tertbutylphenyl) phosphite,
0.2% Irganox.RTM.1076 hindered phenol ester antioxidant from Ciba
Geigy Co., and 0.27% pentaerythritol tetrastearate; based on wt %
of the whole blend.
* * * * *