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United States Patent Application |
20010008920
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Kind Code
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A1
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Arakawa, Kohei
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July 19, 2001
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Norbornene based resin composition and phase difference plate
Abstract
A phase difference plate is provided which can be formed by a single
material at a low cost without a need for forming laminated layers, and
which has excellent performance in a wide band. The phase difference
plate is formed by using a norbornene based resin composition which
includes a norbornene based resin; and a polymer whose birefringence
value is negative, and whose wavelength dispersion of birefringence
values satisfies .vertline..DELTA.n(450)/.DELTA.n(550).vertline..gtoreq.1-
.02, wherein .DELTA.n(450) and .DELTA.n(550) are birefringence values
(.DELTA.n) at a wavelength of 450 nm and a wavelength of 550 nm,
respectively. The polymer is preferably a polystyrene based polymer.
Inventors: |
Arakawa, Kohei; (Kanagawa, JP)
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Correspondence Address:
|
BURNS DOANE SWECKER & MATHIS L L P
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
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Serial No.:
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756730 |
Series Code:
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09
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Filed:
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January 10, 2001 |
Current U.S. Class: |
525/210 |
Class at Publication: |
525/210 |
International Class: |
C08L 045/00 |
Foreign Application Data
Date | Code | Application Number |
Jan 14, 2000 | JP | 2000-5446 |
Claims
What is claimed is:
1. A norbornene based resin composition comprising: a norbornene based
resin; and a polymer whose birefringence value is negative, and whose
wavelength dispersion of birefringence values satisfies
.vertline..DELTA.n(450)/.DELTA.n(550).vertline..gtoreq.1.02, wherein
.DELTA.n(450) and .DELTA.n(550) are birefringence values (.DELTA.n) at a
wavelength of 450 nm and a wavelength of 550 nm, respectively.
2. A norbornene based resin composition according to claim 1, wherein the
norbornene based resin is a thermoplastic norbornene resin.
3. A norbornene based resin composition according to claim 2, wherein the
thermoplastic norbornene resin has a repeating unit expressed by any of
following structural formulas (I) through (IV). 3
4. A norbornene based resin composition according to claim 2, wherein the
thermoplastic norbornene resin is a water-added polymer, which is
obtained by the hydrogen addition of a polymer obtained by metathesis
polymerization of at least one type of tetracyclododecene expressed by
following structural formula (V) and an unsaturated cyclic compound which
is polymerizable therewith. 4
5. A norbornene based resin composition according to claim 1, wherein a
weight average molecular weight of the norbornene based resin is 5,000 to
1,000,000.
6. A norbornene based resin composition according to claim 1, wherein the
wavelength dispersion of birefringence values of the polymer satisfies
.vertline..DELTA.n(450)/.DELTA.n(550).vertline..gtoreq.1.05, wherein
.DELTA.n(450) and .DELTA.n(550) are birefringence values (.DELTA.n) at a
wavelength of 450 nm and a wavelength of 550 nm, respectively.
7. A norbornene based resin composition according to claim 1, wherein the
polymer is a polystyrene based polymer.
8. A norbornene based resin composition according to claim 1, wherein a
weight ratio of the norbornene based resin and the polymer whose
birefringence value is negative (the norbornene based resin:the polymer
whose birefringence value is negative) is 5:5 to 9:1.
9. A norbornene based resin composition according to claim 1, wherein the
norbornene based resin composition is used in a phase difference plate
having birefringence.
10. A phase difference plate formed by using a norbornene based resin
composition comprising: a norbornene based resin; and a polymer whose
birefringence value is negative, and whose wavelength dispersion of
birefringence values satisfies .vertline..DELTA.n(450)/.DELTA.n(550).vert-
line..gtoreq.1.02, wherein .DELTA.n(450) and .DELTA.n(550) are
birefringence values (.DELTA.n) at a wavelength of 450 nm and a
wavelength of 550 nm, respectively.
11. A phase difference plate according to claim 10, wherein the phase
difference plate satisfies Re(450 nm)<Re(550 nm)<Re(650 nm),
wherein Re(450 nm), Re(550 nm), and Re(650 nm) are retardation (Re)
values at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.
12. A phase difference plate according to claim 10, wherein the norbornene
based resin is a thermoplastic norbornene resin.
13. A phase difference plate according to claim 12, wherein the
thermoplastic norbornene resin has a repeating unit expressed by any of
following structural formulas (I) through (IV). 5
14. A phase difference plate according to claim 12, wherein the
thermoplastic norbornene resin is a water-added polymer, which is
obtained by the hydrogen addition of a polymer obtained by metathesis
polymerization of at least one type of tetracyclododecene expressed by
following structural formula (V) and an unsaturated cyclic compound which
is polymerizable therewith. 6
15. A phase difference plate according to claim 10, wherein a weight
average molecular weight of the norbornene based resin is 5,000 to
1,000,000.
16. A phase difference plate according to claim 10, wherein the wavelength
dispersion of birefringence values of the polymer satisfies
.vertline..DELTA.n(450)/.DELTA.n(550).vertline..gtoreq.1.05, wherein
.DELTA.n(450) and .DELTA.n(550) are birefringence values (.DELTA.n) at a
wavelength of 450 nm and a wavelength of 550 nm, respectively.
17. A phase difference plate according to claim 10, wherein the polymer is
a polystyrene based polymer.
18. A phase difference plate according to claim 10, wherein a weight ratio
of the norbornene based resin and the polymer whose birefringence value
is negative (the norbornene based resin:the polymer whose birefringence
value is negative) is 5:5 to 9:1.
19. A phase difference plate according to claim 10, wherein the phase
difference plate is one of a wide band .lambda./4 plate and a wide band
.lambda./2 plate.
20. A phase difference plate according to claim 10, wherein the phase
difference plate is used in a liquid crystal display device.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a phase difference plate which is
suitable for a reflection-type liquid crystal display device which can be
used as a display device in various fields such as personal computers, AV
equipment, portable information communication devices, game and
simulation devices, on-board navigation systems, and the like, and to a
norbornene based resin composition which is suitably used in the phase
difference plate.
[0003] 2. Description of the Related Art
[0004] A .lambda./4 plate, whose retardation (Re) is 1/4of the length of a
wavelength, has various applications in reflection-type LCDs, pick-up for
optical discs, anti-glare films, and the like. A .lambda./2 plate, whose
retardation (Re) is 1/2of the length of a wavelength, is useful as a
liquid crystal projector. In each of these applications, it is preferable
that the .lambda./4 plate and the .lambda./2 plate sufficiently exhibit
functions with respect to all of the incident light in the range of
visible light which can be seen by the human eye.
[0005] For example, Japanese Patent Application Laid-Open (JP-A) Nos.
5-27118, 5-100114, 10-68816 and 10-90521 have proposed, as wide band
phase difference plates functioning as .lambda./4 plates and .lambda./2
plates with respect to incident light in the entire visible light region,
structures in which two polymer films having respective different optical
anisotropy are layered.
[0006] However, in these cases, in the production thereof, it is necessary
to obtain two types of chips in which elongate films, which are each
drawn in one direction, are cut in directions forming different angles
with respect to the directions of drawing, and to laminate these chips
together. In such a .lambda./4 plate, the optical anisotropy (inclination
of the optical axis or the slow axis) of each polymer film is determined
by the angle at which the chip is cut with respect to the direction of
drawing of the drawn film. Thus, a precise cutting technology is
required. Moreover, when the two chips are laminated, an adhesive must be
applied and precise alignment must be carried out, such that the
production processes are complex. Namely, processes such as an adhering
process, a chip-forming process, a laminating process, and the like
result in an increase in costs. Further, dirtying caused by the scum
produced during chip-forming and the like, dispersion in the phase
differences caused by errors in the laminating angle, and the like
adversely affect the actual performances.
[0007] Currently, there has not yet been provided a technology in which a
wide band .lambda./4 plate or a wide band .lambda./2 plate, which has
retardation of 1/4wavelength or 1/2wavelength in the entire region of
visible light and which is sufficiently durable to be able to withstand
use, is formed by a single material without forming layers.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to provide a phase difference
plate which can be formed by a single material at a low cost without
having to form a laminated structure, and which exhibits excellent
performances in a wide band. Moreover, an object of the present invention
is to provide a norbornene based resin composition which is suitably used
in the phase difference plate.
[0009] The norbornene based resin composition of the present invention
comprises: a norbornene based resin; and a polymer whose birefringence
value is negative, and whose wavelength dispersion of birefringence
values satisfies .vertline..DELTA.n(450)/.DELTA.n(550).vertline..gtoreq.1-
.02, wherein .DELTA.n(450) and .DELTA.n(550) are birefringence values
(.DELTA.n) at a wavelength of 450 nm and a wavelength of 550 nm,
respectively.
[0010] The phase difference plate of the present invention is formed by
using the norbornene based resin composition of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a graph showing results of measurement of wavelength
dispersion characteristics of Re values in a visible light range of phase
difference plates manufactured in Example 1, Comparative Example 1, and
Comparative Example 2.
[0012] FIG. 2 is a graph showing results of measurement of wavelength
dispersion characteristics of Re values in a visible light range of phase
difference plates manufactured in Example 2, Comparative Example 3 and
Comparative Example 4.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Norbornene Based Resin Composition
[0013] The norbornene based resin composition of the present invention
comprises a norbornene based resin and a polymer whose birefringence
value is negative, as well as other components which are appropriately
selected as needed.
Norbornene Based Resin
[0014] The norbornene based resin has the characteristic of exhibiting
positive optical uniaxiality when the molecules are oriented in uniaxial
order.
[0015] The norbornene based resin is not particularly limited, and can be
appropriately selected in accordance with the object. However,
thermoplastic norbornene resins are preferable from the standpoints of
excellent transparence, low water absorbency, excellent heat-resistance,
low photoelasticity, and their suitably to optical applications.
[0016] The thermoplastic norbornene resin has, as the repeating unit
thereof, a norbornene skeleton. Specific examples thereof are disclosed
in JP-A-60-168708, 62-252406, 62-252407, 2-133413, 63-145324, 63-264626,
1-240517, Japanese Patent Application Publication (JP-B) No. 57-8815, and
the like. One type of thermoplastic norbornene resin may be used alone,
or two or more types may be used in combination.
[0017] In the present invention, among the thermoplastic norbornene
resins, those having a repeating unit expressed by any of following
structural formulas (I) through (IV) are preferable. 1
[0018] In the above structural formulas, A, B, C and D represent a
hydrogen atom or a monovalent organic group.
[0019] Among the thermoplastic norbornene resins, a hydrogen-added
polymer, which is obtained by the hydrogen addition of a polymer obtained
by metathesis polymerization of at least one type of tetracyclododecene
expressed by following structural formula (V) and an unsaturated cyclic
compound which is polymerizable therewith; is preferable. 2
[0020] In the above structural formula, A, B, C and D represent a hydrogen
atom or a monovalent organic group.
[0021] The weight average molecular weight of the norbornene based resin
is around 5,000 to 1,000,000, and is preferably 8,000 to 200,000.
Polymer whose Birefringence Value is Negative
[0022] The polymer whose birefringence value is negative is a polymer in
which, when the molecules thereof are oriented in order uniaxially, the
overall optical characteristic of the polymer exhibits negative
uniaxiality.
[0023] The polymer whose birefringence value is negative may be a single
polymer exhibiting such a characteristic, or a polymer having such a
characteristic may be obtained by blending two or more polymers.
[0024] The polymer whose birefringence value is negative is selected from
polymers in which the wavelength dispersion of the birefringence value is
large. Specifically, the polymer is selected from polymers whose
wavelength dispersion of the birefringence value satisfies
.vertline..DELTA.n(450)/.DELTA.n(550).vertline..gtoreq.1.02, and
preferably satisfies .vertline..DELTA.n(450)/.DELTA.n(550).vertline..gtor-
eq.1.05, wherein the birefringence values (.DELTA.n) at a wavelength of
450 nm and a wavelength of 550 nm are .DELTA.n(450) and .DELTA.n(550),
respectively.
[0025] Further, the larger the value of .vertline..DELTA.n(450)/.DELTA.n(5-
50).vertline., the better. However, in the case of polymers,
.vertline..DELTA.n(450)/.DELTA.n(550).vertline. is usually 2.0 or less.
[0026] Examples of the polymers are polystyrene based polymers,
polyacrylonitrile based polymers, polymethylmethacrylate based polymers,
cellulose ester based polymers (excluding those having an birefringence
value which is positive), or copolymers (binary, ternary, etc.) thereof.
A single such polymer can be used alone, or two or more types of such
polymers can be used in combination.
[0027] Among these, polystyrene based polymers such as polystyrene,
styrene/acrylonitrile copolymers, styrene/maleic anhydride copolymers,
styrene/methylmethacrylate copolymers, and the like are particularly
preferable.
[0028] The mixing ratio of the polymer whose birefringence value is
negative with respect to the norbornene based resin differs in accordance
with the magnitudes of the absolute values of the birefringence values of
both, the manifestation of birefringence at the molding temperature, and
the like. Although the mixing ratio cannot be unconditionally limited,
the mixing ratio is preferably a weight ratio (norbornene based
resin:polymer having a negative birefringence value) of 5:5 to 9:1, and
more preferably 7:3 to 8:2.
Other Components
[0029] The other components are not particularly limited, provided that
they do not adversely affect the effects of the present invention, and
can be selected appropriately as needed. A suitable example of such other
components are compatibilizing agents.
[0030] A compatibilizing agent is suitably used in cases in which phase
separation occurs when the norbornene based resin and the polymer whose
birefringence value is negative are mixed together. By using a
compatibilizing agent, the mixed-together state of the norbornene based
resin and the birefringence value is satisfactory.
Application
[0031] The norbornene based resin composition of the present invention can
be suitably used in a phase difference plate having birefringence.
Phase Difference Plate
[0032] The phase difference plate of the present invention is formed by
using the norbornene based resin composition of the present invention.
[0033] It is preferable that the phase difference plate satisfies the
inequality Re(450 nm)<Re(550 nm)<Re(650 nm), wherein Re(450 nm),
Re(550 nm), Re(650 nm) are the retardation (Re) values at wavelengths of
450 nm, 550 nm, and 650 nm, respectively.
[0034] The phase difference plate is preferably either a wide band
.lambda./4 plate or a wide band .lambda./2 plate.
[0035] The method of manufacturing the phase difference plate of the
present invention is not particularly limited, and can be selected
appropriately in accordance with the object. For example, the phase
difference plate can be manufactured as follows. Namely, the phase
difference plate can be manufactured by a solution film forming method in
which the norbornene based resin composition of the present invention is
made into a solution and is applied and dried so as to form a film. Or,
the phase difference plate can be manufactured by an extrusion molding
method in which the norbornene based resin composition of the present
invention is made into pellets which are melt extruded and form a film.
[0036] Given that Re(450 nm), Re(550 nm), Re(650 nm) are the retardation
(Re) values at wavelengths of 450 nm, 550 nm, and 650 nm, respectively,
if the phase difference plate obtained as described above satisfies the
inequality Re(450 nm)<Re(550 nm)<Re(650 nm), it can be used as it
is. However, if the phase difference plate does not satisfy this
inequality, it is preferable that the phase difference plate is used
after the retardation (Re) values have been controlled to satisfy the
above inequality, by changing the conditions such as the compositional
ratio, the drawing temperature, or the like.
[0037] Preferable examples of the aforementioned drawing are longitudinal
uniaxial drawing for drawing in the direction of mechanical flow, lateral
uniaxial drawing (e.g., tenter drawing) for drawing in the direction
orthogonal to the direction of mechanical flow, and the like. However, if
there is anisotropy in the drawing, biaxial drawing may be carried out.
Application
[0038] The phase difference plate of the present invention exhibits
desired characteristics with a single molded body. Thus, there is no need
to laminate two or more members, and the phase difference plate can be
manufactured at a low cost, and exhibits excellent performances in a wide
band. The phase difference plate of the present invention is suitably
used in reflective-type liquid crystal display devices which can be used
as display devices in various fields such as personal computers, AV
equipment, portable information communications equipment, game and
simulation devices, on-board navigation systems, and the like.
[0039] Hereinafter, Examples of the present invention will be described.
However, it is to be noted that the present invention is not limited to
these Examples.
EXAMPLE 1
[0040] A coating solution (25 wt %) was prepared by dissolving, in a
methylene chloride solution, 19 parts by weight of a norbornene resin
(ATON F, manufactured by JSR Co.) as the norbornene based resin, and 6
parts by weight of polystyrene (HRM-2-211L manufactured by Toyo Styrene
Co.) as the material whose birefringence value is negative, and a small
amount of a compatibilizing agent (a copolymer of norbornene and
styrene).
[0041] The aforementioned polystyrene had a wavelength dispersion of the
birefringence value of .vertline..DELTA.n(450)/.DELTA.n(550).vertline.=1.-
05, wherein the birefringence values (.DELTA.n) at wavelengths of 450 nm
and 550 nm were .DELTA.n(450) and .DELTA.n(550).
[0042] The above coating solution was flowingly spread onto a glass plate
by using a doctor blade and was dried so that a transparent film having a
thickness of 104 .mu.m was formed. The transparent film was 23%
uniaxially extruded at 150.degree. C. so as to obtain a phase difference
plate. The wavelength dispersion of the Re values of the phase difference
plate was measured by using a retardation measuring device (KOBRA21DH,
manufactured by Oji Keisoku Co.). The results are shown in FIG. 1.
[0043] As can be seen in FIG. 1, the phase difference plate satisfied the
inequality Re(450 nm)<Re(550 nm)<Re(650 nm), wherein Re(450 nm),
Re(550 nm), Re(650 nm) are the retardation (Re) values at wavelengths of
450 nm, 550 nm, and 650 nm, respectively. The phase difference plate
exhibited the characteristic of a .lambda./4 plate in a wide band.
COMPARATIVE EXAMPLE 1
[0044] A phase difference wavelength plate was formed in the same manner
as in Example 1, except that polystyrene was not used, the thickness of
the transparent film was 105 .mu.m, and the transparent film was 36%
uniaxially extruded at 155.degree. C. The wavelength dispersion of the Re
values was measured in the same way as in Example 1. The results are
shown in FIG. 1.
[0045] As can be seen from FIG. 1, this phase difference plate did not
exhibit the characteristics of a wide band .lambda./4 plate.
COMPARATIVE EXAMPLE 2
[0046] A phase difference wavelength plate was formed in the same manner
as in Example 1, except that norbornene resin was not used, the thickness
of the transparent film was 97 .mu.m, and the transparent film was 17%
uniaxially extruded at 110.degree. C. The wavelength dispersion of the Re
values was measured in the same way as in Example 1. The results are
shown in FIG. 1.
[0047] As can be seen from FIG. 1, this phase difference plate did not
exhibit the characteristics of a wide band .lambda./4 plate.
EXAMPLE 2
[0048] A coating solution (25 wt %) was prepared by dissolving, in a
methylene chloride solution, 19 parts by weight of a norbornene resin
(ATON F, manufactured by JSR Co.) as the norbornene based resin, and 6
parts by weight of polystyrene (HRM-2-211L manufactured by Toyo Styrene
Co.) as the material whose birefringence value is negative, and a small
amount of a compatibilizing agent (a copolymer of norbornene and
styrene).
[0049] The aforementioned polystyrene had a wavelength dispersion of the
birefringence values of .vertline..DELTA.n(450)/.DELTA.n(550).vertline.=0-
.82, wherein the birefringence values (.DELTA.n) at wavelengths of 450 nm
and 550 nm were .DELTA.n(450) and .DELTA.n(550).
[0050] The above coating solution was flowingly spread onto a glass plate
by using a doctor blade and was dried so that a transparent film having a
thickness of 210 .mu.m was formed. The transparent film was 23%
uniaxially extruded at 150.degree. C. so as to obtain a phase difference
plate. The wavelength dispersion of the Re values of the phase difference
plate was measured by using a retardation measuring device (KOBRA21DH,
manufactured by Oji Keisoku Co.). The results are shown in FIG. 2.
[0051] As can be seen in FIG. 2, the phase difference plate satisfied the
inequality Re(450 nm)<Re(550 nm)<Re(650 nm), wherein Re(450 nm),
Re(550 nm), and Re(650 nm) are the retardation (Re) values at wavelengths
of 450 nm, 550 nm, and 650 nm, respectively. The phase difference plate
exhibited the characteristic of a .lambda./2 plate in a wide band.
COMPARATIVE EXAMPLE 3
[0052] A phase difference wavelength plate was formed in the same manner
as in Example 1, except that polystyrene was not used, the thickness of
the transparent film was 219 .mu.m, and the transparent film was 35%
uniaxially extruded at 155.degree. C. The wavelength dispersion of the Re
values was measured in the same way as in Example 2. The results are
shown in FIG. 2.
[0053] As can be seen from FIG. 2, this phase difference plate did not
exhibit the characteristics of a wide band .lambda./2 plate.
COMPARATIVE EXAMPLE 4
[0054] A phase difference wavelength plate was formed in the same manner
as in Example 2, except that norbornene resin was not used, the thickness
of the transparent film was 127 .mu.m, and the transparent film was 24%
uniaxially extruded at 110.degree. C. The wavelength dispersion of the Re
values was measured in the same way as in Example 2. The results are
shown in FIG. 2.
[0055] As can be seen from FIG. 2, this phase difference plate did not
exhibit the characteristics of a wide band .lambda./2 plate.
EXAMPLE 3
[0056] A coating solution (25 wt %) was prepared by dissolving, in
toluene, 16 parts by weight of a norbornene resin (ATON F, manufactured
by JSR Co.) as the norbornene based resin, and 9 parts by weight of a
styrene/maleic anhydride copolymer (DAIRAK 232, manufactured by Sekisui
Kagaku Co.) as the material whose birefringence value is negative.
[0057] The aforementioned styrene/maleic anhydride copolymer had a
wavelength dispersion of the birefringence value of
.vertline..DELTA.n(450)/.DELTA.n(550).vertline. =1.06, wherein the
birefringence values (.DELTA.n) at wavelengths of 450 nm and 550 nm were
.DELTA.n(450) and .DELTA.n(550).
[0058] The above coating solution was flowingly spread onto a glass plate
by using a doctor blade and was dried so that a transparent film having a
thickness of 210 .mu.m was formed. The transparent film was 23 %
uniaxially extruded at 150.degree. C. so as to obtain a phase difference
plate. The wavelength dispersion of the Re values of the phase difference
plate was measured by using a retardation measuring device (KOBRA21DH,
manufactured by Oji Keisoku Co.).
[0059] The results thereof were that the phase difference plate of Example
3 satisfied the inequality Re(450 nm)<Re(550 nm)<Re(650 nm),
wherein Re(450 nm), Re(550 nm), Re(650 nm) are the retardation (Re)
values at wavelengths of 450 nm, 550 nm, and 650 nm, respectively. The
phase difference plate exhibited the characteristic of a .lambda./4 plate
in a wide band.
[0060] The present invention provides a phase difference plate which
overcomes the above-described drawbacks of the prior art, and which can
be formed from a single material at a low cost without the need to form
laminated layers, and which has excellent performances in a wide band.
The present invention also provides a norbornene based resin composition
which is suitably used in the phase difference plate.
* * * * *