Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-04-17
2004-07-13
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S281000, C526S282000, C526S916000, C359S506000
Reexamination Certificate
active
06762266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phase retarder that makes it possible to conduct uniform polarizing conversion in a wide wavelength range using a single phase retarder.
2. Description of the Related Art
Commonly used phase retarders are obtained by monoaxial stretching or biaxial stretching of thermoplastic resins such as polycarbonate, polyallylate, polystyrene, polyvinyl alcohol, norbornene resin and the like. When a ratio (R
450
/R
590
) of retardation at light having a wavelength of 450 nm (R
450
) to retardation at light having a wavelength of 590 nm (R
590
) is defined as a wavelength dispersion coefficient &agr;, the wavelength dispersion coefficient &agr; of a phase retarder obtained from these thermoplastic resins is about 1.00 or more. The wavelength dispersion coefficient &agr; is a value peculiar to a substance.
In order to conduct uniform polarizing conversion within a wide wavelength range using a polarizing conversion element such as phase retarder, the wavelength dispersion coefficient &agr; is preferably less than about 1.00. An ideal phase retarder generates retardation so that a ratio of retardation to wavelength has a constant value, for example ¼ or ½, at any wavelength. In other words, a value determined by dividing retardation at each wavelength by its wavelength is constant in an ideal phase retardation film. Therefore, an ideal wavelength dispersion coefficient &agr; of the phase retarder is 450/590 (nearly equal 0.76).
To attain such wavelength dispersion properties, Japanese Unexamined Patent Publication (Kokai) No. 2-120804 proposes to laminate two phase retarders having different wavelength dispersion properties, while Japanese Unexamined Patent Publication (Kokai) No. 5-100114 proposes to laminate a &lgr;/2 plate and a &lgr;/4 plate. However, in case two or more phase retarders are laminated, the cost increases and the thickness inevitably increases, and also there was a problem such as large angle dependence of optical properties.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a phase retarder that makes it possible to conduct uniform polarizing conversion within a wide wavelength range using a single phase retarder.
As a result of diligent research, the present inventors have found that a phase retarder, that can achieve the object described above, can be obtained by stretching a polymer prepared by copolymerizing three kinds of monomers in a composition ratio within a range as described herein. Thus, the present invention has been completed.
That is, the present invention provides a phase retarder comprising a copolymer prepared by polymerizing the following components (A), (B) and (C):
(A) at least one non-cyclic olefin monomer selected from ethylene and &agr;-olefin compound having 3 to 20 carbon atoms;
(B) at least one cyclic olefin monomer selected from cyclic olefin compound; and
(C) at least one aromatic vinyl monomer selected from vinyl compound having a cyclic unit made of an aromatic hydrocarbon, or at least one alicyclic vinyl monomer selected from vinyl compound having a cyclic unit made of an alicyclic hydrocarbon;
wherein (1) the amount of the aromatic vinyl monomer is from about 1 to about 20 mol % and the total amount of the non-cyclic olefin monomer (A) and the cyclic olefin monomer (B) is from about 80 to about 99 mol % in case the component (C) is the aromatic vinyl monomer; or
(2) the amount of the alicyclic vinyl monomer is from about 80 to about 99 mol % and the total amount of the non-cyclic olefin monomer (A) and the cyclic olefin monomer (B) is from about 1 to about 20 mol % in case the component (C) is the alicyclic vinyl monomer.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described in detail. In the phase retarder produced by stretching and orienting a copolymer comprising a repeating unit of a monomer having a positive polarizability and a repeating unit of a monomer having a negative polarizability, retardations originating in each repeating unit offset each other and the retardation of the copolymer becomes a difference in retardation originating in each repeating unit Therefore, the wavelength dispersion properties of the copolymer are decided by wavelength dispersion properties of each repeating unit and magnitude of the retardation of the component originating in each repeating unit. Thus, wavelength dispersion can be controlled with introducing repeating units having different polarizabilities and wavelength dispersions in the polymer.
The role of the repeating unit originating in each of the non-cyclic olefin monomer (A), the cyclic olefin monomer (B), and the aromatic vinyl monomer or alicyclic vinyl monomer (C) as components of the polymer constituting the phase retarder of the present invention will now be described concretely. It is considered that the repeating unit originating in the non-cyclic olefin monomer (A) has the role of imparting the flexibility to the polymer and, moreover, the polarizability is positive to the direction of a main chain of the polymer and the wavelength dispersion coefficient &agr; A is considered to be nearly equal 1.00. It is considered that the repeating unit originating in the cyclic olefin monomer (B) has the role of improving the heat resistance of the polymer and, moreover, the polarizability is generally positive to the direction of a main chain of the polymer and the wavelength dispersion coefficient &agr;
B
is considered to be nearly equal 1.00. It is considered that the repeating unit originating in the aromatic or alicyclic vinyl compound (C) having a cyclic unit made of an aromatic or alicyclic hydrocarbon has the role of improving the transparency to the polymer and, moreover, the polarizability is negative to the direction of a main chain of the polymer and the wavelength dispersion coefficient &agr;
C
is considered to be 1.00 or more. Proper control of a copolymerization ratio of the non-cyclic olefin monomer (A), the cyclic olefin monomer (B), and the aromatic or alicyclic vinyl monomer (C) makes it possible to design a copolymer having excellent balance between the flexibility, transparency, heat resistance and wavelength dispersion properties.
With respect to a component ratio of the repeating unit originating in the non-cyclic olefin monomer (A), the repeating unit originating in the cyclic olefin monomer (B) and the repeating unit originating in the vinyl monomer (C) having a cyclic unit in the copolymer, the amount of the repeating unit originating in the aromatic vinyl monomer is about 1 to about 20 mol % and the total amount of the repeating unit originating in each of the non-cyclic olefin monomer (A) and the cyclic olefin monomer (B) is about 80 to about 99 mol % in case the vinyl monomer (C) is the aromatic vinyl monomer. In view of the flexibility and heat resistance, the amount of the repeating unit originating in the cyclic olefin monomer (B) is preferably about 40 mol % or more. The amount of the repeating unit originating in the non-cyclic olefin monomer (A is preferably about 1 mol % or more.
In case the vinyl monomer (C) is the alicyclic vinyl monomer, the amount of the repeating unit originating in the alicyclic vinyl monomer is about 80 to about 99 mol % and the total amount of the repeating unit originating in each of the non-cyclic olefin monomer (A) and the cyclic olefin monomer (B) is about 1 to about 20 mol %. Each amount of the non-cyclic olefin monomer (A) and the cyclic olefin monomer (B) may be preferably selected within a ran
Higashi Koji
Minakuchi Keiichi
Oi Nobuo
Sumitomo Chemical Company Limited
Teskin Fred
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