JP2002071956A - Lamianted phase difference film and lamianted polarizing film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase difference film giving a phase difference of half- wave to polarized light in a wide wavelength range. SOLUTION: The laminated phase difference film is obtained by stacking plural half-wave films each comprising a polymer film and each of the half-wave films has such characteristics as to ensure a smaller phase difference at a shorter wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated retardation film which can be suitably used in an optical device such as a liquid crystal projection type display device and which can provide a half-wave retardation in a wide wavelength range, and using the same. To a laminated polarizing film.

[0002]

2. Description of the Related Art A method of realizing a phase difference plate that gives a quarter wavelength or a half wavelength to polarized light in a wide wavelength range by using a plurality of laminated phase difference plates has long been known in the optical world. ing. Also, a technique in which the retardation plate is replaced with a polymer stretched film is disclosed in
No. 4 publication.

[0003]

However, when a laminated film is formed from a polymer stretched film by the method described in Japanese Patent Laid-Open No. 5-100114, it is true that only one polymer stretched film is used. Although it is more effective to use a plurality of sheets and cross the film optical axis at a specific bonding angle than when using multiple films, the individual polymer stretched films to be laminated have wavelength dispersion of retardation. A film with a large phase difference is used. For this reason, it is difficult to provide a sufficient broadband property, that is, a half-wave phase difference to polarized light in a wider wavelength range which is the object of the present invention.

It is a primary object of the present invention to provide a retardation film which gives a half-wave retardation to polarized light in a wide wavelength range. Another object of the present invention is to provide a retardation film suitable for an optical device such as a liquid crystal projection display device. Another object of the present invention is to provide a polarizing film suitable for an optical device such as a liquid crystal projection display device.

[0005]

Means for Solving the Problems In order to solve the above problems, the present inventors have conducted intensive studies on the wavelength dispersion of the retardation of each polymer film used in the laminated retardation film and the polymer structure for realizing the wavelength dispersion. By laminating a half-wave film having retardation wavelength dispersion characteristics, a half-wave phase difference was successfully given to polarized light in a wider wavelength range than in the prior art.

That is, the present invention relates to a laminated retardation film obtained by laminating a plurality of half-wave films made of one polymer film, and the half-wave film has a position at wavelengths of 450 nm and 550 nm. The relationship of the phase difference is represented by the following formula (1): R (450) / R (550) <1 (1) (where R (450) and (550) are the in-plane positions of the polymer film at wavelengths of 450 nm and 550 nm, respectively). ) Is achieved by a laminated retardation film that satisfies the following conditions.

[0007] The present invention also includes the following inventions. 1. The retardation of the half-wave film is expressed by the following equation (2).
The laminated retardation film that satisfies both (3) and (3). 0.60 <R (450) / R (550) <0.97 (2) 1.01 <R (650) / R (550) <1.40 (3) (where R (450), R ( 550) and R (650) are 450nm and 550n, respectively.
m, in-plane retardation of the polymer film at 650 nm. )

[0008] 2. The laminated retardation film described above, wherein the retardation of the half-wave film is smaller as the wavelength is shorter at a measurement wavelength of 400 to 700 nm.

3. The above laminated retardation film using two half-wave films.

[0010] 4. The above laminated retardation film, wherein the polymer film is made of a thermoplastic resin and has a glass transition temperature of 180 ° C. or higher.

5. The above laminated retardation film, wherein the water absorption of the polymer film is 1% by weight or less.

6. The above laminated retardation film, wherein the polymer film contains a polycarbonate having a fluorene skeleton.

7. A laminated retardation film characterized in that the dispersion of transmittance in a state where a laminated retardation film is sandwiched between a pair of polarizing films arranged so that polarization axes are orthogonal to each other satisfies the following expressions (4) and (5) simultaneously. . 0.95 ≦ T (400) / T (550) ≦ 1.05 (4) T (550) ≧ 80% (5) (where T (400) and T (550) each have a wavelength of 40)
The transmittance (%) at 0 nm and 550 nm, and the transmittance in an arrangement where the polarization axes of the pair of polarizing films used for the measurement are parallel is 100%. )

8. A laminated polarizing film obtained by combining the above-mentioned laminated retardation film and a polarizing film.

In the present invention, the half-wave film composed of the above-mentioned one polymer film has a measurement wavelength of 5 minutes.
It is a retardation film whose retardation value is measured at 50 nm and has a half wavelength, and practically R (550) is 220 to 330 nm.
It is preferably from 250 to 300 nm, more preferably from 260 to 290 nm.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The laminated retardation film of the present invention comprises:
A plurality of half-wave films are laminated, and each half-wave film is composed of one polymer film.

Each half-wave film has a wavelength dispersion characteristic of the phase difference such that the relation of the phase difference at the wavelengths of 450 nm and 550 nm satisfies the above formula (1) and also satisfies the above (II) and (III). It is necessary to have

By laminating a plurality of half-wave films having such wavelength dispersion, there is provided a laminated retardation film of the present invention which gives a half retardation to polarized light in a wide wavelength range of visible light. be able to.

The relationship of the above equation (1), that is, the wavelength dispersion characteristic of the phase difference where the phase difference is smaller at 450 nm than at the wavelength of 550 nm, is expressed by the following equations (2) and (3): 0.60 <R (450) / R ( (550) <0.97 (2) 1.01 <R (650) / R (550) <1.40 (3) (where R (450), R (550), and R (650) each have a wavelength of 450 nm) , 550n
m, in-plane retardation of the polymer film at 650 nm. ) Is preferably satisfied at the same time, because a half phase difference can be given to polarized light in a wider wavelength range of visible light. Further, it is more preferable that the shorter the wavelength at a measurement wavelength of 400 to 700 nm, the smaller the phase difference.

The half-wave film preferably satisfies the following formulas (2 ') and (3') at the same time. 0.70 <R (450) / R (550) <0.91 (2 ′) 1.02 <R (650) / R (550) <1.30 (3 ′)

Further, in order to obtain a laminated retardation film of the present invention capable of giving a half-wave retardation to polarized light in a wide wavelength range, it is necessary to adjust the optical axis of each of the laminated half-wave films. The intersection angle is important. That is, the crossing angle of the preferred optical axis of a plurality of half-wave films, the number of layers is A, the incident linear polarization direction is 0 degrees,
Assuming that the angle of the output linear polarization direction after transmission through the retardation film is φ, the angle φ _K of each half-wave film is represented by the following equation (6). φ _K = (2K-1) × φ / 2A (6) (where K is an integer from 1 to A)

Here, the optical axis of the half-wave film refers to a slow axis which is a direction having a large in-plane refractive index or a fast axis which is a direction having a small in-plane refractive index. In addition, the number of laminated half-wave films is preferably two to three, and more preferably two. This is because, when the number of laminated layers increases, there is a problem that the transmittance decreases due to an increase in the number of bonding interfaces and the cost increases.
Further, as will be understood from the examples described later, in the laminated retardation film of the present invention, it is possible to realize a sufficient broadband even with two sheets, which is one of the points that the present invention is superior to the prior art. is there.

In the laminated retardation film of the present invention, the dispersion of transmittance when the laminated retardation film is sandwiched between a pair of polarizing films arranged so that the polarization axes are orthogonal to each other is expressed by the following formulas (4) and (5). Is preferably satisfied at the same time. As the polarizing film, those capable of extracting linearly polarized light from natural light in the range of 400 to 700 nm are preferable. For example, a polarizing film used in a liquid crystal display device or the like may be used in this evaluation. Further, it is preferable that the arrangement of the laminated retardation film and the polarizing film satisfy the above-described expression (6).

0.95 ≦ T (400) / T (550) ≦ 1.05 (4) T (550) ≧ 80% (5) (where T (400) and T (550) each have a wavelength of 40)
The transmittance (%) at 0 nm and 550 nm, and the transmittance in an arrangement where the polarization axes of the pair of polarizing films used for the measurement are parallel is 100%. Simultaneously satisfying the above expressions (4) and (5) indicates that the polarizing axis of the linearly polarized light can be bent by 90 degrees with the laminated retardation film and can be performed in a wide wavelength range. . In other words, this is one method of showing that a half wavelength is given to polarized light in a wider wavelength range.

The phase difference (retardation) of a polymer film is determined by the phase difference based on the difference between the light traveling speed (refractive index) in the orientation direction of the film and the direction perpendicular thereto when the light passes through the film having a thickness of d. It is known that the difference Δn · d is the product of the refractive index difference Δn between the orientation direction and the direction perpendicular thereto and the film thickness d.

Since the phase difference Δn · d is proportional to the birefringence Δn when the transparent film is the same, the wavelength dispersion (wavelength dependence) of the phase difference can be represented by the wavelength dispersion (wavelength dependence) of the birefringence Δn. it can.

When the refractive index in the direction of orientation in the plane of the polymer film is larger than the refractive index in the direction perpendicular thereto,
The optical anisotropy is called positive, and the opposite case is called negative optical anisotropy. Here, the orientation direction of the polymer film is, for example,
In the case where the film is uniaxially stretched under a condition of a glass transition temperature Tg (Tg ± 20 ° C.), which is a well-known production condition of a retardation film, the stretching direction is set. In the case of biaxial stretching, it refers to the direction in which the film is stretched to increase the orientation.

In the present invention, the term "phase difference" refers to the absolute value of the phase difference. When the optical anisotropy is negative, the phase difference is negative. However, in the present invention, the sign of the sign is ignored unless otherwise specified.

The same material may be used for a plurality of half-wave films constituting the laminated retardation film of the present invention.
This is preferable in that a half wavelength is given to polarized light in a wider wavelength range.

The half-wave film constituting the laminated retardation film of the present invention can be produced by usually stretching a polymer film. From the viewpoint of the moldability of the half-wave film in the stretching step, the film forming step, and the like, the polymer film is preferably made of a thermoplastic resin. Further, for example, considering the use of the laminated retardation film of the present invention in a projection-type liquid crystal display device, since it is premised that use at a very high temperature, the glass transition temperature is preferably 150 ° C or higher, more preferably. Is 18
The temperature is 0 ° C or higher, more preferably 190 ° C or higher. Similarly, from the viewpoint of durability, the water absorption is preferably 1% by weight or less. The water absorption is preferably not more than 0.5% by weight.

According to the present invention, a half-wave film comprising one polymer film and satisfying the above formula (1) is obtained by a polymer film satisfying the following condition (A) or (B). It was found that it could be done. The measurement wavelength used to determine whether the optical anisotropy is positive or negative is
550 nm.

(A) (1) A polymer monomer unit having a positive refractive index anisotropy (hereinafter referred to as a first monomer unit) and a polymer monomer unit having a negative refractive index anisotropy ( (Hereinafter, referred to as a second monomer unit).) (2) A polymer based on the first monomer unit, wherein R (450) / R (550) of the polymer is A polymer film smaller than R (450) / R (550) of the polymer based on the second monomer unit and (3) having a positive refractive index anisotropy.

(B) (1) A monomer unit forming a polymer having a positive refractive index anisotropy (hereinafter referred to as a first monomer unit) and a polymer having a negative refractive index anisotropy are formed. A film comprising a monomer unit (hereinafter referred to as a second monomer unit) comprising: (2) a polymer R (4) based on the first monomer unit;
50) / R (550) is larger than R (450) / R (550) of the polymer based on the second monomer unit, and (3) has a negative refractive index anisotropy. .

As an example of an embodiment satisfying the above conditions (A) and (B), there is an embodiment satisfying the following conditions (C) and (D).

(C) (1) A blend polymer comprising a polymer having a positive refractive index anisotropy and a polymer having a negative refractive index anisotropy and / or having a positive refractive index anisotropy A film comprising a copolymer comprising a polymer monomer unit and a polymer monomer unit having a negative refractive index anisotropy, wherein (2) the polymer having a positive refractive index anisotropy R (450) / R (550) is smaller than R (450) / R (550) of the polymer having the negative refractive index anisotropy, and (3) has a positive refractive index anisotropy. , Polymer film.

(D) (1) A blend polymer comprising a polymer having a positive refractive index anisotropy and a polymer having a negative refractive index anisotropy and / or having a positive refractive index anisotropy A film comprising a copolymer comprising a polymer monomer unit and a polymer monomer unit having a negative refractive index anisotropy, wherein (2) the polymer having a positive refractive index anisotropy R (450) / R (550) is larger than R (450) / R (550) of the polymer having the negative refractive index anisotropy, and (3) has a negative refractive index anisotropy. , Polymer film.

Here, the polymer having a positive or negative refractive index anisotropy refers to a polymer that gives a polymer film having a positive or negative refractive index anisotropy.

The reason why the phase difference of the polymer film becomes smaller as the measurement wavelength becomes shorter will be described below.

In general, it is known that the birefringence Δn of a polymer blend composed of two components, polymer A and polymer B, is expressed as follows. (H. Saito and T. Inoue,
J. Pol. Sci. Part B, 25, 1629 (1987)) Δn = Δn0 AfAφA + Δn0BfBφB + ΔnF (a) where Δn0A: intrinsic birefringence of polymer A, Δn0
B: intrinsic birefringence of polymer B, fA: orientation function of polymer A, fB: orientation function of polymer B, φA: volume fraction of polymer A, φB: volume fraction of polymer B (= 1) -ΦA),
ΔnF: structural birefringence. In general, the birefringence Δn is Δ
n = fΔn0. Δn0 can be determined by combining dichroic infrared spectroscopy with phase difference measurement or the like.

Although the change in polarizability due to the electronic interaction between the polymers A and B is completely ignored in the equation (a), this assumption will be used in the following. Further, in the retardation film application as in the present invention, the blend is preferably a compatible blend because it is required to be optically transparent. In this case, ΔnF is extremely small and is ignored. I can do it.

Next, with respect to the polymer film in which the birefringence becomes smaller as the measurement wavelength becomes shorter, only 450 and 550 nm are considered here as the measurement wavelength. Assuming that the birefringence of the retardation film at these wavelengths is Δn (450) and Δn (550), respectively, Δn (450) / Δ
n (550) <1. In general, a retardation film composed of a polymer film used for a liquid crystal display device is Δn (4
Needless to say, 50) / Δn (550)> 1, for example, Δn (450) / Δn (550) of polycarbonate obtained from polymerization of bisphenol A and phosgene is about 1.08, and the wavelength dispersion of birefringence is small. It is around 1.01 even for polyvinyl alcohol, which is said to be. This Δn (450) / Δ
Assuming that n (550) is a birefringence wavelength dispersion coefficient, it is expressed as follows using equation (a). Δn (450) / Δn (550) = (Δn0A (450) fAφA + Δn0B (450) fBφB) / (Δn0A (550) fAφA + Δn0B (550) fBφB) (b)

Here, since it is a compatible blend, fA =
Assuming fB, equation (b) can be written as: Δn (450) / Δn (550) = (Δn0A (450) φA + Δn0B (450) φB) / (Δn0A (550) φA + Δn0B (550) φB) (c)

Next, virtual values as shown in Table 4 are shown in (c).
The birefringence wavelength dispersion value was examined using the equation. In Table 4, the birefringence dispersion values of the polymers A and B alone are described in place of Δn0 A (450) and Δn0 B (450).

[0044]

[Table 1]

Equation (c), given the values of Table 4, is expressed as a function of φA as shown in FIGS. Cases 1 to 4 correspond to FIGS. In Table 4, the polymer having the positive refractive index anisotropy is defined as the polymer A, and the polymer having the negative refractive index anisotropy is defined as the polymer B.
In the region where A is small, the optical anisotropy of the blend polymer is negative, while in the region where φB is larger than the asymptote, the anisotropy is positive.

As apparent from FIGS. 5 to 8, Δn (450)
/ Δn (550) <1 for cases 1 and 3 in Table 4.
The positive polymer has a birefringence wavelength dispersion coefficient smaller than that of the negative polymer and the optical anisotropy of the transparent film is positive, or as in cases 2 and 4, It is necessary that the refraction wavelength dispersion coefficient is larger than the negative one and the optical anisotropy of the transparent film is negative. Here, 450 and 550 nm are used as typical wavelengths, but the same holds when other wavelengths are used.

Considering from the equation (c), when the birefringence wavelength dispersion coefficients of the positive and negative polymers are completely equal,
It is difficult to obtain a half-wave film comprising one polymer film constituting the laminated retardation film of the present invention and satisfying R (450) / R (550) <1.

Although the above consideration is based on the above equation (a), this idea is very well established in an actual system as in an embodiment to be described later. Proven. For example, in the polycarbonate copolymer having a fluorene skeleton in Examples described later, when Δn (450) / Δn (550) <1, since the anisotropy is positive, the values are strictly different, but 4 corresponds to Cases 1 and 3, and in the case of a blend of polystyrene and polyphenylene oxide, Δn (450) / Δn
When (550) <1, since the anisotropy is negative, the values are strictly different, but are considered to correspond to cases 2 and 4 in Table 4.

Although the above discussion has described two components,
The above concept holds even with components or more. For example, in a system in which two components having positive optical anisotropy and one component having negative anisotropy, the birefringence value and the birefringence dispersion value of the component having positive optical anisotropy Can be corrected by the volume fraction between two components having positive anisotropy and the like, and the two components can be regarded as one component, and the concept of the consideration given by the above equation (a) can be applied.

Although the description based on the formula (a) has been described as a blend of the polymers A and B, the above-mentioned consideration is similarly applied to a copolymer in which the polymer contains different monomer units. And a homopolymer (polymer A) based on the first monomer unit and a second polymer different from the first monomer unit.
The above concept may be applied assuming that the polymer consists of a homopolymer (polymer B) based on the above monomer unit.

Further, the above considerations can be similarly applied to a polymer blend of a homopolymer and a copolymer or a polymer blend of copolymers. That is, in this case, the polymer blend is divided into the monomer units constituting the component polymer, and the polymer blend is regarded as an aggregate of a homopolymer composed of the respective monomer units. The above consideration may be applied assuming a combination of the component A consisting of the homopolymer group having anisotropy and the component B consisting of the homopolymer group having a negative anisotropy.

For example, polymers X and Y having positive optical anisotropy and monomer units x and z having negative optical anisotropy
When x has a positive optical anisotropy and z has a negative optical anisotropy, the component having a positive optical anisotropy is represented by X, Y and x. Considering these, the birefringence value, the birefringence dispersion value, and the like are corrected by the volume fraction between the three components with positive anisotropy, and these three components are regarded as one component A. The component having the property is regarded as a polymer B composed of the monomer unit z, and for the component A and the component B,
What is necessary is just to apply the concept of the following considerations (a).

In the case of a homopolymer based on the first or second monomer unit, when the homopolymer is a polycarbonate, the polycarbonate is generally obtained by polycondensation of a dihydroxy compound and phosgene. A dihydroxy compound composed of bisphenol and phosgene become monomers. As described above, in the case of polycarbonate, the monomer unit refers to a portion derived from bisphenol, and does not include a portion derived from phosgene.

The material of the polymer film used in the present invention is not particularly limited, and may be a blend or a copolymer satisfying the above conditions, and is excellent in heat resistance, excellent in optical performance, and capable of forming a solution film. Thermoplastic resin materials are preferred. For example, one type or two or more types can be appropriately selected from polyarylate, polyester, polycarbonate, polyolefin, polyether, polysulfone copolymer, polysulfone, polyethersulfone, and the like.

Since a blended polymer needs to be optically transparent, it is preferable that a compatible blend or a refractive index of each polymer be substantially equal. As a specific combination of blended polymers, for example, a polymer having negative optical anisotropy is poly (methyl methacrylate)
And poly (vinylidene fluoride), poly (ethylene oxide), poly (vinylidene fluoride-co-trifluoroethylene) as polymers having positive optical anisotropy
And poly (phenylene oxide) as a polymer having a positive optical anisotropy, and poly (styrene-co-lauroylmaleimide), poly (styrene-co- A combination of cyclohexylmaleimide), poly (styrene-co-phenylmaleimide), poly (styrene-co-maleic anhydride) having negative optical anisotropy and polycarbonate having positive optical anisotropy, Preferable examples include poly (acrylonitrile-co-butadiene) having optical anisotropy and poly (acrylonitrile-co-styrene) having negative optical anisotropy, but are not limited thereto. In particular, from the viewpoint of transparency, polystyrene having negative optical anisotropy and poly (phenylene oxide) such as poly (2,6-dimethyl-1,4-phenylene oxide) having positive optical anisotropy are used. Combinations are preferred. In the case of such a combination, it is preferable that the ratio of the polystyrene accounts for 67% by weight or more and 75% by weight or less of the whole. In the case of a blend, a compatibilizer or the like may be added for the purpose of improving compatibility.

Examples of the copolymer include poly (butadiene-co-polystyrene), poly (ethylene-co-polystyrene), poly (acrylonitrile-co-butadiene), and poly (acrylonitrile-co-butadiene-co-poly).
Styrene), a polycarbonate copolymer, a polyester copolymer, a polyester carbonate copolymer, a polyarylate copolymer, and the like. In particular, since a segment having a fluorene skeleton can have negative optical anisotropy, a polycarbonate copolymer, a polyester copolymer, a polyester carbonate copolymer, a polyarylate copolymer, or the like having a fluorene skeleton is more preferably used. Among them, a polymer film containing (copolymerization, blending) containing a polycarbonate having a fluorene skeleton is preferable as apparent from the examples.

The polymer material may be a blend of two or more copolymers, or may be a blend of one or more copolymers and the above-mentioned blend or another polymer. The above-mentioned blend, copolymer or other polymer blend may be used.

The polycarbonate copolymer produced by reacting a bisphenol with a phosgene or a carbonate-forming compound such as diphenyl carbonate has excellent transparency, heat resistance and productivity, and can be particularly preferably used. The polycarbonate copolymer is preferably a copolymer containing a structure having a fluorene skeleton.
The component having a fluorene skeleton is preferably contained at 1 to 99 mol%.

Specifically, the following formula (I)

[0060]

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(In the above formula (I), R _{1 to} R ₈ are each independently selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms, and X is

[0062]

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Is as follows. ) Is 30.
~ 90 mol% and the following formula (II)

[0064]

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(In the above formula (II), R _{9 to} R ₁₆ each independently represent a hydrogen atom, a halogen atom and a carbon atom having 1 to 2 carbon atoms.
Selected from two hydrocarbon groups, Y is

[0066]

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(R _{17 to} R ₁₉ , R ₂₁ and R _{22 in} Y each independently represent a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms, and R ₂₀ and R ₂₃ represent 1 to 20 carbon atoms. And Ar is at least one group selected from aryl groups having 6 to 10 carbon atoms.) A repeating unit represented by the following formula: Or a blend body is mentioned.

This material is a polycarbonate copolymer comprising a repeating unit having a fluorene skeleton represented by the above formula (I) and a repeating unit represented by the above formula (II), and a fluorene represented by the above formula (I) It is a composition of a polycarbonate comprising a repeating unit having a skeleton and a polycarbonate comprising a repeating unit represented by the above formula (II) (hereinafter sometimes referred to as a blend polymer). In the case of a copolymer, the above formulas (I) and (I)
Two or more of the repeating units represented by I) may be combined, and in the case of a composition, two or more of the above repeating units may be combined.

In the above formula (I), R _{1 to} R ₈ are each independently selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms. Examples of such a hydrocarbon group having 1 to 6 carbon atoms include an alkyl group such as a methyl group, an ethyl group, an isopropyl group and a cyclohexyl group, and an aryl group such as a phenyl group. Of these, a hydrogen atom and a methyl group are preferred.

In the above formula (II), R _{9 to} R ₁₆ are each independently selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms. Examples of the hydrocarbon group having 1 to 22 carbon atoms include a methyl group, an ethyl group, an isopropyl group,
Examples thereof include an alkyl group having 1 to 9 carbon atoms such as a cyclohexyl group, and an aryl group such as a phenyl group, a biphenyl group, and a terphenyl group. Of these, a hydrogen atom and a methyl group are preferred.

In Y of the above formula (II), R _{17 to} R ₁₉ ,
R ₂₁ and R ₂₂ are each independently selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms. Examples of such hydrocarbon groups include the same as those described above. R ₂₀ and R ₂₃ each independently have 1 carbon atom
-20 hydrocarbon groups, and the hydrocarbon groups may be the same as those described above.
Ar is an aryl group having 6 to 10 carbon atoms such as a phenyl group and a naphthyl group.

The content of the above formula (I), that is, the copolymer composition in the case of a copolymer and the blend composition ratio in the case of a composition are 30 to 90 mol% of the entire polycarbonate. If the value is outside this range, it is difficult to obtain a half-wave film having a smaller retardation value as the wavelength becomes shorter. The content of the above formula (I) is 35 to 85 of the entire polycarbonate.
Mol% is preferable, and 50 to 80 mol% is more preferable.

The above molar ratio can be determined by, for example, a nuclear magnetic resonance (NMR) apparatus for the entire polycarbonate bulk constituting the oriented polymer film regardless of the copolymer or the blend polymer.

The polycarbonate in this material is represented by the following formula (III)

[0075]

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(In the above formula (III), R ₂₄ and R ₂₅ are each independently selected from a hydrogen atom and a methyl group.)
The following formula (IV)

[0077]

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(In the formula (IV), R ₂₆ and R ₂₇ are each independently selected from a hydrogen atom and a methyl group, and Z is a group represented by the following formula:

[0079]

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It is particularly preferable to use a polymer film comprising a polycarbonate copolymer and / or a blend, which accounts for 65 to 15 mol% of the whole, as a half-wave film constituting a laminated retardation film.

The above-mentioned copolymer and / or blend polymer can be produced by a known method. As the polycarbonate, a method by polycondensation of a dihydroxy compound and phosgene, a melt polycondensation method, and the like are suitably used. In the case of a blend, a compatible blend is preferable, but even if they are not completely compatible, light scattering between the components can be suppressed and transparency can be improved by adjusting the refractive index between the components.

The limiting viscosity of the above polycarbonate is 0.3 to
Preferably it is 2.0 dl / g. Below this, there are problems such as brittleness and mechanical strength cannot be maintained, and above this, problems such as the occurrence of die lines in solution film formation due to too high solution viscosity and the problem that purification at the end of polymerization becomes difficult are caused. is there.

The laminated retardation film and the half-wave film constituting the same are preferably transparent, have a haze value of 3% or less, and have a total light transmittance of 380 to 78 at the measurement wavelength.
At 0 nm, it is preferably at least 80%, more preferably at least 85%. It is preferably colorless and transparent,
In the L * a * b * color system described in JIS Z-8279, if defined by b * using a twice-view C light source, it is preferably 1.3 or less, more preferably 0.9 or less. It is as follows.

Further, ultraviolet absorbers such as phenylsalicylic acid, 2-hydroxybenzophenone and triphenyl phosphate, bluing agents for changing color,
An antioxidant and the like may be added.

As a method for producing the half-wave film constituting the laminated retardation film of the present invention, a known melt extrusion method, a solution casting method and the like are used. The method is more preferably used. As the solvent in the solution casting method, methylene chloride, dioxolane and the like are preferably used. The amount of residual methyl chloride is preferably 0.5% by weight or less, more preferably 0.3% by weight or less, and further preferably 0.1% by weight or less.

Additives such as plasticizers and liquid crystalline compounds can change the retardation wavelength dispersion of the half-wave film constituting the laminated retardation film of the present invention. Additives are not required to fine tune the retardation chromatic dispersion. The addition amount is 10% of the polymer solid content.
wt% or less is preferable, and 3 wt% or less is more preferable.

The thickness of the half-wave film constituting the laminated retardation film of the present invention is from 5 μm to 20 μm.
0 μm, more preferably 30 to 1 μm.
50 μm.

The thickness of the laminated retardation film of the present invention is preferably from 10 to 300 μm, more preferably from 20 to 250 μm.

It is known that a polymer film having optical anisotropy generally gives a different phase difference value to obliquely incident light as compared with frontally incident light. Here, the three-dimensional refractive index of the polymer material is represented by nx, ny, and nz, where nx is the refractive index in the main orientation direction in the plane of the transparent film, and ny is the main orientation direction in the plane of the transparent film. Nz: the refractive index in the direction normal to the surface of the transparent film. Here, the main orientation direction means, for example, the flow direction of the film, and the chemical structure indicates the orientation direction of the polymer main chain. When nx> nz, the optical anisotropy is referred to as positive, and when nx <nz, the optical anisotropy is referred to as negative. The three-dimensional refractive index is measured by an ellipsometry, which is a technique for analyzing the polarization state of emitted light obtained by entering polarized light into a transparent film. The three-dimensional refractive index is determined by a known method using a refractive index ellipsoidal formula assuming an ellipsoid. Since the three-dimensional refractive index depends on the wavelength of the light source used, it is preferable to define the three-dimensional refractive index with the wavelength of the light source used. As a method of expressing the optical anisotropy using the three-dimensional refractive index, there is the following equation (7) Nz = (nx−nz) / (nx−ny) (7) When Nz is in the range of 0.1 to 1.5, and more preferably in the range of 0.3 to 1.0, the dependence of the phase difference value on the incident angle is very small. In particular, when Nz = 0.5, the dependency of the phase difference value on the incident angle is substantially eliminated, and the same phase difference value is given regardless of the angle at which light enters.

According to the above definition, the slow axis of the polymer film having positive optical anisotropy is nx, and the fast axis is ny.

In order to reduce the retardation of the polymer film used as the half-wave film constituting the laminated retardation film of the present invention as the wavelength becomes shorter, it is important to have a specific chemical structure as described above. Yes, the chromatic dispersion of retardation is determined to a large extent by its chemical structure,
It should be noted that it also varies depending on stretching conditions, blending conditions, molecular weight, and the like.

Examples of the laminated retardation film of the present invention are shown in FIGS.
3, but the present invention is not limited to these. In addition, the laminated polarizing film of another configuration of the present invention is composed of a laminate of the laminated retardation film and the polarizing film. One preferable example is shown in FIG. A known acrylic adhesive or the like is used for the adhesion between the films. The refractive index of the pressure-sensitive adhesive is preferably closer to the refractive index of the film in order to prevent interfacial reflection of light. Further, the laminated retardation film of the present invention, in the laminated polarizing film, for example, a discotic liquid crystal having a fixed orientation, a chiral nematic phase, a nematic phase, an optical compensation layer composed of a polymer liquid crystal exhibiting a smectic phase and the like. It is also possible to improve the viewing angle characteristics in combination.

Examples of the polarizing film include a film in which iodine or a dichroic dye is oriented in a known binder polymer such as polyvinyl alcohol, a stretched oriented polyacetylene, a lyotropic liquid crystal and light absorption dichroism. A coating material having the following is preferably applied and oriented.

The thickness of the polarizing film to be used is 5 to
It is preferably 350 μm, more preferably 10 μm.
２００200 μm.

In a polarization conversion element used in a projection type liquid crystal display device or the like, after a polarization beam splitter splits it into two polarization components S-wave and P-wave, one-sided polarization, for example, P-wave is halved. It is converted into S-wave by the wavelength film, which means that only S-wave is extracted from natural polarized light from the light source, and by using this light in a liquid crystal display device using a polarizing film that can use only one polarized light, A method for increasing the light use efficiency is disclosed. ("Liquid Crystal" Vol. 4, No. 3 (2000),
P38-48)) In such a projection type liquid crystal display device, it is preferable to convert polarized light in the range of visible light, and in the case of the half-wave film described above, convert S waves to P waves in a wide range. That is, the effect of rotating the linear polarization direction by 90 degrees is desired. When the laminated retardation film of the present invention is used in such a polarization conversion element, an ideal polarization conversion action can be expected in a wide wavelength range.

Further, the laminated retardation film of the present invention can be used not only in the above-mentioned projection type liquid crystal display device but also in an optical element which needs to rotate such linearly polarized light, for example. Specifically, it can be suitably used for an optical communication device, a display device, an optical recording device, an optical recording medium, an optical operation element, an input element (such as a touch panel) and the like.

[0097]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

(Evaluation Methods) The material characteristic values and the like described in this specification were obtained by the following evaluation methods. (1) Measurement of retardation value (R = Δn · d (nm)), K value Retardation R value which is the product of birefringence Δn and film thickness d of a half-wave film composed of one polymer film And Nz are trade names “M1” manufactured by JASCO Corporation, a spectroscopic ellipsometer.
50 ". The R value was measured with the incident light and the film surface orthogonal to each other. The K value (nm) is measured by changing the angle between the incident light beam and the film surface, measuring the phase difference value at each angle, and performing curve fitting with a known index ellipsoidal equation to obtain a three-dimensional refractive index. Nx, ny, nz
Was obtained and substituted into the following equation (8). K = (nz- (nx + ny) / 2) * d (8)

(2) Measurement of Water Absorption Measured in accordance with JIS K 7209, "Testing Methods for Water Absorption and Boiling Water Absorption of Plastics" described in JIS K 7209, except that the thickness of the dried film was 130 ± 50 μm. did. The size of the test piece was a 50 mm square, and the sample was immersed in water at 25 ° C. for 24 hours, and the weight change was measured. It is the so-called saturated water absorption and the unit is%.

(3) Measurement of Glass Transition Temperature (Tg) of Polymer “TDS2920 Modulated DSC” (trade name, manufactured by TA Instruments)
]. It was measured not after film formation but after polymer polymerization, in the form of flakes or chips.

(4) Measurement of Film Thickness An electronic micro manufactured by Anritsu Corporation (trade names “K351C, K-402”)
B ").

(5) Measurement of Polymer Copolymerization Ratio Proton NMR of “JNM-alpha600” (trade name, manufactured by JEOL Ltd.)
Was measured by In particular, the monomer unit is bisphenol A
In the case of a copolymer consisting of benzene and biscresol fluorene, heavy benzene was used as a solvent, and calculation was performed from the proton intensity ratio of each methyl group.

(6) Measurement of transmittance A spectrophotometer “U-3500” manufactured by Hitachi, Ltd. was used. The measurement wavelength was 380 to 780 nm, but in the examples, the measurement wavelength is represented as 550 nm.

(7) Evaluation of Laminated Retardation Film The laminated retardation film of the present invention was sandwiched between orthogonal polarizing films, and the transmission spectrum was measured. A test was conducted to determine whether or not the linearly polarized light can be rotated by 90 degrees over a wide wavelength range by giving a phase difference of. That is, the ability to rotate the linearly polarized light by 90 degrees over a wide wavelength range means that in this test, the transmittance is high over a wide wavelength range. In the following Examples and Comparative Examples, two polarizing films were set to parallel Nicols, and the transmittance was measured as 100% in the entire measurement wavelength region. Polarizing film manufactured by Sun Ritz Co., Ltd. (Product name "LLC2-9218")
Was used.

The monomer structures of the polycarbonates used in the following Examples and Comparative Examples are described below.

[0106]

Embedded image

Example 1 An aqueous sodium hydroxide solution and ion-exchanged water were charged into a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, and a monomer [A] having the above structure was added thereto.
And [C] were dissolved in the molar ratio shown in Table 2, and a small amount of hydrosulfite was added. Next, methylene chloride was added thereto, and 2
At 0 ° C., phosgene was blown in for about 60 minutes. further,
After adding and emulsifying p-tert-butylphenol, triethylamine was added and the mixture was stirred at 30 ° C. for about 3 hours to terminate the reaction. After completion of the reaction, the organic phase was separated and methylene chloride was evaporated to obtain a polycarbonate copolymer. The composition ratio of the obtained copolymer was almost the same as the monomer charge ratio.

This copolymer was dissolved in methylene chloride to prepare a dope solution having a solid content of 20% by weight.
A cast film was prepared from this dope solution, and further uniaxially stretched at a temperature of 230 ° C. at a draw ratio of 2.3 times to prepare a half-wave film shown in Table 2.

Using the above half-wave film, the polarization axis of the incident side polarizing film is 0 °, the slow axis of the first half-wave film is 22.5 °, and that of the second half-wave film is The slow axis was set to 67.5 degrees and the polarization axis of the exit side polarizing film was set to 90 degrees. FIG. 1 shows the transmittance spectrum of the laminated film (I).
It writes in. Compared to the comparative example of FIG. 1, the transmittance was higher in a wider wavelength range, and it was found that the polarization axis of linearly polarized light could be rotated by 90 degrees in a wider wavelength range.

Example 2 A polycarbonate copolymer was obtained in the same manner as in Example 1 except that the monomers shown in Table 2 were used. The composition ratio of the obtained copolymer was almost the same as the monomer charge ratio. After forming a film in the same manner as in Example 1, the film was stretched at a stretching temperature of 232 ° C. and a stretching ratio of 2 to obtain a half-wave film having the characteristics shown in Table 2.

Using the above-mentioned half-wave film, the polarization axis of the incident side polarizing film is 0 °, the slow axis of the first half-wave film is 22.5 °, and the second half-wave film is The slow axis was set to 67.5 degrees and the polarization axis of the exit side polarizing film was set to 90 degrees. The transmittance spectrum of the laminated film (II) is shown in FIG.
It writes in. Compared with the comparative example, the transmittance was higher in a wider wavelength range, and it was found that the polarization axis of linearly polarized light could be rotated by 90 degrees in a wider wavelength range.

Further, using the above-mentioned half-wave film, the polarization axis of the incident side polarizing film is 0 degree, the slow axis of the first half-wave film is 15 degrees, and the second half-wave film is The slow axis was set to 45 degrees, the slow axis of the third half-wave film was set to 75 degrees, and the polarization axis of the exit-side polarizing film was set to 90 degrees. FIG. 2 shows the transmittance spectrum of the laminated film (III). Compared with the comparative example, the transmittance is higher in a wider wavelength range, and the polarization axis of linearly polarized light is 90
It turned out that it could be rotated by degrees.

[0113]

[Table 2]

[Example 3] Polystyrene (obtained from Wako Pure Chemical Industries, Ltd.) as a polymer having negative refractive index anisotropy, and polyphenylene oxide (poly ( 2,6-dimethyl 1,4-
(Phenylene oxide) obtained from Wako Pure Chemical Industries, Ltd.)
Were dissolved in chloroform at a ratio of 75 and 25% by weight, respectively, to prepare a dope solution having a solid content of 18% by weight. A cast film was prepared from this dope solution to obtain a polymer film. This film was uniaxially stretched at a stretching temperature of 127 ° C. and a stretching ratio of 2.5 to prepare a half-wave film.

Table 3 summarizes the results of measuring the optical characteristics of the half-wave film. Using the above half-wave film, the polarization axis of the incident side polarizing film is 0 degree, the slow axis of the first half-wave film is 22.5 degrees, and the slow axis of the second half-wave film is Was set to 67.5 degrees, and the polarization axis of the exit-side polarizing film was set to 90 degrees, and they were adhered in this order using an adhesive. The results show almost the same tendency as (II) of Example 2 in FIG. 1, and the transmittance is higher in a wider wavelength range than in the comparative example, and the polarization axis of linearly polarized light is wider in a wider wavelength range. Can be rotated by 90 degrees.

For reference, FIG. 9 shows the relationship between the birefringence wavelength dispersion coefficient and the volume fraction of polyphenylene oxide when the blend ratio of polystyrene and polyphenylene oxide was changed. In the region where the amount of polyphenylene oxide is small, the optical anisotropy is negative and the birefringence wavelength dispersion coefficient is 1
It can be seen that there is a smaller area. On the other hand, the value is larger than 1 in a region where the refractive index anisotropy is large in which polyphenylene oxide is large.

Next, FIG. 10 shows the relationship between the volume fraction and the birefringence chromatic dispersion coefficient as shown in FIG. 9 calculated using the above-mentioned equation (c). FIG. 10 shows the intrinsic birefringence of polystyrene and polyphenylene oxide at a wavelength of 550 nm, respectively.
−0.10, 0.21 (D. Lefebvre, B. Jasse and L. Monneri
e, Polymer 23 706-709 (1982)), and the respective R (450) / R (550) values were calculated as 1.06 and 1.15. The agreement between FIG. 9 and FIG. 10 is good. The densities of polystyrene and polyphenylene oxide are respectively
1.047, 1.060 (g / cm ³ ).

[0118]

[Table 3]

[Comparative Example 1] A film was formed in the same manner as in Example 1 using a commercially available polycarbonate (trade name “PANLITE C1400” manufactured by Teijin Chemicals) consisting of polycondensation of bisphenol A and phosgene. A half-wave film was obtained by uniaxially stretching at a stretching ratio of 1.2 times. Table 3
The measurement results are summarized below. Using the above half-wave film, the polarization axis of the incident side polarizing film is 0 degree, the slow axis of the first half-wave film is 22.5 degrees, and the slow axis of the second half-wave film is Was set to 67.5 degrees, and the polarization axis of the exit-side polarizing film was set to 90 degrees, and they were adhered in this order using an adhesive. FIG. 1 shows the transmittance spectrum of the laminated film (IV). Compared with the examples, the transmittance was particularly low on the long wavelength side and the short wavelength side, and it was found that a laminated retardation film satisfying the object of the present invention could not be produced.

Comparative Example 2 A film was formed in the same manner as in Example 1 using a commercially available norbornene resin, “ARTON” manufactured by JSR, and uniaxially stretched at a temperature of 166 ° C. at a draw ratio of 2 times for two minutes. Was obtained. Table 3 summarizes the measurement results. Using the above half-wave film, the polarization axis of the incident side polarizing film is 0 degree, the slow axis of the first half-wave film is 22.5 degrees, and the slow axis of the second half-wave film is 67.5 degrees, the exit side polarizing film polarization axis is 9
The temperature was set to 0 degrees, and bonding was performed using an adhesive in this order.
FIG. 1 shows the transmittance spectrum of the laminated film (V). As compared with the examples, the transmittance was particularly low on the short wavelength side, and it was found that a laminated retardation film satisfying the object of the present invention could not be produced.

[0121]

[Table 4]

[0122]

As described above, according to the present invention, the phase difference at a wavelength of 450 nm and 550 nm is R (4
50) / R (550) <1 The laminated retardation film obtained by laminating a plurality of half-wave films at an appropriate angle, characterized by satisfying the relationship of 1, is smaller than a conventionally existing retardation film. Since it is possible to perform polarization conversion in a wider wavelength range, by using them in, for example, a polarization conversion element used in a projection-type liquid crystal display device, there is an effect of improving light use efficiency.

[Brief description of the drawings]

FIG. 1 is a spectrum showing the polarization conversion performance of a laminated retardation film in Examples and Comparative Examples.

FIG. 2 is an example of a sectional view of a laminated retardation film of the present invention.

FIG. 3 is an example of a sectional view of a laminated retardation film of the present invention.

FIG. 4 is an example of a sectional view of the laminated polarizing film of the present invention.

FIG. 5 shows the relationship between the wavelength dispersion of birefringence and the volume fraction φA of the binary blend polymer corresponding to Case 1 in Table 4.

FIG. 6 shows the relationship between the wavelength dispersion of birefringence and the volume fraction φA of the binary blend polymer corresponding to Case 2 in Table 4.

FIG. 7 shows the relationship between the wavelength dispersion of birefringence and the volume fraction φA of the binary blend polymer corresponding to Case 3 in Table 4.

FIG. 8 shows the relationship between the wavelength dispersion of birefringence and the volume fraction φA of the binary blend polymers corresponding to cases 1 to 4 in Table 4.

FIG. 9 shows the volume fraction of polyphenylene oxide in a blend of polystyrene and polyphenylene oxide.
It is a graph showing the relationship (actually measured value) of R (450) / R (550).

FIG. 10 is a graph showing the relationship (calculated value) between R (450) / R (550) and the volume fraction of polyphenylene oxide in a blend of polystyrene and polyphenylene oxide.

[Explanation of symbols]

 1: half-wave film 2: adhesive layer 3: half-wave film 4: half-wave film 5: adhesive layer 6: half-wave film 7: adhesive layer 8: half-wave film 9: polarized light Film 10: adhesive layer 11: half-wave film 12: adhesive layer 13: half-wave film 14: laminated retardation film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 BA02 BA06 BA42 BB03 BB47 BB50 BC03 BC12 BC22 2H091 FA11Y FB02 FC11 FC24 FC29 FC30 FD10 FD16 GA17 KA02 LA03 LA11 LA12 4J002 CG001 CG002 GF00 GP00 4J029 AA09 AA10 AB02 BB12B BB12C BB16A BB16B BD09A BD09B BD09C BH02 BH04 DB07 DB13 HC01 HC03

Claims (9)

[Claims] 1. A laminated retardation film obtained by laminating a plurality of half-wave films made of one polymer film, wherein the half-wave film has a wavelength of 450 nm.
And R (450) / R (550) <1 (1) where R (450) and (550) are polymer films at wavelengths of 450 nm and 550 nm, respectively. The laminated retardation film that satisfies the in-plane retardation. 2. The laminated retardation film according to claim 1, wherein the retardation of the half-wave film satisfies the following expressions (2) and (3) simultaneously. 0.60 <R (450) / R (550) <0.97 (2) 1.01 <R (650) / R (550) <1.40 (3) (where R (450), R ( 550) and R (650) are 450nm and 550n, respectively.
m, in-plane retardation of the polymer film at 650 nm. ) 3. At a measurement wavelength of 400 to 700 nm,
3. The laminated retardation film according to claim 1, wherein the retardation of the half-wave film is smaller as the wavelength is shorter. 4. The laminated retardation film according to claim 1, wherein two half-wave films are used. 5. The polymer film is made of a thermoplastic resin and has a glass transition temperature of 180 ° C. or higher.
5. The laminated retardation film according to any one of items 1 to 4. 6. The polymer film having a water absorption of 1% by weight.
The laminated retardation film according to any one of claims 1 to 5, which is: 7. The laminated retardation film according to claim 1, wherein the polymer film contains a polycarbonate having a fluorene skeleton. 8. The dispersion of transmittance in a state where the laminated retardation film is sandwiched between a pair of polarizing films arranged so that the polarization axes are orthogonal to each other, satisfies the following expressions (4) and (5) simultaneously. The laminated retardation film according to claim 1. 0.95 ≦ T (400) / T (550) ≦ 1.05 (4) T (550) ≧ 80% (5) (where T (400) and T (550) each have a wavelength of 40)
The transmittance (%) at 0 nm and 550 nm, and the transmittance in an arrangement where the polarization axes of the pair of polarizing films used for the measurement are parallel is 100%. ) 9. A laminated polarizing film comprising a combination of the laminated retardation film according to claim 1 and a polarizing film.