JP2002048919A - Optical retardation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical retardation film of which the optical retardation gets smaller when a wavelength for measurement gets shorter while using only one sheet of the film. SOLUTION: The optical retardation film is composed of a sheet of a polymer oriented film utilizing a polymer material containing a liquid crystal and is characterized by having retardation at 450 nm and 550 nm wavelengths satisfying following inequalities R (450)/R (550)<1 and/or K (450)/K (550)<1. (In the inequalities, R (450) and R (550) are retardation in a plane of the polymer oriented film at 450 nm and 550 nm wavelengths respectively and K (450) and K (550) are values calculated with an equation K=[nz-(nx+ny)/2]×d of the polymer oriented film at 450 nm and 550 nm wavelengths respectively (in the equation nx, ny, nz are three dimensional refractive indexes of the polymer oriented film corresponding to refractive indexes in the x-, y-, and z-axes directions respectively and d is film thickness).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, a light emitting device, an antiglare film, an optical recording device, and other optical devices.
The present invention relates to a retardation film having a smaller wavelength as the wavelength becomes shorter, and an optical device using the same.

[0002]

2. Description of the Related Art A retardation film is used in a liquid crystal display device such as a STN (super twisted nematic system), and is used to solve problems such as color compensation and expansion of a viewing angle. As the material of the retardation film, polycarbonate, polyvinyl alcohol, polysulfone, polyethersulfone, amorphous polyolefin, or the like is used. As the retardation film material for expanding the viewing angle, in addition to the above-described materials, a polymer liquid crystal, and an alignment-cured disc. Tic liquid crystal or the like is used.

A quarter-wave plate, which is a type of retardation film, can convert circularly polarized light into linearly polarized light and linearly polarized light into circularly polarized light. This is due to the combination of a liquid crystal display device, in particular, a reflective liquid crystal display device with a single polarizing plate using the electrode on the back side as viewed from the observer as a reflective electrode, and a combination of a polarizing plate and a quarter-wave plate. Antireflection film, or a cholesteric liquid crystal or other reflection type polarizing plate that reflects only one of clockwise or counterclockwise circularly polarized light.

A retardation film used in the above-mentioned single-polarizer type reflection type liquid crystal display device or reflection type polarizer has a measurement wavelength in the visible light region of 400 to 700 nm, preferably 4 nm.
It is necessary to have the function of converting linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light in the range of 00 to 780 nm. To realize this with a single retardation film, the measurement wavelength λ = 400
-700 nm, preferably 400-780 nm, the phase difference is λ / 4
(Nm) is the ideal of the retardation film.

Generally, the above-described retardation film material for color compensation and the like are used as a quarter-wave plate, and these materials have wavelength dispersion in birefringence. In general, the birefringence of a polymer film increases as the measurement wavelength decreases, and decreases as the measurement wavelength increases. Therefore, at a measurement wavelength λ = 400 to 700 nm with only one polymer film, it is difficult to obtain a material having a smaller birefringence as the measurement wavelength is shorter, such as the ideal quarter-wave plate described above. there were.

In order to obtain a film in which the shorter the measurement wavelength is, the smaller the birefringence is, like an ideal quarter-wave plate,
JP-A-10-68816 discloses a technique in which a quarter-wave plate and a half-wave plate are bonded at an appropriate angle and used, and JP-A-2-285304 discloses two sheets having different Abbe numbers. And the like are disclosed.

[0007]

In order to obtain a film having a smaller phase difference as the measurement wavelength is shorter, as in the case of the ideal quarter-wave plate described above, in the state of the art, it is not necessary to use two films. However, there are problems such as an increase in the film bonding process, an increase in cost, and an increase in load on optical design.
JP-A-3-29921 discloses a retardation film obtained by uniaxially stretching a mixture or copolymer film of at least two kinds of organic polymers. A phase difference film is disclosed in which one organic polymer has a positive photoelastic coefficient and the second organic polymer has a negative photoelastic coefficient. However, there is no mention of a method of reducing the birefringence as the measurement wavelength is shorter.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to realize a retardation film in which the retardation becomes smaller as the measurement wavelength becomes shorter in one film.

[0009]

Means for Solving the Problems The present inventors have intensively studied a polymer material for a retardation film and the like in order to solve the above-mentioned problems, and have studied a retardation film composed of one polymer oriented film containing a liquid crystal compound. A film having a retardation at wavelengths of 450 nm and 550 nm represented by the following formulas (1) and / or (2): R (450) / R (550) <1 (1) K (450) / K (550) <1 ( 2) [wherein R (450) and R (550) represent wavelengths of 450 nm and 5
The in-plane retardation of the polymer oriented film at 50 nm,
K (450) and K (550) are K = [nz− (nx + n) of the polymer oriented film at wavelengths of 450 nm and 550 nm, respectively.
y) / 2] × d (where nx, ny, and nz are the three-dimensional refractive indices of the polymer oriented film, x-axis, y-axis, and z-axis, respectively)
The axial refractive index, and d is the thickness of the film. )
Is the value calculated by ] Has been successfully provided.

That is, the present invention relates to [1] a retardation film composed of a single polymer oriented film using a polymer material containing a liquid crystal, and having a wavelength of 450
a retardation film at nm and 550 nm satisfying the following formulas (1) and / or (2) and having a haze of 3% or less: R (450) / R (550) <1 ( 1) K (450) / K (550) <1 (2) [wherein R (450) and R (550) have wavelengths of 450 nm and
The in-plane retardation of the polymer oriented film at 550 nm, where K (450) and K (550) are the wavelengths 450 nm and 550 n, respectively.
K of the polymer oriented film at m = [nz− (nx +
ny) / 2] × d (where nx, ny, and nz are the three-dimensional refractive indices of the polymer oriented film in the x-, y-, and z-axis directions, respectively, and d is the thickness of the film. ). ]

[2] The phase difference at wavelengths of 450 nm, 550 nm and 650 nm is given by the following formulas (3) and (4): 0.6 <R (450) / R (550) <0.97 (3) 1.01 <R (650) / R (550) <1.4 (4) [where R (650) is the in-plane retardation of the polymer oriented film at a wavelength of 650 nm. [1].

[3] The retardation film according to [1] or [2], wherein the shorter the wavelength in the wavelength range of 400 to 700 nm, the smaller the retardation. [4] The retardation film according to [1], wherein the content of the liquid crystal is 0.01 to 15% by weight. [5] The retardation film of [1], wherein the polymer oriented film contains a polycarbonate having a fluorene skeleton. [6] The polycarbonate has the following formula (I)

[0013]

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

[0015]

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## EQU1 ## ) Is represented by 5
~ 95 mol% and the following formula (II)

[0017]

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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.
At least one selected from the group consisting of
Is the following formula group

[0019]

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(Where R₁₇~ R₁₉, R_{twenty one}And R_{twenty two}Is it
Each independently represents a hydrogen atom, a halogen atom and a carbon number of 1 to 22;
At least one selected from the group consisting of₂₀
And R _{twenty three}Is a small group selected from hydrocarbon groups having 1 to 20 carbon atoms.
At least one type, and Ar₁~ Ar_ThreeIs German
In the meantime, a small number selected from aryl groups having 6 to 10 carbon atoms
Both are a kind. ) Is the entire repeating unit b
95 to 5 mol% of a polycarbonate copolymer
[1] to [5]. [7] A polarizing film and a retardation film of [1] to [6]
Circularly polarized film. [8] A light source characterized by using the circularly polarizing film of [7].
Optical element. [9] It consists of a polarizing film and the retardation films of [1] to [6].
Elliptically polarizing film. [10] The use of the retardation film of [1] to [6]
Liquid crystal display device. Achieved by

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is directed to a process for obtaining ideal λ / 4 plate and λ / 2 plate independent of wavelength in a visible light wavelength region in one polymer oriented film. The inventors succeeded in providing a single polymer oriented film having a smaller retardation as the wavelength became shorter, achieving the above object and providing a retardation film having unprecedented characteristics.

Further, the present inventor has determined that even a single polymer oriented film that does not already contain liquid crystal can satisfy the above formulas (1) and / or (2). According to the present invention, it has been found that the use of liquid crystal makes it possible to easily control the retardation wavelength dispersion of the retardation film in accordance with the desired value.

The definition of the liquid crystal in the present invention is described below.
Those having a degree of polymerization of about the oligomer are included. According to the physics and chemistry dictionary issued by Iwanami Shoten, p. 185, the fourth edition, an oligomer is a compound having a repeating number of structural units (degree of polymerization) of 2 to 20.
Since there is a description of a low polymer, the oligomer is defined as having 2 to 20 repeating units. That is, a liquid crystal in the present invention is a compound having a low molecular weight compound or a repeating unit of 2 or less.
~ 20 oligomers. If a polymer liquid crystal having a higher degree of polymerization than the oligomer is added, phase separation or the like occurs between the polymer material constituting the polymer oriented film and it is difficult to obtain high transparency. From the same viewpoint, the lower the degree of polymerization of the oligomer is, the more preferable it is, the more preferable is 10 or less, more preferable is 5 or less, and further preferable is 3 or less. This corresponds to the fact that the polymer and the polymer are hardly compatible with each other, but the polymer and the low molecular compound are relatively easily compatible with each other.

Examples of the liquid crystal used in the present invention include discotic liquid crystal, nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, polymerizable liquid crystal, and lyotropic liquid crystal. Specific structures include, for example, Schiff liquid crystal, azoxy liquid crystal, alkyl cyanobiphenyl liquid crystal, alkyl cyano terphenyl liquid crystal, alkyl cyano quater phenyl liquid crystal, cyanophenyl cyclohexane liquid crystal, cyano phenyl ester liquid crystal, and benzoic acid. Examples include, but are not limited to, phenyl ester-based liquid crystals, cyclohexanecarboxylic acid phenyl ester-based liquid crystals, phenylpyrimidine-based liquid crystals, and phenyldioxane-based liquid crystals. The dielectric anisotropy and the refractive index anisotropy of the liquid crystal may be negative or positive.

The liquid crystal may be composed of a mixture of two or more kinds. In the case of a mixture, the mixture exhibits a liquid crystal phase in a certain temperature range or at least one compound among the compounds forming the mixture. May exhibit a liquid crystal phase in a temperature range in which it is independent. When such a liquid crystal is composed of one kind of compound, the compound only needs to exhibit a liquid crystal phase in a certain temperature range. Such liquid crystallinity is defined without being added to the polymer.

The content of the liquid crystal in the polymer oriented film may be such that the retardation wavelength dispersion characteristic of the polymer oriented film is changed when the polymer oriented film is used as a retardation film. Normally 0.01 ~
20% by weight, preferably 0.01 to 15% by weight,
More preferably, it is 0.1 to 10% by weight, further preferably 0.2 to 6% by weight. If the liquid crystal content is too large, there is a concern that the mechanical strength and thermal durability of the retardation film will decrease, and that the haze will increase.If the liquid crystal content is too small, it is difficult to control the wavelength dispersion of the retardation using the liquid crystal. Becomes

By measuring the retardation of the retardation film, the fact that the retardation becomes smaller as the wavelength becomes shorter indicates that R (450) / R (550) <1 or K (450) from a practical viewpoint.
/ K (550) <1. If the wavelength range is expanded, R (650) / R (550)> 1 or K (650) /
It is desirable that K (550)> 1. The more preferable range of these retardation dispersion or K value dispersion will be described later.

Here, in the present invention, the wavelengths 450, 550,
The retardation and the K value in the retardation measurement of the polymer oriented film at 650 nm were R (450), R (550), and R (6
50) and K (450), K (550), K (650).

Here, the retardation (retardation) of a polymer oriented film refers to a retardation value in a retardation measurement, and when light passes through a film having a thickness d, the orientation direction of the film and the direction perpendicular to the orientation direction of the film. Phase difference based on the difference in the traveling speed (refractive index) of light in different directions, the difference Δn in refractive index between the orientation direction and the direction perpendicular thereto and the thickness d of the film
It is known that the product is expressed by the product Δn · d. The polymer oriented film in the present invention refers to a polymer oriented film containing liquid crystals unless otherwise specified.

The transparency of the retardation film is important, and the haze representing the light scattering property of the film must be 3% or less, preferably 2% or less, more preferably 1% or less.
% Or less. Here, the measurement of haze is based on Japanese Industrial Standard JI
SK7105 “Testing method for optical properties of plastics”
It is performed according to. Further, the total light transmittance described in this standard needs to be 80% or more, preferably 85% or more, and more preferably 87% or more.

The orientation of the polymer oriented film in the present invention refers to a state in which the polymer chains of the polymer material constituting the polymer oriented film are mainly arranged in a specific direction. Orientation is usually caused by stretching of the film. The degree of orientation can be evaluated by R (550), K (550), etc., and the orientation here satisfies at least one of | R (550) | ≧ 10 nm or | K (550) | ≧ 10 nm Case. In the present invention, when the polymer molecular chains are arranged, the liquid crystal contained in the polymer is generally aligned. The orientation of the liquid crystal depends on the structure of the polymer, when it is oriented substantially parallel to the polymer main chain,
There are other cases.

It is considered that how the liquid crystal is oriented in the polymer oriented film is determined mainly by the types of the liquid crystal and the polymer material. For example, in the case of a cardo-type polymer having a fluorene group, even if a nematic liquid crystal having a rod shape is added to the polymer, not only the polymer main chain direction but also the major axis direction of the fluorene group, That is, there is a case where the orientation is performed in a direction orthogonal to the polymer main chain.
In this case, the orientation direction of the liquid crystal is considered to depend not only on the material but also on the density of the fluorene group.

Further, the state of the liquid crystal in the polymer oriented film is such that the liquid crystal before being added to the polymer material because it is contained in the polymer oriented film, that is, has no interaction with the polymer material. The phase state may change from the state of no liquid crystal alone. For example, liquid crystal becomes liquid before being added to the polymer material, but when present in the polymer material, the liquid crystal may lose its liquid crystal property due to interaction with the polymer. As described above, the liquid crystallinity is evaluated by a liquid crystal alone without adding a liquid crystal to the polymer material.

The purpose of blending the liquid crystal with the polymer material is to control the optical anisotropy, in particular, the retardation wavelength dispersion of the retardation film. In general, liquid crystals tend to have a large birefringence compared to other compounds, and are considered to be suitable for changing the retardation wavelength dispersion of a polymer oriented film by adding the liquid crystal. The reason why chromatic dispersion of retardation can be controlled by adding liquid crystal, especially the reason why the retardation decreases as the wavelength becomes shorter, is not well understood, but at least the birefringence of the liquid crystal itself, its chromatic dispersion, and alignment. It is thought that the retardation wavelength dispersion of the polymer oriented film can be controlled depending on the state and the like.

Since the retardation Δn · d is proportional to the birefringence Δn if the polymer oriented film is the same, the wavelength dispersion (wavelength dependence) of the phase difference is represented by the wavelength dispersion (wavelength dependence) of the birefringence Δn. be able to.

When the refractive index in the direction of orientation in the plane of the polymer oriented film is larger than the refractive index in the direction perpendicular thereto, the optical anisotropy is positive, and when the refractive index is opposite, the optical anisotropy is negative. That. Here, the orientation direction of the polymer oriented film is
For example, a film may be prepared by using a well-known retardation film manufacturing condition in the vicinity of a glass transition point temperature Tg (a range from Tg-5 to Tg + 20 ° C.).
When the film is uniaxially stretched under the conditions described above, the direction becomes the stretching direction.
In the case of biaxial stretching, it refers to the direction in which the film is stretched to increase the orientation. In addition, the glass transition temperature of the polymer oriented film may change due to the inclusion of liquid crystal. In this case, the temperature near the changed glass transition temperature (Tg-5 to Tg + 2
By performing uniaxial stretching at 0 ° C.), the sign of the optical anisotropy is determined.

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 measurement optical wavelength used to determine the sign of the optical anisotropy is 550 nm.

The birefringence Δn is preferably larger as the wavelength becomes longer in the measurement wavelength region. More specifically, the following formulas (d) and (e): 0.60 <R (450) / R (550) <0.97 (d) In addition, it is preferable to satisfy 1.01 <R (650) / R (550) <1.35 (e). If the value deviates from these values, for example, when using as a λ / 4 plate,
When linearly polarized light having a wavelength of 0 to 700 nm is incident on this film, the obtained polarization state is such that a perfect circular polarization can be obtained at a specific wavelength, but there is a problem that the polarization state largely deviates from the circular polarization at other wavelengths. More preferably, 0.60 <R (450) / R (550) <0.95 (d ') and 1.05 <R (650) / R (550) <1.35 (e').

The above is the phase difference Δn · d or the birefringence Δn
Although the theory is developed based on the above, the same theoretical development is also performed based on the K value of the three-dimensional refractive index (K = [nz− (nx + ny) / 2] × d). This K value is K (450)
In the case of / K (550) <1, the shorter the wavelength, the smaller the wavelength dispersion as with the phase difference (birefringence) for light from an inclined direction that is not perpendicular to the film surface of the polymer oriented film.

As a preferable range of the K value, R in the above equations (d) and (e) is replaced with K.

The polymer material in the retardation film of the present invention may be a blend polymer composed of two or more polymer materials or a copolymer.

The polymer material constituting the retardation film of the present invention preferably has good compatibility with the liquid crystal contained therein, but is not particularly limited and may be a blended polymer or copolymer satisfying the above conditions. It is preferable to use a material which is excellent in heat resistance, good in optical performance and capable of forming a solution film, particularly a thermoplastic polymer. For example, polyarylate, polyester,
One or more types can be appropriately selected from polycarbonate, polyolefin, polyether, polysulfine copolymer, polysulfone, polyethersulfone and the like. It is preferable that the liquid crystal in the polymer loses liquid crystallinity in terms of thermal durability.

The retardation of the retardation film usually changes depending on the temperature. However, the polymer material does not change the temperature dependence of the retardation even when liquid crystal is added as compared with the case where no liquid crystal is added. Is preferred.

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, a combination of polystyrene and poly (phenylene oxide) such as poly (2,6-dimethyl-1,4-phenylene oxide) is preferable.

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, the segment having a fluorene skeleton allows the major axis of the liquid crystal molecule to be oriented in the major axis direction of the fluorene ring as described above, and can give a degree of freedom to the molecular orientation of the liquid crystal. Because it becomes possible to easily control the wavelength difference of retardation of the polymer oriented film according to the purpose,
A polycarbonate copolymer having a fluorene skeleton, a polyester copolymer, a polyester carbonate copolymer, a polyarylate copolymer, or the like is more preferably used. Particularly, a polycarbonate copolymer is more preferable because the copolymerization ratio can be changed relatively easily.

A 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%.

The preferred polymer material for the retardation film of the present invention is represented by the following formula (I)

[0049]

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(In the formula (I), R _{1 to} R ₈ are each independently at least one group selected from a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 6 carbon atoms.
Is the following formula

[0051]

Embedded image

Is as follows. ) Is represented by 5
~ 95 mol% and the following formula (II)

[0053]

Embedded image

(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.
Y is at least one group selected from the group consisting of

[0055]

Embedded image

(Wherein R _{17 to} R ₁₉ , R ₂₁ and R ₂₂ each independently represent a hydrogen atom, a halogen atom and a C 1 to C ₂₂
At least one group selected from hydrocarbon groups of
R ₂₀ and R ₂₃ are at least one group selected from hydrocarbon groups having 1 to 20 carbon atoms, and Ar _{1 to} Ar ₃ are each independently at least one group selected from aryl groups having 6 to 10 carbon atoms. It is a group of. ) Is a polycarbonate copolymer and / or blend in which 95 to 5 mol% of the repeating units b) are occupied.

The above materials include 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. R20 and R23 are each independently selected from hydrocarbon groups having 1 to 20 carbon atoms, and examples of such hydrocarbon groups include the same as those described above. Ar _{1 to} Ar ₃ are aryl groups 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 is 5 to 95 mol% of the whole polycarbonate. Formula (I) above
Is preferably 10 to 90 mol%, more preferably 20 to 80 mol% of the entire polycarbonate.

Here, regardless of the molar ratio, regardless of the copolymer or the blended polymer, for example, nuclear magnetic resonance (NMR)
It can be determined by the device.

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 polymer material of the polymer oriented film constituting the retardation film of the present invention is 0.3 to 2.0.
It is preferably 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.

In the present invention, liquid crystal is mixed with the above-mentioned polymer material. As a mixing method, for example, a so-called solution casting method of dissolving in a common solvent and casting the solution is preferably used, but is not limited thereto. .

The glass transition temperature of the polymer material is 100 ° C.
The temperature is preferably at least 120 ° C, more preferably at least 150 ° C.

Further, in the retardation film of the present invention,
Phenylsalicylic acid, 2-hydroxybenzophenone,
It may contain an ultraviolet absorber such as triphenyl phosphate, a bluing agent for changing color, an antioxidant, and the like.

The retardation film of the present invention uses a film obtained by orienting a film containing liquid crystal in polycarbonate or the like by stretching or the like. As a method for producing such a film, a known melt extrusion method, a solution casting method, or the like is used, and a solution casting method is more preferably used from the viewpoints of uneven film thickness and appearance. As the solvent in the solution casting method, methylene chloride, dioxolane and the like are suitably used.

A known stretching method can be used for the stretching method, but a longitudinal uniaxial stretching is preferred. In the film, for the purpose of improving the stretchability, known plasticizers such as dimethyl phthalate, diethyl phthalate, phthalate esters such as dibutyl phthalate, phosphate esters such as tributyl phosphate, aliphatic dibasic esters, glycerin derivatives, A glycol derivative or the like may be contained. At the time of stretching, the organic solvent used at the time of film formation described above may be left in the film and stretched. The amount of the organic solvent is preferably 1 to 20% by weight based on the solid content of the polymer.

The thickness of the retardation film is not limited, but is preferably 1 μm to 400 μm. In the present invention, the term “retardation film” is used, but it is commonly referred to as “film” or “sheet”.
It is meant to include any of the above.

The retardation film of the present invention is preferably a single quarter-wave plate (λ / 4 plate) or a half-wave plate (λ / plate) having good wavelength dependence and having a single polymer oriented film.
2)), but for this application, R (550) ≧ 50 nm is desirable, more preferably R (550) ≧ 90 nm, and especially for use as a λ / 4 plate. Is preferably 100 nm ≦ R (550) ≦ 180 nm, and 220 ≦ R (550) ≦ 330 nm for use as a λ / 2 plate.

It should be noted that a cellulose acetate film is described as a retardation film in which the retardation becomes smaller as the wavelength is shorter at a measurement wavelength of 400 to 700 nm (Japanese Patent No. 2609139).
FIG. 2 in the official gazette). However, it is difficult to control the retardation wavelength dispersion of the cellulose acetate film. For example, a retardation film having an optimal retardation wavelength dispersion that is controlled by controlling the retardation wavelength dispersion and varies depending on various applications (for example, a reflection type liquid crystal display device). Is difficult to provide. The reason is that cellulose acetate is a material having a water absorption of about 4 to 10%, depending on the degree of acetylation, and this causes problems such as hydrolysis, dimensional deformation, and orientation relaxation. This is because it is difficult to maintain the phase difference chromatic dispersion at a practical level for a long period of time. That is, this is a problem depending on the material, and the cellulose acetate film is inconvenient due to a problem in optical durability. Therefore, the water absorption of the retardation film of the present invention is preferably 2% by weight or less, more preferably 1% by weight or less.

The cellulose acetate film is usually used as a substrate for a polarizing plate or an optical compensator, for example, as R (550).
Is small (a high degree of acetylation and a water absorption of about 4%). In such applications, there is no practical problem even if the orientation of the retardation, particularly R (550), is relaxed, so that this film can be used as a retardation film. However, R
If (550) is larger than that, a highly reliable retardation film cannot be obtained with a cellulose acetate film. Further, in applications where high humidity and heat resistance is required, for example, for use in automobiles, even higher reliability is currently required.

The retardation film of the present invention can be used as a quarter-wave plate. In this case, R = Δn · d
It is preferable to use one having a wavelength of 550 nm, which has the highest visibility in visible light, at a quarter wavelength.

More generally, the retardation film of the present invention has a retardation wavelength dispersion of 0.60 <R (450) / R (550) so that a single film can be used as a broadband λ / 4 plate. ) <0.97 and 1.01 <R (650) / R (550) <1.40, more preferably 0.65 <R (450) / R (550) <0.92 and 1.03 <R (650) / R (550) <1.30. It is preferable that the values fall within the ranges of 0.70 <R (450) / R (550) <0.87 and 1.04 <R (650) / R (550) <1.25.

Such a quarter-wave plate is, for example, used in a reflection type liquid crystal display device having a configuration in which only one polarizing plate is used and the back electrode also serves as a reflection electrode. It is possible to obtain a type display device. Also,
It is also possible to use this retardation film on the back side for the observer of the guest-host type liquid crystal layer. The role of the retardation film in these cases is to convert linearly polarized light into circularly polarized light and circularly polarized light into linearly polarized light in the visible light region, and the retardation film of the present invention satisfies such an object. Is possible.

Thus, as a preferred embodiment of the present invention, a reflection type liquid crystal having a liquid crystal cell including a liquid crystal layer between two substrates having a polarizing plate, a λ / 4 plate, and a transparent electrode in this order. In the display device, the λ / 4 plate is a retardation film composed of a polycarbonate alignment film containing one sheet of liquid crystal, and the retardation at wavelengths of 450 nm and 550 nm is represented by the following formula (1) R (450) / R (550) <1 (1) wherein R (450) and R (550) are wavelengths of 450 nm and 5 respectively.
This is the in-plane retardation of the polymer oriented film at 50 nm. And a reflection type liquid crystal display device using the retardation film of the present invention, wherein R (550) is 100 to 180 nm.

Further, it can be similarly used as an element for converting circularly polarized light into linearly polarized light of a reflective polarizing plate composed of a cholesteric liquid crystal or the like that reflects only one of right and left circularly polarized light.

Further, the retardation film of the present invention is bonded to a polarizing film via an adhesive layer or an adhesive layer to form a circularly polarizing film or an elliptically polarizing film, or by coating a material on the retardation film. The wet heat durability may be improved, or the solvent resistance may be improved.

The retardation film of the present invention has been particularly developed to obtain an ideal λ / 4 plate or λ / 2 plate with a smaller birefringence as the wavelength becomes shorter with a single polymer oriented film. However, as the wavelength is shorter, a polymer oriented film having a smaller birefringence is newly provided. Therefore, the retardation films of the present invention may be laminated, or the retardation films of the present invention and other optical films (transparent films) may be used. Film, a transparent conductive film, a retardation film, a polarizing plate, an optical compensator, etc.) to produce an ideal λ / 4 plate or λ / 2 plate in a wider wavelength range, for example. It is possible to obtain a retardation film or an optical film which is wider and suitable for various uses.

The K value is an index of the three-dimensional refractive index anisotropy of the retardation film, and varies depending on the R value and the film thickness.
Further, the optimum value differs depending on the application. Here, K
Nz is another index of three-dimensional refractive index anisotropy instead of the value
If a preferable range is described by == (nx-nz) / (nx-ny), it is preferably between 0.3 and 1.5 for a retardation film such as a λ / 4 plate or a λ / 2 plate.
In particular, when Nz = 0.5, the phase difference hardly changes even if the angle of incidence on the retardation film changes from the front incidence. If it is a biaxially stretched product, it is preferably from -100 to 100. The three-dimensional refractive indices nx, ny, nz of Nz are those used in the calculation of the K value.

Further, by using such a retardation film in a liquid crystal display device, in particular, a single polarizer type reflection type liquid crystal display device, a display device having excellent image quality can be obtained.
This reflection type liquid crystal display device includes a polarizing plate, a retardation film, a substrate with a transparent electrode, a liquid crystal layer, and a substrate with a scattering reflection electrode, in that order, a polarizing plate, a scattering plate, a retardation film, and a transparent electrode. A substrate, a liquid crystal layer, a substrate with a specular reflective electrode, a polarizing plate, a retardation film, a substrate with a transparent electrode, a liquid crystal layer, a substrate with a transparent electrode, a reflective layer, and the like. . Further, the quarter-wave plate can be used in a liquid crystal display device having both a transmission type and a reflection type. Examples of the configuration of the liquid crystal display device include a polarizing plate, a retardation film, a substrate with a transparent electrode, a liquid crystal layer, a substrate with a reflective / transmissive electrode, a retardation film, a polarizing plate, and a backlight system. Further, in a reflective polarizing plate made of, for example, cholesteric liquid crystal, which reflects only left or right circularly polarized light, if used as an element for converting circularly polarized light into linearly polarized light, good linearly polarized light can be obtained in a wide band.

Further, the retardation film of the present invention comprises:
It can also be used as a 波長 wavelength plate used in an optical head of an optical recording device. In particular, since such a retardation film can give a phase difference of 1/4 wavelength to multiple wavelengths, it can contribute to reducing the number of retardation plates in an optical head using a plurality of laser light sources. it can.

The retardation film of the present invention may be used as an optical member in a liquid crystal projector or the like, for example, as a quarter-wave plate.

Further, in the organic or inorganic electroluminescence element which is a light emitting element, a metal electrode is used on the back side of the light emitting layer. However, since this metal electrode reflects light, contrast is reduced in the presence of external light. , Markedly lower visibility. In order to prevent this, the retardation film and the polarizing film of the present invention are combined into a circularly polarizing film,
It may be used as an antireflection film. Since this circularly polarizing film uses the retardation film of the present invention capable of reducing the retardation to a quarter wavelength in a wide wavelength range of visible light, reflection can be prevented at a wide wavelength range.
It is possible to provide an element which is less colored in reflected light and excellent in visibility.

Further, the retardation film of the present invention can be used as a film for improving the color tone of a transmissive liquid crystal display device and improving the image quality such as the expansion of the viewing angle. As a liquid crystal display device, for example, a twisted nematic mode, a vertical alignment mode, an OCB (Optically compensated bend) alignment mode,
Examples include an in-plane switching mode.

[0087]

EXAMPLES (Evaluation Methods) The material characteristic values and the like described in this specification were obtained by the following evaluation methods. (1) Measurement of R and K values The phase difference R value, which is the product of the birefringence Δn and the film thickness d, and the K value obtained from the three-dimensional refractive index, are trade names of a spectroscopic ellipsometer manufactured by JASCO Corporation. M150 ”. The R value is measured in a state where the incident light beam and the film surface are orthogonal to each other, and R = Δnd · d = (nx−ny) ·
d. The K value is a three-dimensional refractive index nx, which is obtained by measuring the phase difference value at each angle by changing the angle between the incident light beam and the film surface and performing curve fitting using a known refractive index ellipsoidal equation. ny and nz are obtained,
It is determined by substituting K = (nz- (nx + ny) / 2) * d. In this case, an average refractive index n = (nx + ny + nz) / 3 is required as another parameter, which is a trade name of Atago Co., Ltd., which is an Abbe refractometer equipped with a spectral light source. Using "Abbe refractometer 2-T", measurement wavelength λ500, 550, 590, 640nm
Is measured, and Cauchy's formula (n =
a + b / λ2 + c / λ4; a, b, and c are fitting parameters), and the refractive index at other wavelengths was determined.
The unit for both K and R values is nm. Also, nx, ny, n
z is defined here as: nx: Refractive index in the main stretching direction in the film plane ny: Refractive index in the direction perpendicular to the main stretching direction in the film plane nz: Refractive index in the normal direction of the film surface (when the main stretching direction is uniaxial stretching) Means the stretching direction, in the case of biaxial stretching, the direction in which the degree of orientation is further increased, and indicates the orientation direction of the polymer main chain in terms of chemical structure.) R at each wavelength is shown as an actually measured value. When R (550)> 0, the refractive index anisotropy is positive,
Negative when R (550) <0.

(2) Measurement of Total Light Transmittance and Haze Measurement was performed with an integrating sphere light transmittance measuring device according to Japanese Industrial Standards JIS K 7105 “Test Method for Optical Properties of Plastics”. As an evaluation device, a color difference / turbidity meter (trade name “COH-300A”) manufactured by Nippon Denshoku Industries Co., Ltd. was used.

(3) Measurement of Polymer Copolymerization Ratio Proton NM of trade name “JNM-alpha600” manufactured by JEOL Ltd.
Measured by R. In particular, in the case of a copolymer of bisphenol A and biscresol fluorene, heavy benzene was used as a solvent, and calculation was made from the proton intensity ratio of each methyl group.

(4) Measurement of glass transition temperature (Tg) of polymer “DSC2920 ModulatedDSC” (trade name, manufactured by TA Instruments)
Was measured by The measurement was made in the state of flakes or chips after resin polymerization, not after film formation.

(5) Film thickness measurement The film thickness was measured by an electronic micro manufactured by Anritsu Corporation. Further, the monomer structure of the polycarbonate used in the following examples is shown below.

[0092]

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. It was dissolved at a ratio of 50 (mol%), and a small amount of hydrosulfite was added. Next, methylene chloride was added thereto, and phosgene was blown in at 20 ° C. for about 60 minutes. Further, after adding and emulsifying p-tert-butylphenol, triethylamine is added and the mixture is added at 30 ° C. for about 3 hours.
The reaction was terminated by stirring for an hour. 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.

The copolymer and a brand name of “BL007”, a cyanobiphenyl-based mixed liquid crystal manufactured by Merck, were added to 9
A dope solution was prepared by dissolving in methylene chloride at a ratio of 6: 4 (parts by weight). A cast film was prepared from this dope solution and stretched in the free-width uniaxial direction at a temperature of 218 ° C. by a factor of 1.9 to obtain a retardation film.

Table 1 summarizes the measurement results. In this film, the shorter the measurement wavelength, the smaller the phase difference, and
It was confirmed that the in-plane refractive index was the largest in the stretching direction, and the refractive index anisotropy was positive. The values of K (650) / K (550) and R (650) / R (550) were 0.90 and 1.06, respectively.

Further, a retardation film was prepared using only the above-mentioned polymer material without adding the above-mentioned liquid crystal, but R (450) / R (55
0) is 1.01, which indicates that the wavelength dispersion can be greatly changed by adding a liquid crystal.

Example 2 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. It was dissolved at a ratio of 65 (mol%), and a small amount of hydrosulfite was added. Next, methylene chloride was added thereto, and phosgene was blown in at 20 ° C. for about 60 minutes. Further, after adding and emulsifying p-tert-butylphenol, triethylamine is added and the mixture is added at 30 ° C. for about 3 hours.
The reaction was terminated by stirring for an hour. 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 and the product name “E7”, which is a cyanobiphenyl-based mixed liquid crystal manufactured by Merck Co., Ltd., were respectively 97:
Dissolved in methylene chloride at a ratio of 3 (parts by weight)
A dope solution was prepared. A cast film was prepared from this dope solution and stretched uniaxially at 223 ° C. by 1.9 times to obtain a retardation film.

Table 1 also shows the measurement results. In this film, the shorter the measurement wavelength, the smaller the phase difference, and
It was confirmed that the in-plane refractive index was the largest in the stretching direction, and the refractive index anisotropy was positive. In addition, a retardation film was prepared only with the polymer material without adding the liquid crystal, but R (450) / R (550) was 0.81, and the wavelength dispersion was greatly changed by adding the liquid crystal. I found that I could do it.

[0100]

[Table 1]

[0101]

According to the present invention, it is possible to easily obtain a retardation film having a smaller retardation as the wavelength becomes shorter. Further, by containing the liquid crystal, the wavelength dispersion characteristic of the phase difference can be easily controlled. A retardation plate having such retardation wavelength dispersibility and having a retardation of a quarter wavelength can provide a circularly polarizing film having excellent antireflection characteristics in combination with a polarizing film, and In addition, in combination with a reflective liquid crystal display device, a transflective liquid crystal display device, a transmissive liquid crystal display device, or the like, it is possible to contribute to an improvement in image quality.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 69/00 C08L 69/00 5G435 101/00 101/00 G02F 1/1335 510 G02F 1/1335 510 1 / 13363 1/13363 G09F 9/00 313 G09F 9/00 313 (72) Inventor Isao Kawada 4-2-2 Asahigaoka, Hino-shi, Tokyo Teijin Inside the Tokyo Research Center, Inc. (72) Inventor Yuhei Ono Hino-shi, Tokyo 4-3-2 Asahigaoka Teijin Co., Ltd. Tokyo Research Center F-term (reference) 2H049 BA03 BA04 BA06 BA07 BA25 BB03 BB12 BB42 BB44 BB62 BC03 BC09 BC21 BC22 2H091 FA08X FA08Z FA11X FA11Z FB02 KA01 KA02 KA10 4A07A01 A01 A01 A01 BA02 BB02 BC01 4J002 AC071 BB011 BC032 BC051 BC062 BD142 BG061 BH012 BN151 CF001 CF161 CG001 CH001 CH022 CH071 CN0 31 EH146 EL106 EQ016 ER006 ET006 EU136 FD206 GP00 4J029 AA09 AB01 AC02 AD09 AE04 BB12A BB12C BB13A BC07B BD01 BD08 BD09 BE07 BH02 BH04 DB07 DB13 HA01 HC01 HC05 KE09 5G435 AA01 BB12 BB15 BB16 DD12 KK

Claims (10)

[Claims] 1. A retardation film composed of one polymer oriented film containing a liquid crystal, wherein the retardation at wavelengths of 450 nm and 550 nm satisfies the following formulas (1) and / or (2), and the haze is A retardation film having a content of 3% or less. R (450) / R (550) <1 (1) K (450) / K (550) <1 (2) [wherein R (450) and R (550) each have a wavelength of 450 nm.
And the in-plane retardation of the polymer oriented film at 550 nm, where K (450) and K (550) are each 450 nm wavelength.
K = K of the polymer oriented film at m and 550 nm
[Nz- (nx + ny) / 2] × d (where nx, n
y and nz are the three-dimensional refractive indices of the polymer oriented film, which are the refractive indices in the x-axis, y-axis and z-axis directions, respectively, and d is the thickness of the film. ). ] 2. The wavelength of 450 nm, 550 nm and 650.
The phase difference in nm is represented by the following formulas (3) and (4): 0.6 <R (450) / R (550) <0.97 (3) 1.01 <R (650) / R (550) <1 0.4 (4) [wherein, R (650) is an in-plane retardation of the polymer oriented film at a wavelength of 650 nm. The retardation film according to claim 1, which satisfies the following. 3. The retardation film according to claim 1, wherein the shorter the wavelength, the smaller the retardation at a wavelength of 400 to 700 nm. 4. The retardation film according to claim 1, wherein the content of the liquid crystal in the polymer oriented film is 0.01 to 15% by weight. 5. The retardation film according to claim 1, wherein the polymer oriented film contains a polycarbonate having a fluorene skeleton. 6. The polycarbonate according to the following formula (I):(In the above formula (I), R₁~ R₈Are each independently water
Elemental atoms, halogen atoms and hydrocarbon groups having 1 to 6 carbon atoms
X is at least one selected from the group consisting of:It is. 5) to 95 mol% of the repeating unit a)
And the following formula (II):(In the above formula (II), R₉~ R₁₆Are independently
Hydrogen atom, halogen atom and hydrocarbon having 1 to 22 carbon atoms
And Y is at least one member selected from the group consisting of(Where R₁₇~ R₁₉, R_{twenty one}And R_{twenty two}Are each independently water
Elemental atoms, halogen atoms and hydrocarbon groups having 1 to 22 carbon atoms
At least one member selected from the group consisting of R₂₀And R _{twenty three}Is charcoal
At least one selected from hydrocarbon groups having a prime number of 1 to 20
And Ar₁~ Ar_ThreeAre independently 6 carbon atoms
At least one group selected from 10 to 10 aryl groups
is there. ) Represents 95 to 5 mo
% Of the polycarbonate copolymer and / or
The phase difference according to any one of claims 1 to 5, wherein the phase difference is a render.
the film. 7. A circularly polarizing film comprising a polarizing film and the retardation film according to claim 1. 8. A light emitting device using the circularly polarizing film according to claim 7. 9. An elliptically polarizing film comprising a polarizing film and the retardation film according to claim 1. 10. A liquid crystal display device using the retardation film according to claim 1.