JP2003177244A - Optical retardation film and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hitherto unknown optical retardation film with new wavelength dispersion of retardation which upgrades a degree of freedom of optical compensation of a liquid crystal display device and has effect to reduce the required number of sheets of the optical retardation films. <P>SOLUTION: The optical retardation film is composed of a monolayer organic oriented film containing a polymer and is characterized by having at least a maximum value and/or a minimum value of a retardation value in 400-800 nm wavelength range. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation film used for a display device, in particular a liquid crystal display device, an organic electroluminescence element or the like, an optical pickup in an optical recording device, an optical component or the like.

[0002]

2. Description of the Related Art Retardation films are used in STN (Super Twisted Nematic) systems of liquid crystal display devices, and are used for solving problems such as color compensation and widening of viewing angle. Generally, polycarbonate, polyvinyl alcohol, polysulfone, polyether sulfone, amorphous polyolefin or the like is used as the material of the retardation film for color compensation, and a polymer in addition to the above-mentioned materials is used as the retardation film material for widening the viewing angle. Liquid crystals and discotic liquid crystals are used.

Although a liquid crystal display device using a thin film transistor (TFT) has a remarkably better image quality than the STN described above, the image quality viewed obliquely is different from the image quality viewed from the front compared to the CRT. There was a so-called viewing angle problem. In response to this problem, an optimized retardation film or the like has been used, and the viewing angle of the liquid crystal display device has been considerably improved.

However, although it can be said that the viewing angle characteristics are improved as compared with the conventional liquid crystal display device, the CRT is used for problems such as subtle changes in color tone depending on the viewing angle and problems for further contrast optimization. It is still not enough compared to.

Since a normal liquid crystal display device uses polarized light, the problem of these viewing angles is that the degree of change in polarized light passing through the liquid crystal display device differs depending on whether the light is incident on the front or obliquely. Due to that. The existing liquid crystal display device, which is said to have improved the viewing angle problem to some extent, has such a problem. Optimizing this problem by optical design may provide a solution that can be solved by giving a slight retardation using a retardation film. For example, in order to increase the front contrast in the vertical alignment liquid crystal mode, several to several 1
A retardation film having a minute retardation of about 0 nm may be used.

Further, in recent years, liquid crystal display devices using a polymer substrate instead of a glass substrate have begun to appear on the market, but the optical anisotropy of the polymer substrate cannot be ignored as the display quality is improved. At the same time, there are moves to actively use it.

In order to control the delicate polarization state of the liquid crystal display device as described above, it is necessary that the chromatic dispersion of the phase difference is different from the conventional chromatic dispersion of the phase difference. For example, a polycarbonate having a bisphenol A skeleton is widely used as a conventional retardation film. The retardation film made of this material has the property that the retardation value monotonically increases as the wavelength becomes shorter.For example, when trying to obtain different wavelength dispersion, it is necessary to use multiple sheets. There is a problem that there is. Since what kind of retardation wavelength dispersion should be used depends on the design of the liquid crystal display device, it cannot be said unconditionally, but at least a retardation film having a retardation wavelength dispersion which is not available in the past can be used for liquid crystal display. There is no doubt that it is useful in terms of improving the degree of freedom in the optical design of the device and reducing the required number of retardation films. Since the retardation value of a normal retardation film is monotonically increasing or decreasing in visible light, there is a retardation film having a maximum value or a minimum value of at least one retardation value in the wavelength range of 400 nm to 800 nm. Therefore, when such characteristics are desired, the current situation was to use a plurality of films by appropriately laminating them.

[0008]

The main object of the present invention is to:
It is made in view of the above-mentioned actual situation, and has a novel phase difference wavelength which has not been available in the past, which has an effect of increasing the degree of freedom of optical compensation of the liquid crystal display device and reducing the required number of phase difference films. It is to provide a retardation film having dispersion.

[0009]

[Means for Solving the Problems] In order to solve the problems such as increasing the degree of freedom in optical compensation of the above liquid crystal display device, the characteristics of the retardation film were intensively studied, and in the wavelength range of 400 nm to 800 nm, At least 1
The inventors have found that a retardation film having a maximum value and / or a minimum value of one retardation value is effective, and succeeded in uniformly obtaining a retardation film having the characteristics with high productivity.

That is, the present invention is as follows. 1. A retardation film comprising a single-layer organic oriented film containing a polymer, wherein at least one of the maximum and minimum retardation values in a wavelength range of 400 nm to 800 nm and
/ Or a retardation film having a minimum value.

2. 2. The retardation film according to 1 above, wherein the organic oriented film is substantially composed of a polymer.

3. 2. The retardation film according to 1 or 2 above, wherein the glass orientation temperature of the organic oriented film is 120 ° C. or higher.

4. The organic oriented film is composed of a polymer containing a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy. ~ 3 retardation film.

5. The organic oriented film is composed of (1) a polymer monomer unit having positive refractive index anisotropy (hereinafter referred to as “first”).
Of monomer units. ) And a polymer monomer unit having a negative refractive index anisotropy (hereinafter referred to as a second monomer unit), which is (2) the first monomer unit. Polymer based on R
(450) / R (550) is smaller than R (450) / R (550) of the polymer based on the second monomer unit, and (3) a polymer having a positive refractive index anisotropy. 4. The retardation film of 4 above.

6. The organic oriented film forms (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. A film composed of a polymer containing a monomer unit (hereinafter referred to as a second monomer unit), comprising: (2) a polymer R (450) / R (550) based on the first monomer unit. Is R (450) / R (55 of the polymer based on the second monomer unit.
The retardation film of 4 above, which is made of a polymer and is larger than 0) and (3) has negative refractive index anisotropy.

7. 7. The retardation film according to any one of 1 to 6 above, wherein the water absorption rate of the organic oriented film is 1% by weight or less.

8. The retardation film according to any one of 1 to 7 above, wherein the polymer is a polycondensation polymer.

9. The retardation film according to any one of 1 to 8 above, wherein the polymer has a fluorene skeleton.

10. The retardation film according to any one of 1 to 9 above, wherein the polymer is polycarbonate.

11. Polycarbonate has the following formula (I)

[0021]

[Chemical 9]

(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

[0023]

[Chemical 10]

And R ₃₀ and R ₃₁ are each independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms. ) 10 to 90 mol% of the repeating unit represented by the following formula (II)

[0025]

[Chemical 11]

(In the above formula (II), R _{9 to} R ₁₆ are each independently a hydrogen atom, a halogen atom and a carbon number of 1 to 1.
Selected from 22 hydrocarbon groups, Y is

[0027]

[Chemical 12]

Here, R _{17 to} R ₁₉ , R ₂₁ and R in Y are
22 is each independently a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms; R ₂₀ and 23 are each independently a hydrocarbon group having 1 to 20 carbon atoms;
Is selected from aryl groups having 6 to 10 carbon atoms. The repeating unit shown by 1) is a polycarbonate copolymer and / or a blend which occupies 90 to 10 mol% of the whole, The retardation film of 1 to 10 above.

12. Polycarbonate has the formula [II
I]

[0030]

[Chemical 13]

(In the above formula [III], R ₂₄ and R ₂₅ are independently selected from a hydrogen atom and a methyl group.) The repeating unit represented by the following formula [IV] is 45 to 53 mol%. Repeating unit indicated by

[0032]

[Chemical 14]

(In the above formula [IV], R ₂₆ and R ₂₇
Are each independently selected from a hydrogen atom and a methyl group. The repeating unit represented by 4) is a polycarbonate copolymer and / or a blend that accounts for 55 to 47 mol% of the whole, and the retardation film according to any one of 1 to 11 above.

13. A liquid crystal display device using the retardation film of 1 to 12 above.

14. The following formula [III]

[0036]

[Chemical 15]

(In the above formula [III], R ₂₄ and R ₂₅ are independently selected from a hydrogen atom and a methyl group.) The repeating unit represented by the following formula [IV] is 45 to 53 mol% of the whole. Repeating unit indicated by

[0038]

[Chemical 16]

(In the above formula [IV], R ₂₆ and R ₂₇
Are each independently selected from a hydrogen atom and a methyl group. The retardation film which consists essentially of a polycarbonate copolymer and / or a blend which the repeating unit shown by the above-mentioned occupies 55-47 mol% of the whole.

[0040]

DETAILED DESCRIPTION OF THE INVENTION The retardation film in the present invention is a retardation film composed of a single layer containing a polymer, that is, one organic oriented film, and having a wavelength of 400 nm to 800 nm.
In the range, the retardation film has a retardation that has a maximum retardation value or a minimum retardation value. Such a maximum value and a minimum value may have one or two or more in such a wavelength range, and may have both a maximum value and a minimum value. The retardation value is preferably such that the retardation value when measured with incident light from the direction perpendicular to the film surface satisfies the above relationship, but may also satisfy the above relationship with oblique incident light.

The retardation film having such characteristics increases the degree of freedom of optical compensation of the liquid crystal display device, and
It is possible to reduce the number of retardation films used. As described above, the optical design of the liquid crystal display device is diverse, and it cannot be said that certain characteristics of the retardation film are good for all devices. However, for example, for a retardation film that performs optical compensation, a liquid crystal that requires a relatively large retardation near a certain specific wavelength and has a relatively small retardation at other wavelengths is said to be optimal. In the case of a cell, if there is a retardation film having a maximum value in a wavelength region which is a range of visible light, it is possible to perform optical compensation with the single film. However, in a conventional retardation film that monotonically increases or monotonically decreases in visible light, it is possible to optimize the retardation value and the laminating angle so that at least two films are used to appropriately adjust each retardation. Will be needed.

In the retardation film of the present invention, there is only one maximum value, and the maximum value is 400 nm.
Preferably exists in the wavelength range of ~ 550 nm,
More preferably, it is in the wavelength range of 450 nm to 550 nm. When the retardation values measured at wavelengths of 450 nm and 550 nm are R (450) and R (550), respectively, it is preferable that | R (450) | ≧ | R (550) |. Most preferably, the maximum value is 400 nm
There is only one in the wavelength range of 550 nm and | R (4
50) | ≧ | R (550) |. Such characteristics may be particularly preferable in the optical design of the liquid crystal display device.

Next, specific materials for the retardation film of the present invention will be described. The retardation film of the present invention comprises an oriented film containing at least 1% by weight of a polymer, and can contain an organic substance in addition to the polymer. In such an oriented film, the content of the polymer is preferably 70% or more by weight ratio, more preferably 85% or more, further preferably 95% or more, and even more preferably substantially polymer. Consists of. A large amount of the polymer is preferable, because the polymer is excellent in shape retention, moldability, durability and the like. Such a polymer may have liquid crystallinity, or may be a thermoplastic polymer as shown below.

In addition to polymers, examples of organic substances that may be contained in the oriented film include low molecular weight liquid crystals, polymerizable liquid crystals, low molecular weight compounds having an aromatic ring, and organic substances such as oligomers. Organic substances other than these polymers can influence the wavelength dependence of the retardation by being uniformly mixed and substantially oriented in the retardation film.

When the organic oriented film is essentially composed of a polymer, the polymer is oriented in at least one direction. When an organic substance other than polymer is blended,
It is preferable that one or both of the polymer and the organic substance are oriented in one direction.

Most preferably, an organic oriented film composed of only a polymer is used. In this case, durability and workability are particularly excellent.

The glass transition temperature of the organic oriented film is
It is preferably 120 ° C. or higher. If it is less than this, problems such as orientation relaxation may occur depending on the use conditions of the retardation film. The temperature is more preferably 130 ° C or higher, still more preferably 150 ° C or higher.

The water absorption of the organic oriented film is preferably 1% by weight or less. When the water absorption rate of the organic oriented film exceeds 1% by weight, there may be a problem in practical use as a retardation film. The film material has a water absorption rate of 1% by weight or less, preferably 0.5% by weight or less. It is better to choose to meet the conditions.

The polymer used in the present invention may be a blended polymer composed of two or more kinds of polymers or a copolymer.

The polymer constituting the retardation film used in the present invention is not particularly limited, as long as it is a blend or copolymer satisfying the above conditions, it is excellent in heat resistance, has good optical performance, and is made of a solution. Membrane-forming materials are preferred, especially thermoplastic polymers. For example, one kind or two or more kinds can be appropriately selected from polyarylate, polyester, polycarbonate, polyolefin, polyether, polysulfinic copolymer, polysulfone, polyethersulfone and the like. Considering productivity and various physical properties,
The polymer preferably comprises a polycondensation polymer.

Further, the polymer is composed of an organic oriented film containing a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy. Is preferred. This is because the positive component and the negative component are contained, so it is possible to freely adjust the phase difference by adjusting the amount of both components, and as a result, the wavelength range from 400 nm to 800 nm. In, it becomes easy to design a retardation film having at least one maximum and / or minimum retardation value. In this case, the monomer unit does not have to have one component for each of positive and negative components, and may have one component or more for each component.

Further, among retardation films composed of an organic oriented film containing a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy, More preferably, the following conditions (A) or (B) are satisfied. When this condition is satisfied, it becomes easier to design a retardation film having at least one maximum and / or minimum retardation value in the wavelength range of 400 nm to 800 nm.

(Condition 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), which is a film comprising a polymer including (2) R (450) / R (550) of the polymer based on the first monomer unit An organic oriented film which is smaller than R (450) / R (550) of a polymer based on the second monomer unit and (3) has a positive refractive index anisotropy.

(Condition B) (1) A monomer unit forming a polymer having positive refractive index anisotropy (hereinafter referred to as a first monomer unit) and a polymer having negative refractive index anisotropy are prepared. A film composed of a polymer containing a monomer unit to be formed (hereinafter referred to as a second monomer unit), comprising: (2) a polymer R (450) / R (based on the first monomer unit. 550) is a polymer R (450) / R (550) based on the second monomer unit.
Greater than, and (3) negative refractive index anisotropy,
Organic oriented film.

Under the above conditions, the monomer units have positive and negative refractive index anisotropy, which means that a film made of a polymer obtained by polymerizing each monomer alone is uniaxially stretched, The anisotropy is called positive when nx> nz and the anisotropy is negative when nx <nz, which will be described later.
Further, in this judgment of positive / negative, the glass transition temperature Tg
Judgment shall be made based on the refractive index anisotropy obtained when uniaxially stretched under the conditions of the vicinity (range of Tg-5 to Tg + 20 ° C).

Further, under the above conditions, the monomer unit is not limited to the two components and may be three or more components. For example, two positive monomer units and three negative monomer units.
If there is a component, a polymer consisting only of positive monomer units and a polymer consisting only of negative monomer units are prepared, and a film is prepared under the above conditions to determine the refractive index anisotropy and its wavelength dispersion. It shall be.

Since a blended polymer needs to be optically transparent, it is preferable that the compatible blends or the respective polymers have substantially the same refractive index. Specific examples of the blended polymer include poly (methyl methacrylate) as a polymer having negative optical anisotropy.
And poly (vinylidene fluoride), poly (ethylene oxide), poly (vinylidene fluoride-co-trifluoroethylene) as a polymer having positive optical anisotropy
And poly (phenylene oxide) as a polymer having a positive optical anisotropy, and polystyrene, poly (styrene-co-lauroyl maleimide), poly (styrene-co-) as a polymer having a negative optical anisotropy. Cyclohexylmaleimide), poly (styrene-co-phenylmaleimide), poly (styrene-co-maleic anhydride) having negative optical anisotropy and polycarbonate having positive optical anisotropy, and positive Preferable examples include poly (acrylonitrile-co-butadiene) having optical anisotropy and poly (acrylonitrile-co-styrene) having negative optical anisotropy, but are not limited thereto. 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. In this case, the polystyrene takes a minimum value of the phase difference within the range of 60 to 95% by weight, preferably within the range of 65 to 90% by weight, though it depends on the production conditions.

Examples of the copolymer include poly (butadiene-co-polystyrene), poly (ethylene-co-polystyrene), poly (acrylonitrile-co-butadiene), poly (acrylonitrile-co-butadiene-co-).
Styrene), polycarbonate copolymers, polyester copolymers, polyester carbonate copolymers, polyarylate copolymers and the like can be used. In particular, a segment having a fluorene skeleton may have a negative optical anisotropy, and therefore a polycarbonate copolymer having a fluorene skeleton, a polyester copolymer, a polyester carbonate copolymer, a polyarylate copolymer and the like are more preferably used.

A polycarbonate copolymer produced by reacting a bisphenol with a carbonic acid ester-forming compound such as phosgene or diphenyl carbonate is excellent in 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 in an amount of 1 to 99 mol%. More preferably, the following formula (I)

[0060]

[Chemical 17]

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

[0062]

[Chemical 18]

And R ₃₀ and R ₃₁ are each independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms. ) 10 to 90 mol% of the repeating unit represented by the following formula (II)

[0064]

[Chemical 19]

(In the above formula (II), R _{9 to} R ₁₆ are each independently a hydrogen atom, a halogen atom and a carbon number of 1 to 1.
Selected from 22 hydrocarbon groups, Y is

[0066]

[Chemical 20]

Selected from: Here, R ₁₇ in Y-
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, R ₂₀ and R ₂₃ are selected from a hydrocarbon group having 1 to 20 carbon atoms, and Ar is an aryl group having 6 to 10 carbon atoms. Is a polymer composed of a polycarbonate copolymer and / or a blended body in which the repeating unit represented by the above occupies 90 to 10 mol% of the whole.

This material comprises 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, two or more kinds of repeating units represented by the above formulas (I) and (II) may be combined, and in the case of a composition, two or more kinds of 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 the hydrocarbon group having 1 to 6 carbon atoms include alkyl groups such as methyl group, ethyl group, isopropyl group and cyclohexyl group, and aryl groups such as phenyl group. Among these, a hydrogen atom and a methyl group are preferable.

In the X of the above formula (I), R ₃₀ and R
Each ₃₁ is independently selected from a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms.

In the above formula (II), R _{9 to} R ₁₆ are each independently a hydrogen atom, a halogen atom and a carbon number of 1 to 2.
It is selected from two hydrocarbon groups. Examples of the hydrocarbon group having 1 to 22 carbon atoms include alkyl groups having 1 to 9 carbon atoms such as methyl group, ethyl group, isopropyl group and cyclohexyl group, and aryl groups such as phenyl group, biphenyl group and terphenyl group. To be 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,
As the hydrocarbon group, the same ones as described above can be mentioned. R ₂₀ and R ₂₃ are each independently selected from a hydrocarbon group having 1 to 20 carbon atoms, and as the hydrocarbon group, the same ones as described above can be mentioned. Ar has 6 carbon atoms such as phenyl group and naphthyl group
And 10 aryl groups.

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 10 to 90 mol% of the whole polycarbonate. When it is out of such a range, it becomes difficult to obtain a retardation film having at least one maximum and / or minimum retardation value in the wavelength range of 400 nm to 800 nm.
The content ratio of the above formula (I) is 15 in the whole polycarbonate.
It is preferably -85 mol%, more preferably 25-70 mol%. More preferably, the polymer has the following formula [III]

[0074]

[Chemical 21]

(In the above formula [III], R ₂₄ and R ₂₅ are each independently selected from a hydrogen radical tyl group.) The repeating unit represented by the following formula [IV] is 45 to 53 mol% of the whole.

[0076]

[Chemical formula 22]

A polycarbonate in which the repeating unit represented by the following formula (in the formula [IV], R ₂₆ and R ₂₇ are each independently selected from a hydrogen atom and a methyl group) accounts for 55 to 47 mol% of the whole. It is a copolymer and / or a blend polymer. This polycarbonate has a wavelength of 400 depending on the manufacturing conditions of the film.
Within the range of up to 550 nm, the phase difference has one maximum value, which is preferable. Desired optical compensation can be performed in this wavelength range.

In the above formula [III], R ₂₄ and R ₂₅
Are each independently selected from a hydrogen atom or a methyl group. From the viewpoint of mass productivity and environmental resistance, a methyl group is more preferable.

In the above formula [IV], R ₂₆ and R ₂₇ are each independently selected from a hydrogen atom and a methyl group. From the viewpoint of mass productivity, it is more preferably a hydrogen atom.

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

The above-mentioned copolymer and / or blend polymer can be produced by a known method. For polycarbonate, a method by polycondensation of a dihydroxy compound and phosgene, a melt polycondensation method, or the like is preferably used. In the case of blending, a compatible blend is preferable, but even if they are not completely compatible, it is possible to suppress light scattering between the components and improve transparency by matching the refractive index between the components.

The intrinsic viscosity of the polymer constituting the retardation film of the present invention is preferably 0.3 to 2.0 dl / g. If it is less than this, there is a problem that it becomes brittle and the mechanical strength cannot be maintained, and if it exceeds 2.0, the solution viscosity becomes too high and problems such as die line formation in solution film formation and purification at the end of polymerization become difficult. There is such a problem.

The retardation film preferably has a high transparency, a haze value of 3% or less and a total light transmittance of 85% or more.

Further, an ultraviolet absorber such as phenylsalicylic acid, 2-hydroxybenzophenone or triphenyl phosphate, a bluing agent for changing the color,
Antioxidants and the like may be added.

As the retardation film of the present invention, it is preferable to use a film obtained by orienting the film made of a polymer such as polycarbonate described above in one direction usually by stretching or the like. As a method for producing such a film, a known melt extrusion method, solution casting method or the like is used, but the solution casting method is more preferably used from the viewpoints of unevenness in film thickness, appearance and the like. As the solvent in the solution casting method, methylene chloride, dioxolane and the like are preferably used.

A known stretching method may be used as the stretching method, but longitudinal uniaxial stretching is preferable. In the film, for the purpose of improving stretchability, known plasticizers such as dimethyl phthalate, diethyl phthalate, phthalates such as dibutyl phthalate, phosphates 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 during the 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 phase difference film constituent material.

Although the thickness of the retardation film is not limited, it is preferably 1 μm to 400 μm. Although referred to as a retardation film in the present invention, it is commonly referred to as a “film” or a “sheet”.
It is meant to include any of the above.

It is known that the retardation film generally gives a different retardation value to obliquely incident light as compared with front incident light. In the retardation film of the present invention, the three-dimensional refractive index of the polymer material is nx,
Represented by ny and nz, each is defined as follows: nx: refractive index in main stretching direction in retardation film plane ny: refractive index in direction orthogonal to main stretching direction in retardation film nz: retardation film surface Let be the refractive index in the normal direction. Here, the main stretching direction means a stretching direction in the case of uniaxial stretching, and a stretching direction so as to increase the degree of orientation in the case of biaxial stretching. Refers to the orientation direction. When nx> nz, the optical anisotropy is positive, n
When x <nz, the optical anisotropy is called negative here. In addition, the determination of the positive / negative is based on the optical anisotropy obtained when the glass is uniaxially stretched under the conditions of the glass transition temperature Tg vicinity (the range of Tg-5 to Tg + 20 ° C.). In the case of biaxial stretching, it refers to the direction in which the orientation is increased. The glass transition temperature of the organic oriented film may change due to the inclusion of liquid crystals, but in this case, the changed glass transition temperature (Tg-5 to Tg + 20 ° C)
The range of 1) is used to determine whether the optical anisotropy is positive or negative.

This three-dimensional refractive index is measured by a polarization analysis method, which is a method of analyzing the polarization state of outgoing light obtained by entering polarized light into the retardation plate. This three-dimensional refractive index is obtained by the method of obtaining the well-known refractive index ellipsoid by regarding the directionality as an index ellipsoid. Since this three-dimensional refractive index depends on the wavelength of the light source used, it is preferably defined by the wavelength of the light source used. There is the following formula (8) Nz = (nx-nz) / (nx-ny) (8) as a method of expressing the optical anisotropy using this three-dimensional refractive index. If Nz is in the range of 0.3 to 1.5, the dependence of the retardation value on the incident angle becomes extremely small. In particular, when Nz = 0.5, the incident angle dependence of the phase difference value 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 retardation film having positive optical anisotropy is nx and the fast axis is ny.

In order to obtain a retardation film having a maximum value and / or a minimum value of at least one retardation value in the wavelength range of 400 nm to 800 nm,
It is essential to have a specific chemical structure, and the retardation wavelength dispersion is largely determined by its chemical structure, but it should be noted that it also varies depending on additives, stretching conditions, blending state, molecular weight, etc. Is.

Although the retardation film of the present invention can be used alone, a plurality of retardation films can be used depending on the intended use, or as another usage, it can be used in combination with another optical compensation film in a liquid crystal display device. You can By controlling the three-dimensional refractive index of the retardation film of the present invention nx = n
A film having anisotropy such as y> nz, nx = ny <nz, nx>ny> nz, nx>nz> ny can be obtained. These can be combined with a polarizing plate to form a polarizing plate with a wide viewing angle or a wideband wave plate. Further, the retardation film of the present invention is capable of performing optical compensation on all liquid crystal cells such as bend alignment cells, vertical alignment cells, in-plane switching mode cells and twisted nematic cells that are compensated by the optical compensation film. is there. Further, it can be used as an optical film used in a liquid crystal projector or the like.

In addition to the liquid crystal display device, a quarter of the circular polarization film for an antireflection film in a light emitting element such as an organic electroluminescence element, a plasma display, an electroluminescent element, a CRT or an electrophoretic element is used. It can also be used as a one-wave plate.

Further, the retardation film of the present invention may be used instead of the transparent substrate of the liquid crystal display device or the organic light emitting element using the transparent substrate made of the polymer material. Also in this case, optical design can be expected to improve the contrast and the viewing angle evenly.

[0095]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

(Evaluation Method) The material property values and the like described in this specification are obtained by the following evaluation methods. (1) Phase difference value (R = Δn · d (nm)), K value measurement The phase difference R value and Nz, which are the product of the birefringence Δn and the film thickness d, are manufactured by JASCO Corporation, which is a spectroscopic ellipsometer. Product name of "M1
50 ". The R value was measured with the incident light and the film surface orthogonal to each other. Further, the K value (nm) is a three-dimensional refractive index by changing the angle between the incident light and the film surface, measuring the phase difference value at each angle, and performing curve fitting with a known refractive index ellipsoidal formula. Nx, ny, nz
Was obtained and was substituted into the following formula (7). K = (nz- (nx + ny) / 2) * d (7)

(2) Measurement of water absorption rate Measured according to "Testing method for water absorption rate and boiling water absorption rate of plastics" described in JIS K 7209, except that the film thickness was 130 ± 50 μm in the dried film state. did. The size of the test piece was 50 mm square, and the weight change was measured after immersing the sample in water at 25 ° C. for 24 hours. The unit is%.

(3) Measurement of polymer glass transition temperature (Tg) TA Instruments' trade name "DSC2920 Modulated DSC"
] Was measured. The measurement was performed in the state of flakes or chips after resin polymerization, not after film formation.

(4) Film thickness measurement It was measured with an electronic micrometer manufactured by Anritsu.

(5) Measurement of Polymer Copolymerization Ratio Proton NMR of JEOL brand name "JNM-alpha600"
It was measured by. Particularly in the case of a copolymer of bisphenol A and biscresolfluorene, deuterated benzene was used as a solvent, and the calculation was made from the proton intensity ratio of each methyl group. The monomer structure of the polycarbonate used in the following examples and comparative examples is described below.

[0101]

[Chemical formula 23]

Example 1 A reaction vessel equipped with a stirrer, a thermometer and a reflux condenser was charged with an aqueous sodium hydroxide solution and deionized water, and the monomer [A] having the above structure was charged therein.
And [B] were dissolved in the molar ratio shown in Table 1, and a small amount of hydrosulfite was added. Then add methylene chloride to this and add 2
Phosgene was bubbled in at 0 ° C. for about 60 minutes. further,
After p-tert-butylphenol was added and emulsified, triethylamine was added and stirred at 30 ° C. for about 3 hours to complete 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 charging ratio.

This copolymer was dissolved in methylene chloride to prepare a dope solution having a solid content concentration of 20% by weight.
A cast film was prepared from this dope solution and uniaxially stretched at a stretching temperature of 210 ° C. and a stretching ratio of 1.5 times to obtain a retardation film.

Table 1 summarizes the measurement results. Further, FIG. 1 shows the wavelength dispersion of the phase difference.

It was confirmed that this stretched film was a retardation film having a maximum value of one retardation value in the wavelength range of 400 nm to 800 nm.

Example 2 The copolymer prepared in Example 1 was dissolved in methylene chloride to prepare a dope solution having a solid content concentration of 20% by weight. A cast film was prepared from this dope solution and simultaneously biaxially stretched at a stretching temperature of 210 ° C. at a stretching ratio of 1.3 times in the length and width directions to obtain a retardation film.

Table 1 summarizes the measurement results. In addition, wavelength dispersion of the phase difference is shown in FIG. This stretched film has a wavelength of 400n
In the range of m to 800 nm, it was confirmed that the retardation film had a maximum value of one retardation value as in Example 1. By using this film one by one as an optical compensation film for a vertically aligned liquid crystal cell in which Δn · d of liquid crystal is 290 nm (measurement wavelength 550 nm), a liquid crystal display device with a good viewing angle and little coloring can be obtained. done.

Example 3 Polystyrene (obtained from Wako Pure Chemical Industries, Ltd.) was used as a polymer having a negative refractive index anisotropy, and polyphenylene oxide (poly (was used as a polymer having a positive refractive index anisotropy). 2,6-dimethyl 1,4-
(Phenylene oxide) Obtained from Wako Pure Chemical Industries, Ltd.)
Were dissolved in chloroform at a ratio of 75% by weight to 25% by weight to prepare a dope solution having a solid content concentration of 18% by weight. A cast film was prepared from this dope solution and uniaxially stretched at a temperature of 154 ° C. and tripled. The glass transition temperature of this film was 125 ° C.

Table 1 summarizes the measurement results. In addition, wavelength dispersion of the phase difference is shown in FIG. This stretched film has a wavelength of 400n
It was confirmed that the retardation film has a minimum value of one retardation value in the range of m to 800 nm.

[Comparative Example 1] A commercially available polycarbonate obtained by polycondensation of commercially available bisphenol A (monomer structure [A]) with phosgene (trade name "Panlite C1 manufactured by Teijin Chemicals"
400 ″) was used to form a film and draw in the same manner as in Example 1 except that the drawing temperature was 160 ° C. to obtain a retardation plate. Table 1 summarizes the measurement results. In addition, FIG. 4 shows the retardation wavelength dispersion of this retardation film. This stretched film has a wavelength of 400 nm
It was confirmed that the retardation film does not have at least one of the maximum value and the minimum value of the retardation value in the range of 800 nm to 800 nm.

[Comparative Example 2] A commercially available norbornene resin, JSR's trade name "ARTON" was used and the stretching temperature was 162.
The film was formed and stretched in the same manner as in Example 1 except that the temperature was changed to ° C. It was confirmed that this stretched film was not a retardation film having at least one maximum or minimum retardation value in the wavelength range of 400 nm to 800 nm.

[0112]

[Table 1]

[Reference Example 1] A polycarbonate copolymer was obtained in the same manner as in Example 1 except that the monomers shown in Table 1 were used. The composition ratio of the obtained copolymer was almost the same as the monomer charging ratio. A retardation film was obtained by uniaxially stretching in the same manner as in Example 1 except that the film formation was performed in the same manner as in Example 1, the stretching temperature was 200 ° C., and the magnification was 1.4 times. The solvent content of the cast film before stretching was 0.5%. The results are shown in Table 1.
Also described in. It was confirmed that the longer the measurement wavelength, the smaller the retardation of this stretched film in the wavelength range of 400 nm to 800 nm.

[Reference Example 2] A polycarbonate copolymer was obtained in the same manner as in Example 1 except that the monomers shown in Table 1 were used. The composition ratio of the obtained copolymer was almost the same as the monomer charging ratio. A retardation film was obtained by uniaxially stretching in the same manner as in Example 1 except that the film formation was performed in the same manner as in Example 1, the stretching temperature was 230 ° C., and the magnification was 2.0 times. The solvent content of the cast film before stretching was 0.5%. The results are also shown in Table 1. This stretched film has a wavelength of 400 nm to 800 nm
In the range, it was confirmed that the longer the measurement wavelength, the larger the phase difference.

[0115]

As described above, according to the present invention, the wavelength
In the range of 400 nm to 800 nm, it is possible to realize a retardation film characterized by having at least one maximum and / or minimum value of the retardation value. It has an effect that it can contribute to reduction of the number of retardation films.

[Brief description of drawings]

FIG. 1 shows the relationship between the retardation and the measurement wavelength of the retardation film of the present invention in Example 1.

FIG. 2 shows the relationship between the retardation and the measurement wavelength of the retardation film of the present invention in Example 2.

FIG. 3 shows the relationship between the retardation and the measurement wavelength of the retardation film of the present invention in Example 3.

FIG. 4 shows the relationship between the retardation of the retardation film and the measurement wavelength in Comparative Example 1.

Continued front page    F-term (reference) 2H049 BA06 BA25 BB42 BB44 BB48                       BC03 BC09 BC22                 2H091 FA11X FA11Z FA41Z FC08                       FC09 GA01 GA13 HA07 HA10                       LA19 MA07                 4F071 AA50 AA86 AF10 AF12 AF31                       AH19 BA02 BB02 BB07 BC01                 4J029 AA09 AB01 AC02 BB13A                       BB13B BD09A BD09B HC01

Claims (14)

[Claims] 1. A retardation film comprising a single-layer organic alignment film containing a polymer, the wavelength of which is 400 nm to 80 nm.
A retardation film having at least one maximum and / or minimum retardation value in a range of 0 nm. 2. The retardation film according to claim 1, wherein the organic oriented film is substantially composed of a polymer. 3. The glass transition temperature of the organic oriented film is 120 ° C. or higher.
The retardation film described. 4. The organic oriented film is composed of a polymer containing a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy. The retardation film according to any one of claims 2 to 3, which is characterized in that. 5. The polymer having an organic oriented film (1) a polymer unit having a positive refractive index anisotropy (hereinafter referred to as a first monomer unit) and a polymer having a negative refractive index anisotropy. (2) A polymer composed of a polymer containing a monomer unit (hereinafter, referred to as a second monomer unit) of (1), wherein R is a polymer based on the first monomer unit.
(450) / R (550) is smaller than R (450) / R (550) of the polymer based on the second monomer unit, and (3) a polymer having a positive refractive index anisotropy. The retardation film according to claim 4, comprising: 6. The organic oriented film comprises a monomer unit (1) which forms a polymer having positive refractive index anisotropy (hereinafter,
It is called the first monomer unit. ) And a monomer unit forming a polymer having negative refractive index anisotropy (hereinafter referred to as a second monomer unit), the film comprising: (2) the first R (450) / R (550) of the polymer based on the monomer unit is larger than R (450) / R (550) of the polymer based on the second monomer unit, and (3) a negative refractive index. The retardation film according to claim 4, comprising a polymer having anisotropy. 7. The retardation film according to claim 1, wherein the organic oriented film has a water absorption rate of 1% by weight or less. 8. The retardation film according to claim 1, wherein the polymer is a polycondensation polymer. 9. The retardation film according to claim 1, wherein the polymer has a fluorene skeleton. 10. The retardation film according to claim 1, wherein the polymer is polycarbonate. 11. A polycarbonate is represented by the following formula (I): (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 And R ₃₀ and R ₃₁ are each independently a hydrogen atom,
It is a halogen atom or an alkyl group having 1 to 3 carbon atoms. ) The repeating unit represented by 10 to 90 mol%,
The following formula (II): (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, and Y is Here, R _{17 to} R ₁₉ , R ₂₁ and R ₂₂ in Y are each independently a hydrogen atom, a halogen atom and a hydrocarbon group having 1 to 22 carbon atoms, and R ₂₀ and R ₂₃ are each independently 1 carbon atom. ~ 20 hydrocarbon groups, and Ar has 6 to 1 carbon atoms.
Selected from 0 aryl groups. 11. The retardation film according to any one of claims 1 to 10, which is a polycarbonate copolymer and / or a blend having 90 to 10 mol% of the repeating units represented by the formula (1). 12. A polycarbonate is represented by the following formula [III]: (In the above formula [III], R ₂₄ and R ₂₅ are each independently selected from a hydrogen atom and a methyl group.) 45 to 53 mol% of the repeating units are represented by the following formula [IV]. Repeating unit [Chemical formula 6] (In the above formula [IV], R ₂₆ and R ₂₇ are each independently selected from a hydrogen atom and a methyl group.) A polycarbonate copolymer and / or a blend product in which the repeating unit accounts for 55 to 47 mol% of the whole. It is a retardation film in any one of Claims 1-11 characterized by these. 13. A liquid crystal display device using the retardation film according to any one of claims 1 to 12. 14. The following formula [III]: (In the above formula [III], R ₂₄ and R ₂₅ are each independently selected from a hydrogen atom and a methyl group.) 45 to 53 mol% of the repeating units are represented by the following formula [IV]. Repeating unit [Chemical formula 8] (In the above formula [IV], R ₂₆ and R ₂₇ are each independently selected from a hydrogen atom and a methyl group.) A polycarbonate copolymer and / or a blend product in which the repeating unit accounts for 55 to 47 mol% of the whole. The retardation film which consists essentially of.