JP2002162519A - Circular polarized film and display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin circularly polarized film, capable of effectively preventing reflection of light by the highly reflective surface of a metal electrode or the like incorporated into a display device, particularly an electroluminescent display device over a wide wavelength band, and to provide a display device using the polarized film. SOLUTION: The circular polarizing film consists essentially of a quarter- wave film, comprising a polymeric material and having phase contrast at 450 nm and 550 nm wavelengths satisfying the expression R (450)/R (550)<1 (where R (450) and R (550) are the intrasurface phase contrasts of the quarter-wave film at 450 nm and 550 nm wavelengths, respectively) and a polarized layer containing a liquid-crystalline dichroic dye. The circularly polarized film is used in a light emission element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circularly polarizing film and a display element using the same as an antireflection film, particularly a light emitting element.

[0002]

2. Description of the Related Art A light-emitting element, particularly an organic electroluminescent element (sometimes referred to generally as an organic EL element) has a metal electrode on the back side of a light-emitting layer for an observer, so that external light is not emitted. Due to the presence, the reflected light from the metal electrode is generated, and the scene on the observer's side is reflected, so that there is a problem that the display quality is significantly lowered. A technique of using a circularly polarizing film as an antireflection film on a front substrate of a light emitting element for the purpose of preventing the metal reflection is already known. This circularly polarizing film is composed of a polarizing plate and a retardation film that is a quarter-wave plate. As the retardation film, a technique using a polymer oriented film obtained by stretching a polymer film is known.

When such a conventional retardation film is used as a circularly polarizing film, a good antireflection effect can be obtained only at a specific wavelength at which the retardation is a quarter wavelength. For example, good anti-reflection cannot be obtained in a wide band of wavelengths of 400 nm to 700 nm, and as a result, there is a problem that reflected light is colored.

A polarizing film forming a normal circularly polarizing film is a film in which iodine or a dichroic dye is fixedly oriented in a polymer such as polyvinyl alcohol (also referred to as a binder polymer) and a protective film such as a triacetyl cellulose film. Although it has a structure sandwiched between films, the film thickness inevitably increases, and the polarizing film alone has a film thickness of about 130 to 200 μm. On the other hand, a quarter-wave film, which is another film forming a circularly polarizing film, is a film in which a polymer material such as polycarbonate is oriented, and has a thickness of about 50 to 120 μm. Therefore, a device in which both are integrated via an adhesive has a thickness of about 180 μm to 300 μm, and at present, it is difficult to make a display element using a circularly polarizing film thinner. Further, in order to obtain an antireflection effect in a broadband wavelength, a circularly polarizing film using two retardation films, specifically, a combination of a half-wave film and a quarter-wave film was used. However, it is also difficult to reduce the thickness of the circularly polarizing film as compared with the case where only one quarter-wave film is used.

[0005]

SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above-described circumstances, and has been made in consideration of the above circumstances. It is an object of the present invention to provide a circularly polarizing film having a thin film thickness and capable of effectively preventing light reflection by a large reflecting surface over a wide band of wavelengths, and a display element using the same.

[0006]

That is, the present invention is as follows.

[0007] 1. Made of polymer material, wavelength 450nm
And a polarizing film comprising a quarter-wave film whose retardation at 550 nm satisfies the following formula (1) and a polarizing layer containing a liquid crystalline dichroic dye.

[0008]

R (450) / R (550) <1 (1) (where R (450) and R (550) are in-plane retardations of a quarter-wave film at wavelengths of 450 nm and 550 nm, respectively). is there.)

[0009] Wavelength 450n of a quarter-wave film
m, the phase difference at 550 nm and 650 nm are represented by the following equations (2) and (3).

[0010]

0.6 <R (450) / R (550) <0.97 (2) 1.01 <R (650) / R (550) <1.4 (3) (where R ( 650) is the in-plane retardation of the quarter-wave film at a wavelength of 650 nm, and the definitions of R (450) and R (550) are the same as above.)

3. The above-mentioned circularly polarizing film, wherein the retardation of the quarter-wave film at a wavelength of 400 to 700 nm is smaller as the wavelength is shorter.

4. The above-mentioned circularly polarizing film, wherein the polarizing layer comprises a dichroic dye having a lyotropic liquid crystal property.

5.4 The above-mentioned circularly polarizing film, wherein the quarter-wave film has a water absorption of 1% by weight or less.

6. The above circularly polarizing film, wherein the polymer material contains a polycarbonate having a fluorene skeleton.

[0015] 7. The above circularly polarizing film having a thickness of 140 μm or less.

8.4 The above-mentioned circularly polarizing film substantially comprising a quarter-wave film and a polarizing layer.

9. The above-mentioned circularly polarizing film comprising a support film, a polarizing layer, an adhesive layer and a quarter-wave film in this order.

10. A display element using the above circularly polarizing film.

11. The display element described above, wherein the display element is a light-emitting element provided with the circularly polarizing film according to any one of claims 1 to 9 on a light emission side.

[12] The above-mentioned display element, wherein the light-emitting element comprises at least a substrate, a transparent electrode, a hole transport layer, a light-emitting layer, an electron transport layer, and a metal electrode layer in order from the light emitting side.

13. A display device according to claim 1, wherein the quarter-wave film constituting the circularly polarizing film according to any one of claims 1 to 9 also serves as a substrate of the light emitting device.

14. The above display element, wherein the light emitting element is an organic electroluminescent element.

The fact that the retardation of the retardation film becomes smaller as the wavelength becomes shorter can be expressed by the above formula (1) from a practical viewpoint, but R (450) and R (550) need to have the same sign. is there. The present invention is a circularly polarizing film comprising a quarter-wave film and a polarizing layer that satisfies the above formula (1) in one sheet,
In particular, when used in a light-emitting element in which reflection of a metal electrode poses a problem in the presence of external light, a very excellent light-emitting element can be provided. Here, the quarter-wave film is a kind of retardation film.

The quarter-wave film according to the present invention must satisfy the above formula (1), but must have a quarter-wave phase difference for all wavelengths in the visible light region. Or it is more preferable to take a value close to it. Here, a quarter-wave film is defined as having a retardation value R (550) of 110 to 170 nm at a wavelength of 550 nm. Preferably 120-160 nm, more preferably 125-150
nm.

Here, the principle by which the circularly polarizing film of the present invention can prevent reflection in a light-emitting device, particularly an organic electroluminescent device, will be described with reference to FIG.

In FIG. 2, reference numeral 1 denotes external light, which becomes 2 linearly polarized light after passing through the polarizing layer 13. Then, after passing through the quarter-wave film 14, the light becomes clockwise (or counterclockwise) circularly polarized light. Reference numerals 7, 8, 9, 10, and 11 denote a substrate, a transparent electrode, a hole transport layer, a light-emitting layer, and an electron transport layer, respectively. Since these are optically isotropic, the polarization state of 3 hardly changes and 12 Reaches the metal electrode layer. After reflection, the polarization state changes to left-handed (or right-handed) circularly polarized light as shown in 4,
After passing through the fourteenth quarter-wave film again, it becomes linearly polarized light 5 180 degrees out of phase with linearly polarized light 2. Therefore, the linearly polarized light 5 cannot pass through the polarizing plate 13 and absorbs external light, thereby exhibiting an antireflection function. In FIG. 2, the polarizing plate 13 and the quarter-wave film 14 appear to be separated from the substrate 7, but this is for the purpose of explaining the principle. And antireflection effect.

Reference numeral 6 denotes light emitted from the light-emitting element, which is generally unpolarized light, and is not affected by the quarter-wave film 14. Light is absorbed to some extent in the polarizing layer 13 but can be transmitted. Further, in order to improve the luminance, elements for emitting polarized light may be provided in 8 to 11.

The above description is about the wavelength at which the quarter-wave film has a phase difference of or near the quarter wavelength in the visible light region. Thereby, the linearly polarized light becomes circularly polarized light, the reflected light does not leak, the coloring is reduced, and the contrast is improved. In general, retardation films used in super twisted nematic liquid crystal display devices have characteristics that are completely opposite to the ideal quarter-wave film, such that the retardation is small on the long wavelength side and large on the short wavelength side. In this case, it is possible to prevent reflection of light of a specific wavelength, but this is very inconvenient in the case of a light emitting element that requires display quality.

Although the above description has been particularly directed to organic electroluminescent devices, the circularly polarizing film of the present invention can be applied to other electroluminescent devices such as inorganic electroluminescent devices, field emission display devices and plasma display devices. Can be used. Further, the circularly polarizing film of the present invention can be used in a liquid crystal display device, particularly, a reflection type liquid crystal display device.

The quarter-wave film used for the circularly polarizing film of the present invention satisfies the above formula (1), but is preferably used as a material of the quarter-wave film to satisfy the formula (1). It is important to use a polymer oriented film made of a polymer material and satisfying the following condition (a) or (b).

(A) (1) A polymer monomer unit having a positive refractive index anisotropy (hereinafter, referred to as a first monomer unit) and a polymer monomer unit having a negative refractive index anisotropy ( (Hereinafter referred to as a second monomer unit). (2) A polymer based on the first monomer unit, wherein R (450) / R (550) of the polymer is R (450) / R (55) of the polymer based on the second monomer unit
(3) A polymer oriented film having a positive refractive index anisotropy smaller than 0).

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

As an example of an embodiment satisfying the conditions (a) and (b), there is one satisfying the following conditions (c) and (d).

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

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

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

The polarizing layer used in the present invention needs to use a material having a liquid crystal dichroic dye which can be made thin. The liquid crystal dichroic dye is particularly preferably lyotropic. By using this, it is possible to form a polarizing layer as thin as sub-μm. The material having a lyotropic liquid crystal dichroic dye referred to here is described in, for example, WO 97/39.
380, WO96 / 16015, 2000 SID International Symposi
um Digest of Technical Papers, p.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION The circularly polarizing film of the present invention has a wavelength
It is characterized by comprising at least a quarter-wave film whose phase difference at 450 nm and 550 nm satisfies the following formula (1) and a polarizing layer containing a liquid crystal dichroic dye.
R (450) and R (550) need to have the same sign.

[0039]

R (450) / R (550) <1 (1) As the retardation wavelength dispersion of the retardation film, preferably, retardation values R (450) and R (550) at measurement wavelengths of 450 nm, 550 nm and 650 nm. ,
When represented by R (650), the following formulas (2) and (3)

[0040]

0.6 <R (450) / R (550) <0.97 (2) 1.01 <R (650) / R (550) <1.4 (3) . It is more preferable to satisfy the following expressions (4) and (5).

[0041]

0.70 <R (450) / R (550) <0.90 (4) 1.03 <R (650) / R (550) <1.25 (5) Measurement wavelengths 450 nm, 550 nm, When a phase difference of a quarter wavelength is completely given at 650 nm, the phase difference value is R (450) = 11.
Since 2.5 nm, R (550) = 137.5 nm, and R (650) = 162.5 nm, the respective chromatic dispersion values are R (450) / R (550) = 0.
818, R (650) / R (550) = 1.182. By setting the wavelength dispersion range of such a phase difference, an antireflection effect can be obtained in a wide range of visible light, and when used in a light emitting element, excellent contrast is obtained in the presence of external light and a decrease in visibility such as coloring is caused. Problems can be prevented.

Specific materials satisfying the above characteristics will be described below.

The polymer material giving a quarter-wave film has a glass transition temperature of 120 ° C. or higher, preferably 140 ° C.
It is preferable that the temperature is not lower than ° C. If the temperature is lower than 120 ° C., a problem such as relaxation of orientation may occur depending on the use conditions of the display element.

The water absorption is preferably 1% by weight or less. If the water absorption of the polymer material is not 1% by weight or less, there may be a problem in practical use as a quarter-wave film, and the film material has a water absorption of 1% by weight.
Below, it is preferable to select so as to satisfy the condition of preferably 0.5% by weight or less.

The quarter-wave film material used in the present invention may be composed of a blended polymer or a copolymer.

The polymer material constituting the quarter-wave film used in the present invention is not particularly limited, and is a material having excellent heat resistance, good optical performance and capable of forming a solution film, for example, polyarylate, polyester, and the like. Thermoplastic polymers such as polycarbonate, polyolefin, polyether, polysulfine copolymer, polysulfone, and polyethersulfone are preferred.

When this thermoplastic polymer is used, as described above, a blend polymer comprising a polymer having a positive refractive index anisotropy and a polymer having a negative refractive index anisotropy,
A copolymer comprising a polymer monomer unit having a positive refractive index anisotropy and a polymer monomer unit having a negative refractive index anisotropy is more preferable. These may be used in combination of two or more, or one or more blended polymers and one or more copolymers may be used in combination.

In the case of a blended polymer, since it is necessary to be optically transparent, it is preferable that the compatible blend or the refractive index of each polymer is substantially equal. As a specific combination of blended polymers, for example, a polymer having negative optical anisotropy is poly (methyl methacrylate)
And at least one polymer selected from the group consisting of poly (vinylidene fluoride), poly (ethylene oxide) and poly (vinylidene fluoride-co-trifluoroethylene) as a polymer having positive optical anisotropy In combination, a polymer having a positive optical anisotropy is poly (phenylene oxide), and a polymer having a negative optical anisotropy is polystyrene, poly (styrene-co-
Lauroylmaleimide), a combination of at least one polymer selected from the group consisting of poly (styrene-co-cyclohexylmaleimide) and poly (styrene-co-phenylmaleimide), and poly (styrene-copolymer having negative optical anisotropy). -Maleic anhydride) and a polycarbonate having a positive optical anisotropy, a poly (acrylonitrile-co-butadiene) having a positive optical anisotropy and a poly (acrylonitrile-co) having a negative optical anisotropy -Styrene), and a combination of a polycarbonate having a positive optical anisotropy and a polycarbonate having a negative optical anisotropy, but the present invention is not limited thereto. In particular, from the viewpoint of transparency, polystyrene and poly (2,6-dimethyl-
A blend polymer in which a poly (phenylene oxide) such as 1,4-phenylene oxide) is combined, and a blend in which a polycarbonate having a positive optical anisotropy and a polycarbonate having a negative optical anisotropy are combined are preferable. In the former case, the ratio of the polystyrene is
Preferably, it accounts for 67% by weight or more and 75% by weight or less.

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

The polymer material may be a blend of two or more copolymers, a blend of one or more copolymers and the blend or another polymer, or a two-component copolymer. It may be a blend, a copolymer or a blend of other polymers described above.

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 a repeating unit represented by the following formula (A), and preferably contains 1 to 99 mol% of the entire repeating unit.

Specifically, the following formula (A)

[0053]

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(In the above formula (A), 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, and X is

[0055]

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Is as follows. ) Is 3
0 to 90 mol%, and the following formula (B)

[0057]

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(In the above formula (B), R _{9 to} R ₁₆ each independently represent a hydrogen atom, a halogen atom and a C 1 to C 22
Y is at least one selected from the group consisting of

[0059]

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(Here, R _{17 to} R ₁₉ , R ₂₁ and R in Y
₂₂ is 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 each independently selected from a hydrocarbon group having 1 to 20 carbon atoms, and Ar is It is at least one group selected from 10 aryl groups. ) Is 70 units in total.
It is a polycarbonate copolymer and / or blend occupying 〜10 mol%. And a polycarbonate copolymer in which the repeating unit represented by occupies 70 to 10 mol% of the whole.

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

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

The quarter-wave film of the present invention comprises:
Those using a polycarbonate having a fluorene skeleton are preferred. As the polycarbonate having a fluorene skeleton, for example, a polycarbonate copolymer comprising a repeating unit represented by the above formula (A) and a repeating unit represented by the above formula (B), and a repeating unit represented by the above formula (A) And a polycarbonate comprising a repeating unit represented by the above formula (B) are preferred. The content of the above formula (A), that is, the copolymer composition in the case of a copolymer, and the blend composition ratio in the case of a blend, And 30 to 90 mol% of the entire polycarbonate is preferred. The copolymer having the repeating units of formulas (A) and (B) has a different composition ratio from the copolymer having the repeating units of formulas (A) and (B), but the copolymer having the repeating units of formulas (A) and (B) may be blended. Further, the content of the above formula (A) is more preferably 35 to 85 mol% of the whole polycarbonate, and 50 to 8 mol%.
0 mol% is more preferred.

The above copolymer has the above formula (A) or (B)
Or a combination of two or more types of repeating units represented by the formula. In the case of a blend, two or more types of the above repeating units may be combined.

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

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

The limiting viscosity of the above polycarbonate is 0.3
Preferably it is ~ 2.0 dl / g. If it is less than 0.3, there is a problem that it becomes brittle and cannot maintain mechanical strength.
If it exceeds 3.0, the solution viscosity becomes too high, which causes problems such as generation of die lines in solution film formation and difficulty in purification at the end of polymerization.

The polymer oriented film constituting the quarter-wave film is preferably transparent, and has a haze value of 3
% Or less, and the total light transmittance is preferably 85% or more.

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

The quarter-wave film of the present invention comprises a polymer oriented film obtained by stretching a non-stretched film of the above polycarbonate or the like to orient the polymer chains. 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 or the like is preferably used.

A known stretching method can be used for the stretching method, but it is preferably longitudinal uniaxial stretching. 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 above-mentioned additives such as plasticizer and liquid crystal can change the retardation wavelength dispersion of the retardation film of the present invention, but the amount of addition is preferably 10% by weight or less, and more preferably 3% by weight or less based on the solid content of the polymer. Is more preferred.

The thickness of the quarter-wave film is 1
It is preferably from μm to 120 μm. In the present invention, the term “quarter-wave film” is used, but the meaning is commonly referred to as “film” or “sheet”.

As described above, in order to reduce the retardation of the quarter-wave film as the wavelength becomes shorter, the chemical structure of the polymer constituting the polymer oriented film is important, and the retardation wavelength dispersion is considerably large. Is determined by its chemical structure,
It should be noted that it varies depending on film forming conditions, additives, stretching conditions, blending conditions, molecular weight, and the like.

The polarizing layer in the present invention needs to be made of a material having a liquid crystal dichroic dye capable of being formed into a thin film, and it is particularly preferable that the liquid crystal property is lyotropic. Lyotropic liquid crystallinity is a material that exhibits liquid crystallinity in a solvent. Specifically, for example, the following formulas (C) to (G) include chemical structures, but are not limited thereto. Further, a small amount of an additive may be added to improve the orientation and the film forming property. The amount of the additive is 40 in comparison with the liquid crystal dichroic dye.
% By weight, preferably 10% by weight or less, more preferably 3% by weight or less.

[0077]

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[0078]

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Since the lyotropic liquid crystal becomes a liquid crystal in a solvent, for example, it is necessary to prepare a solution comprising the above-mentioned compounds (C) to (G), coat them on a film, and evaporate the solvent. Thereby, the alignment of the liquid crystal can be fixed. Therefore, it is preferable to use such a coating method as a method of forming the polarizing layer of the present invention. As the coating method, a known method such as a bar coating method and a method using a doctor knife can be used. This polarizing layer is very thin and can form a polarizing layer on the order of submicrons, which contributes to thinning of a circularly polarizing film. By forming the polarizing layer in this way, the entire circularly polarizing film can have a thickness of 140 μm or less.

The circularly polarizing film of the present invention is characterized in that
It consists of a combination of a wavelength film and a polarizing layer. It is preferable that the polarizing layer and the quarter-wave film are in close contact with each other. For example, the circularly polarizing film of the present invention may be formed by coating a dichroic dye having a lyotropic liquid crystal property on a quarter-wave film by controlling the molecular orientation direction. In this case, the configuration of the circularly polarizing film of the present invention is a polarizing layer / a quarter wavelength film, and the simplest configuration can be obtained. Also, the polarizing layer is another film,
For example, after being formed on a film made of a known polymer material such as polycarbonate, polyethylene terephthalate, polyethylene naphthalate, amorphous polyolefin, polyether sulfone, polysulfone, and polymethyl methacrylate, a quarter-wave film and an adhesive are interposed. You may stick together. Here, such a film is referred to as a support film, but preferably has no optical retardation. However, for example, for a support film having optical anisotropy such as a biaxially stretched polyethylene terephthalate film (PET film), the arrangement is such as PET film / polarizing layer / adhesive layer / quarter wavelength film. In some cases, the influence of the optical anisotropy of the PET film can be neglected. This support film can also serve as a protective film for the polarizing layer, if necessary. The angle between the slow axis or fast axis of the quarter-wave film and the polarizing axis of the polarizing layer is preferably 45 degrees. Preferred examples of the configuration of the circularly polarizing film of the present invention are shown in FIGS.

One feature of the circularly polarizing film of the present invention is that it has a small thickness, but it is necessary that the thickness be 140 μm or less, preferably 130 μm, more preferably 120 μm or less.

As a material of the substrate 7 in FIG. 2, a glass substrate is usually used, but a film or a sheet made of a polymer material may be used. When a polymer material is used, a barrier layer such as a gas barrier layer or a water vapor barrier layer may be provided on the substrate. As the barrier layer, a curable resin layer,
A metal oxide layer or the like can be used.

In the combination of the light emitting element as shown in FIG. 2 and the circularly polarizing film of the present invention, if the light emitting element has the structure as shown in FIG. Is also possible. In such a case, since the substrate 7 is not required, a cost advantage can be obtained by reducing the weight and reducing the number of members. However, in this case, if deterioration of the light emitting element becomes a problem, a gas barrier layer, a water vapor barrier layer, or the like may be provided on the circularly polarizing film in order to prevent the deterioration. Even in these cases, the combination of the polarizing layer and the quarter-wave film exhibits the antireflection function, that is, it is possible to provide a circularly polarizing film that also serves as the substrate of the light emitting element.

It is known that a retardation film generally gives a different retardation value to obliquely incident light as compared with front incident light. In general, a circularly polarizing film has a different antireflection effect for obliquely incident light. However, as a result of intensive studies on this problem, it was found that such a problem can be avoided by controlling the three-dimensional refractive index of the retardation film. Here, the three-dimensional refractive index of the retardation film is represented by nx, ny, nz, and each definition is nx: the refractive index in the main stretching direction in the plane of the retardation film ny: the refractive index in the plane of the retardation film The refractive index in the direction orthogonal to the stretching direction nz: the refractive index in the direction normal to the surface of the retardation film. Here, the main stretching direction, the stretching direction when the retardation film is uniaxially stretched polymer oriented film,
In the case of biaxial stretching, it means a direction in which the degree of orientation is further increased, and in chemical structure, it refers to the direction of orientation of the polymer main chain. Here, when nx> nz, the optical anisotropy is positive and n
When x <nz, the optical anisotropy is called negative. The three-dimensional refractive index is measured by an ellipsometry, which is a technique for analyzing the polarization state of emitted light obtained by entering polarized light into a retardation plate. In the present invention, the optical anisotropy of the retardation film is determined. The three-dimensional refractive index is determined by a method of determining the refractive index ellipsoid by using a known refractive index ellipsoidal formula assuming the refractive index ellipsoid. Since the three-dimensional refractive index depends on the wavelength of the light source used, it is preferable to define the three-dimensional refractive index with the wavelength of the light source used. As a method of expressing optical anisotropy using the three-dimensional refractive index, the following formula (6) is used.

[0085]

## EQU8 ## Nz = (nx-nz) / (nx-ny) (6). If this is used to define a three-dimensional refractive index, Nz is in the range of 0.3 to 1.5. In some cases, the incident angle dependence of the phase difference value is very small, which is preferable. More preferably, Nz is from 0.4 to 1.1, but especially when Nz = 0.5, the incident angle dependency of the phase difference value is substantially eliminated, and the same phase difference value is obtained regardless of the angle at which light enters. It is particularly preferred because it gives.

According to the above definition, the retardation film of the retardation film having positive optical anisotropy has nx as the slow axis and ny as the fast axis.

In order to give the reflectance of the circularly polarizing film a broadband property, a quarter-wave film and a half-wave film can be used in combination as a retardation film. Here, this is referred to as a two-panel system. When both retardation films are set to Nz = 1, this two-panel system uses only one quarter-wave film satisfying the above-described formula (1). It has been found that viewing angle characteristics are inferior to circularly polarizing films. That is, when the reflectance is measured by changing the angle, the reflectance of the two-sheet configuration is clearly inferior.

The circularly polarizing film of the present invention is provided with a known antireflection film made of a multilayer film or the like, or a so-called anti-glare treatment or the like provided with irregularities on the surface for the purpose of antireflection effect on the surface. May be used. Similarly, a hard coat layer or an anti-contamination layer may be provided.

By providing such a circularly polarizing film on the light emitting surface side of the light emitting element, a display element with good visibility even in the presence of external light can be provided.

In the organic electroluminescent device, a metal electrode is provided on the back side of the light emitting layer as shown in FIG. In this device, it is necessary to manufacture each layer as a flat film for high performance. As a result, the metal electrode is designed to be extremely flat like a mirror surface and not to cause irregular reflection. Therefore, in the presence of external light, external light is reflected by the metal electrode, and visibility is reduced. The circularly polarizing film of the present invention can prevent such external light reflection in a wide wavelength range. In addition, a display element for a portable information terminal must be thinner, and by using the thin circularly polarizing film of the present invention, a display element with good characteristics and thinner than a conventional product can be provided. In addition, each layer of the organic electroluminescent element can use a known layer.

[0091]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. (Evaluation method) The material property values and the like described in this specification were obtained by the following evaluation methods. (1) Measurement of phase difference value (R = Δn · d (nm)) and Nz The phase difference R value and Nz, which are the product of the birefringence Δn and the film thickness d, are measured using a spectroscopic ellipsometer “M150” (JASCO Corporation) Manufactured). The R value was measured with the incident light and the film surface orthogonal to each other. Also, the Nz value is a three-dimensional refractive index nx by changing the angle between the incident light beam and the film surface, measuring the phase difference value at each angle, and performing curve fitting with a known refractive index ellipsoidal equation. , ny, nz were obtained and substituted into the following equation (6). In this case, an average refractive index n = (nx + ny + nz) / 3 is required as another parameter, which is an Abbe refractometer (“Abe refractometer 2-T” manufactured by Atago Co., Ltd.). Was measured by

[0092]

Nz = (nx−nz) / (nx−ny) (6) (2) Organic Electroluminescent Device Evaluation System An organic electroluminescent device emitting green light was manufactured as follows.
FIG. 5 schematically shows the configuration. First, a transparent electrode is formed on a 0.7 mm thick glass substrate 22 by a sputtering method.
An ITO (Indium Tin Oxide) film was laminated. Next, TPD (N, N'-bis (3-methylphenyl) 1,1'-biphenyl-4,4'-diamine), which is a triphenyldiamine derivative, is formed on the ITO film as a hole transport layer 24 by a vacuum evaporation method. Was laminated in a thickness of 50 nm. Next, Alq3 (tris- (8-hydroxyquinoline) aluminum) is used
Deposited to a thickness of nm. This light emitting layer also serves as the electron transport layer 11 in FIG. In addition, magnesium and silver
The metal electrode 26 was deposited by evaporation to a thickness of 200 nm. When a voltage was applied to the light-emitting device, green light emission was confirmed.

One of the objects of the present invention is to suppress the antireflection of the light emitting device over a wide band of wavelengths.
As shown in FIG. 5, in the state where the circularly polarizing film of the present invention is adhered through an adhesive, the degree of reduction of external light reflection is particularly observed.

To see the degree of reduction in external light reflection,
Using a spectrophotometer "U-4000" (manufactured by Hitachi, Ltd.)
The evaluation was performed by performing a reflection measurement at a 10 degree incidence.

Note that Nz (λ) is Nz at the wavelength λ. (3) Measurement of water absorption The measurement was carried out in accordance with "Testing Methods for Water Absorption and Boiling Water Absorption of Plastics" described in JIS K 7209, except that the film thickness of the dried film was 130 ± 50 μm. The size of the test piece was 50 mm square, and the sample was immersed in water at 25 ° C. for 24 hours, and then the weight change was measured. The unit is%. (4) Measurement of glass transition temperature (Tg) of polymer The measurement was performed using "DSC2920 Modulated DSC" (manufactured by TA Instruments). Not after film molding, but after resin polymerization,
Measured in flake or chip condition. (5) Film thickness measurement The film thickness was measured with an electronic micro manufactured by Anritsu Corporation. (6) Measurement of Polymer Copolymerization Ratio It was measured by proton NMR of “JNM-alpha600” (manufactured by JEOL Ltd.). In particular, in the case of a copolymer of bisphenol A and biscresol fluorene, heavy benzene was used as a solvent, and calculation was performed from the proton intensity ratio of each methyl group.

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

[0097]

Embedded image

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

This copolymer was dissolved in methylene chloride to prepare a dope solution having a solid content of 19% by weight.
A cast film was prepared from this dope solution,
The film was uniaxially stretched twice at 30 ° C. to obtain a quarter-wave film.

Table 1 summarizes the measurement results. In this film, it was confirmed that the shorter the measurement wavelength was, the smaller the phase difference was, and the refractive index anisotropy was positive.

Next, for forming a polarizing layer, a biaxially stretched polyethylene terephthalate film having a thickness of 20 μm (P
An ET film) was coated with a lyotropic liquid crystalline solution manufactured by OPTIVA Co., and the orientation was fixed by evaporating the solvent to form a polarizing layer.

Further, the quarter-wave film described above and the PET film on which the polarizing layer was formed were adhered via an adhesive layer to obtain a circularly polarizing film. The constitution is PET film / polarizing layer / adhesive layer / quarter wavelength film. The total thickness was 120 μm. Further, as shown in FIG. 5, this circularly polarized film was bonded to a light emitting element via an adhesive. In FIG. 5, a PET film, an adhesive layer, and the like, which are support films, are omitted.

FIG. 1 shows a reflection spectrum of the organic electroluminescent device when no voltage is applied. It was found that the reflectance was low over a wide band of wavelengths, and good black display was possible even in the presence of external light when no voltage was applied.

Comparative Example 1 A polycarbonate homopolymer 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 homopolymer was almost the same as the monomer charge ratio. A film was formed in the same manner as in Example 1 and stretched at a temperature of 160 ° C. 1.1 times to obtain a retardation film. Table 1 summarizes the measurement results. In this film, it was confirmed that the shorter the measurement wavelength, the larger the absolute value of the retardation.

An evaluation of an organic electroluminescent device using this film was also conducted in the same manner as in Example 1. However, light reflection was large on the long wavelength side and the short wavelength side, and no voltage was applied in the presence of external light. In this state, it looked purple in appearance, and it was found that the display element was inferior in display quality. FIG. 1 shows the reflectance spectral characteristics of this element.

[0106]

[Table 1]

[0107]

As described above, a circularly polarizing film comprising a combination of a quarter-wave film having a specific retardation wavelength dispersion and a polarizing layer comprising a dichroic dye having liquid crystallinity has a retardation. By eliminating the need to use two films and the thinness of the polarizing layer, it is possible to realize a very thin film thickness that has never existed before, and to produce a circularly polarizing film that is excellent in characteristics, especially with a wide range of reflectance. It is possible to obtain. In addition, by using such a circularly polarizing film for a display element, particularly a light-reflecting light-emitting element such as a metal electrode incorporated inside the element, particularly an organic electroluminescent element, it is excellent even in the presence of external light. This has an effect that a light-emitting element having a small thickness and visibility can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a reflection spectrum of Example 1 and Comparative Example 1 with no voltage applied to an organic electroluminescent device.

FIG. 2 is a schematic view illustrating the principle of a circularly polarizing film in the organic electroluminescent device of the present invention.

FIG. 3 is a schematic cross-sectional view of a configuration example of the circularly polarizing film of the present invention.

FIG. 4 is a schematic cross-sectional view of a configuration example of the circularly polarizing film of the present invention.

FIG. 5 is a schematic view of an organic electroluminescent device in Examples and Comparative Examples.

[Explanation of symbols]

1; external light 2; linearly polarized light passing through a polarizing layer 3; clockwise (counterclockwise) passing through a quarter-wave film
Circularly polarized light 4; Left-handed (right-handed) circularly polarized light reflected by the back metal electrode and rotated in the opposite direction. 5; Linearly polarized light (polarized layer that has passed through the quarter-wave film again and is out of phase by 2 and 180 degrees 13; light is absorbed here; 6; emitted light 7; transparent substrate 8; transparent electrode layer (ITO) 9; hole transport layer 10; light emitting layer 11; electron transport layer 12; 13; polarizing layer 14; quarter-wave film 15; circular polarizing film 31 composed of 13, 14; polarizing layer 32; quarter-wave film 41; support film 42; polarizing layer 43; adhesive layer 44; 1 wavelength film 20; polarizing layer 21; quarter wavelength film 22; transparent substrate 23; transparent electrode (ITO) 24; hole transport layer 25; light emitting layer 26; metal electrode 27;

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 69:00 C08L 69:00 F term (Reference) 2H049 BA02 BA03 BA07 BA25 BA26 BA42 BB03 BB42 BB44 BB52 BB63 BC03 BC22 3K007 AB17 BB06 DA00 DB03 EA04 EB00 FA01 4F071 AA50 AF29 AH19 BA02 BB02 BC01 BC10 5G435 AA00 BB05 EE33 FF01 FF05 HH03

Claims (14)

[Claims] 1. A polymer material having a retardation at wavelengths of 450 nm and 550 nm satisfying the following expression (1):
A circularly polarized film comprising at least a half-wave film and a polarizing layer containing a liquid crystal dichroic dye. R (450) / R (550) <1 (1) (where R (450) and R (550) are in-plane retardations of a quarter-wave film at wavelengths of 450 nm and 550 nm, respectively). is there.) 2. The wavelength of the quarter-wave film is 450n.
m, the phase difference at 550 nm and 650 nm is given by the following formulas (2) and (3): 0.6 <R (450) / R (550) <0.97 (2) 1.01 <R (650) ) / R (550) <1.4 (3) (where R (650) is the in-plane retardation of the quarter-wave film at a wavelength of 650 nm, and the definitions of R (450) and R (550)) Is the same as the above.). 3. The retardation of a quarter-wave film at a wavelength of 400 to 700 nm is smaller as the wavelength is shorter.
3. The circularly polarizing film according to any one of 2. 4. The circularly polarizing film according to claim 1, wherein the polarizing layer contains a dichroic dye having a lyotropic liquid crystal property. 5. The circularly polarizing film according to claim 1, wherein the quarter-wave film has a water absorption of 1% by weight or less. 6. The circularly polarizing film according to claim 1, wherein the polymer material includes a polycarbonate having a fluorene skeleton. 7. The method according to claim 1, wherein the thickness is 140 μm or less.
7. The circularly polarizing film according to any one of 6. 8. The circularly polarizing film according to claim 1, which substantially comprises a quarter-wave film and a polarizing layer. 9. The circularly polarizing film according to claim 1, comprising a support film, a polarizing layer, an adhesive layer, and a quarter-wave film. 10. A display device using the circularly polarizing film according to claim 1. 11. The display element according to claim 10, wherein the display element is a light-emitting element in which the circularly polarizing film according to claim 1 is provided on a light emitting side. 12. The display device according to claim 11, wherein the light-emitting device comprises at least a substrate, a transparent electrode, a hole transport layer, a light-emitting layer, an electron transport layer, and a metal electrode layer in order from the light emitting side. 13. The display element according to claim 11, wherein the quarter-wave film constituting the circularly polarizing film according to claim 1 also serves as a substrate of a light emitting element. 14. The display device according to claim 11, wherein the light emitting device is an organic electroluminescent device.