JPWO2014065083A1 - Optical film, circularly polarizing plate and image display device - Google Patents

Abstract

The present invention provides an optical film having high retardation development and excellent reverse wavelength dispersibility, and having little retardation unevenness and haze, and also provided with the optical film and excellent in durability. An object is to provide a circularly polarizing plate and an image display device excellent in black reproducibility and visibility from an oblique direction, and these problems are solved by the following optical films. An optical film containing at least one compound satisfying the following formulas (a1) and (a2), wherein retardation values Ro in the in-plane direction of the optical film at wavelengths of 450 nm and 550 nm are represented by Ro (450) and Ro, respectively. (550), the said Ro (450) and Ro (550) satisfy | fill the following formula (b1) and formula (b2), The optical film characterized by the above-mentioned. (A1) 250 ≦ λmax ≦ 400 (a2) 1000 ≦ ε ≦ 20000 (b1) 1.50 ≦ {Ro (550) −Ro (550) P} /d≦3.00 (b2) 0.72 ≦ Ro ( 450) / Ro (550) ≦ 0.96

Description

  The present invention relates to an optical film having high retardation development and excellent reverse wavelength dispersion, a circularly polarizing plate provided with the optical film, and an image display device.

  The λ / 4 retardation film can convert linearly polarized light into circularly polarized light and elliptically polarized light, and can convert circularly polarized light and elliptically polarized light into linearly polarized light. Such a λ / 4 retardation film is widely used for various optical applications in image display devices, optical pickup devices, and the like.

A λ / 4 retardation film used together with a laser light source of a specific wavelength, such as an optical pickup device, only needs to give a phase difference of ¼ wavelength only to light of a specific wavelength.
On the other hand, a λ / 4 phase difference film used for a color image display device, an antireflection film for visible light, and the like needs to give a phase difference of ¼ wavelength to light in the entire visible light range. For this purpose, the λ / 4 retardation film is required to have reverse wavelength dispersibility in which the longer the wavelength of light, the greater the phase difference imparted to the light.
However, it has been difficult to obtain a film exhibiting sufficient reverse wavelength dispersion while imparting a necessary retardation, particularly a film exhibiting such characteristics with a single layer.

For example, an optical film exhibiting reverse wavelength dispersion has been proposed by setting the degree of acetylation of cellulose acetate contained in the optical film within a specific range (for example, see Patent Document 1). Both the retardation development and wavelength dispersion cannot be controlled sufficiently.
Moreover, in order to control the wavelength dispersibility of an optical film, the method of selecting the substituent which has the molar absorption coefficient of a specific range as a substituent which resin of an optical film has is also proposed (for example, refer patent document 2). . However, an optical film formed from such a resin is not suitable for practical use because of low retardation and large film thickness.

Although optical films using retardation increasing agents and wavelength dispersion adjusting agents have also been proposed (see, for example, Patent Documents 3 to 6), any optical film can exhibit retardation even if the reverse wavelength dispersion can be improved. Sexually lacks. In general, if the retardation development is improved by the phase difference increasing agent, the reverse wavelength dispersion is deteriorated. Conversely, if the reverse wavelength dispersion is improved by the wavelength dispersion adjusting agent, the retardation development is deteriorated. It is.
Further, in order to achieve both the retardation development property and the reverse wavelength dispersion property, a phase difference increasing agent and a wavelength dispersion adjusting agent must be added, which causes haze and durability deterioration. In addition, retardation unevenness is likely to occur during stretching at high temperatures and high magnifications, and when using an optical film in an image display device, black reproducibility is reduced, viewing angle fluctuations are caused, and visibility from an oblique direction is improved. descend.

Japanese Patent No. 345779 JP 2008-31320 A Japanese Patent No. 4583648 Japanese Patent No. 4605908 JP 2007-249180 A JP 2011-94098 A

  The present invention has been made in view of the above circumstances, and its solution is to provide an optical film that has high retardation development and excellent reverse wavelength dispersion, but has little retardation unevenness and haze. That is. Another object of the present invention is to provide a circularly polarizing plate having the optical film and excellent in durability and an image display device excellent in black reproducibility and visibility from an oblique direction.

The present inventors have studied a compound that imparts both high retardation development and excellent reverse wavelength dispersibility to an optical film because the additive tends to cause retardation unevenness and haze.
In general, the resin used for the base material of the film often exhibits forward wavelength dispersion (also referred to as positive wavelength dispersion) in which the phase difference imparted to light decreases as the wavelength of light increases. Some resins, such as cellulose esters, exhibit reverse wavelength dispersibility (also referred to as negative wavelength dispersibility) in which the phase difference imparted to the light increases as the wavelength of light increases, but the phase difference developability is insufficient. In addition, when existing compounds that increase the phase difference are added, the reverse wavelength dispersion is lost. In order to give a constant retardation to light in a wide wavelength region, it is necessary to further improve retardation development and reverse wavelength dispersion as a whole film.
The inventors of the present invention have studied various compounds in order to add a compound having a refractive index anisotropy in the molecule to give the optical film reverse wavelength dispersion. As a result, the maximum wavelength absorption located on the longest wavelength side in the absorption spectrum of the compound improves the reverse wavelength dispersibility as it is located on the longer wavelength side, and the molar extinction coefficient at the maximum absorption maximum point is within a specific range. In other words, it was found that the phase difference expression was not lowered.
Initially, as a compound having refractive index anisotropy in a molecule, a compound having a T-shaped structure having a major axis and a minor axis in the intramolecular structure as shown in Patent Document 5 was studied. It has also been found that the effects of the present invention can be obtained even when compounds having other structures are used as long as λmax and ε satisfy the following formulas (a1) and (a2).
Furthermore, it was also found that the optical film containing the compound according to the present invention can significantly suppress retardation unevenness and haze that are likely to occur during stretching at a high magnification such as oblique stretching, leading to the present invention.

That is, the subject concerning this invention is solved by the following means.
1. An optical film containing at least one compound satisfying the following formulas (a1) and (a2),
When the retardation values Ro in the in-plane direction of the optical film at wavelengths of 450 nm and 550 nm are Ro (450) and Ro (550), respectively, the Ro (450) and Ro (550) are represented by the following formula (b1) and An optical film characterized by satisfying the formula (b2).
(A1) 250 ≦ λmax ≦ 400
(A2) 1000 ≦ ε ≦ 20000
[In the above formula (a1), λmax represents the maximum absorption wavelength (nm) located on the longest wavelength side in the absorption spectrum of the compound. In the above formula (a2), ε represents the molar extinction coefficient at λmax. ]
(B1) 1.50 ≦ {Ro (550) −Ro (550) _P } /d≦3.00
(B2) 0.72 ≦ Ro (450) / Ro (550) ≦ 0.96
[In the above formula (b1), Ro (550) _P represents an in-plane retardation value at a wavelength of 550 nm of an optical film not containing the compound, and {Ro (550) -Ro (550) _P } represents the compound. Represents the amount of change (nm) in the retardation value due to the inclusion of. d represents the film thickness (μm) of the optical film. ]

〔上記一般式（Ａ）において、Ｑは、芳香族炭化水素環、非芳香族炭化水素環、芳香族複素環又は非芳香族複素環を表す。Ｗａ及びＷｂは、それぞれ独立に、Ｑを構成する原子に結合する水素原子又は置換基であり、ＷａとＷｂとは互いに同じでも異なっていてもよく、ＷａとＷｂは互いに結合して環を形成してもよい。Ｒ_３は、置換基を表す。ｍは、０〜２の整数を表し、ｍが２の場合、２つのＲ_３は互いに同じでも異なっていてもよい。ｎは、１〜１０の整数を表し、ｎが２以上である場合、２以上のＱ、Ｌ_２、Ｗａ、Ｗｂ、Ｒ_３及びｍのそれぞれは、互いに同一であっても異なっていてもよい。Ｌ_１及びＬ_２は、それぞれ独立に、アルキレン基、アルケニレン基、アルキニレン基、Ｏ、（Ｃ＝Ｏ）、（Ｃ＝Ｏ）−Ｏ、ＮＲ_Ｌ、Ｓ、（Ｏ＝Ｓ＝Ｏ）及び（Ｃ＝Ｏ）−ＮＲ_Ｌからなる群より選ばれる２価の連結基であるか、それらの組合せか又は単結合を表す。Ｒ_Ｌは、水素原子又は置換基を表す。Ｒ_１及びＲ_２は、それぞれ独立に、置換基を表す。〕2. 2. The optical film according to item 1, wherein the compound is represented by the following general formula (A).

[In the general formula (A), Q represents an aromatic hydrocarbon ring, a non-aromatic hydrocarbon ring, an aromatic heterocyclic ring or a non-aromatic heterocyclic ring. Wa and Wb are each independently a hydrogen atom or a substituent bonded to an atom constituting Q, and Wa and Wb may be the same as or different from each other, and Wa and Wb are bonded to each other to form a ring. May be. R ₃ represents a substituent. m represents an integer of 0 to 2, and when m is 2, two R _{3 s} may be the same as or different from each other. n represents an integer of 1 to 10, and when n is 2 or more, each of 2 or more of Q, L ₂ , Wa, Wb, R ₃ and m may be the same as or different from each other. . L ₁ and L ₂ are each independently an alkylene group, an alkenylene group, an alkynylene group, O, (C═O), (C═O) —O, NR _L , S, (O═S═O) and ( C═O) —NR 2 represents a divalent linking group selected from the group consisting of _L , a combination thereof, or a single bond. R _L represents a hydrogen atom or a substituent. R ₁ and R ₂ each independently represents a substituent. ]

〔上記一般式（Ｂ）において、Ｗａ及びＷｂは、それぞれ独立に、ベンゼン環を構成する原子に結合する水素原子又は置換基であり、ＷａとＷｂとは互いに同じでも異なっていてもよく、ＷａとＷｂは互いに結合して環を形成してもよい。Ｒ_３は、置換基を表す。ｍは、０〜２の整数を表し、ｍが２の場合、２つのＲ_３は互いに同じでも異なっていてもよい。Ｌ_１及びＬ_２は、それぞれ独立に、アルキレン基、アルケニレン基、アルキニレン基、Ｏ、（Ｃ＝Ｏ）、（Ｃ＝Ｏ）−Ｏ、ＮＲ_Ｌ、Ｓ、（Ｏ＝Ｓ＝Ｏ）及び（Ｃ＝Ｏ）−ＮＲ_Ｌからなる群より選ばれる２価の連結基であるか、それらの組合せか又は単結合を表す。Ｒ_Ｌは、水素原子又は置換基を表す。Ｒ_１及びＲ_２は、それぞれ独立に、置換基を表す。〕3. The optical film of item 2, wherein the compound represented by the general formula (A) is represented by the following general formula (B).

[In the general formula (B), Wa and Wb are each independently a hydrogen atom or a substituent bonded to an atom constituting the benzene ring, and Wa and Wb may be the same or different from each other. And Wb may combine with each other to form a ring. R ₃ represents a substituent. m represents an integer of 0 to 2, and when m is 2, two R _{3 s} may be the same as or different from each other. L ₁ and L ₂ are each independently an alkylene group, an alkenylene group, an alkynylene group, O, (C═O), (C═O) —O, NR _L , S, (O═S═O) and ( C═O) —NR 2 represents a divalent linking group selected from the group consisting of _L , a combination thereof, or a single bond. R _L represents a hydrogen atom or a substituent. R ₁ and R ₂ each independently represents a substituent. ]

〔上記一般式（Ｃ）において、Ｗａ及びＷｂは、それぞれ独立に、ベンゼン環に結合する水素原子又は置換基であり、ＷａとＷｂとは互いに同じでも異なっていてもよく、ＷａとＷｂは互いに結合して環を形成してもよい。Ｒ_３は、置換基を表す。ｍは、０〜２の整数を表し、ｍが２の場合、２つのＲ_３は互いに同じでも異なっていてもよい。Ｌ_１及びＬ_２は、それぞれ独立に、アルキレン基、アルケニレン基、アルキニレン基、Ｏ、（Ｃ＝Ｏ）、（Ｃ＝Ｏ）−Ｏ、ＮＲ_Ｌ、Ｓ、（Ｏ＝Ｓ＝Ｏ）及び（Ｃ＝Ｏ）−ＮＲ_Ｌからなる群より選ばれる２価の連結基であるか、それらの組合せか又は単結合を表す。Ｒ_Ｌは、水素原子又は置換基を表す。Ｒ_１及びＲ_２は、それぞれ独立に、置換基を表す。〕4). The optical film according to item 3, wherein the compound represented by the general formula (B) is represented by the following general formula (C).

[In the general formula (C), Wa and Wb are each independently a hydrogen atom or a substituent bonded to the benzene ring, and Wa and Wb may be the same or different from each other, and Wa and Wb are They may combine to form a ring. R ₃ represents a substituent. m represents an integer of 0 to 2, and when m is 2, two R _{3 s} may be the same as or different from each other. L ₁ and L ₂ are each independently an alkylene group, an alkenylene group, an alkynylene group, O, (C═O), (C═O) —O, NR _L , S, (O═S═O) and ( C═O) —NR 2 represents a divalent linking group selected from the group consisting of _L , a combination thereof, or a single bond. R _L represents a hydrogen atom or a substituent. R ₁ and R ₂ each independently represents a substituent. ]

  5. The compound satisfying the formula (a1) and the formula (a2) has at least one maximum absorption within a wavelength range of 200 to 250 nm, according to any one of the first to fourth items, The optical film as described.

  6). The optical film according to any one of claims 1 to 5, wherein the optical film contains a cellulose derivative.

  7). The optical film according to any one of Items 1 to 6, wherein the optical film has a thickness in a range of 10 to 100 μm.

  8). The optical film according to any one of claims 1 to 7, wherein an angle formed by a slow axis in a plane of the optical film and a conveying direction is in a range of 40 to 50 °. .

  9. A circularly polarizing plate comprising the optical film according to any one of items 1 to 8.

  10. An image display device comprising the optical film according to any one of items 1 to 8.

  According to the present invention, it is possible to provide an optical film with high retardation development and excellent reverse wavelength dispersion, but with little retardation unevenness and haze. Further, it is possible to provide a circularly polarizing plate having the optical film and having excellent durability, and an image display device having excellent black reproducibility and visibility from an oblique direction.

With respect to the effects of the present invention, the following operational functions have been considered and various confirmations have been made, leading to the present invention.
The optical film of the present invention is considered to be capable of exhibiting high retardation development and excellent reverse wavelength dispersion even when the film thickness is thin, by the compound satisfying the formulas (a1) and (a2). .
Λmax of the compound contained in the optical film of the present invention is located on the long wavelength side of 250 to 400 nm, and imparts sufficient reverse wavelength dispersion to the optical film.
This maximum absorption of λmax is considered to be caused by a substituent located in a direction orthogonal to the stretching direction of the optical film among the substituents of the compound according to the present invention, and the transition dipole moment derived from this substituent is large. As ε increases, the reverse wavelength dispersion imparted to the optical film by the compound is considered to increase. However, as ε increases, the refractive index in the direction orthogonal to the stretching direction also increases, and the difference from the refractive index in the stretching direction decreases. As a result, the phase difference value (Ro) also becomes small and the phase difference expression is lowered. In the present invention, by setting ε within the range satisfying the above formula (a2), it was considered that an increase in the phase difference in the direction orthogonal to the stretching direction can be moderately suppressed and high retardation development can be obtained.

Further, although the retardation unevenness and haze are considered to be caused by the additive, the compound in which λmax and ε satisfy the above formulas (a1) and (a2) is both a retardation increasing agent and a wavelength dispersion adjusting agent. It has both functions. Therefore, the addition of the compound is sufficient to improve the retardation development and reverse wavelength dispersion of the optical film. In addition, since the retardation imparted by the compound is high and the reverse wavelength dispersibility is sufficient, a small amount is sufficient. Thus, in the optical film of the present invention, it is presumed that a small number and amount of additives leads to suppression of retardation unevenness and haze, and exhibits uniform optical characteristics.
The deterioration of the durability of the circularly polarizing plate, the deterioration of the black reproducibility of the image display device, and the occurrence of color unevenness are caused by the retardation unevenness and haze of the optical film. These can be eliminated by using a film.

The block diagram of the organic electroluminescence display which is an example of an image display apparatus. The figure explaining the reflection preventing function by the circularly-polarizing plate of FIG. 1 is a configuration diagram of a liquid crystal display device which is an example of an image display device.

The optical film of the present invention is characterized by containing at least one compound satisfying the above formulas (a1) and (a2) and having optical properties satisfying the above formulas (b1) and (b2). This feature is a technical feature common to the inventions according to claims 1 to 10.
Thereby, even if the film is thin, it is possible to obtain an optical film with high retardation development and excellent reverse wavelength dispersion, but with little retardation unevenness and haze.

As an embodiment of the present invention, it is preferable that the compound satisfying the above formulas (a1) and (a2) is a compound represented by the above general formula (A) from the viewpoint of manifesting the effects of the present invention.
Moreover, it is preferable that the compound represented by the said general formula (A) is a compound represented by the said general formula (B). Furthermore, it is preferable that the compound represented by the said general formula (B) is a compound represented by the said general formula (C).

The compound satisfying the above formulas (a1) and (a2) preferably has at least one maximum absorption within a wavelength range of 200 to 250 nm.
Thereby, both functions of retardation development and reverse wavelength dispersion can be imparted to the optical film in a well-balanced manner.

Moreover, as an embodiment of the present invention, it is preferable that the optical film contains a cellulose derivative from the viewpoint of expression of the effect of the present invention.
Furthermore, the optical film preferably has a thickness in the range of 10 to 100 μm.

  The optical film of the present invention can be suitably included in a circularly polarizing plate and an image display device. Thereby, durability of a circularly-polarizing plate can be improved and the black reproducibility of an image display apparatus and the visibility from an oblique direction can be improved.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<Optical film>
The optical film of the present invention contains at least one of the following compounds.

(Compound)
The compound used in the present invention satisfies the following formulas (a1) and (a2).
(A1) 250 ≦ λmax ≦ 400
(A2) 1000 ≦ ε ≦ 20000
[In the above formula (a1), λmax represents the maximum absorption wavelength (nm) located on the longest wavelength side in the absorption spectrum of the compound. In the above formula (a2), ε represents the molar extinction coefficient at λmax. ]

When λmax is 250 nm or more, the reverse wavelength dispersion imparted to the optical film by the compound is sufficient. On the other hand, when λmax is 400 nm or less, the light resistance of the optical film is good, and the optical film is not yellowish and is not suitable for practical use.
Among these, it is more preferable that λmax is in the range of 300 to 380 nm.

The compound used in the present invention preferably has at least one maximum absorption in the wavelength range of 200 to 250 nm, apart from the maximum absorption of λmax.
The compound having at least one maximum absorption in this wavelength range imparts to the optical film both functions of retardation development and reverse wavelength dispersion in a well-balanced manner.

The compound in which ε satisfies the above formula (a2) does not trade off the retardation development property and reverse wavelength dispersion property imparted to the optical film, and achieves both high retardation development property and excellent reverse wavelength dispersion property in the optical film. it can.
If ε is 1000 or more, sufficient reverse wavelength dispersion can be imparted to the optical film. If ε is 20000 or less, sufficient retardation can be imparted to the optical film. As a result, in order to obtain desired optical characteristics, it is not necessary to increase the amount of the compound added, and the occurrence of haze and bleed out can be suppressed.
ε is more preferably 2000 ≦ ε ≦ 18000, and further preferably 3000 ≦ ε ≦ 15000.

The λmax and ε are measured as follows.
The compound used in the present invention is dissolved in tetrahydrofuran (without a polymerization inhibitor) at a concentration of 1.0 × 10 ⁻⁵ mol / L, and the absorption spectrum of this solution is measured at 25 ° C. with a normal spectrophotometer. . There may be a plurality of maximum absorptions in the absorption spectrum, and the wavelength at the maximum point of the maximum absorption located on the longest wavelength side among one or a plurality of maximum absorptions is obtained as λmax. Further, the molar extinction coefficient ε is calculated from the absorbance measured at λmax. Note that the maximum absorption of λmax is not always the maximum absorption.

Although the compound used for this invention will not be specifically limited if the said Formula (a1) and Formula (a2) are satisfy | filled, It is preferable that it is a compound represented by the following general formula (A).

Q in the general formula (A) represents an aromatic hydrocarbon ring, a non-aromatic hydrocarbon ring, an aromatic heterocyclic ring or a non-aromatic heterocyclic ring.
The aromatic hydrocarbon ring may be a single ring or a condensed ring, but is preferably a single ring. Preferred examples of the aromatic hydrocarbon ring include benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, tetracene ring, pyrene ring, benzopyrene ring, chrysene ring, triphenylene ring, acenaphthene ring, fluoranthene ring, fluorene ring, etc. And is preferably a benzene ring.

  The non-aromatic hydrocarbon ring may be a single ring or a condensed ring, but is preferably a single ring. Preferred examples of the non-aromatic hydrocarbon ring include a cyclopropane ring, a cyclobutane ring, a cyclopentane ring, a cyclohexane ring, a cycloheptane ring, a cyclooctane ring, a norbornene ring, etc., preferably a cyclohexane ring or a cyclopentane ring. is there.

  The aromatic heterocyclic ring may be a monocyclic ring or a condensed ring, and is preferably a monocyclic ring. Preferred examples of the aromatic heterocycle include furan ring, benzofuran ring, thiophene ring, benzothiophene ring, pyrrole ring, pyrazole ring, imidazole ring, oxadiazole ring, indole ring, carbazole ring, triazole ring, benzimidazole ring, Pyridine ring, pyrazine ring, pyridazine ring, pyrimidine ring, triazine ring, quinoline ring, perimidine ring, quinazoline ring, azulene ring, dibenzofuran ring, dibenzothiophene ring, dibenzocarbazole ring, benzodifuran ring, benzodithiophene ring, phenanthroline ring, benzo A thiazole ring, a benzoxazole ring and the like are included, and a pyridine ring, a benzothiazole ring or a benzoxazole ring is preferable.

  The non-aromatic heterocyclic ring may be a monocyclic ring or a condensed ring, and is preferably a monocyclic ring. Preferred examples of the non-aromatic heterocycle include tetrahydrofuran ring, tetrahydropyran ring, dioxolane ring, dioxane ring, pyrrolidine ring, pyridone ring, pyridazinone ring, imide ring, piperidine ring, dihydropyrrole ring, dihydropyridine ring, tetrahydropyridine ring, A piperazine ring, a morpholine ring, a piperidine ring and the like are included, and a pyridone ring, an imide ring or a pyrrolidine ring is preferable.

Wa and Wb in the general formula (A) are each independently a hydrogen atom or a substituent bonded to an atom constituting the ring of Q, and Wa and Wb may be the same as or different from each other. May combine with each other to form a ring.
Preferably, Wa and Wb are bonded to each other to form a ring, or at least one of Wa and Wb has a ring structure.

In the compound represented by the general formula (A), it is considered that R ₁ , L ₁ , Q, L ₂ and R ₂ form a long chain structure and are located in the stretching direction of the optical film. On the other hand, Wa, Wb and R ₃ form a short chain structure and are located in the direction perpendicular to the stretching direction, and λmax and ε of the compound are substituents located in the direction perpendicular to the stretching direction, particularly Wa and Wb. It is thought to originate from. If λmax and ε satisfying the above formulas (a1) and (a2) are obtained by either Wa or Wb, the other can be any substituent that does not inhibit the expression of λmax and ε.

Examples of the substituent represented by Wa and Wb include the following examples from the viewpoint of obtaining λmax and ε satisfying the above formulas (a1) and (a2), respectively.
Halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.) Cycloalkyl group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl group (vinyl group, allyl group, etc.), cycloalkenyl group (2-cyclopenten-1-yl, 2-cyclohexene-1- Yl group), alkynyl group (ethynyl group, propargyl group, etc.), aryl group (phenyl group, p-tolyl group, naphthyl group, etc.), heteroaryl group (2-pyrrole group, 2-furyl group, 2-thienyl group). , Pyrrole group, imidazolyl group, oxazolyl group, thiazolyl group, benzimidazolyl group, benzoxazolyl 2-benzothiazolyl group, pyrazolinone group, pyridyl group, pyridinone group, 2-pyrimidinyl group, etc.), cyano group, hydroxy group, nitro group, carboxy group, alkoxy group (methoxy group, ethoxy group, isopropoxy group, tert-butoxy group) Group, n-octyloxy group, 2-methoxyethoxy group, etc.), aryloxy group (phenoxy group, 2-methylphenoxy group, 4-tert-butylphenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy) Group), acyl group (acetyl group, pivaloylbenzoyl group, etc.), acyloxy group (formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc.), Amino group (amino group, methylamino Group, dimethylamino group, anilino group, N-methyl-anilino group, diphenylamino group, etc.), acylamino group (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, benzoylamino group, etc.), alkyl and arylsulfonyl Amino group (methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio group (methylthio group, ethylthio group) Group, n-hexadecylthio group, etc.), arylthio group (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (N-ethylsulfamoyl group, N- (3-dodecyloxypropyl)) Sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N′phenylcarbamoyl) sulfamoyl group, etc.), sulfo group, carbamoyl group (carbamoyl group) N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group and the like.

  Among them, as Wa and Wb, since λmax and ε satisfying the above formulas (a1) and (a2) are easily obtained, respectively, a substituted or unsubstituted cycloalkyl group, alkoxy group, aryl group, or heteroaryl, respectively. Groups are preferred.

R _{3 in the} general formula (A) represents a substituent. Since the magnitude of ε of the compound represented by the general formula (A) is proportional to the magnitude of the transition dipole moment of Wa and Wb, from the viewpoint of fine-tuning the transition dipole moment, R _{3 is selected as} necessary. Can be provided. Is not particularly limited as substituent R ₃ represents, include those exemplified below.
Halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.) Alkenyl group (vinyl group, allyl group, etc.), alkynyl group (ethynyl group, propargyl group, etc.), cyano group, hydroxy group, nitro group, carboxy group, alkoxy group (methoxy group, ethoxy group, isopropoxy group, tert- Butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.), acyloxy group (formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, etc.), alkoxycarbonyl group (methoxycarbonyl group, ethoxycarbonyl group, etc.) , Aryloxycarbonyl group (phenoxycarbonyl Etc.), amino group (amino group, methylamino group, dimethylamino group etc.), acylamino group (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group etc.), alkylsulfonylamino group (methylsulfonylamino group, butyl etc.) Sulfonylamino group, etc.), mercapto group, alkylthio group (methylthio group, ethylthio group, n-hexadecylthio group, etc.), sulfamoyl group (N-ethylsulfamoyl group, N- (3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, etc.), sulfo group, acyl group (acetyl group etc.), carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N , N-di-n-octylcarbamoyl group, N (Methylsulfonyl) carbamoyl group etc.), aryl group (phenyl group, p-tolyl group, naphthyl group etc.), heteroaryl group (2-furyl group, 2-thienyl group, 2-pyrimidinyl group, 2-benzothiazolyl group, 2 -Pyridyl group etc.).

Among them, R ₃ represents a halogen atom, an alkyl group (preferably having 1 to 20 carbon atoms), an alkenyl group (preferably having 3 to 20 carbon atoms), an aryl group (preferably having 6 to 20 carbon atoms), a heteroaryl group ( Preferably 4 to 20 carbon atoms, hydroxy group, carboxy group, alkoxy group (preferably 1 to 20 carbon atoms), aryloxy group (preferably 6 to 20 carbon atoms), acyl group, acyloxy group, cyano group or amino group Group is preferable, and a halogen atom, an alkyl group, a cyano group or an alkoxy group is more preferable. These substituents may further have the same substituent.

M in the general formula (A) represents an integer of 0 to 2, and is preferably 0. When m is 2, two R _{3 s} may be the same or different from each other.

N in the general formula (A) represents an integer of 1 to 10, and is preferably 1. When n is 2 or more, each of 2 or more of Q, L ₂ , Wa, Wb, R ₃ and m may be the same as or different from each other.

L ₁ and L _{2 in} the general formula (A) are each independently an alkylene group, an alkenylene group, an alkynylene group, O, (C═O), (C═O) —O, NR _L , S, (O═ S = O) and (C = O) or a divalent connecting group selected from the group consisting of -NR _L, indicates whether a combination thereof or a single bond, preferably O, (C = O) -O , O— (C═O), (C═O) —NH or NH— (C═O).

R _L represents a hydrogen atom or a substituent. Examples of the substituent represented by R _L include an alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.), a cycloalkyl group. (Cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), aryl group (phenyl group, p-tolyl group, naphthyl group, etc.), heteroaryl group (2-furyl group, 2-thienyl group, 2-pyrimidinyl) Group, 2-benzothiazolyl group, 2-pyridyl group and the like), cyano group and the like.

R ₁ and R _{2 in} formula (A) each independently represent a substituent. R ₁ and R ₂ may be the same or different from each other.
Examples of the substituent represented by R ₁ and R ₂ include the following.
Halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), alkyl group (methyl group, ethyl group, n-propyl group, isopropyl group, tert-butyl group, n-octyl group, 2-ethylhexyl group, etc.) Cycloalkyl group (cyclohexyl group, cyclopentyl group, 4-n-dodecylcyclohexyl group, etc.), alkenyl group (vinyl group, allyl group, etc.), cycloalkenyl group (2-cyclopenten-1-yl, 2-cyclohexene-1- Yl group), alkynyl group (ethynyl group, propargyl group, etc.), aryl group (phenyl group, p-tolyl group, naphthyl group, etc.), heteroaryl group (2-furyl group, 2-thienyl group, 2-pyrimidinyl group). , 2-benzothiazolyl group, 2-pyridyl group, etc.), cyano group, hydroxy group, nitro group, carboxy group, a Coxy group (methoxy group, ethoxy group, isopropoxy group, tert-butoxy group, n-octyloxy group, 2-methoxyethoxy group, etc.), aryloxy group (phenoxy group, 2-methylphenoxy group, 4-tert-butyl) Phenoxy group, 3-nitrophenoxy group, 2-tetradecanoylaminophenoxy group, etc.), acyloxy group (formyloxy group, acetyloxy group, pivaloyloxy group, stearoyloxy group, benzoyloxy group, p-methoxyphenylcarbonyloxy group, etc. ), Amino group (amino group, methylamino group, dimethylamino group, anilino group, N-methyl-anilino group, diphenylamino group, etc.), acylamino group (formylamino group, acetylamino group, pivaloylamino group, lauroylamino group, Benzoylamino group ), Alkyl and arylsulfonylamino groups (methylsulfonylamino group, butylsulfonylamino group, phenylsulfonylamino group, 2,3,5-trichlorophenylsulfonylamino group, p-methylphenylsulfonylamino group, etc.), mercapto group, alkylthio Group (methylthio group, ethylthio group, n-hexadecylthio group, etc.), arylthio group (phenylthio group, p-chlorophenylthio group, m-methoxyphenylthio group, etc.), sulfamoyl group (N-ethylsulfamoyl group, N- ( 3-dodecyloxypropyl) sulfamoyl group, N, N-dimethylsulfamoyl group, N-acetylsulfamoyl group, N-benzoylsulfamoyl group, N- (N′phenylcarbamoyl) sulfamoyl group, etc.), sulfo group , Acyl group (acetyl Group, pivaloylbenzoyl group, etc.), carbamoyl group (carbamoyl group, N-methylcarbamoyl group, N, N-dimethylcarbamoyl group, N, N-di-n-octylcarbamoyl group, N- (methylsulfonyl) carbamoyl group And so on.

As described above, R ₁ , L ₁ , Q, L ₂ and R ₂ are considered to form a long chain structure and to be positioned in the stretching direction of the optical film. From the viewpoint of adjusting the length and planarity of the long chain structure of the compound represented by the general formula (A), increasing the refractive index in the stretching direction of the optical film, and improving the retardation development, among the above, R ₁ and R ₂ are an alkyl group (preferably an alkyl group having 1 to 20 carbon atoms), a cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms), an aryl group (preferably having a carbon number of 6 to 20). Aryl group) and a heteroaryl group (preferably an aryl group having 4 to 20 carbon atoms) are preferred, and an aryl group or a cycloalkyl group is more preferred. The aryl group is preferably a substituted or unsubstituted phenyl group, more preferably a phenyl group having a substituent, and still more preferably a phenyl group having a substituent at the 4-position. The cycloalkyl group is preferably a substituted or unsubstituted cyclohexyl group, more preferably a cyclohexyl group having a substituent, and further preferably a cyclohexyl group having a substituent at the 4-position.
The substituent represented by R ₁ and R ₂ may further have the same substituent.

一般式（Ｂ）のＷａ、Ｗｂ、Ｒ_３、ｍ、Ｌ_１、Ｌ_２、Ｒ_Ｌ、Ｒ_１及びＲ_２は、一般式（Ａ）におけるＷａ、Ｗｂ、Ｒ_３、ｍ、Ｌ_１、Ｌ_２、Ｒ_Ｌ、Ｒ_１及びＲ_２とそれぞれ同様に定義される。The compound represented by the general formula (A) is preferably a compound represented by the following general formula (B).

Wa, Wb, R ₃ , m, L ₁ , L ₂ , R _L , R ₁ and R ₂ in the general formula (B) are Wa, Wb, R ₃ , m, L ₁ , L in the general formula (A). ₂ , R _L , R ₁ and R ₂ are defined similarly.

一般式（Ｃ）のＷａ、Ｗｂ、Ｒ_３、ｍ、Ｌ_１、Ｌ_２、Ｒ_Ｌ、Ｒ_１及びＲ_２は、一般式（Ａ）におけるＷａ、Ｗｂ、Ｒ_３、ｍ、Ｌ_１、Ｌ_２、Ｒ_Ｌ、Ｒ_１及びＲ_２とそれぞれ同様に定義される。The compound represented by the general formula (B) is preferably a compound represented by the following general formula (C).

Wa, Wb, R ₃ , m, L ₁ , L ₂ , R _L , R ₁ and R ₂ in the general formula (C) are Wa, Wb, R ₃ , m, L ₁ , L in the general formula (A). ₂ , R _L , R ₁ and R ₂ are defined similarly.

Ｒ_ｉ〜Ｒ_iiiは、それぞれ独立に、水素原子又は置換基を表す。When Wa and Wb of the general formula (C) are bonded to each other to form a ring, the formed ring is preferably a nitrogen-containing heterocycle. Examples of the compound represented by the general formula (C) include the following compounds (C1) to (C6).

R _{i to} R _iii each independently represents a hydrogen atom or a substituent.

  For example, in the compound (C1), Q in the general formula (A) is a benzene ring, Wa is a group containing an oxygen atom bonded to the benzene ring, and Wb is a group containing a nitrogen atom bonded to the benzene ring. is there.

On the other hand, in the following compound (A0), the ring corresponding to Q in the general formula (A) is a naphthalene ring.

Specific examples of the compound represented by the general formula (A), the general formula (B), or the general formula (C) are shown below, but the compounds that can be used in the present invention include the following exemplary compounds (A1) to There is no limitation by (A60).

  In the above compound examples of the present invention, when there are geometrical isomers (trans isomer and cis isomer), any isomer may be used, but the trans isomer can give higher retardation expression than the cis isomer. ,preferable.

The compound represented by general formula (A), general formula (B), or general formula (C) is compoundable by a well-known method. For example, the exemplified compound A30 can be synthesized as follows with reference to JP-A-2008-107767 and the like.

  3 g of 2,5-dihydroxybenzoic acid is dissolved in 30 mL of toluene, and 4.2 mL of thionyl chloride is added dropwise and stirred for 2 hours. Toluene and thionyl chloride are distilled off under reduced pressure, 20 mL of toluene is added, and a solution of 2.4 g of o-aminothiophenol in toluene (5 mL) is added dropwise. Stir at room temperature for 12 hours and extract with water and ethyl acetate. The solvent was distilled off under reduced pressure from the obtained organic layer to obtain 3.5 g of the above compound (m). The yield is 75%.

  Tetrahydrofuran 45mL is added to 7.0g of said compounds (n), and it cools with an ice-water cooling bath. A solution of compound (m) (3.5 g) in tetrahydrofuran (5 mL) and dimethylaminopyridine (2 mg) in tetrahydrofuran (1 mL) are successively added dropwise thereto. After stirring at room temperature for 3 hours, extraction is performed by adding water and ethyl acetate. The solvent is distilled off from the organic layer under reduced pressure, and the resulting crude crystals are purified by silica gel chromatography (ethyl acetate / heptane) to obtain Exemplified Compound A30. The yield is 5.5 g and the yield is 70%.

Further, the compound used in the present invention is not limited to the compound represented by the general formula (A), the general formula (B) or the general formula (C) as long as λmax and ε satisfy the above ranges, Examples compounds D1 to D10 shown below can be used.

  As illustrated, many compounds satisfying the above formulas (a1) and (a2) have a T-shaped structure in which a short chain structure is bonded to a long chain structure. It is considered that this long chain structure is oriented in the stretching direction by stretching, and the short chain structure is positioned in a direction orthogonal to the stretching direction. When the absorption spectrum of the compound is measured, the absorption maximum appearing on the longest wave side is derived from the short chain structure located in the direction orthogonal to the stretching direction. The greater the transition dipole moment of the short chain structure, the greater the absorbance. Become. The absorbance and the refractive index correlate, and the higher the absorbance, the higher the refractive index, and the difference in refractive index between the stretching direction and the direction orthogonal to the stretching direction becomes small, resulting in a decrease in retardation. In the present invention, by selecting the structure of the compound in consideration of the balance between the imparted reverse wavelength dispersion and retardation development, one compound optically exhibits both high retardation development and excellent reverse wavelength dispersion. It can be applied to the film.

The optical film of the present invention contains at least one compound satisfying the formula (a1) and the formula (a2), and two or more compounds can be used in combination.
The content of the compound used in the present invention is appropriately set to such an extent that the reverse wavelength dispersibility and retardation development required for the optical film can be imparted. Specifically, the content of the compound used in the present invention is preferably in the range of 1 to 10% by mass and more preferably in the range of 2 to 8% by mass with respect to the thermoplastic resin. .
If the content of the compound is 1% by mass or more, sufficient reverse wavelength dispersion and high retardation can be imparted to the optical film, and if it is 10% by mass or less, the optical film bleeds out. It is hard to produce.

  Another retardation increasing agent can also be combined with the compound used for this invention. When a retardation increasing agent is combined, the retardation development property of the optical film by the compound used in the present invention is originally high, and a small amount of the retardation increasing agent is sufficient. Therefore, even when stretching at a high magnification at a high temperature, phase difference unevenness does not occur. Examples of the phase difference increasing agent to be combined include a discotic compound, but are not limited thereto.

(Thermoplastic resin)
The thermoplastic resin that can be used as the base material of the optical film of the present invention includes cellulose derivatives (for example, cellulose ester resins, cellulose ether resins, etc.), polycarbonate resins, polystyrene resins, polysulfone resins, polyester resins. , Polyarylate resins, (meth) acrylic resins, olefin resins (for example, norbornene resins, cyclic olefin resins, cyclic conjugated diene resins, vinyl alicyclic hydrocarbon resins), and the like. A cellulose derivative, a (meth) acrylic resin, a polycarbonate resin, or a cyclic olefin resin is preferable, and a cellulose derivative is more preferable, and a cellulose ester resin is most preferable.

(Cellulose derivative)
The cellulose derivative that can be used in the present invention is a compound using cellulose as a raw material (compound having a cellulose skeleton).
Examples of cellulose derivatives include cellulose ethers (eg, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, cyanoethyl cellulose, etc.), cellulose esters, cellulose ether esters (eg, acetyl methyl cellulose, acetyl ethyl cellulose, acetyl hydroxyethyl cellulose, benzoyl hydroxypropyl cellulose) Etc.), cellulose carbonate (eg, cellulose ethyl carbonate, etc.), cellulose carbamate (eg, cellulose phenyl carbamate, etc.), etc., and cellulose ester is preferred.
The cellulose derivative may be one type or a mixture of two or more types.

  The cellulose ester is a compound obtained by esterifying cellulose and at least one of an aliphatic carboxylic acid or an aromatic carboxylic acid having about 2 to 22 carbon atoms, preferably cellulose and a lower carbon number of 6 or less. It is a compound obtained by esterifying a fatty acid.

  The acyl group contained in the cellulose ester may be linear or branched, may form a ring, and may further have another substituent. When the total substitution degree of the acyl group is constant, the birefringence tends to decrease as the carbon number of the acyl group increases. Therefore, the carbon number of the acyl group is preferably in the range of 2-6, more preferably in the range of 2-4, and further preferably in the range of 2-3.

  Specific examples of cellulose esters include mixed fatty acid esters such as cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose acetate propionate butyrate, and cellulose acetate phthalate. Preferred is cellulose acetate, cellulose acetate butyrate, or cellulose acetate propionate. The butyryl group that can be contained in the cellulose ester may be linear or branched.

The total substitution degree of the acyl group of the cellulose ester can be about 2.0 to 3.0. The total substitution degree of the acyl group is preferably in the range of 2.0 to 2.5 from the viewpoint of improving the retardation development property, and from the viewpoint of improving the moisture resistance and the like, 2.5 to 3.0. It is preferable to be within the range.
Of these, the substitution degree of the acyl group having 3 or more carbon atoms is preferably 2.0 or less. If the substitution degree of an acyl group having 3 or more carbon atoms is 2.0 or less, it is possible to suppress a decrease in retardation development.
The substitution degree of the acyl group of cellulose ester can be measured by the method prescribed in ASTM-D817-96.

The number average molecular weight Mn of the cellulose derivative is preferably in the range of 6 × 10 ^{4 to} 3 × 10 ⁵ in order to increase the mechanical strength of the obtained optical film, and is 7 × 10 ⁴ to 2 × 10 ⁵ . More preferably within the range.
The weight average molecular weight Mw and the number average molecular weight Mn of the cellulose derivative are measured using gel permeation chromatography (GPC). The measurement conditions are as follows.
Solvent: methylene chloride;
Column: Three Shodex K806, K805, K803G (made by Showa Denko KK) are connected and used;
Column temperature: 25 ° C .;
Sample concentration: 0.1% by mass;
Detector: RI Model 504 (manufactured by GL Sciences);
Pump: L6000 (manufactured by Hitachi, Ltd.);
Flow rate: 1.0 mL / min
Calibration curve: A calibration curve with 13 samples of standard polystyrene (STK standard polystyrene, manufactured by Tosoh Corporation, Mw = 500 to 1000000) is used. Thirteen samples are used at approximately equal intervals.

  The content of residual sulfuric acid in the cellulose derivative is preferably in the range of 0.1 to 45.0 mass ppm in terms of elemental sulfur, and more preferably in the range of 1.0 to 30.0 mass ppm. Sulfuric acid is considered to remain in the film in a salt state. When the content of residual sulfuric acid is within 45.0 ppm by mass, the film is less likely to break when it is stretched hot or slitting after hot stretching. The residual sulfuric acid content can be measured by a method prescribed in ASTM D817-96.

The free acid content in the cellulose derivative is preferably in the range of 1 to 500 ppm by mass, more preferably in the range of 1 to 100 ppm by mass, and in the range of 1 to 70 ppm by mass. More preferably.
When the content of the free acid is within the above range, as described above, the film is not easily broken during the heat stretching of the film or during the cutting after the heat stretching. The content of free acid can be measured by the method prescribed in ASTM D817-96.

  A cellulose derivative may contain a trace amount metal component. It is thought that a trace amount metal component originates in the water used in the synthesis process of the cellulose derivative. Like these metal components, the content of components that can become insoluble nuclei is preferably as small as possible. In particular, metal ions such as iron, calcium, and magnesium may form an insoluble matter by forming a salt with a resin decomposition product or the like that may contain an organic acidic group. Further, the calcium (Ca) component easily forms a coordination compound (that is, a complex) with an acidic component such as a carboxylic acid or a sulfonic acid, and scum (insoluble) derived from a lot of insoluble calcium. May form turbidity).

  Specifically, the content of the iron (Fe) component in the cellulose derivative is preferably 1 mass ppm or less. Moreover, content of the calcium (Ca) component in a cellulose derivative becomes like this. Preferably it is 60 mass ppm or less, More preferably, it is 0-30 mass ppm. The content of the magnesium (Mg) component in the cellulose derivative is preferably 0 to 70 ppm by mass, and particularly preferably 0 to 20 ppm by mass.

The content of metal components such as an iron (Fe) component, a calcium (Ca) component or a magnesium (Mg) component can be obtained by treating a completely dried cellulose derivative with a micro digest wet decomposition apparatus (sulfuric acid decomposition) or by alkali melting. After pre-processing, it can measure using an inductively coupled plasma emission spectrometer (ICP-AES).
The content of residual alkaline earth metal, residual sulfuric acid and residual acid can be adjusted by thoroughly washing the cellulose derivative obtained by synthesis.

The cellulose derivative used in the present invention can be produced by a known method. For example, in the case of cellulose ester, cellulose is esterified by mixing raw material cellulose and a predetermined organic acid (such as aliphatic carboxylic acid or aromatic carboxylic acid) with a carboxylic acid anhydride and a catalyst (such as sulfuric acid). The raw material cellulose is not particularly limited, and may be cotton linter, wood pulp, kenaf or the like. You may mix and use the cellulose ester from which a raw material differs. The esterification reaction proceeds until a cellulose triester is formed. In the triester, the three hydroxy groups of the glucose unit are substituted with an organic acid acyl acid. When two types of organic acids are used at the same time, mixed cellulose esters such as cellulose acetate propionate and cellulose acetate butyrate can be prepared. Next, a cellulose ester having a desired acyl group substitution degree is synthesized by hydrolyzing the cellulose triester. Thereafter, a cellulose ester is obtained through steps such as filtration, precipitation, washing with water, dehydration, and drying.
Specifically, it can be synthesized with reference to the method described in JP-A-10-45804.

((Meth) acrylic resin)
The (meth) acrylic resin that can be used in the present invention can be a homopolymer of a (meth) acrylic acid ester or a copolymer of a (meth) acrylic acid ester and another copolymerizable monomer. The (meth) acrylic resin may be one type or a mixture of two or more types.
The (meth) acrylic acid ester is preferably methyl methacrylate. The content ratio of the structural unit derived from methyl methacrylate in the copolymer is preferably 50% by mass or more, and more preferably 70% by mass or more.

  The copolymerization monomer that forms a copolymer with methyl methacrylate includes an alkyl methacrylate having 2 to 18 carbon atoms in the alkyl portion; an alkyl acrylate having 1 to 18 carbon atoms in the alkyl portion; and a lactone ring structure described later. C1-C18 alkyl (meth) acrylate having an alkyl moiety having a hydroxyl group (hydroxy group); α, β-unsaturated acid such as acrylic acid or methacrylic acid; Unsaturation such as maleic acid, fumaric acid or itaconic acid Group-containing divalent carboxylic acids; aromatic vinyl compounds such as styrene and α-methylstyrene; α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride Acrylamide derivatives such as acryloylmorpholine (ACMO); N-vinylpyrrolidone (V P) and the like are included. These may be used alone or in combination of two or more.

  Of these, alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate; Alkyl (meth) acrylates having a hydroxy group such as methyl (hydroxymethyl) acrylate and ethyl 2- (hydroxymethyl) acrylate are preferred. In order to enhance the compatibility with the cellulose ester, acryloylmorpholine and the like are preferable.

The (meth) acrylic resin preferably contains a lactone ring structure from the viewpoint of enhancing the heat resistance of the obtained optical film or adjusting the photoelastic coefficient. The lactone ring structure contained in the (meth) acrylic resin is preferably represented by the following general formula (1).

In the general formula ^(1), R 1 ~R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. Examples of organic residues include linear or branched alkyl groups, linear or branched alkylene groups, aryl groups, —OAc groups (Ac is an acetyl group), —CN groups, and the like.
The lactone ring structure represented by the formula (1) is a structure derived from an alkyl (meth) acrylate having a hydroxy group, as will be described later.

〔一般式（２）において、Ｒ^４は、水素原子又はメチル基を表す。Ｘは、水素原子、炭素数１〜２０のアルキル基、アリール基、ＯＡｃ基（Ａｃはアセチル基）、ＣＮ基、アシル基又はＣ−ＯＲ基（Ｒは水素原子又は炭素数１〜２０の有機残基）を表す。〕The (meth) acrylic resin containing a lactone ring structure further contains a structural unit derived from an alkyl (meth) acrylate having 1 to 18 carbon atoms in the alkyl portion, and if necessary, a monomer containing a hydroxy group, unsaturated A structural unit derived from a carboxylic acid, a monomer represented by the following general formula (2), or the like may further be included.

[In General Formula (2), R ⁴ represents a hydrogen atom or a methyl group. X is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an OAc group (Ac is an acetyl group), a CN group, an acyl group, or a C-OR group (R is a hydrogen atom or an organic group having 1 to 20 carbon atoms). Residue). ]

The content ratio of the lactone ring structure represented by the general formula (1) in the (meth) acrylic resin containing a lactone ring structure is preferably in the range of 5 to 90% by mass, more preferably 10 to 80% by mass. %, More preferably in the range of 15 to 70% by mass.
When the content of the lactone ring structure is 5% by mass or more, an optical film having a necessary retardation is easily obtained, and heat resistance, solvent resistance, and surface hardness are sufficient. If the content ratio of the lactone ring structure is within 90% by mass, the moldability is high, and the flexibility of the obtained optical film tends to be high.

The content ratio of the structural unit derived from the alkyl (meth) acrylate in the (meth) acrylic resin containing a lactone ring structure is preferably in the range of 10 to 95% by mass, more preferably 20 to 90% by mass. More preferably, it is in the range of 30 to 85% by mass.
In the (meth) acrylic resin containing a lactone ring structure, the content ratio of the structural unit derived from the hydroxy group-containing monomer, the unsaturated carboxylic acid or the monomer represented by the general formula (2) is preferably preferably 0 to 0, respectively. It is in the range of 30% by mass, more preferably in the range of 0 to 20% by mass, and still more preferably in the range of 0 to 10% by mass.

  A (meth) acrylic resin containing a lactone ring structure is polymerized by a monomer component containing at least an alkyl (meth) acrylate having a hydroxy group and another alkyl (meth) acrylate to form a hydroxy group in the molecular chain. It can be produced through a step of obtaining a polymer having a group and an ester group, and a step of introducing a lactone ring structure by heat-treating the obtained polymer.

The weight average molecular weight Mw of the (meth) acrylic resin is preferably in the range of 8.0 × 10 ^{4 to} 5.0 × 10 ⁵ , more preferably 9.0 × 10 ^{4 to} 4.5 × 10 ⁵ . It is in the range, and more preferably in the range of 1.0 × 10 ^{5 to} 4.0 × 10 ⁵ .
If the weight average molecular weight Mw of the (meth) acrylic resin is 8.0 × 10 ⁴ or more, the resulting optical film is easily improved in brittleness resistance, and if it is 5.0 × 10 ⁵ or less, the obtained optical film is obtained. The haze of the film tends to be low.
The weight average molecular weight Mw of the (meth) acrylic resin can be measured by gel permeation chromatography (GPC) in the same manner as the method for measuring the weight average molecular weight Mw of the cellulose derivative.

The thermoplastic resin may be one type or a mixture of two or more types. Examples of the mixture of two or more types include a mixture of a cellulose derivative and another resin. Examples of other resins include vinyl resins (including polyvinyl acetate resins and polyvinyl alcohol resins), cyclic olefin resins, polyester resins (aromatic polyesters, aliphatic polyesters or copolymers containing them). , (Meth) acrylic resins (including copolymers), and the like.
The content of the other resin in the mixture of the cellulose derivative and the other resin is preferably about 5 to 70% by mass with respect to the entire mixture.

  The optical film of the present invention may further contain an additive as exemplified below as required.

(Sugar ester)
The optical film of the present invention can contain a sugar ester other than the cellulose ester described above from the viewpoint of improving the storage stability and plasticity of the optical film.
The sugar ester that can be used in the present invention is a compound having 1 to 12 furanose structures or pyranose structures, in which all or part of the hydroxy groups in the compound are esterified.
Preferable examples of such sugar esters include sucrose esters represented by the following general formula (FA).

R _{1 to} R _{8 in} the general formula (FA) each independently represent a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group. R _{1 to} R ₈ may be the same as or different from each other.
The substituted or unsubstituted alkylcarbonyl group is preferably a substituted or unsubstituted alkylcarbonyl group having 2 or more carbon atoms. Examples of the substituted or unsubstituted alkylcarbonyl group include a methylcarbonyl group (acetyl group). Examples of the substituent that the alkyl group has include an aryl group such as a phenyl group.
The substituted or unsubstituted arylcarbonyl group is preferably a substituted or unsubstituted arylcarbonyl group having 7 or more carbon atoms. Examples of the arylcarbonyl group include a phenylcarbonyl group. Examples of the substituent that the aryl group has include an alkyl group such as a methyl group, an alkoxyl group such as a methoxy group, and the like.

The average substitution degree of the acyl group of the sucrose ester is preferably in the range of 3.0 to 7.5. When the average substitution degree of the acyl group is within this range, sufficient compatibility with a thermoplastic resin as a film substrate, for example, a cellulose ester is easily obtained.
Specific examples of the sucrose ester compound represented by the general formula (FA) include the following compounds (FA-1) to (FA-24). The table below, the _R 1 to R ₈ in the general formula of the exemplified compound (FA-1) ~ (FA -24) (FA), shows the average degree of substitution of acyl groups.

Examples of other sugar esters include the compounds described in JP-A-62-42996 and JP-A-10-237084.
The content of the sugar ester is preferably in the range of 0.5 to 35.0% by mass and more preferably in the range of 5.0 to 30.0% by mass with respect to the thermoplastic resin.

(Plasticizer)
The optical film of the present invention may contain a plasticizer in order to improve the fluidity of the composition during film production and the flexibility of the film. Examples of plasticizers include polyester plasticizers, polyhydric alcohol ester plasticizers, polycarboxylic acid ester plasticizers (including phthalate ester plasticizers), glycolate plasticizers, ester plasticizers ( Citrate ester plasticizers, fatty acid ester plasticizers, phosphate ester plasticizers, trimellitic ester plasticizers, and the like). These may be used alone or in combination of two or more.

The polyester plasticizer is a compound obtained by reacting a 1-4 carboxylic acid with a 1-6 valent alcohol, and preferably a compound obtained by reacting a divalent carboxylic acid with a glycol. .
Examples of the divalent carboxylic acid include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like. In particular, a compound using adipic acid, phthalic acid or the like as a divalent carboxylic acid can impart good plasticity to the optical film.

  Examples of glycols include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, neopentylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol and the like. included. Each of the divalent carboxylic acid and glycol may be one kind, or two or more kinds may be used in combination.

The polyester plasticizer may be any of ester, oligoester, and polyester. The molecular weight of the polyester plasticizer is preferably in the range of 100 to 10000, and more preferably in the range of 600 to 3000 since the effect of imparting plasticity is great.
The viscosity of the polyester plasticizer depends on the molecular structure and molecular weight, but in the case of an adipic acid plasticizer, it is highly compatible with the thermoplastic resin and has a high effect of imparting plasticity. -It is preferable that it is the range of s (25 degreeC). The polyester plasticizer may be used alone or in combination of two or more.

The polyhydric alcohol ester plasticizer is an ester compound (alcohol ester) of a dihydric or higher aliphatic polyhydric alcohol and a monocarboxylic acid, preferably a 2-20 valent aliphatic polyhydric alcohol ester. The polyhydric alcohol ester compound preferably has an aromatic ring or a cycloalkyl ring in the molecule.
Examples of the aliphatic polyhydric alcohol include ethylene glycol, propylene glycol, trimethylolpropane, pentaerythritol and the like.
The monocarboxylic acid can be an aliphatic monocarboxylic acid, an alicyclic monocarboxylic acid, an aromatic monocarboxylic acid, or the like. One type of monocarboxylic acid may be sufficient and a 2 or more types of mixture may be sufficient as it. Further, all of the OH groups contained in the aliphatic polyhydric alcohol may be esterified, or a part of the OH groups may be left as they are.

The aliphatic monocarboxylic acid is preferably a fatty acid having a straight chain or a side chain having 1 to 32 carbon atoms. The carbon number of the aliphatic monocarboxylic acid is more preferably 1-20, and still more preferably 1-10. Examples of such aliphatic monocarboxylic acids include acetic acid, propionic acid, butyric acid, valeric acid, and the like, and acetic acid may be preferable in order to enhance compatibility with the cellulose ester.
Examples of the alicyclic monocarboxylic acid include cyclopentane carboxylic acid, cyclohexane carboxylic acid, cyclooctane carboxylic acid and the like.
Examples of aromatic monocarboxylic acids include: benzoic acid; one having 1 to 3 alkyl groups or alkoxy groups (for example, methoxy group or ethoxy group) introduced into the benzene ring of benzoic acid (for example, toluic acid); benzene ring Aromatic monocarboxylic acids having two or more (for example, biphenyl carboxylic acid, naphthalene carboxylic acid, tetralin carboxylic acid, etc.) are included, and benzoic acid is preferred.

  The molecular weight of the polyhydric alcohol ester plasticizer is not particularly limited, but is preferably in the range of 300 to 1500, and more preferably in the range of 350 to 750. In order to make it hard to volatilize, the one where molecular weight is larger is preferable. In order to increase moisture permeability and increase compatibility with a film substrate, for example, a cellulose ester, a smaller molecular weight is preferable.

  Specific examples of the polyhydric alcohol ester plasticizer include trimethylolpropane triacetate, pentaerythritol tetraacetate, ester compound (A) represented by the general formula (I) described in JP-A-2008-88292, and the like. It is.

The polycarboxylic acid ester plasticizer is an ester compound of a divalent or higher, preferably 2-20 valent polycarboxylic acid and an alcohol compound. The polyvalent carboxylic acid is preferably a 2-20 valent aliphatic polyvalent carboxylic acid, or a 3-20 valent aromatic polyvalent carboxylic acid or a 3-20 valent alicyclic polyvalent carboxylic acid. .
Examples of polyvalent carboxylic acids include trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acid, trimesic acid, pyromellitic acid or derivatives thereof; succinic acid, adipic acid, azelaic acid, sebacic acid, oxalic acid Contains aliphatic polycarboxylic acids such as fumaric acid, maleic acid and tetrahydrophthalic acid; oxypolycarboxylic acids such as tartaric acid, tartronic acid, malic acid and citric acid, etc., and suppresses volatilization from the film. For this, oxypolycarboxylic acids are preferred.

  Examples of the alcohol compound include an aliphatic saturated alcohol compound having a straight chain or a side chain, an aliphatic unsaturated alcohol compound having a straight chain or a side chain, an alicyclic alcohol compound, an aromatic alcohol compound, and the like. Carbon number of an aliphatic saturated alcohol compound or an aliphatic unsaturated alcohol compound becomes like this. Preferably it is 1-32, More preferably, it is 1-20, More preferably, it is 1-10. Examples of the alicyclic alcohol compound include cyclopentanol, cyclohexanol and the like. Examples of the aromatic alcohol compound include phenol, paracresol, dimethylphenol, benzyl alcohol, cinnamyl alcohol and the like. One kind of alcohol compound may be used, or a mixture of two or more kinds may be used.

  The molecular weight of the polyvalent carboxylic acid ester plasticizer is not particularly limited, but is preferably in the range of 300 to 1000, more preferably in the range of 350 to 750. A larger molecular weight of the polyvalent carboxylic acid ester plasticizer is preferable from the viewpoint of suppressing bleeding out. From the viewpoint of moisture permeability and compatibility with cellulose ester, a smaller one is preferable.

  The acid value of the polyvalent carboxylic acid ester plasticizer is preferably 1 mgKOH / g or less, and more preferably 0.2 mgKOH / g or less. The acid value refers to the number of milligrams of potassium hydroxide necessary for neutralizing the acid (carboxy group present in the sample) contained in 1 g of the sample. The acid value is measured according to JIS K0070.

Examples of the polycarboxylic acid ester plasticizer include an ester compound (B) represented by the general formula (II) described in JP-A-2008-88292.
The polyvalent carboxylic acid ester plasticizer may be a phthalic acid ester plasticizer. Examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate and the like.

Examples of glycolate plasticizers include alkylphthalyl alkyl glycolates. Examples of alkyl phthalyl alkyl glycolates include methyl phthalyl methyl glycolate, ethyl phthalyl ethyl glycolate, propyl phthalyl propyl glycolate, butyl phthalyl butyl glycolate, octyl phthalyl octyl glycolate and the like. .
The ester plasticizer includes a fatty acid ester plasticizer, a citrate ester plasticizer, a phosphate ester plasticizer, a trimellitic acid plasticizer, and the like.

  Examples of the fatty acid ester plasticizer include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate and the like. Examples of the citrate plasticizer include acetyl trimethyl citrate, acetyl triethyl citrate, acetyl tributyl citrate and the like. Examples of the phosphate ester plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate and the like. Examples of trimellitic acid plasticizers include octyl trimellitic acid, n-octyl trimellitic acid, isodecyl trimellitic acid, and isononyl trimellitic acid.

  The content of the plasticizer is preferably in the range of 0.5 to 30% by mass with respect to the thermoplastic resin. If the content of the plasticizer is 30% by mass or less, bleeding out hardly occurs.

(UV absorber)
The optical film of the present invention may further contain an ultraviolet absorber. The ultraviolet absorber may be benzotriazole, 2-hydroxybenzophenone, salicylic acid phenyl ester, or the like. Specifically, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- Triazoles such as (3,5-di-t-butyl-2-hydroxyphenyl) benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4 -Benzophenones such as methoxybenzophenone.

Among them, an ultraviolet absorber having a molecular weight of 400 or more is difficult to volatilize at a high boiling point, and is difficult to scatter even at high temperature molding. Therefore, even if the addition amount is relatively small, weather resistance is imparted to the obtained film. Can do.
Examples of ultraviolet absorbers having a molecular weight of 400 or more include
2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1,1,3,3-tetrabutyl) -6 Benzotriazoles such as (2H-benzotriazol-2-yl) phenol];
Hindered amines such as bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate;
2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy]- A hybrid system having both hindered phenol and hindered amine structures in the molecule such as 2,2,6,6-tetramethylpiperidine;
Preferably, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole or 2,2-methylenebis [4- (1,1,3, 3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol]. These may be used alone or in combination of two or more.

(Fine particles)
The optical film of the present invention may contain fine particles composed of an inorganic compound or an organic compound.
Examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate , Calcium phosphate and the like.
Examples of organic compounds include polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethylene carbonate, acrylic styrene resin, silicone resin, polycarbonate resin, benzoguanamine resin, melamine Resin, polyolefin-based powder, polyester-based resin, polyamide-based resin, polyimide-based resin, pulverized classification of organic polymer compound (polyfluorinated ethylene-based resin, starch, etc.), polymer compound synthesized by suspension polymerization method, spray drying High molecular compounds made spherical by the method, dispersion method, etc. are included.

The fine particles can be composed of a compound containing silicon, preferably silicon dioxide, from the viewpoint that the haze of the film can be kept low.
Examples of the fine particles of silicon dioxide include Aerosil R972, R972V, R974, R812, 200, 200V, 300, R202, OX50, TT600 (above, Nippon Aerosil Co., Ltd.).
Among these, Aerosil 200V or Aerosil R972V is particularly preferable because it can improve the slipperiness of the film surface while keeping the haze of the optical film low.
Examples of the fine particles of zirconium oxide include Aerosil R976, R811 (manufactured by Nippon Aerosil Co., Ltd.) and the like.

  Examples of the polymer compound include a silicone resin, a fluororesin, a (meth) acrylic resin, and the like, preferably a silicone resin, and more preferably a silicone resin having a three-dimensional network structure. Examples of such silicone resins include Tospearl 103, 105, 108, 120, 145, 3120, 240 (above, manufactured by Toshiba Silicone Co., Ltd.) and the like.

The average particle diameter of the primary particles of the fine particles is preferably in the range of 5 to 400 nm, more preferably in the range of 10 to 300 nm. The fine particles may mainly form secondary aggregates having a particle size in the range of 0.05 to 0.30 μm. If the average particle size of the fine particles is in the range of 100 to 400 nm, they can exist as primary particles without agglomeration.
It is preferable to contain fine particles so that the dynamic friction coefficient of at least one surface of the optical film is in the range of 0.2 to 1.0.
The content of the fine particles is preferably in the range of 0.01 to 1.00% by mass, and more preferably in the range of 0.05 to 0.50% by mass with respect to the thermoplastic resin.

(Dispersant)
The optical film of the present invention may further contain a dispersant from the viewpoint of enhancing the dispersibility of the fine particles. The dispersant is one or more selected from amine-based dispersants and carboxy group-containing polymer dispersants.

  The amine dispersant is preferably an alkylamine or an amine salt of polycarboxylic acid, and specific examples thereof include polyester acid, polyether ester acid, fatty acid, fatty acid amide, polycarboxylic acid, alkylene oxide, polyalkylene oxide. , A compound obtained by aminating polyoxyethylene fatty acid ester, polyoxyethylene glycerin fatty acid ester, and the like. Examples of amine salts include amidoamine salts, aliphatic amine salts, aromatic amine salts, alkanolamine salts, polyvalent amine salts and the like.

  Specific examples of the amine dispersant include polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, tripropylamine, diethylaminoethylamine, dimethylaminopropylamine, diethylaminopropylamine and the like. Examples of commercially available products include Solspers series (manufactured by Lubrizol), Ajisper series (manufactured by Ajinomoto Co., Inc.), BYK series (manufactured by Big Chemie), EFKA series (manufactured by EFKA), and the like.

  The carboxy group-containing polymer dispersant is preferably a polycarboxylic acid or a salt thereof, and may be, for example, polycarboxylic acid, ammonium polycarboxylate, sodium polycarboxylate, or the like. Specific examples of the carboxy group-containing polymer dispersant include polyacrylic acid, ammonium polyacrylate, sodium polyacrylate, ammonium polyacrylate copolymer, polymaleic acid, ammonium polymaleate, sodium polymaleate and the like.

The amine-based dispersant and the carboxy group-containing polymer dispersant may be used after being dissolved in a solvent component, or may be commercially available.
The content of the dispersant is preferably 0.2% by mass or more based on the fine particles, although it depends on the type of the dispersant. When the content of the dispersant is 0.2% by mass or more with respect to the fine particles, the dispersibility of the fine particles can be sufficiently improved.

  When the optical film of the present invention further contains a surfactant or the like, adsorption of the dispersant to the surface of the fine particles is less likely to occur than the surfactant, and the fine particles may be easily reaggregated. Since the dispersant is expensive, its content is preferably as small as possible. On the other hand, when the content of the dispersant is too small, poor wettability of fine particles and a decrease in dispersion stability are likely to occur. Therefore, the content of the dispersant when the optical film of the present invention further contains a surfactant or the like can be about 0.05 to 10.00 parts by mass with respect to 10 parts by mass of the fine particles.

(Other additives)
The optical film of the present invention may further contain an antioxidant, an antistatic agent, a flame retardant and the like for preventing thermal decomposition during heating and coloring due to heat.
Phosphorus flame retardants include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphate ester, One or more kinds selected from halogen condensed phosphoric acid ester, halogen-containing condensed phosphonic acid ester, halogen-containing phosphorous acid ester and the like can be mentioned. Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl) phosphate. , Tris (tribromoneopentyl) phosphate, and the like.

<Physical properties of optical film>
In the optical film of the present invention, the retardation value Ro in the in-plane direction of the optical film measured at wavelengths of 450 nm and 550 nm under the conditions of a temperature of 23 ° C. and a relative humidity of 55% is Ro (450) and Ro (550), respectively. ), Ro (450) and Ro (550) satisfy the following formulas (b1) and (b2).
(B1) 1.50 ≦ {Ro (550) −Ro (550) _P } /d≦3.00
(B2) 0.72 ≦ Ro (450) / Ro (550) ≦ 0.96
[In the formula (b1), Ro (550) _P represents the retardation value in the in-plane direction of the optical film which does not contain the compound satisfying the formula (a1) and the formula (a2), measured at a wavelength of 550 nm. {Ro (550) -Ro (550) _P } represents a change amount (nm) of the retardation value due to the inclusion of the compound. d represents the film thickness (μm) of the optical film. ]

In the above formula (b1), {Ro (550) -Ro (550) _P } / d (nm / μm) represents the retardation development property of the optical film per unit film thickness of 1 μm imparted by the compound. The optical film satisfying the above formula (b1) can uniformly impart the necessary phase difference to the light without depending on the wavelength of the light by containing the compound satisfying the formula (a1) and the formula (a2). Can do.
The above Ro (450) / Ro (550) represents the optical wavelength dependency of the retardation of the optical film, that is, the wavelength dispersion. An optical film in which Ro (450) / Ro (550) satisfies the above formula (b2) exhibits excellent reverse wavelength dispersion and can impart a phase difference to light in a wide wavelength region.

In the optical film of the present invention, it is preferable that the Ro (550) further satisfies the following formula (b3). An optical film satisfying the following formula (b3) can be used as a λ / 4 retardation film.
(B3) 110 nm ≦ Ro (550) ≦ 170 nm
Among these, Ro (550) preferably satisfies 120 nm ≦ Ro (550) ≦ 160 nm, and more preferably satisfies 130 nm ≦ Ro (550) ≦ 150 nm.

The optical film of the present invention has Ro (550) and Ro when the retardation value Ro in the in-plane direction of the optical film measured at a wavelength of 650 nm under the conditions of 23 ° C. and 55% RH is Ro (650). (650) preferably satisfies the following formula (b4).
(B4) 0.83 ≦ Ro (550) / Ro (650) ≦ 0.97

  The optical film satisfying the above formulas (b1) to (b4) can uniformly impart a λ / 4 retardation to light in a wide wavelength region, and can preferably function as a λ / 4 retardation film. Moreover, light leakage or the like can also be reduced when an image display device including an optical film satisfying the above formulas (b1) to (b4) is displayed in black. Specifically, when the formula (b2) is satisfied, the blue reproducibility is high, and when the formula (b4) is satisfied, the red reproducibility is high. Among them, Ro (450) and Ro (550) satisfy 0.79 ≦ Ro (450) / Ro (550) ≦ 0.89, and Ro (550) and Ro (650) satisfy 0.84 ≦ Ro. It is more preferable that (550) / Ro (650) ≦ 0.93 is satisfied.

  Ro (550) representing the phase difference expression, and Ro (450) / Ro (550) and Ro (550) / Ro (650) representing the wavelength dispersion represent the above-described formulas (a1) and (a2). It can adjust with the compound to satisfy | fill or extending | stretching conditions.

  Further, in the optical film of the present invention, when the retardation value Rt in the thickness direction of the optical film measured at a wavelength of 550 nm is Rt (550), the Rt (550) is 50 nm ≦ Rt (550) ≦ 250 nm. It is preferable to satisfy.

The above Ro and Rt are defined by the following formulas (I) and (II), respectively.
Formula _{(I): Ro = (n} x -n y) × d
Formula (II): Rt = {(n _x + n _y ) / 2−n _z } × d
In [Formula (I) and (II), n _x represents a refractive index in the slow axis direction x in which the refractive index is maximized in the plane direction of the optical film. n _y represents a refractive index in the direction y orthogonal to the slow axis direction x in the in-plane direction of the optical film. _nz represents the refractive index in the thickness direction z of the optical film. d represents the film thickness (nm) of the optical film. ]

Ro and Rt can be measured using an automatic birefringence meter, for example, AxoScan manufactured by Axometric, KOBRA-21ADH manufactured by Oji Scientific Instruments.
When using AxoScan, specifically, it can be measured by the following method.
1) Condition the optical film at 23 ° C. and 55% RH. The average refractive index of the optical film after humidity adjustment at wavelengths of 450 nm, 550 nm and 650 nm is measured using an Abbe refractometer and a spectral light source, respectively. Moreover, the film thickness d (nm) of an optical film is measured using a film thickness meter.
2) In-plane retardation values Ro (450) and Ro (550) when light having wavelengths of 450 nm, 550 nm, and 650 nm is incident on the optical film after humidity adjustment in parallel with the normal line of the film surface. And Ro (650) are measured with an AxoScan. The measurement can be performed under conditions of 23 ° C. and 55% RH.
3) The in-plane slow axis of the optical film is confirmed by AxoScan. When light having wavelengths of 450 nm, 550 nm, and 650 nm is incident from an angle of φ (incident angle (φ)) with respect to the normal of the surface of the optical film, with the confirmed slow axis as the tilt axis (rotation axis) The phase difference value R (φ) is measured. The measurement can be performed under conditions of 23 ° C. and 55% RH. R (φ) can be measured at 6 points every 10 ° in the range of 0 ° to 50 °.
4) Ro (450), Ro (550) and Ro (650) measured in 2) above, and R (φ) measured in each wavelength of 450 nm, 550 nm and 650 nm in 3) above, and 1) measured average refractive index, and a film thickness d, by _AxoScan, calculates the n x, _{n y} and _{n z.} Based on the above formula (II), thickness direction retardation values Rt (450), Rt (550), and Rt (650) at wavelengths of 450 nm, 550 nm, and 650 nm, respectively, are calculated.

  The angle formed by the slow axis in the plane of the optical film and the film transport direction (referred to as the orientation angle) is preferably in the range of 40 to 50 °. When the orientation angle is within the above range, the film is unwound from the roll body, and is unwound from the roll body with an optical film having a slow axis in an oblique direction with respect to the long direction (conveying direction). A circularly polarizing plate can be easily manufactured by laminating a polarizing film having a transmission axis parallel to the transport direction) in a roll-to-roll manner so that the longitudinal directions overlap each other. Can do. There is little cut loss of the film, which is advantageous in production. The orientation angle of the optical film can be measured with an automatic birefringence meter KOBRA-21ADH (Oji Scientific Instruments).

The film thickness of the optical film is preferably in the range of 10 to 100 μm from the viewpoint of thinning the display device and productivity. If the film thickness is 10 μm or more, a certain level of film strength and retardation can be expressed. If the film thickness is 100 μm or less, fluctuations in phase difference due to heat and humidity can be suppressed. Preferably, it exists in the range of 20-70 micrometers.
The film thickness unevenness of the optical film of the present invention is preferably in the range of 0 to 5 μm, more preferably in the range of 0 to 3 μm, and still more preferably in the range of 0 to 2 μm in both the thickness direction and the width direction. It is.

The haze (total haze) of the optical film is preferably less than 1%, more preferably 0.5% or less, and even more preferably 0.2% or less. If the haze is less than 1%, the transparency of the film does not decrease and the film functions sufficiently as an optical film.
The haze (total haze) of the optical film can be measured with a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7136. The light source of the haze meter may be a 5V9W halogen sphere, and the light receiving portion may be a silicon photocell (with a relative visibility filter). The haze can be measured under conditions of 23 ° C. and 55% RH.

The visible light transmittance of the optical film of the present invention is preferably 90% or more, and more preferably 93% or more.
In the optical film of the present invention, the elongation at break in at least one direction measured in accordance with JIS-K7127-1999 is preferably 10% or more, more preferably 20% or more, and further preferably 30. % Or more.

The optical film of the present invention is used as an optical film for image display devices such as organic EL display devices and liquid crystal display devices. Specifically, it is used as a polarizing plate protective film, a retardation film, an optical compensation film, and an antireflection film, and preferably used as a λ / 4 retardation film.
The λ / 4 retardation film has an in-plane retardation value Ro of about ¼ of a predetermined light wavelength (usually visible light region). The λ / 4 retardation film is preferably composed of a single layer of the optical film of the present invention. The λ / 4 retardation film is preferably used for an antireflection film of an organic EL display device.

<Method for producing optical film>
The optical film of the present invention can be produced by a solution casting method or a melt casting method. The solution casting method is preferable from the viewpoint of suppressing optical defects such as coloring of the optical film, foreign matter defects, and die line, and the melt casting method is preferable from the viewpoint of suppressing the solvent remaining in the optical film.

A) Solution casting method A method for producing an optical film containing a thermoplastic resin by a solution casting method is as follows: A1) A dope is prepared by dissolving at least a thermoplastic resin and, if necessary, other additives in a solvent. A2) a step of casting the dope on an endless metal support, A3) a step of evaporating the solvent from the cast dope to form a web, A4) a step of peeling the web from the metal support, A5) After drying the web, it includes a step of drawing to obtain a film.

A1) Dope preparation step In a melting pot, a dope is prepared by dissolving a thermoplastic resin and, if necessary, other additives in a solvent.
A solvent can be used without a restriction | limiting, if a thermoplastic resin, another additive, etc. are melt | dissolved. For example, as a chlorinated organic solvent, methylene chloride, as a non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Preferably, methylene chloride, methyl acetate, ethyl acetate, acetone or the like can be used.

The dope preferably further contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the ratio of the alcohol in the dope is high, the web is gelled and peeling from the metal support becomes easy. On the other hand, when the ratio of alcohol in the dope is small, dissolution of the thermoplastic resin in the non-chlorine organic solvent system can be promoted.
Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol and the like. Of these, ethanol is preferred because of high dope stability, relatively low boiling point, and high drying properties.
Especially, it is preferable that dope contains the methylene chloride of a solvent, and a C1-C4 linear or branched aliphatic alcohol.

  The concentration of the thermoplastic resin in the dope is preferably higher in order to reduce the drying load. However, if the concentration of the thermoplastic resin is too high, it is difficult to filter. Therefore, the concentration of the thermoplastic resin in the dope is preferably in the range of 10 to 35% by mass, and more preferably in the range of 15 to 25% by mass.

  The method of dissolving the thermoplastic resin in the solvent can be, for example, a method of dissolving under heating and pressure. A higher heating temperature is preferable from the viewpoint of increasing the solubility of the thermoplastic resin. If it is too high, it is necessary to increase the pressure and the productivity is lowered. Therefore, the heating temperature is preferably in the range of 45 to 120 ° C.

The additive may be added batchwise to the dope, or an additive solution may be separately prepared and added inline. In particular, it is preferable to add all or part of the fine particles in-line in order to reduce the load on the filter medium.
When the additive solution is added in-line, it is preferable to dissolve a small amount of thermoplastic resin in order to facilitate mixing with the dope. The content of the preferred thermoplastic resin can be in the range of 1 to 10 parts by mass, more preferably in the range of 3 to 5 parts by mass with respect to 100 parts by mass of the solvent.
For in-line addition and mixing, for example, a static mixer (manufactured by Toray Engineering) or an in-line mixer such as SWJ (Toray static in-tube mixer Hi-Mixer) is preferably used.

The obtained dope may contain insoluble matters such as impurities contained in a thermoplastic resin as a raw material, for example. Such an insoluble matter can become a bright spot foreign material in the obtained film. In order to remove insoluble matter, it is preferable to further filter the obtained dope.
The dope filtration is preferably performed so that the number of bright spot foreign substances in the obtained film is a certain value or less. Specifically, the number of bright spot foreign matters having a diameter of 0.01 mm or more is 200 / cm ² or less, preferably 100 / cm ² or less, more preferably 50 / cm ² or less, and still more preferably 30 Pieces / cm ² or less, particularly preferably 10 pieces / cm ² or less.

The bright spot foreign matter having a diameter of 0.01 mm or less is also preferably 200 pieces / cm ² or less, more preferably 100 pieces / cm ² or less, further preferably 50 pieces / cm ² or less, It is more preferably 30 pieces / cm ² or less, particularly preferably 10 pieces / cm ² or less, and most preferably none.

The number of bright spot foreign matter on the film can be measured by the following procedure.
1) Two polarizing plates are arranged in a crossed Nicol state, and the obtained film is arranged between them.
2) When light is applied from the side of one polarizing plate and observed from the side of the other polarizing plate, the number where the light appears to leak is counted as a foreign object.

A2) Casting step The dope is cast on the endless metal support from the slit of the pressure die.
As the metal support, a stainless steel belt or a drum having a cast-plated surface is preferably used. The surface of the metal support is preferably mirror-finished.
The width of the cast can be in the range of 1-4 m. The surface temperature of the metal support in the casting process is set to −50 ° C. or higher and below the temperature at which the solvent boils and does not foam. A higher temperature is preferable because the web can be dried at a higher speed, but it is within a temperature range in which foaming of the web and deterioration of flatness can be prevented.

  The surface temperature of the metal support is preferably in the range of 0 to 100 ° C, more preferably in the range of 5 to 30 ° C. Alternatively, the metal support may be cooled so that the web is gelled and can be peeled off from the drum in a state containing a large amount of residual solvent.

The method for adjusting the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of bringing hot water into contact with the back side of the metal support. It is preferable to use hot water because heat transfer is more efficient, and the time until the temperature of the metal support becomes constant is shorter.
When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. . In particular, it is preferable to efficiently dry by changing the temperature of the metal support and the temperature of the drying air during the period from casting to peeling.

A3) Solvent evaporation step The web (dope film obtained by casting the dope on the metal support) is heated on the metal support to evaporate the solvent. The drying method and drying conditions of the web can be the same as in the above-described A2) casting step.

A4) Peeling Step The web obtained by evaporating the solvent on the metal support is peeled off at the peeling position on the metal support.
The residual solvent amount of the web at the time of peeling at the peeling position on the metal support is preferably within the range of 10 to 150% by mass in order to improve the flatness of the obtained film. % Or in the range of 60 to 130 mass%, more preferably in the range of 20 to 30 mass% or 70 to 120 mass%.

The amount of residual solvent in the web is defined by the following formula.
Residual solvent amount (%) = (mass before web heat treatment−mass after web heat treatment) / (mass after web heat treatment) × 100
The heat treatment for measuring the residual solvent amount means a heat treatment at 115 ° C. for 1 hour.

A5) Drying and stretching step The web obtained by peeling from the metal support is dried as necessary and then stretched. The web may be dried while being conveyed by a large number of rollers arranged above and below, or may be dried while being conveyed while fixing both ends of the web with clips.
The method of drying the web may be a method of drying with hot air, infrared rays, a heating roller, microwaves, or the like, and a method of drying with hot air is preferable because it is simple.

An optical film having a desired retardation is obtained by stretching the web. The retardation of the optical compensation film can be controlled by adjusting the magnitude of tension on the web.
The web is stretched in any of the web width direction (TD direction), the transport direction (MD direction), or the oblique direction. In order to set the angle formed by the slow axis in the plane of the obtained optical film and the transport direction within the range of 40 to 50 °, at least an oblique direction, specifically, 45 ° with respect to the web transport direction. It is preferable to stretch in the direction.
A polarizing film unwound from a roll body by stretching in an oblique direction and having a transmission axis in the longitudinal direction, and an optical unwinding from the roll body and having a slow axis at an angle of 45 ° with respect to the longitudinal direction A circularly polarizing plate can be easily produced by simply laminating a film with a roll-to-roll so that the longitudinal directions overlap each other. The cut loss of the film can be reduced, which is advantageous in production.

The web may be stretched uniaxially or biaxially. Biaxial stretching may be sequential biaxial stretching or simultaneous biaxial stretching.
The draw ratio depends on the film thickness of the obtained optical film and the required retardation, but may be in the range of 1.5 to 2.5 times in the oblique direction, for example.
The stretching temperature is preferably in the range of 120 to 230 ° C, more preferably in the range of 150 to 220 ° C, and even more preferably in the range of more than 150 ° C and not more than 210 ° C.

  The stretching method of the web is not particularly limited, and a method of making a difference in circumferential speed between a plurality of rollers and stretching in the casting direction (conveying direction) using the circumferential speed difference (roller stretching method), both ends of the web Fix with clips and pins, widen the gap between clips and pins in the casting direction and stretch in the casting direction, spread in the width direction and stretch in the width direction, both in the casting direction and in the width direction It may be a method of expanding and stretching in both the casting direction and the width direction (tenter stretching method).

In order to extend in an oblique direction, a tenter that can independently control the web gripping length (distance from the start of gripping to the end of gripping) left and right by a gripping means that grips the left and right in the width direction may be used. These stretching methods may be combined.
Examples of the stretching apparatus having a mechanism for stretching in an oblique direction include the stretching apparatus described in Example 1 of Japanese Patent Application Laid-Open No. 2003-340916, the stretching apparatus illustrated in FIG. The stretching apparatus described in 2007-30466, the stretching apparatus used in Example 1 of JP 2007-94007 A, and the like are included.
The residual solvent of the web at the start of stretching is preferably 20% by mass or less, more preferably 15% by mass or less.

  The stretched film is dried as necessary and then wound. As described above, the film may be dried while being transported by a large number of rollers arranged on the top and bottom (roller method), or may be dried while being transported while fixing both ends of the web with clips. (Tenter method).

B) Melt Casting Method The method for producing the optical film of the present invention by the melt casting method is as follows: B1) Step of producing molten pellets (pelletizing step), B2) Step of extruding after melting and kneading the molten pellets (melting) Extruding step), B3) a step of cooling and solidifying the molten resin to obtain a web (cooling solidification step), and B4) a step of stretching the web (stretching step).

B1) Pelletization process It is preferable that the resin composition containing the thermoplastic resin as the main component of the optical film is previously kneaded and pelletized. Pelletization can be performed by a known method. For example, a resin composition containing the above-described thermoplastic resin and, if necessary, an additive such as a plasticizer is melt-kneaded with an extruder, and then die-molded. Extruded into strands. The molten resin extruded in a strand form can be cooled with water or air, and then cut to obtain pellets.
The pellet raw material is preferably dried before being supplied to the extruder in order to prevent decomposition.

  The mixture of the antioxidant and the thermoplastic resin may be mixed with each other, may be mixed by impregnating the thermoplastic resin with an antioxidant dissolved in a solvent, or the antioxidant may be thermoplastic. The resin may be sprayed and mixed. The atmosphere around the feeder portion of the extruder and the outlet portion of the die is preferably an atmosphere of dehumidified air or nitrogen gas in order to prevent deterioration of the raw material of the pellet.

In an extruder, it is preferable to knead at a low shearing force or at a low temperature so as not to cause deterioration of the resin (decrease in molecular weight, coloring, gel formation, etc.). For example, when kneading with a twin screw extruder, it is preferable to use a deep groove type screw and to rotate the two screws in the same direction. In order to knead uniformly, it is preferable that two screw shapes mesh with each other.
An optical film may be produced by melting and kneading a thermoplastic resin that has not been melt-kneaded as a raw material with an extruder without pelletizing the resin composition containing the thermoplastic resin.

B2) Melt extrusion step The obtained molten pellets and other additives as required are supplied from the hopper to the extruder. The supply of pellets is preferably performed under vacuum, reduced pressure, or an inert gas atmosphere in order to prevent oxidative decomposition of the pellets. And it melt-kneads the melt pellet which is a film material, and another additive as needed with an extruder.

The melting temperature of the film material in the extruder is preferably in the range of Tg to (Tg + 100) ° C., more preferably when the glass transition temperature of the film is Tg (° C.), although it depends on the type of film material. Is within the range of (Tg + 10) to (Tg + 90) ° C.
Furthermore, when additives such as plasticizers and fine particles are added in the middle of the extruder, a mixing device such as a static mixer is further arranged on the downstream side of the extruder to uniformly mix these components. May be.

The molten resin extruded from the extruder is filtered through a leaf disc filter or the like as necessary, and further mixed with a static mixer or the like, and extruded from a die into a film.
The extrusion flow rate is preferably stabilized using a gear pump. Moreover, it is preferable that the leaf disk filter used for removal of a foreign material is a stainless fiber sintered filter. The stainless steel fiber sintered filter is an integrated, intricately intertwined stainless steel fiber body that is compressed and sintered by integrating the contact points. The density is changed according to the thickness of the fiber and the amount of compression, and the filtration accuracy is adjusted. it can.
The melting temperature of the resin at the exit portion of the die can be in the range of about 200-300 ° C.

B3) Cooling and solidifying step The resin extruded from the die is nipped between the cooling roller and the elastic touch roller to make the film-like molten resin a predetermined thickness. Then, the film-like molten resin is cooled and solidified stepwise by a plurality of cooling rollers.

The surface temperature of the cooling roller can be Tg (° C.) or lower when the glass transition temperature of the obtained film is Tg (° C.). The surface temperatures of the plurality of cooling rollers may be different.
The elastic touch roller is also called a pinching rotary body. A commercially available elastic touch roller can also be used. The film surface temperature on the elastic touch roller side can be in the range of Tg to (Tg + 110) ° C. of the film.

  The film-like molten resin solidified from the cooling roller is peeled off by a peeling roller or the like to obtain a web. When peeling the film-like molten resin, it is preferable to adjust the tension in order to prevent deformation of the obtained web.

B4) Stretching step The obtained web is stretched with a stretching machine to obtain a film. Stretching is performed in any of the web width direction, the conveyance direction, or the oblique direction. In order to set the angle formed by the slow axis in the plane of the obtained optical film and the transport direction within the range of 40 to 50 °, at least an oblique direction, specifically, 45 ° with respect to the web transport direction. It is preferable to stretch in the direction.
The stretching method, stretching ratio, and stretching temperature of the web can be the same as described above.

<Circularly polarizing plate>
The circularly polarizing plate of the present invention comprises a polarizer (linearly polarizing film) and the optical film of the present invention disposed on at least one surface of the polarizer. The optical film of the present invention may be directly bonded to the polarizer, or may be disposed via another layer or film.

  The polarizer may be an iodine polarizing film, a dye polarizing film using a dichroic dye, or a polyene polarizing film. In general, the iodine polarizing film and the dye polarizing film may be a film obtained by uniaxially stretching a polyvinyl alcohol film and then dyeing with iodine or a dichroic dye. After the film is dyed with iodine or a dichroic dye, it may be a uniaxially stretched film (preferably a film further subjected to a durability treatment with a boron compound). The transmission axis of the polarizer is parallel to the stretching direction of the film.

The polyvinyl alcohol film may be a film formed from a polyvinyl alcohol aqueous solution. The polyvinyl alcohol film is preferably an ethylene-modified polyvinyl alcohol film because it is excellent in polarizing performance and durability performance and has few color spots.
Examples of dichroic dyes include azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, anthraquinone dyes, and the like.

The thickness of the polarizer is preferably in the range of 5 to 30 μm, and more preferably in the range of 10 to 20 μm.
The angle at which the transmission axis of the polarizer intersects the in-plane slow axis of the optical film of the present invention is preferably in the range of 40 to 50 °.
A reflective polarizing plate may be further disposed between the polarizer and the optical film of the present invention. The reflective polarizing plate transmits linearly polarized light in a direction parallel to the transmission axis of the polarizer and reflects linearly polarized light in a direction different from the transmission axis. The organic EL display device having such a circularly polarizing plate can emit more light emitted from the light emitting layer to the outside.

  Examples of the reflective polarizing plate include a birefringent optical polarizer (described in JP-A-8-503313) in which polymer thin films having different refractive indexes in one direction are alternately laminated, and a polarization separation film having a cholesteric structure (special Described in Kaihei 11-44816). Moreover, you may arrange | position a protective film further on the surface of a polarizer.

  When the optical film of the present invention is disposed on one surface of the polarizer, a transparent protective film other than the optical film of the present invention may be disposed on the other surface of the polarizer. The transparent protective film is not particularly limited, and may be a normal cellulose ester film or the like. Examples of the cellulose ester film include commercially available cellulose ester films (for example, Konica Minoltak KC8UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-X8 -C, KC8UXW-RHA-NC, KC4UXW-RHA-NC (manufactured by Konica Minolta Advanced Layer Co., Ltd.) and the like are preferably used.

Although the thickness in particular of a transparent protective film is not restrict | limited, It can be set as the range of about 10-200 micrometers, Preferably it is in the range of 10-100 micrometers, More preferably, it is 10-70 micrometers.
When the transparent protective film or λ / 4 retardation film is disposed on the outermost surface of the display, a transparent hard coat layer, an antiglare layer, on the outermost surface of the transparent protective film or λ / 4 retardation film, An antireflection layer or the like may be further provided.

The circularly polarizing plate can be manufactured through a step of laminating the polarizer and the optical film of the present invention. As the adhesive used for bonding, for example, a completely saponified polyvinyl alcohol aqueous solution or the like is preferably used.
The circularly polarizing plate can be preferably used for an image display device such as an organic EL display device or a liquid crystal display device described later.

<Image display device>
The image display device of the present invention includes the optical film of the present invention. Examples of the image display device of the present invention include an organic EL display device and a liquid crystal display device.
FIG. 1 is a schematic diagram illustrating an example of a configuration of an organic EL display device.
As shown in FIG. 1, the organic EL display device 10 includes a light reflecting electrode 12, a light emitting layer 14, a transparent electrode layer 16, a transparent substrate 18, and a circularly polarizing plate 20 in this order. The circularly polarizing plate 20 includes a λ / 4 retardation film 20A and a polarizer 20B. The λ / 4 retardation film 20A can be the optical film of the present invention, and the polarizer 20B is a linear polarizing film.

The light reflecting electrode 12 is preferably made of a metal material having a high light reflectance. Examples of the metal material include Mg, MgAg, MgIn, Al, LiAl, and the like. The flatter surface of the light reflecting electrode 12 is preferable because irregular reflection of light can be prevented.
The light reflecting electrode 12 can be formed by a sputtering method. The light reflecting electrode 12 may be patterned. Patterning can be performed by etching.

The light emitting layer 14 includes an R (red) light emitting layer, a G (green) light emitting layer, and a B (blue) light emitting layer. Each light emitting layer contains a light emitting material. The light emitting material may be an inorganic compound or an organic compound, and is preferably an organic compound.
Each of the R, G, and B light-emitting layers further includes a charge transport material, and may further have a function as a charge transport layer. Each of the R, G, and B light emitting layers further includes a hole transport material, and may further have a function as a hole transport layer. When each of the R, G, and B light emitting layers does not include a charge transport material or a hole transport material, the organic EL display device 10 may further include a charge transport layer or a hole transport layer.

  The light emitting layer 14 can be formed by evaporating a light emitting material. Each of the R, G, and B light emitting layers is obtained by patterning. Patterning can be performed using a photomask or the like.

The transparent electrode layer 16 can generally be an ITO (indium tin oxide) electrode. The transparent electrode layer 16 can be formed by a sputtering method or the like. The transparent electrode layer 16 may be patterned. Patterning can be performed by etching.
The transparent substrate 18 only needs to be capable of transmitting light, and may be a glass substrate, a plastic film, or the like.

  The circularly polarizing plate 20 is arranged such that the λ / 4 retardation film 20A is located on the transparent substrate 18 side, and the polarizer 20B is located on the observer OB side.

  When the organic EL display device 10 is energized between the light reflecting electrode 12 and the transparent electrode layer 16, the light emitting layer 14 emits light and can display an image. In addition, since each of the R, G, and B light-emitting layers is configured to be energized, a full-color image can be displayed.

  The optical film of the present invention or the circularly polarizing plate including the optical film is not limited to the organic EL display device having the above-described configuration, but also includes international patent application WO96 / 34514, JP-A-9-127858, and 11-45058. The present invention can also be applied to the organic EL display device described in the publication. In that case, the optical film or the circularly polarizing plate of the present invention may be disposed in place of or together with the antireflection means of the organic EL display device provided in advance. The optical film or circularly polarizing plate of the present invention can also be applied to an inorganic EL display device described in, for example, “Electroluminescence Display” (Toshio Higuchi, Sangyo Tosho Co., Ltd., published in 1991).

FIG. 2 is a schematic diagram for explaining the antireflection function of the circularly polarizing plate 20.
When light including linearly polarized light a1 and b1 enters from the outside in parallel to the normal line of the display screen of the organic EL display device 10, only linearly polarized light b1 parallel to the transmission axis direction of the polarizer 20B passes through the polarizer 20B. . The other linearly polarized light a1 that is not parallel to the transmission axis of the polarizer 20B is absorbed by the polarizer 20B. The linearly polarized light b1 that has passed through the polarizer 20B is converted to circularly polarized light c2 by passing through the λ / 4 retardation film 20A. When the circularly polarized light c2 is reflected by the light reflecting electrode 12 (see FIG. 1) of the organic EL display device 10, the circularly polarized light c2 becomes reverse circularly polarized light c3. The reversely polarized circularly polarized light c3 passes through the λ / 4 retardation film 20A and is converted into linearly polarized light b3 orthogonal to the transmission axis of the polarizer 20B. The linearly polarized light b3 is absorbed without passing through the polarizer 20B.

  Thus, since all the light (including linearly polarized light a1 and b1) incident on the organic EL display device 10 from the outside is absorbed by the polarizer 20B, even if it is reflected by the light reflecting electrode of the organic EL display device, Does not exit to the outside. Therefore, it is possible to prevent a decrease in image display characteristics due to the reflection of the background.

  The λ / 4 retardation film 20A using the optical film of the present invention exhibits excellent reverse wavelength dispersion, and therefore can impart a λ / 4 retardation to light in a wide wavelength region. Therefore, most of the light incident from the outside can be prevented from leaking to the outside of the organic EL display device 10. As a result, light leakage in the front direction when the organic EL display device 10 is displayed in black can be suppressed, and reflection can be prevented.

  Furthermore, since the λ / 4 retardation film 20A using the optical film of the present invention exhibits high retardation expression in addition to excellent reverse wavelength dispersion, the thickness of the film can be reduced. Therefore, the difference between the color in the front direction and the color in the oblique direction can be reduced, and the visibility from the oblique direction can be enhanced.

  The light from the inside of the organic EL display device 10, that is, the light from the light emitting layer 14, includes two circularly polarized components of circularly polarized light c3 and c4. One circularly polarized light c3 is converted to linearly polarized light b3 by passing through the λ / 4 retardation film 20A as described above, and is absorbed without passing through the polarizer 20B. The other circularly polarized light c4 passes through the λ / 4 retardation film 20A and is converted into linearly polarized light b4 parallel to the transmission axis of the polarizer 20B. The linearly polarized light b4 passes through the polarizer 20B and becomes linearly polarized light b4, which is recognized as an image.

  A reflective polarizing plate (not shown) may be further disposed between the polarizer 20B and the λ / 4 retardation film 20A to reflect the linearly polarized light b3 orthogonal to the transmission axis of the polarizer 20B. The reflective polarizing plate can reflect the linearly polarized light b3 without being absorbed by the polarizer 20B, reflect it again by the light reflecting electrode 12, and convert it into linearly polarized light b4 parallel to the transmission axis of the polarizer 20B. . By further disposing a reflective polarizing plate, all of the light emitted by the light emitting layer 14 (circularly polarized light c3 and c4) can be emitted to the outside.

FIG. 3 is a schematic diagram illustrating an example of the configuration of the liquid crystal display device.
As illustrated in FIG. 3, the liquid crystal display device 30 includes a liquid crystal cell 40, two polarizing plates 50 and 60 that sandwich the liquid crystal cell 40, and a backlight 70.

  The display method of the liquid crystal cell 40 is not particularly limited, and is a TN (Twisted Nematic) method, STN (Super Twisted Nematic) method, IPS (In-Plane Switching) method, OCB (Optically Compensated Birefringence) method, VA (Vertical Alignment). There are methods (including MVA: Multi-domain Vertical Alignment, PVA: Patterned Vertical Alignment), and HAN (Hybrid Aligned Nematic). In order to increase the contrast, the VA (MVA, PVA) method is preferable.

A VA liquid crystal cell includes a pair of transparent substrates and a liquid crystal layer sandwiched between them.
Of the pair of transparent substrates, one transparent substrate is provided with a pixel electrode for applying a voltage to the liquid crystal molecules. The counter electrode may be disposed on one transparent substrate (transparent substrate on which the pixel electrode is disposed) or may be disposed on the other transparent substrate.

  The liquid crystal layer includes liquid crystal molecules having negative or positive dielectric anisotropy. Liquid crystal molecules are liquid crystal molecules when no voltage is applied (when no electric field is generated between the pixel electrode and the counter electrode) due to the alignment regulating force of the alignment film provided on the liquid crystal layer side surface of the transparent substrate. Are oriented so that their long axes are substantially perpendicular to the surface of the transparent substrate.

  In the liquid crystal cell configured as described above, an electric field is generated between the pixel electrode and the counter electrode by applying a voltage corresponding to the image signal to the pixel electrode. Thereby, the liquid crystal molecules initially aligned perpendicularly to the surface of the transparent substrate are aligned so that the major axis thereof is in the horizontal direction with respect to the substrate surface. In this way, the liquid crystal layer is driven, and the image display is performed by changing the transmittance and reflectance of each sub-pixel.

The polarizing plate 50 is disposed on the viewer OB side, and includes a polarizer 52 and protective films 54 and 56 that sandwich the polarizer 52.
The polarizing plate 60 is disposed on the backlight 70 side, and includes a polarizer 62 and protective films 64 and 66 that sandwich the polarizer 62.
One of the protective films 56 and 64 may be omitted as necessary.
Any of the protective films 54, 56, 64, and 66 can be used as the optical film of the present invention.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" may be used in an Example, unless there is particular notice, it represents "mass part" or "mass%".

[Example 1]
<Preparation of optical film 1>
The following components were stirred and mixed with a dissolver for 50 minutes and then dispersed with Manton Gorin to prepare a fine particle dispersion.
(Fine particle dispersion)
Fine particles (Aerosil R972V manufactured by Nippon Aerosil Co., Ltd.) 11 parts by mass Ethanol 89 parts by mass

Among the components of the following fine particle addition liquid, methylene chloride was put into a dissolution tank, and the prepared fine particle dispersion was slowly added with sufficient stirring with the following addition amount. Subsequently, after carrying out dispersion | distribution with an attritor, it filtered by Finemet NF (made by Nippon Seisen Co., Ltd.), and prepared the fine particle addition liquid.
(Particulate additive solution)
99 parts by mass of methylene chloride 5 parts by mass of fine particle dispersion

  Among the main dope components below, methylene chloride and ethanol were added to the pressure dissolution tank. Next, the following thermoplastic resin e1, Exemplified Compound A1, Monopet SB, and the prepared fine particle additive solution were added with stirring, and heated and stirred to completely dissolve. The solution was Azumi Filter Paper No. 1 manufactured by Azumi Filter Paper Co., Ltd. The main dope was prepared by filtration using 244.

(Main dope)
Methylene chloride 340 parts by mass Ethanol 64 parts by mass Thermoplastic resin: Thermoplastic resin e1 (acyl group total substitution degree 2.46, acetyl group substitution degree 1.56, propionyl group substitution degree 0.90, weight average molecular weight Mw 280,000) 100 parts by weight of the compound satisfying the formulas (a1) and (a2): Exemplified Compound A1 4 parts by weight Monopet SB (Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts by weight Fine particle additive liquid 1 part by weight

  The above was put into a sealed container and dissolved with stirring to prepare a dope solution. Next, using an endless belt casting apparatus, the dope solution was uniformly cast on a stainless steel belt support at a temperature of 33 ° C. and a width of 1500 mm. The temperature of the stainless steel belt support was controlled at 30 ° C. On the stainless steel belt support, the solvent was evaporated until the residual solvent amount in the cast (cast) film was 75%, and then peeled off from the stainless steel belt support with a peeling tension of 130 N / m. The peeled film was stretched 30% (1.3 times) in the direction of an angle of 45 ° with respect to the film transport direction using a tenter while applying heat at 145 ° C. The residual solvent at the start of stretching was 14%. Next, drying was completed while the drying zone was conveyed by a number of rollers. The drying temperature was 130 ° C. and the transport tension was 100 N / m. As described above, an optical film 1 having a thickness of 20 μm was obtained.

<Preparation of optical films 2-12, 18-21, 24-34>
In the production of the optical film 1, the optical film 1 except that the type of thermoplastic resin and the type and amount of the compound satisfying the formula (a1) and the formula (a2) were changed as shown in Table 2 and Table 3, respectively. Optical films 2 to 12, 18 to 21, and 24 to 34 were produced in the same manner as described above.
A1 to A10, D1 and D10 in Table 2 and Table 3 represent the exemplified compounds A1 to A10, D1 and D10 described above as specific examples of the compound satisfying the formula (a1) and the formula (a2).
All the optical films 2 to 12, 18 to 21, and 24 to 34 had a film thickness of 30 μm.

Table 1 below shows the thermoplastic resins e1 to e3 in Tables 2 and 3.
In Table 1, PMMA represents a polymethyl methacrylate resin.

<Preparation of optical films 13-17, 22, 23, 35, 36>
In the production of the optical film 1, except that the thermoplastic resin was changed as shown in Tables 2 and 3 without adding a compound satisfying the formulas (a1) and (a2) at the time of preparing the main dope, the optical dope In the same manner as the film 1, optical films 13, 22, and 35 were produced.
Moreover, in preparation of the optical film 1, except having changed the compound and addition amount which satisfy | fill the kind of thermoplastic resin, Formula (a1), and Formula (a2) into the comparative compound and addition amount which are shown in Table 2 and Table 3, respectively. In the same manner as in the optical film 1, optical films 14 to 17, 23, and 36 were produced.
All the optical films 13 to 17, 22, 23, 35, and 36 had a film thickness of 20 μm.

上記比較化合物ｈ２において、−Ｘ^１６−Ｒ^１６、−Ｘ^１３−Ｒ^１３及び−Ｘ^１２−Ｒ^１２は、それぞれ独立に、上記表に示す置換基Ｙ１、Ｙ２又はＹ３を表す。上記表中の極大吸収波長は、各置換基Ｙ１〜Ｙ３をＣＨ_３−Ｙ１、ＣＨ_３−Ｙ２及びＣＨ_３−Ｙ３とした場合に、ジクロロメタン溶液での波長２７０〜４５０ｎｍにおいてモル吸光係数が最大となる波長をいう。上記表において、ＤＳ^１６ _long、ＤＳ^１３ _long及びＤＳ^１２ _longは、それぞれ−Ｘ^１６−Ｒ^１６、−Ｘ^１３−Ｒ^１３及び−Ｘ^１２−Ｒ^１２として置換されている置換基Ｙ１の置換度を表している。また、ＤＳ^１６ _long2、ＤＳ^１３ _long2及びＤＳ^１２ _long2は、それぞれ−Ｘ^１６−Ｒ^１６、−Ｘ^１３−Ｒ^１３及び−Ｘ^１２−Ｒ^１２として置換されている置換基Ｙ２の置換度を表している。ＤＳ_non-aromaは、置換基Ｙ３の置換度を表している。

上記比較化合物ｈ４において、５つの置換基Ｒのうち、２つはアセチル基、３つはベンゾイル基を表す。Comparative compounds h1 to h4 in Table 2 and Table 3 are shown below.
Comparative compound h1 is an exemplary compound (124) described in JP-A-2007-249180. Comparative compound h2 is cellulose compound A-1 described in JP-A-2008-95026. Comparative compound h3 is norbornene-based polymer P-1 described in JP2008-31320A. Comparative compound h4 is carbohydrate derivative 203 described in JP2011-94098A.

In the comparative compound ^{h2, -X 16 -R 16, -X} 13 -R 13 and ^-X 12 ^{-R 12} each independently represent a substituent Y1, Y2 or Y3 shown in Table. The maximum absorption wavelength in the above table, each substituent Y1~Y3 a _CH 3 _-Y1, when a CH 3 --Y2 and _CH 3 -Y3, and a maximum molar extinction coefficient at the wavelength 270~450nm in dichloromethane The wavelength which becomes. In the above table, DS ¹⁶ _long , DS ¹³ _long, and DS ¹² _long represent the degree of substitution of the substituent Y1 that is substituted as -X ¹⁶ -R ¹⁶ , -X ¹³ -R ^13, and -X ¹² -R ¹² , respectively. Represents. DS ¹⁶ _{long 2} , DS ¹³ _{long 2,} and DS ¹² _long 2 represent the degree of substitution of the substituent Y 2 that is substituted as —X ¹⁶ —R ¹⁶ , —X ¹³ —R ^13, and —X ¹² —R ¹² , respectively. Yes. DS _non-aroma represents the degree of substitution of the substituent Y3.

In the comparative compound h4, of the five substituents R, two represent an acetyl group and three represent a benzoyl group.

<Evaluation of optical film>
Each produced optical film 1-36 was evaluated as follows.
(Absorption wavelength of the compound)
Each compound used in the production of the optical films 1 to 36 was dissolved in tetrahydrofuran (without a polymerization inhibitor) at a concentration of 1.0 × 10 ⁻⁵ mol / L, and the absorption spectrum of this solution was measured with a spectrophotometer ( Measurement was performed at 25 ° C. by JASCO Corporation V-570). In the absorption spectrum, the maximum absorption wavelength (nm) located in the wavelength range of 200 to 250 nm and the maximum absorption wavelength λmax (nm) located on the longest wavelength side in the range of 250 to 400 nm were determined.
Further, the molar extinction coefficient ε was calculated from the absorbance measured at λmax.

(Phase difference expression)
The optical films 1 to 36 were conditioned for 2 hours in an environment of 23 ° C. and 55% RH. The retardation value Ro (550) in the in-plane direction when light having a wavelength of 550 nm was incident on each of the optical films 1 to 36 after humidity control in parallel with the normal line of the film surface was measured with an AxoScan. The measurement was performed under conditions of 23 ° C. and 55% RH.

The Ro (550) and the film thickness d (μm) obtained for the optical films 1 to 12 and 14 to 17 are substituted into the above-described formula (b1), and the phase difference developability {Ro (550) −Ro ( 550) _P } / d (nm / μm) was calculated. At this time, Ro (550) obtained about the optical film 13 was used as Ro (550) _P.
Similarly, for the optical films 18 to 21 and 23, Ro (550) obtained for the optical film 22 is Ro (550) _P , and from the formula (b1), {Ro (550) −Ro (550) _P } / D (nm / μm) was calculated.
In addition, for the optical films 24 to 34 and 36, Ro (550) obtained for the optical film 35 is Ro (550) _P , and the formula (b1) to {Ro (550) −Ro (550) _P } / d (Nm / μm) was calculated.

(Wavelength dispersion)
In the same manner as described above, the optical films 1 to 36 were conditioned for 2 hours in an environment of 23 ° C. and 55% RH. In-plane retardation values Ro (450) and Ro (550) when light having wavelengths of 450 nm and 550 nm are incident on each of the optical films 1 to 36 after humidity control in parallel to the normal line of the film surface. Was measured with AxoScan. The measurement was performed under conditions of 23 ° C. and 55% RH. Furthermore, Ro (450) / Ro (550) representing wavelength dispersibility was calculated from the obtained Ro (450) and Ro (550).

(Uneven phase difference)
After conditioning the optical films 1 to 36 at 25 ° C. and 55% RH for 5 hours or more, using an ellipsometer, the phase difference Ro (10 in-plane directions) is shifted by 1 cm in the transport direction (MD direction). 550) was measured. A value obtained by dividing the difference between the maximum value and the minimum value at this time by the average value of 10 points was obtained as phase difference unevenness.

(Haze)
The haze (total haze) of each optical film 1 to 36 was measured with a haze meter NDH-2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7136. The light source of the haze meter was a 5V9W halogen sphere, and the light receiving part was a silicon photocell (with a relative visibility filter). The haze was measured under the conditions of 23 ° C. and 55% RH.

Tables 2 and 3 below show the evaluation results.

  As is clear from Tables 2 and 3, it can be seen that the optical film according to the present invention is excellent in retardation development and exhibits excellent reverse wavelength dispersion as compared with the optical film of the comparative example. In addition, it can be seen that the optical film according to the present invention is extremely excellent in practical use since retardation unevenness is suppressed and haze is good regardless of stretching at high temperature and high magnification.

[Example 2]
<Preparation of optical films 51 to 54 to which a retardation increasing agent other than the compound satisfying formula (a1) and formula (a2) is added>
In preparation of the optical film 1 of Example 1, the kind of thermoplastic resin, the kind of compound satisfying the formula (a1) and the formula (a2), and the addition amount were changed as shown in Table 4 below, and the main dope was prepared. At the same time, optical films 51, 52, and 54 were produced in the same manner except that 5 parts by mass of the following retardation increasing agent was further added. The thermoplastic resin e4 in Table 4 is as shown in Table 1 above.

  In the production of the optical film 51, an optical film 53 was produced in the same manner as the optical film 51, except that the compound satisfying the formulas (a1) and (a2) was not added when the main dope was prepared.

<Evaluation of optical film>
The produced optical films 51 to 54 were evaluated in the same manner as in Example 1.
Table 4 below shows the evaluation results.

  As is clear from Table 4, the optical film of the present invention is superior in retardation development and exhibits good reverse wavelength dispersion as compared with the optical film according to the comparative example. Further, it can be seen that the optical film of the present invention is a practically very excellent optical film with little retardation unevenness and good haze even after being stretched at high temperature and high magnification.

[Example 3]
<Production of Circular Polarizing Plates 1-36>
A 120 μm-thick polyvinyl alcohol film was uniaxially stretched (temperature: 110 ° C., stretch ratio: 5 times). After stretching, the film was immersed in an aqueous solution consisting of 0.075 parts by mass of iodine, 5 parts by mass of potassium iodide, and 100 parts by mass of water for 60 seconds. Subsequently, after immersing in 68 degreeC aqueous solution which consists of 6 mass parts of potassium iodide, 7.5 mass parts boric acid, and 100 mass parts of water, it washed with water and dried and obtained the polarizer.

According to the following processes 1-5, the circularly-polarizing plates 1-36 which each comprised the optical films 1-36 produced in Example 1 were produced.
Step 1: One surface of the optical film was immersed in a 2 mol / L sodium hydroxide solution at 60 ° C. for 90 seconds, washed with water, dried and saponified. The saponified surface is the bonding surface with the polarizer.
Process 2: The produced polarizer was immersed for 1 to 2 seconds in the polyvinyl alcohol adhesive tank of 2 mass% of solid content.
Step 3: After excessively removing the adhesive adhering to the polarizer in Step 2, the polarizer was overlaid on the surface of the optical film saponified in Step 1.
Step 4: On the other surface of the polarizer layered on the optical film in Step 3, Konica Minolta Tack KC4UY (a cellulose ester film manufactured by Konica Minolta Advanced Layer Co., Ltd.) is stacked, and the pressure is 20 to 30 N / cm ² . Bonding was performed at a conveyance speed of about 2 m / min.
Step 5: The optical film, polarizer, and Konica Minoltack KC4UY bonded in Step 4 were dried for 2 minutes in a dryer at 80 ° C. to prepare a circularly polarizing plate.

<Evaluation of circularly polarizing plate>
The durability of each circularly polarizing plate 1 to 36 was evaluated as follows.
(durability)
Two circular polarizing plates 1 to 36 were cut out in units of 500 × 500 mm, and two samples were prepared. Two samples were left to stand at 80 ° C. and 90% RH for 100 hours and subjected to a heat and humidity treatment. The length of the white-out portion of the larger edge of the vertical or horizontal center line portion in the orthogonal state was measured, and the ratio to the side length (500 mm) was calculated. Edge blank means that the edge portion of the circularly polarizing plate that does not transmit light in an orthogonal state is in a state that allows light to pass through, and can be determined visually. If the display of the edge portion becomes invisible in the state of the circularly polarizing plate, a failure occurs.
According to the calculated ratio, the heat and humidity resistance was determined as follows, and the durability was evaluated.
A: Edge blank is less than 5% B: Edge blank is from 5% to less than 10% C: Edge blank is from 10% to less than 20% D: Edge blank is from 20% to 20% where B If it is above the level, there is no practical problem, and the A level is preferred. The C level can be used as a circularly polarizing plate, but is not suitable for practical use, and the D level has a problem as a circularly polarizing plate.

Table 5 shows the evaluation results.

  As is apparent from Table 5, it can be seen that the circularly polarizing plate according to the present invention is superior in durability compared to the circularly polarizing plate according to the comparative example.

[Example 4]
<Production of liquid crystal display devices 1 to 36>
In 40-type display KLV-40J3000 (manufactured by SONY), the double-sided circularly polarizing plates that had been bonded together were peeled off, and each of the circularly polarizing plates 1 to 36 prepared in Example 3 was applied to both sides of the glass surface of the liquid crystal cell. Thus, liquid crystal display devices 1 to 36 were respectively produced.
The circularly polarizing plates were bonded so that the optical film was positioned on the liquid crystal cell side and the absorption axis was oriented in the same direction as the circularly polarizing plate that had been bonded in advance.

<Evaluation of liquid crystal display device>
Each liquid crystal display device 1-36 was evaluated as follows.

(Color unevenness)
Each of the liquid crystal display devices 1 to 36 was displayed in black in an environment of 23 ° C. and 55% RH, and observed from the front and an oblique angle of 45 °, and color unevenness was evaluated according to the following criteria.
A: No color unevenness B: Color unevenness is slightly observed C: Color unevenness is present but practically no problem D: Color unevenness is large and practically problematic There is no problem, it is preferable that it is B level or more, and it is more preferable that it is A level or more.

(Viewing angle fluctuation)
Using EZ-Contrast 160D (manufactured by ELDIM), the viewing angle of each of the liquid crystal display devices 1 to 36 was measured in an environment of 23 ° C. and 55% RH. Next, the viewing angle of each of the manufactured liquid crystal display devices 1 to 36 was measured under an environment of 23 ° C. and 20% RH, and further under an environment of 23 ° C. and 80% RH. evaluated. Finally, viewing angle measurement was performed in an environment of 23 ° C. and 55% RH, and it was confirmed that the viewing angle fluctuation during the measurement was a reversible fluctuation. In addition, these measurements were performed after putting each liquid crystal display device 1-36 in each environment for 5 hours.
A: Viewing angle variation is not recognized B: Viewing angle variation is slightly recognized C: Viewing angle variation is recognized Here, if it is B level or more, there is no practical problem, and it is preferably A level.

Table 6 below shows the evaluation results.

  As is apparent from Table 6, each liquid crystal display device including the circularly polarizing plate according to the present invention has less color unevenness and changes in humidity than the liquid crystal display device using the circularly polarizing plate according to the comparative example. It can be seen that the viewing angle variation is small even under conditions, and the visibility from an oblique direction is excellent. That is, it is clear that the liquid crystal display device according to the present invention realizes an extremely stable viewing angle and is excellent in durability.

  The optical film and the circularly polarizing plate of the present invention can be used as a retardation film that imparts a predetermined retardation to light in the entire visible light range, a highly durable circularly polarizing plate, and the like. The image display device of the present invention can be used as a television device, a portable terminal, a display device, or the like.

DESCRIPTION OF SYMBOLS 10 Organic electroluminescent display device 14 Light emitting layer 20 Circularly-polarizing plate 20A (lambda) / 4 phase difference film 20B Polarizer 30 Liquid crystal display device 40 Liquid crystal cell 50, 60 Polarizing plate 52, 62 Polarizer 54, 56, 64, 66 Protective film

Claims (10)

An optical film containing at least one compound satisfying the following formulas (a1) and (a2),
When the retardation values Ro in the in-plane direction of the optical film at wavelengths of 450 nm and 550 nm are Ro (450) and Ro (550), respectively, the Ro (450) and Ro (550) are represented by the following formula (b1) and An optical film characterized by satisfying the formula (b2).
(A1) 250 ≦ λmax ≦ 400
(A2) 1000 ≦ ε ≦ 20000
[In the above formula (a1), λmax represents the maximum absorption wavelength (nm) located on the longest wavelength side in the absorption spectrum of the compound. In the above formula (a2), ε represents the molar extinction coefficient at λmax. ]
(B1) 1.50 ≦ {Ro (550) −Ro (550) _P } /d≦3.00
(B2) 0.72 ≦ Ro (450) / Ro (550) ≦ 0.96
[In the above formula (b1), Ro (550) _P represents an in-plane retardation value at a wavelength of 550 nm of an optical film not containing the compound, and {Ro (550) -Ro (550) _P } represents the compound. Represents the amount of change (nm) in the retardation value due to the inclusion of. d represents the film thickness (μm) of the optical film. ] The optical film according to claim 1, wherein the compound is represented by the following general formula (A).

[In the general formula (A), Q represents an aromatic hydrocarbon ring, a non-aromatic hydrocarbon ring, an aromatic heterocyclic ring or a non-aromatic heterocyclic ring. Wa and Wb are each independently a hydrogen atom or a substituent bonded to an atom constituting Q, and Wa and Wb may be the same as or different from each other, and Wa and Wb are bonded to each other to form a ring. May be. R ₃ represents a substituent. m represents an integer of 0 to 2, and when m is 2, two R _{3 s} may be the same as or different from each other. n represents an integer of 1 to 10, and when n is 2 or more, each of 2 or more of Q, L ₂ , Wa, Wb, R ₃ and m may be the same as or different from each other. . L ₁ and L ₂ are each independently an alkylene group, an alkenylene group, an alkynylene group, O, (C═O), (C═O) —O, NR _L , S, (O═S═O) and ( C═O) —NR 2 represents a divalent linking group selected from the group consisting of _L , a combination thereof, or a single bond. R _L represents a hydrogen atom or a substituent. R ₁ and R ₂ each independently represents a substituent. ] The optical film according to claim 2, wherein the compound represented by the general formula (A) is represented by the following general formula (B).

[In the general formula (B), Wa and Wb are each independently a hydrogen atom or a substituent bonded to an atom constituting the benzene ring, and Wa and Wb may be the same or different from each other. And Wb may combine with each other to form a ring. R ₃ represents a substituent. m represents an integer of 0 to 2, and when m is 2, two R _{3 s} may be the same as or different from each other. L ₁ and L ₂ are each independently an alkylene group, an alkenylene group, an alkynylene group, O, (C═O), (C═O) —O, NR _L , S, (O═S═O) and ( C═O) —NR 2 represents a divalent linking group selected from the group consisting of _L , a combination thereof, or a single bond. R _L represents a hydrogen atom or a substituent. R ₁ and R ₂ each independently represents a substituent. ] The optical film according to claim 3, wherein the compound represented by the general formula (B) is represented by the following general formula (C).

[In the general formula (C), Wa and Wb are each independently a hydrogen atom or a substituent bonded to the benzene ring, and Wa and Wb may be the same or different from each other, and Wa and Wb are They may combine to form a ring. R ₃ represents a substituent. m represents an integer of 0 to 2, and when m is 2, two R _{3 s} may be the same as or different from each other. L ₁ and L ₂ are each independently an alkylene group, an alkenylene group, an alkynylene group, O, (C═O), (C═O) —O, NR _L , S, (O═S═O) and ( C═O) —NR 2 represents a divalent linking group selected from the group consisting of _L , a combination thereof, or a single bond. R _L represents a hydrogen atom or a substituent. R ₁ and R ₂ each independently represents a substituent. ]   5. The compound satisfying the formula (a1) and the formula (a2) has at least one maximum absorption within a wavelength range of 200 to 250 nm, according to any one of claims 1 to 4. Optical film.   The optical film according to any one of claims 1 to 5, wherein the optical film contains a cellulose derivative.   The optical film according to claim 1, wherein the optical film has a thickness in a range of 10 to 100 μm.   The optical film according to any one of claims 1 to 7, wherein an angle formed by a slow axis in a plane of the optical film and a conveying direction is in a range of 40 to 50 °.   A circularly polarizing plate comprising the optical film according to any one of claims 1 to 8.   An image display device comprising the optical film according to claim 1.

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