JP7530249B2 - Optical film, polarizing plate, and method for producing optical film - Google Patents

Description

The present invention relates to an optical film, a polarizing plate, and a method for manufacturing an optical film.

In recent years, there has been a need in the display market to extend the life of batteries and reduce display brightness to suppress heat generation. For this reason, polarizing plates with high light transmittance are required for use in displays. However, when such polarizing plates with high light transmittance are used in displays, there is an issue that the appearance deteriorates under humid conditions.

Furthermore, in recent years, displays are increasingly being used in environments where they are exposed to ultraviolet light (e.g., PIDs (public information displays), mobile phones), and there is an issue that ultraviolet light can change the hue of the optical film, compromising the quality of the display, particularly in polarizing plates where an optical film is placed on the panel side.

Patent No. 3325560

The present invention has been made to solve the above-mentioned problems of the prior art, and its purpose is to provide an optical film that suppresses changes in retardation under humid conditions, suppresses changes in hue in weather resistance tests in the ultraviolet range, and has excellent adhesion, and a polarizing plate including said optical film.

１つの実施形態においては、上記ポリカーボネート系樹脂は、脂環式ジヒドロキシ化合物に由来する構造単位をさらに含み、該脂環式ジヒドロキシ化合物は、下記一般式（ＩＩ）で表され、Ｒ^１が下記（ＩＩｂ）で表される構造であり、ｎ＝０である。

ＨＯＣＨ_２－Ｒ^１－ＣＨ_２ＯＨ （ＩＩ）

１つの実施形態においては、上記光学フィルムの厚みは１０μｍ～５０μｍである。
本発明の別の実施形態においては、偏光板が提供される。この偏光板は、偏光子と、該偏光子の少なくとも片面に接着剤層を介して貼り合わされた上記光学フィルムとを含む。
本発明の別の局面によれば、上記光学フィルムの製造方法が提供される。この製造方法は、ライン速度が７ｍ／ｍｉｎ～１５ｍ／ｍｉｎである製膜工程を含む。 The optical film according to an embodiment of the present invention is made of a resin having a birefringence Δnxy of 0.015 or more, has a degree of orientation of 5% or more, an in-plane retardation Re(550) of 20 nm or less, a retardation change rate of 10% or less after being held at 65° C. and 90% RH for 500 hours, and a b value change rate of 1% or less in an ultraviolet weather resistance test.
In one embodiment, the resin comprises a polycarbonate-based resin.
In one embodiment, the polycarbonate resin contains a structural unit derived from a dihydroxy compound represented by the following formula (4).

In one embodiment, the polycarbonate-based resin further contains a structural unit derived from an alicyclic dihydroxy compound, and the alicyclic dihydroxy compound is represented by the following general formula (II), R ¹ has a structure represented by the following (IIb), and n=0.

HOCH ₂ -R ¹ -CH ₂ OH (II)

In one embodiment, the optical film has a thickness of 10 μm to 50 μm.
In another embodiment of the present invention, a polarizing plate is provided. The polarizing plate includes a polarizer and the above-mentioned optical film attached to at least one surface of the polarizer via an adhesive layer.
According to another aspect of the present invention, there is provided a method for producing the optical film, comprising the steps of: forming a film at a line speed of 7 m/min to 15 m/min;

According to an embodiment of the present invention, a resin film made of a specific resin and having a birefringence Δnxy of 0.015 or more is produced under specific conditions, so that the degree of orientation is at a certain value or more. As a result, the phase difference change in a humid reliability test is suppressed, the hue change in an ultraviolet weather resistance test is suppressed, and an optical film with excellent adhesion can be realized.

The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
The definitions of terms and symbols used in this specification are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Birefringence (Δnxy)
The birefringence Δnxy is calculated by the formula: Δnxy=nx−ny.

A. Optical Film The optical film according to the embodiment of the present invention is formed from a resin. A representative example of the resin is a polycarbonate resin. Therefore, the optical film according to the embodiment of the present invention is typically a polycarbonate resin film. Furthermore, the optical film according to the embodiment of the present invention preferably does not contain an ultraviolet absorbing agent. Since the optical film does not contain an ultraviolet absorbing agent, it is possible to maintain a neutral hue when applied to an image display device.

The birefringence Δnxy of the resin constituting the optical film is typically 0.015 or more, and preferably 0.018 or more. The upper limit of the birefringence Δnxy of the resin can be, for example, 0.040. By producing a resin film composed of a resin having such birefringence Δnxy at a line speed equal to or higher than a predetermined speed, the degree of orientation becomes equal to or higher than a certain value, and as a result, the change in phase difference under humid conditions is significantly suppressed.

The optical film has an orientation degree of 5% or more, preferably 5.5% or more, and more preferably 6% or more. The upper limit of the orientation degree is, for example, 70%. If the orientation degree of the optical film is in this range, the adhesiveness of the optical film is good. An orientation degree in this range can be achieved by forming the resin film at a line speed in a specified range. The orientation degree is measured, for example, by X-ray diffraction (XRD).

The in-plane retardation Re(550) of the optical film is 20 nm or less, preferably 15 nm or less, and more preferably 10 nm or less. The lower limit of the in-plane retardation can be, for example, 0 nm. That is, the optical film preferably has substantially optical isotropy. Such an in-plane retardation Re(550) of the optical film can be obtained by forming the resin film at a line speed within a predetermined range.

The retardation change of the optical film after storage for 500 hours under conditions of a temperature of 65° C. and a humidity of 90% (humidification test) is preferably 10% or less, more preferably 8% or less. The lower limit can be, for example, 0.01%. The retardation change (%) is expressed as |(Re ₅₀₀ -Re ₀ )/Re ₀ |×100(%). Re ₀ is the in-plane retardation (nm) of the optical film before the start of the test, and Re ₅₀₀ is the in-plane retardation (nm) of the optical film after the test. If the retardation change of the optical film is in such a range, when the optical film is applied to an image display device, the hue change due to the retardation at each location on the image display device is small, and the occurrence of color unevenness on the display can be suppressed.

The optical film suppresses the change in the b value in a weather resistance test in the ultraviolet region. The rate of change in the b value is 1% or less, and preferably 0.95% or less. The lower limit of the rate of change in the b value is, for example, 0%. In other words, the optical film can be used well in applications where weather resistance is required. Such advantages can be obtained by the optical film containing a specific polycarbonate resin described later.

The thickness of the optical film is preferably 10 μm to 50 μm, and more preferably 20 μm to 40 μm.

The moisture permeability of the optical film is preferably 250 g/ ^m2 ·24 h or less, more preferably 150 g/ ^m2 ·24 h or less. The lower limit may be, for example, 1 g/ ^m2 ·24 h. If the moisture permeability of the optical film is in this range, it is possible to obtain an advantage that the change in retardation in a humid environment can be suppressed.

The optical film has an absolute value of the photoelastic coefficient of preferably 2×10 ⁻¹¹ m ² /N or less, more preferably 2.0×10 ⁻¹³ m ² /N to 1.5× ^{10 −11} m ² /N, and even more preferably 1.0×10 ⁻¹² m ² /N to 1.2× ^{10 −11} m ² /N. When the absolute value of the photoelastic coefficient is in such a range, a change in retardation is unlikely to occur when shrinkage stress occurs during heating. As a result, when the optical film is used in an image display device, thermal unevenness in the image display device can be effectively prevented.

According to an embodiment of the present invention, as described above, an optical film having a specific degree of orientation can be obtained by forming a film at a line speed within a predetermined range using a resin having a birefringence Δnxy in a specific range. The optical film satisfies the desired in-plane retardation (effectively optical isotropy), and further suppresses retardation change in a humid reliability test, suppresses hue change in an ultraviolet weather resistance test, and has good adhesion.

By forming the resin film at a line speed equal to or lower than a predetermined speed, an optical film having substantially optical isotropy can be obtained. However, if the line speed is equal to or lower than a certain speed, the degree of orientation of the obtained optical film decreases, leading to a change in phase difference and a decrease in adhesion in a humid reliability test. Therefore, by setting the line speed to a certain speed or higher, the degree of orientation of the optical film increases, the change in phase difference in a humid reliability test is suppressed, and the adhesion is further improved. In other words, by optimizing the range of the line speed, it is possible to achieve both the desired in-plane phase difference, the suppression of the change in phase difference in a humid reliability test, and excellent adhesion. Such an optical film can be suitably used, for example, in PIDs (public information displays) and mobile phones.

B. Constituent Materials As described above, the optical film is typically a resin film containing a polycarbonate resin.

(Polycarbonate resin)
The polycarbonate resin according to the present invention contains at least a constituent unit derived from a dihydroxy compound having a bonding structure represented by the following structural formula (1), and is produced by reacting a dihydroxy compound containing at least a dihydroxy compound having at least one bonding structure -CH ₂ -O- in the molecule with a carbonate diester in the presence of a polymerization catalyst.

Here, as the dihydroxy compound having a bonding structure represented by structural formula (1), any compound having two alcoholic hydroxyl groups, a structure having a linking group -CH ₂ -O- in the molecule, and capable of reacting with a carbonate diester in the presence of a polymerization catalyst to produce a polycarbonate can be used, and a plurality of types may be used in combination. Furthermore, as the dihydroxy compound used in the polycarbonate resin according to the present invention, a dihydroxy compound not having a bonding structure represented by structural formula (1) may be used in combination. Hereinafter, a dihydroxy compound having a bonding structure represented by structural formula (1) may be abbreviated as dihydroxy compound (A), and a dihydroxy compound not having a bonding structure represented by structural formula (1) may be abbreviated as dihydroxy compound (B).

(Dihydroxy Compound (A))
The "linking group -CH ₂ -O-" in dihydroxy compound (A) means a structure which bonds with atoms other than hydrogen atoms to form a molecule. In this linking group, as an atom to which at least an oxygen atom can be bonded or an atom to which a carbon atom and an oxygen atom can be bonded simultaneously, a carbon atom is most preferred. The number of "linking groups -CH ₂ -O-" in dihydroxy compound (A) is preferably 1 or more, more preferably 2 to 4.

More specifically, examples of dihydroxy compound (A) include 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, and 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl). Compounds having an aromatic group in a side chain and an ether group bonded to the aromatic group in a main chain, such as fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, and 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene, bis[4-(2-hydroxyethoxy)phenyl]methane, bis[4-(2-hydroxy 1,1-bis[4-(2-hydroxyethoxy)phenyl]diphenylmethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]ethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-1-phenylethane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)-3-methylphenyl]propane, 2,2-bis[3,5-dimethyl-4-(2-hydroxyethoxy)phenyl]propane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-3,3,5-trimethylcyclohexane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]- (si)phenyl]cyclohexane, 1,4-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,3-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 2,2-bis[4-(2-hydroxyethoxy)-3-phenylphenyl]propane, 2,2-bis[(2-hydroxyethoxy)-3-isopropylphenyl]propane, 2,2-bis[3-tert-butyl-4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]butane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]-4- bis(hydroxyalkoxyaryl)alkanes, such as methylpentane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]octane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]decane, 2,2-bis[3-bromo-4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]propane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,1-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]cyclohexane, 1, bis(hydroxyalkoxyaryl)cycloalkanes, such as 1-bis[4-(2-hydroxyethoxy)phenyl]cyclopentane; dihydroxyalkoxydiaryl ethers, such as 4,4'-bis(2-hydroxyethoxy)diphenyl ether and 4,4'-bis(2-hydroxyethoxy)-3,3'-dimethyldiphenyl ether; bishydroxyalkoxyaryl sulfides, such as 4,4'-bis(2-hydroxyethoxyphenyl)sulfide and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl]sulfide; bishydroxyalkoxyaryl sulfoxides, such as 4,4'-bis(2-hydroxyethoxyphenyl)sulfoxide and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl]sulfoxide; bishydroxyalkoxyaryl sulfones, such as 4,4'-bis(2-hydroxyethoxyphenyl)sulfone and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl]sulfone; 1,4-bishydroxyethoxybenzene, 1,3-bishydroxyethoxybenzene, 1,2-bishydroxyethoxybenzene; Examples of the cyclic ether structure include benzene, 1,3-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene, 1,4-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene, 4,4'-bis(2-hydroxyethoxy)biphenyl, 1,3-bis[4-(2-hydroxyethoxy)phenyl]-5,7-dimethyladamantane, anhydrous sugar alcohols represented by dihydroxy compounds represented by the following formula (4), and spiro glycols represented by the following general formula (6). These may be used alone or in combination of two or more.

These dihydroxy compounds (A) may be used alone or in combination of two or more. In the present invention, the dihydroxy compounds represented by the formula (4) include isosorbide, isomannide, and isoidite, which are stereoisomeric, and may be used alone or in combination of two or more.

Among the dihydroxy compounds (A), isosorbide, which is obtained by dehydration condensation of sorbitol produced from various starches, which are abundant and easily available as resources, is the most preferable in terms of availability and ease of production, optical properties, and moldability. In the present invention, isosorbide is preferably used as the dihydroxy compound (A).

(Dihydroxy Compound (B))
In the present invention, a dihydroxy compound (B) other than the dihydroxy compound (A) may be used as the dihydroxy compound. As the dihydroxy compound (B), for example, an alicyclic dihydroxy compound, an aliphatic dihydroxy compound, an oxyalkylene glycol, an aromatic dihydroxy compound, or a diol having a cyclic ether structure may be used as a dihydroxy compound serving as a structural unit of polycarbonate together with the dihydroxy compound (A), for example, a dihydroxy compound represented by formula (4).

The alicyclic dihydroxy compound that can be used in the present invention is not particularly limited, but preferably, a compound containing a 5-membered ring structure or a 6-membered ring structure is used. The 6-membered ring structure may be fixed in a chair or boat shape by a covalent bond. When the alicyclic dihydroxy compound has a 5-membered ring or a 6-membered ring structure, the heat resistance of the resulting polycarbonate can be increased. The number of carbon atoms contained in the alicyclic dihydroxy compound is usually 70 or less, preferably 50 or less, and more preferably 30 or less. The larger this value, the higher the heat resistance, but the more difficult the synthesis and purification become, and the higher the cost becomes. The smaller the number of carbon atoms, the easier it is to purify and obtain.

Specific examples of the alicyclic dihydroxy compound containing a 5-membered ring structure or a 6-membered ring structure that can be used in the present invention include alicyclic dihydroxy compounds represented by the following general formula (II) or (III).
HOCH ₂ -R ¹ -CH ₂ OH (II)
HO-R ² -OH (III)
(In formulas (II) and (III), R ¹ and R ² each represent a cycloalkylene group having 4 to 20 carbon atoms.)
Cyclohexanedimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (II), includes various isomers represented by the following general formula (IIa) in which R ¹ in general formula (II) is an alkyl group having 1 to ¹² carbon atoms or a hydrogen atom. Specific examples of such isomers include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.

Tricyclodecane dimethanol and pentacyclopentadecanedimethanol, which are alicyclic dihydroxy compounds represented by the above general formula (II), include various isomers in which R ¹ in general formula (II) is represented by the following general formula (IIb) (wherein n is 0 or 1).

Decalin dimethanol or tricyclotetradecane dimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (II), includes various isomers in which R ¹ in general formula (II) is represented by the following general formula (IIc) (wherein m is 0 or 1). Specific examples of such isomers include 2,6-decalin dimethanol, 1,5-decalin dimethanol, and 2,3-decalin dimethanol.

Norbornane dimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (II), includes various isomers in which R ¹ in general formula (II) is represented by the following general formula (IId). Specific examples of such isomers include 2,3-norbornane dimethanol and 2,5-norbornane dimethanol.

Adamantane dimethanol, which is an alicyclic dihydroxy compound represented by general formula (II), includes various isomers in which R ¹ in general formula (II) is represented by the following general formula (IIe), specifically, 1,3-adamantanedimethanol, etc.

Furthermore, cyclohexanediol, which is an alicyclic dihydroxy compound represented by ^the above general formula (III), includes various isomers represented by the following general formula (IIIa) in which ^R2 in the general formula (III) is an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. Specific examples of such isomers include 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol.

Tricyclodecanediol and pentacyclopentadecanediol, which are alicyclic dihydroxy compounds represented by the above general formula (III), include various isomers in which ^R2 in the general formula (III) is represented by the following general formula (IIIb) (wherein n is 0 or 1).

Decalindiol or tricyclotetradecanediol, which is an alicyclic dihydroxy compound represented by the above general formula (III), includes various isomers in which ^R2 in general formula (III) is represented by the following general formula (IIIc) (wherein m is 0 or 1). Specific examples of such isomers include 2,6-decalindiol, 1,5-decalindiol, and 2,3-decalindiol.

The norbornanediol, which is an alicyclic dihydroxy compound represented by the above general formula (III), includes various isomers in which ^R2 in the general formula (III) is represented by the following general formula (IIId). Specific examples of such isomers include 2,3-norbornanediol and 2,5-norbornanediol.

The adamantanediol, which is an alicyclic dihydroxy compound represented by the above general formula (III), includes various isomers in which ^R2 in the general formula (III) is represented by the following general formula (IIIe). Specifically, 1,3-adamantanediol is used as such an isomer.

Of the specific examples of the alicyclic dihydroxy compounds mentioned above, cyclohexane dimethanols, tricyclodecane dimethanols, adamantane diols, and pentacyclopentadecanedimethanols are particularly preferred, and from the viewpoints of ease of availability and ease of handling, 1,4-cyclohexane dimethanol, 1,3-cyclohexane dimethanol, 1,2-cyclohexane dimethanol, and tricyclodecane dimethanol are preferred. In the present invention, tricyclodecane dimethanol is preferably used as the dihydroxy compound (B).

Examples of aliphatic dihydroxy compounds that can be used in the present invention include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 1,5-heptanediol, and 1,6-hexanediol. Examples of oxyalkylene glycols that can be used in the present invention include diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol.

Examples of aromatic dihydroxy compounds that can be used in the present invention include 2,2-bis(4-hydroxyphenyl)propane [=bisphenol A], 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-diethylphenyl)propane, 2,2-bis(4-hydroxy-(3,5-diphenyl)phenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxyphenyl)pentane, 2,4'-dihydroxy-diphenylmethane, bis(4-hydroxyphenyl)methane, bis(4-hydroxy-5-nitrophenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 3,3-bis(4- hydroxyphenyl)pentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)sulfone, 2,4'-dihydroxydiphenyl sulfone, bis(4-hydroxyphenyl)sulfide, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dichlorodiphenyl ether, 4,4'-dihydroxy-2,5-diethoxydiphenyl ether, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene, 9,9-bis[4-(2-hydroxyethoxy-2-methyl)phenyl]fluorene, 9,9-bis(4-hydroxyphenyl)fluorene, and 9,9-bis(4-hydroxy-2-methylphenyl)fluorene.

Examples of diols having a cyclic ether structure that can be used in the present invention include spiroglycols and dioxane glycols. The above-mentioned exemplary compounds are merely examples of alicyclic dihydroxy compounds, aliphatic dihydroxy compounds, oxyalkylene glycols, aromatic dihydroxy compounds, and diols having a cyclic ether structure that can be used in the present invention, and the present invention is not limited to these compounds. One or more of these compounds can be used together with the dihydroxy compound represented by formula (4).

By using these dihydroxy compounds (B), it is possible to obtain effects such as improved flexibility, improved heat resistance, and improved moldability according to the application. The ratio of dihydroxy compounds (A), for example, dihydroxy compounds represented by formula (4), to all dihydroxy compounds constituting the polycarbonate resin of the present invention is not particularly limited, but is preferably 10 mol% or more, more preferably 40 mol% or more, even more preferably 60 mol% or more, preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less. If the content ratio of structural units derived from other dihydroxy compounds is too high, it may deteriorate the performance such as optical properties.

When an alicyclic dihydroxy compound is used among the other dihydroxy compounds, the ratio of dihydroxy compound (A), for example the total ratio of the dihydroxy compound represented by formula (4) and the alicyclic dihydroxy compound to all dihydroxy compounds constituting the polycarbonate is not particularly limited, but is preferably 80 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more.

In addition, the content ratio of the dihydroxy compound (A), for example, the dihydroxy compound represented by formula (4)-derived structural units and the alicyclic dihydroxy compound-derived structural units in the polycarbonate resin according to the present invention can be selected at any ratio, but the ratio of the dihydroxy compound represented by formula (4)-derived structural units and the alicyclic dihydroxy compound-derived structural units is preferably 1:99 to 99:1 (mol%), and particularly preferably the ratio of the dihydroxy compound represented by formula (4)-derived structural units and the alicyclic dihydroxy compound-derived structural units is 10:90 to 90:10 (mol%). If the dihydroxy compound represented by formula (4)-derived structural units are more abundant and the alicyclic dihydroxy compound-derived structural units are less abundant than the above range, the resin tends to be easily discolored, and conversely, if the dihydroxy compound represented by formula (4)-derived structural units are less abundant and the alicyclic dihydroxy compound-derived structural units are more abundant, the molecular weight tends to be difficult to increase.

Furthermore, when an aliphatic dihydroxy compound, an oxyalkylene glycol, an aromatic dihydroxy compound, or a diol having a cyclic ether structure is used, the total ratio of dihydroxy compound (A), for example, a dihydroxy compound represented by formula (4), and each of these dihydroxy compounds to all dihydroxy compounds constituting the polycarbonate is not particularly limited and can be selected at any ratio. In addition, the content ratio of the constituent units derived from dihydroxy compound (A), for example, a dihydroxy compound represented by formula (4), and each of these dihydroxy compounds is not particularly limited and can be selected at any ratio.

Details of polycarbonate-based resins are described, for example, in JP 2012-31370 A (Patent No. 5,448,264). The description of this patent document is incorporated herein by reference.

C. Manufacturing method of optical film The optical film is obtained by, for example, forming a film from a resin such as the polycarbonate-based resin described in section B. Any appropriate molding method can be adopted as a method for forming the film. Specific examples include extrusion molding, blow molding, cast coating (for example, casting), and calendar molding. Among them, extrusion molding or cast coating, which can increase the smoothness of the obtained film and obtain good optical uniformity, is preferable, and cast coating can be more preferably adopted. The line speed of the cast coating method is preferably 7 m/min to 15 m/min, more preferably 7 m/min to 12 m/min. By forming the resin film described in section B at a line speed equal to or lower than a predetermined speed, an optical film having substantially optical isotropy can be obtained. However, if the line speed is equal to or lower than a certain speed, the degree of orientation of the obtained optical film decreases, leading to a change in retardation and a decrease in adhesion in a humid reliability test. Therefore, by setting the line speed to a certain speed or more, the degree of orientation of the optical film is increased, the phase difference change in the humid reliability test is suppressed, and the adhesiveness is further improved. That is, by performing the cast film formation at the line speed in the above range, it is possible to achieve both the desired in-plane phase difference, the suppression of the phase difference change in the humid reliability test, and excellent adhesiveness. Furthermore, by performing the cast film formation at the line speed in the above range, it is possible to suppress the film thickness unevenness in the MD direction (longitudinal direction) and the phase difference unevenness caused by the film thickness unevenness.

D. Polarizing Plate The polarizing plate typically has a polarizer and the optical film laminated to at least one side of the polarizer via an adhesive layer. As described above, the optical film has excellent adhesion to the polarizer. The polarizer may have a protective layer on at least one side of the polarizer. Furthermore, the polarizing plate may have a pressure-sensitive adhesive layer and a separator on the side opposite to the viewing side. The polarizer, protective layer, pressure-sensitive adhesive layer and separator are well known in the art, so detailed description is omitted.

The adhesive composition constituting the adhesive layer is typically an active energy ray-curable adhesive composition. The active energy ray-curable adhesive composition contains an active energy ray-curable compound.

The active energy ray-curable adhesive composition according to the present invention is, for example, an active energy ray-curable adhesive composition containing active energy ray-curable compounds (A), (B) and (C) as curable components, and when the total amount of the composition is taken as 100% by weight, it contains 0.0 to 4.0% by weight of an active energy ray-curable compound (A) having an SP value of 29.0 (MJ/ ^m3 )1/2 or more and 32.0 (MJ/ ^m3 )1/2 or less, 5.0 to 98.0% by weight of an active energy ray-curable compound (B) having an SP value of 18.0 (MJ/ ^m3 )1/2 or more and less than 21.0 (MJ/ ^m3 )1/2, and 5.0 to 98.0% by weight of an active energy ray-curable compound (C) having an SP value of 21.0 (MJ/ ^m3 )1/2 or more and 26.0 (MJ/ ^m3 )1/2 or less. In the present invention, the term "total amount of the composition" refers to the total amount including the active energy ray-curable compound, as well as various initiators and additives.

The active energy ray curable compound (A) can be any compound having a radical polymerizable group such as a (meth)acrylate group and an SP value of 29.0 (MJ/m ³ ) 1/2 or more and 32.0 (MJ/m ³ ) 1/2 or less. Specific examples of the active energy ray curable compound (A) include hydroxyethyl acrylamide (SP value 29.5), N-methylolacrylamide (SP value 31.5), etc. In the present invention, the (meth)acrylate group means an acrylate group and/or a methacrylate group.

The active energy ray curable compound (B) can be any compound having a radical polymerizable group such as a (meth)acrylate group and an SP value of 18.0 (MJ/m ³ ) 1/2 or more and less than 21.0 (MJ/m ³ ) 1/2. Specific examples of the active energy ray curable compound (B) include tripropylene glycol diacrylate (SP value 19.0), 1,9-nonanediol diacrylate (SP value 19.2), tricyclodecane dimethanol diacrylate (SP value 20.3), cyclic trimethylolpropane formal acrylate (SP value 19.1), dioxane glycol diacrylate (SP value 19.4), EO-modified diglycerin tetraacrylate (SP value 20.9), and the like. In addition, as the active energy ray-curable compound (B), commercially available products can also be suitably used, such as ARONIX M-220 (manufactured by Toagosei Co., Ltd., SP value 19.0), Light Acrylate 1,9ND-A (manufactured by Kyoeisha Chemical Co., Ltd., SP value 19.2), Light Acrylate DGE-4A (manufactured by Kyoeisha Chemical Co., Ltd., SP value 20.9), Light Acrylate DCP-A (manufactured by Kyoeisha Chemical Co., Ltd., SP value 20.3), SR-531 (manufactured by SARTOMER Co., Ltd., SP value 19.1), and CD-536 (manufactured by SARTOMER Co., Ltd., SP value 19.4).

The active energy ray curable compound (C) may be any compound having a radical polymerizable group such as a (meth)acrylate group and an SP value of 21.0 (MJ/m ³ ) 1/2 or more and 26.0 (MJ/m ³ ) 1/2 or less. Specific examples of the active energy ray curable compound (C) include acryloylmorpholine (SP value 22.9), N-methoxymethylacrylamide (SP value 22.9), and N-ethoxymethylacrylamide (SP value 22.3). Commercially available products may also be suitably used as the active energy ray curable compound (C), such as ACMO (manufactured by Kojin Co., Ltd., SP value 22.9), Wasmer 2MA (manufactured by Kasano Kosan Co., Ltd., SP value 22.9), Wasmer EMA (manufactured by Kasano Kosan Co., Ltd., SP value 22.3), and Wasmer 3MA (manufactured by Kasano Kosan Co., Ltd., SP value 22.4).

Details of the adhesive composition are described in, for example, JP 2019-147865 A. The description of this patent document is incorporated herein by reference. By bonding the optical film and an adhesive layer composed of the adhesive composition, the adhesive properties of the optical film can be further improved.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring and evaluating each property are as follows.
(1) In-plane retardation The optical films obtained in the examples and comparative examples were cut into a length of 4 cm and a width of 4 cm to prepare a measurement sample. The in-plane retardation Re(550) of the measurement sample was measured using an Axometrics product named "Axoscan."
(2) Refractive index and birefringence Δnxy
The measurement was performed using an Abbe refractometer (DR-M2, manufactured by Atago Co., Ltd.) in an environment of 23°C.
(3) Thickness The thickness of 10 μm or less was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-9800"), and the thickness of more than 10 μm was measured using a digital micrometer (manufactured by Anritsu Co., Ltd., product name "KC-351C").
(4) Degree of Orientation The degrees of orientation of the optical films obtained in the examples and comparative examples were determined by X-ray diffraction (XRD).
(5) Humidification Retardation Change The optical films obtained in the Examples and Comparative Examples were cut into 5 cm x 5 cm pieces, and an adhesive was attached to one side of the pieces using a hand roller. The adhesive side was then attached to one side of an alkaline glass to obtain a test piece. The test piece was stored in an oven at a temperature of 65°C and a humidity of 90% for 500 hours (humidification test), and the change in retardation (%) before and after the test was calculated. A change in retardation of 10% or less was considered good, and a change in retardation of more than 10% was considered bad.
(6) Parallel hue a value and b value The parallel hue a value and the parallel hue b value of the optical films obtained in the examples and comparative examples were determined. The measurements were performed using a spectrophotometer (manufactured by JASCO Corporation, product name "V-7100"). A change rate of 1% or less between the b value before and after 100 hours of exposure to an ultraviolet ray fade tester (device name: ultraviolet ray fade meter tester U48, manufactured by Suga Test Instruments Co., Ltd.) was determined as good, and a change rate of more than 1% was determined as bad.
(7) Adhesion The optical film and the polarizer obtained in the examples and comparative examples were bonded together to obtain a laminate. The obtained laminate was cut into a size of 200 mm parallel to the stretching direction of the polarizer and 15 mm in the perpendicular direction, and the laminate was bonded to a glass plate. Then, a cut was made between the optical film and the polarizer with a cutter knife, and the optical film and the polarizer were peeled off in the 90-degree direction at a peeling speed of 1000 mm/min using a Tensilon universal testing machine RTC (manufactured by A&D Co., Ltd.), and the peel strength (N/15 mm) was measured. A peel strength of 1 N/15 mm or more was considered good, and a peel strength of less than 1 N/15 mm was considered bad.

[Example 1]
81.98 parts by mass of isosorbide (hereinafter sometimes abbreviated as "ISB"), 47.19 parts by mass of tricyclodecane dimethanol (hereinafter sometimes abbreviated as "TCDDM"), 175.1 parts by mass of diphenyl carbonate (hereinafter sometimes abbreviated as "DPC"), and 0.979 parts by mass of a 0.2% by mass aqueous solution of cesium carbonate as a catalyst were charged into a reaction vessel, and in a nitrogen atmosphere, as the first step of the reaction, the temperature of the heating vessel was heated to 150°C, and the raw materials were dissolved while stirring as necessary (about 15 minutes). Next, the pressure was changed from normal pressure to 13.3 kPa, and the temperature of the heating vessel was increased to 190°C over one hour, while the generated phenol was extracted from the reaction vessel. After the entire reaction vessel was kept at 190°C for 15 minutes, the pressure in the reaction vessel was set to 6.67 kPa, the heating tank temperature was raised to 230°C in 15 minutes, and the generated phenol was extracted from the reaction vessel in the second step. As the stirring torque of the stirrer increased, the temperature was raised to 250°C in 8 minutes, and the pressure in the reaction vessel was allowed to reach 0.200 kPa or less in order to remove the further generated phenol. After reaching a predetermined stirring torque, the reaction was terminated, and the reaction product was extruded into water to obtain polycarbonate resin pellets. The birefringence Δnxy of the obtained polycarbonate resin was 0.015. The obtained polycarbonate resin was vacuum-dried at 100 ° C. for 12 hours, and then an optical film composed of polycarbonate resin was produced using a film-forming device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250 ° C.), a T-die (width 1700 mm, set temperature: 250 ° C.), a cast roll (set temperature: 60 ° C.) and a winder, with a film-forming line speed of 7 m / min. The orientation degree of the obtained optical film was 7.4%, the in-plane retardation Re (550) was 6 nm, and the thickness was 40 μm. The obtained optical film was subjected to the above evaluations (5) to (7). The results are shown in Table 1.

[Example 2]
An optical film was obtained in the same manner as in Example 1, except that the film-forming line speed was 8 m/min and the thickness was 30 μm. The degree of orientation of the obtained optical film was 5.7%, and the in-plane retardation Re(550) was 3 nm. The obtained optical film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 3]
An optical film was obtained in the same manner as in Example 1, except that the birefringence Δnxy of the polycarbonate resin was 0.018, the film-forming line speed was 10 m/min, and the thickness was 20 μm. The degree of orientation of the obtained optical film was 6.1%, and the in-plane retardation Re(550) was 2 nm. The obtained optical film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 4]
An optical film was obtained in the same manner as in Example 1, except that the birefringence Δnxy of the polycarbonate resin was 0.024, the film-forming line speed was 12 m/min, and the thickness was 20 μm. The degree of orientation of the obtained optical film was 8.1%, and the in-plane retardation Re(550) was 2 nm. The obtained optical film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
An optical film was obtained in the same manner as in Example 1, except that the birefringence Δnxy of the polycarbonate resin was 0.016 and the film-forming line speed was 5 m/min. The degree of orientation of the obtained optical film was 4.8%, and the in-plane retardation Re(550) was 5 nm. The obtained optical film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
An optical film was obtained in the same manner as in Example 1, except that a triacetyl cellulose (TAC) film (manufactured by Konica Minolta, Inc., product name "KC4UA") with a birefringence Δnxy of 0.018 was used and the line speed was 15 m/min. The degree of orientation of the obtained optical film was 5.1%, and the in-plane retardation Re(550) was 2 nm. The obtained optical film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
(Polymerization of polyester carbonate resin)
Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux condenser controlled at 100°C. 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by mass (0.200 mol) of isosorbide (ISB), 42.28 parts by mass (0.139 mol) of spiroglycol (SPG), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19 x 10 ^-2 parts by mass (6.78 x 10 ^-5 mol) of calcium acetate monohydrate as a catalyst were charged. After the inside of the reactor was replaced with nitrogen under reduced pressure, it was heated with a heat medium, and stirring was started when the inside temperature reached 100°C. The internal temperature was allowed to reach 220°C 40 minutes after the start of the temperature rise, and the pressure was controlled to maintain this temperature while simultaneously starting decompression, and the pressure was reduced to 13.3 kPa in 90 minutes after reaching 220°C. Phenol vapor by-produced during the polymerization reaction was led to a reflux condenser at 100°C, a small amount of monomer components contained in the phenol vapor were returned to the reactor, and uncondensed phenol vapor was led to a condenser at 45°C and recovered. Nitrogen was introduced into the first reactor to restore the pressure to atmospheric pressure once, and the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature rise and decompression in the second reactor were started, and the internal temperature was set to 240°C and the pressure to 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined stirring power was reached. Nitrogen was introduced into the reactor at the time the predetermined power was reached to restore the pressure, and the polyester carbonate resin produced was extruded into water, and the strands were cut to obtain pellets. The birefringence Δnxy of the obtained polycarbonate resin was 0.012.

(Preparation of Optical Film)
The obtained polyester carbonate resin (pellets) was vacuum-dried at 80 ° C for 5 hours, and then a film-forming device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 270 ° C), a T-die (width 1700 mm, setting temperature: 270 ° C), a cast roll (setting temperature: 75 ° C) and a winder was used to produce a long optical film with a thickness of 40 μm at a film-forming line speed of 8 m / min. The orientation degree of the obtained optical film was 4.3%, and the in-plane retardation Re (550) was 7 nm. The obtained optical film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 4]
A triacetyl cellulose film having a thickness of 40 μm was subjected to rubbing treatment and coating. The in-plane retardation Re(550) of the obtained optical film was 3 nm, and the thickness was 2 μm. The obtained optical film was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

As is clear from Table 1, the optical films of the examples of the present invention are excellent in all respects: humidification phase difference change, weather resistance, and adhesion. This is presumably achieved by forming a resin film containing a specific polycarbonate resin having a specific birefringence Δnxy at a specific line speed. Furthermore, a comparison between Examples 1 to 4 and Comparative Example 4 shows that the use of an optical film that does not contain an ultraviolet absorber suppresses hue change in weather resistance tests.

The optical film and polarizing plate according to the embodiment of the present invention are suitable for use in image display devices.

Claims (2)

A method for producing an optical film containing a polycarbonate-based resin, comprising the steps of:
the polycarbonate-based resin contains a structural unit derived from a dihydroxy compound and a structural unit derived from an alicyclic dihydroxy compound,
The dihydroxy compound is represented by the following formula (4):

The alicyclic dihydroxy compound is represented by the following general formula (II), R ¹ is a structure represented by the following (IIb), and n=0;
HOCH ₂ -R ¹ -CH ₂ OH (II)

The polycarbonate-based resin has a birefringence Δnxy of 0.015 or more during polymerization,
The production method includes a film-forming step in which the film-forming line speed in the extrusion molding method or the line speed in the cast coating method is 7 m/min to 12 m/min,
the degree of orientation of the obtained optical film is 5% or more, the in-plane retardation Re(550) is 20 nm or less, the retardation change rate after being kept at 65° C. and 90% RH for 500 hours is 10% or less, and the b value change rate in an ultraviolet weather resistance test is 1% or less;
Manufacturing method. The method for producing an optical film according to claim 1 , wherein the resulting optical film does not contain an ultraviolet absorbing agent.