CN114114510A

CN114114510A - Retardation film and polarizing plate

Info

Publication number: CN114114510A
Application number: CN202111011856.5A
Authority: CN
Inventors: 姜太艳; 中原步梦
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2020-09-01
Filing date: 2021-08-31
Publication date: 2022-03-01
Also published as: KR20220029386A; TW202210561A; JP2022041638A

Abstract

Provided are a retardation film and a polarizing plate which are suppressed in the occurrence of defective processes during conveyance, suppressed in the occurrence of bright spots when the film is pressed, suppressed in the occurrence of whitening and/or cracking, and further excellent in bendability and sebum resistance. A retardation film comprising a specific polycarbonate resin, wherein the retardation film has an in-plane retardation Re (550) of 200 to 400nm, an Re (450)/Re (550) of 0.98 to 1.03, and a puncture modulus of 50gf/mm or more.

Description

Retardation film and polarizing plate

Technical Field

The present invention relates to a retardation film and a polarizing plate.

Background

In recent years, with the spread of thin displays, image display devices (organic EL display devices) equipped with organic EL panels have been proposed. The organic EL panel has a metal layer with high reflectivity, and is prone to problems such as external light reflection and background reflection. Thus, it is known to prevent these problems by providing a phase difference film on the observation side. However, in the conventional retardation film, process defects such as wrinkles, creases, and impact marks may occur during the conveyance of the film, and furthermore, bright spots may occur when the film is pressed. Further, when a conventional retardation film is used on the observation side of an image display device, whitening and/or cracking may occur with use, and further, bendability and sebum resistance may be insufficient.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 3325560

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above conventional problems, and an object thereof is to provide a retardation film which suppresses the occurrence of defective steps during transportation, suppresses the occurrence of bright spots when the film is pressed, suppresses the occurrence of whitening and/or cracks, and is further excellent in bendability and sebum resistance.

Means for solving the problems

A retardation film according to an embodiment of the present invention comprises a polycarbonate resin, and has an in-plane retardation Re (550) of 200 to 400nm, an Re (450)/Re (550) of 0.98 to 1.03, and a puncture modulus of 50gf/mm or more.

In one embodiment, the retardation film has a puncture strength per unit film thickness of 10gf/μm or more.

In one embodiment, the retardation film has a breaking strength of 800MPa or more.

In one embodiment, the retardation film has a thickness of 30 to 50 μm.

In one embodiment, the variation in Re (550) in the width direction of the retardation film is 5nm or less.

In one embodiment, the retardation film has an absolute value of a change rate of the in-plane retardation Re (550) of 3% or less after 500 hours at a temperature of 65 ℃ and a humidity of 90%.

In one embodiment, the retardation film has a moisture permeability of 100g/m²24h or less.

In one embodiment, the retardation film has an elongation at break of 4% or more.

In another embodiment of the present invention, a polarizing plate with a retardation layer is provided. The polarizing plate with a retardation layer comprises a polarizing material and the retardation film, wherein the retardation film is bonded to at least one surface of the polarizing material via an adhesive layer.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the embodiment of the present invention, the retardation film can be obtained which contains the specific polycarbonate-based resin and has the puncture modulus within the specific range, and which is suppressed in the occurrence of process defects during transportation and excellent in the bendability. Further, by setting the puncture strength, the breaking strength, and the breaking elongation per unit film thickness within specific ranges, a retardation film can be realized which is suppressed in the occurrence of bright spots when the film is pressed, and which is excellent in sebum resistance and crack resistance.

Detailed Description

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

(definitions of terms and symbols)

The definitions of terms and symbols in the present specification are as follows.

(1) Refractive index (nx, ny, nz)

"nx" is a refractive index in a direction in which the in-plane refractive index is maximized (i.e., the slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and "nz" is a refractive index in the thickness direction.

(2) In-plane retardation (Re)

"Re (. lamda)" is an in-plane retardation measured by using light having a wavelength of λ nm at 23 ℃. For example, "Re (550)" is an in-plane retardation measured by using light having a wavelength of 550nm at 23 ℃. When the thickness of the layer (film) is d (nm), Re (λ) is obtained by the formula Re (λ) ═ nx-ny × d.

A. Retardation film

The retardation film according to the embodiment of the present invention contains a polycarbonate resin. Typically, the retardation film according to the embodiment of the present invention is a stretched film of a polycarbonate resin film.

The retardation film has an in-plane retardation Re (550) of 200 to 400nm, preferably 220 to 380nm, and more preferably 240 to 360 nm. That is, the retardation film can function as a λ/2 retardation plate.

The retardation film exhibits a flat wavelength dispersion characteristic in which the phase difference value hardly changes depending on the wavelength of the measurement light. The phase difference film has Re (450)/Re (550) of 0.98 to 1.03, preferably 0.99 to 1.03, and more preferably 1.00 to 1.03. By using a polycarbonate-based resin having such Re (450)/Re (550), excellent antireflection properties can be achieved.

The above retardation film has a puncture modulus of 50gf/mm or more, preferably 100gf/mm or more, and more preferably 150gf/mm or more. The puncture modulus is: the value obtained by dividing the force (gf) immediately before the film breaks (or breaks) by the strain (mm) at that time when the needle (piercing jig) pierces the main surface of the film perpendicularly. By providing the retardation film with the puncture modulus as described above, it is possible to obtain a retardation film which is suppressed in occurrence of process defects and the like during transportation and is excellent in bendability.

The puncture strength per unit film thickness of the retardation film is preferably 10gf/μm or more, more preferably 15gf/μm or more, and still more preferably 20gf/μm or more. Puncture strength per unit film thickness is represented by: the needle was lowered perpendicularly to the film, and the strength at the time of breakage of the film was divided by the thickness. By providing the retardation film with the above-described puncture strength per unit film thickness, it is possible to obtain a retardation film which is suppressed in the occurrence of bright spots when pressed against the film and is excellent in sebum resistance.

The fracture strength of the retardation film is preferably 800MPa or more, more preferably 1500MPa or more, and still more preferably 2500MPa or more. The upper limit of the breaking strength of the retardation film may be 7000MPa, for example. The breaking strength indicates the stress at which the film breaks in the tensile test. When the breaking strength of the retardation film is in such a range, a retardation film having excellent crack resistance can be obtained.

The retardation film preferably has an elongation at break of 4% or more, more preferably 5% or more. The upper limit of the elongation at break of the retardation film may be, for example, 300%. Elongation at break is expressed as: after the film was cut, a tensile test was performed, and the film was subjected to strain at break (elongation). When the elongation at break of the retardation film is in such a range, a retardation film having excellent crack resistance can be obtained.

The thickness of the retardation film is preferably 30 to 50 μm, more preferably 35 to 45 μm. By setting the thickness of the retardation film in such a range, the retardation film can be suitably applied to a thin device.

The variation in Re (550) in the width direction of the retardation film is preferably 5nm or less, more preferably 3nm or less, and still more preferably 2nm or less. The lower limit of the variation in Re (550) in the width direction of the retardation film may be, for example, 0.5 nm. By setting the variation in Re (550) to such a range, good optical uniformity of the retardation film can be achieved.

The absolute value of the change rate of the in-plane retardation Re (550) of the retardation film after 500 hours at a temperature of 65 ℃ and a humidity of 90% is preferably 3% or less, and more preferably 2% or less. The lower limit of the absolute value of the rate of change may be, for example, 0.01%. The rate of change of the retardation is | (Re)₅₀₀-Re₀)/Re₀Expressed as | × 100 (%). Re₀The in-plane retardation (nm), Re of the retardation film before the start of the test₅₀₀The in-plane retardation (nm) of the retardation film after the test was obtained. When the absolute value of the rate of change of the in-plane retardation Re (550) of the retardation film is in such a range, when the retardation film is applied to an image display device, the color change due to the retardation at each position on the image display device becomes small, and the occurrence of color unevenness in display can be suppressed.

The moisture permeability of the retardation film is preferably 150g/m²24h or less, more preferably 120g/m²24h or less, more preferably 100g/m²24h or less. The lower limit of the moisture permeability may be, for example, 1g/m²24 h. If the moisture permeability of the retardation film is in such a range, the change in retardation in a humidified environment can be suppressed.

The absolute value of the photoelastic coefficient of the retardation film is preferably 2X 10^-11m²A value of/N or less, more preferably 2.0X 10^-13m²/N～1.5×10^-11m²/N is more preferably 1.0X 10^-12m²/N～1.2×10^-11m²and/N. If the absolute value of the photoelastic coefficient of the retardation film is in this range, the retardation film is less likely to change when a shrinkage stress is generated during heating. As a result, when the retardation film is applied to an image display device, thermal unevenness of the image display device can be prevented satisfactorily.

According to the embodiments of the present invention, as described above, a retardation film satisfying desired in-plane retardation, wavelength dispersion characteristics, and thickness, suppressing occurrence of process defects during transportation, suppressing occurrence of bright spots when the film is pressed, and having excellent flexibility, sebum resistance, and crack resistance can be obtained. Such a retardation film can be suitably applied to, for example, a notebook Personal Computer (PC) and a vehicle display.

B. Constituent Material

As described above, the retardation film is typically a stretched film of a polycarbonate resin film.

(polycarbonate resin)

The polycarbonate resin of the present invention comprises at least a structural unit derived from a dihydroxy compound having a bonding structure represented by the following structural formula (1) by including at least a dihydroxy compound having at least one bonding structure-CH in the molecule₂A dihydroxy compound of the dihydroxy compound of-O-and a carbonic acid diester are reacted in the presence of a polymerization catalyst.

Here, the dihydroxy compound having a bonding structure represented by the formula (1) is not particularly limited as long as it has 2 alcoholic hydroxyl groups and contains a linking group-CH in the molecule₂The compound having the structure of-O-and capable of reacting with a carbonic acid diester in the presence of a polymerization catalyst to produce a polycarbonate may be any compound having any structure, and a plurality of compounds may be used in combination. Further, as the dihydroxy compound used in the polycarbonate resin of the present invention, any combination thereof may be usedA dihydroxy compound having a bonding structure represented by the structural formula (1). Hereinafter, the dihydroxy compound having a bonding structure represented by the structural formula (1) may be abbreviated as the dihydroxy compound (a), and the dihydroxy compound having no bonding structure represented by the structural formula (1) may be abbreviated as the dihydroxy compound (B).

(dihydroxy Compound (A))

"linking group-CH" in dihydroxy Compound (A)₂The term "O-" refers to a structure in which atoms other than hydrogen atom are bonded to each other to constitute a molecule. In the linking group, carbon atoms are most preferable as atoms capable of bonding to at least oxygen atoms or atoms capable of bonding to both carbon atoms and oxygen atoms. "linking group-CH" in dihydroxy Compound (A)₂The number of-O- "is preferably 1 or more, more preferably 2 to 4.

More specifically, examples of the dihydroxy compound (A) include 9, 9-bis (4- (2-hydroxyethoxy) phenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-methylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-isopropylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-isobutylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-tert-butylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-cyclohexylphenyl) fluorene, 9-bis (4- (2-hydroxyethoxy) -3-phenylphenyl) fluorene, 9-bis (2-hydroxyethoxy) -3-phenylphenyl) fluorene, and the like, Compounds having an aromatic group in a side chain and an ether group bonded to the aromatic group in a main chain, such as 9, 9-bis (4- (2-hydroxyethoxy) -3, 5-dimethylphenyl) fluorene, 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-hydroxyethoxy) phenyl ] diphenylmethane, 1-bis [4- (2-hydroxyethoxy) phenyl ] ethane, 1-bis [4- (2-hydroxyethoxy) phenyl ] -1-phenylethane, 2-bis [4- (2-hydroxyethoxy) phenyl ] propane, 2-bis [4- (2-hydroxyethoxy) -3-methylphenyl ] propane, 2-bis [3, 5-dimethyl-4- (2-hydroxyethoxy) phenyl ] propane, 1-bis [4- (2-hydroxyethoxy) phenyl ] -3, 5-trimethylcyclohexane, 1-bis [4- (2-hydroxyethoxy) phenyl ] cyclohexane, 1, 4-bis [4- (2-hydroxyethoxy) phenyl ] cyclohexane, 1, 3-bis [4- (2-hydroxyethoxy) phenyl ] cyclohexane, 2-bis [4- (2-hydroxyethoxy) -3-phenylphenyl ] propane, 2-bis [ (2-hydroxyethoxy) -3-isopropylphenyl ] propane, 2-bis [ 3-tert-butyl-4- (2-hydroxyethoxy) phenyl ] propane, 2-bis [4- (2-hydroxyethoxy) phenyl ] butane, 2-bis [4- (2-hydroxyethoxy) phenyl ] -4-methylpentane, 2-bis [4- (2-hydroxyethoxy) phenyl ] pentane, Bis (hydroxyalkoxyaryl) alkanes such as exemplified by 2, 2-bis [4- (2-hydroxyethoxy) phenyl ] octane, 1-bis [4- (2-hydroxyethoxy) phenyl ] decane, 2-bis [ 3-bromo-4- (2-hydroxyethoxy) phenyl ] propane, and 2, 2-bis [ 3-cyclohexyl-4- (2-hydroxyethoxy) phenyl ] propane; bis (hydroxyalkoxyaryl) cycloalkanes such as 1, 1-bis [4- (2-hydroxyethoxy) phenyl ] cyclohexane, 1-bis [ 3-cyclohexyl-4- (2-hydroxyethoxy) phenyl ] cyclohexane, and 1, 1-bis [4- (2-hydroxyethoxy) phenyl ] cyclopentane; dihydroxyalkoxy diaryl ethers exemplified by 4,4 ' -bis (2-hydroxyethoxy) diphenyl ether and 4,4 ' -bis (2-hydroxyethoxy) -3,3 ' -dimethyldiphenyl ether; bishydroxyalkoxyaryl sulfides exemplified by 4,4 '-bis (2-hydroxyethoxyphenyl) sulfide and 4, 4' -bis [4- (2-dihydroxyethoxy) -3-methylphenyl ] sulfide; bishydroxyalkoxyarylsulfoxides exemplified by 4,4 '-bis (2-hydroxyethoxyphenyl) sulfoxide and 4, 4' -bis [4- (2-dihydroxyethoxy) -3-methylphenyl ] sulfoxide; bishydroxyalkoxyaryl sulfones such as exemplified by 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, 1, 3-bis [2- [4- (2-hydroxyethoxy) phenyl ] propyl ] benzene, 1, 4-bis [2- [4- (2-hydroxyethoxy) phenyl ] propyl ] benzene, 4' -bis (2-hydroxyethoxy) biphenyl, 1, 3-bis [4- (2-hydroxyethoxy) phenyl ] -5, 7-dimethyladamantane, an anhydrosugar alcohol represented by a dihydroxy compound represented by the following formula (4); and a compound having a cyclic ether structure such as spiroglycol represented by the following general formula (6), and these may be used alone or in combination of 2 or more.

These dihydroxy compounds (A) may be used alone or in combination of 2 or more. In the present invention, examples of the dihydroxy compound represented by the formula (4) include isosorbide, isomannide, and isoidide which are stereoisomeric, and 1 kind of these compounds may be used alone or 2 or more kinds may be used in combination.

Among the dihydroxy compounds (a), isosorbide obtained by dehydration condensation of sorbitol produced from various starches which are abundant as resources and easily available is most preferable from the viewpoints of easiness of obtaining and 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, as the dihydroxy compound, a dihydroxy compound (B) which is a dihydroxy compound other than the dihydroxy compound (a) can be used. As the dihydroxy compound (B), for example, an alicyclic dihydroxy compound, an aliphatic dihydroxy compound, an oxyalkylene glycol, an aromatic dihydroxy compound, and a diol having a cyclic ether structure can be used as the dihydroxy compound forming the structural unit of the polycarbonate, together with the dihydroxy compound (A), for example, the dihydroxy compound represented by the formula (4).

The alicyclic dihydroxy compound that can be used in the present invention is not particularly limited, and a compound generally having a five-membered ring structure or a six-membered ring structure is preferably used. Further, the six-membered ring structure may be fixed in a chair or boat shape by means of covalent bonds. The alicyclic dihydroxy compound has a five-membered ring or six-membered ring structure, and thus the heat resistance of the obtained polycarbonate can be improved. 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 the value, the higher the heat resistance, but the synthesis or purification is difficult or the cost is expensive. The smaller the number of carbon atoms, the easier purification and acquisition.

Specific examples of the alicyclic dihydroxy compound containing a five-membered ring structure or a six-membered ring structure that can be used in the present invention include alicyclic dihydroxy compounds represented by the following general formula (II) or (III).

HOCH₂-R¹-CH₂OH (II)

HO-R²-OH (III)

(in the formulae (II) and (III), R¹、R²Each represents a C4-20 cycloalkylene group. )

The cyclohexanedimethanol which is the alicyclic dihydroxy compound represented by the above general formula (II) includes R in the general formula (II)¹Using the following general formula (IIa) (wherein R is³An 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.

The tricyclodecanedimethanol and pentacyclopentadecane dimethanol which are alicyclic dihydroxy compounds represented by the above general formula (II) include R in the general formula (II)¹Various isomers represented by the following general formula (IIb) (wherein n represents 0 or 1).

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

In addition, as toNorbornandimethanol which is an alicyclic dihydroxy compound represented by the above general formula (II) includes R in the general formula (II)¹Various isomers represented by the following general formula (IId). Specific examples of such isomers include 2, 3-norbornanedimethanol and 2, 5-norbornanedimethanol.

Adamantanedimethanol as the alicyclic dihydroxy compound represented by the general formula (II) includes R in the general formula (II)¹Various isomers represented by the following general formula (IIe). Specific examples of such isomers include 1, 3-adamantanedimethanol.

Further, the cyclohexanediols which are the alicyclic dihydroxy compounds represented by the above general formula (III) include R in the general formula (III)²Using the following general formula (IIIa) (wherein R³An 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.

The tricyclodecanediol and pentacyclopentadecane diol as the alicyclic dihydroxy compound represented by the above general formula (III) include R in the general formula (III)²Various isomers represented by the following general formula (IIIb) (wherein n represents 0 or 1).

As the alicyclic ring represented by the above general formula (III)Decahydronaphthalene diol or tricyclotetradetanediol of the formula dihydroxy compound, comprising R in formula (III)²Various isomers represented by the following general formula (IIIc) (wherein m represents 0 or 1). Specific examples of such isomers include 2, 6-decahydronaphthalene diol, 1, 5-decahydronaphthalene diol, and 2, 3-decahydronaphthalene diol.

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

The adamantanediol as the alicyclic dihydroxy compound represented by the above general formula (III) includes R in the general formula (III)²Various isomers represented by the following general formula (IIIe). Specific examples of such isomers include 1, 3-adamantanediol.

Among the specific examples of the alicyclic dihydroxy compound, cyclohexanedimethanol, tricyclodecanedimethanol, adamantanediol, and pentacyclopentadecane dimethanol are particularly preferable, and 1, 4-cyclohexanedimethanol, 1, 3-cyclohexanedimethanol, 1, 2-cyclohexanedimethanol, and tricyclodecanedimethanol are preferable from the viewpoint of ease of acquisition and ease of handling. In the present invention, tricyclodecanedimethanol is suitably used as the dihydroxy compound (B).

Examples of the aliphatic dihydroxy compound 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 the oxyalkylene glycol usable in the present invention include diethylene glycol, triethylene glycol, tetraethylene glycol and polyethylene glycol.

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

The glycols having a cyclic ether structure usable in the present invention include, for example, spiroglycols and dioxane glycols. The above-mentioned exemplary compounds are examples of alicyclic dihydroxy compounds, aliphatic dihydroxy compounds, oxyalkylene glycols, aromatic dihydroxy compounds, and glycols having a cyclic ether structure, which can be used in the present invention, but are not limited thereto at all. 1 or 2 or more of these compounds may be used together with the dihydroxy compound represented by formula (4).

By using these dihydroxy compounds (B), effects such as improvement in flexibility, improvement in heat resistance, and improvement in moldability according to the application can be obtained. The proportion of the dihydroxy compound (a), for example, the dihydroxy compound represented by formula (4), relative to the total 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, and still more preferably 60 mol% or more, and is preferably 90 mol% or less, more preferably 80 mol% or less, and still more preferably 70 mol% or less. If the content ratio of the structural unit derived from another dihydroxy compound is too large, the performance such as optical properties may be deteriorated.

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

The content ratio of the structural unit derived from the dihydroxy compound (a), for example, the dihydroxy compound represented by formula (4), and the structural unit derived from the alicyclic dihydroxy compound in the polycarbonate resin of the present invention may be selected at any ratio, and the structural unit derived from the dihydroxy compound represented by formula (4): the structural unit derived from the alicyclic dihydroxy compound is preferably 1:99 to 99:1 (mol%), and the structural unit derived from the dihydroxy compound represented by formula (4): the structural unit derived from the alicyclic dihydroxy compound is particularly preferably 10:90 to 90:10 (mol%). When the structural unit derived from the dihydroxy compound represented by formula (4) is more and the structural unit derived from the alicyclic dihydroxy compound is less than the above range, coloring tends to be easy, whereas when the structural unit derived from the dihydroxy compound represented by formula (4) is less and the structural unit derived from the alicyclic dihydroxy compound is more, the molecular weight tends to be less likely to increase.

Further, when an aliphatic dihydroxy compound, an oxyalkylene glycol, an aromatic dihydroxy compound, or a diol having a cyclic ether structure is used, the ratio of the dihydroxy compound (a), for example, the dihydroxy compound represented by formula (4), and the total of these various dihydroxy compounds to the total of all dihydroxy compounds constituting the polycarbonate is not particularly limited, and may be selected at any ratio. The content ratio of the structural unit derived from the dihydroxy compound (a), for example, the dihydroxy compound represented by the formula (4) to the structural unit derived from each of these dihydroxy compounds is not particularly limited, and may be selected at any ratio.

The details of the polycarbonate-based resin are described in, for example, Japanese patent laid-open No. 2012-31370 (Japanese patent No. 5448264). The description of this patent document is incorporated herein by reference.

C. Method for producing retardation film

The method for producing a retardation film according to an embodiment of the present invention includes stretching a resin film. The resin film is a film formed of the polycarbonate resin described in the above item B.

In one embodiment, the retardation film may be produced by biaxial stretching. The biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. The stretching ratio in the longitudinal direction is preferably more than 1.0 times and 2.0 times or less, and more preferably 1.1 to 1.5 times. The stretching ratio in the width direction is preferably 1.6 to 2.2 times, and more preferably 1.8 to 2.0 times. By stretching a film made of the polycarbonate resin at such a stretch ratio, not only desired optical properties but also very excellent mechanical properties (e.g., bendability, sebum resistance, and crack resistance) can be realized.

The stretching temperature of the resin film is preferably from Tg-30 ℃ to Tg +30 ℃, more preferably from Tg-15 ℃ to Tg +15 ℃, and still more preferably from Tg-10 ℃ to Tg +10 ℃. By stretching at such a temperature, a retardation film having appropriate properties can be obtained in the present invention. The Tg is the glass transition temperature of the constituent material of the thin film.

D. Polarizing plate with phase difference layer

The retardation film according to any one of the above items A to C may be provided in the form of a laminate with other retardation films and/or optical members. In one embodiment, the retardation film may be provided in the form of a laminate thereof with a polarizing plate (typically, a polarizing plate with a retardation layer). Accordingly, the present invention includes a polarizing plate with a retardation layer, which comprises the above retardation film. In the retardation film, the angle formed by the absorption axis of the polarizer of the polarizing plate and the slow axis of the retardation film can be appropriately set depending on the application and the purpose. In one embodiment, the angle is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and still more preferably about 45 °.

Typically, a polarizing plate with a retardation layer includes a polarizing material and the above retardation film, and the retardation film is bonded to at least one surface of the polarizing material via an adhesive layer. The polarizer may have a protective layer on at least one surface of the polarizer. Further, the polarizing plate may have an adhesive layer and a separator on the surface opposite to the observation side.

As the polarizer, any and appropriate polarizer may be used. For example, the resin film forming the polarizer may be a single-layer resin film, or may be a laminate of two or more layers.

Specific examples of the polarizer made of a single-layer resin film include: a polarizing element obtained by subjecting a hydrophilic polymer film such as a polyvinyl alcohol (PVA) -based film, a partially formalized PVA-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film to a dyeing treatment using a dichroic material such as iodine or a dichroic dye and a stretching treatment; and polyene-based oriented films such as dehydrated products of PVA and desalted products of polyvinyl chloride. From the viewpoint of excellent optical properties, a polarizer obtained by uniaxially stretching a PVA-based film dyed with iodine is preferably used.

The iodine-based dyeing is performed by, for example, immersing a PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. Further, dyeing may be performed after stretching. The PVA-based film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as necessary. For example, by immersing the PVA-based film in water and washing it with water before dyeing, not only dirt and an antiblocking agent on the surface of the PVA-based film can be washed off, but also the PVA-based film can be swollen to prevent uneven dyeing and the like.

Specific examples of the polarizer obtained by using the laminate include: a polarizing element obtained by using a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate of a resin substrate and a PVA-based resin layer applied to the resin substrate. Details of a method for producing such a polarizer are described in, for example, japanese patent laid-open No. 2012 and 73580 (japanese patent No. 5414738). The description of this patent document is incorporated herein by reference. The entire disclosure of this publication is incorporated herein by reference.

In one embodiment, the thickness of the polarizer is preferably 1 μm to 25 μm, more preferably 3 μm to 10 μm, and still more preferably 3 μm to 8 μm. If the thickness of the polarizer is in this range, the warpage during heating can be favorably suppressed and favorable durability of appearance during heating can be obtained.

The protective layer is formed of an arbitrary and appropriate protective film that can be used as a film for protecting the polarizer. Specific examples of the material to be the main component of the protective film include cellulose resins such as Triacetylcellulose (TAC), polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyethersulfone resins, polysulfone resins, polystyrene resins, polynorbornene resins, polyolefin resins, (meth) acrylic resins, and acetate resins. Further, there may be mentioned thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, silicone and the like, ultraviolet-curable resins and the like. In addition, for example, a glassy polymer such as a siloxane polymer can be cited. Further, the polymer film described in Japanese patent application laid-open No. 2001-343529 (WO01/37007) can also be used. As a material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain can be used, and for example, a resin composition containing an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be mentioned. The polymer film may be, for example, an extrusion molded product of the above resin composition.

The thickness of the protective layer is preferably 10 μm to 100 μm. The protective layer may be laminated on the polarizer via an adhesive layer (specifically, an adhesive layer or an adhesive layer), or may be laminated on the polarizer in close contact (without an adhesive layer). If necessary, a surface treatment layer such as a hard coat layer, an antiglare layer, and an antireflection layer may be formed on the protective layer disposed on the outermost surface of the polarizing plate with a retardation layer.

The polarizing plate with the retardation layer can be used on the observation side of an image display device. Further, the retardation layer in the polarizing plate with a retardation layer may be disposed on the observation side or on the display unit side.

As the adhesive for forming the adhesive layer, any and appropriate adhesive can be used. Examples of the base resin of the binder include acrylic resins, styrene resins, silicone resins, urethane resins, and rubber resins. Such a base resin is described in, for example, Japanese patent laid-open Nos. 2015-120337 (Japanese patent No. 6457789) and 2011-201983. The descriptions of these publications are incorporated herein by reference. Examples of the crosslinking agent that the adhesive may contain include isocyanate compounds, epoxy compounds, and aziridine compounds. The binder may comprise, for example, a silane coupling agent. The compounding recipe of the adhesive can be appropriately set according to the target and the desired characteristics.

The storage modulus of the adhesive layer is preferably 1.0X 10⁴Pa～1.0×10⁷Pa, more preferably 2.0X 10⁴Pa～5.0×10⁶Pa. If the storage modulus of the adhesive layer is in such a range, blocking when forming a roll can be suppressed. The storage modulus can be determined by, for example, dynamic viscoelasticity measurement at a temperature of 23 ℃ and an angular velocity of 0.1 rad/s.

The thickness of the pressure-sensitive adhesive layer is preferably 1 to 60 μm, more preferably 3 to 30 μm. If the thickness is too thin, the adhesiveness is insufficient, and air bubbles may enter the adhesion interface. If the thickness is too large, a trouble such as extrusion of the adhesive is likely to occur.

In practice, the separator is temporarily bonded to the surface of the pressure-sensitive adhesive layer in a releasable manner until the retardation film is actually used. Examples of the separator include a plastic (for example, polyethylene terephthalate (PET), polyethylene, or polypropylene) film, a nonwoven fabric, or paper, which is surface-coated with a release agent such as a silicone release agent, a fluorine release agent, or a long chain alkyl acrylate release agent. The thickness of the separator may be any and appropriate thickness according to the purpose. The thickness of the separator is, for example, 10 to 100 μm.

Examples

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement method and evaluation method of each characteristic are as follows.

(1) In-plane retardation and wavelength dispersion characteristics

The retardation films obtained in examples and comparative examples were cut into a length of 4cm and a width of 4cm to obtain measurement samples. The in-plane retardation Re (550) was measured using a sample manufactured by Axometrics under the product name "Axoscan". Further, Re (450) was measured, and Re (450)/Re (550) was calculated.

(2) Thickness of

The thickness of 10 μm or less was measured by using an interference film thickness meter (available under the name "MCPD-3000" manufactured by Otsuka electronics Co., Ltd.). The thickness exceeding 10 μm was measured by using a digital micrometer (product name "KC-351C" manufactured by ANRITSU Co., Ltd.).

(3) Moisture permeability

The retardation films obtained in examples and comparative examples were measured for their water vapor permeability test (cup method) according to JIS Z0208, and their passage area of 1m in 24 hours was measured at 40 ℃ and a humidity of 92% RH²The water vapor amount (g) of the sample (2).

(4) Variation of phase difference

The retardation films obtained in examples and comparative examples were cut into 5cm × 5cm, an adhesive was applied to one surface of the film by a hand roller, and the adhesive surface was applied to one surface of alkali glass to obtain a test piece. The test piece was stored in an oven at a temperature of 65 ℃ and a humidity of 90% for 500 hours (humidified test), and the phase difference change (%) before the start of the test and after the test was calculated.

(5) Deviation of phase difference

The in-plane retardation Re (550) of the retardation films obtained in examples and comparative examples was measured in the same manner as in (1). The retardation film was measured at 9 points in the width direction, and the difference between the maximum value and the minimum value of the retardation value was defined as the deviation of the retardation.

(6) Modulus of puncture

The puncture modulus was determined by dividing the force (gf) immediately before the fracture (or breakage) of the retardation film obtained in examples and comparative examples by the strain (mm) at that time when a needle (puncture jig) was punctured perpendicularly to the main surface of the retardation film. As the needle, a needle having a tip diameter of 1 mm. phi. and 0.5R was used. The puncture speed of the needle was set to 0.33 cm/sec. The measurement was carried out at a temperature of 23 ℃.

(7) Puncture strength

A test machine equipped with a needle having a tip diameter of 1 mm. phi. and 0.5R was used. And clamping the phase difference film by using two jigs with a circular hole in the center, and fixing the phase difference film on the testing machine. The pin is lowered vertically with respect to the retardation film so as to pass through the hole of the jig, and the strength of the retardation film at the time of breakage is measured. As for the test conditions, the puncture speed was set to 0.33 cm/sec in an environment at a temperature of 23. + -. 3 ℃. Puncture tests were performed on 12 test pieces, and the puncture strength per unit film thickness of the retardation film was determined by dividing the average value by the thickness of the retardation film.

(8) Breaking strength and elongation at break

The retardation films obtained in examples and comparative examples were cut into pieces having a width of 1cm × 13cm, and then a tensile test was carried out using an "Autograph ASG-50D" (manufactured by Shimadzu corporation) as a tensile tester under conditions of a tensile speed of 200mm/min, a distance between chucks of 50mm, and a room temperature (23 ℃), to determine a stress at the time of fracture of the retardation film, and as a fracture strength, a strain (elongation) at the time of fracture of the retardation film was determined as a fracture strength.

(9) Adhesion Property

The retardation films obtained in examples and comparative examples were bonded to a polarizer to obtain a laminate. The laminate thus obtained was cut into a size of 200mm in the direction parallel to the stretching direction of the polarizer and 15mm in the orthogonal direction, and the laminate was bonded to a glass plate. Then, a slit was made between the retardation film and the polarizer with a cutter, and the retardation film and the polarizer were peeled off at a peeling speed of 1000mm/min in a 90-degree direction by a TENSILON universal tester RTC (manufactured by A & D), and the peel strength (N/15mm) was measured. The peel strength was considered good when it was 1N/15mm or more, and poor when it was less than 1N/15 mm.

(10) Runnability (evaluation of defective Process during transportation)

When the retardation films obtained in examples and comparative examples were conveyed by guide rolls at a speed of 5m/min to 40m/min, the film was marked as good if no defects such as bending, scratching, and impact marks occurred (if the film could be conveyed without any problem), and as bad if bending, scratching, impact marks occurred.

(11) Flexibility (MIT test)

MIT test was performed according to JIS P8115. Specifically, the retardation films obtained in examples and comparative examples were cut into a length of 15cm and a width of 1.5cm to obtain measurement samples. The measurement sample was mounted on an MIT bending fatigue TESTER BE-202 type (manufactured by TESTER INDUSTRIAL CO., LTD.) (load: 1.0kgf, R: 0.38mm of a jig), and bending was repeated under conditions of a test speed of 90cpm and a bending angle of 90 degrees, and the number of times the measurement sample was broken was defined as a test value. The test value was considered good when the number of the tests was 500 or more, and poor when the number was less than 500.

(12) Evaluation of Bright Point at Press

The same sample as the sample evaluated in the puncture strength test was bonded to a polarizer, and the film side was pressed with a force of 10gf/μm by a puncture tester. Thereafter, 1 polarizing plate was prepared so as to be oriented at 90 ° to the polarizing plate, and transmitted light was transmitted from the opposite side of the film subjected to the puncture test in a state of crossed prisms, and if no bright point was observed, the film was marked as good, and if a bright point was observed, the film was marked as bad.

(13) Sebum resistance

The retardation films obtained in examples and comparative examples were cut into 5cm × 5cm, an adhesive was applied to one surface of the film by a hand roller, and the adhesive surface was applied to one surface of alkali glass to obtain a test piece. The test piece thus obtained was immersed in an oleic acid solution at 65 ℃ and 90% RH for 72 hours, and was considered good when it was transparent after being taken out, and was considered bad when whitening or cracking occurred.

(14) Crack resistance

The retardation films obtained in examples and comparative examples were subjected to a thermal shock test at-40 ℃ to 80 ℃ for 300 cycles, and then, when no crack of 300 μm or more was generated, good was observed, and when a crack of 300 μm or more was generated, poor was observed.

[ example 1]

1. Production of resin film

In a reaction vessel, 47.19 parts by mass of tricyclodecanedimethanol (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 mass% aqueous solution of cesium carbonate as a catalyst were charged to 81.98 parts by mass of isosorbide (hereinafter, sometimes abbreviated as "ISB"), and the heating bath temperature was heated to 150 ℃ in a nitrogen atmosphere, and the raw materials were dissolved with stirring as necessary (about 15 minutes) as a first step of the reaction. Then, the pressure was set to 13.3kPa from the normal pressure, and the generated phenol was taken out of the reaction vessel while increasing the temperature of the heating tank to 190 ℃ over 1 hour. After the entire reaction vessel was maintained at 190 ℃ for 15 minutes, the pressure in the reaction vessel was set to 6.67kPa as a second step, the temperature in the heating tank was increased to 230 ℃ over 15 minutes, and the produced phenol was taken out of the reaction vessel. Since the stirring torque of the stirrer was gradually increased, it took 8 minutes to raise the temperature to 250 ℃, and the pressure in the reaction vessel was set to 0.200kPa or less to remove the generated phenol. After the predetermined stirring torque was reached, the reaction was terminated, and the resultant reaction product was extruded into water to obtain pellets of a polycarbonate resin. The obtained polycarbonate resin was vacuum-dried at 80 ℃ for 5 hours, and then a polycarbonate resin film having a thickness of 90 μm was produced using a film forming apparatus equipped with a single-screw extruder (manufactured by Toshiba machine Co., Ltd., cylinder set temperature: 250 ℃), a T-die (width: 300mm, set temperature: 250 ℃), a chill roll (set temperature: 120 to 130 ℃) and a winder.

2. Production of retardation film

The unstretched polycarbonate resin film was subjected to a preheating treatment and simultaneous biaxial stretching using a simultaneous biaxial stretcher to obtain a retardation film. The preheating temperature was 133 ℃, the stretching temperature was 135 ℃, the stretching ratio in the longitudinal direction was 1.2 times, and the stretching ratio in the width direction was 1.9 times. The resulting retardation film had a chromatic dispersion value of 1.025, an in-plane retardation Re (550) of 269nm, a thickness of 40 μm, and a moisture permeability of 80g/m²24h, the retardation change was 0.8%, and the variation in-plane retardation was 2 nm. Further, the retardation film had a puncture modulus of 375gf/mm, a puncture strength of 24gf/μm, a breaking strength of 2530MPa, and an elongation at break of 5.6%. The obtained retardation film was subjected to the evaluations (9) to (14) above. The results are shown in Table 1.

[ example 2]

A retardation film was obtained in the same manner as in example 1 except that the preheating temperature was 133 ℃, the stretching temperature was 135 ℃, the stretching ratio in the longitudinal direction was 1.2 times, and the stretching ratio in the width direction was 1.9 times. The obtained retardation film had a wavelength dispersion value of 1.021, an in-plane retardation Re (550) of 271nm, a thickness of 40 μm, and a moisture permeability of 97g/m²24h, retardation change was 1%, and variation in-plane retardation was 2 nm. Further, the retardation film had a puncture modulus of 386gf/mm, a puncture strength of 24gf/μm, a breaking strength of 2530MPa, and an elongation at break of 5.6%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

[ example 3]

A retardation film was obtained in the same manner as in example 1 except that the preheating temperature was 133 ℃, the stretching temperature was 135 ℃, the stretching ratio in the longitudinal direction was 1.2 times, and the stretching ratio in the width direction was 1.9 times. The resulting retardation film had a wavelength dispersion value of 1.025, an in-plane retardation Re (550) of 300nm, a thickness of 40 μm, and a moisture permeability of 76g/m²24h, retardation variation of 0.8%, variation in-plane retardationIs 2 nm. Further, the retardation film had a puncture modulus of 398gf/mm, a puncture strength of 23gf/μm, a breaking strength of 2530MPa, and an elongation at break of 5.6%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

Comparative example 1

The axis of rotation of the brush roller was adjusted at 45 degrees counterclockwise with respect to the longitudinal direction of a cellulose Triacetate (TAC) film (manufactured by fuji film corporation), and brushing was performed. And coating liquid crystal on the TAC film subjected to brushing treatment to obtain a liquid crystal coated cellulose Triacetate (TAC) film. A retardation film was obtained in the same manner as in example 1, except that the TAC film was coated with the liquid crystal film without stretching the film. The resulting retardation film had a wavelength dispersion value of 1.09, an in-plane retardation Re (550) of 260nm, a thickness of 2 μm, and a moisture permeability of 330g/m²24h, retardation change was 4%, and variation in-plane retardation was 1 nm. Further, the retardation film had a puncture modulus of 20gf/mm, a puncture strength of 5gf/μm, a breaking strength of 250MPa, and an elongation at break of 3.8%. The obtained retardation film was subjected to the same evaluation as in example 1. The results are shown in Table 1.

[ Table 1]

As is clear from table 1: the retardation film of the examples of the present invention is excellent in adhesiveness, running property, bendability, suppression of generation of bright spots at the time of pressing, sebum resistance, and crack resistance. This is presumably achieved by using a retardation film comprising a specific polycarbonate resin and setting the puncture modulus, puncture strength per unit film thickness, breaking strength and breaking elongation of the retardation film within specific ranges.

Industrial applicability

The retardation film according to the embodiment of the present invention can be suitably used for notebook PCs, in-vehicle displays, and the like.

Claims

1. A retardation film comprising a polycarbonate resin, wherein the retardation film has an in-plane retardation Re (550) of 200 to 400nm, an Re (450)/Re (550) of 0.98 to 1.03, and a puncture modulus of 50gf/mm or more.

2. The retardation film according to claim 1, wherein the puncture strength per unit film thickness is 10gf/μm or more.

3. The retardation film according to claim 1 or 2, which has a breaking strength of 800MPa or more.

4. The retardation film according to any one of claims 1 to 3, which has a thickness of 30 to 50 μm.

5. The retardation film according to any one of claims 1 to 4, wherein the variation in Re (550) in the width direction is 5nm or less.

6. The retardation film according to any one of claims 1 to 5, wherein an absolute value of a rate of change of the in-plane retardation Re (550) after 500 hours at a temperature of 65 ℃ and a humidity of 90% is 3% or less.

7. The retardation film according to any one of claims 1 to 6, having a moisture permeability of 150g/m²24h or less.

8. The retardation film as claimed in any one of claims 1 to 7, which has an elongation at break of 4% or more.

9. A polarizing plate with a retardation layer, comprising a polarizing material and the retardation film according to any one of claims 1 to 8, wherein the retardation film is bonded to at least one surface of the polarizing material via an adhesive layer.