KR101584439B1 - Optical film having inverse wavelength dispersion, polarizing plate and display device comprising the same - Google Patents

Abstract

The present invention relates to an optical film having an inverse wavelength dispersion property satisfying the following formulas (1) and (2), comprising a polyurethane resin obtained by polymerizing a fluorene monomer having two or more hydroxyl groups in a molecule with a diisocyanate monomer, And a polarizing plate and a display device including the same.
0.5? R _in (450) / R _in (550)? 1.0
1.0 < R _in (650) / R _in (550)? 1.5
In the above equations (1) and (2), R _in (450), R _in (550) and R _in (650) are retardation values of the films measured at wavelengths of 450 nm, 550 nm and 650 nm, respectively.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical film having an inverse wavelength dispersion characteristic, a polarizing plate including the polarizing plate,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film having an inverse wavelength dispersion characteristic, a polarizing plate and a display device having the same, and more particularly to a liquid crystal display device having various modes, An optical film, a polarizing plate including the same, and a display device.

BACKGROUND ART [0002] In a display device such as a liquid crystal display (LCD) or an organic light emitting diode (OLED), a retardation film is used for the purpose of improving the viewing angle, improving the display quality or preventing reflection, Dispersion characteristics, flat wavelength dispersion characteristics, and reverse wavelength dispersion characteristics. The retardation film having the regular wavelength dispersion characteristic means a retardation film having a characteristic that the retardation value generated as the wavelength of incident light becomes smaller. The retardation film having flat wavelength dispersion characteristic has a similar degree regardless of the wavelength of the incident light And a retardation film having an inverse wavelength dispersion characteristic means a retardation film having a characteristic in which a retardation value generated as the wavelength of incident light increases.

On the other hand, when? Is a wavelength of incident light and a retardation value that generates Re, the transmittance T is generally defined as T = sin ² (Re /?). As can be seen from the equation representing the transmittance T, The retardation film having a flat wavelength dispersion characteristic or the retardation film having a constant wavelength dispersion property has a large difference in Re /? At a short wavelength and a long wavelength, so that the transmittance becomes uneven, resulting in poor visibility, There is a problem that it is wrong. Therefore, applicability to an organic light emitting device, an IPS mode liquid crystal display device, a VA mode liquid crystal display device and the like which require a phase difference film with little change in color and sensation is lowered. However, in the case of a retardation film having an inverse wavelength dispersion characteristic, since the retardation value generated as the wavelength of the incident light becomes larger, the transmittance becomes uniform irrespective of the wavelength, and thus the above problem does not occur.

On the other hand, since an organic light emitting device emits light by itself, a polarizer is not required unlike a liquid crystal display device. However, since a reflecting plate made of an aluminum material is used as an internal electrode, reflection due to light coming from the outside is significant, . To solve this problem, an antireflective polarizing plate is required for an organic light emitting element, and it is usually composed of a protective film, a polarizing plate and a lambda / 4 retardation film. At this time, the principle of reflection prevention is as follows. First, the natural light incident from the outside is converted into linearly polarized light while passing through the polarizer, and the converted linearly polarized light is converted into circularly polarized light while passing through the retardation film having the optical retardation value of? / 4. The light converted into circularly polarized light is converted into circularly polarized light (left-handed circular polarization <-> right-handed circularly polarized light) opposite to that of the phase reflected by the organic light-emitting device electrode as a reflection plate, and linearly polarized . As a result, the linearly polarized light that has changed by 90 degrees is absorbed by the polarizer and can not pass therethrough, thereby realizing the antireflection characteristic.

However, since the light is composed of various wavelengths, if the phase difference is not λ / 4 for each wavelength, the antireflection effect is different for each wavelength, so that the reflected light is not completely blocked, Thereby causing a problem of showing a specific color. For example, when a retardation film (137.5 nm) showing a flat wavelength dispersion such as a cycloolefin polymer (COP) film is used as a? / 4 retardation film, the green light (550 nm) The light having a wavelength of 450nm should pass through a retardation film of 112.5nm which is? / 4 and the light of 650nm wavelength which is red must pass through a retardation film of 162.5nm. Therefore, the light of blue and red Polarized light is not a circularly polarized light but an elliptically polarized light, so that the reflected light can not be completely blocked. Therefore, there is a problem that specific light leaks out as shown in FIG.

Therefore, the retardation film for use in the antireflective polarizing plate for organic light emitting devices is required to have an inverse wavelength dispersion characteristic more than anything. Further, for the circular polarization, the retardation film is stretched to 45 in the machine direction (MD) And it is required that there is little change in physical light characteristics due to heat or moisture.

However, since the wavelength dispersion property inherently appears depending on the material of the retardation film, it is not practical to find a new raw material in order to produce a retardation film having a reverse wavelength dispersion characteristic in a single sheet. Therefore, conventionally, two or more retardation films having different wavelength dispersibilities are laminated by using an adhesive or an adhesive to produce a retardation film having reverse wavelength dispersion characteristics, or a resin having a positive retardation value and a resin having a negative retardation value A method of forming a laminate by extrusion and stretching it to produce a retardation film having an inverse wavelength dispersion characteristic, and the like have been proposed. However, in the case of the first method, if the optical axes of the two retardation films to be laminated are not precisely arranged, there is a problem that the reverse wavelength dispersion characteristic is not exhibited and the manufacture is very difficult. In the second method, If the glass transition temperature of the resin is not the same as the glass transition temperature, stretching does not occur properly.

As a result, it is possible to effectively realize the inverse wavelength dispersion characteristic even with a single film, so that it can be manufactured in a thin shape, can be easily manufactured, and can be applied to various modes of liquid crystal display devices, / 4-wavelength phase difference film.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a liquid crystal display device and an organic light emitting device having various modes, which can effectively realize reverse wavelength dispersion even with a single film, An optical film applicable as a retardation film, a polarizing plate including the same, and a display device.

In one aspect, the present invention relates to a resin composition comprising a fluorene-based monomer having at least two hydroxyl groups in a molecule and a polyurethane-based resin obtained by polymerizing a diisocyanate-based monomer and having an inverse wavelength dispersion characteristic satisfying the following formulas (1) and &Lt; / RTI &gt; provide optical films.

0.5? R _in (450) / R _in (550)? 1.0

1.0 < R _in (650) / R _in (550)? 1.5

In the above equations (1) and (2), R _in (450), R _in (550) and R _in (650) are retardation values of the films measured at wavelengths of 450 nm, 550 nm and 650 nm, respectively.

At this time, it is preferable that the optical film satisfies the following formula (3).

(3): 30 nm? R _in (550)? 250 nm

In the above formula (3), R _in (550) is the retardation value in the plane direction of the film measured at a wavelength of 550 nm.

It is preferable that the optical film satisfies the following formula (4).

(4): -120 nm? R _th (550)? 120 nm

In the above formula (4), R _th (550) is the thickness direction retardation value of the film measured at a wavelength of 550 nm.

Further, the thickness of the optical film is preferably 20 占 퐉 to 100 占 퐉.

On the other hand, it is preferable that the above-mentioned polyurethane resin is polymerized so that 1.0 mol% to 5.0 mol% of a fluorene monomer having two or more hydroxyl groups in the molecule is contained.

The polyurethane resin preferably has a glass transition temperature of from 110 캜 to 150 캜.

The polyurethane resin preferably has a molecular weight of 40,000 to 500,000 g / mol.

On the other hand, it is preferable that the fluorene monomer having two or more hydroxyl groups in the molecule is a compound represented by the following formula (1), a compound represented by the following formula (2), or a mixture thereof.

[Chemical Formula 1]

In Formula _1, X 1 ~ X ₄ are each independently a C _{1 -6} alkyl group, a C _{5 -6} cycloalkyl group, C _6-10 aryl group, C _{7 -14} arylalkyl group, C _{1 -6} alkoxy, C _{5 -10} cycloalkoxy group, C _{6 -10} aryloxy, C _7-14 alkyloxy aryl, C _{1 -6} acyl, C _{1 -4} alkoxycarbonyl group, a halogen atom, A nitro group, a cyano group or an amino group; a, b, c and d are each independently an integer of 0 to 4; Y ₁ to Y ₂ each independently represent a single bond, -O- (CH 2) _n - or - (CH 2) _m -; n is an integer from 1 to 6; m is an integer of 1 to 6;

(2)

In Formula 2, X ₅ ~ X ₆ each independently represent a C _{1 -6} alkyl group, a C _{5 -6} cycloalkyl group, C _6-10 aryl group, C _{7 -14} arylalkyl group, C _{1 -6} alkoxy, C _{5 -10} cycloalkoxy group, C _{6 -10} aryloxy, C _7-14 alkyloxy aryl, C _{1 -6} acyl, C _{1 -4} alkoxycarbonyl group, a halogen atom, A nitro group, a cyano group or an amino group; e and f are each independently an integer of 0 to 4; Y ₃ to Y ₄ each independently represent a single bond, -O- (CH 2) _p - or - (CH 2) _q -; p is an integer of 1 to 6; q is an integer of 1 to 6;

More particularly, the fluorene-based monomer having the molecule two or more hydroxyl groups is at least 9,9-bis [4- (2-hydroxy C _{1 - 6} alkoxy) phenyl] fluorene, 9,9-bis (3- C _{1 - 6} alkyl-4-hydroxyphenyl) fluorene and 9,9-bis (hydroxy-C _{1 - 6} alkyl) fluorene is more preferred to include at least one selected from the group consisting of fluorene.

On the other hand, the diisocyanate-based monomer preferably includes a diisocyanate-based monomer having an aliphatic hydrocarbon chain in its main chain.

More specifically, the diisocyanate-based monomer includes a diisocyanate-based monomer having an aliphatic hydrocarbon chain in its main chain; And a diisocyanate monomer having an aliphatic hydrocarbon ring in its main chain.

Meanwhile, the optical film may be a quarter wavelength retardation film for an organic light emitting device.

Alternatively, the optical film may be a phase difference film for a VA mode liquid crystal display.

Alternatively, the optical film may be a retardation film for an IPS mode liquid crystal display.

In another aspect, the present invention also provides a polarizing plate and a display device comprising the optical film.

Since the optical film of the present invention can realize an inverse wavelength dispersion characteristic in which the phase difference is reduced as the wavelength is effectively reduced even in a single film, it is possible to manufacture the optical film in a thin shape, to easily manufacture the optical film, It is also suitable for use as a 1/4 wavelength retardation film. Therefore, it can be applied as a retardation film to various display devices such as organic light emitting devices and VA mode liquid crystal display devices.

In addition, the optical film of the present invention is excellent in mechanical properties and hardly changes in physical properties due to heat or moisture.

FIG. 1 is a view showing a problem in the case of applying a? / 4 retardation film which does not have an inverse wavelength dispersion characteristic in an organic light emitting device.

First, terms used in this specification are defined.

(1) R _in means a retardation value in the plane direction _in a visible light wavelength band, for example, 450 nm, 550 nm or 650 nm, and the retardation value R _in = (n _x -n _y ) Is obtained. In this case, n _x is the refractive index in the direction in which the refractive index in the plane direction is the maximum (that is, in the slow axis direction), n _y is the refractive index in the direction perpendicular to the x axis Thickness. Meanwhile, R _in (450), R _in (550) and R _in (650) mean plane retardation values measured at wavelengths of 450 nm, 550 nm and 650 nm, respectively, in the visible light wavelength band. On the other hand, _in the R it can be measured by a known method known in the art and, for example, can be measured using the equipment of Axoscan Axomatrics社.

(2) R _th means a retardation value in the thickness direction in the visible light wavelength band, for example, 450 nm, 550 nm or 650 nm, and is expressed by the thickness direction retardation value R _th = (n _z -n _y ) Is obtained. In this case, n _z is the refractive index in the thickness direction, and n _y and d are as described above. Meanwhile, R _th (450), R _th (550) and R _th (650) represent thickness direction retardation values measured at wavelengths of 450 nm, 550 nm and 650 nm, respectively, in the visible light wavelength band. On the other hand, the R _th also be measured by a known method known in the art and, for example, can be measured using the equipment of Axoscan Axomatrics社.

(3) In the present specification, the 'positive birefringence characteristic' means that the maximum refractive index is expressed along the stretching direction during stretching, and the 'negative birefringence characteristic' means that the maximum birefringence characteristic along the direction perpendicular to the stretching direction Is expressed.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

[Optical film]

The inventors of the present invention have conducted extensive studies to solve the above problems and found that a polyurethane resin is produced by polymerizing a fluorene monomer having at least two hydroxyl groups in a molecule having intrinsic birefringence and a diisocyanate monomer having an intrinsic birefringence And an optical film having wavelength dispersion characteristics, that is, reverse wavelength dispersion characteristics, in which the in-plane retardation value becomes smaller as the wavelength of light becomes shorter, can be obtained when the optical film is produced using the same.

That is, the optical film of the present invention comprises a polyurethane resin obtained by polymerizing a fluorene-based monomer having two or more hydroxyl groups in a molecule with a diisocyanate monomer, and has an optical density of 0.5? R _in (450) / R _in 1.0 < R _in (650) / R _in (550)? 1.5.

(Material of optical film)

First, the optical film of the present invention comprises a polyurethane resin. At this time, in order for the optical film of the present invention to have reverse wavelength dispersion characteristics, a molecule oriented in a direction perpendicular to the main chain should be present in the polyurethane resin, and in the present invention, a fluorene series resin having two or more hydroxyl groups in the molecule The structure in which the repeating units derived by the monomers are oriented in the direction perpendicular to the main chain polyurethane chains. That is, the repeating units derived from the fluorene-based monomer having at least two hydroxyl groups in the molecule are oriented in the direction perpendicular to the polyurethane main chain to have negative birefringence. In this case, the regular wavelength dispersion characteristics of the polyurethane chain are fluorene Is less than that of the repeating unit derived by the monomers, the optical film comprising the polyurethane resin has reverse wavelength dispersion characteristics.

On the other hand, the fluorene-based monomer having two or more hydroxyl groups in the molecule is not particularly limited as long as it contains a fluorene skeleton in the molecule and is capable of reacting with a diisocyanate-based monomer having two or more hydroxyl groups to produce a polyurethane- . For example, the fluorene-based monomer having at least two hydroxides in the molecule may be a compound represented by the following formula (1), a compound represented by the following formula (2), or a mixture thereof.

[Chemical Formula 1]

In Formula _1, X 1 ~ X ₄ are each independently a C _{1 -6} alkyl group, a C _{5 -6} cycloalkyl group, C _6-10 aryl group, C _{7 -14} arylalkyl group, C _{1 -6} alkoxy, C _{5 -10} cycloalkoxy group, C _{6 -10} aryloxy, C _7-14 alkyloxy aryl, C _{1 -6} acyl, C _{1 -4} alkoxycarbonyl group, a halogen atom, A nitro group, a cyano group or an amino group; a, b, c and d are each independently an integer of 0 to 4; Y ₁ to Y ₂ each independently represent a single bond, -O- (CH 2) _n - or - (CH 2) _m -; n is an integer from 1 to 6; m is an integer of 1 to 6;

At this time, in the above-mentioned formula (I), but are not limited thereto, X ₁ ~ X ₄ of the C _{1 - 6} alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t- butyl group As an example; Examples of the C _{5 -6} cycloalkyl group include a cyclopentyl group, a cyclohexyl group and the like; C _{6 -10} aryl group may be a phenyl group, a phenyl group, a 2-methylphenyl group, a dimethylphenyl group, a naphthyl group, etc. For example; To C _7-14 aryl alkyl group may include a benzyl group and the like. Examples; C _{1 -6} alkoxy groups there may be mentioned a methoxy group, an ethoxy group, a propoxy group, butoxy group, isobutoxy group Messenger, t- butoxy group, etc. For example; Examples of the C _{5 -10} cycloalkoxy group include a cyclohexanone group and the like; C _{6 -10} aryloxy groups include phenoxy and the like. Examples; C _{7 -14} arylalkyloxy group include a benzyloxy group and the like. Examples; Examples of the C _{1 -6} acyl group include an acetyl group and the like; C _{1 -4} alkoxycarbonyl groups include a methoxycarbonyl group, etc. Examples.

For example, the compounds represented by Formula 1 include, but are not limited to, 9,9-bis (3-methyl-4-hydroxyphenyl) fluorene, 9,9- (3-propyl-4-hydroxyphenyl) fluorene, 9,9-bis (3-propyl- 4- (2-hydroxyethoxy) phenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) Methylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-dimethylphenyl] ) -3-ethylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) 3-propylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-dipropylphenyl] fluorene, 3-isopropylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) (2-hydroxyethoxy) - 3-n-butylphenyl] fluorene, 9,9-bis [4- Bis [4- (2-hydroxyethoxy) -3-isobutyl] fluorene, 9,9-bis [4- Dihydroxyethoxy) -3,5-diisobutylphenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3- Bis [4- (2-hydroxyethoxy) -3,5-bis (1-methylpropylphenyl) fluorene, 9,9- ] Fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-diphenylphenyl] -Benz [phenyl] fluorene, 9,9-bis [4- (2-hydroxyethoxy) -3,5-dibenzylphenyl] fluorene, Phenyl] fluorene, 9,9-bis [4- (4-hydroxybutoxy) phenyl] fluorene and the like. Among them, 9,9- Roxy phenyl) flu 9,9-fluorene, such as bis (3-C _{1 - 6} alkyl-4-hydroxyphenyl) fluorene and 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene such as 9, 9-bis [4- (2-hydroxy-C _{1 - 6} alkoxy) phenyl] fluorene can be used as is preferred.

(2)

In Formula 2, X ₅ ~ X ₆ each independently represent a C _{1 -6} alkyl group, a C _{5 -6} cycloalkyl group, C _6-10 aryl group, C _{7 -14} arylalkyl group, C _{1 -6} alkoxy, C _{5 -10} cycloalkoxy group, C _{6 -10} aryloxy, C _7-14 alkyloxy aryl, C _{1 -6} acyl, C _{1 -4} alkoxycarbonyl group, a halogen atom, A nitro group, a cyano group or an amino group; e and f are each independently an integer of 0 to 4; Y ₃ to Y ₄ each independently represent a single bond, -O- (CH 2) _p - or - (CH 2) _q -; p is an integer of 1 to 6; q is an integer of 1 to 6;

At this time, in the above formula (2), but are not limited thereto, ₅ X ~ X ₆ of the C _{1 - 6} alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t- butyl group As an example; Examples of the C _{5 -6} cycloalkyl group include a cyclopentyl group, a cyclohexyl group and the like; C _{6 -10} aryl group may be a phenyl group, a phenyl group, a 2-methylphenyl group, a dimethylphenyl group, a naphthyl group, etc. For example; To C _7-14 aryl alkyl group may include a benzyl group and the like. Examples; C _{1 -6} alkoxy groups there may be mentioned a methoxy group, an ethoxy group, a propoxy group, butoxy group, isobutoxy group Messenger, t- butoxy group, etc. For example; Examples of the C _{5 -10} cycloalkoxy group include a cyclohexanone group and the like; C _{6 -10} aryloxy groups include phenoxy and the like. Examples; C _{7 -14} arylalkyloxy group include a benzyloxy group and the like. Examples; Examples of the C _{1 -6} acyl group include an acetyl group and the like; C _{1 -4} alkoxycarbonyl groups include a methoxycarbonyl group, etc. Examples.

For example, the compound represented by Formula 2 may include, but is not limited to, 9,9-bis (hydroxymethyl) fluorene, 9,9-bis (2-hydroxyethyl) fluorene, Bis (4-hydroxybutyl) fluorene, 9,9-bis (hydroxymethoxy) fluorene, 9,9-bis (2- (3-hydroxypropoxy) fluorene, 9,9-bis (4-hydroxybutoxy) fluorene and the like, among which 9, 9-bis (hydroxymethyl) fluorene 9,9-bis such as _fluorene-a (hydroxy-C _{1 6} alkyl) fluorene can be preferably used.

On the other hand, the polyurethane resin preferably contains 1.0 to 5.0 mol% of a fluorene-based monomer having at least two hydroxyl groups in the molecule, preferably 2.5 to 4.5 mol% or 3.0 to 4.0 mol% desirable. When the fluorene-based monomer having two or more hydroxyl groups in the molecule is contained in an amount less than the above range, even if the fluorene backbone is well aligned with the main chain of the polyurethane-based resin, the amount of the fluorene- And if the fluorene-based monomer having two or more hydroxyl groups in the molecule is contained in excess of the above range, the amount of the fluorene-based monomer is excessively large, so that it may be difficult to produce a polyurethane resin having desired physical properties Because.

Next, in the present invention, the diisocyanate monomer is not particularly limited as long as it is capable of reacting with a fluorene-based monomer having at least two isocyanate groups in the molecule and having at least two hydroxyl groups in the molecule to produce a polyurethane resin. For example, the diisocyanate monomer includes, but is not limited to, 1,2-ethylene diisocyanate, 1,3-trimethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate , 1,6-hexamethylene diisocyanate, 1,7-heptamethylene diisocyanate, 1,8-octamethylene diisocyanate, 1,9-nonamethylene diisocyanate, 1,10-decamethylene diisocyanate, m- Diisocyanate, p-phenylene diisocyanate, 1,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, 2,6-naphthalene diisocyanate, 2,7- 2,6-toluene diisocyanate, m-xylene diisocyanate, p-xylene diisocyanate, 2,2-methylene diphenyl diisocyanate, 2,4-methylenediphenyl diisocyanate Methylene diphenyl diisocyanate, 4,4-methylenedicyclohexyl diisocyanate, isophorone diisocyanate, 2,2,4-trimethyl-1,5-pentamethylene diisocyanate, 2,2-dimethyl 1,5-pentamethylene diisocyanate, 3-methoxy-1,6-hexamethylene diisocyanate, 3-butoxy-1,6-hexamethylene diisocyanate and the like. These may be used alone or in combination of two or more to prepare the polyurethane resin of the present invention.

However, in the present invention, the diisocyanate-based monomer preferably includes a diisocyanate-based monomer having an aliphatic hydrocarbon chain in its main chain. The diisocyanate monomer having an aliphatic hydrocarbon chain in its main chain is intended to impart weak positive birefringence while imparting elasticity to the optical film to be produced. Since the alkyl chain is relatively free from the movement of carbon molecules, the poly The urethane chains are well-oriented and the fluorene backbone is oriented perpendicular to the main chain of the polyurethane so that the optical film of the present invention can have better reverse wavelength dispersion characteristics.

Examples of the diisocyanate monomer having the aliphatic hydrocarbon chain in the main chain include, but are not limited to, 1,2-ethylene diisocyanate, 1,3-trimethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,7-heptamethylene diisocyanate, 1,8-octamethylene diisocyanate, 1,9-nonamethylene diisocyanate, And C _{2 -16} alkylene diisocyanates such as methylene diisocyanate. Of these, C _{4 -8} alkylene diisocyanates such as 1,6-hexamethylene diisocyanate can be preferably used.

Meanwhile, in the present invention, the diisocyanate-based monomer includes a diisocyanate-based monomer having an aliphatic hydrocarbon chain in its main chain; And a diisocyanate monomer having an aliphatic hydrocarbon ring in the main chain are mixed and used. The birefringence of the birefringence can be increased more than when the diisocyanate monomer having an aliphatic hydrocarbon chain in the main chain is mixed and the glass transition temperature of the polyurethane resin can be further increased to further improve the heat resistance of the optical film of the present invention It is because.

Examples of the diisocyanate monomer having the aliphatic hydrocarbon ring in the main chain include, but are not limited to, a diisocyanate containing one cyclohexane ring in the molecule, such as isophorone diisocyanate, or a diisocyanate containing 4,4-methylenedicyclohexyl Diisocyanate and the like, and diisocyanates containing two or more cyclohexane rings in the molecule are exemplified. Among them, diisocyanate containing two or more cyclohexane rings in the molecule such as 4,4-methylenedicyclohexyl diisocyanate, Can be preferably used.

On the other hand, it is more preferable that the diisocyanate monomer is a diisocyanate monomer having an aliphatic hydrocarbon chain in its main chain and a diisocyanate monomer having an aliphatic hydrocarbon ring in its main chain in a molar ratio of 2.0: 1 to 3.0: 1 , Particularly preferably in a molar ratio of 2.1: 1 to 2.8: 1 or in a molar ratio of 2.3: 1 to 2.5: 1. When a diisocyanate monomer having an aliphatic hydrocarbon chain in the main chain and a diisocyanate monomer having an aliphatic hydrocarbon ring in the main chain are mixed in the molar ratio as described above, the produced optical film has particularly excellent reverse wavelength dispersion characteristics And can have an appropriate retardation value for the 1/4 wavelength characteristic, and at the same time, the glass transition temperature of the polyurethane resin can be sufficiently increased, which is advantageous in that the heat resistance is excellent.

On the other hand, the polyurethane resin may further contain a fluorene-based monomer having at least two hydroxyl groups in the molecule and other comonomers other than the diisocyanate-based monomer, if necessary. That is, in order to prepare the polyurethane resin, it is not necessarily required to polymerize only the fluorene monomer and the diisocyanate monomer having two or more hydroxyl groups in the molecule.

The polyurethane resin may further contain additives other than the fluorene monomer having two or more hydroxyl groups in the molecule and a diisocyanate monomer such as an antioxidant, a radical scavenger, a UV stabilizer, , And may further include a polymerization catalyst such as dibutyltin dilaurate commonly used in the production of polyurethane.

On the other hand, the polyurethane resin preferably has a glass transition temperature of 110 to 150 ° C, more preferably 110 to 130 ° C. When the glass transition temperature is lower than the above-mentioned range, the optical film produced using the optical film has insufficient heat resistance. If the glass transition temperature is higher than the above range, it is difficult to produce the film. On the other hand, the glass transition temperature can be measured by a differential scanning calorimeter (DSC). For example, in the case of using a differential scanning calorimeter (DSC), when a sample of about 10 mg is sealed in a dedicated pan and heated at a constant temperature, the amount of endothermic heat The transition temperature can be measured.

The polyurethane resin preferably has a molecular weight of 40,000 to 500,000 g / mol. When the molecular weight of the polyurethane resin is in the above range, the retardation property of the optical film produced thereby is not influenced by the molecular weight of the polyurethane resin.

On the other hand, the copolymerization type of the polyurethane resin is not particularly limited and may be, for example, a block copolymer, a random copolymer, an alternating copolymer or a mixture thereof.

On the other hand, the method for producing the polyurethane resin is not limited as long as it is well-known in the art, and examples thereof include any suitable methods such as solution polymerization, bulk polymerization, suspension polymerization, emulsion polymerization and the like. Among them, a bulk polymerization (bulk polymerization) method which is economical since a solvent is not used in particular, the film production process is simple, and the physical properties of the film are evaluated to be superior.

(Optical Film Manufacturing Method)

Next, in the present invention, the production method of the optical film is not limited as long as it is well-known in the art, and examples thereof include a solution casting method (solution casting method), a melt extrusion method, a calendar method, And a suitable film forming method of the above. In the present invention, the solution casting method and the melt extrusion method are more preferable among these film forming methods.

Examples of the apparatus for carrying out the solution casting method include a drum casting machine, a band casting machine and a spin coater. Examples of the melt extrusion method include a T-die method and an inflation method. The molding temperature is preferably 150 to 350 占 폚, more preferably 150 to 250 占 폚.

When a film is formed by the T-die method, a T-die is attached to the tip of a known single-screw extruder or a twin-screw extruder, and a rolled film is obtained by winding a film extruded in a film form. At this time, uniaxial stretching can also be performed by stretching in the extrusion direction by appropriately adjusting the temperature of the winding roll. Further, simultaneous biaxial stretching, sequential biaxial stretching, and the like can also be carried out by stretching the film in a direction perpendicular to the extrusion direction.

On the other hand, the optical film of the present invention may be either an unoriented film or a stretched film. In the case of a stretched film, it may be a uniaxially stretched film or a biaxially stretched film, and in the case of a biaxially stretched film, it may be a simultaneous biaxially stretched film or a sequential biaxially stretched film. When biaxially stretched, the mechanical strength is improved and the film performance is improved. The optical film of the present invention can suppress the increase in retardation and maintain optical isotropy even when stretched by mixing other thermoplastic resin.

At this time, the stretching process may perform longitudinal (MD) stretching, transverse (TD) stretching, or both. Further, in the case of performing both the longitudinal drawing and the transverse drawing, either one may be drawn first, then the other direction, or both directions may be drawn simultaneously. In addition, the stretching may be performed in one step or may be performed in multiple steps. In the case of longitudinal stretching, stretching by the speed difference between rolls can be performed, and in the case of transverse stretching, tenter can be used. The time of railing of the tenter is usually within 10 degrees, thereby suppressing the bowing phenomenon occurring in the transverse direction drawing and controlling the angle of the optical axis regularly. Even when the transverse stretching is performed in multiple stages, the effect of inhibiting the bowing can be obtained. On the other hand, in the longitudinal direction (MD) stretching, since the polymer orientation is oriented only in the longitudinal direction (MD), the film can be easily broken in the stretching process. As a result, stretching in the width direction (TD) More preferable.

The stretching temperature is preferably in the vicinity of the glass transition temperature of the polyurethane resin as the raw material of the film. When the glass transition temperature of the resin is Tg, it is preferably (Tg-30) ° C to (Tg + 100 ) ° C, more preferably within the range of (Tg-20) ° C to (Tg + 80) ° C. If the stretching temperature is lower than (Tg-30) DEG C, there is a possibility that a sufficient stretching ratio can not be obtained. On the other hand, when the stretching temperature exceeds (Tg + 100) 占 폚, there is a fear that the stretching (flow) occurs and stable stretching can not be performed.

The stretching ratio defined by the area ratio is preferably 1.1 to 25 times, more preferably 1.3 to 10 times. If the draw ratio is less than 1.1 times, there is a possibility that the toughness accompanying the draw may not be improved. If the draw ratio is more than 25 times, there is a possibility that the effect of increasing the draw ratio may not be recognized.

In addition, the elongation rate is preferably in the range of 1 to 100 mm / min for a universal testing machine (Zwick / Roell Z010) and in the range of 0.1 to 2 m / min for a pilot drawing machine It is preferable to perform the operation, and the stretching magnification is preferably about 5 to 300%.

On the other hand, in order to stabilize the optical isotropy and mechanical properties of the optical film of the present invention, heat treatment (annealing) after stretching treatment and the like can be performed. The heat treatment conditions are not particularly limited, and any suitable conditions known to those skilled in the art in the oral field of the present invention may be employed.

(Optical characteristics of optical film, etc.)

The optical film of the present invention produced by the above method is, in order to obtain the desired wavelength _{dispersibility, R in (450) / R} in (550) This is a range from 0.5 1.0, more preferably 0.80 to 0.99 or 0.80 and to 0.95 _{degree, R in (650) / R} in (550) is greater than 1.0 and 1.5 or less, more preferably 1.01 to 1.30 or 1.01 to about 1.20. In this case, the optical film of the present invention may have an inverse wavelength dispersion characteristic of a desired wavelength dispersion. When the optical film of the present invention is used as a 1/4 wavelength retardation film for an organic light emitting device or the like, Screen can be implemented.

Meanwhile, the optical film of the present invention preferably has R _in (550) of 30 to 250 nm, more preferably 40 to 200 nm, 80 to 170 nm or 130 to 150 nm. In this case, the optical film of the present invention can be very usefully applied as a retardation film to a VA mode liquid crystal display, an IPS mode liquid crystal display, and the like, and can also be applied to an organic light emitting device as a quarter wavelength retardation film.

Further, the optical film of the invention preferably R _th (550) is a -120㎚ to 120, and more preferably be on the order of -110 to -100 to 100㎚ or 80㎚ or -20 to 60㎚. In the case of a retardation film for an organic light emitting diode, it is required that the retardation value in the thickness direction is small because the viscous feeling is poor when the retardation value in the thickness direction is large. When the retardation value in the thickness direction is within the above range at the wavelength of 550 nm, Is sufficiently small, so that the problem of the above-mentioned feeling does not occur.

Further, the thickness of the optical film of the present invention may be in the range of 20 to 100 탆, more preferably in the range of 20 to 60 탆. At this time, the thickness of the optical film means the final thickness after stretching. When the thickness of the optical film is within the above-described numerical range, it is possible to obtain a thin polarizing plate and desired circular polarization characteristics, and to miniaturize and lighten a display device including the optical film.

[Polarizer, display device]

Meanwhile, the optical film according to the present invention may be included in a polarizing plate as a retardation film. For example, the optical film may be included in a polarizing plate as a retardation film for an IPS mode liquid crystal display device or a retardation film for a VA mode liquid crystal display device. In this case, the optical film according to the present invention may be directly attached to one side or both sides of the polarizer, or may be attached to a protective film of a conventional polarizer having a protective film attached on both sides of the polarizer, and may be usefully used as a retardation film.

When the optical film is directly attached to one surface or both surfaces of the polarizer by a retardation film, for example, the structure may be an upper protective film / a polarizer / a lower protective film / a retardation film or a retardation film / an upper protective film / And so on. The attachment may be carried out by a method in which an adhesive is coated on the surface by using a roll coater, a gravure coater, a bar coater, a knife coater or a capillary coater, and the resultant is heat- . As the adhesive, adhesives used in the related art, for example, a polyvinyl alcohol adhesive, a polyurethane adhesive, an acrylic adhesive and the like may be used without limitation.

On the other hand, the optical film according to the present invention can effectively perform inverse wavelength dispersion even with a single film, satisfies 1/4 wavelength, and does not significantly change color and luminosity, and as a retardation film for an organic light emitting element Can be used. More specifically, the optical film of the present invention may be included as a 1/4 wavelength retardation film in a polarizing plate for an OLED, which is required to change linearly polarized light to circularly polarized light.

Meanwhile, the optical film according to the present invention can be included in various display devices. For example, the optical film may be applied as a retardation film to various display devices such as a liquid crystal display (LCD) and an organic light emitting diode (OLED) as described above.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Manufacturing example  1 - Polyurethane resin A

Polyurethane resin A was prepared by bulk polymerization. More specifically, 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene was melted at 170 占 폚, and the temperature was lowered to 140 占 폚. Thereafter, 1,6-hexamethylene diisocyanate and 4,4-methylenedicyclohexyl diisocyanate were mixed in a molar ratio of 2.35: 1 to obtain 9,9-bis [4- (2-hydroxyethoxy) Phenyl] fluorene and stirred. Finally, the agitated product was cured at 150 DEG C for 15 hours to increase the molecular weight of the resin. As a result of measurement, the molecular weight was 296,000 g / mol. The polyurethane-based resin A contained 3.35 mol% of a fluorene-based monomer and was polymerized. The glass transition temperature of the polyurethane-based resin A measured using DSC was 125 ° C.

Manufacturing example  2 - Polyurethane resin B

Polyurethane resin B was prepared by bulk polymerization. More specifically, 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene was melted at 170 占 폚, and the temperature was lowered to 140 占 폚. Thereafter, 1,6-hexamethylene diisocyanate and 4,4-methylenedicyclohexyl diisocyanate were mixed in a molar ratio of 2: 1 to obtain 9,9-bis [4- (2-hydroxyethoxy) Phenyl] fluorene and stirred. Finally, the agitated product was cured at 150 DEG C for 15 hours to increase the molecular weight of the resin. As a result of measurement, the molecular weight was 296,000 g / mol. The polyurethane-based resin A contained 3.0 mol% of a fluorene-based monomer and was polymerized. The glass transition temperature of the polyurethane-based resin B measured by DSC was 127 ° C.

Manufacturing example  3 - Polyurethane resin C

Polyurethane resin C was prepared by bulk polymerization. More specifically, 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene was melted at 170 占 폚, and the temperature was lowered to 140 占 폚. Thereafter, 1,6-hexamethylene diisocyanate and 4,4-methylenedicyclohexyl diisocyanate were mixed in a molar ratio of 3: 1 to obtain 9,9-bis [4- (2-hydroxyethoxy) Phenyl] fluorene and stirred. Finally, the agitated product was cured at 150 DEG C for 15 hours to increase the molecular weight of the resin. As a result of measurement, the molecular weight was 296,000 g / mol. The polyurethane-based resin A contained 4.0 mol% of a fluorene-based monomer and was polymerized. The glass transition temperature of the polyurethane-based resin C measured by DSC was 122 占 폚.

Example  One

The polyurethane-based resin A prepared in Preparation Example 1 was fed to a 30-mm extruder where the feed hopper was purged with nitrogen and melted at 220 ° C to produce a raw material pellet. Passed through a T-die of a coat hanger type, and a film having a thickness of 100 mu m was produced through a chrome casting roll and a drying roll. This film was biaxially stretched at 132 DEG C in the TD direction at a ratio of 2 times using a lab stretching machine to prepare a biaxially stretched film having a thickness of 50 mu m.

Example  2

The polyurethane-based resin B prepared in Preparation Example 2 was fed to a 30-mm extruder, which had been purged with nitrogen from a hopper to an extruder, and melted at 220 ° C to produce a raw material pellet. Passed through a T-die of a coat hanger type, and a film having a thickness of 100 mu m was produced through a chrome casting roll and a drying roll. This film was biaxially stretched at 134 DEG C in a TD direction at a ratio of 2 times using a lab stretching machine using a laboratory stretching machine to prepare a biaxially stretched film of 50 mu m in thickness.

Example  3

The polyurethane-based resin C prepared in Preparation Example 3 was fed into a 30-mm extruder where the feed hopper was purged with nitrogen and melted at 250 ° C to prepare a raw material pellet. Passed through a T-die of a coat hanger type, and a film having a thickness of 100 mu m was produced through a chrome casting roll and a drying roll. This film was biaxially stretched at a rate of 2 times in the TD direction at 129 DEG C using a laboratory film stretching machine using a wrap stretcher to prepare a biaxially stretched film of 50 mu m in thickness.

Comparative Example  One

An undrawn film having a thickness of 100 占 퐉 was prepared using a polycarbonate resin (DVD1080, manufactured by LG Chemical Co., Ltd.) under a condition of 220 占 폚 by using a T-die die. The unstretched film was stretched 1.5 times in the MD direction at 145 캜 to produce an optical film having a thickness of 50 탆.

Comparative Example  2

A styrene-acrylonitrile resin (82TR, manufactured by LG Chemical Co., Ltd.) was subjected to a T-die shaker under a condition of 220 占 폚 to prepare an unoriented film having a thickness of 100 占 퐉. The unstretched film was stretched twice in the MD direction at 110 DEG C to produce an optical film having a thickness of 50 mu m.

Comparative Example  3

A cycloolefin copolymer resin (TOPAS, a product of TICONA) was used to prepare an undrawn film having a thickness of 100 mu m at a temperature of 220 DEG C by using a T-die kneader. The unstretched film was stretched twice at 145 캜 in the MD direction to produce an optical film having a thickness of 50 탆.

The retardation characteristics of the optical films prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were measured using Axoscan's Axoscan equipment and are shown in Table 1 below.

division R _in (550) R _th (550) R _in (450) / R _in (550) R _in (650) / R _in (550) Example 1 Polyurethane resin A
(2.35: 1) 140 nm -11 nm 0.91 1.03 Example 2 Polyurethane resin B
(2: 1) 107 nm -5 nm 0.91 1.03 Example 3 Polyurethane resin C
(3: 1) 210 nm -8 nm 0.91 1.03 Comparative Example 1 Polycarbonate resin 969 nm 2 nm 1.07 0.96 Comparative Example 2 Styrene-acrylonitrile
Suzy 234 nm 224 nm 1.06 0.97 Comparative Example 3 Cycloolefin copolymer
Suzy 122 nm 0 nm 1.01 0.99

As shown in Table 1, when the ratio of 1,6-hexamethylene diisocyanate to 4,4-methylenedicyclohexyl diisocyanate was adjusted to 2.35: 1 as in Example 1, the retardation, the glass transition temperature , And the wavelength dispersibility reached the target value as shown in the example.

Example 2 In the case of 1,6-hexamethylene diisocyanate and 4,4'-methylene dicyclohexyl diisocyanate, the ratio of the two: a case in which the reaction in a molar ratio of 1, _in R (550) than in the example 1 It can be seen that a glass transition temperature of 127 ° C can be obtained and a value of R _in (450) / R _in (550) approaches the target value.

For the embodiment example 3, _in order to improve the R (550) the proportion of 1,6-hexamethylene diisocyanate and 4,4'-methylene dicyclohexyl diisocyanate 3: in case that the reaction in a molar ratio of 1, R _in ( 550) was slightly larger expression rather than the embodiment 1, a glass transition temperature, but has to slightly decrease, R _in (450) / R the value of the _in (550) having also reverse wavelength dispersion characteristics such as to reach the target value .

R (450) / R (550) = 1.07, R (650) / R (550) = 0.96 in the case of Comparative Example 1, R (650) / R (550) = 0.97, and R (450) / R (550) = 1.01 and R They are not suitable as retardation films for IPS mode or VA mode liquid crystal display devices due to poor luminous efficiency and are limited to only a limited range of wavelengths that can act as quarter wavelength retardation films Which is unsuitable for use as a 1/4 wavelength retardation film for an organic light emitting device.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

1: Protective film
2: Polarizer
3: retardation film
4: Electrode
5: Blue light
6: Green light
7: Red light

Claims (16)

A polyurethane resin obtained by polymerizing a fluorene-based monomer having two or more hydroxyl groups in a molecule with a diisocyanate monomer,
The diisocyanate-based monomer includes a diisocyanate-based monomer having an aliphatic hydrocarbon chain in its main chain; And a diisocyanate monomer having an aliphatic hydrocarbon ring in its main chain,
An optical film having an inverse wavelength dispersion property satisfying the following formulas (1) and (2).
0.5? R _in (450) / R _in (550)? 1.0
1.0 < R _in (650) / R _in (550)? 1.5
In the above equations (1) and (2), R _in (450), R _in (550) and R _in (650) are retardation values of the films measured at wavelengths of 450 nm, 550 nm and 650 nm, respectively.
The method according to claim 1,
Wherein the optical film further satisfies the following formula (3).
(3): 30 nm? R _in (550)? 250 nm
In the above formula (3), R _in (550) is the retardation value in the plane direction of the film measured at a wavelength of 550 nm.
The method according to claim 1,
Wherein the optical film further satisfies the following formula (4).
(4): -120 nm? R _th (550)? 120 nm
In the above formula (4), R _th (550) is the thickness direction retardation value of the film measured at a wavelength of 550 nm.
The method according to claim 1,
Wherein the optical film has an inverse wavelength dispersion property of 20 占 퐉 to 100 占 퐉.
The method according to claim 1,
Wherein the polyurethane resin is polymerized in such a manner that 1.0 mol% to 5.0 mol% of a fluorene monomer having two or more hydroxyl groups in the molecule is contained and polymerized.
The method according to claim 1,
Wherein the polyurethane resin has an inverse wavelength dispersion characteristic with a glass transition temperature of from 110 캜 to 150 캜.
The method according to claim 1,
Wherein the polyurethane resin has an inverse wavelength dispersion property with a molecular weight of 40,000 to 500,000 g / mol.
The method according to claim 1,
The fluorene monomer having two or more hydroxyl groups in the molecule is an optical film having an inverse wavelength dispersion characteristic, which is a compound represented by the following formula (1), a compound represented by the following formula (2), or a mixture thereof.
[Chemical Formula 1]

In Formula _1, X 1 ~ X ₄ are each independently a C _{1 -6} alkyl group, a C _{5 -6} cycloalkyl group, C _6-10 aryl group, C _{7 -14} arylalkyl group, C _{1 -6} alkoxy, C _{5 -10} cycloalkoxy group, C _{6 -10} aryloxy, C _7-14 alkyloxy aryl, C _{1 -6} acyl, C _{1 -4} alkoxycarbonyl group, a halogen atom, A nitro group, a cyano group or an amino group; a, b, c and d are each independently an integer of 0 to 4; Y ₁ to Y ₂ each independently represent a single bond, -O- (CH 2) _n - or - (CH 2) _m -; n is an integer from 1 to 6; m is an integer of 1 to 6;
(2)

In Formula 2, X ₅ ~ X ₆ each independently represent a C _{1 -6} alkyl group, a C _{5 -6} cycloalkyl group, C _6-10 aryl group, C _{7 -14} arylalkyl group, C _{1 -6} alkoxy, C _{5 -10} cycloalkoxy group, C _{6 -10} aryloxy, C _7-14 alkyloxy aryl, C _{1 -6} acyl, C _{1 -4} alkoxycarbonyl group, a halogen atom, A nitro group, a cyano group or an amino group; e and f are each independently an integer of 0 to 4; Y ₃ to Y ₄ each independently represent a single bond, -O- (CH 2) _p - or - (CH 2) _q -; p is an integer of 1 to 6; q is an integer of 1 to 6;
The method according to claim 1,
Fluorene-based monomer having the molecule two or more hydroxyl groups is at least 9,9-bis [4- (2-hydroxy C _{1 - 6} alkoxy) phenyl] fluorene, 9,9-bis (3-C _{1 - 6} alkyl-4-hydroxyphenyl) fluorene and 9,9-bis (hydroxy-C _{1 - 6} alkyl) fluorenyl optical film having a wavelength dispersion property that the station comprises at least one selected from the group consisting of fluorene.
delete delete The method according to claim 1,
Wherein the optical film is a quarter wavelength retardation film for an organic light emitting device.
The method according to claim 1,
Wherein the optical film is a retardation film for a VA mode liquid crystal display.
The method according to claim 1,
Wherein the optical film is a retardation film for an IPS mode liquid crystal display.
A polarizing plate comprising the optical film of any one of claims 1 to 9 and 12 to 14.
A display device comprising the optical film of any one of claims 1 to 9 and 12 to 14.

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