KR20150037444A - Retadation film having anti-wavelength dispersibility and preparing method for retadation film - Google Patents

Abstract

The present invention relates to a retardation film having anti-wavelength dispersibility and preparing method comprising; a biaxially oriented base film having a positive phase difference; a uniaxually oriented coating layer having the negative phase difference and being formed on at least one side of the base film. And it has reverse wavelength dispersibility that meets the below formula (1) and (2); wherein the chemical formula (1): Rin,b (450)/Rin,b (550) > Rin,a (450)/Rin,a (550) (2): Rin,a (550) > Rin,b (550) In the formula (1) and (2), Rin,a (450) and Rin,a (550) indicate plane direction phase difference values that are measured at the wavelength of 450 nm and 550 nm on the base film. Rin,b(450) and Rin,b(550) indicate plane direction phase difference values that are measured at the wavelength of 450nm, 550nm on the coating layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation film having an inverse wavelength dispersion characteristic,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation film having an inverse wavelength dispersion property and a manufacturing method thereof, more specifically, to a retardation film which can realize excellent reverse wavelength dispersion characteristics and can be used as a retardation film in a VA mode liquid crystal display, ≪ / RTI >

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 the incident light becomes smaller. The retardation film having the flat wavelength dispersion characteristic has a similar degree regardless of the wavelength of the incident light Refers to a retardation film having a characteristic of generating a retardation value of a retardation film having an opposite wavelength dispersion characteristic, and a retardation film having an opposite wavelength dispersion characteristic is a retardation film having a characteristic of increasing a retardation value 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 characteristic has a large difference in Re / λ between a short wavelength and a long wavelength, so that the transmittance becomes uneven, resulting in poor visibility, A problem that the color tone is wrong occurs. Therefore, the VA mode liquid crystal display device and the like which require a phase difference film with little change in color and luminosity are less applicable. On the other hand, 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. However, most of the retardation films developed to date have a regular wavelength dispersion property or a flat wavelength dispersion property.

On the other hand, since the wavelength dispersion property inherently appears depending on the material of the retardation film, it is necessary to find a new raw material in order to produce a retardation film having an inverse wavelength dispersion characteristic in a single sheet. A method of producing a retardation film having an opposite wavelength dispersion characteristic by laminating two or more retardation films having different wavelength dispersibility by using an adhesive or an adhesive has been proposed. However, in this case, there has been a problem that the optical properties are lowered due to the presence of the pressure-sensitive adhesive layer, and if the optical axes of the two retardation films to be laminated are not arranged accurately, reverse wavelength dispersion characteristics are not exhibited, .

As a retardation film for a VA mode liquid crystal display device having a current reverse wavelength dispersion characteristic, N-TAC of Konica Co., which is a polymer film mainly composed of cellulose ester comprising an acetyl group and a propionyl group, is mainly used, but N-TAC There is a problem that the moisture permeability is increased due to a large number of hydrophilic functional groups in the molecular chain structure, and thus deformation occurs under heat and humidity conditions or dissociation of iodide ions occurs in the polarizer, thereby deteriorating the polarization performance of the polarizer.

Therefore, a retardation film which is made of a material having low moisture permeability and which has an inverse wavelength dispersion characteristic and which can be used for a VA mode liquid crystal display device and a phase difference film capable of producing such a retardation film by a simple process without using an adhesive or an adhesive, A method for producing a film is required.

SUMMARY OF THE INVENTION 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 which does not use a pressure-sensitive adhesive or an adhesive but uses a material having low moisture permeability, To provide a method of manufacturing a retardation film capable of manufacturing such a retardation film.

In one aspect, the present invention provides a biaxially stretched substrate film having positive phase retardation properties; And a coating layer formed on at least one side of the base film and having a negative retardation characteristic and uniaxially stretched, wherein the retardation film has an inverse wavelength dispersion characteristic satisfying the following expressions (1) and (2).

Equation _{(1): R in, b} (450) / R in, b (550)> R in, a (450) / R in, a (550)

Equation _{(2): R in, a} (550)> R in, b (550)

In the formula (1) and _{(2), R in, a} (450), R in, a (550) are each 450㎚ wavelength, and the plane direction retardation value of the substrate film measured at 550㎚, _{in R, b} (450), and R _{in and b} (550) are retardation values in the plane direction of the coating layer measured at 450 nm and 550 nm, respectively.

On the other hand, it is preferable that the retardation film satisfies the following formulas (3) and (4).

(3): 20 nm < R _{in , a} < 300 nm

(4): -400 nm < R _{th , a} < 0 nm

In the above formulas (3) and (4), R _{in , a} is the retardation value in the plane direction of the base film measured in the visible light wavelength band, and R _{th , a} is the retardation value in the thickness direction of the base film measured in the visible light wavelength band .

It is also preferable that the retardation film satisfies the following formulas (5) and (6).

(5): 10 nm < R _{in , b} < 250 nm

(6): 10 nm < R _{th , b} < 300 nm

In the formulas (5) and (6), R _{in , b} is the retardation value in the plane direction of the coating layer measured in the visible light wavelength band, and R _{th and b} are the retardation values in the thickness direction of the coating layer measured in the visible light wavelength band.

It is preferable that the retardation film satisfies the following formulas (7) and (8).

(7): 0 nm < R _{in , total} < 200 nm

(8): -300 nm < R _{th , total} < 0 nm

In the formulas (7) and (8), R _{in and total} are surface retardation values of the entire retardation film measured in the visible light wavelength band, R _{th and total} are thickness retardation values of the entire retardation film measured in the visible light wavelength band Value.

It is also preferable that the retardation film satisfies the following formulas (9) and (10).

(9): 0.8 <R _{in , total} (450) / R _{in , total} (550) <1.0

Equation _{(10): 1.0 <R in} , total (650) / R in, total (550) <1.2

The formula (9) and (10) _{in, R in, total (450)} , R in, total (550), R in, total (650) are each wavelength 450㎚, 550㎚, the retardation film measured at 650㎚ Plane retardation value of the whole surface.

It is preferable that the retardation film satisfies the following formula (11).

(11): n _{x , total} > n _{y , total} > n _{z , total}

In the formula (8), n _{x and total} are refractive indices in the direction in which the refractive index in the plane direction of the entire retardation film is the maximum (that is, in the slow axis direction), and n _{y and total} are perpendicular the direction the direction of the refractive index (that is, fast axis direction), n _z, is the refractive index of the _total of the entire retardation film thickness direction, in this case, the n _{x, total,} n _{y, total,} n _{z and total} are measured values in the visible light wavelength band.

In addition, the base film preferably contains at least one or more selected from the group consisting of a cycloolefin polymer, a cycloolefin copolymer, an alicyclic polycarbonate, an alicyclic polyester and a polyamide.

The coating layer preferably contains at least one selected from the group consisting of a styrene resin, a fluorene resin, polyvinyl carbazole, and polyvinyl naphthalene.

The retardation film preferably has a moisture permeability of 140 g / m ² · day or less.

In addition, the retardation film is preferably used for a VA mode liquid crystal display device.

The present invention also provides a liquid crystal display device including the retardation film.

In another aspect, the present invention provides a method of manufacturing a polarizing plate comprising: uniaxially stretching a base film having positive retardation characteristics in a longitudinal direction (MD); Forming a coating layer on at least one side of the substrate film uniaxially stretched in the longitudinal direction (MD) using a polymer material having a negative retardation characteristic; And uniaxially stretching the base film on which the coating layer is formed in the width direction (TD), wherein the base film and the coating layer are formed so as to satisfy the following formulas (1) and (2) The present invention also provides a method of producing a retardation film having a characteristic of a retardation film.

Equation _{(1): R in, b} (450) / R in, b (550)> R in, a (450) / R in, a (550)

Equation _{(2): R in, a} (550)> R in, b (550)

In the formula (1) and _{(2), R in, a} (450), R in, a (550) are each 450㎚ wavelength, and the plane direction retardation value of the substrate film measured at 550㎚, _{in R, b} (450), and R _{in and b} (550) are retardation values in the plane direction of the coating layer measured at 450 nm and 550 nm, respectively.

Meanwhile, it is preferable that the step of uniaxially stretching in the longitudinal direction (MD) is performed at a draw magnification ratio of 1.1 to 4.0.

In the uniaxially stretching in the longitudinal direction (MD), the base film is preferably stretched to a thickness of 20 to 250 탆.

Also, in the step of forming the coating layer, it is preferable that the coating layer is coated to a thickness of 1 to 30 탆.

It is also preferable that the stretching is performed at a magnification of 1.2 to 4.0 which is uniaxially stretched in the transverse direction (TD).

In the step of uniaxially stretching in the transverse direction (TD), it is preferable that the base film on which the coating layer is formed is stretched to a thickness of 5 to 80 탆.

The retardation film according to the present invention is formed by stretching a base film having a positive retardation characteristic with a relatively low retardation property and forming a coating layer having a negative retardation property with a relatively high retardation property and stretching it at the same time, And the viewing angle improvement effect is very excellent when used as a phase difference film for VA mode, and it is possible to easily manufacture without going through a complicated process.

Further, since the retardation film according to the present invention uses a material having a low moisture permeability unlike the conventional art, deformation under heat and humidity conditions does not occur and dissociation of the iodide ion of the polarizer does not occur, There is no problem in that the temperature is lowered.

In addition, since the retardation film according to the present invention does not require a step of laminating using an adhesive differently from the prior art, there is no decrease in optical characteristics due to the presence of the adhesive layer or deviation of the retardation plate axis.

First, terms used in this specification are defined.

(1) where n _x is the refractive index in the direction in which the refractive index in the plane direction is the maximum (that is, the slow axis direction), and n _y is the refractive index in the direction perpendicular to the slow axis in the plane direction , and n _z means the refractive index in the thickness direction. The above n _x , n _y , and n _z are generally measured in a visible light wavelength band, more specifically, light having a wavelength of 400 to 780 nm. For example, it can be measured at 450 nm, 550 nm or 650 nm.

On the other hand, n _{x and total} are refractive indices in the direction in which the refractive index in the plane direction of the entire retardation film becomes the maximum (that is, in the slow axis direction), and n _{y and total} are the directions in the direction perpendicular to the slow axis of the entire retardation film , The phase in the fast axis direction), and n _{z , total} is the refractive index in the thickness direction of the entire retardation film.

On the other hand, the n _x, n _y, n _z, and is possible to measure by the conventional method well known in the art, for example, can be measured using the equipment of Axoscan Axomatrics社.

(2) R _in denotes a retardation value _in the visible direction _in a visible light wavelength band, more specifically, _in a light having a wavelength of 400 to 780 nm. The retardation value R _in = (n _x -n _y ) It becomes. In this case, n _x is the direction in which the refractive index in the plane direction is the maximum, n _y is the direction perpendicular to the x axis, d is the retardation value of the base film, the retardation film or the coating layer Lt; / RTI &gt;

Herein, R _in (450), R _in (550), and R _in (650) refer to plane retardation values measured at wavelengths of 450 nm, 550 nm, and 650 nm, respectively, in the visible light wavelength band. In addition, R _{in, a,} R _{in, b,} R _{in, total} is the phase difference film whole including a base film, a coating layer, the substrate film with the coating layer in the 400 to 780nm wavelength light in each of the visible light wavelength region, and more specifically Plane retardation value.

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.

(3) R _th is obtained by the visible light wavelength region, and more specifically by means of the thickness retardation value of from 400 to 780nm wavelength light, the thickness retardation value _{R th = × d (n z} -n y) It becomes. In this case, n _x is the direction in which the refractive index in the plane direction becomes maximum at the wavelength, n _y is the direction perpendicular to the x axis, n _z is the thickness direction, d is the thickness The thickness of the film, the retardation film or the coating layer.

In this case, 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. Further, R _{th , a} , R _{th , b} , R _{th , and total} are respectively the wavelengths of visible light, the base film in the light having a wavelength of 400 to 780 nm, the coating layer, the entirety of the retardation film including the base film and the coating layer Represents a retardation value in the thickness direction.

On the other hand, the R _th can be determined by well-known methods known in the art and, for example, can be measured using the equipment of Axoscan Axomatrics社.

(4) The positive retardation property means that the maximum refractive index is expressed along the stretching direction at the time of stretching, and the negative retardation property means that the maximum refractive index is expressed along the direction perpendicular to the stretching direction at the time of stretching.

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.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, the inventors of the present invention have found that, after stretching a base film having a low moisture permeability and a relatively low wavelength dispersion characteristic and a relatively low wavelength dispersion characteristic, It is possible to realize an excellent reverse wavelength dispersion characteristic when the coating layer is formed and used as a retardation film by stretching them simultaneously and is excellent in the effect of improving the viewing angle when used as a VA mode retardation film and is excellent in heat resistance and moisture resistance And completed the present invention.

More specifically, the present invention relates to a biaxially stretched base film having positive phase retardation properties; And a coating layer formed on at least one surface of the base film and uniaxially stretched having negative retardation characteristics and having an inverse wavelength dispersion characteristic satisfying the following expressions (1) and (2).

Equation _{(1): R in, b} (450) / R in, b (550)> R in, a (450) / R in, a (550)

Equation _{(2): R in, a} (550)> R in, b (550)

In the formula (1) and _{(2), R in, a} (450), R in, a (550) are each 450㎚ wavelength, and the plane direction retardation value of the substrate film measured at 550㎚, _{in R, b} (450), and R _{in and b} (550) are retardation values in the plane direction of the coating layer measured at 450 nm and 550 nm, respectively.

As described above, the retardation film of the present invention has a positive retardation and includes a uniaxially stretched coating layer having a negative retardation characteristic with the biaxially stretched base film, and the optical axis of the base film and the optical axis of the coating layer are orthogonal to each other.

Further, the retardation film of the present invention satisfies the above-mentioned expressions (1) and (2), so that the difference in retardation value between the base film and the coating layer at a wavelength higher than the difference in retardation value between the base film and the coating layer and, also the wavelength dispersion characteristics of the entire retardation film, for example, _{R in, total (450) /} R in, wavelength dispersion property of the _total (550) the value of the substrate film, for example, _{R in, a (450) /} R in, a ( 550). As a result, the retardation film of the present invention has excellent reverse wavelength dispersion characteristics. Therefore, the VA mode liquid crystal display device and the like have excellent viewing angle improving effect when used as a retardation film.

It is also preferable that the retardation film satisfies the following formulas (3) and (4).

(3): 20 nm < R _{in , a} < 300 nm

(4): -400 nm < R _{th , a} < 0 nm

In the above formulas (3) and (4), R _{in , a} is the retardation value in the plane direction of the base film measured in the visible light wavelength band, and R _{th , a} is the retardation value in the thickness direction of the base film measured in the visible light wavelength band . That is, in the retardation film of the present invention, R _{in , a} and R _{th , a} are light in any wavelength range of visible light wavelength band, more specifically 400 to 780 nm wavelength, for example, 450 nm, 550 nm, or 650 nm (3) and (4) are satisfied even when measured by light.

It is also preferable that the retardation film satisfies the following formulas (5) and (6).

(5): 10 nm < R _{in , b} < 250 nm

(6): 10 nm < R _{th , b} < 300 nm

In the formulas (5) and (6), R _{in , b} is the retardation value in the plane direction of the coating layer measured in the visible light wavelength band, and R _{th and b} are the retardation values in the thickness direction of the coating layer measured in the visible light wavelength band. That is, in the retardation film of the present invention, R _{in , b,} and R _{th , b} are light in any wavelength range of visible light wavelength band, more specifically 400 to 780 nm, for example, 450 nm, 550 nm, or 650 nm It is preferable to satisfy the above-mentioned expressions (5) and (6) even when measured by light.

When the base film and the coating layer of the retardation film of the present invention have the retardation value in the plane direction and the retardation in the thickness direction, the retardation value and the retardation value in the thickness direction of the entire retardation film are appropriately applied .

It is preferable that the retardation film satisfies the following formulas (7) and (8). When the retardation film of the present invention satisfies the following formulas (7) and (8), it is possible to secure a wide viewing angle when used as a retardation film in a VA mode liquid crystal display device.

(7): 0 nm < R _{in , total} < 200 nm

(8): -300 nm < R _{th , total} < 0 nm

In the formulas (7) and (8), R _{in and total} are surface retardation values of the entire retardation film measured in the visible light wavelength band, R _{th and total} are thickness retardation values of the entire retardation film measured in the visible light wavelength band Value. That is, in the retardation film of the present invention, R _{in , total} and R _{th, total} are light in a visible light wavelength band, more specifically, light of any wavelength of 400 to 780 nm, for example, 450 nm, 550 nm, or 650 nm (7) and (8) even when measured by light.

It is also preferable that the retardation film satisfies the following formulas (9) and (10). When the retardation film of the present invention satisfies the following formulas (9) and (10), it is possible to obtain the same viewing angle compensation effect in the entire region of the visible light wavelength band.

(9): 0.8 <R _{in , total} (450) / R _{in , total} (550) <1.0

Equation _{(10): 1.0 <R in} , total (650) / R in, total (550) <1.2

The formula (9) and (10) _{in, R in, total (450)} , R in, total (550), R in, total (650) are each wavelength 450㎚, 550㎚, the retardation film measured at 650㎚ Plane retardation value of the whole surface.

It is preferable that the retardation film satisfies the following formula (11). In this case, it can be very usefully applied to a VA mode liquid crystal display as a retardation compensation film.

(11): n _{x , total} > n _{y , total} > n _{z , total}

In the above formula (11), n _{x and total} are refractive indices in the direction in which the refractive index in the plane direction of the entire retardation film becomes the maximum (that is, in the slow axis direction), and n _{y and total} are perpendicular in the direction of the refractive index (that is, fast axis direction) direction, and n _z, is the refractive index of the _total of the entire retardation film thickness direction, in this case, the n _{x, total,} n _{y, total} And n _{z and total} are values measured in the visible light wavelength band. That is, the retardation film of the present invention can be obtained by measuring the above formula (11) even when it is measured in the visible light wavelength band, more specifically, light having any wavelength of 400 to 780 nm, for example, 450 nm, 550 nm, It is preferable to satisfy it.

(1) and (2); And the formula (3) to (11) can be produced by appropriately controlling the raw material for forming the base film, the coating layer, the stretching condition, and the like.

First, in the present invention, the raw material of the base film is a polymer material having a positive phase retardation property, as long as it is low in moisture permeability as compared with a conventional N-TAC film and satisfies the above-mentioned formulas (1) and (2) And the kind thereof is not particularly limited. For example, cycloolefin polymers, cycloolefin copolymers, alicyclic polycarbonates, alicyclic polyesters, polyamides, and the like can be used.

At this time, the cycloolefin polymer and cycloolefin copolymer can be used without limitation, as long as it is a cycloolefin polymer or a cycloolefin polymer generally used in the related art.

Also, the alicyclic polycarbonate is one containing 4 to 14, or 4 to 10, or 4 to 8 ring atom non-aromatic monocyclic, bicyclic, or tricyclic hydrocarbon moieties in the molecule, Any alicyclic polycarbonate commonly used in the art can be used without any particular limitation. The ring atoms may include not only carbon atoms but also oxygen atoms.

Also, the alicyclic polyester includes a nonaromatic monocyclic, bicyclic or tricyclic hydrocarbon moiety of 4 to 14, or 4 to 10, or 4 to 8 ring atoms in the molecule, Any alicyclic polyester commonly used in the art can be used without any particular limitation. The ring atoms may include not only carbon atoms but also oxygen atoms.

In addition, the polyamide can be used without particular limitation as long as it has an amide group in the main chain. For example, but not limited thereto, the polyamide may include a repeating unit represented by the following formula (1) or (2).

[Chemical Formula 1]

In the above Formula 1, A is C _{2 -16} aliphatic hydrocarbon chains, C _{5 -14} aliphatic hydrocarbon ring or an aromatic C _{6 -14} hydrocarbon chain, X ₁ is a halogen atom or a C _{1 -6} alkyl group, a is 0 to 3, and n is an integer of 5 to 10,000.

In the formula (1), the C _{2 -16} aliphatic hydrocarbon chain means a hydrocarbon moiety having 2 to 16, 4 to 14, or 6 to 12 carbon atoms, and includes, but is not limited to, methylene An ethylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, a nonanemethylene group, a decamethylene group, an undecamethylene group, a dodecamethylene group, a tridecamethylene group, A methylene group, a pentadecamethylene group, a hexadecamethylene group, and the like.

Further, in A of Formula 1, C _{5 -14} aliphatic hydrocarbon ring of 5 to 14, or 5 to 10, or 5 to 6 ring carbon cyclic saturated or unsaturated non-aromatic mono-, bicyclic Refers to a tricyclic hydrocarbon moiety and includes, but is not limited to, a cycloalkane ring such as a cyclopentane ring or a cyclohexane ring, a cycloalkene ring such as a cyclopentene ring, a cyclohexene ring, or a cyclooctene ring, And the like.

In the formula (A), the C _{6 -14} aromatic hydrocarbon ring means a monocyclic, bicyclic or tricyclic aromatic hydrocarbon moiety having 6 to 14 or 6 to 12 ring atoms, But are not limited to, benzene rings, naphthalene rings, anthracene rings, biphenyl rings, and the like.

On the other hand, in the above formula (1), the bonding position of the polyamide resin of A with the main chain is not particularly limited and may be an asymmetric position or a symmetric position. For example, when A is a cyclohexane ring, it may be a cyclohexane ring in which the 1,3 carbon is bonded to the main chain, or a cyclohexane ring in which the 1,4 carbon is bonded to the main chain.

Further, in X ₁ of Formula _1, 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 can be given. Examples. At this time, X ₁ is substituted with hydrogen at an arbitrary position of A.

(2)

In Formula 2, B and C are each independently a C _{2 -16} aliphatic hydrocarbon chain, a C _{5 -14} aliphatic hydrocarbon ring, or a C _{6 -14} aromatic hydrocarbon ring, and X ₂ and X ₃ are each independently a halogen atom or a c _{1 -6} alkyl group, b and c are each independently an integer of 0 ~ 3, m is an integer of 5 to 10,000.

Herein, in B and C of the above formula (2), the C _{2 -16} aliphatic hydrocarbon chain means a hydrocarbon part of 2 to 16, or 4 to 14, or 6 to 12 carbon atoms, , Methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, hexamethylene group, heptamethylene group, nonamethylene group, decamethylene group, undecamethylene group, dodecamethylene group, tridecamethylene group, Tetradecamethylene group, tetradecamethylene group, pentadecamethylene group, hexadecamethylene group and the like.

Further, in the B and C in the formula 2, C _{5 -14} aliphatic hydrocarbon ring of 5 to 14, or 5 to 10, or 5 to 6 ring carbon cyclic saturated or unsaturated non-aromatic mono, Bicyclic and tricyclic hydrocarbon moieties, and includes, but is not limited to, cycloalkane rings such as cyclopentane rings and cyclohexane rings, cycloalkane rings such as cyclopentene rings, cyclohexene rings, and cyclooctene rings, ) Rings, and the like.

In the above formulas (B) and (C), the C _{6 -14} aromatic hydrocarbon ring means a monocyclic, bicyclic or tricyclic aromatic hydrocarbon moiety having 6 to 14, or 6 to 12, ring atoms But are not limited to, benzene rings, naphthalene rings, anthracene rings, biphenyl rings, and the like.

On the other hand, in the formula (2), the bonding position of the polyamide resin of B and C to the main chain is not particularly limited and may be an asymmetric position or a symmetric position. For example, when B or C is a cyclohexane ring, it may be a cyclohexane ring in which the 1,3 carbon is bonded to the main chain, or a cyclohexane ring in which the 1,4 carbon is bonded to the main chain.

In the above Formula 2, X ₂ and X ₃ of the C _{1 - 6} alkyl group as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t- butyl group can be given. Examples . X ₂ is substituted and bonded to hydrogen at any position of B, and X ₃ is substituted and bonded to hydrogen at any position of C;

On the other hand, though not limited thereto, it is more preferable that the polyamide contains a repeating unit represented by the following formula (3). In this case, the positive phase difference characteristic can be realized more effectively.

(3)

In the general formula 3, D is a C _{2 -16} aliphatic hydrocarbon chain, E ₁ and E ₂ are each independently a cyclohexane ring or a benzene ring, X _4, X ₅ and X ₆ is a halogen atom or a C each independently ₁ and _-6 alkyl group, X ₇ is a single bond, a methylene group or a dimethylmethylene group, d, e1 and e2 are each independently an integer of 0 ~ 2, k is an integer of 5 to 10,000.

In the formula (D), the C _{2 -16} aliphatic hydrocarbon chain refers to a hydrocarbon moiety of 2 to 16, or 4 to 14, or 6 to 12 carbon atoms, including, but not limited to, methylene An ethylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, a nonanemethylene group, a decamethylene group, an undecamethylene group, a dodecamethylene group, a tridecamethylene group, A methylene group, a pentadecamethylene group, a hexadecamethylene group, and the like.

Further, in the above Formula 3 E ₁ and E _2, wherein E ₁ and E ₂ are, and among them more preferable, especially cyclohexane ring, wherein, with the E ₁ and E ₂ of poly amide-based resin main chain of the The bonding position is not particularly limited and may be an asymmetric position or a symmetric position. For example, when E ₁ and E ₂ are cyclohexane rings, they may be a cyclohexane ring in which the 1,3 carbon is bonded to the main chain, or a cyclohexane ring in which the 1,4 carbon is bonded to the main chain.

In Formula 3, X ₄ and X ₅ And C ₁ of X _{6 - 6} in an alkyl group is a methyl group, may be mentioned an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t- butyl group. Examples. At this time, the X ₄ is bonded is substituted on hydrogen from any desired position of D, X ₅ is bonded is substituted on hydrogen from any desired position of E _1, X ₆ is optionally substituted on hydrogen from any desired position of the E ₂ .

Next, in the present invention, the raw material of the coating layer is a polymeric substance having a negative retardation property as long as it satisfies the above formulas (1) and (2), and the kind thereof is not particularly limited. For example, styrene resin, fluorene resin, polyvinylcarbazole, polyvinylnaphthalene and the like can be used.

At this time, the styrenic resin may be used without particular limitation as long as it contains a styrene-based monomer as a main component. Examples of the styrenic monomer include but are not limited to styrene,? -Methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, ? -Methylstyrene, 4-fluoro-? -Methylstyrene, 4-chlorostyrene, 2,4,6-trimethylstyrene, cis-? -Methylstyrene, trans-? methylstyrene, 4-t-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-difluorostyrene, 2,3 2-chlorostyrene, 4-fluorostyrene, 4-fluorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene, octachlorostyrene, 2- Hydroxystyrene, 2-hydroxystyrene, 4-hydroxystyrene, and the like can be used in combination. Among them, And more preferably in the α- methyl styrene. These may be used alone or in combination.

On the other hand, in addition to the above styrene type monomer, the styrene type resin may be used in combination with a styrene type monomer by mixing two or more kinds of maleic anhydride type monomer, maleimide type monomer, acrylonitrile type monomer and the like. For example, the styrene-based resin includes styrene-based monomers; And at least one monomer selected from the group consisting of maleic anhydride-based monomer, maleimide-based monomer and acrylonitrile-based monomer.

Examples of the maleic anhydride monomer include maleic anhydride, methyl maleic anhydride, ethyl maleic anhydride, propyl maleic anhydride, isopropyl maleic anhydride, cyclohexyl maleic anhydride and phenyl maleic anhydride. Can be; Examples of the maleimide-based monomer include maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-cyclohexylmaleimide, For example; Examples of the acrylonitrile-based monomer include acrylonitrile, methacrylonitrile, ethacrylonitrile, and phenyl acrylonitrile. However, the present invention is not limited thereto.

More specifically, the styrenic resin includes, but is not limited to, styrene-maleic anhydride copolymer, styrene-acrylonitrile copolymer,? -Methylstyrene-acrylonitrile copolymer, N-phenylmaleimide-? -Methylstyrene-acrylonitrile copolymer, N-phenylmaleimide-styrene-acrylonitrile copolymer, N-phenylmaleimide-a-methylstyrene-styrene-acrylonitrile copolymer and the like.

The fluorene resin has a fluorene skeleton in the molecule and can be used without any particular limitation as long as it is a fluorene resin generally used in the related art.

In addition, the polyvinylcarbazole has a carbazole skeleton in the molecule such as poly (9-vinylcarbazole), and polyvinylcarbazole generally used in the art can be used without any particular limitation.

The polyvinylnaphthalene has a naphthalene skeleton in the molecule such as poly (2-vinylnaphthalene), and polyvinylnaphthalene generally used in the art can be used without particular limitation.

In the present invention, the base film preferably has a thickness of 5 to 100 탆, more preferably 10 to 80 탆 or 10 to 50 탆. The thickness of the coating layer is preferably 1 to 30 탆, more preferably 1 to 15 탆 or 1 to 10 탆. Further, the thickness of the retardation film including them is preferably 5 to 80 占 퐉, more preferably 10 to 70 占 퐉 or 10 to 60 占 퐉. If the thickness of the retardation film is less than 5 탆, the thickness of the film becomes too thin, which may result in poor handling properties of the film and the polarizing plate, and may cause breakage or breakage in the manufacturing process of the film and the polarizing plate, If it is more than 80 탆, it may be difficult to reduce the thickness of the polarizing plate.

In the present invention, the retardation film preferably has a moisture permeability of 140 g / m ² · day or less, for example, 0 to 120 or 0.1 to 100 g / m ² · day. When the base film or the coating layer has a moisture permeability of about the above range, the moisture permeability of the entire retardation film may satisfy the above range, and it is more preferable that the moisture permeability of the base film is as low as the above range. On the other hand, when the moisture permeability of the whole retardation film is higher than the above range, there is a problem that deformation occurs under heat and humidity conditions or dissociation of iodide ions occurs in the polarizer, thereby deteriorating the polarization performance of the polarizer. The method of measuring the moisture permeability is not particularly limited, and can be measured by, for example, a method of measuring the weight of moisture permeating the film for one day under conditions of a temperature of 40 DEG C and a relative humidity difference of 90%.

Next, a method for producing a retardation film having an inverse wavelength dispersion characteristic of the present invention will be described.

A method for producing a retardation film of the present invention comprises: uniaxially stretching a base film having a positive retardation property in a longitudinal direction (MD); Forming a coating layer on at least one side of the substrate film uniaxially stretched in the longitudinal direction (MD) using a polymer material having a negative retardation characteristic; And uniaxially stretching the base film on which the coating layer is formed in the width direction (TD), wherein the base film and the coating layer are formed to satisfy the following formulas (1) and (2). As described above, the retardation film satisfying the following formulas (1) and (2) can be formed by appropriately controlling the material for forming the base film and the coating layer, the stretching condition and the like.

Equation _{(1): R in, b} (450) / R in, b (550)> R in, a (450) / R in, a (550)

Equation _{(2): R in, a} (550)> R in, b (550)

In the formula (1) and _{(2), R in, a} (450), R in, a (550) are each 450㎚ wavelength, and the plane direction retardation value of the substrate film measured at 550㎚, _{in R, b} (450), and R _{in and b} (550) are retardation values in the plane direction of the coating layer measured at 450 nm and 550 nm, respectively.

In the present invention, the base film may be formed by a film forming method well known in the art, for example, extrusion molding, solution casting, or extrusion molding, using a polymer material having a positive phase retardation property, Calender molding, film casting, or the like, or may be produced as a multilayer film through co-extrusion with other polymers. Alternatively, a commercially available film having a positive retardation characteristic with a lower moisture permeability than that of a conventional N-TAC film may be used. Specific examples of the polymer material having a positive phase difference characteristic with a low moisture permeability are the same as those described above.

On the other hand, the step of uniaxially stretching the base film having the positive retardation characteristics of the present invention in the machine direction (MD) can be carried out by a stretching method well known in the art. For example, when the glass transition temperature of the base film is Tg, the film is stretched by 1.1 to 4.0 times in a roll-to-roll manner at a temperature of (Tg-30) ° C to (Tg + 30) . &Lt; / RTI &gt;

More specifically, in the present invention, it is preferable that the uniaxially stretching in the longitudinal direction is performed by stretching the base film to 1.1 to 4.0 times, for example, 1.2 to 3.5 times or 1.3 to 3.0 times have. If the stretching ratio is less than 1.1 times, toughness of the film is lowered, and the produced retardation film may be difficult to apply to the polarizing plate. If the stretching ratio is more than 4.0 times, the film may be broken during stretching, Film production can be difficult.

In the present invention, the uniaxially stretching in the longitudinal direction is preferably performed such that the thickness of the base film is 20 to 250 占 퐉. For example, the thickness is 25 to 230 占 퐉 or 30 to 200 占 퐉 So that it can be stretched. If the thickness of the film after uniaxial stretching in the longitudinal direction is less than 20 占 퐉, the thickness of the film becomes too thin when the film is stretched in the width direction, and the handling properties of the film and the polarizing plate may become poor, And if it exceeds 250 탆, it may be difficult to make the polarizer thinner.

In the present invention, the step of uniaxially stretching in the longitudinal direction is preferably performed at a temperature of (Tg-30) DEG C to (Tg + 30) DEG C, where Tg is the glass transition temperature of the base film , More preferably at a temperature of (Tg-20) DEG C to (Tg + 20) DEG C. When the temperature is higher than the above range, toughness and polymer orientation of a desired level are difficult. If the temperature is lower than the above range, fracture is likely to occur. 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 special pen and heated at a constant temperature, the endothermic heat and the heat generation amount of the material due to the phase change occur, The transition temperature can be measured.

A step of uniaxially stretching the base film having the positive phase retardation property in the longitudinal direction and then forming a coating layer having negative phase difference characteristic on at least one surface of the base film. The step of forming the coating layer may be performed by a method well known in the art. For example, a composition including a polymer material having a negative phase difference and a solvent may be applied to the substrate by a microgravure coating method, a comma coating method, a bar coating method, a roller coating method, a spin coating method, a printing method, a dip coating method, , A blade coating method, a gravure printing method, and the like, followed by drying. Here, specific examples of the polymer material having a negative phase difference with a low moisture permeability are the same as described above, and examples of usable solvents include methylene chloride, chloroform, tetrahydrofuran (THF), 1,3-dioxane, , N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), alcohols such as ethanol and methanol, and water. These solvents may be used alone or in combination of two or more.

Meanwhile, in the step of forming the coating layer having the negative retardation characteristics, it is preferable to coat the coating layer so that the thickness of the coating layer is about 1 to 30 mu m. For example, the coating layer may be coated to have a thickness of about 2 to 20 mu m have. The thickness of the coating layer is related to the property of exhibiting retardation. When the coating layer is coated to a thickness of less than 1 탆, the coating exhibits a negative retardation and may not exhibit a desired retardation. On the other hand, When the thickness of the retardation film is coated, there is a problem that the characteristic of developing the retardation of the retardation film becomes too large, and the thickness of the film becomes thick, so that it may be difficult to make the retardation film thinner.

When the coating layer is formed on the base film through the above process, the base film on which the coating layer is formed is stretched in the transverse direction (TD). When the film is stretched in the width direction, the base film having a positive retardation characteristic and the coating layer having a negative retardation characteristic can be simultaneously stretched by one stretching process. Therefore, the base film having the positive retardation characteristics is biaxially stretched in the longitudinal direction and the width direction, and the coating layer having the negative retardation property is uniaxially stretched in the width direction.

On the other hand, the step of uniaxially stretching the base film in which the coating layer of the present invention is formed in the transverse direction (TD) can be similarly conducted by a stretching method well known in the art. For example, when the glass transition temperature of the base film is Tg, the stretching can be performed in the width direction at a temperature of (Tg-30) to (Tg + 30) deg.

More specifically, in the present invention, the uniaxially stretching in the transverse direction preferably stretches the base film on which the coating layer is formed by 1.1 to 4.0 times, for example, 1.2 to 3.5 times or 1.3 to 3.5 times can do. If the stretching ratio is less than 1.1 times, toughness of the film is lowered, and the produced retardation film may be difficult to apply to the polarizing plate. If the stretching ratio exceeds 4.0 times, the film may be broken during stretching, This can be difficult.

In the present invention, the uniaxially stretching in the transverse direction is preferably performed such that the thickness of the base film on which the coating layer is formed is 5 to 80 占 퐉. For example, can do. At this time, the thickness of the base film formed with the coating layer after being uniaxially stretched in the width direction becomes the final thickness of the retardation film of the present invention. If the thickness is less than 5 탆, the thickness of the film becomes too thin, and the handling properties of the film and the polarizing plate may become poor, so that the film and the polarizing plate may bend or break during the manufacturing process or handling of the product. It may be difficult to reduce the thickness of the polarizing plate.

In the present invention, the step of uniaxially stretching in the transverse direction is preferably performed at a temperature of (Tg-10) DEG C to (Tg + 20) DEG C, where Tg is the glass transition temperature of the base film , And more preferably at a temperature of about (Tg) ° C to (Tg + 15) ° C. At a temperature lower than the above range, breakage may occur. At a temperature higher than the above range, the orientation of the polymer chain may be relaxed, resulting in a decrease in toughness of the film and a decrease in phase difference. 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 special pen and heated at a constant temperature, the endothermic heat and the heat generation amount of the material due to the phase change occur, The transition temperature can be measured.

On the other hand, when the retardation film according to the present invention is applied to a VA mode liquid crystal display device, the viewing angle improving effect is very excellent and can be suitably used as a retardation film for a VA mode liquid crystal display device.

Meanwhile, the present invention provides a polarizing plate comprising at least one or more of the retardation films. In this case, the retardation 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 polarizing plate having a protective film on both sides of the polarizer.

When the retardation film is directly attached to one surface or both surfaces of the polarizer, for example, the structure may be a structure of an upper protective film / polarizer / retardation film, retardation film / polarizer / lower protective film, retardation film / Protective film or an upper protective film / polarizer / lower protective film / retardation film.

Meanwhile, the present invention provides a liquid crystal display device including at least one or more of the retardation films. For example, the present invention provides a VA mode liquid crystal display device including at least one or more of the retardation films.

The liquid crystal display may include a liquid crystal cell and a first polarizing plate and a second polarizing plate respectively provided on both surfaces of the liquid crystal cell, and the retardation film may be disposed between the liquid crystal cell and the first polarizing plate and / And may be provided between the polarizing plates. That is, a retardation film may be provided between the first polarizing plate and the liquid crystal cell, and a retardation film may be provided between the second polarizing plate and the liquid crystal cell, or between the first polarizing plate and the liquid crystal cell, 2 or more .

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the invention by the following examples.

Example  One

An unoriented film having a width of 800 mm and a thickness of 70 탆 was prepared using polyamide (Evonik, CX9704) having a positive retardation characteristic under a condition of 250 캜 using a T-die film. The unstretched film was stretched 1.3 times in a roll-to-roll manner at a temperature of 147 캜 in the MD direction to prepare a uniaxially stretched film having a thickness of 62 탆.

A solution (solvent: 1,3-dioxolane) containing 7% by weight of poly (9-vinylcarbazole) (product of Aldrich) was applied to the uniaxially stretched film and coated to a thickness of 3 탆 using a bar coater .

The coated film was stretched 2.0 times in the transverse direction at a temperature of 147 DEG C by tenter stretching to prepare a stretched multilayer film structure retardation film having a thickness of 32 mu m.

Example  2

An unoriented film having a width of 800 mm and a thickness of 125 탆 was prepared by using a polyamide (Evonik, CX9704) having a positive retardation characteristic under a condition of 250 캜 using a T-die film. The unstretched film was stretched 1.6 times in a roll-to-roll manner in the MD direction at a temperature of 145 캜 to prepare a uniaxially stretched film having a thickness of 100 탆.

A solution (solvent: 1,3-dioxolane) containing 7 wt% of poly (2-vinylnaphthalene) (product of Aldrich, Mw 175,000, Tg 135 ° C) was applied to the uniaxially stretched film, Mu] m thick.

Next, the coated film was stretched 2.2 times in the transverse direction at a temperature of 145 캜 in a tenter stretching manner to prepare a retardation film of a stretched multilayer film structure having a thickness of 50 탆.

Example  3

An unoriented film having a width of 800 mm and a thickness of 120 占 퐉 was produced by using a cycloolefin copolymer (Ticona, Topas) having a positive retardation characteristic under a condition of 250 占 폚 by using a T-die kneader. The unstretched film was stretched 1.4 times in a roll-to-roll manner in the MD direction at a temperature of 142 캜 to prepare a uniaxially stretched film having a thickness of 102 탆.

A solution (solvent: 1,3-dioxolane) containing 20 wt% of a styrene-maleic anhydride copolymer (Nova Dylark) was applied to the uniaxially stretched film and coated to a thickness of 15 탆 using a bar coater.

Next, the coated film was stretched 2.2 times in the transverse direction at a temperature of 142 캜 in a tenter stretching manner to prepare a stretched multilayer film structure retardation film having a thickness of 52 탆.

Comparative Example  One

A commercially available N-TAC film (polymer film containing Konica, a cellulose ester consisting of an acetyl group and a propionyl group as a main component) was used as Comparative Example 1.

Comparative Example  2

An unoriented film having a width of 800 mm and a thickness of 50 占 퐉 was produced by using a general aromatic polycarbonate (LG Chem, LUPOY DVD1080) under a condition of 260 占 폚 using a T-die film. The unstretched film was stretched 1.3 times in a roll-to-roll manner at a temperature of 147 캜 in the MD direction to prepare a uniaxially stretched film having a thickness of 45 탆.

A solution (solvent: 1,3-dioxolane) containing 20% by weight of? -Methylstyrene-acrylonitrile copolymer (Chemtura, B-587) was applied to the uniaxially stretched film, Mu m thickness.

Next, the coated film was stretched 2.0 times in the transverse direction at a temperature of 147 캜 in a tenter stretching manner to prepare a retardation film of a stretched multilayer film structure having a thickness of 35 탆.

The retardation, wavelength dispersion and moisture permeability of the retardation films prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured and shown in Table 1 below. The measurement method is as follows.

1. Measurement of phase difference value and wavelength dispersion characteristics: Measured using an Axoscat's axoscan instrument.

2. Moisture permeability of the retardation film: The moisture permeability of the film was measured by measuring the weight of moisture permeating the film during a day under conditions of a temperature of 40 ° C and a relative humidity difference of 90%.

division final
thickness
(탆) R _in (550)
(nm) R _th (550)
(nm) Wavelength dispersion characteristics Phase difference film
Moisture permeability
(g / m ² · day) R _in (450)
/ R _in (550) R _in (650)
/ R _in (550) Example 1 Base film 30 93 -115 1.02 0.98
37 Coating layer 2 44 52 1.10 0.94 Phase difference film 32 49 -105 0.95 1.02 Example 2 Base film 46 100 -220 1.02 0.98
27 Coating layer 4 50 62 1.09 0.95 Phase difference film 50 50 -200 0.95 1.02 Example 3 Base film 46 97 -117 1.01 0.99
12 Coating layer 7 46 63 1.06 0.96 Phase difference film 53 51 -104 0.97 1.02 Comparative Example 1 Phase difference film 43 41 -105 0.96 1.02 459 Comparative Example 2 Base film 23 101 -119 1.08 0.96
82 Coating layer 12 45 60 1.06 0.96 Phase difference film 35 56 -105 1.1 0.95

As can be seen from Table 1, the retardation film of the present invention has excellent reverse wavelength dispersion characteristics and has a retardation value suitable for a retardation film for a VA mode liquid crystal display device, . Further, it can be seen that the moisture permeability of the retardation film produced by using a material having a low moisture permeability is very low.

However, in the case of the conventional N-TAC as in Comparative Example 1, the moisture permeability is so high that it is unsuitable for use in a humidity-resistant environment, and the base film and the base film which do not satisfy the formula (1) When the coating layer is used, it can be seen that the produced retardation film has no reverse wavelength dispersion characteristic.

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.

Claims (17)

A biaxially stretched base film having positive phase retardation properties; And
A coating layer formed on at least one surface of the base film and having uniaxially stretched properties with negative retardation characteristics;
And a retardation film having an inverse wavelength dispersion characteristic satisfying the following formulas (1) and (2).
Equation _{(1): R in, b} (450) / R in, b (550)> R in, a (450) / R in, a (550)
Equation _{(2): R in, a} (550)> R in, b (550)
In the above formulas (1) and (2)
R _{in , a} (450) and R _{in , a} (550) are retardation values in the plane direction of the base film measured at wavelengths of 450 nm and 550 nm, respectively,
R _{in , b} (450) and R _{in , b} (550) are the surface direction retardation values of the coating layer measured at wavelengths of 450 nm and 550 nm, respectively.
The method according to claim 1,
Wherein the retardation film has an inverse wavelength dispersion characteristic satisfying the following expressions (3) and (4).
(3): 20 nm < R _{in , a} < 300 nm
(4): -400 nm < R _{th , a} < 0 nm
In the above formulas (3) and (4)
R _{in , a} is the retardation value in the plane direction of the base film measured in the visible light wavelength band,
_{Rth , a} is the retardation value in the thickness direction of the base film measured in the visible light wavelength band.
The method according to claim 1,
Wherein the retardation film has an inverse wavelength dispersion characteristic satisfying the following expressions (5) and (6).
(5): 10 nm < R _{in , b} < 250 nm
(6): 10 nm < R _{th , b} < 300 nm
In the above formulas (5) and (6)
R _{in , b} is the retardation value in the plane direction of the coating layer measured in the visible light wavelength band,
_{Rth , b} is the retardation value in the thickness direction of the coating layer measured in the visible light wavelength band.
The method according to claim 1,
Wherein the retardation film has an inverse wavelength dispersion characteristic satisfying the following formulas (7) and (8).
(7): 0 nm < R _{in , total} < 200 nm
(8): -300 nm < R _{th , total} < 0 nm
In the above formulas (7) and (8)
R _{in and total} are plane retardation values of the entire retardation film measured in the visible light wavelength band,
_{Rth , total} is the thickness direction retardation value of the entire retardation film measured in the visible light wavelength band.
The method according to claim 1,
Wherein the retardation film has an inverse wavelength dispersion characteristic satisfying the following expressions (9) and (10).
(9): 0.8 <R _{in , total} (450) / R _{in , total} (550) <1.0
Equation _{(10): 1.0 <R in} , total (650) / R in, total (550) <1.2
In the above formulas (9) and (10)
R _{in , total} (450), R _{in , total} (550) and R _{in , total} (650) are the retardation values of the entire retardation film measured at wavelengths of 450 nm, 550 nm and 650 nm, respectively.
The method according to claim 1,
Wherein the retardation film has an inverse wavelength dispersion characteristic satisfying the following formula (11).
(11): n _{x , total} > n _{y , total} > n _{z , total}
In the above formula (11)
n _{x , total} is the refractive index in the direction in which the refractive index in the plane direction of the entire retardation film becomes maximum (that is, in the slow axis direction)
n _{y , total} is the refractive index of the entire retardation film in the direction perpendicular to the slow axis (i.e., the fast axis direction)
n _{z , total} is the refractive index in the thickness direction of the entire retardation film,
At this time, n _{x , total} , n _{y , total} and n _{z , total} is the value measured in the visible light wavelength band.
The method according to claim 1,
Wherein the base film comprises at least one selected from the group consisting of a cycloolefin polymer, a cycloolefin copolymer, an alicyclic polycarbonate, an alicyclic polyester and a polyamide.
The method according to claim 1,
Wherein the coating layer comprises at least one selected from the group consisting of a styrenic resin, a fluorene resin, polyvinylcarbazole, and polyvinylnaphthalene.
The method according to claim 1,
Wherein the retardation film has a moisture permeability of 140 g / m ² · day or less.
The method according to claim 1,
Wherein the retardation film has an inverse wavelength dispersion characteristic for a VA mode liquid crystal display device.
A liquid crystal display device comprising the retardation film according to any one of claims 1 to 10.
Uniaxially stretching a substrate film having positive retardation characteristics in a longitudinal direction (MD);
Forming a coating layer on at least one side of the substrate film uniaxially stretched in the longitudinal direction (MD) using a polymer material having a negative retardation characteristic; And
Uniaxially stretching the base film on which the coating layer is formed in the transverse direction (TD);
Wherein the base film and the coating layer are formed so as to satisfy the following formulas (1) and (2).
Equation _{(1): R in, b} (450) / R in, b (550)> R in, a (450) / R in, a (550)
Equation _{(2): R in, a} (550)> R in, b (550)
In the above formulas (1) and (2)
R _{in , a} (450) and R _{in , a} (550) are retardation values in the plane direction of the base film measured at wavelengths of 450 nm and 550 nm, respectively,
R _{in , b} (450) and R _{in , b} (550) are the surface direction retardation values of the coating layer measured at wavelengths of 450 nm and 550 nm, respectively.
13. The method of claim 12,
Wherein the step of uniaxially stretching in the longitudinal direction (MD) is performed at a stretching ratio of 1.1 to 4.0.
13. The method of claim 12,
Wherein the uniaxially stretching in the longitudinal direction (MD) is stretching the base film to a thickness of 20 to 250 mu m.
13. The method of claim 12,
Wherein the coating layer is formed by coating the coating layer with a thickness of 1 to 30 탆.
13. The method of claim 12,
Is performed at a magnification of 1.2 to 4.0 which is uniaxially stretched in the transverse direction (TD).
13. The method of claim 12,
Wherein the uniaxially stretching in the transverse direction (TD) comprises stretching the base film on which the coating layer is formed to a thickness of 5 to 80 탆.