KR20150037443A - 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 dispersion properties in the plane and thickness directions to satisfy the following equitation (1) to (4) and a method for producing the same. The retardation film having anti-wavelength dispersion properties comprises: a first layer which has positive phase difference characteristics and is biaxially oriented; and a second layer which has negative phase difference characteristics and is biaxially oriented. Equitation (1): R_in,b(450)/R_in,b(550) > R_in,a(450)/R_in,a(550); Equitation (2): R_th,b(450)/R_th,b(550) > R_th,a(450)/R_th,a(550); Equitation (3): R_in,a(550) > R_in,b(550); Equitation (4): ¦R_th,a(550)¦ > ¦R_th,b(550)¦. In the above equitation (1) to (4), R_in,a(450) and R_in,a(550) are the retardation value of the first layer in the plane direction, measured in each wavelength of 450 nm and 550 nm; R_in,b(450) and R_in,b(550) are the retardation value of the second layer in the plane direction, measured in each wavelength of 450 nm and 550 nm; R_th,a(450) and R_th,a(550) are the retardation value of the first layer in the thickness direction, measured in each wavelength of 450 nm and 550 nm; R_th,b(450) and R_th,b(550) are the retardation value of the second layer in the thickness direction, measured in each wavelength of 450 nm and 550 nm; and ¦R_th,a(550)¦ and ¦R_th,b(550)¦ are the absolute value of each R_th,a(550) and R_th,b(550).

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 and more specifically to a retardation film which can realize an excellent reverse wavelength dispersion characteristic and can be used as a retardation film in a VA mode liquid crystal display device, ≪ / 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 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 characteristic has a large difference in Re / λ measured at a short wavelength and at a long wavelength, resulting in non-uniformity of transmittance, 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 increases, the transmittance is uniform regardless 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, a new raw material must be found in order to produce a retardation film having an inverse wavelength dispersion characteristic in a single sheet, which is not realistic. Therefore, in the case where two or more retardation films having different wavelength dispersions are conventionally laminated using an adhesive or an adhesive, or two or more retardation films having the same wavelength dispersion and different retardation values are laminated by a pressure sensitive adhesive or an adhesive at a specific axial angle A method has been proposed in which two retardation films are produced so as to exhibit a behavior as a retardation film exhibiting an inverse wavelength dispersion. However, in this case, there is a problem that the optical properties are lowered due to the presence of the adhesive layer or 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, There was a problem.

As a retardation film for a VA mode liquid crystal display having current reverse wavelength dispersion characteristics, N-TAC of Konica Co., which is a polymer film mainly composed of cellulose ester comprising acetyl group and propionyl group, is mainly used, but N-TAC There is a problem in that the moisture permeability is increased due to a large number of hydrophilic functional groups in the molecular chain structure, so that deformation occurs under heat / 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 first layer having positive phase retardation properties; And a second layer biaxially stretched with negative retardation characteristics, and having inverse wavelength dispersion characteristics in both plane and thickness directions satisfying the following formulas (1) to (4).

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

Equation _{(2): R th, b} (450) / R th, b (550)> R th, a (450) / R th, a (550)

Equation _{(3): R in, a} (550)> R in, b (550)

(4): | R _{th , a} (550) | > | R _{th , b} (550) |

In the formula (1) to _{(4), R in, a} (450), R in, a (550) plane is the retardation value of the first layer measured at each wavelength _450㎚, 550㎚, R _{in, b (450), R in,} b (550) are each 450㎚ wavelength, and the plane direction retardation value of the second layer measured at _{550㎚, R th, a (450} ), R th, a (550) are each 450㎚ wavelength, and the thickness retardation value of the first layer measured at _{550㎚, R th, b (450} ), R th, b (550) is the thickness of the second layer, respectively measured at a wavelength of 450㎚, 550㎚ Direction retardation value, and | R _{th , a} (550) | And R _{th , b} (550) denote the absolute values of R _{th , a} (550) and R _{th , b} (550), respectively.

On the other hand, it is preferable that the retardation film satisfies the following formulas (5) and (6).

(5): 20 nm < R _{in , a} < 300 nm

(6): -400 nm < R _{th , a} < 0 nm

In the above formulas (5) and (6), R _{in , a} is the retardation value of the first layer measured in the visible light wavelength band, R _{th , a} is the retardation in the thickness direction of the first layer measured in the visible light wavelength band Value.

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

(7): 10 nm < R _{in , b} < 250 nm

(8): 10 nm < R _{th , b} < 300 nm

In the above formulas (7) and (8), R _{in and b} are the surface direction retardation values of the second layer measured in the visible light wavelength band, and R _{th and b} are the retardation values in the thickness direction of the second layer Value.

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

(9): 0 nm < R _{in , total} < 200 nm

(10): -300 nm < R _{th , total} < 0 nm

In the formulas (9) and (10), R _{in , total} is the retardation value of the entire retardation film measured in the visible light wavelength band, R _{th and total} are the retardation values of the entire retardation film measured in the visible light wavelength band Value.

It is preferable that the retardation film satisfies the following formulas (11) to (14).

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

(12): 1.0 <R _{in , total} (650) / R _{in , total} (550) <1.2

0.8 <R _{th , total} (450) / R _{th , total} (550) <1.0

(14): 1.0 <R _{th , total} (650) / R _{th , total} (550) <1.2

The formula (11) to (14) _{in, R in, total (450)} , R in, total (550), R in, total (650) are each wavelength 450㎚, 550㎚, the retardation film measured at 650㎚ a plane direction retardation value of the _{total, R th, total (450)} , R th, total (550), R th, total (650) are each wavelength 450㎚, 550㎚, a phase difference film in the entire thickness of the measurement 650㎚ Direction phase difference value.

Further, it is preferable that the retardation film satisfies the following formula (15).

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

In the above formula (15), 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 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 first layer preferably includes 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 second layer preferably includes 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.

Meanwhile, the present invention provides a liquid crystal display device including the retardation film.

In another aspect, the present invention provides a method of forming a laminate, comprising: forming a laminate comprising a first layer having positive retardation characteristics and a second layer having negative retardation characteristics using coating or coextrusion; And a step of biaxially stretching the laminate, wherein the first layer and the second layer are formed so as to satisfy the following formulas (1) to (4) The present invention also provides a method of producing a retardation film having

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

Equation _{(2): R th, b} (450) / R th, b (550)> R th, a (450) / R th, a (550)

Equation _{(3): R in, a} (550)> R in, b (550)

(4): | R _{th , a} (550) | > | R _{th , b} (550) |

In the formula (1) to _{(4), R in, a} (450), R in, a (550) plane is the retardation value of the first layer measured at each wavelength _450㎚, 550㎚, R _{in, b (450), R in,} b (550) are each 450㎚ wavelength, and the plane direction retardation value of the second layer measured at _{550㎚, R th, a (450} ), R th, a (550) are each 450㎚ wavelength, and the thickness retardation value of the first layer measured at _{550㎚, R th, b (450} ), R th, b (550) is the thickness of the second layer, respectively measured at a wavelength of 450㎚, 550㎚ Direction retardation value, and | R _{th , a} (550) | And R _{th , b} (550) denote the absolute values of R _{th , a} (550) and R _{th , b} (550), respectively.

On the other hand, in the step of biaxially stretching the laminate, it is preferable that the laminate is uniaxially stretched in the longitudinal direction (MD) and uniaxially stretched in the width direction (TD).

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.

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).

The retardation film according to the present invention can be obtained by coating or laminating a laminate including a first layer having a positive retardation characteristic with a relatively low retardation characteristic and a second layer having a negative retardation characteristic having a relatively high retardation characteristic And then biaxially stretched to realize excellent reverse wavelength dispersion characteristics. The VA mode retardation film is excellent in the viewing angle improving effect when used, and can be easily manufactured without complicated processes.

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. At this time, 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 thickness of the first layer, the second layer, Represents the thickness of the retardation film.

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. Further, R _{in, a} , R _{in , b} , R _{in , and total} are the first layer and the second layer in the visible light wavelength band, more specifically, the light in the wavelength range of 400 to 780 nm, .

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 the maximum, n _y is the direction perpendicular to the x axis, n _z is the thickness direction, d is the refractive index The thickness of the first layer, the second layer or the retardation film.

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. The _{Rth , a} , _{Rth , b} , _{Rth , and total} values of the thickness direction retardation values of the first layer, the second layer, and the entire retardation film in the visible light wavelength band, more specifically, light having a wavelength of 400 to 780 nm, .

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 problems and have found that by using a material having low moisture permeability, it is possible to provide a first layer having a positive retardation characteristic with a relatively low wavelength dispersion characteristic and a negative retardation film having a relatively high wavelength dispersion characteristic When the laminate is formed by coating or coextrusion and is simultaneously biaxially stretched to be used as a retardation film, the retardation film has inverse wavelength dispersion characteristics both in the plane direction and in the thickness direction, It has been found that the effect of improving the viewing angle when used as a retardation film is excellent, and that heat resistance and moisture resistance are excellent, and the present invention has been completed.

More specifically, the retardation film of the present invention has a biaxially stretched first layer having a positive retardation property; And a biaxially stretched second layer having a negative retardation characteristic and satisfying the following formulas (1) to (4), and having inverse wavelength dispersion characteristics in both the plane direction and the thickness direction.

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

Equation _{(2): R th, b} (450) / R th, b (550)> R th, a (450) / R th, a (550)

Equation _{(3): R in, a} (550)> R in, b (550)

(4): | R _{th , a} (550) | > | R _{th , b} (550) |

In the formula (1) to _{(4), R in, a} (450), R in, a (550) plane is the retardation value of the first layer measured at each wavelength _450㎚, 550㎚, R _{in, b (450), R in,} b (550) are each 450㎚ wavelength, and the plane direction retardation value of the second layer measured at _{550㎚, R th, a (450} ), R th, a (550) are each 450㎚ wavelength, and the thickness retardation value of the first layer measured at _{550㎚, R th, b (450} ), R th, b (550) is the thickness of the second layer, respectively measured at a wavelength of 450㎚, 550㎚ Direction retardation value, and | R _{th , a} (550) | And R _{th , b} (550) denote the absolute values of R _{th , a} (550) and R _{th , b} (550), respectively.

Thus, the retardation film of the present invention has a positive retardation and includes a biaxially stretched first layer and a biaxially stretched second layer having negative retardation characteristics, and the optical axes of the first and second layers are orthogonal to each other.

The retardation film of the present invention satisfies the above-mentioned expressions (1) to (4), so that the retardation of 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 at low wavelengths in both the surface and thickness directions a is the difference between the retardation value largely, and the wavelength dispersion property in the entire surface direction and the thickness of the retardation film orientation, for example, _{R in, total (450) /} R in, total (550) and R _{th, total} (450) / R _{th, total} (550) value of the wavelength dispersion property in the plane direction and the thickness direction of the first layer, for example, _{R in, a (450) /} R in, a (550) and R _{th, a} (450) / _{Rth, a} (550). Thus, the retardation film of the present invention has excellent reverse wavelength dispersion characteristics in both the plane direction and the thickness direction. 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 preferable that the retardation film satisfies the following formulas (5) and (6).

(5): 20 nm < R _{in , a} < 300 nm

(6): -400 nm < R _{th , a} < 0 nm

In the above formulas (5) and (6), R _{in , a} is the retardation value of the first layer measured in the visible light wavelength band, R _{th , a} is the retardation in the thickness direction of the first layer measured in the visible light wavelength band Value. 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 It is preferable to satisfy the above expressions (5) and (6) even when measured by light.

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

(7): 10 nm < R _{in , b} < 250 nm

(8): 10 nm < R _{th , b} < 300 nm

In the above formulas (7) and (8), R _{in and b} are the surface direction retardation values of the second layer measured in the visible light wavelength band, and R _{th and b} are the retardation values in the thickness direction of the second layer Value. 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 (7) and (8) even when measured by light.

When the first layer and the second layer of the retardation film of the present invention have the retardation value in the plane direction and the retardation value in the thickness direction, the retardation value and retardation in thickness direction of the entire retardation film are applied to the VA mode retardation film To an appropriate value for the &lt; / RTI &gt;

It is 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 secure a wide viewing angle when used as a retardation film in a VA mode liquid crystal display device.

(9): 0 nm < R _{in , total} < 200 nm

(10): -300 nm < R _{th , total} < 0 nm

In the formulas (9) and (10), R _{in , total} is the retardation value of the entire retardation film measured in the visible light wavelength band, R _{th and total} are the 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 (9) and (10) are satisfied even when measured by light.

It is preferable that the retardation film satisfies the following formulas (11) to (14). When the retardation film of the present invention satisfies the following formulas (11) to (14), the same viewing angle compensation effect can be obtained in the entire region of the visible light wavelength band.

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

(12): 1.0 <R _{in , total} (650) / R _{in , total} (550) <1.2

0.8 <R _{th , total} (450) / R _{th , total} (550) <1.0

(14): 1.0 <R _{th , total} (650) / R _{th , total} (550) <1.2

The formula (11) to (14) _{in, R in, total (450)} , R in, total (550), R in, total (650) are each wavelength 450㎚, 550㎚, the retardation film measured at 650㎚ a plane direction retardation value of the _{total, R th, total (450)} , R th, total (550), R th, total (650) are each wavelength 450㎚, 550㎚, a phase difference film in the entire thickness of the measurement 650㎚ Direction phase difference value.

Further, it is preferable that the retardation film satisfies the following formula (15). In this case, it can be very usefully applied to a VA mode liquid crystal display as a retardation compensation film.

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

In the above formula (15), 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 satisfy the above-mentioned formula (15) 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) to (4); And the retardation film of the present invention satisfying at least one of the formulas (5) to (15) can be produced by suitably controlling the raw material for forming the first layer and the second layer, the stretching condition and the like.

First, in the present invention, the raw material of the first layer is a polymer material having a positive phase retardation property, and may be any material that has a lower moisture permeability than that of a conventional N-TAC film and can satisfy the above formulas (1) to (4) , 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, Polycarbonates commonly used in the field 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, The polyester commonly used in the field 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 D 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 second layer is a polymeric substance having a negative retardation property as long as it can satisfy the above-mentioned formulas (1) to (4), 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.

In addition, the fluorene resin has a fluorene skeleton in the molecule, and can be used without particular limitation on the polyamide resin commonly used in the 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 first layer preferably has a thickness of 5 to 100 탆, more preferably 10 to 80 탆, or 10 to 55 탆. The thickness of the second layer is preferably 1 to 30 占 퐉, more preferably 1 to 15 占 퐉 or 1 to 10 占 퐉. Further, the thickness of the retardation film including these is preferably 5 to 100 탆, more preferably 10 to 80 탆 or 10 to 70 탆. 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 100 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. In the present invention, when the first layer or the second layer has a moisture permeability of about the above range, the moisture permeability of the entire retardation film can satisfy the above range. For example, if the moisture permeability of the first layer is about the above range, the moisture permeability of the entire retardation film can satisfy the above range even if the moisture permeability of the second layer is high. 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 inverse wavelength dispersion characteristics in both the plane direction and the thickness direction of the present invention will be described.

The method for producing a retardation film having inverse wavelength dispersion characteristics in both the plane direction and the thickness direction of the present invention is a method for producing a retardation film by coating or coextruding a laminate comprising a first layer having a positive retardation property and a second layer having a negative retardation property ; And biaxially stretching the laminate, wherein the first layer and the second layer are formed to satisfy the following expressions (1) to (4). As described above, by appropriately controlling the forming material of the first layer and the second layer and the stretching conditions and the like, it is possible to obtain a retardation film having an inverse wavelength dispersion characteristic both in the plane direction and in the thickness direction satisfying the following formulas (1) to (4) Can be formed.

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

Equation _{(2): R th, b} (450) / R th, b (550)> R th, a (450) / R th, a (550)

Equation _{(3): R in, a} (550)> R in, b (550)

(4): | R _{th , a} (550) | > | R _{th , b} (550) |

In the formula (1) to _{(4), R in, a} (450), R in, a (550) plane is the retardation value of the first layer measured at each wavelength _450㎚, 550㎚, R _{in, b (450), R in,} b (550) are each 450㎚ wavelength, and the plane direction retardation value of the second layer measured at _{550㎚, R th, a (450} ), R th, a (550) are each 450㎚ wavelength, and the thickness retardation value of the first layer measured at _{550㎚, R th, b (450} ), R th, b (550) is the thickness of the second layer, respectively measured at a wavelength of 450㎚, 550㎚ Direction retardation value, and | R _{th , a} (550) | And R _{th , b} (550) denote the absolute values of R _{th , a} (550) and R _{th , b} (550), respectively.

The laminate including the first layer having the positive phase difference characteristics and the second layer having the negative phase difference characteristics may be formed using a coating. More specifically, in this case, the first layer is used as a base film, and the manufacturing method of the first layer is not particularly limited. For example, a film forming method well known in the art, for example, extrusion molding, solution casting, calender molding, film casting, etc., using a polymer material having a lower positive phase difference characteristic than that of a conventional N-TAC film Or a commercially available film containing a polymer material having a lower positive phase retardation than that of a conventional N-TAC film or the like may be used. Specific examples of the polymer material having a low moisture permeability and a positive retardation characteristic are the same as those described above.

When the first layer is prepared, a composition including a polymer material having negative retardation characteristics is applied on the first layer to form a coating layer. 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 characteristic having a low moisture permeability and a solvent may be applied 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 die coating method, a blade coating method, a gravure printing method, and the like, followed by drying. Specific examples of the polymer material having a negative retardation characteristic with low moisture permeability are the same as described above. Examples of usable solvents include methylene chloride, chloroform, tetrahydrofuran (THF), 1,3-dioxane, cyclopenta Alcohols such as N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc), ethanol and methanol, water and the like. These solvents may be used alone or in combination of two or more.

The laminate including the first layer having the positive retardation characteristics and the second layer having negative retardation characteristics may be formed using coextrusion. The coextrusion method usable in the present invention is not particularly limited, and can be carried out by a coextrusion method well known in the art. For example, the polymer material having the positive phase retardation characteristic and the polymer material having the negative retardation characteristic are injected into the co-extruder as the forming materials of the first layer and the second layer, respectively, and the thicknesses of the first layer and the second layer co- The laminate can be formed by controlling it to be in a desired range. More specifically, the polymer material having the positive phase retardation property and the polymer material having the negative phase difference property are melted in respective extruders, and the thickness of the first and second layers is adjusted to a desired range So that the layered product can be formed.

Next, after the laminate is formed using coating or co-extrusion as described above, the step of biaxially stretching the laminate is carried out. By this biaxial stretching, both the first layer having a positive retardation characteristic and the second layer having a negative retardation characteristic are biaxially stretched in the longitudinal direction and the width direction.

At this time, it is preferable that the step of biaxially stretching the laminate is performed by a method of uniaxially stretching the laminate in the longitudinal direction (MD) and uniaxially stretching in the width direction (TD). In the case of uniaxially stretching in the width direction (TD) and uniaxially stretching in the length direction (MD), width shrinkage occurs when the laminate stretched in the width direction (TD) is stretched in the longitudinal direction (MD) It is difficult to produce a stretched film.

On the other hand, the step of uniaxially stretching the laminate of the present invention in the longitudinal direction (MD) can be similarly performed by a stretching method well known in the art. For example, when the glass transition temperature of the first layer is Tg, a method of stretching at a temperature of (Tg-30) to (Tg + 30) ° C in a roll-to- .

More specifically, in the present invention, the step of uniaxially stretching in the longitudinal direction is preferably a step of stretching the laminate to 1.1 to 4.0 times, for example, 1.2 to 3.0 times or 1.5 to 2.5 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 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 first layer And more preferably at a temperature of about (Tg) ° C to (Tg + 20) ° C or (Tg) ° C to (Tg + 15) ° 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.

On the other hand, the step of uniaxially stretching the laminate of the present invention in the transverse direction (TD) can be similarly performed 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, in the step of uniaxially stretching in the transverse direction, the laminate is preferably stretched by 1.2 to 4.0 times, for example, 1.3 to 3.0 times or 1.5 to 2.5 times. . 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 step of uniaxially stretching in the transverse 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 first layer And more preferably at a temperature of about (Tg) ° C to (Tg + 20) ° C or (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 110 탆 was prepared using a polyamide (Evonik, CX9704) having a positive phase retardation property under a condition of 250 캜 by using a T-die kneader. A solution (solvent: 1,3-dioxolane) containing 8 wt% of poly (9-vinylcarbazole) (product of Aldrich Co., Tg 220 ° C) was applied to the undrawn film, Lt; / RTI &gt;

The coated film was stretched 1.5 times in a roll-to-roll manner at a temperature of 145 캜 in the MD direction to prepare a uniaxially stretched film having a thickness of 97 탆. Next, the uniaxially-stretched film was stretched 2.2 times in the transverse direction at a temperature of 145 캜 by tenter stretching to prepare a retardation film of a stretched multilayer film structure having a thickness of 44 탆.

Example  2

An unoriented film having a width of 800 mm and a thickness of 90 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. A solution (solvent: 1,3-dioxolane) containing 13 wt% of poly (2-vinylnaphthalene) (product of Aldrich) was applied to the undrawn film and coated to a thickness of 18 μm using a bar coater.

The coated film was stretched 1.5 times in a roll-to-roll manner in the MD direction at a temperature of (145) 占 폚 to prepare a uniaxially stretched film having an 88 占 퐉 thickness. Next, the uniaxially stretched film was stretched by 2.2 times in the transverse direction at a temperature of 145 DEG C by tenter stretching to prepare a retardation film of a stretched multilayer film structure having a thickness of 40 mu m.

Example  3

A cycloolefin copolymer (Ticona, Topas) and a styrene-maleic anhydride copolymer (Nova, Dylark), which are polymeric materials having positive phase retardation properties, were extruded at 250 ° C in respective extruders, Was used to produce a laminate having a total thickness of 155 mu m consisting of a cycloolefin copolymer layer having a thickness of 130 mu m and a styrene-maleic anhydride copolymer layer having a thickness of 25 mu m.

The laminate was stretched 1.5 times in a roll-to-roll manner at a temperature of 140 캜 in the MD direction to prepare a 128 占 퐉 -thick uniaxially stretched film. Next, the uniaxially stretched film was stretched by 2.0 times in the transverse direction at a temperature of 140 DEG C by tenter stretching to prepare a retardation film of a stretched multilayer film structure having a thickness of 64 mu m.

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 Moisture permeability
(g / m ² · day) R _in (450)
/
R _in (550) R _in (650)
/
R _in (550) R _th (450)
/
R _th (550) R _th (650)
/
R _th (550) E1 The first layer 40 98 -185 1.02 0.98 1.02 0.98
29 Second layer 4 50 131 1.10 0.94 1.10 0.94 Phase difference film 44 48 -104 0.94 1.04 0.94 1.04 E2 The first layer 33 80 -150 1.02 0.98 1.02 0.98
35 Second layer 7 35 92 1.09 0.95 1.09 0.95 Phase difference film 40 45 -95 0.96 1.02 0.96 1.02 E3 The first layer 54 65 -135 1.01 0.99 1.01 0.99
10 Second layer 10 22 60 1.06 0.96 1.06 0.96 Phase difference film 64 43 -97 0.99 1.01 0.99 1.01 CE1 N-TAC 43 41 -105 0.96 1.02 0.96 1.02 459 CE2 The first layer 23 101 -119 1.08 0.96 1.08 0.96
82 Second layer 12 45 60 1.06 0.96 1.06 0.96 Composite film 35 56 -105 1.10 0.95 1.10 0.95 E1: Example 1, E2: Example 2, E3: Example 3, CE1: Comparative Example 1, CE2:

As can be seen from Table 1, the retardation film of the present invention has excellent reverse wavelength dispersion characteristics both in the plane direction and in the thickness direction, while using the manufacturing method through the simplified step, and the retardation film for VA mode liquid crystal display It can be understood that the retardation value is suitable for the retardation film. 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 as in Comparative Example 2, It can be seen that the prepared retardation film does not have reverse wavelength dispersion characteristics in both the plane direction and the thickness direction.

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 (15)

A biaxially stretched first layer having positive phase retardation properties; And
A biaxially stretched second layer having negative retardation characteristics;
, And has an inverse wavelength dispersion property in both a plane direction and a thickness direction satisfying the following formulas (1) to (4).
Equation _{(1): R in, b} (450) / R in, b (550)> R in, a (450) / R in, a (550)
Equation _{(2): R th, b} (450) / R th, b (550)> R th, a (450) / R th, a (550)
Equation _{(3): R in, a} (550)> R in, b (550)
(4): | R _{th , a} (550) | > | R _{th , b} (550) |
In the above formulas (1) to (4)
R _{in , a} 450 and R _{in , a} 550 are plane retardation values of the first layer measured at wavelengths of 450 nm and 550 nm, respectively,
R _{in , b} 450 and R _{in , b} 550 are the retardation values of the second layer measured at 450 nm and 550 nm, respectively,
_{Rth , a} (450), and _{Rth , a} (550) are thickness direction retardation values of the first layer measured at wavelengths of 450 nm and 550 nm, respectively,
_{Rth , b} (450) and _{Rth , b} (550) are thickness direction retardation values of the second layer measured at wavelengths of 450 nm and 550 nm, respectively,
| R _{th , a} (550) | And _{| R th, b (550)} | is the absolute ¹ of R _{th, a} (550) and R _{th, b} (550), respectively.
The method according to claim 1,
Wherein the retardation film has an inverse wavelength dispersion characteristic in both a plane direction and a thickness direction satisfying the following expressions (5) and (6).
(5): 20 nm < R _{in , a} < 300 nm
(6): -400 nm < R _{th , a} < 0 nm
In the above formulas (5) and (6)
R _{in , a} is the retardation value of the first layer measured in the visible light wavelength band,
_{Rth , a} is the thickness direction retardation value of the first layer measured in the visible light wavelength band.
The method according to claim 1,
Wherein the retardation film has an inverse wavelength dispersion characteristic in both a plane direction and a thickness direction satisfying the following expressions (7) and (8).
(7): 10 nm < R _{in , b} < 250 nm
(8): 10 nm < R _{th , b} < 300 nm
In the above formulas (7) and (8)
R _{in , b} is the retardation value of the second layer measured in the visible light wavelength band,
_{Rth , b} is the thickness direction retardation value of the second layer measured in the visible light wavelength band.
The method according to claim 1,
Wherein the retardation film has an inverse wavelength dispersion characteristic in both a plane direction and a thickness direction satisfying the following expressions (9) and (10).
(9): 0 nm < R _{in , total} < 200 nm
(10): -300 nm < R _{th , total} < 0 nm
In the above formulas (9) and (10)
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 in both a plane direction and a thickness direction satisfying the following formulas (11) to (14).
0.8 < R _{in , total} (450) / R _{in , total} (550) < 1.0
(12): 1.0 <R _{in , total} (650) / R _{in , total} (550) <1.2
0.8 <R _{th , total} (450) / R _{th , total} (550) <1.0
(14): 1.0 <R _{th , total} (650) / R _{th , total} (550) <1.2
In the above formulas (11) to (14)
_{R in, total (450),} R in, total (550) and R _{in, total} (650) are each a wavelength 450㎚, the plane direction retardation value of the entire retardation film measured at 550㎚ and 650㎚,
R _{th , total} (450), R _{th , total} (550), and R _{th , total} (650) are thickness direction 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 in both a plane direction and a thickness direction satisfying the following formula (15).
(15): n _{x , total} > n _{y , total} > n _{z , total}
In the above formula (15)
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 first layer comprises 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, / RTI &gt;
The method according to claim 1,
Wherein the second layer comprises at least one or more 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 both in a plane direction and in a thickness direction 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.
Forming a laminate including a first layer having a positive retardation characteristic and a second layer having negative retardation characteristics using coating or coextrusion; And
And biaxially stretching the laminate,
Wherein the first layer and the second layer are formed so as to satisfy the following formulas (1) to (4), wherein the first layer and the second layer have inverse wavelength dispersion characteristics in both the plane direction and the thickness direction.
Equation _{(1): R in, b} (450) / R in, b (550)> R in, a (450) / R in, a (550)
Equation _{(2): R th, b} (450) / R th, b (550)> R th, a (450) / R th, a (550)
Equation _{(3): R in, a} (550)> R in, b (550)
(4): | R _{th , a} (550) | > | R _{th , b} (550) |
In the above formulas (1) to (4)
R _{in , a} 450 and R _{in , a} 550 are plane retardation values of the first layer measured at wavelengths of 450 nm and 550 nm, respectively,
R _{in , b} 450 and R _{in , b} 550 are the retardation values of the second layer measured at 450 nm and 550 nm, respectively,
_{Rth , a} (450), and _{Rth , a} (550) are thickness direction retardation values of the first layer measured at wavelengths of 450 nm and 550 nm, respectively,
_{Rth , b} (450) and _{Rth , b} (550) are thickness direction retardation values of the second layer measured at wavelengths of 450 nm and 550 nm, respectively,
| R _{th , a} (550) | And _{| R th, b (550)} | is the absolute ¹ of R _{th, a} (550) and R _{th, b} (550), respectively.
13. The method of claim 12,
The step of biaxially stretching the laminate is characterized in that the laminate is uniaxially stretched in the longitudinal direction (MD) and uniaxially stretched in the width direction (TD), and the production method of the retardation film having inverse wavelength dispersion characteristics in both the planar direction and the thickness direction .
13. The method of claim 12,
Wherein the uniaxial stretching in the longitudinal direction (MD) is performed at a stretching ratio of 1.1 to 4.0.
13. The method of claim 12,
Is performed at a magnification of from 1.2 to 4.0 which is uniaxially stretched in the transverse direction (TD).