KR20150037445A - Retadation film and preparing method for retadation film - Google Patents

Abstract

A retardation film according to the present invention comprises: an amide-based film having negative C-type or negative B-type retardation; and a coating layer formed on at least one surface of the amide-based film, and having negative retardation properties.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a retardation film,

The present invention relates to a retardation film and a method of manufacturing the same, and more particularly to a retardation film in which a polymer material having negative retardation characteristics is coated on an amide film having a negative C type or negative B type retardation, .

The liquid crystal display device is spreading as an optical display device because its power consumption is lower than that of a cathode ray tube display, its volume is small, its weight is light and it is easy to carry. In general, a liquid crystal display device has a basic structure in which a polarizing plate is provided on both sides of a liquid crystal cell, and the orientation of the liquid crystal cell changes depending on whether an electric field is applied to the driving circuit, and the characteristics of light transmitted through the polarizing plate are changed, Is visualized. At this time, the path of light and the birefringence change depending on the incident angle of the incident light because the liquid crystal is an anisotropic material having two different refractive indices.

Due to such characteristics, the liquid crystal display device has a problem that the contrast ratio, which is a measure for how much the image is seen clearly according to the viewing angle, is changed and the gray scale inversion phenomenon occurs, It has disadvantages. In order to overcome such disadvantages, an optical compensation film for developing an optical retardation generated in a liquid crystal cell is used for a liquid crystal display device.

Various liquid crystal modes have been developed in order to secure a clear image quality and a wide viewing angle in a liquid crystal display device. Typical examples thereof include Double Domain TN (Twisted Nematic), ASM (axially symmetric aligned microcell), OCB blend, VA, multidomain VA, SE, surrounding electrode, patterned VA, in-plane switching (IPS), and fringe-field switching (FFS) . Each of these modes has a unique liquid crystal arrangement and has inherent optical anisotropy.

Therefore, in order to manifest the phase difference due to the optical anisotropy of these liquid crystal modes, an optically anisotropic phase difference film corresponding to each mode is required. Especially, in the case of the IPS mode, since the liquid crystal having a positive dielectric anisotropy is horizontally aligned, the optical anisotropy at the oblique angle in the non-driven state is not greater than that of the other modes, so that an excellent viewing angle can be obtained by using the isotropic protective film alone . In this case, however, compensation for the absorption axis of the polarizer at the high inclination angle is not performed at all, so that the contrast may be deteriorated due to the viewing angle and color modulation may occur. Therefore, in order to secure a perfect viewing angle, the IPS mode liquid crystal display should also use an appropriate retardation film do.

On the other hand, in the case of the IPS mode liquid crystal display device, it is difficult to sufficiently realize the compensating effect when the uniaxial or biaxially stretched film is used alone. Currently, the IPS mode retardation film is a multilayer film composed of two or more layers, A liquid crystal film on which a liquid crystal layer is coated, and the like are generally used. Typically, nematic liquid crystal is coated on a uniaxially stretched COP (cyclic olefin polymer) film to compensate the viewing angle. However, in the case of such a liquid crystal film, even if the alignment of the liquid crystal and the thickness of the coating slightly change, the retardation of the entire compensating film is greatly changed to make it difficult to control the retardation. In addition, And it is disadvantageous in that it is difficult to commercialize it because of high manufacturing cost due to expensive liquid crystal unit price.

Further, although a retardation film for coating a non-liquid crystalline retardation developing material having a negative C characteristic to an acrylic retardation film and controlling a retardation value in a plane direction and a retardation value in a thickness direction has been developed, an acrylic film is usually used in an aromatic Hydrocarbon, or organic chlorine, and when such a retardation developing substance is coated using such a solvent, problems such as poor adhesion, increase in brittleness, decrease in phase difference and occurrence of stain may occur .

SUMMARY OF THE INVENTION The present invention has been accomplished in order to solve the above problems, and it is an object of the present invention to provide a polarizing film having negative phase difference characteristic by coating a polymer material having a negative retardation characteristic on an amide film having a negative C type or negative B type phase difference, And which can be used for an IPS mode, and a simple process for producing such a retardation film. The present invention also provides a method for manufacturing such a retardation film.

In one aspect, the present invention provides an amide-based film having a negative C type or negative B type phase difference; And a coating layer formed on at least one surface of the amide-based film and having a negative retardation characteristic.

At this time, it is preferable that the retardation film satisfies the following formulas (1) and (2).

(1): 50 nm < R _{in , total} < 300 nm

(2): 10 nm < R _{th , total} < 300 nm

In the above formulas (1) and (2)

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.

It is preferable that the retardation film has an Nz value of less than 1, which is represented by the following formula (3).

Equation _{(3): Nz = R th} , total / R in, total

In the above formula (3)

R _{in , total} is the retardation value in the plane direction of the entire retardation film,

_{Rth , total} is the retardation value in the thickness direction of the entire retardation film,

In this case, R _{in , total} and R _{th , total} are the retardation values measured in the visible light wavelength band.

In the retardation film, it is preferable that the coating layer having the negative retardation characteristics satisfies the following expressions (4) and (5).

(4): 50 nm < R _{in , a} < 250 nm

(5): 80 nm < R _{th , a} < 300 nm

In the above formulas (4) and (5)

R _{in , a} is the retardation value in the plane direction of the coating layer having a negative retardation characteristic measured in the visible light wavelength band,

_{Rth , a} is the thickness direction retardation value of the coating layer having a negative retardation characteristic measured in a visible light wavelength band.

It is preferable that the retardation film satisfies the following formulas (6) and (7) as the amide-based film having the negative C type retardation.

(6): -50 nm <R _{in , b 1} <50 nm

(7): -200 nm < R _{th , b 1} < 0 nm

In the above formulas (6) and (7)

R _{in and b 1} are retardation values in the plane direction of an amide-based film having a negative C-type retardation measured in a visible light wavelength band,

_{Rth and b1} are retardation values in the thickness direction of the amide type film having the negative C type retardation measured in the visible light wavelength band.

It is also preferable that the amide-based film having the negative B-type retardation satisfies the following formulas (8) and (9).

Equation _{(8): 0nm <R in} , b2 <100nm

Equation _{(9): -200nm <R th} , b2 <0nm

In the above formulas (8) and (9)

R _{in, b2} is the plane retardation value of the amide-based film having a retardation of the negative type B measured in the visible light wavelength band,

_{Rth and b2} are retardation values in the thickness direction of an amide type film having a negative B type retardation measured in a visible light wavelength band.

It is preferable that the retardation film satisfies the following formula (10).

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

In the above formula (10)

n _{x , total} is a refractive index in a 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)

n _{y , total} is the refractive index in the direction perpendicular to the slow axis of the entire retardation film (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, the n _{x , total} , n _{y , total} , n _{z , total} is the value measured in the visible light wavelength band.

On the other hand, the amide-based film having the negative C type or negative B type retardation may include a polyamide type resin containing units represented by the following formula (1) or (2).

[Chemical Formula 1]

In Formula 1,

A is a C _{2 -16} aliphatic hydrocarbon chain, a C _{5 -14} aliphatic hydrocarbon ring or a C _{6 -14} aromatic hydrocarbon ring,

X ₁ is a halogen atom or a C _{1 -6} alkyl group,

a is an integer of 0 to 3,

n is an integer of 5 to 10,000.

(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,

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 to 3,

and m is an integer of 5 to 10,000.

On the other hand, it is more preferable that the amide-based film having the negative C type or negative B type retardation includes a polyamide type resin containing a unit represented by the following formula (3).

(3)

In 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,

And X _4, X ₅ and X ₆ is an alkyl group each independently a halogen atom or a C _{1 -6,}

X ₇ is a single bond, a methylene group or a dimethylmethylene group,

d, e1 and e2 are each independently an integer of 0 to 2,

and k is an integer of 5 to 10,000.

On the other hand, the coating layer having the negative retardation characteristics may include a styrene resin, polyvinylcarbazole, or polyvinylnaphthalene.

The thickness of the retardation film is preferably 10 to 60 mu m.

Meanwhile, the retardation film is preferably used for a liquid crystal display device of a planar switching (IPS) mode.

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

In another aspect, the present invention provides a method for producing an amide-based film, comprising: uniaxially stretching an amide-based film in a longitudinal direction (MD); Forming a coating layer on at least one surface of the amide-based film uniaxially stretched in the longitudinal direction by using a polymer material having a negative retardation characteristic; And uniaxially stretching the amide-based film formed with the coating layer in the transverse direction (TD).

At this time, in the step of uniaxially stretching in the longitudinal direction (MD), the amide-based film is preferably stretched by 1.1 to 5.0 times.

In the uniaxially stretching in the longitudinal direction (MD), the amide-based film is preferably stretched to a thickness of 20 to 120 탆.

Meanwhile, 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.

On the other hand, in the step of uniaxially stretching in the transverse direction (TD), it is preferable that the amide-based film formed with the coating layer is stretched by 1.1 to 5.0 times.

Also, in the step of uniaxially stretching in the transverse direction (TD), the amide-based film formed with the coating layer is preferably stretched to a thickness of 10 to 60 탆.

The retardation film according to the present invention is excellent in durability because it uses an amide-based film as a film having a retardation of negative C type or negative B type, and because of the high retardation property of the amide type film, a desired retardation As a result, it is possible to form a thin film, and problems such as adhesion failure, increase in brittleness, decrease in phase difference and occurrence of stain do not occur.

Also, the retardation film according to the present invention can easily adjust the retardation value in the plane direction and the retardation value in the thickness direction, and is excellent in the viewing angle improving effect, and can be used as an IPS mode retardation film or the like.

The retardation film according to the present invention can be produced by coating a polymer material having negative retardation characteristics on an uniaxially stretched amide film having a negative C type or negative B type retardation and simultaneously stretching the film, Therefore, the manufacturing method is very simple as compared with the conventional method of coating the liquid crystal and the phase difference developing material.

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 becomes maximum at the wavelength, n _y is the direction perpendicular to the x axis, d is the retardation value of the amide-based film, the retardation film, .

On the other hand, R _{in , a} represents the in-plane retardation value of the coating layer having a negative retardation characteristic _{in a} visible light wavelength band, more specifically, light having a wavelength of 400 to 780 nm, R _{in and b 1} are visible light wavelength bands, to indicate a plane direction retardation value of the amide-based film having a phase difference of a negative C-type at the 780nm wavelength light, R _{in, b2} are negative type B in the visible light wavelength region, more specifically in the 400 to 780nm wavelength And R _{in and total} represent the retardation value of the entire retardation film in the visible light wavelength band, more specifically, 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 is the maximum, n _y is the direction perpendicular to the x axis, n _z is the thickness direction, d is the amide to be measured, Based film, a retardation film, or a coating layer.

R _{th , a} represents the retardation value in the thickness direction of the coating layer having a negative retardation characteristic in the visible light wavelength band, more specifically, light having a wavelength of 400 to 780 nm, R _{in , b 1} is the visible light wavelength band, more specifically 400 Type retardation film of the amide type film having a negative C-type retardation in the light of a wavelength of 780 nm to 780 nm, and R _{in and b 2} represent the thickness direction retardation value _{in the} visible light wavelength band, more specifically negative B type And R _{in and total} denote the retardation values of 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) Nz is in a visible light wavelength band, than that specifically means a ratio of the retardation value in the thickness direction to the retardation value in the plane direction in the 400 to 780nm wavelength light, Nz = R _{th, total} / R _{in, total} . For example, Nz may be a ratio of the retardation value in the thickness direction to the retardation value in the plane direction in the light having a wavelength of 450 nm, 550 nm, or 650 nm.

(5) 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.

(6) The negative C type means that n _x ? N _y > n _z is satisfied, and the negative B type means that n _x > n _y > n _z is satisfied. At this time, as described above, n _x is in the plane of the film, and the refractive index of the refractive index of the large direction, n _y is a refractive index in the direction perpendicular to the n _x direction in the plane of the film, n _z is the thickness Lt; / RTI &gt;

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 found that an amide-based film having a negative C type or negative B type phase difference is coated on a surface of at least one side with a polymer material having negative retardation characteristics and used as a retardation film It is possible to easily adjust the retardation value in the plane direction and the retardation value in the thickness direction, to have excellent durability, to be thin, and to be applied to an IPS mode liquid crystal display device.

More specifically, the retardation film according to the present invention is an amide-based film having a retardation of negative C type or negative B type; And a coating layer formed on at least one surface of the amide-based film and having a negative retardation characteristic. At this time, the amide-based film is preferably biaxially stretched in the longitudinal direction (MD) and the transverse direction (TD), and the coating layer is preferably uniaxially stretched in the width direction (TD).

On the other hand, the retardation film preferably satisfies the following formulas (1) and (2). According to the studies of the present inventors, when the retardation film of the present invention satisfies the following formulas (1) and (2), it has been shown that the IPS mode liquid crystal display device has excellent viewing angle improving effect when used as a retardation film.

(1): 50 nm < R _{in , total} < 300 nm

(2): 10 nm < R _{th , total} < 300 nm

In the above formulas (1) and (2), 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 (1) and (2) even when measured by light.

It is more preferable that the phase retardation film has a retardation value in the range of 60 to 250 nm or 70 to 200 nm as measured in the visible light wavelength band. It is more preferable that the thickness direction retardation value of the entire retardation film measured in the visible light wavelength band is 20 to 250 nm or 30 to 200 nm. In this case, the above-described viewing angle improving effect can be more effectively expressed.

The retardation film preferably has an Nz value of less than 1, more preferably 0.1 to 0.9, particularly preferably 0.2 to 0.8, expressed by the following formula (3). In this case, it is very suitable for use as a retardation film of a liquid crystal display device of various modes, in particular, an IPS mode liquid crystal display device.

Equation _{(3): Nz = R th} , total / R in, total

In the formula (3), R _{in, total} is the plane retardation value of the entire retardation film, R _{th, total} is the retardation value of the entire retardation film thickness direction, wherein said R _{in, total} and R _{th, total} is All of which are retardation values measured in the visible light wavelength band. That is, even if the retardation film of the present invention measures Nz in the visible light wavelength band, more specifically, light having any wavelength of 400 to 780 nm, for example, light having a wavelength of 450 nm, 550 nm, or 650 nm, It is preferable to satisfy it.

In the retardation film, it is preferable that the coating layer having the negative retardation characteristics satisfies the following expressions (4) and (5). In this case, the retardation value in the plane direction and the thickness direction retardation value of the entire retardation film can be adjusted to appropriate values for application to the retardation film for IPS mode.

(4): 50 nm < R _{in , a} < 250 nm

(5): 80 nm < R _{th , a} < 300 nm

In the above formulas (4) and (5), R _{in , a} is the surface direction retardation value of the coating layer having a negative retardation characteristic measured in a visible light wavelength band, and R _{th , a} is a negative retardation characteristic measured in the visible light wavelength band Is a thickness direction retardation value of the coating layer. 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 (4) and (5) even when measured by light.

The retardation film preferably has a retardation value in the range of 70 to 200 nm and a thickness retardation value of 100 to 250 nm in the coating layer having the negative retardation characteristic measured in the visible light wavelength band. In this case, the retardation value in the plane direction and the retardation value in the thickness direction of the entire retardation film can be more effectively adjusted to appropriate values for application as an IPS mode retardation film.

It is preferable that the retardation film satisfies the following formulas (6) and (7) as the amide-based film having the negative C type retardation. In this case, the retardation value in the plane direction and the thickness direction retardation value of the entire retardation film can be adjusted to appropriate values for application to the retardation film for IPS mode.

(6): -50 nm <R _{in , b 1} <50 nm

(7): -200 nm < R _{th , b 1} < 0 nm

In the formulas (6) and (7), R _{in and b 1} are plane retardation values of an amide type film having a negative C type retardation measured in a visible light wavelength band, R _{th and b 1} are measured in a visible light wavelength band Is a thickness direction retardation value of an amide type film having a negative C type retardation. That is, in the retardation film of the present invention, R _{in , b 1} and R _{th , b 1} are visible light wavelength bands, more specifically light of any wavelength of 400 to 780 nm, for example, 450 nm, 550 nm, or 650 nm It is preferable to satisfy the above-mentioned expressions (6) and (7) even when measured by light.

It is more preferable that the phase difference film has a retardation value in the plane direction of -20 to 20 nm and a retardation in the thickness direction of -150 to 0 nm of the amide type film having the negative C type retardation measured in the visible light wavelength band. In this case, the retardation value in the plane direction and the retardation value in the thickness direction of the entire retardation film can be more effectively adjusted to appropriate values for application as an IPS mode retardation film.

It is preferable that the retardation film satisfies the following formulas (8) and (9) for the amide-based film having the negative B-type retardation. In this case, the retardation value in the plane direction and the thickness direction retardation value of the entire retardation film can be adjusted to appropriate values for application to the retardation film for IPS mode.

Equation _{(8): 0nm <R in} , b2 <100nm

Equation _{(9): -200nm <R th} , b2 <0nm

In the above formula (8) and _(9), R _{in, b2} is the plane retardation value of the amide-based film having a retardation of the negative type B measured in the visible light wavelength range, R _{th, b2} is measured in the visible light wavelength band Is the thickness direction retardation value of the amide type film having the negative B type phase difference. That is, the retardation film of the invention wherein R _{in, b2} and R _{th, b2} is the visible light wavelength region, and more specifically, from 400 to 780nm in which any of the wavelengths of the wavelength of light, for example, of 450nm, 550nm, or 650nm wavelength (8) and (9) are satisfied even when measured by light.

It is more preferable that the phase difference film has a retardation value in the plane direction of 0 to 80 nm and a retardation value in the thickness direction of -150 to 0 nm of the amide type film having the negative B type retardation. In this case, the retardation value in the plane direction and the retardation value in the thickness direction of the entire retardation film can be more effectively adjusted to appropriate values for application as an IPS mode retardation film.

It is preferable that the retardation film satisfies the following formula (10). In this case, it can be very usefully applied to the IPS mode liquid crystal display as a retardation compensation film.

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

In the formula (10), n _{x, total} is the refractive index of a phase difference film plane direction and the refractive index of the entire direction is maximum (that is, the direction of the slow axis), n _{y, total} is perpendicular to the slow axis of the entire retardation film in a direction which is the direction of the refractive index (that is, fast axis direction), n _z, the _total refractive index of the entire retardation film thickness direction. That is, even when the retardation film of the present invention is measured in the visible light wavelength band, more specifically, light having any wavelength of 400 to 780 nm, for example, light having a wavelength of 450 nm, 550 nm, or 650 nm, It is preferable to satisfy it.

On the other hand, the retardation film of the present invention satisfying at least one of the above-mentioned formulas (1) to (10) can be produced by appropriately controlling the raw material for forming the coating layer and the amide-based film, .

First, in the present invention, the raw material of the coating layer may be a polymer material having negative retardation characteristics, and the kind thereof is not particularly limited. For example, polyvinylcarbazole, polyvinylnaphthalene, styrene resin 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.

In addition to the above styrene type monomer, the styrene type resin may also be used in combination with a styrene type monomer in combination of 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 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.

On the other hand, the thickness of the coating layer having the negative retardation characteristics is preferably 1 to 20 μm, for example, 1.2 to 15 μm or 1.5 to 10 μm. When the thickness is less than 1 탆, the negative retardation is lowered and the retardation of the desired level may not be exhibited. On the contrary, when the thickness exceeds 20 탆, the negative retardation may become too large, It may be difficult to make the film thinner.

Next, in the present invention, the amide-based film having the negative C type or negative B type retardation preferably contains a polyamide-based resin as a main component, and the polyamide-based resin is not particularly limited as long as it has an amide group in the main chain Can be used without limit. For example, although not limited thereto, the amide-based film may include a polyamide-based resin containing a unit represented by the following general 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, although not limited thereto, it is more preferable that the polyamide resin includes 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 .

On the other hand, the amide-based film having the negative C type or negative B type retardation of the present invention can be thinned because of its high retardation property due to the high retardation property of the amide type film, Mu] m, preferably 10 to 35 [mu] m or 10 to 30 [mu] m. When the thickness of the amide-based film having the negative C type or negative B type phase difference satisfies the above-mentioned range, the phase difference film can be made thinner, and the liquid crystal display including the same can be downsized and lightweight.

Also, since the retardation film of the present invention can exhibit a desired retardation with a thin thickness due to the high retardation property of the amide-based film having the negative C type or negative B type retardation, the thickness of the entire retardation film is preferably 10 to 60 Mu] m, preferably from 13 to 50 [mu] m, from 15 to 40 [mu] m or from 15 to 30 [mu] m. If the thickness of the retardation film is less than 10 탆, the thickness of the film becomes too thin, which may result in poor handling properties of the film and the polarizing plate. As a result, the film or the polarizing plate may be bent or broken If it is more than 60 탆, it may be difficult to make the polarizer thinner.

Next, a method for producing the retardation film of the present invention will be described.

The method for producing a retardation film according to the present invention comprises the steps of uniaxially stretching an amide-based film in a longitudinal direction (MD); Forming a coating layer on at least one surface of the amide-based film uniaxially stretched in the longitudinal direction by using a polymer material having a negative retardation characteristic; And uniaxially stretching the amide-based film formed with the coating layer in the transverse direction (TD). At this time, the amide-based film has a negative C type or negative B type phase difference after being uniaxially stretched in the longitudinal direction and uniaxially stretched in the width direction.

The method of producing a retardation film of the present invention can obtain a desired retardation film only by two consecutive stretches, and can produce a retardation film which can be applied to an IPS mode liquid crystal display device by a simpler process.

First, the amide-based film can be produced by preparing a resin composition comprising the polyamide-based resin described above in the form of a film according to a method well known in the art, such as a solution casting method or an extrusion method. It is more preferable to use the extrusion method in view of the economical aspect. In some cases, an additive such as a modifying agent may be added to the film within a range that does not impair the physical properties of the film.

On the other hand, the step of uniaxially stretching the amide-based film of the present invention in the longitudinal direction (MD) can be carried out by a stretching method well known in the art. For example, when the glass transition temperature of the amide-based film is Tg, the film is stretched by 1.1 to 5.0 times in a roll-to-roll manner at a temperature of (Tg-20) ° C to (Tg + 30) . &Lt; / RTI &gt;

More specifically, in the present invention, the step of uniaxially stretching in the longitudinal direction is preferably a step of stretching the amide-based film to 1.1 to 5.0 times It is preferably stretched to, for example, 1.3 to 4.0 times or 1.5 to 3.0 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 is more than 5.0 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 amide-based film is 20 to 120 탆. For example, the thickness is 25 to 80 탆 or 30 to 60 탆 As shown in Fig. 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 120 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-20) ° C to (Tg + 30) ° C, where Tg is the glass transition temperature of the amide-based film , And more preferably at a temperature of about (Tg) ° C to (Tg + 20) ° C. In this case, when the uniaxial stretching in the longitudinal direction is performed at a temperature lower than (Tg-20) DEG C, the storage elastic modulus of the film may be lowered, and thus the loss elastic modulus may become larger than the storage elastic modulus. Further, when the polymerization is carried out at a temperature higher than (Tg + 30) DEG C, the orientation of the polymer chain may be alleviated and lost. On the other hand, it is more preferable to perform at a temperature of (Tg) ° C to (Tg + 20) ° C in view of stable production of the film and toughness of the film. On the other hand, the glass transition temperature can be measured by a differential scanning calorimeter (DSC). For example, in the case of using a differential scanning calorimeter (DSC), when a sample of about 10 mg is sealed in a 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.

The amide-based film is uniaxially stretched in the longitudinal direction, and then a coating layer is formed on at least one surface of the amide-based film using a polymer material having a negative retardation characteristic on one side. 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. Specific examples of the polymer material having a negative phase difference are as described above, and examples of the usable solvent include methylene chloride, chloroform, tetrahydrofuran (THF), 1,3-dioxane, cyclopentanone, N- Alcohols such as methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc) 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 using the polymer material having the negative retardation characteristic, it is preferable to coat the coating layer so that the thickness of the coating layer is about 1 to 30 탆. For example, the thickness of the coating layer is 2 to 15 탆, 3 to 13 mu m. In this case, the thickness of the coating layer is related to the property of exhibiting the retardation. When the coating layer is coated to a thickness of less than 1 탆, the negative retardation may not be exhibited and the retardation of the desired level may not be exhibited. If the thickness of the retardation film is more than the thickness of the retardation film, the property of exhibiting a negative retardation may become too large, and the thickness of the retardation film may become thin.

On the other hand, if necessary, in order to improve the adhesion between the amide-based film and the coating layer, a step of uniaxially stretching the amide-based film having the negative C type or negative B type phase difference in the longitudinal direction, The surface of the amide-based film may be corona treated between the steps of forming the coating layer.

When the coating layer is formed on the amide-based film through the above process, the amide-based film formed with the coating layer is stretched in the transverse direction (TD). When the film is stretched in the width direction, the amide-based film and the coating layer can be simultaneously stretched by a single stretching process. Therefore, the amide-based film having the negative C type or negative B type phase difference 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 amide-based film in which the coating layer of the present invention is formed in the transverse direction (TD) can likewise be carried out by a stretching method well known in the art. For example, when the glass transition temperature of the amide-based film is Tg, the film may be stretched in the width direction at a temperature of (Tg-20) ° C to (Tg + 30) ° C using a tenter stretcher at a stretching ratio of 1.1 to 5.0 times have.

More specifically, in the present invention, the step of uniaxially stretching in the transverse direction may be carried out by heating the amide-based film formed with the coating layer at 1.1 to 5.0 times It is preferably stretched to, for example, 1.3 to 4.0 times or 1.5 to 3.0 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 is more than 5.0 times, the film may be broken during stretching, Film production can be difficult.

In the present invention, the uniaxially stretching in the transverse direction is preferably performed such that the thickness of the amide-based film formed with the coating layer is 10 to 60 탆, for example, 13 to 50 탆, 15 to 40 탆 or And may be about 15 to 30 mu m. At this time, the thickness of the retardation film after the uniaxially stretching in the width direction is the thickness of the final film, and when the thickness of the final film is less than 10 탆, the thickness of the film becomes too thin and the handling property of the film and the polarizing plate becomes poor And may be bent or broken during the manufacturing process of the film or the polarizing plate or during the handling of the product. If it exceeds 60 탆, it may be difficult to make the polarizing plate thin.

In the present invention, the step of uniaxially stretching in the transverse direction is preferably carried out at a temperature of (Tg-20) ° C to (Tg + 30) ° C, where Tg is the glass transition temperature of the amide-based film , And more preferably at a temperature of about (Tg) ° C to (Tg + 20) ° C. In this case, when the uniaxial stretching in the longitudinal direction is performed at a temperature lower than (Tg-20) DEG C, the storage elastic modulus of the film may be lowered, and thus the loss elastic modulus may become larger than the storage elastic modulus. Further, when the polymerization is carried out at a temperature higher than (Tg + 30) DEG C, the orientation of the polymer chain may be alleviated and lost. On the other hand, it is more preferable to perform at a temperature of (Tg) ° C to (Tg + 20) ° C in view of stable production of the film and toughness of the film. On the other hand, the glass transition temperature can be measured by a differential scanning calorimeter (DSC). For example, in the case of using a differential scanning calorimeter (DSC), when a sample of about 10 mg is sealed in a 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.

Meanwhile, when the retardation film according to the present invention is applied to an IPS mode liquid crystal display device, the retardation film has an excellent viewing angle improving effect and can be suitably used as a retardation film for an IPS 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 planar switching (IPS) mode liquid crystal display including at least one or more 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 60 탆 was prepared using a polyamide resin having an amide bond in the main chain (Evonik CX9704) under a condition of 245 캜 by using a T-die kneader. The unstretched film was stretched twice 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 40 탆.

Next, a solution (solvent: 1,3-dioxolane) containing 7% by weight of poly (2-vinylcarbazole) (product of Aldrich) was coated on the above uniaxially stretched film, Lt; / RTI &gt;

Next, the coated film was stretched twice in the width direction at a temperature of 145 캜 to prepare a thin film of a retardation film having a thickness of 22 탆.

Example  2

An unoriented film having a width of 800 mm and a thickness of 60 탆 was prepared using a polyamide resin having an amide bond in the main chain (Evonik CX9704) under a condition of 245 캜 by using a T-die kneader. The unstretched film was stretched twice 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 40 탆.

Next, a solution (solvent: 1,3-dioxolane) containing 12% by weight of poly (2-vinylnaphthalene) (product of Aldrich) was coated on the uniaxially stretched film, Lt; / RTI &gt;

Next, the coated film was stretched twice in the width direction at a temperature of 145 캜 to prepare a thin film retardation film having a thickness of 26 탆.

Example  3

An unoriented film having a width of 800 mm and a thickness of 60 탆 was produced using a polyamide resin having an amide bond in the main chain (Arkema G350) under a condition of 245 캜 by using a T-die film. The unstretched film was stretched twice in a roll-to-roll manner at a temperature of 152 캜 in the MD direction to prepare a uniaxially stretched film having a thickness of 40 탆. Next, a solution (solvent: 1,3-dioxolane) containing 7% by weight of poly (2-vinylcarbazole) (product of Aldrich) was coated on the above uniaxially stretched film, Lt; / RTI &gt; Next, the coated film was stretched twice in the width direction at a temperature of 152 캜 to prepare a thin film retardation film having a thickness of 21 탆.

Example  4

An unoriented film having a width of 800 mm and a thickness of 60 탆 was produced using a polyamide resin having an amide bond in the main chain (Arkema G350) under a condition of 245 캜 by using a T-die film. The unstretched film was stretched twice in a roll-to-roll manner at a temperature of 152 캜 in the MD direction to prepare a uniaxially stretched film having a thickness of 40 탆. Next, a solution (solvent: 1,3-dioxolane) containing 12% by weight of poly (2-vinylnaphthalene) (product of Aldrich) was coated on the uniaxially stretched film, Lt; / RTI &gt; Next, the coated film was stretched twice in the width direction at a temperature of 152 캜 to prepare a thin film retardation film having a thickness of 25 탆.

Comparative Example  One

Acrylonitrile copolymer (LG Chem, LGC 82TR, acrylonitrile content 20% by weight) and poly (cyclohexylmaleimide-co-methyl methacrylate) (LGMMA, 830HR) At a weight ratio of 80:20, respectively, using a twin extruder at 250 DEG C and 200 rpm to prepare a resin composition. An undrawn film having a width of 800 mm and a thickness of 185 탆 was produced using the resin composition at 250 캜 by using a T-die kneader. The unstretched film was stretched 1.4 times in a roll-to-roll manner at a temperature of 125 ° C in the MD direction, and then stretched 2.9 times in the TD direction using a tenter stretcher at the same temperature to obtain a film having a negative retardation To prepare an acrylic film. The thickness of the prepared stretched film was 50 탆.

Comparative Example  2

The negative C coating liquid was directly coated on the acrylic film having negative phase difference characteristics prepared in Comparative Example 1 to prepare a composite retardation film. The negative C coating solution used herein was prepared by dissolving ethylcellulose (Dow EC100, Mw 180,000, Ethoxyl content: 49%) in a mixed solvent of toluene / ethanol (3/7) at a room temperature with gentle stirring at a solid content of 10% . The completely dissolved coating liquid was coated on an acrylic film having negative retardation characteristics to a final coating thickness of 10 mu m and dried at 80 DEG C for 5 minutes. The thickness of the produced retardation film was 60 탆.

Comparative Example  3

An acrylic negative C film was laminated on the acrylic film having the negative retardation characteristics prepared in Comparative Example 1 to prepare a composite retardation film. The acrylic negative C film used here was prepared by the following method. First, an acrylic resin and a polycarbonate resin (LGPC trade name DVD1080) each containing 77% by weight of methyl methacrylate, 15% by weight of cyclohexyl methacrylate, 2% by weight of alphamethylstyrene and 6% by weight of cyclohexylmaleimide, At a weight ratio of 250 and 200 rpm using a twin extruder to prepare a resin composition. The obtained raw material pellets were dried in vacuo, melted in an extruder at 250 占 폚, passed through a coat hanger type T-die, and a film having a thickness of 185 占 퐉 was produced through a chrome casting roll and a drying roll. The prepared film was biaxially stretched 2.3 times in the MD direction and 2.5 times in the TD direction in this order to obtain a retardation film having a thickness of 42 占 퐉. At this time, the temperature in the MD direction stretching is 128 占 폚 and the stretching temperature in the TD direction is 138 占 폚. The thickness of the produced composite phase difference film was 94 탆.

Experimental Example  One

The retardation films prepared in Examples 1 to 4 and Comparative Example 1 were measured using a Axoscan equipment of Axometrics Co. in the plane direction retardation value (R _in ), the thickness direction retardation value (R _th ) and Nz (R _th / R _in ) was measured and shown in Table 1 below.

A layer having a negative retardation characteristic -C type or -B type
Layer having a phase difference complex
Phase difference film Rin (nm) Rth (nm) Rin (nm) Rth (nm) Rin (nm) Rth (nm) Nz (Rth / Rin) Example 1 120 140 10 -90 110 55 0.50 Example 2 115 137 10 -90 105 50 0.48 Example 3 120 140 7 -88 113 57 0.50 Example 4 115 137 7 -88 108 52 0.48 Comparative Example 1 - - 100 150 100 150 1.50 Comparative Example 2 100 150 25 -103 75 47 0.60 Comparative Example 3 100 150 2 -90 98 60 0.61

As can be seen from the above Table 1, the composite retardation films of Examples 1 to 4 had a retardation value (R _in ) _{in the} range of 50 to 300 nm and a thickness retardation value (R _th ) in the range of 10 to 300 nm range and, Nz (R _th / R _in) to less than 1, it can be seen that it is suitable for application to the phase difference film of the IPS mode liquid crystal display device. However, in Comparative Example 1 For it can be seen that unsuitable to the value Nz (R _th / R _in) applied to the phase difference film or the like IPS-mode liquid crystal display device 1 or more.

Experimental Example  2

In order to compare the embrittlement properties of the retardation films produced in Examples 1 to 4 and Comparative Examples 1 to 3, the impact energy was measured and shown in Table 2 below. Here, the impact energy refers to the degree to which the film can withstand an external impact. In the present invention, the impact energy is measured to such an extent that a constant weight of the apparatus is able to withstand a drop of the film at a predetermined height. More specifically, in the present invention, the impact energy IE is a value defined according to the following equation (11).

Eq. (11): IE = (gravitational acceleration * weight of gravity * height) / (film thickness * film area)

Thickness (㎛) Impact energy (kN * m / m ³⁾ Example 1 22 5430 Example 2 26 5060 Example 3 21 4890 Example 4 25 4520 Comparative Example 1 50 380 Comparative Example 2 60 240 Comparative Example 3 94 500

As can be seen from the above [Table 2], it is confirmed that the compound phase difference film using the amide type film is a thin film and further excellent in brittleness. However, as in Comparative Examples 1 to 3, in the case of a compound phase difference film including only an acrylic film, it is confirmed that the embrittlement is very weak.

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 (19)

An amide-based film having a negative C type or negative B type phase difference; And
And a coating layer formed on at least one side of the amide-based film and having negative retardation characteristics.
The method according to claim 1,
Wherein the retardation film satisfies the following expressions (1) and (2).
(1): 50 nm < R _{in , total} < 300 nm
(2): 10 nm < R _{th , total} < 300 nm
In the above formulas (1) and (2)
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 a Nz value of less than 1, represented by the following formula (3).
Equation _{(3): Nz = R th} , total / R in, total
In the above formula (3)
R _{in , total} is the retardation value in the plane direction of the entire retardation film,
_{Rth , total} is the retardation value in the thickness direction of the entire retardation film,
In this case, R _{in , total} and R _{th , total} are the retardation values measured in the visible light wavelength band.
The method of claim 1, wherein
Wherein the retardation film satisfies the following expressions (4) and (5) as the coating layer having the negative retardation characteristics.
(4): 50 nm < R _{in , a} < 250 nm
(5): 80 nm < R _{th , a} < 300 nm
In the above formulas (4) and (5)
R _{in , a} is the retardation value in the plane direction of the coating layer having a negative retardation characteristic measured in the visible light wavelength band,
_{Rth , a} is the thickness direction retardation value of the coating layer having a negative retardation characteristic measured in a visible light wavelength band.
The method of claim 1, wherein
Wherein the retardation film satisfies the following expressions (6) and (7) when the amide-based film having the negative C-type retardation satisfies the following expressions (6) and (7).
(6): -50 nm <R _{in , b 1} <50 nm
(7): -200 nm < R _{th , b 1} < 0 nm
In the above formulas (6) and (7)
R _{in and b 1} are retardation values in the plane direction of an amide-based film having a negative C-type retardation measured in a visible light wavelength band,
_{Rth and b1} are retardation values in the thickness direction of the amide type film having the negative C type retardation measured in the visible light wavelength band.
The method of claim 1, wherein
Wherein the amide-based film having the negative B type phase difference satisfies the following formulas (8) and (9).
Equation _{(8): 0nm <R in} , b2 <100nm
Equation _{(9): -200nm <R th} , b2 <0nm
In the above formulas (8) and (9)
R _{in, b2} is the plane retardation value of the amide-based film having a retardation of the negative type B measured in the visible light wavelength band,
_{Rth and b2} are retardation values in the thickness direction of an amide type film having a negative B type retardation measured in a visible light wavelength band.
The method according to claim 1,
Wherein the retardation film satisfies the following formula (10).
(10): n _{x , total} > n _{z , total} > n _{y , total}
In the above formula (10)
n _{x , total} is a refractive index in a 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)
n _{y , total} is the refractive index in the direction perpendicular to the slow axis of the entire retardation film (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, the n _{x , total} , n _{y , total} , n _{z , total} is the value measured in the visible light wavelength band.
The method according to claim 1,
Wherein the amide-based film having the negative C type or negative B type phase difference comprises a polyamide type resin containing a unit represented by the following formula (1) or (2).
[Chemical Formula 1]

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

(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,
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 to 3,
and m is an integer of 5 to 10,000.
The method according to claim 1,
Wherein the amide-based film having the negative C type or negative B type phase difference comprises a polyamide type resin containing a unit represented by the following formula (3).
(3)

In 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,
And X _4, X ₅ and X ₆ is an alkyl group each independently a halogen atom or a C _{1 -6,}
X ₇ is a single bond, a methylene group or a dimethylmethylene group,
d, e1 and e2 are each independently an integer of 0 to 2,
and k is an integer of 5 to 10,000.
The method according to claim 1,
Wherein the coating layer having a negative retardation characteristic comprises a styrene resin, polyvinylcarbazole, or polyvinylnaphthalene.
The method according to claim 1,
Wherein the retardation film has a thickness of 10 to 60 mu m.
The method according to claim 1,
Wherein the retardation film is for a planar switching (IPS) mode liquid crystal display device.
A liquid crystal display device comprising the retardation film of any one of claims 1 to 12.
Uniaxially stretching the amide-based film in the longitudinal direction (MD);
Forming a coating layer on at least one surface of the amide-based film uniaxially stretched in the longitudinal direction by using a polymer material having a negative retardation characteristic; And
Uniaxially stretching the amide-based film formed with the coating layer in the transverse direction (TD);
Wherein the retardation film has a thickness of 100 to 500 nm.
15. The method of claim 14,
Wherein the step of uniaxially stretching in the longitudinal direction (MD) comprises stretching the amide-based film by 1.1 to 5.0 times.
15. The method of claim 14,
Wherein the step of uniaxially stretching in the longitudinal direction (MD) comprises stretching the amide-based film to a thickness of 20 to 120 탆.
15. The method of claim 14,
Wherein the step of forming the coating layer comprises coating the coating layer with a thickness of 1 to 30 탆.
15. The method of claim 14,
Wherein the step of uniaxially stretching in the transverse direction (TD) comprises stretching the amide-based film formed with the coating layer by 1.1 to 5.0 times.
15. The method of claim 14,
Wherein the step of uniaxially stretching in the transverse direction (TD) comprises stretching the amide-based film formed with the coating layer to a thickness of 10 to 60 占 퐉.