KR20140000431A - Retardation film and liquid crystal display including the same - Google Patents

Abstract

The present invention provides a retardation film for an in-plane switching (IPS) liquid crystal display and an IPS liquid crystal display including the same, the retardation film comprising: 1) an acrylic film having negative retardation; and 2) an acrylic film having a negative C or B type of retardation, wherein a retardation value in the plane direction represented by equation 1 is 50-300 nm, a retardation value in the thickness direction represented by equation 2 is 10-300 nm, and an Nz(Rth/Rin) value, which is the ratio of the retardation value in the thickness direction to the retardation value in the plane direction, is less than 1, wherein equation 1 is Rin=(nx-ny)×d, and equation 2 is Rth=(nz-ny)×d. In equation 1 and equation 2, nx is a refractive index in a direction where the refractive index is largest in the plane direction of the retardation film; ny is refractive index in a direction perpendicular to the nx direction in the plane direction of the retardation film; nz is a refractive index in the thickness direction of the retardation film; and d is the thickness of the retardation film.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a retardation film and a liquid crystal display device including the retardation film.

The present invention relates to a retardation film for an IPS mode liquid crystal display device and a liquid crystal display device comprising the same, wherein an acrylic film having a negative C type or negative B type phase difference is laminated on an acrylic film having a negative retardation.

BACKGROUND ART Liquid crystal displays have a widespread use as optical display elements because they have lower power consumption, smaller volume, lighter weight, and easier portability than cathode ray tube displays. In general, the liquid crystal display has a basic configuration in which polarizing plates are provided on both sides of the liquid crystal cell, and the orientation of the liquid crystal cell is changed depending on whether an electric field is applied to the driving circuit, thereby changing the characteristics of transmitted light emitted through the polarizing plate. Visualization takes place. At this time, the path and birefringence of the light change according to the incident angle of the incident light, because the liquid crystal is an anisotropic material having two different refractive indices.

Due to these characteristics, the liquid crystal display has a disadvantage in that the contrast ratio, which is a measure of how sharply the image is seen according to the viewing angle, changes, and gray scale inversion occurs, thereby reducing visibility. Has

In order to overcome such disadvantages, an optical compensation film for compensating an optical phase difference generated in a liquid crystal cell is used for a liquid crystal display device.

Meanwhile, various liquid crystal modes have been developed in order to secure clear image quality and wide viewing angle in liquid crystal displays. Representatively, Double Domain Twisted Nematic (TN), axially symmetric aligned microcell (ASM), optically compensated blend (OCB), Vertical alignment (VA), multidomain VA (MVA), surrounding electrode (SE), patterned VA (PVA), in-plane switching (IPS), fringe-field switching (FFS) mode, and the like. Each of these modes has a unique liquid crystal array and has inherent optical anisotropy.

Therefore, in order to compensate for the phase difference due to the optical anisotropy of these liquid crystal modes, the compensation film of the optical anisotropy corresponding to each mode is required. In particular, in the IPS mode, since the liquid crystals having positive dielectric anisotropy are horizontally aligned, the optical anisotropy at the inclination angle in the non-driving state is not as large as that of other modes, so that an excellent wide viewing angle can be obtained only by using an isotropic protective film. . However, in this case, the compensation for the absorption axis of the polarizer is not made at high inclination angles, so contrast reduction and color modulation may still occur due to the viewing angle. Therefore, an IPS mode liquid crystal display also needs to use an appropriate retardation film to obtain a perfect wide viewing angle. do.

Retardation film for the IPS mode is a realistic structure consisting of a multilayer film of two or more layers. Typically, uniaxially stretching a cyclic olefin polymer (COP), and then compensate for the viewing angle by coating a nematic liquid crystal, which is a + C plate. However, in this case, the birefringence of the liquid crystal is so high that the retardation of the entire compensating film largely changes even if the alignment of the liquid crystal and the thickness of the coating slightly change, which makes it difficult to control the retardation. In addition, the manufacturing cost is high due to the expensive liquid crystal unit price, so that it is difficult to commercialize it.

As another method, an IPS mode retardation compensation film has been developed in which an acrylic retardation film is coated with a non-liquid crystalline retardation developing material having a negative C characteristic to adjust a retardation value in a plane direction and a retardation value in a thickness direction. However, the acrylic film is generally vulnerable to an organic solvent such as an aromatic hydrocarbon or an organic chlorine used in a coating process, and when the phase difference developing material is coated using such a solvent, poor adhesion, brittleness, A phase difference decrease and a stain may occur.

Therefore, it is possible to appropriately adjust the retardation value in the plane direction and the retardation value in the thickness direction of the in-plane switching (IPS) mode liquid crystal display device, and to provide a retardation film having durability and productivity, ) Mode liquid crystal display device is required.

One aspect of the present invention relates to an acrylic film having a negative retardation by laminating an acrylic film having a negative C type or negative B type retardation to adjust a retardation value in a plane direction and a retardation in a thickness direction to improve a viewing angle characteristic, And to provide a retardation compensation film of this strong IPS mode liquid crystal display.

Another aspect of the present invention is to provide an IPS (in-plane switching) mode liquid crystal display including at least one phase difference film for the IPS (in-plane switching) mode liquid crystal display.

According to one aspect of the present invention,

1) an acrylic film having a negative phase difference; And

2) an acrylic film having a negative C type or negative B type phase difference, wherein a retardation value in a plane direction represented by the following equation (1) is 50 to 300 nm, a retardation value in a thickness direction represented by the following equation Plane switching mode liquid crystal display (IPS) mode liquid crystal display device characterized in that the value of Nz (Rth / Rin), which is the ratio of the retardation value in the thickness direction to the retardation value in the plane direction, is less than 1.

[Equation 1]

_{Rin = (n x - n y} ) × d

&Quot; (2) "

Rth = (n _z - n _y ) x d

In the above equations (1) and (2), n _x is the refractive index in the direction with the largest refractive index in the plane direction of the film, n _y is the refractive index in the vertical direction in the n _x direction in the plane direction of the film, n _z Is the refractive index in the thickness direction, and d is the thickness of the film.

The acrylic film having negative phase difference of 1) preferably includes a blend resin obtained by blending a polymer containing an acrylic monomer and a styrenic copolymer.

The styrene-based copolymer is preferably a styrene-maleic anhydride copolymer (SMA), a styrene-acrylonitrile copolymer (SAN) or an a-methylstyrene-acrylonitrile copolymer (AMSAN).

The acrylic film having the negative C type or negative B type phase difference of 2) is preferably a resin blended with a polymer containing an acrylic monomer and an aromatic resin having a carbonate moiety in a main chain.

The aromatic resin having a carbonate-based moiety in the main chain preferably contains 5 to 10,000 units of at least one kind represented by the following formula (2).

(2)

Wherein X is a divalent group comprising at least one benzene ring.

X is preferably selected from the group consisting of the following structural formulas.

The acrylic monomer contained in the acrylic film of the above 1) or 2) preferably contains a double bond between carbon atoms conjugated with a carbonyl group of an ester group, wherein methyl methacrylate, ethyl methacrylate , Propyl methacrylate, n -butyl methacrylate, t -butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate and butoxymethyl methacrylate At least one acrylic monomer selected from acrylate, methacrylate, and methacrylate can be used.

An acrylic film having a phase difference of 1); And 2) an acrylic film having a negative C type or negative B type phase difference is preferably produced by attaching it with a UV adhesive or a pressure sensitive adhesive.

According to another aspect of the present invention, there is provided a polarizing plate and an image display device including at least one retardation film for the in-plane switching (IPS) mode liquid crystal display.

The retardation compensation film according to the present invention can appropriately adjust the retardation value in the plane direction and the retardation in the thickness direction, and can provide a polarizer having higher durability and higher productivity than the conventional one. It is particularly suitable as a retardation compensation film used in the IPS mode.

Hereinafter, the present invention will be described in detail.

The retardation film for an IPS (in-plane switching) mode liquid crystal display according to the present invention comprises: 1) an acrylic film having a negative retardation; And 2) an acrylic film having a negative C type or negative B type phase difference, wherein a retardation value in a plane direction represented by the following formula (1) is 50 to 300 nm and a thickness direction retardation value And the value of Nz (Rth / Rin), which is the ratio of the retardation value in the thickness direction to the retardation value in the plane direction, is less than 1. At this time, when the retardation range is satisfied, an excellent viewing angle improving effect can be expected when applied to an IPS mode liquid crystal display device.

[Equation 1]

_{Rin = (n x - n y} ) × d

&Quot; (2) "

_{Rth = (n z - n y} ) × d

In the above formulas (1) and (2), n _x is the refractive index of the largest refractive index in the plane direction of the film, n _y is the refractive index of the vertical direction of the n _x direction in the plane direction of the film, n _z is a refractive index in the thickness direction, and d is the thickness of the film.

On the other hand, the acrylic film of 1) or 2) used in the present invention can be produced from a resin composition containing a polymer containing an acrylic monomer by a melt extrusion method or a solution casting method, and its component is not particularly limited .

At this time, the acrylic monomer preferably contains a double bond between carbon atoms conjugated with a carbonyl group of an ester group, and more specifically, a compound represented by the following formula (1) may be used.

[Chemical Formula 1]

Wherein R ₁ , R ₂ and R ₃ may be a hydrogen atom, a hydrocarbon group or an epoxy group having 1 to 30 carbon atoms, and R ₄ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

On the other hand, the acrylic monomer may include an acrylate derivative as well as an acrylate. More particularly, methyl methacrylate (methyl methacrylate), methacrylate (ethyl methacrylate), methacrylate (propyl methacrylate), n - butyl methacrylate (n -butyl methacrylate), t - butyl methacrylate but are not limited to, t -butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate, Butoxymethyl methacrylate, oligomers thereof, and the like can be used, but the present invention is not limited thereto.

On the other hand, the polymer containing the acrylic monomer includes at least one monomer selected from the group consisting of a lactone system, a lactam system, a glutaric anhydride, a glutarimide, a maleic anhydride system and a maleimide monomer in addition to the acrylic monomer can do. When such monomers are added, the heat resistance of the produced acrylic film is improved.

Examples of the maleic anhydride or maleimide monomer include maleic anhydride, maleimide, N-methyl maleimide, N-ethyl maleimide, N-propyl maleimide, N-isopropyl maleimide, N-cyclohexyl maleimide And the like, but the present invention is not limited thereto.

At this time, if the monomer is further contained in addition to the acrylic monomer, the content of the acrylic monomer is preferably 50 to 95 parts by weight per 100 parts by weight of the entire acrylic film. When the content of the acrylic monomer is less than 50 parts by weight, high durability and high transparency inherent to the acrylic polymer may not be sufficiently exhibited.

The content of the maleic anhydride-based or maleimide-based monomer in the acrylic copolymer is preferably 1 to 20 parts by weight, more preferably 3 to 15 parts by weight, per 100 parts by weight of the entire acrylic film. When the content of the maleic anhydride or maleimide monomer is less than 1 part by weight, the effect of improving the heat resistance is insignificant. When the content is more than 20 parts by weight, the brittleness of the film increases, have.

On the other hand, the acrylic film having the negative phase difference of 1) preferably includes a blending resin obtained by blending a styrene-based copolymer with a polymer containing an acrylic monomer.

Since the polymer containing the acrylic monomer is the same as that described above, detailed description thereof will be omitted.

Meanwhile, the styrenic copolymer includes a styrenic monomer. Examples of the styrenic monomer include styrene,? -Methylstyrene, 4-methylstyrene, and the like, and it is preferably styrene. no.

The content of the styrenic monomer is preferably 5 to 40 parts by weight, more preferably 10 to 30 parts by weight, per 100 parts by weight of the entire acrylic film. If it is less than 5 parts by weight, there is a problem that it is difficult to produce a desired retardation film due to the reduction in phase difference expression property, and if it exceeds 40 parts by weight, the high durability and high transparency originally possessed by the acrylic polymer may not be sufficiently expressed.

On the other hand, the styrenic copolymer is preferably prepared in a copolymerized form with an acrylic monomer. Alternatively, a separate styrenic copolymer may be blended with a polymer comprising the acrylic monomer. For example, the styrene-based copolymer may be styrene-maleic anhydride copolymer (SMA), styrene-acrylonitrile copolymer (SAN), α-methyl styrene-acrylonitrile copolymer (AMSAN), or the like. It is not limited.

Further, in order to improve the toughness, impact resistance and the like of the film, the acrylic film having the negative phase difference of the above 1) may further comprise a rubber component. The rubber component is preferably an acrylic rubber, a rubber-acrylic graft core-shell polymer, or a mixture thereof, but is not limited thereto.

The rubber component is not particularly limited as long as it is an acrylic rubber having a refractive index similar to that of the acrylic resin of 1.480 to 1.550 because a thermoplastic resin composition having excellent transparency can be obtained when the refractive index of the acrylic resin is similar to that of the rubber component. For example, butyl acrylate, alkyl acrylates, such as 2-ethyl hexyl acrylate, etc. are mentioned.

The rubber-acrylic graft core-shell polymer is not particularly limited as long as the rubber-acrylic graft core-shell polymer has a refractive index of 1.480 to 1.550. For example, particles having a size of 50 to 400 nm using a butadiene, butyl acrylate or butyl acrylate-styrene copolymer-based rubber as a core, and polymethyl methacrylate or polystyrene as a shell can be used.

The content of the rubber component is preferably 1 to 20 parts by weight, more preferably 1 to 15 parts by weight based on 100 parts by weight of the total acrylic film. If the content of the rubber component is less than 1 part by weight, it may not be possible to express the excellent mechanical strength of the film, the film is brittle, there is a problem in the processing process, there is a problem that the optical performance is not sufficiently expressed. In addition, when the content exceeds 20 parts by weight, there is a problem that the high heat resistance and high transparency of the acrylic copolymer inherently are not sufficiently expressed, and processing problems such as haze may occur in the stretching process.

In general, acrylic resins have a negative intrinsic birefringence, so it is possible to produce + B type films by uniaxial or biaxial stretching, but it is difficult to achieve a high level of retardation due to the low optical anisotropy of the chain itself. Accordingly, when the styrenic copolymer is included, a retardation film having a negative birefringence sign and a high birefringence value can be produced.

Next, the acrylic film having the negative C type or negative B type phase difference of 2) above is intended to improve the viewing angle compensation performance of the IPS mode liquid crystal display by adjusting the retardation characteristics of the acrylic film having negative phase difference of 1) .

More specifically, the acrylic film having the negative C-type phase difference can control the thickness direction retardation of the acrylic film having the negative phase difference of 1), and the acrylic film having the negative B-type phase difference has the negative phase difference of 1) The retardation in the plane direction of the film can be canceled and the retardation in the thickness direction can be adjusted.

In this case, 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. In this case, n _x is in the plane of the film, the refractive index and the refractive index of the large direction, n _y is a refractive index in the vertical direction of the n _x direction in the plane of the film, n _z Is the refractive index in the thickness direction.

On the other hand, a negative C type or negative B type coating layer may be applied to adjust the retardation in the thickness direction. However, by using the negative C type or negative B type acrylic film of the present invention, It is possible to prevent adhesion failure, increase in brittleness, decrease in phase difference, occurrence of stain and the like due to the coating solvent which may appear in the coating solution.

On the other hand, the acrylic film having the negative C type or negative B type phase difference as described in 2) above may be formed of a resin blended with a polymer containing an acrylic monomer and an aromatic resin having a carbonate moiety in a main chain.

The content of the aromatic resin having a carbonate moiety in the main chain of the acrylic polymer is preferably 5 to 25 parts by weight, more preferably 10 to 20 parts by weight, per 100 parts by weight of the entire acrylic film. When the amount is less than 5 parts by weight, there is a problem that it is difficult to prepare a desired retardation film due to a decrease in the retardation development property, and when it exceeds 25 parts by weight, mixing with an acrylic polymer may not be easy.

On the other hand, the aromatic resin having a carbonate-based moiety in the main chain preferably includes 5 to 10,000 units of at least one kind of units represented by the following formula (2).

(2)

In the above formula, it is preferable that X is a divalent group containing at least one benzene ring.

It is particularly preferable that X is a divalent group selected from the group consisting of the following structural formulas.

On the other hand, the glass transition temperature (Tg) of the acrylic film of 1) or 2) of the present invention is preferably 100 to 160 ° C. The film having a glass transition temperature (Tg) of 100 to 160 ° C. may have excellent durability. Meanwhile, when the glass transition temperature is less than 100 ° C., the film may be poor in heat resistance and thus deformable at high temperature and high humidity. There is a problem that the compensation characteristics become nonuniform.

The acrylic film of 1) or 2) is preferably formed to a thickness of 20 to 100 탆. If the thickness is less than 20 탆, the polarization element is not properly supported, thereby causing element shrinkage, device cracking, curl, etc. If the thickness exceeds 100 탆, a large amount of heat is required for uniform stretching There is a problem that not only high-speed stretching is difficult but also economical.

The acrylic film of 1) or 2) can be subjected to a drawing process such as uniaxial drawing or biaxial drawing, and the drawing magnification can be adjusted according to a phase difference value to be obtained. At this time, the drawing step is not particularly limited, and a method widely known in the art can be used.

More specifically, the stretching process may perform longitudinal (MD) stretching and transverse (TD) stretching, respectively, or may be performed together. When longitudinal direction stretching and transverse direction stretching are carried out together, either one direction may be first stretched, then the other direction, or both directions may be simultaneously stretched. In addition, the drawing step may be performed in one step or may be performed in multiple steps.

At this time, in the case of longitudinal stretching, the stretching can be performed using the speed difference between the rolls, and in the case of transverse stretching, tenter can be used. The stretching is preferably performed at (Tg-20 ° C) to (Tg + 30 ° C), more preferably at (Tg-20 ° C) Tg + 20 < 0 > C.

At this time, it is preferable that the acrylic film of 1) or 2) has a glass transition temperature (Tg) of 100 to 160 ° C. When the above range is satisfied, the retardation film of the present invention has excellent durability have.

As an embodiment of the present invention, (1) an acrylic film having a negative phase difference can be produced such that a plane direction retardation is generated by differentiating a longitudinal direction stretching ratio and a transverse direction stretching ratio during biaxial stretching, and 2) The acrylic film can be produced so that the longitudinal direction stretching ratio and the transverse direction stretching ratio are stretched to be almost the same at the time of biaxial stretching so that only the retardation in the thickness direction can be expressed without manifesting the retardation in the direction of the surface and the acrylic film having the negative B- The longitudinal direction retardation and the thickness direction retardation can be produced by varying the longitudinal stretching ratio and the lateral stretching ratio at the time of stretching.

In the production of the retardation film according to the present invention, a method of laminating an acrylic film having a negative C type retardation 2) to the acrylic film of 1) is not particularly limited, but a method of laminating with an UV adhesive or a pressure- can do.

In addition, the present invention provides an IPS (in-plane switching) mode liquid crystal display including one or two or more of the retardation film. An exemplary liquid crystal display including one or two or more retardation films will be described in more detail as follows.

In a liquid crystal display device comprising a liquid crystal cell and a first polarizing plate and a second polarizing plate respectively provided on both surfaces of the liquid crystal cell, a retardation film may be provided between the liquid crystal cell and the first polarizing plate and / or the second polarizing plate. have. That is, a retardation film may be provided between the first polarizing plate and the liquid crystal cell, and one retardation film is provided between the second polarizing plate and the liquid crystal cell, or between the first polarizing plate and the liquid crystal cell and between the second polarizing plate and the liquid crystal cell. 2 or more It may be provided.

The first polarizing plate and the second polarizing plate may include a protective film on one or both surfaces. The inner protective film may include a triacetate cellulose (TAC) film, a polynorbornene-based film made of ring opening metathesis polymerization (ROMP), and a hydrogenated cyclic olefin-based polymer that is ring-opened polymerized. ring opening metathesis polymerization followed by hydrogenation) may be a polymer film, a polyester film, or a polynorbornene-based film made by addition polymerization. In addition, a film made of a transparent polymer material may be used as a protective film, but is not limited thereto.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are merely provided to more easily understand the present invention, and the contents of the present invention are not limited thereto.

One. Phase difference  Production of film

Production Example 1 Production of acrylic film (I) having negative phase difference of - 1)

Acrylonitrile copolymer (LG Chem, SAN82TR, acrylonitrile content 20 wt%) and poly (cyclohexylmaleimide-co-methyl methacrylate) (LGMMA and PMMA830HR) : 20 in a twin extruder at 250 캜 and 200 rpm to prepare a resin composition. With the resin composition, an unstretched film having a width of 800 mm was prepared using a T-die film forming machine at 250 ° C. and 250 rpm. The unstretched film was stretched 1.4 times in the MD direction at a temperature of 125 캜 in a roll-to-roll manner, and then stretched 2.9 times in the TD direction using a tenter stretcher at the same temperature to obtain an acrylic film . The final stretched film thus obtained had a thickness of about 55 탆, a retardation value in a plane direction (Rin) and a retardation value in a thickness direction (Rth) of 100 nm and 150 nm, respectively.

PREPARATION EXAMPLE 2 Preparation of acrylic film having negative phase difference of (1) (II)

The unstretched film produced in the same manner as in Production Example 1 was stretched 1.3 times in roll-to-roll manner at a temperature of 125 DEG C in the MD direction, and then stretched at a constant temperature of 3.1 To give an acrylic film of 1). The final stretched film thus obtained had a thickness of about 54 mu m, a retardation value in a plane direction (Rin) and a retardation value in a thickness direction (Rth) of 124 nm and 172 nm, respectively.

PREPARATION EXAMPLE 3 Acrylic film (A) having a negative C type retardation of - 2)

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 were mixed at a weight ratio of 85:15 , And compounding was carried out using a twin extruder at 250 DEG C and 200 rpm to prepare a resin composition. The obtained raw material pellets were vacuum-dried and melted with an extruder at 250 degreeC, passed through the coat hanger type T-die, and the film of 185 micrometers in thickness was produced through the chrome plating casting roll, a drying roll, etc. The produced film was biaxially elongated in the order of 230% in the longitudinal direction and 250% in the transverse direction, and a retardation film having a thickness of 42 탆 was obtained. The longitudinal stretching temperature and the transverse stretching temperature at this time are 128 占 폚 and 138 占 폚, respectively. This retardation film had an in-plane retardation of 1.7 nm and a thickness retardation of -90 nm.

(Production Example 4) An acrylic film (B) having a negative C type phase difference of - 2)

The retardation film was prepared in the same manner as in Production Example 2 except that the transverse stretching temperature was set to 136 캜 in the production of the negative C type acrylic film of Example 2. This retardation film had an in-plane retardation of 2.1 nm and a thickness retardation of -101 nm.

PREPARATION EXAMPLE 5 Preparation of an acrylic film (C) having negative C type phase difference of - 2)

The retardation film was produced in the same manner as in Production Example 2 except that the transverse stretching temperature was 134 캜 in the production of the negative C type acrylic film of Example 2. This retardation film had an in-plane retardation of 3.2 nm and a thickness retardation of -115 nm.

≪ Production Example 6 > An acrylic film (D) having a negative B type phase difference of - 2)

Retardation film was produced in the same manner as in Production Example 3, except that the acrylic film having negative C type retardation of 2% had a longitudinal stretching ratio of 200% and a transverse stretching ratio of 250%. The retardation film had a thickness of 47 um, an in-plane retardation of 24 nm, and a retardation in the thickness direction of -96 nm.

≪ Example 1 >

The negative C type acrylic film (A) of 2) prepared in the same manner as in Production Example 3 was laminated using an acrylic film (I) having negative phase difference of 1) produced in Production Example 1 and a pressure sensitive adhesive to form a composite retardation film . Nz (Rth / Rin) of the final composite retardation film was measured and shown in Table 1.

<Example 2>

The negative C type acrylic film (B) 2) produced in the same manner as in Production Example 4 was stuck to the acrylic film (I) having negative phase difference of 1) produced in Production Example 1 using a pressure sensitive adhesive to form a composite retardation film . Nz (Rth / Rin) of the final composite retardation film was measured and shown in Table 1.

<Example 3>

A negative C type acrylic film (C) 2) produced in the same manner as in Production Example 5 was stuck to an acrylic film (I) having negative phase difference of 1) produced in Production Example 1 using a pressure sensitive adhesive to form a composite retardation film . Nz (Rth / Rin) of the final composite retardation film was measured and shown in Table 1.

<Example 4>

A negative-type B-type acrylic film (D) prepared in the same manner as in Production Example 6 was stuck to an acrylic film (II) having negative phase difference of 1) prepared in Production Example 2 and a pressure-sensitive adhesive to prepare a composite retardation film. Nz (Rth / Rin) of the final composite retardation film was measured and shown in Table 1.

&Lt; Comparative Example 1 &

Nz (Rth / Rin) value when the acrylic film having negative phase difference of 1) of Production Example 1 was used as the retardation film for IPS mode was measured and shown in Table 1.

Comparative Example 2

A Negative C coating liquid was directly coated on an acrylic film having negative phase difference of 1) in Production Example 1 to prepare a composite retardation film. The negative C coating solution was prepared by gradually stirring ethyl cellulose (Dow EC100, Mw 180,000, Ethoxyl content: 49%) in a toluene / ethanol (3/7) mixed solvent at room temperature to have a solids content of 10% . The completely dissolved coating liquid was coated on an acrylic film having a negative retardation to a final coating thickness of 10 mu m and then dried at 80 DEG C for 5 minutes. Nz (Rth / Rin) of the final composite retardation film was measured and shown in Table 1.

2. Evaluation of physical properties

(1) Evaluation method

The phase difference of the final film was measured by Axoscan's Axoscan.

(2) evaluation result

Negative retardation film Negative C type film
Or negative B type film   Compound phase difference film Rin (nm) Rth (nm) Rin (nm) Rth (nm) Rin (nm) Rth (nm) Nz (Rth / Rin) Example 1 100 150 1.7 -90 99 59 0.6 Example 2 100 150 2.1 -101 98 49 0.5 Example 3 100 150 3.2 -115 97 36 0.4 Example 4 124 172 24 -96 100 52 0.5 Comparative Example 1 100 150 - - 100 150 1.5 Comparative Example 2 100 150 coating coating 75 47 0.6

As can be seen from Table 1, Nz (Rth / Rin) values of the composite phase difference films for IPS mode of Examples 1 to 4 were measured to be 0.6, 0.5, 0.4 and 0.5, respectively. A retardation film satisfying the condition that the value is less than 1 was obtained.

On the other hand, the retardation film of Comparative Example 1 did not satisfy the condition that the value of Nz (Rth / Rin) was less than 1, and the phase difference value of the retardation film of Comparative Example 2 changed greatly during the coating process, It was confirmed that it is unsuitable for use as a retardation film for a polarizing film.

Claims (12)

1) an acrylic film having a negative phase difference; And
2) an acrylic film having a negative C type or a negative B type retardation, the plane retardation value represented by Equation 1 is 50 to 300 nm, and the thickness retardation value represented by Equation 2 is Retardation film for IPS (in-plane switching) mode liquid crystal display, characterized in that the Nz (Rth / Rin) value of 10 ~ 300nm, the ratio of the thickness direction retardation value to the surface direction retardation value is less than one:
[Equation 1]
_{Rin = (n x - n y} ) × d
&Quot; (2) &quot;
_{Rth = (n z - n y} ) × d
In Equation 1 and Equation 2,
n _x is a refractive index of the direction of the largest refractive index in the plane direction of the film,
n _y is a refractive index in the vertical direction in the n _x direction in the plane direction of the film,
n _z is the refractive index in the thickness direction,
d is the thickness of the film.
The phase difference film for an IPS (in-plane switching) mode liquid crystal display device according to claim 1, wherein the acrylic film having a negative phase difference comprises a blending resin obtained by blending a polymer containing an acrylic monomer and a styrenic copolymer.
The styrenic copolymer according to claim 2, wherein the styrenic copolymer is at least one selected from the group consisting of styrene-maleic anhydride copolymers (SMA), styrene-acrylonitrile copolymers (SAN) or alpha-methylstyrene- acrylonitrile copolymers (AMSAN) in-plane switching mode phase difference film for liquid crystal display.
The phase difference film for an IPS (in-plane switching) mode liquid crystal display device according to claim 1, wherein the acrylic film having a negative phase difference further comprises a rubber component.
The in-plane switching (IPS) of claim 1, wherein the acrylic film having a negative C type or a negative B type retardation is a resin obtained by blending a polymer containing an acrylic monomer and an aromatic resin having a carbonate portion in a main chain thereof. Retardation film for mode liquid crystal display devices.
The in-plane switching (IPS) liquid crystal display device of claim 5, wherein the aromatic resin having a carbonate-based moiety in the main chain is a resin composition containing 5 to 10,000 at least one unit represented by the following Chemical Formula 2. Retardation film:
(2)

Wherein X is a divalent group comprising at least one benzene ring.
The in-plane switching (IPS) mode liquid crystal display device according to claim 6, wherein X is a divalent group selected from the group consisting of the following structural formulas:

The retardation film of claim 2 or 5, wherein the acrylic monomer includes a double bond between a carbonyl group of an ester group and conjugated carbons.
The phase difference film for an IPS (in-plane switching) mode liquid crystal display device according to claim 8, wherein the acrylic monomer is a compound represented by the following formula (1).

[Chemical Formula 1]

Wherein R ₁ , R ₂ and R ₃ may be a hydrogen atom, a hydrocarbon group or an epoxy group having 1 to 30 carbon atoms, and R ₄ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.
[10] The method according to claim 8, wherein the acrylic monomer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, propyl methacrylate, n -butyl methacrylate, t -butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, A phase difference film for an IPS (in-plane switching) mode liquid crystal display, which is a polymer comprising at least one acrylic monomer selected from methoxyethyl methacrylate, ethoxyethyl methacrylate and butoxy methyl methacrylate.
The film according to claim 1, further comprising: an acrylic film having a negative phase difference; And 2) a retardation film for IPS (in-plane switching) mode liquid crystal display, which is produced by attaching an acrylic film having a negative C type or negative B type phase difference with a UV adhesive or a pressure sensitive adhesive.
An in-plane switching (IPS) liquid crystal display device comprising at least one retardation film for an in-plane switching (IPS) mode liquid crystal display device according to any one of claims 1 to 11.