KR102043492B1 - Preparing method for the optical film, optical mamber and optical film by the same method, polarizing plate and liquid crystal display comprising the same - Google Patents

Abstract

Herein is a step of forming a birefringent layer using a negative birefringent material on the shrinkable film to form a laminate; And heat shrinking the laminate, wherein the negative birefringent material is a resin including a main chain and a side chain, wherein the side chain comprises at least one phenyl group, at least one of the main chain and the side chain is a sulfone group, It relates to a method for producing an optical film and an optical film wherein one or two or more are substituted with a substituent selected from the group consisting of a nitrile group and a halogen group.

Description

Method for manufacturing an optical film, an optical member and an optical film manufactured using the same, a polarizing plate and a liquid crystal display device comprising the same THE SAME}

The present invention relates to a method for manufacturing an optical film, an optical member and an optical film manufactured using the same, a polarizing plate and a liquid crystal display device including the same.

Background Art [0002] Liquid crystal displays have a widespread use as optical display elements because they have lower power consumption, smaller volume, and lighter weight than portable cathode ray tube displays. In general, a liquid crystal display device has a basic configuration in which polarizers are provided on both sides of a 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 the transmitted light emitted through the polarizer. Is made visible. 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 this characteristic, the LCD has a contrast ratio, which is a measure of how sharply an image is seen according to a viewing angle, and gray scale inversion occurs, thereby reducing visibility. Has disadvantages In order to overcome the disadvantages described above, an optical retardation film (compensation film) for expressing the optical phase difference generated in the liquid crystal cell is used in the 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 TN (Twisted Nematic), ASM (axially symmetric aligned microcell), and OCB (optically compensated blend) ), VA (vertical alignment), MVA (multidomain VA), SE (surrounding electrode), PVA (patterned VA), 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 express the phase difference resulting from the optical anisotropy of these liquid crystal modes, the optical anisotropy retardation film corresponding to each mode is calculated | 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.

As the retardation film applied to the IPS (In-Plane Switching) mode liquid crystal panel, for example, an optical film having a refractive index distribution of n _x > n _z > n _y should be used. At this time, it is generally known that an optical film having a refractive index distribution as described above is difficult to realize by a single uniaxial / biaxially oriented film alone. Therefore, in order to form a phase difference compensation layer that satisfies the refractive index distribution condition, a method of manufacturing a multilayer film of two or more layers has been proposed. However, when manufacturing a multilayer film, there is a problem that the film is difficult to be thinned, and that manufacturing is very difficult unless the optical axes of two or more layers of films to be laminated are not correctly disposed, and thus do not exhibit desired retardation characteristics.

Therefore, research for producing an optical film having the above refractive index distribution with a single film continues to be carried out, for example, by attaching a shrinkable film on one side or both sides of a resin film through an acrylic pressure-sensitive adhesive, etc. Has been proposed, and a method of stretching the laminate to impart contractile force in a direction orthogonal to the stretching direction has been proposed.

However, when manufacturing the optical film by attaching on the shrinkable film in the form of a resin film as described above, the production process is complicated because the film of each layer must be prepared separately, and then undergo various processes such as adhesion and drying. The manufacturing cost is high, and since the thickness of the retardation film to be manufactured becomes thick, there is a disadvantage in that it does not meet the trend of thinner and lighter display devices including the same. In addition, there is also a problem that a high occurrence rate of defects, such as stains, Kunic, foreign matters mixed with the adhesive.

Japanese Laid-Open Patent No. 193-157911

The present invention provides a method of manufacturing a single optical film having a relatively simple production process, excellent appearance characteristics, and being thin, yet having a refractive index distribution of n _x > n _z > n _y , and optical produced using the same. To provide a member and an optical film, a polarizing plate and a liquid crystal display including the same.

Herein is a step of forming a birefringent layer using a negative birefringent material on the shrinkable film to form a laminate; And heat shrinking the laminate,

The negative birefringent material is a resin containing a main chain and a side chain, wherein the side chain includes one or more phenyl groups, and at least one of the main chain and the side chains is a substituent selected from the group consisting of a sulfone group, a nitrile group and a halogen group. Or a method for producing an optical film wherein two or more are substituted.

In another exemplary embodiment, the heat shrinking is performed so that the birefringent layer satisfies the following formula (1).

Equation (1): n _x > n _z > n _y

In the formula (1), n _x is a refractive index in a direction in which the plane refractive index of the birefringence layer is maximum, n _y is a refractive index in a direction perpendicular to the n _x direction of the birefringence layer, and n _z is a refractive index of the birefringence layer. Refractive index in the thickness direction.

In one embodiment, the negative birefringent material has a refractive index of 0.0005 or more represented by the following formula (2).

Equation (2): Δn ₁₂ = n ₁ -n ₂

In the formula (2), n ₁ means the average value of the refractive index in the thickness direction of the birefringent layer formed on the shrinkable film before the laminate heat shrinkage, n ₂ is the plane of the birefringent layer formed on the shrinkable film before the laminate heat shrinkage Mean value of directional refractive index.

In addition, in an exemplary embodiment of the present specification, one or two or more phenyl groups in the side chain are substituted with a substituent selected from the group consisting of a sulfone group, a nitrile group and a halogen group.

In another exemplary embodiment, the forming of the birefringence layer may include 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 flexible film forming method, and a die coating method. It can be carried out by one or more methods selected from the group consisting of a method, a blade coating method and a gravure printing method.

In another embodiment, the step of heat shrinking the laminate satisfies the following formula (3).

Equation (3): 0% ≤ S ₂ -S ₁ ≤ 5%

In the formula (3), S ₁ is the shrinkage ratio in a direction perpendicular to the stretching direction of the birefringent layer in a laminate state, S ₂ is being shrinkage ratio in a direction perpendicular to the stretching direction of the shrinkable film in the laminate state.

In another exemplary embodiment, the thickness of the birefringent layer after the heat shrinkage of the laminate is preferably 20 μm or less.

On the other hand, the step of heat shrink may be performed by a method of uniaxially stretching the laminate in the longitudinal direction (MD direction). In another aspect, the heat shrinking may be performed by stretching the laminate in the width direction (TD direction) and shrinking in the longitudinal direction (MD direction).

In the present specification, the stretching may be performed at a temperature range of (Tg) ° C. to (Tg + 100) ° C. when the glass transition temperature of the shrinkable film is Tg.

In addition, the draw ratio is preferably carried out in the range of 1 to 3 times.

The manufacturing method of the present invention may further include the step of peeling the birefringent layer from the shrinkable film after the step of heat shrinking the laminate, if necessary.

In another embodiment of the present specification, an optical film manufactured by the above-described method is provided.

In one embodiment of the present specification, the shrinkable film; And a birefringence layer formed on at least one surface of the shrinkable film,

The birefringence layer is formed using a negative birefringent material,

The negative birefringent material is a resin containing a main chain and a side chain,

The side chain comprises one or more phenyl groups,

At least one of the main chain and the side chain provides an optical film wherein one or two or more are substituted with a substituent selected from the group consisting of sulfone groups, nitrile groups and halogen groups.

In another exemplary embodiment, the birefringent layer satisfies the following formula (1).

Equation (1): n _x > n _z > n _y

In the formula (1), n _x is a refractive index in a direction in which the plane refractive index of the birefringence layer is maximum, n _y is a refractive index in a direction perpendicular to the n _x direction of the birefringence layer, and n _z is a refractive index of the birefringence layer. Refractive index in the thickness direction.

In another embodiment, the optical film satisfies the following formulas (4) to (6).

Equation (4): 100 nm ≤ R _in ≤ 350 nm

Equation (5): 50nm ≤ R _th ≤ 250nm

Equation (6): 0.1 ≦ Nz <1

In the formulas (4) to (6), R _in is a plane direction retardation value of the film measured at a wavelength of 550 nm, R _th is a thickness direction retardation value of a film measured at a wavelength of 550 nm, and Nz is a wavelength of 550 nm. The ratio of the thickness retardation value (R _th / R _in ) to the measured surface retardation value.

In another exemplary embodiment of the present specification, a polarizing plate including the above-described optical film is provided.

In another aspect, the polarizing plate comprises at least two optical films, wherein at least two optical films have different Nz values from each other, and the Nz value is a thickness direction phase difference with respect to a plane direction retardation value measured at a wavelength of 550 nm. It provides a polarizing plate which is a ratio of values (R _th / R _in ).

In another aspect, the present invention provides a liquid crystal display device including the optical film.

In another aspect, the liquid crystal display device comprises two or more optical films, the optical films of at least two layers have different Nz values from each other, and the Nz values have a thickness with respect to the plane retardation value measured at a wavelength of 550 nm. A liquid crystal display device having a ratio R _th / R _in of a direction retardation value is provided.

The optical film manufactured by the manufacturing method of the present invention can realize a phase difference characteristic having a refractive index distribution of n _x > n _z > n _y effectively even with a single film, can be manufactured in a thin shape, and the manufacturing method is simple. Compared to this, productivity can be dramatically improved.

Meanwhile, in the manufacturing method of the present invention, a birefringent layer is formed by applying a negative birefringent material on a shrinkable film, and then a birefringence satisfies the refractive index distribution of n _x > n _z > n _y on the shrinkable film through a heat shrinkage process. Since the formation of a layer does not require the use of a separate adhesive, it is possible to significantly reduce the incidence of defects, such as staining, Kunic, and alien substances, and as a result, the optical properties and appearance characteristics of the film to be produced are very excellent. .

An optical film according to an exemplary embodiment of the present invention has an advantage in that visibility is excellent while providing an optical film having a thin thickness.

1 exemplarily shows heat shrinkage results of laminates according to Examples 1 and 2. FIG.

First, terms used in the present specification are defined.

(1) n _x is the refractive index of the direction (ie the slow axis direction) to the maximum in the plane direction refractive index, n _y is the refractive index of the direction (ie, fast axis direction) that is perpendicular to the slow axis in the plane direction , n _z means refractive index in the thickness direction. In addition, n _x , n _y , n _z means a value measured in light of 550nm wavelength. On the other hand, the n _{x ,} n _y, n _z can be measured by a known method well known in the art, for example, by using a prism coupler device (SAIRON TECHNOLOGY Co. SPA-3DR) and the like to average refractive index By measuring the birefringence with an Axoscan of Axomatrics, n _{x ,} n _{y and} n _z can be calculated.

(2) R _in means the plane direction retardation value measured by the light of 550 nm wavelength, and it is calculated | required by the plane direction retardation value R _in (n _x -n _y ) xd. In this case, n _x and n _y are the same as described above, and d means the thickness of the optical film. On the other hand, the R _in can be measured by a known method well known in the art, for example, can be measured using Axoscan equipment of Axomatrics.

(3) R _th means the thickness direction retardation value measured by the light of 550 nm wavelength, and it is calculated | required by thickness direction retardation value R _th = (n _z -n _y ) xd. In this case, n _y and n _z are the same as described above, and d means the thickness of the optical film. On the other hand, R _th can be measured by a known method well known in the art, for example, can be measured using Axoscan equipment of Axomatrics.

(4) Nz means the ratio of the thickness direction retardation value to the surface direction retardation value, and is calculated | required by Nz = R _th / R _in .

(5) n ₁ means the average value of the refractive index of the birefringence layer formed on the shrinkable film before the laminate heat shrinkage, n ₂ is the average value of the planar refractive index of the birefringence layer formed on the shrinkable film before the laminate heat shrinkage it means. That is, n ₁ and n ₂ each mean an average value of the refractive index in the thickness direction and an average value of the planar refractive index before stretching and shrinking of the birefringent layer formed on the shrinkable film. On the other hand, the measuring method of n ₁ and n ₂ can be measured by a known method well known in the art, for example, using the prism coupler equipment (SAIRON TECHNOLOGY Co. SPA-3DR) and the like to average refractive index By measuring the birefringence with Axoscan of Axomatrics, n _{1 and} n ₂ can be calculated, respectively.

(6) Negative birefringent material means a material that expresses the optical axis in the direction perpendicular to the stretching direction after stretching (after orientation), and when coating only (before stretching), a refractive index of n _z > n _x = n _y Means a substance expressing a distribution. Definition A birefringent material refers to a material that expresses an optical axis in a direction parallel to the stretching direction after stretching (after orientation), and when coated only (before stretching), a refractive index distribution of n _x = n _y > n _z is expressed. It means a substance.

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

The inventors of the present invention if after forming the birefringent layer using a result, the birefringent material portion on the shrinkable film of extensive research to solve the above problems at the same time perform the heat shrinkage process, n _x a relatively simple method> It has been found that not only can have n _z > n _y refractive index distributions, but also optical films that are very thin.

In one embodiment of the present specification, the negative birefringent material is a resin including a main chain and a side chain, wherein the side chain includes one or more phenyl groups, and at least one of the main chain and the side chain is a sulfone group, a nitrile group, and One or two or more substituents are substituted with a substituent selected from the group consisting of halogen groups.

In this case, in the case where the main chain or the side chain uses a resin which is not substituted with a sulfone group, a nitrile group or a halogen group, birefringence is small, and it is difficult to realize a desired level of phase difference with a thin coating layer that can be formed as a coating.

Therefore, when the birefringence layer is formed using the negative birefringent material as in the exemplary embodiment of the present specification, the birefringence is improved, and thus, the desired phase difference can be easily implemented in a thin thickness.

In addition, in an exemplary embodiment of the present specification, one or two or more phenyl groups in the side chain are substituted with a substituent selected from the group consisting of a sulfone group, a nitrile group and a halogen group.

In another embodiment of the present specification, the main chain includes two or more carbons, one of the carbons is substituted with a phenyl group, and the other is hydrogen; Sulfone groups; Nitrile group; And one or two or more are substituted with a substituent selected from the group consisting of halogen groups. The phenyl group may act as a side chain in the resin.

Therefore, in one embodiment of the present specification, the main chain includes two or more carbons, and any one of the carbons may be a sulfone group; Nitrile group; And a phenyl group unsubstituted or substituted with one or two or more substituents selected from the group consisting of halogen groups,

The other is hydrogen; Sulfone groups; Nitrile group; And one or two or more are substituted with a substituent selected from the group consisting of halogen groups.

In another embodiment, the negative birefringent material is a carbon atom substituted with a phenyl group unsubstituted or substituted with one or two or more substituents selected from the group consisting of sulfone groups, nitrile groups and halogen groups; And a main chain including a carbon atom substituted with one or two or more substituents selected from the group consisting of a sulfone group, a nitrile group, and a halogen group.

In another exemplary embodiment, the heat shrinking is performed so that the birefringent layer satisfies the following formula (1).

Equation (1): n _x > n _z > n _y

In the formula (1), n _x is a refractive index in a direction in which the plane refractive index of the birefringence layer is maximum, n _y is a refractive index in a direction perpendicular to the n _x direction of the birefringence layer, and n _z is a refractive index of the birefringence layer. Refractive index in the thickness direction.

As described above, when a birefringent layer is formed on the shrinkable film to form a laminate, and then heat shrinks, the birefringent layer formed on the shrinkable film is perpendicular to the stretching direction in the high temperature stretching process by the shrinkable film. It is forcibly contracted and has a maximum refractive index in the direction perpendicular to the stretching direction. As a result, the refractive index in the stretching direction is smaller than the refractive index in the thickness direction, and finally satisfies n _x > n _z > n _y . . As described above, when the birefringence layer finally satisfies n _x > n _z > n _y , it can be very usefully used as an IPS mode retardation film.

On the other hand, the negative birefringent material is preferably a birefringence of 0.0005 or more represented by the following formula (2), more specifically, for example, may be in the range of 0.0005 to 0.05 or 0.001 to 0.5.

Equation (2): Δn ₁₂ = n ₁ -n ₂

In the formula (2), n ₁ means the average value of the refractive index in the thickness direction of the birefringent layer formed on the shrinkable film before the laminate heat shrinkage, n ₂ is the plane of the birefringent layer formed on the shrinkable film before the laminate heat shrinkage Mean value of the direction refractive index.

In another embodiment of the present specification, the step of heat shrinking the laminate may more preferably satisfy the following formula (1) and satisfy the following formula (3). As such, when the birefringence layer shrinks at substantially the same magnification as that of the shrinkable film in the laminate state, all of the birefringence layers, which are precursors of the finally produced optical film, can be sufficiently shrunk, thereby producing an excellent optical film. Is possible. On the other hand, when the difference in the shrinkage rate of the birefringent layer and the shrinkable film in the laminate state is large, the birefringent layer, which is a precursor of the finally produced optical film, cannot be sufficiently contracted, and thus the optical quality of the excellent quality as described above. Film manufacturing is difficult More preferably, the difference between the shrinkage in the direction perpendicular to the stretching direction of the shrinkable film in the laminate state and the shrinkage in the direction perpendicular to the stretching direction of the birefringent layer in the laminate state is about 0% to 3%, and 0% to 2%, or 0% to 1% or so:

Equation (3): 0% ≤ S ₂ -S ₁ ≤ 5%

In the formula (3), S ₁ is the shrinkage ratio in a direction perpendicular to the stretching direction of the birefringent layer in a laminate state, S ₂ is the shrinkage ratio in a direction perpendicular to the stretching direction of the shrinkable film in the laminate state.

In this case, the shrinkage in the direction perpendicular to the stretching direction in the laminate state can be measured by a method well known in the art, for example, after forming the laminate, both the birefringent layer and the shrinkable film After taking the dots at 1 cm intervals, the laminates can be measured by peeling after stretching and heat shrinkage in a UTM apparatus, and then measuring the respective intervals of the dots.

Hereinafter, the manufacturing method of the optical film according to the present invention will be described in more detail.

First, a step of forming a laminate by forming a birefringent layer using a negative birefringent material on a shrinkable film is performed. The forming of the birefringence layer may be performed by, for example, applying a birefringent layer forming composition comprising a negative birefringent material and a solvent directly onto the shrinkable film, and the applying method is, for example, negative birefringence. The birefringent layer forming composition comprising a substance and a solvent is coated with 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 flexible film forming method, a die coating method, a blade coating method. It may be performed using a method such as a method and a gravure printing method, but is not limited thereto.

On the other hand, the said birefringent substance contains 1 type or 2 types chosen from the group which consists of substituted styrene resin, for example. These may be used alone or in combination, and specifically, poly (sodium 4-styrenesulfonate), poly (4-chlorostyrene), poly (penta) Poly (pentafluorostyrene) and the like, but are resins containing a main chain and a side chain, wherein the side chain includes at least one phenyl group, and at least one of the main chain and the side chain is a sulfone group, a nitrile group, and a halogen group. If 1 or 2 or more is substituted with a substituent selected from the group consisting of, it is not limited thereto.

On the other hand, the solvent included in the birefringent layer forming composition can be used without particular limitation as long as it can dissolve the negative birefringent material, it can be appropriately determined according to the negative birefringent material to be used. For example, the solvent may include, but is not limited to, methylene chloride, chloroform, tetrahydrofuran (THF), 1,3-dioxane, N-methyl pyrrolidone (NMP), and dimethylformamide (DMF). ), Dimethylacetamide (DMAc), alcohols such as ethanol, methanol, toluene, methyl ethyl ketone (MEK), methyl isopropyl ketone (MIPK), methyl isobutyl ketone (MIBK), cyclopentanone (CPO) Ketones, 1,3-dioxolane, water, and the like. These solvents may be used alone or in combination of two or more thereof.

At this time, in order to dry the solvent contained in the birefringence layer, a drying process may be performed by a method well known in the art, for example, (boiling point of the solvent-50) ℃ to (boiling point of the solvent + 50 It can be made to dry in hot air, an IR heater, etc. in 1) -10 degreeC temperature range and 1 minute-10 minutes.

On the other hand, the concentration of the negative birefringent material included in the birefringent layer forming composition is preferably 1wt% to 40wt%, for example, may be about 5wt% to 25wt%. If the concentration is less than 1wt%, there is a problem that the thickness of the coating layer becomes thin. If the concentration is more than 40wt%, the coating composition has a high viscosity, so that it is difficult to coat with a uniform thickness, and the drying time is long, so the productivity is remarkable. There is a problem falling.

In addition, the glass transition temperature of the birefringence layer is preferably 20 ℃ or more greater than the glass transition temperature of the shrinkable film to be described later, for example, may be different from about 20 ℃ to 100 ℃ or 30 ℃ to 80 ℃. The measuring method of glass transition temperature is not specifically limited, For example, glass transition temperature can be measured by a differential scanning calorimeter (DSC). For example, when using a differential scanning calorimeter (DSC), when the sample of about 10 mg is sealed in a dedicated pan and heated to a constant temperature condition, the endothermic and calorific value of the material according to the phase change occurs according to the temperature. The transition temperature can be measured.

Next, as long as the shrinkable film usable in the present invention has a heat shrinkage larger than that of the birefringent layer, a known resin film can be used without particular limitation. For example, but not limited to acrylic resins, norbornene resins, polyolefin resins, polyester resins, polyamide resins, polyimide resins, polycarbonate resins, polystyrene resins, polyvinyl chloride resins Resin, polyvinylidene chloride-type resin, cellulose resin, polyether sulfone resin, polysulfone resin, polyacetate resin, polyarylate resin, polyvinyl alcohol resin, etc. can be used. However, the shrinkage in the direction perpendicular to the stretching direction measured in the state of a single film under the same heat shrinkage condition should be larger than that of the birefringence layer, for example, about 10% or more. On the other hand, the shrinkage can be measured by a known method well known in the art. For example, after the film is taken at intervals of 1 cm, the film may be shrunk using Zwick's UTM (Universe Testing Machine) equipment, and may be calculated by measuring the distance of the spot after shrinking.

In particular, the shrinkable film preferably contains a polyester resin, particularly polyethylene terephthalate. The polyethylene terephthalate is not only excellent in price competitiveness, but also has low glass transition temperature, which is excellent in heat shrinkability during high temperature stretching process.

On the other hand, the shrinkable film is preferably a film uniaxially stretched in the width direction (TD) or a film biaxially stretched in the longitudinal direction (MD) and the width direction (TD) in order to effectively shrink the birefringent layer. In this case, the present invention may use a uniaxially stretched film in the width direction (TD) or a biaxially stretched film in the longitudinal direction (MD) and the width direction (TD) as a commercially available shrinkable film, or commercially available shrinkage The unstretched polymer film having the properties may be uniaxially stretched in the width direction (TD) or biaxially stretched in the longitudinal direction (MD) and in the width direction (TD).

In addition, the shrinkable film preferably has a thickness of 10 μm to 100 μm, more preferably about 20 μm to 80 μm. In this case, the thicker the film is, the stronger the shrinkage force is, there is an advantage to express the phase difference of the birefringence layer, but in order to obtain the target phase difference should have a suitable thickness, from this point of view it is preferable that the thickness of the film is within the above range. . In addition, when the thickness of the shrinkable film is too thin, it is advantageous to have a thickness of 10 μm or more because the curl problem that the film is largely bent in the drying process after the birefringence layer is applied on the shrinkable film occurs.

Next, after forming a laminate in which the birefringence layer is formed on the shrinkable film in the same manner as described above, a step of heat shrinking the laminate may be performed.

At this time, the step of heat shrink is preferably carried out by a method of uniaxially stretching the laminate in the longitudinal direction (MD) using a known stretching equipment or the like. For example, in a state where both ends of the longitudinal direction (MD) of the laminate are held in an oven at a high temperature condition, uniaxial stretching may be performed by pulling the laminate in the longitudinal direction (MD) using UTM equipment. It is preferable that the said birefringence layer used for this invention is a negative birefringence layer which expresses a maximum refractive index perpendicular | vertical to a extending | stretching direction. The high temperature stretching causes the laminate to shrink in the width direction TD (see FIG. 1).

On the other hand, the step of heat shrink may be performed using a simultaneous biaxial stretching machine. Specifically, according to one embodiment of the present invention, the heat shrinking step may be performed by stretching the laminate in the width direction (TD direction) and shrinking in the longitudinal direction (MD direction). This method is a method in which a birefringent layer is coated on a shrinkable film and dried, and then stretched in the width direction TD while shrinking in the longitudinal direction MD. Therefore, there is an advantage in that the productivity is higher in that the width of the film can be larger than the method using the UTM.

At this time, the stretching is preferably carried out at a temperature of (Tg) to (Tg + 100 ℃) when the glass transition temperature of the shrinkable film is Tg, for example, (Tg + 20 ℃) to (Tg + 80 ° C.). Although the stretching temperature must satisfy this range, high phase difference is possible. Specifically, at this stretching temperature, the birefringence layer is less likely to shrink, but the shrinkable film is very strongly shrinking, and they are attached by the resin layer, so that the birefringence layer has strong width shrinkage during the stretching process. As a result, it may have a high phase difference.

In addition, the stretching is preferably performed at a draw ratio of 1 to 3 times, for example, may be performed at a draw ratio of 1 to 2.5 times or 1 to 2 times. When stretching is performed at such a draw ratio, the birefringence layer can be shrunk in the width direction as desired by the present invention, and the present invention can realize a high phase difference as desired.

On the other hand, the thickness of the birefringence layer after the step of heat shrinking the laminate is preferably 20㎛ or less, more specifically, for example, may be 1㎛ 20㎛, more preferably 1㎛ 15㎛ or 1 May be on the order of 10 μm to 10 μm. If the thickness of the birefringent layer after stretching is greater than this, it may not be able to meet the trend of thinning and thinning of the polarizing plate or display device including the same, and may be outside the range of the phase difference value pursued by the present invention.

On the other hand, the manufacturing method of the present invention may further comprise the step of uniaxially stretching the shrinkable film in the width direction (TD) using a tenter stretching machine or the like before the step of forming the laminate. This is for use in the state in which the shrinkable film is uniaxially stretched in the width direction (TD), and as described above, when the shrinkable film is a film uniaxially stretched in the width direction (TD), the birefringence layer is effectively It is preferred to shrink. In this case, the stretching may be performed at a draw ratio of 1.5 to 5 times at a temperature of (Tg-20) ° C. to (Tg + 50) ° C. when the glass transition temperature of the shrinkable film is Tg.

According to one embodiment of the present invention, the thickness of the birefringent layer after the heat shrinkage of the laminate is 20 μm or less, more preferably 1 μm to 15 μm or 1 μm to 10 μm, and the birefringence layer is represented by the above formula ( 7) is satisfied. In this case, the polarizing plate and the display device including the same to meet the trend of thin and light, there is an advantage in terms of visibility.

In another aspect of the present disclosure, after the heat shrinking step may further comprise the step of peeling off the birefringent layer from the shrinkable film. That is, in order to use a birefringent layer as a single retardation film, it is preferable to peel. On the other hand, the step of peeling may proceed at room temperature, the peeling method is not particularly limited.

In another embodiment of the present specification, the present invention provides an optical film produced by the above-described manufacturing method.

Specifically, in one embodiment of the present specification, the shrinkable film; And a birefringence layer formed on at least one surface of the shrinkable film,

The birefringence layer is formed using a negative birefringent material,

The negative birefringent material is a resin containing a main chain and a side chain,

The side chain comprises one or more phenyl groups,

At least one of the main chain and the side chain provides an optical film wherein one or two or more are substituted with a substituent selected from the group consisting of sulfone groups, nitrile groups and halogen groups.

At this time, the shrinkable film, the material of the birefringence layer and the formation method are the same as described above.

Moreover, it is more preferable that the said optical film also satisfy | fills said Formula (3) further.

In another aspect of the present specification, the optical film preferably satisfies at least one or more of the following formulas (4) to (6). In this case, it can be very useful as a retardation film for IPS mode. More preferably, the optical film has a range of R _in about 200 nm to 300 nm, a range of R _th about 100 nm to 200 nm, and an Nz value of about 0.2 to 0.9 or about 0.3 to 0.7:

Equation (4): 150 nm ≤ R _in ≤ 350 nm

Equation (5): 50nm ≤ R _th ≤ 250nm

Equation (6): 0.1 ≦ Nz <1

In the formulas (4) to (6), R _in is a plane direction retardation value of the film measured at a wavelength of 550 nm, R _th is a thickness direction retardation value of a film measured at a wavelength of 550 nm, and Nz is a wavelength of 550 nm. It is ratio (R _th / R _in ) of thickness direction retardation value with respect to measured surface direction retardation value.

Further, according to one embodiment of the present invention, the birefringent layer included in the optical film satisfies the above formula (7). In this case, as described above, the optical film including the birefringence layer has a reverse wavelength dispersion, and shows an advantageous effect in terms of visibility.

In addition, according to one embodiment of the present invention, the thickness of the birefringence layer of the optical film is 20 μm or less, more preferably 1 μm to 15 μm or 1 μm to 10 μm, and the birefringence layer is represented by Equation (7) Satisfies. As described above, when the birefringence layer satisfies the thickness range and Equation (7), the birefringence layer satisfies the trend of thinning and reducing the weight of the polarizing plate or display device including the same, and is advantageous in terms of visibility.

In another aspect, the present invention provides a polarizing plate comprising the optical film. The polarizing plate may include one layer or two or more layers of the optical film. Specifically, the optical film according to the present invention is directly attached to one side or both sides of the polarizer, or attached to the protective film of the polarizing plate attached to the protective film on both sides of the polarizer, it can be usefully used as a retardation film.

When the optical film is directly attached to one side or both sides of the polarizer, for example, the structure may include an upper protective film / polarizer / optical film, an optical film / polarizer / low protective film, an optical film / upper protective film / polarizer / lower Protective film or upper protective film / polarizer / lower protective film / optical film.

In another aspect, the polarizing plate includes at least two optical films, at least two optical films have different Nz values from each other, and the Nz value is a thickness direction phase difference with respect to a plane direction retardation value measured at 550 nm. The ratio of values (R _th / R _in ).

As described above, when the Nz values of at least two layers include optical films different from each other, a color closer to black may be realized.

In another aspect of the present specification, the polarizing plate includes two optical films, and the two optical films have different Nz values from each other.

In another aspect, at least two or more optical films having different Nz values from each other are provided in the polarizing plate in a stacked form.

In one aspect of the present specification, at least two or more optical films having different Nz values from each other are provided in contact with each other.

In another aspect, the present invention provides a liquid crystal display device including the optical film. For example, the present invention provides an IPS mode liquid crystal display including at least one optical film.

In this case, 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 optical film may include the liquid crystal cell, the first polarizing plate, and / or the second polarizing plate. It can be provided as a retardation film between polarizing plates. That is, an optical film may be provided between the first polarizing plate and the liquid crystal cell, and one optical 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.

In another aspect, the liquid crystal display device includes two or more optical films, wherein the optical films of at least two layers have different Nz values from each other, and the Nz values have a thickness with respect to a plane direction retardation value measured at 550 nm. The ratio of the direction retardation value (R _th / R _in ).

As described above, when the Nz values of at least two layers include optical films different from each other, a color closer to black may be realized.

In another aspect of the present disclosure, the liquid crystal display device includes two optical films, and the two optical films have different Nz values from each other.

In another aspect, at least two or more optical films having different Nz values from each other are provided in a liquid crystal display device in a stacked form.

In one aspect of the present specification, at least two or more optical films having different Nz values from each other are provided in contact with each other.

"Laminated" herein means that another member is located on one member, which includes not only when one member is in contact with another member, but also when another member is present between the two members.

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

Example  One

A polyethylene terephthalate stretched film (SKC, Inc. TP69C, biaxially stretched, Tg = 77 ° C.) was used as a shrinkable film. On the shrinkable film, a solution (solvent distilled water) containing 7 wt% of poly (sodium 4-styrenesulfonate) (Aldrich) was coated with a bar coater to a thickness of 6 μm. Thus, a laminate in which a birefringent layer was formed on a shrinkable film was produced. Next, after the laminate was uniaxially stretched in the MD direction by 10% in a 150 ° C. oven using a UTM equipment, the laminate was taken out at room temperature and the shrinkable film was peeled off. As a result, an optical film having a thickness of 9 µm was finally obtained. In addition, the shrinkage rate in the width direction (TD) of the birefringent layer was 30%.

Example  2

A polyethylene terephthalate stretched film (SKC, Inc. TP69C, biaxially stretched, Tg = 77 ° C.) was used as a shrinkable film. The birefringence layer was formed on the shrinkable film by coating a solution (solvent methylene chloride) containing 20 wt% of poly (4-chlorostyrene) (Aldrich Co., Ltd.) on the shrinkable film by using a bar coater. Sieve was prepared. Next, the laminate was uniaxially stretched in the MD direction by 10% in a 95 ° C. oven using a UTM equipment, and then the laminate was taken out at room temperature to remove the shrinkable film. As a result, an optical film having a thickness of 10 µm was finally obtained. In addition, the shrinkage rate in the width direction (TD) of the birefringent layer was 25%.

Example  3

A polyethylene terephthalate stretched film (SKC, Inc. TP69C, biaxially stretched, Tg = 77 ° C.) was used as a shrinkable film. A laminate (solvent methylene chloride) containing 20 wt% of poly (pentafluorostyrene) (Aldrich, Inc.) on the shrinkable film was coated with a bar coater to a thickness of 12 μm, thereby forming a laminate having a birefringent layer formed on the shrinkable film. Prepared. Next, after the laminate was uniaxially stretched in the MD direction by 10% in a 77 ° C. oven using a UTM equipment, the laminate was taken out at room temperature and the shrinkable film was peeled off. As a result, an optical film having a thickness of 14 µm was finally obtained. In addition, the shrinkage rate in the width direction (TD) of the birefringent layer was 18%.

Comparative example  One

A polyethylene terephthalate film (SKC, SG31), which is commercially available as a release film, was used, and a solution (solvent distilled water) containing 7 wt% of poly (sodium 4-styrenesulfonate) (Aldrich) on the release film was used as a bar coater. 6 μm thick. The laminate in which the birefringent layer was formed on a release film was stretched 10% uniaxially in the MD direction using a UTM apparatus in a 150 ° C oven. Then, the said birefringence layer was peeled off and the optical film which is 6 micrometers in thickness was finally obtained.

Comparative example  2

A polyethylene terephthalate stretched film (SKC, Inc. TP69C, biaxially stretched, Tg = 77 ° C.) was used as a shrinkable film. A birefringence layer was formed on the shrinkable film by coating a solution (solvent methylene chloride) containing 20 wt% of alphamethylstyrene-based polymer (LGC, 98UH) on the shrinkable film using a bar coater. The laminate was produced. Next, after the laminate was uniaxially stretched in the MD direction by 10% in a 110 ° C. oven using a UTM equipment, the laminate was taken out at room temperature and the shrinkable film was peeled off. As a result, an optical film having a thickness of 10 µm was finally obtained. In addition, the shrinkage rate in the width direction (TD) of the birefringent layer was 25%.

Experimental Example  One. Phase difference  Property measurement

The retardation characteristics of the optical films prepared in Examples 1 to 3 and Comparative Examples 1 and 2 were measured and shown in Table 1 below. The retardation value was measured using Axometrics Axoscan measuring equipment.

Coating layer
Δn ₁₂ Stretching phase difference R _in (nm) R _th (nm) Nz Example 1 0.009 180 116 0.65 Example 2 0.006 152 112 0.73 Example 3 0.003 102 81 0.79 Comparative Example 1 0.009 110 122 1.11 Comparative Example 2 0.001 31 24 0.77

As a result of Table 1, it can be seen that the optical film manufactured in Examples 1 to 3 according to one embodiment of the present specification has a phase difference value which is very suitable for use as a phase difference film in the liquid crystal display device for IPS mode. .

However, in the case of using a release film other than a shrinkable film, as in Comparative Example 1, the Nz value exceeds 1 and does not satisfy the range of the formula (6), so that the liquid crystal display device for IPS mode can be used as a retardation film. It can be confirmed that it is not suitable.

In addition, as in Comparative Example 2, at least one of the main chain and the side chain is an optical film in which a birefringence layer is formed using a resin which is not substituted with a substituent selected from the group consisting of a sulfone group, a nitrile group and a halogen group. Since the thickness direction retardation value and surface direction retardation value of Formula (5) are not satisfied, it can be confirmed that it is not suitable for using as a retardation film for the liquid crystal display device for IPS modes.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations can be made without departing from the technical spirit of the present invention described in the claims. It will be obvious to those of ordinary skill in the field.

2: birefringence layer
3: shrinking film
W: width
L: length

Claims (19)

Forming a laminate by forming a birefringent layer using a negative birefringent material on the shrinkable film; And
Heat shrinking the laminate;
The negative birefringent material is a resin containing a main chain and a side chain,
The side chain comprises one or more phenyl groups,
At least one of the main chain and the side chain is one or two or more substituted with a substituent selected from the group consisting of a sulfone group, a nitrile group and a halogen group. The method of claim 1,
Wherein the heat shrinking step is performed such that the birefringence layer satisfies the following formula (1):
Equation (1): n _x > n _z > n _y
In the formula (1), n _x is a refractive index in a direction in which the plane refractive index of the birefringence layer is maximum, n _y is a refractive index in a direction perpendicular to the n _x direction of the birefringence layer, and n _z is a refractive index of the birefringence layer. Refractive index in the thickness direction. The method of claim 1,
The negative birefringent material has a refractive index of 0.0005 or more represented by the following formula (2):
Equation (2): Δn ₁₂ = n ₁ -n ₂
In the formula (2), n ₁ means the average value of the refractive index in the thickness direction of the birefringent layer formed on the shrinkable film before the laminate heat shrinkage, n ₂ is the plane of the birefringent layer formed on the shrinkable film before the laminate heat shrinkage Mean value of directional refractive index. The method of claim 1,
The phenyl group contained in the side chain is one or two or more substituted with a substituent selected from the group consisting of a sulfone group, a nitrile group and a halogen group. The method of claim 1,
Forming the birefringence layer is a microgravure coating method, comma coating method, bar coating method, roller coating method, spin coating method, printing method, dip coating method, flexible film formation method, die coating method, blade coating method and gravure printing A method for producing an optical film, which is carried out by at least one method selected from the group consisting of methods. The method of claim 1,
Heat shrinkage of the laminate is a method of producing an optical film that satisfies the following formula (3):
Equation (3): 0% ≤ S ₂ -S ₁ ≤ 5%
In the formula (3), S ₁ is the shrinkage ratio in a direction perpendicular to the stretching direction of the birefringent layer in a laminate state, S ₂ is being shrinkage ratio in a direction perpendicular to the stretching direction of the shrinkable film in the laminate state. The method of claim 1,
The birefringence layer has a thickness of 20 μm or less after the heat shrinking of the laminate. The method of claim 1,
The heat shrinking step is performed by the method of uniaxially stretching the laminate in the longitudinal direction (MD direction). The method of claim 1,
The heat shrinking step is performed by the method of stretching the laminate in the width direction (TD direction) and shrinking in the longitudinal direction (MD direction). The method according to claim 8 or 9,
The stretching is performed in the temperature range of (Tg) ℃ to (Tg + 100) ℃ when the glass transition temperature of the shrinkable film is Tg. The method according to claim 8 or 9,
The stretching is a method for producing an optical film which is carried out at a draw ratio of 1 to 3 times. The method of claim 1,
Peeling the birefringent layer from the shrinkable film after the heat shrinking of the laminate. Shrinkable film; And a birefringence layer formed on at least one surface of the shrinkable film,
The birefringence layer is formed using a negative birefringent material,
The negative birefringent material is a resin containing a main chain and a side chain,
The side chain comprises one or more phenyl groups,
At least one of the main chain and the side chain is one or two or more substituted with a substituent selected from the group consisting of a sulfone group, a nitrile group and a halogen group. The method of claim 13,
The birefringence layer satisfies the following formula (1):
Equation (1): n _x > n _z > n _y
In the formula (1), n _x is a refractive index in a direction in which the plane refractive index of the birefringence layer is maximum, n _y is a refractive index in a direction perpendicular to the n _x direction of the birefringence layer, and n _z is a refractive index of the birefringence layer. Refractive index in the thickness direction. The method of claim 13,
The optical film is an optical film satisfying the following formula (4) to formula (6):
Equation (4): 100 nm ≤ R _in ≤ 350 nm
Equation (5): 50 nm ≤ R _th ≤ 250 nm
Equation (6): 0.1 ≤ Nz <1
In the formulas (4) to (6), R _in is a plane direction retardation value of the film measured at a wavelength of 550 nm, R _th is a thickness direction retardation value of a film measured at a wavelength of 550 nm, and Nz is a wavelength of 550 nm. The ratio of the thickness retardation value (R _th / R _in ) to the measured surface retardation value. The polarizing plate containing the optical film in any one of Claims 13-15. The method of claim 16,
The polarizing plate includes two or more optical films,
At least two layers of the optical film have different Nz values from each other,
Nz value is a polarizing plate which is the ratio (R _th / R _in ) of the thickness direction retardation value with respect to the surface direction retardation value measured at wavelength 550nm. A liquid crystal display device comprising the optical film according to any one of claims 13 to 15. The method of claim 18,
The liquid crystal display device comprises two or more optical films,
At least two layers of the optical film have different Nz values from each other,
Nz value is the ratio (R _th / R _in ) of the thickness direction retardation value to the surface direction retardation value measured at a wavelength of 550nm.

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