KR101737177B1 - 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

The present invention relates to a method of manufacturing a birefringent film, comprising: forming a birefringent layer by applying a birefringent material on a release film; Transferring the birefringent layer onto a heat shrinkable film to form a laminate; And a step of heat-shrinking the laminate so that the birefringent layer satisfies the following formula (1), an optical film produced using the same, and a polarizing plate and a liquid crystal display device comprising the same.
Equation (1): n _x > n _z > n _y
In the formula (1), n _x is the plane direction refractive index is the refractive index of the direction in which the maximum of the birefringent layer, n _y is a refractive index in the direction perpendicular to the n _x direction in the birefringent layer, n _z is a birefringent layer Refractive index in the thickness direction.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an optical film, an optical member and an optical film manufactured using the same, a polarizing plate and a liquid crystal display including the polarizing plate and the liquid crystal display, THE SAME}

The present invention relates to a method for producing an optical film, an optical member and an optical film manufactured using the optical film, a polarizing plate and a liquid crystal display including the optical member, and more particularly to an IPS mode liquid crystal display An optical member and an optical film manufactured using the same, a polarizing plate including the same, and a liquid crystal display device.

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

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

As such a retardation film, for example, an optical film having a refractive index distribution of n _x > n _z > n _y is used. At this time, the optical film having the refractive index distribution as described above is difficult to be realized as a single film, and conventionally, a structure composed of two or more layers of multilayer films has been presented. However, in the case of a multilayer film, it is difficult to make the film thinner, and if the optical axis of two or more laminated films is not precisely aligned, the desired retardation characteristics are not exhibited.

Therefore, research for producing an optical film having a refractive index profile as described above has been progressing. For example, a shrinkable film is attached to one side or both sides of a resin film via an acrylic adhesive, And stretching the laminate to give a contracting force in a direction orthogonal to the stretching direction.

However, when an optical film is produced by attaching it on a heat-shrinkable film in the form of a resin film as described above, it is necessary to manufacture each film of each layer, and then various steps such as adhesion and drying are required, The thickness of the optical film is too large, and the display device including the optical film has a drawback in that it can not meet the trend of being thinner and lighter.

The present invention for solving the above problems, a relatively simple way can be manufactured by, and available are made of thin, new n _x> n _z> n _y the method of producing a single optical film having a refractive index profile, And a polarizing plate and a liquid crystal display device using the optical member and the optical film.

On the other hand, the object of the present invention is not limited to the above description. It will be understood by those of ordinary skill in the art that there is no difficulty in understanding the additional problems of the present invention.

In one aspect, the present invention provides a method of manufacturing a light emitting device, comprising: forming a birefringent layer by applying a birefringent material on a release film; Transferring the birefringent layer onto a heat shrinkable film to form a laminate; And heat-shrinking the laminate 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 the plane direction refractive index is the refractive index of the direction in which the maximum of the birefringent layer, n _y is a refractive index in the direction perpendicular to the n _x direction in the birefringent layer, n _z is a birefringent layer Refractive index in the thickness direction.

On the other hand, it is preferable that the thickness of the birefringent layer after the step of heat shrinking the laminate is 30 탆 or less.

Meanwhile, the step of forming the laminate may be performed by a method of transferring the birefringent layer onto a heat shrinkable film through an adhesive or an adhesive.

Meanwhile, it is preferable that the step of forming the laminate is carried out by a method of transferring the birefringent layer onto a heat shrinkable film via an active energy ray curable adhesive.

On the other hand, it is more preferable that the step of heat shrinking the laminate satisfies the following formula (2).

(2): 0%? S ₂ - S ₁ ? 5%

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

On the other hand, it is more preferable that the step of heat shrinking the laminate satisfies the following formulas (3) and (4).

(3): 0.10 N / 2 cm? P _a ? 1.0 N / 2 cm

(4): 0.01 N / 2 cm? P _b ? 0.5 N / 2 cm

In the above formulas (3) and (4), P _a is the adhesive strength between the birefringent layer and the heat shrinkable film before heat shrinkage, and P _b is the adhesive strength between the birefringent layer and the heat shrinkable film after heat shrinkage.

On the other hand, the birefringent material may be at least one positive birefringent material selected from the group consisting of a polyamide resin, a polyimide resin, a polycarbonate resin, a polyarylate resin, and a cyclic olefin resin, And at least one negative birefringent material selected from the group consisting of a sol, a polyvinyl naphthalene, and a styrenic resin.

On the other hand, in the heat shrinking step, it is preferable to uniaxially stretch the laminate in the longitudinal direction (MD).

More preferably, the stretching is performed at a temperature of (Tg) to (Tg + 100 deg. C), more preferably at a stretching magnification of 1.1 to 3.0 times, when the glass transition temperature of the heat shrinkable film is Tg desirable.

In the meantime, the method of manufacturing an optical film of the present invention may further comprise peeling the birefringent layer from the heat shrinkable film after the heat shrinking step.

In another aspect, the present invention provides a heat shrinkable film; And a birefringent layer formed on at least one surface of the heat shrinkable film and satisfying the following formula (1), wherein the birefringent layer is formed by directly applying a birefringent material on a release film to form a birefringent layer, And the birefringent layer is transferred onto the film.

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

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

In another aspect, the present invention provides an optical film produced by the above production method and satisfying the following formulas (5) to (7).

Formula (5): 150 nm? R _in ? 350 nm

(6): 50nm? _Rth ? 250nm

Equation (7): 0.1? Nz? 1

In the formulas (5) to (7), R _in is the retardation value in the plane direction of the film measured at a wavelength of 550 nm, R _th is the retardation value in the thickness direction of the film measured at a wavelength of 550 nm, (R _th / R _in ) of the retardation value in the thickness direction to the retardation value in one direction.

The present invention also provides a polarizing plate and a liquid crystal display device including the optical film.

In addition, the solution of the above-mentioned problems does not list all the features of the present invention. The various features of the present invention and the advantages and effects thereof will be more fully understood by reference to the following specific embodiments.

The optical film produced by the production method of the present invention can realize a retardation property effectively having a refractive index distribution of n _x > n _z > n _y even in a single film, and can be manufactured in a thin shape, Simple.

Meanwhile, the method of the present invention forms a birefringent layer on a heat shrinkable film by applying a birefringent material on a release film to form a birefringent layer, and then transferring the birefringent layer to a heat shrinkable film. It is possible to prevent the deformation of the heat shrinkable film due to the heat shrinkable film, and as a result, the optical properties and appearance of the produced film are excellent compared with the case of forming the birefringent layer by applying the birefringent material directly on the heat shrinkable film.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing an exemplary manufacturing method of the present invention. FIG.
Fig. 2 is a view showing an exemplary result of heat shrinkage of the laminate of the present invention. Fig.

First, terms used in this specification are defined.

(1) where n _x is the refractive index in the direction in which the refractive index in the plane direction is the maximum (that is, the slow axis direction), and n _y is the refractive index in the direction perpendicular to the slow axis in the plane direction , and n _z means the refractive index in the thickness direction. The n _x , n _y , and n _z are measured in light having a wavelength of 550 nm. Meanwhile, n _{x ,} n _{y , and} n _z can be measured by a well-known method well known in the art. For example, measurement can be performed using prism coupler equipment (SPA-3DR manufactured by SAIRON TECHNOLOGY) Do.

(2) R _in means a retardation value in the plane direction in the light having a wavelength of 550 nm, and is obtained by the 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 represents the thickness. On the other hand, _in the R it can be measured by a known method known in the art and, for example, can be measured using the equipment of Axoscan Axomatrics社.

(3) R _th means the retardation value in the thickness direction in the light having the wavelength of 550 nm, and is obtained by the 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 represents the thickness. On the other hand, the R _th can be determined by well-known methods known in the art and, for example, can be measured using the equipment of Axoscan Axomatrics社.

(4) In the present specification, the pressure-sensitive adhesive means the following properties.

- It is a semi-solid substance with high viscosity and low elasticity.

- Combine with the adherend by applying pressure.

- The state does not change during the coupling process.

- It is a type of wide adhesive, which is called a pressure-sensitive adhesive (PSA) because it exhibits an adhesive force after being interposed between adherends.

(5) In the present specification, an adhesive is a concept distinct from the above-mentioned pressure-sensitive adhesive, meaning that it has the following properties.

- When the composition is applied to an adherend, it is sufficiently wetted by the adherend to increase the area of adhesion, and it is cured by irradiation with active energy ray or the like or is dried do.

- In the bonding process, the state irreversibly changes from a liquid phase to a solid phase.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. The shape and size of elements in the drawings may be exaggerated for clarity.

1. Manufacturing method of optical film

The inventors of the present invention have a case in which a result of extensive studies to achieve the foregoing object, after forming the birefringent layer on a heat shrinkable film high-temperature stretching at the same time, n _x> n _z> n _y refractive index distribution in a relatively simple way And it is possible to produce an optical film having a very thin thickness.

However, the inventors of the present invention have found that when a birefringent material is directly applied on a heat shrinkable film to form a birefringent layer, it is produced by erosion of a heat shrinkable film by a solvent and deformation of a heat shrinkable film generated in a solvent drying process It has been found out that the optical properties and appearance of the optical film become poor. As a result of repeated studies to solve this problem, after a birefringent material is applied on the release film to form a birefringent layer, the birefringent layer is thermally shrinkable It has been found that when transferring onto a film, the above problems can also be solved.

More specifically, the method for producing an optical film of the present invention comprises: (a) directly applying a birefringent material on a release film to form a birefringent layer; (b) transferring the birefringent layer onto a heat shrinkable film to form a laminate; And (c) heat shrinking the laminate.

At this time, in the method for producing an optical film of the present invention, the birefringent layer satisfies the following formula (1) by the heat shrinkage step. That is, the birefringent layer laminated with the heat shrinkable film shrinks forcefully in the direction perpendicular to the stretching direction during the hot stretching process due to the heat shrinkable film, and as a result, the refractive index in the direction perpendicular to the stretching direction is smaller than the refractive index in the thickness direction is the expression, is finally satisfies _{n x> n z> n y} . When the birefringent layer finally satisfies n _x > n _z > n _y , it can be very useful as an IPS mode retardation film.

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

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

On the other hand, it is more preferable that the production method of the optical film of the present invention satisfies the following formula (2) by the heat shrinkage step. In this way, when the birefringent layer shrinks at a substantially same magnification as the heat shrinkable film in the laminated state, as shown in the following example of FIG. 2 (a), the birefringent layer, which is a precursor of the finally produced optical film, Can be sufficiently shrunk, and it becomes possible to manufacture an optical film of very high quality. Alternatively, when the difference between the shrinkage ratio of the birefringent layer and the shrinkage percentage of the heat shrinkable film in the laminated state is large, as shown in the following FIG. 2 (b), the birefringence layer Can not be sufficiently shrunk, it is difficult to manufacture such an optical film having excellent quality. More preferably, the difference between the shrinkage ratio in the direction perpendicular to the stretching direction of the heat shrinkable film in the laminated state and the shrinkage rate in the direction perpendicular to the stretching direction of the birefringent layer in the laminated state is 0% to 3%, 0% 2%, or 0 to 1%. On the other hand, the shrinkage ratio in the direction perpendicular to the stretching direction in the following laminate state can be measured by a well-known method well known in the art. For example, before the laminate is formed, both the birefringent layer and the heat shrinkable film It is possible to measure by spotting the points on the one surface at intervals of 1 cm, laminating them, peeling after heat shrinkage, and then measuring the distance between the points.

(2): 0%? S ₂ - S ₁ ? 5%

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

On the other hand, it is more preferable that the production method of the optical film of the present invention satisfies the following formulas (3) and (4) by the heat shrinkage step. When the adhesive force between the birefringent layer and the heat shrinkable film before heat shrinking has an adhesive force of about the following range, there is an advantage that peeling can not easily occur in the heat shrinking step. At the same time, If it has an adhesive strength of about the following range, there is an advantage that it can be easily peeled off without damaging the film during peeling after heat shrinkage. More preferably, the adhesive force between the birefringent layer and the heat shrinkable film before heat shrinkage may be about 0.10 N / 2 cm to 0.50 N / 2 cm or about 0.15 N / 2 cm to 0.30 N / 2 cm, The adhesive force may be about 0.05 N / 2 cm to about 0.30 N / 2 cm or about 0.10 N / 2 cm to about 0.15 N / 2 cm. The following adhesive strength can be measured by a well-known method well known in the art. For example, it can be measured using a Texture Analyzer (Model: TA-XT Plus) equipment of Stable Micro Systems.

(3): 0.10 N / 2 cm? P _a ? 1.0 N / 2 cm

(4): 0.01 N / 2 cm? P _b ? 0.50 N / 2 cm

In the formula (3) and (4), P _a is the adhesive strength of the heat shrink around the birefringent layer and a heat shrinkable film, P _b is the adhesive strength of the double refraction layer and a heat shrinkable film after heat shrinkage.

(a) Birefringent layer  Forming step

First, a birefringent material is directly applied on a release film to form a birefringent layer. The method of applying the birefringent material is not particularly limited and may be performed by a method well known in the art. For example, a composition for forming a birefringent layer containing a birefringent material and a solvent may be formed by a microgravure coating method, a comma coating method, a bar coating method, a roller coating method, a spin coating method, a printing method, a dip coating method, Coating method, blade coating method, gravure printing method, and the like, and then drying it.

At this time, the release film is not particularly limited, and a release film generally used in the art can be used. For example, the release film may be a polyethylene terephthalate film, a polypropylene film, a polyethylene film, a polyimide film, or the like, but is not limited thereto. On the other hand, the release film may be formed with a coating layer containing silica in order to impart excellent slipperiness to at least one side of the release film, and the composition of the coating layer and the like can be applied without any particular limitations as long as they are generally used in the related art.

Next, as the birefringent material, a positive birefringent material or a negative birefringent material commonly used in the related art can be used without any particular limitation. In this case, the positive birefringent material is a material that exhibits a maximum refractive index in the stretching direction And the negative birefringent material means a material exhibiting a maximum refractive index in a direction perpendicular to the stretching direction.

More specifically, the birefringent materials include, but are not limited to, for example, birefringent materials such as polyamide based resins, polyimide based resins, polycarbonate based resins, polyarylate based resins, and cyclic olefin based resins Materials, and negative birefringent materials such as polyvinylcarbazole, polyvinylnaphthalene, and styrenic resins. These materials may be used singly or in combination.

At this time, the polyamide-based resin is also a polyamide-based resin well-known in the art, and can be used without any particular limitation. Among them, from the viewpoint of having particularly high birefringence characteristics, Aromatic rings or aliphatic rings can be preferably used. At this time, the aromatic ring is preferably a benzene ring, and the aliphatic ring is preferably a cyclohexane ring. More specifically, for example, although not limited thereto, Evolik CX9704, Arkema G350, G830 and the like can be used as the above-mentioned polyamide resin.

The polyimide resin may be a polyimide resin well known in the art without any particular limitation. For example, the polyimide resin may be polyimide, polyetherimide, etc. Can be preferably used. However, it is not particularly limited. Among them, those having at least one aromatic ring or aliphatic ring in the main chain can be preferably used, particularly in view of having high positive birefringence characteristics. More specifically, examples of the polyimide-based resin include Sabic Ultem 1000 and XTEM VH1003.

The polycarbonate resin is not particularly limited as long as it is a polycarbonate resin well-known in the art. Among them, from the viewpoint of having a particularly high positive retardation, it is preferable that at least one Aromatic rings or aliphatic rings can be preferably used. The aromatic ring may be a benzene ring, and the aliphatic ring may be a non-aromatic monocyclic, bicyclic or tricyclic ring having 4 to 14, 4 to 10, or 4 to 8 ring atoms Hydrocarbon sites are preferred. The ring atoms may contain oxygen as well as carbon atoms. More specifically, for example, but not limited to, LUPOY DVD 1080, LUPOY PC 1300, etc., available from LG Chemical Co., Ltd. can be used as the polycarbonate resin.

The cyclic olefin-based resin may also be a cyclic olefin polymer (COC), a cycloolefin copolymer (COC), a cycloolefin copolymer ) Can be preferably used. More specifically, for example, the cyclic olefin-based resin may be Zeon zeonor, TOPAS 6013F04, Mitsui's Apel, or the like.

In addition, the polyarylate-based resin may be a polyarylate-based resin well-known in the art without any particular limitation. For example, the polyarylate-based resin may include a bisphenol A derivative and a terephthalic acid derivative Polyarylate and the like can be preferably used. More specifically, U-polymer AX-1500W or U-100 manufactured by UNITIKA, Inc. may be used as the polyarylate resin.

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

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

The styrenic resin may be used without particular limitation as long as it contains a styrenic monomer as a main component. Examples of the styrenic monomer include, but are not limited to, styrene,? -Methylstyrene, etc. These may be used alone or in combination. If necessary, an acrylic monomer, a maleic anhydride monomer, a maleimide monomer, an acrylonitrile monomer, or the like may be used together with the styrene monomer, in addition to the styrene monomer, if necessary. Further, the styrene type resin may be such that the styrene type resin is blended with another resin such as an acrylic resin.

It is more preferable that the birefringent material is a positive birefringent material. Definition In a birefringent material, a maximum refractive index is expressed in a stretching direction. When a heat shrinkable film is used in a high temperature stretching process to forcibly heat shrink in a direction perpendicular to the stretching direction, n _x > n _z > n _y There is an advantage that it can be implemented more easily.

Next, the solvent can be used without particular limitation as long as it can dissolve the birefringent material, and can be appropriately determined according to the birefringent material to be used. Examples of the solvent include, but are not limited to, methylene chloride, chloroform, tetrahydrofuran (THF), 1,3-dioxane, cyclopentanone, N-methylpyrrolidone (NMP) Alcohols such as formamide (DMF), dimethylacetamide (DMAc), ethanol and methanol, and water. These solvents may be used alone or in combination of two or more. The drying conditions of the solvent and the like are not particularly limited. For example, the drying can be carried out by adjusting the temperature and time using hot air or an IR heater.

On the other hand, the concentration of the birefringent material contained in the birefringent layer forming composition is preferably 5 to 50 wt%, and may be, for example, 10 to 30 wt%. When the concentration is too low, coating with a uniform thickness is easy, but it may be difficult to form the coating layer with sufficient thickness. When the concentration is too high, it may be formed with sufficient thickness when it is too high, Also, the drying time may be too long.

On the other hand, the glass transition temperature of the birefringent layer is preferably 20 ° C or higher, more preferably 20 ° C to 100 ° C or 30 ° C to 80 ° C, more than the glass transition temperature of the heat shrinkable film described later. When the glass transition temperature is different, the heat shrinkable film is strongly shrunk in the high temperature stretching process, and the birefringent layer is relatively hard in the state of the polymer, so that the shrinkage is not strong in itself. At this time, the birefringent layer is forcibly contracted by the heat shrinkable film which is strongly contracted, and as a result, the polymer is strongly oriented, and thus a high retardation can be exhibited. The method of measuring the glass transition temperature is not particularly limited, and for example, the glass transition temperature can be measured by a differential scanning calorimeter (DSC). For example, in the case of using a differential scanning calorimeter (DSC), when a sample of about 10 mg is sealed in a dedicated pan and heated at a constant temperature, the amount of endothermic heat The transition temperature can be measured.

(b) Birefringent layer  Transfer stage ( The laminate  Forming step)

Next, when a birefringent layer is formed on the release film, the birefringent layer is transferred to a heat shrinkable film to form a laminate. At this time, the method of transferring the birefringent layer is not particularly limited, and for example, the birefringent layer can be transferred onto the heat shrinkable film using a pressure-sensitive adhesive or an adhesive. More specifically, after forming a pressure-sensitive adhesive or an adhesive layer on a heat shrinkable film, the birefringent layer may be laminated via the pressure-sensitive adhesive or adhesive layer, and the release film may be peeled off.

At this time, if the heat shrinkable film usable in the present invention has heat shrinkability greater than that of the birefringent layer, a known resin film can be used without any 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 Polyvinyl chloride resins, polyvinyl chloride resins, polyvinyl chloride resins, cellulose resins, polyether sulfone resins, polysulfone resins, polyacetate resins, polyarylate resins, and polyvinyl alcohol resins. However, the shrinkage ratio in the direction perpendicular to the stretching direction measured in the single film state under the same heat shrinkage condition must be larger than that of the birefringent layer, for example, about 10% or more. On the other hand, the shrinkage percentage can be measured by a well-known method well known in the art. For example, the film may be spotted at 1 cm intervals, then shrink the film using Zwick Universe Testing Machine (UTM) equipment and measure the distance of the point after shrinkage.

On the other hand, the heat shrinkable film is preferably, but not limited to, a polyester resin, particularly polyethylene terephthalate. Polyethylene terephthalate is not only excellent in price competitiveness but also has excellent heat shrinkability during high temperature stretching due to its low glass transition temperature.

On the other hand, the heat shrinkable film is preferably a film which is uniaxially stretched in the width direction (TD) in order to effectively shrink the birefringent layer. At this time, the present invention can use a film that is uniaxially stretched in the width direction (TD) as a commercially available heat shrinkable film, or a non-stretched polymer film having a shrinkage property on the market, Can be used for uniaxial stretching.

On the other hand, the thickness of the heat shrinkable film is preferably 10 to 100 탆, more preferably 20 to 80 탆. In this case, the birefringent layer can be more effectively shrunk.

Next, the pressure-sensitive adhesive or adhesive for transferring the birefringent layer onto the heat shrinkable film is not particularly limited, and a pressure-sensitive adhesive or an adhesive well-known in the art can be used. However, according to the study of the inventors of the present invention, when a pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive is used, the pressure-sensitive adhesive residue caused by the pressure-sensitive adhesive causes the productivity to be lowered, and the two layers adhered by the pressure- So that the birefringent layer can not be sufficiently shrunk. Further, in the case of using an aqueous adhesive, for example, a polyvinyl alcohol-based water-based adhesive, among the adhesives, bubbles are generated in the film after peeling off by moisture. In contrast, when the active energy ray-curable adhesive is used, the above-mentioned problems do not occur.

On the other hand, the active energy ray curable adhesive that can be used in the present invention is not particularly limited, and various active energy ray curable adhesives having the above-described characteristics can be selected for the birefringent layer and the heat shrinkable film to be selected. That is, not only the above-mentioned formula (1) but also preferably the above-described formula (2) is also satisfied, and more preferably, the formulas (3) and (4) An active energy ray-curable adhesive can be selected and used.

Examples of the active energy ray-curable adhesive generally used in the art include optical radical polymerization such as (meth) acrylate radical curing composition, ene / thiol radical curing composition, and unsaturated polyester radical curing composition , A composition using a cationic photopolymerization reaction such as an epoxy-based cationic curable composition, an oxetane-based cationic curable composition, an epoxy / oxetane-based cationic curable composition, and a vinyl ether-based cationic curable composition.

More specifically, for example, the composition using the photo-radical polymerization reaction may include, but is not limited to, a first compound represented by the following formula (1), a second compound comprising at least one carboxyl group, and a radical initiator Based on the total weight of the composition.

[Chemical Formula 1]

In the above formula (1), R ₁ represents an ester group or an ether group; R ₂ is C _{1 ~ 10} alkyl group, a C _{4 ~ 10,} and a cycloalkyl group, or a combination thereof, wherein R ₂ has at least one hydroxy substituent in the molecule; R ₃ is hydrogen, or a substituted or unsubstituted C _{1 ~ 10} alkyl group; On the other hand, the hydroxy group may be substituted at any position in the alkyl group or the cycloalkyl group. For example, the hydroxy group may be at the terminal of the alkyl group or may be in the middle of the alkyl group. Meanwhile, the remaining hydrogen atoms contained in the alkyl group or the cycloalkyl group may be substituted with any substituent.

At this time, the first compound is a component for realizing an adhesive force, and various compounds represented by Formula 1 may be used. For example, the first compound may be at least one compound selected from compounds represented by the following formulas (2) to (11), though not limited thereto.

(2)

(3)

[Chemical Formula 4]

[Chemical Formula 5]

[Chemical Formula 6]

(7)

[Chemical Formula 8]

[Chemical Formula 9]

[Chemical formula 10]

(11)

Further, the second compound is for improving the heat resistance and the viscosity property of the composition, and includes at least one carboxyl group. More specifically, the second compound may be at least one selected from the group consisting of compounds represented by the following formulas (12) to (26).

[Chemical Formula 12]

[Chemical Formula 13]

[Chemical Formula 14]

또는

이고, p는 1 내지 5의 정수임)(Wherein R 'is

or

And p is an integer of 1 to 5)

[Chemical Formula 15]

[Chemical Formula 16]

[Chemical Formula 17]

[Chemical Formula 18]

[Chemical Formula 19]

[Chemical Formula 20]

[Chemical Formula 21]

[Chemical Formula 22]

(23)

≪ EMI ID =

(25)

(26)

In addition, the radical initiator contained in the radical curable composition is used for promoting radical polymerization to improve the curing rate. As the radical initiator, radical initiators generally used in the art can be used without particular limitation . For example, phosphine oxide, phenyl bis (2,4,6-trimethyl benzoyl), and the like can be preferably used, though not limited thereto .

Meanwhile, the radically curable composition may further contain an acrylic monomer containing a cyclic structure having 7 to 20 carbon atoms, preferably 7 to 15 carbon atoms, as a third compound for viscosity control. More specifically, the third compound is selected from, for example, isobornyl (meth) acrylate, norbornyl (meth) acrylate, dicyclopentanyl (meth) A group consisting of dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate and 1-adamantyl- (meth) acrylate , But the present invention is not limited thereto.

More preferably, the radical curable composition comprises 40 to 80 parts by weight of the first compound, 15 to 50 parts by weight of the second compound, and 0.5 to 10 parts by weight of the radical initiator based on 100 parts by weight of the total composition .

More specifically, for example, but not limited to, the composition using the photo cationic polymerization, the first epoxy compound or homopolymer having a glass transition temperature of 120 캜 or higher of the homopolymer may have a glass transition temperature of 60 캜 or lower A second epoxy compound and a photo cationic polymerization initiator. The epoxy compound means a compound having at least one epoxy group in the molecule, preferably a compound having at least two epoxy groups in the molecule, and a compound in the form of a monomer, a polymer or a resin . Preferably, the epoxy compound of the present invention may be in the form of a resin.

The first epoxy compound may be an epoxy compound having a glass transition temperature of not lower than 120 ° C. and may be used without any particular limitation. For example, the first epoxy compound may be an alicyclic epoxy compound having a glass transition temperature of 120 ° C. or higher and / An aromatic epoxy may be used as the first epoxy compound of the present invention. Specific examples of the epoxy compound having a glass transition temperature of 120 ° C or higher of the homopolymer include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, vinylcyclohexene dioxide dicyclopentadiene dioxide, bis epoxycyclo Pentyl ether, bisphenol A-based epoxy compounds, and bisphenol F-based epoxy compounds. It is more preferable that the glass transition temperature of the homopolymer of the first epoxy compound is about 120 ° C to 200 ° C.

The second epoxy compound can be used without any particular limitation as long as it is an epoxy compound having a glass transition temperature of 60 占 폚 or less of the homopolymer. For example, the second epoxy compound may be an alicyclic epoxy compound, an aliphatic epoxy compound, or the like. At this time, as the alicyclic epoxy compound, a bifunctional epoxy compound, that is, a compound having two epoxy groups is preferably used, and it is more preferable to use a compound in which the two epoxy groups are alicyclic epoxy groups. But is not limited to. As the aliphatic epoxy compound, an epoxy compound having an aliphatic epoxy group rather than an alicyclic epoxy group can be exemplified. For example, polyglycidyl ethers of aliphatic polyhydric alcohols; Polyglycidyl ethers of alkylene oxide adducts of aliphatic polyhydric alcohols; Polyglycidyl ethers of polyester polyols of aliphatic polyhydric alcohols and aliphatic polyvalent carboxylic acids; Polyglycidyl ethers of aliphatic polyvalent carboxylic acids; Polyglycidyl ethers of polyester polycarboxylic acids of aliphatic polyhydric alcohols and aliphatic polyvalent carboxylic acids; Dimers, oligomers or polymers obtained by vinyl polymerization of glycidyl acrylate or glycidyl methacrylate; Or an oligomer or polymer obtained by vinyl polymerization of glycidyl acrylate or glycidyl methacrylate and other vinyl monomers, and preferably an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof polyglycidyl Ethers may be used, but are not limited thereto.

Preferably, the second epoxy compound of the present invention may contain at least one glycidyl ether group, and examples thereof include 1,4-cyclohexanedimethanol diglycidyl ether, 1,4-butanediol di Hexyldiol diglycidyl ether, neopentyldiglycidyl ether, resorcinol diglycidyl ether, diethylene glycol di glycidyl ether, ethylene glycol di glycidyl ether, 1,6-hexanediol diglycidyl ether, One selected from the group consisting of trimethylolpropane triglycidyl ether, n-butyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and o-cresyl glycidyl ether. Or more can be used as the second epoxy compound of the present invention.

On the other hand, the second epoxy compound preferably has a glass transition temperature of the homopolymer of about 0 캜 to 60 캜

It is particularly preferable to use a combination of a first epoxy compound containing at least one epoxidized aliphatic ring group and a second epoxy compound containing at least one glycidyl ether group as the epoxy compound. When such a combination of the first epoxy compound and the second epoxy compound is used, it has been found that not only the low viscosity and the adhesive strength are satisfied but also the thermal shock property of the polarizing plate is improved.

Meanwhile, the second epoxy compound is preferably contained in an amount of 30 to 100 parts by weight based on 100 parts by weight of the first epoxy compound. When the content of the second epoxy compound is more than 100 parts by weight, the glass transition temperature of the whole composition is lowered to lower the heat resistance. If the content is less than 30 parts by weight, the adhesive strength may be lowered.

More preferably, the weight ratio of the first epoxy compound to the second epoxy compound is about 1: 1 to 3: 1, more preferably 1: 1 to 2: 1, An epoxy compound and a second epoxy compound may be mixed and used in a weight ratio of 1: 1. When the weight ratio of the first epoxy compound and the second epoxy compound is in the above range, the most preferable physical properties in terms of the glass transition temperature and the adhesion can be obtained.

On the other hand, the cationic photopolymerization initiator is a compound which produces a cationic species or Lewis acid by irradiation with an active energy ray. Examples of the cationic photopolymerization initiator include onium salts such as aromatic diazonium salts, aromatic iodine aluminum salts and aromatic sulfonium salts, Iron-arene complex, and the like, but the present invention is not limited thereto. On the other hand, the content of the cationic photopolymerization initiator is about 0.5 to 20 parts by weight, preferably about 0.5 to 15 parts by weight, more preferably about 0.5 to 10 parts by weight based on 100 parts by weight of the first epoxy compound .

The cationically curable composition may further contain 100 to 400 parts by weight of an oxetane compound having at least one oxetanyl group in the molecule, if necessary. When an oxetane compound is used, the viscosity of the composition can be lowered to make the resin layer thinner after curing.

On the other hand, the oxetane compound is not particularly limited as long as it has at least one oxetanyl group in the molecule, and various oxetane compounds well known in the art can be used. Examples of the oxetane compound of the present invention include 3-ethyl-3 - [(3-ethyloxetan-3-yl) methoxymethyl] oxetane, 1,4-bis [ 3-yl) methoxymethyl] benzene, 1,4-bis [(3-ethyloxetane-3-yl) methoxy] benzene, 1,3- ) Methoxy] benzene, 1,2-bis [(3-ethyloxetan-3-yl) methoxy] benzene, 4,4'- Phenyl, 3,3 ', 5,5'-tetramethyl-4,4'-bis [3-ethyloxetane-3-yl] 3-yl) methoxy] naphthalene, bis [4 - {(3-ethyloxetan-3-yl) ) Methoxy} phenyl] methane, bis [2 - {(3-ethyloxetane-3-yl) methoxy} phenyl] methane, 2,2- ) Methoxy} phenyl] propane, an etherified product of 3-chloromethyl-3-ethyloxetane of novolak type phenol-formaldehyde resin, 3 (4) Oxetane- (3-ethyloxetan-3-yl) methoxymethyl] norbornane, 1,1,1,3,3-tetramethyl- Methoxy methyl] propane, 1-butoxy-2,2-bis [(3-ethyloxetan-3-yl) methoxymethyl] , [2- (3-ethyloxetan-3-yl) methoxy} ethylthio] ethane, bis [{4- , And 1,6-bis [(3-ethyloxetan-3-yl) methoxy] -2,2,3,3,4,4,5,5-octafluorohexane. On the other hand, the content of the oxetane compound is preferably 100 to 400 parts by weight, more preferably 150 to 300 parts by weight based on 100 parts by weight of the first epoxy compound.

On the other hand, when two oxetanyl groups are used as the oxetane compound, it is effective to increase the glass transition temperature of the resin layer after curing, and it is advantageous in the case of having one oxetanyl group.

Meanwhile, the active energy ray-curable adhesive used in the present invention preferably has a glass transition temperature after curing of 70 ° C or higher, for example, about 70 ° C to 150 ° C or about 80 ° C to 120 ° C. In this case, since it can have sufficient heat resistance, it can have a sufficient adhesive force in the high temperature stretching process for heat shrinkage.

On the other hand, in the case of forming a laminate through such an active energy ray-curable adhesive, there is no particular limitation on the method of forming the laminate. For example, an active energy ray-curable adhesive composition may be applied between the birefringent layer and the heat- And then curing the active energy ray-curable adhesive composition by irradiating active energy rays to the active energy ray curable adhesive composition.

At this time, the method of applying the active energy ray-curable adhesive composition between the birefringent layer and the heat shrinkable film is not particularly limited. For example, the active energy ray-curable adhesive composition is flowed in a dripping manner on the birefringent layer or the heat shrinkable film , A method of forming a sufficient amount of banks (BANK) can be used.

Also, the method of laminating is not particularly limited. For example, a lamination process in which the birefringent layer and the heat shrinkable film are adhered to each other and passes between two rolls rotating in opposite directions can be used.

Also, the method for curing the active energy ray-curable adhesive composition is not particularly limited, and can be performed by, for example, a method of curing through irradiation of active energy ray such as ultraviolet ray, visible ray, electron ray or X-ray. At this time, the method of irradiation is not particularly limited. For example, ultraviolet light having a light intensity of about 500 mJ / cm ² is irradiated using an ultraviolet irradiator (LH10 Fusion D bulb) under conditions of about 2000 mW / cm ² and a speed of about 20 m / min And the like.

(c) Heat shrinkage process

When the laminate is formed in the same manner as described above, the laminate satisfies the formula (1), preferably satisfies the formula (2), and more preferably satisfies the formulas (3) and ) Is further heat-shrunk. At this time, the heat shrinking step is preferably performed by a method of uniaxially stretching the laminate in the longitudinal direction (MD) using a known drawing machine or the like. For example, uniaxial stretching can be performed by pulling the laminate in the longitudinal direction (MD) using UTM equipment while holding both ends of the laminate in the longitudinal direction (MD) in an oven at high temperature. The birefringent layer used in the present invention is preferably a positive birefringent layer in which the maximum refractive index is expressed along the stretching direction. In this case, the longitudinal direction MD becomes the x direction (the direction in which the refractive index becomes maximum) TD) in the y direction (direction perpendicular to the direction in which the refractive index becomes maximum). At this time, there is shrink laminated body in the y direction by the high-temperature stretching, in particular the birefringent layer is relatively contractions better occurs abruptly contracted bar is laminated and heat shrinkable film with, as a result, n _y is more than n _z becomes smaller, n _x> n _z & gt _; n < _y & gt _; can be effectively implemented.

The stretching is preferably performed at a temperature of (Tg) to (Tg + 100 ° C), for example, from (Tg + 20 ° C) to (Tg + 80 < 0 > C). A high retardation can be realized only when the stretching temperature satisfies the above range. Specifically, at such a stretching temperature, the birefringent layer attempts to shrink easily, but the heat shrinkable film tends to shrink very strongly. At this time, the birefringent layer adheres to the resin layer. In the stretching process, And, as a result, can have a high phase difference.

In addition, the stretching is preferably performed at a draw magnification of 1.1 to 3.0 times, for example, at a draw magnification of 1.1 to 2.5 times or 1.1 to 2.0 times. When the stretching at such a stretching magnification is performed, the birefringent layer can be contracted in the width direction as much as desired by the present invention, and the present invention can realize a high retardation as desired.

On the other hand, the thickness of the birefringent layer after heat shrinking the laminate is preferably 30 占 퐉 or less, more preferably 1 占 퐉 to 20 占 퐉 or 1 占 퐉 to 15 占 퐉. If the thickness of the birefringent layer after stretching is larger than the above range, it is not possible to reduce the thickness of the polarizing plate or the display device including the polarizing plate or the display device, and it may deviate from the range of the retardation value pursued by the present invention.

(d) Other processes

Meanwhile, the manufacturing method of the present invention may further include a step of uniaxially stretching the heat shrinkable film in the transverse direction (TD) using a tenter stretcher or the like before the step of forming the laminate. This is to use the heat shrinkable film in the uniaxially stretched state in the width direction (TD). As described above, when the heat shrinkable film is a film uniaxially stretched in the width direction (TD) In order to effectively shrink it. The stretching may be performed at a stretching magnification of 1.5 to 5.0 times at a temperature of (Tg-20) DEG C to (Tg + 50) DEG C, where Tg is the glass transition temperature of the heat shrinkable film.

Meanwhile, the manufacturing method of the present invention may further include peeling the birefringent layer from the heat shrinkable film after the heat shrinking step. That is, peeling is preferable in order to use the birefringent layer as a single retardation film. On the other hand, the peeling step may proceed at room temperature, and the peeling method is not particularly limited.

2. Optical member, optical film, polarizing plate and liquid crystal display

The present invention also provides an optical member manufactured by the above manufacturing method. Specifically, the present invention relates to a heat shrinkable film; And a birefringent layer laminated on at least one surface of the heat shrinkable film, wherein the birefringent layer is formed by directly applying a birefringent material on a release film to form a birefringent layer, And the birefringent layer is transferred and laminated on the film. The material and the lamination method of the heat shrinkable film and the birefringent layer are the same as those described above, and the optical member preferably further satisfies the above formula (2), more preferably the formula (3) ) And (4).

The present invention also provides an optical film produced by the above-mentioned production method. At this time, the optical film of the present invention preferably satisfies at least one of the following formulas (5) to (7). In this case, it can be very useful as a retardation film for IPS mode. More preferably, the optical film is in the range of R _in 150nm to 300nm degree or 200nm to 300nm or so, the range of R _th is 70nm to 200nm extent or degree of 100nm to 200nm, the Nz value of 0.2 to 0.9 degree, 0.3 To about 0.7, or from about 0.4 to about 0.6.

Formula (5): 150 nm? R _in ? 350 nm

(6): 50nm? _Rth ? 250nm

Equation (7): 0.1? Nz? 1

In the formulas (5) to (7), R _in is the retardation value in the plane direction of the film measured at a wavelength of 550 nm, R _th is the retardation value in the thickness direction of the film measured at a wavelength of 550 nm, (R _th / R _in ) of the retardation value in the thickness direction to the retardation value in one direction.

The present invention also provides a polarizing plate comprising at least one or more optical films. In this case, the optical film according to the present invention may be directly attached to one side or both sides of the polarizer, or may be attached to a protective film of a polarizer having a protective film on both sides of the polarizer, and thus may be usefully used as a retardation film.

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

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

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

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

Manufacturing example  1 - release film

As the release film, a commercially available polyethylene terephthalate film (SKC SG31) was used.

Manufacturing example  2 - Heat shrinkable film

A polyethylene terephthalate stretched film (SK19 SP19H, TD uniaxially stretched, Tg = 76 deg. C) commercially available as a heat shrinkable film was used.

Manufacturing example  3 - Radical  Curable composition

Radical curable compositions were prepared for use as active energy ray curable adhesives. Specifically, the radical curable composition is prepared by dissolving 70% by weight of 2-hydroxyethyl acrylate, 10% by weight of itaconic acid, and 4,4 '- ((((propane-2,2-diylbis Bis (oxy)) bis (1- (methacryloyloxy) propane-3,2-diyl)) bis (oxy)) bis (4-oxobutanoic acid) , 3 parts by weight of a radical initiator phenyl bis (2,4,6-trimethylbenzoyl) -phosphine oxide and 5 parts by weight of a photo-acid generator, diphenyl (4-phenylthio) phenylsulfonium hexafluorophosphate . The glass transition temperature of the composition measured using a differential scanning calorimeter (DSC Mettler) was 82 ° C.

Example  One - PC  + For release film use

A solution (solvent 1,3-dioxolane) containing 15 wt% of polycarbonate (LUPOY DVD1080, manufactured by LIG Chemical Co., Ltd.) was coated on the release film to a thickness of 20 탆 using a bar coater to form a birefringent layer To prepare a release film. Next, after the radical curable composition is applied on the heat shrinkable film in a dropwise manner, the release film on which the birefringent layer is formed and the heat shrinkable film are laminated together so that the birefringent layer is attached to the heat shrinkable film, (Light Hammer, Fusion UV) under conditions of light quantity of 500 mJ / cm ² , intensity of 2000 mW / cm ² and speed of 20 m / min, and the release film was removed to prepare a laminate. Next, the laminate was uniaxially stretched by 25% in the MD direction in a 155 ° C oven using UTM equipment, and then the laminate was taken out at room temperature to separate the birefringent layer adhering to the heat shrinkable film. As a result, an optical film having a thickness of 21 mu m was finally obtained.

Example  2 - TPI  + For release film use

A solution (solvent 1,3-dioxolane) containing 13 wt% of a polyetherimide (Sabic Ultem 1000) on the release film was coated to a thickness of 3 탆 using a bar coater to obtain a release film having a birefringent layer . Next, after the radical curable composition is applied on the heat shrinkable film in a dropwise manner, the release film on which the birefringent layer is formed and the heat shrinkable film are laminated together so that the birefringent layer is attached to the heat shrinkable film, (Light Hammer, Fusion UV) under conditions of light quantity of 500 mJ / cm ² , intensity of 2000 mW / cm ² and speed of 20 m / min, and the release film was removed to prepare a laminate. Next, the laminate was uniaxially stretched by 18% in an MD direction in a 155 ° C oven using UTM equipment, and then the laminate was taken out at room temperature to separate the birefringent layer adhering to the heat shrinkable film. As a result, an optical film having a thickness of 5 탆 was finally obtained.

Comparative Example  - PC  In the case of direct application

A solution (solvent 1,3-dioxolane) containing 15 wt% of polycarbonate (LUPOY DVD1080, manufactured by LIG Chemical Co., Ltd.) was directly coated on the heat shrinkable film to a thickness of 20 μm using a bar coater to prepare a laminate Respectively. Next, the laminate was uniaxially stretched by 25% in the MD direction in a 155 ° C oven using UTM equipment, and then the laminate was taken out at room temperature to separate the birefringent layer adhering to the heat shrinkable film. As a result, an optical film having a thickness of 21 mu m was finally obtained.

Experimental Example  1 - Width Shrinkage ( S _One , S ₂ ) And adhesive strength P _a , P _b ) Measure

The width shrinkage ratio (S ₁ ) of the birefringent layer in the laminated state and the width shrinkage ratio (S ₂ ) of the heat shrinkable film in Examples 1 to 2 and Comparative Examples were measured and shown in Table 1 below. At this time, the width shrinkage ratio (S ₁ , S ₂ ) is obtained by taking dots at intervals of 1 cm on both surfaces of the laminate before heat shrinkage, that is, on the birefringent layer and the heat shrinkable film, then peeling off after heat shrinkage, Were measured by ashing method.

(P _a ) between the birefringent layer and the heat shrinkable film before shrinkage and the adhesive force (P _b ) between the birefringent layer and the heat shrinkable film after shrinkage were measured in Examples 1 to 2 and Comparative Examples, Respectively. In this case, the adhesive force (P _a, P _b) is the Texture Analyzer Stable Micro Systems社: was measured using a (model TA-XT Plus) equipment.

division S ₁ (%) S ₂ (%) P _a (N / 2 cm) P _b (N / 2 cm) Example 1 15 15 0.18 0.14 Example 2 50 50 0.15 0.12 Comparative Example 15 15 0.20 0.58

As shown in Table 1, in the case of the laminate produced in Examples 1 and 2 of the present invention, the width shrinkage ratio (S ₁ , S ₂ ) of the birefringent layer and the heat shrinkable film satisfies the formula (2) In addition, before adhesion contraction (P _a) and after shrinkage the adhesive force (P _b) satisfies the formula (3) and (4). As a result, in the case of the laminate produced in Examples 1 and 3 of the present invention, peeling was not easily caused in the heat shrinking process, and as a result, as shown in FIG. 2 (a) It can be seen that the birefringent layer has contracted substantially the same as the heat shrinkable film. Further, it can be seen that peeling after heat shrinking is easy.

On the other hand, in the comparative example, when the birefringent layer was directly coated on the heat shrinkable film, the width shrinkage ratio (S ₁ , S ₂ ) of the birefringent layer and the heat shrinkable film satisfied the formula (2) P _b ) does not satisfy the above formula (4). That is, it can be seen that peeling after heat shrinkage is not easy.

Experimental Example  2 - Phase difference  Characterization

The retardation characteristics of the optical films prepared in Examples 1 to 2 and Comparative Examples were measured and are shown in Table 2 below. n _x , n _y , and n _z were measured using prism coupler equipment (SPA-3DR, SAIRON TECHNOLOGY), and the retardation values were measured using Axoscan's Axoscan measuring equipment.

division Thickness (㎛) n _x / n _y / n _z R _in (nm) R _th (nm) Nz Example 1 23 1.590 / 1.583 / 1.586 150 72 0.48 Example 2 5 1.634 / 1.583 / 1.613 254 149 0.58 Comparative Example 21 1.591 / 1.583 / 1.585 164 42 0.37

As can be seen from Table 2, the optical films prepared in Examples 1 and 2 of the present invention have a phase difference value very suitable for use as a retardation film in an IPS mode liquid crystal display.

However, the optical film is shown a liquid crystal for was the erosion is a heat shrinkable film by the organic solvent used in forming the birefringent layer, as a result, shrinkage force falling R _th expression of the optical film to be produced off the bar, IPS mode produced in Comparative Example It can be seen that the device has a somewhat inadequate phase difference value for use as a phase difference film.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be obvious to those of ordinary skill in the art.

1: release film
2: birefringent layer
3: Heat shrinkable film
W: Width
L: Length

Claims (15)

Applying a birefringent material on the release film to form a birefringent layer;
Transferring the birefringent layer onto a heat shrinkable film to form a laminate; And
And heat-shrinking the laminate so that the birefringent layer satisfies the following formula (1)
The glass transition temperature of the birefringent layer is 20 占 폚 to 100 占 폚 higher than the glass transition temperature of the heat shrinkable film,
Wherein the birefringent material is at least one positive birefringent material selected from the group consisting of a polyamide resin, a polyimide resin, a polyarylate resin, and a cyclic olefin resin; And at least one negative birefringent material selected from the group consisting of polyvinyl carbazole, polyvinyl carbazole, and polyvinyl naphthalene.
Equation (1): n _x > n _z > n _y
In the formula (1), n _x is the plane direction refractive index is the refractive index of the direction in which the maximum of the birefringent layer, n _y is a refractive index in the direction perpendicular to the n _x direction in the birefringent layer, n _z is a birefringent layer Refractive index in the thickness direction.
The method according to claim 1,
Wherein the thickness of the birefringent layer is not less than 1 占 퐉 and not more than 30 占 퐉 after the step of heat shrinking the laminate.
The method according to claim 1,
Wherein the step of forming the laminate is a step of transferring the birefringent layer onto a heat shrinkable film using a pressure sensitive adhesive or an adhesive.
The method of claim 3,
Wherein the step of forming the laminate is a step of transferring the birefringent layer onto a heat shrinkable film using an active energy ray curable adhesive.
The method according to claim 1,
Wherein the step of heat shrinking the laminate satisfies the following formula (2).
(2): 0%? S ₂ - S ₁ ? 5%
In the formula (2), S ₁ is a shrinkage ratio in the direction perpendicular to the stretching direction of the birefringent layer in the laminated state, and S ₂ is a shrinkage ratio in the direction perpendicular to the stretching direction of the heat shrinkable film in the laminated state .
The method according to claim 1,
Wherein the step of heat shrinking the laminate satisfies the following formulas (3) and (4).
(3): 0.10 N / 2 cm? P _a ? 1.0 N / 2 cm
(4): 0.01 N / 2 cm? P _b ? 0.5 N / 2 cm
In the above formulas (3) and (4), P _a is the adhesive strength between the birefringent layer and the heat shrinkable film before heat shrinkage, and P _b is the adhesive strength between the birefringent layer and the heat shrinkable film after heat shrinkage.
delete The method according to claim 1,
Wherein the heat shrinking step uniaxially stretches the laminate in the longitudinal direction (MD).
9. The method of claim 8,
Wherein the stretching is performed at a temperature of (Tg) to (Tg + 100 deg. C), where Tg is the glass transition temperature of the heat shrinkable film.
9. The method of claim 8,
Wherein the stretching is performed at a draw magnification of 1.1 to 3.0 times.
The method according to claim 1,
And peeling the birefringent layer from the heat shrinkable film after the heat shrinking step.
Heat shrinkable film; And a birefringent layer formed on at least one surface of the heat shrinkable film and satisfying the following formula (1)
Wherein the birefringent layer is formed by directly applying a birefringent material on a release film to form a birefringent layer and then transferring the birefringent layer onto a heat shrinkable film,
The glass transition temperature of the birefringent layer is 20 占 폚 to 100 占 폚 higher than the glass transition temperature of the heat shrinkable film,
Wherein the birefringent material is at least one positive birefringent material selected from the group consisting of a polyamide resin, a polyimide resin, a polyarylate resin, and a cyclic olefin resin; Or an optical member that is at least one negative birefringent material selected from the group consisting of polyvinylcarbazole, and polyvinylnaphthalene.
Equation (1): n _x > n _z > n _y
In the formula (1), n _x is the plane direction refractive index is the refractive index of the direction in which the maximum of the birefringent layer, n _y is a refractive index in the direction perpendicular to the n _x direction in the birefringent layer, n _z is a birefringent layer Refractive index in the thickness direction.
11. A process for producing a polyurethane foam, which is produced by the production method of any one of claims 1 to 6 and 8 to 11,
The optical film satisfies the following formulas (5) to (7).
Formula (5): 150 nm? R _in ? 350 nm
(6): 50nm? _Rth ? 250nm
Equation (7): 0.1? Nz? 1
In the formulas (5) to (7), R _in is the retardation value in the plane direction of the film measured at a wavelength of 550 nm, R _th is the retardation value in the thickness direction of the film measured at a wavelength of 550 nm, (R _th / R _in ) of the retardation value in the thickness direction to the retardation value in one direction.
14. A polarizing plate comprising the optical film of claim 13.
14. A liquid crystal display device comprising the optical film of claim 13.

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