KR20150137703A - Preparing method for the optical film, optical member 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 manufacturing method of an optical film comprising: a step of forming a layered body by bonding a heat constructing film on one or more areas of a birefringence film by a medium of an active energy way hardening resin layer; and a step of thermally constructing the layered body to satisfy the equation (1) (n_x > n_z > n_y) and the equation (2) (0% <= S_2 - S_1 <= 5%), an optical member and an optical film manufactured thereby, and a polarizing plate and a liquid crystal display device including the same. In the equation (1) (n_x > n_z > n_y), n_x is the refractive index in the direction in which a plane direction refractive index of the birefringence film becomes the biggest value. The n_y is the refractive index in a direction which is perpendicular to the n_x direction. The n_z is the refractive index of the thickness direction of the birefringence film. In the equation (2) (0% <= S_2 - S_1 <= 5%), S_1 is the construction rate of the direction which is perpendicular to the elongation direction of the birefringence film in a layered body state. The S_2 is the construction rate of the direction which is perpendicular to the elongation direction of the heat constructing film in a layered body state.

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 device, 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 continuously carried out. For example, a shrinkable film is attached to one side or both sides of a resin film through a known adhesive, And stretching the laminate to give a contracting force in a direction orthogonal to the stretching direction. However, the above-mentioned method using a pressure-sensitive adhesive, for example, an acrylic pressure-sensitive adhesive not only deteriorates the productivity due to the occurrence of adhesive residues by the pressure-sensitive adhesive, but also causes the two layers of the film to be easily peeled off during high temperature stretching for heat shrinkage, The resin film as a precursor film of the polymer can not be shrunk as desired. As a result, there is a problem that the quality of the optical film is significantly deteriorated due to poor orientation of the polymer.

In order to solve the above problems, there is a method for producing the above optical film by coating a coating layer capable of developing a retardation on a shrinkable film without using an acrylic pressure-sensitive adhesive, and then shrinking the film in a direction perpendicular to the stretching direction It has been proposed. However, when the coating layer is formed, the orientation of the polymer may not be desired in the process of phase transition from a liquid phase to a solid phase, and thus it is difficult to control the orientation property due to heat shrinkage, .

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above problems, and it is an object of the present invention to provide a novel n _x &gt; n _z > n _y , an optical member and an optical film manufactured using the same, a polarizing plate including the same, and a liquid crystal display device.

According to an aspect of the present invention, there is provided a method of manufacturing a birefringent film, comprising: forming a laminate by laminating a heat shrinkable film on at least one side of a birefringent film through an active energy ray-curable resin layer; And heat-shrinking the laminate so as to satisfy the following expressions (1) and (2).

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

(2): 0%? S ₂ - S ₁ ? 5%

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

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

At this time, it is more preferable that the step of heat shrinking the laminate further 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 ? 0.50 N / 2 cm

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

Meanwhile, in the step of forming the laminate, the active energy ray-curable composition is applied between the birefringent film and the heat-shrinkable film, followed by laminating the two films, and curing the active energy ray-curable composition by irradiating active energy rays It is preferable to carry out the method.

On the other hand, the active energy ray-curable composition may include a first compound represented by the following formula (1), a second compound containing at least one carboxyl group, and a radical initiator.

[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 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;

Alternatively, the active energy ray-curable composition may include a first epoxy compound having a glass transition temperature of 120 ° C or higher of the homopolymer, a second epoxy compound having a glass transition temperature of 60 ° C or lower of the homopolymer, and a photo cationic polymerization initiator.

On the other hand, the birefringent film is preferably a positive birefringent film.

The birefringent film is preferably an unstretched film.

On the other hand, it is preferable that the heat shrinkable film is a film uniaxially stretched in the width direction (TD).

On the other hand, the glass transition temperature of the birefringent film is preferably 20 ° C or more higher than the glass transition temperature of the heat shrinkable film.

On the other hand, the active energy ray-curable resin layer preferably has a glass transition temperature of 70 캜 or higher.

On the other hand, it is preferable that the length (L) of the laminate is 1.5 times or more as large as the width (W).

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

At this time, it is preferable that 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.

The stretching is preferably performed at a draw ratio of 1.1 to 3.0 times.

In another aspect, the invention relates to a birefringent film; And a heat shrinkable film laminated on at least one surface of the birefringent film through an active energy ray-curable resin layer, wherein the optical member satisfies the following expressions (1) and (2).

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

(2): 0%? S ₂ - S ₁ ? 5%

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

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

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? 1.0

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.

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, The color and the change of the sensation are less than those of the laminated film of two or more layers.

In addition, the production method of the present invention has an advantage in that the peeling is not easily caused even in the high-temperature stretching process, and therefore, the shrinkage of the birefringent film by the heat shrinkable film can be effectively performed, and the quality of the finally produced optical film is excellent .

In addition, the manufacturing method of the present invention is advantageous in that the orientation of the polymer is easier and the optical film can be manufactured in a large area, as compared with the case of forming the coating layer.

Fig. 1 (a) is a view showing an example of the result of heat shrinkage of the laminate according to Examples 1 to 3, Fig. 2 (b) is a view showing an example of a result of heat shrinkage of the laminate according to Comparative Example 3 to be.
Fig. 2 is a photograph showing the appearance of optical films prepared according to Example 1 and Comparative Example 4 in comparison.

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 ) x d. Here, n _x and n _y are the same as described above, and d represents the thickness of the film. 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 ) x d. Here, n _y and n _z are the same as described above, and d represents the thickness of the film. 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) A birefringent film refers to a film that exhibits a refractive index in a specific direction by stretching. At this time, when the maximum refractive index is expressed in the stretching direction, the birefringent film is specifically defined as a film having a maximum refractive index Is specifically referred to as a negative birefringent film.

(5) A heat shrinkable film means a film having greater heat shrinkability than the above-mentioned birefringent film, and more specifically, a shrinkage ratio in a direction perpendicular to the stretching direction measured in a single film state under the same heat shrinking condition, Or more than about 10%. 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.

(6) 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.

(7) In this specification, the active energy ray-curable resin layer means that the following properties are distinguished from the above-mentioned pressure-sensitive adhesives.

- When the composition is in a liquid state and has a low viscosity with fluidity, when it is applied to an adherend, the adhesion area is increased by wetting the adherend and cured by irradiation of active energy ray to bond with the adherend.

- Increase in active energy beam irradiation leads to curing through adhesive state.

- 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.

&Lt; Optical Film Manufacturing Method >

The method for producing an optical film of the present invention includes the steps of forming a laminate by laminating a heat shrinkable film on at least one surface of a birefringent film through an active energy ray curable resin layer and heat shrinking the laminate in a high temperature stretching process .

At this time, in the production method of the optical film of the present invention, the birefringent film satisfies the following formula (1) by the heat shrinkage step. That is, the birefringent film laminated with the heat shrinkable film by the active energy ray-curable resin layer shrinks forcefully in the direction perpendicular to the stretching direction during the high temperature stretching process due to the heat shrinkable film, Is expressed to be smaller than the refractive index in the thickness direction, and finally n _x > n _z > n _y is satisfied. When the birefringent film 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 birefringence, and the plane direction refractive index is the refractive index of the direction in which the maximum of the film, n _y is a refractive index in a direction perpendicular to a direction to the n _x direction in the birefringent film, n _z Is the refractive index in the thickness direction of the birefringent film.

In the method for producing an optical film of the present invention, the birefringent film and the heat shrinkable film satisfy the following formula (2) by the heat shrinkage step. When the birefringent film and the heat shrinkable film shrink at substantially the same magnification in the laminated state, the birefringent film as the precursor film of the finally produced optical film can be sufficiently shrunk, Film production becomes possible. 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 ratio in the direction perpendicular to the stretching direction of the birefringent film in the laminated state is about 0% to 3% or 0 To about 2%. 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 technical field. For example, both sides of the laminate, that is, the birefringent film and the heat shrinkable film Measurements can be made by spotting the points at 1 cm intervals, peeling after heat shrinkage, and then measuring the dot spacing of each film.

(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 film 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 adhesive force between the birefringent film and the heat shrinkable film satisfies the following formulas (3) and (4) by the heat shrinkage step of the production method of the optical film of the present invention. As described above, when the adhesive force between the birefringent film and the heat shrinkable film before heat shrinkage has an adhesive force of about the following range, there is an advantage that peeling is not easily caused in the heat shrinking stage. At the same time, When the adhesive force 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 strength between the birefringent film and the heat shrinkable film before heat shrinkage may be about 0.10 N / 2 cm to 0.50 N / 2 cm or 0.15 N / 2 cm to 0.30 N / 2 cm, The adhesive force of the shrinkable film 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 film and a heat shrinkable film, P _b is the adhesive force of the birefringent film and a heat shrinkable film after heat shrinkage.

On the other hand, the method for producing an optical film of the present invention satisfying the above-mentioned expressions (1) and (2) by the heat shrinkage step and preferably satisfying the expressions (3) and (4) The shrinkable film and the active energy ray-curable resin layer, the method of joining the two films, the heat shrinkage condition, and the like.

[Birefringent Film]

The birefringent film used in the present invention may be a positive birefringent film or a negative birefringent film which is generally used in the art as a precursor film of an optical film finally produced. For example, the above-mentioned birefringent film includes, but is not limited to, polyethylene terephthalate, polyamide, polyimide, polycarbonate, polyester, polyurethane, polypropylene, triacetylcellulose, polyamideimide, polyvinyl Those containing an alcohol, polyvinyl chloride, polyphenylene ether, polyarylate, polyaryl ether ketone, polyether ketone, polyester imide, polyfumaric acid ester, polyethersulfone, polyolefin and the like can be used. The negative birefringent film may include, but is not limited to, polymethyl methacrylate, polystyrene, and the like.

On the other hand, the birefringent film is more preferably a positive birefringent film. Definition In a birefringent film, a maximum refractive index is expressed in a stretching direction. When heat shrinkage is forced in a direction perpendicular to a stretching direction by using a heat shrinkable film in a high temperature stretching process, n _x > n _z > n _y There is an advantage that it can be implemented more easily.

The positive birefringent film preferably comprises a polycarbonate, a polyamide, a polyimide, or a polyamideimide including a benzene ring or an alicyclic ring in the main chain. In this case, since the retardation manifestation is excellent, it is possible to effectively realize a high retardation value even in a thin film thickness.

On the other hand, if the birefringent film can satisfy the relationship of n _x > n _z > n _y by the ultimate heat shrinkage treatment, it is possible to use a uniaxially or biaxially stretched film, It is preferable that the new film is the one in which the finally produced optical film satisfies n _x > n _z > n _y .

On the other hand, the thickness of the birefringent film is preferably 10 탆 to 60 탆, for example, 10 탆 to 40 탆 or 10 탆 to 30 탆. In the case of having such a thickness range, thinning can be achieved by drawing for later heat shrinkage, and the range of the retardation value added by the present invention can be effectively implemented.

[Heat shrinkable film]

The heat shrinkable film used in the present invention is a film for forcibly shrinking the birefringent film in a direction perpendicular to the stretching direction so that the birefringent film can satisfy the relationship of n _x > n _z > n _y , And the heat shrinkable film usable in the present invention is not particularly limited as long as it has heat shrinkability greater than that of the birefringent film. For example, but not limited to, polymethyl methacrylate, polyethylene terephthalate, polyamide, polyimide, polycarbonate, polyester, polyurethane, polypropylene, triacetylcellulose, polystyrene, polyamideimide, polyvinyl But it is preferable that the shrinkage ratio in the direction perpendicular to the stretching direction measured in a single film state under the same heat shrinkage condition as described above is higher than the shrinkage ratio in the direction perpendicular to the stretching direction, At least about 10% greater than the sex film.

On the other hand, the heat shrinkable film is not limited thereto, but it preferably contains 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 has been uniaxially stretched in the width direction (TD) in order to effectively shrink the birefringent film. 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 film can be more effectively shrunk.

The glass transition temperature of the birefringent film is preferably 20 ° C or more, more preferably 20 ° C to 100 ° C or 30 ° C to 80 ° C, more than the glass transition temperature of the heat shrinkable film. When the glass transition temperature of the two polymer films is different, the heat shrinkable film relatively shrinks in the high temperature stretching process, and the birefringent film has a relatively high state of the polymer, do. At this time, the birefringent film is forced to shrink more strongly due to the heat shrinkable film which is strongly contracted, and as a result, the polymer is strongly oriented, so that 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.

[Active Energy ray curable resin layer]

The present invention uses an active energy ray-curable resin layer as a means for forming a laminate. According to the studies made by the inventors of the present invention, when a pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive is used as in the prior art, adhesive residue due to the pressure-sensitive adhesive is generated to deteriorate the productivity and the two layers of the pressure- There is a problem in that the birefringent film can not be sufficiently shrunk because of being easily peeled off during the stretching process. 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 resin layer is used, the above-mentioned problems do not occur.

On the other hand, the active energy ray-curable resin layer usable in the present invention is not particularly limited, and various active energy ray-curable compositions capable of having the above-mentioned characteristics can be selected for the birefringent film and the heat shrinkable film to be selected, . That is, the active energy ray-curable composition satisfying the above-mentioned expressions (1) and (2) and preferably satisfying the expressions (3) and (4) can be selected And then curing it.

Examples of the active energy ray curable composition generally used in this technical field include photo radical polymerization such as a (meth) acrylate radical curable composition, an en / thiol radical curable composition, and an unsaturated polyester radical curable 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 is not limited thereto, but it is possible to use 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 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)

In addition, 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)

&Lt; 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 캜 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 resin layer used in the present invention preferably has a glass transition temperature of 70 ° C or higher, for example, about 70 to 150 ° C or about 80 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.

[Layered body forming step]

In the present invention, the above birefringent film and heat shrinkable film are laminated via an active energy ray-curable resin layer to form a laminate. The method for forming the laminate may include, but is not limited to, applying the active energy ray curable composition between the birefringent film and the heat shrinkable film, then laminating the two films, and applying an active energy ray- Ray is irradiated and cured.

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

The method of laminating the two films is also not particularly limited. For example, a lamination process or the like in which two films are passed between two rolls rotating in mutually opposite directions while bonding the two films using an active energy ray curable composition Can be used.

Also, the method of curing the active energy ray curable composition is not particularly limited, and can be performed by, for example, curing the active energy rays such as ultraviolet rays, visible rays, electron beams, and X rays. 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.

Meanwhile, the laminate of the present invention formed by the above-described method may have a length to width ratio of 1.5 times or more, preferably about 2 to 8 times, more preferably about 2 to 5 times. As the length of the laminated body in which the birefringent film and the heat shrinkable film are laminated is longer than the width, the force transmitted to the central portion of the laminated body is weak, so that the shrinkage can be more freely generated .

[Heat shrinkage process]

When the laminate is formed in the same manner as described above, the laminate satisfies the expressions (1) and (2) as described above, and is preferably thermally shrunk to satisfy the expressions (3) and (4). 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 film used in the present invention is preferably a positive birefringent film exhibiting a maximum refractive index along the stretching direction. In this case, the longitudinal direction MD becomes the x direction (the direction in which the refractive index becomes maximum) The direction TD becomes the y direction (direction perpendicular to the direction in which the refractive index becomes the maximum). At this time, the two films there is shrink laminated body in the y direction by the high-temperature stretching, in particular birefringent film is abruptly contracted bar which is laminated with a relatively heat shrinkable film better the shrinkage that occurs, as a result, n _y is n _z , so that n _x > n _z & gt _; n &lt; _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 &lt; 0 &gt; C). A high retardation can be realized only when the stretching temperature satisfies the above range. Specifically, the birefringent film tends to shrink sharply at such a stretching temperature, but the heat shrinkable film tends to shrink very strongly. At this time, the birefringent film adheres to the active energy ray-curable resin layer, A strong width shrinkage occurs in the process, and as a result, a high phase difference can be obtained.

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 stretching is performed at such a stretching magnification, the birefringent film can be shrunk in the width direction as much as desired by the present invention, and the present invention can realize a phase difference as high as desired.

The stretching may be performed such that the thickness of the birefringent film is 5 to 65 占 퐉 by stretching, and may be, for example, 5 占 퐉 to 45 占 퐉 or 10 占 퐉 to 30 占 퐉. If the thickness of the birefringent film after stretching is larger than the above range, it may not be possible to achieve a thin and lightweight polarizer or a 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.

[Other Process]

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 for using the heat shrinkable film in the uniaxially stretched state in the transverse direction (TD). When the thermally shrinkable film is a film uniaxially stretched in the transverse direction (TD) as described above, Which is preferable for effectively shrinking the film. 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 off the heat shrinkable film after the shrinking step. That is, the heat shrinkable film of the present invention may function as a protective film while being adhered to the birefringent film, but it is preferable to peel the birefringent film to use as a single retardation film. At this time, it is also preferable that the active energy ray-curable resin layer is peeled together with the heat shrinkable film by the peeling process. On the other hand, the peeling step may proceed at room temperature, and the peeling method is not particularly limited.

<Optical member, retardation film, polarizing plate and liquid crystal display device>

The present invention also provides an optical member manufactured by the above manufacturing method. Specifically, the present invention relates to a birefringent film; And a heat shrinkable film laminated on at least one surface of the birefringent film through an active energy ray-curable resin layer, wherein optical members satisfying the above-mentioned expressions (1) and (2) are also provided. At this time, the material and method used for forming the optical member are the same as described above, and the optical member also preferably satisfies the above-mentioned expressions (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, wherein the optical film is in the range of 200nm to 300nm _in R extent, the range of R _th is about 100nm to about 200nm, the Nz value can be on the order of 0.2 to 0.9 or 0.3 to 0.7.

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 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  One - Birefringence  film

A pellet was prepared from a 30φ L / D 40 Vent-type Co-rotating Twin Extruder at 250 ° C. using a polycarbonate resin (LG Chem, DVD 1080, Tg = 148 ° C.). An unoriented film having a thickness of 20 탆 was prepared by melting the raw material pellets prepared in the same extruder at 250 캜 with an extruder and then passing them through a coat hanger type T-die. On the other hand, the unstretched film had a shrinkage in the transverse direction (TD) of 15% when uniaxially stretched by 30% in the longitudinal direction (MD) using a UTM equipment in an oven at 155 ° C.

Manufacturing example  2 - Birefringence  film

A pellet was prepared from a 30φ L / D 40 Vent-type Co-rotating Twin Extruder at 250 ° C using polyamide (Evonik Industries, CX9704, Tg = 129 ° C) An unoriented film having a thickness of 60 占 퐉 was prepared by melting the raw material pellets prepared above at 250 占 폚 with an extruder in the same extruder and then passing them through a coat hanger type T-die. On the other hand, the unstretched film had a shrinkage in the width direction (TD) of 20% when uniaxially stretched by 30% in the longitudinal direction (MD) using UTM equipment in an oven at 155 ° C.

Manufacturing example  3 - 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. On the other hand, the stretched film had a shrinkage in the transverse direction (TD) of 78% when uniaxially stretched by 30% in the machine direction (MD) using UTM equipment in an oven at 155 ° C.

Manufacturing example  4 - Radical  Curable composition

Radical curable compositions were prepared for use as active energy ray curable resin layers. 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.

Manufacturing example  5-cationic curable composition

Cationically curable compositions were prepared for use as active energy ray curable resin layers. Specifically, the cationic curable composition was prepared by mixing 25 wt% of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (Celloxide 2021P from Dicel) having a glass transition temperature of 190 ° C of the homopolymer, 25% by weight of 1,4-cyclohexanedimethanol diglycidyl ether having a temperature of 25 ° C, 25% by weight of 3-ethyl-3 - [(3-ethyloxetan- Cetane DOX221), and 5 parts by weight of CPI 100P (Sanapro) as a cationic initiator was added to 100 parts by weight of the resin composition. The glass transition temperature of the composition measured using a differential scanning calorimeter (DSC Mettler) was 102 ° C.

Manufacturing example  6 - Acrylic adhesive

As the acrylic pressure-sensitive adhesive, commercially available NSS-4 manufactured by New Tac Kasei was used.

Manufacturing example  7 - Waterborne Adhesive

As a water-based adhesive, 3.3% of Gohsefiner Z-200H available from Nippon Synthetic Chemical Industry Co., Ltd. was dissolved in water and used.

Example  One

The polycarbonate undrawn film of Production Example 1 and the polyethylene terephthalate stretched film of Production Example 3 were adhered using the radical curable composition of Production Example 4 to produce a laminate. Specifically, the polycarbonate undrawn film and the polyethylene terephthalate stretched film were applied in a dripping manner to the composition, and then the two films were laminated. Thereafter, the laminate was cured under conditions of light quantity of 500 mJ / cm ² , intensity of 2000 mW / cm ² and speed of 20 m / min in a UV curing machine (Light Hammer, Fusion UV). Meanwhile, the lamp used for the UV curing machine was LH10 Fusion D bulb, and the distance between the lamp and the sample was 5.7 cm. On the other hand, the length of the laminate was 10 cm and the width was 5 cm, so that the ratio of the length to the width was about 2 times. The laminate was uniaxially stretched by 25% in a longitudinal direction (MD) in a 147 ° C oven using UTM equipment. The laminate was taken out at room temperature, and the polyethylene terephthalate stretched film was peeled off at room temperature to finally obtain a A polycarbonate stretched film (optical film) was produced.

Example  2

A laminate was prepared in the same manner as in Example 1 except that the polyamide-unstretched film of Production Example 2 was used in place of the polycarbonate undrawn film of Production Example 1. [ The laminate was uniaxially stretched by 55% in the machine direction (MD) in a longitudinal direction (MD) in a 132 ° C oven using UTM equipment. The laminate was taken out at room temperature and the polyethylene terephthalate stretched film was peeled off at room temperature, A polyamide stretched film (optical film) was produced.

Example  3

A laminate was prepared in the same manner as in Example 1 except that the cationically curable composition of Preparation Example 5 was used as the composition. The laminate was uniaxially stretched by 25% in a longitudinal direction (MD) in a 147 ° C oven using UTM equipment. The laminate was taken out at room temperature, and the polyethylene terephthalate stretched film was peeled off at room temperature to finally obtain a A polycarbonate stretched film (optical film) was produced.

Comparative Example  One

The polycarbonate undrawn film of Preparation Example 1 was used as Comparative Example 1.

Comparative Example  2

The polyamide undrawn film of Preparation Example 2 was used as Comparative Example 2.

Comparative Example  3

The polycarbonate undrawn film of Production Example 1 and the polyethylene terephthalate stretched film of Production Example 3 were adhered using the acrylic pressure-sensitive adhesive of Production Example 6 to produce a laminate. The laminate was uniaxially stretched by 25% in the machine direction (MD) in a longitudinal direction (MD) at 145 ° C in an oven, and then the laminate was taken out at room temperature and the polyethylene terephthalate stretched film was peeled off at room temperature. Finally, A polycarbonate stretched film (optical film) was produced.

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 film in the laminated state and the width shrinkage ratio (S ₂ ) of the heat shrinkable film in Examples 1 to 3 and Comparative Example 3 were measured and shown in Table 1 below. At this time, the width shrinkage rates (S ₁ , S ₂ ) are measured on both sides of the laminate before heat shrinkage, that is, on the birefringent film and the heat shrinkable film at intervals of 1 cm and then peeled off after heat shrinkage, The measurement was made by measuring the distance between points.

Further, to measure the above Examples 1 to 3 and comparison as in Example 3, the adhesive force of contraction around the birefringent film and a heat shrinkable film (P _a) and the adhesive force (P _b) of the birefringent film and a heat shrinkable film after shrinkage Table 1 shows the results. 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 30 30 0.18 0.14 Example 2 50 50 0.17 0.13 Example 3 30 30 0.17 0.14 Comparative Example 3 20 30 0.01 0.00

As can be seen from Table 1, in the case of the laminate produced in Examples 1 to 3 of the present invention, the width shrinkage ratio (S ₁ , S ₂ ) of the birefringent film and the heat shrinkable film satisfies the formula (2) , And the adhesive force (P _a ) before shrinkage and the adhesive force (P _b ) after shrinkage satisfy the above-mentioned expressions (3) and (4). As a result, in the case of the laminate produced in Examples 1 to 3 of the present invention, peeling was not easily caused in the heat shrinking process. As a result, as shown in Fig. 1 (a) It can be seen that the birefringent film 1 has contracted substantially like the heat shrinkable film 2. Further, it can be seen that peeling after heat shrinking is easy.

However, Comparative Example For the laminate prepared in the third, birefringent transverse shrinkage (S _1, S ₂₎ of the film and a heat shrinkable film is beyond the above formula (2), and shrink around the adhesive force (P _a) and after shrinkage The adhesive force (P _b ) also deviates from the above-mentioned formulas (3) and (4). As a result, in the case of the laminate produced in Comparative Example 1, peeling occurred in the heat shrinking process. As a result, as shown in the following FIG. 1 (b), only the heat shrinkable film 2 Shrinkage, and the birefringent film (1) was not sufficiently shrunk.

Experimental Example  2 - Phase difference  Characterization

The retardation characteristics of the optical films prepared in Examples 1 to 3 and Comparative Examples 1 to 3 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 22 1.5896 / 1.5785 / 1.5844 243 129 0.53 Example 2 25 1.5326 / 1.5276 / 1.5298 309 138 0.45 Example 3 22 1.5904 / 1.5784 / 1.5838 252 113 0.45 Comparative Example 1 20 1.5847 / 1.5842 / 1.5837 9 -10 -1.11 Comparative Example 2 20 1.5301 / 1.5300 / 1.5299 One -4 -6.13 Comparative Example 3 12 1.6002 / 1.5764 / 1.5760 281 -6 -0.02

As can be seen from Table 2, the optical films prepared in Examples 1 to 3 of the present invention have a phase difference value which is very suitable for use as a retardation film in an IPS mode liquid crystal display device.

However, in Comparative Examples 1 and 2 in which the heat shrinkage step of the present invention is not performed, it is found that the liquid crystal display for IPS mode has a retardation value which is difficult to apply as a retardation film.

In addition, the optical film prepared in Comparative Example 3 using the acrylic pressure-sensitive adhesive had peeling in the heat shrinkage process and the birefringent film was not sufficiently shrunk as described above. As a result, the polycarbonate film was simply uniaxially stretched without a heat shrink film The same result can be obtained.

Comparative Example  4

The polycarbonate undrawn film of Production Example 1 and the polyethylene terephthalate stretched film of Production Example 3 were adhered using the aqueous adhesive of Production Example 7 to produce a laminate. The laminate was uniaxially stretched by 25% in the MD direction in a 145 ° C oven using UTM equipment, and the laminate was taken out at room temperature and the polyethylene terephthalate stretched film was peeled off to produce a polycarbonate stretched film.

Experimental Example  3 - Appearance measurement of film

The appearance of the optical film prepared according to Example 1 and the optical film prepared according to Comparative Example 4 were photographed and shown in FIG. 2, in the case of the optical film (right side) produced according to Comparative Example 4 in comparison with the optical film (left) manufactured according to Embodiment 1 of the present invention, the appearance of the optical 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: birefringent film
2: Heat shrinkable film
W: Width
L: Length

Claims (18)

Forming a laminate by laminating a heat shrinkable film on at least one side of the birefringent film through an active energy ray-curable resin layer; And
And thermally shrinking the laminate so as to satisfy the following expressions (1) and (2).
Equation (1): n _x > n _z > n _y
(2): 0%? S ₂ - S ₁ ? 5%
In the formula (1), n _x is the birefringence, and the plane direction refractive index is the refractive index of the direction in which the maximum of the film, n _y is a refractive index in a direction perpendicular to a direction to the n _x direction in the birefringent film, n _z Is the refractive index in the thickness direction of the birefringent film,
In the formula (2), S ₁ is a shrinkage ratio in the direction perpendicular to the stretching direction of the birefringent film 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 being.
The method according to claim 1,
Wherein the step of heat shrinking the laminate further 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 film and the heat shrinkable film before heat shrinkage, and P _b is the adhesive strength between the birefringent film and the heat shrinkable film after heat shrinkage.
The method according to claim 1,
The step of forming the laminate may include a method of applying an active energy ray curable composition between the birefringent film and the heat shrinkable film, followed by laminating the two films, and curing the active energy ray curable composition by irradiating active energy rays . &Lt; / RTI &gt;
The method of claim 3,
Wherein the active energy ray curable composition comprises a first compound represented by Formula 1, a second compound comprising at least one carboxyl group, and a radical initiator.
[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 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;
The method of claim 3,
Wherein the active energy ray-curable composition comprises a first epoxy compound having a glass transition temperature of not lower than 120 DEG C of a homopolymer, a second epoxy compound having a glass transition temperature of not higher than 60 DEG C of a homopolymer and a photo cationic polymerization initiator Way.
The method according to claim 1,
Wherein the birefringent film is a positive birefringent film.
The method according to claim 1,
Wherein the birefringent film is an unstretched film.
The method according to claim 1,
Wherein the heat shrinkable film is a uniaxially stretched film in the width direction (TD).
The method according to claim 1,
Wherein the glass transition temperature of the birefringent film is 20 占 폚 or more higher than the glass transition temperature of the heat shrinkable film.
The method according to claim 1,
Wherein the active energy ray-curable resin layer has a glass transition temperature of 70 ° C or higher.
The method according to claim 1,
Wherein the laminate has a length to width ratio of 1.5 or more.
The method according to claim 1,
Wherein the heat shrinking step uniaxially stretches the laminate in the longitudinal direction (MD).
11. The method of claim 10,
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.
11. The method of claim 10,
Wherein the stretching is performed at a draw magnification of 1.1 to 3.0 times.
Birefringent film; And a heat shrinkable film laminated on at least one surface of the birefringent film through an active energy ray-curable resin layer, the optical member satisfying the following expressions (1) and (2).
Equation (1): n _x > n _z > n _y
(2): 0%? S ₂ - S ₁ ? 5%
In the formula (1), n _x is the birefringence, and the plane direction refractive index is the refractive index of the direction in which the maximum of the film, n _y is a refractive index in a direction perpendicular to a direction to the n _x direction in the birefringent film, n _z Is the refractive index in the thickness direction of the birefringent film,
In the formula (2), S ₁ is a shrinkage ratio in the direction perpendicular to the stretching direction of the birefringent film 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 being.
A process for producing a polyurethane foam, which is produced by the process of any one of claims 1 to 14,
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.
17. A polarizing plate comprising the optical film of claim 16.
17. A liquid crystal display device comprising the optical film of claim 16.

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