KR20130085197A - Resin composition for optical film and optical film using the same - Google Patents

Abstract

PURPOSE: A resin composition for an optical film and the optical film using the same have excellent transparency, heat resistance and extension rate by including a copolymer with a unit of alkyl (matte) acrylate, a unit of benzyl (matte), a unit of acrylate unit, and a unit of material of chemical formula 1. CONSTITUTION: A resin composition for an optical film and the optical film using the same include copolymer with a unit of alkyl (matte) acrylate, a unit of benzyl (matte), a unit of acrylate unit, and a unit of material of chemical formula 1. The average weight of the molecular weight of the copolymer is 100,000 to 200,000. In the chemical formula 1, X is NR 3 or O and R_1, R_2 and R_3 are respectively hydrogen, C 1-10 alkyl, and C 3-20 cycloalkyl or C 3-20 aryl.

Description

RESIN COMPOSITION FOR OPTICAL FILM AND OPTICAL FILM USING THE SAME}

The present invention relates to a resin composition for an optical film and an optical film using the same, and more particularly to a resin composition for an optical film and an optical film using the same as well as having excellent heat resistance and optical properties. It is about 0.

Recently, with the development of optical technology, various display technologies, such as plasma display (PDP), liquid crystal display (LCD), organic EL display (LED), etc., replacing conventional CRTs, have been proposed and marketed. Meanwhile, various polymer films such as polarizing films, polarizer protective films, retardation films, light guide plates, and plastic substrates are used in these display devices, and the display polymer material has a trend of being further advanced.

Currently, the most widely used polymer film for display is a triacetyl cellulose film (TAC), which is used as a polarizer protective film, and the TAC film has a low polarization degree when used for a long time in a high temperature or high humidity atmosphere, and a polarizer and a film. There is a problem that this separation or optical properties are degraded.

In order to solve this problem, as an alternative to the TAC film, acrylic or polycarbonate-based polymer films such as polystyrene and methyl methacrylate have been proposed. These polymer films have an advantage of excellent heat resistance, but polystyrene or polycarbonate films have an aromatic ring in the polymer, so that birefringence occurs during orientation, which adversely affects optical properties. In this case, the phase difference value is relatively smaller than that of polystyrene or polycarbonate, but it is not sufficient to be applied to an optical material such as a liquid crystal device which requires high precision.

To be applied as a polarizer protective film, the phase difference of the film after film formation and stretching should have a value close to zero.For this purpose, a polymer film material having a high birefringence and a low birefringence and a negative birefringence A method of copolymerizing or blending monomers or polymers having birefringence of has been proposed. Typical examples of these methods include copolymers of benzyl methacrylate and methyl methacrylate.

On the other hand, since the optical film is subjected to the process of stretching and stretching is excellent in the strength of the film forming and stretching process is excellent because the resin for the production of an excellent optical film (Tensile elongation) is required.

The present invention provides a resin composition for an optical film and an optical film using the same, which are excellent in optical properties and heat resistance and at the same time excellent in elongation (Tensile elongation), which is advantageous for film forming and stretching.

To this end, the present invention, the alkyl (meth) acrylate unit; Benzyl (meth) acrylate units; (Meth) acrylic acid units; And a copolymer comprising a unit represented by the following formula (I), wherein the copolymer provides a resin composition for an optical film having a weight average molecular weight of 100,000 to 200,000.

(I)

In Formula 1, X is NR ₃ or O,

Wherein R _1, R ₂ and R ₃ are each independently hydrogen, C _{1 ~ 10} alkyl, C _{3 ~ 20} cycloalkyl or C _{3 ~ 20} aryl.

In another aspect, the present invention provides an optical film comprising the resin composition for an optical film.

The optical film using the resin composition for an optical film according to the present invention can provide a protective film excellent in transparency and heat resistance, and excellent in elongation (Tensile elongation), and thus the optical film formed using the resin composition of the present invention It can be used in information electronic devices such as a display device including a polarizing plate for the purpose of the protective film.

Hereinafter, the present invention will be described in more detail.

The inventors of the present invention have been studied to develop a resin composition for an optical film excellent in optical properties and heat resistance but also excellent in elongation (Tensile elongation), the alkyl (meth) acrylate unit, benzyl (meth) acrylate unit, When using a four-component resin composition containing a (meth) acrylic acid unit and a unit represented by the following formula (I), the retardation value is low, the glass transition temperature is high, the coefficient of thermal expansion is low, and in particular, the specific range composed of the above components. When using the copolymer which has a weight average molecular weight of, it turned out that the optical film excellent in elongation rate can be manufactured, and this invention was completed.

(I)

In Formula 1, X is NR ₃ or O,

Wherein R _1, R ₂ and R ₃ are each independently hydrogen, C _{1 ~ 10} alkyl, C _{3 ~ 20} cycloalkyl or C _{3 ~ 20} aryl.

The resin composition for optical films of this invention contains an alkyl (meth) acrylate unit, a benzyl (meth) acrylate unit, a (meth) acrylic acid unit, and the unit represented by the said general formula (I).

In this case, it is preferable that the resin composition is a four-way copolymer resin in which each unit is included in the form of a repeating unit, and the copolymer preferably has a weight average molecular weight of 100,000 to 200,000. If the weight average molecular weight is less than 100,000, the problem of elongation may be lowered when the film is stretched. If the weight average molecular weight is more than 200,000, the problem of transport and efficiency of resin processing may occur in the polymerization process.

In the resin composition of the present invention, the alkyl (meth) acrylate unit means both alkyl acrylate and alkyl methacrylate, but is not limited thereto, in view of optical transparency, compatibility, processability and productivity, The carbon number of the alkyl group of the alkyl (meth) acrylate is preferably about 1 to about 10, more preferably about 1 to about 4 carbon atoms, and most preferably the alkyl group is a methyl group or an ethyl group.

On the other hand, the content of the alkyl (meth) acrylate unit is preferably about 55 to 94 parts by weight, more preferably 60 to 90 parts by weight, most preferably 70 to 90 with respect to 100 parts by weight of the total resin composition. It may be part by weight. Excellent retardation and optical properties can be obtained when the content of alkyl (meth) acrylate units is within this range.

In the resin composition of the present invention, the benzyl (meth) acrylate unit is to impart the proper phase difference value to the optical film of the present invention and to impart compatibility between the alkyl (meth) acrylate and (meth) acrylic acid. , Benzyl methacrylate or benzyl acrylate, especially benzyl methacrylate.

Meanwhile, the content of the benzyl (meth) acrylate unit may be about 2 to 20 parts by weight, and more preferably 2 to 18 parts by weight based on 100 parts by weight of the total resin composition. When the content of benzyl (meth) acrylate is within the above range, desired retardation characteristics can be obtained.

On the other hand, in the resin composition of the present invention, the (meth) acrylic acid unit serves to improve the heat resistance and to lower the coefficient of thermal expansion by introducing a polar group, for example, acrylic acid, methacrylic acid, methylacrylic acid, methyl meta It may be methacrylic acid, ethylacrylic acid, ethyl methacrylic acid, butylacrylic acid or butyl methacrylic acid, with methacrylic acid being particularly preferred.

On the other hand, the content of the (meth) acrylic acid unit is preferably about 1 to 10 parts by weight, more preferably 1 to 5 parts by weight, even more preferably 1 to 3 parts by weight based on 100 parts by weight of the total resin composition. Parts, most preferably 1 to 2 parts by weight. When the content of the (meth) acrylic acid unit is in the above range, desirable heat resistance characteristics can be obtained. In particular, when the content of (meth) acrylic acid is 2 parts by weight or less, there is an additional advantage that can significantly reduce the generation of bubbles in the film forming process.

In addition, the resin composition of the present invention includes a unit represented by the following formula (1).

(I)

In Formula 1, X is NR ₃ or O, wherein R _1, R ₂ and R ₃ are each independently hydrogen, C _{1 ~ 10} alkyl, C _{3 ~ 20} cycloalkyl or C _{3 ~ 20} aryl group.

The unit represented by Formula 1 is for lowering the coefficient of thermal expansion of the resin composition. When a bulky functional group that inhibits polymer chain rotation is introduced into the polymer backbone, the coefficient of thermal expansion of the polymer can be lowered.

However, for example, when using polymers containing bulky functional groups such as styrene or polycarbonate, the coefficient of thermal expansion may be lowered, but birefringence may be exhibited by stretching, which may cause problems in optical properties. On the other hand, when using the compound represented by the formula (1), as in the present invention, it is possible to effectively lower the coefficient of thermal expansion without adversely affecting the optical properties.

Specific examples of the unit represented by the formula (1) include glutaric anhydride, glutaric acid imide, and the like, and glutaric anhydride is particularly preferable.

On the other hand, the content of the unit represented by the formula (1) is preferably about 3 to 15 parts by weight based on 100 parts by weight of the total resin composition. When the content of the unit represented by the formula (1) is within the above range, it is possible to implement a low coefficient of thermal expansion without compromising the retardation characteristics.

In the resin composition for an optical film of the present invention comprising the above components, the glass transition temperature is preferably about 120 ° C to 150 ° C, more preferably 125 ° C to 150 ° C, and most preferably 125 ° C to 150 ° C. desirable. In addition, the transparency (haze) is preferably about 0.1 to 3%, and the light transmittance is preferably 90% or more. Moreover, it is preferable that a yellow index value is about 0.3-2.0. If the value is out of the above, the display color may change.

On the other hand, the resin composition of the present invention as described above may be prepared according to the copolymer resin production method well known in the art. For example, the resin composition of the present invention may be prepared by mixing monomers of each component, followed by solution polymerization, block polymerization, suspension polymerization or emulsion polymerization.

On the other hand, when the component of the formula (1) of the resin composition of the present invention is glutaric anhydride, without addition of the component of the formula (1), of the alkyl (meth) acrylate, (meth) acrylic acid and benzyl (meth) acrylate The resin composition of this invention can also be manufactured by the method of bulk-polymerizing three components, or carrying out suspension polymerization and heat-treating these. In this case, the alkyl (meth) acrylate and / or benzyl (meth) acrylate and (meth) acrylic acid are hydrolyzed by heat to form glutaric anhydride while forming a quaternary copolymer.

Furthermore, the present invention provides a compounding resin composition for an optical film in which the copolymer of the present invention and a high molecular weight acrylic resin are compounded. On the other hand, the resin composition of the present invention as described above may be prepared according to the blend resin production method well known in the art. For example, the resin composition of the present invention may be prepared by blending the copolymer with a high molecular weight acrylic resin.

The high molecular weight acrylic resin preferably has a molecular weight of 20,000 to 100,000 greater than the weight average molecular weight of the copolymer, and when the weight average molecular weight of the high molecular weight acrylic resin has a weight average molecular weight of less than the above range If the toughness improvement efficiency is not large, and the copolymer has a larger molecular weight of more than 100,000 than the weight average molecular weight of the copolymer, there is a problem that the transparency of the resin may be reduced during processing of the resin blend. Therefore, the weight average molecular weight of the high molecular weight acrylic resin is preferably 120,000 to 300,000.

The high molecular weight acrylic resin is preferably contained in an amount of more than 0 to 15% by weight based on the total compounding resin composition, when the high molecular weight acrylic resin is included as described above to improve the toughness of the resin (toughness) film forming There is an effect of improving the elongation and stretch strength in the stretching process, but when included in an amount exceeding 15% by weight may cause a problem that the transparency of the resin is lowered.

The high molecular weight acrylic resin preferably contains an alkyl (meth) acrylate, the alkyl (meth) acrylate is methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, methyl acrylate And ethyl acrylate.

Meanwhile, the high molecular weight acrylic resin may include a component selected from the group consisting of (meth) acrylic acid, maleic anhydride, and maleimide based together with the alkyl (meth) acrylate, and the high molecular weight acrylic resin is preferably It may be a copolymer form consisting of monomers consisting of the above components. More preferably, it is acrylic resin which consists of alkyl (meth) acrylate units.

In another aspect, the present invention relates to an optical film comprising the resin composition of the present invention.

The optical film of the present invention preferably has elongation (Tensile elongation) of 250 to 400%, if less than 250% there is a problem that may cause a limit in the magnification control according to the stretching conditions. On the other hand, the higher the draw ratio tends to improve the toughness of the resin, but the upper limit of the draw ratio of the resin that can be currently obtained is about 400%. In the present invention, the elongation rate means that a sample having a thickness of 180 µm before stretching at a rate of 100 mm / min is stretched at a temperature near Tg to measure the stretching ratio to break.

The optical film may be prepared in the form of a film according to a method well known in the art, such as a solution caster method or an extrusion method. In view of economics, it is more preferable to use an extrusion method. In some cases, during the film production process, an additive such as a modifier may be further added within a range that does not impair the physical properties of the film, and a uniaxial or biaxial stretching step may be further performed.

The stretching process may perform longitudinal (MD) stretching, transverse (TD) stretching, or both. In the case of performing both the longitudinal drawing and the transverse drawing, either one of them may be stretched in the other direction, or the two directions may be stretched at the same time. In addition, the stretching may be performed in one step or may be performed in multiple steps. In the case of longitudinal stretching, stretching by the speed difference between rolls can be performed, and in the case of transverse stretching, tenter can be used. The time of railing of the tenter is usually within 10 degrees, thereby suppressing the bowing phenomenon occurring in the transverse direction drawing and controlling the angle of the optical axis regularly. Even when the transverse stretching is performed in multiple stages, the effect of inhibiting the bowing can be obtained.

On the other hand, the stretching, when the glass transition temperature of the resin composition is Tg, it is preferably performed in the range of (Tg-20 ° C) ~ (Tg + 30 ° C), which starts to decrease the storage modulus Therefore, it refers to a region from the temperature at which the loss modulus becomes larger than the storage modulus to a temperature at which the orientation of the polymer chain is relaxed and lost. The glass transition temperature of the resin composition can be measured by a differential scanning calorimeter (DSC). The temperature at the time of the stretching step is more preferably the glass transition temperature of the resin composition.

The stretching speed is preferably in the range of 1 to 100 min / min for a universal testing machine (Zwick Z010) and in the range of 0.1 to 2 m / min for a pilot stretching machine And the stretching magnification is preferably about 5 to 300%.

Through the stretching process as described above it is possible to adjust the phase difference characteristics of the film.

On the other hand, the optical film of the present invention prepared by the above method has a plane direction phase value (R _in ) is 0 to 10nm, the thickness direction phase difference value (R _th ) is about -5 to 10nm at a wavelength of 550nm. Here, the plane direction retardation value refers to a value defined by Equation 1 below, and the thickness direction retardation value refers to a value defined by Equation 2 below.

[Equation 1]

R _in = (n _x -n _y ) x d

&Quot; (2) "

R _th = (n _z -n _y ) x d

In [Equation 1] and [Equation 2], n _x is the refractive index of the direction of the largest refractive index in the plane direction of the film, n _y is the vertical direction of the n _x direction in the plane direction of the film It is a refractive index, n _z is a refractive index of a thickness direction, and d is a thickness of a film.

In addition, the optical film of the present invention has a coefficient of thermal expansion of 50 to 70ppm / ℃, has a lower coefficient of thermal expansion than conventional acrylic film. Since the coefficient of thermal expansion is thus low, curling can be suppressed when the optical film of the present invention is applied to a polarizing plate.

Moreover, it is preferable that the optical film of this invention is 20-200 micrometers, Preferably it is 40-120 micrometers, transparency is about 0.1 to 3%, and light transmittance is 90% or more. It is because it is suitable to be used as a polarizing plate protective film when the thickness, transparency, and transmittance of a film exist in the said range.

In another aspect, the present invention relates to a polarizer comprising a polarizer and an optical film according to the present invention provided on at least one surface of the polarizer as a protective film.

The optical film according to the present invention may be provided on both sides of the polarizer, or may be provided only on one surface. When the optical film of the present invention is provided on one side of the polarizer, on the other side, a polarizer protective film well known in the art, for example, TAC film, PET film, COP film, PC film, norbornene-based film, etc. Among them, in consideration of economics and the like, TAC film is particularly preferred. Since the coefficient of thermal expansion of the optical film of the present invention is similar to that of the TAC film, when the TAC film is attached to one side of the polarizer and the optical film of the present invention is attached to the other side, the curl phenomenon caused by the difference in coefficient of thermal expansion is minimized. Can be.

On the other hand, the attachment of the polarizer and the optical film and / or protective film of the present invention, after coating the adhesive on the surface of the film or polarizer using a roll coater, gravure coater, bar coater, knife coater or capillary coater, etc. , The protective film and the polarizer may be carried out by laminating by heating with a lamination roll, or laminating by pressing at room temperature. As the adhesive, adhesives used in the related art, for example, a polyvinyl alcohol adhesive, a polyurethane adhesive, an acrylic adhesive and the like may be used without limitation.

The polarizing plate of the present invention manufactured as described above preferably has a polarizing plate bending angle of 150 degrees or less after being left to stand at 25 ° C. and 50% RH for 24 hours, and particularly preferably about 120 to 150 degrees. When the polarizing plate bending angle exceeds 150 degrees, curls of the polarizing plate are severely generated, which may degrade display quality. Here, the bending angle means a center angle measured by looking at the curved polarizing plate as an arc.

In another aspect, the present invention relates to an image display device including the polarizing plate of the present invention. In this case, the image display device may be, for example, a liquid crystal display (LCD), a plasma display (PDP), an electroluminescent device (LED), or the like.

Hereinafter, the present invention will be described more specifically by way of specific examples. The following examples are given for the purpose of helping to understand the present invention, but the scope of the present invention is not limited thereto.

In the present invention, the physical property evaluation method is as follows.

1. Weight average molecular weight: The prepared resin was dissolved in tetrahydrofuran and measured by gel osmosis chromatography (GPC).

2. Glass transition temperature (Tg): Measured using a differential scanning calorimeter (DSC) of TA Instrument.

3. Haze and light transmittance: Measured according to ASTM 1003 method.

4. Toughness: 60μm thick film was measured by bending by hand, and when it is broken 10 times, it is not broken at all. ◎, 1 ~ 3 times broken, ○ when broken more than 5 times. Marked with x.

5. Thermal Expansion Coefficient (CTE): Measured using Pyris 6 DCS from Perkin Elmer.

6. Phase difference: It was measured using Elli-SE of Ellipso Tech.

7. Resin composition: Measured using C13-NMR.

8. Yellow index (YI): Measured using a Hunter Lab colorimeter.

9. Tensile elongation: A sample of 180 µm before stretching at a rate of 100 mm / min was drawn at a temperature near Tg to measure the elongation to break.

≪ Examples 1-3 >

A methyl methacrylate monomer, a methacrylic acid monomer, and a benzyl methacrylate monomer are mixed with toluene, which is a polymerization solvent, in the amounts shown in Table 1 below, and 0.03 weight of dicumyl peroxide, which is an initiator, based on 100 parts by weight of the mixed solution. After preparing 0.5 parts by weight of t-dodecyl mercaptan, a molecular weight regulator, to prepare a polymerization solution, the polymerization was carried out at 145 ° C. for 2 hours by continuous bulk polymerization, and then the unreacted monomer and solvent were removed from a volatile bath at 250 ° C. and a vacuum degree of 20 torr. After the reaction, a resin containing methyl methacrylate unit, methacrylic acid unit, benzyl methacrylate unit, and glutaric anhydride unit in the amounts shown in the following [Table 1] was prepared as pellets.

The composition of the prepared resin, weight average molecular weight, glass transition temperature, MI (meaning the amount of resin coming out for 10 minutes when pressed at 220 ℃ 10kg weight, the unit is g / 10min.), And the haze was measured. The measurement results are shown in Table 1 below.

division Example 1 Example 2 Example 3 Copolymer polymerization solution BzMA 5 5 7 MMA 85 85 85 MAA 10 101 8 T-dodecylmercaptan 0.4 0.3 0.2 Reaction time 2 2.5 2 Reaction temperature (캜) 145 140 145 Final copolymer components BzMA 4.9 5.1 7.2 MMA 84.8 84.6 84.7 MAA 1.7 1.8 1.8 G / A 8.6 8.5 6.3 Resin properties Weight average molecular weight (Mw * 10 ⁴ ) 11.5 13.2 14.3 Tg (占 폚) 126.7 128.2 125.3 MI (g / 10 min) 2.6 2.1 1.9 Haze (%) 0.2 0.2 0.2

BzMA: benzyl methacrylate

MMA: methyl methacrylate

MAA: methacrylic acid

G / A: glutaric anhydride

Then, the resin was prepared into a 180 μm film by using a T-die extruder, and then biaxially stretched 1.9 times in the MD direction and 1.9 times in the TD direction to prepare an optical film having a thickness of 50 μm. The retardation value, toughness, and elongation rate of the prepared optical film were measured. The measurement results are shown in the following [Table 2].

division Example 1 Example 2 Example 3 Film properties Rin / Rth 0.2 / -0.2 0.2 / -0.1 0.3 / 0.1 tenacity ◎ ◎ ◎ Elongation (%) 290 320 335

<Example 4>

A compound resin composition was prepared by compounding a high molecular weight acrylic resin having a weight average molecular weight of 120,000, wherein methyl methacrylate and methacrylic acid were copolymerized in a weight ratio of 9: 1 to the copolymer prepared in Example 1, as shown in Table 3 below. The resin was prepared into a 180 μm film using a T-die extruder, and biaxially stretched 1.9 times in the MD direction and 1.9 times in the TD direction to prepare an optical film having a thickness of 50 μm. The retardation value, toughness, and elongation rate of the prepared optical film were measured. The measurement results are shown in the following [Table 4].

<Example 5>

A methyl methacrylate monomer, a methacrylic acid monomer, and a benzyl methacrylate monomer are mixed with toluene as a polymerization solvent in the amounts shown in Table 3 below, and 0.03 weight of dicumyl peroxide as an initiator with respect to 100 parts by weight of the mixed solution. In addition, 0.5 weight part of t-dodecyl mercaptan, a molecular weight regulator, was added to prepare a polymerization solution, and then polymerized at 145 ° C. for 2 hours by continuous bulk polymerization. After devolatilization, a resin containing methyl methacrylate unit, methacrylic acid unit, benzyl methacrylate unit, and glutaric anhydride unit in the amounts shown in the following [Table 3] was prepared as pellets.

Compounding a high molecular weight acrylic resin consisting of methyl methacrylate with a weight average molecular weight of 130,000 to a pellet prepared as described above to prepare a compound resin composition, the resin was prepared as a 180㎛ film using a T-die extruder, MD Simultaneous biaxial stretching was performed 1.9 times in the direction and 1.9 times in the TD direction to prepare an optical film having a thickness of 50 µm. The retardation value, toughness, and elongation rate of the prepared optical film were measured. The measurement results are shown in the following [Table 4].

division Example 4 Example 5 Copolymer polymerization solution BzMA 5 7 MMA 85 85 MAA 10 8 T-dodecylmercaptan 0.4 0.4 Reaction time 2 2.5 Reaction temperature (캜) 145 155 Final copolymer components BzMA 4.9 7.3 MMA 84.8 84.7 MAA 1.7 1.5 G / A 8.6 6.5 High molecular weight acrylic resin MMA-MAA (9: 1), 12 * 10 ⁴ 5 MMA, 13 * 10 ⁴ 10 Physical properties before mixing high molecular weight acrylic resin Weight average molecular weight (Mw * 10 ⁴ ) 11.5 11.7 Tg (占 폚) 126.7 125 MI (g / 10 min) 2.6 2.9 Haze (%) 0.4 0.3 Final resin properties after mixing Tg (占 폚) 128 123.2

BzMA: benzyl methacrylate

MMA: methyl methacrylate

MAA: methacrylic acid

G / A: glutaric anhydride

division Example 4 Example 5 Film properties Rin / Rth 0.3 / 0.1 0.3 / 0.4 tenacity ◎ ◎ Elongation (%) 320 355

<Comparative Example 1-2>

The resin composition, the optical film, and the same method as in <Example 1> except that the methyl methacrylate monomer, methacrylic acid monomer, and benzyl methacrylate monomer were mixed in the amounts and molecular weights described in the following [Table 5]. Each polarizing plate was produced.

Composition of the prepared resin composition, weight average molecular weight, glass transition temperature, MI (meaning the amount of resin coming out for 10 minutes when pressed to 10kg weight at 220 ℃, unit is g / 10min.), It measured by the same method and shown in [Table 5].

In addition, the retardation value, toughness and elongation of the prepared optical film was measured in the same manner as in Example and shown in [Table 6].

division Comparative Example 1 Comparative Example 2 Copolymer polymerization solution BzMA 5 7 MMA 85 85 MAA 10 8 T-dodecylmercaptan 0.6 0.7 Reaction time 3 2.5 Reaction temperature (캜) 150 155 Final copolymer components BzMA 4.8 7.2 MMA 85.2 84.6 MAA 1.6 1.5 G / A 8.4 6.7 Resin properties Weight average molecular weight (Mw * 10 ⁴ ) 9 8.5 Tg (占 폚) 125.8 123.3 MI (g / 10 min) 3.7 4.1 Haze (%) 0.2 0.3

BzMA: benzyl methacrylate

MMA: methyl methacrylate

MAA: methacrylic acid

G / A: glutaric anhydride

division Comparative Example 1 Comparative Example 2 Film properties Rin / Rth 0.3 / -0.2 0.3 / 0.3 tenacity ◎ ◎ Elongation (%) 200 160

As can be seen in the above examples and comparative examples, when using the resin composition of the present invention it can be produced an optical film remarkably excellent in elongation (%).

Claims (24)

Alkyl (meth) acrylate units;
Benzyl (meth) acrylate units;
(Meth) acrylic acid units; And
To include a copolymer comprising a unit represented by the formula (I)
The copolymer is a resin composition for an optical film having a weight average molecular weight of 100,000 to 200,000:
(I)

In Formula 1, X is NR ₃ or O,
Wherein R _1, R ₂ and R ₃ are each independently hydrogen, C _{1 ~ 10} alkyl, C _{3 ~ 20} cycloalkyl or C _{3 ~ 20} aryl.
The method of claim 1, wherein the copolymer
55 to 94 parts by weight of alkyl (meth) acrylate units;
2 to 20 parts by weight of benzyl (meth) acrylate units;
1 to 10 parts by weight of (meth) acrylic acid units; And
The resin composition for optical films containing 3-15 weight part of units represented by the said general formula (I).
The method of claim 2,
The resin composition for optical films whose content of the (meth) acrylic acid unit is 1 to 2 parts by weight.
The method of claim 1,
The alkyl group of the said alkyl (meth) acrylate unit has a C1-C10 resin composition for optical films.
5. The method of claim 4,
The said alkyl (meth) acrylate unit is methyl methacrylate resin composition for optical films.
The method of claim 1,
The said benzyl (meth) acrylate unit is benzyl methacrylate, the resin composition for optical films.
The method of claim 1,
The (meth) acrylic acid unit is an optical film resin composition selected from the group consisting of acrylic acid, methacrylic acid, methyl acrylic acid, methyl methacrylic acid, ethyl acrylic acid, ethyl methacrylic acid, butyl acrylic acid and butyl methacrylic acid.
The method of claim 1,
The unit represented by the formula (I) is a resin composition for an optical film, which is glutaric anhydride.
The method of claim 1, wherein the copolymer
55 to 94 parts by weight of methyl methacrylate units;
2 to 20 parts by weight of benzyl methacrylate units;
1 to 10 parts by weight of methacrylic acid units; And
The resin composition for optical films which is a copolymer containing 3-15 weight part glutaric anhydride units.
The method of claim 1,
The resin composition for optical films has a glass transition temperature of 120 ° C to 150 ° C.
The compounding resin composition for optical films in which the copolymer of Claim 1 and the high molecular weight acrylic resin were compounded.
The compounding composition of claim 11, wherein the high molecular weight acrylic resin has a molecular weight of 20,000 to 100,000 more than the weight average molecular weight of the copolymer.
12. The compounding resin composition for optical films according to claim 11, wherein the weight average molecular weight of the high molecular weight acrylic resin is 120,000 to 300,000.
The compounding resin composition of claim 11, wherein the high molecular weight acrylic resin is included in an amount of more than 0 and 15% by weight or less based on the total compounding resin composition.
The compounding resin composition for an optical film according to claim 11, wherein the high molecular weight acrylic resin includes an alkyl (meth) acrylate.
16. The optical film of claim 15, wherein the alkyl (meth) acrylate is selected from the group consisting of methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl acrylate. Compounding resin composition for use.
The optical film containing the resin composition of any one of Claims 1-16.
18. The method of claim 17,
The optical film has an optical direction retardation value of 0 to 10 nm represented by the following Equation 1 at a wavelength of 550 nm, and a thickness direction retardation value of -5 to 10 nm represented by the following Equation 2.
[Equation 1]
R _in = (n _x -n _y ) x d
&Quot; (2) &quot;
R _th = (n _z -n _y ) x d
In Equations 1 and 2,
n _x is a refractive index of the direction of the largest refractive index in the plane direction of the film,
n _y is a refractive index in the vertical direction in the n _x direction in the plane direction of the film,
n _z is the refractive index in the thickness direction,
d is the thickness of the film.
The optical film of claim 17, wherein the optical film has a coefficient of thermal expansion of 50 to 70 ppm / ° C. 18.
The optical film of claim 17, wherein the optical film has a stretch elongation of 250 to 400%.
The method of claim 17, wherein the optical film has a surface direction retardation value represented by the following formula (1) at a wavelength of 580nm 0 to 10nm, the thickness direction retardation value represented by the following formula (2) is -5 to 10nm, the coefficient of thermal expansion Optical film with 50 to 70 ppm / ?.
[Equation 1]
R _in = (n _x -n _y ) x d
&Quot; (2) &quot;
R _th = (n _z -n _y ) x d
In Equations 1 and 2,
n _x is a refractive index of the direction of the largest refractive index in the plane direction of the film,
n _y is a refractive index in the vertical direction in the n _x direction in the plane direction of the film,
n _z is the refractive index in the thickness direction,
d is the thickness of the film.
The optical film of claim 17, wherein the optical film is a polarizing plate protective film.
A polarizer; And
Polarizing plate comprising the optical film of claim 17 attached to at least one surface of the polarizer.
An image display device comprising the optical film of claim 17.