KR101657355B1 - Acrylic resin composition, resin pellet and optical film comprising the same - Google Patents

Abstract

The present invention relates to an acrylic polymer comprising a (meth) acrylate-based monomer; And a compound having an ultraviolet absorptivity of 1 to 40 with respect to 100 parts by weight of a (meth) acrylate monomer, and a resin pellet and an optical film containing the acrylic resin composition.

Description

TECHNICAL FIELD [0001] The present invention relates to an acrylic resin composition, a resin pellet and an optical film containing the same,

The present invention relates to an acrylic resin composition, a resin pellet and an optical film containing the acrylic resin composition, and more particularly, to an acrylic resin composition capable of producing an optical film having excellent ultraviolet absorption performance and surface characteristics, Lt; / RTI >

Recently, various display technologies such as a plasma display (PDP), a liquid crystal display (LCD), and an organic EL display (LED), which replace conventional CRTs, have been proposed and marketed according to the development of optical technology. On the other hand, various optical films such as a polarizing film, a polarizer protective film, a retardation film, a light guide plate, and a plastic substrate are used for such display devices, and the optical film material has a demand for more advanced characteristics.

On the other hand, a technique for imparting ultraviolet ray absorption capability to an optical film has been proposed in order to prevent a liquid crystal or a polarizer from deterioration by ultraviolet rays. Conventionally, a benzotriazole compound or a benzophenone compound, An ultraviolet absorber such as a cyanoacrylate-based compound, a salicylic acid-based compound or the like was added to prepare an optical film having an ultraviolet ray absorbing capability. However, most of the above-mentioned ultraviolet absorbers are decomposed at the time of high-temperature processing and the amount thereof is reduced, so that not only the ultraviolet absorbing ability is lowered but also the resin and film are colored in yellow. When the ultraviolet absorber is added to the resin pellets, the glass transition temperature (Tg) of the resin pellets is greatly lowered and the heat resistance is reduced. When the resin pellets are exposed to ultraviolet rays for a long period of time, And the like.

In addition, in the case of an acrylic resin, compatibility with the ultraviolet absorber is poor, so that the ultraviolet absorber is separated from the resin pellet during the film formation and flows out to the outside, resulting in contamination of film production equipment and film .

The present invention has been made to solve the above problems, and an object of the present invention is to provide a resin composition for an optical film which has a high ultraviolet ray absorbing ability and a high glass transition temperature (Tg) value and does not cause coloring and contamination problems, And an optical film.

In one aspect, the present invention relates to an acrylic polymer comprising (meth) acrylate-based monomer; And a compound having an ultraviolet ray absorbing property with a solubility of 1 to 40 with respect to 100 parts by weight of a (meth) acrylate based monomer.

The compound having an ultraviolet ray absorbing property preferably has a solubility of 0.1 to 60 with respect to 100 parts by weight of an organic solvent containing a hydroxyl group and has a solubility of 50 to 700 with 100 parts by weight of an organic solvent containing a halogen element desirable.

On the other hand, the compound having the ultraviolet absorbing performance and a molecular weight of 300 to 2000 range, may be a triazine compound comprising a C _{4 ~ 20} aliphatic hydrocarbon at least one.

The content of the compound having an ultraviolet absorption property is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the acrylic polymer.

On the other hand, the acrylic polymer containing the (meth) acrylate monomer of the present invention may be an alkyl (meth) acrylate monomer, and the acrylic polymer may include one kind selected from the group consisting of a styrene monomer and a maleimide monomer Or more of the above monomers.

In another aspect, the present invention provides a resin pellet comprising the acrylic resin composition.

In another aspect, the present invention provides an optical film produced using the resin pellet.

INDUSTRIAL APPLICABILITY The acrylic resin composition according to the present invention is useful for the production of an optical film having excellent ultraviolet ray absorbing ability and preventing the glass transition temperature (Tg) from being greatly lowered and having excellent heat resistance.

In addition, according to the method for producing an acrylic resin composition according to the present invention, the uniformity of the pellet size of the resin composition is ensured, thereby preventing a thickness variation due to unstable supply in the extrusion process for melt- The productivity can be improved and the optical film having excellent appearance characteristics can be produced by removing the impurities.

On the other hand, the optical film comprising the acrylic resin composition according to the present invention has an excellent ultraviolet shielding effect, a high linear light transmittance in the visible light region, and excellent heat resistance.

Hereinafter, preferred embodiments of the present invention will be described. 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.

As described above, in order to produce an optical film having an ultraviolet absorbing ability, a method of kneading an ultraviolet absorbent in an acrylic resin in the form of pellets has been used. However, in this case, the kneading property between the acrylic resin and the ultraviolet absorber is poor, and the thermoplastic resin composition is not melted due to the ultraviolet absorber and flows out to the outside, and the additive added to the resin composition is lost during the kneading process There was a problem.

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, they have found that a compound having an ultraviolet absorbing property with a solubility of 1 to 40 with respect to 100 parts by weight of a (meth) acrylate monomer at the time of polymerization of an acrylic polymer It is possible to produce an optical film having excellent ultraviolet shielding effect and excellent physical properties such as transparency, color and heat resistance without mixing a separate ultraviolet absorber into the resin pellets And completed the present invention.

More specifically, the acrylic resin composition according to the present invention comprises an acrylic polymer containing a (meth) acrylate monomer; And a compound having an ultraviolet ray absorbing property with a solubility of 1 to 40 with respect to 100 parts by weight of a (meth) acrylate monomer.

In the present invention, the acrylic resin is preferably in the form of particles, and the particulate acrylic resin may be in the form of, for example, a spherical shape, a dumbbell shape, an elliptical shape and the like, But is not limited thereto. When the thermoplastic acrylic resin is in the form of particles as described above, it is possible to change the composition ratios of the resins relatively freely. Since the polymerization is carried out at a relatively low temperature, the thermal decomposition is small and the additives such as antioxidants, This has the advantage.

When the acrylic resin is in the form of particles, the average size of the particles is preferably from 10 탆 to 500 탆, from 50 탆 to 450 탆, or from 100 탆 to 400 탆. When the average size of the particles satisfies the above-described numerical value range, it is possible to obtain a raw material pellet of a very uniform shape with good extrusion kneadability, and the molecular weight of the resin is relatively uniform and the film has excellent properties. When the average size of the particles is more than 500 mu m, there is a problem that the residual monomers contained in the particles are high and the physical properties of the resin are lowered. When the average size is less than 10 mu m, the apparent density may greatly deteriorate the extrusion kneadability.

On the other hand, the acrylic resin according to the present invention comprises an acrylic polymer containing a (meth) acrylate monomer and a compound having an ultraviolet ray absorbing property, wherein the compound having an ultraviolet ray absorbing property is added during polymerization of the acrylic polymer And is physically bonded to the acrylic polymer. For this purpose, in the present invention, a compound having an ultraviolet ray absorbing property and having a solubility of 1 to 40, 10 to 40 or 15 to 40 with respect to 100 parts by weight of a (meth) acrylate monomer is used. In the present invention, the solubility may be a value measured at a temperature range of 20 ° C to 50 ° C. That is, the compound having an ultraviolet absorption property of the present invention preferably has a solubility of 1 to 40, 10 to 40, or 15 to 40 in 100 parts by weight of the (meth) acrylate monomer at a temperature range of 20 to 50 캜 Do. When the solubility of a compound having an ultraviolet ray absorbing property to a (meth) acrylate monomer is less than 1, a compound having an ultraviolet ray absorbing property is precipitated in the course of the polymerization and the acrylic polymer and the compound having ultraviolet ray absorbing ability are not mixed, If it exceeds 40, the ultraviolet absorber will deteriorate the performance of the initiator used in the polymerization process, resulting in a delay in polymerization time and a problem in that formation of a high-molecular weight material becomes difficult.

On the other hand, the (meth) acrylate monomer may be a substituted or unsubstituted (meth) acrylate monomer contained in the acrylic polymer, and examples thereof include alkyl methacrylates such as methacrylate, acrylate and methyl methacrylate And alkyl acrylates such as methyl acrylate. Among them, the solubility in methacrylate and methyl methacrylate preferably satisfies the above-described numerical range.

On the other hand, it is preferable that the compound having the ultraviolet ray absorbing property has a solubility of 0.1 to 60 or 5 to 60 in 100 g of an organic solvent containing a hydroxy group. In this case, the solubility may be a value measured in a temperature range of 20 ° C to 50 ° C. That is, the compound having an ultraviolet absorption property of the present invention preferably has a solubility of 0.1 to 60 or 5 to 60 in 100 g of an organic solvent containing a hydroxy group at a temperature range of 20 to 50 캜. When the solubility in the organic solvent satisfies the above-described numerical value range, there is an advantage that the compound having ultraviolet ray absorbing ability can be continuously retained in the resin without being precipitated from the resin-polymerized solution. Herein, the solubility means g of a compound having an ultraviolet ray absorbing property dissolved in 100 g of an organic solvent containing a hydroxyl group. Examples of the organic solvent containing a hydroxyl group include, but are not limited to, methyl alcohol, ethyl alcohol, isopropyl alcohol, butanol, ethylene glycol, propylene glycol and phenol.

It is preferable that the compound having the ultraviolet ray absorbing property has a solubility of about 50 to 700 or about 150 to 700 in 100 g of an organic solvent containing a halogen element. In this case, the solubility may be a value measured in a temperature range of 20 ° C to 50 ° C. That is, it is preferable that the compound having an ultraviolet absorption property of the present invention has a solubility in an organic solvent containing halogen element of 50 to 700 or 150 to 700 in a temperature range of 20 to 50 占 폚. When the solubility in an organic solvent containing a halogen element satisfies the above-described numerical value range, there is an advantage that a compound having an ultraviolet ray absorbing property can be continuously retained in the resin without being precipitated from the resin polymerization solution. Examples of the organic solvent containing the halogen element include, but are not limited to, methylene chloride, chloroform, and dichloromethane.

A compound having an available ultraviolet absorbing performance in the present invention, but are not thereby limited, and for example, it is preferable that the triazine-based compound comprising a C _{4 ~ 20} aliphatic hydrocarbon at least one. The triazine type compound containing at least one or more of the C _{4 to} C ₂₀ aliphatic hydrocarbon groups has not only excellent ultraviolet ray absorbing ability but also is not easily decomposed in the heat treatment and the C _{4 to} C ₂₀ aliphatic hydrocarbon is relatively strongly entangled with the resin This is because the film is not deposited on the surface during film formation.

Preferably, the compound having an ultraviolet absorbing property of the present invention may be a compound represented by the following formula (1).

[Chemical Formula 1]

R ₁ to R ₆ are each independently hydrogen, a hydroxyl group, an alkyl group, an alkoxy group or an aromatic group, and R ₁ to R ₆ ≪ / RTI > A C _{4 to} C ₂₀ alkyl group or a C _{4 to} C ₂₀ alkoxy group.

More specifically, the compound having the ultraviolet absorbing property of the present invention is a compound having the above-mentioned R ₁ to R ₆ ≪ / RTI > A C _{4 to} C ₂₀ alkyl group or a C _{4 to} C ₂₀ alkoxy group, R ₁ to R ₆ Is a substituted or unsubstituted phenyl group, or a compound in which at least two of R ₁ to R ₆ At least two of A C _{4 to} C ₂₀ alkyl group or a C _{4 to} C ₂₀ alkoxy group, R ₁ to R ₆ May be a compound having a hydroxyl group.

Specific examples of the compound having ultraviolet ray absorbing ability include 6,6 '- (6- (4-methoxyphenyl) -1,3,5-triazine-2,4-diyl) bis (3- (Ethylhexyl) oxy) phenol), 2,4-di ([1,1'-biphenyl] -4- , 3,5-triazine, 2- (2-hydroxy-4- [1-octyloxycarbonylethoxy] phenyl) 4- [2-hydroxy-4- [1-octyloxycarbonylethoxy] phenyl) -4,6-bis (4-phenylphenyl) (2,4-dimethylphenyl) -1,3,5-triazine (2- [4 - [(2-ethylphenyl) 2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine), 2,4-bis 4-butyloxyphenyl) -6- (2,4-bis-butyloxyphenyl) -1,3,5-triazine (2-hydroxy- - (2,4-bis-butyloxyphenyl) -1,3,5-triazine), but are not limited thereto.

In the present invention, it is preferable that the compound having the ultraviolet ray absorbing property has a molecular weight of 300 to 2000, 500 to 1900 or 400 to 1800 or so. When a compound having an ultraviolet absorption capacity having a molecular weight satisfying the above numerical range is used, the thermal type and mechanical properties of the particulate acrylic resin are excellent, and the ultraviolet absorber is not precipitated outside when the film is processed.

On the other hand, the content of the compound having an ultraviolet ray absorbing property is preferably 0.1 to 10 parts by weight, 0.4 to 10 parts or 0.2 to 9 parts by weight based on 100 parts by weight of the acrylic polymer. When the content of the compound having an ultraviolet absorption property satisfies the above-described numerical value range, it can have excellent heat resistance while having an ultraviolet absorption property.

Meanwhile, the acrylic polymer includes (a) a (meth) acrylate-based monomer, and the (meth) acrylate-based monomer may be, for example, methacrylate, acrylate or methyl methacrylate Alkyl acrylates such as methyl methacrylate, methyl acrylate, and the like. More preferably, the alkyl moiety of the alkyl (meth) acrylate monomer is preferably 1 to 10 carbon atoms in consideration of optical transparency, compatibility, processability, and productivity, More preferably 1 to 4 carbon atoms, and still more preferably a methyl group or an ethyl group. The alkyl methacrylate-based monomer is more preferably methyl methacrylate, but is not limited thereto. In this case, the content of the acrylic monomer may be 70 to 100 parts by weight, 75 to 95 parts by weight or 80 to 90 parts by weight based on 100 parts by weight of the acrylic polymer. When the content of the (meth) acrylate monomer satisfies the above-described numerical value range, the optical film has an excellent transparency and heat resistance and is excellent in heat stability.

On the other hand, the acrylic polymer may further comprise, as necessary, at least one selected from the group consisting of (b) a styrenic monomer and (c) a 3- to 6-membered heterocyclic monomer substituted with at least one carbonyl group as a comonomer .

The styrene monomer (b) may be an unsubstituted styrene monomer, but includes styrene substituted with at least one substituent selected from the group consisting of aliphatic hydrocarbon and heteroatom in the benzene ring or vinyl group of styrene, Advantageously C _{1 - 1} type of compound ₄ can be used for the units substituted with alkyl or halogen, more preferably selected from α- methyl styrene, p- bromo styrene, p- methyl styrene, and the group consisting of p- chlorostyrene Or more can be used. Most preferably at least one substituent selected from the group consisting of styrene,? -Methylstyrene, and p-methylstyrene. The content of the styrenic monomer is preferably 0.1 to 10 parts by weight, 0.5 to 5 parts by weight, or 1 to 3 parts by weight based on 100 parts by weight of the acrylic polymer. When the content of the monomer (b) satisfies the above-described numerical value range, it is advantageous that the retardation of the optical film is easily controlled, the compatibility with the aromatic resin is excellent, and the optical film has excellent transparency and heat resistance.

In addition, the (c) 3- to 6-membered heterocyclic monomers substituted with at least one carbonyl group may be selected from the group consisting of maleic anhydride, maleimide, glutaric anhydride, glutarimide, lactone and lactam. The 3- to 6-membered heterocyclic monomers substituted with at least one carbonyl group can provide excellent heat resistance to the film produced by the resin composition. The monomers listed above exhibit excellent compatibility with the aromatic resin. When the (a) alkyl (meth) acrylate monomer and the (a) listed monomer constitute a copolymer, the compatibility of the copolymer and the aromatic resin is improved . The content of the 3- to 6-membered heterocyclic monomers substituted with the at least one carbonyl group is 0.1 to 12 parts by weight, 1 to 10 parts by weight or 1 to 8 parts by weight per 100 parts by weight of the acrylic polymer . When the content of the monomer (c) satisfies the above-described numerical value range, it is possible to prevent the optical film from being in a state that it is excellent in heat resistance and brittleness, There is an advantage that the color is not discolored.

In the present invention, the alkyl (meth) acrylate-based monomer imparts a negative in-plane retardation (Rin) and a negative thickness direction retardation (Rth) to a weak degree in the stretching process, and the styrenic monomer has a strong negative in- (Rin) and a negative thickness direction retardation (Rth). On the other hand, the 3- to 6-membered heterocyclic monomers substituted with at least one carbonyl group can provide excellent heat resistance to the film produced by the resin composition.

Herein, the negative in-plane retardation means that the refractive index is the largest in the stretching direction and the direction perpendicular to the plane, and the positive in-plane retardation means that the refractive index is the greatest in the stretching direction. Direction average refractive index, and the positive thickness direction retardation means that the in-plane average refractive index is larger than the thickness direction refractive index.

Depending on the characteristics of each monomer described above, the retardation characteristics of the optical film produced therefrom may vary depending on the composition of each component, the stretching direction, the stretching ratio, and the stretching method. Accordingly, in the present invention, it is possible to produce an optical film which can be used as a zero-phase retardation film, that is, a protective film by adjusting the composition of each component and the stretching method.

On the other hand, the form of the copolymer of the acrylic polymer of the present invention is not particularly limited, and may be, for example, a block copolymer or a random copolymer.

On the other hand, the acrylic resin according to the present invention may contain, if necessary, an aromatic resin having a carbonate moiety in the main chain. The aromatic resin having a carbonate moiety in the main chain may impart a positive in-plane retardation (Rin) property and a positive thickness direction retardation (Rth) property.

In the present invention, it is preferable that the aromatic resin having a carbonate moiety in the main chain contains 5 to 10,000 units of at least one kind represented by the following formula (2).

(2)

In Formula 2, X is a divalent group containing at least one benzene ring. More specifically, X is preferably a divalent group selected from the group consisting of the following structural formulas.

In the resin composition of the present invention, it is preferable that the acrylic polymer and the aromatic resin are mixed at a weight ratio of 90:10 to 99.5: 0.5. When the weight ratio of the acrylic polymer and the aromatic resin satisfies the above-described numerical range, the retardation of the optical film is easily controlled, and the miscibility of the acrylic polymer and the aromatic resin is excellent.

In the present invention, the acrylic resin composition comprises 85 to 98 parts by weight of an acrylic monomer; 1 to 3 parts by weight of a styrenic monomer; An acrylic polymer comprising 1 to 8 parts by weight of a 3- to 6-membered heterocyclic monomer substituted with at least one carbonyl group; And 0.1 to 5 parts by weight of a compound having ultraviolet absorbing ability. When the content of the respective monomers and the compound having an ultraviolet ray absorbing property contained in the acrylic resin composition of the present invention satisfies the above-described numerical value range, an optical film excellent in heat resistance and ultraviolet ray absorbing ability can be produced, , It is possible to manufacture an optical film having excellent appearance.

On the other hand, the glass transition temperature of the acrylic resin composition of the present invention containing the above-mentioned components is preferably about 100 ° C to 200 ° C, and may be, for example, 105 ° C to 160 ° C or 110 ° C to 140 ° C. The higher the glass transition temperature of the acrylic resin is, the higher the temperature at which the pellets are fusion-bonded. Therefore, the pellet can be dried at a higher temperature, and consequently acrylic resin pellets with lower water content can be produced. Further, since the produced optical film has a high heat distortion temperature, an optical film having a very high heat resistance can be obtained, which is very advantageous.

At this time, the acrylic resin composition may have a weight average molecular weight of 50,000 to 500,000 or 50,000 to 200,000 in terms of processability, heat resistance and productivity. When the molecular weight of the acrylic resin composition is less than 50,000, the film tends to increase in Brittleness and the film can not be stretched. When the molecular weight exceeds 200,000, the melt viscosity increases greatly, and the film extrusion process is impossible.

In addition, the acrylic resin composition may have a haze of about 0.1% to 3%, and a light transmittance of 90% or more. Further, the yellow index value of the acrylic resin composition may be about 0.3 to 2.0. When the transparency, the light transmittance, and the yellow index value satisfy the above numerical range, a display device having excellent color can be obtained.

The acrylic resin composition according to the present invention having the above-described structure has excellent heat resistance and excellent ultraviolet ray absorbing ability, and thus can be effectively used as an optical film.

Next, a method for producing the acrylic resin composition will be described.

The acrylic resin composition according to the present invention is obtained by mixing a (meth) acrylate monomer and 100 parts by weight of a (meth) acrylate monomer to form a reaction mixture by mixing a compound having an ultraviolet ray absorbing ability of 1 to 40 And then polymerizing the reaction mixture. At this time, the details of the (meth) acrylate monomer and the compound having an ultraviolet ray absorbing ability are the same as those described above, so a detailed description thereof will be omitted.

On the other hand, the polymerization can be carried out, for example, by solution polymerization, bulk polymerization, suspension polymerization or emulsion polymerization. Particularly, in the process for producing a resin composition according to the present invention, when it is intended to prepare an acrylic resin composition in a particle form having an average particle diameter of 10 to 500 m, 50 to 450 m or 100 to 400 m, . ≪ / RTI > This is because, by suspension polymerization, the preparation of the particulate acrylic resin composition as described above is easy. Among the polymerization methods listed above, in the case of solution and bulk polymerization, denaturation of the ultraviolet absorber may occur during the polymerization due to a high polymerization temperature. In the case of emulsion polymerization, it is difficult to satisfy the particle size range, There is a further need for process.

Next, the acrylic resin and the additive according to the present invention may be kneaded to prepare a resin pellet. At this time, the kneading may be performed by a kneader. As the kneading machine, for example, a uniaxial extruder or a biaxial extruder can be used. In particular, a kneader such as a twin screw extruder manufactured by Leistritz may be used, but the present invention is not limited thereto.

In the extruder, the ratio of the kneading portion may be in the range of 0.15 to 0.5 or 0.2 to 0.4. If the ratio of the kneading portion is less than 0.15, there is a problem that the kneading property and the melting property are insufficient and the resin is extruded in an unmelted or unmixed state. If the kneading portion ratio exceeds 0.5, excessive kneading property and meltability cause resin decomposition Lt; / RTI > Meanwhile, the ratio of the kneading portion refers to the ratio of the length of the kneading block to the total screw length.

Meanwhile, the kneading may be performed by a kneader equipped with a gear pump to ensure uniformity of the pellet size of the resin composition. When the uniformity of the pellet size is ensured, it is possible to prevent the pressure instability due to the unevenness of the discharge amount from occurring during the melt processing process, and to prevent the occurrence of the thickness variation and appearance defect of the film. That is, the above-mentioned problem of the thickness deviation and appearance defect of the film can be alleviated by using a kneader equipped with a gear pump capable of supplying resin at a certain pressure, and the resin pellets produced by the above- .

Also, the kneading may be performed by a kneader equipped with a polymer filter. At this time, the polymer filter has a pore size of 50 μm or less. When the kneader equipped with the polymer filter is used, there is an advantage that impurities can be removed by reducing the number of the black spots of the resin composition. As the polymer filter, for example, a polymer filter such as a Leaf Disk type and a Candle type filter may be used. In addition, the polymer filter may be used in combination with a back filter, It is not. On the other hand, when the voids of the polymer filter are 50 탆 or less, it is possible to produce a product having excellent impurity removing performance and excellent appearance characteristics.

The difference between the maximum particle diameter and the minimum particle diameter of the resin pellet of the present invention produced through the above method may be 5 mm or less, 3 mm or less, or 2 mm or less. In the case where the maximum and minimum differences of the pellet size satisfy the above numerical range, it is possible to prevent the pressure instability due to the uneven discharge amount from occurring in the melt processing process using the pellet, It is very advantageous.

The resin pellets may have a number of black spots of 10 / 100g or less, 8 / 100g or less or 5 / 100g or less. When the number of the black spots of the pellet satisfies the above-described numerical value range, it indicates that the occurrence of impurities is small, and as a result, there is an advantage that an optical film having excellent appearance characteristics can be obtained.

Next, the optical film according to the present invention is produced by using a resin pellet containing the acrylic resin.

At this time, the optical film may be produced in the form of a film according to a method well known in the art, such as a solution casting method or an extrusion method. It is more preferable to use the extrusion method in view of the economical aspect. Optionally, an additive such as an improving agent may be added in the film production process within a range that does not deteriorate 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. The stretching may be performed in one step or 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.

The stretching may be performed at (Tg-20 ° C) to (Tg + 30 ° C), where the glass transition temperature of the resin composition is Tg, Thereby indicating the region from the temperature at which the loss elastic modulus becomes larger than the storage modulus, to the temperature at which the orientation of the polymer chain is relaxed and disappears. The glass transition temperature of the resin composition can be measured by a differential scanning calorimeter (DSC). It is more preferable that the temperature at the drawing step is 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%.

The retardation characteristics of the film can be controlled through the stretching process as described above.

The optical film according to the present invention produced by the above method may have a linear light transmittance of 85% to 98% or 90% to 95% at a wavelength of 550 nm when measured in terms of a film thickness of 60 탆. When the linear light transmittance at the wavelength of 550 nm satisfies the above-described numerical range, there is an advantage that the transmittance of the polarizing plate can be improved. In the present specification, the linear light transmittance refers to the transmittance excluding the scattered light transmittance in the total light transmittance.

The optical film according to the present invention produced by the above-described method may have a linear light transmittance of 0.01% to 10% or 0.1% to 8% at a wavelength of 380 nm when the film thickness is measured in terms of 60 탆. When the linear light transmittance at a wavelength of 380 nm satisfies the above-described numerical range, it is possible to prevent the depolarization of the polarizer due to ultraviolet rays, the transmittance is excellent even in the visible light region of 400 nm wavelength, and the change in color of the polarizer can be prevented.

The optical film according to the present invention may have a linear light transmittance of 0.01% to 5% or 0.1% to 3% at a wavelength of 290 nm when the thickness of the film is measured in terms of 60 탆. When the linear light transmittance at the wavelength of 290 nm satisfies the above-described numerical range, the depolarization of the polarizer due to strong ultraviolet energy is prevented, and the yellowing rate of the film is lowered.

The optical film according to the present invention has excellent heat resistance, excellent ultraviolet ray absorbing ability, and has a high linear light transmittance in the visible ray region, and thus can be effectively used as a protective film.

Manufacturing example  One

Methyl methacrylate monomer, 6 parts by weight of N-cyclohexylmaleimide monomer, 2 parts by weight of? -Methylstyrene monomer, 6,6 '- (6- (4-methoxyphenyl) And 4 parts by weight of 3 - ((2-ethylhexyl) oxy) phenol) (hereinafter referred to as "ultraviolet absorber I" for convenience) , 2000 g of distilled water, 8.4 g of a 5% polyvinyl alcohol solution (POVAL PVA217, Kuraray Co.), 0.1 g of boric acid, 2.5 g of n-octyl mercaptan and 1.5 g of 2,2'-azobisisobutyronitrile And dispersed in water phase while stirring at 400 rpm to prepare a suspension.

Next, the suspension was heated to 80 DEG C, and polymerization was carried out for 90 minutes. Then, the suspension was cooled to 30 ° C, washed with distilled water, dehydrated and dried to obtain a resin composition A.

Thereafter, the resin composition A was fed to a twin-screw twin-screw extruder (Leistritz, L / D = 36) substituted with nitrogen from a raw material hopper to an extruder and melted at 260 ° C to obtain a raw material pellet A.

Manufacturing example  2

A resin composition B and a raw material pellet B were obtained in the same manner as in Production Example 1 except that the content of the ultraviolet absorber was changed to 8 parts by weight.

Manufacturing example  3

The ultraviolet absorber was changed to 2,4-di ([1,1'-biphenyl] -4-yl) -6- (4 - ((2-ethylhexyl) oxy) -2-methylphenyl- (Hereinafter, referred to as " ultraviolet absorber II " for convenience), a resin composition C and a raw material pellet C were obtained.

Manufacturing example  4

A resin composition D and a raw material pellet D were obtained in the same manner as in Production Example 3 except that the content of the ultraviolet absorber was changed to 8 parts by weight.

Manufacturing example  5

A resin composition E and a raw material pellet E were obtained in the same manner as in Production Example 1 except that the ultraviolet absorber was changed to LA-F70, which is a triazine-based ultraviolet absorber.

Manufacturing example  6

Resin composition F and raw material pellets F were obtained in the same manner as in Production Example 1 except that the ultraviolet absorber was changed to TINUVIN 360 which is a benzotriazole-based ultraviolet absorber.

Manufacturing example  7

1000 g of a monomer mixture comprising 92 parts by weight of methyl methacrylate monomer, 6 parts by weight of N-cyclohexylmaleimide monomer and 2 parts by weight of? -Methylstyrene monomer was prepared and 2000 g of distilled water, 5% polyvinyl alcohol solution (POVAL PVA217, manufactured by Kuraray Co.), 0.1 g of boric acid, 2.5 g of n-octyl mercaptan and 1.5 g of 2,2'-azobisisobutyronitrile, and dispersed in water phase while stirring at 400 rpm to prepare a suspension.

Next, the suspension was heated to 80 DEG C, and polymerization was carried out for 90 minutes. Then, the suspension was cooled to 30 ° C, washed with distilled water, dehydrated and dried to obtain a resin composition G.

Thereafter, to the resin composition G, 6,6 '- (6- (4-methoxyphenyl) -1,3,5-triazine-2,4-diyl) bis (3- (Leistritz, L / D = 36) having a nitrogen inlet at a feed hopper and an extruder were melted at 260 ° C. to obtain a raw pellet G .

Manufacturing example  8

The ultraviolet absorber was changed to 2,4-di ([1,1'-biphenyl] -4-yl) -6- (4 - ((2-ethylhexyl) oxy) -2-methylphenyl- The raw material pellets J were obtained in the same manner as in Production Example 7,

Types of ultraviolet absorbers Molecular Weight Melting point Solubility (100 g) Turbidity ethyl alcohol MMA MA Dichloromethane MMA 4 wt% solution Ultraviolet absorber I 627 82 53 30 15 620 Clear Ultraviolet absorber II 604 127 8.7 25 13 530 Clear LA-F70 699 146 Does not melt 0.5 11 560 Haze TINUVIN 360 659 195 0.03 0.005 0.006 75 Haze

Example  One

The raw pellets obtained in Preparation Example 1 were hot-air dried at 80 ° C. for 6 hours, melted at 265 ° C. by an extruder, passed through a coat hanger type T-die, Rolls and the like, and then stretched 100% in the longitudinal direction (MD) and the transverse direction (TD), respectively, at a rate of 200 mm / min at 135 ° C. using an experimental film stretching machine.

Example  2 to 4 and Comparative Example  1-4

Optical films according to Examples 2 to 4 and Comparative Examples 1 to 4 were produced in the same manner as in Example 1, using the raw material pellets obtained in Production Examples 2 to 8.

Experimental Example  One

The average particle sizes of the acrylic resin compositions A to H prepared according to Production Examples 1 to 8 were measured using an optical microscope (LV100P, Nikon). The measurement results are shown in Table 2 below.

division Type of resin composition Content of ultraviolet absorber Average particle size
(탆) Example 1 A 4 250 Example 2 B 8 250 Example 3 C 4 250 Example 4 D 8 580 Comparative Example 1 E 4 720 Comparative Example 2 F 4 680 Comparative Example 3 G 4 - Comparative Example 4 H 4 -

Experimental Example  2 - Film appearance measurement

The optical films according to Examples 1 to 4 and Comparative Examples 1 to 4 were observed first with the naked eye and further observed with a light microscope (LV100P, Nikon) against the film having a problem in the appearance of the film, Appearance was measured by dividing the shape of the additive. The measurement results are shown in Table 3 below.

Experimental Example  3 - Measurement of light transmittance

Optical films according to Examples 1 to 4 and Comparative Examples 1 to 4 were measured for linear transmittance at 550 nm, 380 nm and 290 nm when the film thickness was converted into 60 μm using a spectrophotometer (U-3310, Hitachi) Respectively. The measurement results are shown in Table 3 below.

division Film appearance Light transmittance (%) 550 nm 380 nm 290 nm Example 1 Good 92 3.8 0.5 Example 2 Good 92 1.3 0.2 Example 3 Good 92 5.2 0.4 Example 4 Good 92 0.8 0.2 Comparative Example 1 Good 92 77 62 Comparative Example 2 Bubble generation 78 7.8 1.4 Comparative Example 3 Precipitation occurrence 89 5.7 1.1 Comparative Example 4 Precipitation occurrence 87 7.1 0.9

As shown in Tables 2 and 3, the resin compositions used in Examples 1 to 4 have appropriate particle sizes and are easy to produce pellets. In the case of optical films produced using the resin compositions, It is suitable for use as an optical film. However, in the case of the resin compositions used in Comparative Examples 1 to 4, even when the particle size is very large and the particle size is appropriate, in the case of the optical film produced using the resin composition, bubbles are generated or precipitation of additives occurs, It is difficult to use it as an optical film.

In addition, as shown in Table 3, since the optical films according to Examples 1 to 4 have a higher linear light transmittance in the visible light region than the optical films according to Comparative Examples 1 to 4, they are useful as protective films .

Further, in the case of the optical films according to Examples 1 to 4, the linear optical transmittance in the 380 nm and 290 nm wavelength regions is very low as compared with the optical films according to Comparative Examples 1 to 4. When the linear light transmittance in the wavelength regions of 380 nm and 290 nm is low, it is possible to prevent the change of the polarizer due to ultraviolet rays or the color change of the polarizer, and the yellowing rate of the film is lowered.

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.

Claims (17)

(Meth) acrylate-based monomer; And
(Meth) acrylate monomer having a solubility of 1 to 40 with respect to 100 parts by weight of a (meth) acrylate monomer,
The compound having ultraviolet ray absorbing ability has a solubility of 0.1 to 60 in 100 parts by weight of an organic solvent containing a hydroxyl group,
Wherein the compound having an ultraviolet ray absorbing property has a solubility of 50 to 700 with respect to 100 parts by weight of an organic solvent containing a halogen element.
delete delete The method according to claim 1,
Wherein the compound having an ultraviolet ray absorbing property is a triazine type compound having a molecular weight in the range of 300 to 2000 and containing at least one C _{4 to 20} aliphatic hydrocarbon group.
The method according to claim 1,
Wherein the content of the compound having an ultraviolet absorption property is 0.1 to 10 parts by weight based on 100 parts by weight of the acrylic polymer.
The method according to claim 1,
Wherein the (meth) acrylate-based monomer is an alkyl (meth) acrylate-based monomer.
The method according to claim 1,
Wherein the acrylic polymer containing the (meth) acrylate monomer further comprises at least one monomer selected from the group consisting of a styrenic monomer and a 3- to 6-membered heterocyclic monomer substituted with at least one carbonyl group. .
8. The method of claim 7,
The acrylic polymer containing the (meth) acrylate-based monomer may be obtained,
85 to 98 parts by weight of a (meth) acrylate-based monomer;
1 to 3 parts by weight of a styrenic monomer; And
And 1 to 8 parts by weight of a 3- to 6-membered heterocyclic monomer substituted with at least one carbonyl group.
The method according to claim 1,
Wherein the acrylic resin composition is a particle type and has an average particle diameter of 10 to 500 占 퐉.
The method according to claim 1,
Wherein the acrylic resin composition has a glass transition temperature of 100 占 폚 to 200 占 폚.
A resin pellet comprising the acrylic resin composition of any one of claims 1 to 10.
12. The method of claim 11,
Wherein the resin pellet has a difference between a maximum particle diameter and a minimum particle diameter of 5 mm or less.
12. The method of claim 11,
The resin pellet has a number of black spots of 10/100 g or less.
An optical film produced by using the resin pellet of claim 11.
15. The method of claim 14,
Wherein the optical film has a linear light transmittance of 85% to 95% at a wavelength of 550 nm when the thickness of the optical film is measured in terms of 60 탆.
15. The method of claim 14,
Wherein the optical film has a linear light transmittance of 0.01% to 10% at a wavelength of 380 nm when the thickness of the optical film is measured in terms of 60 탆.
15. The method of claim 14,
Wherein the optical film has a linear light transmittance of 0.01% to 5% at a wavelength of 290 nm when the thickness of the optical film is measured in terms of 60 탆.