KR102260108B1 - Acrylic optical film and manufacturing method thereof - Google Patents

Abstract

The present invention relates to an acrylic optical film and a method for manufacturing the same. More specifically, it relates to an acrylic optical film manufactured by a solvent casting method and a manufacturing method thereof. In addition, the present invention relates to a dope solution for solvent casting for producing the acrylic optical film.

Description

Acrylic optical film and manufacturing method thereof

The present invention relates to an acrylic optical film and a method for manufacturing the same. More specifically, it relates to an acrylic optical film manufactured by a solvent casting method and a manufacturing method thereof. In addition, the present invention relates to a dope solution for solvent casting for producing the acrylic optical film.

Recently, with the development of optical technology, the liquid crystal display is required to be thinner, lighter, and larger in the display industry, and technologies such as wide viewing angle, high contrast, uniform screen display, and suppression of image change according to viewing angle are particularly important issues. is becoming

Various polymer films such as a polarizing film, a polarizing plate protective film, a retardation film, a light guide plate, and a plastic substrate are used in these display devices, and the required characteristics of these display polymer materials are becoming more advanced.

Cellulose ester films have been used for photography or as various optical materials because of their high strength and flame retardancy. In particular, since the cellulose acylate film has high optical transparency and optical isotropy, it has been widely used as an optically transparent film for a liquid crystal display device. However, when a cellulose ester film or a film including the same is molded into a thin film, moisture permeability is weak, causing a problem in storage stability due to expansion. In particular, the deterioration of durability in a high-temperature and high-humidity environment greatly affects the deterioration of the function of the liquid crystal display. In addition, there is a problem of a decrease in strength and surface hardness of the film due to thinning, so efforts have been made to replace cellulose ester or a film containing the same.

In order to overcome the above problems, research for manufacturing an optical film using a methacrylic polymer is being conducted.

For example, Korean Patent Publication No. 10-2015-0039089 filed by the present applicant discloses a composition for manufacturing an optical film by melt extrusion of an acrylic copolymer, but it is difficult to control the thickness by melt extrusion. , there is a large difference in thickness,

In order to solve this problem, a method of manufacturing an acrylic copolymer by a solution casting method is newly tried. For example, Korean Patent Publication No. 1838494B discloses an optical film using a copolymer of methyl methacrylate, phenylmaleimide, and butyl acrylate, but surface thickness deviation occurs during film forming, and the uniformity of the haze is also insufficient. , haze itself is high, and there is a problem in that the color of the film itself is generated.

Korean Patent Publication No. 10-2015-0039089 (2015.04.09.) Korean Patent Registration Publication No. 10-1838494 (2018. 3. 8.)

One aspect of the present invention is a novel new invention with low change over time, accelerated solvent drying time, excellent mechanical properties such as tensile strength, easy to manufacture wide film, excellent peel-off property, and excellent optical properties. An acrylic optical film is provided.

One aspect of the present invention is to provide a new krill-based optical film having no surface thickness deviation, uniform haze, and also low haze itself and no color of the film during film forming for use as a polarizing plate protective film or retardation film. .

That is, an aspect of the present invention is to provide an acrylic optical film that is manufactured by a solvent casting method, has excellent smoothness, has a uniform thickness over the entire width, has a low haze, and has a uniform haze over the entire width of the film. .

In addition, one aspect of the present invention can further improve productivity by further shortening the film forming time of the film by increasing the drying rate of the solvent in forming the film by the solvent casting method, and there is no local residue left when the film is peeled off. An object of the present invention is to provide a dope solution capable of easily forming a wide film having a width of 2000 mm or more, and a method for manufacturing an acrylic optical film using the same.

In addition, an aspect of the present invention is to increase the drying rate of the solvent to improve productivity, as well as to provide an optical film in which haze or thickness uniformity of the optical film is further improved.

As a result of research to achieve the above object, (A) a methacrylic polymer polymerized including 80 to 90 wt% of methyl methacrylate and 10 to 20 wt% of n-butyl methacrylate, (B) Crosslinking degree of the core layer is greater than the degree of crosslinking of the intermediate layer, and the outermost layer as the shell layer has a three-layered core-shell acrylic rubber nanopolymer having a non-crosslinked layer containing methyl methacrylate as a main component (hereinafter referred to as 'core-shell particles') and (C) By solvent casting using a dope solution containing an organic solvent, the above problems were solved and the present invention was completed.

In the present invention, the content of solids in the dope solution is preferably 10 to 30% by weight based on the total dope solution, and the core well particles are mixed in an amount of 20 to 100 parts by weight based on 100 parts by weight of the methacrylic polymer. prefer to

In the present invention, the methacrylic polymer preferably has a weight average molecular weight of 400,000 or more, preferably 400,000 to 2.5 million.

In the present invention, the casting film prepared with the dope solution provides an acrylic optical film having a thickness deviation of 5% or less.

In addition, one aspect of the present invention is

a) a methacrylic polymer having a weight average molecular weight of 400,000 or more, preferably 400,000 to 2.5 million, including 80 to 90% by weight of methyl methacrylate and 10 to 20% by weight of butyl methacrylate, the three-layered core-shell applying a dope solution containing acrylic particles and an organic solvent on a support;

b) evaporating the organic solvent and peeling the acrylic film from the support; and

c) a stretching step of uniaxially stretching or biaxially stretching the acrylic film;

It provides a method of manufacturing an acrylic optical film comprising a.

Also in the present invention The three-layered core-shell particle is composed of a core layer, an intermediate layer, and a shell layer, and the core layer is formed by polymerizing 3 to 10 parts by weight of a crosslinking agent based on 100 parts by weight of the total monomer to have a higher degree of crosslinking than the intermediate layer.

In addition, the intermediate layer is a rubbery core layer, containing 60 to 85% by weight of a C4 to C6 alkyl (meth)acrylate monomer based on the total monomer, and 15 to 40% by weight of a styrenic monomer, and a crosslinking agent It is prepared to have a soft rubber layer having a crosslinking degree lower than that of the core layer by including 0.5 to 2 parts by weight based on 100 parts by weight of the monomer mixture.

In addition, the shell layer is a non-crosslinked layer, and is made of methyl methacrylate as a main component.

The dope solution according to the present invention can further shorten the time required for application, drying and peeling of the dope solution by controlling the drying rate of the solvent faster when manufacturing the acrylic optical film by the solvent casting method. Therefore, there is an effect that the productivity of the film can be improved.

In addition, the dope solution according to the present invention has little viscosity change over time, a fast drying rate of the solvent, and excellent heat resistance and mechanical properties of the manufactured optical film, so that it can be easily manufactured into a wide film.

In addition, the optical film prepared with the dope solution of the present invention can provide a new krill-based optical film having little surface thickness deviation, uniform haze, and low haze itself and no film color. That is, the present invention can provide an acrylic optical film having excellent smoothness, uniform thickness over the entire width, low haze, and uniform haze over the entire width of the film when manufactured by the solvent casting method.

Therefore, there is an effect that a wide film having a width of 2000 mm or more can be easily manufactured, and when the film is peeled off from the support after the film is formed, no residue is left on the support and the defect rate can be minimized.

In addition, the acrylic optical film prepared using the dope solution according to the present invention has a low water vapor transmission rate, high heat resistance, and a small number of foreign substances. Accordingly, it is possible to provide a film suitable for use as a polarizing plate protective film or retardation film.

In addition, in the present invention, the dope solution combined using the core-shell particles of the three-layer structure has little change in viscosity over time, so that workability can be increased.

Hereinafter, the present invention will be described in more detail through examples including the accompanying drawings. However, the following examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, the singular forms used in the specification and appended claims may also be intended to include the plural forms unless the context specifically dictates otherwise.

Hereinafter, as a main component in the present invention, it means to include 50% by weight or more, specifically 50 to 99% by weight.

One aspect of the present invention is a methacrylic polymer prepared including 80 to 90% by weight of methyl methacrylate and 10 to 20% by weight of n-butyl methacrylate, the crosslinking degree of the core layer is greater than that of the intermediate layer, and the outermost layer is It is an acrylic optical film manufactured by a solvent casting method using a dope solution containing three-layer core-shell particles and an organic solvent as a non-crosslinked layer containing methyl methacrylate as a main component, and has a thickness deviation of less than 5%.

In one embodiment, the optical film may be a polarizing plate protective film or a retardation film.

In one aspect, the methacrylic polymer may have a weight average molecular weight of 400,000 g/mol or more and a glass transition temperature of 110° C. or more.

In one embodiment, the methyl methacrylate polymer may be prepared by further including any one or two or more monomers selected from acrylic acid, methacrylic acid, acid anhydride, styrene-based monomers and maleimide-based monomers.

In one embodiment, the organic solvent may be a halogenated hydrocarbon alone or a halogenated hydrocarbon and any one or a mixed solvent selected from esters, ketones, ethers and alcohols.

In one aspect, the dope solution has a solid content of 10 to 30% by weight, and contains 20 to 100 parts by weight of a three-layered core-shell rubber based on 100 parts by weight of the methacrylic polymer, and a viscosity of 10,000 at 32°C It may be higher than cps. In addition, the content of solids in the dope solution is preferably 10 to 30% by weight based on the total dope solution, and the core well particles are preferably mixed in an amount of 20 to 100 parts by weight based on 100 parts by weight of the methacrylic polymer. .

In the present invention, the methacrylic polymer preferably has a weight average molecular weight of 400,000 or more, preferably 400,000 to 2.5 million.

In one aspect of the present invention, the casting film prepared with the dope solution provides an acrylic optical film having a thickness deviation of 5% or less.

In addition, one aspect of the present invention is

a) A dope solution comprising a methacrylic polymer polymerized including 80 to 90 wt% of methyl methacrylate and 10 to 20 wt% of butyl methacrylate, the three-layered core-shell acrylic particles, and an organic solvent on a support applying;

b) evaporating the organic solvent and peeling the acrylic film from the support; and

c) a stretching step of uniaxially stretching or biaxially stretching the acrylic film;

It provides a method of manufacturing an acrylic optical film comprising a.

Also in the present invention The three-layered core-shell particle is composed of a core layer, an intermediate layer, and a shell layer, and the core layer is formed by polymerizing 3 to 10 parts by weight of a crosslinking agent based on 100 parts by weight of the total monomer to have a higher degree of crosslinking than the intermediate layer.

In addition, the intermediate layer is a rubbery core layer, containing 60 to 85% by weight of a C4 to C6 alkyl (meth)acrylate monomer based on the total monomer, and 15 to 40% by weight of a styrenic monomer, and a crosslinking agent It is prepared to have a soft rubber layer having a crosslinking degree lower than that of the core layer by including 0.5 to 2 parts by weight based on 100 parts by weight of the monomer mixture.

In addition, the shell layer is a non-crosslinked layer, and is made of methyl methacrylate as a main component.

In one embodiment, the optical film may be a polarizing plate protective film or a retardation film.

In one aspect, the methacrylic polymer may have a weight average molecular weight of 400,000 g/mol or more, preferably 400,000 to 2.5 million, and a glass transition temperature of 110° C. or more.

In one embodiment, the organic solvent may be a halogenated hydrocarbon alone or a halogenated hydrocarbon and any one or a mixed solvent selected from esters, ketones, ethers and alcohols.

In one aspect, the dope solution may further include polycarbonate. When the polycarbonate is further added, mechanical properties such as tensile strength are increased, and when a film of a wide width is manufactured, the moisture permeability is further increased, and the peel-off property is significantly increased to make the film formability better. When using polycarbonate, it is better to use 0.1 to 10% by weight based on the total content of the dope solution.

In one aspect of the present invention, the dope solution is 20 to 100 parts by weight of the core-shell particles of the present invention and the remaining amount is a solvent based on 100 parts by weight of the methyl methacrylate-based copolymer, and the viscosity is 10,000 at 32 ° C. It is preferable that the solid content be 10 to 30% by weight based on the entire dope solution, which may be more than cps.

The acrylic optical film prepared by solvent casting and stretching with the dope solution of the present invention has a water vapor transmission rate of 200 g/m 2 ·24hr or less, preferably 1 to 200 g/m2·24hr, and a number of foreign substances from 0 to 0.3 pieces/1m or less and haze may be 0.1 to 2% or less.

In one aspect, the acrylic optical film produced by casting and stretching with the dope solution may have a film thickness of 10 to 150 μm.

In one aspect, the acrylic optical film may be stretched under the condition that the residual solvent in the film is 1 to 20 wt%.

Another aspect of the present invention is a method for producing an acrylic optical film, a) a methacrylic copolymer polymerized from a monomer comprising 80 to 90% by weight of methyl methacrylate and 10 to 20% by weight of butyl methacrylate, the above 3 applying a dope solution containing layered core-shell particles and an organic solvent onto a support through a die;

b) evaporating the organic solvent and peeling the acrylic film from the support; and

c) a stretching step of uniaxially stretching or biaxially stretching the acrylic film;

may include.

In one aspect, in step b), the film is peeled off when the residual solvent of the acrylic film is 1 to 20% by weight, preferably 5 to 20% by weight, and in the application of step a), step b) It may be produced within 20 minutes, preferably within 10 minutes, and even more preferably within 5 minutes until the peeling of.

In one embodiment, the optical film may be a polarizing plate protective film or a retardation film.

In one embodiment, the stretching step may be stretching 1.1 to 10 times, preferably 1.1 to 5 times under the condition that the residual solvent in the film is 5 to 20 wt%.

In one aspect, the dope solution may further include polycarbonate.

In one aspect, when the dope solution is applied on the support, the viscosity change rate of the dope solution is 20% or less, more preferably 10% or less, even more preferably 5% or less, when the dope solution is prepared and left for 10 minutes. It may be performed within the range of phosphorus.

In the present invention, the methacrylate-based copolymer may be additionally prepared by further including any one or two or more monomers selected from acrylic acid, methacrylic acid, acid anhydride, styrene-based monomer and maleimide-based monomer, in this case, If the content is selected from the range of 0.1 to 10% by weight based on the total monomers, it is better because it can be prepared without impairing the desired effect in the present invention.

In one embodiment, the dope solution of the present invention may have a solid content of 10 to 30% by weight based on the total content.

Hereinafter, the optical film manufacturing method of the present invention will be described.

The acrylic optical film according to the present invention is prepared by solvent casting the dope solution. The production of an optical film by the solvent casting method is to cast a dope solution in which a resin is dissolved in an organic solvent on a support, evaporate the organic solvent to form a film, and then stretch it.

When manufacturing a film by the solvent casting method, if the viscosity of the dope solution is too low or too high, it is difficult to cast the dope solution on the support, and thus the film production may become impossible. In addition, when conditions such as evaporation time and evaporation temperature of the organic solvent used in the dope solution do not match the physical properties of the resin used in the dope solution, the organic solvent is not sufficiently dried and the film is not peeled from the support, or the Water may remain and become contaminated.

However, in the case of manufacturing using the dope solution of the present invention, it is possible to further improve productivity by further shortening the evaporation time of the organic solvent while reinforcing mechanical properties, and the viscosity change rate of the dope solution is 20% or less, good can be maintained at 10% or less, more preferably 5% or less, so that the optical and mechanical properties are more excellent. In addition, when the thin film formed on the support by solvent casting is peeled off, no residue is left on the support, so that defects do not occur, and the support is not contaminated, so that it can be used continuously for a long time, thereby increasing quality and productivity.

In addition, even if the manufactured optical film is manufactured with a wide film, for example, a width of 2000 mm, it is excellent in thickness uniformity and haze uniformity over the entire width, and it is possible to provide an optical film excellent in heat resistance and mechanical properties.

The dope solution of the present invention has a composition of 20 to 100 parts by weight of the three-layered core-shell particles of the present invention with respect to 100 parts by weight of the copolymer, and the effect of the present invention when the solid content of the total dope solution is 10 to 30% by weight can be achieved well, so it is more preferred.

The dope solution of the present invention preferably has a viscosity of 10,000 cps or more at 32°C, specifically 10,000 to 60,000 cps, more specifically 20,000 to 40,000 cps.

When the composition component is satisfied and the dope solution has a solid content and viscosity range of the above categories, the dope solution of the present invention can be cast to a uniform thickness on a support, and a relatively high temperature when the organic solvent is dried after casting on a support It is preferable because it is possible to dry the optical film in a short time, and it is possible to produce a smooth and easily peelable optical film.

When the crosslinking degree of the copolymer and the core layer of the present invention is greater than that of the intermediate layer, and the outermost layer is a non-crosslinked layer containing methyl methacrylate as a main component, three-layered core-shell particles are adopted, the organic solvent is evaporated after film formation The drying rate of the organic solvent can be controlled more quickly in the process of making the film, and thus the production rate of the film can be further improved. In addition, the tensile strength of the film is 2 GPa or more, and the mechanical properties are preferably 2.5 GPa or more, while the optical properties or the film is not damaged when the film is removed from the support. It has the characteristics of being able to easily manufacture a film of 2000 mm or more.

In one aspect of the present invention, the copolymer may be prepared by emulsion polymerization or suspension polymerization, but more preferably, when suspension polymerization is carried out, it is more preferable because it has excellent optical properties.

In the present invention, when the copolymer is prepared by suspension polymerization, a methacrylic polymer having a high molecular weight and less agglomeration of particles can be prepared, and the solvent casting method is preferred because it is possible to produce a film with excellent optical properties. do not limit

In particular, in the present invention, when a dope solution is prepared with an acrylic copolymer prepared by using an acrylic suspension polymerization dispersant prepared by polymerization including the monomers of Chemical Formulas 1 and 2, the transparency is better than 5% (permeability). It is more preferred because it can exhibit an excellent effect of increasing, further lowering the haze by 10% or more, and further lowering the change with time of the dope solution by 10% or more.

[Formula 1]

In Formula 1, R ₁ is hydrogen or C ₁ to C ₃ alkyl, n is an integer selected from 0 to 3, and M is any one selected from lithium, sodium, potassium and ammonium.

[Formula 2]

In Formula 2, R ₂ is hydrogen or C ₁ to C ₃ alkyl, and M is any one selected from lithium, sodium, potassium and ammonium.

More specifically, a monomer mixture consisting of 60 to 70% by weight of the monomer of Formula 1, 5 to 15% by weight of the monomer of Formula 2, and 15 to 35% by weight of an alkyl (meth)acrylate-based monomer is uniformly polymerized in an aqueous solution in the presence of an initiator. it could be

By using the suspension polymerization dispersing agent, the dispersibility is further improved, the content of unreacted monomer is further reduced, the reaction is stable, and the obtained copolymer has an even particle size. can be further improved.

The compound represented by Formula 1 is any one selected from 3-sulfopropyl acrylate potassium salt, 3-sulfopropyl methacrylate potassium salt, 2-sulfoethyl methacrylate sodium salt, and 2-sulfoethyl acrylate sodium salt Or it may be a mixture of two or more.

remind The solid content of the suspension polymerization dispersant may be 1 to 10% by weight, and more preferably 3 to 6% by weight.

When polymerizing the methacrylic copolymer of the present invention, based on 100 parts by weight of the total monomer mixture, 0.001 to 1.0 parts by weight of the suspension polymerization dispersant having a solid content of 1 to 10% by weight, more preferably 0.005 to 0.6 parts by weight. it could be In the above range, good copolymer particles can be obtained, and polymerization stability is excellent, and the loss of copolymer particles is small in the washing and drying process, so workability and economical efficiency are good, which is preferred, but is not necessarily limited thereto.

The weight average molecular weight of the suspension polymerization dispersant may be 100,000 to 5,000,000 g/mol, and more specifically, 500,000 to 3,000,000 g/mol. It is preferable to be able to prepare a polymer having a uniform shape and particle size distribution within the above range.

In the present invention, the methacrylic copolymer may be polymerized in the presence of a suspension polymerization initiator and a chain transfer agent.

More specifically, the initiator may be used without limitation as long as it is an organic peroxide initiator, and specifically, for example, t-butylperoxy-2-ethylhexanoate, t-amylperoxy- 2-ethylhexanoate (t-amylperoxy-2-ethylhexanoate), 1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane (1,1-bis(t-butylperoxy)- 3,3,5-trimethyl cyclohexane), 1,1-bis(t-butylperoxy) cyclohexane (1,1-bis(t-butylperoxy) cyclohexane), 1,1-bis(t-butylperoxy) -2-methyl cyclohexane (1,1-bis (t-butylperoxy) -2-methyl cyclohexane), 2,2-bis (4,4-di-t-butylperoxy cyclohexyl) propane (2,2- bis(4,4-di-t-butylperoxy cyclohexyl)propane), 1,1-di-(t-amylperoxy) cyclohexane (1,1-di-(t-amylperoxy) cyclohexane), lauryl peroxide (lauroyl peroxide) and mixtures thereof, but is not limited thereto. The initiator may be included in an amount of 0.01 to 0.5 parts by weight, more preferably 0.1 to 0.3 parts by weight, based on 100 parts by weight of the total monomer content. A desired molecular weight can be obtained in the above range, and it is preferable because it is easy to control the reaction heat of the reactor.

The chain transfer agent may be used without limitation as long as it is a compound clearly known in the art, and specifically, for example, a C ₁ to C ₁₂ alkyl mercaptan having one thiol functional group or a poly having two or more thiol functional groups Thiol mercaptans can be used. Specifically, for example, isopropyl mercaptan, normal butyl mercaptan, tert-butyl mercaptan, tertiary-dodecyl mercaptan, normal-aryl mercaptan, normal-octyl mercaptan, normal-dodecyl mercaptan, etc. can be used The content may be 0.01 to 0.2 parts by weight, more specifically 0.01 to 0.1 parts by weight, more specifically 0.01 to 0.05 parts by weight, based on 100 parts by weight of the total weight of the monomer, and the weight average molecular weight within the above range is 400,000 g It is preferable because /mol or more methacrylic polymer can be produced.

In addition, a dispersing aid may be further included as needed, and any dispersing aid selected from metal salts or ammonium salts clearly known in the art may be used without limitation. Specific examples include magnesium sulfate, sodium sulfate, ammonium sulfate, and the like. The content of the dispersing aid is not limited, but the dispersing agent: the content of the dispersing aid may be used in a weight ratio of 1: 5 to 5: 1. It is preferable because the average particle diameter and particle size distribution of the polymer particles can be controlled within the above range.

Furthermore, if necessary when manufacturing the methacrylic polymer, various additives commonly used in the art, for example, a plasticizer, antioxidant, UV stabilizer, heat stabilizer, slip agent, etc. may be further included. In this case, the additives may be included in an appropriate amount within a range that does not impair the physical properties of the methacrylic polymer, for example, about 0.1 to 5 parts by weight based on 100 parts by weight of the total monomer content.

In one aspect of the present invention, the dope solution may have a solid content of 10 to 30% by weight based on the total content.

When the viscosity of the dope solution in the solid content range is less than 10,000 cps at 32° C., it is difficult to form a film due to high fluidity. In the solid content range, the viscosity of the dope solution is 10,000 cps or more at 32 ° C., specifically 10,000 to 80,000 cps, more preferably 20,000 to 60,000 cps, even more preferably 30,000 to 40,000 cps. In the range, the weight average molecular weight is 400,000 g / mol or more and it is suitable for continuous film formation using a dope solution using a methacrylic polymer having a glass transition temperature of 110° C. or more.

The optical film for preparing the dope solution of the present invention is preferable because it is suitable for preparing a film having a thickness of, but not limited to, 5 to 200 μm, specifically 10 to 150 μm, preferably 20 to 80 μm.

The organic solvent is not limited as long as it can dissolve the methacrylic polymer of the present invention, but preferably halogenated hydrocarbons such as chlorinated hydrocarbons, methylene chloride and chloroform can be used. Among them, it is most preferable to use methylene chloride. In addition, if necessary, an organic solvent other than halogenated hydrocarbons may be mixed and used. Organic solvents other than halogenated hydrocarbons include esters, ketones, ethers and alcohols. Esters include methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate. As ketones, acetone, methyl ethyl ketone, diethyl ketone, and diisobutyl ketone are available. , cyclopentanone, cyclohexanone, methylcyclohexanone, etc. can be used, and ethers include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetra Hydrofuran, anisole, phenetol, etc. can be used, and as alcohol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl- 2-butanol, cyclohexanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like are used.

More preferably, methylene chloride may be used as a main solvent, and alcohols such as methanol and ethanol may be used as a secondary solvent. Specifically, 80 to 99: 20 to 1 weight ratio of methylene chloride and alcohol, more preferably 85 to 90: 15 to 10 weight ratio can be mixed and used.

In addition, if necessary, various additives, for example, a plasticizer, an ultraviolet inhibitor, a deterioration inhibitor, fine particles, a release agent, an infrared absorber, an additive such as an optical anisotropy control agent may be added. Specific types of these additives may be used without limitation as long as they are commonly used in the relevant field, and the content thereof is preferably used in a range that does not reduce the physical properties of the film. The timing of adding the additive is determined according to the type of additive. The process of adding an additive to the last of dope preparation can also be implemented.

The plasticizer is used to improve the mechanical strength of the film, and when the plasticizer is used, the drying process time of the film can be shortened. The plasticizer may be used without limitation as long as it is conventionally used, and for example, there are carboxylate esters selected from phosphoric acid esters, phthalic acid esters, and citric acid esters. Examples of the phosphoric acid ester include triphenyl phosphate (TPP), biphenyl diphenyl phosphate, and tricresyl phosphate (TCP). Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP), and diethylhexyl phthalate (DEHP). have. Examples of the citric acid ester include o-acetyl triethyl citrate (OACTE) and o-acetyl tributyl citrate (OACTB). Examples of other carboxylate esters include butyl oleate, methylacetyl lysinoleate, dibutyl sebacate and various trimellitic acid esters. Preferably, it is good to use a phthalate ester plasticizer. The content of the plasticizer may be 2 to 20 parts by weight, more preferably 5 to 15 parts by weight, based on 100 parts by weight of the methacrylic polymer.

The UV inhibitor may include a hydroxybenzophenone-based compound, a benzotriazole-based compound, a triazine-based compound, a salicylic acid ester-based compound, and a cyanoacrylate-based compound. The amount of the UV inhibitor may be 0.1 to 3 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the methacrylic polymer.

As the deterioration inhibitor, for example, an antioxidant, a peroxide decomposing agent, a radical inhibitor, a metal deactivator, an oxygen scavenger, a photostabilizer such as a hindered amine, and the like can be used. Examples of particularly preferred degradation inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA). The amount of the degradation inhibitor may be 0.01 to 5 parts by weight, more preferably 0.1 to 1 parts by weight, based on 100 parts by weight of the methacrylic polymer.

The fine particles are added in order to suppress curl of the film, transport property, prevent adhesion in roll form, or maintain good scratch resistance, and any one selected from an inorganic compound and an organic compound may be used. For example, inorganic compounds include compounds containing silicon, silicon dioxide, titanium oxide, zinc oxide, aluminum oxide, barium oxide, zirconium oxide, strontium oxide, antimony oxide, tin oxide, tin/antimony oxide, calcium carbonate, talc, Clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, calcium phosphate, etc. are preferable, and more preferably, an inorganic compound containing silicon, zirconium oxide, etc. can be used. The fine particles may have an average primary particle diameter of 80 nm or less, preferably 5 to 80 nm, more preferably 5 to 60 nm, particularly preferably 8 to 50 nm.

In addition, if necessary, a wavelength dispersion modifier and the like may be further added. These additives can be used without limitation as long as they are conventionally used in the relevant field.

In addition, an optional retardation additive may be further included in order to further increase or decrease the retardation, if necessary. The retardation additive may be used without limitation as long as it is used to control retardation in the related field. In general, an additive for increasing retardation may be used for an optical film to be applied to a liquid crystal display of VA mode, and an additive for reducing retardation may be used for an optical film to be applied to a liquid crystal display of IPS mode. The retardation additive may be used in an amount of 1 to 15 parts by weight, more preferably 3 to 10 parts by weight, based on 100 parts by weight of the methacrylic polymer, and in the above range, bleeding may not occur, and high-quality images may be formed. can do.

In addition, the dope solution of the present invention may further include polycarbonate if necessary.

The polycarbonate may include 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight, based on the total dope solution. The polycarbonate may have a weight average molecular weight of 5,000 to 100,000 g/mol. By adding the polycarbonate, the optical retardation of the acrylic optical film may be reduced, and more specifically, the acrylic optical film may be manufactured as a zero retardation protective film.

Next, the three-layered core-shell particle of the present invention will be described.

Also in the present invention The three-layered core-shell particle is composed of a core layer, an intermediate layer, and a shell layer, and the core layer is formed by polymerizing 3 to 10 parts by weight of a crosslinking agent based on 100 parts by weight of the total monomer to have a higher degree of crosslinking than the intermediate layer.

In addition, the intermediate layer is a rubbery core layer, containing 60 to 85% by weight of a C4 to C6 alkyl (meth)acrylate monomer based on the total monomer, and 15 to 40% by weight of a styrenic monomer, and a crosslinking agent It is prepared to have a soft rubber layer having a crosslinking degree lower than that of the core layer by including 0.5 to 2 parts by weight based on 100 parts by weight of the monomer mixture.

In addition, the shell layer is a non-crosslinked layer, and is made of methyl methacrylate as a main component.

When the three-layered core-shell acrylic particle having the specific structure of the present invention is used, a film having remarkable physical properties of 2.0 GPa, preferably 2.5 GPa or more in tensile strength is produced, and at the same time, the optical properties are excellent, and the Even in the case of manufacturing, it is well detached from the base layer and stretched well, so it exhibits very good properties. In addition, when manufacturing a film with a wide width, it has the characteristic of forming a film well without sagging due to stretching or a residual amount on the surface.

In addition, in the case of using the dope solution of the present invention using the core-shell particles of the present invention, it exhibits very excellent properties such as surface smoothness, optical properties, mechanical properties, and residual amount during the production of the film, and the doping speed of the solvent is further increased. It is even better because it shortens the time from the diagram of

In the core-shell rubber of the present invention, the rate of change with time of the film of the present invention is 20% or less, preferably 10% or less, more preferably 5% compared to the two-layered core-shell rubber or the structurally different three-layered core-shell structure. It was confirmed that the workability and film formability were improved because it could be maintained below, and the film forming workability and processability were improved by improving the peel-off properties during the production of the film as well as the tensile strength and impact resistance of the film. The core-shell rubber may have an average particle diameter of 100 to 400 nm, and has little effect on smoothness when manufacturing a film having a thickness of 20 to 80 μm in the above range, and excellent optical properties of the film and improvement in impact resistance can be expected. have.

In addition, the core-shell rubber may be included in an amount of 1 to 10% by weight in the dope solution, but is not limited thereto, but it is possible to prevent deterioration of the physical properties of the film while further improving the target impact resistance in the above range, It is preferable because the viscosity change rate of the dope solution during film formation can satisfy the physical properties of 20% or less.

In addition, when the core-shell rubber of the present invention is included, the viscosity of the dope solution may be changed as the core-shell rubber swells, but the swelling does not occur within the process time of preparing the film by the solvent casting method after preparing the dope solution. It is possible to make a film before More preferably, when the core-shell rubber of the present invention is included, forming a film in the range where the viscosity change rate of the dope solution is 20% or less, specifically 0 to 20%, and more preferably 0 to 10%, filter clogging is prevented. There is no, and since it is excellent in film forming property, it is good. The viscosity change can be calculated by Equation 1 below.

[Equation 1]

Viscosity change rate = (final viscosity - initial viscosity)/initial viscosity × 100

In Equation 1, the initial viscosity means a viscosity measured initially after preparing the dope solution, and the final viscosity means a viscosity measured after storing the prepared dope solution for 10 minutes.

of the present invention The core-shell rubber may be prepared by emulsion polymerization. More specifically, the core-shell rubber having a three-layer structure of the present invention is prepared by adding an acrylic monomer, an emulsifier, a crosslinking agent, a grafting agent and an initiator to ion-exchanged water to form a core layer having a glass transition temperature of 20 ° C. or higher. first stage polymerization; A second step to form an intermediate layer by grafting a rubbery core having a glass transition temperature of 0° C. or less to the seed particles by adding an acrylic monomer, a comonomer, a crosslinking agent, an emulsifier, an initiator and a grafting agent to the polymer by the first step polymerization. step polymerization; A third-stage polymerization of preparing core-shell particles by grafting a glass-like shell layer having a glass transition temperature of 20° C. or higher to the core by adding an acrylic monomer and an initiator to the polymer obtained by the second step polymerization. can

An example of the method for producing the cowell particles of the present invention is as follows.

First, in the first stage polymerization, when the temperature of the ion-exchanged water in the reactor reaches 70 to 90° C. under a nitrogen stream, an acrylic monomer, an emulsifier, a crosslinking agent, a grafting agent and an initiator are added to obtain glassy seed particles. The acrylic monomer used in the first-stage polymerization is preferably used in an amount of 1 to 40 wt% based on the total weight of the monomer used in manufacturing the core-shell rubber, but is not limited thereto.

In the second stage polymerization, a small amount of an acrylic monomer capable of forming a soft rubber phase on the polymer by the first stage polymerization and a styrene derivative substituted with styrene or halogen or an alkyl or aryl group having 1 to 20 carbon atoms are used as a comonomer. may be doing The content of the acrylic monomer and comonomer for grafting the rubbery core to the seed particle is 40 to 80% by weight, more preferably 50 to 70% by weight, based on the total weight of the monomer used in manufacturing the core-shell rubber. It is preferable because it expresses excellent physical properties of impact resistance, but is not limited thereto. In this case, the acrylic monomer and the comonomer may be mixed in a weight ratio of 4 to 9: 1, but the present invention is not limited thereto.

The three-step polymerization is for grafting the glass-like shell to the core, and the content of the acrylic monomer used in this case is more preferably used in an amount of 10 to 40% by weight based on the total weight of the monomer used in manufacturing the core-shell rubber. . In addition, it is preferable that the particle size of the core-shell rubber grafted with the final glass-like shell is also uniform.

As the acrylic monomer used in the preparation of the core-shell rubber, any one or two or more selected from an aromatic vinyl-based monomer, an alkyl (meth)acrylate monomer having 1 to 15 carbon atoms, and a (meth)acrylic acid monomer having 1 to 15 carbon atoms Mixtures can be preferably used. As a specific example, styrene can be used as the aromatic vinyl-based monomer, and ethyl acrylate, ethyl methacrylate, methyl acrylate, methyl methacrylate, butyl as the alkyl (meth) acrylate monomer having 1 to 15 carbon atoms. Any one or a mixture of two or more selected from acrylate and butyl methacrylate may be used, but the present invention is not limited thereto.

In one aspect of the present invention, the soft rubber as the intermediate layer may be a polymer of an aromatic vinyl-based monomer and an alkyl (meth)acrylate monomer having 1 to 15 carbon atoms among the acrylic monomers, and more specifically, for example, butyl acrylate and It may be a polymer of styrene.

As the emulsifier, anionic emulsifiers such as alkaline alkyl phosphates having 4 to 30 carbon atoms and alkyl sulfate salts such as sodium dodecyl sulfate and sodium dodecylbenzene sulfate can be used, but are not limited thereto. It is preferable to use 0.02 to 4 parts by weight based on 100 parts by weight of the total monomer used in rubber production.

As the crosslinking agent, 1,2-ethanediol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,5-pentanediol di( meth)acrylate, 1,6-hexanediol di(meth)acrylate, divinylbenzene, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, Any selected from triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polybutylene glycol di (meth) acrylate and allyl (meth) acrylate One or a mixture of two or more can be used, but is not limited thereto, and the amount thereof may be 0.1 to 10 parts by weight based on 100 parts by weight of the total monomer used in manufacturing the core-shell rubber.

The content of the crosslinking agent is used in a higher composition ratio in the core layer to set the degree of crosslinking of the core layer higher than that of the soft rubber layer of the intermediate layer, so that mechanical properties such as tensile strength, peeling properties, transparency, optical properties, solvent removal rate, etc. are excellent. It is good because it shows the characteristics.

In the present invention, as the grafting agent, one or more monomers having double bonds with different reactivity, such as allyl (meth)acrylate or diallyl maleate, may be used, but the present invention is not limited thereto. It is preferable to use 0.1 to 10 parts by weight based on 100 parts by weight of the total monomers used in rubber production.

The initiator used for manufacturing the core-shell rubber is any one or a mixture of two or more selected from an azo-based compound, a peroxide-based compound, etc. in the presence of ferrous sulfate, sodium ethylenediaminetetraacetate and sodium formaldehyde sulfoxylate. may be used, but is not limited thereto.

The azo compound is, for example, 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4) -Methoxy-2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis[2-(2-imidazoline-2- 1) Propane] dihydrochloride and 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate may be any one or a mixture of two or more selected from the hydrate no.

The peroxide-based compound is tetramethylbutylperoxy neodecanoate, bis(4-butylcyclohexyl)peroxydicarbonate, di(2-ethylhexyl)peroxycarbonate, butylperoxy neodecanoate, Dipropyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, diethoxyethyl peroxy dicarbonate, diethoxyhexyl peroxy dicarbonate, hexyl peroxy dicarbonate, dimethoxybutyl peroxy dicarbonate, bis (3-methyl oxy-3-methoxybutyl) peroxy dicarbonate, dibutyl peroxy dicarbonate, dicetyl peroxy dicarbonate, dimyristyl peroxy dicarbonate, 1,1,3,3-tetramethylbutyl peroxypivalate, Hexyl peroxy pivalate, butyl peroxy pivalate, trimethyl hexanoyl peroxide, dimethyl hydroxybutyl peroxyneodecanoate, amyl peroxyneodecanoate, butyl peroxyneodecanoate, t-butylperoxy Neoheptanoate, amylperoxy pivalate, t-butylperoxy pivalate, t-amyl peroxy-2-ethylhexanoate, lauryl peroxide, dilauroyl peroxide, didecanoyl peroxide, Benzoyl peroxide, dibenzoyl peroxide, 2,2-bis(tert-butylperoxy)butane, 1,1-bis(tert-butylperoxy)cyclohexane, 2,5-bis(butylperoxy)-2 ,5-Dimethylhexane, 2,5-bis(tert-butylperoxy)-1-methylethyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert -Butyl hydroperoxide, tert-butyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxy isopropyl carbonate, cumene hydroxyperoxide, dicumyl peroxide, lauroyl peroxide, 2,4 - It may be any one or a mixture of two or more selected from -pentanedione peroxide, tert-butyl peracetate, peracetic acid and potassium persulfate, but is not limited thereto.

The amount used may be from 0.001 to 10 parts by weight based on 100 parts by weight of the total monomer used in manufacturing the core-shell rubber, but is not limited thereto.

Hereinafter, a detailed look at the film manufacturing process of the present invention.

In one aspect of the present invention, in order to prepare the acrylic optical film, the dope solution is prepared, the dope solution is cast on the surface of the support through a die, and the dope solution is applied in the form of a sheet, and the solvent present in the casting stock solution is evaporated by a drying facility. to form an acrylic film.

The die is for extruding the casting stock solution, for example, a conventional T-die may be used. The support is a support that forms a film by drying the casting liquid while transporting, and a metal support in the form of a conveyor belt may be used, and more specifically, a stainless steel conveyor belt may be used, and by controlling the movement or rotation speed of the belt The thickness of the film can be adjusted.

The casting undiluted solution applied to the belt moves with the belt for a sufficient time and distance to be formed into a film, and then is peeled off from the belt by a peeling roller which is a guide roller. The peeled film is transferred to a stretching machine, uniaxially stretched in the width direction or biaxially stretched in the width direction and machine direction, dried in a dryer to form a final acrylic film, and then wound on a winder and shipped as a product.

More specifically, a) a methacrylic polymer which is a copolymer polymerized including 80 to 90% by weight of methyl methacrylate and 10 to 20% by weight of n-butyl methacrylate in the monomer content, the degree of crosslinking of the core layer is higher than that of the intermediate layer Applying a dope solution containing three-layered core-shell rubber particles and an organic solvent, which is a large, outermost layer, which is a non-crosslinked layer containing methyl methacrylate as a main component, on a support through a die;

b) evaporating the organic solvent and peeling the acrylic film from the support; and

c) a stretching step of uniaxially stretching or biaxially stretching the acrylic film;

may include.

In the film manufacturing process of the composition of the present invention, the production rate of the film may be improved to 50 to 100 m/min. In addition, when the film is peeled when the residual solvent of the acrylic film is 1 to 20% by weight, preferably 5 to 20% by weight, preferably within 10 minutes from the application in step a) to the peeling in step b) It can be produced within minutes.

That is, by using the dope solution of the present invention, the drying rate of the solvent can be controlled more quickly, and thus the production rate of the film can be further improved, and a film with low haze and thickness change rate when manufacturing a wide film can be manufactured. can In addition, when the film is peeled off after forming the film, the peeling can be performed well without any foreign matter remaining on the support. In addition, by maintaining the viscosity change over time of 20% or less, preferably 10% or less, and more preferably 5% during operation, workability can be uniformed and productivity can be further increased.

The method for manufacturing the acrylic optical film of the present invention will be described in more detail.

In one aspect of the present invention, the acrylic optical film may be prepared according to a conventional solvent casting method.

More specifically, to describe one aspect of the present invention, the prepared dope solution is once stored in a storage tank, and the bubbles contained in the dope solution are defoamed. The defoamed dope is sent from the dope outlet to the pressurized die through the pressurized metering gear pump capable of feeding the liquid with high precision according to the number of revolutions, and the dope is sent to the pressurized die from the slit (slit) of the pressurized die on the metal support running endlessly. By casting uniformly, the less dry casting film is peeled from the metal support at the peeling point at which the metal support has been nearly circled. Both ends of the produced film are sandwiched between clips and transported by a tenter while maintaining the width, and then transported and dried by a roller of a drying device, and then wound to a predetermined length by a winder. In addition, it is also possible to uniaxially stretch in the machine direction or the width direction or biaxially stretch in the machine direction and the width direction after peeling in the state that the residual solvent amount is 0 to 40% by weight, more specifically 5 to 20% by weight during the production of the casting film Do.

Alternatively, it is also possible to stretch off-line after the production of the casting film. The film may be stretched in the machine direction or in the width direction, or may be biaxially stretched simultaneously or sequentially. The degree of stretching may be adjusted as needed, and specifically, for example, 1.1 to 4 times, more specifically, 2 to 3 times stretching. In addition, it may include the step of further drying the film after the stretching. At this time, the drying temperature is not limited as long as the temperature at which the organic solvent can be completely dried, but may preferably be 50 to 120 °C.

_{The stretching temperature is preferably the glass transition temperature (T g} ) ± 10 ℃ of the methacrylic polymer used in the dope solution. The space temperature during application of the solution is preferably -50°C to 50°C, more preferably -30°C to 40°C, and most preferably -20°C to 30°C. More specifically, the stretching temperature may be 100 ~ 200 ℃. Since the dope solution applied at a low space temperature is instantaneously cooled on the support to improve the gel strength, a film with a large amount of organic solvent remaining is obtained. Therefore, the film can be peeled off from the support in a short time without evaporating the organic solvent. As the gas for cooling the space, ordinary air, nitrogen, argon or helium can be used. The relative humidity is preferably 0 to 70%, more preferably 0 to 50%.

The temperature of the support to which the dope solution is applied is preferably -50 to 100°C, more preferably -30°C to 25°C, and most preferably 10°C to 25°C. In order to cool the casting part, a gas cooled into the casting part may be introduced. A cooling device may be disposed in the casting to cool the space. In cooling, it is important to be careful that water does not adhere to the casting part. When cooling with gas, it is preferable to dry the gas.

The thickness of the optical film according to the present invention may be preferably in the range of 10 to 150 μm, more preferably in the range of 20 to 80 μm. In addition, the width of the film may be 1000 mm or more, more preferably 2000 mm or more.

The acrylic optical film according to the present invention may be used not only for a polarizing plate protective film or retardation film, but also for an optical film such as an optical compensation sheet or an optical filter for a stereoscopic image, and may be used by laminating one or two or more sheets.

More specifically, the polarizing plate protective film of the present invention may be used as a protective film of the polarizing plate. An example of the polarizing plate of the present invention may be composed of a polarizer and two polarizing plate protective films protecting both sides thereof, and at least one of the protective films may be composed of a polarizing plate protective film of the present invention.

In addition, in the present invention, an image display device including the polarizing plate is also included in the scope of the present invention. For example, the display device may be a liquid crystal display device. The optical film of the present invention can be used in a liquid crystal display of various display modes, and specifically can be used in modes such as TN, IPS, FLC, AFLC, OCB, STN, ECB, VA and HAN.

One aspect of the liquid crystal display device according to the present invention is a liquid crystal cell; and a polarizing plate disposed on at least one surface of the liquid crystal cell. In this case, the polarizer includes a polarizer; and at least one layer or more of the polarizing plate protective film. In addition, the optical compensation sheet may include an optically anisotropic layer on at least one surface of the polarizing plate protective film, and the optically anisotropic layer may contain a hybrid-oriented disk-shaped compound.

The acrylic optical film according to the present invention has a water vapor transmission rate of 200 g/m 2 ·24 hr or less in a film thickness of 20 to 80 μm. The moisture permeability was measured using a moisture permeability meter (product name: PERME (W3/0120), LabThink Co.), and the temperature applied to the film specimen was 38°C, the external cell RH (relative humidity) 90%, and N ₂ carrier gas conditions. Moisture that has passed through the film from the outer cell to the inner cell is measured.

In addition, the film of the present invention has a very low moisture permeability compared to a conventional cellulose acylate film or a mixed resin of cellulose and acrylic resin, so it is suitable for application as an optical film of a thin film liquid crystal display device, and the water vapor transmission rate satisfies the above range, so a polarizing plate It is possible to prevent the polarizer from being damaged during manufacturing, and it is possible to prevent the physical properties of the optical film from being deformed even under high-temperature, high-humidity conditions during the manufacturing process and transport of the liquid crystal display device.

In addition, the plane direction retardation value represented by the following Equation 1 may be -50 to +50 nm, and the thickness direction retardation value expressed by the following Equation 2 may be -50 to +50 nm.

[Equation 1]

R _in = (n _x - n _y ) xd

[Equation 2]

R _th = (n _z - n _y ) xd

In Equations 1 and 2, n _x is the refractive index in the direction having the largest refractive index in _{the plane direction of the film, n y} is the refractive index in the vertical direction of the _{n x} direction in the plane direction of the film _{, n z} is the refractive index in the thickness direction, and d is the thickness of the film.

In addition, the optical film according to an aspect of the present invention satisfies the physical properties of the thickness deviation within 5%. That is, taking a film having a thickness of 60 μm as an example, it means that the error range is within 5% when the thickness is measured at any point with respect to the entire width of the film.

In addition, the haze is less than 2% and shows excellent physical properties for use as an optical film because there are few foreign substances. More specifically, the haze may be 2% or less, specifically 1.5% or less, more specifically 1% or less, and the number of foreign objects may be 0.3 or less per 1 m, more specifically 0 to 0.3.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the following Examples and Comparative Examples are merely examples for explaining the present invention in more detail, and the present invention is not limited by the following Examples and Comparative Examples.

Hereinafter, the physical properties of the film were measured by the following measurement method.

1. Glass transition temperature (T _g ): It was measured using a differential scanning calorimeter (DSC) under a temperature rise condition of 10 °C / min.

2. Weight average molecular weight: The prepared beads and film were dissolved in tetrahydrofuran and measured using gel permeation chromatography (GPC).

The weight average molecular weight was measured using a gel permeation chromatography (GPC) equipment manufactured by Waters. The equipment consists of a mobile phase pump (M515 Pump), a column heater (ALLCOLHTRB), a detector (2414 RI Detector), and an injector (2695 EB autoinjector). Rate (PMMA) American polymer standard corporation STD was used. HPLC grade tetrahydrofuran (THF) is used as the mobile phase solvent, and the measurement is performed under the conditions of a column heater temperature of 40° C. and a mobile phase solvent flow rate of 1.0 mL/min. The copolymer prepared for sample analysis was dissolved in tetrahydrofuran (THF), a mobile phase solvent, and then injected into the GPC equipment to measure the weight average molecular weight.

3. Residual monomer: After polymerization, the residual monomer in the resin was quantitatively measured through a GC (Gas Chromatography) analysis device.

4. Retardation: The retardation of the prepared film was measured using a birefringence measuring instrument (Axoscan, Axometrics) and the measurement wavelength was performed at 550 nm.

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

The haze deviation was calculated by dividing the film into 5 equal parts in the width direction, measuring the haze at any point of the film divided into 5 equal parts, and then using the following formula.

△ Haze = Maximum value of haze - Minimum value of haze

6. Tensile strength: It was measured according to the ASTM D638 test method using a universal testing machine (UTM, Zwick).

7. Moisture permeability: Using a moisture permeability measuring instrument (LabThink, PERME (W3/0120)), the temperature applied to the film specimen in the sealed chamber was 38℃, RH (relative humidity) of the external cell 90%, N ₂ carrier gas conditions. Moisture that passed through the film from the outer cell to the inner cell was measured for 24 hr.

8. Coating Adhesion: After cutting the coated side of the film to make a total of 100 squares, 10 horizontally and vertically, the degree of adhesion of the coating layer was evaluated while attaching and peeling the 3M tape. Here, if there are more than 95 left, good, if more than 85, normal, and if less than 85, bad.

9. Thickness deviation: The film thickness was measured at 50mm intervals over the entire width of the film, and calculated by the following formula.

Thickness deviation (%) = (maximum value of thickness - minimum value of thickness) / minimum value of thickness × 100

The film thickness was measured with a micrometer measuring device, manufactured by Mahr, Germany.

10. Foreign matter inspection: Unmelted black spots and white spots were detected, including foreign substances such as dust, and the film running after the film was manufactured was measured using a film inspection device of NextI. It is expressed as the number of foreign objects per 1 meter in the longitudinal direction of the film, and if one foreign object occurs while driving 10m, it is expressed as 0.1 pieces/1m.

11. Viscosity and viscosity change over time: After preparing the dope solution at 25°C, the viscosity was measured by the viscosity measurement method by the falling ball method. Brookfield's falling-ball type viscometer Model KF40 was used, and it was measured using the No. 6 ball. The change in viscosity over time means the rate of change in viscosity immediately after preparation of the dope solution and after standing for 10 minutes.

12. Peel-off property: After casting the dope solution on the surface of a stainless support, the film was dried so that the amount of residual solvent in the film was 20% by weight, and then 30x30cm was cut into 10 pieces and peeled for evaluation.

Excellent: The film surface is smooth and peels off easily, and there is no residue on the support.

Normal: When the film is peeled off, it is peeled off without breaking, and a small amount of residue is generated on the support.

Bad: There is a clicking sound when the film is peeled off, some fractures occur, or there is a residue on the support.

[Preparation Example 1] Preparation of a dispersant for suspension polymerization

2700 g of water and 0.3 g of 2,2-azobis (2-amidinopropane) dihydrochloride were put in a three-necked flask with a condenser, and 180 g of the compound of Formula 1 below, 40 g of the compound of Formula 2 below, and meta 70 g of methyl acrylate was added and reacted at 60° C. for 6 hours to obtain an aqueous polymer solution having a solid content of 5 wt%. The weight average molecular weight of the prepared dispersant was 2,000,000 g/mol.

[Formula 1]

In Formula 1, R ₁ is methyl, n is 1, and M is sodium.

[Formula 2]

In Formula 2, R ₂ is methyl, and M is potassium.

[Preparation Example 2] Preparation of core-shell rubber

In the first step, 1500 g of distilled water was added to the 5L reactor, and the temperature was raised to 80 °C after nitrogen substitution. 0.002 g of ferrous sulfate, 0.008 g of EDTA·2Na salt, and 0.2 g of sodium formaldehyde sulfoxylate were added to the reactor and stirred. 200 g of methyl methacrylate, 6.0 g of 1,3-butanediol dimethacrylate as a crosslinking agent, 0.7 g of allyl methacrylate as a grafting agent, 6 g of sodium polyoxyethylene alkyl ether phosphate as an emulsifier, and 0.5 g of tert. The mixed solution was added dropwise for 2 hours, followed by emulsion polymerization while stirring at 80° C. and 500 rpm for 1 hour. The average particle size of the obtained glassy seed particles at this time was 180 nm.

In the second step, 1.0 g of sodium formaldehyde sulfoxylate was dissolved in 20 g of distilled water and then added to the reactor after the glass seed particles prepared in the first step. 250 g of butyl acrylate, 55 g of styrene, 5 g of allyl methacrylate as a grafting agent, 1 g of 1,3-butanediol dimethacrylate as a crosslinking agent, 1 g of cumene hydroperoxide, polyoxyethylene alkyl ether phosphate A mixed solution of 10 g of sodium was added dropwise over 3 hours, followed by polymerization at 80° C. for 2 hours. The average particle size of the polymer obtained at this time was 250 nm.

Finally, in step 3, 1 g of sodium formaldehyde sulfoxylate was added while the temperature was maintained at 80 ° C., methyl methacrylate 285 g, methyl acrylate 15 g, normal octyl mercaptan 1 g, tertiary butyl peroxide A mixed solution of 0.5 g was added dropwise over 2 hours, followed by polymerization at 80° C. for 1 hour. The average particle size of the core-shell rubber, which is the final polymer obtained at this time, was 280 nm.

[Comparative Preparation Example 1] Preparation of core-shell rubber

In the first step, 1500 g of distilled water was added to the 5L reactor, and the temperature was raised to 80 °C after nitrogen substitution. 0.002 g of ferrous sulfate, 0.008 g of EDTA·2Na salt, and 0.2 g of sodium formaldehyde sulfoxylate were added to the reactor and stirred. 200 g of methyl methacrylate, 1 g of 1,3-butanediol dimethacrylate as a crosslinking agent, 0.7 g of allyl methacrylate as a grafting agent, 6 g of sodium polyoxyethylene alkyl ether phosphate as an emulsifier, and 0.5 g of tert. The mixed solution was added dropwise for 2 hours, followed by emulsion polymerization while stirring at 80° C. and 500 rpm for 1 hour. The average particle size of the obtained glassy seed particles at this time was 170 nm.

In the second step, 1.0 g of sodium formaldehyde sulfoxylate was dissolved in 20 g of distilled water and then added to the reactor after the glass seed particles prepared in the first step. 250 g of butyl acrylate, 55 g of styrene, 5 g of allyl methacrylate as a grafting agent, 8 g of 1,3-butanediol dimethacrylate as a crosslinking agent, 1 g of cumene hydroperoxide, polyoxyethylene alkyl ether phosphate A mixed solution of 10 g of sodium was added dropwise over 3 hours, followed by polymerization at 80° C. for 2 hours. The average particle size of the polymer obtained at this time was 240 nm.

Finally, in step 3, 1 g of sodium formaldehyde sulfoxylate was added while the temperature was maintained at 80 ° C., methyl methacrylate 285 g, methyl acrylate 15 g, normal octyl mercaptan 1 g, tertiary butyl peroxide A mixed solution of 0.5 g was added dropwise over 2 hours, followed by polymerization at 80° C. for 1 hour. The average particle size of the core-shell rubber, the final polymer obtained at this time, was 270 nm.

[Comparative Preparation Example 2] Preparation of core-shell rubber

In the first step, 1500 g of distilled water was added to the 5L reactor, and the temperature was raised to 80 °C after nitrogen substitution. 0.002 g of ferrous sulfate, 0.008 g of EDTA·2Na salt, and 0.2 g of sodium formaldehyde sulfoxylate were added to the reactor and stirred. 250 g of butyl acrylate, 55 g of styrene, 5 g of allyl methacrylate as a grafting agent, 6 g of 1,3-butanediol dimethacrylate as a crosslinking agent, 1 g of cumene hydroperoxide, polyoxyethylene alkyl ether phosphate A mixed solution of 10 g of sodium was added dropwise over 3 hours, followed by polymerization at 80° C. for 2 hours. The average particle size of the polymer obtained at this time was 180 nm.

Next, 1 g of sodium formaldehyde sulfoxylate was added while the temperature was maintained at 80 ° C., 285 g of methyl methacrylate, 15 g of methyl acrylate, 1 g of normal octyl mercaptan, and 0.5 g of tertiary butyl peroxide were added. The mixed solution was added dropwise over 2 hours, followed by polymerization at 80° C. for 1 hour. The average particle size of the core-shell rubber, the final polymer obtained at this time, was 220 nm.

[Example 1]

1) Preparation of methacrylic polymer

In a 5 liter reactor, 2000 g of distilled water, 12 g of the suspension polymerization dispersant having a solid content of 5 wt% prepared in Preparation Example 1, and 6 g of sodium sulfate as a dispersing aid were added and dissolved. The types and contents of the monomers were added as described in [Table 1] below, and normal octyl mercaptan was added as an initiator and a chain transfer agent and dispersed in an aqueous phase while stirring at 400 rpm to prepare a suspension.

The suspension was polymerized at 65° C. for 1 hour and 30 minutes, then heated to 105° C. for additional polymerization for 30 minutes, and then cooled to 30° C. The beads obtained by the polymerization reaction were repeatedly washed and dehydrated with distilled water, and then dried. The physical properties of the prepared methacrylic polymer beads were measured and shown in Table 1 below.

2) Preparation of dope solution

15 parts by weight of the core-shell rubber prepared in Preparation Example 2 was mixed with respect to 100 parts by weight of the prepared methacrylic polymer beads, and dissolved in a mixed solvent in which methylene chloride and methanol were mixed in a 9:1 weight ratio to give a solid content of 20 wt% A phosphorus dope solution was prepared. To 100 parts by weight of the dope solution, 3 parts by weight of Tinuvin 918 manufactured by Ciba Specialty as a UV absorber was added to prepare a final dope solution. The viscosity of the dope solution was measured and shown in Table 1 below.

3) Preparation of film

The dope solution was uniformly applied to the surface of the stainless (SUS 304) support using a die. The solvent was evaporated on the stainless support and peeled off when the residual amount of the solvent was 20% by weight. At this time, the solvent drying time from application to 20% by weight of the residual solvent was measured and shown in Table 2. The amount of the residual solvent was calculated by the following formula.

Residual solvent amount (%) = (weight of applied dope solution - weight of film)/weight of film × 100

Fix both ends of the peeled film, stretch 1.5 times in the width direction at a temperature of 125 ° C. when the residual solvent is 12 wt %, relax, and dry in a drying section set at 100 ° C. to produce a film with a film thickness of 60 µm did. The physical properties of the film were measured at the point after drying was completed, and are shown in Table 2 below.

[Examples 2 to 5]

A methacrylic polymer, a dope solution, and a film were prepared in the same manner as in Example 1, except that the composition was changed as shown in Table 1 below.

[Comparative Examples 1 to 3]

A methacrylic polymer, a dope solution, and a film were prepared in the same manner as in Example 1, except that the composition was changed as shown in Table 1 below.

[Comparative Example 4]

It was carried out in the same manner as in Example 4 except that the core-shell particles of Comparative Preparation Example 1 were used, and the results are described in the table below.

[Comparative Example 5]

It was carried out in the same manner as in Example 4 except that the core-shell particles of Comparative Preparation Example 2 were used, and the results are described in the table below.

Hereinafter, in Tables 1 and 2, the abbreviations are as follows.

MMA: methyl methacrylate

AMS: Alpha methyl styrene

PMI: Phenylmaleimide

MA: methyl acrylate

MAA: methacrylic acid

n-BMA: n-butyl methacrylate

LPO: lauroyl peroxide

n-OM: Normaloctylmercaptan

Example comparative example One 2 3 4 5 One 2 3 4 5 monomer
(g) MMA 830 750 850 850 850 880 630 700 850 AMS 20 20 - - - 20 20 - - PMI 50 30 - - - 50 50 - - MA - - - 50 - - - - 50 MAA - - 50 - 50 - - - - n-BMA 100 200 100 100 100 50 300 300 100 polymer Tg(℃) 118.2 113.6 118.6 112.6 118.1 114.6 96.2 90.1 112.6 Mw (× only) 101.5 99.5 107.5 97.5 105 104 785 75.2 97.5 Weight % in dope solution 17 15 17 core shell
particle Weight % in dope solution 3 15 3 Preparation 2 Preparation 3 Preparation 4 dope viscosity cps (× cloth)
32℃ 32 28 34 29 37 27 22 20 28 21

Example comparative example One 2 3 4 5 One 2 3 4 5 solvent drying
hours (minutes) 3 3 3 3 3 10 6 7 6 6 R _in /R _th
(nm) 0.5/
-5 056/
-4 0.4/
-4 0.6/
-6 0.4/
-6 0.7/
-5 0.6/
-7 0.6/
-6 0.7/
-8 0.7/
-8 Haze (%) 0.6 0.6 0.4 0.3 0.4 0.9 0.8 0.8 1.2 1.5 △Heize ≤0.05 ≤0.05 ≤0.05 ≤0.05 ≤0.05 0.1 0.1 0.1 0.13 0.13 ray throw
Overrate (%) 92.1 92.0 92.0 92.1 92.0 91.5 91.6 91.1 89.2 89.1 The tensile strength
(GPa) 2.52 2.24 2.70 2.45 2.76 2.32 2,14 1.9 2,03 1.51 moisture permeability
(g/㎡·24hr) 72 70 75 71 76 73 78 74 83 87 adhesion Good Good Good Good Good Good Good Good usually usually thickness deviation
(%) One One One One 2 6 11 8 13 17 foreign body inspection 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.3 0.5 Peel-off Great Great Great Great Great usually bad bad bad bad rate of change over time
(%) 5 7 5 6 8 25 27 21 29 34

As shown in Table 2, the film according to the present invention was prepared by preparing a dope solution having a mixed composition of three-layer core-well particles having the structure of the present invention and a polymer containing methyl methacrylate and n-butyl methacrylate. It can be seen that the solvent drying time up to 20 wt% of the silver residual solvent can greatly improve the production rate of the film within 5 minutes. In addition, it can be seen that the haze change is small with respect to the entire width of the film, so that the local increase in haze can be eliminated. In addition, it can be seen that a uniform and smooth film can be manufactured due to a small thickness deviation, and it was confirmed that the film was easily peeled off without any foreign matter remaining on the support when the film was peeled off.

In addition, compared to the conventional cellulose film, it was confirmed that it can be used instead of the existing cellulose film by showing similar optical properties, and it was confirmed that a film with lower moisture permeability and excellent optical and mechanical properties can be manufactured. did.

In addition, it can be seen that by adopting the composition according to the present invention, the change rate with time is low, and there is a significant increase effect in foreign matter and other optical properties (transmittance, haze, etc.) and mechanical properties (tensile strength, etc.).

As described above, the present invention has been described with specific details and limited examples and drawings, but these are only provided to help a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention is not limited to the above embodiments. Various modifications and variations are possible from these descriptions by those of ordinary skill in the art.

Therefore, the spirit of the present invention should not be limited to the described embodiments, and not only the claims to be described later, but also all those with equivalent or equivalent modifications to the claims will be said to belong to the scope of the spirit of the present invention. .

Claims (11)

A methacrylic polymer prepared including 80 to 90% by weight of methyl methacrylate and 10 to 20% by weight of n-butyl methacrylate, the crosslinking degree of the core layer is greater than that of the intermediate layer, and the outermost layer contains 50 methyl methacrylate It is prepared by a solvent casting method using a dope solution containing three-layer core-shell particles and an organic solvent, which is a non-crosslinked layer containing at least 20% by weight, and the solvent drying time to 20% by weight of the residual solvent is within 5 minutes, and the thickness deviation Acrylic optical film with less than 5%. The method of claim 1,
The optical film is an acrylic optical film that is a polarizing plate protective film or retardation film. The method of claim 1,
The methacrylic polymer has a weight average molecular weight of 400,000 g/mol or more, and a glass transition temperature of 110° C. or more. The method of claim 1,
The methacrylic polymer is an acrylic optical film prepared by further comprising any one or two or more monomers selected from acrylic acid, methacrylic acid, acid anhydride, styrene-based monomers and maleimide-based monomers. The method of claim 1,
The organic solvent is a halogenated hydrocarbon alone or a halogenated hydrocarbon and any one or a mixed solvent selected from esters, ketones, ethers and alcohols, an acrylic optical film. The method of claim 1,
The dope solution has a solid content of 10 to 30% by weight, contains 20 to 100 parts by weight of a three-layered core-shell rubber with respect to 100 parts by weight of the methacrylic polymer, and a viscosity of 10,000 cps or more at 32°C Acrylic optical film. a) A methacrylic polymer polymerized including 80 to 90% by weight of methyl methacrylate and 10 to 20% by weight of n-butyl methacrylate in the monomer content, the crosslinking degree of the core layer is greater than that of the intermediate layer, and the outermost layer is methyl Applying a dope solution containing three-layered core-shell particles and an organic solvent as a non-crosslinked layer containing 50 wt% or more of methacrylate on a support through a die;
b) evaporating the organic solvent and peeling the acrylic film from the support; and
c) a stretching step of uniaxially stretching or biaxially stretching the acrylic film;
A method for producing an acrylic optical film comprising, a solvent drying time of less than 5 minutes and a thickness deviation of less than 5% up to 20% by weight of the residual solvent. delete 8. The method of claim 7,
A method of producing an acrylic optical film that is performed within a range of 20% or less of the viscosity change rate of the dope solution when the dope solution is applied on the support. 8. The method of claim 7,
The methacrylic polymer has a weight average molecular weight of 400,000 g/mol or more, and a glass transition temperature of 110° C. or more. 8. The method of claim 7,
The dope solution has a solid content of 10 to 30% by weight, contains 20 to 100 parts by weight of the three-layered core-shell rubber with respect to 100 parts by weight of the methacrylic polymer, and an acrylic having a viscosity of 10,000 cps or more at 32°C A method of manufacturing an optical film.