KR102122723B1 - 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 produced by a solvent casting method and a method for manufacturing the same. In addition, the present invention relates to a solvent casting dope solution for producing the acrylic optical film.

Description

Acrylic optical film and its manufacturing method{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 produced by a solvent casting method and a method for manufacturing the same. In addition, the present invention relates to a solvent casting dope solution for producing the acrylic optical film.

With the development of optical technology in recent years, liquid crystal displays are required to be thinner, lighter and larger in the overall display industry, and technologies such as wide viewing angle, high contrast, uniformity of screen display, and suppression of image changes due 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 polymer materials for displays are becoming more advanced.

Cellulose ester films have been used as photographic or various optical materials because of their high strength and flame retardancy. In particular, the cellulose acylate film has been widely used as an optical transparent film for a liquid crystal display device because it has high optical transparency and optical isotropy. For example, in a polarizing plate which is one of the optical films constituting the liquid crystal display device, a cellulose acylate film that can be directly bonded to polyvinyl alcohol (PVA), which is a polarizer, in particular, a triacetyl cellulose film is laminated and protected on both sides of the polarizer. It is mainly used as a polarizing plate protective film which is a film. In addition, it can be stretched under appropriate conditions and used as an optical compensation film.

However, when molding such a cellulose ester film into a thin film type, moisture permeability is generally weak, which causes a problem in storage stability due to expansion, and in particular, due to a decrease in durability in a high temperature and high humidity environment, it has a great influence on the deterioration of the function of the liquid crystal display device. I go crazy. In addition, there is a problem in that the strength and surface hardness of the film are reduced due to thinning.

In order to overcome the above problems, research has been conducted to manufacture an optical film using an acrylic polymer. Korean Patent Application Publication No. 10-2015-0039089 filed by the present applicant describes a resin composition for an optical film comprising an acrylic copolymer and an optical film produced using the same. The patent relates to a resin composition for an optical film for manufacturing an optical film by a melt extrusion method, but when the composition is prepared by a solution casting method, film formation is difficult, and the peel-off does not work well, so it is poor This happens.

Korea Patent Publication No. 10-2015-0039089 (2015.04.09.)

An object of the present invention is to provide an acrylic optical film having excellent heat resistance and low moisture permeability under high temperature and high humidity conditions, compared to the conventional cellulose acylate resin. More specifically, it is an object to provide an acrylic optical film for use as a polarizing plate protective film or a retardation film.

In addition, the present invention has an object to provide an acrylic optical film manufactured by a solvent casting method, having excellent smoothness, uniform thickness over the entire film width, low haze, and uniform haze over the entire film width.

In addition, the present invention can further improve the productivity by further shortening the film forming time of the film by increasing the drying speed of the solvent in forming a film by a solvent casting method, and when the film is peeled, a local residue does not remain, and the width An object of the present invention is to provide a dope solution capable of easily forming a film having a width of 2000 mm or more and a method of manufacturing an acrylic optical film using the dope solution.

In addition, the present invention has an object to provide an optical film with improved productivity by increasing the drying speed of a solvent, and further improved uniformity of haze or thickness of the optical film.

In addition, the present invention can provide a film having excellent polymerization stability and excellent mechanical properties by using a high molecular weight acrylic polymer, and has an object to further improve the productivity of the film.

As a result of research in order to achieve the above object, when preparing an acrylic polymer used for preparing a dope solution, the monomer is used in a specific combination, and polymerized using a vinyl group or a compound having two or more (meth)acrylic groups to obtain a weight average. It is possible to increase the molecular weight, thereby further improving the mechanical properties of the film, and also improving the productivity of the film by improving the drying rate of the solvent during film formation, and producing a film of uniform quality. The present invention was completed. In addition, the present invention was completed by discovering that the film can be formed by a solvent casting method by adjusting the weight average molecular weight and glass transition temperature of the acrylic polymer to a specific range, and an acrylic optical film having excellent physical properties is produced.

More specifically, in order to achieve the above object, in one aspect of the present invention, 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of alkyl (meth)acrylate of C4 to C8, and 1 to 10% by weight of heat-resistant monomer With respect to 100 parts by weight of the monomer mixture (A), chain transfer agent (B) 0.03 to 0.5 parts by weight, a compound having two or more vinyl groups or (meth)acrylic groups (C) 0.005 to 0.1 parts by weight and an initiator (D ) Solvent casting method using a dope solution containing an acrylic polymer, a core-shell rubber, and an organic solvent having a weight average molecular weight of 700,000 g/mol or higher and a glass transition temperature of 110°C or higher, including 0.01 to 0.5 parts by weight. It is manufactured by, and provides an acrylic optical film having a thickness variation of less than 5%.

In addition, in one aspect of the present invention, a) a monomer mixture comprising 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of alkyl (meth)acrylate of C4 to C8, and 1 to 10% by weight of heat-resistant monomer ( A) With respect to 100 parts by weight, the chain transfer agent (B) 0.03 to 0.5 parts by weight, the compound having two or more vinyl groups or (meth)acrylic groups (C) 0.005 to 0.1 parts by weight and the initiator (D) 0.01 to 0.5 parts by weight Including polymerization, the weight average molecular weight of 700,000 g / mol or more, glass transition temperature of 110 ℃ or more acrylic polymer, core-shell rubber and coating a dope solution containing an organic solvent on a support through a die; And

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 for producing an acrylic optical film comprising a.

In addition, in one aspect of the present invention, a monomer mixture (A) comprising 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of alkyl (meth)acrylate of C4 to C8, and 1 to 10% by weight of heat-resistant monomer With respect to 100 parts by weight, the chain transfer agent (B) contains 0.03 to 0.5 parts by weight, a compound having two or more vinyl groups or (meth)acrylic groups (C), 0.005 to 0.1 parts by weight, and an initiator (D) 0.01 to 0.5 parts by weight It provides a dope solution for solvent casting, which is polymerized, has a weight average molecular weight of 700,000 g/mol or more, and a glass transition temperature of 110°C or more, an acrylic polymer, a core-shell rubber, and an organic solvent.

The dope solution containing the acrylic polymer according to the present invention has properties suitable for preparing an acrylic optical film by a solvent casting method, and the drying rate of the solvent is adjusted more quickly to apply the dope solution to drying the solvent and peeling the coating film. There is an effect that can further reduce the time required. Therefore, there is an effect that productivity can be improved by making the production speed of the film faster.

In addition, the dope solution containing the acrylic polymer according to the present invention has an effect of easily producing a wide film since the drying speed of the solvent is high and the heat resistance and mechanical properties are excellent. More specifically, there is an effect that can easily produce a wide-width film having a width of 2000mm or more. More specifically, in manufacturing a wide-width film, there is an effect of producing a film having a uniform haze and a uniform thickness with respect to the entire width of the film. In addition, when the film is peeled from the support after film formation, there is no residue left on the support, and thus there is an effect of minimizing defects.

In addition, the acrylic optical film produced using the dope solution according to the present invention has low moisture permeability, high heat resistance, excellent smoothness, and has a small number of foreign matters. Accordingly, it is possible to provide a film suitable for use as a polarizing plate protective film or a retardation film.

In addition, the present invention has an effect of excellent polymerization stability because it can produce a high molecular weight acrylic polymer. Accordingly, there is an effect that can improve productivity and mechanical properties of the film and uniformity of properties during film production.

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

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the description of the present invention are only for effectively describing a specific embodiment and are not intended to limit the present invention.

Also, the singular form used in the specification and the appended claims may be intended to include the plural form unless otherwise indicated in the context.

In the present invention, the polymer includes a homopolymer or copolymer, and a copolymer means that an element referred to as a monomer in the present invention is polymerized and included as a repeating unit in the copolymer resin, and the copolymer in the present invention. May be a block copolymer or a random copolymer, but is not limited thereto.

One aspect of the present invention is an acrylic optical film, methyl methacrylate 75 to 89% by weight, C4 ~ C8 alkyl (meth) acrylate 10 to 20% by weight, and a monomer mixture containing 1 to 10% by weight of the heat-resistant monomer ( A) With respect to 100 parts by weight, the chain transfer agent (B) 0.03 to 0.5 parts by weight, the compound having two or more vinyl groups or (meth)acrylic groups (C) 0.005 to 0.1 parts by weight and the initiator (D) 0.01 to 0.5 parts by weight Including polymerization, the weight average molecular weight is 700,000 g/mol or more, and the glass transition temperature is 110°C or higher. It is prepared by a solvent casting method using a dope solution containing an acrylic polymer, a core-shell rubber, and an organic solvent, and has a thickness. The deviation may be within 5%.

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

In one aspect, the heat-resistant monomer may be any one or a mixture of two or more selected from acrylic acid, methacrylic acid, acid anhydride, styrene-based monomer and maleimide-based monomer.

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

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

In one embodiment, the core-shell rubber has a two- or three-layer structure including an acrylic rubber layer in the core layer or the intermediate layer, and may have an average particle diameter of 100 to 400 nm.

In one embodiment, the dope solution includes 10 to 40% by weight of the acrylic polymer and 1 to 40% by weight of the core-shell rubber, and the viscosity may be 10,000 cps or more at 32°C.

In one aspect, the acrylic optical film may have a moisture permeability of 200 g/m 2 ·24 hr or less, a number of foreign matters of 0.3 or less, and a haze of 2% or less.

In one aspect, the acrylic optical film may have a film thickness of 10 ~ 150㎛.

In one aspect, the acrylic optical film may be stretched under the condition that the residual solvent in the film is 5 to 20% by weight.

Another aspect of the present invention is a method for producing an acrylic optical film, a) methyl methacrylate 75 to 89% by weight, C4 to C8 alkyl (meth)acrylate 10 to 20% by weight, and heat-resistant monomer 1 to 10% by weight With respect to 100 parts by weight of the monomer mixture (A), chain transfer agent (B) 0.03 to 0.5 parts by weight, a compound having two or more vinyl groups or (meth)acrylic groups (C) 0.005 to 0.1 parts by weight and an initiator (D ) Polymerization including 0.01 to 0.5 parts by weight, a weight average molecular weight of 700,000 g/mol or more, a glass transition temperature of 110° C. or more, an acrylic polymer, a core-shell rubber, and a dope solution containing an organic solvent on a support through a die Applying to; And

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 may be to include.

In one aspect, in step b), when the residual solvent of the acrylic film is 5 to 20% by weight, the film is peeled, and it may be produced within 5 minutes from the application of step a) to the separation of step b). have.

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

In one aspect, the stretching step may be to stretch 1.1 to 4 times under the condition that the residual solvent in the film is 5 to 20% by weight.

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

In one aspect, when the dope solution is applied on a support, the rate of change in viscosity of the dope solution may be performed within a range of 20% or less.

Another aspect of the present invention is a solvent casting dope solution, comprising 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of C4 to C8 alkyl (meth)acrylate, and 1 to 10% by weight of heat-resistant monomer With respect to 100 parts by weight of the monomer mixture (A), chain transfer agent (B) 0.03 to 0.5 parts by weight, a compound having two or more vinyl groups or (meth)acrylic groups (C) 0.005 to 0.1 parts by weight and initiator (D) 0.01 to Polymerization including 0.5 parts by weight, a weight average molecular weight of 700,000 g / mol or more, glass transition temperature of 110 ℃ or more may be one containing an acrylic polymer, a core-shell rubber and an organic solvent.

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

In one embodiment, the dope solution, the dope solution includes 10 to 40% by weight of the acrylic polymer and 1 to 40% by weight of the core-shell rubber, and the viscosity may be 10,000 cps or more at 32°C.

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

The acrylic optical film according to the present invention is prepared by a solvent cast method using a dope solution. The solvent cast method casts a dope solution in which a resin is dissolved in an organic solvent on a support, and evaporates the organic solvent to form a film. If necessary, the film produced as described above can be stretched by a stretching machine to produce a final product film.

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

The inventors of the present invention have been studied to produce an acrylic optical film by a solvent cast method. As a result, the monomers are used in a specific combination, and polymerization is performed using a compound having two or more vinyl groups or (meth)acrylic groups, thereby obtaining a weight average molecular weight. It has been found that the increase and the mechanical properties of the film can be improved. In addition, the evaporation time of the organic solvent can be further shortened to further improve the productivity of the film, and no residue remains when peeling, so that no contamination occurs, and even when manufactured with a wide film, thickness uniformity and haze uniformity over the entire width The present invention was completed by discovering that an optical film having excellent properties, excellent heat resistance and mechanical properties can be provided.

Specifically, with respect to 100 parts by weight of the monomer mixture (A) containing 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of C4 to C8 alkyl (meth)acrylate and 1 to 10% by weight of heat-resistant monomer, Chain transfer agent (B) 0.03 to 0.5 parts by weight, a vinyl group or a compound having at least two (meth)acrylic groups (C) 0.005 to 0.1 parts by weight and initiator (D) 0.01 to 0.5 parts by weight of polymerized acrylic polymer used It has features. In addition, the weight average molecular weight of the acrylic polymer is 700,000 g/mol or more, specifically 700,000 to 1,500,000 g/mol, more specifically 800,000 to 1,200,000 g/mol, and a glass transition temperature of 110°C or more, more specifically 110 to By using an acrylic polymer at 150° C., in preparing an optical film by a solvent cast method, the peel-off property is excellent, film formation is easy, and the drying speed of the solvent can be increased to further improve the production speed. .

It is preferable because it has a viscosity suitable for application to a solvent casting method when preparing a dope solution in a range that satisfies the above range, and it is preferable because it is easy to peel the film from the support after film production. In addition, it is possible to provide a film having more excellent mechanical properties.

In addition, when preparing a film by a solvent cast method, the organic solvent must be evaporated to peel the film from the support. In the process of evaporating the organic solvent, the properties of the acrylic resin are prevented from being changed while drying the organic solvent within a short time. In order to manufacture a thin film, physical properties of an acrylic polymer having a glass transition temperature of 110°C or higher are required. When the glass transition temperature is less than 110°C, the heat resistance is insufficient, and the film is easily deformed under high temperature and high humidity conditions.

In the range that satisfies the weight average molecular weight and glass transition temperature, when mixed with an organic solvent such that the solid content of the acrylic polymer is 10 to 40% by weight, the viscosity at 32°C is 10,000 cps or more, specifically 10,000 to 60,000 cps, more Specifically, a dope solution of 20,000 to 40,000 cps can be prepared.

Since the solid content and viscosity range can be cast to a uniform thickness on a support, and after casting on a support, drying is possible at a relatively high temperature when drying an organic solvent. Thus, an optical film that is smooth and easy to peel can be produced in a short time. desirable. When the solid content is higher than the above range, the content of the solvent is relatively reduced, so even if the viscosity is satisfied, the application of the dope solution is not easy when casting to the film support, and clogging of the nozzle may occur. In addition, when the solid content is lower than the above range, since the content of the solvent is relatively high, a lot of energy is required to dry the organic solvent, and it may be difficult to prepare a smooth optical film.

In one embodiment of the present invention, the acrylic polymer is polymerized with 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of C4 to C8 alkyl (meth)acrylate, and 1 to 10% by weight of heat-resistant monomer. More specifically, with respect to 100 parts by weight of the monomer mixture (A) comprising 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of C4 to C8 alkyl (meth)acrylate and 1 to 10% by weight of heat-resistant monomer, Chain transfer agent (B) 0.03 ~ 0.5 parts by weight of a vinyl group or (meth) acrylic compound having at least two (C) 0.005 ~ 0.1 parts by weight of the initiator and (D) 0.01 ~ 0.5 parts by weight of polymerization.

The C4 ~ C8 alkyl (meth) acrylate is specifically, for example, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, n-butyl acrylate, It may be a mixture of any one or two or more selected from t-butyl acrylate, cyclohexyl acrylate and isobornyl acrylate. More preferably, it may be n-butyl methacrylate, t-butyl methacrylate and n-butyl acrylate, or t-butyl acrylate, and more preferably n-butyl methacrylate.

The alkyl (meth)acrylate of the C4 ~ C8 may be to use 10 to 20% by weight, more specifically 12 to 18% by weight, drying the organic solvent in the process of evaporating the organic solvent after film formation in the above range The speed can be adjusted more quickly, which may further improve the production speed of the film. When used at less than 10% by weight, the effect of improving the production speed of the film is negligible, and when used at more than 20% by weight, the glass transition temperature of the acrylic polymer is lowered to obtain the desired film properties by lowering the heat resistance and durability of the film. No, the weight average molecular weight is low, it is not possible to provide a constant viscosity suitable for application to the solvent casting method when preparing a dope solution, and the solvent casting method can facilitate a film having a wide width, specifically a film having a width of 2000 mm or more. It is difficult to manufacture.

The heat-resistant monomer is not limited as long as it is a monomer for controlling the glass transition temperature of the acrylic polymer to 110° C. or higher, but more specifically, for example, it is selected from acrylic acid, methacrylic acid, acid anhydride, styrene-based monomer, and maleimide-based monomer. It may be any one or a mixture of two or more. Further, the content of the heat-resistant monomer is not limited as long as it is a content for controlling the glass transition temperature to 110° C. or higher, more preferably 1 to 10% by weight. In the above range, it is preferable because it is sufficient to prepare an acrylic polymer capable of solvent casting by compensating for the molecular weight and heat resistance according to the content of the C4 to C8 alkyl (meth)acrylate.

More preferably, the heat-resistant monomer may be used by mixing a styrene-based monomer and a maleimide-based monomer, and more specifically, may be used by mixing in a weight ratio of 20 to 30:70 to 80. In the content range, while having excellent optical properties, a film having excellent heat resistance and mechanical strength can be prepared, but is not limited thereto. In addition, by mixing and using a styrene-based monomer and a maleimide-based monomer within the above range, it is possible to expect an effect of improving polymerization efficiency between each monomer and reducing residual monomers contained in the produced copolymer, and improving heat resistance. An acrylic polymer having low moisture permeability can be obtained.

The acid anhydride may be, for example, any one or a mixture of two or more selected from maleic anhydride and glutaric anhydride.

The styrene-based monomer may be, for example, any one or a mixture of two or more selected from styrene, α-methylstyrene, p-bromo styrene, p-methyl styrene, and p-chloro styrene.

The maleimide-based monomer is specifically, for example, phenyl maleimide, nitrophenyl maleimide, monochlorophenyl maleimide, dichlorophenyl maleimide, monomethylphenyl maleimide, dimethylphenyl maleimide, ethylmethylphenyl maleimide, and cyclohexyl It may be any one or a mixture of two or more selected from maleimide and the like.

In addition to this, it may further include a comonomer in order to adjust the properties of the acrylic polymer as necessary. The comonomer may be, for example, any one or a mixture of two or more selected from methyl acrylate, ethyl acrylate, isopropyl acrylate, ethyl methacrylate and isopropyl methacrylate. By further including a methyl acrylate, it is possible to further improve thermal decomposition properties and further improve flowability.

In one aspect of the present invention, the acrylic polymer may be prepared by emulsion polymerization or suspension polymerization, but may be more preferably suspension polymerized.

More specifically, in suspension polymerization, by performing suspension polymerization in the presence of a dispersing agent for suspension polymerization, it is possible to produce an acrylic polymer having better transparency and excellent optical properties, and at the same time having a high molecular weight and low particle entanglement, and solvent casting. By the method, it becomes possible to manufacture a film having excellent optical properties. In addition, although not described as an example, when preparing a dope solution with an acrylic polymer prepared using the suspension polymerization dispersant, it is possible to exhibit an excellent effect that the change over time of the dope solution is further lowered.

The dispersing agent for suspension polymerization is a suspension polymerization dispersant in which a compound represented by Formula 1, a compound represented by Formula 2 and an alkyl (meth)acrylate are polymerized, a suspension polymerization dispersant which is a copolymer of methyl methacrylate and methacrylic acid, or It may be to use a polyvinyl alcohol, and the like, but is not limited thereto.

[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 the alkyl (meth)acrylate monomer is uniformly polymerized in an aqueous solution in the presence of an initiator. May be Examples of the initiator include 2,2-azobis(2-methylpropionamidine)dihydrochloride, 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-imidazolin-2-yl)propane]dihydrochloride and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate And azo-based initiators, but are not limited thereto. Dispersibility is further improved by using the suspension polymerization dispersant, the content of unreacted monomers is further reduced, the reaction is stable, and the particle size of the obtained copolymer has an even effect. It can be improved further.

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, more preferably 3 to 6% by weight.

In the polymerization of the copolymer of the present invention, with respect to 100 parts by weight of the total monomer mixture, the suspension polymerization dispersant having a solid content of 1 to 10% by weight may be used in an amount of 0.001 to 1.0 parts by weight, more preferably 0.005 to 0.6 parts by weight. . In the above range, good copolymer particles can be obtained, polymerization stability is excellent, and there is little loss of the copolymer particles in the washing and drying process, resulting in good workability and economy.

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

In one aspect when preparing the acrylic polymer, it may be to polymerize 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, 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) -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 are not limited thereto. The initiator may be included in an amount of 0.01 to 0.5 parts by weight, and more preferably 0.1 to 0.3 parts by weight based on 100 parts by weight of the total monomer content. The desired molecular weight can be obtained in the above range, and it is preferable because the reaction heat control of the reactor is easy.

The chain transfer agent may be used without limitation as long as it is a compound known in the art, specifically, for example, C ₁ to C ₁₂ alkyl mercaptan having one thiol functional group or poly having two or more thiol functional groups Thiol mercaptan can be used. Specifically, for example, isopropyl mercaptan, normal butyl mercaptan, tertiary-butyl mercaptan, tertiary-dodecyl mercaptan, normal-aryl mercaptan, normal-octyl mercaptan, normal-dodecyl mercaptan, etc. Can be used. The content may be to use 0.03 to 0.5 parts by weight, more specifically 0.05 to 0.1 parts by weight based on 100 parts by weight of the total monomer, and to produce an acrylic polymer having a weight average molecular weight of 700,000 g/mol or more within the above range. It is preferred because it can.

In addition, in one aspect of manufacturing the acrylic polymer, by polymerizing a compound containing two or more vinyl groups or (meth)acrylic groups, the weight average molecular weight of the acrylic polymer can be increased, and the mechanical properties of the film can be further improved. Can be.

More specifically, an acrylic polymer having a weight average molecular weight of 700,000 g/mol or more can be prepared. Accordingly, it is possible to further improve the mechanical properties and productivity of the film. In addition, the optical properties of the manufactured film are excellent, and local haze reduction phenomenon and the like can be solved.

More specific examples of the vinyl group or a compound having two or more (meth)acrylic groups may include ethylene glycol dimethacrylate (EGDMA) and divinylbenzene (DVB).

The content of the compound having two or more vinyl groups or (meth)acrylic groups may be 0.005 to 0.1 parts by weight, more preferably 0.01 to 0.05 parts by weight based on 100 parts by weight of the total monomer. When used in an amount of less than 0.005 parts by weight relative to 100 parts by weight of the total weight, the crosslinking effect is insignificant to obtain desired properties, and when it is used in excess of 0.1 parts by weight, the degree of crosslinking increases, so that the acrylic polymer does not melt in the solvent and swells. It does not fit. In addition, it is preferable because an acrylic polymer having a weight average molecular weight of 700,000 g/mol or more can be prepared within the above range.

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

Furthermore, if necessary when manufacturing the acrylic polymer, various additives generally used in the art, for example, plasticizer, antioxidant, UV stabilizer, heat stabilizer, and the like may be further included. At this time, the additives may be included in an appropriate amount within a range that does not impair the physical properties of the acrylic polymer, for example, it may be included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the total monomer.

In one aspect of the present invention, the dope solution includes the acrylic polymer and an organic solvent prepared above.

The solid content of the acrylic polymer may be 10 to 40% by weight, more preferably 15 to 35% by weight. It has a viscosity suitable for continuously producing a film in the solid content range, can be completely dissolved in an organic solvent, 5 to 200㎛, specifically 10 to 150㎛, preferably 20 to 80㎛ thick film It is suitable because it is suitable for manufacturing.

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

The organic solvent is not limited as long as it can dissolve the acrylic polymer, but preferably, halogenated hydrocarbons may be used, and halogenated hydrocarbons include chlorinated hydrocarbons, methylene chloride, and chloroform, and methylene chloride is the most preferred. desirable. 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. As the ester, methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, pentyl acetate, etc. can be used. As the ketone, acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone , Cyclopentanone, cyclohexanone, methylcyclohexanone, etc. can be used, and diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetra Hydrofuran, anisole, phenitol, etc. can be used, and alcohols include 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 is used as the main solvent, and alcohols such as methanol and ethanol can be used as the auxiliary solvent. Specifically, methylene chloride and alcohol may be used by mixing in a weight ratio of 80 to 99: 20 to 1, more preferably 85 to 90: 15 to 10.

In addition, various additives such as plasticizers, UV inhibitors, deterioration inhibitors, particulates, release agents, infrared absorbers, and optical anisotropy control agents may be added as necessary. Specific types of these additives can be used without limitation as long as they are commonly used in the field, and the content is preferably used in a range that does not degrade the physical properties of the film. The timing of adding the additive depends on the type of additive. A process of adding an additive at the end of the dope preparation may be carried out.

The plasticizer is used to improve the mechanical strength of the film. When a plasticizer is used, the drying time of the film can be shortened. The plasticizer may be used without limitation as long as it is commonly used, and examples thereof include carboxylic acid esters selected from phosphoric acid esters, phthalic acid esters, and citric acid esters. Examples of phosphate esters 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 carboxylic acid esters include butyl oleate, methyl acetyllysine oleate, dibutyl sebacate and various trimellitic acid esters. It is preferable to use a phthalic 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 acrylic polymer.

The ultraviolet inhibitor may be a hydroxybenzophenone-based compound, a benzotriazole-based compound, a triazine-based compound, a salicylic acid ester-based compound, a cyanoacrylate-based compound, or the like. The amount of the ultraviolet 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 acrylic polymer.

As the deterioration inhibitor, for example, an antioxidant, a peroxide decomposition agent, a radical inhibitor, a metal deactivator, a deoxidizer, and a light stabilizer such as hindered amine may be used. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA). The amount of the deterioration inhibitor may be 0.01 to 5 parts by weight, more preferably 0.1 to 1 part by weight, based on 100 parts by weight of the acrylic polymer.

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

In addition, a wavelength dispersion adjusting agent or the like can be further added as necessary. These additives can be used without limitation as long as they are commonly used in the field.

In addition, an optional retardation additive may be further included to further increase or decrease retardation as necessary. The retardation additive may be used without limitation as long as it is generally used to control retardation in the field. Typically, an additive for increasing retardation may be used as an optical film to be applied to the liquid crystal display device in VA mode, and an additive for reducing retardation may be used as an optical film for application to the liquid crystal display device in IPS mode. The retardation additive may use 1 to 15 parts by weight, more preferably 3 to 10 parts by weight, based on 100 parts by weight of the acrylic polymer, and bleeding may not occur in the above range, thereby forming a high-quality image. Can be.

Further, the dope solution of the present invention may further include a polycarbonate as needed. The polycarbonate may be 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight based on 100 parts by weight of the acrylic polymer. The polycarbonate may have a weight average molecular weight of 5,000 to 50,000 g/mol. By adding the polycarbonate, the optical retardation of the acrylic optical film can be reduced, and more specifically, the acrylic optical film can be manufactured as a zero retardation protection film.

In addition, the dope solution of the present invention may further include a core-shell rubber, more specifically, a core-shell type acrylic rubber, if necessary. The core-shell rubber may be an acrylic latex powder having a two- or three-layer structure including an acrylic rubber layer in a core layer or an intermediate layer. It was confirmed that by further including the core-shell rubber, not only the impact resistance of the film but also the peel-off when manufacturing the film was improved, thereby improving film forming workability and processability. The core-shell rubber may have an average particle diameter of 100 to 400 nm, and has a small effect on smoothness when manufacturing a film having a thickness of 20 to 80 μm in the above range, and has excellent optical properties and improved impact resistance. have. In addition, the core-shell rubber may be contained in 1 to 50% by weight in the dope solution, but is not limited thereto, while further improving the impact resistance aimed at in the above range, it is possible to prevent physical properties of the film from being deteriorated, It is preferable because the property of changing the viscosity of the dope solution to 20% or less during the time required for film formation can be satisfied.

In addition, when the core-shell rubber is further included, the viscosity of the dope solution may be changed due to the swelling of the core-shell rubber, but before the swelling occurs within a process time of producing a film by a solvent casting method after the dope solution is prepared. Film production is possible. More preferably, when the core-shell rubber is included, film formation in the range of the viscosity change rate of the dope solution is 20% or less, specifically 0 to 20%, and more preferably 0 to 10%, without filter clogging and film formation. It is good because it has excellent properties. The viscosity change can be calculated by Equation 1 below.

[Equation 1]

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

In Equation 1, the initial viscosity refers to the viscosity measured initially after the preparation of the dope solution, and the final viscosity refers to the viscosity measured before storing the prepared dope solution and then solvent casting.

More specifically, the first aspect of the core-shell rubber is a two-layer core-shell rubber composed of a core layer and a shell layer, and the core layer may be made of acrylic rubber.

The second aspect of the core-shell rubber is a three-layered core-shell rubber composed of a seed layer, a core layer, and a shell layer, and the core layer or the intermediate layer may be made of acrylic rubber.

The first aspect and the second aspect are exemplified to illustrate the core-shell rubber of the present invention, but are not limited thereto.

In the core-shell rubber according to an aspect of the present invention, the tensile strength of the film may be improved by including a layer made of acrylic rubber. The acrylic rubber layer is not limited, but is preferably 40 to 80% by weight, more preferably 50 to 70% by weight, of the total weight of the core-shell rubber, but is not limited thereto.

remind The core-shell rubber may be prepared by emulsion polymerization. More specifically, the core-shell rubber of the three-layer structure is a first step polymerization in which acrylic monomer, emulsifier, grafting agent and initiator are added to ion-exchanged water to produce seed particles having a glass transition temperature of 20° C. or higher; A second step polymerization in which the polymer by the first step polymerization is added with an acrylic monomer, a comonomer, a crosslinking agent, an emulsifier, an initiator, and a grafting agent to graf the rubber core having a glass transition temperature of 0° C. or less to the seed particles; It is produced by adding a acrylic monomer and an initiator to the polymer by the second-stage polymerization and grafting a glass-like shell having a glass transition temperature of 20° C. or higher to the core to produce a core-shell rubber. Can be.

When the temperature of the ion-exchanged water in the reactor reaches 70 to 90° C. under the nitrogen flow during the first step polymerization, acrylic seed monomers, emulsifiers, grafts and initiators are added to obtain glass seed particles. The acrylic monomer used in the first step polymerization is preferably used at 1 to 40% by weight relative to the total monomer weight used in the preparation of the core-shell rubber.

In the second step polymerization, an acrylic monomer capable of forming a rubber phase on the polymer by the first step polymerization and a styrene derivative substituted with styrene or halogen or an alkyl or aryl group having 1 to 20 carbon atoms as a comonomer to control the refractive index It may be a polymerization using a small amount. The content of the acrylic monomer and the comonomer for grafting the rubbery core to the seed particles is 40 to 80% by weight, more preferably 50 to 70% by weight, based on the total monomer weight used in manufacturing the core-shell rubber. It is preferable to express physical properties with excellent impact resistance, but is not limited thereto. At this time, the acrylic monomer and the comonomer may be used by mixing in a weight ratio of 4 to 9:1.

The three-step polymerization is for grafting the glass-like shell on the core, and the content of the acrylic monomer used at this time is preferably 10 to 40% by weight based on the total monomer weight used in preparing the core-shell rubber. In addition, the particle size of the core-shell rubber grafted to the final glass shell is also preferably uniform.

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

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

As the emulsifier, an anionic emulsifier such as an alkyl sulfate salt having 4 to 30 carbon atoms and an alkyl sulfate salt such as sodium dodecyl sulfate and sodium dodecylbenzene sulfate can be used, but the present invention is 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 the production of rubber.

As the crosslinking agent, 1,2-ethanedioldi(meth)acrylate, 1,3-propanedioldi(meth)acrylate, 1,3-butanedioldi(meth)acrylate, 1,5-pentanedioldi( 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 two or more mixtures may be used, but the present invention is not limited thereto, and their amount 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.

As the grafting agent, one or more monomers having a double bond having 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 monomer used.

As an initiator used in the preparation of the core-shell rubber, any one or two or more mixtures selected from azo-based compounds, peroxide-based compounds, etc. in the presence of ferrous sulfate, sodium ethylenediaminetetraacetate and sodium formaldehyde sulfoxylate It may be to use, but is not limited thereto.

The azo-based 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, and the like. no.

The peroxide-based compound is tetramethylbutyl peroxy neodecanoate, bis(4-butylcyclohexyl)peroxydicarbonate, di(2-ethylhexyl)peroxy carbonate, butylperoxy neodecanoate, Dipropyl peroxy dicarbonate, diisopropyl peroxy dicarbonate, diethoxyethyl peroxy dicarbonate, diethoxyhexyl peroxy dicarbonate, hexyl peroxy dicarbonate, dimethoxybutyl peroxy dicarbonate, bis(3-me Methoxy-3-methoxybutyl) peroxy dicarbonate, dibutyl peroxy dicarbonate, disetylperoxy 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 -Pentanedione peroxide, tert-butyl peracetate, peracetic acid and potassium persulfate may be any one or a mixture of two or more selected from, but is not limited to.

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

When preparing the core-shell rubber of the present invention, the production of the core-shell rubber of the two-layer structure of the first aspect omits the first step polymerization during the production of the core-shell rubber of the three-layer structure of the second aspect. It may be the same as the production method of the second aspect. Specifically, the first step polymerization to produce an acrylic core, a comonomer, a crosslinking agent, an emulsifier, an initiator and a grafting agent in ion-exchanged water to produce a rubbery core having a glass transition temperature of 0° C. or less; And second-stage polymerization to prepare a core-shell rubber by grafting a glass-like shell 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 first-stage polymerization.

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 to the surface of the support through a die, coated in a sheet form, and the solvent present in the casting dope is evaporated by a drying equipment. 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 to form a film by transporting the casting stock solution, and a metal support in the form of a conveyor belt may be used, more specifically, a stainless steel conveyor belt may be used, and by adjusting the movement or rotational speed of the belt. The thickness of the film can be adjusted.

The casting stock solution applied to the belt is moved with the belt for a sufficient time and distance to be formed into a film, and then peeled from the belt by a peeling roller that 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 the machine direction, dried in a dryer to form a final acrylic film, and then wound in a winder and shipped as a product.

More specifically, a) 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of C4 to C8 alkyl (meth)acrylate and 1 to 10% by weight of a monomer mixture (A) 100 parts by weight With respect to, the chain transfer agent (B) is polymerized, including 0.03 to 0.5 parts by weight, 0.005 to 0.1 parts by weight of the compound (C) having two or more vinyl groups or (meth)acrylic groups, and 0.01 to 0.5 parts by weight of the initiator (D), Applying a dope solution comprising an acrylic polymer, a core-shell rubber, and an organic solvent having a weight average molecular weight of 700,000 g/mol or more and a glass transition temperature of 110° C. or more onto the support through a die; And

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 may be to include.

At this time, by using the acrylic polymer, the production speed of the film may be further improved. More specifically, the production speed 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 5 to 20% by weight, it may be produced within 5 minutes from the application of step a) to the separation of step b).

That is, using a polymerized acrylic polymer and core-shell rubber comprising 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of C4 to C8 alkyl (meth)acrylate, and 1 to 10% by weight of heat-resistant monomer Accordingly, the drying speed of the solvent can be adjusted more rapidly, and accordingly, the production speed of the film can be further improved, and a film having a low haze and a low rate of change in thickness can be manufactured when manufacturing a wide film. In addition, when peeling off after film formation, peeling can be performed well without foreign matter remaining on the support.

In addition, by including a compound having two or more vinyl groups or (meth)acrylic groups in the production of an acrylic polymer, the weight average molecular weight can be increased, thereby increasing the content of the chain transfer agent, thereby reducing the viscosity deviation when preparing the dope solution, It is possible to further improve productivity by improving polymerization stability. In addition, it is possible to further improve the mechanical properties of the film.

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, the prepared dope solution is once stored in a storage tank, and bubbles contained in the dope solution are defoamed. The defoamed dope is sent to the pressurized die through a pressurized metering gear pump capable of delivering a high-precision metering amount according to the number of revolutions from the dope outlet, and the dope is placed on a metal support endlessly driven from the detention (slit) of the pressurized die. By casting uniformly, the cast film, which is less dry at the peeling point where the metal support is almost round, is peeled from the metal support. The both ends of the produced film are sandwiched between clips and conveyed with a tenter while maintaining width, and then conveyed with a roller of a drying apparatus to dry and rolled to a predetermined length by a winder. In addition, it is also possible to uniaxially stretch in the machine direction or in the width direction or biaxially stretch in the machine direction and width direction after peeling in a state where the residual solvent amount is 0 to 40% by weight and 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 biaxially stretched simultaneously or sequentially. The elongation may be adjusted as necessary, and specifically, for example, it may be 1.1 to 4 times, more specifically, 2 to 3 times stretching. In addition, after the stretching may further include a step of drying the film. At this time, the drying temperature is not limited as long as the organic solvent is completely dry, but may preferably be 50 to 120°C.

When stretching, the temperature is preferably a glass transition temperature (T _g )±10°C of the acrylic polymer used in the dope solution. The space temperature at the time of 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 temperature during stretching may be 100 to 200°C. Since the dope solution applied at a low space temperature is instantaneously cooled on the support, the gel strength is improved, so that a film with a large amount of organic solvent remaining is obtained. Therefore, the film can be peeled 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%, and 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 portion, a cooled gas may be introduced into the casting portion. It is also possible to cool the space by placing a cooling device in the casting part. In cooling, it is important to be careful that water does not adhere to the casting portion. 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 can be used in an optical film such as a polarizing plate protective film or a retardation film, as well as an optical compensation sheet or an optical filter for stereoscopic images, and can be used by laminating one or two or more.

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

In addition, the present invention also includes an image display device including the polarizing plate within 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 liquid crystal displays 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 it may be to include a polarizing plate disposed on at least one surface of the liquid crystal cell. At this time, the polarizing plate is a polarizer; And at least one layer 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 protective film of the polarizing plate, and the optically anisotropic layer may contain a hybrid alignment-treated disc-like compound.

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

In addition, since the moisture permeability is very low compared to the conventional cellulose acylate film, it is suitable for application as an optical film of a liquid crystal display device to be thinned, and since the moisture permeability satisfies the above range, it is possible to prevent the polarizer from being damaged when the polarizing plate is manufactured. It is possible to prevent the physical properties of the optical film from being deformed even under high temperature and high humidity conditions during the manufacturing process and transport of the display device.

In addition, the phase direction retardation value represented by Equation 1 below may be -50 to +50 nm, and the thickness retardation value represented by Equation 2 below 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 of 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 a physical property having a thickness variation within 5%. That is, when a film having a thickness of 60 μm is taken as an example, it means that the error range is within 5% when the thickness is measured at an arbitrary point with respect to the entire width of the film.

In addition, haze is 2% or less, and there are few foreign matters, so it shows excellent physical properties for use as an optical film. More specifically, haze is 2% or less, specifically 1.5% or less, more specifically 1% or less, and the number of foreign matters is 0.3 or less per 1M, 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 only 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 measuring method.

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

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

The weight average molecular weight was measured using a gel permeation chromatography (GPC) product 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 auto-injector).The analysis column used Styragel HR from WATERS, and polymethylmethacryl as the standard material. Late (PMMA) American polymer standard corporation STD was used. As a mobile phase solvent, HPLC-grade tetrahydrofuran (THF) is used, and the temperature is measured at 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 GPC equipment to measure the weight average molecular weight.

3. Residual monomer: The monomer remaining in the resin after polymerization was quantitatively measured through a GC (Gas Chromatography) analyzer.

4. Phase difference: The phase difference of the prepared film was measured using a birefringence meter (Axoscan, Axometrics), and the measurement wavelength was performed at 550 nm.

5. Haze and light transmittance: measured according to ASTM1003 method.

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

△ Haze = maximum value of haze-minimum value of haze

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

7. Permeability: Temperature applied to the film specimen in a closed chamber using a moisture permeability meter (LabThink, PERME (W3/0120)) at 38℃, RH (relative humidity) 90% of the outer cell under N ₂ carrier gas conditions Moisture permeated through the film from the outer cell and penetrated into the inner cell for 24hr was measured.

8. Coating adhesion: After coating the coated surface on the film, a total of 100 cells were created, 10 horizontally and vertically, and 3M tape was attached and released to evaluate the degree of adhesion of the coating layer. Here, if 95 or more remain, good, 85 or more are normal, and 85 or less are bad

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

Thickness deviation (%) = (Maximum value of thickness-Minimum value of thickness) / Minimum value of thickness × 100

The film thickness was measured by a micrometer measuring instrument of Mahr, Germany.

10. Foreign object inspection: Black spots, white spots, etc. of unmelted melts, including foreign matter such as dust, were detected, and the film in motion after film production was measured using a Next Eye film inspection device. It is expressed as the number of foreign objects per 1M in the longitudinal direction of the film, and if one foreign object occurs during 10M driving, it is indicated as 0.1/1M.

11. Viscosity: After preparing the dope solution at 25°C, the viscosity was measured by a viscosity measurement method using a dropping method. Brookfield's drop-type viscometer Model KF40 was used, and it was measured using a ball number 6.

12. Peel-off property: After casting the dope solution on the surface of the stainless support, dried so that the residual solvent amount in the film was 20% by weight, and the film was peeled off and evaluated as follows.

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

Normal: Peel off without breaking when peeling the film, and a small amount of residue is generated on the support

Poor: When film is peeled off, there is a crackling sound, some rupture occurs, or a residue is present on the support.

[Production Example 1] Preparation of dispersion for suspension polymerization

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

[Formula 1]

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

[Formula 2]

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

[Production Example 2] Preparation of core-shell rubber

As a first step, 1500 g of distilled water was added to a 5 L reactor, and after nitrogen substitution, the temperature was raised to 80 °C. 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, 0.5 g of tertiary butyl peroxide as an initiator The mixed solution was added dropwise for 2 hours, followed by emulsion polymerization at 80° C. for 1 hour with stirring at 500 rpm. The average particle size of the glass seed particles obtained 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, followed by the glass seed particles prepared in the first step, and then added to the reactor.

Here, 250 g of butyl acrylate, 55 g of styrene, 5 g of allyl methacrylate as a graft agent, 1 g of 1,3-butanediol dimethacrylate as a crosslinking agent, 1 g of cumene hydroperoxide, and polyoxyethylene alkyl ether phosphate The mixed solution of 10 g of sodium was added dropwise over 3 hours and then polymerized at 80° C. for 2 hours. The average particle size of the polymer obtained at this time was 250 nm.

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

[Example 1]

1) Preparation of acrylic polymer

In a 5 liter reactor, 2000 g of distilled water, 12 g of a 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 monomers are added as shown in [Table 1], and an initiator, chain transfer agent and ethylene glycol dimethacrylate (EGDMA) are added as shown in [Table 1] and then 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, heated to 105°C, and further polymerized for 30 minutes, and then cooled to 30°C. The beads obtained through the polymerization reaction were washed with distilled water, and dried after being dehydrated. The physical properties of the prepared acrylic polymer beads are measured and are shown in Table 1 below.

2) Preparation of dope solution

20% by weight of the prepared acrylic polymer beads, 12% by weight of the core-shell rubber prepared in Preparation Example 2, and a residual amount of a solvent were mixed, and Tinuvin 918 of Chivas Specialty Co., Ltd. was 3 as an ultraviolet absorber based on 100 parts by weight of the mixed solution. A dope solution was prepared by adding by weight. As the solvent, a mixed solvent in which methylene chloride and methanol were mixed at a weight ratio of 9:1 was used.

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 a 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 the residual solvent to 20% by weight was measured and is shown in Table 2. The residual solvent amount was calculated by the following equation.

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

Both ends of the peeled film are fixed, and when the residual solvent is 12% by weight, the film is stretched 1.5 times in the width direction at a temperature of 125° C., then relaxed and dried in a drying section set at 100° C. to produce a film having a film thickness of 60 μm. Did. The properties of the film at the point after drying was completed are shown in Table 2 below.

[Examples 2 to 5]

An acrylic 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 5]

An acrylic 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.

Hereinafter, in Table 1 and Table 2, abbreviations are as follows.

MMA: methyl methacrylate

AMS: alpha methyl styrene

PMI: Phenylmaleimide

MA: methyl acrylate

MAA: methacrylic acid

n-BMA: n-butyl acrylate

AMPO: Luperox 575, (T-Amyl peroxy 2-ethyl hexanoate)

n-OM: Normal octyl mercaptan

EGDMA: ethylene glycol dimethacrylate

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Monomer content
(g) MMA 830 830 840 850 840 830 830 880 630 700 AMS 20 20 - - - 20 20 20 20 - PMI 50 50 - - - 50 50 50 50 - MA - - - 50 - - - - - - MAA - - 60 - 60 - - - - - n-BMA 100 100 100 100 100 100 100 50 300 300 Initiator
(g) AMPO 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Chain transfer agent
(g) n-OM 0.8 0.8 0.8 0.8 0.8 0.2 0.8 0.8 0.8 0.8 EGDMA (g) 0.1 0.2 0.2 0.2 0.2 - 2 0.3 0.3 0.3 Acrylic polymer
Bead Tg(℃) 119.3 120.4 119.8 112.0 119.5 117.6 121.6 114.0 98.8 93.2 Mw 986,000 1,020,800 1,040,000 937,000 1,068,000 684,000 Measurement impossible 1,063,000 1,024,000 905,000 Total residual monomer (ppm) 2260 2760 2450 2090 2670 2630 1890 2280 2970 2870 Weight percent in dope solution 20 20 20 20 20 20 20 20 20 20 Core-shell rubber Weight percent in dope solution 12 12 12 12 20 12 12 12 12 12 Viscosity of dope solution cps, 25℃ 28,000 33,000 34,100 26,700 34,900 15,800 swelling 45,600 35,100 26,500

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Film production possible possible possible possible possible possible impossible possible possible possible Solvent drying time 3 4 4 3 4 4 - 12 10 9 R _in /R _th
(nm) 0.5/-6 0.9/-7 0.6/-6 0.4/-4 0.6/-7 0.5/-5 - 1.0/-6 0.8/-5 0.8/-8 Haze (%) 0.3 0.4 0.3 0.4 0.4 0.9 - 0.9 0.9 0.8 △ Haze 0.05 or less 0.05 or less 0.05 or less 0.05 or less 0.05 or less 0.1 - 0.1 0.1 0.1 Light transmittance (%) 91.8 91.7 91.4 92.0 91.3 91.8 - 91.3 91.4 91.1 The tensile strength
(GPa) 2.8 2.8 2.6 2.6 2.9 2.2 - 2.7 2.2 1.9 Moisture permeability
(g/㎡·24hr) 76 77 75 71 75 86 - 73 73 74 Adhesion Good Good Good Good Good Good - Good Good Good Thickness deviation
(%) 2 One 2 One 2 4 - 5 7 8 Foreign body inspection 0.1 0.1 0.1 0.1 0.1 0.1 - 0.1 0.1 0.1 Peel off Great Great Great Great Great usually - usually Bad Bad

As shown in Table 2 above, it can be seen that the film according to the present invention can significantly improve the production rate of the film in less than 5 minutes by the solvent drying time up to 20% by weight of the residual solvent. 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 haze increase can be solved. In addition, it can be seen that a uniform and smooth film can be produced due to a small thickness deviation, and it was confirmed that the film easily peels off without any foreign matter remaining on the support when peeling the film.

In addition, compared to the conventional cellulose film, it has been confirmed that the optical properties can be used by replacing the existing cellulose film by showing similar physical properties, and it is confirmed that a film having excellent moisture permeability is lower and the optical properties and mechanical properties can be produced. Did.

In addition, it was confirmed that by manufacturing the film by a solvent cast method, it is possible to provide an acrylic optical film having excellent smoothness and excellent adhesion due to less thickness variation compared to a film produced by melt extrusion.

As described above, in the present invention, it has been described by specific matters and limited embodiments and drawings, which are provided to help the overall understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention Various modifications and variations can be made by those skilled in the art.

Accordingly, the spirit of the present invention should not be limited to the described embodiments, and should not be determined, and all claims that are equivalent or equivalent to the scope of the claims as well as the claims described below belong to the scope of the spirit of the invention. .

Claims (19)

75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of alkyl (meth)acrylate of C4 to C8, and 1 to 20 of 30 to 70 to 80% by weight of styrene-based and maleimide-based monomers. With respect to 100 parts by weight of the monomer mixture (A) containing 10% by weight, 0.03 to 0.5 parts by weight of the chain transfer agent (B), 0.005 to 0.1 parts by weight of the compound (C) having two or more vinyl groups or (meth)acrylic groups, and Initiator (D) is polymerized with 0.01 to 0.5 parts by weight, and has a weight average molecular weight of 700,000 g/mol or more, and a glass transition temperature of 110°C or more using an acrylic polymer, a core-shell rubber, and a dope solution containing an organic solvent. An acrylic optical film manufactured by solvent casting and having a thickness variation of less than 5%. According to claim 1,
The optical film is an acrylic optical film that is a polarizing plate protective film or a retardation film. According to claim 1,
The heat-resistant monomer is an acrylic optical film further comprising any one or two or more selected from acrylic acid, methacrylic acid, acid anhydride monomer. According to claim 1,
The organic solvent is an acrylic optical film that is a halogenated hydrocarbon alone or a mixed solvent of one or more selected from halogenated hydrocarbons and esters, ketones, ethers, and alcohols. According to claim 1,
The dope solution is an acrylic optical film further comprising a polycarbonate. According to claim 1,
The core-shell rubber is an acrylic optical film having a two- or three-layer structure including an acrylic rubber layer in a core layer or an intermediate layer, and having an average particle diameter of 100 to 400 nm. According to claim 1,
The dope solution comprises 10 to 40% by weight of the acrylic polymer and 1 to 40% by weight of the core-shell rubber, and an acrylic optical film having a viscosity of at least 10,000 cps at 32°C. According to claim 1,
The acrylic optical film is an acrylic optical film having a moisture permeability of 200 g/m 2 ·24 hr or less and a haze of 2% or less. According to claim 1,
The acrylic optical film is an acrylic optical film having a film thickness of 10 ~ 150㎛. According to claim 1,
The acrylic optical film is an acrylic optical film that is stretched under the condition that the residual solvent in the film is 5 to 20% by weight. a) Methyl methacrylate 75 to 89% by weight, C4 to C8 alkyl (meth)acrylate 10 to 20% by weight, and styrene-based monomer and maleimide-based monomer 20 to 30: heat-resistant monomer mixed with a weight ratio of 70 to 80 With respect to 100 parts by weight of the monomer mixture (A) containing 1 to 10% by weight, the chain transfer agent (B) 0.03 to 0.5 parts by weight, the compound having two or more vinyl groups or (meth)acrylic groups (C) 0.005 to 0.1% by weight Part and initiator (D) is polymerized to contain 0.01 to 0.5 parts by weight, a weight average molecular weight of 700,000 g / mol or more, glass transition temperature of 110 ℃ or more acrylic polymer, core-shell rubber and a dope solution comprising an organic solvent Applying on a support through a die; And
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;
Method for producing an acrylic optical film having a thickness variation of less than 5%. The method of claim 11,
In step b), when the residual solvent of the acrylic film is 5 to 20% by weight, the film is peeled off, and from the application of step a) to the peeling of step b), the acrylic optical film is produced within 5 minutes. Manufacturing method. The method of claim 11,
The optical film is a method of manufacturing a polarizing plate protective film or a retardation film of an acrylic optical film. The method of claim 11,
The stretching step is a method for producing an acrylic optical film that is 1.1 to 4 times stretching under the condition that the residual solvent in the film is 5 to 20% by weight. The method of claim 14,
The dope solution is a method of manufacturing an acrylic optical film further comprising a polycarbonate. The method of claim 14,
A method of manufacturing an acrylic optical film, which is performed within a range in which the rate of change in viscosity of the dope solution is 20% or less when the dope solution is applied on a support. 75 to 89% by weight of methyl methacrylate, 10 to 20% by weight of alkyl (meth)acrylate of C4 to C8, and 1 to 20 of 30 to 70 to 80% by weight of styrene-based and maleimide-based monomers. With respect to 100 parts by weight of the monomer mixture (A) containing 10% by weight, 0.03 to 0.5 parts by weight of the chain transfer agent (B), 0.005 to 0.1 parts by weight of the compound (C) having two or more vinyl groups or (meth)acrylic groups, and Initiator (D) is polymerized with 0.01 to 0.5 parts by weight, and has a weight average molecular weight of 700,000 g/mol or more, a glass transition temperature of 110°C or more, an acrylic polymer, a thickness variation comprising a core-shell rubber and an organic solvent of 5%. Solvent casting dope solution for producing acrylic optical film. The method of claim 17,
The dope solution is a solvent casting dope solution further comprising a polycarbonate. The method of claim 17,
The dope solution comprises 10 to 40% by weight of the acrylic polymer and 1 to 40% by weight of the core-shell rubber, and a dope solution for solvent casting having a viscosity of at least 10,000 cps at 32°C.