KR102666350B1 - Multilayer optical film and preparation method thereof - Google Patents

Abstract

A method for manufacturing a multilayer optical film according to an exemplary embodiment of the present application is pneumatically shipping an impact reinforcing layer containing a first acrylic resin and an impact modifier, a reclaimed layer containing a recycled acrylic resin, and a surface layer containing a second acrylic resin. steps; and stretching the co-extruded film, wherein the multilayer optical film has a five-layer structure in which a surface layer, a reproduction layer, an impact reinforcing layer, a reproduction layer, and a surface layer are sequentially stacked.

Description

Multilayer optical film and manufacturing method thereof {MULTILAYER OPTICAL FILM AND PREPARATION METHOD THEREOF}

This application relates to multilayer optical films and methods for manufacturing same.

Recently, with the development of optical technology, various display technologies such as plasma displays (PDP), liquid crystal displays (LCD), and organic EL displays (LED), which replace conventional cathode ray tubes (CRTs), have been proposed and sold. Meanwhile, various polymer films such as polarizing films, polarizer protection films, retardation films, light guide plates, and plastic substrates are used in these display devices, and the required characteristics of these display polymer materials are becoming more sophisticated.

Meanwhile, polarizers currently used in image display devices such as liquid crystal displays generally mainly use triacetylcellulose film (hereinafter referred to as TAC film) as a protective film to protect the polyvinyl alcohol polarizer. However, the TAC film does not have sufficient heat-and-moisture resistance, and when used under high temperature or high humidity, there is a problem in that polarizer properties such as polarization degree and color are deteriorated due to film deformation.

Therefore, it has recently been proposed to use a transparent acrylic resin film with excellent heat and moisture resistance instead of TAC film as a material for the polarizer protective film. However, the acrylic resin film has a problem in that its fairability is very weak due to tearing and other reasons.

In addition, the conventional polarizer protective film is composed of a single layer, so there is a limit to improving mechanical properties.

Therefore, in the field of technology, there is a need for research on a polarizer protective film that has excellent processability and excellent mechanical properties.

Republic of Korea Patent Publication No. 10-1737170

This application provides a multilayer optical film and a method for manufacturing the same.

One implementation state of this application is,

Coextruding an impact reinforcement layer containing a first acrylic resin and an impact modifier, a reclaimed layer containing a recycled acrylic resin, and a surface layer containing a second acrylic resin; and

A method for manufacturing a multilayer optical film comprising stretching the coextruded film,

The multilayer optical film provides a method of manufacturing a multilayer optical film having a five-layer structure in which a surface layer, a reproduction layer, an impact reinforcing layer, a reproduction layer, and a surface layer are sequentially stacked.

In addition, another embodiment of the present application provides a multilayer optical film manufactured by the above manufacturing method.

In addition, other embodiments of this application are:

polarizer; and

The multilayer optical film provided on at least one side of the polarizer

Provides a polarizer including a.

The multilayer optical film according to an exemplary embodiment of the present application includes an impact reinforcing layer containing an acrylic resin and an impact modifier in the core layer, so that process loss can be minimized and the breakage of the film can be reduced, Productivity of multilayer optical films can be improved.

In addition, the multilayer optical film according to an exemplary embodiment of the present application can reduce production costs and improve production yield by including a recycled layer containing recycled acrylic resin between the impact reinforcing layer and the surface layer.

In addition, the multilayer optical film according to an exemplary embodiment of the present application has excellent processability by being manufactured through a coextrusion process.

1 is a diagram schematically showing the structure of a multilayer optical film according to an exemplary embodiment of the present application.

Hereinafter, this specification will be described in more detail.

In this specification, when a member is said to be located “on” another member, this includes not only the case where a member is in contact with another member, but also the case where another member exists between the two members.

In this specification, when a part “includes” a certain component, this means that it may further include other components rather than excluding other components unless specifically stated to the contrary.

As mentioned above, research on a polarizer protective film that has excellent processability and excellent mechanical properties is needed in the technical field.

A method for manufacturing a multilayer optical film according to an exemplary embodiment of the present application is pneumatically shipping an impact reinforcing layer containing a first acrylic resin and an impact modifier, a reclaimed layer containing a recycled acrylic resin, and a surface layer containing a second acrylic resin. steps; and stretching the co-extruded film, wherein the multilayer optical film has a five-layer structure in which a surface layer, a reproduction layer, an impact reinforcing layer, a reproduction layer, and a surface layer are sequentially stacked.

Typically, acrylic resin is manufactured into a film of a certain thickness through an extrusion process, surface coating, and stretching process. At this time, the extrusion process generates discarded products during the process due to thickness control, fracture, surface coating, trimming, etc. In this specification, the recycled acrylic resin refers to a recycled resin produced in the form of pellets by pulverizing and compounding waste products generated during the extrusion process. The recycled acrylic resin may have problems such as being yellowish, generating foreign substances, or deteriorating mechanical properties due to high temperature heat history and stretching during the process. Therefore, it is most ideal to separate and recycle only waste products in sheet form before coating and stretching.

According to an exemplary embodiment of the present application, the recycled layer containing the recycled acrylic resin is applied as a separate layer rather than the surface layer of the multilayer optical film, so that the surface characteristics of the multilayer optical film may not be affected.

In an exemplary embodiment of the present application, the recycled layer may include a blended resin of a recycled acrylic resin and a third acrylic resin. At this time, based on the total weight of the blended resin, the content of the recycled acrylic resin may be 50% by weight or less, and may be 10% by weight to 50% by weight. If the content of the recycled acrylic resin exceeds 50% by weight based on the total weight of the blend resin, problems such as yellowishness, increased haze, decreased mechanical properties, generation of foreign substances, quality deviation, and supply and demand of recycled resin may occur, 10 If it is less than % by weight, the economic effect is minimal and operational problems may occur. Therefore, when the content of the recycled acrylic resin is 10% to 50% by weight based on the total weight of the blended resin, the supply and demand of the recycled acrylic resin is adequate, existing quality limits are satisfied, and the economic effect can be maximized.

In an exemplary embodiment of the present application, the first acrylic resin, the second acrylic resin, and the third acrylic resin may include the same acrylic resin or may include different acrylic resins. The acrylic resin may include a copolymer containing an alkyl (meth)acrylate-based unit and a styrene-based unit. Additionally, the acrylic resin may further include an aromatic resin having a carbonate moiety in the main chain.

The term "copolymer" herein means that the elements referred to as "units" herein are polymerized as monomers and included as repeating units in the copolymer resin. In this specification, the copolymer is a block copolymer or a random copolymer. It may be a polymer, but the copolymer form is not limited thereto.

The alkyl (meth)acrylate-based unit includes both an alkyl acrylate-based unit and an alkyl methacrylate-based unit, but is not limited thereto. Considering optical transparency, compatibility, processability, and productivity, the alkyl (meth)acrylate-based unit is not limited thereto. ) The alkyl moiety of the acrylate unit preferably has 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably is a methyl group or an ethyl group. More specifically, the alkyl (meth)acrylate unit is methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, and hydroxyethyl methacrylate. , isobornyl methacrylate, and cyclohexyl methacrylate.

At this time, the alkyl (meth)acrylate-based unit contains about 70 to 98 parts by weight, and more preferably 82 to 97 parts by weight, based on 100 parts by weight of the copolymer. When the content satisfies the above range, an optical film with excellent transmittance and heat resistance can be obtained, and birefringence that occurs during stretching can be minimized.

The styrene-based unit can improve the polymerization efficiency between each monomer, and a film manufactured from a resin composition containing it can more easily control the stretching phase difference, thereby obtaining a film with excellent birefringence.

At this time, the styrene-based unit may be an unsubstituted styrene monomer or a substituted styrene monomer. The substituted styrene monomer may be styrene in which a benzene ring or vinyl group is substituted with a substituent including an aliphatic hydrocarbon or hetero atom. For example, styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 2-methyl-4-chlorostyrene, 2,4,6- Trimethylstyrene, cis-β-methylstyrene, trans-β-methylstyrene, 4-methyl-α-methylstyrene, 4-fluoro-α-methylstyrene, 4-chloro-α-methylstyrene, 4-bromo-α -Methylstyrene, 4-t-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-difluorostyrene, 2,3,4,5,6-pentafluorostyrene , 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene, octachlorostyrene, 2-bromostyrene, 3-bromostyrene, 4-bromo It may be one or more selected from the group consisting of styrene, 2,4-dibromostyrene, α-bromostyrene, and β-bromostyrene, but is not limited thereto. More preferably, styrene substituted with an alkyl group or halogen having 1 to 4 carbon atoms can be used. More specifically, the styrene-based monomer may be one or more selected from the group consisting of styrene, α-methylstyrene, p-bromo styrene, p-methyl styrene, and p-chloro styrene, most preferably styrene, α-methylstyrene and p-methylstyrene.

The content of the styrene-based monomer is preferably about 0.1 parts by weight to 10 parts by weight, and more preferably about 0.5 parts by weight to 5 parts by weight, based on 100 parts by weight of the copolymer. When the content of the styrene-based monomer satisfies the above range, it is easy to control the stretching phase difference of the film, thereby achieving more desirable effects in terms of optical properties of the film.

In an exemplary embodiment of the present application, the impact modifier may be a core-shell type graft copolymer.

Among the core-shell type graft copolymers, the core may include a rubber component, and the shell may be composed of an acrylic polymer.

Conjugated diene-based rubber can be used as the rubber component, and ethylene-propylene diene-based rubber, butadiene-based rubber, etc. can be used as the conjugated diene-based rubber component, and butadiene-based rubber is more preferable. The conjugated diene-based rubber component is preferably included in an amount of 10 to 50 parts by weight, preferably 15 to 45 parts by weight, based on 100 parts by weight of the graft copolymer.

Among the core-shell type graft copolymers, shell components known in the art can be used. For example, homo or copolymers of acrylic monomers; A copolymer of an acrylic monomer and an aromatic vinyl monomer; Copolymers of acrylic monomers, aromatic vinyl monomers, and acrylonitrile monomers; copolymers of acrylic monomers, aromatic vinyl monomers, and acid anhydrides; Alternatively, copolymers of acrylic monomers, aromatic vinyl monomers, acrylonitrile monomers, and acid anhydrides may be mentioned.

The rubber component and acrylic resin can be graft polymerized to have a core-shell structure using methods known in the art, for example, a conventional emulsion polymerization method can be used. Here, the grafting rate is preferably 30% to 60%. If the grafting rate is less than 30%, haze may increase due to stretching of the final film, and if the grafting rate exceeds 60%, manufacturing is difficult.

The impact modifier is preferably included in an amount of 20 to 65 parts by weight based on 100 parts by weight of the first acrylic resin.

In an exemplary embodiment of the present application, the total thickness of the multilayer optical film may be 20 ㎛ to 100 ㎛, and 40 ㎛ to 60 ㎛. If the total thickness of the multilayer optical film is satisfied, post-process handling problems do not occur, and if the total thickness of the multilayer optical film is too thick, it may be unsuitable for the development direction of thinning the film.

In an exemplary embodiment of the present application, based on the total thickness of the multilayer optical film, the thickness of the impact reinforcing layer may be 50% or less, and the total thickness of the two reproduction layers may be 10% to 60%, The total thickness of the two surface layers may be 30% or more. In addition, based on the total thickness of the multilayer optical film, the thickness of the impact reinforcement layer may be 20% to 40%, the total thickness of the two reproduction layers may be 20% to 50%, and the two surface layers The total thickness may be 30% to 60%. If the thickness of the impact reinforcing layer, reproduction layer, and surface layer is satisfied, physical properties (phase difference value, transmittance, haze, etc.) similar to those of a conventional film, which is a single layer composed only of surface layer resin, can be realized within the quality limit, and if the thickness exceeds the above thickness, In this case, it is undesirable because problems such as increased phase difference, decreased transmittance, increased haze, and decreased mechanical properties (tensile strength, elongation, etc.) may occur.

In an exemplary embodiment of the present application, the multilayer optical film may have a plane direction retardation value (R _in ) of -10 nm to 10 nm, and -5 nm to 5 nm, expressed by Equation 1 below at 550 nm. In addition, the multilayer optical film may have a thickness direction retardation value (R _th ) expressed by Equation 2 below at 550 nm of -50 nm to 50 nm, and -10 nm to 40 nm.

[Equation 1]

R _in = (n _x - n _y ) × d

[Equation 2]

R _th = [n _z - (n _x + n _y ) / 2] × d

In Equations 1 and 2 above,

n _x is the refractive index in the direction in which the plane direction refractive index of the multilayer optical film is maximum,

n _y is the refractive index in the direction perpendicular to the n _x direction in the plane direction of the multilayer optical film,

n _z is the refractive index in the thickness direction of the multilayer optical film,

d is the thickness of the multilayer optical film.

If the multilayer optical film satisfies the in-plane retardation value (R _in ) and the thickness direction retardation value (R _th ), it can be commercialized because the quality limit is similar to that of existing products, and the in-plane retardation value (R _in ) And if it deviates from the thickness direction retardation value (R _th ), quality defects such as a rainbow phenomenon may occur on the surface of the film.

In an exemplary embodiment of the present application, the haze of the multilayer optical film may be 10% or less, and may be 3.5% or less. If the haze of the multilayer optical film is satisfied, it can be commercialized at a level of physical properties similar to existing products, but if the haze of the multilayer optical film is outside the haze, quality defects may occur.

The multilayer optical film according to an exemplary embodiment of the present application may be obtained by co-extruding an impact reinforcement layer, a reproduction layer, and a surface layer. When the multilayer optical film is manufactured through a coextrusion process, a multilayer optical film having desired optical properties can be manufactured without any additional processes, and the thickness of each layer can be easily controlled.

The structure of a multilayer optical film according to an exemplary embodiment of the present application is schematically shown in FIG. 1 below. As shown in Figure 1 below, the multilayer optical film according to an exemplary embodiment of the present application includes a surface layer 30, a reproduction layer 20, an impact reinforcing layer 10, a reproduction layer 20, and a surface layer 30 sequentially stacked. It includes a five-story structure.

In an exemplary embodiment of the present application, the step of co-extracting the impact reinforcement layer, the reproduction layer, and the surface layer may be performed as a continuous process. More specifically, it may be performed by a co-extrusion T-die method, a co-extrusion inflation method, a co-extrusion lamination method, etc., but is not limited thereto. The details of the co-extrusion step are described in more detail in the examples described later.

In an exemplary embodiment of the present application, the stretching process in the step of stretching the co-extruded film may be performed in machine direction (MD) stretching, transverse direction (TD) stretching, or both. Additionally, when both longitudinal stretching and transverse stretching are performed, either one may be stretched first and then stretched in the other direction, or both directions may be stretched simultaneously. Additionally, the stretching may be performed in one step or may be performed in multiple steps.

In the case of longitudinal stretching, stretching can be performed by a speed difference between rolls, and in the case of transverse stretching, a tenter can be used. The tenter's rail starting angle is usually within 10° to suppress the bowing phenomenon that occurs during transverse stretching and to regularly control the angle of the optical axis. The bowing suppression effect can be obtained even when transverse stretching is performed in multiple stages. The phase difference characteristics of the film can be adjusted through the stretching process described above.

The stretching ratio in the step of stretching the coextruded film may be 1.3 times to 3.5 times, 1.5 times to 3.0 times, or 1.7 times to 2.7 times in the machine direction (MD). When the longitudinal stretch ratio satisfies the above numerical range, the handling of the film is excellent and breakage of the stretched film can be prevented.

In addition, the stretching ratio in the step of stretching the coextruded film may be 1.3 times to 3.5 times, 1.5 times to 3.0 times, or 1.7 to 2.7 times in the transverse direction (TD). When the transverse stretch ratio satisfies the above numerical range, the handling of the film is excellent and breakage of the stretched film can be prevented.

In this specification, the longitudinal direction (MD, Machine Direction) refers to the film progress direction, and the transverse direction (MD, Machine Direction) refers to the direction perpendicular to the film progress direction.

Additionally, in the stretching step, it is preferable to determine the stretching temperature based on the glass transition temperature of each film layer of the multilayer optical film in order to adjust the phase difference. Specifically, the temperature may be within +30°C or within +20°C of the glass transition temperature of the film with the highest glass transition temperature among each film layer of the multilayer optical film. When the stretching temperature satisfies the above numerical range, the mechanical properties of the optical film are excellent, and the problem of film breakage during stretching can be prevented.

According to an exemplary embodiment of the present application, the step of forming a primer coating layer on at least one side of the multilayer optical film may be further included. The step of forming the primer coating layer may be performed between the step of co-extruding the impact reinforcement layer, the reproduction layer, and the surface layer and the step of stretching the co-extruded film, and may be performed after the step of stretching the co-extruded film. It can be. The primer coating layer can prevent blocking that occurs between films when winding a multilayer optical film and improve adhesion in post-processing. The primer coating layer can use materials and manufacturing methods known in the art, and is not particularly limited.

Additionally, an exemplary embodiment of the present application provides a multilayer optical film manufactured by the above manufacturing method.

In addition, an exemplary embodiment of the present application includes a polarizer; and the multilayer optical film provided on at least one side of the polarizer.

The polarizer may be any one known in the art without limitation, and for example, a film made of polyvinyl alcohol (PVA) containing iodine or a dichroic dye may be used. The polarizer can be manufactured by dyeing iodine or dichroic dye on a PVA film, but the manufacturing method is not particularly limited. In this specification, a polarizer refers to a state that does not include a protective film, and a polarizing plate refers to a state that includes a polarizer and a protective film.

Adhesion between the polarizer and the protective film can be performed using an adhesive layer. The adhesive that can be used when combining the protective film and the polarizing plate is not particularly limited as long as it is known in the art. For example, there are one-component or two-component polyvinyl alcohol (PVA)-based adhesives, polyurethane-based adhesives, epoxy-based adhesives, styrene butadiene rubber (SBR-based) adhesives, or hot melt adhesives.

Furthermore, the adhesion of the polarizer and the protective film is performed by first coating the adhesive on the surface of the protective film for the polarizer or the PVA film as a polarizer using a roll coater, gravure coater, bar coater, knife coater, or capillary coater, This can be performed by laminating the protective film and polarizing film by heat pressing or room temperature pressing with a lamination roll before the adhesive is completely dried. When using a hot melt adhesive, a heat press roll must be used.

Additionally, an adhesive can also be used as long as it can exhibit sufficient adhesive force. It is desirable that the adhesive is sufficiently cured by heat or ultraviolet rays after lamination to improve the mechanical strength to that of an adhesive, and the interfacial adhesion is also large, so that the adhesive has an adhesive strength that does not peel off without destroying either of the two films to which the adhesive is attached. It is desirable.

In particular, specific examples of adhesives that can be used include natural rubber, synthetic rubber or elastomer with excellent optical transparency, vinyl chloride/vinyl acetate copolymer, polyvinyl alkyl ether, polyacrylate, modified polyolefin adhesive, etc., to which hardeners such as isocyanate are added. One curable adhesive may be mentioned.

The polarizing plate according to an exemplary embodiment of the present application can be used for various purposes. Specifically, it can be preferably used in image display devices including polarizers for liquid crystal displays (LCDs) and anti-reflection polarizers for organic EL displays. In addition, the polarizer is a composite polarizer that combines various optical layers such as various functional films, such as retardation plates such as λ/4 plate and λ/2 plate, light diffusion plate, viewing angle enlargement plate, luminance enhancement plate, and reflector. It can be applied to .

The polarizing plate may be provided with an adhesive layer on at least one side to facilitate subsequent application to an image display device, etc. Additionally, a release film may be additionally provided on the adhesive layer to protect the adhesive layer until the polarizing plate is applied to an image display device, etc.

Hereinafter, in order to explain the present application in detail, examples will be given in detail. However, the embodiments according to the present application may be modified into various other forms, and the scope of the present application is not to be construed as being limited to the embodiments described in detail below. The embodiments of the present application are provided to more completely explain the present application to those with average knowledge in the art.

< Example >

< Example 1>

Raw material pellets containing acrylic impact modifiers IR-451 (Kaneka) and M-100 (LG MMA) were dried with hot air at 80°C for 6 hours and melted in a first extruder at 260°C to form an impact reinforcement layer. Raw material pellets containing 30% by weight of recycled acrylic resin and M-100 product (LG MMA) were dried with hot air at 80°C for 6 hours and melted with a second extruder at 265°C to form a recycled layer (RM-100, LG CHEM). was formed. In addition, raw material pellets from MR-1000 (Nippon Shokubai) were dried with hot air at 80°C for 6 hours and melted using a third extruder at 265°C to form a surface layer.

Next, the molten resin layers from the first extruder, second extruder, and third extruder are simultaneously passed through a feed block and then formed into a coat-hanger type T-die coated with chrome. and passed through a chrome casting roll and a drying roll to produce an optical film with a thickness of 140 ㎛ with each layer differentiated. The final thickness of the dried film was measured using a contact thickness gauge.

In the laboratory, a urethane-based primer with a solid content of 20% by weight or less and a viscosity of 100cps or less was used to coat the surface with a coating thickness of 0.5㎛ or less using an applicator, and then dried at 90°C for 3 minutes to prepare a surface-coated film. .

The film was stretched in the longitudinal direction (MD) and transverse direction (TD) at a speed of 50 mm/min at 150°C or lower, which is 20°C to 30°C higher than the glass transition temperature (Tg) of the film, using experimental biaxial stretching equipment. A multilayer optical film with a thickness of 40㎛ was manufactured by sequential stretching 2.7 times.

The structure of the multilayer optical film of Example 1 is a five-layer structure in which a surface layer, a reproduction layer, an impact reinforcing layer, a reproduction layer, and a surface layer are sequentially stacked.

< Comparative example 1>

A multilayer optical film was manufactured in the same manner as in Example 1, except that the impact reinforcing layer was excluded.

The structure of the multilayer optical film of Comparative Example 1 is a three-layer structure in which a surface layer, a reproduction layer, and a surface layer are sequentially stacked.

< Comparative example 2>

A multilayer optical film was manufactured in the same manner as in Example 1 except for the surface layer.

The structure of the multilayer optical film of Comparative Example 2 is a five-layer structure in which a reproduction layer, an impact reinforcing layer, and a reproduction layer are sequentially stacked.

< Comparative example 3>

An optical film was manufactured in the same manner as in Example 1, except that the impact reinforcing layer and the surface layer were excluded.

The structure of the optical film of Comparative Example 3 was a single-layer structure of the reproduction layer.

< Experiment example >

One) phase difference value measurement

For the multilayer optical films manufactured according to Example 1 and Comparative Examples 1 to 3, the retardation values were measured and shown in Table 1 below. For phase difference measurement, 3cm samples were collected in each of the MD/TD directions of the film, and the phase difference values in the plane direction (R _in ) and thickness direction (R _th ) were measured using Axo-scan (Axometrics) equipment.

2) Transmittance and Haze measurement

For the multilayer optical films prepared according to Example 1 and Comparative Examples 1 to 3, the transmittance and haze were measured and shown in Table 1 below. Measurements were made using a Hazemeter (HM150, D65 light source, JIS-K7136) by collecting 3cm samples in each of the MD/TD directions of the film.

3) Impact energy measurement

For the multilayer optical films manufactured according to Example 1 and Comparative Examples 1 to 3, the impact energy was measured and shown in Table 1 below. Measurements were made using a Dupont Impact Tester (JIS K 5400) by collecting 10cm samples in each of the MD/TD directions of the film.

[Table 1]

As shown in Table 1 above, in Example 1, the external shape of the film was excellent, and the retardation value was equivalent to that of a product composed of a conventional acrylic resin layer alone. In addition, it was possible to manufacture a multilayer optical film that satisfies transmittance and haze while being resistant to impact.

In Comparative Example 1, the impact reinforcing layer was not applied, and the problem of film breakage during the stretching process increased. In addition, in the case of Comparative Example 2, the surface layer was not applied, and the retardation value was out of range as the film became cloudy due to the recycled acrylic resin provided on the outermost layer of the film, and the transmittance and haze properties were not satisfied. In addition, in the case of Comparative Example 3, it was composed only of a recycled acrylic resin layer, so the retardation value was out of range and the transmittance and haze properties were not satisfied.

As shown in the above results, the multilayer optical film according to an exemplary embodiment of the present application includes an impact reinforcing layer containing an acrylic resin and an impact modifier in the core layer, thereby minimizing process loss and preventing breakage of the film. Since it can be reduced, the productivity of the multilayer optical film can be improved.

In addition, the multilayer optical film according to an exemplary embodiment of the present application can reduce production costs and improve production yield by including a recycled layer containing recycled acrylic resin between the impact reinforcing layer and the surface layer.

In addition, the multilayer optical film according to an exemplary embodiment of the present application has excellent processability by being manufactured through a coextrusion process.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible without departing from the technical spirit of the present invention as set forth in the claims. It will be self-evident to those with ordinary knowledge.

10: Impact reinforcement layer
20: Regeneration layer
30: surface layer

Claims (12)

Coextruding an impact reinforcement layer containing a first acrylic resin and an impact modifier, a reclaimed layer containing a recycled acrylic resin, and a surface layer containing a second acrylic resin; and
A method for manufacturing a multilayer optical film comprising stretching the coextruded film,
The multilayer optical film has a five-layer structure in which a surface layer, a reproduction layer, an impact reinforcement layer, a reproduction layer, and a surface layer are sequentially stacked,
The recycled layer includes a blended resin of a recycled acrylic resin and a third acrylic resin,
A method for producing a multilayer optical film, wherein the content of the recycled acrylic resin is 50% by weight or less based on the total weight of the blended resin. delete delete The method of claim 1, wherein the impact modifier is a core-shell type graft polymer. The method of claim 1, wherein the total thickness of the multilayer optical film is 20㎛ to 100㎛. The method according to claim 1, wherein the multilayer optical film has a plane direction retardation value (R _in ) expressed by Equation 1 below at 550 nm of -10 nm to 10 nm, and a thickness direction retardation value (R _th ) Method for producing a multilayer optical film wherein is -50 nm to 50 nm:
[Equation 1]
R _in = (n _x - n _y ) × d
[Equation 2]
R _th = [n _z - (n _x + n _y ) / 2] × d
In Equations 1 and 2 above,
n _x is the refractive index in the direction in which the plane direction refractive index of the multilayer optical film is maximum,
n _y is the refractive index in the direction perpendicular to the n _x direction in the plane direction of the multilayer optical film,
n _z is the refractive index in the thickness direction of the multilayer optical film,
d is the thickness of the multilayer optical film. The method of claim 1, wherein the multilayer optical film has a haze of 10% or less. The method of claim 1, wherein the step of co-extruding the impact reinforcing layer, the reproduction layer, and the surface layer is performed by a co-extrusion T-die method. The method of claim 1, wherein the stretching step includes stretching the coextruded film 1.3 times to 3.5 times in the machine direction (MD). The method of claim 1, wherein the stretching step includes stretching the coextruded film 1.3 times to 3.5 times in the transverse direction (TD). A multilayer optical film manufactured by the manufacturing method of any one of claims 1 and 4 to 10. polarizer; and
The multilayer optical film of claim 11 provided on at least one side of the polarizer.
A polarizer containing a.