KR102063204B1 - Optical film, display device comprising the same and display apparatus comprising the same - Google Patents

Abstract

Aromatic vinyl monomers; Acid anhydride monomers; And an optical film derived from a comonomer copolymerizable with the aromatic vinyl monomer or the acid anhydride monomer, wherein the optical film has an in-plane retardation of 15 nm or less, a thickness direction retardation of -2 nm from -150 nm to -10 nm, Provided are an optical film having a glass transition temperature of 110 ° C. to 150 ° C. and a total light transmittance of 90% or more, a display device including the same, and a display device including the same.

Description

Optical film, a display device including the same, and a display device including the same {OPTICAL FILM, DISPLAY DEVICE COMPRISING THE SAME AND DISPLAY APPARATUS COMPRISING THE SAME}

The present invention relates to an optical film, a display element including the same, and a display device including the same.

Recently, display technologies using various methods, such as plasma display panels (PDPs) and liquid crystal displays (LCDs), which replace conventional CRTs, have been proposed and marketed based on the development of optical technologies. Polymer materials for such displays are becoming more sophisticated. For example, in the case of a liquid crystal display, as thin film thickness, light weight, and large screen area are promoted, wide viewing angle, high contrast, suppression of image color tone change according to viewing angle, and uniformity of screen display have become particularly important problems.

Accordingly, various polymer films are used for polarizing films, retardation films, plastic substrates, light guide plates, and the like, and liquid crystals include twisted nematic (TN), super twisted nematic (STN), and VA (vertical alignment). ), Various types of liquid crystal display devices using IPS (in-plane switching) liquid crystal cells, etc. have been developed. All of these liquid crystal cells have a unique liquid crystal array, have inherent optical anisotropy, and in order to compensate for this optical anisotropy, films have been proposed in which various kinds of polymers are extended to impart a retardation function.

For example, Japanese Unexamined Patent Application Publication No. 9-304619 is mentioned as an example using polycarbonate (PC) resin. However, when extending | stretching polycarbonate resin in this way, although sufficient retardation function can be provided as a retardation film, there exists a problem that it is difficult to manufacture the film which has a large retardation change rate according to extension degree, and has a more uniform stable phase difference.

As a method of solving such a problem, a method using a cyclic polyolefin resin (cyclic olefin polymer, COP) has been proposed (Japanese Patent Laid-Open No. 2001-350017, Japanese Patent Laid-Open No. 2004-51928). However, the cyclic polyolefin resin has a problem in that adhesiveness with other substrates and the like is inferior, and there is a problem in that a sufficient retardation is not generated as a retardation film because the retardation change rate is small due to extension.

The problem of acrylic film is that it lacks the brittle strength (brittle), which is an inherent property of acrylic, to apply additives such as rubber, and there are disadvantages such as cost increase and haze increase.

Background art of the present invention is disclosed in Korea Patent Publication No. 2015-0113886.

An object of the present invention is to provide an optical film having an in-plane retardation and a thickness direction retardation satisfying a predetermined range and excellent in heat resistance and optical transparency.

Another object of the present invention is to provide an optical film that is easy to form a liquid crystal layer on one surface.

Another object of the present invention is to provide an optical film having a high elongation at break to reduce the occurrence of break in the process, and improve the impact resistance of the product.

Still another object of the present invention is to provide an optical film having excellent in-plane retardation and thickness direction retardation and excellent film strength.

Still another object of the present invention is to provide an optical film having low haze, high elongation at break, and cracking in the cutting process.

Still another object of the present invention is to provide a display device and a display device including the optical film of the present invention.

The optical film of the present invention is an aromatic vinyl monomer; Acid anhydride monomers; And an optical film derived from a comonomer copolymerizable with the aromatic vinyl monomer or the acid anhydride monomer, wherein the optical film has an in-plane retardation of 15 nm or less, and a thickness direction retardation of Equation 2 from -150 nm to-. 10 nm, glass transition temperature can be 110 ℃ to 150 ℃, total light transmittance of 90% or more:

<Equation 1>

Re = (nx-ny) x d

(In Formula 1, nx and ny are refractive indices in the slow axis direction and the fast axis direction of the optical film, respectively, at a wavelength of 550 nm, and d is the thickness (unit: nm) of the optical film).

<Equation 2>

Rth = ((nx + ny) / 2-nz) x d

(In Formula 2, nx, ny, and nz are refractive indices in the slow axis direction, the fast axis direction, and the thickness direction of the optical film, respectively, at a wavelength of 550 nm, and d is the thickness (unit: nm) of the optical film.

The display device of the present invention may include the optical film of the present invention.

The display device of the present invention may include the optical film or the display element of the present invention.

The present invention provides an optical film having an in-plane retardation and a thickness direction retardation satisfying a predetermined range and excellent in heat resistance and optical transparency.

The present invention provides an optical film that is easy to form a liquid crystal layer on one surface.

The present invention provides an optical film having a high elongation at break to reduce breakage in process and improve impact resistance of the product.

The present invention provides an optical film having low haze, high elongation at break, and no cracking in the cutting process.

The present invention can stably provide in-plane retardation and thickness direction retardation and provided an excellent optical film film strength.

The present invention provides an optical film that can be used for the antireflection film together with the liquid crystal layer.

According to the present invention, an antireflection film is manufactured by forming two layers of liquid crystal layers having a phase difference in a phase difference optical film. However, an antireflection film can be manufactured even by stacking an optical film and a liquid crystal layer by providing a phase difference to the optical film. By minimizing the anti-reflection film manufacturing process, cost reduction was possible.

The present invention provides a display device and a display device including the optical film of the present invention.

By the accompanying examples will be described in detail to be easily carried out by those of ordinary skill in the art. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In order to clearly describe the present invention, parts irrelevant to the description are omitted.

In the present specification, "in-plane retardation (Re)" is represented by the following equation 1, "thickness retardation (Rth)" is represented by the following equation 2, "degree of biaxiality (NZ)" can be represented by the following equation 3. have:

<Equation 1>

Re = (nx-ny) x d

(In Formula 1, nx and ny are refractive indices in the slow axis direction and the fast axis direction of the optical film, respectively, at a wavelength of 550 nm, and d is the thickness (unit: nm) of the optical film).

<Equation 2>

Rth = ((nx + ny) / 2-nz) x d

(In Formula 2, nx, ny, and nz are refractive indices in the slow axis direction, the fast axis direction, and the thickness direction of the optical film, respectively, at a wavelength of 550 nm, and d is the thickness (unit: nm) of the optical film.

<Equation 3>

NZ = (nx-nz) / (nx-ny)

(In Formula 3, nx, ny, and nz are refractive indices in the slow axis direction, the fast axis direction, and the thickness direction of the optical film, respectively, at a wavelength of 550 nm.

As used herein, “total light transmittance” is a value measured in the visible light region by ASTM D 1003.

As used herein, "(meth) acryl" refers to acrylic and / or methacryl.

Hereinafter, an optical film according to an embodiment of the present invention will be described in detail.

The optical film according to an embodiment of the present invention may be an optical compensation film of a uniaxial optical element having a refractive index distribution satisfying nz> nx ≧ ny or nz> ny ≧ nx. "Nx = ny" in "nx≥ny" and "ny≥nx" includes not only the case where nx and ny are exactly the same, but also the case where nx and ny are substantially the same. The case where "nx and ny are substantially the same" includes a case where the in-plane retardation of the optical film is 15 nm or less.

The optical film of an embodiment of the present invention may have an in-plane retardation of 15 nm or less, a thickness retardation of -150 nm to -10 nm, a glass transition temperature of 110 ° C. to 150 ° C., and a total light transmittance of 90% or more. In the above range, the optical film is laminated on the liquid crystal layer having a predetermined range of in-plane retardation and thickness direction retardation to exhibit a target in-plane retardation and thickness direction retardation, and may have good heat resistance, and are optically transparent to display elements. Can be used.

In one embodiment, the optical film has an in-plane retardation of less than 15 nm, 5 nm or less, specifically 0 nm to 5 nm, 0 nm to 3 nm, thickness direction retardation of -130 nm to -50 nm, -120 nm to -70 nm, and glass transition temperature of 110 ° C. to 130 ° C. ℃, the total light transmittance may be 90% to 100%. The present invention satisfies the in-plane retardation, thickness direction retardation, glass transition temperature and total light transmittance at the same time, and is further characterized by an optical film that is easy to form an alignment film for liquid crystal layer formation on one surface.

An optical film is an optical film to which a negative birefringent resin is applied. In order to satisfy the above-mentioned in-plane retardation, thickness retardation, glass transition temperature and total light transmittance at the same time, and to form an alignment layer on one surface to facilitate formation of a liquid crystal layer, aromatic vinyl 5% to 25% by weight of the monomer, 5% to 20% by weight of the acid anhydride monomer, and 60% to 80% by weight of the comonomer copolymerizable with the aromatic vinyl monomer or the acid anhydride monomer. have.

The aromatic vinyl monomer may be included in 5% by weight to 25% by weight of the total of the aromatic vinyl monomer, the acid anhydride monomer and the comonomer. In the above range, the in-plane retardation and the thickness direction retardation of the optical film can be satisfied at the same time, the heat resistance improvement (Tg), the elongation at break upon stretching the film may be not broken. Preferably, the aromatic vinyl monomer may be included in 10% by weight to 25% by weight, 15% by weight to 25% by weight.

The acid anhydride monomer may be included in an amount of 5 wt% to 20 wt% of the total of the aromatic vinyl monomer, the acid anhydride monomer and the comonomer. In the above range, the retardation in the thickness direction of the optical film may come out, the heat resistance of the optical film is good, there is no brittle phenomenon of the film, the compatibility between monomers in the optical film is good, the total light transmittance is good, and the film is stretched The elongation at break may be increased and there may be no break. Preferably the acid anhydride monomer may be included in 5 to 10% by weight.

The comonomer may be included in an amount of 60% to 80% by weight based on the total of the aromatic vinyl monomer, the acid anhydride monomer and the comonomer. In the above range, when breaking the film, there is no breakage and brittleness improvement, the film production can be adjusted to the stretching ratio can be stable phase difference range control, transmittance increase effect. Preferably the comonomer may be included in 65% by weight to 80% by weight, 65% by weight to 75% by weight.

An aromatic vinyl monomer is a monomer in which at least one vinyl group is bonded to an aromatic group, and the "aromatic group" means an unsubstituted benzene ring or a benzene ring in which at least one C1 to C5 alkyl group or halogen is substituted in the benzene ring. Specifically, the aromatic vinyl monomer may be styrene, alpha-styrene, para-styrene or meta-styrene, vinyltoluene, or the like, preferably styrene.

Acid anhydride monomers may include anhydrides of polyhydric carboxylic acids or derivatives thereof. For example, the acid anhydride monomer may be represented by the following Chemical Formula 1. Preferably, the acid anhydride monomer may be maleic anhydride.

<Formula 1>

(In Formula 1, R ₁ and R ₂ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms).

The comonomer may comprise one or more of substituted or unsubstituted alkyl (meth) acrylate-based monomers, monomers having substituted or unsubstituted cycloaliphatic groups, and monomers of Formula 2 below:

<Formula 2>

(In Formula 2, R ₁ is a hydrogen atom or a methyl group;

R ₄ and R ₅ are each independently a substituted or unsubstituted linear alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted branched alkyl group having 3 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 10 carbon atoms , Substituted or unsubstituted C1-C10 linear alkoxy group, substituted or unsubstituted C3-C10 branched alkoxy group, substituted or unsubstituted C3-C10 cycloalkoxy group, halogen atom, or substituted Or an unsubstituted aryl group having 6 to 10 carbon atoms;

m is an integer from 1 to 10; p is an integer from 0 to 4; q is an integer from 0 to 5,

X is a single bond, -C (R ₂ ) (R ₃ )-, -C (= O)-, -O-, -OC (= O)-, -OC (= O) O-, -S-, Is a divalent group selected from the group consisting of -SO-, and -SO _2- (wherein R ₂ and R ₃ are each independently a hydrogen atom, a linear alkyl group having 1 to 10 carbon atoms, and having 3 to 10 carbon atoms). Branched alkyl groups, cycloalkyl groups having 3 to 10 carbon atoms, linear alkoxy groups having 1 to 10 carbon atoms, branched alkoxy groups having 3 to 10 carbon atoms, cycloalkoxy groups having 3 to 10 carbon atoms, or aryl groups having 6 to 10 carbon atoms; R ₂ and R ₃ may be connected to each other to form a cycloalkyl group having 3 to 10 carbon atoms with the carbon atom to which they are bonded).

The alkyl (meth) acrylate monomer may include a (meth) acrylic acid alkyl ester which is substituted or unsubstituted and has an alkyl group having 1 to 10, preferably 1 to 4 carbon atoms in the alkyl group. The monomer having a substituted or unsubstituted alicyclic group may include one or more of (meth) acrylic acid esters which are substituted or unsubstituted and have an alicyclic group having 5 to 20 carbon atoms.

Specifically, comonomers are methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth ) Acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, isobonyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, etc. are mentioned. have. Preferably the comonomer may comprise a (meth) acrylic monomer having an alkyl group, more preferably methyl methacrylate.

"Substituted" in the substituted or unsubstituted is one or more hydrogen atoms of the functional group is a hydroxyl group, an alkyl group of 1 to 10 carbon atoms, a cycloalkyl group of 3 to 10 carbon atoms, an aryl group of 6 to 10 carbon atoms or an arylalkyl group of 7 to 10 carbon atoms It means substituted by.

In one embodiment, the optical film may be a terpolymer copolymer film formed from 60% to 80% by weight of methyl methacrylate 10% to 25% by weight, maleic anhydride 5% to 20% by weight. Preferably, it may be a ternary copolymer film formed of 65 wt% to 80 wt% of methyl methacrylate, 15 wt% to 25 wt% of styrene, and 5 wt% to 10 wt% of maleic anhydride. Within the above range, the optical properties may have an excellent transmittance, a low haze, a target retardation value (in-plane retardation and thickness direction retardation), excellent heat resistance, and easy stretching ratio adjustment.

In addition, in the optical film, the aromatic vinyl monomer may be included in excess of the acid anhydride monomer. In such a case, the haze of the optical film does not rise, the target phase difference (thickness direction phase difference) can be reached, and the brittleness of the film can be improved.

In addition, the optical film may have a degree of biaxiality of -30 or more, preferably -30 or more and -5 or less.

In addition, the optical film may have a refractive index of 1.40 to 1.60, specifically 1.48 to 1.56, preferably 1.50 to 1.52. In the above range, the transmittance is high when the liquid crystal layer is laminated on the optical film can be used as a display element, for example, it can be used as an antireflection film as a display element.

In addition, the optical film may have a haze of 5% or less, preferably 2% or less, more preferably 1% or less. In the above range, it can be used as an optical film.

In addition, the optical film may have an elongation at break of 5% or more, for example, 5% to 10%. In the above range, there can be no breakage and flexibility when drawing the film.

The optical film may have a thickness of 5 μm to 200 μm, preferably 10 μm to 100 μm, more preferably 25 μm to 50 μm. In the above range, it can be used as an optical film.

The optical film may further include conventional additives in addition to units derived from aromatic vinyl monomers, acid anhydride monomers and comonomers. The additive may include, but is not limited to, one or more of antioxidants, ultraviolet absorbers, plasticizers, heat stabilizers, antistatic agents, flame retardants, antistatic agents, compatibilizers, crosslinker thickeners, leveling agents, antifoaming agents, preservatives, pigments. The additive may be included in 20% by weight or less, preferably 5% by weight or less, more preferably 3% by weight or less in the optical film. In the above range, the additive effect can be produced without affecting the physical properties of the optical film.

In one embodiment, the optical film is air polymerized from a monomer mixture comprising 10% to 25% by weight aromatic vinyl monomer, 5% to 20% by weight acid anhydride monomer, and 60% to 80% by weight comonomer. The coalescence can be prepared by molding and stretching the film into a film. Preferably, the copolymer is a ternary copolymer of an aromatic vinyl monomer, an acid anhydride monomer and a comonomer, and may include a homo, alternate or block copolymer.

In another embodiment, the optical film is aromatic vinyl polymerized from a monomer mixture comprising 30% to 70% by weight of an aromatic vinyl monomer, 5% to 30% by weight of an acid anhydride monomer, and 10% to 50% by weight of comonomer. Ternary copolymers of monomers, acid anhydride monomers and comonomers (hereinafter, copolymer A) and homopolymers (hereinafter, copolymer B) polymerized only with comonomers are blended and then molded into a film and stretched. Can be prepared. At this time, the monomer mixture for the copolymer A and the whole monomer for the copolymer B are 60% to 80% by weight of the comonomer, 10% to 25% by weight of the aromatic vinyl monomer, and 5% of the acid anhydride monomer. % To 20% by weight. When blending the copolymer A and the copolymer B as described above, it is possible to exclude the compounding (compounding) of the manufacturing process, the cost saving effect is large, the optical uniformity of the optical film can be excellent. Preferably, copolymer A is polymerized from a monomer mixture comprising 20% to 40% by weight comonomer, 40% to 60% by weight aromatic vinylic monomer, and 5% to 20% by weight acid anhydride monomer. It may be a ternary copolymer of a comonomer, an aromatic vinyl monomer and an acid anhydride monomer.

Copolymer A: copolymer B may be included in a weight ratio of 20:80 to 50:50 in 100 parts by weight of the total of copolymer A and copolymer B. Within this range, the optical characteristics may be excellent, brittleness may be improved, and target phase difference adjustment may be easily performed. Preferably, copolymer A: copolymer B may be included in a weight ratio of 25:75 to 45:55, and in a weight ratio of 30:70 to 50:50.

Polymerization can be accomplished by conventional methods known to those skilled in the art or using commercially available products. For example, the polymerization can be carried out by suspension polymerization of the monomer mixture, solution polymerization, interfacial polymerization and the like.

Film molding may be appropriately selected depending on the composition and type of the copolymer and the molding processing method. When an extrusion molding method is used, for example, a method of discharging a copolymer melted at 200 ° C to 400 ° C by heating to form a sheet, and gradually cooling it from high temperature to low temperature using a take-up roll (cooling drum) or the like may be selected. Can be. It can also be produced by solvent casting.

As the stretching, any suitable stretching method may be employed. As a specific example, longitudinal uniaxial stretching, lateral uniaxial stretching, longitudinal and lateral simultaneous biaxial stretching, longitudinal lateral difference biaxial stretching, etc. are mentioned. In this case, "species" means the machine direction (MD) of the film, and "lateral" means the transverse direction (TD) of the film. As the stretching means, a roll stretching machine, a tender stretching machine, a biaxial stretching machine, or the like may be adopted. The stretching temperature at the time of heating stretching may be performed at (glass transition temperature of the film + 10 ℃) to (glass transition temperature of the film + 20 ℃). The stretching may be performed once, or may be performed in two or more multistage stretching. You may go through a relaxation process at the time of heating extending | stretching. Preferably, a film can be extended | stretched by longitudinal and simultaneous simultaneous biaxial stretching or longitudinal and horizontal sequential biaxial stretching. MD draw ratio when biaxially stretched: The TD draw ratio may be 1: 0.5 to 1: 3, for example 1: 1 to 1: 3. In the above range, while satisfying the glass transition temperature and the total light transmittance of the optical film of the present invention can satisfy the in-plane retardation, thickness direction retardation at the same time. The MD draw ratio may be 1.5 times to 6.0 times, preferably 2.5 times to 5.0 times, and the TD draw ratio may be 1.5 times to 6.0 times, preferably 2.5 times to 5.0 times. Although the transfer speed of the film at the time of extending | stretching does not have a restriction | limiting in particular, It can become a speed | rate of 50 mm / min-300 mm / min preferably from the mechanical precision, stability, etc. of a stretching apparatus.

Hereinafter, an optical film according to another embodiment of the present invention will be described.

The optical film according to the present embodiment is substantially the same as the optical film according to the embodiment of the present invention except that it further includes rod-shaped nanoparticles.

The optical film may be prepared by stretching a film formed by polymerization of an aromatic vinyl monomer, an acid anhydride monomer and a comonomer as described above. The rod-shaped nanoparticles refer to nanoparticles having long and short axes as long and thin rod-shaped nanoparticles. Since the rod-shaped nanoparticles have a higher refractive index in the thickness direction than the plane direction, when the rod-shaped nanoparticles are included in the film and stretched, the rod-shaped nanoparticles are arranged in the stretching direction, thereby increasing the refractive index in the thickness direction, thereby stably realizing the phase difference of the present invention. Can increase the strength of the film. The rod-shaped nanoparticles may have a refractive index ratio of refractive index in the major axis direction: refractive index in the minor axis direction of 1: 1.2 to 1: 1.7. In the above range, the phase difference of the present invention can be exhibited when the film is stretched.

The rod-shaped nanoparticles may have a length aspect ratio of 1.5: 1 to 3: 1, preferably 2: 1 to 3: 1. In the above range, the phase difference of the present invention may be exhibited when the film is stretched, the total light transmittance of the film may be increased, and may not be broken when mixed with the resin. The aspect ratio refers to the ratio of the short axis of the rod-shaped nanoparticles, that is, the length of the long axis of the rod-shaped nanoparticles to the diameter of the cross section.

The rod-shaped nanoparticles may have a short axis of 5 nm to 50 nm, preferably 10 nm to 30 nm, and a long axis of 30 nm to 150 μm. In the above range, the film can be increased in strength, and the desired birefringence can be obtained.

The rod-shaped nanoparticles exhibit negative optical anisotropy and may include, for example, one or more of strontium carbonate (SrCO ₃ ), calcium carbonate, magnesium carbonate, zirconium carbonate, cobalt carbonate, and manganese carbonate, and preferably the present invention. Strontium carbonate can be used for the aromatic vinyl monomer, the acid anhydride monomer and the comonomer. The rod-shaped nanoparticles may be those that are not surface treated, but those that are surface treated with a titanate compound such as titanium.

The rod-shaped nanoparticles may be included in an amount of 1 wt% to 15 wt%, preferably 2 wt% to 10 wt%, in the optical film. Within this range, the refractive index in the thickness direction of the optical film can be increased to produce the effect of the film of the present invention.

The optical film may further include the additive described above.

The optical film may be prepared by mixing the polymer of the aromatic vinyl monomer, the acid anhydride monomer and the comonomer with the rod-shaped nanoparticles, and stretching the same by the above-described method. Preferably biaxial stretching can be prepared by stretching MD 3 times, TD 3 times, but is not limited thereto.

Hereinafter, an optical film according to another embodiment of the present invention will be described.

The optical film according to the present embodiment may further include an impact modifier.

The optical film includes an impact modifier to secure the aforementioned in-plane retardation, thickness retardation, glass transition temperature and total light transmittance, and at the same time, brittle characteristics when forming a film from polymers of aromatic vinyl monomers, acid anhydride monomers and comonomers. Improved elongation at break and no cracking during film cutting can improve fairness and lower a * value while lowering haze. By increasing the elongation at break, it is possible to improve the processability by lowering the occurrence of breakage during film stretching, and by laminating with the liquid crystal layer compensation film by lowering the haze and a * value of the optical film. The optical film may have an elongation at break of 6% or more, for example, 6% to 10%. The optical film may have a haze of 1% or less, and an a * value of less than 0.01, for example, 0 or less.

The impact modifier may comprise core-shell type particles such as core-shell rubber (CSR). By including the core-shell particles, the elongation at break of the film can be increased. Core-shell type particles consist of a core and a shell surrounding the core. The shell means the outermost layer of the core-shell type particles, and the core may be one spherical particle. The core may further comprise an additional layer surrounding the spherical particles.

The core-shell particles may have a refractive index difference of 0.01 or less in the resin (state after curing) constituting the film. Within this range, the haze can be lowered in the unstretched film and the haze can be lowered even if stretched to implement the phase difference of the present invention. The refractive index of the core-shell type particles may be 1.51 to 1.52, preferably 1.515 to 1.517, and the refractive index of the resin constituting the film (state after curing) may be 1.50 to 1.53.

The core of the core-shell type particles may be a polymer or copolymer of lower alkyl acrylates such as n-butyl acrylate, ethyl acrylate, isobutyl acrylate or 2-ethylhexyl acrylate. The core may further contain a copolymer of other copolymerizable unsaturated monomers such as styrene, vinyl acetate, vinyl chloride, methyl methacrylate, and the like. The core may be further polymerized with monomers having two or more unsaturated functional groups such as diallyl maleate, monoallyl fumarate, allyl methacrylate and the like. Preferably, the core may be a copolymer of n-butylacrylate. The shell of core-shell type particles may be rubber grafted or crosslinked to the core. The shell is polymerized from lower alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, t-butyl methacrylate. The shell may be a homopolymer of the lower alkyl methacrylate. The shell may be further polymerized with other monomers such as styrene, vinyl acetate, vinyl chloride, methyl acrylate, ethyl acrylate, butyl acrylate. Preferably the shell may comprise a copolymer of methyl acrylate and styrene. The core of the core-shell particles may consist of 40% to 80% by weight, preferably 60% to 70% by weight, and the shell of 20% to 60% by weight, preferably 40% to 50% by weight. have. Within this range, the elongation at break of the film can be improved.

Core-shell type particles are not particularly limited in shape but may be spherical particles (eg, beads), and the average particle diameter (D50) may be 100 nm to 300 nm, preferably 150 nm to 250 nm. In the above range, it can be included in the film, it is possible to increase the transmittance of the film. The "average particle diameter (D50)" can be measured by conventional methods known to those skilled in the art.

The core-shell particles may be included in 1% to 15% by weight, preferably 3% to 10% by weight of the optical film. In the above range, it is possible to improve the elongation at break and to cause cracking in the film cutting process and to lower the haze.

Resin which comprises an optical film can use the above-mentioned copolymer. In one embodiment, the resin is a blend of the copolymer A and copolymer B and the copolymer B may have a weight average molecular weight of 100,000 or more, preferably 100,000 to 200,000. Within this range, it is possible to improve the elongation at break and cause cracking in the film cutting process. In one embodiment, the resin comprises copolymer A of a monomer mixture comprising 30% to 70% by weight of styrene, 5% to 30% by weight maleic anhydride and 10% to 50% by weight methylmethacrylate. And may include polymethylmethacrylate as copolymer B. Copolymer A and copolymer B may be included in the above content ratios.

In one embodiment, the optical film comprises a copolymer of styrene, maleic anhydride and methylmethacrylate, a polymethylmethacrylate copolymer, and an impact modifier, wherein the polymethylmethacrylate copolymer has a weight average molecular weight It can be more than 100,000. The refractive index difference between the copolymer of the styrene, maleic anhydride and methyl methacrylate and the polymethyl methacrylate copolymer mixture may be 0.01 or less.

The optical film may further include the additive described above.

The optical film may be prepared by mixing the copolymer A, the copolymer B, and the impact modifier and then stretching by the above-described method. Preferably biaxial stretching can be prepared by stretching MD 3 times, TD 3 times, but is not limited thereto.

Hereinafter, the display element of this invention is demonstrated.

The display device of the present invention may include the optical film of the present invention. The display element may be used as an antireflection film, a polarizer protective film, a viewing angle compensation film, or the like.

In one embodiment, the display element may include an optical film of the present invention and a liquid crystal layer formed on one or both surfaces of the optical film of the present invention, that is, the optical film. The optical film and the liquid crystal layer of the present invention are different from each other. The "liquid crystal layer" may include at least one of a liquid crystal film and a liquid crystal coating layer. Preferably, the display element may be an antireflection film. Conventionally, an antireflection film was prepared by forming two layers of a liquid crystal layer having a phase difference in a phase difference optical film. However, by providing the phase difference to the optical film, an antireflection film can be manufactured even by stacking an optical film and a single liquid crystal layer. This minimized the anti-reflection film manufacturing process and enabled cost reduction. An optical film may be formed on one side or both sides of the liquid crystal layer.

The liquid crystal layer may be formed of a liquid crystal composition containing a liquid crystal compound. Examples of the liquid crystal compound include nematic liquid crystal phases, smectic liquid crystal phases, cholesteric liquid crystal phases, cylindrical liquid crystal phases, and the like, but are not limited thereto. The liquid crystal composition may further contain a chiral agent in addition to the liquid crystal compound to obtain a film having a required refractive index. The liquid crystal composition may further include additives such as a leveling agent, a polymerization initiator, an orientation aid, a heat stabilizer, a lubricant, a plasticizer, an antistatic agent, and the like. The liquid crystal layer may have a refractive index of 1.48 to 1.58, preferably 1.51 to 1.55. In the above range, it can represent the function of the display element. The liquid crystal layer may have a thickness of 0.1 μm to 30 μm, specifically, 0.1 μm to 15 μm, and more specifically 0.3 μm to 5 μm. It can be used in the display element in the above range

The liquid crystal layer may be a phase difference liquid crystal layer having a phase difference. The laminate of the liquid crystal layer and the optical film of the present invention may have an in-plane retardation of 120 nm to 160 nm, for example, 130 nm to 145 nm, and a thickness direction retardation of -10 nm to 10 nm. In the above range, when using an OLED product (eg, mobile phone, tablet, etc.) may be effective to block the external light to make the screen well visible.

In the display element, the liquid crystal layer may be laminated on the optical film. The liquid crystal layer may be formed directly on the optical film. The "directly formed" means that no other adhesive layer, adhesive layer, or adhesive layer is interposed between the liquid crystal layer and the optical film. Alternatively, the liquid crystal layer may be formed by forming an alignment layer on the optical film and then coating the liquid crystal composition and orienting the liquid crystal. The alignment film formation and the liquid crystal alignment can be performed by conventional methods known to those skilled in the art.

In another embodiment, the display element may include an optical film of the present invention (hereinafter referred to as a first optical film) and another optical film (second optical film) formed on the optical film of the present invention. The second optical film is different from the first optical film. The second optical film is a film formed of a conventional optically transparent resin, and may include a protective film, a polarizer, a polarizing plate, a retardation film, a polarizer protective film, a viewing angle compensation film, and the like, but is not limited thereto.

EMBODIMENT OF THE INVENTION Hereinafter, the polarizing plate of this invention is demonstrated.

The polarizing plate of the present invention may include a polarizer and an optical film of the present invention formed on one surface of the polarizer.

In one embodiment, the polarizing plate is formed on one surface of the polarizer and the polarizer and may include a laminate of the optical film and the optical compensation film of the present invention. The optical film and the optical compensation film of the present invention are different from each other. The polarizing plate of the present invention may have a side reflectance of 1% or less when applied to a light emitting display device. The "side reflectance" means a reflectance at a polar angle of 60 °, and means a value measured by the following Equation 4.

<Equation 4>

Lateral reflectance = [(average reflection luminance at 60 ° of polarizer)-(average reflection luminance at 60 ° of blackplate)] / [(average reflection luminance at 60 ° of reflector)-(at 60 ° of blackplate Average reflection luminance)] x 100

The polarizer may lower the reflectance by polarizing the external light incident on the polarizer with a conventional polarizer known to those skilled in the art, thereby improving the screen visibility.

The optical compensation film is a negative A plate having reverse wavelength dispersion, and the in-plane retardation may be 120 nm to 160 nm and the thickness direction retardation may be -10 nm to 10 nm when the wavelength is measured at 550 nm. In the above range, the side reflectance increase rate when laminated with the optical film of the present invention can be 1% or less. The optical compensation film is not particularly limited, but may be a liquid crystal film or a liquid crystal coating layer formed of a liquid crystal containing composition. The optical compensation film may have a thickness of 0.5 μm to 5 μm. In the above range, it can be used for the polarizing plate.

In one embodiment, the polarizer may be a polarizer is laminated on one surface of the laminate of the optical film and the optical compensation film of the present invention, the adhesive layer may be formed on the other surface of the laminate. The adhesive layer may allow the polarizer to be stacked on a panel of the light emitting display device. The adhesive layer may be formed of a conventional adhesive (eg, pressure sensitive adhesive (PSA)) known to those skilled in the art. For example, the polarizing plate may be laminated in the order of the optical film, the optical compensation film, and the adhesive layer of the present invention from the polarizer. At this time, the optical film of the present invention may be laminated directly in contact with the polarizer or may be laminated to the polarizer through the adhesive layer.

For example, the polarizing plate may be stacked in the order of the optical compensation film, the optical film of the present invention and the adhesive layer from the polarizer. The optical film and the optical compensation film may be formed in direct contact with each other, but may be laminated through an adhesive layer. The adhesive layer may be formed of a conventional adhesive (eg, pressure sensitive adhesive (PSA)) known to those skilled in the art. An alignment layer may be further formed on one surface of the optical compensation film.

Hereinafter, the display device of the present invention will be described.

The display device of the present invention may include one or more of the display device of the present invention optical film. In one embodiment, the display device may include a liquid crystal display, a light emitting device display, preferably a light emitting device display. The light emitting device display device includes an organic or organic-inorganic light emitting device, and includes, for example, a light emitting material such as a light emitting diode (LED), an organic light emitting diode (OLED), a quantum dot light emitting diode (QLED), or a phosphor. It may mean a light emitting device.

Hereinafter, the configuration and operation of the present invention through the preferred embodiment of the present invention will be described in more detail. However, the following examples are provided to help the understanding of the present invention, and the scope of the present invention is not limited to the following examples.

Example  One

Methyl acrylate, styrene, and maleic anhydride as a monomer and toluene as a polymerization solvent were added to the reaction apparatus provided with a stirring apparatus, a temperature sensor, a cooling tube, and a nitrogen inlet tube, and it heated up adding nitrogen. After the reflux at elevated temperature started, t-amylperoxide was added as a polymerization initiator and polymerized at about 100 ° C to 150 ° C. The obtained polymerization solution was dried under reduced pressure, to prepare a copolymer in which 30% by weight of methyl methacrylate, 50% by weight of styrene and 20% by weight of maleic anhydride were polymerized.

70 parts by weight of methyl methacrylate copolymer was mixed with 30 parts by weight of the prepared methyl methacrylate, styrene and maleic anhydride copolymer, put into a T-die melt extruder and melted, followed by extrusion to prepare a film having a thickness of 300 μm. . Methyl methacrylate copolymers were prepared in a similar manner to the preparation of the methyl methacrylate, styrene and maleic anhydride copolymers. The prepared film was stretched at a transfer rate of 200 mm / min and a stretching temperature of 130 ° C., but biaxially stretched at 3.0 times with film MD and 3.0 times with film TD to prepare an optical film having a thickness of 40 μm.

Example  2

In Example 1, an optical film was prepared in the same manner except that 50 parts by weight of methyl methacrylate copolymer was mixed with 50 parts by weight of methyl methacrylate, styrene and maleic anhydride copolymer.

Example  3

An alignment layer was formed on one surface of the optical film of Example 1, and a nematic liquid crystal layer was formed to manufacture a display device.

Example  4

Methyl acrylate, styrene, and maleic anhydride as a monomer and toluene as a polymerization solvent were added to the reaction apparatus provided with a stirring apparatus, a temperature sensor, a cooling tube, and a nitrogen inlet tube, and it heated up adding nitrogen. After the reflux at elevated temperature started, t-amylperoxide was added as a polymerization initiator and polymerized at about 100 ° C to 150 ° C. The obtained polymerization solution was dried under reduced pressure, to prepare a copolymer in which 65% by weight of methyl methacrylate, 25% by weight of styrene and 10% by weight of maleic anhydride were polymerized.

The prepared copolymer was put into a T-die melt extruder, melted, and extruded to prepare a film having a thickness of 300 μm. The prepared film was stretched at a transfer rate of 200 mm / min and a stretching temperature of 130 ° C., but biaxially stretched at 3.0 times with film MD and 3.0 times with film TD to prepare an optical film having a thickness of 40 μm.

Example  5

An optical film was manufactured in the same manner as in Example 4, except that the monomer content was changed as in Table 2 below.

Example  6

Methyl acrylate, styrene, and maleic anhydride as a monomer and toluene as a polymerization solvent were added to the reaction apparatus provided with a stirring apparatus, a temperature sensor, a cooling tube, and a nitrogen inlet tube, and it heated up adding nitrogen. After the reflux at elevated temperature started, t-amylperoxide was added as a polymerization initiator and polymerized at about 100 ° C to 150 ° C. The obtained polymerization solution was depressurized and dried to prepare a copolymer in which 75% by weight of methyl methacrylate, 10% by weight of styrene and 15% by weight of maleic anhydride were polymerized.

100 parts by weight of the copolymer and 3 parts by weight of rod-shaped nanoparticles of strontium carbonate (SrCO ₃ ) were placed in a T-die melt extruder, melted, and extruded to prepare a film having a thickness of 300 μm. The prepared film was stretched at a transfer rate of 200 mm / min and a stretching temperature of 130 ° C., but biaxially stretched at 3.0 times with film MD and 3.0 times with film TD to prepare an optical film having a thickness of 40 μm.

Example  7

In Example 6, a copolymer obtained by polymerizing 75% by weight of methyl methacrylate, 6% by weight of styrene and 19% by weight of maleic anhydride was prepared, and 100 parts by weight of the copolymer prepared above and 10 parts by weight of strontium carbonate (SrCO ₃ ). The part was put in a T-die melt extruder and melted, and an optical film was manufactured in the same manner as in Example 6.

Example  8

Methyl acrylate, styrene, and maleic anhydride as a monomer and toluene as a polymerization solvent were added to the reaction apparatus provided with a stirring apparatus, a temperature sensor, a cooling tube, and a nitrogen inlet tube, and it heated up adding nitrogen. After the reflux at elevated temperature started, t-amylperoxide was added as a polymerization initiator and polymerized at about 100 ° C to 150 ° C. The obtained polymerization solution was dried under reduced pressure, to prepare a copolymer in which 50% by weight of styrene, 30% by weight of methyl methacrylate and 20% by weight of maleic anhydride were polymerized.

T-die melting by mixing 60 parts by weight of methyl methacrylate copolymer (V040) and 5 parts by weight of core-shell nanoparticles (M732) to 40 parts by weight of the prepared methyl methacrylate, styrene, maleic anhydride copolymer. The film was put into an extruder, melted, and extruded to prepare a film having a thickness of 300 μm. The prepared film was stretched at a transfer rate of 200 mm / min and a stretching temperature of 130 ° C., but biaxially stretched at 3.0 times with film MD and 3.0 times with film TD to prepare an optical film having a thickness of 40 μm.

The refractive index of the whole methyl methacrylate copolymer (V040) 60 weight part in 40 weight part of methyl methacrylate, styrene, and maleic anhydride copolymer is 1.52.

Example  9 to Example  12

Except for changing the type and content of methyl methacrylate, core-shell-type nanoparticles in Example 8 as shown in Table 3 below to prepare an optical film in the same manner.

Comparative example  1 to Comparative example  2

In Example 1, except that the mixing ratio of methyl methacrylate, styrene, maleic anhydride copolymer and methyl methacrylate homocopolymer was changed as shown in Table 1 below, an optical film was prepared.

Comparative example  3

An optical film was prepared in the same manner except that 70 parts by weight of methyl methacrylate homopolymer and 30 parts by weight of styrene homocopolymer were used.

Comparative example  4

An optical film was prepared in the same manner except that 100 parts by weight of methyl methacrylate homocopolymer was used.

Comparative example  5 and Comparative example  6

An optical film was manufactured in the same manner as in Example 4, except that the mixing ratio of methyl methacrylate, styrene, and maleic anhydride in the copolymer was changed as shown in Table 2 below.

The physical properties of Tables 1 and 2 were evaluated for the optical films prepared in Examples 1 to 7 and Comparative Examples 1 to 6.

(1) In-plane retardation, thickness direction retardation: It measured with the phase difference measuring apparatus Axoscan (Axometric) with respect to an optical film at wavelength 550nm.

(2) Glass transition temperature (Tg): The optical film was measured by Discovery (TA instrument) while raising the temperature at a temperature rising rate of 20 ° C./min from 40 ° C. to 200 ° C. under nitrogen purging conditions.

(3) Elongation at break: The optical film was cut into MD x TD 10 cm x 2 cm. The MD length of the optical film before stretching was called L ₀ . The measuring device Instron UTM3300 (universal Testing Machine) was used to stretch the optical film at 25 ° C. at a speed of 100 mm / min at MD, and when the optical film was broken, the length of the optical film was L _{1 in} the MD direction. Elongation at break was calculated as (L ₁ -L ₀ ) / L ₀ x 100.

(4) Total light transmittance: The optical film was measured using a UV-2450 (UV-VIS) spectrometer (Shimadzu) according to the method of ASTM D 1003.

(5) Optical film refractive index: The refractive index of the optical film was measured by ASTM D542 method.

(6) Haze: Haze meter (Nippon Denshoku company model NDH 5000) equipment was used. In accordance with the American Society for Testing and Measurement (ASTM) Test Method D 1003-95 ("Standard Test for Haze and Luminous Transmittance of Transparent Plastic"), Haze was measured.

Example
One Example
2 Comparative example
One Comparative example
2 Comparative example
3 Comparative example
4 Copolymer Blend Ratio * 30:70 50:50 70:30 10:90 - - Monomer
content* methyl
Methacrylate
(weight%) 79 65 51 93 70 100 Styrene
(weight%) 15 25 35 5 30 0 Maleic anhydride
(weight%) 6 10 14 2 0 0 Optical film thickness (㎛) 40 40 40 40 40 40 In-plane retardation (nm) 1.5 1.5 1.5 5 5 3 Thickness direction phase difference
(nm) -75 -100 -160 -25 -110 3 Tg (℃) 120 125 130 108 105 103 Elongation at Break (%) 6 6 4 2 4 2 Total light transmittance (%) 92 92 90 92 85 92 Optical film refractive index 1.51 1.51 1.53 1.49 1.51 1.49 MD draw ratio 3.0 3.0 3.0 3.0 3.0 3.0 TD draw ratio 3.0 3.0 3.0 3.0 3.0 3.0

* Monomer content: The content of the monomer in the total monomer content in the optical film

* Copolymer mixing ratio: Methyl methacrylate, styrene, maleic anhydride copolymer: 100% by weight of methyl methacrylate, styrene, maleic anhydride copolymer and methyl methacrylate copolymer: of methyl methacrylate copolymer Weight ratio

Example
4 Example
5 Example
6 Example
7 Comparative example
5 Comparative example
6 Monomer
content methyl
Methacrylate
(weight%) 65 80 75 75 55 95 Styrene
(weight%) 25 15 10 6 35 3 Maleic anhydride
(weight%) 10 5 15 19 10 2 Rod-shaped nanoparticles
(Part by weight) 0 0 3 10 0 0 Optical film thickness (㎛) 40 40 40 40 40 40 In-plane phase difference
(nm) One One 1.5 1.5 3 One Thickness direction phase difference
(nm) -100 -70 -70 -100 -160 -5 Tg (℃) 125 119 117 117 130 108 Elongation at Break (%) 6 6 5 5 4 2 Total light transmittance (%) 92 92 91 91 89 92 Optical film refractive index 1.51 1.51 1.51 1.51 1.53 1.50 Haze (%) 0.1 0.1 0.97 0.97 0.2 0.1 MD draw ratio 3 3 3 3 3 3 TD draw ratio 3 3 3 3 3 3

As shown in Table 1 and Table 2, in the optical film of the present invention, the in-plane retardation and thickness direction retardation satisfy a predetermined range, and are excellent in heat resistance, optical transparency, and elongation at break.

However, the optical film of the comparative example did not satisfy at least one of in-plane retardation, thickness direction retardation, total light transmittance and glass transition temperature of the present invention.

The physical properties of Table 3 below were evaluated for the optical films prepared in Examples 8 to 12.

In-plane retardation, thickness retardation, glass transition temperature, total light transmittance, haze, and elongation at break were measured in the same manner as in Tables 1 and 2 above.

Optical properties L *, a * and b * were put into a film in CM-3600A (Konica Minolta Co., Ltd.) and the optical surface was measured so that the film surface might face a light source.

YI was measured in each of the yellow index by putting the film in CM-3600A (Konica Minolta Co., Ltd.) and the film surface facing the light source.

The crackability during cutting was evaluated by comparing the thickness of the pressing line generated inside the sample at the cutting surface when the optical film was cut by the cutter. The lower the pressing line thickness, the lower the breakability during cutting, which means that the optical film can be used.

Example 8 Example 9 Example 10 Example 11 Example 12 Copolymer Blend Ratio * 40:60 40:60 40:60 40:60 40:60 Monomer Content *

methyl
Methacrylate
(weight%) 30 30 30 30 30 Styrene
(weight%) 50 50 50 50 50 Maleic anhydride
(weight%) 20 20 20 20 20 Methyl methacrylate copolymer V040 V210C V040 V210C V210C Core-Shell Nanoparticles
Kinds M732 M732 M521 M521 - Core-Shell Nanoparticles
Content (parts by weight) 5 10 5 10 0 Optical film thickness (㎛) 40 40 40 40 40 In-plane retardation (nm) 1.0 1.0 1.0 1.0 1.0 Thickness direction phase difference
(nm) -90 -90 -90 -90 -90 Tg (℃) 118 117 118 117 120 Total light transmittance (%) 91.85 92.51 92.49 92.37 92.54 Haze (%) 0.94 0.87 0.39 0.55 0.16 Elongation at Break (%) 6.2 9.6 9 9 6 Optical properties L * 96.65 96.68 96.72 96.7 96.73 Optical characteristics a * 0 0 0 -0.01 0.01 Optical properties b * 0.21 0.21 0.23 0.29 0.19 Optical properties YI 0.62 0.6 0.65 0.74 0.58 Cracking when cutting 20 ㎛ 10 μm 10 μm 3 μm 40 μm Optical film refractive index 1.516 1.516 1.517 1.517 1.516 MD draw ratio 3.0 3.0 3.0 3.0 3.0 TD draw ratio 3.0 3.0 3.0 3.0 3.0

* Methyl methacrylate copolymer V021C: Arkema, weight average molecular weight: 100,000

* Methyl methacrylate copolymer V040: Arkema, weight average molecular weight: 100,000

Core-shell nanoparticles M732: KANEKA Corporation, average particle diameter: 150nm, core weight 60% by weight and core weight 40% by weight of the shell, the core is butyl acrylate, the shell is a copolymer of styrene and methyl methacrylate, refractive index: 1.515

* Core-shell nanoparticle M521: KANEKA corporation, average particle diameter: 250nm, core 60% by weight and core 40% by weight of the shell, the core is butyl acrylate, the shell is a copolymer of styrene and methyl methacrylate, refractive index: 1.517

Monomer content: Each monomer content in methyl methacrylate, styrene, maleic anhydride copolymer

* Copolymer mixing ratio: Methyl methacrylate, styrene, maleic anhydride copolymer: 100% by weight of methyl methacrylate, styrene, maleic anhydride copolymer and methyl methacrylate copolymer: of methyl methacrylate copolymer Weight ratio

As shown in Table 3, since the optical film of the present invention includes core-shell nanoparticles, no cracking occurs during film cutting, thereby improving processability.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be seen to be included in the scope of the present invention.

Claims (24)

Aromatic vinyl monomers; Acid anhydride monomers; And an optical film derived from a comonomer copolymerizable with the aromatic vinyl monomer or the acid anhydride monomer,
The optical film has an in-plane retardation of 15 nm or less, a thickness direction retardation of -150 nm to -50 nm, a glass transition temperature of 110 ° C. to 150 ° C., and a total light transmittance of 90% or more.
<Equation 1>
Re = (nx-ny) xd
(In Formula 1, nx and ny are refractive indices in the slow axis direction and the fast axis direction of the optical film, respectively, at a wavelength of 550 nm, and d is the thickness of the optical film (unit: nm)),
<Equation 2>
Rth = ((nx + ny) / 2-nz) xd
(In Formula 2, nx, ny, and nz are refractive indices in the slow axis direction, the fast axis direction, and the thickness direction of the optical film, respectively, at a wavelength of 550 nm, and d is the thickness (unit: nm) of the optical film).
The method of claim 1, wherein the optical film is derived from 60% to 80% by weight of the comonomer, 10% to 25% by weight of the aromatic vinyl monomer, and 5% to 20% by weight of the acid anhydride monomer. That, optical film.
The optical film of claim 2, wherein the optical film is formed from a ternary copolymer of the comonomer, the aromatic vinyl monomer, and the acid anhydride monomer.
The optical film of claim 2, wherein the optical film is formed from a blend of a ternary copolymer of the comonomer, the aromatic vinyl monomer and the acid anhydride monomer, and a homo copolymer of the comonomer.
The optical film of claim 4, wherein the ternary copolymer: the homopolymer is included in a weight ratio of 20:80 to 50:50 in 100 parts by weight of the total of the ternary copolymer and the homo copolymer.
The optical film of claim 1, wherein the optical film has a refractive index of 1.40 to 1.60.
The optical film of claim 1, wherein the optical film has a degree of biaxiality of Equation 3 below −30 to −5.
<Equation 3>
NZ = (nx-nz) / (nx-ny)
(In Formula 3, nx, ny, and nz are refractive indexes in the slow axis direction, the fast axis direction, and the thickness direction of the optical film, respectively, at a wavelength of 550 nm).
The optical film of claim 1, wherein a content of the aromatic vinyl monomer in the total of the comonomer, the aromatic vinyl monomer, and the acid anhydride monomer is greater than that of the acid anhydride monomer.
The optical film of claim 1, wherein the optical film is a biaxially stretched film having an MD stretching ratio: TD stretching ratio of 1: 1 to 1: 3.
The method of claim 1, wherein the comonomer is methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, An optical film comprising at least one of cyclohexyl (meth) acrylate, isobonyl (meth) acrylate, hydroxymethyl (meth) acrylate and hydroxyethyl (meth) acrylate.
The optical film of claim 1, wherein the aromatic vinyl monomer comprises one or more of styrene, alpha styrene, parastyrene, metastyrene, and vinyl toluene.
The optical film of claim 1, wherein the acid anhydride monomer comprises maleic anhydride.
The optical film of claim 1, wherein the optical film has a thickness of 10 μm to 100 μm.
The method of claim 1, wherein the optical film is derived from 60% to 80% by weight of methyl methacrylate, 10% to 25% by weight of styrene, and 5% to 20% by weight of maleic anhydride,
Wherein the optical film is formed from a blend of a ternary copolymer of the methyl methacrylate, the styrene and the maleic anhydride, and a homo copolymer of the methyl methacrylate.
The optical film of claim 1, wherein the optical film further includes rod-shaped nanoparticles.
The optical film of claim 15, wherein the rod-shaped nanoparticles include one or more of strontium carbonate, calcium carbonate, magnesium carbonate, zirconium carbonate, cobalt carbonate, and manganese carbonate.
The optical film of claim 15, wherein the rod-shaped nanoparticles are included in an amount of 1 wt% to 15 wt% in the optical film.
The optical film of claim 1, wherein the optical film comprises a copolymer of styrene, maleic anhydride and methylmethacrylate, a polymethylmethacrylate copolymer, and an impact modifier, wherein the polymethylmethacrylate copolymer has a weight average. Molecular weight is 100,000 or more, optical film.
The optical film according to claim 18, wherein the refractive index difference between the copolymer of the styrene, maleic anhydride and methyl methacrylate and the polymethyl methacrylate copolymer mixture is less than or equal to 0.01.
19. The method of claim 18, wherein the impact modifier is a core-shell nanoparticle,
1 to 15% by weight of the optical film will be included, the optical film.
21. A display device comprising the optical film of any one of claims 1-20.
The display device of claim 21, wherein the display device comprises a liquid crystal layer formed on one surface of the optical film and the optical film.
The display element according to claim 22, wherein the liquid crystal layer is a negative A plate having reverse wavelength dispersion.
A display device comprising the display element of claim 21.