KR20120009864A - Preparation of resin composition for optical film using acryl based resin - Google Patents

Abstract

PURPOSE: A resin composition is provided to manufacture a protection film for a polarizer having excellent heat resistance and transparency. CONSTITUTION: An acrylic copolymer resin comprises an alkyl(meth)acrylate based monomer and an imide based monomer, and selectively comprises the copolymer of styrene based monomers. The acrylate based copolymer is a copolymer comprising an alkyl(meth)acrylate based monomer and an imide based monomer, or terpolymer comprising an alkyl(meth)acrylate based monomer, an imide based monomer, and a styrene based monomer. The imide based monomer is a maleimide based monomer substituted by a cycloalkyl group or an aryl group.

Description

Manufacture of resin for optical film using acrylic resin {PREPARATION OF RESIN COMPOSITION FOR OPTICAL FILM USING ACRYL BASED RESIN}

The present invention relates to an acrylic copolymer resin having excellent heat resistance, a resin composition containing the acrylic copolymer resin, a polarizer protective film having excellent heat resistance and optical properties including the resin composition, and a liquid crystal display device including the polarizer protective film. will be.

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 liquid crystal displays, as thin film thickness, light weight, and large screen area are promoted, wide viewing angles, high contrast, suppression of image color tone change according to viewing angle, and uniformity of screen display have become particularly important problems.

The polarizing plate generally has a structure in which a triacetyl cellulose film (hereinafter, referred to as a "TAC film") is laminated on a polarizer with an aqueous adhesive made of a polyvinyl alcohol-based aqueous solution. However, both the polyvinyl alcohol film used as the polarizer and the TAC film used as the protective film for the polarizer do not have sufficient heat resistance and moisture resistance. Accordingly, when the polarizing plate made of the above films is used for a long time in an atmosphere of high temperature or high humidity, the polarization degree is lowered, the polarizer and the protective film are separated, or the optical properties are lowered.

In addition, the TAC film has a large change in the in-plane retardation R _in and the thickness direction retardation R _th , which are included in the reference, according to changes in the ambient temperature / humidity environment. When a polarizing plate including a TAC film having such a property as a protective film is applied to a liquid crystal display device, there is a problem in that the viewing angle characteristic changes according to a change in the ambient temperature / humidity environment, thereby degrading image quality. In addition, the TAC film has a large dimensional change rate according to the change of ambient temperature / humidity environment, and the photoelastic coefficient value is also relatively large. Easy to be

Acrylic resin is well known as a material for compensating for the various disadvantages of the TAC film. However, acrylic resins do not have sufficient heat resistance, and after stretching, in-plane and thickness direction retardation are expressed and thus are not suitable for use as a protective film.

An object of the present invention for solving the problems of the prior art as described above is to provide a resin composition for polarizer protective film excellent in heat resistance and transparency.

Still another object of the present invention is to provide a polarizer protective film excellent in heat resistance, transparency and optical properties including the resin composition, and a liquid crystal display device comprising the polarizer protective film.

One aspect of the present invention for achieving the above object comprises an alkyl (meth) acrylate monomer and an imide monomer, and further provides an acrylic copolymer resin copolymerizable styrene monomer.

A second aspect of the present invention for achieving the above object provides a resin composition comprising the acrylic copolymer resin and polycarbonate resin.

A third aspect of the present invention for achieving the above object provides a polarizer protective film comprising the resin composition.

A fourth aspect of the present invention for achieving the above object provides a liquid crystal display device comprising the polarizer protective film.

The resin composition according to the present invention is excellent in heat resistance and transparency. The polarizer protective film manufactured using the said resin composition is excellent in heat resistance, transparency, and an optical characteristic.

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

One aspect of the present invention provides an acrylic copolymer resin comprising an alkyl (meth) acrylate monomer and an imide monomer, and optionally a styrene monomer.

In the present specification, the copolymer resin containing a monomer means that the monomer is polymerized and included as a repeating unit in the copolymer resin.

The acrylic copolymer may be a block copolymer or a random copolymer, but the copolymer form is not limited thereto. Any polymerization method known for forming the acrylic copolymer can be used, but bulk polymerization is preferred.

The acrylic copolymer is an alkyl (meth) acrylate monomer; And it may be in the form of a binary copolymer comprising an imide-based monomer, it may be in the form of a ternary copolymer further comprising a styrene-based monomer.

In the acrylic copolymer resin, the content of the alkyl (meth) acrylate monomer is preferably 70% by weight to 98% by weight. In addition, the content of the imide monomer is preferably 1% by weight to 30% by weight, and the styrene monomer is preferably more than 0% by weight and 10% by weight or less, and these may be included in the acrylic copolymer simultaneously or alone.

In the acrylic copolymer resin, an alkyl (meth) acrylate monomer means both an alkyl acrylate monomer and an alkyl methacrylate monomer. It is preferable that the alkyl group of the said alkyl (meth) acrylate type monomer is C1-C10, It is more preferable that it is 1-4, It is more preferable that it is a methyl group or an ethyl group. The alkyl (meth) acrylate monomer is more preferably methyl methacrylate, but is not limited thereto.

In the acrylic copolymer resin, the content of the alkyl (meth) acrylate monomer is preferably 70% by weight to 98% by weight, more preferably 75% by weight to 95% by weight. When the content of the alkyl methacrylate monomer is within the above range, excellent transparency may be maintained while heat resistance.

In the acrylic polymer, the imide monomer means a monomer including an imide group, and examples thereof include maleimide monomers. Among these, the maleimide monomer substituted with a cycloalkyl group or an aryl group is preferable in order to improve the heat resistance of an acryl-type copolymer.

The cycloalkyl group which may be substituted in the imide monomer is preferably a cycloalkyl group having 3 to 15 carbon atoms, and more preferably a cyclohexyl group. In addition, the aryl group which may be substituted in the imide monomer is preferably 6 to 15 carbon atoms, more preferably a phenyl group.

Specific examples of the imide monomers include N-phenylmaleimide, N-cyclohexylmaleimide, N-methylphenylmaleimide, N-ethylphenylmaleimide, N-butylphenylmaleimide, N-naphthylmaleimide, N- Hydroxyphenyl maleimide, N-methoxyphenyl maleimide, N-carboxyphenyl maleimide, N-nitrophenyl maleimide, N-tribromophenyl maleimide and the like. These monomers may be used independently and may use 2 or more types together. Of these monomers, N-cyclohexylmaleimide or N-phenylmaleimide is particularly preferred, but is not limited thereto.

In the acrylic copolymer resin, the content of the imide monomer is preferably 1% by weight to 30% by weight, more preferably 1% by weight to 20% by weight. When the content of the imide-based monomer is in the above range, it is preferable because the decrease in mechanical strength can be minimized while ensuring heat resistance.

In the acrylic copolymer, the styrene monomer refers to a monomer including a styrene group, for example, styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5- Dimethylstyrene, 2-methyl-4-chlorostyrene, 2,4,6-trimethylstyrene, cis-ß-methylstyrene, trans-ß-methylstyrene, 4-methyl-α-methylstyrene, 4-fluor-α- Methylstyrene, 4-chloro-α-methylstyrene, 4-bromo-α-methylstyrene, 4-t-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-di Fluorostyrene, 2,3,4,5,6-pentafluorostyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene, octachloro Styrene, 2-bromostyrene, 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene, α-bromostyrene, ß-bromostyrene, 2-hydroxystyrene, 4-hydroxy Roxy tea And the like. Of these monomers, α-methylstyrene is most preferred in view of ease of copolymerization and heat resistance, but is not limited thereto.

In the acrylic copolymer resin, the content of the styrene monomer is preferably more than 0 wt% and 10 wt% or less. When the content of the styrene-based monomer is in the above range, it is preferable to control physical properties of the resin while ensuring heat resistance.

In addition, the molecular weight of the acrylic copolymer resin is preferably in the range of 50,000 to 300,000 in terms of heat resistance, processability and productivity.

Glass transition temperature (Tg) of the said acrylic copolymer resin becomes like this. Preferably it is 120 degreeC or more, More preferably, it is 123 degreeC or more. The glass transition temperature of the acrylic copolymer resin is not particularly limited, but may be 200 ° C. or less.

A second aspect of the present invention relates to a resin composition comprising the acrylic copolymer resin and the polycarbonate resin.

Polycarbonate resin is included in the resin composition for phase difference control, the weight ratio of the acrylic copolymer resin and the polycarbonate resin in the resin composition is preferably 90 ~ 99: 1 ~ 10, 95 ~ 99: 1 ~ It is more preferable that it is five.

It is preferable that the melt index (MI) in 1.2 kg load and 300 degreeC conditions of the polycarbonate resin contained in the said resin composition is 30 g / 10min or more.

The resin composition may be prepared by blending the acrylic copolymer resin and the polycarbonate resin according to a method well known in the art, such as a compounding method, and include sugars such as colorants, flame retardants, reinforcing agents, fillers, UV stabilizers, antioxidants, and the like. It may include additives well known in the art.

It is preferable that it is 120 degreeC or more, and, as for the glass transition temperature of the said resin composition, it is more preferable that it is 123 degreeC or more. Although the glass transition temperature of the said resin composition is not specifically limited, It may be 200 degrees C or less.

Moreover, it is preferable that the weight average molecular weights of the said resin composition are 50,000-300,000 from a viewpoint of heat resistance, sufficient workability, productivity, etc.

The third aspect of the present invention relates to a polarizer protective film containing the resin composition.

The polarizer protective film according to the present invention can be used as a polarizer protective film by adjusting the phase difference according to the content of the polycarbonate-based resin.

When the content of the polycarbonate resin is 1% by weight to 10% by weight, more preferably 1% by weight to 5% by weight, the plane direction retardation value R _in of the polarizer protective film including the resin composition is − 5 nm to 5 nm, preferably -3 nm to 3 nm, more preferably about 0 nm, the thickness direction retardation value (R _th ) may be -5 nm to 5 nm, preferably -3 nm to 3 nm, more preferably May be about 0 nm.

The polarizer protective film may be prepared into a film according to a method well known in the art such as a solution caster method or an extrusion method, of which the extrusion method is preferred.

It may further comprise the step of biaxially stretching the film prepared as described above, may be prepared by adding a modifier in some cases.

When the film is biaxially stretched, the stretching step may be performed in the longitudinal direction (MD) stretching or in the transverse direction (TD) stretching, or both. When extending | stretching both a longitudinal direction and a lateral direction, after extending | stretching either one, you can extend in another direction and you may extend | stretch both directions simultaneously. Stretching can be done in one step or stretched in multiple steps. When extending | stretching in a longitudinal direction, extending | stretching by the speed difference between rolls can be performed, and when extending | stretching in a lateral direction, a tenter can be used. The starting angle of the tenter is usually within 10 degrees to suppress the bowing phenomenon occurring during the lateral stretching and to control the angle of the optical axis regularly. The same boeing suppression effect can also be obtained by making transverse stretching into multiple stages.

The stretching may be performed at a temperature of (Tg-20 ° C) to (Tg + 30 ° C) when the glass transition temperature of the resin composition is Tg. The glass transition temperature refers to a region from the temperature at which the storage modulus of the resin composition begins to decrease, and thus the loss modulus becomes larger than the storage modulus, at which the orientation of the polymer chain is relaxed and lost. Glass transition temperatures can be measured by differential scanning calorimetry (DSC). The temperature at the time of the stretching step is more preferably the glass transition temperature of the film.

The drawing speed is preferably in the range of 1 to 100 mm / min in the case of a universal drawing machine (Zwick Z010) and in the range of 0.1 to 2 m / min in the case of a pilot drawing machine. It is preferable to stretch the film by applying an elongation of 5 to 300%.

The polarizer protective film according to the present invention can be produced by stretching biaxially by the above-described method.

The polarizer protective film prepared as described above may have a plane direction retardation value R _in represented by Equation 1 below −5 nm to 5 nm, preferably −3 nm to 3 nm, and more preferably about 0 nm. The thickness direction retardation value R _th represented by Equation 2 may be -5 nm to 5 nm, preferably -3 nm to 3 nm, and more preferably about 0 nm.

[Equation 1]

R _in = (n _x -n _y ) × d

[Equation 2]

R _th = (n _z -n _y ) × d

In Equations 1 and 2,

n _x is a refractive index of the direction of the largest refractive index in the plane direction of the film,

n _y is a refractive index in the vertical direction in the n _x direction in the plane direction of the film,

n _z is the refractive index in the thickness direction,

d is the thickness of the film.

In the polarizer protective film according to the present invention, the surface direction retardation value and the thickness direction retardation value may be adjusted according to the content of the polycarbonate resin.

A fourth aspect of the present invention relates to a liquid crystal display device comprising the polarizer protective film.

When the polarizer protective film according to the present invention is applied to a liquid crystal display device, it may be provided on only one side of the liquid crystal panel (one sheet type), or may be provided on both sides of the liquid crystal panel (two sheets type).

Since the polarizer combined with the polarizer protective film is made of a uniaxially stretched polyvinyl alcohol film containing a dichroic dye, the polarizer is very fragile and laminated with a protective film because its durability against temperature and moisture is poor.

The polarizer protective film and the polarizer may be laminated by a method known in the art, for example, the lamination of the protective film and the polarizer may be made by an adhesive method using an adhesive. That is, first, an adhesive is coated on the surface of the polarizer protective film or the PVA film which is a polarizer using a roll coater, a gravure coater, a bar coater, a knife coater or a capillary coater. Before the adhesive is completely dried, the polarizer protective film and the polarizing film are laminated by heating or pressing at room temperature with a lamination roll. In the case of using a hot melt adhesive, a heat press roll should be used.

Adhesives that can be used when laminating the polarizer protective film and the polarizer include one-component or two-component PVA adhesives, polyurethane adhesives, epoxy adhesives, styrene butadiene rubber (SBR) adhesives or hot melt adhesives, but are limited thereto. It doesn't work. When using a polyurethane adhesive, it is preferable to use the polyurethane adhesive manufactured using the aliphatic isocyanate type compound which does not yellow by light. When using one-component or two-component dry laminate adhesives or adhesives with relatively low reactivity between isocyanates and hydroxyl groups, a solution-type adhesive diluted with an acetate solvent, a ketone solvent, an ether solvent, or an aromatic solvent may be used. Can also be used. At this time, the adhesive viscosity is preferably low viscosity of 5,000 cps or less. It is preferable that the adhesives have excellent storage stability and have a light transmittance of 90% or more at 400 to 800 nm.

A tackifier can also be used if it can exert sufficient adhesive force. It is preferable that the adhesive is sufficiently cured by heat or ultraviolet rays after lamination, and thus the mechanical strength is improved to the level of the adhesive. The adhesive strength is also large so that the adhesive does not peel off without breaking of either film to which the adhesive is attached. It is preferable.

Specific examples of the pressure-sensitive adhesive that can be used include natural rubber, synthetic rubber or elastomer having excellent optical transparency, a vinyl chloride / vinyl acetate copolymer, polyvinyl alkyl ether, polyacrylate or modified polyolefin-based pressure-sensitive adhesive, and a curing type in which a curing agent such as isocyanate is added thereto. An adhesive is mentioned.

As the polarizer, a film made of polyvinyl alcohol (PVA) containing iodine or dichroic dye may be used. The polarizer may be prepared by dyeing iodine or dichroic dye on the PVA film, but a method of manufacturing the same is not particularly limited.

Hereinafter, preferred examples will be described to aid in understanding the present invention. The following examples are merely to illustrate the invention, but are not intended to limit the scope of the invention.

The physical property evaluation method in this invention is as follows.

1. Tg (glass transition temperature): Measured using a DSC (Differential Scanning Calorimeter) from TA Instrument.

2. Retardation value (Rin / Rth): After stretching at the glass transition temperature of the film + 5 ℃ was measured using AxoScan from Axometrics.

3. Haze value (transparency): The haze value was measured using HAZEMETER HM-150 of Murakami color Research Laboratory.

<Examples>

&Lt; Example 1 >

0.05 part by weight of dicumyl peroxide, 1 part by weight of tert-dodecyl mercaptan, and toluene 20 based on 100 parts by weight of the total amount of the monomer including 90 parts by weight of methyl methacrylate and 10 parts by weight of N-phenyl maleimide. The weight part was added to a reactor equipped with a stirrer, and bulk polymerization was performed to convert the introduced monomer into a polymer while maintaining the reaction temperature at 145 ° C. and the residence time at 2 hours. The copolymerized resin was removed after removing the unreacted monomer and the solvent while maintaining the polymerization reaction at a temperature of 220 ° C. and a vacuum pressure of 30 torr.

The obtained copolymer resin was melt-mixed with 3 parts by weight of polycarbonate (DOW, DVD1080) at 260 ° C. using an extruder including a T-die to prepare a 240 μm thick film, followed by 200% biaxial stretching. Next, the physical properties were measured and the measurement results are shown in Table 2.

<Example 2>

Except for using 87 parts by weight of methyl methacrylate, 10 parts by weight of N-phenyl maleimide, 3 parts by weight of α-methyl styrene, and 4 parts by weight of polycarbonate, the film was prepared in the same manner as in Example 1, and then the physical properties thereof. Was measured.

<Example 3>

Except for 92 parts by weight of methyl methacrylate, 8 parts by weight of cyclohexyl maleimide and 2 parts by weight of polycarbonate, a film was prepared in the same manner as in Example 1, and then the physical properties thereof were measured.

<Example 4>

After the film was prepared in the same manner as in Example 1 except that 90 parts by weight of methyl methacrylate, 5 parts by weight of cyclohexyl maleimide, 5 parts by weight of α-methyl styrene, and 3 parts by weight of polycarbonate were used, Measured.

Comparative Example 1

Except that 100 parts by weight of methyl methacrylate and 3 parts by weight of polycarbonate were used to prepare a film in the same manner as in Example 1, then the physical properties were measured.

Comparative Example 2

Except that 92 parts by weight of methyl methacrylate and 8 parts by weight of cyclohexyl maleimide were used to prepare a film in the same manner as in Example 1, the physical properties thereof were measured.

Comparative Example 3

Except for using 90 parts by weight of methyl methacrylate, 5 parts by weight of cyclohexyl maleimide and 5 parts by weight of α-methylstyrene, a film was prepared in the same manner as in Example 1, and then the physical properties thereof were measured.

The above Examples and Comparative Examples are summarized in Table 1 and Table 2 below.

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Copolymer
Resin composition
(weight%) MMA 90 87 92 90 100 92 90 PMI 10 10 CHMI 8 5 8 5 AMS 3 5 5 PC (wt%) (MI 80) 3 4 2 3 3 0 0

MMA: Methyl Methacrylate

PMI: Phenyl Maleimide

CHMI: N-cyclohexyl maleimide

AMS: Alphamethyl Styrene

PC: Polycarbonate

Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Tg (占 폚) 125 124 126 127 109 125 123 R _in / R _th 2/3 2/2 2/2 2/1 7/13 4/20 Haze 0.3 0.2 0.3 0.3 opacity 0.3 0.3

As described in Table 1 and Table 2, it can be seen that the polarizer protective film comprising the resin composition of the present invention has excellent optical properties while maintaining heat resistance.

Claims (16)

An acrylic copolymer resin comprising an alkyl (meth) acrylate monomer and an imide monomer, and optionally a styrene monomer can be copolymerized. The acrylic copolymer resin according to claim 1, wherein the acrylic copolymer is in the form of a binary copolymer including an alkyl (meth) acrylate monomer and an imide monomer. The acrylic copolymer resin of claim 2, wherein the alkyl (meth) acrylate monomer is 70 wt% to 98 wt%, and the imide monomer is 1 wt% to 30 wt%. The method of claim 1, wherein the acrylic copolymer is an alkyl (meth) acrylate monomer; Imide monomers; And acrylic copolymer resin, characterized in that in the form of a ternary copolymer comprising a styrene monomer. The method according to claim 4, wherein the alkyl (meth) acrylate monomer is 70% to 98% by weight, the imide monomer is 1% to 30% by weight, the styrene monomer is more than 0% by weight 10% by weight or less An acrylic copolymer resin characterized by the above-mentioned. The acrylic copolymer resin according to claim 1, wherein the imide monomer is a maleimide monomer substituted with a cycloalkyl group or an aryl group. The method of claim 1, wherein the imide monomer is N-phenylmaleimide, N-cyclohexylmaleimide, N-methylphenylmaleimide, N-ethylphenylmaleimide, N-butylphenylmaleimide, N-naphthylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide, and N-tribromophenylmaleimide, characterized in that at least one member selected from the group consisting of Acrylic copolymer resin. The method according to claim 1, wherein the styrene monomer is styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 2-methyl-4-chlorostyrene, 2,4,6-trimethylstyrene, cis-ß-methylstyrene, trans-ß-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-bromo Styrene, 4-bromostyrene, 2,4-dibromostyrene, α-bromostyrene, ß-bromostyrene, 2-hydroxystyrene, and 4-hydroxystyrene Arc Based copolymer resin. The resin composition containing resin containing the acrylic copolymer resin of any one of Claims 1-8, and polycarbonate resin. The resin composition according to claim 9, wherein the resin composition has a weight ratio of the acrylic copolymer resin and the polycarbonate resin in a range of 90 to 99: 1 to 10. The resin composition according to claim 9, wherein the melt index (MI) at 1.2 kg load and 300 ° C of the polycarbonate resin is 30 g / 10 min or more. The glass transition temperature of the said resin composition is 120 degreeC or more, The resin composition of Claim 9 characterized by the above-mentioned. The polarizer protective film containing the resin composition of Claim 9. 15. The polarizer protective film of claim 13, wherein the polarizer protective film has a plane direction retardation value represented by Equation 1 below −5 nm to 5 nm, and a thickness direction retardation value represented by Equation 2 below −5 nm to 5 nm. Protective film:
[Equation 1]
R _in = (n _x -n _y ) × d
[Equation 2]
R _th = (n _z -n _y ) × d
In Equations 1 and 2,
n _x is a refractive index of the direction of the largest refractive index in the plane direction of the film,
n _y is a refractive index in the vertical direction in the n _x direction in the plane direction of the film,
n _z is the refractive index in the thickness direction,
d is the thickness of the film. The polarizer protective film of claim 13, wherein the polarizer protective film has a haze value of 1.0 or less. A liquid crystal display device comprising the polarizer protective film of claim 13.