KR101928861B1 - Acryl Film - Google Patents

Abstract

The present invention is formed from a main dope liquid containing an acrylic resin and CSR particles represented by the following general formula (1), and has an excellent slip property and impact strength property.
[Chemical Formula 1]
MMA-MAA
Here, MMA represents a unit of methyl methacrylate, and MAA represents a unit of methacrylic acid.

Description

Acrylic Film {Acryl Film}

The present invention relates to an acrylic film having excellent processability and impact resistance by introducing Core Shell Rubber particles at the time of forming an acrylic resin film.

2. Description of the Related Art In recent years, a liquid crystal display device that consumes a small amount of power and operates at a low voltage and is lightweight and thin has been widely used in information display devices such as a mobile phone, a monitor for a portable information terminal computer, and a television. Such an information display device is required to have reliability under a severe environment depending on its use. For example, in a car navigation system liquid crystal display device, the temperature and humidity inside the vehicle in which it is placed may become very high, and the temperature and humidity conditions required are more stringent than those of ordinary monitors for a television or a personal computer. In a liquid crystal display device, a polarizing plate is used to enable the display. In a liquid crystal display device requiring such a strict temperature and / or humidity condition, a polarizing plate constituting it is required to have high durability.

The polarizing plate usually has a structure in which a transparent protective film is laminated on both sides or one side of a polarizing film made of a polyvinyl alcohol resin in which a dichroic dye is adsorbed and oriented. Conventionally, triacetyl cellulose (TAC) is widely used for this protective film, and this protective film is bonded to the polarizing film through an adhesive composed of an aqueous solution of a polyvinyl alcohol resin. However, the polarizing plate in which the protective film made of triacetylcellulose is laminated has a high moisture permeability of triacetyl cellulose, so that when the polarizing plate is used for a long time under a high humid environment, the polarization performance deteriorates or the protective film and the polarizing film peel off have. In order to solve these problems, attempts have been made to use a (meth) acrylic resin film having a lower moisture permeability as a protective film of a polarizing plate than a triacetylcellulose film.

Conventional acrylic protective films have been manufactured by melt casting method. However, solvent casting method has many merits in terms of environment-friendliness such as thinning, mass production, and recycling of resin when manufactured. The solvent casting method is to melt the acrylic film in a solvent and extrude it into a T-die. Then, the solvent is dried in the belt to form a film. It is necessary to increase the impact strength by adding the optimized particles and secure the slip property for transporting the film. Process is possible. Also, the added particles should not be dissolved or deformed in the solvent.

Korean Patent No. 1265007 discloses a pressure-sensitive type polarizing plate in which light leakage of an image display device does not occur even by a change in use environment. In the pressure-sensitive adhesive type polarizing plate in which the acrylic polymer constituting the pressure-sensitive adhesive layer has an aromatic ring structure ) Acrylate monomer unit and its content is determined according to the value of the photoelastic coefficient X of the transparent protective film, and when the retardation value of the transparent protective film changes due to environmental changes such as heating, the pressure- It is proposed to adjust so as to cause a phase difference change of the opposite sign.

Korean Patent No. 1114354 discloses a protective film for an optical member having a pressure-sensitive adhesive layer containing a photopolymerizable acrylic polymer, an antistatic agent and a cured product of a polymerization initiator composition, wherein a crosslinking reaction is caused by a radical generated in the initiator An appropriate amount of an antistatic agent is added to a composition containing a photopolymerizable acrylic polymer into which a photoactivating group capable of causing photoinitiator is introduced and a polymerization initiator in a predetermined ratio so that the aging process at the time of curing can be omitted and the manufacturing process can be simplified , And a protective film excellent in antistatic property during peeling or use.

Korean Patent Laid-Open Publication No. 2015-0061591 discloses a composition comprising a first functional layer (low moisture-permeable layer) formed using a compound having a cyclic aliphatic hydrocarbon group and an ethylenically unsaturated double bond group, and a composition containing urethane acrylate thereon There is proposed a technique for obtaining a polarizing plate protective film having excellent interlayer adhesion and wind non-uniformity resistance by using a specific amount of a fluoroaliphatic group-containing copolymer having a second functional layer formed thereon and having a specific structure in the first functional layer .

Japanese Patent Application Laid-Open No. 2014-240905 discloses a polarizing plate having a film thickness and a modulus of elasticity within a specific range and having an acrylic resin as a main component in order to produce a polarizing plate excellent in adhesion with a polarizer, , A polarizer, and a retardation film B composed mainly of a cellulose derivative having at least an ether bond and a substituent in a glucose skeleton. The film A and the film B are bonded together through an ultraviolet curable adhesive.

Therefore, there is a need to improve the technique of securing the slip property for film transfer while still facilitating the film forming process when the acrylic protective film is still produced by the solvent casting method.

Korea Patent No. 1265007 Korea Patent No. 1114354 Korean Patent Publication No. 2015-0061591 Japanese Laid-Open Patent Application No. 2014-240905

Disclosure of the Invention The present invention has been devised in order to solve the above-mentioned problems, and an object of the present invention is to provide an acrylic film excellent in slipperiness and impact resistance manufactured by the solvent casting method.

The present invention relates to an acrylic resin composition comprising 70 to 99 parts by weight of a methyl methacrylate unit and 1 to 30 parts by weight of a methacrylic acid unit based on 100 parts by weight of an acrylic resin represented by the following formula (1) Resin and core shell rubber particles formed by a solvent casting method and has a dynamic friction coefficient of 0.1 or more and 1.0 or less and a tear strength of 25 gf or more and 40 gf or less.

[Chemical Formula 1]

MMA-MAA

Here, MMA represents a unit of methyl methacrylate, and MAA represents a unit of methacrylic acid.

The core shell rubber particles of the present invention may contain one or more kinds of core selected from the group consisting of styrene butadiene rubber, polybutadiene (PBD), and acrylic ester, And graft copolymers having one or more core-shell structures selected from the group consisting of methyl methacrylate (MMA), styrene, and acrylic ester, The diameter is 100 nm to 300 nm, and it is preferable that the diameter is 3 to 10 parts by weight based on 100 parts by weight of the main doping solution.

The molecular weight of the acrylic resin of the present invention is preferably 300,000 g / mol to 2,500,000 g / mol.

It is preferable that the solvent of the solvent casting of the present invention is mixed with a halogenated hydrocarbon and an alcohol.

The present invention also provides an acrylic resin composition comprising 70 to 99 parts by weight of a methyl methacrylate unit and 1 to 30 parts by weight of a methacrylic acid based on 100 parts by weight of an acrylic resin, Core Shell Rubber) is stretched at a stretching speed of 30% / min to 90% at a stretching temperature of 100 to 150 ° C when the residual solvent before stretching is 5% to 20% by weight, % / min to a stretching ratio of 120% to 140%.

The acrylic film of the present invention has an effect of facilitating film formation and film transfer.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view illustrating the structure of core shell rubber (CSR) particles of the present invention. FIG.

Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited to these.

The inventors of the present invention have conducted research to develop an acrylic film which is easy to form a film and transfer the film when the acrylic film of the thin film is manufactured by the solvent casting method. As a result, the molecular weight of the acrylic resin is in the range of 300,000 to 2,500,000 g / It has been found that a protective film which can be easily formed and transported can be obtained at the time of film formation by a resin composition containing a specific component, and thus the present invention has been completed.

The acrylic film of the present invention is formed from a main dope liquid containing acrylic resin and core shell rubber (CSR) particles represented by the following formula (1), and has a dynamic friction coefficient of 1.0 or less and a tear strength of 15 or more Is an acrylic film.

[Chemical Formula 1]

MMA-MAA

Here, MMA represents a unit of methyl methacrylate, and MAA represents a unit of methacrylic acid.

First, the acrylic resin of the present invention will be described. The acrylic resin of the present invention is an acrylic resin comprising a methyl methacrylate unit and a methacrylic acid unit, and each of the monomer units is contained in the form of a repeating unit.

(Meth) acrylic acid unit (meth) acrylate unit is preferably used in an amount of 70 to 99 parts by weight, methacrylic acid unit: 1 to 30 parts by weight based on 100 parts by weight of the acrylic resin in consideration of optical characteristics, transparency, compatibility, By weight. When the content of methyl methacrylate units is in the above range, excellent retardation and optical characteristics can be obtained. When the methylmethacrylate unit content is less than 70 parts by weight, the optical performance of the protective film deteriorates. When the methylmethacrylate unit content exceeds 99 parts by weight, the thickness uniformity of the protective film is lowered. The content of the methacrylic acid unit is preferably 1 to 30 parts by weight based on 100 parts by weight of the acrylic resin. When the content of the methacrylic acid unit is within the above range, preferable optical properties can be obtained.

In the present invention, by adding core-shell rubber particles (CSR) which are insoluble in a solvent and do not deform in the acrylic resin, the impact strength of the film is increased, thereby facilitating film formation and film transfer. The core shell rubber particle (CSR) particles preferably have a diameter of 100 nm or more and 300 nm or less. When the diameter of the core-shell rubber particle (CSR) particle is less than 100 nm, the effect of the object of the present invention is not sufficiently exhibited, and when it exceeds 300 nm, the quality of the protective film becomes poor. The core-shell rubber particle (CSR) particle is preferably 3 parts by weight or more and less than 10 parts by weight based on 100 parts by weight of the main dope liquid.

The molecular weight of the resin of the present invention is preferably 300,000 to 2,500,000 g / mol. If the molecular weight is less than 300,000 g / mol, the production efficiency of the film is lowered. If the molecular weight exceeds 2,500,000, the molding process is not easy. The glass transition temperature (Tg) of the acrylic resin of the present invention is preferably 120 ° or more. Even if the glass transition temperature is lower than the above-mentioned range, handling becomes poor, which is not preferable.

The acrylic film of the present invention preferably has a film thickness of 10 to 60 탆. When the thickness of the protective film is less than 10 mu m, sufficient retardation characteristics are not exhibited. When the thickness of the protective film exceeds 60 mu m, it is not suitable for use in a thin polarizer.

Hereinafter, a preferred manufacturing method of the present invention will be described in detail.

Manufacture of acrylic resin

To prepare the protective film of the present invention, first, a copolymer resin solution of a methyl methacrylate monomer and a methacrylic acid monomer is prepared. There is no particular limitation on the method for producing the copolymer of these monomers, and the copolymer can be produced according to a method for producing a copolymer resin well known in the art such as suspension polymerization, emulsion polymerization, bulk polymerization or solution polymerization.

Preparation of Dilute Primary Dope Liquid Containing Acrylic Resin and Nanoparticles

In the present invention, a film is produced by a solvent casting method (solution film forming method). In the solvent casting method, a main dope liquid obtained by dissolving an acrylic resin in a casting solvent is cast on a support, and the solvent is evaporated to form a film. The main dope solution is prepared by mixing the acrylic resin and the auxiliary additive in the casting solvent.

When a film is produced by a solvent casting method, an organic solvent is preferred as the solvent for preparing the main dope solution. As the organic solvent, it is preferable to use halogenated hydrocarbons, and halogenated hydrocarbons include chlorinated hydrocarbons, methylene chloride and chloroform, among which methylene chloride is most preferably used.

If necessary, organic solvents other than halogenated hydrocarbons may be mixed and used. Organic solvents other than halogenated hydrocarbons include esters, ketones, ethers, alcohols and hydrocarbons. Examples of the ester include methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acylate, ethyl acylate and pentyl acylate. Examples of the ketone include acetone, methyl ethyl ketone, diethyl ketone, di Isobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone and the like can be used. As the ether, diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, Ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-butanol and the like can be used. 2-butanol, cyclohexanol, 2-fluoroethanol, 2,2,2, -trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like Lt; / RTI >

More preferably, methylene chloride may be used as the main solvent, and alcohol may be used as the minor solvent. Concretely, a mixed solvent in which the mixing ratio of methylene chloride and alcohol is in the range of 80:20 to 95: 5 is preferable.

In the production of the acrylic film, auxiliary additives may further be used. To the main dope liquid, various auxiliary additives depending on the use in each production step, for example, an auxiliary additive such as an ultraviolet ray inhibitor, a fine particle, an infrared absorbent, and a releasing agent may be added. The specific kind of such additives can be used without limitation as long as they are commonly used in the field, and the content thereof is preferably used within a range that does not deteriorate the physical properties of the film. The timing of adding the additives depends on the type of additive. A step of adding an additive to the end of the main dope liquid preparation may be performed.

In the present invention, core-shell rubber (CSR) particles are used as an additive. The diameter of the particles is 100 to 300 nm, and the content thereof is preferably 3 parts by weight or more and less than 10 parts by weight with respect to 100 parts by weight of the main doping solution. The structure of the nanoparticles can be illustrated as shown in Fig.

The main dope liquid obtained as described above can be produced by an ordinary temperature, high temperature or low temperature dissolution method.

Film forming process

In the solvent casting method of the present invention, the main dope liquid is poured on a metal support from a nozzle of a pressure die and allowed to stand for a predetermined time to form a semi-dry film. Thereafter, the semi-dried film is peeled from the metal support, transferred to a drying system, and dried to remove the solvent. Then, a uniaxial stretching process or a biaxial stretching process is performed on the dried film. By this stretching process, it is possible to improve the film uniformity and the retardation value of the protective film.

Specifically, the main dope liquid obtained as described above is cast on a support through a casting die to form an acrylic sheet. Here, the support serves to evaporate the solvent present in the casting solution while casting the casting solution on the sheet extruded from the die, thereby forming an acrylic film. The support or the surface thereof is preferably made of a metal and has a mirror finished surface, and a steel belt such as a stainless steel belt is preferably used as the support. The surface temperature of the metal support is advantageous because it can accelerate the evaporation of the solvent present in the casting stock solution as the temperature is higher. However, if the temperature is too high, the casting stock solution tends to foam or deteriorate in planarity, But it is preferably 0 to 75 占 폚, more preferably 5 to 45 占 폚. As the support, a metal support in the form of a planar conveyor belt may be used.

The acrylic sheet thus formed is subjected to a stretching step in the tenter, and the preheating step is such that the glass transition temperature (Tg) of the acryl flake is 120 DEG or more. The acrylic film of the present invention may be completed in the dryer under the above conditions after having been subjected to the stretching step in the tenter and then the left and right ends of the film whose surface has been damaged by the clip or pin of the tenter are removed.

In the case of using the tenter stretching device, it is preferable to use a device capable of controlling the holding length of the film from the left and right by the left and right gripping means of the tenter. The stretching operation may be carried out by dividing into a plurality of steps or biaxially stretching in the machine direction and the width direction. When biaxial stretching is carried out, simultaneous biaxial stretching may be carried out or may be performed stepwise. In this case, the stepwise means that the stretching in different stretching directions can be performed sequentially, the stretching in the same direction can be divided into multiple steps, and the stretching in the other direction can be added to any one of them. The simultaneous biaxial stretching may include stretching in one direction and relaxation of the other stretch by shrinking. The preferred stretching magnification of the simultaneous biaxial stretching can be in the range of 1.01 to 2.0 times in both the width direction and the longitudinal direction.

The drying means generally blows hot air on both sides of the web, but there is also a means of heating the micro web in place of the wind. Too rapid drying tends to impair the planarity of the finished film.

The present invention produced by the above method is characterized by an acrylic film having a dynamic friction coefficient of 1 or less and a tear strength of 15 gf or more.

Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited by the following examples.

Example  One

≪ Step 1 >

The content of the methacrylic acid unit was 5%, and acrylic represented by the following formula (2) was used.

(2)

≪ Step 2 > Preparation of main dope liquid containing CSR particles

20.0 parts by weight of the acrylic polymer solution, 5 parts by weight of core-shell rubber (CSR) as nanoparticles, and 75 parts by weight of a mixed solvent of methylene chloride and methanol mixed at a weight ratio of 9: 1 were mixed to obtain a diluted acrylic polymer Solution. CSR was an acrylic type M-210 grade from Kaneka Japan. The size of the nanoparticles is 100 to 300 nm.

≪ Step 3 >

The composition of the main dope solution was 64.17 parts by weight of methylene chloride, 7.13 parts by weight of methanol, 27.98 parts by weight of acrylic resin, 0.72 parts by weight of Tinvuin 928 (manufactured by BASF) and 5 parts by weight of CSR.

Then, the main dope liquid was uniformly plied to a stainless steel band support having a width of 2000 mm by using a belt softener. The solvent was evaporated on the stainless steel band support and peeled off from the stainless band support. Then, both ends of the web were held with a tenter and stretched so that the stretching magnification in the TD direction was 1.5 times in a temperature environment of 130 °. After the stretching, the stretching was maintained for a few seconds, the tension in the width direction was relaxed, the stretching was performed in the width direction, the stretching was continued for 35 minutes in the drying section set at 90 DEG, An acrylic film having a thickness of 40 m and a knurling width of 10 mm and a height of 8 m was produced.

Example  2 to 3

Acrylic resin having a content of core-shell rubber (CSR) of 10% (Example 2) and 3% (Example 3) was used in the same manner as Example 1.

Comparative Example  One

The main dope solution was prepared under the same conditions as those of the above examples, but core-shell rubber (CSR) particles were not added.

Comparative Example  2

The main dope solution was prepared under the same conditions as those of the above example, except that the acrylic resin represented by the following formula (3) was used.

(3)

1. Film Slipperiness  evaluation

With respect to the films of the above Examples and Comparative Examples 1 and 2, the slip property at the time of transferring the roll roll film was visually evaluated, and the results are shown in Table 1.

2. Measurement of friction coefficient

The coefficients of dynamic friction were measured for the thus obtained Examples and Comparative Examples 1 and 2, and the results are shown in Table 1. [

3. Of the retardation value  Measure

The retardation values Ro and Rth were measured at a wavelength of 590 nm under the environment of 23 ° C and 55% RH using the AxoScan (OPMF-1, Axometrics Co.) optical measuring equipment for the films obtained in the thus obtained Examples and Comparative Examples 1 and 2 The results are shown in Table 1.

4. Phosphorus strength  evaluation

In order to evaluate the impact strength of the films obtained in Examples and Comparative Examples 1 and 2, the tearing strength was evaluated using the following specifications and equipment, and the results are shown in Table 1. [

Test specification: Elmendorf method (KS M ISO 6383-2: 2010) Measurement method of plastic film / sheet tear resistance

Manufacturer and model: LabThink SLY-SI model

sample Suzy Slip property The retardation (nm) Impact strength Remarks Visually
evaluation Coefficient of friction Face direction Ro Thickness direction Rth Phosphorus strength
(gf) 2 Modified acrylic
(CSR 5%) good 0.44 One 0 31 Example 1 One Modified acrylic
(CSR 10%) good 0.33 One 0 38 Example 2 3 Modified acrylic
(CSR 3%) good 0.71 One 0 27 Example 3 4 Modified acrylic
(CSR 0%) Poor 1.93 One 3 4 Comparative Example 1 5 acryl Poor 1.52 3 5 22 Comparative Example 2

※ The coefficient of dynamic friction is less than 1.0 and the tear strength is more than 15.

As shown in Table 1, when the acrylic resin and the CSR particles shown in the present invention were used, the slip property, the retardation, and the impact strength property were excellent. If nanoparticles are not added, the slip property and the impact strength are lowered. If a general acrylic resin is used,

Even when the particles are added, an acrylic resin which is not dissolved in a solvent remains in the solvent, which causes a problem in slipperiness due to sticky characteristics.

Claims (5)

delete delete delete delete An acrylic resin composition comprising 95 to 99 parts by weight of a methyl methacrylate unit and 1 to 5 parts by weight of a methacrylic acid unit based on 100 parts by weight of an acrylic resin represented by the following formula (1) Preparing a main dope liquid including a core shell rubber; And
And solvent casting the main dope solution to produce an acrylic film,
The step of producing the acrylic film includes a step of stretching in the width direction and relaxing the tensile force in the width direction while maintaining the width, loosening in the width direction, and conveying and drying in the drying section,
The stretching is performed at an elongation rate of 100 to 150 ° C at a stretching rate of 30% / min to 90% / min at an elongation of 120% to 140% when the residual solvent before stretching is 5% to 20% Including,
The core shell rubber may be one or two or more selected from the group consisting of styrene butadiene rubber, polybutadiene (PBD), and acrylic ester, And a graft copolymer having one or more core-shell structures selected from the group consisting of methacrylic (MMA), styrene, and acrylic ester, and has a diameter of 100 nm to 300 nm And 5 parts by weight to 10 parts by weight with respect to 100 parts by weight of the main doping solution,
The molecular weight of the acrylic resin is 300,000 g / mol to 2,500,000 g / mol,
The solvent of the solvent casting is mixed with a halogenated hydrocarbon and alcohol,
A coefficient of dynamic friction of 0.1 or more and 1.0 or less, and a tear strength of 25 gf or more and 40 gf or less.
[Chemical Formula 1]
MMA-MAA
Here, MMA represents a unit of methyl methacrylate, and MAA represents a unit of methacrylic acid.

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