KR102112028B1 - Acryl Film - Google Patents

Abstract

The present invention relates to an acrylic film prepared by controlling the amount of the residual solvent by adding a specific additive, methyl methacrylate (Methyl Methacrylate) units 70 to 96 parts by weight of alkyl (meth) acrylate excluding methyl methacrylate Acrylic resin consisting of 4 to 30 parts by weight of the unit; And an aromatic ester-based additive, a phenol-based additive and an acrylic-based additive, and one additive selected from the group consisting of a solvent casting method. And, it provides an acrylic film, characterized in that 1 to 10% by weight based on 100% by weight of the main dope containing a solvent.

Description

Acrylic film

The present invention relates to an acrylic film produced by controlling the amount of residual solvent by adding a specific additive.

2. Description of the Related Art In recent years, liquid crystal display devices having low power consumption, low voltage operation, and light weight and thinness have been widely used in information display devices such as mobile phones, portable information terminal computer monitors, and televisions. Reliability in such a harsh environment is required for such information display devices. For example, a liquid crystal display device for a car navigation system may have a very high temperature and humidity in a car in which it is placed, and the required temperature and humidity conditions are stricter than that of a conventional television or personal computer monitor. In addition, a polarizing plate is used in the liquid crystal display device to enable the display. In the liquid crystal display device in which such strict temperature and / or humidity conditions are required, it is required that the polarizing plate constituting it has 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-based resin in which a dichroic dye is adsorbed and oriented. And conventionally, triacetyl cellulose (TAC) is widely used for this protective film, and the protective film is bonded to the polarizing film through an adhesive made of an aqueous solution of a polyvinyl alcohol-based resin. However, the polarizing plate on which the protective film made of triacetylcellulose is stacked has high moisture permeability of triacetylcellulose, so that the polarizing performance may deteriorate or the protective film and the polarizing film peel off when used for a long time in a high-humidity heat environment. have. In order to solve this problem, it has been attempted to use a (meth) acrylic resin film having a low moisture permeability as compared to a triacetyl cellulose film as a protective film for a polarizing plate.

Existing acrylic-based protective films have been manufactured by a melt casting method, but have many advantages in terms of eco-friendliness, such as thinning of the film, mass production, and recycling of resins when manufacturing by the solvent casting method. Solvent casting method is to produce a film through the process of drying the solvent in a belt after extruding the main solution in which the acrylic resin is dissolved in a solvent with a T-die, and then adding optimized particles to impact the film. The above process is possible only when the strength is increased and sufficient slip property is secured for transferring the film. In addition, the particles added at this time should not be dissolved or deformed in the solvent. In particular, since the amount of the solvent remaining in the film acts as an important factor in terms of slip properties, it is important to control the amount of the residual solvent.

Korean Registered Patent No. 12,500,7 discloses an adhesive polarizing plate in which light leakage of an image display device does not easily occur even due to a change in the use environment.The acrylic polymer constituting the adhesive layer has a predetermined amount of (meth) ) Containing an acrylate monomer unit, its content is determined according to the value of the photoelastic coefficient X of the transparent protective film, and when the phase difference value of the transparent protective film changes due to environmental changes such as heating, the pressure-sensitive adhesive layer is a transparent protective film It has been proposed to adjust to generate a phase difference change of the opposite sign.

Korean Registered Patent No. 1114354 is a protective film for an optical member having an adhesive layer containing a cured product of a photopolymerizable acrylic polymer, an antistatic agent, and a polymerization agent composition, and undergoes a crosslinking reaction by radicals generated in an initiator by light irradiation. A composition containing a photopolymerizable acrylic polymer and a polymerization initiator in which a photoactive group that can be introduced is introduced in a predetermined ratio, an appropriate amount of an antistatic agent is added, and the aging process during curing can be omitted, thereby simplifying the manufacturing process. , A protective film excellent in antistatic properties when peeling or using.

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

Japanese Unexamined Patent Publication No. 2014-240905 has a film thickness and an elastic modulus within a specific range, and a protective film containing acrylic resin as a main component in order to produce a polarizing plate excellent in adhesiveness, reworkability, flatness and visibility with a polarizer. , Polarizers, glucose skeletons are stacked in the order of retardation film B, which mainly comprises a cellulose derivative having an ether bond and a substituent, and both films A and B are bonded through an ultraviolet curable adhesive.

Therefore, there is still a need to improve the technology on the aspect of securing slip properties for film transfer when the acrylic protective film is manufactured by a solvent casting method.

Korean Registered Patent No. 1265007 Korean Registered Patent No. 1114354 Korean Patent Publication No. 2015-0061591 Japanese Patent Publication No. 2014-240905

The present invention was devised to solve the above problems, and when the acrylic film is produced by solvent casting, the amount of the residual solvent can be easily controlled by adding a compound having a specific structure to the acrylic resin, so that the film forming process is performed. It is to provide an acrylic film having excellent quality, which is prevented from deteriorating in quality that may occur due to the amount of residual solvent in the process of performing the heavy peeling.

Acrylic film according to embodiments of the present invention, methyl methacrylate (Methyl Methacrylate) 70 to 96 parts by weight of an acrylic resin consisting of 4 to 30 parts by weight of alkyl (meth) acrylate units excluding methyl methacrylate; And an aromatic ester-based additive, a phenol-based additive, and an acryl-based additive, and one additive selected from the group consisting of a solvent casting method. The input amount of the additive is characterized in that 1 to 10% by weight based on 100% by weight of the main dope containing the acrylic resin, the additive, and a solvent.

The aromatic ester-based additive may have a structure of Formula 1, Formula 2, Formula 3 or Formula 4.

[Formula 1]

[Formula 2]

 [Formula 3]

[Formula 4]

(In Formula 1, X1, X2 is a hydrocarbon group having 1 to 20 carbon atoms, including an ester group, an ether group, or a carbonyl group, n is 1 or more, m, n, and l in Formula 2 Is each 1 or more, in Formula 3, m and n are each 1 or more, and in Formula 4, m is 1 or more.)

The phenolic additive may have a structure of Formula 5 below.

[Formula 5]

(In Formula 5, R1 to R5 are each independently a hydrogen atom, a halogen atom, a hydroxyl group, or a hydrocarbon group having 1 to 12 carbon atoms, and X is a hydrocarbon having 4 to 20 carbon atoms including an ester group, an ether group, or a carbonyl group. Group, and n is 0 to 5.)

The acrylic additive may have a structure of Formula 6 below.

[Formula 6]

(In Formula 6, R1, R2 are a hydrogen atom or a hydrocarbon group having 1 or more carbon atoms, X is an ester group, an ether group, or a carbonyl group or a hydrocarbon group containing the above functional group, and n is 1 or more.)

The glass transition temperature (Tg) of the acrylic film may be 94 ° C or higher, and the residual solvent amount may be 150 to 2400 ppm.

 The acrylic film of the present invention is manufactured in a state in which the amount of the residual solvent is easily controlled, so that the amount of the residual solvent in the process of peeling during the film forming process can be prevented from deteriorating the film quality that may occur due to too little or too much. It is possible to provide an acrylic film having a.

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 acrylic film according to the embodiments of the present invention comprises 70 to 96 parts by weight of methyl methacrylate units and 4 to 30 parts by weight of alkyl (meth) acrylate units excluding methyl methacrylate, an aromatic ester-based additive, and phenol. Contains one type of additive selected from the group consisting of system additives and acrylic additives, and is prepared through a solvent casting method, and the amount of the additive added when prepared by the method includes the acrylic resin, the additive, and a solvent. It is characterized in that 1 to 10% by weight based on 100% by weight of the dope.

First, the acrylic resin of the present invention will be described. The acrylic resin of the present invention is a copolymer resin composed of methyl methacrylate units and alkyl (meth) acrylate units excluding methyl methacrylate, and the monomer units are included in the form of repeat units.

In consideration of optical properties, transparency, compatibility, processability and productivity, with respect to 100 parts by weight of the acrylic resin, 70 to 96 parts by weight of methyl methacrylate units, and 4 to 30 of alkyl (meth) acrylate units excluding methyl methacrylate It is preferably made of parts by weight. The content of the alkyl (meth) acrylate unit excluding the methyl methacrylate may be more preferably 5 to 20 parts by weight.

This is because when the content of the methyl methacrylate unit is in the above range, excellent retardation characteristics and optical characteristics can be obtained. When the methyl methacrylate unit content is less than 70 parts by weight, the optical performance of the acrylic film is deteriorated, and when it exceeds 96 parts by weight, the thickness uniformity of the acrylic film may be deteriorated.

In addition, the content of the alkyl (meth) acrylate unit excluding methyl methacrylate can also obtain excellent retardation properties and optical properties within the above range. If the content of the alkyl (meth) acrylate unit excluding methyl methacrylate is less than 4 parts by weight, the optical performance of the protective film deteriorates, and if it exceeds 30 parts by weight, the processability of the film may be deteriorated.

The alkyl (meth) acrylate is methyl acrylate (Methyl Acrylate), butyl acrylate (Butyl Acrylate), butyl methacrylate (Buthyl Methacrylate) and one or two selected from the group consisting of methacrylic acid (Methacrylic Acid) It may include more than one type of copolymerization monomer.

The acrylic film of the present invention includes one additive selected from the group consisting of the acrylic resin and aromatic ester-based additives, phenol-based additives and acrylic-based additives. By adding the additive, it is possible to easily control the amount of the residual solvent, and thus it is possible to prevent the film from being deteriorated by the residual solvent. Deterioration of the quality of the film by the residual solvent may occur when the main dope solution in which the acrylic resin is dissolved in the solvent in the solvent casting process is coated on a metal support to form a semi-dried film and then peeled from the support. Therefore, after the production is completed, the properties as optical and protective films are insufficient. That is, the residual solvent amount can have a significant effect on the quality of the acrylic film, so its control is essential. For example, if the amount of the residual solvent is too small, it may be difficult to peel the film from the support, and damage to the film may occur. If the amount of the residual solvent is too large, the film becomes too soft and lacks self-support, resulting in peeling tension. This can cause problems due to the stretching of the film. In addition, when the amount of the residual solvent is large in the stretching and / or drying process during the film forming process, shrinkage may occur excessively in the film, which may adversely affect the properties of the film. In addition, if the amount of the organic solvent remaining in the film after production is large, it may be a problem in terms of the harmfulness of the product. However, the solvent mainly used in the solvent casting method is a highly volatile organic solvent, and it is not easy to control the amount of the residual solvent inside the film. In the present invention, the amount of the residual solvent can be easily controlled by adding the additive. have.

The content of the additive may be 1 to 10% by weight, preferably 3 to 10% by weight, more preferably 5 to 10% by weight. By adding the additive within the above range, the effect of easily controlling the amount of the residual solvent can be obtained as described above, but if the content is too high, the glass transition temperature of the acrylic film is to an undesired range. It may degrade. The acrylic resin has less free volume between molecules than the triacetyl cellulose material, and the diffusion of the solvent remaining therein is relatively slow when it is made into a film. As a result, a difference in the drying speed of the solvent occurs on the surface and inside of the film during the film forming process, and surface solidification occurs, whereby a larger amount of the solvent may remain inside the film. In the present invention, by adding the additive to the acrylic resin, the gap between molecular chains of the acrylic resin is widened, so that diffusion of the residual solvent inside the resin can be promoted. As a result, the solidification of the film is delayed as the solvent present therein diffuses toward the surface of the film. Accordingly, drying of the residual solvent can be more efficiently performed through the film forming process, and thus the amount of the residual solvent can be more easily performed. Can be controlled.

The aromatic ester-based additive may have a structure of Formula 1, Formula 2, Formula 3 or Formula 4, but is not limited thereto.

[Formula 1]

[Formula 2]

 [Formula 3]

[Formula 4]

(In Formula 1, X1, X2 is a hydrocarbon group having 1 to 20 carbon atoms including an ester group, an ether group, or a carbonyl group, n is 1 or more, and m, n, and l in Formula 2 are each 1 or more, In Formula 3, m and n are each 1 or more, and in Formula 4, m is 1 or more.)

The phenolic additive may have a structure of Formula 5 below.

[Formula 5]

(In Formula 5, R1 to R5 are each independently a hydrogen atom, a halogen atom, a hydroxyl group, or a hydrocarbon group having 1 to 12 carbon atoms, and X is a hydrocarbon having 4 to 20 carbon atoms including an ester group, an ether group, or a carbonyl group. Group, and n is 0 to 5.)

Specific examples of the phenol-based additive may have a structure of the following Chemical Formulas 5-1 to 5-3, but are not limited thereto.

[Formula 5-1]

[Formula 5-2]

[Formula 5-3]

(In Formula 5-1, R1 is a hydrogen atom, a halogen atom, a hydroxyl group, or a hydrocarbon group having 1 to 12 carbon atoms, and in Formula 5-2, R1 is a hydrogen atom, a halogen atom, a hydroxyl group, or a hydrocarbon having 1 to 12 carbon atoms. Group, i-C8H17 means an isooctyl group)

The acrylic additive may have a structure of Formula 6 below.

[Formula 6]

(In Formula 6, R1, R2 are a hydrogen atom or a hydrocarbon group having 1 or more carbon atoms, X is an ester group, an ether group, or a carbonyl group or a hydrocarbon group containing the above functional group, and n is 1 or more.)

A specific example of the acrylic additive may have a structure of Formula 6-1 below, but is not limited thereto, and other acrylic compounds may also be used.

[Formula 6-1]

The acrylic resin used in the present invention preferably has a molecular weight of 300,000 to 2,500,000 g / mol. At this time, if the molecular weight is less than 300,000 g / mol, the production efficiency of the film decreases, and if it exceeds 2,500,000, molding processing may not be easy.

The glass transition temperature (Tg) of the acrylic film according to the embodiments of the present invention is preferably 94 ° C or higher. When the glass transition temperature is less than 94 ° C, sagging occurs in the heated film during the film-forming process, which is not preferable because the handleability of the film is poor.

In addition, the residual solvent amount of the acrylic film of the present invention may be 150 to 2400ppm, preferably 150 to 850ppm, more preferably 150 to 600ppm. The residual solvent amount means the residual solvent amount of the finally produced film. Since the acrylic film of the present invention is peeled in a range most suitable for carrying out the peeling in order to transfer the film in a semi-dry state from the support during the film forming process, it is possible to prevent deterioration in the quality of the film that may occur due to excessive or little residual solvent. . In addition, because of this, the acrylic film finally produced is peeled in a state including the amount of the residual solvent of 150 to 2400 ppm, so that the amount of the residual solvent is excessively small or too large, thereby preventing the film from being deteriorated. In addition, since the acrylic film of the present invention contains a low residual solvent amount as described above, it may not cause harmful problems when using the film.

It is preferable that the acrylic film of the present invention has a film thickness of 10 to 60 µm. When the thickness of the protective film is less than 10 µm, sufficient retardation characteristics as an optical film are not exhibited, and when the thickness of the protective film exceeds 60 µm, it is not suitable for use in thin polarizing plates.

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

Preparation of acrylic resin

To prepare the acrylic film of the present invention, first, a copolymer resin (acrylic resin) solution of an alkyl (meth) acrylate monomer excluding methyl methacrylate monomer and methyl methacrylate is prepared. The alkyl (meth) acrylate is methyl acrylate (Methyl Acrylate), butyl acrylate (Butyl Acrylate), butyl methacrylate (Buthyl Methacrylate) and one or two selected from the group consisting of methacrylic acid (Methacrylic Acid) It may include more than one type of copolymerization monomer.

There is no particular limitation on the method for producing a copolymer of these monomers, and it may be prepared according to a method for preparing a copolymer resin well known in the art, such as suspension polymerization, emulsion polymerization, bulk polymerization or solution polymerization.

Notes containing acrylic resin additives Dope  Produce

In the present invention, a film is produced by a solvent casting method (solution film forming method). The solvent casting method is a method of casting a main dope obtained by dissolving an acrylic resin in a solvent (casting solvent) on a support, and evaporating the solvent to form a film. The main dope solution is prepared by mixing the above-mentioned acrylic resin and the additive in a solvent.

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

Further, if necessary, an organic solvent other than halogenated hydrocarbons may be mixed and used. Organic solvents other than halogenated hydrocarbons include esters, ketones, ethers, alcohols and hydrocarbons. As the ester, methyl formate, ethyl formate, propyl formate, pentyl formate, methyl acylate, ethyl acylate, pentyl acylate, etc. can be used, and acetone, methyl ethyl ketone, diethyl ketone, di as ketone Isobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, etc. can be used, and diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxane can be used as ether. Solan, tetrahydrofuran, anisole, phenitol, etc. can be used, and alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2 -Pentanol, 2-methyl-2-butanol, cyclohexanol, 2-fluoroethanol, 2,2,2, -trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol, etc. Use

More preferably, methylene chloride may be used as the main solvent, and alcohol may be used as the sub-solvent. Specifically, the mixing ratio of methylene chloride and alcohol is preferably a mixed solvent mixed in a weight ratio within the range of 80:20 to 95: 5.

In the present invention, one additive selected from the group consisting of an aromatic ester-based additive, a phenol-based additive and an acrylic-based additive is used as an additive, and the content of the additive is 1 to 10% by weight.

In the preparation of the acrylic film, auxiliary additives may be further used in addition to the additives. In addition to the above-mentioned additives, the main dope solution includes various auxiliary additives according to the use in each manufacturing process, for example, ultraviolet rays, fine particles such as core-shell rubber (CSR) particles or silica particles, infrared absorbers, release agents, etc. Can be added. The CSR particles include styrene butadiene rubber, polybutadiene (PBD), acrylic ester (Acrylic Ester), one or two or more cores, and methyl methacrylate (MMA) ), Styrene (Styrene), acrylic esters (Acrylic Ester) is preferably one or two or more selected from the group consisting of a graft copolymer having a core-shell structure, but is not limited thereto. In addition, specific types of these additives can be used without limitation as long as they are commonly used in the field, and the content is preferably used in a range that does not degrade the physical properties of the film. The timing of adding the additive and the auxiliary additive is determined according to the type of each additive. A process of adding an additive at the end of the main dope preparation may be carried out.

The main dope obtained as described above may be prepared according to the normal temperature, high temperature or low temperature melting method.

Production process

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

Specifically, the main dope 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 main dope while transporting the main dope liquid on the sheet extruded from the die to form a film with an acrylic film. The support or the surface thereof is made of metal, and the surface is preferably mirror-finished, and a metal belt such as a stainless steel belt is preferably used as the support. The surface temperature of the metal support is advantageous because the higher the temperature, the faster the evaporation of the solvent present in the main dope solution, but if it is too high, the main dope solution may be foamed or flattened. Therefore, the surface temperature of the metal support may vary depending on the solvent used, but 0 to 75 ° C is preferable, and 5 to 45 ° C is more preferable. As the support, a metal support in the form of a flat conveyor belt may be used.

The acrylic sheet thus formed is transferred to a tender and undergoes a stretching step in the tender. The acrylic film of the present invention may be completed through a drying step in a dryer after removing the left and right ends of the film whose surface is damaged by a clip or pin of the tender, after the stretching process in the tender under the above conditions.

When using a tender stretching apparatus, it is preferable to use the apparatus which can control the gripping length of a film from left and right by means of the left and right grippers of a tender. The stretching operation may be performed in multiple stages, or biaxial stretching in the flexible direction and the width direction is also preferable. In addition, when biaxial stretching is performed, simultaneous biaxial stretching may be performed or may be carried out stepwise. In this case, stepwise, it is also possible to sequentially perform stretching in different stretching directions, dividing stretching in the same direction into multiple stages, and adding stretching in different directions to any one of them. In addition, simultaneous biaxial stretching also includes stretching in one direction and contracting the other by relaxing the tension. The preferred stretching ratio of simultaneous biaxial stretching can be taken in a range of 1.01 to 2.0 times in both the width direction and the length direction.

As the drying means, it is common to blow hot air on both sides of the web, but there is also a means to heat the micro web instead of the wind. Too rapid drying tends to impair the flatness of the finished film.

Since the acrylic film of the present invention manufactured according to the above method is manufactured by controlling the amount of residual solvent, it can exhibit excellent quality due to excellent slip property during the film forming process and no appearance stain after production.

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 1]

<Step 1-Preparation of acrylic resin>

An acrylic resin having a content of 5 parts by weight of butyl methacrylate in units of 100 parts by weight of the total acrylic resin, a molecular weight of 650,000 g / mol shown in Chemical Formula 7, and a glass transition temperature (Tg) of 115 ° C was used.

 [Formula 7]

(In Formula 7, a and b are each an integer of 1 or more)

<Step 2-Preparation of main dope liquid>

29% by weight of the acrylic resin, 1% by weight of an aromatic ester-based additive having a structure represented by the following Chemical Formula 2, and having a weight average molecular weight of 1000 g / mol, and a mixed solvent 70 of methylene chloride and methanol mixed in a weight ratio of 9: 1 (70) The main dope was prepared by thoroughly mixing the weight percents with an in-line mixer.

[Formula 2]

(In Formula 2, m, n and l are each an integer of 1 or more)

<Step 3-Production process>

Thereafter, the main dope was uniformly flexible to a stainless band support having a width of 2000 mm using a belt casting device. The solvent was evaporated on the stainless band support and peeled from the stainless band support. Subsequently, both ends of the web were gripped with a tender, and stretched so that the draw ratio in the TD direction was 1.5 times in a 130 ° C temperature environment. After stretching, the width is maintained for a few seconds, the tension in the width direction is relaxed, the width direction is relaxed, and then dried by conveying for 35 minutes in a drying section set at 90 °, width is 1900 mm, and further ends An acrylic film having a width of 10 mm and a thickness of 8 μm and a thickness of 40 μm was prepared.

[Example 2]

The main dope solution was prepared in the same manner as in Example 1, except that 27% by weight of the acrylic resin and 3% by weight of an aromatic ester-based additive having the structure represented by Chemical Formula 2 were added.

[Example 3]

The main dope solution was prepared in the same manner as in Example 1, except that 25% by weight of the acrylic resin and 5% by weight of an aromatic ester-based additive having the structure represented by Chemical Formula 2 were added.

[Example 4]

The main dope solution was prepared in the same manner as in Example 1, except that 20% by weight of the acrylic resin and 10% by weight of an aromatic ester-based additive having the structure represented by Chemical Formula 2 were added.

[Example 5]

When the main dope was prepared, the acrylic resin had 29 wt%, a structure represented by the following formula 5-1, and was the same as in Example 1, except that 1 wt% of R1 was a hydrogen (H) phenol-based additive. It was carried out.

[Formula 5-1]

[Example 6]

The main dope was prepared in the same manner as in Example 1, except that 27% by weight of the acrylic resin and 3% by weight of a phenolic additive having the structure represented by Chemical Formula 5-1 were added.

[Example 7]

The main dope was prepared in the same manner as in Example 1, except that 25% by weight of the acrylic resin and 5% by weight of a phenolic additive having a structure represented by Chemical Formula 5-1 were added.

[Example 8]

The main dope was prepared in the same manner as in Example 1, except that 20% by weight of the acrylic resin and 10% by weight of a phenolic additive having a structure represented by Chemical Formula 5-1 were added.

[Example 9]

When preparing the main dope, the acrylic resin had the structure represented by the following formula 6-1, the formula 6-1, and the same as in Example 1, except that 1 wt% of an acrylic additive having a weight average molecular weight of 1000 g / mol was added It was carried out.

[Formula 6-1]

[Example 10]

The main dope was prepared in the same manner as in Example 1, except that 27% by weight of the acrylic resin and 3% by weight of an acrylic additive having a structure represented by Chemical Formula 6-1 were added.

[Example 11]

The main dope was prepared in the same manner as in Example 1, except that 25% by weight of the acrylic resin and 5% by weight of an acrylic additive having a structure represented by Chemical Formula 6-1 were added.

[Example 12]

The main dope was prepared in the same manner as in Example 1 except that 20% by weight of the acrylic resin and 10% by weight of an acrylic additive having a structure represented by Chemical Formula 6-1 were added.

[Comparative Example 1]

When the main dope was prepared, it was carried out in the same manner as in Example 1, except that 30 wt% of the prepared acrylic resin was added without adding the additive.

[Comparative Example 2]

The main dope solution was prepared in the same manner as in Example 1, except that 15% by weight of the acrylic resin and 15% by weight of the aromatic ester-based additive having the structure represented by Chemical Formula 2 were added.

[Comparative Example 3]

The main dope was prepared in the same manner as in Example 1, except that 15% by weight of the acrylic resin and 15% by weight of a phenolic additive having a structure represented by Chemical Formula 5-1 were added.

[Comparative Example 4]

The main dope was prepared in the same manner as in Example 1, except that 15% by weight of the acrylic resin and 15% by weight of an acrylic additive having a structure represented by Chemical Formula 6-1 were added.

Property measurement

Each of the acrylic films prepared in Examples 1 to 12 and Comparative Examples 1 to 4 was prepared into samples cut into pieces of a certain size according to each measuring method, and the physical properties were measured in the following manner. It is shown in 1.

1. Evaluation of residual solvent

The amount of the solvent component released while slowly heating each acrylic film sample was measured by Gas Chromatography.

2. Measurement of glass transition temperature

DSC (Differential Scanning Calroimeter) was used to measure the temperature increase rate of 10 ℃ / min in the range of 40 to 200 ℃.

division Additive type Additive content
(weight%) Residual solvent amount
(ppm) Glass transition temperature
(℃) Example 1 Aromatic ester system One 2400 109 Example 2 3 800 106 Example 3 5 600 102 Example 4 10 200 94 Example 5 Phenolic One 2100 112 Example 6 3 700 110 Example 7 5 400 105 Example 8 10 150 100 Example 9 Acrylic One 2300 110 Example 10 3 850 108 Example 11 5 600 103 Example 12 10 200 97 Comparative Example 1 - - 4000 114 Comparative Example 2 Aromatic ester system 15 150 85 Comparative Example 3 Phenolic 15 100 90 Comparative Example 4 Acrylic 15 100 87

Referring to Table 1, the film prepared without adding the additive of Comparative Example 1 has an excessive amount of residual solvent, and when the additive content of Comparative Examples 2 to 4 exceeds 10% by weight, the residual solvent amount is not large, but is advantageous. The transition temperature is low, making it unsuitable for film production. On the other hand, since the acrylic films of Examples 1 to 12 have a low residual solvent amount and a glass transition temperature suitable for production as a film, the acrylic films according to the embodiments of the present invention can exhibit excellent quality.

Claims (5)

An acrylic resin consisting of 70 to 96 parts by weight of methyl methacrylate units and 4 to 30 parts by weight of alkyl (meth) acrylate units excluding methyl methacrylate; And
It includes one additive selected from the group consisting of an aromatic ester (Aster) additive represented by the following formula (2) and an acrylic (Acryl) additive represented by the following formula (6-1),
Manufactured through solvent casting method,
When prepared by the method, the amount of the additive added is 1 to 10% by weight based on 100% by weight of the main dope containing the acrylic resin, the additive, and a solvent,
Acrylic film characterized in that the glass transition temperature (Tg) is 94 ° C or higher, and the residual solvent amount is 200 to 2400 ppm:
[Formula 2]

[Formula 6-1]

In Formula 2, m, n, and l are each 1 or more, and in Formula 6-1, n is 1 or more.
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