KR20140002308A - Water dispersion composition and optical film using thereof - Google Patents

Abstract

The present invention relates to a water dispersion composition and an optical film using thereof, more specifically to: a water dispersion composition which has high refractive index, reduced rainbow phenomena, and excellent adhesive properties at a high temperature and in a high humidity; and an optical film using thereof. The water dispersion composition contains a first water dispersion composition and a second water dispersion composition.

Description

Aqueous dispersion composition and optical film using same {WATER DISPERSION COMPOSITION AND OPTICAL FILM USING THEREOF}

The present invention relates to an aqueous dispersion composition and an optical film using the same, the refractive index is high, the rainbow phenomenon is improved, and the adhesive composition under high temperature and high humidity, and an optical film coated with the same.

In general, biaxially stretched polyester films have excellent dimensional stability, thickness uniformity, and optical transparency, and thus are widely used for various industrial materials as well as display devices.

When using such a biaxially stretched polyester laminated film for optical use, the primer layer generally forms a primer layer from the copolyester-type resin excellent in adhesiveness with a polyester film. However, when the copolyester-based resin is used alone, the adhesion with the polyester base film is sufficient, but when used after various post-processing treatments such as a prism lens, an antireflection layer, or a hard coating layer, the copolyester-based resin is used. Insufficient In order to compensate for this, it is excellent in easily adhesiveness, flexibility and abrasion resistance when producing polyester, and has a strong adhesiveness, so that the adhesive layer is improved by coating a primer layer using a polyurethane-based resin which is used in many fields requiring adhesiveness. How to make is studied. However, by forming a primer layer made of a polyurethane resin, the adhesive strength with the outer layer such as the hard coat layer is improved, but the adhesive force with the polyester film as the base material is not sufficient, resulting in sufficient adhesiveness with the outer layer. There was a problem not to lose.

In addition, as one of the evaluation methods of the adhesion after the post-processing treatment, when the moisture resistance evaluation of the high temperature and high humidity at 65 ℃, 90% humidity conditions, the poor adhesion due to the moisture penetration into the back surface after the post-processing treatment occurs, to compensate for Research is also in progress.

In order to overcome the above problems, Korean Patent No. 10-1050216 attempts to improve durability by forming a polymer network by applying a crosslinking agent.

Korea Patent Registration 10-1050216 (2011.07.12)

An object of the present invention is to provide an aqueous dispersion composition having excellent adhesion at high temperature and high humidity, a high refractive index and low glass transition temperature, and an optical film coated with the aqueous dispersion composition.

In addition, the present invention is to provide an aqueous dispersion composition having excellent adhesive strength and improved rainbow phenomenon and optical properties by increasing the crosslinking density without using a crosslinking agent and an optical film coated with the aqueous dispersion composition.

Specifically, the present invention is to provide a polyester optical film having no primer, cracks, domains on the surface of the film during the film, in particular, the optical properties such as the rainbow phenomenon is improved, excellent adhesion at high temperature and high humidity.

The present invention is a water dispersion composition comprising a mixture of the first water dispersion composition and the second water dispersion composition,

The first water dispersion composition comprises a water-dispersible polyurethane resin consisting of 10 to 75% by weight of a linear polymer having two terminal groups and 25 to 90% by weight of a branched polymer having three or more terminal groups,

The second water dispersion composition is 20 to 40 mol% of 2,6-naphthalenedicarboxylic acid, 1 to 10 mol% of aromatic dicarboxylic acid containing sulfonate, 1 to 10 mol% of aromatic dicarboxylic acid, Polycondensation of 10-30 mol% of bis [4 (2-hydroxyethoxy) phenyl] fluorene of Formula 1, 1-10 mol% of triglyceride compounds represented by the following Formula 2, and 30-60 mol% of diol compounds Ester resins.

[Formula 1]

(2)

(In Formula 2, R ₁ to R ₃ are each independently selected from (C 1 -C 30) alkyl including or without hydrogen, unsaturated hydrocarbons.)

In addition, in the water dispersion composition of the present invention, the water dispersion composition is 5 to 10% by weight of the mixture of the first and second dispersion composition, 0.1 to 0.5% by weight of the silicone-based wetting agent, 0.1 to 0.5 weight of the colloidal silica particles % And the balance of water.

In addition, in the water dispersion composition of the present invention, the mixture of the first water dispersion composition and the second water dispersion composition may be a mixture of the first water dispersion composition: the second water dispersion composition 1: 1 to 5: 5: 5 by weight. .

In addition, in the water dispersion composition of the present invention, the first water dispersion composition may be a solid content of 10 to 30% by weight, including the water-dispersible polyurethane resin and water.

In addition, in the water dispersion composition of the present invention, the linear polymer of the first water dispersion composition may be a part or all of the terminal group is blocked with an inorganic acid salt group.

In addition, in the water dispersion composition of the present invention, the water-dispersible polyurethane resin of the first water dispersion composition reacts 39 to 45% by weight of polyol, 0.3 to 1.2% by weight of trimethylol propane and 50 to 57% by weight of isocyanate compound to form isocyanate. After preparing the prepolymer having an end group, the inorganic acid may be prepared by blocking 3 to 4% by weight of an ionic group at an isocyanate terminal.

In addition, in the water dispersion composition of the present invention, the water-dispersible polyurethane resin may have a weight average molecular weight of 10,000 ~ 20,000.

In addition, in the water dispersion composition of the present invention, the second water dispersion composition may be a solid content of 10 to 40% by weight, including the polyester resin and water.

In addition, in the water dispersion composition of the present invention, the aromatic dicarboxylic acid is dimethyl terephthalate, terephthalic acid, isophthalic acid, 1,2-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid Any one or a mixture of two or more selected from leric acid, 1,3-cyclopentane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid, and the aromatic dicarboxylic acid including the sulfonate is sodium 2, Any one or a mixture of two or more selected from 5-dicarboxybenzenesulfonate, 5-sulfone isophthalic acid, 2-sulfone isophthalic acid, 4-sulfone isophthalic acid, 4-sulfone naphthalene-2,6-dicarboxylic acid, The diol compound is ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, propylene glycol, tripropylene glycol, 1,3-propane diol, 1,3-butane di , It may be any one or a mixture of two or more selected from propane diol, bisphenol A, bisphenol B.

In addition, in the water dispersion composition of the present invention, the polyester resin of the first water dispersion composition may have a refractive index of 1.58 to 1.64 and a glass transition temperature of 40 to 60 ° C.

In addition, in the water dispersion composition of the present invention, the colloidal silica particles may have an average particle diameter of 50 ~ 1000nm.

In addition, in the water dispersion composition of the present invention, the water dispersion composition may have a refractive index of 1.57 ~ 1.62.

In addition, the present invention is also included in the scope of the present invention an optical film comprising a primer coating layer formed by applying the aqueous dispersion composition.

In the optical film of the present invention, the optical film may include a polyester base film and a primer coating layer formed by coating the water dispersion composition on one or both surfaces thereof.

In addition, in the optical film of the present invention, the dry coating thickness of the primer coating layer may be 50 ~ 100 nm.

The aqueous dispersion composition according to the present invention has a high refractive index, excellent moisture resistance under high temperature and high humidity, and has an effect of improving the rainbow phenomenon.

In addition, the optical film according to the present invention can adjust the refractive index and adhesive force by adjusting the content ratio of the first and second dispersion composition, and when applying the coating composition by the in-line process, by the stretching process The coating thickness can be adjusted to the advantage of the process.

In addition, the refractive index can be adjusted to improve the rainbow phenomenon, and by introducing a prepolymer having a trifunctional group of the polyurethane composition to increase the crosslinking density, there is an effect excellent in moisture resistance under high temperature and high humidity.

The inventors of the present invention are excellent in the adhesive strength with the polyester base film, and researched to introduce a primer layer with controlled interference fringe, polyester resin emulsion of the same series in order to increase the adhesive force with the polyester film as the base film In this case, in order to control the interference fringes to prepare a polyester emulsion having a refractive index of 1.57 ~ 1.62.

In order to increase the adhesive force to the composition, when forming the composition using a water-dispersible polyurethane resin having at least three isocyanate functional groups as terminal groups in the primer layer and blocked with metal ions, the rainbow properties are excellent, and high temperature and high humidity. Moisture resistance is improved under severe conditions of the present invention was confirmed that the excellent adhesion to the optical polymer substrate film, such as a hard coating film during post-processing to complete the present invention.

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

The present invention relates to a water dispersion composition comprising a mixture of a first water dispersion composition for adjusting the refractive index and a second water dispersion composition to improve moisture resistance under severe conditions of high temperature and high humidity so as to have excellent adhesion.

More specifically, an aspect of the present invention is a water dispersion composition comprising a mixture of the first water dispersion composition and the second water dispersion composition,

The first water dispersion composition comprises a water-dispersible polyurethane resin consisting of 10 to 75% by weight of a linear polymer having two terminal groups and 25 to 90% by weight of a branched polymer having three or more terminal groups,

The second water dispersion composition is 20 to 40 mol% of 2,6-naphthalenedicarboxylic acid, 1 to 10 mol% of aromatic dicarboxylic acid containing sulfonate, 1 to 10 mol% of aromatic dicarboxylic acid, Polycondensation of 10-30 mol% of bis [4 (2-hydroxyethoxy) phenyl] fluorene of Formula 1, 1-10 mol% of triglyceride compounds represented by the following Formula 2, and 30-60 mol% of diol compounds Ester resins.

[Formula 1]

(2)

(In Formula 2, R ₁ to R ₃ are each independently selected from (C 1 -C 30) alkyl including or without hydrogen, unsaturated hydrocarbons.)

More specifically, in one embodiment of the present invention, the silicone-based wetting agent and colloidal silica particles may be further used as an additive to facilitate heat-resistant processing on the coating and primer layers on the optical polymer substrate film.

More specifically, in one embodiment of the present invention, the water dispersion composition is 5 to 10% by weight of the mixture of the first and second water dispersion composition, 0.1 to 0.5% by weight silicone-based wetting agent, 0.1 to 0.5 colloidal silica particles Weight percent and balance water.

In one aspect of the present invention, the aqueous dispersion composition may further include a hydrophilic organic solvent and a surfactant as needed to increase dispersion stability.

As the hydrophilic organic solvent, dioxane, acetone, tetrahydrofuran, methyl ethyl ketone, or the like can be used. As the surfactant, anionic surfactants or nonionic surfactants can be used to improve dispersion stability. Preferably 0.1 to 5% by weight is used.

In addition, in one aspect of the present invention, it is preferable that the mixture of the first and second water dispersion compositions is mixed in a weight ratio of 1: 9 to 5: 5 by weight of the first water dispersion composition and the second water dispersion composition. . Compared to the case where the first water dispersion composition and the second water dispersion composition are used, the mixture and the refractive index can be easily adjusted, and the optical properties such as the rainbow phenomenon can be improved. When the mixing ratio of the first water dispersion composition is less than 1 weight ratio, the effect of improving the adhesive strength is insignificant, and when using more than 5 weight ratios, the effect of improving the rainbow phenomenon may be reduced.

It is preferable to use 5 to 10% by weight of the mixture of the first water dispersion composition and the second water dispersion composition in the total water dispersion composition. The coating property is good at less than 5% by weight, it is difficult to implement the adhesive force, when more than 10% by weight may be excellent adhesion but difficult to implement the appearance and transparency of the coating.

The silicon-based wetting agent is preferably used 0.1 to 0.5% by weight,

The colloidal silica particles preferably contain 0.1 to 0.5% by weight. In addition, the colloidal silica particles are preferably used having an average particle diameter of 50 ~ 1000 nm. If the thickness is less than 50 nm, the antiblocking agent may not be expected. If the thickness is more than 1000 nm, optical properties may be degraded due to haze increase.

In one embodiment of the present invention, the first water dispersion composition comprises water dispersible polyurethane resin and water consisting of 10 to 75% by weight of a linear polymer having two terminal groups and 25 to 90% by weight of a branched polymer having three or more terminal groups. Solid content may be 10 to 30% by weight. The linear polymer is a linear polyurethane resin, the branched polymer means a branched polyurethane resin.

The water-dispersible polyurethane resin is a branched polymer having at least three isocyanate functional groups as terminal groups, part or all of the isocyanate groups are blocked with an inorganic acid salt group, and more specifically, blocked with an inorganic salt such as sulfate, Two isocyanate functional groups are included, in which some or all of the isocyanate groups are blocked with inorganic acid groups, and more particularly include linear polymers blocked with inorganic salts such as sulfate.

The water-dispersible polyurethane resin is preferably used 10 to 75% by weight of the linear polymer and 25 to 90% by weight of the branched polymer. When the content of the branched polymer is less than 25% by weight, the swelling degree and the gel fraction cannot be satisfied, and it is difficult to obtain a coating film having excellent adhesion under high temperature and high humidity. In addition, when the content of the branched polymer exceeds 90% by weight, the viscosity rises rapidly due to excessive gelation, making it difficult to prepare the water dispersion composition, and defects in surface appearance such as cracking on the surface when coating on the film surface This can happen. In the present invention, the branched polymer means a resin having 3 or 3 or more isocyanate functional groups.

In the present invention, the water-dispersible polyurethane binder is easy to mix so that the solid content is 10 to 30% by weight, including the water-dispersible polyurethane resin and water, to control the thickness of the dry coating film when applied to the base film It is easy to

For example, a method of preparing the water-dispersible polyurethane resin may include preparing a prepolymer having an isocyanate as an end group by reacting 39 to 45 wt% of a polyol, 0.3 to 1.2 wt% of a trimethylol propane, and 50 to 57 wt% of an isocyanate compound. After the reaction, the inorganic acid may be prepared by blocking 3 to 4% by weight of an ionic group of sulfate at the isocyanate terminal, but is not limited thereto. When prepared by the above method, it is possible to produce a water-dispersible polyurethane resin mixed with a linear polyurethane resin and a branched polyurethane resin, 10 to 75% by weight of the linear polymer and 25 to 90% by weight of the branched polymer Water dispersible polyurethane resins can be prepared.

The water-dispersible polyurethane resin is preferred because it does not gelate in the range of the weight average molecular weight 10,000 ~ 20,000, can be obtained water dispersion and excellent coating properties at high temperature and high humidity.

The weight average molecular weight can be measured using a GPC-MALS (Multi Angle Light Scattering) system (Wyatt, Inc.), the configuration of the MALS system is as follows.

MALS system configuration

GPC; Water 1525 Binary HPLC Pump

RI detector; Optilab rex

MALS; Wyatt Dawn 8+

Column; PLgel 5㎛ Mixed-C (7.5mmΦ × 300mm) × 2 (Polymer Laboratories)

Mobile phase: DMF (50 mM LiCl)

-Flow rate: 0.5mL / min

Temperature: 50 ℃

Injection volume: 0.5%, 500µl

The polyol may be a polyester-based polyol or a polyether-based polyol, preferably a polyester-based polyol. Polyester-based polyols include polyols prepared from the reaction of carboxylic acid, sebacic acid or an acid anhydride with a polyhydric alcohol. The type of the polyol is not limited, and it is preferable to use a polyester polyol having a weight average molecular weight of 600 to 3000. Its content is preferably 39 to 45% by weight. When used at less than 39% by weight, the molecular weight is small, the primer layer is too hard, it is difficult to stretch, the coating appearance is not excellent, and when more than 45% by weight, the ILC layer is too soft (Soft) is poor blocking properties Can be.

The trimethylol propane is used to prepare a prepolymer having a trifunctional group, and it is preferable to use 0.3 to 1.2% by weight. In case of using less than 0.3% by weight, the crosslinking density decreases, and anti-blocking property is inferior, and in the case of using more than 1.2% by weight, the crosslinking density becomes too high and elongation deteriorates. This is not excellent and the adhesion may be bad.

The isocyanate compound is not limited but preferably hexamethylene diisocyanate is used. The content can be prepared a prepolymer having a trifunctional group in the range using 50 to 57% by weight.

The inorganic acid salt is preferably used sodium hydrogen sulfate (Sodium Hydrogen Sulfate), the content is preferably used 3 to 4% by weight.

In one embodiment of the present invention, the second water dispersion composition has a high refractive index and low glass transition temperature, so that no cracks or domains are generated on the surface of the film during stretching after film production, and in particular, it is used to express optical properties such as rainbow phenomenon. When using a polyester film as a base film, it is preferable that refractive index is 1.58-1.64 and glass transition temperature is 40-60 degreeC. When the refractive index is in the above range, the difference in refractive index with the polyester film, which is the base film, is small, so that light interference phenomenon (Rainbow phenomenon) may not occur. In addition, the glass transition temperature is 40 ~ 60 ℃ in the process of coating the aqueous dispersion composition before stretching when the polyester film is produced through the in-line process, and when subjected to the stretching and heat treatment process is sufficiently deteriorated may not cause turbidity in the film. .

In order to satisfy the refractive index and the glass transition temperature, the second aqueous dispersion composition is 20 to 40 mol% of 2,6-naphthalenedicarboxylic acid, 1 to 10 mol% of aromatic dicarboxylic acid including sulfonate, and aromatic dicar 10 to 30 mol% of an acid component containing 1 to 10 mol% of an acid, and a bis [4 (2-hydroxyethoxy) phenyl] fluorene of the formula (1), and a triglyceride compound represented by the following formula (2): Polyester resin which polycondensed the glycol component containing mol% and the diol compound 30-60 mol% is included.

[Formula 1]

(2)

(In Formula 2, R ₁ to R ₃ are each independently selected from (C 1 -C 30) alkyl including or without hydrogen, unsaturated hydrocarbons.)

The aromatic dicarboxylic acid is dimethyl terephthalate, terephthalic acid, isophthalic acid, 1,2-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 1,3-cyclo Any one or a mixture of two or more selected from pentane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid can be used.

The aromatic dicarboxylic acid including the sulfonate salt is sodium 2,5-dicarboxy benzene sulfonate 5-sulfoisophtalic acid, 2-sulfone isophthalic acid (2- one or more selected from sulfoisophtalic acid, 4-sulfoisophtalic acid, 4-sulfo naphtalene-2,6-dicarboxylic acid Mixtures can be used.

The diol compound is ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, propylene glycol, tripropylene glycol, 1,3-propane diol, 1,3-butane diol, propane diol , Bisphenol A, bisphenol B and the like can be used any one or a mixture of two or more.

In addition, the polyester resin in the present invention can satisfy the physical properties of the refractive index is 1.58 ~ 1.64, the glass transition temperature is 40 ~ 60 ℃.

In the present invention, the second water dispersion composition is a water dispersion emulsion containing 10 to 40% by weight of the polyester resin.

In the acid component of the present invention, the 2,6-naphthalenedicarboxylic acid is preferably used because it can increase the refractive index by containing two aromatic rings as shown in the following formula (3) as the dicarboxylic acid component.

(3)

The 2,6-naphthalenedicarboxylic acid is preferably used 20 to 40 mol%, when using less than 20 mol% it is difficult to give a high refractive index to the polyester resin, used in excess of 40 mol% This can be difficult to disperse.

In addition, the aromatic dicarboxylic acid containing the sulfonate is used to ensure dispersibility in water, but is not limited to sodium 2,5-dicarboxybenzenesulfonate, 5-sulfon isophthalic acid, sulfone One or a mixture of two or more selected from terephthalic acid, 4-sulfon naphthalene-2,6-dicarboxylic acid and the like can be used. More preferably, sodium 2,5-dicarboxybenzenesulfonate represented by the following general formula (4) is used. It is preferable to use 1 to 10 mol%, when using less than 1 mol%, the water dispersibility may be lowered, and when using more than 10 mol%, the hydrophilicity becomes stronger and the handleability becomes worse or Can cause blocking

[Chemical Formula 4]

In addition, the aromatic dicarboxylic acid means a dicarboxylic acid component except an aromatic dicarboxylic acid including 2,6-naphthalenedicarboxylic acid and sulfonate, and is not limited, but preferably dimethyl terephthalate, terephthalic acid , Isophthalic acid, 1,2-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 1,3-cyclopentane dicarboxylic acid, 1,4-cyclo Any one or a mixture of two or more selected from hexane dicarboxylic acids can be used. It is preferable to use 1 to 10 mol%, and when it is used below 1 mol%, it is difficult to increase the refractive index, and when it is used more than 10 mol%, it is difficult to disperse in water and when the film is manufactured due to the increase of the aromatic component Increased b value and decreased adhesion may occur.

In the present invention, in the glycol component, bis [4 (2-hydroxyethoxy) phenyl] fluorene of Chemical Formula 1 is used to exhibit high transparency while increasing refractive index, and 10 to 30 mol% is used. In the case of using less than 10 mol%, it is difficult to increase the refractive index, and in the case of using more than 30 mol%, dispersion in water is difficult.

[Formula 1]

In addition, the triglyceride compound represented by the following formula (2) has a glass transition temperature increases with the increase of the refractive index, surface cracks during coating and stretching after coating on the film surface improves the domain formation due to unmelting, uniform coating film and refractive index It is used to lower the glass transition temperature and to introduce the side chain of the long chain. It is preferable to use 1 to 10 mol%, and when it is used below 1 mol%, it may not lower T _g sufficiently, and when it is used more than 10 mol%, the refractive index may fall and blocking of a film may occur.

(2)

(In Formula 2, R ₁ to R ₃ are each independently selected from (C 1 -C 30) alkyl including or without hydrogen, unsaturated hydrocarbons.)

In addition, the diol compound is not limited, but specifically, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, propylene glycol, tripropylene glycol, 1,3- Any one or a mixture of two or more selected from propane diol, 1,3-butane diol, propane diol, bisphenol A, bisphenol B and the like can be used. It is preferable to use 30 to 60 mol%, when using less than 30 mol%, the esterification reaction is not sufficiently achieved, when using more than 60 mol%, blocking of the film occurs and the heat resistance is lowered, The refractive index may be lowered.

It is preferable that the polycondensation polyester resin which condensed the said components of this invention is 0.1-1.0, More preferably, it is 0.1-1.6. In the above range, the polyester resin may be dissolved or dispersed in water or an aqueous solvent to prepare a polyester emulsion.

The polyester resin of the present invention can be prepared according to a conventional polyester resin synthesis method, for example, 20 to 40 mol% of 2,6-naphthalenedicarboxylic acid, aromatic dicarboxylic acid containing sulfonate 1-10 mol% of an acid component containing 1-10 mol% of aromatic dicarboxylic acids, 10-30 mol% of bis [4 (2-hydroxyethoxy) phenyl] fluorene, and 1-10 mol of triglyceride compounds %, Glycol components containing 30 to 60 mol% of diol compounds are mixed in a solvent-free state, put into a reactor, and the esterification reaction proceeds while removing water or methanol, which is a byproduct produced by heating. Thereafter, the polycondensation reaction proceeds while the temperature is raised and the pressure in the reactor is reduced under pressure to recover the diol component as a byproduct.

At this time, a catalyst for promoting a polycondensation reaction, for example, an esterification catalyst, a transesterification catalyst, a polycondensation catalyst and the like can be used, and various additives such as stabilizers and inorganic particles can be added.

In one embodiment of the present invention, the water dispersion composition may have a refractive index of 1.57 to 1.62 of the mixture of the first water dispersion composition and the second water dispersion composition. When the refractive index is applied to the polyester base film within the above range can improve the rainbow improvement effect and optical properties.

Still another aspect of the present invention relates to an optical film comprising a primer coating layer formed by applying the water dispersion composition.

The optical film according to an aspect of the present invention may include a polyester base film and a primer coating layer formed by applying the water dispersion composition to one or both surfaces thereof. The dry coating thickness of the primer coating layer may be 50 ~ 100 nm.

In the optical film according to an aspect of the present invention, the base film is preferably a polyester film, more specifically, polyethylene terephthalate or polyethylene naphthalate film because it is excellent in light transmittance, and may include additives or particles. . The polyethylene terephthalate film is preferably a stretched film, it is possible to use a uniaxial or biaxially stretched film. The base film may have a thickness of 50 μm to 250 μm, but is not limited thereto.

In the optical film according to an aspect of the present invention, the primer layer is formed on one side or both sides of the optical polymer substrate film, and has excellent adhesiveness to facilitate adhesion to other substrates. Indicates the last name.

In the optical film according to an aspect of the present invention, the dry coating thickness of the primer layer is preferably from 50 to 100 nm. The coating method may be coated on an in-line coating applied to the surface during the stretching process of the polyester film, or may be off-line coating after film production. It is also possible to combine both. Preferably, in-line coating is applied at the same time as the film forming, and thus manufacturing cost is reduced, and the thickness of the coating layer may be changed by extension magnification.

In the optical film according to an aspect of the present invention, the primer coating layer has a swelling degree of 35 to 100, as measured by Equation 1 below, a gel fraction of 75 to 85, and a refractive index of 1.54 to 1 as measured by Equation 2 below. All properties of 1.62 can be satisfied.

[Formula 1]

Swelling degree = (Weight after leaving-initial weight) / initial weight × 100

(In the above formula, the weight after standing means the weight measured after soaking the dry coating film of about 1g in 50g of distilled water and left at 70 ℃ for 24 hours.)

[Formula 2]

Gel fraction = (Weight after drying-initial weight) × 100

(In the above formula, the weight after drying refers to the weight measured after soaking about 1g of the dry coating film in 50g of distilled water, and leaving it at 70 ° C. for 24 hours, and drying the left coating film at 120 ° C. for 3 hours.)

Hereinafter, the present invention will be described in detail with reference to the following examples. However, the present invention is not limited to the following examples.

The physical properties were measured by the following measurement method.

1. Measurement of Physical Properties of Coating Film

15 g of the mixture of the first water dispersion composition and the second water dispersion composition is placed in a round bowl having a diameter of 80 mm and a height of 15 mm, and dried at 65 ° C. for 72 hours and 120 ° C. for 3 hours. After dipping 1 g of the dry coating film in 50 g of distilled water, the film was left for 24 hours at 70 ° C., and the swelling ratio was measured. Gel Fraction is measured by drying the coated film for 3 hours at 120 ℃ and recording the weight.

1) Swelling Ratio: After dipping about 1g of dry coating film in 50g of distilled water and leaving it at 70 ℃ for 24 hours, take out the coating film and record the weight.

Swelling Ratio = (Weight after leaving-initial weight) / Initial weight * 100

2) Gel Fraction: After leaving the coating film at 120 ℃ for 3 hours, the weight is recorded.

 Gel Fraction = (Weight after drying / Initial weight) * 100

3) Tg measurement: Using a DSC (using PerkinElmer DSC 7) instrument, measure in 2nd Run mode. 10-11 mg dry coating is measured using PerkinElmer DSC7.

1st Run. = 0 ~ 200 ℃, 200 ℃ / min, Holding Time-3min // 200 ℃ ~ -40 ℃, 200 ℃ / min, Holding Time-5min

2nd Run. = -40 占 폚 to 200 占 폚, and 20 占 폚 / min.

2. Measurement of refractive index

The mixture of the first water dispersion composition and the second water dispersion composition was applied to a polycarbonate film, dried, and measured at room temperature using an ABBE refractometer (DR-M2, @ 550).

3. Total light transmittance measurement

The total light transmittance of the entire film was measured using a total light transmittance meter (NDH-5000, Nippon Denshoku).

10 samples of 5 cm width and width were sampled at 0.5 m intervals in the full width of the film, and the average value was measured.

4. Rainbow phenomenon measurement-1

Water dispersion composition according to Examples and Comparative Examples was applied to one surface of the polyester base film (188㎛ polyethylene terephthalate film) 200nm thickness to prepare an optical film, and then hard coating on one surface (refractive index 1.52) The other side was blackened to determine whether rainbows occurred with the naked eye. Visual evaluation was performed under a three-wavelength lamp in the dark room.

The evaluation criteria are as follows.

Top: Rainbow is not seen and uniform color

Medium: Rainbow phenomenon is soft and uniform color.

Bottom: Strong rainbow, strong color

5. Rainbow phenomenon measurement-2

Water dispersion composition according to Examples and Comparative Examples was applied to one surface of the polyester base film (188㎛ polyethylene terephthalate film) 200nm thickness to prepare an optical film, and then hard coating treatment (refractive index 1.52) on one surface thereof The other side was blackened to measure the reflection pattern of the visible region through UV-Visible (CARY 5000).

Phase: The ripple amplitude is reduced compared to the ripple amplitude in other wavelength ranges from 500 to 600 nm, and the ripple amplitude is less than 1%.

Medium: The ripple amplitude is reduced compared to the ripple amplitude in other wavelength bands from 500 to 600 nm, and the ripple amplitude is less than 3%.

Bottom: When the wavelength band where the ripple amplitude is reduced is not 500 to 600 nm, or when the wavelength where the amplitude is reduced is not visible

6. Coating appearance

When the film coated with the water dispersion composition according to Examples and Comparative Examples was transmitted through a three-wavelength lamp,

◎ If the transmitted light is transparent, it is judged as cloudiness.

7. Adhesion Evaluation (ASTM B905)

After manufacturing the optical film according to the Examples and Comparative Examples, after coating the hard coating composition on one surface coated with the coating composition, the adhesive strength at room temperature in 1cm X 1cm compartment using Cross Hatch Cutter (YCC-230 / 1) Draw 100 squares and use the Adhesive Evaluation Tape (nichban No. 405) to tear three times. In the high temperature and high humidity evaluation, after the high temperature hot water treatment (100 ° C., 10 min), the adhesive strength between the hard coating layer and the easily adhesive layer was evaluated by the above method.

8. Dry coating thickness measurement

The full width of the base film coated with the water dispersion composition according to Examples and Comparative Examples was designated at 5 points (1 point) at intervals of 1 m in the vertical direction (TD) of the machine direction, so that the cross section of the film was SEM (Hitachi S-4300). It was measured and magnified 50,000 times to calculate the average value after measuring 30 points in the interval.

9. Haze

Measured with Nippon Denshoku's NDH-5000

10 samples of 5 cm width and width were sampled at 0.5 m intervals in the full width of the film, and the average value was measured.

[Production Example 1]

Preparation of First Water Dispersion Composition

Theoretically, water-dispersed polyurethanes having a content of 50% by weight of branched polymers were prepared.

40 wt% of polyethyleneadipate diol, 0.6 wt% of trimethylol propane, and 55.9 wt% of hexamethylene diisocyanate were reacted to prepare a prepolymer having an isocyanate functional group as a prepolymer. 3.5 wt% of sodium hydrogen sulfate was reacted with an isocyanate, which is a terminal functional group of the prepolymer, to prepare a polyurethane having a weight average molecular weight of 14,400.

20 wt% of the polyurethane prepared above was dispersed in 80 wt% of water to prepare a first water dispersion composition having a solid content of 20 wt%.

[Production Example 2]

Preparation of Second Water Dispersion Composition

40 mol (26 mol%) of 2,6-naphtalene dicarboxly acid, 5 mol (3.3 mol%) of sodium 2,5-dicarboxylbenzene sulfonate ), 5 mol (3.3 mol%) of dimethyl terephthalic acid and 20 mol (13.3 mol%) of bis [4 (2-hydroxyethoxy) phenyl] fluorene, triglyceride (Triglyceride, product of KAO CORPORATION (trade name 85P)) 10 mol (6.6 mol%) and 70 mol (46.6 mol%) of ethylene glycol are mixed in the absence of solvent and put into the reactor to 1 ℃ per minute from 170 ℃ to 250 ℃ The reaction proceeds while the esterification reaction is carried out while removing by-product water or methanol, the temperature is raised to 260 ° C, and the pressure in the reactor is reduced to 1 mmHg to carry out the polycondensation reaction to recover the by-product diol to obtain an intrinsic viscosity of 1.0. Phosphorus polyester resin was prepared.

80 wt% of water was added to 20 wt% of the polyester resin prepared above, and dispersed to prepare a second water dispersion composition having a solid content of 20 wt%.

Example 1

1) Preparation of Water Dispersion Composition (1): The first and second water dispersion compositions are mixed at a weight ratio of 1: 9.

0.6 wt% of the first water dispersion composition prepared in Preparation Example 1, 5.4 wt% of the second water dispersion composition prepared in Preparation Example 2, and 0.3 wt% of the silicone-based wetting agent (Dow Corning, polyester siloxane copolymer). 0.3 wt% of colloidal silica particles having a particle diameter of 140 nm were added to water, followed by stirring for 2 hours to prepare an aqueous dispersion composition (1).

At this time, by mixing the first water dispersion composition and the second water dispersion composition in a weight ratio of 1: 9 to measure the physical properties of the coating film, the results are shown in Table 1 below.

2) Preparation of double coated polyester film

After the polyethylene terephthalate chip was removed from the moisture in the extruder and melt-extruded, a polyethylene terephthalate sheet having a thickness of 2000㎛ was prepared by quenching and solidifying with a casting drum having a surface temperature of 20 ℃. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Then, the water dispersion composition (1) was coated on both sides by a bar coating method (bar coating), the temperature was increased by 1 ℃ per second up to 110 ~ 150 ℃ by stretching and transversely (TD) 3.5 times in the transverse direction (TD). Thereafter, heat treatment was performed at 230 ° C. in a 5-stage tenter, and thermally fixed at 10 ° C. in the longitudinal and transverse directions at 200 ° C. to prepare a 188 μm biaxially oriented film coated on both sides. The dry coating thickness of the primer coating layer by the water dispersion composition (1) was 100 nm.

The physical properties of the prepared optical film were measured and shown in Table 2 below.

[Example 2]

1) Preparation of Water Dispersion Composition (2): Mixing the First Water Dispersion Composition and the Second Water Dispersion Composition in a 2: 8 Weight Ratio

1.2 wt% of the first water dispersion composition prepared in Preparation Example 1, 4.8 wt% of the second water dispersion composition prepared in Preparation Example 2, and 0.3 wt% of a silicone-based wetting agent (Dow Corning, polyester siloxane copolymer). 0.3 wt% of colloidal silica particles having a particle diameter of 140 nm were added to water, followed by stirring for 2 hours to prepare an aqueous dispersion composition (2).

At this time, the physical properties of the coating film was measured by mixing the first water dispersion composition and the second water dispersion composition in a weight ratio of 2: 8, and the results are shown in Table 1 below.

2) Preparation of double coated polyester film

After the polyethylene terephthalate chip was removed from the moisture in the extruder and melt-extruded, a polyethylene terephthalate sheet having a thickness of 2000㎛ was prepared by quenching and solidifying with a casting drum having a surface temperature of 20 ℃. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Thereafter, the water dispersion composition 2 was coated on both sides by a bar coating method, and heated to 1 ° C. per second to 110 to 150 ° C., followed by preheating and drying, and stretched 3.5 times in the transverse direction (TD). Thereafter, heat treatment was performed at 230 ° C. in a 5-stage tenter, and thermally fixed at 10 ° C. in the longitudinal and transverse directions at 200 ° C. to prepare a 188 μm biaxially oriented film coated on both sides. The dry coating thickness of the primer coating layer by the water dispersion composition (2) was 100 nm.

The physical properties of the prepared optical film were measured and shown in Table 2 below.

[Example 3]

1) Preparation of Water Dispersion Composition (3): Mixing the First Water Dispersion Composition and the Second Water Dispersion Composition in a 3: 7 Weight Ratio

1.8 wt% of the first water dispersion composition prepared in Preparation Example 1, 4.2 wt% of the second water dispersion composition prepared in Preparation Example 2, and 0.3 wt% of a silicone-based wetting agent (Dow Corning, polyester siloxane copolymer) 0.3 wt% of colloidal silica particles having a particle diameter of 140 nm were added to water, followed by stirring for 2 hours to prepare an aqueous dispersion composition (3).

In this case, the physical properties of the coating film was measured by mixing the first water dispersion composition and the second water dispersion composition in a weight ratio of 7: 7, and the results are shown in Table 1 below.

2) Preparation of double coated polyester film

After the polyethylene terephthalate chip was removed from the moisture in the extruder and melt-extruded, a polyethylene terephthalate sheet having a thickness of 2000㎛ was prepared by quenching and solidifying with a casting drum having a surface temperature of 20 ℃. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Thereafter, the water dispersion composition 3 was coated on both sides by a bar coating method, and heated to 1 ° C. per second to 110 to 150 ° C., followed by preheating and drying, and stretched 3.5 times in the transverse direction (TD). Thereafter, heat treatment was performed at 230 ° C. in a 5-stage tenter, and thermally fixed at 10 ° C. in the longitudinal and transverse directions at 200 ° C. to prepare a 188 μm biaxially oriented film coated on both sides. The dry coating thickness of the primer coating layer by the water dispersion composition (3) was 100 nm.

The physical properties of the prepared optical film were measured and shown in Table 2 below.

Example 4

1) Preparation of Water Dispersion Composition (4): Mixing the First Water Dispersion Composition and the Second Water Dispersion Composition in a 4: 6 Weight Ratio

2.4 wt% of the first water dispersion composition prepared in Preparation Example 1, 3.6 wt% of the second water dispersion composition prepared in Preparation Example 2, and 0.3 wt% of a silicone-based wetting agent (Dow Corning, polyester siloxane copolymer). 0.3 wt% of colloidal silica particles having a particle diameter of 140 nm were added to water, followed by stirring for 2 hours to prepare an aqueous dispersion composition (4).

In this case, the physical properties of the coating film was measured by mixing the first water dispersion composition and the second water dispersion composition in a 4: 6 weight ratio, and the results are shown in Table 1 below.

2) Preparation of double coated polyester film

After the polyethylene terephthalate chip was removed from the moisture in the extruder and melt-extruded, a polyethylene terephthalate sheet having a thickness of 2000㎛ was prepared by quenching and solidifying with a casting drum having a surface temperature of 20 ℃. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Thereafter, the water dispersion composition 4 was coated on both sides by a bar coating method, and heated to 1 ° C. per second to 110 to 150 ° C., and stretched 3.5 times in a transverse direction (TD) through preheating and drying. Thereafter, heat treatment was performed at 230 ° C. in a 5-stage tenter, and thermally fixed at 10 ° C. in the longitudinal and transverse directions at 200 ° C. to prepare a 188 μm biaxially oriented film coated on both sides. The dry coating thickness of the primer coating layer by the water dispersion composition 4 was 100 nm.

The physical properties of the prepared optical film were measured and shown in Table 2 below.

[Example 5]

1) Preparation of Water Dispersion Composition (5): The first and second water dispersion compositions are mixed at a weight ratio of 5: 5.

3.0 wt% of the first water dispersion composition prepared in Preparation Example 1, 3.0 wt% of the second water dispersion composition prepared in Preparation Example 2, and 0.3 wt% of a silicone-based wetting agent (Dow Corning, polyester siloxane copolymer). 0.3 wt% of colloidal silica particles having a particle diameter of 140 nm were added to water, followed by stirring for 2 hours to prepare an aqueous dispersion composition (5).

At this time, the first water dispersion composition and the second water dispersion composition were mixed at a weight ratio of 5: 5 to measure physical properties of the coating film, and the results are shown in Table 1 below.

2) Preparation of double coated polyester film

After the polyethylene terephthalate chip was removed from the moisture in the extruder and melt-extruded, a polyethylene terephthalate sheet having a thickness of 2000㎛ was prepared by quenching and solidifying with a casting drum having a surface temperature of 20 ℃. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Thereafter, the water dispersion composition 5 was coated on both sides by a bar coating method, and heated to 1 ° C. per second to 110 to 150 ° C., followed by preheating and drying, and stretched 3.5 times in the transverse direction (TD). Thereafter, heat treatment was performed at 230 ° C. in a 5-stage tenter, and thermally fixed at 10 ° C. in the longitudinal and transverse directions at 200 ° C. to prepare a 188 μm biaxially oriented film coated on both sides. The dry coating thickness of the primer coating layer by the water dispersion composition (5) was 100 nm.

The physical properties of the prepared optical film were measured and shown in Table 2 below.

Comparative Example 1

1) Preparation of Water Dispersion Composition (6): Coating Composition Using First Water Dispersion Composition

6 wt% of the first aqueous dispersion composition prepared in Preparation Example 1, 0.3 wt% of a silicone-based wetting agent (Dow Corning, polyester siloxane copolymer), and 0.3 wt% of colloidal silica particles having an average particle diameter of 140 nm were added to water. After stirring for 2 hours to prepare a water dispersion composition (6).

At this time, the physical properties of the coating film was measured using the first water dispersion composition, and the results are shown in Table 1 below.

2) Preparation of double coated polyester film

After the polyethylene terephthalate chip was removed from the moisture in the extruder and melt-extruded, a polyethylene terephthalate sheet having a thickness of 2000㎛ was prepared by quenching and solidifying with a casting drum having a surface temperature of 20 ℃. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Thereafter, the water dispersion composition 6 was coated on both sides by a bar coating method, and heated to 1 ° C. per second to 110 to 150 ° C. and stretched 3.5 times in the transverse direction (TD) through preheating and drying. Thereafter, heat treatment was performed at 230 ° C. in a 5-stage tenter, and thermally fixed at 10 ° C. in the longitudinal and transverse directions at 200 ° C. to prepare a 188 μm biaxially oriented film coated on both sides. The dry coating thickness of the primer coating layer by the water dispersion composition (6) was 100 nm.

The physical properties of the prepared optical film were measured and shown in Table 2 below.

[Comparative Example 2]

1) Preparation of Water Dispersion Composition (7): Coating Composition Using Second Water Dispersion Composition

6 wt% of the second water dispersion composition prepared in Preparation Example 1, 0.3 wt% of silicone-based wetting agent (Dow Corning, polyester siloxane copolymer), and 0.3 wt% of colloidal silica particles having an average particle diameter of 140 nm were added to water. After stirring for 2 hours to prepare a water dispersion composition (7).

At this time, the physical properties of the coating film was measured using the second water dispersion composition, and the results are shown in Table 1 below.

2) Preparation of double coated polyester film

After the polyethylene terephthalate chip was removed from the moisture in the extruder and melt-extruded, a polyethylene terephthalate sheet having a thickness of 2000㎛ was prepared by quenching and solidifying with a casting drum having a surface temperature of 20 ℃. The prepared polyethylene terephthalate sheet was stretched 3.5 times at 80 DEG C in the machine direction (MD), and then cooled to room temperature. Thereafter, the water dispersion composition 7 was coated on both sides by a bar coating method, and heated to 1 ° C. per second to 110 to 150 ° C., followed by preheating and drying, and stretched 3.5 times in the transverse direction (TD). Thereafter, heat treatment was performed at 230 ° C. in a 5-stage tenter, and thermally fixed at 10 ° C. in the longitudinal and transverse directions at 200 ° C. to prepare a 188 μm biaxially oriented film coated on both sides. The dry coating thickness of the primer coating layer by the water dispersion composition 7 was 100 nm.

The physical properties of the prepared optical film were measured and shown in Table 2 below.

[Table 1]

As shown in the table, when the coating film is formed using the water dispersion composition according to the embodiment of the present invention, the refractive index is higher than 1.57 and the refractive index is high while the glass transition temperature is lower than 48 ℃, excellent moisture resistance Could know.

[Table 2]

As shown in the table, when the coating layer is formed on both sides of the polyester film using the water dispersion composition according to the embodiment of the present invention, the total light transmittance is excellent, 93% or more, low haze, excellent coating appearance And, the rainbow phenomenon is improved, it was confirmed that the adhesive strength is excellent.

Claims (16)

A water dispersion composition comprising a mixture of a first water dispersion composition and a second water dispersion composition,
The first water dispersion composition comprises a water-dispersible polyurethane resin consisting of 10 to 75% by weight of a linear polymer having two terminal groups and 25 to 90% by weight of a branched polymer having three or more terminal groups,
The second water dispersion composition is 20 to 40 mol% of 2,6-naphthalenedicarboxylic acid, 1 to 10 mol% of aromatic dicarboxylic acid containing sulfonate, 1 to 10 mol% of aromatic dicarboxylic acid, Polycondensation of 10-30 mol% of bis [4 (2-hydroxyethoxy) phenyl] fluorene of Formula 1, 1-10 mol% of triglyceride compounds represented by the following Formula 2, and 30-60 mol% of diol compounds A water dispersion composition comprising an ester resin.
[Chemical Formula 1]

(2)

(In Formula 2, R ₁ to R ₃ are each independently selected from (C 1 -C 30) alkyl including or without hydrogen, unsaturated hydrocarbons.) The method of claim 1,
The water dispersion composition comprises 5 to 10% by weight of the mixture of the first and second water dispersion composition, 0.1 to 0.5% by weight of the silicone-based wetting agent, 0.1 to 0.5% by weight of colloidal silica particles and the balance of water Phosphorus dispersion composition. 3. The method of claim 2,
The mixture of the first water dispersion composition and the second water dispersion composition is a water dispersion composition of the first water dispersion composition: the second water dispersion composition 1: 1 to 5: 5 by weight ratio. The method of claim 1,
The first water dispersion composition is a water dispersion composition containing a water content of the polyurethane resin and water, the solid content of 10 to 30% by weight. The method of claim 1,
The linear polymer of the first water dispersion composition is a part or all of the terminal group is blocked with an inorganic acid salt group dispersion composition. The method of claim 1,
The water-dispersible polyurethane resin of the first water dispersion composition is prepared by reacting 39 to 45% by weight of polyol, 0.3 to 1.2% by weight of trimethylol propane and 50 to 57% by weight of isocyanate compound to prepare a prepolymer having an isocyanate as a terminal group. , 3 to 4% by weight of the inorganic acid salt is prepared by dispersing the ionic group in the isocyanate terminal. The method according to claim 6,
The water-dispersible polyurethane resin has a weight average molecular weight of 10,000 ~ 20,000 water dispersion composition. The method of claim 1,
The second water dispersion composition has a solid content of 10 to 40% by weight, including the polyester resin and water. The method of claim 1,
The aromatic dicarboxylic acid is dimethyl terephthalate, terephthalic acid, isophthalic acid, 1,2-naphthalene dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 1,3-cyclo Pentane dicarboxylic acid, any one or a mixture of two or more selected from 1,4-cyclohexane dicarboxylic acid,
The aromatic dicarboxylic acid including the sulfonate salt is sodium 2,5-dicarboxybenzenesulfonate, 5-sulfon isophthalic acid, 2-sulfon isophthalic acid, 4-sulfon isophthalic acid, 4-sulfon naphthalene-2,6-dica Any one or a mixture of two or more selected from leric acids,
The diol compound is ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, propylene glycol, tripropylene glycol, 1,3-propane diol, 1,3-butane diol, propane diol , Bisphenol A, bisphenol B is any one or a mixture of two or more selected from water dispersion composition. The method of claim 1,
The polyester resin of the first water dispersion composition has a refractive index of 1.58 ~ 1.64, the glass transition temperature is 40 ~ 60 ℃ water dispersion composition. 3. The method of claim 2,
The colloidal silica particles have an average particle diameter of 50 ~ 1000nm water dispersion composition. The method of claim 1,
The aqueous dispersion composition has a refractive index of 1.57 ~ 1.62. An optical film comprising a primer coating layer formed by applying the water dispersion composition of any one of claims 1 to 12. 14. The method of claim 13,
The optical film comprises a primer coating layer formed by applying the aqueous dispersion composition on a polyester base film and one or both sides thereof. The method of claim 14,
Dry coating thickness of the primer coating layer is an optical film of 50 ~ 100 nm. 16. The method of claim 15,
The primer coating layer has an swelling degree of 35 to 100 measured by the following formula 1, an optical film having a gel fraction of 75 to 85 and a refractive index of 1.54 to 1.62 measured by the following formula 2.
[Formula 1]
Swelling degree = (Weight after leaving-initial weight) / initial weight × 100
(In the above formula, the weight after standing means the weight measured after soaking the dry coating film of about 1g in 50g of distilled water and left at 70 ℃ for 24 hours.)
[Formula 2]
Gel fraction = (Weight after drying-initial weight) × 100
(In the above formula, the weight after drying refers to the weight measured after soaking about 1g of the dry coating film in 50g of distilled water, and leaving it at 70 ° C. for 24 hours, and drying the left coating film at 120 ° C. for 3 hours.)