KR20170000668A - Hard Coating Composition and Hard Coating Film Using the Same - Google Patents

Abstract

The present invention provides a hard coating composition for a flexible display comprising a silica sol containing nanosilica in a form of a chain, a photocurable resin, a photoinitiator and a solvent, a hard coating film formed by using the same, and a flexible display provided with the hard coating film. The hard coating film according to the present invention has high hardness and excellent flexibility as well as excellent adhesion and excellent optical characteristics.

Description

[0001] The present invention relates to a hard coating composition and a hard coating film using the same,

The present invention relates to a hard coating composition and a hard coating film using the same, and more particularly, to a hard coating composition having excellent hardness and flexibility and a hard coating film formed using the composition and a flexible display having the hard coating film. .

The hard coating film is used for surface protection for image display devices such as a liquid crystal display device, an electroluminescence (EL) display device, a plasma display (PD), and a field emission display (FED).

In recent years, a flexible display capable of maintaining the display performance even if bent like paper by using a flexible material such as plastic instead of a conventional glass substrate has rapidly emerged as a next generation display device, and has a high hardness There is a demand for a hard coating film which is not only excellent in scratch resistance but also does not cause a curl phenomenon at the edge of the film during the production process or use and has appropriate flexibility and does not generate cracks.

Korean Patent Laid-Open Publication No. 2008-0062355 discloses a process for producing a silica particle, which comprises blending a surface hydroxyl group of silica particles with an organic-inorganic silica particle chemically bonded with a polyfunctional silane compound containing a polyfunctional (meth) acrylate, a polyfunctional (meth) , And a solvent, and that the hard coat film produced therefrom has a high hardness and can suppress the peeling and curling phenomenon.

However, the hard coating composition has insufficient hardness and flexibility to be applied to a flexible display.

Korean Patent Publication No. 2008-0062355

It is an object of the present invention to provide a hard coating composition for a flexible display which can be used for producing a hard coating film having excellent hardness and flexibility.

It is another object of the present invention to provide a hardcoat film formed using the hardcoat composition.

It is still another object of the present invention to provide a flexible display provided with the hard coating film.

On the other hand, the present invention provides a hard coating composition for a flexible display comprising a silica sol containing nanosilica in the form of a chain, a photocurable resin, a photoinitiator and a solvent.

In one embodiment of the present invention, the nanosilica may have a diameter of 5 to 15 nm and a length of 40 to 100 nm.

In one embodiment of the present invention, the silica sol is a colloidal form in which the nanosilica is dispersed in an organic solvent.

In one embodiment of the present invention, the organic solvent may be methyl ethyl ketone.

On the other hand, the present invention provides a hard coating film for a flexible display formed using the hard coating composition.

On the other hand, the present invention provides a flexible display provided with the hard coating film.

The hard coating film formed using the hard coating composition according to the present invention has excellent hardness and flexibility as well as excellent adhesiveness and optical characteristics and can be effectively used in a flexible display.

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

An embodiment of the present invention relates to a hard coating composition for a flexible display comprising a silica sol containing nanosilica in the form of a chain, a photocurable resin, a photoinitiator and a solvent.

In one embodiment of the present invention, the silica sol contains nanosilica in the form of an elongated chain having a diameter of 5 to 15 nm and a length of 40 to 100 nm. The silica sol can contain nanosilica in the form of an elongated chain to give the hard coating composition excellent flexibility with sufficient hardness.

The silica sol may be in a colloidal form in which the nanosilica as described above is dispersed in an organic solvent. Examples of the organic solvent include alcohols such as methanol and isopropanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and methyl ethyl ketone is preferred because it improves the adhesion of the hard coating film.

Such a silica sol can be prepared by a method known in the art or commercially available. In the case of commercially available products, nanosilica dispersed in an organic solvent in a concentration of 20 to 60% by weight can be used. Examples thereof include isopropanol silica sol (IPA-ST-UP, NISSAN CHEMICAL, (MEK-ST-UP, NISSAN CHEMICAL, diameter: 9-15 nm, length: 40-100 nm). These may be used alone or in combination of two or more.

The silica sol may be contained in an amount of 10 to 60% by weight, preferably 20 to 40% by weight based on 100% by weight of the total hard coat composition. If it is less than 10% by weight, mechanical properties such as abrasion resistance, scratch resistance and pencil hardness may not be sufficient, and if it exceeds 60% by weight, defective appearance and flexibility may be deteriorated.

In one embodiment of the present invention, the photocurable resin may comprise a photocurable (meth) acrylate oligomer and / or a monomer.

As the photo-curable (meth) acrylate oligomer, epoxy (meth) acrylate, urethane (meth) acrylate and the like are generally used, and urethane (meth) acrylate is more preferable. The urethane (meth) acrylate can be prepared by reacting a polyfunctional (meth) acrylate having a hydroxyl group in the molecule with a compound having an isocyanate group in the presence of a catalyst.

The multifunctional (meth) acrylate having a hydroxyl group in the molecule may be at least one selected from the group consisting of 2-hydroxyethyl (meth) acrylate, 2-hydroxyisopropyl (meth) acrylate, 4-hydroxybutyl (Meth) acrylate mixture, and a mixture of dipentaerythritol penta / hexa (meth) acrylate.

The isocyanate group-containing compound may be at least one compound selected from the group consisting of 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 1,8-diisocyanatooctane, 1,12-diisocyanatododecane, (Isocyanatomethyl) cyclohexane, trans-1,4-cyclohexene diisocyanate, 4,4'-methylene (isocyanatoethyl) isocyanate, Bis (cyclohexyl isocyanate), isophorone diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, xylene-1,4-diisocyanate, tetramethyl xylene- (Isocyanate) derived from isocyanate, 1-chloromethyl-2,4-diisocyanate, 4,4'-methylenebis (2,6-dimethylphenylisocyanate), 4,4'- Trifunctional isocyanate, and trimethane propanol adduct. Toluene diisocyanate From the group true luer may be one or more selected.

The monomer may be one used in the art and specifically includes a compound having an unsaturated group such as a photocurable functional group such as a (meth) acryloyl group, a vinyl group, a styryl group or an allyl group, preferably a (meth) acryloyl group, A compound having an acryloyl group.

Examples of the monomer having a (meth) acryloyl group include neopentyl glycol acrylate, 1,6-hexanediol (meth) acrylate, propylene glycol di (meth) acrylate, triethylene glycol di Acrylate, trimethylolpropane tri (meth) acrylate, trimethylol ethane tri (meth) acrylate, 1,2-propanediol di (meth) acrylate, (Meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tri (Meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (metha) acrylate, tripenta (Meth) acrylate such as erythritol tri (meth) acrylate, tripentaerythritol hexa tri (meth) acrylate, bis (2-hydroxyethyl) isocyanurate di (meth) acrylate, (Meth) acrylate, tetrahydrofurfuryl (meth) acrylate, phenoxybutyl (meth) acrylate, isobutyl (meth) acrylate, isooctyl (Meth) acrylate, isobonol (meth) acrylate, and isobonole (meth) acrylate.

The photocurable resin may be contained in an amount of 20 to 90% by weight, preferably 30 to 60% by weight based on 100% by weight of the entire hard coating composition. If it is less than 20% by weight, it may be difficult to increase the coating thickness, and it may be difficult to secure sufficient mechanical properties. If the amount is more than 90% by weight, the coating property may be considerably deteriorated, resulting in poor appearance and difficulty in ensuring thickness uniformity.

In one embodiment of the present invention, the photoinitiator may be used without limitation as long as it is used in the technical field. Specifically, it is preferable to use 2-methyl-1- [4- (methylthio) phenyl] 2-morpholinopropanone-1, diphenyl ketone benzyl dimethyl ketal, 2- , 4-hydroxycyclophenyl ketone, dimethoxy-2-phenylacetophenone, anthraquinone, fluorene, triphenylamine, carbazole, 3-methylacetophenone, At least one selected from the group consisting of acetophenone, 4,4-diaminobenzophenone, 1-hydroxycyclohexyl phenyl ketone and benzophenone can be used.

The photoinitiator may be included in an amount of 0.1 to 10% by weight based on 100% by weight of the entire hard coating composition. When the content of the photoinitiator is less than 0.1% by weight, the curing rate is slow. When the content of the photoinitiator is more than 10% by weight, excessive cracking may occur in the hard coat layer.

In one embodiment of the present invention, the solvent can be used without limitation as long as it is used in the technical field. Specific examples of the solvent include alcohols such as methanol, ethanol, isopropanol and butanol, cellosolves such as methylcellulose and ethylcellosolve, ketones such as methylethylketone, methylbutylketone, methylisobutylketone, diethyl Hexane, heptane, and octane), benzene (benzene, toluene, xylene, etc.), and the like can be used. These solvents may be used alone or in combination of two or more.

The solvent may be contained in an amount of 10 to 80% by weight, preferably 30 to 60% by weight based on 100% by weight of the total hard coat composition. If the content is less than 10% by weight, the viscosity is high and the workability is poor. When the content is more than 80% by weight, a long time is required in the drying and curing process, and it is difficult to form a high thickness when a hard coating film is formed.

The hard coating composition according to one embodiment of the present invention may contain, in addition to the above-mentioned components, components commonly used in the art such as leveling agents, ultraviolet stabilizers, heat stabilizers, antioxidants, surfactants, And the like may be additionally included.

The leveling agent may be used to impart smoothness and coatability of the coating film when the hard coating composition is coated. Examples of the leveling agent include BYK-323, BYK-331, BYK-333, and BYK-333 manufactured by BYK Corporation, TEGO Glide 411, TEGO Glide 415, TEGO Glide 420, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 440, TEGO Glide 412, BYK- Glide 450, TEGO Glide 455, TEGO Rad 2100, TEGO Rad 2200N, TEGO Rad 2250, TEGO Rad 2300, TEGO Rad 2500, 3M FC-4430 and FC-4432. The leveling agent is preferably used in a range of 0.1 to 1% by weight based on 100% by weight of the entire hard coating composition.

One embodiment of the present invention relates to a hard coating film for a flexible display formed using the hard coating composition described above. The hard coating film according to an embodiment of the present invention is characterized in that a coating layer containing a cured product of the hard coating composition described above is formed on one side or both sides of the transparent substrate.

The transparent substrate may be formed of a rigid or flexible material commonly used in the art. For example, polyether sulfone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethylenenaphthalate (PEN), polyethyelene terephthalate (PET) (PPS), polyphenylene sulfide (PPS), polyallylate, polyimide (PI), polycarbonate (PC), cellulose triacetate (TAC), cellulose acetate propionate cellulose acetate propionate) may be used.

The thickness of the transparent substrate is not particularly limited, but may be 10 to 1000 탆, specifically 20 to 150 탆. If the thickness of the transparent base material is less than 10 탆, the strength of the film is lowered and the workability is deteriorated. If the thickness is more than 1000 탆, the transparency is decreased or the weight of the hard coating film is increased.

The hard coating film according to one embodiment of the present invention can be produced by applying the hard coating composition of the present invention to one side or both sides of a transparent substrate and curing to form a coating layer.

The hard coating composition according to an embodiment of the present invention may be coated on a transparent substrate by appropriately using a known method such as die coater, air knife, reverse roll, spray, blade, casting, gravure, microgravure, ) Is possible.

After the hard coating composition is applied to the transparent substrate, volatiles are evaporated at a temperature of 30 to 150 ° C for 10 seconds to 1 hour, more specifically for 30 seconds to 30 minutes, And cured. The irradiation amount of the UV light may be about 0.01 to 10 J / cm 2, and more specifically, about 0.1 to 2 J / cm 2.

At this time, the thickness of the formed coating layer may be specifically 2 to 30 탆, more specifically 3 to 20 탆. When the thickness of the coating layer is within the above range, an excellent hardness effect can be obtained.

One embodiment of the present invention relates to a flexible display provided with the above-mentioned hard coating film. For example, the hard coating film of the present invention can be attached to a window of a flexible display.

The hard coating film according to one embodiment of the present invention can be used in reflective, transmissive, semi-transmissive LCD or various driving LCDs such as TN type, STN type, OCB type, HAN type, VA type and IPS type. The hard coating film according to one embodiment of the present invention can also be used in various image display devices such as a plasma display, a field emission display, an organic EL display, an inorganic EL display, and an electronic paper.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. It should be apparent to those skilled in the art that these examples, comparative examples and experimental examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example  One:

25 wt% of isopropanol silica sol (IPA-ST-UP, NISSAN CHEMICAL, diameter 9-15 nm, length 40-100 nm) as a silica sol, 15 wt% of a 10-functional urethane acrylate oligomer (UV1000, Shin- A mixture of 18.5 wt% of a functional monomer (M340, MIRAMER), 1.2 wt% of a photoinitiator (I-184, BASF), 0.3 wt% of a leveling agent (BYK-3530, BYK) and 40 wt% of methyl ethyl ketone (MEK) A composition was prepared.

Example  2:

A hard coating composition was prepared in the same manner as in Example 1, except that methyl ethyl ketone silica sol (MEK-ST-UP, NISSAN CHEMICAL, diameter: 9-15 nm, length 40-100 nm) .

Comparative Example  One:

A hard coat composition was prepared in the same manner as in Example 1, except that spherical isopropanol silica sol (IPA-ST, NISSAN CHEMICAL, particle diameter: 10-15 nm) was used as the silica sol.

Comparative Example  2:

A hard coat composition was prepared in the same manner as in Example 1, except that spherical methyl ethyl ketone silica sol (MEK-ST, NISSAN CHEMICAL, particle diameter: 10-15 nm) was used as the silica sol.

Experimental Example  One:

The hard coating compositions prepared in the above Examples and Comparative Examples were dried on one side of a polyimide (PI) film (80 μm), coated to a thickness of 20 μm, dried in an oven at 80 ° C. for 1 minute, And hardened at a light quantity of 350 mJ / cm < 2 > to produce a hard coating film.

The physical properties of the thus-prepared hard coating film were measured by the following method, and the results are shown in Table 1 below.

(1) Pencil Hardness

The pencil hardness was measured by applying a load of 750 g using a pencil hardness tester (PHT, Kobo Scientific Co., Ltd.). The pencil was made using Mitsubishi products and was performed five times per pencil hardness. If two or more pieces of gas were judged to be defective.

<Evaluation Criteria>

Kiss 0: OK

Kiss 1: OK

Gas 2 or higher: NG

(2) Adhesion

11 straight lines were drawn on the coated surface of the film at intervals of 1 mm to form 100 squares, and then peel test was performed three times using a tape (CT-24, Nichii Co., Ltd.). Three 100 squares were tested and the average was recorded. The adhesion was recorded as follows.

Adhesion = n / 100

n: the number of rectangles that are not to be peeled out of the entire rectangle

100: total number of squares

Therefore, when none of them were peeled off, 100/100 was recorded.

(3) Transmittance and Hayes

Haze and total transmittance were measured using a spectrophotometer (HZ-1, Nihon Sagasa).

(4) Flexibility

The hard coating compositions prepared in the above Examples and Comparative Examples were coated on a triacetylcellulose (TAC) film (40 mu m) to evaluate the flexural properties, followed by drying and curing to prepare hard coat films.

Then, each of the mandrel having a diameter of 6 mm and a thickness of 4 mm was visually checked whether a crack occurred in the film when the coating layer of the hard coating film was bent outward. This bending process was repeated 200,000 times.

As can be seen in Table 1 above, the hard coat film prepared using the hard coat compositions of Examples 1 and 2, including nanosilica particles in the form of elongated chains, was comparable to Comparative Example 1 comprising spherical nanosilica particles And 2 as compared with the hard coating film prepared using the hard coating composition. In particular, the hard coat film prepared using the hard coat composition of Example 2 using methyl ethyl ketone as the dispersion solvent of the nanosilica particles was prepared using the hard coat composition of Example 1 using isopropanol as the dispersion solvent of the nanosilica particles The adhesion was excellent as compared with the hard coating film to be produced.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

Claims (8)

A hard coating composition for a flexible display comprising a silica sol containing nanosilica in the form of a chain, a photocurable resin, a photoinitiator and a solvent. The hard coating composition according to claim 1, wherein the nanosilica has a diameter of 5 to 15 nm and a length of 40 to 100 nm. The hard coating composition according to claim 1, wherein the silica sol is in a colloidal form in which the nanosilica is dispersed in an organic solvent. The hard coating composition of claim 3, wherein the organic solvent is isopropanol or methyl ethyl ketone. 5. The hard coating composition of claim 4, wherein the organic solvent is methyl ethyl ketone. The hard coat composition according to claim 1, wherein the silica sol is contained in an amount of 10 to 60% by weight based on 100% by weight of the entire hard coat composition. A hard coating film for a flexible display formed using the hard coating composition according to any one of claims 1 to 6. A flexible display comprising the hard coating film according to claim 7.