KR101948655B1 - Hard coating film and flexible display using the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard coating film, and more particularly, to a pressure-sensitive adhesive layer and a hard coating layer on a pressure-sensitive adhesive layer on one side or both sides of a transparent substrate film, And is capable of alleviating warpage and distortion caused by the high volume shrinkage ratio, as well as to a hard coating film excellent in shock absorption.

Description

TECHNICAL FIELD [0001] The present invention relates to a hard coating film and a flexible display using the same. BACKGROUND OF THE INVENTION [0002]

The present invention relates to a hard coating film which does not cause warping or distortion even after curing and is excellent in bending resistance.

There is a growing demand for hard hard coating film products for display products to exhibit high durability under various environments.

As the material of the hard coating film, resin is mainly used, but the resin is excellent in optical characteristics and is not broken more than glass. Such a resin for a hard coating film can be divided into a thermoplastic film and a curable film by heat or light. Among them, the curable film has a high heat resistance and is widely used.

On the other hand, a method of applying a composition for forming a UV curable hard coating layer on a carrier film by a method of producing a photocurable hard coating film, superimposing the surface on which the composition is applied and the base film and then performing ultraviolet curing and peeling off the carrier resin Lt; / RTI >

When photocuring is performed by this method, there is an advantage that hardening of the hard coat layer is relatively uniform.

However, when the liquid resin composition is subjected to the curing step, volume shrinkage occurs, so that the substrate film or the carrier film bonded to the liquid resin composition may be bent or distorted. The warpage of the carrier film makes it difficult to peel off the carrier film, and the warpage of the base film deteriorates the quality of the produced hard coat film.

In order to solve the above problems, Korean Patent No. 1,036,735 discloses a method of coating a liquid resin composition having a volume shrinkage ratio of 3 to 10% before and after curing in a thickness of 0.03 to 0.4 mm on a base film, A film is laminated to produce a laminate having transparent layers on both sides of the resin layer, and then the resin layer is cured. Then, the distorted portion of the film end caused by the curing shrinkage of the photo-cured resin is cut and removed ≪ / RTI > is disclosed.

When the resin composition is subjected to the curing step, the volume shrinkage is reduced from 1% to 20% by volume, and the composition for forming a substantial number of hard coat layers has a volume shrinkage ratio exceeding 10% before and after curing. However, the manufacturing method disclosed in the Korean patent has a limitation in that when applied to a resin composition having a volumetric shrinkage ratio before and after curing of more than 10%, the problem of warping or distortion of the base film and the carrier film can not be sufficiently improved.

Accordingly, there is a need for a hard coat film which does not cause warpage or distortion even though volume shrinkage is large before and after curing.

It is an object of the present invention to provide a hard coating film improved in quality by fundamentally improving warping and distortion of a hard coating film caused by volume contraction of a composition for forming a hard coating layer during curing.

In order to accomplish the object of the present invention, the present invention provides a hard coating film comprising a pressure-sensitive adhesive layer on one side or both sides of a transparent base film, and a hard coating layer on the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer may have a thickness of 5 to 100 μm.

The pressure-sensitive adhesive layer may contain at least one pressure-sensitive adhesive composition selected from the group consisting of an acrylic adhesive, a rubber adhesive, a styrene-butadiene rubber (SBR) adhesive, an ethylene vinyl acetate (EVA) adhesive, and a silicone adhesive.

The hard coating layer may contain a composition for forming a UV curable hard coating layer.

The composition for forming a UV-curable hard coating layer may have a volume shrinkage ratio between 10% and 20% both before and after curing.

Preferably, the volumetric shrinkage may be greater than 10% to less than 15%.

The thickness of the hard coating layer may be 20 to 60 占 퐉.

The hard coating film may have a pencil hardness of 7H or more and a minimum diameter of the mandrel rod of 18 mm or less that does not cause cracking or peeling in the hard coating film when the mandrel rod is bent.

In order to achieve still another object of the present invention, there is provided a flexible display provided with the hard coating film.

The hard coating film according to the present invention can be applied with a hard coating layer having a high volume shrinkage ratio upon curing by introducing a stretchable pressure-sensitive adhesive layer between the hard coating layer and the base film, and the hard coating layer It is advantageous in that warpage and distortion of the film can be alleviated.

Further, the stretchable pressure-sensitive pressure-sensitive adhesive layer absorbs an external impact and is strong in bending resistance, and has an advantage of having high hardness characteristics as a hard coating film.

Figures 1 and 2 are illustrative hard coating films according to the present invention.

The hard coating film of the present invention is a pressure sensitive adhesive layer on one side or both sides of a transparent base film and a hard coating layer laminated on the pressure sensitive adhesive layer.

Hereinafter, the present invention will be described in more detail, but it is for the purpose of illustrating the present invention and is not intended to limit the scope of the present invention.

1 is a hard coating film in which a pressure sensitive adhesive layer 20 on one side of a transparent base film 30 and a hard coating layer 10 on the pressure sensitive adhesive layer 20 are laminated.

2 is a hard coating film in which a pressure-sensitive adhesive layer 20 and pressure-sensitive adhesive layer 20 are laminated on both sides of a transparent base film 30.

Any transparent plastic film can be used as the transparent substrate film.

Specifically, cycloolefin-based derivatives having units of monomers including cycloolefins such as norbornene or polycyclic norbornene monomers, cellulose (including diacetylcellulose, triacetylcellulose, acetylcellulose butyrate, isobutylester cellulose, propionyl Cellulose, butyryl cellulose, acetyl propionyl cellulose) ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyamide, polyetherimide, polyacryl, polyimide, polyethersulfone, polysulfone, polyethylene, poly There may be mentioned polyolefins such as ethylene, propylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyethersulfone, polymethyl methacrylate, polyethylene terephthalate Phthalate, polyethyl Rhenaphthalate, polycarbonate, polyurethane and epoxy can be used, and unstretched uniaxial or biaxially oriented films can be used.

Among the above-mentioned transparent base films, preferred are monoaxially or biaxially stretched polyester films excellent in transparency and heat resistance, cycloolefin-based derivative films excellent in transparency and heat resistance and capable of coping with the enlargement of films, polymethyl methacrylate films And triacetyl cellulose and isobutyl ester cellulose films having no transparency and optically anisotropy can be used.

The thickness of the transparent base film is not particularly limited, but is preferably 8 to 1000 占 퐉, more preferably 20 to 500 占 퐉. If the thickness of the transparent base film is 8 mu m or less, the strength of the film may be lowered and the workability may be deteriorated. If the thickness is 1000 mu m or more, transparency may be lowered or the weight of the film may be increased.

Pressure sensitive adhesive (PSA) is not particularly limited as long as it is a film having adhesive force and stretchability. The pressure-sensitive adhesive means a pressure-sensitive adhesive which can be adhered to the surface of the adherend by applying a pressure, and can be removed from the adherend without leaving a trace on the adherend when appropriate strength is applied.

For example, the pressure-sensitive adhesive layer may contain at least one pressure-sensitive adhesive composition selected from the group consisting of an acrylic adhesive, a rubber adhesive, a styrene-butadiene rubber (SBR) adhesive, an ethylene vinyl acetate (EVA) adhesive, and a silicone adhesive.

The pressure-sensitive adhesive layer preferably has a thickness of 5 to 100 mu m. If the thickness of the pressure-sensitive adhesive layer is 5 m or less, the stretchability is not sufficient and it may not be sufficient to solve warpage and distortion. On the other hand, when the thickness is 100 m or more, transparency deteriorates or the weight of the film increases.

The hard coat layer contains a composition for forming a UV curable hard coat layer and is formed by curing the composition for forming a hard coat layer.

Specifically, the UV curable hard coating composition may include a photocurable (meth) acrylate oligomer and a monomer, and each may be used alone or in combination of two or more thereof.

As the photo-curable (meth) acrylate oligomer, for example, epoxy (meth) acrylate, urethane (meth) acrylate and the like may be used, and among these, urethane (meth) acrylate is more preferably used.

The urethane (meth) acrylate can be produced in the presence of a catalyst having a polyfunctional (meth) acrylate having a hydroxyl group in the molecule and an isocyanate group.

Examples of the (meth) acrylate having a hydroxyl group in the molecule include 2-hydroxyethyl (meth) acrylate, 2-hydroxyisopropyl (meth) acrylate, 4-hydroxybutyl (Meth) acrylate mixture, and a mixture of dipentaerythritol penta / hexa (meth) acrylate can be used.

Examples of the compound having an isocyanate group in the molecule include 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 1,8-diisocyanatooctane, 1,12-diisocyanatododecane, Diisocyanato-2-methylpentane, trimethyl-1,6-diisocyanatohexane, 1,3-bis (isocyanatomethyl) cyclohexane, trans-1,4-cyclohexane diisocyanate, Methylenebis (cyclohexylisocyanate), isophorone diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, xylene-1,4-diisocyanate, tetramethyl xylene- Diisocyanate, 1-chloromethyl-2,4-diisocyanate, 4,4'-methylenebis (2,6-dimethylphenyl isocyanate), 4,4'-oxybis (phenylisocyanate), hexamethylene diisocyanate Trifunctional isocyanate, and trimethane propanol adduct. Toluene diisocyanate It can be used at least one member selected from the group consisting of.

As the above-mentioned monomers, conventionally used ones can be used. As the photo-curable functional group, those having an unsaturated group such as (meth) acryloyl group, vinyl group, styryl group or allyl group can be used, It is more preferable to use a diary.

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, stearyl (meth) acrylate, tetrahydroperfuryl (meth) acrylate, isobutyl (meth) acrylate, At least one selected from the group consisting of phenoxyethyl (meth) acrylate and isobonol (meth) acrylate can be used.

The hard coating film according to the present invention can be produced by a method of producing a film which is generally used in the art. For example, the pressure-sensitive adhesive layer may be formed by bonding a pressure-sensitive adhesive layer formed on one side of a transparent substrate film and a hard coating layer on one side of a carrier film, or sequentially laminating a pressure-sensitive adhesive layer and a hardcoat layer on a transparent substrate film.

Generally, when the composition for forming a hard coat layer is cured to form a hard coat layer, the composition for forming a coat layer shrinks in volume. Such a shrinkage causes warpage and distortion of the hard coating film and deteriorates the quality of the hard coating film.

In the hard coating film according to the present invention, a stretchable pressure-sensitive pressure-sensitive adhesive layer is introduced between the transparent base film and the hard coating layer. The pressure-sensitive adhesive layer plays a role of buffering the force transmitted to the base film or the like during the volume contraction of the composition for forming a hard coat layer. Therefore, the warpage and distortion of the hard coating film that occurs during curing of the composition for forming a hard coating layer can be alleviated.

Furthermore, the hard coating film containing the pressure-sensitive adhesive layer is characterized in that the impact is absorbed by the stretchability of the pressure-sensitive adhesive layer even when an external impact is applied, and the bending resistance is strong.

The hard coating film according to the present invention can sufficiently alleviate warping or distortion even when the volume shrinkage ratio of the composition for forming a hard coating layer before and after curing is more than 10% to 20% or less. In particular, when the volume shrinkage ratio is more than 10% to 15% or less, warpage or distortion of the hard coat film hardly occurs. However, when the volume shrinkage ratio is more than 20%, the warpage or distortion phenomenon is reduced, but slight warping may occur, as compared with the case where the pressure-sensitive adhesive layer is not present.

The hard coating film according to the present invention has a pencil hardness of 7H or more and maintains a hardness range excellent for display, and at the same time, the minimum diameter of the mandrel rod which does not cause cracking or peeling in the hard coating film when bending the mandrel rod is 18 mm or less So that it is possible to have a characteristic that the bending resistance is large.

In addition, the present invention has another feature in a flexible display including the hard coating film. For example, the hard coating film may be provided on the flexible substrate surface of the flexible display.

The flexible display may be a plastic film LCD, an organic EL, a wearable display, an electronic book, an electronic paper, or the like, although the flexible display is not particularly limited and is commonly used in the art.

Hereinafter, the present invention will be described in more detail with reference to the following examples and comparative examples, but the following examples are only specific examples of the present invention and are not intended to limit or limit the scope of protection of the present invention.

Manufacturing example  One

49 parts by weight Urethane acrylate (product of MIWON Co., Ltd., product of SC2153), 49 parts by weight pentaerythritol triacrylate (product of MIWON Corporation, product of M340), 1 part by weight photoinitiator (product of CIVASA, I-184) Ltd., TPO) were mixed using a stirrer and filtered using a PP filter to prepare a UV curable hard coat layer composition.

Manufacturing example  2

40 parts by weight urethane acrylate (product of MIWON Co., Ltd., product of SC2153), 40 parts by weight of pentaerythritol triacrylate (product of MIWON Co., product of M340), 18 parts by weight of hexanediol diacrylate 1 part by weight of a photoinitiator (product of Shiba, TPO) was blended with a stirrer and filtered using a PP filter to prepare a composition for forming a UV curable hard coat layer.

Manufacturing example  3

10 parts by weight urethane acrylate (product of MIWON Co., Ltd., product of SC2153), 50 parts by weight of pentaerythritol triacrylate (product of MIWON Corporation, product of M340), 38 parts by weight of hexanediol diacrylate 1 part by weight of a photoinitiator (product of Shiba, TPO) was blended with a stirrer and filtered using a PP filter to prepare a composition for forming a UV curable hard coat layer.

Manufacturing example  4

50 parts by weight Pentaerythritol triacrylate (product of MIWON Co., Ltd., product of M340), 48 parts by weight hexane diol diacrylate (product of Miwon Company, M200), 1 part by weight photoinitiator (Product of Shiba, TPO) were mixed using a stirrer and filtered using a PP filter to prepare a UV curable hard coating layer composition.

Manufacturing example  5

59 parts by weight Urethane acrylate (product of MIWON Co., Ltd., product of SC2153), 39 parts by weight of pentaerythritol triacrylate (product of MIWON Corporation, product of M340), 1 part of photoinitiator (product of CIVASA, I-184) Ltd., TPO) were mixed using a stirrer and filtered using a PP filter to prepare a UV curable hard coat layer composition.

Example  One

The composition for forming a hard coat layer (volume shrinkage ratio: 20%) prepared in Production Example 1 was applied on the release-treated surface of a 38 mu m thick PET film 20 having a silicon surface on one side in a thickness of 50 mu m.

Sensitive adhesive 20 having a thickness of 20 um was bonded to one side of a triacetylcellulose film 30 (Fuji Paper Co., Ltd.) having a thickness of 80 mu m, and the releasing film of the pressure-sensitive adhesive 20 was peeled off, The surface to which the composition for forming was applied was bonded.

After the bonding, the composition for forming a UV curable hard coating layer was irradiated with UV light of 500 mJ / cm ² light quantity on the coated surface for curing to form a hard coating layer (10), and the carrier film was removed to prepare a hard coating film. One)

Example  2

The procedure of Example 1 was repeated, except that the composition for forming a hard coat layer (volume shrinkage ratio of 15%) prepared in Preparation Example 2 was used.

Example  3

The procedure of Example 1 was repeated, except that the composition for forming a hard coat layer (volume shrinkage ratio of 11%) prepared in Production Example 3 was used.

Example  4

The procedure of Example 1 was repeated, except that the composition for forming a hard coat layer (volume shrinkage ratio of 8%) prepared in Production Example 4 was used.

Example  5

The procedure of Example 1 was repeated, except that the composition for forming a hard coat layer (volume shrinkage ratio of 23%) prepared in Production Example 5 was used.

Example  6

The procedure of Example 1 was repeated except that the pressure-sensitive adhesive 20 was bonded to both sides of the triacetylcellulose film 30 (Fig. 2)

Comparative Example  One

The procedure of Example 1 was repeated except that the triacetylcellulose film (30) in which the pressure-sensitive adhesive (20) was not laminated was used.

Comparative Example  2

Example 4 was carried out in the same manner as in Example 4, except that the triacetylcellulose film 30 in which the pressure-sensitive adhesive 20 was not laminated was used.

Comparative Example  3

The procedure of Example 6 was repeated, except that the triacetylcellulose film 30 in which the pressure-sensitive adhesive 20 was not laminated was used.

In the case of Comparative Example 3, it was impossible to produce a hard coat film having a degree of compatibility with the resulting hard coat film due to strong bending, and the following experiment was not conducted on Comparative Example 3.

Experimental Example

The physical properties of the hard coat films prepared in Examples 1 to 6 and Comparative Examples 1 and 2 were measured by the following methods, and the results are shown in Table 1. The measuring method and evaluation method used in the present invention are as follows.

(1) Assessment of bending occurrence degree

When the hard coating film was placed on the floor, a warp occurred, and the film was cut into A4 size with a short side in the drying direction. The diameter of the dried cylinder was measured and evaluated in Table 1 below in order to evaluate the degree of bending of the dried hard coating film in a cylindrical form by bending. The larger the diameter, the smaller the occurrence of warpage and the better the anti-warpage performance.

(2) Evaluation of bending resistance

It was visually confirmed whether or not a crack occurred in the film when the hard coating side of the hard coating film was bent with the various diameters of the mandrel bars facing outward. The minimum diameter of the mandrel rod in which cracking or peeling does not occur in the hard coating film is shown in Table 1 below.

(3) Evaluation of pencil hardness

And measured using a Pencil Hardness Tester (Pencil Hardness Tester, Mobo Scientific) according to JIS K5600. The pencil was fixed with a load of 500 g and an angle of 45, and then the surface was scratched by the pencil hardness and judged whether or not it was scratched with the naked eye.

division Presence of pressure-sensitive adhesive layer The volume shrinkage of the composition for forming a hard coat layer
(%) Evaluation results Degree of bending Flexibility Pencil hardness Example 1 U 20 4cm 16 9H Example 2 U 15 4cm 14 8H Example 3 U 11 6cm 12 7H Example 4 U 8 6cm 12 7H Example 5 U 23 3cm 18 9H Example 6 U 20 6cm or more 18 9H Comparative Example 1 radish 20 0.5cm 25 9H Comparative Example 2 radish 8 1cm 20 7H

As shown in Table 1, Examples 1 to 6 according to the present invention show that the degree of flexure after curing is reduced and the flexural resistance is increased, as compared with Comparative Examples 1 and 2 in which no pressure sensitive adhesive layer is present.

10: hard coat layer
20: pressure-sensitive adhesive layer
30: transparent base film

Claims (9)

A pressure sensitive adhesive layer which is adhered to the surface of the adherend by applying pressure only to one side or both sides of the transparent base film and can be removed from the adherend without leaving traces on the adhered surface; A hard coat film comprising a hard coat layer formed by curing a composition for forming a coat layer,
The composition for forming a UV-curable hard coating layer preferably has a volume shrinkage ratio of not less than 10% and not more than 20% before and after curing,
Wherein the hard coating film has a pencil hardness of 7H or more and a minimum diameter of a mandrel rod of 18 mm or less which does not cause cracking or peeling of the hard coating film when bent to a mandrel bar.
The hard coating film according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 5 to 100 μm.
The pressure sensitive adhesive composition according to claim 1, wherein the pressure sensitive adhesive layer comprises at least one pressure sensitive adhesive composition selected from the group consisting of acrylic, rubber, styrene - butadiene rubber (SBR), ethylene vinyl acetate (EVA) Coating film.
delete delete The hard coating film of claim 1, wherein the volume shrinkage is greater than 10% but less than 15%.
The hard coating film of claim 1, wherein the hard coating layer has a thickness of 20 to 60 탆.
delete A flexible display comprising the hard coating film of any one of claims 1 to 3, 6 and 7.

Images