KR20170121889A - An Adhesive composition, window film and display device comprising the same - Google Patents

Abstract

The present invention relates to an adhesive composition which includes a silazane compound, a photocurable cationic epoxy resin, and a photocurable cationic polymerization initiator. More specifically, the adhesive composition has excellent adhesion, adhesive strength, hardness, and flexibility. According to an embodiment of the present invention, the silazane compound can be represented by chemical formula 1 and chemical formula 2. The photocurable cationic epoxy resin does not contain an aromatic ring compound. The photocurable cationic epoxy resin also contains two or more epoxy groups in one molecule.

Description

[0001] The present invention relates to adhesive compositions, window films and display devices comprising the same,

More particularly, the present invention relates to an adhesive composition comprising a silazane compound, a photo-curable cationic epoxy resin, and a photo-curable cationic polymerization initiator, and a window film comprising the adhesive composition.

A resin cured product having an isocyanurate ring as a main skeleton is used for a coating material intended for decoration and protection because of good heat resistance, good surface smoothness even after heat resistance preservation, and light transmittance can be maintained , A liquid crystal television, a personal computer, and a mobile phone.

For the purpose of protection, a certain surface hardness is required for a resin cured product, and it is known that when a polymerizable functional group (for example, olefin, hydroxyl group, etc.) is introduced into a compound constituting the resin cured product, its surface hardness can be increased .

In recent years, as a protective coating material for preventing scratches on various substrate surfaces and for preventing contamination, adhesives for various substrates, and sealants, hardness, flexibility, abrasion resistance, abrasion resistance, low curling property A cured film formed by curing has a small warpage), and a curable composition capable of forming a cured film excellent in adhesion and transparency is required.

In the use of the antireflection film of a film type liquid crystal device, a touch panel, a plastic optical component or the like, a curable composition capable of forming a cured film excellent in hardness, flexibility, scratch resistance, abrasion resistance, low curling, high refractive index, .

However, when a trifunctional or more polyfunctional acrylate having an isocyanurate ring as a main skeleton is used, there is a problem that although the curing rate is high, the flexibility of the cured product is insufficient, and cracks, peeling, It tends to be easy to do.

In order to prevent the coating film from cracking, improvements have been made such as lowering the functional group concentration of the polyfunctional acrylate which is the main component of the coating film, increasing the molecular weight, and the like. However, there are adverse effects such as a decrease in the surface hardness and scratch resistance of the cured product, and it may be difficult to obtain a good hard coat film.

Although various compositions have been proposed, a curable composition having a property that the cured film has high hardness and excellent flexibility has not yet been obtained.

Japanese Patent Laid-Open Nos. 2002-67238 and 2002-69333 disclose a composition comprising a polyfunctional urethane acrylate, a colloidal silica, and a compound having a tetrahydrofurfuryl group and a (meth) acrylate in the molecule, Lt; / RTI > However, this composition has a problem that since the colloidal silica does not have a functional group, sufficient surface hardness can not be obtained, and transparency of the cured coating is also insufficient.

Therefore, it is necessary to develop a curable composition which not only has excellent hardness but also has excellent flexibility.

Japanese Patent Laid-Open No. 2002-67238 Japanese Patent Application Laid-Open No. 2002-69333

An object of the present invention is to provide an adhesive composition excellent in adhesive strength, flexibility, hardness and scratch resistance.

It is another object of the present invention to provide a window film made of the above adhesive composition.

In order to achieve the above object,

The present invention provides an adhesive composition comprising a silazane compound represented by the following general formula (1), a photocurable cationic epoxy resin, and a photocurable cationic polymerization initiator.

[Chemical Formula 1]

Each of R ₁ to R ₁₀ may be the same or different and is hydrogen or an alkyl group having 1 to 10 carbon atoms.

The present invention also provides a window film made of the above adhesive composition.

The present invention also provides a display device including the window film.

The adhesive composition of the present invention has properties of excellent adhesive strength, hardness and scratch resistance.

Further, the adhesive composition of the present invention is excellent in flexibility, so that cracks are not generated in the adhesive layer when the substrate is bent after bonding the substrate using the adhesive composition.

Due to the above effects, the adhesive composition of the present invention can be particularly useful for bonding a flexible substrate coated with a hard coat layer.

Further, the window film made of the adhesive composition of the present invention has properties of excellent flexibility and hardness.

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

The present invention relates to an adhesive composition comprising a silazane compound represented by the following general formula (1), a photocurable cationic epoxy resin, and a photocurable cationic polymerization initiator.

[Chemical Formula 1]

Each of R ₁ to R ₁₀ may be the same or different and is hydrogen or an alkyl group having 1 to 10 carbon atoms.

The conventional adhesive composition is excellent in adhesion and hardness, but has a problem in that it is difficult to apply it to a flexible substrate due to lack of flexibility.

More specifically, the adhesive composition is used to bond different substrates. When joining two flexible substrates, a base material having an excellent elongation ratio is generally used as the base material of the lower part, and a hard coating layer The applied flexible substrate is used.

The two substrates are bonded by an adhesive composition, and when the bonded substrate is bent, a crack may be generated in the adhesive layer if the flexibility of the adhesive layer is insufficient.

Accordingly, an object of the present invention is to provide an adhesive composition having excellent adhesion, scratch resistance and hardness as well as excellent flexibility in order to solve the above problems, that is, to provide an adhesive composition which is excellent in hardness and applicable to flexible substrates .

The adhesive composition of the present invention contains the silazane compound of the above formula (1), thereby exhibiting an excellent durability, adhesive strength and flexibility.

Hereinafter, the adhesive composition of the present invention will be described in more detail for each component.

(A) Silazan  compound

The adhesive composition of the present invention comprises a silazane compound represented by the following formula (1).

[Chemical Formula 1]

R ₁ to R ₁₀ are the same or different and each is hydrogen or an alkyl group having 1 to 10 carbon atoms.

The silazane compound of the formula (1) can be improved in adhesion, durability and flexibility due to the structural characteristic of Si-NH-Si bond.

The silazane compound of formula (1) preferably includes a compound of formula (2).

(2)

The silazane compound of Formula 1 is contained in an amount of 5 to 65% by weight, preferably 15 to 40% by weight based on the total weight of the adhesive composition of the present invention.

When the silazane compound of Formula 1 is contained in an amount of less than 5% by weight, the improvement in scratch resistance is insignificant. When the silazane compound is contained in an amount of more than 65% by weight, hardness characteristics of the adhesive layer are hardly given.

(B) a photocurable cationic epoxy resin

The adhesive composition of the present invention comprises a photocurable cationic epoxy resin.

The photocurable cationic epoxy resin means a compound capable of cationic curing reaction or a polymer thereof. In the present invention, it is preferable to use a photocurable cationic epoxy resin not containing an aromatic ring. By using the photo-curable cationic epoxy resin not containing the aromatic ring, the photo-curability, the adhesive force and the adhesive force are improved, and the curing time can be shortened. In the present invention, the kind of the photocurable cationic epoxy resin not containing the aromatic ring is not particularly limited.

However, in the present invention, it is preferable to use a compound containing two or more epoxy groups in one molecule as the photocurable cationic epoxy resin.

It is more preferable that at least one of the two or more epoxy groups is an alicyclic epoxy group.

In the alicyclic epoxy group, the alicyclic compound is preferably an alicyclic ring having 5 to 7 carbon atoms, more preferably a cyclohexane ring having 6 carbon atoms.

The alicyclic ring may or may not contain a substituent, and when it contains a substituent, the substituent is preferably an alkyl group, and it is preferable that the alkyl group use an alkyl group having 1 to 20 carbon atoms in order to improve hardenability and adhesion desirable.

Specific examples of the structural moiety of the photocurable cationic epoxy resin other than the epoxy group include, but not limited to, saturated hydrocarbon, unsaturated hydrocarbon, perfluoro, ester, ether, ketone and carbonate groups. And the structural moiety preferably has 8 or less carbon atoms.

When the number of carbon atoms is 8 or less, the viscosity of the photocurable cationic epoxy resin is low, so that the improvement in adhesion to the substrate can be improved, which facilitates handling during coating.

The photocurable cationic epoxy resin may preferably contain a compound of the following formula (3).

(3)

Each of A ₁ and A ₂ may be the same or different and is hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alicyclic cyclic compound having 3 to 6 carbon atoms,

And B is oxygen or an alkanediyl group having 1 to 20 carbon atoms.

When the carbon number of the B is 20 or less, the viscosity is lowered and the adhesion can be increased.

The photocurable cationic epoxy resin may be used alone or in combination of two or more.

The photocurable cationic epoxy resin is contained in an amount of 25 to 90% by weight, preferably 30 to 85% by weight, based on the total weight of the adhesive composition of the present invention.

If the photocurable cationic epoxy resin is contained in an amount of less than 25% by weight, the degree of curing is lowered and the adhesion and adhesion are not improved. If the amount is more than 90% by weight, the degree of curing is excessively increased.

(C) Photocurable cationic polymerization Initiator

The adhesive composition of the present invention comprises a photocurable cationic polymerization initiator.

The type of the photocurable cationic polymerization initiator is not particularly limited, and a known photocurable cationic polymerization initiator can be used.

Specific examples thereof include double salts or derivatives thereof, which are onium salts which release Lewis acid by light irradiation. In such a case, the photocurable cationic polymerization initiator can be used together with the photocurable cationic epoxy resin (B) described above to inhibit curing during storage of the adhesive composition and to improve storage stability. For example, it is possible to prevent deterioration and discoloration of the adhesive itself and the object to be bonded, which are caused by thermal history when a thermosetting polymerization initiator is used. Further, it is possible to prevent deformation due to heat shrinkage of the object to be bonded by the thermal history.

Examples of such a compound include a salt of a cation and an anion represented by the general formula [X] ^{a +} [Y] ^a- .

The cation X ^{a +} is preferably onium, and its structure can be represented, for example, by [(R ¹¹ ) _b Q] ^{a +} .

R ¹¹ is a hydrocarbon having 1 to 60 carbon atoms and may further include a metal element, a non-metal element, a transition element, a metal element or a metal element after the transition, and b is an integer of 1 to 5 in addition to carbon. b R ^{11 s} may be independently the same or different. It is preferable that at least one of b R < ¹¹ > is an aryl group having 6 to 20 carbon atoms.

Q is one atom or atomic group selected from the group consisting of S, N, Se, Te, P, As, Sb, Bi, O, I, Br, Cl, F and N =

When the valence of Q in the cation X ^{a +} is c, it is necessary that a = bc.

The anion Y ^{a -} is preferably a halide complex, and its structure can be represented, for example, by [LZs] ^a- .

The L is a metal or a metalloid which is a central atom of the halide complex and is for example B, P, As, Sb, Fe, Sn, Bi, Al, Ca, In, Ti, Zn, Cr, Mn, Co, and the like. Z is halogen, and s is an integer of 3 to 7.

Further, when the valence of L in the anion Y ^{a -} is t, a relation of a = st is required.

Specific examples of the [LZs] ^a- include tetrafluoroborate (BF ₄ ) ^- , hexafluorophosphate (PF ₆ ) ^- , hexafluoroantimonate (SbF ₆ ) ^- , hexafluoroarsenate AsF ₆ ) ^- and hexachloroantimonate (SbCl ₆ ) ^- , and the like.

As a specific example of the anion Y ^{a -} , those having a structure represented by [LZs ^{- 1} (OH)] ^{a -} can also be preferably used. L, Z and s are the same as above.

Examples of other anions that can be used include perchlorate ion (ClO ₄ ) ^- , trifluoromethyl sulfite ion (CF ₃ SO ₃ ) ^- , fluorosulfonate ion (FSO ₃ ) ^- , toluenesulfonic acid anion and trinitrobenzenesulfonic acid Anion and the like.

Further, as the anion Y ^{a -} , tetrakis (pentafluorophenyl) borate can be preferably used.

The photocurable cationic polymerization initiator may be used alone or in combination of two or more.

The photocurable cationic polymerization initiator is contained in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight based on the total weight of the adhesive composition of the present invention.

If the photo-curable cationic polymerization initiator is contained in an amount of less than 0.01% by weight, hardening of the adhesive composition is insufficient and it is difficult to obtain sufficient adhesion and adhesion. If it exceeds 10% by weight, the content of ionic substances in the adhesive layer is excessive, Durability may be deteriorated.

(D) Additive

The adhesive composition of the present invention may further comprise additives as required.

The kind of the additive is not particularly limited and includes, for example, a sensitizer, an adhesion promoter, a leveling agent, an ultraviolet absorber, an antioxidant, a dye, a processing aid, an ion trap agent, an antioxidant, a tackifier, a filler, Antistatic agents, aromatic agents, and the like. These may be used alone or in combination of two or more.

The content of the additive is not particularly limited and can be, for example, 0.01 to 10% by weight based on the total weight of the adhesive composition.

Within the above range, the combination of the silazane compound (A), the photo-curable cationic epoxy resin (B) and the photo-curable cationic polymerization initiator of the formula (1) can improve storage stability, prevent discoloration, improve the curing rate, It is possible to exert the effect of securing it well.

(E)

The base material to be bonded by the adhesive composition of the present invention is not particularly limited as long as it is a transparent polymer film, and a flexible transparent polymer film can be preferably used.

More specifically, the polymer film can be produced by a film-forming method or an extrusion method according to the molecular weight and the film production method, and the type of the transparent polymer film that can be used commercially can be used without particular limitation.

Specific examples include cellulose derivatives such as triacetylcellulose, acetylcellulose butyrate, ethylene-vinyl acetate copolymer, propionylcellulose, butyryl cellulose, acetylpropionyl cellulose, polyester, polystyrene, polyamide, polyetherimide, poly But are not limited to, acrylic, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, , Polymethyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polycarbonate.

The adhesive composition of the present invention can be used to bond two flexible substrates. More specifically, when joining two flexible substrates, a base material having an excellent elongation ratio is generally used as a base material of the lower part, and a flexible base material having a hard coating layer coated thereon is used as an upper base material.

The two substrates are bonded by an adhesive composition, and since the adhesive composition of the present invention is excellent in flexibility, cracks are not generated in the adhesive layer when the bonded substrate is bent.

That is, the adhesive composition of the present invention can be used for bonding a hardcoat base film.

In addition, since the adhesive composition of the present invention is excellent in adhesion, it can be applied to a crystalline polymer base material, an engineering plastic base material, or a polymer base material whose surface has become hydrophilic due to hydrolysis or saponification, , The adhesion can be increased without deteriorating the mechanical properties. In order to further increase the adhesion, the surface of the polymer substrate may be treated by plasma or corona treatment.

The present invention also relates to a window film made of the adhesive composition of the present invention and a display device including the window film.

Conventionally, glass has been used as a window film to be laminated on the upper layer of the display. However, glass is not flexible and can not be used for flexible window films and display devices.

Since the adhesive composition of the present invention exhibits excellent flexibility, the adhesive composition can be applied to a flexible substrate.

Further, since the adhesive composition of the present invention exhibits excellent properties of hardness, it can exhibit flexible properties while exhibiting hardness such as glass.

Therefore, it is possible to provide a flexible window film having high flexibility and high hardness by using the adhesive composition of the present invention, and the window film can be applied to a flexible display device.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

≪ Preparation of adhesive composition >

Example  1 to 3 and Comparative Example  1-3.

The adhesive compositions of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared with the compositions shown in Table 1 below.

(Unit: wt%) division Silazane compound Photocurable cationic epoxy resin Light-curing type
Cation
Polymerization initiator B-1 B-2 B-3 Example 1 20 77 - - 3 Example 2 30 67 - - 3 Example 3 40 57 - - 3 Comparative Example 1 - 90 - - 10 Comparative Example 2 - - 90 - 10 Comparative Example 3 - - - 90 10

Silazane compound

[Chemical Formula 2] (SEJINSHI A H0089)

Photocurable cationic epoxy resin

B-1: Celloxide-2021P (Daicel)

B-2: YD-128 (Kukdo Chemical)

B-3: Celloxide-2081 (Daicel)

Photocurable cationic polymerization initiator: Irgacure 250 (BASF)

Experimental Example  1. Evaluation of properties of adhesive composition

The adhesive composition prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was coated on one side of the first plastic substrate film in a thickness of 50 占 퐉. The second plastic substrate film was bonded to the adhesive composition layer and then irradiated with UV light with a high-pressure mercury lamp (UVA cumulative light quantity: 500 mJ / cm ² , illuminance: 500 mW / cm ² ) to bond the first and second plastic substrate films A film was prepared.

1-1. Evaluation of initial adhesion force expression time

The UV-irradiated bonded films were evaluated for initial adhesion force development time at 5 minutes intervals at a temperature of 23 캜 and a relative humidity of 55%.

The initial adhesive force development time was evaluated based on the time when a cutter knife was inserted into the joint surface of the bonded substrate and when the blade of the cutter blade reached 2 mm or less. The evaluation criteria were as follows. The results are shown in Table 2 below.

≪ Evaluation criteria of initial adhesion force &

◎: Within 1 hour

○: Within 3 hours

△: Within 6 hours

X: over 6 hours

1-2. Adhesion evaluation

The UV-irradiated films were allowed to stand at 23 < 0 > C and 55% relative humidity for 24 hours.

The cutter knife was pushed into the joint surface of the bonded substrate and the adhesive force was evaluated according to the degree of insertion of the blade of the cutter knife.

The evaluation criteria are as follows, and the results are shown in Table 2.

<Adhesive Strength Evaluation Standard>

◎: The blade of the cutter blade does not enter between the joint surfaces of the two substrates

O: The blade of the cutter knife enters 2 mm or less between the joint surfaces of the two substrates

DELTA: The blade of the cutter knife enters between 2 mm and 5 mm or less between the joint surfaces of the two substrates

X: The blade of the cutter blade reaches the end between the joint surfaces of the two substrates

1-3. Flexibility evaluation ( Mandrell  evaluation)

The UV-irradiated films were allowed to stand at 23 &lt; 0 &gt; C and 55% relative humidity for 24 hours. Thereafter, the bonded substrate was cut into a size of 1 x 10 cm to prepare a sample.

The sample was placed on a steel rod having respective diameters, and the sample was manually folded to measure the smallest diameter at which no crack occurred on the surface. The results are shown in Table 2 below.

division Initial adhesive force development time Adhesion Flexibility (φ = mm) Example 1 ◎ ◎ 3φ Example 2 ◎ ◎ 3φ Example 3 ◎ ◎ 3φ Comparative Example 1 ○ △ 9φ Comparative Example 2 ○ △ 10φ Comparative Example 3 ○ △ 10φ

From the results of Table 2, Examples 1 to 3, which are the adhesive compositions of the present invention, showed excellent initial adhesive force development time, adhesive strength and flexibility.

The adhesive compositions of Comparative Examples 1 to 3, which did not contain the silazane compound of Formula 1, exhibited relatively good or good initial adhesive force development time and adhesion, but all had poor flexibility.

Thus, it has been confirmed through experiments that the adhesive composition of the present invention has not only excellent adhesive strength but also excellent flexibility.

Due to the above-mentioned effects, the adhesive composition of the present invention can be used as a flexible substrate, and it can be used for a window film and a display device, and thus a flexible window and a display device can be provided.

Claims (12)

An adhesive composition comprising a silazane compound represented by the following formula (1), a photocurable cationic epoxy resin, and a photocurable cationic polymerization initiator:
[Chemical Formula 1]

Each of R ₁ to R ₁₀ may be the same or different and is hydrogen or an alkyl group having 1 to 10 carbon atoms. The adhesive composition of claim 1, wherein the silazane compound of Formula 1 comprises a silazane compound of Formula 2:
(2)

The adhesive composition according to claim 1, wherein the photocurable cationic epoxy resin does not include an aromatic ring compound. 4. The adhesive composition according to claim 3, wherein the photocurable cationic epoxy resin comprises two or more epoxy groups in one molecule. 5. The adhesive composition according to claim 4, wherein at least one of the two or more epoxy groups in the molecule is an alicyclic epoxy group. The adhesive composition according to claim 5, wherein the photocurable cationic epoxy resin comprises a compound of the following formula (3):
(3)

Each of A ₁ and A ₂ may be the same or different and is hydrogen, an alkyl group having 1 to 6 carbon atoms, or an alicyclic cyclic compound having 3 to 6 carbon atoms,
And B is oxygen or an alkanediyl group having 1 to 20 carbon atoms. The adhesive composition according to claim 1, which comprises 5 to 65% by weight of the silazane compound of the formula 1, 25 to 90% by weight of the photo-curable cationic epoxy resin, and 0.01 to 10% by weight of the photo-curable cationic polymerization initiator based on the total weight of the adhesive composition &Lt; / RTI &gt; The adhesive composition of claim 1, wherein the adhesive composition further comprises an additive. The adhesive composition of claim 1, wherein the adhesive composition is for bonding a hardcoat substrate film. A window film made from the adhesive composition of any one of claims 1 to 9. The window film according to claim 10, wherein the window film is a flexible window film. A display device comprising a window film according to any one of claims 10 to 11.