KR20170021033A - Photocurable Adhesive Composition - Google Patents

Abstract

The present invention provides a photocurable adhesive composition, comprising: (A) an inorganic metal oxide; (B) a cationic photocurable epoxy resin; and (C) a cationic photopolymerization initiator. The photocurable adhesive composition according to the present invention, when a flexible hard coating film is bonded to another film, can improve adhesiveness, adherence and flexibility to the film can have ultraviolet shielding properties.

Description

[0001] Photocurable Adhesive Composition [0002]

The present invention relates to a photo-curing adhesive composition, and more particularly, to a photo-curable adhesive composition capable of imparting excellent adhesion, adhesion and flexibility at the time of bonding a flexible hard coating film, .

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

In recent years, a flexible display capable of maintaining the display performance even if it is bent like paper by using a flexible material such as plastic instead of a conventional glass substrate which is not flexible has rapidly emerged as a next generation display device, has a high hardness There is a demand for a hard coating film which not only has good scratch resistance but also has appropriate flexibility and does not crack. In addition, when the hard coating film is bonded to another film, it is required to develop an adhesive excellent in not only adhesive strength and adhesion but also flexibility. In addition, if the surface of the flexible display is continuously exposed to ultraviolet rays, the adhesive layer or the internal bonded substrate may be decomposed and discolored and may be crushed. Therefore, development of an adhesive capable of preventing such degradation is also required.

Korean Patent Laid-Open Publication No. 2015-0043596 discloses an adhesive composition comprising a photopolymerizable compound, an epoxy-based binder resin and a cationic photoinitiator. However, when the flexible hard coat film is bonded to another film, There is a problem of insufficient adhesive strength, adhesion and flexibility, and it is not provided with ultraviolet shielding property.

Korean Patent Publication No. 2015-0043596

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a method of bonding a flexible hard coating film to another film, which is excellent in adhesive force, adhesion, flexibility, To provide a photo-curable adhesive composition capable of imparting a photo-curable adhesive composition.

Another object of the present invention is to provide a laminated film which can be used as a cover window of a flexible display device formed using the photo-curable adhesive composition.

Still another object of the present invention is to provide an image display apparatus provided with the laminated film.

On the other hand, the present invention provides a photocurable adhesive composition comprising an inorganic metal oxide (A), a cationic photopolymerizable epoxy resin (B) and a cationic photopolymerization initiator (C).

In one embodiment of the present invention, the inorganic metal oxide (A) is at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), barium titanate ₃ ), titanium dioxide (TiO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), titanium oxide (Ti ₃ O ₅ ), indium tin oxide (ITO), indium zinc oxide (IZO), antimony tin oxide And may be selected from the group consisting of zinc-silver (ZnO-Al), niobium oxide (Nb ₂ O ₅ ), tin oxide (SnO), magnesium oxide (MgO)

In one embodiment of the present invention, the inorganic metal oxide (A) may be zinc oxide (ZnO), titanium dioxide (TiO ₂ ), or a mixture thereof.

In one embodiment of the present invention, the inorganic metal oxide (A) may be contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the total adhesive composition based on the solid content.

On the other hand, the present invention relates to a hard coating film in which a hard coating layer is formed on a first base film; An adhesive layer formed from the photo-curable adhesive composition laminated on the surface of the first base film on which the hard coat layer is not formed; And a second base film laminated on the adhesive layer.

In one embodiment of the present invention, the laminated film can be used as a cover window of a flexible display device.

On the other hand, the present invention provides an image display apparatus provided with the above laminated film.

The photo-curable adhesive composition according to the present invention includes inorganic metal oxides, and when the flexible hard coat film is bonded to another film, not only the adhesive strength, adhesion and flexibility to the film are excellent, but also the ultraviolet barrier property can be imparted have.

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

An embodiment of the present invention relates to a photocurable adhesive composition comprising an inorganic metal oxide (A), a cationic photo-curable epoxy resin (B) and a cationic photopolymerization initiator (C).

In one embodiment of the present invention, the inorganic metal oxide (A) is at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), barium titanate ₃ ), titanium dioxide (TiO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), titanium oxide (Ti ₃ O ₅ ), indium tin oxide (ITO), indium zinc oxide (IZO), antimony tin oxide And may be selected from the group consisting of zinc-silver (ZnO-Al), niobium oxide (Nb ₂ O ₅ ), tin oxide (SnO), magnesium oxide (MgO)

In one embodiment of the present invention, the inorganic metal oxide (A) may be zinc oxide (ZnO), titanium dioxide (TiO ₂ ), or a mixture thereof.

The inorganic metal oxide (A) may have an average particle diameter of 20 to 200 nm. When the average particle diameter of the inorganic metal oxide (A) is less than 20 nm, a problem of dispersibility may occur. When the average particle diameter is more than 200 nm, a compatibility problem with the resin composition may occur.

The inorganic metal oxide (A) has a high ultraviolet absorption ratio in the ultraviolet wavelength range, and can impart excellent ultraviolet shielding property to the adhesive, and can improve durability unlike the organic ultraviolet absorber.

The inorganic metal oxide (A) may be contained in an amount of 0.01 to 10 parts by weight, preferably 1 to 5 parts by weight based on 100 parts by weight of the total adhesive composition based on the solid content. When the content of the inorganic metal oxide (A) is less than 0.01 part by weight, the ultraviolet shielding effect is weak. When the content of the inorganic metal oxide (A) exceeds 10 parts by weight, the curing density is lowered.

In one embodiment of the present invention, the cationic photo-curable epoxy resin (B) may be a compound having two or more epoxy groups in the molecule and capable of curing reaction or a polymer thereof, and at least one of the epoxy groups may be an alicyclic epoxy group .

As the cationic photo-curable epoxy resin (B), an epoxy compound known in the art can be used without particular limitation. In particular, an epoxy resin containing no aromatic ring has excellent photo-curability, shortening of curing time, It can be advantageously used.

Among the above cationically curable epoxy resins (B), the number of carbon atoms of the alicyclic ring constituting the alicyclic epoxy group is usually in the range of 5 to 7, and the alicyclic epoxy group having a cyclohexane ring having 6 carbon atoms in the alicyclic ring Cyclohexyl group) is preferable.

In addition, the alicyclic ring may be substituted with a substituent such as an alkyl group, and the substituted alkyl group preferably has 20 or less carbon atoms in terms of improvement in curing degree and improvement in adhesion.

The cationic photo-curable epoxy resin (B) may have a structural moiety other than an epoxy group, for example, a saturated hydrocarbon, an unsaturated hydrocarbon, a peroxy group, an ester, an ether, a ketone, a carbonate, It is advantageous because the viscosity of the resin (B) is lowered to improve the adhesion to the substrate and to facilitate handling in coating.

In one embodiment of the present invention, the cationically curable epoxy resin (B) comprises a compound represented by the following formula (1).

[Chemical Formula 1]

In this formula,

And A ₁ and A ₂ is hydrogen or an alkyl group of C _{1 -6,} each independently,

B is oxygen or an alkylene group of C _{1 -20} .

The cationically curable epoxy resin (B) may be contained in an amount of 80 to 90 parts by weight based on 100 parts by weight of the total adhesive composition based on the solid content. When the content is less than 60 parts by weight, it is difficult to exhibit an improvement in adhesion and adhesion due to a decrease in the degree of curing. When the content is more than 90 parts by weight, flexibility may not be imparted due to an increase in the degree of curing.

In one embodiment of the present invention, the cationic photopolymerization initiator (C) can be a cationic photoinitiator known in the art without particular limitation. For example, an onium salt or a derivative thereof which releases Lewis acid . Such a compound is a salt form of a cation and an anion represented by the general formula [X] ^{x +} [Y] ^x- , and specific examples of the cation include an aromatic diazonium salt, an aromatic iodonium salt, an aromatic halonium salt, Specific examples of the anion include tetrafluoroborate (BF ₄ ), hexafluorophosphate (PF ₆ ), hexafluoroantimonate (SbF ₆ ), hexafluoroarsenate (AsF ₆ ), hexafluoroarsenate Hexachloroantimonate (SbCl ₆ ), and the like. These cationic photopolymerization initiators may be used singly or in combination of two or more.

The content of the cationic photopolymerization initiator (C) is not particularly limited, and may be 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total adhesive composition, based on the solid content. have. When the content is less than 0.01 part by weight, the curing of the adhesive composition is insufficient and it is difficult to obtain sufficient adhesion and adhesion. When the content is more than 10 parts by weight, the hygroscopicity increases due to excessive ionic substance content of the adhesive layer, have.

The photo-curable adhesive composition according to an embodiment of the present invention may further include 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 may be 0.01 to 10 parts by weight based on 100 parts by weight of the total adhesive composition based on the solid content.

One embodiment of the present invention is a hard coating film comprising a hard coat layer formed on a first base film; An adhesive layer formed from the photo-curable adhesive composition laminated on the surface of the first base film on which the hard coat layer is not formed; And a second base film laminated on the adhesive layer.

The laminated film can exhibit both high hardness and high flexibility and can be used as a cover window of a flexible display device.

The first base film and the second base film may be the same or different, and a transparent polymer film may be used without limitation. For example, it is possible to use cellulose derivatives such as triacetylcellulose, acetylcellulose butyrate, ethylene-vinyl acetate copolymer, propionylcellulose, butyrylcellulose, acetylpropionylcellulose, polyester, polystyrene, polyamide, polyetherimide, Polyimide, polyether sulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polyether sulfone, poly Methyl methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, and the like. In addition, 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 may be used, which is difficult to impart adhesion force after coating.

The thicknesses of the first base film and the second base film may be the same or different and are not particularly limited, but may be 10 to 200 탆, specifically 20 to 100 탆, particularly 20 to 80 탆.

The hard coating layer may be formed by applying a hard coating composition comprising a light transmitting resin, a photo initiator and a solvent known in the art onto the first base film and curing the same.

The thickness of the hard coat layer is not particularly limited, but may be 2 to 100 탆, specifically 10 to 60 탆.

The laminated film according to one embodiment of the present invention can be produced by, for example, a coating process for coating the second base film with the photo-curable adhesive of the present invention in an uncured state to form an adhesive coated surface, A bonding step of bonding a hard coating film to the surface of the substrate, and a curing step of curing the photo-curable adhesive.

In one embodiment of the present invention, there is no particular limitation on the coating method of the photocurable adhesive for the second base film, and various coating methods such as doctor blade, wire bar, die coater, comma coater and gravure coater are used .

Before the coating, the surface of the second base film to be bonded to the hard coating film can be easily subjected to bonding. Examples of the easy-to-bond treatment include a dry treatment such as a primer treatment, a plasma treatment and a corona treatment, a chemical treatment such as an alkali treatment (saponification treatment), and a coating treatment for forming an easy adhesive layer.

The second base film and the hard coating film are adhered to each other through the photo-curing adhesive in an uncured state, and then the photo-curable adhesive is cured by irradiating an active energy ray to fix the second base film on the hard coating film.

Although a light source of an active energy ray is not particularly limited, an active energy ray having a light emission distribution with a wavelength of 400 nm or less is preferable. Specific examples thereof include low pressure mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultra high pressure mercury lamp, Mercury lamp, metal halide lamp and the like are preferable. The light irradiation intensity for the photo-curing adhesive is appropriately determined according to the composition of the photo-curable adhesive and is not particularly limited, but the irradiation intensity in the wavelength range effective for activating the polymerization initiator is preferably 0.1 to 6000 mW / cm 2 . When the irradiation intensity is 0.1 mW / cm 2 or more, the reaction time does not become excessively long, and when the irradiation intensity is 6000 mW / cm 2 or less, there is little possibility that heat radiated from the light source and yellowing or deterioration due to heat generation upon curing of the photo- The light irradiation time for the photo-curable adhesive is controlled for each curable photo-curing adhesive and is not particularly limited, but it is preferable that the accumulated light quantity, which is expressed as a product of the irradiation intensity and the irradiation time, is set to 10 to 10,000 mJ / . When the total amount of light for the photo-curing adhesive is 10 mJ / cm 2 or more, a sufficient amount of active species originating from the polymerization initiator can be sufficiently generated to promote the curing reaction more surely. When the amount is less than 10000 mJ / cm 2, Productivity can be maintained.

The thickness of the adhesive layer formed by curing the photocurable adhesive of the present invention is not particularly limited, but may be 0.5 to 50 탆, specifically 1 to 20 탆.

One embodiment of the present invention relates to an image display apparatus provided with the above-described laminated film. For example, the laminated film of the present invention can be used as a cover window of a flexible display device.

The laminated film according to one embodiment of the present invention can be used in various driving type LCDs such as reflective type, transmissive type, transflective type LCD or TN type, STN type, OCB type, HAN type, VA type and IPS type. The laminated 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  1-6 and Comparative Example  1-3: Photocurable  Preparation of adhesive composition

A photocurable adhesive composition having the composition and the content (unit: parts by weight) of the following Table 1 was prepared.

The inorganic metal oxide (A)
(Parts by weight) The epoxy resin (B) The cationic initiator (C)
(Parts by weight) ingredient Weight portion Example 1 ZnO ^{1 )} (2) + TiO ₂ ^{2 )} (3) b-1 90 5 Example 2 _{ZnO (3) + TiO 2 (} 2) b-1 90 5 Example 3 _{ZnO (2) + TiO 2 (} 2) b-1 90 6 Example 4 _{ZnO (4) + TiO 2 (} 1) b-2 90 5 Example 5 _{ZnO (1) + TiO 2 (} 4) b-2 90 5 Example 6 _{ZnO (4) + TiO 2 (} 6) b-3 85 5 Example 7 _{ZnO (6) + TiO 2 (} 4) b-3 85 5 Example 8 _{ZnO (7) + TiO 2 (} 3) b-3 85 5 Example 9 ZnO (5) b-1 85 10 Example 10 TiO ₂ (5) b-2 85 10 Comparative Example 1 - b-3 90 10 Comparative Example 2 Benzophenone-based ultraviolet screening agents ^{3 )} (5) b-1 90 5 Comparative Example 3 Benzotriazole-based ultraviolet screening agents ^{4 )} (5) b-1 90 5

1) ZnO (40 nm, NANOBYK-3842)

2) TiO ₂ (20 nm, Sigma-Aldrich)

3) 4-Allyloxy-2-hydroxybenzophenone (Sigma-Aldrich)

4) 2- (2 H - benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (2- (2 H -Benzotriazol-2 -yl) -4,6 -bis (1-methyl-1-phenylethyl) phenol, Sigma-Aldrich)

b-1: Celloxide-2021P (Daicel)

b-2: YD-128 (Kukdo Chemical)

b-3: Celloxide-2081

Cationic initiator (C): diphenyliodonium hexafluorophosphate (Sigma Aldrich)

Experimental Example  One:

10 parts by weight of urethane acrylate (10-functional group, product of Mitsubishi Chemical Corporation, SC2153), 10 parts by weight of pentaerythritol triacrylate, 50 parts by weight of nano-silica sol (12 nm, solid content 40%, catalysed silica, V8802) 2.7 parts by weight of a photoinitiator (Shibasai, I-184), and 0.3 parts by weight of a leveling agent (BYK-MEMS, BYK-UV3570) , And filtered through a filter made of PP to obtain a composition for forming a hard coat layer.

The composition for forming a hard coat layer was coated on one side of a polyimide film (50 탆, first base film) to a thickness of 20 탆, dried, and cured to form a hard coat layer Respectively. An adhesive composition having a composition and a content as shown in Table 1 was applied on the other surface of the film to a thickness of 5 占 퐉 to form an adhesive layer. Then, a polyethylene terephthalate film (50 占 퐉, second base film) And cured by ultraviolet irradiation (1500 mJ / cm ² ) to produce a laminated film.

The physical properties of the prepared laminated film were measured by a method described below, and the results are shown in Table 2 below.

(1) Evaluation of initial adhesion force development time

The prepared laminated film was evaluated for adhesiveness at intervals of 5 minutes according to the method of Experimental Example (2) described below, and the time when the cutter blade reached 2 mm or less was measured as the initial adhesive force development time.

◎: Within 1 hour

○: Within 3 hours

△: Within 6 hours

X: over 6 hours

(2) Evaluation of adhesion

After the prepared laminated film was allowed to stand at 23 캜 and 55% relative humidity for 24 hours, a cutter blade was inserted between the first base film and the second base film, Respectively.

<Evaluation Criteria>

&Amp; cir &amp;: The cutter blade does not enter between the two substrate films

A: The cutter blade fell below 2 mm between two base films

DELTA: The blade of the cutter enters between 2 mm and 5 mm or less between two base films

X: The blade of the cutter runs smoothly between the two substrate films

(3) Crack resistance  evaluation

The prepared laminated film was cut into a size of 1 cm x 10 cm and placed on a metal rod (Mandorel) of each diameter, and the smallest diameter that did not crack on the surface was displayed by hand folding.

(4) Ultraviolet Barrier property  evaluation

The transmittance of the prepared laminated film at a wavelength of 380 nm was measured using an ultraviolet ray spectrophotometer (V-7100 / VAP-7070, manufactured by Nippon Bunko Co., Ltd.). The lower the transmittance, the better the ultraviolet absorptivity (ultraviolet light shielding property).

<Evaluation Criteria>

A: transmittance less than 20%

B: transmittance 20% or more and less than 50%

C: transmittance 50% or more and less than 80%

D: transmittance 80% or more

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Comparative Example 1 Comparative Example 2 Comparative Example 3 Initial adhesive force development time ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ △ X X Adhesiveness ◎ ◎ ◎ ◎ ◎ ○ ○ ○ ○ ○ △ X X Mandrell 4φ 5φ 5φ 5φ 4φ 5φ 6φ 6φ 7φ 6φ 8φ 10φ 10φ Ultraviolet absorption coefficient B B B B B A A A A B D C C

As can be seen from the above Table 2, the laminated films prepared using the adhesive compositions of Examples 1 to 10 containing an inorganic metal compound according to the present invention exhibited excellent adhesiveness to Comparative Example 1 in which no ultraviolet absorber was used, Was superior to ultraviolet ray shielding in terms of initial adhesive force development time, adhesion and crack resistance, as compared with the case of Comparative Examples 2 and 3.

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 (7)

A photocurable adhesive composition comprising an inorganic metal oxide (A), a cationic photo-curable epoxy resin (B), and a cationic photopolymerization initiator (C). The method according to claim 1, wherein the inorganic metal oxide (A) is at least one selected from the group consisting of aluminum oxide (Al ₂ O ₃ ), silicon dioxide (SiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), barium titanate (BaTiO ₃ ) , Titanium oxide (TiO ₂ ), tantalum pentoxide (Ta ₂ O ₅ ), titanium oxide (Ti ₃ O ₅ ), indium tin oxide (ITO), indium zinc oxide (IZO), antimony tin oxide (ATO) Wherein the photo-curable adhesive composition is selected from the group consisting of silver (ZnO-Al), niobium oxide (Nb ₂ O ₅ ), tin oxide (SnO), magnesium oxide (MgO) The photocurable adhesive composition according to claim 1, wherein the inorganic metal oxide (A) is zinc oxide (ZnO), titanium dioxide (TiO ₂ ), or a mixture thereof. 2. The photocurable adhesive composition according to claim 1, wherein the inorganic metal oxide (A) is contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the total adhesive composition based on the solid content. A hard coat film on which a hard coat layer is formed on the first base film;
An adhesive layer formed from the photo-curable adhesive composition according to any one of claims 1 to 4, laminated on the surface of the first base film on which the hard coat layer is not formed; And
And a second base film laminated on the adhesive layer. The laminated film according to claim 5, which is used as a cover window of a flexible display device. An image display apparatus comprising the laminated film according to claim 6.